bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite-difference modeling of piezoelectric composite transducers
Authors: Hornsby John S. , Das-Gupta D. K.
Published: July 2002

The mechanical and electrical properties of transducers are modeled by finite-difference representations of the relevant physical equations, and the numerical problems are discussed. The theory is applied to (a) a ceramic transducer of dimensions 1 cm×1 cm×200 μm, (b) a polymer P of the same dimensions, and (c) a 1–3 composite transducer consisting of transverse rods of ceramic embedded in a matrix of polymer. The results for the ceramic agree with the one-dimensional model, viz.:voltage of order 4–5 μV and no resonance below 10 MHz. For the polymer, the resonant frequency of 3.9 MHz is close to the 4 MHz predicted by the one-dimensional theory. For the composite, introduction of the ceramic has an immediate effect on s11, s12 and s13, whereas it has little effect on d31 unless the density of the ceramic in the mix is 30% or higher.
Geometries and potential energies of electronic states of GaX2 and GaX3 (X=Cl, Br, and I)
Authors: Dai Dingguo , Balasubramanian K.
Published: July 2002

Twelve electronic states of GaCl2, GaBr2, and GaI2 and the 1A1′ electronic states of GaCl3, GaBr3, and GaI3 are investigated using the complete active space multiconfiguration self-consistent-field (CAS-MCSCF) technique which included up to 58 700 configurations followed by multireference singles+doubles configuration interaction (MRSDCI) method which included a larger configuration space. Potential energy surfaces of four doublet electronic states of GaCl2, GaBr2, and GaI2 are obtained. Seven excited electronic states of GaBr3 are also studied. The ground states of GaX2 (X=Cl, Br, and I) species are found to be of X 2A1 symmetries (C2v), while the ground states of GaX3 species are found to be of X 1A1′ symmetries (D3h). The potential energy surfaces of the excited 2B1 states of GaX2 compounds exhibit double minima. The dissociation energies and the atomization energies of GaX2 and GaX3 are computed.
Calculation of internal conversion rate constants of single vibronic levels in S1 benzene
Authors: Rashev S.
Published: July 2002

In the present work, a direct count procedure designed for the assessment of the decay rates of nonradiative processes in polyatomic molecules has been introduced. Using the described approach the internal conversion (IC) decay rates of a considerable number of single vibronic levels (SVL) in S1 benzene have been estimated. The decay rates of ‘‘bright’’ SVLs were found to increase only slowly, while those of ‘‘dark,’’ out-of-plane modes containing states grew far more rapidly with the excess vibrational energy Ev in S1. The observed behavior with Ev as well as the absolute magnitude of the calculated IC decay rates were in general conformity with the existing experimental evidence.
Frozen structural disorder in a pseudospin model with barriers
Authors: Kovarskiı̆ V. P. , Kuznetsov A. Yu. , Khristov A. V.
Published: July 2002

A pseudospin model for describing structurally disordered crystals is justified and developed. It includes the finite energy barrier between states at the site. A metastable glass state in the model is investigated by the Monte Carlo method. The temperature dependences of the average energy, order parameter, Edwards–Anderson parameter, and autocorrelation function are determined. It is shown that the glass state is maintained to a certain temperature, after which a devitrification occurs. Features are observed in the behavior of the specific heat and susceptibility, and an anomalous slowing of the relaxation in the devitrification region is seen. The role of the energy barrier in the formation of the glassy state is discussed.
Phase fluctuations and pseudogap properties: influence of nonmagnetic impurities
Authors: Loktev V. M. , Sharapov S. G. , Quick R. M. , Sharapov S. G.
Published: July 2002

The presence of nonmagnetic impurities in a 2D “bad” metal depresses the superconducting Berezinskii–Kosterlitz–Thouless transition temperature while leaving the pairing energy scale unchanged. Thus the region of the pseudogap nonsuperconducting phase, in which the modulus of the order parameter is nonzero but its phase is random and which arises at the pairing temperature, is substantially bigger than for the clean system. This supports the premise that fluctuations in the phase of the order parameter can in principle describe the pseudogap phenomena in high-Tc materials over a rather wide range of temperatures and carrier densities. The temperature dependence of the bare superfluid density is also discussed.
On hydrodynamic diffusion and drift in sheared suspensions
Authors: Koch Donald L.
Published: July 2002

It is shown that a migration or drift of particles induced by inhomogeneities in the average shear rate will occur in a suspension of spheres with purely hydrodynamic interactions, even in the absence of inertial effects. Two relationships between the drift velocity, the hydrodynamic tracer- and gradient-diffusion coefficients for the suspended particles, and the diffusivity for a fluid-phase chemical tracer are derived.
Spectral stability of Taylor’s vortex array
Authors: Lin S. P. , Tobak M.
Published: July 2002

It has been proven that the two-dimensional Taylor vortex array, which is an exact solution of the Navier–Stokes equation, is absolutely and monotonically stable, in a global sense, with respect to infinitesimal disturbances of all discrete frequencies.
A Richardson criterion for compressible swirling flows in a toroidal magnetic field
Authors: Fung Y. T.
Published: July 2002

