Tunable electronic transmission gaps in a graphene superlattice

International Nuclear Information System (INIS)

Lu Weitao; Wang Shunjin; Li Wen; Wang Yonglong; Jiang Hua

2012-01-01

The transmission in graphene superlattices with adjustable barrier height is investigated using transfer-matrix method. It is found that one could control the angular range of transmission by changing the ratio of incidence energy and barrier height. The transmission as a function of incidence energy has more than one gaps, due to the appearance of evanescent waves in different barriers. Accordingly, more than one conductivity minimums are induced. The transmission gaps could be controlled by adjusting the incidence angle, the barrier height, and the barrier number, which gives the possibility to construct an energy-dependent wavevector filter.

Barrier Performance of CVD Graphene Films Using a Facile P3HT Thin Film Optical Transmission Test

Directory of Open Access Journals (Sweden)

Srinivasa Kartik Nemani

2018-01-01

Full Text Available The barrier performance of CVD graphene films was determined using a poly(3-hexylthiophene (P3HT thin film optical transmission test. P3HT is a semiconducting polymer that photo-oxidatively degrades upon exposure to oxygen and light. The polymer is stable under ambient conditions and indoor lighting, enabling P3HT films to be deposited and encapsulated in air. P3HT’s stability under ambient conditions makes it desirable for an initial evaluation of barrier materials as a complimentary screening method in combination with conventional barrier tests. The P3HT test was used to demonstrate improved barrier performance for polymer substrates after addition of CVD graphene films. A layer-by-layer transfer method was utilized to enhance the barrier performance of monolayer graphene. Another set of absorption measurements were conducted to demonstrate the barrier performance of graphene and the degradation mechanism of graphene/P3HT over multiple wavelengths from 400 to 800 nm. The absorption spectra for graphene/polymer composite were simulated by solving Fresnel equations. The simulation results were found to be in good agreement with the measured absorption spectra. The P3HT degradation results qualitatively indicate the potential of graphene films as a possible candidate for medium performance barriers.

Attempting to be active: Self-efficacy and barrier limitation differentiate activity levels of working mothers.

Science.gov (United States)

Gierc, Madelaine; Locke, Sean; Jung, Mary; Brawley, Lawrence

2016-07-01

Working mothers are less physically active than working women without children and mothers who do not work. The purpose of this study was to examine concurrent self-regulatory efficacy and barriers to physical activity in a sample of working mothers. Women completed a mixed-methods survey which included measures of physical activity, concurrent self-regulatory efficacy, and barriers. Sufficiently active women experienced significantly greater concurrent self-regulatory efficacy and significantly less barrier limitation and frequency. No significant group differences were found for age, domestic duties performed, and children's extracurricular activities. Thematic analysis of barriers revealed six themes of common and unique factors, including limited time and family activities. © The Author(s) 2014.

[Basic research on BSE transmission to people].

Science.gov (United States)

Bodemer, W; Kaup, F J

2002-08-01

Prion diseases of animal and man belong to neurological diseases with amyloidal deposition of the respective proteins. As to prion disease, the cellular prionprotein is in its abnormal isoform(s) an essential component of prionprotein aggregates found in affected tissue. In contrast to all neurodegenerative diseases like Morbus Alzheimer or Huntington's disease, prion diseases are transmissible. Therefore, prion diseases were designated Transmissible Spongiform Encephalopathies (TSE). The diseases are well known since decades. Scrapie was first described around 1750, a BSE case was reported in the 1850, most likely a misdiagnosis, and in 1920/1930 the human Creutzfeldt-Jakob disease (CJD) had been described. Transmission of CJD i.e. Kuru had been suspected in the early 1950s and erronously classified as slow virus disease. The CJD transmission posed a problem to humans when transplants from CJD cases were used for treatment. Fortunately, these iatrogenic transmissions remained limited. But with the advent of BSE and appearance of variant CJD cases in the UK and some places in Europe scientists suspected that transmission from cattle to man could have happened. From animal models we know of successful transmission via several routes. Species barriers do not completely prevent transmission. Rather transmission barriers might exist controlling individual susceptibility against prions. Modes of transmission, susceptibility for transmission, identification of receptor molecules as well as molecular mechanisms of the transmission process are intensely investigated. Current knowledge let us to assume that inapparent stages of prion infection pretend a (not existing) species barrier. This inapparent infection preceeds overt disease and, thus, most re-search focuses on the development of highly sensitive assay systems for detection of minute amounts of pathological prionprotein in suspected cases. Inapparence also should warn us to underestimate BSE or human vCJD cases; at

Analysis of Optical CDMA Signal Transmission: Capacity Limits and Simulation Results

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Lawrence R. Chen

2005-06-01

Full Text Available We present performance limits of the optical code-division multiple-access (OCDMA networks. In particular, we evaluate the information-theoretical capacity of the OCDMA transmission when single-user detection (SUD is used by the receiver. First, we model the OCDMA transmission as a discrete memoryless channel, evaluate its capacity when binary modulation is used in the interference-limited (noiseless case, and extend this analysis to the case when additive white Gaussian noise (AWGN is corrupting the received signals. Next, we analyze the benefits of using nonbinary signaling for increasing the throughput of optical CDMA transmission. It turns out that up to a fourfold increase in the network throughput can be achieved with practical numbers of modulation levels in comparison to the traditionally considered binary case. Finally, we present BER simulation results for channel coded binary and M-ary OCDMA transmission systems. In particular, we apply turbo codes concatenated with Reed-Solomon codes so that up to several hundred concurrent optical CDMA users can be supported at low target bit error rates. We observe that unlike conventional OCDMA systems, turbo-empowered OCDMA can allow overloading (more active users than is the length of the spreading sequences with good bit error rate system performance.

Analysis of Optical CDMA Signal Transmission: Capacity Limits and Simulation Results

Science.gov (United States)

Garba, Aminata A.; Yim, Raymond M. H.; Bajcsy, Jan; Chen, Lawrence R.

2005-12-01

We present performance limits of the optical code-division multiple-access (OCDMA) networks. In particular, we evaluate the information-theoretical capacity of the OCDMA transmission when single-user detection (SUD) is used by the receiver. First, we model the OCDMA transmission as a discrete memoryless channel, evaluate its capacity when binary modulation is used in the interference-limited (noiseless) case, and extend this analysis to the case when additive white Gaussian noise (AWGN) is corrupting the received signals. Next, we analyze the benefits of using nonbinary signaling for increasing the throughput of optical CDMA transmission. It turns out that up to a fourfold increase in the network throughput can be achieved with practical numbers of modulation levels in comparison to the traditionally considered binary case. Finally, we present BER simulation results for channel coded binary and[InlineEquation not available: see fulltext.]-ary OCDMA transmission systems. In particular, we apply turbo codes concatenated with Reed-Solomon codes so that up to several hundred concurrent optical CDMA users can be supported at low target bit error rates. We observe that unlike conventional OCDMA systems, turbo-empowered OCDMA can allow overloading (more active users than is the length of the spreading sequences) with good bit error rate system performance.

Double Barriers and Magnetic Field in Bilayer Graphene

Science.gov (United States)

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.

Barriers and limitations during implementation of the surgical safety checklist of the World Health Organization

OpenAIRE

Rosa Amalia Arboleda; Andrés Felipe Ausenón; Jairo Alberto Ayala; Diana Carolina Cabezas; Lina Gissella Calvache; Juan Pablo Caicedo; Jose Andres Calvache

2014-01-01

Introduction: The surgical safety checklist of the World Health Organization (WHO) is a tool that checks and evaluates each procedure in the operating room. Despite its demonstrated effectiveness, it has many limitations and barriers to its implementation. The aim of this article was to present the current evidence regarding limitations and barriers to achieve a successful implementation of the surgical safety WHO checklist. Methods: A narrative review was designed. We performed a systematic ...

Efficient transmission and characterization of creutzfeldt-jakob disease strains in bank voles.

Directory of Open Access Journals (Sweden)

2006-02-01

Full Text Available Transmission of prions between species is limited by the "species barrier," which hampers a full characterization of human prion strains in the mouse model. We report that the efficiency of primary transmission of prions from Creutzfeldt-Jakob disease patients to a wild rodent species, the bank vole (Clethrionomys glareolus, is comparable to that reported in transgenic mice carrying human prion protein, in spite of a low prion protein-sequence homology between man and vole. Voles infected with sporadic and genetic Creutzfeldt-Jakob disease isolates show strain-specific patterns of spongiform degeneration and pathological prion protein-deposition, and accumulate protease-resistant prion protein with biochemical properties similar to the human counterpart. Adaptation of genetic Creutzfeldt-Jakob disease isolates to voles shows little or no evidence of a transmission barrier, in contrast to the striking barriers observed during transmission of mouse, hamster, and sheep prions to voles. Our results imply that in voles there is no clear relationship between the degree of homology of the prion protein of the donor and recipient species and susceptibility, consistent with the view that the prion strain gives a major contribution to the species barrier. The vole is therefore a valuable model to study human prion diversity and, being susceptible to a range of animal prions, represents a unique tool for comparing isolates from different species.

Towards an optimal transmission system

International Nuclear Information System (INIS)

Calviou, M.

2005-01-01

This presentation provided background on National Grid USA and discussed transmission investment in the United States (US) and United Kingdom. It also discussed barriers to transmission investments and improvements, thoughts on solutions and a long-term vision. The presentation identified that transmission investment should follow from clear reliability rules designed to promote better operation and management; investment does not necessarily mean new rights-of-way; and transmission investment should target benefits to customers. It was stated that US transmission investment levels have decreased. A comparison between US and UK transmission investment was presented along with a chart of increasing US congestion costs. Barriers to investment in US transmission include vertical integration; misperception of transmission as a market product; federal and state jurisdiction issues; fragmentation in transmission ownership and operation; rate cap based plans that impact transmission; lack of clarity in cost allocation; and the site selection process. Possible solutions include policy and incentives, promoting independence and resolving structural issues. tabs., figs

Radiation transmission data for radionuclides and materials relevant to brachytherapy facility shielding.

Science.gov (United States)

Papagiannis, P; Baltas, D; Granero, D; Pérez-Calatayud, J; Gimeno, J; Ballester, F; Venselaar, J L M

2008-11-01

To address the limited availability of radiation shielding data for brachytherapy as well as some disparity in existing data, Monte Carlo simulation was used to generate radiation transmission data for 60Co, 137CS, 198Au, 192Ir 169Yb, 170Tm, 131Cs, 125I, and 103pd photons through concrete, stainless steel, lead, as well as lead glass and baryte concrete. Results accounting for the oblique incidence of radiation to the barrier, spectral variation with barrier thickness, and broad beam conditions in a realistic geometry are compared to corresponding data in the literature in terms of the half value layer (HVL) and tenth value layer (TVL) indices. It is also shown that radiation shielding calculations using HVL or TVL values could overestimate or underestimate the barrier thickness required to achieve a certain reduction in radiation transmission. This questions the use of HVL or TVL indices instead of the actual transmission data. Therefore, a three-parameter model is fitted to results of this work to facilitate accurate and simple radiation shielding calculations.

Human immunodeficiency virus-associated disruption of mucosal barriers and its role in HIV transmission and pathogenesis of HIV/AIDS disease

Science.gov (United States)

Tugizov, Sharof

2016-01-01

Abstract Oral, intestinal and genital mucosal epithelia have a barrier function to prevent paracellular penetration by viral, bacterial and other pathogens, including human immunodeficiency virus (HIV). HIV can overcome these barriers by disrupting the tight and adherens junctions of mucosal epithelia. HIV-associated disruption of epithelial junctions may also facilitate paracellular penetration and dissemination of other viral pathogens. This review focuses on possible molecular mechanisms of HIV-associated disruption of mucosal epithelial junctions and its role in HIV transmission and pathogenesis of HIV and acquired immune deficiency syndrome (AIDS). PMID:27583187

77 FR 73646 - Essar Steel Minnesota, LLC v. Great Lakes Gas Transmission Limited Partnership; Notice of Complaint

Science.gov (United States)

2012-12-11

... Transmission Limited Partnership (Respondent), alleging that the Respondent has failed to comply with the... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. RP13-313-000] Essar Steel Minnesota, LLC v. Great Lakes Gas Transmission Limited Partnership; Notice of Complaint Take notice that on...

Barriers and limitations during implementation of the surgical safety checklist of the World Health Organization

Directory of Open Access Journals (Sweden)

Rosa Amalia Arboleda

2014-04-01

Full Text Available Introduction: The surgical safety checklist of the World Health Organization (WHO is a tool that checks and evaluates each procedure in the operating room. Despite its demonstrated effectiveness, it has many limitations and barriers to its implementation. The aim of this article was to present the current evidence regarding limitations and barriers to achieve a successful implementation of the surgical safety WHO checklist. Methods: A narrative review was designed. We performed a systematic literature search in PubMed/MEDLINE. Articles that describe or present as primary or secondary endpoints barriers or limitations during the implementation of the checklist WHO were selected. Observational or experimental articles were included from the date of the official launch of the WHO list. To describe the data a summary table was designed. Detailed results were organized qualitatively extracting the most prevalent limitations. Results: 17 studies were included in the final review process. The main findings were: 1 a large number of constraints reported in the literature that hinder the implementation process, 2 limitations were grouped into 9 categories according to their similarities and 3 the most frequently reported category was “knowledge”. Discussion: There are several factors that limit the proper implementation of the surgical safety checklist WHO. Among these, cultural factors, knowledge, indifference and / or relevance, communication, filling completeness, among others. Effective implementation strategies would reach its successful implementation.

Ballistic transport through graphene nanostructures of velocity and potential barriers

International Nuclear Information System (INIS)

Krstajic, P M; Vasilopoulos, P

2011-01-01

We investigate the electronic properties of graphene nanostructures when the Fermi velocity and the electrostatic potential vary in space. First, we consider the transmission T and conductance G through single and double barriers. We show that G for velocity barriers differs markedly from that for potential barriers for energies below the height of the latter and it exhibits periodic oscillations as a function of the energy for strong velocity modulation. Special attention is given to superlattices (SLs). It is shown that an applied bias can efficiently widen or shrink the allowed minibands of velocity-modulated SLs. The spectrum in the Kronig-Penney limit is periodic in the strength of the barriers. Collimation of an electron beam incident on an SL with velocity and potential barriers is present but it disappears when the potential barriers are absent. The number of additional Dirac points may change considerably if barriers and wells have sufficiently different Fermi velocities.

Mycobacterium tuberculosis Acquires Limited Genetic Diversity in Prolonged Infections, Reactivations and Transmissions Involving Multiple Hosts

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Marta Herranz

2018-01-01

Full Text Available Background:Mycobacterium tuberculosis (MTB has limited ability to acquire variability. Analysis of its microevolution might help us to evaluate the pathways followed to acquire greater infective success. Whole-genome sequencing (WGS in the analysis of the transmission of MTB has elucidated the magnitude of variability in MTB. Analysis of transmission currently depends on the identification of clusters, according to the threshold of variability (<5 SNPs between isolates.Objective: We evaluated whether the acquisition of variability in MTB, was more frequent in situations which could favor it, namely intrapatient, prolonged infections or reactivations and interpatient transmissions involving multiple sequential hosts.Methods: We used WGS to analyze the accumulation of variability in sequential isolates from prolonged infections or translations from latency to reactivation. We then measured microevolution in transmission clusters with prolonged transmission time, high number of involved cases, simultaneous involvement of latency and active transmission.Results: Intrapatient and interpatient acquisition of variability was limited, within the ranges expected according to the thresholds of variability proposed, even though bursts of variability were observed.Conclusions: The thresholds of variability proposed for MTB seem to be valid in most circumstances, including those theoretically favoring acquisition of variability. Our data point to multifactorial modulation of microevolution, although further studies are necessary to elucidate the factors underlying this modulation.

75 FR 18497 - Guidance on Simultaneous Transmission Import Limit Studies for the Northwest Region; Notice of...

Science.gov (United States)

2010-04-12

... updated market power analyses associated with their market based rate authorizations, which are due in... Conference ``Guidance on Simultaneous Transmission Import Limit Studies.'' To view the archive of the... Northwest region transmission owners and their pending updated market power analyses. Interested persons...

Perceptions of project managers regarding communication failures and barriers

Directory of Open Access Journals (Sweden)

Marilyn de Souza Cyganczuk

2018-03-01

Full Text Available The management of communication within a project can be considered as important as any other system within an organization because communication transmits and connects ideas, concepts, experiences and information on a project. This article describes an investigation of the problems in communication encountered by project managers in companies of different sizes and sectors in the project management area and compares these problems with what is found in the literature. Based on the study conducted, it was possible to identify the main barriers and failures in communication in these organizations and compare them with what is in the literature. The results showed that the main barriers and flaws found are: the lack of feedback to the members of the project team, the lack of trust among team members, channeling of misleading and distorted information, the lack of transmission of information or its transmission at an inopportune moment, and the limited knowledge and competencies of project managers, representing poor leadership and consequently impacting communication.

Planning Electric Transmission Lines: A Review of Recent Regional Transmission Plans

Energy Technology Data Exchange (ETDEWEB)

Eto, Joseph H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2017-04-13

The first Quadrennial Energy Review (QER) recommends that the U.S. Department of Energy (DOE) conduct a national review of transmission plans and assess the barriers and incentives to their implementation. DOE tasked Lawrence Berkeley National Laboratory (LBNL) to prepare two reports to support the agency’s response to this recommendation. This report reviews regional transmission plans and regional transmission planning processes that have been directed by Federal Energy Regulatory Commission (FERC) Order Nos. 890 and 1000. We focus on the most recent regional transmission plans (those issued in 2015 and through approximately mid-year 2016) and current regional transmission planning processes. A companion report focuses on non-plan-related factors that affect transmission projects.

Extraordinary acoustic transmission mediated by Helmholtz resonators

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Vijay Koju

2014-07-01

Full Text Available We demonstrate perfect transmission of sound through a rigid barrier embedded with Helmholtz resonators. The resonators are confined within a waveguide and they are oriented such that one neck protrudes onto each side of the barrier. Perfect sound transmission occurs even though the open area of the necks is less than 3% of the barrier area. Maximum transmission occurs at the resonant frequency of the Helmholtz resonator. Because the dimensions of the Helmholtz resonators are much smaller than the resonant wavelength, the transmission is independent of the direction of sound on the barrier and of the relative placement of the necks. Further, we show that the transmitted sound experiences a continuous phase transition of π radians as a function of frequency through resonance. In simulations of adjacent resonators with slightly offset resonance frequencies, the phase difference leads to destructive interference. By expanding the simulation to a linear array of tuned Helmholtz resonators we show that it is possible to create an acoustic lens. The ability of Helmholtz resonator arrays to manipulate the phase of a plane acoustic wave enables a new class of sonic beam-forming devices analogous to diffractive optics.

Investigating rate-limiting barriers to nanoscale nonviral gene transfer with nanobiophotonics

Science.gov (United States)

Chen, Hunter H.

Nucleic acids are a novel class of therapeutics poised to address many unmet clinical needs. Safe and efficient delivery remains a significant challenge that has delayed the realization of the full therapeutic potential of nucleic acids. Nanoscale nonviral vectors offer an attractive alternative to viral vectors as natural and synthetic polymers or polypeptides may be rationally designed to meet the unique demands of individual applications. A mechanistic understanding of cellular barriers is necessary to develop guidelines for designing custom gene carriers which are expected to greatly impact this delivery challenge. The work herein focused on the relationships among nanocomplex stability, intracellular trafficking and unpacking kinetics, and DNA degradation. Ultrasensitive nanosensors based on QD-FRET were developed to characterize the biophysical properties of nanocomplexes and study these rate-limiting steps. Quantitative image analysis enabled the distributions of the subpopulation of condensed or released DNA to be determined within the major cellular compartments encountered during gene transfer. The steady state stability and unpacking kinetics within these compartments were found to impact transgene expression, elucidating multiple design strategies to achieve efficient gene transfer. To address enzymatic barriers, a novel two-step QD-FRET nanosensor was developed to analyze unpacking and DNA degradation simultaneously, which has not been accomplished previously. Bioresponsive strategies such as disulfide crosslinking and thermosensitivity were evaluated by QD-FRET and quantitative compartmental analysis as case studies to determine appropriate design specifications for thiolated polymers and thermoresponsive polypeptides. Relevant nanobiophotonic tools were developed as a platform to study major rate-limiting barriers to nanomedicine and demonstrated the feasibility of using mechanistic information gained from these tools to guide the rational design of

CITY TRANSPORT IN BARRIER-FREE ARCHITECTURAL PLANNING SPACE FOR PEOPLE WITH LIMITED MOBILITY

Directory of Open Access Journals (Sweden)

Pryadko Igor’ Petrovich

2014-09-01

Full Text Available This paper reviews the current state of transport organization for people with limited mobility. The article evaluates the results of the actions the executive authorities of Moscow and Moscow Region take. Barrier-free space organization for disabled people and parents with prams is given a special attention. The lack of strategy in the sphere leads to considerable difficulties for people with limited ability. This problem should be solved in cooperation with the survey of other peoples' needs. The article gives examples of comfortable urban space in Sochi, Moscow, Chita, Mytishchi and analyses the ways urbanism influences people with limited abilities.

Quantum coherence in the reflection of above barrier wavepackets

Science.gov (United States)

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

Internal transport barrier and β limit in ohmically heated plasma in TUMAN-3M

International Nuclear Information System (INIS)

Andreiko, M.V.; Askinazi, L.G.; Golant, V.E.

2001-01-01

An Internal Transport Barrier (ITB) was found in ohmically heated plasma in TUMAN-3M (R 0 =53 cm, a l =22 cm - circular limiter configuration, B t ≤0.7T, I p ≤175 kA, ≤6.0·10 19 m -3 ). The barrier reveals itself as a formation of a steep gradient on electron temperature and density radial profiles. The regions with reduced diffusion and electron thermal diffusivity are in between r=0.5a and r=0.7a. The ITB appears more frequently in the shots with higher plasma current. At lower currents (I p N limit in the ohmically heated plasma are presented. Stored energy was measured using diamagnetic loops and compared with W calculated from kinetic data obtained by Thomson scattering and microwave interferometry. Measurements of the stored energy and of the β were performed in the ohmic H-mode before and after boronization and in the scenario with the fast Current Ramp-Down in the ohmic H-mode. Maximum value of β T of 2.0 % and β N of 2 were achieved. The β N limit achieved is 'soft' (nondisruptive) limit. The stored energy slowly decays after the Current Ramp-Down. No correlation was found between beta restriction and MHD phenomena. (author)

Internal transport barrier and β limit in ohmically heated plasma in TUMAN-3M

International Nuclear Information System (INIS)

Andreiko, M.V.; Askinazi, L.G.; Golant, V.E.

1999-01-01

An Internal Transport Barrier (ITB) was found in ohmically heated plasma in TUMAN-3M (R 0 = 53 cm, a l = 22 cm - circular limiter configuration, B t ≤ 0.7 T, I p ≤ 175 kA, ≤ 6.0·10 19 m -3 ). The barrier reveals itself as a formation of a steep gradient on electron temperature and density radial profiles. The regions with reduced diffusion and electron thermal diffusivity are in between r = 0.5a and r = 0.7a. The ITB appears more frequently in the shots with higher plasma current. At lower currents (I p N limit in the ohmically heated plasma are presented. Stored energy was measured using diamagnetic loops and compared with W calculated from kinetic data obtained by Thomson scattering and microwave interferometry. Measurements of the stored energy and of the β were performed in the ohmic H-mode before and after boronization and in the scenario with the fast Current Ramp-Down in the ohmic H-mode. Maximum value of β T of 2.0% and β N of 2 were achieved. The β N limit achieved is 'soft' (non-disruptive) limit. The stored energy slowly decays after the Current Ramp-Down. No correlation was found between beta restriction and MHD phenomena. (author)

The limits of HVDC transmission

International Nuclear Information System (INIS)

Pickard, William F.

2013-01-01

Renewable energy is abundant, but not necessarily near the urban centers where it will be used. Therefore, it must be transported; and this transport entails a systemic energy penalty. In this paper simple qualitative calculations are introduced to show (i) that high-voltage direct-current (HVDC) power lines for megameter and greater distances are unlikely to achieve power capacities much beyond 2 GW, although they can be paralleled; (ii) that most sources and sinks of electric power are rather less than 10,000 km apart; (iii) that such long lines can be constructed to have transmission losses -tilde 2%; and (iv) that lines of such low loss in fact meet minimal standards of intergenerational equity. - Highlights: • Renewable Energy is abundant, but not necessarily near population centers. • Its transportation requires energy and can be a major systemic inefficiency. • HVDC can be transmitted 10,000 km with 2% loss and near-optimal embodied energy. • Such transmission meets the requirements of intergenerational equity

Instantaneous Tunneling Flight Time for Wavepacket Transmission through Asymmetric Barriers.

Science.gov (United States)

Petersen, Jakob; Pollak, Eli

2018-04-12

The time it takes a particle to tunnel through the asymmetric Eckart barrier potential is investigated using Gaussian wavepackets, where the barrier serves as a model for the potential along a chemical reaction coordinate. We have previously shown that the, in principle experimentally measurable, tunneling flight time, which determines the time taken by the transmitted particle to traverse the barrier, vanishes for symmetric potentials like the Eckart and square barrier [ Petersen , J. ; Pollak , E. J. Phys. Chem. Lett. 2017 , 9 , 4017 ]. Here we show that the same result is obtained for the asymmetric Eckart barrier potential, and therefore, the zero tunneling flight time seems to be a general result for one-dimensional time-independent potentials. The wavepacket dynamics is simulated using both an exact quantum mechanical method and a classical Wigner prescription. The excellent agreement between the two methods shows that quantum coherences are not important in pure one-dimensional tunneling and reinforces the conclusion that the tunneling flight time vanishes.

Reaction rate calculations via transmission coefficients

International Nuclear Information System (INIS)

Feit, M.D.; Alder, B.J.

1985-01-01

The transmission coefficient of a wavepacket traversing a potential barrier can be determined by steady state calculations carried out in imaginary time instead of by real time dynamical calculations. The general argument is verified for the Eckart barrier potential by a comparison of transmission coefficients calculated from real and imaginary time solutions of the Schroedinger equation. The correspondence demonstrated here allows a formulation for the reaction rate that avoids difficulties due to both rare events and explicitly time dependent calculations. 5 refs., 2 figs

Barriers and Limitations of Mentoring in Polish Organizations

Directory of Open Access Journals (Sweden)

Joanna Mesjasz

2013-09-01

Full Text Available In Polish organizations one can recognize a lot of barriers in the mentoring implementation. According to the author, at the root of these barriers are hierarchies of values: social, national, organizational, and hierarchies of values represented by individual employees. The purpose of this article is to trace the sources of constraints in the mentoring implementation process. The analysis is carried out on several levels: from the broadest social perspective, through the national to the perspective of the organization. In the article, there are also presented actions that should be taken by Polish organizations to overcome barriers and constraints in the mentoring implementation process.

Electric-field effects on electronic tunneling transport in magnetic barrier structures

International Nuclear Information System (INIS)

Guo Yong; Wang Hao; Gu Binglin; Kawazoe, Yoshiyuki

2000-01-01

Electronic transport properties in magnetic barrier structures under the influence of an electric field have been investigated. The results indicate that the characteristics of transmission resonance are determined not only by the structure and the incident wave vector but also strongly by the electric field. It is shown that the transmission coefficient at resonance in the low-energy range is suppressed by applying the electric field for electron tunneling through the magnetic barrier structure, arranged with identical magnetic barriers and wells. It is also shown that the transmission resonance is first enhanced up to optimal resonance, and then suppressed with further increased electric field for electron tunneling through the magnetic barrier structure, arranged with unidentical building blocks. Strong suppression of the current density is also found in the magnetic barrier structure, arranged with two different building blocks

The Cost of Transmission for Wind Energy: A Review of Transmission Planning Studies

Energy Technology Data Exchange (ETDEWEB)

Mills, Andrew D.; Wiser, Ryan; Porter, Kevin

2009-02-02

The rapid development of wind power that the United States has experienced over the last several years has been coupled with a growing concern that wind development will require substantial additions to the nation's transmission infrastructure. Transmission is particularly important for wind power due to the locational dependence of wind resources, the relatively low capacity factor of wind plants, and the mismatch between the short lead time to build a new wind project and the longer lead time often needed to plan, permit, and construct transmission. It is clear that institutional issues related to transmission planning, siting, and cost allocation will pose major obstacles to accelerated wind power deployment, but also of concern is the potential cost of this infrastructure build out. Simply put, how much extra cost will society bear to deliver wind power to load centers? Without an answer to this question, there can be no consensus on whether or not the cost of developing transmission for wind will be a major barrier to further wind deployment, or whether the institutional barriers to transmission expansion are likely to be of more immediate concern. In this report, we review a sample of 40 detailed transmission studies that have included wind power. These studies cover a broad geographic area, and were completed from 2001-2008. Our primary goal in reviewing these studies is to develop a better understanding of the transmission costs needed to access growing quantities of wind generation. A secondary goal is to gain a better appreciation of the differences in transmission planning approaches in order to identify those methodologies that seem most able to estimate the incremental transmission costs associated with wind development. Finally, we hope that the resulting dataset and discussion might be used to inform the assumptions, methods, and results of higher-level assessment models that are sometimes used to estimate the cost of wind deployment (e.g. NEMS

A novel power efficient location-based cooperative routing with transmission power-upper-limit for wireless sensor networks.

Science.gov (United States)

Shi, Juanfei; Calveras, Anna; Cheng, Ye; Liu, Kai

2013-05-15

The extensive usage of wireless sensor networks (WSNs) has led to the development of many power- and energy-efficient routing protocols. Cooperative routing in WSNs can improve performance in these types of networks. In this paper we discuss the existing proposals and we propose a routing algorithm for wireless sensor networks called Power Efficient Location-based Cooperative Routing with Transmission Power-upper-limit (PELCR-TP). The algorithm is based on the principle of minimum link power and aims to take advantage of nodes cooperation to make the link work well in WSNs with a low transmission power. In the proposed scheme, with a determined transmission power upper limit, nodes find the most appropriate next nodes and single-relay nodes with the proposed algorithm. Moreover, this proposal subtly avoids non-working nodes, because we add a Bad nodes Avoidance Strategy (BAS). Simulation results show that the proposed algorithm with BAS can significantly improve the performance in reducing the overall link power, enhancing the transmission success rate and decreasing the retransmission rate.

A Novel Power Efficient Location-Based Cooperative Routing with Transmission Power-Upper-Limit for Wireless Sensor Networks

Science.gov (United States)

Shi, Juanfei; Calveras, Anna; Cheng, Ye; Liu, Kai

2013-01-01

The extensive usage of wireless sensor networks (WSNs) has led to the development of many power- and energy-efficient routing protocols. Cooperative routing in WSNs can improve performance in these types of networks. In this paper we discuss the existing proposals and we propose a routing algorithm for wireless sensor networks called Power Efficient Location-based Cooperative Routing with Transmission Power-upper-limit (PELCR-TP). The algorithm is based on the principle of minimum link power and aims to take advantage of nodes cooperation to make the link work well in WSNs with a low transmission power. In the proposed scheme, with a determined transmission power upper limit, nodes find the most appropriate next nodes and single-relay nodes with the proposed algorithm. Moreover, this proposal subtly avoids non-working nodes, because we add a Bad nodes Avoidance Strategy (BAS). Simulation results show that the proposed algorithm with BAS can significantly improve the performance in reducing the overall link power, enhancing the transmission success rate and decreasing the retransmission rate. PMID:23676625

Transmission electron microscopy study for investigating high-temperature reliability of Ti10W90-based and Ta-based diffusion barriers up to 600 C

International Nuclear Information System (INIS)

Budhiman, Nando; Schuermann, Ulrich; Kienle, Lorenz; Jensen, Bjoern; Chemnitz, Steffen; Wagner, Bernhard

2016-01-01

Abstractauthoren Transmission electron microscopy (TEM) analysis, including energy dispersive X-ray (EDX) (elemental mapping, line, and point measurements) and energy filtered TEM (EFTEM) methods, is applied to investigate the high temperature reliability, especially material diffusion, of two types of diffusion barriers: titanium-tungsten-based (Ti 10 W 90 -based) and tantalum-based (Ta-based), with nickel (Ni) layer on top. Both barriers were deposited as a form of stacked layers on sili-con (Si) wafers using the physical vapor deposition (PVD) technique. TEM analysis is performed on both barriers before and after annealing (at 600 C for 24 h inside a vacuum chamber). No diffusion of material into the Si substrate as observed. Additionally, only diffusion between the Ni and adjoining Ti 10 W 90 layers, and between Ni and adjoining Ta layers in the Ti 10 W 90 -based and Ta-based barriers, respectively, are observed due to annealing. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

UK Iatrogenic Creutzfeldt-Jakob disease: investigating human prion transmission across genotypic barriers using human tissue-based and molecular approaches.

Science.gov (United States)

Ritchie, Diane L; Barria, Marcelo A; Peden, Alexander H; Yull, Helen M; Kirkpatrick, James; Adlard, Peter; Ironside, James W; Head, Mark W

2017-04-01

Creutzfeldt-Jakob disease (CJD) is the prototypic human prion disease that occurs most commonly in sporadic and genetic forms, but it is also transmissible and can be acquired through medical procedures, resulting in iatrogenic CJD (iCJD). The largest numbers of iCJD cases that have occurred worldwide have resulted from contaminated cadaveric pituitary-derived human growth hormone (hGH) and its use to treat primary and secondary growth hormone deficiency. We report a comprehensive, tissue-based and molecular genetic analysis of the largest series of UK hGH-iCJD cases reported to date, including in vitro kinetic molecular modelling of genotypic factors influencing prion transmission. The results show the interplay of prion strain and host genotype in governing the molecular, pathological and temporal characteristics of the UK hGH-iCJD epidemic and provide insights into the adaptive mechanisms involved when prions cross genotypic barriers. We conclude that all of the available evidence is consistent with the hypothesis that the UK hGH-iCJD epidemic resulted from transmission of the V2 human prion strain, which is associated with the second most common form of sporadic CJD.

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

Science.gov (United States)

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.

Revival of cloaking effect in a driven bilayer graphene vector barrier

Science.gov (United States)

Maiti, S.; Panigrahi, A.; Biswas, R.; Sinha, C.

2018-05-01

Transmission profiles in bilayer graphene are studied theoretically through a rectangular vector potential (magnetic) barrier with and without the presence of an oscillatory potential. Unlike the electrostatic barrier, the Fano resonances (FR) are noted in the transmission spectra both for normal and glancing incidences due to non-conservation of chirality for a static vector barrier. The results for normal incidence indicate that the cloaking effect is a manifestation of the chirality conservation in charge transport through bilayer graphene scalar barriers. It is also noted that the aforesaid FR for a static vector barrier might disappear (photon induced electronic cloaking effect) due to the predominant photon exchange processes in presence of an external oscillating potential. The study of Fano resonances in transmission spectrum is in high demand in respect of localization of charge carriers in graphene nano structures for its potential applications in digital device fabrications.

Confocal soft X-ray scanning transmission microscopy: setup, alignment procedure and limitations

International Nuclear Information System (INIS)

Späth, Andreas; Raabe, Jörg; Fink, Rainer H.

2015-01-01

A conventional STXM setup has been upgraded with a second micro zone plate and aligned to confocal geometry. Two confocal geometries (in-line and off-axis) have been evaluated and a discussion on prospects and limitations is presented. Zone-plate-based scanning transmission soft X-ray microspectroscopy (STXM) is a well established technique for high-contrast imaging of sufficiently transparent specimens (e.g. ultrathin biological tissues, polymer materials, archaeometric specimens or magnetic thin films) with spatial resolutions in the regime of 20 nm and high spectroscopic or chemical sensitivity. However, due to the relatively large depth of focus of zone plates, the resolution of STXM along the optical axis so far stays unambiguously behind for thicker X-ray transparent specimens. This challenge can be addressed by the implementation of a second zone plate in the detection pathway of the beam, resulting in a confocal arrangement. Within this paper a first proof-of-principle study for a confocal STXM (cSTXM) and an elaborate alignment procedure in transmission and fluorescence geometry are presented. Based on first confocal soft X-ray micrographs of well known specimens, the advantage and limitation of cSTXM as well as further development potentials for future applications are discussed

Confocal soft X-ray scanning transmission microscopy: setup, alignment procedure and limitations

Energy Technology Data Exchange (ETDEWEB)

Späth, Andreas [Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Egerlandstraße 3, 91058 Erlangen (Germany); Raabe, Jörg [Paul Scherrer Institut, 5232 Villigen (Switzerland); Fink, Rainer H., E-mail: rainer.fink@fau.de [Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Egerlandstraße 3, 91058 Erlangen (Germany); Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Egerlandstraße 3, 91058 Erlangen (Germany)

2015-01-01

A conventional STXM setup has been upgraded with a second micro zone plate and aligned to confocal geometry. Two confocal geometries (in-line and off-axis) have been evaluated and a discussion on prospects and limitations is presented. Zone-plate-based scanning transmission soft X-ray microspectroscopy (STXM) is a well established technique for high-contrast imaging of sufficiently transparent specimens (e.g. ultrathin biological tissues, polymer materials, archaeometric specimens or magnetic thin films) with spatial resolutions in the regime of 20 nm and high spectroscopic or chemical sensitivity. However, due to the relatively large depth of focus of zone plates, the resolution of STXM along the optical axis so far stays unambiguously behind for thicker X-ray transparent specimens. This challenge can be addressed by the implementation of a second zone plate in the detection pathway of the beam, resulting in a confocal arrangement. Within this paper a first proof-of-principle study for a confocal STXM (cSTXM) and an elaborate alignment procedure in transmission and fluorescence geometry are presented. Based on first confocal soft X-ray micrographs of well known specimens, the advantage and limitation of cSTXM as well as further development potentials for future applications are discussed.

Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

International Nuclear Information System (INIS)

Kaeaeriaeinen, Tommi O.; Maydannik, Philipp; Cameron, David C.; Lahtinen, Kimmo; Johansson, Petri; Kuusipalo, Jurkka

2011-01-01

One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O 2 TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O 2 TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.

