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  • 1
    Electronic Resource
    Electronic Resource
    Infrared laser absorption spectroscopy of the SiH+3 cation (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 1741-1747 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Many vibration–rotation components of the ν2 fundamental of the SiH+3 cation have been measured using diode laser velocity modulation spectroscopy. By comparing the intensities of these components with their nuclear statistical weights, the ion is shown to be planar (D3h). The position of the ν2 band center is 838.0674(7) cm−1 and the ground state rotational constant is B0=5.2153(1) cm−1, r0=0.1462 nm. These results are compared with ab initio calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462129
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  • 2
    Electronic Resource
    Electronic Resource
    Pore structure characterization of thin films using a surface acoustic wave/volumetric adsorption technique (1993)
    s.l. : American Chemical Society
    Langmuir 9 (1993), S. 249-251 
    Details
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/la00025a047
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  • 3
    Electronic Resource
    Electronic Resource
    Diode laser spectroscopy and coupled analysis of the ν2 and ν4 fundamental bands of SiH+3 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6166-6174 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The gas phase infrared spectra of the ν2 and ν4 fundamentals of SiH+3 have been measured between 730 and 1015 cm−1. The ion was produced in an ac glow discharge in silane and hydrogen mixtures. Vibration-rotation transitions were detected using diode laser velocity modulation spectroscopy. 112 transitions were included in a combined fit of both bands which yielded B0=5.214 51(27) and C0=2.585 20(36) cm−1. The ν2 [838.0669(24) cm−1] and ν4 [938.3969(36) cm−1] bands are coupled by a Coriolis x,y resonance for which ξ24=−3.8339(22) based on a calculated value of ξ4=−0.051 27. Experimental band origins and rotational and quartic distortion parameters are compared with recent ab initio calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467081
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  • 4
    Electronic Resource
    Electronic Resource
    Use of threshold electron and fluorescence coincidence techniques to probe the decay dynamics of the valence states of CF+4, SiF+4, SiCl+4, and GeCl+4 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 10559-10575 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Threshold photoelectron–photoion coincidence (TPEPICO), photoion–fluorescence coincidence (PIFCO), and threshold photoelectron–fluorescence coincidence (TPEFCO) spectroscopies have been used to measure, state selectively, the decay pathways of all the valence states of four gas-phase tetrahedral ion CF+4, SiF+4, SiCl+4, and GeCl+4 in the range 11–26 eV. Vacuum UV radiation from a synchrotron source dispersed by a 5 m normal-incidence McPherson monochromator ionizes the parent molecule, and electrons and ions are detected by threshold electron analysis and time-of-flight mass spectrometry, respectively. Undispersed fluorescence from the interaction region can also be detected, allowing the three different types of coincidence experiment to be performed. The optimum resolution of the monochromator is matched to that of the threshold analyzer, and this work improves on preliminary results using a 1 m Seya monochromator [Chem. Phys. 174, 441 and 453 (1993)] where the resolution of the spectra was limited by that of the optical source. TPEPICO spectra are recorded continuously as a function of photon energy, allowing both threshold photoelectron spectra and yields of all the fragment ions to be obtained. Kinetic energy releases can also be measured at fixed photon energies with good time resolution. PIFCO and TPEFCO spectra are recorded at fixed photon energies. The former experiment can yield the fate of the lower electronic state of the parent ion to which fluorescence occurs.The latter experiment yields the lifetime of the fluorescing state; with sufficient resolution of the photoionizing radiation, the lifetime is specific to one vibrational level of the emitting electronic state. For CF+4 and SiF+4 work has concentrated on the third and fourth excited states, C˜ 2T2 and D˜ 2A1, of which only the C˜ state of SiF+4 does not decay radiatively. Vibrationally state-selected fluorescence quantum yields and lifetimes have been measured for four levels of the C˜ state of CF+4, and absolute values of radiative and nonradiative decay rates have been evaluated for these levels. Jahn–Teller distortion of the C˜ state of SiF+4 from Td to C3v geometry assists internal conversion of the C˜ 2T2 state into high vibrational levels of the B˜ 2E state, and is an efficient route for nonradiative decay. A non-Franck–Condon distribution of intensities is observed in the threshold photoelectron spectrum of the D˜ 2A1 state of CF+4, due to autoionization from a high-lying Rydberg