Stability conditions for an adiabatic compressible swirling flow in the presence of a toroidal magnetic field is investigated. In the absence of all the dissipative mechanisms, the flow is found to be stable to all small axisymmetric perturbations if the local Richardson number is equal to or greater than 1/4 throughout the flow domain.
Reconnection rate of magnetic-field lines in hydromagnetic plasma turbulence
Authors: Ichimaru Setsuo
Published: July 2002

Rates of magnetic reconnection are investigated in terms of the spectral functions of magnetic-field turbulence and the density of magnetic helicity. It has been shown that Parker’s scaling of the reconnection rates, sustained through observations in astrophysical and laboratory settings, is a consequence of transverse magnetic fluctuations generated by the influx of fields and plasmas into a reconnection cell, an idea corroborating that of ‘‘forced’’ reconnection. Three-dimensional and helicity-dependent effects in the reconnection processes are also analyzed.
Some additional observations of the vortex instability in electron beams
Authors: Webster H. F.
Published: July 2002

A number of observations have been made of the electron vortices that form in high-density sheet beams traveling along magnetic field lines. The observations were done in sealed off high vacuum tubes. The tubes were equipped with pinhole cameras that permitted measurement of the current densities and the transverse velocities of the electrons in various parts of the beam. The vortex centers were, single sign of charge, plasmas and with increasing current in the beam, the charge density in the center increased until the Brillouin value was reached. Beyond this, the beam discontinuously went through a sequence of shapes, generally with fewer but larger vortices. The pinhole camera was used to measure the transverse velocities of electrons in various parts of the vortex and a surprising broad distribution was found in the center of the vortex of the high current forms.
Vasopressin mRNA localization in nerve cells: Characterization of cis-acting elements and trans-acting factors
Authors: Mohr Evita , Prakash Nilima , Vieluf Kerstin , Fuhrmann Carola , Buck Friedrich , Richter Dietmar
Published: July 2002

mRNA localization is a complex pathway. Besides mRNA sorting
per se
, this process includes aspects of regulated translation. It requires protein factors that interact with defined sequences (or sequence motifs) of the transcript, and the protein/RNA complexes are finally guided along the cytoskeleton to their ultimate destinations. The mRNA encoding the vasopressin (VP) precursor protein is localized to the nerve cell processes
in vivo
and in primary cultured nerve cells. Sorting of VP transcripts to dendrites is mediated by the last 395 nucleotides of the mRNA, the dendritic localizer sequence, and it depends on intact microtubules.
In vitro
interaction studies with cytosolic extracts demonstrated specific binding of a protein, enriched in nerve cell tissues, to the radiolabeled dendritic localizer sequence probe. Biochemical purification revealed that this protein is the multifunctional poly(A)-binding protein (PABP). It is well known for its ability to bind with high affinity to poly(A) tails of mRNAs, prerequisite for mRNA stabilization and stimulation of translational initiation, respectively. With lower affinities, PABP can also associate with non-poly(A) sequences. The physiological consequences of these PABP/RNA interactions are far from clear but may include functions such as translational silencing. Presumably, the translational state of mRNAs subject to dendritic sorting is influenced by external stimuli. PABP thus could be a component required to regulate local synthesis of the VP precursor and possibly of other proteins.
Maternal effort mediates the prevalence of trypanosomes in the offspring of a passerine bird.
Authors: Merino S , Potti J , Moreno J
Published: July 2002

The relationships between parental effort, offspring growth, and offspring blood parasitemias are poorly known. We examined the effect of parental effort on offspring size and prevalence of trypanosomes in peripheral blood of nestling Pied Flycatchers Ficedula hypoleuca aged 13 days. Trypanosome infections were likely to be shared by siblings, indicating the role of a common environment and/or shared genes in the susceptibility to infection. Broods infected by trypanosomes had reduced growth, but this was due to decreased parental, especially maternal, energy expenditure in broods with nestlings infected by trypanosomes. There was no association between parental infection with trypanosomes and both their energy expenditure and the infection of their broods. Under stressful conditions caused by low maternal energy expenditure, the immune response of nestlings during growth was probably impaired, in a way analogous to the relapses of blood parasitemias with reproductive effort in breeding animals.
Patterns of HIV-1 evolution in individuals with differing rates of CD4 T cell decline
Authors: Markham Richard B. , Wang Wei-Cinn , Weisstein Anton E. , Wang Zhe , Munoz Alvaro , Templeton Alan , Margolick Joseph , Vlahov David , Quinn Thomas , Farzadegan Homayoon , Yu Xiao-Fang
Published: July 2002

Evolution of HIV-1
env
sequences was studied in 15 seroconverting injection drug users selected for differences in the extent of CD4 T cell decline. The rates of increase of either sequence diversity at a given visit or divergence from the first seropositive visit were both higher in progressors than in nonprogressors. Viral evolution in individuals with rapid or moderate disease progression showed selection favoring nonsynonymous mutations, while nonprogressors with low viral loads selected against the nonsynonymous mutations that might have resulted in viruses with higher levels of replication. For 10 of the 15 subjects no single variant predominated over time. Evolution away from a dominant variant was followed frequently at a later time point by return to dominance of strains closely related to that variant. The observed evolutionary pattern is consistent with either selection against only the predominant virus or independent evolution occurring in different environments within the host. Differences in the level to which CD4 T cells fall in a given time period reflect not only quantitative differences in accumulation of mutations, but differences in the types of mutations that provide the best adaptation to the host environment.
In vitro
suicide inhibition of self-splicing of a group I intron from
Pneumocystis carinii
by an
N
3′ →
P
5′ phosphoramidate hexanucleotide
Authors: Testa Stephen M. , Gryaznov Sergei M. , Turner Douglas H.
Published: July 2002

