bluuebunny/crossref_metadata_2025 huggingface dataset:
Genomic insights to SAR86, an abundant and uncultivated marine bacterial lineage
Authors: Dupont Chris L , Rusch Douglas B , Yooseph Shibu , Lombardo Mary-Jane , Alexander Richter R , Valas Ruben , Novotny Mark , Yee-Greenbaum Joyclyn , Selengut Jeremy D , Haft Dan H , Halpern Aaron L , Lasken Roger S , Nealson Kenneth , Friedman Robert , Craig Venter J
Published: December 2011

Bacteria in the 16S rRNA clade SAR86 are among the most abundant uncultivated constituents of microbial assemblages in the surface ocean for which little genomic information is currently available. Bioinformatic techniques were used to assemble two nearly complete genomes from marine metagenomes and single-cell sequencing provided two more partial genomes. Recruitment of metagenomic data shows that these SAR86 genomes substantially increase our knowledge of non-photosynthetic bacteria in the surface ocean. Phylogenomic analyses establish SAR86 as a basal and divergent lineage of γ-proteobacteria, and the individual genomes display a temperature-dependent distribution. Modestly sized at 1.25–1.7 Mbp, the SAR86 genomes lack several pathways for amino-acid and vitamin synthesis as well as sulfate reduction, trends commonly observed in other abundant marine microbes. SAR86 appears to be an aerobic chemoheterotroph with the potential for proteorhodopsin-based ATP generation, though the apparent lack of a retinal biosynthesis pathway may require it to scavenge exogenously-derived pigments to utilize proteorhodopsin. The genomes contain an expanded capacity for the degradation of lipids and carbohydrates acquired using a wealth of tonB-dependent outer membrane receptors. Like the abundant planktonic marine bacterial clade SAR11, SAR86 exhibits metabolic streamlining, but also a distinct carbon compound specialization, possibly avoiding competition.
Distinct and complex bacterial profiles in human periodontitis and health revealed by 16S pyrosequencing
Authors: Griffen Ann L , Beall Clifford J , Campbell James H , Firestone Noah D , Kumar Purnima S , Yang Zamin K , Podar Mircea , Leys Eugene J
Published: December 2011

Periodontitis has a polymicrobial etiology within the framework of a complex microbial ecosystem. With advances in sequencing technologies, comprehensive studies to elucidate bacterial community differences have recently become possible. We used 454 sequencing of 16S rRNA genes to compare subgingival bacterial communities from 29 periodontally healthy controls and 29 subjects with chronic periodontitis. Amplicons from both the V1-2 and V4 regions of the 16S gene were sequenced, yielding 1 393 579 sequences. They were identified by BLAST against a curated oral 16S database, and mapped to 16 phyla, 106 genera, and 596 species. 81% of sequences could be mapped to cultivated species. Differences between health- and periodontitis-associated bacterial communities were observed at all phylogenetic levels, and UniFrac and principal coordinates analysis showed distinct community profiles in health and disease. Community diversity was higher in disease, and 123 species were identified that were significantly more abundant in disease, and 53 in health. Spirochaetes, Synergistetes and Bacteroidetes were more abundant in disease, whereas the Proteobacteria were found at higher levels in healthy controls. Within the phylum Firmicutes, the class Bacilli was health-associated, whereas the Clostridia, Negativicutes and Erysipelotrichia were associated with disease. These results implicate a number of taxa that will be targets for future research. Some, such as Filifactor alocis and many Spirochetes were represented by a large fraction of sequences as compared with previously identified targets. Elucidation of these differences in community composition provides a basis for further understanding the pathogenesis of periodontitis.
Effects of Manipulating Eating Frequency During a Behavioral Weight Loss Intervention: A Pilot Randomized Controlled Trial
Authors: Bachman Jessica L. , Raynor Hollie A.
Published: December 2011

Eating frequency has been inversely related to BMI but the impact of eating frequency on weight loss is unclear. This randomized controlled trial pilot study examined the effect of eating frequency on hunger, energy intake, and weight loss during a 6‐month behavioral weight loss intervention. Participants (age: 51.0 ± 9.9 years, BMI: 35.5 ± 4.8 kg/m2, 57.8% female, 94.1% white) were randomized to one of two eating frequency prescriptions: Three meal (n = 25): three eating bouts/day; or grazing (n = 26): eat at least 100 kcals every 2–3 h. Both groups attended 20 sessions and had identical dietary (1,200–1,500 kcals/day, <30% kcals from fat) and physical activity goals (200 min/week). Assessments were conducted at 0, 3, and 6 months. Using intent‐to‐treat analyses, grazing reported a greater eating frequency than three meal at 6 months (5.8 ± 1.1 eating bouts/day vs. 3.2 ± 0.6 eating bouts/day, P < 0.001). Grazing reported a significant reduction in hunger from 0 to 6 months (56.3 ± 15.7 mm vs. 47.9 ± 18.5 mm, P < 0.05). Energy intake and BMI were significantly (P < 0.001) reduced from 0 to 6 months (energy intake: 2,198 ± 692 kcals/day vs. 1,266 ± 353 kcals/day; BMI: 35.5 ± 4.8 kg/m2 vs. 30.6 ± 4.9 kg/m2). There were no significant differences in energy intake or BMI between the groups. While eating more frequently reduced hunger, it may not be related to greater reductions in energy intake or BMI during a behavioral weight loss intervention.
Longitudinal Associations of the Endocrine Environment on Fat Partitioning in Postmenopausal Women
Authors: Goss Amy M. , Darnell Betty E. , Brown Marian A. , Oster Robert A. , Gower Barbara A.
Published: December 2011

