Hypoxanthine is a checkpoint stress metabolite in colonic epithelial energy modulation and barrier function.

PubMed

Lee, J Scott; Wang, Ruth X; Alexeev, Erica E; Lanis, Jordi M; Battista, Kayla D; Glover, Louise E; Colgan, Sean P

2018-04-20

Intestinal epithelial cells form a selectively permeable barrier to protect colon tissues from luminal microbiota and antigens and to mediate nutrient, fluid, and waste flux in the intestinal tract. Dysregulation of the epithelial cell barrier coincides with profound shifts in metabolic energy, especially in the colon, which exists in an energetically depleting state of physiological hypoxia. However, studies that systematically examine energy flux and adenylate metabolism during intestinal epithelial barrier development and restoration after disruption are lacking. Here, to delineate barrier-related energy flux, we developed an HPLC-based profiling method to track changes in energy flux and adenylate metabolites during barrier development and restoration. Cultured epithelia exhibited pooling of phosphocreatine and maintained ATP during barrier development. EDTA-induced epithelial barrier disruption revealed that hypoxanthine levels correlated with barrier resistance. Further studies uncovered that hypoxanthine supplementation improves barrier function and wound healing and that hypoxanthine appears to do so by increasing intracellular ATP, which improved cytoskeletal G- to F-actin polymerization. Hypoxanthine supplementation increased the adenylate energy charge in the murine colon, indicating potential to regulate adenylate energy charge-mediated metabolism in intestinal epithelial cells. Moreover, experiments in a murine colitis model disclosed that hypoxanthine loss during active inflammation correlates with markers of disease severity. In summary, our results indicate that hypoxanthine modulates energy metabolism in intestinal epithelial cells and is critical for intestinal barrier function. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Key Barriers to the Implementation of Solar Energy in Nigeria: A Critical Analysis

NASA Astrophysics Data System (ADS)

Abdullahi, D.; Suresh, S.; Renukappa, S.; Oloke, D.

2017-08-01

Nigeria, potentially, has abundant sunshine throughout the year, making it full thirst for solar energy generation. Even though, the country’s solar energy projects have not realised a fair result over the years, due to many barriers associated with initiatives implementation. Therefore, the entire power sector remains incapacitated to generate, transmit and distribute a clean, affordable and sustainable energy to assist economic growth. The research integrated five African counterpart’s solar energy initiatives, barriers, policies and strategies adopted as a lesson learned to Nigeria. Inadequate solar initiative’s research, lack of technological know-how, short-term policies, lack of awareness and political instability are the major barriers that made the implementation of solar initiatives almost impossible in Nigeria. The shock of the barriers therefore, constitutes a major negative contribution to the crippling of the power sector in the state. Future research will concentrate on initiatives for mitigating solar and other renewable energy barriers.

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

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.

On the enhanced sampling over energy barriers in molecular dynamics simulations.

PubMed

Gao, Yi Qin; Yang, Lijiang

2006-09-21

We present here calculations of free energies of multidimensional systems using an efficient sampling method. The method uses a transformed potential energy surface, which allows an efficient sampling of both low and high energy spaces and accelerates transitions over barriers. It allows efficient sampling of the configuration space over and only over the desired energy range(s). It does not require predetermined or selected reaction coordinate(s). We apply this method to study the dynamics of slow barrier crossing processes in a disaccharide and a dipeptide system.

Energy Dissipating Devices in Falling Rock Protection Barriers

NASA Astrophysics Data System (ADS)

Castanon-Jano, L.; Blanco-Fernandez, E.; Castro-Fresno, D.; Ballester-Muñoz, F.

2017-03-01

Rockfall is a phenomenon which, when uncontrolled, may cause extensive material damage and personal injury. One of the structures used to avoid accidents caused by debris flows or rockfalls is flexible barriers. The energy dissipating devices which absorb the energy generated by rock impact and reduce the mechanical stresses in the rest of the elements of the structure are an essential part of these kinds of structures. This document proposes an overview of the performance of energy dissipating devices, as well as of the role that they fulfil in the barrier. Furthermore, a compilation and a description of the dissipating elements found in the literature are proposed. Additionally, an analysis has been performed of the aspects taken into account in the design, such as experimental (quasi-static and dynamic) tests observing the variation of the behaviour curve depending on the test speed and numerical simulations by means of several finite element software packages.

Free energy and hidden barriers of the β-sheet structure of prion protein.

PubMed

Paz, S Alexis; Abrams, Cameron F

2015-10-13

On-the-fly free-energy parametrization is a new collective variable biasing approach akin to metadynamics with one important distinction: rather than acquiring an accelerated distribution via a history-dependent bias potential, sampling on this distribution is achieved from the beginning of the simulation using temperature-accelerated molecular dynamics. In the present work, we compare the performance of both approaches to compute the free-energy profile along a scalar collective variable measuring the H-bond registry of the β-sheet structure of the mouse Prion protein. Both methods agree on the location of the free-energy minimum, but free-energy profiles from well-tempered metadynamics are subject to a much higher degree of statistical noise due to hidden barriers. The sensitivity of metadynamics to hidden barriers is shown to be a consequence of the history dependence of the bias potential, and we detail the nature of these barriers for the prion β-sheet. In contrast, on-the-fly parametrization is much less sensitive to these barriers and thus displays improved convergence behavior relative to that of metadynamics. While hidden barriers are a frequent and central issue in free-energy methods, on-the-fly free-energy parametrization appears to be a robust and preferable method to confront this issue.

Design and evaluation of an energy-absorbing, reusable roadside/median barrier.

DOT National Transportation Integrated Search

2015-07-01

Further design and evaluation was conducted on an energy-absorbing, restorable and reusable roadside/median barrier, : designated the RESTORE barrier. A series of dynamic component tests were conducted on 11-in. (295-mm) tall x 10-in. : (254-mm) w...

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

Language Barriers of the Culturally Different.

ERIC Educational Resources Information Center

Berg, Paul Conrad

Language differences peculiar to the disadvantaged are discussed as they relate to reading. Linguistic differences, including the interdependence among language, operant feedback, thought, and experience, and the power of these to reconstruct and reassociate through reading constitute one barrier. Another is the effects of language on the total…

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.

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.

Overcoming Codes and Standards Barriers to Innovations in Building Energy Efficiency

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

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 canmore » 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.« less

Energy barrier of bcc-fcc phase transition via the Bain path in Yukawa system

NASA Astrophysics Data System (ADS)

Kiyokawa, Shuji

2018-05-01

In the Yukawa system with the dimensionless screening parameter κ>1.5 , when bcc-fcc transition occurs via Bain path, we show that spontaneous transitions do not occur even if the system temperature reaches the transition point of bcc-fcc because it is necessary to increase once the free energy in the process of transition from bcc to fcc through Bain deformation. Here, we refer the temporary increment of the free energy during Bain deformation as Bain barrier. Since there are the Bain barriers at the transitions between bcc and fcc phases, these phases may coexist as metastable state in the wide region (not a coexistence line) of κ and the coupling constant Γ. We study the excess energy of the system and the free energy difference between bcc and fcc phases by the Monte Carlo method, where the simulation box is divided into a large number of elements with small volume and a particle in the box is restricted be placed in one of these elements. By this method, we can tabulate the values of the interparticle potential and can calculate the internal energy fast and precisely.

Energy Barriers and Hysteresis in Martensitic Phase Transformations

DTIC Science & Technology

2008-08-01

glacial acetic acid (CH3COOH) and 10-15% perchloric acid (HCLO4) by volume, the cathode was stainless steel , the anode was stainless steel or Ti, the...Submitted to Acta Materialia Energy barriers and hysteresis in martensitic phase transformations Zhiyong Zhang, Richard D. James and Stefan Müller...hysteresis based on the growth from a small scale of fully developed austenite martensite needles. In this theory the energy of the transition layer plays a

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.

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.

Wetting transition on patterned surfaces: transition states and energy barriers.

PubMed

Ren, Weiqing

2014-03-18

We study the wetting transition on microstructured hydrophobic surfaces. We use the string method [J. Chem. Phys. 2007, 126, 164103; J. Chem. Phys. 2013, 138, 134105] to accurately compute the transition states, the energy barriers, and the minimum energy paths for the wetting transition from the Cassie-Baxter state to the Wenzel state. Numerical results are obtained for the wetting of a hydrophobic surface textured with a square lattice of pillars. It is found that the wetting of the solid substrate occurs via infiltration of the liquid in a single groove, followed by lateral propagation of the liquid front. The propagation of the liquid front proceeds in a stepwise manner, and a zipping mechanism is observed during the infiltration of each layer. The minimum energy path for the wetting transition goes through a sequence of intermediate metastable states, whose wetted areas reflect the microstructure of the patterned surface. We also study the dependence of the energy barrier on the drop size and the gap between the pillars.

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

2013-04-05

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.

Protecting High Energy Barriers: A New Equation to Regulate Boost Energy in Accelerated Molecular Dynamics Simulations.

PubMed

Sinko, William; de Oliveira, César Augusto F; Pierce, Levi C T; McCammon, J Andrew

2012-01-10

Molecular dynamics (MD) is one of the most common tools in computational chemistry. Recently, our group has employed accelerated molecular dynamics (aMD) to improve the conformational sampling over conventional molecular dynamics techniques. In the original aMD implementation, sampling is greatly improved by raising energy wells below a predefined energy level. Recently, our group presented an alternative aMD implementation where simulations are accelerated by lowering energy barriers of the potential energy surface. When coupled with thermodynamic integration simulations, this implementation showed very promising results. However, when applied to large systems, such as proteins, the simulation tends to be biased to high energy regions of the potential landscape. The reason for this behavior lies in the boost equation used since the highest energy barriers are dramatically more affected than the lower ones. To address this issue, in this work, we present a new boost equation that prevents oversampling of unfavorable high energy conformational states. The new boost potential provides not only better recovery of statistics throughout the simulation but also enhanced sampling of statistically relevant regions in explicit solvent MD simulations.

Negative influence of pKa on activation energy barrier: A case study for double proton transfer reaction in inorganic acid dimers.

PubMed

Parida, Rakesh; Giri, Santanab

2018-06-15

Strength of acid can be determined by means of pK a value. Attempts have been made to find a relationship between pK a and activation energy barrier for a double proton transfer (DPT) reaction in inorganic acid dimers. Negative influence of pK a is observed on activation energy (E a ) which is contrary to the general convention of pK a . Four different levels of theories with two different basis sets have been used to calculate the activation energy barrier of the DPT reaction in inorganic acid dimers. A model based on first and second order polynomial has been created to find the relationship between activation energy for DPT reaction. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Energy shift and conduction-to-valence band transition mediated by a time-dependent potential barrier in graphene

NASA Astrophysics Data System (ADS)

Chaves, Andrey; da Costa, D. R.; de Sousa, G. O.; Pereira, J. M.; Farias, G. A.

2015-09-01

We investigate the scattering of a wave packet describing low-energy electrons in graphene by a time-dependent finite-step potential barrier. Our results demonstrate that, after Klein tunneling through the barrier, the electron acquires an extra energy which depends on the rate of change of the barrier height with time. If this rate is negative, the electron loses energy and ends up as a valence band state after leaving the barrier, which effectively behaves as a positively charged quasiparticle.

Evaluation of energy absorbers for use in a roadside/median barrier.

DOT National Transportation Integrated Search

2014-02-01

Several types of elastomeric energy absorbers were evaluated for use in a Manual for Assessing Safety Hardware (MASH) : Test Level 4 (TL-4) energy-absorbing, urban roadside/median barrier. Twelve dynamic bogie tests were conducted on 60- : and 80-dur...

Best Practices and Barriers to Obesity Prevention in Head Start: Differences Between Director and Teacher Perceptions.

PubMed

Byrd-Williams, Courtney; Dooley, Erin E; Sharma, Shreela V; Chuang, Ru-Jye; Butte, Nancy; Hoelscher, Deanna M

2017-12-21

Practices and barriers to promoting healthy eating and physical activity at Head Start centers may influence children's energy balance behaviors. We examined differences between directors' and teachers' perspectives on best practices and barriers to promoting healthy eating and physical activity in Head Start centers. We conducted a cross-sectional study of directors (n = 23) and teachers (n = 113) at 23 Head Start centers participating in the baseline assessment of the Texas Childhood Obesity Research Demonstration study. Participants completed surveys about practices and barriers to promoting healthy eating and physical activity. Multilevel regression models examined differences between director and teacher responses. More than half of directors and teachers reported meeting most best practices related to nutrition and physical activity; few directors or teachers (<25%) reported conducting physical activity for more than 60 minutes a day, and less than 40% of teachers helped children attend to satiety cues. Significantly more directors than teachers reported meeting 2 nutrition-related best practices: "Teachers rarely eat less healthy foods (especially sweets, salty snacks, and sugary drinks) in front of children" and "Teachers talk to children about trying/enjoying new foods" (P < .05). No barrier to healthy eating or physical activity was reported by more than 25% of directors or teachers. Significantly more teachers than directors reported barriers to healthy eating, citing lack of food service staff support, limited time, and insufficient funds (P < .05). More barriers to healthy eating were reported than were barriers to physical activity indicating that more support may be needed for healthy eating. Differences between responses of directors and teachers may have implications for future assessments of implementation of best practices and barriers to implementation related to nutrition and physical activity in early care and education centers.

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.

8B + 208Pb Elastic Scattering at Coulomb Barrier Energies

NASA Astrophysics Data System (ADS)

La Commara, M.; Mazzocco, M.; Boiano, A.; Boiano, C.; Manea, C.; Parascandolo, C.; Pierroutsakou, D.; Signorini, C.; Strano, E.; Torresi, D.; Yamaguchi, H.; Kahl, D.; Di Meo, P.; Grebosz, J.; Imai, N.; Hirayama, Y.; Ishiyama, H.; Iwasa, N.; Jeong, S. C.; Jia, H. M.; Kim, Y. H.; Kimura, S.; Kubono, S.; Lin, C. J.; Miyatake, H.; Mukai, M.; Nakao, T.; Nicoletto, M.; Sakaguchi, Y.; Sánchez-Benítez, A. M.; Soramel, F.; Teranishi, T.; Wakabayashi, Y.; Watanabe, Y. X.; Yang, L.; Yang, Y. Y.

2018-02-01

The scattering process of weakly-bound nuclei at Coulomb barrier energies provides deep insights on the reaction dynamics induced by exotic nuclei. Within this framework, we measured for the first time the scattering process of the short-lived Radioactive Ion Beam (RIB) 8B (Sp = 0.1375 MeV) from a 208Pb target at 50 MeV beam energy. The 8B RIB was produced by means of the in-flight facility CRIB (RIKEN, Japan) with an average intensity on target of 10 kHz and a purity about 25%. Elastically scattering ions were detected in the angular range θc.m. = 10°-160° by means of the detector array EXPADES. A preliminary optical model analysis indicates a total reaction cross section of about 1 b, a value, once reduced, 2-3 times larger than those obtained for the reactions induced by the stable weakly-bound projectiles 6,7Li on a 208Pb target in the energy range around the Coulomb barrier.

8B + 208Pb Elastic Scattering at Coulomb Barrier Energies

NASA Astrophysics Data System (ADS)

La Commara, M.; Mazzocco, M.; Boiano, A.; Boiano, C.; Manea, C.; Parascandolo, C.; Pierroutsakou, D.; Signorini, C.; Strano, E.; Torresi, D.; Yamaguchi, H.; Kahl, D.; Di Meo, P.; Grebosz, J.; Imai, N.; Hirayama, Y.; Ishiyama, H.; Iwasa, N.; Jeong, S. C.; Jia, H. M.; Kim, Y. H.; Kimura, S.; Kubono, S.; Lin, C. J.; Miyatake, H.; Mukai, M.; Nakao, T.; Nicoletto, M.; Sakaguchi, Y.; Sánchez-Benítez, A. M.; Soramel, F.; Teranishi, T.; Wakabayashi, Y.; Watanabe, Y. X.; Yang, L.; Yang, Y. Y.

2017-11-01

The scattering process of weakly-bound nuclei at Coulomb barrier energies provides deep insights on the reaction dynamics induced by exotic nuclei. Within this framework, we measured for the first time the scattering process of the short-lived Radioactive Ion Beam (RIB) 8B (S p = 0.1375 MeV) from a 208Pb target at 50 MeV beam energy. The 8B RIB was produced by means of the in-flight facility CRIB (RIKEN, Japan) with an average intensity on target of 10 kHz and a purity about 25%. Elastically scattering ions were detected in the angular range θc.m. = 10°-160° by means of the detector array EXPADES. A preliminary optical model analysis indicates a total reaction cross section of about 1 b, a value, once reduced, 2-3 times larger than those obtained for the reactions induced by the stable weakly-bound projectiles 6,7Li on a 208Pb target in the energy range around the Coulomb barrier.

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

PubMed

Roy, Susmita; Bagchi, Biman

2012-03-08

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.

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].

Multinucleon transfer dynamics in heavy-ion collisions near Coulomb-barrier energies

NASA Astrophysics Data System (ADS)

Niu, Fei; Chen, Peng-Hui; Guo, Ya-Fei; Ma, Chun-Wang; Feng, Zhao-Qing

2017-12-01

Multinucleon transfer reactions near barrier energies have been investigated with a multistep model based on the dinuclear system (DNS) concept, in which the capture of two colliding nuclei, the transfer dynamics, and the deexcitation process of primary fragments are described by an analytical formula, diffusion theory, and a statistical model, respectively. The nucleon transfer takes place after forming the DNS and is coupled to the dissipation of relative motion energy and angular momentum by solving a set of microscopically derived master equations within the potential energy surface. Specific reactions of Ca,4840+124Sn , 40Ca(40Ar,58Ni)+232Th , 40Ca(58Ni)+238U , and Ca,4840(58Ni)+248Cm near barrier energies are investigated. It is found that fragments are produced by multinucleon transfer reactions with maximal yields along the β -stability line. The isospin relaxation is particularly significant in the process of fragment formation. The incident energy dependence of heavy target-like fragments in the reaction of 58Ni+248Cm is analyzed thoroughly.

Development of a new energy-absorbing roadside/median barrier system with restorable elastomer cartridges.

DOT National Transportation Integrated Search

2013-07-01

A Manual for Assessing Safety Hardware (MASH) Test Level 4 (TL-4) energy-absorbing, urban roadside/median barrier was developed to reduce lateral vehicle accelerations below those observed during similar crashes into permanent concrete barriers. Seve...

Market and policy barriers to deployment of energy storage

DOE PAGES

Sioshansi, Ramteen; Denholm, Paul; Jenkin, Thomas

2012-04-01

There has recently been resurgent interest in energy storage, due to a number of developments in the electricity industry. Despite this interest, very little storage, beyond some small demonstration projects, has been deployed recently. While technical issues, such as cost, device efficiency, and other technical characteristics are often listed as barriers to storage, there are a number of non-technical and policy-related issues. This paper surveys some of these main barriers and proposes some potential research and policy steps that can help address them. Furthermore, while the discussion is focused on the United States, a number of the findings and observationsmore » may be more broadly applicable.« less

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.

Barriers to oral health care amongst different social classes in India.

PubMed

Garcha, V; Shetiya, S H; Kakodkar, P

2010-09-01

To investigate and compare the influence of social and cultural factors as access barriers to oral health care amongst people from various social classes. A cross sectional survey in Pimpri, was conducted using a pilot tested 15 item-structured, close-ended and self-administered questionnaire. Two hundred and fifty people aged 35-45 years (50 participants each in five social classes as per British Registrar's General classification of occupation) were selected. The chi-square test was applied to check statistical differences between social classes at 5% level of significance. Overall, it was observed that irrespective of the social class difference 88% participants wished to seek only expert/professional advice for the dental treatment. Unavailability of services on Sunday (63%), going to dentist only when in pain (57%), trying self care or home remedy (54%), inadequate government policies (50%), budgetary constraints (40%) were among the major access barriers. Statistically significant difference in the access barriers among the social classes were found related to: Inadequate government policies, budgetary constraints, appointment schedules, far-off located clinics, myths and fear about dental treatment. Social and cultural factors act as access barriers to oral health care and social class differences have a significant influence on the access barriers.

Energy barriers between metastable states in first-order quantum phase transitions

NASA Astrophysics Data System (ADS)

Wald, Sascha; Timpanaro, André M.; Cormick, Cecilia; Landi, Gabriel T.

2018-02-01

A system of neutral atoms trapped in an optical lattice and dispersively coupled to the field of an optical cavity can realize a variation of the Bose-Hubbard model with infinite-range interactions. This model exhibits a first-order quantum phase transition between a Mott insulator and a charge density wave, with spontaneous symmetry breaking between even and odd sites, as was recently observed experimentally [Landig et al., Nature (London) 532, 476 (2016), 10.1038/nature17409]. In the present paper, we approach the analysis of this transition using a variational model which allows us to establish the notion of an energy barrier separating the two phases. Using a discrete WKB method, we then show that the local tunneling of atoms between adjacent sites lowers this energy barrier and hence facilitates the transition. Within our simplified description, we are thus able to augment the phase diagram of the model with information concerning the height of the barrier separating the metastable minima from the global minimum in each phase, which is an essential aspect for the understanding of the reconfiguration dynamics induced by a quench across a quantum critical point.

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.

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

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…

Origin of the Energy Barrier to Chemical Reactions of O2 on Al(111): Evidence for Charge Transfer, Not Spin Selection

DTIC Science & Technology

2012-11-08

change of O2 spin, at the barrier [Fig. 3]; i.e., the corresponding diabatic surfaces cross. Far from the Al surface, the triplet state is...previous theoretical models, in particular nonadiabatic [17] or diabatic [16] approaches, which also find an energy barrier consistent with experiment...crossings of different diabatic O2 spin configuration sur- faces are accommodated by small spin fluctuations within the metal surface. For parallel

Free-Energy Barrier of Filling a Spherical Cavity in the Presence of Line Tension: Implication to the Energy Barrier between the Cassie and Wenzel States on a Superhydrophobic Surface with Spherical Cavities.

PubMed

Iwamatsu, Masao

2016-09-20

The free-energy barrier of filling a spherical cavity having an inner wall of various wettabilities is studied. The morphology and free energy of a lens-shaped droplet are determined from the minimum of the free energy. The effect of line tension on the free energy is also studied. Then, the equilibrium contact angle of the droplet is determined from the generalized Young's equation. By increasing the droplet volume within the spherical cavity, the droplet morphology changes from spherical with an equilibrium contact angle of 180° to a lens with a convex meniscus, where the morphological complete drying transition occurs. By further increasing the droplet volume, the meniscus changes from convex to concave. Then, the lens-shaped droplet with concave meniscus spreads over the whole inner wall, resulting in an equilibrium contact angle of 0° to leave a spherical bubble, where the morphological complete wetting transition occurs. Finally, the whole cavity is filled with liquid. The free energy shows a barrier from complete drying to complete wetting as a function of droplet volume, which corresponds to the energy barrier between the Cassie and Wenzel states of the superhydrophobic surface with spherical cavities. The free-energy maximum occurs when the meniscus of the droplet becomes flat, and it is given by an analytic formula. The effect of line tension is expressed by the scaled line tension, and this effect is largest at the free-energy maximum. The positive line tension increases the free-energy maximum, which thus increases the stability of the Cassie superhydrophobic state, whereas the negative line tension destabilizes the superhydrophobic state.

Nucleus-size pinning for determination of nucleation free-energy barriers and nucleus geometry

NASA Astrophysics Data System (ADS)

Sharma, Abhishek K.; Escobedo, Fernando A.

2018-05-01

Classical Nucleation Theory (CNT) has recently been used in conjunction with a seeding approach to simulate nucleation phenomena at small-to-moderate supersaturation conditions when large free-energy barriers ensue. In this study, the conventional seeding approach [J. R. Espinosa et al., J. Chem. Phys. 144, 034501 (2016)] is improved by a novel, more robust method to estimate nucleation barriers. Inspired by the interfacial pinning approach [U. R. Pedersen, J. Chem. Phys. 139, 104102 (2013)] used before to determine conditions where two phases coexist, the seed of the incipient phase is pinned to a preselected size to iteratively drive the system toward the conditions where the seed becomes a critical nucleus. The proposed technique is first validated by estimating the critical nucleation conditions for the disorder-to-order transition in hard spheres and then applied to simulate and characterize the highly non-trivial (prolate) morphology of the critical crystal nucleus in hard gyrobifastigia. A generalization of CNT is used to account for nucleus asphericity and predict nucleation free-energy barriers for gyrobifastigia. These predictions of nuclei shape and barriers are validated by independent umbrella sampling calculations.

Barrier distributions and signatures of transfer channels in the Ca40+Ni58,64 fusion reactions at energies around and below the Coulomb barrier

NASA Astrophysics Data System (ADS)

Bourgin, D.; Courtin, S.; Haas, F.; Stefanini, A. M.; Montagnoli, G.; Goasduff, A.; Montanari, D.; Corradi, L.; Fioretto, E.; Huiming, J.; Scarlassara, F.; Rowley, N.; Szilner, S.; Mijatović, T.

2014-10-01

Background: The nuclear structure of colliding nuclei is known to influence the fusion process. Couplings of the relative motion to nuclear shape deformations and vibrations lead to an enhancement of the sub-barrier fusion cross section in comparison with the predictions of one-dimensional barrier penetration models. This enhancement is explained by coupled-channels calculations including these couplings. The sub-barrier fusion cross section is also affected by nucleon transfer channels between the colliding nuclei. Purpose: The aim of the present experiment is to investigate the influence of the projectile and target nuclear structures on the fusion cross sections in the Ca40+Ni58 and Ca40+Ni64 systems. Methods: The experimental and theoretical fusion excitation functions as well as the barrier distributions were compared for these two systems. Coupled-channels calculations were performed using the ccfull code. Results: Good agreement was found between the measured and calculated fusion cross sections for the Ca40+Ni58 system. The situation is different for the Ca40+Ni64 system where the coupled-channels calculations with no nucleon transfer clearly underestimate the fusion cross sections below the Coulomb barrier. The fusion excitation function was, however, well reproduced at low and high energies by including the coupling to the neutron pair-transfer channel in the calculations. Conclusions: The nuclear structure of the colliding nuclei influences the fusion cross sections below the Coulomb barrier for both Ca40+Ni58,64 systems. Moreover, we highlighted the effect of the neutron pair-transfer channel on the fusion cross sections in Ca40+Ni64.

Fusion enhancement at near and sub-barrier energies in 19O + 12C

DOE PAGES

Singh, Varinderjit; Vadas, J.; Steinbach, T. K.; ...

2016-12-12

Measuring the fusion excitation function for an isotopic chain of projectile nuclei provides a stringent test of a microscopic description of fusion. We report the first measurement of the fusion excitation function at near-barrier energies for the 19O+ 12C system. The measured excitation function is compared with the fusion excitation function of 18O+ 12C. A significant enhancement in the fusion probability of 19O ions with a 12C target as compared to 18O ions is observed. As a result, the experimental cross-sections observed at near-barrier energies are compared with a state-of-the-art microscopic model.

Free energy barrier for melittin reorientation from a membrane-bound state to a transmembrane state.

PubMed

Irudayam, Sheeba J; Pobandt, Tobias; Berkowitz, Max L

2013-10-31

An important step in a phospholipid membrane pore formation by melittin antimicrobial peptide is a reorientation of the peptide from a surface into a transmembrane conformation. Experiments measure the fraction of peptides in the surface state and the transmembrane state, but no computational study exists that quantifies the free energy curve for the reorientation. In this work we perform umbrella sampling simulations to calculate the potential of mean force (PMF) for the reorientation of melittin from a surface-bound state to a transmembrane state and provide a molecular level insight in understanding the peptide-lipid properties that influence the existence of the free energy barrier. The PMFs were calculated for a peptide to lipid (P/L) ratio of 1/128 and 4/128. We observe that the free energy barrier is reduced when the P/L ratio increases. In addition, we study the cooperative effect; specifically we investigate if the reorientation barrier is smaller for a second melittin, given that another neighboring melittin was already in the transmembrane orientation. We observe that indeed the barrier of the PMF curve is reduced in this case, thus confirming the presence of a cooperative effect.

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

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…

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.

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

Droplets on liquid surfaces: Dual equilibrium states and their energy barrier

NASA Astrophysics Data System (ADS)

Shabani, Roxana; Kumar, Ranganathan; Cho, Hyoung J.

2013-05-01

Floating aqueous droplets were formed at oil-air interface, and two stable configurations of (i) non-coalescent droplet and (ii) cap/bead droplet were observed. General solutions for energy and force analysis were obtained for both configurations and were shown to be in good agreement with the experimental observations. The energy barrier obtained for transition from configuration (i) to configuration (ii) was correlated to the droplet release height and the probability of non-coalescent droplet formation.

Role of codeposited impurities during growth. II. Dependence of morphology on binding and barrier energies

NASA Astrophysics Data System (ADS)

Sathiyanarayanan, Rajesh; Hamouda, Ajmi Bh.; Pimpinelli, A.; Einstein, T. L.

2011-01-01

In an accompanying article we showed that surface morphologies obtained through codeposition of a small quantity (2%) of impurities with Cu during growth (step-flow mode, θ = 40 ML) significantly depends on the lateral nearest-neighbor binding energy (ENN) to Cu adatom and the diffusion barrier (Ed) of the impurity atom on Cu(0 0 1). Based on these two energy parameters, ENN and Ed, we classify impurity atoms into four sets. We study island nucleation and growth in the presence of codeposited impurities from different sets in the submonolayer (θ⩽ 0.7 ML) regime. Similar to growth in the step-flow mode, we find different nucleation and growth behavior for impurities from different sets. We characterize these differences through variations of the number of islands (Ni) and the average island size with coverage (θ). Further, we compute the critical nucleus size (i) for all of these cases from the distribution of capture-zone areas using the generalized Wigner distribution.

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

PubMed

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

2016-03-08

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. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

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

PubMed Central

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

2016-01-01

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

Understanding the free energy barrier and multiple timescale dynamics of charge separation in organic photovoltaic cells.

PubMed

Yan, Yaming; Song, Linze; Shi, Qiang

2018-02-28

By employing several lattice model systems, we investigate the free energy barrier and real-time dynamics of charge separation in organic photovoltaic (OPV) cells. It is found that the combined effects of the external electric field, entropy, and charge delocalization reduce the free energy barrier significantly. The dynamic disorder reduces charge carrier delocalization and results in the increased charge separation barrier, while the effect of static disorder is more complicated. Simulation of the real-time dynamics indicates that the free charge generation process involves multiple time scales, including an ultrafast component within hundreds of femtoseconds, an intermediate component related to the relaxation of the hot charge transfer (CT) state, and a slow component on the time scale of tens of picoseconds from the thermally equilibrated CT state. Effects of hot exciton dissociation as well as its dependence on the energy offset between the Frenkel exciton and the CT state are also analyzed. The current results indicate that only a small energy offset between the band gap and the lowest energy CT state is needed to achieve efficient free charge generation in OPV devices, which agrees with recent experimental findings.

Understanding the free energy barrier and multiple timescale dynamics of charge separation in organic photovoltaic cells

NASA Astrophysics Data System (ADS)

Yan, Yaming; Song, Linze; Shi, Qiang

2018-02-01

By employing several lattice model systems, we investigate the free energy barrier and real-time dynamics of charge separation in organic photovoltaic (OPV) cells. It is found that the combined effects of the external electric field, entropy, and charge delocalization reduce the free energy barrier significantly. The dynamic disorder reduces charge carrier delocalization and results in the increased charge separation barrier, while the effect of static disorder is more complicated. Simulation of the real-time dynamics indicates that the free charge generation process involves multiple time scales, including an ultrafast component within hundreds of femtoseconds, an intermediate component related to the relaxation of the hot charge transfer (CT) state, and a slow component on the time scale of tens of picoseconds from the thermally equilibrated CT state. Effects of hot exciton dissociation as well as its dependence on the energy offset between the Frenkel exciton and the CT state are also analyzed. The current results indicate that only a small energy offset between the band gap and the lowest energy CT state is needed to achieve efficient free charge generation in OPV devices, which agrees with recent experimental findings.

Investigation of complete and incomplete fusion in the 7Li+124Sn reaction near Coulomb barrier energies

NASA Astrophysics Data System (ADS)

Parkar, V. V.; Sharma, Sushil K.; Palit, R.; Upadhyaya, S.; Shrivastava, A.; Pandit, S. K.; Mahata, K.; Jha, V.; Santra, S.; Ramachandran, K.; Nag, T. N.; Rath, P. K.; Kanagalekar, Bhushan; Trivedi, T.

2018-01-01

The complete and incomplete fusion cross sections for the 7Li+124Sn reaction were measured using online and offline characteristic γ -ray detection techniques. The complete fusion (CF) cross sections at energies above the Coulomb barrier were found to be suppressed by ˜26 % compared to the coupled channel calculations. This suppression observed in complete fusion cross sections is found to be commensurate with the measured total incomplete fusion (ICF) cross sections. There is a distinct feature observed in the ICF cross sections, i.e., t capture is found to be dominant compared to α capture at all the measured energies. A simultaneous explanation of complete, incomplete, and total fusion (TF) data was also obtained from the calculations based on the continuum discretized coupled channel method with short range imaginary potentials. The cross section ratios of CF/TF and ICF/TF obtained from the data as well as the calculations showed the dominance of ICF at below-barrier energies and CF at above-barrier energies.

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

Electrical characteristics and energy budget of dielectric barrier discharges in argon at atmospheric pressure

NASA Astrophysics Data System (ADS)

Becker, Markus M.; Hoder, Tomas; Loffhagen, Detlef

2014-10-01

Recently, an asymmetric dielectric barrier discharge ignited in atmospheric pressure argon in a single filament configuration has been analysed by experiments and modelling [1,2]. A special feature of the discharge under consideration is the occurrence of two different discharge modes at different amplitudes of the sinusoidal voltage supply. At voltages below the critical voltage of 2 kV ordinary filamentary discharges occur, while at higher voltages discharges with striated filaments emerge. In the present contribution the mode transition is investigated with respect to the electrical characteristics as well as the electron energy budget by means of numerical modelling. It is found that the mode transition caused by an increase of the voltage amplitude is accompanied by a non-linear change of the power density and a marked rise of the electron energy gain in chemo-ionization processes. This work was partly supported by the German Research Foundation within the Collaborative Research Centre Transregio 24.

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

PubMed

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

2016-06-28

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. 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. 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. 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.

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

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.

The Fusion of Membranes and Vesicles: Pathway and Energy Barriers from Dissipative Particle Dynamics

PubMed Central

Grafmüller, Andrea; Shillcock, Julian; Lipowsky, Reinhard

2009-01-01

The fusion of lipid bilayers is studied with dissipative particle dynamics simulations. First, to achieve control over membrane properties, the effects of individual simulation parameters are studied and optimized. Then, a large number of fusion events for a vesicle and a planar bilayer are simulated using the optimized parameter set. In the observed fusion pathway, configurations of individual lipids play an important role. Fusion starts with individual lipids assuming a splayed tail configuration with one tail inserted in each membrane. To determine the corresponding energy barrier, we measure the average work for interbilayer flips of a lipid tail, i.e., the average work to displace one lipid tail from one bilayer to the other. This energy barrier is found to depend strongly on a certain dissipative particle dynamics parameter, and, thus, can be adjusted in the simulations. Overall, three subprocesses have been identified in the fusion pathway. Their energy barriers are estimated to lie in the range 8–15 kBT. The fusion probability is found to possess a maximum at intermediate tension values. As one decreases the tension, the fusion probability seems to vanish before the tensionless membrane state is attained. This would imply that the tension has to exceed a certain threshold value to induce fusion. PMID:19348749

Theoretical studies of the transition state structures and free energy barriers for base-catalyzed hydrolysis of amides

PubMed Central

Xiong, Ying; Zhan, Chang-Guo

2010-01-01

The transition state structures and free energy barriers for the rate-determining step (i.e. the formation of a tetrahedral intermediate) of base-catalyzed hydrolysis of a series of amides in aqueous solution have been studied by performing first-principle electronic structure calculations using a hybrid supermolecule-polarizable continuum approach. The calculated results and a revisit of recently reported experimental proton inventory data reveal that the favorable transition state structure optimized for the tetrahedral intermediate formation of hydroxide ion-catalyzed hydrolysis of formamide may have three solvating water molecules remaining on the attacking hydroxide oxygen and two additional water molecules attached to the carbonyl oxygen of formamide. The calculated results have also demonstrated interesting substituent effects on the optimized transition state geometries, on the transition-state stabilization, and on the calculated free energy barriers for the base-catalyzed hydrolysis of amides. When some or all of the hydrogen atoms of formamide are replaced by methyl groups, the total number of water molecules hydrogen-bonding with the attacking hydroxide in the transition state decreases from three for formamide to two for N-methylacetamide, N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA). The larger substituents of the amide hinder the solvent water molecules approaching the attacking hydroxide oxygen in the transition state and, therefore, destabilize the transition state structure and increase the free energy barrier. By using the optimized most favorable transition state structures, the calculated free energy barriers, i.e. 21.6 (or 21.7), 22.7, 23.1, and 26.0 kcal/mol for formamide, N-methylacetamide, DMF, and DMA, respectively, are in good agreement with the available experimental free energy barriers, i.e. 21.2, 21.5, 22.6, and 24.1 kcal/mol for formamide, N-methylacetamide, DMF, and DMA, respectively. PMID:17107116

9Be+120Sn scattering at near-barrier energies within a four-body model

NASA Astrophysics Data System (ADS)

Arazi, A.; Casal, J.; Rodríguez-Gallardo, M.; Arias, J. M.; Lichtenthäler Filho, R.; Abriola, D.; Capurro, O. A.; Cardona, M. A.; Carnelli, P. F. F.; de Barbará, E.; Fernández Niello, J.; Figueira, J. M.; Fimiani, L.; Hojman, D.; Martí, G. V.; Martínez Heimman, D.; Pacheco, A. J.

2018-04-01

Cross sections for elastic and inelastic scattering of the weakly bound 9Be nucleus on a 120Sn target have been measured at seven bombarding energies around and above the Coulomb barrier. The elastic angular distributions are analyzed with a four-body continuum-discretized coupled-channels (CDCC) calculation, which considers 9Be as a three-body projectile (α +α +n ). An optical model analysis using the São Paulo potential is also shown for comparison. The CDCC analysis shows that the coupling to the continuum part of the spectrum is important for the agreement with experimental data even at energies around the Coulomb barrier, suggesting that breakup is an important process at low energies. At the highest incident energies, two inelastic peaks are observed at 1.19(5) and 2.41(5) MeV. Coupled-channels (CC) calculations using a rotational model confirm that the first inelastic peak corresponds to the excitation of the 21+ state in 120Sn, while the second one likely corresponds to the excitation of the 31- state.

Excited state free energy calculations of Cy3 in different environments

NASA Astrophysics Data System (ADS)

Sawangsang, Pilailuk; Buranachai, Chittanon; Punwong, Chutintorn

2015-05-01

Cy3, a cyanine dye, is one of the most widely used dyes in investigating the structure and dynamics of biomolecules by means of fluorescence methods. However, Cy3 fluorescence emission is strongly competed by trans-cis isomerization, whose efficiency is dictated by the isomerization energy barrier and the environment of Cy3. The fluorescence quantum yield of Cy3 is very low when the dye is free in homogeneous solution but it is considerably enhanced in an environment that rigidifies the structure, e.g. when it is attached to a DNA strand. In this work, the barriers for isomerization on the excited state of free Cy3, and Cy3 attached to single- and double-stranded DNA in methanol, are presented. The free energy and subsequently the isomerization barrier calculations are performed using the umbrella sampling technique with the weighted histogram analysis method. The hybrid quantum mechanics/molecular mechanics (QM/MM) approach is employed to provide the potential energy surfaces for the excited state dynamics simulations in umbrella sampling. The semiempirical floating occupation molecular orbital configuration interaction method is used for electronic excited state calculations of the QM region (Cy3). From the free energy calculations, the barrier of Cy3 attached to the single-stranded DNA is highest, in agreement with previously reported experimental results. This is likely due to the stacking interaction between Cy3 and DNA. Such a stacking interaction is likely associated with steric hindrance that prevents the rotation around the conjugated bonds of Cy3. If Cy3 experiences high steric hindrance, it has a higher isomerization barrier and thus the efficiency of fluorescence emission increases.

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

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

Yan, Pengxiu; Wang, Yuping; Li, Yida

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 +more » 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.« less

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

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

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 andmore » 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.« less

Simulation study of free-energy barriers in the wetting transition of an oily fluid on a rough surface with reentrant geometry.

PubMed

Savoy, Elizabeth S; Escobedo, Fernando A

2012-11-20

When in contact with a rough solid surface, fluids with low surface tension, such as oils and alkanes, have their lowest free energy in the fully wetted state. For applications where nonwetting by these phillic fluids is desired, some barrier must be introduced to maintain the nonwetted composite state. One way to create this free-energy barrier is to fabricate roughness with reentrant geometry, but the question remains as to whether the free-energy barrier is sufficiently high to prevent wetting. Our goal is to quantify the free-energy landscape for the wetting transition of an oily fluid on a surface of nails and identify significant surface features and conditions that maximize the wetting free-energy barrier (ΔGfwd*). This is a departure from most work on wetting, which focuses on the equilibrium composite and wetted states. We use boxed molecular dynamics (BXD) (Glowacki, D. R.; Paci, E.; Shalashilin, D. V. J. Phys. Chem. B2009, 113, 16603-16611) with a modified control scheme to evaluate both the thermodynamics and kinetics of the transition over a range of surface affinities (chemistry). We find that the reentrant geometry of the nails does create a free-energy barrier to transition for phillic chemistry whereas a corresponding system on straight posts wets spontaneously and, that doubling the nail height more than doubles ΔGfwd*. For neutral to phillic chemistry, the dewetting free-energy barrier is at least an order of magnitude higher than that for wetting, indicating an essentially irreversible wetting transition. Transition rates from BXD simulations and the associated trends agree well with those in our previous study that used forward flux sampling to compute transition rates for similar systems.

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

Sex Differences in Financial Barriers and the Relationship to Recovery After Acute Myocardial Infarction.

