bluuebunny/crossref_metadata_2025 huggingface dataset:
KMUP‐1 inhibits hypertension‐induced left ventricular hypertrophy through regulation of nitric oxide synthases, ERK1/2, and calcineurin
Authors: Yeh Jwu‐Lai , Liu Chung‐Pin , Hsu Jong‐Hau , Tseng Ching‐Jiunn , Wu Ping‐Ju , Wang Yi‐Ya , Wu Jiunn‐Ren , Chen Ing‐Jun
Published: July 2012

Hypertension can induce left ventricular hypertrophy (LVH), and the nitric oxide (NO) pathway plays an important role in the pathogenesis of cardiac hypertrophy. This study aimed to examine whether KMUP‐1, a novel xanthine‐based derivative, could inhibit LVH in spontaneously hypertensive rats (SHRs) and to investigate potential mechanisms underlying its antihypertrophic effects. Two groups of animals with chronic or subacute LVH were treated. In the chronic LVH group, KMUP‐1 (10 or 30 mg/kg/d orally) was administered for 28 days to both normotensive rats and SHRs. In the subacute LVH group, KMUP‐1 (0.5 mg/kg/d intraperitoneally) or sildenafil (0.7 mg/kg/d intraperitoneally) was administered for 10 days with or without co‐treatment with the nitric oxide synthase (NOS) inhibitor N‐omega‐nitro‐l‐arginine (L‐NNA; 20 mg/L orally). After treatment, the effects of KMUP‐1 or sildenafil on hypertension, cardiac hypertrophy, survival, expression of the NO/soluble guanylate cyclase (sGC)/protein kinase G (NO/sGC/PKG) pathway in the aorta andleft ventricle, and calcineurin A/extracellular signal‐regulated kinase 1/2 (ERK1/2) signaling in the left ventricle were examined. In the chronic LVH group, the SHRs developed hypertension with LVH over the 28 days. KMUP‐1 attenuated the hypertension and LVH, increased survival rate, enhanced endothelial NOS/cyclic guanosine monophosphate/PKG (eNOS/cGMP/PKG) and decreased inducible NOS (iNOS) expression in the aorta and left ventricle of the SHRs. In the subacute LVH group, both KMUP‐1 and sildenafil administered for 10 days attenuated the LVH in SHRs, with enhanced eNOS/cGMP/PKG and suppressed iNOS/calcineurin A/ERK1/2 expression in the left ventricle. In addition, both KMUP‐1 and sildenafil attenuated L‐NNA‐induced LVH. KMUP‐1 inhibition of hypertension‐induced LVH with associated upregulation of eNOS, downregulation of iNOS in both the aorta and left ventricle, and attenuation of calcineurin A and ERK1/2 signaling in the left ventricle.
Frostbite and Other Cold Injuries in the Heroic Age of Antarctic Exploration
Authors: Guly Henry R.
Published: July 2012

Frostbite and other cold injuries on the early polar expeditions were common. This paper explains how frostbite was described, prevented, and treated on the Antarctic expeditions of the heroic age, comparing them with modern recommendations. Nonfreezing cold injury probably also occurred but was not differentiated from frostbite, and chilblains were also described.
Prevalence of Mitral Valve Prolapse in Residents Living at Moderately High Altitude
Authors: Güvenç Tolga Sinan , Çanga Yiğit , Karabağ Yavuz , Özen Kaya , Balcı Bahattin
Published: July 2012

Objective

Prolapse of mitral valve leaflets is a frequent disorder and the most common cause of severe mitral regurgitation in western countries. However, little is known about the effects of altitude on mitral valve prolapse. We studied the prevalence and echocardiographic characteristics of mitral valve prolapse at moderately high altitude and sea level.

Methods

A total of 936 consecutive subjects who were admitted to 2 study institutions at Kars, Turkey (1750 m) and Istanbul, Turkey (7 m) were enrolled in this study to determine prevalence of mitral valve prolapse. Demographic and 2-dimensional echocardiographic characteristics of participants were recorded.

Results

Prevalance of mitral valve prolapse was found to be significantly higher in people living at moderate altitude compared with those living at sea level (6.2% vs 2.0%; P = .007). Overall echocardiographic features regarding valve thickness (4.1 ± 0.80 mm vs 3.6 ± 0.66 mm; P = 0.169), maximal valve prolapse (4.6 ± 2.08 mm vs 3.9 ± 0.91 mm; P = .093), and frequency of mitral regurgitation (89% vs 73%; P = .65) were similar between groups, although anterior valve prolapse was seen more frequently at moderate altitude (50% vs 11%; P = .056) and posterior leaflet prolapse was significantly more frequent at sea level (66% vs 10%; P = .002).

Conclusions

Mitral valve prolapse is more frequently observed at moderately high altitudes. Further studies are needed to determine clinical importance of our findings.
Neuropsychological evidence for abnormal neurodevelopment associated with early-onset psychoses
Authors: Bombin I. , Mayoral M. , Castro-Fornieles J. , Gonzalez-Pinto A. , de la Serna E. , Rapado-Castro M. , Barbeito S. , Parellada M. , Baeza I. , Graell M. , Payá B. , Arango C.
Published: July 2012

Background

The longitudinal neuropsychological study of first-episode early-onset psychosis (EOP) patients, whose brain maturation is still in progress at the time of illness onset, provides a unique opportunity to compare their cognitive development with that of healthy subjects, in search of specific patterns resulting from the interaction between neurodevelopmental processes and the presence of psychotic disorders.

