bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancers
Authors: Cho Ken W.Y.
Published: April 2012

Transcription of eukaryotic genes is an exceedingly sophisticated and complicated process, orchestrated by layers of control mechanisms involving a myriad of transcription factors and DNA control sequences, with both groups subject to multiple modifications. The availability of various recent genomic approaches has provided previously unforeseen opportunities to examine the cis‐regulatory landscape of the entire genome, resulting in the identification of a potentially overwhelming number of enhancers and novel enhancer functions. In this review, we focus on the activities of enhancers in metazoans and discuss how they serve to regulate gene expression during early development. WIREs Dev Biol 2012, 1:469–478. doi: 10.1002/wdev.53

This article is categorized under:

Gene Expression and Transcriptional Hierarchies > Regulatory Mechanisms
Cytoplasmic localization and reorganization in ascidian eggs: role of postplasmic/PEM RNAs in axis formation and fate determination
Authors: Makabe Kazuhiro W. , Nishida Hiroki
Published: April 2012

Localization of maternal molecules in eggs and embryos and cytoplasmic movements to relocalize them are fundamental for the orderly cellular and genetic processes during early embryogenesis. Ascidian embryos have been known as ‘mosaic eggs’ because of their autonomous differentiation abilities based on localized cell fate determinants. This review gives a historical overview of the concept of cytoplasmic localization, and then explains the key features such as ooplasmic movements and cell lineages that are essential to grasp the process of ascidian development mediated by localized determinant activities. These activities are partly executed by localized molecules named postplasmic/PEM RNAs, originating from approximately 50 genes, of which the muscle determinant, macho‐1, is an example. The cortical domain containing these RNAs is relocalized to the posterior‐vegetal region of the egg by cytoskeletal movements after fertilization, and plays crucial roles in axis formation and cell fate determination. The cortical domain contains endoplasmic reticulum and characteristic granules, and gives rise to a subcellular structure called the centrosome‐attracting body (CAB), in which postplasmic/PEM RNAs are highly concentrated. The CAB is responsible for a series of unequal partitionings of the posterior‐vegetal cytoplasmic domain and the postplasmic/PEM RNAs at the posterior pole during cleavage. Some components of this domain, which is rich in granules, are eventually inherited by prospective germline cells with particular postplasmic/PEM RNAs such as vasa. The postplasmic/PEM RNAs are classified into two groups according to their final cellular destinations and localization pathways. Localization of these RNAs is regulated by specific nucleotide sequences in the 3′ untranslated regions (3′UTRs). WIREs Dev Biol 2012, 1:501–518. doi: 10.1002/wdev.54

This article is categorized under:

Establishment of Spatial and Temporal Patterns > Cytoplasmic Localization

Early Embryonic Development > Fertilization to Gastrulation

Early Embryonic Development > Development to the Basic Body Plan
Principles and emerging applications of nanomagnetic materials in medicine
Authors: Clavijo‐Jordan Veronica , Kodibagkar Vikram D. , Beeman Scott C. , Hann Bradley D. , Bennett Kevin M.
Published: April 2012

The development of nanometer‐scale magnetic materials for biomedical applications spans the interface between the physical sciences and biology. Applications of these materials are rapidly becoming important in medicine and enable targeted therapies and diagnostics. At the same time, specific applications add focus to the development of novel magnetic materials and facilitate a deeper understanding of the physical mechanisms behind their function. This review presents a broad, nontechnical overview of the basis of magnetism in materials at the nanometer scale and describes how these materials are created, characterized, and used. Specific emerging applications in medical diagnostics and therapies are discussed, including cancer cell targeting for thermal ablation, tissue engineering, and three‐dimensional noninvasive molecular imaging. Challenges in these fields are discussed, including the toxicity and delivery of magnetic nanomaterials and the sensitivity of imaging and therapeutic techniques. The development of novel nanomagnetic nanomaterials should continue to accelerate as new applications are identified and researchers uncover new mechanisms to increase and modulate magnetism at the nanometer scale. WIREs Nanomed Nanobiotechnol 2012, 4:345–365. doi: 10.1002/wnan.1169

This article is categorized under:

Therapeutic Approaches and Drug Discovery > Emerging Technologies

Diagnostic Tools > In Vivo Nanodiagnostics and Imaging

Implantable Materials and Surgical Technologies > Nanomaterials and Implants
Biochemical Profile and Outcomes in Trauma Patients Subjected to Open Cardiopulmonary Resuscitation: A Prospective Observational Pilot Study
Authors: Schnüriger Beat , Talving Peep , Inaba Kenji , Barmparas Galinos , Branco Bernardino C. , Lam Lydia , Demetriades Demetrios
Published: April 2012

Background

The predictive factors to regain a heartbeat following emergency department resuscitative thoracotomy (EDT) for trauma are poorly understood. The objective of the present study was to prospectively assess the electrolyte profile, coagulation parameters, and acid‐base status from intracardiac blood samples in trauma patients subjected to open cardiopulmonary resuscitation (CPR) in the presence of established cardiac arrest.

Methods

All patients who underwent EDT following trauma were considered for inclusion. Prior to the injection of any resuscitative medications, a sample of intracardiac blood from the right ventricle was obtained for analysis.