PubMed

Beckman, Adam L; Bucholz, Emily M; Zhang, Weiwei; Xu, Xiao; Dreyer, Rachel P; Strait, Kelly M; Spertus, John A; Krumholz, Harlan M; Spatz, Erica S

2016-10-14

Financial barriers to health care are associated with worse outcomes following acute myocardial infarction (AMI). Yet, it is unknown whether the prevalence of financial barriers and their relationship with post-AMI outcomes vary by sex among young adults. We assessed sex differences in patient-reported financial barriers among adults aged <55 years with AMI using data from the Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients study. We examined the prevalence of financial barriers and their association with health status 12 months post-AMI. Among 3437 patients, more women than men reported financial barriers to medications (22.3% vs 17.2%; P=0.001), but rates of financial barriers to services were similar (31.3% vs 28.9%; P=0.152). In multivariable linear regression models adjusting for baseline health, psychosocial status, and clinical characteristics, compared with no financial barriers, women and men with financial barriers to services and medications had worse mental functional status (Short Form-12 mental health score: mean difference [MD]=-3.28 and -3.35, respectively), greater depressive symptomatology (Patient Health Questionnaire-9: MD, 2.18 and 2.16), lower quality of life (Seattle Angina Questionnaire-Quality of Life: MD, -4.98 and -7.66), and higher perceived stress (Perceived Stress Score: MD, 3.76 and 3.90; all P<0.05). There was no interaction between sex and financial barriers. Financial barriers to care are common in young patients with AMI and associated with worse health outcomes 1 year post-AMI. Whereas women experienced more financial barriers than men, the association did not vary by sex. These findings emphasize the importance of addressing financial barriers to recovery post-AMI in young adults. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Polymer in a pore: Effect of confinement on the free energy barrier

NASA Astrophysics Data System (ADS)

Kumar, Sanjiv; Kumar, Sanjay

2018-06-01

We investigate the transfer of a polymer chain from cis- side to trans- side through two types of pores: cone-shaped channel and flat-channel. Using the exact enumeration technique, we obtain the free energy landscapes of a polymer chain for such systems. We have also calculated the free-energy barrier of a polymer chain attached to the edge of the pore. The model system allows us to calculate the force required to pull polymer from the pore and stall-force to confine polymer within the pore.

Barrier modification in sub-barrier fusion reaction 64Ni+100Mo using Wong formula with Skyrme forces in semiclassical formalism

NASA Astrophysics Data System (ADS)

Kumar, Raj; Gupta, Raj K.

2011-09-01

We obtain the nuclear proximity potential by using semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), and use it in the extended l-summed Wong formula under frozen density approximation. This method has the advantage of allowing the use of different Skyrme forces, giving different barriers. Thus, for a given reaction, we could choose a Skyrme force with proper barrier characteristics, not-requiring extra "barrier lowering" or "barrier narrowing" for a best fit to data. For the 64Ni+100Mo reaction, the l-summed Wong formula, with effects of deformations and orientations of nuclei included, fits the fusion-evaporation cross section data exactly for the force GSkI, requiring additional barrier modifications for forces SIII and SV. However, the same for other similar reactions, like 58,64Ni+58,64Ni, fit the data best for SIII force. Hence, the barrier modification effects in l-summed Wong expression depend on the choice of Skyrme force in semiclassical ETF method.

Calculation and visualization of free energy barriers for several VOCs and TNT in HKUST-1.

PubMed

Sarkisov, Lev

2012-11-28

A simple protocol based on a lattice representation of the porous space is proposed to locate and characterize the free energy bottle-necks in rigid metal organic frameworks. As an illustration we apply this method to HKUST-1 to demonstrate that there are impassable free energy barriers for molecules of trinitrotoluene in this structure.

Oscillations above the barrier in the fusion of 28Si + 28Si

DOE PAGES

Montagnoli, G.; Stefanini, A.M.; Esbensen, H.; ...

2015-05-13

Fusion cross sections of 28Si+ 28Si have been measured in a range above the barrier with a very small energy step (Delta E lab=0.5 MeV). Regular oscillations have been observed, best evidenced in the first derivative of the energy-weighted excitation function. For the first time, quite different behaviors (the appearance of oscillations and the trend of sub-barrier cross sections) have been reproduced within the same theoretical frame, i.e., the coupled-channel model using the shallow M3Y+repulsion potential. The calculations suggest that channel couplings play an important role in the appearance of the oscillations, and that the simple relation between a peakmore » in the derivative of the energy-weighted cross section and the height of a centrifugal barrier is lost, and so is the interpretation of the second derivative of the excitation function as a barrier distribution for this system, at energies above the Coulomb barrier.« less

Free energy barrier for molecular motions in bistable [2]rotaxane molecular electronic devices.

PubMed

Kim, Hyungjun; Goddard, William A; Jang, Seung Soon; Dichtel, William R; Heath, James R; Stoddart, J Fraser

2009-03-12

Donor-acceptor binding of the pi-electron-poor cyclophane cyclobis(paraquat-p-phenylene) (CBPQT(4+)) with the pi-electron-rich tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) stations provides the basis for electrochemically switchable, bistable [2]rotaxanes, which have been incorporated and operated within solid-state devices to form ultradense memory circuits (ChemPhysChem 2002, 3, 519-525; Nature 2007, 445, 414-417) and nanoelectromechanical systems. The rate of CBPQT(4+) shuttling at each oxidation state of the [2]rotaxane dictates critical write-and-retention time parameters within the devices, which can be tuned through chemical synthesis. To validate how well computational chemistry methods can estimate these rates for use in designing new devices, we used molecular dynamics simulations to calculate the free energy barrier for the shuttling of the CBPQT(4+) ring between the TTF and the DNP. The approach used here was to calculate the potential of mean force along the switching pathway, from which we calculated free energy barriers. These calculations find a turn-on time after the rotaxane is doubly oxidized of approximately 10(-7) s (suggesting that the much longer experimental turn-on time is determined by the time scale of oxidization). The return barrier from the DNP to the TTF leads to a predicted lifetime of 2.1 s, which is compatible with experiments.

Low Li+ Insertion Barrier Carbon for High Energy Efficient Lithium-Ion Capacitor.

PubMed

Lee, Wee Siang Vincent; Huang, Xiaolei; Tan, Teck Leong; Xue, Jun Min

2018-01-17

Lithium-ion capacitor (LIC) is an attractive energy-storage device (ESD) that promises high energy density at moderate power density. However, the key challenge in its design is the low energy efficient negative electrode, which barred the realization of such research system in fulfilling the current ESD technological inadequacy due to its poor overall energy efficiency. Large voltage hysteresis is the main issue behind high energy density alloying/conversion-type materials, which reduces the electrode energy efficiency. Insertion-type material though averted in most research due to the low capacity remains to be highly favorable in commercial application due to its lower voltage hysteresis. To further reduce voltage hysteresis and increase capacity, amorphous carbon with wider interlayer spacing has been demonstrated in the simulation result to significantly reduce Li + insertion barrier. Hence, by employing such amorphous carbon, together with disordered carbon positive electrode, a high energy efficient LIC with round-trip energy efficiency of 84.3% with a maximum energy density of 133 Wh kg -1 at low power density of 210 W kg -1 can be achieved.

Electronic Devices with Strontium Barrier Film and Process for Making Same

DTIC Science & Technology

1998-08-20

structure of the barrier film on an atomic level where the barrier film is comprised of a plurality of contiguous monolayers, while FIG. 7B shows another...another embodiment where the barrier film is comprised of a plurality of contiguous monolayers in which different monolayers thereof are formed of...High Energy Electron 10 Diffraction (RHEED) diagnostic system directed toward the substrate 26. A diffusion barrier precursor compound effusion

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

Energy barriers and rates of tautomeric transitions in DNA bases: ab initio quantum chemical study.

PubMed

Basu, Soumalee; Majumdar, Rabi; Das, Gourab K; Bhattacharyya, Dhananjay

2005-12-01

Tautomeric transitions of DNA bases are proton transfer reactions, which are important in biology. These reactions are involved in spontaneous point mutations of the genetic material. In the present study, intrinsic reaction coordinates (IRC) analyses through ab initio quantum chemical calculations have been carried out for the individual DNA bases A, T, G, C and also A:T and G:C base pairs to estimate the kinetic and thermodynamic barriers using MP2/6-31G** method for tautomeric transitions. Relatively higher values of kinetic barriers (about 50-60 kcal/mol) have been observed for the single bases, indicating that tautomeric alterations of isolated single bases are quite unlikely. On the other hand, relatively lower values of the kinetic barriers (about 20-25 kcal/mol) for the DNA base pairs A:T and G:C clearly suggest that the tautomeric shifts are much more favorable in DNA base pairs than in isolated single bases. The unusual base pairing A':C, T':G, C':A or G':T in the daughter DNA molecule, resulting from a parent DNA molecule with tautomeric shifts, is found to be stable enough to result in a mutation. The transition rate constants for the single DNA bases in addition to the base pairs are also calculated by computing the free energy differences between the transition states and the reactants.

Overcoming free energy barriers using unconstrained molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Hénin, Jérôme; Chipot, Christophe

2004-08-01

Association of unconstrained molecular dynamics (MD) and the formalisms of thermodynamic integration and average force [Darve and Pohorille, J. Chem. Phys. 115, 9169 (2001)] have been employed to determine potentials of mean force. When implemented in a general MD code, the additional computational effort, compared to other standard, unconstrained simulations, is marginal. The force acting along a chosen reaction coordinate ξ is estimated from the individual forces exerted on the chemical system and accumulated as the simulation progresses. The estimated free energy derivative computed for small intervals of ξ is canceled by an adaptive bias to overcome the barriers of the free energy landscape. Evolution of the system along the reaction coordinate is, thus, limited by its sole self-diffusion properties. The illustrative examples of the reversible unfolding of deca-L-alanine, the association of acetate and guanidinium ions in water, the dimerization of methane in water, and its transfer across the water liquid-vapor interface are examined to probe the efficiency of the method.

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.

Differences in psychiatric symptoms and barriers to mental health care between volunteer and career firefighters.

PubMed

Stanley, Ian H; Boffa, Joseph W; Hom, Melanie A; Kimbrel, Nathan A; Joiner, Thomas E

2017-01-01

Firefighters are at increased risk for mental health problems. However, little is known about differences in psychiatric symptoms between volunteer and career firefighters. This study aimed to (1) describe differences in psychiatric symptoms and barriers to mental health care between U.S. firefighters in volunteer-only and career-only departments; and (2) determine if greater self-reported structural barriers to mental health care (e.g., cost, availability of resources) explain the differences in psychiatric symptom levels. Overall, 525 current U.S. firefighters participated. Analyses of covariance and logistic regression analyses were used to evaluate group differences between volunteer (n=204) and career (n=321) firefighters, adjusting for demographic and occupational characteristics. Volunteer firefighters reported significantly elevated levels of depression, posttraumatic stress, and suicidal symptoms compared to career firefighters. Career firefighters reported relatively elevated levels of problematic alcohol use. Volunteer firefighters additionally reported greater structural barriers to mental health care (e.g., cost, availability of resources), and these barriers accounted for the differences in mental health variables between volunteer and career firefighters. Findings suggest that volunteer firefighters report elevated psychiatric symptoms compared to career firefighters and greater structural barriers to mental health treatment may explain this link. Increased efforts are needed to develop firefighter-specific interventions and bolster mental health service utilization. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Electronic Devices with Composite Atomic Barrier Film and Process for Making Same

DTIC Science & Technology

1998-08-20

structure of the barrier film on an atomic level where the barrier film is comprised of a plurality of contiguous monolayers, while FIG. 7B shows...another embodiment where the barrier film is comprised of a plurality of contiguous monolayers in which different monolayers thereof are formed of...High Energy Electron 10 Diffraction (RHEED) diagnostic system directed toward the substrate 26. A diffusion barrier precursor compound effusion

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

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

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 andmore » 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.« less

Sensitivity of the nuclear deformability and fission barriers to the equation of state

NASA Astrophysics Data System (ADS)

Seif, W. M.; Anwer, Hisham

2018-07-01

The model-dependent analysis of the fission data impacts the extracted fission-related quantities, which are not directly observables, such as the super- and hyperdeformed isomeric states and their energies. We investigated the model dependence of the deformability of a nucleus and its fission barriers on the nuclear equation of state. Within the microscopic-macroscopic model based on a large number of Skyrme nucleon-nucleon interactions, the total energy surfaces and the double-humped fission barrier of 230Th are calculated in a multidimensional deformation space. In addition to the ground-state (GS) and the superdeformed (SD) minima, all the investigated forces yielded a hyperdeformed (HD) minimum. The contour map of the shell-plus-pairing energy clearly displayed the three minima. We found that the GS binding energy and the deformation energy of the different deformation modes along the fission path increase with the incompressibility coefficient K0, while the fission barrier heights and the excitation energies of the SD and HD modes decrease with it. Conversely, the surface-energy coefficient asurf, the symmetry-energy, and its density-slope parameter decrease the GS energy and the deformation energies, but increase the fission barrier heights and the excitation energies. The obtained deformation parameters of the different deformation modes exhibit almost independence on K0, and on the symmetry-energy and its density-slope. The principle deformation parameters of the SD and HD isomeric states tend to decrease with asurf.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Barrier-discharge-excited coaxial excilamps with the enhanced pulse energy

NASA Astrophysics Data System (ADS)

Panchenko, A. N.; Tarasenko, V. F.

2008-01-01

The parameters of sealed off barrier excilamps are studied at high excitation powers. The total output pulse energy up to 25 mJ is achieved (the emitting area of a KrCl excilamp was up to 1500 cm2, the output power was above 100 kW, and the efficiency achieved 10%). It is shown that a volume discharge was formed in the coaxial excilamp when the energy supplied to the working mixture was increased and the pulse repetition rate was increased up to 50 Hz. The peak radiation intensity on the excilamp surface achieved ~100 W cm-2. The optimal excitation energy of a barrier excilamp was found to be 0.1-0.2 mJ cm-3. The excilamp efficiency rapidly decreases with further increasing the input energy.

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…

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.

Conductance and refraction across a Barrier in Phosphorene

NASA Astrophysics Data System (ADS)

Dahal, Dipendra; Gumbs, Godfrey

The transmission coefficient and ballistic conductance for monolayer black phosphorene is calculated when a potential step or square barrier is present. The Landauer-B¨uttiker formalism is employed in our calculations of the conductance. We obtain the refractive index for the step potential barrier when an incident beam of electron travel along different paths so as to observe what role the anisotropy of the energy bands plays. Numerical results are presented for various potential heights and barrier widths and these are compared with those for gapless and gapped graphene.

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.

Role of wave packet width in quantum molecular dynamics in fusion reactions near barrier

NASA Astrophysics Data System (ADS)

Cao, X. G.; Ma, Y. G.; Zhang, G. Q.; Wang, H. W.; Anastasi, A.; Curciarello, F.; De Leo, V.

2014-05-01

The dynamical fusion process of 48Ca + 144Sm with different impact parameters near barrier is studied by an extended quantum molecular dynamics (EQMD) model, where width of wavepacket is dynamically treated based on variational principle. The time evolution of different energy components such as potential energy, kinetic energy, Coulomb energy and Pauli potential are analyzed when dynamical or fixed width is assumed in calculation. It is found that the dynamical wavepacket width can enhance the dissipation of incident energy and the fluctuations, which are important to form compound nuclei. Moreover, we compare the fusion barrier dependence on the incident energy when it is determined by both dynamical and fixed wavepacket width.

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.

US-China Clean Energy Research Center on Building Energy Efficiency: Materials that Improve the Cost-Effectiveness of Air Barrier Systems

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

Hun, Diana E.

The US–China Clean Energy Research Center (CERC) was launched in 2009 by US Energy Secretary Steven Chu, Chinese Minister of Science and Technology Wan Gang, and Chinese National Energy Agency Administrator Zhang Guobao. This 5-year collaboration emerged from the fact that the United States and China are the world’s largest energy producers, energy consumers, and greenhouse gas emitters, and that their joint effort could have significant positive repercussions worldwide. CERC’s main goal is to develop and deploy clean energy technologies that will help both countries meet energy and climate challenges. Three consortia were established to address the most pressing energy-relatedmore » research areas: Advanced Coal Technology, Clean Vehicles, and Building Energy Efficiency (BEE). The project discussed in this report was part of the CERC-BEE consortia; its objective was to lower energy use in buildings by developing and evaluating technologies that improve the cost-effectiveness of air barrier systems for building envelopes.« less

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

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

Fujita, K. Sydny

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 socialmore » 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

Simulations of skin barrier function: free energies of hydrophobic and hydrophilic transmembrane pores in ceramide bilayers.

PubMed

Notman, Rebecca; Anwar, Jamshed; Briels, W J; Noro, Massimo G; den Otter, Wouter K

2008-11-15

Transmembrane pore formation is central to many biological processes such as ion transport, cell fusion, and viral infection. Furthermore, pore formation in the ceramide bilayers of the stratum corneum may be an important mechanism by which penetration enhancers such as dimethylsulfoxide (DMSO) weaken the barrier function of the skin. We have used the potential of mean constraint force (PMCF) method to calculate the free energy of pore formation in ceramide bilayers in both the innate gel phase and in the DMSO-induced fluidized state. Our simulations show that the fluid phase bilayers form archetypal water-filled hydrophilic pores similar to those observed in phospholipid bilayers. In contrast, the rigid gel-phase bilayers develop hydrophobic pores. At the relatively small pore diameters studied here, the hydrophobic pores are empty rather than filled with bulk water, suggesting that they do not compromise the barrier function of ceramide membranes. A phenomenological analysis suggests that these vapor pores are stable, below a critical radius, because the penalty of creating water-vapor and tail-vapor interfaces is lower than that of directly exposing the strongly hydrophobic tails to water. The PMCF free energy profile of the vapor pore supports this analysis. The simulations indicate that high DMSO concentrations drastically impair the barrier function of the skin by strongly reducing the free energy required for pore opening.

Simulations of Skin Barrier Function: Free Energies of Hydrophobic and Hydrophilic Transmembrane Pores in Ceramide Bilayers

PubMed Central

Notman, Rebecca; Anwar, Jamshed; Briels, W. J.; Noro, Massimo G.; den Otter, Wouter K.

2008-01-01

Transmembrane pore formation is central to many biological processes such as ion transport, cell fusion, and viral infection. Furthermore, pore formation in the ceramide bilayers of the stratum corneum may be an important mechanism by which penetration enhancers such as dimethylsulfoxide (DMSO) weaken the barrier function of the skin. We have used the potential of mean constraint force (PMCF) method to calculate the free energy of pore formation in ceramide bilayers in both the innate gel phase and in the DMSO-induced fluidized state. Our simulations show that the fluid phase bilayers form archetypal water-filled hydrophilic pores similar to those observed in phospholipid bilayers. In contrast, the rigid gel-phase bilayers develop hydrophobic pores. At the relatively small pore diameters studied here, the hydrophobic pores are empty rather than filled with bulk water, suggesting that they do not compromise the barrier function of ceramide membranes. A phenomenological analysis suggests that these vapor pores are stable, below a critical radius, because the penalty of creating water-vapor and tail-vapor interfaces is lower than that of directly exposing the strongly hydrophobic tails to water. The PMCF free energy profile of the vapor pore supports this analysis. The simulations indicate that high DMSO concentrations drastically impair the barrier function of the skin by strongly reducing the free energy required for pore opening. PMID:18708461

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.

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

Overcoming free energy barriers using unconstrained molecular dynamics simulations.

PubMed

Hénin, Jérôme; Chipot, Christophe

2004-08-15

Association of unconstrained molecular dynamics (MD) and the formalisms of thermodynamic integration and average force [Darve and Pohorille, J. Chem. Phys. 115, 9169 (2001)] have been employed to determine potentials of mean force. When implemented in a general MD code, the additional computational effort, compared to other standard, unconstrained simulations, is marginal. The force acting along a chosen reaction coordinate xi is estimated from the individual forces exerted on the chemical system and accumulated as the simulation progresses. The estimated free energy derivative computed for small intervals of xi is canceled by an adaptive bias to overcome the barriers of the free energy landscape. Evolution of the system along the reaction coordinate is, thus, limited by its sole self-diffusion properties. The illustrative examples of the reversible unfolding of deca-L-alanine, the association of acetate and guanidinium ions in water, the dimerization of methane in water, and its transfer across the water liquid-vapor interface are examined to probe the efficiency of the method. (c) 2004 American Institute of Physics.

Calculation of multidimensional potential energy surfaces for even-even transuranium nuclei: systematic investigation of the triaxiality effect on the fission barrier

NASA Astrophysics Data System (ADS)

Chai, Qing-Zhen; Zhao, Wei-Juan; Liu, Min-Liang; Wang, Hua-Lei

2018-05-01

Static fission barriers for 95 even-even transuranium nuclei with charge number Z = 94–118 have been systematically investigated by means of pairing self-consistent Woods-Saxon-Strutinsky calculations using the potential energy surface approach in multidimensional (β 2, γ, β 4) deformation space. Taking the heavier 252Cf nucleus (with the available fission barrier from experiment) as an example, the formation of the fission barrier and the influence of macroscopic, shell and pairing correction energies on it are analyzed. The results of the present calculated β 2 values and barrier heights are compared with previous calculations and available experiments. The role of triaxiality in the region of the first saddle is discussed. It is found that the second fission barrier is also considerably affected by the triaxial deformation degree of freedom in some nuclei (e.g., the Z=112–118 isotopes). Based on the potential energy curves, general trends of the evolution of the fission barrier heights and widths as a function of the nucleon numbers are investigated. In addition, the effects of Woods-Saxon potential parameter modifications (e.g., the strength of the spin-orbit coupling and the nuclear surface diffuseness) on the fission barrier are briefly discussed. Supported by National Natural Science Foundation of China (11675148, 11505157), the Project of Youth Backbone Teachers of Colleges and Universities of Henan Province (2017GGJS008), the Foundation and Advanced Technology Research Program of Henan Province (162300410222), the Outstanding Young Talent Research Fund of Zhengzhou University (1521317002) and the Physics Research and Development Program of Zhengzhou University (32410017)

Role of tunnelling in complete and incomplete fusion induced by 9Be on 169Tm and 187Re targets at around barrier energies

NASA Astrophysics Data System (ADS)

Kharab, Rajesh; Chahal, Rajiv; Kumar, Rajiv

2017-04-01

We have analyzed the complete and incomplete fusion excitation function for 9Be +169Tm, 187Re reactions at around barrier energies using the code PLATYPUS based on classical dynamical model. The quantum mechanical tunnelling correction is incorporated at near and sub barrier energies which significantly improves the matching between the data and prediction.

Corneal critical barrier against the penetration of dexamethasone and lomefloxacin hydrochloride: evaluation by the activation energy for drug partition and diffusion in cornea.

PubMed

Yasueda, Shin-ichi; Higashiyama, Masayo; Yamaguchi, Masazumi; Isowaki, Akiharu; Ohtori, Akira

2007-08-01

The cornea is a solid barrier against drug permeation. We searched the critical barrier of corneal drug permeation using a hydrophobic drug, dexamethasone (DM), and a hydrophilic drug, lomefloxacin hydrochloride (LFLX). The activation energies for permeability of DM and LFLX across the intact cornea were 88.0 and 42.1 kJ/mol, respectively. Their activation energies for permeability across the cornea without epithelium decreased to 33.1 and 16.6 kJ/mol, respectively. The results show that epithelium is the critical barrier on the cornea against the permeation of a hydrophobic drug of DM as well as a hydrophilic drug of LFLX. The activation energy of partition for DM (66.8 kJ/mol) was approximately 3-fold larger than that of diffusion (21.2 kJ/mol). The results indicate that the partition for the hydrophobic drug of DM to the corneal epithelium is the primary barrier. Thermodynamic evaluation of activation energy for the drug permeation parameters is a good approach to investigate the mechanism of drug permeability.

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

Enhancing the effective energy barrier of a Dy(III) SMM using a bridged diamagnetic Zn(II) ion.

PubMed

Upadhyay, Apoorva; Singh, Saurabh Kumar; Das, Chinmoy; Mondol, Ranajit; Langley, Stuart K; Murray, Keith S; Rajaraman, Gopalan; Shanmugam, Maheswaran

2014-08-18

Field induced single-molecule-magnet behaviour is observed for both a heterodinuclear [ZnDy(L(-))2](3+) complex (1) and a mononuclear [Dy(HL)2](3+) complex (2), with effective energy barriers of 83 cm(-1) and 16 cm(-1), respectively. Insights into the relaxation mechanism(s) and barrier heights are provided via ab initio and DFT calculations. Our findings reveal an interesting observation that the U(eff) of SMMs can be enhanced by incorporating diamagnetic metal ions.

Sex differences in NSAID-induced perturbation of human intestinal barrier function and microbiota.

PubMed

Edogawa, Shoko; Peters, Stephanie A; Jenkins, Gregory D; Gurunathan, Sakteesh V; Sundt, Wendy J; Johnson, Stephen; Lennon, Ryan J; Dyer, Roy B; Camilleri, Michael; Kashyap, Purna C; Farrugia, Gianrico; Chen, Jun; Singh, Ravinder J; Grover, Madhusudan

2018-06-13

Intestinal barrier function and microbiota are integrally related and play critical roles in maintenance of host physiology. Sex is a key biologic variable for several disorders. Our aim was to determine sex-based differences in response to perturbation and subsequent recovery of intestinal barrier function and microbiota in healthy humans. Twenty-three volunteers underwent duodenal biopsies, mucosal impedance, and in vivo permeability measurement. Permeability testing was repeated after administration of indomethacin, then 4 to 6 wk after its discontinuation. Duodenal and fecal microbiota composition was determined using 16S rRNA amplicon sequencing. Healthy women had lower intestinal permeability and higher duodenal and fecal microbial diversity than healthy men. Intestinal permeability increases after indomethacin administration in both sexes. However, only women demonstrated decreased fecal microbial diversity, including an increase in Prevotella abundance, after indomethacin administration. Duodenal microbiota composition did not show sex-specific changes. The increase in permeability and microbiota changes normalized after discontinuation of indomethacin. In summary, women have lower intestinal permeability and higher microbial diversity. Intestinal permeability is sensitive to perturbation but recovers to baseline. Gut microbiota in women is sensitive to perturbation but appears to be more stable in men. Sex-based differences in intestinal barrier function and microbiome should be considered in future studies.-Edogawa, S., Peters, S. A., Jenkins, G. D., Gurunathan, S. V., Sundt, W. J., Johnson, S., Lennon, R. J., Dyer, R. B., Camilleri, M., Kashyap, P. C., Farrugia, G., Chen, J., Singh, R. J., Grover, M. Sex differences in NSAID-induced perturbation of human intestinal barrier function and microbiota.

The GEOFAR Project - Geothermal Finance and Awareness in Europeans Regions - Development of new schemes to overcome non-technical barriers, focusing particularly on financial barriers

NASA Astrophysics Data System (ADS)

Poux, Adeline; Wendel, Marco; Jaudin, Florence; Hiegl, Mathias

2010-05-01

Numerous advantages of geothermal energy like its widespread distribution, a base-load power and availability higher than 90%, a small footprint and low carbon emissions, and the growing concerns about climate changes strongly promote the development of geothermal projects. Geothermal energy as a local energy source implies needs on surface to be located close to the geothermal resource. Many European regions dispose of a good geothermal potential but it is mostly not sufficiently developed due to non-technical barriers occurring at the very early stages of the project. The GEOFAR Project carried out within the framework of EU's "Intelligent Energy Europe" (IEE) program, gathers a consortium of European partners from Germany, France, Greece, Spain and Portugal. Launched in September 2008, the aim of this research project is to analyze the mentioned non-technical barriers, focusing most particularly on economic and financial aspects. Based on this analysis GEOFAR aims at developing new financial and administrative schemes to overcome the main financial barriers for deep geothermal projects (for electricity and direct use, without heat pumps). The analysis of the current situation and the future development of geothermal energy in GEOFAR target countries (Germany, France, Greece, Spain, Portugal, Slovakia, Bulgaria and Hungary) was necessary to understand and expose the diverging status of the geothermal sector and the more and less complicated situation for geothermal projects in different Europeans Regions. A deeper analysis of 40 cases studies (operating, planned and failed projects) of deep geothermal projects also contributed to this detailed view. An exhaustive analysis and description of financial mechanisms already existing in different European countries and at European level to support investors completed the research on non-technical barriers. Based on this profound analysis, the GEOFAR project has made an overview of the difficulties met by project

Temperature dependence of the distribution of the thermally activated energy barriers in Tl2Ba2CaCu2O8 film

NASA Astrophysics Data System (ADS)

Ren, C.; Lin, F. Y.; Ding, S. Y.; Li, Z. M.; Aruna, S. A.; Qiu, L.; Yao, X. X.; Yan, S. L.; Si, M. S.

1999-06-01

The effects of frequency and ac amplitude on ac susceptibility have been measured for a thin Tl2Ba2CaCu2O8 film in the range 100 Hz-100 kHz in magnetic field 0.52 T. A phenomenological equation with an asymmetrical distribution of thermally activated energy barriers has been used to analyse these frequency and amplitude dependences of the ac susceptibility icons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/>(icons/Journals/Common/omega" ALT="omega" ALIGN="TOP"/>,hac) in the vicinity of the peak temperature of icons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/>´´. We obtain the effective energy barrier U against amplitude hac (current density j): Uicons/Journals/Common/propto" ALT="propto" ALIGN="TOP"/> hac-0.38. This U(j) relationship shows that the flux lines are in the 3D collective creep regime. Therefore, we conclude that the effective energy barrier is in fact an average of the barrier's distribution, and the distribution function is a distinguished asymmetrical one in this 3D collective creep regime.

Barriers associated with frequency of leisure-time physical activity among Brazilian adults of different income strata.

PubMed

Silva, K S; Del Duca, G F; Garcia, L M T; da Silva, J A; Bertuol, C; de Oliveira, E S A; de Barros, M V G; Nahas, M V

2016-02-01

This study aimed to estimate the prevalence of the main perceived barriers to leisure-time physical activity (LTPA) and their associations with the frequency of LTPA in a representative sample of industrial workers from Brazil (n = 47,477), according to their income strata (low income: ≤$US280, middle income: $US281-$US1400, and high income: ≥$US1401). Data were collected between 2006 and 2008 via questionnaires about the main perceived barrier to LTPA and the frequency of LTPA. Multinomial logistic regression was performed to evaluate differences among groups. There was a lower prevalence of regular practice of LTPA in the low- (15.8%) and middle-income strata (18.2%) than among the individuals of the high-income stratum (27.6%). A large proportion of workers who regularly participated in LTPA reported no barriers (low: 43.1%; middle: 46.8%; high: 51.6%). Additional obligations and fatigue were the two most common perceived barriers in all family income strata among participants who engaged in different frequencies of LTPA. The odds for all perceived barriers showed a positive trend related to frequency of LTPA (from regular to no LTPA), with higher values according to income. In summary, the ordering of the main perceived barriers to LTPA differed according to workers' income stratum and frequency of engaging in LTPA. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

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.

Electronic transport in armchair graphene nanoribbon under double magnetic barrier modulation

NASA Astrophysics Data System (ADS)

Wang, Haiyan; Wu, Chao; Xie, Fang; Zhang, Xiaojiao; Zhou, Guanghui

2018-03-01

We present a theoretical investigation of the transport properties and the magnetoresistance effect in armchair graphene nanoribbons (AGNRs) under modulation by two magnetic barriers. The energy levels are found to be degenerate for a metallic AGNR but are not degenerate for a semiconducting AGNR. However, the conductance characteristics show quantized plateaus in both the metallic and semiconducting cases. When the magnetization directions of the barriers change from parallel to antiparallel, the conductance plateau in the metallic AGNR shows a degenerate feature due to matching between the transport modes in different regions. As the barrier height increases, the conductance shows more oscillatory behavior with sharp peaks and troughs. Specifically, the initial position of nonzero conductance for the metallic AGNR system moves towards a higher energy regime, which indicates that an energy gap has been opened. In addition, the magnetoresistance ratio also shows plateau structures in certain specific energy regions. These results may be useful in the design of electron devices based on AGNR nanostructures.

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.

Identifying Barriers and Pathways to Success for Renewable Energy Development on American Indian Lands

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

Necefer, Len Edward; Jones, Thomas Elisha

American Indian tribes possess lands rich with renewable energy (RE) resources. Tribes have great potential and need to develop these resources, yet face a host of barriers that continue to impede development. Understanding these challenges as well as the pathways that can be taken to overcome them may facilitate more economic development to meet community needs and better position tribes to play a role in securing a low-carbon energy future for the United States. This paper presents the results of an expert elicitation of 24 tribal energy experts from federal, tribal, academic, and private industry backgrounds to identify barriers andmore » opportunities for federally recognized tribes in the lower 48 states. Experts identified a number of unique challenges facing tribes including financing and funding, infrastructure, tribal leadership and staff, state-level influence, and partnerships. Cultural factors were seen only to be of concern with large-scale development. Tribal sovereignty is a significant motivation for RE development and has yet to be fully realized. Cultural considerations are critical to the success of future projects; smaller residential and community-scale projects may be a better fit. Improving partnerships between tribes and the private sector can increase RE deployment and overcome historical distrust. States can have a double-ended influence on projects within tribal lands through taxation.« less

Rethinking barriers: a novel conceptualization of exercise barriers in cancer survivors.

PubMed

Lee, Morgan S; Small, Brent J; Jacobsen, Paul B

2017-12-01

Previous research suggests different types of barriers may demonstrate different relationships with intention to engage in health behaviors. This study explored global, practical, and health-related barriers' relationships with exercise intention and behavior among cancer survivors. The mediating role of intention in the barriers-behavior relationships was also evaluated. Cancer survivors (N = 152) completed self-report measures of exercise barriers, intention, and behavior at baseline and of exercise behavior two months later. Global barriers were negatively related (p < .01) and practical and health-related barriers were unrelated (ps ≥ .07) to exercise intention. Global and practical barriers were negatively related (ps < .01) and health-related barriers were unrelated (p = .48) to subsequent exercise behavior. Exercise intention did not mediate any barriers-behavior relationships. Results suggest that global and practical barriers should be targeted in barriers reduction interventions and highlight the intention-behavior gap problem. Future research should explore multidimensionality of barriers for other health behaviors.

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.

Nested barriers to low-carbon infrastructure investment

NASA Astrophysics Data System (ADS)

Granoff, Ilmi; Hogarth, J. Ryan; Miller, Alan

2016-12-01

Low-carbon, 'green' economic growth is necessary to simultaneously improve human welfare and avoid the worst impacts of climate change and environmental degradation. Infrastructure choices underpin both the growth and the carbon intensity of the economy. This Perspective explores the barriers to investing in low-carbon infrastructure and some of the policy levers available to overcome them. The barriers to decarbonizing infrastructure 'nest' within a set of barriers to infrastructure development more generally that cause spending on infrastructure--low-carbon or not--to fall more than 70% short of optimal levels. Developing countries face additional barriers such as currency and political risks that increase the investment gap. Low-carbon alternatives face further barriers, such as commercialization risk and financial and public institutions designed for different investment needs. While the broader barriers to infrastructure investment are discussed in other streams of literature, they are often disregarded in literature on renewable energy diffusion or climate finance, which tends to focus narrowly on the project costs of low- versus high-carbon options. We discuss how to overcome the barriers specific to low-carbon infrastructure within the context of the broader infrastructure gap.

Rupturing the hemi-fission intermediate in membrane fission under tension: Reaction coordinates, kinetic pathways, and free-energy barriers

NASA Astrophysics Data System (ADS)

Zhang, Guojie; Müller, Marcus

2017-08-01

Membrane fission is a fundamental process in cells, involved inter alia in endocytosis, intracellular trafficking, and virus infection. Its underlying molecular mechanism, however, is only incompletely understood. Recently, experiments and computer simulation studies have revealed that dynamin-mediated membrane fission is a two-step process that proceeds via a metastable hemi-fission intermediate (or wormlike micelle) formed by dynamin's constriction. Importantly, this hemi-fission intermediate is remarkably metastable, i.e., its subsequent rupture that completes the fission process does not occur spontaneously but requires additional, external effects, e.g., dynamin's (unknown) conformational changes or membrane tension. Using simulations of a coarse-grained, implicit-solvent model of lipid membranes, we investigate the molecular mechanism of rupturing the hemi-fission intermediate, such as its pathway, the concomitant transition states, and barriers, as well as the role of membrane tension. The membrane tension is controlled by the chemical potential of the lipids, and the free-energy landscape as a function of two reaction coordinates is obtained by grand canonical Wang-Landau sampling. Our results show that, in the course of rupturing, the hemi-fission intermediate undergoes a "thinning → local pinching → rupture/fission" pathway, with a bottle-neck-shaped cylindrical micelle as a transition state. Although an increase of membrane tension facilitates the fission process by reducing the corresponding free-energy barrier, for biologically relevant tensions, the free-energy barriers still significantly exceed the thermal energy scale kBT.

Rupturing the hemi-fission intermediate in membrane fission under tension: Reaction coordinates, kinetic pathways, and free-energy barriers.

PubMed

Zhang, Guojie; Müller, Marcus

2017-08-14

Membrane fission is a fundamental process in cells, involved inter alia in endocytosis, intracellular trafficking, and virus infection. Its underlying molecular mechanism, however, is only incompletely understood. Recently, experiments and computer simulation studies have revealed that dynamin-mediated membrane fission is a two-step process that proceeds via a metastable hemi-fission intermediate (or wormlike micelle) formed by dynamin's constriction. Importantly, this hemi-fission intermediate is remarkably metastable, i.e., its subsequent rupture that completes the fission process does not occur spontaneously but requires additional, external effects, e.g., dynamin's (unknown) conformational changes or membrane tension. Using simulations of a coarse-grained, implicit-solvent model of lipid membranes, we investigate the molecular mechanism of rupturing the hemi-fission intermediate, such as its pathway, the concomitant transition states, and barriers, as well as the role of membrane tension. The membrane tension is controlled by the chemical potential of the lipids, and the free-energy landscape as a function of two reaction coordinates is obtained by grand canonical Wang-Landau sampling. Our results show that, in the course of rupturing, the hemi-fission intermediate undergoes a "thinning → local pinching → rupture/fission" pathway, with a bottle-neck-shaped cylindrical micelle as a transition state. Although an increase of membrane tension facilitates the fission process by reducing the corresponding free-energy barrier, for biologically relevant tensions, the free-energy barriers still significantly exceed the thermal energy scale k B T.

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…

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

2012-10-09

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.

Some peculiarities of interactions of weakly bound lithium nuclei at near-barrier energies

NASA Astrophysics Data System (ADS)

Kabyshev, A. M.; Kuterbekov, K. A.; Sobolev, Yu G.; Penionzhkevich, Yu E.; Kubenova, M. M.; Azhibekov, A. K.; Mukhambetzhan, A. M.; Lukyanov, S. M.; Maslov, V. A.; Kabdrakhimova, G. D.

2018-02-01

This paper presents new experimental data on the total cross sections of 9Li + 28Si reactions at low energies as well as the analysis of previously obtained data for 6,7Li. Based on a large collection of data (authors’ and literature data) we carried out a comparative analysis of the two main experimental interaction cross sections (angular distributions of the differential cross sections and total reaction cross sections) for weakly bound lithium (6-9Li, 11Li) nuclei in the framework of Kox parameterization and the macroscopic optical model. We identified specific features of these interactions and predicted the experimental trend in the total reaction cross sections for Li isotopes at energies close to the Coulomb barrier.

I-V characterization of a quantum well infrared photodetector with stepped and graded barriers

NASA Astrophysics Data System (ADS)

Nutku, F.; Erol, A.; Gunes, M.; Buklu, L. B.; Ergun, Y.; Arikan, M. C.

2012-09-01

I-V characterization of an n-type quantum well infrared photodetector which consists of stepped and graded barriers has been done under dark at temperatures between 20-300 K. Different current transport mechanisms and transition between them have been observed at temperature around 47 K. Activation energies of the electrons at various bias voltages have been obtained from the temperature dependent I-V measurements. Activation energy at zero bias has been calculated by extrapolating the bias dependence of the activation energies. Ground state energies and barrier heights of the four different quantum wells have been calculated by using an iterative technique, which depends on experimentally obtained activation energy. Ground state energies also have been calculated with transfer matrix technique and compared with iteration results. Incorporating the effect of high electron density induced electron exchange interaction on ground state energies; more consistent results with theoretical transfer matrix calculations have been obtained.

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

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.

Rotational barriers. 1. 1,2-dihaloethanes

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

Wiberg, K.B.; Murcko, M.A.

1987-06-18

The rotational barrier about the C-C bond of 1,2-dichloroethane has been calculated by using several basis sets (4-31G, 6-31G*, 6-31+G*, and 6-31++G**) and including electron correlation. Corrections for zero-point energy differences, and the differences in enthalpy change from 0 to 298 K, were made by using the calculated geometries and vibrational frequencies. The trans/gauche energy difference was found to be 1.39 kcal/mol as compared to the observed value, 1.1 +/- 0.1 kcal/mol. The intramolecular interactions in the several rotamers are discussed. The trans/gauche energy difference for 1,2-difluoroethane also was calculated (MP3/6-311++G**) and was found to be 0.76 kcal/mol favoring themore » gauche conformer, again in good agreement with the experimental value of 0.57 +/- 0.09 kcal/mol. The trend in trans/gauche energy differences in the series n-butane, 1,2-dichloroethane, 1,2-difluoroethane is noted.« less

A converged calculation of the energy barrier to internal rotation in the ethylene-sulfur dioxide dimer

NASA Astrophysics Data System (ADS)

Resende, Stella M.; De Almeida, Wagner B.; van Duijneveldt-van de Rijdt, Jeanne G. C. M.; van Duijneveldt, Frans B.

2001-08-01

Geometrical parameters for the equilibrium (MIN) and lowest saddle-point (TS) geometries of the C2H4⋯SO2 dimer, and the corresponding binding energies, were calculated using the Hartree-Fock and correlated levels of ab initio theory, in basis sets ranging from the D95(d,p) double-zeta basis set to the aug-cc-pVQZ correlation consistent basis set. An assessment of the effect of the basis set superposition error (BSSE) on these results was made. The dissociation energy from the lowest vibrational state was estimated to be 705±100 cm-1 at the basis set limit, which is well within the range expected from experiment. The barrier to internal rotation was found to be 53±5 cm-1, slightly higher than the (revised) experimental result of 43 cm-1, probably due to zero-point vibrational effects. Our results clearly show that, in direct contrast with recent ideas, the BSSE correction affects differentially the MIN and TS binding energies and so has to be included in the calculation of small energy barriers such as that in the C2H4⋯SO2 dimer. Previous reports of positive MP2 frozen-core binding energies for this complex in basis D95(d,p) are confirmed. The anomalies are shown to be an artifact arising from an incorrect removal of virtual orbitals by the default frozen-core option in the GAUSSIAN program.

