bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconstructing the Avalonia palaeocontinent in the Cambrian: A 519 Ma caliche in South Wales and transcontinental middle Terreneuvian sandstones
Authors: LANDING ED , WESTROP STEPHEN R. , BOWRING SAMUEL A.
Published: May 2013

An Early Cambrian caliche on the St Non's Formation (emended) is the base of the Caerfai Bay Formation (unit-term changed) at Caerfai Bay, South Wales. Subaerial exposure and the caliche mean the two formations were not genetically related units. The St Non's is an older sand sheet (likely tidalitic, not delta-related) referred to Avalonian depositional sequence (ADS) 2, and the Caerfai Bay is a shallow mud basin unit refered to ADS 4A. The similar Random Formation (upper ADS 2) in North American Avalonia has a basal age ofc. 528 Ma and is unconformably overlain by red mudstones or sandstones in fault-bounded basins on the Avalonian inner platform. Coeval British sandstones (lower Hartshill, Wrekin, St Non's, Brand Hills?) are unconformably overlain by latest Terreneuvian (ADS 3) or Epoch 2 (ADS 4A) units. Dates of 519 Ma on Caerfai Bay ashes give an upper bracket on the late appearance of Avalonian trilobites and suggest an ADS 2–4A hiatus of several million years. Post-St Non's and post-Random basin reorganization led to abundant Caerfai Bay Formation volcanic ashes and sparse Brigus Formation ashes in Newfoundland. The broad extent of erosional sequence boundaries that bracket lithologically similar to identical units emphasize that ‘east’ and ‘west’ Avalonia formed one palaeocontinent. The inner platform in southern Britain was larger than the Midlands craton, a tectonically defined later Palaeozoic area unrelated to terminal Ediacaran – Early Palaeozoic depositional belts. The cool-water successions of Early Palaeozoic Avalonia were distant from coeval West Gondwanan carbonate platforms.
The efficacy of dynamic slow motion video endoscopy as a test of eustachian tube function
Authors: Augustine A M , Varghese L , Michael R C , Albert R R , Job A
Published: May 2013

Objective:

To assess the efficacy of dynamic slow motion video endoscopy as a test of eustachian tube function based on its correlation with the eustachian tube swallow test.

Method:

The eustachian tube swallow test and dynamic slow motion video endoscopy were performed on 100 clinically normal middle ears of adults undergoing rigid nasal endoscopy for various indications. The dynamic slow motion video endoscopy findings were interpreted by three observers who were blind to the results of the eustachian tube swallow test, and the findings of both techniques were compared.

Results:

There was a statistically significant correlation between the dynamic slow motion video endoscopy and eustachian tube swallow test results for some of the more lenient criteria. Five of the 100 eustachian tubes had a floppy medial cartilaginous lamina which appeared to contribute to the eustachian tube dysfunction.

Conclusion:

Dynamic slow motion video endoscopy appeared to over-diagnose eustachian tube dysfunction when used as a standalone test of eustachian tube function. However, when used in combination with other tests of eustachian tube function, it can provide valuable information regarding the structural and functional status of the pharyngeal end of the eustachian tube.
On the Sense and Reference of the Concept of Truth
Authors: Rattan Gurpreet
Published: May 2013

This paper analyzes the concept of truth in terms of an account of Fregean sense as cognitive value. The account highlights the importance of understanding-based knowledge of co-reference for the individuation of senses. Explicit truth attributions, like ‘that I smell the scent of violets is true’ involve an inter-level version of understanding-based knowledge of co-reference in the that-clause concepts of thoughts that they employ: one cannot understand the that-clause concept of the thought in the truth attribution without understanding the thought the that-clause concept is a concept of. This is not a redundancy that eliminates or deflates cognitive value, but an exploitation, by the concept of truth, of the inter-level version of understanding-based knowledge of co-reference in critical reflective thinking. The cognitive value of the concept of truth is to combine semantically with explicit ways of thinking of thoughts to make critical reflective thinking possible. This account of the cognitive value of the concept of truth assigns cognitive value not by construing the concept of truth as a way of thinking about some thing, but by articulating its broader cognitive role.
Heidegger as a Post-Darwinian Philosopher
Authors: Chamberlain Lesley
Published: May 2013

Heidegger responded to Darwin's displacement of the Created Universe by seeking value in a new materiality. His 1936 lecture The Origin of the Work of Art spelt out the need to get away from an Aristotelian concept of matter perpetuated by Aquinas and frame an approach more appropriate to a post-Darwinian age. The argument is not that Heidegger was a Darwinist or an evolutionist. It is that he responded to what Dewey called ‘the greatest dissolvent in contemporary thought of old questions’.
To all our relations: evidence of Sámi involvement in the creation of rock paintings in Finland
Authors: Joy Francis
Published: May 2013

Research undertaken between 1960 to 1990 into what was once a rock painting tradition in Finland, lacked a clear understanding of parallels between the painted figures found at rock painting locations in the southern and central areas of the country, and the motifs painted on the heads of Sámi shaman divination drums from Lapland. However, due to the discovery and analysis of the content of more rock painting sites in Finland from 1990 up to the present, a more comprehensive framework has emerged in which scholars from across different academic disciplines have discovered many more similar characteristics linking the rock paintings and drum symbolism. These recent findings point towards the survival of a nature based sacrificial religion from the Stone Age era in Finland. The source of this was shamanistic in its essence, and is seen portrayed on rock and boulder formations by hunters similarly to how figures were illustrated on drum heads by the Sámi shamans from the nomadic era of the 17th and 18th centuries in Lapland. This more recent recognition strengthens the argument for Sámi involvement in the creation of rock paintings in Finland.
Breeding biology and conservation of the Marsh SeedeaterSporophila palustris
Authors: VIZENTIN-BUGONI JEFERSON , ARETA JUAN I. , DI GIACOMO ALEJANDRO G. , DI GIACOMO ADRIAN S. , JACOBS FERNANDO , AFONSO COIMBRA MARCO A. , DIAS RAFAEL A.
Published: May 2013

