bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion-limited hyperbranched polymers with substitution effect
Authors: Wang Long , He Xuehao , Chen Yu
Published: March 2011

Highly branched structure has the essential influence on macromolecular property and functionality in physics and chemistry. In this work, we proposed a diffusion-limited reaction model with the consideration of macromolecular unit relaxations and substitution effect of monomers to study the structure of hyperbranched polymers prepared by slow monomer addition to a core molecule. The exponential relationship (Rg ∼ Nλ) between the radius of gyration Rg and the degree of polymerization N, was systematically analyzed at various branching degrees. It is shown that the effective exponent λeff decreases at lower N and but increases toward that of diffusion-limited aggregation (DLA) clusters (λDLA = 0.4) with the degree of polymerization increasing. The substitution effect of monomers in reaction strongly influences the evolution pathway of λeff. With the static light scattering technique, the fractal property of internal chains was further calculated. A general law about the radial distribution of the units of diffusion-limited hyperbranched polymers was found that, at smaller reactivity ratio k12, the radial density of all monomer units DA declines from the center region to the peripheral layer revealing the dense core structure; however, at larger k12, the density distribution shows a loose–dense–loose structure. These structural characteristics are helpful to deeply understand the property of hyperbranched polymers.
Vertical subwavelength mode confinement in terahertz and mid-infrared quantum cascade lasers
Authors: Strupiechonski E. , Grassani D. , Fowler D. , Julien F. H. , Khanna S. P. , Li L. , Linfield E. H. , Davies A. G. , Krysa A. B. , Colombelli R.
Published: March 2011

We exploit the modal confinement properties of metal-metal ridge waveguides to investigate the effect of reducing the thickness of the active laser cores in both terahertz and mid-infrared quantum cascade lasers. Devices with active regions over 55 times thinner than the free-space emission wavelength are demonstrated. They show only a modest increase in threshold current density compared with conventional-thickness devices. The limited increase in threshold is possibly due to a parasitic current channel in addition to the radiative current channel. These structures could be useful for the development of ultra-low volume lasers.
False multiple exciton recombination and multiple exciton generation signals in semiconductor quantum dots arise from surface charge trapping
Authors: Tyagi Pooja , Kambhampati Patanjali
Published: March 2011

Multiple exciton recombination (MER) and multiple exciton generation (MEG) are two of the main processes for assessing the usefulness of quantum dots (QDs) in photovoltaic devices. Recent experiments, however, have shown that a firm understanding of both processes is far from well established. By performing surface-dependent measurements on colloidal CdSe QDs, we find that surface-induced charge trapping processes lead to false MER and MEG signals resulting in an inaccurate measurement of these processes. Our results show that surface-induced processes create a significant contribution to the observed discrepancies in both MER and MEG experiments. Spectral signatures in the transient absorption signals reveal the physical origin of these false signals.
Transverse instability and magnetic structures associated with electron phase space holes
Authors: Du Aimin , Wu Mingyu , Lu Quanming , Huang Can , Wang Shui
Published: March 2011

Electron phase space holes (electron holes) are found to be unstable to the transverse instability. Two-dimensional (2D) electromagnetic particle-in-cell simulations are performed to investigate the structures of the fluctuating magnetic field associated with electron holes. The combined actions between the transverse instability and the stabilization by the background magnetic field (B0=B0e⃗x) lead a one-dimensional electron hole into several 2D electron holes which are isolated in both the x and y directions. The electrons trapped in these 2D electron holes suffer the electric field drift vE=E×B0/B02 due to the existence of the perpendicular electric field Ey, which generates the current along the z direction. Then, the unipolar and bipolar structures are formed for the parallel cut of the fluctuating magnetic field along the x and y directions, respectively. At the same time, these 2D electron holes move along the x direction, and the unipolar structures are formed for the parallel cut of the fluctuating magnetic field along the z direction.
Lagrangian properties of turbulent diffusion with passive chemical reaction in the framework of the premixed combustion theory
Authors: Zimont V. L. , Pagnini G.
Published: March 2011

In this paper, we analyze two effects caused by the Lagrangian nature of turbulent transfer which are usually ignored in the theory of turbulent premixed combustion. These effects are (i) the nonequilibrium behavior of the turbulent diffusion coefficient, which is important for modeling the initial stage of combustion (for example, in the spark ignition engine), and (ii) the existence of a traveling front of turbulent diffusion with finite speed, which controls the velocity of the steady state flame in strong turbulence. However, in order to derive simple and exact results, the hydrodynamical and the combustion subproblems are stated to be independent by assuming a constant density so that a passive chemical reaction is actually considered. First, we derive a parabolic diffusion equation with both diffusion and chemical source terms expressed by Lagrangian characteristics of turbulence. We show that, in general, the diffusivity of product particles is not zero in the moment of their generation by chemical transformation and this result is important for combustion theories that relate the formation of the initial flame with the development of the diffusion coefficient. Afterward, a hyperbolic diffusion equation based on hydrodynamics is derived with turbulent diffusion front velocity Uf=⟨u′2⟩1/2, where ⟨u′2⟩1/2 is the root mean square of turbulent velocity fluctuations, and we analyze the relationships between Uf and the speed of the steady state premixed flame Utss. In particular, for the flamelet combustion mechanism, we obtain Utss=(Uf2+SL2)1/2, where SL is the normal laminar flame speed. This result shows that, in moderate turbulence (⟨u′2⟩1/2∼SL), the usually assumed relation Utss=Uf+SL is not consistent with an accurate statistical analysis and more when Uf≃SL gives a percent error around 40%, which cannot be neglected in applications. In strong turbulence case (⟨u′2⟩1/2⪢SL), the value of the flame speed is very close to that of the diffusion front velocity.
Doomsday Fieldwork, or, How to Rescue Gaelic Culture? The Salvage Paradigm in Geography, Archaeology, and Folklore, 1955 – 62
Authors: MacDonald Fraser
Published: March 2011

