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  • Column liquid chromatography  (372)
  • kinetics  (355)
  • Springer  (727)
  • Cambridge University Press
  • 1995-1999  (630)
  • 1980-1984  (97)
  • 1955-1959
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  • 1
    Electronic Resource
    Electronic Resource
    Characteristics of manganese current and its comparison with currents carried by other divalent cations in snail soma membranes (1983)
    Springer
    The journal of membrane biology 76 (1983), S. 289-297 
    Details
    ISSN: 1432-1424
    Keywords: neuron ; internal perfusion ; Mn current ; kinetics ; Ca blocker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Characteristics of currents carried by Mn2+ and other divalent cations were studied in the isolated identified neuron in the circumesophageal ganglia ofHelix aspersa using a suction pipette technique which allows internal perfusion of the cell body and voltage clamp. Increases in [Mn2+] 0 induced not only saturation of the peak ofI Mn but also shifts theI–V relationships along the voltage axis to the more positive potentials. Internal perfusion with F−, which blocks Ca channels, depressedI Mn. Diltiazem, an organic Ca blocker, inhibitedI Mn over the entire range of theI–V relation without shifting the threshold and peak voltage of theI–V relation. Co2+, Ni2+, Cd2+ and La3+ also suppressedI Mn. Relative maximum peak currents of the divalent cations wereI Ba=I Sr〉I Ca〉I Mn=I Zn. Time constants for activation (τ m ) and inactivation (τ h ) of these cations were voltage dependent, and both time constants were greater in the sequence ofI Mn=I Zn〉I Ba=I Sr〉I Ca over the whole voltage range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870371
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of variation of ion and methylation of carrier on the rate constants of macrotetralide-mediated ion transport in lipid bilayers (1982)
    Springer
    The journal of membrane biology 68 (1982), S. 191-206 
    Details
    ISSN: 1432-1424
    Keywords: ion transport ; carriers ; lipid bilayers ; kinetics ; nonactin ; methylation ; macrotetralides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effects of methylation on the rate constants of carrier-mediated ion transport have been studied on monooleindecane bilayers with K+, Rb+, NH 4 + , and TI+ ions, using the series of homologue carriers, nonactin, monactin, dinactin, trinactin, and tetranactin, each member of the series differing from the previous one by only one methyl group. Measurements of the amplitude and time constant of the current relaxation after a voltage jump over a large domain of voltage and permeant ion concentration, together with a computer curve-fitting procedure, have allowed us, without the help of steady-state current-voltage data, to deduce and compare the values of the various rate constants for ion transport: formation (k Ri) and dissociation (k Di) of the ion-carrier complex at the interface, translocation across the membrane interior of the carrier (k s) and the complex (k is). With the additional information from steady-state low-voltage conductance measurements, we have obtained the value of the aqueous phase-membrane and torus-membrane partition coefficient of the carrier ({ie191-1} and {ie191-2}). From nonactin to tetranactin with the NH 4 + ion,k is, and {ie191-3} are found to increase by factors of 5 and 3, respectively,k Di and {ie191-4} to decrease respectively by factors 8 and 2, whilek Ri andk s are practically invariant. Nearly identical results are found for K+, Rb+, and Tl+ ions.k Ri,k s andk is are quite invariant from one ion to the other except for Tl+ wherek Ri is about five times larger. On the other hand,k Di depends strongly on the ion, indicating that dissociation is the determining step of the ionic selectivity of a given carrier. The systematic variations in the values of the rate constants with increasing methylation are interpreted in terms of modifications of energy barriers induced by the carrier increasing size. Within this framework, we have been able to establish and verify a fundamental relationship between the variations ofk is andk Di with methylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872264
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  • 3
    Electronic Resource
    Electronic Resource
    Pressure dependence of the potassium currents of squid giant axon (1982)
    Springer
    The journal of membrane biology 69 (1982), S. 35-40 
    Details
    ISSN: 1432-1424
    Keywords: axon ; hydrostatic pressure ; K currents ; kinetics ; activation volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effect of pressure upon the delayed, K, voltage-clamp currents of giant axons from the squidLoligo vulgaris was studied in axons treated with 300nm TTX to block the early, Na, currents. The effect of TTX remained unaltered by pressure. The major change produced by pressures up to 62 MPa is a slowing down of the rising phase of the K currents by a time scaling factor which depends on pressure according to an apparent activation volume, ΔV∓, of 31 cm3/mole at 15°C; ΔV∓ increased to about 42 cm3/mole at 5°C. Pressure slightly increased the magnitude, but did not produce any obvious major change in the voltage dependence, of the steady-state K conductance estimated from the current jump at the end of step depolarizations of small amplitude (to membrane potentials,E, ≦20 mV) and relatively short duration. At higher depolarizations, pressure produced a more substantial increase of the late membrane conductance, associated with an apparent enhancement of a slow component of the K conductance which could not be described within the framework of the Hodgkin-Huxley (HH)n 4 kinetic scheme. The apparent ΔV∓ values that characterize the pressure dependence of the early component of the K conductance are very close to those that describe the effect of pressure on Na activation kinetics, and it is conceivable that they are related to activation volumes involved in the isomerization of the normal K channels. The enhancement of the slow component of membrane conductance by pressure implies either a large increase in the conductance of the ionic channels that are responsible for it or a strong relative hastening of their turn-on kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871239
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  • 4
    Electronic Resource
    Electronic Resource
    Na+, Li+ and Cl− transport by brush border membranes from rabbit jejunum (1983)
    Springer
    The journal of membrane biology 74 (1983), S. 85-94 
    Details
    ISSN: 1432-1424
    Keywords: sodium ; lithium ; chloride ; pH ; transport ; kinetics ; ion permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Na+, Li+, K+, Rb+, Br−, Cl− and SO 4 2− transport were studied in brush border membrane vesicles isolated from rabbit jejunum., Li+ uptakes were measured by flameless atomic absorption spectroscopy, and all others were measured using isotopic flux and liquid scintillation counting. All uptakes were performed with a rapid filtration procedure. A method is presented for separating various components of ion uptake: 1) passive diffusion, 2) mediated transport and 3) binding. It was concluded that a Na+/H+ exchange mechanism exists in the jejunal brush border. The exchanger was inhibited with 300 μm amiloride or harmaline. The kinetic parameters for sodium transport by this mechanism depend on the pH of the intravesicular solution. The application of a pH gradient (pHin=5.5, pHout=7.5) causes an increase inJ max (50 to 125 pmol/mg protein·sec) with no change inK t (≈4.5mm). Competition experiments show that other monovalent cations, e.g. Li+ and NH 4 + , share the Na+/H+ exchanger. This was confirmed with direct measurements of Li+ uptakes. Saturable uptake mechanisms were also observed for K+, Rb+ and SO 4 2− , but not for Br−. TheJ max for K+ and Rb+ are similar to theJ max for Na+, suggesting that they may share a transporter. The SO 4 2− system appears to be a Na+/SO 4 2− cotransport system. There does not appear to be either a Cl−/OH− transport mechanism of the type observed in ileum or a specific Na+/Cl− symporter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870497
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics of sodiumd-glucose cotransport in bovine intestinal brush border vesicles (1984)
    Springer
    The journal of membrane biology 79 (1984), S. 41-51 
    Details
    ISSN: 1432-1424
    Keywords: glucose ; brush borders ; sodium cotransport ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Brush border membrane vesicles (BBMV) purified from steer jejunum were used to study the kinetics of sodiumd-glucose cotransport under voltage clamped, zero-trans conditions. When the initial rate of glucose transport (J gluc) was measured over a wide range of glucose concentrations ([S]=0.01–20mm), curvature of the Woolf-Augustinsson-Hofstee plots was seen, compatible with a diffusional and one major, high capacity (maximal transport rateJ max=5.8–8.8 nmol/mg·min) saturable system. Further studies indicated that changes incis [Na] altered theK t , but not theJ max, suggesting the presence of a rapid-equilibrium, ordered bireactant system with sodium adding first.Trans sodium inhibitedJ gluc hyperbolically. KCl-valinomycin diffusion potentials, inner membrane face positive, loweredJ gluc, while potentials of the opposite polarity raiseJ gluc. At low glucose concentrations ([S]〈0.05mm), a second, minor, high affinity transport system was indicated. Further evidence for this second saturable system was provided by sodium activation curves, which were hyperbolic when [S]=0.5mm, but were sigmoidal when [S]=.0.01mm. Simultaneous fluxes of22Na and [3H]glucose at 1mm glucose and 30mm NaCl yielded a cotransport-dependent flux ratio of 2∶1 sodium/glucose, suggestive of 1∶1 (Na/glucose) high capacity, low affinity system and a ∼3∶1 (Na/glucose) high affinity, low capacity system. Kinetic experiments with rabbit jejunal brush borders revealed two major Na-dependent saturable systems. Extravesicular (cis) Na changed theK t , but not theJ max of the major system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868525
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure dependence of the sodium currents of squid giant axon (1982)
    Springer
    The journal of membrane biology 69 (1982), S. 23-34 
    Details
    ISSN: 1432-1424
    Keywords: axon ; hydrostatic pressure ; Na currents ; kinetics ; temperature ; activation volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effects of hydrostatic pressures up to 62 MPa upon the voltage-clamp currents of intact squid giant axons were measured using mineral oil as the pressure transmitting medium. The membrane resistance and capacitance were not appreciably affected over the whole range of pressures explored. The predominant effect of pressure is to slow the overall kinetics of the voltage-clamp currents. Both the early (Na) currents and the delayed (K) ones were slowed down by approximately the same time scale factor, which was in the range of 2 to 3 when pressure was increased from atmospheric to 62 MPa. Finer details of the effects, most evident at moderate depolarizations, are: the apparent initial delay in the turn-on of Na currents is increased by pressureless than is the phase of steepest time variation, and the later decay is slowedmore than is the rising phase. The initial time course of the currents at high pressures can be made to overlap with that at normal pressure by a constant time compression factor, Θm, together with a small, voltage-dependent delay. In a given axon, Θm was fairly independent of voltage, and it increased exponentially with pressure according to an apparent activation volume, ΔV∓, ranging between 32 and 40 cm3/mole. ΔV∓ tended to decrease with increasing temperature. Contrary to what is observed for moderate or large depolarizations, the kinetics of Na inactivation produced by conditioning prepulses of −50 or −60 mV was little affected over the whole range of pressures explored. Inferences about the pressure dependence of the steady-state Na activation were made from the comparison of the plots of early peak currents,I p, versus membrane potential,E. The Na reversal potential,E Na, and the slope of the plots nearE Na did not change significantly with pressure, but the peak Na conductancevs. E relationship was shifted by about +9 mV upon increasing pressure to 62 MPa. Steady-state Na inactivation,h ∞, was slightly affected by pressure. At 62 MPa the midpoint potential of theh ∞ (E) curve,E h, was shifted negatively by about 4 mV, while the slope atE h decreased by about 38%. Under the tentative assumption that pressure directly affects the gating of Na channels, the Na activation data follows a simple Hodgkin-Huxley scheme if the opening of anm gate involves an activation volume of about 58 Å3 and a net volume increase of about 26 Å3. However, a self-consistent description of the totality of the effects of pressure on Na inactivation cannot be obtained within a similar simple context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871238
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  • 7
    Electronic Resource
    Electronic Resource
    The kinetics of transport inhibition by noncompetitive inhibitors (1983)
    Springer
    The journal of membrane biology 74 (1983), S. 175-182 
    Details
    ISSN: 1432-1424
    Keywords: kinetics ; transport inhibition ; noncompetitive ; competitive ; inhibition mechanism ; carrier model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A new analysis of the conventional carrier model shows that noncompetitive inhibitors can give rise to either competitive, noncompetitive or uncompetitive kinetics; the true mechanism and also the relative affinity of the inhibitor on each surface of the membrane can be decided from the patterns of inhibition observed in different transport experiments. The priciples governing the kinetics of inhibition apply to both reversible and irreversible inhibitors, for in either case the substrate may increase or decrease inhibition or be without effect. Ambiguity arises if the noncompetitive inhibitor acts on only one side of the membrane and if the substrate, in the course of being transported, alters the steady-state distribution of the carrier between inner and outer forms. In facilitated transport systems only equilibrium exchange should give rise to noncompetitive kinetics, whatever the location of the inhibitor. In active systems even the interpretation of exchange in the final steadystate is complicated if the energy-coupling mechanism produces a large displacement in the distribution of the free carrier or the substrate complex: the inhibition could be competitive or uncompetitive, depending on the location of the inhibitor. The actual mechanism is revealed in the uncoupled system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02332121
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  • 8
    Electronic Resource
    Electronic Resource
    Invariant kinetic approach to the description of a rock fracture process and induced seismic events (1996)
    Springer
    Pure and applied geophysics 147 (1996), S. 367-375 
    Details
    ISSN: 1420-9136
    Keywords: Induced seismicity ; kinetics ; rock fracture ; rockburst ; earthquake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Powerful seismic events, such as earthquakes and rockbursts, are caused by the accumulation of energy in rocks and loss of rock mass stability. Usually methods of their forecasting are based on the registration of anomalous behavior of geophysical fields. However an efficiency of this approach is low. The present paper proposes a kinetic approach to the description of rock fracture process, which can be used for the forecasting of seismic events and an investigation of structure and energy distributions in rock. 3-D and 1-D kinetic equations describing a process of cluster formation in rock were obtained. The equations are invariant to deformation conditions and to the scale level of events. They showed a good agreement with the results of field observations and laboratory experiments. It was also shown that these equations well describe the processes of earthquake, rockburst and rock sample failure preparation. Catalogues of rockbursts in mines were analyzed with the use of the kinetic equations to find out evidence of induced seismic events. The proposed approach makes it possible to reveal trends in rock behavior and thus predict the rock failure at different scale levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877489
