bluuebunny/crossref_metadata_2025 huggingface dataset:
Summer temperature reconstruction on the central Tibetan Plateau during 1860–2002 derived from annually resolved ice core pollen
Authors: Yang Bao , Tang Lingyu , Bräuning Achim , Davis Mary E. , Shao Jajun , Jingjing Liu
Published: December 2008

We present a 140‐year ice core pollen record with annual time resolution from the Puruogangri ice field in the central Tibetan Plateau. A linear regression model between the sum of the steppe and meadow pollen taxa and summer temperature at Naqu accounts for 66% of the summer temperature variance for the period 1955–2002. On the basis of this model, we reconstructed summer temperature history for the central Tibetan Plateau from 1860 to 2002. Three marked warm periods during the 1870s, 1890s, and 1990s and five cold periods during the 1860s, 1880s, 1900s, 1950s, and 1960–1970s were identified. Within the last 100 years, late 20th century warming is distinctive and may have had a major role in the present retreat of most glaciers on the Tibetan Plateau. The pollen record is also significantly correlated with average annual temperatures over the whole Tibetan Plateau, suggesting that these proxy data have the potential for reflecting large‐scale regional temperature change. The statistically significant similarity between the Puruogangri ice core pollen record and the δ18O time series indicates that both are reliable indicators of temperature change at annual to multiyear timescales in this region.
Identification of Common Genetic Variants Predisposing to Neurobehavioral Disease by way of Genome-Wide SNP Association Studies
Authors: Craig David
Published: December 2008

Dr. David Craig began by explaining expression and linkage studies. He then focused on genome-wide association studies (GWAS), giving examples from Diabetes Type 2 and Alzheimer’s research. Dr. Craig concluded with the recognition that GWAS cannot at the present adequately account for environmental influences on disease.To watch Dr. Craig’s presentation, please see the Panel 3 "Google Video posting.":http://video.google.com/videoplay?docid=-7775076897136846879&hl=en
Darwin, Dover, ‘Intelligent Design’ and textbooks
Authors: Padian Kevin , Matzke Nicholas
Published: December 2008

ID (‘intelligent design’) is not science, but a form of creationism; both are very different from the simple theological proposition that a divine Creator is responsible for the natural patterns and processes of the Universe. Its current version maintains that a ‘Designer’ must intervene miraculously to accomplish certain natural scientific events. The verdict in the 2005 case Kitzmiller, et al. v. Dover School District, et al. (in Harrisburg, PA, U.S.A.) was a landmark of American jurisprudence that prohibited the teaching of ID as science, identified it as religiously based, and forbade long-refuted ‘criticisms of evolution’ from introduction into public school classes. Much of the science of the trial was based on biochemistry; biochemists and other scientists have several important opportunities to improve scientific literacy and science education in American public schools (‘state schools’) by working with teachers, curriculum developers and textbook writers.
New anti-cancer role for PDK1 inhibitors: preventing resistance to tamoxifen
Authors: Peifer Christian , Alessi Dario R.
Published: December 2008

Tamoxifen is one of the most prescribed anti-breast-cancer drugs, but tumours becoming resistant hinder its efficacy in the clinic. There is therefore great interest in developing strategies to reduce resistance and sensitize breast cancer cells to tamoxifen. A groundbreaking study by Iorns et al. published in this issue of the Biochemical Journal suggests that a signal transduction pathway controlled by PDK1 (phosphoinositide-dependent kinase 1) plays a crucial role in regulating the sensitivity of breast cancer cells to tamoxifen. The implications of this study are that PDK1 or PI3K (phosphoinositide 3-kinase), Akt (also known as protein kinase B), S6K (S6 kinase) and mTOR (mammalian target of rapamycin) inhibitors, already being developed for cancer therapy, are likely to have additional utility in sensitizing breast tumours to tamoxifen. In this commentary we also discuss the possibility that inhibiting the PDK1 pathway may help overcome acquired resistance to other anti-cancer treatments.
Nitrate- and nitrite-responsive sensors NarX and NarQ of proteobacteria
Authors: Stewart V.
Published: December 2008

Nitrate and nitrite are efficient respiratory oxidants for anaerobic growth. In Escherichia coli, the homologous nitrate reductase (Nar) two-component regulatory systems NarX–NarL and NarQ–NarP collaborate to control anaerobic respiratory gene expression in response to nitrate and nitrite. Several other species classified in the γ and β subdivisions of the proteobacteria contain only a single Nar two-component regulatory pair. This raises questions concerning the physiology of anaerobic respiration as well as the evolution, function and cross-regulation of two-component regulatory systems. Here, I focus on the sensor histidine kinases NarX and NarQ, and present a comparison of the deduced NarX and NarQ primary sequences from a broad sampling of proteobacteria. This comparison defines shared features, including a large central region of unknown function that appears to be unique to this family of sensor kinases. I then consider the phylogenetic distribution of narX and narQ genes in relation to anaerobic respiratory enzyme repertoire and physiological function. One noteworthy observation is that narXL genes are specifically associated with the structural genes for membrane-bound nitrate reductase, narGHJI, whereas organization and linkage of the narQ and narP genes is quite variable. I conclude with some speculative thoughts on the evolutionary and functional divergence of the NarX–NarL and NarQ–NarP regulatory systems. Overall, this analysis aims to provide a basis for future hypothesis and experimentation in this area.
Glucocorticoid suppression of nuclear factor-κB: a role for histone modifications
Authors: Kagoshima M. , Ito K. , Cosio B. , Adcock I.M.
Published: December 2008

