bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct and Indirect Roles of Viral Suppressors of RNA Silencing in Pathogenesis
Authors: Díaz-Pendón Juan A. , Ding Shou-Wei
Published: August 2008

Plant and animal viruses overcome host antiviral silencing by encoding diverse viral suppressors of RNA silencing (VSRs). Prior to the identification and characterization of their silencing suppression activities mostly in transgene silencing assays, plant VSRs were known to enhance virus accumulation in the inoculated protoplasts, promote cell-to-cell virus movement in the inoculated leaves, facilitate the phloem-dependent long-distance virus spread, and/or intensify disease symptoms in systemically infected tissues. Here we discuss how the various silencing suppression activities of VSRs may facilitate these distinct steps during plant infection and why VSRs may not play a direct role in eliciting disease symptoms by general impairments of host endogenous small RNA pathways. We also highlight many of the key questions still to be addressed on the role of viral suppression of antiviral silencing in plant infection.
Fed levels of amino acids are required for the somatotropin-induced increase in muscle protein synthesis
Authors: Wilson Fiona A. , Suryawan Agus , Orellana Renán A. , Nguyen Hanh V. , Jeyapalan Asumthia S. , Gazzaneo Maria C. , Davis Teresa A.
Published: August 2008

Chronic somatotropin (pST) treatment in pigs increases muscle protein synthesis and circulating insulin, a known promoter of protein synthesis. Previously, we showed that the pST-mediated rise in insulin could not account for the pST-induced increase in muscle protein synthesis when amino acids were maintained at fasting levels. This study aimed to determine whether the pST-induced increase in insulin promotes skeletal muscle protein synthesis when amino acids are provided at fed levels and whether the response is associated with enhanced translation initiation factor activation. Growing pigs were treated with pST (0 or 180 μg·kg−1·day−1) for 7 days, and then pancreatic-glucose-amino acid clamps were performed. Amino acids were raised to fed levels in the presence of either fasted or fed insulin concentrations; glucose was maintained at fasting throughout. Muscle protein synthesis was increased by pST treatment and by amino acids (with or without insulin) ( P < 0.001). In pST-treated pigs, fed, but not fasting, amino acid concentrations further increased muscle protein synthesis rates irrespective of insulin level ( P < 0.02). Fed amino acids, with or without raised insulin concentrations, increased the phosphorylation of S6 kinase (S6K1) and eukaryotic initiation factor (eIF) 4E-binding protein 1 (4EBP1), decreased inactive 4EBP1·eIF4E complex association, and increased active eIF4E·eIF4G complex formation ( P < 0.02). pST treatment did not alter translation initiation factor activation. We conclude that the pST-induced stimulation of muscle protein synthesis requires fed amino acid levels, but not fed insulin levels. However, under the current conditions, the response to amino acids is not mediated by the activation of translation initiation factors that regulate mRNA binding to the ribosomal complex.
Maternal obesity and fetal programming: effects of a high-carbohydrate nutritional modification in the immediate postnatal life of female rats
Authors: Srinivasan Malathi , Dodds Catherine , Ghanim Husam , Gao Tao , Ross Peter J. , Browne Richard W. , Dandona Paresh , Patel Mulchand S.
Published: August 2008

Our earlier studies have shown that the artificial rearing of newborn rat pups [first generation high carbohydrate (1-HC)] on an HC milk formula resulted in chronic hyperinsulinemia and adult-onset obesity (HC phenotype). Offspring [second-generation HC (2-HC)] of 1-HC female rats spontaneously acquired the HC phenotype in the postweaning period. In this study, we have characterized the development of the abnormal intrauterine environment in the 1-HC female rats and the effects on fetal development under such pregnancy conditions for the offspring. 1-HC female rats demonstrated hyperphagia on laboratory chow and increased body weight gain beginning from the immediate postweaning period along with hyperinsulinemia and hyperleptinemia. During pregnancy, 1-HC female rats showed several metabolic alterations including increased body weight gain and increased plasma levels of insulin, leptin, proinflammatory markers, and lipid peroxidation products. Although there were no significant changes in the body weights or litter size of term 2-HC fetuses, the plasma levels of insulin and leptin were significantly higher compared with those of control term fetuses. Quantitation of mRNA levels by real-time RT-PCR indicated significant increases in the mRNA levels of orexigenic neuropeptides in the hypothalamus of 2-HC term fetuses. Collectively, these results indicate that the HC diet in infancy results in an adverse pregnancy condition in female rats with deleterious consequences for the offspring.
Population Dynamics in Vasopressin Cells
Authors: Leng Gareth , Brown Colin , Sabatier Nancy , Scott Victoria
Published: August 2008

Most neurons sense and code change, and when presented with a constant stimulus they adapt, so as to be able to detect a fresh change. However, for some things it is important to know their absolute level; to encode such information, neurons must sustain their response to an unchanging stimulus while remaining able to respond to a change in that stimulus. One system that encodes the absolute level of a stimulus is the vasopressin system, which generates a hormonal signal that is proportional to plasma osmolality. Vasopressin cells sense plasma osmolality and secrete appropriate levels of vasopressin from the neurohypophysis as needed to control water excretion; this requires sustained secretion under basal conditions and the ability to increase (or decrease) secretion should plasma osmolality change. Here we explore the mechanisms that enable vasopressin cells to fulfill this function, and consider how coordination between the cells might distribute the secretory load across the population of vasopressin cells.
Home-Based Exercise Training as Maintenance after Outpatient Pulmonary Rehabilitation
Authors: du Moulin Marcel , Taube Karin , Wegscheider Karl , Behnke Michaela , van den Bussche Hendrik
Published: August 2008

