bluuebunny/crossref_metadata_2025 huggingface dataset:
Lippmann‐Schwinger equation approach to scattering in quantum wires
Authors: Vargiamidis Vassilios , Valassiades O. , Kyriakos D. S.
Published: March 2003

We apply the Lippmann‐Schwinger equation for obtaining the scattering amplitudes and conductance as a function of Fermi energy for electrons scattering from one and two point defects in a two‐dimensional quantum wire. Further, we discuss the first and higher‐order Born approximation to the scattering wave function and show that keeping five terms in the Born series can lead to a convergent wave function (except for Fermi energy close to the subband energy where it naturally diverges). It has been stated previously that electron transmission through a single point defect in a quantum wire is perfect at every subband minima independent of where the scatterer is located. However, here we demonstrate that perfect transmission at subband minima is strongly affected by the transversal position of the defect. In particular, we show that the perfect transparency effect is modified when the scatterer is located at the nodes of a normal confinement mode.
Pressure dependence of structural phase transition and superconducting transition in CsI
Authors: Nirmala Louis C. , Iyakutti K.
Published: March 2003

The self‐consistent band structure calculation for CsI performed both in CsCl and HCP structures using the TB‐LMTO method is reported. The equilibrium lattice constant, bulk modulus and the phase‐transition pressure at which the compound undergoes structural phase transition from CsCl to HCP are predicted from the total‐energy calculations. The band structure, density of states (DOS), electronic charge distributions, metallization and superconducting transition temperature (Tc) of CsI are obtained as a function of pressure for both the CsCl and HCP structures. It is found that the charge transfer from s and p states to d state causes metallization and superconductivity in CsI. The highest Tc estimated is 2.11 K and the corresponding pressure is 1.8 Mbar. This value is in agreement with the recent experimental observation. The experimental trend – “metallization and superconductivity is rather insensitive to the crystal structure of CsI” – is also confirmed in our work.
The behavior of the 180° domain walls in disordered dielectrics like KTaO3 : Li and KTaO3 : Nb
Authors: Stephanovich Vladimir , Sobolewska Aneta
Published: March 2003

We calculate the structure of 180° domain wall in disordered ferroelectrics with random site electric dipoles (i.e. those like K1–xLixTaO3, KTa1–xNbxO3, where Li+ or Nb5+ are off‐center ions forming impurity dipoles). The calculation is performed on the base of the free energy functional of disordered dielectrics derived earlier [M. D. Glinchuk et al., Phase Transit., 2003 (to be published)] within the framework of a random field method. We obtain the domain wall thickness as a function of impurity dipole concentration n and temperature T. It is shown that in disordered ferroelectrics the domain wall is usually broader than in their ordered counterparts. The thickness increases infinitely near the phase transition temperature, which depends on the impurity dipoles concentration.
X‐ray study of the polarization of the Cu‐cations in CuBr
Authors: Almukhametov R. F. , Yakshibayev R. A. , Abdullin A. R. , Kutusheva R. M.
Published: March 2003

The intensities of the X‐ray lines for Cu+‐cationic conductor CuBr were studied depending on polarization under an electric field. The regular variation in the intensity depending on direction as well as polarization degree was established. A satisfactory agreement was shown for experimental integral intensities depending on copper cation number in the unit cell and those calculated obtained under the condition that all the Cu‐cations in the unit cell are mobile and occupy the tetrahedral sites. The redistribution of the copper cations on tetrahedral sites under the polarization electric field was established.
Ordering in undoped hexagonal AlxGa1–xN grownon sapphire (0001) with 0.09 < x < 0.247
Authors: Laügt M. , Bellet‐Amalric E. , Ruterana P. , Omnès F.
Published: March 2003

In this issue's Editor's Choice [1], multiple ordering in AlxGa1–xN grown by low pressure metal‐organic vapor phase epitaxy on sapphire is observed by comprehensive high resolution X‐ray diffraction as well as transmission electron microscopy investigations.

The cover figure shows a detail of the reciprocal space map taken on a AlxGa1–xN (x = 0.167) sample in the vicinity of the &1macr; 0 1 30 spot. The sapphire asymmetric reflection &1macr; &1 macr; 2 12 is also visible. It is concluded that besides the disordered alloy, an ordered phase with two consecutive AlN monolayers in a 3.1 nm large unit cell is present.

The first author, Marguerite Laügt, is a researcher at the Centre de Recherche sur l'Hétéro‐Epitaxie et ses Applications of the CNRS at Parc de Sophia Antipolis.
Analysing pharmacokinetic drug interaction or comparability studies with missing values in crossover design
Authors: Wei Lynn , Zhang Ji , Larson Patrick
Published: March 2003

In a pharmacokinetic drug interaction study using a three‐period, three‐treatment (drug A, drug B, and drugs A and B concomitantly) crossover design, pharmacokinetic parameters for either drug are only measured in two of the three periods. Similar missing data problems can arise for a four‐period, four‐treatment crossover pharmacokinetic comparability study. This paper investigates whether the usual ANOVA model for the crossover design can be applied under this pattern of missing data. It is shown that the model can still be used, contrary to a belief that a new one is needed. The effect of this type of missing data pattern on the statistical properties of treatment, period and carryover effect estimates was derived and illustrated by means of simulations and an example. Copyright © 2003 John Wiley & Sons, Ltd.
A scientist's viewpoint on promoting effective use of experimental design: Ten things a scientist wants to know about experimental design
Authors: Owen Martin R. , Armitage Mark , Chatfield Marion , Davies Bryan , Emiabata‐Smith David , Freeman Steve , Hayes Doug , Mann Inderjit , Ramsay Tom , Smith Linden , Squires Barney
Published: March 2003

