bluuebunny/crossref_metadata_2025 huggingface dataset:
Postoperative Evolution of Inflammatory Response in a Model of Suprarenal Aortic Cross‐clamping with and without Hemorrhagic Shock. Systemic and Local Reactions
Authors: Lozano Francisco S. , Rodriguez José M. , Garcia‐Criado Francisco J. , Barros Marcello B. , Conde Pilar S. , Gonzalez Luis M. , Rodriguez Manuel , Gomez‐Alonso Alberto
Published: August 2005

Surgery of the abdominal aorta generates a systemic inflammatory response (SIR), a source of operative morbidity‐mortality. In the present work we attempted to evaluate the evolution of SIR in an experimental model that simulates elective and urgent surgery on the abdominal aorta. Fifteen mini‐pigs divided into three groups were used. The animals were subjected to suprarenal aortic/iliac clamping and bypass with a Dacron‐collagen prosthetic graft. Groups were as follows: (1) sham (only aortic dissection); (2) clamping and bypass; (3) hemorrhage of 40%, pre‐clamping, and bypass. Determinations included (1) tumor necrosis factor‐alpha (TNF‐α) interleukin (IL)‐1β, IL‐6, IL‐10, interferon‐gamma; (2) myeloperoxidase (MPO), superoxide anion (SOA), superoxide dismutase (SOD), and malondialdehyde (MDA); (3) nitrites; (4) iNOS, (5) cell adhesion molecules (ICAM‐1, VCAM‐1) at 24 hours, 48 hours, and on day 7; and (6) NFκB at 48 hours. Our results point to an increase in all inflammatory variables, corroborated by their molecular regulators such as the expression of CAMs, iNOS, and NFκB. The alterations tended to normalize by day 7, after reperfusion. The results point to the great importance of SIR at all levels (molecular, nuclear, cellular, and systemic) in situations such as elective and urgent abdominal aorta surgery and the role that control of this response could represent for the future of vascular surgery.
Relationships between Volume, Efficiency, and Quality in Surgery — A Delicate Balance from Managerial Perspectives
Authors: Kraus Thomas W. , Büchler Markus W. , Herfarth Christian
Published: August 2005

Volume, efficiency, and quality in hospital care are often mixed in debate. We analyze how these dimensions are interrelated in surgical hospital management, with particular focus on volume effects: under financial constraints, efficiency is the best form of cost control. External perception of quality is important to attract patients and gain volumes. There are numerous explicit and implicit notions of surgical quality. The relevance of implicit criteria (functionality, reliability, consistency, customaziability, convenience) can change in the time course of hospital competition. Outcome data theoretically are optimal measures of quality, but surgical quality is multifactorially influenced by case mix, surgical technique, indication, process designs, organizational structures, and volume. As quality of surgery is hard to grade, implicit criteria such as customizability currently often overrule functionality (outcome) as the dominant market driver. Activities and volumes are inputs to produce quality. Capability does not translate to ability in a linear function. Adequate process design is important to realize efficiency and quality. Volumes of activities, degree of standardization, specialization, and customer involvement are relevant estimates for process design in services. Flow‐orientated management focuses primarily on resource utilization and efficiency, not on surgical quality. The relationship between volume and outcome in surgery is imperfectly understood. Factors involve learning effects both on process efficiency and quality, increased standardization and task specialization, process flow homogeneity, and potential for process integration. Volume is a structural component to develop efficiency and quality. The specific capabilities and process characteristics that contribute to surgical outcome improvement should be defined and exported. Adequate focus should allow even small institutions to benefit from volume‐associated effects. All volumes‐based learning within standardized processes will finally lead to a plateauing of quality. Only innovations will then further improve quality. Possessing volume can set the optimal ground for continuous process research, subsequent change, innovation, and optimization, while volume itself appears not to be a quality prerequisite.
The care provided by general practitioners for persistent depression
Authors: Van Os Titus W.D.P. , Van den Brink Rob H.S. , Van der Meer Klaas , Ormel Johan
Published: September 2005

Purpose.

To examine the care provided by general practitioners (GPs) for persistent depressive illness and its relationship to patient, illness and consultation characteristics.

Subjects and method.

Using the Composite International Diagnostic Interview-Primary Health Care Version (CIDI-PHC) a sample of 264 patients with ICD-10 depression was identified among consecutive primary care patients in the Netherlands. At 1-year follow-up 78 of these patients (30%) still fulfilled the criteria of an ICD-10 depression and were considered persistent cases. At baseline and follow-up the GPs specified their diagnosis and treatment. The extent of recognition as a mental health problem, accuracy of diagnosis as a depression and treatment in accordance with clinical guidelines for depression was examined. In addition it was examined whether these steps in adequate GP care for persistent depression were related to patient, illness and consultation characteristics.

Results.

Twenty percent of the persistent depression cases were not recognized at baseline or during follow-up, 28% was recognized but not accurately diagnosed, 17% was accurately diagnosed, but did not receive adequate treatment and 35% was treated adequately. Recognition was associated with psychological reason for encounter; accurate diagnosis with absence of activity limitation days; and adequate treatment with severity of depression and higher educational level.

Conclusion.