Binding enhancement by tertiary interactions is a strategy that
takes advantage of the higher order folding of functionally important
RNAs to bind short nucleic acid-based compounds tightly and more
specifically than possible by simple base pairing. For example,
tertiary interactions enhance binding of specific hexamers to a group I
intron ribozyme from the opportunistic pathogen
Pneumocystis
carinii
by 1,000- to 100,000-fold relative to binding by only
base pairing. One such hexamer, d(AnTnGnAnCn)rU, contains an
N
3′ →
P
5′ phosphoramidate
deoxysugar–phosphate backbone (n) that is resistant to chemical and
enzymatic decay. Here, it is shown that this hexamer is also a suicide
inhibitor of the intron’s self-splicing reaction
in
vitro
. The hexamer is ligated in
trans
to the 3′
exon of the precursor, producing dead-end products. At 4 mM
Mg
2+
, the fraction of trans-spliced product is greater than
normally spliced product at hexamer concentrations as low as 200 nM.
This provides an additional level of specificity for compounds that can
exploit the catalytic potential of complexes with RNA targets.
Does Race Make a Difference among Primary Care Patients with Alcohol Problems Who Agree to Enroll in a Study of Brief Interventions?
Authors: Conigliaro Joseph , Maisto Stephen A. , McNeil Melissa , Kraemer Kevin , Kelley Mary E. , Conigliaro Rosemarie , O'Connor Monica
Published: July 2002

This study describes the severity, alcohol consumption, consequences, readiness to change, and coping behaviors of African‐American and white primary care patients enrolled in a trial of brief interventions for problem drinking. In multivariate analysis, unemployment but not race was associated with clinical indicators of alcohol problems. African‐Americans reported no difference in alcohol consumption and similar quality of life scores. African‐American race and unemployment were both associated with increased identification and resolution of alcohol problems. There was no difference in readiness to change, but African‐Americans reported more problems related to alcohol and greater use of coping behaviors to avoid drinking. African‐Americans may be better equipped to manage drinking problems when they do occur due to increased familiarity with coping mechanisms.
The Relationship between Eligibility Criteria for Participation in Alcohol Brief Intervention Trials and Other Alcohol and Health‐Related Variables
Authors: Maisto Stephen A. , Conigliaro Joseph , McNeil Melissa , Kraemer Kevin , Kelley Mary E.
Published: July 2002

In clinical trials of brief interventions for alcohol use, individuals typically are defined as eligible for the research through meeting quantity‐ frequency (QF) of alcohol consumption criteria, alcohol‐related problems criteria, or both. The purpose of this study was to evaluate preintervention and posttreatment differences among three groups of research participants eligible for participation in a brief intervention clinical trial by meeting the AUDIT total score criterion only, the QF criterion only, or both. The participants were 301 men and women 21 years of age or older who presented for medical treatment at one of twelve primary care clinics and were screened for participation in the clinical trial. Participants completed an assessment protocol at preintervention and 1, 3, 6, 9, and 12 months postintervention. The analyses showed statistical differences among the three subgroups on three outcome dimensions of alcohol consumption, related consequences and behaviors, and medical complications; for both consumption and complications, the AUDIT + QF participants showed greater severity than participants in either of the other two groups. For consequences, AU DIT + QF participants scored higher than the QF participants on one variable constituting this dimension. The overall subgroup differences were maintained at six months in the consumption and consequences data. The implications of these findings for sensitivity of brief intervention trial design, the discovery of patient moderators of intervention effectiveness, and clinical practice are discussed.
Self‐Help Strategies Among Patients with Substance Use Disorders
Authors: Westermeyer Joseph , Myott Sarah , Aarts Rembrant , Thuras Paul
Published: July 2002

The objective of this study was to determine (1) the type and extent of self‐help efforts among patients presenting for treatment of substance use disorders, and (2) the association of self‐help with demographic and clinical characteristics. A retrospective report of life self‐help methods, current demographic characteristics, and current and lifetime clinical characteristics was used. Six hundred and forty‐two patients in treatment for substance use disorder were interviewed at one of two university medical centers with Alcohol‐Drug Programs located within departments of psychiatry. A research associate (RA) interviewed patients regarding seven types of self‐help involving specific, mutually exclusive behaviors and rated the patient's lifetime self‐help methods. The patient, RA, and addiction psychiatrists provided demographic, familial, and clinical information. Most patients (78%) had tried one or more types of self‐help, with a mean of 2.7 methods per patient. They more frequently chose methods related to the substance (decreasing amounts or frequency, or changing substance type) or joining a self‐help group than methods that involved changing friends, residence, or occupation/job/school. Certain patterns of self‐help tended to occur together (eg, changing substance frequency and dose), whereas others appeared more independent (eg, joining a self‐help group). Some self‐help approaches occurred mostly in association with other methods rather than alone (eg, changing occupation/job/school). More self‐help was associated with higher socioeconomic class, more relatives with substance use disorder, greater severity of substance use disorder, and more treatment for substance use disorder. Self‐help tends to occur more often after exposure to addicted relatives or addiction treatment. Clinicians and public adult education should promulgate self‐help methods in the general population.
Changing Patterns of Illicit Substance Use Among Schizophrenic Patients: 1984–1996
Authors: Patkar Ashwin A. , Alexander Robert C. , Lundy Allan , Certa Kenneth M.
Published: July 2002

