bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Ongoing Human Immunodeficiency Virus Type 1 (HIV-1) Replication in Residual Viremia during Recombinant HIV-1 Poxvirus Immunizations in Patients with Clinically Undetectable Viral Loads on Durable Suppressive Highly Active Antiretroviral Therapy
Authors: Shiu Carlum , Cunningham Coleen K. , Greenough Thomas , Muresan Petronella , Sanchez-Merino Victor , Carey Vincent , Jackson J. Brooks , Ziemniak Carrie , Fox Lawrence , Belzer Marvin , Ray Stuart C. , Luzuriaga Katherine , Persaud Deborah
Published: July 2009

In most human immunodeficiency virus type 1 (HIV-1)-infected individuals who achieve viral loads of <50 copies/ml during highly active antiretroviral therapy (HAART), low levels of plasma virus remain detectable for years by ultrasensitive methods. The relative contributions of ongoing virus replication and virus production from HIV-1 reservoirs to persistent low-level viremia during HAART remain controversial. HIV-1 vaccination of HAART-treated individuals provides a model for examining low-level viremia, as immunizations may facilitate virus replication and sequence evolution. In a phase 1 trial of modified vaccinia virus Ankara/fowlpox virus-based HIV-1 vaccines in 20 HIV-infected young adults receiving HAART, we assessed the prevalence of low-level viremia and sequence evolution, using ultrasensitive viral load (<6.5 copies/ml) and genotyping (five-copy sensitivity) assays. Viral evolution, consisting of new drug resistance mutations and novel amino acid changes within a relevant HLA-restricted allele (e.g., methionine, isoleucine, glutamine, or arginine for leucine at position 205 of RT), was found in 1 and 3 of 20 subjects, respectively. Sequence evolution was significantly correlated with levels of viremia of between 6.5 and <50 copies/ml (P= 0.03) and was more likely to occur within epitopes presented by relevant HLA alleles (P< 0.001). These findings suggest that ongoing virus replication contributes to low-level viremia in patients on HAART and that this ongoing replication is subject to CD8+T-cell selective pressures.
Distribution of Endogenous Retroviruses in Crocodilians
Authors: Jaratlerdsiri Weerachai , Rodríguez-Zárate Clara J. , Isberg Sally R. , Damayanti Chandramaya Siska , Miles Lee G. , Chansue Nantarika , Moran Chris , Melville Lorna , Gongora Jaime
Published: July 2009

Knowledge of endogenous retroviruses (ERVs) in crocodilians (Crocodylia) is limited, and their distribution among extant species is unclear. Here we analyzed the phylogenetic relationships of these retroelements in 20 species of crocodilians by studying the
pro-pol
gene. The results showed that crocodilian ERVs (CERVs) cluster into two major clades (CERV 1 and CERV 2). CERV 1 clustered as a sister group of the genus
Gammaretrovirus
, while CERV 2 clustered distantly with respect to all known ERVs. Interestingly, CERV 1 was found only in crocodiles (Crocodylidae). The data generated here could assist future studies aimed at identifying orthologous and paralogous ERVs among crocodilians.
Simian Varicella Virus Induces Apoptosis in Monkey Kidney Cells by the Intrinsic Pathway and Involves Downregulation of Bcl-2 Expression
Authors: Pugazhenthi Subbiah , Gilden Donald H. , Nair Sreekala , McAdoo Anne , Wellish Mary , Brazeau Elizabeth , Mahalingam Ravi
Published: July 2009

Simian varicella virus (SVV) causes varicella in primates, becomes latent in ganglionic neurons, and reactivates to produce zoster. SVV produces a cytopathic effect in monkey kidney cells in tissue culture. To study the mechanism by which SVV-infected cells die, we examined markers of apoptosis 24 to 64 h postinfection (hpi). Western blot analysis of virus-infected cell lysates revealed a significant increase in the levels of the cleaved active form of caspase-3, accompanied by a parallel increase in caspase-3 activity at 40 to 64 hpi. Caspase-9, a marker for the intrinsic pathway, was activated significantly in SVV-infected cells at all time points, whereas trace levels of the active form of caspase-8, an extrinsic pathway marker, was detected only at 64 hpi. Bcl-2 expression at the mRNA and protein levels was decreased by 50 to 70% throughout the course of virus infection. Release of cytochrome
c
, an activator of caspase-9, from mitochondria into the cytoplasm was increased by 200% at 64 hpi. Analysis of Vero cells infected with SVV expressing green fluorescent protein (SVV-GFP) at 64 hpi revealed colocalization of the active forms of caspase-3 and caspase-9 and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining with GFP. A significant decrease in the
bcl-2
mRNA levels along with an abundance of mRNA specific for SVV genes 63, 40, and 21 was seen in the fraction of Vero cells that were infected with SVV-GFP. Together, these findings indicate that SVV induces apoptosis in cultured Vero cells through the intrinsic pathway in which Bcl-2 is downregulated.
Hepatitis C Virus Core Protein and Cellular Protein HAX-1 Promote 5-Fluorouracil-Mediated Hepatocyte Growth Inhibition
Authors: Banerjee Arup , Saito Kousuke , Meyer Keith , Banerjee Sutapa , Ait-Goughoulte Malika , Ray Ratna B. , Ray Ranjit
Published: July 2009