Results

During the study period, a total of 22 patients had intracardiac blood samples obtained and were eligible for analysis. Twelve patients never regained cardiac activity, and 10 patients transiently regained a heartbeat for a mean of 51 ± 69 min, but ultimately died. Some 91 % (20/22) of patients presented with severe acidosis (pH < 7.20). The pCO2 was <45 mmHg in 68 % (15/22) of patients, and the pO2 level was >75 mmHg in 77 % (17/22) of patients. Patients who never regained cardiac activity had a significantly higher lactate level than those with a return of cardiac rhythm (17.1 ± 2.6 vs. 10.6 ± 4.9 mmol/L, p = 0.018). The sodium and potassium levels were higher for those who never regained a rhythm than for those who did regain a pulse (sodium: 155 ± 14 vs. 147 ± 9 mmol/L, p = 0.094; potassium: 6.0 ± 1.1 vs. 4.6 ± 1.0 mmol/L, p = 0.014). Severe hyperkalemia (potassium > 5.5 mmol/L) occurred significantly more often in patients who did not regain a heart beat (p = 0.030). Coagulopathy (INR > 1.2 and/or prothrombin time >15 s and/or platelet count <100,000/μL) was noted in 96 % of patients.

Conclusions

Most patients undergoing open CPR have normal blood gas levels. Severe lactic acidosis, hyperkalemia, and hypernatremia are associated with decreased probability for return of cardiac function. Calcium and magnesium levels were not significantly different between the two groups, making the therapeutic role of these electrolytes very questionable.
The value “social responsibility” as a motivating factor for adolescents' readiness to participate in different types of political actions, and its socialization in parent and peer contexts
Authors: Schmid Christine
Published: April 2012

Based on a sample of tetrads (N = 839), including 16 year‐old adolescents, their mothers, fathers, and same‐sex friends, it was analyzed in which way the value social responsibility is related to adolescents' readiness for different types of political participation. Results showed that social responsibility was positively linked to readiness for participation in legal protest actions. No relationships with readiness for participation in federal elections or with readiness for participation in illegal protest actions occurred, and a negative relationship with readiness for participation in political violent actions was found. In a second step, the socialization of the value social responsibility in the parents and peer context was the focus. Value similarities between adolescents, their parents and friends, as well as other contextual factors were considered. Multiple regression analyses revealed differential effects for male and female adolescents. In male adolescents, authoritative parenting and political discussions with parents were positively linked to social responsibility. Furthermore, peer‐group membership had a negative impact. For female adolescents, significant value similarities with their parents, especially with their mothers, occurred. Value similarities with their friend were found in both gender groups, but appeared to be higher in the female group. Also, in both gender groups, a positive parent–child relationship quality was linked to higher social responsibility. In sum, findings show that parents as well as peer contextual factors were contributing to the adolescents' value acquisition.
Competing for a Citizen: “Visible” and “Invisible” Forms of State Identity in Russia
Authors: Sanina Anna
Published: April 2012

This paper is dedicated to the characteristics of phenomenon of state identity in the modern Russian society which has been affected for last 20 years by the processes of virtualization, informatization and political transformation. Today, the Russian Federation, like any other state in the world, is closely connected to non-local events and ideas; the “title nation” and “strong state” ideas are routinely confronted by challenges from multiple agents including immigrants, the mass media and especially the Internet. In the present study, empirical findings from several studies developed with methods of visual sociology, expert interviews and public opinion research are used to understand how people in Russia tend to realize their desire to be the unit of the state forming so-called “invisible” state identity, which is not absolutely loyal to the government institutions and is very stable. This type of identity has been formed under alternative institutional logic which isn't preordained by acting of the state but is shaped as well by cultural, social, and cognitive processes in “real”, but especially in “virtual” spaces of communication. And despite “Russia as a state” is still a way of maintaining the symbolic power of political leaders, there are some strong but hidden tendencies forming “Russia as a community of citizens” under the influence of information technologies, global values, norms and outlooks.
Gesundheitsaspekte in der partizipativen Stadtentwicklung
Authors: Schmitt Jürgen
Published: April 2012

Einleitung

Die Beteiligung der Bürger gewinnt in der Stadtentwicklung an Bedeutung. Am Beispiel von Prozessen im Kontext einer „nachhaltigen Stadtentwicklung“ und im Kontext des Programms „Soziale Stadt“ skizziert der Beitrag, dass in der partizipativen Planung zunehmend auch Gesundheitsaspekte eine Rolle spielen. Gleichzeitig wird angerissen, wo weiterhin Handlungsbedarf besteht, um eine sowohl breite als auch selbstverantwortliche Mitwirkung der Bürger zu etablieren.
Type II solar radio bursts: 2. Detailed comparison of theory with observations
Authors: Hillan D. S. , Cairns Iver H. , Robinson P. A.
Published: April 2012

