bluuebunny/crossref_metadata_2025 huggingface dataset:
Aspergillus
Mycoviruses Are Targets and Suppressors of RNA Silencing
Authors: Hammond T. M. , Andrewski M. D. , Roossinck M. J. , Keller N. P.
Published: December 2007

RNA silencing can function as a virus defense mechanism in a diverse range of eukaryotes, and many viruses are capable of suppressing the silencing machinery targeting them. However, the extent to which this occurs between fungal RNA silencing and mycoviruses is unclear. Here, three
Aspergillus
dsRNA mycoviruses were partially characterized, and their relationship to RNA silencing was investigated.
Aspergillus
virus 1816 is related to
Agaricus bisporus
white button mushroom virus 1 and suppresses RNA silencing through a mechanism that alters the level of small interfering RNA.
Aspergillus
virus 178 is related to RNA virus L1 of
Gremmeniella abietina
and does not appear to affect RNA silencing. The third virus investigated,
Aspergillus
virus 341, is distantly related to
Sphaeropsis sapinea
RNA virus 2. Detection of mycovirus-derived siRNA from this mycovirus demonstrates that it is targeted for degradation by the
Aspergillu
s RNA silencing machinery. Thus, our results indicate that
Aspergillus
mycoviruses are both targets and suppressors of RNA silencing. In addition, they suggest that the morphological and physiological changes associated with some mycoviruses could be a result of their antagonistic relationship with RNA silencing.
Global Transcriptional Profile of
Mycobacterium tuberculosis
during THP-1 Human Macrophage Infection
Authors: Fontán Patricia , Aris Virginie , Ghanny Saleena , Soteropoulos Patricia , Smith Issar
Published: December 2007

During lung infection,
Mycobacterium tuberculosis
resides in macrophages and subverts the bactericidal mechanisms of these professional phagocytes. Comprehension of this host-pathogen relationship is fundamental for the development of new therapies to cure and prevent tuberculosis. In this work, we analyzed the transcriptional profile of
M. tuberculosis
infecting human macrophage-like THP-1 cells in order to identify putative bacterial pathogenic factors that can be relevant for the intracellular survival of
M. tuberculosis.
We compared the gene expression profile of
M. tuberculosis
H37Rv after 4 h and 24 h of infection of human macrophage-like THP-1 cells with the gene expression profile of the strain growing exponentially in broth cultures. We found 585 genes expressed differentially by intracellular
M. tuberculosis
. An analysis of the gene expression profile of
M. tuberculosis
inside THP-1 cells suggests the perturbation of the cell envelope as a major intracellular stress inside THP-1 macrophages.
NF-κB Activation during AcuteHelicobacter pyloriInfection in Mice
Authors: Ferrero Richard L. , Avé Patrick , Ndiaye Delphine , Bambou Jean-Christophe , Huerre Michel R. , Philpott Dana J. , Mémet Sylvie
Published: December 2007

Nuclear factor κB (NF-κB) plays a key regulatory role in host cell responses toHelicobacter pyloriinfection in humans. Although mice are routinely used as a model to studyH. pyloripathogenesis, the role of NF-κB in murine cell responses to helicobacters has not been studied in detail. We thus investigated the abilities of differentHelicobacterisolates to induce NF-κB-dependent responses in murine gastric epithelial cells (GECs) and in transgenic mice harboring an NF-κB-responsivelacZreporter gene.H. pyloriandHelicobacter felisstrains up-regulated the synthesis in mouse GECs of the NF-κB-dependent chemokines KC (CXCL1) and MIP-2 (CXCL2). These responses werecagpathogenicity island (cagPAI) independent and could be abolished by pretreatment with a pharmacological inhibitor of NF-κB. Consistent with the in vitro data, experimentalHelicobacterinfection of transgenic mice resulted in increased numbers of GECs with nuclear β-galactosidase activity, which is indicative of specific NF-κB activation. The numbers of β-galactosidase-positive cells in mice were significantly increased at day 1 postinoculation with wild-typeH. pyloristrains harboring or not harboring a functionalcagPAI, compared to naive animals (P= 0.007 andP= 0.04, respectively). Strikingly, however, no differences were observed in the levels of gastric NF-κB activation at day 1 postinoculation withH. felisor at day 30 or 135 postinoculation withH. pylori. This work demonstrates for the first time the induction of NF-κB activation within gastric mucosal cells during acuteH. pyloriinfection. Furthermore, the data suggest that helicobacters may be able to regulate NF-κB signaling during chronic infection.
Novel Class of Mutations of
pilS
Mutants, Encoding Plasmid R64 Type IV Prepilin: Interface of PilS-PilV Interactions
Authors: Shimoda Eriko , Muto Tatsuya , Horiuchi Takayuki , Furuya Nobuhisa , Komano Teruya
Published: December 2007

The type IV pili of plasmid R64 belonging to the type IVB group are required only for liquid mating. They consist of the major and minor components PilS pilin and PilV adhesin, respectively. PilS pilin is first synthesized as a 22-kDa prepilin from the
pilS
gene and is then processed to a 19-kDa mature pilin by PilU prepilin peptidase. In a previous genetic analysis, we identified four classes of the
pilS
mutants (T. Horiuchi and T. Komano, J. Bacteriol.
180:
4613-4620, 1998). The products of the class I
pilS
mutants were not processed by prepilin peptidase; the products of the class II mutants were not secreted; in the class III mutants type IV pili with reduced activities in liquid mating were produced; and in the class IV mutants type IV pili with normal activities were produced. Here, we describe a novel class, class V, of
pilS
mutants. Mutations in the
pilS
gene at Gly-56 or Tyr-57 produced type IV pili lacking PilV adhesin, which were inactive in liquid mating. Residues 56 and 57 of PilS pilin are suggested to function as an interface of PilS-PilV interactions.
Analysis of Genetic Relatedness of
Haemophilus influenzae
Isolates by Multilocus Sequence Typing
Authors: Erwin Alice L. , Sandstedt Sara A. , Bonthuis Paul J. , Geelhood Jennifer L. , Nelson Kevin L. , Unrath William C. T. , Diggle Mathew A. , Theodore Mary J. , Pleatman Cynthia R. , Mothershed Elizabeth A. , Sacchi Claudio T. , Mayer Leonard W. , Gilsdorf Janet R. , Smith Arnold L.
Published: December 2007

