bluuebunny/crossref_metadata_2025 huggingface dataset:
Time Dependence of Effect of Nitric Oxide Synthase Inhibition on Cerebral Ischemic Damage
Authors: Zhang Fangyi , Xu Sherry , Iadecola Costantino
Published: April 2011

Nitric oxide, a potent vasodilator and an inhibitor of platelet aggregation, may be beneficial in the early stages of focal cerebral ischemia as it may facilitate collateral blood flow to the ischemic territory. Accordingly, the effect of inhibition of nitric oxide synthesis on cerebral ischemic damage may vary depending on the timing of the inhibition relative to the induction of ischemia. We therefore studied the time course of the effect of nitric oxide synthesis inhibition on focal cerebral ischemic damage. The middle cerebral artery was permanently occluded in spontaneously hypertensive rats and the nitric oxide synthase (NOS) inhibitor nitro-l-arginine methyl ester (l-NAME) was administered systemically (3 mg/kg) <5 min or 2, 3, or 6 h later. Arterial pressure, rectal temperature, plasma glucose, and hematocrit were monitored. Infarct volume was determined on thioninstained sections 24 h after induction of ischemia. NOS activity was determined in cerebellum from the conversion of l-[3H]arginine to l-[3H]citrulline. Administration of l-NAME <5 min after arterial occlusion increased the infarct volume by 23 ± 14% (mean ± SD; p < 0.05, analysis of variance), while administration of l-NAME at 2 or 6 h did not affect the size of the infarct (p > 0.05). l-NAME administration 3 h after induction of ischemia reduced neocortical infarct size by 14 ± 11% (p < 0.05). l-NAME decreased cerebellar NOS activity comparably in all groups (range 16–25%). We conclude that the effects of inhibition of nitric oxide synthesis on focal cerebral ischemic damage are time dependent. Thus, inhibition of nitric oxide synthesis worsens ischemic damage when instituted shortly after induction of ischemia and does not affect or reduces damage at later times. The results support the hypothesis that the vascular actions of nitric oxide are beneficial only in the early stages of permanent focal cerebral ischemia.
The Competitive NMDA Antagonist CGP 40116 Permanently Reduces Brain Damage after Middle Cerebral Artery Occlusion in Rats
Authors: Sauer Dirk , Weber Edgar , Lüönd Guido , Da Silva Fernando , Allegrini Peter R.
Published: April 2011

In this study we evaluated the effect of the competitive N-methyl-d-aspartate (NMDA) antagonist d-(E)-4-(3-phosphonoprop-2-enyl)piperazine-2-carboxylic acid (CGP 40116) on both early (2 days) and late (28 days) ischemic brain damage in a rodent model of focal cerebral ischemia by means of magnetic resonance imaging (MRI) and conventional histology. Immediately after occlusion of the left middle cerebral artery (MCA), rats received either CGP 40116 (20 mg/kg i.p.) or isotonic saline. Two MRI scans were performed in each animal 2 and 28 days after MCA occlusion. After the second scan, rats were perfusion fixed for histological evaluation. The volume of lesioned brain tissue as determined by MRI or histology was calculated from the damaged area in single sections and the distance between them. CGP 40116 reduced acute infarct volume as measured by MRI 2 days after MCA occlusion by 44% (p < 0.05, analysis of variance). After 28 days the lesion detected by MRI was still significantly smaller in the drug-treated animals. This finding was confirmed by the histological analysis showing a 64% reduction in the volume of brain atrophy in the CGP 40116 group (p < 0.05, analysis of variance). There was a good correlation between the MRI data and the results of the histological evaluation ( r = 0.9). Our results indicate that (a) the competitive NMDA antagonist CGP 40116 permanently protects brain tissue from the consequences of cerebral ischemia in a rat model for human stroke and (b) early and late pathological changes can be accurately measured by MRI.
Prolonged Pretreatment with α-Lipoic Acid Protects Cultured Neurons against Hypoxic, Glutamate-, or Iron-Induced Injury
Authors: Müller Ute , Krieglstein Josef
Published: April 2011

The antioxidant dihydrolipoic acid has been shown to reduce hypoxic and excitotoxic neuronal damage in vitro. In the present study, we tested whether pretreatment with α-lipoic acid, which presumably allows endogenous formation of dihydrolipoic acid, can protect cultured neurons against injury caused by cyanide, glutamate, or iron ions, using the trypan blue exclusion method to determine neuronal damage. One hour of preincubation with dihydrolipoic acid (1 μ M), but not with α-lipoic acid, reduced damage of neurons from chick embryo telencephalon caused by 1 m M sodium cyanide or iron ions. α-Lipoic acid (1 μ M) reduced cyanide-induced neuronal damage when added 24 h before hypoxia, and pretreatment with α-lipoic acid for >24 h enhanced this neuroprotective effect. Both the R- and the S-enantiomer of α-lipoic acid exerted a similar neuroprotective effect. Pretreatment with α-lipoic acid (1 μ M) from the day of plating onward prevented the degeneration of chick embryo telencephalic neurons that had been exposed to Fe2+/Fe3+. α-Lipoic acid (1 μ M) added to the culture medium the day of plating also reduced neuronal injury induced by 1 m M l-glutamate in rat hippocampal cultures, whereas 30 min of preincubation with α-lipoic acid failed to attenuate glutamate-induced neuronal damage. Our results indicate that neuroprotection by prolonged pretreatment with α-lipoic acid is probably due to the radical scavenger properties of endogenously formed dihydrolipoic acid.
Changes in N-Acetyl-Aspartate Content during Focal and Global Brain Ischemia of the Rat
Authors: Sager Thomas Nikolaj , Laursen Henning , Hansen Anker Jon
Published: April 2011