Method

Seventy-five first-episode EOP patients (schizophrenian = 35; bipolar disordern = 17; other forms of psychosisn = 23) with a mean age of 15.53 years were assessed with a neuropsychological battery that included measures of attention, working memory, memory and executive functions within 6 months following the onset of the first psychotic symptom (baseline) and 2 years later. Psychotic symptoms were assessed at both times with the Positive and Negative Symptom Scale (PANSS). Seventy-nine healthy subjects matched for age and education served as controls.

Results

EOP patients showed significant cognitive impairment at both baseline and the 2-year follow-up, with no significant differences between diagnostic groups at either time. Both healthy controls and EOP patients improved in all cognitive measures, except for patient working memory. Improvement in patient attention lost significance after controlling for psychotic symptom reduction. No significant time/diagnosis interaction was found among patients (p > 0.405).

Conclusions

Cognitive impairment in EOP is already present at the first episode, and cognitive development seems to be arrested early in EOP patients compared to their healthy peers, at least for some cognitive functions. These and previous similar results support the neurodevelopmental hypothesis of psychosis.
Characteristics and contributions of non-kin carers of older people: a closer look at friends and neighbours
Authors: LAPIERRE TRACEY A. , KEATING NORAH
Published: July 2012

Research on informal care-giving has largely neglected the contributions of non-kin carers. This paper investigated the characteristics and contributions of non-kin who care for older adults with a long-term health problem, and investigated friends and neighbours as distinct categories of care providers. Using data from 324 non-kin carers in the 1996 General Social Survey of Canada, this study compared individual and relationship characteristics, care tasks and amount of care provided for the two groups. Interpersonal and socio-demographic characteristics were investigated as mediators of potential differences between friends and neighbours in patterns of care. Results demonstrate that friend and neighbour carers differed on age, marital status, geographical proximity and relationship closeness. Friends were more likely than neighbours to assist with personal care, bills and banking, and transportation. Neighbours were more likely to assist with home maintenance. Friends provided assistance with a greater number of tasks and provided more hours of care per week, suggesting a more prominent role in the care of non-kin than neighbours. Age, income, a minor child in the household, proximity and relationship closeness significantly predicted amount of care provided, and relationship closeness largely explained differences between friends and neighbours. Future research on informal care-giving can build on the findings that distinguish friend and neighbour carers to further discriminate the dynamics of non-kin care.
Neuregulin 3 is associated with attention deficits in schizophrenia and bipolar disorder
Authors: Meier Sandra , Strohmaier Jana , Breuer Rene , Mattheisen Manuel , Degenhardt Franziska , Mühleisen Thomas W. , Schulze Thomas G. , Nöthen Markus M. , Cichon Sven , Rietschel Marcella , Wüst Stefan
Published: July 2012

Linkage and fine mapping studies have established that the neuregulin 3 gene (NRG3) is a susceptibility locus for schizophrenia. Association studies of this disorder have implicated NRG3 variants in both psychotic symptoms and attention performance. Psychotic symptoms and cognitive deficits are also frequent features of bipolar disorder. The aims of the present study were to extend analysis of the association between NRG3 and psychotic symptoms and attention in schizophrenia and to determine whether these associations also apply to bipolar disorder. A total of 358 patients with schizophrenia and 111 patients with bipolar disorder were included. Psychotic symptoms were evaluated using the Operational Criteria Checklist for Psychotic Illness (OPCRIT) and attention performance was assessed using the Trail Making Test (TMT). Symptoms and performance scores were then tested for association with the NRG3 variant rs6584400. A significant association was found between the number of rs6584400 minor alleles and the total OPCRIT score for psychotic symptoms in patients with schizophrenia. Moreover, in both schizophrenia and bipolar disorder patients, minor allele carriers of rs6584400 outperformed homozygous major allele carriers in the TMT. The results suggest that rs6584400 is associated with psychotic symptoms and attention performance in schizophrenia. The finding of a significant association between rs6584400 and attention performance in bipolar disorder supports the hypothesis that this NRG3 variant confers genetic susceptibility to cognitive deficits in both schizophrenia and bipolar disorder.
Improved understanding of the searching behavior of ant colony optimization algorithms applied to the water distribution design problem
Authors: Zecchin A. C. , Simpson A. R. , Maier H. R. , Marchi A. , Nixon J. B.
Published: July 2012

Evolutionary algorithms (EAs) have been applied successfully to many water resource problems, such as system design, management decision formulation, and model calibration. The performance of an EA with respect to a particular problem type is dependent on how effectively its internal operators balance the exploitation/exploration trade‐off to iteratively find solutions of an increasing quality. For a given problem, different algorithms are observed to produce a variety of different final performances, but there have been surprisingly few investigations into characterizing how the different internal mechanisms alter the algorithm's searching behavior, in both the objective and decision space, to arrive at this final performance. This paper presents metrics for analyzing the searching behavior of ant colony optimization algorithms, a particular type of EA, for the optimal water distribution system design problem, which is a classical NP‐hard problem in civil engineering. Using the proposed metrics, behavior is characterized in terms of three different attributes: (1) the effectiveness of the search in improving its solution quality and entering into optimal or near‐optimal regions of the search space, (2) the extent to which the algorithm explores as it converges to solutions, and (3) the searching behavior with respect to the feasible and infeasible regions. A range of case studies is considered, where a number of ant colony optimization variants are applied to a selection of water distribution system optimization problems. The results demonstrate the utility of the proposed metrics to give greater insight into how the internal operators affect each algorithm's searching behavior.
A global evaluation of temperature and carbonate ion control on Mg/Ca ratios of ostracoda genus Krithe
Authors: Elmore A. C. , Sosdian S. , Rosenthal Y. , Wright J. D.
Published: July 2012

