bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterned metallizations in perfluorosulphonate membranes by printing methods
Authors: Scandurra Antonino , Indelli Giuseppe Francesco , Pignataro Salvatore
Published: January 2012

Patterned thin film electrodes of platinum and silver have been obtained by printing techniques onto sodium perfluorosulphonate membranes to prepare ionic polymer–metal composite actuators. Metal adhesion has been improved by oxygen plasma activation of perfluorosulphonate. Plasma treatment produces oxygen‐containing functional groups at surfaces. Platinum‐patterned electrodes have been obtained by two methods: (i) ink‐jet printing solution of [Pt(NH3)4]++ 2Cl− followed by chemical reduction and (ii) carbon black complementary mask printing followed by platinum complex adsorption and reduction. Silver‐patterned electrodes have been obtained by ink‐jet printing of silver‐based nanoparticles ink sintered at 150 °C, ambient pressure for 1 h. The typical surface resistivity values of patterned electrodes are 5 Ω sq−1 for platinum and 0.5–1 Ω sq−1 for sintered silver, respectively. Perfluorosulphonate with platinum‐ and silver‐patterned electrodes shows electrical stimuli responsivity. Copyright © 2012 John Wiley & Sons, Ltd.
Parental Stress and Satisfaction during Children's Hospitalization: Differences between Immigrant and Autochthonous Population
Authors: Fernández‐Castillo Antonio , Vílchez‐Lara Maria J. , López‐Naranjo Isabel
Published: January 2012

This study explored the relation between parents' stress and satisfaction during children's hospitalization, seeking possible differences between immigrant and autochthonous population and also as a function of gender in a sample of parents of hospitalized children in Andalusia, Spain.

A total of 1347 parents participated in this study. Of the sample, 50% were immigrants and the other 50% were autochthonous. The assessment instruments were the Hospitalization Stress Scale and the Satisfaction with Hospitalization Scale.

The results show that stress was associated with the manifestations of the child's illness, the alteration of family life or of parental roles during the process and some aspects of the clinical staff's work. General satisfaction in immigrant parents was higher than in the autochthonous population and the levels of satisfaction were higher in men than in women.

Small changes and initiatives in relation to care could substantially improve the satisfaction of patients and their relatives during the process of hospitalization. Copyright © 2012 John Wiley & Sons, Ltd.
Characterization of nanoparticles prepared by acid hydrolysis of various starches
Authors: Kim Hee‐Young , Lee Ju Hun , Kim Jong‐Yea , Lim Wang‐Jin , Lim Seung‐Taik
Published: January 2012

Various starches of different AM contents and origins such as wx maize, normal maize, high AM maize, potato, and mungbean starches were hydrolyzed using a H2SO4 solution (3.16 M) at 40°C for 7 days, and the starch particles were isolated from the hydrolysates by centrifugation. The hydrolysis rates varied from 61.4 to 90.9% depending on the starch type. Unexpectedly, A‐type starches were more resistant to the acid hydrolysis than B‐type starches. XRD results revealed that the starch particles with B‐crystalline type exhibited a decrease in peak intensity. In addition, in a DSC analysis, the crystals remaining in the B‐type starch particles were readily disrupted in the water dispersion so that no melting endotherm appeared. Electron microscopy confirmed that the starch particles had round or oval shapes with diameters ranging from 40 to 70 nm, which possibly represented the starch blocklets in granules. The acid degraded mainly AM and long AP chains, resulting in increasing the proportion of short chains.
Drug release mechanisms of hot‐melt extruded starch‐based pellets
Authors: Bialleck Sebastian , Rein Hubert
Published: January 2012

Hot‐melt extrusion with die‐face pelletisation is an excellent technique to continuously produce almost monodisperse spherical starch pellets. For a better understanding of drug release mechanisms from hot‐melt extruded starch‐based pellets the swelling behaviour in the release medium was examined by reflected‐light microscopy. From the microscopic images it can be concluded that the drug release mechanism of wx corn starch pellets is almost solely based on erosion. The release mechanism of corn starch, pea starch and potato starch pellets is primarily a swelling‐based process. Although the release mechanism of a swelling dosage form is theoretically complex, it was found that the fractional drug release from the hot‐melt extruded starch pellets can be described with the Noyes–Whitney equation. This facilitates the evaluation of the influence of the physicochemical properties of the matrix and the chemical properties of the active ingredient on the drug release rate. It was found that pellet size, porosity and velocity with which the penetrant diffuses into the pellet‐core the water solubility of the drug as well as the molecular structure and composition of the starches are the main factors influencing drug release from the swelling starch pellets.
Roles of tRNA in cell wall biosynthesis
Authors: Dare Kiley , Ibba Michael
Published: January 2012

Recent research into various aspects of bacterial metabolism such as cell wall and antibiotic synthesis, degradation pathways, cellular stress, and amino acid biosynthesis has elucidated roles of aminoacyl‐transfer ribonucleic acid (aa‐tRNA) outside of translation. Although the two enzyme families responsible for cell wall modifications, aminoacyl‐phosphatidylglycerol synthases (aaPGSs) and Fem, were discovered some time ago, they have recently become of intense interest for their roles in the antimicrobial resistance of pathogenic microorganisms. The addition of positively charged amino acids to phosphatidylglycerol (PG) by aaPGSs neutralizes the lipid bilayer making the bacteria less susceptible to positively charged antimicrobial agents. Fem transferases utilize aa‐tRNA to form peptide bridges that link strands of peptidoglycan. These bridges vary among the bacterial species in which they are present and play a role in resistance to antibiotics that target the cell wall. Additionally, the formation of truncated peptides results in shorter peptide bridges and loss of branched linkages which makes bacteria more susceptible to antimicrobials. A greater understanding of the structure and substrate specificity of this diverse enzymatic family is necessary to aid current efforts in designing potential bactericidal agents. These two enzyme families are linked only by the substrate with which they modify the cell wall, aa‐tRNA; their structure, cell wall modification processes and the physiological changes they impart on the bacterium differ greatly. WIREs RNA 2012, 3:247–264. doi: 10.1002/wrna.1108

