bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in vegetation net primary productivity from 1982 to 1999 in China
Authors: Piao Shilong , Fang Jingyun , Zhou Liming , Zhu Biao , Tan Kun , Tao Shu
Published: June 2005

Terrestrial net primary production (NPP) has been a central focus of ecosystem science in the past several decades because of its importance to the terrestrial carbon cycle and ecosystem processes. Modeling studies suggest that terrestrial NPP has increased in the northern middle and high latitudes in the past 2 decades, and that such increase has exhibited seasonal and spatial variability, but there are few detailed studies on the temporal and spatial patterns of NPP trend over time in China. Here we present the trends in China's terrestrial NPP from 1982 to 1999 and their driving forces using satellite‐derived NDVI (Normalized Difference Vegetation Index), climate data, and a satellite‐based carbon model, CASA (Carnegie ‐Ames‐Stanford Approach). The majority of China (86% of the study area) has experienced an increase in NPP during the period 1982–1999, with an annual mean increase rate of 1.03%. This increase was resulted primarily from plant growth in the middle of the growing season (June to August) (about 43.2%), followed by spring (33.7%). At the national and biome levels, the relative increase is largest in spring (March–May), indicating an earlier onset of the growing season. The changes in the phase of China's seasonal NPP curve may primarily be the result of advanced growing season (earlier spring) and enhanced plant growth in summer. During the past 2 decades the amplitude of the seasonal curve of NPP has increased and the annual peak NPP has advanced. Historical NPP trends also indicated a high degree of spatial heterogeneity, coupled with regional climate variations, agricultural practices, urbanization, and fire disturbance.
Remagnetization of Quaternary eolian deposits: A case study from SE Chinese Loess Plateau
Authors: Wang Xisheng , Løvlie Reidar , Yang Zhenyu , Pei Junling , Zhao Zhizhong , Sun Zhiming
Published: June 2005

The loess‐paleosol succession in the southeastern margin of the Chinese Loess Plateau retains high‐resolution archives of sedimentary and environmental change. In this study, we report a detailed paleomagnetic and rock magnetic investigation of loess‐paleosol sequences in the Sanmenxia area spanning the last 1.1 Myr. The results demonstrate that the Matuyama/Brunhes Boundary occurs at the top of soil S8 and the upper and lower boundaries of the Jaramillo Normal Subchron are encountered at the top of soil S10 and loess L13, respectively, in agreement with the classic Luochuan section. Loess L9, also referred to as “the upper sand layer,” is the coarsest loess unit over the last 1.1 Myr and carries an “imperfect” normal polarity magnetization. Although it is fully separated by a short reversed polarity interval, this thick normal polarity zone is too extensive to represent excursions like Kamikatsura and/or Santa Rosa and is concluded to represent an artifact rather than a record of geomagnetic field directions. Precise multiparameter environmental magnetic determination reveals that the short reversed polarity interval within the middle of this thick normal polarity zone exactly corresponds to a thin pedogenic horizon. Detailed rock magnetic analyses show that there are no intrinsic differences in magnetomineralogical properties between this pedogenic interval and other parts of L9, although the composition of magnetically soft components (magnetite/maghemite) in the short pedogenic interval is relatively higher than that of other parts of L9. Thus it is proposed that extensive remagnetization of parts of L9 most likely reflects a lithology‐dependent process, and the dramatic coarsening of particle size across L9 is the fundamental reason for pervasive remagnetization. Our magnetostratigraphic results strongly imply that we need to reconsider the remanence‐recording fidelity of coarse loess (L9, and probably L15) and care should be taken to interpret excursions in future paleomagnetic investigations of the Chinese loess.
Bridging ocean color observations of the 1980s and 2000s in search of long‐term trends
Authors: Antoine David , Morel André , Gordon Howard R. , Banzon Viva F. , Evans Robert H.
Published: June 2005

A comprehensive revision of the Coastal Zone Color Scanner (CZCS) data‐processing algorithms has been undertaken to generate a revised level 2 data set from the near‐8‐year archive (1979–1986) collected during this “proof‐of‐concept” mission. The final goal of this work is to establish a baseline for a global, multiyear, multisensor ocean color record, to be built from observations of past (i.e., CZCS), present, and future missions. To produce an internally consistent time series, the same revised algorithms also have been applied to the first 5 years of the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) ocean color observations (1998–2002). Such a database is necessary in order to determine whether or not the ocean biogeochemistry has evolved in the past years and, if so, to be able to detect near future trends. Algorithmic and calibration aspects, along with validation results presented in this paper, are tailored toward the identification of long‐term trends, which mandated this reprocessing effort. The analysis of decadal changes from the CZCS to the SeaWiFS era shows an overall increase of the world ocean average chlorophyll concentration by about 22%, mainly due to large increases in the intertropical areas, where the seasonal cycles also substantially changed over the past 2 decades. Increases in higher latitudes, where seasonal cycles did not change, contribute to a lesser extent to the general trend. In contrast, oligotrophic gyres display declining concentrations.
Determining in‐channel (dead zone) transient storage by comparing solute transport in a bedrock channel–alluvial channel sequence, Oregon
Authors: Gooseff Michael N. , LaNier Justin , Haggerty Roy , Kokkeler Kenneth
Published: June 2005