Improving estimates of past ocean temperatures is paramount to our understanding of ocean circulation and its role in climate change. Magnesium/calcium (Mg/Ca) ratios of carapaces of the benthic ostracod genus Krithe were determined from new, globally distributed core top samples from the Norwegian Sea, Cape Hatteras shelf, Gulf of Mexico, Sulawesi Margin (Indonesia), New Zealand shelf, Ceara Rise, and the North Atlantic. A linear regression of the Krithe Mg/Ca ratios and bottom water temperature (BWT) reveals a significant correlation for locations where temperature during carapace calcification was above ∼3°C, which can be described by the equation Mg/Ca = (0.972 ± 0.152) * BWT + (7.948 ± 1.103) consistent with previous North Atlantic calibrations. Deviations from the global calibration line below ∼3°C follow the same pattern observed for benthic foraminifera, suggesting that the incorporation of magnesium into ostracodal calcite may be secondarily controlled by changes in carbonate ion concentration. Therefore, we propose a linear regression that describes the relationship between magnesium incorporation, temperature, and carbonate saturation for low temperatures (<3°C); Mg/Ca = (0.972 ± 0.152) * BWT + (0.100 ± 0.030) * Δ[CO32−]) + (4.440 ± 1.103) (1 SE = ± 0.3°C). While the standard error of the calibration is small, it requires an accurate knowledge of past Δ[CO32−] concentration, which necessitates additional proxy data. Applying the calibration to glacial samples from the deep North Atlantic Ocean we show that estimates of bottom water temperatures generated from the new Δ[CO32−]‐ corrected equations are more consistent with results from oxygen isotopes and pore water studies.
A computational and theoretical analysis of falling frequency VLF emissions
Authors: Nunn David , Omura Yoshiharu
Published: July 2012

Recently much progress has been made in the simulation and theoretical understanding of rising frequency triggered emissions and rising chorus. Both PIC and Vlasov VHS codes produce risers in the region downstream from the equator toward which the VLF waves are traveling. The VHS code only produces fallers or downward hooks with difficulty due to the coherent nature of wave particle interaction across the equator. With the VHS code we now confine the interaction region to be the region upstream from the equator, where inhomogeneity factor S is positive. This suppresses correlated wave particle interaction effects across the equator and the tendency of the code to trigger risers, and permits the formation of a proper falling tone generation region. The VHS code now easily and reproducibly triggers falling tones. The evolution of resonant particle current JE in space and time shows a generation point at −5224 km and the wavefield undergoes amplification of some 25 dB in traversing the nonlinear generation region. The current component parallel to wave magnetic field (JB) is positive, whereas it is negative for risers. The resonant particle trap shows an enhanced distribution function or ‘hill’, whereas risers have a ‘hole’. According to recent theory (Omura et al., 2008, 2009) sweeping frequency is due primarily to the advective term. The nonlinear frequency shift term is now negative (∼−12 Hz) and the sweep rate of −800 Hz/s is approximately nonlinear frequency shift divided by TN, the transition time, of the order of a trapping time.
Influence of interplanetary solar wind sector polarity on the ionosphere
Authors: Liu Jing , Liu Libo , Zhao Biqiang , Wan Weixing
Published: July 2012

Knowledge of solar sector polarity effects on the ionosphere may provide some clues in understanding of the ionospheric day‐to‐day variability and “hysteresis” effect on foF2. Ionospheric response to changes in solar sector polarity has not been fully documented previously, partly due to the limitation of observations. In this study, a solar‐terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbances and ionospheric perturbations has been demonstrated. The increases in interplanetary solar wind speed within three days are seen after SB crossings, while the decreases in solar wind dynamic pressure and magnetic field intensity immediately after SB crossings are confirmed by the superposed epoch analysis results. Furthermore, the interplanetary magnetic field (IMF) Bz component turns from northward to southward in March equinox and June solstice as the Earth passes from a solar sector of outward to inward directed magnetic fields, whereas the reverse situation occurs for the transition from toward to away sectors. The IMF Bz component for the same solar sector polarity has opposite signs between March equinox and September equinox, and also between June solstice and December solstice. In order to know how the ionosphere reacts to the interplanetary solar wind variations linkage of SB crossings, the F2 region critical frequency (foF2) covering about four solar cycles and total electron content (TEC) during 1998–2011 are utilized to extract the related information, revealing that they are not modified significantly and vary within the range of ±15% on average. The responses of the ionospheric TEC to SB crossings exhibit complex temporal and spatial variations and have strong dependencies on season, latitude, and solar cycle. This effect is more appreciable in equinoctial months than in solstitial months, which is mainly caused by larger southwardBzcomponents in equinox. In September equinox, latitudinal profile of relative variations of foF2 at noon is featured by depressions at high latitudes and enhancements in low‐equatorial latitudes during IMF away sectors. The negative phase of foF2 is delayed at solar minimum relative to it during other parts of solar cycle, which might be associated with the difference in longevity of major interplanetary solar wind drivers perturbing the Earth's environment in different phases of solar cycle.
Iron isotope and trace metal records of iron cycling in the proto‐North Atlantic during the Cenomanian‐Turonian oceanic anoxic event (OAE‐2)
Authors: Owens Jeremy D. , Lyons Timothy W. , Li Xiaona , Macleod Kenneth G. , Gordon Gwenyth , Kuypers Marcel M. M. , Anbar Ariel , Kuhnt Wolfgang , Severmann Silke
Published: July 2012

