bluuebunny/crossref_metadata_2025 huggingface dataset:
New formulation of paraquat with lysine acetylsalicylate with low mammalian toxicity and effective herbicidal activity
Authors: Baltazar Maria Teresa , Dinis‐Oliveira Ricardo Jorge , Guilhermino Lúcia , de Lourdes Bastos Maria , Duarte José Alberto , Carvalho Félix
Published: August 2012

Background

Currently, the commercial formulations of the herbicide paraquat are highly toxic to humans, and no effective antidote is available for paraquat poisoning. The aim of the present study was to develop a safe formulation, combining paraquat and the known antidote lysine acetylsalicylate. The toxicity of a mixture of Gramoxone® (20% paraquat) and lysine acetylsalicylate in adult Wistar male rats and the herbicidal efficacy against grass lawn (50% of Poa pratensis and 50% of Festuca arundinacea) were evaluated. This new formulation was administered to Wistar rats by gavage at 125 mg kg−1 of paraquat ion and lysine acetylsalicylate at 79, 158 or 316 mg kg−1 body weight, and the survival rate was observed for 30 days.

Results

The survival rate of the paraquat group was only 40%, while lysine acetylsalicylate provided effective protection, with full survival observed in the groups that received 125 mg kg−1 of paraquat ion and 316 mg kg−1 of lysine acetylsalicylate. Both formulations of paraquat, either in the absence or in the presence of lysine acetylsalicylate, provided the same herbicidal activity against the tested herbal species.

Conclusions

The present formulation of paraquat containing lysine acetylsalicylate, significantly decreases mammalian toxicity while maintaining effective herbicidal activity. © 2012 Society of Chemical Industry
Strain profile and polarization enhancement in Ba0.5Sr0.5TiO3 thin films
Authors: Amir F. Z. , Donner W. , Aspelmeyer M. , Noheda B. , Xi X. X. , Moss S. C.
Published: August 2012

The sensitivity of spontaneous polarization to epitaxial strain for both 10 and 50 nm thick Ba0.5Sr0.5TiO3 (BSTO) ferroelectric thin films has been studied. Crystal truncation rod (CTR) profiles in the 00L directions at different wavelengths, and grazing incidence diffraction (GID) in the 0K0 direction on a single crystal have been recorded. Modeling of the CTR data gives a detailed picture of the strain and provides clear evidence of the film out‐of‐plane expansion at the surface, an increase of the polarization, as well as a contraction at the interface. GID data confirm the fitting of the CTR, showing an in‐plane expansion of the BSTO film at the interface and a contraction at the surface.
Polarity control and growth mode of InN on yttria‐stabilized zirconia (111) surfaces
Authors: Kobayashi Atsushi , Okubo Kana , Ohta Jitsuo , Oshima Masaharu , Fujioka Hiroshi
Published: August 2012

We have found that polarity of epitaxial InN layers has been controlled by choice of a capping material during high‐temperature annealing of yttria‐stabilized zirconia (YSZ) (111) substrates in air. Angle‐resolved X‐ray photoelectron spectroscopy has revealed that the amount of segregation of Y atoms to the YSZ surface depended on the capping material of the substrates. In‐polar and N‐polar InN have been reproducibly grown on Y‐segregated and Y‐segregation‐free YSZ surfaces, respectively. We have also found that the growth of the first monolayer (ML) of N‐polar InN proceeds in a step‐flow mode which then switches to layer‐by‐layer mode after the coverage by 1‐ML‐thick InN.
Effects of magnetic field on the terahertz nonlinear optical properties in donor‐doped GaAs/AlGaAs quantum wells
Authors: Yıldırım Hasan , Aslan Bulent
Published: August 2012

Effects of the magnetic field on nonlinear optical properties at THz range in GaAs/AlGaAs quantum wells doped with donor atoms are investigated. Expressions for the third‐order nonlinear optical susceptibilities are obtained through the solution of the density matrix equations of motion within the rotating wave approximation. Donor binding energies are calculated variationally by means of an iterative shooting algorithm. Magnetic field has strong effect on the nonlinear susceptibility: it removes the degeneracy in energies of 2p± impurity states and increases the absolute value of the nonlinearity. It is also shown that a large and tunable optical nonlinear figure of merit is possible with the magnetic field applied in the growth direction. The nonlinear optical quantities are also calculated for donor distributions with different full width at half maximum values in the absence of magnetic field and the observed features at low energy part are attributed to the increasing homogeneity in the donor distribution.
3D Nanofabrication of Fluidic Components by Corner Lithography
Authors: Berenschot Erwin J. W. , Burouni Narges , Schurink Bart , van Honschoten Joost W. , Sanders Remco G. P. , Truckenmuller Roman , Jansen Henri V. , Elwenspoek Miko C. , van Apeldoorn Aart A. , Tas Niels R.
Published: August 2012