Atomic layer deposition on polymer based flexible packaging materials: Growth characteristics and diffusion barrier properties

Energy Technology Data Exchange (ETDEWEB)

Kaeaeriaeinen, Tommi O., E-mail: tommi.kaariainen@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Maydannik, Philipp, E-mail: philipp.maydannik@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Cameron, David C., E-mail: david.cameron@lut.f [ASTRaL, Lappeenranta University of Technology, Prikaatinkatu 3 E, 50100 Mikkeli (Finland); Lahtinen, Kimmo, E-mail: kimmo.lahtinen@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Johansson, Petri, E-mail: petri.johansson@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland); Kuusipalo, Jurkka, E-mail: jurkka.kuusipalo@tut.f [Tampere University of Technology, Paper Converting and Packaging Technology, P.O. Box 541, 33101 Tampere (Finland)

2011-03-01

One of the most promising areas for the industrial application of atomic layer deposition (ALD) is for gas barrier layers on polymers. In this work, a packaging material system with improved diffusion barrier properties has been developed and studied by applying ALD on flexible polymer based packaging materials. Nanometer scale metal oxide films have been applied to polymer-coated papers and their diffusion barrier properties have been studied by means of water vapor and oxygen transmission rates. The materials for the study were constructed in two stages: the paper was firstly extrusion coated with polymer film, which was then followed by the ALD deposition of oxide layer. The polymers used as extrusion coatings were polypropylene, low and high density polyethylene, polylactide and polyethylene terephthalate. Water vapor transmission rates (WVTRs) were measured according to method SCAN-P 22:68 and oxygen transmission rates (O{sub 2}TRs) according to a standard ASTM D 3985. According to the results a 10 nm oxide layer already decreased the oxygen transmission by a factor of 10 compared to uncoated material. WVTR with 40 nm ALD layer was better than the level currently required for most common dry flexible packaging applications. When the oxide layer thickness was increased to 100 nm and above, the measured WVTRs were limited by the measurement set up. Using an ALD layer allowed the polymer thickness on flexible packaging materials to be reduced. Once the ALD layer was 40 nm thick, WVTRs and O{sub 2}TRs were no longer dependent on polymer layer thickness. Thus, nanometer scale ALD oxide layers have shown their feasibility as high quality diffusion barriers on flexible packaging materials.

Experimental realization of extraordinary acoustic transmission using Helmholtz resonators

Directory of Open Access Journals (Sweden)

Brian C. Crow

2015-02-01

Full Text Available The phenomenon of extraordinary acoustic transmission through a solid barrier with an embedded Helmholtz resonator (HR is demonstrated. The Helmholtz resonator consists of an embedded cavity and two necks that protrude, one on each side of the barrier. Extraordinary transmission occurs for a narrow spectral range encompassing the resonant frequency of the Helmholtz resonator. We show that an amplitude transmission of 97.5% is achieved through a resonator whose neck creates an open area of 6.25% of the total barrier area. In addition to the enhanced transmission, we show that there is a smooth, continuous phase transition in the transmitted sound as a function of frequency. The frequency dependent phase transition is used to experimentally realize slow wave propagation for a narrow-band Gaussian wave packet centered at the maximum transmission frequency. The use of parallel pairs of Helmholtz resonators tuned to different resonant frequencies is experimentally explored as a means of increasing the transmission bandwidth. These experiments show that because of the phase transition, there is always a frequency between the two Helmholtz resonant frequencies at which destructive interference occurs whether the resonances are close or far apart. Finally, we explain how the phase transition associated with Helmholtz-resonator-mediated extraordinary acoustic transmission can be exploited to produce diffractive acoustic components including sub-wavelength thickness acoustic lenses.

Physiologic upper limit of pore size in the blood-tumor barrier of malignant solid tumors

Directory of Open Access Journals (Sweden)

Griffiths Gary L

2009-06-01

Full Text Available Abstract Background The existence of large pores in the blood-tumor barrier (BTB of malignant solid tumor microvasculature makes the blood-tumor barrier more permeable to macromolecules than the endothelial barrier of most normal tissue microvasculature. The BTB of malignant solid tumors growing outside the brain, in peripheral tissues, is more permeable than that of similar tumors growing inside the brain. This has been previously attributed to the larger anatomic sizes of the pores within the BTB of peripheral tumors. Since in the physiological state in vivo a fibrous glycocalyx layer coats the pores of the BTB, it is possible that the effective physiologic pore size in the BTB of brain tumors and peripheral tumors is similar. If this were the case, then the higher permeability of the BTB of peripheral tumor would be attributable to the presence of a greater number of pores in the BTB of peripheral tumors. In this study, we probed in vivo the upper limit of pore size in the BTB of rodent malignant gliomas grown inside the brain, the orthotopic site, as well as outside the brain in temporalis skeletal muscle, the ectopic site. Methods Generation 5 (G5 through generation 8 (G8 polyamidoamine dendrimers were labeled with gadolinium (Gd-diethyltriaminepentaacetic acid, an anionic MRI contrast agent. The respective Gd-dendrimer generations were visualized in vitro by scanning transmission electron microscopy. Following intravenous infusion of the respective Gd-dendrimer generations (Gd-G5, N = 6; Gd-G6, N = 6; Gd-G7, N = 5; Gd-G8, N = 5 the blood and tumor tissue pharmacokinetics of the Gd-dendrimer generations were visualized in vivo over 600 to 700 minutes by dynamic contrast-enhanced MRI. One additional animal was imaged in each Gd-dendrimer generation group for 175 minutes under continuous anesthesia for the creation of voxel-by-voxel Gd concentration maps. Results The estimated diameters of Gd-G7 dendrimers were 11 ± 1 nm and those of Gd-G8

[Neurological disorders and the blood-brain barrier. Strategies and limitations for drug delivery to the brain].

Science.gov (United States)

Domínguez, Alazne; Álvarez, Antonia; Suárez-Merino, Blanca; Goñi-de-Cerio, Felipe

2014-03-01

The incidence in the central nervous system diseases has increased with a growing elderly population. Unfortunately, conventional treatments used to treat the mentioned diseases are frequently ineffective due to the presence of the blood brain barrier. To illustrate the blood-brain barrier properties that limit drug transport into the brain and the main strategies employed to treat neurologic disorders. The blood-brain barrier is mainly composed of a specialized microvascular endothelium and of glial cells. It constitutes a valuable tool to separate the central nervous system from the rest of the body. Nevertheless, it also represents an obstacle to the delivery of therapeutic drugs to the brain. To be effective, drugs must reach their target in the brain. On one hand, therapeutic agents could be designed to be able to cross the blood brain barrier. On the other hand, drug delivery systems could be employed to facilitate the therapeutic agents' entry into the central nervous system. In vivo models of neurological diseases, in addition to in vitro models of the blood brain barrier, have been widely employed for the evaluation of drugs utilized to treat central nervous system diseases.

Interaction of tide and salinity barrier: Limitation of numerical model

Directory of Open Access Journals (Sweden)

Suphat Vongvisessomjai1

2008-07-01

Full Text Available Nowadays, the study of interaction of the tide and the salinity barrier in an estuarine area is usually accomplished vianumerical modeling, due to the speed and convenience of modern computers. However, numerical models provide littleinsight with respect to the fundamental physical mechanisms involved. In this study, it is found that all existing numericalmodels work satisfactorily when the barrier is located at some distance far from upstream and downstream boundary conditions.Results are considerably underestimate reality when the barrier is located near the downstream boundary, usually theriver mouth. Meanwhile, this analytical model provides satisfactory output for all scenarios. The main problem of thenumerical model is that the effects of barrier construction in creation of reflected tide are neglected when specifying thedownstream boundary conditions; the use of the boundary condition before construction of the barrier which are significantlydifferent from those after the barrier construction would result in an error outputs. Future numerical models shouldattempt to account for this deficiency; otherwise, using this analytical model is another choice.

Transmission properties of a single metallic slit: from the subwavelength regime to the geometrical-optics limit.

Science.gov (United States)

Bravo-Abad, J; Martín-Moreno, L; García-Vidal, F J

2004-02-01

In this work we explore the transmission properties of a single slit in a metallic screen. We analyze the dependence of these properties on both slit width and angle of incident radiation. We study in detail the crossover between the subwavelength regime and the geometrical-optics limit. In the subwavelength regime, resonant transmission linked to the excitation of waveguide resonances is analyzed. Linewidth of these resonances and their associated electric-field intensities are controlled by just the width of the slit. More complex transmission spectra appear when the wavelength of light is comparable to the slit width. Rapid oscillations associated with the emergence of different propagating modes inside the slit are the main features appearing in this regime.

Design of electron wave filters in monolayer graphene by tunable transmission gap

OpenAIRE

Chen, Xi; Tao, Jia-Wei

2009-01-01

We have investigated the transmission in monolayer graphene barrier at nonzero angle of incidence. Taking the influence of parallel wave vector into account, the transmission as the function of incidence energy has a gap due to the evanescent waves in two cases of Klein tunneling and classical motion. The modulation of the transmission gap by the incidence angle, the height, and width of potential barrier may lead to potential applications in graphene-based electronic devices.

A tunable acoustic barrier based on periodic arrays of subwavelength slits

Directory of Open Access Journals (Sweden)

Constanza Rubio

2015-05-01

Full Text Available The most usual method to reduce undesirable enviromental noise levels during its transmission is the use of acoustic barriers. A novel type of acoustic barrier based on sound transmission through subwavelength slits is presented. This system consists of two rows of periodic repetition of vertical rigid pickets separated by a slit of subwavelength width and with a misalignment between them. Here, both the experimental and the numerical analyses are presented. The acoustic barrier proposed can be easily built and is frequency tunable. The results demonstrated that the proposed barrier can be tuned to mitigate a band noise without excesive barrier thickness. The use of this system as an environmental acoustic barrier has certain advantages with regard to the ones currently used both from the constructive and the acoustical point of view.

A tunable acoustic barrier based on periodic arrays of subwavelength slits

Science.gov (United States)

Rubio, Constanza; Uris, Antonio; Candelas, Pilar; Belmar, Francisco; Gomez-Lozano, Vicente

2015-05-01

The most usual method to reduce undesirable enviromental noise levels during its transmission is the use of acoustic barriers. A novel type of acoustic barrier based on sound transmission through subwavelength slits is presented. This system consists of two rows of periodic repetition of vertical rigid pickets separated by a slit of subwavelength width and with a misalignment between them. Here, both the experimental and the numerical analyses are presented. The acoustic barrier proposed can be easily built and is frequency tunable. The results demonstrated that the proposed barrier can be tuned to mitigate a band noise without excesive barrier thickness. The use of this system as an environmental acoustic barrier has certain advantages with regard to the ones currently used both from the constructive and the acoustical point of view.

Tunneling effect on double potential barriers GaAs and PbS

Science.gov (United States)

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).

Molecular Modeling of Prion Transmission to Humans

Directory of Open Access Journals (Sweden)

Etienne Levavasseur

2014-10-01

Full Text Available Using different prion strains, such as the variant Creutzfeldt-Jakob disease agent and the atypical bovine spongiform encephalopathy agents, and using transgenic mice expressing human or bovine prion protein, we assessed the reliability of protein misfolding cyclic amplification (PMCA to model interspecies and genetic barriers to prion transmission. We compared our PMCA results with in vivo transmission data characterized by attack rates, i.e., the percentage of inoculated mice that developed the disease. Using 19 seed/substrate combinations, we observed that a significant PMCA amplification was only obtained when the mouse line used as substrate is susceptible to the corresponding strain. Our results suggest that PMCA provides a useful tool to study genetic barriers to transmission and to study the zoonotic potential of emerging prion strains.

Risk Factors for HIV Transmission and Barriers to HIV Disclosure: Metropolitan Atlanta Youth Perspectives.

Science.gov (United States)

Camacho-Gonzalez, Andres F; Wallins, Amy; Toledo, Lauren; Murray, Ashley; Gaul, Zaneta; Sutton, Madeline Y; Gillespie, Scott; Leong, Traci; Graves, Chanda; Chakraborty, Rana

2016-01-01

Youth carry the highest incidence of HIV infection in the United States. Understanding adolescent and young adult (AYA) perspectives on HIV transmission risk is important for targeted HIV prevention. We conducted a mixed methods study with HIV-infected and uninfected youth, ages 18-24 years, from Atlanta, GA. We provided self-administered surveys to HIV-infected and HIV-uninfected AYAs to identify risk factors for HIV acquisition. By means of computer-assisted thematic analyses, we examined transcribed focus group responses on HIV education, contributors to HIV transmission, and pre-sex HIV status disclosure. The 68 participants had the following characteristics: mean age 21.5 years (standard deviation: 1.8 years), 85% male, 90% black, 68% HIV-infected. HIV risk behaviors included the perception of condomless sex (Likert scale mean: 8.0) and transactional sex (88% of participants); no differences were noted by HIV status. Qualitative analyses revealed two main themes: (1) HIV risk factors among AYAs, and (2) barriers to discussing HIV status before sex. Participants felt the use of social media, need for immediate gratification, and lack of concern about HIV disease were risk factors for AYAs. Discussing HIV status with sex partners was uncommon. Key reasons included: fear of rejection, lack of confidentiality, discussion was unnecessary in temporary relationships, and disclosure negatively affecting the mood. HIV prevention strategies for AYAs should include improving condom use frequency and HIV disclosure skills, responsible utilization of social media, and education addressing HIV prevention including the risks of transactional sex.

Barriers to control syphilis and HIV vertical transmission in the health care system in the city of Sao Paulo

Directory of Open Access Journals (Sweden)

Valdete Maria Ramos

2014-12-01

Full Text Available OBJECTIVE: The objective of this study was to identify possible barriers to control vertical transmission of syphilis and HIV through the analysis of the orientation process of pregnant women from prenatal care to the obstetric center at an university hospital in Sao Paulo (Reference and their return (with their exposed babies for follow-up after hospital discharge (counter-reference. METHODS: It is a retrospective cross-sectional study including interviews with healthcare personnel. Pregnant women with syphilis and/or HIV-infection admitted for labor or miscarriage were identified from August 2006 to August 2007. Routine care for mothers and babies were analyzed. RESULTS: 56 pregnant women were identified: 43 were HIV-infected, 11 had syphilis and two were coinfected (syphilis/HIV; 22 health care professionals were interviewed. Prenatal care was identified in 91.1% of these women: 7/11 (63.6% with syphilis; 44/45 (97.8% HIV-infected or coinfected. The reference for delivery was satisfactory for 57.7% of the syphilis-infected women and 97.7% of the HIV-infected ones. The counter-reference was satisfactory for all babies and mothers at hospital discharge, besides the non-adherence to this recommendation. Interviews with health care professionals showed there are better routines for assisting and following-up pregnant women, puerperal women and HIV-infected or exposed babies than for those infected with syphilis. The epidemiological report and surveillance system are also better for HIV-infected patients. CONCLUSION: The difficulties in the reference and counter-reference system of these women and their babies are evident barriers to control the vertical transmission of these infectious diseases.

PIC simulations of conical magnetically insulated transmission line with LTD generator: Transition from self-limited to load-limited flow

Science.gov (United States)

Liu, Laqun; Wang, Huihui; Guo, Fan; Zou, Wenkang; Liu, Dagang

2017-04-01

Based on the 3-dimensional Particle-In-Cell (PIC) code CHIPIC3D, with a new circuit boundary algorithm we developed, a conical magnetically insulated transmission line (MITL) with a 1.0-MV linear transformer driver (LTD) is explored numerically. The values of switch jitter time of LTD are critical parameters for the system, which are difficult to be measured experimentally. In this paper, these values are obtained by comparing the PIC results with experimental data of large diode-gap MITL. By decreasing the diode gap, we find that all PIC results agree well with experimental data only if MITL works on self-limited flow no matter how large the diode gap is. However, when the diode gap decreases to a threshold, the self-limited flow would transfer to a load-limited flow. In this situation, PIC results no longer agree with experimental data anymore due to the anode plasma expansion in the diode load. This disagreement is used to estimate the plasma expansion speed.

Multilayer moisture barrier

Science.gov (United States)

Pankow, Joel W; Jorgensen, Gary J; Terwilliger, Kent M; Glick, Stephen H; Isomaki, Nora; Harkonen, Kari; Turkulainen, Tommy

2015-04-21

A moisture barrier, device or product having a moisture barrier or a method of fabricating a moisture barrier having at least a polymer layer, and interfacial layer, and a barrier layer. The polymer layer may be fabricated from any suitable polymer including, but not limited to, fluoropolymers such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), or ethylene-tetrafluoroethylene (ETFE). The interfacial layer may be formed by atomic layer deposition (ALD). In embodiments featuring an ALD interfacial layer, the deposited interfacial substance may be, but is not limited to, Al.sub.2O.sub.3, AlSiO.sub.x, TiO.sub.2, and an Al.sub.2O.sub.3/TiO.sub.2 laminate. The barrier layer associated with the interfacial layer may be deposited by plasma enhanced chemical vapor deposition (PECVD). The barrier layer may be a SiO.sub.xN.sub.y film.

Barriers to wind power exports from the Maritime provinces to the US northeast

International Nuclear Information System (INIS)

Dalton, J.

2009-01-01

This presentation discussed a study that evaluated wind energy export potential from the Maritime provinces to the northeastern United States. The study assessed key market issues likely to affect the exports. The study showed that the Maritime provinces are capable of generating 5500 to 7500 MW of wind. The current electricity system is capable of integrating 2100 MW. Wind power integration between the 2 regions would require transmission upgrades, increased transmission capacity, and better coordination between system operators. Barriers to exports from the Maritimes include limited capacity on existing interties and high transmission tariffs. Uniform transmission tariffs are needed throughout the Maritime provinces. Coordination and integration of operators and utilities is needed to reduce the costs of wind power integration. Increased wind power production reduces price risks related to high energy prices. It was concluded that wind power is a cost-effective method of providing renewable and low carbon dioxide (CO 2 ) generation electricity in the northeastern United States. tabs., figs

Measurements of Accelerator-Produced Leakage Neutron and Photon Transmission through Concrete

International Nuclear Information System (INIS)

2002-01-01

Optimum shielding of the radiation from particle accelerators requires knowledge of the attenuation characteristics of the shielding material. The most common material for shielding this radiation is concrete, which can be made using various materials of different densities as aggregates. These different concrete mixes can have very different attenuation characteristics. Information about the attenuation of leakage photons and neutrons in ordinary and heavy concrete is, however, very limited. To increase our knowledge and understanding of the radiation attenuation in concrete of various compositions, we have performed measurements of the transmission of leakage radiation, photons and neutrons, from a Varian Clinac 2100C medical linear accelerator operating at maximum electron energies of 6 and 18 MeV. We have also calculated, using Monte Carlo techniques, the leakage neutron spectra and its transmission through concrete. The results of these measurements and calculations extend the information currently available for designing shielding for medical electron accelerators. Photon transmission characteristics depend more on the manufacturer of the concrete than on the atomic composition. A possible cause for this effect is a non-uniform distribution of the high-density aggregate, typically iron, in the concrete matrix. Errors in estimated transmission of photons can exceed a factor of three, depending on barrier thickness, if attenuation in high-density concrete is simply scaled from that of normal density concrete. We found that neutron transmission through the high-density concretes can be estimated most reasonably and conservatively by using the linear tenth-value layer of normal concrete if specific values of the tenth-value layer of the high-density concrete are not known. The reason for this is that the neutron transmission depends primarily on the hydrogen content of the concrete, which does not significantly depend on concrete density. Errors of factors of two

Barriers and facilitating factors to the uptake of antiretroviral drugs for prevention of mother-to-child transmission of HIV in sub-Saharan Africa: a systematic review

Science.gov (United States)

Gourlay, Annabelle; Birdthistle, Isolde; Mburu, Gitau; Iorpenda, Kate; Wringe, Alison

2013-01-01

Objectives To investigate and synthesize reasons for low access, initiation and adherence to antiretroviral drugs by mothers and exposed babies for prevention of mother-to-child transmission (PMTCT) of HIV in sub-Saharan Africa. Methods A systematic literature review was conducted. Four databases were searched (Medline, Embase, Global Health and Web of Science) for studies conducted in sub-Saharan Africa from January 2000 to September 2012. Quantitative and qualitative studies were included that met pre-defined criteria. Antiretroviral (ARV) prophylaxis (maternal/infant) and combination antiretroviral therapy (ART) usage/registration at HIV care and treatment during pregnancy were included as outcomes. Results Of 574 references identified, 40 met the inclusion criteria. Four references were added after searching reference lists of included articles. Twenty studies were quantitative, 16 were qualitative and eight were mixed methods. Forty-one studies were conducted in Southern and East Africa, two in West Africa, none in Central Africa and one was multi-regional. The majority (n=25) were conducted before combination ART for PMTCT was emphasized in 2006. At the individual-level, poor knowledge of HIV/ART/vertical transmission, lower maternal educational level and psychological issues following HIV diagnosis were the key barriers identified. Stigma and fear of status disclosure to partners, family or community members (community-level factors) were the most frequently cited barriers overall and across time. The extent of partner/community support was another major factor impeding or facilitating the uptake of PMTCT ARVs, while cultural traditions including preferences for traditional healers and birth attendants were also common. Key health-systems issues included poor staff-client interactions, staff shortages, service accessibility and non-facility deliveries. Conclusions Long-standing health-systems issues (such as staffing and service accessibility) and community

Persistent current and transmission probability in the Aharonov-Bohm ring with an embedded quantum dot

International Nuclear Information System (INIS)

Wu Suzhi; Li Ning; Jin Guojun; Ma Yuqiang

2008-01-01

Persistent current and transmission probability in the Aharonov-Bohm (AB) ring with an embedded quantum dot (QD) are studied using the technique of the scattering matrix. For the first time, we find that the persistent current can arise in the absence of magnetic flux in the ring with an embedded QD. The persistent current and the transmission probability are sensitive to the lead-ring coupling and the short-range potential barrier. It is shown that increasing the lead-ring coupling or the short-range potential barrier causes the suppression of the persistent current and the increasing resonance width of the transmission probability. The effect of the potential barrier on the number of the transmission peaks is also investigated. The dependence of the persistent current and the transmission probability on the magnetic flux exhibits a periodic property with period of the flux quantum

A High-Speed Power-Line Communication System with Band-Limited OQAM Based Multi-Carrier Transmission

Science.gov (United States)

Kawabata, Naohiro; Koga, Hisao; Muta, Osamu; Akaiwa, Yoshihiko

As a method to realize a high-speed communication in the home network, the power-line communication (PLC) technique is known. A problem of PLC is that leakage radiation interferes with existing systems. When OFDM is used in a PLC system, the leakage radiation is not sufficiently reduced, even if the subcarriers corresponding to the frequency-band of the existing system are never used, because the signal is not strictly band-limited. To solve this problem, each subcarrier must be band-limited. In this paper, we apply the OQAM based multi-carrier transmission (OQAM-MCT) to a high-speed PLC system, where each subcarrier is individually band-limited. We also propose a pilot-symbol sequence suitable for frequency offset estimation, symbol-timing detection and channel estimation in the OQAM-MCT system. In this method, the pilot signal-sequence consists of a repeated series of the same data symbol. With this method, the pilot sequence approximately becomes equivalent to OFDM sequence and therefore existing pilot-assisted methods for OFDM are also applicable to OQAM-MCT system. Computer simulation results show that the OQAM-MCT system achieves both good transmission rate performance and low out-of-band radiation in PLC channels. It is also shown that the proposed pilot-sequence improves frequency offset estimation, symbol-timing detection and channel estimation performance as compared with the case of using pseudo-noise sequence.

Electromagnetic Saturation of Angstrom-Sized Quantum Barriers at Terahertz Frequencies

Science.gov (United States)

Bahk, Young-Mi; Kang, Bong Joo; Kim, Yong Seung; Kim, Joon-Yeon; Kim, Won Tae; Kim, Tae Yun; Kang, Taehee; Rhie, Jiyeah; Han, Sanghoon; Park, Cheol-Hwan; Rotermund, Fabian; Kim, Dai-Sik

2015-09-01

Metal-graphene-metal hybrid structures allow angstrom-scale van der Waals gaps, across which electron tunneling occurs. We squeeze terahertz electromagnetic waves through these λ /10 000 000 gaps, accompanied by giant field enhancements. Unprecedented transmission reduction of 97% is achieved with the transient voltage across the gap saturating at 5 V. Electron tunneling facilitated by the transient electric field strongly modifies the gap index, starting a self-limiting process related to the barrier height. Our work enables greater interplay between classical optics and quantum tunneling, and provides optical indices to the van der Waals gaps.

Electromagnetic Saturation of Angstrom-Sized Quantum Barriers at Terahertz Frequencies.

Science.gov (United States)

Bahk, Young-Mi; Kang, Bong Joo; Kim, Yong Seung; Kim, Joon-Yeon; Kim, Won Tae; Kim, Tae Yun; Kang, Taehee; Rhie, Jiyeah; Han, Sanghoon; Park, Cheol-Hwan; Rotermund, Fabian; Kim, Dai-Sik

2015-09-18

Metal-graphene-metal hybrid structures allow angstrom-scale van der Waals gaps, across which electron tunneling occurs. We squeeze terahertz electromagnetic waves through these λ/10 000 000 gaps, accompanied by giant field enhancements. Unprecedented transmission reduction of 97% is achieved with the transient voltage across the gap saturating at 5 V. Electron tunneling facilitated by the transient electric field strongly modifies the gap index, starting a self-limiting process related to the barrier height. Our work enables greater interplay between classical optics and quantum tunneling, and provides optical indices to the van der Waals gaps.

Analysing black phosphorus transistors using an analytic Schottky barrier MOSFET model.

Science.gov (United States)

Penumatcha, Ashish V; Salazar, Ramon B; Appenzeller, Joerg

2015-11-13

Owing to the difficulties associated with substitutional doping of low-dimensional nanomaterials, most field-effect transistors built from carbon nanotubes, two-dimensional crystals and other low-dimensional channels are Schottky barrier MOSFETs (metal-oxide-semiconductor field-effect transistors). The transmission through a Schottky barrier-MOSFET is dominated by the gate-dependent transmission through the Schottky barriers at the metal-to-channel interfaces. This makes the use of conventional transistor models highly inappropriate and has lead researchers in the past frequently to extract incorrect intrinsic properties, for example, mobility, for many novel nanomaterials. Here we propose a simple modelling approach to quantitatively describe the transfer characteristics of Schottky barrier-MOSFETs from ultra-thin body materials accurately in the device off-state. In particular, after validating the model through the analysis of a set of ultra-thin silicon field-effect transistor data, we have successfully applied our approach to extract Schottky barrier heights for electrons and holes in black phosphorus devices for a large range of body thicknesses.

Possibilities and limitations of optical fibers for the transmission of excimer laser radiation

International Nuclear Information System (INIS)

Klein, K.F.; Hillrichs, G.; Karlitschek, P.; Mann, K.

1997-01-01

For fiber-delivery systems with UV-lasers the candidates are mainly optical fibers with an undoped high-OH silica core and a F-doped silica cladding. However, there are three important limits to UV-applications: surface damage, two-photon-absorption and defect-generation during operation. In the last two years, UV-improved fibers with significantly reduced defects have been developed. This improvement is most pronounced at 248 and 193 nm, because at these critical wavelengths the induced losses are strongly influenced by the main broadband UV-defects with absorption maxima at 165 nm and 215 nm. We will summarize the results including the influence of the main parameters. In addition, the transmission capacity for the 308 nm wavelength is of interest due to medical and industrial applications. At this wavelength the influence of the nonlinearities is much lower; however, the induced losses in standard fibers are still an important factor. To show the advantages of the UV-improved fibers, the transmission characteristics at 308 nm wavelength will be described in more detail, for the first time

Structural and Psycho-Social Limits to Climate Change Adaptation in the Great Barrier Reef Region.

Science.gov (United States)

Evans, Louisa S; Hicks, Christina C; Adger, W Neil; Barnett, Jon; Perry, Allison L; Fidelman, Pedro; Tobin, Renae

2016-01-01

Adaptation, as a strategy to respond to climate change, has limits: there are conditions under which adaptation strategies fail to alleviate impacts from climate change. Research has primarily focused on identifying absolute bio-physical limits. This paper contributes empirical insight to an emerging literature on the social limits to adaptation. Such limits arise from the ways in which societies perceive, experience and respond to climate change. Using qualitative data from multi-stakeholder workshops and key-informant interviews with representatives of the fisheries and tourism sectors of the Great Barrier Reef region, we identify psycho-social and structural limits associated with key adaptation strategies, and examine how these are perceived as more or less absolute across levels of organisation. We find that actors experience social limits to adaptation when: i) the effort of pursuing a strategy exceeds the benefits of desired adaptation outcomes; ii) the particular strategy does not address the actual source of vulnerability, and; iii) the benefits derived from adaptation are undermined by external factors. We also find that social limits are not necessarily more absolute at higher levels of organisation: respondents perceived considerable opportunities to address some psycho-social limits at the national-international interface, while they considered some social limits at the local and regional levels to be effectively absolute.

Performance of intact and partially degraded concrete barriers in limiting mass transport

International Nuclear Information System (INIS)

Walton, J.C.

1992-06-01

Mass transport through concrete barriers and release rate from concrete vaults are quantitatively evaluated. The thorny issue of appropriate diffusion coefficients for use in performance assessment calculations is covered, with no ultimate solution found. Release from monolithic concrete vaults composed of concrete waste forms is estimated with a semi-analytical solution. A parametric study illustrates the importance of different parameters on release. A second situation of importance is the role of a concrete shell or vault placed around typical waste forms in limiting mass transport. In both situations, the primary factor controlling concrete performance is cracks. The implications of leaching behavior on likely groundwater concentrations is examined. Frequently, lower groundwater concentrations can be expected in the absence of engineered covers that reduce infiltration

Spin-dependent scattering by a potential barrier on a nanotube

International Nuclear Information System (INIS)

Abranyos, Yonatan; Gumbs, Godfrey; Fekete, Paula

2010-01-01

The electron spin effects on the surface of a nanotube have been considered through the spin-orbit interaction (SOI), arising from the electron confinement on the surface of the nanotube. This is of the same nature as the Rashba-Bychkov SOI at a semiconductor heterojunction. We estimate the effect of disorder within a potential barrier on the transmission probability. Using a continuum model, we obtain analytic expressions for the spin-split energy bands for electrons on the surface of nanotubes in the presence of SOI. First we calculate analytically the amplitudes of scattering from a potential barrier located around the axis of the nanotube into spin-dependent states. The effect of disorder on the scattering process is included phenomenologically and induces a reduction in the transition probability. We analyze the relative role of SOI and disorder in the transmission probability which depends on the angular and linear momentum of the incoming particle, and its spin orientation. Finally we demonstrate that in the presence of disorder, perfect transmission may not be achieved for finite barrier heights.

Barriers to uptake of prevention of mother-to-child transmission of HIV services among mothers of vertically infected HIV-seropositive infants in Makurdi, Nigeria

Directory of Open Access Journals (Sweden)

Anígilájé EA

2016-01-01

Full Text Available Emmanuel Ademola Anígilájé,1 Bem Ruben Ageda,2 Nnamdi Okechukwu Nweke1 1Department of Paediatrics, 2Department of Obstetrics and Gynaecology, Federal Medical Centre, Makurdi, Nigeria Background: Perinatal transmission of human immunodeficiency virus (HIV continues in Nigeria because of the poor use of prevention of mother-to-child transmission of HIV (PMTCT services. This study reports on the barriers preventing mothers of vertically infected HIV-seropositive infants to use the PMTCT services at the Federal Medical Centre, Makurdi, Nigeria.Methods: This is a descriptive study conducted between January and April, 2014. A quantitative survey was applied to detect barriers along the PMTCT services cascade among 52 mothers of vertically infected HIV-seropositive infants. This includes 22 women who attended antenatal care at the Federal Medical Centre (designated as Group A mothers and 30 women who did not receive any form of PMTCT service (Group B mothers. The study was supplemented with a focused group discussion involving 12 discussants from the two groups.Results: In the quantitative assessment: among the Group A mothers, falling asleep was the most common reason (n=22, 100% for missing therapeutic/prophylactic antiretroviral medicine; financial constraint (n=22, 100% was the most common reason for antenatal care visit defaults; and a lot of the mothers (n=11, 50.0% did not give nevirapine to their newborns because they delivered at home. Among Group B mothers, unawareness of HIV-seropositive status was the most common reason (n=28, 93.3% given for not accessing PMTCT services. In the qualitative study: noninvolvement of male partners, stigma and discrimination experienced by HIV-seropositive mothers, financial constraints in couples, involvement of traditional birth attendants in antenatal care and delivery of HIV-infected women, unawareness of HIV-seropositive status by pregnant women, poor health system, and the lack of funding for PMTCT

Extremal surface barriers

International Nuclear Information System (INIS)

Engelhardt, Netta; Wall, Aron C.

2014-01-01

We present a generic condition for Lorentzian manifolds to have a barrier that limits the reach of boundary-anchored extremal surfaces of arbitrary dimension. We show that any surface with nonpositive extrinsic curvature is a barrier, in the sense that extremal surfaces cannot be continuously deformed past it. Furthermore, the outermost barrier surface has nonnegative extrinsic curvature. Under certain conditions, we show that the existence of trapped surfaces implies a barrier, and conversely. In the context of AdS/CFT, these barriers imply that it is impossible to reconstruct the entire bulk using extremal surfaces. We comment on the implications for the firewall controversy

Structural and Psycho-Social Limits to Climate Change Adaptation in the Great Barrier Reef Region.

Directory of Open Access Journals (Sweden)

Louisa S Evans

Full Text Available Adaptation, as a strategy to respond to climate change, has limits: there are conditions under which adaptation strategies fail to alleviate impacts from climate change. Research has primarily focused on identifying absolute bio-physical limits. This paper contributes empirical insight to an emerging literature on the social limits to adaptation. Such limits arise from the ways in which societies perceive, experience and respond to climate change. Using qualitative data from multi-stakeholder workshops and key-informant interviews with representatives of the fisheries and tourism sectors of the Great Barrier Reef region, we identify psycho-social and structural limits associated with key adaptation strategies, and examine how these are perceived as more or less absolute across levels of organisation. We find that actors experience social limits to adaptation when: i the effort of pursuing a strategy exceeds the benefits of desired adaptation outcomes; ii the particular strategy does not address the actual source of vulnerability, and; iii the benefits derived from adaptation are undermined by external factors. We also find that social limits are not necessarily more absolute at higher levels of organisation: respondents perceived considerable opportunities to address some psycho-social limits at the national-international interface, while they considered some social limits at the local and regional levels to be effectively absolute.

Perceived Barriers to Adherence to Tuberculosis Infection Control Measures among Health Care Workers in the Dominican Republic.

Science.gov (United States)

Chapman, Helena J; Veras-Estévez, Bienvenido A; Pomeranz, Jamie L; Pérez-Then, Eddy N; Marcelino, Belkys; Lauzardo, Michael

2017-01-01

patients within hospitals; and 5) limited availability of protective masks for health care workers. CONCLUSIONS Our results highlight that perceived barriers at the individual or institutional level may hinder how health care workers understand and comply with preventive strategies to reduce risk of tuberculosis transmission. Addressing these barriers by strengthening infection control program infrastructure and implementing educational interventions within institutions may reduce risk of nosocomial tuberculosis transmission to health care workers. KEYWORDS Health care providers, infection control, infectious disease transmission, health care associated infection, nosocomial infection, Mycobacterium tuberculosis occupational exposure, occupational health, qualitative research, tuberculosis, Dominican Republic.

Barriers to clean development mechanism renewable energy projects in Mexico

International Nuclear Information System (INIS)

Lokey, Elizabeth

2009-01-01

Mexico is not reaching its full potential to capture benefits from clean development mechanism (CDM) projects because of its limited market for independent power producers (IPPs) and the barriers imposed on these entities by the state-run electric utility that controls most of the country's generation and transmission. This state-run entity has pursued CDM revenues only in isolated cases where international financial assistance was given because it is bound by law to pursue the least-cost generation option for its customers. Recent changes in Mexican legislation that provide incentives for renewable energy development could open the marketplace for these types of projects. (author)

Conductance and refraction across a Barrier in Phosphorene

Science.gov (United States)

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.

The blood-tendon barrier: identification and characterisation of a novel tissue barrier in tendon blood vessels

Directory of Open Access Journals (Sweden)

C Lehner

2016-05-01

Full Text Available Tissue barriers function as “gate keepers” between different compartments (usually blood and tissue and are formed by specialised membrane-associated proteins, localising to the apicolateral plasma membrane domain of epithelial and endothelial cells. By sealing the paracellular space, the free diffusion of solutes and molecules across epithelia and endothelia is impeded. Thereby, tissue barriers contribute to the establishment and maintenance of a distinct internal and external environment, which is crucial during organ development and allows maintenance of an organ-specific homeostatic milieu. So far, various epithelial and endothelial tissue barriers have been described, including the blood-brain barrier, the blood-retina barrier, the blood-testis barrier, the blood-placenta barrier, and the cerebrospinal fluid (CSF-brain barrier, which are vital for physiological function and any disturbance of these barriers can result in severe organ damage or even death. Here, we describe the identification of a novel barrier, located in the vascular bed of tendons, which we term the blood-tendon barrier (BTB. By using immunohistochemistry, transmission electron microscopy, and tracer studies we demonstrate the presence of a functional endothelial barrier within tendons restricting the passage of large blood-borne molecules into the surrounding tendon tissue. We further provide in vitro evidence that the BTB potentially contributes to the creation of a distinct internal tissue environment impacting upon the proliferation and differentiation of tendon-resident cells, effects which might be fundamental for the onset of tendon pathologies.

Protective barrier development: Overview

International Nuclear Information System (INIS)

Wing, N.R.; Gee, G.W.

1990-01-01

Protective barrier and warning marker systems are being developed to isolate wastes disposed of near the earth's surface at the Hanford Site. The barrier is designed to function in an arid to semiarid climate, to limit infiltration and percolation of water through the waste zone to near-zero, to be maintenance free, and to last up to 10,000 yr. Natural materials (e.g., fine soil, sand, gravel, riprap, clay, asphalt) have been selected to optimize barrier performance and longevity and to create an integrated structure with redundant features. These materials isolate wastes by limiting water drainage; reducing the likelihood of plant, animal, and human intrusion; controlling emission of noxious gases; and minimizing erosion. Westinghouse Hanford Company and Pacific Northwest Laboratory efforts to assess the performance of various barrier and marker designs will be discussed

Electron optics with magnetic vector potential barriers in graphene

International Nuclear Information System (INIS)

Ghosh, Sankalpa; Sharma, Manish

2009-01-01

An analysis of electron transport in graphene in the presence of various arrangements of delta-function like magnetic barriers is presented. The motion through one such barrier gives an unusual non-specular refraction leading to asymmetric transmission. The symmetry is restored by putting two such barriers in opposite directions side by side. Periodic arrangements of such barriers can be used as Bragg reflectors whose reflectivity has been calculated using a transfer matrix formalism. Such Bragg reflectors can be used to make resonant cavities. We also analyze the associated band structure for the case of infinite periodic structures. (fast track communication)

Force transmissibility versus displacement transmissibility

Science.gov (United States)

Lage, Y. E.; Neves, M. M.; Maia, N. M. M.; Tcherniak, D.