N-Acetyl-aspartate (NAA) is almost exclusively localized in neurons in the mature brain and might be used as a neuronal marker. It has been reported that the NAA content in human brain is decreased in neurodegenerative diseases and in stroke. Since the NAA content can be determined by nuclear magnetic resonance techniques, it has potential as a diagnostic and prognostic marker. The objective of this study was to examine the change of NAA content and related substances following cerebral ischemia and compare the results to the damage of the tissue. We used rats to study the changes of NAA, N-acetyl-aspartyl-glutamate (NAAG), glutamate, and aspartate contents over a time course of 24 h in brain regions affected by either permanent middle cerebral artery occlusion (focal ischemia) or decapitation (global ischemia). The decreases of NAA and NAAG contents following global brain ischemia were linear over time but significant only after 4 and 2 h, respectively. After 24 h, the levels of NAA and NAAG were 24 and 44% of control values, respectively. The concentration of glutamate did not change, whereas the aspartate content increased at a rate comparable with the rate of decrease of NAA content. This is consistent with NAA being preferentially degraded by the enzyme amidohydrolase II in global ischemia. In focal ischemia, there was a rapid decline of NAA within the first 8 h of ischemia followed by a slower rate of reduction. The reductions of NAA and NAAG contents in focal ischemia were significant after 4 and 24 h, respectively. After 24 h, the NAA and NAAG contents were 33 and 64% of control values, respectively. Also, the glutamate and aspartate contents exhibited significant decreases in focal ischemic tissue. Our studies show that NAA decreases during brain ischemia, the initial rate being faster in focal ischemia than in global ischemia. In rat transient focal ischemia, others have shown that a middle cerebral artery occlusion of 2- to 3-h duration is sufficient to produce an infarct that is similar in size to that following permanent occlusion for 24 h. The fact that we observed only a 10% decrease of NAA content 2 h after occlusion demonstrates that the NAA content of the tissue does not reflect neuronal viability. Thus, the incompetence with which ischemic/infarcted tissue removes NAA will lead to overestimation of the number of viable neurons in acute situations. Only when steady state prevails may [NAA] be used as a marker of viable nerve cells.
Mitochondrial Hyperoxidation Signals Residual Intracellular Dysfunction after Global Ischemia in Rat Neocortex
Authors: Rosenthal Myron , Feng Zi-Cai , Raffïn Cesar N. , Harrison Madaline , Sick Thomas J.
Published: April 2011

Reperfusion after global ischemia (10–60 min in duration) in rat neocortex most commonly provoked transient hyperoxidation of mitochondrial electron carriers, tissue hyperoxygenation, and CBF hyperemia. These responses were normally accompanied by recovery of K+ homeostasis and EEG spike activity. Goals of this research were to understand putative relationships among these postreperfusion events with special emphasis on determining whether mitochondrial hyperoxidation results from intracellular changes that may modulate residual damage. The amplitude of postischemic mitochondrial hyperoxidation (PIMHo) did not increase when CBF increased above an apparent threshold during reperfusion, and tissue hyperoxygenation was not required for PIMHo to occur or to continue. These findings suggest that PIMHo is not merely a response to increased CBF and tissue hyperoxygenation; rather, PIMHo is modulated, at least in part, by residual intracellular derangements that limit mitochondrial electron transport. This suggestion was supported by observations that NAD became hyper-oxidized after reoxygenation in anoxic hippocampal slices. Also, PIMHo occurred and subsequently resolved in many animals, but K+o never was cleared fully to baseline and/or EEG spike activity never was evident. One suggestion is that PIMHo signals or initiates residual intracellular derangements that in turn impair electrical and metabolic recovery of cerebral neurons after ischemia; an alternative suggestion is that PIMHo and tissue hyperoxygenation are not the sole factors modulating the immediate restoration of electrical activity after ischemia. Present data also support the following: Decreased oxygen consumption, despite adequate oxygen delivery, likely contributes to tissue hyperoxygenation after ischemia; and mitochondrial hyperoxidation is modulated by a limitation in the supply of electrons to the mitochondrial respiratory chain.
Enhanced Cerebrovascular Responsiveness to Hypercapnia following Depletion of Central Serotonergic Terminals
Authors: Kelly Paul A. T. , Ritchie Isobel M. , McBean Douglas E. , Sharkey John , Olverman Henry J.
Published: April 2011