Corticosteroids are by far the most effective treatment for chronic inflammatory diseases such as asthma. Inflammation in asthma is characterized by the increased expression of multiple inflammatory genes, including those that encode cytokines, chemokines, adhesion molecules, and inflammatory enzymes and receptors. Increased expression of inflammatory genes is regulated by pro-inflammatory transcription factors, such as nuclear factor κB (NF-κB). These bind to, and activate, co-activator molecules that then acetylate core histones resulting in elevated gene transcription. Corticosteroids reverse histone acetylation at the site of inflammatory gene transcription, either by direct binding of the activated glucocorticoid receptor to NF-κB-associated co-activators or by recruitment of histone deacetylases to the activated transcription complex. Understanding how corticosteroids work in asthma may help in designing novel corticosteroids with fewer systemic effects, as well as novel anti-inflammatory approaches.
The role of Rap1 in integrin-mediated cell adhesion
Authors: Bos J.L. , de Bruyn K. , Enserink J. , Kuiperij B. , Rangarajan S. , Rehmann H. , Riedl J. , de Rooij J. , van Mansfeld F. , Zwartkruis F.
Published: December 2008

Rap1 is a member of the Ras-like small GTPases. Originally the protein was identified in a genome-wide screen for suppressors of Ras transformation, but the mechanism of this reversion remained elusive. We have investigated the signalling function of Rap1. We observed that Rap1 is activated by a large variety of stimuli, including growth factors, neurotransmitters and cytokines. Common second messengers like cAMP, diacylglycerol and calcium are mediators of this activation. These messengers activate guanine nucleotide exchange factors (GEFs), the most notable of which is Epac (exchange protein directly activated by cAMP). However, the downstream effectors of Rap1 are less clear. Although direct connections of Rap1 with the serine/threonine kinases Raf1 and B-raf have been reported, we were unable to find functional evidence for an interaction of endogenous Rap1 signalling with the Raf/extracellular-signal-regulated kinase (ERK) pathway. Instead we observe a clear connection of Rap1 with inside-out signalling to integrins. Indeed, introduction of a constitutively active Rap1 as well as Epac induces integrin-mediated cell adhesion, whereas inhibition of Rap1 signalling by the introduction of Rap1GAP (GTPase-activating protein) inhibits inside-out activation of integrins. More importantly, activation of a Gs-protein-coupled receptor results in integrin-mediated cell adhesion, by a pathway involving Epac and Rap1. From these results, we conclude that one of the functions of receptor-induced Rap1 activation is inside-out regulation of integrins.
Integrin–protein kinase C relationships
Authors: Ivaska J. , Kermorgant S. , Whelan R. , Parsons M. , Ng T. , Parker P.J.
Published: December 2008

The integrins have an ability to interact with extracellular matrix proteins to confer adhesive and motile properties on cells. The means by which these activities operate and the manner in which they are integrated with cell functions is of particular relevance to many biological processes. In the present paper, the developing understanding of the bi-directional relationship between the protein kinase C family of signal transducers and integrins is discussed.
Grouping of odorant receptors: odour maps in the mammalian olfactory bulb
Authors: Mori K.
Published: December 2008

The olfactory system is unique in that the sensory input is in the form of molecular information carried in a vast variety of odorants. Nearly 1000 types of odorant receptors mediate the initial detection and discrimination of odorants at the molecular-feature level. The discrimination at the molecular level is converted into that at the cellular level (olfactory sensory neurons) by the one sensory neuron–one odorant receptor rule, and then into that at the neuronal circuit level in the olfactory bulb by the specific olfactory axon connectivity pattern. Individual glomeruli in the olfactory bulb represent a single odorant receptor, and the glomerular sheet at the olfactory bulb surface forms odorant receptor maps. This review focuses on the spatial organization of the glomerular sensory map in the olfactory bulb. The analysis using the optical imaging method suggests that odorant receptors having a common molecular-feature receptive site are grouped together and represented by glomeruli that are localized in topographically fixed domains in the olfactory bulb. The domain organization may be a structural unit for the spatial organization of the glomerular sensory map, and might relate to the olfactory submodality.
Olfactory adventures of elephantine pheromones
Authors: Rasmussen L.E.L. , Lazar J. , Greenwood D.R.
Published: December 2008

Understanding the linkage between behaviour of mammals in their natural environment and the molecular basis of their sensory modalities presents challenges to biologists. Our olfactory investigations that involve the largest extant land mammal, the elephant, offer some clues of how these events mesh in sequence. Proboscideans have developed a sophisticatedly organized society and they rank with primates and cetaceans with respect to cognitive abilities. Our studies of discrete, quantifiable pheromone-elicited behaviours demonstrate that Asian elephants utilize their olfactory senses during fundamental, life-strategy decisions, including mate choice, female bonding and male hierarchical sorting. How biologically relevant odorants traverse mucous interfaces to interact with cognate odorant receptors remains a basic question in vertebrate olfaction. We have partially tracked the molecular odour reception trail of behaviourally distinct pheromones, (Z)-7-dodecenyl acetate and frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane), using approaches developed for insect studies and taking advantage of the extensive, highly mucoidal olfactory and vomeronasal systems that permit detailed investigations of pheromone-binding proteins. We have combined studies of quantifiable responses and behaviours with biochemical and biophysical investigations of the properties of protein–ligand complexes, their sequential pathways and associated protein–ligand fluxes. In the delineation of these sequential integrations of behavioural, biochemical and molecular events, we have discovered novel spatial and temporal adaptations in both the main olfactory and vomeronasal systems.
Multiple roles of major urinary proteins in the house mouse, Mus domesticus
Authors: Beynon R.J. , Hurst J.L.
Published: December 2008