2014-10-01

It is well-known that when a single-degree-of-freedom (sdof) system is excited by a continuous motion of the foundation, the force transmissibility, relating the force transmitted to the foundation to the applied force, equals the displacement transmissibility. Recent developments in the generalization of the transmissibility to multiple-degree-of-freedom (mdof) systems have shown that similar simple and direct relations between both types of transmissibility do not appear naturally from the definitions, as happens in the sdof case. In this paper, the authors present their studies on the conditions under which it is possible to establish a relation between force transmissibility and displacement transmissibility for mdof systems. As far as the authors are aware, such a relation is not currently found in the literature, which is justified by being based on recent developments in the transmissibility concept for mdof systems. Indeed, it does not appear naturally, but the authors observed that the needed link is present when the displacement transmissibility is obtained between the same coordinates where the applied and reaction forces are considered in the force transmissibility case; this implies that the boundary conditions are not exactly the same and instead follow some rules. This work presents a formal derivation of the explicit relation between the force and displacement transmissibilities for mdof systems, and discusses its potential and limitations. The authors show that it is possible to obtain the displacement transmissibility from measured forces, and the force transmissibility from measured displacements, opening new perspectives, for example, in the identification of applied or transmitted forces. With this novel relation, it becomes possible, for example, to estimate the force transmissibility matrix with the structure off its supports, in free boundary conditions, and without measuring the forces. As far as force identification is concerned, this

Electronic transport for armchair graphene nanoribbons with a potential barrier

International Nuclear Information System (INIS)

Ben-Hu, Zhou; Ben-Liang, Zhou; Guang-Hui, Zhou; Zi-Gang, Duan

2010-01-01

This paper studies the electronic transport property through a square potential barrier in armchair-edge graphene nanoribbon (AGNR). Using the Dirac equation with the continuity condition for wave functions at the interfaces between regions with and without a barrier, we calculate the mode-dependent transmission probability for both semiconducting and metallic AGNRs, respectively. It is shown that, by some numerical examples, the transmission probability is generally an oscillating function of the height and range of the barrier for both types of AGNRs. The main difference between the two types of systems is that the magnitude of oscillation for the semiconducting AGNR is larger than that for the metallic one. This fact implies that the electronic transport property for AGNRs depends sensitively on their widths and edge details due to the Dirac nature of fermions in the system

A Lifetime Optimization Algorithm Limited by Data Transmission Delay and Hops for Mobile Sink-Based Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Yourong Chen

2017-01-01

Full Text Available To improve the lifetime of mobile sink-based wireless sensor networks and considering that data transmission delay and hops are limited in actual system, a lifetime optimization algorithm limited by data transmission delay and hops (LOA_DH for mobile sink-based wireless sensor networks is proposed. In LOA_DH, some constraints are analyzed, and an optimization model is proposed. Maximum capacity path routing algorithm is used to calculate the energy consumption of communication. Improved genetic algorithm which modifies individuals to meet all constraints is used to solve the optimization model. The optimal solution of sink node’s sojourn grid centers and sojourn times which maximizes network lifetime is obtained. Simulation results show that, in three node distribution scenes, LOA_DH can find the movement solution of sink node which covers all sensor nodes. Compared with MCP_RAND, MCP_GMRE, and EASR, the solution improves network lifetime and reduces average amount of node discarded data and average energy consumption of nodes.

Electron grafted barrier coatings for packaging film modification

International Nuclear Information System (INIS)

Rangwalla, I.J.; Nablo, S.V.

1993-01-01

The O 2 barrier performance of organosilane films, coated, dried and electron beam grafted to polyolefin film has been studied. Excellent anti-scalping properties based upon limonene (dipentene) transmission measurements have also been observed. Results are also reported on O 2 permeability reduction when the process is applied to common barrier polymers such as EVOH and acrylonitrile. Experience with its in-line application on LDPE is discussed. (author)

Trajectory-based understanding of the quantum-classical transition for barrier scattering

Science.gov (United States)

Chou, Chia-Chun

2018-06-01

The quantum-classical transition of wave packet barrier scattering is investigated using a hydrodynamic description in the framework of a nonlinear Schrödinger equation. The nonlinear equation provides a continuous description for the quantum-classical transition of physical systems by introducing a degree of quantumness. Based on the transition equation, the transition trajectory formalism is developed to establish the connection between classical and quantum trajectories. The quantum-classical transition is then analyzed for the scattering of a Gaussian wave packet from an Eckart barrier and the decay of a metastable state. Computational results for the evolution of the wave packet and the transmission probabilities indicate that classical results are recovered when the degree of quantumness tends to zero. Classical trajectories are in excellent agreement with the transition trajectories in the classical limit, except in some regions where transition trajectories cannot cross because of the single-valuedness of the transition wave function. As the computational results demonstrate, the process that the Planck constant tends to zero is equivalent to the gradual removal of quantum effects originating from the quantum potential. This study provides an insightful trajectory interpretation for the quantum-classical transition of wave packet barrier scattering.

Transmission Planning Process and Opportunities for Utility-Scale Solar Engagement within the Western Electricity Coordinating Council (WECC)

Energy Technology Data Exchange (ETDEWEB)

Hein, J.; Hurlbut, D.; Milligan, M.; Coles, L.; Green, B.

2011-11-01

This report is a primer for solar developers who wish to engage directly in expediting the regulatory process and removing market barriers related to policy and planning. Market barriers unrelated to technology often limit the expansion of utility-scale solar power, even in areas with exceptional resource potential. Many of these non-technical barriers have to do with policy, regulation, and planning, and hardly ever do they resolve themselves in a timely fashion. In most cases, pre-emptive intervention by interested stakeholders is the easiest way to remove/address such barriers, but it requires knowing how to navigate the institutional waters of the relevant agencies and boards. This report is a primer for solar developers who wish to engage directly in expediting the regulatory process and removing market barriers related to policy and planning. It focuses on the Western Interconnection (WI), primarily because the quality of solar resources in the Southwest makes utility-scale concentrating solar power (CSP) and photovoltaics (PV) economically feasible, and because the relevant institutions have evolved in a way that has opened up opportunities for removing non-technical market barriers. Developers will find in this report a high-level field manual to identify the venues for mitigating and possibly eliminating systemic market obstacles and ensuring that the economic playing field is reasonably level. Project-specific issues such as siting for transmission and generation resources are beyond the scope of this report. Instead, the aim is to examine issues that pervasively affect all utility-scale PV and CSP in the region regardless of where the project may be. While the focus is on the WI, many of the institutions described here also have their counterparts in the Eastern and the Texas interconnections. Specifically, this report suggests a number of critical engagement points relating to generation and transmission planning.

Methicillin Resistant Staphylococcus aureus Transmission in a Ghanaian Burn Unit: The Importance of Active Surveillance in Resource-Limited Settings

Directory of Open Access Journals (Sweden)

Nana Ama Amissah

2017-10-01

Full Text Available Objectives:Staphylococcus aureus infections in burn patients can lead to serious complications and death. The frequency of S. aureus infection is high in low- and middle-income countries presumably due to limited resources, misuse of antibiotics and poor infection control. The objective of the present study was to apply population genomics to precisely define, for the first time, the transmission of antibiotic resistant S. aureus in a resource-limited setting in sub-Saharan Africa.Methods:Staphylococcus aureus surveillance was performed amongst burn patients and healthcare workers during a 7-months survey within the burn unit of the Korle Bu Teaching Hospital in Ghana.Results: Sixty-six S. aureus isolates (59 colonizing and 7 clinical were obtained from 31 patients and 10 healthcare workers. Twenty-one of these isolates were ST250-IV methicillin-resistant S. aureus (MRSA. Notably, 25 (81% of the 31 patients carried or were infected with S. aureus within 24 h of admission. Genome comparisons revealed six distinct S. aureus clones circulating in the burn unit, and demonstrated multiple transmission events between patients and healthcare workers. Further, the collected S. aureus isolates exhibited a wide range of genotypic resistances to antibiotics, including trimethoprim (21%, aminoglycosides (33%, oxacillin (33%, chloramphenicol (50%, tetracycline (59% and fluoroquinolones (100%.Conclusion: Population genomics uncovered multiple transmission events of S. aureus, especially MRSA, within the investigated burn unit. Our findings highlight lapses in infection control and prevention, and underscore the great importance of active surveillance to protect burn victims against multi-drug resistant pathogens in resource-limited settings.

Methicillin Resistant Staphylococcus aureus Transmission in a Ghanaian Burn Unit: The Importance of Active Surveillance in Resource-Limited Settings.

Science.gov (United States)

Amissah, Nana Ama; Buultjens, Andrew H; Ablordey, Anthony; van Dam, Lieke; Opoku-Ware, Ampomah; Baines, Sarah L; Bulach, Dieter; Tetteh, Caitlin S; Prah, Isaac; van der Werf, Tjip S; Friedrich, Alexander W; Seemann, Torsten; van Dijl, Jan Maarten; Stienstra, Ymkje; Stinear, Timothy P; Rossen, John W

2017-01-01

Objectives: Staphylococcus aureus infections in burn patients can lead to serious complications and death. The frequency of S. aureus infection is high in low- and middle-income countries presumably due to limited resources, misuse of antibiotics and poor infection control. The objective of the present study was to apply population genomics to precisely define, for the first time, the transmission of antibiotic resistant S. aureus in a resource-limited setting in sub-Saharan Africa. Methods: Staphylococcus aureus surveillance was performed amongst burn patients and healthcare workers during a 7-months survey within the burn unit of the Korle Bu Teaching Hospital in Ghana. Results: Sixty-six S. aureus isolates (59 colonizing and 7 clinical) were obtained from 31 patients and 10 healthcare workers. Twenty-one of these isolates were ST250-IV methicillin-resistant S. aureus (MRSA). Notably, 25 (81%) of the 31 patients carried or were infected with S. aureus within 24 h of admission. Genome comparisons revealed six distinct S. aureus clones circulating in the burn unit, and demonstrated multiple transmission events between patients and healthcare workers. Further, the collected S. aureus isolates exhibited a wide range of genotypic resistances to antibiotics, including trimethoprim (21%), aminoglycosides (33%), oxacillin (33%), chloramphenicol (50%), tetracycline (59%) and fluoroquinolones (100%). Conclusion: Population genomics uncovered multiple transmission events of S. aureus , especially MRSA, within the investigated burn unit. Our findings highlight lapses in infection control and prevention, and underscore the great importance of active surveillance to protect burn victims against multi-drug resistant pathogens in resource-limited settings.

First experimental proof for aberration correction in XPEEM: Resolution, transmission enhancement, and limitation by space charge effects

International Nuclear Information System (INIS)

Schmidt, Th.; Sala, A.; Marchetto, H.; Umbach, E.; Freund, H.-J.

2013-01-01

The positive effect of double aberration correction in x-ray induced Photoelectron Emission Microscopy (XPEEM) has been successfully demonstrated for both, the lateral resolution and the transmission, using the Au 4f XPS peak for element specific imaging at a kinetic energy of 113 eV. The lateral resolution is improved by a factor of four, compared to a non-corrected system, whereas the transmission is enhanced by a factor of 5 at a moderate resolution of 80 nm. With an optimized system setting, a lateral resolution of 18 nm could be achieved, which is up to now the best value reported for energy filtered XPEEM imaging. However, the absolute resolution does not yet reach the theoretical limit of 2 nm, which is due to space charge limitation. This occurs along the entire optical axis up to the contrast aperture. In XPEEM the pulsed time structure of the exciting soft x-ray light source causes a short and highly intense electron pulse, which results in an image blurring. In contrast, the imaging with elastically reflected electrons in the low energy electron microscopy (LEEM) mode yields a resolution clearly below 5 nm. Technical solutions to reduce the space charge effect in an aberration-corrected spectro-microscope are discussed. - Highlights: ► First successful double aberration correction in XPEEM. ► Improvement of resolution and transmission by aberration correction. ► Lateral resolution of 18 nm in energy filtered XPEEM is the best up to now reported value. ► First investigation of space charge effects in aberrations corrected PEEM

Renewable Energy Zone (REZ) Transmission Planning Process: A Guidebook for Practitioners

Energy Technology Data Exchange (ETDEWEB)

Lee, Nathan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Flores-Espino, Francisco [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hurlbut, David J. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-09-05

Achieving clean energy goals may require new investments in transmission, especially if planners anticipate economic growth and increased demand for electricity. The renewable energy zone (REZ) transmission planning process can help policymakers ensure their infrastructure investments achieve national goals in the most economical manner. Policymakers, planners, and system operators around the world have used variations of the REZ process to chart the expansion of their transmission networks and overcome the barriers of traditional transmission planning. This guidebook seeks to help power system planners, key decision makers, and stakeholders understand and use the REZ transmission planning process to integrate transmission expansion planning and renewable energy generation planning.

Social and behavioral barriers to pathogen transmission in wild animal populations

Energy Technology Data Exchange (ETDEWEB)

Loehle, C.S.

1988-12-31

Disease and pathogens have been studied as regulators of animal populations but not really as selective forces. The authors propose that pathogens can be major selective forces influencing social behaviors when these are successful at reducing disease transmission. The behaviors whose evolution could have been influenced by pathogen effects include group size, group isolation, mixed species flocking, migration, seasonal sociality, social avoidance, and dominance behaviors. Mate choice, mating system, and sexual selection are put in a new light when examined in terms of disease transmission. It is concluded that pathogen avoidance is a more powerful selective force than has heretofore been recognized.

Spin-polarizated transmissivity in an asymmetrical double barrier

International Nuclear Information System (INIS)

Teixeira, J D S; Frota, H O; Bittencourt, A C R

2014-01-01

The spin-polarized electron resonant tunnelling at zero magnetic field through a double barrier heterostructure like InAs/GaSb/InAs/GaSb/InAs has been calculated as a function of the electron energy. A model is proposed to study the combined effects of Dresselhaus and in-plane Rashba spin-orbit interactions on the spin-dependent tunnelling, taking into account the k 3 dependence of the Dresselhaus Hamiltonian. For the directions ϕ=45 ∘ and 135 ∘ the spin mixing produces a 100% efficiency of polarization. Moreover, the effect of the Dresselhaus and Rashba spin-orbit interactions are shown to be quite favorable for the fabrication of spin filters and spintronic devices. (paper)

Development and psychometric testing of a barriers to HIV testing scale among individuals with HIV infection in Sweden; The Barriers to HIV testing scale-Karolinska version.

Science.gov (United States)

Wiklander, Maria; Brännström, Johanna; Svedhem, Veronica; Eriksson, Lars E

2015-11-19

Barriers to HIV testing experienced by individuals at risk for HIV can result in treatment delay and further transmission of the disease. Instruments to systematically measure barriers are scarce, but could contribute to improved strategies for HIV testing. Aims of this study were to develop and test a barriers to HIV testing scale in a Swedish context. An 18-item scale was developed, based on an existing scale with addition of six new items related to fear of the disease or negative consequences of being diagnosed as HIV-infected. Items were phrased as statements about potential barriers with a three-point response format representing not important, somewhat important, and very important. The scale was evaluated regarding missing values, floor and ceiling effects, exploratory factor analysis, and internal consistencies. The questionnaire was completed by 292 adults recently diagnosed with HIV infection, of whom 7 were excluded (≥9 items missing) and 285 were included (≥12 items completed) in the analyses. The participants were 18-70 years old (mean 40.5, SD 11.5), 39 % were females and 77 % born outside Sweden. Routes of transmission were heterosexual transmission 63 %, male to male sex 20 %, intravenous drug use 5 %, blood product/transfusion 2 %, and unknown 9 %. All scale items had <3 % missing values. The data was feasible for factor analysis (KMO = 0.92) and a four-factor solution was chosen, based on level of explained common variance (58.64 %) and interpretability of factor structure. The factors were interpreted as; personal consequences, structural barriers, social and economic security, and confidentiality. Ratings on the minimum level (suggested barrier not important) were common, resulting in substantial floor effects on the scales. The scales were internally consistent (Cronbach's α 0.78-0.91). This study gives preliminary evidence of the scale being feasible, reliable and valid to identify different types of barriers to HIV testing.

Graphene Oxide Bionanocomposite Coatings with High Oxygen Barrier Properties

Directory of Open Access Journals (Sweden)

Ilke Uysal Unalan

2016-12-01

Full Text Available In this work, we present the development of bionanocomposite coatings on poly(ethylene terephthalate (PET with outstanding oxygen barrier properties. Pullulan and graphene oxide (GO were used as main polymer phase and nanobuilding block (NBB, respectively. The oxygen barrier performance was investigated at different filler volume fractions (ϕ and as a function of different relative humidity (RH values. Noticeably, the impermeable nature of GO was reflected under dry conditions, in which an oxygen transmission rate (OTR, mL·m−2·24 h−1 value below the detection limit of the instrument (0.01 mL·m−2·24 h−1 was recorded, even for ϕ as low as 0.0004. A dramatic increase of the OTR values occurred in humid conditions, such that the barrier performance was totally lost at 90% RH (the OTR of coated PET films was equal to the OTR of bare PET films. Modelling of the experimental OTR data by Cussler’s model suggested that the spatial ordering of GO sheets within the main pullulan phase was perturbed because of RH fluctuations. In spite of the presence of the filler, all the formulations allowed the obtainment of final materials with haze values below 3%, the only exception being the formulation with the highest loading of GO (ϕ ≈ 0.03. The mechanisms underlying the experimental observations are discussed.

Design of patient-specific focused ultrasound arrays for non-invasive brain therapy with increased trans-skull transmission and steering range

Science.gov (United States)

Hughes, Alec; Hynynen, Kullervo

2017-09-01

The use of a phased array of ultrasound transducer elements to sonicate through the skull has opened the way for new treatments and the delivery of therapeutics beyond the blood-brain barrier. The limited steering range of current clinical devices, particularly at higher frequencies, limits the regions of the brain that are considered treatable by ultrasound. A new array design is introduced that allows for high levels of beam steering and increased transmission throughout the brain. These improvements are achieved using concave transducers normal to the outer-skull surface in a patient-specific configuration to target within the skull, so that the far-field of each beam is within the brain. It is shown that by using pulsed ultrasound waves timed to arrive in-phase at the desired target, sufficient levels of acoustic energy are delivered for blood-brain barrier opening throughout the brain.

Direct access tariffs and barriers to choice

International Nuclear Information System (INIS)

Levson, D.

1999-01-01

The current situation of the power market in Alberta was reviewed. Based on this review is was concluded that the province is a long way from being a competitive, liquid power market. Further, it was predicted that unless large power purchasers get actively involved in managing their options, identify realistic and competitive supply options and actively campaign for the removal of barriers to choice, they will experience significant cost increases in the year 2001 and beyond, due in large measure to the market power exercised by the four major utilities (TAU, EPCOR, APL and Powerex). Barriers to new supply such as the high cost of standby, uncertainties about transmission and natural gas prices, the delays to cogeneration caused by low oil prices, and the design of direct access tariffs by utilities, were also explored. The cumulative contribution of these factors to uncertainties in pool price, fixed price and transmission and distribution costs were outlined

Potential for Zika virus introduction and transmission in resource limited countries in Africa and Asia-Pacific: A modeling study

Science.gov (United States)

German, Matthew; Creatore, Maria I.; Brent, Shannon; Watts, Alexander G.; Hay, Simon I.; Kulkarni, Manisha A.; Brownstein, John S.; Khan, Kamran

2016-01-01

Summary Background As the epidemic of Zika virus expands in the Americas, countries across Africa and the Asia-Pacific region are becoming increasingly susceptible to the importation and possible local spread of the virus. To support public health readiness, we aim to identify regions and times where the potential health, economic, and social effects from Zika virus are greatest, focusing on resource-limited countries in Africa and the Asia-Pacific region. Methods Our model combined transportation network analysis, ecological modelling of mosquito occurrences, and vector competence for flavivirus transmission, using data from the International Air Transport Association, entomological observations from Zika’s primary vector species, and climate conditions using WorldClim. We overlaid monthly flows of airline travellers arriving to Africa and the Asia-Pacific region from areas of the Americas suitable for year-round transmission of Zika virus with monthly maps of climatic suitability for mosquito-borne transmission of Zika virus within Africa and the Asia-Pacific region. Findings An estimated 2·6 billion people live in areas of Africa and the Asia-Pacific region where the presence of competent mosquito vectors and suitable climatic conditions could support local transmission of Zika virus. Countries with large volumes of travellers arriving from Zika affected areas of the Americas and large populations at risk of mosquito-borne Zika virus infection include, India (67 422 travellers arriving per year; 1·2 billion residents in potential Zika transmission areas), China (238 415 travellers; 242 million residents), Indonesia (13 865 travellers; 197 million residents), Philippines (35 635 travellers; 70 million residents), and Thailand (29 241 travellers; 59 million residents). Interpretation Many countries across Africa and the Asia-Pacific region are vulnerable to Zika virus. Strategic use of available health and human resources is essential to prevent or mitigate

Current transmission and nonlinear effects in un-gated thermionic cathode RF guns

Energy Technology Data Exchange (ETDEWEB)

Edelen, J. P. [Fermilab; Harris, J. R. [Air Force Weapons Lab

2017-05-03

Un-gated thermionic cathode RF guns are well known as a robust source of electrons for many accelerator applications. These sources are in principle scalable to high currents without degradation of the transverse emittance due to control grids but they are also known for being limited by back-bombardment. While back-bombardment presents a significant limitation, there is still a lack of general understanding on how emission over the whole RF period will affect the nature of the beams produced from these guns. In order to improve our understanding of how these guns can be used in general we develop analytical models that predict the transmission efficiency as a function of the design parameters, study how bunch compression and emission enhancement caused by Schottky barrier lowering affect the output current profile in the gun, and study the onset of space-charge limited effects and the resultant virtual cathode formation leading to a modulation in the output current distribution.

Dissipation, fluctuations and the fusion of heavy ions near the Coulomb barrier

Energy Technology Data Exchange (ETDEWEB)

Canto, L F

1989-01-09

We study the role of internal degrees of freedom in the transmission of a classical particle over a potential barrier. The internal degrees of freedom are represented by harmonic oscillators and a linear approximation is adopted for the coupling. The frequency spectrum of the oscillators and the coupling strength are assumed to be such as to give rise to a weak friction in the particle coordinate. We show that the interaction with the oscillators leads to an effective increase epsilon/sub 0/ in the height of the potential barrier and to an energy-spread sigma in the transmission factor. We show also that epsilon/sub 0/ and sigma satisfy a dissipation-fluctuation relation. The theory is applied to the fusion of heavy ions at energies near the Coulomb barrier and the results are shown to be in agreement with the data.

Aluminum oxide barrier coating on polyethersulfone substrate by atomic layer deposition for barrier property enhancement

International Nuclear Information System (INIS)

Kim, Hyun Gi; Kim, Sung Soo

2011-01-01

Aluminum oxide layers were deposited on flexible polyethersulfone (PES) substrates via plasma enhanced atomic layer deposition (PEALD) process using trimethylaluminum (TMA) and oxygen as precursor and reactant materials. Several process parameters in PEALD process were investigated in terms of refractive index and layer thickness. Number of process cycle increased the thickness and refractive index of the layer to enhance the barrier properties. Non-physisorbed TMA and unreacted oxygen were purged before and after the plasma reaction, respectively. Identical purge time was applied to TMA and oxygen and it was optimized for 10 s. Thinner and denser layer was formed as substrate temperature increased. However, the PES substrate could be deformed above 120 o C. Aluminum oxide layer formed on PES at optimized conditions have 11.8 nm of thickness and reduced water vapor transmission rate and oxygen transmission rate to below 4 x 10 -3 g/m 2 day and 4 x 10 -3 cm 3 /m 2 day, respectively. Polycarbonate and polyethylene naphthalate films were also tested at optimized conditions, and they also showed quite appreciable barrier properties to be used as plastic substrates.

Magneto-transport in CdTe/CdMnTe dilute magnetic semiconductor single barrier structures

International Nuclear Information System (INIS)

Lyons, V.R.

1999-03-01

shown to produce either an enhancement or suppression of the barrier dominated current, dependent on the field orientation and the level of transmission. Current enhancement is seen when the transmission through the barrier is low, i.e. at low fields and voltages. Whereas suppression is seen in the high transmission barrier current and in the leak dominated conduction. Comparisons of the experimental and calculated results suggest that the low voltage current through the barrier is dominated by emission from three dimensional states in the CdTe layers. (author)

Performance of intact and partially degraded concrete barriers in limiting fluid flow

International Nuclear Information System (INIS)

Walton, J.C.; Seitz, R.R.

1991-07-01

Concrete barriers will play a critical role in the long-term isolation of low-level radioactive wastes. Over time the barriers will degrade, and in many cases, the fundamental processes controlling performance of the barriers will be different for intact and degraded conditions. This document examines factors controlling fluid flow through intact and degraded concrete disposal facilities. Simplified models are presented fro predicting build up of fluid above a vault; fluid flow through and around intact vaults, through flaws in coatings/liners applied to a vault, and through cracks in a concrete vault; and the influence of different backfill materials around the outside of the vault. Example calculations are presented to illustrate the parameters and processes that influence fluid flow. 46 refs., 49 figs., 2 tabs

The quantum limit for information transmission

International Nuclear Information System (INIS)

Schiffer, M.

1990-01-01

We give two independent and rigorous derivations for the quantum bound on the information transmission rate as proposed independently Bekenstein and Bremermann, preceded by a heuristic argument showing why such a sort of bound should hold. In both approaches, information carriers are quanta of some field. The first method resembles the microcanonical approach to Statistical Mechanics where the strategy of overestimating the real number of states by relaxing the indistinguishability of quanta was adopted. The second is entirely based upon max-entropy methods. Amazingly enough, the results obtained by these physically unrelated premises turn out to be identical, namely, that the single (noiseless) channel capacity is I sub(max) E/2πh bits s sup(-1). It is further shown that, in a finite time τ no information can ever be conveyed unless the energy threshold 2 πh/τ is reached. (author)

Design of engineered sorbent barriers

International Nuclear Information System (INIS)

Jones, E.O.; Freeman, H.D.

1988-01-01

A sorbent barrier uses sorbent material such as activated carbon or natural zeolites to prevent the migration of radionuclides from a low-level waste site to the aquifer. The sorbent barrier retards the movement of radioactive contaminants, thereby providing time for the radionuclides to decay. Sorbent barriers can be a simple, effective, and inexpensive method for reducing the migration of radionuclides to the environment. Designing a sorbent barrier consists of using soil and sorbent material properties and site conditions as input to a model which will determine the necessary sorbent barrier thickness to meet contaminant limits. The paper covers the following areas: techniques for measuring sorption properties of barrier materials and underlying soils, use of a radionuclide transport model to determine the required barrier thickness and performance under a variety of site conditions, and cost estimates for applying the barrier

The effect of magnetic field on chiral transmission in p-n-p graphene junctions

Science.gov (United States)

Li, Yuan; Wan, Qi; Peng, Yingzi; Wang, Guanqing; Qian, Zhenghong; Zhou, Guanghui; Jalil, Mansoor B. A.

2015-12-01

We investigate Klein tunneling in graphene heterojunctions under the influence of a perpendicular magnetic field via the non-equilibrium Green’s function method. We find that the angular dependence of electron transmission is deflected sideways, resulting in the suppression of normally incident electrons and overall decrease in conductance. The off-normal symmetry axis of the transmission profile was analytically derived. Overall tunneling conductance decreases to almost zero regardless of the potential barrier height when the magnetic field (B-field) exceeds a critical value, thus achieving effective confinement of Dirac fermions. The critical field occurs when the width of the magnetic field region matches the diameter of the cyclotron orbit. The potential barrier also induces distinct Fabry-Pérot fringe patterns, with a “constriction region” of low transmission when is close to the Fermi energy. Application of B-field deflects the Fabry-Pérot interference pattern to an off-normal angle. Thus, the conductance of the graphene heterojunctions can be sharply modulated by adjusting the B-field strength and the potential barrier height relative to the Fermi energy.

The effect of magnetic field on chiral transmission in p-n-p graphene junctions.

Science.gov (United States)

Li, Yuan; Wan, Qi; Peng, Yingzi; Wang, Guanqing; Qian, Zhenghong; Zhou, Guanghui; Jalil, Mansoor B A

2015-12-18

We investigate Klein tunneling in graphene heterojunctions under the influence of a perpendicular magnetic field via the non-equilibrium Green's function method. We find that the angular dependence of electron transmission is deflected sideways, resulting in the suppression of normally incident electrons and overall decrease in conductance. The off-normal symmetry axis of the transmission profile was analytically derived. Overall tunneling conductance decreases to almost zero regardless of the potential barrier height V0 when the magnetic field (B-field) exceeds a critical value, thus achieving effective confinement of Dirac fermions. The critical field occurs when the width of the magnetic field region matches the diameter of the cyclotron orbit. The potential barrier also induces distinct Fabry-Pérot fringe patterns, with a "constriction region" of low transmission when V0 is close to the Fermi energy. Application of B-field deflects the Fabry-Pérot interference pattern to an off-normal angle. Thus, the conductance of the graphene heterojunctions can be sharply modulated by adjusting the B-field strength and the potential barrier height relative to the Fermi energy.

Linear versus non-linear structural information limit in high-resolution transmission electron microscopy

International Nuclear Information System (INIS)

Van Aert, S.; Chen, J.H.; Van Dyck, D.

2010-01-01

A widely used performance criterion in high-resolution transmission electron microscopy (HRTEM) is the information limit. It corresponds to the inverse of the maximum spatial object frequency that is linearly transmitted with sufficient intensity from the exit plane of the object to the image plane and is limited due to partial temporal coherence. In practice, the information limit is often measured from a diffractogram or from Young's fringes assuming a weak phase object scattering beyond the inverse of the information limit. However, for an aberration corrected electron microscope, with an information limit in the sub-angstrom range, weak phase objects are no longer applicable since they do not scatter sufficiently in this range. Therefore, one relies on more strongly scattering objects such as crystals of heavy atoms observed along a low index zone axis. In that case, dynamical scattering becomes important such that the non-linear and linear interaction may be equally important. The non-linear interaction may then set the experimental cut-off frequency observed in a diffractogram. The goal of this paper is to quantify both the linear and the non-linear information transfer in terms of closed form analytical expressions. Whereas the cut-off frequency set by the linear transfer can be directly related with the attainable resolution, information from the non-linear transfer can only be extracted using quantitative, model-based methods. In contrast to the historic definition of the information limit depending on microscope parameters only, the expressions derived in this paper explicitly incorporate their dependence on the structure parameters as well. In order to emphasize this dependence and to distinguish from the usual information limit, the expressions derived for the inverse cut-off frequencies will be referred to as the linear and non-linear structural information limit. The present findings confirm the well-known result that partial temporal coherence has

Alternative approaches to transmission investment

Energy Technology Data Exchange (ETDEWEB)

Thon, S. [AltaLink Management Ltd., Calgary, AB (Canada)

2004-07-01

AltaLink is Canada's first stand-alone power transmission company, serving all major centres in Alberta and 85 per cent of Alberta's population. It has more than $1 billion in assets, 11,500 km of transmission lines and 300 substations. It was noted that there has not been any significant investment in power transmission in Alberta for the past 20 years, partly because transmission assets have a very long lifespan. The new role of the power grid is to ensure reliability, safety, efficiency, market effectiveness and supply diversity. The benefits and costs of AltaLink's 500 kV North-South upgrade project were outlined. It was noted that a healthy transmission system is the basis for economic growth throughout the province and for the development of Alberta's resource base. The transmission policy in Alberta endorses that all consumers pay postage stamp tariffs. It also promotes a proactive plan for transmission projects, the time to maximum rate (TMR) in limited cases only, a congestion-free grid under normal conditions, the financial commitment of generators, specific time limits on permitting processes, and regional interconnections to benefit all customers. tabs., figs.

Design of engineered sorbent barriers

International Nuclear Information System (INIS)

Jones, E.O.; Freeman, H.D.

1988-08-01

A sorbent barrier uses sorbent material such as activated carbon or natural zeolites to prevent the migration of radionuclides from a low-level waste site to the aquifer. The sorbent barrier retards the movement of radioactive contaminants, thereby providing time for the radionuclides to decay. Sorbent barriers can be a simple, effective, and inexpensive method for reducing the migration of radionuclides to the environment. Designing a sorbent barrier consists of using soil and sorbent material properties and site conditions as input to a model which will determine the necessary sorbent barrier thickness to meet contaminant limits. The paper will cover the following areas: techniques for measuring sorption properties of barrier materials and underlying soils, use of a radionuclide transport model to determine the required barrier thickness and performance under a variety of site conditions, and cost estimates for applying the barrier. 8 refs., 6 figs., 1 tab

Omnidirectional ventilated acoustic barrier

Science.gov (United States)

Zhang, Hai-long; Zhu, Yi-fan; Liang, Bin; Yang, Jing; Yang, Jun; Cheng, Jian-chun

2017-11-01

As an important problem in acoustics, sound insulation finds applications in a great variety of situations. In the existing schemes, however, there has always been a trade-off between the thinness of sound-insulating devices and their ventilating capabilities, limiting their potentials in the control of low-frequency sound in high ventilation environments. Here, we design and experimentally implement an omnidirectional acoustic barrier with a planar profile, subwavelength thickness ( 0.18 λ ), yet high ventilation. The proposed mechanism is based on the interference between the resonant scattering of discrete states and the background scattering of continuous states which induces a Fano-like asymmetric transmission profile. Benefitting from the binary-structured design of the coiled unit and hollow pipe, it maximally simplifies the design and fabrication while ensuring the ventilation for all the non-resonant units with open tubes. The simulated and measured results agree well, showing the effectiveness of our proposed mechanism to block low frequency sound coming from various directions while allowing 63% of the air flow to pass. We anticipate our design to open routes to design sound insulators and to enable applications in traditionally unattainable cases such as those calling for noise reduction and cooling simultaneously.

Self-regulation of turbulence bursts and transport barriers

International Nuclear Information System (INIS)

Floriani, E; Ciraolo, G; Ghendrih, Ph; Sarazin, Y; Lima, R

2013-01-01

The interplay between turbulent bursts and transport barriers is analyzed with a simplified model of interchange turbulence in magnetically confined plasmas. The turbulent bursts spread into the transport barriers and, depending on the competing magnitude of the burst and stopping capability of the barrier, can burn through. Simulations of two models of transport barriers are presented: a hard barrier where interchange turbulence modes are stable in a prescribed region and a soft barrier with external plasma biasing. The response of the transport barriers to the non-linear perturbations of the turbulent bursts, addressed in a predator–prey approach, indicates that the barriers monitor an amplification factor of the turbulent bursts, with amplification smaller than one for most bursts and, in some cases, amplification factors that can significantly exceed unity. The weak barriers in corrugated profiles and magnetic structures, as well as the standard barriers, are characterized by these transmission properties, which then regulate the turbulent burst transport properties. The interplays of barriers and turbulent bursts are modeled as competing stochastic processes. For different classes of the probability density function (PDF) of these processes, one can predict the heavy tail properties of the bursts downstream from the barrier, either exponential for a leaky barrier, or with power laws for a tight barrier. The intrinsic probing of the transport barriers by the turbulent bursts thus gives access to the properties of the barriers. The main stochastic variables are the barrier width and the spreading distance of the turbulent bursts within the barrier, together with their level of correlation. One finds that in the case of a barrier with volumetric losses, such as radiation or particle losses as addressed in our present simulations, the stochastic model predicts a leaky behavior with an exponential PDF of escaping turbulent bursts in agreement with the simulation

Devices for overcoming biological barriers: the use of physical forces to disrupt the barriers.

Science.gov (United States)

Mitragotri, Samir

2013-01-01

Overcoming biological barriers including skin, mucosal membranes, blood brain barrier as well as cell and nuclear membrane constitutes a key hurdle in the field of drug delivery. While these barriers serve the natural protective function in the body, they limit delivery of drugs into the body. A variety of methods have been developed to overcome these barriers including formulations, targeting peptides and device-based technologies. This review focuses on the use of physical methods including acoustic devices, electric devices, high-pressure devices, microneedles and optical devices for disrupting various barriers in the body including skin and other membranes. A summary of the working principles of these devices and their ability to enhance drug delivery is presented. Copyright © 2012. Published by Elsevier B.V.

Markers for blood-brain barrier integrity

DEFF Research Database (Denmark)

Saunders, Norman R; Dziegielewska, Katarzyna M; Møllgård, Kjeld

2015-01-01

In recent years there has been a resurgence of interest in brain barriers and various roles their intrinsic mechanisms may play in neurological disorders. Such studies require suitable models and markers to demonstrate integrity and functional changes at the interfaces between blood, brain......, and cerebrospinal fluid. Studies of brain barrier mechanisms and measurements of plasma volume using dyes have a long-standing history, dating back to the late nineteenth-century. Their use in blood-brain barrier studies continues in spite of their known serious limitations in in vivo applications. These were well...... known when first introduced, but seem to have been forgotten since. Understanding these limitations is important because Evans blue is still the most commonly used marker of brain barrier integrity and those using it seem oblivious to problems arising from its in vivo application. The introduction...

Optimizing real power loss and voltage stability limit of a large transmission network using firefly algorithm

Directory of Open Access Journals (Sweden)

P. Balachennaiah

2016-06-01

Full Text Available This paper proposes a Firefly algorithm based technique to optimize the control variables for simultaneous optimization of real power loss and voltage stability limit of the transmission system. Mathematically, this issue can be formulated as nonlinear equality and inequality constrained optimization problem with an objective function integrating both real power loss and voltage stability limit. Transformers taps, unified power flow controller and its parameters have been included as control variables in the problem formulation. The effectiveness of the proposed algorithm has been tested on New England 39-bus system. Simulation results obtained with the proposed algorithm are compared with the real coded genetic algorithm for single objective of real power loss minimization and multi-objective of real power loss minimization and voltage stability limit maximization. Also, a classical optimization method known as interior point successive linear programming technique is considered here to compare the results of firefly algorithm for single objective of real power loss minimization. Simulation results confirm the potentiality of the proposed algorithm in solving optimization problems.

Market and Policy Barriers to Energy Storage Deployment

Energy Technology Data Exchange (ETDEWEB)

Bhatnagar, Dhruv [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Currier, Aileen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hernandez, Jacquelynne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ma, Ookie [Dept. of Energy (DOE), Washington DC (United States) Office of Energy Efficiency and Renewable Energy; Kirby, Brendan [Consultant

2013-09-01

Electric energy storage technologies can provide numerous grid services; there are a number of factors that restrict their current deployment. The most significant barrier to deployment is high capital costs, though several recent deployments indicate that capital costs are decreasing and energy storage may be the preferred economic alternative in certain situations. However, a number of other market and regulatory barriers persist, limiting further deployment. These barriers can be categorized into regulatory barriers, market (economic) barriers, utility and developer business model barriers, cross-cutting barriers and technology barriers.

Self-limiting current for magnetically insulated coaxial vacuum transmission lines

International Nuclear Information System (INIS)

Bergeron, K.D.

1976-11-01

Existing cold fluid theories for magnetic insulation are analyzed and applied to the transmission line configuration. The relevance of these results to the propagating short pulse problem, and to DC operation, are discussed

Elastically frustrated rehybridization: Origin of chemical order and compositional limits in InGaN quantum wells

Science.gov (United States)

Lymperakis, L.; Schulz, T.; Freysoldt, C.; Anikeeva, M.; Chen, Z.; Zheng, X.; Shen, B.; Chèze, C.; Siekacz, M.; Wang, X. Q.; Albrecht, M.; Neugebauer, J.

2018-01-01

Nominal InN monolayers grown by molecular beam epitaxy on GaN(0001) are investigated combining in situ reflection high-energy electron diffraction (RHEED), transmission electron microscopy (TEM), and density functional theory (DFT). TEM reveals a chemical intraplane ordering never observed before. Employing DFT, we identify a novel surface stabilization mechanism elastically frustrated rehybridization, which is responsible for the observed chemical ordering. The mechanism also sets an incorporation barrier for indium concentrations above 25% and thus fundamentally limits the indium content in coherently strained layers.

