bluuebunny/crossref_metadata_2025 huggingface dataset:
Transition from concerted to stepwise processes as a function of leaving group ability: density functional theory and experimental study of lyoxide‐promoted cleavages of phosphorothioate and phosphate triesters in water and methanol
Authors: Maxwell Christopher I. , Liu C. Tony , Neverov Alexei A. , Mosey Nicholas J. , Brown Robert Stan
Published: October 2011

The base‐promoted solvolysis of a series of O,O‐dimethyl O‐aryl and O,O‐dimethyl O‐alkyl phosphorothioates (1) as well as O,O‐dimethyl O‐aryl and O,O‐dimethyl O‐alkyl phosphates (2) was studied computationally by density functional theory methods in methanol and water continuum media to determine the transition between concerted and stepwise processes. In addition, an experimental study was undertaken on the solvolysis of these series in basic methanol and water. The computations indicate that the solvolytic mechanism for series 1 involves lyoxide attack anti to the leaving group in a concerted manner with good leaving groups having pKaLg values < 12.3 in methanol and in a stepwise fashion with the formation of a 5‐coordinate thiophosphorane intermediate when the pKaLg > 12.3. A similar transition from concerted to stepwise mechanism occurs with series 2 in methanol as well as with series 1 and 2 in water, although for the aqueous solvolyses with hydroxide nucleophile, the transitions between concerted and stepwise mechanisms occur with better leaving groups than in the case in methanol. The computational data allow the construction of Brønsted plots of log k2−OS versus pKaLg in methanol and water, which are compared with the experimental Brønsted plots determined with these series previously and with new data determined in this work. Both the computational and experimental Brønsted data reveal discontinuities in the plots between substrates bearing O‐aryl and O‐alkyl leaving groups, with the gradients of the plots being far steeper than, and non‐collinear with, the O‐aryl leaving groups for solvolysis of the O‐alkyl‐containing substrates. These discontinuities signify that care should be exercised in interpreting breaks in Brønsted plots in terms of changes in rate‐limiting steps that signify the formation of an intermediate during a solvolytic process. Copyright © 2011 John Wiley & Sons, Ltd.
Three‐step growth method for high quality AlN epilayers
Authors: Nakarmi M. L. , Cai B. , Lin J. Y. , Jiang H. X.
Published: October 2011

We report a three‐step growth method to grow thick and high quality aluminum nitride (AlN) epilayers on sapphire substrates by metal organic chemical vapor deposition (MOCVD). The three‐step growth method begins with a deposition of a thin AlN buffer layer at 950 °C followed by an intermediate AlN (I‐AlN) layer at 1100 °C, and finally a thick AlN epilayer at high temperature around 1325 °C. AlN epilayers grown by this method have smooth surfaces, narrow width of X‐ray rocking curves, and strong band edge photoluminescence (PL) emissions with low impurity emissions. Transmission electron microscopy revealed that most of the threading dislocations are annihilated within 300 nm. Stacking faults are greatly reduced in epilayers grown by this method resulting in very low screw type threading dislocation density. Dominant threading dislocations in the AlN epilayers are edge type originated from misfit dislocations (MD).
Sensing herpes: more than toll
Authors: Melchjorsen Jesper
Published: October 2011

To launch an effective antiviral immune response, cells must recognize the virus, activate a cytokine response, and initiate inflammatory processes. Herpes simplex virus 1 (HSV‐1) and HSV‐2 are nuclear‐replicating viruses composed of a double‐stranded DNA genome plus glycoproteins that are incorporated into a lipid bilayer envelope that surrounds an icosahedral capsid. Several novel receptors that mediate innate recognition of HSV and that activate the innate immune response have been identified in recent years. The host‐virus interactions that lead to type I interferon (IFN), type III IFN, and cytokine production include cellular recognition of viral envelope and structural proteins, recognition of viral genomic DNA and recognition of virus‐derived double‐stranded RNAs. Such RNAs can interact with cellular pattern‐recognition receptors, including Toll‐like receptors and a number of cytoplasmic and nuclear receptors for virus DNA and virus‐derived RNAs. In this review, I present a systematic overview of innate cellular recognition of HSV infection that leads to immune activation, and I discuss the implications of the known cell‐host interactions. In addition, I discuss the use of innate stimulation to improve anti‐HSV treatment and vaccine response and I discuss future research aims. Copyright © 2011 John Wiley & Sons, Ltd.
Measuring the activation energy of thiol desorption using lateral force microscopy
Authors: Liao Yen‐Chih , Sun Huizhong , Weeks Brandon L.
Published: October 2011

