bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvements in a Mouse Model of Alzheimer's Disease through Sod2 Overexpression Are Due to Functional and Not Structural Alterations
Authors: Bitner Brittany R. , Perez-Torres Carlos J. , Hu Lingyun , Inoue Taeko , Pautler Robia G.
Published: March 2012

Oxidative stress and mitochondrial dysfunction have been implicated in the pathogenesis of Alzheimer's disease. We and others have shown that over expression of the mitochondrial antioxidant superoxide dismutase 2 (SOD-2) can improve many of the pathologies in the Tg2576 mouse model of Alzheimer's disease that harbors the Swedish mutation in the amyloid precursor protein. However, it is not clear if these improvements are due to functional improvements or structural/anatomical changes. To answer this question, we used diffusion tensor imaging (DTI) to assess the structural integrity of white matter tracts in the control mice, Tg2576 mouse and Tg2576 mice over expressing SOD-2. We observed minimal differences in diffusion parameters with SOD-2 over expression in this model indicating that the improvements we previously reported are due to functional changes and not any alterations to the white matter tractography.
Reconciling Multiple Standards
Authors: Kantelo Kip , Del Pozo Pablo Rodriguez
Published: March 2012

Stem cell research by Weill Cornell Medical College in Qatar (WCMC-Q) is subject to the ethical standards of both the Qatar Supreme Council of Health (SCH) and the National Academies of Sciences (NAS) in the United States (US). The authors examined their personal experiences with the policy-making process in Qatar and the ethical review process in both Qatar and the US. The objectives of this examination were to characterize different approaches to ethical oversight of stem cell research; consider factors underlying the different approaches; identify advantages and shortcomings of the approaches;and suggest areas where the approaches could enrich each other.

The authors identified two different approaches. First, Top-down, in which a centralized agency passes a set of regulations, often drawn from different international experiences and intended to be complete and stable. This is the model followed in Qatar. Secondly, Bottom-up, in which various agents (researchers, universities, funders, and others) reach a level of consensus and produce non-mandatory guidelines including a set of principles and accompanying specific points. Institutions later adopt the guidelines. This is the approach of the NAS.

Each approach results from the interplay of several factors, including Local experience, Organization of the state, and Political culture.

Top-down is rapidly available and provides a clear, monolithic framework, generally with few internal contradictions.

However, speed and consistency may limit flexibility. There may not be room for ethically acceptable alternative solutions if the framework poses scientific or practical difficulties. Top-down regulation runs the risk of rapid obsolescence in a dynamic field.

Bottom-up, being the product of deliberation, tends to be more flexible. However, this approach risks being hijacked by interminable discussions. Guidelines are not always immediately available. In a decentralized environment, competing guidelines may emerge. Approaches can enrich each other by establishingbasic guiding principles to inform detailed rules; avoiding too much detail that will be difficult to change; maintaining a mix of guidelines and regulation to provide certainty and flexibility while avoiding arbitrariness; adjusting according to experience of and feedback from stakeholders; and accepting imperfection in details and implementation.
Identification of Two Novel Splice variants of SOX2OT which are Co-expressed with Pluripotency Genes during Neural Differentiation of Stem Cells
Authors: Shahryari AR , Shafiee M , Samaei N , Semnani S , Vesai M , Mowla SJ
Published: March 2012

Our objectives were: Long non-coding RNAs (lncRNAs) are emerging as new regulators of stem cell pluripotency and neurogenesis. Recent studies revealed that the expression of several lncRNAs correlates with the expression of pluripotency regulators such as OCT4 and Nanog. Surprisingly, the SOX2 gene, another master regulator of pluripotency, is embedded within an intron of an lncRNA, known as SOX2OT. SOX2OT and has been suspected to participate in regulation of the SOX2 expression and related processes; nevertheless, its function has still remained untested. In this study, we investigated a potential correlation between the expression pattern of SOX2OT, also its newly discovered splice variants (SOX2OT-S1 and SOX2OT-S2) and master regulators of stem cell pluripotency (SOX2 and OCT4) in mesenchymal stem cells, as well as during the course of neural differentiation of the human EC cell line, NTERA2 (NT2).

We treated the NT2 cells with all-trans retinoic acid (ATRA) for four weeks to differentiate into neural phenotype. By designing specific primers for real-time PCR, we evaluated the expression pattern of SOX2OT, SOX2OT-S1, SOX2OT-S2, SOX2 and OCT4 in mesenchymal stem cells and also during the induction of neural differential of NT2 cells.

Our results showed that by using a different set of primers, we discovered two novel variants of SOX2OT, named SOX2OT-S1 (lacking exon4) and SOX2OT-S2 (lacking exons3 and 4). The expression pattern of SOX2OT variants was positively correlated with the expression of SOX2 and OCT4 in NT2 cells. Surprisingly, SOX2OT variants showed a distinct expression pattern during the course of neural differentiation of NT2 cells. The expression pattern of SOX2OT variants was similar to that of OCT4 and SOX2 during early differentiation of NT2 cells. However, in contrast to OCT4 and SOX2, a low expression of SOX2OT variants persist in later time points of neural differentiation of NT2 cells.

