bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibitory effects of iron on bone morphogenetic protein 2–induced osteoblastogenesis
Authors: Yang Qing , Jian Jinlong , Abramson Steven B , Huang Xi
Published: February 2011

Postmenopausal osteoporosis is characterized by an imbalance of bone resorption exceeding bone formation, resulting in a net loss of bone mineral density (BMD). Estrogen deficiency is known to promote bone resorption. However, the causative factors that impair bone formation have not been identified. Women after menopause experience not only estrogen deficiency but also iron accumulation as a result of cessation of menstruation. In this study we investigated whether increased iron plays a role in osteoporosis. By growing primary mouse osteoclast and osteoblast progenitor cells as well as immortalized cell lines in the presence of iron, we found that increased iron had minimal effects on osteoclast cell differentiation. Interestingly, iron, particularly in its inorganic form, and to a lesser extent ferritin and transferrin all suppressed alkaline phosphatase (ALP) activities in osteoblasts. Moreover, iron downregulated mRNA levels of several other osteoblastogenic markers such as Runx2, osterix, osteopontin, and osteocalcin. To further show that this in vitro finding is relevant to the in vivo condition, we demonstrated that iron-accumulated mice with intact ovaries exhibited a significant decrease in BMD. Although iron inhibited preosteoblast cell differentiation, it did enhance preosteoblast cell proliferation, as evidenced by increased cell growth and expression of cell cycle regulator genes such as CDK4, CDK6, cyclin D1, and cyclin D3 and G2/M phase cell population. Taken together, our results suggest that increased iron could be a factor that slows down bone formation in postmenopausal women. © 2011 American Society for Bone and Mineral Research.
Internal migration and depressive symptoms among migrant factory workers in Shenzhen, China
Authors: Mou Jin , Cheng Jinquan , Griffiths Sian M. , Wong Samuel Y.S. , Hillier Sheila , Zhang Dan
Published: February 2011

There has been a dramatic increase in rural‐urban migration in China over the last two decades but there are few studies on the mental health of Chinese internal migrants. This study assesses the prevalence of depressive symptoms (DS) and their associated factors among migrant factory workers in Shenzhen, China. A questionnaire survey was sent to 4,280 migrant workers in 2009 with a response rate of 95.5%. Clinically relevant DS were identified using the Chinese version of the Centre for Epidemiologic Studies Depressive Scale. There is a high prevalence (21.4%) of clinically relevant DS among internal migrant factory workers. Higher scores were associated with being a minority, shorter intension of stay, working long hours, being a casual smoker or a frequent Internet user, and having better education. Stakeholders should be aware of the needs of these subgroups, particularly in the light of recent publicity about factory worker suicides in Shenzhen. © 2011 Wiley Periodicals, Inc.
Regulatory volume decrease and P receptor signaling in fish cells: mechanisms, physiology, and modeling approaches
Authors: Chara Osvaldo , Espelt María V. , Krumschnabel Gerhard , Schwarzbaum Pablo J.
Published: February 2011

For animal cell plasma membranes, the permeability of water is much higher than that of ions and other solutes, and exposure to hyposmotic conditions almost invariably causes rapid water influx and cell swelling. In this situation, cells deploy regulatory mechanisms to preserve membrane integrity and avoid lysis. The phenomenon of regulatory volume decrease, the partial or full restoration of cell volume following cell swelling, is well‐studied in mammals, with uncountable investigations yielding details on the signaling network and the effector mechanisms involved in the process. In comparison, cells from other vertebrates and from invertebrates received little attention, despite of the fact that e.g. fish cells could present rewarding model systems given the diversity in ecology and lifestyle of this animal group that may be reflected by an equal diversity of physiological adaptive mechanisms, including those related to cell volume regulation. In this review, we therefore present an overview on the most relevant aspects known on hypotonic volume regulation presently known in fish, summarizing transporters and signaling pathways described so far, and then focus on an aspect we have particularly studied over the past years using fish cell models, i.e. the role of extracellular nucleotides in mediating cell volume recovery of swollen cells. We, furthermore, present diverse modeling approaches developed on the basis of data derived from studies with fish and other models and discuss their potential use for gaining insight into the theoretical framework of volume regulation.J. Exp. Zool. 315A:175–202, 2011. © 2011 Wiley‐Liss, Inc.
The Ritual: Death Pronouncement
Authors: Carter Brian S.
Published: February 2011

BACKGROUND:

Death pronouncement comes infrequently for the pediatrician. The place of death for most children is in the hospital. For hospitalists and pediatric intensivists in the neonatal intensive care or pediatric intensive care units, death pronouncement is not uncommon. For hospitalist physicians, the call to attend a code or to pronounce a death may come on any given shift and from almost anywhere in the hospital.

CONCLUSION:

A demonstrative case is provided, followed by key concepts for practice and for educating trainees. Journal of Hospital Medicine 2011;6:94–97. © 2011 Society of Hospital Medicine.
Dry under water: Comparative morphology and functional aspects of air‐retaining insect surfaces
Authors: Balmert Alexander , Bohn Holger Florian , Ditsche‐Kuru Petra , Barthlott Wilhelm
Published: February 2011