A reproducible wafer‐scale method to obtain 3D nanostructures is investigated. This method, called corner lithography, explores the conformal deposition and the subsequent timed isotropic etching of a thin film in a 3D shaped silicon template. The technique leaves a residue of the thin film in sharp concave corners which can be used as structural material or as an inversion mask in subsequent steps. The potential of corner lithography is studied by fabrication of functional 3D microfluidic components, in particular i) novel tips containing nano‐apertures at or near the apex for AFM‐based liquid deposition devices, and ii) a novel particle or cell trapping device using an array of nanowire frames. The use of these arrays of nanowire cages for capturing single primary bovine chondrocytes by a droplet seeding method is successfully demonstrated, and changes in phenotype are observed over time, while retaining them in a well‐defined pattern and 3D microenvironment in a flat array.
Comparison of speciated arsenic levels in the liver and brain of mice between arsenate and arsenite exposure at the early life
Authors: Lu Chunwei , Zhao Fenghong , Sun Di , Zhong Yuan , Yu Xiaoyun , Li Gexin , Lv Xiuqiang , Sun Guifan , Jin Yaping
Published: August 2012

The aim of this study was to compare the risk from exposure to arsenate (iAsV) or arsenite (iAsIII) at the early life. Mother mice were exposed to equimolar dose of iAsV and iAsIII via drinking water during gestation and lactation. Their offspring continually drank the same water after weaning. Levels of speciated arsenic in both liver and brain were analyzed by hydride generation of volatile arsines and atomic absorption spectrophotometry (HG‐AAS). In the liver, inorganic arsenic (iAs) levels significantly increased from postnatal day (PND) 15, and those on PND 35 were significantly higher than on PND 15 and 21 in iAsIII exposed mice, but iAs levels did not significantly differ until PND 35 in iAsV exposed mice; Furthermore, all speciated arsenic levels on PND 35 and dimethylarsinic acid (DMA) levels on PND 1 were significantly higher in iAsIII exposed mice than those in iAsV exposed mice. In the brain, iAs levels increased significantly on PND 21, but those declined sharply on PND 35 in either iAsIII or iAsV exposed mice, however the mean difference between the two exposure groups was not significant; whereas DMA levels in iAsIII exposed mice were significantly higher than those in iAsV exposed mice on both PND 1 and 35. In conclusion, findings from this study suggested that iAsIII was preferentially accumulated into liver, and expected to result in more efficient methylation capacity than iAsV; either iAsV or iAsIII might be accumulated in the brain readily, when immature blood brain barrier can not limit it into brain. Hence, exposure to either iAsV or iAsIII at the early life may increase the risk of iAs exposure in the brain. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 797–803, 2014.
Enzymatic production and in situ separation of natural β-ionone from β-carotene
Authors: Nacke Christoph , Hüttmann Sonja , Etschmann Maria M W , Schrader Jens
Published: August 2012

A biotechnological process concept for generation and in situ separation of natural β-ionone from β-carotene is presented. The process employs carotenoid cleavage dioxygenases (CCDs), a plant-derived iron-containing nonheme enzyme family requiring only dissolved oxygen as cosubstrate and no additional cofactors. Organophilic pervaporation was found to be very well suited for continuous in situ separation of β-ionone. Its application led to a highly pure product despite the complexity of the reaction solution containing cell homogenates. Among three different pervaporation membrane types tested, a polyoctylmethylsiloxane active layer on a porous polyetherimide support led to the best results. A laboratory-scale demonstration plant was set up, and a highly pure aqueous–ethanolic solution of β-ionone was produced from β-carotene. The described process permits generation of high-value flavor and fragrance compounds bearing the desired label “natural” according to US and European food and safety regulations and demonstrates the potential of CCD enzymes for selective oxidative cleavage of carotenoids.
A Micro-Level Event-Centered Approach to Investigating Armed Conflict and Population Responses
Authors: Williams Nathalie E. , Ghimire Dirgha J. , Axinn William G. , Jennings Elyse A. , Pradhan Meeta S.
Published: August 2012

In this article, we construct and test a micro-level event-centered approach to the study of armed conflict and behavioral responses in the general population. Event-centered approaches have been successfully used in the macro-political study of armed conflict but have not yet been adopted in micro-behavioral studies. The micro-level event-centered approach that we advocate here includes decomposition of a conflict into discrete political and violent events, examination of the mechanisms through which they affect behavior, and consideration of differential risks within the population. We focus on two mechanisms: instability and threat of harm. We test this approach empirically in the context of the recent decade-long armed conflict in Nepal, using detailed measurements of conflict-related events and a longitudinal study of first migration, first marriage, and first contraceptive use. Results demonstrate that different conflict-related events independently shaped migration, marriage, and childbearing and that they can simultaneously influence behaviors in opposing directions. We find that violent events increased migration, but political events slowed migration. Both violent and political events increased marriage and contraceptive use net of migration. Overall, this micro-level event-centered approach yields a significant advance for the study of how armed conflict affects civilian behavioral responses.
Ukraine’s ‘muddling through’: National identity and postcommunist transition
Authors: Riabchuk Mykola
Published: August 2012

The paper argues that the profoundidentity split strongly influencesUkraine’s postcommunist development, precluding effectively consolidation of any political system – either democratic or authoritarian. In most cases, the identity issue supersedes all other issues on the agendas of political parties and largely determines the character and results of electoral rivalry, and the way in which both domestic and international politics is viewed and articulated. The paper examines historical roots of competing identities in Ukraine, their essence and impact on two different visions of Ukrainian past, future, and “Ukrainianness” itself. The use and misuse of identity issues by Ukrainian authorities is a special concern of the paper that stresses the need of alternative policy aimed at a national reconciliation.
Making a Difference: Political Efficacy and Policy Preference Construction
Authors: Sulitzeanu-Kenan Raanan , Halperin Eran
Published: August 2012