The gram-negative bacterium
Haemophilus influenzae
is a human-restricted commensal of the nasopharynx that can also be associated with disease. The majority of
H. influenzae
respiratory isolates lack the genes for capsule production and are nontypeable (NTHI). Whereas encapsulated strains are known to belong to serotype-specific phylogenetic groups, the structure of the NTHI population has not been previously described. A total of 656
H. influenzae
strains, including 322 NTHI strains, have been typed by multilocus sequence typing and found to have 359 sequence types (ST). We performed maximum-parsimony analysis of the 359 sequences and calculated the majority-rule consensus of 4,545 resulting equally most parsimonious trees. Eleven clades were identified, consisting of six or more ST on a branch that was present in 100% of trees. Two additional clades were defined by branches present in 91% and 82% of trees, respectively. Of these 13 clades, 8 consisted predominantly of NTHI strains, three were serotype specific, and 2 contained distinct NTHI-specific and serotype-specific clusters of strains. Sixty percent of NTHI strains have ST within one of the 13 clades, and eBURST analysis identified an additional phylogenetic group that contained 20% of NTHI strains. There was concordant clustering of certain metabolic reactions and putative virulence loci but not of disease source or geographic origin. We conclude that well-defined phylogenetic groups of NTHI strains exist and that these groups differ in genetic content. These observations will provide a framework for further study of the effect of genetic diversity on the interaction of NTHI with the host.
Chemotaxis of
Escherichia coli
to Pyrimidines: a New Role for the Signal Transducer Tap
Authors: Liu Xianxian , Parales Rebecca E.
Published: December 2007

Escherichia coli
exhibits chemotactic responses to sugars, amino acids, and dipeptides, and the responses are mediated by methyl-accepting chemotaxis proteins (MCPs). Using capillary assays, we demonstrated that
Escherichia coli
RP437 is attracted to the pyrimidines thymine and uracil and the response was constitutively expressed under all tested growth conditions. All MCP mutants lacking the MCP Tap protein showed no response to pyrimidines, suggesting that Tap, which is known to mediate dipeptide chemotaxis, is required for pyrimidine chemotaxis. In order to confirm the role of Tap in pyrimidine chemotaxis, we constructed chimeric chemoreceptors (Tapsr and Tsrap), in which the periplasmic and cytoplasmic domains of Tap and Tsr were switched. When Tapsr and Tsrap were individually expressed in an
E. coli
strain lacking all four native MCPs, Tapsr mediated chemotaxis toward pyrimidines and dipeptides, but Tsrap did not complement the chemotaxis defect. The addition of the C-terminal 19 amino acids from Tsr to the C terminus of Tsrap resulted in a functional chemoreceptor that mediated chemotaxis to serine but not pyrimidines or dipeptides. These results indicate that the periplasmic domain of Tap is responsible for detecting pyrimidines and the Tsr signaling domain confers on Tapsr the ability to mediate efficient chemotaxis. A mutant lacking dipeptide binding protein (DBP) was wild type for pyrimidine taxis, indicating that DBP, which is the primary chemoreceptor for dipeptides, is not responsible for detecting pyrimidines. It is not yet known whether Tap detects pyrimidines directly or via an additional chemoreceptor protein.
Additional In Vitro and In Vivo Evidence for SecA Functioning as Dimers in the Membrane: Dissociation into Monomers Is Not Essential for Protein Translocation in
Escherichia coli
Authors: Wang Hongyun , Na Bing , Yang Hsiuchin , Tai Phang C.
Published: December 2007

SecA is an essential component in the Sec-dependent protein translocation pathway and, together with ATP, provides the driving force for the transport of secretory proteins across the cytoplasmic membrane of
Escherichia coli
. Previous studies established that SecA undergoes monomer-dimer equilibrium in solution. However, the oligomeric state of functional SecA during the protein translocation process is controversial. In this study, we provide additional evidence that SecA functions as a dimer in the membrane by (i) demonstration of the capability of the presumably monomeric SecA derivative to be cross-linked as dimers in vitro and in vivo, (ii) complementation of the growth of a
secA
(Ts) mutant with another nonfunctional SecA or (iii) in vivo complementation and in vitro function of a genetically tandem SecA dimer that does not dissociate into monomers, and (iv) formation of similar ring-like structures by the tandem SecA dimer and SecA in the presence of lipid bilayers. We conclude that SecA functions as a dimer in the membrane and dissociation into monomers is not necessary during protein translocation.
Lipopolysaccharide O-Antigen Chain Length Regulation in
Pseudomonas aeruginosa
Serogroup O11 Strain PA103
Authors: Kintz Erica , Scarff Jennifer M. , DiGiandomenico Antonio , Goldberg Joanna B.
Published: December 2007

