bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation betweenEnterococcus faecalisBiofilms Development Stage and Quantitative Surface Roughness Using Atomic Force Microscopy
Authors: Santos Ricardo P. , Arruda Theodora T.P. , Carvalho Cibele B.M. , Carneiro Victor A. , Braga Lara Q.V. , Teixeira Edson H. , Arruda Francisco V.S. , Cavada Benildo S. , Havt Alexandre , de Oliveira Taianá M. , Bezerra Gustavo A. , Freire Valder N.
Published: March 2008

Biofilms are assemblages of microorganisms and their associated extracellular products at an interface and typically with an abiotic or biotic surface. The study of the morphology of biofilms is important because they are associated with processes of biofouling, corrosion, catalysis, pollutant transformation, dental caries, drug resistance, and so forth. In the literature, biofilms have been examined by atomic force microscopy (AFM), which has proven to be a potent tool to study different aspects of the biofilm development on solid surfaces. In this work, we used AFM to investigate topographical changes during the development process ofEnterococcus faecalisbiofilms, which were generated on sterile cellulose nitrate membrane (CNM) filters in brain heart infusion (BHI) broth agar blood plates after 24, 36, 72, 192, and 360 h. AFM height images showed topographical changes due to biofilm development, which were used to characterize several aspects of the bacterial surface, such as the presence of extracellular polymeric substance, and the biofilm development stage. Changes in the development stage of the biofilm were shown to correlate with changes in the surface roughness as quantified through the mean roughness.
In Situ Transmission Electron Microscopy Observation of the Growth of Bismuth Oxide Whiskers
Authors: Mima T. , Takeuchi Y. , Arai S. , Kishita K. , Kuroda K. , Saka H.
Published: March 2008

Growth of bismuth oxide (most probably Bi2O3) was observed in situ in a transmission electron microscope. Bi liquid particles were dispersed on the substrates of diamond or SiO2. Introduction of oxygen up to ∼5 × 10−4 Pa resulted in formation of bismuth oxide (most probably Bi2O3) whiskers. The growth mechanism of the whisker was discussed in terms of a vapor-liquid-solid (VLS) mechanism. It is suggested that the liquid droplet of Bi acts as a physical catalyst for growth of bismuth oxide (most probably Bi2O3) whiskers.
An Instant Cell Recognition System Using a Microfabricated Coordinate Standard Chip Useful for Combinable Cell Observation with Multiple Microscopic Apparatuses
Authors: Yamada Yohei , Yamaguchi Naotoshi , Ozaki Masakazu , Shinozaki Yukihiro , Saito Mikako , Matsuoka Hideaki
Published: March 2008

Disposable coordinate standard (CS) chips were fabricated by the ejection of melted polystyrene into a metal mold. The CS chip surface was divided into four parts different in height and width. The edge lines of these parts could be recognized as straight lines 2 μm in width in the microscope view and used as the X and Y axes for the culture dish. The CS chip was attached on the bottom of a culture dish outside. Then the dish was set on the microscope stage and moved by means of a motorized automatic stage. The X-Y coordinates of many single-cells in a culture dish were registered, respectively. Once registered, any single-cell could instantly be brought to the center of the microscope view even after displacing the dish from the stage for a while and setting it again on the stage. Therefore, experimenters can easily search any single-cell in any culture dish on any microscope at any time. Such a system is remarkably useful for various modes of single-cell experiment and named “Suguwaculture,” which means “instantly” (“sugu” in Japanese) + “recognizable” (“wakaru” in Japanese) + “culture” (during culture).
Mackenzie River nutrient delivery to the Arctic Ocean and effects of the Mackenzie Delta during open water conditions
Authors: Emmerton Craig A. , Lesack Lance F. W. , Vincent Warwick F.
Published: March 2008

Large rivers have a strong influence on the Arctic Ocean, but little attention has been given to the biogeochemical effect that lake‐rich delta floodplains may have on river waters prior to marine discharge. We assessed the effect of the Mackenzie Delta on riverine fluxes of nutrients and organic matter to the Arctic Ocean during the open water period of 2004. Using a new estimate of peak off‐channel water storage in the delta floodplain, a two‐source mixing model was developed (channel water plus recovery of off‐channel water) to estimate the volume‐weighted nutrient composition of river water after the off‐channel water was recovered from the delta during the hydrograph recession period. Results with the delta effect included (i.e., with recovery of off‐channel water) relative to results with the effect omitted (i.e., analogous to historical monitoring upstream of the delta) show particulate levels were 10–18% lower, but enriched in organic content (POC:TSS, PN:TSS, PP:TSS) by 75–280%; dissolved inorganic nutrients were lower (NO3– 14%; SRP 14%; SRSi 5%) except for ammonium (10%); and dissolved organic matter was higher (DOC 15%; DON 62%; DOP 239%). The resulting nutrient quality (C:N:P stoichiometry) was more enriched in carbon (TOC:TP) by 79% and in nitrogen (TN:TP) by 77% relative to phosphorus. Model results were compared against nutrient measurements throughout the delta channel network taken three times over this same period, and differences from upstream to downstream matched reasonably well to the model, though they also suggested the delta effect may be more complex than represented by the model. Our results generally indicate the Mackenzie Delta has an important effect on the magnitude and quality of riverine particulates and nutrients prior to entering the sea. Such an effect has not been quantified in prior work and is likely to be important in other arctic rivers with lake‐rich deltas. Our enhanced sampling of the high‐discharge period during early hydrograph recession has also better captured the detailed composition of C, N, and P constituents in the river water, ultimately leading to improved estimates of nutrient levels and overall nutrient quality for the open water period that differ appreciably from prior observations on the Mackenzie River.
Toward a model space and model independence metric
Authors: Abramowitz Gab , Gupta Hoshin
Published: March 2008

