bluuebunny/crossref_metadata_2025 huggingface dataset:
Synergistic Attenuation of Vesicular Stomatitis Virus by Combination of Specific G Gene Truncations and N Gene Translocations
Authors: Clarke David K. , Nasar Farooq , Lee Margaret , Johnson J. Erik , Wright Kevin , Calderon Priscilla , Guo Min , Natuk Robert , Cooper David , Hendry R. Michael , Udem Stephen A.
Published: December 2006

A variety of rational approaches to attenuate growth and virulence of vesicular stomatitis virus (VSV) have been described previously. These include gene shuffling, truncation of the cytoplasmic tail of the G protein, and generation of noncytopathic M gene mutants. When separately introduced into recombinant VSV (rVSV), these mutations gave rise to viruses distinguished from their “wild-type” progenitor by diminished reproductive capacity in cell culture and/or reduced cytopathology and decreased pathogenicity in vivo. However, histopathology data from an exploratory nonhuman primate neurovirulence study indicated that some of these attenuated viruses could still cause significant levels of neurological injury. In this study, additional attenuated rVSV variants were generated by combination of the above-named three distinct classes of mutation. The resulting combination mutants were characterized by plaque size and growth kinetics in cell culture, and virulence was assessed by determination of the intracranial (IC) 50% lethal dose (LD
50
) in mice. Compared to virus having only one type of attenuating mutation, all of the mutation combinations examined gave rise to virus with smaller plaque phenotypes, delayed growth kinetics, and 10- to 500-fold-lower peak titers in cell culture. A similar pattern of attenuation was also observed following IC inoculation of mice, where differences in LD
50
of many orders of magnitude between viruses containing one and two types of attenuating mutation were sometimes seen. The results show synergistic rather than cumulative increases in attenuation and demonstrate a new approach to the attenuation of VSV and possibly other viruses.
Histone Modification Pattern of the T-Cellular
Herpesvirus Saimiri
Genome in Latency
Authors: Alberter Barbara , Ensser Armin
Published: December 2006

Herpesvirus saimiri
(HVS) subgroup C strains are able to growth transform human T lymphocytes in vitro. The stably persisting and nonintegrating HVS episome represents an optimal prerequisite for the investigation of the epigenetic state of latent herpesvirus genomes in vitro. Quantitative chromatin immunoprecipitation experiments using seven different histone acetylation- or methylation-specific antibodies revealed repressive marks at four lytic gene promoters and a variable pattern at the weakly transcribed LANA/
orf73
promoter. The constitutive
stpC/tip
promoter regulating the viral oncoproteins and, more interestingly, the noncoding repetitive H-DNA elements flanking the coding region, showed a permissive chromatin structure. This study provides an appropriate model for the analysis of epigenetic herpesvirus genome modifications and their dynamics in T cells.
CD4 Coexpression Regulates DC-SIGN-Mediated Transmission of Human Immunodeficiency Virus Type 1
Authors: Wang Jian-Hua , Janas Alicia M. , Olson Wendy J. , KewalRamani Vineet N. , Wu Li
Published: December 2006

Dendritic cells (DCs) potently stimulate the cell-cell transmission of human immunodeficiency virus type 1 (HIV-1). However, the mechanisms that underlie DC transmission of HIV-1 to CD4+T cells are not fully understood. DC-SIGN, a C-type lectin, efficiently promotes HIV-1transinfection. DC-SIGN is expressed in monocyte-derived DCs (MDDCs), macrophage subsets, activated B lymphocytes, and various mucosal tissues. MDDC-mediated HIV-1 transmission to CD4+T cells involves DC-SIGN-dependent and -independent mechanisms. DC-SIGN transmission of HIV-1 depends on the donor cell type. HIV-1 Nef can upregulate DC-SIGN expression and promote DC-T-cell clustering and HIV-1 spread. Nef also downregulates CD4 expression; however, the effect of the CD4 downmodulation on DC-mediated HIV-1 transmission has not been examined. Here, we report that CD4 expression levels correlate with inefficient HIV-1 transmission by monocytic cells expressing DC-SIGN. Expression of CD4 on Raji B cells strongly impaired DC-SIGN-mediated HIV-1 transmission to T cells. By contrast, enhanced HIV-1 transmission was observed when CD4 molecules on MDDCs and DC-SIGN-CD4-expressing cell lines were blocked with specific antibodies. Coexpression of CD4 and DC-SIGN in Raji cells promoted the internalization and intracellular retention of HIV-1. Interestingly, internalized HIV-1 particles were sorted and confined to late endosomal compartments that were positive for CD63 and CD81. Furthermore, in HIV-1-infected MDDCs, significant downregulation of CD4 by Nef expression correlated with enhanced viral transmission. These results suggest that CD4, which is present at various levels in DC-SIGN-positive primary cells, is a key regulator of HIV-1 transmission.
Evolutionary Mechanisms of Persistence and Diversification of a Calicivirus within Endemically Infected Natural Host Populations
Authors: Coyne Karen P. , Gaskell Rosalind M. , Dawson Susan , Porter Carol J. , Radford Alan D.
Published: December 2006

