bluuebunny/crossref_metadata_2025 huggingface dataset:
Relaxation of the structure of simple metal ion complexes in aqueous solutions at up to supercritical conditions
Authors: Mayanovic Robert A. , Jayanetti Sumedha , Anderson Alan J. , Bassett William A. , Chou I-Ming
Published: December 2002

Our previous x-ray absorption fine structure studies of aqueous solutions revealed relaxation of the structure of complexes of Zn2+, Fe2+, La3+, and Yb3+ ions with increasing temperature. These complexes in general exhibit reduction of cation–ligand bond lengths with increasing temperature due to hydrogen bond breaking and loss of water of solvation. Because this results in an overall lowering of the equilibrium state of the complex, we refer to the variation of the structure as relaxation. In the case of M(H2O)mn+ (m=6–9 at room temperature, n=2, 3) aquo ion complexes (M: Zn, Fe, La, Yb), there is a similar reduction in the number of coordinating water molecules with temperature. The relaxation of the structure is shown to result in a lowering of the binding energy per cation–ligand pair of a complex with increasing temperature. A comparison of the rate of structure relaxation with temperature, which is framed in the context of volume thermoelastic constriction, shows this quantity to have a gradual and direct dependence on the difference in Pauling’s electronegativity of the cation–ligand pairs making up the ion complex.
Advantages of using piezoelectric quantum structures for photovoltaics
Authors: Romero Manuel J. , Al-Jassim Mowafak M.
Published: December 2002

Recent efforts to increase the photoconversion efficiencies of solar cells have been made by using quantum wells and quantum dots. The benefits of piezoelectric effects for photoconversion in these devices are discussed. By the appropriate use of piezoelectric fields, photogenerated carriers are more efficiently extracted and carrier capture can be prevented. Lastly, the impact of the piezoelectric field on the design of solar cells is discussed.
Model of plastic deformation for extreme loading conditions
Authors: Preston Dean L. , Tonks Davis L. , Wallace Duane C.
Published: December 2002

We present a model of metallic plastic flow suitable for numerical simulations of explosive loading and high velocity impacts. The dependence of the plastic strain rate on applied stress at low strain rates is of the Arrhenius form but with an activation energy that is singular at zero stress so that the deformation rate vanishes in that limit. Work hardening is modeled as a generalized Voce law. At strain rates exceeding 109 s−1, work hardening is neglected, and the rate dependence of the flow stress is calculated using Wallace’s theory of overdriven shocks in metals [D.C. Wallace, Phys. Rev. B 24, 5597 (1981); 24, 5607 (1981)]. The thermal-activation regime is continuously merged into the strong shock limit, yielding a model applicable over the 15 decades in strain rate from 10−3 to 1012 s−1. The model represents all aspects of constitutive behavior seen in Hopkinson bar and low-rate data, including a rapid increase in the constant-strain rate sensitivity, with 10% accuracy. High-pressure behavior is controlled by the shear modulus, G(ρ,T), and the melting temperature, Tm(ρ). There are eleven material parameters in addition to G(ρ,T) and Tm(ρ). Parameters for Cu, U, Ta, Mo, V, Be, 304 SS, and 21-6-9 SS are provided.
Microcanonical unimolecular rate theory at surfaces. I. Dissociative chemisorption of methane on Pt(111)
Authors: Bukoski A. , Blumling D. , Harrison I.
Published: December 2002

A model of gas–surface reactivity is developed based on the ideas that (a) adsorbate chemistry is a local phenomenon, (b) the active system energy of an adsorbed molecule and a few immediately adjacent surface atoms suffices to fix microcanonical rate constants for surface kinetic processes such as desorption and dissociation, and (c) energy exchange between the local adsorbate–surface complexes and the surrounding substrate can be modeled via a Master equation to describe the system/heat reservoir coupling. The resulting microcanonical unimolecular rate theory (MURT) for analyzing and predicting both thermal equilibrium and nonequilibrium kinetics for surface reactions is applied to the dissociative chemisorption of methane on Pt(111). Energy exchange due to phonon-mediated energy transfer between the local adsorbate–surface complexes and the surface is explored and estimated to be insignificant for the reactive experimental conditions investigated here. Simulations of experimental molecular beam data indicate that the apparent threshold energy for CH4 dissociative chemisorption on Pt(111) is E0=0.61 eV (over a C–H stretch reaction coordinate), the local adsorbate–surface complex includes three surface oscillators, and the pooled energy from 16 active degrees of freedom is available to help surmount the dissociation barrier. For nonequilibrium molecular beam experiments, predictions are made for the initial methane dissociative sticking coefficient as a function of isotope, normal translational energy, molecular beam nozzle temperature, and surface temperature. MURT analysis of the thermal programmed desorption of CH4 physisorbed on Pt(111) finds the physisorption well depth is 0.16 eV. Thermal equilibrium dissociative sticking coefficients for methane on Pt(111) are predicted for the temperature range from 250–2000 K. Tolman relations for the activation energy under thermal equilibrium conditions and for a variety of “effective activation energies” under nonequilibrium conditions are derived. Expressions for the efficacy of sticking with respect to normal translational energy and vibrational energy are found. Fractional energy uptakes, fj, defined as the fraction of the mean energy of the complexes undergoing reaction that derives from the jth degrees of freedom of the reactants (e.g., molecular translation, vibration, etc.) are calculated for thermal equilibrium and nonequilibrium dissociative chemisorption. The fractional energy uptakes are found to vary with the relative availability of energy of different types under the specific experimental conditions. For thermal dissociative chemisorption at 500 K the fractional energy uptakes are predicted to be ft=13%, fr=18%, fv=33%, and fs=36%. For this equilibrium scenario relevant to catalysis, the incident gas molecules supply the preponderance of energy used to surmount the barrier to chemisorption, fg=ft+fv+fr=64%, but the surface contribution at fs=36% remains significant.
Radio-frequency photocathode guns triggered by free electron laser light
Authors: Dattoli G. , Giannessi L. , Serafini L.
Published: December 2002