Current stream tracer techniques do not allow separation of in‐channel dead zone (e.g., eddies) and out‐of‐channel (hyporheic) transient storage, yet this separation is important to understanding stream biogeochemical processes. We characterize in‐channel transient storage with a rhodamine WT solute tracer experiment in a 304 m cascade‐pool‐type bedrock reach with no hyporheic zone. We compare the solute breakthrough curve (BTC) from this reach to that of an adjacent 367 m alluvial reach with significant hyporheic exchange. In the bedrock reach, transient storage has an exponential residence time distribution with a mean residence time of 3.0 hours and a ratio of transient storage to stream volume of 0.14, demonstrating that at moderate discharge, bedrock in‐channel storage zones provide a small volume of transient storage with substantial residence time. In the alluvial reach, though pools are similar in size to those in the bedrock reach, transient storage has a power law residence time distribution with a mean residence time of >100 hours (estimated at nearly 1200 hours) and a ratio of storage to stream volume of 105. Because the in‐channel hydraulics of bedrock reaches are simpler than alluvial step‐pool reaches, the bedrock results are probably a lower end‐member with respect to volume and residence time, though they demonstrate that in‐channel storage may be appreciable in some reaches. These results suggest that in‐stream dead zone transient storage may be accurately simulated by exponential RTDs but that hyporheic exchange is better simulated with a power law RTD as a consequence of more complicated flow path and exchange dynamics.
Initial validation comparisons for the Atmospheric Chemistry Experiment (ACE‐FTS)
Authors: Walker Kaley A. , Randall Cora E. , Trepte Charles R. , Boone Christopher D. , Bernath Peter F.
Published: June 2005

The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE‐FTS) is the primary instrument for the ACE satellite mission. The initial validation of ozone profiles from ACE‐FTS is based on comparisons with profiles from satellite‐borne instruments and balloon‐borne ozonesondes. The satellite instruments include the SAGE III and POAM III instruments. The ACE profiles were recorded during March 2004 at high latitudes in the northern hemisphere (>65°N) and were processed with the version 1.0 retrieval algorithm. The ACE‐FTS results were found to agree within 10% with those from the other satellite measurements between 15 and 40 km, with ACE‐FTS measuring less ozone near the profile maximum. The ACE‐FTS has a lower vertical resolution than SAGE III or POAM III and this may contribute to the observed discrepancy. The comparisons with ozonesonde measurements suggest that the ACE‐FTS accurately captures vertical structures in the ozone profile that are on the order of several kilometers thick.
Trends of HF, HCl, CCl2F2, CCl3F, CHClF2 (HCFC‐22), and SF6 in the lower stratosphere from Atmospheric Chemistry Experiment (ACE) and Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements near 30°N latitude
Authors: Rinsland Curtis P. , Boone Chris , Nassar Ray , Walker Kaley , Bernath Peter , Mahieu Emmanuel , Zander Rodolphe , McConnell John C. , Chiou Linda
Published: June 2005

Volume mixing ratios (VMRs) of HF, HCl, CCl2F2, CHClF2 (HCFC‐22), and SF6 in the lower stratosphere have been derived from solar occultation measurements recorded with spaceborne high resolution Fourier transform spectrometers. Atmospheric Chemistry Experiment (ACE) VMRs measured during 2004 have been compared with those obtained in 1985 and 1994 by the Atmospheric Trace MOlecule Spectroscopy (ATMOS) instrument. Trends are estimated by referencing the measured VMRs to those of the long‐lived constituent N2O to account for variations in the dynamic history of the sampled air masses. Pressure‐gridded measurements covering 10–100 hPa (∼16 to 30 km altitude) were used in the analysis that includes typically 25°N–35°N latitude. The VMR changes provide further evidence of the impact of the emission restrictions imposed by the Montreal Protocol and its strengthening amendments and adjustments and are consistent with model predictions and known sources and sinks of halocarbons. Decreases in the lower stratospheric mixing ratios of CCl3F and HCl are measured in 2004 with respect to 1994, providing important confirmation of recent ground‐based solar absorption measurements of a decline in inorganic chlorine. Trends estimates are compared with other reported measurements and model predictions.
Electron holes in the auroral upward current region
Authors: Pottelette Raymond , Treumann Rudolf A.
Published: June 2005

Evidence is given for electron holes in the upward current auroral kilometric radiation (AKR) source region. Isolated parallel electric field structures of tripolar polarity are seen in FAST recordings, being interpreted in terms of trains of nested ion and electron holes such as shown in numerical simulations by Goldman et al. (2003). They are created by beam plasma interaction via the kinetic two‐stream instability upstream of a strong double layer, giving rise to broadband emission spectra below the ion plasma frequency. Field amplitudes reach ∼1 V m−1 peak‐to‐peak and appear to modulate both the particle energy fluxes. The presence of electron holes is responsible for the fine structure of AKR emissions.
Photoproduction of carbon monoxide in first‐year sea ice in Franklin Bay, southeastern Beaufort Sea
Authors: Xie Huixiang , Gosselin Michel
Published: June 2005

The concentration of carbon monoxide ([CO]) in first‐year ice in Franklin Bay, southeastern Beaufort Sea, was ∼40 times higher than in the underlying seawater and ∼15 times higher than in the adjacent open water. The [CO] in the sea ice decreased with increasing depth and increased rapidly at the bottom where there was an abundance of ice microalgae. The depth distribution of [CO] was consistent with a photochemical source of this compound in sea ice, which was further inferred from the vertical profiles of the dissolved organic matter absorption coefficients and directly verified by incubation of ice samples refrozen from melted ice. Results from this study suggest that substantial photooxidation of organic matter occurs in sea ice. This process may affect the organic carbon cycle in the Arctic Ocean. The potential flux of CO from sea ice to the Arctic atmosphere is estimated to be 1.4 × 1010 moles a−1.
Conscientiousness and Health across the Life Course
Authors: Roberts Brent W. , Walton Kate E. , Bogg Tim
Published: June 2005