In this paper, the second in a two paper series, we quantitatively compare a detailed theory for type II solar radio bursts with observations and extract the parameters of the associated shocks. We use the techniques and assessment parameters developed and demonstrated in the companion paper for artificial data sets and solar wind models. Here we investigate three relatively well‐observed type II events with estimates of shock parameters from LASCO/SOHO observations of coronal mass ejections (CMEs) or other data. Using these parameters we obtain reasonable qualitative and semiquantitative agreement (25–40% correlations) between the theory and observed dynamic spectra. Then, using an iterative downhill simplex method with two assessment parameters, we extract model shock parameters that increase the agreement between theory and observation in terms of relative flux levels, spectral intensifications and drift rates. The extracted parameters agree qualitatively and semiquantitatively with the parameters (speed, size and expansion index) estimated from CME observations for one of the studied events. The extracted parameters agree qualitatively with the remaining two events and yield new initial shock speeds. The agreement between this multiprocess theory and observations is promising for these first quantitative comparisons performed here. Quantitatively, the bulk of the radio emission agrees to within 5 to 10 dB with observations, with the theory typically overpredicting the intensity of bright spots in the dynamic spectra. The methods and analyses presented here show potential for the remote inference of CME‐driven shock parameters and the prediction of radio and space weather events.
Tide‐induced vertical mixing in the Laptev Sea coastal polynya
Authors: Dmitrenko Igor A. , Kirillov Sergey A. , Bloshkina Ekaterina , Lenn Yueng‐Djern
Published: April 2012

Enhanced semidiurnal‐band velocity shear across the shelf halocline layer (SHL) was found during land‐fast ice edge mooring‐based acoustic Doppler current profiler (ADCP) and conductivity‐temperature‐depth (CTD) observations over the eastern Laptev Sea shelf (∼74°N, 128°E) in April–May 2008 and April 2009. In 2008, the major axis amplitude for the lunar semidiurnal M2tidal ellipses demonstrated intermediate maximum in the SHL at 11–13 m (15 ± 3 cm/s), gradually decreasing to subice and near‐bottom layers to ∼9 ± 3 cm/s (at 7 m) and 7 ± 2 cm/s (at 19 m), respectively. In 2009, the semidiurnal tidal flow exhibited similar patterns, but velocities were reduced by about factor of 2. Our estimates of gradient Richardson numbers suggest that the velocity shear associated with semidiurnal baroclinic tidal flow may be strong enough to play a role in water mass modification, promoting shear instabilities, turbulence, and vertical mixing of seawater properties across the SHL. This suggestion is consistent with near‐homogeneous water layers episodically occurring in the SHL. Differences in the background stratification and local tidal dynamics between 2008 and 2009, together with rapid responses of the semidiurnal motion to polynya openings, suggest that the baroclinic tide is locally generated.
Chemistry‐climate model simulations of recent trends in lower stratospheric temperature and stratospheric residual circulation
Authors: Wang Lei , Waugh Darryn W.
Published: April 2012

Observations of the lower stratospheric temperature over the last three decades show seasonal variations in tropical trends together with spatial patterns in southern high latitude trends in late winter‐spring, with regions of cooling and warming of comparable magnitude. Neither aspect is reproduced in climate models used in the Intergovernmental Panel on Climate Change's Fourth Assessment Report (IPCC AR4). Here we show that stratosphere‐resolving chemistry‐climate models can produce these aspects of temperature trends. However, the seasonality of temperature trends can vary greatly among simulations of the same model, and even if one ensemble member reproduces the observed seasonality in trends there may be little agreement with observations for another member. The variability in trends among model ensemble members is related to differences in trends in wave activity propagating into the stratosphere. These results suggest that the seasonality of the observed temperature trends could be the result of natural variability as well as, or instead of, a response to external forcing, and that comparison with these trends may not be a robust test of climate models.
Comparison of shadow‐ring correction models for diffuse solar irradiance
Authors: Sánchez G. , Serrano A. , Cancillo M. L. , García J. A.
Published: April 2012

Reliable and accurate measurements of diffuse solar irradiance are needed in order to partition global irradiance into its direct and diffuse components. Diffuse irradiance is commonly measured using sun tracking systems or shadow rings. Data obtained using a shadow ring must be corrected for the portion of diffuse irradiance blocked by the ring. In this paper we have examined and evaluated six of the most widely used correction models. Approaches that account for radiation anisotropy perform notably better than those using only geometric corrections. Our results also argue for the need to adjust empirical models to local conditions. Empirical approaches developed by LeBaron et al. (1990) and by Batlles et al. (1995) perform best when compared with the more theoretical models.
Mapping the Apollo 17 landing site area based on Lunar Reconnaissance Orbiter Camera images and Apollo surface photography
Authors: Haase I. , Oberst J. , Scholten F. , Wählisch M. , Gläser P. , Karachevtseva I. , Robinson M. S.
Published: April 2012

