bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for biological activity in mineralization of secondary sulphate deposits in a basaltic environment: implications for the search for life in the Martian subsurface
Authors: Richardson C. Doc , Hinman Nancy W. , Scott Jill R.
Published: July 2013

Evidence of microbial activity associated with mineralization of secondary Na-sulphate minerals (thenardite, mirabilite) in the basaltic subsurface of Craters of the Moon National Monument (COM), Idaho were examined by scanning electron microscopy, X-ray diffraction, laser desorption Fourier transform ion cyclotron resonance mass spectrometry (LD-FTICR-MS), Fourier transform infrared spectroscopy (FTIR) and isotope ratio mass spectrometry. Peaks suggestive of bio/organic compounds were observed in the secondary Na-sulphate deposits by LD-FTICR-MS. FTIR provided additional evidence for the presence of bio/organic compounds. Sulphur fractionation was explored to assist in determining if microbes may play a role in oxidizing sulphur. The presence of bio/organic compounds associated with Na-sulphate deposits, along with the necessity of oxidizing reduced sulphur to sulphate, suggests that biological activity may be involved in the formation of these secondary minerals. The secondary Na-sulphate minerals probably form from the overlying basalt through leached sodium ions and sulphate ions produced by bio-oxidation of Fe-sulphide minerals. Since the COM basalts are one of the most comparable terrestrial analogues for their Martian counterparts, the occurrence of biological activity in the formation of sulphate minerals at COM has direct implications for the search for life on Mars. In addition, the presence of caves on Mars suggests the importance of these environments as possible locations for growth and preservation of microbial activity. Therefore, understanding the physiochemical pathways of abiotic and biotic mineralization in the COM subsurface and similar basaltic settings has direct implications for the search for extinct or extant life on Mars.
Insight, positive and negative symptoms, hope, depression and self-stigma: a comprehensive model of mutual influences in schizophrenia spectrum disorders
Authors: Schrank B. , Amering M. , Hay A. Grant , Weber M. , Sibitz I.
Published: July 2013

Aims.

Insight, positive and negative symptoms, hope, depression and self-stigma are relevant variables in schizophrenia spectrum disorders. So far, research on their mutual influences has been patchy. This study simultaneously tests the associations between these variables.

Methods.

A total of 284 people with schizophrenia spectrum disorders were assessed using the Schedule for the Assessment of Insight, Positive and Negative Syndrome Scale, Integrative Hope Scale, Centre for Epidemiological Studies Depression Scale and Internalized Stigma of Mental Illness scale. Path analysis was applied to test the hypothesized relationships between the variables.

Results.

Model support was excellent. Strong and mutual causal influences were confirmed between hope, depression and self-stigma. The model supported the assumption that insight diminishes hope and increases depression and self-stigma. While negative symptoms directly affected these three variables, reducing hope and increasing depression and self-stigma, positive symptoms did not. However, positive symptoms diminished self-stigma on a pathway via insight.

Conclusions.

This study provides a comprehensive synopsis of the relationships between six variables relevant for schizophrenia spectrum disorders. Research implications include the need to investigate determinants of consequences of insight, and the sequence of influences exerted by positive and negative symptoms. Clinical implications include the importance of interventions against self-stigma and of taking a contextualized approach to insight.
Tissue-Type Plasminogen Activator Mediates Neuronal Detection and Adaptation to Metabolic Stress
Authors: Wu Fang , Nicholson Andrew D , Haile Woldeab B , Torre Enrique , An Jie , Chen Changhua , Lee Andrew K , Duong Duc M , Dammer Eric B , Seyfried Nicholas T , Tong Frank C , Votaw John R , Yepes Manuel
Published: July 2013

Adenosine monophosphate-activated protein kinase (AMPK) is an energy sensor that regulates cellular adaptation to metabolic stress. Tissue-type plasminogen activator (tPA) is a serine proteinase found in the intravascular space, where its main role is as thrombolytic enzyme, and in neurons, where its function is less well understood. Here, we report that glucose deprivation induces the mobilization and package of neuronal tPA into presynaptic vesicles. Mass spectrometry and immunohistochemical studies show that the release of this tPA in the synaptic space induces AMPK activation in the postsynaptic terminal, and an AMPK-mediated increase in neuronal uptake of glucose and neuronal adenosine 5′(tetrahydrogen triphosphate; ATP) synthesis. This effect is independent of tPA's proteolytic properties, and instead requires the presence of functional N-methyl-D-aspartate receptors (NMDARs). In agreement with these observations, positron emission tomography (PET) studies and biochemical analysis with synaptoneurosomes indicate that the intravenous administration of recombinant tPA (rtPA) after transient middle cerebral artery occlusion (tMCAO) induces AMPK activation in the synaptic space and NMDAR-mediated glucose uptake in the ischemic brain. These data indicate that the release of neuronal tPA or treatment with rtPA activate a cell signaling pathway in the synaptic space that promotes the detection and adaptation to metabolic stress.
TAT-Hsp70 Induces Neuroprotection Against Stroke Via Anti-Inflammatory Actions Providing Appropriate Cellular Microenvironment for Transplantation of Neural Precursor Cells
Authors: Doeppner Thorsten R , Kaltwasser Britta , Fengyan Jin , Hermann Dirk M , Bähr Mathias
Published: July 2013

