bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics and underlying causes of illegal bushmeat trade in Zimbabwe
Authors: Lindsey P. A. , Romañach S.S. , Matema S. , Matema C. , Mupamhadzi I. , Muvengwi J.
Published: February 2011

The prevalence and impacts of the illegal trade in bushmeat are under appreciated in Southern Africa, despite indications that it constitutes a serious conservation threat in parts of the region. Bushmeat trade has emerged as a severe threat to wildlife conservation and the viability of wildlife-based land uses in Zimbabwe during a period of political instability and severe economic decline. We conducted a study around Savé Valley Conservancy in the South-East Lowveld of Zimbabwe to investigate the dynamics and underlying causes of the bushmeat trade, with the objective of developing solutions. We found that bushmeat hunting is conducted mainly by unemployed young men to generate cash income, used mostly to purchase food. Bushmeat is mainly sold to people with cash incomes in adjacent communal lands and population centres and is popular by virtue of its affordability and availability. Key drivers of the bushmeat trade in the South-East Lowveld include: poverty, unemployment and food shortages, settlement of wildlife areas by impoverished communities that provided open access to wildlife resources, failure to provide stakes for communities in wildlife-based land uses, absence of affordable protein sources other than illegally sourced bushmeat, inadequate investment in anti-poaching in areas remaining under wildlife management, and weak penal systems that do not provide sufficient deterrents to illegal bushmeat hunters. Each of these underlying causes needs to be addressed for the bushmeat trade to be tackled effectively. However, in the absence of political and economic stability, controlling illegal bushmeat hunting will remain extremely difficult and the future of wildlife-based land uses will remain bleak.
Invasive species and bushmeat hunting contributing to wildlife conservation: the case of feral pigs in a Neotropical wetland
Authors: Jean Desbiez Arnaud Leonard , Keuroghlian Alexine , Piovezan Ubiratan , Bodmer Richard Ernest
Published: February 2011

An unusual combination of two major conservation threats, invasive species and bushmeat hunting, has had a positive outcome for wildlife conservation in the Brazilian Pantanal. The Pantanal is a wetland and one of the few non-protected areas in the Neotropics where people live but rarely hunt native wildlife. To understand why wildlife hunting is not a major conservation issue in the Pantanal an exploratory survey, semi-structured interviews, skull collection and tooth wear analysis of feral pig Sus scrofa, white-lipped peccary Tayassu pecari and collared peccary Pecari tajacu were conducted, and hunting registers distributed, in the central region of the Pantanal. The results showed that feral pigs are the main hunting target. Feral pigs are effectively acting as a replacement species for hunting of native wildlife because the pigs provide a constant, culturally acceptable, readily available and free source of meat and oil to remote ranches. We cannot evaluate, however, if the buffer from hunting that feral pigs provide to native wildlife outweigh this species’ potential negative ecological impacts.
Wild felid diversity and activity patterns in Sabangau peat-swamp forest, Indonesian Borneo
Authors: Cheyne Susan M. , Macdonald David W.
Published: February 2011

A study to identify the felid biodiversity of the Sabangau Forest, Central Kalimantan, Indonesia, was initiated in May 2008 and involved continuous sampling until October 2009. A total of 44 cameras in 27 locations were used and 5,777 functional trap nights (of 6,542 survey nights) resulted in confirmed sightings of the Sunda clouded leopard Neofelis nebulosa, leopard cat Prionailurus bengalensis, marbled cat Pardofelis marmorata and flat-headed cat Prionailurus planiceps, representing four of the five wild felids of Borneo. The long-term use of fixed and roving cameras provided insight into the movements, occurrence and activity patterns of these elusive felids within a disturbed peat-swamp forest. In an area of 145 km2 (including buffer) the clouded leopard was the most commonly photographed felid (22 photo-captures of 53 total captures), followed by the leopard cat (21), flat-headed cat (7) and marbled cat (3). A total of 231 camera-trap nights were required to obtain the first photograph of a felid, the leopard cat, 704 for the clouded leopard, 3,498 for the flat-headed cat, and 5,423 (476 calendar days) for the marbled cat. A female clouded leopard was not photographed until 5,764 trap nights. This highlights the importance of long-term camera-trapping studies to maximize capture probability of these elusive felids and especially to account for potential differences in home range size and use by clouded leopard males and females.
Field surveys for the Endangered pygmy hippopotamus Choeropsis liberiensis in Sapo National Park, Liberia
Authors: Collen Ben , Howard Robert , Konie John , Daniel Olivia , Rist Janna
Published: February 2011

Conservation of a threatened species is reliant upon good quality monitoring information to provide population estimates and trends to inform management practices. Surveying to establish such data can be costly and difficult, particularly for cryptic species in forest habitats. We therefore used remotely triggered cameras to survey for the presence of the pygmy hippopotamus Choeropsis liberiensis in Sapo National Park in Liberia. In 1,247 trap days we obtained seven camera-trap photographs, the first photographic records of the species in Liberia. Habitat destruction, principally from illegal gold mining, is the greatest threat to the persistence of the pygmy hippopotamus within the Park. A range-wide survey of the pygmy hippopotamus is required to establish a robust baseline from which future conservation efforts can be developed. Understanding how this species is able to cope with the effects of habitat fragmentation across its range, and controlling commercial hunting, will dictate how it is able to survive the ongoing pressures of land conversion in West Africa.
First detection ofBabesia occultansinHyalommaticks from Tunisia
Authors: ROS-GARCÍA A. , M'GHIRBI Y. , BOUATTOUR A. , HURTADO A.
Published: February 2011