Fission barriers at the end of the chart of the nuclides

DOE PAGES

Möller, Peter; Sierk, Arnold J.; Ichikawa, Takatoshi; ...

2015-02-12

We present calculated fission-barrier heights for 5239 nuclides for all nuclei between the proton and neutron drip lines with 171 ≤ A ≤ 330. The barriers are calculated in the macroscopic-microscopic finite-range liquid-drop (FRLDM) with a 2002 set of macroscopic-model parameters. The saddle-point energies are determined from potential-energy surfaces based on more than five million different shapes, defined by five deformation parameters in the three-quadratic-surface shape parametrization: elongation, neck diameter, left-fragment spheroidal deformation, right-fragment spheroidal deformation, and nascent-fragment mass asymmetry. The energy of the ground state is determined by calculating the lowest-energy configuration in both the Nilsson perturbed-spheroid (ϵ) andmore » the spherical-harmonic (β) parametrizations, including axially asymmetric deformations. The lower of the two results (correcting for zero-point motion) is defined as the ground-state energy. The effect of axial asymmetry on the inner barrier peak is calculated in the (ϵ,γ) parametrization. We have earlier benchmarked our calculated barrier heights to experimentally extracted barrier parameters and found average agreement to about one MeV for known data across the nuclear chart. Here we do additional benchmarks and investigate the qualitative and, when possible, quantitative agreement and/or consistency with data on β-delayed fission, isotope generation along prompt-neutron-capture chains in nuclear-weapons tests, and superheavy-element stability. In addition these studies all indicate that the model is realistic at considerable distances in Z and N from the region of nuclei where its parameters were determined.« less

Fission barriers at the end of the chart of the nuclides

NASA Astrophysics Data System (ADS)

Möller, Peter; Sierk, Arnold J.; Ichikawa, Takatoshi; Iwamoto, Akira; Mumpower, Matthew

2015-02-01

We present calculated fission-barrier heights for 5239 nuclides for all nuclei between the proton and neutron drip lines with 171 ≤A ≤330 . The barriers are calculated in the macroscopic-microscopic finite-range liquid-drop model with a 2002 set of macroscopic-model parameters. The saddle-point energies are determined from potential-energy surfaces based on more than 5 000 000 different shapes, defined by five deformation parameters in the three-quadratic-surface shape parametrization: elongation, neck diameter, left-fragment spheroidal deformation, right-fragment spheroidal deformation, and nascent-fragment mass asymmetry. The energy of the ground state is determined by calculating the lowest-energy configuration in both the Nilsson perturbed-spheroid (ɛ ) and the spherical-harmonic (β ) parametrizations, including axially asymmetric deformations. The lower of the two results (correcting for zero-point motion) is defined as the ground-state energy. The effect of axial asymmetry on the inner barrier peak is calculated in the (ɛ ,γ ) parametrization. We have earlier benchmarked our calculated barrier heights to experimentally extracted barrier parameters and found average agreement to about 1 MeV for known data across the nuclear chart. Here we do additional benchmarks and investigate the qualitative and, when possible, quantitative agreement and/or consistency with data on β -delayed fission, isotope generation along prompt-neutron-capture chains in nuclear-weapons tests, and superheavy-element stability. These studies all indicate that the model is realistic at considerable distances in Z and N from the region of nuclei where its parameters were determined.

Worlds apart? A scoping review addressing different stakeholder perspectives on barriers to family involvement in the care for persons with severe mental illness.

PubMed

Landeweer, Elleke; Molewijk, Bert; Hem, Marit Helene; Pedersen, Reidar

2017-05-15

Empirical evidence shows that family involvement (FI) can play a pivotal role in the coping and recovery of persons with severe mental illness (SMI). Nevertheless, various studies demonstrate that FI in mental healthcare services is often not (sufficiently) realized. In order to develop more insights, this scoping review gives an overview of how various stakeholders conceptualize, perceive and experience barriers to FI. Central questions are: 1) What are the main barriers to FI reported by the different key stakeholders (i.e. the persons with SMI, their families and the professionals, and 2) What are the differences and similarities between the various stakeholders' perspectives on these barriers. A systematic search into primary studies regarding FI was conducted in four databases: Medline/Pubmed, Cinahl, PsychInfo and Web of Knowledge with the use of a PICO scheme. Thematic analysis focused on stakeholder perspectives (i.e. which stakeholder group reports the barrier) and types of barriers (i.e. which types of barriers are addressed). Thirty three studies were included. The main barriers reported by the stakeholder groups reveal important similarities and differences between the stakeholder groups and were related to: 1) the person with SMI, 2) the family, 3) the professionals, 4) the organization of care and 5) the culture-paradigm. Our stakeholder approach elicits the different stakeholders' concepts, presuppositions and experiences of barriers to FI, and gives fundamental insights on how to deal with barriers to FI. The stakeholders differing interpretations and perceptions of the barriers related to FI is closely related to the inherent complexity involved in FI in itself. In order to deal better with these barriers, openly discussing and reflecting upon each other's normative understandings of barriers is needed. Differences in perceptions of barriers to FI can itself be a barrier. To deal with barriers to FI, a dialogical approach on how the different

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.

Fusion hindrance at deep sub-barrier energies for the 11B+197Au system

NASA Astrophysics Data System (ADS)

Shrivastava, A.; Mahata, K.; Nanal, V.; Pandit, S. K.; Parkar, V. V.; Rout, P. C.; Dokania, N.; Ramachandran, K.; Kumar, A.; Chatterjee, A.; Kailas, S.

2017-09-01

Fusion cross sections for the 11B+197Au system have been measured at energies around and deep below the Coulomb barrier, to probe the occurrence of fusion hindrance in case of asymmetric systems. A deviation with respect to the standard coupled channels calculations has been observed at the lowest energy. The results have been compared with an adiabatic model calculation that considers a damping of the coupling strength for a gradual transition from sudden to adiabatic regime at very low energies. The data could be explained without inclusion of the damping factor. This implies that the influence of fusion hindrance is not significant within the measured energy range for this system. The present result is consistent with the observed trend between the degree of fusion hindrance and the charge product that reveals a weaker influence of hindrance on fusion involving lighter projectiles on heavy targets.

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

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

Evans, M.W.; Hine, A.C.; David, R.A.

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 aremore » 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.« less

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.

Motivators and Barriers to Engaging in Healthy Eating and Physical Activity

PubMed Central

Ashton, Lee M.; Hutchesson, Melinda J.; Rollo, Megan E.; Morgan, Philip J.; Collins, Clare E.

2016-01-01

Many Australian young men (18-25 years) fail to meet recommendations in national dietary or physical activity (PA) guidelines. However, there is a lack of understanding of their perspectives on PA and diet to inform intervention design. This study examined young men’s motivators and barriers to healthy eating and PA, along with differences by demographic and behavioral factors. A cross-sectional online survey was completed by 282 men aged 18 to 25 years in Australia. Results identified the most common motivators for healthy eating included improving health (63.5%), body image (52.3%), and increasing energy (32.1%). Motivators for PA included improving body image (44.6%), fitness (44.2%), and health (41.0%). Common barriers to healthy eating were access to unhealthy foods (61.1%), time to cook/prepare healthy foods (55.0%), and motivation to cook healthy foods (50.7%). Barriers for PA included motivation (66.3%), time (57.8%), and cost of equipment/facilities (33.3%). Significant differences (p < .01) in motivators to healthy eating and/or PA were identified for BMI category, marital status, PA level, alcohol intake, and stress levels. Significant differences were identified for barriers to healthy eating and/or PA by BMI, PA level, stress, and fruit and vegetable intake, assessed using Pearson’s chi-square test. Findings suggest that promotion of benefits related to health, appearance/body image, increased energy and fitness, and addressing key barriers including motivation, time, financial restraints, and accessibility of unhealthy foods, could engage young men in improving lifestyle behaviors. Differences by demographic and behavioral factors suggest development of tailored programs to address diversity among young men may be required. PMID:27923963

Motivators and Barriers to Engaging in Healthy Eating and Physical Activity.

PubMed

Ashton, Lee M; Hutchesson, Melinda J; Rollo, Megan E; Morgan, Philip J; Collins, Clare E

2017-03-01

Many Australian young men (18-25 years) fail to meet recommendations in national dietary or physical activity (PA) guidelines. However, there is a lack of understanding of their perspectives on PA and diet to inform intervention design. This study examined young men's motivators and barriers to healthy eating and PA, along with differences by demographic and behavioral factors. A cross-sectional online survey was completed by 282 men aged 18 to 25 years in Australia. Results identified the most common motivators for healthy eating included improving health (63.5%), body image (52.3%), and increasing energy (32.1%). Motivators for PA included improving body image (44.6%), fitness (44.2%), and health (41.0%). Common barriers to healthy eating were access to unhealthy foods (61.1%), time to cook/prepare healthy foods (55.0%), and motivation to cook healthy foods (50.7%). Barriers for PA included motivation (66.3%), time (57.8%), and cost of equipment/facilities (33.3%). Significant differences ( p < .01) in motivators to healthy eating and/or PA were identified for BMI category, marital status, PA level, alcohol intake, and stress levels. Significant differences were identified for barriers to healthy eating and/or PA by BMI, PA level, stress, and fruit and vegetable intake, assessed using Pearson's chi-square test. Findings suggest that promotion of benefits related to health, appearance/body image, increased energy and fitness, and addressing key barriers including motivation, time, financial restraints, and accessibility of unhealthy foods, could engage young men in improving lifestyle behaviors. Differences by demographic and behavioral factors suggest development of tailored programs to address diversity among young men may be required.

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.

Oscillatory shear response of moisture barrier coatings containing clay of different shape factor.

PubMed

Kugge, C; Vanderhoek, N; Bousfield, D W

2011-06-01

Oscillatory shear rheology of barrier coatings based on dispersed styrene-butadiene latex and clay of various shape factors or aspect ratio has been explored. Barrier performance of these coatings when applied to paperboard has been assessed in terms of water vapour transmission rates and the results related to shape factor, dewatering and critical strain. It has been shown that a system based on clay with high shape factor gives a lower critical strain, dewatering and water vapour transmission rate compared with clays of lower shape factor. The dissipated energy, as calculated from an amplitude sweep, indicated no attractive interaction between clay and latex implying a critical strain that appears to be solely dependent on the shape factor at a constant volume fraction. Particle size distribution was shown to have no effect on the critical strain while coatings of high elasticity exhibited high yield strains as expected. The loss modulus demonstrated strain hardening before the elastic to viscous transition. The loss modulus peak was identified by a maximum strain which was significantly lower for a coating based on clay with a high shape factor. The characteristic elastic time was found to vary between 0.6 and 1.3s. The zero shear viscosity of barrier dispersion coatings were estimated from the characteristic elastic time and the characteristic modulus to be of the order of 25-100 Pa s. Copyright © 2011 Elsevier Inc. All rights reserved.

Impact of compliance with different guidelines on physical activity during pregnancy and perceived barriers to leisure physical activity.

PubMed

Santos, Paula Clara; Abreu, Sandra; Moreira, Carla; Lopes, Diana; Santos, Rute; Alves, Odete; Silva, Pedro; Montenegro, Nuno; Mota, Jorge

2014-01-01

The aims of the this prospective study were to analyse physical activity (PA) engagement during the first and second trimesters, considering the different guidelines published on PA, to document the individual characteristics associated with the accomplishment of these guidelines and to examine pregnant women's perceived barriers to leisure PA, using a socioecological framework. A sample of 133 pregnant women in two stages--at 10-12 weeks' gestation (T1) and 20-22 weeks' gestation (T2)--were evaluated. PA was assessed by accelerometry during the T1 and T2 evaluation stages. Socio-demographic characteristics, lifestyle factors and barriers to leisure PA were assessed via questionnaire. A large proportion of women (ranging from 32% to 96%) did not reach the levels of PA recommended by the guidelines. There were no significant differences between T1 and T2 with regard to compliance with PA recommendations. A decrease in PA levels from T1 to T2 was noted for all recommendations. No associations were found between participants' characteristics and adherence to the recommendations in T1 and T2. No significant differences were found in barriers to leisure PA between T1 and T2. The most commonly reported barriers to leisure PA were intrapersonal, not health related. Our results indicate that there were no differences between trimesters regarding compliance of PA recommendations, and perceived barriers were similar in both trimesters.

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

NASA Astrophysics Data System (ADS)

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.

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

2016-03-07

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.

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

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

Yang, Y. Isaac; Zhang, Jun; Che, Xing

2016-03-07

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 ofmore » 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.« less

Influence of average ion energy and atomic oxygen flux per Si atom on the formation of silicon oxide permeation barrier coatings on PET

NASA Astrophysics Data System (ADS)

Mitschker, F.; Wißing, J.; Hoppe, Ch; de los Arcos, T.; Grundmeier, G.; Awakowicz, P.

2018-04-01

The respective effect of average incorporated ion energy and impinging atomic oxygen flux on the deposition of silicon oxide (SiO x ) barrier coatings for polymers is studied in a microwave driven low pressure discharge with additional variable RF bias. Under consideration of plasma parameters, bias voltage, film density, chemical composition and particle fluxes, both are determined relative to the effective flux of Si atoms contributing to film growth. Subsequently, a correlation with barrier performance and chemical structure is achieved by measuring the oxygen transmission rate (OTR) and by performing x-ray photoelectron spectroscopy. It is observed that an increase in incorporated energy to 160 eV per deposited Si atom result in an enhanced cross-linking of the SiO x network and, therefore, an improved barrier performance by almost two orders of magnitude. Furthermore, independently increasing the number of oxygen atoms to 10 500 per deposited Si atom also lead to a comparable barrier improvement by an enhanced cross-linking.

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

2016-04-13

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.

Transport barriers in bootstrap-driven tokamaks

NASA Astrophysics Data System (ADS)

Staebler, G. M.; Garofalo, A. M.; Pan, C.; McClenaghan, J.; Van Zeeland, M. A.; Lao, L. L.

2018-05-01

Experiments have demonstrated improved energy confinement due to the spontaneous formation of an internal transport barrier in high bootstrap fraction discharges. Gyrokinetic analysis, and quasilinear predictive modeling, demonstrates that the observed transport barrier is caused by the suppression of turbulence primarily from the large Shafranov shift. It is shown that the Shafranov shift can produce a bifurcation to improved confinement in regions of positive magnetic shear or a continuous reduction in transport for weak or negative magnetic shear. Operation at high safety factor lowers the pressure gradient threshold for the Shafranov shift-driven barrier formation. Two self-organized states of the internal and edge transport barrier are observed. It is shown that these two states are controlled by the interaction of the bootstrap current with magnetic shear, and the kinetic ballooning mode instability boundary. Election scale energy transport is predicted to be dominant in the inner 60% of the profile. Evidence is presented that energetic particle-driven instabilities could be playing a role in the thermal energy transport in this region.

Splaying of aliphatic tails plays a central role in barrier crossing during liposome fusion.

PubMed

Mirjanian, Dina; Dickey, Allison N; Hoh, Jan H; Woolf, Thomas B; Stevens, Mark J

2010-09-02

The fusion between two lipid bilayers involves crossing a complicated energy landscape. The limiting barrier in the process appears to be between two closely opposed bilayers and the intermediate state where the outer leaflets are fused. We have performed molecular dynamics simulations to characterize the free energy barrier for the fusion of two liposomes and to examine the molecular details of barrier crossing. To capture the slow dynamics of fusion, a model using coarse-grained representations of lipids was used. The fusion between pairs of liposomes was simulated for four systems: DPPC, DOPC, a 3:1 mixture of DPPC/DPPE, and an asymmetric lipid tail system in which one tail of DPPC was reduced to half the length (ASTail). The weighted histogram method was used to compute the free energy as a function of separation distance. The relative barrier heights for these systems was found to be ASTail > DPPC > DPPC/DPPE > DOPC, in agreement with experimental observations. Further, the free energy curves for all four can be overlaid on a single curve by plotting the free energy versus the surface separation (differing only in the point of fusion). These simulations also confirm that the two main contributions to the free energy barrier are the removal of water between the vesicles and the deformation of the vesicle. The most prominent molecular detail of barrier crossing in all cases examined was the splaying of lipid tails, where initially a single splayed lipid formed a bridge between the two outer leaflets that promotes additional lipid mixing between the vesicles and eventually leads to fusion. The tail splay appears to be closely connected to the energetics of the process. For example, the high barrier for the ASTail is the result of a smaller distance between terminal methyl groups in the splayed molecule. The shortening of this distance requires the liposomes to be closer together, which significantly increases the cost of water removal and bilayer deformation

Biological and Sociocultural Differences in Perceived Barriers to Physical Activity Among Fifth- to Seventh-Grade Urban Girls.

PubMed

Vermeesch, Amber L; Ling, Jiying; Voskuil, Vicki R; Bakhoya, Marion; Wesolek, Stacey M; Bourne, Kelly A; Pfeiffer, Karin A; Robbins, Lorraine B

2015-01-01

Inadequate physical activity (PA) contributes to the high prevalence of overweight and obesity among U.S. adolescent girls. Barriers preventing adolescent girls from meeting PA guidelines have not been thoroughly examined. The threefold purpose of this study was to (a) determine pubertal stage, racial/ethnic, and socioeconomic status (SES) differences in ratings of interference of barriers to PA; (b) examine relationships between perceived barriers and age, body mass index, recreational screen time, sedentary activity, and PA; and (c) identify girls' top-rated perceived barriers to PA. Girls (N = 509) from eight Midwestern U.S. schools participated. Demographic, pubertal stage, perceived barriers, and recreational screen time data were collected via surveys. Height and weight were measured. Accelerometers measured sedentary activity, moderate-to-vigorous PA (MVPA), and light plus MVPA. Girls of low SES reported greater interference of perceived barriers to PA than those who were not of low SES (1.16 vs. 0.97, p = .01). Girls in early/middle puberty had lower perceived barriers than those in late puberty (1.03 vs. 1.24, p < .001). Girls' perceived barriers were negatively related to MVPA (r = -.10, p = .03) and light plus MVPA (r = -.11, p = .02). Girls' top five perceived barriers included lack of skills, hating to sweat, difficulty finding programs, being tired, and having pain. Innovative interventions, particularly focusing on skill development, are needed to assist girls in overcoming their perceived barriers to PA.

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.

Sub-barrier fusion of Si+Si systems

NASA Astrophysics Data System (ADS)

Colucci, G.; Montagnoli, G.; Stefanini, A. M.; Bourgin, D.; Čolović, P.; Corradi, L.; Courtin, S.; Faggian, M.; Fioretto, E.; Galtarossa, F.; Goasduff, A.; Haas, F.; Mazzocco, M.; Scarlassara, F.; Stefanini, C.; Strano, E.; Urbani, M.; Szilner, S.; Zhang, G. L.

2017-11-01

The near- and sub-barrier fusion excitation function has been measured for the system 30Si+30Si at the Laboratori Nazionali di Legnaro of INFN, using the 30Si beam of the XTU Tandem accelerator in the energy range 47 - 90 MeV. A set-up based on a beam electrostatic deflector was used for detecting fusion evaporation residues. The measured cross sections have been compared to previous data on 28Si+28Si and Coupled Channels (CC) calculations have been performed using M3Y+repulsion and Woods-Saxon potentials, where the lowlying 2+ and 3- excitations have been included. A weak imaginary potential was found to be necessary to reproduce the low energy 28Si+28Si data. This probably simulates the effect of the oblate deformation of this nucleus. On the contrary, 30Si is a spherical nucleus, 30Si+30Si is nicely fit by CC calculations and no imaginary potential is needed. For this system, no maximum shows up for the astrophysical S-factor so that we have no evidence for hindrance, as confirmed by the comparison with CC calculations. The logarithmic derivative of the two symmetric systems highlights their different low energy trend. A difference can also be noted in the two barrier distributions, where the high-energy peak present in 28Si+28Si is not observed for 30Si+30Si, probably due to the weaker couplings in last case.

Debris Flow Risk mitigation by the means of flexible barriers. Experimental and field tests.

NASA Astrophysics Data System (ADS)

Canelli, L.; Ferrero, A. M.; Segalini, A.

2012-04-01

Debris flow risk mitigation using net barriers is an option that was not considered until few years ago, probably because of the lack of scientific evidences about their efficiency and solid guidelines for their design and construction. On site evidences (Segalini et al, 2008) showed that a rock fall deformable barrier can efficiently intercept the whole volume or just a portion of the mobilized debris without losing its stability and efficiency, actually performing a different task form that it was originally designed for. Although the final purpose of both types of barriers (rock fall and debris) is to reduce the impact energy of the moving mass by dissipating impact energy through the deformation of the net and of the dissipating elements, it is noteworthy that the physics of the impact is extremely different between the two phenomena. The rock fall barrier needs to dissipate the energy of a single block generally concentrated on the center of the net panel (design conditions). The debris flow barrier, generally installed inside a debris channel, should be able to dissipate the impact energy that the debris induces across the whole section of the channel. Moreover, the recurring characteristic of the debris flows will cause multiple impact on the barrier and therefore, the structure should be able to absorb a significant amount of energy even if partially filled and considerably deformed. In order to introduce useful guidelines for the design and production of debris flow net barriers, this paper describes: 1. Part of the results obtained from the laboratory experiment carried out in a scaled channel and aimed to estimate the most realistic thrust vs time relationship induced by a debris flow on a deformable and rigid structure; these results were partially presented last year at the EGU 2011; 2. A large scale field test carried out in a quarry located in Tambre d'Alpago (Belluno Province) on the Eastern Italian Dolomites for the analysis of the behavior of a

Fusion reaction cross-sections using the Wong model within Skyrme energy density based semiclassical extended Thomas Fermi approach

NASA Astrophysics Data System (ADS)

Kumar, Raj; Sharma, Manoj K.; Gupta, Raj K.

2011-11-01

First, the nuclear proximity potential, obtained by using the semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), is shown to give more realistic barriers in frozen density approximation, as compared to the sudden approximation. Then, taking advantage of the fact that, in ETF method, different Skyrme forces give different barriers (height, position and curvature), we use the ℓ-summed extended-Wong model of Gupta and collaborators (2009) [1] under frozen densities approximation for calculating the cross-sections, where the Skyrme force is chosen with proper barrier characteristics, not-requiring additional "barrier modification" effects (lowering or narrowing, etc.), for a best fit to data at sub-barrier energies. The method is applied to capture cross-section data from 48Ca + 238U, 244Pu, and 248Cm reactions and to fusion-evaporation cross-sections from 58Ni + 58Ni, 64Ni + 64Ni, and 64Ni + 100Mo reactions, with effects of deformations and orientations of nuclei included, wherever required. Interestingly, whereas the capture cross-sections in Ca-induced reactions could be fitted to any force, such as SIII, SV and GSkI, by allowing a small change of couple of units in deduced ℓ-values at below-barrier energies, the near-barrier data point of 48Ca + 248Cm reaction could not be fitted to ℓ-values deduced for below-barrier energies, calling for a check of data. On the other hand, the fusion-evaporation cross-sections in Ni-induced reactions at sub-barrier energies required different Skyrme forces, representing "modifications of the barrier", for the best fit to data at all incident center-of-mass energies E's, displaying a kind of fusion hindrance at sub-barrier energies. This barrier modification effect is taken into care here by using different Skyrme forces for reactions belonging to different regions of the periodic table. Note that more than one Skyrme force (with identical barrier characteristics) could equally well

DEM Modeling of a Flexible Barrier Impacted by a Dry Granular Flow

NASA Astrophysics Data System (ADS)

Albaba, Adel; Lambert, Stéphane; Kneib, François; Chareyre, Bruno; Nicot, François

2017-11-01

Flexible barriers are widely used as protection structures against natural hazards in mountainous regions, in particular for containing granular materials such as debris flows, snow avalanches and rock slides. This article presents a discrete element method-based model developed in the aim of investigating the response of flexible barriers in such contexts. It allows for accounting for the peculiar mechanical and geometrical characteristics of both the granular flow and the barrier in a same framework, and with limited assumptions. The model, developed with YADE software, is described in detail, as well as its calibration. In particular, cables are modeled as continuous bodies. Besides, it naturally considers the sliding of rings along supporting cables. The model is then applied for a generic flexible barrier to demonstrate its capacities in accounting for the behavior of different components. A detailed analysis of the forces in the different components showed that energy dissipators (ED) had limited influence on total force applied to the barrier and retaining capacity, but greatly influenced the load transmission within the barrier and the force in anchors. A sensitivity analysis showed that the barrier's response significantly changes according to the choice of ED activation force and incoming flow conditions.

Stakeholders identify similar barriers but different strategies to facilitate return-to-work: A vignette of a worker with an upper extremity condition.

PubMed

Peters, Susan E; Truong, Anthony P; Johnston, Venerina

2018-01-01

Stakeholders involved in the return-to-work (RTW) process have different roles and qualificationsOBJECTIVE:To explore the perspectives of Australian stakeholders of the RTW barriers and strategies for a worker with an upper extremity condition and a complex workers' compensation case. Using a case vignette, stakeholders were asked to identify barriers and recommend strategies to facilitate RTW. Content analysis was performed on the open-ended responses. The responses were categorised into RTW barriers and strategies using the biopsychosocial model. Pearson's Chi Square and ANOVA were performed to establish group differences. 621 participants (488 healthcare providers (HCPs), 62 employers, 55 insurers and 16 lawyers) identified 36 barriers (31 modifiable): 4 demographic; 8 biological; 15 psychological and 9 social barriers. 484 participants reported 16 RTW strategies: 4 biological; 6 psychological and 6 social strategies. 'Work relationship stressors' (83.4%) and 'Personal relationship stressors' (64.7%) were the most frequently nominated barriers. HCPs most frequently nominated 'Pain management' (49.6%), while employers, insurers and lawyers nominated 'RTW planning/Suitable duties programs' (40.5%; 42.9%; 80%). Stakeholders perceived similar barriers for RTW but recommended different strategies. Stakeholders appeared to be more proficient in identifying barriers than recommending strategies. Future research should focus on tools to both identify RTW barriers and direct intervention.

Similarities and Differences in Barriers and Opportunities Affecting Climate Change Adaptation Action in Four North American Landscapes

NASA Astrophysics Data System (ADS)

Lonsdale, Whitney R.; Kretser, Heidi E.; Chetkiewicz, Cheryl-Lesley B.; Cross, Molly S.

2017-12-01

Climate change presents a complex set of challenges for natural resource managers across North America. Despite recognition that climate change poses serious threats to species, ecosystems, and human communities, implementation of adaptation measures is not yet happening on a broad scale. Among different regions, a range of climate change trajectories, varying political contexts, and diverse social and ecological systems generate a myriad of factors that can affect progress on climate change adaptation implementation. In order to understand the general versus site-specific nature of barriers and opportunities influencing implementation, we surveyed and interviewed practitioners, decision-makers, and scientists involved in natural resource management in four different North American regions, northern Ontario (Canada), the Adirondack State Park (US), Arctic Alaska (US), and the Transboundary Rocky Mountains (US and Canada). Common barriers among regions related to a lack of political support and financial resources, as well as challenges related to translating complex and interacting effects of climate change into management actions. Opportunities shared among regions related to collaboration, funding, and the presence of strong leadership. These commonalities indicate the importance of cross-site learning about ways to leverage opportunities and address adaptation barriers; however, regional variations also suggest that adaptation efforts will need to be tailored to fit specific ecological, political, social and economic contexts. Comparative findings on the similarities and differences in barriers and opportunities, as well as rankings of barriers and opportunities by region, offers important contextual insights into how to further refine efforts to advance adaptation actions in those regions.

Similarities and Differences in Barriers and Opportunities Affecting Climate Change Adaptation Action in Four North American Landscapes.

PubMed

Lonsdale, Whitney R; Kretser, Heidi E; Chetkiewicz, Cheryl-Lesley B; Cross, Molly S

2017-12-01

Climate change presents a complex set of challenges for natural resource managers across North America. Despite recognition that climate change poses serious threats to species, ecosystems, and human communities, implementation of adaptation measures is not yet happening on a broad scale. Among different regions, a range of climate change trajectories, varying political contexts, and diverse social and ecological systems generate a myriad of factors that can affect progress on climate change adaptation implementation. In order to understand the general versus site-specific nature of barriers and opportunities influencing implementation, we surveyed and interviewed practitioners, decision-makers, and scientists involved in natural resource management in four different North American regions, northern Ontario (Canada), the Adirondack State Park (US), Arctic Alaska (US), and the Transboundary Rocky Mountains (US and Canada). Common barriers among regions related to a lack of political support and financial resources, as well as challenges related to translating complex and interacting effects of climate change into management actions. Opportunities shared among regions related to collaboration, funding, and the presence of strong leadership. These commonalities indicate the importance of cross-site learning about ways to leverage opportunities and address adaptation barriers; however, regional variations also suggest that adaptation efforts will need to be tailored to fit specific ecological, political, social and economic contexts. Comparative findings on the similarities and differences in barriers and opportunities, as well as rankings of barriers and opportunities by region, offers important contextual insights into how to further refine efforts to advance adaptation actions in those regions.

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

DOE PAGES

Mardirossian, Narbe; Head-Gordon, Martin

2016-08-18

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. By and large, the main strength of the hybrid Minnesota density functionals is that the best ones provide verymore » 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). Finally, 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.« less

Degradation of organic pollutants and microorganisms from wastewater using different dielectric barrier discharge configurations--a critical review.

PubMed

Mouele, Emile S Massima; Tijani, Jimoh O; Fatoba, Ojo O; Petrik, Leslie F

2015-12-01

The growing global drinking water crisis requires the development of novel advanced, sustainable, and cost-effective water treatment technologies to supplement the existing conventional methods. One such technology is advanced oxidation based on dielectric barrier discharge (DBD). DBD such as single and double planar and single and double cylindrical dielectric barrier configurations have been utilized for efficient degradation of recalcitrant organic pollutants. The overall performance of the different DBD system varies and depends on several factors. Therefore, this review was compiled to give an overview of different DBD configurations vis-a-viz their applications and the in situ mechanism of generation of free reactive species for water and wastewater treatment. Our survey of the literature indicated that application of double cylindrical dielectric barrier configuration represents an ideal and viable route for achieving greater water and wastewater purification efficiency.

[Diffusion and diffusion-osmosis models of the charged macromolecule transfer in barriers of biosystems].

PubMed

Varakin, A I; Mazur, V V; Arkhipova, N V; Serianov, Iu V

2009-01-01

Mathematical models of the transfer of charged macromolecules have been constructed on the basis of the classical equations of electromigration diffusion of Helmholtz-Smolukhovskii, Goldman, and Goldman-Hodgkin-Katz. It was shown that ion transfer in placental (mimicking lipid-protein barriers) and muscle barriers occurs by different mechanisms. In placental barriers, the electromigration diffusion occurs along lipid-protein channels formed due to the conformational deformation of phospholipid and protein molecules with the coefficients of diffusion D = (2.6-3.6) x 10(-8) cm2/s. The transfer in muscle barriers is due to the migration across charged interfibrillar channels with the negative diffusion activation energy, which is explained by changes in the structure of muscle fibers and expenditures of thermal energy for the extrusion of Cl- from channel walls with the diffusion coefficient D = (6.0-10.0) x 10(-6) cm2/s.

Conductance of graphene-based double-barrier nanostructures.

PubMed

Setare, M R; Jahani, D

2010-12-22

The effect of a mass gap on the conductance of graphene double-barrier heterojunctions is studied. By obtaining the 2D expression for the electronic transport of the low energy excitations of pure graphene through double-barrier systems, it is found that the conductivity of these structures does not depend on the type of charge carriers in the zones of the electric field. However, a finite induced gap in the graphene spectrum makes conductivity dependent on the energy band index. We also discuss a few controversies concerning double-barrier systems stemming from an improper choice of the scattering angle. Then it is observed that, for some special values of the incident energy and potential's height, graphene junctions behave like left-handed materials, resulting in a maximum value for the conductivity.

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.

Oblique wave trapping by vertical permeable membrane barriers located near a wall

NASA Astrophysics Data System (ADS)

Koley, Santanu; Sahoo, Trilochan

2017-12-01

The effectiveness of a vertical partial flexible porous membrane wave barrier located near a rigid vertical impermeable seawall for trapping obliquely incident surface gravity waves are analyzed in water of uniform depth under the assumption of linear water wave theory and small amplitude membrane barrier response. From the general formulation of the submerged membrane barrier, results for bottom-standing and surface-piercing barriers are computed and analyzed in special cases. Using the eigenfunction expansion method, the boundary-value problems are converted into series relations and then the required unknowns are obtained using the least squares approximation method. Various physical quantities of interests like reflection coefficient, wave energy dissipation, wave forces acting on the membrane barrier and the seawall are computed and analyzed for different values of the wave and structural parameters. The study will be useful in the design of the membrane wave barrier for the creation of tranquility zone in the lee side of the barrier to protect the seawall.

Transport Barriers in Bootstrap Driven Tokamaks

NASA Astrophysics Data System (ADS)

Staebler, Gary

2017-10-01

Maximizing the bootstrap current in a tokamak, so that it drives a high fraction of the total current, reduces the external power required to drive current by other means. Improved energy confinement, relative to empirical scaling laws, enables a reactor to more fully take advantage of the bootstrap driven tokamak. Experiments have demonstrated improved energy confinement due to the spontaneous formation of an internal transport barrier in high bootstrap fraction discharges. Gyrokinetic analysis, and quasilinear predictive modeling, demonstrates that the observed transport barrier is due to the suppression of turbulence primarily due to the large Shafranov shift. ExB velocity shear does not play a significant role in the transport barrier due to the high safety factor. It will be shown, that the Shafranov shift can produce a bifurcation to improved confinement in regions of positive magnetic shear or a continuous reduction in transport for weak or negative magnetic shear. Operation at high safety factor lowers the pressure gradient threshold for the Shafranov shift driven barrier formation. The ion energy transport is reduced to neoclassical and electron energy and particle transport is reduced, but still turbulent, within the barrier. Deeper into the plasma, very large levels of electron transport are observed. The observed electron temperature profile is shown to be close to the threshold for the electron temperature gradient (ETG) mode. A large ETG driven energy transport is qualitatively consistent with recent multi-scale gyrokinetic simulations showing that reducing the ion scale turbulence can lead to large increase in the electron scale transport. A new saturation model for the quasilinear TGLF transport code, that fits these multi-scale gyrokinetic simulations, can match the data if the impact of zonal flow mixing on the ETG modes is reduced at high safety factor. This work was supported by the U.S. Department of Energy under DE-FG02-95ER54309 and DE-FC02

Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides

NASA Astrophysics Data System (ADS)

Zhao, Jie; Lu, Bing-Nan; Vretenar, Dario; Zhao, En-Guang; Zhou, Shan-Gui

2015-01-01

Background: Potential energy surfaces (PES's) of actinide nuclei are characterized by a two-humped barrier structure. At large deformations beyond the second barrier, the occurrence of a third barrier was predicted by macroscopic-microscopic model calculations in the 1970s, but contradictory results were later reported by a number of studies that used different methods. Purpose: Triple-humped barriers in actinide nuclei are investigated in the framework of covariant density functional theory (CDFT). Methods: Calculations are performed using the multidimensionally constrained relativistic mean field (MDC-RMF) model, with the nonlinear point-coupling functional PC-PK1 and the density-dependent meson exchange functional DD-ME2 in the particle-hole channel. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Results: Two-dimensional PES's of 226,228,230,232Th and 232,235,236,238U are mapped and the third minima on these surfaces are located. Then one-dimensional potential energy curves along the fission path are analyzed in detail and the energies of the second barrier, the third minimum, and the third barrier are determined. The functional DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and 238U . The third minima in 230 ,232Th are very shallow, whereas those in 226 ,228Th and 238U are quite prominent. With the functional PC-PK1 a third barrier is found only in 226 ,228 ,230Th . Single-nucleon levels around the Fermi surface are analyzed in 226Th, and it is found that the formation of the third minimum is mainly due to the Z =90 proton energy gap at β20≈1.5 and β30≈0.7 . Conclusions: The possible occurrence of a third barrier on the PES's of actinide nuclei depends on the effective interaction used in multidimensional CDFT calculations. More pronounced minima are predicted by the DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third well in Th isotopes decreases

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.

Thermal barrier coatings application in diesel engines

NASA Technical Reports Server (NTRS)

Fairbanks, J. W.

1995-01-01

Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr,. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also to provide protection. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the thermal barrier coatings will be to reduce thermal fatigue as the engine peak cylinder pressure will nearly be doubled. As the coatings result in higher available energy in the exhaust gas, efficiency gains are achieved through use of this energy by turbochargers, turbocompounding or thermoelectric generators.

Electron mobility in InGaN channel heterostructure field effect transistor structures with different barriers

NASA Astrophysics Data System (ADS)

Xie, J.; Leach, J. H.; Ni, X.; Wu, M.; Shimada, R.; Özgür, Ü.; Morkoç, H.

2007-12-01

InGaN possesses higher electron mobility and velocity than GaN, and therefore is expected to lead to relatively better performances for heterostructure field effect transistors (HFETs). However, the reported mobilities for AlGaN /InGaN HFETs are lower than GaN channel HFETs. To address this issue, we studied the effect of different barriers on the Hall mobility for InGaN channel HFETs grown by metal organic chemical vapor deposition. Unlike the conventional AlGaN barrier, the AlInN barrier can be grown at the same temperature as the InGaN channel layer, alleviating some of the technological roadblocks. Specifically, this avoids possible degradation of the thin InGaN channel during AlGaN growth at high temperatures; and paves the way for better interfaces. An undoped In0.18Al0.82N/AlN/In0.04Ga0.96N HFET structure exhibited a μH=820cm2/Vs, with a ns=2.12×1013cm-2 at room temperature. Moreover, with an In-doped AlGaN barrier, namely, Al0.24In0.01Ga0.75N, grown at 900°C, the μH increased to 1230cm2/Vs with a ns of 1.09×1013cm-2 for a similar InGaN channel. Furthermore, when the barrier was replaced by Al0.25Ga0.75N grown at 1030°C, μH dropped to 870cm2/Vs with ns of 1.26×1013cm-2 at room temperature. Our results suggest that to fully realize the potential of the InGaN channel HFETs, AlInN or AlInGaN should be used as the barrier instead of the conventional AlGaN barrier.

Application of dimensional analysis to predict the performance of rockfall barrier

NASA Astrophysics Data System (ADS)

Spadari, M.; Giacomini, A.; Buzzi, O.; Hambleton, J.

2012-04-01

Natural hazards involving rocks or rock slopes are responsible for loss of life and damage to infrastructure and are consequently widely studied. Rock fall barriers are a common type of protection structures that is usually designed on the basis of total impact energy. However, the systems are usually tested in free fall where the predominant component of energy is kinematic and it has been shown that there is not a unique relationship between the response of a barrier and the kinetic energy of the impacting block. In particular, recent studies have discussed the so called "bullet effect" i.e. relatively small blocks traveling at high speed can perforate the barriers yet having acceptable level of energy. This effect compromises the use of kinetic energy as an adequate design criterion since there is not a threshold value defining clearly acceptable and unacceptable values of energy. This issue can be addressed empirically by using different block sizes when it comes to test a system. However, the literature still lacks a characterization of a rockfall barrier performance regarding the bullet effect. This note presents the results of the application of dimensional analysis to the physical problem of the bullet effect. This latter has been formulated as a function involving eight key variables: v = f(ρ, K, σy, H, A, Db,Dw) where v is the minimum speed of a given block to break the barrier, ρgs the density of the block, Kis the stiffness of the system, σy is the strength of the wires, H is the height of the barrier, A is the aperture of the mesh, Db is the dimension of the block and Dw is the diameter of the wire. Applying the Buckingham Pi theorem allows reducing the equation above to a simpler problem involving only three dimensionless parameters: E*=F(S*, G*) Where E* is the performance parameter, S* is the strength-stiffness parameter and G* is the geometrical parameters defined as: E*= (ρ.v2.H)/K S*=K/(H.gσy) And G*=A-0.25.Db-0.75.Db F in the simplified

Biological and Sociocultural Differences in Perceived Barriers to Physical Activity among 5th–7th Grade Urban Girls

PubMed Central

Vermeesch, Amber L.; Ling, Jiying; Voskuil, Vicki R.; Bakhoya, Marion; Wesolek, Stacey M.; Bourne, Kelly A.; Pfeiffer, Karin A.; Robbins, Lorraine B.

2015-01-01

Background Inadequate physical activity (PA) contributes to the high prevalence of overweight and obesity among U.S. adolescent girls. Barriers preventing adolescent girls from meeting PA guidelines have not been thoroughly examined. Objectives The threefold purpose of this study was to: (a) determine pubertal stage, racial/ethnic, and socioeconomic status (SES) differences in ratings of interference of barriers to PA; (b) examine relationships between perceived barriers and age, body mass index (BMI), recreational screen time, sedentary activity, and PA; and (c) identify girls’ top-rated perceived barriers to PA. Methods Girls (N = 509) from eight Midwestern U.S. schools participated. Demographic, pubertal stage, perceived barriers, and recreational screen time data were collected via surveys. Height and weight were measured. Accelerometers measured sedentary activity, moderate-to-vigorous physical activity (MVPA), and light plus MVPA. Results Girls of low SES reported greater interference of perceived barriers to PA than those who were not of low SES (1.16 vs. 0.97, p = .01). Girls in early/middle puberty had lower perceived barriers than those in late puberty (1.03 vs. 1.24, p < .001). Girls’ perceived barriers were negatively related to MVPA (r = −.10, p = .03) and light plus MVPA (r = −.11, p = .02). Girls’ top five perceived barriers included lack of skills, hating to sweat, difficulty finding programs, being tired, and having pain. Discussion Innovative interventions, particularly focusing on skill development, are needed to assist girls in overcoming their perceived barriers to PA. PMID:26325276

Two Series of Homodinuclear Lanthanide Complexes: Greatly Enhancing Energy Barriers through Tuning Terminal Solvent Ligands in Dy2 Single-Molecule Magnets.

