bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid-Structure Interaction Modeling of Spacecraft Parachutes for Simulation-Based Design
Authors: Takizawa Kenji , Spielman Timothy , Moorman Creighton , Tezduyar Tayfun E.
Published: December 2011

Even though computer modeling of spacecraft parachutes involves a number of numerical challenges, advanced techniques developed in recent years for fluid-structure interaction (FSI) modeling in general and for parachute FSI modeling specifically have made simulation-based design studies possible. In this paper we focus on such studies for a single main parachute to be used with the Orion spacecraft. Although these large parachutes are typically used in clusters of two or three parachutes, studies for a single parachute can still provide valuable information for performance analysis and design and can be rather extensive. The major challenges in computer modeling of a single spacecraft parachute are the FSI between the air and the parachute canopy and the geometric complexities created by the construction of the parachute from “rings” and “sails” with hundreds of gaps and slits. The Team for Advanced Flow Simulation and Modeling has successfully addressed the computational challenges related to the FSI and geometric complexities, and has also been devising special procedures as needed for specific design parameter studies. In this paper we present parametric studies based on the suspension line length, canopy loading, and the length of the overinflation control line.
Space-Time Computational Techniques for the Aerodynamics of Flapping Wings
Authors: Takizawa Kenji , Henicke Bradley , Puntel Anthony , Spielman Timothy , Tezduyar Tayfun E.
Published: December 2011

We present the special space-time computational techniques we have introduced recently for computation of flow problems with moving and deforming solid surfaces. The techniques have been designed in the context of the deforming-spatial-domain/stabilized space-time formulation, which was developed by the Team for Advanced Flow Simulation and Modeling for computation of flow problems with moving boundaries and interfaces. The special space-time techniques are based on using, in the space-time flow computations, non-uniform rational B-splines (NURBS) basis functions for the temporal representation of the motion and deformation of the solid surfaces and also for the motion and deformation of the volume meshes computed. This provides a better temporal representation of the solid surfaces and a more effective way of handling the volume-mesh motion. We apply these techniques to computation of the aerodynamics of flapping wings, specifically locust wings, where the prescribed motion and deformation of the wings are based on digital data extracted from the videos of the locust in a wind tunnel. We report results from the preliminary computations.
Flow Modes and Mode Transitions for Falling Films on Flat Tubes
Authors: Wang Xiaofei , Hrnjak P. S. , Elbel S. , Jacobi A. M. , He Maogang
Published: December 2011

Flow mode transitions for a liquid film falling over flat tubes are studied for a wide range of conditions. Hydraulic oil, ethylene glycol, ethylene-glycol-water mixtures (at three different volume ratios), and water are used as working fluids in experiments conducted under adiabatic conditions, without an imposed vapor flow. The flow modes are observed over a range of flow rate and tube spacing. The flow modes are more complex but similar to those manifested on round tubes, and include the sheet, sheet-jet, jet, jet-droplet, and droplet modes. However, the transitions at Ga1/4 ≤ 16 (mainly for hydraulic oil, ethylene glycol) are very different from those on round tubes: there is no sheet-jet mode during transition between the sheet and jet flow modes. Moreover, at all Ga, the Re range over which the jet mode occurs is narrower than that for round tubes, and the hysteresis in mode transitions is not as pronounced as for round tubes. The transitional Re increases slowly with tube spacing, also in contrast to observations of round-tube falling films. The flat-tube falling-film flow regimes are described, and new correlations are provided to relate the transitional Re number to Ga and geometry. By analyzing repeated experiments, it is shown that the standard deviation of the measurements from the correlations is less than 5.2%.
Investigations of Biporous Wick Structure Dryout
Authors: Cai Qingjun , Chen Ya-Chi
Published: December 2011

Dryout in a heat pipe evaporator is caused by insufficient condensate supply through the wick structure. Dryout is generally considered a failure of the heat pipe operation. However, traditional dryout theory may not fully explain the heat and mass transport limitations in the biporous (biwick) wick structure due to new mass transfer mechanisms, such as liquid splash at high heat flux, and vapor bubble/jet occupation of liquid transport passages. This article investigates the dryout phenomenon in carbon nanotube (CNT) based biwick structure. The incipience and expansion of the dryout zone on the CNT biwick structure are visualized. Variation of the evaporator temperatures at various heat fluxes is measured to characterize the temperature responses on the biwick dryout. Results based on both visualization and measurement show that dryout of CNT biwick structures is affected by vapor flow induced droplet splash and vapor occupation of liquid transport passages, which reduces the liquid supply to the hottest region and creates a local dry zone. On the curves of heat flux versus the evaporator temperature, dryout can be defined as the appearance of the inflexion point during the heating period, and associated with the existence of a large temperature hysteresis in a heating and cooling cycle. Experimental measurement also shows that over 12% of the liquid by volume is lost without being phase changed, due to high-speed vapor flow induced liquid splash. Liquid splash and interactions between vapor and liquid flows also increase the pressure drop weight in the evaporator over the system loop and result in more notable heating area effect on biwick structures when compared with traditional monowick structures.
Flux Evaluation in Primal and Dual Boundary-Coupled Problems
Authors: van Brummelen E. H. , van der Zee K. G. , Garg V. V. , Prudhomme S.
Published: December 2011