Hepatitis C virus (HCV) often causes chronic infection and may lead to hepatocellular carcinoma (HCC). We have shown previously that HCV core protein has pleiotropic functions, including transcriptional regulation of a number of cellular genes, although the mechanism for gene regulation remains unclear. In this study, a mammalian two-hybrid screen identified a novel binding partner, HS1-associated protein X-1 (HAX-1), for HCV core protein from a human liver cDNA library. An association between HAX-1 and HCV core protein was further verified by confocal microscopy and coimmunoprecipitation in HepG2 cells expressing HCV core or full-length (FL) gene. Both HCV core protein and a chemotherapeutic agent for HCC, 5-flouorouracil (5-FU), are known to modulate p53. We examined here whether an association between core and HAX-1 has any functional relevance to p53 modulation in 5-FU-treated cells. For this, the role of HAX-1 on 5-FU treatment was examined in HepG2 cells expressing HCV core or FL gene using cell proliferation, p53 expression, and caspase activation analysis. Cells expressing HCV-core or FL gene were more susceptible to 5-FU-induced growth inhibition than control cells, whereas cell survival was enhanced after suppression of HAX-1 by small interfering RNA. Further, 5-FU-mediated p53 expression was reduced with concurrent HAX-1 suppression in core- or polyprotein-expressing cells compared to control HepG2 cells, and caspase-2 and -7 activities were diminished. On the other hand, HCV core protein did not play a detectable role in 5-FU-mediated caspase-7 activation in the absence of functional p53 in Hep3B or Huh-7 cells. These observations underscore an association between HCV core and HAX-1, which promotes 5-FU mediated p53-dependent caspase-7 activation and hepatocyte growth inhibition.
Impact of HLA in Mother and Child on Disease Progression of Pediatric Human Immunodeficiency Virus Type 1 Infection
Authors: Thobakgale Christina F. , Prendergast Andrew , Crawford Hayley , Mkhwanazi Nompumelelo , Ramduth Danni , Reddy Sharon , Molina Claudia , Mncube Zenele , Leslie Alasdair , Prado Julia , Chonco Fundi , Mphatshwe Wendy , Tudor-Williams Gareth , Jeena Prakash , Blanckenberg Natasha , Dong Krista , Kiepiela Photini , Coovadia Hoosen , Ndung'u Thumbi , Walker Bruce D. , Goulder Philip J. R.
Published: July 2009

A broad Gag-specific CD8
+
T-cell response is associated with effective control of adult human immunodeficiency virus (HIV) infection. The association of certain HLA class I molecules, such as HLA-B*57, -B*5801, and -B*8101, with immune control is linked to mutations within Gag epitopes presented by these alleles that allow HIV to evade the immune response but that also reduce viral replicative capacity. Transmission of such viruses containing mutations within Gag epitopes results in lower viral loads in adult recipients. In this study of pediatric infection, we tested the hypothesis that children may tend to progress relatively slowly if either they themselves possess one of the protective HLA-B alleles or the mother possesses one of these alleles, thereby transmitting a low-fitness virus to the child. We analyzed HLA type, CD8
+
T-cell responses, and viral sequence changes for 61 mother-child pairs from Durban, South Africa, who were monitored from birth. Slow progression was significantly associated with the mother or child possessing one of the protective HLA-B alleles, and more significantly so when the protective allele was not shared by mother and child (
P
= 0.007). Slow progressors tended to make CD8
+
T-cell responses to Gag epitopes presented by the protective HLA-B alleles, in contrast to progressors expressing the same alleles (
P
= 0.07; Fisher's exact test). Mothers expressing the protective alleles were significantly more likely to transmit escape variants within the Gag epitopes presented by those alleles than mothers not expressing those alleles (75% versus 21%;
P
= 0.001). Reversion of transmitted escape mutations was observed in all slow-progressing children whose mothers possessed protective HLA-B alleles. These data show that HLA class I alleles influence disease progression in pediatric as well as adult infection, both as a result of the CD8
+
T-cell responses generated in the child and through the transmission of low-fitness viruses by the mother.
Artificial Transmembrane Oncoproteins Smaller than the Bovine Papillomavirus E5 Protein Redefine Sequence Requirements for Activation of the Platelet-Derived Growth Factor β Receptor
Authors: Talbert-Slagle Kristina , Marlatt Sara , Barrera Francisco N. , Khurana Ekta , Oates Joanne , Gerstein Mark , Engelman Donald M. , Dixon Ann M. , DiMaio Daniel
Published: July 2009

The bovine papillomavirus E5 protein (BPV E5) is a 44-amino-acid homodimeric transmembrane protein that binds directly to the transmembrane domain of the platelet-derived growth factor (PDGF) β receptor and induces ligand-independent receptor activation. Three specific features of BPV E5 are considered important for its ability to activate the PDGF β receptor and transform mouse fibroblasts: a pair of C-terminal cysteines, a transmembrane glutamine, and a juxtamembrane aspartic acid. By using a new genetic technique to screen libraries expressing artificial transmembrane proteins for activators of the PDGF β receptor, we isolated much smaller proteins, from 32 to 36 residues, that lack all three of these features yet still dimerize noncovalently, specifically activate the PDGF β receptor via its transmembrane domain, and transform cells efficiently. The primary amino acid sequence of BPV E5 is virtually unrecognizable in some of these proteins, which share as few as seven consecutive amino acids with the viral protein. Thus, small artificial proteins that bear little resemblance to a viral oncoprotein can nevertheless productively interact with the same cellular target. We speculate that similar cellular proteins may exist but have been overlooked due to their small size and hydrophobicity.
Ganglioside GT1b Is a Putative Host Cell Receptor for the Merkel Cell Polyomavirus
Authors: Erickson Kimberly D. , Garcea Robert L. , Tsai Billy
Published: July 2009

The Merkel cell polyomavirus (MCPyV) was identified recently in human Merkel cell carcinomas, an aggressive neuroendocrine skin cancer. Here, we identify a putative host cell receptor for MCPyV. We found that recombinant MCPyV VP1 pentameric capsomeres both hemagglutinated sheep red blood cells and interacted with ganglioside GT1b in a sucrose gradient flotation assay. Structural differences between the analyzed gangliosides suggest that MCPyV VP1 likely interacts with sialic acids on both branches of the GT1b carbohydrate chain. Identification of a potential host cell receptor for MCPyV will aid in the elucidation of its entry mechanism and pathophysiology.
Single-Reaction Genomic Amplification Accelerates Sequencing and Vaccine Production for Classical and Swine Origin Human Influenza A Viruses
Authors: Zhou Bin , Donnelly Matthew E. , Scholes Derek T. , St. George Kirsten , Hatta Masato , Kawaoka Yoshihiro , Wentworth David E.
Published: July 2009