Superhydrophobic surfaces prevent certain body parts of semiaquatic and aquatic insects from getting wet while submerged in water. The air layer on these surfaces can serve the insects as a physical gill. Using scanning electron microscopy, we investigated the morphology of air‐retaining surfaces in five insect species with different levels of adaptation to aquatic habitats. We found surfaces with either large and sparse hairs (setae), small and dense hairs (microtrichia), or hierarchically structured surfaces with both types of hairs. The structural parameters and air‐film persistence of these surfaces were compared. Air‐film persistence varied between 2 days in the beetle Galerucella nymphaea possessing only sparse setae and more than 120 days in the bugs Notonecta glauca and Ilyocoris cimicoides possessing dense microtrichia (up to 6.6 × 106 microtrichia per millimeter square). From our results, we conclude that the density of the surface structures is the most important factor that affects the persistence of air films. Combinations of setae and microtrichia are not decisive for the overall persistence of the air film but might provide a thick air store for a short time and a thin but mechanically more stable air film for a long time. Thus, we assume that a dense cover of microtrichia acts as a “backup system” preventing wetting of the body surface in case the air–water interface is pressed toward the surface. Our findings might be beneficial for the development of biomimetic surfaces for long‐term air retention and drag reduction under water. In addition, the biological functions of the different air retention capabilities are discussed. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.
Scanning electron microscopy of the placental interface in the viviparous lizard Sceloporus jarrovi (Squamata: Phrynosomatidae)
Authors: Anderson Kristie E. , Blackburn Daniel G. , Dunlap Kent D.
Published: February 2011

Placental membranes mediate maternal‐fetal exchange in all viviparous reptilian sauropsids. We used scanning electron microscopy to examine the placental interface in the mountain spiny lizard, Sceloporus jarrovi (Phrynosomatidae). From the late limb bud stage until birth, the conceptus is surrounded by placental membranes formed from the chorioallantois and yolk sac omphalopleure. The chorioallantois lies directly apposed to the uterine lining with no intervening shell membrane. Both fetal and maternal sides of the chorioallantoic placenta are lined by continuous layers of flattened epithelial cells that overlie dense capillary networks. The chorioallantoic placenta shows specializations that enhance respiratory exchange, as well as ultrastructural evidence of maternal secretion and fetal absorption. The yolk sac placenta contains enlarged fetal and maternal epithelia with specializations for histotrophic nutrient transfer. This placenta lacks intrinsic vascularity, although the vascular allantois lies against its inner face, contributing to an omphallantoic placenta. In a specialized region at the abembryonic pole, uterine and fetal tissues are separated by a compact mass of shed shell membrane, yolk droplets, and cellular debris. The omphalopleure in this region develops elongate folds that may contribute to sequestration and absorption of this material. Fetal membrane morphogenesis and composition in S. jarrovi are consistent with those of typical squamates. However, this species exhibits unusual placental specializations characteristic of highly placentotrophic lizards. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.
Homologies of the branchial arch muscles in Zacco platypus (Teleostei: Cypriniformes: Cyprinidae): Evidence from innervation pattern
Authors: Nakae Masanori , Sasaki Kunio , Nakajima Tsuneo , Miyazaki Yusuke , Matsuura Keiichi
Published: February 2011

Homologies of the branchial arch muscles in the cyprinid Zacco platypus are assessed based on their innervation. Muscles serving the first gill arch are innervated by branches of the glossopharyngeal (IX) nerve and those serving other arches by the vagal (X) nerve. Absence of the levator posterior is confirmed. Five pairs of muscles originating from the cranium and inserted onto the specialized 5th ceratobranchial, all unique to cyprinids, are innervated by the 4th branchial trunks of X, indicating that all pairs are derivatives of the sphincter oesophagi, involving reorganization from intrinsic to extrinsic elements. Homologies of some ventral branchial muscles are also discussed and the criteria for homology improved by clarifying the innervation pattern. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.
γ‐Aminobutyric acid type B receptor changes in the rat striatum and substantia nigra following intrastriatal quinolinic acid lesions
Authors: Rekik Letaïef , Daguin‐Nerrière Véronique , Petit Jean‐Yves , Brachet Philippe
Published: February 2011

Changes in the regional distribution of the metabotropic GABA type B receptors (GABAB) were investigated in a rat model of Huntignton's disease. Animals received a unilateral intrastriatal injection of quinolinic acid (QA), and GABAB immunoreactivity was monitored 3, 11, and 21 days postinjection in the striatum and substantia nigra (SN). Two antibodies, recognizing either the GABAB1 or the GABAB2 receptor subtypes, were used. QA injection rapidly induced a protracted increase in GABAB1 or GABAB2 immunoreactivity in the lesioned striatum, despite the neuronal loss. In the SN, a continuous increase in GABAB1 and GABAB2 immunoreactivity was observed at all time points in the ipsilateral pars reticulata (SNr), whereas the pars compacta (SNc) was unaffected by this phenomenon. This increase was supported by a densitometric analysis. At day 21 postlesion induction, intensely labeled stellate cells and processes were found in the ipsilateral SNr, in addition to immunoreactive neurons. Double labeling of GABAB1 and glial fibrillary acidic protein (GFAP) showed that the stellate cells were reactive astrocytes. Hence, part of the sustained increase in GABAB immunoreactivity that takes place in the SNr and possibly the striatum may be ascribed to reactive astrocytes. It is suggested that GABAB receptors are up‐regulated in these reactive astrocytes and that agonists might influence the extent of this astroglial reaction. © 2011 Wiley‐Liss, Inc.
Regulation of cytokine expression by Schwann cells in response to α2‐macroglobulin binding to LRP1
Authors: Shi Yang , Yamauchi Tomonori , Gaultier Alban , Takimoto Shinako , Campana W. Marie , Gonias Steven L.
Published: February 2011