Non-recognition, misdiagnosis and inadequate treatment are not limited to patients with a relatively mild and brief depression but are also prominent in patients with a persistent depression, who consulted their GP 8.2 times on average during the year their depression persisted.
Regulation of the F0F1‐ATP synthase: The conformation of subunit ε might be determined by directionality of subunit γ rotation
Authors: Feniouk Boris A. , Junge Wolfgang
Published: August 2005

We propose that the directionality of the coiled‐coil subunit γ rotation determines whether subunit ε is in contracted or extended form. Block of rotation by MgADP presumably induces the extended conformation of subunit ε. This conformation might serve as a safety lock, stabilizing the ADP‐inhibited state upon de‐energization and preventing spontaneous re‐activation and wasteful ATP hydrolysis. The hypothesis merges the known regulatory effects of ADP, protonmotive force and conformational changes of subunit ε into a consistent picture.
Small GTPase Rho5 is a functional homologue of Rho1, which controls cell shape and septation in fission yeast
Authors: Nakano Kentaro , Arai Ritsuko , Mabuchi Issei
Published: August 2005

The small GTPase Rho1 plays an essential role in controlling the organization of the actin cytoskeleton and synthesis of the cell wall in the fission yeastSchizosaccharomyces pombe. Here we studied the role of Rho5 whose primary structure is very similar to that of Rho1. It was found that elevated expression of Rho5 was able to compensate for the lethality of cells lacking Rho1. Rho5 was localized to the ends of interphase cells and the mid‐region of mitotic cells. Overexpression of Rho5 caused depolarization of F‐actin patches and abnormal formation of the cell wall, as did Rho1. Althoughrho5+was not essential for maintaining the cell shape,rho1 rho5‐double null cells showed more severe defects in cell viability thanrho1‐null cells. Thus, it is likely that Rho5 has an overlapping function with Rho1 in controlling cell growth and division inS. pombe.
Uncovering RNAi mechanisms in plants: Biochemistry enters the foray
Authors: Qi Yijun , Hannon Gregory J.
Published: September 2005

In plants, the RNA interference (RNAi) machinery responds to a variety of triggers including viral infection, transgenes, repeated elements and transposons. All of these triggers lead to silencing outcomes ranging from mRNA degradation to translational repression to chromatin remodeling. Thus, plants offer us a potentially unique opportunity to understand the full range of RNAi effector mechanisms. In this review, we discuss the recent developments in our understanding of plant RNAi mechanisms from a biochemical perspective.
Comparison between Percutaneous Transverse Fixation and Intramedullary K-Wires in Treating Closed Fractures of the Metacarpal Neck of the Little Finger
Authors: WONG T. C. , IP F. K. , YEUNG S. H.
Published: September 2005

We performed a non-randomized controlled clinical trial of 59 clinical cases to compare percutaneous transverse K-wire fixation and intramedullary K-wires in treating closed fractures of the metacarpal neck of the little finger. Twenty-nine patients were treated by percutaneous transverse K-wire fixation and 30 patients were treated with intramedullary K-wires. They were reviewed at a mean follow-up of 24 months for radiological and functional outcome in terms of union rate, union time, complication rate, pain, movement and grip strength. Radiographs did not show any significant differences in the union rate and union time. There was no statistical difference in complication rate, pain scores, total active motion and grip strength between the two groups. The authors suggest that both methods are comparable, good and safe methods of treating closed, displaced fractures of the metacarpal neck of the little finger, without significant complications.
Mass budget and dynamics of polychlorinated biphenyls in the eastern Mediterranean Sea
Authors: Mandalakis M. , Apostolaki M. , Stephanou E. G. , Stavrakakis S.
Published: September 2005

Polychlorinated biphenyls (PCBs) were measured in dry deposition and sediment trap samples from the eastern Mediterranean and the results of the present and previous studies were synthesized in order to construct a mass balance budget describing the status and dynamics of PCBs in this region. According to our calculations, the burden of total PCBs in the euphotic zone of the eastern Mediterranean should approach 84,000 kg, while the corresponding pool in the overlying atmosphere should be about 162 kg. The atmospheric input of PCBs in the respective water basin through dry and wet deposition should be 300 and 1300 kg yr−1, respectively. On the contrary, air‐sea exchange should cause a net volatilization of PCBs from seawater to the atmosphere by 3150 kg yr−1. Moreover, PCBs are removed from the water column with a settling flux of 350 kg yr−1 and under steady state conditions, an additional input of these pollutants should be required to counterbalance the outflows from the water basin. The discharge of urban and industrial sewage, riverine input and transport of more polluted surface waters from western to eastern Mediterranean may account for most of this inflow. In the atmospheric compartment, the removal flux of PCBs due to their destruction by hydroxyl radicals (6650 kg yr−1) was approximately 4 times higher than their deposition flux (wet plus dry). On the basis of these data, 5100 kg of PCBs should enter into the atmosphere of eastern Mediterranean annually in order to achieve steady state conditions. This influx may result from long or short range transport of atmospheric PCBs emitted from contaminated terrestrial surfaces.
Timescale for MeV electron microburst loss during geomagnetic storms
Authors: Thorne R. M. , O'Brien T. P. , Shprits Y. Y. , Summers D. , Horne R. B.
Published: August 2005

Energetic electrons in the outer radiation belt can resonate with intense bursts of whistler‐mode chorus emission leading to microburst precipitation into the atmosphere. The timescale for removal of outer zone MeV electrons during the main phase of the October 1998 magnetic storm has been computed by comparing the rate of microburst loss observed on SAMPEX with trapped flux levels observed on Polar. Effective lifetimes are comparable to a day and are relatively independent of L shell. The lifetimes have also been evaluated by theoretical calculations based on quasi‐linear scattering by field‐aligned waves. Agreement with the observations requires average wide‐band wave amplitudes comparable to 100 pT, which is consistent with the intensity of chorus emissions observed under active conditions. MeV electron scattering is most efficient during first‐order cyclotron resonance with chorus emissions at geomagnetic latitudes above 30 degrees. Consequently, the zone of MeV microbursts tends to maximize in the prenoon (0400–1200 MLT) sector, since nightside chorus is more strongly confined to the equator.
Schmidt number and near‐bed boundary condition effects on a two‐phase dilute sediment transport model
Authors: Amoudry L. , Hsu T.‐J. , Liu P. L.‐F.
Published: September 2005