Pandemic influenza A viruses that emerge from animal reservoirs are inevitable. Therefore, rapid genomic analysis and creation of vaccines are vital. We developed a multisegment reverse transcription-PCR (M-RTPCR) approach that simultaneously amplifies eight genomic RNA segments, irrespective of virus subtype. M-RTPCR amplicons can be used for high-throughput sequencing and/or cloned into modified reverse-genetics plasmids via regions of sequence identity. We used these procedures to rescue a contemporary H3N2 virus and a swine origin H1N1 virus directly from human swab specimens. Together, M-RTPCR and the modified reverse-genetics plasmids that we designed streamline the creation of vaccine seed stocks (9 to 12 days).
The Adenovirus E1B 55-Kilodalton and E4 Open Reading Frame 6 Proteins Limit Phosphorylation of eIF2α during the Late Phase of Infection
Authors: Spurgeon Megan E. , Ornelles David A.
Published: July 2009

During a productive infection, species C adenovirus reprograms the host cell to promote viral translation at the expense of cellular translation. The E1B 55-kilodalton (E1B-55K) and E4 open reading frame 6 (E4orf6) proteins are important in this control of gene expression. As part of a ubiquitin-protein ligase, these viral proteins stimulate viral mRNA export, inhibit cellular mRNA export, promote viral gene expression, and direct the degradation of certain host proteins. We report here that the E1B-55K and E4orf6 proteins limited phosphorylation of eIF2α and the activation of the eIF2α kinase PKR. Phospho-eIF2α levels were observed to rise and fall at least twice during infection. The E1B-55K and E4orf6 proteins prevented a third increase at late times of infection. PKR appeared to phosphorylate eIF2α only in the absence of E1B-55K/E4orf6 function. PKR activation and eIF2α phosphorylation was unrelated to the cytoplasmic levels of the adenovirus inhibitor of PKR, VA-I RNA. Nonetheless, expression of a PKR inhibitor, the reovirus double-stranded RNA-binding protein sigma 3, prevented PKR activation and eIF2α phosphorylation. The sigma 3 protein largely corrected the defect in viral late protein synthesis associated with the E1B-55K and E4orf6 mutant viruses without affecting cytoplasmic levels of the late viral mRNA. The ubiquitin-protein ligase activity associated with the E1B-55K/E4orf6 complex was necessary to prevent activation of PKR and phosphorylation of eIF2α. These findings reveal a new contribution of the E1B-55K/E4orf6 complex to viral late protein synthesis and the existence of multiple layers of regulation imposed on eIF2α phosphorylation and PKR activation in adenovirus-infected cells.
Immune Evasion Proteins Enhance Cytomegalovirus Latency in the Lungs
Authors: Böhm Verena , Seckert Christof K. , Simon Christian O. , Thomas Doris , Renzaho Angélique , Gendig Dorothea , Holtappels Rafaela , Reddehase Matthias J.
Published: July 2009

CD8 T cells control cytomegalovirus (CMV) infection in bone marrow transplantation recipients and persist in latently infected lungs as effector memory cells for continuous sensing of reactivated viral gene expression. Here we have addressed the question of whether viral immunoevasins, glycoproteins that specifically interfere with antigen presentation to CD8 T cells, have an impact on viral latency in the murine model. The data show that deletion of immunoevasin genes in murine CMV accelerates the clearance of productive infection during hematopoietic reconstitution and leads to a reduced latent viral genome load, reduced latency-associated viral transcription, and a lower incidence of recurrence in lung explants.
Class III Phosphatidylinositol 4-Kinase Alpha and Beta Are Novel Host Factor Regulators of Hepatitis C Virus Replication
Authors: Borawski Jason , Troke Philip , Puyang Xiaoling , Gibaja Veronica , Zhao ShanChaun , Mickanin Craig , Leighton-Davies Juliet , Wilson Christopher J. , Myer Vic , CornellaTaracido Ivan , Baryza Jeremy , Tallarico John , Joberty Gerard , Bantscheff Marcus , Schirle Markus , Bouwmeester Tewis , Mathy Joanna E. , Lin Kai , Compton Teresa , Labow Mark , Wiedmann Brigitte , Gaither L. Alex
Published: July 2009

Host factor pathways are known to be essential for hepatitis C virus (HCV) infection and replication in human liver cells. To search for novel host factor proteins required for HCV replication, we screened a subgenomic genotype 1b replicon cell line (Luc-1b) with a kinome and druggable collection of 20,779 siRNAs. We identified and validated several enzymes required for HCV replication, including class III phosphatidylinositol 4-kinases (PI4KA and PI4KB), carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD), and mevalonate (diphospho) decarboxylase. Knockdown of PI4KA could inhibit the replication and/or HCV RNA levels of the two subgenomic genotype 1b clones (SG-1b and Luc-1b), two subgenomic genotype 1a clones (SG-1a and Luc-1a), JFH-1 genotype 2a infectious virus (JFH1-2a), and the genomic genotype 1a (FL-1a) replicon. In contrast, PI4KB knockdown inhibited replication and/or HCV RNA levels of Luc-1b, SG-1b, and Luc-1a replicons. The small molecule inhibitor, PIK93, was found to block subgenomic genotype 1b (Luc-1b), subgenomic genotype 1a (Luc-1a), and genomic genotype 2a (JFH1-2a) infectious virus replication in the nanomolar range. PIK93 was characterized by using quantitative chemical proteomics and in vitro biochemical assays to demonstrate PIK93 is a bone fide PI4KA and PI4KB inhibitor. Our data demonstrate that genetic or pharmacological modulation of PI4KA and PI4KB inhibits multiple genotypes of HCV and represents a novel druggable class of therapeutic targets for HCV infection.
ADAR1 Interacts with PKR during Human Immunodeficiency Virus Infection of Lymphocytes and Contributes to Viral Replication
Authors: Clerzius Guerline , Gélinas Jean-François , Daher Aïcha , Bonnet Marion , Meurs Eliane F. , Gatignol Anne
Published: July 2009