How does individual political efficacy affect the construction of policy preferences? This article presents a model of individual-level politicization of policy preference, which draws on psychological and political explanations and posits that greater external political efficacy results in a stronger effect of political ideology on concrete policy preference. Two empirical studies that test this hypothesis are reported: an original survey experiment conducted in Israel, and an analysis that relies on the 2002 wave of the European Social Survey. The empirical findings support the hypothesis. In contrast to the established conviction that no association exists between political efficacy and policy preferences, these findings reveal that external political efficacy has a polarizing effect on expressed policy preferences.
Endoscopic resection of malignant sinonasal tumours with or without chemotherapy and radiotherapy
Authors: Tojima I , Ogawa T , Kouzaki H , Seno S , Shibayama M , Shimizu T
Published: August 2012

Objective:

An increasing number of transnasal endoscopic surgical procedures are being performed, and these procedures are now also utilised in the management of malignant sinonasal tumours. This study aimed to evaluate the outcome of endoscopic resection of sinonasal malignancies, with or without chemotherapy and radiotherapy.

Methods:

Between 2000 and 2009, six patients with sinonasal malignancies (diagnosed on pre-operative biopsy) underwent endoscopic resection at our hospital. The histopathological diagnoses varied and included squamous cell carcinoma, olfactory neuroblastoma, chordoma, extramedullary plasmacytoma and haemangiopericytoma.

Results:

Surgical resection was combined with chemotherapy and/or radiotherapy in four cases. The mean follow-up period was 43 months. One patient suffered local recurrence of chordoma, 84 months after the first operation, but this was successfully treated with proton beam radiotherapy.

Conclusion:

These results suggest that endoscopic resection may be a valid alternative to conventional resection in selected cases of malignant sinonasal tumour.
The gut endocrine system as a coordinator of postprandial nutrient homoeostasis
Authors: Gribble Fiona M.
Published: August 2012

Hormones from the gastrointestinal (GI) tract are released following food ingestion and trigger a range of physiological responses including the coordination of appetite and glucose homoeostasis. The aim of this review is to discuss the pathways by which food ingestion triggers secretion of cholecystokinin (CCK), glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) and the altered patterns of gut hormone release observed following gastric bypass surgery. Our understanding of how ingested nutrients trigger secretion of these gut hormones has increased dramatically, as a result of physiological studies in human subjects and animal models andin vitrostudies on cell lines and primary intestinal cultures. Specialised enteroendocrine cells located within the gut epithelium are capable of directly detecting a range of nutrient stimuli through a range of receptors and transporters. It is concluded that the arrival of nutrients at the apical surface of enteroendocrine cells is a major stimulus for gut hormone release, thereby coupling these endocrine signals to the arrival of absorbed nutrients in the bloodstream.
Non-persistence of resonant caustics in perturbed elliptic billiards
Authors: PINTO-DE-CARVALHO SÔNIA , RAMÍREZ-ROS RAFAEL
Published: August 2012

A caustic of a billiard table is a curve such that any billiard trajectory, once tangent to the curve, stays tangent after every reflection at the boundary. When the billiard table is an ellipse, any non-singular billiard trajectory has a caustic, which can be either a confocal ellipse or a confocal hyperbola. Resonant caustics—those whose tangent trajectories are closed polygons—are destroyed under generic perturbations of the billiard table. We prove that none of the resonant elliptical caustics persists under a large class of explicit perturbations of the original ellipse. This result follows from a standard Melnikov argument and the analysis of the complex singularities of certain elliptic functions.
TheShigellahuman challenge model
Authors: PORTER C. K. , THURA N. , RANALLO R. T. , RIDDLE M. S.
Published: August 2012

Shigellais an important bacterial cause of infectious diarrhoea globally. TheShigellahuman challenge model has been used since 1946 for a variety of objectives including understanding disease pathogenesis, human immune responses and allowing for an early assessment of vaccine efficacy. A systematic review of the literature regarding experimental shigellosis in human subjects was conducted. Summative estimates were calculated by strain and dose. While a total of 19 studies evaluating nine strains at doses ranging from 10 to 1 × 1010colony-forming units were identified, most studies utilized theS. sonneistrain 53G and theS. flexneristrain 2457T. Inoculum solution and pre-inoculation buffering has varied over time although diarrhoea attack rates do not appear to increase above 75–80%, and dysentery rates remain fairly constant, highlighting the need for additional dose-ranging studies. Expansion of the model to include additional strains from different serotypes will elucidate serotype and strain-specific outcome variability.
Peers and Teachers as Facilitators of the Life Skills Program IPSY
Authors: Weichold Karina , Silbereisen Rainer K.
Published: August 2012

