ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Digitale Medien

The use of TA — GLC — MS as a quantitative specific EGA technique for the investigation of complex thermal decomposition reactions: The thermal decomposition of calcium propanoate (1982)

Barnes, P. A. ; Stephenson, G. ; Warrington, S. B.

Springer

Journal of thermal analysis and calorimetry 25 (1982), S. 299-311

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1572-8943

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Ein vielseitiges und flexibles System zur Analyse von gebildeten Gasen wird beschrieben, das GLC, MS (in Massen-scanning und SIM Betriebsweise) und GLC-MS umfaßt. Damit können die in zwei differentialthermoanalytischen Einheiten, einer Thermowaage oder einem direkt mit dem MS- oder GLC-Gerät gekoppelten Mikroofen aus den zu untersuchenden Substanzen entwickelten Gase analysiert werden. Einzelheiten der komputerkontrollierten Datengewinnung und Steuerung werden angegeben. Die Techniken werden zur Untersuchung der thermischen Zersetzung von Calciumpropionat herangezogen. Mechanismen werden vorgeschlagen, die die beobachteten Zersetzungsprodukte und die Festkörperreaktion erklären. Beweise werden dafür erbracht, daß bei letzterer eine Keimbildung und darauffolgendes zweidimensionales Wachstum vor sich geht, wobei die Aktivierungsenergie 315 kJ·mol−1 und der präexponentielle Faktor 4.8·1021·s−1 beträgt.

Kurzfassung: Резюме Описана многосторон яя и гибкая система анализа выделяющего ся газа на основе использования газо-ж идкостной хроматогр афии (ГЖХ), масс-спектрометрии (MC) и совмещенного метода ГЖХ и MC. Термовес ы или микропечь соеди нены прямо с массспектрометром или газо-жидкостным х роматографом, что поз воляет анализировать газы, выделяющиеся из веще ств в этих двух различ ных термических аналити ческих блоках. Приведены детали сбо ра и обработки данных с помощью ЭВМ. Метод был использ ован для изучения термиче ского разложения про пионата кальция. Предложен ме ханизм реакций образования продукт ов разложения и тверд отельных процессов. Предсравл ены доказательства в пользу того, что твер дотельные процессы п роисходят через стадию образов ания центров кристаллиза ции, за которой следуе т двухразмерный рост с энергией активации 315 кдж.моль−1 и предэкшо ненциальным факторо м 4,8·1021 сек−1.

Notizen: Abstract A versatile and flexible system is described for evolved gas analysis using a GLC, MS (mass scan and SIM modes) and GLC-MS. Gases evolved from materials in two differential thermal analysis units, a thermobalance or a micro-furnace linked directly to the MS or GLC can be analysed. Details are given of computer controlled data acquisition and processing. The techniques are applied to the thermal decomposition of calcium propanoate. Mechanisms are suggested to account for the observed decomposition products and the solid state process. Evidence is presented to support the view that the latter occurs via nucleation followed by two-dimensional growth with an activation energy of 315 kJ mol−1 and a pre-exponential factor of 4.8×1021s−1.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01912955

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

2

Digitale Medien

UV spectroscopy of metal volatilization during thermal plasma processing of waste glass melts (1996)

Wood, Jeffrey W. ; Cortez, Rebecca ; Cahill, David G. ; [weitere]

Springer

Plasma chemistry and plasma processing 16 (1996), S. 449-460

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1572-8986

Schlagwort(e): Spectroscopy ; volatilization ; iron ; nickel ; chromium ; waste vitrification

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein

Notizen: Abstract Atomic emission spectroscopy (AES) is used to monitor volatilization during waste vitrification with thermal plasmas. Model baste specimens consist of am alumino-silicate clay spiked with 10 wt. % Fe, Ni, or Cr. Specimens are vitrified in processing atmospheres with 0, 8.5, and 17 vol. % oxygen/argon concentrations. Particulate generated from condensation of the volatilized materials is collected following each specimen run and analyzed by energy dispersive X-ray analysis to determine composition. Spectra are collected from the ultraviolet range 240–380 nm in where the presence of metal vapor is readily detected. Correlation between line emission intensities and volatilization rates allows the establishment of provisional detection limits for the volatilization of Ni, Cr, Si, and Fe, of 1 × 103 g/s, 4 × 104 g/s, 2 × 104 g/s, and 5 × 105 g/s, respectively. The results of this investigation support the concept of using AES as an in-situ process monitor for feedback to optimize plasma processing of hazardous metal-containing waste.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01447155

