Influence of the ordering of impurities on the appearance of an energy gap and on the electrical conductance of graphene.

PubMed

Repetsky, S P; Vyshyvana, I G; Kruchinin, S P; Bellucci, Stefano

2018-06-14

In the one-band model of strong coupling, the influence of substitutional impurity atoms on the energy spectrum and electrical conductance of graphene is studied. It is established that the ordering of substitutional impurity atoms on nodes of the crystal lattice causes the appearance of a gap in the energy spectrum of graphene with width η|δ| centered at the point yδ, where η is the parameter of ordering, δ is the difference of the scattering potentials of impurity atoms and carbon atoms, and y is the impurity concentration. The maximum value of the parameter of ordering is [Formula: see text]. For the complete ordering of impurity atoms, the energy gap width equals [Formula: see text]. If the Fermi level falls in the region of the mentioned gap, then the electrical conductance [Formula: see text] at the ordering of graphene, i.e., the metal-dielectric transition arises. If the Fermi level is located outside the gap, then the electrical conductance increases with the parameter of order η by the relation [Formula: see text]. At the concentration [Formula: see text], as the ordering of impurity atoms η →1, the electrical conductance of graphene [Formula: see text], i.e., the transition of graphene in the state of ideal electrical conductance arises.

Food Security as a Constraint on National Policy Decision Making in the Arab Region: A Case Study on Food Security in Sudan

DTIC Science & Technology

2009-04-17

12 Food Shortage alld The Killg of Egypt Visioll ----------------------------------------------------------- 13 Arab Security Gap ...intervention widened the gap in the value of food commodities in the Arab countries among investors and farmers. 5. Reduction in food production due to drought...seeds and also conduct pre-harvest crop assessments to identify agricultural and livestock gaps among the Sudanese2o. On the other hand, the UN

Gap Year Students in Lithuania: The Value Orientations of Children from Wealthy Social Groups

ERIC Educational Resources Information Center

Leonavicius, Vylius; Ozolinciute, Egle

2015-01-01

The paper seeks to understand the trajectories of students who defer entry to university. The study was conducted in Lithuania, a former Soviet Union republic. The phenomenon of a "gap year" is usually associated with young people, who decide not to enter higher education schools immediately after receiving secondary education, instead…

Application of Replica Technique and SEM in Accuracy Measurement of Ceramic Crowns

NASA Astrophysics Data System (ADS)

Trifkovic, B.; Budak, I.; Todorovic, A.; Hodolic, J.; Puskar, T.; Jevremovic, D.; Vukelic, D.

2012-01-01

The paper presents a comparative study of the measuring values of the marginal gap related to the ceramic crowns made by dental CAD/CAM system using the replica technique and SEM. The study was conducted using three experimental groups, which consisted of ceramic crowns manufactured by the Cerec CAD/CAM system. The scanning procedure was carried out using three specialized dental 3D digitization systems from the Cerec family - two types of extraoral optical scanning systems and an intraoral optical scanner. Measurements of the marginal gap were carried out using the replica technique and SEM. The comparison of aggregate values of the marginal gap using the replica technique showed a statistically significant difference between the systems. The measured values of marginal gaps of ceramic crowns using the replica technique were significantly lower compared to those measured by SEM. The results indicate that the choice of technique for measuring the accuracy of ceramic crowns influences the final results of investigation.

Provosts' Perceptions of Academic Library Value and Preferences for Communication: A National Study

ERIC Educational Resources Information Center

Murray, Adam; Ireland, Ashley

2018-01-01

While many studies have been conducted under the auspices of calculating academic library value, there are no large-scale studies into the perceptions that college or university provosts have of library value, nor are there studies into how provosts prefer library value data to be communicated. This study addresses that gap through a national…

The CO₂ GAP Project--CO₂ GAP as a prognostic tool in emergency departments.

PubMed

Shetty, Amith L; Lai, Kevin H; Byth, Karen

2010-12-01

To determine whether CO₂ GAP [(a-ET) PCO₂] value differs consistently in patients presenting with shortness of breath to the ED requiring ventilatory support. To determine a cut-off value of CO₂ GAP, which is consistently associated with measured outcome and to compare its performance against other derived variables. This prospective observational study was conducted in ED on a convenience sample of 412 from 759 patients who underwent concurrent arterial blood gas and ETCO₂ (end-tidal CO₂) measurement. They were randomized to test sample of 312 patients and validation set of 100 patients. The primary outcome of interest was the need for ventilatory support and secondary outcomes were admission to high dependency unit or death during stay in ED. The randomly selected training set was used to select cut-points for the possible predictors; that is, CO₂ GAP, CO₂ gradient, physiologic dead space and A-a gradient. The sensitivity, specificity and predictive values of these predictors were validated in the test set of 100 patients.   Analysis of the receiver operating characteristic curves revealed the CO₂ GAP performed significantly better than the arterial-alveolar gradient in patients requiring ventilator support (area under the curve 0.950 vs 0.726). A CO₂ GAP ≥10 was associated with assisted ventilation outcomes when applied to the validation test set (100% sensitivity 70% specificity). The CO₂ GAP [(a-ET) PCO₂] differs significantly in patients requiring assisted ventilation when presenting with shortness of breath to EDs and further research addressing the prognostic value of CO₂ GAP in this specific aspect is required. © 2010 The Authors. EMA © 2010 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

Effects of nanoscale vacuum gap on photon-enhanced thermionic emission devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yuan; Liao, Tianjun; Zhang, Yanchao

2016-01-28

A new model of the photon-enhanced thermionic emission (PETE) device with a nanoscale vacuum gap is established by introducing the quantum tunneling effect and the image force correction. Analytic expressions for both the thermionic emission and tunneling currents are derived. The electron concentration and the temperature of the cathode are determined by the particle conservation and energy balance equations. The effects of the operating voltage on the maximum potential barrier, cathode temperature, electron concentration and equilibrium electron concentration of the conduction band, and efficiency of the PETE device are discussed in detail for different given values of the vacuum gapmore » length. The influence of the band gap of the cathode and flux concentration on the efficiency is further analyzed. The maximum efficiency of the PETE and the corresponding optimum values of the band gap and the operating voltage are determined. The results obtained here show that the efficiency of the PETE device can be significantly improved by employing a nanoscale vacuum gap.« less

Review of CTF s Fuel Rod Modeling Using FRAPCON-4.0 s Centerline Temperature Predictions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toptan, Aysenur; Salko, Robert K; Avramova, Maria

Coolant Boiling in Rod Arrays Two Fluid (COBRA-TF), or CTF1 [1], is a nuclear thermal hydraulic subchannel code used throughout academia and industry. CTF s fuel rod modeling is originally developed for VIPRE code [2]. Its methodology is based on GAPCON [3] and FRAP [4] fuel performance codes, and material properties are included from MATPRO handbook [5]. This work focuses on review of CTF s fuel rod modeling to address shortcomings in CTF s temperature predictions. CTF is compared to FRAPCON which is U.S. NRC s steady-state fuel performance code for light-water reactor fuel rods. FRAPCON calculates the changes inmore » fuel rod variables and temperatures including the eects of cladding hoop strain, cladding oxidation, hydriding, fuel irradiation swelling, densification, fission gas release and rod internal gas pressure. It uses fuel, clad and gap material properties from MATPRO. Additionally, it has its own models for fission gas release, cladding corrosion and cladding hydrogen pickup. It allows finite dierence or finite element approaches for its mechanical model. In this study, FRAPCON-4.0 [6] is used as a reference fuel performance code. In comparison, Halden Reactor Data for IFA432 Rod 1 and Rod 3. CTF simulations are performed in two ways; informing CTF with gap conductance value from FRAPCON, and using CTF s dynamic gap conductance model. First case is chosen to show temperature is predicted correctly with CTF s models for thermal and cladding conductivities once gap conductance is provided. Latter is to review CTF s dynamic gap conductance model. These Halden test cases are selected to be representative of cases with and without any physical contact between fuel-pellet and clad while reviewing functionality of CTF s dynamic gap conductance model. Improving the CTF s dynamic gap conductance model will allow prediction of fuel and cladding thermo-mechanical behavior under irradiation, and better temperature feedbacks from CTF in transient calculations.« less

Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

NASA Astrophysics Data System (ADS)

Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

2017-09-01

ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

Investigation of scanning tunneling spectra on iron-based superconductor FeSe 0.5Te 0.5(in Chinese)

DOE PAGES

Du, Z. -Y.; Fang, D. -L.; Wang, Z. -Y.; ...

2015-05-05

FeSe 0.5Te 0.5 single crystals with superconducting critical temperature of 13.5 K are investigated by scanning tunneling microscopy/spectroscopy (STM/STS) measureflents in detail. STM image on the top surface shows an atomically resolved square lattice consisted by white and dark spots with a constant of about 3.73± 0.03 Å which is consistent with the lattice constant 3.78 Å. The Se and Te atoms with a height difference of about 0.35 Å are successfully identified since the sizes of the two kinds of atoms are different. The tunneling spectra show very large zero-bias conductance value and asymmetric coherent peaks in the superconductingmore » state. According to the positions of coherence peaks, we determine the superconducting gap 2Δ = 5.5 meV, and the reduced gap 2Δ/kBTc = 4.9 is larger than the value predicted by the weak-coupling BCS theory. The zero-bias conductance at 1.7 K only have a decrease of about 40% compared with the normal state conductance, which may originate from some scattering and broadening mechanism in the material. This broadening effect will also make the superconducting gap determined by the distance between the coherence peaks larger than the exact gap value. The asymmetric structure of the tunneling spectra near the superconducting gap is induced by the hump on the background. This hump appears at temperature more than twice the superconducting critical temperature. This kind of hump has also been observed in other iron pnictides and needs further investigation. A possible bosonic mode outside the coherence peak with a mode energy Ω of about 5.5 meV is observed in some tunneling spectra, and the ratio between the mode energy and superconducting transition temperature Ω/kBTc ≈ 4.7 is roughly consistent with the universal ratio 4.3 in iron-based superconductors. The high-energy background of the spectra beyond the superconducting gaps shows a V-shape feature. The slopes of the differential conductance spectra at high energy are very different in the areas of Te-atom cluster and Se-atom cluster, and the difference extends to the energy of more than 300 meV. The differential conductance mapping has very little information about the quasi-particle interference of the superconducting state, which may result from the other strong scattering mechanism in the sample.« less

Investigation of scanning tunneling spectra on iron-based superconductor FeSe 0.5Te 0.5 (in Chinese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Z. -Y.; Fang, D. -L.; Wang, Z. -Y.

FeSe 0.5Te 0.5 single crystals with superconducting critical temperature of 13.5 K are investigated by scanning tunneling microscopy/spectroscopy (STM/STS) measureflents in detail. STM image on the top surface shows an atomically resolved square lattice consisted by white and dark spots with a constant of about 3.73± 0.03 Å which is consistent with the lattice constant 3.78 Å. The Se and Te atoms with a height difference of about 0.35 Å are successfully identified since the sizes of the two kinds of atoms are different. The tunneling spectra show very large zero-bias conductance value and asymmetric coherent peaks in the superconductingmore » state. According to the positions of coherence peaks, we determine the superconducting gap 2Δ = 5.5 meV, and the reduced gap 2Δ/kBTc = 4.9 is larger than the value predicted by the weak-coupling BCS theory. The zero-bias conductance at 1.7 K only have a decrease of about 40% compared with the normal state conductance, which may originate from some scattering and broadening mechanism in the material. This broadening effect will also make the superconducting gap determined by the distance between the coherence peaks larger than the exact gap value. The asymmetric structure of the tunneling spectra near the superconducting gap is induced by the hump on the background. This hump appears at temperature more than twice the superconducting critical temperature. This kind of hump has also been observed in other iron pnictides and needs further investigation. A possible bosonic mode outside the coherence peak with a mode energy Ω of about 5.5 meV is observed in some tunneling spectra, and the ratio between the mode energy and superconducting transition temperature Ω/kBTc ≈ 4.7 is roughly consistent with the universal ratio 4.3 in iron-based superconductors. The high-energy background of the spectra beyond the superconducting gaps shows a V-shape feature. The slopes of the differential conductance spectra at high energy are very different in the areas of Te-atom cluster and Se-atom cluster, and the difference extends to the energy of more than 300 meV. The differential conductance mapping has very little information about the quasi-particle interference of the superconducting state, which may result from the other strong scattering mechanism in the sample.« less

Sub-band-gap absorption in Ga2O3

NASA Astrophysics Data System (ADS)

Peelaers, Hartwin; Van de Walle, Chris G.

2017-10-01

β-Ga2O3 is a transparent conducting oxide that, due to its large bandgap of 4.8 eV, exhibits transparency into the UV. However, the free carriers that enable the conductivity can absorb light. We study the effect of free carriers on the properties of Ga2O3 using hybrid density functional theory. The presence of free carriers leads to sub-band-gap absorption and a Burstein-Moss shift in the onset of absorption. We find that for a concentration of 1020 carriers, the Fermi level is located 0.23 eV above the conduction-band minimum. This leads to an increase in the electron effective mass from 0.27-0.28 me to 0.35-0.37 me and a sub-band-gap absorption band with a peak value of 0.6 × 103 cm-1 at 3.37 eV for light polarized along the x or z direction. Both across-the-gap and free-carrier absorption depend strongly on the polarization of the incoming light. We also provide parametrizations of the conduction-band shape and the effective mass as a function of the Fermi level.

Enhancing electron transport in molecular wires by insertion of a ferrocene center.

PubMed

Sun, Yan-Yan; Peng, Zheng-Lian; Hou, Rong; Liang, Jing-Hong; Zheng, Ju-Fang; Zhou, Xiao-Yi; Zhou, Xiao-Shun; Jin, Shan; Niu, Zhen-Jiang; Mao, Bing-Wei

2014-02-14

We have determined the conductance of alkane-linked ferrocene molecules with carboxylic acid anchoring groups using the STM break junction technique, and three sets of conductance values were found, i.e. high conductance (HC), medium conductance (MC) and low conductance (LC) values. The enhancing effect of the incorporated ferrocene on the electron transport in saturated alkane molecular wires is demonstrated by the increased conductance of the ferrocene molecules, attributed to the reduction of the tunneling barrier and the HOMO-LUMO gap induced by the insertion of ferrocene. Furthermore, the electron-withdrawing carbonyl group on the unconjugated backbone has little or no influence on single-molecule conductance. The current work provides a feasible approach for the design of high-performance molecular wires.

A detailed analysis of the energy levels configuration existing in the band gap of supersaturated silicon with titanium for photovoltaic applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pérez, E.; Dueñas, S.; Castán, H.

2015-12-28

The energy levels created in supersaturated n-type silicon substrates with titanium implantation in the attempt to create an intermediate band in their band-gap are studied in detail. Two titanium ion implantation doses (10{sup 13 }cm{sup -2} and 10{sup 14 }cm{sup -2}) are studied in this work by conductance transient technique and admittance spectroscopy. Conductance transients have been measured at temperatures of around 100 K. The particular shape of these transients is due to the formation of energy barriers in the conduction band, as a consequence of the band-gap narrowing induced by the high titanium concentration. Moreover, stationary admittance spectroscopy results suggest the existencemore » of different energy level configuration, depending on the local titanium concentration. A continuum energy level band is formed when titanium concentration is over the Mott limit. On the other hand, when titanium concentration is lower than the Mott limit, but much higher than the donor impurity density, a quasi-continuum energy level distribution appears. Finally, a single deep center appears for low titanium concentration. At the n-type substrate, the experimental results obtained by means of thermal admittance spectroscopy at high reverse bias reveal the presence of single levels located at around E{sub c}-425 and E{sub c}-275 meV for implantation doses of 10{sup 13 }cm{sup −2} and 10{sup 14 }cm{sup −2}, respectively. At low reverse bias voltage, quasi-continuously distributed energy levels between the minimum of the conduction bands, E{sub c} and E{sub c}-450 meV, are obtained for both doses. Conductance transients detected at low temperatures reveal that the high impurity concentration induces a band gap narrowing which leads to the formation of a barrier in the conduction band. Besides, the relationship between the activation energy and the capture cross section values of all the energy levels fits very well to the Meyer-Neldel rule. As it is known, the Meyer-Neldel rule typically appears in processes involving multiple excitations, like carrier capture and emission in deep levels, and it is generally observed in disordered systems. The obtained Meyer-Neldel energy value, 15.19 meV, is very close to the value obtained in multicrystalline silicon samples contaminated with iron (13.65 meV), meaning that this energy value could be associated to the phonons energy in this kind of substrates.« less

Electro–optical properties of poly(vinyl acetate)/polyindole composite film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhagat, D. J., E-mail: bhagatd@rediffmail.com; Dhokane, G. R.; Bajaj, N. S.

2016-05-06

In present work, electrical and optical properties of poly(vinyl acetate)/polyindole (PVAc/PIN) composite film are reported. The prepared composite was characterized via X–ray diffraction (XRD), UV–Vis spectroscopy and DC conductivity measurements. The polymer chain separation was determined using XRD analysis. An attempt has been made to study the temperature dependence of DC conductivity of PVAc/PIN composite in temperature range 308–373 K. The DC conductivity initially increases and reaches to 2.45×10–7 S/cm. The optical band gap value of composite is determined as 4.77 eV. The semiconducting nature of composite observed from electronic as well as optical band gap and Arrhenius behavior of DCmore » plot.« less

Band gap tuning of amorphous Al oxides by Zr alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Canulescu, S., E-mail: stec@fotonik.dtu.dk; Schou, J.; Jones, N. C.

2016-08-29

The optical band gap and electronic structure of amorphous Al-Zr mixed oxides with Zr content ranging from 4.8 to 21.9% were determined using vacuum ultraviolet and X-ray absorption spectroscopy. The light scattering by the nano-porous structure of alumina at low wavelengths was estimated based on the Mie scattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on the Zr content deviates from linearity and decreases from 7.3 eV for pure anodized Al{sub 2}O{sub 3} to 6.45 eV for Al-Zr mixed oxides with a Zr content of 21.9%. With increasing Zr content, the conduction band minimum changes non-linearlymore » as well. Fitting of the energy band gap values resulted in a bowing parameter of ∼2 eV. The band gap bowing of the mixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction band minimum of anodized Al{sub 2}O{sub 3}.« less

Nonlinear conductivity of a holographic superconductor under constant electric field

NASA Astrophysics Data System (ADS)

Zeng, Hua Bi; Tian, Yu; Fan, Zheyong; Chen, Chiang-Mei

2017-02-01

The dynamics of a two-dimensional superconductor under a constant electric field E is studied by using the gauge-gravity correspondence. The pair breaking current induced by E first increases to a peak value and then decreases to a constant value at late times, where the superconducting gap goes to zero, corresponding to a normal conducting phase. The peak value of the current is found to increase linearly with respect to the electric field. Moreover, the nonlinear conductivity, defined as an average of the conductivity in the superconducting phase, scales as ˜E-2 /3 when the system is close to the critical temperature Tc, which agrees with predictions from solving the time-dependent Ginzburg-Landau equation. Away from Tc, the E-2 /3 scaling of the conductivity still holds when E is large.

Electrical transport and optical band gap of NiFe2Ox thin films

NASA Astrophysics Data System (ADS)

Bougiatioti, Panagiota; Manos, Orestis; Klewe, Christoph; Meier, Daniel; Teichert, Niclas; Schmalhorst, Jan-Michael; Kuschel, Timo; Reiss, Günter

2017-12-01

We fabricated NiFe2Ox thin films on MgAl2O4(001) by reactive dc magnetron co-sputtering varying the oxygen partial pressure. The fabrication of a material with a variable oxygen deficiency leads to controllable electrical and optical properties which are beneficial for the investigations of the transport phenomena and could, therefore, promote the use of such materials in spintronic and spin caloritronic applications. We used several characterization techniques to investigate the film properties, focusing on their structural, magnetic, electrical, and optical properties. From the electrical resistivity, we obtained the conduction mechanisms that govern the systems in the high and low temperature regimes. We further extracted low thermal activation energies which unveil extrinsic transport mechanisms. The thermal activation energy decreases in the less oxidized samples revealing the pronounced contribution of a large amount of electronic states localized in the band gap to the electrical conductivity. The Hall coefficient is negative and decreases with increasing conductivity as expected for n-type conduction, while the Hall- and the drift mobilities show a large difference. The optical band gaps were determined via ultraviolet-visible spectroscopy. They follow a similar trend as the thermal activation energies, with lower band gap values in the less oxidized samples.

Are You Interested? A Meta-Analysis of Relations between Vocational Interests and Employee Performance and Turnover

ERIC Educational Resources Information Center

Van Iddekinge, Chad H.; Roth, Philip L.; Putka, Dan J.; Lanivich, Stephen E.

2011-01-01

A common belief among researchers is that vocational interests have limited value for personnel selection. However, no comprehensive quantitative summaries of interests validity research have been conducted to substantiate claims for or against the use of interests. To help address this gap, we conducted a meta-analysis of relations between…

A potential half-Heusler thermoelectric material ScAuSn: A first principle study

NASA Astrophysics Data System (ADS)

Joshi, H.; Rai, D. P.; Thapa, R. K.

2018-04-01

Density Functional Theory along with semi classical Boltzmann transport theory have been applied to study the electronic and thermoelectric property of the Heusler alloy ScAuSn. It has been found that ScAuSn is an indirect band gap semiconductor with a gap of 0.344 eV. The thermoelectric properties such as electrical conductivity (σ), Seebeck coefficient (S), electronic thermal conductivity (κ) etc. are reported as a function of chemical potential in the region ± 2.0 eV, with respect to constant temperature. The calculated ZT value is almost equal to 1, thus making ScAuSn a potential thermoelectric candidate.

Closing the Social Class Achievement Gap for First-Generation Students in Undergraduate Biology

PubMed Central

Harackiewicz, Judith M.; Canning, Elizabeth A.; Tibbetts, Yoi; Giffen, Cynthia J.; Blair, Seth S.; Rouse, Douglas I.; Hyde, Janet S.

2014-01-01

Many students start college intending to pursue a career in the biosciences, but too many abandon this goal because they struggle in introductory biology. Interventions have been developed to close achievement gaps for underrepresented minority students and women, but no prior research has attempted to close the gap for first-generation students, a population that accounts for nearly a fifth of college students. We report a values affirmation intervention conducted with 798 U.S. students (154 first-generation) in an introductory biology course for majors. For first-generation students, values affirmation significantly improved final course grades and retention in the second course in the biology sequence, as well as overall GPA for the semester. This brief intervention narrowed the achievement gap between first-generation and continuing generation students for course grades by 50% and increased retention in a critical gateway course by 20%. Our results suggest that educators can expand the pipeline for first-generation students to continue studying in the biosciences with psychological interventions. PMID:25049437

Closing Achievement Gaps with a Utility-Value Intervention: Disentangling Race and Social Class

PubMed Central

Harackiewicz, Judith M.; Canning, Elizabeth A.; Tibbetts, Yoi; Priniski, Stacy J.; Hyde, Janet S.

2015-01-01

Many college students abandon their goal of completing a degree in STEM when confronted with challenging introductory-level science courses. In the U.S., this trend is more pronounced for underrepresented minority (URM) and first-generation (FG) students, and contributes to persisting racial and social-class achievement gaps in higher education. Previous intervention studies have focused exclusively on race or social class, but have not examined how the two may be confounded and interact. This research therefore investigates the independent and interactive effects of race and social class as moderators of an intervention designed to promote performance, measured by grade in the course. In a double-blind randomized experiment conducted over four semesters of an introductory biology course (N = 1040), we tested the effectiveness of a utility-value intervention in which students wrote about the personal relevance of course material. The utility-value intervention was successful in reducing the achievement gap for FG-URM students by 61%: the performance gap for FG-URM students, relative to CG-Majority students, was large in the control condition, .84 grade points (d = .98), and the treatment effect for FG-URM students was .51 grade points (d = 0.55). The UV intervention helped students from all groups find utility value in the course content, and mediation analyses showed that the process of writing about utility value was particularly powerful for FG-URM students. Results highlight the importance of examining the independent and interactive effects of race and social class when evaluating interventions to close achievement gaps and the mechanisms through which they may operate. PMID:26524001

Tracing the evolution of the two energy gaps in magnesium diboride under pressure

NASA Astrophysics Data System (ADS)

Kononenko, V.; Tarenkov, V.; Belogolovskii, M.; Döring, S.; Schmidt, S.; Seidel, P.

2015-04-01

We have studied transport characteristics of mesoscopic multiple-mode superconducting contacts formed between two grains in bulk two-gap magnesium diboride. The experimental setup was realized by driving a normal-metal tip into MgB2 polycrystalline sample and proved to be extremely stable, providing possibility to perform pressure experiments at low temperatures. It is argued that in our procedure a small piece of the superconducting electrode is captured by the tip apex and, as a result, two junctions in series are formed: a junction between a tip and MgB2 grain and a mesoscopic disordered contact between two superconducting pellets. Although the relative weight of the first junction resistance was considerably less, its contribution is shown to be important for the comparison of measured data with expected gap values. Two hallmarks of multiple Andreev reflections inside the MgB2-c-MgB2 contact (c stands for a high-transparent constriction), a zero-bias 1/ √{|V | } -like singularity of the dc differential conductance and peaks connected to the two gap values, have been revealed. Finally, we report results of a hydrostatic compression experiment showing the evolution of the MgB2 gap values with pressure. In contrast to the theoretical expectations, we have observed an increase of the smaller gap Δπ whereas the larger gap Δσ decreased with increasing pressure as it should be for the electron-phonon pairing mechanism. We argue that the so-called separable model of anisotropy effects is insufficient to describe such changes and only improved two-band versions are capable to reproduce the pressure effect on the energy gaps in magnesium diboride.

Influence of defects on the absorption edge of InN thin films: The band gap value

NASA Astrophysics Data System (ADS)

Thakur, J. S.; Danylyuk, Y. V.; Haddad, D.; Naik, V. M.; Naik, R.; Auner, G. W.

2007-07-01

We investigate the optical-absorption spectra of InN thin films whose electron density varies from ˜1017tõ1021cm-3 . The low-density films are grown by molecular-beam-epitaxy deposition while highly degenerate films are grown by plasma-source molecular-beam epitaxy. The optical-absorption edge is found to increase from 0.61to1.90eV as the carrier density of the films is increased from low to high density. Since films are polycrystalline and contain various types of defects, we discuss the band gap values by studying the influence of electron degeneracy, electron-electron, electron-ionized impurities, and electron-LO-phonon interaction self-energies on the spectral absorption coefficients of these films. The quasiparticle self-energies of the valence and conduction bands are calculated using dielectric screening within the random-phase approximation. Using one-particle Green’s function analysis, we self-consistently determine the chemical potential for films by coupling equations for the chemical potential and the single-particle scattering rate calculated within the effective-mass approximation for the electron scatterings from ionized impurities and LO phonons. By subtracting the influence of self-energies and chemical potential from the optical-absorption edge energy, we estimate the intrinsic band gap values for the films. We also determine the variations in the calculated band gap values due to the variations in the electron effective mass and static dielectric constant. For the lowest-density film, the estimated band gap energy is ˜0.59eV , while for the highest-density film, it varies from ˜0.60tõ0.68eV depending on the values of electron effective mass and dielectric constant.

Closing achievement gaps with a utility-value intervention: Disentangling race and social class.

PubMed

Harackiewicz, Judith M; Canning, Elizabeth A; Tibbetts, Yoi; Priniski, Stacy J; Hyde, Janet S

2016-11-01

Many college students abandon their goal of completing a degree in science, technology, engineering, or math (STEM) when confronted with challenging introductory-level science courses. In the U.S., this trend is more pronounced for underrepresented minority (URM) and first-generation (FG) students, and contributes to persisting racial and social-class achievement gaps in higher education. Previous intervention studies have focused exclusively on race or social class, but have not examined how the 2 may be confounded and interact. This research therefore investigates the independent and interactive effects of race and social class as moderators of an intervention designed to promote performance, measured by grade in the course. In a double-blind randomized experiment conducted over 4 semesters of an introductory biology course (N = 1,040), we tested the effectiveness of a utility-value intervention in which students wrote about the personal relevance of course material. The utility-value intervention was successful in reducing the achievement gap for FG-URM students by 61%: the performance gap for FG-URM students, relative to continuing generation (CG)-Majority students, was large in the control condition, .84 grade points (d = .98), and the treatment effect for FG-URM students was .51 grade points (d = 0.55). The UV intervention helped students from all groups find utility value in the course content, and mediation analyses showed that the process of writing about utility value was particularly powerful for FG-URM students. Results highlight the importance of intersectionality in examining the independent and interactive effects of race and social class when evaluating interventions to close achievement gaps and the mechanisms through which they may operate. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Gapped fermionic spectrum from a domain wall in seven dimension

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Subir; Rai, Nishal

2018-05-01

We obtain a domain wall solution in maximally gauged seven dimensional supergravity, which interpolates between two AdS spaces and spontaneously breaks a U (1) symmetry. We analyse frequency dependence of conductivity and find power law behaviour at low frequency. We consider certain fermions of supergravity in the background of this domain wall and compute holographic spectral function of the operators in the dual six dimensional theory. We find fermionic operators involving bosons with non-zero expectation value lead to gapped spectrum.

Synthesis and characterization of oligobenzimidazoles: Electrochemical, electrical, optical, thermal and rectification properties

NASA Astrophysics Data System (ADS)

Anand, Siddeswaran; Muthusamy, Athianna

2018-03-01

A series of benzimidazole monomers, (2-(2, 4-dihydroxyphenyl)-1H-benzimidazol-5-yl)(phenyl) methanone (BIKH), 2-(3-ethoxy-2-hydroxyphenyl)-1H-benzo [d]imidazole-5-yl) (phenyl) methanone (BIKE) and 2-(5-bromo-2-hydroxyphenyl)-1H-benzo [d]imidazole-5-yl) (phenyl) methanone (BIKB) were prepared by condensing three substituted aromatic aldehydes with 3, 4-diaminobenzophenone. In aqueous alkaline medium the benzimidazoles were converted in to oligomers by oxidative polycondensation using NaOCl as oxidant. The formation of monomers and oligomers were confirmed with 1H, 13C NMR, FT-IR, and UV-visible spectroscopic techniques. The oligomers were investigated for their optical, electrical, electrochemical and thermal properties. The electrochemical and optical band gaps of monomers and oligomers were calculated using both UV-visible spectroscopy and cyclic voltametry respectively. The band gap values of monomers are compared with band gap values obtained from quantum theoretical calculations with DFT. The electrical conductivity studies of iodine doped and undoped oligomers were done using two point probe technique. It is found that these values are showing good correlation with the charge densities on imidazole nitrogen obtained from Huckel method. The conductivity of oligomers increases with increase in iodine vapour contact time. The dielectric properties of oligomers have been investigated at different temperature and frequency. The dielectric measurement data were used to calculate the AC conductivity and activation energy of oligomers. Oligomer OBIKH is having greater thermal stability due to its number of chain propagation sites than other oligomers and is shown by its high carbines residue of around 60% at 600 °C in thermogravimetric analysis. I-V characteristics of oligobenzimidazole p-n diodes have shown good rectifying nature in the range -4 to 4 V.

Preparation of Highly Conductive Yarns by an Optimized Impregnation Process

NASA Astrophysics Data System (ADS)

Amba Sankar, K. N.; Mohanta, Kallol

2017-12-01

We report the development of the electrical conductivity in textile yarns through impregnation and post-treatment of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The conductive polymer is deposited on fibers, which fills the gap space within the hierarchical structure of the yarns. Organic nonpolar solvents act as reducing agent to increase the density of PEDOT moieties on the yarns, galvanizing increment in conductivity values. Post-treatment by ethylene glycol transforms the resonance configuration of the conductive moieties of conjugated polymer, which helps in further enhancement of electrical conductivity of the yarns. We have optimized the method in terms of loading and conformal change of the polymer to have a lesser resistance of the coated conductive yarns. The minimum resistance achieved has a value of 77 Ωcm-1. This technique of developing conductivity in conventional yarns enables retaining the flexibility of yarns and feeling of softness which would find suitable applications for wearable electronics.

Preparation of Highly Conductive Yarns by an Optimized Impregnation Process

NASA Astrophysics Data System (ADS)

Amba Sankar, K. N.; Mohanta, Kallol

2018-03-01

We report the development of the electrical conductivity in textile yarns through impregnation and post-treatment of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The conductive polymer is deposited on fibers, which fills the gap space within the hierarchical structure of the yarns. Organic nonpolar solvents act as reducing agent to increase the density of PEDOT moieties on the yarns, galvanizing increment in conductivity values. Post-treatment by ethylene glycol transforms the resonance configuration of the conductive moieties of conjugated polymer, which helps in further enhancement of electrical conductivity of the yarns. We have optimized the method in terms of loading and conformal change of the polymer to have a lesser resistance of the coated conductive yarns. The minimum resistance achieved has a value of 77 Ωcm-1. This technique of developing conductivity in conventional yarns enables retaining the flexibility of yarns and feeling of softness which would find suitable␣applications for wearable electronics.

Do Teachers Coming from Diverse Ethno-Cultural Backgrounds Represent an Added Value for the Profession? Findings of a Study Conducted in French-Speaking Switzerland

ERIC Educational Resources Information Center

Akkari, Abdeljalil; Bauer, Stéphanie; Radhouane, Myriam

2017-01-01

Research has drawn attention to a certain gap between the increasing ethno-cultural diversity of school enrolment and the relative ethno-cultural homogeneity of the teaching body. In French-speaking Switzerland very little attention has been paid to this matter. The purpose of this article is to analyse the potential added value associated with…

An evaluation of the 10:30 centerline marking pattern.

DOT National Transportation Integrated Search

1977-01-01

In response to Value Engineering Proposal #M-26, a study of the feasibility of adopting a 10 ft. mark 30 ft. gap centerline pattern for use on 2- and 4-lane rural roads was conducted. The study included a literature review, field studies of traffic s...

Does stapes surgery improve tinnitus in patients with otosclerosis?

PubMed

Ismi, Onur; Erdogan, Osman; Yesilova, Mesut; Ozcan, Cengiz; Ovla, Didem; Gorur, Kemal

Otosclerosis (OS) is the primary disease of the human temporal bone characterized by conductive hearing loss and tinnitus. The exact pathogenesis of tinnitus in otosclerosis patients is not known and factors affecting the tinnitus outcome in otosclerosis patients are still controversial. To find the effect of stapedotomy on tinnitus for otosclerosis patients. Fifty-six otosclerosis patients with preoperative tinnitus were enrolled to the study. Pure tone average Air-Bone Gap values, preoperative tinnitus pitch, Air-Bone Gap closure at tinnitus frequencies were evaluated for their effect on the postoperative outcome. Low pitch tinnitus had more favorable outcome compared to high pitch tinnitus (p=0.002). Postoperative average pure tone thresholds Air-Bone Gap values were not related to the postoperative tinnitus (p=0.213). There was no statistically significant difference between postoperative Air-Bone Gap closure at tinnitus frequency and improvement of high pitch tinnitus (p=0.427). There was a statistically significant difference between Air-Bone Gap improvement in tinnitus frequency and low pitch tinnitus recovery (p=0.026). Low pitch tinnitus is more likely to be resolved after stapedotomy for patients with otosclerosis. High pitch tinnitus may not resolve even after closure of the Air-Bone Gap at tinnitus frequencies. Copyright © 2016 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolgonos, Alex; Mason, Thomas O.; Poeppelmeier, Kenneth R., E-mail: krp@northwestern.edu

2016-08-15

The direct optical band gap of semiconductors is traditionally measured by extrapolating the linear region of the square of the absorption curve to the x-axis, and a variation of this method, developed by Tauc, has also been widely used. The application of the Tauc method to crystalline materials is rooted in misconception–and traditional linear extrapolation methods are inappropriate for use on degenerate semiconductors, where the occupation of conduction band energy states cannot be ignored. A new method is proposed for extracting a direct optical band gap from absorption spectra of degenerately-doped bulk semiconductors. This method was applied to pseudo-absorption spectramore » of Sn-doped In{sub 2}O{sub 3} (ITO)—converted from diffuse-reflectance measurements on bulk specimens. The results of this analysis were corroborated by room-temperature photoluminescence excitation measurements, which yielded values of optical band gap and Burstein–Moss shift that are consistent with previous studies on In{sub 2}O{sub 3} single crystals and thin films. - Highlights: • The Tauc method of band gap measurement is re-evaluated for crystalline materials. • Graphical method proposed for extracting optical band gaps from absorption spectra. • The proposed method incorporates an energy broadening term for energy transitions. • Values for ITO were self-consistent between two different measurement methods.« less

Electronic, Optical and Thermoelectric Properties of 2H-CuAlO2: A First Principles Study

NASA Astrophysics Data System (ADS)

Bhamu, K. C.; Khenata, R.; Khan, Saleem Ayaz; Singh, Mangej; Priolkar, K. R.

2016-01-01

The electronic and optical properties of 2H-CuAlO2, including energy bands, density of states (DOS), optical dielectric behaviour, refractive index, absorption coefficient and optical conductivity, have been investigated within the framework of a full-potential linearized augmented plane wave scheme using different potentials. The direct and indirect band gaps for CuAlO2, computed using the Becke-Johnson potential, are estimated at 3.53 eV and 2.48 eV, respectively, which are in better agreement with the experimentally reported band gaps than those previously computed. The origin of energy bands is elucidated in terms of DOS, while the behaviour of the imaginary part of the dielectric constant is explained in terms of electronic transitions from valence bands to conduction bands. The computed value of the refractive index is 2.25 (1.94) for light perpendicular (parallel) to the c axis, in concordance with the available values. The overall shape of the spectral distribution for absorption coefficient and optical conductivity is also in accord with the reported data. The investigated thermoelectric properties indicate that CuAlO2 is a p-type semiconductor showing high effectiveness at low temperatures.

Poly(aryl-ether-ether-ketone) as a Possible Metalized Film Capacitor Dielectric: Accurate Description of the Band Gap Through Ab Initio Calculation

DTIC Science & Technology

2014-12-01

from standard HSE06 hybrid functional with α = 0.25 and ω = 0.11 bohr–1 and b) from HSE with α = 0.093 and ω of 0.11 bohr–1...better agreement for the band gap value for future calculations, a systemic study was conducted for the (α, ω) parameter space of the HSE ...orthogonal). Future HSE calculations will be performed with the updated parameters. Fig. 7 Density of States of PEEK based on the optimized

Soliton microdynamics and thermal conductivity of uranium nitride at high temperatures

NASA Astrophysics Data System (ADS)

Dubovsky, O. A.; Orlov, A. V.; Semenov, V. A.

2011-09-01

The microdynamics of soliton waves and localized modes of nonlinear vibrations of the acoustic and optical types in uranium nitride has been investigated. It has been shown that, with an increase in the excitation energy in the spectral gap between the bands of optical and acoustic phonons, the energies of solitons increase, whereas the energies of local modes decrease. The previously experimentally observed unidentified quasi-resonant features, which shift in the gap with variations in the temperature, can represent the revealed soliton waves and local modes. The microdynamics of heat conduction of uranium nitride has been studied for the stochastic generation of soliton waves and local modes in the case of spatially distant energy absorption. The thermal conductivity coefficient determined from the temperature gradient and the absorbed energy flux insignificantly exceeds the experimentally observed values, which are decreased because of the presence of structural defects of different types in the material.

Thermoelectric power factor of La0.9M0.1FeO3 (M = Ca and Ba) system: Structural, band gap and electrical transport evaluations

NASA Astrophysics Data System (ADS)

Karthikeyan, N.; Kumar, R. Ramesh; Jaiganesh, G.; Sivakumar, K.

2018-01-01

The search for thermoelectric materials has been incredibly increased due to the increase in global energy demand. Hence the present work focus on preparation and characterization of thermal transport phenomena of pure and Ba/Ca substituted perovskite LaFeO3 orthoferrite system. The conventional solid state reaction technique is utilized for the preparation of LaFeO3 and La0.9M0.1FeO3 (M = Ca and Ba) compounds. Crystal structure analyses of the prepared samples are analyses using Rietveld refinement process which confirms the orthoferrite crystal structure of all the prepared compounds with induced distortion in position of atoms by the incorporation of substituent atoms. The electronic structure calculations are performed by VASP. As the LaFeO3 compound is a strongly energy correlated system, the Density Functional Theory (DFT) calculations are performed by DFT + U (Hubbard function) method. The computed band gap values are compared with the energy gap values calculated from UV-Vis spectral analysis. Electrical conductivity measurement and Arrhenius behavior for the temperature range of room temperature to 650 K are analyzed and the drift increase in conductivity with respect to temperature is due to the thermally activated mobility of charge carriers. Temperature dependent thermopower analysis is also examined using homemade seebeck coefficient measurement system. The calculation of thermoelectric power factor reveals that the Ba substituted LaFeO3 compound show highest power factor value of 3.73 μW/K2 cm at higher temperature and the superior power factor values observed in the Ba substituted compound determine the material's capability in power generating devices based on thermoelectric effect.

AB INITIO STUDY OF OPTOELECTRONIC PROPERTIES OF SPINEL ZnAl2O4 BEYOND GGA AND LDA

NASA Astrophysics Data System (ADS)

Yousaf, Masood; Saeed, M. A.; Isa, Ahmad Radzi Mat; Rahnamaye Aliabad, H. A.; Noor, N. A.

2012-12-01

Electronic band structure and optical parameters of ZnAl2O4 are investigated by first-principles technique based on a new potential approximation, known as modified Becke-Johnson (mBJ). This method describes the excited states of insulators and semiconductors more accurately The recent direct band gap result by EV-GGA is underestimated by about 15% compared to our band gap value using mBJ-GGA. The value of the band gap of ZnAl2O4 decreases as follows: Eg(mBJ-GGA/LDA) > Eg(GGA) > Eg(LDA). The band structure base optical parametric quantities (dielectric constant, index of refraction, reflectivity and optical conductivity) are also calculated, and their variations with energy range are discussed. The first critical point (optical absorption's edge) in ZnAl2O4 occurs at about 5.26 eV in case of mBJ. This study about the optoelectronic properties indicates that ZnAl2O4 can be used in optical devices.

Understanding the carbon dioxide gaps.

PubMed

Scheeren, Thomas W L; Wicke, Jannis N; Teboul, Jean-Louis

2018-06-01

The current review attempts to demonstrate the value of several forms of carbon dioxide (CO2) gaps in resuscitation of the critically ill patient as monitor for the adequacy of the circulation, as target for fluid resuscitation and also as predictor for outcome. Fluid resuscitation is one of the key treatments in many intensive care patients. It remains a challenge in daily practice as both a shortage and an overload in intravascular volume are potentially harmful. Many different approaches have been developed for use as target of fluid resuscitation. CO2 gaps can be used as surrogate for the adequacy of cardiac output (CO) and as marker for tissue perfusion and are therefore a potential target for resuscitation. CO2 gaps are easily measured via point-of-care analysers. We shed light on its potential use as nowadays it is not widely used in clinical practice despite its potential. Many studies were conducted on partial CO2 pressure differences or CO2 content (cCO2) differences either alone, or in combination with other markers for outcome or resuscitation adequacy. Furthermore, some studies deal with CO2 gap to O2 gap ratios as target for goal-directed fluid therapy or as marker for outcome. CO2 gap is a sensitive marker of tissue hypoperfusion, with added value over traditional markers of tissue hypoxia in situations in which an oxygen diffusion barrier exists such as in tissue oedema and impaired microcirculation. Venous-to-arterial cCO2 or partial pressure gaps can be used to evaluate whether attempts to increase CO should be made. Considering the potential of the several forms of CO2 measurements and its ease of use via point-of-care analysers, it is recommendable to implement CO2 gaps in standard clinical practice.

Thermoelectric transport properties of BaBiTe{sub 3}-based materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yiming; Zhao, Li-Dong, E-mail: zhaolidong@buaa.edu.cn

BaBiTe{sub 3}, a material with low thermal conductivity, is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. We choose two types of dopants, K and La, trying to optimize its electrical transport properties. The minority carriers, which harm the Seebeck coefficient in this system, are suppressed by La doping. With the increase of both electrical conductivity and Seebeck coefficient, the power factor of 3% La doped BaBiTe{sub 3} reaches 3.7 μW cm{sup −1} K{sup −2} which increased by 40% from undoped BaBiTe{sub 3}. Besides high power factor, the thermal conductivity is alsomore » reduced in it. Eventually, a high ZT value, 0.25 at 473 K, for n-type BaBiTe{sub 3} is achieved in 3% La doped BaBiTe{sub 3}. - Graphical abstract: BaBiTe{sub 3} possesses a low thermal conductivity. However, it is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. A high ZT value of 0.25 at 473 K for n-type BaBiTe{sub 3} can be achieved through optimizing electrical transport properties via La doping. - Highlights: • BaBiTe{sub 3} is an analogue of these promising thermoelectric materials: such as CsBi{sub 4}Te{sub 6} and K{sub 2}Bi{sub 8}Se{sub 13}, etc. • BaBiTe{sub 3} possesses a low thermal conductivity. • La is an effective dopant to enhance electrical transport properties. • A high ZT value of 0.25 at 473 K can be achieved in n-type La-doped BaBiTe{sub 3}.« less

Additional flow field studies of the GA(W)-1 airfoil with 30-percent chord Fowler flap including slot-gap variations and cove shape modifications

NASA Technical Reports Server (NTRS)

Wentz, W. H., Jr.; Ostowari, C.

1983-01-01

Experimental measurements were made to determine the effects of slot gap opening and flap cove shape on flap and airfoil flow fields. Test model was the GA(W)-1 airfoil with 0.30c Fowler flap deflected 35 degrees. Tests were conducted with optimum, wide and narrow gaps, and with three cove shapes. Three test angles were selected, corresponding to pre-stall and post-stall conditions. Reynolds number was 2,200,000 and Mach number was 0.13. Force, surface pressure, total pressure, and split-film turbulence measurements were made. Results were compared with theory for those parameters for which theoretical values were available.

Ephaptic coupling rescues conduction failure in weakly coupled cardiac tissue with voltage-gated gap junctions

NASA Astrophysics Data System (ADS)

Weinberg, S. H.

2017-09-01

Electrical conduction in cardiac tissue is usually considered to be primarily facilitated by gap junctions, providing a pathway between the intracellular spaces of neighboring cells. However, recent studies have highlighted the role of coupling via extracellular electric fields, also known as ephaptic coupling, particularly in the setting of reduced gap junction expression. Further, in the setting of reduced gap junctional coupling, voltage-dependent gating of gap junctions, an oft-neglected biophysical property in computational studies, produces a positive feedback that promotes conduction failure. We hypothesized that ephaptic coupling can break the positive feedback loop and rescue conduction failure in weakly coupled cardiac tissue. In a computational tissue model incorporating voltage-gated gap junctions and ephaptic coupling, we demonstrate that ephaptic coupling can rescue conduction failure in weakly coupled tissue. Further, ephaptic coupling increased conduction velocity in weakly coupled tissue, and importantly, reduced the minimum gap junctional coupling necessary for conduction, most prominently at fast pacing rates. Finally, we find that, although neglecting gap junction voltage-gating results in negligible differences in well coupled tissue, more significant differences occur in weakly coupled tissue, greatly underestimating the minimal gap junctional coupling that can maintain conduction. Our study suggests that ephaptic coupling plays a conduction-preserving role, particularly at rapid heart rates.

Width-Dependent Band Gap in Armchair Graphene Nanoribbons Reveals Fermi Level Pinning on Au(111)

PubMed Central

2017-01-01

We report the energy level alignment evolution of valence and conduction bands of armchair-oriented graphene nanoribbons (aGNR) as their band gap shrinks with increasing width. We use 4,4″-dibromo-para-terphenyl as the molecular precursor on Au(111) to form extended poly-para-phenylene nanowires, which can subsequently be fused sideways to form atomically precise aGNRs of varying widths. We measure the frontier bands by means of scanning tunneling spectroscopy, corroborating that the nanoribbon’s band gap is inversely proportional to their width. Interestingly, valence bands are found to show Fermi level pinning as the band gap decreases below a threshold value around 1.7 eV. Such behavior is of critical importance to understand the properties of potential contacts in GNR-based devices. Our measurements further reveal a particularly interesting system for studying Fermi level pinning by modifying an adsorbate’s band gap while maintaining an almost unchanged interface chemistry defined by substrate and adsorbate. PMID:29049879

Technique for enhancing the power output of an electrostatic generator employing parametric resonance

DOEpatents

Post, Richard F.

2016-02-23

A circuit-based technique enhances the power output of electrostatic generators employing an array of axially oriented rods or tubes or azimuthal corrugated metal surfaces for their electrodes. During generator operation, the peak voltage across the electrodes occurs at an azimuthal position that is intermediate between the position of minimum gap and maximum gap. If this position is also close to the azimuthal angle where the rate of change of capacity is a maximum, then the highest rf power output possible for a given maximum allowable voltage at the minimum gap can be attained. This rf power output is then coupled to the generator load through a coupling condenser that prevents suppression of the dc charging potential by conduction through the load. Optimized circuit values produce phase shifts in the rf output voltage that allow higher power output to occur at the same voltage limit at the minimum gap position.

Bridging the Gap: Integrating Information Literacy into Communication Courses

ERIC Educational Resources Information Center

Sjoberg, Lisa M.; Ahlfeldt, Stephanie L.

2010-01-01

Information literacy programs focus on teaching students how to conduct effective research. Perhaps even more important is that they teach students how to critically evaluate the information they find. Engaging students in a significant information literacy unit helps them realize the value of the research process and the limitations of relying…

Closing the Gap: Impact of Student Proactivity and Learning Goal Orientation on E-Learning Outcomes

ERIC Educational Resources Information Center

Kickul, Gerard; Kickul, Jill

2006-01-01

To increase flexibility in course offerings and to enhance student-learning experiences, universities and management educators have introduced and incorporated a number of new and innovative e-learning technologies. However, little systematic research has been conducted to examine the value of using the technology to facilitate learning and…

Controlling the optical properties of polyaniline doped by boric acid particles by changing their doping agent and initiator concentration

NASA Astrophysics Data System (ADS)

Cabuk, Mehmet; Gündüz, Bayram

2017-12-01

In this study, polyaniline doped by boric acid (PAni:BA) conducting polymers were chemically synthesized by oxidative polymerization method using (NH4)2S208 (APS) as initiator. Pani:BA conducting polymers were synthesized by using two different APS/aniline molar ratios as 1:1 and 2:1. Their results were compared with PAni doped by HCl (PAni) conducting polymer. Structural properties of the PAni, PAni:BA (1:1) and PAni:BA (2:1) conducting polymers were characterized by using FTIR, SEM, TGA, particle size and apparent density measurements. Effects of doping agents and initiator concentrations on optical properties were investigated in detail. The optoelectronic parameters such as absorption band edge, molar extinction coefficient, direct allowed band gap, refractive index, optical conductance and electrical conductance of the PAni, PAni:BA (1:1) and PAni:BA (2:1) were determined. The absorption band edge and direct allowed band gap of PAni were decreased with doping BA and increasing APS ratio. Also, the refractive index values of the materials were calculated from experimental results and compared with obtained results from Moss, Ravindra, Herve-Vandamme, Reddy and Kumar-Singh relations.

The gender gap in relation to happiness and preferences in married couples after childbirth: evidence from a field experiment in rural Ghana.

PubMed

Kamiya, Yusuke; Akpalu, Bright; Mahama, Emmanuel; Ayipah, Emmanuel Kwesi; Owusu-Agyei, Seth; Hodgson, Abraham; Shibanuma, Akira; Kikuchi, Kimiyo; Jimba, Masamine

2017-03-15

How does the gap in preferences between married couples affect their happiness after childbirth? Are couples that share similar preferences happier? In recent years, gender, marriage, and happiness have been considered to be key issues in public health research. Although much research has examined the happiness status of married couples, practically no study has explored the gender gap in relation to happiness and the preferences of married couples after childbirth. Therefore, our study was conducted to assess the association between the preference gap and the happiness status among married couples in the afterbirth period. We conducted a field experiment in rural communities in the Brong-Ahafo region of Ghana. Participants were 80 married couples who had experienced childbirth within 2 years prior to the survey. As preference indicators, we measured trust, reciprocity, altruism, and risk lovingness through an economic experiment. Then, we assessed how, for a couple, the gap between these preferences affected their happiness. Wives' happiness was positively associated with the absolute value of the gap in risk lovingness between a couple (OR = 4.83, p = 0.08), while husbands' happiness was negatively associated with the gap in trust (OR = -3.58, p = 0.04) or altruism (OR = -3.33, p = 0.02). Within a couple, wives felt greater happiness than their husbands if there was a wider gap in trust (OR = 6.22, p = 0.01), reciprocity (OR = 2.80, p = 0.01), or risk lovingness (OR = 3.81, p = 0.07). The gender gaps in the preference indicators were found to be closely associated with the happiness levels between married couples after childbirth. For the further improvement of maternal and child health, we must consider the gender gaps between couples in relation to happiness and preferences.

High electron doping to a wide band gap semiconductor 12CaO•7Al2O3 thin film

NASA Astrophysics Data System (ADS)

Miyakawa, Masashi; Hirano, Masahiro; Kamiya, Toshio; Hosono, Hideo

2007-04-01

High-density electrons (˜1.9×1021cm-3) were doped into a polycrystalline film of a wide band gap (˜7eV) semiconductor 12CaO•7Al2O3 (C12A7) by an in situ postdeposition reduction treatment using an oxygen-deficient C12A7 overlayer. The resultant film exhibits metallic conduction with a Hall mobility of ˜2.5cm2V-1s-1 and a conductivity of ˜800Scm-1. Optical analyses indicate that most of the doped electrons behave as free carriers with an effective mass of 0.82me and the estimated in-grain mobility is 5.2cm2V-1s-1, which agrees reasonably with the value obtained for high-quality single crystals.

Temperature dependent charge transport in poly(3-hexylthiophene) diodes

NASA Astrophysics Data System (ADS)

Rahaman, Abdulla Bin; Sarkar, Atri; Banerjee, Debamalya

2018-04-01

In this work, we present charge transport properties of poly(3-hexylthiophene) (P3HT) diodes under dark conditions. Temperature dependent current-voltage (J-V) characteristics shows that charge transport represents a transition from ohomic to trap limited current. The forward current density obeys a power law J˜Vm, m>2 represents the space charge limited current region in presence of traps within the band gap. Frequency dependent conductivity has been studied in a temperature range 150K-473K. The dc conductivity values show Arrhenius like behavior and it gives conductivity activation energy 223 meV. Temperature dependent conductivity indicates a thermodynamic transition of our system.

77 FR 56189 - Proposed Information Collection; Comment Request; Elwha River Dam Removal and Floodplain...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-12

... approval for a new information collection to conduct a pilot study to test the Elwha River Dam Removal and... important gap in research on indirect and nonuse values provided by habitat restoration. A study of the... losses associated with the reservoir. The ability to link results of the study to precise measures of...

40 CFR 8.8 - Comprehensive environmental evaluation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... conduct of scientific research and on other existing uses and values; (10) An identification of gaps in... evaluation. (a) Preparation of a CEE. Unless a PERM or an IEE has been submitted and determined to meet the... evaluate the CEE to determine if the CEE meets the requirements under Article 8 and Annex I to the Protocol...

Ethical Crisis in the Nigerian Education System: A Challenge to Educational Administrators and Parents

ERIC Educational Resources Information Center

Ojogwu, C. N.

2008-01-01

Nigeria's National Policy on Education stresses functional knowledge and skills, and development of character and values. But there is a growing gap between policy and practice. This is apparent in the unethical behaviour of many students, and sometimes staff, as manifested in their involvement in secret cults, undisciplined conduct, and…

Electronic transition and electrical transport properties of delafossite CuCr1-xMgxO2 (0 ≤ x ≤ 12%) films prepared by the sol-gel method: A composition dependence study

NASA Astrophysics Data System (ADS)

Han, M. J.; Duan, Z. H.; Zhang, J. Z.; Zhang, S.; Li, Y. W.; Hu, Z. G.; Chu, J. H.

2013-10-01

Highly transparent CuCr1-xMgxO2 (0 ≤ x ≤ 12%) films were prepared on (001) sapphire substrates by sol-gel method. The microstructure, phonon modes, optical band gap, and electrical transport properties have been systematically discussed. It was found that Mg-doping improved the crystal quality and enhanced the (00l) preferred orientation. The spectral transmittance of films approaches about 70%-75% in the visible-near-infrared wavelength region. With increasing Mg-composition, the optical band gap first declines and climbs up due to the band gap renormalization and Burstein-Moss effect. The direct and indirect band gaps of CuCr0.94Mg0.06O2 film are 3.00 and 2.56 eV, respectively. In addition, it shows a crossover from the thermal activation behavior to that of three-dimensional variable range hopping from temperature-dependent electrical conductivity. The crossover temperature decreases with increasing Mg-doping composition, which can be ascribed to the change of spin-charge coupling between the hole and the local spin at Cr site. It should be noted that the electrical conductivity of CuCr1-xMgxO2 films becomes larger with increasing x value. The highest electrical conductivity of 3.85 S cm-1 at room temperature for x = 12% is four-order magnitude larger than that (8.81 × 10-4 S cm-1) for pure CuCrO2 film. The high spectral transmittance and larger conductivity indicate that Mg-doped CuCrO2 films are promising for optoelectronic device applications.

Millimeter wave transmission studies of YBa2Cu3O7-delta thin films in the 26.5 to 40.0 GHz frequency range

NASA Technical Reports Server (NTRS)

Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Heinen, V. O.; Warner, J. D.; Valco, G. J.

1989-01-01

Millimeter wave transmission measurements through YBa2Cu3O(7-delta) thin films on MgO, ZrO2 and LaAlO3 substrates, are reported. The films (approx. 1 micron) were deposited by sequential evaporation and laser ablation techniques. Transition temperatures T sub c, ranging from 89.7 K for the Laser Ablated film on LaAlO3 to approximately 72 K for the sequentially evaporated film on MgO, were obtained. The values of the real and imaginary parts of the complex conductivity, sigma 1 and sigma 2, are obtained from the transmission data, assuming a two fluid model. The BCS approach is used to calculate values for an effective energy gap from the obtained values of sigma sub 1. A range of gap values from 2 DELTA o/K sub B T sub c = 4.19 to 4.35 was obtained. The magnetic penetration depth is evaluated from the deduced values of sigma 2. These results are discussed together with the frequency dependence of the normalized transmission amplitude, P/P sub c, below and above T sub c.

Comparative Evaluation of Marginal and Internal Gap of Co-Cr Copings Fabricated from Conventional Wax Pattern, 3D Printed Resin Pattern and DMLS Tech: An In Vitro Study.

PubMed

Bhaskaran, Eswaran; Azhagarasan, N S; Miglani, Saket; Ilango, T; Krishna, G Phani; Gajapathi, B

2013-09-01

Accuracy of the fit of the restoration has always remained as one of the primary factors in determining success of the restoration. A well fitting restoration needs to be accurate both along its margins and internal surface. This study was conducted to comparatively evaluate the marginal gap and internal gap of cobalt-chromium (Co-Cr) copings fabricated by conventional casting procedures and with direct metal laser sintering (DMLS) technique. Among the total of 30 test samples 10 cast copings were made from inlay casting wax and 10 from 3D printed resin pattern. 10 copings were obtained from DMLS technique. All the 30 test samples were then cemented sequentially on stainless steel model using pressure indicating paste and evaluated for vertical marginal gap in 8 predetermined reference areas. All copings were then removed and partially sectioned and cemented sequentially on same master model for evaluation of internal gap at 4 predetermined reference areas. Both marginal gap and internal gap were measured in microns using video measuring system (VMS2010F). The results obtained for both marginal and internal gap were statistically analyzed and the values fall within the clinically acceptable range. The DMLS technique had an edge over the other two techniques used, as it exhibited minimal gap in the marginal region which is an area of chief concern.

Hearing Outcome With the Use of Glass Ionomer Cement as an Alternative to Crimping in Stapedotomy.

PubMed

Elzayat, Saad; Younes, Ahmed; Fouad, Ayman; Erfan, Fatthe; Mahrous, Ali

2017-10-01

To evaluate early hearing outcomes using glass ionomer cement to fix the Teflon piston prosthesis onto the long process of incus to minimize residual conductive hearing loss after stapedotomy. Original report of prospective randomized control study. Tertiary referral center. A total of 80 consecutive patients with otosclerosis were randomized into two groups. Group A is a control group in which 40 patients underwent small fenestra stapedotomy using the classic technique. Group B included 40 patients who were subjected to small fenestra stapedotomy with fixation of the incus-prosthesis junction with glass ionomer bone cement. Stapedotomy with the classical technique in group A and the alternative technique in group B. The audiometric results before and after surgery. Analysis of the results was performed using the paired t test to compare between pre and postoperative results. χ test was used to compare the results of the two groups. A p value less than 0.05 was considered significant from the statistical standpoint. Significant postoperative improvement of both pure-tone air conduction thresholds and air-bone gaps were reported in the two studied groups. The postoperative average residual air-bone gap and hearing gain were statistically significant in group B (p < 0.05) compared with group A. The use of glass ionomer bone cement in primary otosclerosis surgery using the aforementioned prosthesis and the surgical technique is of significant value in producing maximal closure of the air-bone gap and better audiological outcomes.

Role of the conducting layer substrate on TiO2 nucleation when using microwave activated chemical bath deposition

NASA Astrophysics Data System (ADS)

Zumeta, I.; Espinosa, R.; Ayllón, J. A.; Vigil, E.

2002-12-01

Nanostructured TiO2 is used in novel dye sensitized solar cells. Because of their interaction with light, thin TiO2 films are also used as coatings for self-cleaning glasses and tiles. Microwave activated chemical bath deposition represents a simple and cost-effective way to obtain nanostructured TiO2 films. It is important to study, in this technique, the role of the conducting layer used as the substrate. The influence of microwave-substrate interactions on TiO2 deposition is analysed using different substrate positions, employing substrates with different conductivities, and also using different microwave radiation powers for film deposition. We prove that a common domestic microwave oven with a large cavity and inhomogeneous radiation field can be used with equally satisfactory results. The transmittance spectra of the obtained films were studied and used to analyse film thickness and to obtain gap energy values. The results, regarding different indium-tin oxide resistivities and different substrate positions in the oven cavity, show that the interaction of the microwave field with the conducting layer is determinant in layer deposition. It has also been found that film thickness increases with the power of the applied radiation while the gap energies of the TiO2 films decrease approaching the 3.2 eV value reported for bulk anatase. This indicates that these films are not crystalline and it agrees with x-ray spectra that do not reveal any peak.

Ab initio study of the structural, electronic, elastic and thermal conductivity properties of SrClF with pressure effects

NASA Astrophysics Data System (ADS)

Lv, Zhen-Long; Cui, Hong-Ling; Wang, Hui; Li, Xiao-Hong; Ji, Guang-Fu

2017-04-01

SrClF is an important optical crystal and can be used as pressure gauge in diamond anvil cell at high pressure. In this work, we performed a systematic study on the structural, electronic and elastic properties of SrClF under pressure, as well as its thermal conductivity, by first-principles calculation. Different exchange-correlation functionals were tested and PBESOL was finally chosen to study these properties of SrClF. Studies reveal that SrClF has a bulk modulus of about 56.2 GPa (by fitting equation of states) or 54.3 GPa (derived from elastic constants), which agree well with the experimental result. SrClF is mechanically and dynamically stable up to 50 GPa. Its elastic constants increase with the applied pressure, but its mechanical anisotropy deteriorates as the pressure increases. Investigation of its electronic properties reveals that SrClF is a direct band-gap insulator with a gap value of 5.73 eV at 0 GPa, which decreases with the increasing pressure and the reason is found by analysing the partial density of states. Based on the calculated phonon dispersion curves, thermal conductivity of SrClF is predicated. At ambient conditions, the predicted thermal conductivity is about 3.74 Wm-1 K-1, while that obtained using the simplified Slack model give a slightly larger value of 4.62 Wm-1 K-1.

University of Colorado Faculty Service: A Value Gap?

ERIC Educational Resources Information Center

Snead, Robert C.

2010-01-01

This dissertation investigates a possible service-value gap between faculty valuing of service categories and their perceptions of departmental valuing of these service categories at the University of Colorado. The service gap was shown to be statistically significant for most service categories on most campuses using a t-test for each…

A note on anomalous band-gap variations in semiconductors with temperature

NASA Astrophysics Data System (ADS)

Chakraborty, P. K.; Mondal, B. N.

2018-03-01

An attempt is made to theoretically study the band-gap variations (ΔEg) in semiconductors with temperature following the works, did by Fan and O'Donnell et al. based on thermodynamic functions. The semiconductor band-gap reflects the bonding energy. An increase in temperature changes the chemical bondings, and electrons are promoted from valence band to conduction band. In their analyses, they made several approximations with respect to temperature and other fitting parameters leading to real values of band-gap variations with linear temperature dependences. In the present communication, we have tried to re-analyse the works, specially did by Fan, and derived an analytical model for ΔEg(T). Because, it was based on the second-order perturbation technique of thermodynamic functions. Our analyses are made without any approximations with respect to temperatures and other fitting parameters mentioned in the text, leading to a complex functions followed by an oscillating nature of the variations of ΔEg. In support of the existence of the oscillating energy band-gap variations with temperature in a semiconductor, possible physical explanations are provided to justify the experimental observation for various materials.

Theoretical study of thermopower behavior of LaFeO3 compound in high temperature region

NASA Astrophysics Data System (ADS)

Singh, Saurabh; Shastri, Shivprasad S.; Pandey, Sudhir K.

2018-04-01

The electronic structure and thermopower (α) behavior of LaFeO3 compound were investigated by combining the ab-initio electronic structures and Boltzmann transport calculations. LSDA plus Hubbard U (U = 5 eV) calculation on G-type anti-ferromagnetic (AFM) configuration gives an energy gap of ˜2 eV, which is very close to the experimentally reported energy gap. The calculated values of effective mass of holes (mh*) in valance band (VB) are found ˜4 times that of the effective mass of electrons (me*) in conduction band (CB). The large effective masses of holes are responsible for the large and positive thermopower exhibited by this compound. The calculated values of α using BoltzTraP code are found to be large and positive in the 300-1200 K temperature range, which is in agreement with the experimentally reported data.

The Relationship between Low-Income and Minority Children's Physical Activity and Academic-Related Outcomes: A Review of the Literature

ERIC Educational Resources Information Center

Efrat, Merav

2011-01-01

This article explores an innovative strategy for battling the obesity epidemic. The strategy involves demonstrating to policy makers and education leaders the value of promoting physical activity in school as a way of enhancing academic-related outcomes to narrow the current achievement gap. A literature review was conducted to ascertain the…

Quasiparticle band gap in the topological insulator Bi2Te3

NASA Astrophysics Data System (ADS)

Nechaev, I. A.; Chulkov, E. V.

2013-10-01

We present a theoretical study of dispersion of states that form the bulk band-gap edges in the three-dimensional topological insulator Bi2Te3. Within density functional theory, we analyze the effect of atomic positions varied within the error range of the available experimental data and approximation chosen for the exchange-correlation functional on the bulk band gap and k-space location of valence- and conduction-band extrema. For each set of the positions with different exchange-correlation functionals, we show how many-body corrections calculated within a one-shot GW approach affect the mentioned characteristics of electronic structure of Bi2Te3. We thus also illustrate to what degree the one-shot GW results are sensitive to the reference one-particle band structure in the case of bismuth telluride. We found that for this topological insulator the GW corrections enlarge the fundamental band gap and for certain atomic positions and reference band structure bring its value in close agreement with experiment.

Acceptor-modulated optical enhancements and band-gap narrowing in ZnO thin films

NASA Astrophysics Data System (ADS)

Hassan, Ali; Jin, Yuhua; Irfan, Muhammad; Jiang, Yijian

2018-03-01

Fermi-Dirac distribution for doped semiconductors and Burstein-Moss effect have been correlated first time to figure out the conductivity type of ZnO. Hall Effect in the Van der Pauw configuration has been applied to reconcile our theoretical estimations which evince our assumption. Band-gap narrowing has been found in all p-type samples, whereas blue Burstein-Moss shift has been recorded in the n-type films. Atomic Force Microscopic (AFM) analysis shows that both p-type and n-type films have almost same granular-like structure with minor change in average grain size (˜ 6 nm to 10 nm) and surface roughness rms value 3 nm for thickness ˜315 nm which points that grain size and surface roughness did not play any significant role in order to modulate the conductivity type of ZnO. X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS) have been employed to perform the structural, chemical and elemental analysis. Hexagonal wurtzite structure has been observed in all samples. The introduction of nitrogen reduces the crystallinity of host lattice. 97% transmittance in the visible range with 1.4 × 107 Ω-1cm-1 optical conductivity have been detected. High absorption value in the ultra-violet (UV) region reveals that NZOs thin films can be used to fabricate next-generation high-performance UV detectors.