Aims: This pilot study investigated the feasibility and effectiveness of the Life Skills program IPSY (Information + Psychosocial Competence = Protection) with regard to alcohol and cigarette consumption, expectations of regular use, and resistance skills in early adolescence. Thereby, we were particularly interested in the usefulness of peer educators and teachers as program facilitators in the German school setting. Methods: The design included a longitudinal assessment of a peer-led and teacher-led condition with a control group (pre- and post-assessment with a 2-year follow up; classroom-wise randomization, N = 105, T1 10 yrs. old). Results: Results of a series of ANOVAs with repeated measurement indicated that although IPSY facilitated by older peers was highly accepted by the recipients, it was ineffective regarding expectations to regular smoking, and resistance skills towards the offer of cigarettes, and it revealed negative effects on some of the students’ outcomes (in particular regarding alcohol use). In contrast, the same program facilitated by teachers had positive effects on substance use and resistance skills. Conclusions: The discussion focuses on peers’ characteristics (e. g., experiences in leading a classroom, or own consumption patterns) that might have caused the unexpected findings. This implies that, for target groups in early adolescence, in order to avoid negative outcomes, peer facilitators for universal prevention programs have to be selected and trained with great care.
Simple transfer functions for calculating benthic fixed nitrogen losses and C:N:P regeneration ratios in global biogeochemical models
Authors: Bohlen Lisa , Dale Andrew W. , Wallmann Klaus
Published: August 2012

Empirical transfer functions are derived for predicting the total benthic nitrate loss (LNO3) and the net loss of dissolved inorganic nitrogen (LDIN) in marine sediments, equivalent to sedimentary denitrification. The functions are dynamic vertically integrated sediment models which require the rain rate of particulate organic carbon to the seafloor (RRPOC) and a proposed new variable (O2‐NO3)bw (bottom water O2 concentration minus NO3− concentration) as the only input parameters. Applied globally to maps of RRPOC and (O2‐NO3)bw on a 1° × 1° spatial resolution, the models predict a NO3− drawdown of 196 Tg yr−1 (LNO3) of which 153 – 155 Tg yr−1 is denitrified to N2 (LDIN). This is in good agreement with previous estimates using very different methods. Our approach implicitly accounts for fixed N loss via anammox, such that our findings do not support the idea that the relatively recent discovery of anammox in marine sediments might require current estimates of the global benthic marine N budget to be revised. The continental shelf (0 – 200 m) accounts for >50% of global LNO3 and LDIN, with slope (200 – 2000 m) and deep‐sea (>2000 m) sediments contributing ca. 30% and 20%, respectively. Denitrification in high‐nitrate/low‐oxygen regions such as oxygen minimum zones is significant (ca. 15 Tg N yr−1; 10% of global) despite covering only ∼1% of the seafloor. The data are used to estimate the net fluxes of nitrate (18 Tg N yr−1) and phosphate (27 Tg P yr−1) across the sediment‐water interface. The benthic fluxes strongly deviate from Redfield composition, with globally averaged N:P, N:C and C:P values of 8.3, 0.067 and 122, respectively, indicating world‐wide fixed N losses (by denitrification) relative to C and P. The transfer functions are designed to be coupled dynamically to general circulation models to better predict the feedback of sediments on pelagic nutrient cycling and dissolved O2 distributions.
Cooperative institutions for sustainable common pool resource management: Application to groundwater
Authors: Madani Kaveh , Dinar Ariel
Published: August 2012

Beneficiaries of common pool resources (CPRs) may select available noncooperative and regulatory exogenous institutions for managing the resource, as well as cooperative management institutions. All these institutions may increase the long‐term gains, prolong the life of the resource, and help to escape the tragedy of the commons trap. Cooperative game theory approaches can serve as the backbone of cooperative CPR management institutions. This paper formulates and applies several commonly used cooperative game theoretic solution concepts, namely, the core, Nash‐Harsanyi, Shapley, and nucleolus. Through a numerical groundwater example, we show how CPR users can share the gains obtained from cooperation in a fair and efficient manner based on these cooperative solution concepts (management institutions). Although, based on their fairness rationales, various cooperative management institutions may suggest different allocations that are potentially acceptable to the users, these allocation solutions may not be stable as some users may find them unfair. This paper discusses how different methods, such as application of the plurality rule and power index, stability index, and propensity to disrupt concepts, can help identify the most stable and likely solutions for enforcing cooperation among the CPR beneficiaries. Furthermore, how the noncooperative managerial characteristics of the CPR users can affect the stability and acceptability of the different cooperative CPR management institutions is discussed, providing valuable policy insights for cooperative CPR management at community levels.
Cross‐regional prediction of long‐term trajectory of stream water DOC response to climate change
Authors: Laudon Hjalmar , Buttle Jim , Carey Sean K. , McDonnell Jeff , McGuire Kevin , Seibert Jan , Shanley Jamie , Soulsby Chris , Tetzlaff Doerthe
Published: August 2012

There is no scientific consensus about how dissolved organic carbon (DOC) in surface waters is regulated. Here we combine recent literature data from 49 catchments with detailed stream and catchment process information from nine well established research catchments at mid‐ to high latitudes to examine the question of how climate controls stream water DOC. We show for the first time that mean annual temperature (MAT) in the range from −3° to +10° C has a strong control over the regional stream water DOC concentration in catchments, with highest concentrations in areas ranging between 0° and +3° C MAT. Although relatively large deviations from this model occur for individual streams, catchment topography appears to explain much of this divergence. These findings suggest that the long‐term trajectory of stream water DOC response to climate change may be more predictable than previously thought.
Evidence of formation of submicrometer water‐soluble organic aerosols at a deciduous forest site in northern Japan in summer
Authors: Miyazaki Yuzo , Jung Jinsang , Fu Pingqing , Mizoguchi Yasuko , Yamanoi Katsumi , Kawamura Kimitaka
Published: August 2012