Heat-shock protein 70 (Hsp70) protects against cerebral ischemia, which is attributed to its chaperone activity. However, recent reports also describe pro-inflammatory actions of Hsp70 via activation of Toll-like receptors (TLR). Using membrane-permeable transactivator of transcription (TAT)-Hsp70, we analyzed TAT-Hsp70-induced neuroprotection and its underlying mechanism after cerebral ischemia in mice. Infusion of TAT-Hsp70 reduced infarct volume and enhanced blood–brain barrier integrity on day 3 poststroke, when given no later than 12 hours. The latter was associated with reduction of microglial activation, although upregulation of pro-inflammatory TLR-2/4 was observed both in verum and in control animals. Nevertheless, protein abundance and nuclear translocation of downstream nuclear factor kappa B (NF-κB) as well as proteasomal degradation of the NF-κB regulator Ikappa B alpha (IκB-α) were significantly reduced by TAT-Hsp70. TAT-Hsp70-induced neuroprotection and functional recovery were restricted to 4 weeks only. However, TAT-Hsp70 provided an appropriate extracellular milieu for delayed intravenous transplantation of adult neural precursor cells (NPCs). Thus, NPCs that were grafted 28 days poststroke induced long-term neuroprotection for at least 3 months, which was not due to integration of grafted cells but rather due to paracrine effects of transplanted NPCs. Conclusively, TAT-Hsp70 ameliorates postischemic inflammation via proteasome inhibition, thus providing an appropriate extracellular milieu for delayed NPC transplantation and culminating in long-term neuroprotection.
Development of a Physiologically‐Based Pharmacokinetic Model for Sirolimus: Predicting Bioavailability Based on Intestinal CYP3A Content
Authors: Emoto C , Fukuda T , Cox S , Christians U , Vinks AA
Published: July 2013

Sirolimus is an inhibitor of mammalian target of rapamycin (mTOR) and is increasingly being used in transplantation and cancer therapies. Sirolimus has low oral bioavailability and exhibits large pharmacokinetic variability. The underlying mechanisms for this variability have not been explored to a large extent. Sirolimus metabolism was characterized by in vitro intrinsic clearance estimation. Pathway contribution ranked from CYP3A4 > CYP3A5 > CYP2C8. With the well stirred and Qgut models sirolimus bioavailability was predicted at 15%. Interindividual differences in bioavailability could be attributed to variable intestinal CYP3A expression. The physiologically‐based pharmacokinetics (PBPK) model developed in Simcyp predicted a high distribution of sirolimus into adipose tissue and another elimination pathway in addition to CYP‐mediated metabolism. PBPK model predictive performance was acceptable with Cmax and area under the curve (AUC) estimates within 20% of observed data in a dose escalation study. The model also showed potential to assess the impact of hepatic impairment and drug–drug interaction (DDI) on sirolimus pharmacokinetics.

CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e59; doi:10.1038/psp.2013.33; published online 24 July 2013
Post-metalation of porous aromatic frameworks for highly efficient carbon capture from CO2 + N2 and CH4 + N2 mixtures
Authors: Ma Heping , Ren Hao , Zou Xiaoqin , Meng Shuang , Sun Fuxing , Zhu Guangshan
Published: July 2013

“Light metal, strong power”: new porous aromatic frameworks (PAF-26) with available carboxyl groups are synthesized and further modified with light metal ions (Li+, Na+, K+, Mg2+); the metalized PAF-26 shows a distinct enhancement for CO2 and CH4 uptake.
A simple and straightforward synthesis of phenyl isothiocyanates, symmetrical and unsymmetrical thioureas under ball milling
Authors: Zhang Ze , Wu Hao-Hao , Tan Ya-Jun
Published: July 2013

Anilines were efficiently transformed into isothiocyanates (5.0 equiv. CS2) or thioureas (1.0 equiv. CS2) under ball milling and promoted by KOH.
Idiom, Syntax, and Advanced Theory of Mind Abilities in Children With Autism Spectrum Disorders
Authors: Whyte Elisabeth M. , Nelson Keith E. , Scherf K. Suzanne
Published: July 2013

Purpose

When researchers investigate figurative language abilities (including idioms) in children with autism spectrum disorder (ASD), syntax abilities may be more important than once considered. In addition, there are limitations to the overreliance on false-belief tasks to measure theory of mind (TOM) abilities. In the current study, the authors investigated idiom, syntax, and advanced TOM abilities in children with ASD compared to children with typical development (TD).

Method

Twenty-six children with ASD, ages 5 to 12 years, were compared to individuals in each of 2 control groups of children with TD: 1 matched on chronological age and nonverbal IQ, and 1 matched on syntax age-equivalence and raw scores. Idiom comprehension, syntax, vocabulary, and 2 measures of advanced TOM abilities were examined.

Results

Although children with ASD performed worse on idiom comprehension compared to the age-matched group with TD, they exhibited comparable idiom performance to the syntax-matched group with TD. Advanced TOM abilities were related to idiom comprehension for children with ASD, but not for children with TD, above the contributions of basic language abilities.

