Science.gov

Sample records for barrier energy difference

  1. Fusion of Si28+Si28,30: Different trends at sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Montagnoli, G.; Stefanini, A. M.; Esbensen, H.; Jiang, C. L.; Corradi, L.; Courtin, S.; Fioretto, E.; Grebosz, J.; Haas, F.; Jia, H. M.; Mazzocco, M.; Michelagnoli, C.; Mijatović, T.; Montanari, D.; Parascandolo, C.; Scarlassara, F.; Strano, E.; Szilner, S.; Torresi, D.

    2014-10-01

    Background: The fusion excitation function of the system Si28+Si28 at energies near and below the Coulomb barrier is known only down to ≃15 mb. This precludes any information on both coupling effects on sub-barrier cross sections and the possible appearance of hindrance. For Si28+Si30 even if the fusion cross section is measured down to ≃50 μb, the evidence of hindrance is marginal. Both systems have positive fusion Q values. While Si28 has a deformed oblate shape, Si30 is spherical. Purpose: We investigate 1. the possible influence of the different structure of the two Si isotopes on the fusion excitation functions in the deep sub-barrier region and 2. whether hindrance exists in the Si+Si systems and whether it is strong enough to generate an S-factor maximum, thus allowing a comparison with lighter heavy-ion systems of astrophysical interest. Methods: Si28 beams from the XTU Tandem accelerator of the INFN Laboratori Nazionali di Legnaro were used. The setup was based on an electrostatic beam separator, and fusion evaporation residues (ER) were detected at very forward angles. Angular distributions of ER were measured. Results: Fusion cross sections of Si28+Si28 have been obtained down to ≃600 nb. The slope of the excitation function has a clear irregularity below the barrier, but no indication of a S-factor maximum is found. For Si28+Si30 the previous data have been confirmed and two smaller cross sections have been measured down to ≃4 μb. The trend of the S-factor reinforces the previous weak evidence of hindrance. Conclusions: The sub-barrier cross sections for Si28+Si28 are overestimated by coupled-channels calculations based on a standard Woods-Saxon potential, except for the lowest energies. Calculations using the M3Y+repulsion potential are adjusted to fit the Si28+Si28 and the existing Si30+Si30 data. An additional weak imaginary potential (probably simulating the effect of the oblate Si28 deformation) is required to fit the low-energy trend of

  2. Energy Barriers for Defects in Disordered Solids

    NASA Astrophysics Data System (ADS)

    Wijtmans, Sven; Manning, Lisa

    2015-03-01

    In solids, defects govern flow and failure. In crystals, defects are easily-identified dislocations, while in disordered solids, defects can be found by analyzing the vibrational modes of the system, which are eigenvectors of the matrix describing the linear response. The low frequency modes are typically quasi-localized hybrids of excitations localized at the defects and plane-wave like modes. Additional analysis can separate these components, giving the location of a defect and displacement of particles along that defect. To define an energy barrier for each defect, we displace particles along an isolated defect mode and calculate the energy at which the system transitions to a new energy basin. Different definitions of a new basin, such as a change in the particle contact network or particle displacements above a specific threshold, give different results. We identify several criteria that are consistent and provide a reasonable, robust definition of an energy barrier. Somewhat surprisingly, we find that energy barriers for isolated defects are generally higher than energy barriers for typical quasi-localized modes in the system.

  3. Market barriers to energy efficiency

    SciTech Connect

    Howarth, R.B.; Andersson, B.

    1992-06-01

    Discussions of energy policy in an environmentally constrained world often focus on the use of tax instruments to internalize the external effects of energy utilization or achieve specified reductions in energy use in the most cost-effective manner. A substantial literature suggests, however, that significant opportunities exist to reduce energy utilization by implementing technologies that are cost-effective under prevailing economic conditions but that are not fully implemented by existing market institutions. This paper examines the theory of the market for energy-using equipment, showing that problems of imperfect information and transaction costs may bias rational consumers to purchase devices that use more energy than those that would be selected by a well-informed social planner guided by the criterion of economic efficiency. Consumers must base their purchase decisions on observed prices and expectations of postpurchase equipment performance. If it is difficult or costly for individuals to form accurate and precise expectations, the level of energy efficiency achieved by competitive markets will vary from the socially efficient outcome. Such ``market barriers`` suggest a role for regulatory intervention to improve market performance at prevailing energy prices.

  4. Market barriers to energy efficiency

    SciTech Connect

    Howarth, R.B. ); Andersson, B. )

    1992-06-01

    Discussions of energy policy in an environmentally constrained world often focus on the use of tax instruments to internalize the external effects of energy utilization or achieve specified reductions in energy use in the most cost-effective manner. A substantial literature suggests, however, that significant opportunities exist to reduce energy utilization by implementing technologies that are cost-effective under prevailing economic conditions but that are not fully implemented by existing market institutions. This paper examines the theory of the market for energy-using equipment, showing that problems of imperfect information and transaction costs may bias rational consumers to purchase devices that use more energy than those that would be selected by a well-informed social planner guided by the criterion of economic efficiency. Consumers must base their purchase decisions on observed prices and expectations of postpurchase equipment performance. If it is difficult or costly for individuals to form accurate and precise expectations, the level of energy efficiency achieved by competitive markets will vary from the socially efficient outcome. Such market barriers'' suggest a role for regulatory intervention to improve market performance at prevailing energy prices.

  5. Barriers to improvements in energy efficiency

    SciTech Connect

    Reddy, A.K.N.

    1991-10-01

    To promote energy-efficiency improvements, actions may be required at one or more levels -- from the lowest level of the consumer (residential, commercial, industrial, etc.) through the highest level of the global agencies. But barriers to the implementation of energy-efficiency improvements exist or can arise at all these levels. Taking up each one of these barriers in turn, the paper discusses specific measures that can contribute to overcoming the barriers. However, a one-barrier-one-measure approach must be avoided. Single barriers may in fact involve several sub-barriers. Also, combinations of measures are much more effective in overcoming barriers. In particular, combinations of measures that simultaneously overcome several barriers are most successful. The paper discusses the typology of barriers, explores their origin and suggests measures that by themselves or in combination with other measures, will overcome these barriers. Since most of the barriers dealt with can be found in the ``barriers`` literature, any originality in the paper lies in its systematic organization, synoptic view and holistic treatment of this issue. This paper is intended to initiate a comprehensive treatment of barriers, their origins and the measures that contribute to overcoming them. Hopefully, such a treatment will facilitate the implementation of energy-efficiency improvements involving a wide diversity of ever-changing energy end uses and consumer preferences.

  6. Barriers to improvements in energy efficiency

    SciTech Connect

    Reddy, A.K.N.

    1991-10-01

    To promote energy-efficiency improvements, actions may be required at one or more levels -- from the lowest level of the consumer (residential, commercial, industrial, etc.) through the highest level of the global agencies. But barriers to the implementation of energy-efficiency improvements exist or can arise at all these levels. Taking up each one of these barriers in turn, the paper discusses specific measures that can contribute to overcoming the barriers. However, a one-barrier-one-measure approach must be avoided. Single barriers may in fact involve several sub-barriers. Also, combinations of measures are much more effective in overcoming barriers. In particular, combinations of measures that simultaneously overcome several barriers are most successful. The paper discusses the typology of barriers, explores their origin and suggests measures that by themselves or in combination with other measures, will overcome these barriers. Since most of the barriers dealt with can be found in the barriers'' literature, any originality in the paper lies in its systematic organization, synoptic view and holistic treatment of this issue. This paper is intended to initiate a comprehensive treatment of barriers, their origins and the measures that contribute to overcoming them. Hopefully, such a treatment will facilitate the implementation of energy-efficiency improvements involving a wide diversity of ever-changing energy end uses and consumer preferences.

  7. Energy barriers, entropy barriers, and non-Arrhenius behavior in a minimal glassy model

    NASA Astrophysics Data System (ADS)

    Du, Xin; Weeks, Eric R.

    2016-06-01

    We study glassy dynamics using a simulation of three soft Brownian particles confined to a two-dimensional circular region. If the circular region is large, the disks freely rearrange, but rearrangements are rarer for smaller system sizes. We directly measure a one-dimensional free-energy landscape characterizing the dynamics. This landscape has two local minima corresponding to the two distinct disk configurations, separated by a free-energy barrier that governs the rearrangement rate. We study several different interaction potentials and demonstrate that the free-energy barrier is composed of a potential-energy barrier and an entropic barrier. The heights of both of these barriers depend on temperature and system size, demonstrating how non-Arrhenius behavior can arise close to the glass transition.

  8. Quasifission at extreme sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.

    2012-12-01

    With the quantum diffusion approach the behavior of the capture cross-section is investigated in the reactions 92, 94Mo + 92, 94Mo , 100Ru + 100Ru , 104Pd + 104Pd , and 78Kr + 112Sn at deep sub-barrier energies which are lower than the ground-state energies of the compound nuclei. Because the capture cross-section is the sum of the complete fusion and quasifission cross-sections, and the complete fusion cross-section is zero at these sub-barrier energies, one can study experimentally the unique quasifission process in these reactions after the capture.

  9. Only Above Barrier Energy Components Contribute to Barrier Traversal Time

    NASA Astrophysics Data System (ADS)

    Galapon, Eric A.

    2012-04-01

    A time of arrival operator across a square potential barrier is constructed. The expectation value of the barrier time of arrival operator for a sufficiently localized incident wave packet is compared with the expectation value of the free particle time of arrival operator for the same wave packet. The comparison yields an expression for the expected traversal time across the barrier. It is shown that only the above barrier components of the momentum distribution of the incident wave packet contribute to the barrier traversal time, implying that below the barrier components are transmitted without delay. This is consistent with the recent experiment in attosecond ionization in helium indicating that there is no real tunneling delay time [P. Eckle , Science 322, 1525 (2008)SCIEAS0036-807510.1126/science.1163439].

  10. Barriers to electric energy efficiency in Ghana

    NASA Astrophysics Data System (ADS)

    Berko, Joseph Kofi, Jr.

    Development advocates argue that sustainable development strategies are the best means to permanently improve living standards in developing countries. Advocates' arguments are based on the technical, financial, and environmental advantages of sustainable development. However, they have not addressed the organizational and administrative decision-making issues which are key to successful implementation of sustainable development in developing countries. Using the Ghanaian electricity industry as a case study, this dissertation identifies and analyzes organizational structures, administrative mechanisms, and decision-maker viewpoints that critically affect the success of adoption and implementation of energy efficiency within a sustainable development framework. Utilizing semi-structured interviews in field research, decision-makers' perceptions of the pattern of the industry's development, causes of the electricity supply shortfall, and barriers to electricity-use efficiency were identified. Based on the initial findings, the study formulated a set of policy initiatives to establish support for energy use efficiency. In a second set of interviews, these policy suggestions were presented to some of the top decision-makers to elicit their reactions. According to the decision-makers, the electricity supply shortfall is due to rapid urbanization and increased industrial consumption as a result of the structural adjustment program, rural electrification, and the sudden release of suppressed loads. The study found a lack of initiative and collaboration among industry decision-makers, and a related divergence in decision-makers' concerns and viewpoints. Also, lacking are institutional support systems and knowledge of proven energy efficiency strategies and technologies. As a result, planning, and even the range of perceived solutions to choose from are supply-side oriented. The final chapter of the study presents implications of its findings and proposes that any

  11. Directed transport of active particles over asymmetric energy barriers.

    PubMed

    Koumakis, N; Maggi, C; Di Leonardo, R

    2014-08-21

    We theoretically and numerically investigate the transport of active colloids to target regions, delimited by asymmetric energy barriers. We show that it is possible to introduce a generalized effective temperature that is related to the local variance of particle velocities. The stationary probability distributions can be derived from a simple diffusion equation in the presence of an inhomogeneous effective temperature resulting from the action of external force fields. In particular, transition rates over asymmetric energy barriers can be unbalanced by having different effective temperatures over the two slopes of the barrier. By varying the type of active noise, we find that equal values of diffusivity and persistence time may produce strongly varied effective temperatures and thus stationary distributions. PMID:24978345

  12. Threshold energy for sub-barrier fusion hindrance phenomenon

    NASA Astrophysics Data System (ADS)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.

    2013-02-01

    The relationship between the threshold energy for a deep sub-barrier fusion hindrance phenomenon and the energy at which the regime of interaction changes (the turning-off of the nuclear forces and friction) in the sub-barrier capture process is studied within the quantum diffusion approach. The quasielastic barrier distribution is shown to be a useful tool to clarify whether the slope of capture cross section changes at sub-barrier energies.

  13. Developing effective rockfall protection barriers for low energy impacts

    NASA Astrophysics Data System (ADS)

    Mentani, Alessio; Giacomini, Anna; Buzzi, Olivier; Govoni, Laura; Gottardi, Guido; Fityus, Stephen

    2016-04-01

    Recently, important progresses have been made towards the development of high capacity rockfall barriers (100 kJ - 8000 kJ). The interest of researchers and practitioners is now turning to the development of fences of minor capacity, whose use becomes essential in areas where rockfall events generally have low intensity and the use of high capacity barriers would be accompanied by excessive costs and high environmental impact. Low energy barriers can also provide a cost-effective solution even in areas where high energies events are expected. Results of full-scale tests are vital to any investigation on the behaviour of these structures. An experimental set-up has been developed at The University of Newcastle (AUS), to investigate the response of low energy rockfall barrier prototypes to low energy impacts. The Australian territory, and in particular New South Wales, is in fact characterised by rockfall events of low-to-medium intensity (50 kJ - 500 kJ) and the need of protection structures working within such energy range, is particularly felt [1]. The experiments involved the impact of a test block onto three spans, low energy barrier prototypes, made of steel structural posts, fully fixed at the base, side cables and a steel meshwork constituted by a double twist hexagonal wire net [2]. Test data enabled the development, calibration and assessment of FE models [3], on which non-linear and dynamic analyses have been performed addressing the effect of the block size. Results have shown that the response of the structure is strongly governed by the net. Data from tests conducted on the sole net and on the entire barrier showed in fact a similar trend, different to what typically observed for high capacity barriers, whose behaviour is also led by the presence of uphill cables and brakes. In particular, the numerical analyses have demonstrated a dependence of the net performance on the block size. In particular, a loss of capacity in the order of 50% occurred as the

  14. Barriers to Industrial Energy Efficiency - Study (Appendix A), June 2015

    SciTech Connect

    2015-06-01

    This study examines barriers that impede the adoption of energy efficient technologies and practices in the industrial sector, and identifies successful examples and opportunities to overcome these barriers. Three groups of energy efficiency technologies and measures were examined: industrial end-use energy efficiency, industrial demand response, and industrial combined heat and power. This study also includes the estimated economic benefits from hypothetical Federal energy efficiency matching grants, as directed by the Act.

  15. Barriers to Industrial Energy Efficiency - Report to Congress, June 2015

    SciTech Connect

    2015-06-01

    This report examines barriers that impede the adoption of energy efficient technologies and practices in the industrial sector, and identifies successful examples and opportunities to overcome these barriers. Three groups of energy efficiency technologies and measures were examined: industrial end-use energy efficiency, industrial demand response, and industrial combined heat and power. This report also includes the estimated economic benefits from hypothetical Federal energy efficiency matching grants, as directed by the Act.

  16. Atomistic Simulations of Ion Diffusion in Clay Barriers: Diffusive Path Energy Barriers

    NASA Astrophysics Data System (ADS)

    Newton, A. G.; Kozaki, T.

    2010-12-01

    Ion diffusion in clay-rich media is an important transport process relevant to models of contaminant fate and transport in groundwater and risk assessments for the geologic disposal of high-level radioactive waste (HLW). Smectite clay minerals are used as a buffer material in the geologic disposal of HLW due to their low permeability. Ion diffusion experiments with water-saturated, compacted clays have revealed a non-linear trend in which the diffusive energy barrier in clay media at dry densities near 1.0 Mg m-3 exhibited a smaller energy barrier to diffusion than in liquid water (Kozaki, et al. 2005). Although it is likely that the decreased energy barrier is related to preferential diffusion along smectite basal surfaces, experimental methods cannot unambiguously isolate this diffusion pathway. Atomistic simulations were designed to isolate this diffusive pathway and to test if the decreased energy barrier is related to preferential diffusion along the smectite basal surface. In addition, the simulations provide an atomic-scale perspective of this diffusion pathway as a function of temperature. In the present study, we report the energy barrier to diffusion for sodium ions (Na+) at the smectite basal surface. The energy barrier to diffusion at the Na-montmorillonite basal surface was determined by investigating the temperature dependence of ion diffusion through a series of long (9.0 ns) molecular dynamics (MD) simulations in the canonical ensemble (NVT). We show that the energy barrier to diffusion at the clay basal surface is less than the energy barrier to diffusion in free water and demonstrate that this methodology can provide results that are consistent with laboratory diffusion experiments and nanoscale insights into the interpretation of macroscale experimental investigations of ion diffusion in smectite-rich media. Kozaki, T., A. Fujishima, et al. (2005). Engineering Geology, 81(3): 246-254.

  17. Nontechnical Barriers to Solar Energy Use: Review of Recent Literature

    SciTech Connect

    Margolis, R.; Zuboy, J.

    2006-09-01

    This paper reviews the nontechnical barriers to solar energy use, drawing on recent literature to help identify key barriers that must be addressed as part of the Technology Acceptance efforts under the U.S. Department of Energy (DOE) Solar America Initiative. A broad literature search yielded more than 400 references, which were narrowed to 19 recent documents on nontechnical barriers to the use of solar energy and other energy efficiency and renewable energy (EE/RE) technologies. Some of the most frequently identified barriers included lack of government policy supporting EE/RE, lack of information dissemination and consumer awareness about energy and EE/RE, high cost of solar and other EE/RE technologies compared with conventional energy, and inadequate financing options for EE/RE projects.

  18. Summary of Workshop: Barriers to Energy Efficient Residential Ventilation

    SciTech Connect

    Sherman, Max; Sherman, Max

    2008-01-10

    The objectives for this workshop were to bring together those with different viewpoints on the implementation of energy efficient ventilation in homes to share their perspectives. The primary benefit of the workshop is to allow the participants to get a broader understanding of the issues involved and thereby make themselves more able to achieve their own goals in this area. In order to achieve this objective each participant was asked to address four objectives from their point of view: (1) Drivers for energy efficient residential ventilation: Why is this an important issue? Who cares about it? Where is the demand: occupants, utilities, regulation, programs, etc? What does sustainability mean in this context? (2) Markets & Technologies: What products, services and systems are out there? What kinds of things are in the pipeline? What is being installed now? Are there regional or other trends? What are the technology interactions with other equipment and the envelope? (3) Barriers to Implementation: What is stopping decision makers from implementing energy-efficient residential ventilation systems? What kind of barriers are there: technological, cost, informational, structural, etc. What is the critical path? (4) Solutions: What can be done to overcome the barriers and how can/should we do it? What is the role of public vs. private institutions? Where can investments be made to save energy while improving the indoor environment? Ten participants prepared presentations for the workshop. Those presentations are included in sections at the end of this workshop report. These presentations provided the principal context for the discussions that happened during the workshop. Critical path issues were raised and potential solutions discussed during the workshop. As a secondary objective they have listed key issues and some potential consensus items which resulted from the discussions.

  19. Equation of Energy Injection to a Dielectric Barrier Discharge Reactor

    NASA Astrophysics Data System (ADS)

    Yao, Shuiliang; Weng, Shan; Jin, Qi; Han, Jingyi; Jiang, Boqiong; Wu, Zuliang

    2016-08-01

    The electric energy injection from a pulsed power supply to a planar type of dielectric barrier discharge (DBD) reactor at atmospheric pressure was studied. Relations of the energy injection with barrier materials, barrier thickness, peak voltage, gap distance, electrode area, and operation temperature were experimentally investigated. The energy injection is a function of relative permittivity, barrier thickness, peak voltage, gap distance, and electrode area. The influence of operation temperature on energy injection is slight in the range of 27–300 °C but becomes obvious in the range of 300–500 °C. A model was established using which the energy injection can be easily predicted. supported by National Natural Science Foundation of China (No. 11575159), Zhejiang Provincial Natural Science Foundation of China (No. LY13B070004), Program for Zhejiang Leading Team of S&T Innovation (No. 2013TD07), and National Natural Science Foundation of China (No. 51206146)

  20. Parametric modeling of energy filtering by energy barriers in thermoelectric nanocomposites

    SciTech Connect

    Zianni, Xanthippi E-mail: xzianni@gmail.com; Narducci, Dario

    2015-01-21

    We present a parametric modeling of the thermoelectric transport coefficients based on a model previously used to interpret experimental measurements on the conductivity, σ, and Seebeck coefficient, S, in highly Boron-doped polycrystalline Si, where a very significant thermoelectric power factor (TPF) enhancement was observed. We have derived analytical formalism for the transport coefficients in the presence of an energy barrier assuming thermionic emission over the barrier for (i) non-degenerate and (ii) degenerate one-band semiconductor. Simple generic parametric equations are found that are in agreement with the exact Boltzmann transport formalism in a wide range of parameters. Moreover, we explore the effect of energy barriers in 1-d composite semiconductors in the presence of two phases: (a) the bulk-like phase and (b) the barrier phase. It is pointed out that significant TPF enhancement can be achieved in the composite structure of two phases with different thermal conductivities. The TPF enhancement is estimated as a function of temperature, the Fermi energy position, the type of scattering, and the barrier height. The derived modeling provides guidance for experiments and device design.

  1. Parametric modeling of energy filtering by energy barriers in thermoelectric nanocomposites

    NASA Astrophysics Data System (ADS)

    Zianni, Xanthippi; Narducci, Dario

    2015-01-01

    We present a parametric modeling of the thermoelectric transport coefficients based on a model previously used to interpret experimental measurements on the conductivity, σ, and Seebeck coefficient, S, in highly Boron-doped polycrystalline Si, where a very significant thermoelectric power factor (TPF) enhancement was observed. We have derived analytical formalism for the transport coefficients in the presence of an energy barrier assuming thermionic emission over the barrier for (i) non-degenerate and (ii) degenerate one-band semiconductor. Simple generic parametric equations are found that are in agreement with the exact Boltzmann transport formalism in a wide range of parameters. Moreover, we explore the effect of energy barriers in 1-d composite semiconductors in the presence of two phases: (a) the bulk-like phase and (b) the barrier phase. It is pointed out that significant TPF enhancement can be achieved in the composite structure of two phases with different thermal conductivities. The TPF enhancement is estimated as a function of temperature, the Fermi energy position, the type of scattering, and the barrier height. The derived modeling provides guidance for experiments and device design.

  2. Radiant Barriers Save Energy in Buildings

    NASA Technical Reports Server (NTRS)

    2014-01-01

    Langley Research Center needed to coat the Echo 1 satellite with a fine mist of vaporized metal, and collaborated with industry to create "radiant barrier technology." In 2010, Ryan Garrett learned about a new version of the technology resistant to oxidation and founded RadiaSource in Ogden, Utah, to provide the NASA-derived technology for applications in homes, warehouses, gymnasiums, and agricultural settings.

  3. Deep inelastic scattering at energies near the Coulomb barrier

    SciTech Connect

    Gehring, J.; Rehm, K.E.; Schiffer, J.P.

    1993-10-01

    A large yield for a process that appears to have many of the features of deep inelastic scattering has been observed at energies, near the Coulomb barrier in the systems {sup 112,124}Sn + {sup 58}Ni by Wolfs et al. In order to better understand the mechanisms by which energy dissipation takes place close to the barrier, we have extended the measurements of Wolfs to the system {sup 136}Xe + {sup 64}Ni. The use of inverse kinematics in the present measurements resulted in better mass and energy resolution due to reduced target effects and in more complete angular coverage. We have obtained angular distributions, mass distributions, and total cross sections for deep inelastic scattering at two energies near the barrier. The results on the closed neutron shell nucleus {sup 136}Xe complement those from the closed proton shell Sn nuclei.

  4. Renewable Energy Permitting Barriers in Hawaii: Experience from the Field

    SciTech Connect

    Busche, S.; Donnelly, C.; Atkins, D.; Fields, R.; Black, C.

    2013-03-01

    This white paper presents a summary of the solicited input from permitting agencies and renewable energy developers on the permitting process in Hawaii to provide stakeholders in Hawaii, particularly those involved in permitting, with information on current permitting barriers that renewable energy developers are experiencing.

  5. Energy barriers for point-defect reactions in 3C-SiC

    NASA Astrophysics Data System (ADS)

    Zheng, Ming-Jie; Swaminathan, Narasimhan; Morgan, Dane; Szlufarska, Izabela

    2013-08-01

    Energy barriers of the key annealing reactions of neutral and charged point defects in SiC are calculated with ab initio density functional theory methods. In order to effectively search for the lowest energy migration paths the preliminary path is first established based on ab initio molecular dynamics (AIMD) simulations. The energy barrier of each hop is then calculated via climbing image nudged elastic band methods for paths guided by the AIMD simulations. The final paths and barriers are determined by comparing different pathways. The annealing reactions have important implications in understanding the amorphization, recovery, and other aspects of the radiation response of SiC. The results are compared with the literature data and experimental results on SiC recovery and amorphization. We propose that the C interstitial and Si antisite annealing reaction may provide a critical barrier that governs both the recovery stage III and amorphization processes.

  6. Energy deposition characteristics of nanosecond dielectric barrier discharge plasma actuators: Influence of dielectric material

    NASA Astrophysics Data System (ADS)

    Correale, G.; Winkel, R.; Kotsonis, M.

    2015-08-01

    An experimental study aimed at the characterization of energy deposition of nanosecond Dielectric Barrier Discharge (ns-DBD) plasma actuators was carried out. Special attention was given on the effect of the thickness and material used for dielectric barrier. The selected materials for this study were polyimide film (Kapton), polyamide based nylon (PA2200), and silicone rubber. Schlieren measurements were carried out in quiescent air conditions in order to observe density gradients induced by energy deposited. Size of heated area was used to qualify the energy deposition coupled with electrical power measurements performed using the back-current shunt technique. Additionally, light intensity measurements showed a different nature of discharge based upon the material used for barrier, for a fixed thickness and frequency of discharge. Finally, a characterisation study was performed for the three tested materials. Dielectric constant, volume resistivity, and thermal conductivity were measured. Strong trends between the control parameters and the energy deposited into the fluid during the discharge were observed. Results indicate that efficiency of energy deposition mechanism relative to the thickness of the barrier strongly depends upon the material used for the dielectric barrier itself. In general, a high dielectric strength and a low volumetric resistivity are preferred for a barrier, together with a high heat capacitance and a low thermal conductivity coefficient in order to maximize the efficiency of the thermal energy deposition induced by an ns-DBD plasma actuator.

  7. Perceived Career Barriers and Coping among Youth in Israel: Ethnic and Gender Differences

    ERIC Educational Resources Information Center

    Lipshits-Braziler, Yuliya; Tatar, Moshe

    2012-01-01

    This study investigated gender and ethnic differences in the perception of different types of career barriers among young adults in relation to their views of themselves as individuals (Personal Career Barriers) and their views of their gender and ethnic group (Group Career Barriers). This study also explored gender and ethnic differences in the…

  8. Renewable energy technologies adoption in Kazakhstan: potentials, barriers and solutions

    NASA Astrophysics Data System (ADS)

    Karatayev, Marat; Marazza, Diego; Contin, Andrea

    2015-04-01

    The growth in environmental pollution alongside an increasing demand for electricity in Kazakhstan calls for a higher level of renewable energy penetration into national power systems. Kazakhstan has great potential for renewable energies from wind, solar, hydro and biomass resources that can be exploited for electricity production. In 2013, the Kazakhstani Ministry of Energy initiated a new power development plan, which aims to bring the share of renewable energy to 3% by 2020 rising to 30% by 2030 and 50% by 2050. The current contribution of renewable energy resources in the national electricity mix, however, is less than 1%. As a developing country, Kazakhstan has faced a number of barriers to increase renewable energy use, which have to be analysed and translated into a comprehensive renewable energy policy framework. This study presents an overview of the current conditions of renewable energy development in Kazakhstan. Secondly, it identifies and describes the main barriers that prevent diffusion of renewable energy technologies in Kazakhstan. Finally, the paper provides solutions to overcome specific barriers in order to successfully develop a renewable energy technology sector in Kazakhstan.

  9. Mesoscale geomorphic change on low energy barrier islands in Chesapeake Bay, U.S.A.

    NASA Astrophysics Data System (ADS)

    Cooper, J. Andrew G.

    2013-10-01

    This paper presents an analysis of decadal (mesoscale) geomorphic change on sandy barrier islands in the fetch-limited environment of Chesapeake Bay. Low energy barrier islands exist in two settings: on the fringe of marshes and in open water and this analysis shows the various types of barrier island to be genetically related. Barrier islands that face the dominant wind and wave direction (E or W) retreat via barrier translation, preserving the barrier island volume. Those that exist in re-entrants are dominated by longshore transport processes, are strongly affected by sediment supply and are subject to disintegration. Marsh fringe barrier islands are perched on or draped over the surface of the underlying marsh. They migrate landwards via barrier translation during periodic high water events accompanied by large waves (hurricanes and northeasters). The underlying marsh surface erodes under all water levels and the rate of retreat of the barrier island and underlying marsh may take place at different rates, leading to various configurations from perched barrier islands several metres landward of the marsh edge, to barrier islands that have a sandy shoreface extending into the subtidal zone. The coastal configuration during landward retreat of marsh fringe barrier islands is subject to strong local control exerted by the underyling marsh topography. As erosion of marsh promontories occurs and marsh creeks are intersected and bypassed, the configuration is subject to rapid change. Periodic sediment influxes cause spits to develop at re-entrants in the marsh. The spits are initiated as extensions of adjacent marsh fringe barrier islands, but as the sediment volume is finite, the initial drift-aligned spits become sediment-starved and begin to develop a series of swash-aligned cells as they strive for morphodynamic equilibrium. The individual cells are stretched until breaches form in the barrier islands, creating inlets with tidal deltas. At this stage the low

  10. Surface charge measurements in barrier discharges on different time scales

    NASA Astrophysics Data System (ADS)

    Wild, Robert; Volkhausen, Christian; Benduhn, Johannes; Stollenwerk, Lars

    2015-09-01

    The deposition of surface charge in barrier discharges is a process that influences the ongoing discharge significantly. This contribution presents the measurement of absolute surface charge densities and their dynamics in a laterally extended setup. An electro-optic BSO crystal is used as dielectric. The absolute charge density on its surface is deduced from the change of polarisation of light passing the crystal. Using different temporal resolutions, the behavior of charge is investigated on three different time scales. The highest temporal resolution of the technique is in the order of hundreds of nanoseconds. Therefore it is possible for the first time to observe the charge deposition process during an active discharge. On the time scale of the applied voltage period (several microseconds), the conservation mechanisms of a lateral discharge pattern is investigated. For this, the influence of surface charge and metastable species in the volume is estimated. Further, the behavior of the surface charge spots on a variation of the external voltage and gas pressure is studied. Measurements on a time scale in the magnitude of seconds reveal charge decay and transport phenomena. This work was funded by the Deutsche Forschungsgemeinschaft.

  11. Implementing District Energy Systems: Municipal Approaches To Overcoming Barriers

    NASA Astrophysics Data System (ADS)

    Simpson, Kevin George

    Climate change and energy security are issues facing municipalities throughout the world. Efficient, resilient, sustainable, community-based energy systems, such as district energy systems (DES), fuelled mostly by renewables, are an important tool for addressing both climate change and energy security at the municipal level. In spite of their benefits, DES are not widely adopted in Canada (CDEA, 2011). This is due to the complex nature of the barriers which project proponents face. This thesis examines the experience of the City of Prince George in adopting and implementing the Downtown DES. Using a case study methodology, data was collected through a review of relevant municipal documents and a series of semi-structured, open-ended interviews. A thematic analysis revealed unexpected barriers related to lack of adequate public consultation and negative perceptions regarding biomass as a fuel for the DES. These `lessons learned' were then developed into recommendations for other municipalities considering DES.

  12. Quantum Mechanical Free Energy Barrier for an Enzymatic Reaction

    NASA Astrophysics Data System (ADS)

    Rod, Thomas H.; Ryde, Ulf

    2005-04-01

    We discuss problems related to in silico studies of enzymes and show that accurate and converged free energy changes for complex chemical reactions can be computed if a method based on a thermodynamic cycle is employed. The method combines the sampling speed of molecular mechanics with the accuracy of a high-level quantum mechanics method. We use the method to compute the free energy barrier for a methyl transfer reaction catalyzed by the enzyme catechol O-methyltransferase at the level of density functional theory. The surrounding protein and solvent are found to have a profound effect on the reaction, and we show that energies can be extrapolated easily from one basis set and exchange-correlation functional to another. Using this procedure we calculate a barrier of 69 kJ/mol, in excellent agreement with the experimental value of 75 kJ/mol.

  13. Scattering of Halo Nuclei at Energies below and around the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Borge, M. J. G.; Cubero, M.; Fernández-García, J. P.; Moro, A. M.; Pesudo, V.; Acosta, L.; Alcorta, M.; Alvarez, M. A. G.; Bender, P.; Buchmann, L.; Diget, C. A.; Di Pietro, A.; Escrig, D.; Falou, H. A.; Figuera, P. P.; Fulton, B. R.; Fynbo, H. O. U.; Galaviz, D.; Garnsworthy, A.; Gómez-Camacho, J.; Hackman, G.; Kanungo, R.; Lay, J. A.; Madurga, M.; Martel, I.; Mukha, I.; Nilsson, T.; Rodríguez-Gallardo, M.; Rusek, K.; Sánchez-Benítez, A. M.; Rajabali, M.; Sarazin, F.; Shotter, A.; Tengblad, O.; Unsworth, C.; Walden, P.

    The loosely bound structure of halo nuclei is predicted to affect the collisions with heavy targets at energies around the Coulomb barrier. We report here on the results on a series of experiments done at different facilities to study the behaviour of the scattering of the archetype of the halo nuclei: 6He, 11Li, and 11Be on heavy targets at energies below and around the Coulomb barrier. The results are interpreted in the framework of Continuum-Discretized Coupled-Channel calculations (CDCC). The departure from Rutherford scattering is larger than expected. In first approximation the effect certainly scales with the loosely bound character of the projectile.

  14. Energy management action plan: Developing a strategy for overcoming institutional barriers to municipal energy conservation

    SciTech Connect

    Not Available

    1992-12-31

    Energy offices working to improve efficiency of local government facilities face not only technical tasks, but institutional barriers, such as budget structures that do not reward efficiency, a low awareness of energy issues, and purchasing procedures based only on minimizing initial cost. The bureau, in working to remove such barriers in San Francisco, has identified 37 institutional barriers in areas such as operations & maintenance, purchasing, and facility design; these barriers were then reorganized into three groupings-- policy & attitudes, budget & incentives, and awareness & information-- and mapped. This map shows that the barriers mutually reinforce each other, and that a holistic approach is required for permanent change. The city`s recreation & parks department was used as a model department, and information about facility energy use was compiled into a departmental energy review. Staff interviews showed how barriers affect conservation. The bureau then generated ideas for projects to remove specific barriers and rated them according to potential impact and the resources required to implement them. Four of the six projects selected focused on maintenance staff: a cost- sharing lighting retrofit program, a boiler efficiency program, a departmental energy tracking system, and a budgetary incentive program for conservation. The other two projects are city-wide: promotion of a new term contract supplying energy-efficient light materials, and publication/distribution of ENERGY NEWS newsletter. A general methodology, the EMAP Strategy Guide, has been created to assist other energy offices in developing EMAPs.

  15. Barriers to household investment in residential energy conservation: preliminary assessment

    SciTech Connect

    Hoffman, W.L.

    1982-12-01

    A general assessment of the range of barriers which impede household investments in weatherization and other energy efficiency improvements for their homes is provided. The relationship of similar factors to households' interest in receiving a free energy audits examined. Rates of return that underly household investments in major conservation improvements are assessed. A special analysis of household knowledge of economically attractive investments is provided that compares high payback improvements specified by the energy audit with the list of needed or desirable conservation improvements identified by respondents. (LEW)

  16. Deformation energy of a toroidal nucleus and plane fragmentation barriers

    NASA Astrophysics Data System (ADS)

    Fauchard, C.; Royer, G.

    1996-02-01

    The path leading to pumpkin-like configurations and toroidal shapes is investigated using a one-parameter shape sequence. The deformation energy is determined within the analytical expressions obtained for the various shape-dependent functions and the generalized rotating liquid drop model taking into account the proximity energy and the temperature. With increasing mass and angular momentum, a potential well appears in the toroidal shape path. For the heaviest systems, the pocket is large and locally favourable with respect to the plane fragmentation barriers which might allow the formation of evanescent toroidal systems which would rapidly decay in several fragments to minimize the surface tension.

  17. Market and policy barriers to energy storage deployment : a study for the energy storage systems program.

    SciTech Connect

    Bhatnagar, Dhruv; Currier, Aileen B.; Hernandez, Jacquelynne; Ma, Ookie; Kirby, Brendan

    2013-09-01

    Electric energy storage technologies have recently been in the spotlight, discussed as essential grid assets that can provide services to increase the reliability and resiliency of the grid, including furthering the integration of variable renewable energy resources. Though they can provide numerous grid services, there are a number of factors that restrict their current deployment. The most significant barrier to deployment is high capital costs, though several recent deployments indicate that capital costs are decreasing and energy storage may be the preferred economic alternative in certain situations. However, a number of other market and regulatory barriers persist, limiting further deployment. These barriers can be categorized into regulatory barriers, market (economic) barriers, utility and developer business model barriers, crosscutting barriers and technology barriers. This report, through interviews with stakeholders and review of regulatory filings in four regions roughly representative of the United States, identifies the key barriers restricting further energy storage development in the country. The report also includes a discussion of possible solutions to address these barriers and a review of initiatives around the country at the federal, regional and state levels that are addressing some of these issues. Energy storage could have a key role to play in the future grid, but market and regulatory issues have to be addressed to allow storage resources open market access and compensation for the services they are capable of providing. Progress has been made in this effort, but much remains to be done and will require continued engagement from regulators, policy makers, market operators, utilities, developers and manufacturers.

  18. Universal Pinning Energy Barrier for Driven Domain Walls in Thin Ferromagnetic Films.

    PubMed

    Jeudy, V; Mougin, A; Bustingorry, S; Savero Torres, W; Gorchon, J; Kolton, A B; Lemaître, A; Jamet, J-P

    2016-07-29

    We report a comparative study of magnetic field driven domain wall motion in thin films made of different magnetic materials for a wide range of field and temperature. The full thermally activated creep motion, observed below the depinning threshold, is shown to be described by a unique universal energy barrier function. Our findings should be relevant for other systems whose dynamics can be modeled by elastic interfaces moving on disordered energy landscapes. PMID:27517790

  19. Nucleosome positioning by genomic excluding-energy barriers.

    PubMed

    Milani, Pascale; Chevereau, Guillaume; Vaillant, Cédric; Audit, Benjamin; Haftek-Terreau, Zofia; Marilley, Monique; Bouvet, Philippe; Argoul, Françoise; Arneodo, Alain

    2009-12-29

    Recent genome-wide nucleosome mappings along with bioinformatics studies have confirmed that the DNA sequence plays a more important role in the collective organization of nucleosomes in vivo than previously thought. Yet in living cells, this organization also results from the action of various external factors like DNA-binding proteins and chromatin remodelers. To decipher the code for intrinsic chromatin organization, there is thus a need for in vitro experiments to bridge the gap between computational models of nucleosome sequence preferences and in vivo nucleosome occupancy data. Here we combine atomic force microscopy in liquid and theoretical modeling to demonstrate that a major sequence signaling in vivo are high-energy barriers that locally inhibit nucleosome formation rather than favorable positioning motifs. We show that these genomic excluding-energy barriers condition the collective assembly of neighboring nucleosomes consistently with equilibrium statistical ordering principles. The analysis of two gene promoter regions in Saccharomyces cerevisiae and the human genome indicates that these genomic barriers direct the intrinsic nucleosome occupancy of regulatory sites, thereby contributing to gene expression regulation. PMID:20018700

  20. Do stigma and other perceived barriers to mental health care differ across Armed Forces?

    PubMed Central

    Gould, Matthew; Adler, Amy; Zamorski, Mark; Castro, Carl; Hanily, Natalie; Steele, Nicole; Kearney, Steve; Greenberg, Neil

    2010-01-01

    Summary Objectives Military organizations are keen to address barriers to mental health care yet stigma and barriers to care remain little understood, especially potential cultural differences between Armed Forces. The aim of this study was to compare data collected by the US, UK, Australian, New Zealand and Canadian militaries using Hoge et al.'s perceived stigma and barriers to care measure (Combat duty in Iraq and Afghanistan, mental health problems and barriers to care. New Engl J Med 2004;351:13–22). Design Each member country identified data sources that had enquired about Hoge et al.'s perceived stigma and perceived barriers to care items in the re-deployment or immediate post-deployment period. Five relevant statements were included in the study. Setting US, UK Australian, New Zealand and Canadian Armed Forces. Results Concerns about stigma and barriers to care tended to be more prominent among personnel who met criteria for a mental health problem. The pattern of reported stigma and barriers to care was similar across the Armed Forces of all five nations. Conclusions Barriers to care continue to be a major issue for service personnel within Western military forces. Although there are policy, procedural and cultural differences between Armed Forces, the nations studied appear to share some similarities in terms of perceived stigma and barriers to psychological care. Further research to understand patterns of reporting and subgroup differences is required. PMID:20382906

  1. Anti-terrorist vehicle crash impact energy absorbing barrier

    DOEpatents

    Swahlan, David J.

    1989-01-01

    An anti-terrorist vehicle crash barrier includes side support structures, crushable energy absorbing aluminum honeycomb modules, and an elongated impact-resistant beam extending between, and at its opposite ends through vertical guideways defined by, the side support structures. An actuating mechanism supports the beam at its opposite ends for movement between a lowered barrier-withdrawn position in which a traffic-supporting side of the beam is aligned with a traffic-bearing surface permitting vehicular traffic between the side support structures and over the beam, and a raised barrier-imposed position in which the beam is aligned with horizontal guideways defined in the side support structures above the traffic-bearing surface, providing an obstruction to vehicular traffic between the side support structures. The beam is movable rearwardly in the horizontal guideways with its opposite ends disposed transversely therethrough upon being impacted at its forward side by an incoming vehicle. The crushable modules are replaceably disposed in the horizontal guideways between aft ends thereof and the beam. The beam, replaceable modules, side support structures and actuating mechanism are separate and detached from one another such that the beam and replaceable modules are capable of coacting to disable and stop an incoming vehicle without causing structural damage to the side support structures and actuating mechanism.

  2. Anti-terrorist vehicle crash impact energy absorbing barrier

    SciTech Connect

    Swahlan, D.J.

    1989-04-18

    An anti-terrorist vehicle crash barrier includes side support structures, crushable energy absorbing aluminum honeycomb modules, and an elongated impact-resistant beam extending between, and at its opposite ends through vertical guideways defined by, the side support structures. An actuating mechanism supports the beam at its opposite ends for movement between a lowered barrier-withdrawn position in which a traffic-supporting side of the beam is aligned with a traffic-bearing surface permitting vehicular traffic between the side support structures and over the beam, and a raised barrier-imposed position in which the beam is aligned with horizontal guideways defined in the side support structures above the traffic-bearing surface, providing an obstruction to vehicular traffic between the side support structures. The beam is movable rearwardly in the horizontal guideways with its opposite ends disposed transversely therethrough upon being impacted at its forward side by an incoming vehicle. The crushable modules are replaceably disposed in the horizontal guideways between aft ends thereof and the beam. The beam, replaceable modules, side support structures and actuating mechanism are separate and detached from one another such that the beam and replaceable modules are capable of coacting to disable and stop an incoming vehicle without causing structural damage to the side support structures and actuating mechanism. 6 figs.

  3. Market barriers to energy efficiency: A critical reappraisal of the rationale for public policies to promote energy efficiency

    SciTech Connect

    Golove, W.H.; Eto, J.H.

    1996-03-01

    This report reviews current perspectives on market barriers to energy efficiency. Ratepayer-funded utility energy-efficiency programs are likely to change in scope, size, and nature as the deregulation process proceeds; the authors research focuses on understanding to what extent some form of future intervention may be warranted and how they might judge the success of particular interventions, especially those funded by ratepayers. They find that challenges to the existence of market barriers have, for the most part, failed to provide a testable alternative explanation for evidence suggesting that there is a substantial ``efficiency gap`` between a consumer`s actual investments in energy efficiency and those that appear to be in the consumer`s own interest. They then suggest that differences of opinion about the appropriateness of public policies stem not from disputes about whether market barriers exist, but from different perceptions of the magnitude of the barriers, and the efficacy and (possibly unintended) consequences of policies designed to overcome them. They conclude that there are compelling justifications for future energy-efficiency policies. Nevertheless, in order to succeed, they must be based on a sound understanding of the market problems they seek to correct and a realistic assessment of their likely efficacy. This understanding can only emerge from detailed investigations of the current operation of individual markets.

  4. Correlation between diffusion barriers and alloying energy in binary alloys.

    PubMed

    Vej-Hansen, Ulrik Grønbjerg; Rossmeisl, Jan; Stephens, Ifan E L; Schiøtz, Jakob

    2016-01-28

    In this paper, we explore the notion that a negative alloying energy may act as a descriptor for long term stability of Pt-alloys as cathode catalysts in low temperature fuel cells. Using density functional theory calculations, we show that there is a correlation between the alloying energy of an alloy, and the diffusion barriers of the minority component. Alloys with a negative alloying energy may show improved long term stability, despite the fact that there is typically a greater thermodynamic driving force towards dissolution of the solute metal over alloying. In addition to Pt, we find that this trend also appears to hold for alloys based on Al and Pd. PMID:26750475

  5. Quantum chemical ab initio prediction of proton exchange barriers between CH4 and different H-zeolites.

    PubMed

    Tuma, Christian; Sauer, Joachim

    2015-09-14

    A hybrid MP2:DFT (second-order Møller-Plesset perturbation theory-density functional theory) method that combines MP2 calculations for cluster models with DFT calculations for the full periodic structure is used to localize minima and transition structures for proton jumps at different Brønsted sites in different frameworks (chabazite, faujasite, ferrierite, and ZSM-5) and at different crystallographic positions of a given framework. The MP2 limit for the periodic structures is obtained by extrapolating the results of a series of cluster models of increasing size. A coupled-cluster (CCSD(T)) correction to MP2 energies is calculated for cluster models consisting of three tetrahedra. For the adsorption energies, this difference is small, between 0.1 and 0.9 kJ/mol, but for the intrinsic proton exchange barriers, this difference makes a significant (10.85 ± 0.25 kJ/mol) and almost constant contribution across different systems. The total values of the adsorption energies vary between 22 and 34 kJ/mol, whereas the total proton exchange energy barriers fall in the narrow range of 152-156 kJ/mol. After adding nuclear motion contributions (harmonic approximation, 298 K), intrinsic enthalpy barriers between 134 and 141 kJ/mol and apparent energy barriers between 105 and 118 kJ/mol are predicted for the different sites examined for the different frameworks. These predictions are consistent with experimental results available for faujasite, ferrierite, and ZSM-5. PMID:26374003

  6. Quantum chemical ab initio prediction of proton exchange barriers between CH{sub 4} and different H-zeolites

    SciTech Connect

    Tuma, Christian; Sauer, Joachim

    2015-09-14

    A hybrid MP2:DFT (second-order Møller–Plesset perturbation theory–density functional theory) method that combines MP2 calculations for cluster models with DFT calculations for the full periodic structure is used to localize minima and transition structures for proton jumps at different Brønsted sites in different frameworks (chabazite, faujasite, ferrierite, and ZSM-5) and at different crystallographic positions of a given framework. The MP2 limit for the periodic structures is obtained by extrapolating the results of a series of cluster models of increasing size. A coupled-cluster (CCSD(T)) correction to MP2 energies is calculated for cluster models consisting of three tetrahedra. For the adsorption energies, this difference is small, between 0.1 and 0.9 kJ/mol, but for the intrinsic proton exchange barriers, this difference makes a significant (10.85 ± 0.25 kJ/mol) and almost constant contribution across different systems. The total values of the adsorption energies vary between 22 and 34 kJ/mol, whereas the total proton exchange energy barriers fall in the narrow range of 152–156 kJ/mol. After adding nuclear motion contributions (harmonic approximation, 298 K), intrinsic enthalpy barriers between 134 and 141 kJ/mol and apparent energy barriers between 105 and 118 kJ/mol are predicted for the different sites examined for the different frameworks. These predictions are consistent with experimental results available for faujasite, ferrierite, and ZSM-5.

  7. Multi-neutron transfer reactions at sub-barrier energies.

    SciTech Connect

    Rehm, K. E.

    1998-01-20

    The optimum conditions for multi-neutron transfer have been studied in the system {sup 58}Ni + {sup 124}Sn at bombarding energies at and below the Coulomb barrier. The experiments were performed in inverse kinematics with a {sup 124}Sn beam bombarding a {sup 58}Ni target. The particles were identified with respect to mass and Z in the split-pole spectrograph with a hybrid focal plane detector with mass and Z-resolutions of A/{Delta}A = 150 and Z/{Delta}Z = 70. At all energies the transfer of up to 6 neutrons was observed. The yields for these transfer reactions are found to decrease by about a factor of four for each transferred neutron.

  8. Probing the fusion of 7Li with 64Ni at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Shaikh, Md. Moin; Roy, Subinit; Rajbanshi, S.; Mukherjee, A.; Pradhan, M. K.; Basu, P.; Nanal, V.; Pal, S.; Shrivastava, A.; Saha, S.; Pillay, R. G.

    2016-04-01

    Background: The stable isotopes of Li, 6Li6 and 7Li, have two-body cluster structures of α +d and α +t with α -separation energies or breakup thresholds at 1.47 and 2.47 MeV, respectively. The weak binding of these projectiles introduces several new reaction channels not usually observed in the case of strongly bound projectiles. The impact of these breakup or breakup-like reaction channels on fusion, the dominant reaction process at near-barrier energies, with different target masses is of current interest. Purpose: Our purpose is to explore the fusion, at above and below the Coulmb barrier, of 7Li with 64Ni target in order to understand the effect of breakup or breakup-like processes with medium-mass target in comparison with 6Li, which has a lower breakup threshold. Measurement: The total fusion (TF) excitation of the weakly bound projectile 7Li with the medium-mass target 64Ni has been measured at the near-barrier energies (0.8 to 2 VB). The measurement was performed using the online characteristic γ -ray detection method. The complete fusion (CF) excitation function for the system was obtained using the x n -evaporation channels with the help of statistical model predictions. Results: At the above barrier energies CF cross sections exhibit an average suppression of about 6.5% compared to the one-dimensional barrier penetration model (1DBPM) predictions, while the model describes the measured TF cross section well. But below the barrier, both TF and CF show enhancements compared to 1DBPM predictions. Unlike 6Li, enhancement of CF for 7Li could not be explained by inelastic coupling alone. Conclusion: Whereas the σTF cross sections are almost the same for both the systems in the above barrier region, the suppression of σCF at above the barrier is less for the 7Li+64Ni system than for the 6+64Ni system. Also direct cluster transfer has been identified as the probable source for producing large enhancement in TF cross sections.

  9. Calculation of energy barriers for magnetic vortices in sub-100 nm dots

    NASA Astrophysics Data System (ADS)

    Lapa, Pavel; King, Andrew; Roshchin, Igor V.

    2012-10-01

    In a magnetic vortex, the magnetization is curling in plane everywhere except the ``core,'' where it is out of plane. Interest in switching of magnetic vortices in nanodots is stimulated by their potential application for magnetic memories and nano-oscillators. By combining analytical and micromagnetic techniques, we calculated energy barriers for vortex switching in 20 nm-thick iron dots as a function of applied in-plane field and dot diameter. Using analytical formula for magnetization distribution in the vortex,footnotetextN. A. Usov and S. E. Peschany, J. Magn. Magn. Mater. 118, 290 (1992). we performed micromagnetic calculations of the dot energy for different vortex core positions. In contrast to the ``rigid body approximation,'' the core size and core shape in our calculations were varied to achieve the energy minimum for every core displacement. The energy barriers required for vortex nucleation and annihilation were calculated as a function of magnetic field. By comparing these barriers to the thermal energy kBT we obtained the temperature dependences of the vortex nucleation and annihilation fields in good agreement with the experiment.footnotetextR. K. Dumas et al., Appl. Phys. Lett. 91, 202501 (2007).

  10. Coarse-grained molecular dynamics study of membrane fusion: Curvature effects on free energy barriers along the stalk mechanism.

    PubMed

    Kawamoto, Shuhei; Klein, Michael L; Shinoda, Wataru

    2015-12-28

    The effects of membrane curvature on the free energy barrier for membrane fusion have been investigated using coarse-grained molecular dynamics (CG-MD) simulations, assuming that fusion takes place through a stalk intermediate. Free energy barriers were estimated for stalk formation as well as for fusion pore formation using the guiding potential method. Specifically, the three different geometries of two apposed membranes were considered: vesicle-vesicle, vesicle-planar, and planar-planar membranes. The free energy barriers for the resulting fusion were found to depend importantly on the fusing membrane geometries; the lowest barrier was obtained for vesicular membranes. Further, lipid sorting was observed in fusion of the mixed membranes of dimyristoyl phosphatidylcholine and dioleoyl phosphatidylethanolamine (DOPE). Specifically, DOPE molecules were found to assemble around the stalk to support the highly negative curved membrane surface. A consistent result for lipid sorting was observed when a simple continuum model (CM) was used, where the Helfrich energy and mixing entropy of the lipids were taken into account. However, the CM predicts a much higher free energy barrier than found using CG-MD. This discrepancy originates from the conformational changes of lipids, which were not considered in the CM. The results of the CG-MD simulations reveal that a large conformational change in the lipid takes place around the stalk region, which results in a reduction of free energy barriers along the stalk mechanism of membrane fusion. PMID:26723597

  11. Coarse-grained molecular dynamics study of membrane fusion: Curvature effects on free energy barriers along the stalk mechanism

    SciTech Connect

    Kawamoto, Shuhei; Shinoda, Wataru; Klein, Michael L.

    2015-12-28

    The effects of membrane curvature on the free energy barrier for membrane fusion have been investigated using coarse-grained molecular dynamics (CG-MD) simulations, assuming that fusion takes place through a stalk intermediate. Free energy barriers were estimated for stalk formation as well as for fusion pore formation using the guiding potential method. Specifically, the three different geometries of two apposed membranes were considered: vesicle–vesicle, vesicle–planar, and planar–planar membranes. The free energy barriers for the resulting fusion were found to depend importantly on the fusing membrane geometries; the lowest barrier was obtained for vesicular membranes. Further, lipid sorting was observed in fusion of the mixed membranes of dimyristoyl phosphatidylcholine and dioleoyl phosphatidylethanolamine (DOPE). Specifically, DOPE molecules were found to assemble around the stalk to support the highly negative curved membrane surface. A consistent result for lipid sorting was observed when a simple continuum model (CM) was used, where the Helfrich energy and mixing entropy of the lipids were taken into account. However, the CM predicts a much higher free energy barrier than found using CG-MD. This discrepancy originates from the conformational changes of lipids, which were not considered in the CM. The results of the CG-MD simulations reveal that a large conformational change in the lipid takes place around the stalk region, which results in a reduction of free energy barriers along the stalk mechanism of membrane fusion.

  12. Analytical energy-barrier-dependent Voc model for amorphous silicon solar cells

    NASA Astrophysics Data System (ADS)

    Castro-Carranza, A.; Nolasco, J. C.; Reininghaus, N.; Geißendörfer, S.; Vehse, M.; Parisi, J.; Gutowski, J.; Voss, T.

    2016-07-01

    We show that the open circuit voltage (Voc) in hydrogenated amorphous silicon (a-Si:H) solar cells can be described by an analytical energy-barrier-dependent equation, considering thermionic emission as the physical mechanism determining the recombination current. For this purpose, the current-voltage characteristics of two device structures, i.e., a-Si:H(n)/a-Si:H(i)/a-Si:H(p)/AZO p-i-n solar cells with different p-doping concentrations and a-Si:H(n)/a-Si:H(i)/AZO Schottky structures with different intrinsic layer thicknesses, were analyzed in dark and under illumination, respectively. The calculated barrier in the p-i-n devices is consistent with the difference between the work function of the p-layer and the conduction band edge of the i-layer at the interface in thermal equilibrium.

  13. Low formation energy and kinetic barrier of Stone-Wales defect in infinite and finite silicene

    NASA Astrophysics Data System (ADS)

    Manjanath, Aaditya; Singh, Abhishek K.

    2014-01-01

    Stone-Wales (SW) defects in materials having hexagonal lattice are the most common topological defects that affect the electronic and mechanical properties. Using first principles density functional theory based calculations, we study the formation energy and kinetic barrier of SW-defect in infinite and finite sheets of silicene. The formation energies as well as the barriers in both the cases are significantly lower than those of graphene. Furthermore, compared with the infinite sheets, the energy barriers and formation energies are lower for finite sheets. However, due to low barriers these defects are expected to heal out of the finite sheets.

  14. Permeation of low-Z atoms through carbon sheets: Density functional theory study on energy barriers and deformation effects

    SciTech Connect

    Huber, Stefan E. E-mail: Michael.probst@uibk.ac.at; Mauracher, Andreas; Probst, Michael E-mail: Michael.probst@uibk.ac.at

    2013-12-15

    Energetic and geometric aspects of the permeation of the atoms hydrogen to neon neutral atoms through graphene sheets are investigated by investigating the associated energy barriers and sheet deformations. Density functional theory calculations on cluster models, where graphene is modeled by planar polycyclic aromatic hydrocarbons (PAHs), provide the energies and geometries. Particularities of our systems, such as convergence of both energy barriers and deformation curves with increasing size of the PAHs, are discussed. Three different interaction regimes, adiabatic, planar and vertical, are investigated by enforcing different geometrical constraints. The adiabatic energy barriers range from 5 eV for hydrogen to 20 eV for neon. We find that the permeation of oxygen and carbon into graphene is facilitated by temporary chemical bonding while for other, in principle reactive atoms, it is not. We discuss implications of our results for modeling chemical sputtering of graphite.

  15. Free Energy Wells and Barriers to Ion Transport Across Membranes

    NASA Astrophysics Data System (ADS)

    Rempe, Susan

    2014-03-01

    The flow of ions across cellular membranes is essential to many biological processes. Ion transport is also important in synthetic materials used as battery electrolytes. Transport often involves specific ions and fast conduction. To achieve those properties, ion conduction pathways must solvate specific ions by just the ``right amount.'' The right amount of solvation avoids ion traps due to deep free energy wells, and avoids ion block due to high free energy barriers. Ion channel proteins in cellular membranes demonstrate this subtle balance in solvation of specific ions. Using ab initio molecular simulations, we have interrogated the link between binding site structure and ion solvation free energies in biological ion binding sites. Our results emphasize the surprisingly important role of the environment that surrounds ion-binding sites for fast transport of specific ions. We acknowledge support from Sandia's LDRD program. Sandia National Labs is a multi-program laboratory operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the US DOE's NNSA under contract DE-AC04-94AL85000.

  16. Tuning the Schottky barrier height of the Pd-MoS2 contact by different strains.

    PubMed

    Liu, Biao; Wu, Li-Juan; Zhao, Yu-Qing; Wang, Ling-Zhi; Cai, Meng-Qiu

    2015-10-28

    The structures and electronic properties of the Pd-MoS2 contact are investigated using density functional calculations under different strains. The height of Schottky barrier for the Pd-MoS2 contact can be tuned by different strains. Our results show that the contact nature is of n-type Schottky barrier and the barrier height can be decreased to zero under increased tensile strain (6%). However, under increased compressive strain, the MoS2 layers become indirect bandgap semiconductors, which is a disadvantage for the electron transition in the Pd-MoS2 interface. By analyzing the near band gaps and charge distribution of MoS2 orbitals, we find that the Schottky barrier height is determined by the Mo dz(2) orbitals in the Pd-MoS2 contact. Our calculation results may prove to be instrumental in future design and fabrication of MoS2-based field effect transistors. PMID:26412203

  17. Ethnic differences in cancer symptom awareness and barriers to seeking medical help in England

    PubMed Central

    Niksic, Maja; Rachet, Bernard; Warburton, Fiona G; Forbes, Lindsay J L

    2016-01-01

    Background: Ethnic differences in cancer symptom awareness and barriers to seeking medical help in the English population are not fully understood. We aimed to quantify these differences, to help develop more effective health campaigns, tailored to the needs of different ethnic groups. Methods: Using a large national data set (n=38 492) of cross-sectional surveys that used the Cancer Research UK Cancer Awareness Measure, we examined how cancer symptom awareness and barriers varied by ethnicity, controlling for socio-economic position, age and gender. Data were analysed using multivariable logistic regression. Results: Awareness of cancer symptoms was lower in minority ethnic groups than White participants, with the lowest awareness observed among Bangladeshis and Black Africans. Ethnic minorities were more likely than White British to report barriers to help-seeking. South Asians reported the highest emotional barriers, such as lack of confidence to talk to the doctor, and practical barriers, such as worry about many other things. The Irish were more likely than the White British to report practical barriers, such as being too busy to visit a doctor. White British participants were more likely than any other ethnic group to report that they would feel worried about wasting the doctor's time. Overall, Black Africans had the lowest barriers. All differences were statistically significant (P<0.01 level), after controlling for confounders. Conclusions: Our findings suggest the need for culturally sensitive and targeted health campaigns, focused on improving recognition of cancer symptoms among ethnic minorities. Campaigns should tackle the specific barriers prevalent in each ethnic group. PMID:27280638

  18. Comment on "Compound nucleus aspect of sub-barrier fusion: A new energy scaling behavior"

    NASA Astrophysics Data System (ADS)

    Karpov, A. V.; Rachkov, V. A.; Zagrebaev, V. I.

    2016-01-01

    We comment on a recently published paper by R. Wolski entitled "Compound nucleus aspect of sub-barrier fusion: A new energy scaling behavior" [1], which claims that the sub-barrier fusion is determined mostly by the Q value of the compound nucleus formation. This ignores the dynamical channel-coupling effects at near-barrier energies. We demonstrate that this simplified scaling of fusion cross sections is not a common case and has no predictive power.

  19. Fusion of {sup 6}Li with {sup 159}Tb at near-barrier energies

    SciTech Connect

    Pradhan, M. K.; Mukherjee, A.; Basu, P.; Goswami, A.; Kshetri, R.; Roy, Subinit; Chowdhury, P. Roy; Sarkar, M. Saha; Palit, R.; Parkar, V. V.; Santra, S.; Ray, M.

    2011-06-15

    Complete and incomplete fusion cross sections for {sup 6}Li + {sup 159}Tb have been measured at energies around the Coulomb barrier by the {gamma}-ray method. The measurements show that the complete fusion cross sections at above-barrier energies are suppressed by {approx}34% compared to coupled-channel calculations. A comparison of the complete fusion cross sections at above-barrier energies with the existing data for {sup 11,10}B + {sup 159}Tb and {sup 7}Li + {sup 159}Tb shows that the extent of suppression is correlated with the {alpha} separation energies of the projectiles. It has been argued that the Dy isotopes produced in the reaction {sup 6}Li + {sup 159}Tb at below-barrier energies are primarily due to the d transfer to unbound states of {sup 159}Tb, while both transfer and incomplete fusion processes contribute at above-barrier energies.

  20. Impact of diabetes in blood-testis and blood-brain barriers: resemblances and differences.

    PubMed

    Alves, Marco G; Oliveira, Pedro F; Socorro, Silvia; Moreira, Paula I

    2012-11-01

    Blood-tissue barriers prevent an uncontrolled exchange of large molecules between adjacent but metabolically separated compartments. There are several known barriers and two of the most important and tightest blood-tissue barriers are the blood-testis barrier (BTB) and the blood-brain barrier (BBB). Under normal conditions these barriers, formed by tight junctions between adjacent cells, control the entry of substances and metabolites. However, hyperglycemia and other diabetes-related complications, such as hypertension, impair the function of these biological barriers with dramatic consequences. Although both, BBB and BTB, are responsible for the maintenance of different biological processes, they have some remarkable similarities not always explored when looking at metabolic-related diseases such as diabetes. These barriers possess their own glucose sensing machinery, suffer a tied hormonal control and have specific mechanisms to counteract hyper- and hypoglycemia. In BBB and BTB the insulin signaling is also distinct from other tissues and organs thus evidencing their importance in protecting against or exacerbating the effects of diabetes on glucose metabolism. The control of glucose and lactate levels in brain and testis highlights the role of these barriers in protecting against peripheral glucose and lactate fluctuations that occur in the diabetic individual. We review the role of BBB and BTB in the control of glucose and metabolic dysfunction caused by diabetes in the brain and seminiferous epithelium. Gaining a better understanding of the molecular mechanisms through which glucose metabolism disrupts BBB and BTB function may highlight new opportunities for the treatment of diabetic complications in brain and male reproductive function. PMID:22934551

  1. Technical Barriers, Gaps,and Opportunities Related to Home Energy Upgrade Market Delivery

    SciTech Connect

    Bianchi, Marcus V.A.

    2011-11-01

    This report outlines the technical barriers, gaps, and opportunities that arise in executing home energy upgrade market delivery approaches, as identified through research conducted by the U.S. Department of Energy's Building America program.

  2. Internal rotation barrier of the XH3sbnd YH3 (X, Y = C or Si) molecules. An energy decomposition analysis study

    NASA Astrophysics Data System (ADS)

    Chang, Xin; Su, Peifeng; Wu, Wei

    2014-08-01

    In this paper, the barriers of the internal rotation in ethane, methylsilane, and disilane are investigated by the generalized Kohn-Sham based energy decomposition analysis (GKS-EDA) scheme (P. Su, et al. J. Phys. Chem A 118 (2014) 2531). The rotation barriers and the inter-conversion energies from the three geometrical variation processes are decomposed into the electrostatic, exchange-repulsion, polarization, correlation and geometrical relaxation terms. It is concluded that the rotation barriers of the three molecules are all dominated by exchange-repulsion (Pauli repulsion). The geometry relaxation does not make a difference to the origin of the barrier.

  3. Surface barrier height for different Al compositions and barrier layer thicknesses in AlGaN/GaN heterostructure field effect transistors

    SciTech Connect

    Goyal, Nitin Fjeldly, Tor A.; Iniguez, Benjamin

    2013-12-04

    In this paper, we present a physics based analytical model for the calculation of surface barrier height for given values of barrier layer thicknesses and Al mole fractions. An explicit expression for the two dimensional electron gas density is also developed incorporating the change in polarization charges for different Al mole fractions.

  4. Perceived Barriers to Employment Success: Are There Differences between European American and African American VR Consumers?

    ERIC Educational Resources Information Center

    Zanskas, Stephen A.; Lustig, Daniel C.; Ishitani, Terry T.

    2011-01-01

    Purpose: The primary purpose of this study was to investigate whether there were differences between European and African American vocational rehabilitation consumers' perceptions of the barriers they experience towards obtaining employment. A secondary purpose was to determine whether there were differences in these perceptions based upon gender…

  5. Gender Differences in the Perceived Needs and Barriers of Youth Offenders Preparing for Community Reentry

    PubMed Central

    Abrams, Laura S.

    2010-01-01

    This study explored how gender differences may influence the community reentry experiences of incarcerated youth. Structured surveys assessing risk factors for re-offending, perceived reentry needs, and anticipated barriers to meeting these needs were administered to a convenience sample of males (n = 36) and females (n = 35) who were within 60 days of release from two probation camps in Southern California. Bivariate analyses found significant gender differences in prior risk factors, educational aspirations, expressed mental health needs, anticipated use of services, and reentry concerns. Minimal gender differences were detected in perceived employment needs and barriers and self-efficacy to avoid recidivism. The findings support the need for gender-specific reentry programming in some key areas and also draw attention to the importance of removing barriers to successful reentry for all incarcerated youth. PMID:20730108

  6. Relaxation times and energy barriers of rubbing-induced birefringence in glass-forming polymers

    NASA Astrophysics Data System (ADS)

    Shiu, K. P.; Qin, Zongyi; Yang, Z.

    2008-12-01

    The relaxations of rubbing-induced birefringence (RIB) in several glass-forming polymers, including polycarbonate and polystyrene (PS) derivatives with various modifications to the phenyl ring side group, are studied. Significant relaxations of RIB are observed at temperatures well below the glass transition temperature T g . The relaxation times span a wide range from ˜ 10 s to probably geological time scale. Physical aging effects are absent in the RIB relaxations. The model proposed for the interpretation of RIB in PS describes well the RIB relaxations in all the polymers investigated here. The energy barriers are of the order of a few hundred kJ/mol and decrease with decreasing temperature, in opposition to the trend of Vogel-Fulcher form for polymer segmental relaxations above T g . The relaxation behaviors of different polymers are qualitatively similar but somewhat different in quantitative details, such as in the values of the saturated birefringence, the shape of the initial barrier density distribution functions, the rates of barrier decrease with decreasing temperature, and the dependence of relaxation times on temperature and parameter ξ , etc. The RIB relaxations are different from any of the other relaxations below T g that have been reported in the literature, such as dielectric relaxations or optical probe relaxations. A microscopic model for the relaxations of RIB is much desired.