Thermal stability of self‐assembled monolayers (SAMs) is important for applications in various surface science applications. As a model material, 16‐mercaptohexadecanoic acid (MHA) on template stripped gold surfaces was investigated to determine the effect of temperature on the change of lateral force signal using atomic force microscopy (AFM). Friction force signals were obtained at various temperatures in order to determine whether it was possible to correlate the friction signal with desorption of the thiol molecule from the surface. Samples were heated for up to 10 h ranging from 40 to 80°C in air and scanned every hour. A kinetic model was introduced to correlate the lateral force signal to the activation energy of desorption of the SAM from gold surface with heating. The activation energy of the detachment using this technique is 25.4 kcal/mol, which is consistent with other more complex techniques. SCANNING 34: 200–205, 2012. © 2011 Wiley Periodicals, Inc.
Two‐Fold Emission From the S‐Shell of PbSe/CdSe Core/Shell Quantum Dots
Authors: Grodzińska Dominika , Evers Wiel H. , Dorland Renee , van Rijssel Jos , van Huis Marijn A. , Meijerink Andries , de Mello Donegá Celso , Vanmaekelbergh Daniel
Published: October 2011

The optical properties of PbSe/CdSe core/shell quantum dots with core sizes smaller than 4 nm in the 5–300 K range are reported. The photoluminescence spectra show two peaks, which become increasingly separated in energy as the core diameter is reduced below 4 nm. It is shown that these peaks are due to intrinsic exciton transitions in each quantum dot, rather than emission from different quantum dot sub‐ensembles. Most likely, the energy separation between the peaks is due to inter‐valley coupling between the L‐points of PbSe. The temperature dependence of the relative intensities of the peaks implies that the two emitting states are not in thermal equilibrium and that dark exciton states must play an important role.
Effects of processing on the structure of PVC/montmorillonite composites. I. Melt and solution processes
Authors: Zheng X. , Gilbert M.
Published: October 2011

The effects of processing conditions on the structure of poly(vinyl chloride) (PVC)/clay composites were investigated. Dry‐blending conditions were shown to affect composite structure in compression‐molded samples. PVC/(Cloisite Na) nanocomposites could not be prepared by melt compounding. Partially exfoliated and intercalated PVC/(Cloisite 30B) nanocomposites could be prepared by melt compounding. The effects of the grain structure of PVC resin and the PVC fusion mechanism on nanocomposite formation were considered. The particulate structure of the PVC resin was found to restrict the distribution ofclay, which could be improved by increasing the processing temperature. Almost fully exfoliated PVC/(Cloisite 30B) nanocomposites were prepared from solutions in tetrahydrofuran, and the plasticizer migration resistance of these composites was substantially improved. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers
Morphologic evidence of diffuse vascular damage in human and in the experimental model of ethylmalonic encephalopathy
Authors: Giordano Carla , Viscomi Carlo , Orlandi Maurizia , Papoff Paola , Spalice Alberto , Burlina Alberto , Di Meo Ivano , Tiranti Valeria , Leuzzi Vincenzo , d'Amati Giulia , Zeviani Massimo
Published: October 2011

Ethylmalonic encephalopathy (EE) is a rare autosomal recessive disorder characterized by early onset encephalopathy, chronic diarrhoea, petechiae, orthostatic acrocyanosis and defective cytochrome c oxidase (COX) in muscle and brain. High levels of lactic, ethylmalonic and methylsuccinic acids are detected in body fluids. EE is caused by mutations in ETHE1, a mitochondrial sulphur dioxygenase. By studying a suitable mouse model, we found that loss of ETHE1 leads to accumulation of sulphide, which is a poison for COX and other enzymatic activities thus accounting for the main features of EE. We report here the first autopsy case of a child with a genetically confirmed diagnosis of EE, and compare the histological, histochemical and immunohistochemical findings with those of the constitutive Ethe1−/− mice. In addition to COX depleted cells, widespread endothelial lesions of arterioles and capillaries of the brain and gastrointestinal tract were the pathologic hallmarks in both organisms. Our findings of diffuse vascular damage of target critical organs are in keeping with the hypothesis that the pathologic effects of ETHE1 deficiency may stem from high levels of circulating hydrogen sulphide rather than the inability of specific organs to detoxify its endogenous production.
7000 years of paleostorm activity in the NW Mediterranean Sea in response to Holocene climate events
Authors: Sabatier Pierre , Dezileau Laurent , Colin Christophe , Briqueu Louis , Bouchette Frédéric , Martinez Philippe , Siani Giuseppe , Raynal Olivier , Von Grafenstein Ulrich
Published: October 2011

A high-resolution record of paleostorm events along the French Mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the Gulf of Lions. Integrating grain size, faunal analysis, clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating, we recorded seven periods of increased storm activity at 6300–6100, 5650–5400, 4400–4050, 3650–3200, 2800–2600, 1950–1400 and 400–50 cal yr BP (in the Little Ice Age). In contrast, our results show that the Medieval Climate Anomaly (1150–650 cal yr BP) was characterised by low storm activity.