A crucial aspect in boundary-coupled problems, such as fluid-structure interaction, pertains to the evaluation of fluxes. In boundary-coupled problems, the flux evaluation appears implicitly in the formulation and consequently, improper flux evaluation can lead to instability. Finite-element approximations of primal and dual problems corresponding to improper formulations can therefore be nonconvergent or display suboptimal convergence rates. In this paper, we consider the main aspects of flux evaluation in finite-element approximations of boundary-coupled problems. Based on a model problem, we consider various formulations and illustrate the implications for corresponding primal and dual problems. In addition, we discuss the extension to free-boundary problems, fluid-structure interaction, and electro-osmosis applications.
Liquid Sloshing Damping in an Elastic Container
Authors: Miras Thomas , Schotté Jean-Sébastien , Ohayon Roger
Published: December 2011

It is proposed to investigate in this paper the damped vibrations of an incompressible liquid contained in a deformable tank. A linearized formulation describing the small movements of the system is presented. At first, a diagonal damping is introduced in the reduced equations of the hydroelastic sloshing problem. We obtain a nonclassically damped coupled system with a damping matrix that is not symmetric. Then, by projecting the system onto its complex modes, the frequency and time responses for different type of loads are built. A numerical application is illustrated on a test case.
Physical properties of individual anatase TiO2 nanowires investigated by field emission in a transmission electron microscope
Authors: Shen Jun , Vincent Pascal , Blanchard Nicholas P. , Nicolle Jimmy , Choueib May , Purcell Stephen T. , Poncharal Philippe , Salles Vincent , Brioude Arnaud
Published: December 2011

The authors present studies on the field emission (FE) mechanism and the FE-induced transformation of individual anatase TiO2 nanowires (NWs). The NWs were synthesized by electrospinning followed by calcination at 500 °C which produces polycrystalline anatase nanofibers as determined by Raman spectroscopy and transmission electron microscopy (TEM) characterization. Nanowires of ∼100 nm in diameter were individually mounted at the apexes of tungsten tips for further physical characterization. The FE experiments were carried out in a TEM which allows the measurement of the FE current while simultaneously observing structural modifications leading to the NW’s destruction. For low currents (below 100 nA), we observe reproducible FE Fowler-Nordheim I/V characteristics. Higher currents (up to 1 μA) can be obtained but sudden destruction of the NW may take place. Our observations show that a thermally-activated transition occurs and leads to rapid re-crystallization phenomena and a variation of the FE characteristics. If not controlled, this transition leads to thermal runaway and sample destruction. The understanding of the destruction phenomena is a key parameter to further improve the FE performance of such nanowire cathodes.
Modifying optical properties of GaN nanowires by Ga2O3 overgrowth
Authors: Lee Yi-Kuang , Medina Henry , Chiu Po-Wen
Published: December 2011

The authors report on the modification of optical properties of GaN nanowires by growing a thin Ga2O3 overlayer on GaN surface, forming a core/shell heterostructure. The GaN/Ga2O3 core/shell nanowires were formed first by the axial growth of GaN nanowires, followed by the radical growth of the Ga2O3 overlayer. The GaN core possesses single crystalline wurtzite structure, whereas the Ga2O3 shell layer is monoclinic polycrystalline. For the GaN/Ga2O3 core/shell nanowires, a pronounced blueshift of the Raman A1(LO) mode was found, indicating a compressive stress on the core wire due to the lattice mismatch with the outer shell. This picture is also supported by the photoluminescence spectrum, in which the peak shifts to higher energy after the overgrowth of Ga2O3 on GaN.
Toward an objective measure for a “stream segregation” task
Authors: Richards Virginia M. , Carreira Eva Maria , Shen Yi
Published: December 2011

A procedure to estimate the relative contribution of “A” and “B” tones for a stream-segregation task is described. Listeners detected a delay in the penultimate A tone in an A-B-A-B sequence of tones. For small A-B frequency separations, for most listeners, classification models based on both the A and B tones were superior to models based on just the A tones. For large frequency separations, models based on just the A tones were superior, indicating the A and B tones were segregated. The results also revealed individual differences in the strategies adopted to complete the task.
Do male northern elephant seals recognize individuals or merely relative dominance rank?
Authors: Insley Stephen J. , Holt Marla M.
Published: December 2011

Vocal recognition was tested in a socially dynamic context where many individuals interact: the female defense polygyny practiced by male northern elephant seals. The goal was to tease apart whether animals recognize other individuals or instead use a simple rule-based category (i.e., relative dominance rank). A total of 67 playback experiments conducted with 18 males at Año Nuevo State Reserve, California, tested three aspects of recognition: (1) recognition of relative rank; (2) whether such recognition was continuous or categorical; and (3) recognition of familiarity. Results indicate that males recognize familiar individuals although responses are primarily based on relative dominance rank.
A Method to Separate Nuclear, Cytosolic, and Membrane-Associated Signaling Molecules in Cultured Cells
Authors: Liu Xiaoyong , Fagotto François
Published: December 2011

A semipermeabilization step and a specific Percoll gradient composition enable effective cellular fractionation.
How Aldosterone Can Break Your Heart
Authors: Adler Elizabeth M.
Published: December 2011

Aldosterone promotes postinfarction cardiac rupture through the oxidation of the kinase CaMKII.
Preventing Necrosis by Cleaving a Deubiquitinase
Authors: Wong Wei
Published: December 2011