Descriptions ofBabesia occultanshave previously been restricted to sub-Saharan Africa. Here, we report the finding, for the first time, of this low or non-pathogenic bovineBabesiaspecies in Tunisia, northern Africa.B. occultansDNA was detected by molecular methods inHyalomma marginatumunfed ticks collected in 3 bioclimatic regions of Tunisia. The near-full-length 18S rRNA gene was sequenced and compared with related sequences retrieved from GenBank. Phylogenetic analysis indicated that other sequences deposited asBabesiasp. could also correspond toB. occultans, suggesting that this species may have a wide distribution in Mediterranean and Asiatic regions, and not only in sub-Saharan Africa as previously described. AB. occultans-specific Reverse Line Blot (RLB) oligonucleotide probe was designed for future epidemiological studies that would help to clarify this possibility.
Emotional face processing and flat affect in schizophrenia: functional and structural neural correlates
Authors: Lepage M. , Sergerie K. , Benoit A. , Czechowska Y. , Dickie E. , Armony J. L.
Published: February 2011

Background

There is a general consensus in the literature that schizophrenia causes difficulties with facial emotion perception and discrimination. Functional brain imaging studies have observed reduced limbic activity during facial emotion perception but few studies have examined the relation to flat affect severity.

Method

A total of 26 people with schizophrenia and 26 healthy controls took part in this event-related functional magnetic resonance imaging study. Sad, happy and neutral faces were presented in a pseudo-random order and participants indicated the gender of the face presented. Manual segmentation of the amygdala was performed on a structural T1 image.

Results

Both the schizophrenia group and the healthy control group rated the emotional valence of facial expressions similarly. Both groups exhibited increased brain activity during the perception of emotional faces relative to neutral ones in multiple brain regions, including multiple prefrontal regions bilaterally, the right amygdala, right cingulate cortex and cuneus. Group comparisons, however, revealed increased activity in the healthy group in the anterior cingulate, right parahippocampal gyrus and multiple visual areas. In schizophrenia, the severity of flat affect correlated significantly with neural activity in several brain areas including the amygdala and parahippocampal region bilaterally.

Conclusions

These results suggest that many of the brain regions involved in emotional face perception, including the amygdala, are equally recruited in both schizophrenia and controls, but flat affect can also moderate activity in some other brain regions, notably in the left amygdala and parahippocampal gyrus bilaterally. There were no significant group differences in the volume of the amygdala.
Interaction effects of subjective memory impairment and ApoE4 genotype on episodic memory and hippocampal volume
Authors: Striepens N. , Scheef L. , Wind A. , Meiberth D. , Popp J. , Spottke A. , Kölsch H. , Wagner M. , Jessen F.
Published: February 2011

Background

The apolipoprotein E4 allele (ApoE4) is an established genetic risk factor for Alzheimer's disease (AD). However, its effects on cognitive performance and brain structure in healthy individuals are complex. We investigated the effect of ApoE4 on cognitive performance and medial temporal lobe volumetric measures in cognitively unimpaired young elderly with and without subjective memory impairment (SMI), which is an at-risk condition for dementia.

Method

Altogether, 40 individuals with SMI and 62 without were tested on episodic memory and on tasks of speed and executive function. All participants were ApoE genotyped. 21 subjects with SMI and 47 without received additional structural magnetic resonance imaging. Volumetric measures of the hippocampus, the entorhinal cortex and the amygdala were obtained manually.

Results

In the SMI group, ApoE4 carriers performed worse on the episodic memory (p=0.049) and showed smaller left hippocampal volumes (p=0.030). In the individuals without SMI, the ApoE4 carriers performed better on episodic memory (p=0.018) and had larger right hippocampal volumes (p=0.039). The interaction of group (SMI/no SMI) and ApoE genotype was significant for episodic memory (p=0.005) and right and left hippocampal volumes (p=0.042;p=0.035). There were no within-group differences or interaction effects on speed and executive function composite measures or other volumetric measures.

Conclusions

The negative effect of ApoE4 on episodic memory and hippocampal volume in SMI supports SMI as a prodromal condition of AD. The positive effects of ApoE4 in subjects without SMI adds to a number of reports on positive ApoE4 effects in young and very old individuals.
Haemoglobin A1c, fasting glucose and future risk of elevated depressive symptoms over 2 years of follow-up in the English Longitudinal Study of Ageing
Authors: Hamer M. , Batty G. D. , Kivimaki M.
Published: February 2011

Background

The cross-sectional association between impaired glucose/diabetes and depression is inconsistent. We examined the longitudinal associations between diabetes, indicators of glucose metabolism and depressive symptoms over 2 years of follow-up.