Binding of activated α2‐macroglobulin (α2M) to LDL receptor‐related protein‐1 (LRP1) in Schwann cells activates ERK/MAP kinase and Akt and thereby promotes cell survival and migration. The goal of this study was to determine whether α2M binding to LRP1 regulates expression of cytokines and chemokines. To assess the LRP1 response selectively, we studied primary cultures of rat Schwann cells. In a screening assay that detects 84 gene products, monocyte chemoattractant protein‐1 (MCP‐1/CCL2) mRNA expression was increased more than 13‐fold in Schwann cells treated with activated α2M. The effects of α2M on MCP‐1 expression were selective, because expression of the general proinflammatory cytokine tumor necrosis factor‐α (TNF‐α) was not induced. We confirmed that α2M selectively induces expression of MCP‐1 and not TNF‐α in single‐target qPCR assays. MCP‐1 protein accumulated at increased levels in conditioned medium of α2M‐treated cells. LRP1 was necessary for induction of MCP‐1 expression, as determined in experiments with the LRP1 antagonist receptor‐associated protein, a mutated form of full‐length α2M that does not bind LRP1, and in studies with Schwann cells in which LRP1 was silenced. Inhibiting ERK/MAP kinase activation blocked expression of MCP‐1. These studies support a model in which LRP1 regulates multiple aspects of Schwann cell physiology in the response to PNS injury. © 2011 Wiley‐Liss, Inc.
Calpeptin attenuated apoptosis and intracellular inflammatory changes in muscle cells
Authors: Nozaki Kenkichi , Das Arabinda , Ray Swapan K. , Banik Naren L.
Published: February 2011

In idiopathic inflammatory myopathies (IIMs), extracellular inflammatory stimulation is considered to induce secondary intracellular inflammatory changes including expression of major histocompatibility complex class‐I (MHC‐I) and to produce a self‐sustaining loop of inflammation. We hypothesize that activation of calpain, a Ca2+‐sensitive protease, bridges between these extracellular inflammatory stress and intracellular secondary inflammatory changes in muscle cells. In this study, we demonstrated that treatment of rat L6 myoblast cells with interferon‐γ (IFN‐γ) caused expression of MHC‐I and inflammation‐related transcription factors (phosphorylated‐extracellular signal‐regulated kinase 1/2 and nuclear factor‐κB). We also demonstrated that treatment with tumor necrosis factor‐α (TNF‐α) induced apoptotic changes and activation of calpain and cyclooxygenase‐2. Furthermore, we found that posttreatment with calpeptin attenuated the intracellular changes induced by IFN‐γ or TNF‐α. Our results indicate that calpain inhibition attenuates apoptosis and secondary inflammatory changes induced by extracellular inflammatory stimulation in the muscle cells. These results suggest calpain as a potential therapeutic target for treatment of IIMs. © 2011 Wiley‐Liss, Inc
Trimethyltin initially activates the caspase 8/caspase 3 pathway for damaging the primary cultured cortical neurons derived from embryonic mice
Authors: Kuramoto Nobuyuki , Seko Keiichi , Sugiyama Chie , Shuto Makoto , Ogita Kiyokazu
Published: February 2011

The organotin trimethyltin (TMT) is well known to cause neuronal damage in the central nervous system. To elucidate the mechanisms underlying the toxicity of TMT toward neurons, we prepared primary cultures of neurons from the neocortex of mouse embryos. A continuous exposure to TMT produced a decrease in cell viability as well as an increase in the number of cells with nuclear condensation/shrinkage at the exposure time window up to 24 hr. In addition to the events at the early time window, lactate dehydrogenase released was significantly elevated at the later exposure time from 36 to 48 hr. With a 3‐hr exposure to TMT, a significant increase was observed in the activity of caspase 8, but not in that of caspase 9. TMT exposure produced no elevation in the level of cytochrome c released from mitochondria until 12 hr of exposure, with a significant facilitation of cytochrome c release at the exposure times of 16 and 24 hr. After the activation of caspase 8 by TMT exposure, caspase 3 activation and nuclear translocation of caspase‐activated DNase were caused by exposure for 6 hr or longer. However, nuclear DNase II was elevated at the later time window of exposure. A caspase inhibitor completely prevented TMT from damaging the cells in any time window. Taken together, our data are the first demonstration that TMT toxicity is initially caused by activation of the caspase 8/caspase 3 pathway for nuclear translocation of DNases in cortical neurons in primary culture. © 2011 Wiley‐Liss, Inc.
Waste not, want not: Leading the lean health‐care journey at Seattle Children's Hospital
Authors: Hagan Pat
Published: February 2011

Of the work conducted by health‐care practitioners, 95 percent has no value to the patients they serve—an astounding fact given the spiraling costs of medical care. How well a health‐care organization delivers care lies in the crucial remaining 5 percent. Borrowing techniques from the manufacturing sector, Seattle Children's Hospital in Washington has embarked on a continuous improvement initiative that has streamlined the hospital's myriad processes at all levels to ensure high‐quality and effective delivery of services. As this case study shows, the organization, its staff members at all levels, and its patients are all beneficiaries of the hospital's healthy focus on continuous performance improvement. © 2011 Wiley Periodicals, Inc.
Ionic liquid stationary phases for gas chromatography
Authors: Poole Colin F. , Poole Salwa K.
Published: February 2011

This article provides a summary of the development of ionic liquids as stationary phases for gas chromatography beginning with early work on packed columns that established details of the retention mechanism and established working methods to characterize selectivity differences compared with molecular stationary phases through the modern development of multi‐centered cation and cross‐linked ionic liquids for high‐temperature applications in capillary gas chromatography. Since there are many reviews on ionic liquids dealing with all aspects of their chemical and physical properties, the emphasis in this article is placed on the role of gas chromatography played in the design of ionic liquids of low melting point, high thermal stability, high viscosity, and variable selectivity for separations. Ionic liquids provide unprecedented opportunities for extending the selectivity range and temperature‐operating range of columns for gas chromatography, an area of separation science that has otherwise been almost stagnant for over a decade.
Experimental and quantum chemical studies on two triazole derivatives as corrosion inhibitors for mild steel in acid media
Authors: Li W. , Hu L. , Tao Z. , Tian H. , Hou B.
Published: February 2011