Background: Pulmonary rehabilitation is successful in improving exercise capacity and quality of life in patients with chronic obstructive pulmonary disease (COPD). However, training effects diminish over time. Objectives:We evaluated the effects of simple, daily, structured, self-monitored, home-based exercise training for patients with moderate COPD after a 3-week outpatient rehabilitation. Methods: We conducted a randomized, controlled, observer-blind trial. Twenty patients were recruited. Ten patients performed home-based exercise training (mean age 67 years, 95% confidence interval [CI] 63–72; FEV1 58.6%, 95% CI 53.8–63.4), and 10 patients served as controls (mean age 72 years, 95% CI 69–77; FEV1 62.5%, 95% CI 57.7–67.3). At baseline, and after 3 and 6 months, we assessed exercise capacity (6-min walk test, 6MWT, primary endpoint), health-related quality of life (Chronic Respiratory Questionnaire, CRQ) and lung function. An intention-to-treat analysis was performed using two-way ANOVA models for comparison of time trends between random groups. Results: The training group had better results than the control group in 6MWT (p = 0.033), in CRQ total (p = 0.027), CRQ dyspnea (p = 0.014) and CRQ fatigue (p = 0.016). Improvement in FEV1 was also better in the intervention group than in the control group (p = 0.007). Conclusions: We demonstrated that training effects obtained from an outpatient rehabilitation program can be maintained by home-based exercise training in patients with moderate COPD.
The Role of PI3/Akt Pathway in the Protective Effect of Insulin against Corticosterone Cell Death Induction in Hippocampal Cell Culture
Authors: Moosavi Maryam , Maghsoudi Nader , Zahedi-Asl Saleh , Naghdi Nasser , Yousefpour Mitra , Trounce Ian Andrew
Published: August 2008

Corticosterone induces neuroanatomical and neurochemical changes in the hippocampus that are associated with cognitive impairments. In the present study corticosterone induced cell death in primary hippocampal neurons cultured in Neurobasal + B27 medium. Insulin prevents neuronal cell death induced in a concentration dependent manner. The neuroprotective effect of insulin was reversed by LY294002, a phosphatidylinositol 3′-kinase (PI3 kinase) inhibitor, whereas the mitogen-activated protein kinase (MAPK) inhibitor PD98059, an upstream blocker of MAPK had no effect. Western blot analyses showed that insulin induced the activation of protein kinase B (Akt). These results suggest that insulin can prevent neuronal cell death induced by corticosterone in hippocampal neurons by modulating the activity of the PI3 kinase/Akt pathway.
Estrogen Reduces Aldosterone, Upregulates Adrenal Angiotensin II AT2 Receptors and Normalizes Adrenomedullary Fra-2 in Ovariectomized Rats
Authors: Macova Miroslava , Armando Ines , Zhou Jin , Baiardi Gustavo , Tyurmin Dmitri , Larrayoz-Roldan Ignacio M. , Saavedra Juan M.
Published: August 2008

We studied the effect of ovariectomy and estrogen replacement on expression of adrenal angiotensin II AT1 and AT2 receptors, aldosterone content, catecholamine synthesis, and the transcription factor Fos-related antigen 2 (Fra-2). Ovariectomy increased AT1 receptor expression in the adrenal zona glomerulosa and medulla, and decreased adrenomedullary catecholamine content and Fra-2 expression when compared to intact female rats. In the zona glomerulosa, estrogen replacement normalized AT1 receptor expression, decreased AT1B receptor mRNA, and increased AT2 receptor expression and mRNA. Estrogen treatment decreased adrenal aldosterone content. In the adrenal medulla, the effects of estrogen replacement were: normalized AT1 receptor expression, increased AT2 receptor expression, AT2 receptor mRNA, and tyrosine hydroxylase mRNA, and normalized Fra-2 expression and catecholamine content. We demonstrate that the constitutive adrenal expression of AT1 receptors, catecholamine synthesis and Fra-2 expression are partially under the control of reproductive hormones. Our results suggest that estrogen treatment decreases aldosterone production through AT1 receptor downregulation and AT2 receptor upregulation. AT2 receptor upregulation and modulation of Fra-2 expression may participate in the estrogen-dependent normalization of adrenomedullary catecholamine synthesis in ovariectomized rats. The AT2 receptor upregulation and the decrease in AT1 receptor function and in the production of the fluid-retentive, pro-inflammatory hormone aldosterone partially explain the protective effects of estrogen therapy.
Parathyroid Hormone-Related Peptide-Secreting Pancreatic Neuroendocrine Tumours: Case Series and Literature Review
Authors: Srirajaskanthan Rajaventhan , McStay Mary , Toumpanakis Christos , Meyer Tim , Caplin Martyn E.
Published: August 2008