Method

Participants were 4338 men and women from the English Longitudinal Study of Ageing, a prospective study of community-dwelling older adults [aged 62.9 (s.d.=9.0) years, 45.2% men]. Depressive symptoms were assessed at baseline and after 2 years of follow-up using the eight-item Centre of Epidemiological Studies – Depression (CES-D) scale. Glycated haemoglobin (HbA1c) levels, fasting glucose and other biological and behavioural risk factors were also assessed at baseline.

Results

Approximately 11.5% of the sample were categorized with elevated depressive symptoms at follow-up (a score ⩾4 on the CES-D). There was an association between HbA1c and depressive symptoms at follow-up [per unit increase, odds ratio (OR) 1.17, 95% confidence interval (CI) 1.03–1.33] after adjustment for age and baseline CES-D. Cross-sectionally, the probability of depressive symptoms increased with increasing HbA1c levels until the value of 8.0% after which there was a plateau [p(curve)=0.03]. Compared with those with normal fasting glucose, participants with diabetes (confirmed through self-report or elevated fasting blood glucose) at baseline had an elevated risk of depressive symptoms at follow-up (OR 1.52, 95% CI 1.01–2.30) after adjusting for depressive symptoms at baseline, behavioural and sociodemographic variables, adiposity and inflammation.

Conclusions

These data suggest that poor glucose metabolism and diabetes are risk factors for future depression in older adults. There was no evidence of a U-shaped association.
Individualisierte Medizin 2011
Authors: Blum
Published: February 2011

Die molekular- und zellbiologische Forschung haben in den letzten Jahren nicht nur die Diagnostik, Therapie und Prävention von Erkrankungen revolutioniert, sondern auch zunehmend Einblick in deren molekulare Pathogenese ermöglicht. So ist es heute möglich, mit molekular-genetischen und biochemischen Methoden einerseits Mutationen oder «Single Nucleotide Polymorphismen» (SNP) nachzuweisen und andererseits durch sog. «Arrays» mehrere zehntausend Gene (DNA), Transkripte (RNA) oder Proteine von z.B. Tumorgeweben simultan zu analysieren und damit ein individuelles Krankheitsspezifisches Gen- oder Expressionsprofil (Signatur) zu definieren. Auf der Basis solcher Daten wird es zunehmend möglich, für den Einzelfall Aussagen über bestimmte Krankheitsanlagen zu machen bzw. prädiktiv die Prognose der Erkrankung oder die Wirksamkeit therapeutischer Strategien zu beurteilen (individualisierte Medizin).
The Relationship Between Safety Attitudes and Occupational Accidents
Authors: Tomás J. M. , Cheyne A. , Oliver A.
Published: February 2011

This research provides empirical evidence on the relationships between employee attitudes to safety issues and accident indicators in a Spanish context. The research attempts to review to what degree those attitudes reflect a collective, or shared, climate for safety within a number of organizations. Data were gathered from workers in a number of industries in Valencia (Spain) by questionnaire. A total of 1,234 valid questionnaires were completed and formed the basis for subsequent analysis. Analysis of the attitude dimensions found a similar structure to that found in previous research in other countries, as well as identifying those dimensions shared within groups, more likely to represent safety climate. In terms of explaining accidents, the data showed that variables dealing with the work environment, in particular the presence of Workplace Hazards, and the individual’s approach to working safely were directly related to accident outcomes, explaining 19% of the variability in accident history. These variables were, in turn, related to the assessment of safety climate, suggesting that individual attitude variables act as a mediator between climate and accident occurrence. This paper represents one of the few attempts to explain the influence of safety climate, work environment, and individual attitudes on accident outcomes in the Spanish environment, using a theoretical model developed and validated in another European context.
Leadership and Learning Climate in a Work Setting
Authors: Hetland Hilde , Skogstad Anders , Hetland Jørn , Mikkelsen Aslaug
Published: February 2011

The aim of this study is to investigate the relationship between transformational and passive-avoidant leadership and learning climate in a work setting. A sample consisting of 1,061 employees from the Norwegian Postal Service completed the multifactor leadership questionnaire and the learning climate questionnaire. Learning climate dimensions used in the analyses were time, autonomy, team style, opportunities to develop, and guidelines. Findings revealed significant positive paths between transformational leadership and opportunities to develop (β .53), autonomy (β .34), guidelines (β .30), and team style (β .29). Further, significant negative associations were found between passive-avoidant leadership and time (β −.42), team style (β −.30), and guidelines (β −.20). In conclusion, the findings indicate that there is a substantial relationship between leadership and perceptions of a context supporting creativity and learning. The results reveal systematically different patterns of relationships between transformational and passive-avoidant leadership, and aspects of the learning climate, positive and negative, respectively. Based on the findings we emphasize the interpretation of the results and suggest some practical implications for interventions.
Achievement Goals and Moral Competence in Sport
Authors: Mouratidou Katerina , Barkoukis Vassilis , Rizos Stelios
Published: February 2011

