bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of peel and burst tests for pouches
Authors: Feliú‐Báez Rosamari , Lockhart Hugh E. , Burgess Gary 
Published: September 2002

AbstractTheoretical equations based on force diagrams were developed in order to explain pouch behaviour during a restrained burst test. According to the resulting equation, P = 2 S/D, the burst pressure (P) increases directly with seal strength (S) and inversely with the distance between the restraining plates (D). After performing a restrained burst test and a peel test on Tyvek/plastic pouches, it was found that the theoretical development did not exactly explain burst test results
in terms of peel test values. The test results demonstrate that even though the peeling times for the peel and burst tests were controlled to be the same, the theoretical formula (P = 2 S/D) tends to overestimate the burst pressure. The overestimation increases at smaller gaps. These results are an indication that the formula is not universal and they suggest that it is an oversimplification. It might work for some materials at a particular set of testing conditions but not for others. Copyright © 2001 John Wiley & Sons, Ltd.
Non‐born–oppenheimer density functional theory for excited states by using green's function techniques
Authors: Yoshimoto T. , Ohta Y. , Maki J. , Shigeta Y. , Nagao H. , Nishikawa K. 
Published: September 2002

AbstractWe have proposed a numerical scheme for the non‐Born–Oppenheimer density functional calculation based upon the Green function techniques within the GW approximation for evaluating quasiparticle excitations of the electronic and nuclear motion in the full quantum mechanical treatment. We calculate the excitation energy and the orbital energy of a hydrogen molecule, a muon molecule, and a positronium–hydrogen complex within the treatment of the dynamical screening. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 354–362, 2001
Recent progress in the accurate and rapid evaluation of all Coulomb integrals over slater‐type orbitals
Authors: Safouhi Hassan , Hoggan Philip 
Published: September 2002

AbstractOne of the main objectives in ab initio Slater research is rapid and accurate evaluation of the two‐, three‐, and four‐center Coulomb integrals. General expressions for these integrals were obtained and evaluated for the first time using the single center strategy and requisite orbital translations. The alternative strategy using the Fourier transform of the B functions basis has been thoroughly explored by the Steinborn group. The analytical expressions of these integrals have been shown to be adapted to the use of nonlinear transformations to accelerate their convergence. A complete study of D‐ (due to Levin and Sidi) and \documentclass{article}\pagestyle{empty}\begin{document}$\bar{D}$\end{document}‐transformations (due to Sidi) for all these integrals has led to the improved HD and \documentclass{article}\pagestyle{empty}\begin{document}$H\bar{D}$\end{document} methods, which greatly simplified the application of the above nonlinear transformations. The results presented show that the \documentclass{article}\pagestyle{empty}\begin{document}$H\bar{D}$\end{document} method gives unprecedented accuracy with speedup by a factor of 5 over the \documentclass{article}\pagestyle{empty}\begin{document}$\bar{D}$\end{document} approach and over 70 over the initial STOP method for four center terms. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
A strategy for quantitative bioanalysis of non‐polar neutral compounds by liquid chromatography/electrospray ionization tandem mass spectrometry: determination of TS‐962, a novel acyl‐CoA:cholesterol acyltransferase inhibitor, in rabbit aorta and liver tissues
Authors: Yamaguchi Jun‐ichi , Matsuno Yumiko , Hachiuma Kenji , Ogawa Naoyoshi , Higuchi Shohei 
Published: September 2002

