bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro Raman spectroscopy of healthy mammals crystalline lenses
Authors: Antunes A , Abud-Filho S E , Temperini M L A , Morelhão S L
Published: April 2005

The crystalline lens is a transparent biological
material, and a complex inhomogeneous optical element in the
vision system of mammals. It is a fiber cell structures [1].
Approximately 90% of the fiber cells composition are proteins
responsible for the high refractive index of the lenses. This
paper presents Raman spectroscopy as a tool for identification of
the proteins and further diagnostic of disease in the lenses.
Would all mammal lenses be made of the same proteins? This is the
question motivating this work. Raman spectroscopy is a rapid and
non-destructive optical method for providing chemical information
on molecular structures [2], and has been successfully
applied to a variety of biological systems [2,3]. Our aim
here is to investigate the protein average distribution in the
lenses of distinct mammals by following main differences in the
Raman spectral signature. The Raman signatures of healthy
crystalline lenses from canine, mouse, pig, rabbit and horse were
characterized in vitro. The results indicate that there are no
substantial differences at all animals studied.
Temperature and Pressure Dependence of α‐Relaxation and Free Volume in Poly(vinyl acetate)
Authors: Dlubek Günter , Kilburn Duncan , Alam M. Ashraf
Published: April 2005

Summary: We analysed reported specific volume V from pressure‐volume‐temperature (PVT) experiments for poly(vinyl acetate) (PVAc) using the Simha‐Somcynsky equation of state (S‐S eos) and calculated the specific occupied volume, Vocc, and hole free volume, Vfh We found that Vocc shows almost no thermal expansion but is distinctly compressible (T > Tg). Due to this, Vfh = V − Vocc is not a unique function of V but can depend on the specific values of P and T giving rise to the particular value for V. We observed that with decreasing temperature the α‐relaxation detected via dielectric measurements slows down faster than the shrinkage of hole free volume Vfh would predict on the basis of the free volume theory of Cohen and Turnbull. Vfh becomes zero at approximately 65 K below the Vogel temperature T0, $T'_0 = T_0 - 65\,{\rm K}$. Plots of the α‐relaxation frequency log ωα versus 1/Vfh can be linearised when taking into account this discrepancy by substituting 1/Vfh by 1/(Vfh − ΔV) with $\Delta V = E_{{\rm fh}} (T_0 - T'_0 )$, or by including an energy term of the type exp[−E′/R(T − T0)] in the pre‐exponential factor of the frequency‐volume equation. Our results indicate that the α‐relaxation in PVAc operates via the Cohen‐Turnbull mechanism only when liquid‐like clusters of cells of the S‐S lattice appear which contain a hole free volume of three or more empty S‐S cells. For regions with a smaller number of empty cells an activation energy is required for allowing segmental motion via the cooperative rearranging of cells. The β‐(Johari‐Goldstein) relaxation which is a non‐cooperative, more local, process follows completely the free volume theory. The same seems to be true for the primitive (uncoupled) relaxation of the coupling model.

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Temperature Dependence of Free Volume in Pure and Silica‐Filled Poly(dimethyl siloxane) from Positron Lifetime and PVT Experiments
Authors: Dlubek Günter , De Udayan , Pionteck Jürgen , Arutyunov Nikolai Yu. , Edelmann Matthias , Krause‐Rehberg Reinhard
Published: April 2005

Summary:The microstructure of the free volume and its temperature dependence in two poly(dimethyl siloxane)s (PDMS), one in the pure state and the other filled with 35 wt.‐% of an in situ hydrophobized fumed silica with a specific surface area of 200–300 m2 · g−1, were studied by pressure‐volume‐temperature experiments (PVT, T = 22–156 °C, P = 10–200 MPa) and positron annihilation lifetime spectroscopy (PALS, T = −173–100 °C, P = 10−5 MPa). The Simha‐Somcynsky equation of state was used to estimate the hole free volume fraction, h, and free and occupied volumes, Vf = hV and Vocc = (1 − h)V, from the specific total volume, V. The PALS spectra were analyzed with the routine LT9.0, which allowed for a dispersion, σi, in all three of the lifetimes: the para‐positronium (p‐Ps, τ1), positron (e+, τ2), and ortho‐positronium (o‐Ps) lifetime (τ3). This kind of analysis delivered correct p‐Ps lifetime parameters, τ1, σ1, and I1. It was speculated that e+, like o‐Ps, undergoes Anderson localization at empty sites of the, static or dynamic, disordered structure. The hole size distribution, its mean value, 〈vh〉, and dispersion, σh, were calculated from the o‐Ps lifetimes. A comparison of 〈vh〉 with Vf was used to estimate the specific hole number, $N'_{\rm h}$. During melting of the semicrystalline samples at−38 °C (Tm), 〈vh〉 increased abruptly, and σh suddenly decreased. Both effects are explained by the disappearance of the rigid‐amorphous fraction (RAF) and, thus, a reduction in the dynamic heterogeneity. The following leveling‐off in 〈vh〉 and the low value of σh are attributed to the fast segmental relaxation in the PDMS melts which leads to a smearing of the molecule density distribution around a hole during the o‐Ps lifetime.