We found that close correlation between the expression pattern of SOX2OT variants and master regulators of pluripotency (OCT4 and SOX2) suggests that they may be involved in similar regulatory pathways including: self-renewal, pluripotency, and differentiation.
Unravelling Ovarian Cancer Stem Cells Physiology
Authors: Al Farsi H , Lis R , Al Thawadi H , Azzazen D , Soria J , Therwat A , Pujade Laurain E , Mirshahi M
Published: March 2012

Ovarian cancer is a highly metastatic disease. Epithelial ovarian cancer is the most lethal gynecologic malignancy with the majority of cases being diagnosed after the disease has become metastatic. Recent reports have shown that 25% of cancerous cells within tumors have features of cancer stem cells (CSCs). CSCs have been identified on the basis of their ability for self-renewal and to have the capacity to differentiate into cancer cells and also form tumors in animal models. EMT describes a mechanism by which cells lose their epithelial characteristics and acquire more migratory mesenchymal properties. It also seems to have a key role in the acquisition of invasive and migratory properties in many types of carcinoma cells. The aim of this study is to understand the molecular changes and signaling pathways associated with ovarian cancer cell transformation which may lead to the identification of targets for novel therapeutic interventions.

OVCAR-3 and hospicells were cultured in vitro according to standard procedure. OVCAR cells were stained using anti CD133 –prominin-1 and anti CD117-APC and sorted by FACS system as positive and negative. The supernatant of OVCAR CD117+ and CD117- were analyzed by cytokine array And 174 different membrane coupled anti-cytokines along with appropriate controls were studied. The gene expression patterns of OVCAR-3 cultured with supernatant of Hospicells (clone M16) or control cells were analysed and compared by a two-colour topic-defined microarray. The products of microarray consisted of genes related to cytokines, interleukins and growth factors. The up regulated 86 codes genes were analysed by DAVID functional annotation tool.

We demonstrated that OVCAR-3 cell line for several reasons did not appear to be monoclonal. It contains tow subpopulations: one expressing CD117 and the other not. The fact that OVCAR-3 expresses at the same time CD133 and CD117 is indicative of the stem cell nature of this cell line. The cytokines secreted by CD117+ and CD117- were not the same and indicate the different profile of these cells in cell behavior. Analysis was of OVCAR gene array after 8h incubation of Hospicells by DAVID functional annotation tool intricate gpl 130 (IL6 ST) cytokine receptor interaction (IL6, IL11, OSM, LIF, CNTF ligands) and angiogenic factors expression.

We found that OVCAR-3 is apparently a suitable model for studying ovarian cancer stem cells and Epithelial to Mesenchymal Transition in Ovarian Cancer Cells.
Effect of Tensile Strain and Shear Stress on the Differentiation of Human Mesenchymal Stem Cells into Endothelial Cells
Authors: Safaei Najmeh , Tafazzoli-Shadpour Mohammad , Haghighipour Nooshin , Shokrgozar Mohammad Ali , Shojaei Shahrokh , Mahdian Reza
Published: March 2012

Stem Cells are undifferentiated cells that have special ability to produce similar cells and differentiate to many functionalized cells. Mechanical stimuli have a determinant effect on morphology and function of body cells, because they are constantly affected by internal and external mechanical loadings. In this research, the importance of mechanical stimuli was assessed on the differentiation of human mesenchymal stem cells (hMSCs) to vascular endothelial cells.
Predictors of Metabolic Syndrome in Participants of a Cardiac Rehabilitation Program
Authors: Farias Godoy Alejandra , Ignaszewski Andrew , Frohlich Jiri , Lear Scott A.
Published: March 2012

Metabolic syndrome increases the risk of all-cause mortality, cardiovascular mortality and cardiovascular events in patients with cardiovascular disease (CVD). This study assessed the predictors of metabolic syndrome, both its incidence and resolution in a cohort of cardiac rehabilitation program graduates. Methods. A total of 154 and 80 participants without and with metabolic syndrome respectively were followed for 48 months. Anthropometric measurements, metabolic risk factors, and quality of life were assessed at baseline and at 48 months. Logistic regression models were used to assess the predictors of metabolic syndrome onset and resolution. Results. Increasing waist circumference (OR 1.175, P≤0.001) was an independent predictor for incident metabolic syndrome (R2 for model = 0.46). Increasing waist circumference (OR 1.234, P≤0.001), decreasing HDL-C (OR 0.027, P=0.005), and increasing triglycerides (OR 3.005, P=0.003) were predictors of metabolic syndrome resolution. Conclusion. Patients with CVD that further develop metabolic syndrome are particularly susceptible for the cascade of cardiovascular events and mortality. Increasing waist circumference confers a higher risk for future onset of metabolic syndrome in this group of patients. They will require closer follow-up and should be targeted for further prevention strategies after cardiac rehabilitation program completion.
Dinámica estacional del crecimiento secundario y anatomía del xilema en dos Quercus mediterráneos que coexisten
Authors: Albuixech Marti J. , Camarero J.J. , Montserrat-Marti G.
Published: March 2012