The interferon-induced protein kinase RNA activated (PKR) is activated after virus infection. This activation is transient during the human immunodeficiency virus type 1 (HIV-1) infection of lymphocytes, and the protein is not activated at the peak of infection. We observed that interferon-induced adenosine deaminase acting on RNA 1-p150 (ADAR1-p150) and ADAR1-p110 expression increases while the virus replicates actively. Furthermore, both forms of ADAR1 show enhanced interactions with PKR at the peak of HIV infection, suggesting a role for this protein in the regulation of PKR activation. We observed that ADAR1-p150, as previously shown for the TAR RNA binding protein (TRBP), reverses the PKR inhibition of HIV expression and production in HEK 293T cells. This activity requires the Z-DNA binding motif and the three double-stranded RNA binding domains but not the catalytic domain. In astrocytic cells, ADAR1-p150 increased HIV expression and production to an extent similar to that of TRBP. Small interfering RNAs against ADAR1-p150 moderately decreased HIV production. These results indicate that two interferon-induced proteins, ADAR1 and PKR, have antagonistic functions on HIV production. They suggest that ADAR1 and TRBP belong to a multiprotein complex that inhibits PKR during the HIV infection of lymphocytes.
Surface analysis by imaging mass spectrometry
Authors: Vidová Veronika , Volný Michael , Lemr Karel , Havlíček Vladimír
Published: July 2009

A review of four MS-based techniques available for molecular surface imaging is presented. The main focus is on the commercially available mass spectrometry imaging techniques: secondary ion mass spectrometry (SIMS), matrix assisted laser desorption ionization mass spectrometry (MALDI-MS), desorption electrospray ionization mass spectrometry (DESI-MS) and laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS). A short historical perspective is presented and traditional desorption ionization techniques are also briefly described. The four techniques are compared mainly with respect to their usage for imaging of biological surfaces. MALDI is evaluated as the most successful in life sciences and the only technique usable for imaging of large biopolymers. SIMS is less common but offers superior spatial lateral resolution and DESI is considered to be an emerging alternative approach in mass spectrometry imaging. LA-ICP ionization is unbeatable in terms of limits of detection but does not provide structural information. All techniques are considered extremely useful, representing a new wave of expansion of mass spectrometry into surface science and bioanalysis. A minireview with 121 references.
Bridged bis-Tröger’s base molecular tweezers as new cavitand family
Authors: Havlík Martin , Parchaňský Václav , Bouř Petr , Král Vladimír , Dolensky Bohumil
Published: July 2009

New molecular tweezers based on bis-Tröger’s base with methoxycarbonyl groups on its pincers was prepared. These groups were converted into hydroxymethyl groups, which were interconnected by a linker to give the bridged molecular tweezers, a cavitand. The cavitand was studied and its ability to bind nitrobenzene was compared with similar bis-Tröger’s base molecular tweezers.
Dry beriberi mimicking the Guillain–Barré syndrome
Authors: Murphy C , Bangash I H , Varma A
Published: July 2009

A 44-year-old man is described with severe flaccid quadriparesis that evolved over 3 weeks. He had regularly binged on alcohol—up to 20 cans of beer per day with occasional consumption of spirits—for more than 15 years but had balanced this with regular food intake. However, for a week prior to the current episode he had not eaten anything of significance. Nerve conduction studies revealed a background peripheral, mainly sensory, neuropathy with a superimposed acute motor axonopathy. CSF was normal. He improved with high dose vitamin replacement and physiotherapy but remains dependent on a Zimmer frame for mobility and a splint for wrist drop.
CORRESPONDENCE BETWEEN MODIFIED GRAVITY AND 5D RICCI-FLAT COSMOLOGIES
Authors: ATAZADEH K. , SEPANGI H. R. , DARABI F.
Published: July 2009

We study the correspondence between two theoretical frameworks for describing dark energy: f(R) gravity and higher-dimensional space–time–matter (STM) or induced matter theory. We show that the Hubble expansion parameter in f(R) gravity can be associated with a combination of metric functions in STM theory, and consider a specific example whose properties are consistent with late time acceleration.
COSMOLOGY WITH MINIMAL LENGTH UNCERTAINTY RELATIONS
Authors: VAKILI BABAK
Published: July 2009

We study the effects of the existence of a minimal observable length in the phase space of classical and quantum de Sitter (dS) and anti-de Sitter (AdS) cosmology. Since this length has been suggested in quantum gravity and string theory, its effects in the early universe might be expected. Adopting the existence of such a minimum length results in the generalized uncertainty principle (GUP), which is a deformed Heisenberg algebra between minisuperspace variables and their momenta operators. We extend these deformed commutating relations to the corresponding deformed Poisson algebra in the classical limit. Using the resulting Poisson and Heisenberg relations, we then construct the classical and quantum cosmology of dS and AdS models in a canonical framework. We show that in classical dS cosmology this effect yields an inflationary universe in which the rate of expansion is larger than that of the usual dS universe. Also, for the AdS model it is shown that the GUP might change the oscillatory nature of the corresponding cosmology. We also study the effects of the GUP in quantized models through approximate analytical solutions to the Wheeler–DeWitt (WD) equation, in the limit of a small scale factor for the universe, and compare the results with the ordinary quantum cosmology in each case.
FOCUSING VERSUS DEFOCUSING PROPERTIES OF TRULY NAKED BLACK HOLES
Authors: DADHICH NARESH , ZASLAVSKII OLEG B.
Published: July 2009