Achievement goal approaches proliferated that mastery goals are associated with higher moral competence compared to performance goals. Several demographic characteristics have also been found to influence this relationship. The 2 × 2 achievement goal approach is the newest development in achievement goal approaches suggesting the existence of four achievement goals: mastery approach, mastery avoidance, performance approach, and performance avoidance. So far there has been no research evidence associating these achievement goals to moral competence and the role of demographic characteristics. The present study was designed to examine the effect of the 2 × 2 achievement goals on moral competence and the moderating role of athletes’ age, experience, playing position, level and league of participation, education, job, and perceived ability. The sample of the study was comprised of 208 football and basketball athletes (Mage = 22.71 years old and SD ±5.09 years). The participants completed a Demographic Characteristics Questionnaire, the Achievement Goals Questionnaire – Sport and the Moral Judgment Test. The results of the moderated hierarchical regression analyses indicated that athletes’ adopting performance goals were associated with low moral competence. This relationship was moderated by several demographic characteristics such as age and experience, level of participation, and perceived ability. Among athletes adopting performance-approach goals, less moral competent athletes were found to be the older, the more experienced, and those participating in professional clubs. Among performance-avoidance-oriented athletes those with high perceived ability revealed less moral competence. No significant effect was found regarding mastery goals. These findings provide important information regarding the effect of achievement goals on moral competence and the role several demographic characteristics can play.
Numerical and analytical modeling of advective travel times in realistic three‐dimensional fracture networks
Authors: Frampton A. , Cvetkovic V.
Published: February 2011

Travel time distributions obtained from advective transport in multiple realizations of realistic discrete fracture network simulations are analyzed using the truncated one‐sided stable distribution, which has previously been shown to generalize both the advection‐dispersion solution as well as one‐sided stable distributions. Using this model, it is shown that the Fickian assumption inherent in the advection‐dispersion equation generally fails, despite the first two moments of travel time essentially scaling linearly with distance. It is also observed that the equally probable realizations drawn from the ensemble can produce a wide range of behavior under the current configuration, such that Fickian conditions are almost obtained in some cases for increasing scales. On the basis of a small‐scale calibration against particle breakthrough, the model is then shown to successfully predict limiting bounds of transport for a one order of magnitude increase in scale. Correlation in particle velocity is explicitly shown to be significant for scales close to the characteristic Lagrangian segment length. The network configuration is obtained from extensive site characterization data at the Laxemar region in Sweden and represents a block‐scale domain of reasonably sparse background fractures.
Interventions Targeting Attention in Young Children With Autism
Authors: Patten Elena , Watson Linda R.
Published: February 2011

Purpose

The ability to focus and sustain one’s attention is critical for learning. Children with autism demonstrate unusual characteristics of attention from infancy. It is reasonable to assume that early anomalies in attention influence a child’s developmental trajectories. Therapeutic interventions for autism often focus on core features of autism such as communication and socialization, while very few interventions specifically address attention. The purpose of this article is to provide clinicians a description of attention characteristics in children with autism and discuss interventions thought to improve attention.

Method

Characteristics of attention in children with autism are presented. Intervention studies featuring measures of attention as an outcome variable for young children with autism are reviewed to present interventions that have empirical evidence for improvements in attention. Results are synthesized by strategy, specific feature of attention targeted, and results for both habilitative goals and accommodations for attention.

Conclusion

Although research is not extensive, several strategies to support attention in young children with autism have been investigated. The empirical findings regarding these strategies can inform evidence-based practice.
Script Training Treatment for Adults With Apraxia of Speech
Authors: Youmans Gina , Youmans Scott R. , Hancock Adrienne B.
Published: February 2011

Purpose

Outcomes of script training for individuals with apraxia of speech (AOS) and mild anomic aphasia were investigated. Script training is a functional treatment that has been successful for individuals with aphasia but has not been applied to individuals with AOS. Principles of motor learning were incorporated into training to promote long-term retention of scripts.

Method

Three individuals with AOS completed script training. A multiple-baseline, across-behaviors design examined acquisition of client-selected scripts. Errors and speaking rates were also analyzed. Random practice and delayed feedback were incorporated into training to promote motor learning. Probes for long-term retention were elicited up to 6 months after treatment.

Results

All clients successfully acquired their scripts, and probes demonstrated script retention 6 months after treatment. Errors generally decreased but remained variable even during maintenance and retention probes. Speaking rate increased for 2 clients but also remained variable.

Conclusions

Script training was successful and functional for clients with AOS. Clients reported increased confidence, speaking ease, and speech naturalness. Although scripts did not become errorless, clients retained their scripts and reported using them frequently. Whether principles of motor learning may have promoted the long-term retention of scripts exhibited by participants must be determined through future research.
Establishing Validity of the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V)
Authors: Zraick Richard I. , Kempster Gail B. , Connor Nadine P. , Thibeault Susan , Klaben Bernice K. , Bursac Zoran , Thrush Carol R. , Glaze Leslie E.
Published: February 2011

Purpose

The Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) was developed to provide a protocol and form for clinicians to use when assessing the voice quality of adults with voice disorders (Kempster, Gerratt, Verdolini Abbott, Barkmeier-Kramer, & Hillman, 2009). This study examined the reliability and the empirical validity of the CAPE-V when used by experienced voice clinicians judging normal and disordered voices.

Method

The validity of the CAPE-V was examined in 2 ways. First, we compared judgments made by 21 raters of 22 normal and 37 disordered voices using the CAPE-V and the GRBAS (grade, roughness, breathiness, asthenia, strain; see Hirano, 1981) scales. Second, we compared our raters' judgments of overall severity to a priori consensus judgments of severity for the 59 voices.