The Marsh SeedeaterSporophila palustrisis one of the most endangered and least known of thecapuchinoseedeaters. Breeding populations are patchy, occurring in north-east Argentina, southern Brazil, and Uruguay. We present data on the breeding biology of the species, and describe nests and eggs, behaviour (including courtship, nesting, incubation and parental care), breeding sites and food items. Marsh Seedeaters breed in well-preserved grasslands with wet soils and tall vegetation. In general, these habitats are used for extensive livestock ranching. Main threats are overgrazing, widespread use of fire, conversion of grasslands to pastures of exotic grasses and rice fields, afforestation, and illegal trapping. Most breeding sites are located in Important Bird Areas, but only one in Brazil and one in Argentina are protected. We propose a series of actions to promote the conservation of Marsh Seedeaters and other endangered birds that coexist in grassland habitats.
Susceptibility of Limestone Petrographic Features to Salt Weathering: A Scanning Electron Microscopy Study
Authors: Alves Carlos , Figueiredo Carlos , Maurício António , Aires-Barros Luís
Published: May 2013

Salt weathering is a major erosive process affecting porous materials in buildings. There have been attempts to relate erosive mass loss to physical characteristics of materials, but in the case of natural stone it is necessary to consider the effect of petrographic features that are a source of heterogeneity. In this paper, we use scanning electron microscopy before and after salt weathering tests in cubic specimens of three limestone types (two grainstones and a travertine) in an attempt to built conceptual models that relate petrographic features and salt weathering susceptibility (represented by mass loss). In the grainstones, the most relevant feature in controlling salt weathering processes is the interface between micrite aggregates and sparry cement that constitute weakness surfaces and barriers to fluid migration. Given the small size of the heterogeneities in relation to the test sample dimension and their spatial distribution, the macroscopic erosive patterns are globally homogeneously distributed, affecting edges and corners. In the travertine specimens, there are macroheterogeneities related to the presence of detritic-rich portions that cause heterogeneous erosive patterns in the specimens. Petrological modeling helps to understand results of salt weathering tests, supporting field studies for natural stone selection.
microRNAs as novel antidepressant targets: converging effects of ketamine and electroconvulsive shock therapy in the rat hippocampus
Authors: O'Connor Richard M. , Grenham Susan , Dinan Timothy G. , Cryan John F.
Published: May 2013

Early-life stress is a main contributory factor to the onset of depression. Treatments remain inadequate and as such, a large unmet medical need for novel therapeutics remains. Impeding advancement is the poor understanding of the molecular pathology. microRNAs (miRNAs) are novel regulators of gene expression. A paucity of information regarding their role in depressive pathology and antidepressant action remains. This study investigated changes to hippocampal miRNA levels induced via early-life stress in Sprague–Dawley rats and whether antidepressant treatments could reverse these changes. Investigated were the selective serotonin reuptake inhibitor fluoxetine, the rapid acting N-methyl-d-aspartate receptor antagonist ketamine and electroconvulsive shock therapy (ECT). Microarray analysis revealed early-life stress affected the expression of multiple hippocampal miRNAs. Antidepressant treatments reversed some of these effects including a stress-induced change to miR-451. Ketamine and ECT possessed the highest number of common targets suggesting convergence on common pathways. Interestingly all three treatments possessed miR-598-5p as a common target. This demonstrates that changes to hippocampal miRNA expression may represent an important component of stress-induced pathology and antidepressant action may reverse these.
Antimicrobial resistance and prudent drug use forStreptococcus suis
Authors: Varela Norma P. , Gadbois Pierre , Thibault Claude , Gottschalk Marcelo , Dick Paul , Wilson Jeff
Published: May 2013

This paper reviews information on antimicrobial resistance patterns and prudent use of antimicrobials to reduce the impact and spread of resistantStreptococcus suisstrains.S. suisis an important pathogen in swine, which can cause significant economic loss. Prudent use of antimicrobials forS. suisis essential to preserve the therapeutic efficacy of broad-spectrum antimicrobials and to minimize selection of resistantS. suisstrains. Resistance ofS. suisto antimicrobials commonly used in swine, including lincosamides, macrolides, sulphonamides, and tetracycline, has been documented worldwide, with resistance in up to 85% of strains. Among antimicrobials examined, resistance ofS. suishas been demonstrated to be relatively low for penicillin (0–27%), ampicillin (0.6–23%), and ceftiofur (0–23%). For penicillin, this result may be due in part to the unique mechanism by which resistance is acquired through modifications in the structure of penicillin-binding proteins. Recommendations to controlS. suisinfection include focused and careful choice and appropriate use of antimicrobials, together with preventive measures intended to improve swine management.
Discrimination against people with severe mental illness and their access to social capital: findings from the Viewpoint survey
Authors: Webber M. , Corker E. , Hamilton S. , Weeks C. , Pinfold V. , Rose D. , Thornicroft G. , Henderson C.
Published: May 2013

Aims.