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Glutathione‐S‐transferase‐1 and interleukin‐1β gene polymorphisms in Japanese patients with Parkinson's disease
Authors: Nishimura Masataka , Kuno Sadako , Kaji Ryuji , Yasuno Katsuhito , Kawakami Hideshi
Published: April 2005

We studied genetic polymorphisms in the glutathione‐S‐transferase‐1 (GST‐1) gene region and the interleukin‐1β (IL‐1β) promoter region in patients with Parkinson's disease (PD, n = 361), as well as controls (n = 257). Although we have confirmed the previous results, in a larger sample, that the IL‐1β genotype has affected the age at onset of PD patients, no contribution of the GST‐1 gene polymorphism was observed in the allele frequency or the onset age of the disease in Japanese persons. © 2005 Movement Disorder Society
Synthesis of poly(vinyl chloride)‐b‐poly(2‐ethylhexyl acrylate)‐b‐poly(vinyl chloride) by the competitive single‐electron‐transfer/degenerative‐chain‐transfer mediated living radical polymerization of vinyl chloride initiated from α,ω‐di(iodo)poly(2‐ethylhexyl acrylate) and catalyzed with sodium dithionite in water
Authors: Percec Virgil , Popov Anatoliy V. , Ramirez‐Castillo Ernesto , Hinojosa‐Falcon Luis A.
Published: April 2005

α,ω‐Di(iodo)poly(2‐ethylhexyl acrylate)s [α,ω‐di(iodo)P2EHAs] with number‐average molecular weights of 13,700 and 20,400 were synthesized by the single‐electron‐transfer/degenerative‐chain‐transfer mediated living radical polymerization (SET–DTLRP) of 2‐ethylhexyl acrylate initiated with iodoform and catalyzed by sodium dithionite in water at 23 and 30 °C. These α,ω‐di(iodo)P2EHAs were used as macroinitiators for the SET–DTLRP of vinyl chloride, which was carried out under similar reaction conditions to synthesize ABA block copolymers containing poly(vinyl chloride) in the A blocks and poly(2‐ethylhexyl acrylate) in the B block. Poly(vinyl chloride)‐b‐poly(2‐ethylhexyl acrylate)‐b‐poly(vinyl chloride) was synthesized with 100% initiator efficiency. This synthetic method provides for the first time access to a diversity of block copolymers and other complex architectures based on combinations of thermoplastic poly(vinyl chloride)and elastomeric polyacrylates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2276–2280, 2005
New fluorinated thermoplastic elastomers. III. Novel method of synthesis and characterization of alternating fluorinated polyimide/fluorinated polyhybridsiloxane block copolymers via polycondensation
Authors: Andre S. , Guida‐Pietrasanta F. , Rousseau A. , Boutevin B. , Caporiccio G.
Published: April 2005

The synthesis of fluorinated polyimide/fluorinated polyhybridsiloxane (FPI–FPHSX) block copolymers was achieved through the polycondensation of α,ω‐dichlorosilane fluorinated polyimides and α,ω‐disilanol fluorinated polyhybridsiloxanes. Three FPI–FPHSX block copolymers with 41, 50, and 76 wt % polyimide were synthesized and characterized by the tuning of the number‐average molecular weight of the soft polyhybridsiloxane segments. The influence of the soft‐segment length on the behavior of the thermoplastic elastomer material was studied, including the surface tension and thermal properties. The thermomechanical properties of the FPI–FPHSX block copolymers were also examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2237–2247, 2005
Methods of preparation of novel composites of poly(ϵ‐caprolactone) and a modified Mg/Al hydrotalcite
Authors: Tammaro Loredana , Tortora Mariarosaria , Vittoria Vittoria , Costantino Umberto , Marmottini Fabio
Published: April 2005

12‐Hydroxydodecanoate (HD) anions were intercalated, via an ion‐exchange procedure, onto a Mg/Al hydrotalcite‐like compound with the formula [Mg0.65Al0.35(OH)2](NO3)0.35·0.56H2O. The obtained intercalate, characterized by chemical and thermal analyses, X‐ray powder diffraction, and Fourier transform infrared spectroscopy, had the formula [Mg0.65Al0.35(OH)2](NO3)0.08(HD)0.28·0.56H2O and an interlayer distance of 2.27 nm. Structural considerations indicated that the charge‐balancing HO(CH2)11COO− anions were accommodated in the interlayer region as a monofilm of partially interdigitated alkyl chains in a trans planar conformation and bearing the alcoholic group. The organically modified hydrotalcite was used to prepare novel composites based on poly(ϵ‐caprolactone) (PCL) with different procedures: (1) solvent casting, (2) ring‐opening polymerization of ϵ‐caprolactone, and (3) blending of precursors consisting of a PCL intercalated oligomer with a high‐molecular‐weight PCL. Microcomposites were obtained by the solvent casting of a mixture of a high‐molecular‐weight PCL and the modified hydrotalcite. The ring‐opening polymerization of ϵ‐caprolactone initiated by the OH groups of the alkyl chains intercalated in the hydrotalcite led to hybrid materials in which a low‐molecular‐weight PCL was in part intercalated into the modified hydrotalcite. Nanocomposites containing exfoliated hydrotalcite were obtained through the mixing, in different weight ratios, of hybrids consisting of PCL oligomers and modified hydrotalcite with a commercial high‐molecular‐weight PCL. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2281–2290, 2005
Crystalline morphology evolution in PCL thin films
Authors: Qiao Congde , Zhao Junchai , Jiang Shichun , Ji Xiangling , An Lijia , Jiang Bingzheng
Published: April 2005