  7. Do perceived cues, benefits, and barriers to physical activity differ between male and female adolescents?

    PubMed

    Tergerson, Jennifer L; King, Keith A

    2002-11-01

    A four-page survey was administered to 535 adolescents at two single-sex (one male, one female) high schools in Cincinnati, Ohio, to examine whether perceptions of physical activity differed by gender. More specifically, the survey assessed perceived cues, benefits, and barriers to exercising. Results indicated that the most helpful cue to physical activity for both female and male students was "having a friend to exercise with." The most commonly reported benefit of exercising among females was "to stay in shape," whereas the most commonly reported benefit to exercising among males was "to become strong." Among females, the most common barrier to exercising was "having no time to exercise," whereas males were most likely to report "wanting to do other things with my time." Multivariate analyses of covariance revealed that perceived cues, benefits, and barriers to physical activity differed significantly based on gender. Recommendations on specific strategies to increasing male and female adolescent physical activity levels are offered. PMID:12557633

  8. Influence of rotational energy barriers to the conformational search of protein loops in molecular dynamics and ranking the conformations.

    PubMed

    Tappura, K

    2001-08-15

    An adjustable-barrier dihedral angle potential was added as an extension to a novel, previously presented soft-core potential to study its contribution to the efficacy of the search of the conformational space in molecular dynamics. As opposed to the conventional soft-core potential functions, the leading principle in the design of the new soft-core potential, as well as of its extension, the soft-core and adjustable-barrier dihedral angle (SCADA) potential (referred as the SCADA potential), was to maintain the main equilibrium properties of the original force field. This qualifies the methods for a variety of a priori modeling problems without need for additional restraints typically required with the conventional soft-core potentials. In the present study, the different potential energy functions are applied to the problem of predicting loop conformations in proteins. Comparison of the performance of the soft-core and SCADA potential showed that the main hurdles for the efficient sampling of the conformational space of (loops in) proteins are related to the high-energy barriers caused by the Lennard-Jones and Coulombic energy terms, and not to the rotational barriers, although the conformational search can be further enhanced by lowering the rotational barriers of the dihedral angles. Finally, different evaluation methods were studied and a few promising criteria found to distinguish the near-native loop conformations from the wrong ones. PMID:11455590

  9. Do Perceived Cues, Benefits, and Barriers to Physical Activity Differ between Male and Female Adolescents?

    ERIC Educational Resources Information Center

    Tergerson, Jennifer L.; King, Keith A.

    2002-01-01

    Surveyed adolescents at single-sex high schools to examine whether perceptions of physical activity differed by gender. The most helpful cue to physical activity for males and females was having a friend to exercise with. Parental encouragement and having a parent who exercised were also helpful. Wanting to do other things was a common barrier to…

  10. Gender Differences in the Perceived Needs and Barriers of Youth Offenders Preparing for Community Reentry

    ERIC Educational Resources Information Center

    Fields, Diane; Abrams, Laura S.

    2010-01-01

    This study explored how gender differences may influence the community reentry experiences of incarcerated youth. Structured surveys assessing risk factors for re-offending, perceived reentry needs, and anticipated barriers to meeting these needs were administered to a convenience sample of males (n = 36) and females (n = 35) who were within 60…

  11. Barriers to Energy Efficiency and the Uptake of Green Revolving Funds in Canadian Universities

    ERIC Educational Resources Information Center

    Maiorano, John; Savan, Beth

    2015-01-01

    Purpose: The purpose of this paper is to investigate the barriers to the implementation of energy efficiency projects in Canadian universities, including access to capital, bounded rationality, hidden costs, imperfect information, risk and split incentives. Methods to address these barriers are investigated, including evaluating the efficacy of…

  12. On the economic analysis of problems in energy efficiency: Market barriers, market failures, and policy implications

    SciTech Connect

    Sanstad, A.H.; Koomey, J.G.; Levine, M.D.

    1993-01-01

    In his recent paper in The Energy Journal, Ronald Sutherland argues that several so-called market barriers'' to energy efficiency frequently cited in the literature are not market failures in the conventional sense and are thus irrelevant for energy policy. We argue that Sutherland has inadequately analyzed the idea of market barrier and misrepresented the policy implications of microeconomics. We find that economic theory, correctly interpreted, does not provide for the categorical dismissal of market barriers. We explore important methodological issues underlying the debate over market barriers, and discuss the importance of reconciling the findings of non-economic social sciences with the economic analysis of energy demand and consumer decision-making. We also scrutinize Sutherland's attempt to apply finance theory to rationalize high implicit discount rates observed in energy-related choices, and find this use of finance theory to be inappropriate.

  13. On the economic analysis of problems in energy efficiency: Market barriers, market failures, and policy implications

    SciTech Connect

    Sanstad, A.H.; Koomey, J.G.; Levine, M.D.

    1993-01-01

    In his recent paper in The Energy Journal, Ronald Sutherland argues that several so-called ``market barriers`` to energy efficiency frequently cited in the literature are not market failures in the conventional sense and are thus irrelevant for energy policy. We argue that Sutherland has inadequately analyzed the idea of market barrier and misrepresented the policy implications of microeconomics. We find that economic theory, correctly interpreted, does not provide for the categorical dismissal of market barriers. We explore important methodological issues underlying the debate over market barriers, and discuss the importance of reconciling the findings of non-economic social sciences with the economic analysis of energy demand and consumer decision-making. We also scrutinize Sutherland`s attempt to apply finance theory to rationalize high implicit discount rates observed in energy-related choices, and find this use of finance theory to be inappropriate.

  14. Building America Top Innovations 2012: Thermal Bypass Air Barriers in the 2009 International Energy Conservation Code

    SciTech Connect

    none,

    2013-01-01

    This Building America Top Innovations profile describes Building America research supporting Thermal Bypass Air Barrier requirements. Since these were adopted in the 2009 IECC, close to one million homes have been mandated to include this vitally important energy efficiency measure.

  15. Barriers and opportunities: A review of selected successful energy-efficiency programs

    SciTech Connect

    Worrell, Ernst; Price, Lynn

    2001-03-20

    In industry, barriers may exist at various points in the decision making process, and in the implementation and management of measures to improve energy efficiency. Barriers may take many forms, and are determined by the business environment and include decision-making processes, energy prices, lack of information, a lack of confidence in the information, or high transaction costs for obtaining reliable information, as well as limited capital availability. Other barriers are the ''invisibility'' of energy efficiency measures and the difficulty of quantifying the impacts, and slow diffusion of innovative technology into markets while firms typically under-invest in R and D, despite the high pay-backs. Various programs try to reduce the barriers to improve the uptake of innovative technologies. A wide array of policies has been used and tested in the industrial sector in industrialized countries, with varying success rates. We review some new approaches to industrial energy efficiency improvement in industrialized countries, focusing on voluntary agreements.

  16. Role of neutron transfer in asymmetric fusion reactions at sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Ogloblin, A. A.; Zhang, H. Q.; Lin, C. J.; Jia, H. M.; Khlebnikov, S. V.; Kuzmin, E. A.; Trzaska, W. H.; Xu, X. X.; Yan, F.; Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2014-10-01

    The measured complete fusion (capture) excitation function is presented for the 28Si + 208Pb reaction at deep sub-barrier energies. This excitation function is compared with the one predicted with the quantum diffusion approach.

  17. Energy barriers for dipole moment flipping in PVDF-related ferroelectric polymers

    NASA Astrophysics Data System (ADS)

    Yu, Ying-Ju; McGaughey, Alan J. H.

    2016-01-01

    Energy barriers for flipping the transverse dipole moments in poly(vinylidene fluoride) (PVDF) and related copolymers and terpolymers are predicted using the nudged elastic band method. The dipole moments flip individually along the chain, with an order and energy barrier magnitudes (0.1-1.2 eV) that depend on the chain composition and environment. Trifluoroethylene (TrFE) and chlorofluoroethylene (CFE) monomers have larger energy barriers than VDF monomers, while a chain in an amorphous environment has a similar transition pathway as that of an isolated molecule. In a crystalline environment, TrFE and CFE monomers expand the lattice and lower the energy barriers for flipping VDF monomers. This finding is consistent with experimental observations of a large electrocaloric effect in P(VDF-TrFE-CFE) terpolymers.

  18. Heavy ion fusion at sub-barrier energies: Progress and questions

    SciTech Connect

    Betts, R.R.

    1993-01-01

    The current status of the experimental study of heavy-ion fusion at sub-barrier energies is reviewed. Emphasis is placed on areas of disagreement between experimental data and theoretical predictions. Suggestions for future experiments are discussed.

  19. Heavy ion fusion at sub-barrier energies: Progress and questions

    SciTech Connect

    Betts, R.R.

    1993-04-01

    The current status of the experimental study of heavy-ion fusion at sub-barrier energies is reviewed. Emphasis is placed on areas of disagreement between experimental data and theoretical predictions. Suggestions for future experiments are discussed.

  20. Reaction Pathway and Free Energy Barrier for Urea Elimination in Aqueous Solution

    PubMed Central

    Yao, Min; Chen, Xi; Zhan, Chang-Guo

    2015-01-01

    To accurately predict the free energy barrier for urea elimination in aqueous solution, we examined the reaction coordinates for the direct and water-assisted elimination pathways, and evaluated the corresponding free energy barriers by using the surface and volume polarization for electrostatics (SVPE) model-based first-principles electronic-structure calculations. Based on the computational results, the water-assisted elimination pathway is dominant for urea elimination in aqueous solution, and the corresponding free energy barrier is 25.3 kcal/mol. The free energy barrier of 25.3 kcal/mol predicted for the dominant reaction pathway of urea elimination in aqueous solution is in good agreement with available experimental kinetic data. PMID:25821238

  1. Theoretical study of the elastic breakup of weakly bound nuclei at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Otomar, D. R.; Gomes, P. R. S.; Lubian, J.; Canto, L. F.; Hussein, M. S.

    2015-12-01

    We have performed continuum discretized coupled channel (CDCC) calculations for collisions of 7Li projectiles on 59Co,144Sm, and 208Pb targets at near-barrier energies, to assess the importance of the Coulomb and the nuclear couplings in the breakup of 7Li, as well as the Coulomb-nuclear interference. We have also investigated scaling laws, expressing the dependence of the cross sections on the charge and the mass of the target. This work is complementary to that previously reported by us on the breakup of 6Li. Here we explore the similarities and differences between the results for the two lithium isotopes. The relevance of the Coulomb dipole and quadrupole strengths at low energy for the two-cluster projectile is investigated in detail.

  2. Summary of Gaps and Barriers for Implementing Residential Building Energy Efficiency Strategies

    SciTech Connect

    none,

    2010-08-01

    This report presents the key gaps and barriers to implementing residential energy efficiency strategies in the U.S. market, as identified in sessions at the U.S. Department of Energy's Building America 2010 Residential Energy Efficiency Meeting held in Denver, Colorado, on July 20-22, 2010.

  3. A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

    SciTech Connect

    Tchitchekova, Deyana S.; Morthomas, Julien; Perez, Michel; Ribeiro, Fabienne; Ducher, Roland

    2014-07-21

    A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.

  4. A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress.

    PubMed

    Tchitchekova, Deyana S; Morthomas, Julien; Ribeiro, Fabienne; Ducher, Roland; Perez, Michel

    2014-07-21

    A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress. PMID:25053312

  5. A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress

    NASA Astrophysics Data System (ADS)

    Tchitchekova, Deyana S.; Morthomas, Julien; Ribeiro, Fabienne; Ducher, Roland; Perez, Michel

    2014-07-01

    A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ˜3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.

  6. pH-Regulated Mechanisms Account for Pigment-Type Differences in Epidermal Barrier Function

    PubMed Central

    Gunathilake, Roshan; Schurer, Nanna Y.; Shoo, Brenda A.; Celli, Anna; Hachem, Jean-Pierre; Crumrine, Debra; Sirimanna, Ganga; Feingold, Kenneth R.; Mauro, Theodora M.; Elias, Peter M.

    2009-01-01

    To determine whether pigment type determines differences in epidermal function, we studied stratum corneum (SC) pH, permeability barrier homeostasis, and SC integrity in three geographically disparate populations with pigment type I–II versus IV–V skin (Fitzpatrick I–VI scale). Type IV–V subjects showed: (i) lower surface pH (≈0.5 U); (ii) enhanced SC integrity (transepidermal water loss change with sequential tape strippings); and (iii) more rapid barrier recovery than type I–II subjects. Enhanced barrier function could be ascribed to increased epidermal lipid content, increased lamellar body production, and reduced acidity, leading to enhanced lipid processing. Compromised SC integrity in type I–II subjects could be ascribed to increased serine protease activity, resulting in accelerated desmoglein-1 (DSG-1)/corneodesmosome degradation. In contrast, DSG-1-positive CDs persisted in type IV–V subjects, but due to enhanced cathepsin-D activity, SC thickness did not increase. Adjustment of pH of type I–II SC to type IV–V levels improved epidermal function. Finally, dendrites from type IV–V melanocytes were more acidic than those from type I–II subjects, and they transfer more melanosomes to the SC, suggesting that melanosome secretion could contribute to the more acidic pH of type IV–V skin. These studies show marked pigment-type differences in epidermal structure and function that are pH driven. PMID:19177137

  7. A finite difference analysis of the field present behind an acoustically impenetrable two-layer barrier.

    PubMed

    Hurrell, Andrew M

    2008-06-01

    The interaction of an incident sound wave with an acoustically impenetrable two-layer barrier is considered. Of particular interest is the presence of several acoustic wave components in the shadow region of this barrier. A finite difference model capable of simulating this geometry is validated by comparison to the analytical solution for an idealized, hard-soft barrier. A panel comprising a high air-content closed cell foam backed with an elastic (metal) back plate is then examined. The insertion loss of this panel was found to exceed the dynamic range of the measurement system and was thus acoustically impenetrable. Experimental results from such a panel are shown to contain artifacts not present in the diffraction solution, when acoustic waves are incident upon the soft surface. A finite difference analysis of this experimental configuration replicates the presence of the additional field components. Furthermore, the simulated results allow the additional components to be identified as arising from the S(0) and A(0) Lamb modes traveling in the elastic plate. These Lamb mode artifacts are not found to be present in the shadow region when the acoustic waves are incident upon the elastic surface. PMID:18537372

  8. Removal Of Nitric Oxide From Different Mixtures Of Gases Using Dielectric Barrier Discharge

    SciTech Connect

    Hashim, Siti Aiasah; San, Wong Chiow; Abas, Radzi

    2009-07-07

    Dielectric barrier discharge (DBD) is employed in this project as the processing medium to remove nitric oxide in gas stream. Gas stream containing different components was released continuously into a series of dielectric barrier discharge cells and the output gas was analyzed using a chemiluminescence's type NO analyzer. Almost complete removal (more than 99%) of NO was observed when the gas stream contained only NO and nitrogen. In the presence of SO{sub 2}, the removal rate was decreased to as low as 70%. Adding air into the stream gave a more erratic results. The removal rate was also affected by the number of DBD cell used and the flow rate of the input gas. However, In this paper, only results using 2 cells whilst varying the flow rate are presented.

  9. Managing Free-energy Barriers in Nuclear Pore Transport

    PubMed Central

    Nielsen, Brian; Jeppesen, Claus

    2006-01-01

    The Nuclear Pore Complexes (NPC) facilitate highly selective gateways for transport of macromolecules across the Nuclear Envelope (NE). Based on the current accumulated knowledge of the architecture of NPC we have established a minimal physical model of the pore and the transport mechanism. The barrier properties of the NPC model are analyzed by the recently established Wang–Landau Monte Carlo computer simulation technique and the transport properties are extracted by employing Kramers’ theory of reaction rates. We show that our physical model can account for a range of characteristics observed for nuclear pore transport. PMID:19669451

  10. Educational Barriers of Rural Youth: Relation of Individual and Contextual Difference Variables

    PubMed Central

    Irvin, Matthew J.; Byun, Soo-yong; Meece, Judith L.; Farmer, Thomas W.

    2014-01-01

    The purpose of this study was to examine the relation of several individual and contextual difference factors to the perceived educational barriers of rural youth. Data were from a broader national investigation of students’ postsecondary aspirations and preparation in rural high schools across the United States. The sample involved more than 7,000 rural youth in 73 high schools across 34 states. Results indicated that some individual (e.g., African American race/ethnicity) and contextual (e.g., parent education) difference factors were predictive while others were not. Extensions to, similarities, and variations with previous research are discussed. Implications, limitations, and suggestions for future research are also discussed. PMID:24474843

  11. Evaporation protons from 8B+58Ni at near barrier energies

    NASA Astrophysics Data System (ADS)

    Amador-Valenzuela, P.; Aguilera, E. F.; Martinez-Quiroz, E.; Lizcano, D.; Kolata, J. J.; Roberts, A.; Becchetti, F. D.; Ojaruega, M.; Febbraro, M.; Guimarães, V.; Rossi, E. S., Jr.; Huiza, J. F. P.; Acosta, L.; Belyaeva, T. L.

    2011-10-01

    Yields of evaporated protons from the 8B+58Ni reaction are measured at backward angles, for several near barrier energies. Statistical model calculations using the code PACE are used to extrapolate the measurements to the whole angular region in order to get angle integrated cross sections. Fusion cross sections are deduced by using the calculated proton multiplicities. The obtained fusion excitation function shows a large enhancement as compared to BPM calculations using conventional barrier parameters.

  12. Necessity of an energy barrier for self-correction of Abelian quantum doubles

    NASA Astrophysics Data System (ADS)

    Kómár, Anna; Landon-Cardinal, Olivier; Temme, Kristan

    2016-05-01

    We rigorously establish an Arrhenius law for the mixing time of quantum doubles based on any Abelian group Zd. We have made the concept of the energy barrier therein mathematically well defined; it is related to the minimum energy cost the environment has to provide to the system in order to produce a generalized Pauli error, maximized for any generalized Pauli errors, not only logical operators. We evaluate this generalized energy barrier in Abelian quantum double models and find it to be a constant independent of system size. Thus, we rule out the possibility of entropic protection for this broad group of models.

  13. Coronal microleakage of three different dental biomaterials as intra-orifice barrier during nonvital bleaching

    PubMed Central

    Zarenejad, Nafiseh; Asgary, Saeed; Ramazani, Nahid; Haghshenas, Mohammad Reza; Rafiei, Alireza; Ramazani, Mohsen

    2015-01-01

    Background: This study was designed to assess the microleakage of glass-ionomer (GI), mineral trioxide aggregate (MTA), and calcium-enriched mixture (CEM) cement as coronal orifice barrier during walking bleaching. Materials and Methods: In this experimental study, endodontic treatment was done for 70 extracted human incisors without canal calcification, caries, restoration, resorption, or cracks. The teeth were then divided into three experimental using “Simple randomization allocation” (n = 20) and two control groups (n = 5). The three cements were applied as 3-mm intra-orifice barrier in test groups, and bleaching process was then conducted using a mixture of sodium perborate powder and distilled water, for 9 days. For leakage evaluation, bovine serum albumin marker was traced in a dual-chamber technique with Bradford indicator. The Kruskal-Wallis and Mann-Whitney tests were used for statistical analysis. Results: The mean ± standard deviation leakage of samples from negative control, positive control, GI, MTA, and CEM cement groups were 0.0, 8.9 ± 0.03, 0.47 ± 0.02, 0.48 ± 0.02, and 0.49 ± 0.02 mg/mL, respectively. Statistical analysis showed no significant difference between three experimental groups (P > 0.05). Conclusion: It is concluded that GI, MTA, and CEM cements are considered as suitable intra-orifice barrier to provide coronal seal during walking bleaching. PMID:26759596

  14. Field-dependent energy barriers in Co/CoO core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Nieves, P.; Kechrakos, D.; Chubykalo-Fesenko, O.

    2016-02-01

    We perform atomistic modeling of Co/CoO nanoparticles with a diameter of a few nanometers and realistic values of the exchange and anisotropy parameters in order to study the field-dependent energy barriers under forward and backward reversal of the magnetization. The barriers are extracted from the constrained energy minimization using the integration of the Landau-Lifshitz-Gilbert equations and the Lagrange multiplier method. We show that the applied field and the interface exchange strength have opposite effects on the values of the energy barriers. In particular, while the backward (forward) energy barrier increases (decreases) linearly with the strength of the interface exchange coupling, it decreases (increases) almost quadratically with the applied magnetic field. Our results are in good agreement with the well-known Meiklejohn-Bean model of exchange bias, and allow us to analyze the limits of applicability of the macrospin approach to the study of energy barriers in core-shell Co/CoO nanoparticles.

  15. Financing Projects That Use Clean-Energy Technologies. An Overview of Barriers and Opportunities

    SciTech Connect

    Goldman, D. P.; McKenna, J. J.; Murphy, L. M.

    2005-10-01

    This technical paper describes the importance of project financing for clean-energy technology deployment. It describes the key challenges in financing clean-energy technology projects, including technical risks, credit worthiness risk, revenue security risk, market competition, scale and related cost, as well as first-steps to overcome those barriers.

  16. Factors Affecting Energy Barriers for Pyramidal Inversion in Amines and Phosphines: A Computational Chemistry Lab Exercise

    ERIC Educational Resources Information Center

    Montgomery, Craig D.

    2013-01-01

    An undergraduate exercise in computational chemistry that investigates the energy barrier for pyramidal inversion of amines and phosphines is presented. Semiempirical calculations (PM3) of the ground-state and transition-state energies for NR[superscript 1]R[superscript 2]R[superscript 3] and PR[superscript 1]R[superscript 2]R[superscript 3] allow…

  17. Sensing properties of different classes of gases based on the nanowire-electrode junction barrier modulation

    NASA Astrophysics Data System (ADS)

    Singh, Nandan; Yan, Chaoyi; Lee, Pooi See; Comini, Elisabetta

    2011-04-01

    The role of contact between semiconducting nanowire and metal electrodes in a single nanowire field effect transistor (NW-FET) is investigated for the sensing of different type of gases. Two different types of In2O3nanowire devices, namely; Schottky contact device (SCD) and Ohmic contact device (OCD) are evaluated. SCD has shown a superior response to the reducing gas (CO) compared to oxidizing gas (NO), while OCD has shown high sensitivity towards oxidizing gas (NO) compared to the reducing gas (CO) under similar working conditions. The sensing mechanism is dominated by the contact resistance at the metal-semiconductor junction in SCD and the change in nanowirechannel conductance dominates in OCD. The Schottky barrier height (SBH) was extracted using low temperature current voltage measurement which provided direct evidence for the notion that the barrier height plays a crucial role in the sensing of different types of gases. The sensing mechanism is illustrated in this work for both devices.The role of contact between semiconducting nanowire and metal electrodes in a single nanowire field effect transistor (NW-FET) is investigated for the sensing of different type of gases. Two different types of In2O3nanowire devices, namely; Schottky contact device (SCD) and Ohmic contact device (OCD) are evaluated. SCD has shown a superior response to the reducing gas (CO) compared to oxidizing gas (NO), while OCD has shown high sensitivity towards oxidizing gas (NO) compared to the reducing gas (CO) under similar working conditions. The sensing mechanism is dominated by the contact resistance at the metal-semiconductor junction in SCD and the change in nanowirechannel conductance dominates in OCD. The Schottky barrier height (SBH) was extracted using low temperature current voltage measurement which provided direct evidence for the notion that the barrier height plays a crucial role in the sensing of different types of gases. The sensing mechanism is illustrated in this work

  18. Multinucleon transfer in O,1816,19F+208Pb reactions at energies near the fusion barrier

    NASA Astrophysics Data System (ADS)

    Rafferty, D. C.; Dasgupta, M.; Hinde, D. J.; Simenel, C.; Simpson, E. C.; Williams, E.; Carter, I. P.; Cook, K. J.; Luong, D. H.; McNeil, S. D.; Ramachandran, K.; Vo-Phuoc, K.; Wakhle, A.

    2016-08-01

    Background: Nuclear reactions are complex, involving collisions between composite systems where many-body dynamics determines outcomes. Successful models have been developed to explain particular reaction outcomes in distinct energy and mass regimes, but a unifying picture remains elusive. The irreversible transfer of kinetic energy from the relative motion of the collision partners to their internal states, as is known to occur in deep inelastic collisions, has yet to be successfully incorporated explicitly into fully quantal reaction models. The influence of these processes on fusion is not yet quantitatively understood. Purpose: To investigate the population of high excitation energies in transfer reactions at sub-barrier energies, which are precursors to deep inelastic processes, and their dependence on the internuclear separation. Methods: Transfer probabilities and excitation energy spectra have been measured in collisions of O,1816,19F+208Pb , at various energies below and around the fusion barrier, by detecting the backscattered projectile-like fragments in a Δ E -E telescope. Results: The relative yields of different transfer outcomes are strongly driven by Q values, but change with the internuclear separation. In 16O+208Pb , single nucleon transfer dominates, with a strong contribution from -2 p transfer close to the Coulomb barrier, though this channel becomes less significant in relation to the -2 p 2 n transfer channel at larger separations. For 18O+208Pb , the -2 p 2 n channel is the dominant charge transfer mode at all separations. In the reactions with 19F,-3 p 2 n transfer is significant close to the barrier, but falls off rapidly with energy. Multinucleon transfer processes are shown to lead to high excitation energies (up to ˜15 MeV), which is distinct from single nucleon transfer modes which predominantly populate states at low excitation energy. Conclusions: Kinetic energy is transferred into internal excitations following transfer, with this

  19. The effect of breakup of 6Li on elastic scattering and fusion with 28Si at near barrier energies

    NASA Astrophysics Data System (ADS)

    Sinha, Mandira; Roy, Subinit; Basu, P.; Majumdar, H.

    2016-01-01

    Elastic scattering angular distributions for 6Li+28Si system were measured at Elab = 16, 21MeV and analyzed along with the existing data from the previous measurements in the energy range of Elab = 7.5 - 27MeV. The measured cross-sections and the existing data, forming a set of angular distributions over a range of E/Vb = 0.9 - 3.23, were analyzed using the phenomenological optical model potential (OMP). Three different sets of potential parameters were used. The energy dependence of the real and the imaginary potential strengths were, subsequently, extracted at the radius of sensitivity (Rav) for the system. Continuum Discretized Coupled Channel (CDCC) calculation was performed to explore the contribution of projectile break-up (BU) on the observed energy dependence of the effective potential for elastic scattering of 6Li from 28Si. The energy variation of the strength of the real potential with continuum coupling was found to agree with the energy dependence of the same extracted from the (OMP) analysis at energies around the barrier. But the behavior of the imaginary strength appeared to be different. The calculated fusion cross-sections, including the effect of BU, clearly overestimated the measured fusion excitation function data in the below and near barrier energies but compared well with the data at higher energies.

  20. Environmental Barrier Coatings for the Energy Efficient Heat Engines Program

    SciTech Connect

    Katherine Faber

    2004-10-31

    This program aimed to develop a fundamental understanding of the microstructural, mechanical, and chemical properties of Ta{sub 2}O{sub 5}-based coatings for Si{sub 3}N{sub 4} (AS800) substrates and optimize such coatings for environmental barriers. The program consisted of three tasks: processing of Ta{sub 2}O{sub 5} coatings, phase and microstructural development, and life-limiting phenomena. Northwestern University formed a cross-functional team with Lehigh University, Honeywell Inc., and Oak Ridge National Laboratory. The major accomplishments are: (1) Conditions for the plasma spray of Ta{sub 2}O{sub 5} and its alloys were optimized to provide maximum density and thickness. (2) Adherent small particle plasma spray coatings of Ta{sub 2}O{sub 5} can be routinely prepared. (3) Ta{sub 2}O{sub 5} can be stabilized against its disruptive phase transformation to 1400 C by the addition of one or more oxides of Al, La, and/or Nb. (4) Residual stresses in the Ta{sub 2}O{sub 5} coatings were measured using X-rays and changed with thermal exposure. (5) Properly doped coatings are more resistant against thermal cycling than undoped coatings, and can be cycled many thousand times without spallation. (6) Water vapor testing in the ORNL Keiser Rig of adherent coatings showed that undoped Ta{sub 2}O{sub 5} is not an effective barrier at preventing chemical changes to the AS800. (7) Limited water vapor testing of doped and adherent coatings, which had successfully survived many thermal cycles, showed that in the water vapor environment, de-cohesion may occur.

  1. Numerical determination of the interfacial energy and nucleation barrier of curved solid-liquid interfaces in binary systems

    NASA Astrophysics Data System (ADS)

    Kundin, Julia; Choudhary, Muhammad Ajmal

    2016-07-01

    The phase-field crystal (PFC) technique is a widely used approach for modeling crystal growth phenomena with atomistic resolution on mesoscopic time scales. We use a two-dimensional PFC model for a binary system based on the work of Elder et al. [Phys. Rev. B 75, 064107 (2007), 10.1103/PhysRevB.75.064107] to study the effect of the curved, diffuse solid-liquid interface on the interfacial energy as well as the nucleation barrier. The calculation of the interfacial energy and the nucleation barrier certainly depends on the proper definition of the solid-liquid dividing surface and the corresponding nucleus size. We define the position of the sharp interface at which the interfacial energy is to be evaluated by using the concept of equimolar dividing surface (re) and the minimization of the interfacial energy (rs). The comparison of the results based on both radii shows that the difference re-rs is always positive and has a limit for large cluster sizes which is comparable to the Tolman length. Furthermore, we found the real nucleation barrier for small cluster sizes, which is defined as a function of the radius rs, and compared it with the classical nucleation theory. The simulation results also show that the extracted interfacial energy as function of both radii is independent of system size, and this dependence can be reasonably described by the nonclassical Tolman formula with a positive Tolman length.

  2. Analyzing Barriers to Energy Conservation in Residences and Offices: The Rewire Program at the University of Toronto

    ERIC Educational Resources Information Center

    Stokes, Leah C.; Mildenberger, Matto; Savan, Beth; Kolenda, Brian

    2012-01-01

    Conducting a barriers analysis is an important first step when designing proenvironmental behavior change interventions. Yet, detailed information on common barriers to energy conservation campaigns remains unavailable. Using a pair of original surveys, we leverage the theory of planned behavior to report on the most important barriers for…

  3. The energy barrier at noble metal/TiO{sub 2} junctions

    SciTech Connect

    Hossein-Babaei, F. E-mail: fhbabaei@yahoo.com; Lajvardi, Mehdi M. Alaei-Sheini, Navid

    2015-02-23

    Nobel metal/TiO{sub 2} structures are used as catalysts in chemical reactors, active components in TiO{sub 2}-based electronic devices, and connections between such devices and the outside circuitry. Here, we investigate the energy barrier at the junctions between vacuum-deposited Ag, Au, and Pt thin films and TiO{sub 2} layers by recording their electrical current vs. voltage diagrams and spectra of optical responses. Deposited Au/, Pt/, and Ag/TiO{sub 2} behave like contacts with zero junction energy barriers, but the thermal annealing of the reverse-biased devices for an hour at 523 K in air converts them to Schottky diodes with high junction energy barriers, decreasing their reverse electric currents up to 10{sup 6} times. Similar thermal processing in vacuum or pure argon proved ineffective. The highest energy barrier and the lowest reverse current among the devices examined belong to the annealed Ag/TiO{sub 2} contacts. The observed electronic features are described based on the physicochemical parameters of the constituting materials. The formation of higher junction barriers with rutile than with anatase is demonstrated.

  4. How Organ Donors are Different from Non-donors: Responsibility, Barriers, and Religious Involvement.

    PubMed

    Range, Lillian M; Brazda, Geoffrey F

    2015-12-01

    To see if religious involvement, previously linked to various health behaviors, was linked to organ donation, 143 ethnically diverse undergraduates stated whether they were registered donors (53% were), and completed measures of organ donation attitudes and religious involvement. Compared with non-donors, donors reported fewer barriers, more family responsibility, and more willingness to receive donor organs, but were not different in religious involvement. Even in 2014, when being a "good Samaritan" by agreeing to organ donation is as easy as checking one box on a driver's license application, religious involvement does not seem to be a factor in checking this box. PMID:25524413

  5. Direct measurement of free-energy barrier to nucleation of crystallites in amorphous silicon thin films

    NASA Technical Reports Server (NTRS)

    Shi, Frank G.

    1994-01-01

    A method is introduced to measure the free-energy barrier W(sup *), the activation energy, and activation entropy to nucleation of crystallites in amorphous solids, independent of the energy barrier to growth. The method allows one to determine the temperature dependence of W(sup *), and the effect of the preparation conditions of the initial amorphous phase, the dopants, and the crystallization methds on W(sup *). The method is applied to determine the free-energy barrier to nucleation of crystallites in amorphous silicon (a-Si) thin films. For thermally induced nucleation in a-Si thin films with annealing temperatures in the range of from 824 to 983 K, the free-energy barrier W(sup *) to nucleation of silicon crystals is about 2.0 - 2.1 eV regardless of the preparation conditions of the films. The observation supports the idea that a-Si transforms into an intermediate amorphous state through the structural relaxation prior to the onset of nucleation of crystallites in a-Si. The observation also indicates that the activation entropy may be an insignificant part of the free-energy barrier for the nucleation of crystallites in a-Si. Compared with the free-energy barrier to nucleation of crystallites in undoped a-Si films, a significant reduction is observed in the free-energy barrier to nucleation in Cu-doped a-Si films. For a-Si under irradiation of Xe(2+) at 10(exp 5) eV, the free-energy barrier to ion-induced nucleation of crystallites is shown to be about half of the value associated with thermal-induced nucleation of crystallites in a-Si under the otherwise same conditions, which is much more significant than previously expected. The present method has a general kinetic basis; it thus should be equally applicable to nucleation of crystallites in any amorphous elemental semiconductors and semiconductor alloys, metallic and polymeric glasses, and to nucleation of crystallites in melts and solutions.

  6. Similar barriers and facilitators to physical activity across different clinical groups experiencing lower limb spasticity.

    PubMed

    Hundza, Sandra; Quartly, Caroline; Kim, Jasmine M; Dunnett, James; Dobrinsky, Jill; Loots, Iris; Choy, Kim; Chow, Brayley; Hampshire, Alexis; Temple, Viviene A

    2016-07-01

    Purpose Given the importance of physical activity in maintaining health and wellness, an improved understanding of physical activity patterns across different clinical populations is required. This study examines the facilitators for, and barriers to, participation in physical activity across multiple contexts for three clinical groups with chronic lower limb spasticity (individuals with stroke, multiple sclerosis and incomplete spinal cord injury). Method This cross-sectional study employed quantitative measures for spasticity, ankle range of motion, pain, falls, cognition, mobility, and physical activity as well as qualitative semi-structured interviews. Results There were similar impairments in body functions and structures and limitations in activities across the clinical groups. These impairments and limitations negatively impacted participation in physical activity, which was low. Environmental and personal factors exacerbated or mitigated the limiting effects of body functions and structures and activities on physical activity in many areas of life. Conclusions In this population, participation in physical activity includes activities such as housework which are different than what is typically considered as physical activity. Further, the presence of similar barriers and facilitators across the groups suggests that support and services to promote valued forms of physical activity could be organised and delivered based on limitations in mobility and functioning rather than clinical diagnosis. Implications for rehabilitation Physical activity is of utmost importance in maintaining health and wellness in clinical populations. This research highlights the desired and actual physical activity for these populations can look different than what may traditionally be considered as physical activity (e.g. housework is not typically considered participation physical activity). Therefore, rehabilitation interventions need to be directly designed to enhance clients

  7. Finessing the fracture energy barrier in ballistic seed dispersal.

    PubMed

    Deegan, Robert D

    2012-04-01

    Fracture is a highly dissipative process in which much of the stored elastic energy is consumed in the creation of new surfaces. Surprisingly, many plants use fracture to launch their seeds despite its seemingly prohibitive energy cost. Here we use Impatiens glandulifera as model case to study the impact of fracture on a plant's throwing capacity. I. glandulifera launches its seeds with speeds up to 4 m/s using cracks to trigger an explosive release of stored elastic energy. We find that the seed pod is optimally designed to minimize the cost of fracture. These characteristics may account for its success at invading Europe and North America. PMID:22431608

  8. Finessing the fracture energy barrier in ballistic seed dispersal

    PubMed Central

    Deegan, Robert D.

    2012-01-01

    Fracture is a highly dissipative process in which much of the stored elastic energy is consumed in the creation of new surfaces. Surprisingly, many plants use fracture to launch their seeds despite its seemingly prohibitive energy cost. Here we use Impatiens glandulifera as model case to study the impact of fracture on a plant’s throwing capacity. I. glandulifera launches its seeds with speeds up to 4 m/s using cracks to trigger an explosive release of stored elastic energy. We find that the seed pod is optimally designed to minimize the cost of fracture. These characteristics may account for its success at invading Europe and North America. PMID:22431608

  9. Elastic scattering of {sup 9}Li on {sup 208}Pb at energies around the Coulomb barrier

    SciTech Connect

    Cubero, M.; Fernandez-Garcia, J. P.; Alvarez, M. A. G.; Lay, J. A.; Moro, A. M.; Acosta, L.; Martel, I.; Sanchez-Benitez, A. M.; Alcorta, M.; Borge, M. J. G.; Tengblad, O.; Buchmann, L.; Shotter, A.; Walden, P.; Diget, D. G.; Fulton, B.; Fynbo, H. O. U.; Galaviz, D.; Gomez-Camacho, J.; Mukha, I.

    2011-10-28

    We have studied the dynamical effects of the halo structure of {sup 11}Li on the scattering on heavy targets at energies around the Coulomb barrier. This experiment was performed at ISAC-II at TRIUMF with a world record in production of the post-accelerated {sup 11}Li beam. As part of this study we report here on the first measurement of the elastic cross section of the core nucleus, i.e. {sup 9}Li on {sup 208}Pb, at energies around the Coulomb barrier. A preliminary optical model analysis has been performed in order to extract a global optical potential to describe the measured angular distributions.

  10. Airflow acceleration performance of asymmetric surface dielectric barrier discharge actuators at different exposed needle electrode heights

    NASA Astrophysics Data System (ADS)

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-12-01

    The use of plasma, created by asymmetric surface dielectric barrier discharge (ASDBD), as aerodynamic actuators to control airflows, has been of widespread concern over the past decades. For the single ASDBD, the actuator performance is dependent on the geometry of actuator and the produced plasma. In this work, a new electrode configuration, i.e., a row of needle, is taken as an exposed electrode for the ASDBD plasma actuator, and the electrode height is adjustable. The effects of different electrode heights on the airflow acceleration behavior are experimentally investigated by measuring surface potential distribution, ionic wind velocity, and mean thrust force production. It is demonstrated that the airflow velocity and thrust force increase with the exposed electrode height and the best actuator performance can be obtained when the exposed electrode is adjusted to an appropriate height. The difference, as analyzed, is mainly due to the distinct plasma spatial distributions at different exposed electrode heights.

  11. Chemically accurate energy barriers of small gas molecules moving through hexagonal water rings.

    PubMed

    Hjertenæs, Eirik; Trinh, Thuat T; Koch, Henrik

    2016-07-21

    We present chemically accurate potential energy curves of CH4, CO2 and H2 moving through hexagonal water rings, calculated by CCSD(T)/aug-cc-pVTZ with counterpoise correction. The barriers are extracted from a potential energy surface obtained by allowing the water ring to expand while the gas molecule diffuses through. State-of-the-art XC-functionals are evaluated against the CCSD(T) potential energy surface. PMID:27345929

  12. Technical Barriers, Gaps, and Opportunities Related to Home Energy Upgrade Market Delivery

    SciTech Connect

    Bianchi, M. V. A.

    2011-11-01

    This report outlines the technical barriers, gaps, and opportunities that arise in executing home energy upgrade market delivery approaches, as identified through research conducted by the U.S. Department of Energy's Building America program. The objective of this report is to outline the technical1 barriers, gaps, and opportunities that arise in executing home energy upgrade market delivery approaches, as identified through research conducted by the U.S. Department of Energy's (DOE) Building America program. This information will be used to provide guidance for new research necessary to enable the success of the approaches. Investigation for this report was conducted via publications related to home energy upgrade market delivery approaches, and a series of interviews with subject matter experts (contractors, consultants, program managers, manufacturers, trade organization representatives, and real estate agents). These experts specified technical barriers and gaps, and offered suggestions for how the technical community might address them. The potential benefits of home energy upgrades are many and varied: reduced energy use and costs; improved comfort, durability, and safety; increased property value; and job creation. Nevertheless, home energy upgrades do not comprise a large part of the overall home improvement market. Residential energy efficiency is the most complex climate intervention option to deliver because the market failures are many and transaction costs are high (Climate Change Capital 2009). The key reasons that energy efficiency investment is not being delivered are: (1) The opportunity is highly fragmented; and (2) The energy efficiency assets are nonstatus, low-visibility investments that are not properly valued. There are significant barriers to mobilizing the investment in home energy upgrades, including the 'hassle factor' (the time and effort required to identify and secure improvement works), access to financing, and the opportunity cost of

  13. SCC-DFTB Energy Barriers for Single and Double Proton Transfer Processes in the Model Molecular Systems Malonaldehyde and Porphycene

    SciTech Connect

    Walewski, L.; Krachtus, D; Fischer, S.; Smith, Jeremy C; Bala, P.; Lesyng, B.

    2005-09-01

    Self-consistent charge-density functional tight-binding SCC-DFTB is a computationally efficient method applicable to large (bio)molecular systems in which (bio)chemical reactions may occur. Among these reactions are proton transfer processes. This method, along with more advanced ab initio techniques, is applied in this study to compute intramolecular barriers for single and double proton transfer processes in the model systems, malonaldehyde and porphycene, respectively. SCC-DFTB is compared with experimental data and higher-level ab initio calculations. For malonaldehyde, the SCC-DFTB barrier height is 3.1 kcal/mol in vacuo and 4.2 kcal/mol in water solution. In the case of porphycene, the minimum energy pathways for double intramolecular proton transfer were determined using the conjugate peak refinement (CPR) method. Six isomers of porphycene were ordered according to energy. The only energetically allowed pathway was found to connect two symmetrical trans states via an unstable cis-A isomer. The SCC-DFTB barrier heights are 11.1 kcal/mol for the trans-cis-A process, and 7.4 kcal/mol for the reverse cis-A-trans one with the energy difference of 3.7 kcal/mol between the trans- and cis-A states. The method provides satisfactory energy results when compared with reference ab initio and experimental data.

  14. Toward understanding the nature of internal rotation barriers with a new energy partition scheme: ethane and n-butane.

    PubMed

    Liu, Shubin; Govind, Niranjan

    2008-07-24

    On the basis of an alternative energy partition scheme where density-based quantification of the steric effect was proposed [Liu, S. B. J. Chem. Phys. 2007, 126, 244103], the origin of the internal rotation barrier between the eclipsed and staggered conformers of ethane and n-butane is systematically investigated in this work. Within the new scheme, the total electronic energy is decomposed into three independent components, steric, electrostatic, and fermionic quantum. The steric energy defined in this way is repulsive, exclusive, and extensive and intrinsically linked to Bader's atoms in molecules approach. Two kinds of differences, adiabatic (with optimal structure) and vertical (with fixed geometry), are considered for the molecules in this work. We find that in the adiabatic case the eclipsed conformer possesses a larger steric repulsion than the staggered conformer for both molecules, but in the vertical cases the staggered conformer retains a larger steric repulsion. For ethane, a linear relationship between the total energy difference and the fermionic quantum energy difference is discovered. This linear relationship, however, does not hold for n-butane, whose behaviors in energy component differences are found to be more complicated. The impact of basis set and density functional choices on energy components from the new energy partition scheme has been investigated, as has its comparison with another definition of the steric effect in the literature in terms of the natural bond orbital analysis through the Pauli Exclusion Principle. In addition, profiles of conceptual density functional theory reactivity indices as a function of dihedral angle changes have been examined. Put together, these results suggest that the new energy partition scheme provides insights from a different perspective of internal rotation barriers. PMID:18563887

  15. Evaluation of different pig oral mucosa sites as permeability barrier models for drug permeation studies.

    PubMed

    Franz-Montan, Michelle; Serpe, Luciano; Martinelli, Claudia Cristina Maia; da Silva, Camila Batista; Santos, Cleiton Pita Dos; Novaes, Pedro Duarte; Volpato, Maria Cristina; de Paula, Eneida; Lopez, Renata Fonseca Vianna; Groppo, Francisco Carlos

    2016-01-01

    The objective of the present study was to investigate the influence of preparation and storage conditions on the histology and permeability of different parts of porcine oral mucosa used for in vitro studies of transbuccal formulations. Fresh and frozen (-20°C and -80°C, with or without cryoprotectant) epithelia of porcine palatal, gingival, dorsum of the tongue, and buccal mucosa were submitted for histological analyses to determine the effects of storage conditions on barrier integrity. Permeation of lidocaine hydrochloride (used as a hydrophilic model drug) across fresh and previously frozen oral epithelium was measured in order to evaluate the barrier function. Histological evaluation demonstrated that the oral epithelium was successfully separated from the connective tissue, except for gingival mucosa. After storage under different conditions, all tissues presented desquamation of superficial layers and spherical spaces induced by the freezing process. The permeability of lidocaine hydrochloride varied among the fresh oral mucosa and generally increased after freezing. In conclusion, fresh epithelium from the buccal and dorsum of the tongue mucosa should be used for in vitro studies investigating hydrophilic drug transport when these are the desired clinical application sites. However, when the palate is the target site, both fresh and frozen (for up to 4weeks, without addition of cryoprotectant) samples could be used. The addition of glycerol as a cryoprotectant should be avoided due to increased lidocaine hydrochloride permeability. PMID:26435216

  16. Cross-Cultural Differences in Undergraduate Students' Perceptions of Online Barriers

    ERIC Educational Resources Information Center

    Olesova, Larisa; Yang, Dazhi; Richardson, Jennifer C.

    2011-01-01

    The intent of this study was to learn about students' perceived barriers and the impact of those barriers on the quality of online discussions between two distinct cultural groups in Eastern and Northern Siberia (Russia). A mixed-methods approach utilizing surveys and interviews was used to investigate (1) the types of barriers the students…

  17. Overcoming barriers to residential conservation: do energy audits help

    SciTech Connect

    Hoffman, W.L.

    1982-12-01

    A study on the effects of energy audits on the pace and choice of household investment in energy-saving improvements in the home is reported. An evaluation based on the household's assessment of the usefulness of the audit which was provided for their home was performed. The number and types of recent conservation actions among audited and unaudited samples of households are compared. The audit's effect on household knowledge about the economically attractive options for their home and on the choice of recent improvements is assessed. Possible reasons are suggested for the weak effect of audits in stimulating activity and reorienting investment choices. (LEW)

  18. State Successes: Using Outreach and Eduction to Transcend Barriers to Wind Energy (Poster)

    SciTech Connect

    Kelly, M.; Flowers, L.

    2010-05-01

    Many states projected to contribute significantly to the United States' 20% wind energy by 2030 goal have not yet achieved a first wind farm, and many more have not yet hit the 100-MW mark. These states are struggling with basic barriers of the need for understanding of the wind resource; wind energy benefits and impacts; economic development, water, and carbon impacts; issues such as transmission, utility integration, siting, and wildlife; involvement of key constituents such as the electrical sector, the ag sector, and county commissioners; effective policy; and an educated public and an educated workforce. Other states have partially transcended these barriers and are encountering organized pushback; NIMBYism; siting problems such as zoning, permitting, and environmental issues; and interstate barriers such as transmission.

  19. Analysis of the barriers to renewable energy development on tribal lands

    NASA Astrophysics Data System (ADS)

    Jones, Thomas Elisha

    Native American lands have significant renewable energy resource potential that could serve to ensure energy security and a low carbon energy future for the benefit of tribes as well as the United States. Economic and energy development needs in Native American communities match the energy potential. A disproportionate amount of Native American households have no access to electricity, which is correlated with high poverty and unemployment rates. Despite the vast resources and need for energy, the potential for renewable energy development has not fully materialized. This research explores this subject through three separate articles: 1) a case study of the Navajo Nation that suggests economic viability is not the only significant factor for low adoption of renewable energy on Navajo lands; 2) an expert elicitation of tribal renewable energy experts of what they view as barriers to renewable energy development on tribal lands; and 3) a reevaluation of Native Nation Building Theory to include external forces and the role that inter-tribal collaboration plays with renewable energy development by Native nations. Major findings from this research suggests that 1) many Native nations lack the technical and legal capacity to develop renewable energy; 2) inter-tribal collaboration can provide opportunities for sharing resources and building technical, legal, and political capacity; and 3) financing and funding remains a considerable barrier to renewable energy development on tribal lands.

  20. Energy Savings Certificate Markets: Opportunities and Implementation Barriers

    SciTech Connect

    Friedman, B.; Bird, L.; Barbose, G.

    2009-07-01

    Early experiences with energy savings certificates (ESCs) have revealed their merits and the challenges associated with them. While in the United States ESC markets have yet to gain significant traction, lessons can be drawn from early experiences in the states of Connecticut and New York, as well as from established markets in Italy, France, and elsewhere. The staying power of European examples demonstrates that ESCs can help initiate more efficiency projects. This article compares ESCs with renewable energy certificates (RECs), looks at the unique opportunities and challenges they present, and reviews solutions and best practices demonstrated by early ESC markets. Three major potential ESC market types are also reviewed: compliance, voluntary, and carbon. Additionally, factors that will benefit ESC markets in the United States are examined: new state EEPS policies, public interest in tools to mitigate climate change, and the growing interest in a voluntary market for ESCs.

  1. Consistent energy barrier distributions in magnetic particle chains

    NASA Astrophysics Data System (ADS)

    Laslett, O.; Ruta, S.; Chantrell, R. W.; Barker, J.; Friedman, G.; Hovorka, O.

    2016-04-01

    We investigate long-time thermal activation behaviour in magnetic particle chains of variable length. Chains are modelled as Stoner-Wohlfarth particles coupled by dipolar interactions. Thermal activation is described as a hopping process over a multidimensional energy landscape using the discrete orientation model limit of the Landau-Lifshitz-Gilbert dynamics. The underlying master equation is solved by diagonalising the associated transition matrix, which allows the evaluation of distributions of time scales of intrinsic thermal activation modes and their energy representation. It is shown that as a result of the interaction dependence of these distributions, increasing the particle chain length can lead to acceleration or deceleration of the overall relaxation process depending on the initialisation procedure.

  2. Physical activity in patients with heart failure: barriers and motivations with special focus on sex differences

    PubMed Central

    Klompstra, Leonie; Jaarsma, Tiny; Strömberg, Anna

    2015-01-01

    Background Adherence to recommendations for physical activity is low in both male and female patients with heart failure (HF). Men are more physically active than women. In order to successfully promote physical activity, it is therefore essential to explore how much and why HF patients are physically active and if this is related to sex. The aim of this study was therefore to evaluate physical activity in HF patients, to describe the factors related to physical activity, and to examine potential barriers and motivations to physical activity with special focus on sex differences. Methods The study had a cross-sectional survey design. HF patients living at home received a questionnaire during May–July 2014, with questions on physical activity (from the Short Form-International Physical Activity Questionnaire), and potential barriers and motivations to physical activity. Results A total of 154 HF patients, 27% women, with a mean age of 70±10 were included. In total, 23% of the patients reported a high level of physical activity, 46% a moderate level, and 34% a low level. Higher education, self-efficacy, and motivation were significantly associated with a higher amount of physical activity. Symptoms or severity of the disease were not related to physical activity. All the potential barriers to exercise were reported to be of importance. Psychological motivations were most frequently rated as being the most important motivation (41%) to be physically active. Physical motivations (33%) and social motivations were rated as the least important ones (22%). Women had significantly higher total motivation to be physically active. These differences were found in social, physical, and psychological motivations. Discussion One-third of the HF patients had a low level of physical activity in their daily life. Severity of the disease or symptoms were not related, whereas level of education, exercise self-efficacy, and motivation were important factors to take into account when

  3. Treatment seeking and barriers to weight loss treatments of different intensity levels among obese and overweight individuals.

    PubMed

    Ciao, A C; Latner, J D; Durso, L E

    2012-03-01

    Obesity is a major health concern for a large proportion of the population, yet many obese individuals do not receive weight loss treatment. The present study investigated weight-loss treatment seeking and barriers that may prevent treatment seeking. A community sample of overweight or obese participants (N=154; Mean BMI=33.3 kg/m2) completed an Internet survey assessing treatment seeking behaviors across three categories: Treatments Sought, Treatments Desired, and Treatments Planned. Seven treatments of different intensity levels and five barriers to treatment seeking were evaluated. The weight-loss treatment most frequently sought, desired, and planned was treatment "on own." Higher BMI was correlated with greater number of treatments sought. However, 10% of respondents reported zero treatments sought, and over 25% reported zero treatments desired or planned. Perceived barriers may explain reluctance to seek treatment. The top two barriers for all treatments were lack of money and time. Higher BMI was correlated with more total perceived barriers, and specifically with the barriers "I feel/think I am too heavy" and "I am afraid people will treat me unfairly or badly." More barriers were reported for more intensive treatments such as treatments from a doctor, another professional, or a commercial program. A majority of participants reported zero barriers to less-intensive treatments. These results suggest that many obese individuals who might benefit from weight loss treatment nevertheless do not plan or desire to seek treatment and perceive multiple barriers to treatments. However, these individuals could be encouraged to consider the less intensive treatments that are seen as more barrier-free. PMID:22751277

  4. Asymmetric isolating barriers between different microclimatic environments caused by low immigrant survival

    PubMed Central

    Gosden, Thomas P.; Waller, John T.; Svensson, Erik I.

    2015-01-01

    Spatially variable selection has the potential to result in local adaptation unless counteracted by gene flow. Therefore, barriers to gene flow will help facilitate divergence between populations that differ in local selection pressures. We performed spatially and temporally replicated reciprocal field transplant experiments between inland and coastal habitats using males of the common blue damselfly (Enallagma cyathigerum) as our study organism. Males from coastal populations had lower local survival rates than resident males at inland sites, whereas we detected no differences between immigrant and resident males at coastal sites, suggesting asymmetric local adaptation in a source–sink system. There were no intrinsic differences in longevity between males from the different environments suggesting that the observed differences in male survival are environment-dependent and probably caused by local adaptation. Furthermore, the coastal environment was found to be warmer and drier than the inland environment, further suggesting local adaptation to microclimatic factors has lead to differential survival of resident and immigrant males. Our results suggest that low survival of immigrant males mediates isolation between closely located populations inhabiting different microclimatic environments. PMID:25631994

  5. The barriers encountered by teachers implementing education for sustainable development: discipline bound differences and teaching traditions

    NASA Astrophysics Data System (ADS)

    Borg, Carola; Gericke, Niklas; Höglund, Hans-Olof; Bergman, Eva

    2012-07-01

    Background : According to the Swedish curriculum teachers in all subjects have a responsibility to integrate a holistic perspective of sustainable development (SD) and teach according to an education for sustainable development (ESD) approach. However previous research has shown that teachers from different subjects perceive SD differently. Purpose : The study aimed at investigating if and how teachers' subject area influences their ability to implement a holistic perspective of ESD; we investigated both the impact of teaching traditions and the barriers that teachers experienced. Sample : A stratified sample of 224 Swedish upper secondary schools participated. An online questionnaire was sent and answered by a total of 3229 teachers at these schools. In total, there were 669 science teachers, 373 social science teachers, 483 language teachers, 713 vocational and esthetical-practical teachers, and 739 teachers from other disciplines who participated in the survey. Design and methods : The questionnaire consisted of questions requiring Likert-scale responses and multiple-choice questions. The data from the questionnaire were analyzed using Pearson's Chi-square test and one-way ANOVA. The significance level accepted was p < 0.05. Results : Teachers were influenced by their own subject traditions. Science teachers in our study were grounded in the fact-based tradition and lectures were the most common teaching method used. The teaching tradition of the social science teachers seemed to be most in line to an ESD approach. Many language teachers (41%) stated they did not include SD issues in their teaching at all. Among the barriers identified, the most common obstacles were that the teachers lacked inspiring examples of how to include SD in their teaching and that they lacked the necessary expertise about SD. Conclusion : This study highlights the need for the management within schools to create opportunities for teachers to work collaboratively when teaching ESD. It

  6. 11Li Breakup on 208 at energies around the Coulomb barrier.

    PubMed

    Fernández-García, J P; Cubero, M; Rodríguez-Gallardo, M; Acosta, L; Alcorta, M; Alvarez, M A G; Borge, M J G; Buchmann, L; Diget, C A; Falou, H A; Fulton, B R; Fynbo, H O U; Galaviz, D; Gómez-Camacho, J; Kanungo, R; Lay, J A; Madurga, M; Martel, I; Moro, A M; Mukha, I; Nilsson, T; Sánchez-Benítez, A M; Shotter, A; Tengblad, O; Walden, P

    2013-04-01

    The inclusive breakup for the (11)Li + (208)Pb reaction at energies around the Coulomb barrier has been measured for the first time. A sizable yield of (9)Li following the (11)Li dissociation has been observed, even at energies well below the Coulomb barrier. Using the first-order semiclassical perturbation theory of Coulomb excitation it is shown that the breakup probability data measured at small angles can be used to extract effective breakup energy as well as the slope of B(E1) distribution close to the threshold. Four-body continuum-discretized coupled-channels calculations, including both nuclear and Coulomb couplings between the target and projectile to all orders, reproduce the measured inclusive breakup cross sections and support the presence of a dipole resonance in the (11)Li continuum at low excitation energy. PMID:25166983

  7. Lack of an energy policy remains a major barrier

    SciTech Connect

    Owen, D.

    1991-03-01

    This paper reports that the war with Iraq provided a new dimension to the ongoing oil industry struggle to cope with oppressive government action and regulation. Coming as it did just before the administration was to announce guidelines for a long-awaited National Energy Strategy (NES), the war created a renewed and dramatic focus on the national energy security question. Now, numerous congressmen, senators and administration leaders are taking a fresh look at how the U.S. can extricate itself from excessive dependence on Middle East oil imports. For example, the planned free-trade agreement with Mexico could figure prominently in an alliance that would bring much more Mexican oil to the U.S. Meanwhile, the wild card is proposals to open up U.S. drilling offshore and in the Arctic National Wildlife Region (ANWR). Prior to hostilities, Middle East tensions brought on significant increases in the price of oil, and with it a large gain in oil company profits for fourth-quarter 1990. Result: talk in Congress of a new windfall profits tax.

  8. Finite Element Modeling of the Different Failure Mechanisms of a Plasma Sprayed Thermal Barrier Coatings System

    NASA Astrophysics Data System (ADS)

    Ranjbar-Far, M.; Absi, J.; Mariaux, G.

    2012-12-01

    A new finite element model is used to investigate catastrophic failures of a thermal barrier coatings system due to crack propagation along the interfaces between the ceramic top-coat, thermally grown oxide, and bond-coat layers, as well as between the lamellas structure of the ceramic layer. The thermo-mechanical model is designed to take into account a non-homogenous temperature distribution and the effects of the residual stresses generated during the coating process. Crack propagation is simulated using the contact tool "Debond" present in the ABAQUS finite element code. Simulations are performed with a geometry corresponding to similar or dissimilar amplitudes of asperity, and for different thicknesses of the oxide layer. The numerical results have shown that crack evolution depends crucially on the ratio of the loading rate caused by growth and swelling of the oxide layer and also on the interface roughness obtained during the spraying of coatings.

  9. Technological innovation in community housing development: Barriers to energy efficiency

    SciTech Connect

    Cavallo, J.D.

    1996-05-01

    Community housing developers produce affordable housing and jobs for many residents of low-income neighborhoods through the rehabilitation of existing single and multi-family buildings. Typically operating as small, not-for-profits or community-based organizations, the vast numbers of community housing developers creates high coordinating costs of operating jointly to acquire the shared learning needed to implement new techniques, such as those involving energy efficiency. This paper presents a model of technology adoption that suggests that new profitable technologies will be adopted only with low probability and that strategic interaction between potential adopters further reduces the likelihood of adoption. These features result from the ability of potential adopters to postpone the bearing the costs of adoption of new technologies and their ability to share the knowledge of others who have adopted new technologies. These features are particularly characteristic of community housing developers.

  10. Direct measurement of energy barriers on rough and heterogeneous solid surfaces

    SciTech Connect

    Lloyd, T.B.; LaGow, J.; Connelly, G.M.

    1996-12-31

    This paper will deal with the phenomenon of energy barriers to the spread of liquids on solids. These barriers often manifest themselves as a {open_quotes}pinning{close_quotes} of a sessile drop as liquid is added to it. That is, the volume of the drop increases, but the diameter does not. Thus the advancing contact angle ({theta}{sub a}) increases to a maximum. At the point where the hydrostatic pressure in the drop overcomes the {open_quotes}pinning{close_quotes} force the diameter suddenly increases and the drop relaxes to a metastable configuration which has a lower {theta}{sub a}. Energy barriers should be considered in many applications such as the spreading of liquid adhesives where thorough wetting is the goal. The interfacial forces involved are both long-range Lifshitz-van der Waals (LW) forces and short-range acid-base (AB) forces. The authors will describe how they measure the energy barriers on real surfaces directly and resolve them into their LW and AB components.

  11. Overcoming Codes and Standards Barriers to Innovations in Building Energy Efficiency

    SciTech Connect

    Cole, Pamala C.; Gilbride, Theresa L.

    2015-02-15

    In this journal article, the authors discuss approaches to overcoming building code barriers to energy-efficiency innovations in home construction. Building codes have been a highly motivational force for increasing the energy efficiency of new homes in the United States in recent years. But as quickly as the codes seem to be changing, new products are coming to the market at an even more rapid pace, sometimes offering approaches and construction techniques unthought of when the current code was first proposed, which might have been several years before its adoption by various jurisdictions. Due to this delay, the codes themselves can become barriers to innovations that might otherwise be helping to further increase the efficiency, comfort, health or durability of new homes. . The U.S. Department of Energy’s Building America, a program dedicated to improving the energy efficiency of America’s housing stock through research and education, is working with the U.S. housing industry through its research teams to help builders identify and remove code barriers to innovation in the home construction industry. The article addresses several approaches that builders use to achieve approval for innovative building techniques when code barriers appear to exist.

  12. Experimental Testing of Rockfall Barriers Designed for the Low Range of Impact Energy

    NASA Astrophysics Data System (ADS)

    Buzzi, O.; Spadari, M.; Giacomini, A.; Fityus, S.; Sloan, S. W.

    2013-07-01

    Most of the recent research on rockfall and the development of protective systems, such as flexible rockfall barriers, have been focused on medium to high levels of impacting energy. However, in many regions of the world, the rockfall hazard involves low levels of energy. This is particularly the case in New South Wales, Australia, because of the nature of the geological environments. The state Road and Traffic Authority (RTA) has designed various types of rockfall barriers, including some of low capacity, i.e. 35 kJ. The latter were tested indoors using a pendulum equipped with an automatic block release mechanism triggered by an optical beam. Another three systems were also tested, including two products designed by rockfall specialised companies and one modification of the initial design of the RTA. The research focused on the influence of the system's stiffness on the transmission of load to components of the barrier such as posts and cables. Not surprisingly, the more compliant the system, the less loaded the cables and posts. It was also found that removing the intermediate cables and placing the mesh downslope could reduce the stiffness of the system designed by the RTA. The paper concludes with some multi-scale considerations on the capacity of a barrier to absorb the energy based on experimental evidence.

  13. Thermodynamics of downhill folding: multi-probe analysis of PDD, a protein that folds over a marginal free energy barrier.

    PubMed

    Naganathan, Athi N; Muñoz, Victor

    2014-07-31

    Downhill folding proteins fold in microseconds by crossing a very low or no free energy barrier (<3 RT), and exhibit a complex unfolding behavior in equilibrium. Such unfolding complexity is due to the weak thermodynamic coupling that exists between the various structural segments of these proteins, and it is manifested in unfolding curves that differ depending on the structural probe employed to monitor the process. Probe-dependent unfolding has important practical implications because it permits one to investigate the folding energy landscape in detail using multiprobe thermodynamic experiments. This type of thermodynamic behavior has been investigated in depth on the protein BBL, an example of extreme (one-state) downhill folding in which there is no free energy barrier at any condition, including the denaturation midpoint. However, an open question is, to what extent is such thermodynamic behavior observed on less extreme downhill folders? Here we perform a multiprobe spectroscopic characterization of the microsecond folder PDD, a structural and functional homologue of BBL that folds within the downhill regime, but is not an example of one-state downhill folding; rather at the denaturation midpoint PDD folds by crossing an incipient free energy barrier. Model-free analysis of the unfolding curves from four different spectroscopic probes together with differential scanning calorimetry reveals a dispersion of ∼9 K in the apparent melting temperature and also marked differences in unfolding broadness (from ∼50 to ∼130 kJ mol(-1) when analyzed with a two-state model), confirming that such properties are also observed on less extreme downhill folders. We subsequently perform a global quantitative analysis of the unfolding data of PDD using the same ME statistical mechanical model that was used before for the BBL domain. The analysis shows that this simple model captures all of the features observed on the unfolding of PDD (i.e., the intensity and temperature

  14. The Analytical Parametrization of Fusion Barrier by Using the Skyrme Energy-Density Function Model

    NASA Astrophysics Data System (ADS)

    Zanganeh, V.; Mirzaei, M.; N., Wang

    2015-08-01

    Using the skyrme energy density formalism, a pocket formula is introduced for barrier heights and positions of 95 fusion reactions (48 ≤ ZP ZT ≤ 1520) with respect to the charge and mass numbers of the interacting nuclei. It is shown that the parameterized values of RB and VB are able to reproduce the corresponding experimental data with good accuracy. Moreover, the absolute errors of our formulas are less than those obtained using the analytical parametrization forms of the fusion barrier based on the proximity versions. The ability of the parameterized forms of the barrier heights and its positions to reproduce the experimental data of the fusion cross section have been analyzed using the Wong model.

  15. Current-induced changes of migration energy barriers in graphene and carbon nanotubes.

    PubMed

    Obodo, J T; Rungger, I; Sanvito, S; Schwingenschlögl, U

    2016-05-21

    An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative. PMID:27127889

  16. Role of neutron transfer and deformation effect in capture process at sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.

    2012-12-01

    The roles of nuclear deformation and neutron transfer in sub-barrier capture process are studied within the quantum diffusion approach. The change of the deformations of colliding nuclei with neutron exchange can crucially influence the sub-barrier fusion. The sub-barrier capture reactions following the neutron pair transfer are used for the indirect study of neutron-neutron correlation in the surface region of nucleus. The strong surface enhancement of the neutron pairing in nuclei 48Ca, 64Ni, and 116,124,132Sn is demonstrated. Comparing the capture cross sections calculated without the breakup effect and experimental complete fusion cross sections, the breakup was analyzed in reactions with weakly bound projectiles 6,7,9Li and 9Be. A trend of a systematic behavior for the complete fusion suppression as a function of the target charge and bombarding energy is not achieved.

  17. Ergonomic best practices in masonry: regional differences, benefits, barriers, and recommendations for dissemination.

    PubMed

    Hess, Jennifer; Weinstein, Marc; Welch, Laura

    2010-08-01

    Within construction the masonry trade has particularly high rates of musculoskeletal disorders (MSDs). A NIOSH-sponsored meeting of masonry stakeholders explored current and potential "Best Practices" for reducing MSDs in masonry and identified potential regional differences in use of practices. To verify and better understand the regional effects and other factors associated with differences in practice use, a national telephone survey of masonry contractors was conducted. The United States was divided into four regions for evaluation: Northeast, Southeast, Midwest, and West Coast. Nine practices with the potential to reduce MSDs in masonry workers were evaluated. Masonry contractors, owners, and foremen completed 183 surveys. The results verify regional differences in use of best practices in masonry. Half-weight cement bags and autoclave aerated concrete were rarely used anywhere, while lightweight block and mortar silos appear to be diffusing across the country. The Northeast uses significantly fewer best practices than other regions. This article examines reasons for regional differences in masonry best practice, and findings provide insight into use and barriers to adoption that can be used by safety managers, researchers, and other safety advocates to more effectively disseminate ergonomic solutions across the masonry industry. PMID:20521196

  18. In vivo measurements of skin barrier: comparison of different methods and advantages of laser scanning microscopy

    NASA Astrophysics Data System (ADS)

    Patzelt, A.; Sterry, W.; Lademann, J.

    2010-12-01

    A major function of the skin is to provide a protective barrier at the interface between external environment and the organism. For skin barrier measurement, a multiplicity of methods is available. As standard methods, the determination of the transepidermal water loss (TEWL) as well as the measurement of the stratum corneum hydration, are widely accepted, although they offer some obvious disadvantages such as increased interference liability. Recently, new optical and spectroscopic methods have been introduced to investigate skin barrier properties in vivo. Especially, laser scanning microscopy has been shown to represent an excellent tool to study skin barrier integrity in many areas of relevance such as cosmetology, occupation, diseased skin, and wound healing.

  19. Current-induced changes of migration energy barriers in graphene and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Obodo, J. T.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.

    2016-05-01

    An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative.An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR00534A

  20. Numerical Modelling of a Low-Energy Rockfall Barrier: New Insight into the Bullet Effect

    NASA Astrophysics Data System (ADS)

    Mentani, A.; Giacomini, A.; Buzzi, O.; Govoni, L.; Gottardi, G.; Fityus, S.

    2016-04-01

    This paper investigates the dynamic response of low energy, semi-rigid rockfall barriers. The study is based on a FE model that reproduces the geometry, components and connections of the existing systems that were previously tested at The University of Newcastle. The mechanical behaviour of the relevant barrier components was calibrated from simple mechanical tests and the response of the assembled system, i.e. 2 m high, 15 m long rockfall barrier, was validated against of full-scale tests results. Following a satisfactory validation of the model, further dynamic non-linear analyses were conducted to investigate the dependence of the full system performance to the size of impacting blocks. Interestingly, the total failure energy was found to evolve non-monotonically with block size because of dynamic effects that seem to prevail for impact speeds in the range of 15-20 m/s. The study also highlights the complex effects of adding intermediate longitudinal cables to the system. An improvement of the barrier performance is observed for the large blocks but the bullet effect is exacerbated for small blocks.