AbstractA strategy for the sensitive and reliable quantitative determination of non‐polar neutral compounds in biological matrices by liquid chromatography/electrospray ionization tandem mass spectrometry is described in the context of assay development for TS‐962, a novel acyl‐CoA:cholesterol acyltransferase (ACAT) inhibitor, in rabbit aorta and liver tissues. The electrospray ionization (ESI) mass spectrum of this compound with a mobile phase of water/acetonitrile did not give abundant [M + H]+ ions, but did give alkali metal cation adducts such as [M + Na]+, [M + CH3CN + Na]+ and [M + K]+ ions. The cationized species are acknowledged as unsuitable precursor ions for selected reaction monitoring (SRM) for various reasons, such as difficulty in obtaining characteristic product ions in low‐energy collision‐induced dissociation, and irreproducibility of the adduct‐ion intensities. To overcome this problem, a solution of 3.4 mM trifluoroacetic acid in 2‐propanol was added to the mobile phase as a postcolumn additive, resulting in a decrease of the undesirable adduct formation and significant enhancement of [M + H]+ ion intensity. An attempt was then made to prevent the matrix effect by employing a column‐switching system, which allowed direct injection of a large volume of 2‐propanolic tissue homogenate (950 µL) followed by sufficient clean‐up, separation, and ESI‐SRM on‐line. This enabled development of a sensitive and reliable assay method for TS‐962 in rabbit aorta and liver tissues in the concentration range of 5–500 ng/g wet tissue using a 25‐mg aliquot of tissue sample. Application of this method to the determination of aortic TS‐962 levels at 24 h after repeated oral administration of this compound (3 mg/kg) once a day for 12 weeks to 1% cholesterol‐fed rabbits is also presented. Results showed that TS‐962 is well distributed to both the thoracic and abdominal aorta tissues, at levels higher than the 50% inhibitory concentration value of this compound for microsomal ACAT activity from rabbit aorta. Copyright © 2001 John Wiley & Sons, Ltd.
Proton mobility in protonated glycylglycine and N‐formylglycylglycinamide: a combined quantum chemical and RKKM study
Authors: Paizs Béla , Csonka István Pál , Lendvay György , Suhai Sándor 
Published: September 2002

AbstractTheoretical model calculations were performed to investigate the degree of validity of the mobile proton model of protonated peptides. The structures and energies of the most important minima corresponding to different structural isomers of protonated diglycine and their conformers, as well as the barriers separating them, were determined by DFT calculations. The rate coefficients of the proton transfer reactions between the isomers were calculated using the RRKM method in order to obtain a quantitative measure of the time scale of these processes. The proton transfer reactions were found to be very fast already at and above the threshold to the lowest energy decomposition pathway. Two possible mechanisms of b2+‐ion formation via water loss from the dipeptide are also discussed. The rate‐determining step of the proton migration along a peptide chain is also investigated using the model compound N‐formylglycylglycinamide. The investigations revealed that this process very possibly occurs via the protonation of the carbonyl oxygens of the amide bonds, and its rate‐determining step is an internal rotation‐type transition of the protonated C=O‐H group between two adjacent C=O‐H…O=C bridges. Copyright © 2001 John Wiley & Sons, Ltd.
Evaluation of axial DC offsets during scanning of a quadrupole ion trap for sensitivity improvements
Authors: Vaden Timothy , Ardhal Ben , Lynn Bert C. 
Published: September 2002

AbstractIn the normal operation of quadrupole ion trap mass spectrometers, approximately half of the trapped ions are ejected through the source endcap during a mass‐selective instability scan. This reduces the sensitivity of the instrument by ∼50%. In this preliminary study, a circuit was constructed that produced a dipolar DC offset on the axial modulation waveform to recover this lost ion current. A variable (0 to 10 V DC), positive and negative offset was applied to the source and detector endcap, respectively. This DC offset axially displaced the ion cloud toward the detector endcap increasing the probability of detection. Several compounds, including 11 pesticides, were evaluated. Sensitivity enhancements ranged from 13 to 97% (theoretical 100%). No spectral resolution problems were observed; however, a compound‐dependent mass discrimination was observed in several cases. This mass discrimination problem is currently under investigation. Copyright © 2001 John Wiley & Sons, Ltd.
Stable isotopes and the international system of units
Authors: Slater Christine , Preston Tom , Weaver Lawrence T. 
Published: September 2002

AbstractIt is now over 60 years since Nier built the first isotope ratio mass spectrometer. The introduction of continuous‐flow techniques heralded a huge expansion in the use of stable isotopes in biomedical and environmental sciences, yet there is no consensus on the appropriate units, especially in the biomedical field. Most isotope ratio mass spectrometry (IRMS) instruments calculate isotopic abundance in terms of delta notation (δ, ‰, per mil), which is a convention determined by geochemistry, because most of the original IRMS instruments were developed in isotope geochemistry laboratories to measure natural abundance variations. Delta units are not SI units. This paper considers the appropriate units for studies using stable isotopes based on the International System of Units (SI). The SI base unit for concentration is the mol, from which atom fraction and mol fraction are derived. The units of stable isotope abundance, atom % and mol %, are the atom and mol fractions expressed as percentages. Atom % excess and mol % excess are the SI units of enrichment and are to be recommended for use in tracer studies. Copyright © 2001 John Wiley & Sons, Ltd.
Rapid quality control analysis of 13C‐enriched substrate synthesis by isotope ratio mass spectrometry
Authors: Morrison Douglas J. , Dodson Brian , Preston Tom , Weaver Lawrence T. 
Published: September 2002