The urine of the house mouse, Mus domesticus, contains large amounts of proteins that are specifically synthesized in the liver to be secreted in the urine. These proteins, termed major urinary proteins (MUPs), have multiple roles in the communication of information in urine-derived scent marks. They bind low-molecular-mass volatile pheromones, and effect their delivery to the scent mark, followed by a slow release that is controlled by the rate of dissociation from the MUPs. However, this family of proteins is extremely polymorphic, more than might be expected for a simple role of ligand binding and release. We have analysed the polymorphism in wild mice, and have now shown that the pattern of MUPs in the urine acts as a type of individuality ‘bar code’ that signals the identity of the owner of the scent mark. This multiplicity of function, from a generic ligand-binding property to an extremely specific individuality, sets the MUPs apart from other lipocalin family proteins that are involved in chemical signalling.
Chemical signalling in mice
Authors: Beauchamp G.K. , Yamazaki K.
Published: December 2008

Odours play a critical role in the behaviour and physiology of many species. For mice and probably many other species, including humans, an individual's olfactory identity (its odourtype) is coded in part by a pattern of volatile compounds that is regulated by genes in the major histocompatibility complex, a string of linked genes that is intimately involved in immune function. The mouse olfactory system is exquisitely sensitive to minute variations in odourtypes. Layered within these chemical signals of individuality is information on the age and health status of the mouse. In the case of age, it appears that information is coded based on a pattern of volatile metabolites; we do not know how a mouse detects, for example, the presence of a viral infection in volatiles from an infected mouse. This chemical information serves to regulate mate choice and other aspects of social behaviour.
The future: putting Humpty-Dumpty together again
Authors: Noble D.
Published: December 2008

Successful biological analysis requires that we understand the functional interactions between key components of cells, organs and systems, and how these interactions change in disease. This information resides neither in the genome nor in the individual proteins that genes encode. It lies at the level of protein interactions within the context of sub-cellular, cellular, tissue, organ and system structures. There is therefore no alternative to copying Nature and computing these interactions to determine the logic of healthy and diseased states. The rapid growth in biological databases, models of cells, tissues and organs, and the development of powerful computing hardware and algorithms have made it possible to explore functionality in a quantitative manner all the way from the level of genes to the physiological function of whole organs and regulatory systems. Systems biology of the 21st century is set to become highly quantitative, and therefore one of the most computer-intensive disciplines.
Physiological role of AMP-activated protein kinase (AMPK): insights from knockout mouse models
Authors: Viollet B. , Andreelli F. , Jørgensen S.B. , Perrin C. , Flamez D. , Mu J. , Wojtaszewski J.F.P. , Schuit F.C. , Birnbaum M. , Richter E. , Burcelin R. , Vaulont S.
Published: December 2008

AMP-activated protein kinase (AMPK) is viewed as a fuel sensor for glucose and lipid metabolism. To understand better the physiological role of the catalytic AMPK subunit isoforms, we generated two knockout mouse models with the α1 (AMPKα1−/−) and α2 (AMPKα2−/−) catalytic subunit genes deleted. No defect in glucose homoeostasis was observed in AMPKα1−/− mice. On the other hand, AMPKα2−/− mice presented high plasma glucose levels and low plasma insulin concentrations in the fed period and during the glucose tolerance test. Nevertheless, in isolated AMPKα2−/− pancreatic islets, glucose-stimulated insulin secretion was not affected. Surprisingly, AMPKα2−/− mice were insulin-resistant and had reduced muscle glycogen synthesis as assessed in vivo by the hyperinsulinaemic euglycaemic clamp procedure. Reduction of insulin sensitivity and glycogen synthesis were not dependent on the lack of AMPK in skeletal muscle, since mice expressing a dominant inhibitory mutant of AMPK in skeletal muscle were not affected and since insulin-stimulated glucose transport in incubated muscles in vitro was normal in AMPKα2−/− muscles. Furthermore, AMPKα2−/− mice have a higher sympathetic tone, as shown by increased catecholamine urinary excretion. Increased adrenergic tone could explain both decreased insulin secretion and insulin resistance observed in vivo in AMPKα2−/− mice. We suggest that the α2 catalytic subunit of AMPK plays a major role as a fuel sensor by modulating the activity of the autonomous nervous system in vivo.
Regulation of cell survival and proliferation by the FOXO (Forkhead box, class O) subfamily of Forkhead transcription factors
Authors: Birkenkamp K.U. , Coffer P.J.
Published: December 2008