Discrimination against people with severe mental illness is an international problem. It is associated with reduced social contact and hinders recovery. This paper aims to evaluate if experienced or anticipated discrimination is associated with social capital, a known correlate of mental health.

Methods.

Data from the annual viewpoint cross-sectional survey of people with severe mental illness (n = 1016) were analysed. Exploratory univariate analysis was used to identify correlates of social capital in the sample, which were then evaluated in linear regression models. Additional hypotheses were tested usingttests.

Results.

Experienced discrimination made a modest contribution to the explained variance of social capital. Experienced discrimination from friends and immediate family was associated with reduced access to social capital from these groups, but this was not found for wider family, neighbours or mental health staff. Experience of discrimination in finding or keeping a job was also associated with reduced access to social capital.

Conclusions.

Further longitudinal research is needed to determine how resources within people's networks can help to build resilience, which reduces the harmful effect of discrimination on mental health.
Crystal structures of human cholinesterases in complex with huprine W and tacrine: elements of specificity for anti-Alzheimer's drugs targeting acetyl- and butyryl-cholinesterase
Authors: Nachon Florian , Carletti Eugénie , Ronco Cyril , Trovaslet Marie , Nicolet Yvain , Jean Ludovic , Renard Pierre-Yves
Published: May 2013

The multifunctional nature of Alzheimer's disease calls for MTDLs (multitarget-directed ligands) to act on different components of the pathology, like the cholinergic dysfunction and amyloid aggregation. Such MTDLs are usually on the basis of cholinesterase inhibitors (e.g. tacrine or huprine) coupled with another active molecule aimed at a different target. To aid in the design of these MTDLs, we report the crystal structures of hAChE (human acetylcholinesterase) in complex with FAS-2 (fasciculin 2) and a hydroxylated derivative of huprine (huprine W), and of hBChE (human butyrylcholinesterase) in complex with tacrine. Huprine W in hAChE and tacrine in hBChE reside in strikingly similar positions highlighting the conservation of key interactions, namely, π-π/cation-π interactions with Trp86 (Trp82), and hydrogen bonding with the main chain carbonyl of the catalytic histidine residue. Huprine W forms additional interactions with hAChE, which explains its superior affinity: the isoquinoline moiety is associated with a group of aromatic residues (Tyr337, Phe338 and Phe295 not present in hBChE) in addition to Trp86; the hydroxyl group is hydrogen bonded to both the catalytic serine residue and residues in the oxyanion hole; and the chlorine substituent is nested in a hydrophobic pocket interacting strongly with Trp439. There is no pocket in hBChE that is able to accommodate the chlorine substituent.
Human parainfluenza type 3 virus impairs the efficacy of glucocorticoids to limit allergy-induced pulmonary inflammation in guinea-pigs
Authors: Ford William R. , Blair Alan E. , Evans Rhys L. , John Elinor , Bugert Joachim J. , Broadley Kenneth J. , Kidd Emma J.
Published: May 2013

Viral exacerbations of allergen-induced pulmonary inflammation in pre-clinical models reportedly reduce the efficacy of glucocorticoids to limit pulmonary inflammation and airways hyper-responsiveness to inhaled spasmogens. However, exacerbations of airway obstruction induced by allergen challenge have not yet been studied. hPIV-3 (human parainfluenza type 3 virus) inoculation of guinea-pigs increased inflammatory cell counts in BAL (bronchoalveolar lavage) fluid and caused hyper-responsiveness to inhaled histamine. Both responses were abolished by treatment with either dexamethasone (20 mg/kg of body weight, subcutaneous, once a day) or fluticasone propionate (a 0.5 mg/ml solution aerosolized and inhaled over 15 min, twice a day). In ovalbumin-sensitized guinea-pigs, allergen (ovalbumin) challenge caused two phases of airway obstruction [measured as changes in sGaw (specific airways conductance) using whole body plethysmography]: an immediate phase lasting between 4 and 6 h and a late phase at about 7 h. The late phase, airway hyper-responsiveness to histamine and inflammatory cell counts in BAL were all significantly reduced by either glucocorticoid. Inoculation of guinea-pigs sensitized to ovalbumin with hPIV-3 transformed the allergen-induced airway obstruction from two transient phases into a single sustained response lasting up to 12 h. This exacerbated airway obstruction and airway hyper-responsiveness to histamine were unaffected by treatment with either glucocorticoid whereas inflammatory cell counts in BAL were only partially inhibited. Virus- or allergen-induced pulmonary inflammation, individually, are glucocorticoid-sensitive, but in combination generate a phenotype where glucocorticoid efficacy is impaired. This suggests that during respiratory virus infection, glucocorticoids might be less effective in limiting pulmonary inflammation associated with asthma.
Morphological Variation in the Adult Hard Palate and Posterior Pharyngeal Wall
Authors: Lammert Adam , Proctor Michael , Narayanan Shrikanth
Published: May 2013

Purpose

Adult human vocal tracts display considerable morphological variation across individuals, but the nature and extent of this variation has not been extensively studied for many vocal tract structures. There exists a need to analyze morphological variation and, even more basically, to develop a methodology for morphological analysis of the vocal tract. Such analysis will facilitate fundamental characterization of the speech production system, with broad implications from modeling to explaining interspeaker variability.

