bluuebunny/crossref_metadata_2025 huggingface dataset:
Protection by dietary Spirulina platensis against d-galactosamine- and acetaminophen-induced liver injuries
Authors: Lu Jun , Ren Di-Feng , Wang Jian-Zhong , Sanada Hiroo , Egashira Yukari
Published: January 2010

Increasing attention has been paid to Spirulina for its potential clinical uses. The present study investigated the protection by dietary Spirulina platensis against d-galactosamine (d-GalN)- and acetaminophen (APAP)-induced hepatitis in ICR mice. Mice in each group (n 6) were fed with a standard diet (American Institute of Nutrition (AIN)-93G), a positive control diet containing 0·5 % butylated hydroxytoluene (BHT), or a diet containing 3, 6 or 9 % S. platensis for 1 week. On the last day the mice were treated with d-GalN (300 mg/kg body weight, intraperitoneally) or APAP (150 mg/kg body weight, intraperitoneally) and 24 h later the mice were killed. The doses of both 6 and 9 % S. platensis were found to significantly alleviate the increase of serum glutamate oxaloacetoacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) activities in d-GalN- or APAP-intoxicated mice. The observation was very similar to that of the positive control groups. Two more experiments were carried out to investigate the involvement of thiobarbituric acid-reactive substances (TBARS) and IL-18 in the suppression of 6 % S. platensis on d-GalN- and APAP-induced hepatitis. The significant increase of GOT and GPT activities was found to be accompanied with the elevation of hepatic TBARS level, IL-18 mRNA expression and serum IL-18 concentration, and was significantly alleviated by supplementation with 6 % S. platensis in diets. These results showed that dietary S. platensis could provide a significant protection against d-GalN- and APAP-induced liver injuries, and IL-18 and lipid peroxidation might be involved in the protective influence of S. platensis.
Relative validity of a semi-quantitative food-frequency questionnaire in an elderly Mediterranean population of Spain
Authors: Fernández-Ballart Joan D. , Piñol Josep Lluís , Zazpe Itziar , Corella Dolores , Carrasco Paula , Toledo Estefanía , Perez-Bauer Manuel , Martínez-González Miguel Ángel , Salas-Salvadó Jorge , Martín-Moreno José M.
Published: January 2010

The aim of the present study was to assess reproducibility and relative validity of a self-administered FFQ used in the PREDIMED Study, a clinical trial for primary prevention of CVD by Mediterranean diet in a population at high cardiovascular risk. The FFQ was administered twice (FFQ1 and FFQ2) to explore reproducibility at 1 year. Four 3 d dietary records (DR) were used as reference to explore validity; participants therefore recorded their food intake over 12 d in the course of 1 year. The degree of misclassification in the FFQ was also evaluated by a contingency table of quintiles comparing the information from the FFQ2 and the DR. A total of 158 men and women (aged 55–80 years) were asked not to modify their dietary habits during the study period. Reproducibility for food groups, energy and nutrient intake, explored by the Pearson correlation coefficient (r) ranged 0·50–0·82, and the intraclass correlation coefficient (ICC) ranged from 0·63 to 0·90. The FFQ2 tended to report higher energy and nutrient intake than the DR. The validity indices of the FFQ in relation to the DR for food groups and energy and nutrient intake ranged (r) from 0·24 to 0·72, while the range of the ICC was between 0·40 and 0·84. With regard to food groups, 68–83 % of individuals were in the same or adjacent quintile in both methods, a figure which decreased to 55–75 % for energy and nutrient intake. We concluded that FFQ measurements had good reproducibility and a relative validity similar to those of FFQ used in other prospective studies.
A high-fat diet induces lower expression of retinoid receptors and their target genes GAP-43/neuromodulin and RC3/neurogranin in the rat brain
Authors: Buaud Benjamin , Esterle Laure , Vaysse Carole , Alfos Serge , Combe Nicole , Higueret Paul , Pallet Véronique
Published: January 2010

Numerous studies have reported an association between cognitive impairment in old age and nutritional factors, including dietary fat. Retinoic acid (RA) plays a central role in the maintenance of cognitive processes via its nuclear receptors (NR), retinoic acid receptor (RAR) and retinoid X receptor (RXR), and the control of target genes, e.g. the synaptic plasticity markers GAP-43/neuromodulin and RC3/neurogranin. Given the relationship between RA and the fatty acid signalling pathways mediated by their respective NR (RAR/RXR and PPAR), we investigated the effect of a high-fat diet (HFD) on (1) PUFA status in the plasma and brain, and (2) the expression of RA and fatty acid NR (RARβ, RXRβγ and PPARδ), and synaptic plasticity genes (GAP-43 and RC3), in young male Wistar rats. In the striatum of rats given a HFD for 8 weeks, real-time PCR (RT-PCR) revealed a decrease in mRNA levels of RARβ ( − 14 %) and PPARδ ( − 13 %) along with an increase in RXRβγ (+52 %). Concomitantly, RT-PCR and Western blot analysis revealed (1) a clear reduction in striatal mRNA and protein levels of RC3 ( − 24 and − 26 %, respectively) and GAP-43 ( − 10 and − 42 %, respectively), which was confirmed byin situhybridisation, and (2) decreased hippocampal RC3 and GAP-43 protein levels (approximately 25 %). Additionally, HFD rats exhibited a significant decrease in plasma ( − 59 %) and brain ( − 6 %)n-3 PUFA content, mainly due to the loss of DHA. These results suggest that dietary fat induces neurobiological alterations by modulating the brain RA signalling pathway andn-3 PUFA content, which have been previously correlated with cognitive impairment.
Effect of ground cover vegetation on the abundance and diversity of beneficial arthropods in citrus orchards
Authors: Silva E.B. , Franco J.C. , Vasconcelos T. , Branco M.
Published: January 2010