The global carbon cycle during the mid‐Cretaceous (∼125–88 million years ago, Ma) experienced numerous major perturbations linked to increased organic carbon burial under widespread, possibly basin‐scale oxygen deficiency and episodes of euxinia (anoxic and H2S‐containing). The largest of these episodes, the Cenomanian‐Turonian boundary event (ca. 93.5 Ma), or oceanic anoxic event (OAE) 2, was marked by pervasive deposition of organic‐rich, laminated black shales in deep waters and in some cases across continental shelves. This deposition is recorded in a pronounced positive carbon isotope excursion seen ubiquitously in carbonates and organic matter. Enrichments of redox‐sensitive, often bioessential trace metals, including Fe and Mo, indicate major shifts in their biogeochemical cycles under reducing conditions that may be linked to changes in primary production. Iron enrichments and bulk Fe isotope compositions track the sources and sinks of Fe in the proto‐North Atlantic at seven localities marked by diverse depositional conditions. Included are an ancestral mid‐ocean ridge and euxinic, intermittently euxinic, and oxic settings across varying paleodepths throughout the basin. These data yield evidence for a reactive Fe shuttle that likely delivered Fe from the shallow shelf to the deep ocean basin, as well as (1) hydrothermal sources enhanced by accelerated seafloor spreading or emplacement of large igneous province(s) and (2) local‐scale Fe remobilization within the sediment column. This study, the first to explore Fe cycling and enrichment patterns on an ocean scale using iron isotope data, demonstrates the complex processes operating on this scale that can mask simple source‐sink relationships. The data imply that the proto‐North Atlantic received elevated Fe inputs from several sources (e.g., hydrothermal, shuttle and detrital inputs) and that the redox state of the basin was not exclusively euxinic, suggesting previously unknown heterogeneity in depositional conditions and biogeochemical cycling within those settings during OAE‐2.
A Novel PET Protocol for Visualization of Breast Cancer Resistance Protein Function at the Blood–Brain Barrier
Authors: Wanek Thomas , Kuntner Claudia , Bankstahl Jens P , Mairinger Severin , Bankstahl Marion , Stanek Johann , Sauberer Michael , Filip Thomas , Erker Thomas , Müller Markus , Löscher Wolfgang , Langer Oliver
Published: July 2012

Breast cancer resistance protein (BCRP) is the most abundant multidrug efflux transporter at the human blood–brain barrier (BBB), restricting brain distribution of various drugs. In this study, we developed a positron emission tomography (PET) protocol to visualize Bcrp function at the murine BBB, based on the dual P-glycoprotein (P-gp)/Bcrp substrate radiotracer [11C]tariquidar in combination with the Bcrp inhibitor Ko143. To eliminate the contribution of P-gp efflux to [11C]tariquidar brain distribution, we studied mice in which P-gp was genetically knocked out ( Mdri1a/b(−/−) mice) or chemically knocked out by pretreatment with cold tariquidar. We found that [11C]tariquidar brain uptake increased dose dependency after administration of escalating doses of Ko143, both in Mdr1a/b(−/−) mice and in tariquidar pretreated wild-type mice. After 15 mg/kg Ko143, the maximum increase in [11C]tariquidar brain uptake relative to baseline scans was 6.3-fold in Mdr1a/bf(−/−) mice with a half-maximum effect dose of 4.98 mg/kg and 3.6-fold in tariquidar (8 mg/kg) pretreated wild-type mice, suggesting that the presented protocol is sensitive to visualize a range of different functional Bcrp activities at the murine BBB. We expect that this protocol can be translated to the clinic, because tariquidar can be safely administered to humans at doses that completely inhibit cerebral P-gp.
Characterization of Arabidopsis calcium-dependent protein kinases: activated or not by calcium?
Authors: Boudsocq Marie , Droillard Marie-Jo , Regad Leslie , Laurière Christiane
Published: July 2012

CDPKs (calcium-dependent protein kinases), which contain both calmodulin-like calcium binding and serine/threonine protein kinase domains, are only present in plants and some protozoans. Upon activation by a stimulus, they transduce the signal through phosphorylation cascades to induce downstream responses, including transcriptional regulation. To understand the functional specificities of CDPKs, 14 Arabidopsis CPKs (CDPKs in plants) representative of the three main subgroups were characterized at the biochemical level, using HA (haemagglutinin)-tagged CPKs expressed in planta. Most of them were partially or mainly associated with membranes, in agreement with acylation predictions. Importantly, CPKs displayed highly variable calcium-dependences for their kinase activities: seven CPKs from subgroups 1 and 2 were clearly sensitive to calcium with different intensities, whereas six CPKs from subgroup 3 exhibited low or no calcium sensitivity to two generic substrates. Interestingly, this apparent calcium-independence correlated with significant alterations in the predicted EF-hands of these kinases, although they all bound calcium. The noticeable exception, CPK25, was calcium-independent owing to the absence of functional EF-hands. Taken together, the results of the present study suggest that calcium binding differentially affects CDPK isoforms that may be activated by distinct molecular mechanisms.
MOJAVE: Monitoring of Jets in Active galactic nuclei with VLBA Experiments
Authors: Pushkarev A. B. , Hovatta T. , Kovalev Y. Y. , Lister M. L. , Lobanov A. P. , Savolainen T. , Zensus J. A.
Published: July 2012