Amid a resurgence of interest in histories of scientific fieldwork and in the geographies of the Cold War, this paper presents a comparative history of field practice across the distinct epistemic traditions of geography, archaeology, and folklore. The paper follows the intellectual practices of three research teams attempting to ‘rescue’ Gaelic culture from the development of a missile-testing station in the Scottish Hebrides. The aims of the paper are fivefold: to extend insights from the histories of scientific fieldwork to understand the production of social knowledge, to consider the coconstitution of fieldwork and the region, to expand recent histories of geography in the mid-20th century, to draw out the lingering significance of the ‘salvage paradigm’ in geography and other social sciences, and to reconceptualise this salvage fieldwork as a way of constructing social life as much as rescuing it.
Performing Elusive Mobilities: Ritualization, Play, and the Drama of Scheduled Departures
Authors: Vannini Phillip
Published: March 2011

Drawing upon three years of ethnographic fieldwork conducted in the ferry-dependent islands and remote coastal communities of British Columbia, this paper examines the process of catching a ferry in time for a scheduled sailing. Through performance, interactionist, and nonrepresentational theory, I argue that the weaving of a journey toward the ferry terminal can be a suspenseful drama, within which a scheduled departure works as a potential to be actualized through the performance of skillful acts of mobility. The affective, ritualistic, and playful components of passengers' journeys are examined through the lens of performance. Timing, spacing, and acting occasion differential ecologies of affect.
Engineering neuronal growth cones to promote axon regeneration over inhibitory molecules
Authors: Hur Eun-Mi , Yang In Hong , Kim Deok-Ho , Byun Justin , Saijilafu  , Xu Wen-Lin , Nicovich Philip R. , Cheong Raymond , Levchenko Andre , Thakor Nitish , Zhou Feng-Quan
Published: March 2011

Neurons in the central nervous system (CNS) fail to regenerate axons after injuries due to the diminished intrinsic axon growth capacity of mature neurons and the hostile extrinsic environment composed of a milieu of inhibitory factors. Recent studies revealed that targeting a particular group of extracellular inhibitory factors is insufficient to trigger long-distance axon regeneration. Instead of antagonizing the growing list of impediments, tackling a common target that mediates axon growth inhibition offers an alternative strategy to promote axon regeneration. Neuronal growth cone, the machinery that derives axon extension, is the final converging target of most, if not all, growth impediments in the CNS. In this study, we aim to promote axon growth by directly targeting the growth cone. Here we report that pharmacological inhibition or genetic silencing of nonmuscle myosin II (NMII) markedly accelerates axon growth over permissive and nonpermissive substrates, including major CNS inhibitors such as chondroitin sulfate proteoglycans and myelin-associated inhibitors. We find that NMII inhibition leads to the reorganization of both actin and microtubules (MTs) in the growth cone, resulting in MT reorganization that allows rapid axon extension over inhibitory substrates. In addition to enhancing axon extension, we show that local blockade of NMII activity in axons is sufficient to trigger axons to grow across the permissive–inhibitory border. Together, our study proposes NMII and growth cone cytoskeletal components as effective targets for promoting axon regeneration.
Molecular recognition and substrate mimicry drive the electron-transfer process between MIA40 and ALR
Authors: Banci Lucia , Bertini Ivano , Calderone Vito , Cefaro Chiara , Ciofi-Baffoni Simone , Gallo Angelo , Kallergi Emmanouela , Lionaki Eirini , Pozidis Charalambos , Tokatlidis Kostas
Published: March 2011

Oxidative protein folding in the mitochondrial intermembrane space requires the transfer of a disulfide bond from MIA40 to the substrate. During this process MIA40 is reduced and regenerated to a functional state through the interaction with the flavin-dependent sulfhydryl oxidase ALR. Here we present the mechanistic basis of ALR–MIA40 interaction at atomic resolution by biochemical and structural analyses of the mitochondrial ALR isoform and its covalent mixed disulfide intermediate with MIA40. This ALR isoform contains a folded FAD-binding domain at the C-terminus and an unstructured, flexible N-terminal domain, weakly and transiently interacting one with the other. A specific region of the N-terminal domain guides the interaction with the MIA40 substrate binding cleft (mimicking the interaction of the substrate itself), without being involved in the import of ALR. The hydrophobicity-driven binding of this region ensures precise protein–protein recognition needed for an efficient electron transfer process.
Scavenger receptor CD36 is essential for the cerebrovascular oxidative stress and neurovascular dysfunction induced by amyloid-β
Authors: Park Laibaik , Wang Gang , Zhou Ping , Zhou Joan , Pitstick Rose , Previti Mary Lou , Younkin Linda , Younkin Steven G. , Van Nostrand William E. , Cho Sunghee , Anrather Josef , Carlson George A. , Iadecola Costantino
Published: March 2011