Understanding the relationship between computer‐based models and the environment they simulate is becoming increasingly important as we try to predict how the earth's climate will change. As a surrogate for the representation of uncertainty in a prediction problem, it is common to use the range of behaviour from a set of models (an ensemble), and the ensemble mean as the ‘best guess’ prediction. We suggest a ‘model space’ metric, which, by providing one relevant definition of model independence, could allow us to begin to understand the relationship between model spread and prediction uncertainty. This in turn could allow the minimisation of bias from the inclusion of similar models in ensembles and quantification of how much independent information each model contributes to the prediction problem.
2,000‐year record of atmospheric methyl bromide from a South Pole ice core
Authors: Saltzman Eric S. , Aydin Murat , Tatum Cheryl , Williams Margaret B.
Published: March 2008

This study reports measurements of methyl bromide (CH3Br) in air bubbles from a South Pole ice core, with gas ages covering the past two millennia. The air was extracted by mechanical shredding of the core under vacuum and the evolved gases were analyzed by gas chromatography with high resolution mass spectrometry and isotope dilution. These samples had estimated mean gas ages ranging from 160 BCE to 1860 CE. The mean CH3Br mixing ratio in the ice core samples was 5.39 ±.06 ppt (1s.e., n = 113). The CH3Br measurements from this core agree with those from a Siple Dome ice core for mean gas ages between 1671 and 1860 CE, where there is overlap between the cores. The data show no linear trend over the 2000 year period prior to industrialization. Together, Antarctic ice core and firn air measurements clearly demonstrate that the increase in atmospheric CH3Br during the twentieth century exceeds natural variability during the past 2000 years. There is evidence of centennial‐scale variability in CH3Br on the order of ±10–20% that may indicate a natural climate sensitivity of the atmospheric levels of this ozone depleting substance. The analysis of CH3Br in additional Antarctic ice cores will be needed to confirm that the centennial‐scale variability observed in this core represents a southern hemisphere atmospheric history.
Combined use of MODIS, AVHRR and radiosonde data for the estimation of spatiotemporal distribution of precipitable water
Authors: Chrysoulakis N. , Kamarianakis Y. , Xu L. , Mitraka Z. , Ding J.
Published: March 2008

In this paper, the atmospheric precipitable water (PW) was estimated by means of Advanced Very High Resolution Radiometer (AVHRR) thermal channels brightness temperature difference (ΔT), over the broader area of Greece. The AVHRR derived ΔT was calculated in a grid of 5 × 5 km cells; the corresponding PW value in each grid cell was extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) Level 2 product (near infrared algorithm). MODIS derived PW values were adjusted to the AVHRR overpass time by using PW rates of change. These rates were estimated from time series of radiosonde measurements, provided by four synoptic meteorological stations located in Athens, Thessaloniki, Heraklion and Izmir. Next, to estimate the relationship between adjusted PW and ΔT, a robust linear regression algorithm was applied. Since regression coefficients corresponded to the broader area of Greece, the regression relationship was applied to AVHRR data for the period 2001–2005, to predict the annual and seasonal variability of PW over the study area. Radiosonde derived PW values at the above synoptic stations were used to validate the AVHRR derived PW spatiotemporal distribution. A very good agreement between radiosonde and AVHRR derived PW values was observed since a RMSE of 0.46 cm was calculated using a validation data set that covered a five years period.
Non‐Fickian transport and multiple‐rate mass transfer in porous media
Authors: Berkowitz Brian , Emmanuel Simon , Scher Harvey
Published: March 2008

Non‐Fickian behavior is due to a broad spectrum of rates limiting the solute transport. There are two generic mechanisms that can generate these spectra: the complex flow field of a highly heterogeneous medium and the mass exchange between a mobile phase and a distribution of immobile states. We have developed a physical model that incorporates both of these mechanisms into the continuous time random walk (CTRW) framework. We study their interacting dynamics as a function of the spectra of advective‐diffusive transition times and exchange times and the relative separation of their respective time domains. Examples of interacting transport in a dispersive medium with immobile states include tracer migration in a random fracture network with matrix diffusion and transport in a porous medium with adsorption/desorption sites. To date, non‐Fickian transport has been quantified effectively using the CTRW in a wide variety of porous and fractured geological formations. The basis of the CTRW framework is the portrayal of transport as a sequence of transition rates (e.g., between pore spaces, fracture intersections) and the incorporation of the full spectrum of these rates into the transport equations. The emphasis herein is on systems in which the time domains of the two different types of spectra are distinguishable, so that a more complete characterization of the transport can be obtained (i.e., rather than lumping all the rates together). Experimental data are analyzed from two of these systems: (1) tracer transport in a fractured shear zone and (2) sorbing species transported through a heterogeneous porous domain. The CTRW framework is found to produce excellent fits to and predictions from the experimental data.
Adenosine A2A receptor antagonists: blockade of adenosinergic effects and T regulatory cells
Authors: Sitkovsky M , Lukashev D , Deaglio S , Dwyer K , Robson S C , Ohta A
Published: March 2008