Among postmenopausal women, declining estrogen may facilitate fat partitioning from the periphery to the intra‐abdominal space. Furthermore, it has been suggested that excess androgens contribute to a central fat distribution pattern in women. The objective of this longitudinal study was to identify independent associations of the hormone milieu with fat distribution in postmenopausal women. Fifty‐three healthy postmenopausal women, either using or not using hormone replacement therapy (HRT) were evaluated at baseline and 2 years. The main outcomes were intra‐abdominal adipose tissue (IAAT), subcutaneous abdominal adipose tissue, and total thigh fat analyzed by computed tomography scanning and leg fat and total body fat mass measured by dual‐energy X‐ray absorptiometry. Serum estradiol, estrone, estrone sulfate, total testosterone, free testosterone, androstenedione, dehydroepiandrosterone sulfate), sex hormone‐binding globulin (SHBG), and cortisol were assessed. On average, in all women combined, IAAT increased by 10% (10.5 cm2) over 2 years (P < 0.05). Among HRT users, estradiol was inversely associated with, and estrone was positively associated with, 2‐year gain in IAAT. Among HRT nonusers, free testosterone was inversely associated with, and SHBG was positively associated with, 2‐year gain in IAAT. These results suggest that in postmenopausal women using HRT, greater circulating estradiol may play an integral role in limiting lipid deposition to the intra‐abdominal cavity, a depot associated with metabolically detrimental attributes. However, a high proportion of weak estrogens may promote fat partitioning to the intra‐abdominal cavity over time. Furthermore, among postmenopausal women not using HRT, greater circulating free testosterone may limit IAAT accrual.
Identification and Validity of Accelerometer Cut‐Points for Toddlers
Authors: Trost Stewart G. , Fees Bronwyn S. , Haar Sherry J. , Murray Ann D. , Crowe Linda K.
Published: December 2011

The purpose of this study was to derive ActiGraph cut‐points for sedentary (SED), light‐intensity physical activity (LPA), and moderate‐to‐vigorous physical activity (MVPA) in toddlers and evaluate their validity in an independent sample. The predictive validity of established preschool cut‐points were also evaluated and compared. Twenty‐two toddlers (mean age = 2.1 years ± 0.4 years) wore an ActiGraph accelerometer during a videotaped 20‐min play period. Videos were subsequently coded for physical activity (PA) intensity using the modified Children's Activity Rating Scale (CARS). Receiver operating characteristic (ROC) curve analyses were conducted to determine cut‐points. Predictive validity was assessed in an independent sample of 18 toddlers (mean age = 2.3 ± 0.4 years). From the ROC curve analyses, the 15‐s count ranges corresponding to SED, LPA, and MVPA were 0–48, 49–418, and >418 counts/15 s, respectively. Classification accuracy was fair for the SED threshold (ROC‐AUC = 0.74, 95% confidence interval = 0.71–0.76) and excellent for MVPA threshold (ROC‐AUC = 0.90, 95% confidence interval = 0.88–0.92). In the cross‐validation sample, the toddler cut‐point and established preschool cut‐points significantly overestimated time spent in SED and underestimated time in spent in LPA. For MVPA, mean differences between observed and predicted values for the toddler and Pate cut‐points were not significantly different from zero. In summary, the ActiGraph accelerometer can provide useful group‐level estimates of MVPA in toddlers. The results support the use of the Pate cut‐point of 420 counts/15 s for MVPA.
Unprecedented inhibition of resistant penicillin bindingproteins by bis-2-oxoazetidinylmacrocycles
Authors: Sliwa Aline , Dive Georges , Zervosen Astrid , Verlaine Olivier , Sauvage Eric , Marchand-Brynaert Jacqueline
Published: December 2011

Bis-2-oxoazetidinyl macrocycles, obtained as unexpected products of RCM cyclizations, exhibit good activities against d,d-peptidase from Actinomadura R39 and revealed very promising activities against PBP2a from methicillin-resistant Staphylococcus aureus.
Regulation and function of ribosomal protein S6 kinase (S6K) within mTOR signalling networks
Authors: Magnuson Brian , Ekim Bilgen , Fingar Diane C.
Published: December 2011

The ribosomal protein S6K (S6 kinase) represents an extensively studied effector of the TORC1 [TOR (target of rapamycin) complex 1], which possesses important yet incompletely defined roles in cellular and organismal physiology. TORC1 functions as an environmental sensor by integrating signals derived from diverse environmental cues to promote anabolic and inhibit catabolic cellular functions. mTORC1 (mammalian TORC1) phosphorylates and activates S6K1 and S6K2, whose first identified substrate was rpS6 (ribosomal protein S6), a component of the 40S ribosome. Studies over the past decade have uncovered a number of additional S6K1 substrates, revealing multiple levels at which the mTORC1–S6K1 axis regulates cell physiology. The results thus far indicate that the mTORC1–S6K1 axis controls fundamental cellular processes, including transcription, translation, protein and lipid synthesis, cell growth/size and cell metabolism. In the present review we summarize the regulation of S6Ks, their cellular substrates and functions, and their integration within rapidly expanding mTOR (mammalian TOR) signalling networks. Although our understanding of the role of mTORC1–S6K1 signalling in physiology remains in its infancy, evidence indicates that this signalling axis controls, at least in part, glucose homoeostasis, insulin sensitivity, adipocyte metabolism, body mass and energy balance, tissue and organ size, learning, memory and aging. As dysregulation of this signalling axis contributes to diverse disease states, improved understanding of S6K regulation and function within mTOR signalling networks may enable the development of novel therapeutics.
Multiple roles for the p85α isoform in the regulation and function of PI3K signalling and receptor trafficking
Authors: Mellor Paul , Furber Levi A. , Nyarko Jennifer N. K. , Anderson Deborah H.
Published: December 2011