The Wzz proteins are important for determining the length of the O-antigen side chain attached to lipopolysaccharide (LPS). Several bacteria, including
Pseudomonas aeruginosa
strain PAO1 (serogroup O5), produce two such proteins responsible for the preference of two different chain lengths on the surface. Our group has previously identified one
wzz
gene (
wzz1
) within the O-antigen locus of
P. aeruginosa
strain PA103 (serogroup O11). In this study we have identified the second
wzz
gene (
wzz2
), located in the same region of the genome and with 92% similarity to PAO1's
wzz2
gene. Mutations were generated in both
wzz
genes by interruption with antibiotic resistance cassettes, and the effects of these mutations were characterized. Wild-type PA103 prefers two O-antigen chain lengths, referred to as long and very long. The expression of the long O-antigen chain length was reduced in the
wzz1
mutant, indicating the Wzz1 protein is important for this chain length preference. The
wzz2
mutant, on the other hand, was missing O-antigens of the very long chain length, indicating the Wzz2 protein is responsible for the production of very long O-antigen. The effects of the
wzz
mutations on virulence were also investigated. In both serum sensitivity assays and a mouse pneumonia model of infection, the
wzz1
mutants exhibited greater defects in virulence compared to either wild-type PA103 or the
wzz2
mutant, indicating the long chain length plays a greater role during these infectious processes.
TheCampylobacter jejuniNADH:Ubiquinone Oxidoreductase (Complex I) Utilizes Flavodoxin Rather than NADH
Authors: Weerakoon Dilan R. , Olson Jonathan W.
Published: December 2007

Campylobacter jejuniencodes 12 of the 14 subunits that make up the respiratory enzyme NADH:ubiquinone oxidoreductase (also called complex I). The twonuogenes not present inC. jejuniencode the NADH dehydrogenase, and in their place in the operon are the novel genes designated Cj1575c and Cj1574c. A series of mutants was generated in which each of the 12nuogenes (homologues to known complex I subunits) was disrupted or deleted. Each of thenuomutants will not grow in amino acid-based medium unless supplemented with an alternative respiratory substrate such as formate. Unlike thenuogenes, Cj1574c is an essential gene and could not be disrupted unless an intact copy of the gene was provided at an unrelated site on the chromosome. Anuodeletion mutant can efficiently respire formate but is deficient in α-ketoglutarate respiratory activity compared to the wild type. InC. jejuni, α-ketoglutarate respiration is mediated by the enzyme 2-oxoglutarate:acceptor oxidoreductase; mutagenesis of this enzyme abolishes α-ketoglutarate-dependent O2uptake and fails to reduce the electron transport chain. The electron acceptor for 2-oxoglutarate:acceptor oxidoreductase was determined to be flavodoxin, which was also determined to be an essential protein inC. jejuni. A model is presented in which CJ1574 mediates electron flow into the respiratory transport chain from reduced flavodoxin and through complex I.
Moraxella catarrhalisSynthesizes an Autotransporter That Is an Acid Phosphatase
Authors: Hoopman Todd C. , Wang Wei , Brautigam Chad A. , Sedillo Jennifer L. , Reilly Thomas J. , Hansen Eric J.
Published: December 2007

Moraxella catarrhalisO35E was shown to synthesize a 105-kDa protein that has similarity to both acid phosphatases and autotransporters. The N-terminal portion of theM. catarrhalis acidphosphataseA(MapA) was most similar (the BLAST probability score was 10−10) to bacterial class A nonspecific acid phosphatases. The central region of the MapA protein had similarity to passenger domains of other autotransporter proteins, whereas the C-terminal portion of MapA resembled the translocation domain of conventional autotransporters. Cloning and expression of theM. catarrhalis mapAgene inEscherichia coliconfirmed the presence of acid phosphatase activity in the MapA protein. The MapA protein was shown to be localized to the outer membrane ofM. catarrhalisand was not detected either in the soluble cytoplasmic fraction from disruptedM. catarrhaliscells or in the spent culture supernatant fluid fromM. catarrhalis. Use of the predicted MapA translocation domain in a fusion construct with the passenger domain from another predictedM. catarrhalisautotransporter confirmed the translocation ability of this MapA domain. Inactivation of themapAgene inM. catarrhalisstrain O35E reduced the acid phosphatase activity expressed by this organism, and this mutation could be complemented intranswith the wild-typemapAgene. Nucleotide sequence analysis of themapAgene from sixM. catarrhalisstrains showed that this protein was highly conserved among strains of this pathogen. Site-directed mutagenesis of a critical histidine residue (H233A) in the predicted active site of the acid phosphatase domain in MapA eliminated acid phosphatase activity in the recombinant MapA protein. This is the first description of an autotransporter protein that expresses acid phosphatase activity.
Secreted-Protein Response to σUActivity inStreptomyces coelicolor
Authors: Gordon Nadria D. , Ottaviano Geri L. , Connell Sarah E. , Tobkin Gregory V. , Son Crystal H. , Shterental Sebastian , Gehring Amy M.
Published: December 2007

