bluuebunny/crossref_metadata_2025_split huggingface dataset:
Field-dependent antiferro-ferromagnetic transition in Co/Ru superlattices (abstract)
Authors: Ounadjela K. , Suran G. , Muller D. , Arbaoui A. , Dinia A. , Panissod P. 
Published: July 2002

Co/Ru hcp (0001) superlattices were grown by UHV evaporation onto mica substrates. We demonstrate the growth of epitaxially ordered Co/Ru superlattices–despite the large lattice mismatch (≂8%)–consisting of hcp (0001) Co and Ru sublayers initialized on 150-Å-thick single-crystalline Ru buffer layer by using RHEED and x-ray diffraction. The magnetic properties were studied by magnetization and ferromagnetic resonance (FMR) measurements. For uncoupled Co layers, the resultant anisotropy switch from planar to axial direction (perpendicular to the film plane) with decreasing Co sublayers thickness. For Co sublayer thickness smaller than a critical one tco≂14 Å, the magnetization is directed perpendicular to the film plane. For small Ru interlayer thickness, large antiferromagnetic exchange coupling between the Co sublayers is observed in agreement with precious results. For a certain range of Co and Ru thicknesses, superlattices with unique magnetic parameters are obtained. Indeed, in the absence of an applied field, the magnetization is oriented along the film normal while the adjacent Co layers are coupled antiferromagnetically. For this magnetic structure, the magnetization process exhibits a hysteresis and the FMR spectra an irreversible behavior when the applied field is along the film normal.
As shown by SQUID measurements, when the field is decreased from a quasi-saturated state, the layers are essentially coupled ferromagnetically, the antiferromagnetic state appearing following a spin-flip process (staircaselike on the magnetization curve) for a field smaller than a critical one. However, with increasing field, the antiferromagnetic state disappears by progressive steps suggesting that the spin reorientation process occurs by coherent rotation of the magnetization combined with spin-flip process. The occurrence of this effect is particularly spectacular on the FMR spectra. With decreasing field, a classical FMR absorption is observed due to the basical ferromagnetic state while with increasing field, this absorption is largely reduced or disappears completely due to the antiferromagnetic one. The magnitude of the hysteresis and its evolution with the direction of the applied field, the values of the critical field corresponding to the spin flip and to the field above which the magnetic state is reversible, are very well correlated on the FMR spectra and the magnetization curves.
Calculation of ESR spectra and related Fokker–Planck forms by the use of the Lanczos algorithm. II. Criteria for truncation of basis sets and recursive steps utilizing conjugate gradients
Authors: Vasavada Kashyap V. , Schneider David J. , Freed Jack H. 
Published: July 2002

The complex symmetric Lanczos algorithm (LA) has proven to be a very efficient means of calculating magnetic resonance line shapes and spectral densities associated with Fokker–Planck forms. However, the relative importance of the various components of the basis set in an accurate representation of the spectrum and the proper number of recursive steps are not easily assessed in practice using the Lanczos algorithm. A systematic and objective procedure for the determination of optimal basis sets and number of recursive steps is developed using a generalization of the conjugate gradient method (CGM) appropriate for the type of complex symmetric matrices occuring in these problems. The relative importance of the individual basis vectors is determined by using the CGM to obtain the ‘‘solution vector’’ from the set of algebraic equations defining the spectrum. This is done at several values of the sweep variable (e.g., the frequency or the magnetic field). The maximum (over these values of sweep variable) for each component of the solution vector is taken to be a measure of the overall importance of the corresponding basis
vector in the complete spectrum. Using this method signficant basis set truncation is conveniently possible. The number of recursive steps needed for an accurate representation of the spectrum is easily obtained by monitoring the residual in the approximate solution vector at the center of the spectrum and by recognizing the close relationship between the LA and the CGM. It is this relationship that enables construction of the Lanczos tridiagonal matrix with the CGM which can either be used to calculate the cw ESR spectrum directly or else the eigenvalues. The information obtained from the CGM can be used to ‘‘turbocharge’’ the LA by taking advantage of the nearly optimal basis set and number of recursive steps. Significant savings in computation time are possible, and relative savings are greatest for the most difficult problems. This is illustrated with a variety of examples of slow-motional cw ESR spectra and of the new two-dimensional electron-spin-echo technique. In keeping with the greater sensitivity of the latter technique to motional dynamics, it is consistently found to require significantly larger optimal basis sets and number of recursive steps for an accurate representation. One of the most challenging problems for both types of spectroscopy is the case of macroscopically oriented samples where the macroscopic director is tilted at an angle relative to the applied static magnetic field, since this removes much of the symmetry in the problem. This case is found to yield to very significant truncation of basis sets, and a new symmetry-based decoupling of certain basis vectors was found in this study for the particular example of a 90° tilt angle.
Integral equations for interaction site fluids: The influence of connectivity constraints and auxiliary sites
Authors: Lue Leo , Blankschtein Daniel 
Published: July 2002