Over 1,700 psychiatric emergency room visits of schizophrenic and schizoaffective patients between 1984 and 1996 were reviewed, and urine drug screens (UDS) were recorded. Illicit drug use increased significantly over the 12‐year period, with a large increase for cocaine (0% to 73% of positive UDS), a decline for amphetamines (60% to 0%), and a small increase for marijuana (0% to 27%). Opiate and sedative use remained unchanged. The results support the impression that cocaine use increased dramatically among urban schizophrenic patients beginning in 1988 and continuing to the present. Furthermore, cocaine seems to have replaced amphetamines as the preferred drug of abuse among schizophrenic persons following the crack epidemic.
Environmental intervention and water resource management in the history of the Mezzogiorno
Authors: Bevilacqua Piero
Published: July 2002

This article shows how the discovery of electrical energy that could be transmitted and used in industry triggered a huge effort to take advantage of Southern Italy's water resources and improve its natural environment. In the early years of the twentieth century, primarily through the initiative of Francesco Saverio Nitti, the great statesman and environmental expert, the rivers and forests of the South became an object of particular attention in that they were to be the central element in conservation measures whose aim was to produce cheap electricity, but which also necessarily involved reforestation, state control of forestry, the embankment of rivers and other changes. For southern reformers such plans were envisaged as the way to launch industrialization in the South.
Platelet monoamine oxidase (MAO) activity and alcoholism: is there a genuine association?
Authors: FARREN CONOR K.
Published: July 2002

Abstract Monoamine oxidase (MAO) is a particle‐bound flavoenzyme principally located in the outer mitochondrial membrane, which catalyzes the oxidative deamination of a variety of the amine transmitters in the central nervous system. There have been many reports from different groups around the world over the last 20 years that indicated a lower platelet MAO activity was associated with alcoholism. As there are multiple influences upon measured MAO activity, this article attempts to address each of the issues in turn for potential confounding of the reported association. These issues include: the duration of abstinence from alcohol, the substrate used for analysis, gender issues, association with different subtypes of alcoholics, the influence of other psychopathology, personality traits of alcoholics, the question of smoking, and proposed modes of transmission of MAO activity. The initial promise about MAO activity being a possible marker for alcoholism or a least a genetically predisposed subgroup has receded as the number of negative typology‐based studies increases. The failure to account for a major confounding variable, e.g. smoking and other minor but possibly vital confounds in almost all these studies leaves the whole hypothesis open to criticism. However, the possible association between personality traits that might predispose to some if not all substances of addiction to low MAO activity may make it possible to reframe the hypothesized association in the setting of a generalized predisposition to addictions in particular, and to psychopathology in general. Nonetheless the association remains of great interest and may yet yield vital genetic and clinical information.
A posteriori error estimator for a mixed finite element method for Reissner-Mindlin plate
Authors: Liberman Elsa
Published: July 2002

We present an a posteriori error estimator for a mixed finite element method for the Reissner-Mindlin plate model. The finite element method we deal with, was analyzed by Durán and Liberman in 1992 and can also be seen as a particular example of the general family analyzed by Brezzi, Fortin, and Stenberg in 1991. The estimator is based on the evaluation of the residual of the finite element solution. We show that the estimator yields local lower and global upper bounds of the error in the numerical solution in a natural norm for the problem, which includes the

H
1

H^1

norms of the terms corresponding to the deflection and the rotation and a dual norm for the shearing force. The estimates are valid uniformly with respect to the plate thickness.
The role of strand 1 of the C β‐sheet in the structure and function of α1‐antitrypsin
Authors: Bottomley Stephen P. , Lawrenson Isobel D. , Tew Deborah , Dai Weiwen , Whisstock James C. , Pike Robert N.
Published: July 2002

Serpins inhibit cognate serine proteases involved in a number of important processes including blood coagulation and inflammation. Consequently, loss of serpin function or stability results in a number of disease states. Many of the naturally occurring mutations leading to disease are located within strand 1 of the C β‐sheet of the serpin. To ascertain the structural and functional importance of each residue in this strand, which constitutes the so‐called distal hinge of the reactive center loop of the serpin, an alanine scanning study was carried out on recombinant α1‐antitrypsin Pittsburgh mutant (P1 = Arg). Mutation of the P10′ position had no effect on its inhibitory properties towards thrombin. Mutations to residues P7′ and P9′ caused these serpins to have an increased tendency to act as substrates rather than inhibitors, while mutations at P6′ and P8′ positions caused the serpin to behave almost entirely as a substrate. Mutations at the P6′ and P8′ residues of the C β‐sheet, which are buried in the hydrophobic core in the native structure, caused the serpin to become highly unstable and polymerize much more readily. Thus, P6′ and P8′ mutants of α1‐antitrypsin had melting temperatures 14 degrees lower than wild‐type α1‐antitrypsin. These results indicate the importance of maintaining the anchoring of the distal hinge to both the inhibitory mechanism and stability of serpins, the inhibitory mechanism being particularly sensitive to any perturbations in this region. The results of this study allow more informed analysis of the effects of mutations found at these positions in disease‐associated serpin variants.
A fast method for simulating the propagation of pulses radiated by a rectangular normal transducer into an elastic half-space
Authors: Gridin Dmitri
Published: July 2002