Two triazole derivatives [1‐phenyl‐2‐(5‐(1,2,4) triazol‐1‐ylmethyl‐(1,3,4) oxadizaol‐2‐ylsulphanyl)‐ethanone (PTOE) and 2‐(4‐tert‐butyl‐benzylsulphanyl)‐5‐(1,2,4) triazol‐1‐ylmethyl‐(1,3,4) oxadiazole (TBTO)] were synthesized as new corrosion inhibitors for the corrosion of mild steel in 1 M hydrochloric acid solutions. The inhibiting efficiency of the different inhibitors was evaluated by means of weight loss and electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and polarization curves. The electrochemical investigation results indicate that these compounds act as mixed‐type inhibitors retarding the anodic and cathodic corrosion reactions and do not change the mechanism of either hydrogen evolution reaction or mild steel dissolution. The studied compounds followed the Langmuir adsorption isotherm, and the thermodynamic parameters were determined and discussed. The effect of molecular structure on the inhibition efficiency has been investigated with ab initio calculations. The electronic properties such as highest occupied molecular orbital (HOMO) energy level, lowest unoccupied molecular orbital (LUMO) energy level, dipole moment (µ) and molecular orbital densities were calculated.
Electrochemical corrosion behaviour of Sn–Ag–Cu (SAC) eutectic alloy in a chloride containing environment
Authors: Rosalbino F. , Zanicchi G. , Carlini R. , Angelini E. , Marazza R.
Published: February 2011

The corrosion behaviour of the Sn94.5Ag3.8Cu1.5 (SAC) eutectic alloy was investigated in 0.1 M NaCl solution by potentiodynamic polarization and impedance spectroscopy measurements and compared with that of the conventional Sn73.9Pb23.1 eutectic solder employed for a long time in the packaging of microelectronic components and devices. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were used to characterize the SAC eutectic alloy prior to and after the electrochemical tests. The electrochemical results indicated that the Sn–Ag–Cu eutectic alloy exhibits better corrosion behaviour than the Sn–Pb eutectic solder in NaCl solution. The presence of a corrosion products layer constituted by tin oxy‐chloride was detected at the surface of both alloys investigated after the electrochemical tests. The better corrosion behaviour of SAC eutectic alloy compared to Sn–Pb eutectic solder is ascribed to the formation of a more compact surface film of corrosion products with improved protective properties owing to the presence of copper and silver, as revealed by EPMA.
Effect of alternating voltage treatment on corrosion resistance of AZ91D magnesium alloy
Authors: Liu X. , Zhang T. , Shao Y. , Meng G. , Wang F.
Published: February 2011

AZ91D magnesium alloy was treated by the alternating voltage (AV) treatment technique. The optimal AV‐treatment parameters of the alloy were determined by orthogonal experiments. Polarization curve, electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SECM) were used to understand the effect of AV‐treatment on the corrosion resistance of the alloy. AFM, contact angle, and XPS were employed to investigate further the influence of AV‐treatment on the properties of the surface film formed on the alloy after AV‐treatment. The results showed that a uniform and stable film was formed and the corrosion resistance of AZ91D magnesium alloy was significantly improved after AV‐treatment. This was caused by the noticeable change of the chemical structure and semi‐conducting properties of the surface film after AV‐treatment.
Synthesis of Blockcopolymers P3HT‐b‐PS Using a Combination of Grignard‐Metathesis and Nitroxide‐Mediated Radical Polymerization
Authors: Britze Antje , Möllmann Vera , Grundmeier Guido , Luftmann Heinrich , Kuckling Dirk
Published: February 2011

The synthesis of π‐conjugated NMRP‐macroinitiators using GRIGNARD‐metathesis polymerization in combination with azide/alkyne‐“click” chemistry has been investigated. Alkoxyamine‐functionalized poly(3‐hexylthiophene)s (P3HTs) have been used for block copolymer preparations in presence of styrene. Molecular weight and molecular weight distribution of the polymers have been determined in SEC‐measurements, while end‐group determination was performed with MALDI‐ToF‐MS. The molecular weight of the P3HT macroinitiators was influenced by the amount of Ni‐catalyst during the GRIM reaction. Those macroinitiators have been used to prepare block copolymers in subsequent nitroxide‐mediated radical polymerization (NMRP). Thin‐layer‐morphologies of the block copolymers were investigated using tapping‐mode AFM. Short and disordered rods were observed, as well as continuous and parallel fibrils.

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Microstructure and incubation processes in composite liquid crystalline material (5CB) filled with multi walled carbon nanotubes
Authors: Lisetski L. N. , Minenko S. S. , Ponevchinsky V. V. , Soskin M. S. , Goncharuk A. I. , Lebovka N. I.
Published: February 2011

This work reports a study on microstructure, electrical conductivity and phase transitions of 5CB(4‐pentyl‐4′‐cyanobiphenyl) + multi‐walled carbon nanotubes (MWCNTs) composite materials. The concentration of MWCNTs was varied within 0.025 and 1 wt.%. The unmodified (o) and modified (m) MWCNTs were used. The mild milling was applied for shortening length of MWCNTs. Direct microscopic observation of composites at different concentrationsCof MWCNTs evidenced the presence of aggregation and percolation processes. Formation of percolation networks was observed atCp≈ 0.025–0.05% wt andC=Cp≈ 0.1–0.25% wt foro‐MWCNTs andm‐MWCNTs composites, respectively. Increase of the percolation threshold form‐MWCNTs, possibly, reflected their smaller aspect ratior. The conductivity exponents were approximately the same (t≈ 3.3 ± 0.1) for botho‐MWCNTs andm‐MWCNTs. The microstructure of MWCNT aggregates was not stable in time. The initially formed loose aggregates (L‐aggregates) transformed into the more compact C‐aggregates during the incubation time of one week. The incubation resulted in decrease of anisotropy, change in phase behaviour near the nematic‐isotropic transition, and influenced external electric field response of the studied composite material.