Recently, the FOXO (Forkhead box, class O) subfamily of Forkhead transcription factors has been identified as direct targets of phosphoinositide 3-kinase-mediated signal transduction. The AFX (acute-lymphocytic-leukaemia-1 fused gene from chromosome X), FKHR (Forkhead in rhabdomyosarcoma) and FKHR-L1 (FKHR-like 1) transcription factors are directly phosphorylated by protein kinase B, resulting in nuclear export and inhibition of transcription. This signalling pathway was first identified in the nematode worm Caenorhabditis elegans, where it has a role in regulation of the life span of the organism. Studies have shown that this evolutionarily conserved signalling module has a role in regulation of both cell-cycle progression and cell survival in higher eukaryotes. These effects are co-ordinated by FOXO-mediated induction of a variety of specific target genes that are only now beginning to be identified. Interestingly, FOXO transcription factors appear to be able to regulate transcription through both DNA-binding-dependent and -independent mechanisms. Our understanding of the regulation of FOXO activity, and defining specific transcriptional targets, may provide clues to the molecular mechanisms controlling cell fate decisions to divide, differentiate or die.
Oxygen activation in a copper-containing amine oxidase
Authors: Wilmot C.M.
Published: December 2008

The process by which molecular oxygen is activated to enable it to function as an electron acceptor in biology is poorly understood. The quinoprotein copper-containing amine oxidase (CuAO) catalyses the conversion of primary amines into aldehydes. As well as copper, the enzyme contains an organic cofactor, 2,4,5-trihydroxyphenylalanine quinone (TPQ). Following the formation of aldehyde, the enzyme is left as the two-electron reduced aminoquinol form. Reoxidation of the enzyme back to the resting state uses molecular oxygen, which is reduced to H2O2 in the process, with the additional release of NH3. To understand the structural basis of oxygen activation in Escherichia coli CuAO (ECAO), catalytically competent crystals were used to trap catalytic intermediates by exposing then to amine substrate and then freeze-trapping under aerobic and anaerobic conditions. Single-crystal visible microspectrophotometry was used to probe the oxidation state of the quinone in the intermediates, as TPQ exhibits a rich palette of colour changes during catalytic turnover. This review will focus on one of these structures, that of the rate-determining species in the crystal under steady-state conditions. This structure has revealed many details regarding oxygen activation in ECAO, including the site of dioxygen binding, and the proton-transfer pathways involved in H2O2 formation.
Cofactor processing in galactose oxidase
Authors: Firbank S.J. , Rogers M. , Hurtado-Guerrero R. , Dooley D.M. , Halcrow M.A. , Phillips S.E.V. , Knowles P.F. , McPherson M.J.
Published: December 2008

Galactose oxidase (GO; EC 1.1.3.9) is a monomeric 68 kDa enzyme that contains a single copper and an amino acid-derived cofactor. The mechanism of this radical enzyme has been widely studied by structural, spectroscopic, kinetic and mutational approaches and there is a reasonable understanding of the catalytic mechanism and activation by oxidation to generate the radical cofactor that resides on Tyr-272, one of the copper ligands. Biogenesis of this cofactor involves the post-translational, autocatalytic formation of a thioether cross-link between the active-site residues Cys-228 and Tyr-272. This process is closely linked to a peptide bond cleavage event that releases the N-terminal 17-amino-acid pro-peptide. We have shown using pro-enzyme purified in copper-free conditions that mature oxidized GO can be formed by an autocatalytic process upon addition of copper and oxygen. Structural comparison of pro-GO (GO with the prosequence present) with mature GO reveals overall structural similarity, but with some regions showing significant local differences in main chain position and some active-site-residue side chains differing significantly from their mature enzyme positions. These structural effects of the pro-peptide suggest that it may act as an intramolecular chaperone to provide an open active-site structure conducive to copper binding and chemistry associated with cofactor formation. Various models can be proposed to account for the formation of the thioether bond and oxidation to the radical state; however, the mechanism of prosequence cleavage remains unclear.
On the low-temperature microwave response of a YBa2Cu3O7−σ epitaxial film determined by a new measurement technique
Authors: Barannik A. A. , Bunyaev S. A. , Cherpak N. T.
Published: December 2008

The temperature dependence of the surface resistance RS(T) of a high-quality 600-nm thick YBa2Cu2O7−σ epitaxial film, deposited on a MgO single-crystal substrate, has been investigated. The measurements were performed in the temperature range from Tc to 2K using a new technique—the application of a sapphire hemispherical resonator with whispering gallery mode in the 8-mm wavelength range (Ka band). The new measurement technique makes it possible to reach high measurement sensitivity for RS(T) (to 10μΩ) at low temperatures. A linear dependence of RS(T) was obtained in the range 2–15K, in agreement with d-wave symmetry of the order parameter. The value found in the present work for the residual resistance Rres=RS(T→0) shows that the microwave properties of the film are close to those of single-crystals and, apparently, the internal properties of the superconductor determine Rres. Analysis of the published data shows that Rres(ω)∼ω3∕2 for YBa2Cu3O7−σ single crystals and films, and the nature of the residual microwave resistance remains unknown.
Polariton dynamics of one-dimensional gyrotropic magnetic photonic crystal in an external dc electric field. Effective medium approach
Authors: Kulagin D. V. , Savchenko A. S. , Tarasenko S. V.
Published: December 2008