The intensity and duration of host responses are determined by protective mechanisms that control tissue injury by dampening down inflammation. Adenosine generation and consequent effects, mediated via A2A adenosine receptors (A2AR) on effector cells, play a critical role in the pathophysiological modulation of these responsesin vivo. Adenosine is both released by hypoxic cells/tissues and is also generated from extracellular nucleotides by ecto‐enzymes e.g. CD39 (ENTPD1) and CD73 that are expressed by the vasculature and immune cells, in particular by T regulatory cell. In general, these adenosinergic mechanisms minimize the extent of collateral damage to host tissues during the course of inflammatory reactions. However, induction of suppressive pathways might also cause escape of pathogens and permit dissemination. In addition, adenosinergic responses may inhibit immune responses while enhancing vascular angiogenic responses to malignant cells that promote tumor growth. Novel drugs that block A2AR‐adenosinergic effects and/or adenosine generation have the potential to boost pathogen destruction and to selectively destroy malignant tissues. In the latter instance, future treatment modalities might include novel ‘anti‐adenosinergic’ approaches that augment immune clearance of malignant cells and block permissive angiogenesis. This review addresses several possible pharmacological modalities to block adenosinergic pathways and speculates on their future application together with impacts on human disease.

British Journal of Pharmacology(2008)153, S457–S464; doi:10.1038/bjp.2008.23
Modelling prefrontal cortex deficits in schizophrenia: implications for treatment
Authors: Pratt J A , Winchester C , Egerton A , Cochran S M , Morris B J
Published: March 2008

Current treatments of schizophrenia are compromised by their inability to treat all symptoms of the disease and their side‐effects. Whilst existing antipsychotic drugs are effective against positive symptoms, they have negligible efficacy against the prefrontal cortex (PFC)‐associated cognitive deficits and negative symptoms. New models that reproduce core pathophysiological features of schizophrenia are more likely to have improved predictive validity in identifying new treatments. We have developed a NMDA receptor antagonist model that reproduces core PFC deficits of schizophrenia and discuss this in relation to pathophysiology and treatments. Subchronic and chronic intermittent PCP (2.6 mg/kg i.p.) was administered to rats. PFC activity was assessed by 2‐deoxyglucose imaging, parvalbumin and Kv3.1 mRNA expression, and the attentional set‐shifting test (ASST) of executive function. Affymetrix gene array technology was employed to examine gene expression profile patterns. PCP treatment reduced glucose utilization in the PFC (hypofrontality). This was accompanied by a reduction in markers of GABAergic interneurones (parvalbumin and Kv3.1 mRNA expression) and deficits in the extradimensional shift dimension of the ASST. Consistent with their clinical profile, the hypofrontality was not reversed by clozapine or haloperidol. Transcriptional analysis revealed patterns of change consistent with current neurobiological theories of schizophrenia. This model mirrors core neurobiological deficits of schizophrenia; hypofrontality, altered markers of GABAergic interneurone activity and deficits in executive function. As such it is likely to be a valuable translational model for understanding the neurobiological mechanisms underlying hypofrontality and for identifying and validating novel drug targets that may restore PFC deficits in schizophrenia.

British Journal of Pharmacology (2008) 153, S465–S470; doi:10.1038/bjp.2008.24
Neuropharmacology of alcohol addiction
Authors: Vengeliene V , Bilbao A , Molander A , Spanagel R
Published: March 2008

Despite the generally held view that alcohol is an unspecific pharmacological agent, recent molecular pharmacology studies demonstrated that alcohol has only a few known primary targets. These are the NMDA, GABAA, glycine, 5‐hydroxytryptamine 3 (serotonin) and nicotinic ACh receptors as well as L‐type Ca2+channels and G‐protein‐activated inwardly rectifying K+channels. Following this first hit of alcohol on specific targets in the brain, a second wave of indirect effects on a variety of neurotransmitter/neuropeptide systems is initiated that leads subsequently to the typical acute behavioural effects of alcohol, ranging from disinhibition to sedation and even hypnosis, with increasing concentrations of alcohol. Besides these acute pharmacodynamic aspects of alcohol, we discuss the neurochemical substrates that are involved in the initiation and maintenance phase of an alcohol drinking behaviour. Finally, addictive behaviour towards alcohol as measured by alcohol‐seeking and relapse behaviour is reviewed in the context of specific neurotransmitter/neuropeptide systems and their signalling pathways. The activity of the mesolimbic dopaminergic system plays a crucial role during the initiation phase of alcohol consumption. Following long‐term, chronic alcohol consumption virtually all brain neurotransmission seems to be affected, making it difficult to define which of the systems contributes the most to the transition from controlled to compulsive alcohol use. However, compulsive alcohol drinking is characterized by a decrease in the function of the reward neurocircuitry and a recruitment of antireward/stress mechanisms comes into place, with a hypertrophic corticotropin‐releasing factor system and a hyperfunctional glutamatergic system being the most important ones.