This article is categorized under:

RNA Interactions with Proteins and Other Molecules > Small Molecule–RNA Interactions

RNA Processing > tRNA Processing

RNA in Disease and Development > RNA in Disease
Partial Pathologic Response and Nodal Status as Most Significant Prognostic Factors for Advanced Rectal Cancer Treated With Preoperative Chemoradiotherapy
Authors: Huebner Marianne , Wolff Bruce G. , Smyrk Thomas C. , Aakre Jeremiah , Larson David W.
Published: January 2012

Background

This study evaluated the impact of tumor regression grading (TRG) and other pathologic variates in a cohort of rectal carcinoma patients treated with neoadjuvant chemoradiotherapy (CRT). The value of a grading less than pCR for predicting survival is unknown. Tumor budding has not been systematically studied in rectal cancer after neoadjuvant therapy.

Methods

Pathologic risk factors for survival were evaluated on surgical specimens of 237 patients with stages I, II, and III rectal cancer treated between 1996 and 2006. All patients underwent preoperative CRT followed by surgical resection 6–8 weeks later. TRG, tumor grade, budding, venous invasion, radial margin, and nodal status were evaluated. The prognostic value of TRG categories was calculated with Cox regression models and validated with resampling methods.

Results

TRG of <25% occurred in 61 (25.7%) and a complete response in 39 (16.4%) of the resected specimens. TRG of <25% was shown to be a statistically significant predictor for cancer‐specific survival (CSS) and recurrence‐free survival (RFS) compared to TRG ≥25% (P = 0.013). Tumor budding was present in 24 (10.1%) of the patients and was negatively associated with CSS (P = 0.013). Lymph node involvement was observed in 83 (35.0%) patients. TRG and nodal status (P < 0.001) were the most significant predictors associated with outcome.

Conclusion

Partial pathologic response ≥25% was a superior predictor compared to pCR for improved survival after preoperative CRT. CSS and RFS were adversely affected by the presence of lymph node metastases.
‘TATA MA CHANCE’: ON CONTINGENCY AND THE LOTTERY IN POST-APARTHEID SOUTH AFRICA
Authors: van Wyk Ilana
Published: January 2012

Since its inception in March 2000, the South African National Lottery has been treated as both a developmental boon and a dangerously exploitative new consumer product. In both discourses the poor feature prominently: as recipients of Lotto largesse and as its most frequent victims. Both academics and the National Responsible Gambling Programme have traced the poor's participation in the Lottery to their financial illiteracy and to their extraordinary millennial hopes. Based on twenty months of ethnographic fieldwork in Cape Town's townships in 2008–10, this article puts paid to such interpretations by looking at the economic realities and lottery participation of ‘the poor’. I contend that poor people in these areas have adapted enormously flexible ways of dealing with the multiple contingencies that mark their lives. This flexibility often translates into very modest investments in the Lottery, both financially and in terms of hope. As such, playing the Lottery is just one of a range of ways in which people ‘make a plan’ and ‘tata ma chance’ (take a chance).
Überprüfung des revidierten Trainings zur Förderung der Lesekompetenz und der Lesemotivation (LekoLemo) für die Sekundarstufe I
Authors: Streblow Lilian , Schiefele Ulrich , Riedel Stefanie
Published: January 2012

Zusammenfassung. Angeregt durch die Befunde der PISA-Studie und auf der Basis bisheriger Förderprogramme wurde das Lesetraining LekoLemo (Programm zur Förderung der LEseKOmpetenz und LEseMOtivation) für Schüler der 7. Jahrgangsstufe entwickelt. Das Training unterscheidet sich von bereits existierenden Lesetrainings vor allem durch zwei Aspekte: (1) Es umfasst Aufgaben zu den in der PISA-Studie verwendeten Dimensionen des Lesens Informationen ermitteln, textbezogenes Interpretieren sowie Reflektieren und Bewerten und (2) beinhaltet eine explizite Förderung der Lesemotivation. Die vorliegende Studie überprüfte das revidierte LekoLemo-Training anhand einer Stichprobe von 235 Siebtklässlern. Die Ergebnisse belegen die Wirksamkeit des Trainings und zeigen signifikante Effekte geringer bis mittlerer Größe auf die Lesekompetenz im Follow-up-Test. Demgegenüber erwiesen sich die Effekte auf die intrinsische Lesemotivation und das Selbstkonzept nicht nur als niedrig, sondern auch als nicht nachhaltig.
Vorschulische Förderung der phonologischen Bewusstheit bei Kindern mit Deutsch als Zweitsprache
Authors: Souvignier Elmar , Duzy Dagmar , Glück Daniela , Pröscholdt Marie V. , Schneider Wolfgang
Published: January 2012