PubMed

Qin, Yaru; Zhang, Haifeng; Sun, Hao; Pan, Yangdan; Ge, Yu; Li, Yahong; Zhang, Yi-Quan

2017-11-02

The utilization of 2-ethoxy-6-{[(2-hydroxy-3-methoxybenzyl)imino]methyl}phenol (H 2 L) as a chelating ligand, in combination with the employment of alcohols (EtOH and MeOH) as auxiliary ligands, in 4 f-metal chemistry afforded two series of dinuclear lanthanide complexes of compositions [Ln 2 L 2 (NO 3 ) 2 (EtOH) 2 ] (Ln=Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7)) and [Ln 2 L 2 (NO 3 ) 2 (MeOH) 2 ] (Ln=Sm (8), Eu (9), Gd (10), Tb (11), Dy (12), Ho (13), Er (14)). The structures of 1-14 were determined by single-crystal X-ray crystallography. Complexes 1-7 are isomorphous. The two lanthanide(III) ions in 1-7 are doubly bridged by two deprotonated aminophenoxide oxygen atoms of two μ 2 :η 0 :η 1 :η 2 :η 1 :η 1 :η 0 -L 2- ligands. One nitrogen atom, two oxygen atoms of the NO 3 - anion, two methoxide oxygen atoms of two ligand sets, and one oxygen atom of the terminally coordinated EtOH molecule complete the distorted dodecahedron geometry of each lanthanide(III) ion. Compounds 8-14 are isomorphous and their structures are similar to those of 1-7. The slight difference between 1-7 and 8-14 stems from purposefully replacing the EtOH ligands in 1-7 with MeOH in 8-14. Direct-current magnetic susceptibility studies in the 2-300 K range reveal weak antiferromagnetic interactions for 3, 4, 7, 10, 11, and 14, and ferromagnetic interactions at low temperature for 5, 6, 12, and 13. Complexes 5 and 12 exhibit single-molecule magnet (SMM) behavior with energy barriers of 131.3 K for 5 and 198.8 K for 12. The energy barrier is significantly enhanced by dexterously regulating the terminal ligands. To rationalize the observed difference in the magnetic behavior, complete-active-space self-consistent field (CASSCF) calculations were performed on two Dy 2 complexes. Subtle variation in the angle between the magnetic axes and the vector connecting two dysprosium(III) ions results in a weaker influence on the tunneling gap of individual dysprosium(III) ions

Spontaneous Fission Barriers Based on a Generalized Liquid Drop Model

NASA Astrophysics Data System (ADS)

Guo, Shu-Qing; Bao, Xiao-Jun; Li, Jun-Qing; Zhang, Hong-Fei

2014-05-01

The barrier against the spontaneous fission has been determined within the Generalized Liquid Drop Model (GLDM) including the mass and charge asymmetry, and the proximity energy. The shell correction of the spherical parent nucleus is calculated by using the Strutinsky method, and the empirical shape-dependent shell correction is employed during the deformation process. A quasi-molecular shape sequence has been defined to describe the whole process from one-body shape to two-body shape system, and a two-touching-ellipsoid is adopted when the superdeformed one-body system reaches the rupture point. On these bases the spontaneous fission barriers are systematically studied for nuclei from 230Th to 249Cm for different possible exiting channels with the different mass and charge asymmetries. The double, and triple bumps are found in the fission potential energy in this region, which roughly agree with the experimental results. It is found that at around Sn-like fragment the outer fission barriers are lower, while the partner of the Sn-like fragment is in the range near 108Ru where the ground-state mass is lowered by allowing axially symmetric shapes. The preferable fission channels are distinctly pronounced, which should be corresponding to the fragment mass distributions.

Circularly polarized antennas for active holographic imaging through barriers

DOEpatents

McMakin, Douglas L [Richland, WA; Severtsen, Ronald H [Richland, WA; Lechelt, Wayne M [West Richland, WA; Prince, James M [Kennewick, WA

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.

Technical Report: Installed Cost Benchmarks and Deployment Barriers for

Science.gov Websites

Cost Benchmarks and Deployment Barriers for Residential Solar Photovoltaics with Energy Storage Q1 2016 Installed Cost Benchmarks and Deployment Barriers for Residential Solar with Energy Storage Researchers from NREL published a report that provides detailed component and system-level cost breakdowns for

Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions

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

Rafalskyi, Dmytro; Aanesland, Ane; Dudin, Stanislav

2015-05-15

This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier createdmore » in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.« less

Measuring the continuity of diffusion barriers on porous films using γ-ray energy spectra of escaping positronium

NASA Astrophysics Data System (ADS)

Xu, Jun; Mills, Allen P.; Case, Carlye

2005-08-01

Diffusion barriers for capping porous low dielectric constant films are important for preventing metal migration into a semiconductor circuit. Using the fact that positrons implanted into a porous dielectric form ortho-positronium (o-Ps) copiously, Gidley et al. [D. W. Gidley, W. F. Frieze, T. L. Dull, J. Sun, A. F. Yee, C. V. Nguyen, and D. Y. Yoon, Appl. Phys. Lett. 76, 1282 (2000)], have been able to measure open area fractions as low as 10-5 in porous dielectric film barrier layers from the increase in the ortho-positronium lifetime and intensity associated with positronium escape into vacuum. We demonstrate that it is possible to obtain comparable sensitivities by measuring the gamma-ray energy spectrum of the escaping positronium.

Measuring the continuity of diffusion barriers on porous films using {gamma}-ray energy spectra of escaping positronium

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

Xu Jun; Mills, Allen P. Jr.; Case, Carlye

2005-08-01

Diffusion barriers for capping porous low dielectric constant films are important for preventing metal migration into a semiconductor circuit. Using the fact that positrons implanted into a porous dielectric form ortho-positronium (o-Ps) copiously, Gidley et al. [D. W. Gidley, W. F. Frieze, T. L. Dull, J. Sun, A. F. Yee, C. V. Nguyen, and D. Y. Yoon, Appl. Phys. Lett. 76, 1282 (2000)], have been able to measure open area fractions as low as 10{sup -5} in porous dielectric film barrier layers from the increase in the ortho-positronium lifetime and intensity associated with positronium escape into vacuum. We demonstrate thatmore » it is possible to obtain comparable sensitivities by measuring the gamma-ray energy spectrum of the escaping positronium.« less

Double Barriers and Magnetic Field in Bilayer Graphene

NASA Astrophysics Data System (ADS)

Redouani, Ilham; Jellal, Ahmed; Bahlouli, Hocine

2015-12-01

We study the transmission probability in an AB-stacked bilayer graphene of Dirac fermions scattered by a double-barrier structure in the presence of a magnetic field. We take into account the full four bands structure of the energy spectrum and use the suitable boundary conditions to determine the transmission probability. Our numerical results show that for energies higher than the interlayer coupling, four ways for transmission are possible while for energies less than the height of the barrier, Dirac fermions exhibit transmission resonances and only one transmission channel is available. We show that, for AB-stacked bilayer graphene, there is no Klein tunneling at normal incidence. We find that the transmission displays sharp peaks inside the transmission gap around the Dirac point within the barrier regions while they are absent around the Dirac point in the well region. The effect of the magnetic field, interlayer electrostatic potential, and various barrier geometry parameters on the transmission probabilities is also discussed.

Unified interatomic potential and energy barrier distributions for amorphous oxides.

PubMed

Trinastic, J P; Hamdan, R; Wu, Y; Zhang, L; Cheng, Hai-Ping

2013-10-21

Amorphous tantala, titania, and hafnia are important oxides for biomedical implants, optics, and gate insulators. Understanding the effects of oxide doping is crucial to optimize performance in these applications. However, no molecular dynamics potentials have been created to date that combine these and other oxides that would allow computational analyses of doping-dependent structural and mechanical properties. We report a novel set of computationally efficient, two-body potentials modeling van der Waals and covalent interactions that reproduce the structural and elastic properties of both pure and doped amorphous oxides. In addition, we demonstrate that the potential accurately produces energy barrier distributions for pure and doped samples. The distributions can be directly compared to experiment and used to calculate physical quantities such as internal friction to understand how doping affects material properties. Future analyses using these potentials will be of great value to determine optimal doping concentrations and material combinations for myriad material science applications.

Superluminal tunneling of a relativistic half-integer spin particle through a potential barrier

NASA Astrophysics Data System (ADS)

Nanni, Luca

2017-11-01

This paper investigates the problem of a relativistic Dirac half-integer spin free particle tunneling through a rectangular quantum-mechanical barrier. If the energy difference between the barrier and the particle is positive, and the barrier width is large enough, there is proof that the tunneling may be superluminal. For first spinor components of particle and antiparticle states, the tunneling is always superluminal regardless the barrier width. Conversely, the second spinor components of particle and antiparticle states may be either subluminal or superluminal depending on the barrier width. These results derive from studying the tunneling time in terms of phase time. For the first spinor components of particle and antiparticle states, it is always negative while for the second spinor components of particle and antiparticle states, it is always positive, whatever the height and width of the barrier. In total, the tunneling time always remains positive for particle states while it becomes negative for antiparticle ones. Furthermore, the phase time tends to zero, increasing the potential barrier both for particle and antiparticle states. This agrees with the interpretation of quantum tunneling that the Heisenberg uncertainty principle provides. This study's results are innovative with respect to those available in the literature. Moreover, they show that the superluminal behaviour of particles occurs in those processes with high-energy confinement.

Assessing theoretical uncertainties in fission barriers of superheavy nuclei

DOE PAGES

Agbemava, S. E.; Afanasjev, A. V.; Ray, D.; ...

2017-05-26

Here, theoretical uncertainties in the predictions of inner fission barrier heights in superheavy elements have been investigated in a systematic way for a set of state-of-the-art covariant energy density functionals which represent major classes of the functionals used in covariant density functional theory. They differ in basic model assumptions and fitting protocols. Both systematic and statistical uncertainties have been quantified where the former turn out to be larger. Systematic uncertainties are substantial in superheavy elements and their behavior as a function of proton and neutron numbers contains a large random component. The benchmarking of the functionals to the experimental datamore » on fission barriers in the actinides allows to reduce the systematic theoretical uncertainties for the inner fission barriers of unknown superheavy elements. However, even then they on average increase on moving away from the region where benchmarking has been performed. In addition, a comparison with the results of non-relativistic approaches is performed in order to define full systematic theoretical uncertainties over the state-of-the-art models. Even for the models benchmarked in the actinides, the difference in the inner fission barrier height of some superheavy elements reaches $5-6$ MeV. This uncertainty in the fission barrier heights will translate into huge (many tens of the orders of magnitude) uncertainties in the spontaneous fission half-lives.« less

Peierls-Nabarro barrier and protein loop propagation

NASA Astrophysics Data System (ADS)

Sieradzan, Adam K.; Niemi, Antti; Peng, Xubiao

2014-12-01

When a self-localized quasiparticle excitation propagates along a discrete one-dimensional lattice, it becomes subject to a dissipation that converts the kinetic energy into lattice vibrations. Eventually the kinetic energy no longer enables the excitation to cross over the minimum energy barrier between neighboring sites, and the excitation becomes localized within a lattice cell. In the case of a protein, the lattice structure consists of the Cα backbone. The self-localized quasiparticle excitation is the elemental building block of loops. It can be modeled by a kink that solves a variant of the discrete nonlinear Schrödinger equation. We study the propagation of such a kink in the case of the protein G related albumin-binding domain, using the united residue coarse-grained molecular-dynamics force field. We estimate the height of the energy barriers that the kink needs to cross over in order to propagate along the backbone lattice. We analyze how these barriers give rise to both stresses and reliefs, which control the kink movement. For this, we deform a natively folded protein structure by parallel translating the kink along the backbone away from its native position. We release the transposed kink, and we follow how it propagates along the backbone toward the native location. We observe that the dissipative forces that are exerted on the kink by the various energy barriers have a pivotal role in determining how a protein folds toward its native state.

Reducing Barriers To The Use of High-Efficiency Lighting Systems

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

Peter Morante

2005-12-31

With funding from the U.S. Department of Energy (DOE), the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute completed the four-year research project, Reducing Barriers to the Use of High-Efficiency Lighting Systems. The initial objectives were: (1) identifying barriers to widespread penetration of lighting controls in commercial/industrial (C/I) applications that employ fluorescent lamp technologies, and (2) making recommendations to overcome these barriers. The addition of a fourth year expanded the original project objectives to include an examination of the impact on fluorescent lamps from dimming utilizing different lamp electrode heating and dimming ratios. The scope of the project was narrowedmore » to identify barriers to the penetration of lighting controls into commercial-industrial (C/I) applications that employ fluorescent lamp technologies, and to recommend means for overcoming these barriers. Working with lighting manufacturers, specifiers, and installers, the project identified technological and marketing barriers to the widespread use of lighting controls, specifically automatic-off controls, occupancy sensors, photosensors, dimming systems, communication protocols and load-shedding ballasts. The primary barriers identified include cost effectiveness of lighting controls to the building owner, lack of standard communication protocols to allow different part of the control system to communicate effectively, and installation and commissioning issues. Overcoming the identified barriers requires lighting control products on the market to achieve three main goals: (1) Achieve sufficient functionality to meet the key requirements of their main market. (2) Allow significant cost reduction compared to current market standard systems. Cost should consider: hardware capital cost including wiring, design time required by the specifier and the control system manufacturer, installation time required by the electrician, and commissioning time

Hierarchical structure of the energy landscape of proteins revisited by time series analysis. I. Mimicking protein dynamics in different time scales

NASA Astrophysics Data System (ADS)

Alakent, Burak; Camurdan, Mehmet C.; Doruker, Pemra

2005-10-01

Time series models, which are constructed from the projections of the molecular-dynamics (MD) runs on principal components (modes), are used to mimic the dynamics of two proteins: tendamistat and immunity protein of colicin E7 (ImmE7). Four independent MD runs of tendamistat and three independent runs of ImmE7 protein in vacuum are used to investigate the energy landscapes of these proteins. It is found that mean-square displacements of residues along the modes in different time scales can be mimicked by time series models, which are utilized in dividing protein dynamics into different regimes with respect to the dominating motion type. The first two regimes constitute the dominance of intraminimum motions during the first 5ps and the random walk motion in a hierarchically higher-level energy minimum, which comprise the initial time period of the trajectories up to 20-40ps for tendamistat and 80-120ps for ImmE7. These are also the time ranges within which the linear nonstationary time series are completely satisfactory in explaining protein dynamics. Encountering energy barriers enclosing higher-level energy minima constrains the random walk motion of the proteins, and pseudorelaxation processes at different levels of minima are detected in tendamistat, depending on the sampling window size. Correlation (relaxation) times of 30-40ps and 150-200ps are detected for two energy envelopes of successive levels for tendamistat, which gives an overall idea about the hierarchical structure of the energy landscape. However, it should be stressed that correlation times of the modes are highly variable with respect to conformational subspaces and sampling window sizes, indicating the absence of an actual relaxation. The random-walk step sizes and the time length of the second regime are used to illuminate an important difference between the dynamics of the two proteins, which cannot be clarified by the investigation of relaxation times alone: ImmE7 has lower-energy barriers

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…

Buckling of thermally fluctuating spherical shells: Parameter renormalization and thermally activated barrier crossing

NASA Astrophysics Data System (ADS)

Baumgarten, Lorenz; Kierfeld, Jan

2018-05-01

We study the influence of thermal fluctuations on the buckling behavior of thin elastic capsules with spherical rest shape. Above a critical uniform pressure, an elastic capsule becomes mechanically unstable and spontaneously buckles into a shape with an axisymmetric dimple. Thermal fluctuations affect the buckling instability by two mechanisms. On the one hand, thermal fluctuations can renormalize the capsule's elastic properties and its pressure because of anharmonic couplings between normal displacement modes of different wavelengths. This effectively lowers its critical buckling pressure [Košmrlj and Nelson, Phys. Rev. X 7, 011002 (2017), 10.1103/PhysRevX.7.011002]. On the other hand, buckled shapes are energetically favorable already at pressures below the classical buckling pressure. At these pressures, however, buckling requires to overcome an energy barrier, which only vanishes at the critical buckling pressure. In the presence of thermal fluctuations, the capsule can spontaneously overcome an energy barrier of the order of the thermal energy by thermal activation already at pressures below the critical buckling pressure. We revisit parameter renormalization by thermal fluctuations and formulate a buckling criterion based on scale-dependent renormalized parameters to obtain a temperature-dependent critical buckling pressure. Then we quantify the pressure-dependent energy barrier for buckling below the critical buckling pressure using numerical energy minimization and analytical arguments. This allows us to obtain the temperature-dependent critical pressure for buckling by thermal activation over this energy barrier. Remarkably, both parameter renormalization and thermal activation lead to the same parameter dependence of the critical buckling pressure on temperature, capsule radius and thickness, and Young's modulus. Finally, we study the combined effect of parameter renormalization and thermal activation by using renormalized parameters for the energy

Fusion of 48Ti+58Fe and 58Ni+54Fe below the Coulomb barrier

NASA Astrophysics Data System (ADS)

Stefanini, A. M.; Montagnoli, G.; Corradi, L.; Courtin, S.; Bourgin, D.; Fioretto, E.; Goasduff, A.; Grebosz, J.; Haas, F.; Mazzocco, M.; Mijatović, T.; Montanari, D.; Pagliaroli, M.; Parascandolo, C.; Scarlassara, F.; Strano, E.; Szilner, S.; Toniolo, N.; Torresi, D.

2015-12-01

Background: No data on the fusion excitation function of 48Ti+58Fe in the energy region near the Coulomb barrier existed prior to the present work, while fusion of 58Ni+54Fe was investigated in detail some years ago, down to very low energies, and clear evidence of fusion hindrance was noticed at relatively high cross sections. 48Ti and 58Fe are soft and have a low-lying quadrupole excitation lying at ≈800 -900 keV only. Instead, 58Ni and 54Fe have a closed shell (protons and neutrons, respectively) and are rather rigid. Purpose: We aim to investigate (1) the possible influence of the different structures of the involved nuclei on the fusion excitation functions far below the barrier and, in particular, (2) whether hindrance is observed in 48Ti+58Fe , and to compare the results with current coupled-channels models. Methods: 48Ti beams from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro were used. The experimental setup was based on an electrostatic beam separator, and fusion-evaporation residues (ERs) were detected at very forward angles. Angular distributions of ERs were measured. Results: Fusion cross sections of 48Ti+58Fe have been obtained in a range of nearly six orders of magnitude around the Coulomb barrier, down to σ ≃2 μ b . The sub-barrier cross sections of 48Ti+58Fe are much larger than those of 58Ni+54Fe . Significant differences are also observed in the logarithmic derivatives and astrophysical S factors. No evidence of hindrance is observed, because coupled-channels calculations using a standard Woods-Saxon potential are able to reproduce the data in the whole measured energy range. Analogous calculations for 58Ni+54Fe predict clearly too large cross sections at low energies. The two fusion barrier distributions are wide and display a complex structure that is only qualitatively fit by calculations. Conclusions: It is pointed out that all these different trends originate from the dissimilar low-energy nuclear structures of

A multilayer ΔE-E R telescope for breakup reactions at energies around the Coulomb barrier

NASA Astrophysics Data System (ADS)

Ma, Nan-Ru; Lin, Cheng-Jian; Wang, Jian-Song; Yang, Lei; Wang, Dong-Xi; Zheng, Lei; Xu, Shi-Wei; Sun, Li-Jie; Jia, Hui-Ming; Ma, Jun-Bing; Ma, Peng; Jin, Shi-Lun; Bai, Zhen; Yang, Yan-Yun; Xu, Xin-Xing; Zhang, Gao-Long; Yang, Feng; He, Jian-Jun; Zhang, Huan-Qiao; Liu, Zu-Hua

2016-11-01

The breakup reactions of weakly-bound nuclei at energies around the Coulomb barrier and the corresponding coupling effect on the other reaction channels are hot topics nowadays. To overcome the difficulty in identifying both heavier and lighter fragments simultaneously, a new kind of ionization-chamber based detector telescope has been designed and manufactured. It consists of a PCB ionization chamber and three different thickness silicon detectors installed inside the chamber, which form a multilayer ΔE-E R telescope. The working conditions were surveyed by using an α source. An in-beam test experiment shows that the detector has good particle identification for heavy particles like 17F and 16O as well as light particles like protons and alpha particles. The measured quasi-elastic scattering angular distribution and the related discussions for 17F+208Pb are presented. Supported by National Key Basic Research Development Program of China (2013CB834404) and National Natural Science Foundation of China (11375268, 11475263, U1432127, U1432246).

Material Barriers to Diffusive Mixing

NASA Astrophysics Data System (ADS)

Haller, George; Karrasch, Daniel

2017-11-01

Transport barriers, as zero-flux surfaces, are ill-defined in purely advective mixing in which the flux of any passive scalar is zero through all material surfaces. For this reason, Lagrangian Coherent Structures (LCSs) have been argued to play the role of mixing barriers as most repelling, attracting or shearing material lines. These three kinematic concepts, however, can also be defined in different ways, both within rigorous mathematical treatments and within the realm of heuristic diagnostics. This has lead to a an ever-growing number of different LCS methods, each generally identifying different objects as transport barriers. In this talk, we examine which of these methods have actual relevance for diffusive transport barriers. The latter barriers are arguably the practically relevant inhibitors in the mixing of physically relevant tracers, such as temperature, salinity, vorticity or potential vorticity. We demonstrate the role of the most effective diffusion barriers in analytical examples and observational data. Supported in part by the DFG Priority Program on Turbulent Superstructures.

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

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

DOE PAGES

Ramirez-Cuesta, Anibal J.

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)(2)CH2}(2)Pd2H][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 formore » 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.« less

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

PubMed

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

2016-09-07

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.

Steeplechase barriers affect women less than men.

PubMed

Hunter, Iain; Bushnell, Tyler D

2006-01-01

Women began contesting the 3000 m steeplechase during the 1990's using barriers of different dimensions than men. Whenever a new event is introduced for women, consideration should be taken as to whether different technique or training methods should be utilized. This study investigated three aspects of hurdling technique: 1) Differences in the ratio of the landing step to the penultimate step between men and women around each non-water jump steeplechase barrier, 2) differences in step lengths between the four non-water jump barriers, and 3) changes in the step lengths around the barrier throughout the race. The step lengths around the 28 non-water jump barriers of the top seven men and women at the 2003 USA Track and Field Championships were measured using a two-dimensional analysis. A t-test determined any differences between men and women for the ratio of the landing to penultimate steps. A 2x4 repeated measures ANOVA tested for differences between the four non-water jump barriers. Linear regression tested for changes in step lengths throughout the race. Men exhibited a smaller ratio between the lengths of the landing to penultimate steps than women (0.73 ± 0.09 and 0.77 ± 0.10 for men and women respectively, p = 0.002). No step length differences were observed between the four barriers in the step lengths around each barrier (p = 0.192 and p = 0.105 for men and women respectively). Athletes gradually increased the total length of all steps around the barriers throughout the race (R(2) = 0.021, p = 0.048 and R(2) = 0.137, p < 0.001 for men and women respectively). The smaller ratio between landing to penultimate steps shows that the barriers affect women less than men. There may be a need to train men and women differently for the non-water jump barriers in the steeplechase or slightly alter racing strategy. Key PointsNon-water jump barriers disrupt the stride of men more than women.There is no difference between any of the four non-water jump barriers in the

An overview of near-barrier fusion studies with stable beams

NASA Astrophysics Data System (ADS)

Trotta, M.; Stefanini, A. M.; Beghini, S.; Behera, B. R.; Corradi, L.; Fioretto, E.; Gadea, A.; Itkis, M. G.; Knyazheva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Mărginean, N.; Mason, P.; Montagnoli, G.; Pokrovsky, I. V.; Sagaidak, R. N.; Scarlassara, F.; Silvestri, R.; Szilner, S.

2007-05-01

An overview of results in fusion studies with stable beams spanning different mass regions and energy ranges is presented. The advantages offered by studying channel coupling effects, involving low-lying excited states of the colliding nuclei, as well as the difficulties in understanding the influence of transfer couplings on fusion, are firstly remarked. The competition of fusion with quasi-fission in heavy systems and the unexpected steep falloff of fusion cross sections at far sub-barrier energies are finally discussed.

Interdependence of different symmetry energy elements

NASA Astrophysics Data System (ADS)

Mondal, C.; Agrawal, B. K.; De, J. N.; Samaddar, S. K.; Centelles, M.; Viñas, X.

2017-08-01

Relations between the nuclear symmetry energy coefficient and its density derivatives are derived. The relations hold for a class of interactions with quadratic momentum dependence and a power-law density dependence. The structural connection between the different symmetry energy elements as obtained seems to be followed by almost all reasonable nuclear energy density functionals, both relativistic and nonrelativistic, suggesting a universality in the correlation structure. This, coupled with known values of some well-accepted constants related to nuclear matter, helps in constraining values of different density derivatives of the nuclear symmetry energy, shedding light on the isovector part of the nuclear interaction.

Examining the role of transfer coupling in sub-barrier fusion of Ti 46 , 50 + Sn 124

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

Liang, J. Felix; Allmond, J. M.; Gross, C. J.

2016-08-24

In this study, the presence of neutron transfer channels with positive Q values can enhance sub-barrier fusion cross sections. Recent measurements of the fusion excitation functions for 58Ni+ 132,124Sn found that the fusion enhancement due to the influence of neutron transfer is smaller than that in 40Ca + 132,124Sn although the Q values for multineutron transfer are comparable. The purpose of this study is to investigate the differences observed between the fusion of Sn + Ni and Sn + Ca. Methods: Fusion excitation functions for 46,50Ti + 124Sn have been measured at energies near the Coulomb barrier. As a result,more » a comparison of the barrier distributions for 46Ti+ 124Sn and 40Ca+ 124Sn shows that the 40Ca+ 124Sn system has a barrier strength resulting from the coupling to the very collective octupole state in 40Ca at an energy significantly lower than the uncoupled barrier. In conclusion, the large sub-barrier fusion enhancement in 40Ca induced reactions is attributed to both couplings to neutron transfer and inelastic excitation, with the octupole vibration of 40Ca playing a major role.« less

Systematic study of fission barriers of excited superheavy nuclei

NASA Astrophysics Data System (ADS)

Sheikh, J. A.; Nazarewicz, W.; Pei, J. C.

2009-07-01

A systematic study of fission-barrier dependence on excitation energy has been performed using the self-consistent finite-temperature Hartree-Fock + BCS (FT-HF + BCS) formalism with the SkM* Skyrme energy density functional. The calculations have been carried out for even-even superheavy nuclei with Z ranging between 110 and 124. For an accurate description of fission pathways, the effects of triaxial and reflection-asymmetric degrees of freedom have been fully incorporated. Our survey demonstrates that the dependence of isentropic fission barriers on excitation energy changes rapidly with particle number, pointing to the importance of shell effects even at large excitation energies characteristic of compound nuclei. The fastest decrease of fission barriers with excitation energy is predicted for deformed nuclei around N=164 and spherical nuclei around N=184 that are strongly stabilized by ground-state shell effects. For the nuclei Pu240 and Fm256, which exhibit asymmetric spontaneous fission, our calculations predict a transition to symmetric fission at high excitation energies owing to the thermal quenching of static reflection asymmetric deformations.

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.

Diabat Interpolation for Polymorph Free-Energy Differences.

PubMed

Kamat, Kartik; Peters, Baron

2017-02-02

Existing methods to compute free-energy differences between polymorphs use harmonic approximations, advanced non-Boltzmann bias sampling techniques, and/or multistage free-energy perturbations. This work demonstrates how Bennett's diabat interpolation method ( J. Comput. Phys. 1976, 22, 245 ) can be combined with energy gaps from lattice-switch Monte Carlo techniques ( Phys. Rev. E 2000, 61, 906 ) to swiftly estimate polymorph free-energy differences. The new method requires only two unbiased molecular dynamics simulations, one for each polymorph. To illustrate the new method, we compute the free-energy difference between face-centered cubic and body-centered cubic polymorphs for a Gaussian core solid. We discuss the justification for parabolic models of the free-energy diabats and similarities to methods that have been used in studies of electron transfer.

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…

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.

High Interfacial Barriers at Narrow Carbon Nanotube-Water Interfaces.

PubMed

Varanasi, Srinivasa Rao; Subramanian, Yashonath; Bhatia, Suresh K

2018-06-26

Water displays anomalous fast diffusion in narrow carbon nanotubes (CNTs), a behavior that has been reproduced in both experimental and simulation studies. However, little is reported on the effect of bulk water-CNT interfaces, which is critical to exploiting the fast transport of water across narrow carbon nanotubes in actual applications. Using molecular dynamics simulations, we investigate here the effect of such interfaces on the transport of water across arm-chair CNTs of different diameters. Our results demonstrate that diffusion of water is significantly retarded in narrow CNTs due to bulk regions near the pore entrance. The slowdown of dynamics can be attributed to the presence of large energy barriers at bulk water-CNT interfaces. The presence of such intense barriers at the bulk-CNT interface arises due to the entropy contrast between the bulk and confined regions, with water molecules undergoing high translational and rotational entropy gain on entering from the bulk to the CNT interior. The intensity of such energy barriers decreases with increase in CNT diameter. These results are very important for emerging technological applications of CNTs and other nanoscale materials, such as in nanofluidics, water purification, nanofiltration, and desalination, as well as for biological transport processes.

Tunneling effect on double potential barriers GaAs and PbS

NASA Astrophysics Data System (ADS)

Prastowo, S. H. B.; Supriadi, B.; Ridlo, Z. R.; Prihandono, T.

2018-04-01

A simple model of transport phenomenon tunnelling effect through double barrier structure was developed. In this research we concentrate on the variation of electron energy which entering double potential barriers to transmission coefficient. The barriers using semiconductor materials GaAs (Galium Arsenide) with band-gap energy 1.424 eV, distance of lattice 0.565 nm, and PbS (Lead Sulphide) with band gap energy 0.41 eV distance of lattice is 18 nm. The Analysisof tunnelling effect on double potentials GaAs and PbS using Schrodinger’s equation, continuity, and matrix propagation to get transmission coefficient. The maximum energy of electron that we use is 1.0 eV, and observable from 0.0025 eV- 1.0 eV. The shows the highest transmission coefficient is0.9982 from electron energy 0.5123eV means electron can pass the barriers with probability 99.82%. Semiconductor from materials GaAs and PbS is one of selected material to design semiconductor device because of transmission coefficient directly proportional to bias the voltage of semiconductor device. Application of the theoretical analysis of resonant tunnelling effect on double barriers was used to design and develop new structure and combination of materials for semiconductor device (diode, transistor, and integrated circuit).

Breast cancer awareness and barriers to symptomatic presentation among women from different ethnic groups in East London

PubMed Central

Forbes, L J L; Atkins, L; Thurnham, A; Layburn, J; Haste, F; Ramirez, A J

2011-01-01

Background: During 2001 to 2005, 1-year breast cancer survival was low in ethnically diverse East London. We hypothesised that this was due to low breast cancer awareness and barriers to symptomatic presentation, leading to late stage at diagnosis in women from ethnic minorities. We examined ethnic differences in breast cancer awareness and barriers to symptomatic presentation in East London. Methods: We carried out a population-based survey of 1515 women aged 30+ using the Cancer Research UK Breast Cancer Awareness Measure. We analysed the data using logistic regression adjusting for age group and level of deprivation. Results: South Asian and black women had lower breast cancer awareness than white women. South Asian women, but not black women, reported more emotional barriers to seeking medical help than white women. White women were more likely than non-white women to report worry about wasting the doctor's time as a barrier to symptomatic presentation. Conclusion: Interventions to promote early presentation of breast cancer for South Asian and black women should promote knowledge of symptoms and skills to detect changes, and tackle emotional barriers to symptomatic presentation and for white women tackle the idea that going to the doctor to discuss a breast symptom will waste the doctor's time. PMID:21989188

A new DFT functional based on spin-states and SN2 barriers

NASA Astrophysics Data System (ADS)

Swart, M.; Solà, M.; Bickelhaupt, F. M.

2012-12-01

We recently reported a study into what causes the dramatic differences between OPBE and PBE for reaction barriers, spin-state energies, hydrogen-bonding and π-π stacking energies.1 It was achieved by smoothly switching from OPBE to PBE at a predefined point P of the reduced density gradient s. By letting the point P run as function of the reduced density gradient s, with values from s=0.1 to s=10, we could determine which part of the exchange functional determines its behavior for the different interactions. Based on the thus obtained results, we created a new exchange functional that showed the good results of OPBE for reaction barriers and spin-state energies, and combined it with the good (H-bonds) and reasonable (π-stacking) results of PBE for weak interactions. In other words, it combined the best of OPBE with the best of PBE. Encouraged by these good results, we have further improved the new exchange functional and fine-tuned its parameters.2 Similar to the switched functional from ref. 1, our new SSB functional2 works well for SN2 barriers (see e.g. ref. 3), spin states and H-bonding interactions. Moreover, by including Grimme's dispersion corrections4,5 (to give our final SSB-D functional) it also works well for π-π stacking interactions.2 In summary, we have constructed a new GGA exchange functional that when combined with the sPBE correlation functional6 gives the correct spin ground-state of iron complexes, and small deviations for SN2 barriers (2.7 kcalṡmol-1), geometries (0.005 Å), Hbond distances (0.012 Å), weak interactions (S22 set, 0.5 kcalṡmol-1), and transition-metal ligand distances (0.008 Å).

Racial differences in barriers to blood pressure control in a family practice setting.

PubMed

Scott, Jonathan M; Spees, Colleen K; Taylor, Christopher A; Wexler, Randy

2010-10-01

Hypertension prevalence in the African American community is greater than in all other ethnic groups. Cultural perceptions of health and disease introduce barriers to providing effective care. The purpose of this study was to identify racial differences in the perceived causes of hypertension, current behaviors performed to control blood pressure, and perceived barriers to preventing or treating hypertension. A self-administered survey of patients seen for medical care in a primary care network was conducted. The survey was developed to measure perceptions of hypertension etiology and treatments. Data from African American (n = 69) and Caucasian (n = 218) respondents were used to assess racial differences in perceptions of blood pressure control. About half of respondents knew their current blood pressures. African American patients were significantly less likely to believe that hypertension was caused by a lack of exercise and obesity. Significantly more Caucasians were less likely to report cutting down on table salt and taking prescription medications for blood pressure control. Both African Americans and Caucasians believed that sodium reduction was the most easily changed behavior to control their blood pressure, while both groups identified weight loss as being the most difficult. Racial differences exist in the perceived causes and treatments of high blood pressure, indicating a need for further patient education. When treating and counseling patients, physicians and support staff members must be sensitive to racial diversity and strive to offer culturally relevant solutions, especially for behaviors perceived as most difficult to change.

Effect of a gap opening on the conductance of graphene with magnetic barrier structures

NASA Astrophysics Data System (ADS)

Esmailpour, Mohammad

2018-04-01

In the present study Klein tunneling in a single-layer gapped graphene was investigated by transfer matrix method under normal magnetic field for one and two magnetic barriers. Calculations show that electron transmission through a magnetic barrier is deflected to positive angles and reduces as the magnitude of magnetic field and especially the energy gap increases. This reduction is even more significant in larger fields so that after reaching a specific value of energy gap, an effective confinement for fermions and suppression of Klein tunneling is reached particularly in normal incidence and the conductance becomes zero. Unlike one barrier, the process of tunneling through two magnetic barriers induces symmetric transmission probability versus the incident angle; even, for lower energy gaps, electron transmission probability increases which in turn reduces total conductance via proper changes in the value of the magnetic field and energy gap. In general, it is concluded that confining electrons in asymmetric transmission through one barrier is conducted better than two barriers.

Gas Diffusion Barriers Prepared by Spatial Atmospheric Pressure Plasma Enhanced ALD.

PubMed

Hoffmann, Lukas; Theirich, Detlef; Pack, Sven; Kocak, Firat; Schlamm, Daniel; Hasselmann, Tim; Fahl, Henry; Räupke, André; Gargouri, Hassan; Riedl, Thomas

2017-02-01

In this work, we report on aluminum oxide (Al 2 O 3 ) gas permeation barriers prepared by spatial ALD (SALD) at atmospheric pressure. We compare the growth characteristics and layer properties using trimethylaluminum (TMA) in combination with an Ar/O 2 remote atmospheric pressure plasma for different substrate velocities and different temperatures. The resulting Al 2 O 3 films show ultralow water vapor transmission rates (WVTR) on the order of 10 -6 gm -2 d -1 . In notable contrast, plasma based layers already show good barrier properties at low deposition temperatures (75 °C), while water based processes require a growth temperature above 100 °C to achieve equally low WVTRs. The activation energy for the water permeation mechanism was determined to be 62 kJ/mol.

The Blood–Brain Barrier

PubMed Central

Daneman, Richard; Prat, Alexandre

2015-01-01

Blood vessels are critical to deliver oxygen and nutrients to all of the tissues and organs throughout the body. The blood vessels that vascularize the central nervous system (CNS) possess unique properties, termed the blood–brain barrier, which allow these vessels to tightly regulate the movement of ions, molecules, and cells between the blood and the brain. This precise control of CNS homeostasis allows for proper neuronal function and also protects the neural tissue from toxins and pathogens, and alterations of these barrier properties are an important component of pathology and progression of different neurological diseases. The physiological barrier is coordinated by a series of physical, transport, and metabolic properties possessed by the endothelial cells (ECs) that form the walls of the blood vessels, and these properties are regulated by interactions with different vascular, immune, and neural cells. Understanding how these different cell populations interact to regulate the barrier properties is essential for understanding how the brain functions during health and disease. PMID:25561720

Dynamics of 17F + 58Ni reaction via complete and incomplete fusion processes at above barrier energies

NASA Astrophysics Data System (ADS)

Grover, Neha; Sandhu, Kirandeep; Sharma, Manoj K.

2018-06-01

The dynamics of 17F + 58Ni reaction induced via a loosely bound projectile (17F) is examined using the collective clusterization approach of the dynamical cluster decay model (DCM) with respect to the recent experimental data available at beam energies Ebeam = 54.1 and 58.5 MeV. The calculations are done for quadrupole deformations of fragments using the optimum orientation approach. In view of the loosely bound nature of 17F, the main focus of the present work is on the comparison of complete and incomplete fusion. It is studied using various components such as fragmentation potential, mass distribution, and barrier modification. Different decay modes (ER, IMF, HMF, and fission) are also compared to determine the complete fusion and incomplete fusion paths. Additionally, the decay paths of the nucleus formed from loosely bound (17F) and tightly bound (16O) projectiles are compared. Furthermore, the role of temperature-dependent pairing strength is analyzed in terms of the binary fragmentation of the compound system formed.

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

NASA Astrophysics Data System (ADS)

Fergus, Jeffrey W.

2014-06-01

One of the important applications of yttria-stabilized zirconia (YSZ) is as a thermal barrier coating for gas turbine engines. While YSZ performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite-derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability, and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatings are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.

Differences between African-American and Caucasian students on enrollment influences and barriers in kinesiology-based allied health education programs.

PubMed

Barfield, J P; Cobler, D C; Lam, Eddie T C; Zhang, James; Chitiyo, George

2012-06-01

Kinesiology departments have recently started to offer allied health education programs to attract additional students to teacher education units (9). Although allied health professions offer increased work opportunities, insufficient enrollment and training of minority students in these academic fields contribute to underrepresentation in the workforce (3). To improve workforce diversity, kinesiology departments must understand how enrollment influences and barriers differ by race among prospective students. Therefore, the purpose of this study was to identify differences in allied health education enrollment influences and enrollment barriers between minority and Caucasian students. Participants (n = 601) consisted of students enrolled in kinesiology-based allied health education programs. Multivariate ANOVA was used to compare group differences in enrollment decision making. "Personal influence," "career opportunity," and "physical self-efficacy" were all significantly stronger enrollment influences among African-American students than among Caucasian students, and "social influence," "experiential opportunity," "academic preparation," and "physical self-efficacy" were all perceived as significantly greater barriers compared with Caucasian students. Findings support the need to recruit African-American students through sport and physical education settings and to market program-based experiential opportunities.

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

PubMed

Schotten, Sebastiaan; Meijer, Marieke; Walter, Alexander Matthias; Huson, Vincent; Mamer, Lauren; Kalogreades, Lawrence; ter Veer, Mirelle; Ruiter, Marvin; Brose, Nils; Rosenmund, Christian; Sørensen, Jakob Balslev; Verhage, Matthijs; Cornelisse, Lennart Niels

2015-04-14

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 Ca(2+)-dependent release.

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…

Near-barrier Fusion Evaporation and Fission of 28Si+174Yb and 32S+170Er

NASA Astrophysics Data System (ADS)

Wang, Dongxi; Lin, Chengjian; Jia, Huiming; Ma, Nanru; Sun, Lijie; Xu, Xinxing; Yang, Lei; Yang, Feng; Zhang, Huanqiao; Bao, Pengfei

2017-11-01

Fusion evaporation residues and fission fragments have been measured, respectively, at energies around the Coulomb barrier for the 28Si+174Yb and 32S+170Er systems forming the same compound nucleus 202Po. The excitation function of fusion evaporation, fission as well as capture reactions were deduced. Coupled-channels analyses reveal that couplings to the deformations of targets and the two-phonon states of projectiles contribute much to the enhancement of capture cross sections at sub-barrier energies. The mass and total kinetic energy of fission fragments were deduced by the time-difference method assuming full momentum transfer in a two-body kinematics. The mass-energy and mass-angle distributions were obtained and no obvious quasi-fission components were observed in this bombarding energy range. Further, mass distributions of fission fragments were fitted to extract their widths. Results show that the mass widths decrease monotonically with decreasing energy, but might start to increase when Ec.m./VB < 0.95 for both systems.

Elastic and inelastic scattering for the 10B+58Ni system at near-barrier energies

NASA Astrophysics Data System (ADS)

Scarduelli, V.; Crema, E.; Guimarães, V.; Abriola, D.; Arazi, A.; de Barbará, E.; Capurro, O. A.; Cardona, M. A.; Gallardo, J.; Hojman, D.; Martí, G. V.; Pacheco, A. J.; Rodrígues, D.; Yang, Y. Y.; Deshmukh, N. N.; Paes, B.; Lubian, J.; Mendes Junior, D. R.; Morcelle, V.; Monteiro, D. S.