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

3

Digitale Medien

Effects of Barbiturates on Facilitative Glucose Transporters are Pharmacologically Specific and Isoform Selective (1999)

Haspel, H.C. ; Stephenson, K.N. ; Davies-Hill, T. ; [weitere]

Springer

The journal of membrane biology 169 (1999), S. 45-53

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1432-1424

Schlagwort(e): Key words: Barbiturates — Glucose transport — Anesthetics — Pharmacologic specificity — Isoform selectivity — Binding

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Abstract. Barbiturates inhibit GLUT-1-mediated glucose transport across the blood-brain barrier, in cultured mammalian cells, and in human erythrocytes. Barbiturates also interact directly with GLUT-1. The hypotheses that this inhibition of glucose transport is (i) selective, preferring barbiturates over halogenated hydrocarbon inhalation anesthetics, and (ii) specific, favoring some GLUT-# isoforms over others were tested. Several oxy- and thio-barbiturates inhibited [3H]-2-deoxyglucose uptake by GLUT-1 expressing murine fibroblasts with IC50s of 0.2–2.9 mm. Inhibition of GLUT-1 by barbiturates correlates with their overall lipid solubility and pharmacology, and requires hydrophobic side chains on the core barbiturate structure. In contrast, several halogenated hydrocarbons and ethanol (all ≤10 mm) do not significantly inhibit glucose transport. The interaction of these three classes of anesthetics with purified GLUT-1 was evaluated by quenching of intrinsic protein fluorescence and displayed similar specificities and characteristics. The ability of barbiturates to inhibit other facilitative glucose transporters was determined in cell types expressing predominantly one isoform. Pentobarbital inhibits [3H]-2-deoxyglucose and [14C]-3-O-methyl-glucose uptake in cells expressing GLUT-1, GLUT-2, and GLUT-3 with IC50s of ∼1 mm. In contrast, GLUT-4 expressed in insulin-stimulated rat adipocytes was much less sensitive than the other isoforms to inhibition by pentobarbital (IC50 of 〉10 mm). Thus, barbiturates selectively inhibit glucose transport by some, but not all, facilitative glucose transporter isoforms.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/PL00005900

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

4

Digitale Medien

Models of coupled salt and water transport across leaky epithelia (1981)

Weinstein, Alan M. ; Stephenson, John L.

Springer

The journal of membrane biology 60 (1981), S. 1-20

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1432-1424

Schlagwort(e): isotonic epithelial transport ; lateral intercellular space ; linearized Kedem-Katchalsky equations ; intraepithelial solute polarization

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Summary A general formulation is presented for the verification of isotonic transport and for the assignment of a degree of osmotic coupling in any epithelial model. In particular, it is shown that the concentration of the transported fluid in the presence of exactly equal bathing media is, in general, not a sufficient calculation by which to decide the issue of isotonicity of transport. Within this framework, two epithelial models are considered: (1) A nonelectrolyte compartment model of the lateral intercellular space is presented along with its linearization about the condition of zero flux. This latter approximate model is shown to be useful in the estimation of deviation from isotonicity, intraepithelial solute polarization effects, and the capacity to transport water against a gradient. In the case of uphill water transport, some limitations of a model of fixed geometry are indicated and the advantage of modeling a compliant interspace is suggested. (2) A comprehensive model of cell and channel is described which includes the major electrolytes and the possible presence of intraepithelial gradients. The general approach to verification of isotonicity is illustrated for this numerical model. In addition, the insights about parameter dependence gained from the linear compartment model are shown to be applicable to understanding this large simulation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01870828

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

5

Digitale Medien

Plant volatiles and components influencing behavior of the field slug,Deroceras reticulatum (Müll.) (1980)

Pickett, J. A. ; Stephenson, J. W.