We discuss an example of a free electron laser dedicated to the triggering of a photocathode gun. The advantages offered by such a solution with respect to conventional systems are analyzed.
Path integrals evaluation in two-dimensional de Sitter space
Authors: Grinchuk A. V. , Ushakov E. A.
Published: December 2002

The propagator in de Sitter space is calculated based on the path integrals. The method of evaluation of path integrals for particles with spin is proposed. The calculations are compared with the quantum mechanical ones.
1.31 μm GaAsSb resonant-cavity-enhanced separate absorption, charge and multiplication avalanche photodiodes with low noise
Authors: Sun X. , Wang S. , Zheng X. G. , Li X. , Campbell J. C. , Holmes A. L.
Published: December 2002

A GaAsSb resonant-cavity-enhanced avalanche photodiode with separate absorption, charge, and multiplication regions has been demonstrated. The peak external quantum efficiency was 36% for device with two pairs of λ/4 MgF2/ZnSe layers as the dielectric top mirror and the full width at half maximum was 7 nm. The breakdown occurred at 24 V and a gain up to 40 was obtained. At 90% of the breakdown, the dark current was 5 nA. The device also exhibited very low multiplication noise and keff was approximately 0.1.
Platinum-related defects in silicon observed by optical absorption measurements
Authors: Fukata N. , Suezawa M. , Saito K. , Kasuya A.
Published: December 2002

We investigated platinum (Pt)-related defects in silicon (Si) based on the measurement of their optical absorption and found optical absorption peaks related to Pt clusters. Pt and H were separately doped in FZ–Si by heating at 1000–1300 °C followed by quenching in water. Optical absorption spectra were measured at about 5 K with a Fourier transform infrared spectrometer. In a specimen doped with a higher concentration of H than of Pt, we observed optical absorption peaks due to four types of Pt–H complexes. In specimens with a higher concentration of Pt than of H, peaks were observed in the region from 1300 to 1700 cm−1. Based on the peak shift due to the hydrogen isotope and the dependence on excitation energy and the annealing behavior, these peaks are thought to be due to the electronic transitions of Pt-related defects such as Pt clusters, rather than the local vibrational modes of H. The defect centers which gave rise to optical absorption at about 1301, 1318, 1452, and 1474 cm−1 were IR-active centers under illumination and the optical threshold energy was determined to be about 0.34 eV by applying Lucovsky’s model [Solid State Commun. 3, 299 (1965)].
Resonance vibration of amorphous SiO2 nanowires driven by mechanical or electrical field excitation
Authors: Dikin D. A. , Chen X. , Ding W. , Wagner G. , Ruoff R. S.
Published: December 2002

In this work, we have used the mechanical resonance method to determine the bending modulus of amorphous SiO2 nanowires and to study an electron charge trapping effect that occurs in these nanowires. For uniform amorphous nanowires having diameter ∼100 nm and length over 10 μm, the fit modulus values cluster near 47 GPa; this value is lower than the commonly accepted value of ∼72 GPa for fused silicon oxide (glass) fibers. For some SiO2 nanowires, we observed up to three closely spaced resonances that are a result of the nanowire anisotropy. We have compared the resonance vibration of nanowires driven by mechanical and also ac electrical field loading. All of the measurements were done inside the chamber of a scanning electron microscope where the nanowires were under bombardment of a flux of ∼3 keV energy electrons. By watching the interaction between the ac electrical field and exposed nanowire when driven at resonance frequency, we have observed significant charge trapping in the nanowires. The combination of charge trapping and decay time was nonuniformly distributed along the nanowire. This suggests a nondestructive method that can be used for studying defects in certain types of nanostructures.
Two-dimensional hexagonal-shaped microcavities formed in a two-dimensional photonic crystal on an InP membrane
Authors: Monat C. , Seassal C. , Letartre X. , Regreny P. , Gendry M. , Romeo P. Rojo , Viktorovitch P. , Le Vassor d’Yerville M. , Cassagne D. , Albert J. P. , Jalaguier E. , Pocas S. , Aspar B.
Published: December 2002

We present simulation and experimental results on hexagonal-shaped microcavities formed in two-dimensional (2D) photonic crystals (PC’s). The PC structures, realized with InP-based materials, are studied in two configurations : Air-suspended membranes (A type) and membranes supported by silica (S type). The optical properties of these microcavities are analyzed through photoluminescence experiments. Plane-wave expansion method calculations provide simulation results that are consistent with experimental data. The influence on spectral properties of various parameters, such as cavity size or air filling factor (f), is thoroughly analyzed, and their effect on resonator loss mechanisms is extracted, to give guidance for further PC laser improvement, e.g., threshold reduction.
Thermodynamic model of nucleation and growth of plasma deposited microcrystalline silicon
Authors: Robertson John
Published: December 2002