The filamentous bacteriumStreptomyces coelicolorforms an aerial mycelium as a prerequisite to sporulation, which occurs in the aerial hyphae. Uncontrolled activity of the extracytoplasmic function sigma factor σUblocks the process of aerial mycelium formation in this organism. Using a green fluorescent protein transcriptional reporter, we have demonstrated thatsigUtranscription is autoregulated. We have defined a σU-dependent promoter sequence and used this to identify 22 likely σUregulon members in theS. coelicolorgenome. Since many of these genes encode probable secreted proteins, we characterized the extracellular proteome of a mutant with high σUactivity caused by disruption ofrsuA, the presumed cognate anti-sigma factor of σU. This mutant secreted a much greater quantity and diversity of proteins than the wild-type strain. Peptide mass fingerprinting was used to identify 79 proteins from thersuAmutant culture supernatant. The most abundant species, SCO2217, SCO0930, and SCO2207, corresponded to secreted proteins or lipoproteins of unknown functions whose genes are in the proposed σUregulon. Several unique proteases were also detected in the extracellular proteome of the mutant, and the levels of the protease inhibitor SCO0762 were much reduced compared to those of the wild type. Consequently, extracellular protease activity was elevated about fourfold in thersuAmutant. The functions of the proteins secreted as a result of σUactivity may be important for combating cell envelope stress and modulating morphological differentiation inS. coelicolor.
Influence of repetitive open sea dives and physical exercises on right-to-left shunting in healthy divers: Table 1
Authors: Blatteau J-E , Pény C , Pontier J-M , Gempp E , Louge P
Published: December 2007

Objective:

Paradoxical gas embolism through right-to-left (R/L) shunts is considered as a potential cause of certain types of decompression sickness.

Aim:

To assess whether 4 months of repetitive diving and strenuous exercises would lead to an increased prevalence of R/L shunting in a group of military divers.

Methods:

Using a standardised contrast-enhanced transcranial Doppler technique, 17 divers were re-examined for the presence of a R/L shunt 4 months after their initial examinations. R/L shunts were classified as type I if observed only after a straining manoeuvre, and type II if present at rest.

Results:

Initial prevalence of R/L shunt was 41%: six type I shunts and one type II. At the second examination, prevalence was 47%, with the appearance of one type I shunt that was not previously present. We found no significant increase in the prevalence and size of R/L shunts.

Conclusion:

It is speculated that diving-related phenomena, such as variations in right atrial pressures during the end stages of or events immediately after a dive could generate an R/L shunt. However, extreme conditions of repetitive diving and strenuous exercises do not cause permanent modification in R/L permeability over a period of 4 months.
MRI study of the size, symmetry and function of the trunk muscles among elite cricketers with and without low back pain
Authors: Hides J , Stanton W , Freke M , Wilson S , McMahon S , Richardson C
Published: December 2007

Objectives:

To determine if asymmetry of trunk muscles and deficits of motor control exist among elite cricketers with and without low back pain (LBP).

Design:

Single-blinded observational quasi-experimental design study

Setting:

Assessments were conducted in a hospital setting.

Participants:

Among a total eligible sample of 26 male elite cricketers (mean age 21.2 (SD 2.0) years), selected to attend a national training camp, 21 participated in the study.

Risk factors:

The independent variables were ‘group’ (LBP or asymptomatic) and ‘cricket position’ (fast bowler versus the rest of the squad).

Main outcome measurements:

The dependent variables were the cross-sectional areas (CSA) of the quadratus lumborum (QL), lumbar erector spinae plus multifidus (LES + M) and psoas muscles, the thickness of the internal oblique (IO) and transversus abdominis (TrA) muscles, and the amount of lateral slide of the anterior abdominal fascia.

Results:

The QL and LES + M muscles were larger ipsilateral to the dominant arm. In the subgroup of fast bowlers with LBP, the asymmetry in the QL muscle was the greatest. The IO muscle was larger on the side contralateral to the dominant arm. No difference between sides was found for the psoas and TrA muscles. Cricketers with LBP showed a reduced ability to draw in the abdominal wall and contract the TrA muscle independently of the other abdominal muscles.

Conclusions:

This study provides new insights into trunk muscle size and function in elite cricketers, and evidence of impaired motor control in elite cricketers with LBP. Rehabilitation using a motor control approach has been shown to be effective for subjects with LBP, and this may also benefit elite cricketers.
From measures to models: an evaluation of air pollution exposure assessment for epidemiological studies of pregnant women
Authors: Nethery E , Leckie S E , Teschke K , Brauer M
Published: December 2007

Objectives:

To evaluate exposure estimation methods such as spatially resolved land-use regression models and ambient monitoring data in the context of epidemiological studies of the impact of air pollution on pregnancy outcomes.

Methods:

The study measured personal 48 h exposures (NO, NO2, PM2.5mass and absorbance) and mobility (time activity and GPS) for 62 pregnant women during 2005–2006 in Vancouver, Canada, one to three times during pregnancy. Measurements were compared to modelled (using land-use regression and interpolation of ambient monitors) outdoor concentrations at subjects’ home and work locations.

Results:

Personal NO and absorbance (ABS) measurements were moderately correlated (NO: r = 0.54, ABS: r = 0.29) with monitor interpolations and explained primarily within-subject (temporal) variability. Land-use regression estimates including work location improved correlations for NO over those based on home postal code (for NO: r = 0.49 changed to NO: r = 0.55) and explained more between-subject variance (4–20%); limiting to a subset of samples (n = 61) when subjects spent >65% time at home also improved correlations (NO: r = 0.72). Limitations of the GPS equipment precluded assessment of including complete GPS-based mobility information.