In this paper we investigate a concentration‐dependent Schmidt number description and two near‐bed boundary conditions, empirical pickup and reference concentration, for a dilute two‐phase sediment transport model with a k‐ɛ fluid turbulence closure. The pick‐up approach adopts an empirical formula to calculate the upward sediment flux, whereas the reference concentration approach relates the upward sediment flux to the concentration at a reference location above the initially undisturbed bed. Through model‐data comparisons with data measured in the U tube, we show that the variation of Schmidt number only affects the magnitude of calculated concentration and is insensitive to the predicted phase of concentration time histories. The predicted phase is found more sensitive to the near‐bed sediment boundary condition. A concentration‐dependent Schmidt number is then introduced, which improves the predictions of magnitude and phase of concentration. Using the concentration‐dependent Schmidt number, the reference concentration approach generally predicts suspended sediment concentration better than the pick‐up approach does.
Traditional analysis of aquifer tests: Comparing apples to oranges?
Authors: Wu Cheng‐Mau , Yeh Tian‐Chyi J. , Zhu Junfeng , Lee Tim Hau , Hsu Nien‐Sheng , Chen Chu‐Hui , Sancho Albert Folch
Published: September 2005

Traditional analysis of aquifer tests uses the observed drawdown at one well, induced by pumping at another well, for estimating the transmissivity (T) and storage coefficient (S) of an aquifer. The analysis relies on Theis' solution or Jacob's approximate solution, which assumes aquifer homogeneity. Aquifers are inherently heterogeneous at different scales. If the observation well is screened in a low‐permeability zone while the pumping well is located in a high‐permeability zone, the resulting situation contradicts the homogeneity assumption in the traditional analysis. As a result, what does the traditional interpretation of the aquifer test tell us? Using numerical experiments and a first‐order correlation analysis, we investigate this question. Results of the investigation suggest that the effective T and S for an equivalent homogeneous aquifer of Gaussian random T and S fields vary with time as well as the principal directions of the effective T. The effective T and S converge to the geometric and arithmetic means, respectively, at large times. Analysis of the estimated T and S, using drawdown from a single observation well, shows that at early time both estimates vary with time. The estimated S stabilizes rapidly to the value dominated by the storage coefficient heterogeneity in between the pumping and the observation wells. At late time the estimated T approaches but does not equal the effective T. It represents an average value over the cone of depression but influenced by the location, size, and degree of heterogeneity as the cone of depression evolves.
Hydrothermal activity on near‐arc sections of back‐arc ridges: Results from the Mariana Trough and Lau Basin
Authors: Baker Edward T. , Massoth Gary J. , Nakamura Ko‐ichi , Embley Robert W. , de Ronde Cornel E. J. , Arculus Richard J.
Published: August 2005

The spatial density of hydrothermal venting is strongly correlated with spreading rate on mid‐ocean ridges (with the interesting exception of hot spot–affected ridges), evidently because spreading rate is a reliable proxy for the magma budget. This correlation remains untested on spreading ridges in back‐arc basins, where the magma budget may be complicated by subduction‐induced variations of the melt supply. To address this uncertainty, we conducted hydrothermal plume surveys along slow‐spreading (40–60 mm/yr) and arc‐proximal (10–60 km distant) sections of the southern Mariana Trough and the Valu Fa Ridge (Lau Basin). On both sections we found multiple plumes overlying ∼15–20% of the total length of each section, a coverage comparable to mid‐ocean ridges spreading at similar rates. These conditions contrast with earlier reported results from the two nearest‐arc segments of a faster spreading (60–70 mm/yr) back‐arc ridge, the East Scotia Ridge, which approaches no closer than 100 km to its arc. There, hydrothermal venting is relatively scarce (∼5% plume coverage) and the ridge characteristics are distinctly slow‐spreading: small central volcanic highs bookended by deep median valleys, and axial melt lenses restricted to the volcanic highs. Two factors may contribute to an unexpectedly low hydrothermal budget on these East Scotia Ridge segments: they may lie too far from the adjacent arc to benefit from near‐arc sources of melt supply, and subduction‐aided migration of mantle from the Bouvet hot spot may reduce hydrothermal circulation by local crustal warming and thickening, analogous to the Reykjanes Ridge. Thus the pattern among these three ridge sections appears to mirror the larger global pattern defined by mid‐ocean ridges: a well‐defined trend of spreading rate versus hydrothermal activity on most ridge sections, plus a subset of ridge sections where unusual melt delivery conditions diminish the expected hydrothermal activity.
The inner magnetosphere of Saturn: Cassini RPWS cold plasma results from the first encounter
Authors: Wahlund J.‐E. , Boström R. , Gustafsson G. , Gurnett D. A. , Kurth W. S. , Averkamp T. , Hospodarsky G. B. , Persoon A. M. , Canu P. , Pedersen A. , Desch M. D. , Eriksson A. I. , Gill R. , Morooka M. W. , André M.
Published: September 2005