The p85α protein is best known as the regulatory subunit of class 1A PI3Ks (phosphoinositide 3-kinases) through its interaction, stabilization and repression of p110-PI3K catalytic subunits. PI3Ks play multiple roles in the regulation of cell survival, signalling, proliferation, migration and vesicle trafficking. The present review will focus on p85α, with special emphasis on its important roles in the regulation of PTEN (phosphatase and tensin homologue deleted on chromosome 10) and Rab5 functions. The phosphatidylinositol-3-phosphatase PTEN directly counteracts PI3K signalling through dephosphorylation of PI3K lipid products. Thus the balance of p85α–p110 and p85α–PTEN complexes determines the signalling output of the PI3K/PTEN pathway, and under conditions of reduced p85α levels, the p85α–PTEN complex is selectively reduced, promoting PI3K signalling. Rab5 GTPases are important during the endocytosis, intracellular trafficking and degradation of activated receptor complexes. The p85α protein helps switch off Rab5, and if defective in this p85α function, results in sustained activated receptor tyrosine kinase signalling and cell transformation through disrupted receptor trafficking. The central role for p85α in the regulation of PTEN and Rab5 has widened the scope of p85α functions to include integration of PI3K activation (p110-mediated), deactivation (PTEN-mediated) and receptor trafficking/signalling (Rab5-mediated) functions, all with key roles in maintaining cellular homoeostasis.
New mimetic peptides of the kinase-inhibitory region (KIR) of SOCS1 through focused peptide libraries
Authors: Doti Nunzianna , Scognamiglio Pasqualina L. , Madonna Stefania , Scarponi Claudia , Ruvo Menotti , Perretta Giuseppe , Albanesi Cristina , Marasco Daniela
Published: December 2011

SOCS (suppressor of cytokine signalling) proteins are negative-feedback regulators of the JAK (Janus kinase)/STAT (signal transducer and activator of transcription) pathway. Their expression levels are low under physiological conditions, but they are up-regulated in response to cytokine stimulation in many immune and inflammatory processes. Overexpression of SOCS1 in keratinocyte clones abrogates the IFNγ (interferon γ)-induced expression of many pro-inflammatory genes and the release of related chemokines by blocking the JAK/STAT pathway. SOCS1 inhibits JAK2 kinase activity by binding the catalytic site of JAK2, with its KIR (kinase-inhibitory region) acting as a pseudo-substrate of the enzyme. In the present study, we screened a focused combinatorial peptide library of KIR to identify new peptides able to mimic its function with an improved affinity towards the JAK2 catalytic site. Using an alanine-scanning method, KIR residues that are crucial for the interaction with JAK2 were unveiled. In this way, the KIR sequence was restricted to a shorter segment and ‘non-essential’ residues were replaced by different amino acids following a simplified combinatorial approach. We selected a new unnatural sequence able to bind to JAK2 with Kd values in the nanomolar range. This peptide was tested in human keratinocyte cultures and reduced the phosphorylation of STAT1 and the expression levels of IRF-1 (interferon regulatory factor-1).
Plastoquinone-9 biosynthesis in cyanobacteria differs from that in plants and involves a novel 4-hydroxybenzoate solanesyltransferase
Authors: Sadre Radin , Pfaff Christian , Buchkremer Stephan
Published: December 2011

PQ-9 (plastoquinone-9) has a central role in energy transformation processes in cyanobacteria by mediating electron transfer in both the photosynthetic as well as the respiratory electron transport chain. The present study provides evidence that the PQ-9 biosynthetic pathway in cyanobacteria differs substantially from that in plants. We identified 4-hydroxybenzoate as being the aromatic precursor for PQ-9 in Synechocystis sp. PCC6803, and in the present paper we report on the role of the membrane-bound 4-hydroxybenzoate solanesyltransferase, Slr0926, in PQ-9 biosynthesis and on the properties of the enzyme. The catalytic activity of Slr0926 was demonstrated by in vivo labelling experiments in Synechocystis sp., complementation studies in an Escherichia coli mutant with a defect in ubiquinone biosynthesis, and in vitro assays using the recombinant as well as the native enzyme. Although Slr0926 was highly specific for the prenyl acceptor substrate 4-hydroxybenzoate, it displayed a broad specificity with regard to the prenyl donor substrate and used not only solanesyl diphosphate, but also a number of shorter-chain prenyl diphosphates. In combination with in silico data, our results indicate that Slr0926 evolved from bacterial 4-hydroxybenzoate prenyltransferases catalysing prenylation in the course of ubiquinone biosynthesis.
Akute Hemiparese und ipsilaterales Horner-Syndrom – Eindeutige Indikation zur intravenösen Thrombolyse?
Authors: Ludwig K. , Sitzer M. , Berger F.
Published: December 2011

Die Symptomtrias „akute Hemiparese, ipsilaterales Horner-Syndrom (v. a. Miosis und Ptosis) und Nackenschmerzen“ gilt als typisches Syndrom eines spinalen Infarktes bei akutem Verschluss einer Vertebralarterie (Opalski-Syndrom). Gleichermaßen kann ein spontanes zervikales epidurales Hämatom mit unilateraler Kompression des zervikalen Myelons (Brown-Séquard-Syndrom) zu dieser Symptomtrias führen. Die akuten Therapieoptionen sind divergent (rekanalisierende Therapie vs. operative Entlastung). Eine korrekte Diagnosestellung kann in der Akutphase schwierig sein, insbesondere wenn klinisch die Hemiparese im Vordergrund steht. Der vorgestellte Fall soll auf diese wichtige Differenzialdiagnose aufmerksam machen und Orientierungshilfen im Akutmanagement geben.
Schlaganfallprävention: intrakranielle arterielle Stenosen
Authors: Grams A. E. , Kaps M. , Gizewski E. R.
Published: December 2011