Hydrogen dilution is used to promote the nucleation and growth of microcrystalline Si (μc–Si) by plasma-enhanced chemical-vapor deposition. The free energy of μc–Si and hydrogenated amorphous silicon (a–Si:H) is analyzed as a function of the Si:H composition in order to understand the effect of hydrogen dilution. It is shown that increasing the hydrogen content of the a−SiHx precursor phase increases the relative stability of μc–Si slightly, but strongly increases the driving force for nucleation. The higher stability of μc–Si is the fundamental origin of the higher etch rates of a–Si:H, while surface mobility models do not account for subsurface nucleation of μc–Si.
Interface states at ZnSe/Ge heterojunctions: the role of atomic interdiffusion and disorder
Authors: Peressi M. , Favot F. , Cangiani G. , Baldereschi A.
Published: December 2002

The origin of electronic states localized at ZnSe/Ge (110) interface is investigated by means of ab initio pseudopotential calculations. Some selected interface configurations are considered, one corresponding to the abrupt interface and others corresponding to partially disordered interfaces, with Zn-Ge or Se-Ge swaps. Remarkably, the existence of interface electronic states within the heterojunction band gap critically depends on the atomic-scale morphology of the interface: unlike the abrupt case, disordered interfaces exhibit localized states extending over the whole interface Brillouin zone. The presence of interfacial density of states, experimentally detectable, is therefore an indication of disorder and atomic interdiffusion.
Malformations of the craniofacial region: Evolutionary, embryonic, genetic, and clinical perspectives
Authors: Cohen M. Michael
Published: December 2002

Malformations of the craniofacial region are reviewed with respect to evolutionary, embryonic, genetic, and clinical perspectives under the following headings: How Old Is Our Head?, Head Organization Genes, Genetics of Craniofacial Anomalies, Craniofacial Derivatives, Anencephaly, Cephalocele, Holoprosencephaly, Craniosynostosis, Hypertelorism, Branchial Arch Anomalies, and Orofacial Clefting. © 2002 Wiley‐Liss, Inc.
Clinical and genetic heterogeneity in frontometaphyseal dysplasia: Severe progressive scoliosis in two families
Authors: Morava Éva , Illés Tamás , Weisenbach János , Kárteszi Judit , Kosztolányi György
Published: December 2002

Frontometaphyseal dysplasia is a rare genetic syndrome affecting the skeletal system and connective tissue. It is believed to be inherited as an X‐linked trait. Features of frontometaphyseal dysplasia overlap with other skeletal dysplasias. Prominent supraorbital ridges, radiologic evidence of cranial hyperostosis, and flared metaphyses are characteristic. Scoliosis, a rare associated finding, is usually mild, and familial progressive scoliosis has not been reported so far. The skeletal dysplasia and the associated clinical findings show significant intra‐ and interfamilial variability. The syndrome has been suggested to be an allelic variant of the Melnick‐Needles osteodysplasty, an X‐linked (dominant) entity. We present two families with frontometaphyseal dysplasia, in which both males and females showed the facial and skeletal features of the syndrome in association with progressive scoliosis. Some of the affected members also had hearing loss and urogenital anomalies, supporting the existence of the recently suggested entity “fronto‐otopalatodigital‐osteodysplasty syndome”. © 2002 Wiley‐Liss, Inc.
Mature myelin basic protein‐expressing oligodendrocytes are insensitive to kainate toxicity
Authors: Rosenberg Paul A. , Dai Weimin , Gan Xiao Dong , Ali Sanjida , Fu Jennifer , Back Stephen A. , Sanchez Russell M. , Segal Michael M. , Follett Pamela L. , Jensen Frances E. , Volpe Joseph J.
Published: December 2002

We examined the vulnerability to excitotoxicity of rat oligodendrocytes in dissociated cell culture at different developmental stages. Mature oligodendrocytes that express myelin basic protein were resistant to excitotoxic injury produced by kainate, whereas earlier stages in the oligodendrocyte lineage were vulnerable to this insult. To test the hypothesis that the sensitivity of immature oligodendrocytes and the resistance of mature oligodendrocytes to kainate toxicity were due to differences in membrane responsiveness to kainate, we used whole‐cell patch‐clamp recording. Oligodendrocyte precursors in cultures vulnerable to kainate toxicity responded to 500 μM kainate with large inward currents, whereas mature myelin basic protein‐expressing oligodendrocytes in cultures resistant to kainate toxicity showed no clear response to application of this agonist. We assayed expression of glutamate receptor subunits (GluR) ‐2, ‐4, ‐6, ‐7, and KA2 using immunoblot analysis and found that expression of all of these glutamate receptors was significantly down‐regulated in mature oligodendrocytes. These results suggest a striking developmental regulation of glutamate receptors in oligodendrocytes and suggest that the vulnerability of oligodendrocytes to non‐ N‐methyl‐D‐aspartate receptor‐mediated excitotoxicity might be much greater in developing oligodendrocytes than after the completion of myelination. © 2002 Wiley‐Liss, Inc.
Traumatic brain injury‐induced acute gene expression changes in rat cerebral cortex identified by GeneChip analysis
Authors: Raghavendra Rao Vemuganti L. , Dhodda Vinay K. , Song Guoqing , Bowen Kellie K. , Dempsey Robert J.
Published: December 2002