Barriers to initiating antiretroviral therapy during pregnancy: a ...

African Journals Online (AJOL)

In this qualitative study, 28 HIV-positive pregnant or postpartum women, who either had initiated ART or were eligible for ART, and 21 service providers were interviewed in Cape Town, South Africa, to investigate these barriers. Prevention of vertical transmission of HIV was often the primary motivation for starting treatment.

Wave attenuation over the Great Barrier Reef matrix

NARCIS (Netherlands)

Gallop, S.; Young, I.; Ranasinghe, Ranasinghe W M R J B; Durrant, T.; Haigh, I.; Mynett, Arthur

2015-01-01

This is the first large-scale study of the influence of an offshore reef matrix on wave transmission. The focus was on the Great Barrier Reef (GBR), Australia, utilizing a 16 yr-record of wave height, from seven satellite altimeters. Within the GBR matrix, wave height is not strongly dependent on

Use of electric and bubble barriers to limit the movement of Eurasian ruffe (Gymnocephalus cernuus)

Science.gov (United States)

Dawson, Heather A.; Reinhardt, Ulrich G.; Savino, Jacqueline F.

2006-01-01

Eurasian ruffe (Gymnocephalus cernuus) is an aquatic invasive species accidentally introduced via ballast water to the Great Lakes in the mid-1980s. Fish barrier technology is being studied to stop the spread of invasive fish species such as ruffe. Electrical barriers have been constructed, most notably in the Chicago Sanitary and Ship Canal, to prevent non-indigenous species such as ruffe from spreading into areas where they are currently absent. Information on the response of an invasive fish to barriers can help managers determine strategies to prevent the spread of these species via artificial waterways. In this laboratory study electrical barriers were set up to determine effectiveness of four electrical settings for repelling Eurasian ruffe measuring 10 cm or more in length. In separate tests, airbubble curtains with two bubble sizes and densities were created to test this type of barrier in blocking movement of ruffe less than 10 cm in length. The most effective electrical settings found (5 ms, 6 Hz) repelled only about half of the attempted passes. When ruffe were offered food or shelter on the opposite side of the electrical barrier, neither food-starved nor shelter-deprived ruffe made significantly more attempts to cross the barrier. Ruffe were significantly repelled by all air-bubble curtains, but a large proportion of passes (4.5 passes per fish on average in the treatments) were still observed. Electrical barrier settings and air-bubble curtains used in this study were found ineffective at completely blocking the movement, but somewhat effective at inhibiting the passage of ruffe.

The Achilles’ heel of prevention to mother-to-child transmission of HIV: Protocol implementation, uptake, and sustainability

Science.gov (United States)

Rodriguez, Violeta J.; LaCabe, Richard P.; Privette, C. Kyle; Douglass, K. Marie; Peltzer, Karl; Matseke, Gladys; Mathebula, Audrey; Ramlagan, Shandir; Sifunda, Sibusiso; Prado, Guillermo “Willy”; Horigian, Viviana; Weiss, Stephen M.; Jones, Deborah L.

2017-01-01

Abstract The Joint United Nations Programme on HIV and AIDS proposed to reduce the vertical transmission of HIV from ∼72,200 to ∼8300 newly infected children by 2015 in South Africa (SA). However, cultural, infrastructural, and socio-economic barriers hinder the implementation of the prevention of mother-to-child transmission (PMTCT) protocol, and research on potential solutions to address these barriers in rural areas is particularly limited. This study sought to identify challenges and solutions to the implementation, uptake, and sustainability of the PMTCT protocol in rural SA. Forty-eight qualitative interviews, 12 focus groups discussions (n = 75), and one two-day workshop (n = 32 participants) were conducted with district directors, clinic leaders, staff, and patients from 12 rural clinics. The delivery and uptake of the PMTCT protocol was evaluated using the Consolidated Framework for Implementation Research (CFIR); 15 themes associated with challenges and solutions emerged. Intervention characteristics themes included PMTCT training and HIV serostatus disclosure. Outer-setting themes included facility space, health record management, and staff shortage; inner-setting themes included supply use and availability, staff–patient relationship, and transportation and scheduling. Themes related to characteristics of individuals included staff relationships, initial antenatal care visit, adherence, and culture and stigma. Implementation process themes included patient education, test results delivery, and male involvement. Significant gaps in care were identified in rural areas. Information obtained from participants using the CFIR framework provided valuable insights into solutions to barriers to PMTCT implementation. Continuously assessing and correcting PMTCT protocol implementation, uptake and sustainability appear merited to maximize HIV prevention. PMID:28922974

The Achilles' heel of prevention to mother-to-child transmission of HIV: Protocol implementation, uptake, and sustainability.

Science.gov (United States)

Rodriguez, Violeta J; LaCabe, Richard P; Privette, C Kyle; Douglass, K Marie; Peltzer, Karl; Matseke, Gladys; Mathebula, Audrey; Ramlagan, Shandir; Sifunda, Sibusiso; Prado, Guillermo Willy; Horigian, Viviana; Weiss, Stephen M; Jones, Deborah L

2017-12-01

The Joint United Nations Programme on HIV and AIDS proposed to reduce the vertical transmission of HIV from ∼72,200 to ∼8300 newly infected children by 2015 in South Africa (SA). However, cultural, infrastructural, and socio-economic barriers hinder the implementation of the prevention of mother-to-child transmission (PMTCT) protocol, and research on potential solutions to address these barriers in rural areas is particularly limited. This study sought to identify challenges and solutions to the implementation, uptake, and sustainability of the PMTCT protocol in rural SA. Forty-eight qualitative interviews, 12 focus groups discussions (n = 75), and one two-day workshop (n = 32 participants) were conducted with district directors, clinic leaders, staff, and patients from 12 rural clinics. The delivery and uptake of the PMTCT protocol was evaluated using the Consolidated Framework for Implementation Research (CFIR); 15 themes associated with challenges and solutions emerged. Intervention characteristics themes included PMTCT training and HIV serostatus disclosure. Outer-setting themes included facility space, health record management, and staff shortage; inner-setting themes included supply use and availability, staff-patient relationship, and transportation and scheduling. Themes related to characteristics of individuals included staff relationships, initial antenatal care visit, adherence, and culture and stigma. Implementation process themes included patient education, test results delivery, and male involvement. Significant gaps in care were identified in rural areas. Information obtained from participants using the CFIR framework provided valuable insights into solutions to barriers to PMTCT implementation. Continuously assessing and correcting PMTCT protocol implementation, uptake and sustainability appear merited to maximize HIV prevention.

Flexible barrier film, method of forming same, and organic electronic device including same

Science.gov (United States)

Blizzard, John; Tonge, James Steven; Weidner, William Kenneth

2013-03-26

A flexible barrier film has a thickness of from greater than zero to less than 5,000 nanometers and a water vapor transmission rate of no more than 1.times.10.sup.-2 g/m.sup.2/day at 22.degree. C. and 47% relative humidity. The flexible barrier film is formed from a composition, which comprises a multi-functional acrylate. The composition further comprises the reaction product of an alkoxy-functional organometallic compound and an alkoxy-functional organosilicon compound. A method of forming the flexible barrier film includes the steps of disposing the composition on a substrate and curing the composition to form the flexible barrier film. The flexible barrier film may be utilized in organic electronic devices.

The Barrier Properties of PET Coated DLC Film Deposited by Microwave Surface-Wave PECVD

Science.gov (United States)

Yin, Lianhua; Chen, Qiang

2017-12-01

In this paper we report the investigation of diamond-like carbon (DLC) deposited by microwave surface-wave plasma enhanced chemical vapor deposition (PECVD) on the polyethylene terephthalate (PET) web for the purpose of the barrier property improvement. In order to characterize the properties of DLC coatings, we used several substrates, silicon wafer, glass, and PET web and KBr tablet. The deposition rate was obtained by surface profiler based on the DLC deposited on glass substrates; Fourier transform infrared spectroscope (FTIR) was carried out on KBr tablets to investigate chemical composition and bonding structure; the morphology of the DLC coating was analyzed by atomic force microscope (AFM) on Si substrates. For the barrier properties of PET webs, we measured the oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) after coated with DLC films. We addressed the film barrier property related to process parameters, such as microwave power and pulse parameter in this work. The results show that the DLC coatings can greatly improve the barrier properties of PET webs.

Suburban Poverty: Barriers to Services and Injury Prevention among Marginalized Women Who Use Methamphetamine

Directory of Open Access Journals (Sweden)

Boeri, Miriam

2011-07-01

Full Text Available Objective: This paper aims to identify the needed healthcare and social services barriers for women living in suburban communities who are using or have used methamphetamine. Drug users are vulnerable to injury, violence and transmission of infectious diseases, and having access to healthcare has been shown to positively influence prevention and intervention among this population. Yet little is known regarding the social context of suburban drug users, their risks behaviors, and their access to healthcare.Methods: The data collection involved participant observation in the field, face-to-face interviews and focus groups. Audio-recorded in-depth life histories, drug use histories, and resource needs were collected from 31 suburban women who were former or current users of methamphetamine. The majority was drawn from marginalized communities and highly vulnerable to risk for injury and violence. We provided these women with healthcare and social service information and conducted follow-up interviews to identify barriers to these services.Results: Barriers included (1 restrictions imposed by the services and (2 limitations inherent in the women’s social, economic, or legal situations. We found that the barriers increased the women’s risk for further injury, violence and transmission of infectious diseases. Women who could not access needed healthcare and social resources typically used street drugs that were accessible and affordable to self-medicate their untreated emotional and physical pain.Conclusion: Our findings add to the literatureon how healthcare and social services are related to injury prevention. Social service providers in the suburbs were often indifferent to the needs of drug-using women. For these women, health services were accessed primarily at emergency departments (ED. To break the cycle of continued drug use, violence and injury, we suggest that ED staff be trained to perform substance abuse assessments and provide

Potential for Zika virus introduction and transmission in resource-limited countries in Africa and the Asia-Pacific region: a modelling study.

Science.gov (United States)

Bogoch, Isaac I; Brady, Oliver J; Kraemer, Moritz U G; German, Matthew; Creatore, Maria I; Brent, Shannon; Watts, Alexander G; Hay, Simon I; Kulkarni, Manisha A; Brownstein, John S; Khan, Kamran

2016-11-01

As the epidemic of Zika virus expands in the Americas, countries across Africa and the Asia-Pacific region are becoming increasingly susceptible to the importation and possible local spread of the virus. To support public health readiness, we aim to identify regions and times where the potential health, economic, and social effects from Zika virus are greatest, focusing on resource-limited countries in Africa and the Asia-Pacific region. Our model combined transportation network analysis, ecological modelling of mosquito occurrences, and vector competence for flavivirus transmission, using data from the International Air Transport Association, entomological observations from Zika's primary vector species, and climate conditions using WorldClim. We overlaid monthly flows of airline travellers arriving to Africa and the Asia-Pacific region from areas of the Americas suitable for year-round transmission of Zika virus with monthly maps of climatic suitability for mosquito-borne transmission of Zika virus within Africa and the Asia-Pacific region. An estimated 2·6 billion people live in areas of Africa and the Asia-Pacific region where the presence of competent mosquito vectors and suitable climatic conditions could support local transmission of Zika virus. Countries with large volumes of travellers arriving from Zika virus-affected areas of the Americas and large populations at risk of mosquito-borne Zika virus infection include India (67 422 travellers arriving per year; 1·2 billion residents in potential Zika transmission areas), China (238 415 travellers; 242 million residents), Indonesia (13 865 travellers; 197 million residents), Philippines (35 635 travellers; 70 million residents), and Thailand (29 241 travellers; 59 million residents). Many countries across Africa and the Asia-Pacific region are vulnerable to Zika virus. Strategic use of available health and human resources is essential to prevent or mitigate the health, economic, and social

Tunnel magnetoresistance in asymmetric double-barrier magnetic tunnel junctions

International Nuclear Information System (INIS)

Useinov, N.Kh.; Petukhov, D.A.; Tagirov, L.R.

2015-01-01

The spin-polarized tunnel conductance and tunnel magnetoresistance (TMR) through a planar asymmetric double-barrier magnetic tunnel junction (DBMTJ) have been calculated using quasi-classical model. In DBMTJ nanostructure the magnetization of middle ferromagnetic metal layer can be aligned parallel or antiparallel with respect to the fixed magnetizations of the top and bottom ferromagnetic electrodes. The transmission coefficients of an electron to pass through the barriers have been calculated in terms of quantum mechanics. The dependencies of tunnel conductance and TMR on the applied voltage have been calculated in case of non-resonant transmission. Estimated in the framework of our model, the difference between the spin-channels conductances at low voltages was found relatively large. This gives rise to very high magnitude of TMR. - Highlights: • The spin-polarized conductance through the junction is calculated. • Dependencies of the tunnel conductance vs applied bias are shown. • Bias voltage dependence of tunnel magnetoresistance for the structure is shown

Evaluation of five strategies to limit the impact of fouling in permeable reactive barriers

International Nuclear Information System (INIS)

Li Lin; Benson, Craig H.

2010-01-01

Ground water flow and geochemical reactive transport models were used to assess the effectiveness of five strategies used to limit fouling and to enhance the long-term hydraulic behavior of continuous-wall permeable reactive barriers (PRBs) employing granular zero valent iron (ZVI). The flow model accounted for geological heterogeneity and the reactive transport model included a geochemical algorithm for simulating iron corrosion and mineral precipitation reactions that have been observed in ZVI PRBs. The five strategies that were evaluated are pea gravel equalization zones, a sacrificial pre-treatment zone, pH adjustment, large ZVI particles, and mechanical treatment. Results of simulations show that installation of pea gravel equalization zones results in flow equalization and a more uniform distribution of residence times within the PRB. Residence times within the PRB are less affected by mineral precipitation when a pre-treatment zone is employed. pH adjustment limits the total amount of hydroxide ions in ground water to reduce porosity reduction and to retain larger residence times. Larger ZVI particles reduce porosity reduction as a result of the smaller iron surface area for iron corrosion, and retain longer residence time. Mechanical treatment redistributes the porosity uniformly throughout the PRB over time, which is effective in maintaining residence time.

Transmission through a potential barrier in Luttinger liquids with a topological spin gap

Science.gov (United States)

Kainaris, Nikolaos; Carr, Sam T.; Mirlin, Alexander D.

2018-03-01

We study theoretically the transport of the one-dimensional single-channel interacting electron gas through a strong potential barrier in the parameter regime where the spin sector of the low-energy theory is gapped by interaction (Luther-Emery liquid). There are two distinct phases of this nature, of which one is of particular interest as it exhibits nontrivial interaction-induced topological properties. Focusing on this phase and using bosonization and an expansion in the tunneling strength we calculate the conductance through the barrier as a function of the temperature as well as the local density of states (LDOS) at the barrier. Our main result concerns the mechanism of bound-state-mediated tunneling. The characteristic feature of the topological phase is the emergence of protected zero-energy bound states with fractional spin located at the impurity position. By flipping this fractional spin, single electrons can tunnel across the impurity even though the bulk spectrum for spin excitations is gapped. This results in a finite LDOS below the bulk gap and in a nonmonotonic behavior of the conductance. The system represents an important physical example of an interacting symmetry-protected topological phase, which combines features of a topological spin insulator and a topological charge metal, in which the topology can be probed by measuring transport properties.

A novel concept of fault current limiter based on saturable core in high voltage DC transmission system

Science.gov (United States)

Yuan, Jiaxin; Zhou, Hang; Gan, Pengcheng; Zhong, Yongheng; Gao, Yanhui; Muramatsu, Kazuhiro; Du, Zhiye; Chen, Baichao

2018-05-01

To develop mechanical circuit breaker in high voltage direct current (HVDC) system, a fault current limiter is required. Traditional method to limit DC fault current is to use superconducting technology or power electronic devices, which is quite difficult to be brought to practical use under high voltage circumstances. In this paper, a novel concept of high voltage DC transmission system fault current limiter (DCSFCL) based on saturable core was proposed. In the DCSFCL, the permanent magnets (PM) are added on both up and down side of the core to generate reverse magnetic flux that offset the magnetic flux generated by DC current and make the DC winding present a variable inductance to the DC system. In normal state, DCSFCL works as a smoothing reactor and its inductance is within the scope of the design requirements. When a fault occurs, the inductance of DCSFCL rises immediately and limits the steepness of the fault current. Magnetic field simulations were carried out, showing that compared with conventional smoothing reactor, DCSFCL can decrease the high steepness of DC fault current by 17% in less than 10ms, which verifies the feasibility and effectiveness of this method.

Barriers to condom use: results from a study in Mumbai (Bombay), India.

Science.gov (United States)

Roth, J; Krishnan, S P; Bunch, E

2001-02-01

The consistent and correct use of condoms coupled with risk reduction education strategies, continue to play an important role in the reduction and prevention of HIV/AIDS transmission. Therefore understanding and incorporating strategies to overcome barriers to condom use in such education and prevention efforts are critical. This is particularly necessary in countries such as India, where HIV/AIDS has become a serious public health crisis. The current study documents and provides preliminary data on the use of condoms, reasons for and barriers to condom use, and sources of information about safer sex practices among a sexually active adult sample of 49 women and 203 men in Mumbai, India. Despite limitations such as the use of a nonrandom sample of participants composed predominantly of young, English-speaking males, the study findings provide some insights into the importance of and the need to address issues of privacy regarding condom purchase and use in India. Most notably, the lack of privacy in stores and the social stigma associated with condom use were indicated as the most significant barriers. These and other study findings suggest the need to ease the social costs and constraints to safe behaviors through increased acceptance of condoms and promotion of their consistent use. This could serve as an important means to curb the epidemic of HIV/AIDS in India.

Quantitative annular dark field scanning transmission electron microscopy for nanoparticle atom-counting: What are the limits?

International Nuclear Information System (INIS)

De Backer, A; De Wael, A; Gonnissen, J; Martinez, G T; Béché, A; Van Aert, S; MacArthur, K E; Jones, L; Nellist, P D

2015-01-01

Quantitative atomic resolution annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique for nanoparticle atom-counting. However, a lot of nanoparticles provide a severe characterisation challenge because of their limited size and beam sensitivity. Therefore, quantitative ADF STEM may greatly benefit from statistical detection theory in order to optimise the instrumental microscope settings such that the incoming electron dose can be kept as low as possible whilst still retaining single-atom precision. The principles of detection theory are used to quantify the probability of error for atom-counting. This enables us to decide between different image performance measures and to optimise the experimental detector settings for atom-counting in ADF STEM in an objective manner. To demonstrate this, ADF STEM imaging of an industrial catalyst has been conducted using the near-optimal detector settings. For this experiment, we discussed the limits for atomcounting diagnosed by combining a thorough statistical method and detailed image simulations. (paper)

Barriers to initiating tuberculosis treatment in sub-Saharan Africa: a systematic review focused on children and youth.

Science.gov (United States)

Sullivan, Brittney J; Esmaili, B Emily; Cunningham, Coleen K

2017-01-01

Tuberculosis (TB) is the deadliest infectious disease globally, with 10.4 million people infected and more than 1.8 million deaths in 2015. TB is a preventable, treatable, and curable disease, yet there are numerous barriers to initiating treatment. These barriers to treatment are exacerbated in low-resource settings and may be compounded by factors related to childhood. Timely initiation of tuberculosis (TB) treatment is critical to reducing disease transmission and improving patient outcomes. The aim of this paper is to describe patient- and system-level barriers to TB treatment initiation specifically for children and youth in sub-Saharan Africa through systematic review of the literature. This review was conducted in October 2015 in accordance with preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Six databases were searched to identify studies where primary or secondary objectives were related to barriers to TB treatment initiation and which included children or youth 0-24 years of age. A total of 1490 manuscripts met screening criteria; 152 met criteria for full-text review and 47 for analysis. Patient-level barriers included limited knowledge, attitudes and beliefs regarding TB, and economic burdens. System-level barriers included centralization of services, health system delays, and geographical access to healthcare. Of the 47 studies included, 7 evaluated cost, 19 health-seeking behaviors, and 29 health system infrastructure. Only 4 studies primarily assessed pediatric cohorts yet all 47 studies were inclusive of children. Recognizing and removing barriers to treatment initiation for pediatric TB in sub-Saharan Africa are critical. Both patient- and system-level barriers must be better researched in order to improve patient outcomes.

Tunnel barrier and noncollinear magnetization effects on shot noise in ferromagnetic/semiconductor/ferromagnetic heterojunctions

International Nuclear Information System (INIS)

An Xingtao; Liu Jianjun

2008-01-01

Based on the scattering approach, we investigate transport properties of electrons in a one-dimensional waveguide that contains a ferromagnetic/semiconductor/ferromagnetic heterojunction and tunnel barriers in the presence of Rashba and Dresselhaus spin-orbit interactions. We simultaneously consider significant quantum size effects, quantum coherence, Rashba and Dresselhaus spin-orbit interactions and noncollinear magnetizations. It is found that the tunnel barrier plays a decisive role in the transmission coefficient and shot noise of the ballistic spin electron transport through the heterojunction. When the small tunnel barriers are considered, the transport properties of electrons are quite different from those without tunnel barriers

Limitations of the hCMEC/D3 cell line as a model for Aβ clearance by the human blood-brain barrier.

Science.gov (United States)

Biemans, Elisanne A L M; Jäkel, Lieke; de Waal, Robert M W; Kuiperij, H Bea; Verbeek, Marcel M

2017-07-01

Alzheimer's disease and cerebral amyloid angiopathy are characterized by accumulation of amyloid-β (Aβ) at the cerebrovasculature due to decreased clearance at the blood-brain barrier (BBB). However, the exact mechanism of Aβ clearance across this barrier has not been fully elucidated. The hCMEC/D3 cell line has been characterized as a valid model for the BBB. In this study we evaluated the use of this model to study Aβ clearance across the BBB, with an emphasis on brain-to-blood directional permeability. Barrier integrity of hCMEC/D3 monolayers was confirmed for large molecules in both the apical to basolateral and the reverse direction. However, permeability for smaller molecules was substantially higher, especially in basolateral to apical direction, and barrier formation for Aβ was completely absent in this direction. In addition, hCMEC/D3 cells failed to develop a high TEER, possibly caused by incomplete formation of tight junctions. We conclude that the hCMEC/D3 model has several limitations to study the cerebral clearance of Aβ. Therefore, the model needs further characterization before this cell system can be generally applied as a model to study cerebral Aβ clearance. © 2016 The Authors Journal of Neuroscience Research Published by Wiley Periodicals, Inc. © 2016 The Authors Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

Orbiting transmission source for positron tomography

International Nuclear Information System (INIS)

Huesman, R.H.; Derenzo, S.E.; Cahoon, J.L.; Geyer, A.B.; Moses, W.W.; Uber, D.C.; Vuletich, T.; Budinger, T.F.

1988-01-01

Accidental suppression and effective data rates have been measured for the orbiting transmission source as implemented in the Donner 600-Crystal Positron Tomograph. A mechanical description of the orbiting source and a description of the electronics used to discard scattered and accidental events is included. Since accidental coincidences were the rate-limiting factor in transmission data acquisition, the new method allows us to acquire sufficient transmission data in a shorter time with a more active transmission source

Permeation barrier properties of thin oxide films on flexible polymer substrates

International Nuclear Information System (INIS)

Fahlteich, John; Fahland, Matthias; Schoenberger, Waldemar; Schiller, Nicolas

2009-01-01

Solar cells and organic electronic devices require an encapsulation to ensure sufficient lifetime. Key parameters of the encapsulation are permeation barrier, UV stability, temperature stability, optical transmission spectra and mechanical stability. The requirements depend very much on the specific application. Many work groups suggest multilayer stacks to meet the permeation requirements. In this paper the permeation barrier properties of the different constituents of such a multilayer stack are characterized. Different layer materials are compared regarding their water vapour and oxygen permeability as well as the influence of process parameters is examined. Finally temperature dependent permeation measurements are used to characterize the permeation mechanisms in the different constituents of the multilayer barrier

Barriers to Condom Use among High Risk Men Who Have Sex with Men in Uganda: A Qualitative Study.

Directory of Open Access Journals (Sweden)

Geofrey Musinguzi

Full Text Available Unprotected sexual intercourse is a major risk factor for HIV transmission. Men who have sex with men (MSM face challenges in accessing HIV prevention services, including condoms. However, there is limited in-depth assessment and documentation of the barriers to condom use among MSM in sub-Saharan Africa. In this paper, we examine the barriers to condom use among MSM in Uganda.The data for this study were extracted from a larger qualitative study conducted among 85 self-identified adult (>18 years MSM in 11 districts in Uganda between July and December 2013. Data on sexual behaviours and access and barriers to condom use were collected using semi-structured interviews. All interviews were audio-recorded and transcribed verbatim. This paper presents an analysis of data for 33 MSM who did not use condoms at last sex, with a focus on barriers to condom use. Analysis was conducted using the content analysis approach.Six major barriers to condom use were identified: Difficulties with using condoms, access challenges, lack of knowledge and misinformation about condom use, partner and relationship related issues, financial incentives and socio-economic vulnerability, and alcohol consumption.The findings suggest that several reasons account for lack of condom use among high-risk MSM. The findings are valuable to inform interventions needed to increase condom use among MSM.

Current-voltage relation for thin tunnel barriers: Parabolic barrier model

DEFF Research Database (Denmark)

Hansen, Kim; Brandbyge, Mads

2004-01-01

We derive a simple analytic result for the current-voltage curve for tunneling of electrons through a thin uniform insulating layer modeled by a parabolic barrier. Our model, which goes beyond the Wentzel–Kramers–Brillouin approximation, is applicable also in the limit of highly transparant...

A study on the wireless transmission characteristic in the deep underground

International Nuclear Information System (INIS)

Takamura, Hisashi; Okutsu, Kazuo; Sugahara, Norihisa; Torata, Shinichiro; Ohuchi, Jin

2006-01-01

A wireless transmission technology uses a low frequency electromagnetic wave (100[Hz] - 10[kHz]) as a carrier wave to transmit signals in the deep underground geological condition. However, this electromagnetic wave has not been used so much, because the transmission capacity is less than a high frequency electromagnetic wave, which is used to televisions and cellular phones. On the other hand, the wireless transmission technology that doesn't use the cable is considered to be useful in the radioactive waste disposal repository from the viewpoint of decreasing the influence on the barrier. This paper shows the characteristics of the wireless transmission in the granite on the basis of the in situ testing implemented in the Aespoe Hard Rock Laboratory of SKB. (author)

Spin transport through electric field modulated graphene periodic ferromagnetic barriers

International Nuclear Information System (INIS)

Sattari, F.; Faizabadi, E.

2014-01-01

Using the transfer matrix method, the spin transmission coefficient and the spin conductivity are studied theoretically through the monolayer and bilayer graphene periodic ferromagnetic barriers modulated by a homogeneous electric field. The spin conductivity of the systems has an oscillatory behavior with respect to the external electric field which depends on the spin state of electron. In addition, the oscillation amplitude of the spin conductivity and spin polarization increase by increasing the number of barriers, but for a monolayer system with number of barriers greater than thirty, also for a bilayer system with the number of barriers greater than four, the oscillation amplitude does not change significantly. Our probes show that for bilayer system unlike monolayer structure the highest value of spin polarization achieved can be 1 or (−1). So, for designing spintronic devices, bilayer graphene is more efficient

Prion replication without host adaptation during interspecies transmissions.

Science.gov (United States)

Bian, Jifeng; Khaychuk, Vadim; Angers, Rachel C; Fernández-Borges, Natalia; Vidal, Enric; Meyerett-Reid, Crystal; Kim, Sehun; Calvi, Carla L; Bartz, Jason C; Hoover, Edward A; Agrimi, Umberto; Richt, Jürgen A; Castilla, Joaquín; Telling, Glenn C

2017-01-31

Adaptation of prions to new species is thought to reflect the capacity of the host-encoded cellular form of the prion protein (PrP C ) to selectively propagate optimized prion conformations from larger ensembles generated in the species of origin. Here we describe an alternate replicative process, termed nonadaptive prion amplification (NAPA), in which dominant conformers bypass this requirement during particular interspecies transmissions. To model susceptibility of horses to prions, we produced transgenic (Tg) mice expressing cognate PrP C Although disease transmission to only a subset of infected TgEq indicated a significant barrier to EqPrP C conversion, the resulting horse prions unexpectedly failed to cause disease upon further passage to TgEq. TgD expressing deer PrP C was similarly refractory to deer prions from diseased TgD infected with mink prions. In both cases, the resulting prions transmitted to mice expressing PrP C from the species of prion origin, demonstrating that transmission barrier eradication of the originating prions was ephemeral and adaptation superficial in TgEq and TgD. Horse prions produced in vitro by protein misfolding cyclic amplification of mouse prions using horse PrP C also failed to infect TgEq but retained tropism for wild-type mice. Concordant patterns of neuropathology and prion deposition in susceptible mice infected with NAPA prions and the corresponding prion of origin confirmed preservation of strain properties. The comparable responses of both prion types to guanidine hydrochloride denaturation indicated this occurs because NAPA precludes selection of novel prion conformations. Our findings provide insights into mechanisms regulating interspecies prion transmission and a framework to reconcile puzzling epidemiological features of certain prion disorders.

Barriers for realisation of energy savings in buildings; Barrierer for realisering af energibesparelser i bygninger

Energy Technology Data Exchange (ETDEWEB)

Jensen, O.M.

2004-07-01

Many years' efforts within the energy labelling area have shown large saving potentials in heating and use of electricity in buildings. At the same time it has been proved that these saving potentials, even when economically advantageous, only are cashed to a limited extent. The reason to this is ascribed to barriers that meet the individual building owner who wants to start saving energy. Most barriers are known and a lot of these have been sought overcome for some time. The questions are how many barriers still exist, have new barriers arisen and the character of these barriers. On this background the objective of this survey has been to concretize and study the barriers, which are blocking reasonable energy savings. Focus has especially been on barriers for realisation of heating savings, but through a general evaluation of energy savings of barriers other forms of energy saving methods have been taken into consideration. Special interest has been directed towards houses, typically one family houses, which are affected by the Energy Labelling Scheme. The concept barriers include all kinds of barriers, also barriers that not are acknowledged as barriers by the individual house owner, or that on closer inspection turn out to be something else than actual barriers. This note suggests an alternative inertia model, in order to create an idea of the inertness characteristic of the many house owners who understand the message but fail to act on it. (BA)

Graphene-based stretchable and transparent moisture barrier

Science.gov (United States)

Won, Sejeong; Van Lam, Do; Lee, Jin Young; Jung, Hyun-June; Hur, Min; Kim, Kwang-Seop; Lee, Hak-Joo; Kim, Jae-Hyun

2018-03-01

We propose an alumina-deposited double-layer graphene (2LG) as a transparent, scalable, and stretchable barrier against moisture; this barrier is indispensable for foldable or stretchable organic displays and electronics. Both the barrier property and stretchability were significantly enhanced through the introduction of 2LG between alumina and a polymeric substrate. 2LG with negligible polymeric residues was coated on the polymeric substrate via a scalable dry transfer method in a roll-to-roll manner; an alumina layer was deposited on the graphene via atomic layer deposition. The effect of the graphene layer on crack generation in the alumina layer was systematically studied under external strain using an in situ micro-tensile tester, and correlations between the deformation-induced defects and water vapor transmission rate were quantitatively analyzed. The enhanced stretchability of alumina-deposited 2LG originated from the interlayer sliding between the graphene layers, which resulted in the crack density of the alumina layer being reduced under external strain.

Nonlinear transport theory in the metal with tunnel barrier

Science.gov (United States)

Zubov, E. E.

2018-02-01

Within the framework of the scattering matrix formalism, the nonlinear Kubo theory for electron transport in the metal with a tunnel barrier has been considered. A general expression for the mean electrical current was obtained. It significantly simplifies the calculation of nonlinear contributions to the conductivity of various hybrid structures. In the model of the tunnel Hamiltonian, all linear and nonlinear contributions to a mean electrical current are evaluated. The linear approximation agrees with results of other theories. For effective barrier transmission ?, the ballistic transport is realised with a value of the Landauer conductivity equal to ?.

Velocity barrier-controlled of spin-valley polarized transport in monolayer WSe2 junction

Science.gov (United States)

Qiu, Xuejun; Lv, Qiang; Cao, Zhenzhou

2018-05-01

In this work, we have theoretically investigated the influence of velocity barrier on the spin-valley polarized transport in monolayer (ML) WSe2 junction with a large spin-orbit coupling (SOC). Both the spin-valley resolved transmission probabilities and conductance are strong dependent on the velocity barrier, as the velocity barrier decreases to 0.06, a spin-valley polarization of exceeding 90% is observed, which is distinct from the ML MoS2 owing to incommensurable SOC. In addition, the spin-valley polarization is further increased above 95% in a ML WSe2 superlattice, in particular, it's found many extraordinary velocity barrier-dependent transport gaps for multiple barrier due to evanescent tunneling. Our results may open an avenue for the velocity barrier-controlled high-efficiency spin and valley polarizations in ML WSe2-based electronic devices.

Analog data transmission via fiber optics

International Nuclear Information System (INIS)

Cisneros, E.L.; Burgueno, G.F.

1987-01-01

In the SLAC Linear Collider Detector (SLD), as in most high-energy particle detectors, the electromagnetic noise environment is the limiting factor in electronic readout performance. Front-end electronics are particularly susceptible to electromagnetic interference (EMI), and great care has been taken to minimize its effects. The transfer of preprocessed analog signals from the detector environs, to the remote digital processing electronics, by conventional means (via metal conductors), may ultimately limit the performance of the system. Because it is highly impervious to EMI and ground loops, a fiber-optic medium has been chosen for the transmission of these signals. This paper describes several fiber-optic transmission schemes which satisfy the requirements of the SLD analog data transmission

Analog data transmission via fiber optics

International Nuclear Information System (INIS)

Cisneros, E.L.; Burgueno, G.F.

1986-10-01

In the SLAC Linear Collider Detector (SLD), as in most high-energy particle detectors, the electromagnetic noise environment is the limiting factor in electronic readout performance. Front-end electronics are particulary susceptible to electromagnetic interference (EMI), and great care has been taken to minimize its effects. The transfer of preprocessed analog signals from the detector environs, to the remote digital processing electronics, by conventional means (via metal conductors), may ultimately limit the performance of the system. Because it is highly impervious to EMI and ground loops, a fiber-optic medium has been chosen for the transmission of these signals. This paper describes several fiber-optic transmission schemes which satisfy the requirements of the SLD analog data transmission

Unified Model of Dynamic Forced Barrier Crossing in Single Molecules

Energy Technology Data Exchange (ETDEWEB)

Friddle, R W

2007-06-21

Thermally activated barrier crossing in the presence of an increasing load can reveal kinetic rate constants and energy barrier parameters when repeated over a range of loading rates. Here we derive a model of the mean escape force for all relevant loading rates--the complete force spectrum. Two well-known approximations emerge as limiting cases; one of which confirms predictions that single-barrier spectra should converge to a phenomenological description in the slow loading limit.

Variable speed limit strategies analysis with link transmission model on urban expressway

Science.gov (United States)

Li, Shubin; Cao, Danni

2018-02-01

The variable speed limit (VSL) is a kind of active traffic management method. Most of the strategies are used in the expressway traffic flow control in order to ensure traffic safety. However, the urban expressway system is the main artery, carrying most traffic pressure. It has similar traffic characteristics with the expressways between cities. In this paper, the improved link transmission model (LTM) combined with VSL strategies is proposed, based on the urban expressway network. The model can simulate the movement of the vehicles and the shock wave, and well balance the relationship between the amount of calculation and accuracy. Furthermore, the optimal VSL strategy can be proposed based on the simulation method. It can provide management strategies for managers. Finally, a simple example is given to illustrate the model and method. The selected indexes are the average density, the average speed and the average flow on the traffic network in the simulation. The simulation results show that the proposed model and method are feasible. The VSL strategy can effectively alleviate traffic congestion in some cases, and greatly promote the efficiency of the transportation system.

Space charge effects and coherent stability limits in barrier buckets

Directory of Open Access Journals (Sweden)

Oliver Boine-Frankenheim

2003-03-01

Full Text Available A large-scale Vlasov simulation study of the microwave instability below transition energy in a beam confined between two barrier pulses is performed. Starting from a matched distribution function for the confined ion beam including the space charge impedance the stability threshold in the longitudinal impedance plane is obtained. A simple stability criterium is found to be in good agreement with the simulation results.

Social Barriers to Effective Communication in Old Age

OpenAIRE

Anna Sanecka

2014-01-01

Some communication barriers apply particularly to elderly people. The social barriers to effective communication in old age are the barriers caused by stereotypes of old age/elderly people and the barriers arising from limitations in using mass communication by seniors. Stereotypes of old age/elderly people embrace views regarding old people’s communication skills and the ideas about the correct way of communication with them. Therefore the communication problems of old people are correlated ...

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

Science.gov (United States)

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.

The blood-brain barrier in migraine treatment

DEFF Research Database (Denmark)

Edvinsson, L; Tfelt-Hansen, P

2008-01-01

Salient aspects of the anatomy and function of the blood-barrier barrier (BBB) are reviewed in relation to migraine pathophysiology and treatment. The main function of the BBB is to limit the access of circulating substances to the neuropile. Smaller lipophilic substances have some access...

Reduction of sound transmission through fuselage walls by alternate resonance tuning (A.R.T.)

Science.gov (United States)

Bliss, Donald B.; Gottwald, James A.

1989-01-01

The ability of alternate resonance tuning (ART) to block sound transmission through light-weight flexible paneled walls by controlling the dynamics of the wall panels is considered. Analytical results for sound transmission through an idealized panel wall illustrate the effect of varying system parameters and show that one or more harmonics of the incident sound field can be cancelled by the present method. Experimental results demonstrate that very large transmission losses with reasonable bandwidths can be achieved by a simple ART panel barrier in a duct.

Social Barriers to Effective Communication in Old Age

Directory of Open Access Journals (Sweden)

Anna Sanecka

2014-12-01

Full Text Available Some communication barriers apply particularly to elderly people. The social barriers to effective communication in old age are the barriers caused by stereotypes of old age/elderly people and the barriers arising from limitations in using mass communication by seniors. Stereotypes of old age/elderly people embrace views regarding old people’s communication skills and the ideas about the correct way of communication with them. Therefore the communication problems of old people are correlated with the little and poor communication processes they are participating in. This seems to be a result of impetuses of poor quality sent to seniors by their communication partners. Not only face to face communication but also mass communication is very important for the elderly population. Therefore limitations in using new technologies and new communication channels as well as a limited presence in the mass media of content created by seniors and for seniors have an impact on their life, their well-being, and their interpersonal relationships. These problems are especially important when we faced with the ever growing population of elderly people.

Ferromagnetic barrier-induced negative differential conductance on the surface of a topological insulator

International Nuclear Information System (INIS)

An Xing-Tao

2014-01-01

The effect of the negative differential conductance of a ferromagnetic barrier on the surface of a topological insulator is theoretically investigated. Due to the changes of the shape and position of the Fermi surfaces in the ferromagnetic barrier, the transport processes can be divided into three kinds: the total, partial, and blockade transmission mechanisms. The bias voltage can give rise to the transition of the transport processes from partial to blockade transmission mechanisms, which results in a considerable effect of negative differential conductance. With appropriate structural parameters, the current-voltage characteristics show that the minimum value of the current can reach to zero in a wide range of the bias voltage, and then a large peak-to-valley current ratio can be obtained. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Barriers and attitudes towards hIV Voluntary counselling and Testing ...