We present new results from the inner magnetosphere of Saturn obtained by the Radio and Plasma Wave Science (RPWS) investigation onboard Cassini around the period of the Saturn orbit injection (July 1, 2004). Plasma wave electric field emissions, voltage sweeps by the Langmuir probe (LP) and radio sounder data were used to infer the cold plasma (<100 eV) characteristics within 20 RS of Saturn. A dense (<150 cm−3) and cold (<7 eV) plasma torus was found just outside the visible F‐ring. This torus of partly dusty plasma does not perfectly co‐rotate with Saturn, which suggests the cold plasma is electro‐dynamically coupled to the charged ring‐dust particles. The spacecraft potential was a few volts negative above the E‐ and G‐rings, indicating the dust‐particles were likewise negatively charged. The cold ion characteristics changed near the magnetically conjugate position of Dione, indicating release of volatile material from this icy moon.
Global dimming or local dimming?: Effect of urbanization on sunlight availability
Authors: Alpert Pinhas , Kishcha Pavel , Kaufman Yoram J. , Schwarzbard Rotem
Published: September 2005

From the 1950s to the 1980s, a significant decrease of surface solar radiation has been observed at different locations throughout the world. Here we show that this phenomenon, widely termed global dimming, is dominated by the large urban sites. The global‐scale analysis of year‐to‐year variations of solar radiation fluxes shows a decline of 0.41 W/m2/yr for highly populated sites compared to only 0.16 W/m2/yr for sparsely populated sites (<0.1 million). Since most of the globe has sparse population, this suggests that solar dimming is of local or regional nature. The dimming is sharpest for the sites at 10°N to 40°N with great industrial activity. In the equatorial regions even the opposite trend to dimming is observed for sparsely populated sites.
An air mass with high potential vorticity preceding the formation of the Marcus Convergence Zone
Authors: Sato N. , Sakamoto K. , Takahashi M.
Published: September 2005

We examined the convective activity and dynamical field over the subtropical North Pacific by focusing on the relationship between upper cold lows (UCLs) and the formation of the Marcus Convergence Zone (MCZ). In mid‐July, we detected a UCL near Marcus Island that was associated with the formation of the MCZ. The convective activity associated with the MCZ followed the UCL, implying that the UCL contributed to the MCZ formation. Analysis of the temporal evolution of the dynamic field revealed that the UCL appeared in a large‐scale, high‐potential vorticity (PV) air mass migrating from the east. We had already identified the high‐PV region near the mid‐Pacific trough in late July. It stretched westward and reached Marcus Island in mid‐July, suggesting that the UCL in the high‐PV air mass over the North Pacific contributed to the formation of the MCZ.
Influences of intraseasonal disturbances on the oceanic mixed layer in the western North Pacific ITCZ region
Authors: Sato N.
Published: September 2005

Using the Argo float data, changes in the temperature and salinity in the oceanic mixed layer corresponding to the passage of intraseasonal‐scale disturbances were examined over the western North Pacific (WNP) intertropical convergence zone (ITCZ) region. Events where the near‐surface temperature decreased by more than 1°C within a 10‐day period were identified, corresponding to the intraseasonal variability (ISV) of the atmosphere. Analyzing the vertical profiles and the T‐S relationships of the mixed layer revealed that the water was cooled mainly by mechanical mixing and Ekman upwelling related to the strong sea surface wind. Thermal cooling at the sea surface does not appear to be a predominant process in the abrupt cooling. Such cooling events were observed only when the mixed layer was shallow.
A quasilinear theory of ion “thermalization” and wave excitation downstream of Earth's bow shock
Authors: Liu Yong C.‐M. , Lee Martin A. , Kucharek Harald
Published: August 2005

A quasilinear theory is presented for the relaxation of the proton and helium distribution functions and the associated excitation of ion cyclotron waves, downstream of the quasi‐perpendicular Earth's bow shock. The theory predicts the wave polarization, power and peak frequency, and the proton bulk velocity and temperature anisotropy, sufficiently far downstream of the shock that the ions and waves have relaxed to a quasi‐equilibrium. The results are compared with the AMPTE/IRM crossings of the marginally supercritical bow shock documented by Sckopke et al. (1990), for which the number of “reflected” protons is small and the quasilinear approximation is expected to be valid. The theory starts with the trajectories of the specularly reflected protons and transmitted helium in the laminar electromagnetic fields of the shock transition. In a simplified treatment of the downstream relaxation process, neglecting wave dispersion and assuming that the downstream reflected proton speed v0 is large compared with the Alfven speed VA, the wave and proton quasi‐equilibrium predictions are qualitatively in agreement with the observations. In a more precise treatment limited to a perpendicular configuration, in which dispersion is included and v0 may be comparable with VA, the agreement with the observations is generally very good if the contribution of the transmitted core protons is included. One interesting feature is that the minor ion helium may contribute to the wave power, and in return change the proton and helium distribution functions. The helium contribution is estimated but requires further investigation.
Reconstructing solid precipitation from snow depth measurements and a land surface model
Authors: Cherry Jessie Ellen , Tremblay L. Bruno , Déry Stephen J. , Stieglitz Marc
Published: September 2005