We study the properties of the congruence of null geodesics propagating near the so-called truly naked horizons (TNHs) — objects having a finite Kretschmann scalar but with diverging tidal acceleration for freely falling observers. The expansion of outgoing rays near the future horizon always tends to vanish for the nonextremal case but may be nonzero for the distorted (ultra)extremal one. It tends to diverge for the ingoing rays if the the null energy condition (NEC) is satisfied in the vicinity of the horizon outside. However, it also tends to zero for NEC-violating cases except for the remote horizons. We also discuss the validity of test particle approximation for TNHs and find the sufficient condition for the backreaction to remain small.
ENERGY CONDITIONS IN f(R) GRAVITY AND BRANS–DICKE THEORIES
Authors: ATAZADEH K. , KHALEGHI A. , SEPANGI H. R. , TAVAKOLI Y.
Published: July 2009

The equivalence between f(R) gravity and scalar–tensor theories is invoked to study the null, strong, weak and dominant energy conditions in Brans–Dicke theory. We consider the validity of the energy conditions in Brans–Dicke theory by invoking the energy conditions derived from a generic f(R) theory. The parameters involved are shown to be consistent with an accelerated expanding universe.
CONSTRAINTS ON DARK ENERGY FROM THE OBSERVED EXPANSION OF OUR COSMIC HORIZON
Authors: MELIA FULVIO
Published: July 2009

Within the context of standard cosmology, an accelerating universe requires the presence of a third "dark" component of energy, beyond matter and radiation. The available data, however, are still deemed insufficient to distinguish between an evolving dark energy component and the simplest model of a time-independent cosmological constant. In this paper, we examine the cosmological expansion in terms of observer-dependent coordinates, in addition to the more conventional comoving coordinates. This procedure explicitly reveals the role played by the radius Rh of our cosmic horizon in the interrogation of the data. (In Rindler's notation, Rh coincides with the "event horizon" in the case of de Sitter, but changes in time for other cosmologies that also contain matter and/or radiation.) With this approach, we show that the interpretation of dark energy as a cosmological constant is clearly disfavored by the observations. Within the framework of standard Friedmann–Robertson–Walker cosmology, we derive an equation describing the evolution of Rh, and solve it using the WMAP and Type Ia supernova data. In particular, we consider the meaning of the observed equality (or near-equality) Rh(t0) ≅ ct0, where t0 is the age of the universe. This empirical result is far from trivial, for a cosmological constant would drive Rh(t) toward ct (t is the cosmic time) only once — and that would have to occur right now. Though we are not here espousing any particular alternative model of dark energy, for comparison we also consider scenarios in which dark energy is given by scaling solutions, which simultaneously eliminate several conundrums in the standard model, including the "coincidence" and "flatness" problems, and account very well for the fact that Rh(t0) ≈ ct0.
LUNAR LASER RANGING TESTS OF THE EQUIVALENCE PRINCIPLE WITH THE EARTH AND MOON
Authors: WILLIAMS JAMES G. , TURYSHEV SLAVA G. , BOGGS DALE H.
Published: July 2009

A primary objective of the lunar laser ranging (LLR) experiment is to provide precise observations of the lunar orbit that contribute to a wide range of science investigations. In particular, time series of the highly accurate measurements of the distance between the Earth and the Moon provide unique information used to determine whether, in accordance with the equivalence principle (EP), these two celestial bodies are falling toward the Sun at the same rate, despite their different masses, compositions, and gravitational self-energies. Thirty-five years since their initiation, analyses of precision laser ranges to the Moon continue to provide increasingly stringent limits on any violation of the EP. Current LLR solutions give (-1.0 ± 1.4) × 10-13for any possible inequality in the ratios of the gravitational and inertial masses for the Earth and Moon, Δ(MG/MI). This result, in combination with laboratory experiments on the weak equivalence principle, yields a strong equivalence principle (SEP) test of Δ(MG/MI)SEP= (-2.0 ± 2.0) × 10-13. Such an accurate result allows other tests of gravitational theories. The result of the SEP test translates into a value for the corresponding SEP violation parameter η of (4.4 ± 4.5) × 10-4, where η = 4β - γ - 3 and both γ and β are parametrized post-Newtonian (PPN) parameters. Using the recent result for the parameter γ derived from the radiometric tracking data from the Cassini mission, the PPN parameter β (quantifying the nonlinearity of gravitational superposition) is determined to be β - 1 = (1.2 ± 1.1) × 10-4. We also present the history of the LLR effort and describe the technique that is being used. Focusing on the tests of the EP, we discuss the existing data, and characterize the modeling and data analysis techniques. The robustness of the LLR solutions is demonstrated with several different approaches that are presented in the text. We emphasize that near-term improvements in the LLR accuracy will further advance the research on relativistic gravity in the solar system and, most notably, will continue to provide highly accurate tests of the EP.
MODIFIED AVERAGING PROCESSES IN COSMOLOGY AND THE STRUCTURED FRW MODEL
Authors: KHOSRAVI SHAHRAM , MANSOURI REZA , KOURKCHI EHSAN
Published: July 2009

We study the volume averaging of inhomogeneous metrics within GR and discuss its shortcomings, such as gauge dependence, singular behavior as a result of caustics, and causality violations. To remedy these shortcomings, we suggest some modifications to this method. As a case study we focus on the inhomogeneous structured FRW model based on a flat LTB metric. The effect of averaging is then studied in terms of an effective backreaction fluid. It is shown that, contrary to the claims in the literature, the backreaction fluid behaves like a dark matter component, instead of dark energy, having a density of the order of 10-5 times the matter density, and, most importantly, it is gauge-dependent.
CHARACTERIZATION OF TiB2 COATING ADHERENCE BY A MULTI-PASS SCRATCH TESTING
Authors: TOTIK YASAR , ARSLAN ERSIN , EFEOGLU IHSAN , KAYMAZ IRFAN
Published: July 2009