This paper tackles the practical application of statistical tools. Chemical development is a rich area for collaboration between statisticians and chemists, but most statisticians encounter difficulties in promoting the tools to this client group. This paper, presented from a chemist's perspective, is intended to help bridge the gap between the two professions. The paper explores differences in uptake and attitudes towards adopting these techniques and suggests what has hindered or helped the process of effective application of experimental design. Copyright © 2003 John Wiley & Sons, Ltd.
Computational quantum chemistry in terms of multicenter Slater‐type orbitals: Entirely numerical procedure for the accurate evaluation of the basic integrals
Authors: Guidotti C. , Salvetti O. , Durante N. , Lamanna U. T. , Arrighini G. P.
Published: March 2003

Ab initio quantum mechanical calculations in terms of multicenter Slater‐type orbitals require accurate evaluation of basic one‐ and two‐electron integrals, a difficult mathematical task that becomes in particular challenging in the two‐electron case as four different expansion centers are involved. Here, we propose to illustrate the feasibility of attacking the problem of the multiple integrations needed entirely by numerical quadratures, in conjunction with a strategic program organization that allows evaluating simultaneously sets of thousands of integrals exploiting the mean characteristics of the integrands. This approach, envisaged and implemented many years ago by two of the present authors (C.G., O.S.), perhaps without adequate exposure, is endowed in our experience with good properties. The program package, which allows dealing on the same footing with linear and nonlinear molecular geometries, has been largely revised by introducing suitable adjustments and improvements (in particular extension to orbitals with azimuthal quantum number l = 3). © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Generation of systematic sequences of even‐tempered basis sets: Empirical generating formulae
Authors: Kryachko Eugene S. , Wilson Stephen
Published: March 2003

Some empirical formulae for generating systematic sequences of even‐tempered basis sets are investigated and compared with Schmidt‐Ruedenberg ansatz. The new formulae ensure the asymptotic completeness of the sequence of even‐tempered basis sets but encompass greater flexibility than the Schmidt‐Ruedenberg scheme. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Ab initio model to predict NMR shielding tensors for solutes in liquid crystals
Authors: Mennucci Benedetta , Cammi Roberto
Published: March 2003

We present a model for the ab initio calculation of the nuclear magnetic shielding tensors for molecules in liquid crystalline solvents. The electrostatic interactions between the solute and the anisotropic solvent are described within the integral equation formalism (IEF) framework and the shielding tensors are calculated at the density functional theory linked to the gauge invariant atomic orbital (GIAO) approach. The IEF–GIAO approach is tested on the calculation of the shielding tensors for the different nuclei of CH3CN and C6H5NO2 in positive and negative anisotropic solvents. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Isotopic metrology of carbon dioxide. I. Interlaboratory comparison and empirical modeling of inlet equilibration time, inlet pressure, and ion source conductance
Authors: Verkouteren R. Michael , Allison Colin E. , Studley Steven A. , Leckrone Kristen J.
Published: March 2003

We report a pilot study of high‐precision differential isotope ratio measurements made on replicate samples of pure carbon dioxide using three instruments of identical manufacture. Measurement protocols were designed to explore the effects of sample size, ion source conductance, and inlet changeover equilibration time on the raw measurements. Our goal was better understanding of factors that influence these measurements in order to establish procedures for highly reproducible and accurate determinations of Reference Material (RM) isotopic compositions. Evaluation and modeling of reported data illuminated effects consistent with two instrumental memory sources—one short‐lived (t½ ∼ 10 s) and the other long‐lived (t½ ∼ 6–10 min), uncompensated by normal background measurements—that can significantly influence measurements made by the dual inlet method. These biases, proportional to the difference in isotopic compositions between the measured sample and reference gases, decrease in magnitude with increasing sample size, source conductance, and equilibration time. We observed biases as high as 0.1‰ per 10‰ difference between sample and reference gases. These memory sources may be responsible for measured δ13C values of RMs generally being highly reproducible within any single laboratory but less reproducible among independent laboratories. The magnitude of the bias is consistent with the ranges of δ13C values reported in prior laboratory intercomparisons. Uncertainties are most likely due to high and variable long‐lived memory among the instruments tested. Published in 2003 by John Wiley & Sons, Ltd.
Isotopic metrology of carbon dioxide. II. Effects of ion source materials, conductance, emission, and accelerating voltage on dual‐inlet cross contamination
Authors: Verkouteren R. Michael , Assonov Sergey , Klinedinst Donna B. , Brand Willi A.
Published: March 2003