Serotonin-containing nerve fibres innervate cerebral blood vessels, but the source of this innervation and the physiological effects of perivascular serotonin release remain controversial. The purpose of the present study was to examine the effects of central serotonergic depletion upon the relationship between CBF and glucose utilization under both normo- and hypercapnic conditions. To induce the loss of serotonergic terminals, rats were injected twice daily for 4 consecutive days with 20 mg/kg of the specific serotonergic neurotoxin methylenedioxyamphetamine (MDA). Between 4 and 6 weeks later, local CBF and glucose utilization were measured using the fully quantitative [14C]iodoantipyrine and [14C]2-deoxyglucose autoradiographic techniques, respectively, and the efficacy of the lesioning protocol was assessed using [3H]paroxetine radioligand binding analysis. In all animals treated with MDA, there was a significant decrease in serotonin uptake sites throughout the brain, falling from 223 ± 20 to 40 ± 16 fmol/mg tissue in parietal cortex, for example, although the raphe nuclei themselves were unaffected (300 ± 20 fmol/mg tissue in controls and 291 ± 18 in MDA-treated rats). In normocapnic rats, the effects of MDA pretreatment upon blood flow and glucose use were slight and focally concentrated. However, when the animals were rendered hypercapnic, CBF was significantly higher in MDA-treated rats than in normal controls, for example, increasing from 356 ± 22 ml 100 g−1 min−1 in frontal cortex of hypercapnic controls to 700 ± 81 ml 100 g−1 min−1 in MDA-pretreated rats with similar levels of hypercapnia. In some brain areas of hypercapnic MDA-pretreated rats, blood flows were too high (>800 ml 100 g−1 min−1) to be accurately quantified. The results of this study are consistent with a constrictor role for perivascular serotonergic innervation that becomes manifest when, as in hypercapnia, cerebrovascular tone is low.
A single-molecule study of the inhibition effect of Naringenin on transforming growth factor-β ligand–receptor binding
Authors: Yang Yong , Xu Yongchun , Xia Tie , Chen Fangjin , Zhang Chunling , Liang Wei , Lai Luhua , Fang Xiaohong
Published: April 2011

Single-molecule fluorescence imaging and single-molecule force measurement revealed the inhibitory effect of Naringenin on TGF-β ligand–receptor interaction.
Copper-catalyzed α-amination of aliphatic aldehydes
Authors: Tian Jie-Sheng , Loh Teck-Peng
Published: April 2011

A highly efficient copper-catalyzed α-amination of aliphatic aldehydes for the synthesis of α-amino acetals using secondary amines with readily removable protecting groups as a nitrogen source was developed. This reaction can be operated under very mild conditions, affording the desired products in moderate to good yields.
The analysis of piezomagnetoelastic energy harvesters under broadband random excitations
Authors: Ali S. F. , Adhikari S. , Friswell M. I. , Narayanan S.
Published: April 2011

This paper presents an analysis of piezomagnetoelastic energy harvesters under broadband random ambient excitations for the purpose of powering low-power electronic sensor systems. Their nonlinear behavior as a result of vibration in a magnetic field makes piezomagnetoelastic energy harvesters different from classical piezoelastic energy harvesters. An equivalent linearization-based analytical approach is developed for the analysis of harvested power. A closed-form approximate expression for the ensemble average of the harvested power is derived and validated against numerical Monte Carlo simulation results. Our results show that it is possible to optimally design the system such that the mean harvested power is maximized for a given strength of the input broadband random ambient excitation.
Surfactant-induced delay of leveling of inkjet-printed patterns
Authors: Hanyak Myroslava , Darhuber Anton A. , Ren Maosheng
Published: April 2011

Due to its flexibility, inkjet printing has become a widespread technique for the non-contact deposition of liquids, solutions and melts on a variety of substrates with a lateral resolution down to about 10 μm. Because the patterns are formed via coalescence of many individual droplets, ripples and undulations can appear in the deposited layers, which gradually disappear if sufficient time before ink solidification is given. In this manuscript, we study this spontaneous leveling process of inkjet printed lines that is driven by surface tension and hydrostatic pressure gradients. We show that the process can be significantly retarded if the ink contains soluble or insoluble surfactants, which are common additives to improve print quality. We present qualitative experiments as well as theoretical and numerical models that allow estimation of the leveling time for arbitrary ripple amplitudes and realistic surfactant properties.
Three dimensional piezoresponse force microscopy polarization difference maps
Authors: Jing Yuanyuan , Blendell John E. , Bowman Keith J.
Published: April 2011

We describe a technique, called polarization difference maps (PDMs), that fully reveals ferroelectric switching of regions within individual grains. Using PDMs, domains that have undergone 90° and 180° switching were mapped for a 100 nm thick polycrystalline lead zirconate titanate (PZT) thin film. Almost half of the scanned regions were found to undergo 90° switching during the applied electric field reversal. Some 180° switched domains clearly went through two successive 90° switching.
A variational method for calculating the magnetic flux propagation in long thin ferromagnetic samples
Authors: Pinotti E. , Puppin E.
Published: April 2011

In this paper we present a model for calculating the propagation of magnetic flux in thin ferromagnetic samples, which is based on variational methods applied to magnetostatics. Starting from basic magnetostatic equations this model yields an exponential decay of the flux along the sample, with a decay length depending only on the sample geometry and relative permeability. This result is analytically simpler than the usual Rytov model, and allows for an easier comparison with experiments. The results of our model and Rytov’s are compared to experiments for the cases of cylindrical iron wires and ferromagnetic amorphous strips, and our model is found to accurately describe the behavior of high permeability materials.
A study on the interfacial effect on cancer-cell invasion
Authors: Zhang Linan , Song Jihwan , Kim Dongchoul
Published: April 2011