A new fast method for simulating the propagation of pulses radiated by a rectangular normal ultrasonic transducer which is directly coupled to an isotropic and homogeneous elastic half-space is proposed. First, the so-called two-tier approach introduced in Fradkin et al. [“The radiating near-field asymptotics of a time-harmonic circular normal ultrasonic transducer in an elastic half-space,” J. Acoust. Soc. Am. 104, 1178–1187 (1998)] and the uniform stationary phase method are used to obtain both nonuniform and uniform high-frequency asymptotics of the time-harmonic field. Then, the transient field is described by means of harmonic synthesis. The nonuniform asymptotics elucidate the physics and all the asymptotics give explicit dependence of the radiated waves on model parameters. The formulas are applicable in the radiating near field that is the near field with the evanescent wave zone excluded. The asymptotics involve in geometrical regions elementary and inside boundary layers, well-known special functions (Fresnel integral and generalized Fresnel integral). The code based on the uniform asymptotics has been tested in all regions against an exact numerical solution. It is at least 104 times faster but in many realistic cases the accuracy does not suffer. The trains of pulses generated by rectangular and circular transducers are compared.
A numerical method for vibro-acoustic problems with incompatible finite element meshes using B-spline functions
Authors: Guerich M. , Hamdi M. A.
Published: July 2002

This paper describes a new method for computing fluid–structure coupling with incompatible finite element meshes using uniform cubic B-spline functions (UCBFs). A modal approach is used which has the advantage of computing the individual structural and fluid mode shapes, using independent meshes. In order to compute the fluid–structure coupling for the incompatible meshes, it is necessary to interpolate the structure and fluid mode shapes over a common geometric mesh. This mesh is defined by the shell itself which is also interpolated by UCBF using a minimum number of geometric control nodes. New structural and fluid meshes are first derived from the geometric mesh by defining two different element multiplicities. An extrapolation algorithm is then developed to deduce the values of fluid and structure functions (displacement and pressure) over the two new meshes. The UCBFs are finally used to interpolate mode shapes of fluid and structure from the two previous meshes into a common mesh. Having the two new functions on the same common mesh provides the fluid–structure coupling for incompatible meshes. The method is illustrated for 2-D and 3-D coupled problems corresponding to shells of revolution, plates, and 3-D shells.
Ultrasonic surface waves above a doubly periodic grating
Authors: Allard J. F. , Kelders L. , Lauriks W.
Published: July 2002

Ultrasonic surface waves above a layer indented by a doubly periodic set of holes having a square-shaped cross section are studied experimentally. Measurements are compared with predictions obtained from a modal model inspired by the theory of the diffraction of electromagnetic waves. Predictions obtained with the modal model and a simplified model where the periodic structure is replaced by an impedance plane are compared.
Applications of the causality condition to one-dimensional acoustic reflection problems
Authors: McDaniel J. Gregory
Published: July 2002

The causality condition is examined as a means of determining frequency-domain information about a submerged object from a partial knowledge of its acoustic reflection characteristics. A one-dimensional problem is considered in which an acoustic wave reflects from an object that is described by the impedance it presents to the fluid. Two new applications of the causality condition to the frequency-domain analysis of this problem are investigated and illustrated by numerical examples. In each application, the causality condition is used to find the object’s complex impedance from a knowledge of the reflected wave’s magnitude. The first application is to experimental studies where one desires a knowledge of an object’s complex impedance but practical limitations only allow a measurement of the reflected wave amplitude. Analysis shows that the causality condition may be used to determine the phase of the reflected wave, and hence the object’s impedance, if the reflection coefficient is minimum phase. When this is true, examples suggest that the phase of the reflection coefficient may be accurately determined from the causality condition even in the presence of noise and band-limited data. The second application is to design situations, where one wishes to create an object that reflects sound with a specified frequency-dependent magnitude. The causality condition may aid the designer by providing a knowledge of all causal object impedances that produce the same reflection coefficient magnitude. A numerical example is presented in which a variety of causal object impedances produce the same reflection coefficient magnitude over an infinite frequency range.
Experimental observation of pseudocapillary and Rayleigh modes on soft gels
Authors: Choi P.-K. , Jyounouti E. , Yuuki K. , Onodera Y.
Published: July 2002

Surface wave propagation on agarose gels was studied by measuring the velocity of mechanically excited pulsed waves around sol–gel transition temperature. Two independent modes were clearly observed in the gel state. The velocities of the two modes were successfully fitted to the theoretical calculation of pseudocapillary and Rayleigh modes which were predicted by Onodera and Choi.
Linear and Nonlinear Viscoelastic Measurements, Ultimate Properties, and Processability of Raw Elastomers
Authors: Nakajima N. , Collins E. A.
Published: July 2002