Band alignment and p -type doping of ZnSnN2

NASA Astrophysics Data System (ADS)

Wang, Tianshi; Ni, Chaoying; Janotti, Anderson

2017-05-01

Composed of earth-abundant elements, ZnSnN2 is a promising semiconductor for photovoltaic and photoelectrochemical applications. However, basic properties such as the precise value of the band gap and the band alignment to other semiconductors are still unresolved. For instance, reported values for the band gap vary from 1.4 to 2.0 eV. In addition, doping in ZnSnN2 remains largely unexplored. Using density functional theory with the Heyd-Scuseria-Ernzerhof hybrid functional, we investigate the electronic structure of ZnSnN2, its band alignment to GaN and ZnO, and the possibility of p -type doping. We find that the position of the valence-band maximum of ZnSnN2 is 0.39 eV higher than that in GaN, yet the conduction-band minimum is close to that in ZnO, which suggests that achieving p -type conductivity is likely as in GaN, yet it may be difficult to control unintentional n -type conductivity as in ZnO. Among possible p -type dopants, we explore Li, Na, and K substituting on the Zn site. We show that while LiZn is a shallow acceptor, NaZn and KZn are deep acceptors, which we trace back to large local relaxations around the Na and K impurities due to the atomic size mismatches.

How an antenna launches its input power into radiation: thepattern of the Poynting vector at and near an antenna

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, J.D.

2005-05-18

In this paper I first address the question of whether theseat of the power radiated by an antenna made of conducting members isdistributed over the "arms" of the antenna according tomore » $$ - \\bf J \\cdotE$$, where $$\\bf J$$ is the specified current density and $$\\bf E$$ is theelectric field produced by that source. Poynting's theorem permits only aglobal identification of the total input power, usually from a localizedgenerator, with the total power radiated to infinity, not a localcorrespondence of $$- \\bf J \\cdot E\\ d^3x $$ with some specific radiatedpower, $$r^2 \\bf S \\cdot \\hat r\\ d\\Omega $$. I then describe a modelantenna consisting of two perfectly conducting hemispheres of radius\\emph a separated by a small equatorial gap across which occurs thedriving oscillatory electric field. The fields and surface current aredetermined by solution of the boundary value problem. In contrast to thefirst approach (not a boundary value problem), the tangential electricfield vanishes on the metallic surface. There is no radial Poyntingvector at the surface. Numerical examples are shown to illustrate how theenergy flows from the input region of the gap and is guided near theantenna by its "arms" until it is launched at larger \\emph r/a into theradiation pattern determined by the value of \\emph ka.« less

Subjective experience or objective process: understanding the gap between values and practice for involving patients in designing patient-centred care.

PubMed

Lord, Laura; Gale, Nicola

2014-01-01

Patient-centred care and patient involvement are increasingly central concepts in health policy in the UK and elsewhere. However, there is little consensus regarding their definition or how to achieve "patient-centred" care in everyday practice or how to involve patients in service redesign initiatives. The purpose of this paper is to explore these issues from the perspective of key stakeholders within National Health Service (NHS) hospitals in the UK. Semi-structured interviews, covering a range of topics related to service redesign, were conducted with 77 key stakeholders across three NHS Trusts in the West Midlands. In total, 20 of these stakeholders were re-interviewed 18 months later. Data were managed and analysed using the Framework Method. While patient-centred care and patient involvement were regularly cited as important to the stakeholders, a gap persisted between values and reported practice. This gap is explained through close examination of the ways in which the concepts were used by stakeholders, and identifying the way in which they were adapted to fit other organizational priorities. The value placed on positive subjective experience changed to concerns about objective measurement of the patients as they move through the system. Increased awareness and reflection on the conceptual tensions between objective processes and subjective experiences could highlight reasons why patient-centred values fail to translate into improved practice. The paper describes and explains a previously unarticulated tension in health organisations between values and practice in patient centred care and patient involvement in service redesign.

Correcting the anion gap for hypoalbuminaemia does not improve detection of hyperlactataemia

PubMed Central

Dinh, C H; Ng, R; Grandinetti, A; Joffe, A; Chow, D C

2006-01-01

Background An elevated lactate level reflects impaired tissue oxygenation and is a predictor of mortality. Studies have shown that the anion gap is inadequate as a screen for hyperlactataemia, particularly in critically ill and trauma patients. A proposed explanation for the anion gap's poor sensitivity and specificity in detecting hyperlactataemia is that the serum albumin is frequently low. This study therefore, sought to compare the predictive values of the anion gap and the anion gap corrected for albumin (cAG) as an indicator of hyperlactataemia as defined by a lactate ⩾2.5 mmol/l. Methods A retrospective review of 639 sets of laboratory values from a tertiary care hospital. Patients' laboratory results were included in the study if serum chemistries and lactate were drawn consecutively. The sensitivity, specificity, and predictive values were obtained. A receiver operator characteristics curve (ROC) was drawn and the area under the curve (AUC) was calculated. Results An anion gap ⩾12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 39%, 89%, 79%, and 58%, respectively, and a cAG ⩾12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 75%, 59%, 66%, and 69%, respectively. The ROC curves between anion gap and cAG as a predictor of hyperlactataemia were almost identical. The AUC was 0.757 and 0.750, respectively. Conclusions The sensitivities, specificities, and predictive values of the anion gap and cAG were inadequate in predicting the presence of hyperlactataemia. The cAG provides no additional advantage over the anion gap in the detection of hyperlactataemia. PMID:16858097

Multilayered cuprate superconductor Ba2Ca5Cu6O12(O1-x,Fx) 2 studied by temperature-dependent scanning tunneling microscopy and spectroscopy

NASA Astrophysics Data System (ADS)

Sugimoto, Akira; Ekino, Toshikazu; Gabovich, Alexander M.; Sekine, Ryotaro; Tanabe, Kenji; Tokiwa, Kazuyasu

2017-05-01

Scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on a multilayered cuprate superconductor Ba2Ca5Cu6O12 (O1 -x,Fx )2. STM topography revealed random spot structures with the characteristic length ≤0.5 nm. The conductance spectra d I /d V (V ) show the coexistence of smaller gaps ΔS and large gaps (pseudogaps) ΔL. The pseudogap-related features in the superconducting state were traced with the spatial resolution of ˜0.07 nm. Here, I and V are the tunnel current and bias voltage, respectively. The temperature, T , dependence of ΔS follows the reduced Bardeen-Cooper-Schrieffer (BCS) dependence. The hallmark ratio 2 ΔS(T =0 ) /kBTc equals to 4.9, which is smaller than those of other cuprate superconductors. Here, Tc is the superconducting critical temperature and kB is the Boltzmann constant. The larger gap ΔL survives in the normal state and even increases with T above Tc. The T dependencies of the spatial distributions for both relevant gaps (Δ map), as well as for each gap separately (ΔS and ΔL), were obtained. From the histogram of Δ map, the averaged gap values were found to be Δ¯S=˜24 meV and Δ¯L=˜79 meV. The smaller gap ΔS shows a spatially homogeneous distribution while the larger gap ΔL is quite inhomogeneous, indicating that rather homogeneous superconductivity coexists with the patchy distributed pseudogap. The spatial variation length ξΔ L of ΔL correlates with the scale of the topography spot structures, being approximately 0.4 nm. This value is considerably smaller than the coherence length of this class of superconductors, suggesting that ΔL is strongly affected by the disorder of the apical O/F.

30 CFR 285.652 - How long do I have to conduct activities under an approved GAP?

Code of Federal Regulations, 2010 CFR

2010-07-01

... an approved GAP? 285.652 Section 285.652 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF... SHELF Plans and Information Requirements Activities Under An Approved Gap § 285.652 How long do I have to conduct activities under an approved GAP? After MMS approves your GAP, you have: (a) For a limited...

30 CFR 285.652 - How long do I have to conduct activities under an approved GAP?

Code of Federal Regulations, 2011 CFR

2011-07-01

... an approved GAP? 285.652 Section 285.652 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT... FACILITIES ON THE OUTER CONTINENTAL SHELF Plans and Information Requirements Activities Under An Approved Gap § 285.652 How long do I have to conduct activities under an approved GAP? After MMS approves your GAP...

Association Between Local Bipolar Voltage and Conduction Gap Along the Left Atrial Linear Ablation Lesion in Patients With Atrial Fibrillation.

PubMed

Masuda, Masaharu; Fujita, Masashi; Iida, Osamu; Okamoto, Shin; Ishihara, Takayuki; Nanto, Kiyonori; Kanda, Takashi; Sunaga, Akihiro; Tsujimura, Takuya; Matsuda, Yasuhiro; Mano, Toshiaki

2017-08-01

A bipolar voltage reflects a thick musculature where formation of a transmural lesion may be hard to achieve. The purpose of this study was to explore the association between local bipolar voltage and conduction gap in patients with persistent atrial fibrillation (AF) who underwent atrial roof or septal linear ablation. This prospective observational study included 42 and 36 consecutive patients with persistent AF who underwent roof or septal linear ablations, respectively. After pulmonary vein isolation, left atrial linear ablations were performed, and conduction gap sites were identified and ablated after first-touch radiofrequency application. Conduction gap(s) after the first-touch roof and septal linear ablation were observed in 13 (32%) and 19 patients (53%), respectively. Roof and septal area voltages were higher in patients with conduction gap(s) than in those without (roof, 1.23 ± 0.77 vs 0.73 ± 0.42 mV, p = 0.010; septal, 0.96 ± 0.43 vs 0.54 ± 0.18 mV, p = 0.001). Trisected regional analyses revealed that the voltage was higher at the region with a conduction gap than at the region without. Complete conduction block across the roof and septal lines was not achieved in 3 (7%) and 6 patients (17%), respectively. Patients in whom a linear conduction block could not be achieved demonstrated higher ablation area voltage than those with a successful conduction block (roof, 1.91 ± 0.74 vs 0.81 ± 0.51 mV, p = 0.001; septal, 1.15 ± 0.56 vs 0.69 ± 0.31 mV, p = 0.006). In conclusion, a high regional bipolar voltage predicts failure to achieve conduction block after left atrial roof or septal linear ablation. In addition, the conduction gap was located at the preserved voltage area. Copyright © 2017 Elsevier Inc. All rights reserved.

Degenerate p-type conductivity in wide-gap LaCuOS1-xSex (x=0-1) epitaxial films

NASA Astrophysics Data System (ADS)

Hiramatsu, Hidenori; Ueda, Kazushige; Ohta, Hiromichi; Hirano, Masahiro; Kamiya, Toshio; Hosono, Hideo

2003-02-01

Epitaxial films of LaCuOS1-xSex (x=0-1) solid solution were grown on MgO (001) substrates and their electrical and optical properties were examined. Sharp emission due to room-temperature exciton with binding energy of ˜50 meV is observed for all x values. Hall mobility becomes large with an increase in the Se content and it reaches 8.0 cm2V-1s-1 in LaCuOSe, a comparable value to that of p-type GaN:Mg. Doping of Mg2+ ions at La3+ sites enhances a hole concentration up to 2.2×1020 cm-3, while maintaining the Hall mobility as large as 4.0 cm2V-1s-1. Consequently, a degenerate p-type electrical conduction with a conductivity of 140 S cm-1 was achieved.

Crystal growth and electrical properties of CuFeO 2 single crystals

NASA Astrophysics Data System (ADS)

Dordor, P.; Chaminade, J. P.; Wichainchai, A.; Marquestaut, E.; Doumerc, J. P.; Pouchard, M.; Hagenmuller, P.; Ammar, A.

1988-07-01

Delafossite-type CuFeO 2 single crystals have been prepared by a flux method: crystals obtained in a Cu crucible with LiBO 2 as flux are n-type whereas those prepared in a Pt crucible with a Cu 2O flux are p-type. Electrical measurements have revealed that n-type crystals exhibit weak anisotropic conductivities with large activation energies and small mobilities (r.t. values perpendicular and parallel to the c-axis: μ⊥ = 5 × 10 -5 and μ‖ = 10 -7 cm -2 V -1 sec -1). p-type crystals, less anisotropic, are characterized by low activation energies and higher mobilities ( μ⊥ = 34 and μ‖ = 8.9 cm 2 V -1 sec -1). A two -conduction-band model is proposed to account for the difference observed between the energy gap value deduced from photoelectrochemical measurements and the activation energy of the electrical conductivity in the intrinsic domain.

Heat Transfer Coefficient at Cast-Mold Interface During Centrifugal Casting: Calculation of Air Gap

NASA Astrophysics Data System (ADS)

Bohacek, Jan; Kharicha, Abdellah; Ludwig, Andreas; Wu, Menghuai; Karimi-Sibaki, Ebrahim

2018-06-01

During centrifugal casting, the thermal resistance at the cast-mold interface represents a main blockage mechanism for heat transfer. In addition to the refractory coating, an air gap begins to form due to the shrinkage of the casting and the mold expansion, under the continuous influence of strong centrifugal forces. Here, the heat transfer coefficient at the cast-mold interface h has been determined from calculations of the air gap thickness d a based on a plane stress model taking into account thermoelastic stresses, centrifugal forces, plastic deformations, and a temperature-dependent Young's modulus. The numerical approach proposed here is rather novel and tries to offer an alternative to the empirical formulas usually used in numerical simulations for a description of a time-dependent heat transfer coefficient h. Several numerical tests were performed for different coating thicknesses d C, rotation rates Ω, and temperatures of solidus T sol. Results demonstrated that the scenario at the interface is unique for each set of parameters, hindering the possibility of employing empirical formulas without a preceding experiment being performed. Initial values of h are simply equivalent to the ratio of the coating thermal conductivity and its thickness ( 1000 Wm-2 K-1). Later, when the air gap is formed, h drops exponentially to values at least one order of magnitude smaller ( 100 Wm-2 K-1).

Effect of Sb in thick InGaAsSbN layers grown by liquid phase epitaxy

NASA Astrophysics Data System (ADS)

Donchev, V.; Milanova, M.; Asenova, I.; Shtinkov, N.; Alonso-Álvarez, D.; Mellor, A.; Karmakov, Y.; Georgiev, S.; Ekins-Daukes, N.

2018-02-01

Dilute nitride InGaAsSbN layers grown by low-temperature liquid phase epitaxy are studied in comparison with quaternary InGaAsN layers grown at the same growth conditions to understand the effect of Sb in the alloy. The lattice mismatch to the GaAs substrate is found to be slightly larger for the InGaAsSbN layers, which is explained by the large atomic radius of Sb. A reduction of the band gap energy with respect to InGaAsN is demonstrated by means of photoluminescence (PL), surface photovoltage (SPV) spectroscopy and tight-binding calculations. The band-gap energies determined from PL and ellipsometry measurements are in good agreement, while the SPV spectroscopy and the tight-binding calculations provide lower values. Possible reasons for these discrepancies are discussed. The PL spectra reveal localized electronic states in the band gap near the conduction band edge, which is confirmed by SPV spectroscopy. The analysis of the power dependence of the integrated PL has allowed determining the dominant radiative recombination mechanisms in the layers. The values of the refraction index in a wide spectral region are found to be higher for the Sb containing layers.

L-Asparagine crystals with wide gap semiconductor features: optical absorption measurements and density functional theory computations.

PubMed

Zanatta, G; Gottfried, C; Silva, A M; Caetano, E W S; Sales, F A M; Freire, V N

2014-03-28

Results of optical absorption measurements are presented together with calculated structural, electronic, and optical properties for the anhydrous monoclinic L-asparagine crystal. Density functional theory (DFT) within the generalized gradient approximation (GGA) including dispersion effects (TS, Grimme) was employed to perform the calculations. The optical absorption measurements revealed that the anhydrous monoclinic L-asparagine crystal is a wide band gap material with 4.95 eV main gap energy. DFT-GGA+TS simulations, on the other hand, produced structural parameters in very good agreement with X-ray data. The lattice parameter differences Δa, Δb, Δc between theory and experiment were as small as 0.020, 0.051, and 0.022 Å, respectively. The calculated band gap energy is smaller than the experimental data by about 15%, with a 4.23 eV indirect band gap corresponding to Z → Γ and Z → β transitions. Three other indirect band gaps of 4.30 eV, 4.32 eV, and 4.36 eV are assigned to α3 → Γ, α1 → Γ, and α2 → Γ transitions, respectively. Δ-sol computations, on the other hand, predict a main band gap of 5.00 eV, just 50 meV above the experimental value. Electronic wavefunctions mainly originating from O 2p-carboxyl, C 2p-side chain, and C 2p-carboxyl orbitals contribute most significantly to the highest valence and lowest conduction energy bands, respectively. By varying the lattice parameters from their converged equilibrium values, we show that the unit cell is less stiff along the b direction than for the a and c directions. Effective mass calculations suggest that hole transport behavior is more anisotropic than electron transport, but the mass values allow for some charge mobility except along a direction perpendicular to the molecular layers of L-asparagine which form the crystal, so anhydrous monoclinic L-asparagine crystals could behave as wide gap semiconductors. Finally, the calculations point to a high degree of optical anisotropy for the absorption and complex dielectric function, with more structured curves for incident light polarized along the 100 and 101 directions.

The identification of conduction gaps after pulmonary vein isolation using a new electroanatomic mapping system.

PubMed

Masuda, Masaharu; Fujita, Masashi; Iida, Osamu; Okamoto, Shin; Ishihara, Takayuki; Nanto, Kiyonori; Kanda, Takashi; Tsujimura, Takuya; Matsuda, Yasuhiro; Okuno, Shota; Ohashi, Takuya; Tsuji, Aki; Mano, Toshiaki

2017-11-01

The reconnection of left atrial-pulmonary vein (LA-PV) conduction after the initial procedure of pulmonary vein (PV) isolation is not rare, and is one of the main cause of atrial fibrillation (AF) recurrence after PV isolation. We investigated feasibility of a new ultrahigh-resolution mapping system using a 64-pole small basket catheter for the identification of LA-PV conduction gaps. This prospective study included 31 consecutive patients (20 with persistent AF) undergoing a second ablation after a PV isolation procedure with LA-PV reconnected conduction at any of the 4 PVs. An LA-PV map was created using the mapping system, and ablation was performed at the estimated gap location. The propagation map identified 54 gaps from 39 ipsilateral PV pairs, requiring manual electrogram reannotation for 23 gaps (43%). Gaps at the anterior and carinal regions of left and right ipsilateral PVs required manual electrogram reannotation more frequently than the other regions. The voltage map could identify the gap only in 19 instances (35%). Electrophysiological properties of the gaps (multiple gaps in the same ipsilateral PVs, conduction time, velocity, width, and length) did not differ between those needing and not needing manual electrogram reannotation. During the gap ablation, either the activation sequence alteration or elimination of PV potentials was observed using a circular catheter placed in the PV, suggesting that all the identified gaps were correct. This new electroanatomic mapping system visualized all the LA-PV gaps in patients undergoing a second AF ablation. Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Thermal Conductivity Measurement of Liquids by Using a Suspended Microheater

NASA Astrophysics Data System (ADS)

Oh, Dong-Wook

2017-10-01

In this paper, the traditional 3ω method is modified in order to measure the thermal conductivity of a droplet of liquid. The 3ω sensor is microfabricated using bulk silicon etching on a silicon wafer to form a microheater on a suspended bridge structure. The Si substrate of over 400 μ m thickness beneath the microheater is etched away so that the sample liquid can fill the gap created between the heater and the bottom boundary of the sensor. The frequency of the sinusoidal heating pulses that are generated from the heater is controlled such that the thermal penetration depth is much smaller than the thickness of the liquid layer. The temperature oscillation of the sample fluid is measured at the thin-film heater to calculate the thermal conductivity of the surrounding fluid. The thermal conductivity and measured values of the de-ionized water and ethanol show a good agreement with the theoretical values at room temperature.

Gate-tunable transport characteristics of Bi2S3 nanowire transistors

NASA Astrophysics Data System (ADS)

Kilcoyne, Colin; Ali, Ahmed H.; Alsaqqa, Ali M.; Rahman, Ajara A.; Whittaker-Brooks, Luisa; Sambandamurthy, Ganapathy

2018-02-01

Electrical transport and resistance noise spectroscopy measurements are performed on individual, single crystalline Bi2S3 nanowires in the field-effect geometry. The nanowires exhibit n-type conduction and device characteristics such as activation energy, ON/OFF ratio, and mobility are calculated over a temperature range of 120-320 K and at several bias values. The noise magnitude is measured between 0.01 and 5 Hz at several gate voltages as the device turns from it's OFF to ON state. The presence of mid-gap states which act as charge traps within the band gap can potentially explain the observed transport characteristics. Sulfur vacancies are the likely origin of these mid-gap states which makes Bi2S3 nanowires appealing for defect engineering as a means to enhance its optoelectronic properties and also to better understand the important role of defects in nanoscale semiconductors.

Structural and optical characterization of PVA:KMnO4 based solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Abdullah, Omed Gh.; Aziz, Shujahadeen B.; Rasheed, Mariwan A.

Solid polymer electrolyte films of polyvinyl alcohol (PVA) doped with a different weight percent of potassium permanganate (KMnO4) were prepared by standard solution cast method. XRD and FTIR techniques were performed for structural study. Complex formation between the PVA polymer and KMnO4 salt was confirmed by Fourier transform infrared (FTIR) spectroscopy. The description of crystalline nature of the solid polymer electrolyte films has been confirmed by XRD analysis. The UV-Visible absorption spectra were analyzed in terms of absorption formula for non-crystalline materials. The fundamental optical parameters such as optical band gap energy, refractive index, optical conductivity, and dielectric constants have been investigated and showed a clear dependence on the KMnO4 concentration. The observed value of optical band gap energy for pure PVA is about 6.27 eV and decreases to a value 3.12 eV for the film sample formed with 4 wt% KMnO4 salt. The calculated values of refractive index and the dielectric constants of the polymer electrolyte films increase with increasing KMnO4 content.

A consumption value-gap analysis for sustainable consumption.

PubMed

Biswas, Aindrila

2017-03-01

Recent studies on consumption behavior have depicted environmental apprehension resulting from across wide consumer segments. However, this has not been widely reflected upon the growth in the market shares for green or environment-friendly products mostly because gaps exist between consumers' expectations and perceptions for those products. Previous studies have highlighted the impact of perceived value on potential demand, consumer satisfaction and behavioral intentions. The necessity to understand the effects of gaps in expected and perceived values on consumers' behavioral intention and potential demand for green products cannot be undermined as it shapes the consumers' inclination to repeated purchase and consumption and thus foster potential market demand. Pertaining to this reason, the study aims to adopt a consumption value-gap model based on the theory of consumption values to assess their impact on sustainable consumption behavior and market demand of green products. Consumption value refers to the level of fulfillment of consumer needs by assessment of net utility derived after effective comparison between the benefits (financial or emotional) and the gives (money, time, or energy). The larger the gaps the higher will be the adversarial impact on behavioral intentions. A structural equation modeling was applied to assess data collected through questionnaire survey. The results indicate that functional value-gap and environmental value-gap has the most adversarial impact on sustainable consumption behavior and market demand for green products.

Field dependence of the vortex core size probed by scanning tunneling microscopy

DOE PAGES

Fente, A.; Herrera, E.; Guillamón, I.; ...

2016-07-29

We study the spatial distribution of the density of states (DOS) at zero bias N(r) in the mixed state of single and multigap superconductors. We provide an analytic expression for N(r) based on deGennes' relationship between DOS and the order parameter that reproduces well scanning tunneling microscopy (STM) data in several superconducting materials. In the single gap superconductor β-Bi 2 Pd, we find that N(r) is governed by a length scale ξ H =more » $$\\sqrt{Φ0/2πH}$$ which decreases in rising fields. The vortex core size $C$ ∝ (d Δ/dr| r→0) ₋1 differs from ξ H by a material dependent numerical factor. The new data on the tunneling conductance and vortex lattice of the 2H-NbSe 1.8S 0.2 show the in-plane isotropic vortices, suggesting that substitutional scattering removes the in-plane anisotropy found in the two-gap superconductor 2H-NbSe 2. We fit the tunneling conductance of 2H-NbSe 1.8S 0.2 to a two gap model and calculate the vortex core size $C$ for each band. We find that $C$ is field independent and has the same value for both bands. We also analyze the two-band superconductor 2H-NbSe 2 and find the same result. Lastly, we conclude that, independently of the magnetic field induced variation of the order parameter values in both bands, the spatial variation of the order parameter close to the vortex core is the same for all bands.« less

Field dependence of the vortex core size probed by scanning tunneling microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fente, A.; Herrera, E.; Guillamón, I.

We study the spatial distribution of the density of states (DOS) at zero bias N(r) in the mixed state of single and multigap superconductors. We provide an analytic expression for N(r) based on deGennes' relationship between DOS and the order parameter that reproduces well scanning tunneling microscopy (STM) data in several superconducting materials. In the single gap superconductor β-Bi 2 Pd, we find that N(r) is governed by a length scale ξ H =more » $$\\sqrt{Φ0/2πH}$$ which decreases in rising fields. The vortex core size $C$ ∝ (d Δ/dr| r→0) ₋1 differs from ξ H by a material dependent numerical factor. The new data on the tunneling conductance and vortex lattice of the 2H-NbSe 1.8S 0.2 show the in-plane isotropic vortices, suggesting that substitutional scattering removes the in-plane anisotropy found in the two-gap superconductor 2H-NbSe 2. We fit the tunneling conductance of 2H-NbSe 1.8S 0.2 to a two gap model and calculate the vortex core size $C$ for each band. We find that $C$ is field independent and has the same value for both bands. We also analyze the two-band superconductor 2H-NbSe 2 and find the same result. Lastly, we conclude that, independently of the magnetic field induced variation of the order parameter values in both bands, the spatial variation of the order parameter close to the vortex core is the same for all bands.« less

Distribution Characteristics of Air-Bone Gaps – Evidence of Bias in Manual Audiometry

PubMed Central

Margolis, Robert H.; Wilson, Richard H.; Popelka, Gerald R.; Eikelboom, Robert H.; Swanepoel, De Wet; Saly, George L.

2015-01-01

Objective Five databases were mined to examine distributions of air-bone gaps obtained by automated and manual audiometry. Differences in distribution characteristics were examined for evidence of influences unrelated to the audibility of test signals. Design The databases provided air- and bone-conduction thresholds that permitted examination of air-bone gap distributions that were free of ceiling and floor effects. Cases with conductive hearing loss were eliminated based on air-bone gaps, tympanometry, and otoscopy, when available. The analysis is based on 2,378,921 threshold determinations from 721,831 subjects from five databases. Results Automated audiometry produced air-bone gaps that were normally distributed suggesting that air- and bone-conduction thresholds are normally distributed. Manual audiometry produced air-bone gaps that were not normally distributed and show evidence of biasing effects of assumptions of expected results. In one database, the form of the distributions showed evidence of inclusion of conductive hearing losses. Conclusions Thresholds obtained by manual audiometry show tester bias effects from assumptions of the patient’s hearing loss characteristics. Tester bias artificially reduces the variance of bone-conduction thresholds and the resulting air-bone gaps. Because the automated method is free of bias from assumptions of expected results, these distributions are hypothesized to reflect the true variability of air- and bone-conduction thresholds and the resulting air-bone gaps. PMID:26627469

Prediction of in-depth gap heating ratios from wing glove model test data. [space shuttle orbiter

NASA Technical Reports Server (NTRS)

1977-01-01

In-depth gap heating ratios were predicted down RSI tile sidewalls based on temperature measurements obtained from the JSC arc-jet Wing Glove model tests in order to develop gap heating ratios which resulted in the best possible fit of test data and to produce a set of engineering verification heating ratios similar in shape to one another which could be used at various body points on the Orbiter during reentry. The Rockwell TPS Multidimensional heat conduction program was used to perform 3-D thermal analyses using a 3.0 in. thick section of a curved RSI tile with 283 nodal points. Correlation with test data shows that the predicted heating ratios were significantly higher down in the gap than the zero pressure values for T/C stacks 39 and 38 on the Wing Glove model. For stack 37 (in a low pressure region), the baseline heating ratio overpredicted the temperature data. This analysis, which showed that the heating ratios were a strong function of the product of pressure and pressure gradient, will be used to compare with recent Gap/Step and Ames Double Wedge test/analysis results in the effort to identify the Orbiter gap response to high delta P flight environment.

Oxidative polycondensation of benzimidazole using NaOCl: Synthesis, characterization, optical, thermal and electrical properties of polybenzimidazoles

NASA Astrophysics Data System (ADS)

Anand, Siddeswaran; Muthusamy, Athianna; Dineshkumar, Sengottuvelu; Chandrasekaran, J.

2017-11-01

A series of polybenzimidazole polymers, poly-2-(1H-benzo[d] imidazole-2-yl) phenol (PBIP2), poly-3-(1H-benzo[d] imidazole-2-yl) phenol (PBIP3) and poly-4-(1H-benzo[d] imidazole-2-yl) phenol (PBIP4) were synthesized by oxidative polycondensation of benzimidazole monomers 2-(1H-benzo [d] imidazole-2-yl) phenol (BIP2), 3-(1H-benzo [d] imidazole-2-yl) phenol (BIP3) and 4-(1H-benzo [d] imidazole-2-yl) phenol (BIP4). The structure of benzimidazoles monomers and polybenzimidazoles (PBI) were confirmed by various spectroscopic techniques. The quantum theoretical calculations of band gap energy values of monomers were done with DFT and are compared with its optical band gap energy values. Fluorescence spectra of these compounds showed maximum emission in blue region. The electrical conductivity of PBIs was measured by four-point probe technique and showed good electrical response on iodine doping and conductivity increases with increase iodine doping time. The differences in conductivities among the three PBIs are in accordance with the charge density on imidazole nitrogens calculated by Huckel method. The high carbines residue (∼40%) at 500 °C in thermo gravimetric analysis shows that the PBIs are having reasonably good thermal stability. Polymers have recorded high dielectric constant at low applied frequency of 50 Hz at 393 K. The I-V characteristics of polybenzimidazoles p-n diodes showed rectifying nature with a typical forward to reverse current in the range -4 to 4 V. The high n values are caused by non homogeneities and effect of series resistance.

Peripheral Motor and Sensory Nerve Conduction following Transplantation of Undifferentiated Autologous Adipose Tissue-Derived Stem Cells in a Biodegradable U.S. Food and Drug Administration-Approved Nerve Conduit.

PubMed

Klein, Silvan M; Vykoukal, Jody; Li, De-Pei; Pan, Hui-Lin; Zeitler, Katharina; Alt, Eckhard; Geis, Sebastian; Felthaus, Oliver; Prantl, Lukas

2016-07-01

Conduits preseeded with either Schwann cells or stem cells differentiated into Schwann cells demonstrated promising results for the outcome of nerve regeneration in nerve defects. The concept of this trial combines nerve repair by means of a commercially available nerve guidance conduit and preseeding with autologous, undifferentiated, adipose tissue-derived stem cells. Adipose tissue-derived stem cells were harvested from rats and subsequently seeded onto a U.S. Food and Drug Administration-approved type I collagen conduit. Sciatic nerve gaps 10 mm in length were created, and nerve repair was performed by the transplantation of either conduits preseeded with autologous adipose tissue-derived stem cells or acellular (control group) conduits. After 6 months, the motor and sensory nerve conduction velocity were assessed. Nerves were removed and examined by hematoxylin and eosin, van Gieson, and immunohistochemistry (S100 protein) staining for the quality of axonal regeneration. Nerve gaps treated with adipose tissue-derived stem cells showed superior nerve regeneration, reflected by higher motor and sensory nerve conduction velocity values. The motor and sensory nerve conduction velocity were significantly greater in nerves treated with conduits preseeded with adipose tissue-derived stem cells than in nerves treated with conduits alone (p < 0.05). Increased S100 immunoreactivity was detected for the adipose tissue-derived stem cell group. In this group, axon arrangement inside the conduits was more organized. Transplantation of adipose tissue-derived stem cells significantly improves motor and sensory nerve conduction velocity in peripheral nerve gaps. Preseeded conduits showed a more organized axon arrangement inside the conduit in comparison with nerve conduits alone. The approach used here could readily be translated into a clinical therapy. Therapeutic, V.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hyewon; Cheong, S.W.; Kim, Bog G., E-mail: boggikim@pusan.ac.kr

We have studied the properties of SnO{sub 6} octahedra-containing perovskites and their derived structures using ab initio calculations with different density functionals. In order to predict the correct band gap of the materials, we have used B3LYP hybrid density functional, and the results of B3LYP were compared with those obtained using the local density approximation and generalized gradient approximation data. The calculations have been conducted for the orthorhombic ground state of the SnO{sub 6} containing perovskites. We also have expended the hybrid density functional calculation to the ASnO{sub 3}/A'SnO{sub 3} system with different cation orderings. We propose an empirical relationshipmore » between the tolerance factor and the band gap of SnO{sub 6} containing oxide materials based on first principles calculation. - Graphical abstract: (a) Structure of ASnO{sub 3} for orthorhombic ground state. The green ball is A (Ba, Sr, Ca) cation and the small (red) ball on edge is oxygen. SnO{sub 6} octahedrons are plotted as polyhedron. (b) Band gap of ASnO{sub 3} as a function of the tolerance factor for different density functionals. The experimental values of the band gap are marked as green pentagons. (c) ASnO{sub 3}/A'SnO{sub 3} superlattices with two types cation arrangement: [001] layered structure and [111] rocksalt structure, respectively. (d) B3LYP hybrid functional band gaps of ASnO{sub 3}, [001] ordered superlattices, and [111] ordered superlattices of ASnO{sub 3}/A'SnO{sub 3} as a function of the effective tolerance factor. Note the empirical linear relationship between the band gap and effective tolerance factor. - Highlights: • We report the hybrid functional band gap calculation of ASnO{sub 3} and ASnO{sub 3}/A'SnO{sub 3}. • The band gap of ASnO{sub 3} using B3LYP functional reproduces the experimental value. • We propose the linear relationship between the tolerance factor and the band gap.« less

The gap values in the profile matching method by fuzzy logic

NASA Astrophysics Data System (ADS)

Sitepu, S. A.; Efendi, S.; Situmorang, Z.

2018-03-01

In this research, the determination of the appropriate values of Gap for the assessment of promotion criteria of position in an institution / company. In this study the authors use Fuzzy Sugeno logic on the determination of Gap values used in Profile Matching method. Test results of 5 employees obtained the eligibility of promotion with the position of Z* values between in 3.20 to 4.11.

Study of radiative heat transfer in Ångström- and nanometre-sized gaps

DOE PAGES

Cui, Longji; Jeong, Wonho; Fernández-Hurtado, Víctor; ...

2017-02-15

Radiative heat transfer in Ångström- and nanometre-sized gaps is of great interest because of both its technological importance and open questions regarding the physics of energy transfer in this regime. Here in this paper we report studies of radiative heat transfer in few Å to 5nm gap sizes, performed under ultrahigh vacuum conditions between a Au-coated probe featuring embedded nanoscale thermocouples and a heated planar Au substrate that were both subjected to various surface-cleaning procedures. By drawing on the apparent tunnelling barrier height as a signature of cleanliness, we found that upon systematically cleaning via a plasma or locally pushingmore » the tip into the substrate by a few nanometres, the observed radiative conductances decreased from unexpectedly large values to extremely small ones—below the detection limit of our probe—as expected from our computational results. Our results show that it is possible to avoid the confounding effects of surface contamination and systematically study thermal radiation in Ångström- and nanometre-sized gaps.« less

Effect of zirconium oxide nanofiller and dibutyl phthalate plasticizer on ionic conductivity and optical properties of solid polymer electrolyte.

PubMed

Yasin, Siti Mariah Mohd; Ibrahim, Suriani; Johan, Mohd Rafie

2014-01-01

New solid polymer electrolytes (SPE) based on poly(ethylene oxide) (PEO) doped with lithium trifluoromethanesulfonate (LiCF3SO3), dibutyl phthalate (DBP) plasticizer, and zirconium oxide (ZrO2) nanoparticles were prepared by solution-casting technique. The conductivity was enhanced by addition of dibutyl phthalate (DBP) plasticizer and ZrO2 nanofiller with maximum conductivity (1.38 × 10(-4) Scm(-1)). The absorption edge and band gap values showed decreases upon addition of LiSO3CF3, DBP, and ZrO2 due to the formation of localized states in the SPE and the degree of disorder in the films increased.

Effect of Zirconium Oxide Nanofiller and Dibutyl Phthalate Plasticizer on Ionic Conductivity and Optical Properties of Solid Polymer Electrolyte

PubMed Central

Yasin, Siti Mariah Mohd; Ibrahim, Suriani

2014-01-01

New solid polymer electrolytes (SPE) based on poly(ethylene oxide) (PEO) doped with lithium trifluoromethanesulfonate (LiCF3SO3), dibutyl phthalate (DBP) plasticizer, and zirconium oxide (ZrO2) nanoparticles were prepared by solution-casting technique. The conductivity was enhanced by addition of dibutyl phthalate (DBP) plasticizer and ZrO2 nanofiller with maximum conductivity (1.38 × 10−4 Scm−1). The absorption edge and band gap values showed decreases upon addition of LiSO3CF3, DBP, and ZrO2 due to the formation of localized states in the SPE and the degree of disorder in the films increased. PMID:25133244

Voltage and pace-capture mapping of linear ablation lesions overestimates chronic ablation gap size.

PubMed

O'Neill, Louisa; Harrison, James; Chubb, Henry; Whitaker, John; Mukherjee, Rahul K; Bloch, Lars Ølgaard; Andersen, Niels Peter; Dam, Høgni; Jensen, Henrik K; Niederer, Steven; Wright, Matthew; O'Neill, Mark; Williams, Steven E

2018-04-26

Conducting gaps in lesion sets are a major reason for failure of ablation procedures. Voltage mapping and pace-capture have been proposed for intra-procedural identification of gaps. We aimed to compare gap size measured acutely and chronically post-ablation to macroscopic gap size in a porcine model. Intercaval linear ablation was performed in eight Göttingen minipigs with a deliberate gap of ∼5 mm left in the ablation line. Gap size was measured by interpolating ablation contact force values between ablation tags and thresholding at a low force cut-off of 5 g. Bipolar voltage mapping and pace-capture mapping along the length of the line were performed immediately, and at 2 months, post-ablation. Animals were euthanized and gap sizes were measured macroscopically. Voltage thresholds to define scar were determined by receiver operating characteristic analysis as <0.56 mV (acutely) and <0.62 mV (chronically). Taking the macroscopic gap size as gold standard, error in gap measurements were determined for voltage, pace-capture, and ablation contact force maps. All modalities overestimated chronic gap size, by 1.4 ± 2.0 mm (ablation contact force map), 5.1 ± 3.4 mm (pace-capture), and 9.5 ± 3.8 mm (voltage mapping). Error on ablation contact force map gap measurements were significantly less than for voltage mapping (P = 0.003, Tukey's multiple comparisons test). Chronically, voltage mapping and pace-capture mapping overestimated macroscopic gap size by 11.9 ± 3.7 and 9.8 ± 3.5 mm, respectively. Bipolar voltage and pace-capture mapping overestimate the size of chronic gap formation in linear ablation lesions. The most accurate estimation of chronic gap size was achieved by analysis of catheter-myocardium contact force during ablation.

Optical and electrical properties of heavily indium-doped CdS around the semiconductor-metal phase transition

NASA Astrophysics Data System (ADS)

Broser, I.; Broser, R.; Birkicht, E.

1990-04-01

Heavily indium-doped CdS crystals are studied by comparing their optical and electrical properties. It is shown that in the near infrared spectral region for highly conducting crystals the correlation of electrical conductivity and optical effects can still be understood in the frame of the classical Drude-Lorentz model. Even for high doping the relaxation time τ and the effective mass m ∗ of the electrons are not markedly different from the room temperature values of "pure" crystals. At photon energies near the band gap, however, optical spectra in transmission, reflectivity, and emission show clearly the existence of band-tails and screening effects. A different situation holds for a highly compensated specimen: They are in a wide temperature region highly isolating, show activated photoconductivity and special structures in the optical spectra near the band gap. Their properties can be explained by assuming a meandering bandbending due to the combined action of donors and acceptors and the assumption of spatially isolated electron and hole droplets [6].

Thermoelectric properties of AgSbTe₂ from first-principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rezaei, Nafiseh; Akbarzadeh, Hadi; Hashemifar, S. Javad, E-mail: hashemifar@cc.iut.ac.ir

2014-09-14

The structural, electronic, and transport properties of AgSbTe₂ are studied by using full-relativistic first-principles electronic structure calculation and semiclassical description of transport parameters. The results indicate that, within various exchange-correlation functionals, the cubic Fd3⁻m and trigonal R3⁻m structures of AgSbTe₂ are more stable than two other considered structures. The computed Seebeck coefficients at different values of the band gap and carrier concentration are accurately compared with the available experimental data to speculate a band gap of about 0.1–0.35 eV for AgSbTe₂ compound, in agreement with our calculated electronic structure within the hybrid HSE (Heyd-Scuseria-Ernzerhof) functional. By calculating the semiclassical Seebeckmore » coefficient, electrical conductivity, and electronic part of thermal conductivity, we present the theoretical upper limit of the thermoelectric figure of merit of AgSbTe₂ as a function of temperature and carrier concentration.« less

Micro-CT Evaluation of Ceramic Inlays: Comparison of the Marginal and Internal Fit of Five and Three Axis CAM Systems with a Heat Press Technique.

PubMed

Alajaji, Norah K; Bardwell, David; Finkelman, Matthew; Ali, Ala

2017-02-01

To evaluate the marginal and internal adaptation of CAD/CAM lithium-disilicate inlay restorations fabricated by two milling systems (Five and Three-axis), and a traditional heat-press technique. Fifteen premolar teeth with an MOD cavity preparation were fabricated. Lithium-disilicate inlay restorations were obtained by three fabrication techniques and fitted to their dies (n = 15/gp) as follows: Group-1, three-axis milling system, Group-2, five-axis milling system, Group-3, conventional heat-press technique. Gaps were evaluated by X-ray microtomography. Marginal gap (MG), occlusal-marginal gap (OMG), proximal-marginal gap (PMG), gingival-marginal gap (GMG), absolute marginal discrepancy (AMD), axial-internal gap (AIG), and occlusal-internal gap (OIG) were evaluated at 120 different points per inlay. Data were analyzed using repeated measures ANOVA. Pairwise comparisons were conducted for post-hoc testes and the Bonferroni correction was used to adjust for multiple comparisons (α = 0.007). The heat-press group demonstrated significantly smaller mean-values amongst all outcomes compared with CAD/CAM groups except for GMG, where there was no statistically significant difference between groups in the ANOVA (p = 0.042). Within the CAD/CAM groups, the five-axis group showed significantly lower OMG mean-value compared with the three-axis group p < 0.001, and lower AIG mean-value compared with the three-axis group p < 0.001. There was no significant difference between the five-axis and the three-axis groups' AMD, MG, PMG, and OIG locations. Different fabrication techniques affected the marginal and internal adaptation of ceramic inlay restorations. The heat-press group showed the best marginal and internal adaptation results; however, in every group, all samples were within the clinically acceptable MG limit (100 μm). The marginal fit and internal adaptation of inlay ceramic restorations fabricated by a five-axis milling system have not been tested or compared with those fabricated by three-axis machines and the conventional heat-press method. The preferred method of inlay fabrication, whether in the lab or chair side, may be influenced by the results of this study and could affect future clinical decision-making. (J Esthet Restor Dent 29:49-58, 2017). © 2016 Wiley Periodicals, Inc.

Gaps in college biology students' understanding of photosynthesis: Implications for human constructivist learning theory and college classroom practice

NASA Astrophysics Data System (ADS)

Griffard, Phyllis Baudoin

1999-11-01

The main research question of this study was: What gaps in biochemical understanding are revealed by a range of university introductory biology students as they work through a critically acclaimed multimedia program on photosynthesis, and what are the corresponding implications for elaboration of the Ausubel-Novak-Gowin Learning Theory (ANG, now Human Constructivism)? Twelve students, mixed for ability, gender and ethnicity, were recruited from two sections of "Bio 101." Before and after instruction in photosynthesis, in-depth clinical interviews were conducted during which participants completed a range of cognitive tasks such as sorting, concept mapping, explaining and predicting. Some tasks involved interacting with a computer simulation of photosynthesis. This study primarily employed qualitative case study and verbal analysis methods. Verbal analysis of the clinical interviews revealed numerous gaps that were categorized into typologies. The two major categories were propositional gaps and processing gaps. Propositional gaps were evident in development of participants' concepts, links and constructs. Significant among these were conceptual distance gaps and continuity of matter gaps. Gaps such as convention gaps and relative significance gaps seem to be due to naivete in the discipline. Processing gaps included gaps in graphic decoding skills and relevant cognitive habits such as self-monitoring and consulting prior knowledge. Although the gaps were easier to detect and isolate with the above-average participants, all participants showed evidence of at least some of these gaps. Since some gaps are not unexpected at all but the highest literacy levels, not all the gaps identified are to be considered deficiencies. The gaps identified support the attention given by ANG theorists to the role of prior knowledge and metacognition as well as the value of graphic organizers in knowledge construction. In addition, this study revealed numerous gaps in graphic decoding, indicating that both direct experience and explicit instruction are needed if students are to "learn how to learn with graphics," especially those graphics central to understanding a computer simulation's representations of structures, inputs, processes and outputs. It is hypothesized that gaps similar to those revealed in this study may be at the root of some alternative conceptions documented in the literature.

Tuning the Electronic and Optical Properties of Two-Dimensional Graphene-like C_2N Nanosheet by Strain Engineering

NASA Astrophysics Data System (ADS)

Phuc, Huynh V.; Tuan, Vu V.; Hieu, Nguyen N.; Ilyasov, Victor V.; Fedorov, Igor A.; Hoi, Bui D.; Phuong, Le T. T.; Hieu, Nguyen V.; Feddi, Elmustapha; Nguyen, Chuong V.

2018-05-01

Using density functional theory, we have studied the structural, electronic and optical properties of two-dimensional graphene-like C_2N nanosheet under in-plane strains. Our results indicate that the C_2N nanosheet is a semiconductor with a direct band gap of 1.70 eV at the equilibrium state opening between the highest valence band and lowest conduction band located at the Γ point. The band gap of the C_2N nanosheet decreases with the increasing of both uniaxial/biaxial strains. In the presence of the strain, we found band shift and band splitting of the occupied and unoccupied energy states of the valence and conduction bands, resulting in a decrease of the band gap. Furthermore, the absorption and reflectance spectra for the C_2N nanosheet have a broad peak around 2.6 eV, where a maximum absorption value is up to 3.2 × 10^{-5} cm^{-1} and reflectance is about 0.27%. Moreover, our calculations also show that the optical properties of the C_2N nanosheets can be controlled by applying the biaxial and uniaxial strains. The obtained results might provide potential applications for the C_2N nanosheets in nanoelectronics and optoelectronics.

Effect of data gaps on correlation dimension computed from light curves of variable stars

NASA Astrophysics Data System (ADS)

George, Sandip V.; Ambika, G.; Misra, R.

2015-11-01

Observational data, especially astrophysical data, is often limited by gaps in data that arises due to lack of observations for a variety of reasons. Such inadvertent gaps are usually smoothed over using interpolation techniques. However the smoothing techniques can introduce artificial effects, especially when non-linear analysis is undertaken. We investigate how gaps can affect the computed values of correlation dimension of the system, without using any interpolation. For this we introduce gaps artificially in synthetic data derived from standard chaotic systems, like the Rössler and Lorenz, with frequency of occurrence and size of missing data drawn from two Gaussian distributions. Then we study the changes in correlation dimension with change in the distributions of position and size of gaps. We find that for a considerable range of mean gap frequency and size, the value of correlation dimension is not significantly affected, indicating that in such specific cases, the calculated values can still be reliable and acceptable. Thus our study introduces a method of checking the reliability of computed correlation dimension values by calculating the distribution of gaps with respect to its size and position. This is illustrated for the data from light curves of three variable stars, R Scuti, U Monocerotis and SU Tauri. We also demonstrate how a cubic spline interpolation can cause a time series of Gaussian noise with missing data to be misinterpreted as being chaotic in origin. This is demonstrated for the non chaotic light curve of variable star SS Cygni, which gives a saturated D2 value, when interpolated using a cubic spline. In addition we also find that a careful choice of binning, in addition to reducing noise, can help in shifting the gap distribution to the reliable range for D2 values.

Structural, optical, physical and electrical properties of V2O5.SrO.B2O3 glasses.

PubMed

Sindhu, S; Sanghi, S; Agarwal, A; Seth, V P; Kishore, N

2006-05-01

The present work aims to study the structure and variation of optical band gap, density and dc electrical conductivity in vanadium strontium borate glasses. The glass systems xV2O5.(40-x)SrO.60B2O3 and xV2O5.(60-x)B2O3.40SrO with x varying from 0 to 20 mol% were prepared by normal melt quench technique. Structural studies were made by recording IR transmission spectra. The fundamental absorption edge for all the glasses was analyzed in terms of the theory proposed by Davis and Mott. The position of absorption edge and hence the value of the optical band gap was found to depend on the semiconducting glass composition. The absorption in these glasses is believed to be associated with indirect transitions. The origin of Urbach energy is associated with the phonon-assisted indirect transitions. The change in both density and molar volume was discussed in terms of the structural modifications that take place in the glass matrix on addition of V2O5. dc conductivity of the glass systems is also reported. The change of conductivity and activation energy with composition indicates that the conduction process varies from ionic to polaronic one.

Viscoelastic effect on acoustic band gaps in polymer-fluid composites

NASA Astrophysics Data System (ADS)

Merheb, B.; Deymier, P. A.; Muralidharan, K.; Bucay, J.; Jain, M.; Aloshyna-Lesuffleur, M.; Greger, R. W.; Mohanty, S.; Berker, A.

2009-10-01

In this paper, we present a theoretical analysis of the propagation of acoustic waves through elastic and viscoelastic two-dimensional phononic crystal structures. Numerical calculations of transmission spectra are conducted by extending the finite-difference-time-domain method to account for linear viscoelastic materials with time-dependent moduli. We study a phononic crystal constituted of a square array of cylindrical air inclusions in a solid viscoelastic matrix. The elastic properties of the solid are those of a silicone rubber. This system exhibits very wide band gaps in its transmission spectrum that extend to frequencies in the audible range of the spectrum. These gaps are characteristic of fluid matrix/air inclusion systems and result from the very large contrast between the longitudinal and transverse speeds of sound in rubber. By treating the matrix as a viscoelastic medium within the standard linear solid (SLS) model, we demonstrate that viscoelasticity impacts the transmission properties of the rubber/air phononic crystal not only by attenuating the transmitted acoustic waves but also by shifting the passing bands frequencies toward lower values. The ranges of frequencies exhibiting attenuation or frequency shift are determined by the value of the relaxation time in the SLS model. We show that viscoelasticity can be used to decrease the frequency of pass bands (and consequently stop bands) in viscoelastic/air phononic crystals.

Photo-controllable thermoelectric properties with reversibility and photo-thermoelectric effects of tungsten trioxide accompanied by its photochromic phenomenon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azuma, Chiori; Kawano, Takuto; Kakemoto, Hirofumi

2014-11-07

The addition of photo-controllable properties to tungsten trioxide (WO{sub 3}) is of interest for developing practical applications of WO{sub 3} as well as for interpreting such phenomena from scientific viewpoints. Here, a sputtered crystalline WO{sub 3} thin film generated thermoelectric power due to ultraviolet (UV) light-induced band-gap excitation and was accompanied by a photochromic reaction resulting from generating W{sup 5+} ions. The thermoelectric properties (electrical conductivity (σ) and Seebeck coefficient (S)) and coloration of WO{sub 3} could be reversibly switched by alternating the external stimulus between UV light irradiation and dark storage. After irradiating the film with UV light, σmore » increased, whereas the absolute value of S decreased, and the photochromic (coloration) reaction was detected. Notably, the opposite behavior was exhibited by WO{sub 3} after dark storage, and this reversible cycle could be repeated at least three times. Moreover, photo-thermoelectric effects (photo-conductive effect (photo-conductivity, σ{sub photo}) and photo-Seebeck effect (photo-Seebeck coefficient, S{sub photo})) were also detected in response to visible-light irradiation of the colored WO{sub 3} thin films. Under visible-light irradiation, σ{sub photo} and the absolute value of S{sub photo} increased and decreased, respectively. These effects are likely attributable to the excitation of electrons from the mid-gap visible light absorption band (W{sup 5+} state) to the conduction band of WO{sub 3}. Our findings demonstrate that the simultaneous, reversible switching of multiple properties of WO{sub 3} thin film is achieved by the application of an external stimulus and that this material exhibits photo-thermoelectric effects when irradiated with visible-light.« less

A direct method for computing extreme value (Gumbel) parameters for gapped biological sequence alignments.

PubMed

Quinn, Terrance; Sinkala, Zachariah

2014-01-01

We develop a general method for computing extreme value distribution (Gumbel, 1958) parameters for gapped alignments. Our approach uses mixture distribution theory to obtain associated BLOSUM matrices for gapped alignments, which in turn are used for determining significance of gapped alignment scores for pairs of biological sequences. We compare our results with parameters already obtained in the literature.

Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dileep, K., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in; Sahu, R.; Datta, R., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in

2016-03-21

Layer specific direct measurement of optical band gaps of two important van der Waals compounds, MoS{sub 2} and ReS{sub 2}, is performed at nanoscale by high resolution electron energy loss spectroscopy. For monolayer MoS{sub 2}, the twin excitons (1.8 and 1.95 eV) originating at the K point of the Brillouin zone are observed. An indirect band gap of 1.27 eV is obtained from the multilayer regions. Indirect to direct band gap crossover is observed which is consistent with the previously reported strong photoluminescence from the monolayer MoS{sub 2}. For ReS{sub 2}, the band gap is direct, and a value of 1.52 andmore » 1.42 eV is obtained for the monolayer and multilayer, respectively. The energy loss function is dominated by features due to high density of states at both the valence and conduction band edges, and the difference in analyzing band gap with respect to ZnO is highlighted. Crystalline 1T ReS{sub 2} forms two dimensional chains like superstructure due to the clustering between four Re atoms. The results demonstrate the power of HREELS technique as a nanoscale optical absorption spectroscopy tool.« less

Clinical use of vestibular evoked myogenic potentials in the evaluation of patients with air-bone gaps.

PubMed

Zhou, Guangwei; Poe, Dennis; Gopen, Quinton

2012-10-01

To determine the value of vestibular evoked myogenic potential (VEMP) test in clinical evaluation of air-bone gaps. Retrospective case review. Tertiary referral center. A total of 120 patients underwent VEMP testing during clinical investigation of significant air-bone gaps in their audiograms. Otologic examination and surgeries, high-resolution computerized tomography (CT), air and bone audiometry, tympanometry, acoustic reflex, and VEMP test. Imaging studies demonstrating structural anomalies in the temporal bone. Audiologic outcomes of air-bone gaps and VEMP thresholds. Surgical findings confirming imaging results. Middle ear pathologies, such as otosclerosis and chronic otitis media, were identified in 50 patients, and all of them had absent VEMP responses elicited by air-conduction stimuli. Moreover, 13 of them had successful middle ear surgeries with closures of the air-bone gaps. Abnormally low VEMP thresholds were found in 71 of 73 ears with inner ear anomalies, such as semicircular canal dehiscence and enlarged vestibular aqueduct. Seven patients with superior semicircular canal dehiscence underwent plugging procedure via middle fossa approach, and VEMP thresholds became normalized after the surgery in 3 of them. VEMP test failed to provide accurate diagnosis in only 3 cases. Air-bone gaps may be a result of various otologic pathologies, and the VEMP test is useful during clinical evaluation, better than tympanometry and acoustic reflexes. To avoid unnecessary middle ear surgery for air-bone gaps with unknown or unsure cause, VEMP test should be used in the differential diagnosis before an expensive imaging study.

Application of the Mattis-Bardeen theory in strongly disordered superconductors

NASA Astrophysics Data System (ADS)

Seibold, G.; Benfatto, L.; Castellani, C.

2017-10-01

The low-energy optical conductivity of conventional superconductors is usually well described by Mattis-Bardeen (MB) theory, which predicts the onset of absorption above an energy corresponding to twice the superconducing (SC) gap parameter Δ . Recent experiments on strongly disordered superconductors have challenged the application of the MB formulas due to the occurrence of additional spectral weight at low energies below 2 Δ . Here we identify three crucial items that have to be included in the analysis of optical-conductivity data for these systems: (a) the correct identification of the optical threshold in the Mattis-Bardeen theory and its relation with the gap value extracted from the measured density of states, (b) the gauge-invariant evaluation of the current-current response function needed to account for the optical absorption by SC collective modes, and (c) the inclusion into the MB formula of the energy dependence of the density of states present already above Tc. By computing the optical conductivity in the disordered attractive Hubbard model, we analyze the relevance of all these items, and we provide a compelling scheme for the analysis and interpretation of the optical data in real materials.

Valley-symmetric quasi-1D transport in ballistic graphene

NASA Astrophysics Data System (ADS)

Lee, Hu-Jong

We present our recent studies on gate-defined valley-symmetric one-dimensional (1D) carrier guiding in ballistic monolayer graphene and valley-symmetry-protected topological 1D transport in ballistic bilayer graphene. Successful carrier guiding was realized in ballistic monolayer graphene even in the absence of a band gap by inducing a high distinction ( more than two orders of magnitude) in the carrier density between the region of a quasi-1D channel and the rest of the top-gated regions. Conductance of a channel shows quantized values in units of 4e2/ h, suggesting that the valley symmetry is preserved. For the latter, the topological 1D conduction was realized between two closely arranged insulating regions with inverted band gaps, induced under a pair of split dual gating with polarities opposite to each other. The maximum conductance along the boundary channel showed 4e2/ h, again with the preserved valley symmetry. The 1D topological carrier guiding demonstrated in this study affords a promising route to robust valleytronic applications and sophisticated valley-associated functionalities based on 2D materials. This work was funded by the National Research Foundation of Korea.

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB 6 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.

The Kondo insulator SmB 6 has long been known to display anomalous transport behavior at low temperatures, T < 5 K. In this temperatures range, a plateau is observed in the dc resistivity, contrary to the exponential divergence expected for a gapped system. Some recent theoretical calculations suggest that SmB 6 may be the first topological Kondo insulator (TKI) and propose that the residual conductivity is due to topological surface states which reside within the Kondo gap. Since the TKI prediction many experiments have claimed to observe high mobility surface states within a perfectly insulating hybridization gap. We investigate themore » low energy optical conductivity within the hybridization gap of single crystals of SmB 6 via time domain terahertz spectroscopy. Samples grown by both optical floating zone and aluminum flux methods are investigated to probe for differences originating from sample growth techniques. We find that both samples display significant three-dimensional bulk conduction originating within the Kondo gap. Although SmB 6 may be a bulk dc insulator, it shows significant bulk ac conduction that is many orders of magnitude larger than any known impurity band conduction. The nature of these in-gap states and their coupling with the low energy spin excitons of SmB 6 is discussed. In addition, the well-defined conduction path geometry of our optical experiments allows us to show that any surface states, which lie below our detection threshold if present, must have a sheet resistance of R / square ≥ 1000 Ω .« less

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB 6 single crystals

DOE PAGES

Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.; ...

2016-10-21

The Kondo insulator SmB 6 has long been known to display anomalous transport behavior at low temperatures, T < 5 K. In this temperatures range, a plateau is observed in the dc resistivity, contrary to the exponential divergence expected for a gapped system. Some recent theoretical calculations suggest that SmB 6 may be the first topological Kondo insulator (TKI) and propose that the residual conductivity is due to topological surface states which reside within the Kondo gap. Since the TKI prediction many experiments have claimed to observe high mobility surface states within a perfectly insulating hybridization gap. We investigate themore » low energy optical conductivity within the hybridization gap of single crystals of SmB 6 via time domain terahertz spectroscopy. Samples grown by both optical floating zone and aluminum flux methods are investigated to probe for differences originating from sample growth techniques. We find that both samples display significant three-dimensional bulk conduction originating within the Kondo gap. Although SmB 6 may be a bulk dc insulator, it shows significant bulk ac conduction that is many orders of magnitude larger than any known impurity band conduction. The nature of these in-gap states and their coupling with the low energy spin excitons of SmB 6 is discussed. In addition, the well-defined conduction path geometry of our optical experiments allows us to show that any surface states, which lie below our detection threshold if present, must have a sheet resistance of R / square ≥ 1000 Ω .« less

Theory of g-factor enhancement in narrow-gap quantum well heterostructures.

PubMed

Krishtopenko, S S; Gavrilenko, V I; Goiran, M

2011-09-28

We report on the study of the exchange enhancement of the g-factor in the two-dimensional (2D) electron gas in n-type narrow-gap semiconductor heterostructures. Our approach is based on the eight-band k⋅p Hamiltonian and takes into account the band nonparabolicity, the lattice deformation, the spin-orbit coupling and the Landau level broadening in the δ-correlated random potential model. Using the 'screened' Hartree-Fock approximation we demonstrate that the exchange g-factor enhancement not only shows maxima at odd values of Landau level filling factors but, due to the conduction band nonparabolicity, persists at even filling factor values as well. The magnitude of the exchange enhancement, the amplitude and the shape of the g-factor oscillations are determined by both the screening of the electron-electron interaction and the Landau level width. The 'enhanced' g-factor values calculated for the 2D electron gas in InAs/AlSb quantum well heterostructures are compared with our earlier experimental data and with those obtained by Mendez et al (1993 Phys. Rev. B 47 13937) in magnetic fields up to 30 T.

Velocity and pressure measurements in guide vane clearance gap of a low specific speed Francis turbine

NASA Astrophysics Data System (ADS)

Thapa, B. S.; Dahlhaug, O. G.; Thapa, B.

2016-11-01

In Francis turbine, a small clearance gap between the guide vanes and the cover plates is usually required to pivot guide vanes as a part of governing system. Deflection of cover plates and erosion of mating surfaces causes this gap to increase from its design value. The clearance gap induces the secondary flow in the distributor system. This effects the main flow at the runner inlet, which causes losses in efficiency and instability. A guide vane cascade of a low specific speed Francis turbine has been developed for experimental investigations. The test setup is able to produce similar velocity distributions at the runner inlet as that of a reference prototype turbine. The setup is designed for particle image velocimetry (PIV) measurements from the position of stay vane outlet to the position of runner inlet. In this study, velocity and pressure measurements are conducted with 2 mm clearance gap on one side of guide vane. Leakage flow is observed and measured together with pressure measurements. It is concluded that the leakage flow behaves as a jet and mixes with the main flow in cross-wise direction and forms a vortex filament. This causes non-uniform inlet flow conditions at runner blades.

Fluid helium at conditions of giant planetary interiors

PubMed Central

Stixrude, Lars; Jeanloz, Raymond

2008-01-01

As the second most-abundant chemical element in the universe, helium makes up a large fraction of giant gaseous planets, including Jupiter, Saturn, and most extrasolar planets discovered to date. Using first-principles molecular dynamics simulations, we find that fluid helium undergoes temperature-induced metallization at high pressures. The electronic energy gap (band gap) closes at 20,000 K at a density half that of zero-temperature metallization, resulting in electrical conductivities greater than the minimum metallic value. Gap closure is achieved by a broadening of the valence band via increased s–p hydridization with increasing temperature, and this influences the equation of state: The Grüneisen parameter, which determines the adiabatic temperature–depth gradient inside a planet, changes only modestly, decreasing with compression up to the high-temperature metallization and then increasing upon further compression. The change in electronic structure of He at elevated pressures and temperatures has important implications for the miscibility of helium in hydrogen and for understanding the thermal histories of giant planets.

Doping effects in InN/GaN short-period quantum well structures-Theoretical studies based on density functional methods

NASA Astrophysics Data System (ADS)

Strak, Pawel; Kempisty, Pawel; Sakowski, Konrad; Krukowski, Stanislaw

2014-09-01

Density functional theory studies were conducted to determine an influence of the carrier concentration on the optical and electronic properties of InN/GaN superlattice system. The oscillator strength values, energy gaps and the band profiles were obtained. The band profiles were found to be strongly affected for technically possible heavy n-type doping while for p-type doping the carrier influence, both screening and band shift, is negligible. Blue shift of the transition energy between conduction band minima and valence band maxima was observed for high concentrations of both type carriers.

Effects of anhydrous AlCl3 dopant on the structural, optical and electrical properties of PVA-PVP polymer composite films

NASA Astrophysics Data System (ADS)

Shanmugam, G.; Krishnakumar, V.

2018-05-01

Polymer composite films based on PVA-PVP with AlCl3 as the dopant at different concentrations were prepared using solution casting technique. XRD patterns reveal the increase in amorphousity of the films with AlCl3 doping. Optical absorption studies exhibit that the values of optical absorption coefficient, direct and indirect optical band gaps are found to decrease with increase in AlCl3 concentration. It confirms the charge transfer in complexes between the polymer and the dopant. The dielectric studies show the increase in dielectric constant at low frequency with increasing AlCl3 concentration and temperature. The ac conductivity and ionic conductivity increase with the AlCl3 content and the maximum value at room temperature is found to be 6.89 × 10-4 and 8.05 × 10-5 S/cm for higher AlCl3 doped PVA-PVP film. The estimated ionic conductivity value is three or four orders of magnitude greater than those obtained in the certain representative polymer-salt complexes as reported earlier. Electrical modulus plots confirm the removal of electrode polarization and the low conductivity relaxation time with Al doping. The activation energy estimated from the temperature dependent dc conductivity plot is agreed well with the migration energy calculated from the temperature dependent electric modulus plot.

A method to estimate the additional uncertainty in gap-filled NEE resulting from long gaps in the CO2 flux record

Treesearch

Andrew D. Richardson; David Y. Hollinger

2007-01-01

Missing values in any data set create problems for researchers. The process by which missing values are replaced, and the data set is made complete, is generally referred to as imputation. Within the eddy flux community, the term "gap filling" is more commonly applied. A major challenge is that random errors in measured data result in uncertainty in the gap-...

Silicon quantum dots embedded in a SiO2 matrix: From structural study to carrier transport properties

NASA Astrophysics Data System (ADS)

Garcia-Castello, Nuria; Illera, Sergio; Guerra, Roberto; Prades, Joan Daniel; Ossicini, Stefano; Cirera, Albert

2013-08-01

We study the details of electronic transport related to the atomistic structure of silicon quantum dots embedded in a silicon dioxide matrix using ab initio calculations of the density of states. Several structural and composition features of quantum dots (QDs), such as diameter and amorphization level, are studied and correlated with transport under transfer Hamiltonian formalism. The current is strongly dependent on the QD density of states and on the conduction gap, both dependent on the dot diameter. In particular, as size increases, the available states inside the QD increase, while the QD band gap decreases due to relaxation of quantum confinement. Both effects contribute to increasing the current with the dot size. Besides, valence band offset between the band edges of the QD and the silica, and conduction band offset in a minor grade, increases with the QD diameter up to the theoretical value corresponding to planar heterostructures, thus decreasing the tunneling transmission probability and hence the total current. We discuss the influence of these parameters on electron and hole transport, evidencing a correlation between the electron (hole) barrier value and the electron (hole) current, and obtaining a general enhancement of the electron (hole) transport for larger (smaller) QD. Finally, we show that crystalline and amorphous structures exhibit enhanced probability of hole and electron current, respectively.