Background/Aims: Parathyroid hormone-related peptide (PTHrP) was discovered in 1987 as the tumour product responsible for humoral hypercalcaemia of malignancy (HHM). Pancreatic neuroendocrine tumours (NETs) are uncommon malignancies with an incidence of 1:100,000 population. PTHrP-secreting NETs are rare but are being recognised as a cause of HHM in NETs. We describe the largest series to date and the management of these rare tumours. Methods: One male and 4 female patients were seen in our unit from 1998 to 2006. The average duration of follow-up was 86 months from initial diagnosis. All patients had a histologically confirmed diagnosis of pancreatic NET, all of which were low-grade tumours. PTHrP assay was performed in 4 of 5 cases and was elevated in these patients. Results: Initial management involved surgery in 2 of 5 cases, whilst 2 cases underwent chemotherapy and 1 case was commenced on interferon-α. We discuss the further therapies that all patients underwent and the complexities that arose in managing disease progression as well as resistant hypercalcaemia. Conclusion: PTHrP-secreting tumours should be considered in the differential diagnosis of patients with NETs who present with hypercalcaemia and a disproportionately low PTH. PTHrP tumours may well be underestimated as the assay is difficult to perform and may not be requested. In hypercalcaemic patients the standard management acutely includes intravenous fluids, diuretics and intravenous bisphosphonate. In the further management, somatostatin analogue therapy is the first medical option to consider and we discuss the role of other therapies.
Generating Spike Trains with Specified Correlation Coefficients
Authors: Macke Jakob H. , Berens Philipp , Ecker Alexander S. , Tolias Andreas S. , Bethge Matthias
Published: August 2008

Spike trains recorded from populations of neurons can exhibit substantial pairwise correlations between neurons and rich temporal structure. Thus, for the realistic simulation and analysis of neural systems, it is essential to have efficient methods for generating artificial spike trains with specified correlation structure. Here we show how correlated binary spike trains can be simulated by means of a latent multivariate gaussian model. Sampling from the model is computationally very efficient and, in particular, feasible even for large populations of neurons. The entropy of the model is close to the theoretical maximum for a wide range of parameters. In addition, this framework naturally extends to correlations over time and offers an elegant way to model correlated neural spike counts with arbitrary marginal distributions.
Nonparametric Conditional Density Estimation Using Piecewise-Linear Solution Path of Kernel Quantile Regression
Authors: Takeuchi Ichiro , Nomura Kaname , Kanamori Takafumi
Published: August 2008

The goal of regression analysis is to describe the stochastic relationship between an input vector x and a scalar output y. This can be achieved by estimating the entire conditional density p(y ∣ x). In this letter, we present a new approach for nonparametric conditional density estimation. We develop a piecewise-linear path-following method for kernel-based quantile regression. It enables us to estimate the cumulative distribution function of p(y ∣ x) in piecewise-linear form for all x in the input domain. Theoretical analyses and experimental results are presented to show the effectiveness of the approach.
Synthesis of CdTe Nanocrystals with Mercaptosuccinic Acid as Stabilizer
Authors: Wang Chao , Ma Qiang , Su Xingguang
Published: August 2008

Water soluble high quality CdTe nanocrystals (NCs) with mercaptosuccinic acid (MSA) as stabilizer are prepared by refluxing and hydrothermal synthesis in this paper. The MSA stabilizer which comprises both thioglycolic acid (TGA)-like and 3-mercaptopropionic acid (MPA)-like moieties
can accelerate the whole growth process of CdTe NCs comparing with TGA-like or MPA-like stabilizer. It takes only 5 min and 2 hours to obtain green emitting (luminescence maximum at 526 nm) and red emitting (luminescence maximum at ∼650 nm) from CdTe NCs, respectively. In this study, the
influences of the ratios of precursors and temperature on CdTe NCs synthesis were studied in detail, and the stable CdTe NCs with high photoluminescence quantum yield and narrow size distribution can be obtained under optimal condition by both routes. The luminescence quantum yield of the
green-yellow emitting CdTe NCs obtained in this study can reach 75.2%.
Studying Protein Binding to Conjugated Gold Nanospheres; Application of Mie Light Scattering to Reaction Kinetics
Authors: Lunt E. A. M. , Pitter M. C. , Somekh M. G. , O'Shea P.
Published: August 2008

The study of protein interactions is an area of much interest, particularly towards obtaining more detailed information about biological processes. Current methods involve the use of complicated, specialised techniques which are beyond the scope of most laboratories. Here, we show how
information about the binding of proteins to conjugated gold nanospheres can be obtained using straightforward experimental techniques. A Perkin Elmer LS 55 luminescence spectrometer was used to observe the changes in light scattering caused by the binding of complementary proteins to conjugated
nanoparticles, measured by the intensity change over time. Mie theory simulations have been used to predict the expected observations and to quantify the changes in intensity as a function of surface coverage. Further kinetic studies have been carried out at 530 nm to obtain more detailed
information about the processes involved in the binding reaction. Thus, we have demonstrated that the interaction of proteins can be studied using a straightforward method which provides information about surface coverage and reaction kinetics.
Magnetic, Magneto-optic and Magnetotransport Properties of Nanocrystalline Co/Au Multilayers with Ultrathin Au Interlayers
Authors: Papaioannou E. Th. , Karoutsos V. , Angelakeris M. , Valassiades O. , Fumagalli P. , Flevaris N. K. , Poulopoulos P.
Published: August 2008

A series of nanocrystalline Co/Au multilayers with ultrathin Au interlayers was grown at room temperature by electron beam evaporation on Si(111), glass and polyimide substrates. X-ray diffraction measurements reveal a face centered cubic multilayered structure with very small nanograins
within 7–10 nm in diameter. Magneto-optic polar Kerr effect experiments show an enhancement of the Kerr rotation around 3 eV as the Au interlayer thickness increases. The experimental data are interpreted with the help of simulated Kerr spectra. The magnetization curves and magnetic
force microscopy images indicate the existence of perpendicularly magnetized stripe-domain structures at remanence. The magnitude of the magnetoresistance ratio reaches values of 0.4%. The investigation of the interplay between magnetic and magnetotransport properties demonstrates the contribution
of the domain-wall spin-dependent scattering to the magnetoresistance.
Preparation of Semi-Conducting Polymeric Nanoparticles by Supercritical Carbon Dioxide RESOLV Process
Authors: Ganapathy Hullathy Subban , Kim Jun Ho , Hong Seung-Soo , Lim Kwon Taek
Published: August 2008