  1. Opportunities and barriers for a crop-based energy sector in Ontario

    NASA Astrophysics Data System (ADS)

    Klupfel, Ellen Joanne

    This study investigates the existing opportunities and barriers for expanding the crop-based energy sector in Ontario. The investigation takes place at a time when growing concerns about sustainability---environmental, social, and economic---are encouraging the exploration of alternatives to energy systems based on fossil fuels, and concerns around the future viability of rural communities are making agriculturally-based and rural-based energy production systems attractive to many. To explore opportunities and barriers for the crop-based energy sector, this thesis addresses the question: What is the political-economic context within which the crop-based energy sector operates in Ontario? Taking an institutional approach, the study involved 26 interviews with individuals whose organizations influence Ontario's crop-based energy sector (that includes the biofuels ethanol and biodiesel), developed a model outlining relationships between the crop-based energy sector and other sectors of the economy, as well as the state, and implemented a survey of Ontario Members of Provincial Parliament's perspectives on biofuels. This research examines the balance of power of knowledge, production, security, finance, and technology for Ontario's crop-based energy sector. The overall balance of power currently rests with the petroleum sector. Through force field analysis, the study also identifies the key opportunities and barriers for the growth and development of the biofuels sector. These opportunities include climate change and rural development agendas, and the barriers include the petroleum sector, cost of production, and some sectors of the state. A few overarching conclusions emerge from this research: (1) Change in Ontario's crop-based energy sector is driven foremost by political and economic forces; (2) Climate change is the most significant driving force for the development and expansion of Ontario's crop-based energy sector; (3) Production cost and resistance from the

  2. Regional Differences as Barriers to Body Mass Index Screening Described by Ohio School Nurses

    ERIC Educational Resources Information Center

    Stalter, Ann M.; Chaudry, Rosemary V.; Polivka, Barbara J.

    2011-01-01

    Background: Body mass index (BMI) screening is advocated by the National Association of School Nurses (NASN). Research identifying barriers to BMI screening in public elementary school settings has been sparse. The purpose of the study was to identify barriers and facilitating factors of BMI screening practices among Ohio school nurses working in…

  3. Barriers and Supports for Continuing in Mathematics and Science: Gender and Educational Level Differences

    ERIC Educational Resources Information Center

    Fouad, Nadya A.; Hackett, Gail; Smith, Philip L.; Kantamneni, Neeta; Fitzpatrick, Mary; Haag, Susan; Spencer, Dee

    2010-01-01

    This article presents three studies that provide an in-depth examination of STEM-related supports and barriers. These studies constructed an instrument to identify male and female perceptions of the barriers and supports for pursuing coursework and/or careers in mathematics and sciences domains; to pilot test and refine that instrument; and then…

  4. Numerical determination of the interfacial energy and nucleation barrier of curved solid-liquid interfaces in binary systems.

    PubMed

    Kundin, Julia; Choudhary, Muhammad Ajmal

    2016-07-01

    The phase-field crystal (PFC) technique is a widely used approach for modeling crystal growth phenomena with atomistic resolution on mesoscopic time scales. We use a two-dimensional PFC model for a binary system based on the work of Elder et al. [Phys. Rev. B 75, 064107 (2007)PRBMDO1098-012110.1103/PhysRevB.75.064107] to study the effect of the curved, diffuse solid-liquid interface on the interfacial energy as well as the nucleation barrier. The calculation of the interfacial energy and the nucleation barrier certainly depends on the proper definition of the solid-liquid dividing surface and the corresponding nucleus size. We define the position of the sharp interface at which the interfacial energy is to be evaluated by using the concept of equimolar dividing surface (r^{e}) and the minimization of the interfacial energy (r^{s}). The comparison of the results based on both radii shows that the difference r^{e}-r^{s} is always positive and has a limit for large cluster sizes which is comparable to the Tolman length. Furthermore, we found the real nucleation barrier for small cluster sizes, which is defined as a function of the radius r^{s}, and compared it with the classical nucleation theory. The simulation results also show that the extracted interfacial energy as function of both radii is independent of system size, and this dependence can be reasonably described by the nonclassical Tolman formula with a positive Tolman length. PMID:27575196

  5. Calculating Transition Energy Barriers and Characterizing Activation States for Steps of Fusion.

    PubMed

    Ryham, Rolf J; Klotz, Thomas S; Yao, Lihan; Cohen, Fredric S

    2016-03-01

    We use continuum mechanics to calculate an entire least energy pathway of membrane fusion, from stalk formation, to pore creation, and through fusion pore enlargement. The model assumes that each structure in the pathway is axially symmetric. The static continuum stalk structure agrees quantitatively with experimental stalk architecture. Calculations show that in a stalk, the distal monolayer is stretched and the stored stretching energy is significantly less than the tilt energy of an unstretched distal monolayer. The string method is used to determine the energy of the transition barriers that separate intermediate states and the dynamics of two bilayers as they pass through them. Hemifusion requires a small amount of energy independently of lipid composition, while direct transition from a stalk to a fusion pore without a hemifusion intermediate is highly improbable. Hemifusion diaphragm expansion is spontaneous for distal monolayers containing at least two lipid components, given sufficiently negative diaphragm spontaneous curvature. Conversely, diaphragms formed from single-component distal monolayers do not expand without the continual injection of energy. We identify a diaphragm radius, below which central pore expansion is spontaneous. For larger diaphragms, prior studies have shown that pore expansion is not axisymmetric, and here our calculations supply an upper bound for the energy of the barrier against pore formation. The major energy-requiring deformations in the steps of fusion are: widening of a hydrophobic fissure in bilayers for stalk formation, splay within the expanding hemifusion diaphragm, and fissure widening initiating pore formation in a hemifusion diaphragm. PMID:26958888

  6. Free energy barriers for escape of water molecules from protein hydration layer.

    PubMed

    Roy, Susmita; Bagchi, Biman

    2012-03-01

    Free energy barriers separating interfacial water molecules from the hydration layer at the surface of a protein to the bulk are obtained by using the umbrella sampling method of free energy calculation. We consider hydration layer of chicken villin head piece (HP-36) which has been studied extensively by molecular dynamics simulations. The free energy calculations reveal a strong sensitivity to the secondary structure. In particular, we find a region near the junction of first and second helix that contains a cluster of water molecules which are slow in motion, characterized by long residence times (of the order of 100 ps or more) and separated by a large free energy barrier from the bulk water. However, these "slow" water molecules constitute only about 5-10% of the total number of hydration layer water molecules. Nevertheless, they play an important role in stabilizing the protein conformation. Water molecules near the third helix (which is the important helix for biological function) are enthalpically least stable and exhibit the fastest dynamics. Interestingly, barrier height distributions of interfacial water are quite broad for water surrounding all the three helices (and the three coils), with the smallest barriers found for those near the helix-3. For the quasi-bound water molecules near the first and second helices, we use well-known Kramers' theory to estimate the residence time from the free energy surface, by estimating the friction along the reaction coordinate from the diffusion coefficient by using Einstein relation. The agreement found is satisfactory. We discuss the possible biological function of these slow, quasi-bound (but transient) water molecules on the surface. PMID:22288939

  7. Critical energy barrier for capillary condensation in mesopores: Hysteresis and reversibility

    NASA Astrophysics Data System (ADS)

    Hiratsuka, Tatsumasa; Tanaka, Hideki; Miyahara, Minoru T.

    2016-04-01

    Capillary condensation in the regime of developing hysteresis occurs at a vapor pressure, Pcond, that is less than that of the vapor-like spinodal. This is because the energy barrier for the vapor-liquid transition from a metastable state at Pcond becomes equal to the energy fluctuation of the system; however, a detailed mechanism of the spontaneous transition has not been acquired even through extensive experimental and simulation studies. We therefore construct accurate atomistic silica mesopore models for MCM-41 and perform molecular simulations (gauge cell Monte Carlo and grand canonical Monte Carlo) for argon adsorption on the models at subcritical temperatures. A careful comparison between the simulation and experiment reveals that the energy barrier for the capillary condensation has a critical dimensionless value, Wc* = 0.175, which corresponds to the thermal fluctuation of the system and depends neither on the mesopore size nor on the temperature. We show that the critical energy barrier Wc* controls the capillary condensation pressure Pcond and also determines a boundary between the reversible condensation/evaporation regime and the developing hysteresis regime.

  8. Critical energy barrier for capillary condensation in mesopores: Hysteresis and reversibility.

    PubMed

    Hiratsuka, Tatsumasa; Tanaka, Hideki; Miyahara, Minoru T

    2016-04-28

    Capillary condensation in the regime of developing hysteresis occurs at a vapor pressure, Pcond, that is less than that of the vapor-like spinodal. This is because the energy barrier for the vapor-liquid transition from a metastable state at Pcond becomes equal to the energy fluctuation of the system; however, a detailed mechanism of the spontaneous transition has not been acquired even through extensive experimental and simulation studies. We therefore construct accurate atomistic silica mesopore models for MCM-41 and perform molecular simulations (gauge cell Monte Carlo and grand canonical Monte Carlo) for argon adsorption on the models at subcritical temperatures. A careful comparison between the simulation and experiment reveals that the energy barrier for the capillary condensation has a critical dimensionless value, Wc (*) = 0.175, which corresponds to the thermal fluctuation of the system and depends neither on the mesopore size nor on the temperature. We show that the critical energy barrier Wc (*) controls the capillary condensation pressure Pcond and also determines a boundary between the reversible condensation/evaporation regime and the developing hysteresis regime. PMID:27131561

  9. Random free energy barrier hopping model for ac conduction in chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Murti, Ram; Tripathi, S. K.; Goyal, Navdeep; Prakash, Satya

    2016-03-01

    The random free energy barrier hopping model is proposed to explain the ac conductivity (σac) of chalcogenide glasses. The Coulomb correlation is consistently accounted for in the polarizability and defect distribution functions and the relaxation time is augmented to include the overlapping of hopping particle wave functions. It is observed that ac and dc conduction in chalcogenides are due to same mechanism and Meyer-Neldel (MN) rule is the consequence of temperature dependence of hopping barriers. The exponential parameter s is calculated and it is found that s is subjected to sample preparation and measurement conditions and its value can be less than or greater than one. The calculated results for a - Se, As2S3, As2Se3 and As2Te3 are found in close agreement with the experimental data. The bipolaron and single polaron hopping contributions dominates at lower and higher temperatures respectively and in addition to high energy optical phonons, low energy optical and high energy acoustic phonons also contribute to the hopping process. The variations of hopping distance with temperature is also studied. The estimated defect number density and static barrier heights are compared with other existing calculations.

  10. Energy Transfer of Excitons Between Quantum Wells Separated by a Wide Barrier

    SciTech Connect

    LYO,SUNGKWUN K.

    1999-12-06

    We present a microscopic theory of the excitonic Stokes and anti-Stokes energy transfer mechanisms between two widely separated unequal quantum wells with a large energy mismatch ({Delta}) at low temperatures (T). Exciton transfer through dipolar coupling, photon-exchange coupling and over-barrier ionization of the excitons through exciton-exciton Auger processes are examined. The energy transfer rate is calculated as a function of T and the center-to-center distance d between the two wells. The rates depend sensitively on T for plane-wave excitons. For located excitons, the rates depend on T only through the T-dependence of the localization radius.

  11. Systematical Behavior of Breakup Effects on Complete Fusion at Energies above the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zhao, Wei-Juan; Gomes, P. R. S.; Zhao, En-Guang; Zhou, Shan-Gui

    We investigate the systematical behavior of the breakup effects on the complete fusion (CF) cross sections at energies above the Coulomb barrier. The CF cross sections are suppressed by the prompt breakup of the projectiles. This suppression effect, expressed as the ratio of the reduced fusion function and the universal fusion function (UFF), for reactions induced by the same projectile, is independent of the target and mainly determined by the lowest energy breakup channel of the projectile. There holds a good exponential relation between the suppression factor and the energy corresponding to the lowest breakup threshold.

  12. Gender Differences in Barriers to Physical Activity among College Students Reporting Varying Levels of Regular Physical Activity

    ERIC Educational Resources Information Center

    Munford, Shawn N.

    2011-01-01

    Researchers have studied the primary determinants of physical activity in an effort to enhance health promotion initiatives nationwide. These physical activity determinants have been observed to differ among various segments of the population, suggesting a further examination of physical activity barriers among differing populations. Little…

  13. Formation of hyperdeformed states in capture reactions at sub-barrier energies

    SciTech Connect

    Zubov, A. S.; Antonenko, N. V.; Sargsyan, V. V.; Adamian, G. G.; Scheid, W.

    2010-09-15

    The high-spin hyperdeformed nuclear states treated as dinuclear or quasimolecular configurations are suggested to be directly populated in heavy ion collisions at sub-barrier energies. Tunneling through the Coulomb barrier is considered using the quantum diffusion approach based on the formalism of reduced density matrix. The reactions {sup 48}Ca+{sup 86}Kr,{sup 124}Sn,{sup 136}Xe,{sup 138}Ba,{sup 140}Ce, {sup 58}Ni+{sup 58}Ni, and {sup 40,48}Ca+{sup 40,48}Ca, are suggested for populating high-spin hyperdeformed states. The partial production and identification cross sections for the hyperdeformed states are calculated as the functions of bombarding energy.

  14. Nucleon exchange mechanism in heavy-ion collisions at near-barrier energies

    SciTech Connect

    Yilmaz, B.; Ayik, S.; Lacroix, D.

    2011-06-15

    Nucleon drift and diffusion mechanisms in central collisions of asymmetric heavy ions at near-barrier energies are investigated in the framework of a stochastic mean-field approach. Expressions for diffusion and drift coefficients for nucleon transfer deduced from the stochastic mean-field approach in the semiclassical approximation have similar forms familiar from the phenomenological nucleon exchange model. The variance of fragment mass distribution agrees with the empirical formula {sigma}{sub AA}{sup 2}(t)=N{sub exc}(t). The comparison with the time-dependent Hartree-Fock calculations shows that below barrier energies, the drift coefficient in the semiclassical approximation underestimates the mean number of nucleon transfer obtained in the quantal framework. Motion of the window in the dinuclear system has a significant effect on the nucleon transfer in asymmetric collisions.

  15. The quantum free energy barrier for hydrogen vacancy diffusion in Na3AlH6.

    PubMed

    Poma, Adolfo; Monteferrante, Michele; Bonella, Sara; Ciccotti, Giovanni

    2012-11-28

    The path integral single sweep method is used to assess quantum effects on the free energy barrier for hydrogen vacancy diffusion in a defective Na(3)AlH(6) crystal. This process has been investigated via experiments and simulations due to its potential relevance in the H release mechanism in sodium alanates, prototypical materials for solid state hydrogen storage. Previous computational studies, which used density functional methods for the electronic structure, were restricted to a classical treatment of the nuclear degrees of freedom. We show that, although they do not change the qualitative picture of the process, nuclear quantum effects reduce the free energy barrier height by about 18% with respect to the classical calculation improving agreement with available neutron scattering data. PMID:23064527

  16. Observation of the one- to six-neutron transfer reactions at sub-barrier energies

    SciTech Connect

    Jiang, C.L.; Rehm, K.E.; Gehring, J.

    1995-08-01

    It was suggested many years ago that when two heavy nuclei are in contact during a grazing collision, the transfer of several correlated neutron-pairs could occur. Despite considerable experimental effort, however, so far only cross sections for up to four-neutron transfers have been uniquely identified. The main difficulties in the study of multi-neutron transfer reactions are the small cross sections encountered at incident energies close to the barrier, and various experimental uncertainties which can complicate the analysis of these reactions. We have for the first time found evidence for multi-neutron transfer reactions covering the full sequence from one- to six-neutron transfer reactions at sub-barrier energies in the system {sup 58}Ni + {sup 100}Mo.

  17. OVERVIEW OF THE U.S. DEPARTMENT OF ENERGY AND NUCLEAR REGULATORY COMMISSION PERFORMANCE ASSESSMENT APPROACHES: CEMENTITIOUS BARRIERS PARTNERSHIP

    SciTech Connect

    Langton, C.; Burns, H.

    2009-05-29

    Engineered barriers including cementitious barriers are used at sites disposing or contaminated with low-level radioactive waste to enhance performance of the natural environment with respect to controlling the potential spread of contaminants. Drivers for using cementitious barriers include: high radionuclide inventory, radionuclide characteristics (e.g., long half-live, high mobility due to chemical form/speciation, waste matrix properties, shallow water table, and humid climate that provides water for leaching the waste). This document comprises the first in a series of reports being prepared for the Cementitious Barriers Partnership. The document is divided into two parts which provide a summary of: (1) existing experience in the assessment of performance of cementitious materials used for radioactive waste management and disposal and (2) sensitivity and uncertainty analysis approaches that have been applied for assessments. Each chapter is organized into five parts: Introduction, Regulatory Considerations, Specific Examples, Summary of Modeling Approaches and Conclusions and Needs. The objective of the report is to provide perspective on the state of the practice for conducting assessments for facilities involving cementitious barriers and to identify opportunities for improvements to the existing approaches. Examples are provided in two contexts: (1) performance assessments conducted for waste disposal facilities and (2) performance assessment-like analyses (e.g., risk assessments) conducted under other regulatory regimes. The introductory sections of each section provide a perspective on the purpose of performance assessments and different roles of cementitious materials for radioactive waste management. Significant experience with assessments of cementitious materials associated with radioactive waste disposal concepts exists in the US Department of Energy Complex and the commercial nuclear sector. Recently, the desire to close legacy facilities has created

  18. Reaction Dynamics of Weakly-Bound Few-Body Nuclei at Energies Around the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Boselli, Maddalena; Diaz-Torres, Alexis

    2016-03-01

    We present a quantum reaction approach that unambiguously quantifies the complete and incomplete fusion of weakly-bound few-body nuclei. Calculations carried out within a simple model for 6Li + 209Bi at energies near the Coulomb barrier show that converged probabilities for the total, complete and incomplete fusion as well as for the scattering process can be obtained with the time-dependent wave-packet dynamics.

  19. Barriers to Incorporating Climate Change Science into High School and Community College Energy Course Offerings

    NASA Astrophysics Data System (ADS)

    Howell, C.

    2013-05-01

    In reviewing studies evaluating trends in greenhouse gasses, weather, climate and/or ecosystems, it becomes apparent that climate change is a reality. It has also become evident that the energy sector accounts for most of the greenhouse gas emissions with worldwide emissions of carbon dioxide increasing by 31 percent from 1990 to 2005, higher than in the previous thousands of years. While energy courses and topics are presented in high school and community college classes the topic of Climate Change Science is not always a part of the conversation. During the summer of 2011 and 2012, research undergraduates conducted interviews with a total of 39 national community college and 8 high school instructors who participated in a two week Sustainable Energy Education Training (SEET) workshop. Interview questions addressed the barriers and opportunities to the incorporation of climate change as a dimension of an energy/renewable energy curriculum. Barriers found included: there is not enough instruction time to include it; some school administrators including community members do not recognize climate change issues; quality information about climate change geared to students is difficult to find; and, most climate change information is too scientific for most audiences. A Solution to some barriers included dialogue on sustainability as a common ground in recognizing environmental changes/concerns among educators, administrators and community members. Sustainability discussions are already supported in school business courses as well as in technical education. In conclusion, we cannot expect climate change to dissipate without humans making more informed energy and environmental choices. With global population growth producing greater emissions resulting in increased climate change, we must include the topic of climate change to students in high school and community college classrooms, preparing our next generation of leaders and workforce to be equipped to find solutions

  20. Barriers on the propagation of renewable energy sources and sustainable solid waste management practices in Greece.

    PubMed

    Boemi, Sn; Papadopoulos, Am; Karagiannidis, A; Kontogianni, S

    2010-11-01

    Renewable energy sources (RES), excluding large hydroelectric plants, currently produce 4.21% of total electricity production in Greece. Even when considering the additional production from large hydroelectric plants, which accounts for some 7.8%, the distance to be covered towards the objective of 20% electricity produced from RES by 2010 and respectively towards 20% of total energy production by 2020 is discouraging. The potential, however, does exist; unfortunately so do serious barriers. On the other hand, solid waste management (SWM) is an issue that generates continuously increasing interest due to the extra amounts of solid waste generated; the lack of existing disposal facilities with adequate infrastructure and integrated management plans, also often accompanied by legislative and institutional gaps. However, socio-economic and public awareness problems are still met in the planning and implementation of RES and SWM projects, together with the lack of a complete national cadastre and a spatial development master plan, specifying areas eligible for RES and SWM development. Specific barriers occur for individual RES and the on-going inclusion of waste-derived renewable energy in the examined palette further increases the complexity of the entire issue. The consolidated study of this broad set of barriers was a main task of the present study which was carried out within the frame of a Hellenic-Canadian research project; the main results will be discussed herein. PMID:20630941

  1. Sub-barrier fusion excitation function data and energy dependent Woods-Saxon potential

    NASA Astrophysics Data System (ADS)

    Gautam, Manjeet Singh

    2016-07-01

    This paper analyzed the role of intrinsic degrees of freedom of colliding nuclei in the enhancement of sub-barrier fusion cross-section data of various heavy ion fusion reactions. The influences of inelastic surface vibrations of colliding pairs are found to be dominant and their couplings result in the significantly larger fusion enhancement over the predictions of the one dimensional barrier penetration model at sub-barrier energies. The theoretical calculations are performed by using energy dependent Woods-Saxon potential model (EDWSP model) in conjunction with the one dimensional Wong formula. The effects of dominant intrinsic channels are entertained within framework of the coupled channel calculations obtained by using the code CCFULL. It is quite interesting to note that the energy dependence in Woods-Saxon potential simulates the effects of inelastic surface vibrational states of reactants wherein significantly larger value of diffuseness parameter ranging from a = 0.85 fm to a = 0.95 fm is required to address the observed fusion excitation function data of the various heavy ion fusion reactions.

  2. Effect of four different reflective barriers on black-globe temperatures in calf hutches

    NASA Astrophysics Data System (ADS)

    Friend, T. H.; Haberman, J. A.; Binion, W. R.

    2014-12-01

    Polyethylene hutches are a popular method of housing dairy calves from 0 to 60 or more days of age, although these hutches get hot when in full sun. This study characterized the relative differences in the ability of four different types of radiant barriers to reduce black-globe temperature within these hutches. Treatments included three different types of covers (two types of laminates (Cadpak P and Cadpak ESD) and an aluminized 3.0-mil white low-density polyethylene (LDPE)) and a reflective paint (LO/MIT-1). The reflective covers were 1.8 × 3 m finished size, and covered the top and sides of the hutch down to 0.15 m above the ground, leaving the front and back exposed. The LO/MIT-1 paint covered the entire sides and roof of the hutch. Two 24-h trials 1 week apart were conducted during relatively hot and clear days in early August. Black-globe temperatures were recorded in duplicate and averaged at 20-min intervals using blackened table tennis balls mounted 0.3 m above the floor in the center of each hutch. Ambient temperature (shade) during the hottest 2-h period for both trials averaged 39.9 °C while the uncovered control averaged 41.1 °C, and LO/MIT-1 averaged 39.9 °C; both of which were significantly higher ( P < 0.01) than the Cadpak P (38.9 °C), Cadpak ESD (38.6 °C), and aluminized LDPE (38.7 °C). During periods of high solar radiation, the hutches with covers had lowest black-globe temperatures followed by hutches painted with reflective paint, while control hutches had the highest temperature.

  3. Effect of four different reflective barriers on black-globe temperatures in calf hutches.

    PubMed

    Friend, T H; Haberman, J A; Binion, W R

    2014-12-01

    Polyethylene hutches are a popular method of housing dairy calves from 0 to 60 or more days of age, although these hutches get hot when in full sun. This study characterized the relative differences in the ability of four different types of radiant barriers to reduce black-globe temperature within these hutches. Treatments included three different types of covers (two types of laminates (Cadpak P and Cadpak ESD) and an aluminized 3.0-mil white low-density polyethylene (LDPE)) and a reflective paint (LO/MIT-1). The reflective covers were 1.8 × 3 m finished size, and covered the top and sides of the hutch down to 0.15 m above the ground, leaving the front and back exposed. The LO/MIT-1 paint covered the entire sides and roof of the hutch. Two 24-h trials 1 week apart were conducted during relatively hot and clear days in early August. Black-globe temperatures were recorded in duplicate and averaged at 20-min intervals using blackened table tennis balls mounted 0.3 m above the floor in the center of each hutch. Ambient temperature (shade) during the hottest 2-h period for both trials averaged 39.9 °C while the uncovered control averaged 41.1 °C, and LO/MIT-1 averaged 39.9 °C; both of which were significantly higher (P < 0.01) than the Cadpak P (38.9 °C), Cadpak ESD (38.6 °C), and aluminized LDPE (38.7 °C). During periods of high solar radiation, the hutches with covers had lowest black-globe temperatures followed by hutches painted with reflective paint, while control hutches had the highest temperature. PMID:24619461

  4. Effects of different disturbance types on butterflyfish communities of Australia's Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Emslie, M. J.; Pratchett, M. S.; Cheal, A. J.

    2011-06-01

    The effects of disturbances on coral reef fishes have been extensively documented but most studies have relied on opportunistic sampling following single events. Few studies have the spatial and temporal extent to directly compare the effects of multiple disturbances over a large geographic scale. Here, benthic communities and butterflyfishes on 47 reefs of the Great Barrier Reef were surveyed annually to examine their responses to physical disturbances (cyclones and storms) and/or biological disturbances (bleaching, outbreaks of crown-of-thorns starfish and white syndrome disease). The effects on benthic and butterflyfish communities varied among reefs depending on the structure and geographical setting of each community, on the size and type of disturbance, and on the disturbance history of that reef. There was considerable variability in the response of butterflyfishes to different disturbances: physical disturbances (occurring with or without biological disturbances) produced substantial declines in abundance, whilst biological disturbances occurring on their own did not. Butterflyfishes with the narrowest feeding preferences, such as obligate corallivores, were always the species most affected. The response of generalist feeders varied with the extent of damage. Wholesale changes to the butterflyfish community were only recorded where structural complexity of reefs was drastically reduced. The observed effects of disturbances on butterflyfishes coupled with predictions of increased frequency and intensity of disturbances sound a dire warning for the future of butterflyfish communities in particular and reef fish communities in general.

  5. Reaction Pathway and Free Energy Barrier for Reactivation of Dimethylphosphoryl-inhibited Human Acetylcholinesterase

    PubMed Central

    Liu, Junjun; Zhang, Yingkai; Zhan, Chang-Guo

    2009-01-01

    The dephosphorylation/reactivation mechanism and the corresponding free energy profile of dimethylphosphoryl-inhibited conjugate of human acetylcholinesterase (AChE) has been studied by performing first-principles quantum mechanical/molecular mechanical free energy (QM/MM-FE) calculations. Based on the QM/MM-FE results, for the favorable reaction pathway, the entire dephosphorylation/reactivation process consists of three reaction steps, including the nucleophilic water attack on the P atom, the spatial reorganization of the dimethylphosphoryl group, and the dissociation between the dimethylphosphoryl group and Ser203 of AChE. The overall free energy barrier for the entire dephosphorylation/reactivation reaction is found to be the free energy change from the initial reactant to the transition state associated with the spatial reorganization step, and the calculated overall free energy barrier (20.1 to 23.5 kcal/mol) is reasonably close to the experimentally-derived activation free energy of 22.3 kcal/mol. In addition, key amino acid residues and their specific roles in the reaction process have been identified. PMID:19924840

  6. Validation and divergence of the activation energy barrier crossing transition at the AOT/lecithin reverse micellar interface.

    PubMed

    Narayanan, S Shankara; Sinha, Sudarson Sekhar; Sarkar, Rupa; Pal, Samir Kumar

    2008-03-13

    In this report, the validity and divergence of the activation energy barrier crossing model for the bound to free type water transition at the interface of the AOT/lecithin mixed reverse micelle (RM) has been investigated for the first time in a wide range of temperatures by time-resolved solvation of fluorophores. Here, picosecond-resolved solvation dynamics of two fluorescent probes, ANS (1-anilino-8-naphthalenesulfonic acid, ammonium salt) and Coumarin 500 (C-500), in the mixed RM have been carefully examined at 293, 313, 328, and 343 K. Using the dynamic light scattering (DLS) technique, the size of the mixed RMs at different temperatures was found to have an insignificant change. The solvation process at the reverse micellar interface has been found to be the activation energy barrier crossing type, in which interface-bound type water molecules get converted into free type water molecules. The activation energies, Ea, calculated for ANS and C-500 are 7.4 and 3.9 kcal mol(-1), respectively, which are in good agreement with that obtained by molecular dynamics simulation studies. However, deviation from the regular Arrhenius type behavior was observed for ANS around 343 K, which has been attributed to the spatial heterogeneity of the probe environments. Time-resolved fluorescence anisotropy decay of the probes has indicated the existence of the dyes in a range of locations in RM. With the increase in temperature, the overall anisotropy decay becomes faster revealing the lability of the microenvironment at elevated temperatures. PMID:18281975

  7. Anharmonic force field, vibrational energies, and barrier to inversion of SiH{sub 3}{sup -}

    SciTech Connect

    Aarset, Kirsten; Csaszar, Attila G.; Sibert, Edwin L. III; Allen, Wesley D.; Schaefer, Henry F. III; Klopper, Wim; Theoretical Chemistry Group, Debye Institute, Utrecht University, Padualaan 14, NL-3584 CH Utrecht, The Netherlands ; Noga, Jozef

    2000-03-01

    The full quartic force field of the ground electronic state of the silyl anion (SiH{sub 3}{sup -}) has been determined at the CCSD(T)-R12 level employing a [Si/H]=[16s11p6d5f/7s5p4d] basis set. The vibrational energy levels, using the quartic force field as a representation of the potential energy hypersurface around equilibrium, have been determined by vibrational perturbation theory carried out to second, fourth, and sixth order. The undetected vibrational fundamental for the umbrella mode, {nu}{sub 2}, is predicted to be 844 cm-1. High-quality ab initio quantum chemical methods, including higher-order coupled cluster (CC) and many-body perturbation (MP) theory with basis sets ranging from [Si/H] [5s4p2d/3s2p] to [8s7p6d5f4g3h/7s6p5d4f3g] have been employed to obtain the best possible value for the inversion barrier of the silyl anion. The rarely quantified effects of one- and two-particle relativistic terms, core correlation, and the diagonal Born-Oppenheimer correction (DBOC) have been included in the determination of the barrier for this model system. The final electronic (vibrationless) extrapolated barrier height of this study is 8351{+-}100 cm{sup -1}. (c) 2000 American Institute of Physics.

  8. Differences in Perceptions of Barriers to College Enrollment and the Completion of a Degree among Latinos in the United States

    ERIC Educational Resources Information Center

    Becerra, David

    2010-01-01

    This study examined the differences in perceptions of barriers in education among Latinos in the United States based on the level of linguistic acculturation, generational status, academic achievement, and socioeconomic status of the participants. This study used data from the Pew Hispanic Research Center. Results indicated that later-generation…

  9. Rural/Urban Differences in Barriers to and Burden of Care for Children with Special Health Care Needs

    ERIC Educational Resources Information Center

    Skinner, Asheley Cockrell; Slifkin, Rebecca T.

    2007-01-01

    Purpose: To examine the barriers and difficulties experienced by rural families of children with special health care needs (CSHCN) in caring for their children. Methods: The National Survey of Children with Special Health Care Needs was used to examine rural-urban differences in types of providers used, reasons CSHCN had unmet health care needs,…

  10. Energy efficient engine, high pressure turbine thermal barrier coating. Support technology report

    NASA Technical Reports Server (NTRS)

    Duderstadt, E. C.; Agarwal, P.

    1983-01-01

    This report describes the work performed on a thermal barrier coating support technology task of the Energy Efficient Engine Component Development Program. A thermal barrier coating (TBC) system consisting of a Ni-Cr-Al-Y bond cost layer and ZrO2-Y2O3 ceramic layer was selected from eight candidate coating systems on the basis of laboratory tests. The selection was based on coating microstructure, crystallographic phase composition, tensile bond and bend test results, erosion and impact test results, furnace exposure, thermal cycle, and high velocity dynamic oxidation test results. Procedures were developed for applying the selected TBC to CF6-50, high pressure turbine blades and vanes. Coated HPT components were tested in three kinds of tests. Stage 1 blades were tested in a cascade cyclic test rig, Stage 2 blades were component high cycle fatigue tested to qualify thermal barrier coated blades for engine testing, and Stage 2 blades and Stage 1 and 2 vanes were run in factory engine tests. After completion of the 1000 cycle engine test, the TBC on the blades was in excellent condition over all of the platform and airfoil except at the leading edge above midspan on the suction side of the airfoil. The coating damage appeared to be caused by particle impingement; adjacent blades without TBC also showed evidence of particle impingement.

  11. Driven diffusion against electrostatic or effective energy barrier across α-hemolysin

    SciTech Connect

    Ansalone, Patrizio; Chinappi, Mauro; Rondoni, Lamberto; Cecconi, Fabio

    2015-10-21

    We analyze the translocation of a charged particle across an α-Hemolysin (αHL) pore in the framework of a driven diffusion over an extended energy barrier generated by the electrical charges of the αHL. A one-dimensional electrostatic potential is extracted from the full 3D solution of the Poisson’s equation. We characterize the particle transport under the action of a constant forcing by studying the statistics of the translocation time. We derive an analytical expression of translocation time average that compares well with the results from Brownian dynamic simulations of driven particles over the electrostatic potential. Moreover, we show that the translocation time distributions can be perfectly described by a simple theory which replaces the true barrier by an equivalent structureless square barrier. Remarkably, our approach maintains its accuracy also for low-applied voltage regimes where the usual inverse-Gaussian approximation fails. Finally, we discuss how the comparison between the simulated time distributions and their theoretical prediction results to be greatly simplified when using the notion of the empirical Laplace transform technique.

  12. Evolution of fusion hindrance for asymmetric systems at deep sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Shrivastava, A.; Mahata, K.; Pandit, S. K.; Nanal, V.; Ichikawa, T.; Hagino, K.; Navin, A.; Palshetkar, C. S.; Parkar, V. V.; Ramachandran, K.; Rout, P. C.; Kumar, Abhinav; Chatterjee, A.; Kailas, S.

    2016-04-01

    Measurements of fusion cross-sections of 7Li and 12C with 198Pt at deep sub-barrier energies are reported to unravel the role of the entrance channel in the occurrence of fusion hindrance. The onset of fusion hindrance has been clearly observed in 12C +198Pt system but not in 7Li +198Pt system, within the measured energy range. Emergence of the hindrance, moving from lighter (6,7Li) to heavier (12C, 16O) projectiles is explained employing a model that considers a gradual transition from a sudden to adiabatic regime at low energies. The model calculation reveals a weak effect of the damping of coupling to collective motion for the present systems as compared to that obtained for systems with heavier projectiles.

  13. Experimental study of the 13C+12C fusion reaction at deep sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Tudor, D.; Chilug, A. I.; Straticiuc, M.; Trache, L.; Chesneanu, D.; Toma, S.; Ghita, D. G.; Burducea, I.; Margineanu, R.; Pantelica, A.; Gomoiu, C.; Zhang, N. T.; Tang, X.; Li, Y. J.

    2016-04-01

    Heavy-ion fusion reactions between light nuclei such as carbon and oxygen isotopes have been studied because of their significance for a wide variety of stellar burning scenarios. One important stellar reaction is 12C+12C, but it is difficult to measure it in the Gamow window because of very low cross sections and several resonances occurring. Hints can be obtained from the study of 13C+12C reaction. We have measured this process by an activation method for energies down to Ecm=2.5 MeV using 13C beams from the Bucharest 3 MV tandetron and gamma-ray deactivation measurements in our low and ultralow background laboratories, the latter located in a salt mine about 100 km north of Bucharest. Results obtained so far are shown and discussed in connection with the possibility to go even further down in energy and with the interpretation of the reaction mechanism at such deep sub-barrier energies.

  14. Barriers to referral for elevated blood pressure in the emergency department and differences between provider-type

    PubMed Central

    Souffront, Kimberly; Chyun, Deborah; Kovner, Christine

    2015-01-01

    A multidisciplinary sample of ED providers across the United States (n = 450) were surveyed to identify barriers to referral for elevated blood pressure (BP) in the ED and differences between provider-type. RNs reported less knowledge of Stage I HTN (p = .043) and Pre-HTN (p<.01); were less aware of definitions for HTN (p<.001); reported more difficulty caring for patients who are asymptomatic (p = .007); required financial compensation to refer (p = .048); and perceived BP referrals are influenced by the medical director (p<.001). MDs reported more skills to refer (p = .008) and time as a barrier (p = .038); PAs were more likely to report patients are not aware of health benefits (p = .035) and doubted their concern for their BP (p = .023); and felt emotionally uncomfortable when referring (p = .025). Despite these differences, there was no significant difference between provider-type and referral. PMID:25582763

  15. Search for Monoenergetic Positron Emission from Heavy-Ion Collisions at Coulomb-Barrier Energies

    SciTech Connect

    Ahmad, I.; Back, B.B.; Betts, R.R.; Dunford, R.W.; Freer, M.; Happ, T.; Henderson, D.; Kutschera, W.; Last, J.; Lister, C.J.; Rhein, M.D.; Schiffer, J.P.; Wilt, P.; Wuosmaa, A.H.; Austin, S.M.; Kashy, E.; Maier, M.R.; Mercer, D.J.; Mikolas, D.; Winfield, J.S.; Yurkon, J.E.; Betts, R.R.; Conner, C.; Calaprice, F.P.; Young, A.; Chan, K.C.; Chishti, A.; Kaloskamis, N.I.; Xu, G.; Fox, J.D.; Roa, D.E.; Freedman, S.J.; Freer, M.; Gazes, S.B.; Schiffer, J.P.; Wolanski, M.R.; Hallin, A.L.; Liu, M.; Happ, T.; Rhein, M.D.; Perera, P.A.; Wolfs, F.L.; Trainor, T.A.

    1997-01-01

    Positron production in {sup 238}U+{sup 232}Th and {sup 238}U+{sup 181}Ta collisions near the Coulomb barrier has been studied. Earlier experiments reported narrow lines in the spectra of positrons, accumulated without the requirement of electrons detected in coincidence. No evidence of such structure is observed in the present data. The positron energy spectra are compared with estimates from dynamic atomic processes, and from internal pair conversion of electromagnetic transitions from the excited nuclei. {copyright} {ital 1997} {ital The American Physical Society}

  16. 7Be- and 8B-reaction dynamics at Coulomb barrier energies

    NASA Astrophysics Data System (ADS)

    Mazzocco, M.; Boiano, A.; Boiano, C.; La Commara, M.; Manea, C.; Parascandolo, C.; Pierroutsakou, D.; Signorini, C.; Strano, E.; Torresi, D.; Yamaguchi, H.; Kahl, D.; Acosta, L.; Di Meo, P.; Fernandez-Garcia, J. P.; Glodariu, T.; Grebosz, J.; Guglielmetti, A.; Imai, N.; Hirayama, Y.; Ishiyama, H.; Iwasa, N.; Jeong, S. C.; Jia, H. M.; Keeley, N.; Kim, Y. H.; Kimura, S.; Kubono, S.; Lay, J. A.; Lin, C. J.; Marquinez-Duran, G.; Martel, I.; Miyatake, H.; Mukai, M.; Nakao, T.; Nicoletto, M.; Pakou, A.; Rusek, K.; Sakaguchi, Y.; Sánchez-Benítez, A. M.; Sava, T.; Sgouros, O.; Stefanini, C.; Soramel, F.; Soukeras, V.; Stiliaris, E.; Stroe, L.; Teranishi, T.; Toniolo, N.; Wakabayashi, Y.; Watanabe, Y. X.; Yang, L.; Yang, Y. Y.

    2016-05-01

    We investigated the reaction dynamics induced by the Radioactive Ion Beams 7Be and 8B on a 208Pb target at energies around the Coulomb barrier. The two measurements are strongly interconnected, being 7Be (Sα = 1.586 MeV) the loosely bound core of the even more exotic 8B (Sp = 0.1375 MeV) nucleus. Here we summarize the present status of the data analysis for the measurement of the elastic scattering process for both reactions and the preliminary results for the optical model analysis of the collected data.

  17. Systematics of heavy-ion fusion hindrance at extreme sub-barrier energies

    SciTech Connect

    Jiang, C.L.; Back, B.B.; Esbensen, H.; Janssens, R.V.F.; Rehm, K.E.

    2006-01-15

    The recent discovery of hindrance in heavy-ion induced fusion reactions at extreme sub-barrier energies represents a challenge for theoretical models. Previously, it has been shown that in medium-heavy systems, the onset of fusion hindrance depends strongly on the ''stiffness'' of the nuclei in the entrance channel. In this work, we explore its dependence on the total mass and the Q-value of the fusing systems and find that the fusion hindrance depends in a systematic way on the entrance channel properties over a wide range of systems.

  18. Barriers to Building Energy Efficiency (BEE) promotion: A transaction costs perspective

    NASA Astrophysics Data System (ADS)

    Qian Kun, Queena

    Worldwide, buildings account for a surprisingly high 40% of global energy consumption, and the resulting carbon footprint significantly exceeds that of all forms of transportation combined. Large and attractive opportunities exist to reduce buildings' energy use at lower costs and higher returns than in other sectors. This thesis analyzes the concerns of the market stakeholders, mainly real estate developers and end-users, in terms of transaction costs as they make decisions about investing in Building Energy Efficiency (BEE). It provides a detailed analysis of the current situation and future prospects for BEE adoption by the market's stakeholders. It delineates the market and lays out the economic and institutional barriers to the large-scale deployment of energy-efficient building techniques. The aim of this research is to investigate the barriers raised by transaction costs that hinder market stakeholders from investing in BEES. It explains interactions among stakeholders in general and in the specific case of Hong Kong as they consider transaction costs. It focuses on the influence of transaction costs on the decision-making of the stakeholders during the entire process of real estate development. The objectives are: 1) To establish an analytical framework for understanding the barriers to BEE investment with consideration of transaction costs; 2) To build a theoretical game model of decision making among the BEE market stakeholders; 3) To study the empirical data from questionnaire surveys of building designers and from focused interviews with real estate developers in Hong Kong; 4) To triangulate the study's empirical findings with those of the theoretical model and analytical framework. The study shows that a coherent institutional framework needs to be established to ensure that the design and implementation of BEE policies acknowledge the concerns of market stakeholders by taking transaction costs into consideration. Regulatory and incentive options

  19. IL-33 and IL-4 impair barrier functions of human vascular endothelium via different mechanisms.

    PubMed

    Chalubinski, Maciej; Wojdan, Katarzyna; Luczak, Emilia; Gorzelak, Paulina; Borowiec, Maciej; Gajewski, Adrian; Rudnicka, Karolina; Chmiela, Magdalena; Broncel, Marlena

    2015-10-01

    The vascular endothelium forms a barrier that controls flow of solutes and proteins and the entry of leukocytes into tissue. Injured tissue releases IL-33, which then alarms the immune system and attracts Th2 cells, thus increasing local concentration of IL-4. The aim of the study was to assess the influence of IL-33 and IL-4 on barrier functions of the human endothelium, expression of tight and adherent junction proteins, apoptosis and adhesive molecule surface expression in human endothelium in order to describe the mechanism of this effect. IL-33 and IL-4 decreased endothelial integrity and increased permeability. When added together, both cytokines lowered the endothelial integrity twice as much as used alone. This effect was accompanied by the down-regulation of occludin and VE-cadherin mRNA expression. Additionally, IL-4, but not IL-33, induced cell apoptosis. Both IL-33 and IL-4 showed the additive potency to down-regulate VE-cadherin mRNA expression. IL-33, unlike IL-4, increased the surface expression of ICAM-1, but not PECAM-1 in endothelial cells. Our results indicate that IL-33 may reversibly destabilize the endothelial barrier, thus accelerating the supply with immunomodulators and assisting leukocytes to reach wounded tissue. However, extended and less-controlled down-regulation of endothelial barrier, which may be a consequence of IL-33-initiated, but in fact IL-4-induced apoptosis of endothelial cells, may be deleterious and may eventually lead to the aggravation of inflammatory processes and the prolongation of tissue dysfunction. PMID:26231284

  20. Disintegration locations in 7Li→8Be transfer-triggered breakup at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Simpson, E. C.; Cook, K. J.; Luong, D. H.; Kalkal, Sunil; Carter, I. P.; Dasgupta, M.; Hinde, D. J.; Williams, E.

    2016-02-01

    Background: At above-barrier energies, complete fusion cross sections in collisions of light weakly bound nuclei with heavy target nuclei are suppressed when compared to well-bound nuclei. Breakup of the projectilelike nucleus was proposed to be the cause. In addition to direct breakup, breakup following transfer was shown to be substantial. Purpose: We investigate breakup in reactions with 7Li, triggered by sub-barrier proton pickup to unbound states in 8Be, which subsequently separate into two α particles. Method: Measurements of sub-barrier disintegration of 7Li on a 58Ni target were made using the Heavy Ion Accelerator Facility at the Australian National University. Combining the experimental results with classical simulations of post-breakup acceleration, we study the sensitivity of α -α energy and angle correlations to the proximity of disintegration to the target (proton donor) nucleus. Results: The simulations indicate that disintegration as the colliding nuclei approach each other leads to large angular separations θ12 of the α fragments. The detectors allow for a maximum opening angle of θ12=132∘ , such that the present experiment is largely insensitive to breakup occurring when the collision partners approach each other. The data are consistent with disintegration of (a) the 0+8Be ground state far from the targetlike nucleus, and (b) the 2+8Be resonance near the targetlike nucleus when the 8Be is receding from the targetlike nucleus. Conclusions: The present results shed light on the near-target component of transfer-induced breakup reactions. The distribution of events with respect to the opening angle of the α particles, and the orientation of their relative velocity with respect to the velocity of their center of mass, gives insights into their proximity to the target at the moment of breakup. Further measurements with larger angular coverage and more complete simulations are required to fully understand the influence of breakup on fusion.

  1. Microstructural Evolution of Cu/Solder/Cu Pillar-Type Structures with Different Diffusion Barriers

    NASA Astrophysics Data System (ADS)

    Cheng, Hsi-Kuei; Lin, Yu-Jie; Chen, Chih-Ming; Liu, Kuo-Chio; Wang, Ying-Lang; Liu, Tzeng-Feng

    2016-08-01

    Microstructural evolution of the Cu/solder/Cu pillar-type bonding structures with a reduced solder volume subjected to thermal aging at 423 K to 473 K(150 °C to 200 °C) was investigated. In a bonding structure employing a Ni single layer as the diffusion barrier, solder was consumed with formation of the Ni3Sn4 phase at the bonding interfaces due to an usual Sn/Ni interfacial reaction. However, an unusual Sn/Cu reaction occurred with formation of the Cu6Sn5 (and Cu3Sn) phase on the periphery of the Cu pillar due to out-diffusion of Sn toward the pillar periphery. Consumption of solder was accelerated by the above two reactions which led to the formation of a continuous gap in the bonding structure. Employment of a thicker Ni layer plus a Cu cap layer as the diffusion barrier in the bonding structure effectively blocked out-diffusion of Sn toward the periphery of the Cu pillar and therefore retarded the gap formation. The retardation effect was attributed to an increment of diffusion distance on the pillar periphery due to an effective diffusion barrier composed by Ni and thicker Cu-Sn (Cu6Sn5 + Cu3Sn) phase layers. Detailed phase identification and microstructural evolution in the bonding structures were also investigated using scanning electron microscopy and transmission electron microscopy.

  2. Microstructural Evolution of Cu/Solder/Cu Pillar-Type Structures with Different Diffusion Barriers

    NASA Astrophysics Data System (ADS)

    Cheng, Hsi-Kuei; Lin, Yu-Jie; Chen, Chih-Ming; Liu, Kuo-Chio; Wang, Ying-Lang; Liu, Tzeng-Feng

    2016-06-01

    Microstructural evolution of the Cu/solder/Cu pillar-type bonding structures with a reduced solder volume subjected to thermal aging at 423 K to 473 K(150 °C to 200 °C) was investigated. In a bonding structure employing a Ni single layer as the diffusion barrier, solder was consumed with formation of the Ni3Sn4 phase at the bonding interfaces due to an usual Sn/Ni interfacial reaction. However, an unusual Sn/Cu reaction occurred with formation of the Cu6Sn5 (and Cu3Sn) phase on the periphery of the Cu pillar due to out-diffusion of Sn toward the pillar periphery. Consumption of solder was accelerated by the above two reactions which led to the formation of a continuous gap in the bonding structure. Employment of a thicker Ni layer plus a Cu cap layer as the diffusion barrier in the bonding structure effectively blocked out-diffusion of Sn toward the periphery of the Cu pillar and therefore retarded the gap formation. The retardation effect was attributed to an increment of diffusion distance on the pillar periphery due to an effective diffusion barrier composed by Ni and thicker Cu-Sn (Cu6Sn5 + Cu3Sn) phase layers. Detailed phase identification and microstructural evolution in the bonding structures were also investigated using scanning electron microscopy and transmission electron microscopy.

  3. Barrier heights, polarization switching, and electrical fatigue in Pb(Zr,Ti)O3 ceramics with different electrodes

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Schafranek, Robert; Wachau, André; Zhukov, Sergey; Glaum, Julia; Granzow, Torsten; von Seggern, Heinz; Klein, Andreas

    2010-11-01

    The influence of Pt, tin-doped In2O3, and RuO2 electrodes on the electrical fatigue of bulk ceramic Pb(Zr,Ti)O3 (PZT) has been studied. Schottky barrier heights at the ferroelectric/electrode interfaces vary by more than one electronvolt for different electrode materials and do not depend on crystallographic orientation of the interface. Despite different barrier heights, hysteresis loops of polarization, strain, permittivity, and piezoelectric constant and the switching kinetics are identical for all electrodes. A 20% reduction in polarization after 106 bipolar cycles is observed for all the samples. In contrast to PZT thin films, the loss of remanent polarization with bipolar switching cycles does not significantly depend on the electrode material.

  4. Gender differences in preferences for coaching as an occupation: the role of self-efficacy, valence, and perceived barriers.

    PubMed

    Everhart, C B; Chelladurai, P

    1998-06-01

    This study investigated gender differences in the role of self-efficacy, occupational valence, valence of coaching, and perceived barriers in preference to coach at the high school, 2-year college, Division III, Division II, and Division I levels. The participants, 191 Big Ten university basketball players (94 men, 97 women), responded to a specially constructed instrument. The genders did not differ in their coaching self-efficacy, preferred occupational valence, and perceived barriers. Relative to men, women perceived greater valence in coaching (p < .001). Women with a female coach perceived greater valence in coaching (p < .05) and expressed less concern with perceived discrimination (p < .05) than those with a male coach. Perceived self-efficacy and preferred occupational valence were differentially related to the desire to coach at various levels. Working Hours most negatively affected the desire to coach at every level (R > .20). PMID:9635332

  5. Entrance Channel Mass Asymmetry Effects in Sub-Barrier Fusion Dynamics by Using Energy Dependent Woods-Saxon Potential

    NASA Astrophysics Data System (ADS)

    Manjeet Singh, Gautam

    2015-12-01

    The present article highlights the inconsistency of static Woods-Saxon potential and the applicability of energy dependent Woods-Saxon potential to explore the fusion dynamics of {}4822Ti+58,60,6428Ni, {}4622Ti+{}6428Ni,{}5022Ti+{}6028Ni, and {}199F+9341Nb reactions leading to formation of different Sn-isotopes via different entrance channels. Theoretical calculations based upon one-dimensional Wong formula obtained by using static Woods-Saxon potential unable to provide proper explanation for sub-barrier fusion enhancement of these projectile-target combinations. However, the predictions of one-dimensional Wong formula based upon energy dependent Woods-Saxon potential model (EDWSP model) accurately describe the observed fusion dynamics of these systems wherein the significantly larger value of diffuseness parameter ranging from a = 0.85 fm to a = 0.97 fm is required to address the experimental data in whole range of energy. Therefore, the energy dependence in nucleus-nucleus potential simulates the influence of the nuclear structure degrees of freedom of the colliding pairs. Supported by Dr. D.S. Kothari Post-Doctoral Fellowship Scheme sponsored by University Grants Commission (UGC), New Delhi, India

  6. Condensation on superhydrophobic surfaces: the role of local energy barriers and structure length scale.

    PubMed

    Enright, Ryan; Miljkovic, Nenad; Al-Obeidi, Ahmed; Thompson, Carl V; Wang, Evelyn N

    2012-10-01

    Water condensation on surfaces is a ubiquitous phase-change process that plays a crucial role in nature and across a range of industrial applications, including energy production, desalination, and environmental control. Nanotechnology has created opportunities to manipulate this process through the precise control of surface structure and chemistry, thus enabling the biomimicry of natural surfaces, such as the leaves of certain plant species, to realize superhydrophobic condensation. However, this "bottom-up" wetting process is inadequately described using typical global thermodynamic analyses and remains poorly understood. In this work, we elucidate, through imaging experiments on surfaces with structure length scales ranging from 100 nm to 10 μm and wetting physics, how local energy barriers are essential to understand non-equilibrium condensed droplet morphologies and demonstrate that overcoming these barriers via nucleation-mediated droplet-droplet interactions leads to the emergence of wetting states not predicted by scale-invariant global thermodynamic analysis. This mechanistic understanding offers insight into the role of surface-structure length scale, provides a quantitative basis for designing surfaces optimized for condensation in engineered systems, and promises insight into ice formation on surfaces that initiates with the condensation of subcooled water. PMID:22931378

  7. Electrical Characterization of High Energy Electron Irradiated Ni/4H-SiC Schottky Barrier Diodes

    NASA Astrophysics Data System (ADS)

    Paradzah, A. T.; Omotoso, E.; Legodi, M. J.; Auret, F. D.; Meyer, W. E.; Diale, M.

    2016-05-01

    The effect of high energy electron irradiation on Ni/4H-SiC Schottky barrier diodes was evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. Electron irradiation was achieved by using a radioactive strontium source with peak emission energy of 2.3 MeV. Irradiation was performed in fluence steps of 4.9 × 1013 cm-2 until a total fluence of 5.4 × 1014 cm-2 was reached. The Schottky barrier height determined from I-V measurements was not significantly changed by irradiation while that obtained from C-V measurements increased with irradiation. The ideality factor was obtained before irradiation as 1.05 and this value did not significantly change as a result of irradiation. The series resistance increased from 47 Ω before irradiation to 74 Ω after a total electron fluence of 5.4 × 1014 cm-2. The net donor concentration decreased with increasing irradiation fluence from 4.6 × 1014 cm-3 to 3.0 × 1014 cm-3 from which the carrier removal rate was calculated to be 0.37 cm-1.

  8. Potential energy barriers to ion transport within lipid bilayers. Studies with tetraphenylborate.

    PubMed Central

    Andersen, P S; Fuchs, M

    1975-01-01

    Tetraphenylborate-induced current transients were studied in lipid bilayers formed from bacterial phosphatidylethanolamine in decane. This ion movement was essentially confined to the membrane in terior during the current transients. Charge movement through the interior of the membrane during the current transients was studied as a function of the applied potential. The transferred charge approached an upper limit with increasing potential, which is interpreted to be the amount of charge due to tetraphenylborate ions absorbed into the boundary regions of the bilayer. A further analysis of the charge transfer as a function of potential indicates that the movement of tetraphenylborate ions is only influenced by a certain farction of the applied potential. For bacterial phosphatidylethanolamine bilayers the effective potential is 77 +/- 4% of the applied potential. The initial conductance and the time constant of the current transients were studied as a function of the applied potential using a Nernst-Planck electrodiffusion regime. It was found that an image-force potential energy barrier gave a good prediction of the observed behavior, provided that the effective potential was used in the calculations. We could not get a satisfactory prediction of the observed behavior with an Eyring rate theory model or a trapezoidal potential energy barrier. PMID:1148364

  9. Efficient dynamical correction of the transition state theory rate estimate for a flat energy barrier.

    PubMed

    Mökkönen, Harri; Ala-Nissila, Tapio; Jónsson, Hannes

    2016-09-01

    The recrossing correction to the transition state theory estimate of a thermal rate can be difficult to calculate when the energy barrier is flat. This problem arises, for example, in polymer escape if the polymer is long enough to stretch between the initial and final state energy wells while the polymer beads undergo diffusive motion back and forth over the barrier. We present an efficient method for evaluating the correction factor by constructing a sequence of hyperplanes starting at the transition state and calculating the probability that the system advances from one hyperplane to another towards the product. This is analogous to what is done in forward flux sampling except that there the hyperplane sequence starts at the initial state. The method is applied to the escape of polymers with up to 64 beads from a potential well. For high temperature, the results are compared with direct Langevin dynamics simulations as well as forward flux sampling and excellent agreement between the three rate estimates is found. The use of a sequence of hyperplanes in the evaluation of the recrossing correction speeds up the calculation by an order of magnitude as compared with the traditional approach. As the temperature is lowered, the direct Langevin dynamics simulations as well as the forward flux simulations become computationally too demanding, while the harmonic transition state theory estimate corrected for recrossings can be calculated without significant increase in the computational effort. PMID:27609008

  10. Electrical Characterization of High Energy Electron Irradiated Ni/4 H-SiC Schottky Barrier Diodes

    NASA Astrophysics Data System (ADS)

    Paradzah, A. T.; Omotoso, E.; Legodi, M. J.; Auret, F. D.; Meyer, W. E.; Diale, M.

    2016-08-01

    The effect of high energy electron irradiation on Ni/4 H-SiC Schottky barrier diodes was evaluated by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements at room temperature. Electron irradiation was achieved by using a radioactive strontium source with peak emission energy of 2.3 MeV. Irradiation was performed in fluence steps of 4.9 × 1013 cm-2 until a total fluence of 5.4 × 1014 cm-2 was reached. The Schottky barrier height determined from I- V measurements was not significantly changed by irradiation while that obtained from C- V measurements increased with irradiation. The ideality factor was obtained before irradiation as 1.05 and this value did not significantly change as a result of irradiation. The series resistance increased from 47 Ω before irradiation to 74 Ω after a total electron fluence of 5.4 × 1014 cm-2. The net donor concentration decreased with increasing irradiation fluence from 4.6 × 1014 cm-3 to 3.0 × 1014 cm-3 from which the carrier removal rate was calculated to be 0.37 cm-1.

  11. Electrostatic energy barriers from dielectric membranes upon approach of translocating DNA molecules

    NASA Astrophysics Data System (ADS)

    Buyukdagli, Sahin; Ala-Nissila, T.

    2016-02-01

    We probe the electrostatic cost associated with the approach phase of DNA translocation events. Within an analytical theory at the Debye-Hückel level, we calculate the electrostatic energy of a rigid DNA molecule interacting with a dielectric membrane. For carbon or silicon based low permittivity neutral membranes, the DNA molecule experiences a repulsive energy barrier between 10 kBT and 100 kBT. In the case of engineered membranes with high dielectric permittivities, the membrane surface attracts the DNA with an energy of the same magnitude. Both the repulsive and attractive interactions result from image-charge effects and their magnitude survive even for the thinnest graphene-based membranes of size d ≈ 6 Å. For weakly charged membranes, the electrostatic energy is always attractive at large separation distances but switches to repulsive close to the membrane surface. We also characterise the polymer length dependence of the interaction energy. For specific values of the membrane charge density, low permittivity membranes repel short polymers but attract long polymers. Our results can be used to control the strong electrostatic energy of DNA-membrane interactions prior to translocation events by chemical engineering of the relevant system parameters.

  12. Effect of topographic barriers on the rates of available potential energy conversion of the oceans

    NASA Astrophysics Data System (ADS)

    Stewart, K. D.; Saenz, J. A.; Hogg, A. McC.; Hughes, G. O.; Griffiths, R. W.

    2014-04-01

    Determining the energy budget of the oceans requires evaluating the rates of available potential energy conversion in the circulation. Calculating these conversion rates depends upon the definition of an appropriate “reference” state of the density field, but this definition is complicated in the oceans by the presence of bottom topography. The trapping of dense fluid by topographic barriers means that there are multiple definitions for the reference state. The approach taken in this paper is to examine the sensitivity of the available potential energy budget to several methods for defining the reference state. The first method makes allowances for restrictions imposed on the flow by topography, however it is computationally intensive. The second method is proposed as an inexpensive alternative to the first. These new methods are used to evaluate the energy budget of a model overturning circulation maintained by surface buoyancy forcing. The results are compared with those obtained from two existing methods; one which employs an adiabatic resorting procedure ignoring topography, and one which uses a reference profile developed from the horizontal average of the density field. In our model, the rates of available potential energy conversion are insensitive to the reference state definition providing the reference state is developed from an adiabatic resorting of the domain. These results suggest that any of the adiabatic resorting methods proposed here would be sufficient to evaluate the rates of energy conversion in the ocean.

  13. Investigation of contribution of incomplete fusion in the total fusion process induced by 9Be on 181Ta target at near barrier energies

    NASA Astrophysics Data System (ADS)

    Kharab, Rajesh; Chahal, Rajiv; Kumar, Rajiv

    2016-02-01

    We have studied the relative contribution of incomplete fusion (ICF) and complete fusion (CF) in total fusion (TF) induced by 9Be on 181Ta target at energies in the vicinity of Coulomb barrier using classical dynamical model and Wong's formula in conjugation with energy dependent Woods-Saxon formula. It is found that at above barrier energies ICF contributes almost 30% in TF while at energies below the barrier qualitatively its contribution is much more than thirty percent.

  14. The {sup 6}He Optical Potential at energies around the Coulomb barrier

    SciTech Connect

    Fernandez-Garcia, J. P.; Alvarez, M. A. G.; Moro, A. M.

    2010-04-26

    We present an Optical Model (OM) study of {sup 6}He on {sup 208}Pb elastic scattering data, measured at laboratory energies around the Coulomb barrier (E{sub lab} = 14, 16, 18, 22, and 27 MeV)[1]. For the projectile-target bare interaction, we use the microscopic Sao Paulo Potential (SPP). This bare interaction is supplemented with a Coulomb Dipole Polarization (CDP) potential, as well as a diffuse complex Woods-Saxon potential. Four-body Continuum-Discretized-Coupled-Channels (CDCC) calculations have been performed in order to support the optical model analysis. We have also studied the alpha channel, which is the dominant reaction process. In the analysis of this channel, we compare the angular and energy distributions of the alpha particles measured at 22 MeV, with Distorted Wave Born Approximation (DWBA) calculations.

  15. Breakup threshold anomaly for the 8B + 58Ni system at near-Coulomb barrier energies

    NASA Astrophysics Data System (ADS)

    Gómez Camacho, A.; Aguilera, E. F.; Gomes, P. R. S.; Lubian, J.

    2011-09-01

    By using recent fusion cross section measurements for the system 8B + 58Ni, a simultaneous analysis of elastic scattering, fusion, and total reaction cross sections is performed for the weakly bound system 8B + 58Ni at energies close to the Coulomb barrier. The analysis is carried out with an optical potential with fusion and direct reaction parts (i.e., the nuclear polarization potential U is split into a volume part UF, which accounts for fusion reactions and a surface part UDR, responsible for direct reactions). The parameters of the Woods-Saxon potentials are determined by a χ2 analysis of the data. The presence of the threshold anomaly is investigated from the energy dependence of both the fusion and direct reaction parts of the polarization potential.

  16. Shell effects in damped collisions of Sr88 with Yb176 at the Coulomb barrier energy

    NASA Astrophysics Data System (ADS)

    Kozulin, E. M.; Knyazheva, G. N.; Dmitriev, S. N.; Itkis, I. M.; Itkis, M. G.; Loktev, T. A.; Novikov, K. V.; Baranov, A. N.; Trzaska, W. H.; Vardaci, E.; Heinz, S.; Beliuskina, O.; Khlebnikov, S. V.

    2014-01-01

    This work is a study of the influence of shell effects on the formation of binary fragments in damped collision. We have investigated binary reaction channels of the composite system with Z =108 produced in the reaction Sr88+176Yb at an energy slightly above the Bass barrier (Ec.m./EBass=1.03). Reaction products were detected by using the two-arm time-of-flight spectrometer CORSET at the K130 cyclotron of the Department of Physics, University of Jyväskylä. The mass-energy distribution of primary binary fragments has been measured. For targetlike fragments heavier than 190 u, which correspond to a mass transfer as large as twenty nucleons or more, an enhancement of the yields is observed. This striking result can be ascribed to the proton shells at Z =28 and 82 and implies the persistence of the shell effects in the formation of reaction fragments even for large mass transfers.

  17. The 6He Optical Potential at energies around the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Fernández-García, J. P.; Rodríguez-Gallardo, M.; Alvarez, M. A. G.; Moro, A. M.

    2010-04-01

    We present an Optical Model (OM) study of 6He on 208Pb elastic scattering data, measured at laboratory energies around the Coulomb barrier (Elab = 14, 16, 18, 22, and 27 MeV) [1]. For the projectile-target bare interaction, we use the microscopic São Paulo Potential (SPP). This bare interaction is supplemented with a Coulomb Dipole Polarization (CDP) potential, as well as a diffuse complex Woods-Saxon potential. Four-body Continuum-Discretized-Coupled-Channels (CDCC) calculations have been performed in order to support the optical model analysis. We have also studied the α channel, which is the dominant reaction process. In the analysis of this channel, we compare the angular and energy distributions of the α particles measured at 22 MeV, with Distorted Wave Born Approximation (DWBA) calculations.

  18. Final report. Renewable energy and energy efficiency in Mexico: Barriers and opportunities

    SciTech Connect

    Ashford, Mike

    2000-09-28

    The report describes the prospects for energy efficiency and greenhouse gas emissions reductions in Mexico, along with renewable energy potential. A methodology for developing emissions baselines is shown, in order to prepare project emissions reductions calculations. An application to the USIJI program was also prepared through this project, for a portfolio of energy efficiency projects.

  19. Barrier-Independent, Fitness-Associated Differences in Sofosbuvir Efficacy against Hepatitis C Virus.

    PubMed

    Gallego, Isabel; Sheldon, Julie; Moreno, Elena; Gregori, Josep; Quer, Josep; Esteban, Juan Ignacio; Rice, Charles M; Domingo, Esteban; Perales, Celia

    2016-06-01

    Sofosbuvir displays a high phenotypic barrier to resistance, and it is a component of several combination therapies for hepatitis C virus (HCV) infections. HCV fitness can be a determinant of decreased sensitivity to direct-acting antiviral agents such as telaprevir or daclatasvir, but fitness-dependent decreased drug sensitivity has not been established for drugs with a high phenotypic barrier to resistance. Low- and high-fitness HCV populations and biological clones derived from them were used to infect Huh-7.5 hepatoma cells. Sofosbuvir efficacy was analyzed by measuring virus progeny production during several passages and by selection of possible sofosbuvir resistance mutations determined by sequencing the NS5B-coding region of the resulting populations. Sofosbuvir exhibited reduced efficacy against high-fitness HCV populations, without the acquisition of sofosbuvir-specific resistance mutations. A reduced sofosbuvir efficacy, similar to that observed with the parental populations, was seen for high-fitness individual biological clones. In independently derived high-fitness HCV populations or clones passaged in the presence of sofosbuvir, M289L was selected as the only substitution in the viral polymerase NS5B. In no case was the sofosbuvir-specific resistance substitution S282T observed. High HCV fitness can lead to decreased sensitivity to sofosbuvir, without the acquisition of specific sofosbuvir resistance mutations. Thus, fitness-dependent drug sensitivity can operate with HCV inhibitors that display a high barrier to resistance. This mechanism may underlie treatment failures not associated with selection of sofosbuvir-specific resistance mutations, linked to in vivo fitness of pretreatment viral populations. PMID:27067341

  20. Calculation of energy-barrier lowering by incoherent switching in spin-transfer torque magnetoresistive random-access memory

    SciTech Connect

    Munira, Kamaram; Visscher, P. B.

    2015-05-07

    To make a useful spin-transfer torque magnetoresistive random-access memory (STT-MRAM) device, it is necessary to be able to calculate switching rates, which determine the error rates of the device. In a single-macrospin model, one can use a Fokker-Planck equation to obtain a low-current thermally activated rate ∝exp(−E{sub eff}/k{sub B}T). Here, the effective energy barrier E{sub eff} scales with the single-macrospin energy barrier KV, where K is the effective anisotropy energy density and V the volume. A long-standing paradox in this field is that the actual energy barrier appears to be much smaller than this. It has been suggested that incoherent motions may lower the barrier, but this has proved difficult to quantify. In the present paper, we show that the coherent precession has a magnetostatic instability, which allows quantitative estimation of the energy barrier and may resolve the paradox.

  1. Case histories portraying different methods of installing liners for verticle barriers

    SciTech Connect

    Burke, G.K.; Crockford, R.M.; Achhorner, F.N.

    1997-12-31

    The installation of liners for vertical barriers is difficult and has been a learning experience for every contractor making the attempt. Soil stratigraphy and hydrogeologic conditions can vary over short distances, creating a variety of problems. This is particularly so when working near landfills and documentation of the as-built condition is poor. Successful installation requires detailed planning and knowledge of what to expect, as well as alternate plans for potential problems. Several successful methods of panel connection will be presented as well as a variety of installation techniques. Project case histories will be reviewed, highlighting the challenges associated with specific construction techniques.

  2. Study of surface dielectric barrier discharge generated using liquid electrodes in different gases

    NASA Astrophysics Data System (ADS)

    Galmiz, O.; Pavlinak, D.; Zemanek, M.; Brablec, A.; Cernak, M.