Cancer-cell invasion is a complex biological process involving cell migration through the extracellular matrix, which is driven by haptotaxis, and the interactions between cancer cells and the surrounding matrix. In this paper, a three-dimensional haptotaxis model that simulates the migration of a cancer cell population, including cell–cell adhesion and cell–matrix adhesion, is proposed. We employ a diffuse interface model that incorporates the mechanism of haptotaxis and the interface energy of cancer cells as well as that between cancer cells and the matrix. The semi-implicit Fourier spectral scheme is applied for high efficiency and numerical stability. The simulations systematically reveal the dynamics of cancer-cell migration and the effect of interface energy on the invasion of cancer cells.
Magnetic properties of NdFeO3 single crystal in the spin reorientation region
Authors: Yuan Shujuan , Wang Yabin , Shao Mingjie , Chang Fenfen , Kang Baojuan , Isikawa Yosikazu , Cao Shixun
Published: April 2011

High quality NdFeO3 single crystal has been grown by the four-mirror image floating zone technique. The magnetic properties and specific heat of NdFeO3 single crystal were systematically studied in the temperature range from 2 to 300 K. A clear spin reorientation behavior is observed in a wide temperature range from 100 to 170 K, with the gradual transition of the Fe3+ magnetic moment ordering from {Gz, Mx}-type ordering at low temperatures to {Gx, Mz}-type ordering at high temperatures. In the temperature range from 170 to 300 K, the value of Mx is not equal to zero. It is assumed a single {Gx, Mz}-type ordering mixed with {Gxz, Mxz}-type orderings. During the spin orientation transition process, the hysteresis loops become narrow with very small coercivity. Based on the specific heat measurement, the Schottky anomaly at very low temperature and the thermal anomalies induced by the spin reorientation were also discussed.
Ferromagnetism of polythiophene-capped Au nanoparticles
Authors: Suzuki K. , Zhang H. , Saito K. , Garitaonandia J. S. , Goikolea E. , Insausti M.
Published: April 2011

The magnetic and electrical transport properties of regioregular poly(3-hexylthiophene)-capped Au nanoparticles (NPs) doped with iodine have been investigated to clarify the effectiveness of conductive polymer capping on the induction of ferromagnetism in Au. The room-temperature magnetization curve of the undoped polythiophene-capped Au NPs exhibits a clear hysteresis behavior with a coercive force of 160 Oe. The spontaneous magnetization normalized by the mass of Au is 2.0 × 10−2 emu/g. The spontaneous magnetization was found virtually unaffected by iodine doping, whereas the electrical conductivity is enhanced dramatically to ∼10 S/cm. Our results show that polythiophene capping could lead to spontaneous magnetic polarization in Au NPs, and the conductivity of the polymer capping does not affect the ferromagnetism of the Au nanoparticles, opening a possibility for further investigation into the magnetotransport behavior of ferromagnetic Au NPs.
Microstructure and magnetic properties of sintered Nd–Fe–B magnets with high hydrogen content
Authors: Guo S. , Zhou Q. Y. , Chen R. J. , Lee D. , Yan A. R.
Published: April 2011

The effects of hydrogen contents after the process of hydrogen decrepitation on the magnetic properties and corrosion resistance of sintered Nd–Fe–B permanent magnets have been studied. The intrinsic coercivity of the magnets increases and the remanence decreases with increasing hydrogen content. High residue hydrogen content in the starting ingot leads to the reaction of hydrogenation, disproportionation, desorption and recombination in the sinter process resulting in magnets with low remanence. The results of highly accelerated temperature/humidity stress test indicate that excessive hydrogen contents are harmful to the corrosion resistance of the magnets. The influences of residue hydrogen contents on the corrosion resistance of magnets dominate only when the residue hydrogen content exceeds 1300 parts per million.
Bulk SmCo5/α-Fe nanocomposite permanent magnets fabricated by mould-free Joule-heating compaction
Authors: Rong Chuanbing , Zhang Ying , Poudyal Narayan , Wang Dapeng , Kramer M. J. , Liu J. Ping
Published: April 2011

Bulk SmCo5/α-Fe nanocomposite magnets have been prepared using a Joule-heating compaction technique. Nearly fully dense bulk magnets are obtained by compacting the milled powders under a pressure of 2 GPa at temperatures above 400 °C. Structural analysis shows that the grain size of both the SmCo5 and the α-Fe phases is in the range of 10 to 15 nm when the compaction temperature is lower than 500 °C, which ensures effective interphase exchange coupling. A further increase in compaction temperature leads to significant grain growth and deterioration of magnetic properties. A maximum energy product of about 18.5 MGOe was obtained in the bulk SmCo5/α-Fe nanocomposite magnets, which is 90% higher than that of the single-phase counterpart prepared under the same conditions.
Impact of vane size and separation on radiometric forces for microactuation
Authors: Gimelshein Natalia , Gimelshein Sergey , Ketsdever Andrew , Selden Nathaniel
Published: April 2011

A kinetic approach is used to study the feasibility of increasing the efficiency of microactuators that use radiometric force through etching holes in a single radiometer vane. It has been shown that a radiometer that consists of small vanes is capable of producing at least an order of magnitude larger force than a single-vane radiometer that takes up the same area. The optimum gap between the vanes is found to be slightly smaller than the vane size, with the optimum Knudsen number of about 0.05 based on the vane height.
The electric transport properties of Al-doped ZnO/BiFeO3/ITO glass heterostructure
Authors: Fan Fei , Chen Changle , Luo Bingcheng , Jin Kexin
Published: April 2011