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  • 9
    Electronic Resource
    Electronic Resource
    Assessment of inhibition kinetics of the growth of strain P5 on pentachlorophenol under steady-state conditions in a nutristat (1996)
    Springer
    Archives of microbiology 165 (1996), S. 194-200 
    Details
    ISSN: 1432-072X
    Keywords: Key words Auxostat ; Batch culture ; Chemostat ; Continuous culture ; Fermentation control ; Inhibition ; kinetics ; Nutristat ; On-line measurement ; Pentachlorophenol ; Pollutant ; Sphingomonas ; Steady-state conditions ; Toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A bacterium degrading pentachlorophenol (PCP) as the only source of carbon and energy was grown in a “nutristat”, i.e., a continuous culture with on-line measurement and control of the substrate concentration. We improved the PCP nutristat by incorporation of a personal computer with a proportional integral derivative (PID) algorithm for controlling the medium feed pump. The controlled value deviated from the average (set-point) value by 1% maximally. In the PCP nutristat (30°C), the steady-state dilution rate, and hence, specific growth rate, showed a maximum value of 0.142 ± 0.004 h–1 at set-point PCP concentrations between 37 and 168 μM. At PCP concentrations above 168 μM, the steady-state growth rate decreased because of inhibition. The growth yield coefficient was not seriously affected by the PCP concentration, suggesting that uncoupling was not the inhibitory mechanism. It was concluded that the PCP nutristat is very useful for establishing steady-state conditions that maintain growth-inhibitory PCP concentrations and high cell concentrations, conditions for which the chemostat is not suitable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01692861
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of food and age on the single-dose kinetics and effects of tolbutamide and chlorpropamide (1980)
    Springer
    European journal of clinical pharmacology 17 (1980), S. 285-293 
    Details
    ISSN: 1432-1041
    Keywords: tolbutamide ; chlorpropamide ; kinetics ; food ; age ; blood glucose ; plasma insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food intake (standardized breakfast) on the oral single-dose kinetics and effects of tolbutamide (0.5 g) and chlorpropamide (250 mg) was investigated in young, healthy volunteers. The single-dose kinetics of the two drugs was also studied in elderly healthy subjects. There was great interindividual variation in the elimination rate of both drugs, but food intake influenced neither their AUCs nor their rates of absorption and elimination. The peak concentration of chlorpropamide, but not that of tolbutamide, was reduced by food intake. The peak concentrations of serum tolbutamide were approximately doubled by an increase in dose from 0.5 to 1.0 g, and from 1.0 to 2.0 g. At no time did tolbutamide 0.5 g affect the plasma insulin level, neither in the fasting nor in the non-fasting state. However, this dose did reduce the blood glucose level during fasting and the increase in blood glucose in response to the meal. The latter effect was recorded within 30 min, when the serum level of tolbutamide still was close to zero. Plasma insulin concentrations did increase within 30 min after a higher dose of tolbutamide (1.0 g), when the serum concentration of tolbutamide was about 50 µmol/l. Between 2.5 and 8 h after administration of chlorpropamide 250 mg, serum drug concentrations were lower than those following tolbutamide 0.5 g. The blood glucose response was smaller and occurred later, being significant at 2 h, when the serum concentration of the drug was about 70 µmol/l. There was no significant change in plasma insulin. There was no significant pharmacokinetic difference between young and elderly subjects, except that the peak concentration of tolbutamide was higher in the latter. It appears that both for tolbutamide and chlorpropamide there is great interindividual variation in drug disposition, but food intake does not influence the bioavailability of either drug. The effect of any particular drug concentration seems dependent upon the blood glucose level and hence upon the elapsed time since the last meal. Both drugs can reduce blood glucose without an alteration in the peripheral blood concentration of insulin. This may reflect an extrapancreatic effect of the drugs, but it could also be an expression of increased insulin secretion, which is not detected because of enhanced hepatic degradation of the hormone released into the portal circulation. The observations made in young individuals are also probably relevant for elderly subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625802
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  • 11
    Electronic Resource
    Electronic Resource
    Bioavailability of acetylsalicylic acid and salicylic acid from rapid-and slow-release formulations, and in combination with dipyridamol (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 309-314 
    Details
    ISSN: 1432-1041
    Keywords: acetylsalicylic acid ; salicylic acid ; dipyridamol ; bioavailability ; kinetics ; rapid- and slow-release formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Acetylsalicylic acid (ASA) is a strong, irreversible inhibitor of platelet aggregation, but loses this activity following first-pass deacetylation to salicylic acid (SA). In order to compare the bioavailability of unchanged ASA from rapid- and slow-release formulations, the single-dose concentration profiles of ASA and SA were studied in healthy volunteers following intake of two different rapid-release (conventional and effervescent tablets) and three different slow-release (microencapsulated ASA in tablets and in capsules, and enteric-coated tablets) formulations of ASA, and of one slow-release formulation of sodium salicylate. Since anti-platelet therapy with ASA is often combined with dipyridamol, the influence of this drug was also examined. The concentrations of ASA and SA were measured by high-pressure liquid chromatography. While the bioavailability of SA from the 5 ASA formulations was essentially equal and similar to that of the salicylate formulation, the bioavailability and peak concentrations of ASA appeared to be the much greater after rapid-release than after slow-release formulations. Indeed, ASA was only rarely detected in systemic blood following intake of slow-release ASA. Co-administered dipyridamol did not significantly influence the kinetics of ASA or SA. It appears that rapid-release formulations of ASA should be prefered in anti-platelet therapy, either alone or in combination with dipyridamol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548398
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  • 12
    Electronic Resource
    Electronic Resource
    Kinetics and metabolism of (+)-, (−)- and (±)-bufuralol (1982)
    Springer
    European journal of clinical pharmacology 23 (1982), S. 529-533 
    Details
    ISSN: 1432-1041
    Keywords: beta-blocker ; bufuralol ; enantiomers ; kinetics ; metabolism ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Single oral doses of (+)-, (−)- and (±)-bufuralol were administered to a healthy volunteer to compare the disposition and metabolism of the individual isomers and the racemate. Plasma levels and area under plasma curve (AUC) of the active isomer, (−)-bufuralol, were higher than those of the (+)-isomer; plasma clearance was correspondingly lower. Intermediate values were found for the racemate. The elimination half-life of (−)-bufuralol was shorter than that of (+)-bufuralol, but similar to the racemate. Both isomers were cleared almost entirely by metabolism. The main metabolic pathway for (−)-bufuralol was aromatic hydroxylation, whereas the principal route for (+)-bufuralol was conjugation. Phenol metabolites in the systemic circulation were present mainly as conjugates. Both isomers also underwent aliphatic hydroxylation. This pathway was more favoured by the (+)-isomer, although plasma levels and AUC of the principal product, 2′-hydroxy-bufuralol, were almost identical for the two forms. Major differences in metabolic fate thus had relatively little effect on the disposition of pharmacologically active metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637501
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  • 13
    Electronic Resource
    Electronic Resource
    Increased oral clearance of metoprolol in pregnancy (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 217-220 
    Details
    ISSN: 1432-1041
    Keywords: metoprolol ; pregnancy ; hypertension ; kinetics ; pre-eclampsia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of oral metoprolol was studied in 5 women during the last trimester of pregnancy and 3 to 5 months after delivery. After a single oral dose of 100 mg the individual peak plasma concentration in the pregnant state was only 20–40% of that after pregnancy. The plasma half-lives of metoprolol were about the same during (average 1.3 h) and after pregnancy (average 1.7 h). By contrast, the area under the plasma concentration versus time curve was much smallerduring (mean 262 nmol/l×h) thanafter (mean 1298 nmol/l×h) pregnancy, resulting in an average apparent oral clearance (Clo) of metoprolol that was 4.4times higher during (362 ml×kg−1 body-weight×min−1) than after pregnancy. The increased Clo in pregnancy is assumed to be due to enhanced hepatic metabolism of the drug. The possible clinical consequence of the difference in the disposition of metoprolol is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613820
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  • 14
    Electronic Resource
    Electronic Resource
    Prizidilol, a combined vasodilatory and β-adrenoceptor blocking drug, in primary hypertension (1983)
    Springer
    European journal of clinical pharmacology 25 (1983), S. 179-186 
    Details
    ISSN: 1432-1041
    Keywords: prizidilol ; antihypertensive effect ; acute and long-term blood pressure control ; plasma renin activity ; acetylator phenotype ; antinuclear antibodies ; side effects ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary After an initial placebo period of four weeks 24 patients with primary hypertension were treated with prizidilol, a hydrazinopyridazine derivative with combined vasodilator and non-selective beta-adrenoceptor blocking actions, for a dose titration period of 14 weeks. Prizidilol 200 to 800 mg was given once daily to achieve a target supine diastolic blood pressure (BP)〈90 mmHg. Supine and standing BP recorded 24–27 h after drug intake decreased from 172±17/106±6 mmHg (mean±SD) and 167±18/111±8 mmHg, respectively, after placebo to 159±16/99±8 and 154±18/101±9 mmHg after active treatment for six weeks (mean dose 447 mg), and to 154±16/97±7 and 148±14/97±7 mmHg after treatment for 14 weeks (mean dose 687 mg/day). A slight reduction in HR was seen after treatment for six weeks and in plasma renin activity and urinary methoxycatecholamine excretion after treatment for 14 weeks. A sustained decrease in BP was observed for 10 h after prizidilol 800 mg (n=9), with a maximum antihypertensive effect (mean reduction in supine BP 33/18 mmHg) 2.5 h after dosing, which coincided with the mean peak plasma concentration. The plasma elimination half-life of the drug was 3.9 h (range 2.0–8.9 h). Changing to a twice daily regimen in 17 patients (mean daily dose 748 mg at six months) did not produce any further reduction in the BP (recorded 12–15 h after dosing) as compared to the once daily regimen at 14 weeks. During treatment for up to 24 months, 16 patients did not achieve satisfactory BP control. Eight of them were withdrawn and eight received additional treatment with bendroflumethiazide (2.5–5 mg/day). In 7 of the latter satisfactory BP control was achieved. Side effects were few. Dizziness and tiredness occurred in four patients 2–5 h after prizidilol 600–800 mg once daily. These symptoms partly subsided when the subjects changed to a twice daily regimen. No ocular side-effects were found. Before treatment 13 out of 24 patients had a low titre of IgM antinuclear antibodies (ANA) and one patient also a low titre of IgG ANA. During treatment the frequency of patients with positive ANA-titres became higher, and after treatment for 12 months (n=17) 15 patients had positive IgM and seven patients positive IgG ANA-titres. However, the titres were low and no patient showed a clinical lupus erythematosus syndrome. There was no relation between acetylator phenotype of the patient and acute or longterm effecton BP, pharmacokinetics of the drug or the development of a raised ANA-titre.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00543788
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  • 15
    Electronic Resource
    Electronic Resource
    Pharmacokinetics in man of acebutolol and hydrochlorothiazide as single agents and in combination (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 801-806 
    Details
    ISSN: 1432-1041
    Keywords: acebutolol ; hydrochlorothiazide ; kinetics ; drug combination ; interaction ; diacetolol ; healthy subjects ; renal clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of acebutolol and hydrochlorothiazide (HCT) alone or in combination were studied in 12 healthy subjects in a cross over study. Acebutolol and diacetolol (the main metabolite) in plasma and urine were determined by HPLC and hydrochlorothiazide by GLC. The main pharmacokinetic parameters of acebutolol did not differ significantly: AUC 4492±272 µg l−1 h given alone versus 4118±354 µg l−1 h with HCT, half-life (7,69±0,32 h vs 8,10±0,72 h) and renal clearance (13,1±0,5 lh−1 vs 13,8±0,9 lh−1), respectively. There was no difference in diacetolol pharmacokinetics. HCT values were not significantly different: AUC 784±48 µg l−1 h given alone and 720±42 µg l−1 h with acebutolol, t1/2 (4,79±0,37 h vs 4,73±0,43 h). The renal clearance was slightly higher when HCT was given with acebutolol (26,2±2,6 vs 20,3±2,11 h−1,p〈0,05). This increase, observed during the first four hours, was probably due to competition between the drugs for binding to red blood cells.
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    URL: http://dx.doi.org/10.1007/BF00607091
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  • 16
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    Influence of sulfonylureas on the secretion, disposal and effect of insulin (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 27-32 
    Details
    ISSN: 1432-1041
    Keywords: sulfonylureas ; diabetes ; chlorpropamide ; glipizide ; C-peptide ; insulin ; blood glucose ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of sulfonylurea on the secretion, disposal and effect of insulin was studied in 9 Type 2 diabetics during 3 one-month courses of treatment with a) chlorpropamide (t1/2〉24 h) once daily, b) glipizide (t1/2=2–4 h) once daily, and c) glipizide in divided doses. Food intake by each patient was identical during each period. Blood concentrations of immunoreactive insulin (IRI) and C-peptide (radioimmunoassays), and of glucose (enzymatic assay), chlorpropamide (gas chromatography) and glipizide (high-pressure liquid chromatography) were determined before and after breakfast and lunch on the 4th day of each examination period. All comparisons were intraindividual. Despite the lunch-time dose of glipizide given during the divided dose treatment, once-daily administration of this drug led to higher drug concentrations not only after breakfast but also for the first few hours after lunch. Divided dosage, on the other hand, led to higher concentrations later. In contrast to once-daily dosage, continuous exposure to glipizide was found in most patients. Chlorpropamide gave the most continuous sulfonylurea exposure. The blood glucose levels were inversely related to the concurrent sulfonylurea concentrations; glucose levels after breakfast and lunch were lowest during once-daily glipizide, whereas the fasting level was lowest during chlorpropamide treatment. The IRI response to breakfast was 60%–70% higher during once-daily glipizide than during the other two treatments, but the C-peptide responses to breakfast were almost identical. Thus, the greater after-breakfast availability of peripheral insulin appeared to be due to an effect of glipizide on the extrapancreatic disposal of the hormone.