Aims. We have investigated a frequency-dependent shift in the absolute
position of the optically thick apparent origin of parsec-scale jets (“core shift” effect)
to probe physical conditions in ultra-compact relativistic outflows in active galactic
nuclei.

Methods. We used multi-frequency Very Long Baseline Array (VLBA)
observations of 191 sources carried out in 12 epochs in 2006 within the Monitoring Of Jets
in Active galactic nuclei with VLBA Experiments (MOJAVE) program. The observations were
performed at 8.1, 8.4, 12.1, and 15.4 GHz. We implemented a method of determining the core
shift vector based on (i) image registration by two-dimensional normalized
cross-correlation and (ii) model-fitting the source brightness distribution to take into
account a non-zero core component offset from the phase center.

Results. The 15.4−8.1, 15.4−8.4, and 15.4−12.1 GHz core shift vectors
are derived for 163 sources, and have median values of 128, 125, and
88 μas, respectively, compared to the typical measured errors of 50, 51,
35 μas. The effect occurs predominantly along the jet direction, with
departures smaller than 45° from the median jet position angle in over 80% of the cases.
Despite the moderate ratio of the observed frequencies (<2), core shifts significantly
different from zero (>2σ) are detected for about 55% of the sources.
These shifts are even better aligned with the jet direction, deviating from the latter by
less than 30° in over 90% of the cases. There is an indication that the core shift
decreases with increasing redshift. Magnetic fields in the jet at a distance of 1 parsec
from the central black hole, calculated from the obtained core shifts, are found to be
systematically stronger in quasars (median B1 ≈ 0.9 G) than
those in BL Lacs (median B1 ≈ 0.4 G). We also constrained the
absolute distance of the core from the apex of the jet at 15 GHz as well as the magnetic
field strength in the 15 GHz core region.
Intermittency in premixed turbulent reacting flows
Authors: Hamlington Peter E. , Poludnenko Alexei Y. , Oran Elaine S.
Published: July 2012

Intermittency in premixed reacting flows is studied using numerical simulations of premixed flames at a range of turbulence intensities. The flames are modeled using a simplified reaction mechanism that represents a stoichiometric H2-air mixture. Intermittency is associated with high probabilities of large fluctuations in flow quantities, and these fluctuations can have substantial effects on the evolution and structure of premixed flames. Intermittency is characterized here using probability density functions (pdfs) and moments of the local enstrophy, pseudo-dissipation rate (strain rate magnitude), and scalar (reactant mass fraction) dissipation rate. Simulations of homogeneous isotropic turbulence with a nonreacting passive scalar are also carried out in order to provide a baseline for analyzing the reacting flow results. In the reacting flow simulations, conditional analyses based on local, instantaneous values of the scalar are used to study variations in the pdfs, moments, and intermittency through the flame. For low intensities, pdfs of the local enstrophy vary substantially through the flame, with greater intermittency near the products. Changes in the pseudo-dissipation pdfs are, however, less pronounced. As the intensity increases, both the enstrophy and pseudo-dissipation pdfs become increasingly independent of position in the flame and are similar to results from the nonreacting simulations. The scalar dissipation intermittency is largest near the reactants and increases at all flame locations with increasing turbulence intensity. For low intensities and in the reaction zone, however, scalar dissipation pdfs approximately follow a Gaussian distribution, indicative of substantially reduced intermittency. Deviations from log-normality are observed in the pdfs of all quantities, even for intensities and flame locations characterized by strong intermittency. The implications of these results for the internal structure of the flame are discussed, and we also propose a connection between reacting flow intermittency and anisotropic vorticity suppression by the flame.
Source geometric considerations for OMEGA Dante measurements
Authors: May M. J. , Patterson J. R. , Sorce C. , Widmann K. , Fournier K. B. , Perez F.
Published: July 2012

The Dante is a 15 channel filtered diode array which is installed on the OMEGA laser facility at the Laboratory for Laser Energetics, University of Rochester. The system yields the spectrally and temporally resolved radiation flux from 50 eV to 10 keV from various targets (i.e., Hohlraum, gas pipes, etc.). The absolute flux is determined from the radiometric calibration of the x-ray diodes, filters, and mirrors and an unfold algorithm applied to the recorded voltages from each channel. The unfold algorithm assumes an emitting source that is spatially uniform and has a constant area as a function of photon energy. The emitting x-ray source is usually considered to be the laser entrance hole (LEH) of a given diameter for Hohlraum type targets or the effective wall area of high conversion efficiency K-shell type targets. This assumption can be problematic for several reasons. High intensity regions or “hot spots” in the x-ray are observed where the drive laser beams strike the target. The “hot spots” create non-uniform emission seen by the Dante. Additionally, thinned walled (50 μm) low-Z targets (C22H10N2O5) have an energy dependent source size since the target's walls will be fully opaque for low energies (E < 2–3 keV) yet fully transmissive at higher energies. Determining accurate yields can be challenging for these types of targets. Discussion and some analysis will be presented.
Fermi acceleration and adiabatic invariants for non-autonomous billiards
Authors: Gelfreich V. , Rom-Kedar V. , Turaev D.
Published: July 2012