Springer

Journal of chemical ecology 6 (1980), S. 435-444

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1573-1561

Schlagwort(e): Slug ; Deroceras reticulatum ; plant component ; volatile ; behavior ; attractant ; feeding ; unsaturated C6 alcohols

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Abstract A new bioassay was devised in which slugs were allowed to follow trails of the aqueous volatiles isolated from plants by vacuum distillation. Volatiles from lettuce, carrot and dandelion induced greatest response. Components from lettuce, which at their most active concentrations can cause a response similar to that from the whole plant, were identified.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01402920

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

6

Digitale Medien

Iridoid glycosides in the nectar ofCatalpa speciosa are unpalatable to nectar thieves (1982)

Stephenson, Andrew G.

Springer

Journal of chemical ecology 8 (1982), S. 1025-1034

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1573-1561

Schlagwort(e): Catalpa speciosa ; catalpol ; catalposide ; iridoid glycosides ; nectar thieves ; pollination ; toxic nectar

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Abstract The floral nectar ofCatalpa speciosa has a chemical mechanism that limits thievery. A bioassay employing sphingid larvae,Ceratomia catalpae, shows that catalpa iridoid glycosides are present in the floral nectar. When potential nectar thieves are fed nectar, a sucrose solution of identical concentration, or a sucrose solution plus 0.4% catalpol and 0.4% catalposide (catalpa iridoids), the thieves drink significantly more of the pure sucrose solution than either of the other two sugar sources. Those thieves that drink either the nectar or the sucrose solution plus catalpa iridoids develop behavioral abnormalities including regurgitation and loss of locomotion. The response of the potential nectar thieves to nectar or the sucrose solution plus catalpa iridoids cannot be distinguished by the amount consumed or by their behavior. The legitimate diurnal pollinators ofC. speciosa are not affected by the iridoid glycosides.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00987883

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

7

Digitale Medien

Darstellung und Eigenschaften neuer perhalogenierter 1,3-Dithietan-S-oxide (1983)

Eschwey, Manfred ; Sundermeyer, Wolfgang ; Stephenson, David S.

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1623-1630

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0009-2940

Schlagwort(e): Chemistry ; Inorganic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Synthesis and Properties of New Perhalogenated 1,3-Dithietane S-OxidesNew perchlorinated and perfluorinated 1,3-dithietanes (4, 6, 7, 12, 14, 15), which are partially oxidized at the sulfur atoms, are described. Pyrolysis of the 1,3-dioxides 7 and 15 leads to the sulfoxides 8 and 16, X2C = S = O (X = Cl, F). respectively. Two new oxidizing agents are used: trifluoromethane- and nonafluorobutanepersulfonic acid.

Notizen: Die neuen perchlorierten und perfluorierten, am Schwefel partiell oxidierten 1,3-Dithietane 4, 6, 7, 12, 14 und 15 werden beschrieben. Pyrolysen der 1,3-Dioxide 7 und 15 führen zu den Sulfoxiden 8 bzw. 16, X2C = S = O (X = Cl, F). Zwei neue Oxidationsmittel werden angewendet: Trifluormethan- und Nonafluorbutanpersulfonsäure.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/cber.19831160437

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

8

Digitale Medien

Assessing the conditions forin vivo electrical virtual biopsies in Barrett's oesophagus (2000)

González-Correa, C. A. ; Brown, B. H. ; Smallwood, R. H. ; [weitere]

Springer

Medical & biological engineering & computing 38 (2000), S. 373-376

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1741-0444

Schlagwort(e): Virtual biopsies ; Barrett's oesophagus ; Bio-electrical impedance