    2016-02-01

    Surface dielectric barrier discharges with conductive water-solution electrodes were generated at atmospheric pressure air, nitrogen, oxygen, and argon. The discharges were studied by conventional and high-speed camera photography. Plasma rotational and vibrational temperatures and the electron number density were estimated using optical emission spectroscopy. Surprisingly, especially for oxygen, the discharge was found to generate visually diffuse strongly non-isothermal plasma. This observation indicates the interesting application potential of the discharge for surface plasma treatments of, i.e. the inner and outer surfaces of hollow dielectric bodies.

  3. Breakup and Elastic Scattering in the {sup 9}Be + {sup 144}Sm system at near barrier energies

    SciTech Connect

    Paes, B.; Garcia, V. N.; Lubian, J.; Gomes, P. R. S.; Padron, I.

    2010-05-21

    Breakup and elastic scattering in the Be + {sup 144}Sm system, at near barrier energies, are investigated. We calculate theoretically the non-capture breakup cross section by performing coupled reaction channel calculations. The energy dependence of the optical potential does not show the usual threshold anomaly found in tightly bound systems.

  4. Depositional response to seagrass mortality along a low-energy, barrier-island coast: west-central Florida

    SciTech Connect

    Evans, M.W.; Hine, A.C.; David, R.A.; Belknap, D.F.

    1985-01-01

    Analysis of aerial photographs and surficial sediment samples from the northern islands of the west-central barrier system of Florida indicates that: (1) seagrass beds in the nearshore zone have controlled onshore/longshore sand transport, and (2) resulting sedimentary accumulations within nearshore seagrass beds make differentiation of nearshore and backbarrier facies difficult. Between 1957 and 1973, an extensive seagrass community occupying the nearshore zone off Anclote Key disappeared, thus allowing the sudden and rapid onshore and longshore transport of sand. The 1000 year old barrier island lengthened 30% by recurved spit growth in this very short period of time. Although there are not direct observations, four possible causes of seagrass mortality have been postulated, and of these overgrazing as a result of the accelerated population growth of sea urchins (Lytechinus variegatus) seems to be the most likely cause. Because of the ability of seagrasses to trap fine-grained sediments, contribute organic matter, and provide for low-energy, sheltered, molluscan biocoenosis, there is little depositional difference between these nearshore and backbarrier/lagoonal facies. This work indicates that the development and destruction of benthic floral communities should be considered as a process that generates or accentuates episodicity/cyclicity in the sedimentary record. Additionally, such changes in these communities should be expected to present a blurred distinction between certain types of coastal sedimentary facies.

  5. A Review of Barriers to and Opportunities for the Integration of Renewable Energy in the Southeast

    SciTech Connect

    McConnell, Ben W; Hadley, Stanton W; Xu, Yan

    2011-08-01

    The objectives of this study were to prepare a summary report that examines the opportunities for and obstacles to the integration of renewable energy resources in the Southeast between now and the year 2030. The report, which is based on a review of existing literature regarding renewable resources in the Southeast, includes the following renewable energy resources: wind, solar, hydro, geothermal, biomass, and tidal. The evaluation was conducted by the Oak Ridge National Laboratory for the Energy Foundation and is a subjective review with limited detailed analysis. However, the report offers a best estimate of the magnitude, time frame, and cost of deployment of renewable resources in the Southeast based upon the literature reviewed and reasonable engineering and economic estimates. For the purposes of this report, the Southeast is defined as the states of Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia. In addition, some aspects of the report (wind and geothermal) also consider the extended Southeast, which includes Maryland, Missouri, Oklahoma, and Texas. A description of the existing base of renewable electricity installations in the region is given for each technology considered. Where available, the possible barriers and other considerations regarding renewable energy resources are listed in terms of availability, investment and maintenance costs, reliability, installation requirements, policies, and energy market. As stated above, the report is a comprehensive review of renewable energy resources in the southeastern region of United States based on a literature study that included information obtained from the Southern Bio-Power wiki, sources from the Energy Foundation, sources available to ORNL, and sources found during the review. The report consists of an executive summary, this introductory chapter describing report objectives, a chapter on analysis methods and

  6. Wave energies and wave-induced longshore currents in an unstructured-grid model - circulation in front of barrier islands

    NASA Astrophysics Data System (ADS)

    Jörg-Olaf Wolff, , Prof. _., Dr.; Grashorn, Sebastian, , Dr.; Lettmann, Karsten A., , Dr.; Badewien, Thomas H., , Dr.; Stanev, Emil V., Prof. _., Dr.

    2015-04-01

    An unstructured-grid model (FVCOM) coupled to a wave model (FVCOM-SWAVE) is used to investigate the hydrodynamic and wave energy conditions during a moderate and a storm situation in the southern North Sea. Two different setups are presented. One setup covers the whole North Sea with moderately increased grid resolution at the coast, whereas the other comprises a very high resolution East Frisian Wadden Sea setup, one-way coupled to the coarser North Sea model. The results of both model setups are validated, compared to each other and analysed with a focus on longshore currents and wave energy. The results show that during storm conditions strong wave-induced longshore currents occur in front of the barrier islands of the East Frisian Wadden Sea, resulting in total current speeds up to 2 m/s. This effect is especially pronounced in the high-resolution setup. The wave-current interaction also influences the sea surface elevation by raising the water level in the tidal basins. Calculated wave energies show large differences between moderate wind and storm conditions with time-averaged values up to 200 kW/m. The numerical results indicate that wave-current coupling, albeit numerically expensive, cannot be ignored because it plays an important role in almost all near coastal transport phenomena (sediments, contaminants, bacteria, etc.).

  7. Gas chromatographic determination of the interconversion energy barrier for dialkyl 2,3-pentadienedioate enantiomers.

    PubMed

    Mydlová, J; Krupcík, J; Májek, P; Skacáni, I; Jakubík, T; Sandra, P; Armstrong, D W

    2007-05-25

    The enantiomers of dialkyl 2,3-pentadienedioate undergo interconversion during gas chromatographic separation on chiral stationary phases. In this paper the on-column apparent interconversion kinetic and thermodynamic activation data were determined for dimethyl, diethyl, propylbutyl and dibutyl 2,3-pentadienedioate enantiomers by gas chromatographic separation of the racemic mixtures on a capillary column containing a polydimethylsiloxane stationary phase coupled to 2,3-di-O-methyl-6-O-tertbutyldimethylsilyl-beta-cyclodextrin. A deconvolution method was used to determine the individual enantiomer peak areas and retention times that are needed to calculate the interconversion rate constants and the energy barriers. The apparent rate constants and interconversion energy barriers decrease slightly with an increase in the alkyl chain length of the dialkyl 2,3-pentadienedioate esters. The optimum conformation of the dialkyl 2,3-pentadienedioate molecules, their separation selectivity factors and apparent interconversion enthalpy and entropy data changes with the alkyl chain length. The dependence of the apparent interconversion energy barrier (deltaG(app)(a-->b), deltaG(app)(b-->a)) on temperature was used to determine the apparent activation enthalpy (deltaH(app)(a-->b), deltaH(app)(b-->a)) and apparent entropy (deltaS(app)(a-->b), deltaS(app)(a-->b)) (where a denotes the first and b second eluted enantiomer). The comparison of the activation enthalpy and entropy (deltaS(app)(a-->b), deltaS(app)(a-->b)) indicated that the interconversion of dialkyl 2,3-pentadienedioate enantiomers on the HP-5+Chiraldex B-DM column series is an entropy driven process at 160 degrees C. Data obtained for dimethyl 2,3-pentadienedioate enantiomers on the HP-5+Chiraldex B-DM column series at 120 degrees C (deltaG(app)(a-->b) = 123.3 and deltaG(app)(b-->a) = 124.4 kJ mol(-1)) corresponds (at the 95% confidence interval) with the value of deltaG(#) = 128+/-1 kJ mol(-1) found at this

  8. The Ligand Shell as an Energy Barrier in Surface Reactions on Transition Metal Nanoparticles.

    PubMed

    Smith, Jeremy G; Jain, Prashant K

    2016-06-01

    Transition metal nanoparticles, including those employed in catalytic, electrocatalytic, and photocatalytic conversions, have surfaces that are typically coated with a layer of short or long-chain ligands. There is little systematic understanding of how much this ligand layer affects the reactivity of the underlying surface. We show for Ag nanoparticles that a surface-adsorbed thiol layer greatly impedes the kinetics of an ionic chemical reaction taking place on the Ag surface. The model reaction studied is the galvanic exchange of Ag with Au(3+) ions, the kinetics of which is measured on individual thiol-coated nanoparticles using in situ optical scattering spectroscopy. We observe a systematic lowering of the reactivity of the nanoparticle as the chain length of the thiol is increased, from which we deduce that the ligand layer serves as an energy barrier to the transport of incoming/outgoing reactive ions. This barrier effect can be decreased by light irradiation, resulting from weakened binding of the thiol layer to the metal surface. We find that the influence of the surface ligand layer on reactivity is much stronger than factors such as nanoparticle size, shape, or crystallinity. These findings provide improved understanding of the role of ligand or adsorbates in colloidal catalysis and photocatalysis and have important implications for the transport of reactants and ions to surfaces and for engineering the reactivity of nanoparticles using surface passivation. PMID:27152595

  9. Single-Chain Magnets Based on Octacyanotungstate with the Highest Energy Barriers for Cyanide Compounds

    NASA Astrophysics Data System (ADS)

    Wei, Rong-Min; Cao, Fan; Li, Jing; Yang, Li; Han, Yuan; Zhang, Xiu-Ling; Zhang, Zaichao; Wang, Xin-Yi; Song, You

    2016-04-01

    By introducing large counter cations as the spacer, two isolated 3, 3-ladder compounds, (Ph4P)[CoII(3-Mepy)2.7(H2O)0.3WV(CN)8]·0.6H2O (1) and (Ph4As)[CoII(3-Mepy)3WV(CN)8] (2, 3-Mepy = 3-methylpyridine), were synthesized and characterized. Static and dynamic magnetic characterizations reveal that compounds 1 and 2 both behave as the single-chain magnets (SCMs) with very high energy barriers: 252(9) K for 1 and 224(7) K for 2, respectively. These two compounds display the highest relaxation barriers for cyano-bridged SCMs and are preceded only by two cobalt(II)-radical compounds among all SCMs. Meanwhile, a large coercive field of 26.2 kOe (1) and 22.6 kOe (2) were observed at 1.8 K.

  10. Single-Chain Magnets Based on Octacyanotungstate with the Highest Energy Barriers for Cyanide Compounds

    PubMed Central

    Wei, Rong-Min; Cao, Fan; Li, Jing; Yang, Li; Han, Yuan; Zhang, Xiu-Ling; Zhang, Zaichao; Wang, Xin-Yi; Song, You

    2016-01-01

    By introducing large counter cations as the spacer, two isolated 3, 3-ladder compounds, (Ph4P)[CoII(3-Mepy)2.7(H2O)0.3WV(CN)8]·0.6H2O (1) and (Ph4As)[CoII(3-Mepy)3WV(CN)8] (2, 3-Mepy = 3-methylpyridine), were synthesized and characterized. Static and dynamic magnetic characterizations reveal that compounds 1 and 2 both behave as the single-chain magnets (SCMs) with very high energy barriers: 252(9) K for 1 and 224(7) K for 2, respectively. These two compounds display the highest relaxation barriers for cyano-bridged SCMs and are preceded only by two cobalt(II)-radical compounds among all SCMs. Meanwhile, a large coercive field of 26.2 kOe (1) and 22.6 kOe (2) were observed at 1.8 K. PMID:27071451

  11. Mechanisms and systematics of breakup in reactions of {sup 9}Be at near-barrier energies

    SciTech Connect

    Rafiei, R.; Rietz, R. du; Luong, D. H.; Hinde, D. J.; Dasgupta, M.; Evers, M.; Diaz-Torres, A.

    2010-02-15

    Below-barrier no-capture breakup measurements of the weakly bound {sup 9}Be nucleus, incident on targets ranging in atomic number from 62 to 83, have been carried out using a large-area high-resolution back-angle detector array. It is shown that the three-body reconstructed reaction Q-value and relative energy of the breakup fragments together reveal the full dynamics of the breakup mechanism, identifying all physical processes that lead to the breakup of the projectile-like nucleus. Contrasting with the simple expectation of direct breakup into the most energetically favored clusters, the data show that breakup following n-transfer dominates the total breakup yield. Breakup from long-lived states in the projectile-like nucleus, which on the reaction time scale may be considered stable, has been isolated from the prompt breakup yield. It has been shown that the prompt breakup probability essentially depends on the surface separation of the interacting nuclei. The measured prompt breakup probability functions for each target have been used together with a classical trajectory model to predict the above-barrier suppression of complete fusion. The suppression factor, expressed as the fraction of incomplete fusion, is nearly independent of target charge.

  12. Single-Chain Magnets Based on Octacyanotungstate with the Highest Energy Barriers for Cyanide Compounds.

    PubMed

    Wei, Rong-Min; Cao, Fan; Li, Jing; Yang, Li; Han, Yuan; Zhang, Xiu-Ling; Zhang, Zaichao; Wang, Xin-Yi; Song, You

    2016-01-01

    By introducing large counter cations as the spacer, two isolated 3, 3-ladder compounds, (Ph4P)[Co(II)(3-Mepy)2.7(H2O)0.3W(V)(CN)8]·0.6H2O (1) and (Ph4As)[Co(II)(3-Mepy)3W(V)(CN)8] (2, 3-Mepy = 3-methylpyridine), were synthesized and characterized. Static and dynamic magnetic characterizations reveal that compounds 1 and 2 both behave as the single-chain magnets (SCMs) with very high energy barriers: 252(9) K for 1 and 224(7) K for 2, respectively. These two compounds display the highest relaxation barriers for cyano-bridged SCMs and are preceded only by two cobalt(II)-radical compounds among all SCMs. Meanwhile, a large coercive field of 26.2 kOe (1) and 22.6 kOe (2) were observed at 1.8 K. PMID:27071451

  13. Assembly of single molecular magnets from dinuclear to 2D Dy-compounds with significant change of relaxation energy barriers.

    PubMed

    Chen, Zhi; Fang, Ming; Kang, Xiao-Min; Hou, Yin-Ling; Zhao, Bin

    2016-01-01

    A dinuclear Dy(III) compound (1) was structurally and magnetically characterized, displaying a single-molecule magnet (SMM) behavior with a relaxation energy barrier of 21(1) K. Interestingly, by only adding a suitable substituent on the ligand in , as an SMM building unit, can be further assembled into a two-dimensional (2D) framework (2), which possesses a typical SMM behavior and a high relaxation energy barrier of 68(2) K. The result implied that the assembly of an SMM can effectively tune the energy barrier. To our knowledge, a cluster-based SMM assembled into a new 2D framework with SMM behavior is seldom reported. PMID:26634233

  14. One-neutron stripping processes to excited states of the 6Li+96Zr reaction at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Hu, S. P.; Zhang, G. L.; Yang, J. C.; Zhang, H. Q.; Gomes, P. R. S.; Lubian, J.; Ferreira, J. L.; Wu, X. G.; Zhong, J.; He, C. Y.; Zheng, Y.; Li, C. B.; Li, G. S.; Qu, W. W.; Wang, F.; Zheng, L.; Yu, L.; Chen, Q. M.; Luo, P. W.; Li, H. W.; Wu, Y. H.; Zhou, W. K.; Zhu, B. J.; Sun, H. B.

    2016-01-01

    We report the measurement of one-neutron stripping to excited-state cross sections from the weakly bound projectile 6Li to the 96Zr target at near-barrier energies by the online γ -ray spectroscopy method. Transitions of the 97Zr nucleus were clearly identified by γ -γ coincidences. This cross section was found to be much smaller than the previously reported complete-fusion cross section for this system at energies above the barrier, whereas it becomes of the same magnitude around the Coulomb-barrier energy. No evidence of two-neutron transfer was found. We also performed coupled reaction channel calculations for the one-neutron stripping process. The calculation results are discussed.

  15. Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles.

    PubMed

    Pérez, N; Guardia, P; Roca, A G; Morales, M P; Serna, C J; Iglesias, O; Bartolomé, F; García, L M; Batlle, X; Labarta, A

    2008-11-26

    The effect of surface anisotropy on the distribution of energy barriers in magnetic fine particles of nanometer size is discussed within the framework of the Tln(t/τ(0)) scaling approach. The comparison between the distributions of the anisotropy energy of the particle cores, calculated by multiplying the volume distribution by the core anisotropy, and of the total anisotropy energy, deduced by deriving the master curve of the magnetic relaxation with respect to the scaling variable Tln(t/τ(0)), enables the determination of the surface anisotropy as a function of the particle size. We show that the contribution of the particle surface to the total anisotropy energy can be well described by a size-independent value of the surface energy per unit area which permits the superimposition of the distributions corresponding to the particle core and effective anisotropy energies. The method is applied to a ferrofluid composed of non-interacting Fe(3-x)O(4) particles of 4.9 nm average size and x about 0.07. Even though the size distribution is quite narrow in this system, a relatively small value of the effective surface anisotropy constant K(s) = 2.9 × 10(-2) erg cm(-2) gives rise to a dramatic broadening of the total energy distribution. The reliability of the average value of the effective anisotropy constant, deduced from magnetic relaxation data, is verified by comparing it to that obtained from the analysis of the shift of the ac susceptibility peaks as a function of the frequency. PMID:21836285

  16. Barriers to Point-of-Care Testing in India: Results from Qualitative Research across Different Settings, Users and Major Diseases

    PubMed Central

    Engel, Nora; Ganesh, Gayatri; Patil, Mamata; Yellappa, Vijayashree; Pant Pai, Nitika; Vadnais, Caroline; Pai, Madhukar

    2015-01-01

    Background Successful point-of-care testing, namely ensuring the completion of the test and treat cycle in the same encounter, has immense potential to reduce diagnostic and treatment delays, and impact patient outcomes. However, having rapid tests is not enough, as many barriers may prevent their successful implementation in point-of-care testing programs. Qualitative research on diagnostic practices may help identify such barriers across different points of care in health systems. Methods In this exploratory qualitative study, we conducted 78 semi-structured interviews and 13 focus group discussions in an urban and rural area of Karnataka, India, with healthcare providers (doctors, nurses, specialists, traditional healers, and informal providers), patients, community health workers, test manufacturers, laboratory technicians, program managers and policy-makers. Participants were purposively sampled to represent settings of hospitals, peripheral labs, clinics, communities and homes, in both the public and private sectors. Results In the Indian context, the onus is on the patient to ensure successful point-of-care testing across homes, clinics, labs and hospitals, amidst uncoordinated providers with divergent and often competing practices, in settings lacking material, money and human resources. We identified three overarching themes affecting point-of-care testing: the main theme is ‘relationships’ among providers and between providers and patients, influenced by the cross-cutting theme of ‘infrastructure’. Challenges with both result in ‘modified practices’ often favouring empirical (symptomatic) treatment over treatment guided by testing. Conclusions Even if tests can be conducted on the spot and infrastructure challenges have been resolved, relationships among providers and between patients and providers are crucial for successful point-of-care testing. Furthermore, these barriers do not act in isolation, but are interlinked and need to be examined

  17. Why Density-Gradient Corrections Improve Atomization Energies and Barrier Heights

    NASA Astrophysics Data System (ADS)

    Perdew, John P.; Ernzerhof, Matthias; Zupan, Ales; Burke, Kieron

    While the Hartree-Fock (HF) approximation typically underestimates the strength of the chemical bond, the local spin density (LSD) approximation overestimates it. Thus LSD overbinds atoms in molecules, and underestimates the heights of energy barriers when the transition state is more highly bonded than the initial state. Generalized gradient approximations (GGA's), which incorporate density-gradient corrections to LSD, improve the agreement between calculated and measured energetics. This has been previously understood as a consequence of the fact that gradient corrections favor density inhomogeneity, which increases when a bond is stretched or broken. We show that gradient corrections also favor high density, which increases when a bond is compressed or formed, but that the inhomogeneity effect usually prevails. To quantify the discussion, we present a thermodynamic-like inequality which is satisfied when gradient corrections favor a process.

  18. Spectral and energy parameters of multiband barrier-discharge KrBr excilamps

    SciTech Connect

    Avdeev, S M; Erofeev, M V; Skakun, V S; Sosnin, E A; Suslov, A I; Tarasenko, V F; Schitz, D V

    2008-07-31

    The spectral and energy characteristics of multiband barrier-discharge coaxial KrBr excilamps are studied experimentally at pressures from a few tens of Torr to 0.4 atm. It is shown that an increase in the Br{sub 2} concentration reduces the emission intensity of KrBr* molecules with respect to the emission intensity of Br{sub 2}* molecules and reduces the total emission power of the excilamp. This can be explained by the nonradiative decay of exciplex KrBr* molecules caused by their quenching by molecular bromine. The emission power and efficiency in the Kr:Br{sub 2} = 400:1 mixture at a pressure of {approx}230 Torr and a discharge gap of 8.5 mm were 4.8 W and 2.4%, respectively. (laser applications and other topics in quantum electronics)

  19. Cross sections and barriers for nuclear fission induced by high-energy nucleons

    SciTech Connect

    Grudzevich, O. T.; Yavshits, S. G.

    2013-03-15

    The cross sections for the fission of {sup 232}Th, {sup 235,238}U, {sup 237}Np, and {sup 239}Pu target nuclei that was induced by 20- to 1000-MeV neutrons and protons were calculated. The respective calculations were based on the multiconfiguration-fission (MCFx) model, which was used to describe three basic stages of the interaction of high-energy nucleons with nuclei: direct processes (intranuclear cascade), equilibration of the emerging compound system, and the decay of the compound nucleus (statistical model). Fission barriers were calculated within the microscopic approach for isotopic chains formed by 15 to 20 nuclei of the required elements. The calculated fission cross sections were compared with available experimental data. It was shown that the input data set and the theoretical model used made it possible to predict satisfactorily cross section for nuclear fission induced by 20- to 1000-MeV nucleons.

  20. The free-energy barrier to hydride transfer across a dipalladium complex.

    PubMed

    Vanston, C R; Kearley, G J; Edwards, A J; Darwish, T A; de Souza, N R; Ramirez-Cuesta, A J; Gardiner, M G

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique. PMID:25652724

  1. Threshold anomaly for the 7Be +58Ni system at near-Coulomb-barrier energies

    NASA Astrophysics Data System (ADS)

    Gómez Camacho, A.; Aguilera, E. F.

    2014-12-01

    By using recent fusion cross section measurements for the weakly bound system 7Be+58Ni around the Coulomb barrier, a simultaneous χ2 analysis of elastic scattering and fusion cross section data is performed. The analysis is carried out with optical polarization potentials for the fusion and direct reaction processes. That is, the nuclear polarization potential UN is split into a volume part UF which accounts for fusion reactions and a surface part UD R that is responsible for direct reactions. The parameters of fusion and direct reaction Woods-Saxon polarization potentials are determined by the analysis of the data. The presence of the threshold anomaly is investigated from the energy dependence of these polarization potentials. It is found that, contrary to other weakly bound systems, the 7Be+58Ni reaction presents the usual threshold anomaly.

  2. Fusion cross sections for the {sup 9}Be+{sup 124}Sn reaction at energies near the Coulomb barrier

    SciTech Connect

    Parkar, V. V.; Palit, R.; Sharma, Sushil K.; Naidu, B. S.; Santra, S.; Mahata, K.; Ramachandran, K.; Joshi, P. K.; Rath, P. K.; Trivedi, T.; Raghav, A.

    2010-11-15

    The complete and incomplete fusion cross sections for {sup 9}Be+{sup 124}Sn reaction have been deduced using the online {gamma}-ray measurement technique. Complete fusion at energies above the Coulomb barrier was found to be suppressed by {approx}28% compared to the coupled-channels calculations and is in agreement with the systematics of L. R. Gasques et al. [Phys. Rev. C 79, 034605 (2009)]. Study of the projectile dependence for fusion on a {sup 124}Sn target shows that, for {sup 9}Be nuclei, the enhancement at below-barrier energies is substantial compared to that of tightly bound nuclei.

  3. Elastic scattering of 17O+208Pb at energies near the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Torresi, D.; Strano, E.; Mazzocco, M.; Boiano, A.; Boiano, C.; Di Meo, P.; La Commara, M.; Manea, C.; Nicoletto, M.; Grebosz, J.; Guglielmetti, A.; Molini, P.; Parascandolo, C.; Pierroutsakou, D.; Signorini, C.; Soramel, F.; Toniolo, N.; Filipescu, D.; Gheorghe, A.; Glodariu, T.; Jeong, S.; Kim, Y. H.; Lay, J. A.; Miyatake, H.; Pakou, A.; Sgouros, O.; Soukeras, V.; Stroe, L.; Vitturi, A.; Watanabe, Y.; Zerva, K.

    2016-05-01

    Within the frame of the commissioning of a new experimental apparatus EXPADES we undertook the measurement of the elastic scattering angular distribution for the system 17O+208Pb at energy around the Coulomb barrier. The reaction dynamics induced by loosely bound Radioactive Ion Beams is currently being extensively studied [4]. In particular the study of the elastic scattering process allows to obtain direct information on the total reaction cross section of the exotic nuclei. In order to understand the effect of the low binding energy on the reaction mechanism it is important to compare radioactive weakly bound nuclei with stable strongly-bound nuclei. In this framework the study of the 17O+208Pb elastic scattering can be considered to be complementary to a previous measurement of the total reaction cross section for the system 17F+208Pb at energies of 86, 90.4 MeV [5, 6]. The data will be compared with those obtained for the neighboring systems 16,18O+208Pb and others available in literature.

  4. Effect of different chemical treatments of surface on the height of Al-p-SiGe and Au-n-SiGe barriers

    SciTech Connect

    Atabaev, I. G. Matchanov, N. A.; Hajiev, M. U. Pak, V.; Saliev, T. M.

    2010-05-15

    The effect of different chemical treatments on the properties of Au-n-SiGe and Al-p-SiGe Schottky barriers has been investigated. Etching under different conditions was used to prepare surfaces with different densities of surface states (D{sub ss}). It is shown that the barrier height in the structures under study correlates with the D{sub ss} value and germanium content in the Si{sub 1-x}Ge{sub x} alloy.

  5. Making AlN(x) Tunnel Barriers Using a Low-Energy Nitrogen-Ion Beam

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama; Kleinsasser, Alan; Bumble, Bruce; LeDuc, Henry; Lee, Karen

    2005-01-01

    A technique based on accelerating positive nitrogen ions onto an aluminum layer has been demonstrated to be effective in forming thin (<2 nm thick) layers of aluminum nitride (AlN(x)) for use as tunnel barriers in Nb/Al-AlN(x)/Nb superconductor/insulator/ superconductor (SIS) Josephson junctions. AlN(x) is the present material of choice for tunnel barriers because, to a degree greater than that of any other suitable material, it offers the required combination of low leakage current at high current density and greater thermal stability. While ultra-thin AlN films with good thickness and stoichiometry control are easily formed using techniques such as reactive molecular beam epitaxy and chemical vapor deposition, growth temperatures of 900 C are necessary for the dissociative adsorption of nitrogen from either nitrogen (N2) or ammonia (NH3). These growth temperatures are prohibitively high for the formation of tunnel barriers on Nb films because interfacial reactions at temperatures as low as 200 to 300 C degrade device properties. Heretofore, deposition by reactive sputtering and nitridation of thin Al layers with DC and RF nitrogen plasmas have been successfully used to form AlN barriers in SIS junctions. However, precise control over critical current density Jc has proven to be a challenge, as is attaining adequate process reproducibility from system to system. The present ion-beam technique is an alternative to the plasma or reactive sputtering techniques as it provides a highly controlled arrival of reactive species, independent of the electrical conditions of the substrate or vacuum chamber. Independent and accurate control of parameters such as ion energy, flux, species, and direction promises more precise control of film characteristics such as stoichiometry and thickness than is the case with typical plasma processes. In particular, the background pressure during ion-beam nitride growth is 2 or 3 orders of magnitude lower, minimizing the formation of

  6. Hyperosmolar opening of the blood-brain barrier in the energy-depleted rat brain. Part 1. Permeability studies

    SciTech Connect

    Greenwood, J.; Luthert, P.J.; Pratt, O.E.; Lantos, P.L.

    1988-02-01

    A simple saline perfusion system was used to investigate the effects of hyperosmolar solutions of arabinose and mannitol upon the permeability of the blood-brain barrier. The small, polar molecule (/sup 14/C)mannitol and the larger, visual marker Evans blue were used as indicators of barrier integrity in the perfused energy-depleted brain. One-minute perfusion of hyperosmolar solutions consistently opened the barrier suggesting that the mechanism of osmotic barrier opening is independent of energy-producing metabolism. The accumulation of radiolabel in the brain was expressed as the ratio of tissue to perfusate radioactivity (Rt/Rp) and, for cerebrum, this increased from a control value of 0.0022 +/- 0.0007 (mean +/- SEM; n = 4) to a value of 0.0124 +/- 0.0008 (n = 4) following 0.9 M arabinose and to 0.0495 +/- 0.0072 (n = 4) following 1.8 M arabinose. There was a significant reduction of water content of hyperosmolar perfused brains. These findings support the hypothesis that osmotic barrier opening is the result of the passive shrinkage of endothelial cells and the surrounding tissue.

  7. Imaging the radical channel in acetaldehyde photodissociation: Competing mechanisms at energies close to the triplet exit barrier

    SciTech Connect

    Amaral, G. A.; Arregui, A.; Rodriguez, J. D.; Banares, L.; Rubio-Lago, L.

    2010-08-14

    The photodissociation of acetaldehyde in the radical channel has been studied at wavelengths between 315 and 325 nm using the velocity-map imaging technique. Upon one-photon absorption at 315 nm, the molecule is excited to the first singlet excited state S{sub 1}, which, in turn, undergoes intersystem crossing to the first excited triplet state T{sub 1}. On the triplet surface, the molecule dissociates into CH{sub 3} and HCO radicals with large kinetic energy release (KER), in accordance with the well characterized exit barrier on T{sub 1}. However, at longer wavelengths (>320 nm), which correspond to excitation energies just below the triplet barrier, a sudden change in KER is observed. At these photolysis wavelengths, there is not enough energy to surpass the exit barrier on the triplet state, which leaves the possibility of unimolecular dissociation on S{sub 0} after internal conversion from S{sub 1}. We have characterized the fragments' KER at these wavelengths, as well as determined the energy partitioning for the radical fragments. A new accurate estimate of the barrier height on T{sub 1} is presented.

  8. Influence of hydrodynamic energy on Holocene reef flat accretion, Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Dechnik, Belinda; Webster, Jody M.; Nothdurft, Luke; Webb, Gregory E.; Zhao, Jian-xin; Duce, Stephanie; Braga, Juan C.; Harris, Daniel L.; Vila-Concejo, Ana; Puotinen, Marji

    2016-01-01

    The response of platform reefs to sea-level stabilization over the past 6 ka is well established for the Great Barrier Reef (GBR), with reefs typically accreting laterally from windward to leeward. However, these observations are based on few cores spread across reef zones and may not accurately reflect a reef's true accretional response to the Holocene stillstand. We present a new record of reef accretion based on 49 U/Th ages from Heron and One Tree reefs in conjunction with re-analyzed data from 14 reefs across the GBR. We demonstrate that hydrodynamic energy is the main driver of accretional direction; exposed reefs accreted primarily lagoon-ward while protected reefs accreted seawards, contrary to the traditional growth model in the GBR. Lateral accretion rates varied from 86.3 m/ka-42.4 m/ka on the exposed One Tree windward reef and 68.35 m/ka-15.7 m/ka on the protected leeward Heron reef, suggesting that wind/wave energy is not a dominant control on lateral accretion rates. This represents the most comprehensive statement of lateral accretion direction and rates from the mid-outer platform reefs of the GBR, confirming great variability in reef flat growth both within and between reef margins over the last 6 ka, and highlighting the need for closely-spaced transects.

  9. One-neutron stripping from 9Be to 181Ta, 169Tm, 187Re and at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Fang, Y. D.; Gomes, P. R. S.; Lubian, J.; Ferreira, J. L.; Mendes Junior, D. R.; Zhou, X. H.; Liu, M. L.; Zhang, N. T.; Zhang, Y. H.; Li, G. S.; Wang, J. G.; Guo, S.; Qiang, Y. H.; Gao, B. S.; Zheng, Y.; Lei, X. G.; Wang, Z. G.

    2016-03-01

    We report the measurement of one-neutron stripping of 9Be to the 181Ta, 187Re and nuclei, in the range from subbarrier to above-barrier energies. The activation technique was used, with the detection of off-line γ rays. The results show that the transfer cross sections for the three systems investigated are very similar and are much larger than the corresponding fusion cross sections at subbarrier energies, whereas fusion predominates at energies above the barrier. Data are in good agreement with our coupled reaction channel calculations. We also investigate the ratio, as a function of energy, between experimental transfer and fusion cross sections. The role of transfer couplings on the fusion excitation functions is also discussed.

  10. The Barriers Encountered by Teachers Implementing Education for Sustainable Development: Discipline Bound Differences and Teaching Traditions

    ERIC Educational Resources Information Center

    Borg, Carola; Gericke, Niklas; Hoglund, Hans-Olof; Bergman, Eva

    2012-01-01

    Background: According to the Swedish curriculum teachers in all subjects have a responsibility to integrate a holistic perspective of sustainable development (SD) and teach according to an education for sustainable development (ESD) approach. However previous research has shown that teachers from different subjects perceive SD differently.…

  11. Potential Energy Surfaces of Oxygen Vacancies in Rutile TiO2: Configuration Coordinate and Migration Barrier Schemes

    NASA Astrophysics Data System (ADS)

    Kazempour, Ali

    2013-09-01

    Applying the screened hybrid functional Heyd-Scuseria-Ernzerhof (HSE) method, we studied the polaronic degree of freedom of different charged oxygen vacancies Vo in rutile TiO2. The HSE method not only corrects the band gap, but also allows for correct polaron localization. Due to the important role of phonon in oxygen vacancy associated levels in the gap, we calculated configuration coordinate (CC) potential energy surfaces for all charged Vo's. Our calculated CC diagrams with effective impression on host states, show significant improvement of electron-lattice interaction compared to semi(local) DFT methods. The obtained values of stokes shifts for sequential transitions of charged vacancies agree well with experimental evidences which confirm Ti3+ centers are responsible for photoluminescence. In addition, we explored the effect of polaron localization on diffusive mechanism of Vo along most open [001] direction. Calculated values of migration barriers for V o2+ are found to be in quantitative agreement with experimental migration energy [E. Iguchi and K. Yajima, J. Phys. Soc. Jpn.32 (1971) 1415] of 2.4 eV. These results highlight the small polaronic behavior of Vo's and is consistent with studies suggest the polaronic hopping model for electron transport of n-type conductivity in reduced TiO2 [J.-F. Baumard and F. Gervais, Phys. Rev. B15 (1977) 2316-2323].

  12. Transportation Energy Futures Series. Non-Cost Barriers to Consumer Adoption of New Light-Duty Vehicle Technologies

    SciTech Connect

    Stephens, Thomas

    2013-03-01

    Consumer preferences are key to the adoption of new vehicle technologies. Barriers to consumer adoption include price and other obstacles, such as limited driving range and charging infrastructure; unfamiliarity with the technology and uncertainty about direct benefits; limited makes and models with the technology; reputation or perception of the technology; standardization issues; and regulations. For each of these non-cost barriers, this report estimates an effective cost and summarizes underlying influences on consumer preferences, approximate magnitude and relative severity, and assesses potential actions, based on a comprehensive literature review. While the report concludes that non-cost barriers are significant, effective cost and potential market share are very uncertain. Policies and programs including opportunities for drivers to test drive advanced vehicles, general public outreach and information programs, incentives for providing charging and fueling infrastructure, and development of technology standards were examined for their ability to address barriers, but little quantitative data exists on the effectiveness of these measures. This is one in a series of reports produced as a result of the Transportation Energy Futures project, a Department of Energy-sponsored multi-agency effort to pinpoint underexplored strategies for reducing GHGs and petroleum dependence related to transportation. View all reports on the TEF Web page, http://www.eere.energy.gov/analysis/transportationenergyfutures/index.html.

  13. Molecular origin of high free energy barriers for alkali metal ion transfer through ionic liquid-graphene electrode interfaces.

    PubMed

    Ivaništšev, Vladislav; Méndez-Morales, Trinidad; Lynden-Bell, Ruth M; Cabeza, Oscar; Gallego, Luis J; Varela, Luis M; Fedorov, Maxim V

    2016-01-14

    In this work we study mechanisms of solvent-mediated ion interactions with charged surfaces in ionic liquids by molecular dynamics simulations, in an attempt to reveal the main trends that determine ion-electrode interactions in ionic liquids. We compare the interfacial behaviour of Li(+) and K(+) at a charged graphene sheet in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, and its mixtures with lithium and potassium tetrafluoroborate salts. Our results show that there are dense interfacial solvation structures in these electrolytes that lead to the formation of high free energy barriers for these alkali metal cations between the bulk and direct contact with the negatively charged surface. We show that the stronger solvation of Li(+) in the ionic liquid leads to the formation of significantly higher interfacial free energy barriers for Li(+) than for K(+). The high free energy barriers observed in our simulations can explain the generally high interfacial resistance in electrochemical storage devices that use ionic liquid-based electrolytes. Overcoming these barriers is the rate-limiting step in the interfacial transport of alkali metal ions and, hence, appears to be a major drawback for a generalised application of ionic liquids in electrochemistry. Some plausible strategies for future theoretical and experimental work for tuning them are suggested. PMID:26661060

  14. Protein misfolding occurs by slow diffusion across multiple barriers in a rough energy landscape

    PubMed Central

    Yu, Hao; Dee, Derek R.; Liu, Xia; Brigley, Angela M.; Sosova, Iveta; Woodside, Michael T.

    2015-01-01

    The timescale for the microscopic dynamics of proteins during conformational transitions is set by the intrachain diffusion coefficient, D. Despite the central role of protein misfolding and aggregation in many diseases, it has proven challenging to measure D for these processes because of their heterogeneity. We used single-molecule force spectroscopy to overcome these challenges and determine D for misfolding of the prion protein PrP. Observing directly the misfolding of individual dimers into minimal aggregates, we reconstructed the energy landscape governing nonnative structure formation. Remarkably, rather than displaying multiple pathways, as typically expected for aggregation, PrP dimers were funneled into a thermodynamically stable misfolded state along a single pathway containing several intermediates, one of which blocked native folding. Using Kramers’ rate theory, D was found to be 1,000-fold slower for misfolding than for native folding, reflecting local roughening of the misfolding landscape, likely due to increased internal friction. The slow diffusion also led to much longer transit times for barrier crossing, allowing transition paths to be observed directly for the first time to our knowledge. These results open a new window onto the microscopic mechanisms governing protein misfolding. PMID:26109573

  15. Measuring the Fusion Cross-Section of 18,19 O + 12 C with Low-Intensity Beams at Energies Near and Below the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Steinbach, Tracy; Vadas, Justin; Schmidt, Jon; Singh, Varinderjit; Hudan, Sylvie; Desouza, Romualdo; Baby, Lagy; Kuvin, Sean; Wiedenhover, Ingo; Umar, Sait; Oberacker, Volker

    2015-04-01

    Fusion of neutron-rich light nuclei has been proposed as a heat source that triggers an X-ray superburst in the crust of an accreting neutron star. To investigate this hypothesis the total fusion cross-section for beams of low-intensity, neutron-rich nuclei (<105 ions/s) on light targets has been measured at energies near and below the Coulomb barrier. Evaporation residues, resulting from the fusion of oxygen and 12 C nuclei, were identified by their energy and Time-of-flight. Using this technique, the fusion excitation function was measured in the sub-barrier domain down to the 2 mb level. Comparison of the measured fusion excitation function with the predictions of a density constrained TDHF model reveals that the experimental data exhibit a smaller decrease in cross-section with decreasing energy than is theoretically predicted. This difference can be interpreted as a larger tunneling probability for the experimental data as compared to the theoretical predictions. To determine if this difference increases in magnitude with decreasing incident energy improvements have been implemented to enable measurement of the fusion cross-section to an even lower level. Supported by the US DOE under Grand No. DEFG02-88ER-40404.

  16. Spectral Modeling of Residual Stress and Stored Elastic Strain Energy in Thermal Barrier Coatings

    SciTech Connect

    Donegan, Sean; Rolett, Anthony

    2013-12-31

    Solutions to the thermoelastic problem are important for characterizing the response under temperature change of refractory systems. This work extends a spectral fast Fourier transform (FFT) technique to analyze the thermoelastic behavior of thermal barrier coatings (TBCs), with the intent of probing the local origins of failure in TBCs. The thermoelastic FFT (teFFT) approach allows for the characterization of local thermal residual stress and strain fields, which constitute the origins of failure in TBC systems. A technique based on statistical extreme value theory known as peaks-over-threshold (POT) is developed to quantify the extreme values ("hot spots") of stored elastic strain energy (i.e., elastic energy density, or EED). The resolution dependence of the teFFT method is assessed through a sensitivity study of the extreme values in EED. The sensitivity study is performed both for the local (point-by-point) eld distributions as well as the grain scale eld distributions. A convergence behavior to a particular distribution shape is demonstrated for the local elds. The grain scale fields are shown to exhibit a possible convergence to a maximum level of EED. To apply the teFFT method to TBC systems, 3D synthetic microstructures are created to approximate actual TBC microstructures. The morphology of the grains in each constituent layer as well as the texture is controlled. A variety of TBC materials, including industry standard materials and potential future materials, are analyzed using the teFFT. The resulting hot spots are quantified using the POT approach. A correlation between hot spots in EED and interface rumpling between constituent layers is demonstrated, particularly for the interface between the bond coat (BC) and the thermally grown oxide (TGO) layer.

  17. Transportation Energy Futures Series: Non-Cost Barriers to Consumer Adoption of New Light-Duty Vehicle Technologies

    SciTech Connect

    Stephens, T.

    2013-03-01

    Consumer preferences are key to the adoption of new vehicle technologies. Barriers to consumer adoption include price and other obstacles, such as limited driving range and charging infrastructure; unfamiliarity with the technology and uncertainty about direct benefits; limited makes and models with the technology; reputation or perception of the technology; standardization issues; and regulations. For each of these non-cost barriers, this report estimates an effective cost and summarizes underlying influences on consumer preferences, approximate magnitude and relative severity, and assesses potential actions, based on a comprehensive literature review. While the report concludes that non-cost barriers are significant, effective cost and potential market share are very uncertain. Policies and programs including opportunities for drivers to test drive advanced vehicles, general public outreach and information programs, incentives for providing charging and fueling infrastructure, and development of technology standards were examined for their ability to address barriers, but little quantitative data exists on the effectiveness of these measures. This is one in a series of reports produced as a result of the Transportation Energy Futures project, a Department of Energy-sponsored multi-agency effort to pinpoint underexplored strategies for reducing GHGs and petroleum dependence related to transportation.

  18. Limitations and barriers for adopting sustainable management practices in different farm types across Europe

    NASA Astrophysics Data System (ADS)

    Guzmán, Gema; Portero, Ángela; Vanwalleghem, Tom; Pedrera, Ana; Jesús Gaitán, Antonio; Ten Berge, Hein

    2014-05-01

    Although apparently the conservation of natural resources such as water and soil does not represent important concerns for our society, the evolution of the world population and the degradation of these resources pose a challenge to improving agricultural food production capacity and conserving, and in some cases restoring, the environmental quality. Unfortunately, the history contains numerous examples of abandonment of these resources (McNeill 1992, Montgomery 2007). Although most of the agronomic conservation practices have been known for millennia, their implementation has often been hindered by non-agricultural motives (Davis et al. 2012). The European project CATCH-C (ten Berge 2011) started last year with the aim of evaluating sustainable soil management practices and exploring the difficulties for their adoption, both at farm and institutional level, to overcome them in the near future. As a first step with that purpose, a selection of best management practices (BMPs) based on interviews with advisors and scientific knowledge were proposed for each of the considered farm typologies: arable crops, permanent crops and pasture. These farm types are representative of the Mediterranean area in terms of agroecological properties, extension, economical importance and soil degradation problems. Semi-structured interviews were carried out by addressing different profiles of farmers to identify in a qualitative way the main limitations for adopting these BMPs on their farms. Different questionnaires were prepared based on the farmers' responses and launched at a larger scale, with the aim of achieving approximately 100 responses per each farm typology. Finally, responses from the questionnaires will be analyzed to explore the causes that hinder or impede the adoption of BMPs in different farm typologies. References: Davis A.S. et al. 2012. Plos ONE 7(10): e4719. doi:10.1371/journalpone.0047149. McNeill, J.R. 1992. The mountains of the Mediterranean world. Cambridge

  19. Safe sex? Misconceptions, gender differences and barriers among injection drug users: a focus group approach.

    PubMed

    Weiss, S H; Weston, C B; Quirinale, J

    1993-01-01

    Heterosexual transmission is one factor involved in the spread of the human immunodeficiency virus (HIV) within the injection drug use (IDU) population and between IDU and non-IDU individuals. Insufficient information is currently available to reduce this heterosexual transmission. As a basis for designing a questionnaire aimed at the IDU population, we conducted 5 focus groups to collect information on knowledge of and attitudes toward safe sex as held by male and female IDUs in methadone treatment. We identified misconceptions related to HIV infection, condoms, and sexual behavior. We also found gender-based differences in knowledge and learning style. Also, while individuals felt a responsibility to prevent HIV transmission, they lacked sufficient control to do so. The wide range of responses on questions concerning sexually transmitted diseases (STDs), condoms, reproductive decisions, and methods of promoting safe sex provides a basis for developing a questionnaire designed to identify and target specific subgroups for educational intervention. PMID:8297708

  20. Simulations about self-absorption of tritium in titanium tritide and the energy deposition in a silicon Schottky barrier diode.

    PubMed

    Li, Hao; Liu, Yebing; Hu, Rui; Yang, Yuqing; Wang, Guanquan; Zhong, Zhengkun; Luo, Shunzhong

    2012-11-01

    Simulations on the self-absorption of tritium electrons in titanium tritide films and the energy deposition in a silicon Schottky barrier diode are carried out using the Geant4 radiation transport toolkit. Energy consumed in each part of the Schottky radiovoltaic battery is simulated to give a clue about how to make the battery work better. The power and energy-conversion efficiency of the tritium silicon Schottky radiovoltaic battery in an optimized design are simulated. Good consistency with experiments is obtained. PMID:22935439

  1. Stereotyping as a barrier to collaboration: Does interprofessional education make a difference?

    PubMed

    Ateah, Christine A; Snow, Wanda; Wener, Pamela; MacDonald, Laura; Metge, Colleen; Davis, Penny; Fricke, Moni; Ludwig, Sora; Anderson, Judy

    2011-02-01

    This research was part of a Health Canada funded initiative developed to provide evidence about the effectiveness of interprofessional education (IPE) interventions to promote collaborative patient-centred care. Health professional students' ratings of health professions and the effect of IPE on those ratings were examined. Participants were divided into three groups (N=51); control, education, and practice site immersion. Utilizing the Student Stereotypes Rating Questionnaire (SSRQ) which consists of a five point Likert-type scale each group rated health professionals on nine characteristics: academic ability, interpersonal skills, professional competence, leadership, practical skills, independence, confidence, decision-making, and being a team player (Hean, Macleod-Clark, Adams, and Humphris, 2006). Data were collected at four time points; prior to an IPE classroom intervention, following an IPE classroom intervention, following the IPE immersion experience, and four months post IPE immersion experience. Overall, perceptions of other health professions were more positive following the 2.5day interprofessional education session and immersion experience. Student ratings of the seven professions among the nine characteristics will be presented, highlighting similarities and differences across professional groups. Findings support the incorporation of IPE curricula that address the role and functions of other health care professions to facilitate the development collaborative patient-centred care health care teams. PMID:20655633

  2. Neighborhood context and racial/ethnic differences in young children's obesity: structural barriers to interventions.

    PubMed

    Kimbro, Rachel Tolbert; Denney, Justin T

    2013-10-01

    Numerous studies in the last ten years have investigated racial/ethnic disparities in obesity for young children. Increasing attention is paid to the influence of neighborhood environments - social and physical-on a variety of young children's health outcomes. This work identifies resource-based and community-based mechanisms that impede on the maintenance of healthy weights for young children in socioeconomically depressed areas, and shows consistently higher rates of obesity in more deprived areas. None of this work, however, has explored whether area deprivation or the race/nativity composition of neighborhoods contributes to racial/ethnic disparities in young children's obesity. Utilizing restricted geo-coded data from the Early Childhood Longitudinal Study (Kindergarten) (N = 17,540), we utilize multilevel logistic regression models to show that neighborhood level measures do little to explain racial and ethnic differences in childhood obesity. However, living in neighborhoods with higher levels of poverty, lower levels of education, and a higher proportion of black residents is associated with increased child obesity risk after considering a host of relevant individual level factors. In addition, living in neighborhoods with a higher proportion of foreign-born residents is associated with reduced child obesity risk. Although well-intentioned childhood obesity intervention programs aimed at changing individual-level behaviors are important, our results highlight the importance of considering neighborhood structural factors for child obesity prevention. PMID:23089614

  3. Vibrational analysis on the revised potential energy curve of the low-barrier hydrogen bond in photoactive yellow protein.

    PubMed

    Kanematsu, Yusuke; Kamikubo, Hironari; Kataoka, Mikio; Tachikawa, Masanori

    2016-01-01

    Photoactive yellow protein (PYP) has a characteristic hydrogen bond (H bond) between p-coumaric acid chromophore and Glu46, whose OH bond length has been observed to be 1.21 Å by the neutron diffraction technique [Proc. Natl. Acad. Sci. 106, 440-4]. Although it has been expected that such a drastic elongation of the OH bond could be caused by the quantum effect of the hydrogen nucleus, previous theoretical computations including the nuclear quantum effect have so far underestimated the bond length by more than 0.07 Å. To elucidate the origin of the difference, we performed a vibrational analysis of the H bond on potential energy curve with O…O distance of 2.47 Å on the equilibrium structure, and that with O…O distance of 2.56 Å on the experimental crystal structure. While the vibrationally averaged OH bond length for equilibrium structure was underestimated, the corresponding value for crystal structure was in reasonable agreement with the corresponding experimental values. The elongation of the O…O distance by the quantum mechanical or thermal fluctuation would be indispensable for the formation of a low-barrier hydrogen bond in PYP. PMID:27274362

  4. Vibrational analysis on the revised potential energy curve of the low-barrier hydrogen bond in photoactive yellow protein

    PubMed Central

    Kanematsu, Yusuke; Kamikubo, Hironari; Kataoka, Mikio; Tachikawa, Masanori

    2015-01-01

    Photoactive yellow protein (PYP) has a characteristic hydrogen bond (H bond) between p-coumaric acid chromophore and Glu46, whose OH bond length has been observed to be 1.21 Å by the neutron diffraction technique [Proc. Natl. Acad. Sci. 106, 440–4]. Although it has been expected that such a drastic elongation of the OH bond could be caused by the quantum effect of the hydrogen nucleus, previous theoretical computations including the nuclear quantum effect have so far underestimated the bond length by more than 0.07 Å. To elucidate the origin of the difference, we performed a vibrational analysis of the H bond on potential energy curve with O…O distance of 2.47 Å on the equilibrium structure, and that with O…O distance of 2.56 Å on the experimental crystal structure. While the vibrationally averaged OH bond length for equilibrium structure was underestimated, the corresponding value for crystal structure was in reasonable agreement with the corresponding experimental values. The elongation of the O…O distance by the quantum mechanical or thermal fluctuation would be indispensable for the formation of a low-barrier hydrogen bond in PYP. PMID:27274362

  5. A four-coordinate cobalt(II) single-ion magnet with coercivity and a very high energy barrier

    NASA Astrophysics Data System (ADS)

    Rechkemmer, Yvonne; Breitgoff, Frauke D.; van der Meer, Margarethe; Atanasov, Mihail; Hakl, Michael; Orlita, Milan; Neugebauer, Petr; Neese, Frank; Sarkar, Biprajit; van Slageren, Joris

    2016-02-01

    Single-molecule magnets display magnetic bistability of molecular origin, which may one day be exploited in magnetic data storage devices. Recently it was realised that increasing the magnetic moment of polynuclear molecules does not automatically lead to a substantial increase in magnetic bistability. Attention has thus increasingly focussed on ions with large magnetic anisotropies, especially lanthanides. In spite of large effective energy barriers towards relaxation of the magnetic moment, this has so far not led to a big increase in magnetic bistability. Here we present a comprehensive study of a mononuclear, tetrahedrally coordinated cobalt(II) single-molecule magnet, which has a very high effective energy barrier and displays pronounced magnetic bistability. The combined experimental-theoretical approach enables an in-depth understanding of the origin of these favourable properties, which are shown to arise from a strong ligand field in combination with axial distortion. Our findings allow formulation of clear design principles for improved materials.

  6. A four-coordinate cobalt(II) single-ion magnet with coercivity and a very high energy barrier

    PubMed Central

    Rechkemmer, Yvonne; Breitgoff, Frauke D.; van der Meer, Margarethe; Atanasov, Mihail; Hakl, Michael; Orlita, Milan; Neugebauer, Petr; Sarkar, Biprajit; van Slageren, Joris

    2016-01-01

    Single-molecule magnets display magnetic bistability of molecular origin, which may one day be exploited in magnetic data storage devices. Recently it was realised that increasing the magnetic moment of polynuclear molecules does not automatically lead to a substantial increase in magnetic bistability. Attention has thus increasingly focussed on ions with large magnetic anisotropies, especially lanthanides. In spite of large effective energy barriers towards relaxation of the magnetic moment, this has so far not led to a big increase in magnetic bistability. Here we present a comprehensive study of a mononuclear, tetrahedrally coordinated cobalt(II) single-molecule magnet, which has a very high effective energy barrier and displays pronounced magnetic bistability. The combined experimental-theoretical approach enables an in-depth understanding of the origin of these favourable properties, which are shown to arise from a strong ligand field in combination with axial distortion. Our findings allow formulation of clear design principles for improved materials. PMID:26883902

  7. A four-coordinate cobalt(II) single-ion magnet with coercivity and a very high energy barrier.

    PubMed

    Rechkemmer, Yvonne; Breitgoff, Frauke D; van der Meer, Margarethe; Atanasov, Mihail; Hakl, Michael; Orlita, Milan; Neugebauer, Petr; Neese, Frank; Sarkar, Biprajit; van Slageren, Joris

    2016-01-01

    Single-molecule magnets display magnetic bistability of molecular origin, which may one day be exploited in magnetic data storage devices. Recently it was realised that increasing the magnetic moment of polynuclear molecules does not automatically lead to a substantial increase in magnetic bistability. Attention has thus increasingly focussed on ions with large magnetic anisotropies, especially lanthanides. In spite of large effective energy barriers towards relaxation of the magnetic moment, this has so far not led to a big increase in magnetic bistability. Here we present a comprehensive study of a mononuclear, tetrahedrally coordinated cobalt(II) single-molecule magnet, which has a very high effective energy barrier and displays pronounced magnetic bistability. The combined experimental-theoretical approach enables an in-depth understanding of the origin of these favourable properties, which are shown to arise from a strong ligand field in combination with axial distortion. Our findings allow formulation of clear design principles for improved materials. PMID:26883902

  8. Ab initio calculations of stationary points on the benzene-Ar and p-difluorobenzene-Ar potential energy surfaces: barriers to bound orbiting states

    NASA Astrophysics Data System (ADS)

    Moulds, Rebecca J.; Buntine, Mark A.; Lawrance, Warren D.

    2004-09-01

    The potential energy surfaces of the van der Waals complexes benzene-Ar and p-difluorobenzene-Ar have been investigated at the second-order Møller-Plesset (MP2) level of theory with the aug-cc-pVDZ basis set. Calculations were performed with unconstrained geometry optimization for all stationary points. This study has been performed to elucidate the nature of a conflict between experimental results from dispersed fluorescence and velocity map imaging (VMI). The inconsistency is that spectra for levels of p-difluorobenzene-Ar and -Kr below the dissociation thresholds determined by VMI show bands where free p-difluorobenzene emits, suggesting that dissociation is occurring. We proposed that the bands observed in the dispersed fluorescence spectra are due to emission from states in which the rare gas atom orbits the aromatic chromophore; these states are populated by intramolecular vibrational redistribution from the initially excited level [S. M. Bellm, R. J. Moulds, and W. D. Lawrance, J. Chem. Phys. 115, 10709 (2001)]. To test this proposition, stationary points have been located on both the benzene-Ar and p-difluorobenzene-Ar potential energy surfaces (PESs) to determine the barriers to this orbiting motion. Comparison with previous single point CCSD(T) calculations of the benzene-Ar PES has been used to determine the amount by which the barriers are overestimated at the MP2 level. As there is little difference in the comparable regions of the benzene-Ar and p-difluorobenzene-Ar PESs, the overestimation is expected to be similar for p-difluorobenzene-Ar. Allowing for this overestimation gives the barrier to movement of the Ar atom around the pDFB ring via the valley between the H atoms as ⩽204 cm-1 in S0 (including zero point energy). From the estimated change upon electronic excitation, the corresponding barrier in S1 is estimated to be ⩽225 cm-1. This barrier is less than the 240 cm-1 energy of 302¯, the vibrational level for which the anomalous "free p

  9. Culture and language differences as a barrier to provision of quality care by the health workforce in Saudi Arabia

    PubMed Central

    Almutairi, Khalid M.

    2015-01-01

    Objectives: To identify, synthesize, and summarize issues and challenges related to the culture and language differences of the health workforce in Saudi Arabia. Methods: A comprehensive systematic review was conducted in May 2014 to locate published articles. Two independent researchers in consultation with several experts used 4 electronic databases (ISI Web of Knowledge, Science Direct, PubMed, and Cochrane) to scrutinize articles published from January 2000 - March 2014. Each of the studies was given a quality assessment rating of weak, moderate, or strong, and was evaluated for methodological soundness using Russell and Gregory’s criteria. Results: The online literature search identified 12 studies that met the inclusion criteria. Lack of knowledge of non-Muslim nurses or culture in Saudi Arabia, difficulties in achieving cultural competence, and culture shock were documented as cultural difference factors. Issues in language difference include the clarity of language use by health care providers in giving information and providing adequate explanation regarding their activities. Conclusion: The available information provided by this review study shows that there is a communication barrier between patients and health care workers such as healthcare workers demonstrate low cultural competency. Despite the fact that the government provides programs for expatriate healthcare workers, there is a need to further improve educational and orientation programs regarding the culture and language in Saudi Arabia. PMID:25828278

  10. Utilisation of health services and geography: deconstructing regional differences in barriers to facility-based delivery in Nepal.

    PubMed

    Hodge, Andrew; Byrne, Abbey; Morgan, Alison; Jimenez-Soto, Eliana

    2015-03-01

    While established that geographical inaccessibility is a key barrier to the utilisation of health services, it remains unknown whether disparities are driven only by limited access to these services, or are also attributable to health behaviour. Significant disparities exist in health outcomes and the coverage of many critical health services between the mountains region of Nepal and the rest of the country, yet the principal factors driving these regional disparities are not well understood. Using national representative data from the 2011 Nepal Demographic and Health Survey, we examine the extent to which observable factors explain the overall differences in the utilisation of maternal health services. We apply nonlinear Blinder-Oaxaca-type decomposition methods to quantify the effect that differences in measurable characteristics have on the regional coverage gap in facility-based delivery. The mean coverage of facility-based deliveries was 18.6 and 36.3 % in the mountains region and the rest of Nepal, respectively. Between 54.8 and 74.1 % of the regional coverage gap was explained by differences in observed characteristics. Factors influencing health behaviours (proxied by mothers' education, TV viewership and tobacco use, and household wealth) and subjective distance to the health facility were the major factors, contributing between 52.9 and 62.5 % of the disparity. Mothers' birth history was also noteworthy. Policies simultaneously addressing access and health behaviours appear necessary to achieve greater coverage and better health outcomes for women and children in isolated areas. PMID:24927787

  11. EFFECTS OF NUCLEAR INDUCED BREAKUP ON THE FUSION OF 6Li+12C AND 6He+12C SYSTEMS AROUND BARRIER ENERGIES

    NASA Astrophysics Data System (ADS)

    Duhan, Sukhvinder S.; Singh, Manjeet; Kharab, Rajesh

    2012-06-01

    We have studied the effects of nuclear induced breakup channel coupling on the fusion cross-section for 6Li+12C and 6He+12C systems in the near barrier energy regime using the dynamic polarization potential (DPP) approach. It has been found that there is enhancement in the fusion cross-section with respect to standard one-dimensional barrier penetration model in the below barrier energy regime while at energies above the barrier there is suppression of fusion cross-section with respect to simple barrier penetration model is observed. The agreement between data and predictions for 6Li+12C system improves significantly as a result of the inclusion of nuclear induced DPP.

  12. Market and behavioral barriers to energy efficiency: A preliminary evaluation of the case for tariff financing in California

    SciTech Connect

    Fujita, K. Sydny

    2011-06-23

    Consumers regularly forgo purchases of high efficiency appliances that appear to be cost effective at a reasonable rate of return. While some argue that this is a true revelation of preferences for appliance features, this 'efficiency gap' can be largely explained by a combination of market and behavioral failures that reduce consumers ability to evaluate the relative value of appliances and skew preferences toward initial cost savings, undervaluing future reductions in operating costs. These failures and barriers include externalities of energy use, imperfect competition between manufacturers, asymmetric information, bounded rationality, split incentives, and transaction costs (Golove 1996). Recognizing the social benefit of energy conservation, several major methods are used by policymakers to ensure that efficient appliances are purchased: minimum efficiency standards, Energy Star labeling, and rebates and tax credits. There is no single market for energy services; there are hundreds of uses, thousands of intermediaries, and millions of users, and likewise, no single appropriate government intervention (Golove 1996). Complementary approaches must be implemented, considering policy and institutional limitations. In this paper, I first lay out the rationale for government intervention by addressing the market and behavioral failures and barriers that arise in the context of residential energy efficiency. I then consider the ways in which some of these failures and barriers are addressed through major federal programs and state and utility level programs that leverage them, as well as identifying barriers that are not addressed by currently implemented programs. Heterogeneity of consumers, lack of financing options, and split incentives of landlords and tenants contribute significantly to the under-adoption of efficient appliances. To quantify the size of the market most affected by these barriers, I estimate the number of appliances, and in particular the number

  13. How Accurate Are the Minnesota Density Functionals for Noncovalent Interactions, Isomerization Energies, Thermochemistry, and Barrier Heights Involving Molecules Composed of Main-Group Elements?

    PubMed

    Mardirossian, Narbe; Head-Gordon, Martin

    2016-09-13

    The 14 Minnesota density functionals published between the years 2005 and early 2016 are benchmarked on a comprehensive database of 4986 data points (84 data sets) involving molecules composed of main-group elements. The database includes noncovalent interactions, isomerization energies, thermochemistry, and barrier heights, as well as equilibrium bond lengths and equilibrium binding energies of noncovalent dimers. Additionally, the sensitivity of the Minnesota density functionals to the choice of basis set and integration grid is explored for both noncovalent interactions and thermochemistry. Overall, the main strength of the hybrid Minnesota density functionals is that the best ones provide very good performance for thermochemistry (e.g., M06-2X), barrier heights (e.g., M08-HX, M08-SO, MN15), and systems heavily characterized by self-interaction error (e.g., M06-2X, M08-HX, M08-SO, MN15), while the main weakness is that none of them are state-of-the-art for the full spectrum of noncovalent interactions and isomerization energies (although M06-2X is recommended from the 10 hybrid Minnesota functionals). Similarly, the main strength of the local Minnesota density functionals is that the best ones provide very good performance for thermochemistry (e.g., MN15-L), barrier heights (e.g., MN12-L), and systems heavily characterized by self-interaction error (e.g., MN12-L and MN15-L), while the main weakness is that none of them are state-of-the-art for the full spectrum of noncovalent interactions and isomerization energies (although M06-L is clearly the best from the four local Minnesota functionals). As an overall guide, M06-2X and MN15 are perhaps the most broadly useful hybrid Minnesota functionals, while M06-L and MN15-L are perhaps the most broadly useful local Minnesota functionals, although each has different strengths and weaknesses. PMID:27537680

  14. Similar Students and Different Countries? An Analysis of the Barriers and Drivers for Erasmus Participation in Seven Countries

    ERIC Educational Resources Information Center

    Beerkens, Maarja; Souto-Otero, Manuel; de Wit, Hans; Huisman, Jeroen

    2016-01-01

    Increasing participation in the Erasmus study abroad program in Europe is a clear policy goal, and student-reported barriers and drivers are regularly monitored. This article uses student survey data from seven countries to examine the extent to which student-level barriers can explain the considerable cross-country variation in Erasmus…

  15. Tunneling in Al/Al2 O3 /Al junctions and its direct link with energy gap and tunneling time across the barrier

    NASA Astrophysics Data System (ADS)

    Patino, Edgar; Kelkar, Neelima

    Quantum tunneling has been widely used in order to investigate the density of states of the materials across the barrier and magnetoresistance in magnetic tunnel junctions (MTJs). In spite of the possible applications there is no clear understanding of the barrier parameters as a function of temperature. Measurements of current-voltage (I-V) characteristics of a high quality Al/Al2O3/Al junction at temperatures ranging from 3.5 K to 300 K have been used to extract the barrier properties. Fitting results using Simmons' model led to a constant value of barrier width s ~20.8 Å and a continuous increase in the barrier height with decreasing temperature. The latter is used to determine the energy band gap temperature dependence and average phonon frequency ω = 2.05 × 1013 sec-1 in Al2O3. Finally from the experimentally extracted barrier height and width parameters we calculate the tunneling time for a solid state tunnel junction. The order of magnitude of this time corresponds to the one obtained in sophisticated experiments.The barrier parameters are used to extract the temperature dependent dwell times in tunneling (τD = 3.6 × 10-16 sec at mid-barrier energies) and locate resonances above the barrier.

  16. Nuclear rainbow in the 16O + 27AL system: The role of couplings at energies far above the barrier

    NASA Astrophysics Data System (ADS)

    Pereira, D.; Linares, R.; Oliveira, J. R. B.; Lubian, J.; Chamon, L. C.; Gomes, P. R. S.; Cunsolo, A.; Cappuzzello, F.; Cavallaro, M.; Carbone, D.; Foti, A.

    2012-04-01

    High precision elastic and inelastic angular distributions have been measured for the 16O + 27Al system at a beam energy of 100 MeV. The data analysis confirms a rainbow formation as already predicted by parameter-free Coupled Channel calculations. It also helps to reveal the crucial role of inelastic couplings in the rainbow formation for heavier systems even at energies far above the Coulomb barrier. This feature, well known in atomic/molecular scattering, is experimentally studied for the first time in Nuclear Physics.

  17. Examination of the influence of transfer channels on the barrier height distribution: Scattering of 20Ne on 58Ni,60Ni, and 61Ni at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Trzcińska, A.; Piasecki, E.; Amar, A.; Czarnacki, W.; Keeley, N.; Kisieliński, M.; Kliczewski, S.; Kowalczyk, M.; Lommel, B.; Mutterer, M.; Siudak, R.; Stolarz, A.; Strojek, I.; Tiourin, G.; Trzaska, W. H.

    2016-05-01

    Background: It was suggested that the shape of the barrier height distribution can be determined not only by strong reaction channels (collective excitations) but also by weak channels such as transfers and/or noncollective excitations. Purpose: The study of the barrier height distributions for the 20Ne+58,60,61Ni systems requires information on transfer cross sections at near-barrier energies. Methods: A measurement of the cross sections for various transfer channels at a backward angle (142 degrees), at a near-barrier energy was performed. Identification of products was based on time-of-flight and Δ E -E methods. A measurement of the angular distribution of α stripping in the 20Ne+61Ni system was performed using a gas Δ E -E telescope. Results: For all three systems studied: 20Ne+58Ni ,60Ni, and 61Ni total (sum of all transfer channels) cross sections are similar and dominated by α stripping. Conclusions: The results, as well as coupled reaction channel calculations, suggest that transfer is not responsible for smoothing the barrier height distribution in 20Ne+61Ni , supporting the hypothesis that barrier distribution shapes are influenced by noncollective excitations.

  18. Intermediate-band photosensitive device with quantum dots embedded in energy fence barrier

    DOEpatents

    Forrest, Stephen R.; Wei, Guodan

    2010-07-06

    A plurality of layers of a first semiconductor material and a plurality of dots-in-a-fence barriers disposed in a stack between a first electrode and a second electrode. Each dots-in-a-fence barrier consists essentially of a plurality of quantum dots of a second semiconductor material embedded between and in direct contact with two layers of a third semiconductor material. Wave functions of the quantum dots overlap as at least one intermediate band. The layers of the third semiconductor material are arranged as tunneling barriers to require a first electron and/or a first hole in a layer of the first material to perform quantum mechanical tunneling to reach the second material within a respective quantum dot, and to require a second electron and/or a second hole in a layer of the first semiconductor material to perform quantum mechanical tunneling to reach another layer of the first semiconductor material.

  19. Blood-brain barrier changes and cell invasion differ between therapeutic immune clearance of neurotrophic virus and CNS autoimmunity.