African Journals Online (AJOL)

Official Publication of the Tanzania Medical Students' Association. 20. Barriers and attitudes towards hIV ... risk reduction in certain groups, behaviour change and reduced transmission2. Young people are the ... Of those who ever used VCT services 32.7% were just interested in knowing their HIV status and to get HIV ...

Priority image transmission in wireless sensor networks

International Nuclear Information System (INIS)

Nasri, M.; Helali, A.; Sghaier, H.; Maaref, H.

2011-01-01

The emerging technology during the last years allowed the development of new sensors equipped with wireless communication which can be organized into a cooperative autonomous network. Some application areas for wireless sensor networks (WSNs) are home automations, health care services, military domain, and environment monitoring. The required constraints are limited capacity of processing, limited storage capability, and especially these nodes are limited in energy. In addition, such networks are tiny battery powered which their lifetime is very limited. During image processing and transmission to the destination, the lifetime of sensor network is decreased quickly due to battery and processing power constraints. Therefore, digital image transmissions are a significant challenge for image sensor based Wireless Sensor Networks (WSNs). Based on a wavelet image compression, we propose a novel, robust and energy-efficient scheme, called Priority Image Transmission (PIT) in WSN by providing various priority levels during image transmissions. Different priorities in the compressed image are considered. The information for the significant wavelet coeffcients are transmitted with higher quality assurance, whereas relatively less important coefficients are transmitted with lower overhead. Simulation results show that the proposed scheme prolongs the system lifetime and achieves higher energy efficiency in WSN with an acceptable compromise on the image quality.

Evidence of localized wave transmission

International Nuclear Information System (INIS)

Anon.

1988-01-01

LLNL [Lawrence Livermore National Lab.] experiments to test the feasibility of launching an acoustic, directed-energy pulse train (ADEPT) in water have demonstrated localized transmission of wave energy far beyond the classical Rayleigh length that defines the boundary between near-field and far-field transmission for Gaussian (diffraction-limited) pulses. The results of the experiments are in excellent agreement with computer simulations

Absence of zero-temperature transmission rate of a double-chain tight-binding model for DNA with random sequence of nucleotides in thermodynamic limit

International Nuclear Information System (INIS)

Xiong Gang; Wang, X.R.

2005-01-01

The zero-temperature transmission rate spectrum of a double-chain tight-binding model for real DNA is calculated. It is shown that a band of extended-like states exists only for finite chain length with strong inter-chain coupling. While the whole spectrum tends to zero in thermodynamic limit, regardless of the strength of inter-chain coupling. It is also shown that a more faithful model for real DNA with periodic sugar-phosphate chains in backbone structures can be mapped into the above simple double-chain tight-binding model. Combined with above results, the transmission rate of real DNA with long random sequence of nucleotides is expected to be poor

Development of highly flexible and ultra-low permeation rate thin-film barrier structure for organic electronics

International Nuclear Information System (INIS)

Kim, Namsu; Graham, Samuel

2013-01-01

A flexible thin-film encapsulation architecture for organic electronics was built and consisted of a silicon oxide/alumina and parylene layer deposited over Ca sensors on a barrier-coated polyethylene terephthalate substrate. The film's effective water vapor transmission rate was 2.4 ± 1.5 × 10 −5 g/m 2 /day at 20 °C and 50% relative humidity. Flexural tests revealed that for films deposited on the polyethylene terephthalate substrate, the barrier layer failed due to cracking at a curvature radius of 6.4 mm, corresponding to a strain of 0.8%. Adding an epoxy top coat of suitable thickness shifted the neutral axis toward the encapsulation layer, reducing the induced strain. Barrier performance was maintained under the 6.4 mm radius of curvature in this encapsulation structure. Thus, shifting the neutral axis via device structural design is an effective method of extending the flexibility of thin-film encapsulation structure without compromising the performance loss as a barrier layer. - Highlights: • High performance barrier is fabricated on flexible substrate. • The water vapor transmission rate is 2.4 ± 1.5 × 10 −5 g/m 2 /day. • The structure maintains its performance under a small radius of bending curvature

Self-similar transmission properties of aperiodic Cantor potentials in gapped graphene

Science.gov (United States)

Rodríguez-González, Rogelio; Rodríguez-Vargas, Isaac; Díaz-Guerrero, Dan Sidney; Gaggero-Sager, Luis Manuel

2016-01-01

We investigate the transmission properties of quasiperiodic or aperiodic structures based on graphene arranged according to the Cantor sequence. In particular, we have found self-similar behaviour in the transmission spectra, and most importantly, we have calculated the scalability of the spectra. To do this, we implement and propose scaling rules for each one of the fundamental parameters: generation number, height of the barriers and length of the system. With this in mind we have been able to reproduce the reference transmission spectrum, applying the appropriate scaling rule, by means of the scaled transmission spectrum. These scaling rules are valid for both normal and oblique incidence, and as far as we can see the basic ingredients to obtain self-similar characteristics are: relativistic Dirac electrons, a self-similar structure and the non-conservation of the pseudo-spin.

The influence of the structures and compounds of DLC coatings on the barrier properties of PET bottles

International Nuclear Information System (INIS)

Li, Yang; Zhen-Duo, Wang; Shou-Ye, Zhang; Li-Zhen, Yang; Qiang, Chen

2009-01-01

To reduce the oxygen transmission rate through a polyethylene terephthalate (PET) bottle (an organic plastic) diamond-like carbon (DLC) coatings on the inner surface of the PET bottle were deposited by radio frequency plasma-enhanced chemical vapour deposition (RF-PECVD) technology with C 2 H 2 as the source of carbon and Ar as the diluted gas. As the barrier layer to humidity and gas permeation, this paper analyses the DLC film structure, composition, morphology and barrier properties by Fourier transform infrared, atomic force microscopy, scanning electron microscopy and oxygen transmission rate in detail. From the spectrum, it is found that the DLC film mainly consists of sp 3 bonds. The barrier property of the films is significantly relevant to the sp 3 bond concentration in the coating, the film thickness and morphology. Additionally, it is found that DLC film deposited in an inductively coupled plasma enhanced capacitively coupled plasma source shows a compact, homogeneous and crack-free surface, which is beneficial for a good gas barrier property in PET bottles. (fluids, plasmas and electric discharges)

Roll-to-roll vacuum deposition of barrier coatings

CERN Document Server

Bishop, Charles A

2015-01-01

It is intended that the book will be a practical guide to provide any reader with the basic information to help them understand what is necessary in order to produce a good barrier coated web or to improve the quality of any existing barrier product. After providing an introduction, where the terminology is outlined and some of the science is given (keeping the mathematics to a minimum), including barrier testing methods, the vacuum deposition process will be described. In theory a thin layer of metal or glass-like material should be enough to convert any polymer film into a perfect barrier material. The reality is that all barrier coatings have their performance limited by the defects in the coating. This book looks at the whole process from the source materials through to the post deposition handling of the coated material. This holistic view of the vacuum coating process provides a description of the common sources of defects and includes the possible methods of limiting the defects. This enables readers...

TEr azimuthal modes for a biconic transmission line in the small-gap limit

International Nuclear Information System (INIS)

Johnson, W.A.; Mendel, C.W. Jr.; Seidel, D.B.

1992-01-01

Azimuthally asymmetric modes in a biconic transmission line with a small-gap angle may be approximated by ''transmission-line-like'' modes. It is shown that the errors in these approximations are second order in the gap angle and approximate error bounds are provided. As an example demonstrating the application of this analysis in biconic structures, an analysis to characterize of the electromagnetic waves in the vacuum feed of the Particle Beam Fusion Accelerator II is provided

Limited variation of the 5'cis-control region of the transmission ...

African Journals Online (AJOL)

SERVER

2008-03-04

Mar 4, 2008 ... transmission blocking vaccine candidate Pfs25 amid great genetic diversity of Plasmodium falciparum in ... enzymes were selected whose sequences produced or abolished restriction sites ... as chemotherapy and protection against vectors have ..... acquisition of immunity to malaria infection giving to the.

Waves propagating over a two-layer porous barrier on a seabed

Science.gov (United States)

Lin, Qiang; Meng, Qing-rui; Lu, Dong-qiang

2018-05-01

A research of wave propagation over a two-layer porous barrier, each layer of which is with different values of porosity and friction, is conducted with a theoretical model in the frame of linear potential flow theory. The model is more appropriate when the seabed consists of two different properties, such as rocks and breakwaters. It is assumed that the fluid is inviscid and incompressible and the motion is irrotational. The wave numbers in the porous region are complex ones, which are related to the decaying and propagating behaviors of wave modes. With the aid of the eigenfunction expansions, a new inner product of the eigenfunctions in the two-layer porous region is proposed to simplify the calculation. The eigenfunctions, under this new definition, possess the orthogonality from which the expansion coefficients can be easily deduced. Selecting the optimum truncation of the series, we derive a closed system of simultaneous linear equations for the same number of the unknown reflection and transmission coefficients. The effects of several physical parameters, including the porosity, friction, width, and depth of the porous barrier, on the dispersion relation, reflection and transmission coefficients are discussed in detail through the graphical representations of the solutions. It is concluded that these parameters have certain impacts on the reflection and transmission energy.

Transmission of influenza reflects seasonality of wild birds across the annual cycle

Science.gov (United States)

Hill, Nichola J.; Ma, Eric J.; Meixell, Brandt W.; Lindberg, Mark S.; Boyce, Walter M.; Runstadler, Jonathan A.

2016-01-01

Influenza A Viruses (IAV) in nature must overcome shifting transmission barriers caused by the mobility of their primary host, migratory wild birds, that change throughout the annual cycle. Using a phylogenetic network of viral sequences from North American wild birds (2008–2011) we demonstrate a shift from intraspecific to interspecific transmission that along with reassortment, allows IAV to achieve viral flow across successive seasons from summer to winter. Our study supports amplification of IAV during summer breeding seeded by overwintering virus persisting locally and virus introduced from a wide range of latitudes. As birds migrate from breeding sites to lower latitudes, they become involved in transmission networks with greater connectivity to other bird species, with interspecies transmission of reassortant viruses peaking during the winter. We propose that switching transmission dynamics may be a critical strategy for pathogens that infect mobile hosts inhabiting regions with strong seasonality.

Barriers for the introduction of bioenergy in the Netherlands

International Nuclear Information System (INIS)

Gerlagh, T.; Groenendaal, B.; Van Ree, R.; Dinkelbach, L.; Van Doorn, J.; Hemmes, K.

2000-01-01

The use of biomass for energy in the Netherlands is still limited despite the political incentives to make bio-energy a major source of renewable energy. The hesitation of many stake-holders is due to the limited insight into the potential of biomass in the Netherlands and the presence of numerous other barriers. Availability of biomass, emission regulation and waste treatment regulations are considered important barriers. Analyses of their current state show that these barriers are broadly recognised and possibilities to decrease their impact are present. Some barriers with a minor influence so far will be of increasing importance and could be a threat to the development of bio-energy in future. These are the fast liberalising of the energy market and sustainable energy market, the competition with other renewables and the unclear status of the current technology available. Future research should focus on the possibilities to overcome these new barriers. 5 refs

Transmission line component testing for the ITER Ion Cyclotron Heating and Current Drive System

Science.gov (United States)

Goulding, Richard; Bell, G. L.; Deibele, C. E.; McCarthy, M. P.; Rasmussen, D. A.; Swain, D. W.; Barber, G. C.; Barbier, C. N.; Cambell, I. H.; Moon, R. L.; Pesavento, P. V.; Fredd, E.; Greenough, N.; Kung, C.

2014-10-01

High power RF testing is underway to evaluate transmission line components for the ITER Ion Cyclotron Heating and Current Drive System. The transmission line has a characteristic impedance Z0 = 50 Ω and a nominal outer diameter of 305 mm. It is specified to carry up to 6 MW at VSWR = 1.5 for 3600 s pulses, with transient voltages up to 40 kV. The transmission line is actively cooled, with turbulent gas flow (N2) used to transfer heat from the inner to outer conductor, which is water cooled. High voltage and high current testing of components has been performed using resonant lines generating steady state voltages of 35 kV and transient voltages up to 60 kV. A resonant ring, which has operated with circulating power of 6 MW for 1 hr pulses, is being used to test high power, low VSWR operation. Components tested to date include gas barriers, straight sections of various lengths, and 90 degree elbows. Designs tested include gas barriers fabricated from quartz and aluminum nitride, and transmission lines with quartz and alumina inner conductor supports. The latest results will be presented. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.

75 FR 81157 - Version One Regional Reliability Standard for Transmission Operations

Science.gov (United States)

2010-12-27

... not exceed the path's system operating limits, when the transmission operator implements its real-time... return the actual power flow to within [system operating limits] such that at no time shall the power... return the transmission system to within [system operating limits] within a time certain, only a...

Quantum Transmission Conditions for Diffusive Transport in Graphene with Steep Potentials

Science.gov (United States)

Barletti, Luigi; Negulescu, Claudia

2018-05-01

We present a formal derivation of a drift-diffusion model for stationary electron transport in graphene, in presence of sharp potential profiles, such as barriers and steps. Assuming the electric potential to have steep variations within a strip of vanishing width on a macroscopic scale, such strip is viewed as a quantum interface that couples the classical regions at its left and right sides. In the two classical regions, where the potential is assumed to be smooth, electron and hole transport is described in terms of semiclassical kinetic equations. The diffusive limit of the kinetic model is derived by means of a Hilbert expansion and a boundary layer analysis, and consists of drift-diffusion equations in the classical regions, coupled by quantum diffusive transmission conditions through the interface. The boundary layer analysis leads to the discussion of a four-fold Milne (half-space, half-range) transport problem.

Theory of the electric current transmission coefficient in the superconductor-insulator-superconductor geometry

International Nuclear Information System (INIS)

Navani, R.

1974-01-01

Tunneling in the superconductor-insulator-superconductor (S'-I-S) geometry, where the two superconductors are not necessarily the same, is studied theoretically. Two different models of the S'-I-S geometry - which we call the ''initial model'' and the ''improved model'' are discussed. For the initial model the potential barrier is flat. In the improved model, however, the differing material properties of the three regions - S', I, and S - are taken into account in an approximate fashion. In addition, applied, contact, and image potentials in the insulator are included. The solid state material properties that are taken to be different are the effective electronic masses in the three regions and the Fermi energies in the two superconductors. The quasiparticle wave functions in the S', I, and S regions are determined for both models as solutions to the Bogoliubov-de Gennes equations. The electric current transmission coefficients (also the reflection coefficient for the initial model) are derived and their behavior is extensively analyzed. Their forms in the thick barrier limit - where L greater than or approximately equal to 5 A - are related to the BCS densities of states. The tunneling current density is found to depend strongly on the tunneling angle. A relation between the angular position of the tunneling current peak and the barrier thickness is given. Finally, it is shown that the choice of insulator material effects the tunneling current, and the effect is greater the thicker the insulating film

A theoretical study of resonant tunneling characteristics in triangular double-barrier diodes

International Nuclear Information System (INIS)

Wang Hongmei; Xu Huaizhe; Zhang Yafei

2006-01-01

Resonant tunneling characteristics of triangular double-barrier diodes have been investigated systematically in this Letter, using Airy function approach to solve time-independent Schroedinger function in triangular double-barrier structures. Originally, the exact analytic expressions of quasi-bound levels and quasi-level lifetime in symmetrical triangular double-barrier structures have been derived within the effective-mass approximation as a function of structure parameters including well width, slope width and barrier height. Based on our derived analytic expressions, numerical results show that quasi-bound levels and quasi-level lifetime vary nearly linearly with the structure parameters except that the second quasi-level lifetime changes parabolically with slope width. Furthermore, according to our improved transmission coefficient of triangular double-barrier structures under external electric field, the current densities of triangular double-barrier diodes with different slope width at 0 K have been calculated numerically. The results show that the N-shaped negative differential resistance behaviors have been observed in current-voltage characteristics and current-voltage characteristics depend on the slope width

Memory-induced acceleration and slowdown of barrier crossing

Science.gov (United States)

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.

Acceptability and Barriers to Uptake of Voluntary Counselling and Testing for HIV amongst Pregnant Women in Nigeria

Directory of Open Access Journals (Sweden)

Bukola Olateju Omolase

2010-08-01

Full Text Available AIM: This study was designed to determine the acceptability of voluntary counselling and testing (VCT for HIV and identify possible barriers to it’s uptake amongst pregnant women in a Nigerian community. METHODS: One hundred and twenty seven consenting pregnant women attending antenatal clinic at Federal Medical Centre, Owo were randomly selected and interviewed by the authors and two trained assistants. The study was conducted between August and October, 2007. The information obtained with the aid of semi –structured questionnaire included their bio data, awareness about VCT and vertical transmission of HIV-AIDS. Other information obtained included acceptability of VCT and barriers to its uptake. RESULT: Majority (85% were aware about vertical transmission of HIV, most (83.5% knew of VCT. They were predominantly willing to accept VCT (77.2% and were ready to recommend VCT to others(76.2%. The main identified barriers to uptake of voluntary counseling were fear of possible outcome (82.7% and risk of divorce (70.9%. CONCLUSION: Most respondents were aware of voluntary counselling and testing for HIV as well as the vertical transmission of HIV. Majority were willing to accept HIV test and recommend same to others. Barriers to uptake of HIV test included fear of possible outcome, lack of felt need, stigmatization and financial constraint. There is need to extend voluntary counselling and testing for HIV to all antenatal patients. [TAF Prev Med Bull 2010; 9(4.000: 309-314

Horizontal transfer of facultative endosymbionts is limited by host relatedness

NARCIS (Netherlands)

Lukasik, P.; Guo, H.; van Asch, M.; Henry, L.; Godfray, H.C.J.; Ferrari, J.

2015-01-01

Heritable microbial symbionts can have important effects on many aspects of their hosts' biology. Acquisition of a novel symbiont strain can provide fitness benefits to the host, with significant ecological and evolutionary consequences. We measured barriers to horizontal transmission by

High Performance Multi Barrier Thermionic Devices

National Research Council Canada - National Science Library

Vashaee, Daryoosh; Shakouri, Ali

2003-01-01

Thermoelectric transport perpendicular to layers in multiple barrier superlattice structures is investigated theoretically in two limiting cases of no lateral momentum scattering and strong scattering...

Photonic limiters with enhanced dynamic range

Science.gov (United States)

Kononchuk, Rodion; Limberopoulos, Nicholaos; Anisimov, Igor; Vitebskiy, Ilya; Chabanov, Andrey

2018-02-01

Optical limiters transmit low intensity input light while blocking input light with the intensity exceeding certain limiting threshold. Conventional passive limiters utilize nonlinear optical materials, which are transparent at low light intensity and turn absorptive at high intensity. Strong nonlinear absorption, though, can result in over- heating and destruction of the limiter. Another problem is that the limiting threshold provided by the available optical material with nonlinear absorption is too high for many applications. To address the above problems, the nonlinear material can be incorporated in a photonic structure with engineered dispersion. At low intensity, the photonic structure can display resonant transmission via localized mode(s), while at high intensity the resonant transmission can disappear, and the entire stack can become highly re ective (not absorptive) within a broad frequency range. In the proposed design, the transition from the resonant transmission at low intensity to nearly total re ectivity at high intensity does not rely on nonlinear absorption; instead, it requires only a modest change in the refractive index of the nonlinear material. The latter implies a dramatic increase in the dynamic range of the limiter. The main idea is to eliminate the high-intensity resonant transmission by decoupling the localized (resonant) modes from the input light, rather than suppressing those modes using nonlinear absorption. Similar approach can be used for light modulation and switching.

Evidence for transmission of bluetongue virus serotype 26 through direct contact.

Directory of Open Access Journals (Sweden)

Carrie Batten

Full Text Available The aim of this study was to assess the mechanisms of transmission of bluetongue virus serotype 26 (BTV-26 in goats. A previous study, which investigated the pathogenicity and infection kinetics of BTV-26 in goats, unexpectedly revealed that one control goat may have been infected through a direct contact transmission route. To investigate the transmission mechanisms of BTV-26 in more detail an experimental infection study was carried out in which three goats were infected with BTV-26, three goats were kept uninfected, but were housed in direct contact with the infected goats, and an additional four goats were kept in indirect contact separated from infected goats by metal gates. This barrier allowed the goats to have occasional face-to-face contact in the same airspace, but feeding, watering, sampling and environmental cleaning was carried out separately. The three experimentally infected goats did not show clinical signs of BTV, however high levels of viral RNA were detected and virus was isolated from their blood. At 21 dpi viral RNA was detected in, and virus was isolated from the blood of the three direct contact goats, which also seroconverted. The four indirect barrier contact goats remained uninfected throughout the duration of the experiment. In order to assess replication in a laboratory model species of Culicoides biting midge, more than 300 Culicoides sonorensis were fed a BTV-26 spiked blood meal and incubated for 7 days. The dissemination of BTV-26 in individual C. sonorensis was inferred from the quantity of virus RNA and indicated that none of the insects processed at day 7 possessed transmissible infections. This study shows that BTV-26 is easily transmitted through direct contact transmission between goats, and the strain does not seem to replicate in C. sonorensis midges using standard incubation conditions.

Contaminant Flux Reduction Barriers for Managing Difficult-to-Treat Source Zones in Unconsolidated Media

Science.gov (United States)

2017-06-20

estimated viscosity of 3-4 cP.  Solutions-IES Novel Silica Gel/Veg-Oil Grout: 5 wt- % of emulsified vegetable oil (EVO), 10 wt-% of sodium...site must have a lower low permeability unit such as a clay to prevent up flow; and a four sided barrier is recommended (three sided barriers are...depth to groundwater (ង ft)  Transmissive zone preferably with an underlying clay layer  Good accessibility to source zone  Availability of

The biological significance of brain barrier mechanisms

DEFF Research Database (Denmark)

Saunders, Norman R; Habgood, Mark D; Møllgård, Kjeld

2016-01-01

, but more work is required to evaluate the method before it can be tried in patients. Overall, our view is that much more fundamental knowledge of barrier mechanisms and development of new experimental methods will be required before drug targeting to the brain is likely to be a successful endeavor......Barrier mechanisms in the brain are important for its normal functioning and development. Stability of the brain's internal environment, particularly with respect to its ionic composition, is a prerequisite for the fundamental basis of its function, namely transmission of nerve impulses....... In addition, the appropriate and controlled supply of a wide range of nutrients such as glucose, amino acids, monocarboxylates, and vitamins is also essential for normal development and function. These are all cellular functions across the interfaces that separate the brain from the rest of the internal...

In vitro prion protein conversion suggests risk of bighorn sheep (Ovis canadensis) to transmissible spongiform encephalopathies

Science.gov (United States)

Johnson, Christopher J.; Morawski, A.R.; Carlson, C.M.; Chang, H.

2013-01-01

Background: Transmissible spongiform encephalopathies (TSEs) affect both domestic sheep (scrapie) and captive and free-ranging cervids (chronic wasting disease; CWD). The geographical range of bighorn sheep (Ovis canadensis; BHS) overlaps with states or provinces that have contained scrapie-positive sheep or goats and areas with present epizootics of CWD in cervids. No TSEs have been documented in BHS, but the susceptibility of this species to TSEs remains unknown. Results: We acquired a library of BHS tissues and found no evidence of preexisting TSEs in these animals. The prion protein gene (Prnp) in all BHS in our library was identical to scrapie-susceptible domestic sheep (A136R 154Q171). Using an in vitro prion protein conversion assay, which has been previously used to assess TSE species barriers and, in our study appears to recollect known species barriers in mice, we assessed the potential transmissibility of TSEs to BHS. As expected based upon Prnp genotype, we observed BHS prion protein conversion by classical scrapie agent and evidence for a species barrier between transmissible mink encephalopathy (TME) and BHS. Interestingly, our data suggest that the species barrier of BHS to white-tailed deer or wapiti CWD agents is likely low. We also used protein misfolding cyclic amplification to confirm that CWD, but not TME, can template prion protein misfolding in A136R 154Q171genotype sheep. Conclusions: Our results indicate the in vitro conversion assay used in our study does mimic the species barrier of mice to the TSE agents that we tested. Based on Prnp genotype and results from conversion assays, BHS are likely to be susceptible to infection by classical scrapie. Despite mismatches in amino acids thought to modulate prion protein conversion, our data indicate that A136R154Q171 genotype sheep prion protein is misfolded by CWD agent, suggesting that these animals could be susceptible to CWD. Further investigation of TSE transmissibility to BHS, including

Barriers to adherence to highly active antiretroviral therapy as expressed by people living with HIV/AIDS.

Science.gov (United States)

Proctor, V E; Tesfa, A; Tompkins, D C

1999-09-01

The primary objective of this study was to gain a clearer understanding of the barriers to adherence to highly active antiretroviral therapy (HAART) faced by people living with HIV/AIDS (PLWHIV/AIDS) on Long Island, New York. Focus group, a qualitative research method, was used to study these barriers. The study was conducted in 1998 on Long Island, NY, at five institutions that provide services to 1700 PLWHIV/AIDS. Five focus groups were conducted with 6 to 13 PLWHIV/AIDS in each group, a total of 39 subjects. PLWHIV/AIDS identified eight common barriers to adherence to HAART. In descending order, the barriers include: (1) frequency and severity of side effects, (2) conflicts with daily routines, (3) dietary requirements, (4) frequency of taking medications, (5) number and dosage of medications, (6) psychosocial factors (i.e., stress, feeling good, and bad news), (7) pharmacy refills, and (8) physiological needs (i.e., sleep, hunger, or thirst). Many factors play a role in the success or failure of HAART, including preexisting drug resistance, drug-drug interactions, and the ability of PLWHIV/AIDS to adhere to a rigid and frequently changing medication regimen. The information gleaned from focus groups is limited in that it may not be generalized to a larger population with any known reliability. However, clinicians sensitive to barriers to adherence to HAART, including those identified by PLWHIV/AIDS in this study, may play a more proactive role in supporting adherence to the medication regimen, increasing the durability of effective viral suppression, decreasing morbidity and mortality, and decreasing the selection and transmission of resistant strains of HIV.

Transmission and reflection in a double potential well: doing it the Bohmian way

NARCIS (Netherlands)

Stomphorst, R.G.

2002-01-01

The Bohm interpretation of quantum mechanics is applied to a transmission and reflection process in a double potential well. We consider a time-dependent periodic wave function and study the particle trajectories. The average time, eventually transmitted particles stay inside the barrier is the

On the nature of barriers to climate change adaptation

NARCIS (Netherlands)

Biesbroek, G.R.; Klostermann, J.E.M.; Termeer, C.J.A.M.; Kabat, P.

2013-01-01

Considerable barriers can emerge in developing and implementing climate change adaptation strategies. Understanding the nature of barriers to adaptation is important so as to find strategic ways of dealing with them. However, our current understanding is limited and highly fragmented across the

Enhanced probabilistic decision analysis for radiological confinement barriers of the International Thermonuclear Experimental Reactor

International Nuclear Information System (INIS)

Golinescu, R.P.; Kazimi, M.S.

1998-01-01

To ensure a defence-in-depth approach, several radiological confinement barriers surrounding a tokamak plant can be employed. A methodology using probabilistic risk assessment (PRA) techniques is a useful tool for evaluating the performance of each confinement barrier within the context of a limited allowable risk of accidental radioactivity releases. Such a methodology was developed and applied to the confinement strategy for the International Thermonuclear Experimental Reactor (ITER). Accident sequence models were constructed for each of the confinement barriers to evaluate the probabilities of events leading to radioactive releases from the corresponding confinement barrier. The current ITER design requirements set radioactive release and dose limits for individual event sequences grouped in categories by frequency. To limit the plant's overall risk and account for event uncertainties in both frequency and consequence, an analytical form for a limit line is derived here as a complementary cumulative frequency (CCF) of radioactive releases to the environment. By comparing the releases from each confinement barrier against the limit line, a decision can be made about the number of barriers required to comply with the design requirements. The first barrier is the vacuum vessel (VV) and the primary heat transfer systems. The second confinement barrier consists of the cryostat vessel (CV) and the heat transfer system vaults. In case the outer building is needed to act as a third barrier for ITER, a decision model using the multi-attribute utility theory was constructed to help the designer choose the best type of tokamak building. The decision model allows for performing sensitivity analysis on relevant parameters and for design features of new options for the ITER tokamak building. (orig.)

Effect of glove occlusion on the skin barrier

DEFF Research Database (Denmark)

Tiedemann, Daniel; Clausen, Maja Lisa; John, Swen Malthe

2016-01-01

that the negative effect of occlusion in itself is limited, and that only extensive and long-term occlusion will cause barrier impairment. However, studies investigating combined effect of occlusion and exposure to soaps/detergents indicate that occlusion significantly enhances the skin barrier damage caused...... by detergents/soaps in a dose-response fashion....

Underwater unidirectional acoustic transmission through a plate with bilateral asymmetric gratings

Science.gov (United States)

Song, Ailing; Chen, Tianning; Wang, Xiaopeng; Xi, Yanhui; Liang, Qingxuan

2018-04-01

In this paper, a novel underwater unidirectional acoustic transmission (UAT) device consisting of a plate with bilateral asymmetric gratings is proposed and numerically investigated. The transmission spectra, the acoustic intensity field distributions, and the displacement field distributions are numerically calculated based on the finite element method. The transmission spectra show that the proposed device exhibits different UAT effects in three bands. The acoustic intensity field distributions demonstrate that the proposed device can realize UAT, which agree well with the transmission spectra. The mechanism is discussed by analyzing the displacement field distributions, and the UAT is attributed to the symmetric mode excited in brass plate. Furthermore, the effects of the lattice constant, the upper slit width, and the lower slit width on bands are discussed. Our design provides a good reference for designing underwater UAT devices and has potential applications in some fields, such as medical ultrasonic devices, acoustic barrier, and noise insulation.

Surface pre-treatment for barrier coatings on polyethylene terephthalate

Science.gov (United States)

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.

Surface pre-treatment for barrier coatings on polyethylene terephthalate

International Nuclear Information System (INIS)

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

2013-01-01

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. (paper)

Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions

International Nuclear Information System (INIS)

Schebaum, Oliver; Drewello, Volker; Auge, Alexander; Reiss, Guenter; Muenzenberg, Markus; Schuhmann, Henning; Seibt, Michael; Thomas, Andy

2011-01-01

Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing temperatures were found to be 65% for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The similar tunnel magnetoresistance ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier. - Research highlights: → Transport properties of Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions. → Tunnel barrier consists of MgO, Al-Ox, or MgO/Al-Ox bilayer systems. → Limitation of TMR-ratio in composite barrier tunnel junctions to Al-Ox values. → Limitation indicates that Al-Ox layer is causing incoherent tunneling.

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

Science.gov (United States)

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.

[On Atomic Nuclear Fusion Processes at Low-Temperatures. An Enhancement of the Probability of Transition through a Potential Barrier Due to the So-Called Barrier Anti-Zeno Effect].

Science.gov (United States)

Namiot, V A

2016-01-01

It is known that in quantum mechanics the act of observing the experiment can affect the experimental findings in some cases. In particular, it happens under the so-called Zeno effect. In this work it is shown that in contrast to the "standard" Zeno-effect where the act of observing a process reduces the probability of its reality, an inverse situation when a particle transmits through a potential barrier (a so-called barrier anti-Zeno effect) can be observed, the observation of the particle essentially increases the probability of its transmission through the barrier. The possibility of using the barrier anti-Zeno effect is discussed to explain paradoxical results of experiments on "cold nuclear fusion" observed in various systems including biological ones. (According to the observers who performed the observations, the energy generation, which could not be explained by any chemical processes, as well as the change in the isotope and even element composition of the studied object may occur in these systems.

Transport spectroscopy and modeling of a clean MOS point contact tunnel barrier

Science.gov (United States)

Shirkhorshidian, Amir; Bishop, Nathaniel; Dominguez, Jason; Grubbs, Robert; Wendt, Joel; Lilly, Michael; Carroll, Malcolm

2014-03-01

We present transport spectroscopy of non-implanted and antimony-implanted tunnel barriers formed in MOS split-gate structures at 4K. The non-implanted barrier shows no signs of resonant behavior while the Sb-implanted barrier shows resonances superimposed on the clean transport. We simulate the transmission through the clean barrier over the entire gate and bias range of the experiment using a phenomenological 1D-tunneling model that includes Fowler-Nordheim tunneling and Schottky barrier lowering to capture effects at high bias. The model is qualitatively similar to experiment when the barrier height has a quadratic dependence in contrast to a linear one, which can be a sign of 2D effects such as confinement perpendicular to the transport direction. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. This work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Barrier tunneling of the loop-nodal semimetal in the hyperhoneycomb lattice

Science.gov (United States)

Guan, Ji-Huan; Zhang, Yan-Yang; Lu, Wei-Er; Xia, Yang; Li, Shu-Shen

2018-05-01

We theoretically investigate the barrier tunneling in the 3D model of the hyperhoneycomb lattice, which is a nodal-line semimetal with a Dirac loop at zero energy. In the presence of a rectangular potential, the scattering amplitudes for different injecting states around the nodal loop are calculated, by using analytical treatments of the effective model, as well as numerical simulations of the tight binding model. In the low energy regime, states with remarkable transmissions are only concentrated in a small range around the loop plane. When the momentum of the injecting electron is coplanar with the nodal loop, nearly perfect transmissions can occur for a large range of injecting azimuthal angles if the potential is not high. For higher potential energies, the transmission shows a resonant oscillation with the potential, but still with peaks being perfect transmissions that do not decay with the potential width. These strikingly robust transports of the loop-nodal semimetal can be approximately explained by a momentum dependent Dirac Hamiltonian.

A comparative study for different shielding material composition and beam geometry applied to PET facilities: simulated transmission curves

OpenAIRE

Hoff, Gabriela; Costa, Paulo Roberto

2013-01-01

The aim of this work is to simulate transmission data for different beam geometry and material composition in order to evaluate the effect of these parameters on transmission curves. The simulations are focused on outgoing spectra for shielding barriers used in PET facilities. The behavior of the transmission was evaluated as a function of the shielding material composition and thickness using Geant4 Monte Carlo code, version 9.2 p 03.The application was benchmarked for barited mortar and com...

Subsurface barrier verification technologies, informal report

International Nuclear Information System (INIS)

Heiser, J.H.

1994-06-01

One of the more promising remediation options available to the DOE waste management community is subsurface barriers. Some of the uses of subsurface barriers include surrounding and/or containing buried waste, as secondary confinement of underground storage tanks, to direct or contain subsurface contaminant plumes and to restrict remediation methods, such as vacuum extraction, to a limited area. To be most effective the barriers should be continuous and depending on use, have few or no breaches. A breach may be formed through numerous pathways including: discontinuous grout application, from joints between panels and from cracking due to grout curing or wet-dry cycling. The ability to verify barrier integrity is valuable to the DOE, EPA, and commercial sector and will be required to gain full public acceptance of subsurface barriers as either primary or secondary confinement at waste sites. It is recognized that no suitable method exists for the verification of an emplaced barrier's integrity. The large size and deep placement of subsurface barriers makes detection of leaks challenging. This becomes magnified if the permissible leakage from the site is low. Detection of small cracks (fractions of an inch) at depths of 100 feet or more has not been possible using existing surface geophysical techniques. Compounding the problem of locating flaws in a barrier is the fact that no placement technology can guarantee the completeness or integrity of the emplaced barrier. This report summarizes several commonly used or promising technologies that have been or may be applied to in-situ barrier continuity verification

Barriers to Strategic Design: A Perspective from China

Directory of Open Access Journals (Sweden)

Sylvia Xihui Liu

Full Text Available Strategic design is a driver for innovation that can lead to sustainable competitive advantage. Over the past two decades, the barriers limiting breakthrough strategic design development have been studied in much detail. However, that research is based on well-developed practices in Europe, where strategic design and innovation capabilities have been nurtured for a long period. Barriers to the adoption of strategic design practices and leadership have seldom been studied in high growth economies in which design and innovation competencies are not yet mature. We examined design-led innovation cases from Chinese design clients and consultancies, and uncovered twelve barriers to strategic design practice and leadership in China. Six of these are similar to hindrances experienced elsewhere, and the other six are unique to this study. We found that in China, certain constraints limiting the adoption of strategic design in practice exist in the environment outside the firm. Based on these findings, we offer suggestions to stakeholders for overcoming the barriers to utilizing design at the strategic level. Key words: Breakthrough innovation, Design-led innovation, Design implementation, Strategic design

Transmission of Information: An Overview.

Science.gov (United States)

Thoma, George R.

1981-01-01

Outlines the basic principles underlying the transmission of information, including analog and digital modulation, limitations to communications, configurations of communications networks, optical fiber cables, and earth satellites. Six references are cited. (FM)

Barriers to global health development: An international quantitative survey.

Directory of Open Access Journals (Sweden)

Bahr Weiss

Full Text Available Global health's goal of reducing low-and-middle-income country versus high-income country health disparities faces complex challenges. Although there have been discussions of barriers, there has not been a broad-based, quantitative survey of such barriers.432 global health professionals were invited via email to participate in an online survey, with 268 (62% participating. The survey assessed participants' (A demographic and global health background, (B perceptions regarding 66 barriers' seriousness, (C detailed ratings of barriers designated most serious, (D potential solutions.Thirty-four (of 66 barriers were seen as moderately or more serious, highlighting the widespread, significant challenges global health development faces. Perceived barrier seriousness differed significantly across domains: Resource Limitations mean = 2.47 (0-4 Likert scale, Priority Selection mean = 2.20, Corruption, Lack of Competence mean = 1.87, Social and Cultural Barriers mean = 1.68. Some system-level predictors showed significant but relatively limited relations. For instance, for Global Health Domain, HIV and Mental Health had higher levels of perceived Social and Cultural Barriers than other GH Domains. Individual-level global health experience predictors had small but significant effects, with seriousness of (a Corruption, Lack of Competence, and (b Priority Selection barriers positively correlated with respondents' level of LMIC-oriented (e.g., weeks/year spent in LMIC but Academic Global Health Achievement (e.g., number of global health publications negatively correlated with overall barrier seriousness.That comparatively few system-level predictors (e.g., Organization Type were significant suggests these barriers may be relatively fundamental at the system-level. Individual-level and system-level effects do have policy implications; e.g., Priority Selection barriers were among the most serious, yet effects on seriousness of how LMIC-oriented a professional

Glial diffusion barriers during aging and pathological states

Czech Academy of Sciences Publication Activity Database

Syková, Eva

2001-01-01

Roč. 132, - (2001), s. 339-363 ISSN 0079-6123 R&D Projects: GA MŠk VS96130; GA ČR GV307/96/K226; GA ČR GV309/97/K048; GA ČR GA309/99/0657; GA ČR GA305/99/0655; GA ČR GA309/00/1430 Institutional research plan: CEZ:AV0Z5039906 Keywords : diffusion barriers volume transmission Subject RIV: FH - Neurology Impact factor: 1.409, year: 2001

Investigating the status and barriers of science laboratory activities ...