We report high‐precision isotopic carbon dioxide measurements, made before and after ion source modification to gas isotope ratio mass spectrometry (IRMS) instruments. Measurement protocols were designed to explore the effects of ion source material substitution, source conductance, inlet pressure, electron emission, acceleration potential, and inlet changeover equilibration time. After modification of the IRMS instruments at the National Institute of Standards and Technology (NIST) and the Max‐Planck‐Institute for Chemistry (MPI‐Mainz), immediate changes were observed. At NIST, measurements were no longer sensitive to inlet equilibration times greater than 15 s, and different settings of ion source conductance resulted in δ13C shifts of about 0.04‰ per 10‰ measurement difference between sample and reference, a five‐fold improvement. No significant changes in machine performance were observed after a month of use. After a year, performance had degraded slightly, but was controlled by ion source cleaning and the use of low‐energy ion acceleration to minimize sputtering. At MPI‐Mainz, results were very similar. We report cross‐contamination coefficients measured since 1996, and discuss the role of adsorption, ion implantation, and sputtering on cross contamination in mass spectrometry systems. We recommend that users of high‐precision IRMS instruments test for and minimize the effects described. Published in 2003 by John Wiley & Sons, Ltd.
In vivo processing of LVV‐hemorphin‐7 in rat brain and blood utilizing microdialysis combined with electrospray mass spectrometry
Authors: Nydahl Katarina Sanderson , Pierson Johan , Nyberg Fred , Caprioli Richard M. , Andrén Per E.
Published: March 2003

In vivo microdialysis in combination with liquid chromatography/electrospray time‐of‐flight mass spectrometry was used to study the processing of LVV‐hemorphin‐7, an endogenous decapeptide with opioid activity, in rat brain and blood. A microdialysis probe (flow rate 0.4 μL/min) was used to both introduce LVV‐hemorphin‐7 into the striatum of the brain (1.0 pmol/μL) or the venous blood (10 pmol/μL) and to collect the metabolic products. LVV‐hemorphin‐7 was extracellularly metabolized in the striatum to form C‐terminal fragments 2–10, 3–10, 4–10, 5–10, 6–10, 7–10, and N‐terminal fragments 1–9, 1–8, 1–6. Infusion of the aminopeptidase inhibitor amastatin (1.0 pmol/μL) into the striatum, together with LVV‐hemorphin‐7, decreased the processing of LVV‐hemorphin‐7 to form C‐terminal fragments 2–10, 3–10, 4–10, but increased the relative levels of fragment 5–10 and N‐terminal fragments 1–9, 1–8 and 1–6. The major metabolic product from LVV‐hemorphin‐7 in the striatum was the C‐terminal fragment 5–10, which may be processed by an endopeptidase not sensitive to amastatin. The LVV‐hemorphin‐7 infusion to the venous blood produced the C‐terminal fragments 2–10, 3–10, 4–10, and 5–10, N‐terminal fragment 1–9, and internal fragments 4–7 and 4–9. It is concluded that the combination of microdialysis and electrospray mass spectrometry provides a powerful tool for the study of extracellular metabolism and kinetic processes of complex reaction systems in vivo. Copyright © 2003 John Wiley & Sons, Ltd.
Identification and fragmentation study of plasticizers with post‐source decay matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Kéki Sándor , Szilágyi László Sz. , Deák György , Zsuga Miklós
Published: March 2003

A detailed investigation of the most commonly used plasticizers, such as phthalate, adipate and trimellitate esters, using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) and post‐source decay (PSD) MALDI‐TOFMS/MS is described. It is shown that PSD MALDI‐TOFMS/MS is capable of unambiguous determination of the different types of plasticizers. The determination of the types of plasticizers from different PVC samples by PSD MALDI‐TOFMS/MS, without the need for solvent extraction, is also demonstrated. The fragmentation mechanisms of these plasticizers cationized with protons and sodium ions are also reported. Copyright © 2003 John Wiley & Sons, Ltd.
Identification of thiols and glutathione conjugates of depsipeptide FK228 (FR901228), a novel histone protein deacetylase inhibitor, in the blood
Authors: Xiao Jim J. , Byrd John , Marcucci Guido , Grever Michael , Chan Kenneth K.
Published: March 2003

Four glutathione (GSH) conjugates and two thiols were detected when depsipeptide FK228, formerly FR901228, a naturally occurring potent histone deacetylase (HDAC) inhibitor, was incubated in rat or human plasma in the presence of GSH. Their structures were elucidated by the high‐performance liquid chromatography/electrospray ionization multi‐stage mass spectrometry (HPLC/ESI‐MSn) technique, and in some cases confirmed by accurate mass measurement. These products were also detected in rat and human blood homogenates following their incubation with FK228, but were not detected in GSH solution alone. A possible scheme for its formation is proposed. One of the thiols has recently been found to be more active as a histone deacetylase inhibitor than the parent compound. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of 3‐chlorotyrosine as a specific marker of protein oxidation: the use of N(O,S)‐ethoxycarbonyltrifluoroethyl ester derivatives and gas chromatography/mass spectrometry
Authors: Pietzsch Jens , Kopprasch Steffi , Bergmann Ralf
Published: March 2003

N(O,S)‐Ethoxycarbonyltrifluoroethyl amino acid esters are formed by the reaction of amino acids with ethylchloroformate plus trifluoroethanol plus pyridine. The use of these derivatives for a rapid and sensitive determination of 3‐chlorotyrosine, a highly specific marker of myeloperoxidase‐catalyzed protein oxidation, by using standard gas chromatography/electron impact mass spectrometry, is discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Comparison between electrochemistry/mass spectrometry and cytochrome P450 catalyzed oxidation reactions
Authors: Jurva Ulrik , Wikström Håkan V. , Weidolf Lars , Bruins Andries P.
Published: March 2003