Structural, electronic and optical properties of monoclinic Na{sub 2}Ti{sub 3}O{sub 7} from density functional theory calculations: A comparison with XRD and optical absorption measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Araújo-Filho, Adailton A.; Silva, Fábio L.R.; Righi, Ariete

Powder samples of bulk monoclinic sodium trititanate Na{sub 2}Ti{sub 3}O{sub 7} were prepared carefully by solid state reaction, and its monoclinic P2{sub 1}/m crystal structure and morphology were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. Moreover, the sodium trititanate main energy band gap was estimated as E{sub g}=3.51±0.01 eV employing UV–Vis spectroscopy, which is smaller than the measured 3.70 eV energy gap published previously by other authors. Aiming to achieve a better understanding of the experimental data, density functional theory (DFT) computations were performed within the local density and generalized gradient approximations (LDA and GGA,more » respectively) taking into account dispersion effects through the scheme of Tkatchenko and Scheffler (GGA+TS). Optimal lattice parameters, with deviations relative to measurements Δa=−0.06 Å, Δb=0.02 Å, and Δc=−0.09 Å, were obtained at the GGA level, which was then used to simulate the sodium trititanate electronic and optical properties. Indirect band transitions have led to a theoretical gap energy value of about 3.25 eV. Our results, however, differ from pioneer DFT results with respect to the specific Brillouin zone vectors for which the indirect transition with smallest energy value occurs. Effective masses for electrons and holes were also estimated along a set of directions in reciprocal space. Lastly, our calculations revealed a relatively large degree of optical isotropy for the Na{sub 2}Ti{sub 3}O{sub 7} optical absorption and complex dielectric function. - Graphical abstract: Monoclinic sodium trititanate Na2Ti3O7 was characterized by experiment and dispersion-corrected DFT calculations. An indirect gap of 3.5 eV is predicted, with heavy electrons and anisotropic holes ruling its conductivity. - Highlights: • Monoclinic Na2Ti3O7 was characterized by experiment (XRD, SEM, UV–Vis spectroscopy). • DFT GGA+TS optimized geometry and optoelectronic properties were obtained. • An experimental (theoretical) indirect gap of 3.5 (3.25) eV is predicted. • Heavy electrons and anisotropic holes rule the conductivity. • Ti-O bond lengths and charge states probably cause oxygen reactivity variations.« less

Expedient Gap Definition Using 3D LADAR

DTIC Science & Technology

2006-09-01

Research and Development Center (ERDC), ASI has developed an algorithm to reduce the 3D point cloud acquired with the LADAR system into sets of 2D...ATO IV.GC.2004.02. The GAP Program is conducted by the U.S. Army Engineer Research and Development Center (ERDC) in conjunction with the U.S. Army...Introduction 1 1 Introduction Background The Battlespace Gap Definition and Defeat ( GAP ) Program is conducted by the U.S. Army Engineer Research and

Order, disorder, and tunable gaps in the spectrum of Andreev bound states in a multiterminal superconducting device

NASA Astrophysics Data System (ADS)

Yokoyama, Tomohiro; Reutlinger, Johannes; Belzig, Wolfgang; Nazarov, Yuli V.

2017-01-01

We consider the spectrum of Andreev bound states (ABSs) in an exemplary four-terminal superconducting structure where four chaotic cavities are connected by quantum point contacts to the terminals and to each other forming a ring. We nickname the resulting device 4T-ring. Such a tunable device can be realized in a 2D electron gas-superconductor or a graphene-based hybrid structure. We concentrate on the limit of a short structure and large conductance of the point contacts where there are many ABS in the device forming a quasicontinuous spectrum. The energies of the ABS can be tuned by changing the superconducting phases of the terminals. We observe the opening and closing of gaps in the spectrum upon changing the phases. This concerns the usual proximity gap that separates the levels from zero energy as well as less usual "smile" gaps that split the levels of the quasicontinuous spectrum. We demonstrate a remarkable crossover in the overall spectrum that occurs upon changing the ratio of conductances of the inner and outer point contacts. At big values of the ratio (closed limit), the levels exhibit a generic behavior expected for the spectrum of a disordered system manifesting level repulsion and Brownian "motion" upon changing the phases. At small values of the ratio (open limit), the levels are squeezed into narrow bunches separated by wide smile gaps. Each bunch consists of almost degenerate ABS formed by Andreev reflection between two adjacent terminals. We study in detail the properties of the spectrum in the limit of a small ratio, paying special attention to the crossings of bunches. We distinguish two types of crossings: (i) with a regular phase dependence of the levels and (ii) crossings where the Brownian motion of the levels leads to an apparently irregular phase dependence. We work out a perturbation theory that explains the observations both at a detailed level of random scattering in the device and at a phenomenological level of positively defined random matrices. The unusual properties of the spectrum originate from rather unobvious topological effects. The topology of the first kind is restricted to the semiclassical limit and related to the winding of the semiclassical Green function. It is responsible for the closing of the proximity gaps. The topology of the second kind comes about the discreteness of the number of modes in the point contacts and is responsible for the smile gaps. The topology of the third kind leads to the emergence of Weyl points in the spectrum and is not discussed in the context of this article.

Establishment of the Dual Whole Cell Recording Patch Clamp Configuration for the Measurement of Gap Junction Conductance.

PubMed

Veenstra, Richard D

2016-01-01

The development of the patch clamp technique has enabled investigators to directly measure gap junction conductance between isolated pairs of small cells with resolution to the single channel level. The dual patch clamp recording technique requires specialized equipment and the acquired skill to reliably establish gigaohm seals and the whole cell recording configuration with high efficiency. This chapter describes the equipment needed and methods required to achieve accurate measurement of macroscopic and single gap junction channel conductances. Inherent limitations with the dual whole cell recording technique and methods to correct for series access resistance errors are defined as well as basic procedures to determine the essential electrical parameters necessary to evaluate the accuracy of gap junction conductance measurements using this approach.

Estimation of the geochemical threshold and its statistical significance

USGS Publications Warehouse

Miesch, A.T.

1981-01-01

A statistic is proposed for estimating the geochemical threshold and its statistical significance, or it may be used to identify a group of extreme values that can be tested for significance by other means. The statistic is the maximum gap between adjacent values in an ordered array after each gap has been adjusted for the expected frequency. The values in the ordered array are geochemical values transformed by either ln(?? - ??) or ln(?? - ??) and then standardized so that the mean is zero and the variance is unity. The expected frequency is taken from a fitted normal curve with unit area. The midpoint of an adjusted gap that exceeds the corresponding critical value may be taken as an estimate of the geochemical threshold, and the associated probability indicates the likelihood that the threshold separates two geochemical populations. The adjusted gap test may fail to identify threshold values if the variation tends to be continuous from background values to the higher values that reflect mineralized ground. However, the test will serve to identify other anomalies that may be too subtle to have been noted by other means. ?? 1981.

30 CFR 285.811 - When must I follow my Safety Management System?

Code of Federal Regulations, 2011 CFR

2011-07-01

... Activities Conducted Under SAPs, COPs and GAPs Safety Management Systems § 285.811 When must I follow my... activities described in your approved COP, SAP, or GAP. You must conduct all activities described in your approved COP, SAP, or GAP in accordance with the Safety Management System you described, as required by...

Mechanics of Fluid-Filled Interstitial Gaps. II. Gap Characteristics in Xenopus Embryonic Ectoderm.

PubMed

Barua, Debanjan; Parent, Serge E; Winklbauer, Rudolf

2017-08-22

The ectoderm of the Xenopus embryo is permeated by a network of channels that appear in histological sections as interstitial gaps. We characterized this interstitial space by measuring gap sizes, angles formed between adjacent cells, and curvatures of cell surfaces at gaps. From these parameters, and from surface-tension values measured previously, we estimated the values of critical mechanical variables that determine gap sizes and shapes in the ectoderm, using a general model of interstitial gap mechanics. We concluded that gaps of 1-4 μm side length can be formed by the insertion of extracellular matrix fluid at three-cell junctions such that cell adhesion is locally disrupted and a tension difference between cell-cell contacts and the free cell surface at gaps of 0.003 mJ/m 2 is generated. Furthermore, a cell hydrostatic pressure of 16.8 ± 1.7 Pa and an interstitial pressure of 3.9 ± 3.6 Pa, relative to the central blastocoel cavity of the embryo, was found to be consistent with the observed gap size and shape distribution. Reduction of cell adhesion by the knockdown of C-cadherin increased gap volume while leaving intracellular and interstitial pressures essentially unchanged. In both normal and adhesion-reduced ectoderm, cortical tension of the free cell surfaces at gaps does not return to the high values characteristic of the free surface of the whole tissue. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Ab initio study on half-metallic, electronic and thermodynamic attributes of LaFeO3

NASA Astrophysics Data System (ADS)

Tariq, Saad; Saad, Saher; Jamil, M. Imran; Sohail Gilani, S. M.; Mahmood Ramay, Shahid; Mahmood, Asif

2018-03-01

By using the density functional theory (DFT) the systematic study of the structural, electronic and thermodynamic properties of lanthanum ferrite (LaFeO3) has been conducted. The elastic stability criterion and structural tolerance factor reveal that LaFeO3 exists in the cubic phase and is found to be stable under the ambient conditions. In electronic properties, the optical spectrum of the compound has been found to fall in the range of 488 to 688nm which has been calculated from the electronic band gap values by using the PBE-GGA and mBJ-GGA techniques. The light between 488 to 688nm would cause the valence electrons to jump in the conduction band showing the photoconductivity. The pronounced half-metallic character has been discussed by using the projected electronic density of states. The ferromagnetic response has been observed which may be attributed to the Fe-O bonding situation. The compound exhibits ductile, indirect band gap and half-metallic traits in the bulk phase. We expect the compound to be felicitous for the novel spintronic applications.

Mind the gap: financial London and the regional class pay gap.

PubMed

Friedman, Sam; Laurison, Daniel

2017-09-01

The hidden barriers, or 'gender pay gap', preventing women from earning equivalent incomes to men is well documented. Yet recent research has uncovered that, in Britain, there is also a comparable class-origin pay gap in higher professional and managerial occupations. So far this analysis has only been conducted at the national level and it is not known whether there are regional differences within the UK. This paper uses pooled data from the 2014 and 2015 Labour Force Survey (N = 7,534) to stage a more spatially sensitive analysis that examines regional variation in the class pay gap. We find that this 'class ceiling' is not evenly spatially distributed. Instead it is particularly marked in Central London, where those in high-status occupations who are from working-class backgrounds earn, on average, £10,660 less per year than those whose parents were in higher professional and managerial employment. Finally, we inspect the Capital further to reveal that the class pay gap is largest within Central London's banking and finance sector. Challenging policy conceptions of London as the 'engine room' of social mobility, these findings suggest that class disadvantage within high-status occupations is particularly acute in the Capital. The findings also underline the value of investigating regional differences in social mobility, and demonstrate how such analysis can unravel important and previously unrecognized spatial dimensions of class inequality. © London School of Economics and Political Science 2017.

Comprehensive characterization of measurement data gathered by the pressure tube to calandria tube gap probe

NASA Astrophysics Data System (ADS)

Shokralla, Shaddy Samir Zaki

Multi-frequency eddy current measurements are employed in estimating pressure tube (PT) to calandria tube (CT) gap in CANDU fuel channels, a critical inspection activity required to ensure fitness for service of fuel channels. In this thesis, a comprehensive characterization of eddy current gap data is laid out, in order to extract further information on fuel channel condition, and to identify generalized applications for multi-frequency eddy current data. A surface profiling technique, generalizable to multiple probe and conductive material configurations has been developed. This technique has allowed for identification of various pressure tube artefacts, has been independently validated (using ultrasonic measurements), and has been deployed and commissioned at Ontario Power Generation. Dodd and Deeds solutions to the electromagnetic boundary value problem associated with the PT to CT gap probe configuration were experimentally validated for amplitude response to changes in gap. Using the validated Dodd and Deeds solutions, principal components analysis (PCA) has been employed to identify independence and redundancies in multi-frequency eddy current data. This has allowed for an enhanced visualization of factors affecting gap measurement. Results of the PCA of simulation data are consistent with the skin depth equation, and are validated against PCA of physical experiments. Finally, compressed data acquisition has been realized, allowing faster data acquisition for multi-frequency eddy current systems with hardware limitations, and is generalizable to other applications where real time acquisition of large data sets is prohibitive.

Structural, optical and ac electrical characterization of CBD synthesized NiO thin films: Influence of thickness

NASA Astrophysics Data System (ADS)

Das, M. R.; Mukherjee, A.; Mitra, P.

2017-09-01

We have studied the electrical conductivity, dielectric relaxation mechanism and impedance spectroscopy characteristics of nickel oxide (NiO) thin films synthesized by chemical bath deposition (CBD) method. Thickness dependent structural, optical and ac electrical characterization has been carried out and deposition time was varied to control the thickness. The material has been characterized using X-ray diffraction and UV-VIS spectrophotometer. Impedance spectroscopy analysis confirmed enhancement of ac conductivity and dielectric constant for films deposited with higher deposition time. Decrease of grain size in thicker films were confirmed from XRD analysis and activation energy of the material for electrical charge hopping process was increased with thickness of the film. Decrease in band gap in thicker films were observed which could be associated with creation of additional energy levels in the band gap of the material. Cole-Cole plot shows contribution of both grain and grain boundary towards total resistance and capacitance. The overall resistance was found to decrease from 14.6 × 105 Ω for 30 min deposited film ( 120 nm thick) to 2.42 × 105 Ω for 120 min deposited film ( 307 nm thick). Activation energy value to electrical conduction process evaluated from conductivity data was found to decrease with thickness. Identical result was obtained from relaxation time approach suggesting hopping mechanism of charge carriers.

Persistence of poliovirus-neutralizing antibodies 2-16 years after immunization with live attenuated vaccine. A seroepidemiologic survey in the mainland of Venice.

PubMed Central

Trivello, R.; Renzulli, G.; Farisano, G.; Bonello, C.; Moschen, M.; Gasparini, V.; Benussi, G.

1988-01-01

A seroepidemiological survey was conducted on subjects who had received a full vaccination course with live attenuated poliovirus 2-16 years before. For strains 1 and 2 prevalence of seropositives and median values dropped gradually during the first 10 years; strain 3 showed a much earlier decline. Environmental displacement of wild poliovirus by the attenuated, less immunogenic strain might eventually induce a 'gap', should complacency hamper needed vaccination efforts. PMID:2850939

The influence of surface functionalization on thermal transport and thermoelectric properties of MXene monolayers.

PubMed

Sarikurt, Sevil; Çakır, Deniz; Keçeli, Murat; Sevik, Cem

2018-05-10

The newest members of a two-dimensional material family, involving transition metal carbides and nitrides (called MXenes), have garnered increasing attention due to their tunable electronic and thermal properties depending on the chemical composition and functionalization. This flexibility can be exploited to fabricate efficient electrochemical energy storage (batteries) and energy conversion (thermoelectric) devices. In this study, we calculated the Seebeck coefficients and lattice thermal conductivity values of oxygen terminated M2CO2 (where M = Ti, Zr, Hf, Sc) monolayer MXene crystals in two different functionalization configurations (model-II (MD-II) and model-III (MD-III)), using density functional theory and Boltzmann transport theory. We estimated the thermoelectric figure-of-merit, zT, of these materials by two different approaches, as well. First of all, we found that the structural model (i.e. adsorption site of oxygen atom on the surface of MXene) has a paramount impact on the electronic and thermoelectric properties of MXene crystals, which can be exploited to engineer the thermoelectric properties of these materials. The lattice thermal conductivity κl, Seebeck coefficient and zT values may vary by 40% depending on the structural model. The MD-III configuration always has the larger band gap, Seebeck coefficient and zT, and smaller κl as compared to the MD-II structure due to a larger band gap, highly flat valence band and reduced crystal symmetry in the former. The MD-III configuration of Ti2CO2 and Zr2CO2 has the lowest κl as compared to the same configuration of Hf2CO2 and Sc2CO2. Among all the considered structures, the MD-II configuration of Hf2CO2 has the highest κl, and Ti2CO2 and Zr2CO2 in the MD-III configuration have the lowest κl. For instance, while the band gap of the MD-II configuration of Ti2CO2 is 0.26 eV, it becomes 0.69 eV in MD-III. The zTmax value may reach up to 1.1 depending on the structural model of MXene.

Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chong, E. Z.; Watson, T. F.; Festy, F., E-mail: frederic.festy@kcl.ac.uk

2014-08-11

Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of amore » GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.« less

Features of Superconducting Gaps Revealed by STM/STS in Iron Based Superconductors With and Without Hole Pockets

NASA Astrophysics Data System (ADS)

Wen, Hai-Hu; Hai-Hu Wen Team

The pairing mechanism and gap structure in iron based superconductors (IBS) remains unresolved. We have conducted extensive STM/STS study on the Na(Fe1-xTx) As (T =Co, Cu, Mn), Ba1-xKxFe2As2KFe2As2, and Li1-xFexOHFeSe single crystals. We found the clear evidence of the in-gap quasi-particle states induced by the non-magnetic Cu impurities in Na(Fe0.97- x Co0.03Cux) As, giving strong evidence of the S+/- pairing. Furthermore, we show the presence of the bosonic mode with the energy identical to that of the neutron resonance and a simple linear relation Ω/kBTc ~ 4.3, being explained a consequence of the S+/-pairing. The STS spectrum in Li1-x FexOHFeSe clearly indicates the presence of double superconducting gaps with Δ1 ~ 14.3 meV and Δ2 ~ 8.6 meV. Further analysis based on QPI allows us to assign the larger (smaller) gap to the outer (inner) hybridized electron pockets. The huge value 2Δ1/kBTc = 8.7 discovered here undoubtedly proves the strong coupling mechanism. This work was supported by the Ministry of Science and Technology of China, National Natural Science Foundation of China.

Probing optical band gaps at the nanoscale in NiFe₂O₄ and CoFe₂O₄ epitaxial films by high resolution electron energy loss spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dileep, K.; Loukya, B.; Datta, R., E-mail: ranjan@jncasr.ac.in

2014-09-14

Nanoscale optical band gap variations in epitaxial thin films of two different spinel ferrites, i.e., NiFe₂O₄ (NFO) and CoFe₂O₄ (CFO), have been investigated by spatially resolved high resolution electron energy loss spectroscopy. Experimentally, both NFO and CFO show indirect/direct band gaps around 1.52 eV/2.74 and 2.3 eV, and 1.3 eV/2.31 eV, respectively, for the ideal inverse spinel configuration with considerable standard deviation in the band gap values for CFO due to various levels of deviation from the ideal inverse spinel structure. Direct probing of the regions in both the systems with tetrahedral A site cation vacancy, which is distinct frommore » the ideal inverse spinel configuration, shows significantly smaller band gap values. The experimental results are supported by the density functional theory based modified Becke-Johnson exchange correlation potential calculated band gap values for the different cation configurations.« less

The thermal expansion of (Fe1-y Ni y )Si.

PubMed

Hunt, Simon A; Wann, Elizabeth T H; Dobson, David P; Vočadlo, Lindunka; Wood, Ian G

2017-08-23

We have measured the thermal expansion of (Fe 1-y Ni y )Si for y  =  0, 0.1 and 0.2, between 40 and 1273 K. Above ~700 K the unit-cell volumes of the samples decrease approximately linearly with increasing Ni content. Below ~200 K the unit-cell volume of FeSi falls to a value between that of (Fe 0.9 Ni 0.1 )Si and (Fe 0.8 Ni 0.2 )Si. We attribute this extra contraction of the FeSi, which is a narrow band-gap semiconductor, to the depopulation of the conduction band at low temperatures; in the two alloys the additional electrons introduced by the substitution of Ni lead to the conduction band always being populated. We have fit the unit-cell volume data with a Debye internal energy model of thermal expansion and an additional volume term, above 800 K, to take account of the volumetric changes associated with changes in the composition of the sample. Using the thermophysical parameters of the fit we have estimated the band gap in FeSi to be 21(1) meV and the unit-cell volume change in FeSi associated with the depopulation of the conduction band to be 0.066(35) Å 3 /unit-cell.

Time-Resolved IR-Absorption Spectroscopy of Hot-Electron Dynamics in Satellite and Upper Conduction Bands in GaP

NASA Technical Reports Server (NTRS)

Cavicchia, M. A.; Alfano, R. R.

1995-01-01

The relaxation dynamics of hot electrons in the X6 and X7 satellite and upper conduction bands in GaP was directly measured by femtosecond UV-pump-IR-probe absorption spectroscopy. From a fit to the induced IR-absorption spectra the dominant scattering mechanism giving rise to the absorption at early delay times was determined to be intervalley scattering of electrons out of the X7 upper conduction-band valley. For long delay times the dominant scattering mechanism is electron-hole scattering. Electron transport dynamics of the upper conduction band of GaP has been time resolved.

Relationship between connexin expression and gap-junction resistivity in human atrial myocardium.

PubMed

Dhillon, Paramdeep S; Chowdhury, Rasheda A; Patel, Pravina M; Jabr, Rita; Momin, Aziz U; Vecht, Joshua; Gray, Rosaire; Shipolini, Alex; Fry, Christopher H; Peters, Nicholas S

2014-04-01

The relative roles of the gap-junctional proteins connexin40 (Cx40) and connexin43 (Cx43) in determining human atrial myocardial resistivity is unknown. In addressing the hypothesis that changing relative expression of Cx40 and Cx43 underlies an increase in human atrial myocardial resistivity with age, this relationship was investigated by direct ex vivo measurement of gap-junctional resistivity and quantitative connexin immunoblotting and immunohistochemistry. Oil-gap impedance measurements were performed to determine resistivity of the intracellular pathway (Ri), which correlated with total Cx40 quantification by Western blotting (rs=0.64, P<0.01, n=20). Specific gap-junctional resistivity (Rj) correlated not only with Western immunoquantification of Cx40 (rs=0.63, P=0.01, n=20), but also more specifically, with the Cx40 fraction localized to the intercalated disks on immunohistochemical quantification (rs=0.66, P=0.02, n=12). Although Cx43 expression showed no correlation with resistivity values, the proportional expression of the 2 connexins, (Cx40/[Cx40+Cx43]) correlated with Ri and Rj (rs=0.58, P<0.01 for Ri and rs=0.51, P=0.02 for Rj). Advancing age was associated with a rise in Ri (rs=0.77, P<0.0001), Rj (rs=0.65, P<0.001, n=23), Cx40 quantity (rs=0.54, P=0.01, n=20), and Cx40 gap-junction protein per unit area of en face disk (rs=0.61, P=0.02, n=12). Cx40 is associated with human right atrial gap-junctional resistivity such that increased total, gap-junctional, and proportional Cx40 expression increases gap-junctional resistivity. Accordingly, advancing age is associated with an increase in Cx40 expression and a corresponding increase in gap-junctional resistivity. These findings are the first to demonstrate this relationship and a mechanistic explanation for changing atrial conduction and age-related arrhythmic tendency.

30 CFR 285.811 - When must I follow my Safety Management System?

Code of Federal Regulations, 2010 CFR

2010-07-01

... Environmental and Safety Management, Inspections, and Facility Assessments for Activities Conducted Under SAPs... COP, SAP, or GAP. You must conduct all activities described in your approved COP, SAP, or GAP in...

Preparation and Electrical Properties of La0.9Sr0.1TiO3+δ

PubMed Central

Li, Wenzhi; Ma, Zhuang; Gao, Lihong; Wang, Fuchi

2015-01-01

La1−xSrxTiO3+δ (LST) has been studied in many fields, especially in the field of microelectronics due to its excellent electrical performance. Our previous theoretical simulated work has suggested that LST has good dielectric properties, but there are rare reports about this, especially experimental reports. In this paper, LST was prepared using a solid-state reaction method. The X-rays diffraction (XRD), scanning electron microscope (SEM), broadband dielectric spectroscopy, impedance spectroscopy and photoconductive measurement were used to characterize the sample. The results show that the values of dielectric parameters (the relative dielectric constant εr and dielectric loss tanδ), dependent on temperature, are stable under 350 °C and the value of the relative dielectric constant and dielectric loss are about 52–88 and 6.5 × 10−3, respectively. Its value of conductivity increases with rise in temperature, which suggests its negative temperature coefficient of the resistance. In addition, the band gap of LST is about 3.39 eV, so it belongs to a kind of wide-band-gap semiconductor materials. All these indicate that LST has anti-interference ability and good dielectric properties. It could have potential applications as an electronic material. PMID:28787995

The Effects of Data Gaps on the Calculated Monthly Mean Maximum and Minimum Temperatures in the Continental United States: A Spatial and Temporal Study.

NASA Astrophysics Data System (ADS)

Stooksbury, David E.; Idso, Craig D.; Hubbard, Kenneth G.

1999-05-01

Gaps in otherwise regularly scheduled observations are often referred to as missing data. This paper explores the spatial and temporal impacts that data gaps in the recorded daily maximum and minimum temperatures have on the calculated monthly mean maximum and minimum temperatures. For this analysis 138 climate stations from the United States Historical Climatology Network Daily Temperature and Precipitation Data set were selected. The selected stations had no missing maximum or minimum temperature values during the period 1951-80. The monthly mean maximum and minimum temperatures were calculated for each station for each month. For each month 1-10 consecutive days of data from each station were randomly removed. This was performed 30 times for each simulated gap period. The spatial and temporal impact of the 1-10-day data gaps were compared. The influence of data gaps is most pronounced in the continental regions during the winter and least pronounced in the southeast during the summer. In the north central plains, 10-day data gaps during January produce a standard deviation value greater than 2°C about the `true' mean. In the southeast, 10-day data gaps in July produce a standard deviation value less than 0.5°C about the mean. The results of this study will be of value in climate variability and climate trend research as well as climate assessment and impact studies.

Band gap and conductivity variations of ZnO nano structured thin films annealed under Vacuum

NASA Astrophysics Data System (ADS)

Vattappalam, Sunil C.; Thomas, Deepu; T, Raju Mathew; Augustine, Simon; Mathew, Sunny

2015-02-01

Zinc Oxide thin films were prepared by Successive Ionic layer adsorption and reaction technique(SILAR). The samples were annealed under vacuum and conductivity of the samples were taken at different temperatures. UV Spectrograph of the samples were taken and the band gap of each sample was found from the data. All the results were compared with that of the sample annealed under air. It was observed that the band gap decreases and concequently conductivity of the samples increases when the samples are annealed under vacuum.

Band gap and conductivity variations of ZnO thin films by doping with Aluminium

NASA Astrophysics Data System (ADS)

Vattappalam, Sunil C.; Thomas, Deepu; T, Raju Mathew; Augustine, Simon; Mathew, Sunny

2015-02-01

Zinc Oxide thin films were prepared by Successive Ionic layer adsorption and reaction technique(SILAR). Aluminium was doped for different doping concentrations from 3 at.% to 12 at.% in steps of 3 at.%. Conductivity of the samples were taken at different temperatures. UV Spectrograph of the samples were taken and the band gap of each sample was found from the data. It was observed that as the doping concentration of Aluminium increases, the band gap of the samples decreases and concequently conductivity of the samples increases.

A novel hypothesis about mechanisms affecting conduction velocity of central myelinated fibers.

PubMed

Adriano, Enrico; Perasso, Luisa; Panfoli, Isabella; Ravera, Silvia; Gandolfo, Carlo; Mancardi, Gianluigi; Morelli, Alessandro; Balestrino, Maurizio

2011-10-01

The hypothesis that gap junctions are implicated in facilitating axonal conduction has not yet been experimentally demonstrated at the electrophysiological level. We found that block of gap junctions with oleammide slows down axonal conduction velocity in the hippocampal Schaffer collaterals, a central myelinated pathway. Moreover, we explored the possibility that support by the oligodendrocyte to the axon involves energy metabolism, a hypothesis that has been recently proposed by some of us. In agreement with this hypothesis, we found that the effect of oleammide was reversed by pretreatment with creatine, a compound that is known to increase the energy charge of the tissue. Moreover, conduction velocity was also slowed down by anoxia, a treatment that obviously decreases the energy charge of the tissue, and by ouabain, a compound that blocks plasma membrane Na/K-ATPase, the main user of ATP in the brain. We hypothesize that block of gap junctions slows down conduction velocity in central myelinated pathways because oligodendrocytes synthesize ATP and transfer it to the axon through gap junctions.

Value gaps in dental practice: understanding how differences in core values can adversely affect the practice.

PubMed

Newsome, Philip; Wolfe, Ira S

2003-11-01

The authors explore the importance of human values in dental practice, an area often overlooked as we struggle to deal with the everyday demands of treating patients and managing staff members. Such values are, however, fundamental to the success of any practice; therefore, it is important to understand their significance. Problems arise in dental practices when gaps develop between the values held by the various players involved (that is, between the entire dental team and patients, the dentist/owner's personal values and business goals, the dentist/owner and staff members, and the dental practice and any third-party funding organizations). By understanding the potentially damaging consequences of value gaps for practice viability, dental practice owners and managers can take steps to create a more harmonious workplace in which all parties strive to reach common goals.

Quantum transport in alkane molecular wires: Effects of binding modes and anchoring groups

NASA Astrophysics Data System (ADS)

Sheng, W.; Li, Z. Y.; Ning, Z. Y.; Zhang, Z. H.; Yang, Z. Q.; Guo, H.

2009-12-01

Effects of binding modes and anchoring groups on nonequilibrium electronic transport properties of alkane molecular wires are investigated from atomic first-principles based on density functional theory and nonequilibrium Green's function formalism. Four typical binding modes, top, bridge, hcp-hollow, and fcc-hollow, are considered at one of the two contacts. For wires with three different anchoring groups, dithiol, diamine, or dicarboxylic acid, the low bias conductances resulting from the four binding modes are all found to have either a high or a low value, well consistent with recent experimental observations. The trend can be rationalized by the behavior of electrode-induced gap states at small bias. When bias increases to higher values, states from the anchoring groups enter into the bias window and contribute significantly to the tunneling process so that transport properties become more complicated for the four binding modes. Other low bias behaviors including the values of the inverse length scale for tunneling characteristic, contact resistance, and the ratios of the high/low conductance values are also calculated and compared to experimental results. The conducting capabilities of the three anchoring groups are found to decrease from dithiol, diamine to dicarboxylic-acid, largely owing to a decrease in binding strength to the electrodes. Our results give a clear microscopic picture to the transport physics and provide reasonable qualitative explanations for the corresponding experimental data.

Origin of and tuning the optical and fundamental band gaps in transparent conducting oxides: The case of M2O3(M =Al ,Ga ,In )

NASA Astrophysics Data System (ADS)

Sabino, Fernando P.; Besse, Rafael; Oliveira, Luiz Nunes; Wei, Su-Huai; Da Silva, Juarez L. F.

2015-11-01

Good transparent conducting oxides (TCOs), such as In2O3 :Sn (ITO), usually combine large optical band gaps, essential for high transparency, with relatively small fundamental band gaps due to low conduction-band minima, which favor n -type doping and enhance the electrical conductivity. It has been understood that the optical band gaps are wider than the fundamental band gaps because optical transitions between the band-edge states are forbidden. The mechanism blocking such transitions, which can play a crucial role in the designing of alternative TCOs, nonetheless remains obscure. Here, based on first-principles density functional theory calculations and symmetry analysis of three oxides, M2O3 (M =Al ,Ga ,In ), we identify the physical origin of the gap disparities. Three conditions are necessary: (1) the crystal structure must have global inversion symmetry; (2) in order to belong to the Ag or A1 g irreducible representations, the states at the conduction-band minimum must have cation and oxygen s character; (3) in order to have g parity, the oxygen p orbitals constituting the states near the valence-band maximum must be strongly coupled to the cation d orbitals. Under these conditions, optical excitations across the fundamental gap will be forbidden. The three criteria explain the trends in the M2O3 (M =Al,Ga,In) sequence, in particular, explaining why In2O3 in the bixbyite structure yields the highest figure of merit. Our study provides guidelines expected to be instrumental in the search for new TCO materials.

Synthesis, characterisation and thermoelectric properties of the oxytelluride Bi{sub 2}O{sub 2}Te

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luu, Son D.N.; Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD; Vaqueiro, Paz, E-mail: p.vaqueiro@reading.ac.uk

2015-03-15

Bi{sub 2}O{sub 2}Te was synthesised from a stoichiometric mixture of Bi, Bi{sub 2}O{sub 3} and Te by a solid state reaction. Analysis of powder X-ray diffraction data indicates that this material crystallises in the anti-ThCr{sub 2}Si{sub 2} structure type (space group I4/mmm), with lattice parameters a=3.98025(4) and c=12.70391(16) Å. The electrical and thermal transport properties of Bi{sub 2}O{sub 2}Te were investigated as a function of temperature over the temperature range 300≤T (K)≤665. These measurements indicate that Bi{sub 2}O{sub 2}Te is an n-type semiconductor, with a band gap of 0.23 eV. The thermal conductivity of Bi{sub 2}O{sub 2}Te is remarkably lowmore » for a crystalline material, with a value of only 0.91 W m{sup −1} K{sup −1} at room temperature. - Graphical abstract: Bi{sub 2}O{sub 2}Te, which crystallises in the anti-ThCr{sub 2}Si{sub 2} structure type, is an n-type semiconductor with a remarkably low thermal conductivity. - Highlights: • Bi{sub 2}O{sub 2}Te crystallises in the anti-ThCr{sub 2}Si{sub 2} structure type. • Bi{sub 2}O{sub 2}Te is an n-type semiconductor, with a band gap of 0.23 eV. • The thermal conductivity of Bi{sub 2}O{sub 2}Te approaches values found for amorphous solids. • The thermoelectric figure of merit of undoped Bi{sub 2}O{sub 2}Te reaches 0.13 at 573 K.« less

Capacitance and conductance-frequency characteristics of In-pSi Schottky barrier diode

NASA Astrophysics Data System (ADS)

Dhimmar, J. M.; Desai, H. N.; Modi, B. P.

2015-06-01

The Schottky barrier height (SBH) values have been calculated by using the reverse bias capacitance-voltage (C-V) characteristics at temperature range of 120-360K. The forward bias capacitance-frequency (C-f) and conductance- frequency (G-f) measurement of In-pSi SBD have been carried out from 0-1.0 V with a step up 0.05 V whereby the energy distribution of the interface state has been determined from the forward bias I-V data taking the bias dependence of the effective barrier height and series resistance (RS) into account. The high value of ideality factor (n=2.12) was attributing to high density of interface states and interfacial oxide layer at metal semiconductor interface. The interface state density (NSS) shows a decrease with bias from bottom of conduction band toward the mid gap. In order to examine frequency dependence NSS, RS, C-V and G(ω)/ω-f measurement of the diode were performed at room temperature in the frequency range of 100Hz-100KHz. Experimental result confirmed that there is an influence in the electrical characteristic of Schottky diode.

A promising p-type transparent conducting material: Layered oxysulfide [Cu2S2][Sr3Sc2O5

NASA Astrophysics Data System (ADS)

Liu, Min-Ling; Wu, Li-Bin; Huang, Fu-Qiang; Chen, Li-Dong; Chen, I.-Wei

2007-12-01

Sr3Cu2Sc2O5S2, a layered oxysulfide, composed of anti-PbO-like [Cu2S2] slabs alternating with perovskitelike [Sr3Sc2O5] slabs, was systematically studied as a p-type transparent conducting material. The material has a wide energy gap of 3.1eV and a p-type electrical conductivity of 2.8Scm-1 at room temperature. The hole mobility of +150cm2V-1S-1 at room temperature, which is much higher than the typical value of ˜10-1-10width="0.3em"/>cm2V-1S-1 found in other copper compounds. The performances of bulk undoped Sr3Cu2Sc2O5S2 show the promise of copper oxysulfides as a class of p-type transparent conductive materials that is essential for optoelectronic applications.

Fast events in single-channel currents activated by acetylcholine and its analogues at the frog muscle end-plate.

PubMed Central

Colquhoun, D; Sakmann, B

1985-01-01

The fine structure of ion-channel activations by junctional nicotinic receptors in adult frog muscle fibres has been investigated. The agonists used were acetylcholine (ACh), carbachol (CCh), suberyldicholine (SubCh) and decan-1,10-dicarboxylic acid dicholine ester (DecCh). Individual activations (bursts) were interrupted by short closed periods; the distribution of their durations showed a major fast component ('short gaps') and a minor slower component ('intermediate gaps'). The mean duration of both short and intermediate gaps was dependent on the nature of the agonist. For short gaps the mean durations (microseconds) were: ACh, 20; SubCh, 43; DecCh, 71; CCh, 13. The mean number of short gaps per burst were: ACh, 1.9; SubCh, 4.1; DecCh, 2.0. The mean number of short gaps per burst, and the mean number per unit open time, were dependent on the nature of the agonist, but showed little dependence on agonist concentration or membrane potential for ACh, SubCh and DecCh. The short gaps in CCh increased in frequency with agonist concentration and were mainly produced by channel blockages by CCh itself. Partially open channels (subconductance states) were clearly resolved rarely (0.4% of gaps within bursts) but regularly. Conductances of 18% (most commonly) and 71% of the main value were found. However, most short gaps were probably full closures. The distribution of burst lengths had two components. The faster component represented mainly isolated short openings that were much more common at low agonist concentrations. The slower component represented bursts of longer openings. Except at very low concentrations more than 85% of activations were of this type, which corresponds to the 'channel lifetime' found by noise analysis. The frequency of channel openings increased slightly with hyperpolarization. The short gaps during activations were little affected when (a) the [H+]o or [Ca2+]o were reduced to 1/10th of normal, (b) when extracellular Ca2+ was replaced by Mg2+, (c) when the [Cl-]i was raised or (d) when, in one experiment on an isolated inside-out patch, the normal intracellular constituents were replaced by KCl. Reduction of [Ca2+]O to 1/10 of normal increased the single-channel conductance by 50%, and considerably increased the number of intermediate gaps. No temporal asymmetry was detectable in the bursts of openings. Positive correlations were found between the lengths of successive apparent open times at low SubCh concentrations, but no correlations between burst lengths were detectable. The component of brief openings behaves, at low concentrations, as though it originates from openings of singly occupied channels.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 11 Fig. 14 Plate 1 PMID:2419552

Optical properties of A Fe 2 As 2 ( A = Ca , Sr, and Ba) single crystals

DOE PAGES

Dai, Y. M.; Akrap, Ana; Bud'ko, S. L.; ...

2016-11-23

The detailed optical properties have been determined for the iron-based materials A Fe 2 As 2 , where A = Ca , Sr, and Ba, for light polarized in the iron-arsenic (a-b) planes over a wide frequency range, above and below the magnetic and structural transitions at T N = 138 , 195, and 172 K, respectively. The real and imaginary parts of the complex conductivity are fit simultaneously using two Drude terms in combination with a series of oscillators. Above T N, the free-carrier response consists of a weak, narrow Drude term, and a strong, broad Drude term, both of which show only a weak temperature dependence. Below T N there is a slight decrease of the plasma frequency but a dramatic drop in the scattering rate for the narrow Drude term, and for the broad Drude term there is a significant decrease in the plasma frequency, while the decrease in the scattering rate, albeit significant, is not as severe. The small values observed for the scattering rates for the narrow Drude term for Tmore » $$\\ll$$ T N may be related to the Dirac conelike dispersion of the electronic bands. Below T N new features emerge in the optical conductivity that are associated with the reconstruction Fermi surface and the gapping of bands at Δ 1 ≃ 45 – 80 meV, and Δ 2 ≃ 110 – 210 meV. In conclusion, the reduction in the spectral weight associated with the free carriers is captured by the gap structure; specifically, the spectral weight from the narrow Drude term appears to be transferred into the low-energy gap feature, while the missing weight from the broad term shifts to the high-energy gap.« less

How can we further improve the LDL-cholesterol target level achievement rate based on the Hungarian MULTI GAP 2011 study results and considering the new European dyslipidemia guidelines?

PubMed

Mark, Laszlo; Paragh, György; Karadi, Istvan; Reiber, Istvan; Pados, Gyula; Kiss, Zoltan

2012-09-08

Despite the continuous improvement of the quality of lipid lowering therapy the achievement of target values is still not satisfactory, mainly in the very high cardiovascular risk category patients, where the goal of low density lipoprotein cholesterol (LDL-C) is 1.80 mmol/l. The trends in lipid lowering treatment of 17420 patients from different studies conducted between 2004 and 2010 were compared to that of 1626 patients of MULTI GAP (MULTI Goal Attainment Problem) 2011 treated by general practitioners (GPs) and specialists. In MULTI GAP 2011 the mean LDL-C level ± SD) of patients treated by GPs was found to be 2.87 ±1.01 mmol/l, the target value of 2.50 was achieved by 40% of them, in the specialists' patients the mean LDL-C level proved to be 2.77 ±1.10 mmol/l and the achievement rate was 45%. In the 2.50 mmol/l achievement rate of GPs' patients a satisfactory improvement was observed in the studied years, but the 1.80 mmol/l LDL-C goal in 2011 was attained only in 11% of very high risk cases. There was a linear correlation between the patient compliance estimated by the physicians and the LDL-C achievement rate. As the number of very high risk category patients has been increased according to the new European dyslipidemia guidelines, growing attention needs to be placed on attainment of the 1.80 mmol/l LDL-C level. Based on the results of the MULTI GAP studies, improving patients' adherence and the continuous training of physicians are necessary.

Anisotropic Eliashberg theory of MgB 2: Tc, isotope effects, superconducting energy gaps, quasiparticles, and specific heat

NASA Astrophysics Data System (ADS)

Choi, Hyoung Joon; Cohen, Marvin L.; Louie, Steven G.

2003-03-01

The anisotropic Eliashberg formalism, employing results from the ab initio pseudopotential density functional calculations, is applied to study the superconducting properties of MgB 2. It is shown that the relatively high transition temperature of MgB 2 originates from strong electron-phonon coupling of the hole states in the boron σ-bonds although the coupling strength averaged over the Fermi surface is moderate, and the reduction of the isotope effect arises from the large anharmonicity of the relevant phonons. The superconducting energy gap is nodeless but its value varies strongly on different pieces of the Fermi surface. The gap values Δ( k) cluster into two groups at low temperature, a small value of ∼2 meV and a large value of ∼7 meV, resulting in two thresholds in the quasiparticle density of states and an increase in the specific heat at low temperature due to quasiparticle excitations over the small gap. All of these results are in good agreement with corresponding experiments and support the view that MgB 2 is a phonon-mediated multiple-gap superconductor.

Facilitating women's success in business: Interrupting the process of stereotype threat through affirmation of personal values.

PubMed

Kinias, Zoe; Sim, Jessica

2016-11-01

Two field experiments examined if and how values affirmations can ameliorate stereotype threat-induced gender performance gaps in an international competitive business environment. Based on self-affirmation theory (Steele, 1988), we predicted that writing about personal values unrelated to the perceived threat would attenuate the gender performance gap. Study 1 found that an online assignment to write about one's personal values (but not a similar writing assignment including organizational values) closed the gender gap in course grades by 89.0% among 423 Masters of Business Administration students (MBAs) at an international business school. Study 2 replicated this effect among 396 MBAs in a different cohort with random assignment and tested 3 related mediators (self-efficacy, self-doubt, and self-criticism). Personal values reflection (but not reflecting on values including those of the organization or writing about others' values) reduced the gender gap by 66.5%, and there was a significant indirect effect through reduced self-doubt. These findings show that a brief personal values writing exercise can dramatically improve women's performance in competitive environments where they are negatively stereotyped. The results also demonstrate that stereotype threat (Steele & Aronson, 1995) can occur within a largely non-American population with work experience and that affirming one's core personal values (without organizational values) can ameliorate the threat. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Transport properties through graphene grain boundaries: strain effects versus lattice symmetry

NASA Astrophysics Data System (ADS)

Hung Nguyen, V.; Hoang, Trinh X.; Dollfus, P.; Charlier, J.-C.

2016-06-01

As most materials available at the macroscopic scale, graphene samples usually appear in a polycrystalline form and thus contain grain boundaries. In the present work, the effect of uniaxial strain on the electronic transport properties through graphene grain boundaries is investigated using atomistic simulations. A systematic picture of transport properties with respect to the strain and lattice symmetry of graphene domains on both sides of the boundary is provided. In particular, it is shown that strain engineering can be used to open a finite transport gap in all graphene systems where the two domains are arranged in different orientations. This gap value is found to depend on the strain magnitude, on the strain direction and on the lattice symmetry of graphene domains. By choosing appropriately the strain direction, a large transport gap of a few hundred meV can be achieved when applying a small strain of only a few percents. For a specific class of graphene grain boundary systems, strain engineering can also be used to reduce the scattering on defects and thus to significantly enhance the conductance. With a large strain-induced gap, these graphene heterostructures are proposed to be promising candidates for highly sensitive strain sensors, flexible electronic devices and p-n junctions with non-linear I-V characteristics.

Inhibition of gap junction currents by the abused solvent toluene.

PubMed

Del Re, Angelo M; Woodward, John J

2005-05-09

Abused inhalants are a large class of compounds that are inhaled for their intoxicating and mood altering effects. They include chemicals with known therapeutic uses such as anesthetic gases as well as volatile organic solvents like toluene that are found in paint thinners and adhesives. Because of their widespread commercial use and availability, inhalants are often among the first drugs that children encounter and use of these compounds is often associated with adverse acute and long-term consequences. The cellular and molecular sites of action for abused inhalants is not well known although recent studies report that toluene and other organic solvents alter the activity of specific ligand- and voltage-gated ion channels that regulate cellular excitability. As part of an ongoing effort to define molecular sites of action for abused inhalants, this study examined the effect of toluene on the function of gap junction proteins endogenously expressed in human embryonic kidney (HEK 293) cells. Gap junctions allow cell-to-cell electrical communication as well as passage of small molecular weight substances and are critical for synchronizing cellular activity in certain tissues. Gap junction currents in HEK 293 cells were measured during brief voltage steps using patch-clamp electrophysiology and were blocked by known gap junction blockers confirming expression of connexin proteins in these cells. Toluene dose-dependently inhibited these conductances with threshold effects appearing at approximately 0.4 mM and near complete inhibition occurring at concentrations of 1 mM and higher. The estimated EC50 value for toluene inhibition of gap junction currents in HEK 293 cells was 0.57 mM. The results of these studies suggest that volatile solvents including toluene may produce some of their effects by disrupting inter-cellular communication mediated by gap junction proteins.

Effect of 50MeV Li{sup 3+} ion irradiation on structural, optical and electrical properties of amorphous Se{sub 95}Zn{sub 5} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Shabir, E-mail: shaphyjmi@gmail.com; Sethi, Riti; Nasir, Mohd

2015-08-28

Present work focuses on the effect of swift heavy ion (SHI) irradiation of 50MeV Li{sup 3+} ions by varying the fluencies in the range of 1×10{sup 12} to 5×10{sup 13} ions/cm{sup 2} on the morphological, structural, optical and electrical properties of amorphous Se{sub 95}Zn{sub 5} thin films. Thin films of ~250nm thickness were deposited on cleaned glass substrates by thermal evaporation technique. X-ray diffraction (XRD) analysis shows the pristine thin film of Se{sub 95}Zn{sub 5} growsin hexagonal phase structure. Also it was found that the small peak observed in XRD spectra vanishes after SHI irradiation indicates the defects of themore » material increases. The optical parameters: absorption coefficient (α), extinction coefficient (K), refractive index (n) optical band gap (E{sub g}) and Urbach’s energy (E{sub U}) are determined from optical absorption spectra data measured from spectrophotometry in the wavelength range 200-1000nm. It was found that the values of absorption coefficient, refractive index and extinction coefficient increases while the value optical band gap decreases with the increase of ion fluence. This post irradiation change in the optical parameters was interpreted in terms of bond distribution model. Electrical properties such as dc conductivity and temperature dependent photoconductivity of investigated thin films were carried out in the temperature range 309-370 K. Analysis of data shows activation energy of dark current is greater as compared to activation energy photocurrent. The value of activation energy decreases with the increase of ion fluence indicates that the defect density of states increases.Also it was found that the value of dc conductivity and photoconductivity increases with the increase of ion fluence.« less

Energy-gap reduction in heavily doped silicon: Causes and consequences

NASA Astrophysics Data System (ADS)

Pantelides, Sokrates T.; Selloni, Annabella; Car, Roberto

1985-02-01

The authors review briefly the existing theoretical treatments of the various effects that contribute to the reduction of the energy gap in heavily doped Si, namely electron-electron and electron-impurity interactions and the effect of disorder in the impurity distribution. They then turn to the longstanding question why energy-gap reductions extracted from three different types of experiments have persistently produced values with substantial discrepancies, making it impossible to compare with theoretical values. First, they demonstrate that a meaningful comparison between theory and experiment can indeed be made if theoretical calculations are carried out for actual quantities that experiments measure, e.g. luminescence spectra, as recently done by Selloni and Pantelides. Then, they demonstrate that, independent of any theoretical calculations, the optical absorption spectra are fully consistent with the luminescence spectra and that the discrepancies in the energy-gap reductions extracted from the two sets of spectra are caused entirely by the curve-fitting procedures used in analyzing optical-absorption data. Finally, they show explicitly that, as already believed by many authors, energy-gap reductions extracted from electrical measurements on transistors do not correspond to true gap reductions. They identify two corrections that must be added to the values extracted from the electrical data in order to arrive at the true gap reductions and show that the resulting values are in good overall agreement with luminescence and absorption data. They, therefore, demonstrate that the observed reduction in emitter injection efficiency in bipolar transistors is not strictly due to a gap reduction, as generally believed, but to three very different effects.

The acculturation gap-distress model: Extensions and application to Arab Canadian families.

PubMed

Rasmi, Sarah; Chuang, Susan S; Hennig, Karl

2015-10-01

Using a multidomain and bidimensional approach, the present study applied and extended the acculturation gap-distress model with an immigrant Arab Canadian sample. Consistent with this model, immigrant Arab emerging adults (n = 113) perceived acculturation gaps between themselves and their parents with respect to their heritage and settlement culture orientation and values. Some of these gaps, in turn, were associated with poorer outcomes. Extending the model, the most problematic acculturation gaps were those in which the emerging adult perceived themselves to be more oriented to Arab culture and values than their parents. We also found some support for the moderating role of parent-emerging adult relationships. (c) 2015 APA, all rights reserved).

Evaluation of outpatient service quality in Eastern Saudi Arabia

PubMed Central

Fraihi, Khalid J. Al; FAMCO, Dip; FAMCO, Fellow; Latif, Shahid A.

2016-01-01

Objectives: To investigate perceptions and expectations of patients regarding hospital outpatient services by using a service quality gap model and factors influencing such gaps. Methods: In this cross-sectional descriptive study conducted between October and November 2014 in the outpatient waiting areas of a hospital in the Eastern Province of Saudi Arabia, a sample of 306 patients was selected by convenience sampling technique. The data was collected through an Arabic version of the service quality (SERVQUAL) questionnaire consisting of 2 parts: patients’ demographic characteristics, and 22 items scales of patients’ expectations and perceptions of SERVQUAL. The data was analyzed by confirmatory factor analysis, independent, and paired t samples tests and one way analysis of variance test. Results: The results showed that the proposed model for service quality dimensions had a good fit by satisfying the recommended values. The patients’ expectations exceeded perceptions in all service quality dimensions indicating statistically significant service quality gaps (t=26.3, p<0.000). Findings revealed that the empathy dimension contributed most patients’ expectations (4.7 ± 0.5) and perceptions (3.7 ± 0.8) scores, and responsiveness contributed least to expectations (4.5 ± 0.6) and perceptions (3.2 ± 0.8) scores. Prompt services showed highest service quality gap, while observation of privacy showed the smallest service quality gap in the statements. The study showed a significant association between gender, age, education, multiple visits, and service quality dimensions. Conclusion: The proposed model is valid and reliable and significant service quality gaps of all 5 dimensions need to be prioritized and addressed by focused improvement efforts of hospital management. PMID:27052285

Evaluation of outpatient service quality in Eastern Saudi Arabia. Patient's expectations and perceptions.

PubMed

Al Fraihi, Khalid J; Latif, Shahid A

2016-04-01

To investigate perceptions and expectations of patients regarding hospital outpatient services by using a service quality gap model and factors influencing such gaps. In this cross-sectional descriptive study conducted between October and November 2014 in the outpatient waiting areas of a hospital in the Eastern Province of Saudi Arabia, a sample of 306 patients was selected by convenience sampling technique. The data was collected through an Arabic version of the service quality (SERVQUAL) questionnaire consisting of 2 parts: patients' demographic characteristics, and 22 items scales of patients' expectations and perceptions of SERVQUAL. The data was analyzed by confirmatory factor analysis, independent, and paired t samples tests and one way analysis of variance test The results showed that the proposed model for service quality dimensions had a good fit by satisfying the recommended values. The patients' expectations exceeded perceptions in all service quality dimensions indicating statistically significant service quality gaps (t=26.3, p less than 0.000). Findings revealed that the empathy dimension contributed most patients' expectations (4.7 ± 0.5) and perceptions (3.7 ± 0.8) scores, and responsiveness contributed least to expectations (4.5 ± 0.6) and perceptions (3.2 ± 0.8) scores. Prompt services showed highest service quality gap, while observation of privacy showed the smallest service quality gap in the statements. The study showed a significant association between gender, age, education, multiple visits, and service quality dimensions. The proposed model is valid and reliable and significant service quality gaps of all 5 dimensions need to be prioritized and addressed by focused improvement efforts of hospital management.

Charge-transport in tin-iodide perovskite CH3NH3SnI3: origin of high conductivity.

PubMed

Takahashi, Yukari; Obara, Rena; Lin, Zheng-Zhong; Takahashi, Yukihiro; Naito, Toshio; Inabe, Tamotsu; Ishibashi, Shoji; Terakura, Kiyoyuki

2011-05-28

The structural and electrical properties of a metal-halide cubic perovskite, CH(3)NH(3)SnI(3), have been examined. The band structure, obtained using first-principles calculation, reveals a well-defined band gap at the Fermi level. However, the temperature dependence of the single-crystal electrical conductivity shows metallic behavior down to low temperatures. The temperature dependence of the thermoelectric power is also metallic over the whole temperature range, and the large positive value indicates that charge transport occurs with a low concentration of hole carriers. The metallic properties of this as-grown crystal are thus suggested to result from spontaneous hole-doping in the crystallization process, rather than the semi-metal electronic structure. The present study shows that artificial hole doping indeed enhances the conductivity.

Compositional dependence of optical band gap and refractive index in lead and bismuth borate glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mallur, Saisudha B.; Czarnecki, Tyler; Adhikari, Ashish

2015-08-15

Highlights: • Refractive indices increase with increasing PbO/Bi{sub 2}O{sub 3} content. • Optical band gap arises due to direct forbidden transition. • Optical band gaps decrease with increasing PbO/Bi{sub 2}O{sub 3} content. • New empirical relation between the optical band gap and the refractive index. - Abstract: We prepared a series of lead and bismuth borate glasses by varying PbO/Bi{sub 2}O{sub 3} content and studied refractive index and optical band gap as a function of glass composition. Refractive indices were measured very accurately using a Brewster’s angle set up while the optical band gaps were determined by analyzing the opticalmore » absorption edge using the Mott–Davis model. Using the Lorentz–Lorentz method and the effective medium theory, we calculated the refractive indices and then compared them with the measured values. Bismuth borate glasses show better agreement between the calculated values of the refractive index and experimental values. We used a differential method based on Mott–Davis model to obtain the type of transition and optical band gap (E{sub opt}) which in turn was compared with the value of E{sub opt} obtained using the extinction coefficient. Our analysis shows that in both lead and bismuth borate glasses, the optical band gap arises due to direct forbidden transition. With increasing PbO/Bi{sub 2}O{sub 3} content, the absorption edge shifts toward longer wavelengths and the optical band gap decreases. This behavior can be explained in terms of changes to the Pb−O/Bi−O chemical bonds with glass composition. We obtained a new empirical relation between the optical band gap and the refractive index which can be used to accurately determine the electronic oxide polarizability in lead and bismuth oxide glasses.« less

Key optoelectronic properties of Diiodo-bis(carbamide)-zinc(II): An experimental and computational investigation

NASA Astrophysics Data System (ADS)

Shkir, Mohd.; Irfan, Ahmad; AlFaify, S.; Ganesh, V.; Arora, M.; Muhammad, Shabbir; Al-Sehemi, Abdullah G.; Yahia, I. S.

2018-03-01

Large size single crystals of Diiodo-bis(carbamide)-zinc(II) [ZnI2. 2[CO(NH2)2] were grown successfully for the first time by slow evaporation techniques at room temperature within the evaporation time of two weeks. The single phase and high crystalline nature of the grown crystals was confirmed by X-ray diffraction analysis. Quantum chemically the geometrical parameters were found in good correlation with experimental values calculated at B3LYP/6-31G* (LANL2DZ), B2LYPD/6-31G* (LANL2DZ), M062X/6-31G* (LANL2DZ) and MP2/6-31G* (LANL2DZ) level of theories. Additionally, the experimental vibrational modes also have shown a good agreement with calculated ones. The optical transparency and band gap were calculated and found to be ∼80% and 4.706 eV, respectively. The calculated value of HOMO-LUMO gap was found in correlation with experimental energy gap. The electronic properties were investigated by shedding light on the frontier molecular orbitals, partial density of states (PDOS), and total density of states (TDOS). The mechanical and dielectric studies show that the grown crystals possess quite good mechanical strength and dielectric constant. The dielectric loss revealed that the grown crystal contains low defects. The total ac electrical conductivity was increased with frequency and the frequency components confirm the sudden hoping mechanism in the grown crystal.

Parameters optimization of laser brazing in crimping butt using Taguchi and BPNN-GA

NASA Astrophysics Data System (ADS)

Rong, Youmin; Zhang, Zhen; Zhang, Guojun; Yue, Chen; Gu, Yafei; Huang, Yu; Wang, Chunming; Shao, Xinyu

2015-04-01

The laser brazing (LB) is widely used in the automotive industry due to the advantages of high speed, small heat affected zone, high quality of welding seam, and low heat input. Welding parameters play a significant role in determining the bead geometry and hence quality of the weld joint. This paper addresses the optimization of the seam shape in LB process with welding crimping butt of 0.8 mm thickness using back propagation neural network (BPNN) and genetic algorithm (GA). A 3-factor, 5-level welding experiment is conducted by Taguchi L25 orthogonal array through the statistical design method. Then, the input parameters are considered here including welding speed, wire speed rate, and gap with 5 levels. The output results are efficient connection length of left side and right side, top width (WT) and bottom width (WB) of the weld bead. The experiment results are embed into the BPNN network to establish relationship between the input and output variables. The predicted results of the BPNN are fed to GA algorithm that optimizes the process parameters subjected to the objectives. Then, the effects of welding speed (WS), wire feed rate (WF), and gap (GAP) on the sum values of bead geometry is discussed. Eventually, the confirmation experiments are carried out to demonstrate the optimal values were effective and reliable. On the whole, the proposed hybrid method, BPNN-GA, can be used to guide the actual work and improve the efficiency and stability of LB process.

The is and ought of the Ethics of Neuroenhancement: Mind the Gap.

PubMed

Forlini, Cynthia; Hall, Wayne

2015-01-01

Ethical perspectives on the use of stimulants to enhance human cognitive performance (neuroenhancement) are polarized between conservative and liberal theories offering opposing advice on whether individuals have a right to use neuroenhancers and what the social outcomes of neuroenhancement might be. Meanwhile, empirical evidence shows modest prevalence and guarded public attitudes toward the neuroenhancement use of stimulants. In this Perspective, we argue that the dissonance between the prescriptions of ethical theories (what ought to be) and empirical evidence (what is) has impaired our understanding of neuroenhancement practices. This dissonance is a result of three common errors in research on the ethics of neuroenhancement: (1) expecting that public perspectives will conform to a prescriptive ethical framework; (2) ignoring the socio-economic infrastructures that influence individuals' decisions on whether or not to use neuroenhancement; and (3) overlooking conflicts between fundamental ethical values namely, safety of neuroenhancement and autonomy. We argue that in order to understand neuroenhancement practices it is essential to recognize which values affect individual decisions to use or refuse to use neuroenhancement. Future research on the ethics of neuroenhancement should assess the morally significant values for stakeholders. This will fill the gap between what ought to be done and what is done with an improved understanding of what can be done within a particular context. Clarifying conflicts between competing moral values is critical in conducting research on the efficacy of substances putatively used for neuroenhancement and also on neuroenhancement practices within academic, professional and social environments.

Effect of electronic structure of the diamond surface on the strength of the diamond-metal interface

NASA Technical Reports Server (NTRS)

Pepper, S. V.

1981-01-01

A diamond surface undergoes a transformation in its electronic structure by a vacuum anneal at approximately 900 C. The polished surface has no electronic states in the band gap, whereas the annealed surface has both occupied and unoccupied states in the and gap and exhibits some electrical conductivity. The effect of this transformation on the strength of the diamond metal interface was investigated by measuring the static friction force of an atomically clean meta sphere on a diamond flat in ultrahigh vacuum. It was found that low friction (weak bonding) is associated with the diamond surface devoid of gap states whereas high friction (strong bonding) is associated with the diamond surface with gap states. Exposure of the annealed surface to excited hydrogen also leads to weak bonding. The interfacial bond is discussed in terms of interaction of the metal conduction band electrons with the band gap states on the diamond surface. Effects of surface electrical conductivity on the interfacial bond are also be considered.

An Opportunity to Bridge the Gap Between Clinical Research and Clinical Practice: Implications for Clinical Training

PubMed Central

Hershenberg, Rachel; Drabick, Deborah A. G.; Vivian, Dina

2013-01-01

Clinical researchers and clinical practitioners share a goal of increasing the integration of research and clinical practice, which is reflected in an evidence-based practice (EBP) approach to psychology. The EBP framework involves the integration of research findings with clinical expertise and client characteristics, values, and preferences, and consequently provides an important foundation for conducting clinically relevant research, as well as empirically based and clinically sensitive practice. Given the critical role that early training can play in the integration of science and practice and in promoting the future of the field, the present article addresses predoctoral training programs as a context for adopting an EBP approach to clinical work. We address training in the three components of EBP and provide suggestions for curriculum development and practicum training that we hope will contribute to bridging the gap between research and practice. PMID:22642520

Influence of carbon nanotubes on the optical properties of plasticized solid polymer electrolytes

NASA Astrophysics Data System (ADS)

Ibrahim, Suriani; Yasin, Siti Mariah Mohd; Johan, Mohd Rafie

2013-07-01

Polyethylene oxide (PEO) based solid polymer electrolyte films complexed with lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC) and carbon nanotubes (CNTs) are prepared by solution-casting technique. The complexation of doping materials with polymer is confirmed by X-ray diffraction and infrared studies. The incorporation of LiPF6, EC and CNTs into the host polymer shows a significant increase in conductivity of 10-10 and 10-3 S cm-1. The optical properties such as direct and indirect band gaps are investigated for pure and doped polymer films within a wavelength range of 200-400 nm. It is found that the energy gaps and band edge values shift towards lower energies upon doping. It is shown that LiPF6, EC and CNTs are responsible for the formation of defects in polymer electrolytes, which increases the degree of disorder in the films.

Marginal and internal fit of nano-composite CAD/CAM restorations.

PubMed

Park, So-Hyun; Yoo, Yeon-Jee; Shin, Yoo-Jin; Cho, Byeong-Hoon; Baek, Seung-Ho

2016-02-01

The purpose of this study was to compare the marginal and internal fit of nano-composite CAD-CAM restorations. A full veneer crown and an mesio-occluso-distal (MOD) inlay cavity, which were prepared on extracted human molars, were used as templates of epoxy resin replicas. The prepared teeth were scanned and CAD-CAM restorations were milled using Lava Ultimate (LU) and experimental nano-composite CAD/CAM blocks (EB) under the same milling parameters. To assess the marginal and internal fit, the restorations were cemented to replicas and were embedded in an acrylic mold for sectioning at 0.5 mm intervals. The measured gap data were pooled according to the block types and measuring points for statistical analysis. Both the block type and measuring point significantly affected gap values, and their interaction was significant (p = 0.000). In crowns and inlays made from the two blocks, gap values were significantly larger in the occlusal area than in the axial area, while gap values in the marginal area were smallest (p < 0.001). Among the blocks, the restorations milled from EB had a significantly larger gap at all measuring points than those milled from LU (p = 0.000). The marginal and internal gaps of the two nano-composite CAD/CAM blocks differed according to the measuring points. Among the internal area of the two nano-composite CAD/CAM restorations, occlusal gap data were significantly larger than axial gap data. The EB crowns and inlays had significantly larger gaps than LU restorations.

Influence of the ``second gap'' on the optical absorption of transparent conducting oxides

NASA Astrophysics Data System (ADS)

Ha, Viet-Anh; Waroquiers, David; Rignanese, Gian-Marco; Hautier, Geoffroy

Transparent conducting oxides (TCOs) are critical to many technologies (e.g., thin-film solar cells, flat-panel displays or organic light-emitting diodes). TCOs are heavily doped (n or p-type) oxides that satisfy many design criteria such as high transparency to visible light (i.e., a band gap > 3 eV), high concentration and mobility of carriers (leading to high conductivity), ... In such (highly doped) systems, optical transitions from the conduction band minimum to higher energy bands in n-type or from lower energy bands to the valence band maximum in p-type are possible and can degrade transparency. In fact, it has been claimed that a high energy (> 3eV) for any of these transitions made possible by doping, commonly referred as a high ``second gap'', is a necessary design criterion for high performance TCOs. Here, we study the influence of this second gap on the transparency of doped TCOs by using ab initio calculations within the random phase approximation (RPA) for several well-known p-type and n-type TCOs. Our work highlights how the second gap affects the transparency of doped TCOs, shining light on more accurate design criteria for high performance TCOs.

Electronic and optical properties of the LiCdX (X = N, P, As and Sb) filled-tetrahedral compounds with the Tran–Blaha modified Becke–Johnson density functional

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouhemadou, A., E-mail: a_bouhemadou@yahoo.fr; Bin-Omran, S.; Department of Physics, Faculty of Science & Humanitarian Studies, Salman Bin Abdalaziz University, Alkharj 11942

Highlights: • Electronic and optical properties of the LiCdX compounds have been predicted. • Tran–Blaha-modified Becke–Johnson functional significantly improves the band gap. • We predict a direct band gap in all of the considered LiCdX compounds. • Origin of the peaks in the optical spectra is determined. - Abstract: The structural, electronic and optical properties of the LiCdN, LiCdP, LiCdAs and LiCdSb filled-tetrahedral compounds have been explored from first-principles. The calculated structural parameters are consistent with the available experimental results. Since DFT with the common LDA and GGA underestimates the band gap, we use a new developed functional able tomore » accurately describe the electronic structure of semiconductors, namely the Tran–Blaha-modified Becke–Johnson potential. The four investigated compounds demonstrate semiconducting behavior with direct band gap ranging from about 0.32 to 1.65 eV. The charge-carrier effective masses are evaluated at the topmost valence band and at the bottommost conduction band. The evolution of the value and nature of the energy band gap under pressure effect is also investigated. The frequency-dependent complex dielectric function and some macroscopic optical constants are estimated. The microscopic origins of the structures in the optical spectra are determined in terms of the calculated energy band structures.« less

Revaluation of stockpile amount of PFOS-containing aqueous film-forming foam in Japan: gaps and pitfalls in the stockpile survey.

PubMed

Zushi, Yasuyuki; Yamamoto, Atsushi; Tsunemi, Kiyotaka; Masunaga, Shigeki

2017-03-01

Stockpiles of perfluoro-octane sulfonic acid (PFOS) containing aqueous film-forming foam (AFFF) have the potential to be emitted by leaching, spills, and during use in fire response and other processes. Several studies have discussed the high levels of stockpiled PFOS-containing AFFF and the risk they pose to the environment; however, there are large gaps in the amounts in Japan compared with other countries. For example, 300 tons are stockpiled in Canada, 2200-2600 tons in Switzerland, 1400 tons in Norway, and 19,000 tons in Japan from their reports for publication. The gap is considered to be a result of lack of surveys of several important sources. In this study, we revaluated the stockpile of AFFF in Japan to verify the reported value and identify the source of this gap based on information available in peer-reviewed papers, governmental reports, and business reports. The major reason for the gap between Japan and other countries was considered to be the survey of stockpiles in car-parking facilities, which accounted for 46.7% of the total amounts in Japan, but were not considered in other countries. These stockpiles indicate a high potential for accidental leaching or spilling of the AFFF by careless storage. Therefore, it is recommended that continual surveys of the AFFF stockpile in car-parking facilities be conducted in the rest of the world.