2017-11-01

Full angular distributions of the 10B elastically and inelastically scattered by 58Ni have been measured at different energies around the Coulomb barrier. The elastic and inelastic scattering of 10B on a medium mass target has been measured for the first time. The obtained angular distributions have been analyzed in terms of large-scale coupled reaction channel calculations, where several inelastic transitions of the projectile and the target, as well as the most relevant one- and two-step transfer reactions have been included in the coupling matrix. The roles of the spin reorientation, the spin-orbit interaction, and the large ground-state deformation of the 10B, in the reaction mechanism, were also investigated. The real part of the interaction potential between projectile and target was represented by a parameter-free double-folding potential, whereas no imaginary potential at the surface was considered. In this sense, the theoretical calculations were parameter free and their results were compared to experimental data to investigate the relative importance of the different reaction channels. A striking influence of the ground-state spin reorientation of the 10B nucleus was found, while all transfer reactions investigated had a minimum contribution to the dynamics of the system. Finally, the large static deformation of the 10B and the spin-orbit coupling can also play an important role in the system studied.

Effectiveness of cable barriers, guardrails, and concrete barrier walls in reducing the risk of injury.

PubMed

Zou, Yaotian; Tarko, Andrew P; Chen, Erdong; Romero, Mario A

2014-11-01

Roadway departure crashes tend to be severe, especially when the roadside exposes the occupants of errant vehicles to excessive injury hazards. As a cost-effective method when the clear zone width is insufficient, road barriers are often installed to prevent errant vehicles from colliding with dangerous obstacles or traversing steep slopes. This paper focuses on the safety performance of road barriers in Indiana in reducing the risk of injury. The objective of the study presented here is to compare the risk of injury among different hazardous events faced by an occupant in a single-vehicle crash. The studied hazardous events include rolling over, striking three types of barriers (guardrails, concrete barrier walls, and cable barriers) with different barrier offsets to the edge of the travelled way, and striking various roadside objects. A total of 2124 single-vehicle crashes (3257 occupants) that occurred between 2008 and 2012 on 517 pair-matched homogeneous barrier and non-barrier segments were analyzed. A binary logistic regression model with mixed effects was estimated for vehicle occupants. The segment pairing process and the use of random effects were able to handle the commonality within the same segment pair as well as the heterogeneity across segment pairs. The modeling results revealed that hitting a barrier is associated with lower risk of injury than a high-hazard event (hitting a pole, rollover, etc.). The odds of injury are reduced by 39% for median concrete barrier walls offset 15-18ft from the travelled way, reduced by 65% for a guardrail face offset 5-55ft, reduced by 85% for near-side median cable barriers (offset between 10ft and 29ft), and reduced by 78% with far-side median cable barriers (offset at least 30ft). Comparing different types of barriers is useful where some types of barriers can be used alternatively. This study found that the odds of injury are 43% lower when striking a guardrail instead of a median concrete barrier offset 15-18ft

Surface pre-treatment for barrier coatings on polyethylene terephthalate

NASA Astrophysics Data System (ADS)

Bahre, H.; Bahroun, K.; Behm, H.; Steves, S.; Awakowicz, P.; Böke, M.; Hopmann, Ch; Winter, J.

2013-02-01

Polymers have favourable properties such as light weight, flexibility and transparency. Consequently, this makes them suitable for food packaging, organic light-emitting diodes and flexible solar cells. Nonetheless, raw plastics do not possess sufficient barrier functionality against oxygen and water vapour, which is of paramount importance for most applications. A widespread solution is to deposit thin silicon oxide layers using plasma processes. However, silicon oxide layers do not always fulfil the requirements concerning adhesion and barrier performance when deposited on films. Thus, plasma pre-treatment is often necessary. To analyse the influence of a plasma-based pre-treatment on barrier performance, different plasma pre-treatments on three reactor setups were applied to a very smooth polyethylene terephthalate film before depositing a silicon oxide barrier layer. In this paper, the influence of oxygen and argon plasma pre-treatments towards the barrier performance is discussed examining the chemical and topological change of the film. It was observed that a short one-to-ten-second plasma treatment can reduce the oxygen transmission rate by a factor of five. The surface chemistry and the surface topography change significantly for these short treatment times, leading to an increased surface energy. The surface roughness rises slowly due to the development of small spots in the nanometre range. For very long treatment times, surface roughness of the order of the barrier layer's thickness results in a complete loss of barrier properties. During plasma pre-treatment, the trade-off between surface activation and roughening of the surface has to be carefully considered.

Computing the Free Energy Barriers for Less by Sampling with a Coarse Reference Potential while Retaining Accuracy of the Target Fine Model.

PubMed

Plotnikov, Nikolay V

2014-08-12

Proposed in this contribution is a protocol for calculating fine-physics (e.g., ab initio QM/MM) free-energy surfaces at a high level of accuracy locally (e.g., only at reactants and at the transition state for computing the activation barrier) from targeted fine-physics sampling and extensive exploratory coarse-physics sampling. The full free-energy surface is still computed but at a lower level of accuracy from coarse-physics sampling. The method is analytically derived in terms of the umbrella sampling and the free-energy perturbation methods which are combined with the thermodynamic cycle and the targeted sampling strategy of the paradynamics approach. The algorithm starts by computing low-accuracy fine-physics free-energy surfaces from the coarse-physics sampling in order to identify the reaction path and to select regions for targeted sampling. Thus, the algorithm does not rely on the coarse-physics minimum free-energy reaction path. Next, segments of high-accuracy free-energy surface are computed locally at selected regions from the targeted fine-physics sampling and are positioned relative to the coarse-physics free-energy shifts. The positioning is done by averaging the free-energy perturbations computed with multistep linear response approximation method. This method is analytically shown to provide results of the thermodynamic integration and the free-energy interpolation methods, while being extremely simple in implementation. Incorporating the metadynamics sampling to the algorithm is also briefly outlined. The application is demonstrated by calculating the B3LYP//6-31G*/MM free-energy barrier for an enzymatic reaction using a semiempirical PM6/MM reference potential. These modifications allow computing the activation free energies at a significantly reduced computational cost but at the same level of accuracy compared to computing full potential of mean force.

Computing the Free Energy Barriers for Less by Sampling with a Coarse Reference Potential while Retaining Accuracy of the Target Fine Model

PubMed Central

2015-01-01

Proposed in this contribution is a protocol for calculating fine-physics (e.g., ab initio QM/MM) free-energy surfaces at a high level of accuracy locally (e.g., only at reactants and at the transition state for computing the activation barrier) from targeted fine-physics sampling and extensive exploratory coarse-physics sampling. The full free-energy surface is still computed but at a lower level of accuracy from coarse-physics sampling. The method is analytically derived in terms of the umbrella sampling and the free-energy perturbation methods which are combined with the thermodynamic cycle and the targeted sampling strategy of the paradynamics approach. The algorithm starts by computing low-accuracy fine-physics free-energy surfaces from the coarse-physics sampling in order to identify the reaction path and to select regions for targeted sampling. Thus, the algorithm does not rely on the coarse-physics minimum free-energy reaction path. Next, segments of high-accuracy free-energy surface are computed locally at selected regions from the targeted fine-physics sampling and are positioned relative to the coarse-physics free-energy shifts. The positioning is done by averaging the free-energy perturbations computed with multistep linear response approximation method. This method is analytically shown to provide results of the thermodynamic integration and the free-energy interpolation methods, while being extremely simple in implementation. Incorporating the metadynamics sampling to the algorithm is also briefly outlined. The application is demonstrated by calculating the B3LYP//6-31G*/MM free-energy barrier for an enzymatic reaction using a semiempirical PM6/MM reference potential. These modifications allow computing the activation free energies at a significantly reduced computational cost but at the same level of accuracy compared to computing full potential of mean force. PMID:25136268

Electronic tunneling through a potential barrier on the surface of a topological insulator

NASA Astrophysics Data System (ADS)

Zhou, Benliang; Zhou, Benhu; Zhou, Guanghui

2016-12-01

We investigate the tunneling transport for electrons on the surface of a topological insulator (TI) through an electrostatic potential barrier. By using the Dirac equation with the continuity conditions for all segments of wave functions at the interfaces between regions inside and outside the barrier, we calculate analytically the transmission probability and conductance for the system. It is demonstrated that, the Klein paradox can also been observed in the system same as in graphene system. Interestingly, the conductance reaches the minimum value when the incident electron energy is equal to the barrier strength. Moreover, with increasing barrier width, the conductance turns up some tunneling oscillation peaks, and larger barrier strength can cause lower conductance, shorter period but larger oscillation amplitude. The oscillation amplitude decreases as the barrier width increases, which is similar as that of the system consisting of the compressive uniaxial strain applied on a TI, but somewhat different from that of graphene system where the oscillation amplitude is a constant. The findings here imply that an electrostatic barrier can greatly influence the electron tunneling transport of the system, and may provide a new way to realize directional filtering of electrons.

Isogenic blood-brain barrier models based on patient-derived stem cells display inter-individual differences in cell maturation and functionality.

PubMed

Patel, Ronak; Page, Shyanne; Al-Ahmad, Abraham Jacob

2017-07-01

The blood-brain barrier (BBB) constitutes an important component of the neurovascular unit formed by specialized brain microvascular endothelial cells (BMECs) surrounded by astrocytes, pericytes, and neurons. Recently, isogenic in vitro models of the BBB based on human pluripotent stem cells have been documented, yet the impact of inter-individual variability on the yield and phenotype of such models remains to be documented. In this study, we investigated the impact of inter-individual variability on the yield and phenotype of isogenic models of the BBB, using patient-derived induced pluripotent stem cells (iPSCs). Astrocytes, BMECs, and neurons were differentiated from four asymptomatic patient-derived iPSCs (two males, two females). We differentiated such cells using existing differentiation protocols and quantified expression of cell lineage markers, as well as BBB phenotype, barrier induction, and formation of neurite processes. iPSC-derived BMECs showed barrier properties better than hCMEC/D3 monolayers; however, we noted differences in the expression and activity among iPSC lines. In addition, we noted differences in the differentiation efficiency of these cells into neural stem cells and progenitor cells (as noted by differences in expression of cell lineage markers). Such differences were reflected later in the terminal differentiation, as seen as ability to induce barrier function and to form neurite processes. Although we demonstrated our ability to obtain an isogenic model of the BBB with different patients' iPSCs, we also noted subtle differences in the expression of cell lineage markers and cell maturation processes, suggesting the presence of inter-individual polymorphisms. © 2017 International Society for Neurochemistry.

Performance of two differently designed permeable reactive barriers with sulfate and zinc solutions.

PubMed

Pérez, Norma; Schwarz, Alex O; Barahona, Esteban; Sanhueza, Pamela; Diaz, Isabel; Urrutia, Homero

2018-06-18

For the first time, this laboratory-scale study evaluates the feasibility of incorporating diffusive exchange in permeable reactive barriers. In order to do this, the performance of two permeable reactive barriers (PRB) with different internal substrate arrangements were compared during the administration of a sulfate solution without metals (for 163 days) and with metals (for 60 days), simulating groundwater contaminated with acid mine drainage (AMD). In order to simulate a traditional PRB, a homogeneous distribution was implemented in the first reactor and the other PRB reactor utilized diffusion-active technology (DAPRB). In the DAPRB, the distribution of the reactive material was interspersed with the conductive material. The measurements in the internal ports showed that transverse gradients of sulfide formed in the DAPRB, causing the diffusion of sulfide from the substrate toward the layer interface, which is where the sulfide reacts by forming complexes with the metal. The DAPRB prevents the microorganisms from direct contact with AMD. This protection caused greater activity (sulfide production). Copyright © 2018 Elsevier B.V. All rights reserved.

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

A comparison of freeway median crash frequency, severity, and barrier strike outcomes by median barrier type.

PubMed

Russo, Brendan J; Savolainen, Peter T

2018-08-01

Median-crossover crashes are among the most hazardous events that can occur on freeways, often resulting in severe or fatal injuries. The primary countermeasure to reduce the occurrence of such crashes is the installation of a median barrier. When installation of a median barrier is warranted, transportation agencies are faced with the decision among various alternatives including concrete barriers, beam guardrail, or high-tension cable barriers. Each barrier type differs in terms of its deflection characteristics upon impact, the required installation and maintenance costs, and the roadway characteristics (e.g., median width) where installation would be feasible. This study involved an investigation of barrier performance through an in-depth analysis of crash frequency and severity data from freeway segments where high-tension cable, thrie-beam, and concrete median barriers were installed. A comprehensive manual review of crash reports was conducted to identify crashes in which a vehicle left the roadway and encroached into the median. This review also involved an examination of crash outcomes when a barrier strike occurred, which included vehicle containment, penetration, or re-direction onto the travel lanes. The manual review of crash reports provided critical supplementary information through narratives and diagrams not normally available through standard fields on police crash report forms. Statistical models were estimated to identify factors that affect the frequency, severity, and outcomes of median-related crashes, with particular emphases on differences between segments with varying median barrier types. Several roadway-, traffic-, and environmental-related characteristics were found to affect these metrics, with results varying across the different barrier types. The results of this study provide transportation agencies with important guidance as to the in-service performance of various types of median barrier. Copyright © 2018 Elsevier Ltd. All rights

Determination of the Rotational Barrier in Ethane by Vibrational Spectroscopy and Statistical Thermodynamics

ERIC Educational Resources Information Center

Ercolani, Gianfranco

2005-01-01

The finite-difference boundary-value method is a numerical method suited for the solution of the one-dimensional Schrodinger equation encountered in problems of hindered rotation. Further, the application of the method, in combination with experimental results for the evaluation of the rotational energy barrier in ethane is presented.

Entropic Barriers for Two-Dimensional Quantum Memories

NASA Astrophysics Data System (ADS)

Brown, Benjamin J.; Al-Shimary, Abbas; Pachos, Jiannis K.

2014-03-01

Comprehensive no-go theorems show that information encoded over local two-dimensional topologically ordered systems cannot support macroscopic energy barriers, and hence will not maintain stable quantum information at finite temperatures for macroscopic time scales. However, it is still well motivated to study low-dimensional quantum memories due to their experimental amenability. Here we introduce a grid of defect lines to Kitaev's quantum double model where different anyonic excitations carry different masses. This setting produces a complex energy landscape which entropically suppresses the diffusion of excitations that cause logical errors. We show numerically that entropically suppressed errors give rise to superexponential inverse temperature scaling and polynomial system size scaling for small system sizes over a low-temperature regime. Curiously, these entropic effects are not present below a certain low temperature. We show that we can vary the system to modify this bound and potentially extend the described effects to zero temperature.

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…

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

DOE PAGES

Fergus, Jeffrey W.

2014-04-12

One of the important applications of yttria stabilized zirconia is as a thermal barrier coating for gas turbine engines. While yttria stabilized zirconia performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatingsmore » are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.« less

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

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

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, andmore » 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

Unsupervised Calculation of Free Energy Barriers in Large Crystalline Systems

NASA Astrophysics Data System (ADS)

Swinburne, Thomas D.; Marinica, Mihai-Cosmin

2018-03-01

The calculation of free energy differences for thermally activated mechanisms in the solid state are routinely hindered by the inability to define a set of collective variable functions that accurately describe the mechanism under study. Even when possible, the requirement of descriptors for each mechanism under study prevents implementation of free energy calculations in the growing range of automated material simulation schemes. We provide a solution, deriving a path-based, exact expression for free energy differences in the solid state which does not require a converged reaction pathway, collective variable functions, Gram matrix evaluations, or probability flux-based estimators. The generality and efficiency of our method is demonstrated on a complex transformation of C 15 interstitial defects in iron and double kink nucleation on a screw dislocation in tungsten, the latter system consisting of more than 120 000 atoms. Both cases exhibit significant anharmonicity under experimentally relevant temperatures.

Evaluation of effect of different disposable infection control barriers on light intensity of light-curing unit and microhardness of composite - An in vitro study.

PubMed

Khode, Rajiv Tarachand; Shenoi, Pratima Ramakrishna; Kubde, Rajesh R; Makade, Chetana S; Wadekar, Kanchan D; Khode, Priyanka Tarachand

2017-01-01

This study evaluated effect of infection control barriers on light intensity (LI) of light-curing unit (LCU) and microhardness of composite. Four different disposable barriers ( n = 30) were tested against the control. LI for each barrier was measured with Lux meter. One hundred and fifty Teflon molds were equally divided into five groups of thirty each. Composite was filled in bulk in these molds and cured without and with barrier. Microhardness was evaluated on top and bottom surface of composite specimen with microhardness testing machine and hardness ratio (HR) was derived. One-way analysis of variance, Tukey's honestly significant difference test, and paired t -test using SPSS version 18 software. All barriers had significantly reduced the baseline LI of LCU ( P < 0.0001), but only Cure Elastic Steri-Shield and latex cut glove pieces (LCGP) significantly reduced the microhardness of the composite ( P < 0.05). However, HR determined inadequate curing only with LCGP. Although entire tested barrier significantly reduced the LI; none, except LCGP markedly affected the degree of cure of the composite.

Barrier island facies models and recognition criteria

NASA Astrophysics Data System (ADS)

Mulhern, J.; Johnson, C. L.

2017-12-01

Barrier island outcrops record transgressive shoreline motion at geologic timescales, providing integral clues to understanding how coastlines respond to rising sea levels. However, barrier island deposits are difficult to recognize. While significant progress has been made in understanding the modern coastal morphodynamics, this insight is not fully leveraged in existing barrier island facies models. Excellent outcrop exposures of the paralic Upper Cretaceous Straight Cliffs Formation of southern Utah provide an opportunity to revise facies models and recognition criteria for barrier island deposits. Preserved barrier islands are composed of three main architectural elements (shorefaces, tidal inlets, and tidal channels) which occur independently or in combination to create larger-scale barrier island deposits. Barrier island shorefaces record progradation, while barrier island tidal inlets record lateral migration, and barrier island tidal channels record aggradation within the tidal inlet. Four facies associations are used to describe and characterize these barrier island architectural elements. Barrier islands occur in association with backarrier fill and internally contain lower and upper shoreface, high-energy upper shoreface, and tidal channel facies. Barrier islands bound lagoons or estuaries, and are distinguished from other shoreface deposits by their internal facies and geometry, association with backbarrier facies, and position within transgressive successions. Tidal processes, in particular tidal inlet migration and reworking of the upper shoreface, also distinguish barrier island deposits. Existing barrier island models highlight the short term heterogeneous and dynamic nature of barrier island systems, yet overlook processes tied to geologic time scales, such as multi-directional motion, erosion, and reworking, and their expressions in preserved barrier island strata. This study uses characteristic outcrop expressions of barrier island successions to

Effect of different intraorifice barriers on the fracture resistance of roots obturated with Resilon or gutta-percha.

PubMed

Nagas, Emre; Uyanik, Ozgur; Altundasar, Emre; Durmaz, Veli; Cehreli, Zafer C; Vallittu, Pekka K; Lassila, Lippo V J

2010-06-01

This study investigated and compared the root reinforcement potential of 3 different intraorifice barriers (mineral trioxide aggregate [MTA], resin-modified glass ionomer cement [Vitremer], and fiber-reinforced composite [FRC]) placed over root canals obturated with gutta-percha or Resilon. Crowns of 80 extracted human mandibular premolars were sectioned off to obtain 14-mm-long root specimens. After preparation of root canals with nickel-titanium rotary files, the roots were obturated with either the Resilon/Epiphany system or gutta-percha + AH Plus sealer. In both obturation groups, specimens were further subgrouped with respect to the intraorifice barrier material placed after removal of 3-mm coronal portion of the root fillings: (1) MTA, (2) Vitremer, and (3) FRC. The specimens were loaded vertically at 1 mm/min crosshead speed until vertical root fracture occurred. Results were evaluated statistically with two-way analysis of variance and Tukey tests. Fracture resistance of roots was significantly affected by the type of intraorifice barrier (P < .05), but not by the type of obturation system used (P > .05). The use of Vitremer and FRC significantly improved the fracture resistance, whereas MTA did not exhibit any reinforcing effect as an intraorifice barrier. Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Proteins for breaking barriers in lignocellulosic bioethanol production.

PubMed

Ulaganathan, Kandasamy; Goud, Burragoni S; Reddy, Mettu M; Kumar, Vanaparthi P; Balsingh, Jatoth; Radhakrishna, Surabhi

2015-01-01

Reduction in fossil fuel consumption by using alternate sources of energy is a major challenge facing mankind in the coming decades. Bioethanol production using lignocellulosic biomass is the most viable option for addressing this challenge. Industrial bioconversion of lignocellulosic biomass, though possible now, is not economically viable due to presence of barriers that escalate the cost of production. As cellulose and hemicellulose are the major constituents of terrestrial biomass, which is available in massive quantities, hydrolysis of cellulose and hemicellulose by the microorganisms are the most prominent biochemical processes happening in the earth. Microorganisms possess different categories of proteins associated with different stages of bioethanol production and a number of them are already found and characterized. Many more of these proteins need to be identified which suit the specificities needed for the bioethanol production process. Discovery of proteins with novel specificities and application of genetic engineering technologies to harvest the synergies existing between them with the aim to develop consolidated bioprocess is the major direction of research in the future. In this review, we discuss the different categories of proteins used for bioethanol production in the context of breaking the barriers existing for the economically feasible lignocellulosic bioethanol production.

Identifying barriers to remaining physically active after rehabilitation: differences in perception between physical therapists and older adult patients.

PubMed

Zalewski, Kathryn; Alt, Carlynn; Arvinen-Barrow, Monna

2014-06-01

Cross-sectional study. To describe readiness for change and barriers to physical activity in older adults and to contrast perceptions of physical therapists and patients using the Barriers to Being Active Quiz. Regular physical activity is vital to recovery after discharge from physical therapy. Physical therapists are positioned to support change in physical activity habits for those transitioning to home care. Understanding of readiness for change and barriers to physical activity could optimize recovery. Thirteen physical therapists enrolled in the study and invited patients who met the inclusion criteria to enroll (79 patients enrolled). The physical therapists provided the ICD-9 code, the physical therapist diagnosis, and completed the Barriers to Being Active Quiz as they perceived their patients would. The enrolled patients provided demographics and filled out the Satisfaction With Life Scale, the stages-of-change scale for physical activity, and the Barriers to Being Active Quiz. Patients were predominantly in the early stages of readiness for change. Both patients and physical therapists identified lack of willpower as the primary barrier to physical activity. Patients identified lack of willpower and social influence as critical barriers more often than physical therapists, whereas physical therapists identified fear of injury and lack of time more often than their patients did. Differences between physical therapists and their patients were noted for fear of injury (z = 2.66, P = .008) and lack of time (z = 3.46, P = .001). The stage of change for physical activity impacted perception of social influence (χ2 = 9.64, P<.05), lack of willpower (χ2 = 21.91, P<.01), and lack of skill (χ2 = 12.46, P<.05). Women ranked fear of injury higher than men did (χ2 = 6.76, P<.01). Understanding readiness for change in and barriers to physical activity may allow physical therapists to better tailor intervention strategies to impact physical activity behavior change.

The Infant Skin Barrier: Can We Preserve, Protect, and Enhance the Barrier?

PubMed Central

Telofski, Lorena S.; Morello, A. Peter; Mack Correa, M. Catherine; Stamatas, Georgios N.

2012-01-01

Infant skin is different from adult in structure, function, and composition. Despite these differences, the skin barrier is competent at birth in healthy, full-term neonates. The primary focus of this paper is on the developing skin barrier in healthy, full-term neonates and infants. Additionally, a brief discussion of the properties of the skin barrier in premature neonates and infants with abnormal skin conditions (i.e., atopic dermatitis and eczema) is included. As infant skin continues to mature through the first years of life, it is important that skin care products (e.g., cleansers and emollients) are formulated appropriately. Ideally, products that are used on infants should not interfere with skin surface pH or perturb the skin barrier. For cleansers, this can be achieved by choosing the right type of surfactant, by blending surfactants, or by blending hydrophobically-modified polymers (HMPs) with surfactants to increase product mildness. Similarly, choosing the right type of oil for emollients is important. Unlike some vegetable oils, mineral oil is more stable and is not subject to oxidation and hydrolysis. Although emollients can improve the skin barrier, more studies are needed to determine the potential long-term benefits of using emollients on healthy, full-term neonates and infants. PMID:22988452

Intermediate type excitons in Schottky barriers of A3B6 layer semiconductors and UV photodetectors

NASA Astrophysics Data System (ADS)

Alekperov, O. Z.; Guseinov, N. M.; Nadjafov, A. I.

2006-09-01

Photoelectric and photovoltaic spectra of Schottky barrier (SB) structures of InSe, GaSe and GaS layered semiconductors (LS) are investigated at quantum energies from the band edge excitons of corresponding materials up to 6.5eV. Spectral dependences of photoconductivity (PC) of photo resistors and barrier structures are strongly different at the quantum energies corresponding to the intermediate type excitons (ITE) observed in these semiconductors. It was suggested that high UV photoconductivity of A3B6 LS is due to existence of high mobility light carriers in the depth of the band structure. It is shown that SB of semitransparent Au-InSe is high sensitive photo detector in UV region of spectra.

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

Magnetic tunnel junctions utilizing diamond-like carbon tunnel barriers

NASA Astrophysics Data System (ADS)

Cadieu, F. J.; Chen, Li; Li, Biao

2002-05-01

We have devised a method whereby thin particulate-free diamond-like carbon films can be made with good adhesion onto even room-temperature substrates. The method employs a filtered ionized carbon beam created by the vacuum impact of a high-energy, approximately 1 J per pulse, 248 nm excimer laser onto a carbon target. The resultant deposition beam can be steered and deflected by magnetic and electric fields to paint a specific substrate area. An important aspect of this deposition method is that the resultant films are particulate free and formed only as the result of atomic species impact. The vast majority of magnetic tunnel junctions utilizing thin metallic magnetic films have employed a thin oxidized layer of aluminum to form the tunnel barrier. This has presented reproducibility problems because the indicated optimal barrier thickness is only approximately 13 Å thick. Magnetic tunnel junctions utilizing Co and permalloy films made by evaporation and sputtering have been fabricated with an intervening diamond-like carbon tunnel barrier. The diamond-like carbon thickness profile has been tapered so that seven junctions with different barrier thickness can be formed at once. Magnetoresistive (MR) measurements made between successive permalloy strip ends include contributions from two junctions and from the permalloy and Co strips that act as current leads to the junctions. Magnetic tunnel junctions with thicker carbon barriers exhibit MR effects that are dominated by that of the permalloy strips. Since these tunnel barriers are formed without the need for oxygen, complete tunnel junctions can be formed with all high-vacuum processing.

Finite barrier corrections to the PGH solution of Kramers' turnover theory

NASA Astrophysics Data System (ADS)

Pollak, Eli; Ianconescu, Reuven

2014-04-01

Kramers [Physica 7, 284 (1940)], in his seminal paper, derived expressions for the rate of crossing a barrier in the underdamped limit of weak friction and the moderate to strong friction limit. The challenge of obtaining a uniform expression for the rate, valid for all damping strengths is known as Kramers turnover theory. Two different solutions have been presented. Mel'nikov and Meshkov [J. Chem. Phys. 85, 1018 (1986)] (MM) considered the motion of the particle, treating the friction as a perturbation parameter. Pollak, Grabert, and Hänggi [J. Chem. Phys. 91, 4073 (1989)] (PGH), considered the motion along the unstable mode which is separable from the bath in the barrier region. In practice, the two theories differ in the way an energy loss parameter is estimated. In this paper, we show that previous numerical attempts to resolve the quality of the two approaches were incomplete and that at least for a cubic potential with Ohmic friction, the quality of agreement of both expressions with numerical simulation is similar over a large range of friction strengths and temperatures. Mel'nikov [Phys. Rev. E 48, 3271 (1993)], in a later paper, improved his theory by introducing finite barrier corrections. In this paper we note that previous numerical tests of the finite barrier corrections were also incomplete. They did not employ the exact rate expression, but a harmonic approximation to it. The central part of this paper, is to include finite barrier corrections also within the PGH formalism. Tests on a cubic potential demonstrate that finite barrier corrections significantly improve the agreement of both MM and PGH theories when compared with numerical simulations.

First-principles estimates of free energy barriers for Mg desolvation and intercalation at electrolyte/electrode interfaces

NASA Astrophysics Data System (ADS)

Wan, Liwen; Prendergast, David

2014-03-01

There is a growing interest in developing multivalent ion batteries that could, in principle, double or triple the energy density compared to the monovalent Li-ion batteries. However, the strong electrostatic interaction caused by the extra charge also makes it very challenging to find appropriate intercalation compounds that allow for relatively fast and reversible ion transport. An established working multivalent battery is comprised of Mg(AlCl2BuEt)2 salts in THF solution as the electrolyte, and Mg metal and Mo6S8 Chevrel phase as the anode and cathode, respectively. Currently, we lack a clear understanding of the mechanism for Mg desolvation and intercalation at the interface between the electrolyte and Chevrel phase surfaces, which is critical in designing new advanced battery systems with improved ion diffusion rate. Here, we present a theoretical investigation of the dynamics and kinetics of the Mg desolvation/intercalation process. The surface properties of Mo6S8 are studied for the first time using density functional theory (DFT) and its interaction with the electrolyte is simulated via an ab initio molecular dynamics (AIMD) approach. The free energy barrier for Mg diffusing through the interface is then calculated by performing a set of biased AIMD simulations. This work is supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

Sub-barrier quasifission in heavy element formation reactions with deformed actinide target nuclei

NASA Astrophysics Data System (ADS)

Hinde, D. J.; Jeung, D. Y.; Prasad, E.; Wakhle, A.; Dasgupta, M.; Evers, M.; Luong, D. H.; du Rietz, R.; Simenel, C.; Simpson, E. C.; Williams, E.

2018-02-01

Background: The formation of superheavy elements (SHEs) by fusion of two massive nuclei is severely inhibited by the competing quasifission process. Low excitation energies favor SHE survival against fusion-fission competition. In "cold" fusion with spherical target nuclei near 208Pb, SHE yields are largest at beam energies significantly below the average capture barrier. In "hot" fusion with statically deformed actinide nuclei, this is not the case. Here the elongated deformation-aligned configurations in sub-barrier capture reactions inhibits fusion (formation of a compact compound nucleus), instead favoring rapid reseparation through quasifission. Purpose: To determine the probabilities of fast and slow quasifission in reactions with prolate statically deformed actinide nuclei, through measurement and quantitative analysis of the dependence of quasifission characteristics at beam energies spanning the average capture barrier energy. Methods: The Australian National University Heavy Ion Accelerator Facility and CUBE fission spectrometer have been used to measure fission and quasifission mass and angle distributions for reactions with projectiles from C to S, bombarding Th and U target nuclei. Results: Mass-asymmetric quasifission occurring on a fast time scale, associated with collisions with the tips of the prolate actinide nuclei, shows a rapid increase in probability with increasing projectile charge, the transition being centered around projectile atomic number ZP=14 . For mass-symmetric fission events, deviations of angular anisotropies from expectations for fusion fission, indicating a component of slower quasifission, suggest a similar transition, but centered around ZP˜8 . Conclusions: Collisions with the tips of statically deformed prolate actinide nuclei show evidence for two distinct quasifission processes of different time scales. Their probabilities both increase rapidly with the projectile charge. The probability of fusion can be severely

Dynamics of 28,30S i* compound nuclei formed at sub-barrier energies

NASA Astrophysics Data System (ADS)

Kaur, Manpreet; Singh, Bir Bikram; Kaur, Sarbjeet

2018-05-01

The decay of 28S i* and 30S i* compound nuclei (CN) formed at sub-barrier energies, in the reactions induced by stable projectile 16O and exotic projectile 18O, respectively, has been investigated within the quantum mechanical fragmentation theory based dynamical cluster-decay model (DCM). The collective potential energy surface shows that xα-type (x is an integer) clusters are minimized in the decay of 28S i* while in case of 30S i* in addition to xα-type clusters, np-xα (n, p are neutron and proton, respectively) type clusters are also minimized. These minimized fragments have more preformation probability P0, which is an important factor through which nuclear structure effects of decaying CN are probed, within DCM. The results show that light particles (LPs) are contributing mostly in the fusion cross-section, σfusion. In case of 30S i*, the contribution of 1n is highest and more compared to 4He in case of 28S i*, which seems to play an important role in fusion enhancement. The DCM calculated σfusion for both the CN formed with same Ec.m. = 7.0 MeV gives more value for σfusion of 30S i*, in agreement with the experimental data.

Evaluation of effect of different disposable infection control barriers on light intensity of light-curing unit and microhardness of composite - An in vitro study

PubMed Central

Khode, Rajiv Tarachand; Shenoi, Pratima Ramakrishna; Kubde, Rajesh R.; Makade, Chetana S.; Wadekar, Kanchan D.; Khode, Priyanka Tarachand

2017-01-01

Aims: This study evaluated effect of infection control barriers on light intensity (LI) of light-curing unit (LCU) and microhardness of composite. Materials and Methods: Four different disposable barriers (n = 30) were tested against the control. LI for each barrier was measured with Lux meter. One hundred and fifty Teflon molds were equally divided into five groups of thirty each. Composite was filled in bulk in these molds and cured without and with barrier. Microhardness was evaluated on top and bottom surface of composite specimen with microhardness testing machine and hardness ratio (HR) was derived. Statistical Analysis Used: One-way analysis of variance, Tukey's honestly significant difference test, and paired t-test using SPSS version 18 software. Results: All barriers had significantly reduced the baseline LI of LCU (P < 0.0001), but only Cure Elastic Steri-Shield and latex cut glove pieces (LCGP) significantly reduced the microhardness of the composite (P < 0.05). However, HR determined inadequate curing only with LCGP. Conclusions: Although entire tested barrier significantly reduced the LI; none, except LCGP markedly affected the degree of cure of the composite. PMID:29279622

Spatially inhomogeneous barrier height in graphene/MoS2 Schottky junctions

NASA Astrophysics Data System (ADS)

Tomer, Dushyant; Rajput, Shivani; Li, Lian

Graphene interfaced with a semiconductor forms a Schottky junction with rectifying properties. In this study, graphene Schottky junctions are fabricated by transferring CVD monolayer graphene on mechanically exfoliated MoS2 multilayers. The forward bias current-voltage characteristics are measured in the temperature range of 210-300 K. An increase in the zero bias barrier height and decrease in the ideality factor are observed with increasing temperature. Such behavior is attributed to Schottky barrier inhomogeneities possibly due to graphene ripples and ridges at the junction interface as suggested by atomic force microscopy. Assuming a Gaussian distribution of the barrier height, mean barrier of 0.97+/-0.10 eV is found for the graphene MoS2 junction. Our findings provide significant insight on the barrier height inhomogeneities in graphene/two dimensional semiconductor Schottky junctions. U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering Award No. DEFG02-07ER46228.

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. © 2016 S. Karger AG, Basel.

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

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

Barriers and facilitators of sports in children with physical disabilities: a mixed-method study.

PubMed

Jaarsma, Eva A; Dijkstra, Pieter U; de Blécourt, Alida C E; Geertzen, Jan H B; Dekker, Rienk

2015-01-01

This study explored barriers and facilitators of sports participation of children with physical disabilities from the perspective of the children, their parents and their health professionals. Thirty children and 38 parents completed a questionnaire, and 17 professionals were interviewed in a semi-structured way. Data from the three groups were combined in a mixed-method design, after which the results were triangulated. Mean age (SD) of the children was 14.1 (2.9) years old, 58% were boys. Sixty-seven percent of the children had cerebral palsy and 77% participated in sports after school. Most commonly practiced sports were swimming, cycling and football. Children specifically experienced dependency on others as a barrier, parents did not have enough information about sports facilities, and professionals observed that the family's attitude had influence on the child's sports participation. Facilitators were health benefits, fun and social contacts. Sports participation of children with physical disabilities is a complex phenomenon because children, their parents and professionals reported different barriers. Sports participation is more physically challenging for children with severe physical disabilities, as their daily activities already require much energy. However, the psychosocial benefits of sports are applicable to all children with physical disabilities. IMPLICATION FOR REHABILITATION: Perceived barriers seemed to differ for children, parents and health professionals, suggesting that sports participation is a complex phenomenon. Sports might be more physically challenging for children with severe physical disabilities, as their daily activities already take much energy. The psychosocial benefits of sports should be emphasized by rehabilitation professionals when advising children with physical disabilities about sports.

Dynamic Energy Landscapes of Riboswitches Help Interpret Conformational Rearrangements and Function

PubMed Central

Quarta, Giulio; Sin, Ken; Schlick, Tamar

2012-01-01

Riboswitches are RNAs that modulate gene expression by ligand-induced conformational changes. However, the way in which sequence dictates alternative folding pathways of gene regulation remains unclear. In this study, we compute energy landscapes, which describe the accessible secondary structures for a range of sequence lengths, to analyze the transcriptional process as a given sequence elongates to full length. In line with experimental evidence, we find that most riboswitch landscapes can be characterized by three broad classes as a function of sequence length in terms of the distribution and barrier type of the conformational clusters: low-barrier landscape with an ensemble of different conformations in equilibrium before encountering a substrate; barrier-free landscape in which a direct, dominant “downhill” pathway to the minimum free energy structure is apparent; and a barrier-dominated landscape with two isolated conformational states, each associated with a different biological function. Sharing concepts with the “new view” of protein folding energy landscapes, we term the three sequence ranges above as the sensing, downhill folding, and functional windows, respectively. We find that these energy landscape patterns are conserved in various riboswitch classes, though the order of the windows may vary. In fact, the order of the three windows suggests either kinetic or thermodynamic control of ligand binding. These findings help understand riboswitch structure/function relationships and open new avenues to riboswitch design. PMID:22359488

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).

Low-impact, high toughness transportation barriers.

DOT National Transportation Integrated Search

2012-10-01

Alternatives to existing transportation truck escape ramps and crash barriers are examined using arrays of : wood, bamboo, and fiberglass structural elements that act as energy absorbers as they deform. The : behaviors of each material type are analy...

An exploratory study of physical activity and perceived barriers to exercise in ambulant people with neuromuscular disease compared with unaffected controls.

PubMed

Phillips, Margaret; Flemming, Nicola; Tsintzas, Kostas

2009-08-01

To determine activity patterns and perceived barriers to exercise in ambulant people with neuromuscular disease compared with ambulatory controls. Prospective controlled parallel group design. Outpatient clinic and community. Thirteen ambulatory people with neuromuscular disease and 18 ambulatory controls. Heart rates were recorded during sedentary activity and treadmill walking at various speeds to indicate activity threshold (flex heart rate), followed by ambulatory heart rate monitoring over two weekdays and one weekend day. The EPIC-Norfolk Physical Activity Questionnaire-2 and Barriers to Physical Activity and Disability Survey were completed. Participants with neuromuscular disease were less active than controls as estimated by both the EPIC-Norfolk Physical Activity Questionnaire-2, P<0.004, and the flex heart rate method, P<0.05. The number of perceived barriers was greater in the neuromuscular group, a mean of 7 (SD 4.2) barriers, compared with mean 3 (SD 2.1) barriers for controls, P<0.05. Specific barriers differed, with the barriers of 'pain', 'lack of energy' and 'exercise is too difficult' showing the greatest discrepancy and being higher in the neuromuscular disease group. Physical activity, as determined by two different methods, was less and barriers to exercise greater in people with neuromuscular disease compared with healthy controls. Specific barriers were different in the two groups. This information could assist in the design of achievable and effective exercise programmes for people with neuromuscular disease.

MASH TL-4 crash testing and evaluation of the RESTORE barrier.

DOT National Transportation Integrated Search

2015-11-01

Three full-scale vehicle crash tests were conducted according to the MASH Test Level 4 (TL-4) safety performance criteria on a : restorable and reusable energy-absorbing roadside/median barrier, designated the RESTORE barrier. The system utilized for...

Design of nucleic acid strands with long low-barrier folding pathways.

PubMed

Condon, Anne; Kirkpatrick, Bonnie; Maňuch, Ján

2017-01-01

A major goal of natural computing is to design biomolecules, such as nucleic acid sequences, that can be used to perform computations. We design sequences of nucleic acids that are "guaranteed" to have long folding pathways relative to their length. This particular sequences with high probability follow low-barrier folding pathways that visit a large number of distinct structures. Long folding pathways are interesting, because they demonstrate that natural computing can potentially support long and complex computations. Formally, we provide the first scalable designs of molecules whose low-barrier folding pathways, with respect to a simple, stacked pair energy model, grow superlinearly with the molecule length, but for which all significantly shorter alternative folding pathways have an energy barrier that is [Formula: see text] times that of the low-barrier pathway for any [Formula: see text] and a sufficiently long sequence.

Thermal barrier coatings issues in advanced land-based gas turbines

NASA Technical Reports Server (NTRS)

Parks, W. P.; Lee, W. Y.; Wright, I. G.

1995-01-01

The Department of Energy's Advanced Turbine System (ATS) program is aimed at forecasting the development of a new generation of land-based gas turbine systems with overall efficiencies significantly beyond those of current state-of-the-art machines, as well as greatly increased times between inspection and refurbishment, improved environmental impact, and decreased cost. The proposed duty cycle of ATS turbines will require the use of different criteria in the design of the materials for the critical hot gas path components. In particular, thermal barrier coatings will be an essential feature of the hot gas path components in these machines. While such coatings are routinely used in high-performance aircraft engines and are becoming established in land-based turbines, the requirements of the ATS turbine application are sufficiently different that significant improvements in thermal barrier coating technology will be necessary. In particular, it appears that thermal barrier coatings will have to function on all airfoil sections of the first stage vanes and blades to provide the significant temperature reduction required. In contrast, such coatings applied to the blades and vances of advanced aircraft engines are intended primarily to reduce air cooling requirements and extend component lifetime; failure of those coatings can be tolerated without jeopardizing mechanical or corrosion performance. A major difference is that in ATS turbines these components will be totally reliant on thermal barrier coatings which will, therefore, need to be highly reliable even over the leading edges of first stage blades. Obviously, the ATS program provides a very challenging opportunity for TBC's, and involves some significant opportunities to extend this technology.

Exercise barriers in Korean colorectal cancer patients.

