bluuebunny/crossref_metadata_2025 huggingface dataset:
Large‐scale science education intervention research we can use
Authors: Penuel William R. , Fishman Barry J.
Published: January 2012

This article develops an argument that the type of intervention research most useful for improving science teaching and learning and leading to scalable interventions includes both research to develop and gather evidence of the efficacy of innovations and a different kind of research,design‐based implementation research(DBIR). DBIR in education focuses on what is required to bring interventions and knowledge about learning to all students, wherever they might engage in science learning. This research focuses on implementation, both in the development and initial testing of interventions and in the scaling up process. In contrast to traditional intervention research that focuses principally on one level of educational systems, DBIR designs and tests interventions that cross levels and settings of learning, with the aim of investigating and improving the effective implementation of interventions. The article concludes by outlining four areas of DBIR that may improve the likelihood that new standards for science education will achieve their intended purpose of establishing an effective, equitable, and coherent system of opportunities for science learning in the United States. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 281–304, 2012
Large‐scale interventions in science education: The road to utopia?
Authors: Marx Ronald W.
Published: January 2012

This article provides commentary on the five articles in this issue on large‐scale interventions in science education for diverse student groups in varied educational settings. Using these articles as a point of departure, I discuss three challenges to science education research and practice. The first concerns the changed meaning of science education reform over the past two decades. The science education research and development community must be aware of the shifting policy and public awareness context of their work and react accordingly if it wishes for its work to make a difference in the lives of teachers and students. The second addresses the importance of teacher professional development and the role that well‐designed and internally valid research plays in developing knowledge in this area. The third discusses the chaotic and contradictory nature of educational policy in this country and argues that our field needs to align our research work with the ways in which real and impactful decisions are made about education in general and science education in particular. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 420–427, 2012
The virtual liver: a multidisciplinary, multilevel challenge for systems biology
Authors: Holzhütter Hermann‐Georg , Drasdo Dirk , Preusser Tobias , Lippert Jörg , Henney Adriano M.
Published: January 2012

The liver is the central metabolic organ in human physiology, with functions that are fundamentally important to the detoxification of xenobiotics (drugs), the maintenance of homeostasis of numerous blood metabolites, and the production of mediators of the acute phase response. Liver toxicity, whether actual or implied is the reason for the failure of a significant proportion of many promising novel medicines that consequently never reach the market, and diseases such as atherosclerosis, diabetes, and fatty liver diseases, that are a major burden on current health resources, are directly linked to functional and structural disorders of the liver. This article presents the concepts and approaches underpinning one of the most exciting and ambitious modeling projects in the field of systems biology and systems medicine. This major multidisciplinary research program is aimed at developing a whole‐organ model of the human liver, representing its central physiological functions under normal and pathological conditions The model will be composed of a larger battery of interconnected submodels representing liver anatomy and physiology, integrating processes across hierarchical levels in space, time, and structural organization. In this article, we outline the general architecture of the liver model and present first step taken to reach this ambitious goal. WIREs Syst Biol Med 2012 doi: 10.1002/wsbm.1158

This article is categorized under:

Models of Systems Properties and Processes > Cellular Models

Models of Systems Properties and Processes > Mechanistic Models

Models of Systems Properties and Processes > Organ, Tissue, and Physiological Models

Translational, Genomic, and Systems Medicine > Translational Medicine
Reverse‐engineering human regulatory networks
Authors: Lefebvre Celine , Rieckhof Gabrielle , Califano Andrea
Published: January 2012

The explosion of genomic, transcriptomic, proteomic, metabolomic, and other omics data is challenging the research community to develop rational models for their organization and interpretation to generate novel biological knowledge. The development and use of gene regulatory networks to mechanistically interpret this data is an important development in molecular biology, usually captured under the banner of systems biology. As a result, the repertoire of methods for the reconstruction of comprehensive and cell‐context‐specific maps of regulatory interactions, or interactomes, has also exploded in the past few years. In this review, we focus on Network Biology and more specifically on methods for reverse engineering transcriptional, post‐transcriptional, and post‐translational human interaction networks and show how their interrogation is starting to impact our understanding of cellular pathophysiology and one's ability to predict cellular phenotypes from genome‐wide molecular observations. WIREs Syst Biol Med 2012 doi: 10.1002/wsbm.1159

This article is categorized under:

Analytical and Computational Methods > Analytical Methods

Biological Mechanisms > Regulatory Biology
Überwinde deinen inneren Schweinehund‘‘ - Analyse von Zugangswegen zur Motivierung bewegungsinaktiver Älterer
Authors: Allmer Henning , Allmer Marietta , Euskirchen Julian , Froboese Ingo , Wallmann Birgit , Walter Tina , Walschek Reimund
Published: January 2012

Einleitung

Der gesundheitliche Nutzen der Bewegungs- und Sportaktivität für Ältere ist unbestritten. Da die Bewegungs- und Sportaktivität bei Älteren gering ausgeprägt ist, profitiert der überwiegende Teil der älteren Bevölkerung nicht vom gesundheitlichen Nutzen der Bewegungs- und Sportaktivität. Um bewegungs- und sportinaktive Ältere zu motivieren, wurde eine vergleichende Analyse der Effektivität verschiedener Zugangswege vorgenommen. Als effektiv erwiesen sich zielgruppenspezifische Zugangswege.
Leo Strauss and the Conservative Movement in America
Authors: Gottfried Paul E.
Published: January 2012