Results

Intrarater reliability coefficients for the CAPE-V ranged from .82 for breathiness to .35 for strain; interrater reliability ranged from .76 for overall severity to .28 for pitch.

Conclusions

Although both CAPE-V and GRBAS reliability coefficients varied across raters and parameters, this study reports slightly improved rater reliability using the CAPE-V to make perceptual judgments of voice quality in comparison to the GRBAS scale. The results provide evidence for the empirical (concurrent) validity of the CAPE-V.
Clinical and Research Perspectives on Nonspeech Oral Motor Treatments and Evidence-Based Practice
Authors: Muttiah Nimisha , Georges Katie , Brackenbury Tim
Published: February 2011

Purpose

Evidence-based practice (EBP) involves the incorporation of research evidence, clinical expertise, and client values in clinical decision making. One case in which these factors conflict is the use of nonspeech oral motor treatments (NSOMTs) for children with developmental speech sound disorders. Critical reviews of the research evidence suggest that NSOMTs are not valid, yet they are widely used by clinicians based on their expertise/experience. This investigation presents detailed descriptions of clinicians' and researchers' views and opinions on NSOMTs and EBP.

Method

Individual interviews with 11 clinicians who use NSOMTs and 11 researchers in child phonology were conducted. The interviews were transcribed and organized into themes, following a phenomenological research design.

Results

Five themes were identified: (a) NSOMTs are effective, (b) EBP is useful, (c) there is no published research supporting NSOMTs, (d) research evidence may change clinical use of NSOMTs, and (e) researchers and clinicians have separate but shared roles in clinical decision making.

Conclusions

The participants' responses provided detailed and complex insights into each group’s decisions regarding NSOMTs. These responses also suggested questions that should be considered when making decisions about approaches that are not fully supported by EBP.
Chloroacetone photodissociation at 193 nm and the subsequent dynamics of the CH3C(O)CH2 radical—an intermediate formed in the OH + allene reaction en route to CH3 + ketene
Authors: Alligood Bridget W. , FitzPatrick Benjamin L. , Szpunar David E. , Butler Laurie J.
Published: February 2011

We use a combination of crossed laser-molecular beam experiments and velocity map imaging experiments to investigate the primary photofission channels of chloroacetone at 193 nm; we also probe the dissociation dynamics of the nascent CH3C(O)CH2 radicals formed from C–Cl bond fission. In addition to the C–Cl bond fission primary photodissociation channel, the data evidence another photodissociation channel of the precursor, C–C bond fission to produce CH3CO and CH2Cl. The CH3C(O)CH2 radical formed from C–Cl bond fission is one of the intermediates in the OH + allene reaction en route to CH3 + ketene. The 193 nm photodissociation laser allows us to produce these CH3C(O)CH2 radicals with enough internal energy to span the dissociation barrier leading to the CH3 + ketene asymptote. Therefore, some of the vibrationally excited CH3C(O)CH2 radicals undergo subsequent dissociation to CH3 + ketene products; we are able to measure the velocities of these products using both the imaging and scattering apparatuses. The results rule out the presence of a significant contribution from a C–C bond photofission channel that produces CH3 and COCH2Cl fragments. The CH3C(O)CH2 radicals are formed with a considerable amount of energy partitioned into rotation; we use an impulsive model to explicitly characterize the internal energy distribution. The data are better fit by using the C–Cl bond fission transition state on the S1 surface of chloroacetone as the geometry at which the impulsive force acts, not the Franck–Condon geometry. Our data suggest that, even under atmospheric conditions, the reaction of OH with allene could produce a small branching to CH3 + ketene products, rather than solely producing inelastically stabilized adducts. This additional channel offers a different pathway for the OH-initiated oxidation of such unsaturated volatile organic compounds, those containing a C=C=C moiety, than is currently included in atmospheric models.
A novel method for on-orbit measurement of space materials degradation
Authors: Verker Ronen , Grossman Eitan , Gouzman Irina
Published: February 2011

The low Earth orbit (LEO) environment is considered hazardous to spacecraft, resulting in materials degradation. Currently, in order to evaluate the degradation of materials in LEO, a retrieval of space exposed samples is required. In this study, a novel approach is proposed to evaluate degradation of materials in LEO without the need of retrieval. The method is utilizing photovoltaic cells (PVCs), an existing component onboard of any satellite. The PVCs are coated by various materials which are sensitive to different LEO constituents, such as atomic oxygen (AO) or ultra-violet (UV) radiation. The method's acronym is ORMADD (on-ORbit MAterials Degradation Detector). The ORMADD's principle of operation is based on measuring the PVC output power which depends on the cell coating material's optical transmission. Erosion of the coating by AO or coloring due to UV radiation affects its optical transmission and, accordingly, the PVC output. The ORMADD performance was tested using different coatings, such as polyimide and amorphous carbon (sensitive to AO), and siloxane based coating which is sensitive to UV radiation. The proposed ORMADD reveals sensitivity to different LEO components and can be used either as material degradation detector or as an AO monitor.
Domain formation in membranes with quenched protein obstacles: Lateral heterogeneity and the connection to universality classes
Authors: Fischer T. , Vink R. L. C.
Published: February 2011