The evidence for high storm activity in the NW Mediterranean Sea is in agreement with the changes in coastal hydrodynamics observed over the Eastern North Atlantic and seems to correspond to Holocene cooling in the North Atlantic. Periods of low SSTs there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies. We hypothesise that the increase in storm activity during Holocene cold events over the North Atlantic and Mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large Central Atlantic-European domain.
Turbulence in supersonic boundary layers at moderate Reynolds number
Authors: Pirozzoli Sergio , Bernardini Matteo
Published: October 2011

We study the organization of turbulence in supersonic boundary layers through large-scale direct numerical simulations (DNS) at${M}_{\infty } = 2$, and momentum-thickness Reynolds number up to${\mathit{Re}}_{{\delta }_{2} } \approx 3900$(corresponding to${\mathit{Re}}_{\tau } \approx 1120$) which significantly extend the current envelope of DNS in the supersonic regime. The numerical strategy relies on high-order, non-dissipative discretization of the convective terms in the Navier–Stokes equations, and it implements a recycling/rescaling strategy to stimulate the inflow turbulence. Comparison of the velocity statistics up to fourth order shows nearly exact agreement with reference incompressible data, provided the momentum-thickness Reynolds number is matched, and provided the mean velocity and the velocity fluctuations are scaled to incorporate the effects of mean density variation, as postulated by Morkovin’s hypothesis. As also found in the incompressible regime, we observe quite a different behaviour of the second-order flow statistics at sufficiently large Reynolds number, most of which show the onset of a range with logarithmic variation, typical of ‘attached’ variables, whereas the wall-normal velocity exhibits a plateau away from the wall, which is typical of ‘detached’ variables. The modifications of the structure of the flow field that underlie this change of behaviour are highlighted through visualizations of the velocity and temperature fields, which substantiate the formation of large jet-like and wake-like motions in the outer part of the boundary layer. It is found that the typical size of the attached eddies roughly scales with the local mean velocity gradient, rather than being proportional to the wall distance, as happens for the wall-detached variables. The interactions of the large eddies in the outer layer with the near-wall region are quantified through a two-point amplitude modulation covariance, which characterizes the modulating action of energetic outer-layer eddies.
Intentional Normativism Meets Normative Supervenience and the Because Constraint
Authors: Laurier Daniel
Published: October 2011

ABSTRACT: I explain and rebut four objections to the claim that attributions of intentional attitudes are normative judgments, all stemming, directly or indirectly, from the widespread assumption that the normative supervenes on the non-normative.
Moraliser les conventions
Authors: Dubreuil Benoit
Published: October 2011

Résumé : De nombreux philosophes et psychologues considèrent que les normes morales et les conventions sont des règles de nature différente : alors que nous sommes obligés de respecter les normes morales pour elles-mêmes, notre respect des conventions dépend de notre attitude par rapport à un contexte social particulier. Je conteste cette distinction entre normes morales et conventions. Je soutiens que les conventions dépendent du contexte social parce que le contexte structure les attentes des agents, fixe des points de référence en matière de gains et de pertes et permet à l’observateur d’inférer la présence et la gravité des torts.
How to Be an Epistemic Value Pluralist
Authors: Matheson David
Published: October 2011

ABSTRACT: In this paper I defend an epistemic value pluralism according to which true belief, justified belief, and knowledge are all fundamental epistemic values. After laying out reasons to reject epistemic value monism in its central forms, I present my pluralist alternative and show how it can adequately explain the greater epistemic value of knowledge over both true belief and justified belief, despite their fundamentality. I conclude with a sketch of how this pluralism might be generalized beyond the epistemic domain to the ethical.
Conventional Norms of Reasoning
Authors: Morton Adam
Published: October 2011

ABSTRACT: There are conventional norms of reasoning. That is, we have conventions about which patterns of reasoning weencourageordisapprove of.
Benthic macrofauna associated with decomposition of leaves in a mangrove forest in Ilhéus, State of Bahia, Brazil
Authors: de Oliveira Alexandra Bomfim , Rizzo Alexandra Elaine , da Conceição Erminda , Couto Guerreiro
Published: October 2011

We identified and quantified the benthic macrofauna associated with decomposing leaves of Rhizophora mangle and Laguncularia racemosa, to observe the differences in the abundance and composition of macrofauna between these mangrove species, and to examine whether the abundance and composition of organisms changed with different stations and collection times. Benthic macrofauna, mainly polychaetes and amphipods, were recorded from the fifth day after the installation of the experiment. Annelids including Oligochaeta and Polychaeta were the most numerous group. Crustacea were represented by peracarids (Amphipoda and Tanaidacea) and decapods. Of Hexapoda, only juvenile forms and pupae were present. The most abundant polychaete species was Perinereis brevicirrata, followed by Capitella cf. capitata, Heteromastus filiformis and Neanthes succinea. In one-way analysis of variance (ANOVA) there were no statistical differences between the macrofauna of mangrove species, seasons, or collection times, except among collection times for R. mangle litter bags. Two-way ANOVA showed homogeneity for macrofauna abundance between the groups of collection times for both mangrove species. The richness was similar for R. mangle litter bags, and showed a significant difference for L. racemosa. Abundance and richness were also similar between the mangrove species. The colonization of detritus by benthic invertebrates followed a successional sequence during the decomposition process. This suggests that the density of these organisms and their foraging behaviour affected the decomposition rates of leaves of R. mangle and L. racemosa.
Harpacticoid copepod colonization of coral fragments in a tropical reef lagoon (Zanzibar, Tanzania)
Authors: Callens M. , Gheerardyn H. , Ndaro S.G.M. , De Troch M. , Vanreusel A.
Published: October 2011