For a given piece of raw elastomer the laboratory measurements that must be made in order to determine its processability and the minimum effort required for a thorough characterization of the material behavior over the temperature, time-scale, and deformation range of practical interest are discussed. Interconversion of time or temperature dependence of materials at small deformations or conversions of one type of measurement to another in the linear region of viscoelastic behavior have been well documented. However, these schemes have not been useful in analysis of processability where materials undergo large deformations well into the nonlinear region. This study demonstrates the applicability of a new strain-time correspondence principle by which measurements at either small or large deformations may be calculated from each other. Also considered is how ultimate properties affect processability. This question is illustrated using milling as an example and by contrasting the behavior of elastomers on the mill to the failure envelope expressed as a modulus-strain curve at failure. Further, the failure envelope is represented by a simple equation. The nondestructive part of the visoelastic behavior may be represented by a master curve which includes variation of temperature, time, and magnitude of deformation. The intercepts between the master curve and failure envelope define the ultimate properties.
The Rheology of Solid Polymers Subjected to Large Deformations
Authors: Titomanlio G. , Anshus B. E. , Astarita G. , Metzner A. B.
Published: July 2002

Experimental data on the deformation of polyethylene terephthalate over a range of temperatures below its melting point are presented. The observed behavior is of the type usually considered as “plastic”; in spite of this, it is described by a modification of a constitutive description initially proposed for molten polymers by Tanner and Simmons. The constitutive description proposed here correctly portrays the observed behavior without reference to classical plasticity theory, and is of a type which allows in principle to predict the behavior of the material for every conceivable deformation history.
Uniformly valid approximations for the conformational integrals resulting from Gaussian closure in the Hookean dumbbell model with internal viscositya)
Authors: Sureshkumar R. , Beris Antony N.
Published: July 2002

We consider a computationally more efficient calculation of the conformational integrals resulting from applying a Gaussian closure to evaluate the higher moments of the end-to-end vector, Q, in the Hookean dumbbell model with internal viscosity. First, these integrals are expressed as functions of the eigenvalues of the chain conformation tensor 〈QQ〉. Subsequently, they are evaluated analytically in certain characteristic limiting cases. These results are then used to construct uniformly valid approximations for the integrals. The relative error incurred in these approximations, as measured by a comparison with the results obtained through a direct numerical evaluation, has been shown to be uniformly small, i.e., less than a few percent, in the entire parameter space. Further validation of the approximations to the integrals is provided from the results obtained for the shear viscosity and first normal stress difference as a function of shear rate in a steady, homogeneous shear flow which are in excellent agreement with those provided in the literature also using the Gaussian closure. The approximations are subsequently used to predict the response of the model to the startup of simple shear flow. Excellent agreement is found with the previously reported results using the Gaussian closure in this case as well. Most important, the reduction of computational workload through the use of the approximations to the conformational integrals makes it possible for this model to be used in more complicated flow simulations. As an illustrative example, we provide numerical results for the flow variables in a steady channel Poiseuille flow.
Structure determination and Rietveld refinement of Y0.8Ca0.2Ba1.8La0.2Cu3Oy
Authors: Wu X. S. , Wang F. Z. , Jiang S. S.
Published: July 2002

The structure of the new Y0.8Ca0.2Ba1.8La0.2Cu3Oy (YBLCO) compound was obtained at 298 K from X-ray powder diffraction data and refined by the Rietveld technique. YBLCO has a structure isotypical with YBa2Cu3Oy (YBCO) at room temperature. The crystal data are: Y0.81Ca0.19Ba1.8La0.2Cu3O7.08, Mw=657.69, orthorhombic system, space group Pmmm, a=3.8731(1) Å, b=3.8249(1) Å, c=11.6602(3) Å, V=172.740(13) Å3, Z=1, dx=6.325 g/cm3; the structure was refined with 37 parameters to Rwp=7.66%, Rp=5.86%, and Rexp=5.11% for 2001 data points. Moreover, the proportions of Ca and La were refined to be 0.19 and 0.2, in agreement with the stoichiometric proportion of 0.2.
Association Between Implementation of a Geriatric Trauma Clinical Pathway and Changes in Rates of Delirium in Older Adults With Traumatic Injury
Authors: Park Caroline , Bharija Ankur , Mesias Matthew , Mitchell Ann , Krishna Purnima , Storr-Street Nannette , Brown Alyssa , Martin Marina , Lu Amy C. , Staudenmayer Kristan L.
Published: June 2022

Importance

Older adults (age ≥65 years) are at risk for high rates of delirium and poor outcomes; however, how to improve outcomes is still being explored.

Objective

To assess whether implementation of a geriatric trauma clinical pathway was associated with reduced rates of delirium in older adults with traumatic injury.

Design, Setting, and Participants

A retrospective case-control study of electronic health records of patients aged 65 years or older with traumatic injury from 2018 to 2020 was conducted at a single level I trauma center. Eligible patients were age 65 years or older admitted to the trauma service and who did not undergo an operation.

Intervention

The implementation of a clinical pathway based on geriatric best practices, which included order sets, guidelines, automated consultations, and escalation pathways executed by a multidisciplinary team.