Conclusion

Syntax abilities should be used as a matching variable when examining figurative or other late-developing language skills.
Assistive Technology for Cognition Following Brain Injury: Guidelines for Device and App Selection
Authors: Wild Michelle Ranae
Published: July 2013

The widespread use of mobile technologies and applications (apps) among the non-disabled population in the past several years to stay connected, track appointments, stay organized, etc., has had profound implications for those with cognitive disabilities following acquired brain injury. Assistive technology for cognition (ATC) includes the use of these same systems to compensate for common cognitive challenges following ABI. And although the use of mainstream technologies in this population is a potential boon, it can be difficult for rehabilitation professionals to keep up with the changing world of devices, operating systems, and applications (apps). This article provides an overview of devices and apps currently used as ATC and provides guidelines for device and app selection and a framework for facilitating meta-cognition and generalization through the ATC instruction process. (Note: The devices and apps described in this article are not intended to be an endorsement of any particular system.)
Training-the-Trainer on Assistive Technology for Cognition (ATC): Current Practices
Authors: Ehlhardt Powell Laurie , Wallace Tracey , Wild Michelle ranae
Published: July 2013

Research shows that if clinicians are to deliver effective, evidence-based assistive technology for cognition (ATC) services to clients with acquired brain injury (ABI), they first need opportunities to gain knowledge and experience with ATC assessment and training practices (O'Neil-Pirozzi, Kendrick, Goldstein, & Glenn, 2004). This article describes three examples of train the trainer materials and programs to address this need: (a) a toolkit for trainers to learn more about assessing and training ATC; (b) a comprehensive, trans-disciplinary program for training staff to provide ATC services in a metropolitan area; and (c) an overview of an on-site/online training package for rehabilitation professionals working with individuals with ABI in remote locations.
Acoustics of Infant Pain Cries: Fundamental Frequency as a Measure of Arousal
Authors: Goberman Alexander M. , Whitfield Jason A.
Published: July 2013

Purpose: The goal of the current study is to examine fundamental frequency (F0) from a sample of healthy newborn infant pain cries.

Methods: A total of 58 healthy infants were included in the study. Data were examined from the first cry following a pain stimulus, in addition to a comparison of the first 30 seconds and the last 30 seconds of the entire crying episode.

Results: In the current study, the mean F0 was found to decrease over time (regardless of infant sex, term status, or positioning). The data also showed a significantly higher F0 for preterm female infants (compared to preterm males) in the first cry immediately following the pain stimulus.

Conclusions: These results reflect high levels of laryngeal tension following the pain stimulus, followed by an overall decrease in tension /arousal over time. The results support examination of the first cry following a pain stimulus, along with examination of the entire cry episode. Implications for the study of arousal and sudden infant death syndrome are discussed.
Speech Science: Technique, Concept, Theory
Authors: Weismer Gary
Published: July 2013

The purpose of this paper is to outline a history and a possible future of speech science as a discipline. Two major and sometimes opposing views of speech science are discussed. One view is inspired by Stetson's work, and holds that study of speech movements is most likely to reveal the essentials of speech motor control. The other view regards the speech acoustic signal as part of the control mechanism; in this view, movements and the signals produced by them are intertwined as part of the control mechanism. The importance of understanding these two views of speech science is in the application of speech science skills to clinical disorders of speech motor control. The paper uses motor speech disorders as an example of how the two views can be joined empirically and theoretically for a maximally productive application of speech science to an understanding of disorders of speech motor control.
A dielectric frequency response model to evaluate the moisture content within an oil impregnated paper condenser bushing
Authors: Smith David J. , McMeekin Scott G. , Stewart Brian G. , Wallace Peter A.
Published: July 2013

Increased moisture content within an oil‐paper insulation system can significantly reduce its life expectancy, and for oil impregnated paper condenser type bushings, it is the most common cause of failure. Distinction between moisture contents using traditional power frequency tests of dissipation factor and capacitance can be difficult, particularly at ambient temperatures. Dielectric frequency response is becoming an established technique to measure the dissipation factor and capacitance of a bushing, but to date an accurate model to evaluate the condenser moisture content has not been presented using this technique. In this study, a dielectric frequency response bushing model is proposed and finite element method software is used to simulate the variation in dissipation factor and capacitance of a bushing with varying moisture content, as a function of frequency and temperature. The modelled results are compared with measurements reported in the literature and from the authors’ own field measurements, where a good agreement is demonstrated. It is shown that the distinction in dissipation factor between moisture contents at frequencies <0.1 Hz is in excess of ten times greater than at 50 Hz. The proposed model can be used by practitioners to evaluate moisture content within the condenser insulation and distinguish between moisture contents ranging from 0.2 to 4.0%.
Acquisition system and approximation of brain signals
Authors: Rubio José de Jesús , Vázquez Diana M. , Mújica‐Vargas Dante
Published: July 2013

