bluuebunny/crossref_metadata_2025 huggingface dataset:
THE SPIN-HALL EFFECT IN p-TYPE BULK SEMICONDUCTORS
Authors: LIU S. Y. , HORING N. J. M. , LEI X. L.
Published: May 2008

The spin Hall effect provides a new possible way to effectively inject spins into paramagnetic semiconductors. Here, we investigate the spin-Hall effect in a p-type Luttinger semiconductor employing a two-band kinetic equation analysis. The long-range disorder effect on spin-Hall current (SHC) is considered within the self-consistent Born approximation. We find that in addition to the intrinsic SHC proposed previously, there is a nonvanishing SHC that originates from long-range electron-impurity scattering, but which is independent of impurity density in the diffusive regime. This SHC has an opposite sign from the intrinsic one, leading to a significant reduction of the total SHC. We also carry out a numerical analysis of the hole density dependencies of SHC and spin mobility, finding that with increasing hole density, the SHC first increases and then falls, while the spin mobility monotonically decreases.
TUNABLE GRID GATED DOUBLE-QUANTUM-WELL FET TERAHERTZ DETECTOR
Authors: HORING N. J. M. , LIU S. Y. , POPOV V. V. , CUI H. L.
Published: May 2008

Several aspects of the theory of plasmon resonant DC photoconduction are discussed here, in connection with recent observations involving a THz-irradiated grid-gated double-quantum-well FET.1 In this, we construct a classical model of nonlinear polarizability to second order in the THz field using a “hydrodynamic” type formulation including the roles of a stress-tensor and friction/viscosity. The resulting second order polarizability exhibits resonant behavior when the THz frequency matches plasmon frequencies of the system, sharply reducing the effectiveness of screened impurity scattering potentials which can admit resonant DC photoconduction. Furthermore, we also show that an asymmetric double-quantum-well system with lateral periodicity can mix optical and acoustic plasmons, giving rise to an interlayer THz field which becomes very strong when tuned by gate voltage into the “mode-mode-repulsion” regime wherein the optical and acoustic modes equally share amplitude. This can enhance interlayer electron tunneling and may contribute to photoconductivity.
IN-LINE OPTICAL FIBER STRUCTURES FOR ENVIRONMENTAL SENSING
Authors: DHAWAN A. , GERHOLD M. D. , MUTH J. F.
Published: May 2008

Surface plasmon and evanescent wave sensors are attractive for chemical and biological sensing applications. They can work in aqueous media and when used in conjunction with the appropriate surface chemistry they can have high specificity and high sensitivity. However, most surface plasmon sensors are relatively complex as they are based on the use of attenuated total internal reflection to excite surface plasmon resonance in a thin gold film and require light to be incident at the appropriate angle and polarization. Other surface plasmon and optical affinity sensors have used the evanescent waves in planar waveguides to interact with the environment. These devices are sensitive but, have strict optical coupling requirements and are difficult to fabricate. In optical fiber evanescent wave sensors the interaction with the surrounding environment is usually obtained by tapering an optical fiber, which significantly weakens the structure, or by just utilizing the end of the optical fiber. In this paper, in-line optical fiber structures are presented that are mechanically robust, and provide a large interaction length for high sensitivity. They are compatible with standard chemistries for optical affinity sensing of biological compounds.
PROGRESS IN HIGH EFFICIENCY UV LED RESEARCH FOR REAGENTLESS BIOAGENT DETECTION AND WATER PURIFICATION
Authors: REED MEREDITH L. , GARRETT GREGORY A. , SAMPATH ANAND V. , SHEN PAUL H. , COLLINS CHARLES J. , WRABACK MICHAEL , ZHANG JIANPING , HU XUHONG , DENG JIANYU , LUNEV ALEX , BILENKO YURIY , KATONA THOMAS , GASKA REMIS
Published: May 2008

We present material and device characterization of 280 nm semiconductor ultraviolet light emitting diodes. These devices exhibit low series resistance, wavelength stability with increasing current, and have a half-life in excess of 570hrs, depending upon the injection current. Time-resolved photoluminescence studies of these materials prior to fabrication have been correlated with the device performance. We also discuss the potential for use in water purification.
COUMARIN DYE AS A FLUORESCENCE SENSOR FOR METHANOL VAPOR
Authors: STEVENS NATHAN , AKINS DANIEL L.
Published: May 2008

The sol-gel method has been employed in the fabrication of mesoporous composite films consisting of a nonionic surfactant, Pluronic P123, as the organic component, and silica as the inorganic component. The hybrid nature of these films resulted in their having an internal structure consisting of nanometer size self-assembled organic mesostructures surrounded by a silica framework. These films served as the host matrix for the laser dye coumarin 481 (C481) and an energy transfer complex formed between C481 and J-aggregated meso-tetra(4-sulfonatophenyl)porphyrin (TSPP). Upon exposure to methanol vapor, a rapid and reversible decrease in fluorescence intensity occurs for films containing C481 alone as well as containing both C481 and TSPP. Steady-state and time-resolved spectroscopic studies suggest that the decrease in fluorescence intensity is primarily due to an excited state interaction between methanol and C481; while, additionally, morphological changes within the film appear to play a role for films containing both C481 and TSPP.
NANOSCALE IMAGING TECHNOLOGY FOR THz-FREQUENCY TRANSMISSION MICROSCOPY
Authors: WOOLARD DWIGHT , ZHAO PEIJI , RUTHERGLEN CHRISTOPHER , YU ZHEN , BURKE PETER , BRUECK STEVEN , STINTZ ANDREAS
Published: May 2008