Zusammenfassung. Vorschulische Sprachförderung kann insbesondere für Kinder mit Migrationshintergrund eine wichtige Unterstützung auf dem Weg zum Erwerb der Schriftsprache darstellen. Vor dem Hintergrund von Transfertheorien wird dabei diskutiert, ob muttersprachliche (L1) Fördermaßnahmen möglicherweise empfehlenswerter sind als Programme in der Zweitsprache (L2). In einer Stichprobe von 89 Kindern im Alter von 5;8 Jahren mit einem türkischen Migrationshintergrund wurden daher die Effekte eines muttersprachlichen und eines deutschsprachigen Programms zur Förderung sprachlicher und metasprachlicher Fähigkeiten untersucht. Dabei zeigte sich, dass die jeweils zwei Monate umfassenden Förderungen zu vergleichbaren Verbesserungen in der phonologischen Bewusstheit führten – sowohl in türkischer als auch in deutscher Sprache. Diese Effekte erwiesen sich zudem als unabhängig davon, ob die häusliche Umgangssprache ausschließlich Türkisch oder Deutsch und Türkisch war.
Simulation of a sea ice ecosystem using a hybrid model for slush layer desalination
Authors: Saenz Benjamin T. , Arrigo Kevin R.
Published: January 2012

Porous, slushy layers are a common feature of Antarctic sea ice and are often colonized by high concentrations of algae. Despite its potential importance to the physics and biogeochemistry of the sea ice ecosystem, current knowledge of the evolution of sea ice slush layers is limited. Here we present a model of sea ice that is capable of reproducing the vertical biophysical evolution of sea ice that contains slush layers. The model uses a novel hybrid desalination scheme to calculate salt fluxes and brine motion during freezing using one of two different methods depending on the brine fraction of the ice. Model runs using atmospheric and snow depth forcing from the Ice Station Weddell experiment show that model is able to simulate the magnitude and timing of sea ice temperature, salinity, and associated algal growth of observed slush layers, as well as the surrounding sea ice. The model was designed with regional‐scale simulations in mind and we show that the model performs well at lower vertical resolutions, as long as the slush layer is resolved. Incorporation of our model of slush ice desalination into regional and global simulations has potential to improve model estimates of salt, heat, and biochemical fluxes in polar marine environments.
Early Alterations of the Immune Transcriptome in Cultured Progenitor Cells From Obese African‐American Women
Authors: Pemu Priscilla E. , Anderson Leonard , Gee Beatrice E. , Ofili Elizabeth O. , Ghosh Sujoy
Published: January 2012

Progenitor cells (PCs) are key components of vasculogenic remodeling and hematopoietic development. Decreases in the number and function of angiogenic progenitors have been observed in coronary artery disease, hypertension, and diabetic vasculopathy. Several recent studies have also demonstrated a close relationship between increased visceral fat and cardiovascular disease, implying an association between obesity and vascular dysfunction. However, very little is known about the role of PCs in obesity. We generated whole genome expression profiles of cultured PCs from 18 obese and 6 lean African‐American women on Agilent microarrays and analyzed the data through bioinformatic pathway analysis using multiple databases and analytic tools. False‐discovery rates (FDR) were calculated to assess statistical significance while controlling for multiple testing. We identified 1,145 upregulated and 2,257 downregulated genes associated with obesity (1.5‐fold or greater absolute fold‐change). Pathway analysis further identified a statistically significant downregulation of immune‐response pathways in the obese subjects, including T‐cell receptor signaling, natural killer cell signaling, and chemokine‐signaling pathways (FDR <5%). Chemokine gene‐expression patterns were consistent with an angiogenic‐angiostatic imbalance and a downregulation of CXCR3 receptor‐mediated signaling in the PCs from obese subjects. Overall, these findings reveal a novel transcriptional signature in cultured PCs from obese African‐American women and further suggest that obesity‐associated immune‐compromise may originate much earlier in cellular development than currently appreciated. Clinically, this may translate into a lengthier period of immune dysregulation in obese subjects exposing them to greater risks of infection and other morbidities.
From parathyroid hormone to cytosolic Ca2+ signals
Authors: Taylor Colin W. , Tovey Stephen C.
Published: January 2012

PTHR1 (type 1 parathyroid hormone receptors) mediate the effects of PTH (parathyroid hormone) on bone remodelling and plasma Ca2+ homoeostasis. PTH, via PTHR1, can stimulate both AC (adenylate cyclase) and increases in [Ca2+]i (cytosolic free Ca2+ concentration), although the relationship between the two responses differs between cell types. In the present paper, we review briefly the mechanisms that influence coupling of PTHR1 to different intracellular signalling proteins, including the G-proteins that stimulate AC or PLC (phospholipase C). Stimulus intensity, the ability of different PTH analogues to stabilize different receptor conformations (‘stimulus trafficking’), and association of PTHR1 with scaffold proteins, notably NHERF1 and NHERF2 (Na+/H+ exchanger regulatory factor 1 and 2), contribute to defining the interactions between signalling proteins and PTHR1. In addition, cAMP itself can, via Epac (exchange protein directly activated by cAMP), PKA (protein kinase A) or by binding directly to IP3Rs [Ins(1,4,5)P3 receptors] regulate [Ca2+]i. Epac leads to activation of PLCϵ, PKA can phosphorylate and thereby increase the sensitivity of IP3Rs and L-type Ca2+ channels, and cAMP delivered at high concentrations to IP3R2 from AC6 increases the sensitivity of IP3Rs to InsP3. The diversity of these links between PTH and [Ca2+]i highlights the versatility of PTHR1. This versatility allows PTHR1 to evoke different responses when stimulated by each of its physiological ligands, PTH and PTH-related peptide, and it provides scope for development of ligands that selectively harness the anabolic effects of PTH for more effective treatment of osteoporosis.
cAMP measurements with FRET-based sensors in excitable cells
Authors: Everett Katy L. , Cooper Dermot M.F.
Published: January 2012