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    URL: http://dx.doi.org/10.1007/BF00606421
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  • 17
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    The long-term effect of verapamil on plasma digoxin concentration and renal digoxin clearance in healthy subjects (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 123-127 
    Details
    ISSN: 1432-1041
    Keywords: digoxin ; verapamil ; digoxin-verapamil interaction ; kinetics ; plasma level ; renal clearance ; extra-renal clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Single-dose investigations in healthy subjects have demonstrated substantial impairment of renal and extrarenal clearance of digoxin during coadministration of verapamil. A longitudinal study has been performed to assess the changes in digoxin disposition during long-term verapamil therapy. After one week of verapamil 240 mg/d mean plasma digoxin had risen from 0.21±0.01 ng/ml (SE) to 0.34±0.01 ng/ml (p〈0.01), and renal digoxin clearance had fallen from 197.57±17.37 ml/min to 128.20±10.33 ml/min (p〈0.001). These changes gradually subsided, and after six weeks, renal digoxin clearance had normalized and plasma digoxin had declined to 0.27±0.02 ng/ml (NS). The 24-h urinary recovery of digoxin increased from 46.46±3.23% before to 69.78±3.69% (p〈0.001) after six weeks of verapamil co-administration, and this elevation persisted throughout the study. The verapamil-induced suppression of renal digoxin elimination disappears over a few weeks of drug exposure, whereas the inhibition of the extrarenal clearance of digoxin seems to persist.
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    URL: http://dx.doi.org/10.1007/BF00542456
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  • 18
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    Chloroquine kinetics in the undernourished (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 273-276 
    Details
    ISSN: 1432-1041
    Keywords: undernourished ; chlorquine ; kinetics ; plasma levels ; red cell uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma and whole blood kinetics of chloroquine was studied in 7 normal and 8 undernourished subjects following a single oral dose of 600 mg. The terminal half-lives were similar in both groups. The AUC was also similar in the 2 groups, even though a higher dose per kg body weight was administered to the undernourished. This was probably because of faster clearance in this group. Chloroquine uptake by erythrocytes, its main site of action in malaria, was also comparable in the two groups. The plasma concentration of chloroquine over a period of time was found to be similar in 4 normal and 4 undernourished subjects following administration of 1.5 g of the drug in divided doses. The undernourished appear, therefore, to handle chloroquine in such a way that they do not suffer a greater risk of toxicity than normals.
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    URL: http://dx.doi.org/10.1007/BF00613831
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  • 19
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    Lack of dose dependent kinetics of theophylline (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 525-527 
    Details
    ISSN: 1432-1041
    Keywords: theophylline ; airway obstruction ; biotransformation ; kinetics ; oral dosage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Oral theophylline was given to 6 adults with airways obstruction. The initial dose was 125 mg daily and this was increased by 125 mg each week. The final total daily dose reached was determined by side effects and ranged from 500 mg to 1125 mg. At the end of each week and before the next dosage increment steady state, trough plasma theophylline concentrations were measured. For each individual and for the group as a whole there was a highly significant linear correlation between theophylline dose and trough plasma concentration. This indicates that for oral theophylline, in adults, dose-dependent kinetics do not play a significant role and dose may be adjusted without fear of a disproportionate rise in plasma concentration.
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    URL: http://dx.doi.org/10.1007/BF00609897
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  • 20
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    Amiodarone kinetics after single i.v. bolus and multiple dosing in healthy volunteers (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 491-494 
    Details
    ISSN: 1432-1041
    Keywords: amiodarone ; kinetics ; volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We studied three healthy volunteers after a single i.v. bolus of amiodarone, during 1 month of chronic oral dosing and after the discontinuation of the drug. Blood concentrations of amiodarone declined rapidly in a bi-exponential fashion after i.v. bolus. The terminal half-life ranged from 10 to 17 h; after discontinuation of chronic treatment the terminal half-lives were 8–21 days. The i.v. data, the trough levels during multiple dosing and the washout phase could be simultaneously fitted using a tri-exponential equation. The subjects were carefully monitored for cardiac and thyroid function. One subject had to stop taking amiodarone because of profound bradycardia. A reduction of serum TT3 and FT3 concentrations and an increase of serum rT3 and FT4 was found.
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  • 21
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    The single dose kinetics of chloroquine and its major metabolite desethylchloroquine in healthy subjects (1984)
    Springer
    European journal of clinical pharmacology 26 (1984), S. 521-530 
    Details
    ISSN: 1432-1041
    Keywords: chloroquine ; malaria ; rheumatoid disease ; kinetics ; major metabolite ; optimal dosage ; therapeutic regime ; monodesethylchloroquine ; bidesethylchloroquine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics and disposition of chloroquine (CQ) and its metabolite monodesethylchloroquine (CQM) were investigated in 5 healthy volunteers after incremental (150–300–600 mg CQ base) single oral doses of CQ. The analytical method used (HPLC and fluorescence detection) is the most sensitive known method for CQ and CQM. Plasma and whole blood concentrations of CQ, CQM and a third metabolite, bidesethylchloroquine (CQMM), were determined. The kinetics of CQ was found to be unique. The best fit was obtained by a multicompartmental model. The biological half-life appeared to be between 30–60 days; the volume of distribution (Vd) was ∼ 800l/kg, and the clearance ∼ 11/h/kg when calculated from plasma data. The whole blood concentrations were ∼ 8–10 times higher than in plasma, and consequently the Vd and whole blood clearance were ∼ 10 times lower. The kinetics changed as the dose was increased. An indication of capacity-limited steps in CQ disposition was found, as the rate constants decreased even though the clearance remained the same. The intrinsic half-life of CQM was 1/4 of that of CQ, but was prolonged after the highest dose of CQ. The present knowledge of CQ kinetics could provide a basis for revision of current dosage regimens in malaria suppression and rheumatoid disease to ensure efficacious and safe therapy.
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  • 22
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    Pharmacokinetics of oral and rectal flurbiprofen in children (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 367-369 
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    ISSN: 1432-1041
    Keywords: flurbiprofen ; syrup ; suppository ; kinetics ; children ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Eight subjects, aged 6–12 years and weighing 18.8–36.7 kg, received single doses of flurbiprofen 50 or 75 mg (corresponding to 1.4–2.7 mg/kg) as syrup and suppository in a Latin square design. Half-life (2.7–3.2 h), elimination constant (0.22–0.26 h−1), area under the plasma level curve (72.4–77.3 µg·h·ml−1) and time to reach the concentration peak (1–0.75 h) were similar after the syrup and suppository. Flurbiprofen showed equivalent bioavailability after oral and rectal administration and the same pharmacokinetic profile was confirmed in children as observed in adults.
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    URL: http://dx.doi.org/10.1007/BF00542178
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  • 23
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    Improved effect of glibenclamide on administration before breakfast (1982)
    Springer
    European journal of clinical pharmacology 21 (1982), S. 403-408 
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    ISSN: 1432-1041
    Keywords: glibenclamide ; diabetes ; insulin ; kinetics ; blood glucose ; relationship to meals ; absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In an attempt to assess whether intake of glibenclamide before meals would improve its therapeutic capacity, the present investigation compared the effect of glibenclamide 2.5mg t.i.d. given before and together with meals. In addition, these effects were compared with that of glibenclamide given as a single morning dose of 7.5mg. The subjects studied were six Type 2 diabetics not previously exposed to sulphonylurea drugs. Irrespective of dosage and mode of administration, addition of glibenclamide to a standardized breakfast, lunch and dinner enhanced plasma IRI concentrations and reduced blood glucose concentrations as compared to administration of meals without the drug. The different modes of glibenclamide administration did not differ significantly with respect to IRI responses. However, the blood glucose reduction after breakfast was significantly greater when glibenclaimde 2.5mg had been given before the meal than when 2.5 or 7.5mg were given with the meal; a similar, but non-significant tendency was observed after lunch; no consistent difference was seen after dinner. Food intake did not affect glibenclamide kinetics. It appears that administration of glibenclamide 2.5mg before breakfast improved glucose utilization following the breakfast load, due to earlier attainment of an effective concentration of glibenclamide.
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    URL: http://dx.doi.org/10.1007/BF00542327
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  • 24
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    Pinazepam: A precursor of N-desmethyldiazepam (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 225-228 
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    ISSN: 1432-1041
    Keywords: pinazepam ; N-desmethyldiazepam ; kinetics ; metabolism ; human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma profile of a single oral dose of pinazepam 10 mg was studied in 6 healthy male volunteers, aged 26 to 31 years. The concentrations of the parent compound and of its metabolite in plasma were measured by gas-chromatography. The peak plasma levels of pinazepam was 36.8±5.1 ng/ml and of N-desmethyldiazepam 150±13.3 ng/ml. The plasma concentration of the metabolite become higher than that of the parent compound shortly after administration, suggesting that pinazepam acts as a prodrug.
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    URL: http://dx.doi.org/10.1007/BF00545219
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  • 25
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    Elimination of azlocillin in patients with biliary t-tube drainage (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 435-439 
    Details
    ISSN: 1432-1041
    Keywords: azlocillin ; kinetics ; biliary excretion ; liver dysfunction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic of azlocillin was followed in five elderly patients after biliary surgery. Total clearance was 138.6±17.7 ml/min when 2.0 g was given as an i.v. bolus injection. The half-life of the β-phase averaged 110 min. The total clearance and the half-life of azlocillin were influenced by slight impairment of renal function (creatinine clearance 59.4±13.6 ml/min). In patients with normal liver function biliary excretion of the drug amounted to 5.3±2.8% of the dose (n=3) and the kinetics of biliary excretion were linear. In contrast, in two patients with impaired liver function biliary excretion was 0.2% and 0.5% of the dose, and kinetic analysis of biliary excretion rates revealed at least one zero order step in the excretion process. Renal excretion of the drug amounted to 45.0±17.7% of the dose, which means that 50% of the total clearance of azlocillin has to be accounted for by metabolic clearance.
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    URL: http://dx.doi.org/10.1007/BF00542549
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  • 26
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    Cimetidine-phenytoin interaction: Effect on serum phenytoin concentration and antipyrine test (1981)
    Springer
    European journal of clinical pharmacology 21 (1981), S. 215-220 
    Details
    ISSN: 1432-1041
    Keywords: phenytoin ; cimetidine ; antipyrine test ; drug interaction ; drug metabolism ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a prospective study in nine patients the effects of phenytoin and of cimetidine (1000mg/day) + phenytoin on the antipyrine test and serum phenytoin concentrations were studied. Serum phenytoin increased from the steady state level of 5.7±1.3 mg/l to 9.1±1.4mg/l after three weeks on cimetidine (p〈0.01), and fell to 5.8±1.2 mg/l within two weeks after withdrawal of cimetidine. The protein binding of phenytoin was not changed by cimetidine. After use of phenytoin for 2–4 months, antipyrine clearance increased from 0.67±0.06ml/min/kg to 1.61±0.22 ml/ min/kg, and antipyrine half-live fell from 10.9±1.3h to 4.5±0.6h as compared to the values before phenytoin treatment (p〈0.01). After three weeks combined use of cimetidine and phenytoin, antipyrine clearance was decreased to 1.01±0.07 ml/min/kg and antipyrine half-life was prolonged to 6.1±0.5h, (p〈0.01) compared to the values on phenytoin alone. The distribution volume of antipyrine was not affected by phenytoin nor by cimetidine + phenytoin. The half-life of cimetidine was 2.8±0.3h in the patients on longterm phenytoin treatment. There was a significant positive correlation (p〈0.001) between the increase in serum phenytoin concentration and the prolongation of antipyrine half-life caused by cimetidine. Thus, cimetidine increases serum phenytoin concentration, very probably by inhibiting its metabolism. Care should be taken in the concomitant use of cimetidine and phenytoin, and the dose of phenytoin should be modified according to the clinical symptoms and serum phenytoin concentrations.
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    URL: http://dx.doi.org/10.1007/BF00627923
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  • 27
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    Disposition of the antiepileptic oxcarbazepine and its metabolites in healthy volunteers (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 545-551 
    Details
    ISSN: 1432-1041
    Keywords: oxcarbazepine ; kinetics ; disposition ; metabolites ; renal excretion ; volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Oxcarbazepine (oxcarb) 600 and 900 mg (2360 and 3540 µmol) was taken by 3 volunteers (2 ♀, 1 ♂; 45–67 kg; age 22–34 years) after an overnight fast. Blood, saliva and urine were collected for the next 72 h for assay of oxcarb, 10,11-dihydro-10-hydroxy-carbamazepine (OHcarb), and 10,11-dihydrotrans-10,11-dihydroxy-carbamazepine (diol). Oxcarb reached a maximum level of about 1 µg/ml (3.93 µmol/l) within 1 h and dropped below the detection limit (0.1 µg/ml=0.39 µmol/l) within 3 h. The active metabolite OHcarb appeared in the blood before oxcarb and reached the higher maximum level of 7.4 µg/ml (29 µmol/l) after 7 h. Thereafter serum levels decreased with a t1/2 of about 25 h, and after 40 h with a t1/2 of 9 h, the latter agreeing with the renal excretory t1/2 calculated from the urine data (10 h). The ratio of OHcarb concentration in saliva to that in plasma varied considerably (0.3–1.7; median 1; r〉0.9), whereas that of blood to plasma was 1.25 with only small variation (r〉0.98); OHcarb concentrations in erythrocytes were 50% higher than in plasma. Diol was detected in blood (maximum level 0.5 µg/ml=1.84 µmol/l) in 2 volunteers. 45% of the dose could be recovered in urine (Oxcarb 5%, OH-carb 36%, Diol 4%). Whereas Oxcarb was completely conjugated, only 25% of OHcarb was conjugated and diol was unconjugated.