This book offers an original interpretation of the achievement of Leo Strauss, stressing how his ideas and followers reshaped the American conservative movement. The conservative movement that reached out to Strauss and his legacy was extremely fluid and lacked a self-confident leadership. Conservative activists and journalists felt a desperate need for academic acceptability, which they thought Strauss and his disciples would furnish. They also became deeply concerned with the problem of 'value relativism', which self-described conservatives thought Strauss had effectively addressed. But until recently, neither Strauss nor his disciples have considered themselves to be 'conservatives'. Contrary to another misconception, Straussians have never wished to convert Americans to ancient political ideals and practices, except in a very selective rhetorical fashion. Strauss and his disciples have been avid champions of American modernity, and 'timeless' values as interpreted by Strauss and his followers often look starkly contemporary.
Allies or Antagonists? Philanthropic Reformers and Business Reformers in the Progressive Era
Authors: Mandell Nikki
Published: January 2012

In the early twentieth century, amid heightening industrial tensions, many large corporations introduced welfare work to co-opt their employees' loyalties and pacify public anger. Many of the techniques and ideas of what became known as “welfare capitalism” were adapted from charity aid and settlement work. Over time, however, labor relations moved from being identified as a social reform issue—bound up with other issues on which the new profession of social work concentrated—to a business management prerogative. This article argues that professionalization played a significant role in these developments. Philanthropic reformers initially claimed welfare work as part of their professional agenda. However, in the second decade of the century, the social work profession began to narrow its field of operations. As social work's ambivalent claims on the factory and shop floor atrophied, business schools were introducing elements of industrial social work into their new management curriculums. The burgeoning field of professional labor management incorporated welfare work as one of its essential tools.
The discrepancy in solar EUV‐proxy correlations on solar cycle and solar rotation timescales and its manifestation in the ionosphere
Authors: Chen Yiding , Liu Libo , Wan Weixing
Published: January 2012

This study investigates the correlations between SOHO/Solar EUV Monitor 26–34 nm EUV and the F10.7 and Mg II proxies on solar cycle (long‐term) and solar rotation (short‐term) timescales. The long‐term components of EUV and proxies are well correlated, and the general relation between them can be captured by the 81 day averaged EUV and proxies. Short‐term EUV‐proxy correlation is poorer and variable during the solar cycle. The slopes of short‐term EUV against proxies vary from solar rotation to solar rotation, and they are generally lower than those of long‐term EUV against proxies. EUV and proxies show discrepant evolutions during the episode of major active regions, which should be a primary reason for the poorer short‐term EUV‐proxy correlation and the variable short‐term EUV‐proxy slope. Mg II is a better proxy than F10.7 for 26–34 nm EUV. Its superiority mainly comes from better indications for short‐term EUV. Global electron content (GEC) significantly responds to the long‐term and short‐term variations of EUV. Accordingly, the correlations between short‐term GEC and proxies are poorer, and they are obviously lower than those between short‐term EUV and proxies owing to ionospheric day‐to‐day variability. Short‐term GEC‐proxy slopes are also lower than the long‐term slopes. F10.7 and Mg II are improved by combining the daily and 81 day averaged components of them with weighted factors that are designed to decrease the difference between long‐term and short‐term EUV‐proxy slopes. The improved proxies can effectively upgrade the indications of proxies for EUV though they cannot solve the variability of short‐term EUV‐proxy slope. This method is also used to improve proxies for better indicating GEC, but the improved proxies for GEC differ from those for 26–34 nm EUV.
Correlation between SCIAMACHY, MODIS, and CERES reflectance measurements: Implications for CLARREO
Authors: Jin Zhonghai , Lukachin Constantin , Gopalan Arun , Sun Wenbo
Published: January 2012

We have analyzed the correlation between measurements by three different satellite sensors (SCIAMACHY, MODIS, and CERES) on two independent space platforms (Envisat and Terra). Though the instantaneous measurements from the two satellites are not collocated due to orbit offset, the monthly mean broadband and narrowband reflectances and their anomalies from the three instruments are highly correlated when averaged over large latitude regions. The mean reflectance from MODIS in each of those large domains is nearly the same as that derived from SCIAMACHY spectrum convolved with the filter function of the corresponding MODIS channel, with all correlation coefficients higher than 0.93. The interannual variability of monthly mean reflectance is also correlated with the variations of mean cloud and surface properties in large climate zones. The reflectance variation is correlated with the cloud fraction in low and middle latitude regions with correlation coefficients higher than 0.76 and with the snow and sea ice changes in the polar regions with correlation coefficients higher than 0.6. These correlations indicate that the nadir sampling strategy as proposed for CLARREO is sufficient for climate benchmarking of the reflected solar spectrum and provide the physical foundation for climate fingerprinting. However, the results also show the relatively large differences in trends in reflectance due to different instrument degradations and inconsistent calibrations which will affect the attribution of radiative signals of long‐term climate change.
Geostatistical analysis of centimeter‐scale hydraulic conductivity variations at the MADE site
Authors: Bohling Geoffrey C. , Liu Gaisheng , Knobbe Steven J. , Reboulet Edward C. , Hyndman David W. , Dietrich Peter , Butler James J.
Published: January 2012