    PubMed

    Fabis, Marzena J; Phares, Timothy W; Kean, Rhonda B; Koprowski, Hilary; Hooper, D Craig

    2008-10-01

    CNS tissues are protected from circulating cells and factors by the blood-brain barrier (BBB), a specialization of the neurovasculature. Outcomes of the loss of BBB integrity and cell infiltration into CNS tissues can differ vastly. For example, elevated BBB permeability is closely associated with the development of neurological disease in experimental allergic encephalomyelitis (EAE) but not during clearance of the attenuated rabies virus CVS-F3 from the CNS tissues. To probe whether differences in the nature of BBB permeability changes may contribute to the pathogenesis of acute neuroinflammatory disease, we compared the characteristics of BBB permeability changes in mice with EAE and in mice clearing CVS-F3. BBB permeability changes are largely restricted to the cerebellum and spinal cord in both models but differ in the extent of leakage of markers of different size and in the nature of cell accumulation in the CNS tissues. The accumulation in the CNS tissues of CD4 T cells expressing mRNAs specific for IFN-gamma and IL-17 is common to both, but iNOS-positive cells invade into the CNS parenchyma only in EAE. Mice that have been immunized with myelin basic protein (MBP) and infected exhibit the features of EAE. Treatment with the peroxynitrite-dependent radical scavenger urate inhibits the invasion of iNOS-positive cells into the CNS tissues and the development of clinical signs of EAE without preventing the loss of BBB integrity in immunized/infected animals. These findings indicate that BBB permeability changes can occur in the absence of neuropathology provided that cell invasion is restricted. PMID:18829442

  20. Determination of the surface energy distributions of different processed lactose.

    PubMed

    Thielmann, Frank; Burnett, Daniel J; Heng, Jerry Y Y

    2007-11-01

    Particulate interactions between drug and lactose carrier in dry powder inhaler formulations are affected by the heterogenous energy distribution on the surface of the individual compounds. A new method based on Inverse Gas Chromatography at finite concentration is applied to study the energy heterogeneity of untreated, milled, and recrystallized lactose of similar particle size distribution. Energy distributions for the dispersive surface energy and the specific free energy of ethanol are obtained. Milling causes an increase in surface energy due to formation of amorphous regions. Untreated and recrystallized materials have similar surface energies at low surface coverages but show clear differences in energy distribution. PMID:18058321

  1. Applying Risk Science and Stakeholder Engagement to Overcome Environmental Barriers to Marine and Hydrokinetic Energy Projects

    SciTech Connect

    Copping, Andrea E.; Anderson, Richard M.; Van Cleve, Frances B.

    2010-09-20

    The production of electricity from the moving waters of the ocean has the potential to be a viable addition to the portfolio of renewable energy sources worldwide. The marine and hydrokinetic (MHK) industry faces many hurdles, including technology development, challenges of offshore deployments, and financing; however, the barrier most commonly identified by industry, regulators, and stakeholders is the uncertainty surrounding potential environmental effects of devices placed in the water and the permitting processes associated with real or potential impacts. Regulatory processes are not well positioned to judge the severity of harm due to turbines or wave generators. Risks from MHK devices to endangered or protected animals in coastal waters and rivers, as well as the habitats that support them, are poorly understood. This uncertainty raises concerns about catastrophic interactions between spinning turbine blades or slack mooring lines and marine mammals, birds and fish. In order to accelerate the deployment of tidal and wave devices, there is a need to sort through the extensive list of potential interactions that may cause harm to marine organisms and ecosystems, to set priorities for regulatory triggers, and to direct future research. Identifying the risk of MHK technology components on specific marine organisms and ecosystem components can separate perceived from real risk-relevant interactions. Scientists from Pacific Northwest National Laboratory (PNNL) are developing an Environmental Risk Evaluation System (ERES) to assess environmental effects associated with MHK technologies and projects through a systematic analytical process, with specific input from key stakeholder groups. The array of stakeholders interested in the development of MHK is broad, segmenting into those whose involvement is essential for the success of the MHK project, those that are influential, and those that are interested. PNNL and their partners have engaged these groups, gaining

  2. Hindrance of complete fusion in the {sup 8}Li+{sup 208}Pb system at above-barrier energies

    SciTech Connect

    Aguilera, E. F.; Martinez-Quiroz, E.; Rosales, P.; Kolata, J. J.; DeYoung, P. A.; Peaslee, G. F.; Mears, P.; Guess, C.; Becchetti, F. D.; Lupton, J. H.; Chen, Yu

    2009-10-15

    The {sup 211,212}At yields resulting from the interaction of the radioactive projectile {sup 8}Li with a {sup 208}Pb target have been measured at energies between 3 and 8.5 MeV above the Coulomb barrier. They are signatures for fusion of the whole charge but not necessarily the whole mass of the projectile, so they are included in a corresponding operational definition of complete fusion. Within this definition, a fusion suppression factor of 0.70{+-}0.02 (stat.) {+-}0.04 (syst.) is deduced from a comparison to a one-dimensional barrier-penetration-model calculation using parameters extrapolated from values for {sup 6,7}Li+{sup 209}Bi and {sup 9}Be+{sup 208}Pb taken from the literature. Possible incomplete fusion processes are discussed and the results are fitted with a phenomenological model assuming breakup prior to fusion followed by capture of a {sup 7}Li fragment.

  3. Ordering of Self-Diffusion Barrier Energies on Pt(110)-1x2

    SciTech Connect

    Feibelman, Peter J.

    1999-06-01

    Bond-counting arguments, supported by ab-initio calculations, predict a lower barrier for "leapfrog" diffusion of Pt addimers on Pt(llO)-lx2 than for adatom dif- fusion or addimer dissociation. This conflicts with experiment, possibly signaling contaminant influence.

  4. An in vitro comparative evaluation of different intraorifice barriers on the fracture resistance of endodontically treated roots obturated with gutta-percha

    PubMed Central

    Gupta, Abhishek; Arora, Vipin; Jha, Padmanabh; Nikhil, Vineeta; Bansal, Parul

    2016-01-01

    Aim: To compare and evaluate the root reinforcement potential of four different intraorifice barriers: Mineral trioxide aggregate (MTA), resin-modified glass ionomer cement (RMGIC), fiber-reinforced composite (FRC), and nanohybrid composite (NC). Materials and Methods: Seventy-five mandibular premolars were decoronated to a standardized length, and prepared and obturated with gutta-percha and AH Plus sealer. Except for control specimens, the coronal 3-mm gutta-percha was removed and filled with different materials. The specimens (75) were divided into five groups (n = 15) on the basis of the intraorifice barrier material used. Group 1: MTA, Group 2: RMGIC, Group 3: FRC, Group 4: NC, Group 5: no barrier (control). Fracture resistance of the specimens was tested. Results: Fracture resistance of roots was significantly affected by the type of intraorifice barrier used and the following pattern was observed: RMGIC > FRC > NC > MTA. Conclusion: Intraorifice barriers can be regarded as a viable choice to reduce the occurrence of postendodontic root fractures. Among the four tested materials, RMGIC showed the maximum reinforcement. PMID:27099413

  5. Comparative studies of Coulomb barrier heights for nuclear models applied to sub-barrier fusion

    NASA Astrophysics Data System (ADS)

    Qu, W. W.; Zhang, G. L.; Zhang, H. Q.; Wolski, R.

    2014-12-01

    Coulomb barrier heights provided by different nuclear interaction models including the Bass model, the proximity potential model, and the double folding model have been applied for experimental data of fusion in terms of a recently proposed energy scaling approach. The results show that the proximity potential description of the barrier heights seems to be closest to the values required by the systematics. It is suggested that the proximity potential model is the most suitable model to calculate the barrier height. However, the double folding model gives the lowest barrier heights.

  6. Response of Ni/4H-SiC Schottky barrier diodes to alpha-particle irradiation at different fluences

    NASA Astrophysics Data System (ADS)

    Omotoso, E.; Meyer, W. E.; Auret, F. D.; Diale, M.; Ngoepe, P. N. M.

    2016-01-01

    Irradiation experiments have been carried out on 1.9×1016 cm-3 nitrogen-doped 4H-SiC at room temperature using 5.4 MeV alpha-particle irradiation over a fluence ranges from 2.6×1010 to 9.2×1011 cm-2. Current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been carried out to study the change in characteristics of the devices and free carrier removal rate due to alpha-particle irradiation, respectively. As radiation fluence increases, the ideality factors increased from 1.20 to 1.85 but the Schottky barrier height (SBHI-V) decreased from 1.47 to 1.34 eV. Free carrier concentration, Nd decreased with increasing fluence from 1.7×1016 to 1.1×1016 cm-2 at approximately 0.70 μm depth. The reduction in Nd shows that defects were induced during the irradiation and have effect on compensating the free carrier. The free carrier removal rate was estimated to be 6480±70 cm-1. Alpha-particle irradiation introduced two electron traps (E0.39 and E0.62), with activation energies of 0.39±0.03 eV and 0.62±0.08 eV, respectively. The E0.39 as attribute related to silicon or carbon vacancy, while the E0.62 has the attribute of Z1/Z2.

  7. The Effects of a High-Energy Diet on Hippocampal Function and Blood-Brain Barrier Integrity in the Rat

    PubMed Central

    Kanoski, Scott E.; Zhang, Yanshu; Zheng, Wei; Davidson, Terry L.

    2016-01-01

    Cognitive impairment and Alzheimer’s Disease are linked with intake of a Western Diet, characterized by high levels of saturated fats and simple carbohydrates. In rats, these dietary components have been shown to disrupt hippocampal-dependent learning and memory processes, particularly those involving spatial memory. Using a rat model, the present research assessed the degree to which consumption of a high-energy (HE) diet, similar to those found in modern Western cultures, produces a selective impairment in hippocampal function as opposed to a more global cognitive disruption. Learning and memory performance was examined following 90-days consumption of an HE-diet in three nonspatial discrimination learning problems that differed with respect to their dependence on the integrity of the hippocampus. The results showed that consumption of the HE-diet impaired performance in a hippocampal-dependent feature negative discrimination problem relative to chow-fed controls, whereas performance was spared on two discrimination problems that do not rely on the hippocampus. To explore the mechanism whereby consuming HE-diets impairs cognitive function, we investigated the effect of HE-diets on the integrity of the blood-brain barrier (BBB). We found that HE-diet consumption produced a decrease in mRNA expression of tight junction proteins, particularly Claudin-5 and -12, in the choroid plexus and the BBB. Consequently, an increased blood-to-brain permeability of sodium fluorescein was observed in the hippocampus, but not in the striatum and prefrontal cortex following HE-diet access. There results indicate that hippocampal function may be particularly vulnerable to disruption by HE-diets, and this disruption may be related to impaired BBB integrity. PMID:20413889

  8. Assessing Understanding of the Energy Concept in Different Science Disciplines

    ERIC Educational Resources Information Center

    Park, Mihwa; Liu, Xiufeng

    2016-01-01

    Energy is one of the most central and richly connected ideas across all science disciplines. The purpose of this study was to develop a measurement instrument for assessing students' understanding of the energy concept within and across different science disciplines. To achieve this goal, the Inter-Disciplinary Energy concept Assessment (IDEA) was…

  9. Differences in amyloid-β clearance across mouse and human blood-brain barrier models: Kinetic analysis and mechanistic modeling

    PubMed Central

    Qosa, Hisham; Abuasal, Bilal S.; Romero, Ignacio A.; Weksler, Babette; Couraud, Pierre-Oliver; Keller, Jeffrey N.; Kaddoumi, Amal

    2014-01-01

    Alzheimer’s disease (AD) has a characteristic hallmark of amyloid-β (Aβ) accumulation in the brain. This accumulation of Aβ has been related to its faulty cerebral clearance. Indeed, preclinical studies that used mice to investigate Aβ clearance showed that efflux across blood-brain barrier (BBB) and brain degradation mediate efficient Aβ clearance. However, the contribution of each process to Aβ clearance remains unclear. Moreover, it is still uncertain how species differences between mouse and human could affect Aβ clearance. Here, a modified form of the brain efflux index method was used to estimate the contribution of BBB and brain degradation to Aβ clearance from the brain of wild type mice. We estimated that 62% of intracerebrally injected 125I-Aβ40 is cleared across BBB while 38% is cleared by brain degradation. Furthermore, in vitro and in silico studies were performed to compare Aβ clearance between mouse and human BBB models. Kinetic studies for Aβ40 disposition in bEnd3 and hCMEC/D3 cells, representative in vitro mouse and human BBB models, respectively, demonstrated 30-fold higher rate of 125I-Aβ40 uptake and 15-fold higher rate of degradation by bEnd3 compared to hCMEC/D3 cells. Expression studies showed both cells to express different levels of P-glycoprotein and RAGE, while LRP1 levels were comparable. Finally, we established a mechanistic model, which could successfully predict cellular levels of 125I-Aβ40 and the rate of each process. Established mechanistic model suggested significantly higher rates of Aβ uptake and degradation in bEnd3 cells as rationale for the observed differences in 125I-Aβ40 disposition between mouse and human BBB models. In conclusion, current study demonstrates the important role of BBB in the clearance of Aβ from the brain. Moreover, it provides insight into the differences between mouse and human BBB with regards to Aβ clearance and offer, for the first time, a mathematical model that describes A

  10. Differences in amyloid-β clearance across mouse and human blood-brain barrier models: kinetic analysis and mechanistic modeling.

    PubMed

    Qosa, Hisham; Abuasal, Bilal S; Romero, Ignacio A; Weksler, Babette; Couraud, Pierre-Oliver; Keller, Jeffrey N; Kaddoumi, Amal

    2014-04-01

    Alzheimer's disease (AD) has a characteristic hallmark of amyloid-β (Aβ) accumulation in the brain. This accumulation of Aβ has been related to its faulty cerebral clearance. Indeed, preclinical studies that used mice to investigate Aβ clearance showed that efflux across blood-brain barrier (BBB) and brain degradation mediate efficient Aβ clearance. However, the contribution of each process to Aβ clearance remains unclear. Moreover, it is still uncertain how species differences between mouse and human could affect Aβ clearance. Here, a modified form of the brain efflux index method was used to estimate the contribution of BBB and brain degradation to Aβ clearance from the brain of wild type mice. We estimated that 62% of intracerebrally injected (125)I-Aβ40 is cleared across BBB while 38% is cleared by brain degradation. Furthermore, in vitro and in silico studies were performed to compare Aβ clearance between mouse and human BBB models. Kinetic studies for Aβ40 disposition in bEnd3 and hCMEC/D3 cells, representative in vitro mouse and human BBB models, respectively, demonstrated 30-fold higher rate of (125)I-Aβ40 uptake and 15-fold higher rate of degradation by bEnd3 compared to hCMEC/D3 cells. Expression studies showed both cells to express different levels of P-glycoprotein and RAGE, while LRP1 levels were comparable. Finally, we established a mechanistic model, which could successfully predict cellular levels of (125)I-Aβ40 and the rate of each process. Established mechanistic model suggested significantly higher rates of Aβ uptake and degradation in bEnd3 cells as rationale for the observed differences in (125)I-Aβ40 disposition between mouse and human BBB models. In conclusion, current study demonstrates the important role of BBB in the clearance of Aβ from the brain. Moreover, it provides insight into the differences between mouse and human BBB with regards to Aβ clearance and offer, for the first time, a mathematical model that describes

  11. Sex differences in substrate metabolism and energy homeostasis.

    PubMed

    Cortright, R N; Koves, T R

    2000-08-01

    Females differ remarkably from males in the mechanisms that regulate substrate utilization and energy homeostasis. Females appear to be less affected in terms of growth and loss of body tissues when subjected to chronic periods of negative energy balance. The physiological trade-off appears to be a stronger propensity toward retention of fat mass during times of energy surfeit. The mechanism(s) that account for sex differences in energy metabolism are not known but most likely involve the sex steroids. Recent discoveries in the areas of endocrinology and metabolism may provide new insights into differences in the control of food intake and energy conservation between the sexes. Finally, the study of the mechanism(s) involved in the regulation of skeletal muscle lipid metabolism represents a new frontier in skeletal muscle bioenergetics, and new discoveries may provide further explanations for the observed sex differences in substrate utilization and response(s) to alterations in energy homeostasis. PMID:10953067

  12. Kinetic energy barriers on the GaN(0001) surface: A nucleation study by scanning tunneling microscopy

    SciTech Connect

    Zheng Hao; Xie, M. H.; Wu, H. S.; Xue, Q. K.

    2008-01-15

    Island nucleation of GaN on its (0001) surface is studied by scanning tunneling microscopy. A comparison is made between surfaces with and without excess Ga and among surfaces with different excess Ga coverages. Evidence is provided for the change of step characteristics of GaN(0001) by excess Ga adlayers, where the Ehrlich-Schwoebel effect is seen to be mediated by excess Ga coverage. For single Ga adlayer covered GaN(0001) surfaces, nucleation island densities are evaluated, which are used to derive the kinetic barriers of adatom diffusion on a terrace. A barrier of less than 1 eV is obtained for the system, and the Ga adlayers make GaN growth surfactant mediated.

  13. Spin-unrestricted random-phase approximation with range separation: Benchmark on atomization energies and reaction barrier heights

    SciTech Connect

    Mussard, Bastien; Reinhardt, Peter; Toulouse, Julien; Ángyán, János G.

    2015-04-21

    We consider several spin-unrestricted random-phase approximation (RPA) variants for calculating correlation energies, with and without range separation, and test them on datasets of atomization energies and reaction barrier heights. We show that range separation greatly improves the accuracy of all RPA variants for these properties. Moreover, we show that a RPA variant with exchange, hereafter referred to as RPAx-SO2, first proposed by Szabo and Ostlund [J. Chem. Phys. 67, 4351 (1977)] in a spin-restricted closed-shell formalism, and extended here to a spin-unrestricted formalism, provides on average the most accurate range-separated RPA variant for atomization energies and reaction barrier heights. Since this range-separated RPAx-SO2 method had already been shown to be among the most accurate range-separated RPA variants for weak intermolecular interactions [J. Toulouse et al., J. Chem. Phys. 135, 084119 (2011)], this works confirms range-separated RPAx-SO2 as a promising method for general chemical applications.

  14. Efficient sampling over rough energy landscapes with high barriers: A combination of metadynamics with integrated tempering sampling.

    PubMed

    Yang, Y Isaac; Zhang, Jun; Che, Xing; Yang, Lijiang; Gao, Yi Qin

    2016-03-01

    In order to efficiently overcome high free energy barriers embedded in a complex energy landscape and calculate overall thermodynamics properties using molecular dynamics simulations, we developed and implemented a sampling strategy by combining the metadynamics with (selective) integrated tempering sampling (ITS/SITS) method. The dominant local minima on the potential energy surface (PES) are partially exalted by accumulating history-dependent potentials as in metadynamics, and the sampling over the entire PES is further enhanced by ITS/SITS. With this hybrid method, the simulated system can be rapidly driven across the dominant barrier along selected collective coordinates. Then, ITS/SITS ensures a fast convergence of the sampling over the entire PES and an efficient calculation of the overall thermodynamic properties of the simulation system. To test the accuracy and efficiency of this method, we first benchmarked this method in the calculation of ϕ - ψ distribution of alanine dipeptide in explicit solvent. We further applied it to examine the design of template molecules for aromatic meta-C-H activation in solutions and investigate solution conformations of the nonapeptide Bradykinin involving slow cis-trans isomerizations of three proline residues. PMID:26957155

  15. Barrier anodic coatings formed on 6061-T6 aluminum alloy in electrolytes containing different ethanol to water ratios

    SciTech Connect

    Panitz, J.K.G.; Sharp, D.J.; Martinez, F.E.; Merrill, R.M.; Ward, K.J.

    1988-12-01

    We have studied barrier anodic film formation on 6061-T6 aluminum alloy substrates as a function of electrolyte composition for five mixtures of ammonium tartrate dissolved in water and diluted with different amounts of ethanol. The effects of electrolyte temperatures within the range of 18/degree/C to 38/degree/C were explored. The results of this study indicate that the best dielectric coatings and the shortest processing times occur for the 100% water-ammonium tartrate electrolyte. The second best coatings and processing times occur in conjunction with the use of 98% ethanol, 2% water plus ammonium tartrate electrolyte. In general, visibly flawed coatings, scintillation events at cell voltages in excess of approximately 750-800 volts and/or abnormally long processing times occur in conjunction with the use of electrolyte mixtures containing 20%, 60%, and 90% water. We analysed samples of electrolyte as a function of usage, and evaluated the composition of the coatings using Fourier Transform Infrared Analysis to better understand the mechanisms which contribute to anodic coating growth that result in the observed variations in the dielectric properties. All of the coatings exhibited similar compositions except with regard to the amount of CO2 that was physisorbed in the coatings. The dielectrically inferior coatings that were typically produced by the electrolytes containing ethanol contain substantially more CO2 than the coatings grown in the 100% water-based electrolyte. These results strongly suggest that the ethanol in the electrolyte oxidizes and forms CO2 which is incorporated in the coatings and results in inferior dielectric properties. 8 refs., 7 figs.

  16. Systematic study of suppression of complete fusion in reactions involving weakly bound nuclei at energies above the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zhao, Wei-Juan; Diaz-Torres, Alexis; Zhao, En-Guang; Zhou, Shan-Gui

    2016-01-01

    Complete fusion excitation functions of reactions involving breakup are studied by using the empirical coupled-channel (ECC) model with breakup effects considered. An exponential function with two parameters is adopted to describe the prompt-breakup probability in the ECC model. These two parameters are fixed by fitting the measured prompt-breakup probability or the complete fusion cross sections. The suppression of complete fusion at energies above the Coulomb barrier is studied by comparing the data with the predictions from the ECC model without the breakup channel considered. The results show that the suppression of complete fusion is roughly independent of the target for the reactions involving the same projectile.

  17. Energy barriers for bit-encoding states based on 360° domain walls in ultrathin ferromagnetic nanorings

    NASA Astrophysics Data System (ADS)

    Muratov, C. B.; Osipov, V. V.; Vanden-Eijnden, E.

    2015-05-01

    A numerical thermal stability study of the bit-encoding states in a proposed multi-level magnetic storage element based on an ultrathin ferromagnetic nanoring is presented. The material parameters and the ring dimensions for which there are five distinct metastable magnetization configurations separated by energy barriers exceeding 50kBT at room temperature are identified. The results are obtained, using the string method for the study of rare events to locate the transition states separating the metastable states and to identify the most likely thermally activated pathways.

  18. Elastic Scattering Of {sup 6,7}Li+{sup 80}Se At Near And Above Barrier Energies

    SciTech Connect

    Fimiani, L.; Marti, G. V.; Capurro, O. A.; Barbara, E. de; Testoni, J. E.; Zalazar, L.; Arazi, A.; Cardona, M. A.; Carnelli, P.; Figueira, J. M.; Hojman, D.; Martinez Heimann, D.; Negri, A. E.; Pacheco, A. J.; Fernandez Niello, J. O.

    2010-08-04

    In this work we propose to study the elastic scattering of the weakly bound projectiles {sup 6,7}Li on an intermediate mass target {sup 80}Se. From the experimental results presented here, precise angular distributions at energies below, around and above the nominal Coulomb barriers of the systems were obtained. The final goal of our work is to determine the characteristic parameters of the optical potential and use them to address the question of whether the usual threshold anomaly or the breakup threshold anomaly are present or not in these systems.

  19. Bulk-barrier transistor

    NASA Astrophysics Data System (ADS)

    Mader, H.; Mueller, R.; Beinvogl, W.

    1983-10-01

    Experimental and theoretical results are presented on a bulk-barrier transistor (BBT). In this device the charge-carrier transportation is determined by an energy barrier, which is located inside a semiconductor. The barrier is the result of a space-charge region in a three-layered n-p-n or p-n-p structure with a very thin middle layer. The height of the energy barrier, which is adjustable by technological parameters, can be controlled by an external voltage.

  20. Measuring Energy Differences by BEC Interferometry on a Chip

    SciTech Connect

    Baumgaertner, Florian; Sewell, R. J.; Eriksson, S.; Llorente-Garcia, I.; Dingjan, Jos; Cotter, J. P.; Hinds, E. A.

    2010-12-10

    We investigate the use of a Bose-Einstein condensate trapped on an atom chip for making interferometric measurements of small energy differences. We measure and explain the noise in the energy difference of the split condensates, which derives from statistical noise in the number difference. We also consider systematic errors. A leading effect is the variation of the rf magnetic field in the trap with distance from the wires on the chip surface. This can produce energy differences that are comparable with those due to gravity.

  1. Measuring energy differences by BEC interferometry on a chip.

    PubMed

    Baumgärtner, Florian; Sewell, R J; Eriksson, S; Llorente-Garcia, I; Dingjan, Jos; Cotter, J P; Hinds, E A

    2010-12-10

    We investigate the use of a Bose-Einstein condensate trapped on an atom chip for making interferometric measurements of small energy differences. We measure and explain the noise in the energy difference of the split condensates, which derives from statistical noise in the number difference. We also consider systematic errors. A leading effect is the variation of the rf magnetic field in the trap with distance from the wires on the chip surface. This can produce energy differences that are comparable with those due to gravity. PMID:21231523

  2. Westinghouse thermal barrier coatings development

    SciTech Connect

    Goedjen, J.G.; Wagner, G.

    1995-12-31

    Westinghouse, in conjunction with the Department of Energy and Oak Ridge National Laboratory, has embarked upon a program for the development of advanced thermal barrier coatings for industrial gas turbines. Development of thermal barrier coatings (TBC`s) for industrial gas turbines has relied heavily on the transfer of technology from the aerospace industry. Significant differences in the time/temperature/stress duty cycles exist between these two coating applications. Coating systems which perform well in aerospace applications may not been optimized to meet power generation performance requirements. This program will focus on development of TBC`s to meet the specific needs of power generation applications.

  3. A seven-degree-of-freedom, time-dependent quantum dynamics study on the energy efficiency in surmounting the central energy barrier of the OH + CH{sub 3} → O + CH{sub 4} reaction

    SciTech Connect

    Yan, Pengxiu; Wang, Yuping; Li, Yida; Wang, Dunyou

    2015-04-28

    A time-dependent, quantum reaction dynamics calculation with seven degrees of freedom was carried out to study the energy efficiency in surmounting the approximate center energy barrier of OH + CH{sub 3}. The calculation shows the OH vibration excitations greatly enhance the reactivity, whereas the vibrational excitations of CH{sub 3} and the rotational excitations hinder the reactivity. On the basis of equal amount of total energy, although this reaction has a slight early barrier, it is the OH vibrational energy that is the dominate force in promoting the reactivity, not the translational energy. The studies on both the forward O + CH{sub 4} and reverse OH + CH{sub 3} reactions demonstrate, for these central barrier reactions, a small change of the barrier location can significantly change the energy efficacy roles on the reactivity. The calculated rate constants agree with the experimental data.

  4. Physicians' psychosocial barriers to different modes of withdrawal of life support in critical care: A qualitative study in Japan.

    PubMed

    Aita, Kaoruko; Kai, Ichiro

    2010-02-01

    Despite a number of guidelines issued in Anglo-American countries over the past few decades for forgoing treatment stating that there is no ethically relevant difference between withholding and withdrawing life-sustaining treatments (LST), it is recognized that many healthcare professionals in Japan as well as some of their western counterparts do not agree with this statement. This research was conducted to investigate the barriers that prevent physicians from withdrawing specific LST in critical care settings, focusing mainly on the modes of withdrawal of LST, in what the authors believe was the first study of its kind anywhere in the world. In 2006-2007, in-depth, face-to-face, semistructured interviews were conducted with 35 physicians working at emergency and critical care facilities across Japan. We elicited their experiences, attitudes, and perceptions regarding withdrawal of mechanical ventilation and other LST. The process of data analysis followed the grounded theory approach. We found that the psychosocial resistance of physicians to withdrawal of artificial devices varied according to the modes of withdrawal, showing a strong resistance to withdrawal of mechanical ventilation that requires physicians to halt the treatment when continuation of its mechanical operation is possible. However, there was little resistance to the withdrawal of percutaneous cardiopulmonary support and artificial liver support when their continuation was mechanically or physiologically impossible. The physicians shared a desire for a "soft landing" of the patient, that is, a slow and gradual death without drastic and immediate changes, which serves the psychosocial needs of the people surrounding the patient. For that purpose, vasopressors were often withheld and withdrawn. The findings suggest what the Japanese physicians avoid is not what they call a life-shortening act but an act that would not lead to a soft landing, or a slow death that looks 'natural' in the eyes of those

  5. Through-thickness determination of phase composition and residual stresses in thermall barrier coatings using high- energy x-rays.

    SciTech Connect

    Weyant, , C. M.; Almer, J. D.; Faber, K. T.; Stony Brook Univ.

    2009-01-01

    High-energy X-rays were used to determine the local phase composition and residual stresses through the thickness of as-sprayed and heat-treated plasma-sprayed thermal barrier coatings consisting of a NiCoCrAlY bond coat and an yttria-stabilized zirconia (YSZ) topcoat produced with through-thickness segmentation cracks. The as-sprayed residual stresses reflected the combined influence of quenching stresses from the plasma spray process, thermal expansion mismatch between the topcoat, bond coat and substrate, and stress relief from the segmentation cracks. Heat treatments led to the formation of a thermally grown oxide (TGO) which was in compression in the plane, as well as relief of quenching stresses and development of a stress gradient in the YSZ topcoat. The high-energy X-ray technique used in this study revealed the effects that TGO and segmentation cracks have on the in-plane stress state of the entire coating.

  6. Hindrance of heavy-ion fusion at extreme sub-barrier energies in open-shell colliding systems

    NASA Astrophysics Data System (ADS)

    Jiang, C. L.; Rehm, K. E.; Esbensen, H.; Janssens, R. V.; Back, B. B.; Davids, C. N.; Greene, J. P.; Henderson, D. J.; Lister, C. J.; Pardo, R. C.; Pennington, T.; Peterson, D.; Seweryniak, D.; Shumard, B.; Sinha, S.; Tang, X. D.; Tanihata, I.; Zhu, S.; Collon, P.; Kurtz, S.; Paul, M.

    2005-04-01

    The excitation function for the fusion-evaporation reaction 64Ni+100Mo has been measured down to a cross section of ˜5 nb. Extensive coupled-channels calculations have been performed, which cannot reproduce the steep falloff of the excitation function at extreme sub-barrier energies. Thus, this system exhibits a hindrance for fusion, a phenomenon that has been discovered only recently. In the S-factor representation introduced to quantify the hindrance, a maximum is observed at Es=120.6MeV, which corresponds to 90% of the reference energy Erefs, a value expected from systematics of closed-shell systems. A systematic analysis of Ni-induced fusion reactions leading to compound nuclei with mass A=100-200 is presented in order to explore a possible dependence of fusion hindrance on nuclear structure.

  7. Reactions with Weakly Bound Nuclei, at near Barrier Energies, and the Breakup and Transfer Influences on the Fusion and Elastic Scattering

    NASA Astrophysics Data System (ADS)

    Gomes, P. R. S.; Lubian, J.; Canto, L. F.; Otomar, D. R.; Junior, D. R. Mendes; de Faria, P. N.; Linares, R.; Sigaud, L.; Rangel, J.; Ferreira, J. L.; Ferioli, E.; Paes, B.; Cardozo, E. N.; Cortes, M. R.; Ermamatov, M. J.; Lotti, P.; Hussein, M. S.

    2016-03-01

    We present a brief review of the reaction mechanisms involved in collisions of weakly bound projectiles with tightly bound targets, at near-barrier energies. We discuss systematic behaviors of the data, with emphasis in fusion, breakup, nucleon transfer and elastic scattering. The dependence of the breakup cross section on the charge and mass of the target is discussed, and the influence of the breakup channel on complete fusion is investigated. For this purpose, we compare reduced fusion cross sections with a benchmark universal curve. The behaviors observed in the comparisons are explained in terms of polarization potentials and of nucleon transfer followed by breakup. The influence of the breakup process on elastic scattering is also discussed. Some apparent contradictions between results of different authors are explained and some perspectives of the field are presented.

  8. Revealing highly unbalanced energy barriers in the extension and contraction of the muscle-like motion of a [c2]daisy chain.

    PubMed

    Zhao, Yan-Ling; Zhang, Rui-Qin; Minot, Christian; Hermann, Klaus; Van Hove, Michel A

    2015-07-28

    Nanoscale muscle-like materials have aroused great interest as they may provide controllable mechanical operations by artificial actuations. Molecular designs to achieve the desired motion at the macroscopic scale in experiments require atomic level understanding. By systematic quantum chemical and molecular dynamics calculations we reveal that the length change is not only due to the linear telescoping from the dibenzo[24]crown-8 recognition at two docking stations but also the folding/unfolding of two bulky stoppers. The extension and contraction processes of a [c2]daisy chain under acidic vs. basic conditions are exothermic but need to cross very different energy barriers, being at least double the height under acidic compared to basic conditions, hindering balanced cyclic motions at moderate excitation. Our result suggests that to realize the desired muscle-like motion one should adopt sufficiently high external excitation, using for example reasonably high temperature and further optimizing the solution used. PMID:26096825

  9. Diffusion barriers

    NASA Technical Reports Server (NTRS)

    Nicolet, M. A.

    1983-01-01

    The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

  10. Republic of Korea Reduction of Financing Barriers for Energy Savings Performance Contracts

    SciTech Connect

    Howard, D. L.

    2005-11-01

    This paper discusses the findings developed for strengthening the role of performance contracting in improving energy efficiency in the Republic of Korea. The U.S. Environmental Protection Agency (EPA) sponsored development of this paper by the National Renewable Energy Laboratory (NREL), as a part of the Korean-U.S. Climate Technology Partnerships (CTP) program. The results and recommendations outlined in this paper together with other efforts are designed to assist other countries striving to improve their efficient use of energy.

  11. High-energy electron-energy spectra of atoms undergoing tunneling and barrier-suppression ionization by superintense linearly polarized laser radiation

    SciTech Connect

    Krainov, V.P.; Sofronov, A.V.

    2004-01-01

    The high-energy electron-energy spectra of atoms and atomic ions undergoing direct tunneling or barrier-suppression ionization by superintense linearly polarized femtosecond laser pulse are derived. The Landau-Dykhne adiabatic approximation is used. The new result is the simple analytic expression for the electron momentum spectrum along the polarization axis and along the other directions in the case of the relativistic quiver electron energies. The contribution from the direct tunneling ionization exceeds the contribution from the ionization occurring in the rescattering processes. The energy spectrum is independent of the laser frequency and of the nonrelativistic ionization potential of the atom (atomic ion) considered. The conclusions have been made that (1) the drift electron energy along the polarization axis is much greater than in other directions. (2) the energy distribution depends on the sign of the electron drift momentum along the propagation of laser radiation, and (3) the electron drift energy is the nonrelativistic quantity even when the quiver electron energy has high ultrarelativistic values.

  12. Additive effects on the energy barrier for synaptic vesicle fusion cause supralinear effects on the vesicle fusion rate

    PubMed Central

    Schotten, Sebastiaan; Meijer, Marieke; Walter, Alexander Matthias; Huson, Vincent; Mamer, Lauren; Kalogreades, Lawrence; ter Veer, Mirelle; Ruiter, Marvin; Brose, Nils; Rosenmund, Christian

    2015-01-01

    The energy required to fuse synaptic vesicles with the plasma membrane (‘activation energy’) is considered a major determinant in synaptic efficacy. From reaction rate theory, we predict that a class of modulations exists, which utilize linear modulation of the energy barrier for fusion to achieve supralinear effects on the fusion rate. To test this prediction experimentally, we developed a method to assess the number of releasable vesicles, rate constants for vesicle priming, unpriming, and fusion, and the activation energy for fusion by fitting a vesicle state model to synaptic responses induced by hypertonic solutions. We show that complexinI/II deficiency or phorbol ester stimulation indeed affects responses to hypertonic solution in a supralinear manner. An additive vs multiplicative relationship between activation energy and fusion rate provides a novel explanation for previously observed non-linear effects of genetic/pharmacological perturbations on synaptic transmission and a novel interpretation of the cooperative nature of Ca2+-dependent release. DOI: http://dx.doi.org/10.7554/eLife.05531.001 PMID:25871846

  13. Nucleon-nucleon correlations in heavy ion transfer reactions: Recent investigations at energies far below the Coulomb barrier

    SciTech Connect

    Corradi, Lorenzo

    2015-10-15

    Excitation functions of one- and two-neutron transfer channels have been measured for the {sup 96}Zr+{sup 40}Ca and {sup 116}Sn+{sup 60}Ni systems at bombarding energies ranging from the Coulomb barrier to ∼25% below. Target-like recoils have been identified in A, Z and velocity with the large solid angle magnetic spectrometer PRISMA. The experimental transfer probabilities have been compared, in absolute values and in slope, with semiclassical microscopic calculations which incorporate nucleon-nucleon pairing correlations. For the first time in a heavy ion collision, one was able to provide a consistent description of one and two neutron transfer reactions by incorporating, in the reaction mechanism, all known structure information of entrance and exit channels nuclei. In particular, there is no need to introduce any enhancement factor for the description of two neutron transfer, of course very important are the correlations induced by the pairing interaction.

  14. Total and partial capture cross sections in reactions with deformed nuclei at energies near and below the Coulomb barrier

    SciTech Connect

    Kuzyakin, R. A. Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.

    2013-06-15

    Within the quantum diffusion approach, the capture of a projectile nucleus by a target nucleus is studied at bombarding energies above and below the Coulomb barrier. The effects of deformation of interacting nuclei and neutron transfer between them on the total and partial capture cross sections and the mean angular momentum of the captured system are studied. The results obtained for the {sup 16}O + {sup 112}Cd, {sup 152}Sm, and {sup 184}W; {sup 19}F +{sup 175}Lu; {sup 28}Si +{sup 94,100}Mo and {sup 154}Sm; {sup 40}Ca +{sup 96}Zr; {sup 48}Ca+ {sup 90}Zr; and {sup 64}Ni +{sup 58,64}Ni, {sup 92,96}Zr, and {sup 100}Mo reactions are in good agreement with available experimental data.

  15. Total and partial capture cross sections in reactions with deformed nuclei at energies near and below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Kuzyakin, R. A.; Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.

    2013-06-01

    Within the quantum diffusion approach, the capture of a projectile nucleus by a target nucleus is studied at bombarding energies above and below the Coulomb barrier. The effects of deformation of interacting nuclei and neutron transfer between them on the total and partial capture cross sections and the mean angular momentum of the captured system are studied. The results obtained for the 16O + 112Cd, 152Sm, and 184W; 19F +175Lu; 28Si +94,100Mo and 154Sm; 40Ca +96Zr; 48Ca+ 90Zr; and 64Ni +58,64Ni, 92,96Zr, and 100Mo reactions are in good agreement with available experimental data.

  16. Energy Efficiency of Biogas Produced from Different Biomass Sources

    NASA Astrophysics Data System (ADS)

    Begum, Shahida; Nazri, A. H.

    2013-06-01

    Malaysia has different sources of biomass like palm oil waste, agricultural waste, cow dung, sewage waste and landfill sites, which can be used to produce biogas and as a source of energy. Depending on the type of biomass, the biogas produced can have different calorific value. At the same time the energy, being used to produce biogas is dependent on transportation distance, means of transportation, conversion techniques and for handling of raw materials and digested residues. An energy systems analysis approach based on literature is applied to calculate the energy efficiency of biogas produced from biomass. Basically, the methodology is comprised of collecting data, proposing locations and estimating the energy input needed to produce biogas and output obtained from the generated biogas. The study showed that palm oil and municipal solid waste is two potential sources of biomass. The energy efficiency of biogas produced from palm oil residues and municipal solid wastes is 1.70 and 3.33 respectively. Municipal solid wastes have the higher energy efficiency due to less transportation distance and electricity consumption. Despite the inherent uncertainties in the calculations, it can be concluded that the energy potential to use biomass for biogas production is a promising alternative.

  17. Influence of layer type and order on barrier properties of multilayer PECVD barrier coatings

    NASA Astrophysics Data System (ADS)

    Bahroun, K.; Behm, H.; Mitschker, F.; Awakowicz, P.; Dahlmann, R.; Hopmann, Ch

    2014-01-01

    Due to their macromolecular structure, plastics are limited in their scope of application whenever high barrier functionality against oxygen and water vapour permeation is required. One solution is the deposition of thin silicon oxide coatings in plasma-enhanced chemical vapour deposition (PECVD) processes. A way to improve performance of barrier coatings is the use of multilayer structures built from dyad layers, which combine an inorganic barrier layer and an organic intermediate layer. In order to investigate the influence of type and number of dyads on the barrier performance of coated 23 µm PET films, different dyad setups are chosen. The setups include SiOCH interlayers and SiOx-barrier layers deposited using the precursor hexamethyldisiloxane (HMDSO). A single reactor setup driven in pulsed microwave plasma (MW) mode as well as capacitively coupled plasma (CCP) mode is chosen. In this paper the effects of a variation in intermediate layer recipe and stacking order using dyad setups on the oxygen barrier properties of multilayer coatings are discussed with regard to the chemical structure, morphology and activation energy of the permeation process. Changes in surface nano-morphology of intermediate layers have a strong impact on the barrier properties of subsequent glass-like coatings. Even a complete failure of the barrier is observed. Therefore, when depositing multilayer barrier coatings, stacking order has to be considered.

  18. Comparison of five different defibrillators using recommended energy protocols.

    PubMed

    Zelinka, M; Buić, D; Zelinka, I

    2007-09-01

    Biphasic defibrillators represent a great step ahead in defibrillation. The manufacturers claim that biphasic defibrillators are able to compensate for differences in transthoracic impedance. That should mean that all patients should be defibrillated with approximately the same amount of current, regardless of their transthoracic impedance. We assessed one monophasic and four biphasic defibrillators. The defibrillators were discharged into resistive loads of 50, 90 and 130 Omega, simulating transthoracic impedance. For each waveform we used energy protocols recommended by the manufacturers and guidelines 2005. Waveforms were observed with on a digitising oscilloscope on a current sensing resistor. We compared the electrical properties of different waveforms and two defibrillators with the same type of waveform. The influence of different impedance on shape, duration and amplitude of current flow were also observed for each waveform. Measurements showed a significant difference in current flow at different impedance loads. At low impedance the mean current is well above expectations for all the defibrillators studied and at high impedance load we observed a big reduction of current amplitude. We can conclude that the compensating mechanisms of biphasic defibrillators are, from electrical point of view, negligible. From the laws of physics it is practically impossible to keep same level of current at given time with same energy at higher impedance. That is why we should reconsider the use of different energy equivalents between patients with different transthoracic impedance and not between different defibrillation impulses. PMID:17466431

  19. Paths and ionization losses of proton energy in different substances

    SciTech Connect

    Vasilovskiy, I.M.; Karpov, I.I.; Petrukhin, V.I.; Prokoshkin, Yu.D.

    1986-02-14

    Ionization energy losses of charged particles in a substance are described by the well-known Bethe-Bloch formula. However, the magnitudes of the ionization potentials in region of low proton energies (E < 100 MeV) for heavy elements prove to be considerably larger than those at high energies. Thus, studies of ionization losses in the region of high energies are the main source of the experimental information necessary for the correction of the Bethe-Bloch formula and determination of magnitudes of ionization potentials I. The purpose of this work was to measure the magnitudes of ionization losses dE/ds, paths R and ionization potentials I at a proton energy of E 670 MeV. The measurements were taken by the relative method for different substances of x, and the magnitudes of q sub x=(dE/ds) sub x/(dE/ds) sub Al and px=R sub x/R sub Al were found. Quantities qx and px weakly depend on the energy E where at E=200-600 MeV, a=(2-4).10-2 for different substances. The proton energy was determined with an accuracy of 2 MeV.

  20. Comparing the health and environmental hazards of different energy systems

    SciTech Connect

    Hamilton, L.D.

    1982-01-01

    Energy and environment can pose difficult challenges for policy makers and scientists. Assessing health impacts of different energy sources requires synthesis of research results from many different disciplines into a rational framework. Information is often scanty; qualitatively different risks, or energy systems with quite different end uses, must be put on a common footing. Risk-assessment methods reviewed include examples drawn from work of the Biomedical and Environmental Assessment Division at Brookhaven National Laboratory and elsewhere. Coal and nuclear fuel cycles are compared in respect to morbidity and mortality. Other cycles (oil, gas and renewables) are also examined. In broadening comparisons to include new technologies, one must include the impact of manufacturing the energy-producing devices as part of an expanded fuel cycle, via input-output methods. Input-output analysis allows comparisons of direct and system-wide impacts. Throughout the analysis, uncertainties must be explicitly recognized in the results, including uncertainty in validity of data and uncertainty in choice of appropriate models. No single method of comparative risk assessment is fully satisfactory; each has its limitations. By use of several methods progress has been made in understanding the relative impact of energy technologies.

  1. Energy dependence of the optical potentials for the 9Be +208Pb and 9Be +209Bi systems at near-Coulomb-barrier energies

    NASA Astrophysics Data System (ADS)

    Gómez Camacho, A.; Yu, N.; Zhang, H. Q.; Gomes, P. R. S.; Jia, H. M.; Lubian, J.; Lin, C. J.

    2015-04-01

    We analyze the energy dependence of the interacting optical potential, at near barrier energies, for two systems involving the weakly bound projectile 9Be and the heavy 208Pb and 209Bi targets, by the simultaneous fit of elastic scattering angular distributions and fusion excitation functions. The approach used consists of dividing the optical potential into two parts. A short-range potential VF+i WF that is responsible for fusion, and a superficial potential VDR+i WDR for direct reactions. It is found, for both systems studied, that the fusion imaginary potential WF presents the usual threshold anomaly (TA) observed in tightly bound systems, whereas the direct reaction imaginary potential WDR shows a breakup threshold anomaly (BTA) behavior. Both potentials satisfy the dispersion relation. The direct reaction polarization potential predominates over the fusion potential and so a net overall behavior is found to follow the BTA phenomenon.

  2. Elastic scattering for the system {sup 6}Li+p at near barrier energies with MAGNEX

    SciTech Connect

    Soukeras, V.; Pakou, A.; Sgouros, O.; Cappuzzello, F.; Bondi, M.; Nicolosi, D.; Acosta, L.; Marquinez-Duran, G.; Martel, I.; Agodi, C.; Carbone, D.; Cavallaro, M.; Cunsolo, A.; Di Pietro, A.; Fernández-García, J. P.; Figuera, P.; Fisichella, M.; Alamanos, N.; De Napoli, M.; Foti, A.; and others

    2015-02-24

    Elastic scattering measurements have been performed for the {sup 6}Li+p system in inverse kinematics at the energies of 16, 20, 25 and 29 MeV. The heavy ejectile was detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS) in Catania, in the angular range between ∼2{sup 0} and 12{sup 0} in the laboratory system, giving us the possibility to span almost a full angular range in the center of mass system. Results will be presented and discussed for one of the energies.

  3. High Penetration of Renewable Energy in the Transportation Sector: Scenarios, Barriers, and Enablers; Preprint

    SciTech Connect

    Vimmerstedt, L.; Brown, A.; Heath, G.; Mai, T.; Ruth, M.; Melaina, M.; Simpkins, T.; Steward, D.; Warner, E.; Bertram, K.; Plotkin, S.; Patel, D.; Stephens, T.; Vyas, A.

    2012-06-01

    Transportation accounts for 71% of U.S. petroleum use and 33% of its greenhouse gases emissions. Pathways toward reduced greenhouse gas emissions and petroleum dependence in the transportation sector have been analyzed in considerable detail, but with some limitations. To add to this knowledge, the U.S. Department of Energy has launched a study focused on underexplored greenhouse-gas-abatement and oil-savings opportunities related to transportation. This Transportation Energy Futures study analyzes specific issues and associated key questions to strengthen the existing knowledge base and help cultivate partnerships among federal agencies, state and local governments, and industry.

  4. Constraining the Symmetry Energy:. a Journey in the Isospin Physics from Coulomb Barrier to Deconfinement

    NASA Astrophysics Data System (ADS)

    di Toro, M.; Colonna, M.; Greco, V.; Ferini, G.; Rizzo, C.; Rizzo, J.; Baran, V.; Gaitanos, T.; Prassa, V.; Wolter, H. H.; Zielinska-Pfabe, M.

    Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. In this work we present a selection of reaction observables in dissipative collisions particularly sensitive to the isovector part of the interaction, i.e.to the symmetry term of the nuclear Equation of State (EoS). At low energies the behavior of the symmetry energy around saturation influences dissipation and fragment production mechanisms. We will first discuss the recently observed Dynamical Dipole Radiation, due to a collective neutron-proton oscillation during the charge equilibration in fusion and deep-inelastic collisions. Important Iso - EOS are stressed. Reactions induced by unstable 132Sn beams appear to be very promising tools to test the sub-saturation Isovector EoS. New Isospin sensitive observables are also presented for deep-inelastic, fragmentation collisions and Isospin equilibration measurements (Imbalance Ratios). The high density symmetry term can be derived from isospin effects on heavy ion reactions at relativistic energies (few AGeV range), that can even allow a "direct" study of the covariant structure of the isovector interaction in the hadron medium. Rather sensitive observables are proposed from collective flows and from pion/kaon production. The possibility of the transition to a mixed hadron-quark phase, at high baryon and isospin density, is finally suggested. Some signatures could come from an expected "neutron trapping" effect. The importance of studying violent collisions with radioactive beams from low to relativistic energies is finally stressed.

  5. The role of couplings in nuclear rainbow formation at energies far above the barrier

    SciTech Connect

    Pereira, D.; Linares, R.; and others

    2012-10-20

    A study of the {sup 16}O+{sup 28}Si elastic and inelastic scattering is presented in the framework of Coupled Channel theory. The Sao Paulo Potential is used in the angular distribution calculations and compared with the existing data at 75 MeV bombarding energy. A nuclear rainbow pattern is predicted and becomes more clear above 100 MeV.

  6. Edge energy transport barrier and turbulence in the I-mode regime on Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Hubbard, A. E.; Whyte, D. G.; Churchill, R. M.; Cziegler, I.; Dominguez, A.; Golfinopoulos, T.; Hughes, J. W.; Rice, J. E.; Bespamyatnov, I.; Greenwald, M. J.; Howard, N.; Lipschultz, B.; Marmar, E. S.; Reinke, M. L.; Rowan, W. L.; Terry, J. L.

    2011-05-01

    We report extended studies of the I-mode regime [Whyte et al., Nucl. Fusion 50, 105005 (2010)] obtained in the Alcator C-Mod tokamak [Marmar et al., Fusion Sci. Technol. 51(3), 3261 (2007)]. This regime, usually accessed with unfavorable ion B × ∇B drift, features an edge thermal transport barrier without a strong particle transport barrier. Steady I-modes have now been obtained with favorable B × ∇B drift, by using specific plasma shapes, as well as with unfavorable drift over a wider range of shapes and plasma parameters. With favorable drift, power thresholds are close to the standard scaling for L-H transitions, while with unfavorable drift they are ˜ 1.5-3 times higher, increasing with Ip. Global energy confinement in both drift configurations is comparable to H-mode scalings, while density profiles and impurity confinement are close to those in L-mode. Transport analysis of the edge region shows a decrease in edge χeff, by typically a factor of 3, between L- and I-mode. The decrease correlates with a drop in mid-frequency fluctuations (f ˜ 50-150 kHz) observed on both density and magnetics diagnostics. Edge fluctuations at higher frequencies often increase above L-mode levels, peaking at f ˜ 250 kHz. This weakly coherent mode is clearest and has narrowest width (Δf/f ˜ 0.45) at low q95 and high Tped, up to 1 keV. The Er well in I-mode is intermediate between L- and H-mode and is dominated by the diamagnetic contribution in the impurity radial force balance, without the Vpol shear typical of H-modes.

  7. Fusion cross section of 12C+13C at sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Zhang, N. T.; Tang, X. D.; Chen, H.; Chesneanu, D.; Straticiuc, M.; Trache, L.; Burducea, I.; Li, K. A.; Li, Y. J.; Ghita, D. G.; Margineanu, R.; Pantelica, A.; Gomoiu, C.

    2016-02-01

    In the recent work at Notre Dame, correlations between three carbon isotope fusion systems have been studied and it is found that the fusion cross sections of 12C+13Cand 13C+13C provide an upper limit on the fusion cross section of the astrophysically important 12C+12C reaction.The aim of this work is to continue such research by measuring the fusion cross section of the 12C+13C reaction to lower energies. In this experiment, the off-line activity measurement was performed in the ultra-low background laboratory 12C+13C and the fusion cross section for has been determined in the energy range of Ec.m. =2.5-6.8 MeV. Comparison between this work and several models is also presented.

  8. Angular anisotropy of photofission of even-even nuclei at above-barrier energies

    SciTech Connect

    Rudnikov, V.E.; Smirenkin, G.N.; Soldatov, A.S.; Juhasz, S.

    1988-09-01

    Results of measurements are presented for angular distributions of photofission fragments of /sup 232/Th and /sup 234//sup ,//sup 236//sup ,//sup 238/U by bremsstrahlung ..gamma.. rays in the maximum energy range of E/sub max/ = 6--10 MeV. The observed angular anisotropy of photofission is discussed as a function of E/sub max/ and the nucleon composition of the nucleus.

  9. Influence of the intercalated cations on the surface energy of montmorillonites: consequences for the morphology and gas barrier properties of polyethylene/montmorillonites nanocomposites.

    PubMed

    Picard, E; Gauthier, H; Gérard, J-F; Espuche, E

    2007-03-15

    Organically modified montmorillonites obtained by cation exchange from the same natural layered silicate were studied. The surface properties of the pristine and a series of organically modified clays were determined by inverse gas chromatography and the water adsorption mechanisms were studied by a gravimetric technique coupled with a microcalorimeter. A significant increase of the specific surface area, a decrease of the water adsorption, and a decrease of the dispersive component of the surface energy were observed when the sodium cations of the natural montmorillonite were exchanged for a quaternary ammonium. Slighter differences in surface properties were observed, on the other hand, between the different types of organically modified montmorillonites. Indeed, similar dispersive components of the surface energy were determined on the organoclays. Nevertheless, the specific surface area increased in the range 48-80 m(2)/g with increasing d-spacing values and the presence of specific groups attached to the quaternary ammonium, such as phenyl rings or hydroxyl groups, led to some specific behaviors, i.e., a more pronounced base character and a higher water adsorption at high activity, respectively. Differences in interlayer cation chain organization, denoted as crystallinity, were also observed as a function of the nature of the chains borne by the quaternary ammonium. In a later step, polyethylene-based nanocomposites were prepared with those organically modified montmorillonites. The clay dispersion and the barrier properties of the nanocomposites were discussed as a function of the montmorillonite characteristics and of the matrix/montmorillonite interactions expected from surface energy characterization. PMID:17222420

  10. [The morphological features of stab-and-slash skin wounds inflicted by the blades with differently shaped tips through the multilayer barrier].

    PubMed

    Sarkisian, B A; Fedorov, S Iu

    2014-01-01

    The objective of the present work was to study the shape, size, and morphological features of stab-and-slash skin wounds inflicted by the blades with differently shaped tips taking into consideration the direction of stab through multiple garments (1, 2, and 3 layers). The injuries were inflicted by kitchen knives having the blades of practically identical length and width but differently shaped tips. A total of 480 skin wounds and 720 damaged cloth specimens were available for the examination. The analysis of the data obtained revealed differences between morphological features of the skin wounds. Injuries to the skin unprotected by the cloths had different shape and length of the edge and end portions depending on the shape of the blade tip and the direction of the stab. The length of all wound inflicted through the barrier decreased as the number of layers increased. The wounds had the linear shape, their contusion collar and flattened area became narrower; the shape of the back edges of the wounds inflicted through a three-layer barrier altered. It is concluded that the result of the present study may be useful for the improvement of diagnostics of stab-and-slash skin wounds. PMID:25269167

  11. /sup 64/Ni +/sup 92/Zr fission yields at energies close to the Coulomb barrier

    SciTech Connect

    Wolfs, F.L.H.; Janssens, R.V.F.; Holzmann, R.; Khoo, T.L.; Ma, W.C.; Sanders, S.J.

    1989-03-01

    Fission yields for the /sup 64/Ni+/sup 92/Zr reaction at laboratory energies between 240 and 300 MeV have been measured. ''Elastic scattering'' angular distributions were also obtained and used to deduce the generalized total reaction cross sections. The competition between fission and light-particle evaporation from the compound nucleus is well reproduced by statistical-model calculations. However, the calculated neutron multiplicities for this reaction are larger than those previously measured. Possible reasons for this discrepancy are discussed.

  12. Fission Barriers and Neutron Gas in Compound Superheavy Nuclei

    SciTech Connect

    Pei, Junchen; Nazarewicz, W.; Sheikh, J. A.; Kerman, A. K.

    2010-01-01

    Fission and neutron emission are the principal cooling mechanisms of the compound superheavy nuclei. In the framework of the Finite-Temperature Hartree-Fock-Bogoliubov method, the fission barriers and neutron gas have been studied in the excited superheavy systems. Very different energy dependence of fission barriers has been found for ^{278}112 and ^{292}114. On the other hand, the energy dependence of thermal neutron gas has been found to be almost identical for both systems.

  13. Examination of the different roles of neutron transfer in the sub-barrier fusion reactions 32S+Zr,9694 and 40Ca +Zr,9694

    NASA Astrophysics Data System (ADS)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.

    2015-01-01

    The sub-barrier capture (fusion) reactions 32S+90,94,96Zr, 36S+Zr,9690 , 40Ca +90,94,96Zr, and 48Ca +Zr,9690 with positive and negative Q values for neutron transfer are studied with the quantum diffusion approach and the universal fusion function representation. For these systems, the s -wave capture probabilities are extracted from the experimental excitation functions and are also analyzed. Different effects of the positive Qx n-value neutron transfer in the fusion enhancement are revealed in the relatively close reactions 32S+Zr,9694 and 40Ca +Zr,9694 .

  14. The energy barrier in singlet fission can be overcome through coherent coupling and entropic gain

    NASA Astrophysics Data System (ADS)

    Chan, Wai-Lun; Ligges, Manuel; Zhu, X.-Y.

    2012-10-01

    One strategy to improve solar-cell efficiency is to generate two excited electrons from just one photon through singlet fission, which is the conversion of a singlet (S1) into two triplet (T1) excitons. For efficient singlet fission it is believed that the cumulative energy of the triplet states should be no more than that of S1. However, molecular analogues that satisfy this energetic requirement do not show appreciable singlet fission, whereas crystalline tetracene displays endothermic singlet fission with near-unity quantum yield. Here we probe singlet fission in tetracene by directly following the intermediate multiexciton (ME) state. The ME state is isoenergetic with 2 × T1, but fission is not activated thermally. Rather, an S1 ⇔ ME superposition formed through a quantum-coherent process allows access to the higher-energy ME. We attribute entropic gain in crystalline tetracene as the driving force for the subsequent decay of S1 ⇔ ME into 2 × T1, which leads to a high singlet-fission yield.

  15. Experimental evidence for a fusion enhancement in 19O+12C at near barrier energies

    NASA Astrophysics Data System (ADS)

    Singh, Varinderjit; Steinbach, T. K.; Vadas, J.; Wiggins, B. B.; Hudan, S.; Desouza, R. T.; Baby, L. T.; Tripathi, V.; Kuvin, S. A.; Wiedenhover, I.; Umar, A. S.; Oberacker, V. E.

    2016-03-01

    Fusion of neutron-rich light nuclei in the outer crust of an accreting neutron star has been proposed as responsible for triggering X-ray super-bursts. The underlying hypothesis in this proposition is that the fusion of neutron-rich nuclei is enhanced as compared to stable nuclei. To investigate this hypothesis, an experiment has been performed to measure the fusion excitation function for 18O and 19O nuclei incident on a 12C target. A beam of 19O was produced by the 18O(d,p) reaction at Florida State University and separated using the RESOLUT mass spectrometer. The resulting 19O beam bombarded a 100 μg/cm2 12C target at an intensity of 2-4 x 104p/s. Evaporation residues resulting from the de-excitation of the fusion product were distinguished by measuring their energy and time-of-flight. Evaporation residues were detected with high efficiency by measuring them in the angular range 4.4° <=θlab <= 11.7°. The fusion cross-section has been measured down to 170 mb level. As compared to 18O+12C the fusion cross-section for 19O+12C is enhanced by approximately a factor of 3 times at the lowest energy measured. The measured excitation function will be compared with theoretical calculations. Supported by the US DOE under Grant No. DEFG02-88ER-40404.

  16. Energy radiated by seismic events of different scales and geneses

    NASA Astrophysics Data System (ADS)

    Kocharyan, G. G.; Ivanchenko, G. N.; Kishkina, S. B.

    2016-07-01

    Extensive data comprising about 1500 seismic events with the moment magnitudes M W from-3.5 to 9.2 have been analyzed for identifying the implications of the event size, the type of faulting in the source, and tectonic situations for the efficiency of the radiation. It is shown that there are several hierarchy levels with different patterns of scaling relationships describing the changes in the parameters of seismic events with the event size. This is due to the specificity of the hierarchy in the macroscopic characteristics of the rock mass. The size and mechanism of the earthquake determine the general trends in the variations of its radiation efficiency. The role of the macroscopic parameter controlling the efficiency of a seismic source is played by the stiffness of a fault or a fracture. The scaling relationship of this parameter determines several hierarchical levels within which the changes in the characteristics of the earthquakes follow the different laws. The huge scatter in the values of the scaled energy (the ratio of the radiated seismic energy to the seismic moment, energy-to-moment ratio) about the average requires additional study. Quite probably, the value of the scaled seismic energy is determined by the mesostructure and physicomechanical characteristics of the fault's core. Small variations in these factors may lead to drastic changes in the stress drop amplitude and in the rupture propagation velocity up to the emergence of different regimes of deformation.

  17. Integrated geological-engineering model of Patrick Draw field and examples of similarities and differences among various shoreline barrier systems

    SciTech Connect

    Schatzinger, R.A.; Szpakiewicz, M.J.; Jackson, S.R.; Chang, M.M.; Sharma, B.; Tham, M.K.; Cheng, A.M.

    1992-04-01

    The Reservoir Assessment and Characterization Research Program at NIPER employs an interdisciplinary approach that focuses on the high priority reservoir class of shoreline barrier deposits to: (1) determine the problems specific to this class of reservoirs by identifying the reservoir heterogeneities that influence the movement and trapping of fluids; and (2) develop methods to characterize effectively this class of reservoirs to predict residual oil saturation (ROS) on interwell scales and improve prediction of the flow patterns of injected and produced fluids. Accurate descriptions of the spatial distribution of critical reservoir parameters (e.g., permeability, porosity, pore geometry, mineralogy, and oil saturation) are essential for designing and implementing processes to improve sweep efficiency and thereby increase oil recovery. The methodologies and models developed in this program will, in the near- to mid-term, assist producers in the implementation of effective reservoir management strategies such as location of infill wells and selection of optimum enhanced oil recovery methods to maximize oil production from their reservoirs.

  18. Gender Differences in Insulin Resistance, Body Composition, and Energy Balance

    PubMed Central

    Geer, Eliza B.; Shen, Wei

    2010-01-01

    Background Men and women differ substantially in regard to degrees of insulin resistance, body composition, and energy balance. Adipose tissue distribution, in particular the presence of elevated visceral and hepatic adiposity, plays a central role in the development of insulin resistance and obesity-related complications. Objective This review summarizes published data on gender differences in insulin resistance, body composition, and energy balance, to provide insight into novel gender-specific avenues of research as well as gender-tailored treatments of insulin resistance, visceral adiposity, and obesity. Methods English-language articles were identified from searches of the PubMed database through November 2008, and by reviewing the references cited in these reports. Searches included combinations of the following terms: gender, sex, insulin resistance, body composition, energy balance, and hepatic adipose tissue. Results For a given body mass index, men were reported to have more lean mass, women to have higher adiposity. Men were also found to have more visceral and hepatic adipose tissue, whereas women had more peripheral or subcutaneous adipose tissue. These differences, as well as differences in sex hormones and adipokines, may contribute to a more insulin-sensitive environment in women than in men. When normalized to kilograms of lean body mass, men and women had similar resting energy expenditure, but physical energy expenditure was more closely related to percent body fat in men than in women. Conclusion Greater amounts of visceral and hepatic adipose tissue, in conjunction with the lack of a possible protective effect of estrogen, may be related to higher insulin resistance in men compared with women. PMID:19318219

  19. Differences between the 1992 and 1993 CABO Model Energy Codes

    SciTech Connect

    Conover, D.R.; Lucas, R.G.

    1995-01-01

    This report is one in a series of documents describing research activities in support of the US Department of Energy (DOE) Building Energy Standards Program. The Pacific Northwest Laboratory (PNL) leads the program for DOE. The goal of the Program is to develop and encourage the implementation Of Performance standards to achieve the maximum practicable energy efficiency in the design of new buildings. The program approach to meeting the goal is to initiate and manage individual research and standards and guidelines development efforts that are planned and conducted in cooperation with representatives from throughout the buildings community. Projects under way involve practicing architects and engineers, Professional societies and code organizations, industry representatives, and researchers from the private sector and national laboratories. Research results and technical justifications for standards criteria are provided to standards development and model code organizations and to Federal, State, and local jurisdictions as a basis to update their codes and standards. This effort helps to ensure that building standards incorporate the latest research results to achieve maximum energy savings in new buildings, Yet remain responsive to the needs of the affected professions, organizations, and jurisdictions. Our efforts also support the implementation, deployment, and use of energy-efficient codes and standards. This report identifies the differences between the 1992 and 1993 editions of the Council of American Building Officials, (CABO) Model Energy Code (MEC) and briefly highlights the technical and administrative impacts of these changes.

  20. Energy-Efficient Phase-Change Memory with Graphene as a Thermal Barrier.

    PubMed

    Ahn, Chiyui; Fong, Scott W; Kim, Yongsung; Lee, Seunghyun; Sood, Aditya; Neumann, Christopher M; Asheghi, Mehdi; Goodson, Kenneth E; Pop, Eric; Wong, H-S Philip

    2015-10-14

    Phase-change memory (PCM) is an important class of data storage, yet lowering the programming current of individual devices is known to be a significant challenge. Here we improve the energy-efficiency of PCM by placing a graphene layer at the interface between the phase-change material, Ge2Sb2Te5 (GST), and the bottom electrode (W) heater. Graphene-PCM (G-PCM) devices have ∼40% lower RESET current compared to control devices without the graphene. This is attributed to the graphene as an added interfacial thermal resistance which helps confine the generated heat inside the active PCM volume. The G-PCM achieves programming up to 10(5) cycles, and the graphene could further enhance the PCM endurance by limiting atomic migration or material segregation at the bottom electrode interface. PMID:26308280

  1. Multinucleon transfer study in 206Pb(18O,x ) at energies above the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Sonika, Roy, B. J.; Parmar, A.; Pal, U. K.; Kumawat, H.; Jha, V.; Pandit, S. K.; Parkar, V. V.; Ramachandran, K.; Mahata, K.; Pal, A.; Santra, S.; Mohanty, A. K.; Sekizawa, K.

    2015-08-01

    Single- and multi-nucleon transfer reactions, namely, 206Pb(18O,20O), 206Pb(18O,19O), 206Pb(18O,17O), 206Pb(18O,16O), 206Pb(18O,18N), 206Pb(18O,17N), 206Pb(18O,16N), 206Pb(18O,15N), 206Pb(18O,14N), 206Pb(18O,16C), 206Pb(18O,15C), 206Pb(18O,14C), 206Pb(18O,13C), 206Pb(18O,12C), 206Pb(18O,12B), 206Pb(18O,11B), 206Pb(18O,10B), 206Pb(18O,10Be), and 206Pb(18O,9Be), have been studied at an incident 18O energy of 139 MeV. The total kinetic energy loss (TKEL) spectrum and angular distribution of reaction products have been measured. The Q value and angle integrated cross sections are deduced. Angular distributions for the elastically scattered 18O particles are also measured. Fully microscopic time-dependent Hartree-Fock (TDHF) calculations, based on the independent single-nucleon transfer mode, have been carried out and are compared with experimental data of multinucleon transfer reactions. The TDHF calculations provide reasonable agreement with the experimental data for cases where one- and two-nucleon transfer is involved; the discrepancy is large for multinucleon transfer reactions. The effect of particle evaporation on the production cross sections has been studied. Inclusion of particle evaporation effects, though improving the results, could not reproduce the measured cross sections. Possible origins of these discrepancies are discussed.

  2. Production of unknown neutron-rich isotopes in 238U collisions at near-barrier energy

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Li, Zhuxia; Zhang, Yingxun; Wang, Ning; Li, Qingfeng; Shen, Caiwan; Wang, Yongjia; Wu, Xizhen

    2016-08-01

    The production cross sections for primary and residual fragments with charge number from Z =70 to 120 produced in the collision of 238U at 7.0 MeV/nucleon are calculated by the improved quantum molecular dynamics (ImQMD) model incorporated with the statistical evaporation model (hivap code). The calculation results predict that about 60 unknown neutron-rich isotopes from elements Ra (Z =88 ) to Db (Z =105 ) can be produced with the production cross sections above the lower bound of 10-8 mb in this reaction. And almost all of the unknown neutron-rich isotopes are emitted at the laboratory angles θlab≤60°. Two cases, i.e., the production of the unknown uranium isotopes with A ≥244 and that of rutherfordium with A ≥269 , are investigated to understand the production mechanism of unknown neutron-rich isotopes. It is found that for the former case the collision time between two uranium nuclei is shorter and the primary fragments producing the residues have smaller excitation energies of ≤30 MeV and the outgoing angles of those residues cover a range of 30°-60°. For the latter case, a longer collision time is needed for a large number of nucleons being transferred and thus it results in higher excitation energies and smaller outgoing angles of primary fragments, and eventually results in a very small production cross section for the residues of Rf with A ≥269 which have a small interval of outgoing angles of θlab=40°-50°.