Semicontinuous measurements of submicrometer water‐soluble organic aerosols and particle size distributions were conducted at a deciduous forest site in northern Japan in August 2010. Increases in particle number concentration were frequently observed in daytime, accompanied by an increase in the concentrations of water‐soluble organic carbon (WSOC). We found that daily averaged WSOC concentrations positively correlated with gross primary production of CO2 by the forest ecosystem (r2 = 0.63) and ambient temperature during daytime. These relations suggest that the formation of WSOC is closely linked to photosynthetic activity by the forest ecosystem, which depends on both temperature and solar radiation. Off‐line chemical analysis of samples of particles with aerodynamic diameter smaller than 1 μm collected during a 2 day event of elevated WSOC levels suggests that photochemical aging of both α‐ andβ‐pinene and isoprene oxidation products contributes to the particle growth and the WSOC mass. Organic tracers of primary biological aerosol particles (PBAPs) showed distinct diurnal variations with a maximum around noontime, also indicating that higher temperature and light intensity induce emissions of PBAPs. However, their contribution to the submicrometer WSOC mass was likely insignificant. During the day, the concentrations of 3‐methyl‐1,2,3‐butanetricarboxylic acid (3‐MBTCA) showed a strong dependence on temperature, and the ratios of WSOC to particle volume concentration increased with an increase in the concentration ratios of 3‐MBTCA to pinonic acid (PA). This result supports a previous proposal that the 3‐MBTCA/PA ratios in submicrometer particles can be a useful tracer for chemical aging of biogenic secondary organic aerosol from forest vegetation.
JET divertor diagnostic upgrade for neutral gas analysis
Authors: Kruezi Uron , Sergienko G. , Morgan P. D. , Matthews G. F. , Brezinsek S. , Vartanian S. ,   JET-EFDA Contributors
Published: August 2012

With installation of the ITER-like wall in JET a major diagnostic upgrade to measure the neutral gas pressure and composition in the sub-divertor region has been completed, to characterise retention and outgassing of the new metallic first wall. The upgrade includes two new magnetically shielded systems consisting of sensitive capacitance manometers and residual gas analysers, both capable of providing data during plasma operation. These enable absolute pressure and gas composition measurements (pressure range: 10−5–10−1 mbar, mass range: 1–200 amu, respectively) and have been used to characterise the neutral gas behaviour under various plasma conditions.
Film thickness and grating depth variation in organic second-order distributed feedback lasers
Authors: Navarro-Fuster Víctor , Vragovic Igor , Calzado Eva M. , Boj Pedro G. , Quintana José A. , Villalvilla José M. , Retolaza Aritz , Juarros Aritz , Otaduy Deitze , Merino Santos , Díaz-García María A.
Published: August 2012

We report on the preparation and characterization, under optical pump, of second-order one-dimensional distributed feedback (DFB) lasers based on polystyrene films doped with a perylenediimide derivative, as active media. The DFB gratings were engraved on the substrates (SiO2) by thermal nanoimprint lithography, followed by reactive ion etching. Laser emission wavelength was tuned from 554 to 583 nm by changing film thickness (h) between 240 and 1200 nm. The effect on the performance (emission wavelength, threshold, slope efficiency, number of modes, and spectral shape) of varying the grating depth (d) from 30 to 240 nm, for the whole range of h values, has been investigated. Although there is extensive work in the literature aiming to tune the emission wavelength of organic DFB lasers by h variation, the effect of changing d systematically has not been previously studied. Experimental results have been interpreted by models that take into account the presence of the grating by averaging either h or the effective refractive index. Single-mode emission (λ0) was observed for h < 1000 nm, while for thicker films lasing appeared at two different wavelengths (λ0 and λ1). Models indicate that λ0 and λ1 correspond to the TE0 and TE1 waveguide modes, respectively. It was found that d plays an important role in determining the DFB thresholds and slope efficiencies for two h regimes: (i) For h < 350 nm, lowest thresholds and highest slopes efficiencies were obtained with the shallower gratings; and (ii) for h > 1000 nm, d affects significantly the losses associated with the TE1 mode, so single mode emission was achieved at λ0 or at λ1 for deep and shallow gratings, respectively. Finally, the shape of the emission spectra, both below and above threshold, has also been analyzed in order to clarify the physical mechanisms responsible for the existence of gain. Bragg dips were observed in the spectra below threshold only for devices with d/h larger than around 0.3 and their width increased with increasing d/h. In these cases, single-mode DFB emission appeared at the long-wavelength edge of the Bragg dip, indicating that index-coupling modulation contributes significantly to the gain process. On the other hand, for smaller d/h values, Bragg dips became too small to be detected, so gain coupling becomes the dominant mechanism accounting for the presence of gain.
Dark field photoelectron emission microscopy of micron scale few layer graphene
Authors: Barrett N. , Conrad E. , Winkler K. , Krömker B.
Published: August 2012

