bluuebunny/crossref_metadata_2025_split huggingface dataset:
High strain‐rate shear deformation of a polyurethane elastomer subjected to impact loading
Authors: Gupta Y. M. 
Published: May 2005

AbstractExperimental techniques have been developed to produce and measure large amplitude one dimensional compression and shear waves in a polyurethane elastomer (Solithane 113). Experimental measurements consisted of time‐resolved compression and shear amplitude measurements at different distances from the impact surface. The data were analyzed to provide compression and shear wave velocities, and the corresponding stress‐stain curves on the microsecond time scale. The ability to measure directly the high stain rate shear response is a new development and has provided interesting results. The shear modulus varies between 3 and 9 kbar for compressive stresses ranging between 2 and 14 kbar. In contrast, shear modulus values inferred from quasi‐static measurements of bulk and Young's modulus under static high pressure are negligible. These comparisons suggest a high rate dependence of shear modulus in the glassy state. The shear strain curves suggest an elastic‐plastic response with yield strengths ranging from 0.12 kbar to 0.25 kbar with increasing compression for the compressive stress range investigated. Results of compression experiments are also presented.
Impact modification of poly(vinyl chloride) with chlorinated polyethylene II. Irreversible deformation
Authors: Siegmann A. , English L. K. , Baer E. , Hiltner A. 
Published: May 2005

AbstractThe mechanical behavior of chlorinated polyethylene (CPE)‐modified poly(vinyl chloride) (PVC) has been determined. The nature of the irreversible deformation processes which are responsible for mechanical energy absorption has been investigated by optical and electron microscopic techniques. Addition of CPE results in a decrease in the shear band initiation stress and an increase in void density and stability. The crazing to shear banding transition is observed at a blend composition between 2 and 7 percent CPE at the strain rate employed. It has been established that voiding occurs in the CPE rubber phase. Voiding accounts for at least part of the increased energy absorption of the blend. The stability of the voids to coalescence and fracture is attributed to strong adherence of the CPE to the primary PVC particles.
Fatigue behavior of medium‐density polyethylene pipes
Authors: Nishimura Hiroyuki , Narisawa Ikuo 
Published: May 2005

AbstractA round bar specimen and a square bar specimen cut out from medium‐density polyethylene pipes with a notch were made and a fatigue test was conducted to cause a brittle fracture. The initiation and growth of a craze and crack at the tip of a notch was observed. In the range where loading cycles are few and displacement of the specimen does not increase, the craze prior to crack initiation occurs. Also, the effect of frequency was investigated. The pure creep failure and the fatigue failure at low frequency were compared. The lower the frequency, the smaller the reciprocal of the actual loading timeTfbecomes. It is also found that this tensile fatigue test is a useful test method to assure the quality of pipes.
Low Temperature Plasma‐Based Sterilization: Overview and State‐of‐the‐Art
Authors: Laroussi Mounir 
Published: May 2005

AbstractSummary: Low temperature, high pressure, non‐equilibrium plasmas are now routinely used in several material processing applications, and in some cases are competing with low pressure plasmas in areas where these have historically been dominant. Etching and deposition are examples of such applications. Amongst the novel applications of non‐equilibrium plasmas, biomedical applications such as electrosurgery, surface modification of biocompatible materials, and the sterilization of heat‐sensitive medical tools are particularly interesting. In this paper, first a brief overview of recent research on reduced‐pressure plasma‐based sterilization/decontamination methods is given. Then a detailed review and discussion on the effects of atmospheric pressure non‐equilibrium plasmas on the cells of bacteria is presented. This includes the evaluation of the inactivation kinetics and the roles of the various plasma agents in the inactivation process. Measurements of the plasma temperature, the UV emission, and concentrations of various reactive species for the case of air plasma are presented. Plasma sub‐lethal effects are also briefly discussed, and the prospects of the use of “cold” plasmas in the biomedical field are outlined.
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Aerosol Charge Neutralization by a Radioactive Alpha Source
Authors: Liu Benjamin Y. H. , Pui David Y. H. , Lin Bing Y. 
Published: May 2005