Increasing evidence indicates that cerebrovascular dysfunction plays a pathogenic role in Alzheimer's dementia (AD). Amyloid-β (Aβ), a peptide central to the pathogenesis of AD, has profound vascular effects mediated, for the most part, by reactive oxygen species produced by the enzyme NADPH oxidase. The mechanisms linking Aβ to NADPH oxidase-dependent vascular oxidative stress have not been identified, however. We report that the scavenger receptor CD36, a membrane glycoprotein that binds Aβ, is essential for the vascular oxidative stress and neurovascular dysfunction induced by Aβ
1–40
. Thus, topical application of Aβ
1–40
onto the somatosensory cortex attenuates the increase in cerebral blood flow elicited by neural activity or by endothelium-dependent vasodilators in WT mice but not in CD36-null mice (CD36
0/0
). The cerebrovascular effects of infusion of Aβ
1–40
into cerebral arteries are not observed in mice pretreated with CD36 blocking antibodies or in CD36
0/0
mice. Furthermore, CD36 deficiency prevents the neurovascular dysfunction observed in transgenic mice overexpressing the Swedish mutation of the amyloid precursor protein Tg2576 despite elevated levels of brain Aβ
1–40
. CD36 is also required for the vascular oxidative stress induced by exogenous Aβ
1–40
or observed in Tg2576 mice. These observations establish CD36 as a key link between Aβ
1–40
and the NADPH oxidase-dependent vascular oxidative stress underlying the neurovascular dysfunction and suggest that CD36 is a potential therapeutical target to counteract the cerebrovascular dysfunction associated with Aβ.
Inflammation-dependent secretion and splicing of IL-32γ in rheumatoid arthritis
Authors: Heinhuis Bas , Koenders Marije I. , van de Loo Fons A. , Netea Mihai G. , van den Berg Wim B. , Joosten Leo A. B.
Published: March 2011

Different splice variants of the proinflammatory cytokine IL-32 are found in various tissues; their putative differences in biological function remain unknown. In the present study, we report that IL-32γ is the most active isoform of the cytokine. Splicing to one less active IL-32β appears to be a salvage mechanism to reduce inflammation. Adenoviral overexpression of IL-32γ (AdIL-32γ) resulted in exclusion of the IL-32γ–specific exon in vitro as well as in vivo, primarily leading to expression of IL-32β mRNA and protein. Splicing of the IL-32γ–specific exon was prevented by single-nucleotide mutation, which blocked recognition of the splice site by the spliceosome. Overexpression of splice-resistant IL-32γ in THP1 cells or rheumatoid arthritis (RA) synovial fibroblasts resulted in a greater induction of proinflammatory cytokines such as IL-1β, compared with IL-32β. Intraarticular introduction of IL-32γ in mice resulted in joint inflammation and induction of several mediators associated with joint destruction. In RA synovial fibroblasts, overexpression of primarily IL-32β showed minimal secretion and reduced cytokine production. In contrast, overexpression of splice-resistant IL-32γ in RA synovial fibroblasts exhibited marked secretion of IL-32γ. In RA, we observed increased IL-32γ expression compared with osteoarthritis synovial tissue. Furthermore, expression of TNFα and IL-6 correlated significantly with IL-32γ expression in RA, whereas this was not observed for IL-32β. These data reveal that naturally occurring IL-32γ can be spliced into IL-32β, which is a less potent proinflammatory mediator. Splicing of IL-32γ into IL-32β is a safety switch in controlling the effects of IL-32γ and thereby reduces chronic inflammation.
Prospective separation of normal and leukemic stem cells based on differential expression of TIM3, a human acute myeloid leukemia stem cell marker
Authors: Jan Max , Chao Mark P. , Cha Adriel C. , Alizadeh Ash A. , Gentles Andrew J. , Weissman Irving L. , Majeti Ravindra
Published: March 2011

Hematopoietic tissues in acute myeloid leukemia (AML) patients contain both leukemia stem cells (LSC) and residual normal hematopoietic stem cells (HSC). The ability to prospectively separate residual HSC from LSC would enable important scientific and clinical investigation including the possibility of purged autologous hematopoietic cell transplants. We report here the identification of TIM3 as an AML stem cell surface marker more highly expressed on multiple specimens of AML LSC than on normal bone marrow HSC.
TIM3
expression was detected in all cytogenetic subgroups of AML, but was significantly higher in AML-associated with core binding factor translocations or mutations in
CEBPA
. By assessing engraftment in NOD/SCID/IL2Rγ-null mice, we determined that HSC function resides predominantly in the TIM3-negative fraction of normal bone marrow, whereas LSC function from multiple AML specimens resides predominantly in the TIM3-positive compartment. Significantly, differential TIM3 expression enabled the prospective separation of HSC from LSC in the majority of AML specimens with detectable residual HSC function.
Evolution of introns in the archaeal world
Authors: Tocchini-Valentini Giuseppe D. , Fruscoloni Paolo , Tocchini-Valentini Glauco P.
Published: March 2011