In this study, one acquisition system of one channel is introduced to obtain the biological brain signals. Such system consists of a low‐pass filter, an amplifier, a high‐pass filter and a data acquisition board. A novel slopes algorithm with guaranteed bounded output is proposed for the approximation of the brain signals. The proposed method is compared with both the least‐squares and nearest‐neighbour algorithms.
Design, development and evaluation of optical motion‐tracking system based on active white light markers
Authors: Stancic Ivo , Grujic Supuk Tamara , Panjkota Ante
Published: July 2013

The precise measurement and analysis of human movements is an essential step in biomechanical research used in sports or medicine. Measurement systems used for motion tracking should be non‐invasive, safe to use, widely customisable and cost‐efficient. In this study, complete design, development and evaluation of a high‐speed optical motion tracking and analysis system is described. The system aims to analyse movements for sports and medical applications. The novelty of the proposed system is its design, which is based on visible light light‐emitting diode (LED) markers, rather than infrared markers that are commonly used, and a pair of high‐speed digital cameras. Calibration procedures and a super‐resolution marker model are introduced, ensuring sub‐pixel marker centre detection which results in higher three‐dimensional reconstruction accuracy. Evaluation of the system included an accuracy test of the proposed system on static and moving objects with known dimensions, followed by analysis of kinematic data obtained in dynamic conditions while measuring human gait. The evaluation results are presented, and conclusions about system performance with possible improvements are discussed.
Detection of helium bubble formation at fcc-bcc interfaces using neutron reflectometry
Authors: Kashinath A. , Wang P. , Majewski J. , Baldwin J. K. , Wang Y. Q. , Demkowicz M. J.
Published: July 2013

We use neutron reflectometry to find the critical helium (He) fluence required to form He bubbles at interfaces between fcc and bcc metals. Our findings are in agreement with previous experimental as well as modeling results and provide evidence for the presence of stable He platelets at fcc-bcc interfaces prior to bubble formation. The stable storage of He in interfacial platelets may provide the basis for the design of materials with increased resistance to He-induced degradation.
Proteins in the electric field near the surface of mica
Authors: Starzyk Anna , Cieplak Marek
Published: July 2013

We elucidate the nature of the electric field produced by a model mica surface and show that above some 0.4 nm it is nearly uniform and of order 12 V/nm. The presence of ions in the solvent above the surface, up to the concentration of about 300 mM, does not modify the nature of the field much. We study the conformational changes of a small protein, the tryptophan cage, as induced by (a) uniform electric field and (b) the electric field near mica. We use all-atom molecular dynamics simulations and provide evidence for the existence of unfolded and deformed conformations in each of these cases. The two behaviors are characterized by distinct properties of the radius of gyration and of the distortion parameter that distinguishes between elongated and globular shapes. The overall geometry of the conformations shifts with the strengths of the uniform field in a manner that depends on the nature of the simulation box — whether it is bounded by neutral walls or not — and on the ionic concentration. Near the mica surface, on the other hand, the fraction of unfolded conformations is close to 1/6 at the ionic strength of 350 mM compared to 1/2 at 20 mM. When the electric charge on the mica is fully neutralized by bringing more ions of the opposite charge then unfolded conformations stay unfolded but an evolution from the native state does not lead to any unfolding.
Dissipative electron transfer dynamics in mixed valence dimers: Microscopic approach to the solid state problem
Authors: Palii Andrew , Bosch-Serrano Cristian , Clemente-Juan Juan Modesto , Coronado Eugenio , Tsukerblat Boris
Published: July 2013

We propose a microscopic analytical approach to the description of the low-temperature dissipative intracluster electron transfer dynamics in centrosymmetric one-electron mixed-valence (MV) dimers. The dissipative system (bath) is supposed to consist of the acoustic phonons of the crystal surrounding that are coupled to the delocalized electron(s) of a MV dimer. Although the concept of the bath is the spin-boson model is more generic, the present consideration is relevant, for example, to a MV bi-center impurity in an ionic crystal. The model allows us to develop an approximate microscopic approach within which the relaxation processes are explicitly taken into account without additional assumption regarding spectral function of the bath. It is assumed that initially the extra electron is localized on a certain center and then the time-dependent localization probability (averaged value of the electron dipole moment) is evaluated with the emphasis on the damping of the amplitude of the Rabi oscillations. The approach assumes the following conditions: (i) the vibrational spectrum of the crystal does not show the presence of local modes; (ii) the itinerant electron is weakly coupled to the long-waves acoustic phonons which is peculiar to fully delocalized Robin and Day class III MV systems; (iii) the Debye energy ℏωD exceeds the electronic resonance energy gap 2β (β is the electron transfer parameter). We have demonstrated that the dissipation in this case is super-ohmic with the low-frequency spectral function J(ω) ∝ ω5. The time dependences of the localization probabilities show nearly picosecond damped oscillations. The longitudinal relaxation time T1 has been shown to be two times shorter than the decoherence time T2 thus giving the upper bound for T2, T2 ≤ 2T1.
High intrinsic energy resolution photon number resolving detectors
Authors: Lolli L. , Taralli E. , Portesi C. , Monticone E. , Rajteri M.
Published: July 2013