The effect of ground cover upon the communities of beneficial arthropods established in the canopy of lemon trees was investigated, by comparing three ground-cover management treatments applied: RV, resident vegetation; S, sowed selected species; and BS, bare soil by controlling weeds with herbicide. Over two consecutive years, arthropod communities in the tree canopy were sampled periodically by beating and suction techniques. Significantly higher numbers of beneficial arthropods were found in the RV and S treatments in comparison with bare soil. Spiders and parasitoid wasps were the two most common groups, representing, respectively, 70% and 19% of all catches in beating samples and 33% and 53% in suction samples. For the RV and S treatments, significant seasonal deviations from the bare soil treatment were observed using principal response curves. Similar seasonal patterns were observed over the two years. The RV and S treatments showed significant positive deviations from the BS treatment in late spring and summer, accounted for the higher numbers of parasitoid wasps, coccinelids and lacewings present. By contrast, the seasonal deviations observed for the spider community differed from those of the remaining arthropods. During late winter and early spring, the RV and S treatments presented a higher abundance of spiders in the tree canopy, in comparison with bare soil, whereas in the summer significantly more spiders were found in the bare soil treatment. Spider movements between tree canopy and ground vegetation layers may justify this result.
How does heat shock affect the life history traits of adults and progeny of the aphid parasitoidAphidius avenae(Hymenoptera: Aphidiidae)?
Authors: Roux O. , Le Lann C. , van Alphen J. J. M. , van Baaren J.
Published: January 2010

Because insects are ectotherms, their physiology, behaviour and fitness are influenced by the ambient temperature. Any changes in environmental temperatures may impact the fitness and life history traits of insects and, thus, affect population dynamics. Here, we experimentally tested the impact of heat shock on the fitness and life history traits of adults of the aphid parasitoidAphidius avenaeand on the later repercussions for their progeny. Our results show that short exposure (1 h) to an elevated temperature (36°C), which is frequently experienced by parasitoids during the summer, resulted in high mortality rates in a parasitoid population and strongly affected the fitness of survivors by drastically reducing reproductive output and triggering a sex-dependent effect on lifespan. Heat stress resulted in greater longevity in surviving females and in shorter longevity in surviving males in comparison with untreated individuals. Viability and the developmental rates of progeny were also affected in a sex-dependent manner. These results underline the ecological importance of the thermal stress response of parasitoid species, not only for survival, but also for maintaining reproductive activities.
A bioassay for studying behavioural responses of the common bed bug, Cimex lectularius (Hemiptera: Cimicidae) to bed bug-derived volatiles
Authors: Weeks E.N.I. , Logan J.G. , Gezan S.A. , Woodcock C.M. , Birkett M.A. , Pickett J.A. , Cameron M.M.
Published: January 2010

The common bed bug, Cimex lectularius (Hemiptera: Cimicidae), has recently re-emerged in increasing numbers, distribution and intensity of infestation in many countries. Current control relies on the application of residual pesticides; but, due to the development of insecticide resistance, there is a need for new tools and techniques. Semiochemicals (behaviour and physiology modifying chemicals) could be exploited for management of bed bugs. However, in order to identify semiochemicals that can be utilised in monitoring or control, a suitable olfactometer is needed that enables the study of the responses of bed bugs to volatile chemicals. Previous studies have used olfactometers that do not separate olfactory responses from responses to physical contact. In this study, a still-air olfactometer was used to measure behavioural responses to different bed bug-derived volatiles presented in an odour pot. Bed bugs were significantly more likely to visit the area above the odour pot first, and more frequently, in the presence of volatiles from bed bug-exposed paper but not in the presence of volatiles from conspecific bed bugs. Bed bug activity was found to be dependent on the presence of the volatiles from bed bug-exposed paper, the time during the scotophase and the sex of the insect being tested. The still-air olfactometer could be used to test putative semiochemicals, which would allow an understanding of their behavioural role in bed bug ecology. Ultimately, this could lead to the identification of new semiochemical tools for bed bug monitoring and control.
Methodical approaches in the identification of areas with a potential risk of infection by bird schistosomes causing cercarial dermatitis
Authors: Kolářová L. , Horák P. , Skírnisson K.
Published: January 2010

Larval stages (cercariae) of schistosomatid flukes represent the causative agents of swimmer's itch (cercarial dermatitis), a waterborne allergic disease. Cercariae of bird schistosomes are the most frequently reported agent. Recent studies on parasite behaviour in mammals showed that infections by cercariae can be linked to more than skin syndromes. Despite the failure of complete development in mammals, bird schistosomes can escape from the skin and migrate transitorily in the hosts. These findings brought novel insights into the fate and potential pathogenic effect of the parasites in non-compatible hosts, including humans. Cercarial dermatitis occurs globally and recently is considered to be re-emerging; however, there are no data on the number of afflicted persons per year. This might be explained by a relatively low interest in human skin infections arising after bathing in fresh water. In addition, the real occurrence of bird schistosomes in the field is known only for a few areas. The paucity of epidemiological/biogeographical data is probably caused by difficulties associated with detection of the parasites in intermediate and definitive hosts. Therefore, based on personal experience and data available in the literature, we have summarized methodological approaches enabling the detection of bird schistosomes in various hosts and environments.
Deficits in facial, body movement and vocal emotional processing in autism spectrum disorders
Authors: Philip R. C. M. , Whalley H. C. , Stanfield A. C. , Sprengelmeyer R. , Santos I. M. , Young A. W. , Atkinson A. P. , Calder A. J. , Johnstone E. C. , Lawrie S. M. , Hall J.
Published: January 2010

Background

Previous behavioural and neuroimaging studies of emotion processing in autistic spectrum disorder (ASD) have focused on the use of facial stimuli. To date, however, no studies have examined emotion processing in autism across a broad range of social signals.