The extent to which electrochemistry on‐line with electrospray mass spectrometry can be used to mimic cytochrome P450 catalyzed oxidations has been investigated. Comparisons on the mechanistic level have been made for most reactions in an effort to explain why certain reactions can, and some cannot, be mimicked by electrochemical oxidations. The EC/MS/MS system used successfully mimics in cases where the P450 catalyzed reactions are supposed to proceed via a mechanism initiated by a one‐electron oxidation, such as N‐dealkylation, S‐oxidation, P‐oxidation, alcohol oxidation and dehydrogenation. The P450 catalyzed reactions initiated via direct hydrogen atom abstraction, such as O‐dealkylation and hydroxylation of unsubstituted aromatic rings, generally had a too high oxidation potential to be electrochemically oxidized below the oxidation potential limit of water, and were not mimicked by the EC/MS/MS system. Even though the EC/MS/MS system is not able to mimic all oxidations performed by cytochrome P450, valuable information can be obtained concerning the sensitivity of the substrate towards oxidation and in which position of the molecule oxidations are likely to take place. For small‐scale electrochemical synthesis of metabolites, starting from the drug, the EC/MS/MS system should be very useful for quick optimization of the electrochemical conditions. The simplicity of the system, and the ease and speed with which it can be applied to a large number of compounds, make it a useful tool in drug metabolism research. Copyright © 2003 John Wiley & Sons, Ltd.
Method development for the concentration determination of a protein in human plasma utilizing 96‐well solid‐phase extraction and liquid chromatography/tandem mass spectrometric detection
Authors: Ji Qin C. , Gage Eric M. , Rodila Ramona , Chang Min S. , El‐Shourbagy Tawakol A.
Published: March 2003

Although liquid chromatography/tandem mass spectrometry (LC/MS/MS) technology has been widely used for quantitative analysis of small organic molecules, it has been a challenging task to quantitatively analyze protein samples utilizing this technology in biological matrices for pre‐clinical and clinical studies. Here we present our initial results in method development for the quantitative determination of rK5 protein concentrations in human plasma samples utilizing LC/MS/MS technology. A protein similar in structure to rK5, but with a slightly reduced molecular weight, was used as internal standard. A 96‐well solid‐phase extraction procedure was developed to effectively extract protein analytes from plasma samples. Quantitative analysis was obtained by a novel approach of protein monitoring that employed selective reaction monitoring (SRM). Even though mass spectrometry of the internal standard protein gave no fragment ions, SRM monitoring greatly reduced background interference. Using samples prepared in human plasma with sodium EDTA as anticoagulant, a correlation coefficient (r2) of 0.9940 was obtained by producing a single standard curve with the injection of six rows of standards with a concentration range from 100 ng/mL to 10 μg/mL. The mean analytical recovery for these standards ranged from 91.5 to 103.6%. The CVs for individual standard levels ranged from 3.7 to 20.9%. The experiment was also repeated using samples prepared in human plasma with sodium heparin as anticoagulant, which produced a correlation coefficient (r2) of 0.9952 obtained from a single standard curve with the injection of four rows of standards with a concentration range from 50 ng/mL to 10 μg/mL. The mean analytical recovery for the standards ranged from 96.2 to 104.6%. The CVs for individual standard levels ranged from 2.6 to 15.6%. Copyright © 2003 John Wiley & Sons, Ltd.
Monitoring the synthetic reaction of a polyamide/peptide conjugate using electrospray ionization mass spectrometry
Authors: Zhu Changjin , Yang Xiaoli , Cao Shuxia , Liu Yan , Yuan Gu , Liu Dan , Zhao Yufen
Published: March 2003

Recently, the chemical structures of a series of monoimidazole/polyamine conjugates were studied in this laboratory using electrospray ionization mass spectrometry (ESI‐MS) combined with tandem mass spectrometry (ESI‐MS/MS). The method was found to be a powerful tool for the identification of this class of compounds. During the synthesis of targeted polyamide/peptide conjugates as derivatives or analogues of netropsin and distamycin, the method was applied to analyze and track the coupling reaction for the formation of the polyamide, which was difficult to achieve using thin layer chromatography (TLC). Characteristic fragmentation pathways for a nitro‐monoimidazole conjugate, an amino‐monoimidazole conjugate, and the final product (a nitro‐diimidazole conjugate) were explored. The fragmentations of these conjugates were strongly affected by the presence of an amino group instead of a nitro group in the molecule, and led to the identification of the three compounds in the reacting solution or in the final reaction mixture. Consequently, the reaction could be monitored successfully and the synthetic route optimized. Copyright © 2003 John Wiley & Sons, Ltd.
Amide bond cleavage in deprotonated tripeptides: a newly discovered pathway to ″b2 ions
Authors: Harrison Alex G. , Michael Siu K. W. , El Aribi Houssain
Published: March 2003