We show that lateral fluidity in membranes containing quenched protein obstacles belongs to the universality class of the two-dimensional random-field Ising model. The main feature of this class is the absence of a phase transition: there is no critical point and macroscopic domain formation does not occur. Instead there is only one phase. This phase is highly heterogeneous with a structure consisting of microdomains. The presence of quenched protein obstacles thus provides a mechanism to stabilize lipid rafts in equilibrium. Crucial for two-dimensional random-field Ising universality is that the obstacles are randomly distributed and have a preferred affinity to one of the lipid species. When these conditions are not met standard Ising or diluted Ising universality applies. In these cases a critical point does exist which then marks the onset toward macroscopic demixing.
Ring-polymer instanton method for calculating tunneling splittings
Authors: Richardson Jeremy O. , Althorpe Stuart C.
Published: February 2011

The semiclassical instanton expression for the tunneling splitting between two symmetric wells is rederived, starting from the ring-polymer representation of the quantum partition function. This leads to simpler mathematics by replacing functional determinants with matrix determinants. By exploiting the simple Hückel-like structure of the matrices, we derive an expression for the instanton tunneling splitting in terms of a minimum on the potential surface of a linear polymer. The latter is a section cut out of a ring polymer, consisting of an infinite number of beads, which describes a periodic orbit on the inverted potential surface. The approach is straightforward to generalize to multiple dimensions, and we demonstrate that it is computationally practical by carrying out instanton calculations of tunneling splittings in \documentclass[12pt]{minimal}\begin{document}${\rm HO}_2$\end{document} HO 2 and malonaldehyde in full dimensionality.
Molecular dynamics study of thermal transport in GaAs-self-assembly monolayer-GaAs junctions with ab initio characterization of thiol-GaAs bonds
Authors: Luo Tengfei , Lloyd John R.
Published: February 2011

Thermal dissipation in molecular electronic devices is a critical issue for the proper functioning of such devices. In this work, molecular dynamics (MD) simulations were carried out to study the thermal energy transport in GaAs-SAM (self-assembly monolayer)-GaAs junctions, with alkanedithiols being the SAM molecules. In order to characterize the molecule-GaAs interface, ab initio density functional theory (DFT) was used to study the structural and binding properties of alkanethiolates on GaAs(001) surfaces. Parameters of classical potentials, which were used to model the molecule-GaAs interactions, were obtained by fitting to the results from the DFT calculations. Then, nonequilibrium MD (NEMD) simulations were performed to reveal the GaAs-SAM interfacial thermal conductance at different temperatures. The results from this work showed that the GaAs-SAM interfaces are the major sources of thermal resistance in the GaAs-SAM-GaAs junctions. The delocalized phonon modes carry thermal energy efficiently inside the molecule chains, and the anharmonicity at the interface plays an important role in the thermal transport between the substrate and the molecules.
Misfit dislocation formation at heterointerfaces in (Al,In)GaN heteroepitaxial layers grown on semipolar free-standing GaN substrates
Authors: Wu F. , Tyagi A. , Young E. C. , Romanov A. E. , Fujito K. , DenBaars S. P. , Nakamura S. , Speck J. S.
Published: February 2011

Semipolar GaN-based light emitting devices show great promise because of reduced polarization-related electric fields in the quantum wells and the potential for high indium uptake in InxGa1−xN quantum wells. In semipolar GaN, the (0001) slip plane is inclined with respect to the film normal, thus shear stresses are present on this plane for nominally misfitting layer growth. We present scattering contrast transmission electron microscopy studies of (112¯2) and (202¯1) semipolar GaN-based laser diode structures. Misfit dislocations were observed at the nominally misfitting heterointerfaces in the (112¯2) structures with line direction [11¯00] and Burgers vector in the (0001) plane. Similar observations are reported for the (202¯1) structures. Overall, the results are consistent with stress relaxation by threading dislocation glide.
Microstructural analysis of interfaces in a ferromagnetic-multiferroic epitaxial heterostructure
Authors: Rama Krishnan P. S. Sankara , Arredondo Miryam , Saunders Martin , Ramasse Q. M. , Valanoor Nagarajan , Munroe Paul
Published: February 2011

We report a study on multiferroic bismuth ferrite (BiFeO3, BFO)-ferromagnetic lanthanum strontium manganese oxide (La0.7Sr0.3MnO3, LSMO) epitaxial interfaces by scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) and energy-filtered transmission electron microscopy (EFTEM). Epitaxial (001) oriented LSMO/BFO heterostructures were fabricated on a (001) strontium titanate (SrTiO3, STO) substrate using pulsed laser deposition (PLD). Different cooling conditions to room temperature (rapid or slow) were used to investigate the effect of fabrication conditions on the structural quality of the interfaces. The combined analysis of bright field transmission electron microscopy imaging, STEM-EDS and EFTEM data reveals that the LSMO-BFO heterostructure interface is free from any defects but the phases are chemically interdiffused over a length scale of ∼4 nm.
Three-dimensional acoustic wavefront imaging in anisotropic systems by picosecond acoustics
Authors: Zhang Shuo , Péronne Emmanuel , Belliard Laurent , Vincent Serge , Perrin Bernard
Published: February 2011