Newly acquired high resolution Lunar Reconnaissance Orbiter Camera (LROC) images allow accurate determination of the coordinates of Apollo hardware, sampling stations, and photographic viewpoints. In particular, the positions from where the Apollo 17 astronauts recorded panoramic image series, at the so‐called “traverse stations”, were precisely determined for traverse path reconstruction. We analyzed observations made in Apollo surface photography as well as orthorectified orbital images (0.5 m/pixel) and Digital Terrain Models (DTMs) (1.5 m/pixel and 100 m/pixel) derived from LROC Narrow Angle Camera (NAC) and Wide Angle Camera (WAC) images. Key features captured in the Apollo panoramic sequences were identified in LROC NAC orthoimages. Angular directions of these features were measured in the panoramic images and fitted to the NAC orthoimage by applying least squares techniques. As a result, we obtained the surface panoramic camera positions to within 50 cm. At the same time, the camera orientations, North azimuth angles and distances to nearby features of interest were also determined. Here, initial results are shown for traverse station 1 (northwest of Steno Crater) as well as the Apollo Lunar Surface Experiment Package (ALSEP) area.
Weak influences of climate and mineral supply rates on chemical erosion rates: Measurements along two altitudinal transects in the Idaho Batholith
Authors: Ferrier Ken L. , Kirchner James W. , Finkel Robert C.
Published: April 2012

Chemical weathering promotes regolith production, physical erosion, nutrient supply, and drawdown of atmospheric CO2. Although mineral dissolution rates show dependences on temperature and moisture in theoretical models and laboratory experiments, effects of climate on chemical erosion rates in nature remain uncertain, in part because variations in physical erosion rates and lithology can obscure climatic signals in chemical erosion rate measurements. Here we present new estimates of millennial‐scale chemical and physical erosion rates along two altitudinal transects in the Idaho Batholith. Our measurements suggest that chemical erosion rates and the extent of regolith chemical alteration are insensitive to mean annual regolith temperature, even though the study sites span a wide range in temperatures (4.8°C–10.9°C). These data also suggest that rates of chemical erosion and the extent of regolith chemical alteration are weakly correlated with the annual duration of high regolith moisture conditions. Lastly, our measurements show that the sampled regoliths tend to grow more chemically weathered with increasing regolith residence time, implying that weathering at these sites is primarily limited by mineral dissolution kinetics rather than mineral supply rates to the regolith. The lack of strong control by mineral supply means that chemical erosion rates at these sites could potentially vary in response to climatic factors. Such climatically driven variation in chemical erosion rates is not obvious in our data, however. Instead, our measurements suggest that chemical erosion rates at these sites are insensitive to mean annual regolith temperature and only weakly dependent on the length of the wet season.
Consistency of groundwater flow patterns in mountainous topography: Implications for valley bottom water replenishment and for defining groundwater flow boundaries
Authors: Welch L. A. , Allen D. M.
Published: April 2012

Topographic influences on groundwater flow processes that contribute to baseflow and mountain block recharge (MBR) are conceptually investigated using three‐dimensional numerical models of saturated groundwater flow. Model domains for conceptual and real topographies are developed as “mountain groundwatershed units” (MGUs) to represent regional‐scale watershed systems. Results indicate regularity in groundwater flow patterns that reflect consistency of prominent topographic features, providing a basis for conceptualizing three‐dimensional groundwater flow. Baseflow is generated mainly from recharge within the watershed area. MBR is produced primarily from recharge that is focused across triangular facets near the mountain front (∼73%–97% of total MBR), with additional contributions originating within the watershed (up to ∼27% of MBR). MBR contributions originating from recharge near the highest‐elevation watershed boundaries are minimal but are greater for topography with less stream incision. With orographic influences, more MBR originates within the watershed. MBR rates are relatively consistent between models because of similarities in mountain front topography, while baseflow is variable. Gains and losses to systems via cross‐watershed groundwater flux, generated because of topographic differences between adjacent watersheds, cause baseflow to vary by up to ∼10% but do not significantly influence MBR. In data‐sparse regions such as mountains, a basic numerical modeling approach, using the MGU concept with topography data and mapped watershed boundaries, can be used to develop site‐specific conceptual models to constrain water budgets, to delineate recharge areas, and to guide further investigation and data collection.
Less water: How will agriculture in Southern Mountain states adapt?
Authors: Frisvold George B. , Konyar Kazim
Published: April 2012

This study examined how agriculture in six southwestern states might adapt to large reductions in water supplies, using the U.S. Agricultural Resource Model (USARM), a multiregion, multicommodity agricultural sector model. In the simulation, irrigation water supplies were reduced 25% in five Southern Mountain (SM) states and by 5% in California. USARM results were compared to those from a “rationing” model, which assumes no input substitution or changes in water use intensity, relying on land fallowing as the only means of adapting to water scarcity. The rationing model also ignores changes in output prices. Results quantify the importance of economic adjustment mechanisms and changes in output prices. Under the rationing model, SM irrigators lose $65 in net income. Compared to this price exogenous, “land‐fallowing only” response, allowing irrigators to change cropping patterns, practice deficit irrigation, and adjust use of other inputs reduced irrigator costs of water shortages to $22 million. Allowing irrigators to pass on price increases to purchasers reduced income losses further, to $15 million. Higher crop prices from reduced production imposed direct losses of $130 million on first purchasers of crops, which include livestock and dairy producers, and cotton gins. SM agriculture, as a whole, was resilient to the water supply shock, with production of high value specialty crops along the Lower Colorado River little affected. Particular crops were vulnerable however. Cotton production and net returns fell substantially, while reductions in water devoted to alfalfa accounted for 57% of regional water reduction.
On the effects of seasonality on soil water balance and plant growth
Authors: Feng Xue , Vico Giulia , Porporato Amilcare
Published: April 2012