TiB 2 films deposited using various deposition techniques are used to increase the wear lifetime of industrial components. The performance of TiB 2 films is dependent on the coating–substrate adhesion. In this study, the fatigue behavior of TiB 2 films was investigated using the multi-mode scratch method. Films of TiB 2 were deposited on silicon wafers and AISI M2 steel substrates at different frequencies by pulsed-dc closed field unbalanced magnetron sputtering (CFUBMS). The microstructures of the films were investigated using SEM techniques, and the hardness was measured using a microhardness tester. A multi-mode operation was used for sliding-fatigue, like multi-pass scratching in the same track at different fractions of critical load (bidirectional sliding) and a standard mode using progressive load operation. It was observed that the films deposited at low frequencies had higher adhesion strength and microhardness, and a denser microstructure.
STUDY ON NANO COPPER-BASED CATALYSTS FOR THE HYDROGENATION OF METHYL 3-HYDROXYPROPIONATE TO 1, 3-PROPANEDIOL
Authors: YING YUZHOU , FENG KANKA , LV ZHIGUO , GUO ZHENMEI , GAO JINSHENG
Published: July 2009

Nano copper-based catalysts were prepared by co-precipitation method and the performance of catalytic hydrogenation for methyl 3-hydroxypropionate (MHP) to 1, 3-propanediol (1, 3-PDO) on the nano catalysts were studied under a high-pressure microcontinuum fixed-bed reactor. The effects of structure, texture, and composition of the catalysts on the catalytic performance were investigated by characterizing the catalysts with XRD, TG–DTG, SEM, and N 2 adsorption/desorption analysis technique. The results showed that addition of promoters enhanced the activity and selectivity of copper-based catalysts, which promoted the dispersion of the active components effectively and stabilized the active center of the catalysts. Especially, the copper-based catalyst of loaded P could restrain side-reaction effectively and improve selectivity obviously, the conversion of MHP and the selectivity of 1, 3-PDO could be 91.30% and reach 90.15%, respectively.
OPTICAL TRANSITION OF POROUS SILICON PREPARED AT DIFFERENT ANODIZATION TEMPERATURES
Authors: PAN LIKUN , LI HAIBO , SUN ZHUO , SUN CHANGQING
Published: July 2009

Photoluminescence, photoabsorption, and X-ray photoelectron spectroscopic study revealed that an optical transition of porous silicon from red-shift to blue-shift, and Si -2p binding energy transition from low to high at a critical anodization temperature, 343 K. Possible origin for the reverse variations happening at temperature below and above the critical temperature is discussed.
EXPERIMENTAL OBSERVATIONS OF ORDERLY STRUCTURES IN COPPER FILMS DEPOSITED ON LIQUID SUBSTRATES
Authors: CHEN MIAO-GEN , YU SEN-JIANG , FENG YUAN-XIN , JIAO ZHI-WEI , YANG BO
Published: July 2009

In this paper, an optical microscopy study of orderly structures, namely bands, which are observed in a nearly free sustained copper ( Cu ) film system, is presented. The band is composed of a large number of parallel key-formed domains with different width w but nearly uniform length L. This study shows that the morphologies of the Cu films are very susceptible to the deposition rate, i.e. with the increase in the deposition rate f, the bands with rectangular domains first become irregular gradually and then disappear completely. The experiment indicates that the growth mechanism of the orderly patterns can be explained in terms of the relaxation of the internal stress in the films, which is related to the characteristic boundary condition of the films on the liquid substrates and the nearly zero adhesion of the solid–liquid interface.
ENHANCED LIGHT EXTRACTION FROM COLLOIDAL ZnO QD FILM BY ADDING ON PHOTONIC CRYSTALS USING UV-NANOIMPRINT LITHOGRAPHY
Authors: LI XIALI , YANG GUANGQIAN , CHEN JIAN , ZHANG RONGJUN , ZHOU WEIMIN , LIU YANBO , ZHANG JING , WANG QINGKANG
Published: July 2009

A significant enhancement in light extraction from colloidal ZnO QD films was observed on an addition of a layer of two-dimensional photonic crystal (2D-PC) structure. The PCs with a rectangular-lattice air-hole array pattern with the period of 1.4 μm and the hole-size of 400 nm were fabricated by UV-nanoimprint lithography (UV-NIL). Unlike the commonly utilized electron-beam lithographic technique, the UV-NIL process can make patterns over a large area with high throughput. The resultant colloidal zinc oxide ( ZnO ) QD films with a PC pattern add-on had nearly double the output power, as measured from the top of the film.
MICROSTRUCTURE AND OXIDATION RESISTANCE OF NiCoCrAlYTa COATING BY LOW PRESSURE PLASMA SPRAYING
Authors: LIANG X.-H. , ZHOU K. S. , LIU M. , HONG R. J. , DENG C. G. , LUO S. , CHEN Z. K.
Published: July 2009

The NiCoCrAlYTa coating was prepared on Ni -based single crystal super-alloys by low pressure plasma spraying (LPPS). The phases and microstructures for the coatings were characterized by X-ray diffraction and scanning electron microscopy, and the fracture toughness and micro-hardness for both coatings and substrate were also investigated. The relationship between coating properties and oxidation was analyzed. The result shows that elementary distribution of NiCoCrAlYTa coatings, which consists of γ- Ni , β- NiAl , γ'- Ni 3 Al , and CrCoTa phases, is much homogeneous. The composition changes with depth from the surface to substrate for the coatings. The micro-hardness of coatings is 350.8 HV0.3 and fracture toughness is 2.73 MPa m1/2. The oxidation resistance of coatings excelled than Ni -based single crystal super-alloys.
DEPOSITION OF SINGLE-PHASE CuInSe2 THIN FILMS UNDER LOW VACUUM LEVEL BY A TWO-STAGE GROWTH TECHNIQUE
Authors: CHU J. B. , ZHU H. B. , WANG Z. A. , BIAN Z. Q. , SUN Z. , CHEN Y. W. , HUANG S. M.
Published: July 2009