In dieser Arbeit werden die Mikrostruktur, die elektrische Leitfähigkeit und die Phasenübergänge in Kompositen aus 5CB (4‐pentyl‐4′‐cyanobiphenyl) und mehrschichtigen Kohlenstoff‐Nanoröhren (MWCNTs) behandelt. Die Konzentration der MWCNTs liegt im Bereich zwischen 0.025 und 1 Gew.‐%. Es wurden unbehandelte (o) und modifizierte (m) MWCNTs verwendet. Um die Länge der MWCNTs zu verkürzen, wurden sie schonend gemahlen. Die direkte mikroskopische Beobachtung der Komposite bei unterschiedlichen Konzentrationen von MWCNTs zeigte das Vorhandensein von Aggregations‐ und Perkolationsprozessen an. Die Bildung eines Perkolationsnetzwerkes wurde im Konzentrationsbereich 0,025–0,05% Gew.‐% für o‐MWCNTS und 0,1–0,25 Gew.‐% fürm‐MWCNTs beobachtet. Eine Erhöhung der Perkolationsschwelle für diem‐MWCNTs könnte mit dem kleineren Aspektverhältnis r zusammenhängen. Die Leitfähigkeitsexponenten sind für beide MWCNTs ungefähr gleich (t≈ 3,3 ± 0,1). Die Mikrostruktur der MWCNT Aggregate war zeitlich nicht stabil. Die urspünglich gebildeten losen Aggregate (L‐Aggregate) wandeln sich in die mehr kompakten Aggregate (C‐Aggregate) während der Inkubation innerhalb von einer Woche um. Die Inkubation führt zu einer Abnahme der Anisotropie, einem Wechsel der Phase in der Nähe der nematischen‐isotropen Umwandlung und beeinflusst die Antwort auf ein externes elektrisches Feld der studierten Kompositmaterialien.
Electronic structure and temperature dependence of the linear size of the nanoscale magnetic domains in a disordered bcc‐Fe‐Co alloy
Authors: Len E. G. , Melnyk I. M. , Repetsky S. P. , Lizunov V. V. , Tatarenko V. A.
Published: February 2011

The formation of the homogeneous magnetic short‐range‐ordered regions in disordered bcc‐Fe0.5Co0.5 alloy under the influence of the electron‐energy spectrum realignment with temperature is considered. For the description of electron states in a crystal, the multiband tight‐binding model and the developed method for the cluster expansion of Green's functions and thermodynamic potential of a disordered crystal were applied. Within the scope of the mentioned approach, calculations of both the electron‐energy spectrum and the temperature‐dependent equilibrium values of the pair‐wise magnetic‐correlation parameters of disordered bcc‐Fe0.5Co0.5 alloy were performed. The equilibrium values of parameters of magnetic and interatomic correlations were obtained at minimum free energy.

Die Bildung von homogenen magnetisch über kurze Distanzen geordneten Regionen in ungeordneten kubisch raumzentrierten Fe0.5Co0.5‐Legierungen wurde unter dem Einfluss der Ausrichtung des Elektronenenergiespektrums mit der Temperatur untersucht. Für die Beschreibung der elektronischen Zustände im Kristall wurden das tight‐binding‐Modell, die Methode der Cluster‐Ausdehnung der Greenschen Funktion und das thermodynamische Potenzial von ungeordneten Kristallen benutzt. Im Rahmen der erwähnten Ansätze wurden die Berechnungen sowohl der Elektronenergiespektren als auch der temperaturabhängigen Gleichgewichtswerte der paarweise magnetischen Korrelationsparameter von ungeordnetem bcc‐Fe0.5Co0.5‐Legierungen durchgeführt. Die Gleichgewichtsparameter der magnetischen und interatomischen Korrelationen wurden unter der Bedingung erhalten, dass die freie Energie minimiert wurde.
Structure and properties of C60 fullerene films with titanium atoms
Authors: Shpilevsky E.M. , Shpilevsky M.E. , Prylutskyy Y.I. , Matzuy L.Y. , Zakharenko M.I. , Le Normand F.
Published: February 2011

Structure, mechanical and electrical properties of thin films prepared by means of co‐deposition of fullerenes C60 and titanium were studied. The obtained results show the potential applicability of titanium‐fullerene films as electrotechnical materials and coatings.

Die Struktur und die mechanischen und elektrischen Eigenschaften von dünnen Fulleren C60‐Titan‐Schichten, die über Abscheidungsverfahren hergestellt wurden, wurden untersucht. Die erzielten Ergebnisse zeigen mögliche Anwendungen von Titan‐Fulleren‐Filmen als elektrotechnische Materialien und Beschichtungen.
Simulation of percolation threshold in composites filled with conducting particles of various morphologies
Authors: Vovchenko L. , Vovchenko V.
Published: February 2011

Three‐dimensional (3‐D) Monte Carlo simulation has been performed for predicting the percolation threshold in electrical conductivity of polymer composites filled with randomly oriented conductive particles of various morphologies. The conductive fillers like graphite nanoplatelets have been simulated as interpenetrating thin disks and oblate ellipsoids of revolution. For large aspect ratios we find close agreement between disks and oblate ellipsoids of revolution for the average number of bonds per object BC ≈ 2.3, that is in agreement with previous calculations for other shapes of filler (e. g. oblate prisms). The vermicular particles of thermoexfoliated graphite (TEG) have been simulated as the chains of disks jointed in a special manner. The values of percolation threshold have been calculated for various configuration of graphite chains (fragments of vermicular TEG particles) using the Monte Carlo method. The percolation threshold was shown to be determined by the number of disks m and angle between connected disks. It was found that critical volume fraction strongly depends on disks' aspect ratio ε, their orientation within a chain and length of this chain: ϕc decreases with increase of m and ε. The comparison of numerical results with our previous experimental data showed a reasonably good agreement.