BiFeO3 (BFO) and 4 wt. % Al-doped ZnO (ZAO) layers were grown on indium tin oxide (ITO) glass substrate using a pulsed laser deposition (PLD) method. I–V curves of the ZAO/BFO/ITO glass structure were investigated over the temperature range from 60 to 240 K. Analysis of the leakage current demonstrates that Poole–Frenkel emission is the dominant mechanism in our sample. The relations between resistance and temperature at positive and negative bias voltages are different, and the difference arises from the ferroelectric switching in BFO and the interfacial depletion layer between the semiconducting and the ferroelectric layers. Magnetoresistance (MR) effect is observed and the negative MR is related to the electron spin-dependent scattering and the interface resistance of the heterostructure.
Ballistic transport and electrical spin signal enhancement in a nanoscale three-terminal spintronic device
Authors: Zhu Lei , Yu Edward T.
Published: April 2011

Ballistic electron transport at nanoscale dimensions is investigated and exploited in a nanoscale three-terminal, all-electrical spintronic semiconductor device. Charge current cancellation under appropriate device biasing yields a large, spin-dependent current signal even with modest spin injection efficiency into the semiconductor, while reliance on ballistic, rather than diffusive, carrier transport is expected to enable robust scalability to smaller dimensions. Magnetocurrent in excess of 200% is measured with spin injection efficiency of 5%, and a spin-dependent ballistic carrier transport model is shown to yield accurate, quantitative predictions of current-voltage behavior.
Cavity formation in a liquid Sn droplet driven by laser ablation pressure for an extreme ultraviolet light source target
Authors: Yuspeh S. , Ueno Y. , Tillack M. S. , Burdt R. , Tao Y. , Najmabadi F.
Published: April 2011

An in situ approach to the formation of cavities in liquid Sn droplets for the purpose of increasing ion density from Sn plasma produced by a CO2 laser is investigated. Two-dimensional hydrodynamic simulations, treating the laser as a pulsed pressure source, are compared both spatially and temporally to experimental shadowgraphs for verification of cavity formation. It is shown that a 15 ns pulse from a 1.064 μm laser with intensity of 2 × 1010 W/cm2 creates a cavity approximately 300 μm wide and 100 μm deep in approximately 1.4 μs. The presence of the cavity enhances the conversion of laser energy to 13.5 nm radiation from the plasma.
Effect of impurities on thermal stability of pseudomorphically strained Si:C layer
Authors: Chuang Yao-Teng , Wang Sheng-Hao , Woon Wei-Yen
Published: April 2011

We investigate the thermal stability of pseudomorphically strained Si:C layer using high resolution x-ray diffraction (HRXRD) and Fourier transform infrared (FTIR) spectroscopy. Far below β-SiC precipitation threshold, almost complete strain relaxation is found without significant substitutional carbon (Csub) loss. FTIR shows the strain relaxation is related to volume compensation by Csub-interstitial complex formation through oxidation injection of interstitial. By multilayer HRXRD kinematical simulation, we find correlation of the enhanced strain relaxation to P distribution, implying P’s role as additional interstitial promoter during postannealing treatment. We relate our findings to recent reports on strain relaxation issues in Si:C devices fabrication.
A simple proof of Lieb concavity theorem
Authors: Aujla Jaspal Singh
Published: April 2011

The purpose of this paper is to give a simple proof of the well known Lieb concavity theorem.
Quasi one-dimensional transport in single GaAs/AlGaAs core-shell nanowires
Authors: Lucot D. , Jabeen F. , Harmand J.-C. , Patriarche G. , Giraud R. , Faini G. , Mailly D.
Published: April 2011

We present an original approach to fabricate single GaAs/AlGaAs core-shell nanowire with robust and reproducible transport properties. The core-shell structure is buried in an insulating GaAs overlayer and connected as grown in a two-probe setup using the highly doped growth substrate and a top diffused contact. The measured conductance shows a non-Ohmic behavior with temperature and voltage-bias dependences following power laws, as expected for a quasi one- dimensional system.
Direct thrust measurement of a permanent magnet helicon double layer thruster
Authors: Takahashi K. , Lafleur T. , Charles C. , Alexander P. , Boswell R. W. , Perren M. , Laine R. , Pottinger S. , Lappas V. , Harle T. , Lamprou D.
Published: April 2011

Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.
Manipulating stress in Cu/low-k dielectric nanocomposites
Authors: Murray Conal E. , Besser Paul R. , Ryan E. Todd , Jordan-Sweet Jean L.
Published: April 2011

The interaction of x-rays with organic dielectric materials, which alters their mechanical properties, affects values of stress generated within encapsulated Cu structures. In particular, the evolution of stress within submicron Cu interconnect structures encapsulated by an organosilicate glass can be investigated in situ using synchrotron-based x-ray diffraction. The overall geometry of the composite, along with the amount of irradiation, dictates the change in stress of the Cu features. A quantitative comparison of these findings to mechanical modeling results reveals two modes of modification within the dielectric film: a densification that changes the effective eigenstrain followed by an increase in elastic modulus.
Does susceptibility to heat stress confound screening for drought tolerance in rice?
Authors: Jagadish Krishna S. V. , Cairns Jill E. , Kumar Arvind , Somayanda Impa M. , Craufurd Peter Q.
Published: April 2011