Cleavage of the deubiquitinase CYLD by caspase 8 prevents necrosis in response to the cytokine TNF.
Better Is Not Always Best
Authors: Ray L. Bryan
Published: December 2011

Low-affinity nutrient transporters sense depletion earlier than high-affinity transporters, thus preparing cells for starvation.
Plant Defenses
Authors: Hines Pamela J.
Published: December 2011

Coordination of different defense pathways across cell compartments produces a fully effective innate immune response.
Phosphatases Fight over fMLF
Authors: Foley John F.
Published: December 2011

Receptor-like tyrosine phosphatases have opposing roles in regulating chemoattractant receptor signaling in mouse neutrophils.
Pharmacodynamic Analysis of a Serine Protease Inhibitor, MK-4519, against Hepatitis C Virus Using a NovelIn VitroPharmacodynamic System
Authors: Brown Ashley N. , McSharry James J. , Adams Jonathan R. , Kulawy Robert , Barnard Richard J. O. , Newhard W. , Corbin A. , Hazuda Daria J. , Louie Arnold , Drusano George L.
Published: December 2011

The development of new antiviral compounds active against hepatitis C virus (HCV) has surged in recent years. In order for these new compounds to be efficacious in humans, optimal dosage regimens for each compound must be elucidated. We have developed a novelin vitropharmacokinetic/pharmacodynamic system, the BelloCell system, to identify optimal dosage regimens for anti-HCV compounds. In these experiments, genotype 1b HCV replicon-bearing cells (2209-23 cells) were inoculated onto carrier flakes in BelloCell bottles and treated with MK-4519, a serine protease inhibitor. Our dose-ranging studies illustrated that MK-4519 inhibited replicon replication in a dose-dependent manner, yielding a 50% effective concentration (EC50) of 1.8 nM. Dose-fractionation studies showed that shorter dosing intervals resulted in greater replicon suppression, indicating that the time that the concentration is greater than the EC50is the pharmacodynamic parameter for MK-4519 linked with inhibition of replicon replication. Mutations associated with resistance to serine protease inhibitors were detected in replicons harvested from all treatment arms. These data suggest that MK-4519 is highly active against genotype 1b HCV, but monotherapy is not sufficient to prevent the amplification of resistant replicons. In summary, our findings show that the BelloCell system is a useful and clinically relevant tool for predicting optimal dosage regimens for anti-HCV compounds.
Identification, Characterization, and Recombinant Expression of Epidermicin NI01, a Novel Unmodified Bacteriocin Produced by Staphylococcus epidermidis That Displays Potent Activity against Staphylococci
Authors: Sandiford Stephanie , Upton Mathew
Published: December 2011

We describe the discovery, purification, characterization, and expression of an antimicrobial peptide, epidermicin NI01, which is an unmodified bacteriocin produced by
Staphylococcus epidermidis
strain 224. It is a highly cationic, hydrophobic, plasmid-encoded peptide that exhibits potent antimicrobial activity toward a wide range of pathogenic Gram-positive bacteria including methicillin-resistant
Staphylococcus aureus
(MRSA), enterococci, and biofilm-forming
S. epidermidis
strains. Purification of the peptide was achieved using a combination of hydrophobic interaction, cation exchange, and high-performance liquid chromatography (HPLC). Matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) analysis yielded a molecular mass of 6,074 Da, and partial sequence data of the peptide were elucidated using a combination of tandem mass spectrometry (MS/MS) and
de novo
sequencing. The draft genome sequence of the producing strain was obtained using 454 pyrosequencing technology, thus enabling the identification of the structural gene using the
de novo
peptide sequence data previously obtained. Epidermicin NI01 contains 51 residues with four tryptophan and nine lysine residues, and the sequence showed approximately 50% identity to peptides lacticin Z, lacticin Q, and aureocin A53, all of which belong to a new family of unmodified type II-like bacteriocins. The peptide is active in the nanomolar range against
S. epidermidis
, MRSA isolates, and vancomycin-resistant enterococci. Other unique features displayed by epidermicin include a high degree of protease stability and the ability to retain antimicrobial activity over a pH range of 2 to 10, and exposure to the peptide does not result in development of resistance in susceptible isolates. In this study we also show the structural gene alone can be cloned into
Escherichia coli
strain BL21(DE3), and expression yields active peptide.
Identification of a Cryptococcus neoformans Cytochrome P450 Lanosterol 14α-Demethylase (Erg11) Residue Critical for Differential Susceptibility between Fluconazole/Voriconazole and Itraconazole/Posaconazole
Authors: Sionov Edward , Chang Yun C. , Garraffo H. Martin , Dolan Michael A. , Ghannoum Mahmoud A. , Kwon-Chung Kyung J.
Published: December 2011