Se estudió la contribución de los patrones de crecimiento secundario y la anatomía de la madera a la coexistencia de dos especies de Quercus (Quercus ilex subsp. ballota —especie de madera de porosidad semi-difusa— y Quercus faginea —especie de madera de porosidad en anillo—), en una localidad de clima mediterráneo continental, durante dos años de climatología contrastada. Según nuestros resultados el patrón de crecimiento secundario de Q. faginea se concentra en primavera, iniciándose antes, y respondiendo más que el de Q. ilex a un incremento de la precipitación durante este periodo. Q. ilex prolonga la formación de madera hacia el otoño y el crecimiento del verano tardío tiene una mayor importancia en términos de conductividad hidráulica teórica que en Q. faginea, que concentra la conductividad hidráulica en los vasos formados en primavera. Por tanto, la distinta respuesta de la fenología de formación de la madera y de la anatomía del xilema de ambas especies al patrón estacional de precipitación podría contribuir a explicar la coexistencia de Q. ilex y Q. faginea.
Selected Aspects of the Copenhagen Economics Study on Reduced VAT Rates in the Current Conditions of the Moravian-Silesian Region
Authors: Randová Kateřina , Krajňák Michal
Published: March 2012

This paper deals with a long-debated issue of the application of value added tax rates to labour-intensive services. The level of value added tax rates has a dominant influence on the tax liability of suppliers of these services and subsequently on the amount of available funds that they could use for development of their business. The aim of this paper is a presentation of results of the student grant “Quantification of Impacts of Application of Reduced Value Added Tax Rate to Locally Supplied Services on the Suppliers of these Services”, which is focused on selected aspects of the “Study on reduced VAT applied to goods and services in the Member States of the European Union” in the conditions of the providers of these services from the Moravian-Silesian Region. For this paper the methods of regression analysis and analysis of variance – ANOVA were used. The deductive method and method of analysis have also been used.
Identifying freshwater mussels (Unionoida) and parasitic glochidia larvae from host fish gills: a molecular key to the North and Central European species
Authors: Zieritz Alexandra , Gum Bernhard , Kuehn Ralph , Geist Juergen
Published: March 2012

Freshwater mussels (order Unionoida) represent one of the most severely endangered groups of animals due to habitat destruction, introduction of nonnative species, and loss of host fishes, which their larvae (glochidia) are obligate parasites on. Conservation efforts such as habitat restoration or restocking of host populations are currently hampered by difficulties in unionoid species identification by morphological means. Here we present the first complete molecular identification key for all seven indigenous North and Central European unionoid species and the nonnative Sinanodonta woodiana, facilitating quick, low‐cost, and reliable identification of adult and larval specimens. Application of this restriction fragment length polymorphisms (RFLP) key resulted in 100% accurate assignment of 90 adult specimens from across the region by digestion of partial ITS‐1 (where ITS is internal transcribed spacer) polymerase chain reaction (PCR) products in two to four single digestions with five restriction endonucleases. In addition, we provide protocols for quick and reliable extraction and amplification of larval mussel DNA from complete host fish gill arches. Our results indicate that this new method can be applied on infection rates as low as three glochidia per gill arch and enables, for the first time, comprehensive, large‐scale assessments of the relative importance of different host species for given unionoid populations.
Variation of landfill leachate phytotoxicity due to landfill ageing
Authors: Kalčíková Gabriela , Zagorc‐Končan Jana , Zupančič Marija , Gotvajn Andreja Žgajnar
Published: March 2012

BACKGROUND: Landfill leachate is a heavily polluted liquid with important environmental impact. It can be generated in a landfill for a long time. During each phase of a landfill life cycle, landfill leachate with specific composition is produced and its treatment has to be optimized accordingly. Phytoremediation offers many benefits compared with conventional treatment methods. However, leachate can have a negative impact on plants and thus it is essential to evaluate the potential risk of landfill leachate for plants employed in phytoremediation.

RESULTS: Phytotoxicity and composition of two landfill leachates were studied. Phytotoxicity testing and physico‐chemical parameters showed that the leachate generated in the active part of the landfill was significantly polluted and more toxic to plants than the leachate generated in the closed part of the landfill, which did not cause any significant adverse effects on root growth of plants tested in soil. However, the highest toxic effect of both leachates has been observed in the first days of plant germination.

CONCLUSION: Phytotoxic pollutants have probably been degraded in the closed part of the landfill and leachates from such landfills are not significantly toxic to plants. Therefore phytoremediation appeared to be an appropriate restoration and treatment method. Copyright © 2012 Society of Chemical Industry
The Hsp90 inhibitor 17‐AAG represses calcium‐induced cytokeratin 1 and 10 expression in HaCaT keratinocytes
Authors: Miyoshi Sadanori , Yamazaki Shota , Uchiumi Asato , Katagata Yohtaro
Published: March 2012

Hsp90 is essential for maintaining the activity of numerous signaling factors, and plays a key role in cellular signal transduction networks. 17‐Allylamino‐17‐demethoxygeldanamycin (17‐AAG) is an ansamycin antibiotic that binds to Hsp90 and inhibits its function. HaCaT human keratinocytes were used to investigate the cellular and molecular functions of Hsp90 in keratinocyte differentiation. Inhibition of Hsp90 by 17‐AAG leads to downregulation of the differentiation markers cytokeratin 1 and cytokeratin 10 at the protein and mRNA levels.
Wavelet analysis of near-field pressure fluctuations generated by a subsonic jet
Authors: Grizzi S. , Camussi R.
Published: March 2012