Conclusions:

The study found moderate agreement between short-term personal measurements and estimates of ambient air pollution at home based on interpolation of ambient monitors and land-use regression. These results support the use of land-use regression models in epidemiological studies, as the ability of such models to characterise high resolution spatial variability is “reflected” in personal exposure measurements, especially when mobility is characterised.
Morphological and anatomical development in the Vitaceae. IX. Comparative ontogeny and phylogenetic implications ofVitis rotundifoliaMichx.
Authors: Timmons Susan A. , Posluszny Usher , Gerrath Jean M.
Published: December 2007

The grape family, Vitaceae, is an economically important fruit family. Although the Vitaceae have been used for conservation, viticulture, and horticulture, little is known about the phylogenetic relationships of this family. Recent phylogenetic reconstructions using DNA data have disagreed with traditional classifications and other DNA-based phylogenies by grouping Vitis and Cissus species within one clade and linking Vitis rotundifolia Michx. (muscadine grape) more closely with these Cissus species. This study uses comparative developmental morphology as an independent method to investigate whether V. rotundifolia is more similar to Cissus antarctica Vent. (kangaroo vine) than other Vitis species. Results obtained using epi-illumination light microscopy and histology were compared with those from similar studies of Vitis ‘Ventura’, Vitis riparia Michx., and C. antarctica. Twelve vegetative and floral characters including axillary bud dorsiventrality, uncommitted primordium shape, calyptra, and ring-shaped gynoecial disk placed V. rotundifolia in with other Vitis species. Only two characters, stipule timing and simple tendrils, were common to C. antarctica and V. rotundifolia, suggesting that V. rotundifolia is more similar to Vitis spp. than to C. antarctica, and supporting traditional classifications contrary to ITS1 and trnL DNA phylogenies.
Effective thermal expansion coefficient of frozen granite soil
Authors: Song Weon-Keun
Published: December 2007

The paper focuses on the development of a model for the coupled thermal transfer and frost action of a soil medium, considering the phase-change effect in the frozen fringe, for a closed system. The frost pressure of the cylindrical soil specimens observed in the freezing test gave a reference value to determine the effective thermal expansion coefficient numerically. Through the proposed numerical technique, the effective thermal expansion coefficient was defined for the frozen granite soil as a function of subzero temperature and initial in situ pore-water content. A comparative analyses between the numerical results and the measurements obtained in the freezing chamber test was conducted to verify the performance of the effective thermal expansion coefficient and the agreement was good.
High resolution O 1s XPS spectral, NMR, and thermodynamic evidence bearing on anionic silicate moieties (units) in PbO-SiO2 and Na2O-SiO2 glasses
Authors: Nesbitt H W , Dalby K N
Published: December 2007

Recent technical advances in X-ray photoelectron spectroscopy (XPS) have largely overcome differential charging of insulator surfaces, with the result that O 1s linewidths for silicates can be routinely collected that are 50% to 100% narrower than had been previously obtainable. The bridging and nonbridging oxygen signals of glasses are well resolved and now can be accurately measured by XPS without resorting to ad hoc fitting procedures. All O 1s spectra of silicates collected so far are somewhat asymmetric to the high binding energy side of the peak, a characteristic due primarily to vibrational contributions in the ion state produced by photoemission (electronic excited state). This asymmetry must be considered if the proportion of bridging to nonbridging oxygen ratios are to be accurately determined from the XPS O 1s spectra of silicates. X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR) experiments yield similar silicon-bridging oxygen (Si-O-Si) concentrations for PbO-SiO2 glasses. The data are proof that the reaction, 2PbO + SiO2 [Formula: see text] Pb2SiO4, does not go to completion (i.e., one or other reactant is not completely consumed). Instead, the data indicate that an equilibrium exists among these constituents, with the equilibrium constant for the reaction being near 15; ergo, some metal bridging oxygen (MBO or Pb-O-Pb), silicon bridging oxygen (BO or Si-O-Si), and nonbridging oxygen (NBO or M-O-Si) are present over the entire range of binary melt compositions. NMR and XPS spectroscopic techniques yield substantially different Si-O-Si concentrations in Na2O-SiO2 glasses of intermediate to high Na2O content. XPS experiments indicate higher proportions of Si-O-Si in Na2O-rich glasses than do the NMR studies. In spite of the different results, three independently collected sets of NMR experiments are similar and yield similar Si-O-Si concentrations. Five XPS experimental studies are likewise self-consistent (but different from the NMR studies). Comparison of data from the two spectroscopic techniques indicates that all experimental spectra are of good or reasonable quality, so that systematic experimental problems or the interpretation (i.e., fitting) of these spectra may be incorrect for one or both types of spectral data. Viscosity, conductivity, and the XPS data are consistent with (but not proof for) formation of an Na2Si2O5 species in the Na2O-SiO2 glasses. The most comprehensive NMR study is, by contrast, consistent with the formation of an orthosilicate species (Na4SiO4). The NMR and XPS results cannot yet be reconciled and additional experimental studies are required to resolve and to understand better Na2O-SiO2 liquids and glasses.Key words: XPS, high resolution, silicate glass, NMR.
CHINA'S EXCHANGE RATE SYSTEM REFORM
Authors: YIP PAUL S. L.
Published: December 2007

This paper first documents the rationales behind the transitional exchange rate system reform adopted by China on 21 July 2005. It then outlines the theory behind the medium- and long-term exchange rate arrangements that could be adopted. Thereafter, the paper provides recommendations on supplementary packages that could increase the chance of a successful reform, and increase China's immunity and resilience against financial crises in the future. Finally, the paper discusses the market and economic developments after the transitional reform, and highlights that failure to check the stock market bubble and rampant property inflation could turn the initial success of the reform to an eventual failure and bring disasters to China in the longer future.
THE FINITE-SIZE SCALING STUDY OF THE SPECIFIC HEAT AND THE BINDER PARAMETER FOR THE FIVE-DIMENSIONAL ISING MODEL
Authors: KALAY M. , MERDAN Z.
Published: December 2007