Cryptococcus neoformans
strains resistant to azoles due to mutations causing alterations in the
ERG11
gene, encoding lanosterol 14α-demethylase, have rarely been reported. In this study, we have characterized a
C. neoformans
serotype A strain that is resistant to high concentrations of fluconazole (FLC). This strain, which was isolated from an FLC-treated patient, contained five missense mutations in the
ERG11
gene compared to the sequence of reference strain H99. Molecular manipulations of the
ERG11
gene coupled with susceptibility to triazole revealed that a single missense mutation resulting in the replacement of tyrosine by phenylalanine at amino acid 145 was sufficient to cause the high FLC resistance of the strain. Importantly, this newly identified point mutation in the
ERG11
gene of
C. neoformans
afforded resistance to voriconazole (VRC) but increased susceptibility to itraconazole (ITC) and posaconazole (PSC), which are structurally similar to each other but distinct from FLC/VRC. The
in vitro
susceptibility/resistance of the strains with or without the missense mutation was reflected in the therapeutic efficacy of FLC versus ITC in the animals infected with the strains. This study shows the importance of the Y145F alteration of Erg11 in
C. neoformans
for manifestation of differential susceptibility toward different triazoles. It underscores the necessity of
in vitro
susceptibility testing for each FLC-resistant
C. neoformans
clinical isolate against different groups of azoles in order to assist patient management.
Ethambutol Pharmacokinetic Variability Is Linked to Body Mass in Overweight, Obese, and Extremely Obese People
Authors: Hall Ronald G. , Swancutt Mark A. , Meek Claudia , Leff Richard D. , Gumbo Tawanda
Published: December 2011

We conducted a prospective study of 18 adult volunteers (male-to-female ratio of 1) whose body mass index fell into categories of <25, 25 to 40, or >40 kg/m
2
, who received a single oral dose of 1,600 mg ethambutol. Only individuals with normal renal function were recruited. The minimum body mass (M) was 45.6 kg, the median was 90.8 kg, and the maximum weight was 160.4 kg. Ethambutol pharmacokinetics were best described by a two-compartment model. Inclusion of weight as a covariate dramatically improved the model, with a relative likelihood approaching infinity. The typical clearance was 42.6 liters/h. Ethambutol systemic clearance was proportional to (M/45.6)
3/4
and thus obeyed fractal geometry-based laws. This means that the area under the concentration-time curve (AUC) actually decreased for obese patients compared to that for leaner patients, reducing chances of concentration-dependent toxicity. On the other hand, such reduced AUCs could lead to therapy failure. Thus, new and individualized ethambutol dosing regimens need to be designed for obese and extremely obese patients.
Mechanism of Interaction of Human Mitochondrial DNA Polymerase γ with the Novel Nucleoside Reverse Transcriptase Inhibitor 4′-Ethynyl-2-Fluoro-2′-Deoxyadenosine Indicates a Low Potential for Host Toxicity
Authors: Sohl Christal D. , Singh Kamlendra , Kasiviswanathan Rajesh , Copeland William C. , Mitsuya Hiroaki , Sarafianos Stefan G. , Anderson Karen S.
Published: December 2011

The potent antiretroviral 4′-ethynyl-2-fluoro-2′-deoxyadenosine (EFdA) is a promising experimental agent for treating HIV infection. Pre-steady-state kinetics were used to characterize the interaction of EFdA-triphosphate (EFdA-TP) with human mitochondrial DNA polymerase γ (Pol γ) to assess the potential for toxicity. Pol γ incorporated EFdA-TP 4,300-fold less efficiently than dATP, with an excision rate similar to ddATP. This strongly indicates EFdA is a poor Pol γ substrate, suggesting minimal Pol γ-mediated toxicity, although this should be examined under clinical settings.
Agreement Assessment of Tigecycline Susceptibilities Determined by the Disk Diffusion and Broth Microdilution Methods among Commonly Encountered Resistant Bacterial Isolates: Results from the TigecyclineIn VitroSurveillance in Taiwan (TIST) Study, 2008 to 2010
Authors: Liu Jien-Wei , Ko Wen-Chien , Huang Cheng-Hua , Liao Chun-Hsing , Lu Chin-Te , Chuang Yin-Ching , Tsao Shih-Ming , Chen Yao-Shen , Liu Yung-Ching , Chen Wei-Yu , Jang Tsrang-Neng , Lin Hsiu-Chen , Chen Chih-Ming , Shi Zhi-Yuan , Pan Sung-Ching , Yang Jia-Ling , Kung Hsiang-Chi , Liu Chun-Eng , Cheng Yu-Jen , Chen Yen-Hsu , Lu Po-Liang , Sun Wu , Wang Lih-Shinn , Yu Kwok-Woon , Chiang Ping-Cherng , Lee Ming-Hsun , Lee Chun-Ming , Hsu Gwo-Jong , Hsueh Po-Ren
Published: December 2011

The TigecyclineIn VitroSurveillance in Taiwan (TIST) study, initiated in 2006, is a nationwide surveillance program designed to longitudinally monitor thein vitroactivity of tigecycline against commonly encountered drug-resistant bacteria. This study compared thein vitroactivity of tigecycline against 3,014 isolates of clinically important drug-resistant bacteria using the standard broth microdilution and disk diffusion methods. Species studied included methicillin-resistantStaphylococcus aureus(MRSA;n= 759), vancomycin-resistantEnterococcus faecium(VRE;n= 191), extended-spectrum β-lactamase (ESBL)-producingEscherichia coli(n= 602), ESBL-producingKlebsiella pneumoniae(n= 736), andAcinetobacter baumannii(n= 726) that had been collected from patients treated between 2008 and 2010 at 20 hospitals in Taiwan. MICs and inhibition zone diameters were interpreted according to the currently recommended U.S. Food and Drug Administration (FDA) criteria and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. The MIC90values of tigecycline against MRSA, VRE, ESBL-producingE. coli, ESBL-producingK. pneumoniae, andA. baumanniiwere 0.5, 0.125, 0.5, 2, and 8 μg/ml, respectively. The total error rates between the two methods using the FDA criteria were high: 38.4% for ESBL-producingK. pneumoniaeand 33.8% forA. baumannii. Using the EUCAST criteria, the total error rate was also high (54.6%) forA. baumanniiisolates. The total error rates between these two methods were <5% for MRSA, VRE, and ESBL-producingE. coli. For routine susceptibility testing of ESBL-producingK. pneumoniaeandA. baumanniiagainst tigecycline, the broth microdilution method should be used because of the poor correlation of results between these two methods.
Oseltamivir Inhibits H7 Influenza Virus Replication in Mice Inoculated by the Ocular Route
Authors: Belser Jessica A. , Sleeman Katrina , Pearce Melissa B. , Katz Jacqueline M. , Gubareva Larisa V. , Tumpey Terrence M.
Published: December 2011