The self-splicing group I introns are removed by an autocatalytic mechanism that involves a series of transesterification reactions. They require RNA binding proteins to act as chaperones to correctly fold the RNA into an active intermediate structure in vivo. Pre-tRNA introns in Bacteria and in higher eukaryote plastids are typical examples of self-splicing group I introns. By contrast, two striking features characterize RNA splicing in the archaeal world. First, self-splicing group I introns cannot be found, to this date, in that kingdom. Second, the RNA splicing scenario in Archaea is uniform: All introns, whether in pre-tRNA or elsewhere, are removed by tRNA splicing endonucleases. We suggest that in Archaea, the protein recruited for splicing is the preexisting tRNA splicing endonuclease and that this enzyme, together with the ligase, takes over the task of intron removal in a more efficient fashion than the ribozyme. The extinction of group I introns in Archaea would then be a consequence of recruitment of the tRNA splicing endonuclease. We deal here with comparative genome analysis, focusing specifically on the integration of introns into genes coding for 23S rRNA molecules, and how this newly acquired intron has to be removed to regenerate a functional RNA molecule. We show that all known oligomeric structures of the endonuclease can recognize and cleave a ribosomal intron, even when the endonuclease derives from a strain lacking rRNA introns. The persistance of group I introns in mitochondria and chloroplasts would be explained by the inaccessibility of these introns to the endonuclease.
Cryoelectron microscopy structures of the ribosome complex in intermediate states during tRNA translocation
Authors: Fu Jie , Munro James B. , Blanchard Scott C. , Frank Joachim
Published: March 2011

mRNA–tRNA translocation is a central and highly regulated process during translational elongation. Along with the mRNA, tRNA moves through the ribosome in a stepwise fashion. Using cryoelectron microscopy on ribosomes with a P-loop mutation, we have identified novel structural intermediates likely to exist transiently during translocation. Our observations suggest a mechanism by which the rate of translocation can be regulated.
Elephants know when they need a helping trunk in a cooperative task
Authors: Plotnik Joshua M. , Lair Richard , Suphachoksahakun Wirot , de Waal Frans B. M.
Published: March 2011

Elephants are widely assumed to be among the most cognitively advanced animals, even though systematic evidence is lacking. This void in knowledge is mainly due to the danger and difficulty of submitting the largest land animal to behavioral experiments. In an attempt to change this situation, a classical 1930s cooperation paradigm commonly tested on monkeys and apes was modified by using a procedure originally designed for chimpanzees (Pan troglodytes) to measure the reactions of Asian elephants (Elephas maximus). This paradigm explores the cognition underlying coordination toward a shared goal. What do animals know or learn about the benefits of cooperation? Can they learn critical elements of a partner's role in cooperation? Whereas observations in nature suggest such understanding in nonhuman primates, experimental results have been mixed, and little evidence exists with regards to nonprimates. Here, we show that elephants can learn to coordinate with a partner in a task requiring two individuals to simultaneously pull two ends of the same rope to obtain a reward. Not only did the elephants act together, they inhibited the pulling response for up to 45 s if the arrival of a partner was delayed. They also grasped that there was no point to pulling if the partner lacked access to the rope. Such results have been interpreted as demonstrating an understanding of cooperation. Through convergent evolution, elephants may have reached a cooperative skill level on a par with that of chimpanzees.
Mutator activity induced by microRNA-155 (
miR-155
) links inflammation and cancer
Authors: Tili Esmerina , Michaille Jean-Jacques , Wernicke Dorothee , Alder Hansjuerg , Costinean Stefan , Volinia Stefano , Croce Carlo M.
Published: March 2011

Infection-driven inflammation has been implicated in the pathogenesis of ~15–20% of human tumors. Expression of microRNA-155 (
miR-155
) is elevated during innate immune response and autoimmune disorders as well as in various malignancies. However, the molecular mechanisms providing
miR-155
with its oncogenic properties remain unclear. We examined the effects of
miR-155
overexpression and proinflammatory environment on the frequency of spontaneous hypoxanthine phosphoribosyltransferase (
HPRT
) mutations that can be detected based on the resistance to 6-thioguanine. Both
miR-155
overexpression and inflammatory environment increased the frequency of
HPRT
mutations and down-regulated WEE1 (WEE1 homolog-S. pombe), a kinase that blocks cell-cycle progression. The increased frequency of
HPRT
mutation was only modestly attributable to defects in mismatch repair machinery. This result suggests that
miR-155
enhances the mutation rate by simultaneously targeting different genes that suppress mutations and decreasing the efficiency of DNA safeguard mechanisms by targeting of cell-cycle regulators such as WEE1. By simultaneously targeting tumor suppressor genes and inducing a mutator phenotype,
miR-155
may allow the selection of gene alterations required for tumor development and progression. Hence, we anticipate that the development of drugs reducing endogenous
miR-155
levels might be key in the treatment of inflammation-related cancers.
TDRD5 is required for retrotransposon silencing, chromatoid body assembly, and spermiogenesis in mice
Authors: Yabuta Yukihiro , Ohta Hiroshi , Abe Takaya , Kurimoto Kazuki , Chuma Shinichiro , Saitou Mitinori
Published: March 2011