The amount and distribution of snowfall in the Arctic has significant effects on global climate. However, measurements of snowfall from gauges are strongly biased. A new method is described for reconstructing snowfall from observed snow depth records, meteorological observations, and running the NASA Seasonal‐to‐Interannual Prediction Project Catchment Land Surface Model (NSIPP CLSM) in an inverse mode. This method is developed and tested with observations from Reynolds Creek Experimental Watershed. Results show snowfall can be accurately reconstructed on the basis of how much snow must have fallen to produce the observed snow depth. The mean cumulative error (bias) of the reconstructed precipitation for 11 snow seasons is 29 mm snow water equivalent (SWE) for the corrected gauge measurement compared to ‒77 mm SWE for the precipitation from the corrected snow gauges. This means the root‐mean‐square error of reconstructed solid precipitation is 30% less than that of gauge corrections. The intended application of this method is the pan‐Arctic landmass, where estimates of snowfall are highly uncertain but where more than 60 years of historical snow depth and air temperature records exist.
Metabolic Activation Pattern of Distinct Hippocampal Subregions during Spatial Learning and Memory Retrieval
Authors: Ros Jacqueline , Pellerin Luc , Magara Fulvio , Dauguet Julien , Schenk Françoise , Magistretti Pierre J
Published: August 2005

Activation dynamics of hippocampal subregions during spatial learning and their interplay with neocortical regions is an important dimension in the understanding of hippocampal function. Using the (14C)-2-deoxyglucose autoradiographic method, we have characterized the metabolic changes occurring in hippocampal subregions in mice while learning an eight-arm radial maze task. Autoradiogram densitometry revealed a heterogeneous and evolving pattern of enhanced metabolic activity throughout the hippocampus during the training period and on recall. In the early stages of training, activity was enhanced in the CA1 area from the intermediate portion to the posterior end as well as in the CA3 area within the intermediate portion of the hippocampus. At later stages, CA1 and CA3 activations spread over the entire longitudinal axis, while dentate gyrus (DG) activation occurred from the anterior to the intermediate zone. Activation of the retrosplenial cortex but not the amygdala was also observed during the learning process. On recall, only DG activation was observed in the same anterior part of the hippocampus. These results suggest the existence of a functional segmentation of the hippocampus, each subregion being dynamically but also differentially recruited along the acquisition, consolidation, and retrieval process in parallel with some neocortical sites.
Neurogenin 1 Mediates Erythropoietin Enhanced Differentiation of Adult Neural Progenitor Cells
Authors: Wang Lei , Zhang Zheng G , Zhang Rui L , Jiao Zhong X , Wang Ying , D S Pourabdollah-Nejad , LeTourneau Yvonne , Gregg Sara R , Chopp Michael
Published: August 2005

Proneuronal basic helix–loop–helix (bHLH) transcription factor, neurogenin 1 (Ngn1), regulates neuronal differentiation during development of the cerebral cortex. Akt mediates proneuronal bHLH protein function to promote neuronal differentiation. Here, we show that recombinant human erythropoietin (rhEPO) significantly increased Akt activity and Ngn1 mRNA levels in neural progenitor cells derived from the subventricular zone (SVZ) of adult rat, which was coincident with increases of neural progenitor cell proliferation, differentiation, and neurite outgrowth. Inhibition of Akt activity by the phosphatidylinositol 3-kinase/Akt (PI3K/Akt) inhibitor, LY294002, abolished rhEPO-increased Ngn1 mRNA levels and the effects of rhEPO on neural progenitor cells. In addition, reducing expression of endogenous Ngn1 by means of short-interfering RNA (siRNA) blocked rhEPO-enhanced neuronal differentiation and neurite outgrowth but not rhEPO-increased proliferation. Furthermore, treatment of stroke rat with rhEPO significantly increased Ngn1 mRNA levels in SVZ cells. These data suggest that rhEPO acts as an extracellular molecule that activates the PI3K/Akt pathway, which enhances adult neural progenitor cell proliferation, differentiation, and neurite outgrowth, and Ngn1 is required for Akt-mediated neuronal differentiation and neurite outgrowth.
Hyperbaric Oxygen Preconditioning Induces Tolerance against Spinal Cord Ischemia by Upregulation of Antioxidant Enzymes in Rabbits
Authors: Nie Huang , Xiong Lize , Lao Ning , Chen Shaoyang , Xu Ning , Zhu Zhenghua
Published: August 2005

The present study examined the hypothesis that spinal cord ischemic tolerance induced by hyperbaric oxygen (HBO) preconditioning is triggered by an initial oxidative stress and is associated with an increase of antioxidant enzyme activities as one effector of the neuroprotection. New Zealand White rabbits were subjected to HBO preconditioning, hyperbaric air (HBA) preconditioning, or sham pretreatment once daily for five consecutive days before spinal cord ischemia. Activities of catalase (CAT) and superoxide dismutase were increased in spinal cord tissue in the HBO group 24 h after the last pretreatment and reached a higher level after spinal cord ischemia for 20 mins followed by reperfusion for 24 or 48 h, in comparison with those in control and HBA groups. The spinal cord ischemic tolerance induced by HBO preconditioning was attenuated when a CAT inhibitor, 3-amino-1,2,4-triazole,1 g/kg, was administered intraperitoneally 1 h before ischemia. In addition, administration of a free radical scavenger, dimethylthiourea, 500 mg/kg, intravenous, 1 h before each day's preconditioning, reversed the increase of the activities of both enzymes in spinal cord tissue. The results indicate that an initial oxidative stress, as a trigger to upregulate the antioxidant enzyme activities, plays an important role in the formation of the tolerance against spinal cord ischemia by HBO preconditioning.
The Effects of Cerebral Ischemia on the Rat Choroid Plexus
Authors: Ennis Steven R , Keep Richard F
Published: August 2005