The five-dimensional Ising model with nearest-neighbor pair interactions is simulated on the Creutz cellular automaton by using finite-size lattices with the linear dimensions L=4, 6, 8, 10, 12, 14, and 16. The temperature variations and the finite-size scaling plots of the specific heat and Binder parameter verify the theoretically-predicted expression near the infinite-lattice critical temperature. The approximate values for the critical temperature of the infinite-lattice, T c =8.8063, T c =8.7825 and T c =8.7572, are obtained from the intersection points of specific heat curves, Binder parameter curves and the straight line fit of specific heat maxima, respectively. These results are in agreement with the more precise value of T c =8.7787. The value obtained for the critical exponent of the specific heat, i.e. α=0.009, is also in agreement with α=0 predicted by the theory.
STUDY OF ESR, DEFECT STRUCTURE AND SURFACE MORPHOLOGY OF Cu2+ IN CdS CRYSTALS
Authors: EITSSAYEAM SUKUM , TAWICHAI NATTAYA , PENGPAT KAMONPAN , TUNKASIRI TAWEE , UDOMKAN NITINAI , INTATHA URAIWAN
Published: December 2007

Cu -doped Cadmium sulfide ( CdS ) films were prepared by chemical bath deposition method. Various quantities of Cu were used for mixing. Surface characterization, structure, morphology and defect structures of the films were studied. The structure of all Cu -doped CdS films was a unique CdS cubic phase. The grain size of CdS was decreased when doped with Cu . The F-type defect in the undoped CdS is clearly confirmed by an ESR signal arising from the hyperfine interaction of electron spin (S=1/2) trapped in sulfur vacancies and neighboring cadmium nuclear spin (I=1/2). In the Cu -doped CdS films, the ESR peaks shift towards low fields as the copper concentration is increased. This is due to the change in crystal field experience by Cu 2+ (3 d 9) ions while the Cd 2+ signal disappears. The Cu 2+ ions in the Cd 1-x Cu x S itself are ESR silent due to a very short relaxation time. The dark resistance increased with increasing amount of Cu concentrations up to about 0.03 M. This 0.03 M Cu -doped CdS sample also possesses the maximum photosensitivity.
Liquidity-Adjusted Benchmark Yield Curves: A Look at Trading Concentration and Information
Authors: Lin William T. , Sun David S.
Published: December 2007

Estimation of benchmark yield curve in developing markets is often influenced by liquidity concentration. Based on an affine term structure model, we develop a long run liquidity weighted fitting method to address the trading concentration phenomenon arising from horizon-induced clientele equilibrium as well as information discovery. Specifically, we employ arguments from models of liquidity concentration and benchmark security information. After examining time series behavior of price errors against our fitted model, we find results consistent with both the horizon and information hypotheses. Our evidence indicates that trading liquidity carries information effect in the long run, which cannot be fully captured in the short run. Trading liquidity plays a key role in long run term structure fitting. Markets for liquid benchmark government bond issues collectively form a long term equilibrium. Compared with previous studies, our results provide a robust and realistic characterization of the spot rate term structure and related price forecasting over time, which in turn help portfolio investment of fixed income and long run pricing of financial instruments.
Transitory Price Changes in the Chinese Stock Markets
Authors: Zhang Zhaohui , Nemiroff Howard , Wang Jiamin , Karim Khondkar
Published: December 2007

This paper examines opening and closing return patterns on the Chinese stock markets. We find that open-to-open returns are significantly more volatile than close-to-close returns. In addition, the correlation of the overnight return with the following daytime return is significantly negative, while the correlation of the daytime return with the following overnight return is strongly positive. The results show strong price continuation around the close and strong price reversal at the open, and the findings are not sensitive to trading volume. The findings are less likely to be caused by price limits. Our results are inconsistent with previous findings from the Tokyo Stock Exchange, yet similar to those from the New York Stock Exchange, albeit under a different market structure.
Cross-Market Linkages of Taiwan Index Futures Contracts Listed on the Taiwan Futures Exchange and the Singapore Exchange
Authors: Fung Hung-Gay , Liu Qingfeng "Wilson" , Park Gyoungsin "Daniel"
Published: December 2007

Cointegration tests and ex ante trading rules are applied to study cross-market linkages between the Taiwan Index futures contracts listed on the Singapore Exchange and the Taiwan Stock Exchange Capitalization-weighted Stock Index futures contracts listed on the Taiwan Futures Exchange. The exchange rate-adjusted returns of the two futures series do not differ significantly in mean but in variances, and show significant mean-reverting tendencies between them. Our trading strategies are able to generate statistically significant, if economically insignificant, profits, while our Granger causality tests demonstrate that information flows primarily from the Singapore market to the Taiwan market, a result confirming other research.
Denudation rates for the southern Drakensberg escarpment, SE Africa, derived from
in-situ-
produced cosmogenic
36
C1: initial results
Authors: FLEMING A. , SUMMERFIELD M. A. , STONE J. O. , FIFIELD L. K. , CRESSWELL R. G.
Published: December 2007

Cosmogenic
36
C1 concentrations in basalt samples from the Drakensberg escarpment on the SE African passive margin give quantitative estimates of denudation and scarp retreat rates. Over the 10
4
–10
6
year timespan addressed by these data, the calculated escarpment retreat rate has been 50–95 m Ma
-1
and the average summit denudation rate 6 m Ma
-1
. The scarp retreat rate is an order of magnitude less than previously suggested. The rate of summit lowering is sufficient to prevent the long-term intact survival of erosion cycle surfaces formed in the Mesozoic that were previously inferred for this region.
Extensional and compressional faults in the Everest–Lhotse massif, Khumbu Himalaya, Nepal
Authors: SEARLE M. P.
Published: December 2007