CsSnI[subscript 3]: Semiconductor or Metal? High Electrical Conductivity and Strong Near-Infrared Photoluminescence from a Single Material. High Hole Mobility and Phase-Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, In; Song, Jung-Hwan; Im, Jino

CsSnI{sub 3} is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI{sub 3} have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI{sub 3}, coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI{submore » 3}. The black orthorhombic form of CsSnI{sub 3} demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI{sub 3} indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of {approx} 10{sup 17} cm{sup -3} and a hole mobility of {approx} 585 cm{sup 2} V{sup -1} s{sup -1}. The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from Sn defects in the crystal structure, which arise intrinsically. Thus, although stoichiometric CsSnI{sub 3} is a semiconductor, the material is prone to intrinsic defects associated with Sn vacancies. This creates highly mobile holes which cause the materials to appear metallic.« less

The Approach to Equilibrium in a Reflex Triode

DTIC Science & Technology

1990-09-24

once to yield dT ±---27yT"= ’, where y = d/A and the prime also denotes d/ de . The damping length scale is now just a parameter that can be obtained from...pressures near K2 which will figure in the gap shorting time, and the boundary condition evolution at the anode. Aside from the steady conduction...phase evolution of 77 to values near the sin- gular point, one finds that (from an operational point of view in fixing 3) all such auxillary physics

Asian cultural values gap, cognitive flexibility, coping strategies, and parent-child conflicts among Korean Americans.

PubMed

Ahn, Annie J; Kim, Bryan S K; Park, Yong S

2008-10-01

The study examined Korean American college students' perceived Asian cultural values gap between themselves and their parents, cognitive flexibility, and coping strategies. The relationships between these factors were studied with the intensities and types of parent-child conflicts. The results indicated that the participants adhered less strongly to Asian values than their parents. When faced with conflicts, the participants reported using problem solving coping strategy to the greatest extent, followed by social support coping strategy, and then avoidance coping strategy. Simultaneous regression analyses revealed a positive relationship between the participant-perceived parent-child values gap and the intensity of conflicts, particularly in the area of dating and marriage. There were inverse relationships between cognitive flexibility and the intensity of conflicts, specifically in the area of dating and marriage. A positive relationship was observed between the use of social support coping strategy and intensity of conflicts. Hierarchical regression analyses revealed a significant interaction effect in which participant-perceived parent-child values gap and cognitive flexibility were related to increased frequency of dating and marriage conflicts.

Gap state analysis in electric-field-induced band gap for bilayer graphene.

PubMed

Kanayama, Kaoru; Nagashio, Kosuke

2015-10-29

The origin of the low current on/off ratio at room temperature in dual-gated bilayer graphene field-effect transistors is considered to be the variable range hopping in gap states. However, the quantitative estimation of gap states has not been conducted. Here, we report the systematic estimation of the energy gap by both quantum capacitance and transport measurements and the density of states for gap states by the conductance method. An energy gap of ~ 250 meV is obtained at the maximum displacement field of ~ 3.1 V/nm, where the current on/off ratio of ~ 3 × 10(3) is demonstrated at 20 K. The density of states for the gap states are in the range from the latter half of 10(12) to 10(13) eV(-1) cm(-2). Although the large amount of gap states at the interface of high-k oxide/bilayer graphene limits the current on/off ratio at present, our results suggest that the reduction of gap states below ~ 10(11) eV(-1) cm(-2) by continual improvement of the gate stack makes bilayer graphene a promising candidate for future nanoelectronic device applications.

Dependence of the optical conductivity on the uniaxial and biaxial strains in black phosphorene

NASA Astrophysics Data System (ADS)

Yang, C. H.; Zhang, J. Y.; Wang, G. X.; Zhang, C.

2018-06-01

By using the Kubo formula, the optical conductivity of strained black phosphorene was studied. The anisotropic band dispersion gives rise to an orientation dependent optical conductivity. The energy gap can be tuned by the uniaxial and biaxial strains which can be observed from the interband optical conductivity polarized along the armchair (x ) direction. The preferential conducting direction is along the x direction. The dependence of the intraband optical conductivity along the zigzag (y ) direction on the Fermi energy and strain exhibits increasing or decreasing monotonously. However, along the x direction this dependence is complicated which originates from the carriers' inverse-direction movements obtained by two types of the nearest phosphorus atom interactions. The modification of the biaxial strain on the energy structure and optical-absorption property is more effective. The imaginary part of the total optical conductivity (Im σ ) can be negative around the threshold of the interband optical transition by modifying the chemical potential. Away from this frequency region, Im σ exhibits positive value. It can be used in the application of the surface plasmon propagations in multilayer dielectric structures.

Effect of annealing on structural, optical and electrical properties of SILAR synthesized CuO thin film

NASA Astrophysics Data System (ADS)

Das, M. R.; Mukherjee, A.; Mitra, P.

2017-05-01

Nano crystalline CuO thin films were synthesize on glass substrate using SILAR technique. The structural, optical and electrical properties of the films were carried out for as deposited as well as for films post annealed in the temperature range 300 - 500° C. The X-ray diffraction pattern shows all the films are polycrystalline in nature with monoclinic phase. The crystallite size increase and lattice strain decreases with increase of annealing temperature indicating high quality of the films for annealed films. The value of band gap decreases with increases of annealing temperature of the film. The effect of annealing temperature on ionic conductivity and activation energy to electrical conduction process are discussed.

Evaluation of the thermal conductance of flip-chip bonding structure utilizing the measurement based on Fourier's law of heat conduction at steady-state

NASA Astrophysics Data System (ADS)

Wu, Chia-Yu; Huang, Yin-Hsien; Wu, Hsin-Han; Hsieh, Tsung-Eong

2018-06-01

Fourier's law of heat conduction at steady-state was adopted to establish a measurement method utilizing platinum (Pt) thin-film electrodes as the heater and the temperature sensor. The thermal conductivities (κ's) of Pyrex glass, an epoxy resin and a commercial underfill for flip-chip devices were measured and a good agreement with previously reported values was obtained. The thermal boundary resistances (RTBR's) of Pt/sample interfaces were also extracted for discussing their influence on the thermal conduction of samples. Afterward, the flip-chip samples with 2×2 solder joint array utilizing Si wafers as the die and the substrate, without and with the underfills, were prepared and their thermal conductance were measured. For the sample without underfill, the air presenting in the gap of die and the substrate led to the poor thermal conductance of sample. With the insertion of underfills, the thermal conductance of flip-chip samples improved. The resistance to heat transfer across Si/underfill interfaces was also suppressed and to promote the thermal conductance of samples. The thermal properties of underfill and RTBR at Si/underfill interface were further implanted in the calculation of thermal conductance of flip-chip samples containing various solder joint arrays. The increasing number of solder joints diminished the influence of thermal conduction of underfill and RTBR of Si/underfill interface on the thermal conductance of samples. The insertion of underfill with high-κ value might promote the heat conductance of samples containing low-density solder joint arrays; however, it became insignificant in improving the heat conductance of samples containing high-density solder joint arrays.

Review and bibliometric analysis of published literature citing data produced by the Gap Analysis Program (GAP)

USGS Publications Warehouse

Ratz, Joan M.; Conk, Shannon J.

2014-01-01

The Gap Analysis Program (GAP) of the U.S. Geological Survey (USGS) produces geospatial datasets providing information on land cover, predicted species distributions, stewardship (ownership and conservation status), and an analysis dataset which synthesizes the other three datasets. The intent in providing these datasets is to support the conservation of biodiversity. The datasets are made available at no cost. The initial datasets were created at the state level. More recent datasets have been assembled at regional and national levels. GAP entered an agreement with the Policy Analysis and Science Assistance branch of the USGS to conduct an evaluation to describe the effect that using GAP data has on those who utilize the datasets (GAP users). The evaluation project included multiple components: a discussion regarding use of GAP data conducted with participants at a GAP conference, a literature review of publications that cited use of GAP data, and a survey of GAP users. The findings of the published literature search were used to identify topics to include on the survey. This report summarizes the literature search, the characteristics of the resulting set of publications, the emergent themes from statements made regarding GAP data, and a bibliometric analysis of the publications. We cannot claim that this list includes all publications that have used GAP data. Given the time lapse that is common in the publishing process, more recent datasets may be cited less frequently in this list of publications. Reports or products that used GAP data may be produced but never published in print or released online. In that case, our search strategies would not have located those reports. Authors may have used GAP data but failed to cite it in such a way that the search strategies we used would have located those publications. These are common issues when using a literature search as part of an evaluation project. Although the final list of publications we identified is not comprehensive, this set of publications can be considered a sufficient sample of those citing GAP data and suitable for the descriptive analyses we conducted.

First-principles studies of electronic, transport and bulk properties of pyrite FeS2

NASA Astrophysics Data System (ADS)

Banjara, Dipendra; Malozovsky, Yuriy; Franklin, LaShounda; Bagayoko, Diola

2018-02-01

We present results from first principle, local density approximation (LDA) calculations of electronic, transport, and bulk properties of iron pyrite (FeS2). Our non-relativistic computations employed the Ceperley and Alder LDA potential and the linear combination of atomic orbitals (LCAO) formalism. The implementation of the LCAO formalism followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). We discuss the electronic energy bands, total and partial densities of states, electron effective masses, and the bulk modulus. Our calculated indirect band gap of 0.959 eV (0.96), using an experimental lattice constant of 5.4166 Å, at room temperature, is in agreement with the measured indirect values, for bulk samples, ranging from 0.84 eV to 1.03 ± 0.05 eV. Our calculated bulk modulus of 147 GPa is practically in agreement with the experimental value of 145 GPa. The calculated, partial densities of states reproduced the splitting of the Fe d bands to constitute the dominant upper most valence and lower most conduction bands, separated by the generally accepted, indirect, experimental band gap of 0.95 eV.

Tuning the structural and electronic properties of novel thiophene-pyrrole based 1,2,3,4-tetrazine

NASA Astrophysics Data System (ADS)

Dutta, Rakesh; Kalita, Dhruba Jyoti

2017-04-01

Here, we have studied the structural and optoelectronic behaviour of a series of conjugated heterocyclic polymers. The basic monomer unit of the conjugated polymers contains a backbone of novel thiophene and pyrrole based 1,2,3,4-tetrazine. The other oligomers are designed by substituting the basic monomer unit with different electron-donating and electron-withdrawing groups at the nitrogen and the 3rd C-atom of the pyrrole and the thiophene ring respectively. We have calculated dihedral angles, HOMO-LUMO gaps, excitation energies and oscillator strengths by employing TD-DFT method. Our study reveals that compounds having bulky substituents exhibit larger dihedral angles. This in turn renders an increase in the band gaps (ΔH - L). Presence of the electron-withdrawing substituents also increases the ΔH - L values of the oligomers. However, the electron-donating groups decrease the ΔH - L values of the oligomers. Therefore, small electron-donating substituents have an overwhelming effect on the optoelectronic properties of the conjugated polymers which in turn makes them interesting materials with good conduction properties for fabrication of optoelectronic devices such as OLEDs, OFETs and solar cells.

Electronic structure and linear optical properties of ZnSe and ZnSe:Mn.

PubMed

Su, Kang; Wang, Yuhua

2010-03-01

As an important wide band-gap II-VI semiconductor, ZnSe has attracted much attention for its various applications in photo-electronic devices such as blue light-emitting diodes and blue-green diode lasers. Mn-doped ZnSe is an excellent quantum dot material. The electronic structures of the sphalerite ZnSe and ZnSe:Mn were calculated using the Vienna ab initio Simulation Package with ultra-soft pseudo potentials and Material Studio. The calculated equilibrium lattice constants agree well with the experimental values. Using the optimized equilibrium lattice constants, the densities of states and energy band structures were further calculated. By analyzing the partial densities of states, the contributions of different electron states in different atoms were estimated. The p states of Zn mostly contribute to the top of the valence band, and the s states of Zn and the s states of Se have major effects on the bottom of the conduction band. The calculated results of ZnSe:Mn show the band gap was changed from 2.48 to 1.1 eV. The calculated linear optical properties, such as refractive index and absorption spectrum, are in good agreement with experimental values.

Arterial to end-tidal carbon dioxide tension difference (CO2 gap) as a prognostic marker for adverse outcomes in emergency department patients presenting with suspected sepsis.

PubMed

Shetty, Amith; Sparenberg, Sebastian; Adams, Kristian; Selvedran, Selwyn; Tang, Benjamin; Hanna, Kim; Iredell, Jonathan

2018-05-13

The arterial to end-tidal carbon dioxide tension difference (CO 2 gap) correlates with physiologic dead space. The prognostic value of increased CO 2 gap in trauma and respiratory distress patients is documented. Transpulmonary arteriovenous shunting is identified as a predictor of mortality in non-pulmonary sepsis. We set out to investigate the prognostic value of the CO 2 gap in a pilot study of patients with suspected sepsis from non-respiratory causes. Patients presenting to tertiary Australian ED with suspected sepsis (n = 215) underwent near-simultaneous end-tidal carbon dioxide and partial pressure of carbon dioxide measurements. We investigated the correlation of CO 2 gap levels with the primary outcome of in-hospital mortality (IHM) and secondary outcomes of sepsis (ΔSOFA ≥2) and IHM and/or intensive care unit stay ≥72 h (IHM/ICU72h) in patients with sepsis because of non-respiratory causes. Among patients included in the analysis (n = 165), the CO 2 gap showed modest positive correlation with qSOFA (ρ = 0.39) and weak positive correlation with SOFA scores (ρ = 0.29) (both P < 0.01). The CO 2 gap had modest predictive value for primary outcome (IHM), area under receiver operating curve (AUROC 0.85, 95% confidence interval [CI] 0.78-0.90) and IHM/ICU72h outcome (AUROC 0.80, 95% CI 0.73-0.86), but lower predictive value for sepsis outcome (AUROC 0.64, 95% CI 0.55-0.71) (all P < 0.001). We report modest test performance for primary outcome at CO 2 gap ≥5 and ≥10 mmHg cut-offs. In this pilot study of patients with suspected sepsis from non-respiratory causes, an increased CO 2 gap demonstrates value in risk stratification and needs to be further evaluated and compared to other existent biomarkers. © 2018 Australasian College for Emergency Medicine & Australasian Society for Emergency Medicine.

Family affection as a protective factor against the negative effects of perceived Asian values gap on the parent-child relationship for Asian American male and female college students.

PubMed

Park, Yong S; Vo, Leyna P; Tsong, Yuying

2009-01-01

The study examined whether family affection (i.e., affective responsiveness, affectionate communication, and affective orientation) protected against the negative effects of perceived parent-child Asian values gap on the quality of their parent relationships for 259 female and 77 male Asian American college students. Asian values gap was higher for women than men, and inversely related to a perceived healthy parent-child relationship for both genders. Participants rated the relationship with their mothers as more positive and affectionate than with their fathers. Both parents were reported to communicate more supportive affection than verbal and nonverbal affection. Affective responsiveness was identified as a protective factor in the father-son relationship whereas verbal affection protected the mother-daughter relationship. The study also revealed that daughters' affective orientation had beneficial effects on the father-daughter relationship at lower levels of Asian values gap. Clinical implications and directions for future research are discussed.

Good on paper: the gap between programme theory and real-world context in Pakistan's Community Midwife programme.

PubMed

Mumtaz, Z; Levay, A; Bhatti, A; Salway, S

2015-01-01

To understand why skilled birth attendance-an acknowledged strategy for reducing maternal deaths-has been effective in some settings but is failing in Pakistan and to demonstrate the value of a theory-driven approach to evaluating implementation of maternal healthcare interventions. Implementation research was conducted using an institutional ethnographic approach. National programme and local community levels in Pakistan. Observations, focus group discussions, and in-depth interviews were conducted with 38 Community Midwives (CMWs), 20 policymakers, 45 healthcare providers and 136 community members. A critical policy document review was conducted. National and local level data were brought together. Alignment of programme theory with real-world practice. Data revealed gaps between programme theory, assumptions and reality on the ground. The design of the programme failed to take into account: (1) the incongruity between the role of a midwife and dominant class and gendered norms that devalue such a role; (2) market and consumer behaviour that prevented CMWs from establishing private practices; (3) the complexity of public-private sector cooperation. Uniform deployment policies failed to consider existing provider density and geography. Greater attention to programme theory and the 'real-world' setting during design of maternal health strategies is needed to achieve consistent results in different contexts. © 2014 The Authors. BJOG An International Journal of Obstetrics and Gynaecology published by John Wiley & Sons Ltd on behalf of Royal College of Obstetricians and Gynaecologists.

Off-stoichiometric silver antimony telluride: An experimental study of transport properties with intrinsic and extrinsic doping

DOE PAGES

Nielsen, Michele D.; Jaworski, Christopher M.; Heremans, Joseph P.

2015-03-20

AgSbTe 2 is a thermoelectric semiconductor with an intrinsically low thermal conductivity and a valence band structure that is favorable to obtaining a high thermoelectric figure of merit zT. It also has a very small energy gap Eg ~ 7.6 ± 3 meV. As this gap is less than the thermal excitation energy at room temperature, near-intrinsic AgSbTe 2 is a two carrier system having both holes (concentration p) and electrons ( n). Good thermoelectric performance requires heavy p-type doping ( p > > n). This can be achieved with native defects or with extrinsic doping, e.g. with transition metalmore » element. The use of defect doping is complicated by the fact that many of the ternary Ag-Sb-Te and pseudo-binary Sb 2Te 3-Ag 2Te phase diagrams are contradictory. This paper determines the compositional region most favorable to creating a single phase material. Through a combination of intrinsic and extrinsic doping, values of zT > 1 are achieved, though not on single-phased material. In addition, we show that thermal conductivity is not affected by defects, further demonstrating that the low lattice thermal conductivity of I-V-VI 2 materials is due to an intrinsic mechanism, insensitive to changes in defect structure.« less

Good on paper: the gap between programme theory and real-world context in Pakistan's Community Midwife programme

PubMed Central

Mumtaz, Z; Levay, A; Bhatti, A; Salway, S

2015-01-01

Objective To understand why skilled birth attendance—an acknowledged strategy for reducing maternal deaths—has been effective in some settings but is failing in Pakistan and to demonstrate the value of a theory-driven approach to evaluating implementation of maternal healthcare interventions. Design Implementation research was conducted using an institutional ethnographic approach. Setting and population National programme and local community levels in Pakistan. Methods Observations, focus group discussions, and in-depth interviews were conducted with 38 Community Midwives (CMWs), 20 policymakers, 45 healthcare providers and 136 community members. A critical policy document review was conducted. National and local level data were brought together. Main outcomes Alignment of programme theory with real-world practice. Results Data revealed gaps between programme theory, assumptions and reality on the ground. The design of the programme failed to take into account: (1) the incongruity between the role of a midwife and dominant class and gendered norms that devalue such a role; (2) market and consumer behaviour that prevented CMWs from establishing private practices; (3) the complexity of public–private sector cooperation. Uniform deployment policies failed to consider existing provider density and geography. Conclusions Greater attention to programme theory and the ‘real-world’ setting during design of maternal health strategies is needed to achieve consistent results in different contexts. PMID:25315837

Direct charge carrier injection into Ga2O3 thin films using an In2O3 cathode buffer layer: their optical, electrical and surface state properties

NASA Astrophysics Data System (ADS)

Cui, W.; Zhao, X. L.; An, Y. H.; Guo, D. Y.; Qing, X. Y.; Wu, Z. P.; Li, P. G.; Li, L. H.; Cui, C.; Tang, W. H.

2017-04-01

Conductive Ga2O3 thin films with an In2O3 buffer layer have been prepared on c-plane sapphire substrates using a laser molecular beam epitaxy technique. The effects of the In2O3 buffer layer on the structure and optical, electrical and surface state properties of the Ga2O3 films have been studied. The change in conductivity of the thin films is attributed to different thicknesses of the In2O3 buffer layer, which determine the concentration of charge carriers injected into the upper Ga2O3 layer from the interface of the bilayer thin films. In addition, the increase in flat band voltage shift and capacitance values as the In2O3 buffer layer thickens are attributed to the increase in surface state density, which also contributes to the rapid shrinkage of the optical band gap of the Ga2O3. With transparency to visible light, high n-type conduction and the ability to tune the optical band gap and surface state density, we propose that Ga2O3/In2O3 bilayer thin film is an ideal n-type semiconductor for fabrication of transparent power devices, solar cell electrodes and gas sensors.

30 CFR 285.800 - How must I conduct my activities to comply with safety and environmental requirements?

Code of Federal Regulations, 2011 CFR

2011-07-01

..., Inspections, and Facility Assessments for Activities Conducted Under SAPs, COPs and GAPs § 285.800 How must I... approved SAP, COP, or GAP, as required under §§ 285.615(c), 285.633(b), or 285.653(c). ...

Holographic conductivity of holographic superconductors with higher-order corrections

NASA Astrophysics Data System (ADS)

Sheykhi, Ahmad; Ghazanfari, Afsoon; Dehyadegari, Amin

2018-02-01

We analytically and numerically disclose the effects of the higher-order correction terms in the gravity and in the gauge field on the properties of s-wave holographic superconductors. On the gravity side, we consider the higher curvature Gauss-Bonnet corrections and on the gauge field side, we add a quadratic correction term to the Maxwell Lagrangian. We show that, for this system, one can still obtain an analytical relation between the critical temperature and the charge density. We also calculate the critical exponent and the condensation value both analytically and numerically. We use a variational method, based on the Sturm-Liouville eigenvalue problem for our analytical study, as well as a numerical shooting method in order to compare with our analytical results. For a fixed value of the Gauss-Bonnet parameter, we observe that the critical temperature decreases with increasing the nonlinearity of the gauge field. This implies that the nonlinear correction term to the Maxwell electrodynamics makes the condensation harder. We also study the holographic conductivity of the system and disclose the effects of the Gauss-Bonnet and nonlinear parameters α and b on the superconducting gap. We observe that, for various values of α and b, the real part of the conductivity is proportional to the frequency per temperature, ω /T, as the frequency is large enough. Besides, the conductivity has a minimum in the imaginary part which is shifted toward greater frequency with decreasing temperature.

Anisotropic superconductivity in β-(BDA-TTP)2SbF6: STM spectroscopy

NASA Astrophysics Data System (ADS)

Nomura, K.; Muraoka, R.; Matsunaga, N.; Ichimura, K.; Yamada, J.

2009-03-01

We have investigated the gap symmetry in the superconducting phase of β-(BDA-TTP)2SbF6 with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to κ-(BEDT-TTF)2X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and π. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d like superconducting pair is formed in this system as the case of κ-(BEDT-TTF)2X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet.

Tunneling Spectroscopy of MoN and NbxTi1-xN Thin Films Grown by Atomic Layer Deposition

NASA Astrophysics Data System (ADS)

Cao, Chaoyue; Groll, Nickolas; Klug, Jeffrey; Becker, Nicholas; Altin, Serdar; Proslier, Thomas; Zasadzinski, John

2014-03-01

Tunneling I(V) and dI/dV vs. V are reported on superconducting thin films of MoN and NbxTi1-xN using a point contact method with a Au tip. The films are grown by the chemical process of atomic layer deposition (ALD) onto various substrates (Si, quartz, sapphire) held at 450 C. Resistively measured superconducting Tc values up to 12K and 13K are found for the MoN and NbxTi1-xN respectively. Artificial tunnel barriers (1-3 nm thick) of Al2O3, also grown by ALD, are shown to provide much improved tunneling characteristics compared to the native oxides. Relatively high quality gap features are observed with zero-bias conductance values as low as ~ 10% of the high bias values. Gap parameters Δ ~ 2.0meV are found for the MoN and Δ ~ 2.0-2.4 meV for the NbxTi1-xN which follow the BCS temperature dependence and close near the measured film Tc indicating bulk superconductivity at the surface. The suitability of such conformal ALD grown films for potential superconducting devices is discussed. This work was supported by the U.S. Department of Energy, Office of Science under contract No. DE-AC02-06CH11357.

Structural and optical analysis of 60Co gamma-irradiated thin films of polycrystalline Ga10Se85Sn5

NASA Astrophysics Data System (ADS)

Ahmad, Shabir; Asokan, K.; Shahid Khan, Mohd.; Zulfequar, M.

2015-12-01

The present study focuses on the effects of gamma irradiation on structural and optical properties of polycrystalline Ga10Se85Sn5 thin films with a thickness of ∼300 nm deposited by the thermal evaporation technique on cleaned glass substrates. X-ray diffraction patterns of the investigated thin films show that crystallite growth occurs in the orthorhombic phase structure. The surface study carried out by using the scanning electron microscope (SEM) confirms that the grain size increases with gamma irradiation. The optical parameters were estimated from optical transmission spectra data measured from a UV-vis-spectrophotometer in the wavelength range of 200-1100 nm. The refractive index dispersion data of the investigated thin films follow the single oscillator model. The estimated values of static refractive index n0, oscillator strength Ed, zero frequency dielectric constant ε0, optical conductivity σoptical and the dissipation factor increases after irradiation, while the single oscillator energy Eo decreases after irradiation. It was found that the value of the optical band gap of the investigated thin films decreases and the corresponding absorption coefficient increases continuously with an increase in the dose of gamma irradiation. This post irradiation changes in the values of optical band gap and absorption coefficient were interpreted in terms of the bond distribution model.

Effect of interstitial palladium on plasmon-driven charge transfer in nanoparticle dimers.

PubMed

Lerch, Sarah; Reinhard, Björn M

2018-04-23

Capacitive plasmon coupling between noble metal nanoparticles (NPs) is characterized by an increasing red-shift of the bonding dipolar plasmon mode (BDP) in the classical electromagnetic coupling regime. This model breaks down at short separations where plasmon-driven charge transfer induces a gap current between the NPs with a magnitude and separation dependence that can be modulated if molecules are present in the gap. Here, we use gap contained DNA as a scaffold for the growth of palladium (Pd) NPs in the gap between two gold NPs and investigate the effect of increasing Pd NP concentration on the BDP mode. Consistent with enhanced plasmon-driven charge transfer, the integration of discrete Pd NPs depolarizes the capacitive BDP mode over longer interparticle separations than is possible in only DNA-linked Au NPs. High Pd NP densities in the gap increases the gap conductance and induces the transition from capacitive to conductive coupling.

Evaluation of service quality of hospital outpatient department services.

PubMed

Chakravarty, Abhijit

2011-07-01

It has become essential for hospital managers to understand and measure consumer perspectives and service quality gaps, so that any perceived gap in delivery of service is identified and suitably addressed. A study was conducted at a peripheral service hospital to ascertain any service gap between consumer expectations and perceptions in respect of the hospital outpatient department (OPD) services. A cross-sectional study was conducted using SERVQUAL as the survey instrument, the instrument being validated for use in the hospital environment. Consumer ratings across 22 items of the survey instrument were collected in paired expectation and perception scores and then service quality gaps were identified and statistically analysed. Service quality gaps were identified to exist across all the five dimensions of the survey instrument, with statistically significant gaps across the dimensions of 'tangibles' and 'responsiveness.' The quality gaps were further validated by a total unweighted SERVQUAL score of (-) 1.63. The study concludes that significant service quality gaps existed in the delivery of the hospital OPD services, which need to be addressed by focused improvement efforts by the hospital management.

Columbia River Component Data Gap Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

L. C. Hulstrom

2007-10-23

This Data Gap Analysis report documents the results of a study conducted by Washington Closure Hanford (WCH) to compile and reivew the currently available surface water and sediment data for the Columbia River near and downstream of the Hanford Site. This Data Gap Analysis study was conducted to review the adequacy of the existing surface water and sediment data set from the Columbia River, with specific reference to the use of the data in future site characterization and screening level risk assessments.

Fundamentals of undervoltage breakdown through the Townsend mechanism

NASA Astrophysics Data System (ADS)

Cooley, James E.

The conditions under which an externally supplied pulse of electrons will induce breakdown in an undervoltaged, low-gain, DC discharge gap are experimentally and theoretically explored. The phenomenon is relevant to fundamental understanding of breakdown physics, to switching applications such as triggered spark gaps and discharge initiation in pulsed-plasma thrusters, and to gas-avalanche particle counters. A dimensionless theoretical description of the phenomenon is formulated and solved numerically. It is found that a significant fraction of the charge on the plates must be injected for breakdown to be achieved at low avalanche-ionization gain, when an electron undergoes fewer than approximately 10 ionizing collisions during one gap transit. It is also found that fewer injected electrons are required as the gain due to electron-impact ionization (alpha process) is increased, or as the sensitivity of the alpha process to electric field is enhanced by decreasing the reduced electric field (electric field divided by pressure, E/p). A predicted insensitivity to ion mobility implies that breakdown is determined during the first electron avalanche when space charge distortion is greatest. A dimensionless, theoretical study of the development of this avalanche reveals a critical value of the reduced electric field to be the value at the Paschen curve minimum divided by 1.6. Below this value, the net result of the electric field distortion is to increase ionization for subsequent avalanches, making undervoltage breakdown possible. Above this value, ionization for subsequent avalanches will be suppressed and undervoltage breakdown is not possible. Using an experimental apparatus in which ultraviolet laser pulses are directed onto a photo-emissive cathode of a parallel-plate discharge gap, it is found that undervoltage breakdown can occur through a Townsend-like mechanism through the buildup of successively larger avalanche generations. The minimum number of injected electrons required to achieve breakdown is measured in argon at pd values of 3-10 Torr-m. The required electron pulse magnitude was found to scale inversely with pressure and voltage in this parameter range. When higher-power infrared laser pulses were used to heat the cathode surface, a faster, streamer-like breakdown mechanism was occasionally observed. As an example application, an investigation into the requirements for initiating discharges in Gas-fed Pulsed Plasma Thrusters (GFPPTs) is conducted. Theoretical investigations based on order-of-magnitude characterizations of previous GFPPT designs reveal that high-conductivity arc discharges are required for critically-damped matching of circuit components, and that relatively fast streamer breakdown is preferable to minimize delay between triggering and current sheet formation. The faster breakdown mechanism observed in the experiments demonstrates that such a discharge process can occur. However, in the parameter space occupied by most thrusters, achieving the phenomenon by way of a space charge distortion caused purely by an electron pulse should not be possible. Either a transient change in the distribution of gas density, through ablation or desorption, or a thruster design that occupies a different parameter space, such as one that uses higher mass bits, higher voltages, or smaller electrode spacing, is required for undervoltage breakdown to occur.

Thermal, dielectric characteristics and conduction mechanism of azodyes derived from quinoline and their copper complexes.

PubMed

El-Ghamaz, N A; Diab, M A; El-Bindary, A A; El-Sonbati, A Z; Nozha, S G

2015-05-15

A novel series of (5-(4'-derivatives phenyl azo)-8-hydroxy-7-quinolinecarboxaldehyde) (AQLn) (n=1, p-OCH3; n=2, R=H; and n=3; p-NO2) and their complexes [Cu(AQLn)2]·5H2O are synthesized and investigated. The optimized bond lengths, bond angles and the calculated quantum chemical parameters for AQLn are investigated. HOMO-LUMO energy gap, absolute electronegativities, chemical potentials, and absolute hardness are also calculated. The thermal properties, dielectric properties, alternating current conductivity (σac) and conduction mechanism are investigated in the frequency range 0.1-100kHz and temperature range 293-568K for AQL1-3 and 318-693K for [Cu(AQL1-3)2]·5H2O complexes. The thermal properties are of ligands (AQLn) and their Cu(II) complexes investigated by thermogravimetric analysis (TGA). The temperature and frequency dependence of the real and the imaginary part of the dielectric constant are studied. The values of the thermal activation energy of conduction mechanism for AQLn and their complexes [Cu(AQLn)2]·5H2O under investigation are calculated at different test frequencies. The values of thermal activation energies ΔE1 and ΔE2 for AQLn and [Cu(AQLn)2]·5H2O decrease with increasing the values of frequency. The ac conductivity is found to be depending on the chemical structure of the compounds. Different conduction mechanisms have been proposed to explain the obtained experimental data. The small polaron tunneling (SPT) is the dominant conduction mechanism for AQL1 and its complex [Cu(AQL1)2]·5H2O. The quantum mechanical tunneling (QMT) is the dominant conduction mechanism for AQL2 and its complex [Cu(AQL2)2]·5H2O. The correlated barrier hopping (CBH) is the dominant conduction mechanism for AQL3 and its complex [Cu(AQL3)2]·5H2O, and the values of the maximum barrier height (Wm) are calculated. Copyright © 2015 Elsevier B.V. All rights reserved.

Evidence-based practice, research utilization, and knowledge translation in chiropractic: a scoping review.

PubMed

Bussières, André E; Al Zoubi, Fadi; Stuber, Kent; French, Simon D; Boruff, Jill; Corrigan, John; Thomas, Aliki

2016-07-13

Evidence-based practice (EBP) gaps are widespread across health disciplines. Understanding factors supporting the uptake of evidence can inform the design of strategies to narrow these EBP gaps. Although research utilization (RU) and the factors associated with EBP have been reported in several health disciplines, to date this area has not been reviewed comprehensively in the chiropractic profession. The purpose of this review was to report on the current state of knowledge on EBP, RU, and knowledge translation (KT) in chiropractic. A scoping review using the Arksey and O'Malley framework was used to systematically select and summarize existing literature. Searches were conducted using a combination of keywords and MeSH terms from the earliest date available in each database to May 2015. Quantitative and thematic analyses of the selected literature were conducted. Nearly 85 % (56/67) of the included studies were conducted in Canada, USA, UK or Australia. Thematic analysis for the three categories (EBP, RU, KT) revealed two themes related to EBP (attitudes and beliefs of chiropractors; implementation of EBP), three related to RU (guideline adherence; frequency and sources of information accessed; and perceived value of websites and search engines), and three related to KT (knowledge practice gaps; barriers and facilitators to knowledge use; and selection, tailoring, and implementation of interventions). EBP gaps were noted in the areas of assessment of activity limitation, determination of psychosocial factors influencing pain, general health indicators, establishing a prognosis, and exercise prescription. While most practitioners believed EBP and research to be important and a few studies suggested that traditional and online educational strategies could improve patient care, use of EBP and guideline adherence varied widely. Findings suggest that the majority of chiropractors hold favourable attitudes and beliefs toward EBP. However, much remains to be done for chiropractors to routinely apply evidence into clinical practice. Educational strategies aimed at practicing chiropractors can lead to more EBP and improved patient care. The chiropractic profession requires more robust dissemination and implementation research to improve guideline adherence and patient health outcomes.

30 CFR 285.650 - When may I begin conducting activities under my GAP?

Code of Federal Regulations, 2011 CFR

2011-07-01

... GAP? 285.650 Section 285.650 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE RENEWABLE ENERGY ALTERNATE USES OF EXISTING FACILITIES ON THE... conducting the approved activities that do not involve a project easement or the construction of facilities...

Closing the gap between research and management

Treesearch

Deborah M. Finch; Marcia Patton-Mallory

1993-01-01

In this paper, we evaluate the reasons for gaps in communication between researchers and natural resource managers and identify methods to close these gaps. Gaps originate from differing patterns of language use, disparities in organizational culture and values, generation of knowledge that is too narrowly-focused to solve complex problems, failure by managers to relay...

Clinical investigation and mechanism of air-bone gaps in large vestibular aqueduct syndrome.

PubMed

Merchant, Saumil N; Nakajima, Hideko H; Halpin, Christopher; Nadol, Joseph B; Lee, Daniel J; Innis, William P; Curtin, Hugh; Rosowski, John J

2007-07-01

Patients with large vestibular aqueduct syndrome (LVAS) often demonstrate an air-bone gap at the low frequencies on audiometric testing. The mechanism causing such a gap has not been well elucidated. We investigated middle ear sound transmission in patients with LVAS, and present a hypothesis to explain the air-bone gap. Observations were made on 8 ears from 5 individuals with LVAS. The diagnosis of LVAS was made by computed tomography in all cases. Investigations included standard audiometry and measurements of umbo velocity by laser Doppler vibrometry (LDV) in all cases, as well as tympanometry, acoustic reflex testing, vestibular evoked myogenic potential (VEMP) testing, distortion product otoacoustic emission (DPOAE) testing, and middle ear exploration in some ears. One ear with LVAS had anacusis. The other 7 ears demonstrated air-bone gaps at the low frequencies, with mean gaps of 51 dB at 250 Hz, 31 dB at 500 Hz, and 12 dB at 1,000 Hz. In these 7 ears with air-bone gaps, LDV showed the umbo velocity to be normal or high normal in all 7; tympanometry was normal in all 6 ears tested; acoustic reflexes were present in 3 of the 4 ears tested; VEMP responses were present in all 3 ears tested; DPOAEs were present in 1 of the 2 ears tested, and exploratory tympanotomy in 1 case showed a normal middle ear. The above data suggest that an air-bone gap in LVAS is not due to disease in the middle ear. The data are consistent with the hypothesis that a large vestibular aqueduct introduces a third mobile window into the inner ear, which can produce an air-bone gap by 1) shunting air-conducted sound away from the cochlea, thus elevating air conduction thresholds, and 2) increasing the difference in impedance between the scala vestibuli side and the scala tympani side of the cochlear partition during bone conduction testing, thus improving thresholds for bone-conducted sound. We conclude that LVAS can present with an air-bone gap that can mimic middle ear disease. Diagnostic testing using acoustic reflexes, VEMPs, DPOAEs, and LDV can help to identify a non-middle ear source for such a gap, thereby avoiding negative middle ear exploration. A large vestibular aqueduct may act as a third mobile window in the inner ear, resulting in an air-bone gap at low frequencies.

Low lattice thermal conductivity and good thermoelectric performance of cinnabar

NASA Astrophysics Data System (ADS)

Zhao, Yinchang; Dai, Zhenhong; Lian, Chao; Zeng, Shuming; Li, Geng; Ni, Jun; Meng, Sheng

2017-11-01

Based on the combination of first-principles calculations, Boltzmann transport equation, and electron-phonon interaction (EPI), we investigate the thermal and electronic transport properties of crystalline cinnabar (α -HgS ). The calculated lattice thermal conductivity κL is remarkably low, e.g., 0.60 Wm-1K-1 at 300 K , which is about 30 % of the value for the typical thermoelectric material PbTe. Via taking fully into account the k dependence of the electron relaxation time computed from the EPI matrix, the accurate numerical results of thermopower S , electrical conductivity σ , and electronic thermal conductivity κE are obtained. The calculated power factor S2σ is relatively high while the value of κE is negligible, which, together with the fairly low κL, leads to a good thermoelectric performance in the n -type doped α -HgS , with the figure of merit z T even exceeding 1.4. Our analyses reveal that (i) the large weighted phase space and the quite low phonon group velocity result in the low κL, (ii) the presence of flat band around the Fermi level combined with the large band gap causes the high S , and (iii) the small electron linewidths of the conduction band lead to a large relaxation time and thus a relatively high σ . These results support that α -HgS is a potential candidate for thermoelectric applications.

Introduction

NASA Astrophysics Data System (ADS)

Nouwen, Rick; van Rooij, Robert; Sauerland, Uli; Schmitz, Hans-Christian

One could define vagueness as the existence of borderline cases and characterise the philosophical debate on vagueness as being about the nature of these. The prevalent theories of vagueness can be divided into three categories, paralleling three logical interpretations of borderline cases: (i) a borderline case is a case of a truth-value gap; it is neither true nor false; (ii) a borderline case is a case of a truth-value glut; it is both true and false; and (iii) a borderline case is a case where the truth-value is non-classical. The third of these is proposed in the fuzzy logic approach to vagueness. Three-valued approaches have only 1/2 as a value in addition to the standard values 1 and 0. These approaches can be interpreted either as allowing for gaps or gluts, depending on how the notion of satisfaction or truth is defined. If a sentence is taken to be true only if its value is 1, it allows for gaps, but if it is taken to be true already if its value is at least 1/2 it allows for gluts. The most popular theories advertising gluts and gaps, however, are supervaluationism and subvaluationism, both of which make use of the notion of precisifications, that is, ways of making things precise. Truth-value gaps in supervaluationism are due to the way truth simpliciter, or supertruth, is defined: A proposition is supertrue (superfalse) if it is true (false) at all precisifications. This means that a proposition can be neither true nor false in case there exist two precisifications, one of which make it true and one of which makes it false. Conversely, in subvaluation theory, the same scenario would lead to a truth-value glut. That is, the proposition would be both true and false. This is because subvaluationism defines truth simpliciter as being true at some precisifcation.

Marginal and internal fit of nano-composite CAD/CAM restorations

PubMed Central

Park, So-Hyun; Shin, Yoo-Jin

2016-01-01

Objectives The purpose of this study was to compare the marginal and internal fit of nano-composite CAD-CAM restorations. Materials and Methods A full veneer crown and an mesio-occluso-distal (MOD) inlay cavity, which were prepared on extracted human molars, were used as templates of epoxy resin replicas. The prepared teeth were scanned and CAD-CAM restorations were milled using Lava Ultimate (LU) and experimental nano-composite CAD/CAM blocks (EB) under the same milling parameters. To assess the marginal and internal fit, the restorations were cemented to replicas and were embedded in an acrylic mold for sectioning at 0.5 mm intervals. The measured gap data were pooled according to the block types and measuring points for statistical analysis. Results Both the block type and measuring point significantly affected gap values, and their interaction was significant (p = 0.000). In crowns and inlays made from the two blocks, gap values were significantly larger in the occlusal area than in the axial area, while gap values in the marginal area were smallest (p < 0.001). Among the blocks, the restorations milled from EB had a significantly larger gap at all measuring points than those milled from LU (p = 0.000). Conclusions The marginal and internal gaps of the two nano-composite CAD/CAM blocks differed according to the measuring points. Among the internal area of the two nano-composite CAD/CAM restorations, occlusal gap data were significantly larger than axial gap data. The EB crowns and inlays had significantly larger gaps than LU restorations. PMID:26877989

Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

NASA Technical Reports Server (NTRS)

Nellis, W. J.; Mitchell, A. C.; Mccandless, P. C.; Erskine, D. J.; Weir, S. T.

1992-01-01

Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

Disorder-induced half-integer quantized conductance plateau in quantum anomalous Hall insulator-superconductor structures

NASA Astrophysics Data System (ADS)

Huang, Yingyi; Setiawan, F.; Sau, Jay D.

2018-03-01

A weak superconducting proximity effect in the vicinity of the topological transition of a quantum anomalous Hall system has been proposed as a venue to realize a topological superconductor (TSC) with chiral Majorana edge modes (CMEMs). A recent experiment [Science 357, 294 (2017), 10.1126/science.aag2792] claimed to have observed such CMEMs in the form of a half-integer quantized conductance plateau in the two-terminal transport measurement of a quantum anomalous Hall-superconductor junction. Although the presence of a superconducting proximity effect generically splits the quantum Hall transition into two phase transitions with a gapped TSC in between, in this Rapid Communication we propose that a nearly flat conductance plateau, similar to that expected from CMEMs, can also arise from the percolation of quantum Hall edges well before the onset of the TSC or at temperatures much above the TSC gap. Our Rapid Communication, therefore, suggests that, in order to confirm the TSC, it is necessary to supplement the observation of the half-quantized conductance plateau with a hard superconducting gap (which is unlikely for a disordered system) from the conductance measurements or the heat transport measurement of the transport gap. Alternatively, the half-quantized thermal conductance would also serve as a smoking-gun signature of the TSC.

Effectiveness of presurgical nasoalveolar molding therapy on unilateral cleft lip nasal deformity

PubMed Central

Kinouchi, Nao; Horiuchi, Shinya; Yasue, Akihiro; Kuroda, Yuko; Kawai, Nobuhiko; Watanabe, Keiichiro; Izawa, Takashi; Hashimoto, Ichiro; Hassan, Ali H.; Tanaka, Eiji

2018-01-01

Objectives: To evaluate the effectiveness of pre-surgical nasoalveolar molding (PNAM) in patients with unilateral cleft lip nasal deformities. Methods: This was a retrospective study involving 29 patients with unilateral cleft lip and palate defects, of whom 13 were treated with palatal devices with nasal stents (PNAM group) and 16 were treated with palatal devices without nasal stents or surgical tapes (control group). Submental oblique photographs and orthodontic models were longitudinally obtained at the initial visit (T1) and immediately before (T2) and after cheiloplasty (T3). Asymmetry of the external nose, degree of columellar shifting, nasal tip/ala nose ratio, nasal base angle, interalveolar gap, and the sagittal difference in the alveolar gap were measured. The study was conducted in the Orthodontic Clinic at Tokushima University Hospital, Tokushima, Japan between 1997 and 2012. Results: At T1, there were no significant intergroup differences in the first 4 asymmetry parameters. At T2, the PNAM group showed a significant improvement in all values compared to the control group. At T3, the PNAM group showed significant improvement in nasal asymmetry and columellar shifting. Model analysis showed significantly greater changes in the inter-alveolar gap and the sagittal difference of the alveolar cleft gap from T1 to T2 in the PNAM group. Conclusion: The use of PNAM is indispensable for pre-surgical orthodontic treatment at the early postnatal age. PMID:29436566

Effectiveness of presurgical nasoalveolar molding therapy on unilateral cleft lip nasal deformity.

PubMed

Kinouchi, Nao; Horiuchi, Shinya; Yasue, Akihiro; Kuroda, Yuko; Kawai, Nobuhiko; Watanabe, Keiichiro; Izawa, Takashi; Hashimoto, Ichiro; Hassan, Ali H; Tanaka, Eiji

2018-02-01

To evaluate the effectiveness of pre-surgical nasoalveolar molding (PNAM) in patients with unilateral cleft lip nasal deformities. Methods: This was a retrospective study involving 29 patients with unilateral cleft lip and palate defects, of whom 13 were treated with palatal devices with nasal stents (PNAM group) and 16 were treated with palatal devices without nasal stents or surgical tapes (control group). Submental oblique photographs and orthodontic models were longitudinally obtained at the initial visit (T1) and immediately before (T2) and  after cheiloplasty (T3). Asymmetry of the external nose, degree of columellar shifting, nasal tip/ala nose ratio, nasal base angle, interalveolar gap, and the sagittal difference in the alveolar gap were measured. The study was conducted in the Orthodontic Clinic at Tokushima University Hospital, Tokushima, Japan between 1997 and 2012. Results: At T1, there were no significant intergroup differences in the first 4 asymmetry parameters. At T2, the PNAM group showed a significant improvement in all values compared to the control group. At T3, the PNAM group showed significant improvement in nasal asymmetry and columellar shifting. Model analysis showed significantly greater changes in the inter-alveolar gap and the sagittal difference of the alveolar cleft gap from T1 to T2 in the PNAM group. Conclusion: The use of PNAM is indispensable for pre-surgical orthodontic treatment at the early postnatal age.

Effect of particle size on band gap and DC electrical conductivity of TiO2 nanomaterial

NASA Astrophysics Data System (ADS)

Avinash, B. S.; Chaturmukha, V. S.; Jayanna, H. S.; Naveen, C. S.; Rajeeva, M. P.; Harish, B. M.; Suresh, S.; Lamani, Ashok R.

2016-05-01

Materials reduced to the Nano scale can exhibit different properties compared to what they exhibit on a micro scale, enabling unique applications. When TiO2 is reduced to Nano scale it shows unique properties, of which the electrical aspect is highly important. This paper presents increase in the energy gap and decrease in conductivity with decrease in particle size of pure Nano TiO2 synthesized by hydrolysis and peptization of titanium isopropoxide. Aqueous solution with various pH and peptizing the resultant suspension will form Nano TiO2 at different particle sizes. As the pH of the solution is made acidic reduction in the particle size is observed. And it is confirmed from XRD using Scherer formula and SEM, as prepared samples are studied for UV absorbance, and DC conductivity from room temperature to 400°C. From the tauc plot it was observed, and calculated the energy band gap increases as the particle size decreases and shown TiO2 is direct band gap. From Arrhenius plot clearly we encountered, decrease in the conductivity for the decrease in particle size due to hopping of charge carriers and it is evident that, we can tailor the band gap by varying particle size.

30 CFR 585.811 - When must I follow my Safety Management System?

Code of Federal Regulations, 2013 CFR

2013-07-01

..., COPs and GAPs Safety Management Systems § 585.811 When must I follow my Safety Management System? Your... COP, SAP, or GAP. You must conduct all activities described in your approved COP, SAP, or GAP in...

30 CFR 585.811 - When must I follow my Safety Management System?

Code of Federal Regulations, 2014 CFR

2014-07-01

..., COPs and GAPs Safety Management Systems § 585.811 When must I follow my Safety Management System? Your... COP, SAP, or GAP. You must conduct all activities described in your approved COP, SAP, or GAP in...

30 CFR 585.811 - When must I follow my Safety Management System?

Code of Federal Regulations, 2012 CFR

2012-07-01

..., COPs and GAPs Safety Management Systems § 585.811 When must I follow my Safety Management System? Your... COP, SAP, or GAP. You must conduct all activities described in your approved COP, SAP, or GAP in...

Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ito, Kota, E-mail: kotaito@mosk.tytlabs.co.jp; Research Center for Advanced Science and Technology; Miura, Atsushi

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed tomore » the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics.« less

Effect of electrical coupling on ionic current and synaptic potential measurements.

PubMed

Rabbah, Pascale; Golowasch, Jorge; Nadim, Farzan

2005-07-01

Recent studies have found electrical coupling to be more ubiquitous than previously thought, and coupling through gap junctions is known to play a crucial role in neuronal function and network output. In particular, current spread through gap junctions may affect the activation of voltage-dependent conductances as well as chemical synaptic release. Using voltage-clamp recordings of two strongly electrically coupled neurons of the lobster stomatogastric ganglion and conductance-based models of these neurons, we identified effects of electrical coupling on the measurement of leak and voltage-gated outward currents, as well as synaptic potentials. Experimental measurements showed that both leak and voltage-gated outward currents are recruited by gap junctions from neurons coupled to the clamped cell. Nevertheless, in spite of the strong coupling between these neurons, the errors made in estimating voltage-gated conductance parameters were relatively minor (<10%). Thus in many cases isolation of coupled neurons may not be required if a small degree of measurement error of the voltage-gated currents or the synaptic potentials is acceptable. Modeling results show, however, that such errors may be as high as 20% if the gap-junction position is near the recording site or as high as 90% when measuring smaller voltage-gated ionic currents. Paradoxically, improved space clamp increases the errors arising from electrical coupling because voltage control across gap junctions is poor for even the highest realistic coupling conductances. Furthermore, the common procedure of leak subtraction can add an extra error to the conductance measurement, the sign of which depends on the maximal conductance.

The quasiparticle band structure of zincblende and rocksalt ZnO.

PubMed

Dixit, H; Saniz, R; Lamoen, D; Partoens, B

2010-03-31

We present the quasiparticle band structure of ZnO in its zincblende (ZB) and rocksalt (RS) phases at the Γ point, calculated within the GW approximation. The effect of the p-d hybridization on the quasiparticle corrections to the band gap is discussed. We compare three systems, ZB-ZnO which shows strong p-d hybridization and has a direct band gap, RS-ZnO which is also hybridized but includes inversion symmetry and therefore has an indirect band gap, and ZB-ZnS which shows a weaker hybridization due to a change of the chemical species from oxygen to sulfur. The quasiparticle corrections are calculated with different numbers of valence electrons in the Zn pseudopotential. We find that the Zn(20+) pseudopotential is essential for the adequate treatment of the exchange interaction in the self-energy. The calculated GW band gaps are 2.47 eV and 4.27 eV respectively, for the ZB and RS phases. The ZB-ZnO band gap is underestimated compared to the experimental value of 3.27 by ∼ 0.8 eV. The RS-ZnO band gap compares well with the experimental value of 4.5 eV. The underestimation for ZB-ZnO is correlated with the strong p-d hybridization. The GW band gap for ZnS is 3.57 eV, compared to the experimental value of 3.8 eV.

Active terahertz metamaterial devices

DOEpatents

Chen, Houtong; Padilla, Willie John; Averitt, Richard Douglas; O'Hara, John F.; Lee, Mark

2010-11-02

Metamaterial structures are taught which provide for the modulation of terahertz frequency signals. Each element within an array of metamaterial (MM) elements comprises multiple loops and at least one gap. The MM elements may comprise resonators with conductive loops and insulated gaps, or the inverse in which insulated loops are present with conductive gaps; each providing useful transmissive control properties. The metamaterial elements are fabricated on a semiconducting substrate configured with a means of enhancing or depleting electrons from near the gaps of the MM elements. An on to off transmissivity ratio of about 0.5 is achieved with this approach. Embodiments are described in which the MM elements incorporated within a Quantum Cascade Laser (QCL) to provide surface emitting (SE) properties.

Impurities or a neutral Fermi surface? A further examination of the low-energy ac optical conductivity of SmB6

NASA Astrophysics Data System (ADS)

Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.; Phelan, W. A.; McQueen, T. M.; Armitage, N. P.

2018-05-01

Recent experiments have uncovered evidence of low energy excitations in the bulk of SmB6 that are perhaps associated with unconventional quasiparticles, bringing into question whether this Kondo "insulator" is truly insulating in the bulk. Recently, we demonstrated that SmB6 possesses significant in-gap bulk ac conduction far in excess of typical disordered semiconductors. Whether such conduction is an intrinsic feature of SmB6, suggesting the formation of an exotic state, or residual conduction from impurities continues to be a topic of debate. Here, we further examine the origin of the ac optical conductivity of SmB6 in light of recent experimental and theoretical developments. The optical conductivity of SmB6 is shown to possess distinct regimes of either dominant free carrier or localized response contributions. The free carrier response is found to be in good qualitative agreement with previous literature, although quantitative differences are revealed and discussed. The localized response, which dominates at the lowest temperatures, is analyzed in the context of models of either in-gap impurity states or an exotic neutral Fermi surface. The charge density or effective mass of this low temperature in-gap conductivity is extracted through a conductivity sum rule analysis and found to be in general alignment with both models in the appropriate limits. Our results shed further light on the nature of the in-gap states of SmB6.

Aging and the 4 kHz Air-bone Gap

PubMed Central

Nondahl, David M.; Tweed, Ted S.; Cruickshanks, Karen J.; Wiley, Terry L.; Dalton, Dayna S.

2011-01-01

Purpose To assess age- and gender-related patterns in the prevalence and 10-year incidence of 4 kHz air-bone gaps, and associated factors. Method Data were obtained as part of the longitudinal, population-based Epidemiology of Hearing Loss Study. An air-bone gap at 4 kHz was defined as an air-conduction threshold ≥15 dB higher than the bone-conduction threshold in the right ear. Results Among 3,553 participants aged 48 to 92 years at baseline (1993-1995), 3.4% had a 4 kHz air-bone gap in the right ear. The prevalence increased with age. Among the 120 participants with an air-bone gap, 60.0% did not have a flat tympanogram or an air-bone gap at .5 kHz. Ten years later we assessed 2093 participants who did not have a 4 kHz air-bone gap at baseline; 9.2% had developed a 4 kHz air-bone gap in the right ear. The incidence increased with age. Among the 192 participants who had developed an air-bone gap, 60.9% did not have a flat tympanogram or air-bone gaps at other frequencies. Conclusions These results suggest that a finding of a 4 kHz air-bone gap may reflect a combination of aging and other factors and not necessarily exclusively abnormal middle ear function. PMID:22232408

Transparent, conducting films based on metal/dielectric photonic band gaps

NASA Astrophysics Data System (ADS)

Bloemer, Mark J.; Scalora, Michael; D'Aguanno, G.; Bowden, Charles M.; Baglio, Salvatore; Sibilia, Concita; Centini, Marco; Bertolotti, Mario

1999-07-01

A transparent conductor has been developed based on 1D metal/dielectric photonic band gap structures. Laminated metal/dielectric filters containing 100 nm of silver have been fabricated with > 50% transmittance. Applications for transparent, conducting films include antennas embedded in windshields, electrodes on flat panel displays, electromagnetic shielding, and solar window panes.

Effects of spin entropy and lattice strain from mixed-trivalent Fe3+/Cr3+ on the electronic, thermoelectric and optical properties of delafossite CuFe1-x Cr x O2 (x  =  0.25, 0.5, 0.75)

NASA Astrophysics Data System (ADS)

Ruttanapun, Chesta; Maensiri, Santi

2015-12-01

Mixed-trivalent Fe3+/Cr3+ content CuFe1-x Cr x O2 (x  =  0.25, 0.5, and 0.75) compounds were synthesized to investigate the effects of spin entropy, and lattice strain on their electronic, thermoelectric and optical properties. The XPS results showed the existence of mixed Cu1+/Cu2+, Fe3+/Fe4+ and Cr2+/Cr3+ ion states in the structures. The mixed Fe3+/Cr3+ions caused a strong correlation to occur between the spin and the orbitals of the carriers in the octahedral layer of the sample, affecting the carrier degeneracy Seebeck coefficient behaviour, and the Cu2+ and Fe4+ ions caused an effect of enhancing the electric conductivity. These effects meant that CuFe0.75Cr0.25O2 had the highest electrical conductivity, an enhanced Seebeck coefficient compared to that of CuFeO2-based compounds, and the highest thermopower value. The lowest thermal conductivity was that of CuFe0.5Cr0.5O2, which was a result of the mismatched atomic radii of the mixed trivalent Fe3+(0.645 Å)/Cr3+(0.615 Å), which caused the lattice strain to occur in the structure and thus affected the point defect scattering of the phonon thermal conductivity. The lowest total thermal conductivity was that of CuFe0.5Cr0.5O2, because it had the maximum lattice strain. Overall, the effect of the mixed trivalent elements caused CuFe0.75Cr0.25O2 to have the highest value of the dimensionless figure of merit ZT, with a value that was four times that of CuFeO2-based compounds and six times that of CuCrO2-based compounds. With regard to optical properties, the lattice strain causes the indirect optical gap to increase with increasing x content, but has no effect on the direct optical gap. These results verified that the mixed-trivalent Fe3+/Cr3+ content of CuFe1-x Cr x O2 (x  =  0.25, 0.5, and 0.75) affected the electronic, thermoelectric and optical properties of the structure by causing spin entropy and lattice strain to occur.

Technology of fast spark gaps

NASA Astrophysics Data System (ADS)

Standler, Ronald B.

1989-09-01

To protect electronic systems from the effects of electromagnetic pulse (EMP) form nuclear weapons and high-power microwave (HPM) weapons, it is desirable to have fast responding protection components. The gas-filled spark gap appears to be an attractive protection component, except that it can be slow to conduct under certain conditions. This report reviews the literature and presents ideas for construction of a spark gap that will conduct in less than one nanosecond. The key concept to making a fast-responding spark gap is to produce a large number of free electrons quickly. Seven different mechanisms for production of free electrons are reviewed, and several that are relevant to miniature spark gaps for protective applications are discussed in detail. These mechanisms include: inclusion of radioactive materials, photoelectric effect, secondary electrode emission from the anode, and field emission from the cathode.

Optical properties of BaO added bioactive Na2O-CaO-P2O5 glasses

NASA Astrophysics Data System (ADS)

Edathazhe, Akhila B.; Shashikala, H. D.

2018-04-01

This paper deals with the effect of BaO addition on the optical properties of bioactive Na2O-CaO-P2O5 glasses for biomedical optics applications. The phosphate glasses with composition (26-x)Na2O-xBaO-29CaO-45P2O5 (x = 0, 5, 10, 15 mol%) have been prepared by melt-quenching technique at 1100°C. The refractive index of glasses increased with BaO content. The optical band gap and Urbach energy of synthesized glasses were derived from the optical absorption spectra by using UV-Visible spectrometer. The addition of 5 mol% of BaO increased the band gap energy of glasses due to the formation of ionic cross-links in the glass structure. The defect and interstitial bonds formation in theglasses decreased with BaO additions as indicated by reductions in the Urbach energy values. No such variations in the band gap and Urbach energy values of glasses were observed with BaO content from 5 to 15 mol%. The molar and oxide ion polarizability values were calculated from the band gap and molar volume of glasses. The increase in the calculated optical basicity and metallization criteria of glasses supported the rise in band gap energy values with BaO additions. As the melting temperature of glasses decreased from 1200 to 1100°C, the refractive index increased as supported by the measured density values. The band gap energy is not changed with melting temperature. The Urbach energy decreased with decrease in melting temperature in case of BaO-free Na2O-CaO-P2O5 glasses, whereas it increased in case of BaO added glasses due to the role of BaO as modifying oxide.

A Thin Lens Model for Charged-Particle RF Accelerating Gaps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, Christopher K.

Presented is a thin-lens model for an RF accelerating gap that considers general axial fields without energy dependence or other a priori assumptions. Both the cosine and sine transit time factors (i.e., Fourier transforms) are required plus two additional functions; the Hilbert transforms the transit-time factors. The combination yields a complex-valued Hamiltonian rotating in the complex plane with synchronous phase. Using Hamiltonians the phase and energy gains are computed independently in the pre-gap and post-gap regions then aligned using the asymptotic values of wave number. Derivations of these results are outlined, examples are shown, and simulations with the model aremore » presented.« less

Meta-metallic coils and resonators: Methods for high Q-value resonant geometries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mett, R. R.; Department of Physics and Chemistry, Milwaukee School of Engineering, Milwaukee, Wisconsin 53202; Sidabras, J. W.

A novel method of decreasing ohmic losses and increasing Q-value in metallic resonators at high frequencies is presented. The method overcomes the skin-depth limitation of rf current flow cross section. The method uses layers of conductive foil of thickness less than a skin depth and capacitive gaps between layers. The capacitive gaps can substantially equalize the rf current flowing in each layer, resulting in a total cross-sectional dimension for rf current flow many times larger than a skin depth. Analytic theory and finite-element simulations indicate that, for a variety of structures, the Q-value enhancement over a single thick conductor approachesmore » the ratio of total conductor thickness to skin depth if the total number of layers is greater than one-third the square of the ratio of total conductor thickness to skin depth. The layer number requirement is due to counter-currents in each foil layer caused by the surrounding rf magnetic fields. We call structures that exhibit this type of Q-enhancement “meta-metallic.” In addition, end effects due to rf magnetic fields wrapping around the ends of the foils can substantially reduce the Q-value for some classes of structures. Foil structures with Q-values that are substantially influenced by such end effects are discussed as are five classes of structures that are not. We focus particularly on 400 MHz, which is the resonant frequency of protons at 9.4 T. Simulations at 400 MHz are shown with comparison to measurements on fabricated structures. The methods and geometries described here are general for magnetic resonance and can be used at frequencies much higher than 400 MHz.« less

Meta-metallic coils and resonators: Methods for high Q-value resonant geometries

PubMed Central

Mett, R. R.; Hyde, J. S.

2016-01-01

A novel method of decreasing ohmic losses and increasing Q-value in metallic resonators at high frequencies is presented. The method overcomes the skin-depth limitation of rf current flow cross section. The method uses layers of conductive foil of thickness less than a skin depth and capacitive gaps between layers. The capacitive gaps can substantially equalize the rf current flowing in each layer, resulting in a total cross-sectional dimension for rf current flow many times larger than a skin depth. Analytic theory and finite-element simulations indicate that, for a variety of structures, the Q-value enhancement over a single thick conductor approaches the ratio of total conductor thickness to skin depth if the total number of layers is greater than one-third the square of the ratio of total conductor thickness to skin depth. The layer number requirement is due to counter-currents in each foil layer caused by the surrounding rf magnetic fields. We call structures that exhibit this type of Q-enhancement “meta-metallic.” In addition, end effects due to rf magnetic fields wrapping around the ends of the foils can substantially reduce the Q-value for some classes of structures. Foil structures with Q-values that are substantially influenced by such end effects are discussed as are five classes of structures that are not. We focus particularly on 400 MHz, which is the resonant frequency of protons at 9.4 T. Simulations at 400 MHz are shown with comparison to measurements on fabricated structures. The methods and geometries described here are general for magnetic resonance and can be used at frequencies much higher than 400 MHz. PMID:27587143

Specific Heat Capacities of Martian Sedimentary Analogs at Low Temperatures

NASA Astrophysics Data System (ADS)

Vu, T. H.; Piqueux, S.; Choukroun, M.; Christensen, P. R.; Glotch, T. D.; Edwards, C. S.

2017-12-01

Data returned from Martian missions have revealed a wide diversity of surface mineralogies, especially in geological structures interpreted to be sedimentary or altered by liquid water. These terrains are of great interest because of their potential to document the environment at a time when life may have appeared. Intriguingly, Martian sedimentary rocks show distinctly low thermal inertia values (300-700 J.m-2.K-1.s-1/2, indicative of a combination of low thermal conductivity, specific heat, and density) that are difficult to reconcile with their bedrock morphologies (where hundreds of magmatic bedrock occurrences have been mapped with thermal inertia values >> 1200 J.m-2.K-1.s-1/2). While low thermal conductivity and density values are sometimes invoked to lower the thermal inertia of massive bedrock, both are not sufficient to lower values below 1200 J.m-2.K-1.s-1/2, far above the numbers reported in the literature for Martian sedimentary/altered rocks. In addition, our limited knowledge of the specific heat of geological materials and their temperature dependency, especially below room temperature, have prevented accurate thermal modeling and impeded interpretation of the thermal inertia data. In this work, we have addressed that knowledge gap by conducting experimental measurements of the specific heat capacities of geological materials relevant to Martian sedimentary rocks at temperatures between 100 and 350 K. The results show that variation of the specific heat with temperature, while appreciable to some extent, is rather small and is unlikely to contribute significantly in the lowering of thermal inertia values. Therefore, thermal conductivity is the parameter that has the most potential in explaining this phenomenon. Such scenario could be possible if the sedimentary rocks are finely layered with poor thermal contact between each internal bed. As the density of most geological materials is well-known, the obtained specific heat data can be used to uniquely constrain the thermal conductivity, thereby improving thermal prediction models for Martian surface temperatures. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Support from the NASA Solar System Workings Program and government sponsorship are acknowledged.

In Defense of a Social Value Requirement for Clinical Research

PubMed Central

Wendler, David; Rid, Annette

2017-01-01

Many guidelines and commentators endorse the view that clinical research is ethically acceptable only when it has social value, in the sense of collecting data which might be used to improve health. A version of this social value requirement is included in the Declaration of Helsinki and the Nuremberg Code, and is codified in many national research regulations. At the same time, there have been no systematic analyses of why social value is an ethical requirement for clinical research. Recognizing this gap in the literature, recent articles by Alan Wertheimer and David Resnik argue that the extant justifications for the social value requirement are unpersuasive. Both authors conclude, contrary to almost all current guidelines and regulations, that it can be acceptable across a broad range of cases to conduct clinical research which is known prospectively to have no social value. The present paper assesses this conclusion by critically evaluating the ethical and policy considerations relevant to the claim that clinical research must have social value. This analysis supports the standard view that social value is an ethical requirement for the vast majority of clinical research studies and should be mandated by applicable guidelines and policies. PMID:28060427

In Defense of a Social Value Requirement for Clinical Research.

PubMed

Wendler, David; Rid, Annette

2017-02-01

Many guidelines and commentators endorse the view that clinical research is ethically acceptable only when it has social value, in the sense of collecting data which might be used to improve health. A version of this social value requirement is included in the Declaration of Helsinki and the Nuremberg Code, and is codified in many national research regulations. At the same time, there have been no systematic analyses of why social value is an ethical requirement for clinical research. Recognizing this gap in the literature, recent articles by Alan Wertheimer and David Resnik argue that the extant justifications for the social value requirement are unpersuasive. Both authors conclude, contrary to almost all current guidelines and regulations, that it can be acceptable across a broad range of cases to conduct clinical research which is known prospectively to have no social value. The present article assesses this conclusion by critically evaluating the ethical and policy considerations relevant to the claim that clinical research must have social value. This analysis supports the standard view that social value is an ethical requirement for the vast majority of clinical research studies and should be mandated by applicable guidelines and policies. © 2017 John Wiley & Sons Ltd.

Electron affinity and surface states of GaN m -plane facets: Implication for electronic self-passivation

NASA Astrophysics Data System (ADS)

Portz, V.; Schnedler, M.; Eisele, H.; Dunin-Borkowski, R. E.; Ebert, Ph.

2018-03-01

The electron affinity and surface states are of utmost importance for designing the potential landscape within (heterojunction) nanowires and hence for tuning conductivity and carrier lifetimes. Therefore, we determined for stoichiometric nonpolar GaN (10 1 ¯0 ) m -plane facets, i.e., the dominating sidewalls of GaN nanowires, the electron affinity to 4.06 ±0.07 eV and the energy of the empty Ga-derived surface state in the band gap to 0.99 ±0.08 eV below the conduction band minimum using scanning tunneling spectroscopy. These values imply that the potential landscape within GaN nanowires is defined by a surface state-induced Fermi-level pinning, creating an upward band bending at the sidewall facets, which provides an electronic passivation.