Although the blood-brain barrier effects of cerebral ischemia have been extensively examined, less attention has focused on ischemia-induced damage to the choroid plexuses that form the blood-cerebrospinal fluid (CSF) barrier (BSCFB). This study examined the rat lateral ventricle choroid plexuses (LVCP) in three ischemic models, bilateral common carotid artery occlusion (2VO) + hypotension with or without reperfusion and permanent middle cerebral artery (MCA) occlusion with or without a tandem common carotid artery occlusion. Blood flow was assessed using [14C]- N-isopropyl- p-iodoamphetamine, and LVCP injury by tissue edema, alterations in [14C]glutamine transport and BSCFB disruption (measured with [3H]inulin). 2VO + hypotension caused an 87% reduction in LVCP blood flow ( P < 0.01) and a progressive reduction in LVCP glutamine transport. In contrast to cortex, there was no LVCP hyperemia or delayed hypoperfusion on reperfusion, but there was marked BSCFB disruption. After 30 mins of 2VO + hypotension with 6 h of reperfusion, the [3H]inulin entry into CSF was increased threefold ( P < 0.05). Blood-CSF barrier rather than blood-brain barrier disruption appeared to be the main cause of enhanced [3H]inulin entry into hippocampus. Middle cerebral artery occlusion with and without a tandem common carotid artery occlusion only caused 53% and 38% reductions in LVCP blood flow but induced LVCP edema. Results suggest that the LVCP is selectively vulnerable to ischemic injury in terms of the absolute blood flows or, for the MCA occlusion models, the % reductions in flows required to induce injury. BCSFB disruption early after ischemia may enhance the movement of compounds from blood to areas close to the ventricular system and participate in delayed neuronal death.
Evidence of a Common Founder for SCA12 in the Indian Population
Authors: Bahl S. , Virdi K. , Mittal U. , Sachdeva M. P. , Kalla A. K. , Holmes S. E. , O'Hearn E. , Margolis R. L. , Jain S. , Srivastava A. K. , Mukerji M.
Published: September 2005

Spinocerebellar ataxia type 12 (SCA12) is an autosomal dominant cerebellar ataxia associated with the expansion of an unstable CAG repeat in the 5′ region of the PPP2R2B gene on chromosome 5q31–5q32. We found that it accounts for ∼16% (20/124) of all the autosomal dominant ataxia cases diagnosed in AIIMS, a major tertiary referral centre in North India. The length of the expanded allele in this population ranges from 51–69 CAG triplets. Interestingly, all the affected families belong to an endogamous population, which originated in the state of Haryana, India. We identified four novel SNPs and a dinucleotide marker spanning ∼137 kb downstream of CAG repeat in the PPP2R2B gene. Analysis of 20 Indian SCA12 families and ethnically matched normal unrelated individuals revealed one haplotype to be significantly associated with the affected alleles (P= 0.000), clearly indicating the presence of a common founder for SCA12 in the Indian population. This haplotype was not shared by the American pedigree with SCA12. Therefore, the SCA12 expansion appears to have originated at least twice.
Vibronic interactions and possible electron pairing in positively charged cyanodienes
Authors: Kato Takashi , Yamabe Tokio
Published: August 2005

The conditions under which the attractive electron-electron interactions are realized in the monocations of σ-conjugated cyanodienes such as C6N4H4 (2cn), C8N6H4 (3cn), and C10N8H4 (4cn) and of π-conjugated acenes are discussed. The total electron-phonon coupling constants for the monocations lHOMO of cyanodienes are much larger than those for the monocations of acenes. The strong σ orbital interactions between two neighboring atoms in the highest occupied molecular orbitals (HOMO) of σ-conjugated cyanodienes are the main reason for the calculated results. Furthermore, we discuss how the conditions under which the monocation crystals become good conductor are related to the molecular size. Both the lHOMO values and the reorganization energies between the neutral molecules and the monocations decrease with an increase in molecular size in cyanodienes. The calculated results for the σ-conjugated cyanodienes are compared with those for the π-conjugated acenes in order to investigate how the CH—N substitutions in cyanodienes are closely related to the lHOMO values and the reorganization energies. Both the lHOMO and the reorganization energies in the positively charged σ-conjugated cyanodienes are much larger than those in the positively charged π-conjugated acenes. This means that in order to become good conductors, the positively charged σ-conjugated cyanodienes need larger overlap integral between two adjacent molecules than the positively charged π-conjugated acenes. On the other hand, since the lHOMO values for cyanodienes are much larger than those for acenes, the condition of attractive electron-electron interactions is more easily to be realized in the monocations of cyanodienes than in the monocations of acenes. It is suggested that the positively charged σ-conjugated cyanodienes cannot easily become good conductors, but the conditions under which the electron-electron interactions become attractive are realized more easily in the positively charged σ-conjugated cyanodienes than in the positively charged π-conjugated acenes.
Speed up of dynamic observables in coarse-grained molecular-dynamics simulations of unentangled polymers
Authors: Depa Praveen K. , Maranas Janna K.
Published: August 2005

Coarse-grained models that preserve atomistic detail display faster dynamics than atomistic systems alone. We show that this “ indirect speed up” is robust: coarse-grained dynamic observables computed with time scaled by a constant factor are in excellent agreement with their underlying atomistic counterparts. Borrowing from accelerated dynamics methods used in the field of rare events, we predict the scaling factor within 7%, based on reduced intermolecular attraction yielding faster neighbor cage escapes.
Improvement of AlGaN∕GaN high electron mobility transistor structures by in situ deposition of a Si3N4 surface layer
Authors: Derluyn J. , Boeykens S. , Cheng K. , Vandersmissen R. , Das J. , Ruythooren W. , Degroote S. , Leys M. R. , Germain M. , Borghs G.
Published: August 2005