Main Outcomes and Measures

The primary outcome was delirium. The secondary outcome was hospital length of stay. Process measures for pathway compliance were also assessed.

Results

Of the 859 eligible patients, 712 patients were included in the analysis (442 [62.1%] in the baseline group; 270 [37.9%] in the postimplementation group; mean [SD] age: 81.4 [9.1] years; 394 [55.3%] were female). The mechanism of injury was not different between groups, with 247 in the baseline group (55.9%) and 162 in the postimplementation group (60.0%) (P = .43) experiencing a fall. Injuries were minor or moderate in both groups (261 in baseline group [59.0%] and 168 in postimplementation group [62.2%]; P = .87). The adjusted odds ratio for delirium in the postimplementation cohort was 0.54 (95% CI, 0.37-0.80; P < .001). Goals of care documentation improved significantly in the postimplementation cohort vs the baseline cohort with regard to documented goals of care notes (53.7% in the postimplementation cohort [145 of 270] vs 16.7% in the baseline cohort [74 of 442]; P < .001) and a shortened time to discussion from presenting to the emergency department (36 hours in the postimplementation cohort vs 50 hours in the baseline cohort; P = .03).

Conclusions and Relevance

In this study, implementation of a multidisciplinary clinical pathway for injured older adults at a single level I trauma center was associated with improved care and clinical outcomes. Interventions such as these may have utility in this vulnerable population, and findings should be confirmed across multiple centers.
Fluorescence CLEM in biology: historic developments and current super‐resolution applications
Authors: van den Dries Koen , Fransen Jack , Cambi Alessandra
Published: June 2022

Correlative light and electron microscopy (CLEM) is a powerful imaging approach that allows the direct correlation of information obtained on a light and an electron microscope. There is a growing interest in the application of CLEM in biology, mainly attributable to technical advances in field of fluorescence microscopy in the past two decades. In this review, we summarize the important developments in CLEM for biological applications, focusing on the combination of fluorescence microscopy and electron microscopy. We first provide a brief overview of the early days of fluorescence CLEM usage starting with the initial rise in the late 1970s and the subsequent optimization of CLEM workflows during the following two decades. Next, we describe how the engineering of fluorescent proteins and the development of super‐resolution fluorescence microscopy have significantly renewed the interest in CLEM resulting in the present application of fluorescence CLEM in many different areas of cellular and molecular biology. Lastly, we present the promises and challenges for the future of fluorescence CLEM discussing novel workflows, probe development and quantification possibilities.
Practical Graphene Technologies for Electrochemical Energy Storage
Authors: Jia Yiran , Zhang Jun , Kong Debin , Zhang Chen , Han Daliang , Han Junwei , Tao Ying , Lv Wei , Yang Quan‐Hong
Published: June 2022

Killer applications of graphenes are always being pursued and critical for realizing industrialization. Since the first attempt for using graphene in lithium‐ion batteries, graphene has been demonstrated as a key component in electrochemical energy storage technologies. However, the unique roles of graphene beyond traditional carbon in energy storage are still unclear and need to be clarified. Here, this review starts with a glance over the history of graphene in electrochemical energy storage applications, and then briefly discusses the different dimensional graphenes and representative synthesis methods that are believed to be essential for energy‐related applications. Importantly, three typical graphene technologies showing their practical potentials in electrochemical energy storage are illustrated in details, including the uses as conductive additives, in heat dissipation, and compact energy storage. The methodologies of science and technology for the above applications are systematically elaborated. This review also gives perspectives on the opportunities and challenges of practical graphene technologies in electrochemical energy storage. The authors expect this review to provide a comprehensive view of how graphene can be uniquely and practically used for electrochemical energy storage, paving the way for promoting the development of the graphene industry.
Photo‐Responsive Water Filtration Membranes Based on Polymerizable Columnar Liquid Crystals with Azo Moieties
Authors: Marín San Román Patricia P. , Sijbesma Rint P.
Published: June 2022

New materials developed in the last years promise to contribute significantly to the preparation of membranes with improved performance in water filtration. Specifically, the use of dynamic‐responsive systems provides reversibility of the membrane properties. In this work, a reversible photo‐switchable membrane based on templated liquid crystals is presented. Crosslinking of a columnar network, formed by the self‐assembly of a discotic supramolecular complex with a photo‐responsive moiety, results in a switchable filtration membrane. The azo groups in the membrane undergo a photoinduced trans‐cis isomerization by irradiation with 365 nm light and relax back to the cis isomer with a lifetime of 5.7 h or within a few minutes by irradiation at 455 nm. The membranes have a light‐induced reversible change in the water permeability and molecular weight cut off of poly (ethylene glycol). The effective pore size of the trans isomer (1.2 nm) increases to 1.4 nm for the cis isomer. Rejection of the organic dye Rhodamine B is reversibly switched between 50 and 85% by alternating irradiation at 365 nm and 455 nm. The reversible and specific switching demonstrates the potential of this system for light‐controlled separation in nanoporous membranes.
Electrocatalyst Modulation toward Bidirectional Sulfur Redox in Li–S Batteries: From Strategic Probing to Mechanistic Understanding
Authors: Shi Zixiong , Ding Yifan , Zhang Qiang , Sun Jingyu
Published: June 2022