Open-Air Biowarfare Testing and the Evolution of Values

PubMed Central

2016-01-01

The United States and the United Kingdom ended outdoor biological warfare testing in populated areas nearly half a century ago. Yet, the conduct, health effects, and propriety of those tests remain controversial. The varied views reflect the limits of currently available test information and evolving societal values on research involving human subjects. Western political culture has changed since the early days of the American and British testing programs. People have become less reluctant to question authority, and institutional review boards must now pre-approve research involving human subjects. Further, the heightened stringency of laboratory containment has accentuated the safety gap between a confined test space and one without physical boundaries. All this makes it less likely that masses of people would again be unwittingly subjected to secret open-air biological warfare tests. PMID:27564984

Gap Analysis between Perceptions and Expectations of Medical-Surgical Patients in a Public Hospital in Saudi Arabia.

PubMed

Al-Momani, Mohammed Mahmoud

2016-01-01

To investigate patients' satisfaction with nursing care by measuring the gap between patients' expectations of care and perceptions of the actual care provided and to identify the areas of nursing care that need improvement. A cross-sectional survey was conducted among patients who were admitted to the Departments of Medicine and Surgery at King Saud Medical City, Riyadh, Saudi Arabia. A modified Service Quality (SERVQUAL) instrument was adapted to collect information from a convenience sample of 432 patients from November 25, 2012, to February 3, 2013. The instrument comprised 22 pairs of questions assessing 5 dimensions of the nursing care provided to patients during hospitalizations. The mean patient expectations and perceptions as well as the gap score values for each dimension of nursing service were tested for differences between the mean scores of the sample at a level of significance of 0.05 using a t test. The gap score for all of the 5 dimensions of nursing services were: responsiveness, -1.71; reliability, -1.48; tangibles, -1.36; assurance, -1.26, and empathy, -0.96. Service quality across the dimensions of responsiveness and reliability was statistically significant (p < 0.05). This result indicated that patients were not satisfied with the nursing service quality in relation to all dimensions. Our study showed negative gaps for the 5 nursing service quality dimensions evaluated. This could provide nurses with information about the aspects of nursing care that promote more positive patient outcomes and satisfaction. © 2015 S. Karger AG, Basel.

A strategic approach to physico-chemical analysis of bis (thiourea) lead chloride - A reliable semi-organic nonlinear optical crystal

NASA Astrophysics Data System (ADS)

Rajagopalan, N. R.; Krishnamoorthy, P.; Jayamoorthy, K.

2017-03-01

Good quality crystals of bis thiourea lead chloride (BTLC) have been grown by slow evaporation method from aqueous solution. Orthorhombic structure and Pna21 space group of the crystals have been identified by single crystal X-ray diffraction. Studies on nucleation kinetics of grown BTLC has been carried out from which meta-stable zone width, induction period, free energy change, critical radius, critical number and growth rate have been calculated. The experimental values of interfacial surface energy for the crystal growth process have been compared with theoretical models. Ultra violet transmittance studies resulted in a high transmittance and wide band gap energy suggested the required optical transparency of the crystal. The second harmonic generation (SHG) and phase matching nature of the crystal have been justified by Kurtz-Perry method. The SHG nature of the crystal has been further attested by the higher values of theoretical hyper polarizability. The dielectric nature of the crystals at different temperatures with varying frequencies has been thoroughly studied. The activation energy values of the electrical process have been calculated from ac conductivity study. Solid state parameters including valence electron plasma energy, Penn gap, Fermi energy and polarisability have been unveiled by theoretical approach and correlated with the crystal's SHG efficiency. The values of hardness number, elastic stiffness constant, Meyer's Index, minimum level of indentation load, load dependent constant, fracture toughness, brittleness index and corrected hardness obtained from Vicker's hardness test clearly showed that the BTLC crystal has good mechanical stability required for NLO device fabrication.

Thermal Conductivity and Large Isotope Effect in GaN from First Principles

DTIC Science & Technology

2012-08-28

August 2012) We present atomistic first principles results for the lattice thermal conductivity of GaN and compare them to those for GaP, GaAs, and GaSb ...weak scattering results from stiff atomic bonds and the large Ga to N mass ratio, which give phonons high frequencies and also a pronounced energy gap...66.70.f, 63.20.kg, 71.15.m Introduction.—Gallium nitride (GaN) is a wide band gap semiconductor and a promising candidate for use in opto- electronic

Gap-minimal systems of notations and the constructible hierarchy

NASA Technical Reports Server (NTRS)

Lucian, M. L.

1972-01-01

If a constructibly countable ordinal alpha is a gap ordinal, then the order type of the set of index ordinals smaller than alpha is exactly alpha. The gap ordinals are the only points of discontinuity of a certain ordinal-valued function. The notion of gap minimality for well ordered systems of notations is defined, and the existence of gap-minimal systems of notations of arbitrarily large constructibly countable length is established.

Reducing the gender achievement gap in college science: a classroom study of values affirmation.

PubMed

Miyake, Akira; Kost-Smith, Lauren E; Finkelstein, Noah D; Pollock, Steven J; Cohen, Geoffrey L; Ito, Tiffany A

2010-11-26

In many science, technology, engineering, and mathematics disciplines, women are outperformed by men in test scores, jeopardizing their success in science-oriented courses and careers. The current study tested the effectiveness of a psychological intervention, called values affirmation, in reducing the gender achievement gap in a college-level introductory physics class. In this randomized double-blind study, 399 students either wrote about their most important values or not, twice at the beginning of the 15-week course. Values affirmation reduced the male-female performance and learning difference substantially and elevated women's modal grades from the C to B range. Benefits were strongest for women who tended to endorse the stereotype that men do better than women in physics. A brief psychological intervention may be a promising way to address the gender gap in science performance and learning.

The Influence of Joint Distraction Force on the Soft-Tissue Balance Using Modified Gap-Balancing Technique in Posterior-Stabilized Total Knee Arthroplasty.

PubMed

Nagai, Kanto; Muratsu, Hirotsugu; Takeoka, Yoshiki; Tsubosaka, Masanori; Kuroda, Ryosuke; Matsumoto, Tomoyuki

2017-10-01

During modified gap-balancing technique, there is no consensus on the best method for obtaining appropriate soft-tissue balance and determining the femoral component rotation. Sixty-five varus osteoarthritic patients underwent primary posterior-stabilized total knee arthroplasty using modified gap-balancing technique. The influence of joint distraction force on the soft-tissue balance measurement during the modified gap-balancing technique was evaluated with Offset Repo-Tensor between the osteotomized surfaces at extension, and between femoral posterior condyles and tibial osteotomized surface at flexion of the knee before the resection of femoral posterior condyles. The joint center gap (millimeters) and varus ligament balance (°) were measured under 20, 40, and 60 pounds of joint distraction forces, and the differences in these values at extension and flexion (the value at flexion minus the value at extension) were also calculated. The differences in joint center gap (-6.7, -6.8, and -6.9 mm for 20, 40, and 60 pounds, respectively) and varus ligament balance (3.5°, 3.8°, and 3.8°) at extension and flexion were not significantly different among different joint distraction forces, although the joint center gap and varus ligament balance significantly increased stepwise at extension and flexion as the joint distraction force increased. The difference in joint center gap and varus ligament balance at extension and flexion were consistent even among the different joint distraction forces. This novel index would be useful for the determination of femoral component rotation during the modified gap-balancing technique. Copyright © 2017 Elsevier Inc. All rights reserved.

Follow-on to a report on the Applicability of the “Gallet equation” to the vegetation clearances of NERC Reliability Standard FAC-003-2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirkham, Harold

2012-08-31

In earlier work, a study done at the Pacific Northwest National Laboratory examined a NERC proposed standard specifying clearances between vegetation and power lines. The method proposed for calculating the clearances was based on the results of testing for high-voltage line designs. An equation developed to relate the results of testing with rod-plane gaps to proposed tower window sizes was incorporated into the calculations. The equation in question, sometimes called the “Gallet equation,” describes the insulation performance of the atmosphere for air gaps of a few meters. The equation was described in the PNNL study as a good and simple-to-usemore » way to solve a problem made difficult by the nonlinear interactions of the variables. For calculations based on this equation, a certain set of assumptions must be made. In particular, a value for a quantity called the “gap factor” is needed. This is the amount by which the gap to be modeled by the equation is stronger than the reference gap that was used in developing the Gallet equation. That reference gap is the gap between a rod and a plane. This follow-on report examines the effect on flashover probabilities of assuming an incorrect value for the gap factor. In particular, the flashover probability is found that would result from using a value of 1.3 when a gap factor of 1.0 should be applied. It is shown that with these assumptions the probability of a flashover changes from being extremely unlikely (about 1 in 1000 chance) to a virtual certainty (about 97% chance).« less

Two Photon Absorption And Refraction in Bulk of the Semiconducting Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumari, Vinay; Department of Physics, DCRUST Murthal, Haryana; Kumar, Vinod

2011-10-20

Fast electronic detection systems have opened up a number of new fields like nonlinear optics, optical communication, coherent optics, optical bistability, two/four wave mixing. The interest in this field has been stimulated by the importance of multiphoton processes in many fundamental aspects of physics. It has proved to be an invaluable tool for determining the optical and electronic properties of the solids because of the fact that one gets the information about the bulk of the material rather than the surface one. In this paper we report, the measurement of the nonlinear absorption and refraction from the band gap tomore » half-band gap region of bulk of semiconductors in the direct and indirect band gap crystals with nanosecond laser. The measured theoretical calculated values of two-photon absorption coefficients ({beta}) and nonlinear refraction n{sub 2}({omega}) of direct band gap crystal match the earlier reported theoretical predictions. By making use of these theoretical calculated values, we have estimated {beta} and n{sub 2}({omega}) in the case of indirect band gap crystals. Low value of absorption coefficient in case of indirect band gap crystals have been attributed to phonon assisted transition while reduction in nonlinear refraction is due to the rise in saturation taking place in the absorption.« less

FDI technology spillover and threshold effect of the technology gap: regional differences in the Chinese industrial sector.

PubMed

Wang, Hui; Liu, Huifang; Cao, Zhiyong; Wang, Bowen

2016-01-01

This paper presents a new perspective that there is a double-threshold effect in terms of the technology gap existing in the foreign direct investment (FDI) technology spillover process in different regional Chinese industrial sectors. In this paper, a double-threshold regression model was established to examine the relation between the threshold effect of the technology gap and technology spillover. Based on the provincial panel data of Chinese industrial sectors from 2000 to 2011, the empirical results reveal that there are two threshold values, which are 1.254 and 2.163, in terms of the technology gap in the industrial sector in eastern China. There are also two threshold values in both the central and western industrial sector, which are 1.516, 2.694 and 1.635, 2.714, respectively. The technology spillover is a decreasing function of the technology gap in both the eastern and western industrial sectors, but a concave curve function of the technology gap is in the central industrial sectors. Furthermore, the FDI technology spillover has increased gradually in recent years. Based on the empirical results, suggestions were proposed to elucidate the introduction of the FDI and the improvement in the industrial added value in different regions of China.

Effect of air gap variation on the performance of single stator single rotor axial flux permanent magnet generator

NASA Astrophysics Data System (ADS)

Kasim, Muhammad; Irasari, Pudji; Hikmawan, M. Fathul; Widiyanto, Puji; Wirtayasa, Ketut

2017-02-01

The axial flux permanent magnet generator (AFPMG) has been widely used especially for electricity generation. The effect of the air gap variation on the characteristic and performances of single rotor - single stator AFPMG has been described in this paper. Effect of air gap length on the magnetic flux distribution, starting torque and MMF has been investigated. The two dimensional finite element magnetic method has been deployed to model and simulated the characteristics of the machine which is based on the Maxwell equation. The analysis has been done for two different air gap lengths which were 2 mm and 4 mm using 2D FEMM 4.2 software at no load condition. The increasing of air gap length reduces the air-gap flux density. For air gap 2 mm, the maximum value of the flux density was 1.04 T while 0.73 T occured for air gap 4 mm.. Based on the experiment result, the increasing air gap also reduced the starting torque of the machine with 39.2 Nm for air gap 2 mm and this value decreased into 34.2 Nm when the air gap increased to 4 mm. Meanwhile, the MMF that was generated by AFPMG decreased around 22% at 50 Hz due to the reduction of magnetic flux induced on stator windings. Overall, the research result showed that the variation of air gap has significant effect on the machine characteristics.

On the optical band gap of zinc oxide

NASA Astrophysics Data System (ADS)

Srikant, V.; Clarke, D. R.

1998-05-01

Three different values (3.1, 3.2, and 3.3 eV) have been reported for the optical band gap of zinc oxide single crystals at room temperature. By comparing the optical properties of ZnO crystals using a variety of optical techniques it is concluded that the room temperature band gap is 3.3 eV and that the other values are attributable to a valence band-donor transition at ˜3.15 eV that can dominate the optical absorption when the bulk of a single crystal is probed.

Form of silicon and method of making the same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strobel, Timothy A.; Kim, Duck Young; Kurakevych, Oleksandr O.

The invention relates to a new phase of silicon, Si.sub.24, and a method of making the same. Si.sub.24 has a quasi-direct band gap, with a direct gap value of 1.34 eV and an indirect gap value of 1.3 eV. The invention also relates to a compound of the formula Na.sub.4Si.sub.24 and a method of making the same. N.sub.a4Si.sub.24 may be used as a precursor to make Si.sub.24.

Homebound patients' perspectives on technology and telemedicine: A qualitative analysis.

PubMed

Huang, Kristin T L; Lu, Tracy J; Alizadeh, Forootan; Mostaghimi, Arash

2016-01-01

Telemedicine holds promise in bridging the gap between homebound patients and high quality health care, but uptake of such technology remains limited. Qualitative interviews conducted with 17 homebound patients found two major barriers to telemedicine. First, participants who lack familiarity with technology are hesitant about telemedicine, as baseline use of technology in the home is limited, participants did not feel capable of learning, and the advantages of telemedicine were unclear. Second, homebound patients place a high value on in-office visits due to therapeutic benefit, face-to-face communication, and the social aspect of medical appointments.

Hydraulic architecture and photoinhibition influence spatial distribution of the arborescent palm Euterpe edulis in subtropical forests.

PubMed

Gatti, M Genoveva; Campanello, Paula I; Villagra, Mariana; Montti, Lía; Goldstein, Guillermo

2014-06-01

Physiological characteristics of saplings can be considered one of the most basic constraints on species distribution. The shade-tolerant arborescent palm Euterpe edulis Mart. is endemic to the Atlantic Forest of Argentina, Brazil and Paraguay. At a local scale, saplings of this species growing in native forests are absent in gaps. We tested the hypothesis whether sensitivity to photoinhibition or hydraulic architecture constrains the distribution of E. edulis saplings in sun-exposed forest environments. Using shade houses and field studies, we evaluated growth, survival, hydraulic traits and the susceptibility of Photosystem II to photoinhibition in E. edulis saplings under different growth irradiances. Survival rates in exposed sites in the field were very low (a median of 7%). All saplings exhibited photoinhibition when exposed to high radiation levels, but acclimation to a high radiation environment increased the rate of recovery. Petiole hydraulic conductivity was similar across treatments regardless of whether it was expressed per petiole cross-sectional area or per leaf area. At the plant level, investment in conductive tissues relative to leaf area (Huber values) increased with increasing irradiance. Under high irradiance conditions, plants experienced leaf water potentials close to the turgor-loss point, and leaf hydraulic conductance decreased by 79% relative to its maximum value. Euterpe edulis saplings were able to adjust their photosynthetic traits to different irradiance conditions, whereas hydraulic characteristics at the leaf level did not change across irradiance treatments. Our results indicate that uncoupling between water demand and supply to leaves apparently associated with high resistances to water flow at leaf insertion points, in addition to small stems with low water storage capacity, weak stomatal control and high vulnerability of leaves to hydraulic dysfunction, are the main ecophysiological constraints that prevent the growth and survival of E. edulis saplings in gaps in the native forest where native lianas and bamboos show aggressive growth. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Fluctuation-induced conductivity analyses of Be-doped (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-δ superconductors in the critical regime and beyond

NASA Astrophysics Data System (ADS)

Khan, Nawazish A.; Qurat-ul-Ain; Firdous, Umber; Shaheryar

2012-02-01

We have successfully synthesized (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-δ and (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10-δ samples and studied their excess conductivity analyses (fluctuation-induced conductivity) of resistivity data. The main objective of such analyses is to investigate the influence of Be-substitution on the superconductivity parameters at the microscopic level. The width of the 3D-2D Lawrence-Doniach regime is increased with the doping of Be at the Ca sites. The energy required to break apart the Cooper pairs is increased from 0.03 eV to 0.08 eV in Be-doped samples. Using the Ginzburg-Landau number (NG) and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth λp.d are also calculated from these analyses. The values of critical fields [Bc(0) Bc1(0)], Jc(0), and phase relaxation time τϕ are increased whereas the penetration depth λp.d and κ values are suppressed with Be-doping. It is most likely that as a result of the enhancement in the density of the carriers in the (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10-δ sample, this charge density gap is suppressed, which in turn suppresses the pseudo-gap resulting into enhancement of Bc (0), Bc1(0), and Jc(0).

Competence-Based Approach in Value Chain Processes

NASA Astrophysics Data System (ADS)

Azevedo, Rodrigo Cambiaghi; D'Amours, Sophie; Rönnqvist, Mikael

There is a gap between competence theory and value chain processes frameworks. While individually considered as core elements in contemporary management thinking, the integration of the two concepts is still lacking. We claim that this integration would allow for the development of more robust business models by structuring value chain activities around aspects such as capabilities and skills, as well as individual and organizational knowledge. In this context, the objective of this article is to reduce this gap and consequently open a field for further improvements of value chain processes frameworks.

Chiral zero energy modes in two-dimensional disordered Dirac semimetals

NASA Astrophysics Data System (ADS)

Liu, Lei; Yu, Yan; Wu, Hai-Bin; Zhang, Yan-Yang; Liu, Jian-Jun; Li, Shu-Shen

2018-04-01

The vacancy-induced chiral zero energy modes (CZEMs) of chiral-unitary-class (AIII) and chiral-symplectic-class (CII) two-dimensional (2 D ) disordered Dirac semimetals realized on a square bipartite lattice are investigated numerically by using the Kubo-Greenwood formula with the kernel polynomial method. The results show that, for both systems, the CZEMs exhibit the critical delocalization. The CZEM conductivity remains a robust constant (i.e., σ CZEM≈1.05 e2/h ), which is insensitive to the sample sizes, the vacancy concentrations, and the numbers of moments of Chebyshev polynomials, i.e., the dephasing strength. For both kinds of chiral systems, the CZEM conductivities are almost identical. However, they are not equal to that of graphene (i.e., 4 e2/π h ), which belongs to the chiral orthogonal class (BDI) semimetal on a 2 D hexagonal bipartite lattice. In addition, for the case that the vacancy concentrations are different in the two sublattices, the CZEM conductivity vanishes, and thus both systems exhibit localization at the Dirac point. Moreover, a band gap and a mobility gap open around zero energy. The widths of the energy gaps and mobility gaps are increasing with larger vacancy concentration difference. The width of the mobility gap is greater than that of the band gap, and a δ -function-like peak of density of states emerges at the Dirac point within the band gap, implying the existence of numerous localized states.

Rural Connected Vehicle Gap Analysis : Factors Impeding Deployment and Recommendations for Moving Forward

DOT National Transportation Integrated Search

2017-08-25

The intent of the Rural Connected Vehicle Gap Analysis project was to identify any current gaps in the connected vehicle program that may result in a reduced deployment potential in the rural areas of the United States. Through a workshop conducted a...

Virtual gap dielectric wall accelerator

DOEpatents

Caporaso, George James; Chen, Yu-Jiuan; Nelson, Scott; Sullivan, Jim; Hawkins, Steven A

2013-11-05

A virtual, moving accelerating gap is formed along an insulating tube in a dielectric wall accelerator (DWA) by locally controlling the conductivity of the tube. Localized voltage concentration is thus achieved by sequential activation of a variable resistive tube or stalk down the axis of an inductive voltage adder, producing a "virtual" traveling wave along the tube. The tube conductivity can be controlled at a desired location, which can be moved at a desired rate, by light illumination, or by photoconductive switches, or by other means. As a result, an impressed voltage along the tube appears predominantly over a local region, the virtual gap. By making the length of the tube large in comparison to the virtual gap length, the effective gain of the accelerator can be made very large.

Clinical Investigation and Mechanism of Air-Bone Gaps in LargeVestibular Aqueduct Syndrome

PubMed Central

Merchant, Saumil N.; Nakajima, Hideko H.; Halpin, Christopher; Nadol, Joseph B.; Lee, Daniel J.; Innis, William P.; Curtin, Hugh; Rosowski, John J.

2008-01-01

Objectives Patients with large vestibular aqueduct syndrome (LVAS) often demonstrate an air-bone gap at the low frequencies on audiometric testing. The mechanism causing such a gap has not been well elucidated. We investigated middle ear sound transmission in patients with LVAS, and present a hypothesis to explain the air-bone gap. Methods Observations were made on 8 ears from 5 individuals with LVAS. The diagnosis of LVAS was made by computed tomography in all cases. Investigations included standard audiometry and measurements of umbo velocity by laser Doppler vibrometry (LDV) in all cases, as well as tympanometry, acoustic reflex testing, vestibular evoked myogenic potential (VEMP) testing, distortion product otoacoustic emission (DPOAE) testing, and middle ear exploration in some ears. Results One ear with LVAS had anacusis. The other 7 ears demonstrated air-bone gaps at the low frequencies, with mean gaps of 51 dB at 250 Hz, 31 dB at 500 Hz, and 12 dB at 1,000 Hz. In these 7 ears with air-bone gaps, LDV showed the umbo velocity to be normal or high normal in all 7; tympanometry was normal in all 6 ears tested; acoustic reflexes were present in 3 of the 4 ears tested; VEMP responses were present in all 3 ears tested; DPOAEs were present in 1 of the 2 ears tested, and exploratory tympanotomy in 1 case showed a normal middle ear. The above data suggest that an air-bone gap in LVAS is not due to disease in the middle ear. The data are consistent with the hypothesis that a large vestibular aqueduct introduces a third mobile window into the inner ear, which can produce an air-bone gap by 1) shunting air-conducted sound away from the cochlea, thus elevating air conduction thresholds, and 2) increasing the difference in impedance between the scala vestibuli side and the scala tympani side of the cochlear partition during bone conduction testing, thus improving thresholds for bone-conducted sound. Conclusions We conclude that LVAS can present with an air-bone gap that can mimic middle ear disease. Diagnostic testing using acoustic reflexes, VEMPs, DPOAEs, and LDV can help to identify a non–middle ear source for such a gap, thereby avoiding negative middle ear exploration. A large vestibular aqueduct may act as a third mobile window in the inner ear, resulting in an air-bone gap at low frequencies. PMID:17727085

Modeling of laser-induced ionization of solid dielectrics for ablation simulations: role of effective mass

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly

2010-11-01

Modeling of laser-induced ionization and heating of conduction-band electrons by laser radiation frequently serves as a basis for simulations supporting experimental studies of laser-induced ablation and damage of solid dielectrics. Together with band gap and electron-particle collision rate, effective electron mass is one of material parameters employed for the ionization modeling. Exact value of the effective mass is not known for many materials frequently utilized in experiments, e.g., fused silica and glasses. Because of that reason, value of the effective mass is arbitrary varied around "reasonable values" for the ionization modeling. In fact, it is utilized as a fitting parameter to fit experimental data on dependence of ablation or damage threshold on laser parameters. In this connection, we study how strong is the influence of variations of the effective mass on the value of conduction-band electron density. We consider influence of the effective mass on the photo-ionization rate and rate of impact ionization. In particular, it is shown that the photo-ionization rate can vary by 2-4 orders of magnitude with variation of effective mass by 50%. Impact ionization shows a much weaker dependence on effective mass, but it significantly enhances the variations of seed-electron density produced by the photo-ionization. Utilizing those results, we demonstrate that variation of effective mass by 50% produces variations of conduction-band electron density by 6 orders of magnitude. In this connection, we discuss the general issues of the current models of laser-induced ionization.

Determining Perceptual Gaps of Service Quality and Value in Higher Education: A Midwestern Bible College

ERIC Educational Resources Information Center

McIntosh, Benjamin T.

2017-01-01

This doctoral research project examined perceptual gaps of service quality and value in the context of higher education. The researcher performed quantitative analysis of survey data gathered from students at a small, Midwestern Bible college. Students self-selected to participate in this research project and, using class status as an independent…

SACRIFICING THE ECOLOGICAL RESOLUTION OF VEGETATION MAPS AT THE ALTAR OF THEMATIC ACCURACY: ASSESSED MAP ACCURACIES FOR HIERARCHICAL VEGETATION CLASSIFICATIONS IN THE EASTERN GREAT BASIN OF THE SOUTHWEST REGIONAL GAP ANALYSIS PROJECT (SW REGAP)

EPA Science Inventory

The Southwest Regional Gap Analysis Project (SW ReGAP) improves upon previous GAP projects conducted in Arizona, Colorado, Nevada, New Mexico, and Utah to provide a
consistent, seamless vegetation map for this large and ecologically diverse geographic region. Nevada's compone...

Efforts to Bridge the Gap between Research and Practice in Social Work: Precedents and Prospects: Keynote Address at the Bridging the Gap Symposium

ERIC Educational Resources Information Center

Rubin, Allen

2015-01-01

This keynote address discusses previous and ongoing efforts to reduce the persistent gap between research and practice in social work and offers recommendations for further bridging that gap. Key among those recommendations is the need to conduct descriptive outcome studies of efforts to adapt research-supported interventions in everyday practice…

Targeted functional imaging of estrogen receptors with 99mTc-GAP-EDL.

PubMed

Takahashi, Nobukazu; Yang, David J; Kohanim, Saady; Oh, Chang-Sok; Yu, Dong-Fang; Azhdarinia, Ali; Kurihara, Hiroaki; Zhang, Xiaochun; Chang, Joe Y; Kim, E Edmund

2007-03-01

To evaluate the feasibility of using (99m)Tc-glutamate peptide-estradiol in functional imaging of estrogen receptor-positive [ER(+)] diseases. 3-Aminoethyl estradiol (EDL) was conjugated to glutamate peptide (GAP) to yield GAP-EDL. Cellular uptake studies of (99m)Tc-GAP-EDL were conducted in ER(+) cell lines (MCF-7, 13762 and T47D). To demonstrate whether GAP-EDL increases MAP kinase activation, Western blot analysis of GAP-EDL was performed in 13762 cells. Biodistribution was conducted in nine rats with 13762 breast tumors at 0.5-4 h. Each rat was administered (99m)Tc-GAP-EDL. Two animal models (rats and rabbits) were created to ascertain whether tumor uptake of (99m)Tc-GAP-EDL was via an ER-mediated process. In the tumor model, breast tumor-bearing rats were pretreated with diethylstilbestrol (DES) 1 h prior to receiving (99m)Tc-GAP-EDL. In the endometriosis model, part of the rabbit uterine tissue was dissected and grafted to the peritoneal wall. The rabbit was administered with (99m)Tc-GAP-EDL. There was a 10-40% reduction in uptake of (99m)Tc-GAP-EDL in cells treated with DES or tamoxifen compared with untreated cells. Western blot analysis showed an ERK1/2 phosphorylation process with GAP-EDL. Biodistribution studies showed that tumor uptake and tumor-to-muscle count density ratio in (99m)Tc-GAP-EDL groups were significantly higher than those in (99m)Tc-GAP groups at 4 h. Among (99m)Tc-GAP-EDL groups, region of interest analysis of images showed that tumor-to muscle ratios were decreased in blocking groups. In the endometriosis model, the grafted uterine tissue could be visualized by (99m)Tc-GAP-EDL. Cellular or tumor uptake of (99m)Tc-GAP-EDL occurs via an ER-mediated process. (99m)Tc-GAP-EDL is a useful agent for imaging functional ER(+) disease.

A toy model to investigate the existence of excitons in the ground state of strongly-correlated semiconductor

NASA Astrophysics Data System (ADS)

Karima, H. R.; Majidi, M. A.

2018-04-01

Excitons, quasiparticles associated with bound states between an electron and a hole and are typically created when photons with a suitable energy are absorbed in a solid-state material. We propose to study a possible emergence of excitons, created not by photon absorption but the effect of strong electronic correlations. This study is motivated by a recent experimental study of a substrate material SrTiO3 (STO) that reveals strong exitonic signals in its optical conductivity. Here we conjecture that some excitons may already exist in the ground state as a result of the electronic correlations before the additional excitons being created later by photon absorption. To investigate the existence of excitons in the ground state, we propose to study a simple 4-energy-level model that mimics a situation in strongly-correlated semiconductors. The four levels are divided into two groups, lower and upper groups separated by an energy gap, Eg , mimicking the valence and the conduction bands, respectively. Further, we incorporate repulsive Coulomb interactions between the electrons. The model is then solved by exact diagonalization method. Our result shows that the toy model can demonstrate band gap widening or narrowing and the existence of exciton in the ground state depending on interaction parameter values.

Cu doping concentration effect on the physical properties of CdS thin films obtained by the CBD technique

NASA Astrophysics Data System (ADS)

Albor Aguilera, M. L.; Flores Márquez, J. M.; Remolina Millan, A.; Matsumoto Kuwabara, Y.; González Trujillo, M. A.; Hernández Vásquez, C.; Aguilar Hernandez, J. R.; Hernández Pérez, M. A.; Courel-Piedrahita, M.; Madeira, H. T. Yee

2017-08-01

Cu(In, Ga)Se2 (CIGS) and Cu2ZnSnS4 (CZTS) semiconductors are direct band gap materials; when these types of material are used in solar cells, they provide efficiencies of 22.1% and 12.6%, respectively. Most traditional fabrication methods involve expensive vacuum processes including co-evaporation and sputtering techniques, where films and doping are conducted separately. On the other hand, the chemical bath deposition (CBD) technique allows an in situ process. Cu-doped CdS thin films working as a buffer layer on solar cells provide good performing devices and they may be deposited by low cost techniques such as chemical methods. In this work, Cu-doped CdS thin films were deposited using the CBD technique on SnO2:F (FTO) substrates. The elemental analysis and mapping reconstruction were conducted by EDXS. Morphological, optical and electrical properties were studied, and they revealed that Cu doping modified the CdS structure, band-gap value and the electrical properties. Cu-doped CdS films show high resistivity compared to the non-doped CdS. The appropriate parameters of Cu-doped CdS films were determined to obtain an adequate window or buffer layer on CIGS and CZTS photovoltaic solar cells.

Effect of Pulse and dc Formation on the Performance of One-Transistor and One-Resistor Resistance Random Access Memory Devices

NASA Astrophysics Data System (ADS)

Liu, Hong-Tao; Yang, Bao-He; Lv, Hang-Bing; Xu, Xiao-Xin; Luo, Qing; Wang, Guo-Ming; Zhang, Mei-Yun; Long, Shi-Bing; Liu, Qi; Liu, Ming

2015-02-01

We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor (1T1R) resistance random access memory (RRAM) device. All the devices are operated under the same test conditions, except for the initial formation process with different modes. Based on the statistical results, the high resistance state (HRS) under the dc forming mode shows a lower value with better distribution compared with that under the pulse mode. One of the possible reasons for such a phenomenon originates from different properties of conductive filament (CF) formed in the resistive switching layer under two different modes. For the dc forming mode, the formed filament is thought to be continuous, which is hard to be ruptured, resulting in a lower HRS. However, in the case of pulse forming, the filament is discontinuous where the transport mechanism is governed by hopping. The low resistance state (LRS) can be easily changed by removing a few trapping states from the conducting path. Hence, a higher HRS is thus observed. However, the HRS resistance is highly dependent on the length of the gap opened. A slight variation of the gap length will cause wide dispersion of resistance.

Mechanical signaling coordinates the embryonic heartbeat.

PubMed

Chiou, Kevin K; Rocks, Jason W; Chen, Christina Yingxian; Cho, Sangkyun; Merkus, Koen E; Rajaratnam, Anjali; Robison, Patrick; Tewari, Manorama; Vogel, Kenneth; Majkut, Stephanie F; Prosser, Benjamin L; Discher, Dennis E; Liu, Andrea J

2016-08-09

In the beating heart, cardiac myocytes (CMs) contract in a coordinated fashion, generating contractile wave fronts that propagate through the heart with each beat. Coordinating this wave front requires fast and robust signaling mechanisms between CMs. The primary signaling mechanism has long been identified as electrical: gap junctions conduct ions between CMs, triggering membrane depolarization, intracellular calcium release, and actomyosin contraction. In contrast, we propose here that, in the early embryonic heart tube, the signaling mechanism coordinating beats is mechanical rather than electrical. We present a simple biophysical model in which CMs are mechanically excitable inclusions embedded within the extracellular matrix (ECM), modeled as an elastic-fluid biphasic material. Our model predicts strong stiffness dependence in both the heartbeat velocity and strain in isolated hearts, as well as the strain for a hydrogel-cultured CM, in quantitative agreement with recent experiments. We challenge our model with experiments disrupting electrical conduction by perfusing intact adult and embryonic hearts with a gap junction blocker, β-glycyrrhetinic acid (BGA). We find this treatment causes rapid failure in adult hearts but not embryonic hearts-consistent with our hypothesis. Last, our model predicts a minimum matrix stiffness necessary to propagate a mechanically coordinated wave front. The predicted value is in accord with our stiffness measurements at the onset of beating, suggesting that mechanical signaling may initiate the very first heartbeats.

Direct imaging of band profile in single layer MoS2 on graphite: quasiparticle energy gap, metallic edge states, and edge band bending.

PubMed

Zhang, Chendong; Johnson, Amber; Hsu, Chang-Lung; Li, Lain-Jong; Shih, Chih-Kang

2014-05-14

Using scanning tunneling microscopy and spectroscopy, we probe the electronic structures of single layer MoS2 on graphite. The apparent quasiparticle energy gap of single layer MoS2 is measured to be 2.15 ± 0.06 eV at 77 K, albeit a higher second conduction band threshold at 0.2 eV above the apparent conduction band minimum is also observed. Combining it with photoluminescence studies, we deduce an exciton binding energy of 0.22 ± 0.1 eV (or 0.42 eV if the second threshold is use), a value that is lower than current theoretical predictions. Consistent with theoretical predictions, we directly observe metallic edge states of single layer MoS2. In the bulk region of MoS2, the Fermi level is located at 1.8 eV above the valence band maximum, possibly due to the formation of a graphite/MoS2 heterojunction. At the edge, however, we observe an upward band bending of 0.6 eV within a short depletion length of about 5 nm, analogous to the phenomena of Fermi level pinning of a 3D semiconductor by metallic surface states.

Data on energy-band-gap characteristics of composite nanoparticles obtained by modification of the amorphous potassium polytitanate in aqueous solutions of transition metal salts

PubMed Central

Zimnyakov, D.A.; Sevrugin, A.V.; Yuvchenko, S.A.; Fedorov, F.S.; Tretyachenko, E.V.; Vikulova, M.A.; Kovaleva, D.S.; Krugova, E.Y.; Gorokhovsky, A.V.

2016-01-01

Here we present the data on the energy-band-gap characteristics of composite nanoparticles produced by modification of the amorphous potassium polytitanate in aqueous solutions of different transition metal salts. Band gap characteristics are investigated using diffuse reflection spectra of the obtained powders. Calculated logarithmic derivative quantity of the Kubelka–Munk function reveals a presence of local maxima in the regions 0.5–1.5 eV and 1.6–3.0 eV which correspond to band gap values of the investigated materials. The values might be related to the constituents of the composite nanoparticles and intermediate products of their chemical interaction. PMID:27158654

Effect of Se addition on optical and electrical properties of chalcogenide CdSSe thin films

NASA Astrophysics Data System (ADS)

Hassanien, A. S.; Akl, Alaa A.

2016-01-01

Compositional dependence of optical and electrical properties of chalcogenide CdSxSe1-x (0.4 ≥ x ≥ 0.0 at. %) thin films was studied. Cadmium sulphoselenide films were deposited by thermal evaporation technique at vacuum (8.2 × 10-4 Pa) onto preheated glass substrates (523 K). The evaporation rate and film thickness were kept constant at 2.50 nm/s and 375 ± 5 nm, respectively. X-ray diffractograms showed that, the deposited films have the low crystalline nature. Energy dispersive analysis by X-ray (EDAX) was used to check the compositional elements of deposited films. The absorption coefficient was determined from transmission and reflection measurements at room temperature in the wavelength range 300-2500 nm. Optical density, skin depth, optical energy gap and Urbach's parameters of CdSSe thin films have also been estimated. The direct optical energy gap decreased from 2.248 eV to 1.749 eV when the ratio of Se-content was increased from 0.60 to 1.00 . Conduction band and valance band positions were evaluated. The temperature dependence of dc-electrical resistivity in the temperature range (293-450 K) has been reported. Three conduction regions due to different conduction mechanisms were detected. Electrical sheet resistance, activation energy and pre-exponential parameters were discussed. The estimated values of optical and electrical parameters were strongly dependent upon the Se-content in CdSSe matrix.

Technology acceptance perception for promotion of sustainable consumption.

PubMed

Biswas, Aindrila; Roy, Mousumi

2018-03-01

Economic growth in the past decades has resulted in change in consumption pattern and emergence of tech-savvy generation with unprecedented increase in the usage of social network technology. In this paper, the technology acceptance value gap adapted from the technology acceptance model has been applied as a tool supporting social network technology usage and subsequent promotion of sustainable consumption. The data generated through the use of structured questionnaires have been analyzed using structural equation modeling. The validity of the model and path estimates signifies the robustness of Technology Acceptance value gap in adjudicating the efficiency of social network technology usage in augmentation of sustainable consumption and awareness. The results indicate that subjective norm gap, ease-of-operation gap, and quality of green information gap have the most adversarial impact on social network technology usage. Eventually social networking technology usage has been identified as a significant antecedent of sustainable consumption.

Nanostructured GdxZn1-xO thin films by nebulizer spray pyrolysis technique: Role of doping concentration on the structural and optical properties

NASA Astrophysics Data System (ADS)

Mariappan, R.; Ponnuswamy, V.; Suresh, P.; Suresh, R.; Ragavendar, M.

2013-07-01

Nanostructured GdxZn1-xO thin films with different Gd concentration from 0% to 10% deposited at 400 °C using the NSP technique. The films were characterized by structural, surface and optical properties, respectively. X-ray diffraction analysis shows that the Gd doped ZnO films have lattice parameters a = 3.2497 Å and c = 5.2018 Å with hexagonal structure and preferential orientation along (0 0 2) plane. The estimated values compare well with the standard values. When film thickness increases from 222 to 240 nm a high visible region transmittance (>70%) is observed. The optical band gap energy, optical constants (n and k), complex dielectric constants (ɛr and ɛi) and optical conductivities (σr and σi) were calculated from optical transmittance data. The optical band gap energy is 3.2 eV for pure ZnO film and 3.6 eV for Gd0.1Zn0.9O film. The PL studies confirm the presence of a strong UV emission peak at 399 nm. Besides, the UV emission of ZnO films decreases with the increase of Gd doping concentration correspondingly the ultra-violet emission is replaced by blue and green emissions.

Fluctuating asymmetry and mentum gaps in populations of the midge Chironomus riparius (Diptera: Chironomidae) from a metal-contaminated River

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groenendijk, D.; Zeinstra, L.W.M.; Postma, J.F.

1998-10-01

The developmental stability of both metal-exposed and nonexposed Chironomus riparius populations from the lowland River Dommel was investigated using fluctuating asymmetry (FA) and the incidence of mentum gaps. It was hypothesized that larval development was affected by the influx of Cd, Zn, Fe, Cu, and Pb directly by chemical stress, as well as through inbreeding of metal-adapted and nonadapted specimens. Morphological para/meters were therefore assessed in field-collected larvae and in clean, laboratory-cultured, first-generation (F1) larvae. Fluctuating asymmetry values and mentum gap incidence at contaminated field sites were significantly higher than at clean, upstream locations. Furthermore, FA values of clean, laboratory-culturedmore » F1 larvae generally fell to reference values, indicating the direct effect of metal pollution on developmental aberrations. Mentum gaps were not observed in clean F1 cultures. Slightly elevated FA values were, however, still observed in clean F1 larvae from polluted locations downstream from the metal input. This residual disturbance was thought to reflect genetic stress emerging from interbreeding between metal-adapted and nonadapted specimens. Fluctuating asymmetry and mentum gaps together serve as a useful ecotoxicological marker for metal stress and, when combined with in situ studies and F1 cultures, allow for analysis of the response of animal populations to spatial and temporal gradients in metal exposure.« less

Patients' Expectations and Perceptions of Service Quality in the Selected Hospitals.

PubMed

Nadi, Aliasghar; Shojaee, Jalil; Abedi, Ghassem; Siamian, Hasan; Abedini, Ehsan; Rostami, Farideh

2016-04-01

Hospital's success depends on patients' expectations, perceptions, and judgment on the quality of services provided by hospitals. This study was conducted to assess the patients' perceptions and expectations from the quality of inpatient health care in Vali-Asr hospital, Ghaemshahr, and Imam Khomeini and Shafa Hospitals, Sari. This study is applied regarding the objective of the study. Considering the research methodology, it is a descriptive - analytical study. The sample of this study consists of 600 patients with at least 24 hours of being hospitalized in internal, surgery, women, and children sectors of Vali-Asr, Ghaemshahr, Imam Khomeini, and Shafa Hospitals. Using random sampling method, the classifications relevant to the size of each class were selected. The data required was collected through the standard SERVQUAL questionnaire and then it was analyzed using the SPSS software. The overall mean value and standard deviation of expectations were equal to 10.4 and 28, respectively. The mean value for the field of perception was 69.2 and the relevant standard deviation was 26. In terms of patients and hospital visits in concrete cases, the highest priority is related to empathy. The second priority is related to physical appearance, the third priority is related to responsiveness, the fourth priority is related to assurance, and the lowest priority is related to the reliability of the SERVQUAL approach. Examining the gap between patients' perceptions and expectations, the widest gap was observed in the Vali-Asr Hospital with the mean and SD (-92.0±39.0) and the lowest gap was observed in Shafa Hospital with the mean value of (-39.9±44.0). According to The Kruskal-Wallis test, the difference observed in these three hospitals were significant. The results showed that patients' expectations had not been met in any of the examined dimensions and their consent has not been achieved. It seemed that necessary for managers and relevant authorities to plan and pay special attention to this important issue.

Ab-initio study of thermal expansion in pure graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, Sarita; Kumar, Ranjan; Jindal, V. K., E-mail: jindal@pu.ac.in

Graphene is a zero band gap semiconductor with exceptionally high thermal conductivity. The electronic properties having been studied, therole of phonon in contributing to thermal expansion, thermal conductivity and other thermodynamic properties, is required to be investigated. This paper focuses more on thermal expansion. Some others results like phonon dispersion, Grüneisenparameters and bulk modulus,which are essential to estimation of thermal expansion, are also presented. The dynamical matrix was calculated using VASP code using both DFT and DFPT and the phonon frequencies were calculated using phonopy code under harmonic approximation. The linear thermal expansion coefficient of graphene is found to bemore » strongly dependent on temperature but remains negative upto 470 K and positive thereafter, with a room temperature value of −1.44×10{sup −6}. The negative expansion coefficient is very interesting and is found to be in conformity with experimental as well as with recent theoretical estimates. There is only qualitative agreement of our results with experimental data and motivates further investigation, primarily on the high negative values of Grüneisen parameters.« less

Enhanced thermoelectric properties of graphene oxide patterned by nanoroads.

PubMed

Zhou, Si; Guo, Yu; Zhao, Jijun

2016-04-21

The thermoelectric properties of two-dimensional (2D) materials are of great interest for both fundamental science and device applications. Graphene oxide (GO), whose physical properties are highly tailorable by chemical and structural modifications, is a potential 2D thermoelectric material. In this report, we pattern nanoroads on GO sheets with epoxide functionalization, and investigate their ballistic thermoelectric transport properties based on density functional theory and the nonequilibrium Green's function method. These graphene oxide nanoroads (GONRDs) are all semiconductors with their band gaps tunable by the road width, edge orientation, and the structure of the GO matrix. These nanostructures show appreciable electrical conductance at certain doping levels and enhanced thermopower of 127-287 μV K(-1), yielding a power factor 4-22 times of the graphene value; meanwhile, the lattice thermal conductance is remarkably reduced to 15-22% of the graphene value; consequently, attaining the figure of merit of 0.05-0.75. Our theoretical results are not only helpful for understanding the thermoelectric properties of graphene and its derivatives, but also would guide the theoretical design and experimental fabrication of graphene-based thermoelectric devices of high performance.

Health Services Research in Rehabilitation and Disability-The Time is Now.

PubMed

Graham, James E; Middleton, Addie; Roberts, Pamela; Mallinson, Trudy; Prvu-Bettger, Janet

2018-01-01

Policy drives practice, and health services research (HSR) is at the intersection of policy, practice, and patient outcomes. HSR specific to rehabilitation and disability is particularly needed. As rehabilitation researchers and providers, we are uniquely positioned to provide the evidence that guides reforms targeting rehabilitative care. We have the expertise to define the value of rehabilitation in a policy-relevant context. HSR is a powerful tool for providing this evidence. We need to continue building capacity for conducting rigorous, timely rehabilitation-related HSR. Fostering stakeholder engagement in these research efforts will ensure we maintain a patient-centered focus as we address the "Triple Aim" of better care, better health, and better value. In this Special Communication we discuss the role of rehabilitation researchers in HSR. We also provide information on current resources available in our field for conducting HSR and identify gaps for capacity building and future research. Health care reforms are a reality, and through HSR we can give rehabilitation a strong voice during these transformative times. Copyright © 2017 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

High voltage-derived enhancement of electric conduction in nanogap devices for detection of prostate-specific antigen

NASA Astrophysics Data System (ADS)

Park, Hyung Ju; Chi, Young Shik; Choi, Insung S.; Yun, Wan Soo

2010-07-01

We report a simple method of enhancing electric conductance in nanogap devices without any additional treatments, such as silver-enhancing process. The low electric conductance after selective immobilization of biofunctionalized gold nanoparticles in the gap region was greatly enhanced by repeated I-V scans at relatively high voltage ranges of -5 to 5 V, which was attributed to the formation of a new conduction pathway across the gap. The higher conduction state of the nanogap device showed a very stable I-V curve, which was used as an excellent measure of the existence of prostate-specific antigen.

A head to head evaluation of 8 biochemical scanning tools for unmeasured ions.

PubMed

Morgan, Thomas J; Anstey, Chris M; Wolf, Matthew B

2017-04-01

We aimed to evaluate the sensitivity and specificity of 8 biochemical scanning tools in signalling the presence of unmeasured anions. We used blood gas and biochemical data from 15 patients during and after cardio-pulmonary bypass. Sampling time-points were pre-bypass (T1), 2 min post equilibration with priming fluid containing acetate and gluconate anions (T2), late bypass (T3) and 4 h after surgery (T4). We calculated the anion gap (AG), albumin-corrected anion gap (AGc), whole blood base excess (BE) gap, plasma BE gap, standard BE gap and the strong ion gap (SIG), plus 2 new indices-the unmeasured ion index (UIX) and unmeasured plasma anions according to the interstitial, plasma and erythrocyte acid-base model (IPEua). Total measured plasma concentrations of acetate and gluconate [XA] were proxies for unmeasured plasma anions. [XA] values (mmol/L) were 1.41 (0.87) at T1, 11.73 (3.28) at T2, 4.80 (1.49) at T3 and 1.36 (0.73) at T4. Corresponding [albumin] values (g/L) were 32.3 (2.0), 19.8 (2.6), 21.3 (2.5) and 29.1 (2.3) respectively. Only the AG failed to increase significantly at T2 in response to a mean [XA] surge of >10 mEq/L. At an [XA] threshold of 6 mEq/L, areas under receiver -operator characteristic curves in rank order were IPEua and UIX (0.88 and 0.87 respectively), SIG (0.81), AGc (0.79), standard BE gap (0.77), plasma BE gap (0.71), BE gap (0.70) and AG (0.59). Similar ranking hierarchies applied to positive and negative predictive values. We conclude that during acute hemodilution UIX and IPEua are superior to the anion gap (with and without albumin correction) and 4 other indices as scanning tools for unmeasured anions.

Hybridization gap and dual nature of the heavy-fermion compound UPd 2Al 3 via quasiparticle scattering spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaggi, N. K.; Mehio, O.; Dwyer, M.

We present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd 2Al 3 : Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature and magnetic field and analyzed using a theory of cotunneling into an Anderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi liquid is formed. Both the hybridization gap, found to be 7.2 ± 0.3 meV at 4 K, and the conductance enhancement above a flat background decrease upon increasing temperature. While themore » hybridization gap is extrapolated to remain finite up to ~28 K, close to the temperature around which the magnetic susceptibility displays a broad peak, the conductance enhancement vanishes at ~18 K, slightly above the antiferromagnetic transition temperature (T N ≈ 14 K) . This rapid decrease of the conductance enhancement is understood as a consequence of the junction drifting away from the ballistic regime due to increased scattering off magnons associated with the localized U 5 f electrons. This shows that while the hybridization gap opening is not directly associated with the antiferromagnetic ordering, its visibility in the conductance is greatly affected by the temperature-dependent magnetic excitations. Our findings are not only consistent with the 5 f dual-nature picture in the literature but also shed new light on the interplay between the itinerant and localized electrons in UPd 2Al 3 .« less

Hybridization gap and dual nature of the heavy-fermion compound UPd 2Al 3 via quasiparticle scattering spectroscopy

DOE PAGES

Jaggi, N. K.; Mehio, O.; Dwyer, M.; ...

2017-04-17

We present results from point-contact spectroscopy of the antiferromagnetic heavy-fermion superconductor UPd 2Al 3 : Conductance spectra are taken from single crystals with two major surface orientations as a function of temperature and magnetic field and analyzed using a theory of cotunneling into an Anderson lattice. Spectroscopic signatures are clearly identified, including the distinct asymmetric double-peak structure arising from the opening of a hybridization gap when a coherent heavy-Fermi liquid is formed. Both the hybridization gap, found to be 7.2 ± 0.3 meV at 4 K, and the conductance enhancement above a flat background decrease upon increasing temperature. While themore » hybridization gap is extrapolated to remain finite up to ~28 K, close to the temperature around which the magnetic susceptibility displays a broad peak, the conductance enhancement vanishes at ~18 K, slightly above the antiferromagnetic transition temperature (T N ≈ 14 K) . This rapid decrease of the conductance enhancement is understood as a consequence of the junction drifting away from the ballistic regime due to increased scattering off magnons associated with the localized U 5 f electrons. This shows that while the hybridization gap opening is not directly associated with the antiferromagnetic ordering, its visibility in the conductance is greatly affected by the temperature-dependent magnetic excitations. Our findings are not only consistent with the 5 f dual-nature picture in the literature but also shed new light on the interplay between the itinerant and localized electrons in UPd 2Al 3 .« less

Inner ear anomalies and conductive hearing loss in children with Apert syndrome: an overlooked otologic aspect.

PubMed

Zhou, Guangwei; Schwartz, Lynn Thomas; Gopen, Quinton

2009-02-01

To identify the occurrence of inner ear structural anomalies and conductive hearing loss (CHL) in children with Apert syndrome. Retrospective review. Pediatric tertiary referral center. Twenty pediatric patients with Apert syndrome were found; all patients (38/40 ears) had inner ear anomalies. Computerized tomography of the head/temporal bone, pure-tone (including air and bone conduction) audiometry, and tympanometry. Imaging demonstrating inner ear anomalies, including malformations of the cochlea, dilated vestibule, and/or semicircular canal; audiologic findings of air-bone gap(s). Hearing loss was found in 90% of the patients with Apert syndrome, and 80% of them had CHL. Air-bone gaps were found at all frequencies, with larger gaps at low frequencies. Fifty percent (20/40) of the ears had better than 0 dB hearing level bone conduction thresholds at 250 and/or 500 Hz. Normal middle ear pressure and mobility were found in all ears with intact eardrum. Inner ear anomalies were found in all patients, and 90% of them had bilateral involvement. Most frequently observed inner ear anomalies were dilated vestibule, malformed lateral semicircular canal, and cochlear dysplasia. Children with Apert syndrome may present with significant CHL that cannot be explained by minor middle ear pathologies alone. This conductive loss may be, at least partially, attributed to the inner ear anomalies; however, these structural anomalies are usually not recognized in these patients. Failure to close air-bone gap after surgical intervention may raise the suspicion of inner ear anomalies, and computed tomographic scan of the temporal bone can provide definitive proof.

Second-harmonic generation at angular incidence in a negative-positive index photonic band-gap structure.

PubMed

D'Aguanno, Giuseppe; Mattiucci, Nadia; Scalora, Michael; Bloemer, Mark J

2006-08-01

In the spectral region where the refractive index of the negative index material is approximately zero, at oblique incidence, the linear transmission of a finite structure composed of alternating layers of negative and positive index materials manifests the formation of a new type of band gap with exceptionally narrow band-edge resonances. In particular, for TM-polarized (transverse magnetic) incident waves, field values that can be achieved at the band edge may be much higher compared to field values achievable in standard photonic band-gap structures. We exploit the unique properties of these band-edge resonances for applications to nonlinear frequency conversion, second-harmonic generation, in particular. The simultaneous availability of high field localization and phase matching conditions may be exploited to achieve second-harmonic conversion efficiencies far better than those achievable in conventional photonic band-gap structures. Moreover, we study the role played by absorption within the negative index material, and find that the process remains efficient even for relatively high values of the absorption coefficient.

Band gap engineering for poly(p-phenylene) and poly(p-phenylene vinylene) copolymers using the tight-binding approach

NASA Astrophysics Data System (ADS)

Giro, R.; Caldas, M. J.; Galvão, D. S.

The interest in poly(p-phenylene) (PPP) and poly(p-phenylene vinylene) (PPV) copolymers stems from the fact that these homopolymers present interesting optical and electronic properties that allow a great variety of technological applications. Combining different numbers of PPP and PPV units it is possible, in principle, to obtain new structures presenting intermediate gap values (2.8 eV and 2.4 eV for PPP and PPV, respectively). For this study we used a Hückel Hamiltonian tight-binding coupled to the negative factor counting (NFC) technique. We carried out a systematic search to determine optimum relative concentrations for disordered binary polymeric alloys with predefined gap values. Once these structures were obtained, we used the semiempirical methods AM1/PM3 and ZINDO/S-CI for geometrical and optical studies, respectively. Our theoretical results show that it is possible to obtain copolymers of PPP and PPV with intermediate gap values of their parent structures.

Stereotyped: investigating gender in introductory science courses.

PubMed

Lauer, Shanda; Momsen, Jennifer; Offerdahl, Erika; Kryjevskaia, Mila; Christensen, Warren; Montplaisir, Lisa

2013-01-01

Research in science education has documented achievement gaps between men and women in math and physics that may reflect, in part, a response to perceived stereotype threat. Research efforts to reduce achievement gaps by mediating the impact of stereotype threat have found success with a short values-affirmation writing exercise. In biology and biochemistry, however, little attention has been paid to the performance of women in comparison with men or perceptions of stereotype threat, despite documentation of leaky pipelines into professional and academic careers. We used methodologies developed in physics education research and cognitive psychology to 1) investigate and compare the performance of women and men across three introductory science sequences (biology, biochemistry, physics), 2) document endorsement of stereotype threat in these science courses, and 3) investigate the utility of a values-affirmation writing task in reducing achievement gaps. In our study, analysis of final grades and normalized learning gains on content-specific concept inventories reveals no achievement gap in the courses sampled, little stereotype threat endorsement, and no impact of the values-affirmation writing task on student performance. These results underscore the context-dependent nature of achievement gaps and stereotype threat and highlight calls to replicate education research across a range of student populations.

Stereotyped: Investigating Gender in Introductory Science Courses

PubMed Central

Lauer, Shanda; Momsen, Jennifer; Offerdahl, Erika; Kryjevskaia, Mila; Christensen, Warren; Montplaisir, Lisa

2013-01-01

Research in science education has documented achievement gaps between men and women in math and physics that may reflect, in part, a response to perceived stereotype threat. Research efforts to reduce achievement gaps by mediating the impact of stereotype threat have found success with a short values-affirmation writing exercise. In biology and biochemistry, however, little attention has been paid to the performance of women in comparison with men or perceptions of stereotype threat, despite documentation of leaky pipelines into professional and academic careers. We used methodologies developed in physics education research and cognitive psychology to 1) investigate and compare the performance of women and men across three introductory science sequences (biology, biochemistry, physics), 2) document endorsement of stereotype threat in these science courses, and 3) investigate the utility of a values-affirmation writing task in reducing achievement gaps. In our study, analysis of final grades and normalized learning gains on content-specific concept inventories reveals no achievement gap in the courses sampled, little stereotype threat endorsement, and no impact of the values-affirmation writing task on student performance. These results underscore the context-dependent nature of achievement gaps and stereotype threat and highlight calls to replicate education research across a range of student populations. PMID:23463226

Electrical properties of epitaxial yttrium iron garnet ultrathin films at high temperatures

NASA Astrophysics Data System (ADS)

Thiery, N.; Naletov, V. V.; Vila, L.; Marty, A.; Brenac, A.; Jacquot, J.-F.; de Loubens, G.; Viret, M.; Anane, A.; Cros, V.; Ben Youssef, J.; Beaulieu, N.; Demidov, V. E.; Divinskiy, B.; Demokritov, S. O.; Klein, O.

2018-02-01

We report a study on the electrical properties of 19-nm-thick yttrium iron garnet (YIG) films grown by liquid phase epitaxy on gadolinium gallium garnet single crystal. The electrical conductivity and Hall coefficient are measured in the high-temperature range [300,400] K using a Van der Pauw four-point probe technique. We find that the electrical resistivity decreases exponentially with increasing temperature following an activated behavior corresponding to a band gap of Eg≈2 eV. It drops to values about 5 ×103Ω cm at T =400 K, thus indicating that epitaxial YIG ultrathin films behave as large gap semiconductors. We also infer the Hall mobility, which is found to be positive (p type) at 5 cm2V-1sec-1 and almost independent of temperature. We discuss the consequence for nonlocal spin transport experiments performed on YIG at room temperature and demonstrate the existence of electrical offset voltages to be disentangled from pure spin effects.

From tunable core-shell nanoparticles to plasmonic drawbridges: Active control of nanoparticle optical properties

PubMed Central

Byers, Chad P.; Zhang, Hui; Swearer, Dayne F.; Yorulmaz, Mustafa; Hoener, Benjamin S.; Huang, Da; Hoggard, Anneli; Chang, Wei-Shun; Mulvaney, Paul; Ringe, Emilie; Halas, Naomi J.; Nordlander, Peter; Link, Stephan; Landes, Christy F.

2015-01-01

The optical properties of metallic nanoparticles are highly sensitive to interparticle distance, giving rise to dramatic but frequently irreversible color changes. By electrochemical modification of individual nanoparticles and nanoparticle pairs, we induced equally dramatic, yet reversible, changes in their optical properties. We achieved plasmon tuning by oxidation-reduction chemistry of Ag-AgCl shells on the surfaces of both individual and strongly coupled Au nanoparticle pairs, resulting in extreme but reversible changes in scattering line shape. We demonstrated reversible formation of the charge transfer plasmon mode by switching between capacitive and conductive electronic coupling mechanisms. Dynamic single-particle spectroelectrochemistry also gave an insight into the reaction kinetics and evolution of the charge transfer plasmon mode in an electrochemically tunable structure. Our study represents a highly useful approach to the precise tuning of the morphology of narrow interparticle gaps and will be of value for controlling and activating a range of properties such as extreme plasmon modulation, nanoscopic plasmon switching, and subnanometer tunable gap applications. PMID:26665175

Ion beam sputter deposited zinc telluride films

NASA Technical Reports Server (NTRS)

Gulino, D. A.

1986-01-01

Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter deposition are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq cm resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x 10 to the -6th/ohm cm for 300 angstrom film to 2.56 x 10 to the -1/ohm cm for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

Ion beam sputter deposited zinc telluride films

NASA Technical Reports Server (NTRS)

Gulino, D. A.

1985-01-01

Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter depoairion are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq. cm. resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x to to the -6/ohm. cm. for 300 angstrom film to 2.56 x 10 to the -1/ohm. cm. for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

Measurement of Single Channel Currents from Cardiac Gap Junctions

NASA Astrophysics Data System (ADS)

Veenstra, Richard D.; Dehaan, Robert L.

1986-08-01

Cardiac gap junctions consist of arrays of integral membrane proteins joined across the intercellular cleft at points of cell-to-cell contact. These junctional proteins are thought to form pores through which ions can diffuse from cytosol to cytosol. By monitoring whole-cell currents in pairs of embryonic heart cells with two independent patch-clamp circuits, the properties of single gap junction channels have been investigated. These channels had a conductance of about 165 picosiemens and underwent spontaneous openings and closings that were independent of voltage. Channel activity and macroscopic junctional conductance were both decreased by the uncoupling agent 1-octanol.

Thickness dependence of optical properties of amorphous indium oxide thin films deposited by reactive evaporation

NASA Astrophysics Data System (ADS)

Uluta, K.; Deer, D.; Skarlatos, Y.

2006-08-01

The electrical conductivity and absorption coefficient of amorphous indium oxide thin films, thermally evaporated on glass substrates at room temperature, were evaluated. For direct transitions the variation of the optical band gap with thickness was determined and this variation was supposed to appear due to the variation of localized gap states, whereas the variation of conductivity with thickness was supposed to be due to the variation of carrier concentration. We attribute the variation of absorption coefficient with thickness to the variation of optical band gap energy rather than optical interference.

Impurity-Band Model for GaP1-xNx

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fluegel, B.; Zhang, Y.; Geisz, J. F.

2005-11-01

Low-temperature absorption studies on free-standing GaP1-xNx films provide direct experimental evidence that the host conduction-band minimum (CBM) near X1C does not plunge downward with increased nitrogen doping, contrary to what has been suggested recently; rather, it remains stationary for x up to 0.1%. This fact, combined with the results of earlier studies of the CBM at ..GAMMA.. and conduction-band edge near L, confirms that the giant bandgap lowering observed in GaP1-xNx results from a CBM that evolves purely from nitrogen impurity bands.

Gender Gaps in North American Research Productivity: Examining Faculty Publication Rates in Mexico, Canada, and the U.S.

ERIC Educational Resources Information Center

Padilla-Gonzalez, Laura; Metcalfe, Amy Scott; Galaz-Fontes, Jesus F.; Fisher, Donald; Snee, Iain

2011-01-01

The present study addresses gender gaps in North American research productivity, which may be influenced by personal and family variables, as well as professional and work-related variables. The study was conducted as part of the "Changing Academic Profession (CAP) International Survey", conducted in 2007-08. Using articles as indicator…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elizondo-Decanini, Juan M.

Short pulse neutron generators are described herein. In a general embodiment, the short pulse neutron generator includes a Blumlein structure. The Blumlein structure includes a first conductive plate, a second conductive plate, a third conductive plate, at least one of an inductor or a resistor, a switch, and a dielectric material. The first conductive plate is positioned relative to the second conductive plate such that a gap separates these plates. A vacuum chamber is positioned in the gap, and an ion source is positioned to emit ions in the vacuum chamber. The third conductive plate is electrically grounded, and themore » switch is operable to electrically connect and disconnect the second conductive plate and the third conductive plate. The at least one of the resistor or the inductor is coupled to the first conductive plate and the second conductive plate.« less

Electronic, optical and photocatalytic behavior of Mn, N doped and co-doped TiO{sub 2}: Experiment and simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Ya Fei; Li, Can, E-mail: canli1983@gmail.com; Lu, Song

2016-03-15

The crystal phase structure, surface morphology, chemical states and optical properties of Mn, N mono-doped and co-doped TiO{sub 2} nanoparticles were investigated by X-ray powder diffractometry, Raman spectra, scanning electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. Meanwhile, geometry structures, formation energies, electronic and optical properties of all systems have been also analyzed by density functional theory. The results showed that the band gap values and the carrier mobility in the valence band, conduction band and impurity levels have a synergetic influence on the visible-light absorption and photocatalytic activity of the doped TiO{sub 2}. The number and themore » carrier mobility of impurity level jointly influence the photocatalytic activity of catalyst under visible-light. Especially, the photocatalytic activity of Mn-2N co-doped TiO{sub 2} beyond three-fold than that of pure TiO{sub 2} under visible-light. - Graphical abstract: The ILs formed by N-2p orbital in N single doped specimen lie above the VB, while the ILs formed by Mn-3d orbital in Mn single doped specimen appear below the CB. However, a large amount of ILs formed by N-2p orbital and Mn-3d orbital in N and Mn codoped specimens. The band gap values and the carrier mobility in the valence band, conduction band and impurity levels have a synergetic influence on the visible-light absorption and photocatalytic activity of the doped TiO{sub 2}. The number and the carrier mobility of impurity level jointly influence the photocatalytic activity of catalyst under visible-light.« less

Relation of Thermal Conductivity with Process Induced Anisotropic Void Systems in EB-PVD PYSZ Thermal Barrier Coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renteria, A. Flores; Saruhan-Brings, B.; Ilavsky, J.

2008-03-03

Thermal barrier coatings (TBCs) deposited by Electron-beam physical deposition (EB-PVD) protect the turbine blades situated at the high pressure sector of the aircraft and stationary turbines. It is an important task to uphold low thermal conductivity in TBCs during long-term service at elevated temperatures. One of the most promising methods to fulfil this task is to optimize the properties of PYSZ-based TBC by tailoring its microstructure. Thermal conductivity of the EB-PVD produced PYSZ TBCs is influenced mainly by the size, shape, orientation and volume of the various types of porosity present in the coatings. These pores can be classified asmore » open (inter-columnar and between feather arms gaps) and closed (intra-columnar pores). Since such pores are located within the three-dimensionally deposited columns and enclose large differences in their sizes, shapes, distribution and anisotropy, the accessibility for their characterization is very complex and requires the use of sophisticated methods. In this work, three different EB-PVD TBC microstructures were manufactured by varying the process parameters, yielding various characteristics of their pores. The corresponding thermal conductivities in as-coated state and after ageing at 11000C/1h and 100h were measured via Laser Flash Analysis Method (LFA). The pore characteristics and their individual effect on the thermal conductivity are analysed by USAXS which is supported by subsequent modelling and LFA methods, respectively. Evident differences in the thermal conductivity values of each microstructure were found in as-coated and aged conditions. In summary, broader columns introduce higher values in thermal conductivity. In general, thermal conductivity increases after ageing for all three investigated microstructures, although those with initial smaller pore surface area show smaller changes.« less

Relation of thermal conductivity with process induced anisotropic void system in EB-PVD PYSZ thermal barrier coatings.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renteria, A. F.; Saruhan, B.; Ilavsky, J.

2007-01-01

Thermal barrier coatings (TBCs) deposited by Electron-beam physical deposition (EB-PVD) protect the turbine blades situated at the high pressure sector of the aircraft and stationary turbines. It is an important task to uphold low thermal conductivity in TBCs during long-term service at elevated temperatures. One of the most promising methods to fulfil this task is to optimize the properties of PYSZ-based ,TBC by tailoring its microstructure. Thermal conductivity of the EB-PVD produced PYSZ TBCs is influenced mainly by the size, shape, orientation and volume of the various types of porosity present in the coatings. These pores can be classified asmore » open (inter-columnar and between feather arms gaps) and closed (intra-columnar pores). Since such pores are located within the three-dimensionally deposited columns and enclose large differences in their sizes, shapes, distribution and anisotropy, the accessibility for their characterization is very complex and requires the use of sophisticated methods. In this work, three different EB-PVD TBC microstructures were manufactured by varying the process parameters, yielding various characteristics of their pores. The corresponding thermal conductivities in as-coated state and after ageing at 1100C/1h and 100h were measured via Laser Flash Analysis Method (LFA). The pore characteristics and their individual effect on the thermal conductivity are analysed by USAXS which is supported by subsequent modelling and LFA methods, respectively. Evident differences in the thermal conductivity values of each microstructure were found in as-coated and aged conditions. In summary, broader columns introduce higher values in thermal conductivity. In general, thermal conductivity increases after ageing for all three investigated microstructures, although those with initial smaller pore surface area show smaller changes.« less

The Influence of a "Gap Year" on Medical Students

ERIC Educational Resources Information Center

Paterson-Brown, Lucy; Paterson-Brown, Flora; Simon, Elizabeth; Loudon, Joanna; Henderson-Howat, Susanna; Robertson, Josephine; Paterson-Brown, Simon

2015-01-01

This study reports the views of second year medical students from 6 Universities on the value or not of deferring entry to medical school in order to take a "Gap Year" obtained from an anonymous questionnaire. Data were analysed using Fisher's exact test to produce a two tailed P value, with significance defined as p <0.05. A total of…

Characteristics and distributions of atmospheric mercury ...