The development of FRET (fluorescence resonance energy transfer)-based sensors for measuring cAMP has opened the door to sophisticated insights into single-cell cAMP dynamics. cAMP can be measured in distinct cell populations and even in distinct microdomains within cells. However, there is still only limited information on cAMP dynamics in excitable cells, particularly as a function of the activity of voltage-gated Ca2+ channels. A major reason for this is the pH shifts that can occur in excitable cells and their effects on fluorescent proteins.
Putative roles for phospholipase Cη enzymes in neuronal Ca2+ signal modulation
Authors: Popovics Petra , Stewart Alan J.
Published: January 2012

The most recently identified PLC (phospholipase C) enzymes belong to the PLCη family. Their unique Ca2+-sensitivity and their specific appearance in neurons have attracted great attention since their discovery; however, their physiological role(s) in neurons are still yet to be established. PLCη enzymes are expressed in the neocortex, hippocampus and cerebellum. PLCη2 is also expressed at high levels in pituitary gland, pineal gland and in the retina. Driven by the specific localization of PLCη enzymes in different brain areas, in the present paper, we discuss the roles that they may play in neural processes, including differentiation, memory formation, circadian rhythm regulation, neurotransmitter/hormone release and the pathogenesis of neurodegenerative disorders associated with aberrant Ca2+ signalling, such as Alzheimer's disease.
Regulation of signalling by microRNAs
Authors: Avraham Roi , Yarden Yosef
Published: January 2012

Stringent regulation of biochemical signalling pathways involves feedback and feedforward loops, which underlie robust cellular responses to external stimuli. Regulation occurs in all horizontal layers of signalling networks, primarily by proteins that mediate internalization of receptor–ligand complexes, dephosphorylation of kinases and their substrates, as well as transcriptional repression. Recent studies have unveiled the role of miRNAs (microRNAs), post-transcriptional regulators that control mRNA stability, as key modulators of signal propagation. By acting as genetic switches or fine-tuners, miRNAs can directly and multiply regulate cellular outcomes in response to diverse extracellular signals. Conversely, signalling networks temporally control stability, biogenesis and abundance of miRNAs, by regulating layers of the miRNA biogenesis pathway. In the present mini-review, we use a set of examples to illustrate the extensive interdependence between miRNAs and signalling networks.
Protein kinase D in the hypertrophy pathway
Authors: Sin Yuan Yan , Baillie George S.
Published: January 2012

Chronic neurohormonal stimulation can have direct adverse effects on the structure and function of the heart. Heart failure develops and progresses as a result of the deleterious changes. It is well established that phosphorylation of class II HDAC5 (histone deacetylase 5) is an important event in the transcriptional regulation of cardiac gene reprogramming that results in the hypertrophic growth response. To date, experimentation on phosphorylation-mediated translocation of HDAC5 has focused on the regulatory properties of PKD (protein kinase D) within intact cells. With regard to the potential role of PKD in myocardium, recent observations raise the possibility that PKD-mediated myocardial regulatory mechanisms may represent promising therapeutic avenues for the treatment of heart failure. The present review summarizes the most recent and important insights into the role of PKD in hypertrophic signalling pathways.
DNA double-strand break repair within heterochromatic regions
Authors: Murray Johanne M. , Stiff Tom , Jeggo Penny A.
Published: January 2012

DNA DSBs (double-strand breaks) represent a critical lesion for a cell, with misrepair being potentially as harmful as lack of repair. In mammalian cells, DSBs are predominantly repaired by non-homologous end-joining or homologous recombination. The kinetics of repair of DSBs can differ widely, and recent studies have shown that the higher-order chromatin structure can dramatically affect the pathway utilized, the rate of repair and the genetic factors required for repair. Studies of the repair of DSBs arising within heterochromatic DNA regions have provided insight into the constraints that higher-order chromatin structure poses on repair and the processing that is uniquely required for the repair of such DSBs. In the present paper, we provide an overview of our current understanding of the process of heterochromatic DSB repair in mammalian cells and consider the evolutionary conservation of the processes.
Growth and metabolic control of lipid signalling at the Golgi
Authors: Piao Hailan , Mayinger Peter
Published: January 2012

PtdIns4P is a key regulator of the secretory pathway and plays an essential role in trafficking from the Golgi. Our recent work demonstrated that spatial control of PtdIns4P at the ER (endoplasmic reticulum) and Golgi co-ordinates secretion with cell growth. The central elements of this regulation are specific phosphoinositide 4-kinases and the phosphoinositide phosphatase Sac1. Growth-dependent translocation of Sac1 between the ER and Golgi modulates the levels of PtdIns4P and anterograde traffic at the Golgi. In yeast, this mechanism is largely dependent on the availability of glucose, but our recent results in mammalian cells suggest that Sac1 phosphatases play evolutionarily conserved roles in the growth control of secretion. Sac1 lipid phosphatase plays also an essential role in the spatial control of PtdIns4P at the Golgi complex. A restricted pool of PtdIns4P at the TGN (trans-Golgi network) is required for Golgi integrity and for proper lipid and protein sorting. In mammalian cells, the stress-activated MAPK (mitogen-activated protein kinase) p38 appears to play a critical role in transmitting nutrient signals to the phosphoinositide signalling machinery at the ER and Golgi. These results suggest that temporal and spatial integration of metabolic and lipid signalling networks at the Golgi is required for controlling the secretory pathway.
cGMP–cAMP interplay in cardiac myocytes: a local affair with far-reaching consequences for heart function
Authors: Stangherlin Alessandra , Zaccolo Manuela
Published: January 2012