Die dreidimensionale (3‐D) Monte‐Carlo‐Simulation wurde zur Ermittlung der Perkolationsschwelle bei der elektrischen Leitfähigkeit von Polymer‐Kompositen, die mit regellos orientierten leitfähigen Teilchen unterschiedlicher Struktur gefüllt sind, eingesetzt. Leitfähige Füllstoffe wie Graphit‐Nanoplatten werden als durchdringende Dünnplatten und abgeplattete Sphäroide simuliert. Bei den großen Seitenverhältnissen wurde eine gute Übereinstimmung zwischen Platten und abgeplatteten Sphäroiden für die Durchschnittszahl der Verbindungen pro Objekt BC ≈ 2.3, entsprechend den vorigen Berechnungen für die anderen ähnlichen Formen wie abgeplattete Prismen gefunden. Weiterhin wurden die fadenförmigen Teilchen eines thermoexfolierten Graphits als Ketten von den auf besondere Weise verbundenen m Platten simuliert. Durch das Monte‐Carlo‐Verfahren wurde die Perkolationsschwelle für unterschiedliche Formen von Graphit‐Verbindungen (Bestandteile der wurmförmigen TEG‐Teilchen), bestimmt von m‐Zahl der Platten und vom Winkel zwischen den verbundenen Platten, berechnet. Es wurde festgestellt, dass die Fraktion des kritischen Volumens von den Platten‐Seitenverhältnissen ε, der Platten‐Orientierung in der Kette und von der Ketten‐Länge abhängig ist: ϕc wird durch die Erhöhung von m und ε reduziert. Die numerischen Ergebnisse wurden dann mit den experimentellen Werten verglichen.
Persistent photocurrent and defects in TlBr
Authors: Kažukauskas V. , Ziminskij A. , Bozhko V. , Muronchuk G.
Published: February 2011

We had observed the persistent photoconductivity in TlBr. The long lasting current relaxations took place after the band‐to‐band light excitation at the temperatures below about 200 K. It was demonstrated by the thermally stimulated current method that this phenomenon is related to the trapping states with the thermal activation energy of 0.08–0.12 eV. Moreover, upon filling of the traps the enhanced photoconductivity was induced that could be thermally quenched above about 180 K. The quenching of the photoconductivity is initiated by the emptying of the trapping states with the activation energy of 0.63–0.65 eV.

Es wurde eine persistente Photoleitfähigkeit in TlBr beobachtet. Die langzeitigen Strom‐Relaxationen fanden auch nach der Band‐zu‐Band Lichtanregung bei Temperaturen unter 200 K statt. Bei der Anwendung der Methode des thermisch stimulierten Stroms wurde gezeigt, dass dieser Effekt durch Zustände mit thermischen Aktivierungsenergien von 0.08–0.12 eV verursacht werdenkönnte. Darüber hinaus führte eine Füllung dieser Zustände zu der erhöhten Photoleitfähigkeit. Dieser Zustand konnte bei Temperaturen über 180 K thermisch gelöscht werden. Die Löschung der Photoleitfähigkeit erfolgte bei der Entleerung der Zustände mit Aktivierungsenergien von 0.63–0.65 eV.
Characterization of carbon black‐filled immiscible polypropylene/polystyrene blends
Authors: Tan Yeqiang , Song Yihu , Cao Qing , Zheng Qiang
Published: February 2011

The electrical and rheological behaviors of carbon black (CB)‐filled immiscible polypropylene (PP)/polystyrene (PS) blends were investigated. The compounding sequence influences the phase morphology of the ternary CB/PP/PS composites and the distribution of CB aggregates. Simultaneous measurements of resistance and dynamic modulus were carried out to monitor the phase coalescence of the ternary composites and CB migration and agglomeration in the PS phase during annealing at temperatures above the melting point of PP. The variation of resistivity is mainly attributed to CB agglomeration in the PS phase and the interfacial region, while the variation of dynamic modulus is regarded as the superimposition of the phase coalescence and CB agglomeration in the PS phase. The ternary composites with the majority of CB particles distributed in the interfacial region show the lowest conductive percolation threshold and the most stable resistivity–temperature performance during heating–cooling cycles. Copyright © 2011 Society of Chemical Industry
Proteomic characterization of the multiple forms of the PLAs from the venom of the social wasp Polybia paulista
Authors: dos Santos Lucilene Delazari , da Silva Menegasso Anally Ribeiro , dos Santos Pinto José Roberto Aparecido , Santos Keity Souza , Castro Fabio Morato , Kalil Jorge Elias , Palma Mario Sergio
Published: February 2011

The phospholipases A1 (PLA1s) from the venom of the social wasp Polybia paulista occur as a mixture of different molecular forms. To characterize the molecular origin of these structural differences, an experimental strategy was planned combining the isolation of the pool of PLAs from the wasp venom with proteomic approaches by using 2‐D, MALDI‐TOF‐TOF MS and classical protocols of protein chemistry, which included N‐ and C‐terminal sequencing. The existence of an intact form of PLA1 and seven truncated forms was identified, apparently originating from controlled proteolysis of the intact protein; in addition to this, four of these truncated forms also presented carbohydrates attached to their molecules. Some of these forms are immunoreactive to specific‐IgE, while others are not. These observations permit to raise the hypothesis that naturally occurring proteolysis of PLA1, combined with protein glycosylation may create a series of different molecular forms of these proteins, with different levels of allergenicity. Two forms of PLA2s, apparently related to each other, were also identified; however, it was not possible to determine the molecular origin of the differences between both forms, except that one of them was glycosylated. None of these forms were immunoreactive to human specific IgE.
Mining the soluble chloroplast proteome by affinity chromatography
Authors: Bayer Roman G. , Stael Simon , Csaszar Edina , Teige Markus
Published: February 2011