Method

This study addressed this issue by investigating emotion processing in a group of 23 adults with ASD and 23 age- and gender-matched controls. Recognition of basic emotions (‘happiness’, ‘sadness’, ‘anger’, disgust' and ‘fear’) was assessed from facial, body movement and vocal stimuli. The ability to make social judgements (such as approachability) from facial stimuli was also investigated.

Results

Significant deficits in emotion recognition were found in the ASD group relative to the control group across all stimulus domains (faces, body movements and voices). These deficits were seen across a range of emotions. The ASD group were also impaired in making social judgements compared to the control group and this correlated with impairments in basic emotion recognition.

Conclusions

This study demonstrates that there are significant and broad-ranging deficits in emotion processing in ASD present across a range of stimulus domains and in the auditory and visual modality; they cannot therefore be accounted for simply in terms of impairments in face processing or in the visual modality alone. These results identify a core deficit affecting the processing of a wide range of emotional information in ASD, which contributes to the impairments in social function seen in people with this condition.
Surgical robotics and its development and progress
Authors: Dai Jian S
Published: January 2010

Surgical robotics is the study and application of advanced robotic technology to diverse surgical procedures, particularly to minimally invasive surgery. The advanced robotic technology in minimally invasive surgery leads to momentous change in and generates a tremendous impact on surgery, resulting in less pain and scarring, reduced blood loss and transfusions, lower risk of complication, shorter hospital stays and faster recovery periods.
Cardiopulmonary resuscitation in older people – a review
Authors: Lannon R , O'Keeffe ST
Published: January 2010

Survival to discharge after in-hospital cardiopulmonary resuscitation (CPR) is about 20% in those aged 65–69 years, declining with advancing age to about 10% in those aged 90 years or more. There are conflicting reports on whether or not advanced age, independent of the severity of acute and chronic illness, is a determinant of outcome. Recognition that the outcome of CPR in hospital patients is often poor has prompted extensive debate regarding the appropriate use of this procedure. In particular, there has been concern about unnecessary CPR in extended-care and hospice settings. Conversely, there has also been evidence that doctors and families may be prone to underestimate the quality of life and likelihood of benefit from CPR in older people and to make resuscitation decisions without considering the preferences of older people themselves. Recent guidelines have attempted to strike a balance between ensuring patient participation whenever possible but without offering illusory choices where CPR is very unlikely to succeed.
Long lengths of stay, large numbers, and trends of the Black-tailed GodwitLimosa limosain rice fields during spring migration
Authors: MASERO JOSÉ A. , SANTIAGO-QUESADA FRANCISCO , SÁNCHEZ-GUZMÁN JUAN M. , VILLEGAS AUXILIADORA , ABAD-GÓMEZ JOSÉ M. , LOPES RICARDO J. , ENCARNAÇÃO VITOR , CORBACHO CASIMIRO , MORÁN RICARDO
Published: January 2010

Rice fields provide functional wetlands for declining shorebirds and other waterbirds around the world, but fundamental aspects of their stopover ecology in rice fields remain unknown. We estimated the length of stay of Black-tailed GodwitsLimosa limosamigrating through rice fields, and showed the international importance of Extremadura’s rice fields (south-west Spain) for this Near Threatened shorebird species. Overall, large numbers of Black-tailed Godwits en route to their breeding grounds had long lengths of stay in the rice fields (34.7 ± 1.7, 14.4 ± 2.0 and 8.3 ± 1.2 days in godwits radio-tagged in late January, early February, and late February, respectively). The long lengths of stay of godwits in rice fields, together with some aspects of their feeding ecology, suggest that rice fields are suitable staging habitats, and therefore they could play an important role as buffer habitats against the loss or degradation of natural wetlands. Extremadura’s rice fields supported at least 14% of the declining Western European population of Black-tailed Godwit, and its increasing number in south-west Spain probably reflects a population shift towards the northern part of the winter range. We strongly suggest the inclusion of Extremadura’s rice fields as a Special Protection Area for birds under the European Union Directive on the conservation of wild birds.
Krankheitskonzepte zu HIV und AIDS
Authors: Salewski Christel , Bleher Julia
Published: January 2010