cAMP and cGMP signalling pathways are common targets in the pharmacological treatment of heart failure, and often drugs that modulate the level of these second messengers are simultaneously administered to patients. cGMP can potentially affect cAMP levels by modulating the activity of PDEs (phosphodiesterases), the enzymes that degrade cyclic nucleotides. This biochemical cross-talk provides the means for drugs that increase cGMP to concomitantly affect cAMP signals. Recent studies using FRET (fluorescence resonance energy transfer) reporters and real-time imaging show that, in cardiac myocytes, the interplay between cGMP and cAMP has different outcomes depending on the specific location where the cross-modulation occurs. cGMP can either increase or decrease the cAMP response to catecholamines, based on the cyclase that generates it and on the PDEs associated with each subcellular compartment. cGMP-mediated modulation of cAMP signals has functional relevance as it affects protein phosphorylation downstream of protein kinase A and myocyte contractility. The physical separation of positive and negative modulation of cAMP levels by cGMP offers the previously unrecognized possibility to selectively modulate local cAMP signals to improve the efficacy of therapy.
Human epidermal growth factor receptor (HER1) aligned on the plasma membrane adopts key features of Drosophila EGFR asymmetry
Authors: Martin-Fernandez Marisa L.
Published: January 2012

Current models suggest that ligand-binding heterogeneity in HER1 [human EGFR (epidermal growth factor receptor] arises from negative co-operativity in signalling HER1 dimers, for which the asymmetry of the extracellular region of the Drosophila EGFR has recently provided a structural basis. However, no asymmetry is apparent in the current crystal structure of the isolated extracellular region of HER1. This receptor also differs from the Drosophila EGFR in that negative co-operativity is found only in full-length receptors in cells. Structural insights into HER1 in epithelial cells, derived from FLIM (fluorescence lifetime imaging microscopy) and two-dimensional FRET (Förster resonance energy transfer) combined with Monte Carlo and molecular dynamics simulations, have demonstrated a high-affinity ligand-binding HER1 conformation consistent with the extracellular region aligned flat on the plasma membrane. This conformation shares key features with that of the Drosophila EGFR, suggesting that the structural basis for negative co-operativity is conserved from invertebrates to humans, but that, in HER1, the extracellular region asymmetry requires interactions with the plasma membrane.
The regulatory role of the juxtamembrane region in the activity of the epidermal growth factor receptor
Authors: Boran Aislyn D.W.
Published: January 2012

Although the EGFR (epidermal growth factor receptor) was discovered over 30 years ago, its mechanism of activation is still the subject of intense study. There are many published studies on the mechanism of EGFR activation and regulation, including biochemical and biophysical analyses and crystallographic structures of EGFR in different activation states and conformations, mutated at various amino acids or bound to different pharmacological inhibitors. The cumulative biochemical, biophysical and structural data have led to a nearly complete account of the mechanism of activation of EGFR. The role of the JXM (juxtamembrane) domain in EGFR structure and activity has only recently begun to be elucidated through biochemical, biophysical and structural studies. In the present article, I review the studies that have highlighted the role of the JXM domain in EGFR activation.
Absorption spectroscopy measurements of argon metastable and resonant atom density in atmospheric pressure Ar-He surface-wave plasmas using a low pressure lamp
Authors: Muñoz J. , Margot J. , Calzada M. D.
Published: January 2012

The densities of metastable and resonant atom were measured in atmospheric pressure Ar-He surface-wave plasmas. Measurements were performed using an absorption spectroscopy method taking into account the Voigt profiles of the plasma lines. The density values of the argon 3P2, 3P0 (metastable atoms) and 3P1 (resonant atoms) levels measured in pure argon discharges are in good agreement with those reported in the literature. A drastic decrease of metastable and resonant densities is observed when introducing helium in amounts as low as 2%. The influence of electron density and gas temperature on the population mechanisms (direct electron excitation from the ground state and dissociative recombination) of metastable and resonant atoms is discussed using a simplified theoretical model.
Soliton cellular automaton associated with $G_2^{(1)}$G2(1) crystal base
Authors: Misra Kailash C. , Okado Masato , Wilson Evan A.
Published: January 2012

We calculate the combinatorial R matrix for all elements of $\mathcal {B}_l\otimes \mathcal {B}_1$Bl⊗B1 where $\mathcal {B}_l$Bl denotes the $G_2^{(1)}$G2(1)-perfect crystal of level l, and then study the soliton cellular automaton constructed from it. The solitons of length l are identified with elements of the $A_1^{(1)}$A1(1)-crystal $\tilde{\mathcal {B}}_{3l}$B̃3l. The scattering rule for our soliton cellular automaton is identified with the combinatorial R matrix for $A_1^{(1)}$A1(1)-crystals.
Influence of plasma loss area on transport of charged particles through a transverse magnetic field
Authors: Das B. K. , Bandyopadhyay M. , Chakraborty M.
Published: January 2012