Intrakranielle arterielle Stenosen (IAS) sind für etwa 6,5–8% aller ischämischen Schlaganfälle verantwortlich. Für Patienten mit einer symptomatischen IAS wurde bislang trotz medikamentöser Sekundärprophylaxe innerhalb eines Jahres ein hohes Reinsultrisiko bis zu 12% in dem zugehörigen Gefäßterritorium beschrieben. Dabei haben IAS mit einem Stenosegrad ≥ 70% das höchste Reinsultrisiko (18%). Die Warfarin vs. Aspirin for Symptomatic Intracranial Stenosis Studie (WASID) führte zu der Empfehlung, dass bei symptomatischen IAS zunächst eine medikamentöse Sekundärprophylaxe mit Azetylsalizylsäure erfolgen sollte. Bei einem unter Thrombozytenfunktionshemmern auftretenden erneuten ischämischen Schlaganfall/TIA im Gefäßterritorium der symptomatischen IAS kann insbesondere bei Stenosen ≥ 70% eine interventionelle (stentgestützte) Angioplastie in einem spezialisierten Zentrum empfohlen werden. Zahlreiche aktuelle Veröffentlichungen legten nahe, dass durch die zunehmende Erfahrung der interventionell tätigen Neuroradiologen die periprozedurale Komplikationsrate zwischen 6 und 7% liegt, das Reinfraktrisiko bei bis zu 7,8% bei IAS > 70% liegen. Allerdings zeigte eine neue randomisierte Studie (SAMMPRIS), die bei symptomatischen IAS eine aggressive medikamentöse Sekundärprophylaxe mit der interven­tionellen Therapie vergliechen hat, dass in dieser Kohorte die Letalität im interventionellen Arm bei 14% lag, im medikamentösen Arm nur bei 5,8%. Eine abschließende Bewertung dieser noch sehr neuen Daten kann aktuell noch nicht erfolgen; ein Zwischenfazit könnte sein, dass eine endovaskuläre Therapie an speziellen Zentren in Betracht gezogen werden sollte wenn Patienten unter doppelter Thrombozytenfunktionshemmung weiterhin symptomatisch sind. Die Leitlinien werden sicher eine Weiterentwicklung und erneute Diskussion erfahren.
Cross-correlation based time delay estimation for turbulent flow velocity measurements: Statistical considerations
Authors: Tal Balazs , Bencze Attila , Zoletnik Sándor , Veres Gabor , Por Gabor
Published: December 2011

Time delay estimation methods (TDE) are well-known techniques to investigate poloidal flows in hot magnetized plasmas through the propagation properties of turbulent structures in the medium. One of these methods is based on the estimation of the time lag at which the cross-correlation function (CCF) estimation reaches its maximum value. The uncertainty of the peak location refers to the smallest determinable flow velocity modulation, and therefore the standard deviation of the time delay imposes important limitation to the measurements. In this article, the relative standard deviation of the CCF estimation and the standard deviation of its peak location are calculated analytically using a simple model of turbulent signals. This model assumes independent (non interacting) overlapping events (coherent structures) with randomly distributed spatio-temporal origins moving with background flow. The result of our calculations is the derivation of a general formula for the CCF variance, which is valid not exclusively in the high event density limit, but also for arbitrary event densities. Our formula reproduces the well known expression for high event densities previously published in the literature. In this paper we also present a derivation of the variance of time delay estimation that turns out to be inversely proportional to the applied time window. The derived formulas were tested in real plasma measurements. The calculations are an extension of the earlier work of Bencze and Zoletnik [Phys. Plasmas 12, 052323 (2005)] where the autocorrelation-width technique was developed. Additionally, we show that velocities calculated by a TDE method possess a broadband noise which originates from this variance, its power spectral density cannot be decreased by worsening the time resolution and can be coherent with noises of other velocity measurements where the same turbulent structures are used. This noise should not be confused with the impact of zero mean frequency zonal flow modulations and can be the explanation for the TEXTOR velocity spectra measured by beam emission spectroscopy.
Current-free double layers: A review
Authors: Singh Nagendra
Published: December 2011

During the last decade, there has been an upsurge in the research on current-free DLs (CFDLs). Research includes theory, laboratory measurements, and various applications of CFDLs ranging from plasma thrusters to acceleration of charged particles in space and astrophysical plasmas. The purpose of this review is to present a unified understanding of the basic plasma processes, which lead to the formation of CFDLs. The review starts with the discussion on early research on electric fields and double layers (DLs) and ion acceleration in planar plasma expansion. The review continues with the formation of DLs and rarefaction shocks (RFS) in expanding plasma with two electron populations with different temperatures. The basic theory mitigating the formation of a CFDL by two-electron temperature population is reviewed; we refer to such CFDLs as double layers structures formation by two-temperature electron populations (TET-CFDLs). Application of TET-CFDLS to ion acceleration in laboratory and space plasmas was discussed including the formation of stationary steady-state DLs. A quite different type of CFDLs forms in a helicon plasma device (HPD), in which plasma abruptly expands from a narrow plasma source tube into a wide diffusion tube with abruptly diverging magnetic fields. The formation mechanism of the CFDL in HPD, referred here as current free double layer structure in helicon plasma device (HPD-CFDL), and its applications are reviewed. The formation of a TET-CFDL is due to the self-consistent separation of the two electron populations parallel to the ambient magnetic field. In contrast, a HPD-CFDL forms due to self-consistent separation of electrons and ion perpendicular to the abruptly diverging magnetic field in conjunction with the conducting wall of the expansion chamber in the HPD. One-dimensional theoretical models of CFDLs based on steady-state solution of Vlasov-Poisson system of equations are briefly discussed. Applications of CFDLs ranging from helicon double-layer thrusters (HDLTs) to the accelerations of ions in space and astrophysical plasmas are summarized.
Hot hole-induced dissociation of NO dimers on a copper surface
Authors: García Rey Natalia , Arnolds Heike
Published: December 2011