Method

A data-driven methodology to automatically analyze the extent and variety of morphological variation is proposed and applied to a diverse subject pool of 36 adults. Analysis is focused on two key aspects of vocal tract structure: the midsagittal shape of the hard palate and the posterior pharyngeal wall.

Result

Palatal morphology varies widely in its degree of concavity but also in anteriority and sharpness. Pharyngeal wall morphology, by contrast, varies mostly in terms of concavity alone. The distribution of morphological characteristics is complex, and analysis suggests that certain variations may be categorical in nature.

Conclusion

Major modes of morphological variation are identified, including their relative magnitude, distribution, and categorical nature. Implications of these findings for speech articulation strategies and speech acoustics are discussed.
Optimised design of a transformer and an electronic circuit for IGBT drivers signal impulse transmission function based on a virtual prototyping tool
Authors: Lefranc Pierre , Jannot Xavier , Dessante Philippe
Published: May 2013

In this study, a signal impulse transmission function is investigated which provides high insulation voltage capabilities for IGBT drivers devices. This electrical insulation is achieved with a printed circuit board (PCB) and classical copper windings. Two ferrite cores are added to improve the magnetic coupling effect and thus decrease the impulse current maximum value in the primary side. The electronic circuit involves a series resonant topology in the primary side and a parallel one in the secondary side. The classical electronic components lead potentially to cost‐effective solutions. However, so as to optimise the proposed system, a design methodology based on virtual prototyping tools is carried out. The simulation results presented on a Pareto front are analysed with the help of propagation delay and average power consumption. Moreover, measurement results with a 1.6 mm PCB are compared with simulation ones. Finally, the proposed solution and the methodology design are clearly accurate and suitable for power electronic designers and especially for IGBT driver devices designers.
Single‐stage pickup with a bidirectional zero‐voltage turn‐on switch
Authors: Juan Yu Lin , He Yi Lin
Published: May 2013

In this study, a single‐stage pickup with zero‐voltage turn‐on to reduce the switching loss is proposed for parallel resonant compensated contactless power transmission systems (CPTS). A bidirectional switch composed of two back‐to‐back connected active switches is integrated to regulate the output voltage. The relationship between the output voltage and the duty ratio of the bidirectional switch is derived and verified. To evaluate the validity and performance of the proposed pickup circuit, a 500 W prototype CPTS is constructed. The experimental results show that the power conversion efficiency of the proposed pickup is about 95%. Moreover, compared with common two‐stage pickup, the number of required passive components in the proposed topology is reduced. The resulted volume of proposed pickup is also reduced which is more suitable for space‐limited applications.
μ‐based robust controller design of LCLC resonant inverter for high‐frequency power distribution system
Authors: Liu Junfeng , Cheng Ka Wai Eric
Published: May 2013

High‐frequency AC (HFAC) power distribution system (PDS) has recently received more and more attentions and has a broad application from electric vehicle to Micro‐grid. The resonant inverter is commonly used to provide the fixed frequency output for point of load (POL). However, the control and implementation of high‐frequency resonant inverter is complicated to provide good steady and dynamic performance, because of the worse operating circumstance from parameter uncertainties, inaccuracy model, as well as load and line perturbations. Although H∞ robust controller has already been widely examined, the feedback voltage controller designed by μ‐synthesis accurately provides more effective analysis and design framework to achieve robust stability and robust tracking performance. In this study, the perturbations and control target are analysed to construct the unstructured and structured uncertainties for resonant inverter. A new μ‐based controller is designed by μ‐synthesis to testify its tracking performance under the given perturbations, and the robust performance of proposed controller is theoretically evaluated by μ‐analysis. The prototype of simulation and experiment are implemented with a rated output power of 120 W and operation frequency of 25 kHz. The results prove its superiority over traditional PI and H∞ controllers for HFAC power source constructed by LCLC resonant inverter.
Quenching of plasmons modes in air-exposed graphene-Ru contacts for plasmonic devices
Authors: Politano Antonio , Chiarello Gennaro
Published: May 2013

High-resolution electron energy loss spectroscopy has been used to investigate the effects of air exposure on the plasmon modes of a graphene-Ru contact. We found that graphene plasmons are quenched after the exposure of the sample to ambient air humidity. This finding represents a severe hurdle for THz plasmonic graphene-based devices, in which graphene-metal contacts are inevitable components.
Feedback control of instabilities in the two-dimensional Blasius boundary layer: The role of sensors and actuators
Authors: Belson Brandt A. , Semeraro Onofrio , Rowley Clarence W. , Henningson Dan S.
Published: May 2013

We analyze the effects of different types and positions of actuators and sensors on controllers’ performance and robustness in the linearized 2D Blasius boundary layer. The investigation is carried out using direct numerical simulations (DNS). To facilitate controller design, we find reduced-order models from the DNS data using a system identification procedure called the Eigensystem Realization Algorithm. Due to the highly convective nature of the boundary layer and corresponding time delays, the relative position of the actuator and sensor has a strong influence on the closed-loop dynamics. We address this issue by considering two different configurations. When the sensor is upstream of the actuator, corresponding to disturbance-feedforward control, good performance is observed, as in previous work. However, feedforward control can be degraded by additional disturbances or uncertainties in the plant model, and we demonstrate this. We then examine feedback controllers in which the sensor is a short distance downstream of the actuator. Sensors farther downstream of the actuator cause inherent time delays that limit achievable performance. The performance of the resulting feedback controllers depends strongly on the form of actuation introduced, the quantities sensed, and the observability of the structures deformed by the controller's action. These aspects are addressed by varying the spatial distribution of actuator and sensor. We find an actuator-sensor pair that is well-suited for feedback control, and demonstrate that it has good performance and robustness, even in the presence of unmodeled disturbances.
A self-adjusting flow dependent formulation for the classical Smagorinsky model coefficient
Authors: Ghorbaniasl G. , Agnihotri V. , Lacor C.
Published: May 2013