An experimental study of the pressure field generated by a subsonic, single stream, round jet is presented. The investigation is conducted in the near-field region at subsonic Mach numbers (up to 0.9) and Reynolds numbers $\mathit{Re}\gt 1{0}^{5} $. The main task of the present work is the analysis of the near-field acoustic pressure and the characterization of its spectral properties. To this aim, a novel post-processing technique based on the application of wavelet transforms is presented. The method accomplishes the separation of nearly Gaussian background fluctuations, interpreted as acoustic pressure, from intermittent pressure peaks induced by the hydrodynamic components. With respect to more standard approaches based on Fourier filtering, the new technique permits one to recover the whole frequency content of both the acoustic and the hydrodynamic contributions and to reconstruct them as independent signals in the time domain. The near-field acoustic pressure is characterized in terms of spectral content, sound pressure level and directivity. The effects of both the Mach number and the distance from the jet axis are analysed and the results are compared with published far-field observations and theoretical predictions. Simultaneous velocity/pressure measurements have been also performed using a hot-wire probe and a microphone pair in the near field. It is shown that the cross-correlation between the near-field acoustic pressure and the axial velocity is large (of the order of 0.2) in the potential core region whereas large velocity/hydrodynamic pressure correlations are located at the nozzle exit and downstream of the potential core.
Computing uncertainties in ionosphere‐airglow models: II. The Martian airglow
Authors: Gronoff Guillaume , Simon Wedlund Cyril , Mertens Christopher J. , Barthélemy Mathieu , Lillis Robert J. , Witasse Olivier
Published: March 2012

One of the objectives of spectrometers onboard space missions is to retrieve atmospheric parameters (notably density, composition and temperature). To fulfill this objective, comparisons between observations and model results are necessary. Knowledge of these model uncertainties is therefore necessary, although usually not considered, to estimate the accuracy in planetary upper atmosphere remote sensing of these parameters. In Part I of this study, “Computing uncertainties in ionosphere‐airglow models: I. Electron flux and species production uncertainties for Mars” (Gronoff et al., 2012), we presented the uncertainties in the production of excited states and ionized species from photon and electron impacts, computed with a Monte‐Carlo approach, and we applied this technique to the Martian upper atmosphere. In the present paper, we present the results of propagation of these production errors to the main UV emissions and the study of other sources of uncertainties. As an example, we studied several aspects of the model uncertainties in the thermosphere of Mars, and especially the O(1S) green line (557.7 nm, with its equivalent, the trans‐auroral line at 297.2 nm), the Cameron bands CO(a3Π), and CO2+(B2Σu+) doublet emissions. We first show that the excited species at the origin of these emissions are mainly produced by electron and photon impact. We demonstrate that it is possible to reduce the computation time by decoupling the different sources of uncertainties; moreover, we show that emission uncertainties can be large (>30%) because of the strong sensitivity to the production uncertainties. Our study demonstrates that uncertainty calculations are a crucial step prior to performing remote sensing in the atmosphere of Mars and the other planets and can be used as a guide to subsequent adjustments of cross sections based on aeronomical observations. Finally, we compare the simulations with observations from the SPICAM spectrometer on the Mars Express spacecraft. The production of excited species at the origin of the green line, the CO Cameron bands and the CO2+(B) doublet is found to be on the dayside, consistent with photon and electron impact on CO2 as the main source of excitation of the three emissions, in contrast to the findings of Huestis et al. (2010) for the O(1S) case. Moreover, we re‐examine the cross section for the production of the Cameron bands by electron impact on CO2.
Dynamic models of interseismic deformation and stress transfer from plate motion to continental transform faults
Authors: Takeuchi Christopher S. , Fialko Yuri
Published: March 2012

We present numerical models of earthquake cycles on a strike‐slip fault that incorporate laboratory‐derived power law rheologies with Arrhenius temperature dependence, viscous dissipation, conductive heat transfer, and far‐field loading due to relative plate motion. We use these models to explore the evolution of stress, strain, and thermal regime on “geologic” timescales (∼106–107 years), as well as on timescales of the order of the earthquake recurrence (∼102 years). Strain localization in the viscoelastic medium results from thermomechanical coupling and power law dependence of strain rate on stress. For conditions corresponding to the San Andreas fault (SAF), the predicted width of the shear zone in the lower crust is ∼3–5 km; this shear zone accommodates more than 50% of the far‐field plate motion. Coupled thermomechanical models predict a single‐layer lithosphere in case of “dry” composition of the lower crust and upper mantle, and a “jelly sandwich” lithosphere in case of “wet” composition. Deviatoric stress in the lithosphere in our models is relatively insensitive to the water content, the far‐field loading rate, and the fault strength and is of the order of 102 MPa. Thermomechanical coupling gives rise to an inverse correlation between the fault slip rate and the ductile strength of the lithosphere. We show that our models are broadly consistent with geodetic and heat flow constrains from the SAF in Northern California. Models suggest that the regionally elevated heat flow around the SAF may be at least in part due to viscous dissipation in the ductile part of the lithosphere.
A Diurnal Rhythm in Glucose Uptake in Brown Adipose Tissue Revealed by In Vivo PET‐FDG Imaging
Authors: van der Veen Daan R. , Shao Jinping , Chapman Sarah , Leevy W. Matthew , Duffield Giles E.
Published: March 2012