PubMed

Kang, Dong-Woo; Chung, Jae Youn; Lee, Mi Kyung; Lee, Junga; Park, Ji-Hye; Kim, Dong-Il; Jones, Lee W; Ahn, Joong Bae; Kim, Nam Kyu; Jeon, Justin Y

2014-01-01

To identify barriers to exercise in Korean colorectal cancer patients and survivors, and to analyze differences in exercise barriers by age, gender, treatment status, and physical activity level. A total of 427 colorectal cancer patients and survivors from different stages and medical status completed a self-administered questionnaire that surveyed their barriers to exercise and exercise participation. The greatest perceived exercise barriers for the sampled population as a whole were fatigue, low level of physical fitness, and poor health. Those under 60-years old reported lack of time (p=0.008), whereas those over 60 reported low level of physical fitness (p=0.014) as greater exercise barriers than their counterparts. Women reported fatigue as a greater barrier than men (p<0.001). Those who were receiving treatment rated poor health (p=0.0005) and cancer-related factors as greater exercise barriers compared to those who were not receiving treatment. A multivariate model found that other demographic and medical status were not potential factors that may affect exercise participation. Further, for those who were not participating in physical activity, tendency to be physically inactive (p<0.001) and lack of exercise skill (p<0.001) were highly significant barriers, compared to those who were participating in physical activity. Also, for those who were not meeting ACSM guidelines, cancer-related exercise barriers were additionally reported (p<0.001), compared to those who were. Our study suggests that fatigue, low level of physical fitness, and poor health are most reported exercise barriers for Korean colorectal cancer survivors and there are differences in exercise barriers by age, sex, treatment status, and physical activity level. Therefore, support for cancer patients should be provided considering these variables to increase exercise participation.

Multiple kinetic k-essence, phantom barrier crossing and stability

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

Sur, Sourav; Das, Saurya, E-mail: sourav.sur@uleth.ca

We investigate models of dark energy with purely kinetic multiple k-essence sources that allow for the crossing of the phantom divide line, without violating the conditions of stability. It is known that with more than one kinetic k-field one can possibly construct dark energy models whose equation of state parameter w{sub X} crosses -1 (the phantom barrier) at recent red-shifts, as indicated by the Supernova Ia and other observational probes. However, such models may suffer from cosmological instabilities, as the effective speed of propagation c{sub X} of the dark energy density perturbations may become imaginary while the w{sub X} =more » -1 barrier is crossed. Working out the expression for c{sub X} we show that multiple kinetic k-essence fields do indeed lead to a w{sub X} = -1 crossing dark energy model, satisfying the stability criterion c{sub X}{sup 2} {>=} 0 as well as the condition c{sub X} {<=} 1 (in natural units), which implies that the dark energy is not super-luminal. As a specific example, we construct a phantom barrier crossing model involving three k-fields for which c{sub X} is a constant, lying between 0 and 1. The model fits well with the latest Supernova Ia Union data, and the best fit shows that w{sub X} crosses -1 at red-shift z {approx} 0.2, whereas the dark energy density nearly tracks the matter density at higher red-shifts.« less

InGaP Heterojunction Barrier Solar Cells

NASA Technical Reports Server (NTRS)

Welser, Roger E.

2010-01-01

A new solar-cell structure utilizes a single, ultra-wide well of either gallium arsenide (GaAs) or indium-gallium-phosphide (InGaP) in the depletion region of a wide bandgap matrix, instead of the usual multiple quantum well layers. These InGaP barrier layers are effective at reducing diode dark current, and photogenerated carrier escape is maximized by the proper design of the electric field and barrier profile. With the new material, open-circuit voltage enhancements of 40 and 100 mV (versus PIN control systems) are possible without any degradation in short-circuit current. Basic tenets of quantum-well and quantum- dot solar cells are utilized, but instead of using multiple thin layers, a single wide well works better. InGaP is used as a barrier material, which increases open current, while simultaneously lowering dark current, reducing both hole diffusion from the base, and space charge recombination within the depletion region. Both the built-in field and the barrier profile are tailored to enhance thermionic emissions, which maximizes the photocurrent at forward bias, with a demonstrated voltage increase. An InGaP heterojunction barrier solar cell consists of a single, ultra-wide GaAs, aluminum-gallium-arsenide (AlGaAs), or lower-energy-gap InGaP absorber well placed within the depletion region of an otherwise wide bandgap PIN diode. Photogenerated electron collection is unencumbered in this structure. InGaAs wells can be added to the thick GaAs absorber layer to capture lower-energy photons.

Diverse variation of reproductive barriers in three intraspecific rice crosses.

PubMed Central

Harushima, Yoshiaki; Nakagahra, Masahiro; Yano, Masahiro; Sasaki, Takuji; Kurata, Nori

2002-01-01

Reproductive barriers are thought to play an important role in the processes of speciation and differentiation. Asian rice cultivars, Oryza sativa, can be classified into two main types, Japonica and Indica, on the basis of several characteristics. The fertility of Japonica-Indica hybrids differs from one cross to another. Many genes involved in reproductive barriers (hybrid sterility, hybrid weakness, and gametophytic competition genes) have been reported in different Japonica-Indica crosses. To clarify the state of Japonica-Indica differentiation, all reproductive barriers causing deviation from Mendelian segregation ratios in F(2) populations were mapped and compared among three different Japonica-Indica crosses: Nipponbare/Kasalath (NK), Fl1084/Dao Ren Qiao (FD), and Fl1007/Kinandang puti (FK). Mapping of reproductive barriers was performed by regression analysis of allele frequencies of DNA markers covering the entire genome. Allele frequencies were explained by 33 reproductive barriers (15 gametophytic and 18 zygotic) in NK, 32 barriers (15 gametophytic and 17 zygotic) in FD, and 37 barriers (19 gametophytic and 18 zygotic) in FK. The number of reproductive barriers in the three crosses was similar; however, most of the barriers were mapped at different loci. Therefore, these reproductive barriers formed after Japonica-Indica differentiation. Considering the high genetic similarity within Japonica and Indica cultivars, the differences in the reproductive barriers of each cross were unexpectedly numerous. The reproductive barriers of Japonica-Indica hybrids likely evolved more rapidly than other genetic elements. One possible force responsible for such rapid evolution of the barriers may have been the domestication of rice. PMID:11805066

Breakup and n -transfer effects on the fusion reactions Li,76+Sn,119120 around the Coulomb barrier

NASA Astrophysics Data System (ADS)

Fisichella, M.; Shotter, A. C.; Figuera, P.; Lubian, J.; Di Pietro, A.; Fernandez-Garcia, J. P.; Ferreira, J. L.; Lattuada, M.; Lotti, P.; Musumarra, A.; Pellegriti, M. G.; Ruiz, C.; Scuderi, V.; Strano, E.; Torresi, D.; Zadro, M.

2017-03-01

This paper presents values of complete fusion cross sections deduced from activation measurements for the reactions 6Li+120Sn and 7Li+119Sn , and for a projectile energy range from 17.5 to 28 MeV in the center-of-mass system. A new deconvolution analysis technique is used to link the basic activation data to the actual fusion excitation function. The complete fusion cross sections above the barrier are suppressed by about 70 % and 85 % with respect to the universal fusion function, used as a standard reference, in the 6Li and 7Li induced reactions, respectively. From a comparison of the excitation functions of the two systems at energies below the barrier, no significant differences can be observed, despite the two systems have different n -transfer Q values. This observation is supported by the results of coupled reaction channels (CRC) calculations.

Female and Male Juvenile Offenders with Disabilities: Differences in the Barriers to Their Transition to the Community

ERIC Educational Resources Information Center

Unruh, Deanne; Bullis, Michael

2005-01-01

This article examined differences between young women and men who were incarcerated juvenile offenders with disabilities in Oregon in terms of the barriers they faced in their transition from the correctional system back into the community. Data were gathered on 72 females and 276 males, all of whom presented disabilities and who were…

Hurdling barriers through market uncertainty: Case studies ininnovative technology adoption

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

Payne, Christopher T.; Radspieler Jr., Anthony; Payne, Jack

The crisis atmosphere surrounding electricity availability in California during the summer of 2001 produced two distinct phenomena in commercial energy consumption decision-making: desires to guarantee energy availability while blackouts were still widely anticipated, and desires to avoid or mitigate significant price increases when higher commercial electricity tariffs took effect. The climate of increased consideration of these factors seems to have led, in some cases, to greater willingness on the part of business decision-makers to consider highly innovative technologies. This paper examines three case studies of innovative technology adoption: retrofit of time-and-temperature signs on an office building; installation of fuel cellsmore » to supply power, heating, and cooling to the same building; and installation of a gas-fired heat pump at a microbrewery. We examine the decision process that led to adoption of these technologies. In each case, specific constraints had made more conventional energy-efficient technologies inapplicable. We examine how these barriers to technology adoption developed over time, how the California energy decision-making climate combined with the characteristics of these innovative technologies to overcome the barriers, and what the implications of hurdling these barriers are for future energy decisions within the firms.« less

The rotational barrier in ethane: a molecular orbital study.

PubMed

Quijano-Quiñones, Ramiro F; Quesadas-Rojas, Mariana; Cuevas, Gabriel; Mena-Rejón, Gonzalo J

2012-04-20

The energy change on each Occupied Molecular Orbital as a function of rotation about the C-C bond in ethane was studied using the B3LYP, mPWB95 functional and MP2 methods with different basis sets. Also, the effect of the ZPE on rotational barrier was analyzed. We have found that σ and π energies contribution stabilize a staggered conformation. The σ(s) molecular orbital stabilizes the staggered conformation while the stabilizes the eclipsed conformation and destabilize the staggered conformation. The π(z) and molecular orbitals stabilize both the eclipsed and staggered conformations, which are destabilized by the π(v) and molecular orbitals. The results show that the method of calculation has the effect of changing the behavior of the energy change in each Occupied Molecular Orbital energy as a function of the angle of rotation about the C-C bond in ethane. Finally, we found that if the molecular orbital energy contribution is deleted from the rotational energy, an inversion in conformational preference occurs.

Barriers to and Correlates of Retention in Behavioral Health Treatment among Latinos in Two Different Host Countries: U.S. and Spain

PubMed Central

Falgas, I.; Ramos, Z.; Herrera, L.; Qureshi, A.; Chavez, L.; Bonal, C.; McPeck, S.; Wang, Y.; Cook, B.; Alegría, M.

2015-01-01

Context Latino immigrants constitute a large portion of the Spanish and U.S. immigrant populations, yet a dearth of research exists regarding barriers to retention in behavioral health care. Objectives To identify and compare perceived barriers related to behavioral health care among first and second generation Latinos in Boston, Madrid, and Barcelona, and evaluate whether the frequency of behavioral health care use in the last year was related to these barriers. Design, Setting and Participants Data come from the International Latino Research Partnership project. First or second generation self-identified Latino immigrants ages 18+ who resided more than one year in the host country were recruited from community agencies and primary care, mental health, substance abuse, and HIV clinics. Main Outcome Measures Eleven barriers were assessed and compared across sites. The relationship between barriers and behavioral services visits within the last year was evaluated, adjusting for socio-demographics, clinical measures, degree of health literacy, cultural and social factors. Results Wanting to handle the problem on one's own, thinking that treatment would not work, and being unsure of where to go or who to see were the most frequently reported barriers for Latino immigrants. Previous treatment failure, difficulties in transportation or scheduling, and linguistic barriers were more likely to be reported in Boston; trying to deal with mental health problems on one's own was more commonly reported in Barcelona and Madrid. Two barriers associated with number of visits were concerns about the cost of services and uncertainty about where to go or who to see. Conclusions After adjusting for socio-demographics, clinical measures, degree of health literacy, cultural and social factors, barriers still differed significantly across sites. Efforts to improve behavioral health services must be tailored to immigrants' context, with attention to changing attitudes of self-reliance and

Free Energy Calculations using a Swarm-Enhanced Sampling Molecular Dynamics Approach.

PubMed

Burusco, Kepa K; Bruce, Neil J; Alibay, Irfan; Bryce, Richard A

2015-10-26

Free energy simulations are an established computational tool in modelling chemical change in the condensed phase. However, sampling of kinetically distinct substates remains a challenge to these approaches. As a route to addressing this, we link the methods of thermodynamic integration (TI) and swarm-enhanced sampling molecular dynamics (sesMD), where simulation replicas interact cooperatively to aid transitions over energy barriers. We illustrate the approach by using alchemical alkane transformations in solution, comparing them with the multiple independent trajectory TI (IT-TI) method. Free energy changes for transitions computed by using IT-TI grew increasingly inaccurate as the intramolecular barrier was heightened. By contrast, swarm-enhanced sampling TI (sesTI) calculations showed clear improvements in sampling efficiency, leading to more accurate computed free energy differences, even in the case of the highest barrier height. The sesTI approach, therefore, has potential in addressing chemical change in systems where conformations exist in slow exchange. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Perceived barriers to physical activity among Polish adolescents.

PubMed

Jodkowska, Maria; Mazur, Joanna; Oblacińska, Anna

2015-01-01

To identify barriers to physical activity (PA) for adolescents according to the gender and age and examine the association between these barriers and youths' physical activity. 3346 students aged 10-16 years (1759 girls) took part in the cross-sectional, nationally representative study. For this paper the dataset was created from adolescents who reported perceived barriers to PA, N = 2300, (1259 girls), range 13-16 years. Barriers and physical activity (MVPA) were analysed for all participants, as well as by gender, age group and place of residence. Multiple regression analysis was used to examine the relationships between perceived barriers and physical inactivity for all and than separately for boys and girls. Lack of energy, lack of time and lack of support were three of the five barriers reported by more than 40% of adolescents, statistically more likely by girls than boys and older youth than younger. For boys - lack of time (OR = 2.56; CI = 1.66-3.96), lack of skills (OR = 2.35; CI = 1.94-3.95), lack of willpower (OR = 1.71, CI = 1.05-2.80) and lack of support (OR = 1.64, CI = 1.11-2.41) were the predictors contributing to low level of PA. For girls lack of skills (OR = 3.16, CI = 1.62-6.18), lack of energy (OR = 1.84, CI = 1.14-2.96), lack of support (OR = 1.64, CI = 1.07-2.54) and lack of time (OR = 1.61,CI = 1.00-2.60) were positively and statistically significant associated with physical inactivity. 1. Perceived barriers to physical activity among adolescents have strong negative impact on recommended PA level. For girls lack of skills is the strongest predictor of low PA, for boys - lack of time. 2. Identification more precisely barriers to physical activity among adolescents will enable to developed more effective interventions in high-risk populations.

A Free Energy Barrier Caused by the Refolding of an Oligomeric Intermediate Controls the Lag Time of Amyloid Formation by hIAPP.

PubMed

Serrano, Arnaldo L; Lomont, Justin P; Tu, Ling-Hsien; Raleigh, Daniel P; Zanni, Martin T

2017-11-22

Transiently populated oligomers formed en route to amyloid fibrils may constitute the most toxic aggregates associated with many amyloid-associated diseases. Most nucleation theories used to describe amyloid aggregation predict low oligomer concentrations and do not take into account free energy costs that may be associated with structural rearrangements between the oligomer and fiber states. We have used isotope labeling and two-dimensional infrared spectroscopy to spectrally resolve an oligomeric intermediate during the aggregation of the human islet amyloid protein (hIAPP or amylin), the protein associated with type II diabetes. A structural rearrangement includes the F 23 G 24 A 25 I 26 L 27 region of hIAPP, which starts from a random coil structure, evolves into ordered β-sheet oligomers containing at least 5 strands, and then partially disorders in the fibril structure. The supercritical concentration is measured to be between 150 and 250 μM, which is the thermodynamic parameter that sets the free energy of the oligomers. A 3-state kinetic model fits the experimental data, but only if it includes a concentration independent free energy barrier >3 kcal/mol that represents the free energy cost of refolding the oligomeric intermediate into the structure of the amyloid fibril; i.e., "oligomer activation" is required. The barrier creates a transition state in the free energy landscape that slows fibril formation and creates a stable population of oligomers during the lag phase, even at concentrations below the supercritical concentration. Largely missing in current kinetic models is a link between structure and kinetics. Our experiments and modeling provide evidence that protein structural rearrangements during aggregation impact the populations and kinetics of toxic oligomeric species.

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…

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,…

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.

Enhanced Ligand Sampling for Relative Protein–Ligand Binding Free Energy Calculations

PubMed Central

2016-01-01

Free energy calculations are used to study how strongly potential drug molecules interact with their target receptors. The accuracy of these calculations depends on the accuracy of the molecular dynamics (MD) force field as well as proper sampling of the major conformations of each molecule. However, proper sampling of ligand conformations can be difficult when there are large barriers separating the major ligand conformations. An example of this is for ligands with an asymmetrically substituted phenyl ring, where the presence of protein loops hinders the proper sampling of the different ring conformations. These ring conformations become more difficult to sample when the size of the functional groups attached to the ring increases. The Adaptive Integration Method (AIM) has been developed, which adaptively changes the alchemical coupling parameter λ during the MD simulation so that conformations sampled at one λ can aid sampling at the other λ values. The Accelerated Adaptive Integration Method (AcclAIM) builds on AIM by lowering potential barriers for specific degrees of freedom at intermediate λ values. However, these methods may not work when there are very large barriers separating the major ligand conformations. In this work, we describe a modification to AIM that improves sampling of the different ring conformations, even when there is a very large barrier between them. This method combines AIM with conformational Monte Carlo sampling, giving improved convergence of ring populations and the resulting free energy. This method, called AIM/MC, is applied to study the relative binding free energy for a pair of ligands that bind to thrombin and a different pair of ligands that bind to aspartyl protease β-APP cleaving enzyme 1 (BACE1). These protein–ligand binding free energy calculations illustrate the improvements in conformational sampling and the convergence of the free energy compared to both AIM and AcclAIM. PMID:25906170

Experimental testing of flexible barriers for containment of debris flows

USGS Publications Warehouse

DeNatale, Jay S.; Iverson, Richard M.; Major, Jon J.; LaHusen, Richard G.; Fliegel, Gregg L.; Duffy, John D.

1999-01-01

In June 1996, six experiments conducted at the U.S. Geological Survey Debris Flow Flume demonstrated that flexible, vertical barriers constructed of wire rope netting can stop small debris flows. All experimental debris flows consisted of water-saturated gravelly sand with less than two percent finer sediment by weight. All debris flows had volumes of about 10 cubic meters, masses of about 20 metre tons, and impact velocities of 5 to 9 meters per second. In four experiments, the debris flow impacted pristine, unreformed barriers of varying design; in the other two experiments, the debris flow impacted barriers already loaded with sediment from a previous flow. Differences in barrier design led to differences in barrier performance. Experiments were conducted with barriers constructed of square-mesh wire-rope netting with 30centimeter, 20centimeter, and 15 centimeter mesh openings as well as 30centimeter diameter interlocking steel rings. In all cases, sediment cascading downslope at the leading edge of the debris flows tended to spray through the nets. Nets fitted with finer-mesh chain link or chicken wire liners contained more sediment than did unlined nets, and a ring net fitted with a synthetic silt screen liner contained nearly 100 percent of the sediment. Irreversible net displacements of up to 2 meters and friction brake engagement on the support and anchor cables dissipated some of the impact energy. However, substantial forces developed in the steel support columns and the lateral and tie-back anchor cables attached to these columns. As predicted by elementary mechanics, the anchor cables experienced larger tensile forces when the support columns were hinged at the base rather than bolted rigidly to the foundation. Measured loads in the lateral anchor cables exceeded those in the tie-back anchor cables and the load cell capacity of 45 kilo-Newtons. Measurements also indicated that the peak loads in the tie- back anchors were highly transient and occurred at

Phase-dependent above-barrier ionization of excited-state electrons.

PubMed

Yang, Weifeng; Song, Xiaohong; Chen, Zhangjin

2012-05-21

The carrier-envelope phase (CEP)-dependent above-barrier ionization (ABI) has been investigated in order to probe the bound-state electron dynamics. It is found that when the system is initially prepared in the excited state, the ionization yield asymmetry between left and right sides can occur both in low-energy and high-energy parts of the photoelectron spectra. Moreover, in electron momentum map, a new interference effect along the direction perpendicular to the laser polarization is found. We show that this interference is related to the competition among different excited states. The interference effect is dependent on CEPs of few-cycle probe pulses, which can be used to trace the superposition information and control the electron wave packet of low excited states.

Direct computation of general chemical energy differences: Application to ionization potentials, excitation, and bond energies.

PubMed

Beste, A; Harrison, R J; Yanai, T

2006-08-21

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.

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.

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.

Effects of surface dielectric barrier discharge on aerodynamic characteristic of train

NASA Astrophysics Data System (ADS)

Dong, Lei; Gao, Guoqiang; Peng, Kaisheng; Wei, Wenfu; Li, Chunmao; Wu, Guangning

2017-07-01

High-speed railway today has become an indispensable means of transportation due to its remarkable advantages, including comfortability, convenience and less pollution. The increase in velocity makes the air drag become the main source of energy consumption, leading to receiving more and more concerns. The surface dielectric barrier discharge has shown some unique characteristics in terms of active airflow control. In this paper, the influences of surface dielectric barrier discharge on the aerodynamic characteristics of a scaled train model have been studied. Aspects of the discharge power consumption, the temperature distribution, the velocity of induced flow and the airflow field around the train model were considered. The applied AC voltage was set in the range of 20 kV to 28 kV, with a fixed frequency of 9 kHz. Results indicated that the discharge power consumption, the maximum temperature and the induced flow velocity increased with increasing applied voltage. Mechanisms of applied voltage influencing these key parameters were discussed from the point of the equivalent circuit. The airflow field around the train model with different applied voltages was observed by the smoke visualization experiment. Finally, the effects of surface dielectric barrier discharge on the train drag reduction with different applied voltages were analyzed.

On colloid retention in saturated porous media in the presence of energy barriers: The failure of α, and opportunities to predict η

NASA Astrophysics Data System (ADS)

Johnson, William P.; Tong, Meiping; Li, Xiqing

2007-12-01

This contribution reviews recent findings that illuminate the processes governing colloid retention in porous media under environmentally relevant conditions. In the environment, colloids act as conveyors of contaminants, or even as contaminants themselves; however, despite decades of research, we are unable to accurately predict the retention of colloids in granular aquifer media under environmental conditions, where repulsion exists between colloids and surfaces. This failure cannot be blamed solely on the complexities of the subsurface, since colloid filtration theory (CFT) works well in the absence of colloid-collector repulsion despite its idealization of porous media as consisting of spherical grains completely surrounded by fluid envelopes. Rather, the failure of CFT stems from failure to incorporate the correct mechanisms of retention when repulsion exists. Recent observations implicate wedging in grain-to-grain contacts and retention in secondary energy minima as dominant mechanisms of colloid retention in the presence of an energy barrier. Mechanistic simulations in unit cells containing grain-to-grain contacts corroborate these mechanisms of colloid retention. The resulting concept for colloid retention in the presence of an energy barrier involves translation of colloids across the collector surfaces until they become wedged within grain-to-grain contacts, or are retained via secondary energy minima (without attachment) in zones where the balance of fluid drag, diffusion, gravitational, and colloid-collector interaction forces allow retention. The above findings highlight the pore domain geometry as a dominant governor of colloid retention in so far as the geometry gives rise to grain-to-grain contacts and zones of relatively low fluid drag.

Energy Levels in Quantum Wells.

NASA Astrophysics Data System (ADS)

Zang, Jan Xin

Normalized analytical equations for eigenstates of an arbitrary one-dimensional configuration of square potentials in a well have been derived. The general formulation is used to evaluate the energy levels of a particle in a very deep potential well containing seven internal barriers. The configuration can be considered as a finite superlattice sample or as a simplified model for a sample with only several atom layers. The results are shown in graphical forms as functions of the height and width of the potential barriers and as functions of the ratio of the effective mass in barrier to the mass in well. The formation of energy bands and surface eigenstates from eigenstates of a deep single well, the coming close of two energy bands and a surface state which are separate ordinarily, and mixing of the wave function of a surface state with the bulk energy bands are seen. Then the normalized derivation is extended to study the effect of a uniform electric field applied across a one-dimensional well containing an internal configuration of square potentials The general formulation is used to calculate the electric field dependence of the energy levels of a deep well with five internal barriers. Typical results are shown in graphical forms as functions of the barrier height, barrier width, barrier effective mass and the field strength. The formation of Stark ladders and surface states from the eigenstates of a single deep well in an electric field, the localization process of wave functions with changing barrier height, width, and field strength and their anticrossing behaviors are seen. The energy levels of a hydrogenic impurity in a uniform medium and in a uniform magnetic field are calculated with variational methods. The energy eigenvalues for the eigenstates with major quantum number less than or equal to 3 are obtained. The results are consistent with previous results. Furthermore, the energy levels of a hydrogenic impurity at the bottom of a one

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…

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…

Smart Building: Decision Making Architecture for Thermal Energy Management

PubMed Central

Hernández Uribe, Oscar; San Martin, Juan Pablo; Garcia-Alegre, María C.; Santos, Matilde; Guinea, Domingo

2015-01-01

Smart applications of the Internet of Things are improving the performance of buildings, reducing energy demand. Local and smart networks, soft computing methodologies, machine intelligence algorithms and pervasive sensors are some of the basics of energy optimization strategies developed for the benefit of environmental sustainability and user comfort. This work presents a distributed sensor-processor-communication decision-making architecture to improve the acquisition, storage and transfer of thermal energy in buildings. The developed system is implemented in a near Zero-Energy Building (nZEB) prototype equipped with a built-in thermal solar collector, where optical properties are analysed; a low enthalpy geothermal accumulation system, segmented in different temperature zones; and an envelope that includes a dynamic thermal barrier. An intelligent control of this dynamic thermal barrier is applied to reduce the thermal energy demand (heating and cooling) caused by daily and seasonal weather variations. Simulations and experimental results are presented to highlight the nZEB thermal energy reduction. PMID:26528978

Smart Building: Decision Making Architecture for Thermal Energy Management.

PubMed

Uribe, Oscar Hernández; Martin, Juan Pablo San; Garcia-Alegre, María C; Santos, Matilde; Guinea, Domingo

2015-10-30

Smart applications of the Internet of Things are improving the performance of buildings, reducing energy demand. Local and smart networks, soft computing methodologies, machine intelligence algorithms and pervasive sensors are some of the basics of energy optimization strategies developed for the benefit of environmental sustainability and user comfort. This work presents a distributed sensor-processor-communication decision-making architecture to improve the acquisition, storage and transfer of thermal energy in buildings. The developed system is implemented in a near Zero-Energy Building (nZEB) prototype equipped with a built-in thermal solar collector, where optical properties are analysed; a low enthalpy geothermal accumulation system, segmented in different temperature zones; and an envelope that includes a dynamic thermal barrier. An intelligent control of this dynamic thermal barrier is applied to reduce the thermal energy demand (heating and cooling) caused by daily and seasonal weather variations. Simulations and experimental results are presented to highlight the nZEB thermal energy reduction.

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

Hospital networks: how to make them work in Belgium? Facilitators and barriers of different governance models.

PubMed

De Pourcq, Kaat; De Regge, Melissa; Van den Heede, Koen; Van de Voorde, Carine; Gemmel, Paul; Eeckloo, Kristof

2018-03-29

Objectives This study aims to identify the facilitators and barriers to governance models of hospital collaborations. The country-specific characteristics of the Belgian healthcare system and legislation are taken into account. Methods A case study was carried out in six Belgian hospital collaborations. Different types of governance models were selected: two health systems, two participant-governed networks, and two lead-organization-governed networks. Within these collaborations, 43 people were interviewed. Results All structures have both advantages and disadvantages. It is important that the governance model fits the network. However, structural, procedural, and especially contextual factors also affect the collaborations, such as alignment of hospitals' and professionals' goals, competition, distance, level of integrated care, time needed for decision-making, and legal and financial incentives. Conclusion The fit between the governance model and the collaboration can facilitate the functioning of a collaboration. The main barriers we identified are contextual factors. The Belgian government needs to play a major role in facilitating collaboration.

Homogenous Nucleation and Crystal Growth in a Model Liquid from Direct Energy Landscape Sampling Simulation

NASA Astrophysics Data System (ADS)

Walter, Nathan; Zhang, Yang

Nucleation and crystal growth are understood to be activated processes involving the crossing of free-energy barriers. Attempts to capture the entire crystallization process over long timescales with molecular dynamic simulations have met major obstacles because of molecular dynamics' temporal constraints. Herein, we circumvent this temporal limitation by using a brutal-force, metadynamics-like, adaptive basin-climbing algorithm and directly sample the free-energy landscape of a model liquid Argon. The algorithm biases the system to evolve from an amorphous liquid like structure towards an FCC crystal through inherent structure, and then traces back the energy barriers. Consequently, the sampled timescale is macroscopically long. We observe that the formation of a crystal involves two processes, each with a unique temperature-dependent energy barrier. One barrier corresponds to the crystal nucleus formation; the other barrier corresponds to the crystal growth. We find the two processes dominate in different temperature regimes. Compared to other computation techniques, our method requires no assumptions about the shape or chemical potential of the critical crystal nucleus. The success of this method is encouraging for studying the crystallization of more complex

Recommend, but also Discuss: Different Patterns of Physician-Perceived Barriers to Discussing HPV Vaccination and Their Association with Vaccine Administration in 11-12 Year-Old Girls.

PubMed

Kulczycki, Andrzej; Qu, Haiyan; Shewchuk, Richard

2016-12-01

Objectives We examined variation in primary care physicians' (PCPs') perceptions of barriers to physician-initiated discussion of HPV vaccination, and how this is associated with the rates at which they discuss, initiate and continue to administer vaccination with 11-12 year-old girls. Methods We surveyed 301 PCPs using systematic random sampling. PCP variation in perceived barriers to discussing HPV vaccination was modeled using latent class analysis (LCA). The distinct PCP groups identified were compared with each other using three iterative logistic regression models to predict the likelihood of initiating vaccine discussion and the reported percentages of 11-12 year-old patients who initiated HPV vaccination and received follow-up shots. Results LCA revealed three groups of PCPs who perceived major, moderately significant and relatively minor barriers (17.9, 41.9 and 40.2 % of respondents, respectively). Pediatricians, PCPs who were female, had minority racial/ethnic status and who perceived only minor barriers had significantly higher odds of initiating discussion. PCPs were more likely to initiate HPV vaccination if they had initiated discussion and perceived minor or moderate communication barriers. Increased likelihood to administer follow-up HPV vaccine was associated with having initiated discussion, perceiving only minor barriers and working outside Deep South states, but not with having initiated vaccination. Conclusions for Practice PCPs who discuss HPV vaccination with girls aged 11-12 and their mothers are more likely to start and sustain vaccine administration. However, different PCPs perceive barriers to discussion in different ways. Interventions tailored to different groups of PCPs should assist them in overcoming barriers to discussing their recommendations when necessary.

A framework for monitoring-based commissioning: Identifying variables that act as barriers and enablers to the process

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

Harris, Nora; Shealy, Tripp; Kramer, Hannah

The practice of monitoring-based commissioning (MBCx) using energy management and information systems (EMIS) has been shown to enable and help sustain up to 20% energy savings in buildings. Despite research that has quantified the costs, benefits, and energy savings of MBCx, the process remains under-utilized. To understand why MBCx is not more frequently adopted and how to encourage its use, this research synthesizes qualitative data from over 40 organizations, currently engaging in MBCx. The outcome of this research is a framework containing variables that emerged from the qualitative data, marked as barriers or enablers, organized by phases of the MBCxmore » process. The framework is comprised of 51 emergent variables that fall within 13 different categories. The variables that most frequently act as barriers are data configuration, measurement & verification (M&V), developing specifications for EMIS, and data architecture. Although some variables that act as barriers for one organization were identified as enablers for another. For example, payback/ROI was considered a barrier 7 times and an enabler 3 times. One organization had difficulty making the business case for the initial investment for MBCx due to lack of cost information, while another was able to justify large investments with documented savings of previously implemented measures identified through MBCx. The framework formally validates barriers found in previous research, and can be used by practitioners to better understand common experiences with MBCx. This research also highlights the need for a similar collective data set to validate common enablers to MBCx and also the need for empirical research to determine relationships between variables.« less

A framework for monitoring-based commissioning: Identifying variables that act as barriers and enablers to the process

DOE PAGES

Harris, Nora; Shealy, Tripp; Kramer, Hannah; ...

2018-03-16

The practice of monitoring-based commissioning (MBCx) using energy management and information systems (EMIS) has been shown to enable and help sustain up to 20% energy savings in buildings. Despite research that has quantified the costs, benefits, and energy savings of MBCx, the process remains under-utilized. To understand why MBCx is not more frequently adopted and how to encourage its use, this research synthesizes qualitative data from over 40 organizations, currently engaging in MBCx. The outcome of this research is a framework containing variables that emerged from the qualitative data, marked as barriers or enablers, organized by phases of the MBCxmore » process. The framework is comprised of 51 emergent variables that fall within 13 different categories. The variables that most frequently act as barriers are data configuration, measurement & verification (M&V), developing specifications for EMIS, and data architecture. Although some variables that act as barriers for one organization were identified as enablers for another. For example, payback/ROI was considered a barrier 7 times and an enabler 3 times. One organization had difficulty making the business case for the initial investment for MBCx due to lack of cost information, while another was able to justify large investments with documented savings of previously implemented measures identified through MBCx. The framework formally validates barriers found in previous research, and can be used by practitioners to better understand common experiences with MBCx. This research also highlights the need for a similar collective data set to validate common enablers to MBCx and also the need for empirical research to determine relationships between variables.« less

Nonaxial hexadecapole deformation effects on the fission barrier

NASA Astrophysics Data System (ADS)

Kardan, A.; Nejati, S.

2016-06-01

Fission barrier of the heavy nucleus 250Cf is analyzed in a multi-dimensional deformation space. This space includes two quadrupole (ɛ2,γ) and three hexadecapole deformation (ɛ40,ɛ42,ɛ44) parameters. The analysis is performed within an unpaired macroscopic-microscopic approach. Special attention is given to the effects of the axial and non-axial hexadecapole deformation shapes. It is found that the inclusion of the nonaxial hexadecapole shapes does not change the fission barrier heights, so it should be sufficient to minimize the energy in only one degree of freedom in the hexadecapole space ɛ4. The role of hexadecapole deformation parameters is also discussed on the Lublin-Strasbourg drop (LSD) macroscopic and the Strutinsky shell energies.

Oxygen plasma etching of graphene: A first-principles dynamical inspection of the reaction mechanisms and related activation barriers

NASA Astrophysics Data System (ADS)

Koizumi, Kenichi; Boero, Mauro; Shigeta, Yasuteru; Oshiyama, Atsushi; Dept. of Applied Physics Team; Institute of Physics and Chemistry of Strasbourg (IPCMS) Collaboration; Department Of Materials Engineering Science Collaboration

2013-03-01

Oxygen plasma etching is a crucial step in the fabrication of electronic circuits and has recently received a renovated interest in view of the realization of carbon-based nanodevices. In an attempt at unraveling the atomic-scale details and to provide guidelines for the control of the etching processes mechanisms, we inspected the possible reaction pathways via reactive first principles simulations. These processes involve breaking and formation of several chemical bonds and are characterized by different free-energy barriers. Free-energy sampling techniques (metadynamics and blue moon), used to enhance the standard Car-Parrinello molecular dynamics, provide us a detailed microscopic picture of the etching of graphene surfaces and a comprehensive scenario of the activation barriers involved in the various steps. MEXT, Japan - contract N. 22104005

Fission barriers from multidimensionally-constrained covariant density functional theories

NASA Astrophysics Data System (ADS)

Lu, Bing-Nan; Zhao, Jie; Zhao, En-Guang; Zhou, Shan-Gui

2017-11-01

In recent years, we have developed the multidimensionally-constrained covariant density functional theories (MDC-CDFTs) in which both axial and spatial reflection symmetries are broken and all shape degrees of freedom described by βλμ with even μ, such as β20, β22, β30, β32, β40, etc., are included self-consistently. The MDC-CDFTs have been applied to the investigation of potential energy surfaces and fission barriers of actinide nuclei, third minima in potential energy surfaces of light actinides, shapes and potential energy surfaces of superheavy nuclei, octupole correlations between multiple chiral doublet bands in 78Br, octupole correlations in Ba isotopes, the Y32 correlations in N = 150 isotones and Zr isotopes, the spontaneous fission of Fm isotopes, and shapes of hypernuclei. In this contribution we present the formalism of MDC-CDFTs and the application of these theories to the study of fission barriers and potential energy surfaces of actinide nuclei.

Thermal stability and formation barrier of a high-energetic material N8 polymer nitrogen encapsulated in (5,5) carbon nanotube

NASA Astrophysics Data System (ADS)

Ji, Wei; Timoshevskii, V.; Guo, H.; Abou-Rachid, Hakima; Lussier, Louis-Simon

2009-07-01

We report the density functional theory total energy calculations of thermal stability and formation barrier of polymer nitrogen confined in carbon nanotubes (CNT). The analysis suggests that N8 polymer nitrogen encapsulated in (5,5) carbon nanotube [N8@CNT(5,5)] is thermally (meta)stable at a finite temperature up to energy scale of at least 5000 K, similar to nitrogen molecule gas phase confined in CNT [N2@CNT(5,5)]. The energetic difference between these two phases of N does not significantly change with temperature. A barrier of 1.07 eV was found for the formation of N8@CNT(5,5) from N2@CNT(5,5), while the dissociation barrier was found to be 0.2 eV. Snapshots of the reaction pathway show that the transition state is composed by a N2 and a N6 inside a CNT(5,5).

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.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Measuring Perceived Barriers to Healthful Eating in Obese, Treatment-Seeking Adults

ERIC Educational Resources Information Center

Welsh, Ericka M.; Jeffery, Robert W.; Levy, Rona L.; Langer, Shelby L.; Flood, Andrew P.; Jaeb, Melanie A.; Laqua, Patricia S.

2012-01-01

Objective: To characterize perceived barriers to healthful eating in a sample of obese, treatment-seeking adults and to examine whether changes in barriers are associated with energy intake and body weight. Design: Observational study based on findings from a randomized, controlled behavioral weight-loss trial. Participants: Participants were 113…

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.

Simple realization of efficient barrier performance of a single layer silicon nitride film via plasma chemistry.

PubMed

Lee, Jun Suk; Sahu, Bibhuti Bhusan; Han, Jeon Geon

2016-11-30

Due to the problem of degradation by moisture or oxygen, there is growing interest in efficient gas diffusion barriers for organic optoelectronic devices. Additionally, for the continuous and long-term operation of a device, dedicated flexible thin film encapsulation is required, which is the foremost challenge. Many efforts are being undertaken in the plasma assisted deposition process control for the optimization of film properties. Control of the plasma density along with the energy of the principal plasma species is critical to inducing alteration of the plasma reactivity, chemistry, and film properties. Here, we have used the radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) technique to deposit amorphous silicon nitride (SiN x ) barrier films onto a plastic substrate at different pressures. A large part of our efforts is devoted to a detailed study of the process parameters controlling the plasma treatment. Numerous plasma diagnostic techniques combined with various characterization tools are purposefully used to characterize and investigate the plasma environment and the associated film properties. This contribution also reports a study of the correlations between the plasma chemistry and the chemical, mechanical, barrier, and optical properties of the deposited films. The data reveal that the film possesses a very low stress for the condition where the net energy imparted on the substrate is at a minimum. Simultaneously, a relatively high ion flux and high energy of the ions impinging on the film growth surfaces are crucial for controlling the film stress and the resulting barrier properties.

Thermal barrier coatings application in diesel engines

NASA Technical Reports Server (NTRS)

Fairbanks, J. W.

1995-01-01

Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also provide protection. Roy Kamo introduced thermal barrier coatings in his 'Adiabatic Diesel Engine' in the late 70's. Kamo's concept was to eliminate the engine block water cooling system and reduce heat losses. Roy reported significant performance improvements in his thermally insulated engine at the SAE Congress in 1982. Kamo's work stimulates major programs with insulated engines, particularly in Europe. Most of the major diesel engine manufacturers conducted some level of test with insulated combustion chamber components. They initially ran into increased fuel consumption. The German engine consortium had Prof. Woschni of the Technical Institute in Munich. Woschni conducted testing with pistons with air gaps to provide the insulation effects. Woschni indicated the hot walls of the insulated engine created a major increase in heat transfer he refers to as 'convection vive.' Woschni's work was a major factor in the abrupt curtailment of insulated diesel engine work in continental Europe. Ricardo in the UK suggested that combustion should be reoptimized for the hot-wall effects of the insulated combustion chamber and showed under a narrow range of conditions fuel economy could be improved. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the

Understanding the fusion cross section among light nuclei around the Coulomb barrier

NASA Astrophysics Data System (ADS)

Del Zoppo, Antonio; La Cognata, Marco

2017-11-01

In this work we investigate fusion induced by a radioactive 8Li projectile on a 4He gas target, at center-of-mass energies between 0.6 and 5 MeV. The main result is the tendency of the dimensionless fusion cross section to form well visible plateaus alternated to steep rises. This is likely to be the most genuine consequence of the discrete nature of the intervening angular momenta observed so far in fusion reactions right above the Coulomb barrier. A partial-wave analysis, exclusively based on a pure quantal penetration fusion model, identifies a remarkably low-height barrier. Indeed, these plateaus allow enhanced experimental sensitivity to the fusion barrier given that the most barrier-sensitive lowest partial waves are well separated. We expect that the present results for 8Li+4He will promote further investigations of the fusion reaction mechanism between very light ions at energies much below the interaction barrier. For the moment, we believe that understanding the plateau origin in the cross section above the barrier will almost certainly be useful to corroborate the extrapolation to the important astrophysical region below the Coulomb barrier, not only in the case of the 8Li+4He fusion but also for other systems, such as the 12C+12C.

Use of empirical and full Bayes before-after approaches to estimate the safety effects of roadside barriers with different crash conditions.