The partitioning of rainfall into evapotranspiration, runoff, and deep infiltration in seasonally dry climates is influenced by strong temporal variability in rainfall and potential evapotranspiration at the intra‐annual scale, which cannot be captured by conventional steady state water balance models. Guided by dimensional analysis and using simplified stochastic soil moisture models, we develop analytical expressions describing the annual partitioning of rainfall into evapotranspiration and deep percolation/runoff in seasonally dry, surface water dependent landscapes. We discuss the related changes to Budyko's curve under different seasonality scenarios, showing that an increase in seasonal rainfall and potential evapotranspiration variability as well as dry season length can lead to a decrease in the annual evapotranspiration ratio. In addition, our model shows that although increased soil water storage can compensate for the decrease in evapotranspiration due to climate seasonality, this effect is more marked in drier climates (higher annual dryness index) compared to wetter climates. Finally, the coupling of the soil moisture model to a minimalist plant growth model shows that in seasonally dry climates, a maximum in biomass is to be expected for a wet season of optimal length, for which the limitations imposed by both water availability and growth duration are at a minimum.
Transforming community access to space science models
Authors: MacNeice Peter , Hesse Michael , Kuznetsova Maria , Maddox Marlo , Rastaetter Lutz , Berrios David , Pulkkinen Antti
Published: April 2012

Researching and forecasting the ever changing space environment (often referred to as space weather) and its influence on humans and their activities are model‐intensive disciplines. This is true because the physical processes involved are complex, but, in contrast to terrestrial weather, the supporting observations are typically sparse. Models play a vital role in establishing a physically meaningful context for interpreting limited observations, testing theory, and producing both nowcasts and forecasts. For example, with accurate forecasting of hazardous space weather conditions, spacecraft operators can place sensitive systems in safe modes, and power utilities can protect critical network components from damage caused by large currents induced in transmission lines by geomagnetic storms.
Anthropogenic forcings and climate change in the northern Pacific region
Authors: Zhang Jing , Saito Hiroaki , Ju Se‐Jong
Published: April 2012

5th China‐Japan‐Korea IMBER Symposium and Training; Shanghai, China, 22–25 November 2011 This past November, scientists from China, Japan, and Korea gathered in Shanghai to share and discuss their latest achievements from the international Integrated Marine Biogeochemistry and Ecosystem Research (IMBER) project. The symposium focused on the impact of climate change and anthropogenic forcings on physical processes and biogeochemical cycles, ecosystem structure and functions, and fisheries in the northwestern Pacific region and how these complex interactions, in turn, influence marine ecosystems and human society. Scientists from China, Japan, and Korea have been working actively in the areas of Global Ocean Ecosystem Dynamics (GLOBEC) and IMBER science since the early 1990s. Since 2002 the biennial China‐ Japan‐Korea GLOBEC‐IMBER symposia have provided scientists from these countries with the opportunity to collaborate and exchange and compare their research in the northwestern Pacific and marginal seas. Following the GLOBEC‐IMBER merger in 2010, the IMBER community decided to continue organizing these symposia.
Kirschvink receives 2011 William Gilbert Award: Citation
Authors: Weiss Benjamin P.
Published: April 2012

Joseph Kirschvink received the William Gilbert Award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif. The award recognizes outstanding and unselfish work in magnetism of Earth materials and of the Earth and planets.
Warming set stage for deadly heat wave
Authors: Schultz Colin
Published: April 2012

In the summer of 2010, soaring temperatures and widespread forest fires ravaged western Russia, killing 55,000 and causing $15 billion in economic losses. In the wake of the record‐setting heat wave, two studies sought to identify the contribution that human activities made to the event. One showed that temperatures seen during the deadly heat wave fell within the bounds of natural variability, while another attributed the heat wave to human activity, arguing that anthropogenic warming increased the chance of record‐breaking temperatures occurring. Merging the stances of both studies, Otto et al. sought to show that while human contributions to climate change did not necessarily cause the deadly heat wave, they did play a role in setting the stage for its occurrence. Using an ensemble of climate simulations, the authors assessed the expected magnitude and frequency of an event like the 2010 heat wave under both 1960s and 2000s environmental conditions. The authors found that although the average temperature in July 2010 was 5°C higher than the average July temperature from the past half decade, the deadly heat wave was within the natural variability of 1960s, as well as 2000s, climate conditions
Improving understanding of type III solar radio bursts
Authors: Balcerak Ernie
Published: April 2012

Solar radio bursts are associated with solar events that can interfere with GPS and communications systems, so scientists would like to learn more about the dynamics of these bursts. Type III solar radio bursts, which are generated when high‐energy electrons are ejected from the Sun, are characterized by a rapid drift in frequency from hundreds of megahertz to tens of kilohertz. Scientists believe that the process of producing type III solar radio bursts is associated with the excitation of Langmuir waves, which are oscillations in the electron density in a plasma, followed by the conversion of these waves into radio emissions. However, there are some open questions about these bursts.Thejappa et al. applied a method known as trispectral analysis to an observed Langmuir wave packet associated with a type III solar radio burst. The scientists show that four different spectral components of this wave packet interact strongly with one another in an interaction known as the oscillating two‐stream instability. The researchers suggest that this could explain some features of the solar radio bursts. (Geophysical Research Letters, doi:10.1029/2012GL051017, 2012)
Reforestation efforts reshape Hawaii's soil hydrology
Authors: Schultz Colin
Published: April 2012