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    Pharmacokinetics of metoprolol and its metabolite α-OH-metoprolol in healthy, non-smoking, elderly individuals (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 221-226 
    Details
    ISSN: 1432-1041
    Keywords: metoprolol ; age ; disposition ; elderly subjects ; kinetics ; metabolism ; alpha-OH-metoprolol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption and disposition of metoprolol have been evaluated in 10 healthy, non-smoking, elderly individuals (mean age 73.1 years) by simultaneous determination of [3H]-metoprolol and unlabelled metoprolol. The labelled drug was given as an intravenous tracer dose, immediately followed by oral metoprolol 25 mg. The experiment was preceded by administration of metoprolol 25 mg b.i.d. for 3 days. The volume of distribution, elimination half-life and total body clearance were almost the same as previously observed in healthy, young subjects. The mean systemic availability was about 39% in the elderly, which is lower than the mean of 55% observed in a control group of young volunteers who received 50 mg b.i.d. In the elderly, the mean plasma concentration of α-OH-metoprolol was about twice as high as that of the parent drug, whereas the opposite was true of the control group. The results indicate that age-related physiological changes have a negligible effect on the pharmacokinetics of metoprolol.
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  • 29
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    Influence of hyperthyroidism on the kinetics of methimazole, propranolol, metoprolol and atenolol (1982)
    Springer
    European journal of clinical pharmacology 21 (1982), S. 379-384 
    Details
    ISSN: 1432-1041
    Keywords: hyperthyroidism ; propranolol ; methimazole ; metoprolol ; atenolol ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetic profiles of oral methimazole 40mg, propranolol 80mg, metoprolol 100mg and atenolol 100mg were compared in hyperthyroid patients both during the hyper-and euthyroid states. For methimazole, neither the peak concentration (Cmax), the time to reach peak concentration (tmax), the elimination half-life (t1/2) nor the area under the curve (AUC) value was affected by the hyperthyroid state. For propranolol and metoprolol, which undergo extensive presystemic clearance, the AUC values were lower (p〈0.02) when the patients were hyperthyroid than when they had become euthyroid, but the t1/2's were not significantly altered. For atenolol, there were no significant kinetic differences between the hyperthyroid and euthyroid states. The findings are compatible with the assumption that hyperthyroidism does not affect the kinetics of methimazole or atenolol, but that it may enhance presystemic clearance of propranolol and metoprolol.
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    Effect of rifampicin treatment on the kinetics of mexiletine (1982)
    Springer
    European journal of clinical pharmacology 23 (1982), S. 261-266 
    Details
    ISSN: 1432-1041
    Keywords: mexiletine ; rifampicin ; kinetics ; enzyme induction ; excretion ; antipyrine clearance ; dosage adjustment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To study the effects of enzyme induction on its pharmacokinetics, a single oral dose of the new antiarrhythmic agent mexiletine hydrochloride 400 mg was administered to 8 healthy volunteers before and after treatment with rifampicin 300 mg b.i.d. for ten days. The absorption and distribution of mexiletine were not changed after rifampicin, but its elimination half-life fell from 8.5±0.8 h (mean±SE) to 5.0±0.4 h (p〈0.01), and its nonrenal clearance increased from 435±68 ml/min to 711±101 ml/min (p〈0.01). The mean renal clearance of mexiletine did not change, but it showed an exponential correlation with urinary pH. The amount of unchanged mexiletine excreted in urine over two days decreased from 32±7 to 18±3 mg (p〈0.01). The half-life of antipyrine fell from 11.8±0.4 to 5.5±0.3 h and its clearance increased from 40±3 ml to 74±3 ml/min (p〈0.01). There was a significant (p〈0.05) positive linear correlation between both the half-lives and the clearances of antipyrine and mexiletine. The clearances were positively correlated with serum γ-glutamyl transpeptidase. The results suggest that the dosage of mexiletine should be adjusted when enzyme inducing drugs are started or stopped during therapy with it.
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    Glibenclamide pharmacokinetics in acarbose-treated type 2 diabetics (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 233-236 
    Details
    ISSN: 1432-1041
    Keywords: glibenclamide ; acarbose ; kinetics ; alpha-glucosidase inhibitor ; blood glucose control ; plasma insulin ; Type 2 diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A single dose of glibenclamide 5 mg was administered to six Type 2 diabetics, randomly treated for 7 days either with acarbose (3×100 mg daily) or with placebo. The serum concentration of the drug was measured for 10 h. Peak concentrations, times-to-peak concentration, elimination half-lives and the extent of bioavailability of the drug were not significantly modified by acarbose. The combined administration of glibenclamide and acarbose resulted in a modest improvement in the blood glucose profile after breakfast and lunch, together with a significant diminution in plasma insulin. Thus, acarbose appears a useful additional treatment for Type 2 diabetics already receiving sulphonylurea derivatives.
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    Pharmacokinetics of furosemide in neonates (1982)
    Springer
    European journal of clinical pharmacology 22 (1982), S. 39-45 
    Details
    ISSN: 1432-1041
    Keywords: furosemide ; neonates ; kinetics ; placental transfer ; intravenous therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of furosemide was evaluated in 12 newborns who received the drug transplacentally, and in 21 neonates who received it directly for therapeutic reasons. In the first group, the apparent plasma half-lives ranged from 96 to 6.8 h with a significant inverse relationship (p〈0.01) between the gestational age and the elimination rate. In two cases a clear effect on diuresis was also observed. In the neonates receiving the drug i.v. for therapeutic reasons, the elimination kinetics appeared to follow a two-compartment open model, with a significant difference in the therminal plasma half-life between premature (26.8±12.2 h) and full-term newborns (13.4±8.6 h). In this group no relationship was observed between elimination rate and either gestational or conceptional age. In the case of repeated administration, an increase in plasma clearance and reduction in t1/2 β was noticed.
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    Kinetics of phenobarbital in normal subjects and epileptic patients (1982)
    Springer
    European journal of clinical pharmacology 23 (1982), S. 87-92 
    Details
    ISSN: 1432-1041
    Keywords: phenobarbital ; epilepsy ; kinetics ; bioavailability ; epileptic patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of phenobarbital (PB) were evaluated in six normal subjects and six epileptic patients treated with phenytoin or carbamazepine. Each normal subject received three single doses of PB: PB-sodium 130 mg i.v. (IV), PB sodium 130 mg i.m. (IM), and PB acid 100 mg orally (PO), in random order at least one month apart. After IV PB distributive half-lives varied from 0.13 to 0.70 h, disposition half-lives were 75 to 126 h, steady state volume of distribution (Vss) was 0.54±0.03 l/kg, and clearance (CL) was 3.8±0.77 ml/h/kg. Absolute bioavailability of IM PB was 101±13%, of PO PB (corrected for dose) 100±11%. Peak serum PB concentrations were achieved from 2 to 8 h after IM administration, and from 0.5 to 4 h after PO administration. Epileptic patients exhibited similar PB kinetics: disposition half-lives were 77 to 128 h, Vss 0.61±0.05 l/kg, and Cl 3.9±0.76 ml/h/kg. Phenobarbital appears to represent an exception among antiepileptic drugs, in that pharmacokinetic data obtained in normals can reasonably be extrapolated to the epileptic population.
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    Effect of quinidine on digoxin bioavailability (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 41-47 
    Details
    ISSN: 1432-1041
    Keywords: quinidine ; digoxin ; interaction ; kinetics ; absorption ; elimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To evaluate the possible effect of quinidine on digoxin bioavailability, the steady state digoxin kinetics was examined with and without concomitant quinidine therapy, in 7 cardiac patients after simultaneous administration of oral digoxin and intravenous [3H]-digoxin. In the presence of quinidine, the absorption rate constant of digoxin (ka) increased from 2.72±1.04 to 3.53±1.34 h−1 (p〈0.05), whereas lag time and peak time decreased from 0.16±0.10 to 0.05±0.04 h (p〈0.05) and from 0.92±0.27 to 0.69±0.19 h (p〈0.02), respectively. Predose plasma digoxin increased from 0.41±0.25 to 0.70±0.31 ng/ml (p〈0.02), while peak plasma digoxin increased from 0.93±0.34 to 1.63±0.46 ng/ml (p〈0.02). The systemic availability of digoxin increased from 68.48±13.35 to 79.09±14.89% (p〈0.05) in the presence of quinidine. Quinidine had no effect on the biotransformation pattern of digoxin, as assessed by thin layer chromatography. Quinidine increases the rate and extent of digoxin absorption, and this interaction contributes significantly to the elevation in plasma digoxin during both its distribution and elimination phases.
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    Effect of activated charcoal on absorption of tolbutamide and valproate in man (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 243-246 
    Details
    ISSN: 1432-1041
    Keywords: tolbutamide ; valproate ; intoxication ; activated charcoal ; inhibition of absorption ; sulphonylureas ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The claim that activated charcoal should be ineffective or even contraindicated in intoxication due to tolbutamide is based only on limited in vitro studies. To test the claim, the effect of activated charcoal 50 g on the absorption of tolbutamide and, as a reference, of sodium valproate, was studied in 6 healthy volunteers. Each volunteer swallowed tolbutamide 500 mg and sodium valproate 300 mg with 50 ml water 1 h after a light breakfast, and within 5 min they took in randomized order either a suspension of activated charcoal or water. The absorption of tolbutamide, calculated as the peak concentration and the area under the serum drug concentration-time curve during 0–48 h, was reduced by 90% by charcoal (p〈0.001). The absorption of valproate in these conditions was reduced on average by 65% (p〈0.01). In each subject charcoal had a greater effect on the absorption of tolbutamide than of valproate. According to these findings and preliminary in vitro studies on other sulphonylureas high doses of activated charcoal can be recommended for the preventing the absorption of sulphonylureas in acute intoxications. The poor aqueous solubility of these substances at the gastric pH probably delays their gastrointestinal absorption, so that they may be adsorbed on to charcoal even given several hours later.
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    Bioavailability and saturation of the presystemic metabolism of oral lorcainide therapy initiated in three different dose regimens (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 517-519 
    Details
    ISSN: 1432-1041
    Keywords: lorcainide ; oral antiarrhythmic therapy ; nor-lorcainide ; first-pass metabolism ; kinetics ; alternative dosage ; regimens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The feasibility of giving a supplementary starting dose of the antiarrhythmic drug lorcainide, in order to minimalize the impact of the extensive, but saturable first-pass metabolism, was evaluated. Twenty-five adult patients were given 100 mg lorcainide tablets according to one of 3 different dosage schedules: Eight patients took one tablet at 0, 12 and 24h, 8 took 1 tablet at 0, 1, 12 and 24h and 9 took 1 tablet at 0, 2, 12 and 24h. Levels of lorcainide and its metabolite, nor-lorcainide, during treatment were determined by gas-liquid chromatography. The results show that giving a second tablet 1 or 2h after the first may produce faster saturation of the pre-systemic metabolism of lorcainide in the liver.
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    Differential kinetics of cinromide and two of its metabolites in epileptic patients (1981)
    Springer
    European journal of clinical pharmacology 21 (1981), S. 149-153 
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    ISSN: 1432-1041
    Keywords: cinromide ; epilepsy ; kinetics ; metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Cinromide is an experimental anticonvulsant currently in phase II testing. A single oral dose (900 mg) of cinromide was administered to 8 epileptic subjects on phenytoin therapy. Plasma samples drawn during the next 36 h were analyzed for cinromide and its amide and acid metabolites. The absorption rate of cinromide varied widely between subjects producing maximum cinromide concentrations between 0.5 and 2.5 h after the dose. The median elimination half lives of cinromide and the amide and acid metabolites were 0.73, 1.65, and 4.85 h respectively. The oral clearance of cinromide (median=135 l/h) suggests that it is subject to first pass metabolism. In all subjects the area under the curve (AUC) of acid metabolite (632 to 1777 µM/l) was greater than the AUC of amide metabolite (77 to 185 µM/l) which was greater than the AUC of cinromide (5 to 89 µM/l). Steady-state concentration ratios of metabolite to parent drug predicted from the AUC data were 3.8 for the amide and 35.8 for the acid metabolite. The amide metabolite is known to have anticonvulsant properties and, until the relative contributions of metabolites and parent drug to the efficacy of cinromide are resolved, the monitoring of metabolites as well as parent drug is imperative.
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    Bioavailability of a new effervescent tablet of ibuprofen in healthy volunteers (1997)
    Springer
    European journal of clinical pharmacology 52 (1997), S. 505-506 
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    ISSN: 1432-1041
    Keywords: Key words Ibuprofen; effervescent tablets ; kinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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    URL: http://dx.doi.org/10.1007/s002280050327
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    Pharmacokinetics of diphemanil methylsulphate in neonates and in premature infants (1996)
    Springer
    European journal of clinical pharmacology 50 (1996), S. 429-430 
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    ISSN: 1432-1041
    Keywords: Key words Diphemanil methylsulphate ; Neonate; antimuscarinic agent ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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    URL: http://dx.doi.org/10.1007/s002280050136
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    Molecular structure of trans-[Co(NH3)4(NH2CH3)Cl](ClO4)2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 69-72 
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    ISSN: 1572-8854
    Keywords: Co(III) complex ; crystal structure ; kinetics ; steric effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the orthorhombic space group Pnma, with a = 7.9209(5), b = 9.818(1), c = 16.867(2) Å, and Z = 4. The structure was solved employing 1864 independent x-ray reflections with I〉2σ(I) by Patterson and difference Fourier techniques and refined by full-matrix least-squares to R = 0.036. The trans-[CO(NH3)4(NH2CH3)Cl](ClO4)2 molecule is on a crystallographic mirror plane. The cobalt ion is in an elongated octahedral coordination with four equatorial ammonia ligands [average Co–N distance equal to 1.966(2) Å], an axial methylamine [Co–N=1.965(3)Å], and an axial chlorine ion [Co–Cl=2.2771(9)Å]. Kinetic steric effects of the complex are interpreted in terms of structural results.