Zusammenfassung. Subjektive Konzepte über die eigene Erkrankung sind von hoher Bedeutung für die Anpassung an eine schwerwiegende Erkrankung wie HIV/AIDS. Die inhaltliche Ausgestaltung solcher Krankheitskonzepte ist abhängig von einer Vielzahl von Faktoren, etwa die konkreten Erfahrungen mit der Symptomatik, die Kommunikation mit dem medizinischen System oder medial vermitteltem Wissen über eine Erkrankung. Diese Faktoren können je nach Art des kulturellen Gesamtsystems, in dem Betroffene leben, stark variieren. In der vorliegenden Studie wurden die Krankheitskonzepte zu HIV/AIDS von Betroffenen in Südafrika (N = 72) und Deutschland (N = 69) miteinander verglichen. Es zeigten sich signifikante Unterschiede zwischen beiden Gruppen bezüglich der Wahrnehmung des Krankheitsverlaufs, der erlebten Symptombelastung, der Konsequenzen, der emotionalen Belastung, der wahrgenommenen Kontrolle des Krankheitsverlaufs sowie der Ursachenannahmen. Weiterhin wurden die Zusammenhänge zwischen der Zukunftserwartung, als Marker des Wohlbefindens, und den Krankheitskonzepten regressionsanalytisch geprüft. Hier ergaben sich unterschiedliche Zusammenhangsmuster für beide Gruppen: In der südafrikanischen Stichprobe hing eine negative Zukunftserwartung mit der Wahrnehmung hoher persönlicher Kontrolle und einer gering ausgeprägten Wahrnehmung der Wirksamkeit von HIV-spezifischen Medikamenten zusammen, während in der deutschen Stichprobe ein signifikanter Varianzanteil der negativen Zukunftserwartung durch eine starke Symptombelastung und eine hohe emotionale Belastung aufgeklärt wurde. Die Ergebnisse werden hinsichtlich möglicher Einflussfaktoren, die sich aus den unterschiedlichen kulturellen Bedingungen beider Länder ergeben, diskutiert.
Wie wirken sich akkulturative Prozesse auf Wahrnehmungen aus?
Authors: Rüdell Katja , Bhui Kamaldeep
Published: January 2010

Zusammenfassung. Resultate zu kulturellen Unterschieden in Krankheitswahrnehmungen legen nahe, dass diese auch Unterschiede im hilfesuchenden Verhalten erklären könnten. Diese Studie untersuchte die Wahrnehmungen von schwerem Stress (Distress) und hilfesuchendem Verhalten bei 153 Einwanderern und 113 Nichteinwanderern in England. Ein signifikant größerer Anteil von Einwanderern berichtete, dass spirituelle Faktoren die Ursache ihres Stresserlebnisses wären. Signifikant weniger Einwanderer als Nichteinwanderer sahen ihr eigenes Verhalten als Ursache des Distress, beschrieben Verhaltensänderungen (z.B. Rauchen, Alkoholkonsum) als Konsequenzen und bewerteten informelle Behandlungsmethoden als hilfreich. Es wurde weiterhin untersucht, ob es Zusammenhänge zwischen den Wahrnehmungen und der Aufenthaltsdauer bei Einwanderern gab. Eine Korrelationsanalyse ergab, dass die Aufenthaltsdauer mit einzelnen Arten von Ursachenannahmen signifikant zusammenhingen (spirituelle Ursachenglaube, verhaltensbezogene Ursachen). Es zeigten sich auch Zusammenhänge mit dem Ausmaß an informellen und formellen Behandlungsmethoden. Zusammen mit der Aufenthaltsdauer und dem Vorliegen einer psychiatrischen Auffälligkeit konnten folgende Kategorien der Distress-Wahrnehmungen die Hälfte der Varianz in der Anzahl der bisher ausprobierten Behandlungsmethoden erklären: somatische Symptome, psychosoziale Ursachen und Verhaltensveränderungen als Konsequenzen. Implikationen für gesundheitpsychologische Theorien und Anwendungen werden diskutiert.
Item Imputation Without Specifying Scale Structure
Authors: van Buuren Stef
Published: January 2010

Imputation of incomplete questionnaire items should preserve the structure among items and the correlations between scales. This paper explores the use of fully conditional specification (FCS) to impute missing data in questionnaire items. FCS is particularly attractive for items because it does not require (1) a specification of the number of factors or classes, (2) a specification of which item belongs to which scale, and (3) assumptions about conditional independence among items. Imputation models can be specified using standard features of the R package MICE 1.16. A limited simulation shows that MICE outperforms two-way imputation with respect to Cronbach’s α and the correlations between scales. We conclude that FCS is a promising alternative for imputing incomplete questionnaire items.
Analysis of Incomplete Data Using Inverse Probability Weighting and Doubly Robust Estimators
Authors: Vansteelandt Stijn , Carpenter James , Kenward Michael G.
Published: January 2010

This article reviews inverse probability weighting methods and doubly robust estimation methods for the analysis of incomplete data sets. We first consider methods for estimating a population mean when the outcome is missing at random, in the sense that measured covariates can explain whether or not the outcome is observed. We then sketch the rationale of these methods and elaborate on their usefulness in the presence of influential inverse weights. We finally outline how to apply these methods in a variety of settings, such as for fitting regression models with incomplete outcomes or covariates, emphasizing the use of standard software programs.
Interannual changes in mass consistent energy budgets from ERA‐Interim and satellite data
Authors: Chiodo Gabriel , Haimberger Leopold
Published: January 2010