British Journal of Pharmacology(2008)154, 299–315; doi:fn1; published online 3 March 2008
The neurocircuitry of addiction: an overview
Authors: Feltenstein M W , See R E
Published: March 2008

Drug addiction presents as a chronic relapsing disorder characterized by persistent drug‐seeking and drug‐taking behaviours. Given the significant detrimental effects of this disease both socially and economically, a considerable amount of research has been dedicated to understanding a number of issues in addiction, including behavioural and neuropharmacological factors that contribute to the development, loss of control and persistence of compulsive addictive behaviours. In this review, we will give a broad overview of various theories of addiction, animal models of addiction and relapse, drugs of abuse, and the neurobiology of drug dependence and relapse. Although drugs of abuse possess diverse neuropharmacological profiles, activation of the mesocorticolimbic system, particularly the ventral tegmental area, nucleus accumbens, amygdala and prefrontal cortex via dopaminergic and glutamatergic pathways, constitutes a common pathway by which various drugs of abuse mediate their acute reinforcing effects. However, long‐term neuroadaptations in this circuitry likely underlie the transition to drug dependence and cycles of relapse. As further elucidated in more comprehensive reviews of various subtopics on addiction in later sections of this special issue, it is anticipated that continued basic neuroscience research will aid in the development of effective therapeutic interventions for the long‐term treatment of drug‐dependent individuals.

British Journal of Pharmacology(2008)154, 261–274; doi:10.1038/bjp.2008.51; published online 3 March 2008
Short‐term or long‐term treatments with a phosphodiesterase‐4 (PDE4) inhibitor result in opposing agonist‐induced Ca2+ responses in endothelial cells
Authors: Campos‐Toimil M , Keravis T , Orallo F , Takeda K , Lugnier C
Published: March 2008

Background and purpose: We previously reported that agonist‐induced rises in cytoplasmic Ca2+ concentration ([Ca2+]i) in human umbilical vein endothelial cells (HUVEC) were inhibited after a short‐term (2 min) pre‐treatment with cAMP‐elevating agents. The aim of this work was to study the effects of longer term (8 h) pre‐treatment with dibutyryl‐cAMP (db‐cAMP) or rolipram, a specific inhibitor of phosphodiesterase‐4 (PDE4), on [Ca2+]i, cAMP levels and PDE activity and expression in HUVEC.

Experimental approach: [Ca2+]i changes were measured in isolated HUVEC by Fura‐2 imaging. Intracellular cAMP levels and PDE4 activity were assessed by enzyme‐immunoassay and radio‐enzymatic assay, respectively. PDE expression was measured by northern and western blot analysis.

Key results: Long‐term pre‐treatment of HUVEC with rolipram or db‐cAMP significantly increased ATP‐, histamine‐ and thrombin‐induced [Ca2+]i rises. Short‐term pre‐treatment with rolipram was associated with an increase in cAMP, whereas long‐term pre‐treatment was associated with a decrease in cAMP. Long‐term pre‐treatment with rolipram or db‐cAMP induced a significant increase in PDE4 activity and the expression of 74 kDa‐PDE4A and 73 kDa‐PDE4B was specifically enhanced. All these effects were suppressed by cycloheximide.

Conclusions and implications: Our data suggest that sustained inhibition of PDE4 by rolipram induced an increase in PDE4 activity, possibly as a compensatory mechanism to accelerate cAMP degradation and that PDE4A and PDE4B were implicated in the regulation of [Ca2+]i. Thus, isozyme‐specific PDE4 inhibitors might be useful as therapeutic agents in diseases where [Ca2+]i handling is altered, such as atherosclerosis, hypertension and tolerance to β‐adrenoceptor agonists.
Signalling pathways for transactivation by dexmedetomidine of epidermal growth factor receptors in astrocytes and its paracrine effect on neurons
Authors: Li B , Du T , Li H , Gu L , Zhang H , Huang J , Hertz L , Peng L
Published: March 2008

Background and purpose: Stimulation of astrocytes by the α2‐adrenoceptor agonist dexmedetomidine, a neuroprotective drug, transactivates epidermal growth factor (EGF) receptors. The present study investigates signal pathways leading to release of an EGF receptor ligand and those activated during EGF receptor stimulation, and the response of neurons to dexmedetomidine and to astrocyte‐conditioned medium.

Experimental approach: Phosphorylation of ERK1/2 was determined by western blotting and immunocytochemistry, and phosphorylation of EGF receptors by immunoprecipitation and western blotting. mRNA expression of fos family was measured by RT‐PCR.

Key results: Pertussis toxin (0.2 μg ml−1) an inhibitor of βγ subunit dissociation from Gαi protein, and GF 109203X (500 nM), a protein kinase C inhibitor, abolished ERK1/2 phosphorylation. PP1 (10 μM), inhibiting Src kinase and GM 6001 (10 μM), an inhibitor of Zn‐dependent metalloproteinase, abolished ERK1/2 phosphorylation by dexmedetomidine (50 nM), but not that by EGF (10 ng ml−1), showing Src kinase and metalloproteinase activation during the first stage only; AG 1478 (1 μM), an inhibitor of the EGF receptor tyrosine kinase, abolished ERK1/2 phosphorylation. Dexmedetomidine‐induced EGF receptor phosphorylation was prevented by AG 1478, GM 6001, PP1 and GF 109203X and its induction of cfos and fosB by AG 1478 and by U0126 (10 μM), an inhibitor of ERK phosphorylation, indicating downstream effects of ERK1/2 phosphorylation. EGF and conditioned medium from dexmedetomidine‐treated astrocytes, but not dexmedetomidine itself, induced ERK phosphorylation in primary cultures of cerebellar neurons.