The majority of human infections associated with H7 influenza viruses have resulted in ocular and not respiratory disease. While oseltamivir has been prescribed to individuals presenting with conjunctivitis following H7 virus exposure, it is unknown if oseltamivir inhibits virus replication in ocular tissue. We demonstrate that H7 viruses possess sensitivity to neuraminidase inhibitors and that administration of oseltamivir before ocular virus challenge in mice inhibits H7N7 and H7N3 virus replication in ocular and respiratory tissues.
Identification of Antigen-Specific Antibody Responses Associated with Upper Genital Tract Pathology in Mice Infected with Chlamydia muridarum
Authors: Zeng Hao , Gong Siqi , Hou Shuping , Zou Quanming , Zhong Guangming
Published: December 2011

Urogenital infection withChlamydia trachomatisin some women can lead to upper genital tract pathologies, such as hydrosalpinx, potentially affecting fertility. In the current study, 27 of 40 mice intravaginally infected withChlamydia muridarumdeveloped visible hydrosalpinges in the oviduct while the remaining 13 did not, although all infected mice displayed similar infection time courses. Antisera from the 40 mice recognized 130 out of 257C. muridarumproteins as antigens and 17 as immunodominant antigens. Importantly, the 27 mice with hydrosalpinges preferentially recognized twoC. muridarumproteins (TC0582 and TC0912, designated pathology-associated antigens) while the 13 mice with no hydrosalpinx preferentially recognized 10 proteins (TC0047, TC0117, TC0190, TC0197, TC0257, TC0279, TC0326, TC0630, TC0689, and TC0816, designated nonpathology antigens). The preferential recognition was validated by absorption and independently confirmed in Western blots. TheC. trachomatishomolog of TC0912 is encoded by a highly polymorphic gene that is associated with ocular pathogenesis. A fragment of TC0912 was found to improve the differentiation of hydrosalpinx from nonhydrosalpinx mice. TC0582 is a highly conserved ATP synthase, and it may contribute to chlamydial pathogenesis via mechanisms similar to those hypothesized for the highly conserved HSP60. Thus, we have identified chlamydial antigens and epitopes that are associated with either susceptibility or resistance to upper genital tract pathology, which will help us to further understand chlamydial pathogenesis and to develop anti-Chlamydiasubunit vaccines.
Unidentified Chronic Fatigue Syndrome/myalgic encephalomyelitis (CFS/ME) is a major cause of school absence: surveillance outcomes from school-based clinics
Authors: Crawley Esther M , Emond Alan M , Sterne Jonathan A C
Published: December 2011

Objective

To investigate the feasibility of conducting clinics for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) in schools.

Design

School-based clinical project.

Participants

Children aged 11–16 years were enrolled in three state secondary schools in England.

Main outcome measures

Number of children newly diagnosed as having CFS/ME.

Methods

Attendance officers identified children missing ≥20% of school in a 6-week term without a known cause, excluding those with a single episode off school, a known medical illness explaining the absence or known to be truanting. Children with fatigue were referred to a specialist CFS/ME service for further assessment. The authors compared children with CFS/ME identified through school-based clinics with those referred via health services. Outcomes of CFS/ME were evaluated at 6 weeks and 6 months.

Results

461 of the 2855 enrolled children had missed ≥20% school over a 6-week period. In 315, of whom three had CFS/ME, the reason for absence was known. 112 of the 146 children with unexplained absence attended clinical review at school; two had been previously diagnosed as having CFS/ME and 42 were referred on to a specialist clinic, where 23 were newly diagnosed as having CFS/ME. Therefore, 28 of the 2855 (1.0%) children had CFS/ME. Children with CFS/ME identified through surveillance had been ill for an amount of time comparable to those referred via health services but had less fatigue (mean difference 4.4, 95% CI 2.2 to 6.6), less disability (mean difference −5.7, 95% CI −7.9 to −3.5) and fewer symptoms (mean difference 1.86, 95% CI 0.8 to 2.93). Of 19 children followed up, six had fully recovered at 6 weeks and a further six at 6 months.