The fragmentation reactions of the [MH]− ions of the tripeptides H‐Gly‐Leu‐Sar‐OH, H‐Leu‐Gly‐Pro‐OH and H‐Gly‐Leu‐Gly‐OH have been investigated in detail using energy‐resolved mass spectrometry, isotopic labelling and MS3 experiments. It is shown that the major route to the ″b2 ions involves loss of a neutral amine from the a3 ([MHCO2]−) ion rather than being formed directly by fragmentation of the [MH]− ion. When there is no C‐terminal amidic hydrogen (Sar, Pro), loss of a neutral amine is the dominant primary fragmentation reaction of the a3 ion. However, when there is a C‐terminal amidic hydrogen (Gly), elimination of the N‐terminal amino acid residue is the major fragmentation reaction of the a3 ion and formation of the ″b2 ion is greatly reduced in importance. It is proposed that the ″b2 ions are deprotonated oxazolones. Copyright © 2003 John Wiley & Sons, Ltd.
An atmospheric pressure matrix‐assisted laser desorption/ionization ion trap with enhanced sensitivity
Authors: Miller Christine A. , Yi Donghui , Perkins Patrick D.
Published: March 2003

When atmospheric pressure matrix‐assisted laser desorption/ionization (AP‐MALDI) became commercially available, the technique generated a great deal of interest because ion production was decoupled from mass analysis. Mass accuracy and resolution were therefore dependent on parameters governing the mass analyzer rather than the matrix and sample preparation. Researchers have successfully used AP‐MALDI sources with both orthogonal acceleration time‐of‐flight (oaTOFMS) and ion trap mass spectrometers. However, one limitation of the technique has been sensitivity, especially for mixtures of peptides generated from tryptic digests. In this work, data are presented documenting an increase in sensitivity of approximately two orders of magnitude as compared with results previously reported in the literature. The improvement in sensitivity is thought to derive primarily from the novel use of a countercurrent heated gas stream directed at the sample, although the target plate position and ion sampling configuration have also been optimized to reduce chemical noise from low molecular weight ions. A tryptic digest of BSA containing 125 attomoles on the plate was successfully identified in MS‐only mode, while MS/MS analysis of 250 attomoles of the same digest provided product ion spectra with sufficient information to identify the protein. More complicated mixtures of standard proteins were used to model proteomics experiments, and preliminary data suggest a minimum working dynamic range of 20‐fold for the analysis of mixtures of protein digests. Copyright © 2003 John Wiley & Sons, Ltd.
Surface and interface characterization of polyester‐based polyurethane/nano‐silica composites
Authors: Chen Xichong , You Bo , Zhou Shuxue , Wu Limin
Published: March 2003

Polyester‐based polyurethane/nanosilica composites were prepared via in situ polymerization and investigated by contact angle measurement, transmission electron microscopy (TEM), atomic force microscopy (AFM) and peel testing in an Instron testing machine. The contact angle and surface free energy results show that nanosilica tended to enrich at the interface between nanocomposite polymers and the substrates, TEM indicated that nanosilica particles were evenly dispersed in the bulk and AFM demonstrated that nanoparticles were located at both the surfaces and interfaces of nanocomposite polymers and that the roughness of both the surfaces and interfaces had a decreasing tendency as the nanosilica content increased, as did the adhesion strength between the nanocomposite polymers and substrates. Copyright © 2003 John Wiley & Sons, Ltd.
Novel floating‐type low‐energy ion gun for high‐resolution depth profiling in ultrahigh vacuum
Authors: Mizuhara Y. , Kato J. , Nagatomi T. , Takai Y. , Aoyama T. , Yoshimoto A. , Inoue M. , Shimizu R.
Published: March 2003

A floating‐type low‐energy ion gun (FLIG) has been developed for high‐resolution depth profiling in ultrahigh vacuum (UHV). This UHV‐FLIG allows Ar+ ions of primary energy down to 50 eV to be provided with high current intensity. The developed UHV‐FLIG was sufficiently compact, being ∼30 cm long, to be attached to a commercial surface analytical instrument. The performance of the UHV‐FLIG was measured by attaching it to a scanning Auger electron microprobe (JAMP‐10, Jeol), the base pressure of which in the analysis chamber was ∼1 × 10−7 Pa. The vacuum condition of ∼5 × 10−6 Pa was maintained during operation of the UHV‐FLIG without a differential pumping facility. Current density ranged from 41 to 138 µA cm−2 for Ar+ ions of primary energy 100–500 eV at the working distance of 50 mm. This ensures a sputtering rate of ∼10 nm h−1 with 100 eV Ar+ ions for Si, leading to depth profiling of high resolution in practical use. Copyright © 2003 John Wiley & Sons, Ltd.
Quantitative chemical composition of thin films with infrared spectroscopic ellipsometry: application to hydrated oxide films on aluminium
Authors: Van Gils S. , Melendres C. A. , Terryn H.
Published: March 2003

A method to quantify the composition of thin films using infrared spectroscopic ellipsometry (IRSE), supplemented by visible spectroscopic ellipsometry (VISSE), is proposed. Because ellipsometry measures the thickness and optical constants of a surface layer simultaneously, the absorption coefficient of the film as a function of wavelength can be obtained. Using values of the absorption coefficients for the pure components of the film, the percentages (mol.% or wt.%) of each component in the film can be calculated. The method is demonstrated in a study of the hydration of oxide films on electropolished aluminium and the anodically formed barrier oxide film. The IRSE technique shows that hydration of the films by immersion in boiling water results in the conversion of aluminium oxide to pseudoboehmite. Copyright © 2003 John Wiley & Sons, Ltd.
Radiation‐induced migration of additives in PVC‐based biomedical disposable devices. Part 1. Surface morphology by AFM and SEM/XEDS
Authors: Manfredini M. , Marchetti A. , Atzei D. , Elsener B. , Malagoli M. , Galavotti F. , Rossi A.
Published: March 2003

Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices—extruded and injection moulded—were studied in the non‐sterilized condition and after 25 and 50 kGy of beta irradiation. The polymer surfaces were analysed by scanning electron microscopy (SEM) equipped with an x‐ray energy‐dispersive spectroscopy (XEDS) and by atomic force microscopy (AFM). The inner surface of two parts of a venous line showed a different morphology according to their original formulation (for extrusion or injection moulding process) and reacted differently on sterilization with beta irradiation. Moulded parts were affected only slightly by the radiation step, whereas the variations were bigger for the extruded parts. In order to gain the best performances for the medical devices studied, the utmost care must be taken in the sterilization step, which should be optimized as well as the other steps of the manufacturing process. Copyright © 2003 John Wiley & Sons, Ltd.
Family Homelessness: State or Trait?
Authors: Shinn Marybeth
Published: March 2003

Compares conceptualizations of homelessness as a temporary state through which people pass or a permanent trait that emanates from individual characteristics. Evidence from a longitudinal study of 564 homeless families in New York City and additional secondary sources supports the view that for families, homelessness is a temporary state that is resolved by the provision of subsidized housing. Even for single individuals with severe mental disturbances, housing is a key factor in ending homelessness, although here there is more evidence that social services also contribute. Policy implications are that governments should take a more active role in reducing homelessness by providing access to subsidized housing.
Giving and Receiving Help: Interpersonal Transactions in Mutual‐Help Meetings and Psychosocial Adjustment of Members
Authors: Roberts Linda J. , Salem Deborah , Rappaport Julian , Toro Paul A. , Luke Douglas A. , Seidman Edward
Published: March 2003

The helping transactions that occur in group meetings have been theorized to be important therapeutic mechanisms within mutual‐help (or self‐help) groups. Hypothesized links between giving and receiving help and psychosocial adjustment were examined in a mutual‐help group for individuals with serious mental illness (GROW). Participants' adjustment was assessed at two time points and helping behaviors were measured with observational coding of weekly group interactions during the period between assessments. Frequencies of helping behaviors were used to predict Time 2 adjustment after controlling for initial adjustment. Consistent with the helper therapy principle, giving help to others predicted improvements in psychosocial adjustment; giving advice was a unique predictor. Total amount of help received was not associated with adjustment, but receiving help that provided cognitive reframing was associated with better social adjustment. A predicted interaction suggested that receiving help was related to better functioning when members experienced high levels of group integration.
Differential Rhodopsin Regeneration in Photoreceptor Membranes is Correlated with Variations in Membrane Properties
Authors: Boesze-Battaglia Kathleen , Allen Cindy
Published: March 2003

Rhodopsin, the major transmembrane protein in both the plasma membrane and the disk membranes of photoreceptor rod outer segments (ROS) forms the apo-protein opsin upon the absorption of light. In vivo the regeneration of rhodopsin is necessary for subsequent receptor activation and for adaptation, in vitro this regeneration can be followed after the addition of 11-cis retinal. In this study we investigated the ability of bleached rhodopsin to regenerate in the compositionally different membrane environments found in photoreceptor rod cells. When 11-cis retinal was added to bleached ROS plasma membrane preparations, rhodopsin did not regenerate within the same time course or to the same extent as bleached rhodopsin in disk membranes. Over 80% of the rhodopsin in newly formed disks regenerated within 90 minutes while only 40% regenerated in older disks. Since disk membrane cholesterol content increases as disks are displaced from the base to the apical tip of the outer segment, we looked at the affect of membrane cholesterol content on the regeneration process. Enrichment or depletion of disk membrane cholesterol did not alter the % rhodopsin that regenerated. Bulk membrane properties measured with a sterol analog, cholestatrienol and a fatty acid analog, cis parinaric acid, showed a more ordered, less “fluid”, lipid environment within plasma membrane relative to the disks. Collectively these results show that the same membrane receptor, rhodopsin, functions differently as monitored by regeneration in the different lipid environments within photoreceptor rod cells. These differences may be due to the bulk properties of the various membranes.
If It's Offered, Will They Come? Influences on Parents' Participation in a Community‐Based Conduct Problems Prevention Program
Authors: Orrell-Valente Joan K. , Pinderhughes Ellen E. , Valente Ernest , Laird Robert D. , Bierman Karen L. , Coie John D. , Dodge Kenneth A. , Greenberg Mark T. , Lochman John E. , McMahon Robert J. , Pinderhughes Ellen E.
Published: March 2003

This study examined influences on the rate and quality of parent participation in the Fast Track Program, a multi‐system, longitudinal preventive intervention for children who are at risk for conduct problems. A theoretical model of the relations among family coordinator characteristics, parent characteristics, the therapeutic engagement between family coordinator and parent, and rate and quality of parent participation was the basis for this study. “Family coordinators” are the Fast Track program personnel who conduct group‐based parent‐training sessions and home visits. Participants in this study included 12 family coordinators (42% were African American, 58% European American) and 87parents (55% were African American, 45% European American). The level of therapeutic engagement between the parent and the family coordinator was positively associated with the rate of parent attendance at group training sessions. The extent of family coordinator‐parent racial and socioeconomic similarity and the extent of the family coordinator's relevant life experiences were highly associated with the level of therapeutic engagement. The quality, but not the rate, of participation was lower for African American parents. Implications of these findings for preventive intervention with this population are discussed.
Volunteer Participation in Context: Motivations and Political Efficacy Within Three AIDS Organizations
Authors: Stewart Eric , Weinstein Rhona S.
Published: March 2003