Proper CNS function depends on concerted expression of thousands of genes in a controlled and timely manner. Traumatic brain injury (TBI) in mammals results in neuronal death and neurological dysfunction, which might be mediated by altered expression of several genes. By employing a CNS‐specific GeneChip and real‐time polymerase chain reaction (PCR), the present study analyzed the gene expression changes in adult rat cerebral cortex in the first 24 hr after a controlled cortical impact injury. Many functional families of genes not previously implicated in TBI‐induced brain damage are altered in the injured cortex. These include up‐regulated transcription factors (SOCS‐3, JAK‐2, STAT‐3, CREM, IRF‐1, SMN, silencer factor‐B, ANIA‐3, ANIA‐4, and HES‐1) and signal transduction pathways (cpg21, Narp, and CRBP) and down‐regulated transmitter release mechanisms (CITRON, synaptojanin II, ras‐related rab3, neurexin‐1β, and SNAP25A and ‐B), kinases (IP‐3‐kinase, Pak1, Ca2+/CaM‐dependent protein kinases), and ion channels (K+channels TWIK, RK5, X62839, and Na+channel I). In addition, several genes previously shown to play a role in TBI pathophysiology, including proinflammatory genes, proapoptotic genes, heat shock proteins, immediate early genes, neuropeptides, and glutamate receptor subunits, were also observed to be altered in the injured cortex. Real‐time PCR analysis confirmed the GeneChip data for many of these transcripts. The novel physiologically relevant gene expression changes observed here might explain some of the molecular mechanisms of TBI‐induced neuronal damage. © 2002 Wiley‐Liss, Inc.
Source Regions and Formation of the Loess Sediments on the High Mountain Regions of Northwestern China
Authors: Sun Jimin
Published: December 2002

Loess on the high mountains of northwestern China is largely controlled by the topographic features, distributed mainly on the northern slopes of the Tianshan and Kunlun Mountains as well as in the Ili Valley (between the northern and central Tianshan ranges). Loess distributed in different regions has different ages, with the oldest (early Pleistocene) loess occurring in the Ili Valley. Geochemical, mineralogical and granulometric analyses demonstrate that the loess in the three different regions has different provenance. The loess on the northern Tianshan and Kunlun Mountains is mainly derived from the Junggar and Taklimakan Deserts, respectively, whereas the loess in the Ili Valley is derived mainly from the Sary–Ishikotrau Desert located in the Republic of Kazakhstan. However, these deserts serve mostly as holding areas for the silts rather than original source regions. The production of the silt-sized particles is mainly associated with glacial abrasion and tectonic-induced rock denudation. Thus, the loess in the studied regions can be described as “mountainous” loess rather than simply “glacial” loess or “desert” loess. It is unlikely that the mechanisms of loess formation are the same in different regions, given their dependence on specific geomorphological conditions and associated processes.
Ring and zipper formation is the key to understanding the structural variety in all‐β proteins
Authors: Koike Ryotaro , Kinoshita Kengo , Kidera Akinori
Published: December 2002

A novel structural classification of β proteins is presented from the viewpoint of the ring‐shaped structure and the zipper‐like contact pattern, based on the fact that 92% and 60% of β proteins have the ring topology and the zippered contact pattern, respectively. We discuss the implication of the unexpectedly high preference for the ring and zippered structures in connection with the folding process of β proteins.
Belief systems as coping factors for traumatized refugees: a pilot study
Authors: Brune Michael , Haasen Christian , Krausz Michael , Yagdiran Oktay , Bustos Enrique , Eisenman David
Published: December 2002

The severity of traumatization seems to correlate with a more severe course of post-traumatic stress disorder (PTSD) (and other post-traumatic disorders), while firm belief systems have been found to be a protective factor against post-traumatic disorders. This study sought to determine the role of belief systems in the outcome of psychotherapy for traumatized refugees. The charts of 141 consecutively treated refugees were evaluated retrospectively. A firm belief system was found to be an important predictor for a better therapy outcome. The importance of a firm belief system as a coping factor, which should be used as an instrument in therapy, is discussed. © 2002 Éditions scientifiques et médicals Elsevier SAS
2001 INVITED ADDRESS: The Mystery of Human Context and Coping: An Unraveling of Clues
Authors: Moos Rudolf H.
Published: December 2002

Community and clinical psychology share a fundamental focus: to understand the interplay between human contexts, coping, and adaptation. To highlight recent progress in this area, I offer a guiding conceptual framework and discuss 8 propositions about environment and coping. The propositions consider such issues as patterns of social climate and coping and their links to personal development and dysfunction, the connections between ongoing life circumstances and intervention programs, the role of personal characteristics in matching individuals and environments, and the value of placing specific settings in an ecological context. I then focus on 8 enigmas, such as how to identify conceptually unifying dimensions of diverse social contexts, how to model the processes involved in person–environment transactions, how to understand the link between adversity and personal growth, how to examine the generality of models across ethnic and cultural groups, and how to enhance positive carryover from intervention programs to ongoing life contexts. I close by addressing some implications of these issues for a vision of a dynamic community psychology.
Natural Mentors and Adolescent Resiliency: A Study with Urban Youth
Authors: Zimmerman Marc A. , Bingenheimer Jeffrey B. , Notaro Paul C.
Published: December 2002