Colonization experiments were conducted in a tropical lagoon (Zanzibar Island, off the coast of Tanzania) to investigate the temporal dynamics and mode of colonization of the harpacticoid copepods community on dead coral fragments. There was fast colonization of the coral fragments attaining a substantial diversity after only two days. The ability to colonize dead coral fragments is thought to be related to the morphology and life style of different harpacticoid species. Phytal taxa (e.g. Tisbidae) were fast colonizers, reaching high abundances during the initial colonization phase. Sediment-associated and eurytopic taxa (e.g. Ameiridae, Miraciidae and Ectinosomatidae) showed lower colonization rates and became the dominant group during the later colonization phase. Most species are able to colonize the coral fragments through the water column. However, colonization along the substrate surface is also considered to be an important colonization mode, especially for sediment-associated taxa, which showed lower colonization rates when migration through the sediment was hindered.
Effects of trawling on fish and invertebrates from deep-sea coral facies of Isidella elongata in the western Mediterranean
Authors: Maynou Francesc , Cartes Joan E.
Published: October 2011

Deep-water corals are known to provide essential habitat for fish and invertebrates along the continental slope in different areas of the world, offering prey to coral predators, protection or attachment substrate to other suspension feeders. In the Mediterranean Sea the coral Isidella elongata (Esper, 1788) characterizes a facies of bathyal compact mud substrates between 500 and 1200 m depth. Based on 4 experimental surveys carried out between 1985 and 2008, we obtained quantitative data on the fauna associated with live coral stands. We show that species richness of invertebrates and crustaceans, as well as abundance and biomass of crustaceans, is higher in areas with large stands of the coral. Some commercial fishery species are also more abundant or reach larger sizes in areas with high density of the coral, particularly the red shrimps Aristeus antennatus (Risso, 1816) and Plesionika martia (A. Milne Edwards, 1883). Trawling over I. elongata facies causes direct impacts on the biological assemblages by removing the habitat-forming corals, decreasing invertebrate species diversity and negatively affecting fisheries production in the long term.
The burden of self-reported acute gastrointestinal illness in Italy: a retrospective survey, 2008–2009
Authors: SCAVIA G. , BALDINELLI F. , BUSANI L. , CAPRIOLI A.
Published: October 2011

A retrospective telephone survey (n=3490) was conducted in Italy between 2008 and 2009 to estimate the occurrence of self-reported acute gastrointestinal illness (AGI) and to describe subjects' recourse to healthcare, using a symptom-based case definition. Three hundred and ten AGI cases were identified. The annual incidence rate was 1·08 episodes/person-year (95% confidence interval 0·90–1·14). The proportion of subjects consulting physicians was 39·5% while only 0·3% submitted a specimen for laboratory investigation. Risk factors for AGI and medical care-seeking were identified using logistic regression analysis. Females, children and young adults had a significantly higher incidence rate of AGI. Factors associated with medical care-seeking were age <10 years, presence of fever, diarrhoea, and duration of illness >3 days. Our results provide a relevant contribution towards estimating the global burden of AGI using standard methods that ensure a good level of comparability with other studies.
Seroprevalence, correlates and trends of Helicobacter pylori infection in the Israeli population
Authors: MUHSEN K. , COHEN D. , SPUNGIN-BIALIK A. , SHOHAT T.
Published: October 2011

We examined the prevalence, correlates and trends of H. pylori infection in Israel using residual sera obtained in 2007–2008 from 1466 Jewish subjects aged 0–77 years and 897 Arabs aged 0–19 years, and in 2000–2001 from 627 Jewish and 575 Arab subjects aged 0–19 years. H. pylori IgG antibodies were measured by ELISA. The age-adjusted H. pylori seroprevalence was 45·2% in Jewish participants. Seropositivity increased with age, reaching 60% at age ⩾50 years and ranged from 24·3% in subjects originating from North America/Western Europe/Australia, to 63·2% in those from Asia/Africa/South America. Among Arabs, H. pylori seroprevalence was 42·1% and reached 65% in adolescents. There was no significant change in seroprevalence between 2000–2001 and 2007–2008. High prevalence of H. pylori was found in Arabs, and in Jews originating from countries of high H. pylori endemicity. These findings are characteristic of countries of diverse ethnic structure and recent immigration.
Childhood adversity and allostatic overload of the hypothalamic–pituitary–adrenal axis: A vulnerability model for depressive disorders
Authors: Wilkinson Paul O. , Goodyer Ian M.
Published: October 2011