Using a micro‐positron emission tomography (PET)/computerized tomography scanner, we have measured 18F‐fluorodeoxyglucose (FDG) uptake in interscapular brown adipose tissue (iBAT) in C57Bl/6 mice at intervals across a 24‐h light‐dark cycle. Our data reveal a strong 24‐h profile of glucose uptake of iBAT, peaking at ∼9 h into the light phase of the 12‐h light, 12‐h dark day. BAT is increasingly gaining attention as being involved in metabolic phenotypes and obesity, where BAT, as observed by PET analysis, negatively correlates with obesity and age. Conversely, animals that show perturbations in circadian clocks, behavior, and physiology show metabolic phenotypes. The observation of a 24‐h rhythm in glucose uptake in iBAT makes this tissue a candidate site of interaction between metabolic and circadian systems.
Non-contacting characterization of the electrical and mechanical properties of rocks at submillimeter scales
Authors: Greeney Nathan S. , Scales John A.
Published: March 2012

At the meso and macro-scale, the connection between the elastic and the electromagnetic properties of granular materials such as rocks is complicated and involves, among other things, the chemical, mineralogical, and geometric features of the grains and their host medium. In the previous work, we showed how to perform rapid near-field millimeter wave scanning to obtain high-spatial resolution maps of the spatially varying dielectric permittivity of heterogeneous materials, including rocks. Here, we extend this concept to laser ultrasound and map the spatially varying mechanical properties of materials with similar resolution.
Narrow band gap (1 eV) InGaAsSbN solar cells grown by metalorganic vapor phase epitaxy
Authors: Kim T. W. , Garrod T. J. , Kim K. , Lee J. J. , LaLumondiere S. D. , Sin Y. , Lotshaw W. T. , Moss S. C. , Kuech T. F. , Tatavarti Rao , Mawst L. J.
Published: March 2012

Heterojunction solar cell structures employing InGaAsSbN (Eg ∼ 1 eV) base regions are grown lattice-matched to GaAs substrates using metalorganic vapor phase epitaxy. Room temperature (RT) photoluminescence (PL) measurements indicate a peak spectral emission at 1.04 eV and carrier lifetimes of 471–576 ps are measured at RT from these structures using time-resolved PL techniques. Fabricated devices without anti-reflection coating demonstrate a peak efficiency of 4.58% under AM1.5 direct illumination. Solar cells with a 250 nm-thick InGaAsSbN base layer exhibit a 17% improvement in open circuit voltage (Voc), 14% improvement in fill factor, and 12% improvement in efficiency over the cells with a thicker (500 nm-thick) base layer.
Band alignment of HfO2 on SiO2/Si structure
Authors: Wang Xiaolei , Han Kai , Wang Wenwu , Xiang Jinjuan , Yang Hong , Zhang Jing , Ma Xueli , Zhao Chao , Chen Dapeng , Ye Tianchun
Published: March 2012

Band alignment of HfO2 with various thicknesses on SiO2/Si structure is investigated by x-ray photoelectron spectroscopy (XPS). Band bending of HfO2/SiO2/Si system is found to vary with HfO2 thickness. Band alignment of entire HfO2/SiO2/Si is demonstrated using concepts of interfacial or surface gap states and charge neutrality level (CNL). The XPS results are interpreted and attributed to lower CNL of HfO2 than SiO2/Si which induces electron transfer from SiO2/Si to HfO2, resulting in band bending upward for SiO2/Si. These further confirm feasibility of gap state based theory in investigating band alignments of oxide/semiconductor and oxide/oxide interfaces.
Trapping induced nonlinear behavior of backward stimulated Raman scattering in multi-speckled laser beams
Authors: Yin L. , Albright B. J. , Rose H. A. , Bowers K. J. , Bergen B. , Kirkwood R. K. , Hinkel D. E. , Langdon A. B. , Michel P. , Montgomery D. S. , Kline J. L.
Published: March 2012

In inertial confinement fusion experiments, stimulated Raman scattering (SRS) occurs when electron density fluctuations are amplified resonantly by the incident laser beams and scattered light. These beams comprise several thousands of individual laser speckles. We have found in single-speckle studies that electron trapping lowers the threshold intensity for SRS onset to a value below that from linear theory and enhances scattering. The trapping-induced plasma-wave frequency shift leads to wave-front bowing and filamentation processes that saturate SRS and limit scattering within a speckle. With large-scale simulations, we have now examined how laser speckles interact with one another through three-dimensional (3D) particle-in-cell (PIC) simulations of two interacting speckles and 2D PIC simulations of ensembles of laser speckles (hundreds of speckles). Our work shows that kinetic trapping physics also governs the onset and saturation of SRS in ensembles of speckles. Speckles interact in a manner that is nonlinear and nonlocal: An intense speckle can destabilize its neighbors through transport of hot electrons and SRS waves, resulting in enhanced emission of particles and waves that, in turn, act upon the original speckle. In this manner, speckles below threshold when in isolation can be above the threshold in multi-speckled beams under conditions for laser-driven fusion experiments at the National Ignition Facility (NIF) and ensembles of speckles are thus found to collectively lower the SRS onset threshold. Simulations of the hohlraum interior where laser beams overlap show that multi-speckled laser beams at low average intensity (a few times 1014 W/cm2) have correspondingly lower thresholds for enhanced SRS and that the sub-ps bursts of SRS saturate through trapping induced nonlinearities. Because of electron trapping effects, SRS reflectivity grows slowly with average laser intensity. While SRS reflectivity saturates under NIF conditions, SRS hot electron energy increases with increasing laser intensity and may contribute to capsule preheat.
Ultrahigh efficient single-crystalline TiO2 nanorod photoconductors
Authors: Chen R. S. , Chen C. A. , Tsai H. Y. , Wang W. C. , Huang Y. S.
Published: March 2012