We use reflection-absorption infrared spectroscopy (RAIRS) to study the photochemistry of NO on Cu(110) in the UV-visible range. We observe that the only photoactive species of NO on Cu(110) is the NO dimer, which is asymmetrically bound to the surface. RAIRS shows that photoinduced dissociation proceeds via breaking of the weak N–N bond of the dimer, photodesorbing one NOg to the gas phase and leaving one NOads adsorbed on the surface in a metastable atop position. We model the measured wavelength-dependent cross sections assuming both electron- and hole-induced processes and find that the photochemistry can be described by either electron attachment to a level 0.3 eV above the Fermi energy EF or hole attachment to a level 2.2 eV below EF. While there is no experimental or theoretical evidence for an electron attachment level so close to EF, an occupied NO-related molecular orbital is known to exist at EF − 2.52 eV on the Cu(111) surface [I. Kinoshita, A. Misu, and T. Munakata, J. Chem. Phys. 102, 2970 (1995)]. We, therefore, propose that photoinduced dissociation of NO dimers on Cu(110) in the visible wavelength region proceeds by the creation of hot holes at the top of the copper d-band.
Ultrafast electrical measurements of polarization dynamics in ferroelectric thin-film capacitors
Authors: Grigoriev Alexei , Azad Mandana Meisami , McCampbell John
Published: December 2011

We have developed a new approach to measure fast electrical signals during polarization switching in ferroelectric thin-film capacitors. This article describes a simple method for probing transient currents and voltages in a broad range of time scales from microseconds to hundreds of picoseconds. In order to test our approach, we probed polarization dynamics in commercial PbZr0.2Ti0.8O3 ferroelectric capacitors in which the measured switching time was as fast as 1.7 ns.
Boiling point determination using adiabatic Gibbs ensemble Monte Carlo simulations: Application to metals described by embedded-atom potentials
Authors: Gelb Lev D. , Chakraborty Somendra Nath
Published: December 2011

The normal boiling points are obtained for a series of metals as described by the “quantum-corrected Sutton Chen” (qSC) potentials [S.-N. Luo, T. J. Ahrens, T. Çağın, A. Strachan, W. A. Goddard III, and D. C. Swift, Phys. Rev. B 68, 134206 (2003)]. Instead of conventional Monte Carlo simulations in an isothermal or expanded ensemble, simulations were done in the constant-NPH adabatic variant of the Gibbs ensemble technique as proposed by Kristóf and Liszi [Chem. Phys. Lett. 261, 620 (1996)]. This simulation technique is shown to be a precise tool for direct calculation of boiling temperatures in high-boiling fluids, with results that are almost completely insensitive to system size or other arbitrary parameters as long as the potential truncation is handled correctly. Results obtained were validated using conventional NVT-Gibbs ensemble Monte Carlo simulations. The qSC predictions for boiling temperatures are found to be reasonably accurate, but substantially underestimate the enthalpies of vaporization in all cases. This appears to be largely due to the systematic overestimation of dimer binding energies by this family of potentials, which leads to an unsatisfactory description of the vapor phase.
Low-temperature treatment of semiconducting interlayers for high-efficiency light-emitting diodes based on a green-emitting polyfluorene derivative
Authors: Lazzerini G. M. , Di Stasio F. , Fléchon C. , Caruana D. J. , Cacialli F.
Published: December 2011

We investigate the scope for low-temperature treatment of exciton/electron blocking interlayers in light-emitting diodes based on poly(9,9′-dioctylfiuorene-alt-benzothiadiazole) (F8BT). We focus on poly(9,9′-dioctylfluorene-alt-N-(4-butylphenyl)-diphenylamine) (TFB) interlayers processed at temperatures up to 50 °C, i.e., far below the glass transition temperature of TFB (∼156 °C). Continuous-wave and time-resolved photoluminescence studies confirm the formation of both excitons and exciplex species, as a result of the F8BT/TFB intermixing. Interestingly, however, we can still increase the electroluminescence external quantum efficiency from 0.05% to 0.5% and 1% for progressively thicker TFB films. We propose that a degree of intermixing may become acceptable as a trade-off to achieve low-temperature processability.
Communication: Branching ratio measurements in the predissociation of 12C16O by time-slice velocity-map ion imaging in the vacuum ultraviolet region
Authors: Gao Hong , Song Yu , Yang Lei , Shi Xiaoyu , Yin Qingzhu , Ng C. Y. , Jackson William M.
Published: December 2011

The first direct branching ratio measurement of the three lowest energy dissociation channels of CO that produce C(3P) + O(3P), C(1D) + O(3P), and C(3P) + O(1D) is reported. Rotational resolved carbon ion yield spectra for two Π bands (W(3sσ)1Π (v′ = 3) at 108 012.6 cm−1 and 1Π(v′ = 2) at 109 017 cm−1) and two Σ bands ((4sσ)1Σ+(v′ = 4) at 109 452 cm−1 and (4pσ)1Σ+(v′ = 3) at 109 485 cm−1) of CO were obtained. Our measurements show that the branching ratio in this energy region is strongly dependent on the electronic and vibrational energy but it is independent or just weakly dependent on the parity and rotational energy levels. To our knowledge, this is the first time that the triplet channel producing O(1D) has been experimentally observed and this is also the first time that a direct measurement of the branching ratio for the different channels in the predissociation of CO in this energy region has been made.
The dynamics of a vesicle in a wall-bound shear flow
Authors: Zhao Hong , Spann Andrew P. , Shaqfeh Eric S. G.
Published: December 2011