AbstractThere is a growing interest in the use of 13C‐enriched substrates to investigate metabolic processes in humans. The non‐invasive nature of 13C breath tests makes them attractive to clinicians, particularly because they can be safely used in children. The availability of suitable 13C‐enriched substrates can limit the application of this biotechnology. We have used isotope ratio mass spectrometry to assay the chemical purity and isotopic enrichment of substrates that were synthesised to study gut transit and colonic fermentation. Lactose ureide and lactose [13C]ureide were synthesised by acid‐catalysed condensation of lactose and urea or 13C urea, respectively. Glucose ureide and glucose [13C]ureide were synthesised by similar methods but required an additional purification step to remove urea of crystallisation. Substrates were analysed by standard analytical techniques and combustion isotope ratio mass spectrometry for carbon and nitrogen content and 13C‐enrichment. Monitoring the C/N ratio proved to be a sensitive assay of chemical purity. Analysis of the percentage composition of C and N (and hence O + H) suggested that lactose ureide crystallises as the dihydrate. It was synthesised with ∼99% chemical purity and with the theoretical enrichment. Glucose ureide was synthesised with ∼98% chemical purity but with lower than theoretical enrichment. Copyright © 2001 John Wiley & Sons, Ltd.
The search for charge‐remote reactions of even‐electron anions derived from 1,3‐disubstituted adamantanes in the gas phase. Retro Diels‐Alder and Norrish II processes
Authors: Dua Suresh , Bowie John H. 
Published: September 2002

AbstractThe collision induced decompositions of 3‐substituted adamantane carboxylate anions have been studied with a view to uncovering charge‐remote fragmentations of the 3‐substituent. The 3‐substituent is chosen so that it cannot approach the anion site, and so any fragmentations of that substituent should proceed independently of the charged centre, viz. charge‐remote reactions. The following systems have been studied (i) the 3‐cyclohexenyl system shows no charge‐remote retro Diels‐Alder fragmentation (ΔH = +157 kJ mol−1), instead, charge‐remote loss of the cyclohexenyl radical is noted, (ii) the 3‐isobutyl ketone system shows no Norrish II cleavage (loss of C3H6, ΔH = +18 kJ mol−1), instead, the competitive losses of CO2 from the charged carboxyl centre, together with charge‐remote radical loss of the 3‐substituent are observed, and (iii) the corresponding 3‐isopropyl ester does show the ‘Norrish II’ loss of C3H6, together with competitive losses of CO2 and the 3‐substituent. It is concluded for cases (ii) and (iii), that an adamantane carboxylate anion system with a carbonyl group directly attached at the 3‐position is not a suitable model system for studying charge‐remote reactions. Copyright © 2001 John Wiley & Sons, Ltd.
Application of the combination of isotope ratio monitoring with isotope dilution mass spectrometry to the determination of glucose in serum
Authors: Dube Gunther , Henrion André , Ohlendorf Rüdiger , Vidal Christian 
Published: September 2002