The Tudor domain–containing proteins (TDRDs) are an evolutionarily conserved family of proteins involved in germ cell development. We show here that in mice, TDRD5 is a novel component of the intermitochondrial cements (IMCs) and the chromatoid bodies (CBs), which are cytoplasmic ribonucleoprotein granules involved in RNA processing for spermatogenesis. Tdrd5-deficient males are sterile because of spermiogenic arrest at the round spermatid stage, with occasional failure in meiotic prophase. Without TDRD5, IMCs and CBs are disorganized, with mislocalization of their key components, including TDRD1/6/7/9 and MIWI/MILI/MIWI2. In addition, Tdrd5-deficient germ cells fail to repress LINE-1 retrotransposons with DNA-demethylated promoters. Cyclic adenosine monophosphate response element modulator (CREM) and TRF2, key transcription factors for spermiogenesis, are expressed in Tdrd5-deficient round spermatids, but their targets, including Prm1/Prm2/Tnp1, are severely down-regulated, which indicates the importance of IMC/CB-mediated regulation for postmeiotic gene expression. Strikingly, Tdrd5-deficient round spermatids injected into oocytes contribute to fertile offspring, demonstrating that acquisition of a functional haploid genome may be uncoupled from TDRD5 function.
Distinct ATOH1 and Neurog3 requirements define tuft cells as a new secretory cell type in the intestinal epithelium
Authors: Gerbe François , van Es Johan H. , Makrini Leila , Brulin Bénédicte , Mellitzer Georg , Robine Sylvie , Romagnolo Béatrice , Shroyer Noah F. , Bourgaux Jean-François , Pignodel Christine , Clevers Hans , Jay Philippe
Published: March 2011

The unique morphology of tuft cells was first revealed by electron microscopy analyses in several endoderm-derived epithelia. Here, we explore the relationship of these cells with the other cell types of the intestinal epithelium and describe the first marker signature allowing their unambiguous identification. We demonstrate that although mature tuft cells express DCLK1, a putative marker of quiescent stem cells, they are post-mitotic, short lived, derive from Lgr5-expressing epithelial stem cells, and are found in mouse and human tumors. We show that whereas the ATOH1/MATH1 transcription factor is essential for their differentiation, Neurog3, SOX9, GFI1, and SPDEF are dispensable, which distinguishes these cells from enteroendocrine, Paneth, and goblet cells, and raises from three to four the number of secretory cell types in the intestinal epithelium. Moreover, we show that tuft cells are the main source of endogenous intestinal opioids and are the only epithelial cells that express cyclooxygenase enzymes, suggesting important roles for these cells in the intestinal epithelium physiopathology.
VISTA, a novel mouse Ig superfamily ligand that negatively regulates T cell responses
Authors: Wang Li , Rubinstein Rotem , Lines Janet L. , Wasiuk Anna , Ahonen Cory , Guo Yanxia , Lu Li-Fan , Gondek David , Wang Yan , Fava Roy A. , Fiser Andras , Almo Steve , Noelle Randolph J.
Published: March 2011

The immunoglobulin (Ig) superfamily consists of many critical immune regulators, including the B7 family ligands and receptors. In this study, we identify a novel and structurally distinct Ig superfamily inhibitory ligand, whose extracellular domain bears homology to the B7 family ligand PD-L1. This molecule is designated V-domain Ig suppressor of T cell activation (VISTA). VISTA is primarily expressed on hematopoietic cells, and VISTA expression is highly regulated on myeloid antigen-presenting cells (APCs) and T cells. A soluble VISTA-Ig fusion protein or VISTA expression on APCs inhibits T cell proliferation and cytokine production in vitro. A VISTA-specific monoclonal antibody interferes with VISTA-induced suppression of T cell responses by VISTA-expressing APCs in vitro. Furthermore, anti-VISTA treatment exacerbates the development of the T cell–mediated autoimmune disease experimental autoimmune encephalomyelitis in mice. Finally, VISTA overexpression on tumor cells interferes with protective antitumor immunity in vivo in mice. These findings show that VISTA, a novel immunoregulatory molecule, has functional activities that are nonredundant with other Ig superfamily members and may play a role in the development of autoimmunity and immune surveillance in cancer.
Impact of Methicillin-ResistantStaphylococcus aureusPrevalence among S.aureusIsolates on Surgical Site Infection Risk after Coronary Artery Bypass Surgery
Authors: Miller Loren G. , McKinnell James A. , Vollmer Michael E. , Spellberg Brad
Published: March 2011

Objective.

Cephalosporins are recommended for antibiotic prophylaxis to prevent cardiothoracic surgical site infections (SSIs) except in patients withβ-lactam allergy or in settings with a “high” prevalence of methicillin-resistantStaphylococcus aureus(MRSA) among S.aureusisolates (hereafter, “MRSA prevalence”); however, “high” remains undefined. We sought to identify the MRSA prevalence at which glycopeptide prophylaxis would minimize SSIs relative toβ-lactam prophylaxis.

Methods.

We developed a decision analysis model to estimate SSI likelihood when either glycopeptides orβ-lactams were used for prophylaxis in cardiothoracic surgery. Event probabilities were derived from a systematic literature review. A similar cost-minimization model was also developed.

Results.

At 0% MRSA prevalence, SSI probability was 3.64% with glycopeptide prophylaxis and 3.49% withβ-lactam prophylaxis. At MRSA prevalences of 10%, 20%, 30%, or 40%, SSI probabilities with glycopeptide prophylaxis did not change, but they were 3.98%, 4.48%, 4.97%, and 5.47% withβ-lactam prophylaxis. The threshold of MRSA prevalence at which glycopeptide prophylaxis minimized SSI probability and cost was 3%. In sensitivity analyses, variations in most model estimates only modestly affected the threshold.

Conclusion.