The transition of crystalline morphology is revealed in poly(ϵ‐caprolactone) (PCL) thin films as the polymer film thickness changes from hundreds of nanometers to several nanometers. The PCL can crystallize into spherulites, dense‐branching morphology (DBM), or dendrites, depending on the polymer film thickness. It was found that when the polymer film thickness approaches 2Rg (radius of gyration of polymer), there is a remarkable change in crystalline morphology. Under this condition, the polymer crystallization is a diffusion‐controlled process. When the value of polymer film thickness closes to Rg, PCL cannot crystallize, and a dewetting phenomenon will take place. Moreover, polymer morphology can be controlled by varying supercooling. The effect of molecular weight on polymer morphology has been investigated. The main factors that affected pattern formation in nonequilibrium crystallization are also discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1303–1309, 2005
Evaluation of piezoelectric poly(vinylidene fluoride) polymers for use in space environments. I. Temperature limitations
Authors: Dargaville Tim R. , Celina Mathew , Chaplya Pavel M.
Published: April 2005

Smart materials, such as thin‐film piezoelectric polymers, are interesting for potential applications on Gossamer spacecraft. This investigation aims to predict the performance and long‐term stability of the piezoelectric properties of poly(vinylidene fluoride) (PVDF) and its copolymers under conditions simulating the low‐Earth‐orbit environment. To examine the effects of temperature on the piezoelectric properties of PVDF, poly(vinylidenefluoride‐co‐trifluoroethylene), and poly(vinylidenefluoride‐co‐hexafluoropropylene), the d33 piezoelectric coefficients were measured up to 160 °C, and the electric displacement/electric field (D–E) hysteresis loops were measured from −80 to +110 °C. The room‐temperature d33 coefficient of PVDF homopolymer films, annealed at 50, 80, and 125 °C, dropped rapidly within a few days of thermal exposure and then remained unchanged. In contrast, the TrFE copolymer exhibited greater thermal stability than the homopolymer, with d33 remaining almost unchanged up to 125 °C. The HFP copolymer exhibited poor retention of d33 at temperatures above 80 °C. In situ D–E loop measurements from −80 to +110 °C showed that the remanent polarization of the TrFE copolymer was more stable than that of the PVDF homopolymer. D–E hysteresis loop and d33 results were also compared with the deflection of the PVDF homopolymer and TrFE copolymer bimorphs tested over a wide temperature range. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1310‐1320, 2005
Effects of salmon carcasses on experimental stream ecosystems in Hokkaido, Japan
Authors: Yanai Seiji , Kochi Kaori
Published: April 2005

The effects of salmon carcasses on dissolved nutrients, epilithic production, leaf decomposition rates, and aquatic invertebrates were examined using 10‐m‐long artificial channels fed by an adjacent natural stream in Hokkaido, northern Japan. Bags containing maple leaf litter were placed in nine channels, each of which was assigned to one of three treatments with three replicates, for 6 weeks in fall 2002. The three treatments were: (1) salmon carcasses+invertebrates, (2) invertebrates only, and (3) control (no salmon carcasses or invertebrates added). Nutrient concentrations, biomass of epilithic algae (chlorophyll), leaf weight loss, abundance and biomass of invertebrates in the leaf packs were compared among the three treatments at 14, 27, and 40 days after the beginning of the experiment. The NH4+ in stream water and chlorophyll concentrations of epilithic algae were higher in the salmon treatment than the other treatments, and the maple leaves decomposed faster in the salmon treatment than in the other treatments. Moreover, the N content of the leaves was highest and the C/N ratio was lowest in the salmon treatment, although not significantly so. The abundance and biomass of the dominant leaf‐shredding invertebrate Goerodes satoi did not differ between the first two treatments. However, the stable N isotope ratio in G. satoi was nearly 3‰ higher in the salmon treatment, suggesting that around 20% of salmon‐derived N was taken up by this shredder. Our results indicate that salmon carcasses affect stream ecosystems directly by enhancing primary production, indirectly by accelerating woody leaf decomposition, and finally by incorporating into the food web primary consumers that utilize fertilized woody leaves.
Morphological and phenotypical characterization of human endothelial progenitor cells in an early stage of differentiation
Authors: Bellik Lydia , Ledda Fabrizio , Parenti Astrid
Published: April 2005

The exact phenotype and lineage of endothelial progenitor cells (EPCs) are still a matter of debate and different expansion protocols are used to obtain them. In this study, EPC expansion from peripheral blood mononuclear cells was analyzed within the first week of culture. Both the adherent and suspended cells, of which the latter usually discarded, were considered. We provide, for the first time, a systematic study of EPC phenotype and functional features within the first 3 days of culture. Moreover, within the 2nd day, both cellular fractions displayed a significant increase in endothelial marker expression which correlated with EPC properties.
THE RETURN OF IMPERIALISM TO SOCIAL SCIENCE
Authors: CHIBBER VIVEK
Published: April 2005

ONE OF THE CURIOUS DEVELOPMENTS in intellectual circles over the past few years is that the subject of imperialism is no longer a bailiwick of the Left. To be sure, so long as colonial empires were in strength, there was no denying the reality of European and American imperial expansion. But over the course of the post-war era, as decolonization rippled through the Third World and the formal mechanisms of colonial control were thrown overboard, any insistence on the continuing salience of imperialism became identified with left-wing ideologies. If it did enter mainstream debates, it was inevitably Soviet or, more generically, Communist imperial ambitions that were subjected to scrutiny.
Emerging tick-borne infections: rediscovered and better characterized, or truly ‘new’?
Authors: TELFORD S. R. , GOETHERT H. K.
Published: April 2005