Childhood adversity is associated with increased risk for onset of depressive episodes. This review will present evidence that allostatic overload of the hypothalamic–pituitary–adrenal axis (HPAA) partially mediates this association. The HPAA is the physiological system that regulates levels of the stress hormone cortisol. First, data from animals and humans has shown that early environmental adversity is associated with long-term dysregulation of the HPAA. This may occur due to permanent epigenetic modification of the glucocorticoid receptor. Second, data from humans has demonstrated that HPAA dysregulation is associated with increased risk of future depression onset in healthy individuals, and pharmacological correction of HPAA dysregulation reduces depressive symptoms. HPAA dysregulation may result in corticoid-mediated abnormalities in neurogenesis in early life and/or neurotoxicity on neural systems that subserve emotion and cognition.
Allostatic and environmental load in toddlers predicts anxiety in preschool and kindergarten
Authors: Buss Kristin A. , Davis Elizabeth L. , Kiel Elizabeth J.
Published: October 2011

Psychobiological models of allostatic load have delineated the effects of multiple processes that contribute to risk for psychopathology. This approach has been fruitful, but the interactive contributions of allostatic and environmental load remain understudied in early childhood. Because this developmental period encompasses the emergence of internalizing problems and biological sensitivity to early experiences, this is an important time to examine this process. In two studies, we examined allostatic and environmental load and links to subsequent internalizing and externalizing problems. Study 1 examined relations between load indices and maladjustment, concurrently and at multiple times between age 2 and kindergarten; Study 2 added more comprehensive risk indices in a sample following a group of highly fearful toddlers from 2 to 3 years of age. Results from both studies showed that increased allostatic load related to internalizing problems as environmental risk also increased. Study 2, in addition, showed that fearfulness interacted with allostatic and environmental load indices to predict greater anxiety among the fearful children who had high levels of allostatic and environmental load. Taken together, the findings support a model of risk for internalizing characterized by the interaction of biological and environmental stressors, and demonstrate the importance of considering individual differences and environmental context in applying models of allostatic load to developmental change in early childhood.
Allostasis and the development of internalizing and externalizing problems: Changing relations with physiological systems across adolescence
Authors: Hastings Paul D. , Shirtcliff Elizabeth A. , Klimes-Dougan Bonnie , Allison Amber L. , Derose Laura , Kendziora Kimberley T. , Usher Barbara A. , Zahn-Waxler Carolyn
Published: October 2011

Allostasis, or the maintenance of stability through physiological change, refers to the process by which individuals adjust to the continually changing demands that are put upon somatic activity by salient events. Bauer and colleagues proposed that allostasis could be detected through patterns of the joint reactivity of the autonomic nervous system (ANS) and hypothalamic–pituitary–adrenal (HPA) axis system under stressful conditions. We examined the associations between ANS and HPA reactivity and the development of externalizing and internalizing problems over 2 years in a sample of 215 adolescents. The interactions of ANS and HPA reactivity were contemporaneously associated with, and longitudinally predictive of, adolescents' emotional and behavioral problems. Adolescents with symmetrical high reactivity across systems had more internalizing and fewer externalizing problems initially. Over time, both symmetrical and asymmetrical reactivity predicted increasing internalizing problems in girls, depending on the measure of ANS activity that was examined, heart rate, or blood pressure reactivity. Implications for the understanding of allostasis and the dynamic nature of the relations between multiple physiological regulatory systems and adolescents' developing psychopathology are discussed.
Developing and applying a socio-ecological model to the promotion of healthy eating in the school
Authors: Townsend Nick , Foster Charlie
Published: October 2011

Objective

To develop and apply a socio-ecological model (SEM) for healthy eating in school students, to better understand the association between factors at different levels of the SEM and pupils’ dietary choices.

Design

Student-level data, collected through anonymised questionnaires, included reported dietary choices and correlates to these; data on school approaches to food were collected through postal surveys. We used multilevel analysis to study the association of each level of the SEM on student dietary choice while controlling for factors found at other levels.

Setting

Data were collected from secondary schools in Wales that were a part of the 2005/2006 Health Behaviour in School-aged Children (HBSC) study.

Subjects

The final sample for analysis included data from 6693 students aged 11–16 years and 289 teachers from sixty-four secondary schools in Wales.

Results

Student interpersonal factors, an individual's social environment, had a greater association with the dietary choices students made for lunch than student intrapersonal characteristics, those that reside within the person, which were found to have a greater association with the dietary choices made outside school. School organisational factors, such as rules and policies, had a greater association with whether students ate unhealthy foods, whereas the community nature of the school had a greater association with the choosing of healthy foods.

Conclusions

Using the SEM and multilevel analysis allowed us to study how factors were associated with the choice of different foods at different times of the day by students. Interventions can use an SEM to target specific correlates and change health outcomes in the school.
How much does the Supplemental Nutrition Assistance Program alleviate food insecurity? Evidence from recent programme leavers
Authors: Nord Mark
Published: October 2011

Objective

To estimate the effect of the US Supplemental Nutrition Assistance Program (SNAP) on the food security (consistent access to adequate food) of recipients, net of the effect of the self-selection of more food-needy households into the programme.

Design

The food security of current SNAP recipients and recent leavers is compared in cross-sectional survey data, adjusting for economic and demographic differences using multivariate logistic regression methods. A similar analysis in 2-year longitudinal panels provides additional control for selection on unobserved variables based on food security status in the previous year.