For the example of a semi-infinite thin-layer one-dimensional gyrotropic magnetic photonic crystal of the weak ferromagnet-nonmagnetic insulator type in an external electric field, we determine the conditions under which the quadratic magnetooptic interaction will lead to various anomalies in the reflection and localization of TM or TE waves incident on the surface of the photonic crystal from outside. The electric field is a uniform dc field collinear with the equilibrium antiferromagnetic vector.
Structure, phase transitions, and thermal expansion of ethane C2H6
Authors: Klimenko N. A. , Gal’tsov N. N. , Prokhvatilov A. I.
Published: December 2008

X-Ray investigations of polycrystalline ethane in the temperature interval 6–90K have been performed. A previous suggestion that the structure of the orientationally ordered low-temperature phase III is monoclinic is confirmed, and the presence of an orthorhombic II and cubic I BCC phases near the melting temperature is also confirmed. It is shown that the intermediate phase II possesses a unit cell with the parameters a=4.289Å, b=5.660Å, and c=5.865Å. The volume jump ΔV at the III–II phase transition is found to be 0.21cm3∕mole (0.5%). It is suggested on the basis of the lack of reproducibility in the heating and cooling regimes that the phase II is metastable. It is determined that the volume change at the monoclinic-BCC phase transition in the interval 89.5–90K reaches ΔV=3.05cm3∕mole or 7.1%. The temperature dependences of the parameters and the volume of the low-temperature monoclinic phase III are studied for the first time. The linear and cubic thermal expansion coefficients are determined. It is found that the linear thermal expansion is anisotropic in the monoclinicity plane ac, increasing substantially as the phase transition temperature is approached. The specific heat of ethane at constant volume CV and the Gruneisen constant are calculated and the difference CP−CV is determined. It is shown that at temperatures above 50K CP−CV increases substantially as a result of an intensification of the rotational motion of the molecules.
Multifunctional metal-doped carbon nanocapsules
Authors: Stoyanov Stanislav R. , Král Petr
Published: December 2008

We present an ab initio study of carbon fullerenes, such as C20, C36, C56, C60, and C68, that are substitutionally doped with transition metals coordinated to several nitrogen atoms. These capsules with porphyrinlike metal sites have remarkable electronic and spin polarizations. Additional doping by boron increases their highest occupied molecular orbital–lowest unoccupied molecular orbital gap, stabilizes their electronic structure, and causes their ground states to have higher spin multiplicity, where the spin density is spread over the capsule. These capsules could be applied in molecular electronics, catalysis, light harvesting, and nanomechanics.
The rotational spectrum of HS32OH and HS34OH above 1 THz
Authors: Baum Oliver , Koerber Monika , Ricken Oliver , Winnewisser Gisbert , Yurchenko Sergei N. , Schlemmer Stephan , Yamada Koichi M. T. , Giesen Thomas F.
Published: December 2008

Accurate spectral data of HS32OH and HS34OH at 1.3 THz were recorded using a synthesizer based multiplier spectrometer. The spectra were analyzed together with data from an earlier study which contain measurements at 1.9 THz. The combination of both data sets allows to determine experimentally the tunneling splitting of energy levels with Ka=4 and 5 for the first time. The obtained results are essential to test a novel model on torsional tunneling splitting in HSOH. Transitions with Ka=1←0, Ka=2←1, and Ka=3←2 all exhibit strong c-type and somewhat weaker b-type transitions. In contrary, transitions with Ka=4←3 display only c-type but no b-type transitions. The absence of b-type transitions is completely unexpected and yet not well understood. For the HS34OH isotopolog the data set has been substantially extended by the new measurements of Qr3-branch transitions at 1.3 THz. Based on the new data the accuracy of the HS34OH molecular parameters has been significantly improved.
Effect of an external electric field on the diffusion-influenced reversible reaction of a neutral particle and a charged particle in three dimensions
Authors: Reigh Shang Yik , Shin Kook Joe , Tachiya Masanori
Published: December 2008

The diffusion-influenced reversible reaction of a neutral particle and a charged particle in an external field is analytically solved in three dimensions. A generalized nonisotropic boundary condition is used and a kinetic equation for the probability density function is set up. A tridiagonal matrix equation is derived for the coefficients of the series solution and we obtain the solution within the diagonal approximation in the Laplace domain. We also find that the long time asymptotic behavior of the first term solution shows a kinetic transition from a power law to an exponential behavior as the field strength is increased. The full numerical calculation reveals that the first term solution deviates slightly at short times but gives good result at long times. Thus it contributes dominantly to the kinetic transition behavior at long times. For the irreversible limit, we find a different kinetic transition behavior from a power law to an exponential increase through a constant in the transition region for the initially bound state.
Theoretical study of unimolecular decomposition of allene cations
Authors: Mebel A. M. , Bandrauk A. D.
Published: December 2008