Conclusions

Chronic fatigue is an important cause of unexplained absence from school. Children diagnosed through school-based clinics are less severely affected than those referred to specialist services and appear to make rapid progress when they access treatment.
Transmission of HIV-1 drug resistance in Benin could jeopardise future treatment options
Authors: Chamberland Annie , Diabaté Souleymane , Sylla Mohamed , Anagounou Séverin , Geraldo Nassirou , Zannou Djimon Marcel , Labbé Annie-Claude , Worobey Michael , Alary Michel , Tremblay Cécile
Published: December 2011

Objectives

As access to antiretrovirals (ARV) increases in developing countries, the identification of optimal therapeutic regimens and prevention strategies requires the identification of resistance pathways in non-B subtypes as well as the surveillance of drug mutation resistance (SDMR) including the trafficking of viral strains between high-risk groups such as commercial sex workers (CSW) and the general population (GP). In this study, the authors evaluated the rate of primary resistance mutations and the epidemiological link between isolates from GP and CSW from Bénin.

Methods

Plasma samples were obtained from 129 HIV-1-infected treatment-naïve individuals. Drug resistance mutations were identified using SDMR list and compared with other resistance algorithms.

Results

No nucleoside reverse transcriptase inhibitor resistance mutations were found. Four patients had non-nucleoside reverse transcriptase inhibitor resistance (K103N, G190A). One patient exhibited protease inhibitors resistance mutation, F53Y. Using the SDMR list, the authors obtained a rate of 3.9% of primary resistance. Nevertheless, the authors observed several mutations not on SDMR list but included in others resistance database, taking those mutations into account, the authors obtained a rate of 15.5%.

Conclusions

Although our results show a low rate of SDMR, this algorithm may underestimate resistance mutations that may impact treatment options in developing countries. Primary resistance rates were similar in CSW and in the GP. Our phylogenetic analysis confirmed the genetic exchange between groups.
ON THE TRANSLATIONAL SYMMETRY OF INFINITE U HUBBARD MODEL
Authors: JAKUBCZYK D.
Published: December 2011

We investigate two commonly used methods of obtaining the solution of the one-dimensional Hubard model, in the regime of infinite intrasite Coulomb repulsion U, that is the nested Bethe ansatz and the Gutzwiller projection operator approach. These two formalisms give rise to different kinds of the wavefunctions, received via the additional operator and as a general feature, in Gutzwiller and Bethe methods, respectively. We consider the finite system consisting of three particles on a four site closed chain. We investigate the consequences of the dissimilarities in the translational symmetry of the representations of the Hamiltonian for these two approaches. We look for the proof of the decoupling of the spin and charge degrees of freedom, known in context of high-temperature superconductors, in this case.
DOMAINS OF SOLVATED IONS IN AQUEOUS SOLUTIONS, THEIR CHARACTERISTICS AND IMPACT ON ELECTRIC CONDUCTIVITY: THEORY AND EXPERIMENTAL EVIDENCE
Authors: YINNON TAMAR A. , YINNON CARMI A.
Published: December 2011

In this paper, we identify a yet unreported, quantum-electro-dynamic (QED) interactions induced, self-organization in aqueous solutions. We show that its characteristics conform to hitherto unexplained experimental findings, reported in the literature. Specifically, our analysis shows: (a) Solvated ions may organize into micrometer (μm) sized domains, wherein the plasma oscillations of identical ions are in-phase. (b) These liquid domains have a crystalline-like lattice structure. (c) For salt solutions, for concentrations C below a solute specific transition concentration C trans , the ions organize into the "in-phase" domains. For C larger than C trans , domains form wherein the plasma oscillations of the solvated ions are just coherent. Previous studies provided theoretical and experimental evidence for the "coherent" domains. However, they did not show that the "coherent" domains only exist for C > C trans . Typically, at room temperature and pressure, C trans is about 10-4 M or below. (d) At C trans , the molar electric conductivity sharply changes, i.e. for C < C trans , the slope of the molar electric conductivity dependence on concentration is several times larger than for C > C trans .
EXACT SOLVING q DEFORMED BOSON MODEL UNDER OPEN BOUNDARY CONDITION
Authors: LI BO , WANG YAN-SHEN
Published: December 2011

Utilizing the algebraic Bethe–Ansatz method, the Hamiltonian of q deformed boson model and its eigenvalue equation are calculated under the integrable open boundary condition. Rely on them, we give the exact energy spectrum and discuss two limit cases of the model.
COUPLING MULTIPHASE PORE-SCALE MODELS TO ACCOUNT FOR BOUNDARY CONDITIONS: APPLICATION TO 2D QUASI-STATIC PORE NETWORKS
Authors: PETERSEN ROBERT THOMAS , BALHOFF MATTHEW THOMAS , BRYANT STEVEN
Published: December 2011

Accurate predictions of macroscopic multiphase flow properties (relative permeability and capillary pressure) are necessary for modeling flow and transport in subsurface applications, such as hydrocarbon recovery, carbon sequestration and nuclear waste storage. These properties are usually measured experimentally, but pore-scale network modeling has become an efficient alternative for understanding fundamental flow behavior and predicting macroscopic properties. In many cases, network modeling gives excellent agreement with experiment by using models physically representative of real media. Void space within a rock sample can be extracted from high resolution images and converted to a topologically equivalent network of pores and throats. Multiphase fluid transport is then modeled in the network and macroscopic properties extracted from the model. Advancements continue to be made in making multiphase network models (both quasistatic and dynamic) predictive, but one limitation is that arbitrary (e.g., constant pressure) boundary conditions are usually assumed; they do not reflect the local saturations and pressure distributions that are affected by flow and transport in the surrounding media. In this work we demonstrate that transport behavior at the pore scale, and therefore, upscaled macroscopic properties are directly affected by the boundary conditions. Pore-scale drainage in 2D quasi-static networks is modeled by direct coupling to other pore-network models so that the boundary conditions reflect local variations of transport behavior in the surrounding media. Phase saturations are coupled at model boundaries to ensure continuity between adjacent models. Macroscopic petrophysical properties are shown to be largely dependent upon the surrounding media, which are manifested in the form of boundary conditions. The predictive ability of network simulations is thus improved using the novel network coupling scheme.
A MULTI-SCALE SEISMIC RESPONSE OF TWO-DIMENSIONAL SEDIMENTARY VALLEYS DUE TO THE COMBINED EFFECTS OF TOPOGRAPHY AND GEOLOGY
Authors: GATMIRI B. , LE PENSE S. , MAGHOUL P.
Published: December 2011