In this paper, we propose an efficient formula for estimating the model coefficient of a Smagorinsky model based subgrid scale eddy viscosity. The method allows vanishing eddy viscosity through a vanishing model coefficient in regions where the eddy viscosity should be zero. The advantage of this method is that the coefficient of the subgrid scale model is a function of the flow solution, including the translational and the rotational velocity field contributions. Furthermore, the value of model coefficient is optimized without using the dynamic procedure thereby saving significantly on computational cost. In addition, the method guarantees the model coefficient to be always positive with low fluctuation in space and time. For validation purposes, three test cases are chosen: (i) a fully developed channel flow at ${\mathop{\rm Re}\nolimits} _\tau = 180,\,395$ Re τ=180,395, (ii) a fully developed flow through a rectangular duct of square cross section at ${\mathop{\rm Re}\nolimits} _\tau = 300$ Re τ=300, and (iii) a smooth subcritical flow past a stationary circular cylinder, at a Reynolds number of ${\mathop{\rm Re}\nolimits} = 3900$ Re =3900, where the wake is fully turbulent but the cylinder boundary layers remain laminar. A main outcome is the good behavior of the proposed model as compared to reference data. We have also applied the proposed method to a CT-based simplified human upper airway model, where the flow is transient.
Photoactive self-assembled monolayers for optically switchable organic thin-film transistors
Authors: Salinas Michael , Halik Marcus
Published: May 2013

We investigate the photoconductive and photovoltaic effects in organic thin-film transistors with thin hybrid dielectrics composed of aluminum oxide and self-assembled monolayers (SAMs). By using SAM molecules with an electro-optical functionality tuning of the photoinduced charge transfer at the interface of semiconductor and SAM upon illumination with laser light can be achieved. Control of the threshold voltage by the SAM composition enables the optical operation of the transistors without applying a gate voltage and affects the dynamics of photoinduced charge transfer.
Supersymmetry algebra cohomology. IV. Primitive elements in all dimensions from D = 4 to D = 11
Authors: Brandt Friedemann
Published: May 2013

The primitive elements of the supersymmetry algebra cohomology as defined in previous work are derived for standard supersymmetry algebras in dimensions D = 5, …, 11 for all signatures of the related Clifford algebras of gamma matrices and all numbers of supersymmetries. The results are presented in a uniform notation along with results of previous work for D = 4, and derived by means of dimensional extension from D = 4 up to D = 11.
Temperature dependence of the structural, magnetic, and magnetostrictive properties of zinc-substituted cobalt ferrite
Authors: Nlebedim I. C. , Vinitha M. , Praveen P. J. , Das D. , Jiles D. C.
Published: May 2013

This study presents the effects of substitution of Zn2+ for Co2+ at low concentrations and the effects of temperature variations on the structural, magnetic, and magnetostrictive properties of cobalt ferrite. Although the Zn-substituted cobalt ferrite samples, Co1−xZnxFe2O4 (x = 0.02, 0.04, 0.06, 0.09, and 0.17) did not show observable changes in crystal structure, the magnetic and magnetostrictive properties were strongly affected. The variation in magnetic susceptibility with composition can be related to the variations in magnetization, coercive field and magnetocrystalline anisotropy. The changes in coercive field were found to be primarily due to the variations in the magnetocrystalline anisotropy. The effect of magnetocrystalline anisotropy on magnetization was stronger at lower cation concentration than at higher concentrations. The decrease in magnetization around 150 K is attributed to the high magnetocrystalline anisotropy at low temperatures which prevented the maximum applied field of 4 MA/m from causing the saturation of magnetization in the samples. Because the magnetocrystalline anisotropy was determined with the magnetization data using the Law of Approach to saturation magnetization, the reliability of the result was found to decrease with decrease in temperature. Peak-to-peak magnetostriction amplitude and the strain sensitivity decreased with increase in Zn substitution.
Apparatus for measuring Seebeck coefficient and electrical resistivity of small dimension samples using infrared microscope as temperature sensor
Authors: Jaafar W. M. N. Wan , Snyder J. E. , Min Gao
Published: May 2013

An apparatus for measuring the Seebeck coefficient (α) and electrical resistivity (ρ) was designed to operate under an infrared microscope. A unique feature of this apparatus is its capability of measuring α and ρ of small-dimension (sub-millimeter) samples without the need for microfabrication. An essential part of this apparatus is a four-probe assembly that has one heated probe, which combines the hot probe technique with the Van der Pauw method for “simultaneous” measurements of the Seebeck coefficient and electrical resistivity. The repeatability of the apparatus was investigated over a temperature range of 40 °C–100 °C using a nickel plate as a standard reference. The results show that the apparatus has an uncertainty of ±4.9% for Seebeck coefficient and ±5.0% for electrical resistivity. The standard deviation of the apparatus against a nickel reference sample is −2.43 μVK−1 (−12.5%) for the Seebeck coefficient and −0.4 μΩ cm (−4.6%) for the electrical resistivity, respectively.
Germanium-tin n-channel tunneling field-effect transistor: Device physics and simulation study
Authors: Yang Yue , Lu Low Kain , Wang Wei , Guo Pengfei , Wang Lanxiang , Han Genquan , Yeo Yee-Chia
Published: May 2013