AbstractIsotope ratio monitoring combined with n(13C)/n(12C) isotope dilution mass spectrometry (IRM/IDMS) provides results of low uncertainty of the order of 0.1% if it is applied to the analysis of simple mixtures as found in organic chemistry, even if only low 13C spike additives to the sample are used. If the method is applied to the analysis of systems that require large‐scale sample preparation prior to the measurement, such as the determination of glucose in serum, the results obtained exhibit a higher uncertainty that is comparable to that of the conventional gas chromatography/isotope dilution mass spectrometry (GC/IDMS) method. The reason for this observation is that the small contribution that the IRM/IDMS method makes to the uncertainty budget of the result is superimposed on a large contribution due to the sample preparation. It appears therefore that the IRM/IDMS method has no advantage over the conventional GC/IDMS method. However, if a series of measurements is carried out, and if a suitable experimental design is chosen, the IRM/IDMS method can provide valuable additional information. The influence of sample preparation on each individual result can be quantified as its deviation from the average value of all results of the series. From these data conclusions can be drawn for an improvement in sample preparation. Copyright ©2001 John Wiley & Sons, Ltd.
Theoretical evaluation of error in the isotopic analysis of carbon and oxygen as CO: considerations for determining two different isotopic abundance ratios simultaneously
Authors: Datta B. P. 
Published: September 2002

AbstractThe computations involved in the ${\bf CO_{2}^{+}}$ ion beam method of determining simultaneously a pair of constituent elemental isotopic abundance ratios P and Q (viz. 13C/12C and 17O/16O, or 13C/12C and 18O/16O, or 17O/16O and 18O/16O) are worked out, and the possible implications of their involvement as an analytical step are evaluated theoretically. It is shown, as an immediate consequence, that accurate measurements of the required isotopic ${\bf CO_{2}^{+}}$ abundance ratios (Rj and Rk) do not necessarily mean that the results (P; Q) are equally accurate. It is demonstrated that, and also explained why, the results can be far more inaccurate, or even in some cases more accurate, than the (Rj;Rk) values themselves. It is clarified how the errors of analysis (δP and δQ) are actually governed, and elaborated further by evaluating their variations as a function of different possible parameters which control their magnitudes. The investigations thus help to predict the required analytical conditions for accurate isotopic analysis of carbon and/or oxygen samples of any origin as ${\bf CO_{2}^{+}}$. The considerations for the case of natural samples predict that, while it should be generally possible to simultaneously determine the isotopic abundance ratios of 13C/12C and 18O/16O with an accuracy better than the measurements themselves, the determination of either the (13C/12C and 17O/16O) ratios or the (17O/16O and 18O/16O) ratios, with an accuracy as good as that of the measurements, would be extremely difficult and may, in practice, be impossible. Copyright © 2001 John Wiley & Sons, Ltd.
Application of automated matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry for the measurement of enzyme activities
Authors: Kang Min‐Jung , Tholey Andreas , Heinzle Elmar 
Published: September 2002

AbstractSample preparation methods and data acquisition protocols were optimized for the application of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) to high‐throughput quantitative analysis of low molecular mass substrates and products of an enzyme‐catalyzed reaction. Using a deuterlum‐labeled internal standard, precise standard curves were obtained (r2 = 0.9998) over two orders of magnitude of concentration of rac‐1‐phenylethylamine (PEA), which is converted to 2‐methoxy‐N‐[(1R)‐1‐phenylethyl]acetamide (MET) by a lipase‐catalyzed reaction with ethylmethoxyacetate (EMA) as second substrate. Reliable relative standard deviations were achieved (≤5%) using automated analysis with peak intensity ratios between 0.2 and 5 of analyte to internal standard. This method permitted quantitative analysis of the lipase reaction, producing results comparable to those from gas chromatographic (GC) analysis in the dynamic range of GC. This work shows that MALDI‐TOFMS can be applied for the high‐throughput screening of enzymes. Copyright © 2001 John Wiley & Sons, Ltd.
Effect of temperature on the degradation of ZnS FED phosphors
Authors: Swart H. C. , Hillie K. T. , Greeff A. P. 
Published: September 2002

AbstractThe changes in cathodoluminescent brightness and changes in the surface chemistry of ZnS:Cu,Al,Au have been investigated using Auger electron spectroscopy (AES) and a photospectrometer. The ZnS:Cu,Al,Au phosphor powders have been subjected to electron beam bombardment of 2 keV, with an electron beam current density of 88 mA cm−2 at an oxygen pressure of 2 × 10−6 Torr. The studies were carried out between room temperature and 310 °C. Degradation was manifested by a non‐luminescent ZnO layer that formed on the surface of the phosphor according to the electron‐stimulated surface chemical reaction (ESSCR) mechanism. An increase in temperature led to a decrease in the surface reaction rate due to a decrease in the mean surface lifetime of the oxygen molecules on the surface, with a direct decrease in the ESSCR probability. Without the presence of the electron beam, no chemical reactions occurred on the surface up to 310 °C. Local heating due to the electron beam irradiation is not responsible for the chemical reactions on the ZnS phosphor surface. Copyright © 2001 John Wiley & Sons, Ltd.
Nanoalignment mask fabricated directly on Si by AFM
Authors: Huang WenHao , Dang Xueming , Hu Qiao , Xia Yi , Telllo Marta , Calleja Montserrat , García Ricardo , Gómez‐Rodńguez J. M. , Baro A. 
Published: September 2002