A novel nanoscale-engineering methodology is presented that has potential for the first-time development of a microscope-system capable of collecting terahertz (THz) frequency spectroscopic signatures from microscopic biological (bio) structures. This unique THz transmission microscopy approach is motivated by prior studies on bio-materials and bio-agents (e.g., DNA, RNA and bacterial spores) that have produced spectral features within the THz frequency regime (i.e., ~ 300 GHz to 1000 GHz) that appear to be representative of the internal structure and characteristics of the constituent bio-molecules. The suggested THz transmission microscopy is a fundamentally new technological approach that seeks to avoid the limitations that exist in traditional experiments (i.e., that must average over large numbers of microscopic molecules) by prescribing a viable technique whereby the THz frequency signatures may be collected from individual bio-molecules and/or microscopic biological constructs. Specifically, it is possible to envision the development of a “nanoscale imaging array” that possesses the characteristics necessary (e.g., sub-wavelength resolution) for successfully performing “THz-frequency microscopy.”
Combinatorial Materials Sciences: Experimental Strategies for Accelerated Knowledge Discovery
Authors: Rajan Krishna
Published: May 2008

Combinatorial materials science offers an exciting experimental strategy for rapidly surveying a wide array of materials chemistries and process variables coupled to the screening of structure and properties. Adapting approaches used in synthetic organic chemistry for applications such as pharmaceutical sciences and chemical discovery, materials scientists have developed a variety of approaches to create libraries in the solid state in order to rapidly examine a broad range of materials characteristics; the ultimate hope is to accelerate the discovery of new materials and/or new materials properties. This article provides an overview of the different experimental strategies used in combinatorial experimentation and high-throughput screening in materials science and engineering and the challenges to analyzing the information obtained from such experiments. Particular focus is placed on the use of informatics to convert the data from high-throughput experimentation to high-throughput knowledge discovery. The review also raises the broader issue of future needs in combinatorial materials science, such as making this area an experimental platform for multiscale modeling, and the need for a stronger materials-theory-driven approach to combinatorial experimentation.
Segregation Phenomena at Thermally Grown Al2O3/Alloy Interfaces
Authors: Hou P.Y.
Published: May 2008

Experimental results on S segregation at growing Al2O3/alloy interfaces are reviewed for binary FeAl, NiAl alloys, and ternary alloys with additions of Cr, Pt, or a reactive element, such as Zr, Hf, or Y. The segregation behavior is thermodynamic in nature, but the segregation energy can change not only with alloying elements but also with oxidation time and temperature as the oxide growth process changes. Although reactive elements are capable of eliminating interfacial S segregation, they do not stop such segregation to alloy surfaces. The segregation of a reactive element at the interface further strengthens the interfacial bonding. Cosegregation of S and Cr can occur, resulting in higher levels of S at the interface. Pt usually suppresses S segregation, but this effect can be easily overwhelmed by S-Cr cosegregation. Synergisms between alloying elements and how they affect segregation, as well as the relationship between segregation and the oxidation process, are areas that demand further investigation.
Wetting in Soldering and Microelectronics
Authors: Matsumoto T. , Nogi K.
Published: May 2008

Wettability of solid metals by molten solders is reviewed. The contact angle and wetting force are tabulated for various combinations of solid metals and molten solders such as Sn-Pb base alloys, Sn-Ag base alloys, Sn-Zn base alloys, Sn-Cu base alloys, and Sn-Bi base alloys. Studies on the wetting rate are also discussed.
Bamboo and Wood in Musical Instruments
Authors: Wegst Ulrike G.K.
Published: May 2008

Over centuries and millennia, our ancestors worldwide found the most appropriate materials for increasingly complex acoustical applications. In the temperate climate of Europe, where the instruments of the Western symphony orchestra were developed and perfected, instrument makers still primarily take advantage of the unique property combination and the aesthetic appeal of wood. In all other continents, one material dominates and is frequently chosen for the manufacture of wind, string, and percussion instruments: the grass bamboo. Here, we review from a materials science perspective bamboo's and wood's unique and highly optimized structure and properties. Using material property charts plotting acoustic properties such as the speed of sound, the characteristic impedance, the sound radiation coefficient, and the loss coefficient against one another, we analyze and explain why bamboo and specific wood species are ideally suited for the manufacture of xylophone bars and chimes, flutes and organs, violins and zithers, violin bows, and even strings.
Dietary Protein and Bone Health: Roles of Amino Acid–Sensing Receptors in the Control of Calcium Metabolism and Bone Homeostasis
Authors: Conigrave A. D. , Brown E. M. , Rizzoli R.
Published: May 2008

In this article, we review the evidence that dietary protein has a positive influence on bone health, reduces hip fracture risk, and promotes postfracture recovery, and we consider the molecular, cellular, and endocrine bases of the interactions that link protein and calcium metabolism, including effects via IGF-1 and PTH. In addition, we consider the roles of amino acid–sensing mechanisms in coupling dietary protein intake to metabolic change as well as the central role of calcium-sensing receptors (CaRs) in the control of calcium metabolism. Finally, we consider how recently identified broad-spectrum amino acid–sensing receptors from class 3 of the G-protein coupled receptor superfamily including, remarkably, the CaR itself may contribute to the impact of dietary protein on bone.
Transcription factor PU.1 is expressed in white adipose and inhibits adipocyte differentiation
Authors: Wang Fei , Tong Qiang
Published: May 2008