We demonstrate dark field imaging in photoelectron emission microscopy (PEEM) of heterogeneous few layer graphene (FLG) furnace grown on SiC(000-1). Energy-filtered, threshold PEEM is used to locate distinct zones of FLG graphene. In each region, selected by a field aperture, the k-space information is imaged using appropriate transfer optics. By selecting the photoelectron intensity at a given wave vector and using the inverse transfer optics, dark field PEEM gives a spatial distribution of the angular photoelectron emission. In the results presented here, the wave vector coordinates of the Dirac cones characteristic of commensurate rotations of FLG on SiC(000-1) are selected providing a map of the commensurate rotations across the surface. This special type of contrast is therefore a method to map the spatial distribution of the local band structure and offers a new laboratory tool for the characterisation of technically relevant, microscopically structured matter.
A density functional and quantum Monte Carlo study of glutamic acid in vacuo and in a dielectric continuum medium
Authors: Floris Franca Maria , Filippi Claudia , Amovilli Claudio
Published: August 2012

We present density functional theory (DFT) and quantum Monte Carlo (QMC) calculations of the glutamic acid and glutamate ion in vacuo and in various dielectric continuum media within the polarizable continuum model (PCM). In DFT, we employ the integral equation formalism variant of PCM while, in QMC, we use a PCM scheme we have developed to include both surface and volume polarization. We investigate the gas-phase protonation thermochemistry of the glutamic acid using a large set of structural conformations, and find that QMC is in excellent agreement with the best available theoretical and experimental results. For the solvated glutamic acid and glutamate ion, we perform DFT calculations for dielectric constants, ε, between 4 and 78. We find that the glutamate ion in the zwitterionic form is more stable than the non-zwitterionic form over the whole range of dielectric constants, while the glutamic acid is more stable in its non-zwitterionic form at ε = 4. The dielectric constant at which the two glutamic acid species have the same energy depends on the cavity size and lies between 5 and 12.5. We validate these results with QMC for the two limiting values of the dielectric constant, and find qualitative agreement with DFT even though the solvent polarization is less pronounced at the QMC level.
The internal disruption as hard Magnetohydrodynamic limit of 1/2 sawtooth like activity in large helical device
Authors: Varela J. , Watanabe K. Y. , Ohdachi S.
Published: August 2012

Large helical device (LHD) inward-shifted configurations are unstable to resistive MHD pressure-gradient-driven modes. Sawtooth like activity was observed during LHD operation. The main drivers are the unstable modes 1/2 and 1/3 in the middle and inner plasma region which limit the plasma confinement efficiency of LHD advanced operation scenarios. The aim of the present research is to study the hard MHD limit of 1/2 sawtooth like activity, not observed yet in LHD operation, and to predict its effects on the device performance. Previous investigations pointed out this system relaxation can be an internal disruption [J. Varela et al., “Internal disruptions and sawtooth like activity in LHD,” 38th EPS Conference on Plasma Physics (2011), P5.077]. In the present work, we simulate an internal disruption; we study the equilibria properties before and after the disruptive process, its effects on the plasma confinement efficiency during each disruptive phase, the relation between the n/m = 1/2 hard MHD events and the soft MHD events, and how to avoid or reduce their adverse effects. The simulation conclusions point out that the large stochastic region in the middle plasma strongly deforms and tears the flux surfaces when the pressure gradient increases above the hard MHD limit. If the instability reaches the inner plasma, the iota profiles will be perturbed near the plasma core and three magnetic islands can appear near the magnetic axis. If the instability is strong enough to link the stochastic regions in the middle plasma (around the half minor radius ρ) and the plasma core (ρ<0.25), an internal disruption is driven.
Axial force imparted by a current-free magnetically expanding plasma
Authors: Takahashi Kazunori , Lafleur Trevor , Charles Christine , Alexander Peter , Boswell Rod W.
Published: August 2012

The axial force imparted from a magnetically expanding, current-free, radiofrequency plasma is directly measured. For an argon gas flow rate of 25 sccm and an effective rf input power of ∼800W, a maximum force of ∼6mN is obtained; ∼3mN of which is transmitted via the expanding magnetic field. The measured forces are reasonably compared with a simple fluid model associated with the measured electron pressure. The model suggests that the total force is the sum of an electron pressure inside the source and a Lorentz force due to the electron diamagnetic drift current and the applied radial magnetic field. It is shown that the Lorentz force is greatest near the magnetic nozzle surface where the radial pressure gradient is largest.
Sixty Years Young: The Diverse Biological Activities of Metal Polypyridyl Complexes Pioneered by Francis P. Dwyer
Authors: Kilah Nathan L. , Meggers Eric
Published: August 2012

Sixty years ago, the Australian chemist Francis P. Dwyer pioneered the use of ruthenium polypyridyl complexes as biologically active compounds. These chemically inert and configurationally stable complexes revealed an astonishing range of interesting biological activities, such as the inhibition of the enzyme acetylcholinesterase, anti-cancer activity in vivo, and bacteriostatic/bacteriocidal action. This review commemorates the sixtieth anniversary of Dwyer and co-workers’ landmark 1952 publication, summarises their broader achievements in biological inorganic chemistry, and discusses the contribution of this work to the development of modern biological and medicinal inorganic chemistry.
Weak temporal signals can synchronize and accelerate the transition dynamics of biopolymers under tension
Authors: Kim Won Kyu , Hyeon Changbong , Sung Wokyung
Published: August 2012