This article provides an overview of the role conscientiousness plays in the health process over the life course. The authors describe their research on the underlying structure of conscientiousness and how conscientiousness predicts social environmental factors and health behaviors that have a known relationship to health and longevity. The authors then show that conscientiousness continues to develop in young adulthood, midlife, and even potentially in old age. Finally, they show that the life paths and health behaviors that are associated with health are also associated with changes in conscientiousness across the life course.
P2 receptor blockade attenuates fever and cytokine responses induced by lipopolysaccharide in rats
Authors: Gourine Alexander V , Poputnikov Dmitry M , Zhernosek Nikolai , Melenchuk Ekaterina V , Gerstberger Rüdiger , Spyer K Michael , Gourine Valery N
Published: June 2005

Adenosine 5′‐triphosphate (ATP) has been shown to induce release of cytokines implicated in fever, including interleukin(IL)‐1β, IL‐6, and tumour necrosis factor‐α (TNF‐α). The role of ATP‐mediated purinergic signalling in fever and cytokine release during systemic inflammation was investigated by studying the effects of P2 receptor antagonists suramin, pyridoxal‐5′‐phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS), and Brilliant Blue G (BBG) on changes in body temperature and the increases in plasma levels of IL‐1β, IL‐6, and TNFα induced by bacterial lipopolysaccharide (LPS) in rats.

LPS (Escherichia coli; 50 μg kg−1)‐induced febrile response was attenuated by suramin (25 mg kg−1 and 100 mg kg−1), PPADS (25 mg kg−1), and a more selective P2X7 receptor antagonist BBG (100 mg kg−1) injected intraperitoneally before the induction of fever.

The increase in plasma concentrations of IL‐1β and IL‐6, measured 1 h after LPS treatment, was reduced by PPADS (25 mg kg−1) and BBG (100 mg kg−1). LPS‐induced increase in plasma TNF‐α concentration was also markedly attenuated by BBG (100 mg kg−1), but not by PPADS (25 mg kg−1).

These data indicate that purinergic signalling plays an important role in the mechanisms responsible for the LPS‐induced febrile response and increases in the levels of circulating cytokines. We suggest that ATP acting via P2X7 receptors induces release of pyrogenic cytokines to mediate fever during systemic inflammation.

British Journal of Pharmacology (2005) 146, 139–145. doi:10.1038/sj.bjp.0706287
High-mobility-group A1 (HMGA1) proteins down-regulate the expression of the recombination activating gene 2 (RAG2)
Authors: BATTISTA Sabrina , FEDELE Monica , HOYOS Josefina Martinez , PENTIMALLI Francesca , PIERANTONI Giovanna Maria , VISONE Rosa , De MARTINO Ivana , CROCE Carlo Maria , FUSCO Alfredo
Published: June 2005

HMGA1 (high-mobility-group A1) proteins are architectural transcription factors that are found overexpressed in embryogenesis and malignant tumours. We have shown previously that they have a role in lymphopoiesis, since the loss of HMGA1 expression leads to an impairment of T-cell development and to an increase in B-cell population. Since RAGs (recombination activating genes) are key regulators of lymphoid differentiation, in the present study we investigate whether RAG2 expression is dependent on HMGA1 activity. We show that RAG2 gene expression is up-regulated in Hmga1−/− ES (embryonic stem) cells and EBs (embryoid bodies) as well as in yolk sacs and fibroblasts from Hmga1−/− mice, suggesting that HMGA1 proteins control RAG2 gene expression both in vitro and in vivo. We show that the effect of HMGA1 on RAG2 expression is direct, identify the responsible region in the RAG2 promoter and demonstrate binding to the promoter in vivo using chromatin immunoprecipitation. Since RAG2 is necessary for lymphoid cell development, our results suggest a novel mechanism by which HMGA1 might regulate lymphoid differentiation.
The human checkpoint sensor and alternative DNA clamp Rad9–Rad1–Hus1 modulates the activity of DNA ligase I, a component of the long-patch base excision repair machinery
Authors: SMIRNOVA Ekaterina , TOUEILLE Magali , MARKKANEN Enni , HÜBSCHER Ulrich
Published: June 2005

The human checkpoint sensor and alternative clamp Rad9–Rad1–Hus1 can interact with and specifically stimulate DNA ligase I. The very recently described interactions of Rad9–Rad1–Hus1 with MutY DNA glycosylase, DNA polymerase β and Flap endonuclease 1 now complete our view that the long-patch base excision machinery is an important target of the Rad9–Rad1–Hus1 complex, thus enhancing the quality control of DNA.
Towards a better understanding of the substrate specificity of the UDP-N-acetylglucosamine C4 epimerase WbpP
Authors: DEMENDI Melinda , ISHIYAMA Noboru , LAM Joseph S. , BERGHUIS Albert M. , CREUZENET Carole
Published: June 2005