PU.1 transcription factor is a critical regulator of hematopoiesis and leukemogenesis. Because PU.1 interacts with transcription factors GATA-2 and C/EBPα, and both are involved in the regulation of adipogenesis, we investigated whether PU.1 plays a role in the regulation of adipocyte differentiation. Our data indicate that PU.1 is expressed in white adipose tissue. PU.1 protein can also be detected in cultured 3T3-L1 adipocytes. Forced expression of PU.1 in 3T3-L1 cells inhibits adipocyte differentiation, whereas deletion of the transactivation domain of PU.1 abolishes this effect. The inhibition of adipocyte differentiation by PU.1 is achieved, at least in part, through repression of the transcriptional activity of C/EBPα and C/EBPβ. Furthermore, GATA-2 and PU.1 have an additive inhibitory effect on C/EBP transactivation and adipogenesis. Finally, the expression of PU.1 is increased in white adipose of obese mice.
Downregulation of connexin40 is associated with coronary endothelial cell dysfunction in streptozotocin-induced diabetic mice
Authors: Makino Ayako , Platoshyn Oleksandr , Suarez Jorge , Yuan Jason X.-J. , Dillmann Wolfgang H.
Published: May 2008

Vascular endothelial cells (ECs) play a major role in regulating vascular tone and in revascularization. There is increasing evidence showing endothelial dysfunction in diabetes, although little is known about the contribution of connexins (Cxs) to vascular complications in the diabetic heart. This study was designed to investigate the role of Cxs in coronary endothelial dysfunction in diabetic mice. Coronary ECs isolated from diabetic mice exhibit lowered protein levels of Cx37 and Cx40 (but not Cx43) and a loss of gap junction intercellular communication (GJIC). Vasodilatation induced by the assumed contribution of EC-dependent hyperpolarization was significantly reduced in the diabetic coronary artery (CA). Cx40-specific inhibitory peptide 40GAP27 strongly attenuated endothelium-dependent relaxation in diabetic CA at the concentration that does not affect the relaxation in control CA, suggesting that the total amount of Cx40 is lower in diabetic CA than in control CA. In diabetic mice, coronary capillary density was significantly decreased in vivo. In vitro, GJIC inhibitor attenuated the ability of EC capillary network formation. High-glucose treatment caused a decrease in Cx40 protein expression in ECs and impaired endothelial capillary network formation, which was restored by Cx40 overexpression. Furthermore, we found that the hyperglycemia-induced decrease in Cx40 was associated with inhibited protein expression of Sp1, a transcriptional factor that regulates Cx40 expression. These data suggest that downregulation of Cx40 protein expression and resultant inhibition of GJIC contribute to coronary vascular dysfunction in diabetes.
Regulation of H2O2-induced necrosis by PKC and AMP-activated kinase signaling in primary cultured hepatocytes
Authors: Saberi Behnam , Shinohara Mie , Ybanez Maria D. , Hanawa Naoko , Gaarde William A. , Kaplowitz Neil , Han Derick
Published: May 2008

Recent studies have suggested that, in certain cases, necrosis, like apoptosis, may be programmed, involving the activation and inhibition of many signaling pathways. In this study, we examined whether necrosis induced by H2O2 is regulated by signaling pathways in primary hepatocytes. A detailed time course revealed that H2O2 treated to hepatocytes is consumed within minutes, but hepatocytes undergo necrosis several hours later. Thus, H2O2 treatment induces a “lag phase” where signaling changes occur, including PKC activation, Akt (PKB) downregulation, activation of JNK, and downregulation of AMP-activated kinase (AMPK). Investigation of various inhibitors demonstrated that PKC inhibitors were effective in reducing necrosis caused by H2O2 (∼80%). PKC inhibitor treatment decreased PKC activity but, surprisingly, also upregulated Akt and AMPK, suggesting that various PKC isoforms negatively regulate Akt and AMPK. Akt did not appear to play a significant role in H2O2-induced necrosis, since PKC inhibitor treatment protected hepatocytes from H2O2 even when Akt was inhibited. On the other hand, compound C, a selective AMPK inhibitor, abrogated the protective effect of PKC inhibitors against necrosis induced by H2O2. Furthermore, AMPK activators protected against H2O2-induced necrosis, suggesting that much of the protective effect of PKC inhibition was mediated through the upregulation of AMPK. Work with PKC inhibitors suggested that atypical PKC downregulates AMPK in response to H2O2. Knockdown of PKC-α using antisense oligonucleotides also slightly protected (∼22%) against H2O2. Taken together, our data demonstrate that the modulation of signaling pathways involving PKC and AMPK can alter H2O2-induced necrosis, suggesting that a signaling “program” is important in mediating H2O2-induced necrosis in primary hepatocytes.
Central pathway for spontaneous and prostaglandin E2-evoked cutaneous vasoconstriction
Authors: Rathner Joseph A. , Madden Christopher J. , Morrison Shaun F.
Published: May 2008