In order to understand the evolutionary mechanisms of persistence and diversification within the
Caliciviridae
, we have been exploiting endemic infection of feline calicivirus within five geographically distinct household groups of cats. By sequencing immunodominant and variable regions of the capsid gene, we identified the relative contribution of the different evolutionary processes employed by the virus to ensure its long-term survival in the host population. Such strategies included progressive evolution of a given variant of a strain through mutation accumulation within an individual, sequential reinfection with either a variant of the same strain or with a different strain, and mixed infection. Recombination between different strains in this study has been reported in detail elsewhere (K. P. Coyne et al., J. Gen. Virol.
87:
921-926, 2006). Here, we provide evidence to suggest that true long-term persistent infection in individuals is relatively rare, with the majority of apparent viral carriers undergoing a combination of progressive evolution and cyclical reinfection. Progressive evolution at the individual level and variant reinfection at both the individual and population levels were associated with positive selection. Two measures of evolution rate were determined; for a virus progressively evolving within an individual (1.32 × 10
−2
to 2.64 × 10
−2
substitutions per nucleotide per year, i.e., no transmission) and for a strain circulating within a population (3.84 × 10
−2
to 4.56 × 10
−2
substitutions per nucleotide per year, i.e., including transmission). Reiteration of both progressive evolution and variant reinfection appeared to lead to a gradual increase in the diversity of a given strain of virus, both in the individual and in the population, until eventually new strains emerged.
Monoclonal Antibodies to Phosphatidylinositol Phosphate Neutralize Human Immunodeficiency Virus Type 1: Role of Phosphate-Binding Subsites
Authors: Brown Bruce K. , Karasavvas Nicos , Beck Zoltan , Matyas Gary R. , Birx Deborah L. , Polonis Victoria R. , Alving Carl R.
Published: December 2006

Both a murine monoclonal antibody to phosphatidylinositol phosphate (PIP) and a human monoclonal antibody (4E10) that is known to have broadly neutralizing capabilities against primary isolates of human immunodeficiency virus type 1 (HIV-1) bound to PIP, as determined by enzyme-linked immunosorbent assay. Each of the antibodies had antigen subsite binding specificities in aqueous medium for small phosphate-containing molecules and for inositol. The anti-PIP monoclonal antibody inhibited infection by two HIV-1 primary isolates in neutralization assays employing primary human peripheral blood mononuclear cells. The data suggest that PIP or related lipids having free phosphates could serve as targets for the neutralization of HIV-1.
Intracellular Tat of Human Immunodeficiency Virus Type 1 Activates Lytic Cycle Replication of Kaposi's Sarcoma-Associated Herpesvirus: Role of JAK/STAT Signaling
Authors: Zeng Yi , Zhang Xunhai , Huang Zan , Cheng Lin , Yao Shuihong , Qin Di , Chen Xiuying , Tang Qiao , Lv Zhigang , Zhang Ling , Lu Chun
Published: December 2006

Human immunodeficiency virus type 1 (HIV-1) infection significantly increases the risk of Kaposi's sarcoma (KS) occurrence in individuals infected with Kaposi's sarcoma-associated herpesvirus (KSHV). KSHV infection appears to be necessary but not sufficient for KS development without other cofactors. However, factors that facilitate KSHV to cause KS have not been well defined. Previously, we determined that human herpesvirus 6 was one of the cofactors that activated lytic cycle replication of KSHV. Here, we demonstrate that the Tat protein of HIV-1 is a potentially important factor in the pathogenesis of KS, as determined by production of lytic phase mRNA transcripts and viral proteins in BCBL-1 cells. Mechanistic studies showed ectopic expression of Tat induced the production of human interleukin-6 (huIL-6) and its receptor (huIL-6Ra) and activated STAT3 signaling. Neutralization of huIL-6 or huIL-6R or inhibition of STAT3 signaling enhanced the replication. In addition, IL-4/STAT6 signaling also partially contributed to Tat-induced KSHV replication. These findings suggest that Tat may participate in KS pathogenesis by inducing KSHV replication and increasing KSHV viral load. These data also suggest that JAK/STAT signaling may be of therapeutic value in AIDS-related KS patients.
Herpes Simplex Virus Type 2 (HSV-2) Establishes Latent Infection in a Different Population of Ganglionic Neurons than HSV-1: Role of Latency-Associated Transcripts
Authors: Margolis Todd P. , Imai Yumi , Yang Li , Vallas Vicky , Krause Philip R.
Published: December 2006

Herpes simplex virus type 1 (HSV-1) and HSV-2 cause very similar acute infections but differ in their abilities to reactivate from trigeminal and dorsal root ganglia. To investigate differences in patterns of viral infection, we colabeled murine sensory ganglia for evidence of HSV infection and for the sensory neuron marker A5 or KH10. During acute infection, 7 to 10% of HSV-1 or HSV-2 antigen-positive neurons were A5 positive and 13 to 16% were KH10 positive, suggesting that both viruses reach each type of neuron in a manner proportional to their representation in uninfected ganglia. In murine trigeminal ganglia harvested during HSV latency, 25% of HSV-1 latency-associated transcript (LAT)- and 4% of HSV-2 LAT-expressing neurons were A5 positive, while 12% of HSV-1 LAT- and 42% of HSV-2 LAT-expressing neurons were KH10 positive. A similar difference was observed in murine dorsal root ganglia. These differences could not be attributed to differences in LAT expression levels in A5- versus KH10-positive neurons. Thus, HSV-1 demonstrated a preference for the establishment of latency in A5-positive neurons, while HSV-2 demonstrated a preference for the establishment of latency in KH10-positive neurons. A chimeric HSV-2 mutant that expresses the HSV-1 LAT exhibited an HSV-1 phenotype, preferentially establishing latency in A5-positive neurons. These data imply that the HSV-1 and HSV-2 LAT regions influence the ability of virus to establish latency in different neuronal subtypes. That the same chimeric virus has a characteristic HSV-1 reactivation phenotype further suggests that LAT-influenced establishment of latency in specific neuronal subtypes could be an important part of the mechanism by which LAT influences viral reactivation phenotypes.
Isolation and Characterization of Replication-Competent Human Immunodeficiency Virus Type 1 from a Subset of Elite Suppressors
Authors: Blankson Joel N. , Bailey Justin R. , Thayil Seema , Yang Hung-Chih , Lassen Kara , Lai Jun , Gandhi Shiv K. , Siliciano Janet D. , Williams Thomas M. , Siliciano Robert F.
Published: December 2006