We present a laser ultrasonics experiment with imaging capabilities performed in transmission through semiconductor substrates. Such experiment provides a new kind of bulk wavefront imaging using an ultrafast optical generation and detection scheme for gigahertz waves. The data may be viewed as two-dimensional slices of the three-dimensional acoustic wavefront revealing the basic anisotropy of the solid with 0.3 ps time resolution and 3 μm space resolution and allowing the determination of the whole set of elastic constants for various experimental conditions. As examples, measurements are carried out in a Si(001), GaAs(001), and GaAs(111) sample at 20 and 300 K.
Self-assembly in block polyelectrolytes
Authors: Yang Shuang , Vishnyakov Aleksey , Neimark Alexander V.
Published: February 2011

The self-consistent field theory (SCFT) complemented with the Poisson–Boltzmann equation is employed to explore self-assembly of polyelectrolyte copolymers composed of charged blocks A and neutral blocks B. We have extended SCFT to dissociating triblock copolymers and demonstrated our approach on three characteristic examples: (1) diblock copolymer (AB) melt, (2) symmetric triblock copolymer (ABA) melt, (3) triblock copolymer (ABA) solution with added electrolyte. For copolymer melts, we varied the composition (that is, the total fraction of A-segments in the system) and the charge density on A blocks and calculated the phase diagram that contains ordered mesophases of lamellar, gyroid, hexagonal, and bcc symmetries, as well as the uniform disordered phase. The phase diagram of charged block copolymer melts in the charge density – system composition coordinates is similar to the classical phase diagram of neutral block copolymer melts, where the composition and the Flory mismatch interaction parameter $\chi _{\it AB}$χAB are used as variables. We found that the transitions between the polyelectrolyte mesophases with the increase of charge density occur in the same sequence, from lamellar to gyroid to hexagonal to bcc to disordered morphologies, as the mesophase transitions for neutral diblocks with the decrease of $\chi _{\it AB}$χAB. In a certain range of compositions, the phase diagram for charged triblock copolymers exhibits unexpected features, allowing for transitions from hexagonal to gyroid to lamellar mesophases as the charge density increases. Triblock polyelectrolyte solutions were studied by varying the charge density and solvent concentration at a fixed copolymer composition. Transitions from lamellar to gyroid and gyroid to hexagonal morphologies were observed at lower polymer concentrations than the respective transitions in the similar neutral copolymer, indicating a substantial influence of the charge density on phase behavior.
Analyzing the components of the free-energy landscape in a calcium selective ion channel by Widom's particle insertion method
Authors: Boda Dezső , Giri Janhavi , Henderson Douglas , Eisenberg Bob , Gillespie Dirk
Published: February 2011

The selectivity filter of the L-type calcium channel works as a Ca2 + binding site with a very large affinity for Ca2 + versus Na+. Ca2 + replaces half of the Na+ ions in the filter even when these ions are present in 1 μM and 30 mM concentrations in the bath, respectively. The energetics of this strong selectivity is analyzed in this paper. We use Widom's particle insertion method to compute the space-dependent profiles of excess chemical potential in our grand canonical Monte Carlo simulations. These profiles define the free-energy landscape for the various ions. Following Gillespie [Biophys. J. 94, 1169 (2008)], the difference of the excess chemical potentials for the two competing ions defines the advantage that one of the ions has over the other in the competition for space in the crowded selectivity filter. These advantages depend on ionic bath concentrations: the ion that is present in the bath in larger quantity (Na+) has the “number” advantage which is balanced by the free-energy advantage of the other ion (Ca2 +). The excess chemical potentials are decomposed into hard sphere exclusion and electrostatic components. The electrostatic terms correspond to interactions with the mean electric field produced by ions and induced charges as well to ionic correlations beyond the mean field description. Dielectrics are needed to produce micromolar Ca2 + versus Na+ selectivity in the L-type channel. We study the behavior of these terms with changes in bath concentrations of ions, charges, and diameters of ions, as well as geometrical parameters such as radius of the pore and the dielectric constant of the protein. Ion selectivity in calcium binding proteins probably has a similar mechanism.
Clusters in strong polyelectrolyte solutions in the condensation theory approach
Authors: Perico Angelo , Rapallo Arnaldo
Published: February 2011

The interaction free energy of parallel clusters of like-charged rod polyelectrolytes in solution is calculated in the framework of the extended condensation theory. For sufficiently high linear charge density of the polyelectrolyte, clustering takes place. The greater is the number of polyelectrolytes participating to the cluster, the smaller is the equilibrium interpolyelectrolyte distance, and the deeper is the corresponding free energy minimum. It is a counterintuitive organization due to the increasing of the counterion condensed charge and condensation volume, taking place as the polyelectyrolytes approach each other.
Urania vapor composition at very high temperatures
Authors: Pflieger Rachel , Colle Jean-Yves , Iosilevskiy Igor , Sheindlin Michael
Published: February 2011