Spatial variations in hydraulic conductivity (K) provide critical controls on solute transport in the subsurface. Recently, new direct‐push tools were developed for high‐resolution characterization of K variations in unconsolidated settings. These tools were applied to obtain 58 profiles (vertical resolution of 1.5 cm) from the heavily studied macrodispersion experiment (MADE) site. We compare the data from these 58 profiles with those from the 67 flowmeter profiles that have served as the primary basis for characterizing the heterogeneous aquifer at the site. Overall, the patterns of variation displayed by the two data sets are quite similar, in terms of both large‐scale structure and autocorrelation characteristics. The direct‐push K values are, on average, roughly a factor of 5 lower than the flowmeter values. This discrepancy appears to be attributable, at least in part, to opposite biases between the two methods, with the current versions of the direct‐push tools underestimating K in the highly permeable upper portions of the aquifer and the flowmeter overestimating K in the less permeable lower portions. The vertically averaged K values from a series of direct‐push profiles in the vicinity of two pumping tests at the site are consistent with the K estimates from those tests, providing evidence that the direct‐push estimates are of a reasonable magnitude. The results of this field demonstration show that direct‐push profiling has the potential to characterize highly heterogeneous aquifers with a speed and resolution that has not previously been possible.
Neutrophils—the unexpected helpers of B‐cell activation
Authors: Harwood Naomi E , Barral Patricia , Batista Facundo D
Published: January 2012

A specific subpopulation of neutrophils, termed NBH, has been shown recently to provide help for the differentiation and function of B cells and plasma cells. These novel findings are put in the context of our current understanding of B‐cell help.
Acyl homoserine lactone-based quorum sensing in a methanogenic archaeon
Authors: Zhang Guishan , Zhang Fan , Ding Gang , Li Jie , Guo Xiaopeng , Zhu Jinxing , Zhou Liguang , Cai Shichun , Liu Xiaoli , Luo Yuanming , Zhang Guifeng , Shi Wenyuan , Dong Xiuzhu
Published: January 2012

Acyl homoserine lactone (AHL)-based quorum sensing commonly refers to cell density-dependent regulatory mechanisms found in bacteria. However, beyond bacteria, this cell-to-cell communication mechanism is poorly understood. Here we show that a methanogenic archaeon, Methanosaeta harundinacea 6Ac, encodes an active quorum sensing system that is used to regulate cell assembly and carbon metabolic flux. The methanogen 6Ac showed a cell density-dependent physiology transition, which was related to the AHL present in the spent culture and the filI gene-encoded AHL synthase. Through extensive chemical analyses, a new class of carboxylated AHLs synthesized by FilI protein was identified. These carboxylated AHLs facilitated the transition from a short cell to filamentous growth, with an altered carbon metabolic flux that favoured the conversion of acetate to methane and a reduced yield in cellular biomass. The transcriptomes of the filaments and the short cell forms differed with gene expression profiles consistent with the physiology. In the filaments, genes encoding the initial enzymes in the methanogenesis pathway were upregulated, whereas those for cellular carbon assimilation were downregulated. A luxI–luxR ortholog filI–filR was present in the genome of strain 6Ac. The carboxylated AHLs were also detected in other methanogen cultures and putative filI orthologs were identified in other methanogenic genomes as well. This discovery of AHL-based quorum sensing systems in methanogenic archaea implies that quorum sensing mechanisms are universal among prokaryotes.
3′-5′ Phosphoadenosine phosphate is an inhibitor of PARP-1 and a potential mediator of the lithium-dependent inhibition of PARP-1 in vivo
Authors: Toledano Elie , Ogryzko Vasily , Danchin Antoine , Ladant Daniel , Mechold Undine
Published: January 2012

pAp (3′-5′ phosphoadenosine phosphate) is a by-product of sulfur and lipid metabolism and has been shown to have strong inhibitory properties on RNA catabolism. In the present paper we report a new target of pAp, PARP-1 [poly(ADP-ribose) polymerase 1], a key enzyme in the detection of DNA single-strand breaks. We show that pAp can interact with PARP-1 and inhibit its poly(ADP-ribosyl)ation activity. In vitro, inhibition of PARP-1 was detectable at micromolar concentrations of pAp and altered both PARP-1 automodification and heteromodification of histones. Analysis of the kinetic parameters revealed that pAp acted as a mixed inhibitor that modulated both the Km and the Vmax of PARP-1. In addition, we showed that upon treatment with lithium, a very potent inhibitor of the enzyme responsible for pAp recycling, HeLa cells exhibited a reduced level of poly(ADP-ribosyl)ation in response to oxidative stress. From these results, we propose that pAp might be a physiological regulator of PARP-1 activity.
Cardiac troponin T levels and exercise stress testing in patients with suspected coronary artery disease: the Akershus Cardiac Examination (ACE) 1 study
Authors: Røysland Ragnhild , Kravdal Gunnhild , Høiseth Arne Didrik , Nygård Ståle , Badr Pirouz , Hagve Tor-Arne , Omland Torbjørn , Røsjø Helge
Published: January 2012