Elite suppressors (ES) are untreated human immunodeficiency virus type 1 (HIV-1)-infected individuals who control viremia to levels below the limit of detection of current assays. The mechanisms involved in this control have not been fully elucidated. Several studies have demonstrated that some ES are infected with defective viruses, but it remains unclear whether others are infected with replication-competent HIV-1. To answer this question, we used a sensitive coculture assay in an attempt to isolate replication-competent virus from a cohort of 10 ES. We successfully cultured six replication-competent isolates from 4 of the 10 ES. The frequency of latently infected cells in these patients was more than a log lower than that seen in patients on highly active antiretroviral therapy with undetectable viral loads. Full-length sequencing of all six isolates revealed no large deletions in any of the genes. A few mutations and small insertions and deletions were found in some isolates, but phenotypic analysis of the affected genes suggested that their function remained intact. Furthermore, all six isolates replicated as well as standard laboratory strains in vitro. The results suggest that some ES are infected with HIV-1 isolates that are fully replication competent and that long-term immunologic control of replication-competent HIV-1 is possible.
MUC1 Induced by Epstein-Barr Virus Latent Membrane Protein 1 Causes Dissociation of the Cell-Matrix Interaction and Cellular Invasiveness via STAT Signaling
Authors: Kondo Satoru , Yoshizaki Tomokazu , Wakisaka Naohiro , Horikawa Toshiyuki , Murono Shigeyuki , Jang Kyung Lib , Joab Irene , Furukawa Mitsuru , Pagano Joseph S.
Published: December 2006

Disruption of cellular adhesion is an essential pathobiologic step leading to tumor dissemination. Mucin 1 (MUC1) is a mucinous glycoprotein expressed at the surfaces of epithelial cells in many tissues and their carcinomas. MUC1 plays crucial roles in tumor invasion and metastasis, especially in opposing cell adhesion. We have shown that virus infection, specifically by the human tumor virus Epstein-Barr virus (EBV) induces a spectrum of cellular invasiveness and metastasis factors. Here we show that expression of MUC1 is increased in diverse latently EBV-infected cell lines that express latent membrane protein 1 (LMP1), the main viral oncoprotein, and that the level of MUC1 was suppressed by expression of a dominant-negative mutant of LMP1. Expression of LMP1 in EBV-negative nasopharyngeal cell lines induces expression of MUC1 through activation of the MUC1 promoter via binding of STAT1 and STAT3. Finally, LMP1 reduces cell adhesion ability, which is restored by inhibition of MUC1 expression with MUC1 small interfering RNA (siRNA). In addition, LMP1 increases cell invasiveness, which is suppressed by MUC1 siRNA. Thus, LMP1 induces MUC1, a factor important in an early step of detachment and release of tumor cells, which along with induction of other invasiveness and angiogenic factors may combine to act in a complex sequential process that culminates in metastasis of EBV-infected tumor cells.
Mapping of Key Functions of the Herpes Simplex Virus 1 U
S
3 Protein Kinase: the U
S
3 Protein Can Form Functional Heteromultimeric Structures Derived from Overlapping Truncated Polypeptides
Authors: Poon Alice P. W. , Roizman Bernard
Published: December 2006

Earlier studies have shown that the herpes simplex virus (HSV) U
S
3 encodes two transcriptional units directing the synthesis of the U
S
3 (residues 1 to 481) and U
S
3.5 (residues 77 to 481) protein kinases. Both kinases phosphorylate histone deacetylase 1 (HDAC1) and HDAC2 and enable the expression of genes cotransduced into U2OS cells by recombinant baculoviruses, an activity designated the “helper function.” The two kinases differ with respect to antiapoptotic activity. In the studies reported here, we made a series of FLAG-tagged amino- and carboxyl-terminal truncations of U
S
3 and these were tested for antiapoptotic activity, phosphorylation of HDAC1, and the helper function. We report the following. (i) HDAC1 phosphorylation and the helper function were expressed in cells transduced by the truncation encoding residues 182 to 481 but not in cells transduced by the truncation encoding residues 189 to 481 or the amino-terminal polypeptides encompassing the first 188 amino acids. (ii) The self-posttranslational modification requires residues 164 to 481. (iii) The antiapoptotic activity requires both the amino-terminal and the carboxyl-terminal domains, of which the truncated protein containing residues 1 to 163 and that containing residues 164 to 481, respectively, were the smallest fragments tested to be effective. The two domains need not be on the same molecule, but they must overlap. The smallest overlapping pair tested was the fragment containing residues 1 to 181 and that containing residues 164 to 481. Consistent with the hypothesis that the effective overlapping truncations form a heteromultimeric structure, antibody to FLAG coprecipitated untagged U
S
3 from lysates of cells cotransduced with FLAG-tagged, truncated U
S
3 constructs. Although U
S
3 has been reported to be a monomeric enzyme, the results indicate that it can form enzymatically active multimeric structures.
A Kinetic Study of the Cytochrome c-Hydrogen Peroxide Reaction
Authors: Perez-Benito Joaquin F.
Published: December 2006