Starting with the arrival in Hawaii of Polynesian settlers in the fourth century and peaking in the mid‐1800s, the destructive forces of wildfires and pests and the grazing of feral pigs, goats, and cattle reduced the native forests of Maui to just one tenth of their original extent. Maui's native vegetation was replaced largely by imported or invasive species. Over time, the invasive grasses that took root reshaped the hydrological properties of the soil, reducing the viability of native plant species, which had evolved to thrive under Hawaii's previous hydrological dynamics. Maui's ecosystem had been changed for so long that scientists were uncertain whether the region could actually again support the native flora
Longitudinal Association Between Marital Disruption and Child BMI and Obesity
Authors: Arkes Jeremy
Published: April 2012

This research examines whether family disruptions (i.e., divorces and separation) contribute to children's weight problems. The sample consists of 7,299 observations for 2,333 children, aged 5–14, over the 1986–2006 period, from a US representative sample from the Child and Young Adult Survey accompanying the National Longitudinal Survey of Youth (NLSY). The study uses individual‐fixed‐effects models in a longitudinal framework to compare children's BMI and weight problems before and after a disruption. Furthermore, besides doing a before—after comparison for children, the study also estimates the effects at various periods relative to the disruption in order to examine whether children are affected before the disruption and whether any effects change as time passes from the disruption, as some effects may be temporary or slow to develop. Despite having a larger sample than the previous studies, the results provide no evidence that, on average, children's BMI and BMI percentile scores (measured with continuous outcomes) are affected before the disruption, after the disruption, and as time passes from the disruption, relative to a baseline period a few years before the disruption. However, children experiencing a family disruption do have an increased risk of obesity (having a BMI percentile score of 95 or higher) in the two years leading up to the disruption as well as after the disruption, and as time passes from the disruption.
Inflammatory and Prothrombotic States in Obese Children of European Descent
Authors: Stoppa‐Vaucher Sophie , Dirlewanger Mirjam A. , Meier Christoph A. , de Moerloose Philippe , Reber Guido , Roux‐Lombard Pascale , Combescure Christoph , Saudan Sonja , Schwitzgebel Valerie M.
Published: April 2012

Adipose tissue may release mediators that induce a chronic inflammatory state and alterations in coagulation, which contribute to insulin resistance, atherosclerosis, and thrombosis. We investigated whether inflammatory and/or prothrombotic states exist in obese children and assessed their interrelationship. Sixty‐one subjects were recruited, aged between 6 and 16 years, to participate in a cross‐sectional study at Children's University Hospital of Geneva. Selected pro/anti‐inflammatory cytokines/chemokines and hemostasis parameters were measured in obese children and lean controls. Cardiovascular risk factors in the family were indexed. Fasting glucose level, insulin, prothrombin time (PT), fibrinogen, activated partial thromboplastin time (aPTT), D‐dimer, endogenous thrombin potential (ETP), C‐reactive protein (CRP), interleukin‐6 (IL‐6), interleukin‐10 (IL‐10), interferon‐γ‐inducible‐protein (IP‐10), monocyte chemoattractant protein 1 (MCP‐1), and interleukin‐1 receptor antagonist (IL‐1Ra) were measured. We estimated insulin resistance by homeostatic model assessment (HOMA). Anti‐ (IL‐1Ra) and proinflammatory cytokines (MCP‐1, IL‐6) were significantly increased in obese children in comparison to the control group, even before puberty. Hemostasis was also altered in obese children with a significantly increased fibrinogen level, increased D‐dimer, a shortened PT, as well as an increased ETP. No correlation was found between cytokine levels and hemostasis parameters, except for IL‐6 and fibrinogen. Obese children present with inflammatory and prothrombotic states as early as 6 years of age and these states are similar in prepubertal and pubertal obese children. The cytokines IL‐1Ra and MCP‐1 were most significantly increased in obese children. Further investigation is necessary to determine if these cytokines, together with ETP, can reliably predict the development of diabetes and atherosclerosis.
Charge trapping induced drain-induced-barrier-lowering in HfO2/TiN p-channel metal-oxide-semiconductor-field-effect-transistors under hot carrier stress
Authors: Lo Wen-Hung , Chang Ting-Chang , Tsai Jyun-Yu , Dai Chih-Hao , Chen Ching-En , Ho Szu-Han , Chen Hua-Mao , Cheng Osbert , Huang Cheng-Tung
Published: April 2012

This letter studies the channel hot carrier stress (CHCS) behaviors on high dielectric constant insulator and metal gate HfO2/TiN p-channel metal-oxide-semiconductor field effect transistors. It can be found that the degradation is associated with electron trapping, resulting in Gm decrease and positive Vth shift. However, Vth under saturation region shows an insignificant degradation during stress. To compare that, the CHC-induced electron trapping induced DIBL is proposed to demonstrate the different behavior of Vth between linear and saturation region. The devices with different channel length are used to evidence the trapping-induced DIBL behavior.
Phase behavior of mixed submonolayer films of krypton and xenon on graphite
Authors: Patrykiejew A. , Sokołowski S.
Published: April 2012