Drought affected rice areas are predicted to double by the end of this century, demanding greater tolerance in widely adapted mega-varieties. Progress on incorporating better drought tolerance has been slow due to lack of appropriate phenotyping protocols. Furthermore, existing protocols do not consider the effect of drought and heat interactions, especially during the critical flowering stage, which could lead to false conclusion about drought tolerance. Screening germplasm and mapping-populations to identify quantitative trait loci (QTL)/candidate genes for drought tolerance is usually conducted in hot dry seasons where water supply can be controlled. Hence, results from dry season drought screening in the field could be confounded by heat stress, either directly on heat sensitive processes such as pollination or indirectly by raising tissue temperature through reducing transpirational cooling under water deficit conditions. Drought-tolerant entries or drought-responsive candidate genes/QTL identified from germplasm highly susceptible to heat stress during anthesis/flowering have to be interpreted with caution. During drought screening, germplasm tolerant to water stress but highly susceptible to heat stress has to be excluded during dry and hot season screening. Responses to drought and heat stress in rice are compared and results from field and controlled environment experiments studying drought and heat tolerance and their interaction are discussed.
Chickpea genotypes contrasting for seed yield under terminal drought stress in the field differ for traits related to the control of water use
Authors: Zaman-Allah Mainassara , Jenkinson David M. , Vadez Vincent
Published: April 2011

Chickpea (Cicer arietinum L.) is often exposed to terminal drought, and deep, profuse rooting has been proposed as the main breeding target to improve terminal drought tolerance. This work tested whether plant water use at the vegetative stage and under non-limited water conditions could relate to the degree of sensitivity of chickpea to terminal drought. Transpiration response to a range of vapour pressure deficits under controlled and outdoor conditions was measured with canopy conductance using gravimetric measurements and thermal imagery in eight chickpea genotypes with comparable phenology and contrasting seed yield under terminal drought in the field. Additionally, the response of plant growth and transpiration to progressive soil moisture depletion was assayed in the same genotypes. Drought-tolerant genotypes had a lower canopy conductance under fully irrigated conditions at the vegetative stage; this trend was reversed at the early pod filling stage. While two sensitive genotypes had high early growth vigour and leaf development, there was a trend of lower growth in tolerant genotypes under progressive soil drying than in sensitive ones. Tolerant genotypes also exhibited a decline of transpiration in wetter soil compared to sensitive genotypes. Canopy conductance could be proxied by measuring leaf temperature with an infrared camera, although the relationship lost sensitivity at the pod filling stage. This work suggests that some traits contribute to water saving when water does not limit plant growth and development in drought-tolerant chickpea. It is hypothesised that this water would be available for the reproduction and grain filling stages.
Prognostic gene-expression signature of carcinoma-associated fibroblasts in non-small cell lung cancer
Authors: Navab Roya , Strumpf Dan , Bandarchi Bizhan , Zhu Chang-Qi , Pintilie Melania , Ramnarine Varune Rohan , Ibrahimov Emin , Radulovich Nikolina , Leung Lisa , Barczyk Malgorzata , Panchal Devang , To Christine , Yun James J. , Der Sandy , Shepherd Frances A. , Jurisica Igor , Tsao Ming-Sound
Published: April 2011

The tumor microenvironment strongly influences cancer development, progression, and metastasis. The role of carcinoma-associated fibroblasts (CAFs) in these processes and their clinical impact has not been studied systematically in non-small cell lung carcinoma (NSCLC). We established primary cultures of CAFs and matched normal fibroblasts (NFs) from 15 resected NSCLC. We demonstrate that CAFs have greater ability than NFs to enhance the tumorigenicity of lung cancer cell lines. Microarray gene-expression analysis of the 15 matched CAF and NF cell lines identified 46 differentially expressed genes, encoding for proteins that are significantly enriched for extracellular proteins regulated by the TGF-β signaling pathway. We have identified a subset of 11 genes (13 probe sets) that formed a prognostic gene-expression signature, which was validated in multiple independent NSCLC microarray datasets. Functional annotation using protein–protein interaction analyses of these and published cancer stroma-associated gene-expression changes revealed prominent involvement of the focal adhesion and MAPK signaling pathways. Fourteen (30%) of the 46 genes also were differentially expressed in laser-capture–microdissected corresponding primary tumor stroma compared with the matched normal lung. Six of these 14 genes could be induced by TGF-β1 in NF. The results establish the prognostic impact of CAF-associated gene-expression changes in NSCLC patients.
Effect of remote field electromagnetic boundary conditions on microwave-induced plasma torches
Authors: Jimenez-Diaz M , van Dijk J , van der Mullen J J A M
Published: April 2011