The kinetics of the reaction of cytochromecwith H2O2was studied in aqueous phosphate media near physiological pH (5.7-7.2). The UV-VIS spectra indicated that the heme prosthetic group of the protein suffered an oxidative degradation during the reaction. The experimental rate law wasv=kexp[cytochromec] [H2O2], withkexp= (A+B[H+])/(1 +C[H+]). The apparent activation parameters associated withkexpwereEa= 46 ± 2 kJ mol-1, ∆Ho≠= 43 ± 2 kJ mol-1and ∆So≠= -111 ± 5 J K-1mol-1. The reaction showed base catalysis and was also catalyzed by both CrO42-and acrylamide. It was inhibited by the oxidants WO42-, MoO42-, VO3-and [Fe(CN)6]3-as well as by the reductants [Fe(CN)6]4-and D-mannitol, whereas Zn2+and superoxide dismutase had no appreciable effect. The results are consistent with initial reduction of iron from Fe(III) to Fe(II) (supported by inhibition caused by most oxidants), followed by a hydroxyl-radical mediated oxidative degradation of the heme prosthetic group (supported by the inhibition caused by both [Fe(CN)6]4-and D-mannitol).
Silicon Complementary Metal–Oxide–Semiconductor Field-Effect Transistors with Dual Work Function Gate
Authors: Na Kee-Yeol , Kim Yeong-Seuk
Published: December 2006

This paper discusses silicon complementary metal–oxide–semiconductor (CMOS) field-effect transistors with dual work function gates (DWFG) to improve transconductance (g
m) and drain conductance (g
ds) characteristics. For a n-channel metal–oxide–semiconductor field-effect transistor (MOSFET) device, the polycrystalline silicon (poly-Si) gate on the source and drain side are doped p+ and n+, respectively and vice versa for a p-channel MOSFET. The work function difference in a poly-Si gate affects channel potential distribution and increases the lateral electric field inside the channel. The increased electric field inside the channel improves carrier drift velocity. Experimental results from the fabricated DWFG devices show improved g
m and g
ds over conventional single work function gate devices.
Time Dependence of the Mechanical Quality Factor in “Hard” Lead Zirconate Titanate Ceramics: Development of an Internal Dipolar Field and High Power Origin
Authors: Gao Yongkang , Uchino Kenji , Viehland Dwight
Published: December 2006

The time dependences after poling of the mechanical quality factor Q
m, electromechanical coupling coefficient k
31 and dielectric constant K have been investigated for both “soft” and “hard” lead zirconate titanate (PZT) ceramics. A significant increase of Q
m with time was observed for “hard” PZTs, however “soft” ones did not exhibit any changes during the same time period. The initial Q
m value of rare earth modified Pb(Zr,Ti)O3–Pb(Sb,Mn)O3 was only 400 at 10 min after poling; however, at t=2800 min after poling, it had increased to 1600. Correspondingly, a pronounced increase in E
int was observed with ln
t. The aging rate after poling was found related to the degree of “hard” characteristics. For 10<t<2800 min after poling, the value of Q
m for Yb modified Pb(Zr,Ti)O3 increased from 160 to 250, whereas for Yb modified Pb(Zr,Ti)O3–Pb(Sb,Mn)O3
Q
m increased from 400 to 1600 during the same time period. Polarization–electric field (P–E) measurements revealed the development of a shift of the response along the E axes with time. It is believed that an internal dipolar field develops with time, due to a reorientation of defect dipoles along the direction of spontaneous polarization. This results in domain stabilization and increased Q
m. It is proposed that internal dipolar field is the high power origin for “hard” type PZTs.
Characteristics of Fatigue Induced by Distribution of Defect Charges in SrBi2Ta2O9 Capacitors
Authors: Xie Dan , Zhang Zhigang , Ren Tianling , Liu Litian
Published: December 2006

Pt/SrBi2Ta2O9 (SBT)/Pt capacitors have been successfully fabricated using a metalorganic decomposition (MOD) technique. The switchable polarization of SBT capacitors showed a tendency to increase with the number of switching cycles at first and then decrease after 2×109 switching cycles. During the switching process, a competition existed between the depinning behavior of domains and the aggregation of defect charges at the interfaces between SBT thin films and electrodes. It was this competition that determined the fatigue characterization for SBT capacitors. Higher external voltages facilitated the recovery of polarization suppression, which suggests that more domains in the SBT thin films were easily depinned by a higher external field and the pinning depth due to defect charges was different.
Crystal Structure and Atomic Arrangement of δ-Phase Sb–Te Binary Alloy
Authors: Sun C. W. , Lee J. Y. , Youm M. S. , Kim Y. T.
Published: December 2006

The composition modulated Sb–Te binary thin films deposited by a RF sputtering method on SiO2/Si substrates annealed through a rapid thermal annealing process and conducted a high-resolution transmission electron microscopy (HR-TEM) study in order to investigate the atomic arrangement of the δ-phase Sb–Te binary alloys which contain Te from 16 to 37 at. %. Through the comparison with HR-TEM image and diffraction patterns viewed along <2110> and <1010> direction, we have revealed that the δ-phase Sb–Te alloy crystallized into P3m1 or R3m space group whether the number of layers is the multiple of three or not. We also expect from analogous Bi–Te system in earlier reports that as the Sb/Te ratio increases, total number of Sb layers in a unit cell increases. Therefore, based on above result, we suggested the atomic arrangement model composed of appropriate Sb2 and Sb2Te3 layer and obtained simulated images of <2110> zone axis.
Strong Electron Emission from Ferroelectric Cathode
Authors: Hayashi Yasushi , Hotta Eiki
Published: December 2006