Photoconductive gain and normalized gain, which determine the device and material properties on photoconduction, respectively, have been defined for single-crystalline titanium dioxide (TiO2) nanorods (NRs) with various diameter sizes. The gain values of the NR photodetectors can reach 105 easily at a low bias of 0.1 V. By excluding the contributions of experimental parameters, the optimal normalized gain of the indirect-bandgap TiO2 NRs at 5.4 × 10−5 m2V−1 is comparable with that estimated from the direct-bandgap ZnO nanowires. The average normalized gain value at 3.3 ± 2.2 × 10−5 m2V−1 obtained from eight individual TiO2 NRs with diameters ranging from 120 to 1250 nm is also over three orders of magnitude higher than the polycrystalline nanotube counterpart. The results demonstrate the superior photoconductivity efficiency in boundary-free titania one-dimensional nanostructure, which is crucial for ultraviolet photodetector, dye-sensitized solar cell, and photochemical device applications.
Light trapping beyond the 4n2 limit in thin waveguides
Authors: Munday Jeremy N. , Callahan Dennis M. , Atwater Harry A.
Published: March 2012

We describe a method for determining the maximum absorption enhancement in thin film waveguides based on optical dispersion relations. For thin film structures that support one, well-confined guided mode, we find that the absorption enhancement can surpass the traditional limit of 4n2 when the propagation constant is large and/or the modal group velocity is small compared to the bulk value. We use this relationship as a guide to predicting structures that can exceed the 4n2 light trapping limit, such as plasmonic and slot waveguides. Finally, we calculate the overall absorption for both single and multimode waveguides, and show examples of absorption enhancements in excess of 4n2 for both cases.
Enlargement of a locally resonant sonic band gap by using double-sides stubbed phononic plates
Authors: Badreddine Assouar M. , Oudich Mourad
Published: March 2012

We report on the theoretical analysis of the enlargement of locally resonant acoustic band gap in two-dimensional sonic crystals based on a double-side stubbed plate. A significant enlargement of the relative bandwidth by a factor of 2 compared to the classical one-side stubbed plates is obtained and discussed. Based on an efficient finite element method, we show that this band gap enlargement is due to the coupling between the same nature of the resonant eigenmodes (in-plane or out-of-plane) of the stubs located in each plate side, producing a strong interaction with the plate’s Lamb modes. Acoustic displacement fields are computed to illustrate such mechanism and to discuss the physics behind it.
Effect of bending stress on structures and quantum conduction of Cu nanowires
Authors: He C. , Zhang W. X. , Shi Z. Q. , Wang J. P. , Pan H.
Published: March 2012

The ballistic transport properties of Cu nanowires under different bending stresses are investigated for future application in flexible displays and flexible solar cell using first-principles density-function theory. The stability and quantum conduction of both nonhelical and helical atomic strands are reduced by applying a bending stress f. With increasing of f, the helical wire becomes disorder, suffering a phase transition to similar nonhelical one and collapsing eventually. Our calculations show that the maximum bearable bending stress is fmax = 3 nN for the helical atomic strands while is more stable than fmax = 2.5 nN for the nonhelical atomic strands.
Grating-coupled silicon microring resonators
Authors: Shi W. , Wang X. , Zhang W. , Yun H. , Lin C. , Chrostowski L. , Jaeger N. A. F.
Published: March 2012

We propose to integrate grating-assisted asymmetric couplers with microring resonators for selective resonance excitation and control of coupling efficiency. A grating-coupled microring add-drop filter is experimentally demonstrated using a silicon-on-insulator technology compatible with complementary metal-oxide-semiconductor processing. A dominant longitudinal mode with a side-mode suppression ratio of 8 dB has been obtained across a broad spectral range of over 130 nm. The selected mode shows an out-of-band-rejection ratio of 19 dB and a quality factor (Q) of 25 000. The concept of integrating grating-assisted couplers for mode selectivity can be applied to other microring-based devices for high-Q, single-mode operations.
Enhanced optical nonlinearity in β-AgVO3 nanobelts on decoration with Ag nanoparticles
Authors: Parida Manas R. , Vijayan C. , Rout C. S. , Suchand Sandeep C. S. , Philip Reji
Published: March 2012