A flexible versatile electromagnetic model constructed with the PLASIMO platform is employed to explore electromagnetic features of microwave-induced plasma torches. The bases, formed by a full-vector formulation of the Maxwell equations, provide the possibility to formulate the boundary conditions in a natural way. Together with the use of a direct matrix solver this gives a convergence speed-up of more than a factor of 100 when compared with a scalar formulation on an azimuthal magnetic field that uses an iterative solver. As a result, this electromagnetic model is ready to act in future studies as part of the self-consistent description of plasma–electromagnetic coupling. With the electromagnetic model three types of configuration were studied: the closed, semi-open and open configurations, all three based on the same simplified model plasmas. It is found that the closed configuration, acting as a cavity for which (de)tuning is extremely sensitive for the plasma conditions, is less suitable for applications in which changes in plasma compositions can be expected. The semi-open configuration can be seen as a model for the practice often used in laboratories to place microwave-induced plasma torches in a grid that aims at protecting the environment against microwave electromagnetic radiation. Calculations show that this is good practice provided the radius of this cylindrical grid is in the order of 90 mm. For the most often used configuration, the open version, we found that the power balance as expressed by the coefficients of absorption, transmission and reflection depends on the electron density of the plasma. The reason is that the plasma acts as an antenna, which converts the electromagnetic waves from the coaxial structure to that of the expansion region, and that this antenna function depends on the electron density. The influence of various other antenna elements is investigated as well.
Performance assessment of copy number microarray platforms using a spike-in experiment
Authors: Halper-Stromberg Eitan , Frelin Laurence , Ruczinski Ingo , Scharpf Robert , Jie Chunfa , Carvalho Benilton , Hao Haiping , Hetrick Kurt , Jedlicka Anne , Dziedzic Amanda , Doheny Kim , Scott Alan F. , Baylin Steve , Pevsner Jonathan , Spencer Forrest , Irizarry Rafael A.
Published: April 2011

Motivation: Changes in the copy number of chromosomal DNA segments [copy number variants (CNVs)] have been implicated in human variation, heritable diseases and cancers. Microarray-based platforms are the current established technology of choice for studies reporting these discoveries and constitute the benchmark against which emergent sequence-based approaches will be evaluated. Research that depends on CNV analysis is rapidly increasing, and systematic platform assessments that distinguish strengths and weaknesses are needed to guide informed choice.

Results: We evaluated the sensitivity and specificity of six platforms, provided by four leading vendors, using a spike-in experiment. NimbleGen and Agilent platforms outperformed Illumina and Affymetrix in accuracy and precision of copy number dosage estimates. However, Illumina and Affymetrix algorithms that leverage single nucleotide polymorphism (SNP) information make up for this disadvantage and perform well at variant detection. Overall, the NimbleGen 2.1M platform outperformed others, but only with the use of an alternative data analysis pipeline to the one offered by the manufacturer.

Availability: The data is available from http://rafalab.jhsph.edu/cnvcomp/.

Contact:  pevsner@jhmi.edu; fspencer@jhmi.edu; rafa@jhu.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.
Absence of pneumococcal PcsB is associated with overexpression of LysM domain-containing proteins
Authors: Giefing-Kröll Carmen , Jelencsics Kira E. , Reipert Siegfried , Nagy Eszter
Published: April 2011

The streptococcalprotein required forcellseparationB(PcsB) is predicted to play an important role in peptidoglycan metabolism, based on sequence motifs and altered phenotypes of gene deletion mutant cells exhibiting defects in cell separation. However, no enzymic activity has been demonstrated for PcsB so far. By generating gene deletion mutant strains in four different genetic backgrounds we could demonstrate thatpcsBis not essential for cell survival inStreptococcus pneumoniae, but is essential for proper cell division. Deletion mutant cells displayed cluster formation due to aberrant cell division, reduced growth and antibiotic sensitivity that were fully reverted by transformation with a plasmid carryingpcsB. Immunofluorescence staining revealed that PcsB was localized to the cell poles, similarly to PBP3 and LytB, enzymes with demonstrated peptidoglycan-degrading activity required for daughter cell separation. Similarly to other studies with PcsB homologues, we could not detect peptidoglycan-lytic activity with recombinant or native pneumococcal PcsBin vitro. In addition to defects in septum placement and separation, the absence of PcsB induced an increased release of several proteins, such as enolase, MalX and the SP0107 LysM domain protein. Interestingly, genes encoding both LysM domain-containing proteins that are present in the pneumococcal genome (SP0107 and SP2063) and predicted to be involved in cell wall metabolism were found to be highly overexpressed (14–33-fold increase) in ΔpcsBcells in two different genetic backgrounds. Otherwise, we detected very few changes in the global gene expression profile of cells lacking PcsB. Thus our data suggest that LysM domain proteins partially compensate for the lack of PcsB function and allow the survival and slow growth of the pneumococcus.
Broad-Spectrum Suppression of Innate Immunity Is Required for Colonization of Arabidopsis Roots by the FungusPiriformospora indica
Authors: Jacobs Sophie , Zechmann Bernd , Molitor Alexandra , Trujillo Marco , Petutschnig Elena , Lipka Volker , Kogel Karl-Heinz , Schäfer Patrick
Published: April 2011

Piriformospora indica is a root-colonizing basidiomycete that confers a wide range of beneficial traits to its host. The fungus shows a biotrophic growth phase in Arabidopsis (Arabidopsis thaliana) roots followed by a cell death-associated colonization phase, a colonization strategy that, to our knowledge, has not yet been reported for this plant. P. indica has evolved an extraordinary capacity for plant root colonization. Its broad host spectrum encompasses gymnosperms and monocotyledonous as well as dicotyledonous angiosperms, which suggests that it has an effective mechanism(s) for bypassing or suppressing host immunity. The results of our work argue that P. indica is confronted with a functional root immune system. Moreover, the fungus does not evade detection but rather suppresses immunity triggered by various microbe-associated molecular patterns. This ability to suppress host immunity is compromised in the jasmonate mutants jasmonate insensitive1-1 and jasmonate resistant1-1. A quintuple-DELLA mutant displaying constitutive gibberellin (GA) responses and the GA biosynthesis mutant ga1-6 (for GA requiring 1) showed higher and lower degrees of colonization, respectively, in the cell death-associated stage, suggesting that P. indica recruits GA signaling to help establish proapoptotic root cell colonization. Our study demonstrates that mutualists, like pathogens, are confronted with an effective innate immune system in roots and that colonization success essentially depends on the evolution of strategies for immunosuppression.
Dyskeratosis congenita and the DNA damage response
Authors: Kirwan Michael , Beswick Richard , Walne Amanda J. , Hossain Upal , Casimir Colin , Vulliamy Tom , Dokal Inderjeet
Published: April 2011