AbstractThe performance of a Po‐210 radioactive ionizer for aerosol charge neutralization and bipolar charging has been evaluated. Monodisperse neutral and singly charged aerosols have been passed through the ionizer and their approach to the steady‐state Boltzmann charge measured by measuring the fraction of particles that are electrically charged. The result shows that an Nt of approximately 2.5 × 105 cm−3 s is needed for the development of a steady‐state charge fraction equal to that given by the Boltzmann' s law where N is the ion concentration and t is the residence time of the aerosol in the neutralizer. In addition, the performance of the ionizer for particle charge neutralization in a vibrating‐orifice aerosol generator has been evaluated and the result shows that the source is less effective for this application and the residual charge on the particles is considerably higher than that given by the Boltzmann's law.
Comparison of the three‐dimensional structure of two human rhinoviruses (HRV2 and HRV14)
Authors: Blaas Dieter , Kuechier Ernst , Vriend Gerrit , Arnold Edward , Luo Ming , Rossmann Michael G. 
Published: May 2005

AbstractAn attempt has been made to build a model of human rhinovirus 2 (HRV2) based on the known human rhinovirus 14 (HRV14) structure. HRV2 was selected because its amino acid sequence is known and because it belongs to the minor rhinovirus receptor class as compared to HRV14, which belongs to the major class. Initial alignment of HRV2 with HRV14 based on the primary sequence and the knowlege of the three‐dimensional structure of HRV14 showed that most probable position of the majority of insertions and deletions occurred in the vicinity of the neutralizing immunogenic sites (NIm). Out of a total of 855 amino acids present in one copy of each of the capsid proteins VP1 through VP4 of HRV14, 411 are different between the two viruses. There are also 6 amino acids residues inserted and 14 residues deleted in HRV2 relative to HRV14. Examination of amino acid interactions showed several cases of conservation of function, e.g., salt bridges or the filling of restricted space. The largest variation amongst the residues lining the canyon, the putative receptor binding site, was in the carboxy‐terminal residues of VP1.
Normal modes of vibration in bovine pancreatic trypsin inhibitor and its mechanical property
Authors: Nishikawa Tetsuo , Gō Nobuhiro 
Published: May 2005

AbstractThe normal mode analysis of conformational fluctuation is carried out for a small globular protein, bovine pancreatic trypsin inhabitor. Results are analyzed mainly to reveal the mechanical construction of the protein molecule. We take dihedral angles, including peptide ω angles, as independent variables for the normal mode analysis. There are 306 such angles in this molecule. Motions in modes with frequencies lower than 120 cm−1 are showned to involve atoms in the whole protein molecule, and spatial change of displacement vectors is continues, i.e., those of atoms near in space are similar. To quantitate the observation of the continuity, a correlation function of direction vectors of atomic displacement is calculated. From this function we define a Quantity that is interpreted as the wave length of an equivalent elastic plane wave. From this Quantity we deduce eefective young's modulus for each mode. For the mode with the lowest frequency 4.4 cm−1, it terned out to be 0.8 × 109 dyn cm−2, the value two orders magnitude softer than, for instance, α‐helices. Prompted by this observation, the four lowest frequency modes and also the harmonic motions in the thermal equilibrium are analyzed further mainly to detect relatively rigid structural elements in the molecule. From this analysis emerges a mechanical picture of the protein molecule that is made up of relatively rigid elements held together by very soft parts.
Validation of the first step of the heuristic refinement method for the derivation of solution structures of proteins from NMR data
Authors: Lichtarge Olivier , Cornelius Craig W. , Buchanan Bruce G. , Jardetzky Oleg 
Published: May 2005

AbstractA new method for the analysis of NMR data in terms of the solution structure of proteins has been developed. The method consists of two steps: first systematic search of the conformational space to define the region allowed by the initial set of experimental constraints, and second, the narrowing of this region by the introduction of aaditional constraint and optional refinement procedures. The search of the conformational space is guided by heuristics to make it computationally feasible. The method is therfore called the heuristic refinement method and is coded in an expert system called PROTEAN. The paper describe the validation of the first step of the method using an artificial NMR data set generated from the known crystal structure of sperm whale carbon monoxymyoglodin. It is shown that the initial search procedure yields a low‐resolution structure of the myoglobin molecule, accurately reproducing its main topological features, and that the precision of the structure depend on the quality of the intial data set.
The building of protein structures form α‐carbon coordinates
Authors: Correa Paul E. 
Published: May 2005