Chloroplasts are fundamental organelles enabling plant photoautotrophy. Besides their outstanding physiological role in fixation of atmospheric CO2, they harbor many important metabolic processes such as biosynthesis of amino acids, vitamins or hormones. Technical advances in MS allowed the recent identification of most chloroplast proteins. However, for a deeper understanding of chloroplast function it is important to obtain a complete list of constituents, which is so far limited by the detection of low‐abundant proteins. Therefore, we developed a two‐step strategy for the enrichment of low‐abundant soluble chloroplast proteins from Pisum sativum and their subsequent identification by MS. First, chloroplast protein extracts were depleted from the most abundant protein ribulose‐1,5‐bisphosphate carboxylase/oxygenase by SEC or heating. Further purification was carried out by affinity chromatography, using ligands specific for ATP‐ or metal‐binding proteins. By these means, we were able to identify a total of 448 proteins including 43 putative novel chloroplast proteins. Additionally, the chloroplast localization of 13 selected proteins was confirmed using yellow fluorescent protein fusion analyses. The selected proteins included a phosphoglycerate mutase, a cysteine protease, a putative protein kinase and an EF‐hand containing substrate carrier protein, which are expected to exhibit important metabolic or regulatory functions.
2‐D DIGE analysis of the mitochondrial proteome from human skeletal muscle reveals time course‐dependent remodelling in response to 14 consecutive days of endurance exercise training
Authors: Egan Brendan , Dowling Paul , O'Connor Paul L. , Henry Michael , Meleady Paula , Zierath Juleen R. , O'Gorman Donal J.
Published: February 2011

Adaptation of skeletal muscle to repeated bouts of endurance exercise increases aerobic capacity and improves mitochondrial function. However, the adaptation of human skeletal muscle mitochondrial proteome to short‐term endurance exercise training has not been investigated. Eight sedentary males cycled for 60 min at 80% of peak oxygen consumption (VO2peak) each day for 14 consecutive days, resulting in an increase in VO2peak of 17.5±3.8% (p<0.01). Mitochondria‐enriched protein fractions from skeletal muscle biopsies taken from m. vastus lateralis at baseline, and on the morning following the 7th and 14th training sessions were subjected to 2‐D DIGE analysis with subsequent MS followed by database interrogation to identify the proteins of interest. Thirty‐one protein spots were differentially expressed after either 7 or 14 days of training (ANOVA, p<0.05). These proteins included subunits of the electron transport chain, enzymes of the tricarboxylic acid cycle, phosphotransfer enzymes, and regulatory factors in mitochondrial protein synthesis, oxygen transport, and antioxidant capacity. Several proteins demonstrated a time course‐dependent induction during training. Our results illustrate the phenomenon of skeletal muscle plasticity with the extensive remodelling of the mitochondrial proteome occurring after just 7 days of exercise training suggestive of enhanced capacity for adenosine triphosphate generation at a cellular level.
Generation of well‐defined clickable glycopolymers from aqueous RAFT polymerization of isomaltulose‐derived acrylamides
Authors: Abdelkader Ouaiss , Moebs‐Sanchez Sylvie , Queneau Yves , Bernard Julien , Fleury Etienne
Published: February 2011

Original carbohydrate‐based acrylamides bearing one azide group in C‐2 or C‐6 position namely, 2‐[(2‐deoxy‐2‐azido‐α‐D‐mannopyranosyloxy)ethanamido]‐ethyl acrylamide (II) and 2‐[(6‐deoxy‐6‐azido‐α‐D‐glucopyranosyloxy)ethanamido]‐ethyl acrylamide (III), and their azide‐free analogue, 2‐[(α‐D‐glucopyranosyloxy)ethanamido]‐ethyl acrylamide (I), have been designed. Whereas the reversible addition fragmentation chain transfer (RAFT) process ensured the preparation of well‐defined glycopolymers from I, the polymerization of monomers II and III proved to be challenging at temperatures compatible with a thermally initiated radical process, due to the presumed concomitant 1,3‐cycloaddition reactions between the azide and the acrylamide moieties. In contrast to III, for which no polymer could be obtained under any conditions, performing the RAFT polymerization of II at 30 °C clearly favored the radical polymerization and conferred a controlled character to the process, affording well‐defined azide‐functionalized glycopolymers and block copolymers. The presence of numerous azide moieties was finally exploited to introduce carbohydrates onto the glycopolymer backbone through copper catalyzed azide‐alkyne cycloaddition. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Design and synthesis of dithieno[3,2‐b:2′3′‐d]pyrrole‐based conjugated polymers for photovoltaic applications: consensus between low bandgap and low HOMO energy level
Authors: Shi Min‐Min , Deng Dan , Chen Lin , Ling Jun , Fu Lei , Hu Xiao‐Lian , Chen Hong‐Zheng
Published: February 2011