Whether reversible ischaemia in patients referred for exercise stress testing and MPI (myocardial perfusion imaging) is associated with changes in circulating cTn (cardiac troponin) levels is controversial. We measured cTnT with a sensitive assay before, immediately after peak exercise and 1.5 and 4.5 h after exercise stress testing in 198 patients referred for MPI. In total, 19 patients were classified as having reversible myocardial ischaemia. cTnT levels were significantly higher in patients with reversible myocardial ischaemia on MPI at baseline, at peak exercise and after 1.5 h, but not at 4.5 h post-exercise. In patients with reversible ischaemia on MPI, cTnT levels did not change significantly after exercise stress testing [11.1 (5.2–14.9) ng/l at baseline compared with 10.5 (7.2–16.3) ng/l at 4.5 h post-exercise, P=0.27; values are medians (interquartile range)]. Conversely, cTnT levels increased significantly during testing in patients without reversible myocardial ischaemia [5.4 (3.0–9.0) ng/l at baseline compared with 7.5 (4.6–12.4) ng/l, P<0.001]. In conclusion, baseline cTnT levels are higher in patients with MPI evidence of reversible myocardial ischaemia than those without reversible ischaemia. However, although cTnT levels increase during exercise stress testing in patients without evidence of reversible ischaemia, this response appears to be blunted in patients with evidence of reversible ischaemia. Mechanisms other than reversible myocardial ischaemia may play a role for acute exercise-induced increases in circulating cTnT levels.
A new general Renner-Teller (including ɛ ≳ 1) spectroscopic formalism for triatomic molecules
Authors: Mitrushchenkov Alexander O.
Published: January 2012

We present a general approach and its implementation for calculating the rovibronic levels and spectra of rigid or floppy Renner-Teller triatomic molecules, which is not limited in the number and quantum numbers (Λ, S) of electronic states. The case of strong Renner-Teller coupling (ɛ ≳ 1) is specially studied and it is shown that the proposed implementation provides very accurate and stable results for this complicated problem. Few examples (BF2, HBF, and CCO) illustrate the performance of the code.
Resistive pulse sensing of magnetic beads and supraparticle structures using tunable pores
Authors: Willmott Geoff R. , Platt Mark , Lee Gil U.
Published: January 2012

Tunable pores (TPs) have been used for resistive pulse sensing of 1 μm superparamagnetic beads, both dispersed and within a magnetic field. Upon application of this field, magnetic supraparticle structures (SPSs) were observed. Onset of aggregation was most effectively indicated by an increase in the mean event magnitude, with data collected using an automated thresholding method. Simulations enabled discrimination between resistive pulses caused by dimers and individual particles. Distinct but time-correlated peaks were often observed, suggesting that SPSs became separated in pressure-driven flow focused at the pore constriction. The distinct properties of magnetophoretic and pressure-driven transport mechanisms can explain variations in the event rate when particles move through an asymmetric pore in either direction, with or without a magnetic field applied. Use of TPs for resistive pulse sensing holds potential for efficient, versatile analysis and measurement of nano- and microparticles, while magnetic beads and particle aggregation play important roles in many prospective biosensing applications.
Scaling laws for slippage on superhydrophobic fractal surfaces
Authors: Cottin-Bizonne C. , Barentin C. , Bocquet L.
Published: January 2012

We study the slippage on hierarchical fractal superhydrophobic surfaces and find an unexpected rich behavior for hydrodynamic friction on these surfaces. We develop a scaling law approach for the effective slip length, which is validated by numerical resolution of the hydrodynamic equations. Our results demonstrate that slippage does strongly depend on the fractal dimension and is found to be always smaller on fractal surfaces as compared with surfaces with regular patterns. This shows that in contrast to naive expectations, the value of effective contact angle is not sufficient to infer the amount of slippage on a fractal surface: depending on the underlying geometry of the roughness, strongly superhydrophobic surfaces may, in some cases, be fully inefficient in terms of drag reduction. Finally, our scaling analysis can be directly extended to the study of heat transfer at fractal surfaces, in order to estimate the Kapitsa surface resistance on patterned surfaces, as well as to the question of trapping of diffusing particles by patchy hierarchical surfaces, in the context of chemoreception.
Characterization of deep levels in n-type and semi-insulating 4H-SiC epitaxial layers by thermally stimulated current spectroscopy
Authors: Muzykov Peter G. , Krishna Ramesh M. , Mandal Krishna C.
Published: January 2012

We have investigated deep level centers in n-type and semi-insulating (SI) 4H-SiC epitaxial layers by thermally stimulated current (TSC) spectroscopy. The epitaxial layers were grown using chemical vapor deposition utilizing a dichlorosilane precursor. Both epitaxial layers exhibited relatively shallow levels related to Al, B, L- and D-centers. A deep level center with an activation energy of 1.1 eV, peaked at ∼400 K, was detected in the n-type epitaxial layer and correlated with the IL2 level and the 1.1 eV center in a high purity bulk SI 4H-SiC. The TSC spectra of the SI epitaxial layer was dominated by the peaks at 525–585 K that we attributed to intrinsic defects and their complexes with energy levels close to the middle of the bandgap. The TSC spectra of SI epitaxial layer exhibited peaks with different current polarity which is explained by thermoelectric effect and the built-in electric field reversal. The results of the transfer length method measurements of the SI epitaxial layer and the room temperature current-voltage (I-V) characteristics of both epitaxial layers are also reported.
Resonant inelastic x-ray scattering of methyl chloride at the chlorine K edge
Authors: El Khoury L. , Journel L. , Guillemin R. , Carniato S. , Stolte W. C. , Marin T. , Lindle D. W. , Simon M.
Published: January 2012