  3. Vehicle barrier

    DOEpatents

    Hirsh, Robert A.

    1991-01-01

    A vehicle security barrier which can be conveniently placed across a gate opening as well as readily removed from the gate opening to allow for easy passage. The security barrier includes a barrier gate in the form of a cable/gate member in combination with laterally attached pipe sections fixed by way of the cable to the gate member and lateral, security fixed vertical pipe posts. The security barrier of the present invention provides for the use of cable restraints across gate openings to provide necessary security while at the same time allowing for quick opening and closing of the gate areas without compromising security.

  4. Ab initio study of the torsional potential energy surfaces of N2O3 and N2O4: Origin of the torsional barriers

    NASA Astrophysics Data System (ADS)

    Halpern, Arthur M.; Glendening, Eric D.

    2007-04-01

    Intrinsic reaction coordinate (IRC) torsional potentials were calculated for N2O4 and N2O3 based on optimized B3LYP/aug-cc-pVDZ geometries of the respective 90°-twisted saddle points. These potentials were refined by obtaining CCSD(T )/aug-cc-pVXZ energies [in the complete basis set (CBS) limit] of points along the IRC. A comparison is made between these ab initio potentials and an analytical form based on a two-term cosine expansion in terms of the N-N dihedral angle. The shapes of these two potential curves are in close agreement. The torsional barriers in N2O4 and N2O3 obtained from the CCSD(T)/CBS//B3LYP/aug-cc-pVDZ calculations are 2333 and 1704cm-1, respectively. For N2O4 the torsion fundamental frequency from the IRC potential is 87.06cm-1, which is in good agreement with the experimentally reported value of 81.73cm-1. However, in the case of N2O3 the torsional frequency found from the IRC potential, 144cm-1, is considerably larger than the reported experimental values 63-76cm-1. Consistent with this discrepancy, the torsional barrier obtained from several different calculations, 1417-1718cm-1, is higher than the value of 350cm-1 deduced from experimental studies. It is suggested that the assignment of the torsional mode in N2O3 should be reexamined. N2O4 and N2O3 exhibit strong hyperconjugative interactions of in-plane O lone pairs with the central N-N σ* antibond. Hyperconjugative stabilization is somewhat stronger at the planar geometries because 1,4 interactions of lone pairs on cis O atoms promote delocalization of electrons into the N-N antibond. Calculations therefore suggest that the torsional barriers in these molecules arise principally from a combination of 1,4 interactions and hyperconjugation.

  5. Free Energy Barriers for the N-Terminal Asparagine to Succinimide Conversion: Quantum Molecular Dynamics Simulations for the Fully Solvated Model.

    PubMed

    Kaliman, Ilya; Nemukhin, Alexander; Varfolomeev, Sergei

    2010-01-12

    Deamidation of asparagine residues represents one of the main routes for the post-translational modification of protein sequences. We computed the estimates of the free energy barriers for three stages of the deamidation process, deprotonation, cyclization, and deamination, of the conversion of asparagine to the succinimide intermediate within the fully solvated model with explicit water molecules. The Born-Oppenheimer molecular dynamics in the Gaussian and Plane Wave (GPW) approximation as implemented in the CP2K quantum chemistry package was utilized to sample the configurational space. By applying the metadynamics technique, the estimates of the free energy barriers were obtained for three separated stages of the reaction. In agreement with the experimental kinetic measurements, the estimated activation barriers do not exceed 21 kcal/mol. We demonstrate that the use of fully solvated models is the critical issue in theoretical studies of these reactions. We also conclude that more extensive sampling is necessary to obtain full free energy profiles and accurate barriers for the reaction stages. PMID:26614331

  6. Simultaneous escaping of explicit and hidden free energy barriers: application of the orthogonal space random walk strategy in generalized ensemble based conformational sampling.

    PubMed

    Zheng, Lianqing; Chen, Mengen; Yang, Wei

    2009-06-21

    To overcome the pseudoergodicity problem, conformational sampling can be accelerated via generalized ensemble methods, e.g., through the realization of random walks along prechosen collective variables, such as spatial order parameters, energy scaling parameters, or even system temperatures or pressures, etc. As usually observed, in generalized ensemble simulations, hidden barriers are likely to exist in the space perpendicular to the collective variable direction and these residual free energy barriers could greatly abolish the sampling efficiency. This sampling issue is particularly severe when the collective variable is defined in a low-dimension subset of the target system; then the "Hamiltonian lagging" problem, which reveals the fact that necessary structural relaxation falls behind the move of the collective variable, may be likely to occur. To overcome this problem in equilibrium conformational sampling, we adopted the orthogonal space random walk (OSRW) strategy, which was originally developed in the context of free energy simulation [L. Zheng, M. Chen, and W. Yang, Proc. Natl. Acad. Sci. U.S.A. 105, 20227 (2008)]. Thereby, generalized ensemble simulations can simultaneously escape both the explicit barriers along the collective variable direction and the hidden barriers that are strongly coupled with the collective variable move. As demonstrated in our model studies, the present OSRW based generalized ensemble treatments show improved sampling capability over the corresponding classical generalized ensemble treatments. PMID:19548709

  7. Impact of oral bisphenol A at reference doses on intestinal barrier function and sex differences after perinatal exposure in rats.

    PubMed

    Braniste, Viorica; Jouault, Aurore; Gaultier, Eric; Polizzi, Arnaud; Buisson-Brenac, Claire; Leveque, Mathilde; Martin, Pascal G; Theodorou, Vassilia; Fioramonti, Jean; Houdeau, Eric

    2010-01-01

    Bisphenol A (BPA), a chemical estrogen widely used in the food-packaging industry and baby bottles, is recovered in human fluids (0.1-10 nM). Recent studies have reported that BPA is hormonally active at low doses, emphasizing the debate of a risk for human health. Estrogen receptors are expressed in the colon, and although the major route of BPA exposure is food, the effects on gut have received no attention. We first examined the endocrine disrupting potency of BPA on colonic paracellular permeability (CPP), experimental colitis, and visceral sensitivity in ovariectomized rats orally exposed to 5 mg/kg/d BPA (i.e., the no observed adverse effect level), 50 microg/kg/d BPA (i.e., tolerable daily intake), or lower doses. BPA dose-dependently decreased basal CPP, with a half-maximal inhibitory dose of 5.2 microg/kg/d, 10-fold below the tolerable daily intake. This correlated with an increase in epithelial tight junction sealing, also observed in Caco-2 cells exposed to 10 nM BPA. When ovariectomized rats were fed with BPA at the no observed adverse effect level, the severity of colitis was reduced, whereas the same dose increased pain sensitivity to colorectal stimuli. We then examined the impact of perinatal exposure to BPA on intestinal permeability and inflammatory response in the offspring. In female rats, but not in male rats, perinatal BPA evoked a decrease of CPP in adulthood, whereas the proinflammatory response of colonic mucosa was strengthened. This study first demonstrates that the xenoestrogen BPA at reference doses influences intestinal barrier function and gut nociception. Moreover, perinatal exposure promotes the development of severe inflammation in adult female offspring only. PMID:20018722

  8. Measurement of the fusion excitation function for 19O + 12C at near barrier energies

    NASA Astrophysics Data System (ADS)

    Singh, Varinderjit; Steinbach, T. K.; Vadas, J.; Wiggins, B. B.; Hudan, S.; Desouza, R. T.; Baby, L. T.; Tripathi, V.; Kuvin, S. A.; Wiedenhover, I.

    2015-10-01

    Fusion of neutron-rich light nuclei in the outer crust of an accreting neutron star has been proposed as responsible for triggering X-ray super-bursts. The underlying hypothesis in this proposition is that the fusion of neutron-rich nuclei is enhanced as compared to stable nuclei. To investigate this hypothesis, an experiment has been performed to measure the fusion excitation function for 18O and 19O nuclei incident on a 12C target. A beam of 19O was produced by the 18O(d,p) reaction at Florida State University and separated using the RESOLUT mass spectrometer. The resulting 19O beam bombarded a 100 μg/cm2 12C target at an intensity of 2-4 × 103 p/s. Evaporation residues resulting from the de-excitation of the fusion product were distinguished by measuring their energy and time-of-flight. Using silicon detectors, micro-channel plate detectors, and an ionization chamber, evaporation residues were detected in the angular range θlab <= 23° with high efficiency. Initial experimental results including measurement of the fusion cross-section to approximately the 100 mb level will be presented. The measured excitation function will be compared to theoretical predictions. Supported by the US DOE under Grand No. DEFG02-88ER-40404.

  9. Local environment dependance of the water diffusion energy barrier onto the (101) anatase surface

    NASA Astrophysics Data System (ADS)

    Agosta, Lorenzo; Gala, Fabrizio; Zollo, Giuseppe

    2016-06-01

    The adsorption properties of TiO2 surfaces with biological environments have shown to be very important for bio-compatibility properties. Interactions of biological molecules with inorganic materials in aqueous systems, are mediated by water molecules. Hence the understanding of the possible conformations that water molecules can assume on the inorganic surfaces it is very important. Many studies concerning the structural conformations of adsorbed water molecules on rutile and anatase, the most likely exposed surface phases, show that the first layer of adsorbed water molecules play a crucial role in mediating the structural and physical properties of the upper interacting environment layers. In this contest we performed a detailed analysis of the possible conformations of the first layer of water molecules adsorbed on the (101) TiO2 surface; total energy calculations and NEB techniques, in contest of the DFT theory, has been used to study the stability and the diffusion properties as a further insight of our previous studies about this topic.

  10. Static and dynamic deformation effects in the fusion cross section of light heavy ions at sub-barrier energies

    SciTech Connect

    Hussein, M.S.; Canto, L.F.; Donangelo, R.

    1980-02-01

    The static and dynamic deformation effects on the sub-barrier fusion cross section of light heavy ions are investigated by performing a coupled channel calculation for the system /sup 12/C+/sup 16/O. It is found that dynamic effects are negligible whereas static effects could be important, and they appear to show up partly through absorption under the barrier.

  11. Heavy-element fission barriers

    SciTech Connect

    Moeller, Peter; Sierk, Arnold J.; Ichikawa, Takatoshi; Iwamoto, Akira; Bengtsson, Ragnar; Uhrenholt, Henrik; Angstromberg, Sven

    2009-06-15

    We present calculations of fission properties for heavy elements. The calculations are based on the macroscopic-microscopic finite-range liquid-drop model with a 2002 parameter set. For each nucleus we have calculated the potential energy in three different shape parametrizations: (1) for 5 009 325 different shapes in a five-dimensional deformation space given by the three-quadratic-surface parametrization, (2) for 10 850 different shapes in a three-dimensional deformation space spanned by {epsilon}{sub 2}, {epsilon}{sub 4}, and {gamma} in the Nilsson perturbed-spheroid parametrization, supplemented by a densely spaced grid in {epsilon}{sub 2}, {epsilon}{sub 3}, {epsilon}{sub 4}, and {epsilon}{sub 6} for axially symmetric deformations in the neighborhood of the ground state, and (3) an axially symmetric multipole expansion of the shape of the nuclear surface using {beta}{sub 2}, {beta}{sub 3}, {beta}{sub 4}, and {beta}{sub 6} for intermediate deformations. For a fissioning system, it is always possible to define uniquely one saddle or fission threshold on the optimum trajectory between the ground state and separated fission fragments. We present such calculated barrier heights for 1585 nuclei from Z=78 to Z=125. Traditionally, actinide barriers have been characterized in terms of a ''double-humped'' structure. Following this custom we present calculated energies of the first peak, second minimum, and second peak in the barrier for 135 actinide nuclei from Th to Es. However, for some of these nuclei which exhibit a more complex barrier structure, there is no unique way to extract a double-humped structure from the calculations. We give examples of such more complex structures, in particular the structure of the outer barrier region near {sup 232}Th and the occurrence of multiple fission modes. Because our complete results are too extensive to present in a paper of this type, our aim here is limited: (1) to fully present our model and the methods for determining the

  12. Determining photon energy absorption parameters for different soil samples.

    PubMed

    Kucuk, Nil; Tumsavas, Zeynal; Cakir, Merve

    2013-05-01

    The mass attenuation coefficients (μs) for five different soil samples were measured at 661.6, 1173.2 and 1332.5 keV photon energies. The soil samples were separately irradiated with (137)Cs and (60)Co (370 kBq) radioactive point gamma sources. The measurements were made by performing transmission experiments with a 2″ × 2″ NaI(Tl) scintillation detector, which had an energy resolution of 7% at 0.662 MeV for the gamma-rays from the decay of (137)Cs. The effective atomic numbers (Zeff) and the effective electron densities (Neff) were determined experimentally and theoretically using the obtained μs values for the soil samples. Furthermore, the Zeff and Neff values of the soil samples were computed for the total photon interaction cross-sections using theoretical data over a wide energy region ranging from 1 keV to 15 MeV. The experimental values of the soils were found to be in good agreement with the theoretical values. Sandy loam and sandy clay loam soils demonstrated poor photon energy absorption characteristics. However, clay loam and clay soils had good photon energy absorption characteristics. PMID:23179375

  13. Laser energy distribution on detector under the different incident angle

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Wang, G.; Chen, Q.; Hao, Y.; Zhang, W.; Li, H.; Ren, G.; Zhu, R.

    2015-11-01

    Laser active suppressing jamming is one of the most important technologies in the domain of electro-optical countermeasures. The propagation direction of laser is not always in the same line with the principal axis of electro-optical imaging system, so it is necessary to investigate laser energy distribution on detector under the different incident angle. This paper toke optical system with wide field of view for example. We firstly analyzed the system's structure based on the inverting prism and evaluated image quality. Laser energy distribution caused by diffraction effect of optical system was secondly simulated based on Kirchhoff 's diffraction theory. Thirdly, we built the system's analysis model of stray light, traced a large number of light propagation, and obtained laser energy distribution on detector caused by scattering effect. At last, combine the above two kinds of energy distribution into total laser energy distribution on detector. According to the detector's saturated threshold, we can count up the saturated number and evaluate laser disturbing effect. The research results can provide theoretical reference and technical support for evaluating laser disturbing effect of electro-optical imaging system.

  14. Determining photon energy absorption parameters for different soil samples

    PubMed Central

    Kucuk, Nil; Tumsavas, Zeynal; Cakir, Merve

    2013-01-01

    The mass attenuation coefficients (μs) for five different soil samples were measured at 661.6, 1173.2 and 1332.5 keV photon energies. The soil samples were separately irradiated with 137Cs and 60Co (370 kBq) radioactive point gamma sources. The measurements were made by performing transmission experiments with a 2″ × 2″ NaI(Tl) scintillation detector, which had an energy resolution of 7% at 0.662 MeV for the gamma-rays from the decay of 137Cs. The effective atomic numbers (Zeff) and the effective electron densities (Neff) were determined experimentally and theoretically using the obtained μs values for the soil samples. Furthermore, the Zeff and Neff values of the soil samples were computed for the total photon interaction cross-sections using theoretical data over a wide energy region ranging from 1 keV to 15 MeV. The experimental values of the soils were found to be in good agreement with the theoretical values. Sandy loam and sandy clay loam soils demonstrated poor photon energy absorption characteristics. However, clay loam and clay soils had good photon energy absorption characteristics. PMID:23179375

  15. Examples of Department of Energy Successes for Remediation of Contaminated Groundwater: Permeable Reactive Barrier and Dynamic Underground Stripping ASTD Projects

    SciTech Connect

    Purdy, C.; Gerdes, K.; Aljayoushi, J.; Kaback, D.; Ivory, T.

    2002-02-27

    Since 1998, the Department of Energy's (DOE) Office of Environmental Management has funded the Accelerated Site Technology Deployment (ASTD) Program to expedite deployment of alternative technologies that can save time and money for the environmental cleanup at DOE sites across the nation. The ASTD program has accelerated more than one hundred deployments of new technologies under 76 projects that focus on a broad spectrum of EM problems. More than 25 environmental restoration projects have been initiated to solve the following types of problems: characterization of the subsurface using chemical, radiological, geophysical, and statistical methods; treatment of groundwater contaminated with DNAPLs, metals, or radionuclides; and other projects such as landfill covers, purge water management systems, and treatment of explosives-contaminated soils. One of the major goals of the ASTD Program is to deploy a new technology or process at multiple DOE sites. ASTD projects are encouraged to identify subsequent deployments at other sites. Some of the projects that have successfully deployed technologies at multiple sites focusing on cleanup of contaminated groundwater include: Permeable Reactive Barriers (Monticello, Rocky Flats, and Kansas City), treating uranium and organics in groundwater; and Dynamic Underground Stripping (Portsmouth, and Savannah River), thermally treating DNAPL source zones. Each year more and more new technologies and approaches are being used at DOE sites due to the ASTD program. DOE sites are sharing their successes and communicating lessons learned so that the new technologies can replace the baseline or standard approaches at DOE sites, thus expediting cleanup and saving money.

  16. A salen-type Dy4 single-molecule magnet with an enhanced energy barrier and its analogues.

    PubMed

    Luan, Fang; Yan, Pengfei; Zhu, Jing; Liu, Tianqi; Zou, Xiaoyan; Li, Guangming

    2015-03-01

    Four isomorphic tetranuclear lanthanide complexes, namely [Ln4(L)2(HL)2(NO3)2(OH)2](NO3)2·4H2O (Ln = Dy (1); Tb (2); Ho (3); Er (4)), constructed using hexadentate salen-type ligand N,N'-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine, have been isolated. X-ray crystallographic analysis reveals that all of the complexes 1-4 are of discrete tetranuclear structure with a unique {Ln4O8} core in which four lanthanide ions are coplanar in a rhombic frame. There are two crystallographically unequivalent lanthanide ions, that is the Ln1(III) ion which is nine-coordinated in a monocapped square-antiprismatic geometry of the C(4v) point group and the Ln2(III) ion which is eight-coordinated in a distorted bicapped trigonal-prismatic geometry of the C(2v) point group. Magnetic analysis reveals that complex 1 exhibits two slow magnetic relaxations with the highest energy barrier among the reported tetranuclear salen-type dysprosium SMMs. This further extends the available SMMs of salen-type lanthanide complexes. PMID:25619145

  17. First-principles molecular dynamics simulations of condensed-phase V-type nerve agent reaction pathways and energy barriers.

    PubMed

    Gee, Richard H; Kuo, I-Feng W; Chinn, Sarah C; Raber, Ellen

    2012-03-14

    Computational studies of condensed-phase chemical reactions are challenging in part because of complexities in understanding the effects of the solvent environment on the reacting chemical species. Such studies are further complicated due to the demanding computational resources required to implement high-level ab initio quantum chemical methods when considering the solvent explicitly. Here, we use first-principles molecular dynamics simulations to examine condensed-phase decontamination reactions of V-type nerve agents in an explicit aqueous solvent. Our results include a detailed study of hydrolysis, base-hydrolysis, and nucleophilic oxidation of both VX and R-VX, as well as their protonated counterparts (i.e., VXH(+) and R-VXH(+)). The decontamination mechanisms and chemical reaction energy barriers, as determined from our simulations, are found to be in good agreement with experiment. The results demonstrate the applicability of using such simulations to assist in understanding new decontamination technologies or other applications that require computational screening of condensed-phase chemical reaction mechanisms. PMID:22298156

  18. Power law size-distributed heterogeneity explains colloid retention on soda lime glass in the presence of energy barriers.

    PubMed

    Pazmino, Eddy; Trauscht, Jacob; Dame, Brittany; Johnson, William P

    2014-05-20

    This article concerns reading the nanoscale heterogeneity thought responsible for colloid retention on surfaces in the presence of energy barriers (unfavorable attachment conditions). We back out this heterogeneity on glass surfaces by comparing mechanistic simulations incorporating discrete heterogeneity with colloid deposition experiments performed across a comprehensive set of experimental conditions. Original data is presented for attachment to soda lime glass for three colloid sizes (0.25, 1.1, and 1.95 μm microspheres) under a variety of ionic strengths and fluid velocities in an impinging jet system. A comparison of mechanistic particle trajectory simulations incorporating discrete surface heterogeneity represented by nanoscale zones of positive charge (heterodomains) indicates that a power law size distribution of heterodomains ranging in size from 120 to 60 nm in radius was able to explain the observed retention for all conditions examined. In contrast, uniform and random placement of single-sized heterodomains failed to capture experimentally observed colloid retention across the range of conditions examined. PMID:24773424

  19. Evaluation of the energy barrier for failure of Au atomic contact based on temperature dependent current-voltage characteristics.

    PubMed

    Aiba, Akira; Kaneko, Satoshi; Fujii, Shintaro; Nishino, Tomoaki; Kiguchi, Manabu

    2016-08-01

    We investigated the mechanical stability of single gold atomic contacts at an applied bias voltage of 0-1 V using a nano-fabricated mechanically controllable break junction technique at 300-400 K under ambient conditions. The single atomic contact shows the quantized conductance (G0 = 2e(2)/h) and can carry considerably large current, which results in the current-induced failure of the contact. The contact failure behaviour under the applied bias conditions was studied by statistical analysis of the current-voltage (I-V) curves of the single Au contacts. We demonstrated that, at the elevated temperature of 300-400 K, the current-induced local heating effect is negligibly small and current-induced forces in the contact are responsible for the observed failure of the single gold contacts under the high bias voltage conditions (>0.4 V). Furthermore, based on the temperature dependence of the contact failure behaviour in the I-V curves, the energy barrier of the contact-failure was evaluated to be ca. 0.1 V. PMID:27427285

  20. Analysis of Elastic Scattering of 8He+208Pb System at around the Coulomb Barrier Energies

    NASA Astrophysics Data System (ADS)

    Direkci, M.; Kucuk, Y.; Boztosun, I.

    2015-04-01

    The elastic scattering angular distribution of 8He+208Pb system is investigated at Elab = 22.0 MeV within the framework of Optical Model by using phenomenological and microscopic potentials. For the phenomenological Optical Model calculations, both real and imaginary parts of the complex nuclear potential have been chosen to have the Wood-Saxon shape. In the microscopic Optical Model calculations, we have used double folding procedure to calculate the real part of optical potential for different kinds of density distributions of 8He. A comparative study of this system has been conducted for the fist time by using phenomenological and microscopic potentials. It is observed that large imaginary radius value due to the existence of long-range absorption mechanism acting at large distances provides a very good agreement between theoretical results and experimental data with small χ2/N values.

  1. How well do we understand quasi-elastic reactions at energies close to the barrier

    SciTech Connect

    Rehm, K.E.

    1988-01-01

    In collisions between too heavy nuclei a wide spectrum of different reaction modes is observed covering the range from simple processes like elastic scattering to complicated multistep transfers and fusion. On the theoretical side heavy ion reactions are usually analyzed using models that were developed first for light ion induced reactions: the optical model for elastic scattering and the DWBA for more inelastic processes like transfer and inelastic scattering. Some of the assumptions going into these approximations, however, are not valid for heavy ion induced reactions. The region between fusion and quasi-elastic reactions is not well understood theoretically. This region is associated with deep inelastic collisions, which are complex multiparticle reactions involving transfer of several protons and neutrons. In this paper, the author discusses to what extent experiments in the field of quasi-elastic scattering are understood within the framework of various theoretical models and in what areas more work is needed.

  2. Coastal Ohio Wind Project for Reduced Barriers to Deployment of Offshore Wind Energy

    SciTech Connect

    Gorsevski, Peter; Afjeh, Abdollah; Jamali, Mohsin; Carroll, Michael

    2014-04-09

    The Coastal Ohio Wind Project was created to establish the viability of wind turbines on the coastal and offshore regions of Northern Ohio. The project’s main goal was to improve operational unit strategies used for environmental impact assessment of offshore turbines on lake wildlife by optimizing and fusing data from the multi-instrument surveillance system and providing an engineering analysis of potential design/operational alternatives for offshore wind turbines. The project also developed a general economic model for offshore WTG deployment to quantify potential revenue losses due to wind turbine shutdown related to ice and avian issues. In a previous phase of this project (Award Number: DE-FG36-06GO86096), we developed a surveillance system that was used to collect different parameters such as passage rates, flight paths, flight directions, and flight altitudes of nocturnal migrating species, movements of birds and bats, and bird calls for assessing patterns and peak passage rates during migration. To derive such parameters we used thermal IR imaging cameras, acoustic recorders, and marine radar Furuno (XANK250), which was coupled with a XIR3000B digitizing card from Russell Technologies and open source radR processing software. The integration yielded a development of different computational techniques and methods, which we further developed and optimized as a combined surveillance system. To accomplish this task we implemented marine radar calibration, optimization of processing parameters, and fusion of the multi-sensor data in order to make inferences about the potential avian targets. The main goal of the data fusion from the multi-sensor environment was aimed at reduction of uncertainties while providing acceptable confidence levels with detailed information about the migration patterns. Another component comprised of an assessment of wind resources in a near lake environment and an investigation of the effectiveness of ice coating materials to

  3. Protein-inhibitor flexible docking by a multicanonical sampling: native complex structure with the lowest free energy and a free-energy barrier distinguishing the native complex from the others.

    PubMed

    Kamiya, Narutoshi; Yonezawa, Yasushige; Nakamura, Haruki; Higo, Junichi

    2008-01-01

    Flexible docking between a protein (lysozyme) and an inhibitor (tri-N-acetyl-D-glucosamine, tri-NAG) was carried out by an enhanced conformational sampling method, multicanonical molecular dynamics simulation. We used a flexible all-atom model to express lysozyme, tri-NAG, and water molecules surrounding the two bio-molecules. The advantages of this sampling method are as follows: the conformation of system is widely sampled without trapping at energy minima, a thermally equilibrated conformational ensemble at an arbitrary temperature can be reconstructed from the simulation trajectory, and the thermodynamic weight can be assigned to each sampled conformation. During the simulation, exchanges between the binding and free (i.e., unbinding) states of the protein and the inhibitor were repeatedly observed. The conformational ensemble reconstructed at 300 K involved various conformational clusters. The main outcome of the current study is that the most populated conformational cluster (i.e., the cluster of the lowest free energy) was assigned to the native complex structure (i.e., the X-ray complex structure). The simulation also produced non-native complex structures, where the protein and the inhibitor bound with different modes from that of the native complex structure, as well as the unbinding structures. A free-energy barrier (i.e., activation free energy) was clearly detected between the native complex structures and the other structures. The thermal fluctuations of tri-NAG in the lowest free-energy complex correlated well with the X-ray B-factors of tri-NAG in the X-ray complex structure. The existence of the free-energy barrier ensures that the lowest free-energy structure can be discriminated naturally from the other structures. In other words, the multicanonical molecular dynamics simulation can predict the native complex structure without any empirical objective function. The current study also manifested that the flexible all-atom model and the physico

  4. Differences in energy transfer of a cyanobacterium, Synechococcus sp. PCC 7002, grown in different cultivation media.

    PubMed

    Niki, Kenta; Aikawa, Shimpei; Yokono, Makio; Kondo, Akihiko; Akimoto, Seiji

    2015-08-01

    Currently, cyanobacteria are regarded as potential biofuel sources. Large-scale cultivation of cyanobacteria in seawater is of particular interest because seawater is a low-cost medium. In the present study, we examined differences in light-harvesting and energy transfer processes in the cyanobacterium Synechococcus sp. PCC 7002 grown in different cultivation media, namely modified A medium (the optimal growth medium for Synechococcus sp. PCC 7002) and f/2 (a seawater medium). The concentrations of nitrate and phosphate ions were varied in both media. Higher nitrate ion and/or phosphate ion concentrations yielded high relative content of phycobilisome. The cultivation medium influenced the energy transfers within phycobilisome, from phycobilisome to photosystems, within photosystem II, and from photosystem II to photosystem I. We suggest that the medium also affects charge recombination at the photosystem II reaction center and formation of a chlorophyll-containing complex. PMID:25577255

  5. Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies

    SciTech Connect

    Beste, Ariana; Harrison, Robert J; Yanai, Takeshi

    2006-01-01

    Chemists are mainly interested in energy differences. In contrast, most quantum chemical methods yield the total energy which is a large number compared to the difference and has therefore to be computed to a higher relative precision than would be necessary for the difference alone. Hence, it is desirable to compute energy differences directly, thereby avoiding the precision problem. Whenever it is possible to find a parameter which transforms smoothly from an initial to a final state, the energy difference can be obtained by integrating the energy derivative with respect to that parameter (c.f., thermodynamic integration or adiabatic connection methods). If the dependence on the parameter is predominantly linear, accurate results can be obtained by single-point integration. In density functional theory (DFT) and Hartree-Fock, we applied the formalism to ionization potentials, excitation energies, and chemical bond breaking. Example calculations for ionization potentials and excitation energies showed that accurate results could be obtained with a linear estimate. For breaking bonds, we introduce a non-geometrical parameter which gradually turns the interaction between two fragments of a molecule on. The interaction changes the potentials used to determine the orbitals as well as constraining the orbitals to be orthogonal.

  6. Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies

    NASA Astrophysics Data System (ADS)

    Beste, A.; Harrison, R. J.; Yanai, T.

    2006-08-01

    Chemists are mainly interested in energy differences. In contrast, most quantum chemical methods yield the total energy which is a large number compared to the difference and has therefore to be computed to a higher relative precision than would be necessary for the difference alone. Hence, it is desirable to compute energy differences directly, thereby avoiding the precision problem. Whenever it is possible to find a parameter which transforms smoothly from an initial to a final state, the energy difference can be obtained by integrating the energy derivative with respect to that parameter (cf. thermodynamic integration or adiabatic connection methods). If the dependence on the parameter is predominantly linear, accurate results can be obtained by single-point integration. In density functional theory and Hartree-Fock, we applied the formalism to ionization potentials, excitation energies, and chemical bond breaking. Example calculations for ionization potentials and excitation energies showed that accurate results could be obtained with a linear estimate. For breaking bonds, we introduce a nongeometrical parameter which gradually turns the interaction between two fragments of a molecule on. The interaction changes the potentials used to determine the orbitals as well as the constraint on the orbitals to be orthogonal.

  7. Fission barriers of compound superheavy nuclei.

    PubMed

    Pei, J C; Nazarewicz, W; Sheikh, J A; Kerman, A K

    2009-05-15

    The dependence of fission barriers on the excitation energy of the compound nucleus impacts the survival probability of superheavy nuclei synthesized in heavy-ion fusion reactions. In this work, we investigate the isentropic fission barriers by means of the self-consistent nuclear density functional theory. The relationship between isothermal and isentropic descriptions is demonstrated. Calculations have been carried out for 264Fm, 272Ds, ;{278}112, ;{292}114, and ;{312}124. For nuclei around ;{278}112 produced in "cold-fusion" reactions, we predict a more rapid decrease of fission barriers with excitation energy as compared to the nuclei around ;{292}114 synthesized in "hot-fusion" experiments. This is explained in terms of the difference between the ground-state and saddle-point temperatures. The effect of the particle gas is found to be negligible in the range of temperatures studied. PMID:19518948

  8. Ubiquitous human ‘master’ origins of replication are encoded in the DNA sequence via a local enrichment in nucleosome excluding energy barriers

    NASA Astrophysics Data System (ADS)

    Drillon, Guénola; Audit, Benjamin; Argoul, Françoise; Arneodo, Alain

    2015-02-01

    As the elementary building block of eukaryotic chromatin, the nucleosome is at the heart of the compromise between the necessity of compacting DNA in the cell nucleus and the required accessibility to regulatory proteins. The recent availability of genome-wide experimental maps of nucleosome positions for many different organisms and cell types has provided an unprecedented opportunity to elucidate to what extent the DNA sequence conditions the primary structure of chromatin and in turn participates in the chromatin-mediated regulation of nuclear functions, such as gene expression and DNA replication. In this study, we use in vivo and in vitro genome-wide nucleosome occupancy data together with the set of nucleosome-free regions (NFRs) predicted by a physical model of nucleosome formation based on sequence-dependent bending properties of the DNA double-helix, to investigate the role of intrinsic nucleosome occupancy in the regulation of the replication spatio-temporal programme in human. We focus our analysis on the so-called replication U/N-domains that were shown to cover about half of the human genome in the germline (skew-N domains) as well as in embryonic stem cells, somatic and HeLa cells (mean replication timing U-domains). The ‘master’ origins of replication (MaOris) that border these megabase-sized U/N-domains were found to be specified by a few hundred kb wide regions that are hyper-sensitive to DNase I cleavage, hypomethylated, and enriched in epigenetic marks involved in transcription regulation, the hallmarks of localized open chromatin structures. Here we show that replication U/N-domain borders that are conserved in all considered cell lines have an environment highly enriched in nucleosome-excluding-energy barriers, suggesting that these ubiquitous MaOris have been selected during evolution. In contrast, MaOris that are cell-type-specific are mainly regulated epigenetically and are no longer favoured by a local abundance of intrinsic NFRs

  9. Ubiquitous human 'master' origins of replication are encoded in the DNA sequence via a local enrichment in nucleosome excluding energy barriers.

    PubMed

    Drillon, Guénola; Audit, Benjamin; Argoul, Françoise; Arneodo, Alain

    2015-02-18

    As the elementary building block of eukaryotic chromatin, the nucleosome is at the heart of the compromise between the necessity of compacting DNA in the cell nucleus and the required accessibility to regulatory proteins. The recent availability of genome-wide experimental maps of nucleosome positions for many different organisms and cell types has provided an unprecedented opportunity to elucidate to what extent the DNA sequence conditions the primary structure of chromatin and in turn participates in the chromatin-mediated regulation of nuclear functions, such as gene expression and DNA replication. In this study, we use in vivo and in vitro genome-wide nucleosome occupancy data together with the set of nucleosome-free regions (NFRs) predicted by a physical model of nucleosome formation based on sequence-dependent bending properties of the DNA double-helix, to investigate the role of intrinsic nucleosome occupancy in the regulation of the replication spatio-temporal programme in human. We focus our analysis on the so-called replication U/N-domains that were shown to cover about half of the human genome in the germline (skew-N domains) as well as in embryonic stem cells, somatic and HeLa cells (mean replication timing U-domains). The 'master' origins of replication (MaOris) that border these megabase-sized U/N-domains were found to be specified by a few hundred kb wide regions that are hyper-sensitive to DNase I cleavage, hypomethylated, and enriched in epigenetic marks involved in transcription regulation, the hallmarks of localized open chromatin structures. Here we show that replication U/N-domain borders that are conserved in all considered cell lines have an environment highly enriched in nucleosome-excluding-energy barriers, suggesting that these ubiquitous MaOris have been selected during evolution. In contrast, MaOris that are cell-type-specific are mainly regulated epigenetically and are no longer favoured by a local abundance of intrinsic NFRs encoded in

  10. Nonstochastic effects of different energy beta emitters on pig skin.

    PubMed

    Peel, D M; Hopewell, J W; Wells, J; Charles, M W

    1984-08-01

    Circular areas of pig skin from 1- to 40-mm diameter were irradiated with beta emitters of high, medium, and low energies, 90Sr, 170Tm, and 147Pm, respectively. The study provides information for radiological protection problems of localized skin exposures. During the first 16 weeks after irradiation 90Sr produced a first reaction due to epithelial cell death followed by a second reaction attributable to damage to the dermal blood vessels. 170Tm and 147Pm produced the epithelial reaction only. The epithelial dose response varied as a function of beta energy. The doses required to produce moist desquamation in 50% of 15- to 22.5-mm fields (ED50) were 30-45 Gy from 90Sr, approximately 80 Gy from 170Tm, and approximately 500 Gy from 147Pm. A model involving different methods of epithelial repopulation is proposed to explain this finding. An area effect was observed in the epithelial response to 90Sr irradiation. The ED50 for moist desquamation ranged from approximately 25 Gy for a 40-mm source to approximately 450 Gy for a 1-mm source. The 5-, 9-, and 19-mm 170Tm sources all produced an ED50 of approximately 80 Gy, while the value for the 2-mm source was approximately 250 Gy. It is also suggested that the area effects could be explained by different modes of epithelial repopulation after irradiation. After high energy beta irradiation repopulation would be mainly from the field periphery, while after lower energy irradiation repopulation from hair follicle epithelium would predominate. PMID:6463213

  11. Apoplastic Diffusion Barriers in Arabidopsis

    PubMed Central

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  12. Investigation of the energy barrier to the rotation of amide CN bonds in ACE inhibitors by NMR, dynamic HPLC and DFT.

    PubMed

    Bouabdallah, S; Ben Dhia, M T; Driss, M R; Touil, S

    2016-09-01

    The isomerizations of Enalapril, Perindopril, Enalaprilat and Lisinopril have been investigated using NMR spectroscopic, dynamic chromatographic, unified equation and DFT theoretical calculations. The thermodynamic parameters (ΔH, ΔS and ΔG) were determined by varying the temperature in the NMR experiments. At the coalescence temperature, we can evaluate the isomerization barrier to the rotation (ΔG(≠)) around the amide bond. Using dynamics chromatography and an unified equation introduced by Trap, we can determine isomerization rate constants and Gibbs activation energies. Molecular mechanics calculations also provided evidence for the presence of low energy conformers for the ACE due to restricted amide rotation. With the value of barriers (ΔE) between them of the order of (20kJmol(-1)), which is in agreement with the dynamic NMR results and DFT calculations. PMID:27344631

  13. Deep inelastic scattering near the Coulomb barrier

    SciTech Connect

    Gehring, J.; Back, B.; Chan, K.

    1995-08-01

    Deep inelastic scattering was recently observed in heavy ion reactions at incident energies near and below the Coulomb barrier. Traditional models of this process are based on frictional forces and are designed to predict the features of deep inelastic processes at energies above the barrier. They cannot be applied at energies below the barrier where the nuclear overlap is small and friction is negligible. The presence of deep inelastic scattering at these energies requires a different explanation. The first observation of deep inelastic scattering near the barrier was in the systems {sup 124,112}Sn + {sup 58,64}Ni by Wolfs et al. We previously extended these measurements to the system {sup 136}Xe + {sup 64}Ni and currently measured the system {sup 124}Xe + {sup 58}Ni. We obtained better statistics, better mass and energy resolution, and more complete angular coverage in the Xe + Ni measurements. The cross sections and angular distributions are similar in all of the Sn + Ni and Xe + Ni systems. The data are currently being analyzed and compared with new theoretical calculations. They will be part of the thesis of J. Gehring.

  14. A Ploidy Difference Represents an Impassable Barrier for Hybridisation in Animals. Is There an Exception among Botiid Loaches (Teleostei: Botiidae)?

    PubMed Central

    Bohlen, Jörg; Šlechtová, Vendula; Šlechta, Vlastimil; Šlechtová, Vera; Sember, Alexandr; Ráb, Petr

    2016-01-01

    One of the most efficient mechanisms to keep animal lineages separate is a difference in ploidy level (number of whole genome copies), since hybrid offspring from parents with different ploidy level are functionally sterile. In the freshwater fish family Botiidae, ploidy difference has been held responsible for the separation of its two subfamilies, the evolutionary tetraploid Botiinae and the diploid Leptobotiinae. Diploid and tetraploid species coexist in the upper Yangtze, the Pearl River and the Red River basins in China. Interestingly, the species ‘Botia’ zebra from the Pearl River basin combines a number of morphological characters that otherwise are found in the diploid genus Leptobotia with morphological characters of the tetraploid genus Sinibotia, therefore the aim of the present study is to test weather ‘B.’ zebra is the result of a hybridisation event between species from different subfamilies with different ploidy level. A closer morphological examination indeed demonstrates a high similarity of ‘B.’ zebra to two co-occurring species, the diploid Leptobotia guilinensis and the tetraploid Sinibotia pulchra. These two species thus could have been the potential parental species in case of a hybrid origin of ‘B.’ zebra. The morphologic analysis further reveals that ‘B.’ zebra bears even the diagnostic characters of the genera Leptobotia (Leptobotiinae) and Sinibotia (Botiinae). In contrast, a comparison of six allozyme loci between ‘B.’ zebra, L. guilinensis and S. pulchra showed only similarities between ‘B.’ zebra and S. pulchra, not between ‘B.’ zebra and L. guilinensis. Six specimens of ‘B.’ zebra that were cytogenetically analysed were tetraploid with 4n = 100. The composition of the karyotype (18% metacentric, 18% submetacentric, 36% subtelocentric and 28% acrocentric chromosomes) differs from those of L. guilinensis (12%, 24%, 20% and 44%) and S. pulchra (20%, 26%, 28% and 26%), and cannot be obtained by any

  15. A Ploidy Difference Represents an Impassable Barrier for Hybridisation in Animals. Is There an Exception among Botiid Loaches (Teleostei: Botiidae)?

    PubMed

    Bohlen, Jörg; Šlechtová, Vendula; Šlechta, Vlastimil; Šlechtová, Vera; Sember, Alexandr; Ráb, Petr

    2016-01-01

    One of the most efficient mechanisms to keep animal lineages separate is a difference in ploidy level (number of whole genome copies), since hybrid offspring from parents with different ploidy level are functionally sterile. In the freshwater fish family Botiidae, ploidy difference has been held responsible for the separation of its two subfamilies, the evolutionary tetraploid Botiinae and the diploid Leptobotiinae. Diploid and tetraploid species coexist in the upper Yangtze, the Pearl River and the Red River basins in China. Interestingly, the species 'Botia' zebra from the Pearl River basin combines a number of morphological characters that otherwise are found in the diploid genus Leptobotia with morphological characters of the tetraploid genus Sinibotia, therefore the aim of the present study is to test weather 'B.' zebra is the result of a hybridisation event between species from different subfamilies with different ploidy level. A closer morphological examination indeed demonstrates a high similarity of 'B.' zebra to two co-occurring species, the diploid Leptobotia guilinensis and the tetraploid Sinibotia pulchra. These two species thus could have been the potential parental species in case of a hybrid origin of 'B.' zebra. The morphologic analysis further reveals that 'B.' zebra bears even the diagnostic characters of the genera Leptobotia (Leptobotiinae) and Sinibotia (Botiinae). In contrast, a comparison of six allozyme loci between 'B.' zebra, L. guilinensis and S. pulchra showed only similarities between 'B.' zebra and S. pulchra, not between 'B.' zebra and L. guilinensis. Six specimens of 'B.' zebra that were cytogenetically analysed were tetraploid with 4n = 100. The composition of the karyotype (18% metacentric, 18% submetacentric, 36% subtelocentric and 28% acrocentric chromosomes) differs from those of L. guilinensis (12%, 24%, 20% and 44%) and S. pulchra (20%, 26%, 28% and 26%), and cannot be obtained by any combination of genomes from L

  16. Computation of the Gibbs free energy difference between polymorphs

    NASA Astrophysics Data System (ADS)

    Sinkovits, Daniel W.; Kumar, Sanat K.

    2015-03-01

    Semi-crystalline polymers commonly crystallize into several different polymorphs; for example, the alpha and beta phases of isotactic polypropylene. While it is possible to favor particular polymorphs by kinetic means, such as with varying degrees of supercooling or through the use of different solvents in solution casting, we focus on the question of thermodynamic stability; that is, which polymorph possesses the lowest Gibbs free energy for a given temperature and pressure. We implement a version of the Bennett Acceptance Ratio method and find phase diagrams for several polymers. We also demonstrate agreement with phonon analysis in the quasi-harmonic approximation. The advantages and drawbacks of these methods will be discussed. Multidisciplinary University Research Initiative (MURI).

  17. The difference between energy consumption and energy cost: Modelling energy tariff structures for water resource recovery facilities.

    PubMed

    Aymerich, I; Rieger, L; Sobhani, R; Rosso, D; Corominas, Ll

    2015-09-15

    The objective of this paper is to demonstrate the importance of incorporating more realistic energy cost models (based on current energy tariff structures) into existing water resource recovery facilities (WRRFs) process models when evaluating technologies and cost-saving control strategies. In this paper, we first introduce a systematic framework to model energy usage at WRRFs and a generalized structure to describe energy tariffs including the most common billing terms. Secondly, this paper introduces a detailed energy cost model based on a Spanish energy tariff structure coupled with a WRRF process model to evaluate several control strategies and provide insights into the selection of the contracted power structure. The results for a 1-year evaluation on a 115,000 population-equivalent WRRF showed monthly cost differences ranging from 7 to 30% when comparing the detailed energy cost model to an average energy price. The evaluation of different aeration control strategies also showed that using average energy prices and neglecting energy tariff structures may lead to biased conclusions when selecting operating strategies or comparing technologies or equipment. The proposed framework demonstrated that for cost minimization, control strategies should be paired with a specific optimal contracted power. Hence, the design of operational and control strategies must take into account the local energy tariff. PMID:26048700

  18. Complementary Barrier Infrared Detector

    NASA Technical Reports Server (NTRS)

    Ting, David Z.; Bandara, Sumith V.; Hill, Cory J.; Gunapala, Sarath D.

    2009-01-01

    The complementary barrier infrared detector (CBIRD) is designed to eliminate the major dark current sources in the superlattice infrared detector. The concept can also be applied to bulk semiconductor- based infrared detectors. CBIRD uses two different types of specially designed barriers: an electron barrier that blocks electrons but not holes, and a hole barrier that blocks holes but not electrons. The CBIRD structure consists of an n-contact, a hole barrier, an absorber, an electron barrier, and a p-contact. The barriers are placed at the contact-absorber junctions where, in a conventional p-i-n detector structure, there normally are depletion regions that produce generation-recombination (GR) dark currents due to Shockley-Read- Hall (SRH) processes. The wider-bandgap complementary barriers suppress G-R dark current. The barriers also block diffusion dark currents generated in the diffusion wings in the neutral regions. In addition, the wider gap barriers serve to reduce tunneling dark currents. In the case of a superlattice-based absorber, the superlattice itself can be designed to suppress dark currents due to Auger processes. At the same time, the barriers actually help to enhance the collection of photo-generated carriers by deflecting the photo-carriers that are diffusing in the wrong direction (i.e., away from collectors) and redirecting them toward the collecting contacts. The contact layers are made from materials with narrower bandgaps than the barriers. This allows good ohmic contacts to be made, resulting in lower contact resistances. Previously, THALES Research and Technology (France) demonstrated detectors with bulk InAsSb (specifically InAs0.91Sb0.09) absorber lattice-matched to GaSb substrates. The absorber is surrounded by two wider bandgap layers designed to minimize impedance to photocurrent flow. The wide bandgap materials also serve as contacts. The cutoff wavelength of the InAsSb absorber is fixed. CBIRD may be considered as a modified

  19. Density functional studies on wurtzite piezotronic transistors: influence of different semiconductors and metals on piezoelectric charge distribution and Schottky barrier

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2016-05-01

    The mechanical–electrical coupling properties of piezoelectric semiconductors endow these materials with novel device applications in microelectromechanical systems, sensors, human–computer interfaces, etc. When an applied strain is exerted on a piezoelectric semiconductor, piezoelectric charges are generated at the surface or interface of the semiconductor, which can be utilized to control the electronic transport characteristics. This is the fundamental working mechanism of piezotronic devices, called the piezotronic effect. In the present report, a series of piezotronic transistors composed of different electrode metals and semiconductors is examined using density functional theory calculation. It is found that the influence of semiconductors on the piezotronic effect is larger than the impact of metals, and GaN and CdS are promising candidates for piezotronic and piezo-phototronic devices, respectively. The width of the piezoelectric charge distribution obtained in the present study can be used as a parameter in classical finite-element-method based simulations, which provide guidance on designing high-performance piezotronic devices.

  20. Density functional studies on wurtzite piezotronic transistors: influence of different semiconductors and metals on piezoelectric charge distribution and Schottky barrier.

    PubMed

    Liu, Wei; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2016-05-20

    The mechanical-electrical coupling properties of piezoelectric semiconductors endow these materials with novel device applications in microelectromechanical systems, sensors, human-computer interfaces, etc. When an applied strain is exerted on a piezoelectric semiconductor, piezoelectric charges are generated at the surface or interface of the semiconductor, which can be utilized to control the electronic transport characteristics. This is the fundamental working mechanism of piezotronic devices, called the piezotronic effect. In the present report, a series of piezotronic transistors composed of different electrode metals and semiconductors is examined using density functional theory calculation. It is found that the influence of semiconductors on the piezotronic effect is larger than the impact of metals, and GaN and CdS are promising candidates for piezotronic and piezo-phototronic devices, respectively. The width of the piezoelectric charge distribution obtained in the present study can be used as a parameter in classical finite-element-method based simulations, which provide guidance on designing high-performance piezotronic devices. PMID:27053577

  1. Fission barriers in a macroscopic-microscopic model

    SciTech Connect

    Dobrowolski, A.; Pomorski, K.; Bartel, J.

    2007-02-15

    In the framework of the macroscopic-microscopic model, this study investigates fission barriers in the region of actinide nuclei. A very effective four-dimensional shape parametrization for fissioning nuclei is proposed. Taking, in particular, the left-right mass asymmetric and nonaxial shapes into account is demonstrated to have a substantial effect on fission barrier heights. The influence of proton versus neutron deformation differences on the potential energy landscape of fissioning nuclei is also discussed.

  2. Multilayer coatings for flexible high-barrier materials

    NASA Astrophysics Data System (ADS)

    Vaško, Karol; Noller, Klaus; Mikula, Milan; Amberg-Schwab, Sabine; Weber, Ulrike

    2009-06-01

    A multilayer, flexible, and transparent high-barrier system based on flexible plastic foils, polyethyleneterephthalate (PET) and ethylene-tetrafluoroethylene-copolymer (ETFE), combined with vacuum-deposited, inorganic SiOx layers and hybrid ORMOCER® varnish layers were prepared in different orders on a semiproduction level. Barrier properties of prepared systems, as water vapour transmission (WVTR) and oxygen transmission (OTR), were measured and studied in connection with surface energy, surface topography, and water vapour adsorption properties. Correlations among layers sequence, barrier properties, and other parameters are presented, including some basic principles of permeation of substances through multilayer barrier systems. A combination of several inorganic and hybrid varnish layers is necessary to achieve the technological demands from a barrier standpoint. It is easier to suppress the oxygen transport than the water transport, due to the additional active penetration of water through hydrogen bonds and silanol creations at oxide interfaces, capillary condensation, and swelling with high internal pressure, leading to new defects.

  3. Multilayer coatings for flexible high-barrier materials

    NASA Astrophysics Data System (ADS)

    Vaško, Karol; Noller, Klaus; Mikula, Milan; Amberg-Schwab, Sabine; Weber, Ulrike

    2009-06-01

    A multilayer, flexible, and transparent high-barrier system based on flexible plastic foils, polyethyleneterephthalate (PET) and ethylene-tetrafluoroethylene-copolymer (ETFE), combined with vacuum-deposited, inorganic SiOx layers and hybrid ORMOCER® varnish layers were prepared in different orders on a semiproduction level. Barrier properties of prepared systems, as water vapour transmission (WVTR) and oxygen transmission (OTR), were measured and studied in connection with surface energy, surface topography, and water vapour adsorption properties. Correlations among layers sequence, barrier properties, and other parameters are presented, including some basic principles of permeation of substances through multilayer barrier systems. A combination of several inorganic and hybrid varnish layers is necessary to achieve the technological demands from a barrier standpoint. It is easier to suppress the oxygen transport than the water transport, due to the additional active penetration of water through hydrogen bonds and silanol creations at oxide interfaces, capillary condensation, and swelling with high internal pressure, leading to new defects.

  4. Intra-Subtype Variation in Enteroadhesion Accounts for Differences in Epithelial Barrier Disruption and Is Associated with Metronidazole Resistance in Blastocystis Subtype-7

    PubMed Central

    Tan, Kevin Shyong Wei

    2014-01-01

    Blastocystis is an extracellular, enteric pathogen that induces intestinal disorders in a range of hosts including humans. Recent studies have identified potential parasite virulence factors in and host responses to this parasite; however, little is known about Blastocystis-host attachment, which is crucial for colonization and virulence of luminal stages. By utilizing 7 different strains of the parasite belonging to two clinically relevant subtypes ST-4 and ST-7, we investigated Blastocystis-enterocyte adhesion and its association with parasite-induced epithelial barrier disruption. We also suggest that drug resistance in ST-7 strains might result in fitness cost that manifested as impairment of parasite adhesion and, consequently, virulence. ST-7 parasites were generally highly adhesive to Caco-2 cells and preferred binding to intercellular junctions. These strains also induced disruption of ZO-1 and occludin tight junction proteins as well as increased dextran-FITC flux across epithelial monolayers. Interestingly, their adhesion was correlated with metronidazole (Mz) susceptibility. Mz resistant (Mzr) strains were found to be less pathogenic, owing to compromised adhesion. Moreover, tolerance of nitrosative stress was also reduced in the Mzr strains. In conclusion, the findings indicate that Blastocystis attaches to intestinal epithelium and leads to epithelial barrier dysfunction and that drug resistance might entail a fitness cost in parasite virulence by limiting entero-adhesiveness. This is the first study of the cellular basis for strain-to-strain variation in parasite pathogenicity. Intra- and inter-subtype variability in cytopathogenicity provides a possible explanation for the diverse clinical outcomes of Blastocystis infections. PMID:24851944

  5. Differing impact of a major biogeographic barrier on genetic structure in two large kangaroos from the monsoon tropics of Northern Australia

    PubMed Central

    Eldridge, Mark D B; Potter, Sally; Johnson, Christopher N; Ritchie, Euan G

    2014-01-01

    Tropical savannas cover 20–30% of the world's land surface and exhibit high levels of regional endemism, but the evolutionary histories of their biota remain poorly studied. The most extensive and unmodified tropical savannas occur in Northern Australia, and recent studies suggest this region supports high levels of previously undetected genetic diversity. To examine the importance of barriers to gene flow and the environmental history of Northern Australia in influencing patterns of diversity, we investigated the phylogeography of two closely related, large, vagile macropodid marsupials, the antilopine wallaroo (Macropus antilopinus; n = 78), and the common wallaroo (Macropus robustus; n = 21). Both species are widespread across the tropical savannas of Australia except across the Carpentarian Barrier (CB) where there is a break in the distribution of M. antilopinus. We determined sequence variation in the hypervariable Domain I of the mitochondrial DNA control region and genotyped individuals at 12 polymorphic microsatellite loci to assess the historical and contemporary influence of the CB on these species. Surprisingly, we detected only limited differentiation between the disjunct Northern Territory and QueenslandM. antilopinus populations. In contrast, the continuously distributedM. robustus was highly divergent across the CB. Although unexpected, these contrasting responses appear related to minor differences in species biology. Our results suggest that vicariance may not explain well the phylogeographic patterns in Australia's dynamic monsoonal environments. This is because Quaternary environmental changes in this region have been complex, and diverse individual species’ biologies have resulted in less predictable and idiosyncratic responses. PMID:25035797

  6. Double binding energy differences: Mean-field or pairing effect?

    NASA Astrophysics Data System (ADS)

    Qi, Chong

    2012-10-01

    In this Letter we present a systematic analysis on the average interaction between the last protons and neutrons in atomic nuclei, which can be extracted from the double differences of nuclear binding energies. The empirical average proton-neutron interaction Vpn thus derived from experimental data can be described in a very simple form as the interplay of the nuclear mean field and the pairing interaction. It is found that the smooth behavior as well as the local fluctuations of the Vpn in even-even nuclei with N ≠ Z are dominated by the contribution from the proton-neutron monopole interactions. A strong additional contribution from the isoscalar monopole interaction and isovector proton-neutron pairing interaction is seen in the Vpn for even-even N = Z nuclei and for the adjacent odd-A nuclei with one neutron or proton being subtracted.

  7. Phase transition in the Jarzynski estimator of free energy differences.

    PubMed

    Suárez, Alberto; Silbey, Robert; Oppenheim, Irwin

    2012-05-01

    The transition between a regime in which thermodynamic relations apply only to ensembles of small systems coupled to a large environment and a regime in which they can be used to characterize individual macroscopic systems is analyzed in terms of the change in behavior of the Jarzynski estimator of equilibrium free energy differences from nonequilibrium work measurements. Given a fixed number of measurements, the Jarzynski estimator is unbiased for sufficiently small systems. In these systems the directionality of time is poorly defined and the configurations that dominate the empirical average, but which are in fact typical of the reverse process, are sufficiently well sampled. As the system size increases the arrow of time becomes better defined. The dominant atypical fluctuations become rare and eventually cannot be sampled with the limited resources that are available. Asymptotically, only typical work values are measured. The Jarzynski estimator becomes maximally biased and approaches the exponential of minus the average work, which is the result that is expected from standard macroscopic thermodynamics. In the proper scaling limit, this regime change has been recently described in terms of a phase transition in variants of the random energy model. In this paper this correspondence is further demonstrated in two examples of physical interest: the sudden compression of an ideal gas and adiabatic quasistatic volume changes in a dilute real gas. PMID:23004704

  8. Phase transition in the Jarzynski estimator of free energy differences

    NASA Astrophysics Data System (ADS)

    Suárez, Alberto; Silbey, Robert; Oppenheim, Irwin

    2012-05-01

    The transition between a regime in which thermodynamic relations apply only to ensembles of small systems coupled to a large environment and a regime in which they can be used to characterize individual macroscopic systems is analyzed in terms of the change in behavior of the Jarzynski estimator of equilibrium free energy differences from nonequilibrium work measurements. Given a fixed number of measurements, the Jarzynski estimator is unbiased for sufficiently small systems. In these systems the directionality of time is poorly defined and the configurations that dominate the empirical average, but which are in fact typical of the reverse process, are sufficiently well sampled. As the system size increases the arrow of time becomes better defined. The dominant atypical fluctuations become rare and eventually cannot be sampled with the limited resources that are available. Asymptotically, only typical work values are measured. The Jarzynski estimator becomes maximally biased and approaches the exponential of minus the average work, which is the result that is expected from standard macroscopic thermodynamics. In the proper scaling limit, this regime change has been recently described in terms of a phase transition in variants of the random energy model. In this paper this correspondence is further demonstrated in two examples of physical interest: the sudden compression of an ideal gas and adiabatic quasistatic volume changes in a dilute real gas.

  9. Differences in demographic traits of four butterflyfish species between two reefs of the Great Barrier Reef separated by 1,200 km

    NASA Astrophysics Data System (ADS)

    Berumen, M. L.; Trip, E. D. L.; Pratchett, M. S.; Choat, J. H.

    2012-03-01

    Many species demonstrate variation in life history attributes in response to gradients in environmental conditions. For fishes, major drivers of life history variation are changes in temperature and food availability. This study examined large-scale variation in the demography of four species of butterflyfishes ( Chaetodon citrinellus, Chaetodon lunulatus, Chaetodon melannotus, and Chaetodon trifascialis) between two locations on Australia's Great Barrier Reef (Lizard Island and One Tree Island, separated by approximately 1,200 km). Variation in age-based demographic parameters was assessed using the re-parameterised von Bertalanffy growth function. All species displayed measurable differences in body size between locations, with individuals achieving a larger adult size at the higher latitude site (One Tree Island) for three of the four species examined. Resources and abundances of the study species were also measured, revealing some significant differences between locations. For example, for C. trifascialis, there was no difference in its preferred resource or in abundance between locations, yet it achieved a larger body size at the higher latitude location, suggesting a response to temperature. For some species, resources and abundances did vary between locations, limiting the ability to distinguish between a demographic response to temperature as opposed to a response to food or competition. Future studies of life histories and demographics at large spatial scales will need to consider the potentially confounding roles of temperature, resource usage and availability, and abundance/competition to disentangle the effects of these environmental variables.

  10. Barriers and opportunities for improving energy efficiency in the social housing sector: Case study of E4C's Division of Housing and Mental Health

    NASA Astrophysics Data System (ADS)

    Marchand-Smith, Patrick

    Energy efficiency improvements in the social housing sector have the potential to produce a range of environmental and social benefits. These improvements can be produced through retrofits that deliver energy savings or new construction built to a high standard of energetic efficiency. However, implementation of these approaches is hindered by economic and organizational constraints affecting the agencies that provide society with social housing and the governments that support the provision of these services. This thesis builds on the work of other researchers studying these constraints by supplying an in-depth case study from Alberta and a discussion based on its findings. The case study focuses on E4C, a social service agency with several housing projects. Overall, findings matched important themes identified in the academic literature. The in-depth nature of the case study added additional insight to many of these themes. Most barriers are economic in nature and related to a lack of sufficient funding or the up-front costs of energy-saving retrofits. The recommendations presented are based on consideration of the multiple barriers and opportunities faced. Most of these require a considerable investment of time on the part of agencies and would be followed up by capital investments to implement energy-saving changes. Therefore it is important to note that the most significant barrier is commitment, which is one of E4C's central values. This thesis showed that commitment cannot exceed capacity to act. Greater commitment on the part of governments, agencies or society at large could have significant impacts in improving the energy efficiency of buildings in the Albertan, and Canadian, social housing sector.

  11. Comparision between different metal oxide nanostructures and nanocomposites for sensing, energy generation, and energy harvesting

    NASA Astrophysics Data System (ADS)

    Willander, Magnus; Alnoor, Hatim; Elhag, Sami; Ibupoto, Zafar Hussain; Nour, Eiman Satti; Nur, Omer

    2016-02-01

    Highlights from research on different nanocomposites and nanostructures for sensing and other energy related applications will be presented. The synthesized nanostructures and nanocomposites presented here were all obtained using the low temperature (< 100 °C) chemical approach. Nanostructures featured by small foot-print and synthesized by the low temperature aqueous chemical approach allows the utilization of non-conventional solid and soft substrates like e.g. glass, plastic, textile and paper. We here present results from different metal oxide nanostructures employed for chemical sensing and some innovative energy related applications. Efficient sensitive and selective sensing of dopamine, melamine, and glucose are presented as some examples of self-powered sensors utilizing the electrochemical phenomenon i.e. transferring chemical energy into electrical signal. Further the use of nanomaterials for developing selfpowered devices utilizing mechanical ambient energy is presented via piezoelectric and triboelectric effects. Here the self-powered devices and systems were relying on utilizing the electormechanical phenomenon i.e. transferring ambient mechanical energy into useful electrical energy. Finally the visibility of nanomaterials prepared by the low temperature chemical synthesis as possible low cost replacement of Pt electrodes for hydrogen production is briefly presented and discussed.

  12. One- and two-nucleon transfer in the {sup 28} Si+{sup 68}Zn system at energies below the Coulomb barrier

    SciTech Connect

    Kataria, D.O.; Sinha, A.K.; Das, J.J.; Madhavan, N.; Sugathan, P.; Baby, L.T.; Mazumdar, I.; Singh, R.; Baba, C.V.; Agarwal, Y.K.; Vinodkumar, A.M.; Varier, K.M.

    1997-10-01

    Excitation functions for one- and two-nucleon transfer in {sup 28}Si + {sup 68}Zn system have been measured at energies below the Coulomb barrier. The experiment was carried out by detecting the forward recoiling targetlike nuclei using the recoil mass separator, HIRA. With a pulsed beam, the time-of-flight of the recoils was measured and used to resolve the M/q ambiguity. This enabled the determination of the two-nucleon transfer yields. The role of one- and two-nucleon transfer in the sub-barrier fusion cross-section enhancement has been investigated. It turns out that the coupling of the positive Q-value two-neutron transfer channel results in a significant contribution to the enhancement. Coupling to both the transfer and the inelastic channels is able to explain the observed enhancement. {copyright} {ital 1997} {ital The American Physical Society}

  13. Interstellar Isomers: The Importance of Bonding Energy Differences

    NASA Technical Reports Server (NTRS)

    Remijan, Anthony J.; Hollis, J. M.; Lovas, F. J.; Plusquellic, D. F.; Jewell, P. R.

    2005-01-01

    We present strong detections of methyl cyanide (CH3CN), vinyl cyanide (CH2CHCN), ethyl cyanide (CH3CH2CN) and cyanodiacetylene (HC4CN) molecules with the Green Bank Telescope (GBT) toward the Sgr B2(N) molecular cloud. Attempts to detect the corresponding isocyanide isomers were only successful in the case of methyl isocyanide (CH3NC) for its J(sub K) = 1(sub 0) - 0(sub 0) transition, which is the first interstellar report of this line. To determine the spatial distribution of CH3NC, we used archival Berkeley-Illinois-Maryland Association (BIMA) array data for the J(sub K) = 1(sub 0) - 0(sub 0) transitions but no emission was detected. From ab initio calculations, the bonding energy difference between the cyanide and isocyanide molecules is greater than 8500 per centimeter (greater than 12,000 K). Thus, cyanides are the more stable isomers and would likely be formed more preferentially over their isocyanide counterparts. That we detect CH3NC emission with a single antenna (Gaussian beamsize(omega(sub B))=1723 arcsec(sup 2)) but not with an interferometer (omega(sub b)=192 arcsec(sup 2)), strongly suggests that CH3NC has a widespread spatial distribution toward the Sgr B2(N) region. Other investigators have shown that CH3CN is present both in the LMH hot core of Sgr B2(N) and in the surrounding medium, while we have shown that CH3NC appears to be deficient in the LMH hot core. Thus, largescale, non-thermal processes in the surrounding medium may account for the conversion of CH3CN to CH3NC while the LMH hot core, which is dominated by thermal processes, does not produce a significant amount of CH3NC. Ice analog experiments by other investigators have shown that radiation bombardment of CH3CN can produce CH3NC, thus supporting our observations. We conclude that isomers separated by such large bonding energy differences are distributed in different interstellar environments, making the evaluation of column density ratios between such isomers irrelevant unless it can

  14. Submerged Barriers in the Ni(+) Assisted Decomposition of Propionaldehyde.

    PubMed

    Mansell, A; Theis, Z; Gutierrez, M G; Faza, O Nieto; Lopez, C Silva; Bellert, D J

    2016-04-21

    The reaction dynamics of the Ni(+) mediated decarbonylation of propionaldehyde was assessed using the single photon initiated decomposition rearrangement reaction (SPIDRR) technique. The exothermic production of Ni(+)CO was temporally monitored and the associated rate constants, k(E), were extracted as a function of activating photon energy. In addition, the reaction potential energy surface was calculated at the UCCSD(T)/def2-TZVP//PBEPBE/cc-pVDZ level of theory to provide an atomistic description of the reaction profile. The decarbonylation of propionaldehyde can be understood as proceeding through parallel competitive reaction pathways that are initiated by Ni(+) insertion into either the C-C or C-H bond of the propionaldehyde carbonyl carbon. Both paths lead to the elimination of neutral ethane and are governed by submerged barriers. The lower energy sequence is a consecutive C-C/C-H addition process with a submerged barrier of 14 350 ± 600 cm(-1). The higher energy sequence is a consecutive C-H/C-C addition process with a submerged barrier of 15 400 ± 600 cm(-1). Both barriers were determined using RRKM calculations fit to the experimentally determined k(E) values. The measured energy difference between the two barriers agrees with the DFT computed difference in rate limiting transition-state energies, 18 413 and 19 495 cm(-1). PMID:27054589

  15. Activation Energy of Extracellular Enzymes in Soils from Different Biomes

    PubMed Central

    Steinweg, J. Megan; Jagadamma, Sindhu; Frerichs, Joshua; Mayes, Melanie A.

    2013-01-01

    Enzyme dynamics are being incorporated into soil carbon cycling models and accurate representation of enzyme kinetics is an important step in predicting belowground nutrient dynamics. A scarce number of studies have measured activation energy (Ea) in soils and fewer studies have measured Ea in arctic and tropical soils, or in subsurface soils. We determined the Ea for four typical lignocellulose degrading enzymes in the A and B horizons of seven soils covering six different soil orders. We also elucidated which soil properties predicted any measurable differences in Ea. β-glucosidase, cellobiohydrolase, phenol oxidase and peroxidase activities were measured at five temperatures, 4, 21, 30, 40, and 60°C. Ea was calculated using the Arrhenius equation. β-glucosidase and cellobiohydrolase Ea values for both A and B horizons in this study were similar to previously reported values, however we could not make a direct comparison for B horizon soils because of the lack of data. There was no consistent relationship between hydrolase enzyme Ea and the environmental variables we measured. Phenol oxidase was the only enzyme that had a consistent positive relationship between Ea and pH in both horizons. The Ea in the arctic and subarctic zones for peroxidase was lower than the hydrolases and phenol oxidase values, indicating peroxidase may be a rate limited enzyme in environments under warming conditions. By including these six soil types we have increased the number of soil oxidative enzyme Ea values reported in the literature by 50%. This study is a step towards better quantifying enzyme kinetics in different climate zones. PMID:23536898

  16. Imaging dynamics on the F + H2O -> HF + OH potential energy surfaces from wells to barriers.

    PubMed

    Otto, Rico; Ma, Jianyi; Ray, Amelia W; Daluz, Jennifer S; Li, Jun; Guo, Hua; Continetti, Robert E

    2014-01-24

    The study of gas-phase reaction dynamics has advanced to a point where four-atom reactions are the proving ground for detailed comparisons between experiment and theory. Here, a combined experimental and theoretical study of the dissociation dynamics of the tetra-atomic FH2O system is presented, providing snapshots of the F + H2O → HF + OH reaction. Photoelectron-photofragment coincidence measurements of the dissociative photodetachment (DPD) of the F(-)(H2O) anion revealed various dissociation pathways along different electronic states. A distinct photoelectron spectrum of stable FH-OH complexes was also measured and attributed to long-lived Feshbach resonances. Comparison to full-dimensional quantum calculations confirms the sensitivity of the DPD measurements to the subtle dynamics on the low-lying FH2O potential energy surfaces over a wide range of nuclear configurations and energies. PMID:24407479

  17. Identifying perceived barriers and benefits to reducing energy consumption in an affordable housing complex using the Community-Based Social Marketing model

    NASA Astrophysics Data System (ADS)

    Reaves, Daniel

    Energy production and consumption has a negative impact on both environmental and human health. Energy consumption can be directly impacted by human behavior, especially in the residential sector. As a result, this sector has been studied significantly; however, energy reducing behavior change research focusing on the affordable housing sector has not been studied thoroughly to date. This study seeks to implement the first two phases of the Community Based Social Marketing (CBSM) framework in an affordable housing setting. The goals were to identify the optimal behaviors for energy reduction based on phase one survey results and to identify the perceived benefits and barriers associated with those behaviors. Additionally, this study identified nuances in the CBSM process that researchers should take into consideration when implementing CBSM in an affordable housing environment.