Setting

Household survey data collected for the US Department of Agriculture by the US Census Bureau.

Subjects

Households interviewed in the Current Population Survey Food Security Supplements from 2001 to 2009.

Results

The odds of very low food security among households that continued on SNAP through the end of a survey year were 28 % lower than among those that left SNAP prior to the 30-d period during which food security was assessed. In 2-year panels with controls for the severity of food insecurity in the previous year, the difference in odds was 45 %.

Conclusions

The results are consistent with, or somewhat higher than, the estimates from the strongest previous research designs and suggest that the ameliorative effect of SNAP on very low food security is in the range of 20–50 %.
Synthesis of randomness in the radiated fields of antenna array
Authors: Malik Praveen Kumar , Parthasarthy Harish
Published: October 2011

An alternative approach is based on statistically computed signal analysis technique for the design of antenna array exhibiting lower side lobes in their radiation pattern. New and generalized expressions for the array factor of all physically realizable linear antenna arrays are introduced. An algorithm based on the statistically computed signal analysis is designed. By considering the random elements, distance between the sensors, their mean, variance, average amplitude pattern and correlation of the amplitude between the two angles, some mathematical formulations have been done and shown with the help of MATLAB. Based on these generalized expressions, a new way of synthesizing arrays with reduced side lobes is available. It applies to end fire antenna array, which may have either even or odd numbers of sensors with restricted elements spacing. Final expressions shown are a clear relationship between elements excitation and null location in the radiation patterns.
Production and fate of transparent exopolymer particles in the ocean
Authors: Wurl Oliver , Miller Lisa , Vagle Svein
Published: October 2011

The production and fate of transparent exopolymer particles (TEP) have been investigated in various oceanic regions (tropical, temperate, and polar), from the sea surface microlayer (SML) to the deep ocean. Accumulation of TEP within the mixed layer was observed even in the absence of phytoplankton blooms, indicating abiotic processes are important in TEP production. The abiotic TEP aggregation rates measured in the tropical and temperate North Pacific and the Arctic Ocean averaged between 8 and 12 μmol C L−1 d−1. Depth profiles from under sea ice in the Arctic revealed the highest TEP concentrations, potentially released by sympagic algal activity at the bottom of the sea ice. The aggregation rates in the SML, the interfacial layer between the ocean and atmosphere, were generally enhanced over those in the bulk surface waters by factors of 2 to 30. This finding further strengthens a developing consensus on the gelatinous nature of the SML, which will also affect microbial life, light penetration, and surface wave properties. We present a conceptual model implying that abiotic aggregation is an important factor for TEP production in the ocean, in particular in sea surface microlayers, while consumption by zooplankton and protists recycle TEP, providing a new pool of dissolved precursor material. Overall, TEP is recycled within the water column through heterotrophic grazing and degradation, providing a new pool of TEP precursor materials, while enhanced aggregation rates of TEP in the SML indicates the importance of this thin surface film in the marine carbon cycle.
Fast transcription rates of RNA polymerase II in human cells
Authors: Maiuri Paolo , Knezevich Anna , De Marco Alex , Mazza Davide , Kula Anna , McNally Jim G , Marcello Alessandro
Published: October 2011

Averaged estimates of RNA polymerase II (RNAPII) elongation rates in mammalian cells have been shown to range between 1.3 and 4.3 kb min−1. In this work, nascent RNAs from an integrated human immunodeficiency virus type 1‐derived vector were detectable at the single living cell level by fluorescent RNA tagging. At steady state, a constant number of RNAs was measured corresponding to a minimal density of polymerases with negligible fluctuations over time. Recovery of fluorescence after photobleaching was complete within seconds, indicating a high rate of RNA biogenesis. The calculated transcription rate above 50 kb min−1 points towards a wide dynamic range of RNAPII velocities in living cells.
Endothelial laminins underlie the tip cell microenvironment
Authors: Kitajewski Jan
Published: October 2011

The role of basement membrane laminin 411 in specifying tip cell behaviour during angiogenesis is described in this issue of EMBO reports. Here, these findings are contextualized with the rest of the players in the tip cell microenvironment.
Small molecules DNAmethyltransferasesinhibitors
Authors: Martinet Nadine , Michel Benoît Y. , Bertrand Philippe , Benhida Rachid
Published: October 2011

This review describes current knowledge concerning DNA methyltransferases (DNMT) biology and the two main classes of DNMT inhibtors.
Inactivation of mitochondrial aspartate aminotransferase contributes to the respiratory deficit of yeast frataxin-deficient cells
Authors: Sliwa Dominika , Dairou Julien , Camadro Jean-Michel , Santos Renata
Published: October 2011