We examine two central features of two well-known integral equations for interaction site fluids: (i) the Chandler–Silbey–Ladanyi equations, and (ii) the site–site Ornstein–Zernike equation. The first feature involves the influence of connectivity constraints. Specifically, we identify the restrictions imposed on the site–site correlation functions arising from the constraints of connectivity between sites within a molecule. We find that when the Chandler–Silbey–Ladanyi (CSL) equations, a set of diagrammatically proper integral equations, are combined with a general approximate closure, they do not necessarily satisfy these connectivity constraints. On the other hand, the site–site Ornstein–Zernike (SSOZ) equation, combined with a simple fluid closure, does satisfy these constraints. These findings profoundly affect the long-range behavior of the correlation functions and the dielectric constant of the bulk fluid. These findings are also important for the development of computational methods to obtain accurate numerical solutions of the CSL and SSOZ equations.
When theories do not satisfy the above-mentioned connectivity constraints, we find that the resulting correlation functions do not satisfy the local neutrality constraints, which is a necessary requirement for any theory to properly predict the fluid dielectric constant. Instead, the correlation functions satisfy the constraints applicable to ionic fluids, that is, the Stillinger–Lovett moment conditions. This leads to the prediction of an infinite fluid dielectric constant. The second feature which we examine involves the influence of auxiliary sites on the prediction of the site–site total correlation functions. We prove that the addition of certain types of auxiliary sites does not affect the correlations between real sites when the Chandler–Silbey–Ladanyi equations are combined with a general approximate closure. The predictions of the SSOZ equation, combined with a general approximate closure, have been shown to depend on the presence of auxiliary sites. However, in the case of the Percus–Yevick closure for systems characterized by hard-sphere interaction sites, we are able to prove that the SSOZ equation does not exhibit this dependence for certain types of auxiliary sites.
Effect of dynamical asymmetry on the viscosity of a random copolymer melt
Authors: Kumaran V. 
Published: July 2002

The variation of the viscosity as a function of the sequence distribution in an A–B random copolymer melt is determined. The parameters that characterize the random copolymer are the fraction of A monomers f, the parameter λ which determines the correlation in the monomer identities along a chain and the Flory chi parameter χF which determines the strength of the enthalpic repulsion between monomers of type A and B. For λ≳0, there is a greater probability of finding like monomers at adjacent positions along the chain, and for λ&lt;0 unlike monomers are more likely to be adjacent to each other. The traditional Markov model for the random copolymer melt is altered to remove ultraviolet divergences in the equations for the renormalized viscosity, and the phase diagram for the modified model has a binary fluid type transition for λ≳0 and does not exhibit a phase transition for λ&lt;0. A mode coupling analysis is used to determine the renormalization of the viscosity due to the dependence of the bare viscosity on the local concentration field. Due to the dissipative nature of the coupling, there are nonlinearities both in the transport equation and in the noise correlation.
The concentration dependence of the transport coefficient presents additional difficulties in the formulation due to the Ito–Stratonovich dilemma, and there is some ambiguity about the choice of the concentration to be used while calculating the noise correlation. In the Appendix, it is shown using a diagrammatic perturbation analysis that the Ito prescription for the calculation of the transport coefficient, when coupled with a causal discretization scheme, provides a consistent formulation that satisfies stationarity and the fluctuation dissipation theorem. This functional integral formalism is used in the present analysis, and consistency is verified for the present problem as well. The upper critical dimension for this type of renormalization is 2, and so there is no divergence in the viscosity in the vicinity of a critical point. The results indicate that there is a systematic dependence of the viscosity on λ and χF. The fluctuations tend to increase the viscosity for λ&lt;0, and decrease the viscosity for λ≳0, and an increase in χF tends to decrease the viscosity.
An exact solution for axial flow in cylindrically symmetric, steady-state detonation in polytropic explosive with an arbitrary rate of decomposition
Authors: Cowperthwaite M. 
Published: July 2002