Dyskeratosis congenita (DC) is a heterogeneous bone marrow failure disorder with known mutations in components of telomerase and telomere shelterin. Recent work in a mouse model with a dyskerin mutation has implicated an increased DNA damage response as part of the cellular pathology, while mouse models with Terc and Tert mutations displayed a normal response. To clarify how these contradictory results might apply to DC pathology in humans, we studied the cellular phenotype in primary cells from DC patients of several genetic subtypes, focussing on T lymphocytes to remain close to the haematopoietic system. We observed novel cell cycle abnormalities in conjunction with impaired growth and an increase in apoptosis. Using flow cytometry and confocal microscopy we examined induction of the DNA damage proteins γ‐H2AX and 53BP1 and the cell cycle protein TP53 (p53). We found an increase in damage foci at telomeres in lymphocytes and an increase in the basal level of DNA damage in fibroblasts, but crucially no increased response to DNA damaging agents in either cell type. As the response to induced DNA damage was normal and levels of global DNA damage were inconsistent between cell types, DNA damage may contribute differently to the pathology in different tissues.
Timothy grass pollen extract‐induced gene expression and signalling pathways in airway epithelial cells
Authors: Röschmann K I. L. , Luiten S. , Jonker M. J. , Breit T. M. , Fokkens W. J. , Petersen A. , van Drunen C. M.
Published: April 2011

Cite this as: K. I. L. Röschmann, S. Luiten, M. J. Jonker, T. M. Breit, W. J. Fokkens, A. Petersen and C. M. van Drunen, Clinical & Experimental Allergy, 2011 (41) 830–841.

Background
Grass pollen allergy is one of the most common allergies worldwide and airborne allergens are the major cause of allergic rhinitis. Airway epithelial cells (AECs) are the first to encounter and respond to aeroallergens and are therefore interesting targets for the development of new therapeutics. Our understanding of the epithelial contribution to immune responses is limited as most studies focus on only a few individual genes or proteins.

Objective
To describe in detail the Timothy grass pollen extract (GPE)‐induced gene expression in AECs.

Methods
NCI‐H292 cells were exposed to GPE for 24 h, and isolated RNA and cell culture supernatants were used for microarray analysis and multiplex ELISA, respectively.

Results
Eleven thousand and seven hundred fifty‐eight transcripts were affected after exposure to GPE, with 141 genes up‐regulated and 121 genes down‐regulated by more than threefold. The gene ontology group cell communication was among the most prominent categories. Network analysis revealed that a substantial part of regulated genes are related to the cytokines IL‐6, IL‐8, IL‐1A, and the transcription factor FOS. After analysing significantly regulated signalling pathways, we found, among others, epidermal growth factor receptor 1, IL‐1, Notch‐, and Wnt‐related signalling members. Unexpectedly, we found Jagged to be down‐regulated and an increased release of IL‐12, in line with a more Th1‐biased response induced by GPE.

Conclusion and Clinical Relevance
Our data show that the stimulation of AECs with GPE results in the induction of a broad response on RNA and protein level by which they are able to affect the initiation and regulation of local immune responses. Detailed understanding of GPE‐induced genes and signalling pathways will allow us to better define the pathogenesis of the allergic response and to identify new targets for treatment.
Uncertainty of variance component estimates in nested sampling: a case study on the field‐scale spatial variability of a restored soil
Authors: Papritz A. , Dümig A. , Zimmermann C. , Gerke H. H. , Felderer B. , Kögel‐Knabner I. , Schaaf W. , Schulin R.
Published: April 2011

We studied the variation of soil properties on a 6‐ha artificial catchment constructed near Cottbus, Germany, to investigate processes of initial ecosystem genesis. We wanted to evaluate whether spatial auto‐correlation patterns could be identified 3 years after site construction. Topsoil was sampled at 192 locations using a balanced nested design involving six spatial scales (0.2 to 60 m) and analysed for particle size, organic matter content, pH, soluble P and various fractions of selected metals. Variance components were estimated by residual maximum likelihood. The uncertainty of variance estimates was characterized by the Fisher Information matrix and likelihood joint confidence regions. The latter approach was used for the first time to characterize uncertainties of variance estimates in spatial nested sampling. Likelihood ratio tests showed that all variables were spatially auto‐correlated but the allocation of the variance to specific spatial scales was highly uncertain. For most variables, at least one variance component could not be estimated precisely because the profile likelihood was either flat or the maximum lay on the boundary of the parameter space. Uncertainty estimates derived from the Fisher Information matrix either could not be computed or were unrealistic in these cases. Likelihood joint confidence regions gave more realistic uncertainty estimates. Joint confidence regions for accumulated variance components showed that the shape of the estimated variograms was poorly defined for most variables. Simulations indicated that poor identification of variance components might be a general problem of nested sampling surveys, which has been under‐estimated in the past. Hence, our work provides some incentive for re‐examining the statistical properties of the methodology.