Employed quantitative and qualitative data in a contextual examination of participation in three San Francisco‐area HIV/AIDS organizations: an urban, gay community‐based social change setting; an urban, broadly focused information/referral setting; and a suburban individual support setting. The settings attracted different kinds of volunteers and engaged them differently with the setting, each other, and community. In quantitative analyses external political efficacy (belief in the responsiveness of sociopolitical systems to change efforts) significantly distinguished settings, but was best predicted by setting‐moderated relationships to scaled motivations. Qualitative data more clearly illuminated volunteers' motivations for participation, as well as complex, embedded relationships between setting, motivations, attitudes about sociopolitical participation, and personal and community experience and identification. Together the findings underscore three unique but related stories for the three AIDS organizations, and the value of contextual approaches to participation and empowerment.
Ethnicity and Social Support During Pregnancy
Authors: Sagrestano Lynda M. , Feldman Pamela , Rini Christine Killingsworth , Woo Grace , Dunkel-Schetter Christine
Published: March 2003

Data from two multi‐ethnic prospective studies of African American, Latina, and non‐Hispanic White pregnant women were used to examine the influence of contextual factors on social support processes during pregnancy. Multiple types of support (perceived support, received support, support satisfaction, network support) and sources of support (baby's father, family, friends) were assessed. The role of ethnicity in social support was examined after controlling for the contribution of related contextual factors (SES, marital status, age, parity, employment) to these processes. The impact of ethnicity and related contextual factors differed across sources of social support. Ethnic differences in support from family and friends, but not from the baby's father, emerged. However, marital status was a consistent predictor of support from the baby's father, and SES was a consistent predictor of support from friends. Overall, the findings of two studies suggest that although ethnicity is associated with support from friends and family, other contextual factors, such as marital status and SES, influence support processes during pregnancy.
Substance Use and Psychological Adjustment in Homeless Adolescents: A Test of Three Models
Authors: MacLean Michael G. , Paradise Matthew J. , Cauce Ana Mari
Published: March 2003

Three models of adolescent substance use, the deviance‐prone, affect‐regulation, and normative development models, were assessed regarding their ability to predict the substance use of a high‐risk homeless adolescent sample with high rates of deviance, depression, and substance use. Hierarchical multiple regression analyses that included tests for curvilinear and gender interaction effects were performed. Results supported the deviance‐prone model most strongly, with delinquency but not aggressive behavior predicting substance use. The affect‐regulation model received support for females but not for males. With respect to the normative development model, results did not indicate that moderate substance users were better off than abstainers in terms of negative affect or interpersonal relationships.
The Nitric Oxide Synthase Inhibitor NG-nitro-L-Arginine Methyl Ester Potentiates Insulin Secretion Stimulated by Glucose and L-Arginine Independently of its Action on ATP-Sensitive K+ Channels
Authors: Salehi Albert , Parandeh Fariborz , Lundquist Ingmar
Published: March 2003

The nature of the action of the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) on hormone release from isolated islets was investigated. We found that glucose-induced insulin release was potentiated by L-NAME in the absence or presence of diazoxide, a potent K+ATP channel opener, as well as in the presence of diazoxide plus a depolarizing concentration of K+. At a low, physiological glucose concentration L-NAME did not influence insulin secretion induced by K+ but inhibited glucagon secretion. L-arginine-induced insulin release was potentiated by L-NAME. This potentiation was observed also in the presence of K+ plus diazoxide. Further, glucagon release induced by L-arginine as well as by L-arginine plus K+ and diazoxide was suppressed by L-NAME. The results strongly suggest that the L-NAME-induced potentiation of insulin secretion in response to glucose or L-arginine as well as the inhibitory effects on glucagon secretion are largely mediated by L-NAME directly suppressing islet NOS activity. Hence NO apparently affects insulin and glucagon secretion independently of membrane depolarization events.
Fertile Ground for Community: Inner‐City Neighborhood Common Spaces
Authors: Kuo Frances E. , Sullivan William C. , Coley Rebekah Levine , Brunson Liesette
Published: March 2003

Research suggests that the formation of neighborhood social ties (NSTs) may substantially depend on the informal social contact which occurs in neighborhood common spaces, and that in inner‐city neighborhoods where common spaces are often barren no‐man's lands, the presence of trees and grass supports common space use and informal social contact among neighbors. We found that for 145 urban public housing residents randomly assigned to 18 architecturally identical buildings, levels of vegetation in common spaces predict both use of common spaces and NSTs; further, use of common spaces mediated the relationship between vegetation and NSTS. In addition, vegetation and NSTs were significantly related to residents' senses of safety and adjustment. These findings suggest that the use and characteristics of common spaces may play a vital role in the natural growth of community, and that improving common spaces may be an especially productive focus for community organizing efforts in inner‐city neighborhoods.
Use of An ipsilateral Vascularized Ulnar Transposition Autograft for Limb‐Sparing Surgery of the Distal Radius in Dogs: An Anatomic and Clinical Study
Authors: Séguin Bernard , Walsh Peter J. , Mason David R. , Wisner Erik R. , Parmenter Jessica L. , Dernell William S.
Published: March 2003

Objective— To develop a surgical technique for using the distal aspect of the ulna as a transposition autograft in a distal radial defect and to assess patency of vascular supply and viability of the distal ulna in a heterotopic position.