state of neutral CF4. For the two chloride molecules, SiCl4 and GeCl4, fragmentation of the ground (X˜) and the first four excited states (A˜–D˜) of the parent ion have been studied at slightly lower resolution. For SiCl+4 an important result is confirmation of the stability of its electronic ground state with respect to dissociation to SiCl+3+Cl. By contrast, a substantial part of the Franck–Condon zone of the ground state of GeCl+4 is energetically unstable with respect to GeCl+3+Cl. Radiative decay from the C˜ 2T2 state of both ions is an important process. The decay dynamics of all the valence states of this family of tetrahedral ions are reviewed. Dynamical, rather than statistical, processes generally dominate, and reasons for these surprising phenomena are discussed. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467873
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamic Rheological Properties and Microstructure of Partially lnsolubilized Whey Protein Concentrate Gels (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 58 (1993), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Viscoelasticity and microstructure of gels prepared with four whey protein concentrates (WPC) with solubilities from 27.5 to 98.1% in 0.1M NaCl, pH 7.0 were evaluated. Dynamic moduli were determined while 16% (w/w protein) WPC in 0.6M NaCl, pH 7.0, was heated isothermally at 90°C for 15 min. Storage moduli (G′) increased and tangent δ decreased when 80.0 and 98.1% soluble WPC were heated, whereas G' and tangent δ of 27.5 and 41.0% soluble WPC did not change. The 27.5% soluble WPC had the highest G' throughout the heating period. Rheological measurements suggested that globular aggregates observed in 80.0% and 98.1% soluble WPC were formed during heating, whereas aggregates in 27.5 and 41.0% WPC were present prior to heating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1993.tb06108.x
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  • 6
    Electronic Resource
    Electronic Resource
    1,4-Bis(4-chlorobenzoyl)-2,3,5,6-tetramethylbenzene (1993)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 190-192 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270192010539
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  • 7
    Electronic Resource
    Electronic Resource
    Rheological Properties and Adhesion Characteristics of Flour-Based Batters for Chicken Nuggets as affected by Three Hydrocolloids (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 57 (1992), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Time-dependency, apparent viscosity, shear-thinning behavior, recovery and adhesion characteristics were determined on 30% solids flour-based batters containing hydrocolloids (guar, xanthan and carboxymethylcellulose, CMC) at 0.25, 0.5, and 1.0%. Most batters were thixotropic. Batters containing xanthan gum had the greatest apparent viscosity followed in decreasing order by guar gum, CMC and control batters. Apparent viscosity correlated highly positively with batter adhesion characteristics measured on chicken nuggets as coating pickup, overall yield, and cooked yield. Mixer viscometry techniques were useful to follow changes in rheological properties caused by mixing speed and time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1992.tb05414.x
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  • 8
    Electronic Resource
    Electronic Resource
    A comparison of pyridoxal 5′-phosphate dependent decarboxylase and transaminase enzymes at a molecular level (1991)
    Springer
    Cellular and molecular life sciences 47 (1991), S. 1104-1118 
    Details
    ISSN: 1420-9071
    Keywords: Transaminase ; decarboxylase ; serine hydroxymethyltransferase ; pyridoxal 5′-phosphate ; enzyme mechanism ; stereochemistry ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Pyridoxal 5′-phosphate is a coenzyme for a number of enzymes which catalyse reactions at Cα of amino acid substrates including transaminases, decarboxylases and serine hydroxymethyltransferase. Using the X-ray coordinates for a transaminase, aspartate aminotransferase, and the results of stereochemical and mechanistic studies for decarboxylases and serine hydroxymethyltransferase, an active-site structure for the decarboxylase group is constructed. The structure of the active-site is further refined through active-site pyridoxyllysine peptide sequence comparison and a 3-D catalytic mechanism for the L-α-amino acid decarboxylases is proposed. The chemistry of serine hydroxymethyltransferase is re-examined in the light of the proposed decarboxylase mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01918374
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  • 9
    Electronic Resource
    Electronic Resource
    Lipid-class composition of organs and tissues of the tiger prawnPanaeus esculentus during the moulting cycle and during starvation (1991)
    Springer