AbstractThe alignment mask with submicrometre and nanometre sensitivity is very important and useful in the microelectronics industry and for nanoscience and technology in the near future. Here we report for the first time a nanoalignment mask that has been fabricated directly on Si by atomic force microscopy. Copyright © 2001 John Wiley & Sons, Ltd.
XPS and surface resistivity measurements of plasma‐treated LDPE and ageing effects
Authors: Simon D. , Liesegang J. , Pigram P. J. , Brack N. , Pura J. L. 
Published: September 2002

AbstractLow‐density polyethylene (LDPE) film containing a polydimethylsiloxane (PDMS) additive has been investigated using x‐ray photoelectron spectroscopy (XPS) and surface resistivity measurements. The samples measured were: as‐received; plasma‐treated; washed with ethyl acetate; aged in air; and combinations of these treatments. Analysis by XPS has been used to characterize surface species concurrently with resistivity in the surface region to assist in understanding the relationship between charge transport and surface electronic structure. Radiofrequency plasma treatment causes major oxidation effects and lowering of resistivity in the first 4 s. With the same treatment time, in the case of washed samples, surface segregation of PDMS is enhanced, causing an initial increase of surface region resistivity. Plasma treatment beyond 4 s causes saturation of the O : C ratio in the surface and a loss of charged bonds. These points also allow a description of resistivity change with ageing, which includes hydration effects on exposure to air. Copyright © 2001 John Wiley & Sons, Ltd.
Partial reduction of Si(IV) in SiO2 thin film by deposited metal particles: an XPS study
Authors: Komiyama Masaharu , Shimaguchi Takemi 
Published: September 2002

AbstractMetal–support interactions in systems of dispersed metals supported on thin‐film silica surfaces were examined by x‐ray photoelectron spectroscopy. Four metal–silica systems—Pt–, Pd–, Ag–and Au–SiO2—all indicated the formation of partially reduced Si(IV) species by the metal deposition. The extent of the reduction varied little with the kind or amount of deposited metal species. On the other hand, the amount of this newly formed Si(IV–δ) indicated a strong metal species dependence. Copyright © 2001 John Wiley & Sons, Ltd.
EXAFS study of molybdenum oxide on the structure Al2O3
Authors: Shi Weiping , Cai Xiaohai , Wei Jiying , Ma Jun , Hu Tiandou , Wu Nianzu , Xie Youchang 
Published: September 2002

AbstractIn this paper, MoO3dispersed on an alumina support was studied. The dispersion threshold was determined by x‐ray diffraction and the Mo–O coordination structure was detected by extended x‐ray absorption fine structure (EXAFS), which shows that the preferred dispersion phase is made up of [MoO4] polyhedrons. Copyright © 2001 John Wiley & Sons, Ltd.
Angular distribution of the surface excitation probability for medium‐energy electrons backscattered from a polycrystalline Au surface
Authors: Werner Wolfgang S. M. , Smekal Werner , Störi Herbert 
Published: September 2002

AbstractReflection electron energy‐loss spectra have been measured for medium‐energy electrons backscattered from a polycrystalline Au surface for emission angles between 15 and 90° with respect to the surface normal as well as for incidence angles in the same range. The surface excitation parameter (SEP) was extracted from each spectrum by fitting the raw data to theory and determining the ratio of the first surface loss peak to the elastic peak intensity. Both the energy and angular dependence of the SEP can be described by free electron theory when the electron momentum is rescaled by a material‐dependent parameter allowing the SEP in Au to be predicted for medium energies and arbitrary geometries. Copyright © 2001 John Wiley & Sons, Ltd.