The emergence of Lyme borreliosis as a public health burden within the last two decades has stimulated renewed interest in tick-borne infections. This attention towards ticks, coupled with advances in detection technologies, has promoted the recognition of diverse emergent or potentially emerging infections, such as monocytic and granulocytic ehrlichiosis, local variants of spotted fever group rickettsioses, WA-1 babesiosis, or a Lyme disease mimic (Masters' Disease). The distribution of pathogens associated with well-described tick-borne zoonoses such as human babesiosis due toBabesia microtiorB.divergensseems wider than previously thought. Bartonellae, previously known to be maintained by fleas, lice or sandflies, have been detected within ticks. Purported ‘new’ agents, mainly identified by sequencing of PCR products and comparison with those sequences present in GenBank, are being increasingly reported from ticks. We briefly review the diversity of these infectious agents, identify aetiological enigmas that remain to be solved, and provide a reminder about ‘old friends’ that should not be forgotten in our pursuit of novelty. We suggest that newly recognised agents or tick/pathogen associations receive careful scrutiny before being declared as potential public health burdens.
Chemical control of ticks on cattle and the resistance of these parasites to acaricides
Authors: GEORGE J. E. , POUND J. M. , DAVEY R. B.
Published: April 2005

Toward the end of the nineteenth century a complex of problems related to ticks and tick-borne diseases of cattle created a demand for methods to control ticks and reduce losses of cattle. The discovery and use of arsenical solutions in dipping vats for treating cattle to protect them against ticks revolutionized tick and tick-borne disease control programmes. Arsenic dips for cattle were used for about 40 years before the evolution of resistance of ticks to the chemical, and the development and marketing of synthetic organic acaricides after World War II provided superior alternative products. Most of the major groups of organic pesticides are represented on the list of chemicals used to control ticks on cattle. Unfortunately, the successive evolution of resistance of ticks to acaricides in each chemical group with the concomitant reduction in the usefulness of a group of acaricides is a major reason for the diversity of acaricides. Whether a producer chooses a traditional method for treating cattle with an acaricide or uses a new method, he must recognize the benefits, limitations and potential problems with each application method and product. Simulation models and research were the basis of recommendations for tick control strategies advocating approaches that reduced reliance on acaricides. These recommendations for controlling ticks on cattle are in harmony with recommendations for reducing the rate of selection for acaricide resistance. There is a need to transfer knowledge about tick control and resistance mitigation strategies to cattle producers.
Pheromones and other semiochemicals of ticks and their use in tick control
Authors: SONENSHINE D. E.
Published: April 2005

This review addresses the role of compounds secreted into the external environment that mediate important aspects of tick behaviour. Known as semiochemicals, these information-containing compounds include pheromones (used for conspecific communication), allomones (defence secretions) and kairomones (used for host identification and location). An impressive body of knowledge has accumulated concerning the identification of the compounds that comprise these semiochemicals. Pheromones are the best known and intensively studied, including arrestment (=assembly) pheromones, attraction–aggregation–attachment (AAA) pheromones and sex pheromones. Arrestment behaviour is mediated by contact with excreta from other ticks. In contrast, aggregating and sexual behaviours comprise a hierarchy of responses to different types of chemical compounds that must be recognized in a sequential order to achieve the end result. Ixodid ticks also produce an allomone that protects against certain insect predators. Finally, ticks use kairomones for host identification, e.g. volatiles such as CO2and NH3and various oils such as glandular secretions from deer. Knowledge of tick pheromones has been used to develop innovative new technologies for tick control. These products incorporate tick pheromones and small amounts of pesticide to attract and kill ticks on their hosts or in vegetation. The kairomones and the tick allomone also may be of interest for use in controlling ticks.
Biological control of ticks
Authors: SAMISH M. , GINSBERG H. , GLAZER I.
Published: April 2005

Ticks have numerous natural enemies, but only a few species have been evaluated as tick biocontrol agents (BCAs). Some laboratory results suggest that several bacteria are pathogenic to ticks, but their mode of action and their potential value as biocontrol agents remain to be determined. The most promising entomopathogenic fungi appear to beMetarhizium anisopliaeandBeauveria bassiana, strains of which are already commercially available for the control of some pests. Development of effective formulations is critical for tick management. Entomopathogenic nematodes that are pathogenic to ticks can potentially control ticks, but improved formulations and selection of novel nematode strains are needed. Parasitoid wasps of the genusIxodiphagusdo not typically control ticks under natural conditions, but inundative releases show potential value. Most predators of ticks are generalists, with a limited potential for tick management (one possible exception is oxpeckers in Africa). Biological control is likely to play a substantial role in future IPM programmes for ticks because of the diversity of taxa that show high potential as tick BCAs. Considerable research is required to select appropriate strains, develop them as BCAs, establish their effectiveness, and devise production strategies to bring them to practical use.
Steady-state convection-diffusion problems
Authors: Stynes Martin
Published: April 2005

In convection-diffusion problems, transport processes dominate while diffusion effects are confined to a relatively small part of the domain. This state of affairs means that one cannot rely on the formal ellipticity of the differential operator to ensure the convergence of standard numerical algorithms. Thus new ideas and approaches are required.