PubMed

Park, Juneyoung; Abdel-Aty, Mohamed; Lee, Jaeyoung

2016-09-01

Although many researchers have estimated the crash modification factors (CMFs) for specific treatments (or countermeasures), there is a lack of prior studies that have explored the variation of CMFs. Thus, the main objectives of this study are: (a) to estimate CMFs for the installation of different types of roadside barriers, and (b) to determine the changes of safety effects for different crash types, severities, and conditions. Two observational before-after analyses (i.e. empirical Bayes (EB) and full Bayes (FB) approaches) were utilized in this study to estimate CMFs. To consider the variation of safety effects based on different vehicle, driver, weather, and time of day information, the crashes were categorized based on vehicle size (passenger and heavy), driver age (young, middle, and old), weather condition (normal and rain), and time difference (day time and night time). The results show that the addition of roadside barriers is safety effective in reducing severe crashes for all types and run-off roadway (ROR) crashes. On the other hand, it was found that roadside barriers tend to increase all types of crashes for all severities. The results indicate that the treatment might increase the total number of crashes but it might be helpful in reducing injury and severe crashes. In this study, the variation of CMFs was determined for ROR crashes based on the different vehicle, driver, weather, and time information. Based on the findings from this study, the variation of CMFs can enhance the reliability of CMFs for different roadway conditions in decision making process. Also, it can be recommended to identify the safety effects of specific treatments for different crash types and severity levels with consideration of the different vehicle, driver, weather, and time of day information. Copyright © 2016 Elsevier Ltd and National Safety Council. All rights reserved.

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.

Coulomb energy differences in isobaric multiplets

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

Lenzi, S. M.; Farnea, E.; Bazzacco, D.

2007-02-12

By comparing the excitation energies of analogue states in isobaric multiplets, several nuclear structure properties can be studied as a function of the angular momentum up to high spin states. In particular, the mirror nuclei 35Ar and 35Cl show large differences between the excitation energies of analogue negative-parity states at high spin, confirming the important contribution of the relativistic electromagnetic spin-orbit interaction to the Coulomb energy. The single-particle character of the configuration of these states is reproduced with very good accuracy by shell model calculations in the sd and pf shells valence space. In addition, evidence of isospin mixing ismore » deduced from the El transitions linking positive and negative parity states.« less

Resonances for Symmetric Two-Barrier Potentials

ERIC Educational Resources Information Center

Fernandez, Francisco M.

2011-01-01

We describe a method for the accurate calculation of bound-state and resonance energies for one-dimensional potentials. We calculate the shape resonances for symmetric two-barrier potentials and compare them with those coming from the Siegert approximation, the complex scaling method and the box-stabilization method. A comparison of the…

Barriers to Physical Activity on University Student

NASA Astrophysics Data System (ADS)

Jajat; Sultoni, K.; Suherman, A.

2017-03-01

The purpose of the research is to analyze the factors that become barriers to physical activity in university students based on physical activity level. An internet-based survey was conducted. The participants were 158 University students from Universitas Pendidikan Indonesia. Barriers to Physical Activity Quiz (BPAQ) were used to assessed the factors that become barriers to physical activity in university students. IPAQ (short form) were used to assessed physical activity level. The results show there was no differences BPAQ based on IPAQ level. But when analyzed further based on seven factors barriers there are differences in factors “social influence and lack of willpower” based IPAQ level. Based on this it was concluded that the “influence from other and lack of willpower” an inhibiting factor on students to perform physical activity.

Assessing Controls on the Geometry and Dimensions of Modern Barrier Islands

NASA Astrophysics Data System (ADS)

Mulhern, J.; Johnson, C. L.; Martin, J. M.

2015-12-01

Barrier islands are highly ephemeral features, shaped by wave, tide, and storm energy. The processes that govern the size, shape, and motion of barrier islands are not well constrained, yet central to coastal dynamics. While the global distribution of barrier islands has been mapped and assessed, there is little consensus on the forces controlling barrier island formation, motion, or preservation. This study presents a new semi-global database of modern barrier islands to better understand their morphology and spatial distribution. We have mapped, in Google Earth, the subaerial extent of >350 barrier islands and spits, measuring spatial characteristic such as exposed area, perimeter, length, and width. These objects are cross-referenced with parameters that potentially control morphology, including tidal range, wave height, climate, distance from the continental shelf, proximity to fluvial output, and tectonic setting. This approach provides a more optimal framework to assess controls on coastal features, including barrier island morphology, and to investigate potential geometric scaling relationships. Preliminary analysis shows trends in the spatial characteristics of barrier islands. There is a strong linear relationship between the perimeter and length (y= -0.59 + 0.42x, R2=0.95). Linear trends also relate length to area when the data are separated by tidal range to wave height ratio. Assessment of barrier island shape supports the hypothesis of Hayes (1979) that barrier islands in wave-dominated settings are long and linear while those in mixed energy setting are more rounded. The barrier islands of the Texas Gulf of Mexico are larger than the global average for the database, with distinctly longer length values (41.16 km vs. 15.77 km respectively) and larger areas (103.81 km2 vs. 42.14 km2 respectively). Initial assessment shows that tidal range and wave height are primary controls barrier island dimensions. Future work will consider climate, latitude, fluvial

Control of Internal Transport Barriers in Magnetically Confined Fusion Plasmas

NASA Astrophysics Data System (ADS)

Panta, Soma; Newman, David; Sanchez, Raul; Terry, Paul

2016-10-01

In magnetic confinement fusion devices the best performance often involves some sort of transport barriers to reduce the energy and particle flow from core to edge. Those barriers create gradients in the temperature and density profiles. If gradients in the profiles are too steep that can lead to instabilities and the system collapses. Control of these barriers is therefore an important challenge for fusion devices (burning plasmas). In this work we focus on the dynamics of internal transport barriers. Using a simple 7 field transport model, extensively used for barrier dynamics and control studies, we explore the use of RF heating to control the local gradients and therefore the growth rates and shearing rates for barrier initiation and control in self-heated fusion plasmas. Ion channel barriers can be formed in self-heated plasmas with some NBI heating but electron channel barriers are very sensitive. They can be formed in self-heated plasmas with additional auxiliary heating i.e. NBI and radio-frequency(RF). Using RF heating on both electrons and ions at proper locations, electron channel barriers along with ion channel barriers can be formed and removed demonstrating a control technique. Investigating the role of pellet injection in controlling the barriers is our next goal. Work supported by DOE Grant DE-FG02-04ER54741.

The role of perceived barriers in explaining socio-economic status differences in adherence to the fruit, vegetable and fish guidelines in older adults: a mediation study.

PubMed

Dijkstra, S Coosje; Neter, Judith E; van Stralen, Maartje M; Knol, Dirk L; Brouwer, Ingeborg A; Huisman, Martijn; Visser, Marjolein

2015-04-01

We aimed to identify barriers for meeting the fruit, vegetable and fish guidelines in older Dutch adults and to investigate socio-economic status (SES) differences in these barriers. Furthermore, we examined the mediating role of these barriers in the association between SES and adherence to these guidelines. Cross-sectional. Longitudinal Aging Study Amsterdam (LASA), the Netherlands. We used data from 1057 community-dwelling adults, aged 55-85 years. SES was measured by level of education and household income. An FFQ was used to assess dietary intake and barriers were measured with a self-reported lifestyle questionnaire. Overall, 48.9 % of the respondents perceived a barrier to adhere to the fruit guideline, 40.0 % for the vegetable and 51.1 % for the fish guideline. The most frequently perceived barriers to meet the guidelines were the high price of fruit and fish and a poor appetite for vegetables. Lower-SES groups met the guidelines less often and perceived more barriers. The association between income and adherence to the fruit guideline was mediated by 'perceiving any barrier to meet the fruit guideline' and the barrier 'dislike fruit'. The association between income and adherence to the fish guideline was mediated by 'perceiving any barrier to meet the fish guideline' and the barrier 'fish is expensive'. Perceived barriers for meeting the dietary guidelines are common in older adults, especially in lower-SES groups. These barriers and in particular disliking and cost concerns explained the lower adherence to the guidelines for fruit and fish in lower-income groups in older adults.

Primary care providers’ beliefs about teen and parent barriers to depression care

PubMed Central

Radovic, Ana; Farris, Coreen; Reynolds, Kerry; Reis, Evelyn C.; Miller, Elizabeth; Stein, Bradley D.

2015-01-01

Objective Only one-third of U.S. adolescents with depression obtain treatment for depression. Teen and parent barriers differ, but both contribute to low treatment rates. Primary care providers (PCPs) may be able to elicit and address such barriers, but little is known about their perceptions of teen and parent barriers, and whether they recognize these differences. Methods We administered a survey to 58 PCPs assessing their perceptions of the importance of specific barriers to depression care for teens and parents using McNemar’s test to examine differences. Results Most PCPs believed barriers for parents included difficulty making appointments, worry about what others would think, and cost. PCPs believed barriers for teens included not wanting treatment and worry about what others would think. PCPs believed parents and teens differed in the extent to which they would perceive cost, difficulty making appointments, and not wanting care as a barrier (ps<.001). Conclusions PCPs recognize teens and parents have different barriers to care, but may have discordant perceptions of the importance of certain barriers for teens and their parents. PCPs may need to probe parents and teens individually about barriers which impede depression care to enhance shared decision making and treatment uptake. PMID:25098692

[Prevalence of barriers for physical activity in adolescents].

PubMed

Santos, Mariana Silva; Hino, Adriano Akira Ferreira; Reis, Rodrigo Siqueira; Rodriguez-Añez, Ciro Romélio

2010-03-01

The aim of this study was to analyze the prevalence and association of barriers to physical activity among adolescents. This cross-sectional study evaluated a representative sample of public high school students in Curitiba-PR, Brazil. A total of 1,609 school adolescents (59.7% male) between 14 and 18 years of age answered a questionnaire on physical activity status and barriers to physical activity. Logistic regressions were conducted for each barrier investigated to verify the association between the prevalence of barriers and physical activity, adjusting for confounding variables (age and socioeconomic status). Analyses were done separately for boys and girls. Only 22% of boys and 9% of girls achieved the current physical activity recommendation. Among the 12 barriers investigated, only "there is nobody to take" did not differ between boys and girls. The perception of barriers was higher for girls than boys (p < 0.05) for all other barriers. "Lack of friends company" and "feel lazy" were the barriers most often reported by boys (30.4%) and girls (51.8%) respectively; however, the barrier most strongly associated with prevalence of physical inactivity was "prefer to do other things" for both boys (OR = 5.02 (2.69 - 9.37); p < 0.05) and girls (OR = 7.10 (3.71 - 13.60); p < 0.05). Perceived barriers for the practice of physical activity were more prevalent in girls and differed as to the extent of importance between genders.

Assessment of skin barrier function and biochemical changes of ex vivo human skin in response to physical and chemical barrier disruption.

PubMed

Döge, Nadine; Avetisyan, Araks; Hadam, Sabrina; Pfannes, Eva Katharina Barbosa; Rancan, Fiorenza; Blume-Peytavi, Ulrike; Vogt, Annika

2017-07-01

Topical dermatotherapy is intended to be used on diseased skin. Novel drug delivery systems even address differences between intact and diseased skin underlining the need for pre-clinical assessment of different states of barrier disruption. Herein, we studied how short-term incubation in culture media compared to incubation in humidified chambers affects human skin barrier function and viability. On both models we assessed different types and intensities of physical and chemical barrier disruption methods with regard to structural integrity, biophysical parameters and cytokine levels. Tissue degeneration and proliferative activity limited the use of tissue cultures to 48h. Viability is better preserved in cultured tissue. Tape-stripping (50×TS) and 4h sodium lauryl sulfate (SLS) pre-treatment were identified as highly reproducible and effective procedures for barrier disruption. Transepidermal water loss (TEWL) values reproducibly increased with the intensity of disruption while sebum content and skin surface pH were of limited value. Interleukin (IL)-6/8 and various chemokines and proteases were increased in tape-stripped skin which was more pronounced in SLS-treated skin tissue extracts. Thus, albeit limited to 48h, cultured full-thickness skin maintained several barrier characteristics and responded to different intensities of barrier disruption. Potentially, these models can be used to assess pre-clinically the efficacy and penetration of anti-inflammatory compounds. Copyright © 2016 Elsevier B.V. All rights reserved.

Transient effects of drying creep in nanoporous solids: understanding the effects of nanoscale energy barriers

NASA Astrophysics Data System (ADS)

Sinko, Robert; Vandamme, Matthieu; Bažant, Zdeněk P.; Keten, Sinan

2016-07-01

The Pickett effect is the phenomenon of creep enhancement during transient drying. It has been observed for many nanoporous solids, including concrete, wood and Kevlar. While the existing micromechanical models can partially explain this effect, they have yet to consider nanoscale dynamic effects of water in nanopores, which are believed to be of paramount importance. Here, we examine how creep deformations in a slit pore are accelerated by the motion of water due to drying forces using coarse-grained molecular dynamics simulations. We find that the drying that drives water flow in the nanopores lowers both the activation energy of pore walls sliding past one another and the apparent viscosity of confined water molecules. This lowering can be captured with an analytical Arrhenius relationship accounting for the role of water flow in overcoming the energy barriers. Notably, we use this model and simulation results to demonstrate that the drying creep strain is not linearly dependent on the applied creep stress at the nanopore level. Our findings establish the scaling relationships that explain how the creep driving force, drying force and fluid properties are related. Thus, we establish the nanoscale origins of the Pickett effect and provide strategies for minimizing the additional displacements arising from this effect.

Transient effects of drying creep in nanoporous solids: understanding the effects of nanoscale energy barriers

PubMed Central

Sinko, Robert; Vandamme, Matthieu; Keten, Sinan

2016-01-01

The Pickett effect is the phenomenon of creep enhancement during transient drying. It has been observed for many nanoporous solids, including concrete, wood and Kevlar. While the existing micromechanical models can partially explain this effect, they have yet to consider nanoscale dynamic effects of water in nanopores, which are believed to be of paramount importance. Here, we examine how creep deformations in a slit pore are accelerated by the motion of water due to drying forces using coarse-grained molecular dynamics simulations. We find that the drying that drives water flow in the nanopores lowers both the activation energy of pore walls sliding past one another and the apparent viscosity of confined water molecules. This lowering can be captured with an analytical Arrhenius relationship accounting for the role of water flow in overcoming the energy barriers. Notably, we use this model and simulation results to demonstrate that the drying creep strain is not linearly dependent on the applied creep stress at the nanopore level. Our findings establish the scaling relationships that explain how the creep driving force, drying force and fluid properties are related. Thus, we establish the nanoscale origins of the Pickett effect and provide strategies for minimizing the additional displacements arising from this effect. PMID:27493584

Transient effects of drying creep in nanoporous solids: understanding the effects of nanoscale energy barriers.

PubMed

Sinko, Robert; Vandamme, Matthieu; Bažant, Zdeněk P; Keten, Sinan

2016-07-01

The Pickett effect is the phenomenon of creep enhancement during transient drying. It has been observed for many nanoporous solids, including concrete, wood and Kevlar. While the existing micromechanical models can partially explain this effect, they have yet to consider nanoscale dynamic effects of water in nanopores, which are believed to be of paramount importance. Here, we examine how creep deformations in a slit pore are accelerated by the motion of water due to drying forces using coarse-grained molecular dynamics simulations. We find that the drying that drives water flow in the nanopores lowers both the activation energy of pore walls sliding past one another and the apparent viscosity of confined water molecules. This lowering can be captured with an analytical Arrhenius relationship accounting for the role of water flow in overcoming the energy barriers. Notably, we use this model and simulation results to demonstrate that the drying creep strain is not linearly dependent on the applied creep stress at the nanopore level. Our findings establish the scaling relationships that explain how the creep driving force, drying force and fluid properties are related. Thus, we establish the nanoscale origins of the Pickett effect and provide strategies for minimizing the additional displacements arising from this effect.

Photovoltaic conversion of laser energy

NASA Technical Reports Server (NTRS)

Stirn, R. J.

1976-01-01

The Schottky barrier photovoltaic converter is suggested as an alternative to the p/n junction photovoltaic devices for the conversion of laser energy to electrical energy. The structure, current, output, and voltage output of the Schottky device are summarized. The more advanced concepts of the multilayer Schottky barrier cell and the AMOS solar cell are briefly considered.

Adherence and barriers to colorectal cancer screening varies among Arab Americans from different countries of origin.

PubMed

Talaat, Nizar

2015-01-01

Arab-Americans (ArA) in Michigan, USA had the lowest colorectal cancer screening (CRCS) in 2008 compared to the state's general population (45.6% vs. 60.8%). The adherence rate and barriers to CRCS have been identified in a previous study; however, these differences have been not examined among ArA from different countries of origin. Community-based study through a survey filled by 130 Arab-Americans aged ⩾50years. Demographic information and information about CRC screening knowledge were obtained. Responses were compared between the two largest population groups (Lebanese and Yemenis). The majority of the participants (80%) were from Lebanon (52.3%) and Yemen (27.7%). Majority of the Yemenis group have never been screened for CRC (72.2% vs. 27.9%, p<0.001). Majority of the unscreened Yemenis were males (100% vs. 63.2%, p=0.002). Both unscreened groups had similar length of residence in U.S., citizenship status, education level, health insurance and access to primary care physicians. Unscreened Lebanese had a higher family history of CRCS (31.6% vs. 0%, p=0.002). The most common reported barrier for both groups was the misconception that CRCS is not necessary (62% for Yemenis & 42% for Lebanese, p=0.197). Unscreened Yemenis were more unaware about CRCS (46% vs. 11%, p=0.002). CRC screening rates vary among Arab-Americans from different countries of origin. Physicians should consider the country of origin when recommending CRC screening to Arab-Americans. Copyright © 2015 Arab Journal of Gastroenterology. Published by Elsevier B.V. All rights reserved.

Schottky barrier height of Ni to β-(AlxGa1-x)2O3 with different compositions grown by plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Ahmadi, Elaheh; Oshima, Yuichi; Wu, Feng; Speck, James S.

2017-03-01

Coherent β-(AlxGa1-x)2O3 films (x = 0, 0.038, 0.084, 0.164) were grown successfully on a Sn-doped β-Ga2O3 (010) substrate using plasma-assisted molecular beam epitaxy. Atom probe tomography, transmission electron microscopy, and high resolution x-ray diffraction were used to verify the alloy composition and high quality of the films. Schottky diodes were then fabricated using Ni as the Schottky metal. Capacitance-voltage measurements revealed a very low (<7 × 1015 cm-3) free charge density in the nominally undoped films. The barrier height and ideality factor were estimated by current-voltage (I-V) measurements performed at temperatures varying from 300 K to 500 K on the Schottky diodes. These measurements revealed that the apparent Schottky barrier height could have similar values for different compositions of β-(AlxGa1-x)2O3. We believe this is attributed to the lateral fluctuation in the alloy’s composition. This results in a lateral variation in the barrier height. Therefore, the average Schottky barrier height extracted from I-V measurements could be similar for β-(AlxGa1-x)2O3 films with different compositions.

Memory-induced acceleration and slowdown of barrier crossing

NASA Astrophysics Data System (ADS)

Kappler, Julian; Daldrop, Jan O.; Brünig, Florian N.; Boehle, Moritz D.; Netz, Roland R.

2018-01-01

We study the mean first-passage time τMFP for the barrier crossing of a single massive particle with non-Markovian memory by Langevin simulations in one dimension. In the Markovian limit of short memory time τΓ, the expected Kramers turnover between the overdamped (high-friction) and the inertial (low-friction) limits is recovered. Compared to the Markovian case, we find barrier crossing to be accelerated for intermediate memory time, while for long memory time, barrier crossing is slowed down and τMFP increases with τΓ as a power law τM F P˜τΓ2. Both effects are derived from an asymptotic propagator analysis: while barrier crossing acceleration at intermediate memory can be understood as an effective particle mass reduction, slowing down for long memory is caused by the slow kinetics of energy diffusion. A simple and globally accurate heuristic formula for τMFP in terms of all relevant time scales of the system is presented and used to establish a scaling diagram featuring the Markovian overdamped and the Markovian inertial regimes, as well as the non-Markovian intermediate memory time regime where barrier crossing is accelerated and the non-Markovian long memory time regime where barrier crossing is slowed down.

Thermal model of attic systems with radiant barriers

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

Wilkes, K.E.

This report summarizes the first phase of a project to model the thermal performance of radiant barriers. The objective of this phase of the project was to develop a refined model for the thermal performance of residential house attics, with and without radiant barriers, and to verify the model by comparing its predictions against selected existing experimental thermal performance data. Models for the thermal performance of attics with and without radiant barriers have been developed and implemented on an IBM PC/AT computer. The validity of the models has been tested by comparing their predictions with ceiling heat fluxes measured inmore » a number of laboratory and field experiments on attics with and without radiant barriers. Cumulative heat flows predicted by the models were usually within about 5 to 10 percent of measured values. In future phases of the project, the models for attic/radiant barrier performance will be coupled with a whole-house model and further comparisons with experimental data will be made. Following this, the models will be utilized to provide an initial assessment of the energy savings potential of radiant barriers in various configurations and under various climatic conditions. 38 refs., 14 figs., 22 tabs.« less

Simulation of Nanowires on Metal Vicinal Surfaces: Effect of Growth Parameters and Energetic Barriers

NASA Astrophysics Data System (ADS)

Hamouda, Ajmi B. H.; Blel, Sonia; Einstein, T. L.

2012-02-01

Growing one-dimensional metal structures is an important task in the investigation of the electronic and magnetic properties of new devices. We used kinetic Monte-Carlo (kMC) method to simulate the formation of nanowires of several metallic and non-metallic adatoms on Cu and Pt vicinal surfaces. We found that mono-atomic chains form on step-edges due to energetic barriers (the so-called Ehrlich-shwoebel and exchange barriers) on step-edge. Creation of perfect wires is found to depend on growth parameters and binding energies. We measure the filling ratio of nanowires for different chemical species in a wide range of temperature and flux. Perfect wires were obtained at lower deposition rate for all tested adatoms, however we notice different temperature ranges. Our results were compared with experimental ones [Gambardella et al., Surf. Sci.449, 93-103 (2000), PRB 61, 2254-2262, (2000)]. We review the role of impurities in nanostructuring of surfaces [Hamouda et al., Phys. Rev. B 83, 035423, (2011)] and discuss the effect of their energetic barriers on the obtained quality of nanowires. Our work provides experimentalists with optimum growth parameters for the creation of a uniform distribution of wires on surfaces.

Molecular gap and energy level diagram for pentacene adsorbed on filled d-band metal surfaces

NASA Astrophysics Data System (ADS)

Baldacchini, Chiara; Mariani, Carlo; Betti, Maria Grazia; Gavioli, L.; Fanetti, M.; Sancrotti, M.

2006-10-01

The authors present a combined photoemission and scanning-tunneling spectroscopy study of the filled electronic states, the molecular energy gap, and the energy level diagram of highly ordered arrays of pentacene deposited on the Cu(119) vicinal surface. The states localized at the interface are clearly singled out, comparing the results at different pentacene thicknesses and with gas-phase photoemission data. The molecular gap of 2.35eV, the hole injection barrier of 1.05eV, and the electron injection barrier of 1.30eV determine the energy level diagram of the states localized at the pentacene molecules.

Determining collective barrier operation skew in a parallel computer

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

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:more » 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.« less

Determining collective barrier operation skew in a parallel computer

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

Faraj, Daniel A.

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:more » 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.« less

Transformer coupling for transmitting direct current through a barrier

DOEpatents

Brown, Ralph L.; Guilford, Richard P.; Stichman, John H.

1988-01-01

The transmission system for transmitting direct current from an energy source on one side of an electrical and mechanical barrier to a load on the other side of the barrier utilizes a transformer comprising a primary core on one side of the transformer and a secondary core on the other side of the transformer. The cores are magnetically coupled selectively by moving a magnetic ferrite coupler in and out of alignment with the poles of the cores. The direct current from the energy source is converted to a time varying current by an oscillating circuit, which oscillating circuit is optically coupled to a secondary winding on the secondary core to interrupt oscillations upon the voltage in the secondary winding exceeding a preselected level.

Transformer coupling for transmitting direct current through a barrier

DOEpatents

Brown, R.L.; Guilford, R.P.; Stichman, J.H.

1987-06-29

The transmission system for transmitting direct current from an energy source on one side of an electrical and mechanical barrier to a load on the other side of the barrier utilizes a transformer comprising a primary core on one side of the transformer and a secondary core on the other side of the transformer. The cores are magnetically coupled selectively by moving a magnetic ferrite coupler in and out of alignment with the poles of the cores. The direct current from the energy source is converted to a time varying current by an oscillating circuit, which oscillating circuit is optically coupled to a secondary winding on the secondary core to interrupt oscillations upon the voltage in the secondary winding exceeding a preselected level. 4 figs.

Feasibility study of tank leakage mitigation using subsurface barriers

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

Treat, R.L.; Peters, B.B.; Cameron, R.J.

1994-09-21

The US Department of Energy (DOE) has established the Tank Waste Remediation System (TWRS) to satisfy manage and dispose of the waste currently stored in the underground storage tanks. The retrieval element of TWRS includes a work scope to develop subsurface impermeable barriers beneath SSTs. The barriers could serve as a means to contain leakage that may result from waste retrieval operations and could also support site closure activities by facilitating cleanup. Three types of subsurface barrier systems have emerged for further consideration: (1) chemical grout, (2) freeze walls, and (3) desiccant, represented in this feasibility study as a circulatingmore » air barrier. This report contains analyses of the costs and relative risks associated with combinations retrieval technologies and barrier technologies that from 14 alternatives. Eight of the alternatives include the use of subsurface barriers; the remaining six nonbarrier alternative are included in order to compare the costs, relative risks and other values of retrieval with subsurface barriers. Each alternative includes various combinations of technologies that can impact the risks associated with future contamination of the groundwater beneath the Hanford Site to varying degrees. Other potential risks associated with these alternatives, such as those related to accidents and airborne contamination resulting from retrieval and barrier emplacement operations, are not quantitatively evaluated in this report.« less

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.

Investigation the electroplating behavior of self formed CuMn barrier.

PubMed

Wu, Chia-Yang; Lee, Wen-Hsi; Chang, Shih-Chieh; Wang, Ying-Lang

2013-08-01

The electrical and material properties of Copper (Cu) mixed with [0-10 atomic% manganese (Mn)] and pure Cu films deposited on silicon oxide (SiO2)/silicon (Si) are explored. Cu electroplating on self formed CuMn barrier was investigated with different Mn content. The electrochemical deposition of the Cu thin film onto the electrode using CuMn barrier was investigated. Scanning electron microscopic (SEM) micrographs of copper electroplating on CuMn films were examined, and the copper nucleation behaviors changed with the Mn content. Since the electrochemical impedance spectroscopy (EIS) is widely recognized as a powerful tool for the investigation of electrochemical behaviors, the tool was also used to verify the phenomena during plating. It was found that the charge-trasfer impedance decrease with the rise in the Mn content below 5%, but increase with the rise in the Mn content higher than 5%. The result was corresponded to the surface energy, the surface morphology, the corrosion and the oxidation of the substrate.

Visual selective attention with virtual barriers.

PubMed

Schneider, Darryl W

2017-07-01

Previous studies have shown that interference effects in the flanker task are reduced when physical barriers (e.g., hands) are placed around rather than below a target flanked by distractors. One explanation of this finding is the referential coding hypothesis, whereby the barriers serve as reference objects for allocating attention. In five experiments, the generality of the referential coding hypothesis was tested by investigating whether interference effects are modulated by the placement of virtual barriers (e.g., parentheses). Modulation of flanker interference was found only when target and distractors differed in size and the virtual barriers were beveled wood-grain objects. Under these conditions and those of previous studies, the author conjectures that an impression of depth was produced when the barriers were around the target, such that the target was perceived to be on a different depth plane than the distractors. Perception of depth in the stimulus display might have led to referential coding of the stimuli in three-dimensional (3-D) space, influencing the allocation of attention beyond the horizontal and vertical dimensions. This 3-D referential coding hypothesis is consistent with research on selective attention in 3-D space that shows flanker interference is reduced when target and distractors are separated in depth.

New Global Calculation of Nuclear Masses and Fission Barriers for Astrophysical Applications

NASA Astrophysics Data System (ADS)

Möller, P.; Sierk, A. J.; Bengtsson, R.; Ichikawa, T.; Iwamoto, A.

2008-05-01

The FRDM(1992) mass model [1] has an accuracy of 0.669 MeV in the region where its parameters were determined. For the 529 masses that have been measured since, its accuracy is 0.46 MeV, which is encouraging for applications far from stability in astrophysics. We are developing an improved mass model, the FRDM(2008). The improvements in the calculations with respect to the FRDM(1992) are in two main areas. (1) The macroscopic model parameters are better optimized. By simulation (adjusting to a limited set of now known nuclei) we can show that this actually makes the results more reliable in new regions of nuclei. (2) The ground-state deformation parameters are more accurately calculated. We minimize the energy in a four-dimensional deformation space (ɛ2, V3, V4, V6,) using a grid interval of 0.01 in all 4 deformation variables. The (non-finalized) FRDM (2008-a) has an accuracy of 0.596 MeV with respect to the 2003 Audi mass evaluation before triaxial shape degrees of freedom are included (in progress). When triaxiality effects are incorporated preliminary results indicate that the model accuracy will improve further, to about 0.586 MeV. We also discuss very large-scale fission-barrier calculations in the related FRLDM (2002) model, which has been shown to reproduce very satisfactorily known fission properties, for example barrier heights from 70Se to the heaviest elements, multiple fission modes in the Ra region, asymmetry of mass division in fission and the triple-humped structure found in light actinides. In the superheavy region we find barriers consistent with the observed half-lives. We have completed production calculations and obtain barrier heights for 5254 nuclei heavier than A = 170 for all nuclei between the proton and neutron drip lines. The energy is calculated for 5009325 different shapes for each nucleus and the optimum barrier between ground state and separated fragments is determined by use of an ``immersion'' technique.

New Global Calculation of Nuclear Masses and Fission Barriers for Astrophysical Applications

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

Moeller, P.; Sierk, A. J.; Bengtsson, R.

The FRDM(1992) mass model [1] has an accuracy of 0.669 MeV in the region where its parameters were determined. For the 529 masses that have been measured since, its accuracy is 0.46 MeV, which is encouraging for applications far from stability in astrophysics. We are developing an improved mass model, the FRDM(2008). The improvements in the calculations with respect to the FRDM(1992) are in two main areas. (1) The macroscopic model parameters are better optimized. By simulation (adjusting to a limited set of now known nuclei) we can show that this actually makes the results more reliable in new regionsmore » of nuclei. (2) The ground-state deformation parameters are more accurately calculated. We minimize the energy in a four-dimensional deformation space ({epsilon}{sub 2}, {epsilon}{sub 3}, {epsilon}{sub 4}, {epsilon}{sub 6},) using a grid interval of 0.01 in all 4 deformation variables. The (non-finalized) FRDM (2008-a) has an accuracy of 0.596 MeV with respect to the 2003 Audi mass evaluation before triaxial shape degrees of freedom are included (in progress). When triaxiality effects are incorporated preliminary results indicate that the model accuracy will improve further, to about 0.586 MeV.We also discuss very large-scale fission-barrier calculations in the related FRLDM (2002) model, which has been shown to reproduce very satisfactorily known fission properties, for example barrier heights from {sup 70}Se to the heaviest elements, multiple fission modes in the Ra region, asymmetry of mass division in fission and the triple-humped structure found in light actinides. In the superheavy region we find barriers consistent with the observed half-lives. We have completed production calculations and obtain barrier heights for 5254 nuclei heavier than A = 170 for all nuclei between the proton and neutron drip lines. The energy is calculated for 5009325 different shapes for each nucleus and the optimum barrier between ground state and separated fragments is

Barriers to Liposomal Gene Delivery: from Application Site to the Target.

PubMed

Saffari, Mostafa; Moghimi, Hamid Reza; Dass, Crispin R

2016-01-01

Gene therapy is a therapeutic approach to deliver genetic material into cells to alter their function in entire organism. One promising form of gene delivery system (DDS) is liposomes. The success of liposome-mediated gene delivery is a multifactorial issue and well-designed liposomal systems might lead to optimized gene transfection particularly in vivo. Liposomal gene delivery systems face different barriers from their site of application to their target, which is inside the cells. These barriers include presystemic obstacles (epithelial barriers), systemic barriers in blood circulation and cellular barriers. Epithelial barriers differ depending on the route of administration. Systemic barriers include enzymatic degradation, binding and opsonisation. Both of these barriers can act as limiting hurdles that genetic material and their vector should overcome before reaching the cells. Finally liposomes should overcome cellular barriers that include cell entrance, endosomal escape and nuclear uptake. These barriers and their impact on liposomal gene delivery will be discussed in this review.

Laser-Driven Recollisions under the Coulomb Barrier.

PubMed

Keil, Th; Popruzhenko, S V; Bauer, D

2016-12-09

Photoelectron spectra obtained from the ab initio solution of the time-dependent Schrödinger equation can be in striking disagreement with predictions by the strong-field approximation (SFA), not only at low energy but also around twice the ponderomotive energy where the transition from the direct to the rescattered electrons is expected. In fact, the relative enhancement of the ionization probability compared to the SFA in this regime can be several orders of magnitude. We show for which laser and target parameters such an enhancement occurs and for which the SFA prediction is qualitatively good. The enhancement is analyzed in terms of the Coulomb-corrected action along analytic quantum orbits in the complex-time plane, taking soft recollisions under the Coulomb barrier into account. These recollisions in complex time and space prevent a separation into sub-barrier motion up to the "tunnel exit" and subsequent classical dynamics. Instead, the entire quantum path up to the detector determines the ionization probability.

Perceived barriers to physical activity among Nigerian stroke survivors.

PubMed

Idowu, Opeyemi Ayodiipo; Adeniyi, Ade Fatai; Ogwumike, Omoyemi Olubunmi; Fawole, Henrietta Oluwafunmilola; Akinrolie, Olayinka

2015-01-01

Benefits of physical activity in the prevention and management of stroke are well documented in the literature. There is increasing evidence that stroke survivors in South-West Nigeria are physically inactive. Data on barriers to the achievement of the recommended physical activity levels including its differences along socio-demographic characteristics among stroke survivors in South-West Nigeria are needed. The Exercise Benefits and Barrier Scale and the International Physical Activity Questionnaire were administered on 121 stroke survivors to determine their perceived barriers to physical activity and physical activity levels respectively. Information on socio-demographic data and clinical variables were also collected. The sample included 70.2% males, with majority of the participants reporting low physical activity levels (80.2%) and high perceived barriers (Mean = 48.13, SD = 7.88). The four most reported common barriers among stroke survivors were access to exercise facilities (95.0%), being embarrassed to exercise (94.2%), economic cost demands of exercise (94.2%) and notion that people in exercise clothes look funny (94.2%) respectively. There were no significant differences found in barriers to physical activity between gender (U = 1471.00, P = 0.74) and across each of: occupational status (H = 4.37, P = 0.22), age group (H = 0.82, P = 0.84) and educational levels (H = 4.56, P = 0.33). Significant difference however existed in perceived barriers across marital status categories (H = 12.87, P = 0.05). Stroke survivors indicated high perceived barriers to physical activity and these barriers were associated with marital status.

Surface tension, surface energy, and chemical potential due to their difference.

PubMed

Hui, C-Y; Jagota, A

2013-09-10

It is well-known that surface tension and surface energy are distinct quantities for solids. Each can be regarded as a thermodynamic property related first by Shuttleworth. Mullins and others have suggested that the difference between surface tension and surface energy cannot be sustained and that the two will approach each other over time. In this work we show that in a single-component system where changes in elastic energy can be neglected, the chemical potential difference between the surface and bulk is proportional to the difference between surface tension and surface energy. By further assuming that mass transfer is driven by this chemical potential difference, we establish a model for the kinetics by which mass transfer removes the difference between surface tension and surface energy.

Lifelong consumption of sodium selenite: gender differences on blood-brain barrier permeability in convulsive, hypoglycemic rats.

PubMed

Seker, F Burcu; Akgul, Sibel; Oztas, Baria

2008-07-01

The aim of this study was to compare the effects of hypoglycemia and induced convulsions on the blood-brain barrier permeability in rats with or without lifelong administration of sodium selenite. There is a significant decrease of the blood-brain barrier permeability in three brain regions of convulsive, hypoglycemic male rats treated with sodium selenite when compared to sex-matched untreated rats (p<0.05), but the decrease was not significant in female rats (p>0.05). The blood-brain barrier permeability of the left and right hemispheres of untreated, moderately hypoglycemic convulsive rats of both genders was better than their untreated counterparts (p<0.05). Our results suggest that moderate hypoglycemia and lifelong treatment with sodium selenite have a protective effect against blood-brain barrier permeability during convulsions and that the effects of sodium selenite are gender-dependent.

Aligning Utility Incentives with Investment in Energy Efficiency

EPA Pesticide Factsheets

Learn more about the financial effects on a utility of its spending on energy efficiency programs, how those effects could constitute barriers to utility investment in energy efficiency, and how various policies can reduce these barriers.

Barriers to evidence-based medicine: a systematic review.

PubMed

Sadeghi-Bazargani, Homayoun; Tabrizi, Jafar Sadegh; Azami-Aghdash, Saber

2014-12-01

Evidence-based medicine (EBM) has emerged as an effective strategy to improve health care quality. The aim of this study was to systematically review and carry out an analysis on the barriers to EBM. Different database searching methods and also manual search were employed in this study using the search words ('evidence-based' or 'evidence-based medicine' or 'evidence-based practice' or 'evidence-based guidelines' or 'research utilization') and (barrier* or challenge or hinder) in the following databases: PubMed, Scopus, Web of Knowledge, Cochrane library, Pro Quest, Magiran, SID. Out of 2592 articles, 106 articles were finally identified for study. Research barriers, lack of resources, lack of time, inadequate skills, and inadequate access, lack of knowledge and financial barriers were found to be the most common barriers to EBM. Examples of these barriers were found in primary care, hospital/specialist care, rehabilitation care, medical education, management and decision making. The most common barriers to research utilization were research barriers, cooperation barriers and changing barriers. Lack of resources was the most common barrier to implementation of guidelines. The result of this study shows that there are many barriers to the implementation and use of EBM. Identifying barriers is just the first step to removing barriers to the use of EBM. Extra resources will be needed if these barriers are to be tackled. © 2014 John Wiley & Sons, Ltd.

Anomalous anisotropies of fission fragments in near- and sub-barrier fusion-fussion reactions

NASA Astrophysics Data System (ADS)

Huanqiao, Zhang; Zuhua, Liu; Jincheng, Xu; Jun, Lu; Ming, Ruan; Kan, Xu

1992-03-01

Fission cross sections and angular distributions have been measured for the reactions of 16O + 232Th and238U, and19F + 208Pb and232Th at near- and sub-barrier energies. The fission excitation functions are rather well reproduced on the basis of Wong model or coupled channels theory. However, the models which reproduce the sub-barrier fusion cross sections fail to account for the experimental anisotropies of fission fragments. It is found that the observed anisotropies are much larger than expected. For the first time it has been observed that the anisotropies as a function of the center-of-mass energy show a peak centered near 4.5 MeV below the fusion barrier for several reaction systems. The present approaches fail to explain these anomalies. For 19F + 208Pb systems, our results confirm the prediction of an approximately constant value for the mean square spin of the compound nucleus produced in far sub-barrier fusion reaction.

The perceived value of using BIM for energy simulation

NASA Astrophysics Data System (ADS)

Lewis, Anderson M.

Building Information Modeling (BIM) is becoming an increasingly important tool in the Architectural, Engineering & Construction (AEC) industries. Some of the benefits associated with BIM include but are not limited to cost and time savings through greater trade and design coordination, and more accurate estimating take-offs. BIM is a virtual 3D, parametric design software that allows users to store information of a model within and can be used as a communication platform between project stakeholders. Likewise, energy simulation is an integral tool for predicting and optimizing a building's performance during design. Creating energy models and running energy simulations can be a time consuming activity due to the large number of parameters and assumptions that must be addressed to achieve reasonably accurate results. However, leveraging information imbedded within Building Information Models (BIMs) has the potential to increase accuracy and reduce the amount of time required to run energy simulations and can facilitate continuous energy simulations throughout the design process, thus optimizing building performance. Although some literature exists on how design stakeholders perceive the benefits associated with leveraging BIM for energy simulation, little is known about how perceptions associated with leveraging BIM for energy simulation differ between various green design stakeholder user groups. Through an e-survey instrument, this study seeks to determine how perceptions of using BIMs to inform energy simulation differ among distinct design stakeholder groups, which include BIM-only users, energy simulation-only users and BIM and energy simulation users. Additionally, this study seeks to determine what design stakeholders perceive as the main barriers and benefits of implementing BIM-based energy simulation. Results from this study suggest that little to no correlation exists between green design stakeholders' perceptions of the value associated with using

The effects of temperature on the lattice barrier for twin wall motion

NASA Astrophysics Data System (ADS)

Zreihan, Noam; Faran, Eilon; Shilo, Doron

2015-07-01

The sideways motion of twin walls in ferroic materials requires overcoming an intrinsic energy barrier that originates from the periodicity of the crystal structure. Here, we measure the temperature dependence of the lattice barrier in a ferromagnetic Ni-Mn-Ga crystal using the pulsed magnetic field method. Our results reveal a monotonic decrease in the lattice barrier with increasing temperature. Yet, the barrier does not vanish as the temperature approaches the temperature of the martensite to austenite transformation. These findings enable the formulation of an analytical expression that correlates the lattice barrier to the physical properties of the twin wall, such as its thickness and the associated transformation strain. The derived relation provides a good quantitative description of the data measured in Ni-Mn-Ga.

Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode

NASA Astrophysics Data System (ADS)

Hu, J.; Stoffels, S.; Lenci, S.; Bakeroot, B.; Venegas, R.; Groeseneken, G.; Decoutere, S.

2015-02-01

This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5 V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ϕB increase) together with RON degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.

The changes in the reproductive barrier between hexaploid wheat (Triticum aestivum L.) and rye (Secale cereale L.): different states lead to different fates.