    Marine biology 108 (1991), S. 235-245 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Neutral lipid and phospholipid fractions and their component lipid classes in the digestive gland, abdominal muscle, epidermis and cuticle ofPenaeus esculentus Haswell were analysed and compared during the moulting cycle and during starvation. The prawns were collected from Moreton Bay, Queensland, Australia, by trawling during 1985–1987, and were fed on a standard, semi-purified diet. The digestive gland appears to be a major site of lipid synthesis, storage and mobilisation in preparation for moulting. Neutral lipid, 59 to 80% of which was triacylglycerol, was the larger fraction. It accumulated during early premoult, mainly due to the increase in triacylglycerol. The digestive gland contained only 18% of the total body lipid, or 8% of body lipid as triacylglycerol. Thus, the reserve lipid available for energy production is very small. Digestive gland triacylglycerol was markedly depleted after 4 d starvation and was almost completely absent after 8 d. In the other tissues, the major fraction was phospholipid, of which over 50% was phosphatidylcholine and up to 20% phoshatidylethanolamine; cholesterol was the major class in the neutral lipid fraction and appeared to be very stable. Most of this lipid was probably a component of cellular membranes. The lipid composition of muscle changed very little during the moulting cycle: total lipid levels in the epidermis were high in late premoult and early postmoult, when new cuticle is being secreted, but the proportions of the component lipids were closely similar. Cuticle lipid, together with other major components, was resorbed from the old cuticle prior to ecdysis, but the cuticle phospholipids appeared to be labile at all moult stages. The total of all lipids in fedP. esculentus was about 3.6% dry weight, of which about 70% was phospholipid. Earlier research had shown that when digestive gland lipid is exhausted after a short period of starvation, muscle is metabolised for energy. The present research showed that in the remaining muscle only about 13% of lipid was lost after 21 d starvation, mostly as phosphatidylcholine. This is in keeping with the need to maintain this tissue in a functional state. In contrast, epidermal lipid levels were markedly reduced after only 4 d starvation and the proportions of phospholipids changed significantly. This sensitivity of the cuticle lipids to starvation may be the cause of delayed moulting, which is characteristic of poor nutrition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01344338
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  • 10
    Electronic Resource
    Electronic Resource
    Fatty acid composition of organs and tissues of the tiger prawn Penaeus esculentus during the moulting cycle and during starvation (1992)
    Springer
    Marine biology 113 (1992), S. 45-55 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fatty acids (FA) in neutral lipid (NL) and polar lipid (PL) of digestive gland, muscle and integument of Penaeus esculentus Haswell were analysed and compared during the moulting cycle and during starvation. The prawns were collected from Moreton Bay, Queensland, Australia, by trawling during 1985–1987, and were fed with a standard semi-purified diet. Compared with a natural diet, the artificial diet had much higher levels of 18:1n-9 and 18:2n-6, but only trace amounts of 20:4n-6, but there was no evidence of dietary imbalance. The fatty acid composition (percentage of total lipid) of the digestive gland changed markedly during the moulting cycle and during starvation, but the small changes observed in both muscle and integument suggested that these tissues maintained their composition under both conditions. When the fatty acids were calculated as absolute amounts, muscle composition, as well as that of the digestive gland, changed significantly. In the digestive gland, saturated FA (SFA), monounsaturated FA (MUFA), diunsaturated FA (DUFA) and polyunsaturated FA (PUFA) all increased up to the middle of the moulting cycle and then declined; with starvation all groups decreased. In muscle, SFA, MUFA and DUFA all increased during the moulting cycle; starvation caused SFA, MUFA and PUFA to decrease, whereas DUFA did not vary. Starvation caused both 18:2n-6 (linoleic) and 18:3n-3 (linolenic) in the digestive gland to reach or almost reach zero. The other essential PUFA, 20:4n-6 (arachidonic), 20:5n-3 (eicosapentaenoic) and 22:6n-3 (docosahexaenoic), decreased during the moulting cycle, but during starvation 20:4n-6 did not decrease as much. In muscle, the levels of 18:2n-6 and 18:3n-3 increased, while 20:4n-6, 20:5n-3 and 22:6n-3 remained approximately constant during the moulting cycle. Starvation reduced 20:5n-3 and 22:6n-3 to about 60%. The data suggest that levels of 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3 are regulated, and that 20:4n-6 can be synthesised from 18:2n-6. There is no clear evidence that 20:5n-3 and 22:6n-3 are essential in P. esculentus, but tissue catabolism of cell membranes during starvation may have provided sufficient amounts for maintenance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367637
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