  18. The barrier to the methyl rotation in Cis-2-butene and its isomerization energy to Trans-2-butene, revisited.

    PubMed

    Matta, Chérif F; Sadjadi, SeyedAbdolreza; Braden, Dale A; Frenking, Gernot

    2016-01-01

    We respond to the two questions posed by Weinhold, Schleyer, and McKee (WSM) in their study of cis-2-butene (Weinhold et al., J Comput Chem 2014, 35, 1499), in which they solicit explanations for the relative conformational energies of this molecule in terms of the Quantum Theory of Atoms in Molecules (QTAIM). WSM requested answers to the questions: (1) why is cis-2-butene less stable than trans-2-butene despite the presence of a hydrogen-hydrogen (H⋯H) bond path in the former but not in the latter if the H⋯H bond path is stabilizing? (2) Why is the potential well of the conformational global minimum of cis-2-butene only 0.8 kcal/mol deep when the H⋯H bonding is stabilizing by 5 kcal/mol? Both questions raised by WSM are answered by considering the changes in the energies of all atoms as a function of the rotation of one of the two methyl groups from the minimum-energy structure, which exhibits the H⋯H bond path, to the transition state, which is devoid of this bond path. It is found that the stability gained by the H⋯H bonding interaction is cancelled by the destabilization of one of the ethylenic carbon atoms which, alone, destabilizes the system by as much as 5 kcal/mol in the global minimum conformation. Further, it is found that the 1.1 kcal/mol stability of trans-2-butene with respect to the cis-isomer is driven by the considerable destabilization of the ethylenic carbons by 11 kcal/mol, while the changes in the atomic energies of the other corresponding atoms in the two isomers account for the observed different stabilities. The error introduced into QTAIM atomic energies by neglecting the virials of the forces on the nuclei for partially optimized structures is discussed. PMID:26581645

  19. Interhabitat differences in energy acquisition and expenditure in a lizard

    SciTech Connect

    Karasov, W.H.; Anderson, R.A.

    1984-02-01

    Cnemidophorus hyperythrus, a small (approx. =4-g) teiid lizard, occurs along an elevational thorn scrub - thorn woodland - thorn forest habitat gradient in the cape region of Baja California. Body size, daily energy expenditure (DEE, measured with doubly labeled water), relative feeding rate (as reflected by H/sub 2/O influx rate), behavior, and abundance of this species at two sites along the gradient were compared. At the inland thorn woodland site C. hyperythrus were more abundant (approx. =100 lizards/ha) than at the thorn scrub site near the ocean (approx. =50 lizards/ha). Mean body mass of woodland site lizards was 13% greater than that of scrub lizards. The DEE of the thorn woodland lizards, 330 J x g/sup -1/ x d/sup -1/,> and their H/sub 2/O influx, 99 mm/sup 3/ x g/sup -1/ x d/sup -1/, were also higher than the thorn scrub lizards', 219 J x g/sup -1/ x d/sup -1/ and 52 mm/sup 3/ x g/sup -1/ x d/sup -1/. Diets at the two sites were similar. There were no differences between sexes in diet, DEE, or H/sub 2/O influx. Daily maintenance energy costs were calculated based upon laboratory measures of O/sub 2/ consumption of resting lizards at a series of temperatures that represented the daily range of body temperatures experienced by lizards in the field. Activity costs (=DEE minus maintenance) were three times higher in the woodland lizards. Behavioral observations showed that woodland lizards were active most of the day (approx. =9 h/d) whereas scrub lizards were active primarily in the morning (approx. =3.5 h/d). Thus, the higher activity cost, DEE, and feeding rate of woodland lizards can be explained by their longer daily activity period. Causal factors for the difference in daily activity period are suggested, and implications of length of daily foraging period for adult body, size, population density, and various life history parameters of lizards are discussed.

  20. Interhabitat differences in energy acquisition and expenditure in a lizard

    SciTech Connect

    Karasov, W.H.; Anderson, R.A.

    1984-02-01

    Cnemidophorus hyperythrus, a small (approx. =4-g) teiid lizard, occurs along an elevational thorn scrub-thorn woodland-thorn forest habitat gradient in the cape region of Baja California. The authors compared body size, daily energy expenditure (DEE, measured with double labeled water), relative feeding rate (as reflected by H/sub 2/O influx rate), behavior, and abundance of this species at two sites along the gradient. At the inland thorn woodland site C. hyperythrus were more abundant (approx. =50 lizards/ha.). Mean body mass of woodland site lizards was 13% greater than that of scrub lizards. The DEE of the thorn woodland lizards, 330 site J x g/sup -1/ x d/sup -1/, and their H/sub 2/O influx, 99 mm/sup 3/ x g/sup -1/ x d/sup -1/, were also higher than the thorn scrub lizards', 219 J x g/sup -1/ x d/sup -1/ and 52 mm/sup 3/ x g/sup -1/ x d/sup -1/. Diets at the two sites were similar. There were no differences between sexes in diet, DEE, or H/sub 2/ influx. Daily maintenance energy costs were calculated based upon laboratory measures of O/sub 2/ consumption of resting lizards at a series of temperatures that represented the daily range of body temperatures experienced by lizards in the field. Activity costs (=DEE minus maintenance) were three times higher in the woodland lizards. Behavioral observations showed that woodland lizards were active most of the day (approx. =9 h/d) whereas scrub lizards were active primarily in the morning (approx. =3.5 h/d). Thus, the higher activity cost, DEE, and feeding rate of woodland lizards can be explained by their longer daily activity period. We suggest causal factors for the difference in daily activity period, and discuss implications of length of daily forging period for adult body size, population density, and various life history parameters of lizards.

  1. Comparative study of different waste biomass for energy application.

    PubMed

    Motghare, Kalyani A; Rathod, Ajit P; Wasewar, Kailas L; Labhsetwar, Nitin K

    2016-01-01

    Biomass is available in many varieties, consisting of crops as well as its residues from agriculture, forestry, and the agro-industry. These different biomass find their way as freely available fuel in rural areas but are also responsible for air pollution. Emissions from such solid fuel combustion to indoor, regional and global air pollution largely depend on fuel types, combustion device, fuel properties, fuel moisture, amount of air supply for combustion and also on climatic conditions. In both economic and environment point of view, gasification constitutes an attractive alternative for the use of biomass as a fuel, than the combustion process. A large number of studies have been reported on a variety of biomass and agriculture residues for their possible use as renewable fuels. Considering the area specific agriculture residues and biomass availability and related transportation cost, it is important to explore various local biomass for their suitability as a fuel. Maharashtra (India) is the mainstay for the agriculture and therefore, produces a significant amount of waste biomass. The aim of the present research work is to analyze different local biomass wastes for their proximate analysis and calorific value to assess their potential as fuel. The biomass explored include cotton waste, leaf, soybean waste, wheat straw, rice straw, coconut coir, forest residues, etc. mainly due to their abundance. The calorific value and the proximate analysis of the different components of the biomass helped in assessing its potential for utilization in different industries. It is observed that ash content of these biomass species is quite low, while the volatile matter content is high as compared to Indian Coal. This may be appropriate for briquetting and thus can be used as a domestic fuel in biomass based gasifier cook stoves. Utilizing these biomass species as fuel in improved cook-stove and domestic gasifier cook-stoves would be a perspective step in the rural energy and

  2. A simplified confinement method for calculating absolute free energies and free energy and entropy differences.

    PubMed

    Ovchinnikov, Victor; Cecchini, Marco; Karplus, Martin

    2013-01-24

    A simple and robust formulation of the path-independent confinement method for the calculation of free energies is presented. The simplified confinement method (SCM) does not require matrix diagonalization or switching off the molecular force field, and has a simple convergence criterion. The method can be readily implemented in molecular dynamics programs with minimal or no code modifications. Because the confinement method is a special case of thermodynamic integration, it is trivially parallel over the integration variable. The accuracy of the method is demonstrated using a model diatomic molecule, for which exact results can be computed analytically. The method is then applied to the alanine dipeptide in vacuum, and to the α-helix ↔ β-sheet transition in a 16-residue peptide modeled in implicit solvent. The SCM requires less effort for the calculation of free energy differences than previous formulations because it does not require computing normal modes. The SCM has a diminished advantage for determining absolute free energy values, because it requires decreasing the MD integration step to obtain accurate results. An approximate confinement procedure is introduced, which can be used to estimate directly the configurational entropy difference between two macrostates, without the need for additional computation of the difference in the free energy or enthalpy. The approximation has convergence properties similar to those of the standard confinement method for the calculation of free energies. The use of the approximation requires about 5 times less wall-clock simulation time than that needed to compute enthalpy differences to similar precision from an MD trajectory. For the biomolecular systems considered in this study, the errors in the entropy approximation are under 10%. Practical applications of the methods to proteins are currently limited to implicit solvent simulations. PMID:23268557

  3. Language barriers

    PubMed Central

    Ngwakongnwi, Emmanuel; Hemmelgarn, Brenda R.; Musto, Richard; King-Shier, Kathryn M.; Quan, Hude

    2012-01-01

    Abstract Objective To assess use of regular medical doctors (RMDs), as well as awareness and use of telephone health lines or telehealth services, by official language minorities (OLMs) in Canada. Design Analysis of data from the 2006 postcensal survey on the vitality of OLMs. Setting Canada. Participants In total, 7691 English speakers in Quebec and 12 376 French speakers outside Quebec, grouped into those who experienced language barriers and those with no language barriers. Main outcome measures Health services utilization (HSU) by the presence of language barriers; HSU measures included having an RMD, use of an RMD’s services, and awareness of and use of telephone health lines or telehealth services. Multivariable models examined the associations between HSU and language barriers. Results After adjusting for age and sex, English speakers residing in Quebec with limited proficiency in French were less likely to have RMDs (adjusted odds ratio [AOR] 0.66, 95% CI 0.50 to 0.87) and to use the services of their RMDs (AOR 0.65, 95% CI 0.50 to 0.86), but were more likely to be aware of the existence of (AOR 1.50, 95% CI 1.16 to 1.93) and to use (AOR 1.43, 95% CI 0.97 to 2.11) telephone health lines or telehealth services. This pattern of having and using RMDs and telehealth services was not observed for French speakers residing outside of Quebec. Conclusion Overall we found variation in HSU among the language barrier populations, with lower use observed in Quebec. Age older than 45 years, male sex, being married or in common-law relationships, and higher income were associated with having RMDs for OLMs. PMID:23242902

  4. Problems in characterizing barrier performance

    NASA Technical Reports Server (NTRS)

    Jordan, Harry F.

    1988-01-01

    The barrier is a synchronization construct which is useful in separating a parallel program into parallel sections which are executed in sequence. The completion of a barrier requires cooperation among all executing processes. This requirement not only introduces the wait for the slowest process delay which is inherent in the definition of the synchronization, but also has implications for the efficient implementation and measurement of barrier performance in different systems. Types of barrier implementation and their relationship to different multiprocessor environments are described. Then the problem of measuring the performance of barrier implementations on specific machine architecture is discussed. The fact that the barrier synchronization requires the cooperation of all processes makes the problem of performance measurement similarly global. Making non-intrusive measurements of sufficient accuracy can be tricky on systems offering only rudimentary measurement tools.

  5. Observations of Surface Energy Fluxes and Boundary-Layer Structure Over Heron Reef, Great Barrier Reef, Australia

    NASA Astrophysics Data System (ADS)

    MacKellar, Mellissa C.; McGowan, Hamish A.; Phinn, Stuart R.; Soderholm, Joshua S.

    2013-02-01

    Over warm, shallow coral reefs the surface radiation and energy fluxes differ from those of the open ocean and result in modification to the marine atmospheric boundary layer via the development of convective internal boundary layers. The complex interrelationships between the surface energy balance and boundary-layer characteristics influence local weather (wind, temperature, humidity) and hydrodynamics (water temperature and currents), as well as larger scale processes, including cloud field properties and precipitation. The nature of these inter-relationships has not been accurately described for coral reef environments. This study presents the first measurements of the surface energy balance, radiation budget and boundary layer thermodynamics made over a coral reef using an eddy-covariance system and radiosonde aerological profiling of the lower atmosphere. Results show that changes in surface properties and the associated energetics across the ocean-reef boundary resulted in modification to the marine atmospheric boundary layer during the Austral winter and summer. Internal convective boundary layers developed within the marine atmospheric boundary layer over the reef and were found to be deeper in the summer, yet more unstable during the winter when cold and drier flow from the mainland enhances heat and moisture fluxes to the atmosphere. A mixed layer was identified in the marine atmospheric boundary layer varying from 375 to 1,200 m above the surface, and was deeper during the summer, particularly under stable anticyclonic conditions. Significant cloud cover and at times rain resulted in the development of a stable stratified atmosphere over the reef. Our findings show that, for Heron Reef, a lagoonal platform reef, there was a horizontal discontinuity in surface energy fluxes across the ocean-reef boundary, which modified the marine atmospheric boundary layer.

  6. Measurement of metastable He{sup *}(2{sup 3}S{sub 1}) density in dielectric barrier discharges with two different configurations operating at around atmospheric pressure

    SciTech Connect

    Tachibana, K.; Kishimoto, Y.; Sakai, O.

    2005-06-15

    We have measured the density of metastable He atoms in the lowest triplet state (2{sup 3}S{sub 1}) with a diode-laser absorption spectroscopic technique in atmospheric pressure plasmas produced by dielectric barrier discharge schemes. Two different types of electrode configuration are employed: one is a conventional parallel-plate system and the other is a microdischarge integrated system with stacked metal-mesh electrodes covered by insulating films. We have analyzed the pressure-broadened spectral line corresponding to the 2{sup 3}S{sub 1}{yields}2{sup 3}P{sub J} (J=0-2) transition to derive the broadening coefficient and to calibrate absolute densities. The measured density ranges from 10{sup 11} to 10{sup 12} cm{sup -3}, but the values in the mesh-type system are larger than those in the parallel-plate system by about one order of magnitude. The density, however, depends strongly on the gas flow rate, showing the influence of quenching by the Penning-ionization process with impurities. Those behaviors are consistent with the variation of the electron density estimated by millimeter-wave transmittance measurement.

  7. Measurement of metastable He*(23S1) density in dielectric barrier discharges with two different configurations operating at around atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Tachibana, K.; Kishimoto, Y.; Sakai, O.

    2005-06-01

    We have measured the density of metastable He atoms in the lowest triplet state (2S13) with a diode-laser absorption spectroscopic technique in atmospheric pressure plasmas produced by dielectric barrier discharge schemes. Two different types of electrode configuration are employed: one is a conventional parallel-plate system and the other is a microdischarge integrated system with stacked metal-mesh electrodes covered by insulating films. We have analyzed the pressure-broadened spectral line corresponding to the 2S13→2PJ3 (J=0-2) transition to derive the broadening coefficient and to calibrate absolute densities. The measured density ranges from 1011 to 1012cm-3, but the values in the mesh-type system are larger than those in the parallel-plate system by about one order of magnitude. The density, however, depends strongly on the gas flow rate, showing the influence of quenching by the Penning-ionization process with impurities. Those behaviors are consistent with the variation of the electron density estimated by millimeter-wave transmittance measurement.

  8. Target or barrier? The cell wall of early- and later-diverging plants vs cadmium toxicity: differences in the response mechanisms.

    PubMed

    Parrotta, Luigi; Guerriero, Gea; Sergeant, Kjell; Cai, Giampiero; Hausman, Jean-Francois

    2015-01-01

    Increasing industrialization and urbanization result in emission of pollutants in the environment including toxic heavy metals, as cadmium and lead. Among the different heavy metals contaminating the environment, cadmium raises great concern, as it is ecotoxic and as such can heavily impact ecosystems. The cell wall is the first structure of plant cells to come in contact with heavy metals. Its composition, characterized by proteins, polysaccharides and in some instances lignin and other phenolic compounds, confers the ability to bind non-covalently and/or covalently heavy metals via functional groups. A strong body of evidence in the literature has shown the role of the cell wall in heavy metal response: it sequesters heavy metals, but at the same time its synthesis and composition can be severely affected. The present review analyzes the dual property of plant cell walls, i.e., barrier and target of heavy metals, by taking Cd toxicity as example. Following a summary of the known physiological and biochemical responses of plants to Cd, the review compares the wall-related mechanisms in early- and later-diverging land plants, by considering the diversity in cell wall composition. By doing so, common as well as unique response mechanisms to metal/cadmium toxicity are identified among plant phyla and discussed. After discussing the role of hyperaccumulators' cell walls as a particular case, the review concludes by considering important aspects for plant engineering. PMID:25814996

  9. Target or barrier? The cell wall of early- and later-diverging plants vs cadmium toxicity: differences in the response mechanisms

    PubMed Central

    Parrotta, Luigi; Guerriero, Gea; Sergeant, Kjell; Cai, Giampiero; Hausman, Jean-Francois

    2015-01-01

    Increasing industrialization and urbanization result in emission of pollutants in the environment including toxic heavy metals, as cadmium and lead. Among the different heavy metals contaminating the environment, cadmium raises great concern, as it is ecotoxic and as such can heavily impact ecosystems. The cell wall is the first structure of plant cells to come in contact with heavy metals. Its composition, characterized by proteins, polysaccharides and in some instances lignin and other phenolic compounds, confers the ability to bind non-covalently and/or covalently heavy metals via functional groups. A strong body of evidence in the literature has shown the role of the cell wall in heavy metal response: it sequesters heavy metals, but at the same time its synthesis and composition can be severely affected. The present review analyzes the dual property of plant cell walls, i.e., barrier and target of heavy metals, by taking Cd toxicity as example. Following a summary of the known physiological and biochemical responses of plants to Cd, the review compares the wall-related mechanisms in early- and later-diverging land plants, by considering the diversity in cell wall composition. By doing so, common as well as unique response mechanisms to metal/cadmium toxicity are identified among plant phyla and discussed. After discussing the role of hyperaccumulators’ cell walls as a particular case, the review concludes by considering important aspects for plant engineering. PMID:25814996

  10. Penetration barrier contributes to bacterial biofilm-associated resistance against only select antibiotics, and exhibits genus-, strain- and antibiotic-specific differences.

    PubMed

    Singh, Rachna; Sahore, Simmi; Kaur, Preetinder; Rani, Alka; Ray, Pallab

    2016-08-01

    Bacterial biofilms are implicated in a wide range of implant-based and chronic infections. These infections are often associated with adverse therapeutic outcomes, owing to the decreased antibiotic susceptibility of biofilms compared with their planktonic counterparts. This altered biofilm susceptibility has been attributed to multiple factors, including a reduced antibiotic penetration. Although several studies have addressed the role of penetration barrier in biofilm-associated drug resistance, it remains inconclusive. This study was done to elucidate antibiotic penetration through biofilms formed by Staphylococcus aureus, S. epidermidis, Escherichia coli and Klebsiella pneumoniae, using an agar disk diffusion assay. Penetration capacity of six antimicrobial drugs from different classes (β-lactams, aminoglycosides, tetracyclines, phenicols, fluoroquinolones and glycopeptides) through biofilms formed by standard strains and clinical isolates from catheter-related bloodstream infections (CRBSI) was elucidated by measuring their growth-inhibition zones in lawn cultures on Mueller-Hinton agar, following diffusion of an antibiotic from an overlying disk through their biofilm to the agar medium. Penetration of only select antimicrobials (vancomycin and chloramphenicol) was hindered through biofilms. There was considerable variation in biofilm-permeating capacity depending upon the genus, strain/CRBSI isolate and antibiotic tested. Furthermore, antibiotics failed to kill the biofilm cells independent of penetration, indicating that other factors contributed substantially to biofilm resistance. PMID:27402781

  11. Quasihomogeneous nucleation of amyloid beta yields numerical bounds for the critical radius, the surface tension, and the free energy barrier for nucleus formation

    NASA Astrophysics Data System (ADS)

    Garai, K.; Sahoo, B.; Sengupta, P.; Maiti, S.

    2008-01-01

    Amyloid aggregates are believed to grow through a nucleation mediated pathway, but important aggregation parameters, such as the nucleation radius, the surface tension of the aggregate, and the free energy barrier toward aggregation, have remained difficult to measure. Homogeneous nucleation theory, if applicable, can directly relate these parameters to measurable quantities. We employ fluorescence correlation spectroscopy to measure the particle size distribution in an aggregating solution of Alzheimer's amyloid beta molecule (Aβ1-40) and analyze the data from a homogeneous nucleation theory perspective. We observe a reproducible saturation concentration and a critical dependence of various aspects of the aggregation process on this saturation concentration, which supports the applicability of the nucleation theory to Aβ aggregation. The measured size distributions show a valley between two peaks ranging from 5to50nm, which defines a boundary for the value of the nucleation radius. By carefully controlling the conditions to inhibit heterogeneous nucleation, we can hold off nucleation in a 25 times supersaturated solution for at least up to 3h at room temperature. This quasi-homogeneous kinetics implies that at room temperature, the surface energy of the Aβ /water interface is ⩾4.8mJ/m2, the free energy barrier to nucleation (at 25 times supersaturation) is ⩾1.93×10-19J, and the number of monomers in the nucleus is ⩾29.

  12. Polarization Energies at Organic-Organic Interfaces: Impact on the Charge Separation Barrier at Donor-Acceptor Interfaces in Organic Solar Cells.

    PubMed

    Ryno, Sean M; Fu, Yao-Tsung; Risko, Chad; Brédas, Jean-Luc

    2016-06-22

    We probe the energetic landscape at a model pentacene/fullerene (C60) interface to investigate the interactions between positive and negative charges, which are critical to the processes of charge separation and recombination in organic solar cells. Using a polarizable force field, we find that polarization energy, i.e., the stabilization a charge feels due to its environment, is larger at the interface than in the bulk for both a positive and a negative charge. The combination of the charge being more stabilized at the interface and the Coulomb attraction between the charges results in a barrier to charge separation at the pentacene/C60 interface that can be in excess of 0.7 eV for static configurations of the donor and acceptor locations. However, the impact of molecular motions, i.e., the dynamics, at the interface at room temperature results in a distribution of polarization energies and in charge separation barriers that can be significantly reduced. The dynamic nature of the interface is thus critical, with the polarization energy distributions indicating that sites along the interface shift in time between favorable and unfavorable configurations for charge separation. PMID:27244215

  13. Simultaneous optical model analysis of elastic scattering, fusion, and breakup for the Be9+Sm144 system at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Gómez Camacho, A.; Gomes, P. R. S.; Lubian, J.; Padrón, I.

    2008-05-01

    A simultaneous optical model calculation of elastic scattering, complete fusion, and breakup cross sections for energies around the Coulomb barrier is presented for reactions involving the weakly bound projectile Be9 on the medium size target Sm144. In the calculations, the nuclear polarization potential U is split into a volume part UF, which is responsible for fusion reactions, and a surface part UDR, which accounts for direct reactions. A simultaneous χ2 analysis of elastic and complete fusion data shows that the extracted optical potential parameters of the real VF and imaginary WF parts of UF and the corresponding parts VDR and WDR of UDR satisfy separately the dispersion relation. Energy-dependent forms for the fusion and direct reaction potentials indicate that, at the strong absorption radius, the direct reaction potentials dominate over the fusion potentials. Moreover, the imaginary direct reaction potential results in a rather smooth function of E around the barrier energy. These findings show that the threshold anomaly, usually present in reactions with tightly bound projectiles, is not exhibited for the system Be9+Sm144. Within this formalism, the effect of breakup reactions on complete fusion is studied by turning on and off the potentials responsible for breakup reactions.

  14. Investigation of Neutron-Rich Osmium Isotopes in the Reaction 136Xe+208Pb at the Energies Close to Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Novikov, K.; Kozulin, E.; Dmitriev, S.; Greenlees, P.; Hannape, F.; Itkis, I. M.; Khlebnikov, S.; Knyazheva, G.; Loktev, T.; Maurer, J.; di Nitto, A.; Pakarinen, J.; Ruotsalainen, P.; Sandzelius, M.; Sorri, J.; Trzaska, W. H.; Vardaci, E.; Zagrebaev, V.

    2013-06-01

    At the present time, a great interest is paid to the research of the properties of atomic nuclei (isotopes) located far from the beta stability line. Neutron-rich osmium isotopes of multi-nucleon transfer reactions investigated in this work. The reaction 136Xe+208Pb with energy near Coulomb barrier is used for production osmium isotopes. The CORSAR-V setup was created in framework of our investigations. Method of separation volatile reaction products from non-volatile products was realized from experimental setup. The fist experimental results were obtained at this time.

  15. Superheavy nuclei and fission barriers

    NASA Astrophysics Data System (ADS)

    Lu, Bing-Nan; Zhao, Jie; Zhao, En-Guang; Zhou, Shan-Gui

    In this chapter, we will present relativistic mean field (RMF) description of heavy and superheavy nuclei (SHN). We will discuss the shell structure and magic numbers in the mass region of SHN, binding energies and α decay Q values, shapes of ground states and potential energy surfaces and fission barriers. We particularly focus on the multidimensionally-constrained covariant density functional theories (CDFT) and the applications of CDFT to the study of exotic nuclear shapes and fission barriers.

  16. The crystal-fluid interfacial free energy and nucleation rate of NaCl from different simulation methods

    NASA Astrophysics Data System (ADS)

    Espinosa, Jorge R.; Vega, Carlos; Valeriani, Chantal; Sanz, Eduardo

    2015-05-01

    In this work, we calculate the crystal-fluid interfacial free energy, γcf, for the Tosi-Fumi model of NaCl using three different simulation techniques: seeding, umbrella sampling, and mold integration. The three techniques give an orientationaly averaged γcf of about 100 mJ/m2. Moreover, we observe that the shape of crystalline clusters embedded in the supercooled fluid is spherical. Using the mold integration technique, we compute γcf for four different crystal orientations. The obtained interfacial free energies range from 100 to 114 mJ/m2, being (100) and (111) the crystal planes with the lowest and highest γcf, respectively. Within the accuracy of our calculations, the interfacial free energy either does not depend on temperature or changes very smoothly with it. Combining the seeding technique with classical nucleation theory, we also estimate nucleation free energy barriers and nucleation rates for a wide temperature range (800-1040 K). The obtained results compare quite well with brute force calculations and with previous results obtained with umbrella sampling [Valeriani et al., J. Chem. Phys, 122, 194501 (2005)].

  17. Energy Use and Quality of Foods Cooked by Different Appliances.

    ERIC Educational Resources Information Center

    Odland, Dianne; And Others

    1987-01-01

    The authors compared energy consumption, cooking time, and quality of five foods cooked using electric range surface units and oven, induction cooktop, electric frypan, microwave oven, and toaster oven. The induction cooktop was among the most energy conserving. For most products, cooking treatment had little impact on quality. (Author/CH)

  18. Sex Differences in Attitudes Toward New Energy Resource Developments.

    ERIC Educational Resources Information Center

    Stout-Wiegand, Nancy; Trent, Roger B.

    A survey to examine male and female attitudes toward locally proposed energy developments (e.g., coal production, refineries) in an Appalachian community is reported. Four hundred and eighty-five residents were questioned on whether they favor the proposed developments; whether they were currently employed in an energy-related occupation; and…

  19. Barrier rf systems in synchrotrons

    SciTech Connect

    Chandra M. Bhat

    2004-06-28

    Recently, many interesting applications of the barrier RF system in hadron synchrotrons have been realized. A remarkable example of this is the development of longitudinal momentum mining and implementation at the Fermilab Recycler for extraction of low emittance pbars for the Tevatron shots. At Fermilab, we have barrier RF systems in four different rings. In the case of Recycler Ring, all of the rf manipulations are carried out using a barrier RF system. Here, the author reviews various uses of barrier rf systems in particle accelerators including some new schemes for producing intense proton beam and possible new applications.

  20. Barriers of the peripheral nerve

    PubMed Central

    Peltonen, Sirkku; Alanne, Maria; Peltonen, Juha

    2013-01-01

    This review introduces the traditionally defined anatomic compartments of the peripheral nerves based on light and electron microscopic topography and then explores the cellular and the most recent molecular basis of the different barrier functions operative in peripheral nerves. We also elucidate where, and how, the homeostasis of the normal human peripheral nerve is controlled in situ and how claudin-containing tight junctions contribute to the barriers of peripheral nerve. Also, the human timeline of the development of the barriers of the peripheral nerve is depicted. Finally, potential future therapeutic modalities interfering with the barriers of the peripheral nerve are discussed. PMID:24665400

  1. The Oklahoma Field Test: Air-conditioning electricity savings from standard energy conservation measures, radiant barriers, and high-efficiency window air conditioners

    SciTech Connect

    Ternes, M.P.; Levins, W.P.

    1992-08-01

    A field test Involving 104 houses was performed in Tulsa, Oklahoma, to measure the air-conditioning electricity consumption of low-income houses equipped with window air conditioners, the reduction in this electricity consumption attributed to the installation of energy conservation measures (ECMS) as typically installed under the Oklahoma Weatherization Assistance Program (WAP), and the reduction achieved by the replacement of low-efficiency window air conditioners with high-efficiency units and the installation of attic radiant barriers. Air-conditioning electricity consumption and indoor temperature were monitored weekly during the pre-weatherization period (June to September 1988) and post-weatherization period (May to September 1989). House energy consumption models and regression analyses were used to normalize the air-conditioning electricity savings to average outdoor temperature conditions and the pre-weatherization indoor temperature of each house. The following conclusions were drawn from the study: (1) programs directed at reducing air-conditioning electricity consumption should be targeted at clients with high consumption to improve cost effectiveness; (2) replacing low-efficiency air conditioners with high-efficiency units should be considered an option in a weatherization program directed at reducing air-conditioning electricity consumption; (3) ECMs currently being installed under the Oklahoma WAP (chosen based on effectiveness at reducing space-heating energy consumption) should continue to be justified based on their space-heating energy savings potential only; and (4) attic radiant barriers should not be included in the Oklahoma WAP if alternatives with verified savings are available or until further testing demonstrates energy savings or other benefits in this typo of housing.

  2. Gene expression of fatty acid transport and binding proteins in the blood-brain barrier and the cerebral cortex of the rat: differences across development and with different DHA brain status.

    PubMed

    Pélerin, Hélène; Jouin, Mélanie; Lallemand, Marie-Sylvie; Alessandri, Jean-Marc; Cunnane, Stephen C; Langelier, Bénédicte; Guesnet, Philippe

    2014-11-01

    Specific mechanisms for maintaining docosahexaenoic acid (DHA) concentration in brain cells but also transporting DHA from the blood across the blood-brain barrier (BBB) are not agreed upon. Our main objective was therefore to evaluate the level of gene expression of fatty acid transport and fatty acid binding proteins in the cerebral cortex and at the BBB level during the perinatal period of active brain DHA accretion, at weaning, and until the adult age. We measured by real time RT-PCR the mRNA expression of different isoforms of fatty acid transport proteins (FATPs), long-chain acyl-CoA synthetases (ACSLs), fatty acid binding proteins (FABPs) and the fatty acid transporter (FAT)/CD36 in cerebral cortex and isolated microvessels at embryonic day 18 (E18) and postnatal days 14, 21 and 60 (P14, P21 and P60, respectively) in rats receiving different n-3 PUFA dietary supplies (control, totally deficient or DHA-supplemented). In control rats, all the genes were expressed at the BBB level (P14 to P60), the mRNA levels of FABP5 and ACSL3 having the highest values. Age-dependent differences included a systematic decrease in the mRNA expressions between P14-P21 and P60 (2 to 3-fold), with FABP7 mRNA abundance being the most affected (10-fold). In the cerebral cortex, mRNA levels varied differently since FATP4, ACSL3 and ACSL6 and the three FABPs genes were highly expressed. There were no significant differences in the expression of the 10 genes studied in n-3 deficient or DHA-supplemented rats despite significant differences in their brain DHA content, suggesting that brain DHA uptake from the blood does not necessarily require specific transporters within cerebral endothelial cells and could, under these experimental conditions, be a simple passive diffusion process. PMID:25123062

  3. C sbnd N rotational barrier, MP4 and CCSD(T) energies of formohydrazide and formohydroxamic acid and vibrational spectral analysis of the hydrazide

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.

    2009-02-01

    The C sbnd N internal rotations in formohydrazide OHC sbnd NH sbnd NH 2 and formohydroxamic acid OHC sbnd NH sbnd OH were investigated at the B3LYP/6-311+G** and MP2/6-311+G** levels of theory. The C sbnd N rotational barrier in the molecules was calculated to be about 28-30 kcal/mol. The energies of the molecules were calculated at the B3LYP, MP2, MP4(SDTQ) and CCSD(T) levels of theory with both 6-311G** and 6-311+G** basis sets. From the calculations at all the levels formohydroxamic acid was predicted to exist predominantly in a non-planar near- cis conformation at ambient temperature. From all the calculations formohydrazide was predicted to have a planar cis-syn (C dbnd O and N sbnd N bonds eclipse each other and NH 2 moiety is syn to C sbnd N bond) conformation as the lowest energy structure. The NH 2 inversion barrier in formohydrazide was predicted to be about 5-7 kcal/mol. The vibrational frequencies of the cis-syn formohydrazide were computed at the B3LYP/6-311+G** level and normal coordinate calculations were carried out. Complete vibrational assignments were made on the basis of normal coordinate analyses and experimental infrared and Raman data of the molecule.

  4. Influence of chlorine substitution on intramolecular hydrogen bond energy and ESIPT barrier: Experimental and theoretical measurements on the photophysics of 3,5-dichlorosalicylic acid

    NASA Astrophysics Data System (ADS)

    Paul, Bijan Kumar; Samanta, Anuva; Guchhait, Nikhil

    2010-08-01

    The effect of chlorine atom on the intramolecular hydrogen bond strength and excited state proton transfer barrier in pharmaceutically important chloro-substituted derivative of salicylic acid viz., 3,5-dichlorosalicylic acid (3,5DCSA) has been explored through steady-state absorption, emission and time-resolved fluorescence spectroscopy. Stokes shifted emission band with negligible solvent polarity dependency corresponds to the spectroscopic signature of excited state intramolecular proton transfer (ESIPT) reaction. The spectral signature was compared with its parent molecule salicylic acid (SA) and 5-chlorosalicylic acid (5ClSA). Quantum chemical calculations by ab initio Hartree-Fock (HF) and Density Functional Theory (DFT) methods have been fruitfully employed to correlate experimental findings. Calculated S0 and S1 states potential energy surfaces across the proton transfer co-ordinate substantiates the experimental evidence for the occurrence of ESIPT process and negates the ground state intramolecular proton transfer (GSIPT) reaction. Weakening of intramolecular hydrogen bond (IMHB) energy and subsequent enhancement of barrier to ESIPT reaction in 3,5DCSA as compared to SA and 5ClSA appears to be a reflection of conjugate impact of electron withdrawing inductive and electron donating resonance effects of chlorine substitutions depending on its location on the aromatic benzene nucleus.

  5. Health and climate benefits of different energy-efficiency and renewable energy choices

    NASA Astrophysics Data System (ADS)

    Buonocore, Jonathan J.; Luckow, Patrick; Norris, Gregory; Spengler, John D.; Biewald, Bruce; Fisher, Jeremy; Levy, Jonathan I.

    2016-01-01

    Energy efficiency (EE) and renewable energy (RE) can benefit public health and the climate by displacing emissions from fossil-fuelled electrical generating units (EGUs). Benefits can vary substantially by EE/RE installation type and location, due to differing electricity generation or savings by location, characteristics of the electrical grid and displaced power plants, along with population patterns. However, previous studies have not formally examined how these dimensions individually and jointly contribute to variability in benefits across locations or EE/RE types. Here, we develop and demonstrate a high-resolution model to simulate and compare the monetized public health and climate benefits of four different illustrative EE/RE installation types in six different locations within the Mid-Atlantic and Lower Great Lakes of the United States. Annual benefits using central estimates for all pathways ranged from US$5.7-US$210 million (US$14-US$170 MWh-1), emphasizing the importance of site-specific information in accurately estimating public health and climate benefits of EE/RE efforts.

  6. Regional differences in blood-brain barrier permeability changes and inflammation in the apathogenic clearance of virus from the central nervous system.

    PubMed

    Phares, Timothy W; Kean, Rhonda B; Mikheeva, Tatiana; Hooper, D Craig

    2006-06-15

    The loss of blood-brain barrier (BBB) integrity in CNS inflammatory responses triggered by infection and autoimmunity has generally been associated with the development of neurological signs. In the present study, we demonstrate that the clearance of the attenuated rabies virus CVS-F3 from the CNS is an exception; increased BBB permeability and CNS inflammation occurs in the absence of neurological sequelae. We speculate that regionalization of the CNS inflammatory response contributes to its lack of pathogenicity. Despite virus replication and the expression of several chemokines and IL-6 in both regions being similar, the up-regulation of MIP-1beta, TNF-alpha, IFN-gamma, and ICAM-1 and the loss of BBB integrity was more extensive in the cerebellum than in the cerebral cortex. The accumulation of CD4- and CD19-positive cells was higher in the cerebellum than the cerebral cortex. Elevated CD19 levels were paralleled by kappa-L chain expression levels. The timing of BBB permeability changes, kappa-L chain expression in CNS tissues, and Ab production in the periphery suggest that the in situ production of virus-neutralizing Ab may be more important in virus clearance than the infiltration of circulating Ab. The data indicate that, with the possible exception of CD8 T cells, the effectors of rabies virus clearance are more commonly targeted to the cerebellum. This is likely the result of differences in the capacity of the tissues of the cerebellum and cerebral cortex to mediate the events required for BBB permeability changes and cell invasion during virus infection. PMID:16751414

  7. Development of Simultaneous Corrosion Barrier and Optimized Microstructure in FeCrAl Heat-Resistant Alloy for Energy Applications. Part 1: The Protective Scale

    NASA Astrophysics Data System (ADS)

    Pimentel, G.; Aranda, M. M.; Chao, J.; González-Carrasco, J. L.; Capdevila, C.

    2015-09-01

    Coarse-grained Fe-based oxide dispersion-strengthened (ODS) steels are a class of advanced materials for combined cycle gas turbine systems to deal with operating temperatures and pressures of around 1100°C and 15-30 bar in aggressive environments, which would increase biomass energy conversion efficiencies up to 45% and above. This two-part paper reports the possibility of the development of simultaneous corrosion barrier and optimized microstructure in a FeCrAl heat-resistant alloy for energy applications. The first part reports the mechanism of generating a dense, self-healing α-alumina layer by thermal oxidation, during a heat treatment that leads to a coarse-grained microstructure with a potential value for high-temperature creep resistance in a FeCrAl ODS ferritic alloy, which will be described in more detail in the second part.

  8. Overcoming Barriers.

    PubMed

    Neal-Boylan, Leslie; Schmidt, Kari L

    2015-01-01

    Dr. Neal-Boylan's program of scholarship has always focused on nurse workforce issues. She recently published two books related to how nurses work. One (The Nurse's Reality Gap: Overcoming Barriers Between Academic Achievement and Clinical Success; Neal-Boylan, 2013) focused on the experience of new graduates from baccalaureate, master's, and doctoral programs. The second book, The Nurse's Reality Shift: Using Our History to Transform Our Future (Neal-Boylan, 2014), focuses on the problems nursing continues to face throughout our history and has failed to correct. PMID:26200309

  9. Consumer Attitudes About Renewable Energy. Trends and Regional Differences

    SciTech Connect

    Bird, Lori; Sumner, Jenny

    2011-04-01

    The data in this report are taken from Natural Marketing Institute's (NMI's) Lifestyles of Health and Sustainability Consumer Trends Database. Created in 2002, the syndicated consumer database contains responses from 2,000 to 4,000 nationally representative U.S. adults (meaning the demographics of the sample are consistent with U.S. Census findings) each year. NMI used the database to analyze consumer attitudes and behavior related to renewable energy and to update previously conducted related research. Specifically, this report will explore consumer awareness, concerns, perceived benefits, knowledge of purchase options, and usage of renewable energy as well as provide regional comparisons and trends over time.

  10. Consumer Attitudes About Renewable Energy: Trends and Regional Differences

    SciTech Connect

    Natural Marketing Institute, Harleysville, Pennsylvania

    2011-04-01

    The data in this report are taken from Natural Marketing Institute's (NMI's) Lifestyles of Health and Sustainability Consumer Trends Database. Created in 2002, the syndicated consumer database contains responses from 2,000 to 4,000 nationally representative U.S. adults (meaning the demographics of the sample are consistent with U.S. Census findings) each year. NMI used the database to analyze consumer attitudes and behavior related to renewable energy and to update previously conducted related research. Specifically, this report will explore consumer awareness, concerns, perceived benefits, knowledge of purchase options, and usage of renewable energy as well as provide regional comparisons and trends over time.

  11. Fusion barrier distribution described by above-barrier resonances

    NASA Astrophysics Data System (ADS)

    Sahu, B.; Agarwalla, S. K.; Shastry, C. S.

    2003-01-01

    We have constructed an analytically solvable, smooth, short-ranged, realistic and composite barrier potential with parameters controlling the flatness at the top, the range and the asymmetry of the barrier. When certain condition on flatness is obeyed, the transmission coefficient (T) across this barrier is found to be oscillatory in the above-barrier region of energy representing above-barrier resonances (ABR). Using this T with proper dependence on angular momentum, we estimate the results of fusion cross section σ f and the distribution function {d2(Eσ f) }/{dE 2} in the cases of two best studied examples namely 16O +144Sm and 16O +208Pb systems. On comparison with the corresponding experimental data we find good explanations of these fusion data. The asymmetry in the composite barrier addresses the problem of sub-barrier enhancement of σ f data. On the other hand, for the first time, the oscillatory structure in the results of {d2(Eσ f) }/{dE 2} is proved to be the manifestation of ABR sustained by the composite barrier by virtue of its flatness at the top.

  12. Bonneville Power Administration and the Industrial Technologies Program Leverage Support to Overcome Energy Efficiency Barriers in the Northwest

    SciTech Connect

    2010-06-18

    Through its Energy Smart Industrial program, BPA is informing and assisting utilities and industries to have a better understanding of the benefits that come from participating in energy-savings programs. Read about how BPA is encouraging energy efficiency projects through its utilities.

  13. Barrier Formation

    PubMed Central

    Lyaruu, D.M.; Medina, J.F.; Sarvide, S.; Bervoets, T.J.M.; Everts, V.; DenBesten, P.; Smith, C.E.; Bronckers, A.L.J.J.

    2014-01-01

    Enamel fluorosis is an irreversible structural enamel defect following exposure to supraoptimal levels of fluoride during amelogenesis. We hypothesized that fluorosis is associated with excess release of protons during formation of hypermineralized lines in the mineralizing enamel matrix. We tested this concept by analyzing fluorotic enamel defects in wild-type mice and mice deficient in anion exchanger-2a,b (Ae2a,b), a transmembrane protein in maturation ameloblasts that exchanges extracellular Cl− for bicarbonate. Defects were more pronounced in fluorotic Ae2a,b−/− mice than in fluorotic heterozygous or wild-type mice. Phenotypes included a hypermineralized surface, extensive subsurface hypomineralization, and multiple hypermineralized lines in deeper enamel. Mineral content decreased in all fluoride-exposed and Ae2a,b−/− mice and was strongly correlated with Cl−. Exposure of enamel surfaces underlying maturation-stage ameloblasts to pH indicator dyes suggested the presence of diffusion barriers in fluorotic enamel. These results support the concept that fluoride stimulates hypermineralization at the mineralization front. This causes increased release of protons, which ameloblasts respond to by secreting more bicarbonates at the expense of Cl− levels in enamel. The fluoride-induced hypermineralized lines may form barriers that impede diffusion of proteins and mineral ions into the subsurface layers, thereby delaying biomineralization and causing retention of enamel matrix proteins. PMID:24170372

  14. Binary association complexes of LiH, BeH/sub 2/, and BH/sub 3/. Relative isomer stabilities and barrier heights for their interconversion: energy barriers in the dimerization reactions

    SciTech Connect

    DeFrees, D.J.; Raghavachari, K.; Schlegel, H.B.; Pople, J.A.; Schleyer, P.v.R.

    1987-03-26

    Ab initio molecular orbital theory has been used to study the six compounds Li/sub 2/H/sub 2/, LiBeH/sub 3/, LiBH/sub 4/, Be/sub 2/H/sub 4/, BeBH/sub 5/, and B/sub 2/H/sub 6/. Geometry optimizations and vibrational analysis at the HF/6-31G* level indicate Li--(H)/sub 2/--Li (D/sub 2h/), Li--(H)/sub 2/--BeH (C/sub 2v/), Li--(H)/sub 3/--BH (C/sub 3v/), HBe--(H)/sub 2/--BeH (D/sub 2h/), HBe--(H)/sub 3/--BH (C/sub 3v/), and H/sub 2/B--(H)/sub 2/--BH/sub 2/ (D/sub 2h/) to the most stable forms. Inclusion of electron correlation corrections at the MP4/6-31G** level does not alter these conclusions. Other isomers were also examined in detail, and it was found that the potential energy surfaces for the species are generally flat. Activation energies for isomer interconversion and hydrogen scrambling reactions are generally less than 10 kcal mol/sup -1/. Examination of the HF/3-21 G potential surfaces indicates that there is no activation energy for the dimerization of LiH or BeH/sub 2/. The same is true for the dimerization of BH/sub 3/ at the correlated MP26-31G* level, although a small barrier is found on the HF/6-31G* surface. Enthalpies of complexation at 298 K from separate LiH, BeH/sub 2/, and BH/sub 3/ fragments, ..delta..H/sup 0//sub 298/, computed by using the HF/6-31G* harmonic frequencies and the MP4/6-31G** electronic energies are as follows: Li/sub 2/H/sub 2/, -45.9; LiBeH/sub 3/, -43.6; LiBH/sub 4/, -60.1; Be/sub 2/H/sub 4/, -30.5; BeBH/sub 5/, -45.7; B/sub 2/H/sub 6/, -36.0 kcal mol/sup -1/.

  15. Competition of different methods for recovering energy from waste.

    PubMed

    Friege, Henning; Fendel, Ansgar

    2011-10-01

    Waste-to-energy (WtE) facilities have been established worldwide as a sustainable method for the disposal of residual waste. In the present study the following competing WtE systems were compared: (1) municipal solid waste incinerators (MSWIs) with energy recovery; (2) co-incineration of waste in old lignite or coal-fired power plants; (3) substitute [refuse-derived fuel (RDF)] incinerators with energy recovery; and (4) co-incineration of defined waste fractions in cement kilns. In general the municipal solid waste incinerators in Europe are designed for a broad range of municipal and commercial waste without a pre-treatment of the waste. All other WtE processes including the cement kilns require a pre-treatment and are more limited in terms of RDF composition; namely particle size, chlorine content, calorific value. As to Germany, the emission limit values for all facilities are similar. A sensitivity analysis of the economics of boilers using RDF and municipal solid waste leads to the conclusion that the feasibility of RDF incinerators might partially recover if the prices for primary energy increase again. On the other hand, pre-treatment of waste leads to higher costs for RDF. Incineration and recycling capacities are large enough in middle Europe to avoid landfilling of organic waste. The steep decline of gate fees observed in some national spot markets is a clear indicator of an already existing overcapacity. Considering the enormous amount of greenhouse gas emissions saved by WtE facilities in comparison with landfilling, free capacities of WtE installations should be used to incinerate waste from EU member states where waste disposal is still predominantly based on landfilling. PMID:21824986

  16. Translocation of LRP1 targeted carbon nanotubes of different diameters across the blood–brain barrier in vitro and in vivo

    PubMed Central

    Kafa, Houmam; Wang, Julie Tzu-Wen; Rubio, Noelia; Klippstein, Rebecca; Costa, Pedro M.; Hassan, Hatem A.F.M.; Sosabowski, Jane K.; Bansal, Sukhvinder S.; Preston, Jane E.; Abbott, N. Joan; Al-Jamal, Khuloud T.

    2016-01-01

    Brain glioblastoma and neurodegenerative diseases are still largely untreated due to the inability of most drugs to cross the blood–brain barrier (BBB). Nanoparticles have emerged as promising tools for drug delivery applications to the brain; in particular carbon nanotubes (CNTs) that have shown an intrinsic ability to cross the BBB in vitro and in vivo. Angiopep-2 (ANG), a ligand for the low-density lipoprotein receptor-related protein-1 (LRP1), has also shown promising results as a targeting ligand for brain delivery using nanoparticles (NPs). Here, we investigate the ability of ANG-targeted chemically-functionalised multi-walled carbon nanotubes (f-MWNTs) to cross the BBB in vitro and in vivo. ANG was conjugated to wide and thin f-MWNTs creating w-MWNT-ANG and t-MWNT-ANG, respectively. All f-MWNTs were radiolabelled to facilitate quantitative analyses by γ-scintigraphy. ANG conjugation to f-MWNTs enhanced BBB transport of w- and t-MWNTs-ANG compared to their non-targeted equivalents using an in vitro co-cultured BBB model consisting of primary porcine brain endothelial cells (PBEC) and primary rat astrocytes. Additionally, following intravenous administration w-MWNTs-ANG showed significantly higher whole brain uptake than the non-targeted w-MWNT in vivo reaching ~ 2% injected dose per g of brain (%ID/g) within the first hour post-injection. Furthermore, using a syngeneic glioma model, w-MWNT-ANG showed enhanced uptake in glioma brain compared to normal brain at 24 h post-injection. t-MWNTs-ANG, on the other hand, showed higher brain accumulation than w-MWNTs. However, no significant differences were observed between t-MWNT and t-MWNT-ANG indicating the importance of f-MWNTs diameter towards their brain accumulation. The inherent brain accumulation ability of f-MWNTs coupled with improved brain-targeting by ANG favours the future clinical applications of f-MWNT-ANG to deliver active therapeutics for brain glioma therapy. PMID:26809004

  17. Energy Inputs Uncertainty: Total Amount, Distribution and Correlation Between Different Forms of Energy

    NASA Technical Reports Server (NTRS)

    Deng, Yue

    2014-01-01

    Describes solar energy inputs contributing to ionospheric and thermospheric weather processes, including total energy amounts, distributions and the correlation between particle precipitation and Poynting flux.

  18. Energies and wave functions of an off-centre donor in hemispherical quantum dot: Two-dimensional finite difference approach and ritz variational principle

    NASA Astrophysics Data System (ADS)

    Nakra Mohajer, Soukaina; El Harouny, El Hassan; Ibral, Asmaa; El Khamkhami, Jamal; Assaid, El Mahdi

    2016-09-01

    Eigenvalues equation solutions of a hydrogen-like donor impurity, confined in a hemispherical quantum dot deposited on a wetting layer and capped by an insulating matrix, are determined in the framework of the effective mass approximation. Conduction band alignments at interfaces between quantum dot and surrounding materials are described by infinite height barriers. Ground and excited states energies and wave functions are determined analytically and via one-dimensional finite difference approach in case of an on-center donor. Donor impurity is then moved from center to pole of hemispherical quantum dot and eigenvalues equation is solved via Ritz variational principle, using a trial wave function where Coulomb attraction between electron and ionized donor is taken into account, and by two-dimensional finite difference approach. Numerical codes developed enable access to variations of donor total energy, binding energy, Coulomb correlation parameter, spatial extension and radial probability density with respect to hemisphere radius and impurity position inside the quantum dot.

  19. Barrier infrared detector

    NASA Technical Reports Server (NTRS)

    Ting, David Z. (Inventor); Khoshakhlagh, Arezou (Inventor); Soibel, Alexander (Inventor); Hill, Cory J. (Inventor); Gunapala, Sarath D. (Inventor)

    2012-01-01

    A superlattice-based infrared absorber and the matching electron-blocking and hole-blocking unipolar barriers, absorbers and barriers with graded band gaps, high-performance infrared detectors, and methods of manufacturing such devices are provided herein. The infrared absorber material is made from a superlattice (periodic structure) where each period consists of two or more layers of InAs, InSb, InSbAs, or InGaAs. The layer widths and alloy compositions are chosen to yield the desired energy band gap, absorption strength, and strain balance for the particular application. Furthermore, the periodicity of the superlattice can be "chirped" (varied) to create a material with a graded or varying energy band gap. The superlattice based barrier infrared detectors described and demonstrated herein have spectral ranges covering the entire 3-5 micron atmospheric transmission window, excellent dark current characteristics operating at least 150K, high yield, and have the potential for high-operability, high-uniformity focal plane arrays.

  20. Tissue Barriers: Introducing an exciting new journal

    PubMed Central

    Ivanov, Andrei I

    2014-01-01

    This Editorial is written to introduce Tissue Barriers, a new Taylor & Francis journal, to the readers of Temperature. It describes the role of temperature in the regulation of different tissue barriers under normal and disease conditions. It also highlights the most interesting articles published in the first volume of Tissue Barriers.

  1. Epistemological barriers to radical behaviorism

    PubMed Central

    O'Donohue, William T.; Callaghan, Glenn M.; Ruckstuhl, L. E.

    1998-01-01

    The historian and philosopher of science Gaston Bachelard proposed the concept of epistemological barriers to describe the intellectual challenges encountered by scientists in their work. In order to embrace novel ways of approaching a problem in science, scientists must overcome barriers or obstacles posed by their prior views. For example, Einsteinian physics presents scientists with claims that space is curved and that time and space are on the same continuum. We utilize Bachelard's concept of epistemological barriers to describe the differences between the intellectual journeys students pursuing advanced studies face when attempting to accept cognitive psychology or radical behaviorism. We contend that the folk psychological beliefs that students typically hold when entering these studies pose less challenge to cognitive psychology than to radical behaviorism. We also suggest that these barriers may also partly be involved in the problematic exegesis that has plagued radical behaviorism. In close, we offer some suggestions for dealing with these epistemological barriers. PMID:22478314

  2. The impact of energy barrier height on border traps in the metal insulator semicondoctor gate stacks on III–V semiconductors

    NASA Astrophysics Data System (ADS)

    Yoshida, Shinichi; Taniguchi, Satoshi; Minari, Hideki; Lin, Dennis; Ivanov, Tsvetan; Watanabe, Heiji; Nakazawa, Masashi; Collaert, Nadine; Thean, Aaron

    2016-08-01

    We investigated the effect of a thin interfacial layer (IL) made of silicon or germanium between high-k dielectrics and III–V semiconductors on the frequency dispersion of the capacitance–voltage (C–V) curves in detail. We demonstrated experimentally that the frequency dispersion at accumulation voltage is strongly dependent on the energy barrier height (ΦB) between high-k dielectrics and semiconductors. It was revealed that the improvement of frequency dispersion for n-type III–V semiconductors with IL is attributed to the increase in ΦB realized by inserting Ge IL. Moreover, the border trap density did not necessarily decrease with IL through the assessment of border trap density using a distributed bulk-oxide trap model. Finally, we proved that it is important to increase ΦB to suppress the carrier exchange and improve high-k/III–V gate stack reliability.

  3. Structural anisotropy of cyanido-bridged {CoW} single-molecule magnets induced by bidentate ligands: towards the rational enhancement of an energy barrier.

    PubMed

    Chorazy, Szymon; Rams, Michał; Hoczek, Anna; Czarnecki, Bernard; Sieklucka, Barbara; Ohkoshi, Shin-Ichi; Podgajny, Robert

    2016-04-01

    Pentadecanuclear {Co[W(V)(CN)8]6} clusters were combined with bidentate 2,2'-bipyridine N,N'-dioxide (2,2'-bpdo) ligands resulting in two distinct molecules, {Co9W6(2,2'-bpdo)7} (cluster A) and {Co9W6(2,2'-bpdo)6} (cluster B), capped by seven and six 2,2'-bpdo ligands, respectively. They crystallize within a single {Co9W6(2,2'-bpdo)7}·{Co9W6(2,2'-bpdo)6}·solvent (1) supramolecular network, and reveal single-molecule magnet behaviour with an enhanced energy barrier, a ΔE/kB of 30.0(8) K, which was tentatively ascribed to seven-capped axially deformed cluster A. PMID:26933695

  4. Fission Barriers of Compound Superheavy Nuclei

    SciTech Connect

    Pei, Junchen; Nazarewicz, Witold; Sheikh, J. A.; Kerman, A. K.

    2009-01-01

    The dependence of fission barriers on the excitation energy of the compound nucleus impacts the survival probability of superheavy nuclei synthesized in heavy-ion fusion reactions. We study the temperature-dependent fission barriers by means of the self-consistent nuclear density functional theory. The equivalence of isothermal and isentropic descriptions is demonstrated. The effect of the particle gas is found to be negligible in the range of temperatures studied. Calculations have been carried out for ^{264}Fm, ^{272}Ds, ^{278}112, ^{292}114, and ^{312}124. For nuclei around ^{278}112 produced in "cold fusion" reactions, we predict a more rapid decrease of fission barriers with temperature as compared to the nuclei around ^{292}114 synthesized in "hot fusion" experiments. This is explained in terms of the difference between the ground-state and fission-barrier temperatures. Our calculations are consistent with the long survival probabilities of the superheavy elements produced in Dubna with the ^{48}Ca beam.

  5. PLATYPUS: A code for reaction dynamics of weakly-bound nuclei at near-barrier energies within a classical dynamical model

    NASA Astrophysics Data System (ADS)

    Diaz-Torres, Alexis

    2011-04-01

    A self-contained Fortran-90 program based on a three-dimensional classical dynamical reaction model with stochastic breakup is presented, which is a useful tool for quantifying complete and incomplete fusion, and breakup in reactions induced by weakly-bound two-body projectiles near the Coulomb barrier. The code calculates (i) integrated complete and incomplete fusion cross sections and their angular momentum distribution, (ii) the excitation energy distribution of the primary incomplete-fusion products, (iii) the asymptotic angular distribution of the incomplete-fusion products and the surviving breakup fragments, and (iv) breakup observables, such as angle, kinetic energy and relative energy distributions. Program summaryProgram title: PLATYPUS Catalogue identifier: AEIG_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIG_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 332 342 No. of bytes in distributed program, including test data, etc.: 344 124 Distribution format: tar.gz Programming language: Fortran-90 Computer: Any Unix/Linux workstation or PC with a Fortran-90 compiler Operating system: Linux or Unix RAM: 10 MB Classification: 16.9, 17.7, 17.8, 17.11 Nature of problem: The program calculates a wide range of observables in reactions induced by weakly-bound two-body nuclei near the Coulomb barrier. These include integrated complete and incomplete fusion cross sections and their spin distribution, as well as breakup observables (e.g. the angle, kinetic energy, and relative energy distributions of the fragments). Solution method: All the observables are calculated using a three-dimensional classical dynamical model combined with the Monte Carlo sampling of probability-density distributions. See Refs. [1,2] for further details. Restrictions: The

  6. Westinghouse thermal barrier coatings development

    SciTech Connect

    Goedjen, J.G.; Wagner, G.

    1995-10-01

    Westinghouse, in conjunction with the Department of Energy and Oak Ridge National Laboratory, has embarked upon a program for the development of advanced thermal barrier coatings for industrial gas turbines. Development of thermal barrier coatings (TBC`s) for industrial gas turbines has relied heavily on the transfer of technology from the aerospace industry. Significant differences in the time/temperature/stress duty cycles exist between these two coating applications. Coating systems which perform well in aerospace applications may not been optimized to meet power generation performance requirements. This program will focus on development of TBC`s to meet the specific needs of power generation applications. The program is directed at developing a state-of-the-art coating system with a minimum coating life of 25,000 hours at service temperatures required to meet increasing operating efficiency goals. Westinghouse has assembled a team of university and industry leaders to accomplish this goal. Westinghouse will coordinate the efforts of all program participants. Chromalloy Turbine Technologies, Inc. and Sermatech International, Inc. will be responsible for bond coat and TBC deposition technology. Praxair Specialty Powders, Inc. will be responsible for the fabrication of all bond coat and ceramic powders for the program. Southwest Research Institute will head the life prediction modelling effort; they will also be involved in coordinating nondestructive evaluation (NDE) efforts. Process modelling will be provided by the University of Arizona.

  7. Circularly polarized antennas for active holographic imaging through barriers

    SciTech Connect

    McMakin, Douglas L; Severtsen, Ronald H; Lechelt, Wayne M; Prince, James M

    2011-07-26

    Circularly-polarized antennas and their methods of use for active holographic imaging through barriers. The antennas are dielectrically loaded to optimally match the dielectric constant of the barrier through which images are to be produced. The dielectric loading helps to remove barrier-front surface reflections and to couple electromagnetic energy into the barrier.

  8. Over the Barrier in Wave Mechanics.

    ERIC Educational Resources Information Center

    Burge, E. J.

    1984-01-01

    Discusses the transmission of incident energies at a one-dimensional square barrier when energies are greater than the barrier height and the region accommodates a whole number of half wavelengths of psi. Describes sketching the probability density curve, physical interpretation, and special cases. An appendix develops the mathematics in greater…

  9. [Food energy expenditure by the moth Lymantria dispar L. (Lepidoptera, Lymantriidae) at different stages of ontogenesis].

    PubMed

    Vshivkova, T A

    2003-01-01

    Food energy expenditures by gypsy moth at different developmental stages under conditions of feeding on larch needles are described. The distribution of total food energy (%) for metabolism, the formation of exuvia (throughout ontogeny), and the formation of an adult insect is assessed. The proportion of food energy lost with excrements over the entire period of feeding is the same (58%) in females and males. The assimilated part of food energy is distributed differently: energy expenditures for the formation of exuvia and adult insects are greater in females than in males. The proportion of food energy expended for metabolism throughout the insect life span is approximately 30% in both females and males. PMID:14735789

  10. Point Mutations in Membrane Proteins Reshape Energy Landscape and Populate Different Unfolding Pathways

    PubMed Central

    Sapra, K. Tanuj; Balasubramanian, G. Prakash; Labudde, Dirk; Bowie, James U.; Muller, Daniel J.

    2009-01-01

    Using single-molecule force spectroscopy, we investigated the effect of single point mutations on the energy landscape and unfolding pathways of the transmembrane protein bacteriorhodopsin. We show that the unfolding energy barriers in the energy landscape of the membrane protein followed a simple two-state behavior and represent a manifestation of many converging unfolding pathways. Although the unfolding pathways of wild-type and mutant bacteriorhodopsin did not change, indicating the presence of same ensemble of structural unfolding intermediates, the free energies of the rate-limiting transition states of the bacteriorhodopsin mutants decreased as the distance of those transition states to the folded intermediate states decreased. Thus, all mutants exhibited Hammond behavior and a change in the free energies of the intermediates along the unfolding reaction coordinate and, consequently, their relative occupancies. This is the first experimental proof showing that point mutations can reshape the free energy landscape of a membrane protein and force single proteins to populate certain unfolding pathways over others. PMID:18191146

  11. Field study of moisture damage in walls insulated without a vapor barrier. Final report for the Oregon Department of Energy

    SciTech Connect

    Tsongas, G.A.

    1980-05-01

    Considerable uncertainty has existed over whether or not wall insulation installed without a vapor barrier causes an increased risk of moisture damage (wood decay) within walls. This report describes the results of one of the first major studies in the country aimed at finding out if such a moisture problem really exists. The exterior walls of a total of 96 homes in Portland, Oregon were opened, of which 70 had retrofitted insulation and 26 were uninsulated and were a control group. The types of insulation included urea-formaldehyde foam (44), mineral wool (16), and cellulose (10). In each opened wall cavity the moisture content of wood was measured and insulation and wood samples were taken for laboratory analysis of moisture content and for the determination of the presence of absence of decay fungi. Foam shrinkage was also measured. To evaluate the possible influence of the relative air tightness of the homes, fan depressurization tests were run using a door blower unit. The field and laboratory test results indicating the lack of a moisture damage problem in existing homes with wood siding in climates similar to that of western Oregon are described along with results of a statistical analysis of the data. Related problems of interest to homeowners and insulation installers are noted. The standard operating procedures used throughout the study are discussed, including the home selection process, quantitative and qualitative techniques used to identify wall locations with the highest moisture content, wall opening and data/sample collection methodology, laboratory analysis of samples, data processing and analysis, and applicability of the results. Recommendations for furutre tests are made. Finally, the potential and desirability for future retrofitting of wall insulation is explored.

  12. Exploring the origin of the internal rotational barrier for molecules with one rotatable dihedral angle

    PubMed Central

    Liu, Shubin; Govind, Niranjan; Pedersen, Lee G.

    2008-01-01

    Continuing our recent endeavor, we systematically investigate in this work the origin of internal rotational barriers for small molecules using the new energy partition scheme proposed recently by one of the authors [S. B. Liu, J. Chem. Phys. 126, 244103 (2007)], where the total electronic energy is decomposed into three independent components, steric, electrostatic, and fermionic quantum. Specifically, we focus in this work on six carbon, nitrogen, and oxygen containing hydrides, CH3CH3, CH3NH2, CH3OH, NH2NH2, NH2OH, and H2O2, with only one rotatable dihedral angle ∠H–X–Y–H (X,Y=C,N,O). The relative contributions of the different energy components to the total energy difference as a function of the internal dihedral rotation will be considered. Both optimized-geometry (adiabatic) and fixed-geometry (vertical) differences are examined, as are the results from the conventional energy partition and natural bond orbital analysis. A wealth of strong linear relationships among the total energy difference and energy component differences for different systems have been observed but no universal relationship applicable to all systems for both cases has been discovered, indicating that even for simple systems such as these, there exists no omnipresent, unique interpretation on the nature and origin of the internal rotation barrier. Different energy components can be employed for different systems in the rationalization of the barrier height. Confirming that the two differences, adiabatic and vertical, are disparate in nature, we find that for the vertical case there is a unique linear relationship applicable to all the six molecules between the total energy difference and the sum of the kinetic and electrostatic energy differences. For the adiabatic case, it is the total potential energy difference that has been found to correlate well with the total energy difference except for ethane whose rotation barrier is dominated by the quantum effect. PMID:19044862

  13. Hydrogen-Bond Networks: Strengths of Different Types of Hydrogen Bonds and An Alternative to the Low Barrier Hydrogen-Bond Proposal

    SciTech Connect

    Shokri, Alireza; Wang, Yanping; O'Doherty, George A.; Wang, Xue B.; Kass, Steven R.

    2013-11-27

    We report quantifying the strengths of different types of hydrogen bonds in hydrogen bond networks (HBNs) via measurement of the adiabatic electron detachment energy of the conjugate base of a small covalent polyol model compound (i.e., (HOCH2CH2CH(OH)CH2)2CHOH) in the gas phase and the pKa of the corresponding acid in DMSO. The latter result reveals that the hydrogen bonds to the charged center and those that are one solvation shell further away (i.e., primary and secondary) provide 5.3 and 2.5 pKa units of stabilization per hydrogen bond in DMSO. Computations indicate that these energies increase to 8.4 and 3.9 pKa units in benzene and that the total stabilizations are 16 (DMSO) and 25 (benzene) pKa units. Calculations on a larger linear heptaol (i.e., (HOCH2CH2CH(OH)CH2CH(OH)CH2)2CHOH) reveal that the terminal hydroxyl groups each contribute 0.6 pKa units of stabilization in DMSO and 1.1 pKa units in benzene. All of these results taken together indicate that the presence of a charged center can provide a powerful energetic driving force for enzyme catalysis and conformational changes such as in protein folding due to multiple hydrogen bonds in a HBN.

  14. Assessment of Orbital-Optimized MP2.5 for Thermochemistry and Kinetics: Dramatic Failures of Standard Perturbation Theory Approaches for Aromatic Bond Dissociation Energies and Barrier Heights of Radical Reactions.

    PubMed

    Soydaş, Emine; Bozkaya, Uğur

    2015-04-14

    An assessment of orbital-optimized MP2.5 (OMP2.5) [ Bozkaya, U.; Sherrill, C. D. J. Chem. Phys. 2014, 141, 204105 ] for thermochemistry and kinetics is presented. The OMP2.5 method is applied to closed- and open-shell reaction energies, barrier heights, and aromatic bond dissociation energies. The performance of OMP2.5 is compared with that of the MP2, OMP2, MP2.5, MP3, OMP3, CCSD, and CCSD(T) methods. For most of the test sets, the OMP2.5 method performs better than MP2.5 and CCSD, and provides accurate results. For barrier heights of radical reactions and aromatic bond dissociation energies OMP2.5-MP2.5, OMP2-MP2, and OMP3-MP3 differences become obvious. Especially, for aromatic bond dissociation energies, standard perturbation theory (MP) approaches dramatically fail, providing mean absolute errors (MAEs) of 22.5 (MP2), 17.7 (MP2.5), and 12.8 (MP3) kcal mol(-1), while the MAE values of the orbital-optimized counterparts are 2.7, 2.4, and 2.4 kcal mol(-1), respectively. Hence, there are 5-8-folds reductions in errors when optimized orbitals are employed. Our results demonstrate that standard MP approaches dramatically fail when the reference wave function suffers from the spin-contamination problem. On the other hand, the OMP2.5 method can reduce spin-contamination in the unrestricted Hartree-Fock (UHF) initial guess orbitals. For overall evaluation, we conclude that the OMP2.5 method is very helpful not only for challenging open-shell systems and transition-states but also for closed-shell molecules. Hence, one may prefer OMP2.5 over MP2.5 and CCSD as an O(N(6)) method, where N is the number of basis functions, for thermochemistry and kinetics. The cost of the OMP2.5 method is comparable with that of CCSD for energy computations. However, for analytic gradient computations, the OMP2.5 method is only half as expensive as CCSD. PMID:26574366

  15. The Oklahoma Field Test: Air-Conditioning Electricity Savings from Standard Energy Conservation Measures, Radiant Barriers, and High-Efficiency Window Air Conditioners

    SciTech Connect

    Ternes, M.P.