Natural mentors may play an important role in the lives of adolescents. We interviewed 770 adolescents from a large Midwestern city. Fifty‐two percent reported having a natural mentor. Those with natural mentors were less likely to smoke marijuana or be involved in nonviolent delinquency, and had more positive attitudes toward school. Natural mentors had no apparent effect on anxiety or depression. Using the resiliency theory framework, natural mentors were found to have compensatory but not protective effects on problem behaviors, and both compensatory and protective effects on school attitudes. Direct and indirect (mediated) effects of natural mentors are explored for problem behaviors and school attitudes. The potential importance of natural mentors is supported, and implications for future research are considered.
Naturally Occurring Mentoring in Japan and the United States: Social Roles and Correlates
Authors: Darling Nancy , Hamilton Stephen , Toyokawa Teru , Matsuda Sei
Published: December 2002

Although the word “mentor” has traditionally been used to describe a relationship between an older adult and a younger person, recent work has extended its usage to relationships with peers and groups rather than with individuals and uncoupled the instrumental and affective qualities of the role. This paper examines (a) the extent to which adolescents' relationships with significant others in different social roles are characterized by mentoring and (b) the extent to which mentoring and other relationship functions covary. Adolescents' naturally occurring social relationships are explored in two very different contexts—Japan and the United States—that differ in the norms and patterning of social interactions. College students (N = 365) used questionnaires to describe the extent to which relations with significant others were characterized by mentoring. Results indicate striking similarity in the patterning of results in the two countries and support the traditional view of mentoring. Mentoring is most likely to occur in relationships with adults (especially parents), rather than with peers, and with same‐gender, rather than other‐gender associates. Mentoring by parents appears to covary with other aspects of positive relationships, but be more independent in relationships with unrelated adults or peers. Although more of the variability in experienced mentoring is attributed to differences between associates than to differences between adolescents in both the United States and Japan, this is especially true of the United States. Results suggest that although “classic” mentoring is most common in both countries, mentoring is somewhat less constrained by social role differences in Japan than is in the United States.
NOBEL LECTURE: The Molecular Biology of Memory Storage: A Dialog Between Genes and Synapses
Authors: Kandel Eric R.
Published: December 2002

The biology of learning, and short-term and long-term memory, as revealed by Aplysia and other organisms, is reviewed.
Lipid Status and Long‐Chain Polyunsaturated Fatty Acid Concentrations in Adults and Adolescents with Phenylketonuria on Phenylalanine‐Restricted Diet
Authors: Moseley K. , Koch R. , Moser A.B.
Published: December 2002

Blood lipid studies are reported in 25 adults and 2 adolescents with PKU who had been on phenylalanine‐restricted diets for a mean period of 22.6 years (range 7[ndash ]39 years). Measurements included plasma concentrations of phenylalanine, cholesterol, lipoproteins, triglycerides and fatty acid profiles, including the analysis of seven fatty acids in plasma and red blood cells. Lipid screening identified 7 subjects with significantly elevated cholesterol/HDL ratios ranging from 5.6 to 10.3. Triglyceridaemia was documented in 5 of these 7, with concentrations ranging between 0.24 and 4.5 mmol/L (219[ndash ]402 mg/dl) with a mean of 3.5 mmol/L (310 mg/dl). The fatty acid analyses demonstrated slight but statistically significant reductions in the concentrations of long‐chain polyunsaturated fatty acids (LCPUFA), including plasma docosahexaenoic (DHA) and arachidonic acid (AA), and red blood cell DHA concentrations. The pattern resembles that reported previously in children, but alterations in the mean levels are less severe. In six of the adult patients plasma DHA or AA concentrations were less than 50% of controls. Since DHA and AA have important physiological roles, including brain and retinal function, it is recommended that blood lipid concentrations be monitored in all patients with PKU, including adults, and that DHA and AA supplementation be provided, particularly in those patients in whom the blood concentrations of these substances are reduced significantly.
D‐2‐Hydroxyglutaric Aciduria in a Patient with a Severe Clinical Phenotype and Unusual MRI Findings
Authors: Wajner M. , Vargas C. R. , Funayama C. , Fernandez A. , Elias M. L. C. , Goodman S. I. , Jakobs C. , van der Knaap M. S.
Published: December 2002

We report an infant with intermittent urinary excretion of D‐2‐hydroxyglutaric (D‐2‐OHG) acid who died at the age of 10 months from cardiogenic shock due to cardiomyopathy. High urinary concentrations of D‐2‐OHG and succinic acid, as well as increased levels of lactic acid were detected on three different occasions, whereas a normal urinary profile of organic acids was found on one occasion. The clinical findings of our patient consisted of generalized hypotonia, irritability, developmental delay, generalized tonic seizures, lethargy, cardiomyopathy, and respiratory distress. Cerebral MRI revealed bilateral lesions in the substantia nigra, the periaqueductal area, the medial part of the thalamus, the hypothalamus, the caudate nucleus, putamen and globus pallidus. This pattern is suggestive of a mitochondriopathy. However, respiratory chain enzyme activities were normal in fibroblasts. Exogenous supplementation of D‐2‐OHG acid strongly inhibited cytochrome‐c oxidase activity in fibroblasts from the patient and from normal controls in vitro. The results suggest that our patient has an unusual form of D‐2‐hydroxyglutaric aciduria (D‐2‐OHGA), different from the patients published so far, and that the increase of lactic acid and some citric acid cycle intermediates encountered in some patients with D‐2‐OHGA may be due to a functional defect of the respiratory chain caused by D‐2‐OHG acid.
Shame and posttraumatic stress disorder
Authors: Leskela Jennie , Dieperink Michael , Thuras Paul
Published: December 2002