On the basis of our past research on the strong electron emission from Pb(Zr,Ti)O3 (PZT) ferroelectric materials and its applications to microwave amplification, a new model of ferroelectric emission is proposed. The model suggests that the strong ferroelectric emission is caused by the intrinsic nature of the material's ferroelectricity, – by consecutive domain switching or oscillation due to the application of a trigger pulse. It also includes, in most cases, the direct and indirect effects of the surface plasma. The model is capable of providing a reasonable explanation for the fact that the strong emission can only be obtained with grid electrodes; this is not been explained by the existing theory on ferroelectric emission.
Improvement of Permeation of Solvent-Free Multilayer Encapsulation of Thin Films on Poly(ethylene terephthalate)
Authors: Han Jin-Woo , Kang Hee-Jin , Kim Jong-Yeon , Kim Gwi-Yeol , Seo Dae-Shik
Published: December 2006

In this study, inorganic multilayer thin-film encapsulation is adopted for the first time to protect an organic layer from moisture and oxygen. Inorganic multilayer thin-film encapsulation is deposited onto poly(ethylene terephthalate) (PET) using an electron beam and sputtering. The SiON/SiO2 and parylene layer show the most suitable properties. Under these conditions, the water vapor transmission rate (WVTR) for PET can be reduced from a level of 0.57 g m-2 day-1 (bare substrate) to 1×10-5 g m-2 day-1 after the application of a SiON and SiO2 layer. These results indicate that PET/parylene/SiO2/SiON barrier coatings have high potential for flexible organic light-emitting diode (OLED) applications.
Nonreciprocal Propagation Characteristics of 671 GHz Submillimeter Wave in Image Guide Consisting of Transversely Magnetized p-InSb Slab
Authors: Yodokawa Shinichi , Takahashi Motoi , Kosaka Satoru , Obunai Tetsuo
Published: December 2006

The temperature and magnetic field dependences of 671 GHz submillimeter-wave propagation characteristics in a transversely magnetized image guide consisting of a p-InSb slab have been studied experimentally and theoretically. The result of the theoretical analysis indicates that the propagation loss of this image guide is as small as about 0.116 dB/mm at liquid-nitrogen temperature. As the sample temperature increases to 240 K, a surface wave resonance occurs and a nonreciprocity of more than 20 dB appears in the transmission in an applied magnetic field B of 0.45 T. Experimentally observed results are in good quantitative agreement with theoretical predictions. These findings indicate the possibility of fabricating nonreciprocal devices embedded in a submillimeter-wave image guide consisting of a p-InSb slab. It is also shown that the attenuation of and nonreciprocity in the wave propagation in this image guide can be controlled by injecting plasma into the p-InSb slab.
Evaluations of Electron Density and Temperature in Atmospheric-Pressure Radio-Frequency Helium Plasma Jet
Authors: Li Shou-Zhe , Wang De-Zhen , Zhu Wen-Chao , Pu Yi-Kang
Published: December 2006

In this study, the electrical discharge characteristics of an atmospheric-pressure helium plasma jet using radio-frequency power supply are investigated by measuring the electrical parameters (voltage, current, power, and phase angle). The plasma parameters (electron temperature and electron density) are estimated on the basis of the electrical experiment data using the equivalent circuit model and the power balance equation. By varying input power, a “phase saturation” region is identified. The optimized flow rate ratio between oxygen and helium is found to be 0.1/40 slpm in the experiment.
Plasma Parameter Variations in Ion Beam Formation Mode of a Double Plasma Device
Authors: Mishra Mrinal Kr. , Phukan Arindam , Chakraborty Monojit
Published: December 2006

In the present investigation, our focus is to study the plasma parameter variation occurring in the diffused plasma (target chamber) of a double plasma device, where an ion beam can be injected by two different methods. A low energy ion beam (10–30 eV) is produced in our present study. It is observed that depending on the method by which the beam is formed, the target (diffused) plasma parameters alter significantly. Also it is observed that, the ion-sheath formed at the separation grid of the device expands or contracts depending on the method, which forms the beam.
Flow Field Computation for Simplified High Voltage Gas Circuit Breaker Model by Upwind Meshfree Method
Authors: Choe Hi Jun , Ahn Mu-Young , Song Ki Dong , Park Kyong-Yop , Park Seong-Kwan
Published: December 2006

To effectively design high voltage (HV) circuit breakers, a meshfree method which was proposed by the authors is tested. The meshfree method is implemented to a simplified model for the HV circuit breaker and showed a robust behavior even in a severe boundary condition. A good shock capturing is shown in the computations and a delicate gas diffusion through a slit is also computed, which is usually difficult to catch. Vector splitting method is employed to exploit the merit of meshfree methods in the hyperbolic problems.
Evidence for anoxia at the Ediacaran–Cambrian boundary: the record of redox-sensitive trace elements and rare earth elements in Oman
Authors: Schröder S. , Grotzinger J.P.
Published: December 2006