It is well known that the response of a site to seismic excitation depends on the local topographical and geological conditions. The current building codes already take into account unidimensional site effects but ignore complex site effects due to two-dimensional irregular configurations. The aim of this work is to contribute to the establishment of a simple predictive method to estimate site effects. The horizontal ground movements at the surface of sedimentary valleys subjected to SV waves with vertical incidence are calculated by using the HYBRID program, combining finite elements in the near field and boundary elements in the far field (FEM/BEM). A parametric study is conducted to examine the combined effects of topography and geology on the amplification of the response spectrum at various points across the valley. The influence of different parameters is considered, such as filling ratios (from empty to full valleys), impedance contrasts between bedrock and sediments, and dimensions.
Quantifying the deep-sea rock and fossil record bias using coccolithophores
Authors: Lloyd Graeme T. , Smith Andrew B. , Young Jeremy R.
Published: December 2011

While many studies show a correlation between observed taxonomic richness and various measures of geological sampling, all have been based on the same record of terrestrial and marine sediments collected from the land. Here we present the first analyses of how rock and fossil records vary in the deep-sea. We have developed a novel database of species occurrences of coccolithophores sampled during major drilling programs of the North Atlantic, including the Mediterranean and Caribbean. Our sampling proxy, the number of deep-sea sites sampled – perhaps the most direct measure of sampling used so far – shows an exponential rise towards the Recent. Over the same period species-richness has grown in an approximately linear fashion, but genus-level richness shows a sharp initial increase followed by a much slower decline. However, correlations between both richness measures and sampling are extremely strong and a model assuming true diversity to be constant accurately predicts much of observed richness. We conclude that the deep-sea fossil record, like its land-based counterpart, bears a rock record bias.
Skeletal mineralogy and biodiversity of marine invertebrates: size matters more than seawater chemistry
Authors: Cherns Lesley , Wright V. Paul
Published: December 2011

It is now well established that seawater chemistry, as well as influencing non-skeletal marine precipitation (‘calcite’ and ‘aragonite seas’), has affected skeletal mineral secretion in some algal and marine invertebrate groups. Skeletal mineralogy has had a yet more profound consequence on fossil preservation. The realization that the fossil record of marine organisms with an aragonite shell is widely depleted in some shelf settings through early, effectively syn-depositional, dissolution (‘missing molluscs’ effect) has led to a re-evaluation of the composition, diversity, ecological and trophic structure of marine benthic communities. Comparisons of molluscan lagerstätten from ‘calcite’ and ‘aragonite seas’ show a similar pattern of skeletal mineralogical loss, that is, no differences are discernibly linked to changed seawater geochemistry. It is notable that the rare mollusc-rich skeletal lagerstätten faunas in the fossil record include many small individuals. Micromolluscs are quantitatively important among modern shell assemblages, yet small size is a major source of taphonomic and biodiversity loss in the fossil record. In skeletal lagerstätten faunas, micromolluscs contribute variably to mollusc biodiversity but appear particularly significant through at least to Triassic times. They highlight a further ‘missing molluscs’ effect of taphonomic loss through early dissolution.
Variation in stratigraphic congruence (GER) through the Phanerozoic and across higher taxa is partially determined by sources of bias
Authors: O'Connor Anne , Moncrieff Clive , Wills Matthew A.
Published: December 2011

Many published cladograms report measures of stratigraphic congruence. Strong congruence between cladistic branching order and the order of first fossil occurrences is taken to support both the accuracy of cladograms and the fidelity of the record. Poor congruence may reflect inaccurate trees, a misleading fossil record, or both. However, it has been demonstrated that most congruence indices are logically or empirically biased by parameters that are not uniformly distributed across taxa or through time. These include tree size and balance, mean ghost range duration (gap size) and the range and distribution of origination dates. This study used 650 published cladograms to investigate the influence of these variables on the Gap Excess Ratio (GER). In a range of multivariate models, factors other than congruence
per se
explained up to 74.5% of the observed variance in GER amongst trees. Arthropods typically have poorer GER values than other groups, but the residual differences from our models are much less striking. The models also show no clear residual trend in GER through the Phanerozoic. Because the GER is strongly influenced by parameters related to cladogram size, balance and duration, comparisons across trees should be made with caution.