The survey begins by examining the asymptotic nature of solutions to stationary convection-diffusion problems. This provides a suitable framework for the understanding of these solutions and the difficulties that numerical techniques will face. Various numerical methods expressly designed for convection-diffusion problems are then presented and extensively discussed. These include finite difference and finite element methods and the use of special meshes.
PARP inhibitors for cancer therapy
Authors: Curtin Nicola J.
Published: April 2005

Poly(ADP-ribose) polymerase 1 (PARP-1) is a zinc-finger DNA-binding enzyme that is activated by binding to DNA breaks. Poly(ADP-ribosyl)ation of nuclear proteins by PARP-1 converts DNA damage into intracellular signals that activate either DNA repair by the base-excision pathway or cell death. A family of 18 PARPs has been identified, but only the most abundant, PARP-1 and PARP-2, which are both nuclear enzymes, are activated by DNA damage. PARP inhibitors of ever-increasing potency have been developed in the 40 years since the discovery of PARP-1, both as tools for the investigation of PARP-1 function and as potential modulators of DNA-repair-mediated resistance to cytotoxic therapy. Owing to the high level of homology between the catalytic domains of PARP-1 and PARP-2, the inhibitors probably affect both enzymes. Convincing biochemical evidence, which has been corroborated by genetic manipulation of PARP-1 activity, shows that PARP inhibition is associated with increased sensitivity to DNA-alkylating agents, topoisomerase I poisons and ionising radiation. Novel PARP inhibitors of sufficient potency and suitable pharmacokinetic properties to allow evaluation in animal models have been shown to enhance the antitumour activity of temozolomide (a DNA-methylating agent), topoisomerase poisons and ionising radiation; indeed, the combination with temozolomide resulted in complete tumour regression in two independent studies. The combination of a PARP inhibitor and temozolomide is currently undergoing clinical evaluation for the first time.
Mid‐ocean microseisms
Authors: Bromirski Peter D. , Duennebier Fred K. , Stephen Ralph A.
Published: April 2005

The Hawaii‐2 Observatory (H2O) is an excellent site for studying the source regions and propagation of microseisms since it is located far from shorelines and shallow water. During Leg 200 of the Ocean Drilling Program, the officers of the JOIDES Resolution took wind and wave measurements for comparison with double‐frequency (DF) microseism data collected at nearby H2O. The DF microseism band can be divided into short‐period and long‐period bands, SPDF and LPDF, respectively. Comparison of the ship's weather log with the seismic data in the SPDF band from about 0.20 to 0.45 Hz shows a strong correlation of seismic amplitude with wind speed and direction, implying that the energy reaching the ocean floor is generated locally by ocean gravity waves. Nearshore land seismic stations see similar SPDF spectra, also generated locally by wind seas. At H2O, SPDF microseism amplitudes lag sustained changes in wind speed and direction by several hours, with the lag increasing with wave period. This lag may be associated with the time necessary for the development of opposing seas for DF microseism generation. Correlation of swell height above H2O with the LPDF band from 0.085 to 0.20 Hz is often poor, implying that a significant portion of this energy originates at distant locations. Correlation of the H2O seismic data with NOAA buoy data, with hindcast wave height data from the North Pacific, and with seismic data from mainland and island stations, defines likely source areas of the LPDF signals. Most of the LPDF energy at H2O appears to be generated by high‐amplitude storm waves impacting long stretches of coastline nearly simultaneously, and the Hawaiian Islands appear to be a significant source of LPDF energy in the North Pacific when waves arrive from particular directions. The highest levels observed at mid‐ocean site H2O occur in the SPDF band when two coincident nearby storm systems develop. Deep water, mid‐ocean‐generated DF microseisms are not observed at continental sites, indicating high attenuation of these signals. At near‐coastal seismic stations, both SPDF and LPDF microseism levels are generally dominated by local generation at nearby shorelines.
Cyclicity of Peru‐Chile trench sediments between 36° and 38°S: A footprint of paleoclimatic variations?
Authors: Rauch Klaus
Published: April 2005

At active continental margins, the subduction of lithospherical plates often leads to trench building; such is the case where the oceanic Nazca Plate meets the continental South American Plate. As part of the Subduction Processes Off Chile (SPOC) project, 2D reflection seismic data were acquired by the German Bundesanstalt für Geowissenschaften und Rohstoffe covering the Peru‐Chile trench between 28°S and 44°S. To the south of 31°S, the trench is filled with terrigenous sediments. The images of the subsurface along some lines are characterized by a depth‐dependent quasi‐periodic variation of the reflections. This variation was investigated using a cross‐correlation technique.The maxima of the seismic cross‐correlation function were compared to those of the temperature curve over the past 420 kyr. We hypothesize that the variation of the climate over this period is mirrored in the seismic reflection coefficient series of the sediments. As this effect is not seen equally well on all lines, it seems that this is a function of the profile location relative to the sediment sources, i.e. submarine canyons.
Study of chemical composition of rainwater at an urban (Pune) and a rural (Sinhagad) location in India
Authors: Momin G. A. , Ali K. , Rao P. S. P. , Safai P. D. , Chate D. M. , Praveen P. S. , Rodhe Henning , Granat Lennart
Published: April 2005