Using the results of extensive Monte Carlo simulations in the canonical and grand canonical ensembles, we discuss the phase behavior of mixed submonolayer films of krypton and xenon adsorbed on the graphite basal plane. The calculations have been performed using two- and three-dimensional models of the systems studied. It has been demonstrated that out-of-plane motion does not affect the properties of the films as long as the total density is well below the monolayer completion and at moderate temperatures. For the total densities close to the monolayer completion, the promotion of particles to the second layer considerably affects the film properties. Our results are in a reasonable agreement with the available experimental data. The melting point of submonolayer films has been shown to exhibit non-monotonous changes with the film composition, and reaches minimum for the xenon concentration of about 50%. At the temperatures below the melting point, the structure of solid phases depends upon the film composition and the temperature; one can also distinguish commensurate and incommensurate phases. Two-dimensional calculations have demonstrated that for the xenon concentration between about 15% and 65% the adsorbed film exhibits the formation of a superstructure, in which each Xe atom is surrounded by six Kr atoms. This superstructure is stable only at very low temperatures and transforms into the mixed commensurate \documentclass[12pt]{minimal}\begin{document}$(\sqrt{3}\times \sqrt{3})R30$\end{document}(3×3)R30° phase upon the increase of temperature. Such a superstructure does not appear when a three-dimensional model is used. Grand canonical ensemble calculations allowed us to show that for the xenon concentration of about 3% the phase diagram topology of monolayer films changes from the krypton-like (with incipient triple point) to the xenon-like (with ordinary triple point).
Mathematical modeling of a prototype of parabolic trough solar collector
Authors: Coccia Gianluca , Latini Giovanni , Sotte Marco
Published: April 2012

In this paper, a mathematical model of a parabolic trough collector (PTC) is described in detail and tested by comparing the efficiency predicted by the model with the efficiency measured through outdoor tests on a PTC prototype. The model accounts for optical and thermal losses, thus allowing the calculation of optical, thermal, and global efficiencies, and of all working parameters such as temperatures or heat fluxes on all parts of the receiver. The model is presented in detail and its implementation in a specific ambient for technical computation is also described. The application of the model to a specific prototype of parabolic trough collector is described: this prototype has been developed and tested at Università Politecnica delle Marche and is intended for industrial process heat production. The comparison between experimental and calculated results shows an average error of about 3.82% and a maximum error of 14% on global efficiencies for tests with water in the temperature range 25–75 °C.
Quasi-classical trajectories study of Ne2Br2(B) vibrational predissociation: Kinetics and product distributions
Authors: Arbelo-González Wilmer , González-Martínez Maykel L. , Reed Stewart K. , Rubayo-Soneira Jesús , Shalashilin Dmitrii V.
Published: April 2012

The vibrational predissociation of the Ne2Br2(B) van der Waals complex has been investigated using the quasi-classical trajectory method (QCT), in the range of vibrational levels v′ = 16–23. Extensive comparison is made with the most recent experimental observations [Pio et al., J. Chem. Phys. 133, 014305 (2010)]10.1063/1.3456550, molecular dynamics with quantum transitions simulations [Miguel et al., Faraday Discuss. 118, 257 (2001)]10.1039/b009222n, and preliminary results from 24-dimensional Cartesian coupled coherent state (CCCS) calculations. A sequential mechanism is found to accurately describe the theoretical dynamical evolution of intermediate and final product populations, and both QCT and CCCS provide very good estimates for the dissociation lifetimes. The capabilities of QCT in the description of the fragmentation kinetics are analyzed in detail by using reduced-dimensionality models of the complexes and concepts from phase-space transport theory. The problem of fast decoupling of the different coherent states in CCCS simulations, resulting from the high dimensionality of phase space, is tackled using a re-expansion scheme. QCT ro-vibrational product state distributions are reported. Due to the weakness of the van der Waals couplings and the low density of vibrational states, QCT predicts a larger than observed propensity for Δv′ = −1 and −2 channels for the respective dissociation of the first and second Ne atoms.
A simple device for dielectric spectroscopy of polymers with temperature regulation close to 300 K based on a Peltier junction
Authors: Raihane A. , Tourbot R. , Ladieu F. , L’Hôte D.
Published: April 2012

We present a simple thermostat device for performing dielectric spectroscopy measurements on polymers close to their glass transition temperature. By using a vacuum chamber containing a Peltier junction with its regulator, we show that a very simple setup yields a temperature accuracy which is good enough for accurate studies of polymer dielectric properties. This technique is also more cost effective than standard setups using cryogenic fluids.
Photoluminescence quenching processes by NO2 adsorption in ZnO nanostructured films
Authors: Cretì A. , Valerini D. , Taurino A. , Quaranta F. , Lomascolo M. , Rella R.
Published: April 2012