The Ediacaran–Cambrian boundary in Oman is characterized by a globally correlative negative δ
13
C
carb
excursion in platform carbonate rocks, and deposition of basinal organic-rich rocks. These observations may relate to the development of local, and possibly global, anoxia. We have studied redox-sensitive trace elements (TE) and REE from basinal and platform successions. Detrital input and authigenic element enrichment were the main factors controlling the record of TE and REE. Trace elements in the basin are enriched relative to crustal concentrations. In siliceous rocks, TE enrichment was decoupled from detrital input, suggesting authigenic concentration of TE under anoxic (possibly sulphidic) water column conditions. Trace elements and REE indicate higher detrital input in shales. Element enrichment was minimally influenced by detrital input in the platform carbonate rocks; it is strongest in the basal platform section, coincident with the carbon isotope excursion. The results suggest development of anoxia in a stagnant basinal water mass. Overturn or upward expansion of the deep water charged with TE and isotopically light C produced anoxia on the platform, and was probably related to development of the isotope excursion. These results are consistent with anoxia in boundary strata of Iran, and with the hypothesis of global anoxia at this time.
SHRIMP U–Pb zircon and Sm–Nd garnet ages from the granulite-facies basement of SE Kenya: evidence for Neoproterozoic polycyclic assembly of the Mozambique Belt
Authors: Hauzenberger Christoph A. , Sommer Holger , Fritz Harald , Bauernhofer Andreas , Kröner Alfred , Hoinkes Georg , Wallbrecher Eckart , Thöni Martin
Published: December 2006

The Taita Hills–Galana River region is a key area to demonstrate the polycyclic nature of the Mozambique Belt in SE Kenya. On the basis of petrological and tectonic data, this area is composed of two different granulite-facies terranes, which are separated by the 20–30 km wide Galana Shear Zone. The Taita Hills and adjoining Sagala Hills exhibit a metamorphic overprint at 630–645 Ma, similar to areas in Tanzania. An emplacement age for the magmatic precursor rocks of 850–960 Ma was derived from zircon cores. Sm–Nd garnet–whole-rock analyses give an age of 585 Ma, interpreted as the cooling age after 630–645 Ma metamorphism. Nd crustal residence ages are between 1000 and 1500 Ma. The Galana Shear Zone east of the Taita Hills contains strongly deformed tonalitic migmatites with interlayered pegmatites that date a younger tectonometamorphic event at 560–580 Ma. East of the shear zone only a young metamorphic age of 550 Ma was found. The Nd model ages are
c
. 1500 Ma to
c
. 2900 Ma. In a continental configuration prior to Gondwana break-up our study area was located close to Madagascar, where several large shear zones are observed. One of these shear zones (Ranotsara Shear Zone) may be a continuation of the Galana Shear Zone.
Concurrent HP metamorphism on both margins of Iapetus: Ordovician ages for eclogites and garnet pyroxenites from the Seve Nappe Complex, Swedish Caledonides
Authors: BRUECKNER HANNES K. , VAN ROERMUND HERMAN L.M.
Published: December 2006

Eclogites and garnet pyroxenites from the Seve Nappe Complex in the Jämtland area of the Scandinavian Caledonides give Sm–Nd mineral ages (garnet–clinopyroxene–whole rock ± orthopyroxene ± amphibole) that are identical within error and give a weighted average age of 457.9 ± 4.5 Ma (95% confidence). The age is 50 Ma younger than ages determined from eclogites from the apparently similar Norrbotten terrane, roughly 200 km to the north. Both terranes are correlated with the western margin of Baltica, suggesting that at least two eclogite-facies metamorphic events affected this margin prior to the final closure of Iapetus during the 430–400 Ma Scandian Orogeny. The
c
. 458 Ma ages are nearly identical to ages determined from the eclogite-bearing Tromsø Nappe of the uppermost allochthon. The uppermost allochthon is generally considered part of the Laurentian margin, which, if true, requires that it evolved independently of Baltica until the Scandian Orogeny, when Laurentia and Baltica collided. Thus high-pressure eclogite-facies metamorphism and the introduction of mantle peridotite bodies into the crust appear to have occurred concurrently on opposite sides of Iapetus. We suggest that the HP collision recorded in the Jämtland area be called the ‘Jämtlandian Orogeny’ if further studies confirm its Early Ordovician age.
Structural contacts in subduction complexes and their tectonic significance: the Late Palaeozoic coastal accretionary wedge of central Chile
Authors: Richter Peter P. , Ring Uwe , Willner Arne P. , Leiss Bernd
Published: December 2006

Understanding the contact between the very low-grade metagreywacke of the Eastern Series and high-pressure metamorphosed schist of the Western Series in the Late Palaeozoic accretionary wedge of central Chile is fundamental for the understanding of the evolution of ancient accretionary wedges. We show the progressive development of structures and finite strain from the least deformed rocks in the eastern part of the Eastern Series of the accretionary wedge to high-pressure schist of the Western Series at the Pacific coast. Upright chevron folds of sedimentary layering are associated with an axial-plane foliation, S
1
. As the F
1
folds became slightly overturned to the west, S
1
was folded about west-vergent open F
2
folds and an S
2
axial-plane foliation developed. Near the contact between the Western and Eastern Series S
2
represents a penetrative subhorizontal transposition foliation. Towards the structurally deepest units in the west the transposition foliation becomes progressively flattened. Finite-strain data as obtained by
R
f
/ϕ analysis in metagreywacke and X-ray texture goniometry in phyllosilicate-rich rocks show a smooth and gradual increase in strain magnitude from east to west. Overturned folds and other shear-sense indicators show a uniform top-to-the-west shear sense in moderately deformed rocks, whereas the shear sense is alternating top-to-the-west and top-to-the-east in the strongly flattened high-pressure rocks of the Western Series near the Pacific coast. We interpret the progressive structural and strain evolution across the contact between the two series to reflect a continuous change in the mode of accretion in the subduction wedge. Initially, the rocks of the Eastern Series were frontally accreted to the pre-Andean margin before
c
. 300 Ma. Frontal accretion caused horizontal shortening, and upright folds and subvertical axial-plane foliations developed. At
c
. 300 Ma the mode of accretion changed and the rocks of the Western Series were underplated below the Andean margin. This basal accretion caused a major change in the flow field within the wedge and gave rise to vertical shortening and the development of the penetrative subhorizontal transposition foliation. Subsequent differential exhumation was resolved gradually over a wide region, implying that exhumation was not tectonically controlled.
Episodic fire, runoff and deposition at the Palaeocene–Eocene boundary
Authors: Collinson M.E. , Steart D.C. , Scott A.C. , Glasspool I.J. , Hooker J.J.
Published: December 2006