In addition to thermal noise, which is essential to promote conformational transitions in biopolymers, the cellular environment is replete with a spectrum of athermal fluctuations that are produced from a plethora of active processes. To understand the effect of athermal noise on biological processes, we studied how a small oscillatory force affects the thermally induced folding and unfolding transition of an RNA hairpin, whose response to constant tension had been investigated extensively in both theory and experiments. Strikingly, our molecular simulations performed under overdamped condition show that even at a high (low) tension that renders the hairpin (un)folding improbable, a weak external oscillatory force at a certain frequency can synchronously enhance the transition dynamics of RNA hairpin and increase the mean transition rate. Furthermore, the RNA dynamics can still discriminate a signal with resonance frequency even when the signal is mixed among other signals with nonresonant frequencies. In fact, our computational demonstration of thermally induced resonance in RNA hairpin dynamics is a direct realization of the phenomena called stochastic resonance and resonant activation. Our study, amenable to experimental tests using optical tweezers, is of great significance to the folding of biopolymers in vivo that are subject to the broad spectrum of cellular noises.
Electric fields yield chaos in microflows
Authors: Posner Jonathan D. , Pérez Carlos L. , Santiago Juan G.
Published: August 2012

We present an investigation of chaotic dynamics of a low Reynolds number electrokinetic flow. Electrokinetic flows arise due to couplings of electric fields and electric double layers. In these flows, applied (steady) electric fields can couple with ionic conductivity gradients outside electric double layers to produce flow instabilities. The threshold of these instabilities is controlled by an electric Rayleigh number,
Ra

e

. As
Ra

e

increases monotonically, we show here flow dynamics can transition from steady state to a time-dependent periodic state and then to an aperiodic, chaotic state. Interestingly, further monotonic increase of
Ra

e

shows a transition back to a well-ordered state, followed by a second transition to a chaotic state. Temporal power spectra and time-delay phase maps of low dimensional attractors graphically depict the sequence between periodic and chaotic states. To our knowledge, this is a unique report of a low Reynolds number flow with such a sequence of periodic-to-aperiodic transitions. Also unique is a report of strange attractors triggered and sustained through electric fluid body forces.
High genetic load in an old isolated butterfly population
Authors: Mattila Anniina L. K. , Duplouy Anne , Kirjokangas Malla , Lehtonen Rainer , Rastas Pasi , Hanski Ilkka
Published: August 2012

We investigated inbreeding depression and genetic load in a small (Ne∼ 100) population of the Glanville fritillary butterfly (Melitaea cinxia), which has been completely isolated on a small island [Pikku Tytärsaari (PT)] in the Baltic Sea for at least 75 y. As a reference, we studied conspecific populations from the well-studied metapopulation in the Åland Islands (ÅL), 400 km away. A large population in Saaremaa, Estonia, was used as a reference for estimating genetic diversity andNe. We investigated 58 traits related to behavior, development, morphology, reproductive performance, and metabolism. The PT population exhibited high genetic load (L =1 −WPT/WÅL) in a range of fitness-related traits including adult weight (L =0.12), flight metabolic rate (L= 0.53), egg viability (L= 0.37), and lifetime production of eggs in an outdoor population cage (L= 0.70). These results imply extensive fixation of deleterious recessive mutations, supported by greatly reduced diversity in microsatellite markers and immediate recovery (heterosis) of egg viability and flight metabolic rate in crosses with other populations. There was no significant inbreeding depression in most traits due to one generation of full-sib mating. Resting metabolic rate was significantly elevated in PT males, which may be related to their short lifespan (L =0.25). The demographic history and the effective size of the PT population place it in the part of the parameter space in which models predict mutation accumulation. This population exemplifies the increasingly common situation in fragmented landscapes, in which small and completely isolated populations are vulnerable to extinction due to high genetic load.
Energy landscape analysis of native folding of the prion protein yields the diffusion constant, transition path time, and rates
Authors: Yu Hao , Gupta Amar Nath , Liu Xia , Neupane Krishna , Brigley Angela M. , Sosova Iveta , Woodside Michael T.
Published: August 2012

Protein folding is described conceptually in terms of diffusion over a configurational free-energy landscape, typically reduced to a one-dimensional profile along a reaction coordinate. In principle, kinetic properties can be predicted directly from the landscape profile using Kramers theory for diffusive barrier crossing, including the folding rates and the transition time for crossing the barrier. Landscape theory has been widely applied to interpret the time scales for protein conformational dynamics, but protein folding rates and transition times have not been calculated directly from experimentally measured free-energy profiles. We characterized the energy landscape for native folding of the prion protein using force spectroscopy, measuring the change in extension of a single protein molecule at high resolution as it unfolded/refolded under tension. Key parameters describing the landscape profile were first recovered from the distributions of unfolding and refolding forces, allowing the diffusion constant for barrier crossing and the transition path time across the barrier to be calculated. The full landscape profile was then reconstructed from force-extension curves, revealing a double-well potential with an extended, partially unfolded transition state. The barrier height and position were consistent with the previous results. Finally, Kramers theory was used to predict the folding rates from the landscape profile, recovering the values observed experimentally both under tension and at zero force in ensemble experiments. These results demonstrate how advances in single-molecule theory and experiment are harnessing the power of landscape formalisms to describe quantitatively the mechanics of folding.
Myosin IC generates power over a range of loads via a new tension-sensing mechanism
Authors: Greenberg Michael J. , Lin Tianming , Goldman Yale E. , Shuman Henry , Ostap E. Michael
Published: August 2012