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie , Medizin

Notizen: Abstract It has previously been shown that it is possible to differentiate between squamous and columnar epithelia in rat and resected human tissues using an impedance probe to makein vitro measurements. This probe can be passed down an endoscope allowing measurements to be made in patients. However, the probe emerges parallel to the oesophageal wall, with little room to manoeuvre. The conditions of control required to give reliable readings have been investigated. The importance of pressure applied and the angle of approach to the oesophagus was assessed. Pressures in the range 26.6 Pa to 46.3 kPa and angles in the range 15–90 degrees were considered. Inin vitro studies it was observed that it was possible to obtain consistent readings with pressures greater than 2.9 kPa and with angles greater than 15 degrees between the probe and the oesophagus. These conditions can be achievedin vivo, and readings obtained from twelve patients are shown (45 readings on normal squamous, 34 on Barrett's oesophagus and 22 on stomach). At low frequencies (9.6–153.2 kHz), a Mann-Whitney test shows a significant difference (p〈0.001) when comparing the means from squamous and columnar, and also when readings from Barrett's and normal gastric epithelia are compared (p〈0.001).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02345004

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

9

Digitale Medien

Synthesis of [1.1.1]Propellanes by Bridging of Bicyclo[1.1.0]butanes (1996)

Werner, Markus ; Stephenson, David S. ; Szeimies, Günter

Weinheim : Wiley-Blackwell

Liebigs Annalen 1996 (1996), S. 1705-1715

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0947-3440

Schlagwort(e): [1.1.1]Propellanes ; 13C-13C coupling constants ; Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Several [1.1.1]propellanes were synthesized by bridging the 1,3-positions of the corresponding bicyclo[1.1.0]butane. The synthesis of 1-bromo-3-(chloromethyl)bicyclobutanes and the bridging were carried out in a one-pot reaction by addition of 2.0 equiv. of MeLi to 1,1-dibromo-2,2-bis(chlormethyl)-cyclopropanes 10. Three routes to 10 were investigated: Firstly, the Wittig reaction of 1,3-dichloroacetone leading to (chloromethyl)allyl chlorides 6 was, with the exception of 6m, successful only with Wittig reagents derived from primary alkyl halides, Secondly, reduction of diethyl alkylidenemalonates with LiAlH4 in benzene afforded carbinols 12 which were converted into 6 by reaction with N-chlorosuccinimide/dimethyl sulfide. The cyclopropanation of 6 to 10 was achieved by reaction with bromoform/NaOH under phase-transfer catalysis conditions. Finally, starting from diethyl alkylidenemalonates, the sequence of reduction and cyclopropanation could be interchanged, according to the sequence 11 → 13 → 14 → 10. Propellanes 5b and 3 were reduced with LiAlH4 to bicyclo[1.1.1]pentanes 15b and e. 2-D INADEQUATE NMR spectra of 5d and 5p indicate that the coupling constants J(13C-13C) between the bridgehead positions are very small, i.e. 0.47 and 0.53 Hz, respectively.

Zusätzliches Material: 6 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jlac.199619961103

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

10

Digitale Medien

1-Vinyltricyclo[4.1.0.02,7]heptanes: Synthesis and Reactions with Electrophilic Dienophiles (1998)

Kreuzholz, Rüdiger ; Schmid-Vogt, Wolfgang ; Maierhofer, Monika ; [weitere]

Weinheim : Wiley-Blackwell

Liebigs Annalen 1998 (1998), S. 29-41

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1434-193X

Schlagwort(e): Strained molecules ; 1-Vinyltricyclo[4.1.0.02,7]heptanes ; Electrophilic additions ; Rearrangements ; Cyclic ketene imine ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A series of 1-vinyltricyclo[4.1.0.02,7]heptanes 4 has been obtained by Ni0-catalyzed cross-coupling reactions of the corresponding Grignard reagent with vinyl halides or via reaction of 4b with various electrophiles. Selected model compounds 4 were treated with tetracyanoethylene (TCNE), N-phenyl-1,2,4-triazoline-3,5-dione (PTAD), and dimethyl acetylenedicarboxylate (DMAD). Product studies revealed that TCNE and PTAD attacked the CC double bond forming a zwitterion, which in most cases underwent several carbenium ion rearrangements until internal bond formation of the ionic centers took place. The main reaction path of DMAD and 4 led via attack at the bicyclo[1.1.0]butane bridgehead to a biradical of type 38, which after H abstraction and CC bond formation gave rise to the tricyclic system 37.

Materialart: Digitale Medien

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)