Friedreich's ataxia is a hereditary neurodegenerative disease caused by reduced expression of mitochondrial frataxin. Frataxin deficiency causes impairment in respiratory capacity, disruption of iron homoeostasis and hypersensitivity to oxidants. Although the redox properties of NAD (NAD+ and NADH) are essential for energy metabolism, only few results are available concerning homoeostasis of these nucleotides in frataxin-deficient cells. In the present study, we show that the malate–aspartate NADH shuttle is impaired in Saccharomyces cerevisiae frataxin-deficient cells (Δyfh1) due to decreased activity of cytosolic and mitochondrial isoforms of malate dehydrogenase and to complete inactivation of the mitochondrial aspartate aminotransferase (Aat1). A considerable decrease in the amount of mitochondrial acetylated proteins was observed in the Δyfh1 mutant compared with wild-type. Aat1 is acetylated in wild-type mitochondria and deacetylated in Δyfh1 mitochondria suggesting that inactivation could be due to this post-translational modification. Mutants deficient in iron–sulfur cluster assembly or lacking mitochondrial DNA also showed decreased activity of Aat1, suggesting that Aat1 inactivation was a secondary phenotype in Δyfh1 cells. Interestingly, deletion of the AAT1 gene in a wild-type strain caused respiratory deficiency and disruption of iron homoeostasis without any sensitivity to oxidative stress. Our results show that secondary inactivation of Aat1 contributes to the amplification of the respiratory defect observed in Δyfh1 cells. Further implication of mitochondrial protein deacetylation in the physiology of frataxin-deficient cells is anticipated.
Crystallographic and X-ray absorption spectroscopic characterization of Helicobacter pylori UreE bound to Ni2+ and Zn2+ reveals a role for the disordered C-terminal arm in metal trafficking
Authors: Banaszak Katarzyna , Martin-Diaconescu Vlad , Bellucci Matteo , Zambelli Barbara , Rypniewski Wojciech , Maroney Michael J. , Ciurli Stefano
Published: October 2011

The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni2+ ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni2+ insertion into the apoenzyme. Crystals of apo-HpUreE (H. pylori UreE) and its Ni2+- and Zn2+-bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni2+) and 2.52 Å (Zn2+) resolution, show the conserved proximal and solvent-exposed His102 residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apoprotein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His152. The analysis of X-ray absorption spectral data obtained using solutions of Ni2+- and Zn2+-bound HpUreE provided accurate information of the metal-ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal-ion binding, and the mutual influence of protein framework and metal-ion stereo-electronic properties in establishing co-ordination number and geometry leading to metal selectivity.
Graphene p-n junctions with nonuniform Rashba spin-orbit coupling
Authors: Rataj Marek , Barnaś Józef
Published: October 2011

Linear conductance of graphene-based p-n junctions with Rashba spin-orbit coupling is considered theoretically. A square potential step is used to model the junctions, while the coupling is introduced in terms of the Kane-Mele model (C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 226801 (2005)). The main objective is a description of electronic transport in junctions where Rashba parameter is nonuniform. Such a nonuniformity can appear when graphene is asymmetrically covered with atomic layers, or when Rashba coupling is strongly dependent on electric field. It is shown that conductance is significantly modified by the considered nonuniformity, which is most clearly manifested by an anomalous minimum at a certain potential step height.
Flow-turbulence interaction in magnetic reconnection
Authors: Yokoi N. , Hoshino M.
Published: October 2011

Roles of turbulence in the context of magnetic reconnection are investigated with special emphasis on the mutual interaction between flow (large-scale inhomogeneous structure) and turbulence. In order to evaluate the effective transport due to turbulence, in addition to the intensity information of turbulence represented by the turbulent energy, the structure information represented by pseudoscalar statistical quantities (helicities) is important. On the basis of the evolution equation, mechanisms that provide turbulence with cross helicity are presented. Magnetic-flux freezing in highly turbulent media is considered with special emphasis on the spatial distribution of the turbulent cross helicity. The cross-helicity effects in the context of magnetic reconnection are also investigated. It is shown that the large-scale flow and magnetic-field configurations favorable for the cross-helicity generation is compatible with the fast reconnection. Difference between the spatial distributions of the turbulent MHD energy and cross helicity plays an essential role for localizing the reconnection region. In this sense, turbulence and large-scale structures promote magnetic reconnection mediated by the turbulent cross helicity.
Theory of coupled whistler-electron temperature gradient mode in high beta plasma: Application to linear plasma device
Authors: Singh S. K. , Awasthi L. M. , Singh R. , Kaw P. K. , Jha R. , Mattoo S. K.
Published: October 2011

This paper presents a theory of coupled whistler (W) and electron temperature gradient (ETG) mode using two-fluid model in high beta plasma. Non-adiabatic ion response, parallel magnetic field perturbation (δBz), perpendicular magnetic flutter (δB⊥), and electron collisions are included in the treatment of theory. A linear dispersion relation for whistler-electron temperature gradient (W-ETG) mode is derived. The numerical results obtained from this relation are compared with the experimental results observed in large volume plasma device (LVPD) [Awasthi et al., Phys. Plasma 17, 42109 (2010)]. The theory predicts that the instability grows only where the temperature gradient is finite and the density gradient flat. For the parameters of the experiment, theoretically estimated frequency and wave number of W-ETG mode match with the values corresponding to the peak in the power spectrum observed in LVPD. By using simple mixing length argument, estimated level of fluctuations of W-ETG mode is in the range of fluctuation level observed in LVPD.
Plasma diffusion in self-consistent fluctuations
Authors: Smets R. , Belmont G. , Aunai N. , Rezeau L.
Published: October 2011