WbpP is the only genuine UDP-GlcNAc (UDP-N-acetylglucosamine) C4 epimerase for which both biochemical and structural data are available. This represents a golden opportunity to elucidate the molecular basis for its specificity for N-acetylated substrates. Based on the comparison of the substrate binding site of WbpP with that of other C4 epimerases that convert preferentially non-acetylated substrates, or that are able to convert both acetylated and non-acetylated substrates equally well, specific residues of WbpP were mutated, and the substrate specificity of the mutants was determined by direct biochemical assays and kinetic analyses. Most of the mutations tested were anticipated to trigger a significant switch in substrate specificity, mostly towards a preference for non-acetylated substrates. However, only one of the mutations (A209H) had the expected effect, and most others resulted in enhanced specificity of WbpP for N-acetylated substrates (Q201E, G102K, Q201E/G102K, A209N and S143A). One mutation (S144K) totally abolished enzyme activity. These data indicate that, although all residues targeted in the present study turned out to be important for catalysis, determinants of substrate specificity are not confined to the substrate-binding pocket and that longer range interactions are essential in allowing proper positioning of various ligands in the binding pocket. Hence prediction or engineering of substrate specificity solely based on sequence analysis, or even on modelling of the binding pocket, might lead to incorrect functional assignments.
Comparison of density functionals for differences between the high- (T2g5) and low- (A1g1) spin states of iron(II) compounds. IV. Results for the ferrous complexes [Fe(L)(‘NHS4’)]
Authors: Ganzenmüller Georg , Berkaïne Nabil , Fouqueau Antony , Casida Mark E. , Reiher Markus
Published: June 2005

Previous work testing density functionals for use in calculating high-spin–low-spin energy differences, ΔEHL, for iron(II) spin-crossover transitions has tended to conclude that only properly reparametrized hybrid functionals can predict ΔEHL since it seems to depend critically on a correct description of the electron pairing energy governed by the exchange term. Exceptions to this rule are the previous three papers (I, II, and III in the present series of papers) where it was found that modern generalized gradient approximations (GGAs) and meta-GGAs could do as well as hybrid functionals, if not better, for this type of problem. In the present paper, we extend these previous studies to five more molecules which are too large to treat with high-quality ab initio calculations, namely, the series [Fe(L)(‘NHS4’)], where NHS4=2.2′-bis(2-mercaptophenylthio)diethylamine dianion, and L=NH3, N2H4, PMe3, CO, and NO+. Since we know of no reliable experimental estimate of ΔEHL, we content ourselves with a comparison against the experimentally determined ground-state spin symmetry including, in so far as possible, finite-temperature effects. Together with the results of Papers I, II, and III, this paper provides a test of a large number of functionals against the high-spin/low-spin properties of a diverse set of Fe(II) compounds, making it possible to draw some particulary interesting conclusions. Trends among different classes of functionals are discussed and it is pointed out that there is at least one functional, namely, the OLYP generalized gradient approximation, which is able to give a reasonably good description of the delicate spin energetics of Fe(II) coordination compounds without resorting to hybrid functionals which require the relatively more expensive calculation of a Hartree–Fock-type exchange term.
Flux effect on the ion-beam nitriding of austenitic stainless-steel AISI 304L
Authors: Abrasonis G. , Rivière J. P. , Templier C. , Pranevičius L. , Barradas N. P.
Published: June 2005

The effect of flux and Ar pretreatment during ion-beam nitriding of austenitic stainless steel is investigated. The ion energy and temperature were 1.2keV and 400°C, respectively, the ion current densities were 0.5, 0.67, and 0.83mAcm−2. The nitrogen distribution profiles were measured using nuclear reaction analysis. The obtained nitrogen distribution profiles were analyzed by the means of the nitrided layer thickness evolution due to sputtering and diffusion and the model of trapping–detrapping. Both approaches could fit well the experimental results, however, different diffusion coefficients have to be assumed for each current density. In addition, the diffusion coefficients are higher for higher current densities. On the other hand, it is shown that the pretreatment with Ar-ion beam at nitriding temperatures produces only a thermal effect without any other influence on the following nitrogen diffusion. The results are discussed in relation with surface and temperature effects and atomic transport mechanisms.
Low resistance AL2O3 magnetic tunnel junctions optimized through in situ conductance measurements
Authors: Wolfman J. , Mauri D. , Lin T. , Yang J. , Chen T.
Published: June 2005

In situ electrical conductance is used to monitor the growth and natural oxidation of aluminum on top of a CoFe electrode. Light oxidation is found to enhance the electron specular scattering of the CoFe/vacuum interface. Aluminum deposited onto CoFe intermixes to a depth of a few atomic layers, however, subsequent natural oxidation tends to reverse this interdiffusion through oxygen-driven A1 segregation. At the right A1 thickness, natural oxidation creates a clean and specular CoFe∕AlOx interface very similar to the best achievable CoFe/vacuum interface. For thicker A1, natural oxidation leaves behind underoxidized AlOx and most importantly an interdiffused CoFe∕Al interface. Using 2Torr×150-s natural oxidation, we have fabricated magnetic tunnel junctions (MTJs) with a peak tunnel magnetoresistance (TMR) of 18% for a resistance area product of 7Ωμm2, at the A1 metal thickness of 6 Å. With the same oxidation process TMR drops to only 8% when A1 is increased to 9 Å. Contrary to the accepted view, we do not attribute this TMR drop to A1 underoxidation, but primarily to the interdiffusion at the CoFe∕Al interface. This assertion is strongly supported by a second set of MTJs differing only by the insertion of a nano-oxide layer (NOL) on top of CoFe. In this case when Al is increased from 6 to 9 Å, the TMR does not drop but increases from 16% to 27%. This is significant because NOL is found to effectively prevent Al diffusion into CoFe. NOL is also found to act as a reservoir of oxygen, which is subsequently consumed by Al.
Triplet excitation transfer in glassy systems: Spatial and spectral diffusion
Authors: Ito Naoki , Richert Ranko
Published: June 2005