We have made AlGaN∕GaN high electron mobility transistors with a Si3N4 passivation layer that was deposited in situ in our metal-organic chemical-vapor deposition reactor in the same growth sequence as the rest of the layer stack. The Si3N4 is shown to be of high quality and stoichiometric in composition. It reduces the relaxation, cracking, and surface roughness of the AlGaN layer. It also neutralizes the charges at the top AlGaN interface, which leads to a higher two-dimensional electron-gas density. Moreover, it protects the surface during processing and improves the Ohmic source and drain contacts. This leads to devices with greatly improved characteristics.
Gigahertz range electromagnetic wave absorbers made of amorphous-carbon-based magnetic nanocomposites
Authors: Liu Jiu Rong , Itoh Masahiro , Horikawa Takashi , Machida Ken-ichi , Sugimoto Satoshi , Maeda Toru
Published: September 2005

Nanocomposite magnetic materials α-Fe∕C(a), Fe2B∕C(a), and Fe1.4Co0.6B∕C(a) were prepared by mechanically grinding α-Fe, Fe2B, or Fe1.4Co0.6B with amorphous carbon [C(a)] powders. Complex permittivity, permeability, and electromagnetic wave absorption properties of resin compacts containing 40-vol% composite powders of α-Fe∕C(a), Fe2B∕C(a), and Fe1.4Co0.6B∕C(a) were characterized according to a conventional reflection/transmission technique. The real part (εr′) and imaginary part (εr″) of the relative permittivity are low and almost independent of frequency between 0.05 and 40GHz. The Imaginary part (μr″) of the relative permeability exhibited wide peaks in the 1–9-GHz range for α-Fe∕C(a), in the 2–18-GHz range for Fe2B∕C(a), and in the 18–40-GHz range for Fe1.4Co0.6B∕C(a) owing to their different magnetocrystalline anisotropy field (HA) values. Consequently, the resin compacts of 40-vol% α-Fe∕C(a), Fe2B∕C(a), and Fe1.4Co0.6B∕C(a) powders provided good electromagnetic (em) wave absorption performances (reflection loss<−20dB) in ranges of 4.3–8.2GHz (G band), 7.5–16.0GHz (X band), and 26.5–40GHz (Q band) over absorber thicknesses of 1.8–3.3, 1.2–2.2, and 0.63–0.82mm, respectively. Our experimental results demonstrate that the amorphous-carbon-based magnetic nanocomposites are promising for the application to produce thin and light EM wave absorbers.
Quasiclassical determination of reaction probabilities as a function of the total angular momentum
Authors: Aoiz F. J. , Sáez-Rábanos V. , Martínez-Haya Bruno , González-Lezana Tomás
Published: September 2005

This article presents a quasiclassical trajectory (QCT) method to determine the reaction probability as a function of the total angular momentum J for any given value of the initial rotational angular momentum j. The proposed method is based on a discrete sampling of the total and orbital angular momenta for each trajectory and on the development of equations that have a clear counterpart in the quantum-mechanical (QM) case. The reliability of the method is illustrated by comparing QCT and time-dependent wave-packet QM results for the H+D2(υ=0,j=4,10) reaction. The small discrepancies between both sets of calculations, when they exist, indicate some genuine quantum effects. In addition, a procedure to extract the reaction probabilities as a function of J when trajectories are calculated in the usual way using a continuous distribution of impact parameters is also described.
Role of S∕Se ratio in chemical bonding of As–S–Se glasses investigated by Raman, x-ray photoelectron, and extended x-ray absorption fine structure spectroscopies
Authors: Li Wenyan , Seal Sudipta , Rivero Clara , Lopez Cedric , Richardson Kathleen , Pope April , Schulte Alfons , Myneni Satish , Jain Himanshu , Antoine Keisha , Miller Alfred C.
Published: August 2005

Chalcogenide glasses have attracted considerable attention and found various applications due to their infrared transparency and other optical properties. The As–S–Se chalcogenide glass, with its large glass-formation domain and favorable nonlinear property, is a promising candidate system for tailoring important optical properties through modification of glass composition. In this context, a systematic study on ternary As–S–Se glass, chalcogen-rich versus well-studied stochiometric compositions, has been carried out using three different techniques: Raman spectroscopy, x-ray photoelectron spectroscopy, and extended x-ray absorption fine structure spectroscopy. These complementary techniques lead to a consistent understanding of the role of S∕Se ratio in chalcogen-rich As–S–Se glasses, as compared to stochiometric composition, and to provide insight into the structural units (such as the mixed pyramidal units) and evidence for the existence of homopolar bonds (such as Se–Se, S–S, and Se–S), which are the possible structural origin of the high nonlinearity in these glasses.
Intensity and wavelength control of a single molecule reaction: Simulation of photodissociation of cold-trapped MgH+
Authors: Jørgensen Solvejg , Drewsen Michael , Kosloff Ronnie
Published: August 2005