Recent results concerned with the energy growth of particles inside a container with slowly moving walls are summarized, augmented, and discussed. For breathing bounded domains with smooth boundaries, it is proved that for all initial conditions the acceleration is at most exponential. Anosov-Kasuga averaging theory is reviewed in the application to the non-autonomous billiards, and the results are corroborated by numerical simulations. A stochastic description is proposed which implies that for periodically perturbed ergodic and mixing billiards averaged particle energy grows quadratically in time (e.g., exponential acceleration has zero probability). Then, a proof that in non-integrable breathing billiards some trajectories do accelerate exponentially is reviewed. Finally, a unified view on the recently constructed families of non-ergodic billiards that robustly admit a large set of exponentially accelerating particles is presented.
Measuring shape with topology
Authors: MacPherson Robert , Schweinhart Benjamin
Published: July 2012

We propose a measure of shape which is appropriate for the study of a complicated geometric structure, defined using the topology of neighborhoods of the structure. One aspect of this measure gives a new notion of fractal dimension. We demonstrate the utility and computability of this measure by applying it to branched polymers, Brownian trees, and self-avoiding random walks.
Comparison of some dispersion-corrected and traditional functionals as applied to peptides and conformations of cyclohexane derivatives
Authors: Marianski Mateusz , Asensio Amparo , Dannenberg J. J.
Published: July 2012

We compare the energetic and structural properties of fully optimized α-helical and antiparallel β-sheet polyalanines and the energetic differences between axial and equatorial conformations of three cyclohexane derivatives (methyl, fluoro, and chloro) as calculated using several functionals designed to treat dispersion (B97-D, ωB97x-D, M06, M06L, and M06-2X) with other traditional functionals not specifically parametrized to treat dispersion (B3LYP, X3LYP, and PBE1PBE) and with experimental results. Those functionals developed to treat dispersion significantly overestimate interaction enthalpies of folding for the α-helix and predict unreasonable structures that contain Ramachandran ϕ and ψ and C = O…N H-bonding angles that are out of the bounds of databases compiled the β-sheets. These structures are consistent with overestimation of the interaction energies. For the cyclohexanes, these functionals overestimate the stabilities of the axial conformation, especially when used with smaller basis sets. Their performance improves when the basis set is improved from D95** to aug-cc-pVTZ (which would not be possible with systems as large as the peptides).
High-speed thermo-microscope for imaging thermal desorption phenomena
Authors: Staymates Matthew , Gillen Greg
Published: July 2012

In this work, we describe a thermo-microscope imaging system that can be used to visualize atmospheric pressure thermal desorption phenomena at high heating rates and frame rates. This versatile and portable instrument is useful for studying events during rapid heating of organic particles on the microscopic scale. The system consists of a zoom lens coupled to a high-speed video camera that is focused on the surface of an aluminum nitride heating element. We leverage high-speed videography with oblique incidence microscopy along with forward and back-scattered illumination to capture vivid images of thermal desorption events during rapid heating of chemical compounds. In a typical experiment, particles of the material of interest are rapidly heated beyond their boiling point while the camera captures images at several thousand frames/s. A data acquisition system, along with an embedded thermocouple and infrared pyrometer are used to measure the temperature of the heater surface. We demonstrate that, while a typical thermocouple lacks the response time to accurately measure temperature ramps that approach 150 °C/s, it is possible to calibrate the system by using a combination of infrared pyrometry, melting point standards, and a thermocouple. Several examples of high explosives undergoing rapid thermal desorption are also presented.
Single-molecule enzyme kinetics in the presence of inhibitors
Authors: Saha Soma , Sinha Antara , Dua Arti
Published: July 2012

Recent studies in single-molecule enzyme kinetics reveal that the turnover statistics of a single enzyme is governed by the waiting time distribution that decays as mono-exponential at low substrate concentration and multi-exponential at high substrate concentration. The multi-exponentiality arises due to protein conformational fluctuations, which act on the time scale longer than or comparable to the catalytic reaction step, thereby inducing temporal fluctuations in the catalytic rate resulting in dynamic disorder. In this work, we study the turnover statistics of a single enzyme in the presence of inhibitors to show that the multi-exponentiality in the waiting time distribution can arise even when protein conformational fluctuations do not influence the catalytic rate. From the Michaelis-Menten mechanism of inhibited enzymes, we derive exact expressions for the waiting time distribution for competitive, uncompetitive, and mixed inhibitions to quantitatively show that the presence of inhibitors can induce dynamic disorder in all three modes of inhibitions resulting in temporal fluctuations in the reaction rate. In the presence of inhibitors, dynamic disorder arises due to transitions between active and inhibited states of enzymes, which occur on time scale longer than or comparable to the catalytic step. In this limit, the randomness parameter (dimensionless variance) is greater than unity indicating the presence of dynamic disorder in all three modes of inhibitions. In the opposite limit, when the time scale of the catalytic step is longer than the time scale of transitions between active and inhibited enzymatic states, the randomness parameter is unity, implying no dynamic disorder in the reaction pathway.
Trapping in dendrimers and regular hyperbranched polymers
Authors: Wu Bin , Lin Yuan , Zhang Zhongzhi , Chen Guanrong
Published: July 2012