The rapid expansion of supercritical carbon dioxide solutions into a liquid solvent (RESOLV) technique with environmentally benign supercritical carbon dioxide was used to produce semi-conducting polymeric nanoparticles of fluoroalkyl ester substituted thiophenes. When the supercritical
solutions of the conjugated polymer, poly[2-(3-thienyl) acetyl-3,3,4,4,5,5,6,6,7,7,8,8,8, tridecafluoro-1-octanate] (PSFTE) were expanded into aqueous solutions through a small capillarynozzle (150 μm), spherical nanoparticles in the range of 50–100 nm were obtained. However,
after 15 min of expansion, the particles tended to aggregate to form larger objects due to the high surface energy of the polymeric nanoparticles. In order to prevent the agglomeration of particles, a relatively low concentration of sodium dodecyl sulphate (SDS) or NaCl was used as a stabilizing
agent in aqueous solution. While NaCl did not give enough stabilization to the system, uniform spherical nanoparticles of PSFTE having an average size of 45 nm were successfully obtained by SDS stabilization.
Facile Covalent Attachment of Well-Defined Poly(t-butyl acrylate) on Carbon Nanotubes via Radical Addition Reaction
Authors: Oh Saet Byeol , Kim Hye Lynn , Chang Jun Ho , Lee Yong-Won , Han Jong Hun , An Seong Soo A. , Joo Sang-Woo , Kim Hyung-Kook , Choi Insung S. , Paik Hyun-jong
Published: August 2008

We developed a new method to covalently attach well-defined polymers onto carbon nanotubes (CNTs) using a radical reaction. Well-defined poly(t-butyl acrylate) [p(tBA)] was first prepared by atom transfer radical polymerization, which formed radicals at the end of the
polymer chain through an atom transfer. The generated radicals at the chain ends added CNTs to generate covalently functionalized p(tBA)-grafted CNTs. The polymer-attached CNTs showed much improved solubility in organic solvents. The synthesized MWNT-g-p(tBA) and SWNT-g-p(tBA)
were characterized by IR, TGA and Raman spectroscopy, clearly indicating the formation of covalent bonding between p(tBA) and CNTs.
Removal of Cetyltrimethylammonium Bromide to Enhance the Biocompatibility of Au Nanorods Synthesized by a Modified Seed Mediated Growth Process
Authors: Choi Byung-Sang , Iqbal Muhammad , Lee Takhee , Kim Young Ha , Tae Giyoong
Published: August 2008

Previously, we reported the synthesis of stable gold nanorods with higher aspect ratio (∼15–20) and more enhanced uniformity by a modified seed mediated growth approach using a binary surfactant system consisting of CTAB and Pluronic F-127. For the in vivo application
of gold nanorods, the removal of CTABs that are strongly bound on prepared Au nanorods is necessary due to their cytotoxicity. Use of heat or acid at various conditions was performed to achieve the complete removal of CTAB from the synthesized Au nanorods while maintaining their stability.
Here, we report the appropriate conditions for both treatments that can remove CTAB efficiently without hampering the stability of Au nanorods. After the removal of CTAB, Pluronic F-127 was added additionally for the stabilization and further potential functionalization of Au nanorods to make
useful for various applications. VIS-NIR absorption spectroscopy, SEM, TEM, and FTIR were used for characterization.
Preparation and Properties of the Nanocomposites Based on Poly(methyl methacrylate-co-butyl acrylate) and Multiwalled Carbon Nanotube
Authors: Jin Sung-Hun , Lee Dai-Soo
Published: August 2008

Nanocomposites, based on multiwalled carbon nanotube (MWCNT) and various acrylic copolymers of poly(methyl methacrylate-co-butyl acrylate)s, were prepared and the effects of the copolymer compositions on the electrical and the dynamic mechanical properties of the nanocomposites investigated.
Latices of the acrylic copolymer were prepared by emulsion polymerization, and then mixed with MWCNT dispersed in N-methylpyrrolidone to prepare the nanocomposites. The electrical resistivities of the nanocomposites showed threshold decreases with increasing MWCNT content, due to percolation.
The critical MWCNT content (Pc) in the nanocomposites for percolation showed minimum with increasing butyl acrylate content within the poly(methyl methacrylate-co-butyl acrylate). Specifically, the nanocomposites of the acrylic copolymer with a butyl acrylate content of 20∼40
wt% showed the lowest Pc value of all the nanocomposites investigated. The nanocomposites showed large increases in the storage moduli in the rubbery plateau region. A decrease in the glass transition temperature (Tg) was observed with the nanocomposites
and attributed to the characteristics of the nanocomposites, where the large surface area of MWCNT makes the matrix polymers similar to those of free stand thin film polymers.
Possible Magnetism of Be-Doped Boron Nitride Nanotubes
Authors: Rahman Gul , Hong Soon Cheol
Published: August 2008