Methods of differential geometry and Bernoulli’s equation, written as B=0, are used to develop a new approach for constructing an exact solution for axial flow in a classical, two-dimensional, ZND detonation wave in a polytropic explosive with an arbitrary rate of decomposition. This geometric approach is fundamentally different from the traditional approaches to this axial flow problem formulated by Wood and Kirkwood (WK) and Fickett and Davis (FD), and gives equations for the axial particle velocity (u), the sound speed (c), the pressure (p), and the density (ρ), that are expressed in terms of the detonation velocity (D), the extent of decomposition (λ), the polytropic index (K), and two nonideal parameters ε3 and ε1, and reduce to the equations for steady-state, one-dimensional detonation as ε3 and ε1 approach zero. In contrast to the FD approach, the equations for u and c are obtained from first integrals of a tangent vector Ã on (u,c,λ) space, and the invariant condition, ÃB=aB=0, bypasses the FD eigenvalue problem by defining ε3 in terms of the detonation velocity deficit D/D∞ and K. In contrast to the WK approach, the equations for p and ρ are obtained from equations expressing the conservation of axial momentum and energy. Because the equations for these flow variables are derived without using the conservation of mass, the axial radial particle velocity gradient (war) associated with the flow can be obtained from the continuity equation without making approximations.
The relationship between ε1 and ε3 that closes the solution is obtained from equations expressing constraints imposed on the axial flow at the shock front by the axial and radial momentum equations, the curved shock and the decomposition rate law, and a particular solution is constructed from the ε1–ε3 relationship determined by a prescribed rate law and value of K. Properties of particular solutions are presented to provide a better understanding of two-dimensional detonation, and a new axial condition for detonation failure is used to show that detonation failure can occur before the curve relating D/D∞ to the axial radius of curvature of the shock (Sa) becomes infinite.
Reassessing naltrexone maintenance as a treatment for illicit heroin users
Authors: Hulse G. K. , Basso M. R. 
Published: July 2002

AbstractMost studies investigating the efficacy of naltrexone maintenance as a treatment for illicit heroin users have reported poor outcomes. Many of these studies, however, classify patients who periodically return to heroin use while receiving naltrexone maintenance as treatment failures. This study investigated 6‐month outcome status in 100 illicit heroin users who commenced naltrexone maintenance in a community‐based out‐patient treatment programme. The study aimed to assess patient status at 6 months using contrasting outcome criteria. In the first analysis periodic heroin use was not considered to constitute treatment failure (hence naltrexone was continued and they remained under observation). In the second analysis, return to heroin use was considered to represent treatment failure. Using the first approach, we found that 60% of patients were still on naltrexone maintenance at 6 months, with only a small number (28%) having returned to heroin use. In contrast, when return to heroin use for 7 or more consecutive days was regarded as a treatment failure, only 31% of patients were “retained in treatment” with the majority (62%) having returned to heroin use. It is argued that since periods of heroin use are commonly associated with attempting to manage heroin dependence, the analysis that allowed periodic heroin use during treatment, and produced positive outcome data, represented a more valid assessment of naltrexone maintenance as a treatment for illicit heroin users. It is suggested that this outcome criterion should therefore be employed in future research. Poor outcomes reported in many previous studies may be an artefact of using inappropriate outcome criteria to assess illicit heroin use.
The impact of naloxone/lofexidine combination treatment on the opiate withdrawal syndrome
Authors: Bearn J. , Bennett J. , Martin T. , Gossop M. , Strang J. 
Published: July 2002