Triplet excitation transfer among benzophenone molecules dissolved in glassy 2-methyltetrahydrofuran is studied by recording the emission and the optical depolarization as a function of wavelength and time. The transport mechanism is based upon exchange interaction and subject to the random character of both jump distances and site energies. Optical anisotropy data are used to gauge the probability of an excitation to remain on its original site. The anisotropy is observed to decrease by a factor of 2 from high to low energies within the inhomogeneously broadened emission band, clearly indicating hopping-mediated thermalization within the density of states. Within their excited-state lifetime the excitons do not reach the steady-state energies, but solvation allows the observation of that energy level. Unexpectedly, we find that the transfers at very short times do not contribute as much to spectral diffusion as the subsequent transport. Because the short-time hops target sites as close as ≈1nm, this observation suggests spatially correlated site energies for these short distances.
Optical properties of a nematic sample in the low-frequency regime of an external electric field
Authors: Reyes J. A. , Provenzano C. , Cipparrone G. , Barbero G.
Published: June 2005

We analyze the optical response of a nematic sample submitted to an external periodic square wave representing an electric voltage of low frequency. To this end we extend a model previously proposed by us to investigate the response to a dc electric field. We determine, analytically, the time evolution of the electrical potential across the sample and the bulk and surface densities of the ions. Our analysis is performed by assuming that the ions are identical in all the aspects, except for the sign of the electrical charge. We evaluate the characteristic times of the problem by limiting our study to the case in which the distortion induced by the electric field on the nematic liquid crystal is small. This implies that the amplitude of the applied voltage is of the order of the threshold voltage of the Freedericksz transition. The theoretical model is in reasonable agreement with our experimental data.
The effect of salt concentration on the optical modes of charged cylindrical nanotubes
Authors: Iwaki Takafumi , Shew Chwen-Yang , Gumbs Godfrey
Published: June 2005

We have conducted calculations of the collective plasmon excitations for an electron gas confined to the surface of a charged single-walled cylindrical nanotube in salt solutions. Both positively and negatively charged nanotubes are investigated. At high salt concentration, the surface potential approaches zero, and the spectrum is close to that of a neutral nanotube. The highest-frequency branch of the plasmon excitation spectrum exhibits a redshift and a blueshift for negatively and positively charged nanotubes, respectively. Such a result can be attributed to the change of the number of eigenstates around the Fermi energy. As salt concentration is increased, the surface potential is screened out, and the spectral line shift diminishes. Our results also show that the negatively charged nanotube can be more sensitive to the ambient salt concentration than the positively charged one. The optimal sensor device occurs when the nanotube carries a linear charge density close to that of DNA. The theoretical predictions suggest that charged nanotubes have the potential as sensors to probe salt concentration.
Ion dynamics and mixed mobile ion effect in fluoride glasses
Authors: Ghosh S. , Ghosh A.
Published: June 2005

We report the ionic relaxation and mixed mobile ion effect in 50ZrF4−10BaF2−10YF3−(30−x)LiF−xNaF fluoride glass series, where fluorine anions participate in the diffusion process in addition to alkali cations, unlike mixed alkali oxide glasses and crystals. By analyzing the ion dynamics in the framework of a power-law model as well as modulus formalism we have observed mixed mobile ion effect in the dc conductivity and its activation energy, the crossover frequency and its activation energy, the conductivity relaxation frequency and its activation energy, and also in the decoupling index. We have correlated these phenomena with the fractal dimension of the conduction pathways in the mixed alkali fluoride glasses compared to the single alkali glasses. We have shown that the relaxation dynamics in mixed alkali fluoride glasses is independent of temperature but dependent on glass composition.
Canonical quantization of SU(3) Skyrme model in a general representation
Authors: Jurčiukonis D. , Norvaišas E. , Riska D. O.
Published: June 2005

A complete canonical quantization of the SU(3) Skyrme model performed in the collective coordinate formalism in general irreducible representations. In the case of SU(3) the model differs qualitatively in different representations. The Wess-Zumino-Witten term vanishes in all self-adjoint representations in the collective coordinate method for separation of space and time variables. The canonical quantization generates representation dependent quantum mass corrections, which can stabilize the soliton solution. The standard symmetry breaking mass, which in general leads to representation mixing, degenerates to the SU(2) form in all self-adjoint representations.
Behavior of liquid lithium jet irradiated by 1 MeV electron beams up to 20 kW
Authors: Nolen J. A. , Reed C. B. , Novick V. J. , Specht J. R. , Bogaty J. M. , Plotkin P. , Momozaki Y.
Published: June 2005

Experiments were conducted to demonstrate the stable operation of the windowless liquid lithium target under extreme thermal loads that are equivalent to uranium beams from the proposed Rare Isotope Accelerator (RIA) driver linac. The cross section of the windowless liquid lithium target was 5mm×10mm and the velocity of the liquid lithium was varied up to 6m∕s. Thermal loads up to 20 kW within a beam spot of 1 mm in diameter were applied on the windowless liquid lithium target by 1 MeV electron beams. The maximum power density and total power deposited within the target was equivalent to that of a 200 kW, 400MeV∕u uranium beam. It was demonstrated that the windowless liquid lithium target flowing at as low as 1.8m∕s stably operates at a beam energy deposition up to 20 kW without disruption or excess vaporization.
A quasioptical transient electron spin resonance spectrometer operating at 120 and 240 GHz
Authors: van Tol J. , Brunel L.-C. , Wylde R. J.
Published: June 2005