Single-phase CuInSe 2 films were grown by high vapor selenization of CuIn alloy precursors within a partially closed graphite box. The CuIn precursors were prepared using Cu x In y alloy targets with different composition rates under low vacuum level by a homemade sputtering system. The Cu and In composition rates of the used targets are 11:9, 10:10, and 9:11, respectively. The metallic precursor films were selenized using a two-step temperature profile, i.e. at 250°C and 400–500°C, respectively. The influence of the temperature at the second selenization step on the quality of the CIS absorbing layers was investigated. The CIS films were characterized by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. The deposited CIS absorbers selenized at a high temperature of 500°C for 30 min exhibited a single-phase chalcopyrite structure with a preferential orientation in the (112) direction. These layers display uniform, large, and densely packed crystals with a grain size of about 3–5 μm. Cadmium sulfide buffer layer was manufactured by chemical bath deposition method. Bilayers ZnO / ZnO : Al were prepared by RF magnetron sputtering deposition. CIS solar cells with an efficiency of about 6.5% were produced without antireflective films. The method to fabricate CIS solar cells by a combination of the low vacuum sputtering deposition and the graphite box selenization process has provided a simple control process and shown a promising potential for developing high efficient and low-cost CuInSe 2 solar cells.
PREPARATION OF MICROARC OXIDATION COATINGS ON 6061 ALUMINUM ALLOYS AND THEIR THERMAL SHOCK RESISTANCE
Authors: XUE WENBIN , ZHANG YING , JIANG XINGLI , YANG ZHUO
Published: July 2009

The thick ceramic coatings were prepared on 6061 aluminum alloys by microarc oxidation in a silicate electrolyte. The morphology and phase constituent of the coatings with different thickness were studied by scanning electron microscope, and X-ray diffraction. Scratch and thermal shock tests were employed to evaluate the adhesion between the coating and alloy substrate. The maximum microhardness and its position away from alloy/coating interface increases with increasing the coating thickness. The critical scratch force for the coating break was about 55 N in the 50 μm thick coating. Thermal shock resistance of the coatings depend on their thickness and thinner coating has better thermal shock resistance. The coated alloy with 50 μm thick coating can be subjected to 50 times thermal cycles of heating up to 500°C followed by quenching into water.
INVESTIGATION OF ADSORPTION AND INHIBITIVE EFFECT OF CALIXARENE DERIVATIVE NEWLY SYNTHESIZED TOWARDS C38 STEEL IN MOLARHCl
Authors: SOUANE R. , KADDOURI M. , BOUKLAH M. , CHERIAA N. , HAMMOUTI B. , VICENS J.
Published: July 2009

The focus of this study is to synthesize a new calixarene derivative namely calix[6]arene (C21) and to test its performance as corrosion inhibitor of C38 steel in molar HCl at 308 K. Polarization and weight loss measurements were used. Weight loss tests show that C21 retards until to stop corrosion phenomenon at 5 × 10-5M . C21 is an excellent inhibitor and its inhibition efficiency increases with its concentration to reach 100% since 5 × 10-5M . Polarization curves revealed that C21 affects both cathodic and anodic domains by decreasing current densities and then it may be classified as a mixed type inhibitor. The calixarene tested is adsorbed on the surface according to the Langmuir adsorption isotherm. Free enthalpy of adsorption reveals that C21 acts from chemisorption onto the steel surface.
EFFECT OF ACID–BASE PROPERTY OF INORGANIC NANOPARTICLES ON ANTIFOULING PERFORMANCE OF PVDF COMPOSITE ULTRAFILTRATION MEMBRANES
Authors: HE MINGJIA , SHI BAOLI
Published: July 2009

Pure poly(vinylidene fluoride) (PVDF) membrane and PVDF composite membranes modified by three kinds of inorganic nanoparticles ( SiO 2, Al 2 O 3, and TiO 2) were made using a phase inversion method and characterized by pure water flux, retention efficiency of Bovine serum albumin (BSA), flux reduction coefficient, and scanning electron microscope (SEM). The results of flux reduction coefficient illustrated that PVDF membrane modified by nanoparticles had better antifouling property in the order of TiO 2, Al 2 O 3, SiO 2. The Lewis acid–base properties of the nanoparticle materials were measured by inverse gas chromatography (IGC). The Lewis acid number, Ka, and Lewis base number, Kb, had the following order Ka TiO 2 < Ka Al 2 O 3 < Ka SiO 2, and Kb TiO 2 > Kb Al 2 O 3 > Kb SiO 2. The experimental results indicated that PVDF membrane modified by nanoparticles with relatively strong base exhibited excellent antifouling performance.
X-RAY EMISSION FROM THE METASTABLE COMPONENTS OF SLOW Ar16+ BEAM ON METALLIC SURFACES
Authors: ZHANG H. Q. , CHEN X. M. , LIU Z. Y. , YANG Z. H. , XU J. Z. , CUI Y. , XU X. , SHAO J. X. , ZHANG X. A. , ZHAO Y. T. , ZHANG Y. P. , XIAO G. Q.
Published: July 2009

K-shell X-ray emission was observed in the neutralization process of Ar 16+ interacting with beryllium and molybdenum at slow speed (less than Bohr velocity). The K-shell X-ray emission came from the metastable component of Ar 16+ beam with the configuration (1s2s) produced from electron cyclotron resonance ion source. The intensity ratio of K β X-ray emission to K α X-ray emission (I K β/I K α) in the neutralization process decreased when the kinetic energy of the projectile increased. This is closely related to the flight time the projectiles spend above the surface, which is dominated by both the work function of the metal and the normal velocity component of the incident ions to the surface according to the classical over-barrier model. As the relation between I K β/I K α and the above-flight time shows, the longer time above the surface the larger ratio due to the above-surface contribution. Furthermore, the smaller work function leads to the smaller contribution from the above surface.
COMPARISON OF CdS AND ZnS THIN FILMS PREPARED BY CHEMICAL BATH DEPOSITION
Authors: LIU QI , MAO GUOBING
Published: July 2009