The problem of particle diffusion in position space, as a consequence of electromagnetic fluctuations is addressed. Numerical results obtained with a self-consistent hybrid code are presented, and a method to calculate diffusion coefficient in the direction perpendicular to the mean magnetic field is proposed. The diffusion is estimated for two different types of fluctuations. The first type (resulting from an agyrotropic initial setting) is stationary, wide band white noise, and associated to Gaussian probability distribution function for the magnetic fluctuations. The second type (resulting from a Kelvin-Helmholtz instability) is non-stationary, with a power-law spectrum, and a non-Gaussian probability distribution function. The results of the study allow revisiting the question of loading particles of solar wind origin in the Earth magnetosphere.
Versatile computer-controlled system for characterization of gas sensing materials
Authors: Zhao M. , Huang J. X. , Wong M. H. , Tang Y. M. , Ong C. W.
Published: October 2011

Design of a system used for characterizing gas sensing materials is described. It is distinctive of being able to measure electrical and optical responses of a sample simultaneously, control a number of measurement parameters, perform fast exchange of gaseous environment, and be fully controlled automatically. These features make the system to be versatile in determining most concerned performance indexes of a gas sensing material (e.g., sensitivity, stability, selectivity, response/recovery times, etc.) as functions of various combinations of measurement conditions (e.g., gas concentrations, temperature, total pressure, content of interferants, photo assist, relative humidity, soaking time in a fixed gas concentration, and number of switching cycles in a dynamic test, etc.). Rationales of the designs associated with general gas sensing mechanics are discussed.
Fast template tracking in video sequences
Authors: Nicoud Florent , Castellazzi Guillaume , Lesniewski Peter J. , Thomas John C.
Published: October 2011

Tracking of poorly defined, rotating and/or distorted objects in a video sequence poses significant problems especially in medical diagnostics including ultrasound (sonographic) video used for examination and diagnosis of internal movement of tissue or muscle and nerve action. Cross-correlation techniques have been successful in retrieving dynamic information directly from ultrasound video data. We outline a fast implementation of tracking based on normalized cross-correlation using an adaptive template and present results from our application, developed in MATLAB™, which successfully tracks arbitrarily selected objects in deformed or severely compromised images. Common ultrasound image evaluation is qualitative but there is need to retrieve quantitative dynamic information such as the trajectory or velocity of selected areas. Our approach uses normalized two-dimensional cross-correlation to find the position of an initially selected template enclosing the feature of interest and map its trajectory frame-by-frame to produce displacement and velocity plots. We illustrate operation of the application using routine ultrasound data and demonstrate its performance using test video of objects rotating full circle and rolling down a ramp. We analyse errors associated with sampling to compare performance of our implementation with a more rigorous but tedious and computationally expensive correlation of a resampled, rotated, and shifted template.
Origin of large Landau-Placzek ratio in a liquid metallic alloy
Authors: Bryk Taras , Wax J.-F.
Published: October 2011

Dynamic structure factors for NacK1 − c liquid metallic alloys and pure components are studied by molecular dynamics simulations. Large values of Landau-Placzek ratio for four compositions of the liquid alloy are analyzed by wave-number dependent contributions from relaxation and propagating processes within the generalized collective modes method. The origin of the large Landau-Placzek ratio for liquid alloys is discussed.
Envelope equations for cylindrically symmetric space charge dominated multi species beam
Authors: Sing Babu P. , Goswami A. , Pandit V. S.
Published: October 2011

We have derived differential equations for the beam envelope of a cylindrically symmetric space charge dominated multi-species beam. The major contribution here is the inclusion of the emittance growth of each species of the beam resulting from the nonlinear space charge effect of the other species which arises if the beam radius of that particular species is greater than the other species. In addition, we have also discussed the beam selection using slits and considered only the effective values of the current and emittance of each species after the slit for further transport in case the beam size of any species is larger than the slit size or the finite aperture of the beam pipe. Finally, we have studied the transport of proton from 2.45 GHz microwave ion source in the presence of H2+, H3+ species to demonstrate the application of these results. Numerical results are presented for various values of the total beam current and different fractions of p, H2+, and H3+ species.
Origin of higher temperatures in multidipolar plasma devices
Authors: Knappmiller Scott , Robertson Scott
Published: October 2011

Hot-filament discharge devices with multidipolar surface magnetic fields have densities and temperatures higher than in these devices without multidipolar fields. Probe data show a much higher density of secondary electrons from the wall with multidipolar fields that is best explained by the wall secondaries being confined by the magnetic mirror effect. A relatively simple mathematical model for energy balance shows that the heating of the bulk plasma electrons by collisions with the greater number of secondaries from the wall accounts quantitatively for the increased temperature.