Data are presented on the chemical composition of rainwater collected at a rural site (Sinhagad) near Pune, India, between August 2002 and August 2003 and at an urban site in Pune between April 2002 and August 2003. Both bulk water samples and wet‐only samples were alkaline at both sites, with an average pH of 6.6 (both bulk and wet‐only) at Pune and 6.4 (bulk) and 6.2 (wet‐only) at Sinhagad. Only one case of acidic rain was recorded: at Sinhagad with pH of 5.2 (bulk) and 4.9 (wet‐only). The major cations were Ca2+ and Na+, and the major anions were Cl− and SO42−. Higher concentrations of both SO42− and Cl− at Pune compared to Sinhagad were balanced by higher concentration of Ca2+ such that the pH remained approximately similar and, on average, well on the alkaline side. The difference in ionic composition between the two sites, available so far only for the monsoon period, is quite small (especially in case of wet only samples) and interpreted as an influence of local sources at the Pune site. At both sites the concentrations in the bulk samples were only slightly larger than those in the wet‐only samples. Our analysis demonstrates that the Sinhagad site provides useful data representative of the regional situation. The data are also analyzed in terms of seasonal (monsoon versus postmonsoon) variations and air mass trajectories. Surprisingly high concentrations of SO42− at the rural site (Sinhagad) during the SW monsoon period may indicate transport from the African continent.
Estimation of water vapor source/sink distribution and evapotranspiration over broadleaved Koreanpine forest in Changbai Mountain using inverse Lagrangian dispersion analysis
Authors: Wang Anzhi , Jin Changjie , Diao Yiwei , Guan Dexin , Pei Tiefan
Published: April 2005

The inverse Lagrangian dispersion analysis method was used with the aim of calculating the evapotranspiration and the H2O source/sink distribution within and over broadleaved Koreanpine forest canopy, using only gradient measurement of microclimate parameters as the input of the model from 1 May to 30 September 2003. The results showed that the model produced agreement between modeled and measured daily daytime evapotranspiration. The total daytime evapotranspiration was equal to 204.88 mm compared with the measured value, 194.26 mm. However, the total calculated evapotranspiration, 298.91 mm, is much higher than the measured result, 240.33 mm. The variation of the source/sink with time and depth were also discussed at the same time.
A paired‐watershed budget study to quantify interbasin groundwater flow in a lowland rain forest, Costa Rica
Authors: Genereux David P. , Jordan Michael T. , Carbonell David
Published: April 2005

A paired‐watershed budget study was used to quantify the annual water and major ion (sodium, potassium, magnesium, calcium, chloride, and sulfate) budgets of two adjacent lowland rain forest watersheds in Costa Rica. Interbasin groundwater flow (IGF) accounted for about two thirds of the water input and about 97% of the solute input (an average over the six major ions) to one watershed but little or none of the inputs to the adjacent watershed in which IGF was at most marginally distinguishable from zero. Results underscore the significance of IGF as a potential control on the hydrology and water quality of lowland watersheds, the spatial complexity of its occurrence in lowlands (where its influence may range from dominating to negligible on adjacent watersheds), and the importance of accounting for IGF in the design and execution of watershed studies and in water management.
Photodissociation of (SO2)m(H2O)n clusters employing femtosecond pump-probe spectroscopy
Authors: Knappenberger K. L. , Castleman A. W.
Published: April 2005

A femtosecond pump-probe technique was employed to study the photodissociation dynamics of (SO2)m(H2O)n clusters in real time for clusters, where m=1, 2 and n as large as 11. The pump (excitation) step occurs through a multiphoton process which populates the dissociative E state as well as a lower-lying bound state of the sulfur dioxide (SO2) chromosphore. Dissociation of the SO2 monomer occurs through the E state and the decay is fit to a lifetime of 230 fs. The present study is in agreement with our previous investigations of homogeneous (SO2)m clusters that have shown that cluster formation inhibits the dissociation process owing to a steric effect induced by the cluster environment [K. L. Knappenberger, Jr. and A. W. Castleman, Jr., J. Chem. Phys. 121, 3540 (2004)]. The E state lifetime increases sequentially as a function of cluster size to as much as 668 fs when 11 water molecules solvate the chromophore. We have employed a method to compare the ratio of amplitude coefficients, which reflect a respective component of the mathematical fit, to determine the nature of the wave packet evolution in binary clusters. An increase of this ratio by as much as 440% was observed for large cluster sizes. A preferential ion state charge transfer, rather than dissociation, was observed in binary clusters. The significance of cluster size on evaporation processes has been investigated.
Accessing ultrahigh-pressure, quasi-isentropic states of matter
Authors: Lorenz K. T. , Edwards M. J. , Glendinning S. G. , Jankowski A. F. , McNaney J. , Pollaine S. M. , Remington B. A.
Published: April 2005

A new approach to the study of material strength of metals at extreme pressures has been developed on the Omega laser, using a ramped plasma piston drive. The laser drives a shock through a solid plastic reservoir that unloads at the rear free surface, expands across a vacuum gap, and stagnates on the metal sample under study. This produces a gently increasing ram pressure, compressing the sample nearly isentropically. The peak pressure on the sample, inferred from interferometric measurements of velocity, can be varied by adjusting the laser energy and pulse length, gap size, and reservoir density, and obeys a simple scaling relation [J. Edwards et al., Phys. Rev. Lett. 92, 075002 (2004)]. In an important application, using in-flight x-ray radiography, the material strength of solid-state samples at high pressure can be inferred by measuring the reductions in the growth rates (stabilization) of Rayleigh–Taylor unstable interfaces. This paper reports the first attempt to use this new laser-driven, quasi-isentropic technique for determining material strength in high-pressure solids. Modulated foils of Al-6061-T6 were accelerated and compressed to peak pressures of ∼200kbar. Modulation growth was recorded at a series of times after peak acceleration and well into the release phase. Fits to the growth data, using a Steinberg–Guinan constitutive strength model, give yield strengths 38% greater than those given by the nominal parameters for Al-6061-T6. Calculations indicate that the dynamic enhancement to the yield strength at ∼200kbar is a factor of ∼3.6× over the ambient yield strength of 2.9kbar. Experimental designs based on this drive developed for the National Ignition Facility laser [W. Hogan, E. Moses, B. Warner, M. Sorem, and J. Soures, Nuclear Fusion 41, 567 (2001)] predict that solid-state samples can be quasi-isentropically driven to pressures an order of magnitude higher than on Omega, accessing new regimes of dense, high-pressure matter.
Copper precipitation in large-diameter Czochralski silicon
Authors: Xi Zhenqiang , Chen Jun , Yang Deren , Lawerenz A. , Moeller H. J.
Published: April 2005