We present a combined experimental and theoretical study of isolated CH3Cl molecules using resonant inelastic x-ray scattering (RIXS). The high-resolution spectra allow extraction of information about nuclear dynamics in the core-excited molecule. Polarization-resolved RIXS spectra exhibit linear dichroism in the spin-orbit intensities, a result interpreted as due to chemical environment and singlet-triplet exchange in the molecular core levels. From analysis of the polarization-resolved data, Cl 2px, y and 2pz electronic populations can be determined.
The linear stability of oscillating pipe flow
Authors: Thomas C. , Bassom A. P. , Blennerhassett P. J.
Published: January 2012

An investigation is made of the three-dimensional linear stability of the Stokes layer generated within a fluid contained inside a long oscillating cylinder. Both longitudinal and torsional vibrations are examined and the system of disturbance equations derived using Floquet theory are solved using pseudospectral methods. Critical parameters for instability are obtained for an extensive range of pipe radii and longitudinal and azimuthal wavenumbers. For sufficiently small pipe diameters, three-dimensional perturbations are sometimes found to be more unstable than their two-dimensional counterparts. In contrast, at larger radii, the three-dimensional disturbance modes are less important and the two-dimensional versions are expected to be observed in practice. These results imply constraints on experiments that are designed to exhibit shear modes in oscillatory flow.
Temperature-driven evolution of hierarchical nanodomain structure in tetragonal-like BiFeO3 films
Authors: Qi Yajun , Chen Zuhuang , Wang Lihua , Han Xiaodong , Wang Junling , Sritharan Thirumany , Chen Lang
Published: January 2012

Transmission electron microscopy study of tetragonal-like BiFeO3 films reveals a hitherto unreported hierarchical nanodomain structure. The 30-50 nm wide stripe domains with {110} domain walls consist of a substructure of lamellar nanodomains of 8-10 nm width in a herringbone-like arrangement. In situ heating and cooling reveal a reversible transition from the hierarchical nanodomain structure to a tweed-like domain structure which is accompanied by a first-order phase transition near 120 °C with a thermal hysteresis.
Mn substitution-driven structural and magnetic phase evolution in Bi1−xSmxFeO3 multiferroics
Authors: Khomchenko V. A. , Troyanchuk I. O. , Kovetskaya M. I. , Paixão J. A.
Published: January 2012

X-ray diffraction and magnetization measurements of the Bi0.9Sm0.1Fe1−yMnyO3 and Bi0.86Sm0.14Fe1−zMnzO3 (y ≤ 0.4, z ≤ 0.3) series were carried out in order to follow the effect of Mn doping on the room temperature crystal structure and magnetic properties of Sm-substituted BiFeO3. Initially polar rhombohedral Bi0.9Sm0.1FeO3 compound (space group R3c) was shown to undergo the Mn-substitution driven structural transformation into the orthorhombic Pnam phase at y ∼ 0.2. Further increasing of the Mn content stabilizes the modified structural phase demonstrating the features of incommensurability. In the Bi0.86Sm0.14Fe1−zMnzO3 series, the initially dominant antipolar orthorhombic Pnam phase transforms toward the nonpolar Pnma structure (z ∼ 0.3). Changes of the main magnetic state (from mixed antiferromagnetic/weak ferromagnetic to weak ferromagnetic) were found to correlate with the rhombohedral-to-orthorhombic transition; however, within the compositional range of the orthorhombically distorted compounds, the room temperature spontaneous magnetization rapidly decreases with increasing Mn content.
Correlation of phonon characteristics and crystal structures of Ba[Zn1/3(Nb1−xTax)2/3]O3 solid solutions
Authors: Shi Feng , Dong Helei
Published: January 2012

The Ba[Zn1/3(Nb1−xTax)2/3]O3 (BZNT, x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions were synthesized by conventional solid-state sintering technique. Vibration spectra (Raman spectroscopy) and x-ray diffraction (XRD) were employed to evaluate the correlation between crystal structures and vibration modes of these solid solutions as a function of Nb5+ ions replaced by Ta5+ ions. Spectroscopic and structural data show sensitivity to sample structural evolution with Ta5+ concentration. It is verified that these ceramics present a phase transition with increasing Ta5+ content, from cubic (x = 0 and x = 0.2) to hexagonal (x = 0.8 and x = 1). Raman results show that the samples of x = 0.4 and 0.6, which have a pseudocubic structure, are of the transition phases, and the 1:2 ordering degree increases and the BZNT ceramics decrease in the crystal symmetry with Ta5+ concentration. Tilting of oxygen octahedra is the main reason for phase transition. The phonon modes of the vibration spectra were assigned, the position and width were determined, and the correlation of phonon vibrations with the crystal structures for the different atoms substituted in B″-site was found.
Percolation model for the threshold voltage of field-effect transistors with nanocrystalline channels
Authors: Steinke I. P. , Ruden P. P.
Published: January 2012