Conclusions and implications: Dexmedetomidine‐induced transactivation pathways were delineated. Its paracrine effect on neurons may account for its neuroprotective effects.
Molecular epidemiology of clinically significant antibiotic resistance genes
Authors: Hawkey P M
Published: March 2008

Antimicrobials were first introduced into medical practice a little over 60 years ago and since that time resistant strains of bacteria have arisen in response to the selective pressure of their use. This review uses the paradigm of the evolution and spread of beta‐lactamases and in particular beta‐lactamases active against antimicrobials used to treat Gram‐negative infections. The emergence and evolution particularly of CTX‐M extended‐spectrum beta‐lactamases (ESBLs) is described together with the molecular mechanisms responsible for both primary mutation and horizontal gene transfer. Reference is also made to other significant antibiotic resistance genes, resistance mechanisms in Gram‐negative bacteria, such as carbepenamases, and plasmid‐mediated fluoroquinolone resistance. The pathogen Staphylococcus aureus is reviewed in detail as an example of a highly successful Gram‐positive bacterial pathogen that has acquired and developed resistance to a wide range of antimicrobials. The role of selective pressures in the environment as well as the medical use of antimicrobials together with the interplay of various genetic mechanisms for horizontal gene transfer are considered in the concluding part of this review.

British Journal of Pharmacology (2008) 153, S406–S413; doi:10.1038/sj.bjp.0707632
BNL test electron beam ion source operation on a 100kV platform (abstract)
Authors: Beebe E. N. , Alessi J. G. , Gould O. , Kponou A. , Lockey R. , Lambiase R. , Pikin A. , Prelec K. , Ritter J. , Zajic V.
Published: March 2008

At BNL, we are preparing to build an electron beam ion source (EBIS) that will satisfy the requirements of the relativistic heavy ion collider (RHIC), e.g., Au32+ ions of about 3×109 particles/pulse in 10–40μs pulses at 5Hz. In addition, the EBIS is required to deliver beams such as He2+, C6+, O8+, Si14+, Ti18+, Fe21+, and Cu22+ in ∼2–3mA, 10μs pulses at 5Hz to meet the demands of the NASA Space Radiation Laboratory (NSRL) experimental program. Development studies continue to be carried out on the BNL test EBIS, a half-length full electron beam power prototype of the RHIC EBIS which is in the construction phase. In preparation for acceleration of EBIS ions by a radio frequency quadrupole, we have upgraded the test EBIS for operation on a nominal 100kV pulsed platform to allow seed ion injection at 10–20kV and ion extraction up to 100qkV. The installation includes a pulsed high voltage power supply, a 200kVA 100kV isolation transformer, and a capacitive electron collector supply and electron gun bias supply which allows operation in a similar mode to the RHIC EBIS design. Initial testing has been made using ion beams of He2+ and Ar10+ formed from gas injection and ions have been extracted with energies up to 88qkeV. Total ion current measurement has been made and charge state distributions have been obtained using a Mamyrin time of flight. Results of emittance measurements and profile distributions, obtained at various energies using both pepperpot and slit-foil emittance meters, will be presented.
Resonant two-photon ionization spectroscopy of jet-cooled OsC
Authors: Krechkivska Olha , Morse Michael D.
Published: March 2008

The optical spectrum of diatomic OsC has been investigated for the first time, with transitions recorded in the range from 17390to22990cm−1. Six bands were rotationally resolved and analyzed to obtain ground and excited state rotational constants and bond lengths. Spectra for six OsC isotopomers, Os192C12 (40.3% natural abundance), Os190C12(26.0%), Os189C12(16.0%), Os188C12(13.1%), Os187C12(1.9%), and Os186C12(1.6%), were recorded and rotationally analyzed. The ground state was found to be XΔ33, deriving from the 4δ316σ1 electronic configuration. Four bands were found to originate from the XΔ33 ground state, giving B0″=0.533492(33)cm−1 and r0″=1.67267(5)Å for the Os192C12 isotopomer (1σ error limits); two of these, the 0-0[19.1]2←XΔ33 and 1-0[19.1]2←XΔ33 bands, form a vibrational progression with ΔG′1∕2=953.019cm−1. The remaining two bands were identified as originating from an Ω″=0 level that remains populated in the supersonic expansion. This level is assigned as the low-lying AΣ0+−3 state, which derives from the 4δ216σ2 electronic configuration. The OsC molecule differs from the isovalent RuC molecule in having an XΔ33 ground state, rather than the X2δ4, Σ+1 ground state found in RuC. This difference in electronic structure is due to the relativistic stabilization of the 6s orbital in Os, an effect which favors occupation of the 6s-like 16σ orbital. The relativistic stabilization of the 16σ orbital also lowers the energy of the 4δ216σ2, Σ−3 term, allowing this term to remain populated in the supersonically cooled molecular beam.
Estimation of cell membrane permeability of the rat brain using diffusion magnetic resonance imaging
Authors: Imae T. , Shinohara H. , Sekino M. , Ueno S. , Ohsaki H. , Mima K. , Ootomo K.
Published: March 2008