A strategy of the fine‐tuning of the degree of intrachain charge transfer and aromaticity of polymer backbone was adopted to design and synthesize new polymers applicable in photovoltaics. Three conjugated polymers P1, P2, and P3 were synthesized by alternating the electron‐donating dithieno[3,2‐b:2′3′‐d]pyrrole (D) and three different electron‐accepting (A) segments (P1: N‐(2‐ethylhexyl)phthalimide; P2: 1,4‐diketo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole; and P3: thiophene‐3‐hexyl formate) in the polymer main chain. Among the three polymers, P2 possessed the broadest absorption band ranging from 300 to 760 nm, the lowest bandgap (1.63 eV), and enough low HOMO energy level (−5.27 eV) because of the strong intrachain charge transfer from D to A units and the appropriate extent of quinoid state in the main chain of P2, which was convinced by the theoretical simulation of molecular geometry and front orbits. Photovoltaic study of solar cells based on the blends of P1–P3 and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) demonstrated that P2:PCBM exhibited the best performance: a power conversion efficiency of 1.22% with a high open‐circuit voltage (VOC) of 0.70 V and a large short‐circuit current (ISC) of 5.02 mA/cm2 were achieved. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Synthesis of polynorbornene‐poly(tert‐butyl acrylate) nanoparticles with original morphologies by tandem ROMP and ATRP in microemulsion
Authors: Nguyen Minh Ngoc , Mougnier Sébastien‐Jun , Ibarboure Emmanuel , Heroguez Valérie
Published: February 2011

Composite latex particles based on homopolymers and graft‐copolymers composed of polynorbornene (PNB) and poly(tert‐butyl acrylate) (PtBA) were synthesized in microemulsion conditions by simultaneous combination of two distinct methods of polymerization: Ring‐opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Only one commercial compound (first generation Grubbs catalyst) was used to initiate the ROMP of norbornene (NB) and activate the ATRP of tert‐butyl acrylate (tBA). Well‐defined nanoparticles with hydrodynamic diameters smaller than 50 nm were prepared with original morphologies depending on the monomer compositions, the type of combination (polymer blend or graft‐copolymer), and the conditions of microemulsion polymerizations. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Fluctuation‐induced conductivity of (YCe)Ba2Cu3O7–δ superconductor
Authors: Ferreira Talita Rosas , Pinheiro Lincoln Brum de Leite Gusmão , Júnior Pedro Rodrigues , Serbena Francisco Carlos , Jurelo Alcione Roberto
Published: February 2011

Systematic measurements of the in‐plane and out‐of‐plane in conductivity fluctuations have been used to investigate the role of the cerium ion on the splitting of the pairing transition. This splitting, associated with a phase separation, was firstly observed in single crystals and polycrystalline samples of Y1–xPrxBa2Cu3O7–δ. Considering that Ce is the rare‐earth element most easily ionized to the +4 state and that in melt‐textured sample, it is possible to observe anisotropic effects, we examined the effect of this ion in the Y1–xCexBa2Cu3O7–δ compound. We prepared three different samples: polycrystalline, pure melt‐textured and Ce‐doped melt‐textured. Melt‐textured samples were prepared using the top‐seeding growth technique and the polycrystalline sample by the standard solid‐state reaction technique. The samples were characterized by X‐ray diffraction, scanning electron microscopy (SEM) and electrical resistivity. To identify power‐law divergences in the conductivity, the results were analyzed in terms of the temperature derivative of the resistivity (${\rm d}\rho /{\rm d}T$) and of the logarithmic temperature derivative of the conductivity (${-} {\rm d}{\ln} (\Delta \sigma )/{\rm d}T$). In the normal phase, Gaussian and critical regimes were clearly seen for melt‐textured samples and no important differences between pure and Ce‐doped samples were observed. On the other hand, for the polycrystalline sample and from the critical exponent analysis, a splitting of the pairing transition was clearly observed. It is suggested that the occurrence of a phase separation and its association with Ce doping as already observed for Pr‐doped samples.
Kondo effect in a double quantum dot interferometer with Rashba spin–orbit interaction
Authors: Liu Xiao‐Jie , Yin Hai‐Tao , Wan Wei‐Long , Li Hua , Wang Xian‐Zhang , Yao Cheng‐Bao
Published: February 2011

Electronic transport through a double quantum dot interferometer with Rashba spin–orbit interaction is investigated. By means of the slave‐boson mean‐field approximation and Green function technique, we calculated the local density of states (DOS) and the linear conductance in the Kondo regime at zero temperature. It is shown that the local DOS and the linear conductance of each spin component can be tuned by the Rashba spin–orbit interaction with help of the magnetic flux. In particular, by modulating the strength of the Rashba spin–orbit interaction properly, only one spin component electron can be allowed to transport through this structure.
Bandgap modulations of silicon carbon nanoribbons by transverse electric fields: A theoretical study
Authors: Zheng Fang‐Ling , Zhang Yan , Zhang Jian‐Min , Xu Ke‐Wei
Published: February 2011

Under external transverse electronic fields, the electronic and magnetic properties of silicon carbon nanoribbons with zigzag edge (ZSiCNRs) and armchair edge (ASiCNRs) are studied by using the first‐principles projector augmented wave (PAW) potential within the density‐function theory (DFT) framework. Our results for the narrow ZSiCNRs by the VASP computer code are in good agreement with those of Lou and coworkers. Thus, in this paper we showed the new results for the wide ZSiCNRs as a complementary study as well as for the narrow and wide ASiCNRs. The ground state of the ZSiCNR is a ferrimagnetic semiconductor with two different direct bandgaps for the spin‐up and the spin‐down channels near the zone boundary Z, and converts to a ferromagnetic metal when a suitable transverse electric field is applied. However, the ground state of the ASiCNR is a nonmagnetic semiconductor and its bandgap decreases with increasing absolute value of the field strength. After a suitable critical field, the ASiCNR changes to a metal, and the larger ribbon width, the larger decrease rate and thus the smaller critical field.