We studied the electronic and magnetic properties of pristine and Be-doped (5, 5) boron nitride (BN) nanotubes using density functional theory within a generalized gradient approximation. We found that the pristine (5, 5) BN nanotube is an indirect band gap material, which is in agreement
with previous findings. Doping with Be induces spontaneous magnetization (∼1 μB/Be atom) in the (5, 5) BN nanotube. The defect states are not localized to the Be atoms themselves, but spread out over their neighboring B and N atoms. In particular, the system becomes
a half metal when Be is substituted for B.
Fabrication and Characterization of PEDOT/Au Films by Chemical Vapor Polymerization Using Au+3 Oxidant
Authors: Kim Soyeon , Cho Misuk , Nam Jaedo , Lee Youngkwan
Published: August 2008

Thin composite films of poly (3,4-ethylenedioxythiophene) (PEDOT)/Au were obtained by a vapor-phase polymerization technique using HAuCl4 as an oxidant on the PET film substrate. The PEDOT/Au films were synthesized with metallic gold originating from the redox reaction between
3,4-ethylenedioxythiophene (EDOT) and Au ions. The formation of the PEDOT/Au film was confirmed by UV-vis absorption spectroscopy and scanning electron microscopy (SEM). The reduction to zero-valent gold was confirmed by X-ray spectrometer (EDX) and X-ray diffraction (XRD). In addition, the
enhancement of the thermal stability of the PEDOT/Au film was studied by measuring the change in the conductivity at high temperature. The conductivities of the PEDOT films prepared using FTS and HAuCl4 were 260 and 200 Scm−1 and their thicknesses were 100 and 120
nm, respectively.
Physical Properties of Thin PVDF/MWNT (Multi-Walled Carbon Nanotube) Composite Films by Melt Blending
Authors: Hong Soon Man , Hwang Seung Sang
Published: August 2008

Poly(vinylidene fluoride)(PVDF)/Multi-walled carbon nanotube (MWNT) composites were melt blended using internal mixer. The relationships between structures and physical properties of thin PVDF/MWNT composite films were studied. With increasing the content of MWNT, the size of spherulites
in PVDF decreased. MWNT was used as a nucleating agent. The incorporation of MWNT produced a polar β-form crystal structure of PVDF. The permittivities of thin PVDF/MWNT composite films were increased with increasing the MWNT content. The percolation level in electrical conductivity
occurred between 2 and 2.5 wt%. The critical conductivity saturation point for the electrical conductivity in PVDF was confirmed. Similar tendency was also observed in thermal conductivity.
A Facile Synthesis of Poly(3-octylthiophene)-Titanium Dioxide Nanocomposite Particles in Supercritical CO2
Authors: Yuvaraj Haldorai , Woo Min Hee , Park Eun Ju , Gal Yeong-Soon , Lim Kwon Taek
Published: August 2008

Poly(3-octylthiophene) (P3OT)-titanium dioxide (TiO2) nanocomposite powder where TiO2 was embedded with homogeneous dispersion was synthesized by in-situ chemical oxidative polymerization of 3-octylthiophene in the presence of TiO2 nanoparticles
in supercritical carbon dioxide (scCO2), using ferric chloride as the oxidant. The synthesized materials could be obtained as dry powder upon venting of CO2 after the polymerization. The composites were subsequently characterized by FT-IR spectroscopy, transmission electron
microscopy (TEM), X-ray diffraction studies (XRD), thermogravimetric analysis (TGA) and photoluminescence (PL). The incorporation of TiO2 in the composite was endorsed by FT-IR studies. TGA revealed enhanced thermal stability of P3OT/TiO2 nanocomposite compared to 3-octylthiophene.
TEM analysis showed that well dispersed TiO2 nanoparticles in the polymer matrix. Photoluminescence quenching increased with increasing TiO2 concentration in the composite.
Electrical Characterization of ZnO Single Nanowire Device for Chemical Sensor Application
Authors: Kim E. K. , Lee H.-Y. , Moon S. E. , Park J. , Park S.-J. , Kwak J.-H. , Maeng S. , Park K.-H. , Kim J. , Kim S. W. , Ji H. J. , Kim G. T.
Published: August 2008

Vertically well-aligned high quality ZnO nanowires were grown on GaN epilayer on c-plane sapphire via a vapor-liquid-solid (VLS) process by introducing an Au thin film (3 nm) as a catalyst. ZnO single nanowire device was ingenuously fabricated by combining conventional optical lithography
and high resolution electron beam lithography and its current–voltage characteristics were measured with doing the post process to acquire reproducible performance as a chemical gas sensor. And its temperature dependent current–voltage characteristics were measured to investigate
temperature dependant electrical transport. The ZnO nanowire device showed slightly non-ohmic current–voltage characteristics which may be due to back-to-back configuration of the diodes with the insulating contact barriers and showed an relatively small activation energy of 0.2 eV.
To test our device as a chemical sensor, the NO2 gas response was reported at the elevated temperature.
Synthesis and Hole-Transporting Properties of Various Bicarbazyl Derivatives
Authors: Lee Yoon-Mi , Kim Soo-Kang , Lee Chang-Jun , Lee Ji-Hoon , Park Jong-Wook
Published: August 2008

This paper reports a new HTL material that has high glass-transition temperatures (Tg) and excellent thermal properties. The synthesized material was N,N-diethyl-3,3′-bicarbazyl (DEBC), N,N-diphenyl-3,3′-bicarbazyl (DPBC) and N,N-dinaphthyl-3,3′-bicarbazyl
(DNBC). The device that used DPBC as HTL showed the highest efficiency of 4.95 cd/A and 2.22 lm/W at 10 mA/cm2. This is an improvement by more than 10% from the luminance efficiency of NPB, a commercialized material.
A Climatology of Ocean–Atmosphere Heat Flux Estimates over the Great Barrier Reef and Coral Sea: Implications for Recent Mass Coral Bleaching Events
Authors: Weller Evan , Nunez Manuel , Meyers Gary , Masiri Itsara
Published: August 2008

A regional-scale estimate of the surface heat budget of the Great Barrier Reef and Coral Sea (10°–26°S, 142°–155°E) has been developed for the period 1995–2005 in the hope of understanding the trends of sea surface temperatures and the surface heat balance. This report describes the methodology to acquire input parameters from satellite observations, the resultant individual components of the surface heat budget, and their validation with existing datasets and surface measurements.