Diagnostic comparisons and evaluations of the global atmospheric energy and water budgets have been carried out with the new ERA‐Interim reanalysis product and with satellite‐derived fluxes. In the first part of this paper, we address time discretization, mass imbalance, and spin‐up effects, which affect diagnostics from analysis and forecast fields in reanalysis. We discuss two ways of calculating vertically integrated horizontal energy and moisture flux divergence: (1) direct computation using analyzed fields and (2) indirectly from forecast model fluxes and vertically integrated tendencies. The spatial divergence patterns from the indirect method are found to be more realistic than those from direct computation from 6‐hourly analyses since they are much less affected by temporal sampling errors, but corrections were nevertheless necessary to ensure mass consistency. The second part of this paper is focused on the interannual variability of ERA‐Interim vertical fluxes and on comparisons with satellite flux data. Time series of vertically integrated energy/moisture tendencies and the corresponding analysis increments are also investigated, since shifts in these important quantities indicate artificial jumps in ERA‐Interim, and relationships with vertical fluxes indicate internal consistency of the budgets. All data agree in that the most prominent changes in global budgets are internally forced (El Niño–Southern Oscillation). Broad agreement is found in ERA‐Interim and Hamburg ocean atmosphere parameters and fluxes from satellite data (HOAPS‐3) on a trend in the surface turbulent energy fluxes. Some of this trend may be caused by artificial shifts in ERA‐Interim and especially HOAPS‐3 in 1992 and possibly 2007. A strong increase in tropical land precipitation during the past decade is found in ERA‐Interim and Global Precipitation Climatology Project 2. While large improvements have been made in terms of temporal homogeneity compared with ERA‐40, especially with regard to precipitation, the homogeneity issue still needs to be carefully addressed when interpreting surface flux data from reanalyses or other sources.
Time resolved imaging of carrier and thermal transport in silicon
Authors: Hurley D. H. , Wright O. B. , Matsuda O. , Shinde S. L.
Published: January 2010

We use ultrashort optical pulses to microscopically image carrier and thermal diffusion in two spatial dimensions in pristine and mechanically polished surfaces of crystalline silicon. By decomposing changes in reflectivity in the latter sample into a transient component that varies with delay time and a steady-state component that varies with pump chopping frequency, the influence of thermal diffusion is isolated from that of carrier diffusion and recombination. Additionally, studies using carrier injection density as a parameter are used to clearly identify the carrier recombination pathway.
Triplet states of cyclopropenylidene and its isomers
Authors: Wu Qunyan , Cheng Qianyi , Yamaguchi Yukio , Li Qianshu , Schaefer Henry F.
Published: January 2010

The unique importance of the cyclopropenylidene molecule conveys significance to its low-lying isomers. Eleven low-lying electronic triplet stationary points as well as the two lowest singlet structures of C3H2 have been systematically investigated. This research used coupled cluster (CC) methods with single and double excitations and perturbative triple excitations [CCSD(T)] and Dunning’s correlation-consistent polarized valence cc-pVXZ (where X=D, T, and Q) basis sets. Geometries, dipole moments, vibrational frequencies, and associated infrared intensities of the targeted molecules have been predicted. The electronic ground state of cyclopropenylidene (3S, the global minimum) is the X̃ A11 state with C2v point group symmetry. Among the 11 triplet stationary points, 7 structures are found to be minima, 2 structures to be transition states, and 2 structures to be higher-order saddle points. For the six lowest-lying triplet structures and singlet propadienylidene (2S), relative energies (zero-point vibrational energy corrected values in parentheses) with respect to the global minimum [ X̃ A11 (3S)] at the cc-pVQZ-UCCSD(T) level of theory are predicted to be propynylidene B3(1aT)15.5(11.3)<propadienylidene[A11(2S)]14.2(13.3)<propadienylidene[B31(2T)]45.0(43.8)<cyclopropenylidene[A3(3aT)]53.8(52.5)<cyclopropyne[B32(4aT)]70.0(70.6)<cyclopropenylidene [B31(3cT)]71.2(69.9)<trans-propenediylidene [A3″(5T)]73.6(70.7) kcal mol−1. The combined energy for the [C(P3)+C2H2(X̃ Σ1g+)] system with respect to the global minimum (3S) is determined to be 107.4(103.8) kcal mol−1. Therefore, these six triplet equilibrium structures are all energetically well below the dissociation limit to [C(P3)+C2H2(X̃ Σ1g+)].
Coexistence of the bipolar and unipolar resistive-switching modes in NiO cells made by thermal oxidation of Ni layers
Authors: Goux L. , Lisoni J. G. , Jurczak M. , Wouters D. J. , Courtade L. , Muller Ch.
Published: January 2010

In this paper, we show the coexistence of the bipolar and unipolar resistive-switching modes in NiO cells realized using an optimized oxidation process of a Ni blanket layer used as the bottom electrode. The two switching modes can be activated independent of the cell switching history provided the appropriate programming conditions are applied. The bipolar and unipolar switching modes are discussed as driven by electrochemical- and thermal-based mechanisms, respectively. The switching versatility between these two modes is demonstrated both for large oxidized Ni films and for Ni films oxidized at the bottom of small dimension contact holes. The perspective of selecting the desired switching mode in a scaled device made in a small diameter single hole is highly attractive because the specific advantages of the two modes broaden the application scope of the cell and enable larger flexibility in terms of memory architecture.
Optical properties of InGaN/GaN nanopillars fabricated by postgrowth chemically assisted ion beam etching
Authors: Kawakami Y. , Kaneta A. , Su L. , Zhu Y. , Okamoto K. , Funato M. , Kikuchi A. , Kishino K.
Published: January 2010