Dendrimers and regular hyperbranched polymers are two classic families of macromolecules, which can be modeled by Cayley trees and Vicsek fractals, respectively. In this paper, we study the trapping problem in Cayley trees and Vicsek fractals with different underlying geometries, focusing on a particular case with a perfect trap located at the central node. For both networks, we derive the exact analytic formulas in terms of the network size for the average trapping time (ATT)—the average of node-to-trap mean first-passage time over the whole networks. The obtained closed-form solutions show that for both Cayley trees and Vicsek fractals, the ATT display quite different scalings with various system sizes, which implies that the underlying structure plays a key role on the efficiency of trapping in polymer networks. Moreover, the dissimilar scalings of ATT may allow to differentiate readily between dendrimers and hyperbranched polymers.
Moist turbulent Rayleigh-Bénard convection with Neumann and Dirichlet boundary conditions
Authors: Weidauer Thomas , Schumacher Jörg
Published: July 2012

Turbulent Rayleigh-Bénard convection with phase changes in an extended layer between two parallel impermeable planes is studied by means of three-dimensional direct numerical simulations for Rayleigh numbers between 104 and 1.5 × 107 and for Prandtl number Pr = 0.7. Two different sets of boundary conditions of temperature and total water content are compared: imposed constant amplitudes which translate into Dirichlet boundary conditions for the scalar field fluctuations about the quiescent diffusive equilibrium and constant imposed flux boundary conditions that result in Neumann boundary conditions. Moist turbulent convection is in the conditionally unstable regime throughout this study for which unsaturated air parcels are stably and saturated air parcels unstably stratified. A direct comparison of both sets of boundary conditions with the same parameters requires to start the turbulence simulations out of differently saturated equilibrium states. Similar to dry Rayleigh-Bénard convection the differences in the turbulent velocity fluctuations, the cloud cover, and the convective buoyancy flux decrease across the layer with increasing Rayleigh number. At the highest Rayleigh numbers the system is found in a two-layer regime, a dry cloudless and stably stratified layer with low turbulence level below a fully saturated and cloudy turbulent one which equals a classical Rayleigh-Bénard convection layer. Both are separated by a strong inversion that gets increasingly narrower for growing Rayleigh number.
Quantitative description of the self-assembly of patchy particles into chains and rings
Authors: Tavares José Maria , Rovigatti Lorenzo , Sciortino Francesco
Published: July 2012

We numerically study a simple fluid composed of particles having a hard-core repulsion complemented by two patchy attractive sites on the particle poles. An appropriate choice of the patch angular width allows for the formation of ring structures which, at low temperatures and low densities, compete with the growth of linear aggregates. The simplicity of the model makes it possible to compare simulation results and theoretical predictions based on the Wertheim perturbation theory, specialized to the case in which ring formation is allowed. Such a comparison offers a unique framework for establishing the quality of the analytic predictions. We find that the Wertheim theory describes remarkably well the simulation results.
Study of ultrathin magnetic cobalt films on MgO(001)
Authors: Sharma Gagan , Deshpande U. P. , Kumar Dileep , Gupta Ajay
Published: July 2012

In-situ magneto-optical Kerr effect measurements have been done to study the evolution of the magnetic properties of ultrathin cobalt films on MgO(001)surface. A magnetic dead layer is found to exist at the MgO/Co interface, thickness of which is influenced by possible surface contamination of MgO substrate. X-ray photoelectron spectroscopy measurements show that etching the substrate with 500 eV Ar ions results in partial removal of carbon contamination. A lower carbon contamination results in reduction of the thickness of dead layer from 2.2 nm to 1.3 nm. At thicknesses below 3 nm, Co islands exhibit superparamagnetic relaxation. For higher film thickness, a well-defined uniaxial magnetic anisotropy develops along (100) direction.
Plasmonic multilayer nanoparticles enhanced photocurrent in thin film hydrogenated amorphous silicon solar cells
Authors: Ho Chung-I , Yeh Dan-Ju , Su Vin-Cent , Yang Chieh-Hung , Yang Po-Chuan , Pu Ming-Yi , Kuan Chieh-Hsiung , Cheng I-Chun , Lee Si-Chen
Published: July 2012

A plasmonic-structure incorporated double layer of Au nanoparticles embedded in the transparent conducting oxide at the back-reflector of the hydrogenated amorphous silicon (a-Si:H) solar cells is demonstrated. These devices exhibit an increase of energy conversion efficiency of 18.4% and short-circuit current density of 9.8% while improving fill-factor and without sacrificing open-circuit voltage. The increase in photocurrent is correlated with the enhanced optical absorption in the cell, with improved optical-path-length by a factor of 7 at the wavelength of 800 nm, due to enhanced diffuse scattering of light through resonant plasmon excitations within Au nanoparticles. In addition to enhanced scattering, applying high-work-function Au nanoparticles can improve the work function match at TCO/a-Si:H interface.
Magnetism in transition-metal-doped ZnO: A first-principles study
Authors: Gu Gangxu , Xiang Gang , Luo Jia , Ren Hongtao , Lan Mu , He Duanwei , Zhang Xi
Published: July 2012