Transition Edge Sensors (TESs) are characterized by the intrinsic figures of merit to resolve both the energy and the statistical distribution of the incident photons. These properties lead TES devices to become the best single photon detectors for quantum technology experiments. For a TES based on titanium and gold, has been reached, at telecommunication wavelength, an unprecedented intrinsic energy resolution (0.113 eV). The uncertainty analysis of both energy resolution and photon state assignment has been discussed. The thermal properties of the superconductive device have been studied by fitting the bias curves to evaluate the theoretical limit of the energy resolution.
Global solutions of the Vlasov-Poisson-Boltzmann system in a cosmological setting
Authors: Lee Ho
Published: July 2013

In this paper, the Vlasov-Poisson-Boltzmann system is studied in the context of Newtonian cosmology. An explicit background solution which describes the evolution of our universe is constructed, and global existence of homogeneous solutions that are perturbations around the background solution is obtained. Depending on the rate of expansion of the universe it is observed that the solutions have different behaviours at a large time. At a slow rate of expansion the solutions tend to an equilibrium state, but it turns out that such a slow rate is not physically well-motivated. At a rapid rate of expansion it is showed that the solutions behave like solutions of the Vlasov equation.
Phase transitions, relaxor behavior, and large strain response in LiNbO3-modified Bi0.5(Na0.80K0.20)0.5TiO3 lead-free piezoceramics
Authors: Hao Jigong , Bai Wangfeng , Li Wei , Shen Bo , Zhai Jiwei
Published: July 2013

The effect of LiNbO3 (LN) addition on the ferroelectric behavior and piezoelectric properties of Bi0.5(Na0.80K0.20)0.5TiO3 (BNKT20) lead-free piezoceramics were systematically investigated. Results showed that the LN substitution into BNKT20 induced a transition from coexistence of ferroelectric tetragonal and rhombohedral phases to relaxor pseudocubic phases, which is accompanied by the significant disruption of ferroelectric order and with the shift of the ferroelectric-relaxor transition temperature TF-R down to room temperature. Accordingly, a large accompanying normalized strain of ∼0.38% (corresponding to a large signal d33* of ∼475 pm/V) were obtained in BNKT20 with 2.5 mol. %LN addition near the phase boundary. Temperature-dependent measurements of both polarization and strain from room temperature to 120 °C suggested that the origin of the large strain is due to a reversible field-induced ergodic relaxor-to-ferroelectric phase transformation. Moreover, an attractive property for application as high-temperature dielectrics was obtained in this system modified with 8 mol. %LN with a high permittivity of 1760 ± 15% from room temperature up to 500 °C, spanning a range of about 450 °C.
The investigation of donor-acceptor compatibility in bulk-heterojunction polymer systems
Authors: Huang Jen-Hsien , Hsiao Yu-Sheng , Richard Eric , Chen Chun-Chao , Chen Peilin , Li Gang , Chu Chih-Wei , Yang Yang
Published: July 2013

The fullerene derivative, indene-C60 bisadduct (ICBA), has been introduced into poly(3-hexylthiophene) (P3HT) to improve the efficiency of P3HT-based devices. However, we found that ICBA is not suitable for most low bandgap polymers. In this study, we have correlated the cell performance with surface energy between the donor and acceptor materials in a bulk-heterojunction cell. These results show that higher photocurrent can be attributed to the morphology improvement induced by larger surface energy difference (Δγ) between the low bandgap polymer and fullerene. These results also suggest that synthetic strategies which adjust the Δγ between donor and acceptor should be considered.
Characterization of low-resistance ohmic contacts to n- and p-type InGaAs
Authors: Lin J. C. , Yu S. Y. , Mohney S. E.
Published: July 2013

Multilayer ohmic contacts with differing first metal layers (M = Mo, Pd, Pt) beneath a Ti/Pt diffusion barrier and Au cap were fabricated on n+ and p+-InGaAs, and the relationship between their specific contact resistance and interfacial chemistry was examined. Palladium-based contacts offered the lowest specific contact resistances of ρc=3.2×10−8 and 1.9×10−8 Ω-cm2 to n+- and p+-InGaAs, respectively. The low resistances of the Pd-based contact were correlated with the formation of a uniform PdxInGaAs phase in direct contact with InGaAs, as observed using transmission electron microscopy and energy dispersive spectroscopy. On the other hand, the Mo-based contact to n+ and p+-InGaAs had much higher specific contact resistances, even though its specific contact resistance on lightly doped n-InGaAs was nearly the same as that of the Pd-based contact. The cause of this discrepancy was identified to be the native oxide layer that remained between the contact and semiconductor in the Mo-based contacts, as revealed using transmission electron microscopy, energy dispersive spectroscopy, and electron energy loss spectroscopy. The effect of the native oxide in series with the Schottky barrier is significant only when the contact is doped heavily enough that tunneling of carriers through the Schottky barrier introduces a very low resistance.
The electronic properties of a two-electron multi-shell quantum dot-quantum well heterostructure
Authors: Aydin Rasit , Sahin Mehmet
Published: July 2013