A reduction of heat loss to the environment through increased cutaneous vasoconstrictor (CVC) sympathetic outflow contributes to elevated body temperature during fever. We determined the role of neurons in the dorsomedial hypothalamus (DMH) in increases in CVC sympathetic tone evoked by PGE2 into the preoptic area (POA) in chloralose/urethane-anesthetized rats. The frequency of axonal action potentials of CVC sympathetic ganglion cells recorded from the surface of the tail artery was increased by 1.8 Hz following nanoinjections of bicuculline (50 pmol) into the DMH. PGE2 nanoinjection into the POA elicited a similar excitation of tail CVC neurons (+2.1 Hz). Subsequent to PGE2 into the POA, muscimol (400 pmol/side) into the DMH did not alter the activity of tail CVC neurons. Inhibition of neurons in the rostral raphé pallidus (rRPa) eliminated the spontaneous discharge of tail CVC neurons but only reduced the PGE2-evoked activity. Residual activity was abolished by subsequent muscimol into the rostral ventrolateral medulla. Transections through the neuraxis caudal to the POA increased the activity of tail CVC neurons, which were sustained through transections caudal to DMH. We conclude that while activation of neurons in the DMH is sufficient to activate tail CVC neurons, it is not necessary for their PGE2-evoked activity. These results support a CVC component of increased core temperature elicited by PGE2 in POA that arises from relief of a tonic inhibition from neurons in POA of CVC sympathetic premotor neurons in rRPa and is dependent on the excitation of CVC premotor neurons from a site caudal to DMH.
Renoprotection by statins is linked to a decrease in renal oxidative stress, TGF-β, and fibronectin with concomitant increase in nitric oxide bioavailability
Authors: Zhou Ming-Sheng , Schuman Ivonne Hernandez , Jaimes Edgar A. , Raij Leopoldo
Published: May 2008

Clinical and experimental studies have provided evidence suggesting that statins exert renoprotective effects. To investigate the mechanisms by which statins may exert renoprotection, we utilized the hypertensive Dahl salt-sensitive (DS) rat model, which manifests cardiovascular and renal injury linked to increased angiotensin II-dependent activation of NADPH oxidase and decreased nitric oxide (NO) bioavailability. DS rats given high salt diet (4% NaCl) for 10 wk exhibited hypertension [systolic blood pressure (SBP) 200 ± 8 vs. 150 ± 2 mmHg in normal salt diet (0.5% NaCl), P < 0.05], glomerulosclerosis, and proteinuria (158%). This was associated with increased renal oxidative stress demonstrated by urinary 8-F2α-isoprostane excretion and NADPH oxidase activity, increased protein expression of transforming growth factor (TGF)-β (63%) and fibronectin (181%), increased mRNA expression of the proinflammatory molecules monocyte chemoattractant protein-1 (MCP-1) and lectin-like oxidized LDL receptor-1 (LOX-1), as well as downregulation of endothelial NO synthase (eNOS) activity (−44%) and protein expression. Return to normal salt had no effect on SBP or any of the measured parameters. Atorvastatin (30 mg·kg−1·day−1) significantly attenuated proteinuria and glomerulosclerosis and normalized renal oxidative stress, TGF-β1, fibronectin, MCP-1 and LOX-1 expression, and eNOS activity and expression. Atorvastatin-treated rats showed a modest reduction in SBP that remained in the hypertensive range (174 ± 8 mmHg). Atorvastatin combined with removal of high salt normalized SBP and proteinuria. These findings suggest that statins mitigate hypertensive renal injury by restoring the balance among NO, TGF-β1, and oxidative stress and explain the added renoprotective effects observed in clinical studies using statins in addition to inhibitors of the renin-angiotensin system.
Acute moderate-intensity exercise in middle-aged men has neither an anti- nor proinflammatory effect
Authors: Markovitch Daniella , Tyrrell Rex M. , Thompson Dylan
Published: May 2008

Strenuous exercise induces an initial pro- and subsequent anti-inflammatory response, and it has been suggested that this may be one of the ways that regular exercise reduces chronic inflammation and therefore the risk of cardiovascular disease. However, public health recommendations emphasize moderate-intensity physical activity, and it is important to understand whether moderate-intensity exercise has a similar anti-inflammatory effect. Twelve sedentary male volunteers (age 54 ± 4 yr) completed two main trials, moderate-intensity exercise and rest (30 min at 50% maximal oxygen uptake vs. sitting, respectively). There were no significant changes in circulating neutrophils, lymphocytes, monocytes, or serum interleukin-6, interleukin-10, and C-reactive protein concentration over the 7 days following exercise. Similarly, lymphocyte adhesion to cultured endothelial cells and heme oxygenase-1 (HO-1) expression in lymphocytes and monocytes were not affected by walking at any time point. These results suggest that the long-term anti-inflammatory and antiatherogenic effects of regular moderate-intensity physical activity must be explained by something other than a profound net anti-inflammatory response to each exercise bout since a single bout of walking did not lead to a change in various markers of inflammation or lymphocyte adherence to cultured endothelial cells.
The influence of physical activity on lean mass accrual during adolescence: a longitudinal analysis
Authors: Baxter-Jones Adam D. G. , Eisenmann Joey C. , Mirwald Robert L. , Faulkner Robert A. , Bailey Donald A.
Published: May 2008

During childhood, physical activity is likely the most important modifiable factor for the development of lean mass. However, the effects of normal growth and maturation must be controlled. To distinguish effects of physical activity from normal growth, longitudinal data are required. One hundred nine boys and one hundred thirteen girls, participating in the Saskatchewan Pediatric Bone Mineral Accrual Study, were repeatedly assessed for 6 yr. Age at entry was 8–15 yr. Stature, body mass, and physical activity were assessed biannually. Body composition was assessed annually by dual-energy X-ray absorptiometry. Physical activity was determined using the physical activity questionnaires for children and adolescence. Biological age was defined as years from age of peak height velocity. Data were analyzed using multilevel random-effects models. In boys, it was found that physical activity had a significant time-dependent effect on lean mass accrual of the total body (484.7 ± 157.1 g), arms (69.6 ± 27.2 g), legs (197.7 ± 60.5 g), and trunk (249.1 ± 91.4 g) ( P < 0.05). Although the physical activity effects were similar in the girls (total body: 306.9 ± 96.6 g, arms: 31.4 ± 15.5 g, legs: 162.9 ± 40.0 g, and trunk: 119.6 ± 58.2 g; P < 0.05), boys for the same level of activity accrued, depending on the site, between 21 and 120% more absolute lean mass (g). In conclusion, habitual physical activity had a significant independent influence on the growth of lean body mass during adolescence, once biological maturity and stature were controlled.
Are the dynamic response characteristics of brachial artery flow-mediated dilation sensitive to the magnitude of increase in shear stimulus?
Authors: Pyke K. E. , Hartnett J. A. , Tschakovsky M. E.
Published: May 2008