We present a model for determining the threshold voltage of field-effect transistors with nanocrystalline active channel layers. In this type of device, the multiple boundaries between neighboring crystalline grains limit the charge-carrier transport. Electrons in the channel may either populate the conduction band within a grain or be trapped at an interface between neighboring grains. The relative distribution of the electrons over these states determines the conductances of the grains and of the boundaries between them. We employ simple carrier statistics to calculate the macroscopic densities of free and trapped carriers, and these densities are then used to define site and bond occupation probabilities for a two-dimensional site-bond percolation problem. The dependence of the threshold voltage on the primary model parameters: the energy of the trap states, the total density of traps, and the temperature, is explored.
Probing grain boundaries in ceramic scintillators using x-ray radioluminescence microscopy
Authors: Podowitz Stephen R. , Gaumé Romain M. , Feigelson Robert S.
Published: January 2012

X-ray radioluminescence microscopy (XRLM), a novel fluorescence microscopy technique under focused x-ray excitation, was used to characterize micro-scale luminescence of Eu:Y2O3 and Ce:YAG transparent ceramics and bicrystals. The diffusion length of a known semiconductor measured by XRLM was found to be in agreement with previously measured values, illustrating its use for characterizing charge carrier transport. Emission intensity was found to drop at the boundaries in both Eu:Y2O3 and Ce:YAG ceramics and bicrystals. The depletion in emission at grain boundaries was ultimately found to be related to charge carrier depletion (through either deep trapping or non-radiative recombination). A charge carrier diffusion model was used to understand the effect of grain boundaries on charge carrier transport in these scintillators. The diffusion model was found to accurately predict the spatial distribution of emission in a Ce:YAG single-crystal as a function of x-ray excitation energy. Structural and chemical characterization of grain boundaries in an Eu:Y2O3 ceramic using transmission electron microscopy and secondary ion mass spectrometry mapping showed an ordered boundary region and no detectable segregation of impurities or Eu, justifying the use of an abrupt boundary condition to determine boundary recombination velocities in these materials. The boundary recombination velocities were then used to show that, for ceramics with grain sizes > ∼20 μm, there would be a minimal effect from the detected charge carrier depletion at grain boundaries on their bulk x-ray radioluminescence intensity. Ultimately, this study illustrates how this new XRLM technique can be used to measure charge carrier diffusion properties and how it may be coupled with microstructural and micro-scale chemical analyses to fully investigate the effect of grain boundaries on scintillator properties.
Confinement of magnetic nanoparticles inside multisegmented nanotubes by means of magnetic field gradients
Authors: Neumann R. F. , Bahiana M. , Allende S. , Escrig J. , Altbir D.
Published: January 2012

The possibility of confining magnetic nanoparticles inside multisegmented nanotubes by using strong field gradients is considered by means of Monte Carlo simulations. The problem is reduced to the random walk performed by the nanoparticle on the energy landscape produced by the tube’s magnetic field. The role of tube material, number of segments, and spacer thickness in the amount of time spent by the particle inside the tube is examined, concluding that it is possible to control the encapsulation time by using different architectures.
Ferromagnetism in graphene-Mn(x)Si(1−x) heterostructures grown on 6H-SiC(0001)
Authors: Magnano E. , Bondino F. , Cepek C. , Sangaletti L. , Mozzati M. C. , Parmigiani F.
Published: January 2012

The fabrication of Mn-doped SiC materials by thermal reaction is an interesting method for obtaining SiC-based ferromagnetic semiconductors. Here we used x-ray photoemission and absorption measurements to study the reaction and diffusion of Mn in a 6 H-SiC single crystal substrate induced by a thermal treatment. In particular we have detected the formation of Mn-Si alloys completely covered by a graphene layer. The temperature dependence of the magnetization curves reveals the presence of two distinct magnetic phases. Interestingly, one of these phases displays ferromagnetic character at temperatures close to room temperature.
Limitations on cloning in classical mechanics
Authors: Fenyes Aaron
Published: January 2012

In this paper, we show that a result precisely analogous to the traditional quantum no-cloning theorem holds in classical mechanics. This classical no-cloning theorem does not prohibit classical cloning, we argue, because it is based on a too-restrictive definition of cloning. Using a less popular, more inclusive definition of cloning, we give examples of classical cloning processes. We also prove that a cloning machine must be at least as complicated as the object it is supposed to clone.
Conformal doping mechanism for fin field effect transistors by self-regulatory plasma doping with AsH3 plasma diluted with He
Authors: Sasaki Yuichiro , Okashita Katsumi , Mizuo Bunji , Kubota Masafumi , Ogura Mototsugu , Nishijima Osamu
Published: January 2012

Key parameters for achieving n-type conformal doping desirable for source/drain extension regions of Si n-channel fin field effect transistors (FinFETs) have been determined for self-regulatory plasma doping using an AsH3 plasma diluted with He. Two-dimensional scanning spreading resistance microscopy revealed that this technique is advantageous for conformal doping of fin structures. An excellent resistivity conformality was obtained with the ratio of the resistivity of fin sidewall to that of the fin top surface being 0.85. A high total gas flow rate and a high AsH3 concentration were found to be important conditions for realizing conformal doping. The results revealed that a short gas residence time and high molar concentrations of AsH3 and He in the process chamber are essential physical parameters for realizing large amounts of dopant species with finite decomposition times. When these conditions are realized, a sufficiently large amount of As is supplied to both the top surface and the sidewall so that the lowest resistivity is uniformly obtained in these regions because the activated As concentration is saturated even when excess As is supplied to the fin surfaces. The trade-off that exists between conformal doping and fin erosion is discussed. This technique will be useful for realizing conformal doping for the extension regions of n-channel FinFETs for the 22 nm node and beyond.
Solid polyelectrolyte-gated surface conductive diamond field effect transistors
Authors: Dankerl M. , Tosun M. , Stutzmann M. , Garrido J. A.
Published: January 2012