AbstractA procedure for the construction of complete protein structures from only αcarbon coordinates is described. This involves building the backbone by sequential addition of Pro, Gly, or Ala residues. This main chain structure is then refined using molecular dynamics. Side chains are constructed by sequential addition of atoms with intermediate molecular dynamics refinement. For α lytic protease (a structure that is mostly β sheet) a backbone root mean square deviation (RMSD) of 0.19 Å and an overall RMSD of 1.24 Å from the crystallographic coordinates are attained. For troponin C (67% β‐helix), where the coordinates are available only for the α‐carbons, a backbone RMSD of 0.41 Å and an overall RMSD of 1.68 Å are attained (fits kindly provided by Dr. Michael James and Natalie Strynadka). For flavodoxin a backbone RMSD of 0.49 Å and an overall RMSD of 1.64 Å were attained.
Purification, crystallization, and preliminary X‐ray diffraction analyses of the bacterial chemotaxis receptor modifying enzymes
Authors: West Ann H. , Djordjevic Snezana , Stock Ann M. , Martinez‐Hackert Erik 
Published: May 2005

AbstractBacterial chemotaxis receptor modifying enzymes from Salmonella typhimurium have been crystallized using microseeding techniques. The crystals of the S‐adenosyl‐L‐methionine‐dependent methyl transferase, CheR, belong to the monoclinic space group P21 with cell constants a = 55.1 Å, b = 48.1 Å, c = 63.1 Å, β = 112.3°. The crystals of the catalytic domain of the methylesterase, CheB, belong to the trigonal space group P3221 or P3121 with unit cell dimensions of a = b = 63.4 Å, c = 86.8 Å. Both crystals contain one molecule per asymmetric unit and have calculated Matthews' volumes of 2.4 Å3/Da. © 1995 Wiley‐Liss, Inc.
Crystallization and preliminary X‐ray diffraction studies of a bacterial flavohemoglobin protein
Authors: Ermler Ulrich , Siddiqui Roman A. , Cramm Rainer , Friedrich Bärbel , Schröder Dirk 
Published: May 2005

AbstractA flavohemoglobin protein (FHP) was isolated from Alcaligenes eutrophus and has been crystallized by vapor diffusion methods using PEG 3350 as precipitant. The crystals of the FAD‐ and heme‐containing protein belong to the monoclinic space group P21 with unit cell parameters of 52.2 Å, 85.8 Å, 103.9 Å, and 81.8° corresponding to two molecules per asymmetric unit. The crystals diffract at least to a resolution of 2.0 Å and are suitable for an X‐ray structure analysis. © 1995 Wiley‐Liss, Inc.
Electrospray ionization mass spectrometry of some β‐agonists
Authors: Debrauwer Laurent , Bories Georges 
Published: May 2005

AbstractPositive‐ion electrospray spectra of some β‐agonists have been acquired under various ion acceleration conditions. Collisional activation of β‐agonists allows control of their mass spectral patterns, i.e., the molecular ion or several characteristic fragmentations can be favored by changing the energy of the ions extracted into the vacuum system. Some preliminary observations are presented, showing the potential of electrospray ionization for the mass spectrometric analysis of β‐agonists.
Electron ionization mass spectrometry of some 1‐and 2‐alkylimidazoles and 1,3‐dialkylimidazole iodides
Authors: Sala Alberto , Ferrario Francesco , Rizzi Emanuele , Catinella Silvia , Traldi Pietro 
Published: May 2005

AbstractThe mass spectrometric beheviour of four differently substituted imidazoles and three 1,3 disubstituted imidazole iodides are discussed in detail with the aid of metastable‐ion data, daughter‐ion spectra, deuterium‐labelling experiments and comparison with model compounds. The results thus obtained indicate the presence of molecular species in an open, distonic ion structure and seem to exclude the occurrence of ring enlargement reactions that have been proposed in the literature.
Stabilization of cycloalkyl carbanions in the gas phase
Authors: Peerboom Renée A. L. , Rademaker Geert Jan , de Koning Leo J. , Nibbering Nico M. M. 
Published: May 2005