The three-dimensional dynamics of a lipid vesicle in a wall-bound shear flow is simulated by a Stokes-flow boundary integral equation method. When the vesicle is far away from the wall, the wall induces a lift velocity that is proportional to the wall normal component of the particle stresslet and is inversely proportional to the square of its centroid height. When the vesicle is in close contact with the wall under the action of gravity, its bottom surface height scales linearly with the shear rate, with a scaling constant that depends strongly on its nonsphericity. The numerical results are in quantitative agreement with the experimental measurements. The wall boundary causes the particle shear stress and normal stress differences to increase, but the effect diminishes when the centroid height is more than twice the vesicle radius. The simulation shows that the presence of the wall delays the transition (i.e., creates higher critical viscosity ratios) from the tank-treading motion to trembling and tumbling.
Temperature and size dependence of time-resolved exciton recombination in ZnO quantum dots
Authors: Musa I. , Massuyeau F. , Cario L. , Duvail J. L. , Jobic S. , Deniard P. , Faulques E.
Published: December 2011

ZnO nanocrystals with various sizes were prepared and characterized. Their photoluminescence dynamics has been investigated at low temperatures. For the smallest particles (3 nm), a defect-induced long-lived photoluminescence occurs around 2.5 eV which is slowed down at decay times longer than 3 ns when sample temperature T decreases. From thermal quenching of the 2.5 eV band, the exciton dissociation energy at defect centers is estimated around ∼11.8 meV. For larger crystallites (10 and 20 nm), the ultraviolet emission observed at 3.32 eV decays in less than 85 ps and follows a Varshni law [Y. P. Varshni, Physica (Amsterdam) 34, 149 (1967)].
Plasmonic terahertz detection by a double-grating-gate field-effect transistor structure with an asymmetric unit cell
Authors: Popov V. V. , Fateev D. V. , Otsuji T. , Meziani Y. M. , Coquillat D. , Knap W.
Published: December 2011

Plasmonic terahertz detection by a double-grating gate field-effect transistor structure with an asymmetric unit cell is studied theoretically. Detection responsivity exceeding 8 kV/W at room temperature in the photovoltaic response mode is predicted for strong asymmetry of the structure unit cell. This value of the responsivity is an order of magnitude greater than reported previously for the other types of uncooled plasmonic terahertz detectors. Such enormous responsivity can be obtained without using any supplementary antenna elements because the double-grating gate acts as an aerial matched antenna that effectively couples the incoming terahertz radiation to plasma oscillations in the structure channel.
Silicon-compatible compound semiconductor tunneling field-effect transistor for high performance and low standby power operation
Authors: Cho Seongjae , Man Kang In , Kamins Theodore I. , Park Byung-Gook , Harris James S.
Published: December 2011

In this study, we propose and characterize by simulation a silicon-compatible compound semiconductor tunneling field-effect transistor (TFET) based on germanium (Ge)/gallium arsenide (GaAs) heterojunction aiming the various integrated systems on silicon substrate. By introducing Ge as p+ source and GaAs as the high-mobility channel and n+ drain materials, we maximize on-state current (Ion) and minimize off-state current (Ioff) to obtain a TFET for high performance and low standby power capabilities. The effects of physical parameters such as aluminum content, source-gate overlap length, and gate workfunction on device performance were examined thoroughly. Further, we evaluate its radio frequency performance and confirm that it shows superb current and power gain characteristics.
Three-dimensional fit-to-flow microfluidic assembly
Authors: Chen Arnold , Pan Tingrui
Published: December 2011

Three-dimensional microfluidics holds great promise for large-scale integration of versatile, digitalized, and multitasking fluidic manipulations for biological and clinical applications. Successful translation of microfluidic toolsets to these purposes faces persistent technical challenges, such as reliable system-level packaging, device assembly and alignment, and world-to-chip interface. In this paper, we extended our previously established fit-to-flow (F2F) world-to-chip interconnection scheme to a complete system-level assembly strategy that addresses the three-dimensional microfluidic integration on demand. The modular F2F assembly consists of an interfacial chip, pluggable alignment modules, and multiple monolithic layers of microfluidic channels, through which convoluted three-dimensional microfluidic networks can be easily assembled and readily sealed with the capability of reconfigurable fluid flow. The monolithic laser-micromachining process simplifies and standardizes the fabrication of single-layer pluggable polymeric modules, which can be mass-produced as the renowned Lego® building blocks. In addition, interlocking features are implemented between the plug-and-play microfluidic chips and the complementary alignment modules through the F2F assembly, resulting in facile and secure alignment with average misalignment of 45 μm. Importantly, the 3D multilayer microfluidic assembly has a comparable sealing performance as the conventional single-layer devices, providing an average leakage pressure of 38.47 kPa. The modular reconfigurability of the system-level reversible packaging concept has been demonstrated by re-routing microfluidic flows through interchangeable modular microchannel layers.
Fast magnetization switching in GaMnAs induced by electrical fields
Authors: Balestrière P. , Devolder T. , Kim Joo-Von , Lecoeur P. , Wunderlich J. , Novák V. , Jungwirth T. , Chappert C.
Published: December 2011