Qualitative and quantitative coal petrological analyses have been undertaken on the laminated lignite at the base of the Cobham Lignite Bed, from Scalers Hill, Kent, England. The maximum negative carbon isotope excursion, which marks the beginning of the Palaeocene–Eocene thermal maximum (PETM), occurs near the top of the laminated lignite. The lignite contains inertinite, a petrographic term used to describe charcoal. The laminated lignite has inertinite-rich and inertinite-poor layers indicative of episodic fires and post-fire erosion. Charcoal clasts are derived from living or recently senesced plants and are dominated by the leaf stalks of herbaceous ferns and wood fragments from flowering plants. The charcoal assemblage reflects a low-diversity flora, possibly adapted to disturbance by fire, derived from a source vegetation subjected to seasonal surface wildfires. The environmental conditions leading up to and across the onset of the PETM are, therefore, interpreted as incorporating a persistent fire regime with episodic wildfires followed by rainfall and runoff events. Abundant charcoal indicates near-modern oxygen levels whereas the absence of charred peat in this area calls into question previous suggestions that burning of Palaeocene peats might have contributed to the short-lived negative carbon isotope excursion at the Palaeocene–Eocene boundary.
The Highland Border Complex, Scotland: a paradox resolved
Authors: TANNER P.W. GEOFF , SUTHERLAND STUART
Published: December 2006

A previously inexplicable difference between the Highland Border Complex, Scotland, and its correlative in Ireland, the Clew Bay Complex, is that rocks of Caradoc–Ashgill age occur only in the former. We reject evidence from supposed chitinozoa for this dichotomy: no sedimentary rocks of proven age younger than Arenig occur in the Highland Border Complex. Consequentially, the stratigraphy must be totally recast, and the ‘exotic terrane model’ replaced by one in which a largely autochthonous Highland Border Complex in stratigraphical continuity with the Dalradian (Grampian terrane), was overridden by the Highland Border ophiolite (Midland Valley terrane). Tectonic models for SE Laurentia are thereby considerably simplified.
Super sizing the giants: first cartilage preservation at a sauropod dinosaur limb joint
Authors: Schwarz Daniela , Wings Oliver , Meyer Christian A.
Published: December 2006

Re-examination of the sauropod dinosaur
Cetiosauriscus greppini
von Huene 1922
(Reuchenette Formation; Kimmeridgian, Late Jurassic) from northwestern Switzerland has revealed a well-preserved cartilage capsule at the distal extremity of the right humerus. The capsule represents hyaline cartilage together with fibrocartilage and can be distinguished by colour, surface structure and histology from the periosteum of the bone. This is the first fossil evidence for articular cartilage in a sauropodomorph dinosaur. It indicates the presence of a large articular capsule on sauropod forelimbs, which was only hypothesized until now, and shows that the forelimb length of sauropods was larger than previously assumed.
Tectonic models for accretion of the Central Asian Orogenic Belt
Authors: Windley Brian F. , Alexeiev Dmitriy , Xiao Wenjiao , Kröner Alfred , Badarch Gombosuren
Published: December 2006

The Central Asian Orogenic Belt (
c
. 1000–250 Ma) formed by accretion of island arcs, ophiolites, oceanic islands, seamounts, accretionary wedges, oceanic plateaux and microcontinents in a manner comparable with that of circum-Pacific Mesozoic–Cenozoic accretionary orogens. Palaeomagnetic and palaeofloral data indicate that early accretion (Vendian–Ordovician) took place when Baltica and Siberia were separated by a wide ocean. Island arcs and Precambrian microcontinents accreted to the active margins of the two continents or amalgamated in an oceanic setting (as in Kazakhstan) by roll-back and collision, forming a huge accretionary collage. The Palaeo-Asian Ocean closed in the Permian with formation of the Solonker suture. We evaluate contrasting tectonic models for the evolution of the orogenic belt. Current information provides little support for the main tenets of the one- or three-arc Kipchak model; current data suggest that an archipelago-type (Indonesian) model is more viable. Some diagnostic features of ridge–trench interaction are present in the Central Asian orogen (e.g. granites, adakites, boninites, near-trench magmatism, Alaskan-type mafic–ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, rhyolitic ash-fall tuffs). They offer a promising perspective for future investigations.
Geodynamic settings of mineral deposit systems
Authors: Groves David I. , Bierlein Frank P.
Published: December 2006

Mineral deposits represent extraordinary metal concentrations that form by magmatic, magmatic–hydrothermal or hydrothermal processes in geodynamic environments typified by anomalously high thermal and/or mechanical energy near plate boundaries. As they require the conjunction of specific environmental conditions to form, particular mineral deposit types tend to occupy specific geodynamic niches. The temporal distributions of mineral deposit types reflect both formational and preservational processes. In the Archaean and Palaeoproterozoic, these were linked because of preservation in continental crust connected to thick buoyant subcontinental lithospheric mantle (SCLM), but were decoupled by the Neoproterozoic and Phanerozoic as a result of evolution to thinner, increasingly dense SCLM. The transition marks a change from mantle plume-influenced plate tectonics to modern-style plate tectonics, with broadly coincident environmental changes and a major impact on the nature and abundance of preserved mineral deposit types. As mineral deposits represent an integral part of tectonic process, they are essential indicators of that process and geodynamic settings, and should be incorporated into any holistic tectonic terrane analysis. Their distribution also provides a particularly critical test on ancient continental reconstructions derived from palaeomagnetic data. Conversely, such reconstructions provide a first-order targeting tool for the conceptual exploration required to discover new mineral provinces and deposits under cover.
Charnia
and sea pens are poles apart
Authors: Antcliffe Jonathan B. , Brasier Martin D.
Published: December 2006