The behavior of the copper precipitation in the large-diameter Czochralski silicon (Cz–Si) annealed at 1100°C followed by air cooling or slow cooling was studied by means of scanning infrared microscopy (SIRM), optical microscopy, and surface photovoltage. For the air-cooled specimen, a high density of copper-precipitate colonies with strong contrast could be easily found in the A-defect zone, while in the D-defect zone of the same specimen almost no colonies could be observed through SIRM. However, optical images showed that the higher density of the etching pits induced by the copper-precipitate colonies occurred in the D-defect zone, which indicates that the copper-precipitate colonies in the D-defect zone was below the detection limitation of SIRM. This suggestion was confirmed by minority-carrier diffusion-length mapping, which revealed that the diffusion length of the minority carriers in the D-defect zone was noticeably lower than that in the A-defect zone. As for the slow-cooled specimen, big star-like colonies formed both in the D-defect zone and A-defect zone, but the diffusion length of the minority carriers in the D-defect zone was also lower than that in the A-defect zone. On the basis of experiments, it is suggested that the as-grown vacancies or their related defects in the D-defect zone enhance the nucleation of copper precipitation either under air cooling or under slow cooling, resulting in the lower diffusion length of minority carriers.
Saturation of stimulated Brillouin backscattering in two-dimensional kinetic ion simulations
Authors: Cohen B. I. , Divol L. , Langdon A. B. , Williams E. A.
Published: April 2005

Two-dimensional simulations with a hybrid code (kinetic particle ions and Boltzmann fluid electrons) have been used to investigate the saturation of stimulated Brillouin backscatter (SBBS) instability. The simulations address the interplay of wave breaking and ion trapping (and the associated nonlinear frequency shift of the ion wave and nonlinear modification of the kinetic dissipation), two-ion-wave decay instability, harmonic generation, and pump depletion in affecting SBBS saturation as a function of the population of resonant ions, which is controlled by ZTe∕Ti in a single ion species plasma (Z is the ion charge state and Te,i are the electron and ion temperatures). The role of ponderomotive filamentation in these simulations is also examined. The peak SBBS reflectivities in two dimensions relax to values that are much less than in one dimension. Two-dimensional physics facilitates higher ion wave dissipation rates (including significant residual ion Landau damping) that account for the relaxation and suppression of SBBS.
Self-oscillations in chemoresponsive gels: A theoretical approach
Authors: Boissonade J.
Published: April 2005

Some gels can swell or shrink in function of the concentration of the solutes contained in the solvent. We develop and discuss an algorithm based on Stefan-Maxwell equations to study the dynamics of a sphere of chemoresponsive gel immersed in a medium kept far from equilibrium. We show that the coupling of the reaction with these volume changes creates some feedback that can lead to chemomechanical instabilities. As a result, a reaction that is not oscillatory in homogeneous conditions or in a nonresponsive gel can induce self-oscillations of volume and concentrations in a responsive gel. We also show that chemical oscillations related to long range activation can be strongly modified in such gels, even when the changes of volume are small.
Improved target stability using picket pulses to increase and shape the ablator adiabat
Authors: Knauer J. P. , Anderson K. , Betti R. , Collins T. J. B. , Goncharov V. N. , McKenty P. W. , Meyerhofer D. D. , Radha P. B. , Regan S. P. , Sangster T. C. , Smalyuk V. A. , Frenje J. A. , Li C. K. , Petrasso R. D. , Séguin F. H.
Published: April 2005

Hydrodynamic simulations have shown that a picket pulse preceding the main target drive pulse in a direct-drive inertial confinement fusion implosion can reduce both the ablation-interface Rayleigh–Taylor (RT) seed and growth rate by increasing the adiabat (ratio of the plasma pressure to the Fermi-degenerate pressure) while maintaining the low adiabat in the inner-fuel layer for optimal target compression and a minimal drive energy for ignition. Experiments with planar and spherical targets have been carried out on the OMEGA [T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, and C. P. Verdon, Opt. Commun. 133, 495 (1997)] laser system, showing that the RT growth of nonuniformities was reduced by picket-pulse laser illumination. Adiabat shaping in spherical targets has been investigated with two types of picket pulses—a “decaying shock wave” and a “relaxation” picket. Planar growth measurements using a wide, intense picket to raise the adiabat of a CH foil showed that the growth of short-wavelength perturbations was reduced, and even stabilized, by adjusting the intensity of the picket. Planar imprint experiments showed the expected reduction of imprinting when a picket pulse is used. The data show that the imprint level was reduced when a picket was added and for short wavelengths was as effective as one-dimensional (1D), 1.5 Å smoothing by spectral dispersion. A series of implosion experiments with a 130 ps wide picket pulse showed a clear improvement in the performance of direct-drive implosions when the picket pulse was added to the drive pulse. Results from relaxation-picket implosions show larger yields from fusion reactions when the picket drive was used. These adiabat-shaping concepts make the likelihood of achieving ignition with direct-drive implosions on the National Ignition Facility [W. S. Hogan et al., Nucl. Fusion 41, 567 (2001)] significantly more probable.
Coupling between the exciton and cavity modes in a GaAs∕GaAlAs asymmetric microcavity structure
Authors: Lin D. Y. , Chou Y. H. , Huang Y. S. , Tiong K. K.
Published: April 2005