Plasma transport in a double plasma device from the source region to the target region through a physical window comprising of electrically grounded magnet channels (filled with permanent magnet bars) for transverse magnetic field (TMF) and a pair of stainless steel (SS) plates is studied and presented in this manuscript. The study has relevance in negative ion source research and development where both TMF created by magnet channels and bias plate are used. The experiment is performed in two stages. In the first stage, a TMF is introduced between the two regions along with the SS plates, and corresponding plasma parameter data in the two regions are recorded by changing the distance between the TMF channels. In the second stage, the TMF is withdrawn from the system, and corresponding data are taken by changing the separation between the SS plates. The experimental results are then compared with a theoretical model. In the presence of TMF, where electrons are magnetized and ions are un-magnetized, it is observed that plasma transport perpendicular to the TMF is dominated by the ambipolar diffusion of ions. In the absence of TMF, plasma is un-magnetized, and plasma transport through the SS window aperture is almost independent of open area of the SS window.
Measurement of insulating and dielectric properties of acrylic elastomer membranes at high electric fields
Authors: Di Lillo L. , Schmidt A. , Carnelli D. A. , Ermanni P. , Kovacs G. , Mazza E. , Bergamini A.
Published: January 2012

This work reports on the investigation of VHB 4910 acrylic elastomer insulating and dielectric properties. This material is widely exploited for the realization of actuators with large deformations, dielectric elastomer actuators (DEA), and belongs to the group of so-called electroactive polymers (EAP). Extensive investigations concerning its mechanical properties are available in literature while its electric behavior at working conditions has not received the same level of attention. In this work, the relative permittivity and the volume resistivity have been measured on VHB 4910 membranes under different fixed stretch conditions (λ1, λ2 = 3, 3.6, 4, 5) using circular gold electrodes sputtered onto both sides of the specimens. The measured values of relative permittivity are in fairly good agreement with the results previously published by other groups. The volume resistivity, at field values close to the operational ones, has shown a field-dependent behavior revealing dissipative properties that should be considered in real applications. Further, measurements on circular actuators verify these findings. Consequences for modeling of VHB 4910 are drawn and new material model parameters proposed to account for the value of relative permittivity at high electric fields.
Electrochemical behavior of LiNi1−y−zCoyMnzO2 probed through structural and magnetic properties
Authors: Dahbi Mohammed , Wikberg J. Magnus , Saadoune Ismael , Gustafsson Torbjörn , Svedlindh Peter , Edström Kristina
Published: January 2012

We have investigated LixNi1−y−zCoyMnzO2 compounds with y = 1/3, 0.25, 0.2, 0.1 and z = 1/3, 0.2, 0.1, 0.05 in order to study the influence of Ni and Mn concentration, cationic disorder, and crystallite size on the magnetic and charge/discharge behavior. The samples have been studied by means of x-ray diffraction, scanning electron microscopy, voltammetry, cycling capacity, and magnetometry. The discharge capacity increases with increasing Ni concentration as does the number of ferromagnetic interactions. With higher Mn concentration a higher capacity is observed together with formation of strong antiferromagnetic interactions driving the magnetic frustration to lower temperatures. Our results show that for sufficiently low Co concentrations a stable and magnetically more ordered structure can be obtained with excellent electrochemical properties, although a relatively large amount of Ni is present.
Activation energy for a model ferrous-ferric half reaction from transition path sampling
Authors: Drechsel-Grau Christof , Sprik Michiel
Published: January 2012

Activation parameters for the model oxidation half reaction of the classical aqueous ferrous ion are compared for different molecular simulation techniques. In particular, activation free energies are obtained from umbrella integration and Marcus theory based thermodynamic integration, which rely on the diabatic gap as the reaction coordinate. The latter method also assumes linear response, and both methods obtain the activation entropy and the activation energy from the temperature dependence of the activation free energy. In contrast, transition path sampling does not require knowledge of the reaction coordinate and directly yields the activation energy [C. Dellago and P. G. Bolhuis, Mol. Simul. 30, 795 (2004)10.1080/08927020412331294869]. Benchmark activation energies from transition path sampling agree within statistical uncertainty with activation energies obtained from standard techniques requiring knowledge of the reaction coordinate. In addition, it is found that the activation energy for this model system is significantly smaller than the activation free energy for the Marcus model, approximately half the value, implying an equally large entropy contribution.
Note: Phase sensitive detection of photoluminescence with Fourier transform spectroscopy
Authors: Ullrich B. , Brown G. J.
Published: January 2012

Although known for more than twenty years, there is limited information in the literature regarding the experimental parameters of lock-in based phase sensitive emission detection in conjunction with Fourier spectrometers. For this technique – also known as double modulation spectroscopy – we present a guideline for parameter optimization by measuring the photoluminescence of InSb:Te at cryogenic temperatures.
Experimental determination of current spill-over and its effect on the efficiency droop in InGaN/GaN blue-light-emitting-diodes
Authors: Ahn Byung-Jun , Kim Tae-Soo , Dong Yanqun , Hong Moon-Taek , Song Jung-Hoon , Song Jae-Ho , Yuh Hwan-Kuk , Choi Sung-Chul , Bae Duk-Kyu , Moon Youngboo
Published: January 2012