A new multifrequency quasioptical electron paramagnetic resonance (EPR) spectrometer is described. The superheterodyne design with Schottky diode mixer/detectors enables fast detection with subnanosecond time resolution. Optical access makes it suitable for transient EPR (TR-EPR) at 120 and 240 GHz. These high frequencies allow for an accurate determination of small g-tensor anisotropies as are encountered in excited triplet states of organic molecules like porphyrins and fullerenes. The measured concentration sensitivity for continuous-wave (cw) EPR at 240 GHz and at room temperature without cavity is 1013spins∕cm3 (15 nM) for a 1 mT linewidth and a 1 Hz bandwidth. With a Fabry-Perot cavity and a sample volume of 30 nl, the sensitivity at 240 GHz corresponds to ≈3×109 spins for a 1 mT linewidth. The spectrometer’s performance is illustrated with applications of transient EPR of excited triplet states of organic molecules, as well as cw EPR of nitroxide reference systems and a thin film of a colossal magnetoresistance material.
Nondissipative current in a quantum wire
Authors: Guseinov N. M. , Seyid-Rzayeva S. M.
Published: June 2005

A theoretical study is made of the nondissipative current of a two-dimensional degenerate electron gas in a planar quantum wire with a parabolic confining potential in a magnetic field perpendicular to the plane of the wire. With the aid of a solution of the equation of the density matrix an expression for the nondissipative conductivity in a magnetic field of arbitrary strength is obtained. It is found that the conductivity has metallic properties and the quantum Hall effect should not arise in a wire with a parabolic confining potential. At high magnetic fields the expression for the nondissipative conductivity corresponds to the “classical” one. At low fields the conductivity is directly proportional to the first power of the magnetic field strength.
Dynamics of domain inversion in LiNbO3 poled using topographic electrode geometries
Authors: Johnston Benjamin F. , Withford Michael J.
Published: June 2005

We report results of an investigation studying the domain inversion kinetics of lithium niobate when electric field poling using laser-machined topographical electrodes. Inversion is shown to begin with a single nucleation spike and the domains evolve in a unique fashion governed by the topographical structure. We also demonstrate control of the resulting domain widths when poling using this technique. The results presented have implications for rapid prototyping of chirped and aperiodic domain structures in lithium niobate.
Template-directed carbon nanotube network using self-organized Si nanocrystals
Authors: Yang B. , Marcus M. S. , Keppel D. G. , Zhang P. P. , Li Z. W. , Larson B. J. , Savage D. E. , Simmons J. M. , Castellini O. M. , Eriksson M. A. , Lagally M. G.
Published: June 2005

We demonstrate a way to direct carbon nanotube growth using Si nanocrystals that are self-ordered via the thermal decomposition of thin silicon-on-insulator substrates. The Si nanocrystals are about 90nm wide and 100–150nm tall, with 200nm spacing. Nanotubes connect the silicon nanocrystals to form a network. Nanotubes selectively appear between tops of the Si nanocrystals. We show that the flow pattern of the carbon feedstock in the chemical vapor deposition growth process is disturbed by the geometric effect of the Si nanocrystals, providing a mechanism for growth between the tops of the Si nanocrystals.
Manganese-modified BiScO3–PbTiO3 piezoelectric ceramic for high-temperature shear mode sensor
Authors: Zhang Shujun , Eitel Richard E. , Randall Clive A. , Shrout Thomas R. , Alberta Edward F.
Published: June 2005

The bismuth-based perovskite solid solution (100−x)BiScO3−xPbTiO3 (BSPT) was investigated for use at temperatures up to 400°C and above. The high-temperature resistivity, together with dielectric and piezoelectric behaviors of the shear mode for manganese-modified BSPT ceramics near the morphotropic phase boundary composition were studied. The resistivity and time constant were found to be 3×107Ωcm and 0.08s, respectively, at 450°C for modified BSPT66. The dielectric constant Κ11T and dielectric loss were found to be 1112 and 1%, respectively, at room temperature, showing a Curie temperature at 468°C. The electromechanical coupling factor k15 was calculated to be 61%, staying nearly constant up to 440°C, expanding the temperature usage range significantly. The properties indicate that the modified BSPT66 material is a promising candidate for high-temperature shear sensor applications.
Molecular-beam epitaxy of p-type m-plane GaN
Authors: McLaurin M. , Mates T. E. , Speck J. S.
Published: June 2005

We report on the plasma-assisted molecular-beam epitaxy of Mg-doped (101¯0) GaN on (101¯0) 6H–SiC. Secondary ion mass spectroscopy measurements show the incorporation of Mg into the GaN films with an enhanced Mg incorporation under N-rich conditions relative to Ga-rich growth. Transport measurements of Mg-doped layers grown under Ga-rich conditions show hole concentrations in the range of p=1×1018 to p=7×1018cm−3 and a dependence between hole concentration and Mg beam equivalent pressure. An anisotropy in in-plane hole mobilities was observed, with the hole mobility parallel to [112¯0] being higher than that parallel to [0001] for the same hole concentration. Mobilities parallel to [112¯0] were as high as ∼11.5cm2∕Vs (at p∼1.8×1018cm−3).
Insights into regulation of human Schwann cell proliferation by Erk1/2 via a MEK-independent and p56Lck-dependent pathway from leprosy bacilli
Authors: Tapinos Nikos , Rambukkana Anura
Published: June 2005