We propose a method to noninvasively evaluate the permeability of the cell membrane in the rat brain using diffusion magnetic resonance imaging (MRI). Diffusion MRI reflects the intra- and extracellular diffusion coefficients of water and cell membrane permeability. The images were acquired using a 4.7T MRI system with applications to motion-probing gradients in six directions. Numerical simulations based on the finite-difference method were carried out for estimating diffusion MRI signals with various combinations of membrane permeability and intracellular diffusion coefficient values. We defined an evaluative function as the difference between the signals estimated by simulation and experimentally obtained signals. We found that the combination of membrane permeability and intracellular diffusion coefficient in the simulation corresponding to the minimum value of the evaluative function leads to an estimation of these properties of the rat brain. The estimated intracellular diffusion coefficient and membrane permeability were (1.3±0.1)×10−3mm2∕s and 74±23μm∕s, respectively. Our method is useful for noninvasively estimating the cell membrane permeability of biological tissues, and is easily applicable to human tissues.
Evidence for excited spin-orbit state reaction dynamics in F+H2: Theory and experiment
Authors: Lique François , Alexander Millard H. , Li Guoliang , Werner Hans-Joachim , Nizkorodov Sergey A. , Harper Warren W. , Nesbitt David J.
Published: March 2008

We describe fully quantum, time-independent scattering calculations of the F+H2→HF+H reaction, concentrating on the HF product rotational distributions in v′=3. The calculations involved two new sets of ab initio potential energy surfaces, based on large basis set, multireference configuration-interaction calculations, which are further scaled to reproduce the experimental exoergicity of the reaction. In addition, the spin-orbit, Coriolis, and electrostatic couplings between the three quasidiabatic F+H2 electronic states are included. The calculated integral cross sections are compared with the results of molecular beam experiments. At low collision energies, a significant fraction of the reaction is due to Born–Oppenheimer forbidden, but energetically allowed reaction of F in its excited (P1∕22) spin-orbit state. As the collision energy increases, the Born–Oppenheimer allowed reaction of F in its ground (P3∕22) spin-orbit state rapidly dominates. Overall, the calculations agree reasonably well with the experiment, although there remains some disagreement with respect to the degree of rotational excitation of the HF(v′=3) products as well as with the energy dependence of the reactive cross sections at the lowest collision energies.
Formation of the diphenyl molecule in the crossed beam reaction of phenyl radicals with benzene
Authors: Zhang Fangtong , Gu Xibin , Kaiser Ralf I.
Published: March 2008

The chemical dynamics to form the D5-diphenyl molecule, C6H5C6D5, via the neutral-neutral reaction of phenyl radicals (C6H5) with D6-benzene (C6D6), was investigated in a crossed molecular beams experiment at a collision energy of 185kJmol−1. The laboratory angular distribution and time-of-flight spectra of the C6H5C6D5 product were recorded at mass to charge m∕z of 159. Forward-convolution fitting of our data reveals that the reaction dynamics are governed by an initial addition of the phenyl radical to the π electron density of the D6-benzene molecule yielding a short-lived C6H5C6D6 collision complex. The latter undergoes atomic deuterium elimination via a tight exit transition state located about 30kJmol−1 above the separated reactants; the overall reaction to form D5-diphenyl from phenyl and D6-benzene was found to be weakly exoergic. The explicit identification of the D5-biphenyl molecules suggests that in high temperature combustion flames, a diphenyl molecule can be formed via a single collision event between a phenyl radical and a benzene molecule.
High-field study of the magnetization in Ti doped ErCo2 compound
Authors: Guillot Maurice , Öner Yildirhan
Published: March 2008

The magnetization of powdered MgCu2 structure-type intermetallic ErCo1.95Ti0.05 was studied in the temperature range of 4.2–123K in magnetic fields up to 23T. A field-cooled magnetization jump at certain temperatures (TC) corresponds to a first-order magnetic phase transition from a paramagnetic to a ferrimagnetic state indicating cobalt moment formation. We observe that TC approach asymptotically T=50K with the cooling field Hc. The magnetization above TC stays constant (temperature independent), but does not saturate even in the field of 23T. The moment per unit formula was found to be approximately 7.25μB for this field. This behavior may be attributed to domain structures with the enhanced magnetocrystalline anisotropy field with titanium impurities. Magnetization versus magnetic field curves has also been recorded for both zero-field-cooled and field-cooled cases at various temperatures below and above TC. These curves below TC show typical ferrimagnetic phase; in the intermediate temperature range of 34–50K metamagnetism was observed and the sample becomes pure paramagnetic above 50K. In addition, the resistivity measurement was performed in the temperature range of 4.2–273K. A jumplike drop in the resistivity was observed at TC. In comparison with that of ErCo2, this transition temperature shifts to higher temperature as much as 2K, consistent with the slight increase of the lattice parameter. This drop in resistivity becomes much deeper presumably due to the internal magnetoresistance within the large domains. Analysis of the resistivity data in terms of spin fluctuations including s-d electron scattering and electron-phonon interaction reveals that T2 behavior becomes dominant in the temperature range of 34–50K where the magnetization data exhibit metamagnetism. Therefore, we assert based on both magnetization and resistivity results that the spin-fluctuation effects are driving force for the cobalt moment formations.
Electronic structure of halogen doped CuCr2Se4
Authors: Liberati M. , Neulinger J. R. , Chopdekar R. V. , Bettinger J. S. , Arenholz E. , Butler W. H. , Stacy A. M. , Idzerda Y. I. , Suzuki Y.
Published: March 2008

We have employed element and chemically sensitive x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) in order to address a long standing controversy regarding the electronic and magnetic states of CuCr2Se4 via halogen doping of the Se anion site in CuCr2Se4−xYx (Y=Cl and Br). Long range magnetic order is observed above room temperature for all samples. The Cr L2,3 XAS spectra show a prevalent 3+ valence for the Cr ions independent of doping concentration and doping agent. The Cu L2,3 XAS spectra show a combination of 1+ and 2+ valence states for all samples. XMCD spectra indicate the presence of a magnetic moment associated with the Cu ions that is aligned antiparallel to the Cr moment.
rf-driven ion sources for industrial applications (invited) (abstract)
Authors: Leung Ka-Ngo
Published: March 2008