Study Design— Cadaveric study and clinical cases.

Animals— Twenty‐two normal canine thoracic limbs; 3 dogs with distal radial osteosarcoma.

Methods— The arteries and veins of 12 limbs were injected with latex. Barium sulfate suspension was injected into the brachial artery of 10 other limbs after removal of the distal radius only (n = 2), ulna transposition (UT) (n = 6), or no procedure (n = 2). The distal ulna grafts were then harvested and decalcified in formic acid. The grafts were cut into 3–5 mm transverse sections and radiographed with a nonscreen film system to determine filling of intramedullary vessels with barium suspension. UT was performed in 3 dogs with distal radial osteosarcoma. Bone scintigraphy was performed 2–7 days after surgery to assess viability of the transposed ulna graft.

Results— Angiography confirmed patency of the caudal interosseous artery in all but 2 limbs in which the UT technique was performed; however, barium‐filled vessels were identified in the medullary cavity of all ulnar grafts. Scintigraphy confirmed graft viability in the 3 dogs, all of which had good to excellent limb function.

Conclusions— The distal aspect of the canine ulna can be used as a vascularized transposition autograft to replace distal radial defects, and viability can be maintained.

Clinical Relevance— The UT technique appears to be an acceptable limb‐sparing technique for dogs with tumors of the distal aspect of the radius.
Evaluation of a Collagen Patch as a Method of Enhancing Ventriculotomy Healing in Japanese Quail (Coturnix Coturnix Japonica)
Authors: Ferrell Shannon , Werner Jonathan , Kyles Andrew , Lowenstine Linda , Kass Phillip , Tell Lisa
Published: March 2003

Objective— To assess the ability of a porcine submucosal collagen patch to enhance ventriculotomy healing in quail.

Study Design— Histologic assessment of wound repair after ventriculotomy.

Animal Population— Eighteen adult Japanese quail.

Methods— All quail had a ventriculotomy through the caudoventral thin muscle. The quail were randomly assigned to 1 of 2 groups: group I (n = 9) had routine closure and group II (n = 9) had routine closure and the application of a porcine submucosal collagen patch over the serosal surface of the ventricular suture line. Three quail from each group underwent necropsy at 7, 14, and 21 days after surgery and healing of the ventriculotomy site was evaluated by microscopy.

Results— Ventricular mucosal epithelium was completely healed at 21 days postoperatively. Time to restoration of the ventricular submucosal integrity was variable in both groups. There was evidence of a gross or microscopic perforation in 4 quail in group II, which was statistically significant (P= .041). Quail with perforations had significantly elevated numbers of ventricular serosal lymphoid aggregates compared with those without perforations (P= .029). There were no other significant temporal differences between group I and group II for mortality or histopathologic grading of wound healing.

Conclusions— A porcine collagen patch did not enhance ventriculotomy wound healing. Subjectively, the collagen patch might have contributed to perforation by the generation of a lymphocytic xenograft rejection response.

Clinical Relevance— Ventriculotomy can be safely performed using routine closure methods in healthy birds.
Pulmonary Embolism Associated With Canine Total Hip Replacement
Authors: Liska William D. , Poteet Brian A.
Published: March 2003

Objective— To determine by pulmonary perfusion scans and ultrasonography if embolemia occurs during total hip replacement (THR) surgery in dogs.

Study Design— Prospective clinical study.

Animals— Forty client‐owned dogs that had THR surgery.

Methods— Thoracic radiographs were taken immediately after THR and immediately after completion of 99mTc‐MAA lung scans. Scintigraphy was performed in 28 dogs, 48 hours after THR. Intraoperative ultrasonography (intercostal or transesophageal) was performed in another 12 dogs that had THR. The right atrium and ventricle and pulmonary outflow tract were observed during and for 5 to 8 minutes after femoral component insertion into medullary canals prepared by reaming, and lavage and aspiration of debris before filling with polymethylmethacrylate in dough stage. A modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) classification system was used to evaluate lung scans.

Results— No pulmonary radiographic abnormalities were identified. Segmental and subsegmental perfusion defects occurred in 23 (82%) dogs and were classified as severe in 9 (32%) dogs, moderate in 11, and mild in 3. There was no particular lobe predilection. Patchy mulberry‐appearing defects, indicative of fat embolism, were most common. Embolemia was observed by ultrasound in 10 dogs. Variable‐sized particles occurred in 8 dogs, particles and bubbles in 2 dogs, and no emboli were observed in 2 dogs. Embolemia was observed within 10 seconds after femoral stem insertion and lasted < 1 minute. Pneumoemboli remained in the right atrium for > 8 minutes before dislodgement.

Conclusions— Embolemia of either air, particles, or both occurs in most dogs during THR surgery.

Clinical Relevance— Most dogs seemingly spontaneously recover from pulmonary embolism that occurs during THR. The risk of clinical complications from this pulmonary embolism should be taken seriously, even though the exact morbidity and mortality rates are unknown.