Guilt about surviving a traumatic event is thought to be an associated feature of posttraumatic stress disorder (PTSD). Shame is an emotion closely related to guilt but is a distinct affective state. Little is known regarding the role of shame in PTSD and there are no studies of PTSD where shame and guilt are examined simultaneously. We used a measure of shame‐ and guilt‐proneness in 107 community residing former prisoner of war veterans all of whom had been exposed to trauma. The measure of shame‐proneness was positively correlated with PTSD symptom severity whereas guilt‐proneness was not. This study provides the first empirical data regarding a possible role for shame in PTSD and may have important therapeutic and theoretical implications.
Phase-Transition-Driven Synaptic Exocytosis: A Hypothesis and Its Physiological and Evolutionary Implications
Authors: Kharakoz Dmitri P.
Published: December 2002

It is proposed that the plasma membrane in the active zones of synaptic terminals contains self-assembling cooperative domains whose Ca2+-induced solidification may be the driving force of the fast neurotransmitter release in the central synapses. This hypothesis and a qualitative model of the phase-transition-driven exocytosis provide formulation of a unitary approach to a number of general problems in the physiology of animals. It allows answering the following questions, among others: (i) What is the physical reason for the existence of a narrow optimum range of body temperatures in warm-blooded species? (ii) What is the physical reason for the inevitable necessity of regular sleep in animals? (iii) Does there indeed exist any general mechanism of general anesthesia?
Renal failure and abdominal hypertension after liver transplantation: Determination of critical intra-abdominal pressure
Authors: Biancofiore Gianni , Bindi Lucia , Romanelli Anna Maria , Bisà Massimo , Boldrini Antonella , Consani Giovanni , Danella Augusta , Urbani Lucio , Filipponi Franco , Mosca Franco
Published: December 2002

There is growing interest in measuring intra-abdominal pressure (IAP) in postsurgical and critically ill patients because increased pressure can impair various organs and functions. The aim of this study was to evaluate the effect of different IAP levels on the postoperative renal function of subjects undergoing orthotopic liver transplantation. IAP was measured every 8 hours with the urinary bladder pressure method for at least 72 hours after surgery. At the end of the study, the patients were classified on the basis of their IAP values: ≤ 18 mm Hg (group A), 19 to 24 mm Hg (group B), ≥ 25 mm Hg (group C). The three groups were compared in terms of the incidence of acute renal failure (defined as blood creatinine > 1.5 mg/dL or an increase in the same of > 1.1 mg/dL within 72 hours of surgery), hourly diuresis, blood creatinine, the filtration gradient, hemodynamic variations, and outcome. The incidence of renal failure was higher among the subjects in group C (P < .05 versus group A and < .01 versus group B), who also had higher creatinine levels (P < .01), a greater need for diuretics (P < .01) and a worse outcome (P < .05). Receiver Operator Characteristic curve analysis showed that an abdominal pressure of 25 mm Hg had the best sensitivity/specificity ratio for renal failure. An intra-abdominal pressure of ≥ 25 mm Hg is an important risk factor for renal failure in subjects undergoing liver transplant.
Intraoperative hemodynamics and liver function in adult-to-adult living liver donors
Authors: Niemann Claus U. , Roberts John P. , Ascher Nancy L. , Yost Spencer C.
Published: December 2002

Indocyanine green (ICG) can be used to measure cardiac output (CO), hepatic function, and blood volume. We used ICG to describe the effect of right hepatectomy for living liver donation on intraoperative hemodynamics and perioperative liver function. ICG disposition was determined in 12 healthy adult living liver donors during the dissection phase and immediately after removal of the right hepatic lobe. In addition, measurements were repeated postoperative day 5. After injecting ICG, plasma concentrations were obtained for approximately 10 minutes by noninvasive pulse dye densitometry. CO was significantly higher and systemic vascular resistance was significantly lower immediately after removal of the right lobe compared with those obtained before resection (6.02 ± 1.12 v 10.28 ± 3.84 L/min; P < .05; 639 ± 254 v 1,007 ± 264 dyn.s.cm−5; P < .05). Heart rate also increased significantly after removal of the right lobe from 62 ± 10 to 83 ± 9 beats/min (P < .05). Mean arterial pressure and central venous pressure were not different between measurements. The average elimination rate constant of ICG (KICG) was reduced by more than 50% immediately after resection of the right lobe in comparison to baseline (0.25 ± 0.096 v 0.12 ± 0.03; P < .05). Day 5, KICG was still decreased from baseline (0.25 ± 0.096 v 0.16 ± 0.04; P < .05), but approximately 25% greater than the immediate postresection KICG (0.16 ± 0.04 v 0.12 ± 0.03; P > .05). Findings show profound intraoperative hemodynamic changes during living liver donation. In addition, we show that functional recovery of the liver is likely to be slower than morphological recovery, and such clinical parameters as coagulation profile may not be a good index of fully restored hepatic function.
Role of intramolecular energy on polyolefin miscibility: Isotactic polypropylene/polyethylene blends
Authors: Heine David , Wu David T. , Curro John G. , Grest Gary S.
Published: December 2002