We investigate germanium-tin alloy (Ge1−xSnx) as a material for the design of tunneling field-effect transistor (TFET) operating at low supply voltages. Compared with Ge, Ge1−xSnx has a smaller band-gap. The reported band-gap of Ge0.89Sn0.11 is 0.477 eV, ∼28% smaller than that of Ge. More importantly, Ge1−xSnx becomes a direct band-gap material when Sn composition x is higher than 0.11. By employing Ge1−xSnx in TFET, direct band-to-band tunneling (BTBT) is realized. Direct BTBT generally has higher tunneling probability than indirect BTBT. The drive current of TFET is boosted due to the direct BTBT and the reduced band-gap of Ge1−xSnx. Device simulations show that the drive current and subthreshold swing S characteristics of Ge1−xSnx TFETs with x ranging from 0 to 0.2 are improved by increasing the Sn composition x. For Ge0.8Sn0.2 TFET, sub-60 mV/decade S is achieved at a high current level of ∼8 μA/μm. For x higher than 0.11, Ge1−xSnx TFETs show higher on-state current ION compared to Ge TFET at a supply voltage of 0.3 V. Ge1−xSnx alloy is a potential candidate for high performance TFET composed of group IV materials.
Capacitive readout and gating of superconducting single photon detectors
Authors: Azzouz Hatim , Heeres Reinier W. , Dorenbos Sander N. , Schouten Raymond N. , Zwiller Valery
Published: May 2013

We propose and develop a readout scheme for superconducting single-photon detectors based on an integrated circuit, relaxing the need for large bandwidth amplification and resulting in voltage steps proportional to the number of detected photons. We also demonstrate time gating, to filter scattered light in time and reduce dark counts. This could lead to a higher signal-to-noise ratio. The gate pulse is generated on the detection of a photon created by a spontaneous parametric down-conversion source, heralding the presence of a second photon. These two schemes could find applications within advanced multi-array imaging detection systems.
Electron Linac design to drive bright Compton back-scattering gamma-ray sources
Authors: Bacci A. , Alesini D. , Antici P. , Bellaveglia M. , Boni R. , Chiadroni E. , Cianchi A. , Curatolo C. , Di Pirro G. , Esposito A. , Ferrario M. , Gallo A. , Gatti G. , Ghigo A. , Migliorati M. , Mostacci A. , Palumbo L. , Petrillo V. , Pompili R. , Ronsivalle C. , Rossi A. R. , Serafini L. , Spataro B. , Tomassini P. , Vaccarezza C.
Published: May 2013

The technological development in the field of high brightness linear accelerators and high energy/high quality lasers enables today designing high brilliance Compton-X and Gamma-photon beams suitable for a wide range of applications in the innovative field of nuclear photonics. The challenging requirements of this kind of source comprise: tunable energy (1–20 MeV), very narrow bandwidth (0.3%), and high spectral density (104 photons/s/eV). We present here a study focused on the design and the optimization of an electron Linac aimed to meet the source specifications of the European Extreme Light Infrastructure—Nuclear Physics project, currently funded and seeking for an innovative machine design in order to outperform state-of-the-art facilities. We show that the phase space density of the electron beam, at the collision point against the laser pulse, is the main quality factor characterizing the Linac.
Low-energy electron collisions with thiophene
Authors: da Costa R. F. , Varella M. T. do N. , Lima M. A. P. , Bettega M. H. F.
Published: May 2013

We report on elastic integral, momentum transfer, and differential cross sections for collisions of low-energy electrons with thiophene molecules. The scattering calculations presented here used the Schwinger multichannel method and were carried out in the static-exchange and static-exchange plus polarization approximations for energies ranging from 0.5 eV to 6 eV. We found shape resonances related to the formation of two long-lived π* anion states. These resonant structures are centered at the energies of 1.00 eV (2.85 eV) and 2.82 eV (5.00 eV) in the static-exchange plus polarization (static-exchange) approximation and belong to the B1 and A2 symmetries of the C2v point group, respectively. Our results also suggest the existence of a σ* shape resonance in the B2 symmetry with a strong d-wave character, located at around 2.78 eV (5.50 eV) as obtained in the static-exchange plus polarization (static-exchange) calculation. It is worth to mention that the results obtained at the static-exchange plus polarization level of approximation for the two π* resonances are in good agreement with the electron transmission spectroscopy results of 1.15 eV and 2.63 eV measured by Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004)10.1021/jp048759a]. The existence of the σ* shape resonance is in agreement with the observations of Dezarnaud-Dandiney et al. [J. Phys. B 31, L497 (1998)10.1088/0953-4075/31/11/004] based on the electron transmission spectra of dimethyl(poly)sulphides. A comparison among the resonances of thiophene with those of pyrrole and furan is also performed and, altogether, the resonance spectra obtained for these molecules point out that electron attachment to π* molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds.
Conversion mechanism of conductivity of phosphorus-doped ZnO films induced by post-annealing
Authors: Li Jichao , Yao Bin , Li Yongfeng , Ding Zhanhui , Xu Ying , Zhang Ligong , Zhao Haifeng , Shen Dezhen
Published: May 2013