The purpose of this study was to determine the dynamic characteristics of brachial artery dilation in response to step increases in shear stress [flow-mediated dilation (FMD)]. Brachial artery diameter (BAD) and mean blood velocity (MBV) (Doppler ultrasound) were obtained in 15 healthy subjects. Step increases in MBV at two shear stimulus magnitudes were investigated: large (L; maximal MBV attainable), and small (S; MBV at 50% of the large step). Increase in shear rate (estimate of shear stress: MBV/BAD) was 76.8 ± 15.6 s−1 for L and 41.4 ± 8.7 s−1 for S. The peak %FMD was 14.5 ± 3.8% for L and 5.7 ± 2.1% for S ( P < 0.001). Both the L (all subjects) and the S step trials (12 of 15 subjects) elicited a biphasic diameter response with a fast initial phase (phase I) followed by a slower final phase. Relative contribution of phase I to total FMD when two phases occurred was not sensitive to shear rate magnitude ( r2 = 0.003, slope P = 0.775). Parameters quantifying the dynamics of the FMD response [time delay (TD), time constant (τ)] were also not sensitive to shear rate magnitude for both phases (phase I: TD r2 = 0.03, slope P = 0.376, τ r2 = 0.04, slope P = 0.261; final phase: TD r2 = 0.07, slope P = 0.169, τ r2 = 0.07, slope P = 0.996). These data support the existence of two distinct mechanisms, or sets of mechanisms, in the human conduit artery FMD response that are proportionally sensitive to shear stimulus magnitude and whose dynamic response is not sensitive to shear stimulus magnitude.
Effect of an inhaled glucocorticoid on endothelial function in healthy smokers
Authors: Mendes Eliana S. , Horvath Gabor , Rebolledo Patricia , Monzon Maria Elena , Casalino-Matsuda S. Marina , Wanner Adam
Published: May 2008

Cigarette smoking is associated with attenuated endothelium-dependent vasodilation (endothelial dysfunction) in the systemic circulation, including the airway circulation. We wished to determine whether an inhaled corticosteroid could restore endothelial function in the airway of lung-healthy current smokers, ex-smokers, and nonsmokers. We measured baseline airway blood flow (Q̇aw) and Q̇aw reactivity to inhaled albuterol as an index of endothelium-dependent vasodilation and to sublingual nitroglycerin as an index of endothelium-independent vasodilation in lung-healthy current smokers, ex-smokers, and nonsmokers. Current smokers were then treated with inhaled fluticasone for 3 wk, and all measurements were repeated after fluticasone treatment and after a subsequent 3-wk fluticasone washout period. Baseline mean Q̇aw and endothelium-independent Q̇aw reactivity were similar in the three groups. Mean endothelium-dependent Q̇aw reactivity was 49.5% in nonsmokers, 42.7% in ex-smokers, and 10.8% in current smokers ( P < 0.05 vs. nonsmokers). In current smokers, mean baseline Q̇aw was unchanged after fluticasone treatment, but endothelium-dependent Q̇aw reactivity significantly increased to 34.9%. Q̇aw reactivity was again blunted after fluticasone washout. Endothelial dysfunction, as assessed by vascular reactivity, can be corrected with an inhaled corticosteroid in the airway of lung-healthy current smokers. This proof of concept can serve as the basis for future clinical investigations on the effect of glucocorticoids on endothelial function in smokers.
The Gly482Ser genotype at the PPARGC1A gene and elevated blood pressure: a meta-analysis involving 13,949 individuals
Authors: Vimaleswaran Karani Santhanakrishnan , Luan Jian'an , Andersen Gitte , Muller Y. Li , Wheeler Eleanor , Brito Ema C. , O'Rahilly Stephen , Pedersen Oluf , Baier Leslie J. , Knowler William C. , Barroso Inês , Wareham Nicholas J. , Loos Ruth J. F. , Franks Paul W.
Published: May 2008