Glycopeptide prophylaxis minimizes the risk of SSIs and cost when MRSA prevalence exceeds 3%. At very low MRSA prevalence (between 3% and 10%), the SSI minimization provided by glycopeptide prophylaxis is small and may be within the error of the model. Given the current MRSA prevalence in most community and healthcare settings, clinicians should consider routine prophylaxis with vancomycin. Our findings may have important policy implications, as benefits in cardiothoracic surgery antibiotic prophylaxis must be weighed against the limitations of increased glycopeptide use.
Highly Resistant Gram-Negative Microorganisms Incidence Density and Occurrence of Nosocomial Transmission (TRIANGLe Study)
Authors: Willemsen I. , Elberts S. , Verhulst C. , Rijnsburger M. , Filius M. , Savelkoul P. , Kluytmans J. ,   TRIANGLe Study Group, Lommerse E. , Spanjaard L. , Vlaminckx B. , Vos A. , Wulf M. , Vos M. , Wintermans R. , Andriesse G. , van Zeijl J. , van der Vorm E. , Buiting A. , Sturm P. , Blok H. , Troelstra A. , Kaiser A. , Vandenbroucke-Grauls C.
Published: March 2011

Objectives.

The objectives of this study were to determine the incidence density and the occurrence of horizontal spread of highly resistant gram-negative rods (HR-GNRs) in Dutch hospitals. The factors that influence these outcome measures were also investigated.

Methods.

All patients with HR-GNRs, as determined by sample testing, who were hospitalized in 1 of 18 hospitals during a 6-month period (April through October 2007) were included in this study. For all available isolates, the species was identified, susceptibility was determined (including the presence of extended-spectrumβ-lactamases [ESBLs]), and molecular typing was performed. On the basis of a combination of species identification, molecular typing, and epidemiological data, the occurrence of nosocomial transmission was determined.

Results.

The mean incidence density of patients with HR-GNRs was 55 per 100,000 patient-days (cumulative incidence, 39 per 10,000 patients admitted). A facility being a university hospital was a statistically significant (P= .03) independent determinant of a higher incidence of patients with HR-GNRs. The majority of HR-GNR isolates were ESBL producers. The adjusted transmission index—the ratio between secondary and primary cases—in the participating hospitals ranged from 0.0 to 0.2. The overall adjusted transmission index of HR-GNRs was 0.07. No determinants for a higher transmission index were identified.

Discussion.

The nosocomial transmission rate of HR-GNRs was relatively low in all hospitals where well-established transmission-based precautions were used. The incidence density of patients with HR-GNRs was higher in university hospitals, probably due to the patient population and the complexity of the care provided.
Dependence of transmittance and group index on the coupling strength between constituents of a metamaterial
Authors: Thuy Vu Tran Thanh , Nguyen Thanh Tung , Rhee Joo Yull , Vu Dinh Lam , Lee Young Pak
Published: March 2011

Recent studies on the coupling effects between constituent elements of metamaterials have opened up a new gateway to many fascinating electromagnetic properties and functionalities that cannot be explained by the uncoupled point of view. In this work, we numerically investigated, in a THz regime, the coupling between a cut wire and a split-ring resonator, which gives rise to an interesting phenomenon—the so-called electromagnetically induced transparency-like effect. The trade-off between the maximum transmittance of the transmission window and the group index, which depends on the coupling strength between constituent elements, was systematically studied. Furthermore, by characterizing this trade-off by the transmittance-delay product (figure of merit), a criterion for slow-light applications was provided.
The effect of sintering temperature on the mechanical properties of a Cu/CNT nanocomposite prepared via a powder metallurgy method
Authors: Pham Van Trinh , Bui Hung Thang , Tran Bao Trung , Nguyen Van Tu , Le Dinh Quang , Than Xuan Tinh , Nguyen Van Chuc , Doan Dinh Phuong , Phan Ngoc Minh
Published: March 2011

Metal matrix nanocomposites have become popular in industrial applications. Carbon nanotubes (CNTs), since theirs appearance, with their unique properties such as exceptionally small diameters and high Young's modulus, tensile strength and high chemical stability, are considered to be an attractive reinforcement material for lightweight and high-strength metallic matrix composites. The powder metallurgy method allows nanocomposite materials, notably metal–ceramic composites, to be produced by sintering a mixture of powders.

In this study, we have utilized the powder metallurgy method to fabricate a Cu/CNT nanocomposite. Sintering is the important process in this method; it is the process whereby powder compacts are heated so that adjacent particles fuse together. The aim of this paper is to investigate the effect of sintering temperature on the mechanical properties of the Cu/CNT nanocomposite. The sintering temperature was in the range of 850–950 °C for 2 h. A correlation between the microstructure and mechanical properties, including the microstructure, density, hardness and compressive strength, is established. In this process, the density, and the physical and mechanical properties of the nanocomposites, can be changed, depending on the rate of sintering as well as the sintering temperature.
The origin of visible light photocatalytic activity of N-doped and weak ferromagnetism of Fe-doped TiO
2 anatase
Authors: Cao Khang Nguyen , Van Khanh Nguyen , Hoai Anh Nguyen , Thi Nga Do , Van Minh Nguyen
Published: March 2011