Myosin IC (myo1c), a widely expressed motor protein that links the actin cytoskeleton to cell membranes, has been associated with numerous cellular processes, including insulin-stimulated transport of GLUT4, mechanosensation in sensory hair cells, endocytosis, transcription of DNA in the nucleus, exocytosis, and membrane trafficking. The molecular role of myo1c in these processes has not been defined, so to better understand myo1c function, we utilized ensemble kinetic and single-molecule techniques to probe myo1c’s biochemical and mechanical properties. Utilizing a myo1c construct containing the motor and regulatory domains, we found the force dependence of the actin-attachment lifetime to have two distinct regimes: a force-independent regime at forces < 1 pN, and a highly force-dependent regime at higher loads. In this force-dependent regime, forces that resist the working stroke increase the actin-attachment lifetime. Unexpectedly, the primary force-sensitive transition is the isomerization that follows ATP binding, not ADP release as in other slow myosins. This force-sensing behavior is unique amongst characterized myosins and clearly demonstrates mechanochemical diversity within the myosin family. Based on these results, we propose that myo1c functions as a slow transporter rather than a tension-sensitive anchor.
An RNA virus hijacks an incognito function of a DNA repair enzyme
Authors: Virgen-Slane Richard , Rozovics Janet M. , Fitzgerald Kerry D. , Ngo Tuan , Chou Wayne , van der Heden van Noort Gerbrand J. , Filippov Dmitri V. , Gershon Paul D. , Semler Bert L.
Published: August 2012

A previously described mammalian cell activity, called VPg unlinkase, specifically cleaves a unique protein–RNA covalent linkage generated during the viral genomic RNA replication steps of a picornavirus infection. For over three decades, the identity of this cellular activity and its normal role in the uninfected cell had remained elusive. Here we report the purification and identification of VPg unlinkase as the DNA repair enzyme, 5′-tyrosyl–DNA phosphodiesterase-2 (TDP2). Our data show that VPg unlinkase activity in different mammalian cell lines correlates with their differential expression of TDP2. Furthermore, we show that recombinant TDP2 can cleave the protein–RNA linkage generated by different picornaviruses without impairing the integrity of viral RNA. Our results reveal a unique RNA repair-like function for TDP2 and suggest an unusual role in host–pathogen interactions for this cellular enzyme. On the basis of the identification of TDP2 as a potential antiviral target, our findings may lead to the development of universal therapeutics to treat the millions of individuals afflicted annually with diseases caused by picornaviruses, including myocarditis, aseptic meningitis, encephalitis, hepatitis, and the common cold.
Species richness and morphological diversity of passerine birds
Authors: Ricklefs Robert E.
Published: August 2012

The relationship between species richness and the occupation of niche space can provide insight into the processes that shape patterns of biodiversity. For example, if species interactions constrained coexistence, one might expect tendencies toward even spacing within niche space and positive relationships between diversity and total niche volume. I use morphological diversity of passerine birds as a proxy for diet, foraging maneuvers, and foraging substrates and examine the morphological space occupied by regional and local passerine avifaunas. Although independently diversified regional faunas exhibit convergent morphology, species are clustered rather than evenly distributed, the volume of the morphological space is weakly related to number of species per taxonomic family, and morphological volume is unrelated to number of species within both regional avifaunas and local assemblages. These results seemingly contradict patterns expected when species interactions constrain regional or local diversity, and they suggest a larger role for diversification, extinction, and dispersal limitation in shaping species richness.
Dual recognition of phosphoserine and phosphotyrosine in histone variant H2A.X by DNA damage response protein MCPH1
Authors: Singh Namit , Basnet Harihar , Wiltshire Timothy D. , Mohammad Duaa H. , Thompson James R. , Héroux Annie , Botuyan Maria Victoria , Yaffe Michael B. , Couch Fergus J. , Rosenfeld Michael G. , Mer Georges
Published: August 2012

Tyr142, the C-terminal amino acid of histone variant H2A.X is phosphorylated by WSTF (Williams-Beuren syndrome transcription factor), a component of the WICH complex (WSTF-ISWI chromatin-remodeling complex), under basal conditions in the cell. In response to DNA double-strand breaks (DSBs), H2A.X is instantaneously phosphorylated at Ser139 by the kinases ATM and ATR and is progressively dephosphorylated at Tyr142 by the Eya1 and Eya3 tyrosine phosphatases, resulting in a temporal switch from a postulated diphosphorylated (pSer139, pTyr142) to monophosphorylated (pSer139) H2A.X state. How mediator proteins interpret these two signals remains a question of fundamental interest. We provide structural, biochemical, and cellular evidence that Microcephalin (MCPH1), an early DNA damage response protein, can read both modifications via its tandem BRCA1 C-terminal (BRCT) domains, thereby emerging as a versatile sensor of H2A.X phosphorylation marks. We show that MCPH1 recruitment to sites of DNA damage is linked to both states of H2A.X.