This paper reports on the optical nonlinearity of β-AgVO3 nanobelts and the modification in the physical mechanisms of nonlinear response on decorating with silver nanoparticles. The nanobelts are synthesized by a hydrothermal technique and characterized using SEM, TEM, and XRD etc. The nanobelts are found to exhibit large nonlinear optical absorption as revealed by open Z-scan measurements using 5 ns laser pulses at 532 nm. Nonlinearity appears to be arising from a combination of mechanisms of two photon absorption and saturable absorption (SA). Decoration with Ag nanoparticles is found to enhance the saturable absorption and alter the coefficient of nonlinear absorption of the nanobelts. Efficient optical limiting is demonstrated in both the nanobelt systems.
Enhanced fluid mixing and separation of magnetic bead agglomerates based on dipolar interaction in rotating magnetic fields
Authors: Wittbracht F. , Weddemann A. , Eickenberg B. , Zahn M. , Hütten A.
Published: March 2012

The exposure of a highly concentrated suspension of magnetic beads in a carrier liquid to a homogeneous magnetic field results in the formation of magnetic bead superstructures due to dipolar interactions. We present a microfluidic system which employs such agglomerates to simultaneously allow for mixing and separation applications. Within the chosen structure, an increase of the diffusivity of about 32% was observed and further a separation efficiency of about 80% is achieved for flow rates up to 100 μm/s.
Are all atmospheric pressure cold plasma jets electrically driven?
Authors: Xian YuBin , Lu XinPei , Wu ShuQun , Chu Paul K. , Pan Yuan
Published: March 2012

Up to now, all studies on the dynamics behavior of non-equilibrium plasma plumes were focussed on noble gas plasma plumes. It was found out that they are electrically driven rather than gas flow dependent. Our study on the dynamics of a non-equilibrium N2 plasma plume reveals that the propagation velocity of the N2 plasma plume is several orders magnitude lower than those previously reported and further studies show that it is close to the gas flow velocity. The gas flow has a significant effect on the length of the plasma plume, and the results provide some fundamental knowledge about atmospheric pressure plasma jets.
InGaN channel high electron mobility transistor structures grown by metal organic chemical vapor deposition
Authors: Laboutin O. , Cao Y. , Johnson W. , Wang R. , Li G. , Jena D. , Xing H.
Published: March 2012

High electron mobility transistor (HEMT) structures of AlInGaN/AlN/InGaN/GaN were grown by metal-organic chemical vapor deposition. A combination of low growth rate and high growth temperature during synthesis of the InGaN channel layer led to significant improvement in HEMT electron transport properties. The improvement was correlated with an evolution of both surface roughness and photoluminescence intensity of InGaN. Record electron mobilities from 1070 to 1290 cm2/V·s with associated sheet charge density of ∼2 × 1013 cm−2 were obtained across the InxGa1-xN channel composition range x = 0.05 to 0.10.
Manipulation of magnetic anisotropy of Fe/graphene by charge injection
Authors: Gong S. J. , Duan Chun-Gang , Zhu Zi-Qiang , Chu Jun-Hao
Published: March 2012

We propose that charge injection can be used to tune the magnetic anisotropy of transition metal monolayer adsorbed on graphene substrate. Using relativistic density-functional calculations, we calculate magnetocrystalline anisotropy energy (MAE) of freestanding Fe monolayer and Fe/graphene complex system. We find MAE of Fe atom is drastically changed, from meV/atom in freestanding Fe monolayer to μeV/atom in Fe/graphene system. The more interesting finding is, through charge injection, the suppressed MAE of Fe atoms in Fe/graphene system can be restored back, which provides an effective approach to control MAE. We expect such strategy would be beneficial to graphene based spintronic devices.
Lasing in a hybrid GaAs/silver Tamm structure
Authors: Symonds C. , Lemaître A. , Senellart P. , Jomaa M. H. , Aberra Guebrou S. , Homeyer E. , Brucoli G. , Bellessa J.
Published: March 2012

We demonstrate that lasing can be obtained with the Tamm plasmon modes appearing at the interface between a multilayered dielectric structure and a metal. The sample consists in InGaAs/GaAs quantum wells embedded in an AlAs/AlGaAs Bragg reflector, on top of which a silver film was evaporated. A superlinear increase of the emission is observed under optical pumping as well as a drastic concentration of the emission pattern around the vertical direction, evidencing a lasing effect. Due to the particular features of these surface modes, Tamm lasers open interesting perspectives for the realization of integrated microlasers.
Grain boundaries as preferential sites for resistive switching in the HfO2 resistive random access memory structures
Authors: Lanza M. , Zhang K. , Porti M. , Nafría M. , Shen Z. Y. , Liu L. F. , Kang J. F. , Gilmer D. , Bersuker G.
Published: March 2012

Resistive switching (RS) phenomenon in the HfO2 dielectric has been indirectly observed at device level in previous studies using metal-insulator-metal structures, but its origin remains unclear. In this work, using the enhanced conductive atomic force microscope (ECAFM), we have been able to obtain in situ direct observation of RS with nanometric resolution. The ECAFM measurements reveal that the conductive filaments exhibiting the RS are primarily formed at the grain boundaries, which were shown exhibiting especially low breakdown voltage due to their intrinsic high density of the oxygen vacancies.
Design of three-well indirect pumping terahertz quantum cascade lasers for high optical gain based on nonequilibrium Green’s function analysis
Authors: Liu Tao , Kubis Tillmann , Jie Wang Qi , Klimeck Gerhard
Published: March 2012