Solid polyelectrolytes have been used in transistor devices to achieve gating with high capacitance. We use a solid polyethylene oxide/LiClO4 electrolyte to replace aqueous electrolytes as a gate for surface-conductive diamond field-effect transistors (FET). The resulting transistor shows characteristics comparable to those of aqueous electrolyte-gated diamond FETs. We investigate the polyelectrolyte/diamond interface with impedance spectroscopy and cyclic voltammetry, showing the electrochemical stability of the interface and capacitive gating up to 100 Hz. Hall effect measurements on the polyelectrolyte-gated devices are compared to those with liquid gates. The solid and transparent polyelectrolyte gates promise further applications for surface-conductive diamond FETs.
Biomolecule detection based on Si single-electron transistors for highly sensitive integrated sensors on a single chip
Authors: Kudo Takashi , Nakajima Anri
Published: January 2012

Biomolecule detection was achieved using a Si single-electron transistor (SET) for highly-sensitive detection. A multiple-island channel-structure was used for the SET to enable room-temperature operation and to increase sensitivity. Coulomb oscillation shifted against the gate voltage due to biotin-streptavidin binding. Coulomb oscillation has a possibility to increase transconductance (gm), and a higher gm leads to greater sensitivity to a charged target. Since a Si structure is important for integrating label-free-biomolecule and/or ion sensors into large-scale-integrated circuits, a Si SET with multiple islands should enable the integration of a sensor system on a single chip for multiplexed detections and simultaneous diagnoses.
Theoretical and numerical assessments of spin-flip time-dependent density functional theory
Authors: Li Zhendong , Liu Wenjian
Published: January 2012

Spin-flip time-dependent density functional theory (SF-TD-DFT) with the full noncollinear hybrid exchange-correlation kernel and its approximate variants are critically assessed, both formally and numerically. As demonstrated by the ethylene torsion and the C2v ring-opening of oxirane, SF-TD-DFT is very useful for describing nearly degenerate situations. However, it may occasionally yield unphysical results. This stems from the noncollinear form of the generalized gradient approximation, which becomes numerically instable in the presence of spin-flip excitations from the closed- to vacant-shell orbitals of an open-shell reference. To cure this defect, a simple modification, dubbed as ALDA0, is proposed in the spirit of adiabatic local density approximation (ALDA). It is applicable to all kinds of density functionals and yields stable results without too much loss of accuracy. In particular, the combination of ALDA0 with the Tamm-Dancoff approximation is a promising tool for studying global potential energy surfaces. In addition to the kernel problem, SF-TD-DFT is also rather sensitive to the choice of reference states, as demonstrated by the spin multiplet states of closed-shell molecules of H2O, CH2O, and C2H4. Surprisingly, SF-TD-DFT with pure density functionals may also fail for valance excitations with large orbital overlaps, at variance with the spin-conserving counterpart (SC-TD-DFT). In this case, the inclusion of a large amount of Hartree-Fock exchange is mandatory for quantitative results. Nonetheless, for spatially degenerate cases such as CF, CH, and NH+, SF-TD-DFT is more advantageous than SC-TD-DFT, unless the latter is also space adapted. These findings are very instructive for future development and applications of TD-DFT.
Bismuth nanowire growth under low deposition rate and its ohmic contact free of interface damage
Authors: Tian Ye , Fei Guo Chuan , Guo Shengming , Wang Yongsheng , Miao Junjie , Wang Qi , Liu Qian
Published: January 2012

High quality bismuth (Bi) nanowire and its ohmic contact free of interface damage are quite desired for its research and application. In this paper, we propose one new way to prepare high-quality single crystal Bi nanowires at a low deposition rate, by magnetron sputtering method without the assistance of template or catalyst. The slow deposition growth mechanism of Bi nanowire is successfully explained by an anisotropic corner crossing effect, which is very different from existing explanations. A novel approach free of interface damage to ohmic contact of Bi nanowire is proposed and its good electrical conductivity is confirmed by I-V characteristic measurement. Our method provides a quick and convenient way to produce high-quality Bi nanowires and construct ohmic contact for desirable devices.
Dissipative drift instability in dusty plasma
Authors: Das Nilakshi , Baruah Swati
Published: January 2012