PubMed

Tikhenko, Natalia; Rutten, Twan; Senula, Angelika; Rubtsova, Myroslava; Keller, E R Joachim; Börner, Andreas

2017-09-01

The changes in the reproductive barrier between hexaploid wheat ( Triticum aestivum L.) and rye ( Secale cereale L.) can be induced using in situ embryo rescue of abnormal embryos, yielding stable fertile amphidiploid plants. In intergeneric crosses between hexaploid wheat (Triticum aestivum L.) and rye (Secale cereale L.), postzygotic barriers may occur at different stages of hybrid development. One such mechanism is embryo lethality, which is genetically determined by the interaction and expression of two incompatible genes in wheat (Eml-A1) and rye (Eml-R1). Using in vitro culture methods as stressors, we overcame this hybrid lethality. Normal and abnormal embryos were observed to build embryogenic calli and produce regenerated plantlets in a similar manner. The high regenerative capacity of the abnormal embryos led us to conclude that the reproductive barrier in these intergeneric hybrids may have an epigenetic origin that can be easily overcome by culturing immature embryos via callus induction. After colchicine treatment during callus culture, amphidiploid plants were obtained. However, most of these plants did not produce seeds, due mainly to sterility of the pollen but also of the embryo sacs. These findings demonstrate that hybrid sterility affects both male and female gametophytes in plants obtained from abnormal embryos. The key roles of double fertilization and stress factors in the implementation of the apical meristem formation program in embryos from incompatible intergeneric crosses between hexaploid wheat and rye during in vitro culture are discussed. We also propose a hypothetical model for a wheat-rye lethality system involving differential expression of incompatible wheat Eml-A1 and rye Eml-R1b alleles in an identical genetic background.

Blood-brain barrier dysfunction in brain diseases: clinical experience.

PubMed

Schoknecht, Karl; Shalev, Hadar

2012-11-01

The blood-brain barrier, a unique feature of the cerebral vasculature, is gaining attention as a feature in common neurologic disorders including stroke, traumatic brain injury, epilepsy, and schizophrenia. Although acute blood-brain barrier dysfunction can induce cerebral edema, seizures, or neuropsychiatric symptoms, epileptogenesis and cognitive decline are among the chronic effects. The mechanisms underlying blood-brain barrier dysfunction are diverse and may range from physical endothelial damage in traumatic brain injury to degradation of extracellular matrix proteins via matrix metalloproteinases as part of an inflammatory response. Clinically, blood-brain barrier dysfunction is often detected using contrast-enhanced imaging. However, these techniques do not give any insights into the underlying mechanism. Elucidating the specific pathways of blood-brain barrier dysfunction at different time points and in different brain diseases using novel imaging techniques promises a more accurate blood-brain barrier terminology as well as new treatment options and personalized treatment. Wiley Periodicals, Inc. © 2012 International League Against Epilepsy.

An observational study of emergency department utilization among enrollees of Minnesota Health Care Programs: financial and non-financial barriers have different associations.

PubMed

Shippee, Nathan D; Shippee, Tetyana P; Hess, Erik P; Beebe, Timothy J

2014-02-08

Emergency department (ED) use is costly, and especially frequent among publicly insured populations in the US, who also disproportionately encounter financial (cost/coverage-related) and non-financial/practical barriers to care. The present study examines the distinct associations financial and non-financial barriers to care have with patterns of ED use among a publicly insured population. This observational study uses linked administrative-survey data for enrollees of Minnesota Health Care Programs to examine patterns in ED use-specifically, enrollee self-report of the ED as usual source of care, and past-year count of 0, 1, or 2+ ED visits from administrative data. Main independent variables included a count of seven enrollee-reported financial concerns about healthcare costs and coverage, and a count of seven enrollee-reported non-financial, practical barriers to access (e.g., limited office hours, problems with childcare). Covariates included health, health care, and demographic measures. In multivariate regression models, only financial concerns were positively associated with reporting ED as usual source of care, but only non-financial barriers were significantly associated with greater ED visits. Regression-adjusted values indicated notable differences in ED visits by number of non-financial barriers: zero non-financial barriers meant an adjusted 78% chance of having zero ED visits (95% C.I.: 70.5%-85.5%), 15.9% chance of 1(95% C.I.: 10.4%-21.3%), and 6.2% chance (95% C.I.: 3.5%-8.8%) of 2+ visits, whereas having all seven non-financial barriers meant a 48.2% adjusted chance of zero visits (95% C.I.: 30.9%-65.6%), 31.8% chance of 1 visit (95% C.I.: 24.2%-39.5%), and 20% chance (95% C.I.: 8.4%-31.6%) of 2+ visits. Financial barriers were associated with identifying the ED as one's usual source of care but non-financial barriers were associated with actual ED visits. Outreach/literacy efforts may help reduce reliance on/perception of ED as usual source of care

An observational study of emergency department utilization among enrollees of Minnesota Health Care Programs: financial and non-financial barriers have different associations

PubMed Central

2014-01-01

Background Emergency department (ED) use is costly, and especially frequent among publicly insured populations in the US, who also disproportionately encounter financial (cost/coverage-related) and non-financial/practical barriers to care. The present study examines the distinct associations financial and non-financial barriers to care have with patterns of ED use among a publicly insured population. Methods This observational study uses linked administrative-survey data for enrollees of Minnesota Health Care Programs to examine patterns in ED use—specifically, enrollee self-report of the ED as usual source of care, and past-year count of 0, 1, or 2+ ED visits from administrative data. Main independent variables included a count of seven enrollee-reported financial concerns about healthcare costs and coverage, and a count of seven enrollee-reported non-financial, practical barriers to access (e.g., limited office hours, problems with childcare). Covariates included health, health care, and demographic measures. Results In multivariate regression models, only financial concerns were positively associated with reporting ED as usual source of care, but only non-financial barriers were significantly associated with greater ED visits. Regression-adjusted values indicated notable differences in ED visits by number of non-financial barriers: zero non-financial barriers meant an adjusted 78% chance of having zero ED visits (95% C.I.: 70.5%-85.5%), 15.9% chance of 1(95% C.I.: 10.4%-21.3%), and 6.2% chance (95% C.I.: 3.5%-8.8%) of 2+ visits, whereas having all seven non-financial barriers meant a 48.2% adjusted chance of zero visits (95% C.I.: 30.9%-65.6%), 31.8% chance of 1 visit (95% C.I.: 24.2%-39.5%), and 20% chance (95% C.I.: 8.4%-31.6%) of 2+ visits. Conclusions Financial barriers were associated with identifying the ED as one’s usual source of care but non-financial barriers were associated with actual ED visits. Outreach/literacy efforts may help reduce reliance

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…

Reductive half-reaction of aldehyde oxidoreductase toward acetaldehyde: Ab initio and free energy quantum mechanical/molecular mechanical calculations.

PubMed

Dieterich, Johannes M; Werner, Hans-Joachim; Mata, Ricardo A; Metz, Sebastian; Thiel, Walter

2010-01-21

Energy and free energy barriers for acetaldehyde conversion in aldehyde oxidoreductase are determined for three reaction pathways using quantum mechanical/molecular mechanical (QM/MM) calculations on the solvated enzyme. Ab initio single-point QM/MM energies are obtained at the stationary points optimized at the DFT(B3LYP)/MM level. These ab initio calculations employ local correlation treatments [LMP2 and LCCSD(T0)] in combination with augmented triple- and quadruple-zeta basis sets, and the final coupled cluster results include MP2-based corrections for basis set incompleteness and for the domain approximation. Free energy perturbation (FEP) theory is used to generate free energy profiles at the DFT(B3LYP)/MM level for the most important reaction steps by sampling along the corresponding reaction paths using molecular dynamics. The ab initio and FEP QM/MM results are combined to derive improved estimates of the free energy barriers, which differ from the corresponding DFT(B3LYP)/MM energy barriers by about 3 kcal mol(-1). The present results confirm the qualitative mechanistic conclusions from a previous DFT(B3LYP)/MM study. Most favorable is a three-step Lewis base catalyzed mechanism with an initial proton transfer from the cofactor to the Glu869 residue, a subsequent nucleophilic attack that yields a tetrahedral intermediate (IM2), and a final rate-limiting hydride transfer. The competing metal center activated pathway has the same final step but needs to overcome a higher barrier in the initial step on the route to IM2. The concerted mechanism has the highest free energy barrier and can be ruled out. While confirming the qualitative mechanistic scenario proposed previously on the basis of DFT(B3LYP)/MM energy profiles, the present ab initio and FEP QM/MM calculations provide corrections to the barriers that are important when aiming at high accuracy.

[Energy power in mountains: difference in metabolism pattern results in different adaption traits in Tibetans].

PubMed

Bai, Zhen-Zhong; Jin, Guo-En; Wu-Ren, Tana; Ga, Qin; Ge, Ri-Li

2012-11-01

Energy metabolism plays an important role in life survival for species living in high altitude hypoxia condition. Air-breathing organisms require oxygen to create energy. Tibetans are the well-adapted highlanders in Qinghai-Tibetan Plateau. It was thought that different metabolic approaches could lead to different adaptation traits to high altitude hypoxia. Recently identified hypoxia inducible factors pathway regulators, endothelial PAS domain protein1 (EPAS1)/HIF-2a and PPARA, were involved in decreasing hemoglobin concentrations in Tibetans. Because EPAS1 and PPARA also modulated the energy metabolism during hypoxia, we hypothesized that positive selected EPAS1 and PPARA genes were also involved in unique energy metabolisms in Tibetans. In this brief review, we take a look into genetic determinations to energy metabolisms for hypoxia adaptations traits in Tibetans and mal-adaptive conditions such as high altitude diseases.

Identification of potential barriers to nurse-sensitive outcome demonstration.

PubMed

Beckel, Jean; Wolf, Gail; Wilson, Roxanne; Hoolahan, Susan

2013-12-01

The objective of this study was to determine differences in chief nursing officer, Magnet(®) program director, nurse leader, and direct care RN perspectives of potential barriers to demonstration of nurse-sensitive outcomes. The Magnet Recognition Program(®) and other designations are focusing on patient outcomes. No evidence is available addressing barriers to demonstration of nursing outcomes at multiple levels of practice. A Likert scale tool was developed and administered to 526 attendees at the 2012 national Magnet conference. Questions related to available resources, benchmarks, outcome demonstration process understanding, perception of value, and competing priorities. Significant perception differences by role were demonstrated related to available resources, competing priorities, and process understanding supporting demonstration of nurse-sensitive outcomes. No significant differences were identified related to benchmarks or perception of process value to the organization. This study provides new information demonstrating potential barriers to demonstration of nurse-sensitive outcomes differing by role. Opportunity exists to develop systems and processes to reduce perceived barriers among the nursing workforce.

Minimum free-energy paths for the self-organization of polymer brushes.

PubMed

Gleria, Ignacio; Mocskos, Esteban; Tagliazucchi, Mario

2017-03-22

A methodology to calculate minimum free-energy paths based on the combination of a molecular theory and the improved string method is introduced and applied to study the self-organization of polymer brushes under poor solvent conditions. Polymer brushes in a poor solvent cannot undergo macroscopic phase separation due to the physical constraint imposed by the grafting points; therefore, they microphase separate forming aggregates. Under some conditions, the theory predicts that the homogeneous brush and the aggregates can exist as two different minima of the free energy. The theoretical methodology introduced in this work allows us to predict the minimum free-energy path connecting these two minima as well as the morphology of the system along the path. It is shown that the transition between the homogeneous brush and the aggregates may involve a free-energy barrier or be barrierless depending on the relative stability of the two morphologies and the chain length and grafting density of the polymer. In the case where a free-energy barrier exists, one of the morphologies is a metastable structure and, therefore, the properties of the brush as the quality of the solvent is cycled are expected to display hysteresis. The theory is also applied to study the adhesion/deadhesion transition between two opposing surfaces modified by identical polymer brushes and it is shown that this process may also require surpassing a free-energy barrier.

Determination of Fusion Barrier Distributions from Quasielastic Scattering Cross Sections towards Superheavy Nuclei Synthesis

NASA Astrophysics Data System (ADS)

Tanaka, Taiki; Narikiyo, Yoshihiro; Morita, Kosuke; Fujita, Kunihiro; Kaji, Daiya; Morimoto, Kouji; Yamaki, Sayaka; Wakabayashi, Yasuo; Tanaka, Kengo; Takeyama, Mirei; Yoneda, Akira; Haba, Hiromitsu; Komori, Yukiko; Yanou, Shinya; Jean-Paul Gall, Benoît; Asfari, Zouhair; Faure, Hugo; Hasebe, Hiroo; Huang, Minghui; Kanaya, Jumpei; Murakami, Masashi; Yoshida, Atsushi; Yamaguchi, Takayuki; Tokanai, Fuyuki; Yoshida, Tomomi; Yamamoto, Shoya; Yamano, Yuki; Watanabe, Kenyu; Ishizawa, Satoshi; Asai, Masato; Aono, Ryuji; Goto, Shin-ichi; Katori, Kenji; Hagino, Kouichi

2018-01-01

In order to study the nucleus-nucleus interactions for syntheses of superheavy nuclei, we measured excitation functions for the quasielastic scattering of 48Ca+208Pb, 50Ti+208Pb, and 48Ca+248Cm using the gas-filled-type recoil ion separator GARIS. The quasielastic scattering events were clearly separated from deep-inelastic events by using GARIS and its focal plan detectors, except for high-incident-energy points. The quasielastic barrier distributions were successfully extracted for these systems, and compared with coupled-channels calculations. The results of the calculations indicate that vibrational and rotational excitations of the colliding nuclei, as well as neutron transfers before contact, strongly affect the structure of the barrier distribution. For the reactions of 48Ca+208Pb and 50Ti+208Pb, a local maximum of the barrier distribution occurred at the same energy as the peak of the 2n evaporation cross section of the system. On the other hand, for the hot fusion reaction of 48Ca+248Cm, the 4n evaporation cross section of the system peaks at energies well above the maximum of the barrier distribution. This may be attributed to the deformation of the target nucleus. We argue that these findings can be utilized to locate the optimal energy for future searches for undiscovered superheavy nuclei.

Connecting Free Energy Surfaces in Implicit and Explicit Solvent: an Efficient Method to Compute Conformational and Solvation Free Energies

PubMed Central

Deng, Nanjie; Zhang, Bin W.; Levy, Ronald M.

2015-01-01

The ability to accurately model solvent effects on free energy surfaces is important for understanding many biophysical processes including protein folding and misfolding, allosteric transitions and protein-ligand binding. Although all-atom simulations in explicit solvent can provide an accurate model for biomolecules in solution, explicit solvent simulations are hampered by the slow equilibration on rugged landscapes containing multiple basins separated by barriers. In many cases, implicit solvent models can be used to significantly speed up the conformational sampling; however, implicit solvent simulations do not fully capture the effects of a molecular solvent, and this can lead to loss of accuracy in the estimated free energies. Here we introduce a new approach to compute free energy changes in which the molecular details of explicit solvent simulations are retained while also taking advantage of the speed of the implicit solvent simulations. In this approach, the slow equilibration in explicit solvent, due to the long waiting times before barrier crossing, is avoided by using a thermodynamic cycle which connects the free energy basins in implicit solvent and explicit solvent using a localized decoupling scheme. We test this method by computing conformational free energy differences and solvation free energies of the model system alanine dipeptide in water. The free energy changes between basins in explicit solvent calculated using fully explicit solvent paths agree with the corresponding free energy differences obtained using the implicit/explicit thermodynamic cycle to within 0.3 kcal/mol out of ~3 kcal/mol at only ~8 % of the computational cost. We note that WHAM methods can be used to further improve the efficiency and accuracy of the explicit/implicit thermodynamic cycle. PMID:26236174

Connecting free energy surfaces in implicit and explicit solvent: an efficient method to compute conformational and solvation free energies.

PubMed

Deng, Nanjie; Zhang, Bin W; Levy, Ronald M

2015-06-09

The ability to accurately model solvent effects on free energy surfaces is important for understanding many biophysical processes including protein folding and misfolding, allosteric transitions, and protein–ligand binding. Although all-atom simulations in explicit solvent can provide an accurate model for biomolecules in solution, explicit solvent simulations are hampered by the slow equilibration on rugged landscapes containing multiple basins separated by barriers. In many cases, implicit solvent models can be used to significantly speed up the conformational sampling; however, implicit solvent simulations do not fully capture the effects of a molecular solvent, and this can lead to loss of accuracy in the estimated free energies. Here we introduce a new approach to compute free energy changes in which the molecular details of explicit solvent simulations are retained while also taking advantage of the speed of the implicit solvent simulations. In this approach, the slow equilibration in explicit solvent, due to the long waiting times before barrier crossing, is avoided by using a thermodynamic cycle which connects the free energy basins in implicit solvent and explicit solvent using a localized decoupling scheme. We test this method by computing conformational free energy differences and solvation free energies of the model system alanine dipeptide in water. The free energy changes between basins in explicit solvent calculated using fully explicit solvent paths agree with the corresponding free energy differences obtained using the implicit/explicit thermodynamic cycle to within 0.3 kcal/mol out of ∼3 kcal/mol at only ∼8% of the computational cost. We note that WHAM methods can be used to further improve the efficiency and accuracy of the implicit/explicit thermodynamic cycle.

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.

Enhancement of fusion at near-barrier energies for neutron-rich light nuclei: 19O +12 C

NASA Astrophysics Data System (ADS)

Singh, Varinderjit; Vadas, J.; Steinbach, T. K.; Wiggins, B. B.; Hudan, S.; Desouza, R. T.; Baby, L. T.; Kuvin, S. A.; Tripathi, Vandana; Wiedenhover, I.; Umar, A. S.

2017-01-01

Measuring the fusion excitation function for an isotopic chain of projectile nuclei provides a sensitive test of a microscopic description of fusion. To investigate the theoretically predicted fusion enhancement for neutron-rich light nuclei, an experiment was performed to measure the fusion excitation functions for 19 O +12 C and 18 O +12 C . Using the 18O(d,p) reaction and the RESOLUT mass spectrometer at Florida State University, a beam of 19O was produced with an intensity of 2-4 x 103 p/s. This beam bombarded a 100 μg/cm2 carbon target. Using an approach optimized for the measurement of fusion with a low-intensity beam, evaporation residues (ERs) resulting from the de-excitation of the fusion product were measured. The ERs were identified by measuring their energy and time-of-flight. At near-barrier energies, an enhancement of fusion by a factor of three has been observed for 19 O +12 C in comparison to 18 O +12 C . Comparison of the experimental results with the predictions of a density constrained time-dependent Hartree-Fock (DC-TDHF) model provide evidence for the importance of pairing in the fusion process. Supported by the US DOE under Grant No. DEFG02-88ER-40404.

Increasing the effective energy barrier promoted by the change of a counteranion in a Zn-Dy-Zn SMM: slow relaxation via the second excited state.

PubMed

Oyarzabal, I; Ruiz, J; Ruiz, E; Aravena, D; Seco, J M; Colacio, E

2015-08-11

The trinuclear complex [ZnCl(μ-L)Dy(μ-L)ClZn]PF6 exhibits a single-molecule magnetic behaviour under zero field with a relatively large effective energy barrier of 186 cm(-1). Ab initio calculations reveal that the relaxation of the magnetization is symmetry-driven (the Dy(III) ion possesses a C2 symmetry) and occurs via the second excited state.

Small Barriers Trigger Liftoff of Unconfined Dilute Heated Laboratory Density Currents

NASA Astrophysics Data System (ADS)

Fauria, K.; Andrews, B. J.; Manga, M.

2015-12-01

Dilute pyroclastic density currents (PDCs) are hot, turbulent, particle-laden flows that propagate because they are denser than air. PDCs can traverse tens to hundreds of kilometers and surmount ridges 100s of m tall, yet the effects of complex topography on PDC liftoff and runout distance are uncertain. Here we used scaled laboratory experiments to explore how barriers affect dilute density current dynamics and the occurrence of liftoff. We created dilute density currents by heating and suspending 20 μm diameter talc in air in an 8.5 x 6.1 x 2.6 m tank. We scaled the currents with respect to Froude, densimetric and thermal Richardson, particle Stokes and Settling numbers such that they were dynamically similar to natural PDCs. While currents were fully turbulent, their Reynolds numbers were not as high as those for natural PDCs. We performed the first set of experiments in a laterally unconfined volume, used laser sheets to illuminate the currents, measured bulk sedimentation rates down the current centerlines, and positioned four to twenty-four cm tall ridge-like barriers in the path of the currents. We found that relatively small barriers (~ half the current height) caused PDC liftoff. By comparison, conservation of kinetic and potential energy predicts that incompressible density currents are able to surmount barriers twice their height. Furthermore, we observed increased sedimentation immediately upstream of barriers and conclude that small barriers initiated buoyancy reversal through a combination of increased air entrainment and sedimentation. We conducted a second set of experiments with the same thermal scaling and mass flux rates but where the currents were laterally confined within a 0.6 m wide channel. We found that small barriers also triggered liftoff of confined currents, but that the body of these currents reattached after liftoff. Those results suggest that lateral confinement inhibits buoyancy reversal by limiting the surface area of the current

Regional differences as barriers to body mass index screening described by Ohio school nurses.

PubMed

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

2011-08-01

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 suburban, rural, and urban public elementary schools. This descriptive study used focus groups with 25 school nurses in 3 geographic regions of Ohio. An adapted Healthy People 2010 model guided the development of semistructured focus group questions. Nine regional themes related to BMI screening emerged specific to suburban, rural, and/or urban school nurses' experiences with BMI screening practice, policy, school physical environment, school social environment, school risk/protection, and access to quality health care. Key facilitating factors to BMI screening varied by region. Key barriers to BMI screening were a lack of privacy, time, policy, and workload of school nurses. Regionally specific facilitating factors to BMI screening in schools provide opportunities for schools to accentuate the positive and to promote school health. © 2011, American School Health Association.

Extended optical model analyses of elastic scattering and fusion cross sections for heavy-ion collisions with loosely bound projectiles at near-Coulomb-barrier energies

NASA Astrophysics Data System (ADS)

So, W. Y.; Hong, S. W.; Kim, B. T.; Udagawa, T.

2004-06-01

Within the framework of an extended optical model, simultaneous χ2 analyses are performed for elastic scattering and fusion cross-section data for 9Be + 209 Bi and 6Li + 208 Pb systems, both involving loosely bound projectiles, at near-Coulomb-barrier energies to determine the polarization potential as decomposed into direct reaction (DR) and fusion parts. We show that both DR and fusion potentials extracted from χ2 analyses separately satisfy the dispersion relation, and that the expected threshold anomaly appears in the fusion part. The DR potential turns out to be a rather smooth function of the incident energy, and has a magnitude at the strong absorption radius much larger than the fusion potential, explaining why a threshold anomaly has not been seen in optical potentials deduced from fits to the elastic-scattering data without such a decomposition. Using the extracted DR potential, we examine the effects of projectile breakup on fusion cross sections σF . The observed suppression of σF in the above-barrier region can be explained in terms of the flux loss due to breakup. However, the observed enhancement of σF in the subbarrier region cannot be understood in terms of the breakup effect. Rather, the enhancement can be related to the Q value of the neutron transfer within the systems, supporting the ideas of

Optical properties of thin gold films applied to Schottky barrier solar cells

NASA Technical Reports Server (NTRS)

YEH Y. M.

1974-01-01

The Schottky barrier solar cell is considered a possible candidate for converting solar to electrical energy both for space and terrestrial applications. Knowledge of the optical constants of the ultrathin metal film used in the cell is essential for analyzing and designing higher efficiency Schottky barrier cells. The optical constants of 7.5 -nm (75-A) gold films on gallium arsenide have been obtained. In addition, the absolute collection efficiency of Schottky barrier solar cells has been determined from measured spectral response and optical constants of the gold film.

Barrier properties of cultured retinal pigment epithelium.

PubMed

Rizzolo, Lawrence J

2014-09-01

The principal function of an epithelium is to form a dynamic barrier that regulates movement between body compartments. Each epithelium is specialized with barrier functions that are specific for the tissues it serves. The apical surface commonly faces a lumen, but the retinal pigment epithelium (RPE) appears to be unique by a facing solid tissue, the sensory retina. Nonetheless, there exists a thin (subretinal) space that can become fluid filled during pathology. RPE separates the subretinal space from the blood supply of the outer retina, thereby forming the outer blood-retinal barrier. The intricate interaction between the RPE and sensory retina presents challenges for learning how accurately culture models reflect native behavior. The challenge is heightened by findings that detail the variation of RPE barrier proteins both among species and at different stages of the life cycle. Among the striking differences is the expression of claudin family members. Claudins are the tight junction proteins that regulate ion diffusion across the spaces that lie between the cells of a monolayer. Claudin expression by RPE varies with species and life-stage, which implies functional differences among commonly used animal models. Investigators have turned to transcriptomics to supplement functional studies when comparing native and cultured tissue. The most detailed studies of the outer blood-retinal barrier have focused on human RPE with transcriptome and functional studies reported for human fetal, adult, and stem-cell derived RPE. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quantum coherence in the reflection of above barrier wavepackets

NASA Astrophysics Data System (ADS)

Petersen, Jakob; Pollak, Eli

2018-02-01

The quantum phenomenon of above barrier reflection is investigated from a time-dependent perspective using Gaussian wavepackets. The transition path time distribution, which in principle is experimentally measurable, is used to study the mean flight times ⟨t⟩R and ⟨t⟩T associated with the reflection and the transmission over the barrier paying special attention to their dependence on the width of the barrier. Both flight times, and their difference Δt, exhibit two distinct regimes depending on the ratio of the spatial width of the incident wavepacket and the length of the barrier. When the ratio is larger than unity, the reflection and transmission dynamics are coherent and dominated by the resonances above the barrier. The flight times ⟨t⟩R/T and the flight time difference Δt oscillate as a function of the barrier width (almost in phase with the transmission probability). These oscillations reflect a momentum filtering effect related to the coherent superposition of the reflected and transmitted waves. For a ratio less than unity, the barrier reflection and transmission dynamics are incoherent and the oscillations are absent. The barrier width which separates the coherent and incoherent regimes is identified analytically. The oscillatory structure of the time difference Δt as a function of the barrier width in the coherent regime is absent when considered in terms of the Wigner phase time delays for reflection and transmission. We conclude that the Wigner phase time does not correctly describe the temporal properties of above barrier reflection. We also find that the structure of the reflected and transmitted wavepackets depends on the coherence of the process. In the coherent regime, the wavepackets can have an overlapping peak structure, but the peaks are not fully resolved. In the incoherent regime, the wavepackets split in time into distinct separated Gaussian like waves, each one reflecting the number of times the wavepacket crosses the barrier

Impenetrable barriers for positrons in neighbourhood of superheavy nuclei with Z>118

NASA Astrophysics Data System (ADS)

Neznamov, V. P.

2017-12-01

Analysis of quantum mechanical motion of charged half-spin particles in the repulsive Coulomb field results in that an impenetrable potential barrier not explored earlier was found. For a particle at rest with a reduced mass m, the barrier radius is equal to half classical radius: the barrier radius decreases with increase in the particle energy. For the stable and quasi-stable nuclei with Z > 118, presence of an impenetrable barrier as β +-decay leads to the existence of “traps” for positrons in the neighbourhood of nuclei and as Zcr ≃ 170 (with emission of electron-positron pairs by vacuum) leads to the existence of a quasi-constant source of annihilation quanta.

[Blood-brain barrier part III: therapeutic approaches to cross the blood-brain barrier and target the brain].

PubMed

Weiss, N; Miller, F; Cazaubon, S; Couraud, P-O

2010-03-01

Over the last few years, the blood-brain barrier has come to be considered as the main limitation for the treatment of neurological diseases caused by inflammatory, tumor or neurodegenerative disorders. In the blood-brain barrier, the close intercellular contact between cerebral endothelial cells due to tight junctions prevents the passive diffusion of hydrophilic components from the bloodstream into the brain. Several specific transport systems (via transporters expressed on cerebral endothelial cells) are implicated in the delivery of nutriments, ions and vitamins to the brain; other transporters expressed on cerebral endothelial cells extrude endogenous substances or xenobiotics, which have crossed the cerebral endothelium, out of the brain and into the bloodstream. Recently, several strategies have been proposed to target the brain, (i) by by-passing the blood-brain barrier by central drug administration, (ii) by increasing permeability of the blood-brain barrier, (iii) by modulating the expression and/or the activity of efflux transporters, (iv) by using the physiological receptor-dependent blood-brain barrier transport, and (v) by creating new viral or chemical vectors to cross the blood-brain barrier. This review focuses on the illustration of these different approaches. Copyright (c) 2009 Elsevier Masson SAS. All rights reserved.

Electronic Devices with Barrier Film and Process for Making Same

DTIC Science & Technology

1998-08-20

the barrier film on an atomic level where the barrier film is comprised of a plurality of contiguous monolayers, while FIG. 7B shows another...embodiment where the barrier film is comprised of a plurality of contiguous monolayers in which different monolayers thereof are formed of different...compound effusion cell, for example a barium fluoride, strontium fluoride or the like effusion cell, is provided at 32, and has a shutter 33. A

Experimental and computational study of dielectric barrier discharges for environmental applications

NASA Astrophysics Data System (ADS)

Aerts, Robby

Air pollution has become a major global concern which affects all inhabitants of our precious earth. Nowadays it is fact that our climate is changing and the sea level is rising. Moreover, we are facing an energy crisis because all our fossil fuel resources will sooner or later be running empty. It is clear that drastic measures are needed to keep our planet as it is today for generations to come. One of these measures is the 20-20-20 targets imposed by the European Commission, which stimulates the research for environmental energy applications. In this PhD dissertation two environmental applications of plasma technology are investigated. The first one is the abatement of flue gases, and more specifically the destruction of volatile organic compounds (VOCs). The second one is the conversion of CO2 into valuable chemicals. Both of these applications suffer from a large energy cost under classical (thermodynamic) conditions, due to the chemical stability of these molecules. Plasma technology is quite promising to overcome these thermodynamic barriers. Plasmas allow reactions at different time-scales with different species, such as electrons, ions, radicals, molecules and excited species, creating new chemical pathways. Indeed, in a plasma the applied electrical energy is directly transferred to the electrons, which activate the gas by ionization, excitation and dissociation, hence creating reactive species (ions, excited species, radicals), that can further easily undergo other chemical reactions. Especially gas discharges, which are low temperature plasmas, show promising results in the destruction of pollutants at mild conditions. A common type of gas discharge is the dielectric barrier discharge (DBD) which has been successfully scaled up for industrial ozone generation and is widely investigated in the field of environmental applications. The complexity of DBDs creates difficulties for experimental diagnostics and therefore numerical studies can help to improve

Dirac quasiparticle tunneling in a NG/ferromagnetic barrier/SG graphene junction

NASA Astrophysics Data System (ADS)

Soodchomshom, Bumned; Tang, I.-Ming; Hoonsawat, Rassmidara

2009-07-01

We study the tunneling conductance in a spin dependent barrier NG/F B/SG graphene junction, where NG, F B and SG are normal graphene, gate ferromagnetic graphene barrier with thickness d and the graphene s-wave superconductor, respectively. In our work, the quasiparticle scattering process at the interfaces is based on quasi particles governed by the Dirac Bogoliubov-de Gennes equation with effective speed of light vF ∼ 10 6 m/s. The conductance of the junction is calculated based on Blonder-Tinkham-Klapwijk (BTK) formalism. The oscillatory conductance under varying gate potential and exchange energy in F B and the conductance induced by specular Andreev reflection are studied. By taking into account both effects of barrier strengths due to the gate potential χ∼Vd/ℏv and the exchange energy χ∼Ed/ℏv in the F B region, we find that the zero bias conductance of junction depends only on the ferromagnetic barrier strength χex in F B, when the Fermi energy in SG is very much larger than that the Fermi energy in NG ( EFS ≫ EFN). The oscillatory conductance peaks can be controlled by either varying χex or χG. In the limiting case, by setting Eex = 0, the conductance in a NG/N B/SG graphene junction, where SG is the s-wave superconductor, is also studied in order to compare with two earlier contradicted data. Our result agrees with what was obtained by Linder and Sudbo [J. Linder, A. Sudbo, Phys. Rev. B 77 (2008) 64507], which confirms the contradiction to what was given by Bhattacharjee and Sengupta [S. Bhattacharjee, K. Sengupta, Phys. Rev. Lett. 97 (2006) 217001].

Exercising at work: barriers to women's participation.

PubMed

Verhoef, M J; Hamm, R D; Love, E J

1993-06-01

Only a minority of women in an urban random sample have the opportunity to exercise at work, and even fewer women use these opportunities. Lack of time and inconvenient times are the major reasons for not participating in exercise programs at work. Exercise programs at work are used by women who are already physically active, suggesting that workplace exercise programs do not serve the needs of women who may need exercise programs most. Multivariate analysis shows that age, having children, lack of energy, and lack of support are significant barriers to women's exercise participation at work. The results of this study suggest a leadership opportunity for on site occupational health nurses in addressing these barriers to workplace exercise.

Review of Graphene as a Solid State Diffusion Barrier.

PubMed

Morrow, Wayne K; Pearton, Stephen J; Ren, Fan

2016-01-06

Conventional thin-film diffusion barriers consist of 3D bulk films with high chemical and thermal stability. The purpose of the barrier material is to prevent intermixing or penetration from the two materials that encase it. Adhesion to both top and bottom materials is critical to the success of the barrier. Here, the effectiveness of a single atomic layer of graphene as a solid-state diffusion barrier for common metal schemes used in microelectronics is reviewed, and specific examples are discussed. Initial studies of electrical contacts to graphene show a distinct separation in behavior between metallic groups that strongly or weakly bond to it. The two basic classes of metal reactions with graphene are either physisorbed metals, which bond weakly with graphene, or chemisorbed metals, which bond strongly to graphene. For graphene diffusion barrier testing on Si substrates, an effective barrier can be achieved through the formation of a carbide layer with metals that are chemisorbed. For physisorbed metals, the barrier failure mechanism is loss of adhesion at the metal–graphene interface. A graphene layer encased between two metal layers, in certain cases, can increase the binding energy of both films with graphene, however, certain combinations of metal films are detrimental to the bonding with graphene. While the prospects for graphene's future as a solid-state diffusion barrier are positive, there are open questions, and areas for future research are discussed. A better understanding of the mechanisms which influence graphene's ability to be an effective diffusion barrier in microelectronic applications is required, and additional experiments are needed on a broader range of metals, as well as common metal stack contact structures used in microelectronic applications. The role of defects in the graphene is also a key area, since they will probably influence the barrier properties. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rocket Motor Joint Construction Including Thermal Barrier

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Inventor); Dunlap, Patrick H., Jr. (Inventor)

2002-01-01

A thermal barrier for extremely high temperature applications consists of a carbon fiber core and one or more layers of braided carbon fibers surrounding the core. The thermal barrier is preferably a large diameter ring, having a relatively small cross-section. The thermal barrier is particularly suited for use as part of a joint structure in solid rocket motor casings to protect low temperature elements such as the primary and secondary elastomeric O-ring seals therein from high temperature gases of the rocket motor. The thermal barrier exhibits adequate porosity to allow pressure to reach the radially outward disposed O-ring seals allowing them to seat and perform the primary sealing function. The thermal barrier is disposed in a cavity or groove in the casing joint, between the hot propulsion gases interior of the rocket motor and primary and secondary O-ring seals. The characteristics of the thermal barrier may be enhanced in different applications by the inclusion of certain compounds in the casing joint, by the inclusion of RTV sealant or similar materials at the site of the thermal barrier, and/or by the incorporation of a metal core or plurality of metal braids within the carbon braid in the thermal barrier structure.

Characterization of WB/SiC Schottky Barrier Diodes Using I-V-T Method

NASA Astrophysics Data System (ADS)

Aldridge, James; Oder, Tom

2009-04-01

The importance of silicon carbide (SiC) semiconductor for high temperature and high power microelectronic device applications has long been established. We have fabricated SiC Schottky barrier diodes using tungsten boride (WB) as the Schottky contact. The diodes were characterized using the current-voltage-temperature method. The sample was mounted on a heated stage and the temperature varied from about 25 ^oC to 300 ^oC at intervals of 25 ^oC. From the Richardson's plot, we obtained an energy barrier height of 0.96 eV and a Richardson's constant of 71.2 AK-1cm-2. Using the modified Richardson's plot, we obtained a barrier height of 1.01 eV. From the variation of the ideality factor and the temperature, we determined a characteristic energy of 0.02 eV to 0.04 eV across the range of the measurement temperature. This implies that thermionic emission is dominant in the low measurement temperature range. Our results confirm the excellent thermal stability of WB/SiC Schottky barrier diodes.

Quantum Dynamics Study of the Potential Energy Minima Effect on Energy Efficiency for the F- + CH3Cl → FCH3 + Cl- Reaction.

PubMed

Li, Yida; Wang, Yuping; Wang, Dunyou

2017-04-13

The Polanyi rules on the energy efficiency on reactivity are summarized solely from the locations of barriers on the potential energy surfaces. Here, our quantum dynamics study for the F - + CH 3 Cl → FCH 3 + Cl - reaction shows that the two potential energy minima in the entrance channel on the potential energy surface play an essential role in energy efficiency on reactivity. The reactivity of this reaction is dominated by the low collision energies where two distinctive reaction mechanisms involve the two minima in the entrance channel. Overall, the Cl-CH 3 stretching motion and C-H 3 umbrella motion both are more efficient than the translational motion in promoting this reaction. Although this reaction has a negative energy barrier, our study shows that it is the minima in the entrance channel, together with the energy barrier relative to these minima, that determine the energy efficacy on reactivity.

Going global: do consumer preferences, attitudes, and barriers to using e-mental health services differ across countries?

PubMed

Clough, Bonnie A; Zarean, Mostafa; Ruane, Ilse; Mateo, Niño Jose; Aliyeva, Turana A; Casey, Leanne M

2017-08-31

e-Mental health services have the capacity to overcome barriers to care and reduce the unmet need for psychological services, particularly in developing countries. However, it is unknown how acceptable e-mental health interventions may be to these populations. The purpose of the current study was to examine consumer attitudes and perceived barriers to e-mental health usage across four countries: Australia, Iran, the Philippines and South Africa. An online survey was completed by 524 adults living in these countries, assessing previous contact with e-mental health services, willingness to use e-mental health services, and perceived barriers and needs for accessing e-mental health services. Although previous contact with e-mental health services was low, the majority of respondents in each sample reported a willingness to try e-mental health services if offered. Barriers toward e-mental health usage were higher among the developing countries than Australia. The most commonly endorsed barriers concerned needing information and assurances regarding the programmes. Across countries, participants indicated a willingness to use e-mental health programmes if offered. With appropriate research and careful implementation, e-mental health has the potential to be a valuable part of mental healthcare in developing countries.

Gut barrier in health and disease: focus on childhood.

PubMed

Viggiano, D; Ianiro, G; Vanella, G; Bibbò, S; Bruno, G; Simeone, G; Mele, G

2015-01-01

The gut barrier is a functional unit, organized as a multi-layer system, made up of two main components: a physical barrier surface, which prevents bacterial adhesion and regulates paracellular diffusion to the host tissues, and a deep functional barrier, that is able to discriminate between pathogens and commensal microorganisms, organizing the immune tolerance and the immune response to pathogens. Other mechanisms, such as gastric juice and pancreatic enzymes (which both have antibacterial properties) participate in the luminal integrity of the gut barrier. From the outer layer to the inner layer, the physical barrier is composed of gut microbiota (that competes with pathogens to gain space and energy resources, processes the molecules necessary to mucosal integrity and modulates the immunological activity of deep barrier), mucus (which separates the intraluminal content from more internal layers and contains antimicrobial products and secretory IgA), epithelial cells (which form a physical and immunological barrier) and the innate and adaptive immune cells forming the gut-associated lymphoid tissue (which is responsible for antigen sampling and immune responses). Disruption of the gut barrier has been associated with many gastrointestinal diseases, but also with extra-intestinal pathological condition, such as type 1 diabetes mellitus, allergic diseases or autism spectrum disorders. The maintenance of a healthy intestinal barrier is therefore of paramount importance in children, for both health and economic reasons. Many drugs or compounds used in the treatment of gastrointestinal disorders act through the restoration of a normal intestinal permeability. Several studies have highlighted the role of probiotics in the modulation and reduction of intestinal permeability, considering the strong influence of gut microbiota in the modulation of the function and structure of gut barrier, but also on the immune response of the host. To date, available weapons for the

Systematic study on the isotopic behavior of fusion barrier using the density-dependent nucleon-nucleon interactions

NASA Astrophysics Data System (ADS)

Ghodsi, O. N.; Khalaj, M.

By changing the neutron and nuclear matter incompressibility constant K, we investigate the isotopic behavior of the fusion barriers for the collision of large number of different isotopes with condition of 0.7 ≤ N/Z ≤ 1.36. Here, the double folding (DF) model which is accompanied by density-dependent (DD) versions of M3Y interactions is adopted as a basic heavy ion-ion potential. We show that the selected DD potentials predict a linear behavior for the calculated fusion barrier heights as a function of (N/Z - 1) for both proton- and neutron-rich systems. Moreover, the results indicate that the isotopic behavior of these values depend linearly on the change in the K constant. The isotopic studies conducted on the fusion cross-section also shows that the properties of the nuclear matter in the range of energy which is below the fusion barrier will quite affect the fusion process.

Factors of Renewable Energy Deployment and Empirical Studies of United States Wind Energy

NASA Astrophysics Data System (ADS)

Can Sener, Serife Elif

Considered essential for countries' development, energy demand is growing worldwide. Unlike conventional sources, the use of renewable energy sources has multiple benefits, including increased energy security, sustainable economic growth, and pollution reduction, in particular greenhouse gas emissions. Nevertheless, there is a considerable difference in the share of renewable energy sources in national energy portfolios. This dissertation contains a series of studies to provide an outlook on the existing renewable energy deployment literature and empirically identify the factors of wind energy generation capacity and wind energy policy diffusion in the U.S. The dissertation begins with a systematic literature review to identify drivers and barriers which could help in understanding the diverging paths of renewable energy deployment for countries. In the analysis, economic, environmental, and social factors are found to be drivers, whereas political, regulatory, technical potential and technological factors are not classified as either a driver or a barrier (i.e., undetermined). Each main category contains several subcategories, among which only national income is found to have a positive impact, whereas all other subcategories are considered undetermined. No significant barriers to the deployment of renewable energy sources are found over the analyzed period. Wind energy deployment within the states related to environmental and economic factors was seldom discussed in the literature. The second study of the dissertation is thus focused on the wind energy deployment in the United States. Wind energy is among the most promising clean energy sources and the United States has led the world in per capita newly installed generation capacity since 2000. In the second study, using a fixed-effects panel data regression analysis, the significance of a number of economic and environmental factors are investigated for 39 states from 2000 to 2015. The results suggested that the