EPA Pesticide Factsheets

Continuous measurements of speciated atmospheric mercury (Hg), including gaseous elemental mercury (GEM), particulate mercury (PHg), and reactive gaseous mercury (RGM) were conducted in Guizhou Province, southwestern China. Guiyang Power Plant (GPP), Guiyang Wujiang Cement Plant, Guizhou Aluminum Plant (GAP), and Guiyang Forest Park (GFP) in Guiyang were selected as study sites. Automatic Atmospheric Mercury Speciation Analyzers (Tekran 2537A) were used for GEM analysis. PHg and RGM were simultaneously collected by a manual sampling system, including elutriator, coupler/impactor, KCl-coated annular denuder, and a filter holder. Results show that different emission sources dominate different species of Hg. The highest average GEM value was 22.2 ± 28.3 ng·m−3 and the lowest 6.1 ± 3.9 ng·m−3, from samples collected at GPP and GAP, respectively. The maximum average PHg was 1984.9 pg·m−3 and the minimum average 55.9 pg·m−3, also from GPP and GAP, respectively. Similarly, the highest average RGM of 68.8 pg·m−3 was measured at GPP, and the lowest level of 20.5 pg·m−3 was found at GAP. We conclude that coal combustion sources are still playing a key role in GEM; traffic contributes significantly to PHg; and domestic pollution dominates RGM. Mercury (Hg) is a persistent hazardous pollutant with adverse effects on human health and wildlife due mainly to bioaccumulation and biomagnification in aquatic food webs (Lindqvist et al. 1991; Schroeder and Munt

Multicomponent Electron-Hole Superfluidity and the BCS-BEC Crossover in Double Bilayer Graphene

NASA Astrophysics Data System (ADS)

Conti, S.; Perali, A.; Peeters, F. M.; Neilson, D.

2017-12-01

Superfluidity in coupled electron-hole sheets of bilayer graphene is predicted here to be multicomponent because of the conduction and valence bands. We investigate the superfluid crossover properties as functions of the tunable carrier densities and the tunable energy band gap Eg. For small band gaps there is a significant boost in the two superfluid gaps, but the interaction-driven excitations from the valence to the conduction band can weaken the superfluidity, even blocking the system from entering the Bose-Einstein condensate (BEC) regime at low densities. At a given larger density, a band gap Eg˜80 - 120 meV can carry the system into the strong-pairing multiband BCS-BEC crossover regime, the optimal range for realization of high-Tc superfluidity.

The serum anion gap in the evaluation of acid-base disorders: what are its limitations and can its effectiveness be improved?

PubMed

Kraut, Jeffrey A; Nagami, Glenn T

2013-11-01

The serum anion gap has been utilized to identify errors in the measurement of electrolytes, to detect paraproteins, and, most relevant to the nephrologist, to evaluate patients with suspected acid-base disorders. In regard to the latter purpose, traditionally an increased anion gap is identified when it exceeds the upper limit of normal for a particular clinical laboratory measurement. However, because there is a wide range of normal values (often 8-10 mEq/L), an increase in anion concentration can be present in the absence of an increased anion gap. In addition, the type of retained anion can affect the magnitude of the increase in anion gap relative to change in serum [HCO3(-)] being greater with lactic acidosis compared with ketoacidosis. This review examines the methods of calculation of the serum anion gap in textbooks and published literature, the effect of perturbations other than changes in acid-base balance, and its effectiveness in identifying mild and more severe disturbances in acid-base balance. Limitations of the present methods of determining the normal anion gap and change in the anion gap are highlighted. The possibility of identifying the baseline value for individuals to optimize the use of the calculation in the detection of metabolic acidosis is suggested.

Addressing the "Research Gap" in Special Education through Mixed Methods

ERIC Educational Resources Information Center

Klingner, Janette K.; Boardman, Alison G.

2011-01-01

At least some of the challenges faced in special education, such as the disproportionate representation of culturally and linguistically diverse students, the gap between research and practice, and inequitable educational opportunities, can be explained in part by a research gap, or, in other words, a failure to conduct the different types of…

Global foot-and-mouth disease research update and gap analysis: 3 - vaccines

USDA-ARS?s Scientific Manuscript database

In 2014, the Global Foot-and-mouth disease Research Alliance (GFRA) conducted a gap analysis of FMD research. In this paper, we report updated findings in the field of FMD vaccine research. This paper consists of the following four sections: 1) Research priorities identified in the 2010 GFRA gap ana...

The optoelectronic properties and role of Cu concentration on the structural and electrical properties of Cu doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Omri, K.; Bettaibi, A.; Khirouni, K.; El Mir, L.

2018-05-01

In the current study, we synthesized a Cu-doped ZnO (CZO) nanoparticles material using a sol-gel method with different doping concentrations of Cu (0, 2, 3 and 4 at.%). The control of the Cu concentration on structural, electrical and optical properties of CZO nanoparticles was investigated in detail. The XRD analysis of the CZO nanoparticles reveals the formation of ZnO hexagonal wurtzite structure for all samples which confirm the incorporation of Cu2+ ions into the ZnO lattice by substitution. Furthermore, CZO nanoparticles showed a small red shift of absorption band with the incorporation of Cu from 0 to 4 at.%; i.e. a decreased band gap value from 3.34 eV to 3.27 eV with increasing of Cu doping content. The frequency dispersion of the electric conductivity were studied using the Jonscher universal power law, according to relation σ(ω) = σDC + A ωs(T). Alternative current conductivity increases with increasing Cu content in spite of the decrease the activation energy with copper loading. It was found that the conductivity reached its maximum value for critical Cu concentration of 3 at.%. The frequency relaxation phenomenon was also investigated and all results were discussed in term of the copper doping concentration.

Structural, electronic, mechanical, and thermoelectric properties of a novel half Heusler compound HfPtPb

NASA Astrophysics Data System (ADS)

Kaur, Kulwinder; Rai, D. P.; Thapa, R. K.; Srivastava, Sunita

2017-07-01

We explore the structural, electronic, mechanical, and thermoelectric properties of a new half Heusler compound HfPtPb, an all metallic heavy element, recently proposed to be stable [Gautier et al., Nat. Chem. 7, 308 (2015)]. In this work, we employ density functional theory and semi-classical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties, such as shear modulus, Young's modulus, elastic constants, Poisson's ratio, and shear anisotropy factor, have been investigated. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. Pugh's ratio and Frantsevich's ratio demonstrate its ductile behavior, and the shear anisotropic factor reveals the anisotropic nature of HfPtPb. The band structure predicts this compound to be a semiconductor with a band gap of 0.86 eV. The thermoelectric transport parameters, such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, have been calculated as a function of temperature. The highest value of Seebeck coefficient is obtained for n-type doping at an optimal carrier concentration of 1.0 × 1020 e/cm3. We predict the maximum value of figure of merit (0.25) at 1000 K. Our investigation suggests that this material is an n-type semiconductor.

Meclofenamic acid blocks the gap junction communication between the retinal pigment epithelial cells.

PubMed

Ning, N; Wen, Y; Li, Y; Li, J

2013-11-01

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to manage the pain and inflammation. NSAIDs can cause serious side effects, including vision problems. However, the underlying mechanisms are still unclear. Therefore, we aimed to investigate the effect of meclofenamic acid (MFA) on retinal pigment epithelium (RPE). In our study, we applied image analysis and whole-cell patch clamp recording to directly measure the effect of MFA on the gap junctional coupling between RPE cells. Analysis of Lucifer yellow (LY) transfer revealed that the gap junction communication existed between RPE cells. Functional experiments using the whole-cell configuration of the patch clamp technique showed that a gap junction conductance also existed between this kind of cells. Importantly, MFA largely inhibited the gap junction conductance and induced the uncoupling of RPE cells. Other NSAIDs, like aspirin and flufenamic acid (FFA), had the same effect. The gap junction functionally existed in RPE cells, which can be blocked by MFA. These findings may explain, at least partially, the vision problems with certain clinically used NSAIDs.

The model of self-compensation and pinning of the Fermi level in irradiated semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brudnyi, V. N.; Kolin, N. G.; Smirnov, L. S.

2007-09-15

A model is developed to analyze numerically the electrical properties and the steady-state (limiting) position of the Fermi level (F{sub lim}) in tetrahedral semiconductors irradiated with high-energy particles. It is shown that an irradiated semiconductor represents a highly compensated material, in which F{sub lim} is identical to /2, where is the average energy gap between the conduction band and valence band within the entire Brillouin zone of the crystal. The experimental values of F{sub lim}, the calculated values of /2, and the data on the electrical properties of irradiated semiconductors are presented. The chemical trends controllingmore » the variation in the quantity F{sub lim} in groups of semiconductors with the similar types of chemical bonding are analyzed.« less

Conductivity of higher dimensional holographic superconductors with nonlinear electrodynamics

NASA Astrophysics Data System (ADS)

Sheykhi, Ahmad; Hashemi Asl, Doa; Dehyadegari, Amin

2018-06-01

We investigate analytically as well as numerically the properties of s-wave holographic superconductors in d-dimensional spacetime and in the presence of Logarithmic nonlinear electrodynamics. We study three aspects of this kind of superconductors. First, we obtain, by employing analytical Sturm-Liouville method as well as numerical shooting method, the relation between critical temperature and charge density, ρ, and disclose the effects of both nonlinear parameter b and the dimensions of spacetime, d, on the critical temperature Tc. We find that in each dimension, Tc /ρ 1 / (d - 2) decreases with increasing the nonlinear parameter b while it increases with increasing the dimension of spacetime for a fixed value of b. Then, we calculate the condensation value and critical exponent of the system analytically and numerically and observe that in each dimension, the dimensionless condensation get larger with increasing the nonlinear parameter b. Besides, for a fixed value of b, it increases with increasing the spacetime dimension. We confirm that the results obtained from our analytical method are in agreement with the results obtained from numerical shooting method. This fact further supports the correctness of our analytical method. Finally, we explore the holographic conductivity of this system and find out that the superconducting gap increases with increasing either the nonlinear parameter or the spacetime dimension.

Transformation of nonlinear behaviors: from bright- to dark-gap soliton in a one-dimensional photonic crystal containing a nonlinear indefinite metamaterial defect.

PubMed

Zhang, Wei; Chen, Yuanyuan; Hou, Peng; Shi, Jielong; Wang, Qi

2010-12-01

Nonlinear propagation characteristics are investigated theoretically in a one-dimensional photonic band-gap structure doped with a nonlinear indefinite metamaterial defect for five distinct frequency intervals. It is found from the electric field distribution that there exists the bright gap solitonlike when the nonlinear indefinite metamaterial defect is a cut-off medium, while the dark gap solitonlike can appear in the nonlinear never cut-off defect layer. It is also found that there exists corresponding bistable lateral shift the properties of which are strongly dependent on the permittivity and permeability of nonlinear indefinite metamaterials. Moreover, in contrast to the switch-down threshold value, the switch-up threshold value is more sensitive to the incident frequency.

Dust coagulation and magnetic field strength in a planet-induced gap subject to MRI turbulence

NASA Astrophysics Data System (ADS)

Carballido, Augusto; Matthews, Lorin; Hyde, Truell

2017-01-01

We investigate the coagulation of dust particles in and around a gap opened by a Jupiter-mass planet. To this end, we carry out a high-resolution magnetohydrodynamic (MHD) simulation of the gap environment, which is turbulent due to the magneto rotational instability. From the MHD simulation, we obtain values of the gas velocities, densities and turbulent stresses close to the gap edge, in one of the two gas streams that accrete onto the planet, and inside the low-density gap. The MHD values are then supplied to a Monte Carlo dust coagulation algorithm, which models grain sticking, compaction and bouncing. We consider two dust populations for each region: one whose initial size distribution is monodisperse, with monomer radius equal to 1 micron, and another one whose initial size distribution follows the Mathis-Rumpl-Nordsieck distribution for interstellar dust grains, with an initial range of monomer radii between 0.5 and 10 microns. Without bouncing, our Monte Carlo calculations show steady growth of dust aggregates in all regions, and the mass-weighted (MW) average porosity of the initially mono disperse population reaches extremely high final values of 98%. The final MW porosities in all other cases without bouncing range from 30% to 82%. The efficiency of compaction is due to high turbulent relative speeds between dust particles. When bouncing is introduced, growth is slowed down in the planetary wake and inside the gap.We also analyze the strength of the magnetic field threading the gaps opened by planets of different sub-Jovian masses. Preliminary results show that, in a gap opened by a large-mass planet (~ 1 MJ), the time-averaged radial profile of the vertical component of the field (Bz) increases sharply inside the gap, and less sharply in the case of less massive planets. In gaps opened by intermediate-mass planets (~ 0.5 — 0.75 MJ), the radial profile of Bz exhibits local maxima in the vicinity of the planet, but not at the gap center.

Relaxation process of the discharge channel near the anode in long air gaps under positive impulse voltages

NASA Astrophysics Data System (ADS)

Zhao, Xiangen; He, Junjia; Luo, Bing; Jia, Lei; Yang, Yongchao; Xiao, Pei

2017-12-01

The relaxation process of the discharge channel near the anode in a long air gap was observed using a Schlieren system with a temporal resolution of 5 µs and a spatial resolution of 70 µm. The dynamic characteristics of the decay process in the vicinity of the anode are obtained. The discharge channel evolves just as a growing mushroom in nature during the relaxation phase. Two physical quantities, angle θ and velocity v, are defined to describe the process in this paper. The average value of the angle and velocity under lightning impulses are 71.7° and 3.3 m s-1 respectively, while 7.7 m s-1 under switching impulses. A simplified model was established to simulate the formation of mushroom-shaped channel. The simulation and experimental results show that the formation and development of the mushroom-shaped channel are due to two factors. One is the convection of the high temperature and high pressure air near the anode produced by the first corona discharge; the other is the ionic migration. These two factors result in the phenomena that the cooling process in the vicinity of the anode is much more efficient than further into the gap, whereas the thermal conductivity of the anode may have little contribution to that.

Spectroscopic views of high-Tc superconductors

NASA Astrophysics Data System (ADS)

Wendin, Göran

1989-01-01

Recent progress in the fields of photoelectron spectroscopy, electron energy loss spectroscopy, inverse photoemission, and infrared- and optical reflectivity applied to high-Tc superconductors is analyzed in terms of correlation effects, transport properties and Fermi liquid behaviour. For the CuO2 based materials, a picture emerges of localized holes in copper 3d levels and itinerant holes in oxygen 2p-like bands. A Fermi liquid picture and a superconducting gap is indicated by angle-resolved photo-emission, infrared absorption, and NMR. A Fermi surface is indicated by positron annihilation. Infrared absorption reveals strongly frequency and temperature dependent scattering and polaronic behaviour for frequencies below 0.1 eV. Infrared absorption indicates a maximum superconducting gap of 2Δ/kBTc = 8 and suggests that ordinary samples may show a range of gaps 2 < 2Δ/kBTc < 8 resulting in commonly measured average values of 2Δ/kBTc = 5. An interesting possibility in YBaCuO, suggested by infrared reflectivity and photoconductivity measurements, is that polarons in the CuO2 planes with 0.13 eV excitation energy mediate an attractive interaction between quasi-holes in O 2p-derived conduction bands. The polarons will involve important lattice distortions even if, as is frequently assumed, magnetic polaron effects may be the essential thing.

Polarization effects on spectra of spherical core/shell nanostructures: Perturbation theory against finite difference approach

NASA Astrophysics Data System (ADS)

Ibral, Asmaa; Zouitine, Asmaa; Assaid, El Mahdi; El Achouby, Hicham; Feddi, El Mustapha; Dujardin, Francis

2015-02-01

Poisson equation is solved analytically in the case of a point charge placed anywhere in a spherical core/shell nanostructure, immersed in aqueous or organic solution or embedded in semiconducting or insulating matrix. Conduction and valence band-edge alignments between core and shell are described by finite height barriers. Influence of polarization charges induced at the surfaces where two adjacent materials meet is taken into account. Original expressions of electrostatic potential created everywhere in the space by a source point charge are derived. Expressions of self-polarization potential describing the interaction of a point charge with its own image-charge are deduced. Contributions of double dielectric constant mismatch to electron and hole ground state energies as well as nanostructure effective gap are calculated via first order perturbation theory and also by finite difference approach. Dependencies of electron, hole and gap energies against core to shell radii ratio are determined in the case of ZnS/CdSe core/shell nanostructure immersed in water or in toluene. It appears that finite difference approach is more efficient than first order perturbation method and that the effect of polarization charge may in no case be neglected as its contribution can reach a significant proportion of the value of nanostructure gap.

Influence of axial tensile strain on the electronic and structural properties as well as NO gas sensitivity and reactivity of C-doped SW-BNNTs

NASA Astrophysics Data System (ADS)

Roohi, Hossein; Maleki, Layla

2017-11-01

The insulating character of BNNTs strongly imposes a great restriction on their applicability in nano-electronic devices. Therefore, it is desirable to find the practical routes for reducing the H-L gap. In this work, we demonstrate that the structural and electronic properties of the C-doped SW-BNNT can be significantly engineered and tuned by applying the axial tensile strain. Defect formation energies, cohesive energies, dipole moments, NBO charges, and global reactivity descriptors for un-doped SW-BNNT and C1-3-doped SW-BNNTs are calculated upon the axial strain. The B3LYP/6-31 +G(d) calculated H-L gap for five C-doped SW-BNNTs are expected to be smaller than that of un-doped SW-BNNT. At 10% axial tensile strain, CB NT is a suitable conductance with a 1.947 eV H-L gap. The decrease in the H-L gap for 2C-doped CN,B (-0.839 eV) NT within 15% strain is greater than 1C- and 3C-doped SW-BNNTs. In the second part of this work, reactivity and the sensitivity of strained C1-2-doped SW-BNNTs toward NO gas were evaluated at M06-2X/6-31 ++G(d,p) level of theory. Optimized structures, molecular graphs, adsorption energies (AE), dispersion corrected AEs, H-L gap, NBO charges, charge transfer values, density of states and electrostatic potentials were calculated. The strained C1-doped SW-BNNTs showed an increased ability for the sensitivity and adsorption of NO molecule, as compared with unstrained doped SW-BNNT. In general, the CN,B NTs have practically less potential for the adsorption of NO molecule than CB and CN ones.

Investigation on the influence of electrode geometry on characteristics of coaxial dielectric barrier discharge reactor driven by an oscillating microsecond pulsed power supply

NASA Astrophysics Data System (ADS)

Miao, Chuanrun; Liu, Feng; Wang, Qian; Cai, Meiling; Fang, Zhi

2018-03-01

In this paper, an oscillating microsecond pulsed power supply with rise time of several tens of nanosecond (ns) is used to excite a coaxial DBD with double layer dielectric barriers. The effects of various electrode geometries by changing the size of inner quartz tube (different electrode gaps) on the discharge uniformity, power deposition, energy efficiency, and operation temperature are investigated by electrical, optical, and temperature diagnostics. The electrical parameters of the coaxial DBD are obtained from the measured applied voltage and current using an equivalent electrical model. The energy efficiency and the power deposition in air gap of coaxial DBD with various electrode geometries are also obtained with the obtained electrical parameters, and the heat loss and operation temperature are analyzed by a heat conduction model. It is found that at the same applied voltage, with the increasing of the air gap, the discharge uniformity becomes worse and the discharge power deposition and the energy efficiency decrease. At 2.5 mm air gap and 24 kV applied voltage, the energy efficiency of the coaxial DBD reaches the maximum value of 68.4%, and the power deposition in air gap is 23.6 W and the discharge uniformity is the best at this case. The corresponding operation temperature of the coaxial DBD reaches 64.3 °C after 900 s operation and the temperature of the inner dielectric barrier is 114.4 °C under thermal balance. The experimental results provide important experimental references and are important to optimize the design and the performance of coaxial DBD reactor.

Design of single-winding energy-storage reactors for dc-to-dc converters using air-gapped magnetic-core structures

NASA Technical Reports Server (NTRS)

Ohri, A. K.; Wilson, T. G.; Owen, H. A., Jr.

1977-01-01

A procedure is presented for designing air-gapped energy-storage reactors for nine different dc-to-dc converters resulting from combinations of three single-winding power stages for voltage stepup, current stepup and voltage stepup/current stepup and three controllers with control laws that impose constant-frequency, constant transistor on-time and constant transistor off-time operation. The analysis, based on the energy-transfer requirement of the reactor, leads to a simple relationship for the required minimum volume of the air gap. Determination of this minimum air gap volume then permits the selection of either an air gap or a cross-sectional core area. Having picked one parameter, the minimum value of the other immediately leads to selection of the physical magnetic structure. Other analytically derived equations are used to obtain values for the required turns, the inductance, and the maximum rms winding current. The design procedure is applicable to a wide range of magnetic material characteristics and physical configurations for the air-gapped magnetic structure.

Pavement Subsidence in the Cumberland Gap Tunnel, USA: A Story of Groundwater Chemistry

NASA Astrophysics Data System (ADS)

Zhu, J.; Currens, J. C.; Webb, S. E.; Rister, B. W.

2014-12-01

Cumberland Gap Tunnel was constructed in 1996 to improve highway travel between southeastern Kentucky and northeastern Tennessee and to restore Cumberland Gap to its historical appearance. About five years after construction, the concrete pavement in the tunnel began to exhibit noticeable signs of subsidence. Ground penetrating radar surveys detected voids in many areas of the limestone roadbed aggregate beneath the pavement. Field investigations conducted by the Kentucky Geological Survey and Kentucky Transportation Center from 2006 to 2008 discovered that groundwater was flowing from the bedrock invert into the aggregate along many parts of the tunnel. Average groundwater discharge from the tunnel was measured at approximately 1700 m3/d. We analyzed 265 groundwater samples collected from aggregate in different parts of the tunnel roadbed during low and high flow conditions. Calculated calcite saturation indices indicated that the groundwater was geochemically aggressive and capable of continuously dissolving calcite in the limestone aggregate although pH values of these water samples were near neutral. We also conducted an in-situ dissolution experiment by placing eight baskets filled with limestone aggregate beneath the roadbed in different locations in the tunnel for 178 days. At the end of the experiment, the limestone aggregate in contact with groundwater exhibited visual signs of dissolution and lost mass, and the highest mass loss recorded was 3.4 percent. Mass loss calculations based on kinetic models of calcite mineral and water samples taken near the baskets matched well with the actual measured mass losses, confirming that dissolution of calcite by the groundwater was the primary cause of the roadbed subsidence problem. Based on these findings, we suggested the limestone aggregate be replaced with noncarbonate (granite) aggregate to mitigate future road subsidence. The suggestion was adopted, and the repair was completed in early 2014.

The network modifier and former role of the bismuth ions in the bismuth-lead-germanate glasses

NASA Astrophysics Data System (ADS)

Rada, M.; Rus, L.; Rada, S.; Culea, E.; Rusu, T.

2014-11-01

The present work is focused on the enhancement of network former environment in lead-germanate glasses by bismuth ions doping. A series of bismuth-lead-germanate glasses with the xBi2O3·(100 - x)[7GeO2·3PbO] composition glass where 0 ⩽ x ⩽ 30 mol% Bi2O3 were synthesized by melt-quenching method. The FTIR, UV-VIS spectroscopy and cyclic voltammetry were conducted on these samples to evaluate the doping effect of structure of the host matrix network. Our results indicate that direct incorporation of Bi2O3 into the lead-germanate network modifies the lead-germanate network and the internal structure of glass network is rearranged. The structural flexibility of the lead-germanate network is possible due to its incapacity to accommodate with the excess of oxygen atoms and the creation of bridging oxygen ions. Optical gap energy and refractive index were obtained as a function of Bi2O3 content. Gap energy values decrease as Bi2O3 content increased from 0 to 10 mol%. Further increase of Bi2O3 concentration beyond 10 mol% increased the gap energy values. These behaviors of the glass system can be explained by two mechanisms: (i) for x ⩽ 10 mol% Bi2O3 - increase of degree of disorder of the host matrix because Bi2O3 is network modifier and (ii) for x > 10 mol% - Bi2O3 acts as a network former. Cyclic voltammetry measurements using the glass system with 10Bi2O3·90[7GeO2·3PbO] composition as working electrode show the mobility of the lead ions, in agreement with UV-VIS data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nieroda, Pawel; Zybala, Rafal; Wojciechowski, Krzysztof T.

The aim of the study was to develop a fast and simple method for preparation of polycrystalline Mg{sub 2}Si. For this purpose a Spark Plasma Sintering (SPS) method was used and synthesis conditions were adjusted in such a manner that no excess Mg was required. Materials were synthesized by the direct reaction of Mg and Si raw powders. To determine the phase and chemical composition, the fabricated samples were studied by X-ray diffraction and SEM microscopy coupled with EDX chemical analysis. Thermoelectric properties of samples (thermal conductivity, electrical conductivity and Seebeck coefficient) were measured all over temperature range of 300-650more » K. The analysis by the scanning thermoelectric microprobe (STM) shows that samples have uniform distribution of Seebeck coefficient with mean value of about -405 {mu}VK{sup -1} and standard deviation of 94 {mu}VK{sup -1}. Prepared materials have intrinsic band gap of 0.45 eV and thermal conductivity {lambda}= 7.5 Wm{sup -1}K{sup -1} at room temperature.« less

Band Degeneracy, Low Thermal Conductivity, and High Thermoelectric Figure of Merit in SnTe-CaTe Alloys

NASA Astrophysics Data System (ADS)

Al Rahal Al Orabi, R.; Mecholsky, N.; Hwang, J. P.; Kim, W.; Rhyee, J. S.; Wee, D.; Fornari, M.

Pure lead-free SnTe has limited thermoelectric potentials because of the low Seebeck coeffcients and the relatively large thermal conductivity. In this study, we provide experimental evidence and theoretical understanding that alloying SnTe with Ca greatly improves the transport properties leading to ZT of 1.35 at 873 K, the highest ZT value so far reported for singly doped SnTe materials. The introduction of Ca (0-9%) in SnTe induces multiple effects: (1) Ca replaces Sn and reduces the hole concentration due to Sn vacancies, (2) the energy gap increases limiting the bipolar transport, (3) several bands with larger effective masses become active in transport, and (4) the lattice thermal conductivity is reduced of about 70% due to the contribution of concomitant scattering terms associated with the alloy disorder and the presence of nanoscale precipitates. An effciency of 10% (for ΔT = 400 K) was predicted for high temperature thermoelectric power generation using SnTe-based n- and p-type materials.

How wide is the gap in defining quality care? Comparison of patient and nurse perceptions of important aspects of patient care.

PubMed

Young, W B; Minnick, A F; Marcantonio, R

1996-05-01

The authors determine the importance that patients, nurses, and nurse managers place on aspects of care and measure nurses' care values based on their perceptions of their patients and nurse manager care values and their desire to meet these care expectations. The literature has documented gaps in how nurses and patients define quality and value specific care aspects, but little is known about the situation in the current continuous quality improvement and patient-centered care environment, which emphasizes a customer focus. Misunderstanding patients' values and expectations may impede service improvement. Information about any existing gaps could help managers begin to devise patient satisfaction improvement strategies. Two thousand fifty-one medical-surgical patients, 1264 staff members, and 97 nurse managers from 17 randomly selected hospitals participated in study activities related to selected aspects of patient care. Trained interviewers surveyed patients by telephone within 26 days of discharge using a pretested instrument. Staff members and managers completed a coordinated written tool. Descriptive and correlational statistics were used in individual and unit-level analyses. Staff members perceive correctly that patients value differently various aspects of care but do not agree with their managers on patients' value of aspects of care. Unit staff members' and managers' beliefs regarding patients' care values did not match those of their patients (-14 to 0.11 and -0.01 to 0.06 zero order correlations, respectively). A unit's errors in defining patients' values may be self-reinforcing. Strategies to reorient personnel, including adoption of those suggested by the diffusion of innovation literature, may help bridge the gap and change practice.

Strain and electric field induced metallization in the GaX (X = N, P, As & Sb) monolayer

NASA Astrophysics Data System (ADS)

Bahuguna, Bhagwati Prasad; Saini, L. K.; Sharma, Rajesh O.; Tiwari, Brajesh

2018-05-01

We investigate the strain and electric field dependent electronic properties of two dimensional Ga-based group III-V monolayer from the first-principles approach within density functional theory. The energy bandgap of GaX monolayer increases upto the certain value of compressive strain and then decreases. On the other hand, the energy bandgap of GaX monolayer is monotonically decreased with increasing tensile strain and become metallic at the higher value. Furthermore, the perpendicular electric field decreases the energy band gap of unstrained GaX monolayer and shows semiconductor to metal transition. These results suggest that the nature of energy bands and value of energy bandgap in GaX monolayer can be tuned by the biaxial mechanical strain or perpendicular electrical field. Additionally, we have also studied the optical response of unstrained GaX monolayer in term of optical conductivity. These findings may provide valuable information to develop the Ga-based optoelectronic devices and further the understanding of the GaX monolayer.

A Unifying Perspective on Oxygen Vacancies in Wide Band Gap Oxides.

PubMed

Linderälv, Christopher; Lindman, Anders; Erhart, Paul

2018-01-04

Wide band gap oxides are versatile materials with numerous applications in research and technology. Many properties of these materials are intimately related to defects, with the most important defect being the oxygen vacancy. Here, using electronic structure calculations, we show that the charge transition level (CTL) and eigenstates associated with oxygen vacancies, which to a large extent determine their electronic properties, are confined to a rather narrow energy range, even while band gap and the electronic structure of the conduction band vary substantially. Vacancies are classified according to their character (deep versus shallow), which shows that the alignment of electronic eigenenergies and CTL can be understood in terms of the transition between cavity-like localized levels in the large band gap limit and strong coupling between conduction band and vacancy states for small to medium band gaps. We consider both conventional and hybrid functionals and demonstrate that the former yields results in very good agreement with the latter provided that band edge alignment is taken into account.

Nonreciprocity of spin waves in magnonic crystals created by surface acoustic waves in structures with yttrium iron garnet

NASA Astrophysics Data System (ADS)

Kryshtal, R. G.; Medved, A. V.

2015-12-01

Experimental results of investigations of nonreciprocity for surface magnetostatic spin waves (SMSW) in the magnonic crystal created by surface acoustic waves (SAW) in yttrium iron garnet films on a gallium gadolinium garnet substrate as without metallization and with aluminum films with different electrical conductivities (thicknesses) are presented. In structures without metallization, the frequency of magnonic gaps is dependent on mutual directions of propagation of the SAW and SMSW, showing nonreciprocal properties for SMSW in SAW - magnonic crystals even with the symmetrical dispersion characteristic. In metalized SAW - magnonic crystals the shift of the magnonic band gaps frequencies at the inversion of the biasing magnetic field was observed. The frequencies of magnonic band gaps as functions of SAW frequency are presented. Measured dependencies, showing the decrease of magnonic gaps frequency and the expansion of the magnonic band gap width with the decreasing of the metal film conductivity are given. Such nonreciprocal properties of the SAW - magnonic crystals are promising for signal processing in the GHz range.

Quantum Phase Transition in Few-Layer NbSe2 Probed through Quantized Conductance Fluctuations

NASA Astrophysics Data System (ADS)

Kundu, Hemanta Kumar; Ray, Sujay; Dolui, Kapildeb; Bagwe, Vivas; Choudhury, Palash Roy; Krupanidhi, S. B.; Das, Tanmoy; Raychaudhuri, Pratap; Bid, Aveek

2017-12-01

We present the first observation of dynamically modulated quantum phase transition between two distinct charge density wave (CDW) phases in two-dimensional 2 H -NbSe2 . There is recent spectroscopic evidence for the presence of these two quantum phases, but its evidence in bulk measurements remained elusive. We studied suspended, ultrathin 2 H -NbSe2 devices fabricated on piezoelectric substrates—with tunable flakes thickness, disorder level, and strain. We find a surprising evolution of the conductance fluctuation spectra across the CDW temperature: the conductance fluctuates between two precise values, separated by a quantum of conductance. These quantized fluctuations disappear for disordered and on-substrate devices. With the help of mean-field calculations, these observations can be explained as to arise from dynamical phase transition between the two CDW states. To affirm this idea, we vary the lateral strain across the device via piezoelectric medium and map out the phase diagram near the quantum critical point. The results resolve a long-standing mystery of the anomalously large spectroscopic gap in NbSe2 .

Design and Fabrication of an Experimental Microheater Array Powder Sintering Printer

NASA Astrophysics Data System (ADS)

Holt, Nicholas; Zhou, Wenchao

2018-03-01

Microheater array powder sintering (MAPS) is a novel additive manufacturing process that uses an array of microheaters to selectively sinter powder particles. MAPS shows great promise as a new method of printing flexible electronics by enabling digital curing of conductive inks on a variety of substrates. For MAPS to work effectively, a microscale air gap needs to be maintained between the heater array and the conductive ink. In this article, we present an experimental MAPS printer with air gap control for printing conductive circuits. First, we discuss design aspects necessary to implement MAPS. An analysis is performed to validate that the design can maintain the desired air gap between the microheaters and the sintering layer, which consists of a silver nanoparticle ink. The printer is tested by printing conductive lines on a flexible plastic substrate with silver nanoparticle ink. Results show MAPS performs on par with or better than the existing fabrication methods for printed electronics in terms of both the print quality (conductivity of the printed line) and print speed, which shows MAPS' great promise as a competitive new method for digital production of printed electronics.

Differential conductance fluctuation of curved nanographite sheets in the mesoscopic regime

NASA Astrophysics Data System (ADS)

Wang, Haomin; Choong, Catherine; Zhang, Jun; Teo, Kie Leong; Wu, Yihong

2008-02-01

Excess conductance fluctuations with peculiar temperature dependence from 1.4 to 250 K were observed in curved nanographite sheets with electrode gap lengths of 300 and 450 nm, whereas the conductance fluctuation is greatly suppressed above 4.2 K when the electrode gap lengths increase to 800 and 1000 nm. The former is discussed in the context of the presence of a small energy bandgap in the nanographite sheets, while the latter is attributed to the crossover from the coherent transport to diffusive transport regime.

Can carbon nanotube fibers achieve the ultimate conductivity?—Coupled-mode analysis for electron transport through the carbon nanotube contact

NASA Astrophysics Data System (ADS)

Xu, Fangbo; Sadrzadeh, Arta; Xu, Zhiping; Yakobson, Boris I.

2013-08-01

Recent measurements of carbon nanotube (CNT) fibers electrical conductivity still show the values lower than that of individual CNTs, by about one magnitude order. The imperfections of manufacturing process and constituent components are described as culprits. What if every segment is made perfect? In this work, we study the quantum conductance through the parallel junction of flawless armchair CNTs using tight-binding method in conjunction with non-equilibrium Green's function approach. Short-range oscillations within the long-range oscillations as well as decaying envelopes are all observed in the computed Fermi-level (low bias) conductance as a function of contact length, L. The propagation of CNTs' Bloch waves is cast in the coupled-mode formalism and helps to reveal the quantum interference nature of various behaviors of conductance. Our analysis shows that the Bloch waves at the Fermi-level propagate through a parallel junction without reflection only at an optimal value of contact length. For quite a long junction, however, the conductance at the Fermi level diminishes due to the perturbation of periodic potential field of close-packed CNTs. Thus, a macroscopic fiber, containing an infinite number of junctions, forms a filter that permits passage of electrons with specific wave vectors, and these wave vectors are determined by the collection of all the junction lengths. We also argue that the energy gap introduced by long junctions can be overcome by small voltage (˜0.04 V) across the whole fiber. Overall, developing long individual all-armchair metallic CNTs serves as a promising way to the manufacture of high-conductivity fibers.

Cultural factors influencing Japanese nurses' assertive communication: Part 2 - hierarchy and power.

PubMed

Omura, Mieko; Stone, Teresa E; Levett-Jones, Tracy

2018-03-23

Hierarchy and power characterize health-care relationships around the world, constituting a barrier to assertive communication and a risk to patient safety. This issue is more problematic and complex in countries such as Japan, where deep-seated cultural values related to hierarchy and power persist. The current paper is the second of two that present the findings from a study exploring Japanese nurses' views and experiences of how cultural values impact assertive communication for health-care professionals. We conducted semistructured interviews with 23 registered nurses, following which data were analyzed using directed content analysis. Two overarching themes emerged from the analysis: hierarchy/power and collectivism. In the present study, we focus on cultural values related to hierarchy and power, including differences in professional status, gender imbalance, seniority/generation gap, bullying, and humility/modesty. The findings from our research provide meaningful insights into how Japanese cultural values influence and constrain nurses' communication and speaking up behaviors, and can be used to inform educational programs designed to teach assertiveness skills. © 2018 John Wiley & Sons Australia, Ltd.

Closing the Gap: The Maturing of Quality Assurance in Australian University Libraries

ERIC Educational Resources Information Center

Tang, Karen

2012-01-01

A benchmarking review of the quality assurance practices of the libraries of the Australian Technology Network conducted in 2006 revealed exemplars of best practice, but also sector-wide gaps. A follow-up review in 2010 indicated the best practices that remain relevant. While some gaps persist, there has been improvement across the libraries and…

The Effects of Reading Recovery™ on the American Indian/Non-American Indian Achievement Gap

ERIC Educational Resources Information Center

Collins, Mary L.

2012-01-01

Despite the attention being paid to the achievement gap of minorities, the regulations and laws being enacted, the research being conducted, and the funding made available to narrow the achievement gap, there is evidence that shows it still exists for American Indians. This study examined the effects of Reading Recovery, an early literacy…

The Achievement Gap in Reading: Complex Causes, Persistent Issues, Possible Solutions

ERIC Educational Resources Information Center

Horowitz, Rosalind, Ed.; Samuels, S. Jay, Ed.

2017-01-01

In this volume prominent scholars, experts in their respective fields and highly skilled in the research they conduct, address educational and reading research from varied perspectives and address what it will take to close the achievement gap--with specific attention to reading. The achievement gap is redefined as a level at which all groups can…

Assessment of Adoption Gaps in Management of Aflatoxin Contamination of Groundnut ("Arachis Hypogaea" L.)

ERIC Educational Resources Information Center

Kumar, G. D. S.; Popat, M. N.

2010-01-01

One of the major impediments for diversification of groundnut ("Arachis Hypogaea" L.) as food crop is aflatoxin contamination. The study was conducted with an objective to assess the adoption gaps in aflatoxin management practices of groundnut (AMPG) and the farmer's characteristics influencing these gaps. The study used an expost-facto…

Large enhancement of thermoelectric effects in a tunneling-coupled parallel DQD-AB ring attached to one normal and one superconducting lead

NASA Astrophysics Data System (ADS)

Yao, Hui; Zhang, Chao; Li, Zhi-Jian; Nie, Yi-Hang; Niu, Peng-bin

2018-05-01

We theoretically investigate the thermoelectric properties in a tunneling-coupled parallel DQD-AB ring attached to one normal and one superconducting lead. The role of the intrinsic and extrinsic parameters in improving thermoelectric properties is discussed. The peak value of figure of merit near gap edges increases with the asymmetry parameter decreasing, particularly, when asymmetry parameter is less than 0.5, the figure of merit near gap edges rapidly rises. When the interdot coupling strengh is less than the superconducting gap the thermopower spectrum presents a single-platform structure. While when the interdot coupling strengh is larger than the gap, a double-platform structure appears in thermopower spectrum. Outside the gap the peak values of figure of merit might reach the order of 102. On the basis of optimizing internal parameters the thermoelectric conversion efficiency of the device can be further improved by appropriately matching the total magnetic flux and the flux difference between two subrings.

Theoretical study of optical conductivity of graphene with magnetic and nonmagnetic adatoms

NASA Astrophysics Data System (ADS)

Majidi, Muhammad Aziz; Siregar, Syahril; Rusydi, Andrivo

2014-11-01

We present a theoretical study of the optical conductivity of graphene with magnetic and nonmagnetic adatoms. First, by introducing an alternating potential in a pure graphene, we demonstrate a gap formation in the density of states and the corresponding optical conductivity. We highlight the distinction between such a gap formation and the so-called Pauli blocking effect. Next, we apply this idea to graphene with adatoms by introducing magnetic interactions between the carrier spins and the spins of the adatoms. Exploring various possible ground-state spin configurations of the adatoms, we find that the antiferromagnetic configuration yields the lowest total electronic energy and is the only configuration that forms a gap. Furthermore, we analyze four different circumstances leading to similar gaplike structures and propose a means to interpret the magneticity and the possible orderings of the adatoms on graphene solely from the optical conductivity data. We apply this analysis to the recently reported experimental data of oxygenated graphene.

Conductance modulation in Weyl semimetals with tilted energy dispersion without a band gap

NASA Astrophysics Data System (ADS)

Yesilyurt, Can; Siu, Zhuo Bin; Tan, Seng Ghee; Liang, Gengchiau; Jalil, Mansoor B. A.

2017-06-01

We investigate the tunneling conductance of Weyl semimetal with tilted energy dispersion by considering electron transmission through a p-n-p junction with one-dimensional electric and magnetic barriers. In the presence of both electric and magnetic barriers, we found that a large conductance gap can be produced with the aid of tilted energy dispersion without a band gap. The origin of this effect is the shift of the electron wave-vector at barrier boundaries caused by (i) the pseudo-magnetic field induced by electrical potential, i.e., a newly discovered feature that is only possible in the materials possessing tilted energy dispersion, (ii) the real magnetic field induced by a ferromagnetic layer deposited on the top of the system. We use a realistic barrier structure applicable in current nanotechnology and analyze the temperature dependence of the tunneling conductance. The new approach presented here may resolve a major problem of possible transistor applications in topological semimetals, i.e., the absence of normal backscattering and gapless band structure.

Low-temperature charged impurity scattering-limited conductivity in relatively high doped bilayer graphene

NASA Astrophysics Data System (ADS)

Hu, Bo

2015-08-01

Based on semiclassical Boltzamnn transport theory in random phase approximation, we develop a theoretical model to investigate low-temperature carrier transport properties in relatively high doped bilayer graphene. In the presence of both electron-hole puddles and band gap induced by charged impurities, we calculate low-temperature charged impurity scattering-limited conductivity in relatively high doped bilayer graphene. Our calculated conductivity results are in excellent agreement with published experimental data in all compensated gate voltage regime of study by using potential fluctuation parameter as only one free fitting parameter, indicating that both electron-hole puddles and band gap induced by charged impurities play an important role in carrier transport. More importantly, we also find that the conductivity not only depends strongly on the total charged impurity density, but also on the top layer charged impurity density, which is different from that obtained by neglecting the opening of band gap, especially for bilayer graphene with high top layer charged impurity density.

Enhancement of nonlinear optical susceptibility of CuPc films by ITO layer

NASA Astrophysics Data System (ADS)

Ganesh, V.; Zahran, H. Y.; Yahia, I. S.; Shkir, Mohd; AlFaify, S.

2016-12-01

In the present study, the Copper Phthalocyanine (CuPc)/ITO thin film was fabricated using thermal evaporation method. The structural property was analyzed by X-ray diffraction study and confirms that the thin film has been preferentially grown along (200) plane. The atomic force microscope study was carried out on deposited film and quality of thin films is assessed by calculating the roughness of the films. The direct and indirect band gap, linear and nonlinear optical characteristics of grown films were calculated by using UV-Vis-NIR spectrometer studies. The calculated values of the first direct and indirect band gaps (Eg1(d) &Eg1(ind)) are 1.879 and 1.644 eV as a fundamental gap, while the values of second direct and indirect band gap (Eg2(d) &Eg2(ind)) are 1.660 and 1.498 eV as an onset gap for CuPc. The values of nonlinear refractive index (n2) and third order nonlinear optical susceptibility (χ3) are found to be 5 × 10-8 and 8 × 10-9 (theoretical) and 5.2 × 10-8 and 1.56 × 10-7 (experimental) respectively. The optical band and third order nonlinear properties suggest that the as-prepared films are may be applied in optoelectronic and nonlinear applications.

Electronic properties of 3R-CuAlO2 under pressure: Three theoretical approaches

NASA Astrophysics Data System (ADS)

Christensen, N. E.; Svane, A.; Laskowski, R.; Palanivel, B.; Modak, P.; Chantis, A. N.; van Schilfgaarde, M.; Kotani, T.

2010-01-01

The pressure variation in the structural parameters, u and c/a , of the delafossite CuAlO2 is calculated within the local-density approximation (LDA). Further, the electronic structures as obtained by different approximations are compared: LDA, LDA+U , and a recently developed “quasiparticle self-consistent GW ” (QSGW) approximation. The structural parameters obtained by the LDA agree very well with experiments but, as expected, gaps in the formal band structure are underestimated as compared to optical experiments. The (in LDA too high lying) Cu3d states can be down shifted by LDA+U . The magnitude of the electric field gradient (EFG) as obtained within the LDA is far too small. It can be “fitted” to experiments in LDA+U but a simultaneous adjustment of the EFG and the gap cannot be obtained with a single U value. QSGW yields reasonable values for both quantities. LDA and QSGW yield significantly different values for some of the band-gap deformation potentials but calculations within both approximations predict that 3R-CuAlO2 remains an indirect-gap semiconductor at all pressures in its stability range 0-36 GPa, although the smallest direct gap has a negative pressure coefficient.

Trilateral Bridge Rating Criteria.

DTIC Science & Technology

1982-04-01

and vehicle impact factor (i.e., V= VDES , G - G S , D- dm , I - imS). We take the Mud load as 0.8 times the design values (i.e., M - 0.8 ?S) and set...Artur D Ittek ln TABLE 4.1 SUMMARY OF VALUES USED IN NORMAL CROSSING Symbol Meaning Value VDES Design code vehicle weight 60 tons 9DES Design code gap...a caution crossing we first parametrically increase in vehicle weight or gap size, by V = (1+pv) VDES (5.1a) G = (1+pg) 9DES (5.1b) where 1 V is the

Passive Gas-Gap Heat Switches for Use in Adiabatic Demagnetization Refrigerators

NASA Technical Reports Server (NTRS)

Shirron, P. J.; Canavan, E. R.; DiPirro, M. J.; Jackson, M.; Panek, J.; Tuttle, J. G.; Krebs, Carolyn (Technical Monitor)

2001-01-01

We have designed, built, and tested a gas gap heat switch that works passively, without the need for a separate, thermally activated getter. This switch uses He-3 condensed as a thin film on alternating plates of copper. The switch is thermally conductive at temperatures above about 0.2 K, and is insulating if either end of the switch is below about 0.15 K. The "on" conductance (7 mW/K at 0.25K) is limited by the surface area and gap between the copper leaves, the saturated vapor pressure of the He-3, and the Kapitza boundary resistance between the He-3 and the copper. The "off" conductance is determined by the helium containment shell which physically supports the two conductive ends. We have also designed and are building passive gas gap heat switches which will passively turn off near 1 K and 4 K. For these switches we rely on the rapidly changing vapor pressure of He-4 above neon or copper substrates, respectively, when the coverage is less than one monolayer. The different binding energies of the He-4 to the neon or copper give rise to the different temperatures where the switches transition between the on and off states.

The Possible Value of a Gap Year: A Case Study

ERIC Educational Resources Information Center

Coetzee, M.; Bester, S.

2009-01-01

The taking of a "gap year", immediately after completing their secondary school education, to explore life before embarking on formal studies or starting their career, is a growing phenomenon among young people in South Africa. This research study explores the experiences of three young people who engaged in a gap year and focuses on the…

Reciprocal Modulation of IK1–INa Extends Excitability in Cardiac Ventricular Cells

PubMed Central

Varghese, Anthony

2016-01-01

The inwardly rectifying potassium current (IK1) and the fast inward sodium current (INa) are reciprocally modulated in mammalian ventricular myocytes. An increase in the expression of channels responsible for one of these two currents results in a corresponding increase in expression of the other. These currents are critical in the propagation of action potentials (AP) during the normal functioning of the heart. This study identifies a physiological role for IK1–INa reciprocal modulation in ventricular fiber activation thresholds and conduction. Simulations of action potentials in single cells and propagating APs in cardiac fibers were carried out using an existing model of electrical activity in cardiac ventricular myocytes. The conductances, GK1, of the inwardly rectifying potassium current, and GNa, of the fast inward sodium current were modified independently and in tandem to simulate reciprocal modulation. In single cells, independent modulation of GK1 alone resulted in changes in activation thresholds that were qualitatively similar to those for reciprocal GK1–GNa modulation and unlike those due to independent modulation of GNa alone, indicating that GK1 determines the cellular activation threshold. On the other hand, the variations in conduction velocity in cardiac cell fibers were similar for independent GNa modulation and for tandem changes in GK1–GNa, suggesting that GNa is primarily responsible for setting tissue AP conduction velocity. Conduction velocity dependence on GK1–GNa is significantly affected by the intercellular gap junction conductance. While the effects on the passive fiber space constant due to changes in both GK1 and the intercellular gap junction conductance, Ggj, were in line with linear cable theory predictions, both conductances had surprisingly large effects on fiber activation thresholds. Independent modulation of GK1 rendered cardiac fibers inexcitable at higher levels of GK1 whereas tandem GK1–GNa changes allowed fibers to remain excitable at high GK1 values. Reciprocal modulation of the inwardly rectifying potassium current and the fast inward sodium current may have a functional role in allowing cardiac tissue to remain excitable when IK1 is upregulated. PMID:27895596

Influence of the solid dielectric over the electric field from the ozone cell gap with double dielectric barrier

NASA Astrophysics Data System (ADS)

Ganea, I.

2017-05-01

The distilled water has the advantage of high value dielectric constant (ε = 81) in relation to ceramic glass materials, currently used for constructing the dielectric barrier. It was necessary to build a thin-walled enclosure of solid insulating material that contain distilled water to achieve a dielectric barrier. This was necessary to avoid exposing the liquid to the direct action of ozone. Dielectric permittivity of the solid dielectric material and the thickness of these walls have diminished the value of the electric field form the gaseous gap of the ozone cell compared to the case with the dielectric barrier from distilled water. The author of this work deduced theoretical relationships that express the values of the electric field intensity in the gap of the cell with two dielectrics and compared them with similar relationships of the intensity of the electric field from the gap of the ozone cell with one dielectric. In this work the author presenting experimental results which confirm the theoretical deducting regarding the use of the solid dielectric as enclosure for the liquid dielectric.

Quasiparticle interference in multiband superconductors with strong coupling

NASA Astrophysics Data System (ADS)

Dutt, A.; Golubov, A. A.; Dolgov, O. V.; Efremov, D. V.

2017-08-01

We develop a theory of the quasiparticle interference (QPI) in multiband superconductors based on the strong-coupling Eliashberg approach within the Born approximation. In the framework of this theory, we study dependencies of the QPI response function in the multiband superconductors with the nodeless s -wave superconductive order parameter. We pay special attention to the difference in the quasiparticle scattering between the bands having the same and opposite signs of the order parameter. We show that at the momentum values close to the momentum transfer between two bands, the energy dependence of the quasiparticle interference response function has three singularities. Two of these correspond to the values of the gap functions and the third one depends on both the gaps and the transfer momentum. We argue that only the singularity near the smallest band gap may be used as a universal tool to distinguish between the s++ and s± order parameters. The robustness of the sign of the response function peak near the smaller gap value, irrespective of the change in parameters, in both the symmetry cases is a promising feature that can be harnessed experimentally.

The Serum Anion Gap in the Evaluation of Acid-Base Disorders: What Are Its Limitations and Can Its Effectiveness Be Improved?

PubMed Central

Nagami, Glenn T.

2013-01-01

Summary The serum anion gap has been utilized to identify errors in the measurement of electrolytes, to detect paraproteins, and, most relevant to the nephrologist, to evaluate patients with suspected acid-base disorders. In regard to the latter purpose, traditionally an increased anion gap is identified when it exceeds the upper limit of normal for a particular clinical laboratory measurement. However, because there is a wide range of normal values (often 8–10 mEq/L), an increase in anion concentration can be present in the absence of an increased anion gap. In addition, the type of retained anion can affect the magnitude of the increase in anion gap relative to change in serum [HCO3−] being greater with lactic acidosis compared with ketoacidosis. This review examines the methods of calculation of the serum anion gap in textbooks and published literature, the effect of perturbations other than changes in acid-base balance, and its effectiveness in identifying mild and more severe disturbances in acid-base balance. Limitations of the present methods of determining the normal anion gap and change in the anion gap are highlighted. The possibility of identifying the baseline value for individuals to optimize the use of the calculation in the detection of metabolic acidosis is suggested. PMID:23833313

Bipolar doping and band-gap anomalies in delafossite transparent conductive oxides.

PubMed

Nie, Xiliang; Wei, Su-Huai; Zhang, S B

2002-02-11

Doping wide-gap materials p type is highly desirable but often difficult. This makes the recent discovery of p-type delafossite oxides, CuM(III)O2, very attractive. The CuM(III)O2 also show unique and unexplained physical properties: Increasing band gap from M(III) = Al,Ga, to In, not seen in conventional semiconductors. The largest gap CuInO2 can be mysteriously doped both n and p type but not the smaller gaps CuAlO2 and CuGaO2. Here, we show that both properties are results of a large disparity between the fundamental gap and the apparent optical gap, a finding that could lead to a breakthrough in the study of bipolarly dopable wide-gap semiconductor oxides.

Comprehensive comparison of gap filling techniques for eddy covariance net carbon fluxes

NASA Astrophysics Data System (ADS)

Moffat, A. M.; Papale, D.; Reichstein, M.; Hollinger, D. Y.; Richardson, A. D.; Barr, A. G.; Beckstein, C.; Braswell, B. H.; Churkina, G.; Desai, A. R.; Falge, E.; Gove, J. H.; Heimann, M.; Hui, D.; Jarvis, A. J.; Kattge, J.; Noormets, A.; Stauch, V. J.

2007-12-01

Review of fifteen techniques for estimating missing values of net ecosystem CO2 exchange (NEE) in eddy covariance time series and evaluation of their performance for different artificial gap scenarios based on a set of ten benchmark datasets from six forested sites in Europe. The goal of gap filling is the reproduction of the NEE time series and hence this present work focuses on estimating missing NEE values, not on editing or the removal of suspect values in these time series due to systematic errors in the measurements (e.g. nighttime flux, advection). The gap filling was examined by generating fifty secondary datasets with artificial gaps (ranging in length from single half-hours to twelve consecutive days) for each benchmark dataset and evaluating the performance with a variety of statistical metrics. The performance of the gap filling varied among sites and depended on the level of aggregation (native half- hourly time step versus daily), long gaps were more difficult to fill than short gaps, and differences among the techniques were more pronounced during the day than at night. The non-linear regression techniques (NLRs), the look-up table (LUT), marginal distribution sampling (MDS), and the semi-parametric model (SPM) generally showed good overall performance. The artificial neural network based techniques (ANNs) were generally, if only slightly, superior to the other techniques. The simple interpolation technique of mean diurnal variation (MDV) showed a moderate but consistent performance. Several sophisticated techniques, the dual unscented Kalman filter (UKF), the multiple imputation method (MIM), the terrestrial biosphere model (BETHY), but also one of the ANNs and one of the NLRs showed high biases which resulted in a low reliability of the annual sums, indicating that additional development might be needed. An uncertainty analysis comparing the estimated random error in the ten benchmark datasets with the artificial gap residuals suggested that the techniques are already at or very close to the noise limit of the measurements. Based on the techniques and site data examined here, the effect of gap filling on the annual sums of NEE is modest, with most techniques falling within a range of ±25 g C m-2 y-1.

Deterministic multidimensional nonuniform gap sampling.

PubMed

Worley, Bradley; Powers, Robert

2015-12-01

Born from empirical observations in nonuniformly sampled multidimensional NMR data relating to gaps between sampled points, the Poisson-gap sampling method has enjoyed widespread use in biomolecular NMR. While the majority of nonuniform sampling schemes are fully randomly drawn from probability densities that vary over a Nyquist grid, the Poisson-gap scheme employs constrained random deviates to minimize the gaps between sampled grid points. We describe a deterministic gap sampling method, based on the average behavior of Poisson-gap sampling, which performs comparably to its random counterpart with the additional benefit of completely deterministic behavior. We also introduce a general algorithm for multidimensional nonuniform sampling based on a gap equation, and apply it to yield a deterministic sampling scheme that combines burst-mode sampling features with those of Poisson-gap schemes. Finally, we derive a relationship between stochastic gap equations and the expectation value of their sampling probability densities. Copyright © 2015 Elsevier Inc. All rights reserved.

Effect of pH on the electrical properties and conducting mechanism of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Periathai, R. Sudha; Abarna, S.; Hirankumar, G.; Jeyakumaran, N.; Prithivikumaran, N.

2017-03-01

Semiconductor nanoparticles have attracted more interests because of their size-dependent optical and electrical properties.SnO2 is an oxygen-deficient n-type semiconductor with a wide band gap of 3.6 eV (300 K). It has many remarkable applications as sensors, catalysts, transparent conducting electrodes, anode material for rechargeable Li- ion batteries and optoelectronic devices. In the present work, the role of pH in determining the electrical and dielectric properties of SnO2 nanoparticles has been studied as a function of temperature ranging from Room temperature (RT) to 114 °C in the frequency range of 7 MHz to 50 mHz using impedance spectroscopic technique. The non linear behavior observed in the thermal dependence of the conductance of SnO2 nanoparticles is explained by means of the surface property of SnO2 nanoparticles where proton hopping mechanism is dealt with. Jonscher's power law has been fitted for the conductance spectra and the frequency exponent ("s" value) gives an insight about the ac conducting mechanism. The temperature dependence of electrical relaxation phenomenon in the material has been observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation.

Electrical Conductivity of HgTe at High Temperatures

NASA Technical Reports Server (NTRS)

Li, C.; Lehoczky, S. L.; Su, C.-H.; Scripa, R. N.

2004-01-01

The electrical conductivity of HgTe was measured using a rotating magnetic field method from 300 K to the melting point (943 K). A microscopic theory for electrical conduction was used to calculate the expected temperature dependence of the HgTe conductivity. A comparison between the measured and calculated conductivities was used to obtain the estimates of the temperature dependence of Gamma(sub 6)-Gamma(sub 8) energy gap from 300 K to 943 K. The estimated temperature coefficient for the energy gap was comparable to the previous results at lower temperatures (less than or equal to 300 K). A rapid increase in the conductivity just above 300 K and a subsequent decrease at 500 K is attributed to band crossover effects. This paper describes the experimental approach and some of the theoretical calculation details.

A preliminary investigation of the air-bone gap: Changes in intracochlear sound pressure with air- and bone-conducted stimuli after cochlear implantation

PubMed Central

Banakis Hartl, Renee M.; Mattingly, Jameson K.; Greene, Nathaniel T.; Jenkins, Herman A.; Cass, Stephen P.; Tollin, Daniel J.

2016-01-01

Hypothesis A cochlear implant electrode within the cochlea contributes to the air-bone gap (ABG) component of postoperative changes in residual hearing after electrode insertion. Background Preservation of residual hearing after cochlear implantation has gained importance as simultaneous electric-acoustic stimulation allows for improved speech outcomes. Postoperative loss of residual hearing has previously been attributed to sensorineural changes; however, presence of increased postoperative air-bone gap remains unexplained and could result in part from altered cochlear mechanics. Here, we sought to investigate changes to these mechanics via intracochlear pressure measurements before and after electrode implantation to quantify the contribution to postoperative air-bone gap. Methods Human cadaveric heads were implanted with titanium fixtures for bone conduction transducers. Velocities of stapes capitulum and cochlear promontory between the two windows were measured using single-axis laser Doppler vibrometry and fiber-optic sensors measured intracochlear pressures in scala vestibuli and tympani for air- and bone-conducted stimuli before and after cochlear implant electrode insertion through the round window. Results Intracochlear pressures revealed only slightly reduced responses to air-conducted stimuli consistent with prior literature. No significant changes were noted to bone-conducted stimuli after implantation. Velocities of the stapes capitulum and the cochlear promontory to both stimuli were stable following electrode placement. Conclusion Presence of a cochlear implant electrode causes alterations in intracochlear sound pressure levels to air, but not bone, conducted stimuli and helps to explain changes in residual hearing noted clinically. These results suggest the possibility of a cochlear conductive component to postoperative changes in hearing sensitivity. PMID:27579835

Electronic structure and thermoelectric properties of half-Heusler compounds with eight electron valence count—KScX (X = C and Ge)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciftci, Yasemin O.; Mahanti, Subhendra D.

Electronic band structure and structural properties of two representative half-Heusler (HH) compounds with 8 electron valence count (VC), KScC and KScGe, have been studied using first principles methods within density functional theory and generalized gradient approximation. These systems differ from the well studied class of HH compounds like ZrNiSn and ZrCoSb which have VC = 18 because of the absence of d electrons of the transition metal atoms Ni and Co. Electronic transport properties such as Seebeck coefficient (S), electrical conductivity (σ), electronic thermal conductivity (κ{sub e}) (the latter two scaled by electronic relaxation time), and the power factor (S{sup 2}σ) havemore » been calculated using semi-classical Boltzmann transport theory within constant relaxation time approximation. Both the compounds are direct band gap semiconductors with band extrema at the X point. Their electronic structures show a mixture of heavy and light bands near the valance band maximum and highly anisotropic conduction and valence bands near the band extrema, desirable features of good thermoelectric. Optimal p- or n-type doping concentrations have been estimated based on thermopower and maximum power factors. The optimum room temperature values of S are ∼1.5 times larger than that of the best room temperature thermoelectric Bi{sub 2}Te{sub 3}. We also discuss the impact of the band structure on deviations from Weidemann-Franz law as one tunes the chemical potential across the band gap.« less

Net use, care and repair practices following a universal distribution campaign in Mali.

PubMed

Leonard, Lori; Diop, Samba; Doumbia, Seydou; Sadou, Aboubacar; Mihigo, Jules; Koenker, Hannah; Berthe, Sara; Monroe, April; Bertram, Kathryn; Weber, Rachel

2014-11-18

The Government of Mali and the President's Malaria Initiative conducted a long-lasting, insecticidal net (LLIN) distribution campaign in April 2011 in the Sikasso region of Mali, with the aim of universal coverage, defined as one insecticide-treated net for every two persons. This study examines how households in post- and pre-campaign regions value and care for nets. The study was conducted in October 2012 in Sikasso and Kayes in the southeast and western regions of Mali, respectively. The regions were purposively selected to allow for comparison between areas that had already had a mass distribution campaign (Sikasso) and areas that had not yet had a mass distribution campaign (Kayes). Study sites and households were randomly selected. Sleeping space questionnaires and structured interviews with household heads were conducted to obtain information on net use, perceived value of free nets in relation to other malaria prevention activities, and net care and repair practices. The study included 40 households, split evenly across the two regions. Forty interviews were conducted with household heads and 151 sleeping spaces were inventoried using the sleeping space questionnaire. Nets obtained through the free distribution were reported to be highly valued in comparison to other malaria prevention strategies. Overall, net ownership and use were higher among households in areas that had already experienced a mass distribution. While participants reported using and valuing these nets, care and repair practices varied. National net use is high in Mali, and comparatively higher in the region covered by the universal distribution campaign than in the region not yet covered. While the Government of Mali and implementing partners have made strides to ensure high net coverage, some gaps remain related to communication messaging of correct and consistent net use throughout the year, and on improving net care and repair behaviour. By focusing on these areas as well as improved access to nets, coverage and use rates should continue to increase, contributing to improvements in malaria control.

DUST COAGULATION IN THE VICINITY OF A GAP-OPENING JUPITER-MASS PLANET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carballido, Augusto; Matthews, Lorin S.; Hyde, Truell W., E-mail: Augusto_Carballido@baylor.edu

We analyze the coagulation of dust in and around a gap opened by a Jupiter-mass planet. To this end, we carry out a high-resolution magnetohydrodynamic (MHD) simulation of the gap environment, which is turbulent due to the magnetorotational instability. From the MHD simulation, we obtain values of the gas velocities, densities, and turbulent stresses (a) close to the gap edge, (b) in one of the two gas streams that accrete onto the planet, (c) inside the low-density gap, and (d) outside the gap. The MHD values are then input into a Monte Carlo dust-coagulation algorithm which models grain sticking andmore » compaction. We also introduce a simple implementation for bouncing, for comparison purposes. We consider two dust populations for each region: one whose initial size distribution is monodisperse, with monomer radius equal to 1 μ m, and another one whose initial size distribution follows the Mathis–Rumpl–Nordsieck distribution for interstellar dust grains, with an initial range of monomer radii between 0.5 and 10 μ m. Without bouncing, our Monte Carlo calculations show steady growth of dust aggregates in all regions, and the mass-weighted (m-w) average porosity of the initially monodisperse population reaches extremely high final values of 98%. The final m-w porosities in all other cases without bouncing range between 30% and 82%. The efficiency of compaction is due to high turbulent relative speeds between dust particles. When bouncing is introduced, growth is slowed down in the planetary wake and inside the gap. Future studies will need to explore the effect of different planet masses and electric charge on grains.« less

An ERP Study of Causative Cleft Construction in Japanese: Evidence for the Preference of Shorter Linear Distance in Sentence Comprehension

ERIC Educational Resources Information Center

Yano, Masataka; Sakamoto, Tsutomu

2016-01-01

This study examined the processing of two types of Japanese causative cleft constructions (subject-gap vs. object-gap) by conducting an event-related brain potential experiment to clarify the processing mechanism of long-distance dependencies. The results demonstrated that the subject-gap constructions elicited larger P600 effects than the…

30 CFR 585.902 - What are the general requirements for decommissioning for facilities authorized under my SAP, COP...

Code of Federal Regulations, 2012 CFR

2012-07-01

... decommissioning for facilities authorized under my SAP, COP, or GAP? 585.902 Section 585.902 Mineral Resources..., Inspections, and Facility Assessments for Activities Conducted Under SAPs, COPs and GAPs Decommissioning... authorized under my SAP, COP, or GAP? (a) Except as otherwise authorized by BOEM under § 585.909, within 2...

Illusory Continuity without Sufficient Sound Energy to Fill a Temporal Gap: Examples of Crossing Glide Tones

ERIC Educational Resources Information Center

Kuroda, Tsuyoshi; Nakajima, Yoshitaka; Eguchi, Shuntarou

2012-01-01

The gap transfer illusion is an auditory illusion where a temporal gap inserted in a longer glide tone is perceived as if it were in a crossing shorter glide tone. Psychophysical and phenomenological experiments were conducted to examine the effects of sound-pressure-level (SPL) differences between crossing glides on the occurrence of the gap…

Data correlation and analysis of arc tunnel and wind tunnel tests of RSI joints and gaps. Volume 2: Data base

NASA Technical Reports Server (NTRS)

Christensen, H. E.; Kipp, H. W.

1974-01-01

Wind tunnel tests were conducted to determine the aerodynamic heating created by gaps in the reusable surface insulation (RSI) thermal protection system (TPS) for the space shuttle. The effects of various parameters of the RSI on convective heating characteristics are described. The wind tunnel tests provided a data base for accurate assessment of gap heating. Analysis and correlation of the data provide methods for predicting heating in the RSI gaps on the space shuttle.