AbstractClinical studies in opiate‐dependent patients suggest that detoxification treatment with opiate antagonists may accelerate the resolution of the opiate withdrawal syndrome, permitting early induction onto naltrexone maintenance treatment. The present open study compared the clinical efficacy of daily naloxone injections in conjunction with lofexidine, with conventional lofexidine monotherapy, in 49 polysubstance‐misusing opiate‐dependent patients. Overall, the addition of naloxone did not confer substantial benefit over lofexidine monotherapy, although area‐under‐the‐curve analysis showed that withdrawal severity in the naloxone/lofexidine combination group was significantly less than in the lofexidine monotherapy group, who experienced more severe withdrawal symptoms on days 4, 7, 9 and 13 of treatment. There were no significant differences in rates of completion of detoxification. Blood pressure remained within normal limits in both groups. Naltrexone maintenance treatment acceptability was low; only four patients continued with treatment for 5 or more days. The modest benefit of adding naloxone to lofexidine compared to the findings of previous opiate antagonist detoxification treatment studies is discussed in the context of the hypothesis that a critical level of opiate receptor occupancy is required to accelerate resolution of opiate withdrawal; the neurochemical mechanisms which may promote this are discussed.
Phenylalkylamine abuse among opiate addicts attending a methadone treatment programme in the Republic of Ireland
Authors: Kavanagh P. , Dunne J. , Feely J. , Maguire R. , Corrigan D. , Keating J. J. , Meegan M. J. , Clancy J. M. , Burdett J. 
Published: July 2002

AbstractSince the early 1990s ring‐substituted derivatives of amphetamine have been abused widely in the Republic of Ireland. The main ring‐substituted amphetamines being abused include methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA) and methylenedioxyethamphetamine (MDEA). A newer illicit synthetic analogue, which has been seized to a lesser extent by Irish police, is N‐methyl‐1‐(3,4‐methylenedioxyphenyl)‐2‐butanamine (MBDB). The work presented here involved the determination of the type of ring‐substituted amphetamines being abused by a group of recovering opiate abusers participating in a methadone maintenance programme in a Dublin Drug Rehabilitation Centre. Urine samples which tested positive for amphetamines and ring‐substituted amphetamines via EMIT immunoassay were subjected to further analysis using GC‐MS with MBTFA flash derivatization. It was found that the methylenedioxypropanamines were being abused, as was amphetamine itself. However, no abuse of methylenedioxybutanamines or thioamphetamines was observed.
Book and Media Reviews
Authors: BALL DAVID 
Published: July 2002

Books reviewed in this article:Book reviews in this column will primarily be of titles focusing completely, or in part, on biological aspects of addiction. However, significant titles of general relevance to the addictions field will also be included, even if they are not “biological”, as will titles of general methodological and clinical relevance, even if they are not on “addictions”. Similar considerations will apply to other media (software, audio tapes and CDs, videos, etc.). However, specific “addictions” software applications seem to be relatively uncommon and, as these items are rarely reviewed elsewhere, we will endeavour to include reviews of some of the older programmes that are still useful, as well as new titles that appear. I would appreciate suggesti ons of any items suitable for reviews, but especially software and other media of specifi c relevance to the addictions. Please contact: Dr David Ball, National Addiction Centre, 4 Windsor Walk, London SE5 8AF, UK. Email: media@addictionbiology.com Peer Review in Health Sciences F. GODLEE & T. JEFFERSON Controlling our Destinies: historical, philosophical, ethical and theological perspectives on the Human Genome Project P.R. SLOAN (Ed.) The Human Brain: essentials of behavioural neuroscience J. BEATTY Modern Chromatographic Analysis of Vitamins, 3rd edition A. P. DE LEENHEER, W.E LAMBERT & J.F. VAN BOCXLAER Multivariate Applications in Substance Use Research: new methods for new questions J.S. ROSE, L. CHASSIN, C.C. PRESSON & S.J. SHERMAN (Eds)
Background genotype modulates the effects of γ‐PKC on the development of rapid tolerance to ethanol‐induced hypothermia
Authors: Bowers Barbara J. , Collins Allan C. , Wehner Jeanne M. 
Published: July 2002