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    Reaction Kinetics for the Anionic Ring-Opening Polymerization of Tetraphenyltetramethylcyclotetrasiloxane Using a Fast Initiator System (1998)
    Springer
    Journal of inorganic and organometallic polymers and materials 8 (1998), S. 111-117 
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    ISSN: 1572-8870
    Keywords: Organosiloxane ; kinetics ; poly(phenylmethylsiloxane) ; catalyst ; anionic ; ring-opening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is well known that the rate of polymerization for an anionic mechanism is dependent on the ability of the bulk material or solvent system to disassociate the ion pair at the propagating chain end. In the anionic ring-opening polymerization of cyclic organosiloxanes in particular, the larger and softer the counter ion, the more rapidly the reaction proceeds. A recently developed phosphazene initiator system provides a large, soft counter ion relative to other traditional initiators used for the polymerization of poly(dimethylsiloxane) (PDMS). This novel initiator system was used in this investigation for the ring-opening polymerization of tetraphenyltetramethylcyclotetrasiloxane (P4) and the reaction kinetics under bulk and solution conditions were investigated. The new initiator system showed a dramatic increase in the rate of polymerization over the conventional potassium hydroxide-catalyzed system. Furthermore, this initiator was sufficiently reactive to be useful for the ring-opening polymerization of P4 at 293 K.
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    Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 41-51 
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    ISSN: 1572-8900
    Keywords: Cellulose ; alkaline degradation ; peeling off ; degree of polymerization ; kinetics ; (gluco)isosaccharinic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are α- and β-(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.
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    Thermodynamic parameters of coupled chemical reactions from temperature jump relaxation amplitudes (1981)
    Springer
    Journal of solution chemistry 10 (1981), S. 39-50 
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    ISSN: 1572-8927
    Keywords: Temperature jump ; kinetics ; thermodynamics ; TRIS ; iminodiacetic acid ; magnesium ion ; phenol red
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Equations describing the temperature jump amplitudes associated with a system of two coupled reactions (TRIS-phenol red) as well as the ternary system (Mg2+-iminodiacetic acid-phenol red) are presented. The termodynamic parameters calculated from experimentally measured temperature perturbation amplitudes using a multiparametric curve fitting procedure are found to be in good agreement with those determined from pH- and costant rate thermometric titrations. For phenol red, pK I =7.55, ΔH I =3.45 kcal, and for Mg2+ iminodiacetic acid, log K M =2.84, ΔH M =3.25 kcal, were obtained. It is shown that this method can be used to determine accurate thermodynamic enthalpy changes over a narrow temperature interval of less than 1.0°C from a single experiment requiring about 50 μl of sample solution.
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    Rate and thermodynamic studies of the interaction between water and iso-butyl cellosolve by ultrasonic methods (1983)
    Springer
    Journal of solution chemistry 12 (1983), S. 771-781 
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    ISSN: 1572-8927
    Keywords: Ultrasonics ; kinetics ; aqueous solution ; iso-butyl cellosolve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ultrasonic absorption and velocity measurements in aqueous solution of iso-butyl cellosolve (ethylene glycol iso-butyl ether) as a function of the concentration are reported. The two relaxational absorptions have been attributed to the perturbation of the equilibria expressed by AB⇌A+B and Aα(1/n)An where A is the solute, B is the solvent, AB is the complex and A n is the solute aggregate. The rate constants for each step have been determined. From the concentration dependence of the maximum excess absorption per wave length, the enthalpy change and the volume change for the reaction between the solute and the solvent have been determined for aqueous solutions of butyl cellosolve (ethylene glycol n-butyl ether), iso-butyl cellosolve and propyl cellosolve (ethylene glycol n-propyl ether). The results are consistent with a hydrogen bonding reaction. The effect of the ethers on water structure are considered and it is clear that the fraction of water molecules which can hydrogen bond to the solute decreases with the increasing hydrophobicity of the solute.
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    Sensitivity of PSA process performance to input variables (1995)
    Springer
    Adsorption 1 (1995), S. 133-151 
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    ISSN: 1572-8757
    Keywords: PSA process ; sensitivity ; equilibria ; kinetics ; heats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Mathematical models for pressure swing adsorption (PSA) processes essentially require the simultaneous solutions of mass, heat and momentum balance equations for each step of the process using appropriate boundary conditions for the steps. The key model input variables needed for estimating the separation performance of the process are the multicomponent adsorption equilibria, kinetics and heats of adsorption for the system of interest. A very detailed model of an adiabatic Skarstrom PSA cycle for production of high purity methane from a ethylene-methane bulk mixture is developed to study the sensitivity of the process performance to the input variables. The adsorption equilibria are described by the heterogeneous Toth model which accounts for variations of isosteric heats of adsorption of the components with adsorbate loading. A linear driving force model is used to describe the kinetics. The study shows that small errors in the heats of adsorption of the components can severely alter the overall performance of the process (methane recovery and productivity). The adsorptive mass transfer coefficients of the components also must be known fairly accurately in order to obtain precise separation performance.
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    Frequency response analysis of a closed diffusion cell with two resonators (1996)
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    Adsorption 2 (1996), S. 265-277 
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    ISSN: 1572-8757
    Keywords: frequency response ; diffusion cell ; kinetics ; diffusion ; heat effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with frequency response (FR) analysis of a closed diffusion cell system with two resonators, that is both the LHS and RHS volumes are modulated. The analysis is made for a homogeneous particle described by a single effective diffusivity as well as a biporous pellet described by macropore and micropore diffusions. It is shown that if the perturbation of the volume of the reservoir #2 is lagged behind that of the reservoir #1 by 3π/2, the pressure response in reservoir #1 is significantly enhanced with larger amplitude as well as phase angle. When the perturbations of the two reservoirs are out of phase, the heat effect is reduced and can become insignificant when the two perturbations are completely out of phase (ψ = π). Under such a condition, the pressure difference between the two reservoirs could be doubled. In the case of biporous pellets, it is shown that the FR behaviours obtained for micropore diffusion control and macropore diffusion control are well distinguished. In the former case, the FR system reduces to a traditional batch adsorber one while in the latter case, the FR behaviour is the same as for a two resonator system with homogeneous particles. This difference can be used for the discrimination of micropore and macropore diffusion processes.
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    Equilibria and kinetics characterisation of two different structured nutshell-derived activated carbons (1997)
    Springer
    Adsorption 3 (1997), S. 267-275 
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    ISSN: 1572-8757
    Keywords: characterisation ; equilibria ; kinetics ; micropore size distribution ; n-butane ; nutshell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Adsorption equilibria and dynamics ofn-butane on two activated carbon samples prepared from the physical activation of nutshell are studied in this paper. The micropore size distribution (MPSD) is considered as the main source of solid heterogeneity. Lennard-Jones' potential theory and Dubinin's theory (TVFM) are used in the equilibria data to derive the MPSD, which is well fitted by a Gamma distribution function. The adsorption energy distribution derived from the MPSD is very asymmetric for both the samples studied, and this energy distribution used in the HMSD/HMSMD kinetics models for the study of adsorption dynamics ofn-butane.
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    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
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    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
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    Kinetic studies on oxidation of aromatic donor molecules by horseradish peroxidase and lactoperoxidase (1997)
    Springer
    BioMetals 10 (1997), S. 23-26 
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    ISSN: 1572-8773
    Keywords: aromatic donor molecules ; horseradish peroxidase ; kinetics ; lactoperoxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Based on kinetic evidence, it has been shown for the first time that the mode of binding of aromatic donor molecules is similar in horseradish peroxidase and lactoperoxidase; also that the nature of the heme plays an important role in the reaction with hydrogen peroxide, and has no effect on the reaction of the intermediate compound II with aromatic substrates.
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    Factors affecting bioleaching kinetics of sulfide ores using acidophilic micro-organisms (1999)
    Springer
    BioMetals 12 (1999), S. 1-10 
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    ISSN: 1572-8773
    Keywords: acidophilic ; strain ; oxidation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Recovery of metal values from sulfide ores by use of acidophilic microorganisms is gaining importance. A number of commercial/pilot plants are setup to find out the techno-economic feasibility of the overall process. The main drawback in the process is the slow kinetics of dissolution of metal values from the sulfide ores. To make the technology e attractive the kinetics should be improved considerably. There are various factors which determine the overall kinetics such as bacterial activity and concentration, iron and sulfur oxidation, oxygen consumption, reactor design and nature of ore. A brief review has been made dealing with the above parameters
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    Non-uniform surface kinetics with two types of sites: the case of ethanol oxidation on molybdenum oxide (1996)
    Springer
    Catalysis letters 39 (1996), S. 67-71 
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    ISSN: 1572-879X
    Keywords: non-uniform surface ; kinetics ; ethanol ; oxidation ; molybdenum oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temkin's theory of rates of catalytic reactions on non-uniform surfaces is extended to the MoO3-catalyzed oxidation of ethanol to acetaldehyde. Two types of sites are assumed to be present, an oxygen atom site that can be modeled with uniform properties and a metal atom site characterized by non-uniform properties both for ethanol chemisorption to an ethoxide intermediate and the conversion of this intermediate to acetaldehyde. The rate-limiting step is the cleavage of a C-H bond in the absorbed ethoxide intermediate. Non-uniform surface kinetics leads to a kinetic rate expression of the form $$v = kP_{C_2 H_5 OH}^{1 - m} P_{O_2 }^{(1 - m)/4} P_{H_2 O}^{ - (1 - m)/2} $$ . Such a rate expression, withm=0.14, is shown to provide a good fit to kinetic data for the selective oxidation of ethanol on a silica supported molybdenum oxide catalyst.
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    Reaction pathway and kinetics of the thermal decomposition of synthetic brochantite (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 1467-1475 
    Details
    ISSN: 1572-8943
    Keywords: CRTA ; DSC ; kinetics ; synthetic brochantite ; TG-DTA ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction pathway of the thermal decomposition of synthetic brochantite, Cu4(OH)6SO4, to copper(II) oxide was investigated through the detailed kinetic characterization of the thermal dehydration and desulferation processes. The dehydration process was characterized by dividing into two overlapped kinetic processes with a possible formation of an intermediate compound, Cu4O(OH)4SO4. The dehydrated sample, Cu4O3SO4, was found first to be amorphous by means of XRD, followed by the crystallization to a mixture of CuO and CuO-CuSO4 at around 776 K. The specific surface area and the crystallization behaviour of the amorphous dehydrated compound depend largely on the dehydration conditions. The thermal desulferation process is influenced by the gross diffusion of the gaseous product SO3, which is governed by the advancement of the overall reaction interface from the top surface of the sample particle assemblage to the bottom.
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    Thermal Decomposition Kinetics of Lanthanum Complexes of 1,2-(Diimino-4'-Antipyrinyl)ethane (1998)
    Springer
    Journal of thermal analysis and calorimetry 52 (1998), S. 475-480 
    Details
    ISSN: 1572-8943
    Keywords: complexes of lanthanum ; entropy of activation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics and mechanism of the thermal decomposition of perchlorate, nitrate and iodide complexes of lanthanum with the Schiff base 1,2-(diimino-4'-antipyrinyl)ethane (abbreviated as GA) have been studied by TG and DTG techniques. The kinetic parameters like the activation energy, the pre-exponential factor and the entropy of activation were calculated for the major decomposition stages (Stages I and II) using Coats-Redfern equation. The rate controlling process obey ‘Mampel model’ with random nucleation with one nucleus on each particle. The kinetic parameters indicate that the ligands are loosely bound to metal ion and the activated complex formed in the decomposition reaction is more ordered than the reactants.
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    Kinetics and Mechanism of the Oxidation of Molybdenum Sulphide (1998)
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 263-267 
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    ISSN: 1572-8943
    Keywords: kinetics ; molybdenum sulphide ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper reports on the results attained in the determination of the mechanism of oxidation of molybdenum sulphide under non-isothermal conditions in an air atmosphere. The mechanism of the process was determined by simultaneous DTA-TG-DTG, and the kinetic parameters of the reactions involved were obtained according to the methods of Kissinger and Ozawa.
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    Mechanism and Kinetics of Thermal Dissociation of Inclusion Complex of Benzaldehyde with β-Cyclodextrin (1998)
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 825-833 
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    ISSN: 1572-8943
    Keywords: benzaldehyde ; β-cyclodextrin ; inclusion complex ; kinetics ; mechanism ; thermal dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The inclusion complex of benzaldehyde (BA) with β-cyclodextrin (β-CD) was prepared and was studied by thermal analysis and X-ray diffractometry. The composition of the complex was identified by TG and elemental analysis as β-CD·BA·9H2O. TG and DSC studies showed that the thermal dissociation of β-CD·BA·9H2O took place in three stages: dehydration in the range 70-120°C; dissociation of β-CD·BA in the range 235-270°C; and decomposition of β-CD above 280°C. The kinetics of dissociation of β-CD·BA in flowing dry nitrogen was studied by means of TG both at constant temperature and at linearly increasing temperature. The results showed that the dissociation of β-CD·BA was dominated by a one-dimensional random nucleation and subsequent growth process (A2). The activation energy E was 124. 8 kJ mol-1, and the pre-exponential factor A 5.04·1011 min-1.