Ab initio coupled clusters and multireference perturbation theory calculations with geometry optimization at the density functional or complete active space self-consistent-field levels have been carried out to compute ionization energies and to unravel the dissociation mechanism of allene and propyne cations, C3H4n+ (n=1–3). The results indicate that the dominant decomposition channel of the monocation is c-C3H3++H, endothermic by 37.9 kcal/mol and occurring via a barrier of 43.1 kcal/mol, with possible minor contributions from H2CCCH++H and HCCCH++H2. For the dication, the competing reaction channels are predicted to be c-C3H3++H+, H2CCCH++H+, and CCCH++H3+, with dissociation energies of −20.5, 8.5, and 3.0 kcal/mol, respectively. The calculations reveal a H2-roaming mechanism for the H3+ loss, where a neutral H2 fragment is formed first, then roams around and abstracts a proton from the remaining molecular fragment before leaving the dication. According to Rice–Ramsperger–Kassel–Marcus calculations of energy-dependent rate constants for individual reaction steps, relative product yields vary with the available internal energy, with c-C3H3++H+ being the major product just above the dissociation threshold of 69.6 kcal/mol, in the energy range of 70–75 kcal/mol, and CCCH++H3+ taking over at higher energies. The C3H43+ trication is found to be not very stable, with dissociation thresholds of 18.5 and 3.7 kcal/mol for allene and propyne, respectively. Various products of Coulomb explosion of C3H43+, H2CCCH2++H+, CHCHCH2++H+, C2H22++CH2+, and CCH22++CH2+ are highly exothermic (by 98–185 kcal/mol). The tetracation of C3H4 is concluded to be unstable and therefore no more than three electrons can be removed from this molecule before it falls apart. The theoretical results are compared to experimental observations of Coulomb explosions of allene and propyne.
From multilayered graphite flakes to nanostructures: A tight-binding molecular dynamics study
Authors: Xu Lei , Lin Yi , Cai Wensheng , Shao Xueguang
Published: December 2008

The nucleation of nanostructures from multilayered graphite flakes with different sizes has been studied by tight-binding molecular dynamics simulations. In agreement with the previous studies, double-layered graphite flakes can be curled up to form the classical carbon nanotubes of different diameters. More interestingly, in given conditions, the transformations from four or six layers of graphite flakes to nanotube bends, heterojunctions, and T or Y junctions have also been observed in the simulations. All of the corresponding results show a two-step dynamic process. This may be a possible mechanism for the nucleation of various carbon nanotube junctions. Additionally, by analyzing and comparing the nucleation processes, it is found that the interlayer distances of multilayered graphite flakes affect the structural transformations to heterojunctions, T or Y junctions.
Dendritic-to-faceted crystal pattern transition of ultrathin poly(ethylene oxide) films
Authors: Zhang Guoliang , Jin Liuxin , Ma Zhenpeng , Zhai Xuemei , Yang Miao , Zheng Ping , Wang Wei , Wegner Gerhard
Published: December 2008

The detailed Tc-sensitive crystal pattern transition from dendrites through fourfold-symmetric structures to faceted crystals of ultrathin poly(ethylene oxide) films has been experimentally observed using atomic force microscopy. The transition has been quantitatively described by the Tc-dependences of the fractal dimension and of the velocity ratio caused by forward and transverse growths in crystal tips. The essential aspect of the pattern selection and transition is mainly the competition of two macroscopic mechanisms: Nucleation-limited and diffusion-limited growths which create faceted and dendritic crystal patterns, respectively. Their combination is a facet growth within a diffusion field which will create a faceted dendrite.
Measurement of the electron attachment rates for SF6 and C7F14 at Te=0.2 eV in a magnetized Q machine plasma
Authors: Merlino Robert L. , Kim Su-Hyun
Published: December 2008

Electron attachment rates for SF6 and C7F14 were measured in a magnetized Q machine plasma at an electron temperature of 0.2±0.02 eV and with neutral gas pressures of P∼10−4 Torr. The rate constants for attachment to SF6 and C7F14 were (7.6±2.0)×10−8 and (2.2±0.9)×10−7 cm3 s−1, respectively.
Controlled three-dimensional manipulation of vanadium oxide nanotubes with optical tweezers
Authors: Hernández-Pozos Jose Luis , Lee Woei Ming , Vera-Robles Liliana Irais , Campero Antonio , Dholakia Kishan
Published: December 2008

We present a direct nanotube-microsphere tagging technique for the controlled three-dimensional (3D) manipulation and transportation of vanadium oxide nanotubes (VOx-NTs) with optical tweezers. The high scattering and absorptive nature of the VOx-NTs preclude the 3D optical trapping of such nanostructures. VOx-NTs are adhered to 3-aminopropyl-triethoxysilane functionalized silica microspheres, which act as handles for indirectly manipulating and transporting the nanotubes in three dimensions with optical tweezers. The optical tweezers can also operate as optical scissors that can remove the dielectric handles and trim these nanotubes. This technique may be extended to the optical manipulation of nanotubes of any material.
A calculation of backscattering factor database for quantitative analysis by Auger electron spectroscopy
Authors: Zeng R. G. , Ding Z. J. , Li Y. G. , Mao S. F.
Published: December 2008

A systematic calculation of the backscattering factor in quantitative analysis by Auger electron spectroscopy has been performed for the primary electron beam of energy from the threshold energy of inner-shell ionization to 30 keV at the incident angle of 0°–89° and for principal Auger transition and Auger electrons emitted from over 28 pure elements at an emission angle of 0°–89° by using a Monte Carlo simulation method. The calculation employs a general definition of backscattering factor, Casnati’s ionization cross section, up-to-date Monte Carlo model of electron scattering, and a large number of electron trajectories to ensure less statistical error. Both the configuration geometry of concentric hemispherical analyzer and the cylindrical mirror analyzer for Auger electron detection are considered in the calculation. The calculated backscattering factors are found to describe very well an experimental dependence of Auger electron intensity on primary energy and on incident angle for Si, Cu, Ag, and W in literature. The calculated numerical values of backscattering factor are stored in an open and online database at http://micro.ustc.edu.cn/BSFDataBase/BFAES.htm.
The mutual promotional effect of Au–Pd bimetallic nanoparticles on silicon nanowires: A study of preparation and catalytic activity
Authors: Shao Mingwang , Wang Hong , Zhang Mingliang , Duo Duo Ma Dorothy , Lee Shuit-Tong
Published: December 2008