Single Step In Situ Synthesis and Optical Properties of Polyaniline/ZnO Nanocomposites

PubMed Central

Kaith, B. S.; Rajput, Jaspreet

2014-01-01

Polyaniline/ZnO nanocomposites were prepared by in situ oxidative polymerization of aniline monomer in the presence of different weight percentages of ZnO nanostructures. The steric stabilizer added to prevent the agglomeration of nanostructures in the polymer matrix was found to affect the final properties of the nanocomposite. ZnO nanostructures of various morphologies and sizes were prepared in the absence and presence of sodium lauryl sulphate (SLS) surfactant under different reaction conditions like in the presence of microwave radiation (microwave oven), under pressure (autoclave), under vacuum (vacuum oven), and at room temperature (ambient condition). The conductivity of these synthesized nanocomposites was evaluated using two-probe method and the effect of concentration of ZnO nanostructures on conductivity was observed. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV-visible (UV-VIS) spectroscopy techniques were used to characterize nanocomposites. The optical energy band gap of the nanocomposites was calculated from absorption spectra and ranged between 1.5 and 3.21 eV. The reported values depicted the blue shift in nanocomposites as compared to the band gap energies of synthesized ZnO nanostructures. The present work focuses on the one-step synthesis and potential use of PANI/ZnO nanocomposite in molecular electronics as well as in optical devices. PMID:24523653

Mechanical signaling coordinates the embryonic heartbeat

PubMed Central

Chiou, Kevin K.; Rocks, Jason W.; Chen, Christina Yingxian; Cho, Sangkyun; Merkus, Koen E.; Rajaratnam, Anjali; Robison, Patrick; Tewari, Manorama; Vogel, Kenneth; Majkut, Stephanie F.; Prosser, Benjamin L.; Discher, Dennis E.; Liu, Andrea J.

2016-01-01

In the beating heart, cardiac myocytes (CMs) contract in a coordinated fashion, generating contractile wave fronts that propagate through the heart with each beat. Coordinating this wave front requires fast and robust signaling mechanisms between CMs. The primary signaling mechanism has long been identified as electrical: gap junctions conduct ions between CMs, triggering membrane depolarization, intracellular calcium release, and actomyosin contraction. In contrast, we propose here that, in the early embryonic heart tube, the signaling mechanism coordinating beats is mechanical rather than electrical. We present a simple biophysical model in which CMs are mechanically excitable inclusions embedded within the extracellular matrix (ECM), modeled as an elastic-fluid biphasic material. Our model predicts strong stiffness dependence in both the heartbeat velocity and strain in isolated hearts, as well as the strain for a hydrogel-cultured CM, in quantitative agreement with recent experiments. We challenge our model with experiments disrupting electrical conduction by perfusing intact adult and embryonic hearts with a gap junction blocker, β-glycyrrhetinic acid (BGA). We find this treatment causes rapid failure in adult hearts but not embryonic hearts—consistent with our hypothesis. Last, our model predicts a minimum matrix stiffness necessary to propagate a mechanically coordinated wave front. The predicted value is in accord with our stiffness measurements at the onset of beating, suggesting that mechanical signaling may initiate the very first heartbeats. PMID:27457951

Patient engagement in research with older adults with cancer.

PubMed

Puts, Martine T E; Sattar, Schroder; Ghodraty-Jabloo, Vida; Hsu, Tina; Fitch, Marg; Szumacher, Ewa; Ayala, Ana Patricia; Alibhai, Shabbir M H

2017-11-01

Cancer is a disease that mostly affects older adults. Older adults have been under-represented in clinical cancer research. Around the world there is a push for patient engagement on study teams as it is anticipated to improve study design, recruitment and dissemination of findings. In the current overview we examined the evidence with regard to: 1) the history of patient engagement in research and frameworks developed; 2) impact of patient engagement on patient and research outcomes; 3) use of patient engagement in geriatrics and oncology, 4) recommendations for successful engagement; and 5) gaps in the literature that should be studied further. A narrative review was conducted. Articles published in English were searched in Medline with the help of a librarian. Patient engagement has been shown to improve the conduct of studies by making the study design more relevant and feasible, and improving recruitment rates and uptake of research findings by patients. However, the best way to engage patients is not clear yet. Several resources have been developed to support researchers engaging older adults with cancer in research. While patient engagement in research seems promising to improve study outcomes, little evidence is available thus far in geriatric oncology settings. Several gaps in the literature are identified that should be further studied to determine the value of, and best approaches to, patient engagement with older adults with cancer. Copyright © 2017 Elsevier Ltd. All rights reserved.

Meteodrones - Meteorological Planetary Boundary Layer Measurements by Vertical Drone Soundings

NASA Astrophysics Data System (ADS)

Lauer, Jonas; Fengler, Martin

2017-04-01

As of today, there is a gap in the operational data collection of meteorological observations in the Planetary Boundary Layer (PBL). This lack of spatially and temporally reliable knowledge of PBL conditions and energy fluxes with the surface causes shortcomings in the prediction of micro- and mesoscale phenomena such as convection, temperature inversions, local wind systems or fog. The currently used remote sensing instruments share the drawback of only partially covering necessary variables. To fill this data gap, since 2012, Meteomatics has been developing a drone measurement system, the Meteodrone, to measure the parameters wind speed, wind direction, dewpoint, temperature and air pressure of the PBL up to 1.5 km above ground. Both the data quality and the assimilation into a regional numerical weather model could be determined in several pilot studies. Besides, a project in cooperation with the NSSL (National Severe Storms Laboratory) was launched in October 2016 with the goal of capturing pre-convective conditions for improved severe storm forecasts in Oklahoma. Also, related measurements, such as air pollution measurements in the Misox valley to determine LDSP values, were successfully conducted. The main goal of the project is the operational data collection of PBL measurements and the assimilation of this data into regional numerical weather forecast models. Considering the high data quality indicated in all conducted studies as well as the trouble-free execution, this goal is both worthwhile and realistic.

An impurity intermediate band due to Pb doping induced promising thermoelectric performance of Ca5In2Sb6.

PubMed

Feng, Zhenzhen; Wang, Yuanxu; Yan, Yuli; Zhang, Guangbiao; Yang, Jueming; Zhang, Jihua; Wang, Chao

2015-06-21

Band engineering is one of the effective approaches for designing ideal thermoelectric materials. Introducing an intermediate band in the band gap of semiconducting thermoelectric compounds may largely increase the carrier concentration and improve the electrical conductivity of these compounds. We test this hypothesis by Pb doping in Zintl Ca5In2Sb6. In the current work, we have systematically investigated the electronic structure and thermoelectric performances of substitutional doping with Pb on In sites at a doping level of 5% (0.2 e per cell) for Ca5In2Sb6 by using density functional theory combined with semi-classical Boltzmann theory. It is found that in contrast to Zn doping, Pb doping introduces a partially filled intermediate band in the band gap of Ca5In2Sb6, which originates from the Pb s states by weakly hybridizing with the Sb p states. Such an intermediate band dramatically increases the electrical conductivity of Ca5In2Sb6 and has little detrimental effect on its Seebeck coefficient, which may increase its thermoelectric figure of merit, ZT. Interestingly, a maximum ZT value of 2.46 may be achieved at 900 K for crystalline Pb-doped Ca5In2Sb6 when the carrier concentration is optimized. Therefore, Pb-doped Ca5In2Sb6 may be a promising thermoelectric material.

Thermal-Structural Analysis of PICA Tiles for Solar Tower Test

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Empey, Daniel M.; Squire, Thomas H.

2009-01-01

Thermal protection materials used in spacecraft heatshields are subjected to severe thermal and mechanical loading environments during re-entry into earth atmosphere. In order to investigate the reliability of PICA tiles in the presence of high thermal gradients as well as mechanical loads, the authors designed and conducted solar-tower tests. This paper presents the design and analysis work for this tests series. Coupled non-linear thermal-mechanical finite element analyses was conducted to estimate in-depth temperature distribution and stress contours for various cases. The first set of analyses performed on isolated PICA tile showed that stresses generated during the tests were below the PICA allowable limit and should not lead to any catastrophic failure during the test. The tests results were consistent with analytical predictions. The temperature distribution and magnitude of the measured strains were also consistent with predicted values. The second test series is designed to test the arrayed PICA tiles with various gap-filler materials. A nonlinear contact method is used to model the complex geometry with various tiles. The analyses for these coupons predict the stress contours in PICA and inside gap fillers. Suitable mechanical loads for this architecture will be predicted, which can be applied during the test to exceed the allowable limits and demonstrate failure modes. Thermocouple and strain-gauge data obtained from the solar tower tests will be used for subsequent analyses and validation of FEM models.

Prospects for Problems Associated with Integrative and Inter-comparative Analysis of Eddy Flux Data Sets

NASA Astrophysics Data System (ADS)

Kobayashi, Y.; Miyata, A.; Nagai, H.; Mano, M.; Yamamoto, S.

2005-12-01

In last decade, numerous long-term eddy flux measurements have been conducted worldwide to assess annual/seasonal energy, water and carbon exchanges between terrestrial ecosystem and the atmosphere. And FLUXNET communities now seem to come into a next phase with the objectives: integration of flux data observed at various ecosystems and/or inter-sites comparative studies. For example, a big research project "S-1" is ongoing in Japan and other eastern Asian region to set up terrestrial carbon management of Asia in the 21st century. One of the highlights of S-1 project is to provide a carbon budget map of all over Asia based on integrated and inter-compared eddy flux data collected at 15 sites of S-1 membership. FLUXNET communities including S-1 project have recognized that integration and inter-comparison of eddy flux data are the key issues to understand aspects of energy, water and carbon budgets at regional scale. However, the issues have difficulties to be settled because each flux site applies own data processing methods and gap-filling methods with site-specified classification and threshold values. In order to conduct appropriate integrative and inter-comparative analysis for eddy flux data effectively, we made it clear that how the differences in the data processing method affect the obtained flux values and searched for suitable and common gap-filling methodology. The differences in the data processing methods affect the obtained flux data in the present study was discussed based on a comparative experiment in S-1 project. We prepared one-month common test data sets, which consisted of 10 Hz eddy covariance raw data and related half-hourly meteorological data obtained at a larch forest site and a paddy site, in the comparative experiment. The 15 sites of S-1 memberships processed the test data by using their own processing methods. The results indicated that combined influences of coordinate rotation, detrending and frequency response correction brought about up to 10% of flux discrepancy, and that the forest sites were more sensitive to differences in the data processing methods than the non-forest sites. Multiple imputation method (MI), one of the statistical operations for analyzing incomplete multivariate data set, is likely to be an easy-to-use and objective gap-filling method to account for missing eddy flux data. We also discussed validity of application of MI to fill missing flux data by comparing a gap-filled complete eddy flux data set obtained by MI with that by nonlinear regression method and look-up table method. It was revealed that, with suitable separation of the periods to be filled and proper selection of reference variables, MI has potential to be applied commonly to gap-filling missing flux data, and that MI can be a useful tool for FLUXNET communities to make inter-site comparison of long-term flux data.

Organic Electronic Devices Using Crosslinked Polyelectrolyte Multilayers as an Ultra-Thin Dielectric Material

DTIC Science & Technology

2006-09-01

energy band diagram illustrating the allowed energies for valence and conducting electrons. The dashes within the band gap (Eg) represent localized ...allowed energies for valence and conducting electrons. The dashes within the band gap (Eg) represent localized electron energy states, or traps, that...been observed with the formation of alternating bond lengths along the backbone.43 The localization of the π-electrons while forming the shorter double

Superconducting properties of under- and over-doped BaxK1‑xBiO3 perovskite oxide

NASA Astrophysics Data System (ADS)

Szczȩśniak, D.; Kaczmarek, A. Z.; Szczȩśniak, R.; Turchuk, S. V.; Zhao, H.; Drzazga, E. A.

2018-06-01

In this study, we investigate the thermodynamic properties of the BaxK1‑xBiO3 (BKBO) superconductor in the under- (x = 0.5) and over-doped (x = 0.7) regime, within the framework of the Migdal-Eliashberg formalism. The analysis is conducted to verify that the electron-phonon pairing mechanism is responsible for the induction of the superconducting phase in the mentioned compound. In particular, we show that BKBO is characterized by the relatively high critical value of the Coulomb pseudopotential, which changes with doping level and does not follow the Morel-Anderson model. In what follows, the corresponding superconducting band gap size and related dimensionless ratio are estimated to increase with the doping, in agreement with the experimental predictions. Moreover, the effective mass of electrons is found to take on high values in the entire doping and temperature region. Finally, the characteristic dimensionless ratios for the superconducting band gap, the critical magnetic field and the specific heat for the superconducting state are predicted to exceed the limits set within the Bardeen-Cooper-Schrieffer theory, suggesting pivotal role of the strong-coupling and retardation effects in the analyzed compound. Presented results supplement our previous investigations and account for the strong-coupling phonon-mediated character of the superconducting phase in BKBO at any doping level.

Towards band structure and band offset engineering of monolayer Mo(1-x)W(x)S2 via Strain

NASA Astrophysics Data System (ADS)

Kim, Joon-Seok; Ahmad, Rafia; Pandey, Tribhuwan; Rai, Amritesh; Feng, Simin; Yang, Jing; Lin, Zhong; Terrones, Mauricio; Banerjee, Sanjay K.; Singh, Abhishek K.; Akinwande, Deji; Lin, Jung-Fu

2018-01-01

Semiconducting transition metal dichalcogenides (TMDs) demonstrate a wide range of optoelectronic properties due to their diverse elemental compositions, and are promising candidates for next-generation optoelectronics and energy harvesting devices. However, effective band offset engineering is required to implement practical structures with desirable functionalities. Here, we explore the pressure-induced band structure evolution of monolayer WS2 and Mo0.5W0.5S2 using hydrostatic compressive strain applied in a diamond anvil cell (DAC) apparatus and theoretical calculations, in order to study the modulation of band structure and explore the possibility of band alignment engineering through different compositions. Higher W composition in Mo(1-x)W(x)S2 contributes to a greater pressure-sensitivity of direct band gap opening, with a maximum value of 54 meV GPa-1 in WS2. Interestingly, while the conduction band minima (CBMs) remains largely unchanged after the rapid gap increase, valence band maxima (VBMs) significantly rise above the initial values. It is suggested that the pressure- and composition-engineering could introduce a wide variety of band alignments including type I, type II, and type III heterojunctions, and allow to construct precise structures with desirable functionalities. No structural transition is observed during the pressure experiments, implying the pressure could provide selective modulation of band offset.

Solar cells with gallium phosphide/silicon heterojunction

NASA Astrophysics Data System (ADS)

Darnon, Maxime; Varache, Renaud; Descazeaux, Médéric; Quinci, Thomas; Martin, Mickaël; Baron, Thierry; Muñoz, Delfina

2015-09-01

One of the limitations of current amorphous silicon/crystalline silicon heterojunction solar cells is electrical and optical losses in the front transparent conductive oxide and amorphous silicon layers that limit the short circuit current. We propose to grow a thin (5 to 20 nm) crystalline Gallium Phosphide (GaP) by epitaxy on silicon to form a more transparent and more conducting emitter in place of the front amorphous silicon layers. We show that a transparent conducting oxide (TCO) is still necessary to laterally collect the current with thin GaP emitter. Larger contact resistance of GaP/TCO increases the series resistance compared to amorphous silicon. With the current process, losses in the IR region associated with silicon degradation during the surface preparation preceding GaP deposition counterbalance the gain from the UV region. A first cell efficiency of 9% has been obtained on ˜5×5 cm2 polished samples.

Long Chain Saturated and Unsaturated Carboxylic Acids: Filling a Large Gap of Knowledge in Their Enthalpies of Formation.

PubMed

Rogers, Donald W; Zavitsas, Andreas A

2017-01-06

Despite their abundance in nature and their importance in biology, medicine, nutrition, and in industry, gas phase enthalpies of formation of many long chain saturated and unsaturated fatty acids and of dicarboxylic acids are either unavailable or have been estimated with large uncertainties. Available experimental values for stearic acid show a spread of 68 kJ mol -1 . This work fills the knowledge gap by obtaining reliable values by quantum theoretical calculations using G4 model chemistry. Compounds with up to 20 carbon atoms are treated. The theoretical results are in excellent agreement with well established experimental values when such values exist, and they provide a large number of previously unavailable values.

Enhanced thermoelectric performance in three-dimensional superlattice of topological insulator thin films

PubMed Central

2012-01-01

We show that certain three-dimensional (3D) superlattice nanostructure based on Bi2Te3 topological insulator thin films has better thermoelectric performance than two-dimensional (2D) thin films. The 3D superlattice shows a predicted peak value of ZT of approximately 6 for gapped surface states at room temperature and retains a high figure of merit ZT of approximately 2.5 for gapless surface states. In contrast, 2D thin films with gapless surface states show no advantage over bulk Bi2Te3. The enhancement of the thermoelectric performance originates from a combination of the reduction of lattice thermal conductivity by phonon-interface scattering, the high mobility of the topologically protected surface states, the enhancement of Seebeck coefficient, and the reduction of electron thermal conductivity by energy filtering. Our study shows that the nanostructure design of topological insulators provides a possible new way of ZT enhancement. PMID:23072433

Enhanced thermoelectric performance in three-dimensional superlattice of topological insulator thin films.

PubMed

Fan, Zheyong; Zheng, Jiansen; Wang, Hui-Qiong; Zheng, Jin-Cheng

2012-10-16

We show that certain three-dimensional (3D) superlattice nanostructure based on Bi2Te3 topological insulator thin films has better thermoelectric performance than two-dimensional (2D) thin films. The 3D superlattice shows a predicted peak value of ZT of approximately 6 for gapped surface states at room temperature and retains a high figure of merit ZT of approximately 2.5 for gapless surface states. In contrast, 2D thin films with gapless surface states show no advantage over bulk Bi2Te3. The enhancement of the thermoelectric performance originates from a combination of the reduction of lattice thermal conductivity by phonon-interface scattering, the high mobility of the topologically protected surface states, the enhancement of Seebeck coefficient, and the reduction of electron thermal conductivity by energy filtering. Our study shows that the nanostructure design of topological insulators provides a possible new way of ZT enhancement.

Electronic, transport, and optical properties of bulk and mono-layer PdSe 2

DOE PAGES

Sun, Jifeng; Shi, Hongliang; Siegrist, Theo; ...

2015-10-13

In this study, the electronic and optical properties of bulk and monolayer PdSe 2 are investigated using firstprinciples calculations. Using the modified Becke-Johnson potential, we find semiconductor behavior for both bulk and monolayer PdSe 2 with indirect gap values of 0.03 eV for bulk and 1.43 eV for monolayer, respectively. Our sheet optical conductivity results support this observation and show similar anisotropic feature in the 2D plane. We further study the thermoelectric properties of the 2D PdSe 2 using Blotzmann transport model and find interestingly high Seebeck coefficients (>200 μV/K) for both p- and n-type up to high doping levelmore » (–2 x 10 13 cm 2) with an anisotropic character in an electrical conductivity suggesting better thermoelectric performance along y direction in the plane.V« less

Experimental evidence for the correlation between the weak inversion hump and near midgap states in dielectric/InGaAs interfaces

NASA Astrophysics Data System (ADS)

Krylov, Igor; Kornblum, Lior; Gavrilov, Arkady; Ritter, Dan; Eizenberg, Moshe

2012-04-01

Temperature dependent capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were performed to obtain activation energies (EA) for weak inversion C-V humps and parallel conductance peaks in Al2O3/InGaAs and Si3N4/InGaAs gate stacks. Values of 0.48 eV (slightly more than half of the band gap of the studied In0.53Ga0.47As) were obtained for EA of both phenomena for both gate dielectrics studied. This indicates an universal InGaAs behavior and shows that both phenomena are due to generation-recombination of minority carriers through near midgap located interface states. The C-V hump correlates with the interface states density (Dit) and can be used as a characterization tool for dielectric/InGaAs systems.

Electronic Structures of Purple Bronze KMo6O17 Studied by X-Ray Photoemission Spectra

NASA Astrophysics Data System (ADS)

Qin, Xiaokui; Wei, Junyin; Shi, Jing; Tian, Mingliang; Chen, Hong; Tian, Decheng

X-ray photoemission spectroscopy study has been performed for the purple bronze KMo6O17. The structures of conduction band and valence band are analogous to the results of ultraviolet photoemission spectra and are also consistent with the model of Travaglini et al., but the gap between conduction and valence band is insignificant. The shape of asymmetric and broadening line of O-1s is due to unresolved contributions from the many inequivalent oxygen sites in this crystal structure. Mo 3d core-level spectrum reveals that there are two kinds of valence states of Molybdenum (Mo+5 and Mo+6). The calculated average valence state is about +5.6, which is consistent with the expectation value from the composition of this material. The tail of Mo-3d spectrum toward higher binding energy is the consequence of the excitation of electron-hole pairs with singularity index of 0.21.

Many-body design of highly strained GaInNAs electroabsorption modulators on GaInAs ternary substrates

NASA Astrophysics Data System (ADS)

Fujisawa, Takeshi; Arai, Masakazu; Kano, Fumiyoshi

2010-05-01

Electroabsorption in highly strained GaInAs and GaInNAs quantum wells (QWs) grown on GaInAs or quasi-GaInAs substrates is investigated by using microscopic many-body theory. The effects of various parameters, such as strain, barrier height, substrate composition, and temperature are thoroughly examined. It is shown that the value of the absorption coefficient strongly depends on the depth of the QWs under large bias electric field due to the small overlap integral of wave functions between the conduction and valence bands. The use of GaInNAs QWs makes the strain in the well layer very small. Further, the effective quantum-well depth is increased in GaInNAs QWs due to the anticrossing interaction between the conduction and N-resonant bands, making it possible to obtain larger absorption coefficient under large bias electric fields without using wide-band gap materials for barriers.

Optimal Decay of Wannier functions in Chern and Quantum Hall Insulators

NASA Astrophysics Data System (ADS)

Monaco, Domenico; Panati, Gianluca; Pisante, Adriano; Teufel, Stefan

2018-01-01

We investigate the localization properties of independent electrons in a periodic background, possibly including a periodic magnetic field, as e. g. in Chern insulators and in quantum Hall systems. Since, generically, the spectrum of the Hamiltonian is absolutely continuous, localization is characterized by the decay, as {|x| → ∞} , of the composite (magnetic) Wannier functions associated to the Bloch bands below the Fermi energy, which is supposed to be in a spectral gap. We prove the validity of a localization dichotomy in the following sense: either there exist exponentially localized composite Wannier functions, and correspondingly the system is in a trivial topological phase with vanishing Hall conductivity, or the decay of any composite Wannier function is such that the expectation value of the squared position operator, or equivalently of the Marzari-Vanderbilt localization functional, is {+ ∞} . In the latter case, the Bloch bundle is topologically non-trivial, and one expects a non-zero Hall conductivity.

Low Cost CaTiO3 Perovskite Synthesized from Scallop (Anadara granosa) Shell as Antibacterial Ceramic Material

NASA Astrophysics Data System (ADS)

Fatimah, Is; Nur Ilahi, Rico; Pratami, Rismayanti

2018-01-01

Research on perovskite CaTiO3 synthesis from scallop (Anadara granosa) shell and its test as material for antibacterial ceramic application have been conducted. The synthesis was performed by calcium extraction from the scallop shell followed by solid-solid reaction of obtained calcium with TiO2. Physicochemical character of the perovskite wasstudied by measurement of crystallinity using x-ray diffraction (XRD), diffuse-reflectance UV Visible spectrophotometry, scanning electrone microscope-energy dispersive x-ray (SEM-EDX) and Fourier-Transform InfraRed. Considering the future application of the perovskite as antibacterial agent, laboratory test of the peroskite as material in antibacterial ceramic preparation was also conducted. Result of research indicated that perovskite formation was obtained and the material demonstrated photocatalytic activity as identified by band gap energy (Eg) value. The significant activity was also reflected by the antibacterial action of formed ceramic.

Evaluation of marginal gap of Ni-Cr copings made with conventional and accelerated casting techniques.

PubMed

Tannamala, Pavan Kumar; Azhagarasan, Nagarasampatti Sivaprakasam; Shankar, K Chitra

2013-01-01

Conventional casting techniques following the manufacturers' recommendations are time consuming. Accelerated casting techniques have been reported, but their accuracy with base metal alloys has not been adequately studied. We measured the vertical marginal gap of nickel-chromium copings made by conventional and accelerated casting techniques and determined the clinical acceptability of the cast copings in this study. Experimental design, in vitro study, lab settings. Ten copings each were cast by conventional and accelerated casting techniques. All copings were identical, only their mold preparation schedules differed. Microscopic measurements were recorded at ×80 magnification on the perpendicular to the axial wall at four predetermined sites. The marginal gap values were evaluated by paired t test. The mean marginal gap by conventional technique (34.02 μm) is approximately 10 μm lesser than that of accelerated casting technique (44.62 μm). As the P value is less than 0.0001, there is highly significant difference between the two techniques with regard to vertical marginal gap. The accelerated casting technique is time saving and the marginal gap measured was within the clinically acceptable limits and could be an alternative to time-consuming conventional techniques.

Orbital superconductivity, defects, and pinned nematic fluctuations in the doped iron chalcogenide FeSe 0.45 Te 0.55

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, Saheli; Van Dyke, John; Sprau, Peter O.

We demonstrate that the differential conductance, dI/dV, measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe0.45Te0.55, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields nearly isotropic superconducting gaps on the two holelike Fermi surfaces, and a strongly anisotropic gap on the electronlike Fermi surface. Moreover, we show that the pinning of nematic fluctuations by defects can give rise to a dumbbell-like spatial structure of the induced impurity bound states, and explains the related C-2 symmetry in the Fourier transformed differential conductance.

Aerodynamic pressure and heating-rate distributions in tile gaps around chine regions with pressure gradients at a Mach number of 6.6

NASA Technical Reports Server (NTRS)

Hunt, L. Roane; Notestine, Kristopher K.

1990-01-01

Surface and gap pressures and heating-rate distributions were obtained for simulated Thermal Protection System (TPS) tile arrays on the curved surface test apparatus of the Langley 8-Foot High Temperature Tunnel at Mach 6.6. The results indicated that the chine gap pressures varied inversely with gap width because larger gap widths allowed greater venting from the gap to the lower model side pressures. Lower gap pressures caused greater flow ingress from the surface and increased gap heating. Generally, gap heating was greater in the longitudinal gaps than in the circumferential gaps. Gap heating decreased with increasing gap depth. Circumferential gap heating at the mid-depth was generally less than about 10 percent of the external surface value. Gap heating was most severe at local T-gap junctions and tile-to-tile forward-facing steps that caused the greatest heating from flow impingement. The use of flow stoppers at discrete locations reduced heating from flow impingement. The use of flow stoppers at discrete locations reduced heating in most gaps but increased heating in others. Limited use of flow stoppers or gap filler in longitudinal gaps could reduce gap heating in open circumferential gaps in regions of high surface pressure gradients.

Comparison of the optical responses of O-poor and O-rich thermochromic VOX films during semiconductor-to-metal transition

NASA Astrophysics Data System (ADS)

Luo, Zhenfei; Wu, Zhiming; Wang, Tao; Xu, Xiangdong; Li, Weizhi; Li, Wei; Jiang, Yadong

2012-09-01

O-poor and O-rich thermochromic vanadium oxide (VOX) nanostructured thin films were prepared by applying reactive direct current magnetron sputtering and post-annealing in oxygen ambient. UV-visible spectrophotometer and spectroscopic ellipsometry were used to investigate the optical properties of films. It was found that, when the O-poor VOX thin film underwent semiconductor-to-metal transition, the values of optical conductivity and extinction coefficient in the visible region increased due to the existence of occupied band-gap states. This noticeable feature, however, was not observed for the O-rich film, which showed a similar optical behavior with the stoichiometric crystalline VO2 films reported in the literatures. Moreover, the O-poor VOX film exhibits consistent variations of transmission values in the visible/near-infrared region when it undergoes semiconductor-to-metal transition.

Resonant indirect optical absorption in germanium

NASA Astrophysics Data System (ADS)

Menéndez, José; Noël, Mario; Zwinkels, Joanne C.; Lockwood, David J.

2017-09-01

The optical absorption coefficient of pure Ge has been determined from high-accuracy, high-precision optical measurements at photon energies covering the spectral range between the indirect and direct gaps. The results are compared with a theoretical model that fully accounts for the resonant nature of the energy denominators that appear in perturbation-theory expansions of the absorption coefficient. The model generalizes the classic Elliott approach to indirect excitons, and leads to a predicted optical absorption that is in excellent agreement with the experimental values using just a single adjustable parameter: the average deformation potential DΓ L coupling electrons at the bottom of the direct and indirect valleys in the conduction band. Remarkably, the fitted value, DΓ L=4.3 ×108eV /cm , is in nearly perfect agreement with independent measurements and ab initio predictions of this parameter, confirming the validity of the proposed theory, which has general applicability.

Determining the Capacity Model of Urban Roundabouts, Considering the Drivers’ Behaviour in Accepting and Rejecting of Gaps

NASA Astrophysics Data System (ADS)

Bargegol, Iraj; Hamze Hosseini, Seyyed; Jahangir Samet, Mehdi

2017-10-01

Nowadays, urban roundabouts are one of the most popular types of intersections that have grown highly all over the world. Thus, the accurate and engineering design of these types of intersections has a significant effect on improving their traffic performance. The capacity is one of the important traffic parameters in different intersections, which represents the maximum volume of vehicles entering the roundabouts. There are two general methods for determining the capacity of intersections including the use of analytical models such as gap acceptance model and the use of empirical methods (regression model). In the present paper, using the collected data such as entry and circulating volume, both accepted and rejected gaps were studied for three urban roundabouts and the capacity model have been determined by the use of analytical method. After implementation of the data, they became consistent and homogeneous in four different groups and the most optimized range of critical gaps as well as the follow up time were separately determined for each of these groups by using conventional methods such as Sigloch, Raff, Wu, and Harder and according to statistical analyses with a confidence level of 95%. From the obtained results, a range of 3.03 - 3.32 s for critical gap of the studied roundabouts and the range of 1.3 - 1.7 s for follow up time could be mentioned. It was used from the theory of gap acceptance in order to determine urban roundabouts capacity model, in which these gaps have a random nature and follow negative exponential distribution and by conducting this analysis (also has been used by Sigloch), some relations were obtained for determining the capacity of the roundabouts according to the impact of circulating volume and drivers’ behaviour. The results indicate that the maximum capacity of the roundabouts in the microscopic models is equal to 2400 veh/h, when the circulating flow rate is reached zero. Moreover, according to the obtained capacity model, the circulating flow never falls down to zero in the case that it reaches its peak value.

A Quasi-Classical Model of the Hubbard Gap in Lightly Compensated Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poklonski, N. A.; Vyrko, S. A.; Kovalev, A. I.

2016-03-15

A quasi-classical method for calculating the narrowing of the Hubbard gap between the A{sup 0} and A{sup +} acceptor bands in a hole semiconductor or the D{sup 0} and D{sup –} donor bands in an electron semiconductor is suggested. This narrowing gives rise to the phenomenon of a semiconductor transition from the insulator to metal state with an increase in doping level. The major (doping) impurity can be in one of three charge states (–1, 0, or +1), while the compensating impurity can be in states (+1) or (–1). The impurity distribution over the crystal is assumed to be randommore » and the width of Hubbard bands (levels), to be much smaller than the gap between them. It is shown that narrowing of the Hubbard gap is due to the formation of electrically neutral acceptor (donor) states of the quasicontinuous band of allowed energies for holes (electrons) from excited states. This quasicontinuous band merges with the top of the valence band (v band) for acceptors or with the bottom of the conduction band (c band) for donors. In other words, the top of the v band for a p-type semiconductor or the bottom of the c band for an n-type semiconductor is shifted into the band gap. The value of this shift is determined by the maximum radius of the Bohr orbit of the excited state of an electrically neutral major impurity atom, which is no larger than half the average distance between nearest impurity atoms. As a result of the increasing dopant concentration, the both Hubbard energy levels become shallower and the gap between them narrows. Analytical formulas are derived to describe the thermally activated hopping transition of holes (electrons) between Hubbard bands. The calculated gap narrowing with increasing doping level, which manifests itself in a reduction in the activation energy ε{sub 2} is consistent with available experimental data for lightly compensated p-Si crystals doped with boron and n-Ge crystals doped with antimony.« less

Single-junction solar cells with the optimum band gap for terrestrial concentrator applications

DOEpatents

Wanlass, M.W.

1994-12-27

A single-junction solar cell is described having the ideal band gap for terrestrial concentrator applications. Computer modeling studies of single-junction solar cells have shown that the presence of absorption bands in the direct spectrum has the effect of ''pinning'' the optimum band gap for a wide range of operating conditions at a value of 1.14[+-]0.02 eV. Efficiencies exceeding 30% may be possible at high concentration ratios for devices with the ideal band gap. 7 figures.

Single-junction solar cells with the optimum band gap for terrestrial concentrator applications

DOEpatents

Wanlass, Mark W.

1994-01-01

A single-junction solar cell having the ideal band gap for terrestrial concentrator applications. Computer modeling studies of single-junction solar cells have shown that the presence of absorption bands in the direct spectrum has the effect of "pinning" the optimum band gap for a wide range of operating conditions at a value of 1.14.+-.0.02 eV. Efficiencies exceeding 30% may be possible at high concentration ratios for devices with the ideal band gap.

The Expanded Large Scale Gap Test

DTIC Science & Technology

1987-03-01

NSWC TR 86-32 DTIC THE EXPANDED LARGE SCALE GAP TEST BY T. P. LIDDIARD D. PRICE RESEARCH AND TECHNOLOGY DEPARTMENT ’ ~MARCH 1987 Ap~proved for public...arises, to reduce the spread in the LSGT 50% gap value.) The worst charges, such as those with the highest or lowest densities, the largest re-pressed...Arlington, VA 22217 PE 62314N INS3A 1 RJ14E31 7R4TBK 11 TITLE (Include Security CIlmsilficatiorn The Expanded Large Scale Gap Test . 12. PEIRSONAL AUTHOR() T

Design, Construction, Demonstration and Delivery of an Automated Narrow Gap Welding System.

DTIC Science & Technology

1983-03-31

evaluated on the Narrow Gap welding system. By using the combinational qas shielding assembly, it is now possible to reduce the gas flow rates to a value...AD-A145 496 DESIGN CONSTRUCTION DEMONSTRATION AND DE IVER OF AN AUTOMATED NARROW GAP WELDING SYSTEM(U) CRC AUTOMATIC WELDING CO HODSTON SX 31 MAR 83...STANDARDS-963 - A CRC REPORT NO. NAV A/W 7 0PHASE 3 REPORT ON SDESIGN, CONSTRUCTION, DEMONSTRATION AND DELIVERY OF AN AUTOMATED NARROW GAP WELDING

Bounds of cavitation inception in a creeping flow between eccentric cylinders rotating with a small minimum gap

NASA Astrophysics Data System (ADS)

Monakhov, A. A.; Chernyavski, V. M.; Shtemler, Yu.

2013-09-01

Bounds of cavitation inception are experimentally determined in a creeping flow between eccentric cylinders, the inner one being static and the outer rotating at a constant angular velocity, Ω. The geometric configuration is additionally specified by a small minimum gap between cylinders, H, as compared with the radii of the inner and outer cylinders. For some values H and Ω, cavitation bubbles are observed, which are collected on the surface of the inner cylinder and equally distributed over the line parallel to its axis near the downstream minimum gap position. Cavitation occurs for the parameters {H,Ω} within a region bounded on the right by the cavitation inception curve that passes through the plane origin and cannot exceed the asymptotic threshold value of the minimum gap, Ha, in whose vicinity cavitation may occur at H < Ha only for high angular rotation velocities.

Overdentures on natural teeth: a new approach.

PubMed

Previgliano, V; Barone Monfrin, S; Santià, G; Preti, G

2004-01-01

The study presents a new type of copings for overdentures on natural teeth. A new type of custom-made copings was prepared on 10 extracted teeth and their marginal fit was observed microscopically by means of a mechanical device, and software was employed to measure the gap. The marginal fit evaluation gave satisfactory values with mean values of the gap measurements below the clinically accepted limits (mean gap: 25.3 microm; minimum 7.3 microm, maximum 56.5 microm). The advantages of these new copings are: the rapidity of their preparation; the protection of the root canal treatment, because the coping with this chair-side method is prepared and cemented in one session; the low costs.

Stapedotomy in osteogenesis imperfecta: a prospective study of 32 consecutive cases.

PubMed

Vincent, Robert; Wegner, Inge; Stegeman, Inge; Grolman, Wilko

2014-12-01

To prospectively evaluate hearing outcomes in patients with osteogenesis imperfecta undergoing primary stapes surgery and to isolate prognostic factors for success. A nonrandomized, open, prospective case series. A tertiary referral center. Twenty-five consecutive patients who underwent 32 primary stapedotomies for osteogenesis imperfecta with evidence of stapes fixation and available postoperative pure-tone audiometry. Primary stapedotomy with vein graft interposition and reconstruction with a regular Teflon piston or bucket handle-type piston. Preoperative and postoperative audiometric evaluation using conventional 4-frequency (0.5, 1, 2, and 4 kHz) audiometry. Air-conduction thresholds, bone-conduction thresholds, and air-bone gap were measured. The overall audiometric results as well as the results of audiometric evaluation at 3 months and at least 1 year after surgery were used. Overall, postoperative air-bone gap closure to within 10 dB was achieved in 88% of cases. Mean (standard deviation) gain in air-conduction threshold was 22 (9.4) dB for the entire case series, and mean (standard deviation) air-bone gap closure was 22 (9.0) dB. Backward multivariate logistic regression showed that a model with preoperative air-bone gap closure and intraoperatively established incus length accurately predicts success after primary stapes surgery. Stapes surgery is a feasible and safe treatment option in patients with osteogenesis imperfecta. Success is associated with preoperative air-bone gap and intraoperatively established incus length.

Apparatus and method for tuned unsteady flow purging of high pulse rate spark gaps

DOEpatents

Thayer, III, William J.

1990-01-01

A spark gap switch apparatus is disclosed which is capable of operating at a high pulse rate which comprises an insulated housing; a pair of spaced apart electrodes each having one end thereof within a first bore formed in the housing and defining a spark gap therebetween; a pressure wave reflector in the first bore in the housing and spaced from the spark gap and capable of admitting purge flow; and a second enlarged bore contiguous with the first bore and spaced from the opposite side of the spark gap; whereby pressure waves generated during discharge of a spark across the spark gap will reflect off the wave reflector and back from the enlarged bore to the spark gap to clear from the spark gap hot gases residues generated during the discharge and simultaneously restore the gas density and pressure in the spark gap to its initial value.

Communication: electronic band gaps of semiconducting zig-zag carbon nanotubes from many-body perturbation theory calculations.

PubMed

Umari, P; Petrenko, O; Taioli, S; De Souza, M M

2012-05-14

Electronic band gaps for optically allowed transitions are calculated for a series of semiconducting single-walled zig-zag carbon nanotubes of increasing diameter within the many-body perturbation theory GW method. The dependence of the evaluated gaps with respect to tube diameters is then compared with those found from previous experimental data for optical gaps combined with theoretical estimations of exciton binding energies. We find that our GW gaps confirm the behavior inferred from experiment. The relationship between the electronic gap and the diameter extrapolated from the GW values is also in excellent agreement with a direct measurement recently performed through scanning tunneling spectroscopy.

Modification of CuI based Hole Transport Material for Solid State DSSC Application

NASA Astrophysics Data System (ADS)

Hanif, Q. A.; Ramelan, A. H.; Saputri, L. N. M. Z.; Wahyuningsih, S.

2018-03-01

Modification of Hole Transport Material (HTM) with addition of tetramethylethylenediamine (TMED) and ammonium thiocyanate (NH4SCN) have been conducted. Copper Iodide (CuI) were used as the main component of HTM. Several volume variations of TMED (0.1; 0.2; and 0.4 mL) was added into 0.05 M CuI solutions. While TMED: NH4SCN ratio were 1:1,1:2,2:1 also introduced to the dissolved CuI. Optical properties of these materials showed the band gap energy value ranging from 2.38 to 3.79 eV. The conductivity of HTM has been measured and showed the maximum value in CuI added with 0.4 mL TMED = 0.29 S m-1, and ratio of TMED: NH4SCN=2:1 added into CuI = 0.39 S m-1, these value were increased compared to the CuI conductivity itself (0.26 S m-1). The effect of this modification towards SS DSSC efficiency also has been monitored. The SS DSSC construction consists of TiO2 nanorods sensitized by N3, HTM, and platinum as a counter electrode. The performance of SS DSSC showed rising efficiency as follows TiO2|N3|CuI

Temperature dependence of differential conductance in Co-based Heusler alloy Co2TiSn and superconductor Pb junctions

NASA Astrophysics Data System (ADS)

Ooka, Ryutaro; Shigeta, Iduru; Umetsu, Rie Y.; Nomura, Akiko; Yubuta, Kunio; Yamauchi, Touru; Kanomata, Takeshi; Hiroi, Masahiko

2018-05-01

We investigated temperature dependence of differential conductance G (V) in planar junctions consisting of Co-based Heusler alloy Co2TiSn and superconductor Pb. Ferromagnetic Co2TiSn was predicted to be half-metal by first-principles band calculations. The spin polarization P of Co2TiSn was deduced to be 60.0% at 1.4 K by the Andreev reflection spectroscopy. The G (V) spectral shape was smeared gradually with increasing temperature and its structure was disappeared above the superconducting transition temperature Tc. Theoretical model analysis revealed that the superconducting energy gap Δ was 1.06 meV at 1.4 K and the Tc was 6.8 K , indicating that both values were suppressed from bulk values. However, the temperature dependent Δ (T) behavior was in good agreement with that of the Bardeen-Cooper-Schrieffer (BCS) theory. The experimental results exhibit that the superconductivity of Pb attached to half-metallic Co2TiSn was kept the conventional BCS mechanism characterized strong-coupling superconductors while its superconductivity was slightly suppressed by the superconducting proximity effect at the Co2TiSn/Pb interface.

Distal gap junctions and active dendrites can tune network dynamics.

PubMed

Saraga, Fernanda; Ng, Leo; Skinner, Frances K

2006-03-01

Gap junctions allow direct electrical communication between CNS neurons. From theoretical and modeling studies, it is well known that although gap junctions can act to synchronize network output, they can also give rise to many other dynamic patterns including antiphase and other phase-locked states. The particular network pattern that arises depends on cellular, intrinsic properties that affect firing frequencies as well as the strength and location of the gap junctions. Interneurons or GABAergic neurons in hippocampus are diverse in their cellular characteristics and have been shown to have active dendrites. Furthermore, parvalbumin-positive GABAergic neurons, also known as basket cells, can contact one another via gap junctions on their distal dendrites. Using two-cell network models, we explore how distal electrical connections affect network output. We build multi-compartment models of hippocampal basket cells using NEURON and endow them with varying amounts of active dendrites. Two-cell networks of these model cells as well as reduced versions are explored. The relationship between intrinsic frequency and the level of active dendrites allows us to define three regions based on what sort of network dynamics occur with distal gap junction coupling. Weak coupling theory is used to predict the delineation of these regions as well as examination of phase response curves and distal dendritic polarization levels. We find that a nonmonotonic dependence of network dynamic characteristics (phase lags) on gap junction conductance occurs. This suggests that distal electrical coupling and active dendrite levels can control how sensitive network dynamics are to gap junction modulation. With the extended geometry, gap junctions located at more distal locations must have larger conductances for pure synchrony to occur. Furthermore, based on simulations with heterogeneous networks, it may be that one requires active dendrites if phase-locking is to occur in networks formed with distal gap junctions.

Making Sense of the Atmospheric Science Gender Gap: Do Female and Male Graduate Students Have Different Career Motives, Goals, and Challenges?

ERIC Educational Resources Information Center

Canetto, Silvia Sara; Trott, Carlie D.; Thomas, Jenifer J.; Wynstra, Cheryl A.

2012-01-01

There is a persisting gap in the participation of women in atmospheric science (ATS), particularly at the higher levels of ATS education and occupations. This gap raises questions about ATS women's career motives, plans, and challenges relative to men's. To explore these questions, in-depth interviews were conducted with 10 female and male ATS…

A Capstone Project: Closing the Achievement Gap of English Learners in Literacy at Sunshine Elementary School Using the Gap Analysis Model

ERIC Educational Resources Information Center

Herrera, Juan Carlos

2013-01-01

This project was an alternative capstone dissertation conducted by a team of three doctoral students. The project focused on systematic and long-term underachievement of the English Language (EL) population of a single school, Sunshine Elementary, using the gap analysis model (Clark and Estes, 2008). More specifically, the purpose of the analysis…

A Capstone Project: Closing the Achievement Gap of English Language Learners at Sunshine Elementary School Using the Gap Analysis Model

ERIC Educational Resources Information Center

Mingo-Long, Enyetta

2013-01-01

This project was an alternative capstone dissertation conducted by a team of three doctoral students. The project focused on systematic and long-term underachievement of the English Language Learner (ELL) population of a single school, Sunshine Elementary, using the gap analysis model (Clark and Estes, 2008). More specifically, the purpose of the…

Closing the Gap between the Theory and Practice of Teaching: Implications for Teacher Education Programmes in Hong Kong

ERIC Educational Resources Information Center

Cheng, May M. H.; Cheng, Annie Y. N.; Tang, Sylvia Y. F.

2010-01-01

The gap between the theory and practice of teaching is an issue of concern in teacher education. Although researching this gap is not new, few studies have been conducted in Hong Kong. It is worth investigating the contemporary Asian models of teacher education that can provide reference to the international literature. This paper examines this…

Creativity and Innovation in Science and Technology: Bridging the Gap between Secondary and Tertiary Levels of Education

ERIC Educational Resources Information Center

Ramma, Yashwantrao; Samy, Martin; Gopee, Ajit

2015-01-01

Purpose: This paper stems from a study which was conducted as a means to first, find out whether there is a gap between the secondary and tertiary education levels, second identify any existing gap in Science and Technology education, and third, examine the impact of the above upon students' creativity and innovativeness at university level. The…

Spin-polarized Second Harmonic Generation from the Antiferromagnetic CaCoSO Single Crystal

NASA Astrophysics Data System (ADS)

Reshak, A. H.

2017-04-01

The spin-polarized second harmonic generation (SHG) of the recently synthesized CaCoSO single crystal is performed based on the calculated electronic band structure. The calculation reveals that the spin-up (↑) channel of CaCoSO possesses a direct energy gap (Γv-Γc) of about 2.187 eV, 1.187 eV (Kv-Kc) for the spin-down (↓) channel and an indirect gap (Γv-Kc) of about 0.4 eV for the spin-polarized CaCoSO single crystal. The linear optical properties obtained reveal that the recently synthesized crystal exhibits considerable anisotropy with negative uniaxial anisotropy and birefringence favor to enhance the SHG. We have calculated the three non-zero tensor components of the SHG and found the is the dominat component, one with a large SHG of about (d33 = 6.936 pm/V at λ = 1064 nm), the half value of KTiOPO4 (KTP). As the values of (↑) < (↓) < spin-polarized are related to the values of the energy gap of (↑) 2.187 eV> (↓) 1.187 eV> spin-polarized gap 0.4 eV therefore, a smaller energy gap gives better SHG performance. Furthermore, the microscopic first hyperpolarizability, βijk, is calculated.

IMF B(y) and day-night conductivity effects in the expanding polar cap convection model

NASA Technical Reports Server (NTRS)

Moses, J. J.; Gorney, D. J.; Siscoe, G. L.; Crooker, N. U.

1987-01-01

During southward B(z) periods the open field line region in the ionosphere (polar cap) expands due to increased dayside merging. Ionospheric plasma flow patterns result which can be classified by the sign of the interplanetary magnetic field (IMF) B(y) component. In this paper, a time-dependent ionospheric convection model is constructed to simulate these flows. The model consists of a spiral boundary with a gap in it. The sign of the IMF B(y) component determines the geometry of the gap. A potential is applied across the gap and distributed around the boundary. A flow results which enters the polar cap through the gap and uniformly pushes the boundary outward. Results of the model show that B(y) effects are greatest near the gap and virtually unnoticeable on the nightside of the polar cap. Adding a day-night ionospheric conductivity gradient concentrates the polar cap electric field toward dawn. The resulting flow curvature gives a sunward component that is independent of B(y). These patterns are shown to be consistent with published observations.

Comparison between five CAD/CAM systems for fit of zirconia copings.

PubMed

Habib, Syed Rashid; Al Otaibi, Asim Khaled; Al Anazi, Talal Ali; Al Anazi, Samer Mosleh

2018-01-01

The aim of this in-vitro study was to investigate the marginal and internal fit of zirconia copings fabricated by five CAD/CAM (computer-aided design/computer-assisted manufacture) systems. A typodont mandibular right first molar was prepared according to ideal parameters for a zirconia crown, scanned digitally, and 100 identical resin dies fabricated by 3D printing. Samples were randomly divided into five groups and sent to CAD/CAM systems for zirconia copings (A, Ceramill-Motion 2, Amann Girrbach; B, Weiland, Ivoclar Vivadent; C, Cerec, Ivoclar Vivadent; D, Prettau Zirconia, Zirkonzahn; E, Cad4dent). CAD of the copings included standardized cement space of 30 µm and CAM was carried out. Copings were tried/adjusted on the respective dies and embedded under a standardized load of 20 N in self-curing resin. Samples were sectioned mesiodistally into two halves. Marginal and internal gap values were measured with a digital microscope at 50 to 200 × magnification at nine sites. The lowest and highest mean gap values of 46.93 ± 13.50 and 101.65 ± 35.56 μm were found for Group A and Group D, respectively. ANOVA showed a statistically significant difference between the mean values of all the groups (P = .000). Multiple comparisons with post hoc Tukey test indicated a statistically significant difference (P < .05) between: Group A and all groups except B; B with D; C with A; D with A; and B and E with A. Mean buccal/lingual gap value was found to be 51.54 ± 58.54 μm. Of the nine sites, the least gap resulted at the buccal axial wall and the greatest at the central groove. The overall mean gap recorded for the copings was 72.43 ± 57.56 μm. Marginal and internal adaptations of CAD/CAM zirconia copings is influenced by manufacturing technique, and variations exist for different systems. Measurement sites showed different levels. CAD/CAM systems investigated showed a clinically acceptable level of gap values (< 120 µm).

The magnetic field inside a protoplanetary disc gap opened by planets of different masses

NASA Astrophysics Data System (ADS)

Carballido, Augusto; Matthews, Lorin S.; Hyde, Truell W.

2017-12-01

We perform magnetohydrodynamic simulations of protoplanetary disc gaps opened by planets of various masses, with the aim of calculating the strength of the vertical magnetic field threading such gaps. We introduce a gravitational potential at the centre of a shearing box to compute the tidal interaction between the planets and the disc gas, which is turbulent due to the magnetorotational instability. Two types of simulations are executed: 1) In type 'Z', the initial magnetic field has only a uniform, vertical component, and ten planet masses between 0.66 and 6.64 thermal masses are used; 2) In type 'YZ', the initial magnetic field has both toroidal and vertical components, and five planet masses covering the same mass range are used. Our results show that, for low planet masses, higher values of the vertical magnetic field occur inside the gaps than outside, in agreement with the previous work. However, for massive planets, we find that the radial profiles of the field show dips near the gap centre. The interior of the Hill sphere of the most massive planet in the Z runs contains more low-plasma β values (i.e. high magnetic pressure) compared to lower-mass planets. Values of β at a distance of one Hill radius from each planet show a moderate decrease with planet mass. These results are relevant for the magnetic structure of circumplanetary discs and their possible outflows, and may be refined to aid future observational efforts to infer planet masses from high-resolution polarimetric observations of discs with gaps.

An effective approach for gap-filling continental scale remotely sensed time-series

PubMed Central

Weiss, Daniel J.; Atkinson, Peter M.; Bhatt, Samir; Mappin, Bonnie; Hay, Simon I.; Gething, Peter W.

2014-01-01

The archives of imagery and modeled data products derived from remote sensing programs with high temporal resolution provide powerful resources for characterizing inter- and intra-annual environmental dynamics. The impressive depth of available time-series from such missions (e.g., MODIS and AVHRR) affords new opportunities for improving data usability by leveraging spatial and temporal information inherent to longitudinal geospatial datasets. In this research we develop an approach for filling gaps in imagery time-series that result primarily from cloud cover, which is particularly problematic in forested equatorial regions. Our approach consists of two, complementary gap-filling algorithms and a variety of run-time options that allow users to balance competing demands of model accuracy and processing time. We applied the gap-filling methodology to MODIS Enhanced Vegetation Index (EVI) and daytime and nighttime Land Surface Temperature (LST) datasets for the African continent for 2000–2012, with a 1 km spatial resolution, and an 8-day temporal resolution. We validated the method by introducing and filling artificial gaps, and then comparing the original data with model predictions. Our approach achieved R2 values above 0.87 even for pixels within 500 km wide introduced gaps. Furthermore, the structure of our approach allows estimation of the error associated with each gap-filled pixel based on the distance to the non-gap pixels used to model its fill value, thus providing a mechanism for including uncertainty associated with the gap-filling process in downstream applications of the resulting datasets. PMID:25642100

Spin- and valley-dependent electrical conductivity of ferromagnetic group-IV 2D sheets in the topological insulator phase

NASA Astrophysics Data System (ADS)

Hoi, Bui Dinh; Yarmohammadi, Mohsen; Mirabbaszadeh, Kavoos; Habibiyan, Hamidreza

2018-03-01

In this work, based on the Kubo-Greenwood formalism and the k . p Hamiltonian model, the impact of Rashba spin-orbit coupling on electronic band structure and electrical conductivity of spin-up and spin-down subbands in counterparts of graphene, including silicene, stanene, and germanene nanosheets has been studied. When Rashba coupling is considered, the effective mass of Dirac fermions decreases significantly and no significant change is caused by this coupling for the subband gaps. All these nanosheets are found to be in topological insulator quantum phase at low staggered on-site potentials due to the applied perpendicular external electric field. We point out that the electrical conductivity of germanene increases gradually with Rashab coupling, while silicene and stanene have some fluctuations due to their smaller Fermi velocity. Furthermore, some critical temperatures with the same electrical conductivity values for jumping to the higher energy levels are observed at various Rashba coupling strengths. For all structures, a broad peak appears at low temperatures in electrical conductivity curves corresponding to the large entropy of systems when the thermal energy reaches to the difference between the energy states. Finally, we have reported that silicene has the larger has the larger electrical conductivity than two others.

Electronic Structures of Free-Standing Nanowires made from Indirect Bandgap Semiconductor Gallium Phosphide

PubMed Central

Liao, Gaohua; Luo, Ning; Chen, Ke-Qiu; Xu, H. Q.

2016-01-01

We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP)—a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the bands show anti-crossing structures, while the bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the conduction bands, while the maximum of the valence bands is always at the Γ-point. Using double group theory, we analyze the symmetry properties of the lowest conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest conduction bands and the highest valence bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula. PMID:27307081

Remodelling of cellular excitation (reaction) and intercellular coupling (diffusion) by chronic atrial fibrillation represented by a reaction-diffusion system

NASA Astrophysics Data System (ADS)

Zhang, Henggui; Garratt, Clifford J.; Kharche, Sanjay; Holden, Arun V.

2009-06-01

Human atrial tissue is an excitable system, in which myocytes are excitable elements, and cell-to-cell electrotonic interactions are via diffusive interactions of cell membrane potentials. We developed a family of excitable system models for human atrium at cellular, tissue and anatomical levels for both normal and chronic atrial fibrillation (AF) conditions. The effects of AF-induced remodelling of cell membrane ionic channels (reaction kinetics) and intercellular gap junctional coupling (diffusion) on atrial excitability, conduction of excitation waves and dynamics of re-entrant excitation waves are quantified. Both ionic channel and gap junctional coupling remodelling have rate dependent effects on atrial propagation. Membrane channel conductance remodelling allows the propagation of activity at higher rates than those sustained in normal tissue or in tissue with gap junctional remodelling alone. Membrane channel conductance remodelling is essential for the propagation of activity at rates higher than 300/min as seen in AF. Spatially heterogeneous gap junction coupling remodelling increased the risk of conduction block, an essential factor for the genesis of re-entry. In 2D and 3D anatomical models, the dynamical behaviours of re-entrant excitation waves are also altered by membrane channel modelling. This study provides insights to understand the pro-arrhythmic effects of AF-induced reaction and diffusion remodelling in atrial tissue.

Gaps in agricultural climate adaptation research

NASA Astrophysics Data System (ADS)

Davidson, Debra

2016-05-01

The value of the social sciences to climate change research is well recognized, but notable gaps remain in the literature on adaptation in agriculture. Contributions focus on farmer behaviour, with important research regarding gender, social networks and institutions remaining under-represented.

Testing for a Sterile Neutrino in Computer Models of the RNPS Short Baseline Nuclear Reactor Experiments.

NASA Astrophysics Data System (ADS)

Hunter, Rachel; Ernst, David; Vastola, John; Austin, Noah

In the 1980's and 90's a series of experiments were conducted to search for evidence of neutrino oscillations. Data was collected on five of the six independent fundamental parameters relating to oscillation rates. The data was then used to produce an exclusion region plot for values of the parameters. However, it was discovered that the experiments were not analyzed correctly and there are large gaps between theoretical and experimental data. A fourth type of neutrino could be to blame for these gaps. The goal of this research project is to find evidence for or against a fourth type of neutrino by a reanalysis of the old experiments. This part of the project attempts to reproduce the exclusion region plots for data taken at Rovno Nuclear Power Station in order to validate a model of the original analysis. Thus far the reproduction of their exclusion region is close, but not a complete success. Further work on the coding program will need to be completed in order to proceed with the next step in the reanalysis procedure. National Science Foundation Grant #1263045.

What do We Know about Family Interventions for Psychosis at the Process Level? A Systematic Review.

PubMed

Grácio, Jaime; Gonçalves-Pereira, Manuel; Leff, Julian

2016-03-01

The evidence regarding effectiveness of family interventions for psychosis (FIP) is strong and consistent. However, there is a gap in the research on the process of these interventions, and little is known about their active ingredients. This review aims to identify the active ingredients of FIP. We conducted a systematic literature review, focusing on qualitative research, and analyzed 22 papers in total. We found a single study comprehensively exploring the process of FIP. All other studies focused on particular aspects of process-related variables. The key elements of FIP seem to be the so-called "common therapeutic factors", followed by education about the illness and coping skills training. This review supports the value of a stepped model of intervention according to the needs of the families. However, the evidence reviewed also reveals a gap in the research findings based on the limited research available. FIP are complex, psychosocial interventions with multiple components, and more intensive, qualitative research is needed to establish linkages between process and outcome. © 2015 Family Process Institute.

Wavelength dependence of nanosecond infrared laser-induced breakdown in water: Evidence for multiphoton initiation via an intermediate state

NASA Astrophysics Data System (ADS)

Linz, Norbert; Freidank, Sebastian; Liang, Xiao-Xuan; Vogelmann, Hannes; Trickl, Thomas; Vogel, Alfred

2015-04-01

Investigation of the wavelength dependence (725-1025 nm) of the threshold for nanosecond optical breakdown in water revealed steps consistent with breakdown initiation by multiphoton ionization, with an initiation energy of about 6.6 eV. This value is considerably smaller than the autoionization threshold of about 9.5 eV, which can be regarded as band gap relevant for avalanche ionization. Breakdown initiation is likely to occur via excitation of a valence band electron into a solvated state, followed by rapid excitation into the conduction band. Theoretical analysis based on these assumptions suggests that the seed electron density required for initiating avalanche ionization amounts to 2.5 ×1015c m-3 at 725 nm and drops to 1.1 ×1012c m-3 at 1025 nm. These results demand changes of future breakdown modeling for water, including the use of a larger band gap than previously employed, the introduction of an intermediate energy level for initiation, and consideration of the wavelength dependence of seed electron density.

Synthesis, spectral, thermal and optical properties of Schiff-base complexes derived from 2(E)-2-((z)-4-hydroxypent-3-en-2-ylideneamino)-5-guanidinopentanoic acid and acetylacetone

NASA Astrophysics Data System (ADS)

Hosny, Nasser Mohammed; Hussien, Mostafa A.; Radwan, Fatima M.; Nawar, Nagwa

2017-09-01

New metal complexes derived from the in situ reaction of Cu(II), Co(II), Ni(II) and Zn(II) acetates with the Schiff-base ligand (H2L) resulted from the condensation of 2-amino-5-guanidinopentanoic acid (arginine) and acetylacetone have been synthesized. The resulting complexes have been characterized by, elemental analyses, ES-MS, IR, Raman spectra, UV-Vis., 1HNMR, ESR, thermal analyses (TGA and DTG) and magnetic measurements. The results showed that, The Schiff-base ligand acts as bi-negative tridentate coordinating via azomethine nitrogen, enolic carbonyl oxygen and carboxylate oxygen after displacement of hydrogen. The thermodynamic parameters E∗, ΔH, ΔG and ΔS of the isolated complexes have been calculated. The optical band gap (Eg) values of Cu, Co, Ni and Zn were found to be 3.3, 3.4, 3.7 and 4.3 eV, respectively, arising from direct transitions. Optical band gap measurements indicate the semi-conductivity nature of these complexes.

High thermoelectric performances of monolayer SnSe allotropes.

PubMed

Hu, Zi-Yu; Li, Kai-Yue; Lu, Yong; Huang, Yan; Shao, Xiao-Hong

2017-10-26

α-SnSe is one of the most promising thermoelectric materials with low thermal conductivity and a high power factor. Since the thermoelectric properties of a material have a strong dependence on its crystal structure, we study the energetic and thermoelectric properties of four new monolayer phases of SnSe (β, γ, δ and ε) together with α-SnSe using the ab initio density functional theory method. The calculated electronic structures show that all five phases are semiconductors with different band gaps. The α, β, γ, and δ phases have an indirect band gap with the hybridization of sp 2 orbitals, whereas the ε phase has a direct band with the hybridization of sp 3 orbitals. The thermoelectric transport properties and coefficients are obtained from the electronic structure using semi-classical Boltzmann theory, and the results indicate that the four new phases of SnSe (β, γ, δ and ε) all have better thermoelectric properties compared with the reported α phase. The predicted ZT value for the β-SnSe phase is 2.06 at 300 K, suggesting that it has great potential for novel thermoelectric applications.

Recursive processes in self-affirmation: intervening to close the minority achievement gap.

PubMed

Cohen, Geoffrey L; Garcia, Julio; Purdie-Vaughns, Valerie; Apfel, Nancy; Brzustoski, Patricia

2009-04-17

A 2-year follow-up of a randomized field experiment previously reported in Science is presented. A subtle intervention to lessen minority students' psychological threat related to being negatively stereotyped in school was tested in an experiment conducted three times with three independent cohorts (N = 133, 149, and 134). The intervention, a series of brief but structured writing assignments focusing students on a self-affirming value, reduced the racial achievement gap. Over 2 years, the grade point average (GPA) of African Americans was, on average, raised by 0.24 grade points. Low-achieving African Americans were particularly benefited. Their GPA improved, on average, 0.41 points, and their rate of remediation or grade repetition was less (5% versus 18%). Additionally, treated students' self-perceptions showed long-term benefits. Findings suggest that because initial psychological states and performance determine later outcomes by providing a baseline and initial trajectory for a recursive process, apparently small but early alterations in trajectory can have long-term effects. Implications for psychological theory and educational practice are discussed.

Theory of nitrogen doping of carbon nanoribbons: Edge effects

DOE PAGES

Jiang, Jie; Turnbull, Joseph; Lu, Wenchang; ...

2012-01-01

Nitrogen doping of a carbon nanoribbon is profoundly affected by its one-dimensional character, symmetry, and interaction with edge states. Using state-of-the-art ab initio calculations, including hybrid exact-exchange density functional theory, we find that, for N-doped zigzag ribbons, the electronic properties are strongly dependent upon sublattice effects due to the non-equivalence of the two sublattices. For armchair ribbons, N-doping effects are different depending upon the ribbon family: for families 2 and 0, the N-induced levels are in the conduction band, while for family 1 the N levels are in the gap. In zigzag nanoribbons, nitrogen close to the edge is amore » deep center, while in armchair nanoribbons its behavior is close to an effective-mass-like donor with the ionization energy dependent on the value of the band gap. In chiral nanoribbons, we find strong dependence of the impurity level and formation energy upon the edge position of the dopant, while such site-specificity is not manifested in the magnitude of the magnetization.« less

Density Functional Calculations of Native Defects in CH 3 NH 3 PbI 3 : Effects of Spin–Orbit Coupling and Self-Interaction Error

DOE PAGES

Du, Mao-Hua

2015-04-02

We know that native point defects play an important role in carrier transport properties of CH3NH3PbI3. However, the nature of many important defects remains controversial due partly to the conflicting results reported by recent density functional theory (DFT) calculations. In this Letter, we show that self-interaction error and the neglect of spin–orbit coupling (SOC) in many previous DFT calculations resulted in incorrect positions of valence and conduction band edges, although their difference, which is the band gap, is in good agreement with the experimental value. Moreover, this problem has led to incorrect predictions of defect-level positions. Hybrid density functional calculations,more » which partially correct the self-interaction error and include the SOC, show that, among native point defects (including vacancies, interstitials, and antisites), only the iodine vacancy and its complexes induce deep electron and hole trapping levels inside of the band gap, acting as nonradiative recombination centers.« less

Polymer Assisted Functional Ceramic Nanofibrous Structures for Potential Optoelectronic and Photocatalytic Applications

NASA Astrophysics Data System (ADS)

Aykut, Yakup

The use of fossil fuels adversely effects the environment and hence increases global warming. On the other hand the lack of fuel reservoirs triggers people to find environmentally friendly new energy sources. Solar cell technology is one of the developing energy production technologies in green productions. Currently, many solar cells are made of highly purified silicon crystals. However silicon based solar cells have high energy conversion efficiency, they are highly brittle, expensive, and time consuming during the fabrication process. Organic and metal oxide based photovoltaic materials are a more cost-effective alternative to silicon based solar cells. In ceramic materials, Titanium dioxide (TiO2), zinc oxide (ZnO) and magnesium zinc oxide (MgxZn 1-xO) have intensive research interest owing to their optoelectronic and photocatalytic properties, and they have been used in dye sensitized solar cells as electron acceptor layer due to their high band gap properties and having low conduction band levels than electron donor dye molecules or quantum dots. On the other hand, energy band levels of the ceramic materials are considerable affected by their crystal microstructures, shapes and doping materials. Because of their high surface to volume ratio, nanofibers are suitable as active energy conversions layers in organic and dye sensitized solar cells. Using nanofibrous ceramic structure instead of film provides higher energy conversion efficiency since the high surface areas of the electrospun mats may accommodate a greater concentration of dye molecules or quantum dots, which could result in greater efficiency of electron transfer within the material, as compared to traditional film-based technologies. Also, the continuous structure of nanofibers may allow for effective electron transfer as a result of the direct conduction pathway of the photoelectrons along the fibers. Moreover, 3D structures of nanofibrous mat allow scattering and absorbing the photons multiple times. Sol-Gel electrospinning procedure has been widely used to obtain ceramic nanofibers. Briefly, at sol-gel electrospinning procedure, a carrier polymer and ceramic precursor is dissolved in an appropriate solvent, and polymer/ceramic precursor composite nanofibers are produced with a following electrospinning process. Then, as spun nanofibers are calcined at high temperatures to remove polymer and other organic residues from the fibers and convert ceramic precursor into ceramic nanofibers. We investigate temperature dependent crystal phase transformations of electrospun TiO2 nanofibers regardless of other parameters and observed their microstructures and optical properties due to different calcination temperatures. Quantum dots are semi conductive metallic nanocrystals with very wide light absorption range in UV, visible and even in near-infrared regions depending on the size of the quantum dots. On the other hand, TiO2 is a high band gap semiconductor material and absorbs the light in UV range that limits its photovoltaic applications. In order to extend its light absorption through visible region, we sensitized and incorporated low band gap CdSe quantum dot on electrospun TiO2 nanofibers. Zinc oxide (ZnO) is another high band gap ceramic materials with promising optical properties have been used for photonic applications. Intrinsic lattice defects in ZnO are one of the main limitation factors that affect the device performance tremendously and could be controlled due to fabrication process. We investigated the effect of different type of surfactants with different charge groups on fiber morphology, microstructure and optical properties of sol-gel electrospun ZnO nanofibers. Finally, in order to tune band gap energy level of ZnO nanofibers to higher values, we doped Mg2+ into ZnO nanofibers. Because Zn2+ and Mg2+ have similar atomic radii, some of Zn2+ ions are replaced with Mg 2+ ions in the structure to produce different "x" value of MgxZn1-xO due to amount of Mg content. We produced tuned band gap MgxZn1-xO nanofibers via sol-gel electrospinning.