Photodissociation of cold magnesium hydride ions MgH+ leading to either Mg++H or Mg+H+ is simulated from first principles. The purpose is to study the possibility of single molecule control of the products in the presence of two laser fields. The system evolves on four electronic potential-energy curves, X1Σ, A1Σ, B1Π, and C1Σ. These potential-energy curves are calculated from first principles using multireference self-consistent field theory. The accuracy of the electronic potential curves has been checked by calculating the energies of the rovibrational eigenstates and comparing them to experimental findings. The photodissociation dynamics has furthermore been simulated by solving the time-dependent Schrödinger equation. It is shown that the branching ratio of the two dissociation channels, Mg++H or Mg+H+, can be controlled by changing the intensity and wavelength of the two driving laser fields.
Synthesis and characterization of metal-dielectric composites with copper nanoparticles embedded in a glass matrix: A multitechnique approach
Authors: Lipinska-Kalita Kristina E. , Krol Denise M. , Hemley Russell J. , Mariotto Gino , Kalita Patricia E. , Ohki Yoshimichi
Published: August 2005

The precipitation and growth of copper nanoparticles in an optically transparent aluminosilicate glass matrix was investigated. The size of particles in this heterophase glass-based composite was modified in a controlled manner by isothermal heat treatments. A multitechnique approach, consisting of Raman scattering spectroscopy, high-resolution transmission electron microscopy, x-ray diffraction technique, and optical absorption spectroscopy, has been used to study the nucleation and crystallization processes. Optical absorption spectroscopy revealed the presence of intense absorption bands attributed to oscillations of free electrons, known as the surface-plasmon resonance band of copper particles, and confirmed a gradual increase of the particles’ mean size and density with annealing time. The Raman scattering on acoustical phonons from Cu quantum dots in the glass matrix measured for off-resonance conditions demonstrated the presence of intense, inhomogeneously broadened peaks that have been assigned to the confined acoustic eigenmodes of copper nanoparticles. The particle-size dependence of the acoustic peak energies and the relation between the size distribution and bandwidths of these peaks were derived. High-resolution transmission electron microscopy was used to monitor the nucleation of the nanoparticles and to estimate their mean size.
Efficient transition path sampling for systems with multiple reaction pathways
Authors: Chen L. Y. , Nash P. L. , Horing N. J. M.
Published: September 2005

A new algorithm is developed for sampling transition paths and computing reaction rates. To illustrate the use of this method, we study a two-dimensional system that has two reaction pathways: one pathway is straight with a relatively high barrier and the other is roundabout with a lower barrier. The transition rate and the ratio between the numbers of the straight and roundabout transition paths are computed for a wide range of temperatures. Our study shows that the harmonic approximation for fluctuations about the steepest-descent paths is not valid even at relatively low temperatures and, furthermore, that factors related to entropy have to be determined by the global geometry of the potential-energy surface (rather than just the local curvatures alone) for complex reaction systems. It is reasonable to expect that this algorithm is also applicable to higher dimensional systems.
Relaxation of a strained quantum well at a cleaved surface. Part II: Effect of cubic symmetry
Authors: Davies John H. , Offermans Peter , Koenraad Paul M.
Published: August 2005

In a previous paper [J. H. Davies, D. M. Bruls, J. W. A. M. Vugs, and P. M. Koenraad, J. Appl. Phys. 91, 4171 (2002). Part I.] we compared theory and experiment for the relaxation at a cleaved surface of a strained quantum well of InGaAs in GaAs. The measurements were taken with a scanning tunneling microscope and the analytic calculation used classical elastic theory for a linear, isotropic, homogeneous medium. Qualitative agreement was good but the theory gave only about 80% of the observed displacement. We have therefore extended the calculation to explore the effect of cubic symmetry and the orientation of the cleaved surface. The “strain suppression” method reduces the problem to the response of a half space to traction on its surface. We have calculated this for orthotropic symmetry, which includes the common orientations of orthorhombic, tetragonal, hexagonal, and cubic crystals. Anisotropy has no effect on the shape of the relaxed surface but the magnitude of relaxation changes. For cubic material there is no effect on the strain along the direction of growth if the cleaved surface is a {001} plane and a reduction of a few percent for a {011} plane, which is the case of experimental interest. The outward relaxation is reduced by about 20% due to cubic symmetry for a {001} plane because the shear stiffness of GaAs is higher than in the isotropic model, and is a further 10% smaller for a {011} plane. Thus the results for cubic symmetry lie further from the measurements than those calculated for isotropic material. Interfacial forces may contribute to this discrepancy but we suggest that nonlinear elasticity is probably responsible.
Molecular-beam epitaxy and characteristics of GaNyAs1−x−yBix
Authors: Huang Wei , Oe Kunishige , Feng Gan , Yoshimoto Masahiro
Published: August 2005

Ga N y As 1 − x − y Bi x alloys were grown by molecular-beam epitaxy using solid Ga, Bi, and As sources and nitrogen radicals generated from nitrogen gas in rf plasma. Changing the growth temperature is found to be a convenient method for controlling the GaBi molar fraction in the alloy reproducibly. The photoluminescence (PL) spectra show that the PL peak energy of GaNyAs1−x−yBix alloy decreased with increasing GaBi and GaN molar fractions. The redshift coefficients of ∼62meV∕%Bi and ∼130meV∕%N at the PL peak energy of GaNyAs1−x−yBix were observed at room temperature. The temperature dependence of the PL peak energy in the temperature range of 150–300K is much smaller than the temperature dependence of the band gap of InGaAsP. The temperature coefficients of GaAs1−xBix and GaNyAs1−x−yBix band gaps are governed by the GaBi molar fraction and they decrease with increasing GaBi molar fraction. GaNyAs1−x−yBix alloys with different PL peak energies and lattice matched to GaAs substrates were obtained. The photoluminescence peak energy was located at a predicted wavelength for the sample lattice matched to GaAs which was found to have the structure of Ga(N0.33Bi0.67)zAs1−z.