We report the experimental determination of current spill-over in InGaN/GaN blue light emitting diodes by measuring the change in the forward current generated by a resonant excitation. To quantify accurately, the absorption of the laser as a function of the forward current was also determined. Two samples that have clearly different behavior of efficiency droop were compared to clarify the relationship between the current spill-over and the efficiency droop. We conclude that the carrier spill-over does occur and can be a significant cause for the efficiency droop but cannot single-handedly account for the efficiency droop.
Double-waveguide quantum cascade laser
Authors: Blanchard Romain , Grezes Cécile , Menzel Stefan , Pflügl Christian , Diehl Laurent , Huang Yong , Ryou Jae-Hyun , Dupuis Russell D. , Capasso Federico
Published: January 2012

We demonstrate 1.1 W peak power at room-temperature from a double-waveguide quantum cascade laser (QCL) grown by metal-organic chemical vapor deposition. Two full broadband QCL active regions were grown on top of each other separated by thick cladding layers to reduce gain competition. Simultaneous lasing on Fabry-Perot modes separated by as much as 360 cm−1 is obtained. This design paves the way for high-brightness broadband mid-infrared sources, as well as more complex three-terminal devices.
Probing transconductance spatial variations in graphene nanoribbon field-effect transistors using scanning gate microscopy
Authors: Soudi A. , Aivazian G. , Shi S.-F. , Xu X. D. , Gu Y.
Published: January 2012

We have used scanning gate microscopy to probe local transconductance in graphene nanoribbon (GNR) field-effect transistors (FETs) fabricated from chemical vapor deposition-grown graphene. Particularly, nanometer-scale (≤100 nm, resolution limited) areas characterized by significant transconductance spatial variations were observed along the FET channel. These were attributed to the impurities at or close to the edges of the GNRs. Our results further show that a single such impurity site in a long-channel (∼2 μm) GNR FET can essentially control the global device characteristics. This finding demonstrates the importance of controlling the spatial inhomogeneity of electronic properties in graphene and related nanostructures in order to realize their envisioned applications in new electronics.
Improvement of hole injection and electron overflow by a tapered AlGaN electron blocking layer in InGaN-based blue laser diodes
Authors: Yang Wei , Li Ding , Liu Ningyang , Chen Zhao , Wang Lei , Liu Lei , Li Lei , Wan Chenghao , Chen Weihua , Hu Xiaodong , Du Weimin
Published: January 2012

We studied the influence of a tapered AlGaN electron blocking layer (EBL) with step-graded aluminum composition on hole injection and electron overflow effects in InGaN-based laser diodes (LDs) theoretically. Schrödinger-Poisson self-consistent method together with transfer matrix method was applied to calculate carrier distribution and transport properties for both electrons and holes in tapered EBL and conventional EBL. The results indicate that the new structure favors the tunneling of low energy holes from the p-side to the active region. Meanwhile, more uniform carrier distribution and better balance between electrons and holes are obtained for the tapered structure by proper modification of band diagrams. An advanced device simulation shows the elimination of electron overflow even at a current of 180 mA in the LD with tapered EBL. Decrease of threshold current density from 2.0 kA/cm2 to 1.6 kA/cm2 is benefited from the more uniform local gain profile.
Communication: The rotational excitation of D2 by H: On the importance of the reactive channels
Authors: Lique François , Faure Alexandre
Published: January 2012

We report fully-quantum time-independent calculations of cross sections and rate coefficients for the collisional excitation and dissociation of D2 by H, two astrophysically relevant processes. Our calculations are based on the recent H3 global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)10.1063/1.1432319]. Results of exact three-dimensional calculations, i.e., including the reactive channels, are compared to pure inelastic two-dimensional calculations based on the rigid rotor approximation. A reasonable agreement is found between the two sets of inelastic cross sections over the whole energy range 10–9000 cm−1. At the highest collisional energies, where the reactive channels are significant, the rigid rotor approach slightly overestimates the cross sections, as expected. At moderate collisional energies, however, the opposite behaviour is observed. The rigid rotor approach is found to be reliable at temperatures below ∼500 K, with a significant but moderate contribution from reactive channels
Squeeze-and-breathe evolutionary Monte Carlo optimization with local search acceleration and its application to parameter fitting
Authors: Beguerisse-Díaz Mariano , Wang Baojun , Desikan Radhika , Barahona Mauricio
Published: January 2012

Estimating parameters from data is a key stage of the modelling process, particularly in biological systems where many parameters need to be estimated from sparse and noisy datasets. Over the years, a variety of heuristics have been proposed to solve this complex optimization problem, with good results in some cases yet with limitations in the biological setting. In this work, we develop an algorithm for model parameter fitting that combines ideas from evolutionary algorithms, sequential Monte Carlo and direct search optimization. Our method performs well even when the order of magnitude and/or the range of the parameters is unknown. The method refines iteratively a sequence of parameter distributions through local optimization combined with partial resampling from a historical prior defined over the support of all previous iterations. We exemplify our method with biological models using both simulated and real experimental data and estimate the parameters efficiently even in the absence ofa prioriknowledge about the parameters.
Drosophilapoly suggests a novel role for the Elongator complex in insulin receptor–target of rapamycin signalling
Authors: Bolukbasi Ekin , Vass Sharron , Cobbe Neville , Nelson Bryce , Simossis Victor , Dunbar Donald R. , Heck Margarete M. S.
Published: January 2012