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    The Non-Parametric Kinetics A New Method for the Kinetic Study of Thermoanalytical Data (1998)
    Springer
    Journal of thermal analysis and calorimetry 52 (1998), S. 933-943 
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    ISSN: 1572-8943
    Keywords: kinetics ; non-parametric kinetics method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of the new method non-parametric kinetics for kinetic analysis is discussed. It is shown that this method is able to obtain all the kinetic information needed to reproduce accurately the experimental data. To validate this method a set of numerical simulations of the most commonly used kinetic models has been performed and analysed with the method.
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    Thermal Analysis and Kinetic Study of Decomposition processes of Some Commercial Pesticides I. Triazine derivatives (1998)
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 937-956 
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    ISSN: 1572-8943
    Keywords: enthalpy ; GC—MS measurements ; kinetics ; simultaneous TG—DSC ; thermal stability ; 1,3,5 triazine derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal behaviour of some commercial pesticides was studied by means of simultaneous TG-DSC measurements. Kinetic parameters relating to liquid—gas-phase transition processes were determined via a dynamic TG technique. Gas chromatography-mass spectrometry were used to make measurements on the gaseous products. The liquid—gas-phase transition processes of these compounds seem to be influenced by the substituent groups rather than by the side-chains. A chlorine substituent destabilizes some compounds, bringing closer together the temperatures of melting and liquid—gas-phase transition processes.
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    Determination of the Kinetic Parameters of Chemical Reactions on the Basis of Non-Isothermal Measurements A critical review (1998)
    Springer
    Journal of thermal analysis and calorimetry 54 (1998), S. 399-406 
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    ISSN: 1572-8943
    Keywords: activation energy ; kinetics ; non-isothermal measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A detailed analysis is presented of the applicability of several dependences commonly used for the determination of activation energies from non-isothermal measurements. Reactions proceeding according to different kinetic equations are simulated and the validity of the activation energy values obtained is discussed. The general conclusion is drawn that none of the examined dependences should be used to determine the activation energy. For a rough estimation of activation energy, the Kissinger equation can be applied according to Ockham's razor.
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    Non-isothermal Decomposition Kinetics of Complex of Co(III), Ni(II) with O,O'-dialkyldithiophosphates and Adducts of Ni-complex with Pyridines (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 197-203 
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    ISSN: 1572-8943
    Keywords: adducts ; cobalt complex ; DSC ; kinetics ; nickel complex ; O,O'-dialkyldithiophosphate ; pyridine ; TG-DTG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III), Co(dptp)3 and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)2 and its adducts with pyridine, Ni(detp)2(py)2 or 4-methylpyridine, Ni(detp)(mpy)2 in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC techniques, which showed a medium endothermic peak for the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate. The thermal stability and decomposition patterns for these compounds were compared and interpreted in terms of structural features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved for all these complexes were obtained employing the non-isothermal kinetic analysis method suggested by Malek et al., which showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activation energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two ligands are of different type.
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    Kinetics of Dehydration of Lanthanide(III) 2-Amino-4-Chlorobenzoates (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 653-659 
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    ISSN: 1572-8943
    Keywords: dehydration ; kinetics ; lanthanide complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The 2-amino-4-chlorobenzoates of Y(III), La(III), Pr(III), Sm(III), Gd(III), Dy(III), Tm(III) and Lu(III) were prepared. Their general formula is Ln(C6H3NH2ClCOO)3·H2O. X-ray analysis demonstrated that all the prepared complexes are isostructural. This indicates the same mode of coordination of water and organic ligands throughout the whole series of lanthanide(III) 2-amino-4-chlorobenzoates. The dehydrations of the complexes were studied under non-isothermal conditions in air. From the thermogravimetric data on the dehydrations, the kinetic models best fitting the experimental TG curves were selected. These models suggest that the dehydration is governed by diffusion processes. Kinetic parameters such as the activation energy and pre-exponential factor were calculated by means of the differential and integral methods.
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    A Dilatometric Investigation of the Thermal Compaction of Ferrite Powders Prepared by Coprecipitation (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 603-610 
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    ISSN: 1572-8943
    Keywords: coprecipitation ; ferrite ; kinetics ; sintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The authors report on a non-isothermal kinetic investigation (at constant heating rate) of the sintering of manganese and nickel-zinc ferrite powders prepared by coprecipitation. The kinetic results point to the thermal compaction of the powders, which occurs mainly in the intermediate stage of sintering. A comparative study was performed in order to determine the influence of the sample characteristics (such as chemical nature, density and shape) and the heating rate on the kinetics and mechanism of the compaction.
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    Crystallization Kinetics of Lithium Diborate Glass by DTA (1999)
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    Journal of thermal analysis and calorimetry 56 (1999), S. 755-761 
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    ISSN: 1572-8943
    Keywords: crystallization ; DTA ; kinetics ; Kissinger plot ; lithium diborate glass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystallization process of Li2B4O7 in the glass of stoichiometric composition, characterized by the crystal growth of pre-existing nuclei, was analyzed kinetically by means of DTA. Because the number of pre-existing nuclei for the subsequent growth varies depending on the cooling rate of the glass-forming melt and heating rate of the as-prepared glass, a modified Kissinger plot was applied for evaluating the apparent activation energy to the crystal growth in the glass samples with three different thermal histories, i.e., the pre-annealed, slowly quenched and quickly quenched glasses. The process was characterized by the three dimensional growth of pre-existing nuclei with the apparent activation energy of ca 340 kJ mol−1.
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    Isothermal and Non-Isothermal Kinetics When Mechanistic Information Available (1999)
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    Journal of thermal analysis and calorimetry 56 (1999), S. 783-792 
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    ISSN: 1572-8943
    Keywords: complex process ; DSC ; isoconversional methods ; kinetics ; model-free kinetics ; peak maximum evolution methods ; simulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In the case of a complex mechanism of two parallel independent reactions, peak maximum evolution methods and model-fitting methods give only a mean value of the kinetic parameters, while isoconversional methods are useful to describe the complexity of the mechanism. Isothermal and non-isothermal isoconversional methods can be used to elucidate the kinetics of the process. Nevertheless, isothermal isoconversional methods can be limited by restrictions on the temperature regions experimentally available because of duration times or detection limits.
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    Characterization of Oil Shales by High Pressure DSC (1999)
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    Journal of thermal analysis and calorimetry 56 (1999), S. 939-946 
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    ISSN: 1572-8943
    Keywords: combustion ; high pressure DSC ; kinetics ; oil shale ; pyrolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pressurised differential scanning calorimeter (PDSC) has been used to obtain information on the pyrolysis and combustion characteristics of oil shales. Two distinct exothermic peaks were identified in combustion experiments known as low temperature oxidation (LTO) and high temperature oxidation (HTO) reaction regions. The pyrolysis process of all studied oil shale samples showed one exothermic effect at each total pressure studied. Kinetic data were analysed by Roger & Morris and Arrhenius methods and the results are discussed.
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    Kinetic Study of Thermal Decomposition of the DMIT Complex of Cobalt (1999)
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    Journal of thermal analysis and calorimetry 56 (1999), S. 805-810 
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    ISSN: 1572-8943
    Keywords: cobalt ; dmit ligand ; kinetics ; non-linear method ; Zsakó method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this work, a cobalt complex with dmit (1,3-dithiol-2-thione-4,5-dithiolate) as ligand was prepared and its thermal stability was studied by thermogravimetric analysis and kinetics by means of the Zsakó method and a non-linear method. For both methods, numerical binomial and polynomial filters were used, where points in the central interval were utilized.
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    Kinetics of Thermal Decomposition of Dolomite (1999)
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    Journal of thermal analysis and calorimetry 56 (1999), S. 829-833 
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    ISSN: 1572-8943
    Keywords: dolomite ; kinetics ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition reactions of calcitic dolomite were investigated. Simultaneous TG/DTG/DTA were applied under non-isothermal conditions. From the recorded curves, the activation energies, pre-exponential factors and thermodynamic parameters of activation were calculated for the two thermal decomposition steps.
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    Determination of Activation Energies by Using Different Factors Φ in Adiabatic Calorimetry (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 215-223 
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    ISSN: 1572-8943
    Keywords: adiabatic calorimetry ; kinetics ; Kissinger method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Traditionally, the kinetic treatment of adiabatic calorimetry data has been based on the results of one or more experiments, but always with the assumption of the kinetic model that the reaction follows to calculate the kinetic parameters. In this paper a method for the determination of the activation energy that uses a set of adiabatic calorimetry data is developed. To check the method, the thermal decompositions of two peroxides were studied.
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    Preparation and Study of Epoxidized Natural Rubber (1999)
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    Journal of thermal analysis and calorimetry 58 (1999), S. 293-299 
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    ISSN: 1572-8943
    Keywords: ENR ; kinetics ; thermal degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Epoxidized natural rubbers (ENRs) with different extents of epoxidation (B) were prepared under various reaction conditions. The effects of the amount of H2O2 and the reaction time on B are discussed. The glass transition temperature Tg, the thermal degradation temperature and the activation energy of thermal degradation of the ENRs increase with B. The results indicate that the thermal stability of the ENRs increases with B.
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    Kinetics of Direct Reduction of Chrome Iron Ore (1999)
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    Journal of thermal analysis and calorimetry 58 (1999), S. 317-322 
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    ISSN: 1572-8943
    Keywords: chrome iron ore ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of direct reduction of artificial chrome iron ore was studied by isothermal and non-isothermal methods. In the initial, middle and final periods, the reaction is controlled by nucleation and growth, a phase boundary reaction, and diffusion, respectively. In the main reaction region, the kinetic equation is 1−(1−α)1/3=kt and the apparent activation energy is 270 kJ mol−1. The kinetic mechanisms found with the isothermal and non-isothermal methods do not differ, and the activation energy values are approximately the same. However, the non-isothermal method can demonstrate the kinetic process completely.
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    Study of the Kinetics of the Combustion Reaction on Shuangya Mountain Coal Dust by TG (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 447-453 
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    ISSN: 1572-8943
    Keywords: coal ; combustion reaction ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The combustion behavior of Shuangya Mountain (SYM) coal dust has been investigated by means of TG in this paper. The reaction fraction α can be obtained from isothermal TG data. The regressions of g(α), an integral function of α vs. t for different reaction mechanisms were performed. The mechanism of nucleation and nuclei growth is determined as the controlling step of the coal dust combustion reaction by the correlation coefficient of the regression, and the kinetic equation of the SYM coal dust combustion reaction has been established.
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    Electron Delocalization in 3d Complexes Caused by Dimethylurea Checked by Positron Annihilation (1999)
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    Structural chemistry 10 (1999), S. 433-437 
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    ISSN: 1572-9001
    Keywords: Positronium Chemistry ; kinetics ; spin exchange reactions ; paramagnetic 3d complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate constants, k CR, of ortho- into para-positronium conversion reactions promoted by paramagnetic 3d complexes are linearly correlated with the electron delocalization, β, of unpaired metal electrons caused by ligands, β being the ratio between the inter-electronic repulsion parameters in complexes and in the free gaseous ions. By applying a procedure previously described the β values of MnII, CoII, NiII complexes with dimethylurea were deduced from the mentioned correlations and compared with those of complexes with urea obtained both by the method of Ps reactions here applied and that based on UV-Vis absorption spectroscopy.
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    Prediction of paper permanence by accelerated aging I. Kinetic analysis of the aging process (1996)
    Springer
    Cellulose 3 (1996), S. 243-267 
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    ISSN: 1572-882X
    Keywords: aging tests ; cellulose degradation ; durability ; kinetics ; paper properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The validity of accelerated aging tests to predict and rank papers on their permanence has been under question, preventing the development of performance-based standards for permanent paper. We conducted a general kinetic analysis to investigate the aging process of paper. A general kinetic model is proposed to describe the depolymerization of cellulose. Experimentally it was shown that in the case of aging, cellulose degradation follows classic first-order kinetics as a special case of our general kinetic model. The Arrhenius equation was critically re-examined for the case of a multiple reaction system. It was shown analytically that the Arrhenius equation is still applicable when certain conditions are met. This was convincingly supported by experimental results. We also analysed the dependence of the degradation rate on the moisture content and hydrogen ion concentration. By conducting systematic experiments on these two factors, a general and quantitative relationship was established to explain the contribution of each factor and their interactions. Finally, based on this kinetic analysis, the effects of storage conditions on the life expectancy of paper were estimated.
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    On the kinetics of degradation of cellulose (1997)
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    Cellulose 4 (1997), S. 1-5 
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    ISSN: 1572-882X
    Keywords: paper ; degradation ; ageing ; kinetics ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
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    Kinetics of the Gas-Phase Reactions of OH and NO3 Radicals and O3 with the Monoterpene Reaction Products Pinonaldehyde, Caronaldehyde, and Sabinaketone (1998)
    Springer
    Journal of atmospheric chemistry 31 (1998), S. 281-297 
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    ISSN: 1573-0662
    Keywords: hydroxyl radical ; nitrate radical ; ozone ; pinonaldehyde ; caronaldehyde ; sabinaketone ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Using a relative rate method, rate constants have been measured for the gas-phase reactions of OH and NO3 radicals with pinonaldehyde, caronaldehyde and sabinaketone at 296 ± 2 K. The OH radical reaction rate constants obtained are (in units of 10−12 cm3 molecule−1 s−1): pinonaldehyde, 48 ± 8; caronaldehyde, 48 ± 8; and sabinaketone, 5.1 ± 1.4, and the NO3 radical reaction rate constants are (in units of 10−14 cm3 molecule−1 s−1): pinonaldehyde, 2.0 ± 0.9; caronaldehyde, 2.5 ± 1.1; and sabinaketone, 0.036 ± 0.023, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. Upper limits to the O3 reaction rate constants were also obtained, of 〈2 × 10−20 cm3 molecule−1 s−1 for pinonaldehyde and caronaldehyde, and 〈5 × 10−20 cm3 molecule−1 s−1 for sabinaketone. These reaction rate constants are combined with estimated ambient tropospheric concentrations of OH radicals, NO3 radicals and O3 to calculate tropospheric lifetimes and dominant transformation process(es) of these and other monoterpene reaction products.