The accuracy of individual flux components of the heat budget were analyzed with an array of surface measurements. Derived monthly averaged latent and sensible heat flux estimates show RMS errors of approximately 25.2 and 3.4 W m−2, respectively. Monthly averaged longwave and shortwave radiation flux estimates show RMS errors of approximately 6.7 and 13.3 W m−2, respectively. These improved estimates allow a higher confidence in studies that examine recent sea surface temperature (SST) trends and observed mass coral bleaching for the region.

It is proposed that the greatest uptake of heat occurs over the spring/summer period in the central and southern regions of the Great Barrier Reef, agreeing well with areas where anomalously high sea surface temperatures are observed and where the most significant coral bleaching has occurred, and not in the most northern, more tropical region, as might be expected. The surface heat budget climatology was used to examine the mass bleaching episode that occurred in 2002. Results show that areas of maximum and minimum bleaching are better discriminated by the anomaly from mean seasonal values in the net surface heat flux (QNET), with accuracy of 86% and 79%, respectively, than by absolute QNET, absolute SST, or SST anomaly. Possible reasons for this are discussed.
An Investigation of Warm-Season Spatial Rainfall Variability in Oklahoma City: Possible Linkages to Urbanization and Prevailing Wind
Authors: Hand Lauren M. , Shepherd J. Marshall
Published: August 2008

This study used 9 yr (1998–2006) of warm-season (June–September) mean daily cumulative rainfall data from both the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis and rain gauge stations to examine spatial variability in warm-season rainfall events around Oklahoma City (OKC). It was hypothesized that with warm-season rainfall variability, under weakly forced conditions, a rainfall anomaly would be present in climatological downwind areas of OKC. Results from both satellite and gauge-based analyses revealed that the north-northeastern (NNE) regions of the metropolitan OKC area were statistically wetter than other regions. Climatological sounding and reanalysis data revealed that, on average, the NNE area of OKC was the climatologically downwind region, confirming that precipitation modification by the urban environment may be more dominant than agricultural/topographic influences on weakly forced days. The study also established that satellite precipitation estimates capture spatial rainfall variability as well as traditional ground-based resources do. TRMM products slightly underestimate the precipitation recorded by gauges, but the correlation R improves dramatically when the analysis is restricted to mean daily rainfall estimates from OKC urban grid cells containing multiple gauge stations (R2 = 0.878). It was also quantitatively confirmed, using a relatively new concentration factor analysis, that prevailing wind–rainfall yields were consistent with the overall framework of an urban rainfall effect. Overall, the study establishes a prototype method for utilizing satellite-based rainfall estimates to examine rainfall modification by urbanization on global scales and in parts of the world that are not well instrumented with rain gauge or radar networks.
Planetary Wave Breaking and Tropospheric Forcing as Seen in the Stratospheric Sudden Warming of 2006
Authors: Coy Lawrence , Eckermann Stephen , Hoppel Karl
Published: August 2008

The major stratospheric sudden warming (SSW) of January 2006 is examined using meteorological fields from Goddard Earth Observing System version 4 (GEOS-4) analyses and forecast fields from the Navy Operational Global Atmospheric Prediction System–Advanced Level Physics, High Altitude (NOGAPS-ALPHA). The study focuses on the upper tropospheric forcing that led to the major SSW and the vertical structure of the subtropic wave breaking near 10 hPa that moved low tropical values of potential vorticity (PV) to the pole. Results show that an eastward-propagating upper tropospheric ridge over the North Atlantic with its associated cold temperature perturbations (as manifested by high 360-K potential temperature surface perturbations) and large positive local values of meridional heat flux directly forced a change in the stratospheric polar vortex, leading to the stratospheric subtropical wave breaking and warming. Results also show that the anticyclonic development, initiated by the subtropical wave breaking and associated with the poleward advection of the low PV values, occurred over a limited altitude range of approximately 6–10 km. The authors also show that the poleward advection of this localized low-PV anomaly was associated with changes in the Eliassen–Palm (EP) flux from equatorward to poleward, suggesting an important role for Rossby wave reflection in the SSW of January 2006. Similar upper tropospheric forcing and subtropical wave breaking were found to occur prior to the major SSW of January 2003.
A 10–15-Yr Modulation Cycle of ENSO Intensity
Authors: Sun Fengpeng , Yu Jin-Yi
Published: August 2008