A detailed investigation of the electronic properties of a double electron in a core/shell/well/shell quantum dot heterostructure has been systematically studied for cases with and without an on-center donor impurity. For this purpose, the Poisson-Schrödinger equations have been solved self-consistently in the frame of the single band effective mass approximation and Hartree treatment. The variation of the binding energies of negatively charged donor impurity (D−) have been examined for different core radii, shell thicknesses, and well widths. The results obtained have been presented comparatively as a function of layer thicknesses and probable physical reasons behind in their behavior have been discussed.
Cold atomic beam ion source for focused ion beam applications
Authors: Knuffman B. , Steele A. V. , McClelland J. J.
Published: July 2013

We report measurements and modeling of an ion source that is based on ionization of a laser-cooled atomic beam. We show a high brightness and a low energy spread, suitable for use in next-generation, high-resolution focused ion beam systems. Our measurements of total ion current as a function of ionization conditions support an analytical model that also predicts the cross-sectional current density and spatial distribution of ions created in the source. The model predicts a peak brightness of 2 × 107 A m−2 sr−1 eV−1 and an energy spread less than 0.34 eV. The model is also combined with Monte-Carlo simulations of the inter-ion Coulomb forces to show that the source can be operated at several picoamperes with a brightness above 1 × 107 A m−2 sr−1 eV−1. We estimate that when combined with a conventional ion focusing column, an ion source with these properties could focus a 1 pA beam into a spot smaller than 1 nm. A total current greater than 5 nA was measured in a lower-brightness configuration of the ion source, demonstrating the possibility of a high current mode of operation.
Yttrium antisite reduction and improved photodiode performance in Ce doped Y3Al5O12 by Czochralski growth in alumina rich melts
Authors: Haven Drew T. , Dickens Peter T. , Weber Marc H. , Lynn Kelvin G.
Published: July 2013

Single crystal cerium doped yttrium aluminum garnet boules were grown by the Czochralski method. Cerium concentrations were held at 1.0 at. % (with respect to yttrium in an on stoichiometric charge) but melt stoichiometry ranged from 10.0 at. % yttria rich to 10.0 at. % alumina rich in 5.0% increments. Photo-luminescence, lifetime, and scintillation data demonstrate a measureable decrease in UV defect emission as the melt becomes alumina rich. This is strongly consistent with a suppression of equilibrium YAl3+ antisite defect concentrations in the boule as melt stoichiometry shifts towards alumina rich. This decrease does not alter thermoluminescence behavior, making the case that carrier traps and YAl3+ antisites are independent defects. Additionally, an aluminum in-diffusion post growth treatment indicates the observed change is from reduction of YAl3+ antisite defect concentrations alone, as opposed to alteration of antisite-vacancy complexes. The results culminate in a large increase in visible emission and produce an excellent resolution of 5.04 ± 0.07% (662 keV; 10 mm thick) with electronic noise subtraction on a photodiode.
Manipulation of domain propagation dynamics with the magnetostatic interaction in a pair of Fe-rich amorphous microwires
Authors: Gawroński P. , Zhukova V. , Zhukov A. , Gonzalez J.
Published: July 2013

We studied the domain wall dynamics in a system of two magnetostatically interacting Fe-rich glass coated amorphous microwires paying attention on the influence of the interaction and the external tensile stress on the velocity of the domain wall propagation. We measured and analyzed numerically the dependence of the shape of the hysteresis loops on the frequency of the applied field considering its origin related with the finite domain wall velocity. The critical condition for the disappearance of the plateau on the hysteresis loops separating two remagnetization events in a system of two microwires was investigated.
Plasmonic biosensor for detection of hemoglobin concentration in human blood: Design considerations
Authors: Sharma Anuj K.
Published: July 2013

Surface plasmon resonance (SPR) sensor for the detection of hemoglobin concentration in human blood is proposed. Previous experimental results describing variation of refractive index of human blood with hemoglobin concentration at different wavelengths are considered for theoretical calculations. The angular interrogation method along with silica substrate and gold layer is considered. The sensor's performance is closely analyzed in terms of well-defined performance parameters: sensitivity, accuracy, resolution, and signal-to-noise ratio, in order to achieve reliable and accurate hemoglobin detection. The influence of operating wavelength on the performance of sensor scheme is critically investigated. Performance comparison for two different substrates is carried out. The results are explained in terms of light coupling and plasmon resonance condition. The proposed biosensor has the potential to provide high sensitivity, accuracy, and large operating range of hemoglobin detection, along with much higher resolution compared with existing methods, thereby opening an easy and reliable window for biomedical applications.
Low temperature study of structural phase transitions in niobium hydrides
Authors: Tao R. , Romanenko A. , Cooley L. D. , Klie R. F.
Published: July 2013

Niobium (Nb) and its hydrides have been the focus of many studies due to applications as a hydrogen storage material, as a dielectric coating in semiconductor devices and in superconducting radio-frequency cavities. In this paper, we will present the atomic-scale characterization of Nb hydrides using scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) at room and liquid nitrogen temperatures. Although such cavities are formed from ultrahigh purity Nb, using electron beam diffraction, we found that at LN2 temperature, the grains near the surface of cold-worked Nb sheets contain regions exhibiting three different superlattice features, which are identified as β, ε, and ζ-NbHx phases. Z-contrast imaging and EELS at LN2 temperature are utilized to qualify their atomic and electronic structures.
Direct characterization of the electrocaloric effects in thin films supported on substrates
Authors: Jia Yanbing , Sungtaek Ju Y.
Published: July 2013