Au–Pd nanoparticles were synthesized on the surface of silicon nanowires and used in the degradation of the p-nitroaniline, which exhibited the mutual promotional effect compared with Au/Si and Pd/Si catalysts. This synergistic effect factor was calculated as 2.35. The Au–Pd/Si catalysts might be recycled and used again. The catalytic rate of the catalysts only decreased by 20% after recycling for five times.
Multilevel sensitization of Er3+ in low-temperature-annealed silicon-rich SiO2
Authors: Savchyn Oleksandr , Todi Ravi M. , Coffey Kevin R. , Kik Pieter G.
Published: December 2008

The dynamics of Er3+ excitation in low-temperature-annealed Si-rich SiO2 are studied. It is demonstrated that Si-excess-related indirect excitation is fast (transfer time τtr<27 ns) and occurs into higher lying Er3+ levels as well as directly into the first excited state (I413/2). By monitoring the time-dependent Er3+ emission at 1535 nm, the multilevel nature of the Er3+ sensitization is shown to result in two types of excitation of the I413/2 state: a fast excitation process (τtr<27 ns) directly into the I413/2 level and a slow excitation process due to fast excitation into Er3+ levels above the I413/2 level, followed by internal Er3+ relaxation with a time constant τ32>2.3 μs. The fast and slow excitations of the I413/2 level account for an approximately equal fraction of the excitation events: 45%–50% and 50%–55%, respectively.
Organic heterostructure device with nonvolatile memory behavior using electrically doped layers
Authors: Lindner Frank , Walzer Karsten , Leo Karl
Published: December 2008

Recently, several memory devices based on organic semiconductors were reported. In most cases, single organic layers were employed, and the switching mechanisms were not fully understood. Here, we report on a novel device structure based on electrically doped organic heterostructures showing highly stable memory behavior. The organic layers are embedded between a bottom indium tin oxide and a top metal contact and form a quantum well-like structure. The device shows a hysteresis in the current-voltage characteristics and well-defined switching behavior. We achieved reproducible bistable electrical switching and stable memory phenomena in these organic multilayer heterostructure devices. The two states were retained for up to several days without noticeable decrease of their on/off ratio. Further, it was found that the ratio of the on/off current depends on the writing voltage, allowing the use as multistate memory.
Residual strain in nonpolar a-plane Zn1−xMgxO (<x<0.55) and its effect on the band structure of (Zn,Mg)O/ZnO quantum wells
Authors: Chauveau J.-M. , Vives J. , Zuniga-Perez J. , Laügt M. , Teisseire M. , Deparis C. , Morhain C. , Vinter B.
Published: December 2008

We investigate the dependence on Mg content of the lattice parameters and the surface morphology of nonpolar a-(112¯0) Zn1−xMgxO (x≤0.55) grown by molecular beam epitaxy. The anisotropy of the lattice parameters gives rise to an unusual in-plane strain state in the ZnO QWs: tensile strain along [11¯00] and compressive strain along [0001]. For a Zn0.6Mg0.4O barrier, the strain in a ZnO QW reaches −1.3% along [0001] and +0.3% along [11¯00]. This induces a strong blueshift of the excitonic transitions, in addition to the confinement effects, which we observe in photoluminescence excitation experiments.
Invariant critical stress for shear banding in a bulk metallic glass
Authors: Han Z. , Yang H. , Wu W. F. , Li Y.
Published: December 2008

Through uncovering the macroscopic true stress after correction with the instant load-bearing area, we found that the critical stress for continuous shear banding of a bulk metallic glass (BMG) maintains invariant on and after yielding as the plastic deformation progresses. This finding is in strong contrast with the previous reports of either “strain hardening” or “strain softening” associated with the plastic deformation of BMGs. Our results point out that atomic cohesive energy constantly serves to be the controlling factor of the critical stress for shear banding.
(001) FePt nanoparticles with ultrahigh density of 10 T dots/in.2 on amorphous SiO2 substrates
Authors: Wu Yun-Chung , Wang Liang-Wei , Lai Chih-Huang
Published: December 2008

Highly ordered single-crystalline (001) FePt nanoparticles (NPs) with controllable sizes and a well-aligned easy axis were obtained by tuning the layer numbers and the SiO2-layer thickness of atomic-scale [Fe/Pt/SiO2]n multilayers deposited on SiO2∥Si substrates. After 700 °C annealing, quasi-self-assembled NPs with ultrahigh areal density of 1.0×1013 dots/in.2 and large out-of-plane coercivity (Hc,⊥) of 31 kOe were achieved. All particles were embedded into the SiO2 substrates due to the low surface energy of SiO2, which significantly prevented the coarsening during annealing and resulted in a reduced particle size of 5.6 nm and small size distribution of 14.1%.
Design and evaluation of a silicon based multi-nozzle for addressable jetting using a controlled flow rate in electrohydrodynamic jet printing
Authors: Lee Jun-Sung , Kim Sang-Yoon , Kim Young-Jae , Park Jaehong , Kim Yong , Hwang Jungho , Kim Yong-Jun
Published: December 2008