This study examines the slow modulation of El Niño–Southern Oscillation (ENSO) intensity and its underlying mechanism. A 10–15-yr ENSO intensity modulation cycle is identified from historical and paleoclimate data by calculating the envelope function of boreal winter Niño-3.4 and Niño-3 sea surface temperature (SST) indices. Composite analyses reveal interesting spatial asymmetries between El Niño and La Niña events within the modulation cycle. In the enhanced intensity periods of the cycle, El Niño is located in the eastern tropical Pacific and La Niña in the central tropical Pacific. The asymmetry is reversed in the weakened intensity periods: El Niño centers in the central Pacific and La Niña in the eastern Pacific. El Niño and La Niña centered in the eastern Pacific are accompanied with basin-scale surface wind and thermocline anomalies, whereas those centered in the central Pacific are accompanied with local wind and thermocline anomalies. The El Niño–La Niña asymmetries provide a possible mechanism for ENSO to exert a nonzero residual effect that could lead to slow changes in the Pacific mean state. The mean state changes are characterized by an SST dipole pattern between the eastern and central tropical Pacific, which appears as one leading EOF mode of tropical Pacific decadal variability. The Pacific Walker circulation migrates zonally in association with this decadal mode and also changes the mean surface wind and thermocline patterns along the equator. Although the causality has not been established, it is speculated that the mean state changes in turn favor the alternative spatial patterns of El Niño and La Niña that manifest as the reversed ENSO asymmetries. Using these findings, an ENSO–Pacific climate interaction mechanism is hypothesized to explain the decadal ENSO intensity modulation cycle.
A Simple Atmospheric Model of the Local and Teleconnection Responses to Tropical Heating Anomalies
Authors: Lee Sang-Ki , Wang Chunzai , Mapes Brian E.
Published: August 2008

A minimal complexity model of both the local and remote stationary responses of the atmosphere to tropical heating anomalies is described and demonstrated. Two levels are recast as baroclinic and barotropic components with thermal advection in the tropics neglected. The model is linearized about some idealized and realistic background wind fields and forced with a localized heating for illustration. In the tropics, the baroclinic responses are familiar from the Matsuno–Gill model; these excite barotropic responses by advective interactions with vertical background wind shear. The barotropic signals are in turn transmitted to high latitudes only in the presence of barotropic background westerly winds. For an El Niño–like equatorial heating, the barotropic response has anticyclones to the north and south of the heating reinforcing (opposing) the anticyclonic (cyclonic) baroclinic gyres in the upper (lower) troposphere. With realistic background flows, the model reproduces the hemispheric asymmetry of ENSO teleconnections. Further experiments show that the winter hemisphere is favored mainly because the summer hemispheric subtropical jet is farther from the heating latitude, suggesting that the summer hemisphere can still host robust stationary Rossby waves if the heating occurs in the vicinity of the jet. As an example, it is shown that summer heating over the Atlantic warm pool (AWP) can have a remote influence on the summer climate of North America and Europe.
An Evaluation of Calibration Techniques for In Situ Carbon Dioxide Measurements Using a Programmable Portable Trace-Gas Measuring System
Authors: Burns Sean P. , Delany Anthony C. , Sun Jielun , Stephens Britton B. , Oncley Steven P. , Maclean Gordon D. , Semmer Steven R. , Schröter Joel , Ruppert Johannes
Published: August 2008

The construction and deployment of a portable trace-gas measurement system (TGaMS) is described. The air-collection system (dubbed HYDRA) collects air samples from 18 different locations and was connected to either one or two LI-COR LI-7000 gas analyzers to measure CO2. An in situ “field calibration” method, that uses four calibration gases with an uncertainty on the order of ±0.1 μmol mol−1 relative to the WMO CO2 mole fraction scale, revealed CO2 output from the LI-7000 had a slightly nonlinear relationship relative to the CO2 concentration of the calibration gases. The sensitivity of the field-calibrated CO2 to different forms of the field-calibration equation is investigated. To evaluate TGaMS performance, CO2 from collocated inlets, portable gas cylinders, and nearby independent CO2 instruments are compared. Results are as follows: 1) CO2 measurements from HYDRA multiple inlets are feasible with a reproducibility of ±0.4 μmol mol−1 (based on the standard deviation of the CO2 difference between collocated inlets when HYDRA was operating with two LI-7000s); 2) CO2 differences among the various field-calibration equations were on the order of ±0.3 μmol mol−1; and 3) comparison of midday hourly CO2 measurements at 30 m AGL between TGaMS and an independent high-accuracy CO2 measurement system (within 300 m of TGaMS) had a median difference and standard deviation of 0.04 ± 0.81 μmol mol−1 over two months.
Development of a Long-Range Lightning Detection Network for the Pacific: Construction, Calibration, and Performance*
Authors: Pessi Antti T. , Businger Steven , Cummins K. L. , Demetriades N. W. S. , Murphy M. , Pifer B.
Published: August 2008

The waveguide between the earth’s surface and the ionosphere allows very low-frequency (VLF) emissions generated by lightning, called sferics, to propagate over long distances. The new Pacific Lightning Detection Network (PacNet), as a part of a larger long-range lightning detection network (LLDN), utilizes this attribute to monitor lightning activity over the central North Pacific Ocean with a network of ground-based lightning detectors that have been installed on four widely spaced Pacific islands (400–3800 km). PacNet and LLDN sensors combine both magnetic direction finding (MDF) and time-of-arrival (TOA)-based technology to locate a strike with as few as two sensors. As a result, PacNet/LLDN is one of the few observing systems, outside of geostationary satellites, that provides continuous real-time data concerning convective storms throughout a synoptic-scale area over the open ocean.