The optical properties of InGaN/GaN quantum wells, which were nanopatterned into cylindrical shapes with diameters of 2 μm, 1 μm, or 500 nm by chemically assisted ion beam etching, were investigated. Photoluminescence (PL) and time-resolved PL measurements suggest inhomogeneous relaxation of the lattice-mismatch induced strain in the InGaN layers. By comparing to a strain distribution simulation, we found that partial stain relaxation occurs at the free side wall, but strain remains in the middle of the pillar structures. The strain relaxation leads to an enhanced radiative recombination rate by a factor of 4–8. On the other hand, nonradiative recombination processes are not strongly affected, even by postgrowth etching. Those characteristics are clearly reflected in the doughnut-shape emission patterns observed by optical microscopy.
O-vacancy-mediated spin-spin interaction in Co-doped ZnO: First-principles total-energy calculations
Authors: Liu En-Zuo , Jiang J. Z.
Published: January 2010

The effects of O vacancy (VO) on the electronic and magnetic properties of Co-doped ZnO are examined through first-principles total-energy calculations. Our results suggest that due to the presence of VO, O 2p states are coupled with the Co 3d states. Co 3d empty minority states are broadened and move up towards the Fermi level. VO at metastable sites can induce the ferromagnetic (FM) coupling between nearest-neighbor (NN) Co ions, and the atoms around the FM-coupled NN Co ions are spin-polarized which leads to the long-ranged FM coupling between Co ions. Our results based on first-principles total-energy calculations give a possible explanation for the controversial magnetic properties of Co-doped ZnO reported in the literature.
Low-frequency acoustic absorption of localized resonances: Experiment and theory
Authors: Zhao Honggang , Wen Jihong , Yu Dianlong , Wen Xisen
Published: January 2010

The idea of localized resonance in phononic crystals is introduced to improve the low-frequency acoustic absorption of viscoelastic materials, which are widely used underwater to absorb the unwanted noise and meet a difficult challenge to enhance low-frequency absorption. Experimental measurements for acoustic absorptances of various viscoelastic polymer slabs embedded with locally resonant scatterers, i.e., heavy spheres coated by soft silicon rubber, are reported. Theoretical investigations using a layer-multiple-scattering method show good agreement with the experiment results, which supports unambiguously the observed low-frequency absorption phenomenon. The physical mechanism for the low-frequency absorption is also investigated by referring the elements of the Mie scattering matrix. The observations suggest that the scattered energy tends to remain in transverse waves, which enhance the multiple scattering, damp rapidly in viscoelastic polymer and dominate the acoustic absorption.
Exchange bias in Fe and Ni codoped CuO nanocomposites
Authors: Liu K. L. , Yuan S. L. , Duan H. N. , Zheng X. F. , Yin S. Y. , Tian Z. M. , Wang C. H. , Huo S. X.
Published: January 2010

Exchange bias nanocomposites were obtained by the chemical concentration precipitation method, in which the ferrimagnetic MFe2O4 (M=Cu,Ni) particles were embedded in the antiferromagnetic (AFM) CuO matrix. The dependence of magnetization on temperature measurements show that the exchange bias effect in these composites is ascribed to the exchange coupling at the interface between the ferrimagnetic particles and spin-glass-like phase. With continuous introduction of magnetic Ni ions, the existence of domain state structure and the formation of soft magnetic phase in AFM matrix are responsible for the different behaviors of the exchange bias field and coercivity in these nanocomposites.
Possible origin of photoconductivity in La0.7Ca0.3MnO3
Authors: Sagdeo P. R. , Choudhary R. J. , Phase D. M.
Published: January 2010

The effect of photon energy on the density of states near Fermi level of pulsed laser deposited La0.7Ca0.3MnO3 thin film has been studied to investigate the possible origin of change in the conductivity of these manganites upon photon exposure. For this purpose the photoelectron spectroscopy measurements were carried out using CSR beamline (BL-2) on Indus-1 synchrotron radiation source. The valance band spectra were measured at room temperature with photon energy ranging from 40 to 60 eV. We could see huge change in the density of states near Fermi level and this change is observed to be highest at 56 eV which is due to the resonance between Mn 3p to Mn 3d level. Our results suggest that the probability of electron transfer from deep Mn 3p level to Mn 3d-eg level is higher than that of Mn 3d-t2g level. It appears that this transfer of electron from deep Mn level to Mn 3d-eg level not only modifies the density of state near Fermi level but also changes the mobility of electrons by modifying the electron lattice coupling due to presence of Mn+3 Jahn–Teller ion.
Band-gap nonlinearity in perovskite structured solid solutions
Authors: Lee Soonil , Levi Roni D. , Qu Weiguo , Lee Sung Chan , Randall Clive A.
Published: January 2010

Compositional effects on optical band-gap energy using end members of ABO3 perovskites have been investigated through an optical absorption with a UV-spectroscopy. Three examples are selected, namely, BaTiO3–CaTiO3, BaTiO3–BaZrO3, and SrTiO3–BaZrO3 solid solutions. To understand the role of high temperature phase equilibria on the band-gap compositional trends, structural and microscopy data were determined. In simple systems such as Si–Ge, the nonlinear variations in band gap with composition is usually associated with the effect of the local lattice relaxations and provides a parabolic dependence, often referred to as the “bowing” phenomena. In the case of perovskite solutions, the cases are more complex, and a modified Vegard’s law is introduced to account for the trends. This has to be considered in relation to high temperature phase formation where incomplete solid solutions and two-phase regions exist. In addition to high temperature phases, low temperature displacive phase transitions and complex nonstoichiometry also perturb the band-gap variation in perovskite oxide materials.
Positron annihilation study of the interfacial defects in ZnO nanocrystals: Correlation with ferromagnetism
Authors: Wang Dong , Chen Z. Q. , Wang D. D. , Qi N. , Gong J. , Cao C. Y. , Tang Z.
Published: January 2010