We report a direct characterization of the electrocaloric (EC) effect in thin films clamped on substrates using micro-thermometers integrated onto the substrates. The measured temporal temperature profiles are analyzed using a 3D heat diffusion model to extract the adiabatic temperature changes. Thin-film thermometers with very different temperature coefficients of resistance are used to verify that experimental errors due to electric or electromagnetic coupling are negligible. Our approach captured asymmetry between the electrocaloric heating and cooling due to hysteresis and yielded adiabatic temperature changes that are consistent with the existing data on free-standing ter- and co-polymer films of similar compositions.
Morphological, compositional, and geometrical transients of V-groove quantum wires formed during metalorganic vapor-phase epitaxy
Authors: Dimastrodonato Valeria , Pelucchi Emanuele , Zestanakis Panagiotis A. , Vvedensky Dimitri D.
Published: July 2013

We present a theoretical model of the formation of self-limited (Al)GaAs quantum wires within V-grooves on GaAs(001) substrates during metalorganic vapor-phase epitaxy. We identify the facet-dependent rates of the kinetic processes responsible for the formation of the self-limiting profile, which is accompanied by Ga segregation along the axis perpendicular to the bottom of the original template, and analyze their interplay with the facet geometry in the transient regime. A reduced model is adopted for the evolution of the patterned profile, as determined by the angle between the different crystallographic planes as a function of the growth conditions. Our results provide a comprehensive phenomenological understanding of the self-ordering mechanism on patterned surfaces which can be harnessed for designing the quantum optical properties of low-dimensional systems.
Magnetic-resonance imaging of the human brain with an atomic magnetometer
Authors: Savukov I. , Karaulanov T.
Published: July 2013

Magnetic resonance imaging (MRI) is conventionally performed in very high fields, and this leads to some restrictions in applications. To remove such restrictions, the ultra-low field MRI approach has been proposed. Because of the loss of sensitivity, the detection methods based on superconducting quantum interference devices (SQUIDs) in a shielded room were used. Atomic magnetometers have similar sensitivity as SQUIDs and can also be used for MRI, but there are some technical difficulties to overcome. We demonstrate that MRI of the human brain can be obtained with an atomic magnetometer with in-plane resolution of 3 mm in 13 min.
Defect controlled ultra high ultraviolet photocurrent gain in Cu-doped ZnO nanorod arrays: De-trapping yield
Authors: Sarkar Sanjit , Basak Durga
Published: July 2013

Understanding the mechanism behind high photocurrent gain is very important to realize a highly functional material for photodetector devices. Herein, we report a very high ultraviolet photocurrent gain of 2.8 × 105 in hydrothermally grown Cu-doped ZnO nanorod arrays which is two orders of magnitude higher as compared to the undoped sample. Trapping of carriers under dark and de-trapping them under illumination by Cu-related defects is responsible for high gain. The trap state at ∼1.65 eV is attributed to the [{CuZn+(3d10)}− − Zni+(4s1)]0 type of defects. A model is shown to explain the dark and photocurrent states in the doped samples.
Optical transfer function of three-dimensional photonic crystals by volume holographic recording
Authors: Orlic Susanna , Bernstein Fabian , Kratz Christoph , Schlösser Alexander
Published: July 2013

We investigate optical transformations by three-dimensional photonic crystals fabricated via holographic lithography. Large-area three-dimensional photonic crystal structures are created by multiple-beam interference in photosensitive materials. We perform calculations of the optical transfer function for monochromatic incident light. Our approach is based on three-dimensional vector rigorous coupled-wave approach, which allows modeling the dynamic interaction of light waves generated by diffraction inside a crystal grating. We analyze the Bragg-conditioned energy transfer for different crystal structures and address the influence of the refractive index contrast. Diffractive-optical properties of the fabricated crystals are investigated by laser scanning and monitoring the transmitted light in three-dimensional angular space. The scan results agree well with the modeling predictions for different crystals and recording photopolymers.
Trap-induced light enhancement from a polymer light emitting device
Authors: Zhang Xiaojin , He Zhiqun , Liang Chunjun , Wang Yongsheng , Zhuang Qixin , Han Zhewen
Published: July 2013

In this work, a series of poly(p-phenylene benzobisoxazole) (PBO) light emitting devices was fabricated. Doping non-fluorescent copper phthalocyanine into the PBO light emitting layer caused a substantial enhancement in electroluminescence from the PBO matrix. Current-voltage characteristics revealed hole-trapping at low doping levels, and hole-transportation at high doping concentrations. The performance of the device improved substantially, reaching a brightness of 3.4 × 104 cd/m2 and current efficiency of 10.9 cd/A or more. This offers a practical approach to develop a single-layered device structure by simply tuning the trap densities.
Enhanced buckled-beam piezoelectric energy harvesting using midpoint magnetic force
Authors: Zhu Yang , Zu Jean W.
Published: July 2013