The coupling effect between the cavity mode and excitonic states in a GaAs∕GaAlAs asymmetric microcavity structure was studied via angle and temperature dependent reflectance and piezoreflectance (PzR) measurements in the angular range 10°<θinc<60° and temperature range 20K<T<300K. The so-called cavity mode (CM) consists of photonic waves confined in the microcavity, and shifts to higher energy with increasing angle or decreasing temperature, whereas the angle independent excitonic states of the quantum well structure shift to higher energy with decreasing temperature. By varying the angle of incidence of the probe beam and temperature, the coupling strength between the excitonic transitions and CM can be tuned. The related PzR features have shown significant enhancement when the cavity mode matches up with the excitonic transitions. A detailed experimental study of the resonance enhancement effect between the excitonic transitions and CM is presented.
Nonparabolic macroscopic transport models for device simulation based on bulk Monte Carlo data
Authors: Grasser T. , Kosik R. , Jungemann C. , Kosina H. , Selberherr S.
Published: April 2005

We derive higher-order macroscopic transport models for semiconductor device simulation from Boltzmann’s transport equation using the method of moments. To obtain a tractable equation set suitable for numerical implementation the validity of the diffusion limit will be assumed which removes the convective terms from the equation system. The infinite hierarchy of equations is then truncated at the orders two (drift-diffusion model), four (energy-transport model), and six. Nonparabolicity correction factors are included in the streaming terms. Closure relations for the highest-order moments are obtained from a cold Maxwell distribution (drift-diffusion) and a heated Maxwell distribution (energy-transport). For the six moments model this issue is more complicated. In particular, this closure relation is identified to be crucial both in terms of accuracy and in terms of numerical stability. Various possible closure relations are discussed and compared. In addition to the closure of the highest-order moment, various transport parameters such as mobilities and relaxation times appear in the models and need to be accurately modeled. Particularly for higher-order transport models this is a complicated issue and since the analytical models used in our previous attempts did not deliver satisfactory results we extract all these parameters using homogeneous Monte Carlo simulations. Since all macroscopic transport models are based on rather stringent assumptions a practical evaluation is mandatory. Therefore, the proposed six moments model, a corresponding energy-transport model, and the drift-diffusion model are carefully compared to self-consistent Monte Carlo simulations.
Resistive wall mode stabilization of high-β plasmas in the National Spherical Torus Experiment
Authors: Sontag Aaron C. , Sabbagh S. A. , Zhu W. , Bialek J. M. , Menard J. E. , Gates D. A. , Glasser A. H. , Bell R. E. , LeBlanc B. P. , Bell M. G. , Bondeson A. , Callen J. D. , Chu M. S. , Hegna C. C. , Kaye S. M. , Lao L. L. , Liu Y. , Maingi R. , Mueller D. , Shaing K. C. , Stutman D. , Tritz K.
Published: April 2005

The resistive wall mode (RWM) poses a limit to the maximum β that can be sustained in magnetic fusion experiments. RWM stabilization physics at low aspect ratio is studied in high-β National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, Y.-K. M. Peng et al., Nucl. Fusion 40, 557 (2000)] plasmas (βt up to 39%; βN up to 6.8) to understand and alleviate this constraint. Plasmas with increased q in NSTX have been maintained with β above the computed ideal no-wall β limit for more than 20 wall times with no signs of RWM growth in cases where toroidal rotation ωϕ>ωA∕4q2 across the entire plasma cross section. Plasmas that violate this stability criterion can suffer a RWM induced collapse within a few wall times. This critical rotation profile for stabilization is in agreement with drift-kinetic theory applied to low frequency magnetohydrodynamics modes [A. Bondeson and M. S. Chu, Phys. Plasmas 3, 3013 (1996)]. A toroidally symmetric array of internal sensors has been used to observe n=1–3 RWMs in NSTX. This array consists of Bp and Br sensors both above and below the midplane at 12 toroidal locations instrumented to detect toroidal mode numbers of n=1–3. RWM perturbations exceeding 30G have been measured with mode growth rates on the order of 5ms. Small modes (δB<10G) which cause minor drops in β, with growth rates ∼1500s−1 have been observed when βN exceeds 6. Resonant field amplification of an externally applied error field by the stable RWM has been observed.
Harmonics of electromagnetic and electrostatic plasma waves
Authors: Yoon Peter H. , Yi Sumin , Ryu Chang-Mo
Published: April 2005

This paper shows that there are two types of nonlinear harmonics in a turbulent plasma. Until recently, it was not clear whether the electromagnetic second-harmonic mode [P. H. Yoon, Phys. Plasmas 2, 537 (1995)] and the electrostatic harmonic at 2ωpe [P. H. Yoon, Phys. Plasmas 7, 4858 (2000)] were separate branches of nonlinear dispersion relation or whether one was a more general solution which includes the other as a special case. This paper shows that the former is true, namely, the two modes are independent solutions. This reconciles previous, apparently contradictory, predictions by showing that electromagnetic harmonic is a long-wavelength mode, while the electrostatic harmonic is characterized by short wavelengths.