High purity ZnO nanopowders were pressed into pellets and annealed in air between 100 and 1200 °C. The crystal quality and grain size of the ZnO nanocrystals were investigated by x-ray diffraction 2θ scans. Annealing induces an increase in the grain size from 25 to 165 nm with temperature increasing from 400 to 1200 °C. Scanning electron microscopy and high-resolution transmission electron microscopy observations also confirm the grain growth during annealing. Positron annihilation measurements reveal vacancy defects including Zn vacancies, vacancy clusters, and voids in the grain boundary region. The voids show an easy recovery after annealing at 100–700 °C. However, Zn vacancies and vacancy clusters observed by positrons remain unchanged after annealing at temperatures below 500 °C and begin to recover at higher temperatures. After annealing at temperatures higher than 1000 °C, no positron trapping by the interfacial defects can be observed. Raman spectroscopy studies confirm the recovery of lattice disorder after annealing. Hysteresis loops are observed for the 100 and 400 °C annealed samples, which indicate ferromagnetism in ZnO nanocrystals. However, the ferromagnetism disappears after annealing above 700 °C, suggesting that it might originate from the surface defects such as Zn vacancies.
Metamaterial as a controllable template for nanoscale field localization
Authors: Kao T. S. , Huang F. M. , Chen Y. , Rogers E. T. F. , Zheludev N. I.
Published: January 2010

We report that subwavelength localization of light in the near-field of a double-periodic photonic metamaterial may be efficiently controlled by the polarization and wavelength of the incident radiation. A dramatic variation in the periodic near-field landscapes, including a transition from a pattern of isolated subwavelength plasmon hot-spots to a blurred, low contrast pattern, accompanied by a change in the pattern’s symmetry has been observed in the proximity of an aluminum nanowire “fish-scale” nanostructure. Hot-spots as small as 0.23λ have been achieved and their position has been controlled by tuning the wavelength of incident light across the dipole absorption resonance of the metamaterial. A simple switch of the polarization state can lead to a spatial period doubling in the landscape pattern.
First-principles analysis of the C–N bond scission of methylamine on Mo-based model catalysts
Authors: Lv Cun-Qin , Li Jun , Tao Shu-Xia , Ling Kai-Cheng , Wang Gui-Chang
Published: January 2010

The C–N bond breaking of methylamine on clean, carbon (nitrogen, oxygen)-modified Mo(100) [denoted as Mo(100) and Mo(100)–C(N,O), respectively], Mo2C(100), MoN(100), and Pt(100) surfaces has been investigated by the first-principles density functional theory (DFT) calculations. The results show that the reaction barriers of the C–N bond breaking in CH3NH2 on Mo(100)–C(N,O) are higher than that on clean Mo(100). The calculated energy barrier can be correlated linearly with the density of Mo 4d states at the Fermi level after the adsorption of CH3NH2 for those surfaces. Moreover, the DFT results show that the subsurface atom, e.g., carbon, can reduce the reaction barrier. In addition, We noticed that the activation energies for the C–N bond breaking on Mo2C(100) and MoN(100) are similar to that on Pt(100), suggesting that the catalytic properties of the transition metal carbides and nitrides for C–N bond scission of CH3NH2 might be very similar to the expensive Pt-group metals.
Arbitrary waveguide bends using isotropic and homogeneous metamaterial
Authors: Ding Weiqiang , Tang Donghua , Liu Yan , Chen Lixue , Sun Xiudong
Published: January 2010

We propose a method for arbitrary waveguide bends using impedance matched metamaterial with negative index of refraction. We analyze the operation principles and verify the performances using the finite difference in time domain method. Results show that nearly perfect transmission without mode distortion can be obtained when the bending angle changes within (0,180) degrees. The bending structure is very efficient and compact in size, and no anisotropic or inhomogeneous materials are required, which make the bend very easy in fabrication and application.
Coupling of twist and writhe in short DNA loops
Authors: Medalion Shlomi , Rappaport Shay M. , Rabin Yitzhak
Published: January 2010

While bending and twist can be treated as independent degrees of freedom for linear DNA molecules, the loop closure constraint introduces a coupling between these variables in circular DNA. We performed Monte Carlo simulations of wormlike rods with both bending and twist rigidity in order to study the coupling between the writhe and twist distributions for various DNA lengths. We find that for sufficiently short DNA, the writhe distribution differs from that of a model with bending energy only. We show that the factorization approximation introduced by previous researchers coincides, within numerical accuracy, with our simulation results, and conclude that the closure constraint is fully accounted for by the White–Fuller relation. Experimental tests of our results for short DNA plasmids are proposed.
Phase diagram of colloid-rod system
Authors: Lai S. K. , Xiao Xuhui
Published: January 2010