The Plasma and Ion Source Technology Group at the Lawrence Berkeley National Laboratory have been developing rf-driven ion sources for the last two decades. These sources are being used to generate both positive and negative ion beams. Some of these sources are operating in particle accelerators such as the Spallation Neutron Source (SNS) at Oak Ridge, while others are being employed in various industrial ion beam systems. There are four areas where the rf-driven ion sources are commonly used in industry. (1) In semiconductor manufacturing, rf-driven sources have found important applications in plasma etching, ion beam implantation, and ion beam lithography. (2) In material analysis and surface modification, miniature rf-ion sources can be found in focused ion beam systems. They can provide ion beams of essentially any element in the Periodic Table. The newly developed combined rf ion-electron beam unit improves greatly the performance of the secondary ion mass spectrometry tool. (3) For neutron production, rf ion source is a major component of compact, high flux D-D, D-T, or T-T neutron generators. These neutron sources are now being employed in boron neutron capture therapy (BNCT) as well as in neutron imaging and material interrogation. (4) Large area rf-driven ion source will be used in an industrial design neutral beam diagnostic system for probing fusion plasmas. Such sources can be easily scaled to provide large ion beam current for future fusion reactor applications.
Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells
Authors: Song Jang-Kun , Sufin M. J. , Vij J. K.
Published: March 2008

Solitary wave propagation in surface stabilized ferroelectric liquid crystal cells controlled by surface anchoring of the alignment layers is investigated for different conditions of alignment on the two opposite surfaces. We show that the critical field Ec, where the speed of the solitary wave becomes zero, is finite for asymmetric alignment on two surfaces. We also show that the polar anchoring energy difference (Δwp) between the alignment layers can be calculated by measuring Ec, and this depends on the rubbing condition and the material of the alignment layer.
Experimental study on large-scale streak structure in the core region of turbulent plane Couette flow
Authors: Kitoh O. , Umeki M.
Published: March 2008

A physical experiment confirmed the existence of a large-scale streak structure in the core region of turbulent Couette flow at Re=Uwh∕ν=3750. In the low- or high-speed streak, large-scale wavy-like structures exist, the streamwise and spanwise wavelength of which are (40−65)h and (4−5)h. The low (high) -speed streak pattern is a sequence of wavy and nonwavy (tilted line or irregular) patterns. The large-scale structure is reconstructed using the wavelet components of the streamwise fluctuating velocity that have high energy on a large scale. The reconstructed flow field shows the existence of large-scale structures with a tilted pattern. The tilting angle is ±(3°−5°) against the flow direction. In some places, they constitute a weakly wavy pattern and in other places a simple tilted pattern. The weakly wavy structures appear intermittently in space along the streamwise direction. The rough estimation of the streamwise separation between large-scale structures is 300h.
A note on the multispecies model for identical particles
Authors: Yu M. Y. , Luo Huaqiang
Published: March 2008

It is pointed out that the multispecies model for identical particles is in general not suitable for considering quasistationary nonlinear plasma structures. For phenomena on long time scales, the a priori partitioning of electrons into hot and cold species is often unrealistic unless the latter are actually separated in the phase space by external or self-consistent fields.
Actively stabilized optical fiber interferometry technique for online/in-process surface measurement
Authors: Wang Kaiwei , Martin Haydn , Jiang Xiangqian
Published: March 2008

In this paper, we report the recent progress in optical-beam scanning fiber interferometry for potential online nanoscale surface measurement based on the previous research. It attempts to generate a robust and miniature measurement device for future development into a multiprobe array measurement system. In this research, both fiber-optic-interferometry and the wavelength-division-multiplexing techniques have been used, so that the optical probe and the optical interferometer are well spaced and fast surface scanning can be carried out, allowing flexibility for online measurement. In addition, this system provides a self-reference signal to stabilize the optical detection with high common-mode noise suppression by adopting an active phase tracking and stabilization technique. Low-frequency noise was significantly reduced compared with unstabilized result. The measurement of a sample surface shows an attained repeatability of 3.3nm.
Quantum symmetry algebras of spin systems related to Temperley–Lieb R-matrices
Authors: Kulish P. P. , Manojlovic N. , Nagy Z.
Published: March 2008

A reducible representation of the Temperley–Lieb algebra is constructed on the tensor product of n-dimensional spaces. One obtains as a centralizer of this action a quantum algebra (a quasitriangular Hopf algebra) Uq with a representation ring equivalent to the representation ring of the sl2 Lie algebra. This algebra Uq is the symmetry algebra of the corresponding open spin chain.
Growth behavior and intrinsic properties of vapor-deposited iron palladium thin films
Authors: Kock I. , Edler T. , Mayr S. G.
Published: March 2008

Iron palladium based alloys are promising candidates to realize miniaturized magnetic shape memory devices on a thin film basis and also bear interesting magnetic properties, particularly for the area of magnetic recording. To address the impact of growth conditions on physical properties, thin vapor-deposited Fe70Pd30 films are analyzed with respect to structure, texture, and stress as a function of processing parameters. We find that deposition at room temperature leads to a bct structure, while deposition at elevated temperature as well as annealing results in austenitic films in the fcc phase, which is desirable for magnetic shape memory applications.
Child–Langmuir flow in a planar diode filled with charged dust impurities
Authors: Tang Xiao-yan , Shukla Padma Kant
Published: March 2008