Aiming to improve the functionality of a buckled-beam piezoelectric energy harvester, a midpoint magnetic force is utilized to enable snap-through motions under low-frequency (<30 Hz) small-amplitude (0.2 g–0.8 g) excitations. The noncontact midpoint magnetic force is introduced through a local magnetic levitation system created by neodymium magnets and is capable of triggering the second buckling mode that helps the beam easily snap through between equilibriums when subjected to excitations. Significant enhancements, along with distinct nonlinear phenomena, are observed at low frequencies in terms of large-amplitude voltage output and extended frequency bandwidth. Frequency tuning is also achievable by adjusting the separation distance between magnets.
Note: The universal relations for the critical point parameters
Authors: Apfelbaum E. M. , Vorob'ev V. S.
Published: July 2013

The universal correlation between the reduced critical pressure, density, and temperature for different substances and model systems was found on the basis of analysis of experimental and numerical simulation data. We choose the Zeno line (ZL) parameters as the reducing units (ZL is the line along which the compressibility factor is unity). In these variables the critical and ZL parameters satisfy simple relations, which are valid for a great number of substances.
Time evolution analysis of the electron distribution in Thomson/Compton back-scattering
Authors: Petrillo V. , Bacci A. , Curatolo C. , Maroli C. , Serafini L. , Rossi A. R.
Published: July 2013

We present the time evolution of the energy distribution of a relativistic electron beam after the Compton back-scattering with a counter-propagating laser field, performed in the framework of the Quantum Electrodynamics, by means of the code CAIN. As the correct angular distribution of the spontaneous emission is accounted, the main effect is the formation of few stripes, followed by the diffusion of the more energetic particles toward lower values in the longitudinal phase space. The Chapman-Kolmogorov master equation gives results in striking agreement with the numerical ones. An experiment on the Thomson source at SPARC-LAB is proposed.
Correlation between blue luminescence intensity and resistivity in β-Ga2O3 single crystals
Authors: Onuma T. , Fujioka S. , Yamaguchi T. , Higashiwaki M. , Sasaki K. , Masui T. , Honda T.
Published: July 2013

Temperature-dependent cathodoluminescence spectra were measured from (001) unintentionally doped, (100) Si-doped, and (010) Mg-doped β-Ga2O3 substrates prepared by either the floating zone growth or edge-defined film-fed growth methods. Although β-Ga2O3 is expected to be an indirect bandgap material, direct Γ-Γ transitions were found to be dominant in the optical transmittance spectra. The substrates exhibited no near-band-edge emission and instead exhibited ultraviolet luminescence, blue luminescence (BL), and green luminescence bands. Since the BL intensity strongly depended on the resistivity in the crystals, there was evidence of a correlation between the BL intensity and formation energy of oxygen vacancies.
Experimental study on rheological characteristics of high solid content sludge and it is mesophilic anaerobic digestion
Authors: Fubin Yin , Zifu Li , Huanhuan Ma , Lei Xun , Xiaofeng Bai , Yi Yin
Published: July 2013

Compared to conventional low solid content anaerobic digestion, high solid content anaerobic digestion can offer attractive advantages such as higher biogas generation and smaller reactor volume demand. However, high solid content sludge has the negative impacts on the anaerobic digestion for mixing and mass transfer efficiency, which should be investigated in order to improve mixing and mass transfer effects. In the first part of this study, the rheological characters of high solid content sludge was studied using the DNJ-1 rotating viscometer. The second part of the experiment was conducted by using an anaerobic reactor (10 l) to evaluate the potential biogas production and mesophilic anaerobic process stability. This was operated at mesophilic condition (37±1)°C with high solid content (11% total solid). The results showed that the sludge belongs to the pseudoplastic non-Newtonian fluid which has the characteristics of the shear thinning. Under the optimal mixing and mesophilic conditions, the experiment was operated for 42 days. The total biogas production of this experiment was about 45.5 l, i.e., biogas production per gram volatile substance was about 0.30 l/g volatile solid (VS). Besides, VS reduction ratio was 49.5%, and the methane content of biogas was about 68%. During the operation, the pH value in the reactor changed between 6.4 and 7.6; the total alkalinity was kept between 6000 and 12 000 mg/l. The results showed that high solid mesophilic anaerobic digestion process for waste activated sludge could be operated steadily, which could reduce the volume demand of anaerobic reactor dramatically. This concept has a great potential to be used as a practicable alternative for activated sludge anaerobic treatment.
Non-enzymatic Glucose Sensor Based on Palladium Coated Nanoporous Gold Film Electrode
Authors: Tavakkoli Nahid , Nasrollahi Shekofe
Published: July 2013

The non-enzymatic voltammetric and amperometric detection of glucose using a palladium coated nanoporous gold film electrode is described. The effect of surfactant on the fabrication of nanoporous gold film was also investigated. The voltammetric detection of glucose was performed by cyclic voltammetry. The sensor had good electrocatalytic activity towards oxidation of glucose, exhibited a rapid response (~6 s), and gave a linear range from 1 to 33 mM with a detection limit of 5 μM (with a signal to noise ratio of 3). The wide dynamic range, long-term stability, high sensitivity and selectivity, good reproducibility, and high resistance towards electrode fouling resulted in an ideal inexpensive amperometric glucose biosensor applicable for complex matrices.