The semigrand ensemble theory [H. N. W. Lekkerkerker, W. C. K. Poon, P. N. Pusey, A. Stroobants, and P. B. Warren, Europhys. Lett. 20, 559 (1992)] in conjunction with the fundamental measure density functional theory [V. B. Warshavsky and X. Song, Phys. Rev. E 69, 061113 (2004)] are used to construct the Helmholtz free energy densities of a mixture of uncharged colloidal hard spheres and colloidal rods in its solid and liquid phases. Given these free energy density functions, we apply the free energy density minimization method [G. F. Wang and S. K. Lai, Phys. Rev. E 70, 051402 (2004)] to crosshatch the system’s regions of phases in coexistence. The calculated results show that the triangular area bounded by gas-liquid, gas-solid, and liquid-solid coexisting two phases which has been called the coexistence region of gas-liquid-solid corresponds in fact to sets of two phases in coexistence. The phase boundaries which define our calculated coexistence domains compare very well with previous theoretical calculations. The relevance of the phase-diagram domains to three phases in coexistence will be discussed.
Polymer/carbon nanotube composite patterns via laser induced forward transfer
Authors: Boutopoulos Christos , Pandis Christos , Giannakopoulos Konstantinos , Pissis Polycarpos , Zergioti Ioanna
Published: January 2010

Direct and high spatial resolution printing of polymer/carbon nanotube (CNT) composite layers has been demonstrated by means of laser induced forward transfer (LIFT). Laser irradiation of composite target materials, such as poly(acrylic acid)/CNT and polyvinylpyrrolidone/CNT, enabled dry deposition of well resolved composite pixels onto glass substrates. The dispersion of the CNT into the deposited composite pixels was investigated by transmission electron microscopy. The LIFT technique was also employed for the accurate deposition of polymer/CNT composite pixels onto aluminum microelectrodes for the fabrication of chemical sensors based on polymer/CNT compounds.
A first-principles study of weakly bound molecules using exact exchange and the random phase approximation
Authors: Nguyen Huy-Viet , Galli Giulia
Published: January 2010

We present a study of the binding energy (BE) curves of rare gas and alkaline-earth dimers using an energy functional that includes exact exchange (EXX) and correlation energies within the random phase approximation (RPA). Our results for the equilibrium positions and long range behavior of the potential energy curves show great improvements over those obtained at the density functional theory level, within local and semilocal approximations. BEs are improved as well in the case of rare gas dimers. For Ar and Kr, the accuracy of our results is comparable to that of so-called van der Waals density functionals, although EXX/RPA yields BE curves that agree better with experiment for large separation distances, as expected. We also discuss shortcomings of the EXX/RPA perturbative approach and analyze possible sources of error in the description of the potential energy curve of alkaline-earth dimers, in particular, Be2, exhibiting an unphysical maximum at large separations. We suggest that the lack of self-consistency in current EXX/RPA approaches might be largely responsible for most of the observed shortcomings. Finally, we present a tight-binding approach to obtain the eigenvalues of the dielectric matrix entering the calculation of the RPA correlation energy that greatly improves the efficiency of EXX/RPA calculations.
Temperature dependence of the fine-structure resolved rate coefficients for collisions of O2(XΣ3g−) with He
Authors: Lique François
Published: January 2010

Rotational excitation of the O2(XΣ3g−) with He is investigated. The calculations are based on the potential energy surface of Groenenboom and Struniewicz [J. Chem. Phys. 113, 9562 (2000)]. Close coupling calculations of the collisional excitation cross sections of the fine-structure levels of O2 by He are calculated for energies up to 2500 cm−1 which yield, after thermal average, rate coefficients up to 350 K. The exact level splitting is taken into account. The propensity rules between fine-structure levels are studied and it is shown that F-conserving cross sections are much larger, especially for high-N rotational levels, than F-changing cross sections, as expected from theoretical considerations. The rate coefficients are almost independent of the rotational quantum number of the O2 molecule for F-conserving transitions. The new rate coefficients can induce important consequences on astrophysical modeling.
Performance evaluation of the semicylindrical solar tunnel dryer for drying handmade paper
Authors: Sevda M. S. , Rathore N. S.
Published: January 2010

A walk in type semicylindrical solar tunnel dryer for drying 1500 handmade papers per batch has been commissioned at M/s Cellulosic Waste Recycling Education Project, Vidhya Bhawan Society, Udaipur, Rajasthan, India. A solar tunnel dryer with 122.95 m2 solar collector area was sufficient for drying handmade paper from 53.85% to 9.96% moisture content (dry basis) in 4–5 h. In this paper the results are shown in terms of the variation of air temperature, solar flux density, relative humidity, air flow rate, moisture content, etc., which indicate that the performance of solar tunnel dryer was quite satisfactory. The performance of the dryer for drying handmade papers has been analyzed through no load and full load test. Technoeconomic analysis of solar tunnel dryers was also carried out by using different economic indicators.
Topological interactions between ring polymers: Implications for chromatin loops
Authors: Bohn Manfred , Heermann Dieter W.
Published: January 2010

Chromatin looping is a major epigenetic regulatory mechanism in higher eukaryotes. Besides its role in transcriptional regulation, chromatin loops have been proposed to play a pivotal role in the segregation of entire chromosomes. The detailed topological and entropic forces between loops still remain elusive. Here, we quantitatively determine the potential of mean force between the centers of mass of two ring polymers, i.e., loops. We find that the transition from a linear to a ring polymer induces a strong increase in the entropic repulsion between these two polymers. On top, topological interactions such as the noncatenation constraint further reduce the number of accessible conformations of close-by ring polymers by about 50%, resulting in an additional effective repulsion. Furthermore, the transition from linear to ring polymers displays changes in the conformational and structural properties of the system. In fact, ring polymers adopt a markedly more ordered and aligned state than linear ones. The forces and accompanying changes in shape and alignment between ring polymers suggest an important regulatory function of such a topology in biopolymers. We conjecture that dynamic loop formation in chromatin might act as a versatile control mechanism regulating and maintaining different local states of compaction and order.