The nonequilibrium Green’s function approach is applied to the design of three-well indirect pumping terahertz (THz) quantum cascade lasers (QCLs) based on a resonant phonon depopulation scheme. The effects of the anticrossing of the injector states and the dipole matrix element of the laser levels on the optical gain of THz QCLs are studied. The results show that a design that results in a more pronounced anticrossing of the injector states will achieve a higher optical gain in the indirect pumping scheme compared to the traditional resonant-tunneling injection scheme. This offers in general a more efficient coherent resonant-tunneling transport of electrons in the indirect pumping scheme. It is also shown that, for operating temperatures below 200 K and low lasing frequencies, larger dipole matrix elements, i.e., vertical optical transitions, offer a higher optical gain. In contrast, in the case of high lasing frequencies, smaller dipole matrix elements, i.e., diagonal optical transitions are better for achieving a higher optical gain.
A microstructurally motivated description of the deformation of vertically aligned carbon nanotube structures
Authors: Hutchens Shelby B. , Needleman Alan , Greer Julia R.
Published: March 2012

Vertically aligned carbon nanotube’s extreme compliance and mechanical energy absorption/dissipation capabilities are potentially promising aspects of their multi-functionality. Mathematical models have revealed that a hardening-softening-hardening material relation can capture the unique sequential, periodic buckling behavior displayed by vertically aligned carbon nanotubes under uniaxial compression. Yet the physical origins of these models remain unknown. We provide a microstructure-based motivation for such a phenomenological constitutive relation and use it to explore changes in structural response with nanotube volume fraction.
Field-induced evolution of metallic nano-tips in indium tin oxide-tris-(8-hydroxyquinoline) aluminum-aluminum device
Authors: You Y. T. , Zeng Q. , Yao Y. , Wang M. L. , Wu B. , He Y. , Hu Y. M. , Wu C. Q. , Hou X. Y.
Published: March 2012

The effect of electric field and temperature on bistable characteristics of indium tin oxide/tris-(8-hydroxyquinoline) aluminum (Alq3)/aluminum (Al) device has been investigated. The switching time, during which the device turns from a high resistive (OFF) state to a low resistive (ON) state, increases with decreasing field and temperature. The observed phenomena are accounted for by a phenomenological model that metallic nano-tips may evolve under the influence of the electric field and temperature.
Assessment of gene flow in white clover (Trifolium repens L.) under field conditions in Australia using phenotypic and genetic markers
Authors: De Lucas J. A. , Forster J. W. , Smith K. F. , Spangenberg G. C.
Published: March 2012

White clover is one of the most important pasture legumes in global temperate regions. It is an outcrossing, insect-pollinated species with gene flow occurring naturally between plants. A 2-year study was conducted to assess the relationship between gene flow and physical distance in white clover under field conditions in southern Australia. White clover plants exhibiting a red leaf mark phenotypic trait acted as pollen donors to recipient plants lacking leaf markings at distances up to 200 m distant from the donor plants. Progeny were scored for the dominant red-leafed phenotype and gene flow was modelled. Paternity was confirmed using simple sequence repeat markers. A leptokurtic pattern of gene flow was observed under conditions designed to measure maximised gene flow with the majority of pollination occurring in the first 50 m from the donor pollen source. The combined use of simple sequence repeat and visual markers confirmed that there was also a white clover pollen source in addition to the donor plants. This research confirms the difficulty in ensuring absolute containment of gene flow in an outcrossing species grown in an environment when endemic populations are known to exist.
Estimating pup production in a mammal with an extended and aseasonal breeding season, the Australian sea lion (Neophoca cinerea)
Authors: McIntosh Rebecca R. , Goldsworthy Simon D. , Shaughnessy Peter D. , Kennedy Clarence W. , Burch Paul
Published: March 2012

Context
The Australian sea lion population at Seal Bay Conservation Park, South Australia, was estimated to be declining at a rate of 1.14% per breeding season, on the basis of maximum counts of live pups in each of 13 breeding seasons (Shaughnessy et al. 2006). The reliability of the pup-production estimates used to identify this decline is uncertain.

Aims
Our aims were to obtain representative and repeatable estimates of pup production and to assess the current rate of decline.

Methods
We compared four estimates of pup abundance over five breeding seasons (2002–03, 2004, 2005–06, 2007, 2008–09), including the count of cumulative new births, the maximum live-pup count, the number of pups given passive integrated transponder (PIT) tags, and mark–recapture methods using the Petersen estimate.

Key results
A total of 90% of pup births occurred over a mean of 124 days (s.d. = 14). Final estimates of pup production (from the largest of the four estimation methods used) in the five seasons were 227 (CL 221–239), 288 (CL 273–302), 219 (NA), 260 (CL 254–272) and 268 (CL 268–269). The average estimate of pup mortality was 28.6% (s.d. = 6.3%). The decline in the population at Seal Bay over 17 breeding seasons on the basis of maximum counts of live pups was 0.51% per year or 0.76% per breeding season. However, this trend was not based on best estimates of pup production. On the basis of final estimates for the last five breeding seasons, there is no declining trend.

Conclusions
The count of cumulative new births was the most reliable measure of pup production; the Petersen mark–recapture estimate provided a check for accuracy and confidence limits about the estimate.

Implications
The actual rate of change and the expected trajectory of the Seal Bay population remain uncertain. Ongoing monitoring is a priority for this site, using the reliable methods of estimating pup production identified in the present study.