AbstractThe gas‐phase proton affinities of five cycloalkyl carbanions and five other hydrocarbon anions have been determined by a desilylation method with use of a Fourier‐transform ion cyclotron resonance mass spectrometer. The determined proton affinites of the cycloalkyl carbonions and the electron affinities of the corresponding cycloalkyl radicals given in parenthesis are: 1708(49), 1757(−41), 1750(−38), 1750(−38) and 1739(−40)kJ mol−1, for cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl, respectively. The results indicate that, except for the cyclopropyl carbanion, the cycloalkyl carbanions are significantly destab‐lized relative to the methyl anion. This destabilization is accounted for by the electron‐releasing effect of the alkyl groups. Furthermore, it is recognized that this destabilization is partially compensated by a stabilizing effect associated with the polarizability of the alkyl groups. Yet, this polarizability seems to be less effective in the rigid cycloalkyl carbanions than in the acyclic alkyl carbanions probably due to the anisotropic character of the polarizability effect. In contrast to its homologues, the cyclopropyl carbanion appears to be strongly stabilized relative to the methyl anion, from which it may be concluded that the alkyl electron‐releasing destabilization effect is superseded by a stabilization caused by a significant enhancement of the s‐character of the lone‐pair orbital of the carbanion which promotes the electronegativity of the atom accommadating the negative charge.
Detection of plasticers in skin and glandular extracts of the green tree frog Litoria splendida
Authors: Stone David J. M. , Blumenthal Thomas , Bowie John H. , Tyler Michael J. 
Published: May 2005

AbstractSkin and glandular secretions of the green tree frog Litora splendida contain a mixture of the plasticers di‐octyl phthalate and di‐octyl adipate. The fast‐atom bombardment mass spwectra of the plasticers are described.
Investigation of complexes between some glycopeptide antibiotics and bacterial cell‐wall analogues by electrospray‐ and capillary zone electrophoresis/electrospray‐mass spectrometry
Authors: Hamdan Mahmoud , Curcuruto Ornella , Modugno Enza Di 
Published: May 2005

AbstractComplexation in aqueous solutions between vancomycin, ristocetin A, teicoplanin and two bacterial cell‐wall analogues, Ac2‐L‐Lys‐D‐Ala‐D‐Ala (tripeptide) and Ac‐D‐Ala‐D‐Ala (dipeptide) has been examined by positiveion electrospray mass spectrometry (ES‐MS) and capillary zone electrophoresis (CZE)/ES‐MS. The ES‐MS data demonstrate that as well as complexes between monomeric antibiotics and either peptide, the investigated solutions contained complexes ranging from the simple homodimer of the antibiotic to a more complex association giving ions of the type [2(antibiotic)+3(tripeptide)+3H]3+. The same data also demonstrate that the homodimers of the investigated antibiotics are significantly suppressed in the presence of the tripeptide. The use of CZE/ES‐MS made it evident that the complexes between the antibiotic and the tripeptide were present in the solution prior to their introduction into the ion source. The two sets of data are compared with existing UV difference spectroscopy and nuclear magnetic resonance data on complexation and dimerization.
The identification of in vitro metabolites of bupropion using ion trap mass spectrometry
Authors: Taylor Lester C. E. , Singh Rominder , Chang Sai Y. , Johnson Robert L. , Schwartz Jae 
Published: May 2005

AbstractWe have identified in vitro metabolites of bupropion (Wellbutrin®) from incubations with human liver S9 fraction and human liver microsomes based on molecular weight information from full scan experiments using a liquid chromatograph coupled to a quadrupole ion trap mass spectrometer capable of multi‐stage operation (LC/MSn). Preliminary experiments have shown that this instrument provides comparable sensitivity to conventional LC‐coupled triple quadrupole instruments for metabolic studies, while allowing detailed structural studies using MSn experiments and routine on‐line coupling with high performance liquid chromatography via an external atmospheric pressure chemical ionization (APCI) source. The LC/MS analysis of human S9 showed the presence of three isomeric monohydroxylated metabolites of bupropion. These were further characterized in a series of MS/MS experiments which gave characteristic spectra for the three isomers. A minor dihydroxylated species was also identified in the human S9 sample and further characterized in a series of MSn experiments. Detailed structural information was generated by the use of on‐line LC/MSn type experiments. We have followed the fragmentation pathways of several molecular ion species in a series of sequential LC/MSn experiments, extending as far as MS6 with scan cycle times of less than 1.5 s. Such experiments have provided insights into the structure of specific fragment ions. Additional metabolic products were identified in the rat liver microsomes incubation sample.
Analysis of enzymatic DNA sequencing reactions by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Shaler Thomas A. , Becker Christopher H. , Tan Yuping , Wickham Juanita N. , Wu Kuang Jen 
Published: May 2005