This letter reports on the development and evaluation of a electrohydrodynamic jet printing that uses an addressable multinozzle. To reduce the interference and distortion in the electric field, a multinozzle was fabricated from a silicon wafer. The experimental conditions were optimized to prevent the jet from bending at the end of the multinozzle and to allow for independent control of each nozzle. To better evaluate this technique, simulations were performed and compared with the experimental results. We observed a strong correlation between the simulated and experimental results. In addition, each nozzle in this multinozzle could be individually controlled.
On unitary unipotent representations of 𝑝-adic groups and affine Hecke algebras with unequal parameters
Authors: Ciubotaru Dan
Published: December 2008

We determine the unitary dual of the geometric graded Hecke algebras with unequal parameters which appear in Lusztig’s classification of unipotent representations for exceptional

p
p

-adic groups. The largest such algebra is of type

F
4

.

F_4.

Via the Barbasch-Moy correspondence of unitarity applied to this setting, this is equivalent to the identification of the corresponding unitary unipotent representations with real central character of the

p
p

-adic groups. In order for this correspondence to be applicable here, we show (following Lusztig’s geometric classification, and Barbasch and Moy’s original argument) that the set of tempered modules with real central character for a geometric graded Hecke algebra is linearly independent when restricted to the Weyl group.
Discovery of a Novel Molecule that Regulates Tumor Growth and Metastasis
Authors: Whipple Chery A. , Lander Arthur D. , Korc Murray
Published: December 2008

The heparan sulfate proteoglycan, Glypican-1 (GPC1), significantly impacts the growth of pancreatic cancer cellsin vivoand markedly attenuates tumor angiogenesis and metastasis in athymic mice. Interestingly, both cancer cell–derived and host-derived GPC1 play an important role in tumor development and spread. These data suggest that GPC1 may be a valid therapeutic target for pancreatic cancer.
Safety and efficacy of rasburicase (SR29142) in a Japanese phase II study
Authors: Ishizawa Kenichi , Ogura Michinori , Hamaguchi Motohiro , Hotta Tomomitsu , Ohnishi Kazunori , Sasaki Tsuneo , Sakamaki Hisashi , Yokoyama Hisayuki , Harigae Hideo , Morishima Yasuo
Published: December 2008

The purpose of this study was to investigate the safety profile of SR29142 when administered as a single agent both prior to chemotherapy and during treatment, and to compare the efficacy of SR29142 administered at two dose levels in adult Japanese patients with leukemia or lymphoma. During this open‐label, multicenter, phase II study, patients received SR29142 for 5 days, administered at either 0.15 or 0.20 mg/kg per day. Chemotherapy was started 4–24 h after the first infusion of SR29142. The primary end‐point was overall response rate, defined as the normalization of plasma uric acid to 7.5 mg/dL or less, from 48 h after the first infusion to 24 h after the last infusion of SR29142. SR29142‐related adverse events including hypersensitivity (allergic) reactions were assessed. Overall, 50 patients received SR29142 at either 0.15 mg/kg per day (n = 25) or 0.20 mg/kg per day (n = 25) followed by chemotherapy. The overall response rate was 100.0% (95% confidence interval, 86.3–100.0%) with 0.15 mg/kg and 96.0% (95% confidence interval, 79.6–99.9%) with 0.20 mg/kg. Both dose levels of SR29142 were equally effective at reducing plasma uric acid levels. In six patients, seven drug‐related adverse events of grade 1/2 occurred before chemotherapy. SR29142‐related, hypersensitivity‐associated reactions occurred in three patients, and rash, anorexia, application site pain and pyrexia occurred in one patient each; only five patients (10%) showed anti‐SR29142 antibodies by day 29. In conclusion, SR29142 is effective at reducing plasma uric acid levels with a tolerable safety profile as a single agent both prior to chemotherapy and during treatment. (Trial register: ClinicalTrials.gov, NCT00631579.) (Cancer Sci 2009; 100: 357–362)
Newer antifungal agents for invasive fungal infections in patients with haematological malignancy
Authors: Rogers Thomas R. , Frost Susanna
Published: December 2008

Since 2001 five new systemically administered antifungal agents have been approved for clinical use. This represents a major advance for antifungal therapy in haematological malignancy patients undergoing chemotherapy or haematopoietic stem cell transplant (HSCT). The echinocandins are a new class of antifungals with a novel mode of action. Capsofungin has already established itself as a valuable therapy for candidaemia and salvage therapy of invasive aspergillosis. Although both anidulafungin and micafungin are approved for treatment of candidiasis, their role in invasive aspergillosis requires more clinical trial evaluation. Of the two newer triazoles, voriconazole has been recommended in international guidelines as primary therapy for acute invasive aspergillosis. Posaconazole has a broad spectrum of activity in vitro and a potentially key role in antifungal prophylaxis in high‐risk HSCT recipients and during prolonged neutropenia. Although some of these drugs have important interactions with other medications, and potential toxicities, they are safer to use and more efficacious than amphotericin B deoxycholate. Their arrival gives more choices to treat rarer mycoses and will facilitate clinical trial assessment of combination therapy of aspergillosis where single agent therapy gives less than 50% success rates.