The protein encoded by the PPARGC1A gene is expressed at high levels in metabolically active tissues and is involved in the control of oxidative stress via reactive oxygen species detoxification. Several recent reports suggest that the PPARGC1A Gly482Ser (rs8192678) missense polymorphism may relate inversely with blood pressure. We used conventional meta-analysis methods to assess the association between Gly482Ser and systolic (SBP) or diastolic blood pressures (DBP) or hypertension in 13,949 individuals from 17 studies, of which 6,042 were previously unpublished observations. The studies comprised cohorts of white European, Asian, and American Indian adults, and adolescents from South America. Stratified analyses were conducted to control for population stratification. Pooled genotype frequencies were 0.47 (Gly482Gly), 0.42 (Gly482Ser), and 0.11 (Ser482Ser). We found no evidence of association between Gly482Ser and SBP [Gly482Gly: mean = 131.0 mmHg, 95% confidence interval (CI) = 130.5–131.5 mmHg; Gly482Ser mean = 133.1 mmHg, 95% CI = 132.6–133.6 mmHg; Ser482Ser: mean = 133.5 mmHg, 95% CI = 132.5–134.5 mmHg; P = 0.409] or DBP (Gly482Gly: mean = 80.3 mmHg, 95% CI = 80.0–80.6 mmHg; Gly482Ser mean = 81.5 mmHg, 95% CI = 81.2–81.8 mmHg; Ser482Ser: mean = 82.1 mmHg, 95% CI = 81.5–82.7 mmHg; P = 0.651). Contrary to previous reports, we did not observe significant effect modification by sex (SBP, P = 0.966; DBP, P = 0.715). We were also unable to confirm the previously reported association between the Ser482 allele and hypertension [odds ratio: 0.97, 95% CI = 0.87–1.08, P = 0.585]. These results were materially unchanged when analyses were focused on whites only. However, statistical evidence of gene-age interaction was apparent for DBP [Gly482Gly: 73.5 (72.8, 74.2), Gly482Ser: 77.0 (76.2, 77.8), Ser482Ser: 79.1 (77.4, 80.9), P = 4.20 × 10−12] and SBP [Gly482Gly: 121.4 (120.4, 122.5), Gly482Ser: 125.9 (124.6, 127.1), Ser482Ser: 129.2 (126.5, 131.9), P = 7.20 × 10−12] in individuals <50 yr ( n = 2,511); these genetic effects were absent in those older than 50 yr ( n = 5,088) (SBP, P = 0.41; DBP, P = 0.51). Our findings suggest that the PPARGC1A Ser482 allele may be associated with higher blood pressure, but this is only apparent in younger adults.
Cell Type–Specific GABAA Receptor–Mediated Tonic Inhibition in Mouse Neocortex
Authors: Vardya Irina , Drasbek Kim R. , Dósa Zita , Jensen Kimmo
Published: May 2008

Activity of extrasynaptic GABAA receptors mediating tonic inhibition is thought to play an important role for the excitability of the mammalian cerebral cortex. However, little is known about the cell type–specific expression of tonic inhibition in particular types of cortical interneurons. Here, we used transgenic mice expressing green fluorescent protein (GFP) in somatostatin-positive (SOM) interneurons and investigated tonic inhibition in SOM interneurons versus pyramidal cells in neocortical layers 2/3. In brain slices, pyramidal cells showed a tonic current of 66 ± 19 pA in response to the δ-subunit selective GABAA agonist THIP (1 μM). On the other hand, tonic inhibition was absent in SOM interneurons (8 ± 1 pA) in response to THIP. As opposed to pyramidal cells, SOM interneurons were also insensitive to the δ-subunit preferring neurosteroid allotetrahydrodeoxycorticosterone (THDOC) (100 nM) and to elevated endogenous GABA levels in the slice. Finally, SOM interneurons received only 45% of the phasic charge transfer during GABAA receptor–mediated synaptic activity compared with pyramidal cells. Altogether, our study indicates that SOM interneurons receive relatively weak inhibitory input and cannot be brought under the influence of tonic inhibition.
Relating Retinotopic and Object-Selective Responses in Human Lateral Occipital Cortex
Authors: Sayres Rory , Grill-Spector Kalanit
Published: May 2008

What is the relationship between retinotopy and object selectivity in human lateral occipital (LO) cortex? We used functional magnetic resonance imaging (fMRI) to examine sensitivity to retinal position and category in LO, an object-selective region positioned posterior to MT along the lateral cortical surface. Six subjects participated in phase-encoded retinotopic mapping experiments as well as block-design experiments in which objects from six different categories were presented at six distinct positions in the visual field. We found substantial position modulation in LO using standard nonobject retinotopic mapping stimuli; this modulation extended beyond the boundaries of visual field maps LO-1 and LO-2. Further, LO showed a pronounced lower visual field bias: more LO voxels represented the lower contralateral visual field, and the mean LO response was higher to objects presented below fixation than above fixation. However, eccentricity effects produced by retinotopic mapping stimuli and objects differed. Whereas LO voxels preferred a range of eccentricities lying mostly outside the fovea in the retinotopic mapping experiment, LO responses were strongest to foveally presented objects. Finally, we found a stronger effect of position than category on both the mean LO response, as well as the distributed response across voxels. Overall these results demonstrate that retinal position exhibits strong effects on neural response in LO and indicates that these position effects may be explained by retinotopic organization.
Learning to Recognize Visual Objects With Microstimulation in Inferior Temporal Cortex
Authors: Kawasaki Keisuke , Sheinberg David L.
Published: May 2008

The malleability of object representations by experience is essential for adaptive behavior. It has been hypothesized that neurons in inferior temporal cortex (IT) in monkeys are pivotal in visual association learning, evidenced by experiments revealing changes in neural selectivity following visual learning, as well as by lesion studies, wherein functional inactivation of IT impairs learning. A critical question remaining to be answered is whether IT neuronal activity is sufficient for learning. To address this question directly, we conducted experiments combining visual classification learning with microstimulation in IT. We assessed the effects of IT microstimulation during learning in cases where the stimulation was exclusively informative, conditionally informative, and informative but not necessary for the classification task. The results show that localized microstimulation in IT can be used to establish visual classification learning, and the same stimulation applied during learning can predictably bias judgments on subsequent recognition. The effect of induced activity can be explained neither by direct stimulation-motor association nor by simple detection of cortical stimulation. We also found that the learning effects are specific to IT stimulation as they are not observed by microstimulation in an adjacent auditory area. Our results add the evidence that the differential activity in IT during visual association learning is sufficient for establishing new associations. The results suggest that experimentally manipulated activity patterns within IT can be effectively combined with ongoing visually induced activity during the formation of new associations.
Rapid Motor Responses Are Appropriately Tuned to the Metrics of a Visuospatial Task
Authors: Pruszynski J. Andrew , Kurtzer Isaac , Scott Stephen H.
Published: May 2008