C

harnia

from the Ediacara biota is here examined in terms of its growth and development. The Ediacara biota comes from the critical period of evolution just before the Cambrian Explosion and is key to our understanding of the origin of animal life. We show that

Charnia

cannot be related to the modern cnidarian group the sea pens (Pennatulacea) with which it has for so long been compared, as generative zones cannot be homologized between these forms.
Laccolithic, as opposed to cauldron subsidence, emplacement of the Eastern Mourne pluton, N. Ireland: evidence from anisotropy of magnetic susceptibility
Authors: Stevenson Carl T.E. , Owens William H. , Hutton Donald H.W. , Hood David N. , Meighan Ian G.
Published: December 2006

The structural evolution and emplacement of the Eastern Mourne pluton was investigated using anisotropy of magnetic susceptibility (AMS) measurements (carried out on 112 oriented block samples) and structural data from the host rocks. From these new data cauldron subsidence, as the emplacement mechanism, is disputed and evidence for an alternative, laccolithic style model involving inflation is presented. This includes deflection and uplift of host-rock bedding close to contacts and the magnetic fabric pattern, which has a gentle dome geometry, even close to contacts. The magnetic lineations usually plunge down-dip near the external margins but otherwise have a general SSW–NNE trend that diverges northward. This suggests a northward-directed inflow direction. The model for the emplacement of the Eastern Mourne pluton is a laterally fed laccolith, emplaced south to north. The eastern margin is interpreted as a faulted contact facilitating the inflation of an asymmetrical ‘breached’ laccolith.
Extracellular signal-regulated kinase pathway is differentially involved in β-agonist-induced hypertrophy in slow and fast muscles
Authors: Shi H. , Zeng C. , Ricome A. , Hannon K. M. , Grant A. L. , Gerrard D. E.
Published: December 2006

The molecular mechanisms controlling β-adrenergic receptor agonist (BA)-induced skeletal muscle hypertrophy are not well known. We presently report that BA exerts a distinct muscle- and muscle fiber type-specific hypertrophy. Moreover, we have shown that pharmacologically or genetically attenuating extracellular signal-regulated kinase (ERK) signaling in muscle fibers resulted in decreases ( P < 0.05) in fast but not slow fiber type-specific reporter gene expressions in response to BA exposure in vitro and in vivo. Consistent with these data, forced expression of MAPK phosphatase 1, a nuclear protein that dephosphorylates ERK1/2, in fast-twitch skeletal muscle ablated ( P < 0.05) the hypertrophic effects of BA feeding (clenbuterol, 20 parts per million in water) in vivo. Further analysis has shown that BA-induced phosphorylation and activation of ERK occurred to a greater ( P < 0.05) extent in fast myofibers than in slow myofibers. Analysis of the basal level of ERK activity in slow and fast muscles revealed that ERK1/2 is activated to a greater extent in fast- than in slow-twitch muscles. These data indicate that ERK signaling is differentially involved in BA-induced hypertrophy in slow and fast skeletal muscles, suggesting that the increased abundance of phospho-ERK1/2 and ERK activity found in fast-twitch myofibers, compared with their slow-twitch counterparts, may account, at least in part, for the fiber type-specific hypertrophy induced by BA stimulation. These data suggest that fast myofibers are pivotal in the adaptation of muscle to environmental cues and that the mechanism underlying this change is partially mediated by the MAPK signaling cascade.
TNF-α regulates myogenesis and muscle regeneration by activating p38 MAPK
Authors: Chen Shuen-Ei , Jin Bingwen , Li Yi-Ping
Published: December 2006

Although p38 MAPK activation is essential for myogenesis, the upstream signaling mechanism that activates p38 during myogenesis remains undefined. We recently reported that p38 activation, myogenesis, and regeneration in cardiotoxin-injured soleus muscle are impaired in TNF-α receptor double-knockout (p55−/−p75−/−) mice. To fully evaluate the role of TNF-α in myogenic activation of p38, we tried to determine whether p38 activation in differentiating myoblasts requires autocrine TNF-α, and whether forced activation of p38 rescues impaired myogenesis and regeneration in the p55−/−p75−/− soleus. We observed an increase of TNF-α release from C2C12 or mouse primary myoblasts placed in low-serum differentiation medium. A TNF-α-neutralizing antibody added to differentiation medium blocked p38 activation and suppressed differentiation markers myocyte enhancer factor (MEF)-2C, myogenin, p21, and myosin heavy chain in C2C12 myoblasts. Conversely, recombinant TNF-α added to differentiation medium stimulated myogenesis at 0.05 ng/ml while inhibited it at 0.5 and 5 ng/ml. In addition, differentiation medium-induced p38 activation and myogenesis were compromised in primary myoblasts prepared from p55−/−p75−/− mice. Increased TNF-α release was also seen in cardiotoxin-injured soleus over the course of regeneration. Forced activation of p38 via the constitutive activator of p38, MKK6bE, rescued impaired myogenesis and regeneration in the cardiotoxin-injured p55−/−p75−/− soleus. These results indicate that TNF-α regulates myogenesis and muscle regeneration as a key activator of p38.