Zn(x)Cd(1-x)Se nanomultipods with tunable band gaps: synthesis and first-principles calculations.

PubMed

Wei, Hao; Su, Yanjie; Han, Ziyi; Li, Tongtong; Ren, Xinglong; Yang, Zhi; Wei, Liangming; Cong, Fengsong; Zhang, Yafei

2013-06-14

In this paper, we demonstrate that ZnxCd1-xSe nanomultipods can be synthesized via a facile and nontoxic solution-based method. Interesting aspects of composition, morphology and optical properties were deeply explored. The value of Zn/(Zn+Cd) could be altered across the entire range from 0.08 to 0.86 by varying the ratio of cation precursor contents. The band gap energy could be linearly tuned from 1.88 to 2.48 eV with respect to the value of Zn/(Zn+Cd). The experiment also showed that oleylamine played a dominant role in the formation of multipod structure. A possible growth mechanism was further suggested. First-principles calculations of band gap energy and density of states in the Vienna ab initio simulation package code were performed to verify the experimental variation tendency of the band gap. Computational results indicated that dissimilarities of electronic band structures and orbital constitutions determined the tunable band gap of the as-synthesized nanomultipod, which might be promising for versatile applications in relevant areas of solar cells, biomedicine, sensors, catalysts and so on.

Values Affirmation Intervention Reduces Achievement Gap between Underrepresented Minority and White Students in Introductory Biology Classes

PubMed Central

Jordt, Hannah; Eddy, Sarah L.; Brazil, Riley; Lau, Ignatius; Mann, Chelsea; Brownell, Sara E.; King, Katherine; Freeman, Scott

2017-01-01

Achievement gaps between underrepresented minority (URM) students and their white peers in college science, technology, engineering, and mathematics classrooms are persistent across many white-majority institutions of higher education. Attempts to reduce this phenomenon of underperformance through increasing classroom structure via active learning have been partially successful. In this study, we address the hypothesis that the achievement gap between white and URM students in an undergraduate biology course has a psychological and emotional component arising from stereotype threat. Specifically, we introduced a values affirmation exercise that counters stereotype threat by reinforcing a student’s feelings of integrity and self-worth in three iterations of an intensive active-learning college biology course. On average, this exercise reduced the achievement gap between URM and white students who entered the course with the same incoming grade point average. This result suggests that achievement gaps resulting from the underperformance of URM students could be mitigated by providing students with a learning environment that removes psychological and emotional impediments of performance through short psychosocial interventions. PMID:28710060

On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

NASA Astrophysics Data System (ADS)

Chattopadhyay, P.; Karim, B.; Guha Roy, S.

2013-12-01

The sub-band gap optical absorption in chemical bath deposited cadmium sulphide thin films annealed at different temperatures has been critically analyzed with special reference to Urbach relation. It has been found that the absorption co-efficient of the material in the sub-band gap region is nearly constant up to a certain critical value of the photon energy. However, as the photon energy exceeds the critical value, the absorption coefficient increases exponentially indicating the dominance of Urbach rule. The absorption coefficients in the constant absorption region and the Urbach region have been found to be sensitive to annealing temperature. A critical examination of the temperature dependence of the absorption coefficient indicates two different kinds of optical transitions to be operative in the sub-band gap region. After a careful analyses of SEM images, energy dispersive x-ray spectra, and the dc current-voltage characteristics, we conclude that the absorption spectra in the sub-band gap domain is possibly associated with optical transition processes involving deep levels and the grain boundary states of the material.

Predictors for Long-Term Hip Survivorship Following Acetabular Fracture Surgery: Importance of Gap Compared with Step Displacement.

PubMed

Verbeek, Diederik O; van der List, Jelle P; Tissue, Camden M; Helfet, David L

2018-06-06

Historically, the greatest residual (gap or step) displacement is used to predict clinical outcome following acetabular fracture surgery. Gap and step displacement may, however, impact the outcome to different degrees. We assessed the individual relationship between gap or step displacement and hip survivorship and determined their independent association with conversion to total hip arthroplasty. Patients who had acetabular fracture fixation (from 1992 through 2014), follow-up of ≥2 years (or early conversion to total hip arthroplasty), and postoperative computed tomography (CT) scans were included. Of 227 patients, 55 (24.2%) had conversion to total hip arthroplasty at a mean follow-up (and standard deviation) of 8.7 ± 5.6 years. Residual gap and step displacement were measured using a standardized CT-based method, and assessors were blinded to the outcome. Kaplan-Meier survivorship curves for the hips were plotted and compared (log-rank test) using critical cutoff values for gap and step displacement. These values were identified using receiver operating characteristic curves. Multivariate analysis was performed to identify independent variables associated with conversion to total hip arthroplasty. Subgroup analysis was performed in younger patients (<50 years old). The critical CT cutoff value for total hip arthroplasty conversion was 5 mm for gap and 1 mm for step displacement. Hip survivorship at 10 years was 82.0% for patients with a gap of <5 mm compared with 56.5% for a gap of ≥5 mm (p < 0.001) and 80.0% for a step of <1.0 mm versus 65.5% for a step of ≥1.0 mm (p = 0.012). A gap of ≥5 mm (hazard ratio [HR], 2.3; p = 0.012) and an age of ≥50 years (HR, 4.2; p < 0.001) were independently associated with conversion to total hip arthroplasty in all patients. In the subgroup of younger patients, only a step of ≥1 mm (HR, 6.4; p = 0.017) was an independent factor for conversion to total hip arthroplasty. Residual gap and step displacement as measured on CT scans are both related to long-term hip survivorship, but step displacement (1 mm) is tolerated less than gap displacement (5 mm). Of the 2 types of displacement, only a large gap displacement (≥5 mm) was independently associated with conversion to total hip arthroplasty. In younger patients who had less articular impaction with smaller residual gaps, only step displacement (≥1 mm) appeared to be associated with this outcome. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Electrical conductivity of oxidized-graphenic nanoplatelets obtained from bamboo: effect of the oxygen content

NASA Astrophysics Data System (ADS)

Gross, K.; Prías Barragán, J. J.; Sangiao, S.; De Teresa, J. M.; Lajaunie, L.; Arenal, R.; Ariza Calderón, H.; Prieto, P.

2016-09-01

The large-scale production of graphene and reduced-graphene oxide (rGO) requires low-cost and eco-friendly synthesis methods. We employed a new, simple, cost-effective pyrolytic method to synthetize oxidized-graphenic nanoplatelets (OGNP) using bamboo pyroligneous acid (BPA) as a source. Thorough analyses via high-resolution transmission electron microscopy and electron energy-loss spectroscopy provides a complete structural and chemical description at the local scale of these samples. In particular, we found that at the highest carbonization temperature the OGNP-BPA are mainly in a sp2 bonding configuration (sp2 fraction of 87%). To determine the electrical properties of single nanoplatelets, these were contacted by Pt nanowires deposited through focused-ion-beam-induced deposition techniques. Increased conductivity by two orders of magnitude is observed as oxygen content decreases from 17% to 5%, reaching a value of 2.3 × 103 S m-1 at the lowest oxygen content. Temperature-dependent conductivity reveals a semiconductor transport behavior, described by the Mott three-dimensional variable range hopping mechanism. From the localization length, we estimate a band-gap value of 0.22(2) eV for an oxygen content of 5%. This investigation demonstrates the great potential of the OGNP-BPA for technological applications, given that their structural and electrical behavior is similar to the highly reduced rGO sheets obtained by more sophisticated conventional synthesis methods.

Band Gap Optimization Design of Photonic Crystals Material

NASA Astrophysics Data System (ADS)

Yu, Y.; Yu, B.; Gao, X.

2017-12-01

The photonic crystal has a fundamental characteristic - photonic band gap, which can prevent light to spread in the crystals. This paper studies the width variation of band gaps of two-dimension square lattice photonic crystals by changing the geometrical shape of the unit cells’ inner medium column. Using the finite element method, we conduct numerical experiments on MATLAB 2012a and COMSOL 3.5. By shortening the radius in vertical axis and rotating the medium column, we design a new unit cell, with a 0.3*3.85e-7 vertical radius and a 15 degree deviation to the horizontal axis. The new cell has a gap 1.51 percent wider than the circle medium structure in TE gap and creates a 0.0124 wide TM gap. Besides, the experiment shows the first TM gap is partially overlapped by the second TE gap in gap pictures. This is helpful to format the absolute photonic band gaps and provides favorable theoretical basis for designing photonic communication material.

Identifying knowledge-attitude-practice gaps to enhance HPV vaccine diffusion.

PubMed

Cohen, Elisia L; Head, Katharine J

2013-01-01

To examine differences in knowledge, attitudes, and related practices among adopters and nonadopters of the human papillomavirus (HPV) vaccine, the researchers conducted 83 in-depth interviews with 18- to 26-year-old women. The study identified knowledge-attitude-practice gaps in the context of the HPV vaccine to explain why diffusion of a preventive innovation (such as the HPV vaccine) requires targeted risk communication strategies in order to increase demand. Salient findings included similarities between vaccinated and unvaccinated women's lack of knowledge and uncertainties about HPV and cervical cancer. Vaccinated women who had no knowledge of HPV or no-risk/low-risk perceptions of HPV reported receiving vaccination, indicating HPV risk protection behavior could precede knowledge acquisition for vaccinated women. These vaccinated women identified an interpersonal network supportive of vaccination and reported supportive social influences. Among unvaccinated women, unsupportive vaccination attitudes included low perceived personal risk of HPV. In contrast, unvaccinated women often cited erroneous beliefs that HPV could be avoided by abstinence, monogamy, and knowledge of their partners' sexual history as reasons that the vaccine was not personally relevant. Unvaccinated women cited interpersonal influences that activated short- and long-term vaccination safety and efficacy concerns. Different levels of fear regarding the HPV vaccine may underlie (a) attitudinal differences between vaccinated and unvaccinated women in perceived vaccination value and (b) attitude-practice gaps.

Factors impacting on nurses' transference of theoretical knowledge of holistic care into clinical practice.

PubMed

Henderson, Saras

2002-12-01

Since nurse education moved to universities, a reoccurring concern of health consumers, health administrators, and some practising nurses is that nurses are not able to transfer the theoretical knowledge of holistic care into practice. Much has been written about this concern usually under the heading of the theory-practice gap. A common reason that has been highlighted as the cause of this gap is that the theoretical knowledge that nurses learn in academia is predicated on concepts such as humanism and holistic caring. In contrast, the bureaucratic organisation where nurses provide care tends to be based on management concepts where cost containment and outcome measures are more acceptable. Hence nurses' learned values of holistic caring are pitted against the reality of the practice setting. So what is this practice reality? This paper attempts to provide an insider view of why the theoretical knowledge of holistic care may be difficult to enact in the clinical setting. In-depth taped interviews with nurses and participant observation were conducted in acute care hospitals in Western Australia. The interviews were transcribed verbatim and analysed using the constant comparative method. The findings indicated that utilitarian nursing and role models had impacted on the transference of theoretical knowledge of holistic care into practice. The paper outlines some measures that nurses themselves can undertake to ensure the narrowing of the theory-practice gap in this area.

Effect of the Crystallization Process on the Marginal and Internal Gaps of Lithium Disilicate CAD/CAM Crowns.

PubMed

Kim, Jae-Hong; Oh, Seunghan; Uhm, Soo-Hyuk

2016-01-01

The aim of this study is to quantify the effect of the crystallization process on lithium disilicate ceramic crowns fabricated using a computer-aided design/computer-aided manufacturing (CAD/CAM) system and to determine whether the effect of crystallization is clinically acceptable by comparing values of fit before and after the crystallization process. The mandibular right first molar was selected as the abutment for the experiments. Fifteen working models were prepared. Lithium disilicate crowns appropriate for each abutment were prepared using a commercial CAD/CAM system. Gaps in the marginal area and 4 internal areas of each crown were measured twice-before and after crystallization-using the silicone replica technique. The mean values of fit before and after crystallization were analyzed using a paired t-test to examine whether the conversion that occurred during crystallization affected marginal and internal gaps (α = 0.05). Gaps increased in the marginal area and decreased in the internal areas after crystallization. There were statistically significant differences in all of the investigated areas (P < 0.05). None of the values for marginal and internal fit of lithium disilicate CAD/CAM crowns after crystallization exceeded 120 μm, which is the clinically acceptable threshold.

A Validation Study of the Impression Replica Technique.

PubMed

Segerström, Sofia; Wiking-Lima de Faria, Johanna; Braian, Michael; Ameri, Arman; Ahlgren, Camilla

2018-04-17

To validate the well-known and often-used impression replica technique for measuring fit between a preparation and a crown in vitro. The validation consisted of three steps. First, a measuring instrument was validated to elucidate its accuracy. Second, a specimen consisting of male and female counterparts was created and validated by the measuring instrument. Calculations were made for the exact values of three gaps between the male and female. Finally, impression replicas were produced of the specimen gaps and sectioned into four pieces. The replicas were then measured with the use of a light microscope. The values received from measuring the specimen were then compared with the values received from the impression replicas, and the technique was thereby validated. The impression replica technique overvalued all measured gaps. Depending on location of the three measuring sites, the difference between the specimen and the impression replicas varied from 47 to 130 μm. The impression replica technique overestimates gaps within the range of 2% to 11%. The validation of the replica technique enables the method to be used as a reference when testing other methods for evaluating fit in dentistry. © 2018 by the American College of Prosthodontists.

Coulomb gap triptych in a periodic array of metal nanocrystals.

PubMed

Chen, Tianran; Skinner, Brian; Shklovskii, B I

2012-09-21

The Coulomb gap in the single-particle density of states (DOS) is a universal consequence of electron-electron interaction in disordered systems with localized electron states. Here we show that in arrays of monodisperse metallic nanocrystals, there is not one but three identical adjacent Coulomb gaps, which together form a structure that we call a "Coulomb gap triptych." We calculate the DOS and the conductivity in two- and three-dimensional arrays using a computer simulation. Unlike in the conventional Coulomb glass models, in nanocrystal arrays the DOS has a fixed width in the limit of large disorder. The Coulomb gap triptych can be studied via tunneling experiments.

Carbon Nanotube Conditioning: Ab Initio Simulations of the Effect of Interwall Interaction, Defects And Doping on the Electronic Properties of Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Castillo, Matias Soto

Using carbon nanotubes for electrical conduction applications at the macroscale has been shown to be a difficult task for some time now, mainly, due to defects and impurities present, and lack of uniform electronic properties in synthesized carbon nanotube bundles. Some researchers have suggested that growing only metallic armchair nanotubes and arranging them with an ideal contact length could lead to the ultimate electrical conductivity; however, such recipe presents too high of a cost to pay. A different route is to learn to manage the defects, impurities, and the electronic properties of carbon nanotubes present in bundles grown by current state-of-the-art reactors, so that the electrical conduction of a bundle or even wire may be enhanced. In our work, we have used first-principles density functional theory calculations to study the effect of interwall interaction, defects and doping on the electronic structure of metallic, semi-metal and semiconducting single- and double-walled carbon nanotubes in order to gain a clear picture of their properties. The electronic band gap for a range of zigzag single-walled carbon nanotubes with chiral indices (5,0) - (30,0) was obtained. Their properties were used as a stepping stone in the study of the interwall interaction in double-walled carbon nanotubes, from which it was found that the electronic band gap depends on the type of inner and outer tubes, average diameter, and interwall distance. The effect of vacancy defects was also studied for a range of single-walled carbon nanotubes. It was found that the electronic band gap is reduced for the entire range of zigzag carbon nanotubes, even at vacancy defects concentrations of less than 1%. Finally, interaction potentials obtained via first-principles calculations were generalized by developing mathematical models for the purpose of running simulations at a larger length scale using molecular dynamics of the adsorption doping of diatomic iodine. An ideal adsorption site was found using a stochastic approach and with an adsorption energy higher than other values in the literature.

Value of eddy-covariance data for individual-based, forest gap models

NASA Astrophysics Data System (ADS)

Roedig, Edna; Cuntz, Matthias; Huth, Andreas

2014-05-01

Individual-based forest gap models simulate tree growth and carbon fluxes on large time scales. They are a well established tool to predict forest dynamics and successions. However, the effect of climatic variables on processes of such individual-based models is uncertain (e.g. the effect of temperature or soil moisture on the gross primary production (GPP)). Commonly, functional relationships and parameter values that describe the effect of climate variables on the model processes are gathered from various vegetation models of different spatial scales. Though, their accuracies and parameter values have not been validated for the specific model scales of individual-based forest gap models. In this study, we address this uncertainty by linking Eddy-covariance (EC) data and a forest gap model. The forest gap model FORMIND is applied on the Norwegian spruce monoculture forest at Wetzstein in Thuringia, Germany for the years 2003-2008. The original parameterizations of climatic functions are adapted according to the EC-data. The time step of the model is reduced to one day in order to adapt to the high resolution EC-data. The FORMIND model uses functional relationships on an individual level, whereas the EC-method measures eco-physiological responses at the ecosystem level. However, we assume that in homogeneous stands as in our study, functional relationships for both methods are comparable. The model is then validated at the spruce forest Waldstein, Germany. Results show that the functional relationships used in the model, are similar to those observed with the EC-method. The temperature reduction curve is well reflected in the EC-data, though parameter values differ from the originally expected values. For example at the freezing point, the observed GPP is 30% higher than predicted by the forest gap model. The response of observed GPP to soil moisture shows that the permanent wilting point is 7 vol-% lower than the value derived from the literature. The light response curve, integrated over the canopy and the forest stand, is underestimated compared to the measured data. The EC-method measures a yearly carbon balance of 13 mol(CO2)m-2 for the Wetzstein site. The model with the original parameterization overestimates the yearly carbon balance by nearly 5 mol(CO2)m-2 while the model with an EC-based parameterization fits the measured data very well. The parameter values derived from EC-data are applied on the spruce forest Waldstein and clearly improve estimates of the carbon balance.

Tuning the optical bandgap in multi-cation compound transparent conducting-oxides: The examples of In2ZnO4 and In4Sn3O12

NASA Astrophysics Data System (ADS)

Sabino, Fernando P.; Oliveira, Luiz N.; Wei, Su-Huai; Da Silva, Juarez L. F.

2018-02-01

Transparent conducting oxides such as the bixbyite In2O3 and rutile SnO2 systems have large disparities between the optical and fundamental bandgaps, ΔEgO F , because selection rules forbid dipolar transitions from the top of the valence band to the conduction-band minimum; however, the optical gaps of multi-cation compounds with the same chemical species often coincide with their fundamental gaps. To explain this conundrum, we have employed density-functional theory to compute the optical properties of multi-cation compounds, In2ZnO4 and In4Sn3O12, in several crystal structures. We show that a recently proposed mechanism to explain the disparity between the optical and fundamental gaps of M2O3 (M = Al, Ga, and In) applies also to other binary systems and to multi-compounds. Namely, a gap disparity will arise if the following three conditions are satisfied: (i) the crystal structure has inversion symmetry; (ii) the conduction-band minimum is formed by the cation and O s-orbitals; and (iii) there is strong p-d coupling and weak p-p in the vicinity of the valence-band maximum. The third property depends critically on the cationic chemical species. In the structures with inversion symmetry, Zn (Sn) strengthens (weakens) the p-d coupling in In2ZnO4 (In4Sn3O12), enhancing (reducing) the gap disparity. Furthermore, we have also identified a In4Sn3O12 structure that is 31.80 meV per formula unit more stable than a recently proposed alternative model.

Emergent central pattern generator behavior in gap-junction-coupled Hodgkin-Huxley style neuron model.

PubMed

Horn, Kyle G; Memelli, Heraldo; Solomon, Irene C

2012-01-01

Most models of central pattern generators (CPGs) involve two distinct nuclei mutually inhibiting one another via synapses. Here, we present a single-nucleus model of biologically realistic Hodgkin-Huxley neurons with random gap junction coupling. Despite no explicit division of neurons into two groups, we observe a spontaneous division of neurons into two distinct firing groups. In addition, we also demonstrate this phenomenon in a simplified version of the model, highlighting the importance of afterhyperpolarization currents (I(AHP)) to CPGs utilizing gap junction coupling. The properties of these CPGs also appear sensitive to gap junction conductance, probability of gap junction coupling between cells, topology of gap junction coupling, and, to a lesser extent, input current into our simulated nucleus.

Origin of band gap bowing in dilute GaAs1-xNx and GaP1-xNx alloys: A real-space view

NASA Astrophysics Data System (ADS)

Virkkala, Ville; Havu, Ville; Tuomisto, Filip; Puska, Martti J.

2013-07-01

The origin of the band gap bowing in dilute nitrogen doped gallium based III-V semiconductors is largely debated. In this paper we show the dilute GaAs1-xNx and GaP1-xNx as representative examples that the nitrogen-induced states close to the conduction band minimum propagate along the zigzag chains on the {110} planes. Thereby states originating from different N atoms interact with each other resulting in broadening of the nitrogen-induced states which narrows the band gap. Our modeling based on ab initio theoretical calculations explains the experimentally observed N concentration dependent band gap narrowing both qualitatively and quantitatively.

Tunneling spectroscopy measurements on hydrogen-bonded supramolecular polymers.

PubMed

Vonau, François; Shokri, Roozbeh; Aubel, Dominique; Bouteiller, Laurent; Guskova, Olga; Sommer, Jens-Uwe; Reiter, Günter; Simon, Laurent

2014-07-21

We studied the formation of hydrogen-bonded supramolecular polymers of Ethyl Hexyl Urea Toluene (EHUT) on a gold (111) surface by low temperature scanning tunneling microscopy. Tunneling spectroscopy performed along an individual molecule embedded in a self-assembled layer revealed strong changes in the value of the HOMO-LUMO gap. A variation of the LUMO state is attributed to the effect of space charge accumulation resulting from anisotropic adhesion of the molecule. In addition, for specific tunneling conditions, changes induced through the formation of hydrogen bonds became visible in the differential conductance (dI/dV) maps; isolated molecules, hydrogen bonded dimers and supramolecular polymers of EHUT were distinguishable through their electronic properties.

Black Lives Matter: A Commentary on Racism and Public Health.

PubMed

Jee-Lyn García, Jennifer; Sharif, Mienah Zulfacar

2015-08-01

The recent nonindictments of police officers who killed unarmed Black men have incited popular and scholarly discussions on racial injustices in our legal system, racialized police violence, and police (mis)conduct. What is glaringly absent is a public health perspective in response to these events. We aim to fill this gap and expand the current dialogue beyond these isolated incidents to a broader discussion of racism in America and how it affects the health and well-being of people of color. Our goal is not only to reiterate how salient structural racism is in our society, but how critical antiracist work is to the core goals and values of public health.

Tunneling spectroscopy measurements on hydrogen-bonded supramolecular polymers

NASA Astrophysics Data System (ADS)

Vonau, François; Shokri, Roozbeh; Aubel, Dominique; Bouteiller, Laurent; Guskova, Olga; Sommer, Jens-Uwe; Reiter, Günter; Simon, Laurent

2014-06-01

We studied the formation of hydrogen-bonded supramolecular polymers of Ethyl Hexyl Urea Toluene (EHUT) on a gold (111) surface by low temperature scanning tunneling microscopy. Tunneling spectroscopy performed along an individual molecule embedded in a self-assembled layer revealed strong changes in the value of the HOMO-LUMO gap. A variation of the LUMO state is attributed to the effect of space charge accumulation resulting from anisotropic adhesion of the molecule. In addition, for specific tunneling conditions, changes induced through the formation of hydrogen bonds became visible in the differential conductance (dI/dV) maps; isolated molecules, hydrogen bonded dimers and supramolecular polymers of EHUT were distinguishable through their electronic properties.

Black Lives Matter: A Commentary on Racism and Public Health

PubMed Central

Jee-Lyn García, Jennifer

2015-01-01

The recent nonindictments of police officers who killed unarmed Black men have incited popular and scholarly discussions on racial injustices in our legal system, racialized police violence, and police (mis)conduct. What is glaringly absent is a public health perspective in response to these events. We aim to fill this gap and expand the current dialogue beyond these isolated incidents to a broader discussion of racism in America and how it affects the health and well-being of people of color. Our goal is not only to reiterate how salient structural racism is in our society, but how critical antiracist work is to the core goals and values of public health. PMID:26066958

Orbital superconductivity, defects, and pinned nematic fluctuations in the doped iron chalcogenide FeSe 0.45 Te 0.55

DOE PAGES

Sarkar, Saheli; Van Dyke, John; Sprau, Peter O.; ...

2017-08-09

We demonstrate that the differential conductance, dI/dV , measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe0.45Te0.55, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields nearly isotropic superconducting gaps on the two hole-like Fermi surfaces, and a strongly anisotropic gap on the electron-like Fermi surface. Moreover, we show that the pinning of nematic fluctuations by defects can give rise to a dumbbell-like spatial structure of the induced impurity bound states, and explains the related C 2-symmetry in the Fourier transformed differential conductance.

Orbital superconductivity, defects, and pinned nematic fluctuations in the doped iron chalcogenide FeSe 0.45 Te 0.55

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, Saheli; Van Dyke, John; Sprau, Peter O.

We demonstrate that the differential conductance, dI/dV , measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe0.45Te0.55, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields nearly isotropic superconducting gaps on the two hole-like Fermi surfaces, and a strongly anisotropic gap on the electron-like Fermi surface. Moreover, we show that the pinning of nematic fluctuations by defects can give rise to a dumbbell-like spatial structure of the induced impurity bound states, and explains the related C 2-symmetry in the Fourier transformed differential conductance.

30 CFR 585.815 - What must I do if I have facility damage or an equipment failure?

Code of Federal Regulations, 2014 CFR

2014-07-01

... Conducted Under SAPs, COPs and GAPs Equipment Failure and Adverse Environmental Effects § 585.815 What must... failure under § 585.831, BOEM may require you to revise your SAP, COP, or GAP to describe how you will address the facility damage or failure as required by § 585.634 (COP), § 585.617 (SAP), § 585.655 (GAP...

30 CFR 585.815 - What must I do if I have facility damage or an equipment failure?

Code of Federal Regulations, 2012 CFR

2012-07-01

... Conducted Under SAPs, COPs and GAPs Equipment Failure and Adverse Environmental Effects § 585.815 What must... failure under § 585.831, BOEM may require you to revise your SAP, COP, or GAP to describe how you will address the facility damage or failure as required by § 585.634 (COP), § 585.617 (SAP), § 585.655 (GAP...

30 CFR 585.815 - What must I do if I have facility damage or an equipment failure?

Code of Federal Regulations, 2013 CFR

2013-07-01

... Conducted Under SAPs, COPs and GAPs Equipment Failure and Adverse Environmental Effects § 585.815 What must... failure under § 585.831, BOEM may require you to revise your SAP, COP, or GAP to describe how you will address the facility damage or failure as required by § 585.634 (COP), § 585.617 (SAP), § 585.655 (GAP...

Response of reptile and amphibian communities to canopy gaps created by wind disturbance in the Southern Appalachians

Treesearch

Cathryn H. Greenberg

2001-01-01

Reptile and amphibian communities were sampled in intact gaps created by wind disturbance, salvage-logged gaps, and closed canopy mature forest (controls). Sampling was conducted during June–October in 1997 and 1998 using drift fences with pitfall and funnel traps. Basal area of live trees, shade, leaf litter coverage, and litter depth was highest in controls and...

Effects of quantum confinement and shape on band gap of core/shell quantum dots and nanowires

NASA Astrophysics Data System (ADS)

Gao, Faming

2011-05-01

A quantum confinement model for nanocrystals developed is extended to study for the optical gap shifts in core/shell quantum dots and nanowires. The chemical bond properties and gap shifts in the InP/ZnS, CdSe/CdS, CdSe/ZnS, and CdTe/ZnS core/shell quantum dots are calculated in detail. The calculated band gaps are in excellent agreement with experimental values. The effects of structural taping and twinning on quantum confinement of InP and Si nanowires are elucidated. It is found theoretically that a competition between the positive Kubo energy-gap shift and the negative surface energy shift plays the crucial role in the optical gaps of these nanosystems.

Evidence for k-dependent, in-plane anisotropy of the superconducting gap in Bi2Sr2CaCu2O8+δ

NASA Astrophysics Data System (ADS)

Wells, B. O.; Shen, Z. X.; Dessau, D. S.; Spicer, W. E.; Mitzi, D. B.; Lombardo, L.; Kapitulnik, A.; Arko, A. J.

1992-11-01

We find the superconducting gap in Bi2Sr2CaCu2O8+δ single crystals is anisotropic in k space by roughly a factor of 2 using angle-resolved photoemission spectroscopy. Matching the k-space symmetry of the gap values provides a stringent constraint on theories of the mechanism of high-temperature superconductivity. A review of the literature shows that many puzzling results can be explained by anisotropic gaps in the high-Tc cuprates.

Marginal and Internal Adaptation of Zirconia Crowns: A Comparative Study of Assessment Methods.

PubMed

Cunali, Rafael Schlögel; Saab, Rafaella Caramori; Correr, Gisele Maria; Cunha, Leonardo Fernandes da; Ornaghi, Bárbara Pick; Ritter, André V; Gonzaga, Carla Castiglia

2017-01-01

Marginal and internal adaptation is critical for the success of indirect restorations. New imaging systems make it possible to evaluate these parameters with precision and non-destructively. This study evaluated the marginal and internal adaptation of zirconia copings fabricated with two different systems using both silicone replica and microcomputed tomography (micro-CT) assessment methods. A metal master model, representing a preparation for an all-ceramic full crown, was digitally scanned and polycrystalline zirconia copings were fabricated with either Ceramill Zi (Amann-Girrbach) or inCoris Zi (Dentslpy-Sirona), n=10. For each coping, marginal and internal gaps were evaluated by silicone replica and micro-CT assessment methods. Four assessment points of each replica cross-section and micro-CT image were evaluated using imaging software: marginal gap (MG), axial wall (AW), axio-occlusal angle (AO) and mid-occlusal wall (MO). Data were statistically analyzed by factorial ANOVA and Tukey test (a=0.05). There was no statistically significant difference between the methods for MG and AW. For AO, there were significant differences between methods for Amann copings, while for Dentsply-Sirona copings similar values were observed. For MO, both methods presented statistically significant differences. A positive correlation was observed determined by the two assessment methods for MG values. In conclusion, the assessment method influenced the evaluation of marginal and internal adaptation of zirconia copings. Micro-CT showed lower marginal and internal gap values when compared to the silicone replica technique, although the difference was not always statistically significant. Marginal gap and axial wall assessment points showed the lower gap values, regardless of ceramic system and assessment method used.

Switching of the electrical conductivity of plasticized PVC films under uniaxial pressure

NASA Astrophysics Data System (ADS)

Vlasov, D. V.; Apresyan, L. A.; Vlasova, T. V.; Kryshtob, V. I.

2011-11-01

The jumplike switching of the electrical conductivity in wide-band-gap polymer (antistatic plasticized polyvinylchloride) films under uniaxial pressure is studied. In various plasticized PVC materials, the uniaxial pressure inducing a conductivity jump by four orders of magnitude or higher changes from several to several hundreds of bars, and this effect is retained at a film thickness of several hundred microns, which is two orders of magnitude larger than the critical film thicknesses known for other wide-band-gap polymers. In addition to the earlier interpretation of the conductivity anomalies in plasticized PVC, we proposed a phenomenological electron-molecular dynamic nanotrap model, in which local charge transfer is provided by mobile molecule segments in a plasticized polymer.

Gap detection threshold in the rat before and after auditory cortex ablation.

PubMed

Syka, J; Rybalko, N; Mazelová, J; Druga, R

2002-10-01

Gap detection threshold (GDT) was measured in adult female pigmented rats (strain Long-Evans) by an operant conditioning technique with food reinforcement, before and after bilateral ablation of the auditory cortex. GDT was dependent on the frequency spectrum and intensity of the continuously present noise in which the gaps were embedded. The mean values of GDT for gaps embedded in white noise or low-frequency noise (upper cutoff frequency 3 kHz) at 70 dB sound pressure level (SPL) were 1.57+/-0.07 ms and 2.9+/-0.34 ms, respectively. Decreasing noise intensity from 80 dB SPL to 20 dB SPL produced a significant increase in GDT. The increase in GDT was relatively small in the range of 80-50 dB SPL for white noise and in the range of 80-60 dB for low-frequency noise. The minimal intensity level of the noise that enabled GDT measurement was 20 dB SPL for white noise and 30 dB SPL for low-frequency noise. Mean GDT values at these intensities were 10.6+/-3.9 ms and 31.3+/-4.2 ms, respectively. Bilateral ablation of the primary auditory cortex (complete destruction of the Te1 and partial destruction of the Te2 and Te3 areas) resulted in an increase in GDT values. The fifth day after surgery, the rats were able to detect gaps in the noise. The values of GDT observed at this time were 4.2+/-1.1 ms for white noise and 7.4+/-3.1 ms for low-frequency noise at 70 dB SPL. During the first month after cortical ablation, recovery of GDT was observed. However, 1 month after cortical ablation GDT still remained slightly higher than in controls (1.8+/-0.18 for white noise, 3.22+/-0.15 for low-frequency noise, P<0.05). A decrease in GDT values during the subsequent months was not observed.

A comprehensive study of g-factors, elastic, structural and electronic properties of III-V semiconductors using hybrid-density functional theory

NASA Astrophysics Data System (ADS)

Bastos, Carlos M. O.; Sabino, Fernando P.; Sipahi, Guilherme M.; Da Silva, Juarez L. F.

2018-02-01

Despite the large number of theoretical III-V semiconductor studies reported every year, our atomistic understanding is still limited. The limitations of the theoretical approaches to yield accurate structural and electronic properties on an equal footing, is due to the unphysical self-interaction problem that mainly affects the band gap and spin-orbit splitting (SOC) in semiconductors and, in particular, III-V systems with similar magnitude of the band gap and SOC. In this work, we report a consistent study of the structural and electronic properties of the III-V semiconductors by using the screening hybrid-density functional theory framework, by fitting the α parameters for 12 different III-V compounds, namely, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb, to minimize the deviation between the theoretical and experimental values of the band gap and SOC. Structural relaxation effects were also included. Except for AlP, whose α = 0.127, we obtained α values that ranged from 0.209 to 0.343, which deviate by less than 0.1 from the universal value of 0.25. Our results for the lattice parameter and elastic constants indicate that the fitting of α does not affect those structural parameters when compared with the HSE06 functional, where α = 0.25. Our analysis of the band structure based on the k ṡ p method shows that the effective masses are in agreement with the experimental values, which can be attributed to the simultaneous fitting of the band gap and SOC. Also, we estimate the values of g-factors, extracted directly from the band structure, which are close to experimental results, which indicate that the obtained band structure produced a realistic set of k ṡ p parameters.

Electronic structure of p-type transparent conducting oxide CuAlO2

NASA Astrophysics Data System (ADS)

Mo, Sung-Kwan; Yoon, Joonseok; Liu, Xiaosong; Yang, Wanli; Mun, Bongjin; Ju, Honglyoul

2014-03-01

CuAlO2 is a prototypical p-type transparent conducting oxide. Despite its importance for potential applications and number of studies on its band structure and gap characteristics, experimental study on the momentum-resolved electronic structure has been lacking. We present angle-resolved photoemission data on single crystalline CuAlO2 using synchrotron light source to reveal complete band structure. Complemented by the x-ray absorption and emission spectra, we also study band gap characteristics and compare them with theory.

Maintenance of working capacity of movement mechanism of load trolley with linear traction electric drive of bridge type crane.

NASA Astrophysics Data System (ADS)

Goncharov, K. A.; Denisov, I. A.

2017-10-01

The article considers the influence of the air gap size between the linear motor elements on the stability of the traction drive of the movement mechanism of the trolley of the bridge type crane. The main factors affecting the air gap size and the causes of their occurrence are described. The technique of calculating the magnitude of air gap variation is described in relation to the general deformation of the crane metal structure. Recommendations on the need for installation of additional equipment for load trolleys of various designs are given. The optimal values of the length of the trolley base are proposed. Observance of these values ensures normal operation of the traction drive.

The energy gap in a-Si 1 - xC g: H alloys

NASA Astrophysics Data System (ADS)

Valladares, Ariel A.; Valladares, Alexander; Enrique Sansores, L.; Nelis, Mary Ann Me

1997-02-01

The electronic structure of amorphous tetrahedral clusters of the type a-Si 1 - xC g: H are studied using the pseudopotential SCF Hartree-Fock approximation. The reduced energy gap isgiven by Egr( x) - 1 + 0.84 x for x ⩽ 0.5, whereas experimentally Egr( x) = 1 + 0.96 x. For x ⩾ 0.5 the dip in the gap value reported experimentally is verified.

Dijets with 2, 1 or 0 rapidity gap: factorization breaking at the Tevatron

NASA Astrophysics Data System (ADS)

Bialas, A.; Peschanski, R.

2003-11-01

Central production cross-sections of hard dijets with 2, 1 or 0 rapidity gap at Tevatron are analyzed in terms of diffractive ("a la Good-Walker") and non-diffractive fluctuations of the incident particles. The observed large factorization breaking and the unexpected high value of the 2 to 1 gap cross-section ratio are explained in terms of scattering with and between the incident particles.

Influence of different gaps among the split targets with gradient potential to the discharge effects generated by hypervelocity impact

NASA Astrophysics Data System (ADS)

Tang, Enling; Zhao, Liangliang; Han, Yafei; Zhang, Qingming; Wang, Ruizhi; He, Liping; Liu, Shuhua

2018-04-01

Due to the actual situation of spacecraft surface' charging, such as convex corners, weld line, whalebone and a multiple-interfaces with different materials, all these are main factors leading to uneven charging of spacecraft surface, even creating gradient potential. If the charging spacecraft surface is impacted by debris or micrometeor, discharge effect induced by impacting will pose a serious threat to spacecraft in orbit. So realizing spacecraft charging surface with different potential differences and grasping discharge characteristics are a decisive importance at the different experimental conditions in laboratory. To simulate the spacecraft surface with a gradient potential in laboratory, spacecraft surface is split into different parts, which different gaps reserved in 2 adjacent surface is added resistance to create different potential surfaces, and the high potential surface as a impact target in the split targets. Charging circuit system realizing different gradient potential and discharge test system are built by ourselves, combining with two-stage light gas gun loading system, six sets of experiments have been performed about hypervelocity impact on 2A12 aluminum split targets with gradient potentials. In the experiments, gaps of 2A12 aluminum target are the same among different parts in every experiments, the gaps of the split targets are 2mm, 3mm, 5mm, 7mm and 10mm in the experiments, respectively. And the applied voltage is 300V in all the experiments and high-potential 2A12 aluminum plate as the impact target. The experiments have been performed at the impact velocity of about 3km/s and the incidence angles of 60o and 90o (between projectile flying trajectory and target plane), respectively. Voltage probe and current probes are used for acquiring discharge voltages and currents during the process of the impact. The experimental results showed that the discharge induced by impact plasma were generated among high and low-potential target by forming a plasma discharge channel. With the increasing of the gaps among the high and low-potential targets, the peak values of the discharge current decreased first then increased. When the gaps of split targets reached a certain value, the peak values of the discharge current decreased again. Meanwhile, the gaps among high and low-potential targets was 5mm, the peak value of the discharge current was the smallest. With the increasing of the gaps among the split targets, a primary discharge duration also increased. However, when the gaps among the split targets were greater than 5mm, increasing trend of discharge duration would slow down. When the gaps among the split targets were greater than 7mm, there was a secondary discharge phenomenon, and the physical explanations were given about the influence of different gaps among the split targets on the discharge effects created by hypervelocity impact.

Optical and structural properties of amorphous Se x Te100- x aligned nanorods

NASA Astrophysics Data System (ADS)

Al-Agel, Faisal A.

2013-12-01

In the present work, we report studies on optical and structural phenomenon in as-deposited thin films composed of aligned nanorods of amorphous Se x Te100- x ( x = 3, 6, 9, and 12). In structural studies, field emission scanning electron microscopic (FESEM) images suggest that these thin films contain high yield of aligned nanorods. These nanorods show a completely amorphous nature, which is verified by X-ray diffraction patterns of these thin films. Optical studies include the measurement of spectral dependence of absorption, reflection, and transmission of these thin films, respectively. On the basis of optical absorption data, a direct optical band gap is observed. This observation of a direct optical band gap in these nanorods is interesting as chalcogenides normally show an indirect band gap, and due to this reason, these materials could not become very popular for semiconducting devices. Therefore, this is an important report and will open up new directions for the application of these materials in semiconducting devices. The value of this optical band gap is found to decrease with the increase in selenium (Se) concentration. The reflection and absorption data are employed to estimate the values of optical constants (extinction coefficient ( k) and refractive index ( n)). From the spectral dependence of these optical constants, it is found that the values of refractive index ( n) increase, whereas the values of extinction coefficient ( k) decrease with the increase in photon energy. The real and imaginary parts of dielectric constants calculated with the values of extinction coefficient ( k) and refractive index ( n), are found to vary with photon energy and dopant concentration.

Approach to the evaluation of a patient with an increased serum osmolal gap and high-anion-gap metabolic acidosis.

PubMed

Kraut, Jeffrey A; Xing, Shelly Xiaolei

2011-09-01

An increase in serum osmolality and serum osmolal gap with or without high-anion-gap metabolic acidosis is an important clue to exposure to one of the toxic alcohols, which include methanol, ethylene glycol, diethylene glycol, propylene glycol, or isopropanol. However, the increase in serum osmolal gap and metabolic acidosis can occur either together or alone depending on several factors, including baseline serum osmolal gap, molecular weight of the alcohol, and stage of metabolism of the alcohol. In addition, other disorders, including diabetic or alcoholic ketoacidosis, acute kidney injury, chronic kidney disease, and lactic acidosis, can cause high-anion-gap metabolic acidosis associated with an increased serum osmolal gap and therefore should be explored in the differential diagnosis. It is essential for clinicians to understand the value and limitations of osmolal gap to assist in reaching the correct diagnosis and initiating appropriate treatment. In this teaching case, we present a systematic approach to diagnosing high serum osmolality and increased serum osmolal gap with or without high-anion-gap metabolic acidosis. Published by Elsevier Inc.

Negative space charge effects in photon-enhanced thermionic emission solar converters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Segev, G.; Weisman, D.; Rosenwaks, Y.

2015-07-06

In thermionic energy converters, electrons in the gap between electrodes form a negative space charge and inhibit the emission of additional electrons, causing a significant reduction in conversion efficiency. However, in Photon Enhanced Thermionic Emission (PETE) solar energy converters, electrons that are reflected by the electric field in the gap return to the cathode with energy above the conduction band minimum. These electrons first occupy the conduction band from which they can be reemitted. This form of electron recycling makes PETE converters less susceptible to negative space charge loss. While the negative space charge effect was studied extensively in thermionicmore » converters, modeling its effect in PETE converters does not account for important issues such as this form of electron recycling, nor the cathode thermal energy balance. Here, we investigate the space charge effect in PETE solar converters accounting for electron recycling, with full coupling of the cathode and gap models, and addressing conservation of both electric and thermal energy. The analysis shows that the negative space charge loss is lower than previously reported, allowing somewhat larger gaps compared to previous predictions. For a converter with a specific gap, there is an optimal solar flux concentration. The optimal solar flux concentration, the cathode temperature, and the efficiency all increase with smaller gaps. For example, for a gap of 3 μm the maximum efficiency is 38% and the optimal flux concentration is 628, while for a gap of 5 μm the maximum efficiency is 31% and optimal flux concentration is 163.« less

Role of surface energy on the morphology and optical properties of GaP micro & nano structures grown on polar and non-polar substrates

NASA Astrophysics Data System (ADS)

Roychowdhury, R.; Kumar, Shailendra; Wadikar, A.; Mukherjee, C.; Rajiv, K.; Sharma, T. K.; Dixit, V. K.

2017-10-01

Role of surface energy on the morphology, crystalline quality, electronic structure and optical properties of GaP layer grown on Si (001), Si (111), Ge (111) and GaAs (001) is investigated. GaP layers are grown on four different substrates under identical growth kinetics by metal organic vapour phase epitaxy. The atomic force microscopy images show that GaP layer completely covers the surface of GaAs substrate. On the other hand, the surfaces of Si (001), Si (111), Ge (111) substrates are partially covered with crystallographically morphed GaP island type micro and nano-structures. Origin of these crystallographically morphed GaP island is explained by the theoretical calculation of surface energy of the layer and corresponding substrates respectively. The nature of GaP island type micro and nano-structures and layers are single crystalline with existence of rotational twins on Si and Ge (111) substrates which is confirmed by the phi, omega and omega/2theta scans of high resolution x-ray diffraction. The electronic valence band offsets between the GaP and substrates have been determined from the valence band spectra of ultraviolet photoelectron spectroscopy. The valence electron plasmon of GaP are investigated by studying the energy values of Ga (3d) core level along with loss peaks in the energy dependent photoelectron spectra. The peak observed within the range of 3-6 eV from the Ga (3d) core level in the photoelectron spectra are associated to inter band transitions as their energy values are estimated from the pseudo dielectric function by the spectroscopic ellipsometry.

Spatial Noise in Coupling Strength and Natural Frequency within a Pacemaker Network; Consequences for Development of Intestinal Motor Patterns According to a Weakly Coupled Phase Oscillator Model

PubMed Central

Parsons, Sean P.; Huizinga, Jan D.

2016-01-01

Pacemaker activities generated by networks of interstitial cells of Cajal (ICC), in conjunction with the enteric nervous system, orchestrate most motor patterns in the gastrointestinal tract. It was our objective to understand the role of network features of ICC associated with the myenteric plexus (ICC-MP) in the shaping of motor patterns of the small intestine. To that end, a model of weakly coupled oscillators (oscillators influence each other's phase but not amplitude) was created with most parameters derived from experimental data. The ICC network is a uniform two dimensional network coupled by gap junctions. All ICC generate pacemaker (slow wave) activity with a frequency gradient in mice from 50/min at the proximal end of the intestine to 40/min at the distal end. Key features of motor patterns, directly related to the underlying pacemaker activity, are frequency steps and dislocations. These were accurately mimicked by reduction of coupling strength at a point in the chain of oscillators. When coupling strength was expressed as a product of gap junction density and conductance, and gap junction density was varied randomly along the chain (i.e., spatial noise) with a long-tailed distribution, plateau steps occurred at pointsof low density. As gap junction conductance was decreased, the number of plateaus increased, mimicking the effect of the gap junction inhibitor carbenoxolone. When spatial noise was added to the natural interval gradient, as gap junction conductance decreased, the number of plateaus increased as before but in addition the phase waves frequently changed direction of apparent propagation, again mimicking the effect of carbenoxolone. In summary, key features of the motor patterns that are governed by pacemaker activity may be a direct consequence of biological noise, specifically spatial noise in gap junction coupling and pacemaker frequency. PMID:26869875

Structural, electrical and optical properties of Al-Sn codoped ZnO transparent conducting layer deposited by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Bedia, A.; Bedia, F. Z.; Aillerie, M.; Maloufi, N.

2017-11-01

Low cost Al-Sn codoped ZnO (ATZO) Transparent Conductive Oxide films were deposited by spray pyrolysis on glass substrate. The influence of Al-Sn codoping on the structural, optical and electrical properties of ZnO thin films was studied by comparing the same properties obtained in undoped ZnO, Al doped ZnO (AZO) and Sn doped ZnO (TZO) thin films. The so-obtained films crystallized in hexagonal wurtzite structure. The morphology and structural defects have been investigated by both High resolution Field Effect Scanning Electron Microscopy (FE-SEM) and Raman spectroscopy at 532 nm excitation source. In the visible region, the undoped and doped films show an average transmittance of the order of 85%, while for ATZO thin film, it is of the order of 72%, which points out a degradation of the optical properties due to the co-doping. The optical band gap of ATZO thin film achieves 3.31eV and this shift, compared to the referred samples is attributed to the Burstein-Moss (BM) and band gap narrowing (BGN) opposite effects which is due to the increase of the carrier concentration in degenerate semiconductors. Within all the samples, the ATZO thin film exhibits the lowest electrical resistivity of 4.56 × 10-3 Ωcm with a Hall mobility equal to 2.13 cm2 V-1s-1, and the highest carrier concentration of 6.41 × 1020 cm-3. The performance of ATZO transparent conductive oxide film are determined by its figure of merit (φTC), found equal to 1.69 10-4 Ω-1, which is a suitable value for potentially high-performance solar cell applications.

Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by cyclic atomic layer reduction technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Si-Yong; Hsieh, Chien-Te; Lin, Tzu-Wei

The present work develops an atomic layer reduction (ALR) method to accurately tune oxidation level, electrical conductance, band-gap structure, and photoluminescence (PL) response of graphene oxide (GO) sheets. The ALR route is carried out at 200 °C within ALR cycle number of 10–100. The ALR treatment is capable of striping surface functionalities (e.g., hydroxyl, carbonyl, and carboxylic groups), producing thermally-reduced GO sheets. The ALR cycle number serves as a controlling factor in adjusting the crystalline, surface chemistry, electrical, optical properties of GO sheets. With increasing the ALR cycle number, ALR-GO sheets display a high crystallinity, a low oxidation level, anmore » improved electrical conductivity, a narrow band gap, and a tunable PL response. Finally, on the basis of the results, the ALR technique offers a great potential for accurately tune electrical and optical properties of carbon materials through the cyclic removal of oxygen functionalities, without any complicated thermal and chemical desorption processes.« less

Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by cyclic atomic layer reduction technique

DOE PAGES

Gu, Si-Yong; Hsieh, Chien-Te; Lin, Tzu-Wei; ...

2018-05-12

The present work develops an atomic layer reduction (ALR) method to accurately tune oxidation level, electrical conductance, band-gap structure, and photoluminescence (PL) response of graphene oxide (GO) sheets. The ALR route is carried out at 200 °C within ALR cycle number of 10–100. The ALR treatment is capable of striping surface functionalities (e.g., hydroxyl, carbonyl, and carboxylic groups), producing thermally-reduced GO sheets. The ALR cycle number serves as a controlling factor in adjusting the crystalline, surface chemistry, electrical, optical properties of GO sheets. With increasing the ALR cycle number, ALR-GO sheets display a high crystallinity, a low oxidation level, anmore » improved electrical conductivity, a narrow band gap, and a tunable PL response. Finally, on the basis of the results, the ALR technique offers a great potential for accurately tune electrical and optical properties of carbon materials through the cyclic removal of oxygen functionalities, without any complicated thermal and chemical desorption processes.« less

Pseudogap and conduction dimensionalities in high-Tc superconductors

NASA Astrophysics Data System (ADS)

Das Arulsamy, Andrew; Ong, P. C.; Ong, M. T.

2003-01-01

The nature of normal state charge-carriers' dynamics and the transition in conduction and gap dimensionalities between 2D and 3D for YBa2Cu3O7-δ and Bi2Sr2Ca1- xYxCu2O8 high-Tc superconductors were described by computing and fitting the resistivity curves, /ρ(T,δ,x). These were carried out by utilizing the 2D and 3D Fermi liquid and ionization energy (EI) based resistivity models coupled with charge-spin separation based /t-/J model (Phys. Rev. B 64 (2001) 104516). /ρ(T,δ,x) curves of Y123 and Bi2212 samples indicate the beginning of the transition of conduction and gap from 2D to 3D with reduction in oxygen content /(7-δ) and Ca2+(1-x) as such, /c-axis pseudogap could be a different phenomenon from superconductor and spin gaps. These models also indicate that the recent MgB2 superconductor is at least not Y123 or Bi2212 type.

Development of mix design procedures for gap-graded asphalt-rubber asphalt concrete

DOT National Transportation Integrated Search

2007-11-01

A research project was conducted to identify and document current modifications to ARIZONA 815c (75-blow Marshall method) used to develop gap-graded asphalt rubber asphalt concrete (GG AR AC) mix designs, and to develop and test improvements to provi...

Discussing Conflict in Contemporary China

ERIC Educational Resources Information Center

Miletic, Tania; Bretherton, Diane

2016-01-01

The research suggests there is a gap in the peace studies and conflict resolution literature, with little representation or understanding of Chinese perspectives. In a project to address this gap, the researchers conducted interviews individually with 30 participants identified as "emerging leaders," who came from diverse universities…

A Capstone Project Using the Gap Analysis Model: Closing the College Readiness Gap for Latino English Language Learners with a Focus on College Affordability and Student Grades

ERIC Educational Resources Information Center

Kurland, Michael A. T.

2013-01-01

This capstone dissertation inquiry project focused on the underperformance of English language learners (ELLs) at a high school. The Clark and Estes' (2008) gap analysis model was the analytical framework used to conduct this inquiry. At the request of the school, the inquiry focus was on gaining a better understanding of the underachievement…

Gap heating with pressure gradients. [for Shuttle Orbiter thermal protection system tiles

NASA Technical Reports Server (NTRS)

Scott, C. D.; Maraia, R. J.

1979-01-01

The heating rate distribution and temperature response on the gap walls of insulating tiles is analyzed to determine significant phenomena and parameters in flows where there is an external surface pressure gradient. Convective heating due to gap flow, modeled as fully developed pipe flow, is coupled with a two-dimensional thermal model of the tiles that includes conduction and radiative heat transfer. To account for geometry and important environmental parameters, scale factors are obtained by curve-fitting measured temperatures to analytical solutions. These scale factors are then used to predict the time-dependent gap heat flux and temperature response of tile gaps on the Space Shuttle Orbiter during entry.

Problem-based, peer-to-peer global mental health e-learning between the UK and Somaliland: a pilot study.

PubMed

Murphy, Roberta; Clissold, Elliot; Keynejad, Roxanne C

2017-11-01

WHO's mental health gap action programme intervention guide (mhGAP-IG) is an evidence-based tool aimed at front-line health workers in low-income and middle-income countries (LMICs). Its potential to improve global mental health education, especially through digital technologies, has been little studied. Problem-based learning (PBL) is usually conducted face-to-face, but its remote application could facilitate cross-cultural education. To evaluate PBL, applied to peer-to-peer global mental health e-learning (Aqoon), using mhGAP-IG. Twelve pairs of UK and Somaliland medical students completed the full programme. Participants self-directedly met online, via the low-bandwidth Medicine Africa website, for PBL-style tutorials focused on modules of the mhGAP-IG, V.2.0. Preparticipation and postparticipation surveys used mixed methods to evaluate Aqoon, including the Attitudes Toward Psychiatry (ATP-30) instrument. Median ATP-30 scores for Somaliland (82.0 vs 95.0, p=0.003) and UK students (82.0 vs 95.0, p = 0.011) improved significantly following Aqoon. Qualitative feedback showed that participants valued peer connectivity and learning about cultural and psychosocial differences in their partner's country. Somaliland students were motivated by clinical learning and UK students by global health education. Feedback on the PBL structure was positive. Digital PBL represents an innovative method to extend the benefits of mhGAP-IG beyond front-line clinical staff, to healthcare students in LMICs. Educational resource limitations in LMICs may be overcome using digital platforms and PBL. Replication with non-medical healthcare students is the next step for this model to explore Aqoon's relevance to pressing global mental health workforce challenges. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

[Study of cubic boron nitride crystal UV absorption spectroscopy].

PubMed

Liu, Hai-Bo; Jia, Gang; Chen, Gang; Meng, Qing-Ju; Zhang, Tie-Chen

2008-07-01

UV absorption spectroscopy of artificial cubic boron nitride (cBN) single crystal flake, synthesized under high-temperature and high-pressure, was studied in the present paper. UV WINLAB spectrometer was used in the experiments, and MOLECULAR SPECTROSCOPY software was used for data analysis. The UV-cBN limit of 198 nm was showed in this test by a special fixture quartz sample. We calculated the energy gap by virtue of the formula: lambda0 = 1.24/E(g) (microm). The energy gap is 6. 26 eV. There are many viewpoints about the gap of cBN. By using the first-principles theory to calculate energy band structure and density of electronic states of cBN, an indirect transition due to electronics in valence band jumping into conduction band by absorbing photon can be confirmed. That leads to UV absorption. The method of calculation was based on the quantum mechanics of CASTEP in the commercial software package of Cerius2 in the Co. Accerlrys in the United States. The theory of CASTEP is based on local density approximation or gradient corrected LDA. The crystal parameter of cBN was input to the quantum mechanics of CASTEP in order to construct the crystal parameter model of cBN. We calculated the energy gap of cBN by the method of gradient corrected LDA. The method underestimates the value of nonconductor by about 1 to 2 eV. We gaot some opinions as follows: cBN is indirect band semiconductor. The energy gap is 4.76 eV, less than our experiment. The reason may be defect that we ignored in calculating process. It was reported that the results by first principles method of calculation of the band generally was less than the experimental results. This paper shows good UV characteristics of cBN because of the good agreement of experimental results with the cBN band width. That is a kind of development prospect of UV photo-electronic devices and high-temperature semiconductor devices.

Efficiency arcjet thruster with controlled arc startup and steady state attachment

NASA Technical Reports Server (NTRS)

Smith, William W. (Inventor); Knowles, Steven C. (Inventor)

1989-01-01

An improved efficiency arcjet thruster has a constrictor and electrically-conductive nozzle anode defining an arc chamber, and an electrically-conductive rod having a tip spaced upstream from the constrictor and defining a cathode spaced from the anode by a gap generally coextensive with the arc chamber. An electrical potential is applied to the anode and cathode to generate an electrical arc in the arc chamber from the cathode to anode. Catalytically decomposed hydrazine is supplied to the arc chamber with generation of the arc so as to produce thermal heating and expansion thereof through the nozzle. The constrictor can have a electrically insulative portion disposed between the cathode tip and the nozzle anode, and an electrically-conductive anode extension disposed along the insulative portion so as to define an auxiliary gap with the cathode tip substantially smaller than the gap defined between the cathode and nozzle anode for facilitating startup of arc generation. The constrictor can also include an electrically-conductive electrode with a variable electrical potential to vary the shape of the arc generated in the arc chamber. Also, the cathode is mounted for axial movement such that the gap between its tip and the nozzle anode can be varied to facilitate a generally nonerosive generation of the electrical arc at startup and reliable steady state operation. Further, the arc chamber can have a nonparallel subsonic-to-supersonic transition configuration, or alternatively solely a nonparallel supersonic configuration, for improved arc attachment.

A comparative study of thermoelectric properties of CuGaTe2 by using PBE and MBJ potentials

NASA Astrophysics Data System (ADS)

Sharma, Sonu; Singh, Birender; Kumar, Pradeep

2018-04-01

We have investigated the electronic and thermoelectric properties of CuGaTe2 by combining the first principle calculations with Boltzmann transport theory. The electronic properties show that CuGaTe2 is a direct band semiconductor with large band gap at r-point. The band gaps are computed by using PBE and mBJ potentials and value obtained with mBJ is much closer to the experimental value. Partial density of states plots show that the band gap is formed by the hybridization between 3d states of Cu atom, 4s and 4p states of Ga atom and 5p states of Te atom. Very large value (˜300 µVK-1) of Seebeck coefficient is obtained for this compound. Figure-of-merit calculated by using transport coefficients is also found to be very large for the entire temperature range and CuGaTe2 is a good thermoelectric material.

Electronic properties of copper aluminate examined by three theoretical approaches

NASA Astrophysics Data System (ADS)

Christensen, Niels; Svane, Axel

2010-03-01

Electronic properties of 3R.CuAlO2 are derived vs. pressure from ab initio band structure calculations within the local-density approximation (LDA), LDA+U scheme as well as the quasiparticle self-consistent GW approximation (QSGW, van Schilfgaarde, Kotani, and Falaev). The LDA underestimates the gap and places the Cu-3d states at too high energies. An effective U value, 8.2 eV, can be selected so that LDA+U lowers the 3d states to match XPS data and such that the lowest gap agrees rather well with optical absorption experiments. The electrical field gradient (EFG) on Cu is in error when calculated within the LDA. The agreement with experiment can be improved by LDA+U, but a larger U, 13.5 eV, is needed for full adjustment. QSGW yields correct Cu-EFG and, when electron-hole correlations are included, also correct band gaps. The QSGW and LDA band gap deformation potential values differ significantly.

Origin of multiple band gap values in single width nanoribbons

PubMed Central

Goyal, Deepika; Kumar, Shailesh; Shukla, Alok; Kumar, Rakesh

2016-01-01

Deterministic band gap in quasi-one-dimensional nanoribbons is prerequisite for their integrated functionalities in high performance molecular-electronics based devices. However, multiple band gaps commonly observed in graphene nanoribbons of the same width, fabricated in same slot of experiments, remain unresolved, and raise a critical concern over scalable production of pristine and/or hetero-structure nanoribbons with deterministic properties and functionalities for plethora of applications. Here, we show that a modification in the depth of potential wells in the periodic direction of a supercell on relative shifting of passivating atoms at the edges is the origin of multiple band gap values in nanoribbons of the same width in a crystallographic orientation, although they carry practically the same ground state energy. The results are similar when calculations are extended from planar graphene to buckled silicene nanoribbons. Thus, the findings facilitate tuning of the electronic properties of quasi-one-dimensional materials such as bio-molecular chains, organic and inorganic nanoribbons by performing edge engineering. PMID:27808172

Spark gap device for precise switching

DOEpatents

Boettcher, Gordon E.

1984-01-01

A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centrigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed chamber filled with an inert, ionizable gas, such as pure xenon. A quantity of solid radioactive carbon-14 within the chamber adjacent the spark gap serves as a radiation stabilizer. The sides of the electrodes and the inner wall of the insulating cylinder are spaced apart a sufficient distance to prevent unwanted breakdown initiation. A conductive sleeve may envelop the outside of the insulating member from the midpoint of the spark gap to the cap adjacent the cathode. The outer metallic surfaces of the device may be coated with a hydrogen-impermeable coating to lengthen the shelf life and operating life of the device. The device breaks down at about 1,700 volts for input voltage rates up to 570 volts/millisecond and allows peak discharge currents of up to 3,000 amperes from a 0.3 microfarad energy storage capacitor for more than 1,000 operations.

Making the Case for the Outlier: Researcher Reflections of an African-American Female Deputy Superintendent Who Decided to Close the Achievement Gap

ERIC Educational Resources Information Center

Beard, Karen Stansberry

2012-01-01

This article presents researcher reflections of a case study of a Black female deputy superintendent who made the value-driven decision to close the achievement gap in her district. I posit that she is an outlier because she is Black and female in a predominantly white male field of practice, she effectively closed the achievement gap through her…

Fully gapped superconductivity in single crystals of noncentrosymmetric Re6Zr with broken time-reversal symmetry

NASA Astrophysics Data System (ADS)

Pang, G. M.; Nie, Z. Y.; Wang, A.; Singh, D.; Xie, W.; Jiang, W. B.; Chen, Y.; Singh, R. P.; Smidman, M.; Yuan, H. Q.

2018-06-01

The noncentrosymmetric superconductor Re6Zr has attracted much interest due to the observation of broken time-reversal symmetry in the superconducting state. Here we report an investigation of the superconducting gap structure of Re6Zr single crystals by measuring the magnetic penetration depth shift Δ λ (T ) and electronic specific heat Ce(T ) . Δ λ (T ) exhibits an exponential temperature dependence behavior for T ≪Tc , which indicates a fully open superconducting gap. Our analysis shows that a single gap s -wave model is sufficient to describe both the superfluid density ρs(T ) and Ce(T ) results, with a fitted gap magnitude larger than the weak coupling BCS value, providing evidence for fully gapped superconductivity in Re6Zr with moderate coupling.

Determination of shelf heat transfer coefficients along the shelf flow path of a freeze dryer using the shelf fluid temperature perturbation approach.

PubMed

Kuu, Wei Y; Nail, Steven L; Hardwick, Lisa M

2007-01-01

The spatial distribution of local shelf heat transfer coefficients, Ks, was determined by mapping the transient temperature response of the shelf surface along the serpentine internal channels of the shelf while the temperature of the heat transfer fluid was ramped from -40 degrees to 40 degrees C. The solution of a first-order non-steady-state differential equation resulted in a predicted shelf surface temperature as a function of the shelf fluid temperature at any point along the flow path. During the study, the shelf surfaces were maintained under a thermally insulated condition so that the heat transfers by gas conduction and radiation were negligible. To minimize heat conduction by gas, the chamber was evacuated to a low pressure, such as 100 mTorr. To minimize heat transfers between shelves, shelves were moved close together, with a gap of approximately 3 mm between any two shelves, because the shelf surface temperatures at corresponding vertical locations of two shelves are virtually equal. In addition, this also provides a shielding from radiation heat transfer from shelf to walls. Local heat transfer coefficients at the probed locations h(x) ( approximately Ks) were calculated by fitting the experimental shelf temperature response to the theoretical value. While the resulting values of K(s) are in general agreement with previously reported values, the values of Ks close to the inlet are significantly higher than those of other locations of the shelf channel. This observation is most likely attributed to the variation of the flow pattern of heat transfer fluid within the channels.

A simplified approach to the band gap correction of defect formation energies: Al, Ga, and In-doped ZnO

NASA Astrophysics Data System (ADS)

Saniz, R.; Xu, Y.; Matsubara, M.; Amini, M. N.; Dixit, H.; Lamoen, D.; Partoens, B.

2013-01-01

The calculation of defect levels in semiconductors within a density functional theory approach suffers greatly from the band gap problem. We propose a band gap correction scheme that is based on the separation of energy differences in electron addition and relaxation energies. We show that it can predict defect levels with a reasonable accuracy, particularly in the case of defects with conduction band character, and yet is simple and computationally economical. We apply this method to ZnO doped with group III elements (Al, Ga, In). As expected from experiment, the results indicate that Zn substitutional doping is preferred over interstitial doping in Al, Ga, and In-doped ZnO, under both zinc-rich and oxygen-rich conditions. Further, all three dopants act as shallow donors, with the +1 charge state having the most advantageous formation energy. Also, doping effects on the electronic structure of ZnO are sufficiently mild so as to affect little the fundamental band gap and lowest conduction bands dispersion, which secures their n-type transparent conducting behavior. A comparison with the extrapolation method based on LDA+U calculations and with the Heyd-Scuseria-Ernzerhof hybrid functional (HSE) shows the reliability of the proposed scheme in predicting the thermodynamic transition levels in shallow donor systems.

The effects of the chemical composition and strain on the electronic properties of GaSb/InAs core-shell nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ning, Feng; Wang, Dan; Tang, Li-Ming, E-mail: lmtang@hnu.edu.cn

2014-09-07

The effects of the chemical composition and strain on the electronic properties of [111] zinc-blende (ZB) and [0001] wurtzite (WZ) GaSb/InAs core-shell nanowires (NWs) with different core diameters and shell thicknesses are studied using first-principles methods. The band structures of the [111] ZB GaSb/InAs core-shell NWs underwent a noticeable type-I/II band alignment transition, associated with a direct-to-indirect band gap transition under a compressive uniaxial strain. The band structures of the [0001] WZ GaSb/InAs core-shell NWs preserved the direct band gap under either compressive or tensile uniaxial strains. In addition, the band gaps and the effective masses of the carriers couldmore » be tuned by their composition. For the core-shell NWs with a fixed GaSb-core size, the band gaps decreased linearly with an increasing InAs-shell thickness, caused by the significant downshift of the conduction bands. For the [111] ZB GaSb/InAs core-shell NWs, the calculated effective masses indicated that the transport properties could be changed from hole-dominated conduction to electron-dominated conduction by changing the InAs-shell thickness.« less

Psychosocial Characteristics of Optimum Performance in Isolated and Confined Environments (ICE)

NASA Technical Reports Server (NTRS)

Palinkas, Lawrence A.; Keeton, Kathryn E.; Shea, Camille; Leveton, Lauren B.

2010-01-01

The Behavioral Health and Performance (BHP) Element addresses human health risks in the NASA Human Research Program (HRP), including the Risk of Adverse Behavioral Conditions and the Risk of Psychiatric Disorders. BHP supports and conducts research to help characteristics and mitigate the Behavioral Medicine risk for exploration missions, and in some instances, current Flight Medical Operations. The Behavioral Health and Performance (BHP) Element identified research gaps within the Behavioral Medicine Risk, including Gap BMed6: What psychosocial characteristics predict success in an isolated, confined environment (ICE)? To address this gap, we conducted an extensive and exhaustive literature review to identify the following: 1) psychosocial characteristics that predict success in ICE environments; 2) characteristics that are most malleable; and 3) specific countermeasures that could enhance malleable characteristics.