Activation of extracellular signal-regulated kinase (Erk) 1/2, which plays a critical role in diverse cellular processes, including cell proliferation, is known to be mediated by the canonical Raf-mitogen-activated protein kinase kinase (MEK) kinase cascade. Alternative MEK-independent signaling pathways for Erk1/2 activation in mammalian cells are not known. During our studies of human primary Schwann cell response to long-term infection ofMycobacterium leprae, the causative organism of leprosy, we identified that intracellularM. lepraeactivated Erk1/2 directly by lymphoid cell kinase (p56Lck), a Src family member, by means of a PKCε-dependent and MEK-independent signaling pathway. Activation of this signaling induced nuclear accumulation of cyclin D1, G1/S-phase progression, and continuous proliferation, but without transformation. Thus, our data reveal a previously unknown signaling mechanism of glial cell proliferation, which might play a role in dedifferentiation as well as nerve regeneration and degeneration. Our findings may also provide a potential mechanism by which an obligate intracellular bacterial pathogen likeM. lepraesubverts nervous system signaling to propagate its cellular niche for colonization and long-term bacterial survival.
RETRACTED: S1P
3
receptor-induced reorganization of epithelial tight junctions compromises lung barrier integrity and is potentiated by TNF
Authors: Gon Yasuhiro , Wood Malcolm R. , Kiosses William B. , Jo Euijung , Sanna M. Germana , Chun Jerold , Rosen Hugh
Published: June 2005

Pulmonary pathologies including adult respiratory distress syndrome are characterized by disruption of pulmonary integrity and edema compromising respiratory function. Sphingosine 1-phosphate (S1P) is a lipid mediator synthesized and/or stored in mast cells, platelets, and epithelial cells, with production up-regulated by the proinflammatory cytokines IL-1 and TNF. S1P administration via the airways but not via the vasculature induces lung leakage. Using receptor-null mice, we show that S1P, acting on S1P
3
receptor expressed on both type I and type II alveolar epithelial cells but not vascular endothelium, induces pulmonary edema by acute tight junction opening. WT but not S1P
3
-null mice showed disruption of pulmonary epithelial tight junctions and the appearance of paracellular gaps between epithelial cells by electron microscopy within 1 h of airways exposure to S1P. We further show by fluorescence microscopy that S1P induced rapid loss of ZO-1 reactivity, an essential component of the cytoplasmic plaque associated with tight junctions, as well as of the tetraspannin Claudin-18, an integral membrane organizer of tight junctions. S1P shows synergistic activity with the proinflammatory cytokine TNF, showing both pulmonary edema and mortality at subthreshold S1P doses. Specifically, preexposure of mice to subthreshold doses of TNF, which alone induced no lung edema, exacerbated S1P-induced edema and impaired survival. S1P, acting through S1P
3
, regulates epithelial integrity and acts additively with TNF in compromising respiratory barrier function. Because S1P
3
-null mice are resistant to S1P-induced pulmonary leakage, either alone or in the presence of TNF, S1P
3
antagonism may be useful in protecting epithelial integrity in pulmonary disease.
Regulation of dopaminergic transmission and cocaine reward by the
Clock
gene
Authors: McClung Colleen A. , Sidiropoulou Kyriaki , Vitaterna Martha , Takahashi Joseph S. , White Francis J. , Cooper Donald C. , Nestler Eric J.
Published: June 2005

Although there are clear interactions between circadian rhythms and drug addiction, mechanisms for such interactions remain unknown. Here we establish a role for the
Clock
gene in regulating the brain's reward circuit. Mice lacking a functional
Clock
gene display an increase in cocaine reward and in the excitability of dopamine neurons in the midbrain ventral tegmental area, a key brain reward region. These phenotypes are associated with increased expression and phosphorylation of tyrosine hydroxylase (the rate-limiting enzyme in dopamine synthesis), as well as changes in several genes known to regulate dopamine activity in the ventral tegmental area. These findings demonstrate the involvement of a circadian-associated gene,
Clock
, in regulating dopamine function and cocaine reward.
An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent
Authors: Beatty J. Thomas , Overmann Jörg , Lince Michael T. , Manske Ann K. , Lang Andrew S. , Blankenship Robert E. , Van Dover Cindy L. , Martinson Tracey A. , Plumley F. Gerald
Published: June 2005

The abundance of life on Earth is almost entirely due to biological photosynthesis, which depends on light energy. The source of light in natural habitats has heretofore been thought to be the sun, thus restricting photosynthesis to solar photic environments on the surface of the Earth. If photosynthesis could take place in geothermally illuminated environments, it would increase the diversity of photosynthetic habitats both on Earth and on other worlds that have been proposed to possibly harbor life. Green sulfur bacteria are anaerobes that require light for growth by the oxidation of sulfur compounds to reduce CO
2
to organic carbon, and are capable of photosynthetic growth at extremely low light intensities. We describe the isolation and cultivation of a previously unknown green sulfur bacterial species from a deep-sea hydrothermal vent, where the only source of light is geothermal radiation that includes wavelengths absorbed by photosynthetic pigments of this organism.
Degrees and kinds of selection in spontaneous neoplastic transformation: An operational analysis
Authors: Rubin Harry
Published: June 2005