AbstractThe role of γ‐PKC in initial sensitivity and in the development of rapid tolerance to the hypothermic effects of ethanol were investigated in γ‐PKC null mutant mice. Effects of the single gene mutation were evaluated on three different genetic backgrounds. Null mutants from a C57BL/6J X 129/SvJ mixed genetic background failed to develop rapid tolerance after 4 days of i.p. ethanol injections. However, when the null mutation was introgressed onto a C57BL/6J background for six generations to create a congenic line, the expression of rapid tolerance unexpectedly reoccurred in the null mutant mice. Subsequent outcrossing of the γ‐PKC null mutation to a C57BL/6J X 129/SvEvTac mixed background did not restore the no tolerance phenotype. These observations, taken together with similar results reported previously concerning the development of chronic tolerance to ethanol in these same genotypes, 1 indicate that the gene coding for γ‐PKC has pleiotropic effects in the expression of both rapid and chronic tolerance to ethanol‐induced hypothermia. However, the impact of γ‐PKC is modulated by the background genotype. These results stress the necessity of understanding interactions with genetic background when interpreting the effects of single gene mutations on complex behavioral traits.
KLP38B: A Mitotic Kinesin-related Protein That Binds PP1
Authors: Alphey Luke , Parker Louise , Hawcroft Gillian , Guo Yiquan , Kaiser Kim , Morgan Gareth 
Published: July 2002

We have identified a new member of the kinesin superfamily in Drosophila, KLP38B (kinesin-like protein at 38B). KLP38B was isolated through its two-hybrid interaction with the catalytic subunit of type 1 serine/threonine phosphoprotein phosphatase (PP1). We demonstrate that recombinant KLP38B and PP1 associate in vitro. This is the first demonstration of direct binding of a kinesin-related protein to a regulatory enzyme.
Though most closely related to the Unc-104 subfamily of kinesin-related proteins, KLP38B is expressed only in proliferating cells. KLP38B mutants show cell proliferation defects in many tissues. KLP38B is required for normal chromatin condensation as embryos from KLP38B mutant mothers have undercondensed chromatin at metaphase and anaphase. This is the first time that a kinesin-related protein has been shown to have such a role. Incomplete lethality of a strong KLP38B allele suggests partial redundancy with one or more additional kinesin-related proteins.
Time‐Resolved Potential‐Induced Changes in Fe/N/C‐Catalysts Studied by In Situ Modulation Excitation X‐Ray Absorption Spectroscopy
Authors: Ebner Kathrin , Clark Adam H. , Saveleva Viktoriia A. , Smolentsev Grigory , Chen Jingfeng , Ni Lingmei , Li Jingkun , Zitolo Andrea , Jaouen Frédéric , Kramm Ulrike I. , Schmidt Thomas J. , Herranz Juan 
Published: February 2022

AbstractTo advance the widespread implementation of electrochemical energy storage and conversion technologies, the development of inexpensive electrocatalysts is imperative. In this context, Fe/N/C‐materials represent a promising alternative to the costly noble metals currently used to catalyze the oxygen reduction reaction (ORR), and also display encouraging activities for the reduction of CO2. Nevertheless, the application of these materials in commercial devices requires further improvements in their performance and stability that are currently hindered by a lack of understanding of the nature of their active sites and the associated catalytic mechanisms. With this motivation, herein the authors exploit the high sensitivity of modulation excitation X‐ray absorption spectroscopy toward species undergoing potential‐induced changes to elucidate the operando local geometry of the active sites in two sorts of Fe/N/C‐catalysts. While the ligand environment of a part of both materials’ sites appears to change from six‐/five‐ to fourfold coordination upon potential decrease, they differ substantially when it comes to the geometry of the coordination sphere, with the more ORR‐active material undergoing more pronounced restructuring. Furthermore, these time‐resolved spectroscopic measurements yield unprecedented insights into the kinetics of Fe‐based molecular sites’ structural reorganization, identifying the oxidation of iron as a rate‐limiting process for the less ORR‐active catalyst.