    1992-01-01

    A field test involving 104 houses was performed in Tulsa, Oklahoma, to measure the air-conditioning electricity consumption of low-income houses equipped with window air conditioners, the reduction in this electricity consumption attributed to the installation of energy conservation measures (ECMs) as typically installed under the Oklahoma Weatherization Assistance Program (WAP), and the reduction achieved by the replacement of low-efficiency window air conditioners with high-efficiency units and the installation of attic radiant barriers. Air-conditioning electricity consumption and indoor temperature were monitored weekly during the pre-weatherization period (June to September 1988) and post-weatherization period (May to September 1989). House energy consumption models and regression analyses were used to normalize the air-conditioning electricity savings to average outdoor temperature conditions and the pre-weatherization indoor temperature of each house. The average measured pre-weatherization air-conditioning electricity consumption was 1664 kWh/year ($119/year). Ten percent of the houses used less than 250 kWh/year, while another 10% used more than 3000 kWh/year. An average reduction in air-conditioning electricity consumption of 535 kWh/year ($38/year and 28% of pre-weatherization consumption) was obtained from replacement of one low-efficiency window air conditioner (EER less than 7.0) per house with a high-efficiency unit (EER greater than 9.0). For approximately the same cost, savings tripled to 1503 kWh/year ($107/year and 41% of pre-weatherization consumption) in those houses with initial air-conditioning electricity consumption greater than 2750 kWh/year. For these houses, replacement of a low-efficiency air conditioner with a high-efficiency unit was cost effective using the incremental cost of installing a new unit now rather than later; the average installation cost for these houses under a weatherization program was estimated to be $786. The

  16. Sprache als Barriere (Language as a Barrier)

    ERIC Educational Resources Information Center

    Mattheier, Klaus

    1974-01-01

    The concept of language barrier has its derivations in the fields of dialectology, sociology and psychology. In contemporary usage however, the concept has two meanings i.e. regional-cultural barrier and socio-cultural barrier. (Text is in German.) (DS)

  17. INFORMATION BARRIERS - A HISTORICAL PERSPECTIVE

    SciTech Connect

    D. CLOSE; D. MACARTHUR; N. NICHOLAS

    2001-05-01

    The concept ''transparency'' was introduced into the safeguards lexicon in the early 1990s, and the term ''information barrier'' was introduced into the safeguards lexicon in the late 1990s. Although the terms might have been new, the concepts were not. Both concepts have been used by the International Atomic Energy Agency (IAEA) and its inspectors since the early 1980s, but the terms ''transparency'' and ''information barrier'' were not used for those concepts then. The definitions of these concepts have evolved in recent years, and these concepts have been applied to a broader category of special nuclear material measurement problems. The origin and features of the information barrier concept will be traced from an early implementation by the IAEA to the current state-of-the-art information barrier technology used in nonproliferation, arms control, and dismantlement.

  18. The effects of energy intake of four different feeding patterns in rats.

    PubMed

    Gong, Huan; Han, Yi-wen; Sun, Liang; Zhang, Yan; Zhang, En-yi; Li, Yi; Zhang, Tie-mei

    2016-01-01

    Energy intake can affect the metabolism. But it is not very clear that how and to what degree the metabolism can be changed by energy intake quantity and change. Here we applied four feeding patterns in male Sprague-Dawley rats--normal ad libitum diet (NFal), high-fat diet (HFal), caloric restriction (CR) after HFal (HFal-NFcr), and refeeding from CR to ad libitum (HFal-NFcr-NFal). Food intake and body weight, along with fat mass, insulin sensitivity, fasting plasma insulin, and glucose level were used to calculate the energy efficiency and compared the quantitative effects of energy intake. Energy intake changed little in NFal or HFal group; while it changed greatly and suddenly in HFal-NFcr or HFal-NFcr-NFal group. All the parameters we detected were different between these four feeding patterns. Excess of energy intake from high-fat diet induced adverse outcomes with low energy efficiency. CR reversed the impairment of high-fat diet with very high energy efficiency in a short period. However, dramatic response with high energy efficiency induced by recovery to feeding ad libitum after CR, which was possible harmful to health. In conclusion, energy intake quantity and change are key determinants of metabolism. Different energy intake quantity and change affect body weight, white adipose tissue weight, insulin sensitivity, etc. at different degrees and speeds because of different energy efficiency. PMID:25966980

  19. Energy Cost of Walking in Boys Who Differ in Adiposity but Are Matched For Body Mass.

    ERIC Educational Resources Information Center

    Ayub, Beatriz Volpe; Bar-Or, Oded

    2003-01-01

    Compared the energy cost of treadmill walking in pairs of obese and lean adolescent boys matched for total body mass. Results found no intergroup differences in the net energy cost at the two lower speeds, but obese boys expended more energy at a higher speed. Heart rate was considerably higher in obese boys. Body mass, rather than adiposity, was…

  20. Socio-Demographic Differences in Energy Drink Consumption and Reasons for Consumption among US College Students

    ERIC Educational Resources Information Center

    Poulos, Natalie S.; Pasch, Keryn E.

    2016-01-01

    Background: Energy drink consumption has become increasingly prevalent among US college students, yet little is known about current rates of consumption and reasons for consumption among current energy drink users, particularly differences related to gender and race/ethnicity. Objectives: To better understand energy drink consumption alone and…

  1. Ion energy and angular distributions onto polymer surfaces delivered by dielectric barrier discharge filaments in air: II. Particles

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu; Kushner, Mark J.

    2011-06-01

    Atmospheric pressure streamers intersecting particles are of interest in the context of plasma aided combustion, where the particle may be a fuel aerosol droplet, or in sterilization of air, where the particle may be a bacterium. The ion energy and angular distributions (IEADs) incident on the particles, small curved dielectric surfaces, then in part determine the propensity for activating chemical reactions or, in the case of bacteria, the plasma's sterilization capability. In this paper, we discuss results from a computational investigation of IEADs on small particles (45 µm radius) produced by atmospheric pressure discharge. Streamers intersecting a particle momentarily generate a large sheath potential as the streamer passes by as the particle charges towards the plasma floating potential. During that time, ions of energies up to 3-10 eV can strike the particle. The permittivity of the particle and the streamer polarity in part determine the character of the IEAD.

  2. Energy Systems Based on Polyacetylene: Rechargeable Batteries and Schottky Barrier Solar Cells. Final Report, March 1, 1981-February 29, 1984

    DOE R&D Accomplishments Database

    MacDiarmid, A. G.

    1984-02-01

    The chief thrust of the research has been directed towards the evaluation of polyacetylene (CH){sub x}, the prototype conducting polymer as an electrode- active material in novel, rechargeable batteries employing nonaqueous electrolytes. The p-doped material, [(CH{sup +y})A{sub y}{sup -}]{sub x}, (where A{sup -} is an anion) in conjunction with a Li anode, shows excellent discharge characteristics, e.g., very little change in discharge voltage with change in discharge current and a high power density. Its energy density is also good but it shows poor shelf life. When (CH){sub x} is used as a cathode (Li anode), which results in the formation of the n-doped polymer, [Li{sub y} {sup +}(CH/sup -y/)]{sub x}, during discharge, good discharge plateaus and power densities are obtained together with excellent shelf life and good recyclability. The energy density is, however only moderate. Cells employing an [M{sub y}{sup +}(CH/sup -y/)]{sub x} (where M = Li, Na) anode and a TiS{sub 2} cathode show very good discharge and recycling characteristics but their energy density is poor.

  3. Energy systems based on polyacetylene: rechargeable batteries and Schottky barrier solar cells. Final report, March 1, 1981-February 29, 1984

    SciTech Connect

    MacDiarmid, A.G.

    1984-02-01

    The chief thrust of the research has been directed towards the evaluation of polyacetylene (CH)/sub x/, the prototype conducting polymer as an electrode-active material in novel, rechargeable batteries employing nonaqueous electrolytes. The p-doped material, ((CH/sup +y/)A/sub y//sup -/)/sub x/, (where A/sup -/ is an anion) in conjunction with a Li anode, shows excellent discharge characteristics, e.g., very little change in discharge voltage with change in discharge current and a high power density. Its energy density is also good but it shows poor shelf life. When (CH)/sub x/ is used as a cathode (Li anode), which results in the formation of the n-doped polymer, (Li/sub y//sup +/(CH/sup -y/))/sub x/, during discharge, good discharge plateaus and power densities are obtained together with excellent shelf life and good recyclability. The energy density is, however only moderate. Cells employing an (M/sub y//sup +/(CH/sup -y/))/sub x/ (where M = Li, Na) anode and a TiS/sub 2/ cathode show very good discharge and recycling characteristics but their energy density is poor.

  4. Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

    PubMed Central

    Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

    2015-01-01

    Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition. PMID:26658159

  5. Improving the efficiency of cadmium sulfide-sensitized titanium dioxide/indium tin oxide glass photoelectrodes using silver sulfide as an energy barrier layer and a light absorber

    PubMed Central

    2014-01-01

    Cadmium sulfide (CdS) and silver sulfide (Ag2S) nanocrystals are deposited on the titanium dioxide (TiO2) nanocrystalline film on indium tin oxide (ITO) substrate to prepare CdS/Ag2S/TiO2/ITO photoelectrodes through a new method known as the molecular precursor decomposition method. The Ag2S is interposed between the TiO2 nanocrystal film and CdS nanocrystals as an energy barrier layer and a light absorber. As a consequence, the energy conversion efficiency of the CdS/Ag2S/TiO2/ITO electrodes is significantly improved. Under AM 1.5 G sunlight irradiation, the maximum efficiency achieved for the CdS(4)/Ag2S/TiO2/ITO electrode is 3.46%, corresponding to an increase of about 150% as compared to the CdS(4)/TiO2/ITO electrode without the Ag2S layer. Our experimental results show that the improved efficiency is mainly due to the formation of Ag2S layer that may increase the light absorbance and reduce the recombination of photogenerated electrons with redox ions from the electrolyte. PMID:25411566

  6. Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

    NASA Astrophysics Data System (ADS)

    Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

    2015-12-01

    Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition.

  7. Origin of translocation barriers for polyelectrolyte chains.

    PubMed

    Kumar, Rajeev; Muthukumar, M

    2009-11-21

    For single-file translocations of a charged macromolecule through a narrow pore, the crucial step of arrival of an end at the pore suffers from free energy barriers, arising from changes in intrachain electrostatic interaction, distribution of ionic clouds and solvent molecules, and conformational entropy of the chain. All contributing factors to the barrier in the initial stage of translocation are evaluated by using the self-consistent field theory for the polyelectrolyte and the coupled Poisson-Boltzmann description for ions without radial symmetry. The barrier is found to be essentially entropic due to conformational changes. For moderate and high salt concentrations, the barriers for the polyelectrolyte chain are quantitatively equivalent to that of uncharged self-avoiding walks. Electrostatic effects are shown to increase the free energy barriers, but only slightly. The degree of ionization, electrostatic interaction strength, decreasing salt concentration, and the solvent quality all result in increases in the barrier. PMID:19929072

  8. Fission fragment angular distribution for the 19F+197Au fusion-fission reaction at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Tripathi, R.; Sudarshan, K.; Sodaye, S.; Reddy, A. V.; Mahata, K.; Goswami, A.

    2005-04-01

    Angular distribution of fission fragments have been measured for 19F+197Au reaction at bombarding energies from 91 to 110 MeV. Fission fragment angular distributions have been calculated by transition state model with the transmission coefficients obtained using the coupled-channels theory. The calculated angular anisotropies are in good agreement with the experimental anisotropies. The experimental fission cross sections have also been reproduced on the basis of the coupled-channels theory. The results of angular distribution measurement do not show any significant contribution from quasifission as was reported in the literature based on the measurement of evaporation residues and mass distribution.

  9. Elastic and inelastic scattering of 16O and 18O ions from 64Zn at energies near the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Salém-Vasconcelos, S.; Takagui, E. M.; Bechara, M. J.; Koide, K.; Dietzsch, O.; Bairrio Nuevo, A., Jr.; Takai, H.

    1994-08-01

    Coulomb-nuclear interference effects were investigated in the inelastic scattering of 16O and 18O by 64Zn. Measurements of elastic and inelastic angular distributions of 18O were performed at a laboratory energy of 49 MeV, over the angular range from θlab~30° to 85°. The excitation functions of 16O and 18O ions were measured at incident energies between 29 and 46 MeV at θlab=174°. The experimental angular distributions show structures which are more pronounced for projectile excitation than for target excitation. The interference minimum for the excitation of the 18O first 2+ state was found to be shifted towards forward angles by approximately 5° (c.m.) with respect to the distorted-wave Born approximation calculations and by approximately 3.5° (c.m.) with respect to the coupled-channels calculations. A pronounced Coulomb-nuclear interference minimum was seen in the excitation of 64Zn(2+) state by inelastic scattering of 16O projectiles, whereas no pronounced minimum was observed in target excitation by 18O projectiles. The elastic scattering data were analyzed with the optical model. The inelastic differential cross sections for the excitation of the first 2+ states in the target and in the 18O projectile were analyzed using the distorted-wave Born approximation and also the coupled-channels approach with collective form factors.

  10. Identification of Key Barriers in Workforce Development

    SciTech Connect

    2008-03-31

    This report documents the identification of key barriers in the development of an adequate national security workforce as part of the National Security Preparedness Project, being performed under a Department of Energy/National Nuclear Security Administration grant. Many barriers exist that prevent the development of an adequate number of propertly trained national security personnel. Some barriers can be eliminated in a short-term manner, whereas others will involve a long-term strategy that takes into account public policy.

  11. Thermal barrier research

    SciTech Connect

    Moses, K.G.

    1990-03-07

    The thermal barrier region in the TARA device is a complex arrangement combining ion-plugging by sloshing ions with an ECRH-generated thermal barrier plasma. An axisymmetric, high-mirror-ratio magnetic field, adjacent to the central cell, provides the confinement of the thermal barrier plasma and sloshing ions. This paper discusses research being done in this thermal barrier region.

  12. Deceleration-Limiting Roadway Barrier

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); Locke, P. James (Inventor)

    2006-01-01

    Roadway barrier system and method are disclosed for decelerating a moving vehicle in a controlled manner and for retaining the decelerated vehicle. A net or mesh of the roadway barrier system receives and captures the moving vehicle. The net or mesh is secured to anchors by energy absorbing straps. The energy absorbing straps deploy under a tensional load to decelerate the moving vehicle, the straps providing a controlled resistance to the tensional load over a predefined displacement or stroke to bring the moving vehicle to rest. Additional features include a sacrificial panel or sheet in front of the net that holds up the net or mesh while deflecting vehicles that collide only tangentially with the roadway barrier system.

  13. A nanosecond surface dielectric barrier discharge in air at high pressures and different polarities of applied pulses: transition to filamentary mode

    NASA Astrophysics Data System (ADS)

    Stepanyan, S. A.; Starikovskiy, A. Yu; Popov, N. A.; Starikovskaia, S. M.

    2014-08-01

    The development of a nanosecond surface dielectric barrier discharge in air at pressures 1-6 bar is studied. At atmospheric pressure, the discharge develops as a set of streamers starting synchronously from the high-voltage electrode and propagating along the dielectric layer. Streamers cover the dielectric surface creating a ‘quasi-uniform’ plasma layer. At high pressures and high voltage amplitudes on the cathode, filamentation of the discharge is observed a few nanoseconds after the discharge starts. Parameters of the observed ‘streamers-to-filaments’ transition are measured; physics of transition is discussed on the basis of theoretical estimates and numerical modeling. Ionization-heating instability on the boundary of the cathode layer is suggested as a mechanism of filamentation.

  14. Investigation of complete and incomplete fusion dynamics of {sup 20}Ne induced reactions at energies above the Coulomb barrier

    SciTech Connect

    Singh, D.; Ali, R.; Kumar, Harish; Ansari, M. Afzal; Rashid, M. H.; Guin, R.

    2014-08-14

    Experiment has been performed to explore the complete and incomplete fusion dynamics in heavy ion collisions using stacked foil activation technique. The measurement of excitation functions of the evaporation residues produced in the {sup 20}Ne+{sup 165}Ho system at projectile energies ranges ≈ 4-8 MeV/nucleon have been done. Measured cumulative and direct cross-sections have been compared with the theoretical model code PACE-2, which takes into account only the complete fusion process. The analysis indicates the presence of contributions from incomplete fusion processes in some α-emission channels following the break-up of the projectile {sup 20}Ne in the nuclear field of the target nucleus {sup 165}Ho.

  15. Elastic and inelastic angular distributions of the 7Li+120Sn system for energies near the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Zagatto, V. A. B.; Oliveira, J. R. B.; Gasques, L. R.; Alcántara-Núñez, J. A.; Duarte, J. G.; Aguiar, V. P.; Medina, N. H.; Seale, W. A.; Pires, K. C. C.; Freitas, A.; Lubian, J.; Shorto, J. M. B.; Genezini, F. A.; Rossi, E. S., Jr.

    2016-06-01

    The reaction of 7Li+120Sn has been measured at bombarding energies of 21, 24 and 27 MeV. The {2}+\\to {0}+ γ -ray transition in 120Sn was observed and the angular distribution for the 2+ excited state was obtained. Coupled channels and coupled-reaction channels calculations, including the dynamical polarization potential due to the projectile break-up, obtained from continuum discretized coupled channel calculations, were performed. The comparison between the existing experimental elastic angular distribution with the coupled-reaction channels calculations indicates that the 1n stripping transfer is the most intense channel to be coupled and the 2n stripping reaction occurs sequentially rather than directly, however, further data must be analyzed to confirm this indication. The experimental elastic and inelastic scattering data were well described by the calculations, but some discrepancies in these channels may indicate the need for corrections to the nuclear potential and/or the necessity to incorporate further channels.

  16. A method to predict different mechanisms for blood-brain barrier permeability of CNS activity compounds in Chinese herbs using support vector machine.

    PubMed

    Jiang, Ludi; Chen, Jiahua; He, Yusu; Zhang, Yanling; Li, Gongyu

    2016-02-01

    The blood-brain barrier (BBB), a highly selective barrier between central nervous system (CNS) and the blood stream, restricts and regulates the penetration of compounds from the blood into the brain. Drugs that affect the CNS interact with the BBB prior to their target site, so the prediction research on BBB permeability is a fundamental and significant research direction in neuropharmacology. In this study, we combed through the available data and then with the help of support vector machine (SVM), we established an experiment process for discovering potential CNS compounds and investigating the mechanisms of BBB permeability of them to advance the research in this field four types of prediction models, referring to CNS activity, BBB permeability, passive diffusion and efflux transport, were obtained in the experiment process. The first two models were used to discover compounds which may have CNS activity and also cross the BBB at the same time; the latter two were used to elucidate the mechanism of BBB permeability of those compounds. Three optimization parameter methods, Grid Search, Genetic Algorithm (GA), and Particle Swarm Optimization (PSO), were used to optimize the SVM models. Then, four optimal models were selected with excellent evaluation indexes (the accuracy, sensitivity and specificity of each model were all above 85%). Furthermore, discrimination models were utilized to study the BBB properties of the known CNS activity compounds in Chinese herbs and this may guide the CNS drug development. With the relatively systematic and quick approach, the application rationality of traditional Chinese medicines for treating nervous system disease in the clinical practice will be improved. PMID:26632324

  17. A Learner Perspective on Barriers to E-Learning

    ERIC Educational Resources Information Center

    Becker, Karen; Newton, Cameron; Sawang, Sukanlaya

    2013-01-01

    This study aims to identify and categorize barriers to e-learning adoption and the relative impact of those barriers on learners. It contributes to the understanding of learner perceptions of barriers, the different types of barriers and their relative importance. This study used a quantitative methodology grounded in previous literature. The…

  18. Design of Protein Multi-specificity Using an Independent Sequence Search Reduces the Barrier to Low Energy Sequences.

    PubMed

    Sevy, Alexander M; Jacobs, Tim M; Crowe, James E; Meiler, Jens

    2015-07-01

    Computational protein design has found great success in engineering proteins for thermodynamic stability, binding specificity, or enzymatic activity in a 'single state' design (SSD) paradigm. Multi-specificity design (MSD), on the other hand, involves considering the stability of multiple protein states simultaneously. We have developed a novel MSD algorithm, which we refer to as REstrained CONvergence in multi-specificity design (RECON). The algorithm allows each state to adopt its own sequence throughout the design process rather than enforcing a single sequence on all states. Convergence to a single sequence is encouraged through an incrementally increasing convergence restraint for corresponding positions. Compared to MSD algorithms that enforce (constrain) an identical sequence on all states the energy landscape is simplified, which accelerates the search drastically. As a result, RECON can readily be used in simulations with a flexible protein backbone. We have benchmarked RECON on two design tasks. First, we designed antibodies derived from a common germline gene against their diverse targets to assess recovery of the germline, polyspecific sequence. Second, we design "promiscuous", polyspecific proteins against all binding partners and measure recovery of the native sequence. We show that RECON is able to efficiently recover native-like, biologically relevant sequences in this diverse set of protein complexes. PMID:26147100

  19. On statistical properties of transport barriers in magnetospheric and laboratory boundary layers

    NASA Astrophysics Data System (ADS)

    Savin, Sergey; Budaev, Viacheslav; Zeleniy, Lev; Amata, Ermanno; Kozak, Lyudmila; Buechner, Joerg; Romanov, Stanislav; Blecki, Jan; Balikhin, Michael A.; Lezhen, Liudmila

    Transport barriers at outer magnetospheric boundaries have a dualistic feature: being effec-tive in limitation of the momentum transfer and serving as an effective obstacle, they display the super-diffusive statistical properties and provide partial exchange of plasmas. In tokamaks namely the statistical properties of transport barriers look to control the high and low heating modes, while small size of the barriers prevents their detailed studies. We tend to use magne-tospheric multi-spacecraft data to improve understanding of common physics in the transport barriers. We show examples from Interball-1 and Cluster with quiet solar wind. The inherently turbulent crossings in this equilibrium cases demonstrate ion heating namely in the transport barrier. It agrees with the kinetic energy transformation into the thermal one inside the barrier -the turbulent dissipation of the magnetosheath kinetic energy -as simultaneously with the ion temperature rise, the general velocity component drops from its model prediction. In sense of the momentum transfer the transport turbulent barriers effectively isolate the high-alti-tude cusp from fast-flowing magnetosheath. Contrary to that, several examples from different missions and different plasma parameters demonstrate the super-diffusive transport character. The individual coherent structures inside the barriers, which we call Alfvenic 'collapsons', have similar scale chains to that of high kinetic plasma pressure jets, showing mutual interaction features. We think that the interacting jets and barriers, accompanying by classic and/ or micro-reconnection, have rather general importance for the plasma physics, and for understanding of turbulence and mechanisms of magnetic field generation. These coherent, nonlinear interacting structures, most probably, provide intermittency a long-range correlations inside the transport barriers (c.f. blobs and flow spikes in fusion devices). We recall that very high-amplitude turbulence in

  20. Bioenergetic Progress and Heat Barriers

    NASA Astrophysics Data System (ADS)

    Zotin, A. A.; Lamprecht, I.; Zotin, A. I.

    2001-07-01

    Progressing biological evolution is discussed in the framework of nonequilibrium thermodynamics. It is connected with an increase of the mass specific standard metabolism given by coefficient a in the allometric relation (1) between oxygen consumption rate and body mass of an animal. Three “heat barriers” are found in the course of such a bioenergetic evolution. The first heat barrier concerns an animal's overheating during active movement and is overcome by the development of thermoregulation and the appearance of homeothermic animals. A second barrier arises when the coefficient a reaches values connected with lethal body temperatures. The transition across this second heat barrier occurs as result of reasonable activities and the appearance of civilization. The third heat barrier will arise during the further development of human civilization, connected with a highly increased energy production and a fatal warming of the Earth atmosphere. The manner to overcome this barrier will probably depend on the assimilation of space and the establishment of energy consuming industries outside the Earth. The bioenergetic evolution discussed in this paper does not exclude other trends of evolution, e.g. increase of size, and does not mean to be the only aspect of biological evolution.

  1. Dielectric barrier discharges in analytical chemistry.

    PubMed

    Meyer, C; Müller, S; Gurevich, E L; Franzke, J

    2011-06-21

    The present review reflects the importance of dielectric barrier discharges in analytical chemistry. Special about this discharge is-and in contrast to usual discharges with direct current-that the plasma is separated from one or two electrodes by a dielectric barrier. This gives rise to two main features of the dielectric barrier discharges; it can serve as dissociation and excitation device and as ionization mechanism, respectively. The article portrays the various application fields for dielectric barrier discharges in analytical chemistry, for example the use for elemental detection with optical spectrometry or as ionization source for mass spectrometry. Besides the introduction of different kinds of dielectric barrier discharges used for analytical chemistry from the literature, a clear and concise classification of dielectric barrier discharges into capacitively coupled discharges is provided followed by an overview about the characteristics of a dielectric barrier discharge concerning discharge properties and the ignition mechanism. PMID:21562672

  2. Preparation and characterization of nanocrystalline ZrO2-7%Y2O3 powders for thermal barrier coatings by high-energy ball milling

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Zhao, Lidong; Schlaefer, Thomas; Warda, Thomas

    2011-06-01

    High-energy ball milling is an effective method to produce nanocrystalline oxides. In this study, a conventional ZrO2-7%Y2O3 spray powder was ball-milled to produce nanocrystalline powders with high levels of crystalline disorders for deposition of thermal barrier coatings. The powder was milled both with 100Cr6 steel balls and with ZrO2-3%Y2O3 ceramic balls as grinding media. The milling time was varied in order to investigate the effect of the milling time on the crystallite size. The powders were investigated in terms of their crystallite sizes and morphologies by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that under given milling conditions the powder was already nanostructured after 40 min milling. The crystallite size decreased significantly with increasing milling time within first 120 min. After that, a further increase of milling time did not lead to a significant reduction of the crystallite size. Ball-milling led to lattice microstrains. Milling with the steel balls resulted in finer nano-sized crystal grains, but caused the contamination of the powder. The nano-sized crystal grains coarsened during the heat-treatment at 1250°C.

  3. Determining collective barrier operation skew in a parallel computer

    SciTech Connect

    Faraj, Daniel A.

    2015-11-24

    Determining collective barrier operation skew in a parallel computer that includes a number of compute nodes organized into an operational group includes: for each of the nodes until each node has been selected as a delayed node: selecting one of the nodes as a delayed node; entering, by each node other than the delayed node, a collective barrier operation; entering, after a delay by the delayed node, the collective barrier operation; receiving an exit signal from a root of the collective barrier operation; and measuring, for the delayed node, a barrier completion time. The barrier operation skew is calculated by: identifying, from the compute nodes' barrier completion times, a maximum barrier completion time and a minimum barrier completion time and calculating the barrier operation skew as the difference of the maximum and the minimum barrier completion time.

  4. Fission-fragment angular distributions and excitation functions in fission following complete fusion and targetlike-fragment fission reactions of 19F+232Th at near- and sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Majumdar, N.; Bhattacharya, P.; Biswas, D. C.; Choudhury, R. K.; Nadkarni, D. M.; Saxena, A.

    1995-06-01

    The fragment angular distributions and excitation functions of the fission following complete fusion (FFCF) have been measured after separating them from targetlike-fragment fission (TLFF) for the 19F+232Th system in the bombarding energy range of 84.5 to 106.5 MeV. The fraction of the targetlike-fragment fission was observed to increase with decreasing bombarding energy below the Coulomb barrier. The excitation function for fission following complete fusion reaction agrees well with coupled channel calculations. However, the values derived from the fragment anisotropy data of the FFCF events are found to be much larger than those calculated using the coupled channel transmission coefficient values. The discrepancy between the experimental and calculated values increases as the bombarding energy is decreased below the barrier.

  5. SLF27 energy difference method to specify printability of contact hole defects

    NASA Astrophysics Data System (ADS)

    Suleni, T. M.; Peng, T. Y.

    2003-12-01

    The CD measurement method has been long used by the industry to specify contact hole mis-sizing defects on reticles. However with the shrinking of feature size beyond sub-wavelength, it has been found that this method of specifying contact hole defects do not always correlate well to CD differences on wafers. A better correlation can be achieved by using the energy difference (total flux energy) review tool available on the SLF27. The energy difference review tool measures the total energy transmitted through a manually drawn box. In this paper, defects from production reticles are used to compare the sizes of these defects with their energy differences on reticle against the CD measurements on wafers. Defect data from Binary reticles of undersized and oversized contacts holes are evaluated. Strong correlation between mis-sized contact holes measurement on wafer SEM and energy difference review tool on the SLF27 (Reticle Inspection tool with 365nm UV wavelength) is observed. The correlation is particularly strong for undersized contact holes. The correlation is helpful in identifying good repair and bad repair, since the correlation still holds true on contact holes with repair stain. Though it is believed the correlation stays true for PSM, a more thorough evaluation is required for PSM reticles at this time. From these data, a new defect control specification on reticles, using the energy difference method has been determined and used to specify mis-sizing or acceptable localized CD error on reticle to prevent yield impact on wafer.

  6. Energy Consumption Analysis Procedure for Robotic Applications in different task motion

    NASA Astrophysics Data System (ADS)

    Ahmed, Iman; Aris, Ishak b.; Hamiruce Marhaban, Mohammad; Juraiza Ishak, Asnor

    2015-11-01

    This work proposes energy analysis method for humanoid robot, seen from simple motion task to complex one in energy chain. The research developed a procedure suitable for analysis, saving and modelling of energy consumption not only in this type of robot but also in most robots that based on electrical power as an energy source. This method has validated by an accurate integration using Matlab software for the power consumption curve to calculate the energy of individual and multiple servo motors. Therefore, this study can be considered as a procedure for energy analysis by utilizing the laboratory instruments capabilities to measure the energy parameters. We performed a various task motions with different angular speed to find out the speed limits in terms of robot stability and control strategy. A battery capacity investigation have been searched for several types of batteries to extract the power modelling equation and energy density parameter for each battery type, Matlab software have been built to design the algorithm and to evaluate experimental amount of the energy which is represented by area under the curve of the power curves. This will provide a robust estimation for the required energy in different task motions to be considered in energy saving (i.e., motion planning and real time scheduling).

  7. Endothelial Cells Derived from the Blood-Brain Barrier and Islets of Langerhans Differ in their Response to the Effects of Bilirubin on Oxidative Stress Under Hyperglycemic Conditions.

    PubMed

    Kapitulnik, Jaime; Benaim, Clara; Sasson, Shlomo

    2012-01-01

    Unconjugated bilirubin (UCB) is a neurotoxic degradation product of heme. Its toxic effects include induction of apoptosis, and ultimately neuronal cell death. However, at low concentrations, UCB is a potent antioxidant that may protect cells and tissues against oxidative stress by neutralizing toxic metabolites such as reactive oxygen species (ROS). High glucose levels (hyperglycemia) generate reactive metabolites. Endothelial cell dysfunction, an early vascular complication in diabetes, has been associated with hyperglycemia-induced oxidative stress. Both glucose and UCB are substrates for transport proteins in microvascular endothelial cells of the blood-brain barrier (BBB). In the current study we show that UCB (1-40 μM) induces apoptosis and reduces survival of bEnd3 cells, a mouse brain endothelial cell line which serves as an in vitro model of the BBB. These deleterious effects of UCB were enhanced in the presence of high glucose (25 mM) levels. Interestingly, the bEnd3 cells exhibited an increased sensitivity to the apoptotic effects of UCB when compared to the MS1 microcapillary endothelial cell line. MS1 cells originate from murine pancreatic islets of Langerhans, and are devoid of the barrier characteristics of BBB-derived endothelial cells. ROS production was increased in both bEnd3 and MS1 cells exposed to high glucose, as compared with cells exposed to normal (5.5 mM) glucose levels. While UCB (0.1-40 μM) did not alter ROS production in cells exposed to normal glucose, relatively low ("physiological") UCB concentrations (0.1-5 μM) attenuated ROS generation in both cell lines exposed to high glucose levels. Most strikingly, higher UCB concentrations (20-40 μM) increased ROS generation in bEnd3 cells exposed to high glucose, but not in similarly treated MS1 cells. These results may be of critical importance for understanding the vulnerability of the BBB endothelium upon exposure to increasing UCB levels under hyperglycemic conditions

  8. Endothelial Cells Derived from the Blood-Brain Barrier and Islets of Langerhans Differ in their Response to the Effects of Bilirubin on Oxidative Stress Under Hyperglycemic Conditions

    PubMed Central

    Kapitulnik, Jaime; Benaim, Clara; Sasson, Shlomo

    2012-01-01

    Unconjugated bilirubin (UCB) is a neurotoxic degradation product of heme. Its toxic effects include induction of apoptosis, and ultimately neuronal cell death. However, at low concentrations, UCB is a potent antioxidant that may protect cells and tissues against oxidative stress by neutralizing toxic metabolites such as reactive oxygen species (ROS). High glucose levels (hyperglycemia) generate reactive metabolites. Endothelial cell dysfunction, an early vascular complication in diabetes, has been associated with hyperglycemia-induced oxidative stress. Both glucose and UCB are substrates for transport proteins in microvascular endothelial cells of the blood-brain barrier (BBB). In the current study we show that UCB (1–40 μM) induces apoptosis and reduces survival of bEnd3 cells, a mouse brain endothelial cell line which serves as an in vitro model of the BBB. These deleterious effects of UCB were enhanced in the presence of high glucose (25 mM) levels. Interestingly, the bEnd3 cells exhibited an increased sensitivity to the apoptotic effects of UCB when compared to the MS1 microcapillary endothelial cell line. MS1 cells originate from murine pancreatic islets of Langerhans, and are devoid of the barrier characteristics of BBB-derived endothelial cells. ROS production was increased in both bEnd3 and MS1 cells exposed to high glucose, as compared with cells exposed to normal (5.5 mM) glucose levels. While UCB (0.1–40 μM) did not alter ROS production in cells exposed to normal glucose, relatively low (“physiological”) UCB concentrations (0.1–5 μM) attenuated ROS generation in both cell lines exposed to high glucose levels. Most strikingly, higher UCB concentrations (20–40 μM) increased ROS generation in bEnd3 cells exposed to high glucose, but not in similarly treated MS1 cells. These results may be of critical importance for understanding the vulnerability of the BBB endothelium upon exposure to increasing UCB levels under hyperglycemic

  9. An unconditionally energy stable finite difference scheme for a stochastic Cahn-Hilliard equation

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Qiao, ZhongHua; Zhang, Hui

    2016-09-01

    In this work, the MMC-TDGL equation, a stochastic Cahn-Hilliard equation is solved numerically by using the finite difference method in combination with a convex splitting technique of the energy functional. For the non-stochastic case, we develop an unconditionally energy stable difference scheme which is proved to be uniquely solvable. For the stochastic case, by adopting the same splitting of the energy functional, we construct a similar and uniquely solvable difference scheme with the discretized stochastic term. The resulted schemes are nonlinear and solved by Newton iteration. For the long time simulation, an adaptive time stepping strategy is developed based on both first- and second-order derivatives of the energy. Numerical experiments are carried out to verify the energy stability, the efficiency of the adaptive time stepping and the effect of the stochastic term.

  10. Statefinder Parameters for Different Dark Energy Models with Variable G Correction in Kaluza-Klein Cosmology

    NASA Astrophysics Data System (ADS)

    Chakraborty, Shuvendu; Debnath, Ujjal; Jamil, Mubasher; Myrzakulov, Ratbay

    2012-07-01

    In this work, we have calculated the deceleration parameter, statefinder parameters and EoS parameters for different dark energy models with variable G correction in homogeneous, isotropic and non-flat universe for Kaluza-Klein Cosmology. The statefinder parameters have been obtained in terms of some observable parameters like dimensionless density parameter, EoS parameter and Hubble parameter for holographic dark energy, new agegraphic dark energy and generalized Chaplygin gas models.

  11. The ratios of partition functions at different temperatures - Sensitivity to potential energy shape II

    NASA Astrophysics Data System (ADS)

    Buchowiecki, Marcin

    2016-05-01

    The ratios of partition functions at different temperatures are calculated and its dependence on potential energy shape is analyzed. The role of anharmonicity and non-rigidity of rotations is discussed in the context of the angular frequency and the shape of potential energy curve. A role of inflection point of potential energy curve for the quality of rigid rotor harmonic oscillator and rigid rotor Morse oscillator is elucidated.

  12. MENDING THE IN SITU MANIPULATION BARRIER

    SciTech Connect

    PETERSEN, S.W.

    2006-02-06

    In early 2004, the U.S. Department of Energy (DOE) Richland and Fluor Hanford requested technical assistance from the DOE Headquarters EM-23 Technical Assistance Program to provide a team of technical experts to develop recommendations for mending the In Situ Redox Manipulation (ISRM) Barrier in the 100-D Area of the Hanford Site in Washington State. To accommodate this request, EM-23 provided support to convene a group of technical experts from industry, a national laboratory, and a DOE site to participate in a 2 1/2-day workshop with the objective of identifying and recommending options to enhance the performance of the 100-D Area reactive barrier and of a planned extension to the northeast. This report provides written documentation of the team's findings and recommendations. In 1995, a plume of dissolved hexavalent chromium [Cr(VI)], which resulted from operation of the D/DR Reactors at the Hanford site, was discovered along the Columbia River shoreline and in the 100-D Area. Between 1999 and 2003, a reactive barrier using the In Situ Redox Manipulation (ISRM) technology, was installed a distance of 680 meters along the river to reduce the Cr(VI) in the groundwater. The ISRM technology creates a treatment zone within the aquifer by injection of sodium dithionite, a strong reducing agent that scavenges dissolved oxygen (DO) from the aquifer and reduces ferric iron [Fe(III)], related metals, and oxy-ions. The reduction of Fe(III) to ferrous [Fe(II)] iron provides the primary reduction capacity to reduce Cr(VI) to the +3 state, which is less mobile and less toxic. Bench-scale and field-scale treatability tests were initially conducted to demonstrate proof-of principle and to provide data for estimation of barrier longevity. These calculations estimated barrier longevity in excess of twenty years. However, several years after initial and secondary treatment, groundwater in a number of wells has been found to contain elevated chromium (Cr) concentrations, indicating

  13. Efficiency of single noise barriers

    NASA Astrophysics Data System (ADS)

    Hothersall, D. C.; Chandler-Wilde, S. N.; Hajmirzae, M. N.

    1991-04-01

    A numerical model is described which enables the sound field in the region of outdoor noise barriers to be calculated by using the boundary element method. The non-uniqueness of solution of the method, producing unreliable results in some conditions, is discussed. The model can be applied to barriers of arbitrary cross-sectional shape and arbitrary distribution of surface cover. The model is two-dimensional, but results are shown to agree well with those obtained for the three-dimensional problem of propagation from a point source over a noise barrier of infinite length. The model is used to compare the efficiency of a wide range of constructions of single noise barriers of different height, cross-sectional shape and surface cover. The effects of the ground cover are also considered. Comparison is made by examining spectra of the insertion loss of the barriers, and also broadband insertion losses for a source with a characteristic A-weighted road traffic noise spectrum. Single-figure estimates are presented of the relative efficiency, in terms of insertion loss, in the deep shadow zone, of a wide range of barrier configurations.

  14. Influence of breakup on fusion barrier distributions

    NASA Astrophysics Data System (ADS)

    Patel, D.; Nayak, B. K.; Mukherjee, S.; Biswas, D. C.; Mirgule, E. T.; John, B. V.; Gupta, Y. K.; Mukhopadhyay, S.; Prajapati, G.; Danu, L. S.; Rath, P. K.; Desai, V.; Deshmukh, N.; Saxena, A.

    2013-04-01

    Fusion barrier distributions have been extracted from the quasi-elastic scattering excitation functions, measured at backward angle θlab = 160° in reactions of 6,7Li+209Bi. The present results have been compared with the barrier distributions obtained from the fusion excitation function measurements for the above mentioned systems. The fusion barrier distributions from the quasi-elastic scattering excitation functions have been analyzed with simplified Coupled Channels calculations using Fresco. Inclusions of resonant states for both 6,7Li projectiles improve the predictions to describe the measured quasi-elastic scattering excitation functions and barrier distributions. For both the reactions peak positions of fusion barrier distributions are shifted towards a lower energy side in comparison to that obtained from the fusion excitation function measurements. The observed discrepancy in peak positions of barrier distributions obtained from quasi-elastic scattering and fusion excitation function measurements has been discussed in terms of total reaction threshold distribution.

  15. Accurate calculation of conformational free energy differences in explicit water: the confinement-solvation free energy approach.

    PubMed

    Esque, Jeremy; Cecchini, Marco

    2015-04-23

    The calculation of the free energy of conformation is key to understanding the function of biomolecules and has attracted significant interest in recent years. Here, we present an improvement of the confinement method that was designed for use in the context of explicit solvent MD simulations. The development involves an additional step in which the solvation free energy of the harmonically restrained conformers is accurately determined by multistage free energy perturbation simulations. As a test-case application, the newly introduced confinement/solvation free energy (CSF) approach was used to compute differences in free energy between conformers of the alanine dipeptide in explicit water. The results are in excellent agreement with reference calculations based on both converged molecular dynamics and umbrella sampling. To illustrate the general applicability of the method, conformational equilibria of met-enkephalin (5 aa) and deca-alanine (10 aa) in solution were also analyzed. In both cases, smoothly converged free-energy results were obtained in agreement with equilibrium sampling or literature calculations. These results demonstrate that the CSF method may provide conformational free-energy differences of biomolecules with small statistical errors (below 0.5 kcal/mol) and at a moderate computational cost even with a full representation of the solvent. PMID:25807150

  16. Penetration through the Skin Barrier.

    PubMed

    Nielsen, Jesper Bo; Benfeldt, Eva; Holmgaard, Rikke

    2016-01-01

    The skin is a strong and flexible organ with barrier properties essential for maintaining homeostasis and thereby human life. Characterizing this barrier is the ability to prevent some chemicals from crossing the barrier while allowing others, including medicinal products, to pass at varying rates. During recent decades, the latter has received increased attention as a route for intentionally delivering drugs to patients. This has stimulated research in methods for sampling, measuring and predicting percutaneous penetration. Previous chapters have described how different endogenous, genetic and exogenous factors may affect barrier characteristics. The present chapter introduces the theory for barrier penetration (Fick's law), and describes and discusses different methods for measuring the kinetics of percutaneous penetration of chemicals, including in vitro methods (static and flow-through diffusion cells) as well as in vivo methods (microdialysis and microperfusion). Then follows a discussion with examples of how different characteristics of the skin (age, site and integrity) and of the penetrants (size, solubility, ionization, logPow and vehicles) affect the kinetics of percutaneous penetration. Finally, a short discussion of the advantages and challenges of each method is provided, which will hopefully allow the reader to improve decision making and treatment planning, as well as the evaluation of experimental studies of percutaneous penetration of chemicals. PMID:26844902

  17. Energy consumption analysis for various memristive networks under different learning strategies

    NASA Astrophysics Data System (ADS)

    Deng, Lei; Wang, Dong; Zhang, Ziyang; Tang, Pei; Li, Guoqi; Pei, Jing

    2016-02-01

    Recently, various memristive systems emerge to emulate the efficient computing paradigm of the brain cortex; whereas, how to make them energy efficient still remains unclear, especially from an overall perspective. Here, a systematical and bottom-up energy consumption analysis is demonstrated, including the memristor device level and the network learning level. We propose an energy estimating methodology when modulating the memristive synapses, which is simulated in three typical neural networks with different synaptic structures and learning strategies for both offline and online learning. These results provide an in-depth insight to create energy efficient brain-inspired neuromorphic devices in the future.

  18. Hole spins in quantum dot molecules: novel tuning by GaBiAs barriers

    NASA Astrophysics Data System (ADS)

    Flowers, Jackson; Bryant, Garnett; Doty, Matthew

    Hole spins in semiconductor quantum dots (QD) are promising qubits. Tunneling in vertical quantum dot molecules (QDM) provides additional freedom to use fields to manipulate hole g-factors and induce spin mixing. Interdot barriers made from GaBiAs should provide novel opportunities to further engineer these hole spin properties, because heavy- and light-holes in GaBiAs are modified by the Bi concentration without affecting conduction electrons or split off bands. For low Bi concentrations, GaBiAs provides a lower barrier for hole tunneling, allowing hole tunneling more comparable to electron tunneling and enhancing opportunities for g-factor modification. We use atomistic tight-binding theory for InAs QDMs with GaBiAs in the interdot barrier to assess the utility of this barrier material. We model the alloy barrier regions both with the virtual crystal approximation and with random realizations of atomic configurations for the alloy region in the barrier. Results are presented for electron and hole energies in QDMs with GaBiAs barriers as a function of applied electric and magnetic fields. These results allow us to quantify g-factor modification and hole-spin mixing in asymmetric structures to show how different GaBiAs barrier configurations modify hole spin physics in QDMs.

  19. Climate impacts on extreme energy consumption of different types of buildings.

    PubMed

    Li, Mingcai; Shi, Jun; Guo, Jun; Cao, Jingfu; Niu, Jide; Xiong, Mingming

    2015-01-01

    Exploring changes of building energy consumption and its relationships with climate can provide basis for energy-saving and carbon emission reduction. Heating and cooling energy consumption of different types of buildings during 1981-2010 in Tianjin city, was simulated by using TRNSYS software. Daily or hourly extreme energy consumption was determined by percentile methods, and the climate impact on extreme energy consumption was analyzed. The results showed that days of extreme heating consumption showed apparent decrease during the recent 30 years for residential and large venue buildings, whereas days of extreme cooling consumption increased in large venue building. No significant variations were found for the days of extreme energy consumption for commercial building, although a decreasing trend in extreme heating energy consumption. Daily extreme energy consumption for large venue building had no relationship with climate parameters, whereas extreme energy consumption for commercial and residential buildings was related to various climate parameters. Further multiple regression analysis suggested heating energy consumption for commercial building was affected by maximum temperature, dry bulb temperature, solar radiation and minimum temperature, which together can explain 71.5 % of the variation of the daily extreme heating energy consumption. The daily extreme cooling energy consumption for commercial building was only related to the wet bulb temperature (R2= 0.382). The daily extreme heating energy consumption for residential building was affected by 4 climate parameters, but the dry bulb temperature had the main impact. The impacts of climate on hourly extreme heating energy consumption has a 1-3 hour delay in all three types of buildings, but no delay was found in the impacts of climate on hourly extreme cooling energy consumption for the selected buildings. PMID:25923205

  20. Climate Impacts on Extreme Energy Consumption of Different Types of Buildings

    PubMed Central

    Li, Mingcai; Shi, Jun; Guo, Jun; Cao, Jingfu; Niu, Jide; Xiong, Mingming

    2015-01-01

    Exploring changes of building energy consumption and its relationships with climate can provide basis for energy-saving and carbon emission reduction. Heating and cooling energy consumption of different types of buildings during 1981-2010 in Tianjin city, was simulated by using TRNSYS software. Daily or hourly extreme energy consumption was determined by percentile methods, and the climate impact on extreme energy consumption was analyzed. The results showed that days of extreme heating consumption showed apparent decrease during the recent 30 years for residential and large venue buildings, whereas days of extreme cooling consumption increased in large venue building. No significant variations were found for the days of extreme energy consumption for commercial building, although a decreasing trend in extreme heating energy consumption. Daily extreme energy consumption for large venue building had no relationship with climate parameters, whereas extreme energy consumption for commercial and residential buildings was related to various climate parameters. Further multiple regression analysis suggested heating energy consumption for commercial building was affected by maximum temperature, dry bulb temperature, solar radiation and minimum temperature, which together can explain 71.5 % of the variation of the daily extreme heating energy consumption. The daily extreme cooling energy consumption for commercial building was only related to the wet bulb temperature (R2= 0.382). The daily extreme heating energy consumption for residential building was affected by 4 climate parameters, but the dry bulb temperature had the main impact. The impacts of climate on hourly extreme heating energy consumption has a 1-3 hour delay in all three types of buildings, but no delay was found in the impacts of climate on hourly extreme cooling energy consumption for the selected buildings. PMID:25923205

  1. Impact behaviour of Napier/polyester composites under different energy levels

    NASA Astrophysics Data System (ADS)

    Fahmi, I.; Majid, M. S. Abdul; Afendi, M.; Haslan, M.; Helmi E., A.; M. Haameem J., A.

    2016-07-01

    The effects of different energy levels on the impact behaviour of Napier fibre/polyester reinforced composites were investigated. Napier fibre was extracted using traditional water retting process to be utilized as reinforcing materials in polyester composite laminates. 25% fibre loading composite laminates were prepared and impacted at three different energy levels; 2.5,5 and 7.5 J using an instrumented drop weight impact testing machine (IMATEK IM10). The outcomes show that peak force and contact time increase with increased impact load. The energy absorption was then calculated from the force displacement curve. The results indicated that the energy absorption decreases with increasing energy levels of the impact. Impacted specimens were observed visually for fragmentation fracture using an optical camera to identify the failure mechanisms. Fracture fragmentation pattern from permanent dent to perforation with radial and circumferential was observed.

  2. Extracting a record of Holocene storm erosion and deposition preserved in the morphostratigraphy of a prograded coastal barrier

    NASA Astrophysics Data System (ADS)

    Dougherty, Amy J.

    2014-09-01

    Prograded barriers preserve palaeoenvironmental records within their varied morphologies and buried stratigraphy. In order to extract historical records of particular events, such as storms, the morphostratigraphy of these barriers must be detailed and the evolution deciphered. This study examines the progradation of Omaha barrier, New Zealand, using an integrated high-resolution geophysical and sedimentological approach. The barrier evolution appears complex, both spatially and temporally, with two different linear morphologies forming simultaneously alongshore, which both transition into a third type of ridge morphology across-shore. To determine what influenced the formation of these different morphologies, within the barrier and through time, various geological controls are investigated. The results are threefold: (1) a fall of sea level from a +2 m highstand drove barrier progradation, (2) differences in sediment supply driven by an exposure related longshore energy gradient dictated ridge morphology, and (3) storms punctuating barrier progradation formed the swales that define all morphologic ridges. High-energy events are recorded throughout the formation of Omaha barrier. Storm signatures are the most prominent features identified along the active beach and throughout the barrier morphostratigraphy. Observations of a high-energy event in 2007 document a unique depositional ridge emplaced landward of the characteristic erosional dune scarp and flattened beachface composed of course-grained/heavy mineral lag. A total of 25 paleo-beachfaces with the same post-storm geometry are identified within ground penetrating radar records of the barrier stratigraphy, including one associated with a known event in 1978 that has since been buried. Using limited ages available and the variable preservation of storm events in the morphostratigraphy, a speculative record of storm frequency and intensity is hypothesized. Future work aims to test this hypothesis by acquiring a

  3. Tandem-structured, hot electron based photovoltaic cell with double Schottky barriers

    PubMed Central

    Lee, Young Keun; Lee, Hyosun; Park, Jeong Young

    2014-01-01

    We demonstrate a tandem-structured, hot electron based photovoltaic cell with double Schottky barriers. The tandem-structured, hot electron based photovoltaic cell is composed of two metal/semiconductor interfaces. Two types of tandem cells were fabricated using TiO2/Au/Si and TiO2/Au/TiO2, and photocurrent enhancement was detected. The double Schottky barriers lead to an additional pathway for harvesting hot electrons, which is enhanced through multiple reflections between the two barriers with different energy ranges. In addition, light absorption is improved by the band-to-band excitation of both semiconductors with different band gaps. Short-circuit current and energy conversion efficiency of the tandem-structured TiO2/Au/Si increased by 86% and 70%, respectively, compared with Au/Si metal/semiconductor nanodiodes, showing an overall solar energy conversion efficiency of 5.3%. PMID:24694838

  4. Probing Difference in Binding Modes of Inhibitors to MDMX by Molecular Dynamics Simulations and Different Free Energy Methods.

    PubMed

    Shi, Shuhua; Zhang, Shaolong; Zhang, Qinggang

    2015-01-01

    The p53-MDMX interaction has attracted extensive attention of anti-cancer drug development in recent years. This current work adopted molecular dynamics (MD) simulations and cross-correlation analysis to investigate conformation changes of MDMX caused by inhibitor bindings. The obtained information indicates that the binding cleft of MDMX undergoes a large conformational change and the dynamic behavior of residues obviously change by the presence of different structural inhibitors. Two different methods of binding free energy predictions were employed to carry out a comparable insight into binding mechanisms of four inhibitors PMI, pDI, WK23 and WW8 to MDMX. The data show that the main factor controlling the inhibitor bindings to MDMX arises from van der Waals interactions. The binding free energies were further divided into contribution of each residue and the derived information gives a conclusion that the hydrophobic interactions, such as CH-CH, CH-π and π-π interactions, are responsible for the inhibitor associations with MDMX. PMID:26513747

  5. Probing Difference in Binding Modes of Inhibitors to MDMX by Molecular Dynamics Simulations and Different Free Energy Methods

    PubMed Central

    Shi, Shuhua; Zhang, Shaolong; Zhang, Qinggang

    2015-01-01

    The p53-MDMX interaction has attracted extensive attention of anti-cancer drug development in recent years. This current work adopted molecular dynamics (MD) simulations and cross-correlation analysis to investigate conformation changes of MDMX caused by inhibitor bindings. The obtained information indicates that the binding cleft of MDMX undergoes a large conformational change and the dynamic behavior of residues obviously change by the presence of different structural inhibitors. Two different methods of binding free energy predictions were employed to carry out a comparable insight into binding mechanisms of four inhibitors PMI, pDI, WK23 and WW8 to MDMX. The data show that the main factor controlling the inhibitor bindings to MDMX arises from van der Waals interactions. The binding free energies were further divided into contribution of each residue and the derived information gives a conclusion that the hydrophobic interactions, such as CH-CH, CH-π and π-π interactions, are responsible for the inhibitor associations with MDMX. PMID:26513747

  6. The Potential Field of Carbon Bodies as a Basis for Sorption Properties of Barrier Gas Systems

    NASA Astrophysics Data System (ADS)

    Bubenchikov, A. M.; Bubenchikov, M. A.; Potekaev, A. I.; Libin, É. E.; Khudobina, Yu. P.

    2015-11-01

    A modification of the Lennard-Jones potential allowed us, via integration over the volume of the bodies of different shapes, to determine the integral action (potential energy barrier) generated by the distributed force centers. The body generating the potential barrier was a carbon plate and the test particles overcoming this barrier were atoms or molecules of a number of gases (hydrogen, helium and methane). When considering the transit of particles (gas atoms or molecules) over this barrier, use was made of the energy barrier wave theory and the potential of a continuous body was used as a barrier. In so doing, the Schrödinger equation was integrated numerically for the molecular density. This integration yielded the expected wave pattern of the process of transit and reflection of the molecules, so a phase averaging procedure had to be applied. By varying the parameters of the layer containing force centers - field sources, the dimensions and density of the carbon plate possessing high selectivity towards separation of gas mixture containing helium, hydrogen and methane were determined. The data obtained provide an interpretation of the sorption properties of barrier carbon systems capable of filtering or separating gases.

  7. Modeling Fe0 permeable reactive barriers for groundwater remediation

    NASA Astrophysics Data System (ADS)

    Carniato, Luca; Schoups, Gerrit; Seuntjens, Piet; Bastiaens, Leen

    2010-05-01

    Remediation of groundwater pollution has traditionally been achieved by energy-intensive and drastic methods such as pump and treat (P&T) systems. Recently, more economically viable and less invasive methods such as permeable reactive barriers have been used to clean up a wide variety of groundwater pollutants (volatile organic compounds, VOCl). Permeable reactive barriers are installed in the subsurface and the naturally present hydraulic gradient makes the groundwater flow through the barrier where the contaminants are removed by different removal processes (biodegradation, sorption, precipitation, chemical destruction). Effective application of these techniques requires a solid understanding of the site-specific hydrogeological and biochemical conditions, as well as a predictive assessment of long-term remediation efficiency. For example, secondary mineral precipitation has been shown to reduce reactivity and efficiency of permeable reactive barriers and the interactions between biological and chemical processes may also influence the long-term efficiency of such systems. In this study a multi-component transport model based on PHAST USGS has been developed to simulate the removal processes in the barrier and to make quantitative predictions about the long-term efficiency of the system. In particular the modelling approach will be presented together with the model application in lab-scale experiments and in field.

  8. Sub- and near-barrier fusion reactions experimental results

    NASA Astrophysics Data System (ADS)

    Montagnoli, G.

    2016-05-01

    Early data of sub-barrier fusion teached us that cross sections may strongly depend on the structure of colliding nuclei and on couplings to transfer channels. The influence of transfer is clearly indicated in the excitation functions of different nickel isotopes and various Ca+Zr systems. Fusion barrier distributions often yield the fingerprint of the relevant inelastic and transfer couplings. At lower energies, far below the barrier the slope of the excitation function keeps increasing in many cases, so that the cross sections are strongly over-predicted by standard coupled-channels (CC) calculations; this was named a hindrance effect. Furthermore, light heavy-ion systems show cross section oscillations above the Coulomb barrier. Recent experiments have been performed on the fusion of 28,30Si+28,30Si systems where all phenomena cited above show up. In particular regular oscillations that have been revealed above the barrier for 28Si+28Si and have been interpreted as the consequence of the strong channel couplings and/or the oblate deformation of 28Si.

  9. Puncture detecting barrier materials

    DOEpatents

    Hermes, Robert E.; Ramsey, David R.; Stampfer, Joseph F.; Macdonald, John M.

    1998-01-01

    A method and apparatus for continuous real-time monitoring of the integrity of protective barrier materials, particularly protective barriers against toxic, radioactive and biologically hazardous materials has been developed. Conductivity, resistivity or capacitance between conductive layers in the multilayer protective materials is measured by using leads connected to electrically conductive layers in the protective barrier material. The measured conductivity, resistivity or capacitance significantly changes upon a physical breach of the protective barrier material.

  10. Puncture detecting barrier materials

    DOEpatents

    Hermes, R.E.; Ramsey, D.R.; Stampfer, J.F.; Macdonald, J.M.

    1998-03-31

    A method and apparatus for continuous real-time monitoring of the integrity of protective barrier materials, particularly protective barriers against toxic, radioactive and biologically hazardous materials has been developed. Conductivity, resistivity or capacitance between conductive layers in the multilayer protective materials is measured by using leads connected to electrically conductive layers in the protective barrier material. The measured conductivity, resistivity or capacitance significantly changes upon a physical breach of the protective barrier material. 4 figs.

  11. Renewable Energy and Efficiency Modeling Analysis Partnership (REMAP): An Analysis of How Different Energy Models Addressed a Common High Renewable Energy Penetration Scenario in 2025

    SciTech Connect

    Blair, Nate; Jenkin, Thomas; Milford, James; Short, Walter; Sullivan, Patrick; Evans, David; Lieberman, Elliot; Goldstein, Gary; Wright, Evelyn; Jayaraman, Kamala R.; Venkatesh, Boddu; Kleiman, Gary; Namovicz, Christopher; Smith, Bob; Palmer, Karen; Wiser, Ryan; Wood, Frances

    2009-09-01

    Energy system modeling can be intentionally or unintentionally misused by decision-makers. This report describes how both can be minimized through careful use of models and thorough understanding of their underlying approaches and assumptions. The analysis summarized here assesses the impact that model and data choices have on forecasting energy systems by comparing seven different electric-sector models. This analysis was coordinated by the Renewable Energy and Efficiency Modeling Analysis Partnership (REMAP), a collaboration among governmental, academic, and nongovernmental participants.

  12. Energy barrier at the N719-dye/CsSnI₃ interface for photogenerated holes in dye-sensitized solar cells.

    PubMed

    Zhang, Jin; Yu, Chunhui; Wang, Lili; Li, Yizhi; Ren, Yuhang; Shum, Kai

    2014-01-01

    This report is to address the question if black γ-polymorph of cesium tin tri-iodide (B-γ-CsSnI3) can be used as a solid-state hole-transport material in the conventional DSSCs with the N719 dye to replace the liquid electrolyte as reported by I. Chung et al. on Nature 485, 486, (2012). Here we demonstrate rigorously that B-γ-CsSnI3 is not energetically possible to collect photogenerated holes because of the large energy barrier at the interface of N719/B-γ-CsSnI3. Therefore, it cannot serve as a hole-transporter for the conventional DSSCs although it is a good hole-conducting material. A solution-based method was employed to synthesize the B-γ-CsSnI3 polycrystalline thin-films used for this work. These thin-films were then characterized by X-ray diffraction, Hall measurements, optical reflection, and photoluminescence (PL). Particularly, spatially resolved PL intensity images were taken after B-γ-CsSnI3 was incorporated in the DSSC structure to insure the material integrity. The means of ultraviolet photoemission spectroscopy (UPS) was used to reveal why B-γ-CsSnI3 could not act as the substitute of liquid electrolyte in the conventional DSSCs. For the completeness, other two related compounds, one is the yellow polymorph of CsSnI3 and other is Cs2SnI6 with tetravalent tin instead of double-valent tin in CsSnI3 were also investigated by UPS. PMID:25378076

  13. Estimation of free energy barriers in the cytoplasmic and mitochondrial aspartate aminotransferase reactions probed by hydrogen-exchange kinetics of C alpha-labeled amino acids with solvent

    SciTech Connect

    Julin, D.A.; Wiesinger, H.; Toney, M.D.; Kirsch, J.F. )

    1989-05-02

    The existence of the postulated quinonoid intermediate in the cytoplasmic aspartate amino-transferase catalyzed transamination of aspartate to oxaloacetate was probed by determining the extent of transfer of tritium from the C alpha position of tritiated L-aspartate to pyridoxamine 5'-phosphate in single turnover experiments in which washout from the back-reaction was obviated by product trapping. The maximum amount of transferred tritium observed was 0.7%, consistent either with a mechanism in which a fraction of the net transamination reaction proceeds through a quinonoid intermediate or with a mechanism in which this intermediate is formed off the main reaction pathway. It is shown that transfer of labeled hydrogen from the amino acid to cofactor cannot be used to differentiate a stepwise from a concerted transamination mechanism. The amount of tritium transferred is a function of the rate constant for torsional equilibration about the epsilon-amino group of Lys-258, the presumptive abstractor of the C alpha proton; the relative rate constants for hydrogen exchange with solvent versus cofactor protonation; and the tritium isotope effect on this ratio. The free energy barriers facing the covalent intermediate between aldimine and keto acid product (i.e., ketimine and possibly quinonoid) were evaluated relatively by comparing the rates of C alpha-hydrogen exchange in starting amino acid with the rates of keto acid formation. The value of theta (= kexge/kprod) was found to be 2.6 for the reaction of cytoplasmic isozyme with aspartate and ca. 0.5 for that of the mitochondrial form with glutamate.

  14. Energy barrier at the N719-dye/CsSnI3 interface for photogenerated holes in dye-sensitized solar cells

    PubMed Central

    Zhang, Jin; Yu, Chunhui; Wang, Lili; Li, Yizhi; Ren, Yuhang; Shum, Kai

    2014-01-01

    This report is to address the question if black γ-polymorph of cesium tin tri-iodide (B-γ-CsSnI3) can be used as a solid-state hole-transport material in the conventional DSSCs with the N719 dye to replace the liquid electrolyte as reported by I. Chung et al. on Nature 485, 486, (2012). Here we demonstrate rigorously that B-γ-CsSnI3 is not energetically possible to collect photogenerated holes because of the large energy barrier at the interface of N719/B-γ-CsSnI3. Therefore, it cannot serve as a hole-transporter for the conventional DSSCs although it is a good hole-conducting material. A solution-based method was employed to synthesize the B-γ-CsSnI3 polycrystalline thin-films used for this work. These thin-films were then characterized by X-ray diffraction, Hall measurements, optical reflection, and photoluminescence (PL). Particularly, spatially resolved PL intensity images were taken after B-γ-CsSnI3 was incorporated in the DSSC structure to insure the material integrity. The means of ultraviolet photoemission spectroscopy (UPS) was used to reveal why B-γ-CsSnI3 could not act as the substitute of liquid electrolyte in the conventional DSSCs. For the completeness, other two related compounds, one is the yellow polymorph of CsSnI3 and other is Cs2SnI6 with tetravalent tin instead of double-valent tin in CsSnI3 were also investigated by UPS. PMID:25378076

  15. Efficiency droop enhancement in AlGaN deep ultraviolet light-emitting diodes by making whole barriers but the bottom Mg doped

    NASA Astrophysics Data System (ADS)

    Sun, Jie; Sun, Huiqing; Yi, Xinyan; Yang, Xian; Fan, Xuancong; Zhang, Cheng; Zhang, Zhuding; Guo, Zhiyou

    2016-09-01

    Ultra violet light-emitting diodes (UVLEDs) with different types of Mg-doped barriers have been studied. The energy band diagrams, internal quantum efficiency, total output power and radiative recombination rate are investigated by APSYS software. The simulation results show that the UVLED with only a p-doped top barrier get little enhancement comparing to the conventional one, on the contrary the structure with p-doping in all but the bottom barriers has a much better optical and electrical properties due to enhancement of the holes' injection and the electrons' confinement. The efficiency droop is significantly alleviated and the light output power is greatly enhanced. To avoid forming a PN junction by the bottom barrier and the n-AlGaN in the proposed structure, therefore, the bottom barrier isn't p-doped. Then structures with different hole densities in the Mg-doped barriers have been studied numerically and that confirmed the best.

  16. Ablation of atheroma by laser energy: a comparative study of the efficacy of different temporal rates of energy deposition

    NASA Astrophysics Data System (ADS)

    Ramsay, Donald J.; Walker, Philip J.; Dadswell, Nicola G.; May, James; Piper, James A.; Wacher, Christine

    1990-06-01

    Laser angioplasty continues to attract interest as a potential method for treating atherosclerotic arterial disease. Current efforts are aimed at finding the most effective combination of laser and delivery system. High energy pulsed ultraviolet or infrared lasers demonstrate good photoablative properties but there remain practical difficulties with the optical fibre delivery. Continuous wave lasers are widely used in conjunction with "hot-tip" fibres for thermal ablation but their direct (optical) ablation efficiency is low, causing significant surrounding thermal damage in soft tissue. While considerable attention has been directed previously at the ablative effects for different laser wavelengths, little systematic study has been made of the efficacy for different temporal rates of energy deposition. We have compared the efficacy for tissue ablation in cadaveric human aorta of three different laser systems with similar wavelengths in the visible (green) but different temporal rates of energy deposition. The laser sources were the continuous wave argon ion laser (514.5 nm), the high pulse energy, frequency doubled Nd:YAG laser (532 nm) and the copper vapour laser. The copper vapour laser is a high repetition rate, high average power, pulsed laser emitting in the green (511 nm) and yellow (578 nm) which has temporal characteristics intermediate between those of the Nd:YAG laser and the argon ion laser, and has the potential to be effective both for direct optical ablation and hot-tip thermal ablation.

  17. Nuclear structure and sub-barrier fusion

    SciTech Connect

    Esbensen, H. . Cyclotron Lab. Argonne National Lab., IL )

    1990-01-01

    The influence of nuclear structure on heavy-ion fusion and elastic scattering, at energies near and below the Coulomb barrier, is discussed within the coupled channels formalism. The coupled channels approach provides a consistent description of the enhancement of sub-barrier fusion and the energy dependence of the effective potential for elastic scattering. This is illustrated by comparison to the data for several systems. 48 refs., 4 figs.

  18. Anisotropic capillary barrier for waste site surface covers

    DOEpatents

    Stormont, J.C.

    1996-08-27

    Waste sites are capped or covered upon closure. The cover structure incorporates a number of different layers each having a contributory function. One such layer is the barrier layer. Traditionally the barriers have been compacted soil and geosynthetics. These types of barriers have not been successfully implemented in unsaturated ground conditions like those found in dry climates. Capillary barriers have been proposed as barrier layers in dry environments, but the divergence length of these barriers has been found to be inadequate. An alternative to the capillary barrier is a anisotropic capillary barrier. An anisotropic capillary barrier has an increased divergence length which results in more water being diverted laterally preventing the majority of water from percolating in a downward direction through the barrier. 10 figs.

  19. Anisotropic capillary barrier for waste site surface covers

    DOEpatents

    Stormont, John C.

    1996-01-01

    Waste sites are capped or covered upon closure. The cover structure incorporates a number of different layers each having a contributory function. One such layer is the barrier layer. Traditionally the barriers have been compacted soil and geosynthetics. These types of barriers have not been successfully implemented in unsaturated ground conditions like those found in dry climates. Capillary barriers have been proposed as barrier layers in dry environments, but the divergence length of these barriers has been found to be inadequate. An alternative to the capillary barrier is a anisotropic capillary barrier. An anisotropic capillary barrier has an increased divergence length which results in more water being diverted laterally preventing the majority of water from percolating in a downward direction through the barrier.

  20. Energy conversion method in the ocean using the density difference of water

    SciTech Connect

    Mochizuki, H.; Mitsuhashi, W.

    1981-01-01

    A new method which produces energy from the ocean by utilizing the density difference of water, by means of a ''chimney effect'', is proposed. Density difference of water in the ocean occurs in two ways, namely differences of consistency and water temperature. For instance, fresh river water and melting flows and icebergs are pointed out as some origins of the former, while thermal effects of volcanoes and hot springs may account for the latter. 5 refs.