Multi-cellular organisms need to successfully link cell growth and metabolism to environmental cues during development. Insulin receptor–target of rapamycin (InR–TOR) signalling is a highly conserved pathway that mediates this link. Herein, we describepoly, an essential gene inDrosophilathat mediates InR–TOR signalling. Loss ofpolyresults in lethality at the third instar larval stage, but only after a stage of extreme larval longevity. Analysis inDrosophilademonstrates that Poly and InR interact and thatpolymutants show an overall decrease in InR–TOR signalling, as evidenced by decreased phosphorylation of Akt, S6K and 4E-BP. Metabolism is altered inpolymutants, as revealed by microarray expression analysis and a decreased triglyceride : protein ratio in mutant animals. Intriguingly, the cellular distribution of Poly is dependent on insulin stimulation in bothDrosophilaand human cells, moving to the nucleus with insulin treatment, consistent with a role in InR–TOR signalling. Together, these data reveal that Poly is a novel, conserved (from flies to humans) mediator of InR signalling that promotes an increase in cell growth and metabolism. Furthermore, homology to small subunits of Elongator demonstrates a novel, unexpected role for this complex in insulin signalling.
Altered receptor specificity and fusion activity of the haemagglutinin contribute to high virulence of a mouse-adapted influenza A virus
Authors: Koerner Iris , Matrosovich Mikhail N. , Haller Otto , Staeheli Peter , Kochs Georg
Published: January 2012

The viral haemagglutinin (HA) and the viral polymerase complex determine the replication fitness of a highly virulent variant of influenza A virus strain A/PR/8/34 (designated hvPR8) and its high pathogenicity in mice. We report here that the HA of the hvPR8 differs from the HA of a low virulent strain (lvPR8) by the efficiency of receptor binding and membrane fusion. hvPR8 bound to 2,6-linked as well as 2,3-linked sialic acid-containing receptors, whereas lvPR8 bound exclusively to 2,3-linked sialic acids with high avidity. Remarkably, hvPR8 infected its target cells faster than lvPR8 and tolerated an elevated pH for efficient membrane fusion. In spite of these differences, both viruses targeted type II but not type I pneumocytes in the lung of infected mice. The HA of hvPR8 differs from that of lvPR8 by 16 aa substitutions and one insertion. Mutational analyses revealed that amino acid at HA position 190 (H3 numbering) primarily determined the specificity of receptor binding, while the insertion at position 133 influenced the avidity of receptor binding. Both amino acid positions also strongly influenced viral virulence. Furthermore, leucine at position 78 and glutamine at position 354 were critical determinants of increased fusion activity and virulence of hvPR8. Our data suggest that the HA of hvPR8 enhances virulence by mediating optimal receptor binding and membrane fusion thereby promoting rapid and efficient viral entry into host cells.
Human cytomegalovirus transcriptome activity differs during replication in human fibroblast, epithelial and astrocyte cell lines
Authors: Towler James C. , Ebrahimi Bahram , Lane Brian , Davison Andrew J. , Dargan Derrick J.
Published: January 2012

Broad cell tropism contributes to the pathogenesis of human cytomegalovirus (HCMV), but the extent to which cell type influences HCMV gene expression is unclear. A bespoke HCMV DNA microarray was used to monitor the transcriptome activity of the low passage Merlin strain of HCMV at 12, 24, 48 and 72 h post-infection, during a single round of replication in human fetal foreskin fibroblast cells (HFFF-2s), human retinal pigmented epithelial cells (RPE-1s) and human astrocytoma cells (U373MGs). In order to correlate transcriptome activity with concurrent biological responses, viral cytopathic effect, growth kinetics and genomic loads were examined in the three cell types. The temporal expression pattern of viral genes was broadly similar in HFFF-2s and RPE-1s, but dramatically different in U373MGs. Of the 165 known HCMV protein-coding genes, 41 and 48 were differentially regulated in RPE-1s and U373MGs, respectively, compared with HFFF-2s, and 22 of these were differentially regulated in both RPE-1s and U373MGs. In RPE-1s, all differentially regulated genes were downregulated, but, in U373MGs, some were down- and others upregulated. Differentially regulated genes were identified among the immediate-early, early, early late and true-late viral gene classes. Grouping of downregulated genes according to function at landmark stages of the replication cycle led to the identification of potential bottleneck stages (genome replication, virion assembly, and virion maturation and release) that may account for cell type-dependent viral growth kinetics. The possibility that cell type-specific differences in expressed cellular factors are responsible for modulation of viral gene expression is discussed.
Discovery of drugs that possess activity against feline leukemia virus
Authors: Greggs Willie M. , Clouser Christine L. , Patterson Steven E. , Mansky Louis M.
Published: January 2012

Feline leukemia virus (FeLV) is a gammaretrovirus that is a significant cause of neoplastic-related disorders affecting cats worldwide. Treatment options for FeLV are limited, associated with serious side effects, and can be cost-prohibitive. The development of drugs used to treat a related retrovirus, human immunodeficiency virus type 1 (HIV-1), has been rapid, leading to the approval of five drug classes. Although structural differences affect the susceptibility of gammaretroviruses to anti-HIV drugs, the similarities in mechanism of replication suggest that some anti-HIV-1 drugs may also inhibit FeLV. This study demonstrates the anti-FeLV activity of four drugs approved by the US FDA (Food and Drug Administration) at non-toxic concentrations. Of these, tenofovir and raltegravir are anti-HIV-1 drugs, while decitabine and gemcitabine are approved to treat myelodysplastic syndromes and pancreatic cancer, respectively, but also have anti-HIV-1 activity in cell culture. Our results indicate that these drugs may be useful for FeLV treatment and should be investigated for mechanism of action and suitability for veterinary use.