AbstractThe products from base‐specific, dideoxy‐nucleotide chain‐termination DNA sequencing reactions catalyzed by the modified T7 DNA polymerase have been analyzed by using the technique of matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometry. Preliminary experiments were performed to determine detection limits for a synthetic mixture of mixed‐base single‐stranded DNA which contained a 14‐mer, a 21‐mer, and a 41‐mer; acceptable spectra, showing peaks for each component, were obtainable for samples that contained as little as 5 fmol per component. Initial sequencing reactions were therefore carried out on 2‐pmol amounts of a short synthetic template that was 45 nucleotides in length, employing 2 pmol of 12‐mer as the primer strand. This provided readable sequence information out to the 19th base past the primer. Using a 21‐mer primer, nearly the entire sequence of the template could be read.
Quantitative analysis of cytokinins by electrospray tandem mass spectrometry
Authors: Prinsen Els , Redig Pascale , Van Onckelen Henri A. , Van Dongen Walter , Esmans Eddy L. 
Published: May 2005

AbstractA methodology was developed for the analysis of cytokinins from plant tissue using electrospray tandem mass spectrometry in combination with HPLC. A detection limit of 1 pmol zeatin‐riboside injected on‐column was achieved under multiple reaction monitoring conditions. Linearity was observed within a concentration range of 1–100 pmol injected on‐column. In view of the analysis of a considerable amount of samples, the chromatographic conditions were selected which were a compromise between speed of analysis and resolution. This approach, in combination with multiple reaction monitoring, allowed the analysis of up to 150 samples a day, and quantitation of 16 different cytokinins per sample.
Effect of gas phase composition on chromium segregation in NiOCr2O3 solid solutions
Authors: Hirschwald W. , Sikora I. , Stolze F. 
Published: May 2005

AbstractThe SIMS method was applied to determine the near‐surface segregation profiles of Cr in Cr‐doped NiO single crystals annealed at 1353 K in air and in argon. The decrease of oxygen partial pressure in the gas atmosphere favours surface segregation of Cr. Furthermore, the enrichment factor increases when the Cr bulk concentration decreases. The present research indicates a dynamic state of the surface layer of oxide crystals which may vary as a result of changes in gas composition.
Application of environmental electron spectroscopy to AES of bulk ceramics
Authors: Ohlendorf G. , Koch W. , Kempter V. , Borchardt G. 
Published: May 2005

AbstractAuger spectra from highly samples (Al2O3, Si3N4) are collected in a gaseous environment. It is demonstrated that the build‐up of negative surface charge can be reduced considerably under suitable conditions. It is proposed that the decharging of the surface is initiated by Auger neutralization of the ions formed in the gaseous environment in collisions with the primary keV electrons.
Estimation of depth profiles from inelastic backgrounds in XPS. I. General relationships
Authors: Aminov Kamil L. , Jørgensen Jørgen S. , Pedersen J. Boiden 
Published: May 2005

AbstractThe accuracy by which an unknown concentration profile can be found by analysis of XPS spectra is investigated theoretically by analytical and numerical techniques. The problem of determining the profile is reformulated as an optimization problem. By use of analytical techniques we obtain qualitative statements about the depth resolution and we derive fundamental relationships between the different parameters that indicate their relative importance. In order to illustrate the various dependencies of the variability of the model parameters, we derive analytical expressions for the standard errors of the model parameters for two simple models: a dalta layer and an exponentially decreasing profile. Furthermore, the complete probability distribution of the model parameters for a rectangular model is investigated numerically.