Self-consistent polymer reference interaction site model (PRISM) calculations and molecular dynamics (MD) simulations were performed for a blend of isotactic polypropylene (iPP) and polyethylene (PE) at various compositions and chain lengths. United atom models were used for both components. Both PRISM theory and MD simulations predicted that the change in intramolecular energy going from the melt to the blend for each species was a significant positive contribution to the total mixing energy. Furthermore, this intramolecular heat of mixing was dominated by the torsional and van der Waals contributions. Constant pressure MD simulations indicated that, with the united atom parameters used, the iPP/PE blend had essentially zero volume change of mixing. MD simulations were used to compute the partial structure factors for the blend and together with the standard random phase approximation analysis were used to estimate the small angle neutron scattering (SANS) χ parameter. Good agreement was found between estimates from PRISM and MD of both the enthalpic and SANS χ parameters.
Exciton exciton annihilation dynamics in chromophore complexes. I. Multiexciton density matrix formulation
Authors: Brüggemann B. , May V.
Published: December 2002

The multiexciton (MX) description of excitation energy transfer in chromophore complexes and biological light harvesting antenna systems is extended to the incorporation of exciton exciton annihilation (EEA) processes. To achieve a complete microscopic description the approach is based on intrachromophore internal conversion processes leading to nonradiative transitions from higher to lower lying exciton manifolds. Besides an inclusion of EEA the MX density matrix theory which has been utilized for a description of excitation energy transfer also accounts for a coupling to low-frequency vibrational modes and the radiation field. Concentrating on transitions from the two to the single-exciton manifold exact and approximate expressions for the EEA rate are derived. In part II of this paper the approach is applied to the LH2 antenna putting emphasis on the EEA induced change of transient absorption spectra.
Persistent energy transfer in CaAl2O4:Tb3+, Ce3+
Authors: Jia D. , Wang X. J. , Jia W. , Yen W. M.
Published: December 2002

Ceramic samples of Tb3+ and Ce3+ singly doped and co-doped CaAl2O4 with 0.1 and 1 at. % doping concentrations have been prepared. The emission of the Ce3+ singly doped sample is at 413 nm. The persistence time of its afterglow is longer than 10 h. The strongest emission of the Tb3+ singly doped sample is at 543 nm and its afterglow persists for about 1 h. In the co-doped sample, the Ce3+ excitation is transferred to Tb3+ ion with an energy transfer rate of 109–1010 s−1 in the high concentration samples. The Ce3+ energy transfer occurs during its afterglow decay, so that the Tb3+ afterglow emission duration is also extended to about 10 h. Photoconductivity and thermoluminescence measurements have also been performed in these systems; the persistent sensitization of Tb3+ is also confirmed by these measurements.
Linear aspects of streamer formation in electron temperature gradient turbulence
Authors: Kendl Alexander
Published: December 2002

The dependence of radially elongated streamer formation in toroidal electron temperature gradient driven turbulence on the magnetic field geometry (specified by shear s and shift α) is well described by means of a linear gyrokinetic analysis of the radial mode number spectrum.
Glass-forming tendency of bulk La–Al–Ni–Cu–(Co) metallic glass-forming liquids
Authors: Lu Z. P. , Li Y. , Liu C. T.
Published: December 2002

The excess Gibbs free-energy difference, ΔG1−s, between the undercooled liquid and the crystalline solid for La–Al–Ni–Cu–(Co) alloys was calculated by using directly measured heat capacity data. The glass-forming tendency of these liquids correlated well with the computed Gibbs free-energy difference. The small value of Gibbs free energy of the undercooled liquid with respect to the crystalline solid is a contributing factor to the high glass-forming ability in this system. The kinetics of bulk La–Al–Ni–Cu–(Co) glass-forming liquids were also investigated using differential scanning calorimetry. The fragility plot of the viscosities indicate that these bulk metallic glass formers are strong liquids. The glass-forming ability of these alloys is also explained in the light of this fragility concept.
All-optical single-electron read-out devices based on GaN quantum dots
Authors: D’Amico Irene , Fossi Fausto
Published: December 2002

We study few-particle interactions in GaN-coupled quantum dots and discuss how the built-in field characteristic of these structures strongly reinforce dipole–dipole and dipole–monopole interactions. We introduce a semi-analytical model that allows for a rapid and easy estimate of the magnitude of few-particle interactions and whose predictions are closer than 10% to “exact” results. We apply our study to the design of an all-optical read-out device that exploits long-range dipole–monopole interactions and may be also used to monitor the charge status of a quantum dot system.
Resonance-enhanced laser-induced plasma spectroscopy for sensitive elemental analysis: Elucidation of enhancement mechanisms
Authors: Lui S. L. , Cheung N. H.
Published: December 2002

When performing laser-induced plasma spectroscopy for elemental analysis, the analyte signal-to-noise ratio increased from four to over fifty if the plume was reheated by a dye laser pulse tuned to resonant absorption. Time-resolved studies showed that the enhancement was not due to resonance photoionization. Rather, efficient and controlled rekindling of a larger plume volume was the key mechanism. The signal-to-noise ratio further increased to over a hundred if the atmosphere was replaced by a low-pressure heavy inert gas. The ambient gas helped confine and thermally insulate the expanding vapor.
Dielectric functions and critical points of BexZn1−xTe alloys measured by spectroscopic ellipsometry
Authors: Buckley M. R. , Peiris F. C. , Maksimov O. , Muñoz M. , Tamargo M. C.
Published: December 2002