In this paper, we present the experimental result as well as the theoretical calculation of the electronic band structures and the optical absorption spectra for N-doped and Fe-doped TiO
2 anatase. The main purpose is to provide evidence in the viewpoint of visible light photocatalytic activity of N-doped and weak ferromagnetism of Fe-doped in TiO
2 anatase. Accordingly, to evaluate the separate contributions of nitrogen doping and iron doping in anatase, we present the results of spin-polarized density functional theory (DFT) calculations that have been used to calculate the electronic band structures and optical absorption spectra that arise for a range of concentrations of (i) substitutional nitrogen and (ii) substitutional iron in anatase TiO
2. Our results show that absorption in the visible range is mainly due to nitrogen states located above the valence bands, whereas weak ferromagnetism of Fe-doped in TiO
2 anatase is mainly caused by spin polarization. These results have important implications for the understanding and further development of photocatalytic materials that are active under visible light. These findings agree favorably with our own experimental data and enable conclusions to be drawn about the nature of the practical catalyst in N-doped and the ferromagnetic origin in Fe-doped TiO
2 anatase.
Evaluation of Antioxidant, Lipid, and Protein Fractions of Accessions of Oryza Species
Authors: Bergman C. , Goffman F. , Chen M.‐H.
Published: March 2011

The genus Oryza has given rise to rice (Oryza sativa L.), a major source of food for much of the human population. The Oryza genus is small, including only 23 species, but it is remarkably diverse in terms of its ecological adaptation. This diversity may not be only restricted to ecological characteristics but also to kernel end‐use quality characteristics. This study was undertaken to evaluate Oryza species as a gene pool for improving the properties of rice bran for human consumption. Several accessions of 13 Oryza species were grown in a greenhouse, along with eight rice (Oryza sativa L.) accessions displaying low and high bran oil content, as well as low and high palmitic acid content. The total lipid content of the Oryza species was within the range found for Oryza sativa accessions. However, the level of palmitic acid in the O. species was as high as that reported for soybean high‐palmitic acid mutants. Oryza species also contained higher levels of the γ‐oryzanol and phenolic fractions compared to cultivated rice. Low or not significant phenotypic correlations between lipid, palmitic acid, and γ‐oryzanol suggest that these fractions in cultivated rice could be increased simultaneously using several of the Oryza species accessions identified in this study. A cultivar with enhanced levels of these fractions would be suitable for use in the production of high γ‐oryzanol margarine, shortening, and frying oils.
Sensitivity of Monilinia fructicola from Brazil to Tebuconazole, Azoxystrobin, and Thiophanate-Methyl and Implications for Disease Management
Authors: May-De Mio Louise L. , Luo Yong , Michailides Themis J.
Published: March 2011

The aim of this study was to investigate the sensitivity of Monilinia fructicola isolates to tebuconazole (demethylation inhibitor [DMI]), azoxystrobin (quinone outside inhibitor), and thiophanate-methyl (methyl benzimidazole carbamate) in 118 isolates collected from four states in Brazil from orchards with different histories of fungicide use. Sensitivity to fungicides was determined by inhibition of mycelial growth and spore germination on fungicide-amended media. Polymerase chain reaction was used to determine the frequencies of M. fructicola genotypes exhibiting high (HR) and low (LR) resistance to thiophanate-methyl among sampled populations. Resistance to tebuconazole was found in 15.8% of isolates collected from São Paulo State. The 50% effective concentration (EC50) values varied from 0.01 to greater than 100 μg/ml. The EC50 values for tebuconazole corresponded to its historic use frequency in the orchard; for instance, isolates from orchards with no DMI fungicide use had the lowest mean EC50 value (0.04 μg/ml), while those collected from orchards where more than five DMI fungicide sprays were applied per season had a mean EC50 value of 21.17 μg/ml. All isolates were sensitive to azoxystrobin but their EC50, based on tests of inhibition of conidial germination, increased from 0.05 in 2002 to 0.44 μg/ml in 2008. The EC50 values based on mycelial growth inhibition for thiophanate-methyl were >162 μg/ml, 1.99 to 12.5 μg/ml, and <1.0 μg/ml for HR, LR, and sensitive isolates, respectively.
Evaluation of African Cultivated Rice Oryza glaberrima for Resistance to Bacterial Blight
Authors: Djedatin Gustave , Ndjiondjop Marie-Noëlle , Mathieu Thierry , Cruz Casiana M. Vera , Sanni Ambaliou , Ghesquière Alain , Verdier Valérie
Published: March 2011

Xanthomonas oryzae pv. oryzae is the causal agent of bacterial blight in rice, one of the most devastating diseases of rice worldwide. African X. oryzae pv. oryzae strains belong to a clear genetic group distinct from those of Asia. Three new races of the pathogen were characterized among strains from West Africa. We evaluated 107 Oryza glaberrima accessions for resistance to bacterial blight under greenhouse conditions. Six-week-old seedlings were inoculated with five different African X. oryzae pv. oryzae strains originating from the West African nations of Burkina and Mali and representing different races (A1, A2, and A3). Philippine X. oryzae pv. oryzae strain PXO86 (race 2) was also used. Most (48%) of the accessions of O. glaberrima were highly susceptible to X. oryzae pv. oryzae strains from Burkina, while 20 and 36 were resistant to X. oryzae pv. oryzae strains from Mali and the Philippines, respectively. CAPS markers and dot blot assays were used for detection of resistance genes xa5 and Xa21 from a selected set of O. glaberrima accessions. Our results suggest that the O. glaberrima germplasm contains a narrow genetic base for resistance to X. oryzae pv. oryzae. Sources of resistance identified among O. glaberrima are recommended for rice breeding programs to develop bacterial blight-resistant cultivars for West Africa.
Control of vortex shedding on two- and three-dimensional aerofoils
Authors: Colonius Tim , Williams David R.
Published: March 2011