Due to the chemically unstable nature of uranium dioxide its vapor composition at very high temperatures is, presently, not sufficiently studied though more experimental knowledge is needed for risk assessment of nuclear reactors. We used laser vaporization coupled to mass spectrometry of the produced vapor to study urania vapor composition at temperatures in the vicinity of its melting point and higher. The very good agreement between measured melting and freezing temperatures and between partial pressures measured on the temperature increase and decrease indicated that the change in stoichiometry during laser heating was very limited. The evolutions with temperature (in the range 2800–3400 K) of the partial pressures of the main vapor species (UO2, UO3, and UO2+) were compared with theoretically predicted evolutions for equilibrium noncongruent gas-liquid and gas-solid phase coexistences and showed very good agreement. The measured main relative partial pressure ratios around 3300 K all agree with calculated values for total equilibrium between condensed and vapor phases. It is the first time the three main partial pressure ratios above stoichiometric liquid urania have been measured at the same temperature under conditions close to equilibrium noncongruent gas-liquid phase coexistence.
Structure evolution of gold cluster anions between the planar and cage structures by isoelectronic substitution: Aun− (n = 13–15) and MAun− (n = 12–14; M = Ag, Cu)
Authors: Pal Rhitankar , Wang Lei-Ming , Huang Wei , Wang Lai-Sheng , Zeng Xiao Cheng
Published: February 2011

The structural and electronic effects of isoelectronic substitution by Ag and Cu atoms on gold cluster anions in the size range between 13 and 15 atoms are studied using a combination of photoelectron spectroscopy and first-principles density functional calculations. The most stable structures of the doped clusters are compared with those of the undoped Au clusters in the same size range. The joint experimental and theoretical study reveals a new C3v symmetric isomer for Au13−, which is present in the experiment, but has hitherto not been recognized. The global minima of Au14− and Au15− are resolved on the basis of comparison between experiment and newly computed photoelectron spectra that include spin-orbit effects. The coexistence of two isomers for Au15− is firmly established with convincing experimental evidence and theoretical calculations. The overall effect of the isoelectronic substitution is minor on the structures relative to those of the undoped clusters, except that the dopant atoms tend to lower the symmetries of the doped clusters.
Temperature- and wavelength-dependent two-photon and free-carrier absorption in GaAs, InP, GaInAs, and InAsP
Authors: Krishnamurthy Srini , Yu Zhi Gang , Gonzalez Leonel P. , Guha Shekhar
Published: February 2011

We present full-band structure calculations of temperature- and wavelength-dependent two-photon absorption coefficients and free-carrier absorption cross sections in GaAs, InP, and 0.92 eV-band gap Ga64In36As and InP60As40 alloys. The calculated coefficient decreases with increasing wavelength and band gap but increases with temperature. Using detailed band structure analysis, we identify various contributions to the free-carrier absorption in GaAs and InP. Although the free-carrier absorption is found to arise predominantly from hole absorption, we show that direct absorption by excited electrons is possible, leading to an enhanced free-carrier absorption coefficient. This excited state absorption could be exploited to modulate the transmission of light at communication wavelengths (of 1.33 or 1.55 μm) with, for example, the more commonly available 0.8 μm diode laser. We further show that the high-intensity transmission calculated with our values of nonlinear parameters in GaAs agrees very well with the measured values.
A statistical nanomechanism of biomolecular patterning actuated by surface potential
Authors: Lin Chih-Ting , Lin Chih-Hao
Published: February 2011

Biomolecular patterning on a nanoscale/microscale on chip surfaces is one of the most important techniques used in vitro biochip technologies. Here, we report upon a stochastic mechanics model we have developed for biomolecular patterning controlled by surface potential. The probabilistic biomolecular surface adsorption behavior can be modeled by considering the potential difference between the binding and nonbinding states. To verify our model, we experimentally implemented a method of electroactivated biomolecular patterning technology and the resulting fluorescence intensity matched the prediction of the developed model quite well. Based on this result, we also experimentally demonstrated the creation of a bovine serum albumin pattern with a width of 200 nm in 5 min operations. This submicron noncovalent-binding biomolecular pattern can be maintained for hours after removing the applied electrical voltage. These stochastic understandings and experimental results not only prove the feasibility of submicron biomolecular patterns on chips but also pave the way for nanoscale interfacial-bioelectrical engineering.
Defect engineering in GaAs using high energy light ion irradiation: Role of electronic energy loss
Authors: Kabiraj D. , Ghosh Subhasis
Published: February 2011

We report on the application of high energy light ions (Li and O) irradiation for modification of defects, in particular, for annihilation of point defects using electronic energy loss in GaAs to minimize the defects produced by nuclear collisions. The high resolution x-ray diffraction and micro-Raman spectroscopy have been used to monitor that no lattice damage or amorphization take place due to irradiating ions. The effects of irradiation on defects and their energy levels have been studied using thermally stimulated current spectroscopy. It has been observed that till an optimum irradiation fluence of 1013 ions/cm2 there is annihilation of native defects but further increase in irradiation fluence results in accumulation of defects, which scales with the nuclear energy loss process, indicating that the rate of defects produced by the binary collision process exceeds rate of defect annihilation. Defect annihilation due to electronic energy loss has been discussed on the basis of breaking of bonds and enhanced diffusivity of ionized native defects.