African Journals Online (AJOL)

This study aims at investigating the barriers encountered by science teachers in laboratory activities in Rwandan teacher training colleges (TTCs) using questionnaires and interviews. The results confirmed that teachers face barriers like time limitation, material scarcity and lack of improvising skills in their everyday science ...

Multilayer TiC/TiN diffusion barrier films for copper

International Nuclear Information System (INIS)

Yoganand, S.N.; Raghuveer, M.S.; Jagannadham, K.; Wu, L.; Karoui, A.; Rozgonyi, G.

2002-01-01

TiC/TiN thin films deposited by reactive magnetron sputtering on Si (100) substrates were investigated by transmission electron microscopy for microstructure and by deep level transient spectroscopy (DLTS) for diffusion barrier against copper. TiN thin films deposited on Si substrates at a substrate temperature of 600 deg. C were textured, and TiC thin films deposited at the same temperature were polycrystalline. TiC/TiN multilayer films also showed the same characteristics with the formation of an additional interaction layer. The diffusion barrier characteristics of the TiC/TiN/Si were determined by DLTS and the results showed that the films completely prevented diffusion of copper into Si

Reactive diffusion in Sc/Si multilayer X-ray mirrors with CrB2 barrier layers

International Nuclear Information System (INIS)

Pershyn, Y.P.; Zubarev, E.N.; Kondratenko, V.V.; Sevryukova, V.A.; Kurbatova, S.V.

2011-01-01

Processes undergoing in Sc/Si multilayer X-ray mirrors (MXMs) with periods of ∝27 nm and barrier layers of CrB 2 0.3- and 0.7-nm thick within the temperature range of 420-780 K were studied by methods of small-angle X-ray reflectivity (λ=0.154 nm) and cross-sectional transmission electron microscopy. All layers with the exception of Sc ones are amorphous. Barrier layers are stable at least up to a temperature of 625 K and double the activation energy of diffusional intermixing at moderate temperatures. Introduction of barriers improves the thermal stability of Sc/Si MXMs at least by 80 degrees. Diffusion of Si atoms through barrier layers into Sc layers with formation of silicides was shown to be the main degradation mechanism of MXMs. A comparison of the stability for Sc/Si MXMs with different barriers published in the literature is conducted. The ways of further improvement of barrier properties are discussed. (orig.)

Strategies to improve drug delivery across the blood-brain barrier.

Science.gov (United States)

de Boer, Albertus G; Gaillard, Pieter J

2007-01-01

The blood-brain barrier (BBB), together with the blood-cerebrospinal-fluid barrier, protects and regulates the homeostasis of the brain. However, these barriers also limit the transport of small-molecule and, particularly, biopharmaceutical drugs such as proteins, genes and interference RNA to the brain, thereby limiting the treatment of many brain diseases. As a result, various drug delivery and targeting strategies are currently being developed to enhance the transport and distribution of drugs into the brain. In this review, we discuss briefly the biology and physiology of the BBB as the most important barrier for drug transport to the brain and, in more detail, the possibilities for delivering large-molecule drugs, particularly genes, by receptor-mediated nonviral drug delivery to the (human) brain. In addition, the systemic and intracellular pharmacokinetics of nonviral gene delivery, together with targeted brain imaging, are reviewed briefly.

Selected socioeconomic barriers of education in Sub-Saharan Africa

OpenAIRE

Tillová, Petra

2015-01-01

Selected socioeconomic barriers of education in Sub-Saharan Africa Abstract The aim of bachelor thesis is to describe and understand the process of education in Sub-Saharan Africa and analyze components that cause limited access to education. The first part of the thesis describes the process of education in Sub-Saharan Africa using selected indicators. The second main part focuses on the description and possible relations between selected socioeconomic barriers and literacy. Selected barrier...

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

Science.gov (United States)

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.

Compliance with barrier precautions during paediatric trauma resuscitations.

Science.gov (United States)

Kelleher, Deirdre C; Carter, Elizabeth A; Waterhouse, Lauren J; Burd, Randall S

2013-03-01

Barrier precautions protect patients and providers from blood-borne pathogens. Although barrier precaution compliance has been shown to be low among adult trauma teams, it has not been evaluated during paediatric resuscitations in which perceived risk of disease transmission may be low. The purpose of this study was to identify factors associated with compliance with barrier precautions during paediatric trauma resuscitations. Video recordings of resuscitations performed on injured children (compliance with an established policy requiring gowns and gloves. Depending on activation level, trauma team members included up to six physicians, four nurses, and a respiratory therapist. Multivariate logistic regression was used to determine the effect of team role, resuscitation factors, and injury mechanism on barrier precaution compliance. Over twelve weeks, 1138 trauma team members participated in 128 resuscitations (4.7% penetrating injuries, 9.4% highest level activations). Compliance with barrier precautions was 81.3%, with higher compliance seen among roles primarily at the bedside compared to positions not primarily at the bedside (90.7% vs. 65.1%, pcompliance, while surgical attendings (20.8%) had the lowest (prole, increased compliance was observed during resuscitations of patients with penetrating injuries (OR=3.97 [95% CI: 1.35-11.70], p=0.01), during resuscitations triaged to the highest activation level (OR=2.61 [95% CI: 1.34-5.10], p=0.005), and among team members present before patient arrival (OR=4.14 [95% CI: 2.29-7.39], pCompliance with barrier precautions varies by trauma team role. Team members have higher compliance when treating children with penetrating and high acuity injuries and when arriving before the patient. Interventions integrating barrier precautions into the workflow of team members are needed to reduce this variability and improve compliance with universal precautions during paediatric trauma resuscitations. Copyright © 2012 Elsevier

Open access to transmission

International Nuclear Information System (INIS)

Keith, D.M.

1996-01-01

For the past 12 to 15 years, the US electric power and energy industry and its federal regulators have been going through a prolonged exercise leading to opening up the national interconnected transmission grid for all qualified wholesale users to have open and equal access. The debates have been painful in a sense that not all parties - especially some of the transmission system owning utilities - believe that the concept of Open Access is achievable, due to technical constraints on the systems. The present Open Access activity is limited to wholesales transaction under the federal jurisdiction, but several states are either experimenting with or considering retail wheeling. In fact, the FERC - Federal Energy Regulatory Commission - has already expanded its view to embrace retail transmission, if the retail transaction involves the use of the interstate transmission systems which are under FERC's jurisdiction. This paper delves into some of the results of the technical cost and pricing analysis for open access. The statutes and resulting regulations are not addressed herein. (author). 1 fig

Barriers to health care for undocumented immigrants: a literature review

Science.gov (United States)

Hacker, Karen; Anies, Maria; Folb, Barbara L; Zallman, Leah

2015-01-01

With the unprecedented international migration seen in recent years, policies that limit health care access have become prevalent. Barriers to health care for undocumented immigrants go beyond policy and range from financial limitations, to discrimination and fear of deportation. This paper is aimed at reviewing the literature on barriers to health care for undocumented immigrants and identifying strategies that have or could be used to address these barriers. To address study questions, we conducted a literature review of published articles from the last 10 years in PubMed using three main concepts: immigrants, undocumented, and access to health care. The search yielded 341 articles of which 66 met study criteria. With regard to barriers, we identified barriers in the policy arena focused on issues related to law and policy including limitations to access and type of health care. These varied widely across countries but ultimately impacted the type and amount of health care any undocumented immigrant could receive. Within the health system, barriers included bureaucratic obstacles including paperwork and registration systems. The alternative care available (safety net) was generally limited and overwhelmed. Finally, there was evidence of widespread discriminatory practices within the health care system itself. The individual level focused on the immigrant’s fear of deportation, stigma, and lack of capital (both social and financial) to obtain services. Recommendations identified in the papers reviewed included advocating for policy change to increase access to health care for undocumented immigrants, providing novel insurance options, expanding safety net services, training providers to better care for immigrant populations, and educating undocumented immigrants on navigating the system. There are numerous barriers to health care for undocumented immigrants. These vary by country and frequently change. Despite concerns that access to health care attracts

Super Oxygen and Improved Water Vapor Barrier of Polypropylene Film with Polyelectrolyte Multilayer Nanocoatings.

Science.gov (United States)

Song, Yixuan; Tzeng, Ping; Grunlan, Jaime C

2016-06-01

Biaxially oriented polypropylene (BOPP) is widely used in packaging. Although its orientation increases mechanical strength and clarity, BOPP suffers from a high oxygen transmission rate (OTR). Multilayer thin films are deposited from water using layer-by-layer (LbL) assembly. Polyethylenimine (PEI) is combined with either poly(acrylic acid) (PAA) or vermiculite (VMT) clay to impart high oxygen barrier. A 30-bilayer PEI/VMT nanocoating (226 nm thick) improves the OTR of 17.8 μm thick BOPP by more than 30X, rivaling most inorganic coatings. PEI/PAA multilayers achieve comparable barrier with only 12 bilayers due to greater thickness, but these films exhibit increased oxygen permeability at high humidity. The PEI/VMT coatings actually exhibit improved oxygen barrier at high humidity (and also improve moisture barrier by more than 40%). This high barrier BOPP meets the criteria for sensitive food and some electronics packaging applications. Additionally, this water-based coating technology is cost effective and provides an opportunity to produce high barrier polypropylene film on an industrial scale. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A permeability barrier surrounds taste buds in lingual epithelia

Science.gov (United States)

Dando, Robin; Pereira, Elizabeth; Kurian, Mani; Barro-Soria, Rene; Chaudhari, Nirupa

2014-01-01

Epithelial tissues are characterized by specialized cell-cell junctions, typically localized to the apical regions of cells. These junctions are formed by interacting membrane proteins and by cytoskeletal and extracellular matrix components. Within the lingual epithelium, tight junctions join the apical tips of the gustatory sensory cells in taste buds. These junctions constitute a selective barrier that limits penetration of chemosensory stimuli into taste buds (Michlig et al. J Comp Neurol 502: 1003–1011, 2007). We tested the ability of chemical compounds to permeate into sensory end organs in the lingual epithelium. Our findings reveal a robust barrier that surrounds the entire body of taste buds, not limited to the apical tight junctions. This barrier prevents penetration of many, but not all, compounds, whether they are applied topically, injected into the parenchyma of the tongue, or circulating in the blood supply, into taste buds. Enzymatic treatments indicate that this barrier likely includes glycosaminoglycans, as it was disrupted by chondroitinase but, less effectively, by proteases. The barrier surrounding taste buds could also be disrupted by brief treatment of lingual tissue samples with DMSO. Brief exposure of lingual slices to DMSO did not affect the ability of taste buds within the slice to respond to chemical stimulation. The existence of a highly impermeable barrier surrounding taste buds and methods to break through this barrier may be relevant to basic research and to clinical treatments of taste. PMID:25209263

A permeability barrier surrounds taste buds in lingual epithelia.

Science.gov (United States)

Dando, Robin; Pereira, Elizabeth; Kurian, Mani; Barro-Soria, Rene; Chaudhari, Nirupa; Roper, Stephen D

2015-01-01

Epithelial tissues are characterized by specialized cell-cell junctions, typically localized to the apical regions of cells. These junctions are formed by interacting membrane proteins and by cytoskeletal and extracellular matrix components. Within the lingual epithelium, tight junctions join the apical tips of the gustatory sensory cells in taste buds. These junctions constitute a selective barrier that limits penetration of chemosensory stimuli into taste buds (Michlig et al. J Comp Neurol 502: 1003-1011, 2007). We tested the ability of chemical compounds to permeate into sensory end organs in the lingual epithelium. Our findings reveal a robust barrier that surrounds the entire body of taste buds, not limited to the apical tight junctions. This barrier prevents penetration of many, but not all, compounds, whether they are applied topically, injected into the parenchyma of the tongue, or circulating in the blood supply, into taste buds. Enzymatic treatments indicate that this barrier likely includes glycosaminoglycans, as it was disrupted by chondroitinase but, less effectively, by proteases. The barrier surrounding taste buds could also be disrupted by brief treatment of lingual tissue samples with DMSO. Brief exposure of lingual slices to DMSO did not affect the ability of taste buds within the slice to respond to chemical stimulation. The existence of a highly impermeable barrier surrounding taste buds and methods to break through this barrier may be relevant to basic research and to clinical treatments of taste. Copyright © 2015 the American Physiological Society.

Permanent isolation surface barrier development plan

International Nuclear Information System (INIS)

Wing, N.R.

1994-01-01

The exhumation and treatment of wastes may not always be the preferred alternative in the remediation of a waste site. In-place disposal alternatives, under certain circumstances, may be the most desirable alternatives to use in the protection of human health and the environment. The implementation of an in-place disposal alternative will likely require some type of protective covering that will provide long-term isolation of the wastes from the accessible environment. Even if the wastes are exhumed and treated, a long-term barrier may still be needed to adequately dispose of the treated wastes or any remaining waste residuals. Currently, no open-quotes provenclose quotes long-term barrier is available. The Hanford Site Permanent Isolation Surface Barrier Development Program (BDP) was organized to develop the technology needed to provide a long-term surface barrier capability for the Hanford Site. The permanent isolation barrier technology also could be used at other sites. Permanent isolation barriers use engineered layers of natural materials to create an integrated structure with redundant protective features. Drawings of conceptual permanent isolation surface barriers are shown. The natural construction materials (e.g., fine soil, sand, gravel, riprap, asphalt) have been selected to optimize barrier performance and longevity. The objective of current designs is to use natural materials to develop a maintenance-free permanent isolation surface barrier that isolates wastes for a minimum of 1,000 years by limiting water drainage to near-zero amounts; reducing the likelihood of plant, animal, and human intrusion; controlling the exhalation of noxious gases; and minimizing erosion-related problems

Permanent isolation surface barrier development plan

Energy Technology Data Exchange (ETDEWEB)

Wing, N.R.

1994-01-01

The exhumation and treatment of wastes may not always be the preferred alternative in the remediation of a waste site. In-place disposal alternatives, under certain circumstances, may be the most desirable alternatives to use in the protection of human health and the environment. The implementation of an in-place disposal alternative will likely require some type of protective covering that will provide long-term isolation of the wastes from the accessible environment. Even if the wastes are exhumed and treated, a long-term barrier may still be needed to adequately dispose of the treated wastes or any remaining waste residuals. Currently, no {open_quotes}proven{close_quotes} long-term barrier is available. The Hanford Site Permanent Isolation Surface Barrier Development Program (BDP) was organized to develop the technology needed to provide a long-term surface barrier capability for the Hanford Site. The permanent isolation barrier technology also could be used at other sites. Permanent isolation barriers use engineered layers of natural materials to create an integrated structure with redundant protective features. Drawings of conceptual permanent isolation surface barriers are shown. The natural construction materials (e.g., fine soil, sand, gravel, riprap, asphalt) have been selected to optimize barrier performance and longevity. The objective of current designs is to use natural materials to develop a maintenance-free permanent isolation surface barrier that isolates wastes for a minimum of 1,000 years by limiting water drainage to near-zero amounts; reducing the likelihood of plant, animal, and human intrusion; controlling the exhalation of noxious gases; and minimizing erosion-related problems.

Transparent, Ultrahigh-Gas-Barrier Films with a Brick-Mortar-Sand Structure.

Science.gov (United States)

Dou, Yibo; Pan, Ting; Xu, Simin; Yan, Hong; Han, Jingbin; Wei, Min; Evans, David G; Duan, Xue

2015-08-10

Transparent and flexible gas-barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh-gas-barrier films with a brick-mortar-sand structure fabricated by layer-by-layer (LBL) assembly of XAl-layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO2 infilling, denoted as (XAl-LDH/PAA)n-CO2. The near-perfectly parallel orientation of the LDH "brick" creates a long diffusion length to hinder the transmission of gas molecules in the PAA "mortar". Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO2 acts like "sand" to fill the free volume at the organic-inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl-LDH/PAA)n-CO2 film is among the best gas barrier films ever reported. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Barriers to the implementation of programs for the prevention of mother-to-child transmission of HIV: A cross-sectional survey in rural and urban Uganda

Directory of Open Access Journals (Sweden)

Bajunirwe Francis

2005-10-01

Full Text Available Abstract Background Implementation of programs for the prevention of mother-to-child transmission (PMTCT of HIV faces a variety of barriers and challenges. The assessment of these challenges has generally been conducted in large urban health facilities. As programs expand into rural areas, the potential barriers that may be encountered there also need to be assessed. This study examines potential barriers that might affect the acceptability of interventions for PMTCT in rural and urban settings. Results Four hundred and four women at a large urban hospital and three rural clinics that had recently started implementing PMTCT were interviewed. Level of knowledge of MTCT and preference for rapid HIV testing were equally high in both areas, but rural women had a higher tendency to think that they should consult their husbands before testing, with borderline statistical significance (72% vs. 64% p = 0.09. Health facility-based deliveries were significantly lower among mothers in rural areas compared to those in the urban setting. Overall, significant predictors of willingness to test for HIV were post-primary education (OR = 3.1 95% CI 1.2, 7.7 and knowledge about rapid HIV tests (OR = 1.8, 95% CI 1.01, 3.4. The strongest predictor of willingness to accept an HIV test was the woman's perception that her husband would approve of her testing for HIV. Women who thought their husbands would approve were almost six times more likely to report a willingness to be tested compared to those who thought their husbands would not approve (OR = 5.6, 95% CI 2.8, 11.2. Conclusion Lessons learned in large urban hospitals can be generalized to rural facilities, but the lower proportion of facility-based deliveries in rural areas needs to be addressed. Same-day results are likely to ensure high uptake of HIV testing services but male spousal involvement should be considered, particularly for rural areas. Universal Primary Education will support the success of PMTCT

Transmission of equine influenza virus during an outbreak is characterized by frequent mixed infections and loose transmission bottlenecks.

Directory of Open Access Journals (Sweden)

Joseph Hughes

2012-12-01

Full Text Available The ability of influenza A viruses (IAVs to cross species barriers and evade host immunity is a major public health concern. Studies on the phylodynamics of IAVs across different scales - from the individual to the population - are essential for devising effective measures to predict, prevent or contain influenza emergence. Understanding how IAVs spread and evolve during outbreaks is critical for the management of epidemics. Reconstructing the transmission network during a single outbreak by sampling viral genetic data in time and space can generate insights about these processes. Here, we obtained intra-host viral sequence data from horses infected with equine influenza virus (EIV to reconstruct the spread of EIV during a large outbreak. To this end, we analyzed within-host viral populations from sequences covering 90% of the infected yards. By combining gene sequence analyses with epidemiological data, we inferred a plausible transmission network, in turn enabling the comparison of transmission patterns during the course of the outbreak and revealing important epidemiological features that were not apparent using either approach alone. The EIV populations displayed high levels of genetic diversity, and in many cases we observed distinct viral populations containing a dominant variant and a number of related minor variants that were transmitted between infectious horses. In addition, we found evidence of frequent mixed infections and loose transmission bottlenecks in these naturally occurring populations. These frequent mixed infections likely influence the size of epidemics.

Transmission reliability faces future challenges

International Nuclear Information System (INIS)

Beaty, W.

1993-01-01

The recently published Washington International Energy Group's 1993 Electric Utility Outlook states that nearly one-third (31 percent) of U.S. utility executives expect reliability to decrease in the near future. Electric power system stability is crucial to reliability. Stability analysis determines whether a system will stay intact under normal operating conditions, during minor disturbances such as load fluctuations, and during major disturbances when one or more parts of the system fails. All system elements contribute to reliability or the lack of it. However, this report centers on the transmission segment of the electric system. The North American Electric Reliability Council (NERC) says the transmission systems as planned will be adequate over the next 10 years. However, delays in building new lines and increasing demands for transmission services are serious concerns. Reliability concerns exist in the Mid-Continent Area Power Pool and the Mid-America Interconnected Network regions where transmission facilities have not been allowed to be constructed as planned. Portions of the transmission systems in other regions are loaded at or near their limits. NERC further states that utilities must be allowed to complete planned generation and transmission as scheduled. A reliable supply of electricity also depends on adhering to established operating criteria. Factors that could complicate operations include: More interchange schedules resulting from increased transmission services. Increased line loadings in portions of the transmission systems. Proliferation of non-utility generators

Avian influenza virus transmission to mammals.

Science.gov (United States)

Herfst, S; Imai, M; Kawaoka, Y; Fouchier, R A M

2014-01-01

Influenza A viruses cause yearly epidemics and occasional pandemics. In addition, zoonotic influenza A viruses sporadically infect humans and may cause severe respiratory disease and fatalities. Fortunately, most of these viruses do not have the ability to be efficiently spread among humans via aerosols or respiratory droplets (airborne transmission) and to subsequently cause a pandemic. However, adaptation of these zoonotic viruses to humans by mutation or reassortment with human influenza A viruses may result in airborne transmissible viruses with pandemic potential. Although our knowledge of factors that affect mammalian adaptation and transmissibility of influenza viruses is still limited, we are beginning to understand some of the biological traits that drive airborne transmission of influenza viruses among mammals. Increased understanding of the determinants and mechanisms of airborne transmission may aid in assessing the risks posed by avian influenza viruses to human health, and preparedness for such risks. This chapter summarizes recent discoveries on the genetic and phenotypic traits required for avian influenza viruses to become airborne transmissible between mammals.

Evaluation of diffusion barrier and electrical properties of tantalum oxynitride thin films for silver metallization

International Nuclear Information System (INIS)

Misra, E.; Wang, Y.; Theodore, N.D.; Alford, T.L.

2004-01-01

The thermal stability and the diffusion barrier properties of DC reactively sputtered tantalum oxynitride (Ta-O-N) thin films, between silver (Ag) and silicon (Si) p + n diodes were investigated. Both materials characterization (X-ray diffraction analysis, Rutherford backscattering spectrometry (RBS), Auger depth profiling) and electrical measurements (reverse-biased junction leakage current-density) were used to evaluate diffusion barrier properties of the thin films. The leakage current density of p + n diodes with the barrier (Ta-O-N) was approximately four orders of magnitude lower than those without barriers after a 30 min, 400 deg. C back contact anneal. The Ta-O-N barriers were stable up to 500 deg. C, 30 min anneals. However, this was not the case for the 600 deg. C anneal. RBS spectra and cross-sectional transmission electron microscopy of as-deposited and vacuum annealed samples of Ag/barrier (Ta-O-N)/Si indicate the absence of any interfacial interaction between the barrier and substrate (silicon). The failure of the Ta-O-N barriers has been attributed to thermally induced stresses, which cause the thin film to crack at elevated temperatures

Edible moisture barriers: how to assess of their potential and limits in food products shelf-life extension?

Science.gov (United States)

Bourlieu, C; Guillard, V; Vallès-Pamiès, B; Guilbert, S; Gontard, N

2009-05-01

Control of moisture transfer inside composite food products or between food and its environment remains today a major challenge in food preservation. A wide rage of film-forming compounds is now available and facilitates tailoring moisture barriers with optimized functional properties. Despite these huge potentials, a realistic assessment of the film or coating efficacy is still critical. Due to nonlinear water sorption isotherms, water-dependent diffusivities, and variations of physical state, modelling transport phenomena through edible barriers is complex. Water vapor permeability can hardly be considered as an inherent property of films and only gives a relative indication of the barrier efficacy. The formal or mechanistic models reported in literature that describe the influence of testing conditions on the barrier properties of edible films are reviewed and discussed. Most of these models have been validated on a narrow range of conditions. Conversely, few original predictive models based on Fick's Second Law have been developed to assess shelf-life extension of food products including barriers. These models, assuming complex and realistic hypothesis, have been validated in various model foods. The development of nondestructive methods of moisture content measurement should speed up model validation and allow a better comprehension of moisture transfer through edible films.

Human-to-human transmission of Brucella - a systematic review.

Science.gov (United States)

Tuon, Felipe F; Gondolfo, Regina B; Cerchiari, Natacha

2017-05-01

The most common form of transmitting human brucellosis is through contaminated food or direct contact with infected animals. Human-to-human transmission (HHT) has been described as isolated case reports. The aim of this systematic review was to describe all cases of HHT of human brucellosis reported in the medical literature. A literature search was conducted using PubMed, Scopus and Scielo databases using specific search terms published until March 2016. Two investigators independently determined study eligibility. All clinical data were evaluated to construct a table comprising the most important clinical aspects, age, gender, confirmed infection and detection method, transmission method and HHT confirmation and potential source of infection for human transmission. No statistical method was employed in this study. The initial search resulted in 615 publications, but only 35 were included. 45 brucellosis HHT cases were identified. 61% of patients who acquired brucellosis from another human were <1 year old (newborn and breastfeeding). Other cases include sexual transmission, blood transfusion, bone marrow transplantation and aerosol from an infected patient. Most patients (40/45) presented symptoms upon diagnosis. Diagnostic tests included culture, molecular methods and serum testing. Human brucellosis is a disease liable to transmission between humans by placental barrier, lactation, sexual and tissues such as blood and bone marrow. The indication for screening in tissue banks, transplants, blood and pregnancy is not yet established. © 2017 John Wiley & Sons Ltd.

Synthesis of polymer hybrid latex poly(methyl methacrylate-co-butyl acrylate) with organo montmorillonite via miniemulsion polymerization method for barrier paper

Science.gov (United States)

Chanra, J.; Budianto, E.; Soegijono, B.

2018-03-01

Hybrid polymer latex based on combination of organic-inorganic materials, poly(methyl methacrylate-co-butyl acrylate) (PMMBA) and organo-montmorillonite (OMMT) were synthesized via miniemulsion polymerization technique. Modification of montmorillonite (MMT) through the incorporation of myristyltrimethylammonium bromide (MTAB) into the clay’s interlayer spaces were investigated by Small-Angle X-ray Scattering (SAXS), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Transmission Electron Microscopy (TEM). Barrier property and thermal stability of polymer latex film sample were investigated through its Water Vapor Transmission Rate (WVTR) and Thermogravimetric Analysis (TGA). The results indicated that addition of OMMT as filler in PMMBA increased the barrier property and thermal stability of the latex film. Addition of 8.0% (wt) OMMT increased the barrier property and thermal stability. Miniemusion polymerization process with higher addition (>8.0 wt%) of OMMT resulting in high latex viscosity, particle size, and high amount of coagulum. The utilization of this hybrid polymer could benefits paper and board industries to produce high quality barrier paper for food packaging.

Feline APOBEC3s, Barriers to Cross-Species Transmission of FIV?

Directory of Open Access Journals (Sweden)

Zeli Zhang

2018-04-01

Full Text Available The replication of lentiviruses highly depends on host cellular factors, which defines their species-specific tropism. Cellular restriction factors that can inhibit lentiviral replication were recently identified. Feline immunodeficiency virus (FIV was found to be sensitive to several feline cellular restriction factors, such as apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3 (APOBEC3 and tetherin, but FIV evolved to counteract them. Here, we describe the molecular mechanisms by which feline APOBEC3 restriction factors inhibit FIV replication and discuss the molecular interaction of APOBEC3 proteins with the viral antagonizing protein Vif. We speculate that feline APOBEC3 proteins could explain some of the observed FIV cross-species transmissions described in wild Felids.

Feline APOBEC3s, Barriers to Cross-Species Transmission of FIV?

Science.gov (United States)

Zhang, Zeli; Gu, Qinyong; Marino, Daniela; Lee, Kyeong-Lim; Kong, Il-Keun; Häussinger, Dieter; Münk, Carsten

2018-01-01

The replication of lentiviruses highly depends on host cellular factors, which defines their species-specific tropism. Cellular restriction factors that can inhibit lentiviral replication were recently identified. Feline immunodeficiency virus (FIV) was found to be sensitive to several feline cellular restriction factors, such as apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3 (APOBEC3) and tetherin, but FIV evolved to counteract them. Here, we describe the molecular mechanisms by which feline APOBEC3 restriction factors inhibit FIV replication and discuss the molecular interaction of APOBEC3 proteins with the viral antagonizing protein Vif. We speculate that feline APOBEC3 proteins could explain some of the observed FIV cross-species transmissions described in wild Felids. PMID:29642583

Handling transmission limitations in the central power network; Haandtering av overfoeringsbegrensninger

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-12-01

From 1996, the Norwegian and Swedish power markets were joined and a common power exchange was established. The two countries deal differently with bottlenecks (transmission obstruction) in their central networks. This report compares methods for dealing with such bottlenecks and looks at the alternatives. It emphasises the efficiency of pricing and incentives and the possibility of exercising market power under the different methods. Norway uses a method of price regions, or bottleneck tax. Prices are determined for the various price regions so as to keep the power flow below specified bounds. A surplus region is assigned a lower price than a deficit region and the bottleneck tax is the difference in price between two such price regions. The Swedish system is based on a counter purchase concept. In his offer to the spotmarket, the supplier has bound himself to provide a certain amount to the current system price regardless of network limitations. Up-regulation means that he produces more than this amount. Down-regulation means that he is paid for supplying less than he had offered to the current system price. In up- or down-regulation, compensation is given as the difference between the system price and the price on the counter purchase market. The main conclusions are: (1) Counter purchase is unsuitable as the main strategy for Norway. (2) Counter purchase may be suitable with short-lived and unpredicted bottlenecks; price regions may be suitable for long-lasting and predicted bottlenecks. Time is a central factor. (3) Present-day models for bottleneck management in Norway and Sweden do not give the optimum short-term load distribution on the network. In general, the current Norwegian system works fairly well, although it might be worthwhile to consider a system that approaches node pricing. 3 refs., 34 figs., 3 tabs.

A Transmission-Cost-Based Model to Estimate the Amount of Market-Integrable Wind Resources

DEFF Research Database (Denmark)

Morales González, Juan Miguel; Pinson, Pierre; Madsen, Henrik

2012-01-01

are made to share the expenses in transmission derived from their integration, they may see the doors of electricity markets closed for not being competitive enough. This paper presents a model to decide the amount of wind resources that are economically exploitable at a given location from a transmission......In the pursuit of the large-scale integration of wind power production, it is imperative to evaluate plausible frictions among the stochastic nature of wind generation, electricity markets, and the investments in transmission required to accommodate larger amounts of wind. If wind producers......-cost perspective. This model accounts for the uncertain character of wind by using a modeling framework based on stochastic optimization, simulates market barriers by means of a bi-level structure, and considers the financial risk of investments in transmission through the conditional value-at-risk. The major...

European concerted action on offshore wind energy deployment: inventory and analysis of power transmission barriers in eight member states

International Nuclear Information System (INIS)

Woyte, Achim; Gardner, Paul; Snodin, Helen

2007-01-01

The European Concerted Action for Offshore Wind Energy Deployment (COD) was carried out by eight sea-bordering European Union member states, with the objective to remove not explicitly technical barriers to offshore wind energy. Within the COD, an inventory of relevant aspects affecting the grid integration of offshore wind energy on a large scale in the eight countries has been made. Collected data items for this inventory are national plans and prospects for offshore wind energy, information about the transmission system, possibilities for grid connection, aspects of the grid codes, balancing, connection and energy pricing. The comprehensive COD reports were published and presented in October 2005 during the Copenhagen Offshore wind conference. This paper provides a short description of the situation for each country. Thereafter, country-specific information is grouped based on geography and membership in a synchronous zone. Additionally, a view is developed on the desirable facilities for the trans-European exchange of power from large wind farms. Finally, we elaborate overall conclusions in order to arrive at generalized observations, recommendations for policy makers and issues that will emerge in the near future. As a general conclusion, many things need to be done on a technical level in order to integrate large amounts of offshore wind power into our power systems. However, none of these measures is technically unknown. Therefore, the feasibility of integrating large amounts of offshore wind power is mainly a question of finance and hence based on political decisions. (Author)

Noninvasive evaluation of the barrier properties of the skin

Directory of Open Access Journals (Sweden)

Utz S.R.

2014-09-01

Full Text Available Skin as an organ of protection covers the body and accomplishes multiple defensive functions. The intact skin represents a barrier to the uncontrolled loss of water, proteins, and plasma components from the organism. Due to its complex structure, the epidermal barrier with its major component, stratum corneum, is the rate-limiting unit for the penetration of exogenous substances through the skin. The epidermal barrier is not a static structure. The permeability barrier status can be modified by different external and internal factors such as climate, physical stressors, and a number of skin and systemic diseases. Today, different non-invasive approaches are used to monitor the skin barrier physical properties in vivo. The quantification of parameters such as transepidermal water loss, stratum corneum hydration, and skin surface acidity is essential for the integral evaluation of the epidermal barrier status. This paper will allow the readership to get acquainted with the non-invasive, in vivo methods for the investigation of the skin barrier.

Shakeoff Ionization near the Coulomb Barrier Energy

Science.gov (United States)

Sharma, Prashant; Nandi, T.

2017-11-01

We measure the projectile K x-ray spectra as a function of the beam energies around the Coulomb barrier in different collision systems. The energy is scanned in small steps around the barrier aiming to explore the nuclear effects on the elastically scattered projectile ions. The variation of the projectile x-ray energy with the ion-beam energies exhibits an unusual increase in between the interaction barrier and fusion barrier energies. This additional contribution to the projectile ionization can be attributed to the shakeoff of outer-shell electrons of the projectile ions due to the sudden nuclear recoil (˜10-21 sec ) caused by the attractive nuclear potential, which gets switched on near the interaction barrier energy. In the sudden approximation limit, the theoretical shakeoff probability calculation due to the nuclear recoil explains the observed data well. In addition to its fundamental interest, such processes can play a significant role in dark matter detection through the possible mechanism of x-ray emissions, where the weakly interacting massive particle-nucleus elastic scattering can lead to the nuclear-recoil-induced inner-shell vacancy creations. Furthermore, the present work may provide new prospects for atomic physics research at barrier energies as well as provide a novel technique to perform barrier distribution studies for two-body systems.

DETERMINATION OF TRANSMISSION GEAR RATIO IN MECHANICAL PART OF TRACTOR ELECTRO-MECHANICAL TRANSMISSION

Directory of Open Access Journals (Sweden)

Ch. I. Zhdanovich

2016-01-01

Full Text Available A methodology has been developed for selection of gear number and transmission gear ratios in mechanical part of a wheel-type tractor with electro-mechanical transmission containing a propulsion asynchronous electric motor with variablefrequency control. The paper proposes to determine a transmission gear ratio on the basis of the following: provision of wheel torque dependence on tractor speed which is the best one for a traction process and during transfer from one gear to the other; provision of nominal operational mode of the electric motor for all tractor operations where it is working for a long period of time; provision of minimum possible number of gears; complete realization of internal combustion engine power on the tractor wheels at limit operational mode of the electric motor. As a characteristic of the asynchronous electric motor with variable-frequency control contains various portions which can be used either completely or partially due to operating conditions, the gear number is determined in the process of transmission gear ration finding but not prior to this. A wheel torque of the tractor with electro-mechanical transmission can be limited according to the following factors: grip of wheel with supporting surface; maximum power of an internal combustion engine which can be transferred to the wheels and a torque which is developed by a propulsion electric motor. It is not proposed to exceed nominal operational mode of the propulsion electric motor for all the operations of the tractor if it is working for a long period of time because in the case of significant excess of the nominal operational mode of the asynchronous electric motor its rather long operation leads to low efficiency and high losses in power, large heat liberation and consequently requires to develop more complicated system for electric motor cooling. An excess of nominal electric motor torque can be justified for short-term operational modes because in this case

Optical transitions in Ge/SiGe multiple quantum wells with Ge-rich barriers

Science.gov (United States)

Bonfanti, M.; Grilli, E.; Guzzi, M.; Virgilio, M.; Grosso, G.; Chrastina, D.; Isella, G.; von Känel, H.; Neels, A.

2008-07-01

Direct-gap and indirect-gap transitions in strain-compensated Ge/SiGe multiple quantum wells with Ge-rich SiGe barriers have been studied by optical transmission spectroscopy and photoluminescence experiments. An sp3d5s∗ tight-binding model has been adopted to interpret the experimental results. Photoluminescence spectra and their comparison with theoretical calculations prove the existence of type-I band alignment in compressively strained Ge quantum wells grown on relaxed Ge-rich SiGe buffers. The high quality of the transmission spectra opens up other perspectives for application of these structures in near-infrared optical modulators.

Efficient sound barrier calculations with the BEM

DEFF Research Database (Denmark)

Juhl, Peter Møller; Cutanda Henriquez, Vicente

2018-01-01

The Boundary Element Method has been used for calculating the effect of introducing sound barriers for some decades. The method has also been used for optimizing the shape of the barrier and in some cases the effects of introducing sound absorption. However, numerical calculations are still quite...... time consuming and inconvenient to use, which is limiting their use for many practical problems. Moreover, measurements are mostly taken in one-third or full octave bands opposed to the numerical computations at specific frequencies, which then has to be conducted using a fine density in frequencies....... This paper addresses some of the challenges and possible solutions for developing BEM into a more efficient tool for sound barrier calculations....

Transmission of Human Respiratory Syncytial Virus in the Immunocompromised Ferret Model

Science.gov (United States)

de Waal, Leon; Smits, Saskia L.; Veldhuis Kroeze, Edwin J. B.; van Amerongen, Geert; Pohl, Marie O.; Osterhaus, Albert D. M. E.; Stittelaar, Koert J.

2018-01-01

Human respiratory syncytial virus (HRSV) causes substantial morbidity and mortality in vulnerable patients, such as the very young, the elderly, and immunocompromised individuals of any age. Nosocomial transmission of HRSV remains a serious challenge in hospital settings, with intervention strategies largely limited to infection control measures, including isolation of cases, high standards of hand hygiene, cohort nursing, and use of personal protective equipment. No vaccines against HRSV are currently available, and treatment options are largely supportive care and expensive monoclonal antibody or antiviral therapy. The limitations of current animal models for HRSV infection impede the development of new preventive and therapeutic agents, and the assessment of their potential for limiting HRSV transmission, in particular in nosocomial settings. Here, we demonstrate the efficient transmission of HRSV from immunocompromised ferrets to both immunocompromised and immunocompetent contact ferrets, with pathological findings reproducing HRSV pathology in humans. The immunocompromised ferret-HRSV model represents a novel tool for the evaluation of intervention strategies against nosocomial transmission of HRSV. PMID:29301313

The Dragons of Inaction: Psychological Barriers That Limit Climate Change Mitigation and Adaptation

Science.gov (United States)

Gifford, Robert

2011-01-01

Most people think climate change and sustainability are important problems, but too few global citizens engaged in high-greenhouse-gas-emitting behavior are engaged in enough mitigating behavior to stem the increasing flow of greenhouse gases and other environmental problems. Why is that? Structural barriers such as a climate-averse infrastructure…

44 CFR 206.344 - Limitations on Federal expenditures.

Science.gov (United States)

2010-10-01

..., DEPARTMENT OF HOMELAND SECURITY DISASTER ASSISTANCE FEDERAL DISASTER ASSISTANCE Coastal Barrier Resources Act... within the Coastal Barrier Resources System, including but not limited to: (a) Construction... any project to prevent the erosion of, or to otherwise stabilize, any inlet, shoreline, or inshore...

Barriers and Misperceptions Limiting Widespread Use of Intrauterine Contraception Among Canadian Women.