Spontaneous neoplastic transformation develops within days in the NIH 3T3 line of cells through differential inhibition of their proliferation under contact inhibition. A small fraction of the population continues to multiply after saturation density is reached and is selected to progressively increase saturation density in successive rounds of confluence. The degree of selection at confluence depends on the extent of proliferation of some cells in a heterogeneous population. The development of transformed foci is an extension of the same selective process that increases saturation density. The expression of the foci is enhanced with increases in the saturation density of the surrounding cells. Transformation is also induced by moderately reducing the concentration of calf serum in the medium during low-density passages, which allows selection of cells that require less growth factor. Further stepwise reductions in serum increase the degree of transformation. Contact inhibition and reduction in serum concentration select for the same phenotype of cell that increases saturation density and generates transformed foci. There is mounting evidence that selection is a major factor in the development of common epithelial tumors of humans, but it extends over decades rather than days, and thein vivomicroenvironment selects from more stable populations of cells than those in culture. The many progressive levels of increased saturation density and transformed focus formation suggest that a very large number of genes participate in neoplastic development. The operational model of variation and selection presented here may aid in understanding chemical carcinogenesis and cancer recurrence after chemotherapy.
Stress duration modulates the spatiotemporal patterns of spine formation in the basolateral amygdala
Authors: Mitra Rupshi , Jadhav Shantanu , McEwen Bruce S. , Vyas Ajai , Chattarji Sumantra
Published: June 2005

It has long been hypothesized that morphological and numerical alterations in dendritic spines underlie long-term structural encoding of experiences. Here we investigate the efficacy of aversive experience in the form of acute immobilization stress (AIS) and chronic immobilization stress (CIS) in modulating spine density in the basolateral amygdala (BLA) of male rats. We find that CIS elicits a robust increase in spine density across primary and secondary branches of BLA spiny neurons. We observed this CIS-induced spinogenesis in the BLA 1 d after the termination of CIS. In contrast, AIS fails to affect spine density or dendritic arborization when measured 1 d later. Strikingly, the same AIS causes a gradual increase in spine density 10 d later but without any effect on dendritic arbors. Thus, by modulating the duration of immobilization stress, it is possible to induce the formation of new spines without remodeling dendrites. However, unlike CIS-induced spine formation, the gradual increase in spine density 10 d after a single exposure to AIS is localized on primary dendrites. Finally, this delayed induction of BLA spinogenesis is paralleled by a gradual development of anxiety-like behavior on the elevated plus-maze 10 d after AIS. These findings demonstrate that stressful experiences can lead to the formation of new dendritic spines in the BLA, which is believed to be a locus of storage for fear memories. Our results also suggest that stress may facilitate symptoms of chronic anxiety disorders like post-traumatic stress disorder by enhancing synaptic connectivity in the BLA.
Intracellular collagen degradation mediated by uPARAP/Endo180 is a major pathway of extracellular matrix turnover during malignancy
Authors: Curino Alejandro C. , Engelholm Lars H. , Yamada Susan S. , Holmbeck Kenn , Lund Leif R. , Molinolo Alfredo A. , Behrendt Niels , Nielsen Boye Schnack , Bugge Thomas H.
Published: June 2005

We recently reported that uPARAP/Endo180 can mediate the cellular uptake and lysosomal degradation of collagen by cultured fibroblasts. Here, we show that uPARAP/Endo180 has a key role in the degradation of collagen during mammary carcinoma progression. In the normal murine mammary gland, uPARAP/Endo180 is widely expressed in periductal fibroblast-like mesenchymal cells that line mammary epithelial cells. This pattern of uPARAP/Endo180 expression is preserved during polyomavirus middle T–induced mammary carcinogenesis, with strong uPARAP/Endo180 expression by mesenchymal cells embedded within the collagenous stroma surrounding nests of uPARAP/Endo180-negative tumor cells. Genetic ablation of uPARAP/Endo180 impaired collagen turnover that is critical to tumor expansion, as evidenced by the abrogation of cellular collagen uptake, tumor fibrosis, and blunted tumor growth. These studies identify uPARAP/Endo180 as a key mediator of collagen turnover in a pathophysiological context.
Interleukin (IL)-4 inhibits IL-10 to promote IL-12 production by dendritic cells
Authors: Yao Yongxue , Li Wei , Kaplan Mark H. , Chang Cheong-Hee
Published: June 2005

Interleukin (IL)-4 is known to be the most potent cytokine that can initiate Th2 cell differentiation. Paradoxically, IL-4 instructs dendritic cells (DCs) to promote Th1 cell differentiation. We investigated the mechanisms by which IL-4 directs CD4 T cells toward the Th1 cell lineage. Our study demonstrates that the IL-4–mediated induction of Th1 cell differentiation requires IL-10 production by DCs. IL-4 treatment of DCs in the presence of lipopolysaccharide or CpG resulted in decreased production of IL-10, which was accompanied by enhanced IL-12 production. In IL-10–deficient DCs, the level of IL-12 was greatly elevated and, more importantly, the ability of IL-4 to up-regulate IL-12 was abrogated. Interestingly, IL-4 inhibited IL-10 production by DCs but not by B cells. The down-regulation of IL-10 gene expression by IL-4 depended on Stat6 and was at least partly caused by decreased histone acetylation of the IL-10 promoter. These data indicate that IL-4 plays a key role in inducing Th1 cell differentiation by instructing DCs to produce less IL-10.