An investigation has been done on the very low-frequency electrostatic drift waves in a collisional dusty plasma. The dust density gradient is taken perpendicular to the magnetic field \documentclass[12pt]{minimal}\begin{document}$\overrightarrow{B_{0}}$\end{document}B0⃗, which causes the drift wave. In this case, low-frequency drift instabilities can be driven by \documentclass[12pt]{minimal}\begin{document}$\overrightarrow{E_{1}}\times \overrightarrow{B_{0}}$\end{document}E1⃗×B0⃗ and diamagnetic drifts, where \documentclass[12pt]{minimal}\begin{document}$\overrightarrow{E_{1}}$\end{document}E1⃗ is the perturbed electric field. Dust charge fluctuation is also taken into consideration for our study. The dust- neutral and ion-neutral collision terms have been included in equations of motion. It is seen that the low-frequency drift instability gets damped in such a system. Both dust charging and collision of plasma particles with the neutrals may be responsible for the damping of the wave. Both analytical and numerical techniques have been used while developing the theory.
Enhanced life time and suppressed efficiency roll-off in phosphorescent organic light-emitting diodes with multiple quantum well structures
Authors: Koo Ja-Ryong , Lee Seok Jae , Hyung Gun Woo , Im Dong Whan , Yu Han Sung , Park Jung-Hwan , Lee Kum Hee , Yoon Seung Soo , Kim Woo Young , Kim Young Kwan
Published: January 2012

We demonstrate red phosphorescent organic light-emitting diodes (OLEDs) with multiple quantum well structures which confine triplet exciton inside an emitting layer (EML) region. Five types of OLEDs, from a single to five quantum wells, are fabricated with charge control layers to produce high efficiencies, and the performance of the devices is investigated. The improved quantum efficiency and lifetime of the OLED with four quantum wells, and its suppressed quantum efficiency roll-off of 17.6%, can be described by the increased electron–hole charge balance owing to the bipolar property as well as the efficient triplet exciton confinement within each EML, and by prevention of serious triplet–triplet and/or triplet–polaron annihilation as well as the Förster self-quenching due to charge control layers.
Enhancing humoral responses to a malaria antigen with nanoparticle vaccines that expand T
fh
cells and promote germinal center induction
Authors: Moon James J. , Suh Heikyung , Li Adrienne V. , Ockenhouse Christian F. , Yadava Anjali , Irvine Darrell J.
Published: January 2012

For subunit vaccines, adjuvants play a key role in shaping immunological memory. Nanoparticle (NP) delivery systems for antigens and/or molecular danger signals are promising adjuvants capable of promoting both cellular and humoral immune responses, but in most cases the mechanisms of action of these materials are poorly understood. Here, we studied the immune response elicited by NPs composed of multilamellar “stapled” lipid vesicles carrying a recombinant
Plasmodium vivax
circumsporozoite antigen, VMP001, both entrapped in the aqueous core and anchored to the lipid bilayer surfaces. Immunization with these particles and monophosphoryl lipid A (MPLA), a US Food and Drug Administration–approved immunostimulatory agonist for Toll-like receptor-4, promoted high-titer, high-avidity antibody responses against VMP001, lasting more than 1 y in mice at 10-fold lower doses than conventional adjuvants. Compared to soluble VMP001 mixed with MPLA, VMP001-NPs promoted broader humoral responses, targeting multiple epitopes of the protein and a more balanced Th1/Th2 cytokine profile from antigen-specific T cells. To begin to understand the underlying mechanisms, we examined components of the B-cell response and found that NPs promoted robust germinal center (GC) formation at low doses of antigen where no GC induction occurred with soluble protein immunization, and that GCs nucleated near depots of NPs accumulating in the draining lymph nodes over time. In parallel, NP vaccination enhanced the expansion of antigen-specific follicular helper T cells (T
fh
), compared to vaccinations with soluble VMP001 or alum. Thus, NP vaccines may be a promising strategy to enhance the durability, breadth, and potency of humoral immunity by enhancing key elements of the B-cell response.
Family social support during the predeparture period: The experience of British migrants
Authors: Tabor Aidan S. , Milfont Taciano L.
Published: January 2012

This study explored the stress, wellbeing and social support of predeparture British migrants to New Zealand. The main research questions addressed the relationship between family support and psychological outcomes, differences in migration desire between couples, and the impact of extended family support. A survey recruited 95 participants from online forums for migrants to New Zealand and results indicated that support from immediate family was related to better wellbeing and lower stress. Migrants who considered themselves the driving force behind the move reported significantly more stress and less family support than migrants who had partners who were equally enthusiastic about the move abroad. Sojourners perceived more support from extended family than did migrants who intended to leave permanently. The most difficult parts of the migration process were leaving loved ones, logistical demands, and uncertainty. The most positive parts of the process were adventure and becoming closer as a family. Overall, migration stress and coping began well before departure from the country of origin.
Spatial Anxiety Relates to Spatial Abilities as a Function of Working Memory in Children
Authors: Ramirez Gerardo , Gunderson Elizabeth A. , Levine Susan C. , Beilock Sian L.
Published: January 2012

Spatial ability is a strong predictor of students' pursuit of higher education in science and mathematics. However, very little is known about the affective factors that influence individual differences in spatial ability, particularly at a young age. We examine the role of spatial anxiety in young children's performance on a mental rotation task. We show that even at a young age, children report experiencing feelings of nervousness at the prospect of engaging in spatial activities. Moreover, we show that these feelings are associated with reduced mental rotation ability among students with high but not low working memory (WM). Interestingly, this WM × spatial anxiety interaction was only found among girls. We discuss these patterns of results in terms of the problem-solving strategies that boys versus girls use in solving mental rotation problems.