Science.gov (United States)

Hauck, Brian; Costescu, Dustin

2015-07-01

Unintended pregnancy is a major social and public health problem with adverse effects on neonatal and developmental outcomes, as well as maternal health and wellbeing. Traditionally, family planning policies have focused on increasing contraceptive uptake in non-users; however, rates of non-use are low in many developed nations. A high proportion of unintended pregnancies are attributable to contraceptive failure, particularly when using barrier and short-acting hormonal contraceptives. Intrauterine contraceptive devices (IUCDs) are highly effective and have been shown to reduce unintended pregnancy rates. Despite this, global utilization rates are low, and IUCD uptake in Canada has been particularly low. In this review we explore why IUCDs are not more widely used, and specifically focus on barriers and misperceptions that may influence IUCD uptake, particularly in Canada. We reviewed relevant articles published in English between 1990 and 2014, through searches of PubMed and Medline, including primary studies of any design containing information on the knowledge and attitudes of health care providers and women. Providing education to care providers, women, and policy makers may help overcome misperceptions about the use of IUCDs, and may facilitate greater use. Increased support from federal and provincial health programs may also encourage the use of IUCDs in Canadian women, and help to reduce unintended pregnancy rates.

On the generalized Hartman effect for symmetric double-barrier point potentials

International Nuclear Information System (INIS)

Lee, Molly A; Manzoni, Luiz A; Nyquist, Erik A; Lunardi, José T

2015-01-01

We consider the scattering of a non-relativistic particle by a symmetrical arrangement of two identical barriers in one-dimension, with the barriers given by the well-known four-parameter family of point interactions. We calculate the phase time and the stationary Salecker-Wigner-Peres clock time for the particular cases of a double δ and a double δ' barrier and investigate the off-resonance behavior of these time scales in the limit of opaque barriers, addressing the question of emergence of the generalized Hartman effect

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

Science.gov (United States)

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.

The effect of pH on hydrolysis, cross-linking and barrier properties of starch barriers containing citric acid.

Science.gov (United States)

Olsson, Erik; Menzel, Carolin; Johansson, Caisa; Andersson, Roger; Koch, Kristine; Järnström, Lars

2013-11-06

Citric acid cross-linking of starch for e.g. food packaging applications has been intensely studied during the last decade as a method of producing water-insensitive renewable barrier coatings. We managed to improve a starch formulation containing citric acid as cross-linking agent for industrial paper coating applications by adjusting the pH of the starch solution. The described starch formulations exhibited both cross-linking of starch by citric acid as well as satisfactory barrier properties, e.g. fairly low OTR values at 50% RH that are comparable with EVOH. Furthermore, it has been shown that barrier properties of coated papers with different solution pH were correlated to molecular changes in starch showing both hydrolysis and cross-linking of starch molecules in the presence of citric acid. Hydrolysis was shown to be almost completely hindered at solution pH≥4 at curing temperatures≤105 °C and at pH≥5 at curing temperatures≤150 °C, whereas cross-linking still occurred to some extent at pH≤6.5 and drying temperatures as low as 70 °C. Coated papers showed a minimum in water vapor transmission rate at pH 4 of the starch coating solution, corresponding to the point where hydrolysis was effectively hindered but where a significant degree of cross-linking still occurred. Copyright © 2013 Elsevier Ltd. All rights reserved.

Richards Barrier LA Reference Design Feature Evaluation

International Nuclear Information System (INIS)

N.E. Kramer

1999-01-01

The Richards Barrier is one of the design features of the repository to be considered for the License Application (LA), Richards was a soil scientist who first described the diversion of moisture between two materials with different hydrologic properties. In this report, a Richards Barrier is a special type of backfill with a fine-grained material (such as sand) overlaying a coarse-grained material (such as gravel). Water that enters an emplacement drift will first encounter the fine-grained material and be transported around the coarse-grained material covering the waste package, thus protecting the waste package from contact with most of the groundwater. The objective of this report is to discuss the benefits and liabilities to the repository by the inclusion of a Richards Barrier type backfill in emplacement drifts. The Richards Barrier can act as a barrier to water flow, can reduce the waste package material dissolution rate, limit mobilization of the radionuclides, and can provide structural protection for the waste package. The scope of this report is to: (1) Analyze the behavior of barrier materials following the intrusion of groundwater for influxes of 1 to 300 mm per year. The report will demonstrate diversion of groundwater intrusions into the barrier over an extended time period when seismic activity and consolidation may cause the potential for liquefaction and settlement of the Richards Barrier. (2) Review the thermal effects of the Richards Barrier on material behavior. (3) Analyze the effect of rockfall on the performance of the Richards Barrier and the depth of the barrier required to protect waste packages under the barrier. (4) Review radiological and heating conditions on placement of multiple layers of the barrier. Subsurface Nuclear Safety personnel will perform calculations to determine the radiation reduction-time relationship and shielding capacity of the barrier. (5) Evaluate the effects of ventilation on cooling of emplacement drifts and

Hanford Permanent Isolation Barrier Program: Asphalt technology test plan

Energy Technology Data Exchange (ETDEWEB)

Freeman, H.D.; Romine, R.A.

1994-05-01

The Hanford Permanent Isolation Barriers use engineered layers of natural materials to create an integrated structure with backup protective features. The objective of current designs is to develop a maintenance-free permanent barrier that isolates wastes for a minimum of 1000 years by limiting water drainage to near-zero amounts. Asphalt is being used as an impermeable water diversion layer to provide a redundant layer within the overall barrier design. Data on asphalt barrier properties in a buried environment are not available for the required 100-year time frame. The purpose of this test plan is to outline the activities planned to obtain data with which to estimate performance of the asphalt layers.

Hanford Permanent Isolation Barrier Program: Asphalt technology test plan

International Nuclear Information System (INIS)

Freeman, H.D.; Romine, R.A.

1994-05-01

The Hanford Permanent Isolation Barriers use engineered layers of natural materials to create an integrated structure with backup protective features. The objective of current designs is to develop a maintenance-free permanent barrier that isolates wastes for a minimum of 1000 years by limiting water drainage to near-zero amounts. Asphalt is being used as an impermeable water diversion layer to provide a redundant layer within the overall barrier design. Data on asphalt barrier properties in a buried environment are not available for the required 100-year time frame. The purpose of this test plan is to outline the activities planned to obtain data with which to estimate performance of the asphalt layers

Expertise, Time, Money, Mentoring, and Reward: Systemic Barriers That Limit Education Researcher Productivity-Proceedings From the AAMC GEA Workshop.

Science.gov (United States)

Yarris, Lalena M; Juve, Amy Miller; Artino, Anthony R; Sullivan, Gail M; Rougas, Steven; Joyce, Barbara; Eva, Kevin

2014-09-01

To further evolve in an evidence-based fashion, medical education needs to develop and evaluate new practices for teaching, learning, and assessment. However, educators face barriers in designing, conducting, and publishing education research. To explore the barriers medical educators face in formulating, conducting, and publishing high-quality medical education research, and to identify strategies for overcoming them. A consensus workshop was held November 5, 2013, at the Association of American Medical Colleges annual meeting. A working group of education research experts and educators completed a preconference literature review focusing on barriers to education research. During the workshop, consensus-based and small group techniques were used to refine the broad themes into content categories. Attendees then ranked the most important barriers and strategies for overcoming them with the highest potential impact. Barriers participants faced in conducting quality education research included lack of (1) expertise, (2) time, (3) funding, (4) mentorship, and (5) reward. The strategy considered most effective in overcoming these barriers involved building communities of education researchers for collaboration and networking, and advocating for education researchers' interests. Other suggestions included trying to secure increased funding opportunities, developing mentoring programs, and encouraging mechanisms to ensure protected time. Barriers to education research productivity clearly exist. Many appear to result from feelings of isolation that may be overcome with systemic efforts to develop and enable communities of practice across institutions. Finally, the theme of "reward" is novel and complex and may have implications for education research productivity.

Quantum Limits of Space-to-Ground Optical Communications

Science.gov (United States)

Hemmati, H.; Dolinar, S.

2012-01-01

For a pure loss channel, the ultimate capacity can be achieved with classical coherent states (i.e., ideal laser light): (1) Capacity-achieving receiver (measurement) is yet to be determined. (2) Heterodyne detection approaches the ultimate capacity at high mean photon numbers. (3) Photon-counting approaches the ultimate capacity at low mean photon numbers. A number of current technology limits drive the achievable performance of free-space communication links. Approaching fundamental limits in the bandwidth-limited regime: (1) Heterodyne detection with high-order coherent-state modulation approaches ultimate limits. SOA improvements to laser phase noise, adaptive optics systems for atmospheric transmission would help. (2) High-order intensity modulation and photon-counting can approach heterodyne detection within approximately a factor of 2. This may have advantages over coherent detection in the presence of turbulence. Approaching fundamental limits in the photon-limited regime (1) Low-duty cycle binary coherent-state modulation (OOK, PPM) approaches ultimate limits. SOA improvements to laser extinction ratio, receiver dark noise, jitter, and blocking would help. (2) In some link geometries (near field links) number-state transmission could improve over coherent-state transmission

Disease management programs: barriers and benefits.

Science.gov (United States)

Magnezi, Racheli; Kaufman, Galit; Ziv, Arnona; Kalter-Leibovici, Ofra; Reuveni, Haim

2013-04-01

The healthcare system in Israel faces difficulties similar to those of most industrialized countries, including limited resources, a growing chronically ill population, and demand for high quality care. Disease management programs (DMPs) for patients with a chronic illness aim to alleviate some of these problems, primarily by improving patient self-management skills and quality of care. This study surveyed the opinions of senior healthcare administrators regarding barriers, benefits, and support for implementing DMPs. Cross-sectional survey. A 21-item questionnaire was self-completed by 87 of 105 (83%) healthcare administrators included in the study. Participants were 65.5% male and 47% physicians, 25.3% nurses, 17.3% administrators, and 10.3% other healthcare professionals. The main perceived benefit of DMPs among all respondents was improving quality of care. Other benefits noted were better contact with patients (81.6%) and better compliance with treatment (75.9%). Efficient long-term utilization of system resources was perceived as a benefit by only 58.6%. The main perceived barriers to implementing DMPs were lack of budgetary resources (69%) and increased time required versus financial compensation received (63.2%). The benefits of DMPs were patient oriented; barriers were perceived as financial and limiting professional autonomy. Information regarding long-term benefits (better patient outcomes) that ultimately provide better value for the system versus short-term barriers (increased costs and expenditures of time without compensation) might encourage the implementation of DMPs in countries faced with a growing population of patients with at least 1 chronic illness.

On the front line of HIV virological monitoring: barriers and facilitators from a provider perspective in resource-limited settings.

Science.gov (United States)

Rutstein, S E; Golin, C E; Wheeler, S B; Kamwendo, D; Hosseinipour, M C; Weinberger, M; Miller, W C; Biddle, A K; Soko, A; Mkandawire, M; Mwenda, R; Sarr, A; Gupta, S; Mataya, R

2016-01-01

Scale-up of viral load (VL) monitoring for HIV-infected patients on antiretroviral therapy (ART) is a priority in many resource-limited settings, and ART providers are critical to effective program implementation. We explored provider-perceived barriers and facilitators of VL monitoring. We interviewed all providers (n = 17) engaged in a public health evaluation of dried blood spots for VL monitoring at five ART clinics in Malawi. All ART clinics were housed within district hospitals. We grouped themes at patient, provider, facility, system, and policy levels. Providers emphasized their desire for improved ART monitoring strategies, and frustration in response to restrictive policies for determining which patients were eligible to receive VL monitoring. Although many providers pled for expansion of monitoring to include all persons on ART, regardless of time on ART, the most salient provider-perceived barrier to VL monitoring implementation was the pressure of work associated with monitoring activities. The work burden was exacerbated by inefficient data management systems, highlighting a critical interaction between provider-, facility-, and system-level factors. Lack of integration between laboratory and clinical systems complicated the process for alerting providers when results were available, and these communication gaps were intensified by poor facility connectivity. Centralized second-line ART distribution was also noted as a barrier: providers reported that the time and expenses required for patients to collect second-line ART frequently obstructed referral. However, provider empowerment emerged as an unexpected facilitator of VL monitoring. For many providers, this was the first time they used an objective marker of ART response to guide clinical management. Providers' knowledge of a patient's virological status increased confidence in adherence counseling and clinical decision-making. Results from our study provide unique insight into provider

Recent Advances in Gas Barrier Thin Films via Layer-by-Layer Assembly of Polymers and Platelets.

Science.gov (United States)

Priolo, Morgan A; Holder, Kevin M; Guin, Tyler; Grunlan, Jaime C

2015-05-01

Layer-by-layer (LbL) assembly has emerged as the leading non-vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide-based barrier films. This Feature Article is a mini-review of LbL-based multilayer thin films with a 'nanobrick wall' microstructure comprising polymeric mortar and nano-platelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water-based thin films exhibit oxygen transmission rates below 5 × 10(-3) cm(3) m(-2) day(-1) atm(-1) and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake-filled polymers are briefly reviewed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Information barriers

International Nuclear Information System (INIS)

Fuller, J.L.; Wolford, J.

2001-01-01

measurement equipment, that the system is functioning properly and does not incorporate any hidden features (or 'switches') that allows the host to pass out-of-spec items. Authentication of information barrier systems is an extremely important concept to consider in designing and assembling these types of inspection systems. There are a limited set of straightforward approaches to authenticate such systems, when applied in conjunction with open and cooperative system design and fabrication, that will provide a high degree of confidence to both host and inspector that the system will prevent the release of classified information and yet still inspect items in a manner consistent with the objectives of an inspection agreement. These principles have been outlined in this paper, along with areas where additional studies would be helpful. (author)

Development of large high-voltage pressure insulators for the Princeton TFTR [Tokamak Fusion Test Reactor] flexible transmission lines

International Nuclear Information System (INIS)

Scalise, D.T.; Fong, E.; Haughian, J.; Prechter, R.

1986-10-01

Specially formulated insulator materials with improved strength and high-voltage properties were developed and used for critical components of the flexible transmission lines to the TFTR neutral beam ion sources. These critical components are plates which support central conductors as they exit the high-voltage power supply and enter the ion source enclosure. Each plate acts both as a high-voltage insulator and as a pressure barrier to the SF 6 insulating gas. The original plate was made of commercial glass-epoxy laminate which limited the plate voltage capacity. The newly developed insulator is made of specially-formulated cycloalphatic Di-epoxide whose isotropic properties exhibit increased arc resistance. It is cast in one piece with skirts which greatly increase the breakdown voltage. This paper discusses the design, fabrication and testing of the new insulator

Super conducting fault current limiter and inductor design

International Nuclear Information System (INIS)

Rogers, J.; Boenig, H.; Chowdhuri, P.; Schermer, R.; Weldon, D.; Wollan, J.

1983-01-01

A superconducting fault current limiter (SFCL) that uses a biased superconducting inductor in a diode or thyristor bridge circuit was analyzed for transmission systems in 69, 138, and 230 rms kV utility transmission systems. The limiter was evaluated for costs with all components--superconducting coil, diode and/or SCR power electronics, high voltage insulation, high voltage bushings and vapor cooled leads, dewar, and refrigerator--included. A design was undertaken for the superconducting cable and coils for both diode and SCR 69 kV limiter circuits

Hanford prototype-barrier status report: FY 1995

International Nuclear Information System (INIS)

Gee, G.W.; Ward, A.L.; Gilmore, B.G.; Ligotke, M.W.; Link, S.O.

1995-11-01

Surface barriers (or covers) have been proposed for use at the Hanford Site as a means to isolate certain waste sites that, for reasons of cost or worker safety or both, may not be exhumed. Surface barriers are intende to isolated the wastes from the accessible environment and to provide long-term protection to future populations that might use the Hanford Site. Currently, no ''proven'' long-term barrier system is available. For this reason, the Hanford Site Permanent Isolation Surface-Barrier Development Program (BDP) was organized to develop the technology needed to provide long-term surface barrier capability for the Hanford Site for the US Department of Energy (DOE). Designs have been proposed to meet the most stringent needs for long-term waste disposal. The objective of the current barrier design is to use natural materials to develop a protective barrier system that isolates wastes for at least 1000 years by limiting water, plant, animal, and human intrusion; and minimizing erosion. The design criteria for water drainage has been set at 0.5 mm/yr. While other design criteria are more qualitative, it is clear that waste isolation for an extended time is the prime objective of the design. Constructibility and performance. are issues that can be tested and dealt with by evaluating prototype designs prior to extensive construction and deployment of covers for waste sites at Hanford

Fabrication of magnetic tunnel junctions with a single-crystalline LiF tunnel barrier

Science.gov (United States)

Krishna Narayananellore, Sai; Doko, Naoki; Matsuo, Norihiro; Saito, Hidekazu; Yuasa, Shinji

2018-04-01

We fabricated Fe/LiF/Fe magnetic tunnel junctions (MTJs) by molecular beam epitaxy on a MgO(001) substrate, where LiF is an insulating tunnel barrier with the same crystal structure as MgO (rock-salt type). Crystallographical studies such as transmission electron microscopy and nanobeam electron diffraction observations revealed that the LiF tunnel barrier is single-crystalline and has a LiF(001)[100] ∥ bottom Fe(001)[110] crystal orientation, which is constructed in the same manner as MgO(001) on Fe(001). Also, the in-plane lattice mismatch between the LiF tunnel barrier and the Fe bottom electrode was estimated to be small (about 0.5%). Despite such advantages for the tunnel barrier of the MTJ, the observed tunnel magnetoresistance (MR) ratio was low (˜6% at 20 K) and showed a significant decrease with increasing temperature (˜1% at room temperature). The results imply that indirect tunneling and/or thermally excited carriers in the LiF tunnel barrier, in which the current basically is not spin-polarized, play a major role in electrical transport in the MTJ.

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

Science.gov (United States)

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.

Reactions with weakly bound nuclei at near barrier energies

International Nuclear Information System (INIS)

Nanal, Vandana

2014-01-01

In reactions with weakly bound nuclei, the effect of breakup on fusion process has attracted much attention in recent years. The experimental study shows that breakup channel leads to suppression of complete fusion at above barrier energies due to loss of flux. The fusion barrier distribution can provide a further insight into understanding the influence of coupling to the breakup channels. Similar information could be obtained from the elastic and quasielastic (QEL) scattering because of the conservation of the reaction flux (i.e. R+T= 1), where R is the reflection probability and T is the transmission probability. Thus, quasi-elastic scattering at backward angles is the counterpart of the fusion process and it is expected that the barrier distributions extracted from two processes, namely, QEL and fusion should be similar. While this is true for tightly bound reaction systems, in reactions involving weakly bound projectiles significant differences have been observed for QEL barrier distributions with and without inclusion of breakup processes. This talk will present the recent results for fusion and quasi-elastic scattering in "6","7Li + "1"9"7Au system. Developmental efforts towards a momentum achromatic separator, MARIE, to extract projectile-like secondary ion beams following the reactions of heavy-ion beams from superconducting LINAC booster at Mumbai will also be presented. (author)

Community voices: barriers and opportunities for programmes to successfully prevent vertical transmission of HIV identified through consultations among people living with HIV.

Science.gov (United States)

Anderson, Ginna; Caswell, Georgina; Edwards, Olive; Hsieh, Amy; Hull, Beri; Mallouris, Christoforos; Mason, Naisiadet; Nöstlinger, Christiana

2012-07-11

In 2010, two global networks of people living with HIV, the International Community of Women Living with HIV (ICW Global) and the Global Network of People living with HIV (GNP+) were invited to review a draft strategic framework for the global scale up of prevention of vertical transmission (PVT) through the primary prevention of HIV and the prevention of unintended pregnancies among women living with HIV. In order to ensure recommendations were based on expressed needs of people living with HIV, GNP+ and ICW Global undertook a consultation amongst people living with HIV which highlighted both facilitators and barriers to prevention services. This commentary summarizes the results of that consultation. The consultation was comprised of an online consultation (moderated chat-forum with 36 participants from 16 countries), an anonymous online e-survey (601 respondents from 58 countries), and focus-group discussions with people living with HIV in Jamaica (27 participants). The consultation highlighted the discrepancies across regions with respect to access to essential packages of PVT services. However, the consultation participants also identified common barriers to access, including a lack of trustworthy sources of information, service providers' attitudes, and gender-based violence. In addition, participant responses revealed common facilitators of access, including quality counselling on reproductive choices, male involvement, and decentralized services. The consultation provided some understanding and insight into the participants' experiences with and recommendations for PVT strategies. Participants agreed that successful, comprehensive PVT programming require greater efforts to both prevent primary HIV infection among young women and girls and, in particular, targeted efforts to ensure that women living with HIV and their partners are supported to avoid unintended pregnancies and to have safe, healthy pregnancies instead. In addition to providing the insights

Design and performance evaluation of a 1000-year evapotranspiration-capillary surface barrier

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhuanfang Fred; Strickland, Christopher E.; Link, Steven O.

2017-02-01

Surface barrier technology is used to isolate radioactive waste and to reduce or eliminate recharge water to the waste zone for 1000 years or longer. However, the design and evaluation of such a barrier is challenging because of the extremely long design life. The Prototype Hanford Barrier (PHB) was designed as a 1000-year barrier with pre-determined design and performance objectives and demonstrated in field from 1994 to present. The barrier was tested to evaluate surface-barrier design and performance at the field scale under conditions of enhanced and natural precipitation and of no vegetation. The monitoring data demonstrate that the barrier satisfied nearly all key objectives. The PHB far exceeded the Resource Conservation and Recovery Act criteria, functioned in Hanford’s semiarid climate, limited drainage to well below the 0.5 mm yr-1 performance criterion, limited runoff, and minimized erosion. Given the two-decade record of successful performance and consideration of all the processes and mechanisms that could degrade the stability and hydrology in the future, the results suggest the PHB is very likely to perform for its 1000-year design life. This conclusion is based on two assumptions: (1) the exposed subgrade receives protection against erosion and (2) institutional controls prevent inadvertent human activity at the barrier. The PHB design can serve as the base for site-specific barriers over waste sites containing underground nuclear waste, uranium mine tailings, and hazardous mine waste.

Barriers to and drivers for energy efficiency in the Swedish foundry industry

International Nuclear Information System (INIS)

Rohdin, Patrik; Thollander, Patrik; Solding, Petter

2007-01-01

Despite the need for increased industrial energy efficiency, studies indicate that cost-efficient energy conservation measures are not always implemented, explained by the existence of barriers to energy efficiency. This paper investigates the existence of different barriers to and driving forces for the implementation of energy efficiency measures in the energy intensive Swedish foundry industry. The overall results from a questionnaire show that limited access to capital constitutes by far the largest barrier to energy efficiency according to the respondents. A comparison between group-owned and privately owned foundries shows that, except for limited access to capital, they face different high-ranked barriers. While barriers within group owned companies are more related to organizational problems, barriers within private foundries are more related to information problems. This study also found that energy consultants or other actors working with energy issues in foundries are of major importance in overcoming the largest barriers, as the foundries consider them trustworthy. They may thus help the foundries overcome organizational problems such as lack of sub-metering and lack of budget funds by quantifying potential energy efficiency investments. The two, by far, most important drivers were found to be people with real ambition and long-term energy strategies

Hearing in the matter of an application by Erie Shores Wind Farm Limited Partnership for an Order granting leave to construct transmission facilities to connect a wind farm to the transmission facilities of Hydro One Network Inc.[In the matter of the Ontario Energy Board Act, 1998, S.O. 1998, c. 15, Schedule B

Energy Technology Data Exchange (ETDEWEB)

Kaiser, G.; Vlahos, P.; Betts, B.

2005-06-20

This document presents the transcripts of an Ontario Energy Board hearing regarding an application filed by Erie Shores Wind Farm Limited to construct transmission facilities that will connect Erie Shores' wind farm on the north shore of Lake Erie to the transmission facilities of Hydro One Network. This document presents the examinations by representatives of the Board Counsel, Erie Shores Wind Farm Limited Partnership, Hydro One Networks Inc., Ontario's Independent Electricity System Operator and intervenors. Erie Shores is a limited partnership between AIM PowerGen Corporation and Clean Power Income Fund. The proposed wind farm is to be located along the north shore of Lake Erie, covering about 14,000 acres of farmland in the townships of Bayham, Malahide and Norfolk County. It consists of 66 wind turbines with a net output of 99 MW. The construction of transmission facilities would involve the construction of a new transformer station with a 34.5/115 kV transformer, a capacitor bank, switch gear, and space for a future transformer. It would also include a transmission line from the Port Burwell transmission station to Hydro One's circuits at Cranberry Junction near Tillsonburg. Erie Shores also proposes to construct 27 km of the transmission line within the existing Otter Valley utility corridor, 3 km along the active Canadian Pacific Rail corridor, and over certain private lands located south of Tillsonburg Junction. Erie Shores was one of the successful bidders that has entered into a 20-year renewable energy supply contract with the Ontario Electricity Financial Corporation. The Board considers that the project is in the public interest and granted approval for the project, subject to certain conditions regarding communications, monitoring and reporting requirements. 2 refs., 1 appendix.

Rumor propagation with heterogeneous transmission in social networks

Science.gov (United States)

Vega-Oliveros, Didier A.; Costa, Luciano da F.; Rodrigues, Francisco A.

2017-02-01

Rumor models consider that information transmission occurs with the same probability between each pair of nodes. However, this assumption is not observed in social networks, which contain influential spreaders. To overcome this limitation, we assume that central individuals have a higher capacity to convince their neighbors than peripheral subjects. From extensive numerical simulations we find that spreading is improved in scale-free networks when the transmission probability is proportional to the PageRank, degree, and betweenness centrality. In addition, the results suggest that spreading can be controlled by adjusting the transmission probabilities of the most central nodes. Our results provide a conceptual framework for understanding the interplay between rumor propagation and heterogeneous transmission in social networks.

HVDC transmission preferred to 750 kV ac

Energy Technology Data Exchange (ETDEWEB)

1965-06-25

It is unlikely that there will be a need in Britain for ac transmission voltages above 400 kV. But with the growing load density in the large conurbations with no possibility of local generation, high voltage dc transmission is likely to be most useful. It was concluded that by 1971 the 400 kV supergrid would be nation-wide and 6,200 circuit miles should be in service. With the expansion to accommodate the large new generating stations, the 400 kV supergrid would become an extremely high power distribution network rather than a transmission system. A higher voltage for transmission is outside the rational limit of speculation for a country the size of Britain.

Strategic disruption of nuclear pores structure, integrity and barrier for nuclear apoptosis.

Science.gov (United States)

Shahin, Victor

2017-08-01

Apoptosis is a programmed cell death playing key roles in physiology and pathophysiology of multi cellular organisms. Its nuclear manifestation requires transmission of the death signals across the nuclear pore complexes (NPCs). In strategic sequential steps apoptotic factors disrupt NPCs structure, integrity and barrier ultimately leading to nuclear breakdown. The present review reflects on these steps. Copyright © 2017 Elsevier Ltd. All rights reserved.

Signal Propagation Delay as a Barrier to Control Applications in WAN

DEFF Research Database (Denmark)

Knudsen, Thomas Phillip; Patel, A.; Pedersen, Jens Myrup

With the advent in WAN of delay sensitive technical applications, such as remote control, signal propagation delay becomes a major problem. The extent of the problem is analysed by lower bounding the delay in relation to different transmission media. Requirements for reliability and bandwidth are...... are considered. The consequences of this bounding for communication network planning and provisioning are discussed in relation to mitigating the effects of signal propagation delay as a barrier to the penetration of control applications into WAN......With the advent in WAN of delay sensitive technical applications, such as remote control, signal propagation delay becomes a major problem. The extent of the problem is analysed by lower bounding the delay in relation to different transmission media. Requirements for reliability and bandwidth...

Almost there: transmission routes of bacterial symbionts between trophic levels.

Directory of Open Access Journals (Sweden)

Elad Chiel

Full Text Available Many intracellular microbial symbionts of arthropods are strictly vertically transmitted and manipulate their host's reproduction in ways that enhance their own transmission. Rare horizontal transmission events are nonetheless necessary for symbiont spread to novel host lineages. Horizontal transmission has been mostly inferred from phylogenetic studies but the mechanisms of spread are still largely a mystery. Here, we investigated transmission of two distantly related bacterial symbionts--Rickettsia and Hamiltonella--from their host, the sweet potato whitefly, Bemisia tabaci, to three species of whitefly parasitoids: Eretmocerus emiratus, Eretmocerus eremicus and Encarsia pergandiella. We also examined the potential for vertical transmission of these whitefly symbionts between parasitoid generations. Using florescence in situ hybridization (FISH and transmission electron microscopy we found that Rickettsia invades Eretmocerus larvae during development in a Rickettsia-infected host, persists in adults and in females, reaches the ovaries. However, Rickettsia does not appear to penetrate the oocytes, but instead is localized in the follicular epithelial cells only. Consequently, Rickettsia is not vertically transmitted in Eretmocerus wasps, a result supported by diagnostic polymerase chain reaction (PCR. In contrast, Rickettsia proved to be merely transient in the digestive tract of Encarsia and was excreted with the meconia before wasp pupation. Adults of all three parasitoid species frequently acquired Rickettsia via contact with infected whiteflies, most likely by feeding on the host hemolymph (host feeding, but the rate of infection declined sharply within a few days of wasps being removed from infected whiteflies. In contrast with Rickettsia, Hamiltonella did not establish in any of the parasitoids tested, and none of the parasitoids acquired Hamiltonella by host feeding. This study demonstrates potential routes and barriers to horizontal

Optimization of a tunneling barrier in magnetic tunneling junction by tilted-plasma oxidation

International Nuclear Information System (INIS)

Nam, C.H.; Shim, Heejae; Kim, K.S.; Cho, B.K.

2004-01-01

Oxidation of an AlO x insulating barrier in a magnetic tunneling junction (MTJ) was carried out by a tilted-plasma oxidation method. It was found that the tilted-plasma oxidation induced a gradual change in the extent of oxidation of an insulating layer, which consequently led to a gradual change in the tunneling magnetoresistance (TMR) and specific junction resistance (RA) of the MTJ. We found a linear relation in the TMR versus RA curve with positive and negative slopes for less- and overoxidized junctions, respectively, and a parabolic relation for optimally oxidized junctions. The crossover in the TMR versus RA curves provides an effective and useful way to optimize (and monitor) the oxidation condition of a tunneling barrier in MTJs especially of a tunneling barrier less than 10 A thick. The tunneling junctions were also investigated after thermal annealing at various temperatures. The observations after thermal annealing were found to be consistent with transmission electrons microscopy images and a scenario of the partial formation of an additional ultrathin tunneling barrier at the top surface of the bottom magnetic layer

Barriers to Participation in Parenting Programs: The Relationship between Parenting Stress, Perceived Barriers, and Program Completion.

Science.gov (United States)

Rostad, Whitney L; Moreland, Angela D; Valle, Linda Anne; Chaffin, Mark J

2018-04-01

Families experiencing child maltreatment or risk factors for child maltreatment often receive referrals to interventions focused on changing parenting practices. Compliance with specific parenting programs can be challenging as many of the stressors that place families at-risk may also interfere with program participation. Because families may receive limited benefit from programs they do not fully receive, it is critical to understand the relationship between parenting stress and barriers to program completion. We used structural equation modeling to examine the relationship among parenting stress, perceived barriers to program participation, and program completion in two datasets involving low-income parents. Data were collected at two time points from a sample of parents involved with child welfare services and a sample of parents considered at-risk of future involvement (total study n = 803). Direct paths from parenting stress at time 1 to barriers to participation and parenting stress at time 2, and from parenting stress at time 2 to program completion were significant. Interestingly, increased barriers to participation were related to increased parenting stress at time 2, and greater parenting stress was related to increased program completion. Results suggest that with increasing levels of parenting stress, parents have an increased likelihood of completing the program. Assessing and addressing the influence of perceived barriers and parenting stress on program participation may decrease the likelihood of treatment attrition.

Defining the Interaction of HIV-1 with the Mucosal Barriers of the Female Reproductive Tract

Science.gov (United States)

Carias, Ann M.; McCoombe, Scott; McRaven, Michael; Anderson, Meegan; Galloway, Nicole; Vandergrift, Nathan; Fought, Angela J.; Lurain, John; Duplantis, Maurice; Veazey, Ronald S.

2013-01-01

Worldwide, HIV-1 infects millions of people annually, the majority of whom are women. To establish infection in the female reproductive tract (FRT), HIV-1 in male ejaculate must overcome numerous innate and adaptive immune factors, traverse the genital epithelium, and establish infection in underlying CD4+ target cells. How the virus achieves this remains poorly defined. By utilizing a new technique, we define how HIV-1 interacts with different tissues of the FRT using human cervical explants and in vivo exposure in the rhesus macaque vaginal transmission model. Despite previous claims of the squamous epithelium being an efficient barrier to virus entry, we reveal that HIV-1 can penetrate both intact columnar and squamous epithelial barriers to depths where the virus can encounter potential target cells. In the squamous epithelium, we identify virus entry occurring through diffusive percolation, penetrating areas where cell junctions are absent. In the columnar epithelium, we illustrate that virus does not transverse barriers as well as previously thought due to mucus impediment. We also show a statistically significant correlation between the viral load of inocula and the ability of HIV-1 to pervade the squamous barrier. Overall, our results suggest a diffusive percolation mechanism for the initial events of HIV-1 entry. With these data, we also mathematically extrapolate the number of HIV-1 particles that penetrate the mucosa per coital act, providing a biological description of the mechanism for HIV-1 transmission during the acute and chronic stages of infection. PMID:23966398

Nurse-patient communication barriers in Iranian nursing.

Science.gov (United States)

Anoosheh, M; Zarkhah, S; Faghihzadeh, S; Vaismoradi, M

2009-06-01

Providing effective communication with patients is an essential aspect of nursing care. Understanding the barriers that inhibit nurse-patient communication can provide an opportunity to eliminate them. To investigate nurse-patient and environment-related communication barriers perceived by patients and nurses in Iranian nursing. A descriptive survey was carried out in three randomly selected educational hospitals in a large urban city in Iran. Data were collected by questionnaire; the study sample consisted of 61 patients and 75 nurses. Participants were asked to rate the importance of each communication barriers item. Finally, data were analysed using descriptive statistics, and to compare the perceived importance of communication barriers between patients and nurses, item means were calculated and the t-test for independent samples was applied. Similarities and differences between the two groups were identified. According to nurses' views, 'heavy nursing workload', 'hard nursing tasks' and 'lack of welfare facilities for nurses' were the main communication barriers. From patients' views, 'unfamiliarity of nurses with dialect', 'having contagious diseases' and 'sex differences between nurses and patients' were determined as the main communication barriers. The shared communication barriers were 'age difference', 'social class difference' and 'having contagious diseases'. It can be concluded that nursing managers and healthcare system planners should focus on eliminating or modifying the barriers stated by the two groups, particularly the shared ones. It is suggested that understanding the cultural aspects of nurse-patient communication barriers in various contexts can help nurses. The study relied on self-report by a limited sample of nurses and patients. The responses should now be tested by a larger sample and then by empirical research into actual practice in order to test whether the nurses' and patients' perceived ideas of communication barriers are

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

Science.gov (United States)

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.

Recent Transmission of Tuberculosis - United States, 2011-2014.

Directory of Open Access Journals (Sweden)

Courtney M Yuen

Full Text Available Tuberculosis is an infectious disease that may result from recent transmission or from an infection acquired many years in the past; there is no diagnostic test to distinguish the two causes. Cases resulting from recent transmission are particularly concerning from a public health standpoint. To describe recent tuberculosis transmission in the United States, we used a field-validated plausible source-case method to estimate cases likely resulting from recent transmission during January 2011-September 2014. We classified cases as resulting from either limited or extensive recent transmission based on transmission cluster size. We used logistic regression to analyze patient characteristics associated with recent transmission. Of 26,586 genotyped cases, 14% were attributable to recent transmission, 39% of which were attributable to extensive recent transmission. The burden of cases attributed to recent transmission was geographically heterogeneous and poorly predicted by tuberculosis incidence. Extensive recent transmission was positively associated with American Indian/Alaska Native (adjusted prevalence ratio [aPR] = 3.6 (95% confidence interval [CI] 2.9-4.4, Native Hawaiian/Pacific Islander (aPR = 3.2, 95% CI 2.3-4.5, and black (aPR = 3.0, 95% CI 2.6-3.5 race, and homelessness (aPR = 2.3, 95% CI 2.0-2.5. Extensive recent transmission was negatively associated with foreign birth (aPR = 0.2, 95% CI 0.2-0.2. Tuberculosis control efforts should prioritize reducing transmission among higher-risk populations.

Application of Face-Gear Drives in Helicopter Transmissions

Science.gov (United States)

Litvin, F. L.; Wang, J.-C.; Bossler, R. B., Jr.; Chen, Y.-J. D.; Heath, G.; Lewicki, D. G.

1992-01-01

The use of face gears in helicopter transmissions was explored. A light-weight, split torque transmission design utilizing face gears was described. Face-gear design and geometry were investigated. Topics included tooth generation, limiting inner and outer radii, tooth contact analysis, contact ratio, gear eccentricity, and structural stiffness. Design charts were developed to determine minimum and maximum face-gear inner and outer radii. Analytical study of transmission error showed face-gear drives were relatively insensitive to gear misalignment, but tooth contact was affected by misalignment. A method of localizing bearing contact to compensate for misalignment was explored. The proper choice of shaft support stiffness enabled good load sharing in the split torque transmission design. Face-gear experimental studies were also included and the feasibility of face gears in high-speed, high-load applications such as helicopter transmissions was demonstrated.

Sprache als Barriere (Language as a Barrier)

Science.gov (United States)

Mattheier, Klaus

1974-01-01

The concept of language barrier has its derivations in the fields of dialectology, sociology and psychology. In contemporary usage however, the concept has two meanings i.e. regional-cultural barrier and socio-cultural barrier. (Text is in German.) (DS)

Accelerated high fidelity prion amplification within and across prion species barriers.

Directory of Open Access Journals (Sweden)

Kristi M Green

2008-08-01

Full Text Available Experimental obstacles have impeded our ability to study prion transmission within and, more particularly, between species. Here, we used cervid prion protein expressed in brain extracts of transgenic mice, referred to as Tg(CerPrP, as a substrate for in vitro generation of chronic wasting disease (CWD prions by protein misfolding cyclic amplification (PMCA. Characterization of this infectivity in Tg(CerPrP mice demonstrated that serial PMCA resulted in the high fidelity amplification of CWD prions with apparently unaltered properties. Using similar methods to amplify mouse RML prions and characterize the resulting novel cervid prions, we show that serial PMCA abrogated a transmission barrier that required several hundred days of adaptation and subsequent stabilization in Tg(CerPrP mice. While both approaches produced cervid prions with characteristics distinct from CWD, the subtly different properties of the resulting individual prion isolates indicated that adaptation of mouse RML prions generated multiple strains following inter-species transmission. Our studies demonstrate that combined transgenic mouse and PMCA approaches not only expedite intra- and inter-species prion transmission, but also provide a facile means of generating and characterizing novel prion strains.