We study the electrical field induced magnetization reversal in a GaMnAs thin film magnet at the nanosecond scale. Quasi-static electrical fields deplete partially the magnetic material, reducing its magneto-crystalline cubic anisotropy and affecting its transport properties. We demonstrate that electrical field pulses can trigger the nucleation of domains with reversed magnetization. Pulse durations of 2.5 ns are enough to induce the nucleation, indicating precessional effects in the dynamical magnetic response. Full reversal can be obtained with 10 ns and 3 V and the assistance of magnetic fields substantially lower than the coercivity of the material in the absence of gate voltage.
Assessing weeds at risk of evolving glyphosate resistance in Australian sub-tropical glyphosate-resistant cotton systems
Authors: Werth Jeff , Thornby David , Walker Steve
Published: December 2011

Glyphosate resistance will have a major impact on current cropping practices in glyphosate-resistant cotton systems. A framework for a risk assessment for weed species and management practices used in cropping systems with glyphosate-resistant cotton will aid decision making for resistance management. We developed this framework and then assessed the biological characteristics of 65 species and management practices from 50 cotton growers. This enabled us to predict the species most likely to evolve resistance, and the situations in which resistance is most likely to occur. Species with the highest resistance risk were Brachiaria eruciformis, Conyza bonariensis, Urochloa panicoides, Chloris virgata, Sonchus oleraceus and Echinochloa colona. The summer fallow and non-irrigated glyphosate-resistant cotton were the highest risk phases in the cropping system. When weed species and management practices were combined, C. bonariensis in summer fallow and other winter crops were at very high risk. S. oleraceus had very high risk in summer and winter fallow, as did C. virgata and E. colona in summer fallow. This study enables growers to identify potential resistance risks in the species present and management practices used on their farm, which will to facilitate a more targeted weed management approach to prevent development of glyphosate resistance.
Genetic diversity and population structure of Eurasian populations of reed canarygrass: cytotypes, cultivars, and interspecific hybrids
Authors: Jakubowski Andrew R. , Jackson Randall D. , Johnson R. C. , Hu Jinguo , Casler Michael D.
Published: December 2011

Reed canarygrass (Phalaris arundinacea L.) is an important forage crop and potential biofuel feedstock due to its wide environmental adaptation. The P. arundinacea ‘species complex’ is made up of three cytotypes, 2x, 4x, and 6x, with the 4x cytotype (P. arundinacea L.) most common. Active breeding programs have developed cultivars since the early 20th Century, but little is known about the genetics of the species complex. With the aid of DNA markers, we evaluated the population structure of 83 wild accessions collected throughout Eurasia, 24 cultivars, and the genetic relationship between 4x and 6x cytotypes. Seven subpopulations were present in Europe with a high level of admixture, suggesting that reed canarygrass germplasm has spread throughout Eurasia, either naturally or by humans for use in agriculture. Our results indicate that cultivars have incorporated much of the diversity found in wild populations, although modern low-alkaloid cultivars appear to come from a relatively small gene pool. We also found some evidence that the 6x cytotype is made up of three sub-genomes that are a combination of genomes present in 4x P. arundinacea and 4x P. aquatica, although the 6x cytotype does not appear to be a direct hybrid between the species.
Dextran hydrogel scaffolds enhance angiogenic responses and promote complete skin regeneration during burn wound healing
Authors: Sun Guoming , Zhang Xianjie , Shen Yu-I , Sebastian Raul , Dickinson Laura E. , Fox-Talbot Karen , Reinblatt Maura , Steenbergen Charles , Harmon John W. , Gerecht Sharon
Published: December 2011

Neovascularization is a critical determinant of wound-healing outcomes for deep burn injuries. We hypothesize that dextran-based hydrogels can serve as instructive scaffolds to promote neovascularization and skin regeneration in third-degree burn wounds. Dextran hydrogels are soft and pliable, offering opportunities to improve the management of burn wound treatment. We first developed a procedure to treat burn wounds on mice with dextran hydrogels. In this procedure, we followed clinical practice of wound excision to remove full-thickness burned skin, and then covered the wound with the dextran hydrogel and a dressing layer. Our procedure allows the hydrogel to remain intact and securely in place during the entire healing period, thus offering opportunities to simplify the management of burn wound treatment. A 3-week comparative study indicated that dextran hydrogel promoted dermal regeneration with complete skin appendages. The hydrogel scaffold facilitated early inflammatory cell infiltration that led to its rapid degradation, promoting the infiltration of angiogenic cells into the healing wounds. Endothelial cells homed into the hydrogel scaffolds to enable neovascularization by day 7, resulting in an increased blood flow significantly greater than treated and untreated controls. By day 21, burn wounds treated with hydrogel developed a mature epithelial structure with hair follicles and sebaceous glands. After 5 weeks of treatment, the hydrogel scaffolds promoted new hair growth and epidermal morphology and thickness similar to normal mouse skin. Collectively, our evidence shows that customized dextran-based hydrogel alone, with no additional growth factors, cytokines, or cells, promoted remarkable neovascularization and skin regeneration and may lead to novel treatments for dermal wounds.
Crystal structures of
Drosophila
N-cadherin ectodomain regions reveal a widely used class of Ca
2+
-free interdomain linkers
Authors: Jin Xiangshu , Walker Melissa A. , Felsövályi Klára , Vendome Jeremie , Bahna Fabiana , Mannepalli Seetha , Cosmanescu Filip , Ahlsen Goran , Honig Barry , Shapiro Lawrence
Published: December 2011