The effects of post-annealing on conductivity of phosphorus-doped ZnO (PZO) films grown at 500 °C by radio frequency magnetron sputtering are investigated in a temperature ranging from 600 °C to 900 °C. The as-grown PZO exhibits n-type conductivity with an electron concentration of 1.19 × 1020 cm−3, and keeps n-type conductivity as annealed at 600 °C-700 °C but electron concentration decreases with increasing temperature. However, it converts to p-type conductivity as annealed at 800 °C. Further increasing temperature, it still shows p-type conductivity but the hole concentration decreases. It is found that the P occupies mainly Zn site (PZn) in the as-grown PZO, which accounts for good n-type conductivity of the as-grown PZO. The amount of the PZn decreases with increasing temperature, while the amount of Zn vacancy (VZn) increases from 600 °C to 800 °C but decreases greatly at 900 °C, resulting in that the amount of PZn-2VZn complex increases with increasing temperature up to 800 °C but decreases above 800 °C. It is suggested that the PZn-2VZn complex acceptor is responsible for p-type conductivity, and that the conversion of conductivity is due to the change of the amount of the PZn and PZn-2VZn with annealing temperature.
The striped phases of ethylthiolate monolayers on the Au(111) surface: A scanning tunneling microscopy study
Authors: Li Fangsen , Tang Lin , Voznyy Oleksandr , Gao Jianzhi , Guo Quanmin
Published: May 2013

Striped phases of ethylthiolate monolayers, corresponding to surface coverage in between 0.2 ML and 0.27 ML, were studied using high-resolution scanning tunneling microscopy. Striped phases consist of rows of Au-adatom-diethythiolate (AAD) aligned along the $[11\bar 2]$[112¯] direction. In the perpendicular $[1\bar 10]$[11¯0] direction, the AAD rows adjust their spacing according to the surface coverage. A (5√3 × √3)-R30° striped phase with 0.27 ML thiolate and a (6√3 × √3)-R30° striped phase with 0.23 ML thiolate, both with long-range order, are found. A localized (5 × √3)-rect. phase is also found as a minority phase embedded in the 5√3 × √3)-R30° phase. This (5 × √3)-rect. phase can be constructed using di-Au-adatom-tri-thiolate species.
High-resolution chemical imaging of gold nanoparticles using hard x-ray ptychography
Authors: Hoppe R. , Reinhardt J. , Hofmann G. , Patommel J. , Grunwaldt J.-D. , Damsgaard C. D. , Wellenreuther G. , Falkenberg G. , Schroer C. G.
Published: May 2013

We combine resonant scattering with (ptychographic) scanning coherent diffraction microscopy to determine the chemical state of gold nanoparticles with high spatial resolution. Ptychographic images of the sample are recorded for a series of energies around the gold L3 absorption edge. From these data, chemical information in the form of absorption and resonant scattering spectra is reconstructed at each location in the sample. For gold nanoparticles of about 100 nm diameter, a spatial resolution of about 20–30 nm is obtained. In the future, this microscopy approach will open the way to operando studies of heterogeneous catalysts on the nanometer scale.
Second harmonic effect on geodesic modes in tokamak plasmas
Authors: Elfimov A. G. , Smolyakov A. I. , Melnikov A. V. , Galvão R. M. O.
Published: May 2013

Results of a kinetic treatment of Geodesic Acoustic Modes (GAMs) that fully takes into account ion parallel dynamics, including the magnetic field component, are presented. The finite-orbit-width (FOW) parameter is considered in the calculation of the second harmonic effect on GAMs. For larger values of the FOW parameter, it is shown that dispersive effects related to the m = 2 harmonics is the cause of the mode frequency splitting and the modes appear due to the interaction with the ion sound mode. Furthermore, the modes may have enhanced damping rates due to second harmonic Landau damping.
Fabrication and scanning tunneling microscopy characterization of suspended monolayer graphene on periodic Si nanopillars
Authors: Zhao Xin , Zhai Xiaofang , Zhao Aidi , Wang Bing , Hou J. G.
Published: May 2013

We present the fabrication and scanning tunneling microscopy (STM) characterization of suspended monolayer graphene (SMG) on periodic Si nanostructure. Monolayer graphene (MG) was grown on Cu foils by chemical vapor deposition (CVD) and transferred onto a Si substrate with etched array of periodic nanopillars, obtaining partly suspended MG. Low-temperature STM characterization was performed on the suspension area of the MG with atomic resolution images obtained. The scanning tunneling spectroscopy of SMG shows a nonlinear behavior near the Fermi level (EF), which is attributed to the Dirac cone reshaped by electron-electron interaction.
Thermoluminescence properties of Tl2Ga2S3Se layered single crystals
Authors: Delice S. , Isik M. , Bulur E. , Gasanly N. M.
Published: May 2013

The trap center(s) in Tl2Ga2S3Se single crystals has been investigated from thermoluminescence (TL) measurements in the temperature range of 10–300 K. Curve fitting, initial rise, and peak shape methods were applied to observed TL glow curve to evaluate the activation energy, capture cross section, and attempt-to-escape frequency of the trap center. One trapping center has been revealed with activation energy of 16 meV. Moreover, the characteristics of trap distribution have been studied using an experimental technique based on different illumination temperature. An increase of activation energy from 16 to 58 meV was revealed for the applied illumination temperature range of 10–25 K.
Nanorods of Co/Pd multilayers fabricated by glancing angle deposition for advanced media
Authors: Su Hao , Natarajarathinam Anusha , Gupta Subhadra
Published: May 2013