Using a rotating analyzer spectroscopic ellipsometer, we have investigated the complex dielectric function of a series of ternary BexZn1−xTe thin films in the energy range between 0.7 and 6.5 eV for alloy concentrations between x=0.0 and x=0.52. After determining the alloy concentrations using x-ray diffraction and photoluminescence techniques, a standard inversion technique was used to obtain the optical constants from the measured ellipsometric spectra. Analyzing the second derivative of both the real and the imaginary parts of the dielectric constant, we have deduced the critical point parameters corresponding to the electronic transitions in the Brillouin zone. We find that the energy of the critical points with respect to Be concentration does not show any bowing effects unlike many other II–VI semiconductor ternary alloys.
Resource Letter: OTS-1: Observations and theory of supernovae
Authors: Wheeler J. Craig
Published: December 2002

This Resource Letter provides a guide to the literature on the observations of supernovae and the theory of their explosion mechanisms. Journal articles and books are cited for the following topics: observations of the spectra, spectropolarimetry, and light curves of supernovae of various types, theory of thermonuclear explosions, core collapse, and radioactive decay, applications to cosmology, and possible connections to gamma-ray bursts.
High Prevalence of Premalignant Lesions in Prophylactically Removed Breasts From Women at Hereditary Risk for Breast Cancer
Authors: Hoogerbrugge N. , Bult P. , de Widt-Levert L.M. , Beex L.V. , Kiemeney L.A. , Ligtenberg M.J.L. , Massuger L.F. , Boetes C. , Manders P. , Brunner H.G.
Published: December 2002

Purpose: Women with a hereditary predisposition for breast cancer have an extremely high risk of developing invasive breast carcinoma, and many women consider prophylactic mastectomy to avoid this risk. The use of prophylactic mastectomy is still debated. Identification of frequent premalignant lesions in mastectomy specimens would support the preventive concept of prophylactic mastectomy.

Patients and Methods: We performed a prospective study of breast specimens from 67 women at extremely high genetic risk of breast cancer, with or without previous breast cancer, who were undergoing prophylactic mastectomy (66% were carriers of a BRCA1 or BRCA2 mutation). Breast specimens were studied by radiographic and macroscopic examination of 5-mm tissue slices, with subsequent histology of suspicious lesions and random samples from each quadrant of the breast and the nipple area.

Results: In 57% of the women, one or more different types of high-risk histopathologic lesions were present: 37% atypical lobular hyperplasia, 39% atypical ductal hyperplasia, 25% lobular carcinoma-in-situ, and 15% ductal carcinoma-in-situ. A 4-mm invasive ductal carcinoma was found in one woman with ductal carcinoma-in-situ. None of these lesions was detected at palpation or mammography, which were performed before the mastectomy. The presence of high-risk lesions was independently related to age older than 40 years (odds ratio, 6.6; P = .01) and to bilateral oophorectomy before prophylactic mastectomy (odds ratio, 0.2; P = 0.02).

Conclusion: Many women at high risk of hereditary breast cancer develop high-risk histopathologic lesions, especially after the age of 40 years. Surveillance does not detect such high-risk histopathologic lesions.
Increased Risk of Systemic Relapses Associated With Bone Marrow Micrometastasis and Circulating Tumor Cells in Localized Ewing Tumor
Authors: Schleiermacher Gudrun , Peter Martine , Oberlin Odile , Philip Thierry , Rubie Hervé , Mechinaud Françoise , Sommelet-Olive Danièle , Landman-Parker Judith , Bours Danièle , Michon Jean , Delattre Olivier
Published: December 2002

Purpose: The presence of metastasis is a major prognostic factor in Ewing tumor (ET). The relapse pattern of patients with localized tumors has long indicated that cases with disseminated ET cells escape detection at diagnosis. ET cells are characterized by specific gene fusions that can be detected with high sensitivity and specificity by reverse transcriptase polymerase chain reaction (RT-PCR).

Patients and Methods: RT-PCR targeting EWS-FLI-1 or EWS-ERG transcripts was used to search for occult tumor cells in peripheral blood (PB) and bone marrow (BM) at diagnosis in 172 patients with ET, and the prognostic significance of this parameter was assessed.

Results: As we suggested previously in a smaller series of patients, RT-PCR positivity of the BM was correlated with a high risk of adverse outcome in the overall study population (P = .007). More interestingly, among patients with otherwise localized tumors, BM micrometastasis also predicted significantly poorer disease-free survival rates (P = .043). The presence of circulating tumor cells (CTC) was more frequently observed in patients with large tumors (P = .006). CTC were associated with a poor outcome among patients with clinically localized disease (P = .045). Patients with clinically localized disease and peripheral occult tumor cells as evidenced by BM and/or PB RT-PCR positivity had axial or proximal tumors and experienced relapses at a systemic rather than at a local level.

Conclusion: Patients with localized ET and BM micrometastasis or CTC are comparable to patients with metastases in terms of the localization of the primary tumor, outcome, and relapse pattern.