The Child–Langmuir (CL) flow in a planar diode in the presence of stationary charged dust particles is studied. The limiting electron current density and other diode properties, such as the electrostatic potential, the electron flow speed, and the electron number density, are calculated analytically. A comparison of the results with the case without dust impurities reveals that the diode parameters mentioned above decrease with the increase of the dust charge density. Furthermore, it is found that the classical scaling of D−2 (the gap spacing D) for the CL current density remains exactly valid, while the scaling of V3∕2 (the applied gap voltage V) can be a good approximation for low applied gap voltage and for low dust charge density.
Amplified spontaneous emission in quaterthiophene single crystals
Authors: Polo Marco , Camposeo Andrea , Tavazzi Silvia , Raimondo Luisa , Spearman Peter , Papagni Antonio , Cingolani Roberto , Pisignano Dario
Published: March 2008

The authors demonstrate amplified spontaneous emission (ASE) from quaterthiophene single crystals and study its behavior at low temperature. The room temperature photoluminescence exhibits line narrowing (spectral width down to 10nm) at 553nm for excitation fluence larger than 1mJcm−2. At low temperature (10K), ASE is observed from two vibronic transitions at 510nm (0-1) and 553nm (0–2), with line narrowing down to 5Å, for fluences larger than 100μJcm−2. The stimulated emission cross section is of the order of 10−15cm2, and the ASE is found to be strongly affected by thermally induced dynamic disorder. The emission stability under photopumping is also studied and discussed.
Noise measurement of a quantized charge pump
Authors: Maire N. , Hohls F. , Kaestner B. , Pierz K. , Schumacher H. W. , Haug R. J.
Published: March 2008

We study the noise properties of a gate controlled single electron pump at a driving frequency fp=400MHz. We observe a significant reduction of the noise power on the current plateaus. This is a strong indication for true quantized charge pumping. We furthermore observe a small level of low frequency fluctuations which indicates a good frequency stability of the pump.
Morphology evolution and magnetic properties improvement in FePt epitaxial films by in situ annealing after growth
Authors: Casoli F. , Nasi L. , Albertini F. , Fabbrici S. , Bocchi C. , Germini F. , Luches P. , Rota A. , Valeri S.
Published: March 2008

This paper presents a detailed study of structure, morphology, and magnetic properties in FePt thin films epitaxially grown on MgO(100) at intermediate temperatures (≅380°C). It focuses on the effects obtained by in situ annealing the FePt films after deposition. We have demonstrated that the annealing allows one to complete the ordering, thus obtaining an epitaxial L10-FePt film with large perpendicular anisotropy (up to 3×107erg∕cm3) and high perpendicular squareness and remanence ratio (both higher than 0.85). At the same time, we have found a peculiar morphology evolution by increasing the annealing time: the interconnected mazelike grains evolve towards interconnected dotlike grains of reduced size (down to 10nm). Due to the interconnection at the grains basis, the increase in the film perpendicular coercivity with the annealing process is moderate (up to 4.1kOe), leading to an increasing anisotropy/coercivity ratio with the annealing time. As a further step towards the understanding of the properties evolution with annealing, we have investigated the magnetic domain pattern and analyzed the domain-period dependence on the anisotropy constant in comparison with the behavior expected by the Kooy–Enz theory [C. Kooy and U. Enz, Philips Res. Rep. 15, 7 (1960)]. The main magnetic properties and reduced grain size obtained after the in situ annealing are promising to realize perpendicular recording media with reduced bit size, high thermal stability, and suitable switching field.
An angle-resolved study of early oxidation (<3.0nm) of Si–Ge alloys
Authors: Kilpatrick S. J. , Jaccodine R. J.
Published: March 2008

A study was completed involving the mechanisms of Si1−xGex oxidation. Either pure or mixed oxides of Si and Ge were grown. All oxides were grown in situ in a Scienta ESCA-300 system designed for oxidation. Angle-resolved x-ray photoelectron spectroscopy was the principal tool in assessing interfacial chemistry. The sub-bonded species of both Si and Ge were investigated as a function of composition. Values for the number of interfacial states were determined in addition to their spatial extension in the actual oxidation interface. The role of interfacial cleaning and the initiation of growth in thin films were determined.
Strongly coupled multiple-dot characteristics in dual recess structured silicon channel
Authors: Manoharan M. , Kawata Yoshiyuki , Tsuchiya Yoshishige , Oda Shunri , Mizuta Hiroshi
Published: March 2008

Silicon single electron transistors were fabricated by using the highly doped silicon channel with dual recess structure along with two recess gates and one central island gate as a pattern. The transition of Coulomb oscillation characteristics from a single dot to a strongly coupled multiple dot was demonstrated for the different oxidation times and recess dimensions. The multiple-dot characteristic in the longer post lithography oxidized sample is attributed to the formation of a single dot in each recess due to the stress induced pattern-dependent oxidation, which leads to multiple dot in the channel. The temperature variation measurement, which was performed after two thermal cycling of the same sample to 20 and 4.2K with 1month gap, revealed the highly stable nature of the multiple-dot device transport characteristics. The multiple-dot device can also be operated as a unique nonlinear tunable resistance single electron transistor.