Two large-scale north-dipping, low-angle normal faults cut the Everest massif at the top of the High Himalayan slab in Nepal. The upper fault the Qomolangma Detachment, follows the north slope of Everest from above the 'Yellow Band' at
c.
8500 m on the Southwest Face down to the Rongbuk glacier. On the south side of Everest this fault places unmetamorphosed Ordovician mudstones and limestones above biotite-grade marbles, calc-silicates and greenschists (Everest series pelites). The lower normal fault, the Lhotse Detachment, places greenschist grade calc-silicates and pelites above sillimanite–K-feldspar-grade gneisses (quartz+biotite+garnet + K-feldspar+plagioclase+sillimanite ± cordierite assemblages) formed at temperatures above 650°C. Abundant sheet intrusions, sills and dykes of leucogranite containing tourmaline+muscovite ± biotite ± garnet are restricted to the footwall of the Lhotse Detachment. The mid–upper greenschist grade Everest pelites, some 2000 m thick on the SW face of Everest, form a northward tapering wedge bounded by normal faults below and above. A major compressional fault, the Khumbu Thrust, bounds the base of a
c
. 3–6 km thick sheet which consists of a series of flat-lying leucogranite sills or sheets extending more than 25 km south of Everest. The leucogranite peaks of Ama Dablam, Kangteiga and Tamserku are all part of the same sheet, which, prior to erosion, was probably originally continuous. The main granite emplacement mechanism was by syn-tectonic magma injection by hydraulic fracture propagation during simple shear, along a series of large sills from their source region at depth to the north. Granite emplacement occurred during upper crustal extension along the top of the High Himalayan slab, although final motion on the Lhotse Detachment post-dated granite emplacement. Both the normal faults at the top of the slab and the Khumbu thrust at the base of the leucogranite sheets were mechanically linked, resulting in the southward extrusion of rocks formed at
c.
12–30 km depth within the High Himalayan slab.
Geological and geomorphological observations in relation to the 20 September 1899 Menderes earthquake, Western Turkey
Authors: ALTUNEL ERHAN
Published: December 2007

The 20 September 1899 Menderes earthquake was the most damaging event that has occurred in the Büyük Menderes graben in the last 100 years. The earthquake involved normal faulting along the northern margin of the Büyük Menderes graben from west of Aydin to Nazilli. A detailed investigation along the northern margin of the graben showed the presence of faults cutting actively depositing graben floor deposits in the foot of Neogene hills. Along an E–W trend east of Aydin, a normal fault was located having an observable length of at least 3 km and a maximum vertical displacement of about 3.5 m. A stream entering to the graben changed its cause due to this fault. Field evidence suggests that, in addition to south-side down-throw by as much as 2 m during the 1899 event, there was also at least 1.5 m opening along the surface break. Field evidence also showed that the 1899 surface break follows a pre-existing break which might have ruptured during the 26 (or 25) BC and 22 February 1653 events; again south-side down-thrown by at least 1 m and 1.5 m, respectively.
Deformation-induced resetting of Rb/Sr and
40
Ar/
39
Ar mineral systems in a low-grade, polymetamorphic terrane (Eastern Alps, Austria)
Authors: MÜLLER WOLFGANG , DALLMEYER R. DAVID , NEUBAUER FRANZ , THÖNI MARTIN
Published: December 2007

A paradox in dating metamorphic events in low-grade, polymetamorphic terranes is exemplified by the eastern Lower Austroalpine nappes of the Eastern Alps. Here, the last metamorphic event, best recorded in post-Variscan cover rocks, is dated as Late Cretaceous in age
(c.
80–85 Ma) by white mica Rb/Sr and
40
Ar/
39
Ar systems. Within the underlying polymetamorphic basement,
40
Ar/
39
Ar and Rb/Sr ages of phengitic white mica record only Early and/or Late Variscan ages (375–270 Ma), indicating that the Alpine greenschist facies metamorphic overprint virtually caused no rejuvenation of Variscan mineral ages.

Based on these results, the timing of a penetrative, ductile, top–to-WNW simple shear deformation recorded within both basement and cover rocks was contradictory. Deformation within the post-Variscan cover rocks had to be Alpine in age, whereas phengite
40
Ar/
39
Ar ages from basement mylonites yield Variscan ages. To date this deformation directly, we isolated different mineral size fractions (63–30 and 30–10 μm) from highly strained shearbands within the Wechsel basement nappe. A resulting Rb/Sr errorchron pointed to an Upper Cretaceous age
(c.
85 Ma) for the deformation, consistent with the timing of Alpine metamorphism in the cover rocks. Coarser-grained white mica (150–300 μim) from similar basement mylonites do not reflect any Alpine overprint of either K/Ar and/or Rb/Sr systems. It follows that dynamic re-and/or neocrystallization induced by ductile deformation within the shearbands was the dominant process by which the Rb/Sr system locally virtually re-equilibrated. This is valid even for overprinting metamorphic conditions below the temperatures required for Ar diffusional loss in phengitic white mica
(c.
<350°C). The data suggest that mineral ages that date low-grade mylonitization (e.g., white mica
40
Ar/
39
Ar) should be considered with caution.
Constraints on the age of the British Tertiary Volcanic Province from ion microprobe U-Pb (SHRIMP) ages for acid igneous rocks from NE Ireland
Authors: GAMBLE J. A. , WYSOCZANSKI R. J. , MEIGHAN I. G.
Published: December 2007