Considerable research has established that rapid motor responses (traditionally called reflexes), can be modified by a subject's voluntary goals. Here, we expand on past observations using verbal instructions by defining the voluntary goal via visual target position. This approach allowed us to objectively enforce task adherence and explore a richer set of variables, such as target direction and distance, metrics that modify voluntary control and that—according to our hypothesis—will influence rapid motor responses. Our first experiment tested whether upper-limb responses are categorically modulated by target direction by placing targets such that the same perturbation could push the hand into one target and out of the other, a spatial analogue to “resist/yield” verbal instructions. Consistent with these classical results, we found that the short-latency rapid response (R1, 20–45 ms) was not modulated by target direction, whereas long-latency rapid responses (R2/R3, 45–105 ms) were modified in a manner approaching the voluntary response (VOL, 120–180 ms). Our second experiment tested whether upper-limb responses are continuously modulated by target distance by distributing five targets along one axis centered on the hand. Here, the long-latency and voluntary response mirrored the task demands by increasing activity in a graded fashion with increasing target distance. Our final experiment explored how upper-limb responses incorporate two-dimensional spatial information by placing targets radially around the hand. Notably, long-latency responses exhibited smooth tuning functions to target direction that were similar to those observed for the voluntary response. Taken together, these results illustrate the flexibility of long-latency rapid responses and emphasize their similarity to later voluntary responses.
Extracellular Stimulation of Mammalian Neurons Through Repetitive Activation of Na+ Channels by Weak Capacitive Currents on a Silicon Chip
Authors: Schoen Ingmar , Fromherz Peter
Published: May 2008

Reliable extracellular stimulation of neuronal activity is the prerequisite for electrical interfacing of cultured networks and brain slices, as well as for neural implants. Safe stimulation must be achieved without damage to the cells. With respect to a future application of highly integrated semiconductor chips, we present an electrophysiological study of capacitive stimulation of mammalian cells in the geometry of adhesion on an insulated titanium dioxide/silicon electrode. We used HEK293 cells with overexpressed NaV1.4 channels and neurons from rat hippocampus. Weak biphasic stimuli of falling and rising voltage ramps were applied in the absence of Faradaic current and electroporation. We recorded the response of the intra- and extracellular voltage and evaluated the concomitant polarization of the attached and free cell membranes. Falling ramps efficiently depolarized the central area of the attached membrane. A transient sodium inward current was activated that gave rise to a weak depolarization of the cell on the order of 1 mV. The depolarization could be enhanced step by step by a train of biphasic stimuli until self-excitation of sodium channels set in. We applied the same protocol to cultured rat neurons and found that pulse trains of weak capacitive stimuli were able to elicit action potentials. Our results provide a basis for safe extracellular stimulation not only for cultured neurons on insulated semiconductor electrodes, but also more generally for metal electrodes in cell culture and brain tissue.
Estimation of the Contribution of Intrinsic Currents to Motoneuron Firing Based on Paired Motoneuron Discharge Records in the Decerebrate Cat
Authors: Powers Randall K. , Nardelli Paul , Cope T. C.
Published: May 2008

Motoneuron activation is strongly influenced by persistent inward currents (PICs) flowing through voltage-sensitive channels. PIC characteristics and their contribution to the control of motoneuron firing rate have been extensively described in reduced animal preparations, but their contribution to rate modulation in human motoneurons is controversial. It has recently been proposed that the analysis of discharge records of a simultaneously recorded pair of motor units can be used to make quantitative estimates of the PIC contribution, based on the assumption that the firing rate of an early recruited (reporter) unit can be used as a measure of the synaptic drive to a later recruited (test) unit. If the test unit's discharge is augmented by PICs, less synaptic drive will be required to sustain discharge than required to initially recruit it, and the difference in reporter unit discharge (Δ F) at test recruitment and de-recruitment is a measure of the size of the PIC contribution. We applied this analysis to discharge records of pairs of motoneurons in the decerebrate cat preparation, in which motoneuron PICs have been well-characterized and are known to be prominent. Mean Δ F values were positive in 58/63 pairs, and were significantly greater than zero in 40/63 pairs, as would be expected based on PIC characteristics recorded in this preparation. However, several lines of evidence suggest that the Δ F value obtained in a particular motoneuron pair may depend on a number of factors other than the PIC contribution to firing rate.
Ca2+-Induced Ca2+Release inAplysiaBag Cell Neurons Requires Interaction Between Mitochondrial and Endoplasmic Reticulum Stores
Authors: Geiger Julia E. , Magoski Neil S.
Published: May 2008