The optical response by NO2 gas adsorption at different concentrations has been investigated, at room temperature, in ZnO nanostructured films grown by controlled vapor phase deposition. The variation (quenching) in the photoluminescence signal from excitonic and defects bands, due to the interactions between the oxidizing gas molecules and the sample surface, has been detected and dynamic responses and calibration curves as a function of gas concentration have been obtained and analyzed for each band. We showed that the sensing response results larger in excitonic band than in defect one and that the emission signal rises from two different quenchable and unquenchable states. A simple model was proposed in order to explain the quenching processes on the emission intensity and to correlate them to the morphological features of the samples. Finally, the reversibility of the quenching effects has also been tested at high gas concentration.
Electronic coherence dynamics in trans-polyacetylene oligomers
Authors: Franco Ignacio , Brumer Paul
Published: April 2012

Electronic coherence dynamics in trans-polyacetylene oligomers are considered by explicitly computing the time dependent molecular polarization from the coupled dynamics of electronic and vibrational degrees of freedom in a mean-field mixed quantum-classical approximation. The oligomers are described by the Su-Schrieffer-Heeger Hamiltonian and the effect of decoherence is incorporated by propagating an ensemble of quantum-classical trajectories with initial conditions obtained by sampling the Wigner distribution of the nuclear degrees of freedom. The electronic coherence of superpositions between the ground and excited and between pairs of excited states is examined for chains of different length, and the dynamics is discussed in terms of the nuclear overlap function that appears in the off-diagonal elements of the electronic reduced density matrix. For long oligomers the loss of coherence occurs in tens of femtoseconds. This time scale is determined by the decay of population into other electronic states through vibronic interactions, and is relatively insensitive to the type and class of superposition considered. By contrast, for smaller oligomers the decoherence time scale depends strongly on the initially selected superposition, with superpositions that can decay as fast as 50 fs and as slow as 250 fs. The long-lived superpositions are such that little population is transferred to other electronic states and for which the vibronic dynamics is relatively harmonic.
Magnetic-field-induced martensitic transformation in MnNiAl:Co alloys
Authors: Feng L. , Ma L. , Liu E. K. , Wu G. H. , Wang W. H. , Zhang W. X.
Published: April 2012

A series of Heusler-type MnNiCoAl alloys have been prepared, and the composition dependence of the martensitic transformation has been investigated. Due to the formation of a local Mn-Co-Mn ferromagnetic structure in the antiferromagnetic matrix, a large magnetization difference of 48 Am2/kg and a driving efficiency of 2.14 K/T can be observed in Mn50Ni32Co6Al12 sample in which a field-induced transformation can be realized. X-ray diffraction results further indicate that the high temperature phase has a high level of atomic disorder which causes an increase of the thermal hysteresis of the transformation when increasing Co content.
Communication: Competition between π⋯π interaction and halogen bond in solution: A combined 13C NMR and density functional theory study
Authors: Zhang Yu , Ji Baoming , Tian Anmin , Wang Weizhou
Published: April 2012

Competition between π⋯π interaction and halogen bond in solution has been investigated by using carbon nuclear magnetic resonance spectroscopy (13C NMR) combined with density functional theory calculation. Both experimental and theoretical results clearly show that there are no C–Cl⋯π or C–Br⋯π halogen bonds and only the π⋯π interactions exist in the binary liquid mixtures of C6D6 with C6F5Cl and C6F5Br, respectively. The case is totally different for the binary liquid mixtures of C6D6 with C6F5I in which the C–I⋯π halogen bonds not the π⋯π interactions are present. The important role of entropy in the competition between π⋯π interaction and halogen bond in solution was also discussed.
Time-dependent wave packet theory for state-to-state differential cross sections of four-atom reactions in full dimensions: Application to the HD + OH → H2O + D reaction
Authors: Liu Shu , Xu Xin , Zhang Dong H.
Published: April 2012

Time-dependent wave packet method has been developed to calculate differential cross section for four-atom reactions in full dimension, utilizing an improved version of reactant-product-decoupling scheme. Differential cross sections for the title reaction were calculated for collision energy up to 0.4 eV. It is found that the differential cross sections for the reaction are all peaked in the backward direction. The majority of H2O is produced in the first stretch excited state, with a large fraction of available energy for the reaction going into H2O internal motion. As compared in a previous report by Xiao et al. [Science 333, 440 (2011)]10.1126/science.1205770, the differential cross section at Ec = 0.3 eV and the differential cross section at the backward direction as a function of collision energy agree with experiment very well, indicating it is possible now to calculate complete dynamical information for some simple four-atom reactions, as have been done for three-atom reactions in the past decades.
Scaling growth kinetics of self-induced GaN nanowires
Authors: Dubrovskii Vladimir G. , Consonni Vincent , Geelhaar Lutz , Trampert Achim , Riechert Henning
Published: April 2012

We present a kinetic model showing why self-induced GaN nanowires synthesized by molecular beam epitaxy obey the scaling growth laws. Our model explains the scaling behavior from kinetic considerations of the step flow radial growth and the shadow effect. The nanowire length L and radius R scale with time as [1+C(t-t0)]α/(α+1) and [1+C(t-t0)]1/(α+1), respectively. Consequently, the length scales with the radius as L∝Rα. The power index α equals 2.46 in our conditions. This scaling behavior is paramount for understanding the self-induced growth of nanowires in general as well as for tuning their morphology to the desired properties.