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    Absolute Rate Coefficients for the Gas-Phase Reactions of NO3 Radical with a Series of Monoterpenes at T = 298 to 433 K (1999)
    Springer
    Journal of atmospheric chemistry 33 (1999), S. 265-282 
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    ISSN: 1573-0662
    Keywords: atmosphere ; kinetics ; nitrate radical ; monoterpenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The aim of this work is to study the reactivity of some naturally emitted terpenes, 2-carene, sabinene, myrcene, α-phellandrene, d-limonene, terpinolene and γ-terpinene, towards NO3 radical to evaluate the importance of these reactions in the atmosphere and their atmospheric impact. The experiments with these monoterpenes have been carried out under second-order kinetic conditions over the range of temperature 298–433 K, using a discharge flow system and monitoring the NO3 radical by Laser Induced Fluorescence (LIF). This work is the first temperature dependence study for the reactions of the nitrate radical with the above-mentioned monoterpenes. The measured rate constants at 298 K for the reaction of NO3 with such terpenes are as follows: 2-carene, 16.6 ± 1.8, sabinene 10.7 ± 1.6, myrcene 12.8 ± 1.1, α-phellandrene 42 ± 10, d-limonene 9.4 ± 0.9, terpinolene 52 ± 9 and γ-terpinene 24 ± 7, in units of 10-12 cm3 molecule-1 s-1. The proposed Arrhenius expressions, for the reactions of NO3 with 2-carene, sabinene, myrcene and α-phellandrene are, respectively k1 = (1.4 ± 0.7) × 10-12 exp[(741 ± 190/T)] (cm3 molecule-1 s-1), k2=(2.3 ± 1.3) × 10-10 exp[−(940 ± 200/T)] (cm3 molecule-1 s-1), k3 = (2.2 ± 0.2) × 10-12 exp[(523 ± 35/T)] (cm3 molecule1 s-1) and k4 = (1.9 ± 1.3) × 10-9 exp[−(1158 ± 270/T)] (cm3 molecule-1 s-1). A decrease in the rate constants when raising the temperature has also been found for the reaction of d-limonene with NO3 while an increase in the rate constant with temperature has been observed for the reactions of terpinolene and γ-terpinene with NO3. Tropospheric half-lives for these terpenes have been calculated at night and during the day for typical NO3 and OH concentrations showing that both radicals provide an effective tropospheric sink for these compounds and that the night-time reaction with NO3 radical can be an important, if not dominant, loss process for these naturally emitted organics and for NO3 radicals.
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    Laboratory Kinetic Studies of the Reactions of Cl Atoms with Species of Biogenic Origin: δ3-Carene, Isoprene, Methacrolein and Methyl Vinyl Ketone (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 163-170 
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    ISSN: 1573-0662
    Keywords: δ3-carene ; chlorine atoms ; isoprene ; kinetics ; methacrolein and methyl vinyl ketone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The rate coefficients for the reaction between atomic chlorine and a number of naturally occurring species have been measured at ambient temperature and atmospheric pressure using the relative rate technique. The values obtained were (4.0 ± 0.8) × 10-10, (2.1 ± 0.5) × 10-10, (3.2 ± 0.5) × 10-10, and (4.9 ± 0.5) × 10-10 cm3 molecule-1 s-1, for reactions with isoprene, methyl vinyl ketone, methacrolein and δ3-carene, respectively. The value obtained for isoprene compares favourably with previously reported values. No values have been reported to date for the rate constants of the other reactions.
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    Biodegradability of diesel oil (1996)
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    Biodegradation 7 (1996), S. 73-81 
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    ISSN: 1572-9729
    Keywords: diesel oil ; biodegradation ; CSTR ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In batch culture diesel oil was degraded rapidly, with a maximum growth rate (for a consortium of microorganisms) of 0.55 h-1. The corresponding yield Y SX was 0.1 Cmol/Cmol. In a continuous stirred tank reactor the maximum dilution rate was about 0.25 h-1, with a yield of 0.3 Cmol/Cmol. With a residence time of 1 day 82% of the influent oil was degraded. In the batch reactor, of the mixture of linear and branched alkanes the linear alkanes were degraded fastest and with the highest yield. Only after most of the linear alkanes had disappeared were the branched alkanes consumed. In a CSTR a large part of the branched alkanes was not degraded.
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    Effect of concentration and environmental form of tetradecenyl succinic acid on its mineralization in soil (1996)
    Springer
    Biodegradation 7 (1996), S. 377-382 
    Details
    ISSN: 1572-9729
    Keywords: bioavailability ; builders ; detergents ; kinetics ; mineralization ; sewage sludge ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tetradecenyl succinic acid (TSA) is the major component of a detergent builder (C12-C14 alkenyl succinic acid), which is inherently biodegradable. 14C-TSA was dosed as a component of sewage sludge into a soil with a history of sludge amendment at final added concentrations of 1.5 and 30 mg (kg soil)-1. In addition, it was dosed to the soil in an aqueous solution to a final added concentration of 30 mg (kg soil)-1. Dose and form were found to have a pronouced effect on the mineralization kinetics. When dosed in a realistic form and concentration (i.e. 1.5 mg (kg soil)-1 as a component of sludge), TSA was mineralized at its highest rate and to its greatest extent, and the mineralization half-life was 2.4 days. When dosed at 30 mg (kg soil)-1 as a component of sludge, mineralization began immediately, and the half-life was 23 days. In contrast, when dosed at this concentration in aqueous solution, the onset of mineralization was preceded by a 13 day lag period and the mineralization half-life was 69 days. Primary biodegradation and mineralization rates of TSA were very similar. Approximately, half the radioactivity was evolved as 14CO2, while the remaining radioactivity became non-extractable, having presumably been incorporated into biomass or natural soil organic matter (humics). This study demonstrated that TSA is effectively removed from sludge-amended soils as a result of biodegradation. Furthermore, it showed the effect that dose form and concentration have on the biodegradation kinetics and the importance of dosing a chemical not only at a relevant concentration but also in the environmental form in which it enters the soil environment.
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    URL: http://dx.doi.org/10.1007/BF00056421
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    Growth of Ordered Domains in a Computer Model Alloy with Lattice Misfit (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 23-43 
    Details
    ISSN: 1572-9613
    Keywords: model alloy ; Monte Carlo ; elastic interactions ; phase separation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study via Monte Carlo simulations the influence of elastic interactions on the ordering and decomposition of a two-dimensional model binary alloy with antiferromagnetic nearest and ferromagnetic next nearest neighbor type interactions following a quench into the coexistence region. The elastic interaction leads to the development of a platelet morphology for the segregated ordered and disordered regions. A length scale characterizing the coarsening process follows a law of the type R=a+bt 1/3 with the growth b decreasing with the amount of ordered phase; this appears to be due to the presence of anti-phase boundaries between neighboring domains ordered on different sublattices which are difficult to eliminate. The application of uniaxial external stress results in “rafting” of the domains. Many of the simulation results are in agreement with experimentally observed effects in nickel-base superalloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004569209618
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    Kinetics of Phase Ordering on Curved Surfaces (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 949-979 
    Details
    ISSN: 1572-9613
    Keywords: numerical simulations ; interface description ; kinetics ; phase ordering ; relaxation ; dynamical scaling ; model A ; curved surface ; lipid bilayer ; dominant length scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An interface description and numerical simulations of model A kinetics are used for the first time to investigate the intrasurface kinetics of phase ordering on corrugated surfaces. Geometrical dynamical equations are derived for the domain interfaces. The dynamics is shown to depend strongly on the local Gaussian curvature of the surface, and can be fundamentally different from that in flat systems: dynamical scaling breaks down despite the persistence of the dominant interfacial undulation mode; growth laws are slower than t 1/2 and even logarithmic; a new very-late-stage regime appears characterized by extremely slow interface motion; finally, the zero-temperature fixed point no longer exists, leading to metastable states. Criteria for the existence of the latter are derived and discussed in the context of more complex systems.
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    URL: http://dx.doi.org/10.1023/A:1004502500899
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    Polymerization of acrylamide initiated by Ce(IV)-lactic acid redox system (1983)
    Springer
    Colloid & polymer science 261 (1983), S. 188-189 
    Details
    ISSN: 1435-1536
    Keywords: Polymerization ; kinetics ; redox polymerization ; acrylamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410701
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    The effect of TiO2 on the kinetics of polyamide 6 crystallization (1983)
    Springer
    Colloid & polymer science 261 (1983), S. 621-625 
    Details
    ISSN: 1435-1536
    Keywords: Polyamide 6 ; crystallisation ; kinetics ; titania
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The kinetics of isothermal and nonisothermal crystallization of polyamide-6 (PA6) containing titania was studied by means of DSC. It was found thatTiO 2 causes an acceleration in the crystallization of polyamide-6 and lowers the value of the Avrami exponent,n. The presence of TiO2 does not affect equilibrium melting pointT m 0 , glass temperatureT g, or surface free energiesσ e andσ of the basal and lateral surfaces.
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    Influence of specimen thickness on isothermal crystallization kinetics. A theoretical analysis (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 366-373 
    Details
    ISSN: 1435-1536
    Keywords: kinetics ; isothermal crystallization ; polymer ; spherulite ; differential scanning calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the DSC technique, isothermal crystallization experiments are usually performed on thin flat specimens, but their interpretation generally uses theories developed for an unbounded volume. In this paper, isothermal crystallization of spherical entities in the volume limited by two parallel infinite planes is considered. Our model, derived from Avrami's theory, gives an analytical expression for the transformed volume fraction as a function of time. It is shown that the influence of thickness becomes important when thickness becomes of the order of or smaller than the average spherulite radius. The main effects of a decreasing thickness are a slower crystallization kinetics and a decrease in the Avrami exponent. These results can be used to interpret experimental data obtained in isothermal polymer crystallization.
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    URL: http://dx.doi.org/10.1007/BF01410254
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    Dynamic measurements of adsorption of hydrolyzed polyacrylamide (HPAM) onto hematite (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1028-1032 
    Details
    ISSN: 1435-1536
    Keywords: Hydrolyzed polyacrylamide ; hematite ; adsorption ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The adsorption measurements of hydrolyzed polyacrylamide (HPAM) onto hematite suspension are carried out to study the dynamics of the polymer adsorption onto the suspension particles and to investigate the mode of the polymer adsorption. The polymer is found to show much affinity for the adsorption because of the opposite charges possessed by the polymeric flocculant and the suspension particles. Various adsorption parameters such as adsorption coefficient, the rate constants for the adsorption and desorption, are evaluated with the help of a recently proposed kinetic scheme. It is found that the extent of adsorption and the adsorption rate are adequately affected by increasing the pH of the suspension while, unexpectedly, the adsorption is found to show only a marginal increase on addition of Na2SO4. Both the amount of the adsorbed polymer and the adsorption rate are also found to increase with the degree of hydrolysis of the polyelectrolyte.
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    Dielectric method for detection of phase separation and its kinetics in TMPC/PS blends (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 524-532 
    Details
    ISSN: 1435-1536
    Keywords: Blends ; tetramethyl polycarbonate ; polystyrene ; LCST ; phase separation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new method for the detection of phase separation and its kinetics through real-time measurements is presented using the dielectric technique. The kinetics of phase separation were determined for a blend of tetramethyl bisphenol-A polycarbonate TMPC and polystyrene PS at different temperatures. The temperature dependence of the rate constant of phase separation was determined. The activation energy of phase separation process is found to be equal to 46 kcal/mole. In addition, it was possible to determine the variation in the composition of the TMPC-rich phase with time. The results obtained were compared with the literature data and were found to be in good agreement.
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    URL: http://dx.doi.org/10.1007/BF00658681
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    Kinetics of interaction of 3-aminopropyltriethoxysilane with silica gel using elemental analysis and 29Si NMR spectra (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 672-680 
    Details
    ISSN: 1435-1536
    Keywords: Key words 3-aminopropyltriethoxy silane ; silica gel ; interaction ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Three silica gel sample systems, modified with 3-amino-propyltriethoxy silane (APTS), were prepared by sequentially sampling the reaction mixture at various time intervals. The concentrations of 3-aminopropylsilyl groups (APS) bound on the silica surface were determined by elemental analysis. For the same sample systems, 29Si NMR intensities of an (–O)4Si species belonging only to the silica gel particles and corrected by a cross-polarization correction factor were also measured. Both the APS-concentrations and the correc-ted 29Si NMR intensities depended upon reaction time, reflecting the rate of the APTS–silica gel reaction. Kinetic analysis of these data was made by use of the Gauss–Newton method, and the overall reaction was found to consist of three reaction processes (an initial fast reaction, a slower second reaction and a much slower third reaction). In particular, the conversion of (–O)3SiOH to (–O)4Si is predominant in the second reaction process and the pore size of a silica gel particle affects the reaction mechanism.