Electrocatalyst design has stimulated considerable attention and strenuous effort to tackle a multitude of detrimental issues in lithium–sulfur (Li–S) systems, mainly pertaining to the severe polysulfide shuttle effect and sluggish sulfur redox kinetics. In this context related advances in expediting bidirectional sulfur reactions have lately surged. Nonetheless, the structure–activity correlation and electrocatalytic mechanism remain rather elusive, as a result of elusory active sites, complicated aprotic environments, and multistep conversion pathways. This review summarizes burgeoning strategies in the modulation of heterogeneous and homogeneous electrocatalysts, wherein the advanced electrokinetic measurements, operando instrumental probing, and theoretical simulations are elucidated with an emphasis on deciphering bidirectional sulfur electrochemistry. Notably, a “3s” electrocatalysis model is proposed to deepen the mechanistic understanding in this realm. Finally, a development roadmap is sketched and future research layouts are discussed, aiming in essence, to realize favorable bidirectional redox kinetics and ultimately bridge the gap between reality and ideal systems in working Li–S batteries.
Site‐specific fabrication of gold nanocluster‐based fluorescence photoswitch enabled by the dual roles of albumin proteins
Authors: Zhong Wencheng , Yan Xiaojian , Qu Shaohua , Shang Li
Published: June 2022

Fluorescence photoswitch is becoming increasingly desirable for many applications, but its controllable fabrication still remains challenging yet. In this paper, a new strategy is proposed to fabricate fluorescence photoswitch by harnessing dual roles of albumin proteins as both photochrome carriers and biotemplates of fluorophore. As an example, we demonstrated the successful fabrication of a fluorescence photoswitch by incorporating both the photochromic diarylethene dye (CMTE) and red‐emitting fluorescent gold nanoclusters (AuNCs) into the specific domains of bovine serum albumin (BSA) in a highly controllable manner. Detailed spectral and photophysical characterisation showed that CMTE well‐retains the photochromic properties within the CMTE–BSA–AuNC construct, although its photoconversion rate is slightly retarded. Different from previously reported photoswitches, the fluorescence of the present system is mainly modulated via the inner filter effect (IFE) mechanism, which exhibits high switching efficiency with an on–off ratio up to 90%, reversible fluorescence response and good antifatigue performance. This work provides a new, generable albumin protein‐assisted strategy of fabricating advanced fluorescence photoswitch, which can find wide applications in biological, optical and information fields.
Umpolung in a Pair of Cobalt(III) Terminal Imido/Imidyl Complexes
Authors: Mao Weiqing , Fehn Dominik , Heinemann Frank W. , Scheurer Andreas , van Gastel Maurice , Jannuzzi Sergio A. V. , DeBeer Serena , Munz Dominik , Meyer Karsten
Published: June 2022

Reaction of the CoI complex [(TIMMNmes)CoI](PF6) (1) (TIMMNmes=tris‐[2‐(3‐mesityl‐imidazolin‐2‐ylidene)‐methyl]amine) with mesityl azide yields the CoIII imide [(TIMMNmes)CoIII(NMes)](PF6) (2). Oxidation of 2 with [FeCp2](PF6) provides access to a rare CoIII imidyl [(TIMMNmes)Co(NMes)](PF6)2 (3). Single‐crystal X‐ray diffractometry and EPR spectroscopy confirm the molecular structure of 3 and its S=
ground state. ENDOR, X‐ray absorption spectroscopy and computational analyses indicate a ligand‐based oxidation; thus, an imidyl‐radical electronic structure for 3. Migratory insertion of one ancillary NHC to the imido ligand in 2 gives the CoI N‐heterocyclic imine (4) within 12 h. Conversely, it takes merely 0.5 h for 3 to transform to the CoII congener (5). The migratory insertion in 2 occurs via a nucleophilic attack of the imido ligand at the NHC to give 4, whereas in 3, a nucleophilic attack of the NHC at the electrophilic imidyl ligand yields 5. The reactivity shunt upon oxidation of 2 to 3 confirms an umpolung of the imido ligand.
Ligand‐Shell Engineering of a Au28 Nanocluster Boosts Electrocatalytic CO2 Reduction
Authors: Wang Jie , Xu Fan , Wang Zhao‐Yang , Zang Shuang‐Quan , Mak Thomas C. W.
Published: June 2022

Subtle tailoring of gold nanoclusters (NCs) could significantly change their physicochemical properties. However, direct comparison of the catalytic performance of gold NCs with identical metal cores but distinct ligand shells is rarely elucidated. In this work, a novel gold NC, Au28(C2B10H11S)12(tht)4Cl4 (Au28‐S), was isolated by a facile self‐reducing synthesis. Au28‐S adopts an identical Au28 metal framework to that of the reported alkynyl‐protected Au28‐C. The different protective layers lead to distinctions in their electronic structure and optical properties. Furthermore, Au28‐S shows better catalytic activity for the electrochemical reduction of CO2 to CO. Theoretical calculations identified the active sites and shed light on the catalytic mechanism to elucidate the different catalytic performances. This work provides an ideal platform to study the protective layer‐activity relationship of gold NCs, and may also provide guidance in the design of metal NC‐based catalysts.