In this paper, we reported a comparative study of process and structural characterization of cadmium sulfide ( CdS ) and zinc sulfide ( ZnS ) thin films by chemical bath deposition (CBD) technique. Their deposition process is similar which clearly shows three different growth phases, a none-film one, a quasi-linear one, and a saturation one. And the growth rate of CBD- CdS is higher than that of CBD- ZnS . Through calculating the activation energy of reaction, we can conclude that the rate determining step of CBD- CdS in the deposition process is a chemical one, in contrast with the CBD- ZnS in which the determining step can be a diffusion step. The XRD analysis of the as-deposited films shows that the CBD- CdS films present cubic and hexagonal mixed structure and CBD- ZnS films are in cubic ZnS structure. The deposition time significantly influenced the crystal structure of CdS thin film. Transmission measurement shows that when the wavelength is below 500 nm, the optical transmission of CBD- ZnS film is higher than that of CBD- CdS film. Optical transmission of both CBD- ZnS and CBD- CdS films is about 90% when the wavelength is over 600 nm. The band gap (Eg) value of CBD- CdS is about 2.41 eV and that of CBD- ZnS is about 3.51 eV.
ABRASIVE WEAR BEHAVIOR OF WC REINFORCED Ni-BASED COMPOSITE COATING SPRAYED AND FUSED BY OXY-ACETYLENE FLAME
Authors: WANG QUN , CHEN ZHENHUA , DING ZHANG XIONG , CHEN DING
Published: July 2009

Microstructure of WC reinforced Ni -based self-fluxing alloy composite coating sprayed and fused by oxy-acetylene flame was investigated by scanning electron microscopy and energy dispersive X-ray Spectrometry, X-ray diffraction, and transmission electron microscopy. The wear performance of the coating was studied by a MLS-225 wet sand rubber wheel abrasive wear tester at various loads and sizes of abrasive particles. Also, the wear resistance of the coating was compared with uncoated ASTM1020 steel. The results indicated that the coating is bonded metallurgically to the substrate and has a homogeneous microstructure composed of both coarse WC and fine carbide and boride grains such as Cr 7 C 3, Cr 23 C 6, and Ni 2 B which disperse uniformly in the matrix of γ- Ni solid solution and Ni 3 B . The worn mass loss of the coating and ASTM1020 steel both increased with the load and size of abrasive particles, also, the coating has exhibited excellent abrasive wear resistance compared with ASTM1020 steel.
COMPARISON ON THE EFFECT OF SrRuO3 AND La0.5Sr0.5CoO3 BOTTOM ELECTRODE ON DIELECTRIC PROPERTIES OF Ba0.6Sr0.4TiO3 THIN FILMS PREPARED BY PULSED LASER DEPOSITION
Authors: QIN WENFENG , XIONG JIE , LI YANRONG
Published: July 2009

The dielectric properties of Ba 0.6 Sr 0.4 TiO 3 (BST) thin films deposited using SrRuO 3 (SRO) materials as bottom electrode were compared with those of the films grown using La 0.5 Sr 0.5 CoO 3 (LSCO) materials as bottom electrode. X-ray diffraction scanning revealed that the two kinds of films could be epitaxially grown in pure single-oriented perovskite phases and atomic force microscopy showed that the root mean square roughness of BST/SRO films were similar to BST/LSCO films. The dielectric properties of the BST/SRO and BST/LSCO thin films were measured at 10 kHz and 300 K with a parallel-plate capacitor configuration. Compared with BST/LSCO, the dielectric tunability for BST/SRO films slightly decreased, while the loss decreased synchronously. The figure of merit factor value increases from 25.67 for BST/LSCO films to 48.76 for BST/SRO films under an applied voltage of 6 V. The leakage current density of the thin films at a positive voltage of 2 V decreases from 2.41 × 10-7 A/cm 2 for BST/LSCO to 8.41 × 10-8 A/cm 2 for BST/SRO. This phenomenon is ascribed to the smaller strain induced in BST/SRO materials.
Ca2+ removal mechanisms in mouse embryonic stem cell-derived cardiomyocytes
Authors: Guo Ang , Yang Huang-Tian
Published: July 2009

In mammalian adult cardiomyocytes, sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA) plays a major role in controlling the decline of cytosolic free Ca2+ concentration ([Ca2+]i) in comparison with sarcolemmal Na+/Ca2+ exchanger (NCX). However, the functional importance of SERCA and NCX in cytosolic Ca2+ removal during early cardiomyogenesis is still debated. In this study, the functional contributions of Ca2+ transporters to [Ca2+]i decline in mouse embryonic stem cell-derived cardiomyocytes (mESCMs), a suitable model for investigation of early cardiogenesis, at various differentiation stages were investigated. We estimated that even at early differentiation stages of mESCMs, SERCA was responsible for ∼76% of total Ca2+ removal, while NCX was responsible for ∼21%. The contributions of SERCA and NCX to cytosolic Ca2+ clearance were increased to ∼88% and decreased to ∼10%, respectively, at the late differentiation stage. Dynamical analysis of the transient decay phases in normal and Na+-free solutions suggests that the contribution of NCX to [Ca2+]i decline is more apparent in the terminal slow decay phase than that in the initial fast phase. When SR function was suppressed in type 2 ryanodine receptor-null mESCMs or with ryanodine receptor and SERCA inhibitors (ryanodine and thapsigargin), NCX acted as the main pathway for [Ca2+]i decline. We conclude that the rapid [Ca2+]i decline is mainly achieved by the SR uptake even at the early differentiation stage of mESCMs, while NCX acts as the main Ca2+ remover when SR function is suppressed. These findings suggest a critical role of SR in the regulation of [Ca2+]i homeostasis even in differentiating cardiomyocytes.