Vertebrate classical cadherins mediate selective calcium-dependent cell adhesion by mechanisms now understood at the atomic level. However, structures and adhesion mechanisms of cadherins from invertebrates, which are highly divergent yet function in similar roles, remain unknown. Here we present crystal structures of three- and four-tandem extracellular cadherin (EC) domain segments from
Drosophila
N-cadherin (DN-cadherin), each including the predicted N-terminal EC1 domain (denoted EC1’) of the mature protein. While the linker regions for the EC1’-EC2’ and EC3’-EC4’ pairs display binding of three Ca
2+
ions similar to that of vertebrate cadherins, domains EC2’ and EC3’ are joined in a “kinked” orientation by a previously uncharacterized Ca
2+
-free linker. Biophysical analysis demonstrates that a construct containing the predicted N-terminal nine EC domains of DN-cadherin forms homodimers with affinity similar to vertebrate classical cadherins, whereas deleting the ninth EC domain ablates dimerization. These results suggest that, unlike their vertebrate counterparts, invertebrate cadherins may utilize multiple EC domains to form intercellular adhesive bonds. Sequence analysis reveals that similar Ca
2+
-free linkers are widely distributed in the ectodomains of both vertebrate and invertebrate cadherins.
Home Range Size and Seasonal Movement of Juvenile Lake Sturgeon in a Large River in the Hudson Bay Drainage Basin
Authors: Barth Cameron C. , Anderson W. Gary , Henderson L. M. , Peake Stephan J.
Published: December 2011

Development of rehabilitation strategies and accurate assessment of anthropogenic impacts relies on a thorough understanding of a species’ life history. In the case of the lake sturgeon Acipenser fulvescens, a better understanding of the juvenile life history stages is needed to improve conservation efforts for this imperiled species. Home range size and seasonal movement of juvenile lake sturgeon in the Winnipeg River, Manitoba, were examined using mark–recapture and acoustic telemetry. Over a 30‐month period (May 2006–October 2008), 5,671 juvenile lake sturgeon (213–879 mm fork length [FL]) were marked with Floy tags and the movements of 23 juvenile lake sturgeon (364–505 mm FL) were monitored by means of acoustic transmitters. Despite the potential for movement over 49 km of naturally connected riverine habitat, the results indicated that juvenile lake sturgeon exhibited strong site fidelity. As determined from the mark–recapture data set, 90.8% of recaptured fish were recaptured less than 2.0 river kilometers (rkm) from their original capture location. Similarly, acoustic telemetry data indicated that 50% of the tagged fish moved 1.5 rkm or less from their initial release locations. Finally, the results of both methodologies indicated that juvenile lake sturgeon rarely move through rapids characterized by high water velocities (>1.5 m/s), complex turbulent flows, boulder and bedrock substrates, and various cross‐sectional water depths ranging from 1.0 m to approximately 15.0 m in either an upstream or downstream direction. These results suggest that the year‐round habitat requirements for juvenile lake sturgeon can be met in relatively short sections of a large river. Furthermore, owing to strong site fidelity and a lack of movement through rapids, macroscale habitat use in juvenile lake sturgeon occupying large rivers may be dependent on dispersal at either the larval or young of the year life history stages.
Laws Pertaining to Healthcare-Associated Infections: A Review of 3 Legal Requirements
Authors: Reagan Julie , Hacker Carl
Published: December 2011

We reviewed US state and territorial healthcare-associated infection (HAI) laws, specifically addressing 3 legal requirements: data submission, reporting of data to the public, and inclusion of facility identifiers in public reports. The majority of US states and territories have HAI laws. The 3 studied legal provisions are all commonly included in state HAI laws in varying forms; however, only a minority of states and territories specifically mandate all 3 legal requirements. The laws of the remaining states vary considerably.

Infect Control Hosp Epidemiol2012;33(1):75-80
Voluntary to Mandatory: Evolution of Strategies and Attitudes toward Influenza Vaccination of Healthcare Personnel
Authors: Quan Kathleen , Tehrani David M. , Dickey Linda , Spiritus Eugene , Hizon Denise , Heck Kristie , Samuelson Pamela , Kornhauser Elliott , Zeitany Raja , Mancia Susan , Thrupp Lauri , Tiso Susan M. , Huang Susan S.
Published: December 2011

Background.

Assessing the relative success of serial strategies for increasing healthcare personnel (HCP) influenza vaccination rates is important to guide hospital policies to increase vaccine uptake.

Objective.

To evaluate serial campaigns that include a mandatory HCP vaccination policy and to describe HCP attitudes toward vaccination and reasons for declination.

Design.

Retrospective cohort study.

Methods.

We assessed the impact of serial vaccination campaigns on the proportions of HCP who received influenza vaccination during die 2006–2011 influenza seasons. In addition, declination data over these 5 seasons and a 2007 survey of HCP attitudes toward vaccination were collected.

Results.

HCP influenza vaccination rates increased from 44.0% (2,863 of 6,510 HCP) to 62.9% (4,037 of 6,414 HCP) after institution of mobile carts, mandatory declination, and peer-to-peer vaccination efforts. Despite maximal attempts to improve accessibility and convenience, 27.2% (66 of 243) of die surveyed HCP were unwilling to wait more than 10 minutes for a free influenza vaccination, and 23.3% (55 of 236) would be indifferent if they were unable to be vaccinated. In this context, institution of a mandatory vaccination campaign requiring unvaccinated HCP to mask during the influenza season increased rates of compliance to over 90% and markedly reduced the proportion of HCP who declined vaccination as a result of preference.

Conclusions.

A mandatory influenza vaccination program for HCP was essential to achieving high vaccination rates, despite years of intensive vaccination campaigns focused on increasing accessibility and convenience. Mandatory vaccination policies appear to successfully capture a large portion of HCP who are not opposed to receipt of die vaccine but who have not made vaccination a priority.

Infect Control Hosp Epidemiol 2012;33(1):63-70