Perpendicular anisotropy magnetic nanorods composed of Co/Pd multilayers have been successfully fabricated by glancing angle deposition (GLAD) in a planetary sputtering system. Co and Pd layer thickness, ratio, and bilayer number were optimized for both normal and GLAD depositions. Scanning electron micrographs estimated the nanorods to be about 12 nm in diameter. M-H loops showed that the coercivity for the GLAD nanorods increased from 1.3 kOe for the normally deposited continuous films to 2.9 kOe for the GLAD nanorod array, a 123% increase.
Core-shell magnetic exchange model for Co3O4 nanowires
Authors: Chen Lan , Yang Yurong , Meng Xiangkang
Published: May 2013

First-principles calculations are performed to investigate the magnetic properties of Co3O4 nanowires. A microscopic core-shell magnetic exchange model, including intra-core, intra-plane, core-shell (core-plane), and plane-plane (shell-shell) interactions, is proposed. The sign of magnetic exchange constants (ferromagnetic or antiferromagnetic coupling) for the four interactions is computed and discussed with respect to nanowire diameter. Competition between plane-plane and core-plane interactions is found in nanowire larger than 15.4 Å. The four magnetic interactions and their competition in the nanostructures give an explanation of exchange bias effect, two order temperatures, spin-glass behavior, and magnetic fingerprints found in core-shell structures experimentally.
Interfacial electronic structure of trimethyl-aluminum and water on an In0.20Ga0.80As(001)-4 × 2 surface: A high-resolution core-level photoemission study
Authors: Pi T. W. , Lin H. Y. , Chiang T. H. , Liu Y. T. , Wertheim G. K. , Kwo J. , Hong M.
Published: May 2013

In atomic-layer deposition (ALD), organoaluminum as trimethyl-aluminum (TMA) on a freshly molecular beam epitaxy grown In0.20Ga0.80As(001)-4 × 2 surface has three forms: Al bonding with 1, 2, and 3 methyl groups. The ALD method of using one pulse (0.1 s) of TMA plus one pulse (0.1 s) of water was ineffective in passivating the surface, as demonstrated by the increased intensity of the reacted surface components with high numbers of pulses. The intact TMA was physisorbed on the trough In atoms, while the methyl-deficient precursors are either bridged with two As atoms or on the row-edge As atoms. After the water pulse on the TMA-covered surface, a bond in the bridged As atoms was scissored off to produce the As-Al-CH3 and As-OH, and the physisorbed TMA was unaffected. TMA removed some row In atoms, which allowed the In and Ga atoms in the second layer to form OH bonds after the water exposure. The appearance of the As-OH bonds may cause interfacial defect density (Dit) a peak at the midgap.
Exchange-spring like magnetic behavior of the tetragonal Heusler compound Mn2FeGa as a candidate for spin-transfer torque
Authors: Gasi Teuta , Nayak Ajaya K. , Winterlik Jürgen , Ksenofontov Vadim , Adler Peter , Nicklas Michael , Felser Claudia
Published: May 2013

We report structural, magnetic, and Mössbauer studies of the Heusler compound Mn2FeGa. Theoretical calculations predict that a tetragonal phase in Mn2FeGa could be an interesting candidate for spin torque transfer applications due to the presence of perpendicular magnetic anisotropy. Experimentally, we found that Mn2FeGa crystallizes in a tetragonal structure after annealing at low temperatures (≤400 °C), whereas, it becomes pseudocubic for higher annealing temperatures. The sample annealed at 400 °C shows a high Curie temperature of 650 K and a hard-magnetic behavior. We observed a nonsaturating and exchange-spring type of hysteresis loops, which indicates that the sample contains two different magnetic states. The Mössbauer measurements clearly support the structural and magnetic data. All these properties make the material a potential candidate for spintronic devices, especially in thin films with perpendicular magnetic anisotropy.
All-optical measurement of vertical charge carrier transport in mid-wave infrared InAs/GaSb type-II superlattices
Authors: Olson B. V. , Murray L. M. , Prineas J. P. , Flatté M. E. , Olesberg J. T. , Boggess T. F.
Published: May 2013

Time-resolved differential transmission measurements were used to investigate vertical charge carrier transport in mid-wave infrared InAs/GaSb type-II superlattices (T2SLs). By optically generating excess carriers near one end of the mid-wave T2SL and measuring the transit time to a thin, lower-bandgap T2SL at the other end, the time-of-flight of vertically diffusing carriers was measured. Through investigation of both unintentionally doped and p-type T2SLs, the vertical hole and electron diffusion coefficients were measured to be 0.04 ± 0.03 cm2/s and 4.7 ± 0.5 cm2/s, corresponding to vertical mobilities of 6 ± 5 cm2/Vs and 700 ± 80 cm2/Vs, respectively, at a temperature of 77 K.
Diagnosis of femtosecond plasma filament by channeling microwaves along the filament
Authors: Alshershby Mostafa , Ren Yu , Qin Jiang , Hao Zuoqiang , Lin Jingquan
Published: May 2013

We introduce a simple, fast, and non-intrusive experimental method to obtain the basic parameters of femtosecond laser-generated plasma filament. The method is based on the channeling of microwaves along both a plasma filament and a well-defined conducting wire. By comparing the detected microwaves that propagate along the plasma filament and a copper wire with known conductivity and spatial dimension, the basic parameters of the plasma filament can be easily obtained. As a result of the possibility of channeling microwave radiation along the plasma filament, we were then able to obtain the plasma density distribution along the filament length.