Intracellular Ca2+is influenced by both Ca2+influx and release. We examined intracellular Ca2+following action potential firing in the bag cell neurons of Aplysia californica. Following brief synaptic input, these neuroendocrine cells undergo an afterdischarge, resulting in elevated Ca2+and the secretion of neuropeptides to initiate reproduction. Cultured bag cell neurons were injected with the Ca2+indicator, fura-PE3, and subjected to simultaneous imaging and electrophysiology. Delivery of a 5-Hz, 1-min train of action potentials (mimicking the fast phase of the afterdischarge) produced a Ca2+rise that markedly outlasted the initial influx, consistent with Ca2+-induced Ca2+release (CICR). This response was attenuated by about half with ryanodine or depletion of the endoplasmic reticulum (ER) by cyclopiazonic acid. However, depletion of the mitochondria, with carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone, essentially eliminated CICR. Dual depletion of the ER and mitochondria did not reduce CICR further than depletion of the mitochondria alone. Moreover, tetraphenylphosphonium, a blocker of mitochondrial Ca2+release, largely prevented CICR. The Ca2+elevation during and subsequent to a stimulus mimicking the full afterdischarge was prominent and enhanced by protein kinase C activation. Traditionally, the ER is seen as the primary Ca2+source for CICR. However, bag cell neuron CICR represents a departure from this view in that it relies on store interaction, where Ca2+released from the mitochondria may in turn liberate Ca2+from the ER. This unique form of CICR may be used by both bag cell neurons, and other neurons, to initiate secretion, activate channels, or induce gene expression.
Perception‐Based Filtering for MMOGs
Authors: El Merhebi Souad , Hoelt Jean-Christophe , Torguet Patrice , Jessel Jean-Pierre
Published: May 2008

Online games have exploded in the last few years. These games face several problems linked to scalability and interactivity. In fact, online games should provide a quick feedback of users′ interactions as well as a coherent view of the shared world. However, the search for enhanced scalability dramatically increases message exchange. Such an increase consumes processing power and bandwidth, and thus limits interactivity, consistency, and scalability. To reduce the rate of message exchange, distributed virtual environment systems use filtering techniques such as interest management that filters messages according to users′ interests in the world. These interests are influenced by perceptual facts which we study in this paper in order to build upon them a perception‐based filtering technique. This technique satisfies users′ needs by precisely providing an exact filtering which is more efficient than other techniques.
A Note on Almost Periodic Points and Minimal Sets in T1‐ and T2‐Spaces
Authors: Mai Jie-Hua , Liu Xin-He
Published: May 2008

We show that (1) there exist almost periodic orbits in T2‐spaces of which the closures are not minimal sets; (2) there exist minimal sets in
locally compact T1‐spaces which are not compact; (3) there exist almost periodic orbits in T2‐spaces of which the closures contain not only almost periodic points. These
give answers to the three problems given by Mai and Sun in (2007).
Structure and Property Investigation of Composite ZnO/SnO2 Nanocrystalline Particles after High‐Pressure Treatment
Authors: Zhenya Sun , Yundi Deng , Weiying Zhang
Published: May 2008

Composite ZnO/SnO2 nanocrystalline particles (ZnO/SnO2) were synthesized by sol‐gel method and with treatment of high pressure at 6 GPa. The crystallinity and the particle size of the prepared samples were analyzed by X‐ray diffraction (XRD) spectroscopy. The results indicated that all the samples had the good crystallinity, and the particle size of ZnO and ZnO/SnO2 decreased after high‐pressure treatment. The infrared (IR) spectra showed that the distance of crystal lattice was shortened after high‐pressure treatment, and the size distribution became more uneven after SnO2 doping. With the high‐resolution transmission electron microscope (HRTEM), we got some morphology information and evidence to support the IR and XRD analysis results. The results of ultraviolet‐visible absorption (UV‐Vis) spectra showed that ZnO/SnO2 might improve the photocatalytic property of the samples after high‐pressure treatment.
Pancreatic Mass with an Unusual Pathology: A Case Report
Authors: Healey Andrew J. , Reed Anna , Jiao Long R.
Published: May 2008

Intra-abdominal abscesses formation in patients with no preceding symptoms is rare. Infection of the pancreas occurs in 5–9% of patients with acute pancreatitis, more commonly as a complication of necrotising or severe pancreatitis. We have reported a case of a 64-year-old almost entirely asymptomatic man who underwent a Whipple's procedure following extensive investigation of a pancreatic mass. The pathology and histology showed no evidence of malignancy, and instead a true pancreatic abscess, centred around an impacted cholesterol calculus in the distal CBD. Of suspicious pancreatic masses that are resected, chronic choledocholithiasis is the aetiology in less than 5% of nonmalignant or false positives. This report describes such a case.
Recent Insights in Islet Amyloid Polypeptide‐Induced Membrane Disruption and Its Role in β‐Cell Death in Type 2 Diabetes Mellitus
Authors: Khemtémourian Lucie , Antoinette Killian J. , Höppener Jo W. M. , Engel Maarten F. M.
Published: May 2008

The presence of fibrillar protein deposits (amyloid) of human islet amyloid polypeptide (hIAPP) in the pancreatic islets of Langerhans is thought to be related to death of the insulin‐producing islet β‐cells in type 2 diabetes mellitus (DM2). The mechanism of hIAPP‐induced β‐cell death is not understood. However, there is growing evidence that hIAPP‐induced disruption of β‐cell membranes is the cause of hIAPP cytotoxicity. Amyloid cytotoxicity by membrane damage has not only been suggested for hIAPP, but also for peptides and proteins related to other misfolding diseases, like Alzheimer_s disease, Parkinson′s disease, and prion diseases. Here we review the interaction of hIAPP with membranes, and discuss recent progress in the field, with a focus on hIAPP structure and on the proposed mechanisms of hIAPP‐induced membrane damage in relation to β‐cell death in DM2.