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    URL: http://dx.doi.org/10.1007/s003960050134
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    Effect of potassium on the high pressure kinetics of ammonia synthesis over fused iron catalyst (1996)
    Springer
    Catalysis letters 37 (1996), S. 173-179 
    Details
    ISSN: 1572-879X
    Keywords: ammonia synthesis ; iron catalysts ; potassium promotion ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Measurements were performed of reaction rate in the process of ammonia synthesis (T=370–470°C) on doubly promoted (DP) (Al2O3, CaO) and triply promoted (TP) (K2O, Al2O3, CaO) iron catalysts. The latter were obtained by impregnation of the reduced and subsequently passivated DP precursors with alcoholic solution of KOH. The studies were carried out under high total pressure (10 MPa) in a wide range of ammonia partial pressure in the gas phase: from 0.25 to about 7 bar. The results are shown to be authoritative for the so-called kinetic regime. The effect of the presence of K+ cations in the catalyst was the stronger, as the temperature of the reaction was the lower and, in particular, the ammonia pressure in the gas phase the higher. The obtained results are in good accordance with the results of Somorjai's studies on activity of iron single crystal surfaces both clean and covered with (K+O) adlayer.
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    Prediction of paper permanence by accelerated aging II. Comparison of the predictions with natural aging results (1996)
    Springer
    Cellulose 3 (1996), S. 269-279 
    Details
    ISSN: 1572-882X
    Keywords: accelerated tests ; aging tests ; cellulose degradation ; durability ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Accelerated aging tests are credible and useful to predict paper permanence only if such tests can be shown to correlate with natural aging. In the first part of this study, a kinetic model was developed based on the accelerated aging results. In this report, we have shown that this kinetic model can indeed predict the natural aging results of lignin-free sheets with a statistical confidence. This is the first quantitative comparison of accelerated aging with natural aging.
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    URL: http://dx.doi.org/10.1007/BF02228806
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    Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions (1999)
    Springer
    Adsorption 5 (1999), S. 25-37 
    Details
    ISSN: 1572-8757
    Keywords: micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.
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    URL: http://dx.doi.org/10.1023/A:1026481704926
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    Partial hydrogenation of benzene to cyclohexene in a continuously operated slurry reactor (1995)
    Springer
    Catalysis letters 31 (1995), S. 431-438 
    Details
    ISSN: 1572-879X
    Keywords: partial hydrogenation of benzene ; production of cyclohexene ; kinetics ; reaction mechanism ; ruthenium catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method has been developed for direct measurement of reaction rates in a continuously operated slurry (CST-) reactor. In contrast to the usual procedure in a two-liquid-phase system the reactor contains only one liquid phase, an aqueous zinc chloride solution in which a ruthenium lanthanoxide catalyst is suspended. The selectivity of benzene hydrogenation with respect to cyclohexene is higher when the new one-liquid-phase procedure is applied. With decreasing degree of benzene conversion the selectivity with respect to cyclohexene approaches 100%. The conclusion is that cyclohexane is formed only by consecutive hydrogenation of cyclohexene.
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    Platinum particle size effect on the oxidative dehydrogenation of aqueous ethanol (1996)
    Springer
    Catalysis letters 36 (1996), S. 31-36 
    Details
    ISSN: 1572-879X
    Keywords: ethanol ; kinetics ; oxidation ; oxydehydrogenation ; platinum ; structure sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of the platinum particle size was investigated for the catalytic oxidative dehydrogenation of aqueous ethanol to ethanal at a temperature of 303 K, an ethanol concentration of 260 mol m−3, a partial oxygen pressure 60 kPa, a pH of 9, and an ethanal and ethanoate concentration of 20 mol m−3. A particle size effect on the turnover frequency was observed but only for particle sizes smaller than 2 nm. Hence, the reaction shows a limited structure sensitivity.
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    The dissociation kinetics of H2S over an alumina supported Co-Mo sulphide catalyst (1996)
    Springer
    Catalysis letters 37 (1996), S. 167-172 
    Details
    ISSN: 1572-879X
    Keywords: dissociation ; kinetics ; Co-Mo sulphide ; H2S
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study, a high surface area 4Co∶6Mo∶100γ-Al2O3 sulphide prepared using precipitation from homogeneous solution (PFHS) has been used for the catalytic splitting of hydrogen sulphide into H2 and elemental sulphur. The activity of this new formulation was significantly better than previously reported recipes. Kinetic data collected over a wide range of H2S partial pressures between 883 and 983 K revealed that, although the decomposition followed a first-order law, a mechanism involving H2S adsorption on co-ordinative unsaturation sites of the Co-Mo sulphide catalyst gave a Langmuir-Hinshelwood rate expression that yielded satisfactory model parameters. In particular, the scission of the surface H-S bond appeared to be the rate determining step.
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    Solvent effects in the kinetics of the enantioselective hydrogenation of ethyl pyruvate (1998)
    Springer
    Catalysis letters 55 (1998), S. 73-77 
    Details
    ISSN: 1572-879X
    Keywords: enantioselectivity ; hydrogenation of ethyl pyruvate ; Pt/alumina catalyst ; solvent effects ; kinetics ; solvent polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of solvent on the kinetics of enantioselective hydrogenation of ethyl pyruvate by Pt/Al2O3/dihydrocinchonidine is reported. In a non‐polar solvent, toluene, the reaction is approximately zero order in substrate at constant hydrogen pressure, while under the same conditions and at the same substrate concentration, in the polar solvents ethanol and propylene carbonate the reaction shows a first‐order substrate concentration dependence. Fits to a Michaelis–Menten rate expression show that these differences are the expression of the relative magnitudes of the adsorption term in the rate expression, which in turn reflects the influence of the solvent on the adsorption–desorption processes which take place at the catalyst surface.
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    The detailed kinetics of the desorption of hydrogen from polycrystalline copper catalysts (1999)
    Springer
    Catalysis letters 59 (1999), S. 143-149 
    Details
    ISSN: 1572-879X
    Keywords: hydrogen ; desorption ; copper ; activation energy ; kinetics ; order of desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of desorption of hydrogen from the copper component of an alumina-supported polycrystalline copper catalyst has been studied in detail by temperature-programmed desorption (TPD). Line-shape analysis of the hydrogen TPD spectra shows: (i) that the desorption is second order, (ii) that the desorption activation energy is in the range 64–68 kJ mol−1 in the coverage range 7–44% of a monolayer, and (iii) that the desorption pre-exponential term has a value ∼10−5 cm2 s−1 atom−1 consistent with the desorption being second order, involving mobile adsorbates and a mobile desorption transition state.
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    Furfural hydrogenation over carbon‐supported copper (1999)
    Springer
    Catalysis letters 60 (1999), S. 51-57 
    Details
    ISSN: 1572-879X
    Keywords: furfural hydrogenation ; Cu/carbon catalysts ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Furfural hydrogenation over copper dispersed on three forms of carbon – activated carbon, diamond and graphitized fibers – were studied. Only hydrogenation of the C=O bond to form either furfuryl alcohol or 2‐methyl furan occurred at temperatures from 473 to 573 K. Reduction at 573 K gave the most active catalysts, all three catalysts had activation energies of 16 kcal/mol, and turnover frequencies were 0.018–0.032 s-1 based on the number of Cu0 + Cu+ sites, which were counted by N2O adsorption at 363 K and CO adsorption at 300 K, respectively. The Cu/activated carbon catalyst showed no deactivation during 10 h on stream, in contrast to the other two catalysts. A simple Langmuir–Hinshelwood model invoking two types of sites was able to fit all kinetic data quite satisfactorily, thus it was consistent with the presence of both Cu0 and Cu+ sites.
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    Study of the ammonia decomposition over iron catalysts (1999)
    Springer
    Catalysis letters 60 (1999), S. 167-171 
    Details
    ISSN: 1572-879X
    Keywords: ammonia decomposition ; iron catalyst ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The decomposition of ammonia is a reaction associated with the process of the nitriding of metals. The kinetics of the ammonia decomposition on iron catalysts has been studied using a differential reactor with internal mixing. The balance between the inlet and outlet ammonia quantity has been used to determine the degree of conversion. The rate of ammonia decomposition could be described by the following expression: r = k0 exp (Ea/RT)pNH3. The activation energy of the ammonia decomposition process has been found for samples with potassium as E a= 96 kJ/mol, for samples without potassium as E a= 87 kJ/mol.
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    Isothermal and Nonisothermal Decomposition of Famotidine in Aqueous Solution (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 599-604 
    Details
    ISSN: 1573-904X
    Keywords: famotidine ; degradation ; isothermal ; nonisothermal ; kinetics ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of hydrolysis of famotidine in aqueous solution was studied by isothermal and nonisothermal method over the pH range of 1.71 to 10.0. Nonisothermal kinetics was studied with the purpose of determining its use in the establishment of the expiration date of pharmaceutical preparations, particularly drugs in solutions and for assessment of stability characteristics of pharmaceutical formulations during the development stage. A comparison of isothermal (55, 70 and 85°C) and nonisothermal kinetics was performed. Aqueous solutions of famotidine were buffered at pH 1.71, 2.24, 2.66, 4.0, 8.5, 9.0 and 10.0 were used. In the nonisothermal studies, the temperature rate of the reaction was continuously varied throughout the experiment. The energies of activation were found to be in close agreement for isothermal and nonisothermal studies, indicating that nonisothermal studies may save considerable amount of time in the early stages of drug development and stability testing. Logk-pH profiles were constructed for 55, 70 and 85°C from the first-order rate constants obtained from isothermal studies at pH values ranging from 1.71 to 10.00. The pH-rate profile indicated that famotidine undergoes specific acid catalysis in the acidic region and general base catalysis in the alkaline region. Hydrolysis in the acidic and alkaline media resulted in the formation of four and five degradation products, respectively. A possible degradation pathway for the acidic and alkaline hydrolysis was discussed.
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    A Novel Oligodeoxynucleotide Inhibitor of Thrombin. I. In VitroMetabolic Stability in Plasma and Serum (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 1937-1942 
    Details
    ISSN: 1573-904X
    Keywords: oligodeoxynucleotides ; nuclease degradation ; plasma stability ; kinetics ; in vitrometabolism ; thrombin inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine the degradation rates and pathways of GS-522, a potent oligodeoxynucleotide (GGTTGGTGTGGTTGG) inhibitor of thrombin, in serum and plasma. Methods. A stability-indicating, anion-exchange HPLC method was developed and used to determine concentrations of GS-522 and metabolites. Results. In monkey plasma at 2 µM or below, the degradation of GS-522 can be fit to a first-order exponential with a kp obs ~ 0.01 min−1. At 3 µM and above the degradation process deviates from a monoexponential decay profile. An initial fast degradation process is followed by a slower phase with an observed rate constant equal to that observed at 2 µM and below. In monkey serum, the KMand Vmaxare 8.4 µM and 0.87 µM min−1, respectively. Conclusions. The kinetics are consistent with an equilibrium binding of GS-522 to prothrombin in plasma (Kd = 50 nM) which saturates at GS-522 concentrations 〉2 µM. Compared to a scrambled sequence (GGTGGTGGTTGTGGT), with no defined tertiary structure, GS-522 is 4-fold more stable in serum. The metabolic profile in plasma is consistent with a 3′-exonuclease catalyzed hydrolysis of GS-522.
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    Study of the Influence of Alkaline Ions (Li, Na and K) on the Structure of the Silicate Entities in Silico Alkaline Sol and on the Formation of the Silico-Calco-Alkaline Gel (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 353-358 
    Details
    ISSN: 1573-4846
    Keywords: silicate ; alkaline ; gelation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The study of silico-calco-alkaline gel is essential to warn against the degradation of concrete due to the alkali-silica reaction. In the laboratory, those gels are simulated by the destabilization of a silico-alkaline sol by calcium ions. Their speed of formation depends on the alkali species. The influence of alkaline ions (Li, Na and K) on the structure of silicate entities in sol and on the gel formation has been studied. The state of polymerization of the silico-alkaline sol was determined by NMR and depends on the alkali species and the molar ratio (Rm = [SiO2]/[A2O] with A = Li, Na or K). It appears that lithium enhances the polymerization. By scattering techniques (SAXS and ELS), the evolution of size and number of scattering particles during gelation can be determined from scattering curves with Guinier approximation. The mechanism of gelation appears as a hierarchic structure composed of several discrete sizes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008644405473
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    Electronic Resource
    Characterization of the heat shock protein response of Atlantic salmon (Salmo salar) (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 279-292 
    Details
    ISSN: 1573-5168
    Keywords: heat shock proteins ; hsp70 ; kinetics ; in vitro ; salmon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The heat shock protein (hsp) response of juvenile Atlantic salmon, Salmo salar was investigated in isolated tissues subjected to various degrees of thermal shock. Distinct but overlapping arrays of proteins from the major hsp families (hsps 100, 90, 70, 60 and small hsps) were induced in branchial lamellae, hepatic tissue and erythrocytes. The two most prominent proteins induced by heat shock (MW ≅ 65 and 66 kDa) were found to be antigenic homologues of mammalian hsps72/73. A 2.6 kb transcript upregulated by the same conditions hybridized with cDNA probes to both human and salmon hsp70. Branchial lamellae exhibited the greatest degree of thermotolerance and mounted the most significant heat shock response. Moderate thermal shock induced more species of proteins in branchial lamellae than in hepatic tissue or erythrocytes, with the rate of hsp65/66 synthesis increased by as much as five fold. Thermal shock induced hsp65/66 eight fold in erythrocytes. In contrast, hepatic tissue which was least tolerant of thermal shock, lacked the inducible hsp65 and exhibited minimal induction of hsp66. Persistence of hsps was tested in erythrocytes, where elevated levels remained in the cells for at least 48 h after heat shock. The temporal pattern and magnitude of the hsp response in the stenothermal Atlantic salmon differed from that previously reported for eurythermal species. Also notable was the limited hsp response mounted by salmon tissues exposed to sodium arsenite, a known inducer of hsps. The characteristics of the hsp response to thermal shock support the significance of these proteins in adaptation of Atlantic salmon to environmental insult.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007743329892
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