Supplementary material:

Data legends are available at
http://www.geolsoc.org.uk/SUP18484
Impact of outcrop area on estimates of Phanerozoic terrestrial biodiversity trends
Authors: Wall P. D. , Ivany L. C. , Wilkinson B. H.
Published: December 2011

Studies of biodiversity through time have primarily focused on the marine realm which is generally considered to have a more complete record than terrestrial environments. Recently, this assumption has been challenged, and it has been argued that the record of life on land is comparable or even more robust than that of the shallow oceans. Moreover, it has been claimed that terrestrial successions preserve an exponential rise in diversity, even when corrected for sampling biases such as changes in continental rock volume through time. We evaluate relations between terrestrial diversity and exposed areas of terrestrial sediments using our compiled data on areas of global continental outcrops and generic diversity from the Paleobiology Database. Terrestrial global generic diversity and terrestrial outcrop area are highly correlated following a linear relation. No significant correlation is observed between habitat area and either outcrop area or biodiversity, suggesting that the observed relation between diversity and outcrop area is not driven by a common cause, such as eustasy. We do find evidence for a small residual increase in diversity through time after removing the effect of outcrop area, but caution that this may be driven by an increased proportion of terrestrial fauna with high preservation potential.
Macrostratigraphy and macroevolution in marine environments: testing the common-cause hypothesis
Authors: Peters Shanan E. , Heim Noel A.
Published: December 2011

Quantitative patterns in the sedimentary rock record predict many different macroevolutionary patterns in the fossil record, but the reasons for this predictability remain uncertain. There are two competing, but non-mutually exclusive, hypotheses: (1) similarities reflect a sampling bias imposed by variable and incomplete sampling of fossils, and (2) similarities reflect environmental perturbations that influence both the patterns of sedimentation and macroevolution (i.e., common-cause). Macrostratigraphy, which is based on the quantitative analysis of hiatus-bound rock packages, permits variation in the rock record to be expressed in terms of rock quantity and, more importantly, spatiotemporal continuity. In combination with spatially-explicit fossil occurrence data in the Paleobiology Database, it is now possible to more rigorously test alternative hypotheses for similarities in the rock and fossil records and to start distinguishing between geologically-controlled sampling bias and the common-cause hypothesis. Here we summarize results from measuring the intersection of Macrostrat and the Paleobiology Database. Our results suggest that patterns in the fossil record are not dominated by large-scale stratigraphic biases. Instead, they suggest that linkages between multiple Earth systems are driving both spatiotemporal patterns of sedimentation and macroevolution.
The fossil record and spatial structuring of environments and biodiversity in the Cenozoic of New Zealand
Authors: Crampton James S. , Foote Michael , Cooper Roger A. , Beu Alan G. , Peters Shanan E.
Published: December 2011

There is increasing evidence to suggest that drivers of bias in the fossil record have also affected actual biodiversity history, so that controls of artefact and true pattern are confounded. Here we examine the role of spatial structuring of the environment as one component of this common cause hypothesis. Our results are based on sampling standardized analyses of the post-Middle Eocene record of shelf molluscs from New Zealand. We find that spatial structuring of the environment directly influenced the quality of the fossil record. Contrary to our expectations, however, we find no evidence to suggest that spatial structuring of the environment was a strong or direct driver of taxic rates, net diversity, or spatial structuring in mollusc faunas at the scale of analysis. Stage-to-stage variation in sampling standardized diversity over the past 40 Ma exhibits two superficially independent dynamics: (a) changes in net diversity were associated primarily with changes in origination rate; and (b) an unknown common cause related extinction rate to the quality of the fossil record and, indirectly, to spatial structuring of the environment. We suggest that tectonic drivers, manifest as second-order sequence stratigraphic cycles, are likely to have been a key element of this common cause.
Relativistic Causality and Clockless Circuits
Authors: Matherat Philippe , Jaekel Marc-Thierry
Published: December 2011

Time plays a crucial role in the performance of computing systems. The accurate modelling of logical devices, and of their physical implementations, requires an appropriate representation of time and of all properties that depend on this notion. The need for a proper model, particularly acute in the design of clockless delay-insensitive (DI) circuits, leads one to reconsider the classical descriptions of time and of the resulting order and causal relations satisfied by logical operations. This questioning meets the criticisms of classical spacetime formulated by Einstein when founding relativity theory and is answered by relativistic conceptions of time and causality. Applying this approach to clockless circuits and considering the trace formalism, we rewrite Udding’s rules, which characterize communications between DI components. We exhibit their intrinsic relation with relativistic causality. For that purpose, we introduce relativistic generalizations of traces, called R-traces, which provide a pertinent description of communications and compositions of DI components.
Distributed application configuration, management, and visualization with plush
Authors: Albrecht Jeannie , Tuttle Christopher , Braud Ryan , Dao Darren , Topilski Nikolay , Snoeren Alex C. , Vahdat Amin
Published: December 2011

Support for distributed application management in large-scale networked environments remains in its early stages. Although a number of solutions exist for subtasks of application deployment, monitoring, and maintenance in distributed environments, few tools provide a unified framework for application management. Many of the existing tools address the management needs of a single type of application or service that runs in a specific environment, and these tools are not adaptable enough to be used for other applications or platforms. To this end, we present the design and implementation of Plush, a fully configurable application management infrastructure designed to meet the general requirements of several different classes of distributed applications. Plush allows developers to specifically define the flow of control needed by their computations using application building blocks. Through an extensible resource management interface, Plush supports execution in a variety of environments, including both live deployment platforms and emulated clusters. Plush also uses relaxed synchronization primitives for improving fault tolerance and liveness in failure-prone environments. To gain an understanding of how Plush manages different classes of distributed applications, we take a closer look at specific applications and evaluate how Plush provides support for each.