Using the sensitive high resolution ion microprobe (SHRIMP), U-Pb ages have been determined for zircons separated from rhyolitic obsidian from the Tardree (Sandy Braes) Rhyolite Centre and granites of the Mourne Mountains and Slieve Gullion central igneous complexes of the British Tertiary Volcanic Province. These ages (Tardree, 58.4 ±0.7 Ma; Mourne, 56.4 ±1.4 Ma and 55.3 ± 0.8 Ma and Slieve Gullion, 56.5 ±1.3 Ma) are in close agreement (within error) with results from independent dating methods (Rb-Sr, K-Ar and
40
Ar/
39
Ar) and are interpreted as crystallization ages. The euhedral, clear, bipyramidal nature of all separated zircons is indicative of a magmatic origin and, combined with the paucity of zircon grains with any history of inheritance, has implications for granite petrogenesis. When considered with recently published high-precision
40
Ar/
39
Ar ages for sanidine separates from the Hebrides, these data help to establish a timeframe for Tertiary magmatism in the NW British sector of the North Atlantic Tertiary Volcanic Province and show that central complex magmatism in NE Ireland was confined to the later stages of activity.
Eocene inversion history of the Sandown Pericline, Isle of Wight, southern England
Authors: GALE A. S. , JEFFERY P. A. , HUGGETT J. M. , CONNOLLY P.
Published: December 2007

Study of the composition and distribution of derived lithoclast and fossil suites collected from the Selsey, Barton and Becton Formations in Whitecliff Bay, Isle of Wight has enabled a detailed reconstruction of Mid-Late Eocene uplift of 500 m + on the northern limb of the Sandown Pericline. The stratigraphical distribution of clasts and fossils derived from older formations demonstrates the erosion of progressively older Eocene, Palaeocene and Cretaceous sediments during growth of the structure. The presence of delicate reworked fossils and clasts, together with limited palaeocurrent data support very local derivation from the south. The preservational state of the derived materials is used to identify the diverse processes of erosion and transport. Two phases of uplift (Lutetian, Bartonian), separated by a period of quiescence and peneplanation have been identified; rates of Eocene uplift of about 100 m Ma –
1
are postulated to have taken place.
A mutual climatic range method for reconstructing palaeoclimate from plant remains
Authors: SINKA K. J. , ATKINSON T. C.
Published: December 2007

The mutual climatic range (MCR) technique for reconstructing palaeoclimate relies on establishing the present-day climatic tolerance ranges of living species which are also found as fossils in Quaternary deposits. The palaeoclimate under which the species in a fossil assemblage co-existed can be inferred to lie within the intersection of the individual species' tolerance ranges. This paper describes a factor analysis of modern European climate data to determine two compound variables that describe the main features of the climate: 'summer warmth and dryness' and 'wetness and winter warmth'. Distribution maps of 80 plants from
Atlas Florae Europaeae
were combined with the climate data to determine each species' climatic range in factor space. MCRs were determined for two living plant assemblages from southeast England and found to give a reliable, although rather imprecise, reconstruction of the true thermal and precipitation climate. Reconstructions for two plant macro-fossil assemblages from Devensian gravels at Earith, Cambridgeshire, demonstrated palaeoclimates that were colder and more continental than the present, but with similar total amounts of precipitation. The study demonstrates the potential of the MCR method for use with Quaternary macrofossil plant remains, although there are methodological drawbacks in employing a climate-space defined by factor analysis.
Climate variations in Britain during the Last Glacial–Holocene transition (15.0–11.5 cal ka
bp
): comparison with the GRIP ice-core record
Authors: MAYLE F. E. , BELL M. , BIRKS HILARY H. , BROOKS S. J. , COOPE G. R. , LOWE J. J. , SHELDRICK C. , SHIJIE Li , TURNEY C. S. M. , WALKER M. J. C.
Published: December 2007

Stratigraphic records from four sequences in Britain that span the Last Glacial-Holocene transition
(c.
15.0–11.5 cal ka
bp)
are summarized and compared using a calibrated timescale. Palaeoclimatic changes are defined using temperature estimates based on coleopteran data at two of the sites, and chironomid assemblages at the other sites. An attempt is made to distingish between the timing of (a) climate shifts and (b) ecosystem responses at all four sites. The British data are compared with the
GRIP
ice-core record, recently advocated by Björck
et al.
as the type-sequence for the Last Termination in the North Atlantic region. There is a degree of compatibility between the British and
GRIP
palaeoclimatic records. The clearest climatic signals in the British lake records are (a) a period of warm conditions (a thermal maximum) between 15.0 and 14.5 cal ka BP, which equates approximately with GRIP zone GI-le; (b) the onset of climatic cooling, which appears to have commenced
during
GRIP
zone GI-le, at
c.
14.5 cal ka
bp
; (c) a period of marked climatic instability from 14.4 to 12.7 cal ka BP, the regional effects of which are difficult to resolve using the evidence presently available; (d) further climatic cooling, which commenced at around 13.0 cal ka
bp
, after which the lake biota, catchment soils and vegetation cover, at least in some parts of Britain, did not recover until the onset of the Holocene; (e) continued climatic cooling, with the most severe impact on lake ecosystems occurring during the period
c.
12.6 to 11.5 cal ka
bp
.
The last climatic cycle at Kopais, central Greece
Authors: TZEDAKIS P. C.
Published: December 2007

Thick lacustrine sequences from southern Europe provide an opportunity to derive continuous records where the chronostratigraphical position of pre-Holocene stages can be determined with increased confidence. Here, high-resolution sediment and pollen analytical results from a 60 m core recovered from the Kopais basin, central Greece, spanning the interval from the last interglacial to the early Holocene are presented. The record shows distinct shifts between open vegetation periods of increased erosion with sediment inwashing and forest periods associated with calcite precipitation in the lake. The sequence of major events of the last climatic cycle contained at Kopais bears strong similarities to other records in Greece, but also reveals the presence of high-frequency oscillations with higher amplitudes than previously seen at other sites.