The magnetic properties and clustering behaviors of the transition-metal (TM)-doped ZnO have been studied by first-principles calculations. We demonstrate the relationship between the types of TM (Co, Fe, Ni, and Cu) pairs and the energetic most stable configurations in ZnO:TM. Further calculations show that Co pairs have no tendency to form clusters, showing paramagnetic (PM) state in ZnO:Co samples in an equilibrium state and without excessive defects, as evidenced by various experiments, while ferromagnetic (FM) state is possible for the samples prepared under non-equilibrium conditions. Finally, systematical studies of a series of TM elements reveal different types of TM pairs in terms of clustering behaviors determined by spin-polarized and non-spin-polarized contributions: Co pairs and Fe pairs have no tendency to form clusters, showing PM and FM states, respectively, while Ni pairs and Cu pairs have a clustering tendency and show intrinsic FM ordering.
First-principle investigations of structural stability of beryllium under high pressure
Authors: Hao Aimin , Zhu Yan
Published: July 2012

We investigate the phase transition, elastic constants, and phonon dispersion curves of beryllium at high pressure using density functional theory. By comparing the Gibbs free energy, in the quasiharmonic approximation, of hexagonal-closed-packed (hcp, α) with those of body-centered-cubic (bcc, β), we find that α phase is stable up to 320 GPa, and then transforms to β phase. We further investigate high-pressure elastic behavior of α-Be by computing the second-order elastic constants and their variation with pressure. Using Born conditions of mechanical stability at high pressure, we confirm that α-Be structure is an unstable phase at 320 GPa. The phonon dispersion curves of α-Be under high pressure up to 320 GPa do not show any imaginary frequencies. Contrarily to α phase, β-Be phonon dispersion curves show anomalous features at zero pressure. The imaginary frequencies become real ones as pressure increases up to 320 GPa, indicating that β-Be becomes one mechanical stability structure at this pressure.
Genotype - environment interaction for post-weaning traits in Nellore beef cattle
Authors: Guidolin D. G. F. , Buzanskas M. E. , Ramos S. B. , Venturini G. C. , Lôbo R. B. , Paz C. C. P. , Munari D. P. , Oliveira J. A.
Published: July 2012

Identification of genotype–environment interaction in beef cattle may help the artificial selection process and increase the efficiency of genetic evaluation on sires submitted to different environments. Post-weaning traits are economically important and are more influenced by the effects of genotype–environment interactions than pre-weaning traits. Thus, the aim of this study was to investigate whether this interaction has any effect on bodyweight at 365, 450, and 550 days of age in Nellore cattle reared in Brazil. Analyses considered the states of Goiás, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Pará, and São Paulo. Genetic parameters were estimated for each trait, per state, using the restricted maximum likelihood method, in two-trait analysis under an animal model. Genetic correlations regarding the same trait in two different states were used to evaluate the effect of the genotype–environment interaction on the traits studied. Genetic correlation estimates smaller than 0.80 between observations for the same trait in different states were taken to be indicative of genotype–environment interaction. It was observed that there is evidence of genotype–environment interaction in some of the states studied, and they tend to increase when the weight measurements are made at later ages. From this, it was concluded that selection conducted using data from one state might be different from selection based on data from another state. Summaries of bulls that consider different environments could contribute greatly to the genetic improvement of livestock.
Effects of subcutaneous administration of caffeine on the physiometabolic profile of low-birthweight neonate piglets
Authors: Orozco-Gregorio H. , Bonilla-Jaime H. , Mota-Rojas D. , Trujillo-Ortega M. E. , Roldan-Santiago P. , Martínez-Rodríguez R. , Borderas-Tordesillas F. , Flores-Peinado S. , Mora-Medina P. , Ramírez-Necoechea R.
Published: July 2012

Caffeine administration has been used to stimulate respiration and reverse metabolic alterations in high-birthweight piglets that suffer neonatal asphyxia. However, its effect has not been evaluated on low-birthweight neonates. This study determined the effect of subcutaneously administering caffeine on the physiometabolic profile of neonate piglets with low birthweight and neonatal asphyxia. A 35-mg subcutaneous dose of caffeine, or an equivalent placebo, was randomly administered at 0 and 24 h to neonate piglets (n = 120) diagnosed with intrapartum asphyxia and classified as low-(LW) or high weight (HW) in a 2 by 2 experimental design. Blood samples were obtained at 0, 2 and 24 h postpartum. At 2 h, blood glucose concentrations diminished in the animals in both groups that were treated with caffeine (P < 0.005). Of those animals, only the ones in HW showed increased glucose concentrations by 24 h. At 0 h, group LW exhibited the highest levels of pCO2 (P < 0.005). In contrast, from 2 to 24 h only the neonates in group HW treated with caffeine reached the levels of pCO2 and pO2 characteristic of non-asphyxiated piglets. At the conclusion of the experiment, the weight of the piglets in group LW that were treated with caffeine was less than that of those that received the placebo. In contrast, the weight of the piglets in group HW that were treated with caffeine was 19% higher than that of those which received the placebo (P < 0.005). In this study, administering two doses of 35 mg of caffeine to LW neonate piglets significantly accelerated their energy expenditure, thus reducing their weight gain at 8 days of life; in contrast, the physiometabolic profile of the HW neonate piglets improved and they showed greater weight gain.