We review and expand on the control of separated flows over flat plates and aerofoils at low Reynolds numbers associated with micro air vehicles. Experimental observations of the steady-state and transient lift response to actuation, and its dependence on the actuator, aerofoil geometry and flow conditions, are discussed and an attempt is made to unify them in terms of their excitation of periodic and transient vortex shedding. We also examine strategies for closed-loop flow and flight control using actuation of leading-edge vortices.
On active control of laminar–turbulent transition on two-dimensional wings
Authors: Erdmann Ralf , Pätzold Andreas , Engert Marcus , Peltzer Inken , Nitsche Wolfgang
Published: March 2011

This paper gives an overview of drag reduction on aerofoils by means of active control of Tollmien–Schlichting (TS) waves. Wind-tunnel experiments at Mach numbers of up to
M

x

=0.42 and model Reynolds numbers of up to
Re
c
=2×10
6
, as well as in-flight experiments on a wing glove at Mach numbers of
M
<0.1 and at a Reynolds number of
Re
c
=2.4×10
6
, are presented. Surface hot wires were used to detect the linearly growing TS waves in the transitional boundary layer. Different types of voice-coil- and piezo-driven membrane actuators, as well as active-wall actuators, located between the reference and error sensors, were demonstrated to be effective in introducing counter-waves into the boundary layer to cancel the travelling TS waves. A control algorithm based on the filtered-
x
least mean square (FxLMS) approach was employed for in-flight and high-speed wind-tunnel experiments. A model-predictive control algorithm was tested in low-speed experiments on an active-wall actuator system. For the in-flight experiments, a reduction of up to 12 dB (75% TS amplitude) was accomplished in the TS frequency range between 200 and 600 Hz. A significant reduction of up to 20 dB (90% TS amplitude) in the flow disturbance amplitude was achieved in high-speed wind-tunnel experiments in the fundamental TS frequency range between 3 and 8 kHz. A downstream shift of the laminar–turbulent transition of up to seven TS wavelengths is presented. The cascaded sensor–actuator arrangement given by Sturzebecher & Nitsche in 2003 for low-speed wind-tunnel experiments was able to shift the transition Δ
x
=240 mm (18% 
x
/
c
) downstream by a TS amplitude reduction of 96 per cent (30 dB). By using an active-wall actuator, which is much shorter than the cascaded system, a transition delay of seven TS wavelengths (16 dB TS amplitude reduction) was reached.
Drag reduction: enticing turbulence, and then an industry
Authors: Spalart Philippe R. , McLean J. Douglas
Published: March 2011

We examine drag-reduction proposals, as presented in this volume and in general, first with concrete examples of how to bridge the distance from pure science through engineering to what makes inventions go into service; namely, the value to the public. We point out that the true drag reduction can be markedly different from an estimate based simply on the difference between turbulent and laminar skin friction over the laminarized region, or between the respective skin frictions of the baseline and the riblet-treated flow. In some situations, this difference is favourable, and is due to secondary differences in pressure drag. We reiterate that the benefit of riblets, if it is expressed as a percentage in skin-friction reduction, is unfortunately lower at full-size Reynolds numbers than in a small-scale experiment or simulation. The Reynolds number-independent measure of such benefits is a shift of the logarithmic law, or ‘Δ
U
+
’. Anticipating the design of a flight test and then a product, we note the relative ease in representing riblets or laminarization in computational fluid dynamics, in contrast with the huge numerical and turbulence-modelling challenge of resolving active flow control systems in a calculation of the full flow field. We discuss in general terms the practical factors that have limited applications of concepts that would appear more than ready after all these years, particularly riblets and laminar-flow control.
Genes for embryo development are packaged in blocks of multivalent chromatin in zebrafish sperm
Authors: Wu Shan-Fu , Zhang Haiying , Cairns Bradley R.
Published: March 2011

In mature human sperm, genes of importance for embryo development (i.e., transcription factors) lack DNA methylation and bear nucleosomes with distinctive histone modifications, suggesting the specialized packaging of these developmental genes in the germline. Here, we explored the tractable zebrafish model and found conceptual conservation as well as several new features. Biochemical and mass spectrometric approaches reveal the zebrafish sperm genome packaged in nucleosomes and histone variants (and not protamine), and we find linker histones high and H4K16ac absent, key factors that may contribute to genome condensation. We examined several activating (H3K4me2/3, H3K14ac, H2AFV) and repressing (H3K27me3, H3K36me3, H3K9me3, hypoacetylation) modifications/compositions genome-wide and find developmental genes packaged in large blocks of chromatin with coincident activating and repressing marks and DNA hypomethylation, revealing complex “multivalent” chromatin. Notably, genes that acquire DNA methylation in the soma (muscle) are enriched in transcription factors for alternative cell fates. Remarkably, whereas H3K36me3 is located in the 3′ coding region of heavily transcribed genes in somatic cells, H3K36me3 is present in the promoters of “silent” developmental regulators in sperm, suggesting different rules for H3K36me3 in the germline and soma. We also reveal the chromatin patterns of transposons, rDNA, and tDNAs. Finally, high levels of H3K4me3 and H3K14ac in sperm are correlated with genes activated in embryos prior to the mid-blastula transition (MBT), whereas multivalent genes are correlated with activation at or after MBT. Taken together, gene sets with particular functions in the embryo are packaged by distinctive types of complex and often atypical chromatin in sperm.