The performance of the PacNet/LLDN was carefully assessed. Long-range lightning flash detection efficiency (DE) and location accuracy (LA) models were developed with reference to accurate data from the U.S. National Lightning Detection Network (NLDN). Model calibration procedures are detailed, and comparisons of model results with lightning observations from the PacNet/LLDN in correlation with NASA’s Lightning Imaging Sensor (LIS) are presented. The daytime and nighttime flash DE in the north-central Pacific is in the range of 17%–23% and 40%–61%, respectively. The median LA is in the range of 13–40 km. The results of this extensive analysis suggest that the DE and LA models are reasonably able to reproduce the observed performance of PacNet/LLDN.

The implications of this work are that the DE and LA model outputs can be used in quantitative applications of the PacNet/LLDN over the North Pacific Ocean and elsewhere. For example, by virtue of the relationship between lightning and rainfall rates, these data also hold promise as input for NWP models as a proxy for latent heat release in convection. Moreover, the PacNet/LLDN datastream is useful for investigations of storm morphology and cloud microphysics over the central North Pacific Ocean. Notably, the PacNet/LLDN lightning datastream has application for planning transpacific flights and nowcasting of squall lines and tropical storms.
Spectral Partitioning and Identification of Wind Sea and Swell
Authors: Portilla Jesús , Ocampo-Torres Francisco J. , Monbaliu Jaak
Published: August 2008

In this paper, different partitioning techniques and methods to identify wind sea and swell are investigated, addressing both 1D and 2D schemes. Current partitioning techniques depend largely on arbitrary parameterizations to assess if wave systems are significant or spurious. This makes the implementation of automated procedures difficult, if not impossible, to calibrate. To avoid this limitation, for the 2D spectrum, the use of a digital filter is proposed to help the algorithm keep the important features of the spectrum and disregard the noise. For the 1D spectrum, a mechanism oriented to neglect the most likely spurious partitions was found sufficient for detecting relevant spectral features. Regarding the identification of wind sea and swell, it was found that customarily used methods sometimes largely differ from one another. Evidently, methods using 2D spectra and wind information are the most consistent. In reference to 1D identification methods, attention is given to two widely used methods, namely, the steepness method used operationally at the National Data Buoy Center (NDBC) and the Pierson–Moskowitz (PM) spectrum peak method. It was found that the steepness method systematically overestimates swell, while the PM method is more consistent, although it tends to underestimate swell. Consistent results were obtained looking at the ratio between the energy at the spectral peak of a partition and the energy at the peak of a PM spectrum with the same peak frequency. It is found that the use of partitioning gives more consistent identification results using both 1D and 2D spectra.
Automated Processing of Sea Surface Images for the Determination of Whitecap Coverage
Authors: Callaghan Adrian H. , White Martin
Published: August 2008

Sea surface images have been collected to determine the percentage whitecap coverage (W) since the late 1960s. Image processing methods have changed dramatically since the beginning of whitecap studies. An automated whitecap extraction (AWE) technique has been developed at the National University of Ireland, Galway, that allows images to be analyzed for percentage whitecap coverage without the need of a human analyst. AWE analyzes digital images and determines a suitable threshold with which whitecaps can be separated from unbroken background water. By determining a threshold for each individual image, AWE is suitable for images obtained in conditions of changing ambient illumination. AWE is also suitable to process images that have been taken from both stable and nonstable platforms (such as towers and research vessels, respectively). Using techniques based on derivative analysis, AWE provides an objective method to determine an appropriate threshold for the identification of whitecaps in sea surface images without the need for a human analyst. The automated method allows large numbers of images to be analyzed in a relatively short amount of time. AWE can be used to analyze hundreds of images per individual W data point, which produces more convergent values of W.
Elucidating the bonds of workplace humor: A relational process model
Authors: Cooper Cecily
Published: August 2008

A number of studies have demonstrated that humor can impact both horizontal and vertical relationships in organizations, but little is known about the interpersonal processes underlying this link. By integrating theory and research from the fields of philosophy, social psychology, communications, and leadership, it is possible to illuminate a combination of processes which, considered collectively, explain humor's ability to create, maintain, impede, or destroy relationships at work. I first review the classical theories of humor, which explain what motivates individuals to express humor and what determines humor enjoyment. However, since these frameworks focus on humor at the individual-level of analysis, they cannot speak to the social processes involved in a humor exchange. Research in the fields of social psychology, communications, and leadership provides insight regarding the remaining social mechanisms. In sum, it appears that interpersonal humor operates through four related but distinct processes: affect-reinforcement, similarity-attraction, self-disclosure, and hierarchical salience. These social processes are proposed to function in addition to (not in lieu of) the individual-level mechanisms the classical humor theories describe. The discussion, thus, culminates in a relational process model of humor, contributing a more fine-grained understanding of interpersonal humor to the organizational literature.
Intraracial Dynamics of Black Professors’ and Black Students’ Communication in Traditionally White Colleges and Universities
Authors: Moore Penelope J. , Toliver Susan D.
Published: August 2008

While the literature suggests that Black students are more successful in traditionally White colleges and universities when they see professors with whom they can identify, it has been relatively silent about aspects of the relationship between Black professors and Black students that may be perceived as negative. The authors explored the strengths and limitations of this important relationship from the perspectives of Black faculty in six institutions of higher education in New York City and Westchester County, New York. Focus group findings highlighted the unique role of Black faculty members as mentors based on the professors’ subjective perceptions, thoughts, and feelings about mentoring Black students. Equally important, the findings pointed out the need for further research that explores the efficacy of the role of Black professors as mentors from Black students’ perspectives, as well as the implications of such an investigation on Black faculty member and student retention rates.