Clusters of incompatible genotypes evolve with limited dispersal

Science.gov (United States)

Erin L. Landguth; Norman A. Johnson; Samuel A. Cushman

2015-01-01

Theoretical and empirical studies have shown heterogeneous selection to be the primary driver for the evolution of reproductively isolated genotypes in the absence of geographic barriers. Here, we ask whether limited dispersal alone can lead to the evolution of reproductively isolated genotypes despite the absence of any geographic barriers or heterogeneous...

Analysis of Power Network for Line Reactance Variation to Improve Total Transmission Capacity

Directory of Open Access Journals (Sweden)

Ikram Ullah

2016-11-01

Full Text Available The increasing growth in power demand and the penetration of renewable distributed generations in competitive electricity market demands large and flexible capacity from the transmission grid to reduce transmission bottlenecks. The bottlenecks cause transmission congestion, reliability problems, restrict competition, and limit the maximum dispatch of low cost generations in the network. The electricity system requires efficient utilization of the current transmission capability to improve the Available Transfer Capability (ATC. To improve the ATC, power flow among the lines can be managed by using Flexible AC Transmission System (FACTS devices as power flow controllers, which alter the parameters of power lines. It is important to place FACTS devices on suitable lines to vary the reactance for improving Total Transmission Capacity (TTC of the network and provide flexibility in the power flow. In this paper a transmission network is analyzed based on line parameters variation to improve TTC of the interconnected system. Lines are selected for placing FACTS devices based on real power flow Performance Index (PI sensitivity factors. TTC is computed using the Repeated Power Flow (RPF method using the constraints of lines thermal limits, bus voltage limits and generator limits. The reactance of suitable lines, selected on the basis of PI sensitivity factors are changed to divert the power flow to other lines with enough transfer capacity available. The improvement of TTC using line reactance variation is demonstrated with three IEEE test systems with multi-area networks. The results show the variation of the selected lines’ reactance in improving TTC for all the test networks with defined contingency cases.

Market and policy barriers to energy storage deployment :

Energy Technology Data Exchange (ETDEWEB)

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

2013-09-01

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

Metamaterial polarization converter analysis: limits of performance

DEFF Research Database (Denmark)

Markovich, Dmitry L.; Andryieuski, Andrei; Zalkovskij, Maksim

2013-01-01

and a single layer with a ground plane can have 100 % polarization conversion efficiency. We tested our conclusions numerically reaching the designated limits of efficiency using a simple metamaterial design. Our general analysis provides useful guidelines for the metamaterial polarization converter design......In this paper, we analyze the theoretical limits of a metamaterial-based converter with orthogonal linear eigenpolarizations that allow linear-to-elliptical polarization transformation with any desired ellipticity and ellipse orientation. We employ the transmission line approach providing a needed...... level of the design generalization. Our analysis reveals that the maximal conversion efficiency for transmission through a single metamaterial layer is 50 %, while the realistic reflection configuration can give the conversion efficiency up to 90 %. We show that a double layer transmission converter...

Performance of engineered barriers for low-level waste

International Nuclear Information System (INIS)

Taplin, D.; Claridge, F.B.

1987-09-01

Geotechnical Resources Ltd., in association with Komex Consultants Ltd., was retained to collect, synthesize and evaluate the available information on the long term performance of engineered barriers for low-level radioactive wastes disposed in Canada. Literature was researched from Canadian, United States and European sources. A variety of barrier materials were assessed in the study and included natural clays, concrete and cement, metals, bentonite-sand admixes, bitumen and bituminous admixes, soil cement and polymeric membranes. The generalized geological and geotechnical conditions encountered within the soil and rock host media currently under consideration for disposal sites in southern Ontario were also summarized. Both internal barriers, or buffers, to immobilize the waste material and reduce radionuclide mobility, as well as external barriers to limit the migration of contaminants were examined. Microbial activities within the waste forms were analyzed, including cellulose degradation, methanogenesis and bicarbonate and organic reactions. Microbial interactions with the various engineered barrier materials under consideration were also assessed. Finally, the anticipated long term performances of the respective barrier materials under consideration were evaluated, along with the general suitability of the geological host media being proposed for disposal sites

Barriers to health care for undocumented immigrants: a literature review

Directory of Open Access Journals (Sweden)

Hacker K

2015-10-01

Full Text Available Karen Hacker,1,2 Maria Anies,2 Barbara L Folb,2,3 Leah Zallman4–6 1Allegheny County Health Department, Pittsburgh, PA, USA; 2Graduate School of Public Health, 3Health Sciences Library System, University of Pittsburgh, Pittsburgh, PA, USA; 4Institute for Community Health, Cambridge, MA, USA; 5Cambridge Health Alliance, Cambridge, MA, USA; 6Harvard School of Medicine, Boston, MA, USA Abstract: With the unprecedented international migration seen in recent years, policies that limit health care access have become prevalent. Barriers to health care for undocumented immigrants go beyond policy and range from financial limitations, to discrimination and fear of deportation. This paper is aimed at reviewing the literature on barriers to health care for undocumented immigrants and identifying strategies that have or could be used to address these barriers. To address study questions, we conducted a literature review of published articles from the last 10 years in PubMed using three main concepts: immigrants, undocumented, and access to health care. The search yielded 341 articles of which 66 met study criteria. With regard to barriers, we identified barriers in the policy arena focused on issues related to law and policy including limitations to access and type of health care. These varied widely across countries but ultimately impacted the type and amount of health care any undocumented immigrant could receive. Within the health system, barriers included bureaucratic obstacles including paperwork and registration systems. The alternative care available (safety net was generally limited and overwhelmed. Finally, there was evidence of widespread discriminatory practices within the health care system itself. The individual level focused on the immigrant’s fear of deportation, stigma, and lack of capital (both social and financial to obtain services. Recommendations identified in the papers reviewed included advocating for policy change to increase

Diffusion barrier performances of thin Mo, Mo-N and Mo/Mo-N films between Cu and Si

International Nuclear Information System (INIS)

Song Shuangxi; Liu Yuzhang; Mao Dali; Ling Huiqin; Li Ming

2005-01-01

In this work, we have studied the diffusion barrier performances of Mo, Mo-N and Mo/Mo-N metallization layers deposited by sputtering Mo in Ar/N 2 atmospheres, respectively. Samples were subsequently annealed at different temperatures ranging from 400 to 800 deg C in vacuum condition. The film properties and their suitability as diffusion barriers and protective coatings in silicon devices were characterized using four-point probe measurement, X-ray diffractometry, scanning electron microscopy, Auger electron spectroscopy and transmission electron microscopy analyses. Experimental results revealed that the Mo (20 nm)/Mo-N (30 nm) layer was able to prevent the diffusion reaction between Cu and Si substrate after being annealed at 600 deg C for 30 min. The adhesion between layers and the content of N atoms are the key parameters to improve the properties of Mo-based barrier materials. The Mo layer interposed between Cu and Mo-N diluted the high nitrogen concentration of the barrier and so enhanced the barrier performances

Centralized Coordination of Load Shedding & Protection System of Transmission Lines

DEFF Research Database (Denmark)

Hoseinzadeh, Bakhtyar; Bak, Claus Leth

2018-01-01

The power system integrity is vulnerable to thermal limit of transmission lines due to overloading and consequently activation of their protection devices following severe contingencies. In this paper, the loading rate of transmission lines is monitored online and is considered in the centralized......, over current protection....

GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Tseng, H. Y.; Yang, W. C.; Lee, P. Y.; Lin, C. W.; Cheng, Kai-Yuan; Hsieh, K. C.; Cheng, K. Y., E-mail: kycheng@ee.nthu.edu.tw [Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Hsu, C.-H. [Division of Scientific Research, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China)

2016-08-22

GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.

Numerical Modelling of Building Vibrations due to Railway Traffic: Analysis of the Mitigation Capacity of a Wave Barrier

Directory of Open Access Journals (Sweden)

Fran Ribes-Llario

2017-01-01

Full Text Available Transmission of train-induced vibrations to buildings located in the vicinity of the track is one of the main negative externalities of railway transport, since both human comfort and the adequate functioning of sensitive equipment may be compromised. In this paper, a 3D FEM model is presented and validated with data from a real track stretch near Barcelona, Spain. Furthermore, a case study is analyzed as an application of the model, in order to evaluate the propagation and transmission of vibrations induced by the passage of a suburban train to a nearby 3-storey building. As a main outcome, vertical vibrations in the foundation slab are found to be maximum in the corners, while horizontal vibrations keep constant along the edges. The propagation within the building structure is also studied, concluding that vibrations invariably increase in their propagation upwards the building. Moreover, the mitigation capacity of a wave barrier acting as a source isolation is assessed by comparing vibration levels registered in several points of the building structure with and without the barrier. In this regard, the wave barrier is found to effectively reduce vibration in both the soil and the structure.

Patterns of measles transmission among airplane travelers.

Science.gov (United States)

Edelson, Paul J

2012-09-01

With advanced air handling systems on modern aircraft and the high level of measles immunity in many countries, measles infection in air travelers may be considered a low-risk event. However, introduction of measles into countries where transmission has been controlled or eliminated can have substantial consequences both for the use of public health resources and for those still susceptible. In an effort to balance the relatively low likelihood of disease transmission among largely immune travelers and the risk to the public health of the occurrence of secondary cases resulting from importations, criteria in the United States for contact investigations for measles exposures consider contacts to be those passengers who are seated within 2 rows of the index case. However, recent work has shown that cabin air flow may not be as reliable a barrier to the spread of measles virus as previously believed. Along with these new studies, several reports have described measles developing after travel in passengers seated some distance from the index case. To understand better the potential for measles virus to spread on an airplane, reports of apparent secondary cases occurring in co-travelers of passengers with infectious cases of measles were reviewed. Medline™ was searched for articles in all languages from 1946 to week 1 of March 2012, using the search terms "measles [human] or rubeola" and ("aircraft" or "airplane" or "aeroplane" or "aviation" or "travel" or "traveler" or "traveller"); 45 citations were returned. Embase™ was searched from 1988 to week 11 2012, using the same search strategy; 95 citations were returned. Papers were included in this review if they reported secondary cases of measles occurring in persons traveling on an airplane on which a person or persons with measles also flew, and which included the seating location of both the index case(s) and the secondary case(s) on the plane. Nine reports, including 13 index cases and 23 apparent secondary cases

Vector independent transmission of the vector-borne bluetongue virus.

Science.gov (United States)

van der Sluijs, Mirjam Tineke Willemijn; de Smit, Abraham J; Moormann, Rob J M

2016-01-01

Bluetongue is an economically important disease of ruminants. The causative agent, Bluetongue virus (BTV), is mainly transmitted by insect vectors. This review focuses on vector-free BTV transmission, and its epizootic and economic consequences. Vector-free transmission can either be vertical, from dam to fetus, or horizontal via direct contract. For several BTV-serotypes, vertical (transplacental) transmission has been described, resulting in severe congenital malformations. Transplacental transmission had been mainly associated with live vaccine strains. Yet, the European BTV-8 strain demonstrated a high incidence of transplacental transmission in natural circumstances. The relevance of transplacental transmission for the epizootiology is considered limited, especially in enzootic areas. However, transplacental transmission can have a substantial economic impact due to the loss of progeny. Inactivated vaccines have demonstrated to prevent transplacental transmission. Vector-free horizontal transmission has also been demonstrated. Since direct horizontal transmission requires close contact of animals, it is considered only relevant for within-farm spreading of BTV. The genetic determinants which enable vector-free transmission are present in virus strains circulating in the field. More research into the genetic changes which enable vector-free transmission is essential to better evaluate the risks associated with outbreaks of new BTV serotypes and to design more appropriate control measures.

Antibacterial, mechanical, and barrier properties of sago starch film incorporated with Betel leaves extract.

Science.gov (United States)

Nouri, Leila; Mohammadi Nafchi, Abdorreza

2014-05-01

The antimicrobial, mechanical and barrier properties and light transmission of sago starch film incorporated with different percentage of Betel leaf extract (5%, 10%, 20%, and 30%) were evaluated. With regard to mechanical properties, tensile strength decreased when the percentage of extract increased. Elongation at break (%) and seal strength (N/m) increased with increasing percentage of extract from 5% to 20%, while decreased for films containing 30% extract due to heterogeneity of films in this percentage. With regard to barrier properties, water vapour and oxygen barrier properties decreased in all samples when percentage of the extract increased. Antimicrobial activity of all the films increased against both Gram positive and Gram negative bacteria as percentage of Betel leaf extract increased, except for Psuedomonas aeruginosa, which was not susceptible at any percentage of the extract. Copyright © 2014 Elsevier B.V. All rights reserved.

Karakteristik Traksi dan Kinerja Transmisi pada Sistem Gear Transmission dan Gearless Transmission

Directory of Open Access Journals (Sweden)

A.A.I.A. Sri Komaladewi

2015-07-01

transform out of the engine torque to the torque that occurs at the drivewheels. Transmission ratio affects the amount of torque that can be transmitted, while the numberof speed levels affect the fineness (smoothness transmission process and the transformation ofpower in the transmission system. Traction characteristics and transmission performance vehiclesare tested on Toyota Kijang Inova 2012. Modeling traction performance is realized with simulationmethods. Traction characteristics of the vehicle transmission system is analyzed at several levels ofspeed to overcome various obstacles along the vehicle operating conditions. Preliminarycalculations of the gear ratio between the highest and lowest can be found using GeometryProgression law. Ratio of last gear (the lowest is determined by the maximum speed of the vehicleto be designed. While the maximum traction or maximum incline determine the initial gear ratio (thehighest. Then the ratio between the two limits is made such that the resulting traction vehicle canapproach the ideal characteristics. Modification of the transmission gear ratio from the standardcondition yield traction needs which is smaller in the same speed, whether the installation of 4levels, 5 levels, more even at 6 levels of speed.The distance of traction curve between 2 of gearratio indicates the amount of unused traction. From the graph of transmission performance indicatethat the more the level of transmission, the less traction is wasted. Traction characteristicsapproaching the its ideal characteristics at gearless transmission system with 10 levels.Keywords: drive train, transmission ratio, traction performance, geometric progression, gearlesstransmission

Design and performance evaluation of a 1000-year evapotranspiration-capillary surface barrier.

Science.gov (United States)

Zhang, Zhuanfang Fred; Strickland, Christopher E; Link, Steven O

2017-02-01

Surface barrier technology is used to isolate radioactive waste and to reduce or eliminate recharge water to the waste zone for 1000 years or longer. However, the design and evaluation of such a barrier is challenging because of the extremely long design life. After establishing a set of design and performance objectives, a package of design solutions was developed for 1000-year surface barriers over nuclear waste sites. The Prototype Hanford Barrier (PHB) was then constructed in 1994 in the field over an existing waste site as a demonstration. The barrier was tested to evaluate surface-barrier design and performance at the field scale under conditions of enhanced and natural precipitation and of no vegetation. The monitoring data demonstrate that the barrier satisfied nearly all objectives in the past two decades. The PHB far exceeded the Resource Conservation and Recovery Act criteria, functioned in Hanford's semiarid climate, limited drainage to well below the 0.5 mm yr -1 performance criterion, limited runoff, and minimized erosion and bio-intrusion. Given the two-decade record of successful performance and consideration of the processes and mechanisms that could affect barrier stability and hydrology in the future, the results suggest the PHB is very likely to perform for its 1000-year design life. This conclusion is based on two assumptions: (1) the exposed subgrade receives protection against erosion and (2) institutional controls prevent inadvertent human activity at the barrier. The PHB design can serve as the basis for site-specific barriers over waste sites containing underground nuclear waste, uranium mine tailings, and hazardous mine waste. Copyright © 2016 Elsevier Ltd. All rights reserved.

Relativistic tunneling through two successive barriers

International Nuclear Information System (INIS)

Lunardi, Jose T.; Manzoni, Luiz A.

2007-01-01

We study the relativistic quantum mechanical problem of a Dirac particle tunneling through two successive electrostatic barriers. Our aim is to study the emergence of the so-called generalized Hartman effect, an effect observed in the context of nonrelativistic tunneling as well as in its counterparts and which is often associated with the possibility of superluminal velocities in the tunneling process. We discuss the behavior of both the phase (or group) tunneling time and the dwell time, and show that in the limit of opaque barriers the relativistic theory also allows the emergence of the generalized Hartman effect. We compare our results with the nonrelativistic ones and discuss their interpretation

Robust ultra-thin RuMo alloy film as a seedless Cu diffusion barrier

International Nuclear Information System (INIS)

Hsu, Kuo-Chung; Perng, Dung-Ching; Wang, Yi-Chun

2012-01-01

Highlights: ► A 5 nm-thick Mo added Ru film has been investigated as a Cu diffusion barrier layer. ► RuMo film provides over 175 °C improvement in thermal stability than that of pure Ru layer. ► The 5 nm-thick RuMo film shows excellent barrier performance against Cu diffusion upon 725 °C. - Abstract: This study investigated the properties of 5 nm-thick RuMo film as a Cu diffusion barrier. The sheet resistance variation and X-ray diffraction patterns show that the RuMo alloy film has excellent barrier performance and that it is stable upon annealing at 725 °C against Cu. The transmission electron microscopy micrograph and diffraction patterns show that the RuMo film is an amorphous-like structure, whereas pure Ru film is a nano-crystalline structure. The elements’ depth profiles, analyzed by X-ray photoelectron spectroscopy, indicate no inter-diffusion behavior between the Cu and Si layer, even annealing at 700 °C. Lower leakage current has been achieved from the Cu/barrier/insulator/Si test structure using RuMo film as the barrier layer. A 5 nm ultrathin RuMo film provided two orders of magnitude improvement in leakage current and also exhibited a 175 °C improvement in thermal stability than that of the pure Ru film. It is a potential candidate as a seedless Cu diffusion barrier for advanced Cu interconnects.

Barrier mechanisms in the Drosophila blood-brain barrier

Directory of Open Access Journals (Sweden)

Samantha Jane Hindle

2014-12-01

Full Text Available The invertebrate blood-brain barrier field is growing at a rapid pace and, in recent years, studies have shown a physiologic and molecular complexity that has begun to rival its vertebrate counterpart. Novel mechanisms of paracellular barrier maintenance through GPCR signaling were the first demonstrations of the complex adaptive mechanisms of barrier physiology. Building upon this work, the integrity of the invertebrate blood-brain barrier has recently been shown to require coordinated function of all layers of the compound barrier structure, analogous to signaling between the layers of the vertebrate neurovascular unit. These findings strengthen the notion that many blood-brain barrier mechanisms are conserved between vertebrates and invertebrates, and suggest that novel findings in invertebrate model organisms will have a significant impact on the understanding of vertebrate BBB functions. In this vein, important roles in coordinating localized and systemic signaling to dictate organism development and growth are beginning to show how the blood-brain barrier can govern whole animal physiologies. This includes novel functions of blood-brain barrier gap junctions in orchestrating synchronized neuroblast proliferation, and of blood-brain barrier secreted antagonists of insulin receptor signaling. These advancements and others are pushing the field forward in exciting new directions. In this review, we provide a synopsis of invertebrate blood-brain barrier anatomy and physiology, with a focus on insights from the past 5 years, and highlight important areas for future study.

Transmission line capital costs

International Nuclear Information System (INIS)

Hughes, K.R.; Brown, D.R.

1995-05-01

The displacement or deferral of conventional AC transmission line installation is a key benefit associated with several technologies being developed with the support of the U.S. Department of Energy's Office of Energy Management (OEM). Previous benefits assessments conducted within OEM have been based on significantly different assumptions for the average cost per mile of AC transmission line. In response to this uncertainty, an investigation of transmission line capital cost data was initiated. The objective of this study was to develop a database for preparing preliminary estimates of transmission line costs. An extensive search of potential data sources identified databases maintained by the Bonneville Power Administration (BPA) and the Western Area Power Administration (WAPA) as superior sources of transmission line cost data. The BPA and WAPA data were adjusted to a common basis and combined together. The composite database covers voltage levels from 13.8 to 765 W, with cost estimates for a given voltage level varying depending on conductor size, tower material type, tower frame type, and number of circuits. Reported transmission line costs vary significantly, even for a given voltage level. This can usually be explained by variation in the design factors noted above and variation in environmental and land (right-of-way) costs, which are extremely site-specific. Cost estimates prepared from the composite database were compared to cost data collected by the Federal Energy Regulatory Commission (FERC) for investor-owned utilities from across the United States. The comparison was hampered because the only design specifications included with the FERC data were voltage level and line length. Working within this limitation, the FERC data were not found to differ significantly from the composite database. Therefore, the composite database was judged to be a reasonable proxy for estimating national average costs

Classical and quantum transport through entropic barriers modeled by hardwall hyperboloidal constrictions

International Nuclear Information System (INIS)

Hales, R.; Waalkens, H.

2009-01-01

We study the quantum transport through entropic barriers induced by hardwall constrictions of hyperboloidal shape in two and three spatial dimensions. Using the separability of the Schroedinger equation and the classical equations of motion for these geometries, we study in detail the quantum transmission probabilities and the associated quantum resonances, and relate them to the classical phase structures which govern the transport through the constrictions. These classical phase structures are compared to the analogous structures which, as has been shown only recently, govern reaction type dynamics in smooth systems. Although the systems studied in this paper are special due their separability they can be taken as a guide to study entropic barriers resulting from constriction geometries that lead to non-separable dynamics.

Contact heterogeneity, rather than transmission efficiency, limits the emergence and spread of canine influenza virus.

Directory of Open Access Journals (Sweden)

Benjamin D Dalziel

2014-10-01

Full Text Available Host-range shifts in influenza virus are a major risk factor for pandemics. A key question in the study of emerging zoonoses is how the evolution of transmission efficiency interacts with heterogeneity in contact patterns in the new host species, as this interplay influences disease dynamics and prospects for control. Here we use a synergistic mixture of models and data to tease apart the evolutionary and demographic processes controlling a host-range shift in equine H3N8-derived canine influenza virus (CIV. CIV has experienced 15 years of continuous transfer among dogs in the United States, but maintains a patchy distribution, characterized by sporadic short-lived outbreaks coupled with endemic hotspots in large animal shelters. We show that CIV has a high reproductive potential in these facilities (mean R(0 = 3.9 and that these hotspots act as refugia from the sparsely connected majority of the dog population. Intriguingly, CIV has evolved a transmission efficiency that closely matches the minimum required to persist in these refugia, leaving it poised on the extinction/invasion threshold of the host contact network. Corresponding phylogenetic analyses show strong geographic clustering in three US regions, and that the effective reproductive number of the virus (R(e in the general dog population is close to 1.0. Our results highlight the critical role of host contact structure in CIV dynamics, and show how host contact networks could shape the evolution of pathogen transmission efficiency. Importantly, efficient control measures could eradicate the virus, in turn minimizing the risk of future sustained transmission among companion dogs that could represent a potential new axis to the human-animal interface for influenza.

Barriers to Leisure-Time Physical Activities in Individuals with Spinal Cord Injury.

Science.gov (United States)

Hwang, Eric J; Groves, Mary D; Sanchez, Jacqueline N; Hudson, Cassandra E; Jao, Rachel G; Kroll, Meghan E

2016-07-01

This study investigated the personal, environmental, and activity barriers to leisure-time physical activities (LTPAs) among individuals with spinal cord injury (SCI). A survey instrument was administered to 85 participants with SCI. Personal barriers to LTPAs included issues involving motivation, pain, scheduling, and financial resources. Environmental barriers marked the issues regarding availability and accessibility to specialized programs, activities, and professional services. Activity barriers included limitations in equipment, training, and personal skills required by the selected activities. Significant negative correlations were found between these barriers and the levels of physical activity and satisfaction with physical activity. While working with clients with SCI, occupational therapists should identify those LTPA barriers and possible solutions in order to establish individualized action plans for enhancing participation in LTPAs.

Barrier penetration effects on thermopower in semiconductor quantum wells

International Nuclear Information System (INIS)

Vaidya, R. G.; Sankeshwar, N. S.; Mulimani, B. G.

2014-01-01

Finite confinement effects, due to the penetration of the electron wavefunction into the barriers of a square well potential, on the low–temperature acoustic-phonon-limited thermopower (TP) of 2DEG are investigated. The 2DEG is considered to be scattered by acoustic phonons via screened deformation potential and piezoelectric couplings. Incorporating the barrier penetration effects, the dependences of diffusion TP and phonon drag TP on barrier height are studied. An expression for phonon drag TP is obtained. Numerical calculations of temperature dependences of mobility and TP for a 10 nm InN/In x Ga 1−x N quantum well for different values of x show that the magnitude and behavior of TP are altered. A decrease in the barrier height from 500 meV by a factor of 5, enhances the mobility by 34% and reduces the TP by 58% at 20 K. Results are compared with those of infinite barrier approximation

Transmission expansion in an oligopoly considering generation investment equilibrium

DEFF Research Database (Denmark)

Taheri, S. Saeid; Kazempour, Jalal; Seyedshenava, Seyedjalal

2017-01-01

the future generation investment actions. However, in such an oligopolistic market, each producer makes its own strategic generation investment decisions. This motivates the transmission system planner to consider the generation investment decision-making problem of all producers within its TEP model......Transmission expansion planning (TEP) is a sophisticated decision-making problem, especially in an oligopolistic electricity market in which a number of strategic (price-maker) producers compete together. A transmission system planner, who is in charge of making TEP decisions, requires considering....... This paper proposes a tri-level TEP decision-making model to be solved by the transmission system planner, whose objective is to maximize the social welfare of the market minus the expansion costs, and whose constraints are the transmission expansion limits as well as the generation investment equilibrium...

Barriers to innovation in service SMEs: Evidence from Mexico

OpenAIRE

Maldonado Guzman, G.; Garza-Reyes, J. A.; Pinzón-Castro, S. Y.; Kumar, V.

2017-01-01

Purpose – Specific research related to the study of innovation barriers in service SMEs in the Latin American region is limited. This study thus investigates the effects that external environmental, financial and human barriers have on innovation activities, particularly, within the context of Mexican service SMEs.\\ud \\ud Design/methodology/approach – Three hypotheses were formulated and tested using structural equation modelling (SEM). Data were collected through an instrument that was devel...

Quantum tunneling through a very narrow triangular potential barrier exact and WKB solution

International Nuclear Information System (INIS)

Ballo, P.; Harmatha, L.

2011-01-01

We have investigated the quantum-mechanical transmission of an electron in narrow potential barrier. It has been shown that application of WKB approximation could give enormous error if the slope of potential is rapid. Edification of this work is that unreasonable application of numerical approximations without the deep knowledge of theory should give wrong result. This we should remember every second, every day. (authors)

Quantum finance Hamiltonian for coupon bond European and barrier options.

Science.gov (United States)

Baaquie, Belal E

2008-03-01

Coupon bond European and barrier options are financial derivatives that can be analyzed in the Hamiltonian formulation of quantum finance. Forward interest rates are modeled as a two-dimensional quantum field theory and its Hamiltonian and state space is defined. European and barrier options are realized as transition amplitudes of the time integrated Hamiltonian operator. The double barrier option for a financial instrument is "knocked out" (terminated with zero value) if the price of the underlying instrument exceeds or falls below preset limits; the barrier option is realized by imposing boundary conditions on the eigenfunctions of the forward interest rates' Hamiltonian. The price of the European coupon bond option and the zero coupon bond barrier option are calculated. It is shown that, is general, the constraint function for a coupon bond barrier option can -- to a good approximation -- be linearized. A calculation using an overcomplete set of eigenfunctions yields an approximate price for the coupon bond barrier option, which is given in the form of an integral of a factor that results from the barrier condition times another factor that arises from the payoff function.

Environmental barriers, person-environment fit and mortality among community-dwelling very old people.

Science.gov (United States)

Rantakokko, Merja; Törmäkangas, Timo; Rantanen, Taina; Haak, Maria; Iwarsson, Susanne

2013-08-28

Environmental barriers are associated with disability-related outcomes in older people but little is known of the effect of environmental barriers on mortality. The aim of this study was to examine whether objectively measured barriers in the outdoor, entrance and indoor environments are associated with mortality among community-dwelling 80- to 89-year-old single-living people. This longitudinal study is based on a sample of 397 people who were single-living in ordinary housing in Sweden. Participants were interviewed during 2002-2003, and 393 were followed up for mortality until May 15, 2012.Environmental barriers and functional limitations were assessed with the Housing Enabler instrument, which is intended for objective assessments of Person-Environment (P-E) fit problems in housing and the immediate outdoor environment. Mortality data were gathered from the public national register. Cox regression models were used for the analyses. A total of 264 (67%) participants died during follow-up. Functional limitations increased mortality risk. Among the specific environmental barriers that generate the most P-E fit problems, lack of handrails in stairs at entrances was associated with the highest mortality risk (adjusted RR 1.55, 95% CI 1.14-2.10), whereas the total number of environmental barriers at entrances and outdoors was not associated with mortality. A higher number of environmental barriers indoors showed a slight protective effect against mortality even after adjustment for functional limitations (RR 0.98, 95% CI 0.96-1.00). Specific environmental problems may increase mortality risk among very-old single-living people. However, the association may be confounded by individuals' health status which is difficult to fully control for. Further studies are called for.

The critical role of the barrier thickness in spin filter tunneling

International Nuclear Information System (INIS)

Miller, Casey W.

2009-01-01

Spin filter tunneling is considered in the low bias limit as functions of the temperature dependent barrier parameters. We demonstrate the generation of spin polarized tunneling currents in relation to the magnetic order parameter, and discuss how an interfacially suppressed order parameter leads to a temperature dependent tunneling current asymmetry. Analyzing the full parameter space reveals that the often overlooked barrier thickness plays a critical role in spin filter tunneling. With all else fixed, thicker barriers yield higher spin polarization, and allow a given polarization to be achieved at higher temperatures. This insight may open the door for new materials to serve as spin filter barriers.

Absorption-Edge-Modulated Transmission Spectra for Water Contaminant Monitoring

Science.gov (United States)

2016-03-31

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--16-9675 Absorption- Edge -Modulated Transmission Spectra for Water Contaminant...ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Absorption- Edge -Modulated Transmission Spectra for Water Contaminant Monitoring...contaminants, within a volume of sampled solution, requires sufficient sensitivity. The present study examines the sensitivity of absorption- edge

Limited english proficiency, primary language at home, and disparities in children's health care: how language barriers are measured matters.

Science.gov (United States)

Flores, Glenn; Abreu, Milagros; Tomany-Korman, Sandra C

2005-01-01

Approximately 3.5 million U.S. schoolchildren are limited in English proficiency (LEP). Disparities in children's health and health care are associated with both LEP and speaking a language other than English at home, but prior research has not examined which of these two measures of language barriers is most useful in examining health care disparities. Our objectives were to compare primary language spoken at home vs. parental LEP and their associations with health status, access to care, and use of health services in children. We surveyed parents at urban community sites in Boston, asking 74 questions on children's health status, access to health care, and use of health services. Some 98% of the 1,100 participating children and families were of non-white race/ethnicity, 72% of parents were LEP, and 13 different primary languages were spoken at home. "Dose-response" relationships were observed between parental English proficiency and several child and parental sociodemographic features, including children's insurance coverage, parental educational attainment, citizenship and employment, and family income. Similar "dose-response" relationships were noted between the primary language spoken at home and many but not all of the same sociodemographic features. In multivariate analyses, LEP parents were associated with triple the odds of a child having fair/poor health status, double the odds of the child spending at least one day in bed for illness in the past year, and significantly greater odds of children not being brought in for needed medical care for six of nine access barriers to care. None of these findings were observed in analyses of the primary language spoken at home. Individual parental LEP categories were associated with different risks of adverse health status and outcomes. Parental LEP is superior to the primary language spoken at home as a measure of the impact of language barriers on children's health and health care. Individual parental LEP

Modelling water vapour permeability through atomic layer deposition coated photovoltaic barrier defects

Energy Technology Data Exchange (ETDEWEB)

Elrawemi, Mohamed, E-mail: Mohamed.elrawemi@hud.ac.uk [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Blunt, Liam; Fleming, Leigh [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Bird, David, E-mail: David.Bird@uk-cpi.com [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Robbins, David [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Sweeney, Francis [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom)

2014-11-03

Transparent barrier films such as Al{sub 2}O{sub 3} used for prevention of oxygen and/or water vapour permeation are the subject of increasing research interest when used for the encapsulation of flexible photovoltaic modules. However, the existence of micro-scale defects in the barrier surface topography has been shown to have the potential to facilitate water vapour ingress, thereby reducing cell efficiency and causing internal electrical shorts. Previous work has shown that small defects (≤ 3 μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥ 3 μm lateral dimension) seem to be more detrimental to the barrier functionality. Experimental results based on surface topography segmentation analysis and a model presented in this paper will be used to test the hypothesis that the major contributing defects to water vapour transmission rate are small numbers of large defects. The model highlighted in this study has the potential to be used for gaining a better understanding of photovoltaic module efficiency and performance. - Highlights: • A model of water vapour permeation through barrier defects is presented. • The effect of the defects on the water vapour permeability is investigated. • Defect density correlates with water vapour permeability. • Large defects may dominate the permeation properties of the barrier film.

Viscosity-Induced Crossing of the Phantom Barrier

Directory of Open Access Journals (Sweden)

Iver Brevik

2015-09-01

Full Text Available We show explicitly, by using astrophysical data plus reasonable assumptions for the bulk viscosity in the cosmic fluid, how the magnitude of this viscosity may be high enough to drive the fluid from its position in the quintessence region at present time t = 0 across the barrier w = −1 into the phantom region in the late universe. The phantom barrier is accordingly not a sharp mathematical divide, but rather a fuzzy concept. We also calculate the limiting forms of various thermodynamical quantities, including the rate of entropy production, for a dark energy fluid near the future Big Rip singularity.

Frequency division transmission imaging and synthetic aperture reconstruction

DEFF Research Database (Denmark)

Gran, Fredrik; Jensen, Jørgen Arendt

2006-01-01

In synthetic transmit aperture imaging only a few transducer elements are used in every transmission, which limits the signal-to-noise ratio (SNR). The penetration depth can be increased by using all transmitters in every transmission. In this paper, a method for exciting all transmitters in every...... corresponding to the excitation waveforms, the different transmitters can be decoded at the receiver. The matched filter of a specific waveform will allow information only from this waveform to pass through, thereby separating it from the other waveforms. This means that all transmitters can be used in every...... transmission, and the information from the different transmitters can be separated instantaneously. Compared to traditional synthetic transmit aperture (STA) imaging, in which the different transmitters are excited sequentially, more energy is transmitted in every transmission, and a better signal...

Experienced Barriers to Lean in Swedish Manufacturing and Health Care

Directory of Open Access Journals (Sweden)

Bengt Halling

2013-12-01

Full Text Available The purpose is to compare similarities and divergences in how the concepts of Lean and barriers to Lean are described by key informants at a production unit in a large manufacturing company and two emergency health care units in Sweden. Data was collected via semi-structured interviews and analyzed with the constant comparative method (CCM and Porras and Robertson’s (1992 change model. : In both organizations, the view of Lean changed from a toolbox to a human behavior view. Eight barriers were experienced in both organizations. Three barriers were unique to manufacturing or to health care, respectively. Nine barriers were elements of social factors; five were elements of organizing arrangements. Only people practically involved and responsible for the implementation at the two organizations participated in the study. Persons responsible for implementing Lean should consider organizational arrangements and social factors in order to limit barriers to successful implementation. Most research on Lean has been about successful Lean implementations. This study focuses on how Lean is viewed and what barriers personnel in manufacturing and health care have experienced. In comparing the barriers to Lean experienced in the two groups, common, archetypical, and unique barriers for manufacturing and health care can be identified, thus contributing to knowledge about barriers to Lean implementation.

Barriers to guideline-compliant psoriasis care: analyses and concepts.

Science.gov (United States)

Eissing, L; Radtke, M A; Zander, N; Augustin, M

2016-04-01

Despite the availability of effective therapeutics and evidence-based treatment guidelines, a substantial proportion of patients with moderate-to-severe psoriasis does not receive appropriate care. This under-provision of health care may cause further worsening of health, remarkable limitations of the patient's quality of life, and indirect costs for the health care system. In order to provide guideline-compliant care for every psoriasis patient, it is important to identify barriers obstructing optimal care. Studies have identified various barriers on the physician's and on the patient's side; however, respective studies approached only single barriers, and not all of them in the context of psoriasis. Other publications that describe barriers systematically did not focus on psoriasis either. The objective of this literature review was to identify barriers and facilitators, based on studies analysing quality of care and single barriers, resulting in a comprehensive model of causal factors. Our analyses revealed three categories of barriers - patient-related, physician-related and external factors: On the patient side, we found non-adherence to therapies to be an important barrier, often in close association with psychiatric factors. Barriers on the physician's side predominantly are incomplete knowledge of the guidelines as well as the complexity of psoriasis comorbidity. In some countries, payment for patients with complex disease status is poor and inconsistent reimbursement regulations potentially interfere with optimal care. The current analysis indicates that most barriers are interdependent. Thus, measures approaching related barriers simultaneously are required. To improve care for psoriasis patients, further studies systematically addressing all potentially relevant barriers in conjoint are needed. © 2015 European Academy of Dermatology and Venereology.

Overcoming barriers to wind project finance in Australia

International Nuclear Information System (INIS)

Kann, Shayle

2009-01-01

The wind power industry in Australia is expected to grow rapidly over the next decade, primarily due to a forthcoming expanded national renewable energy target (RET) which will mandate that renewable sources provide approximately 20% of Australia's electricity production by 2020. However, development of new wind generation in Australia has stalled as a result of several barriers to project finance, the mechanism through which most wind farms have been developed historically. This paper provides an overview of wind power financing in Australia in light of recent political and financial trends. Drawing upon existing literature and a series of stakeholder interviews, it identifies three primary barriers to project finance: regulatory risk surrounding legislation of the RET, semi-privatization of electricity retailers in New South Wales, and limited capital availability resulting from the recent global credit crisis. The paper concludes that the confluence of these barriers limits the availability of long-term contracts that provide revenue certainty for pre-construction wind projects, while simultaneously making these contracts a necessity in order to obtain project finance. In an attempt to mitigate these effects, this paper identifies four alternative development strategies that can be pursued.

Frequencies and predictors of barriers to mental health service use: a longitudinal study of Hurricane Ike survivors.

Science.gov (United States)

Lowe, Sarah R; Fink, David S; Norris, Fran H; Galea, Sandro

2015-01-01

The majority of disaster survivors suffering from psychological symptoms do not receive mental health services. Research on barriers to service use among disaster survivors is limited by a lack of longitudinal studies of representative samples and investigations of predictors of barriers. The purpose of this study was to address these limitations through analysis of a three-wave population-based study of Hurricane Ike survivors (N = 658). Frequencies of preference, outcome expectancy, resource, and stigma barriers among participants with unmet mental health needs were documented and logistic regression using a generalized estimating equations approach explored predisposing (e.g., age), illness-related (e.g., posttraumatic stress) and enabling (e.g., insurance coverage) factors as predictors of each type of barrier. Preference barriers were most frequently cited at each wave, whereas stigma barriers were least frequently cited. Older age and higher emotional support predicted preference barriers; being a parent of a child under 18-years old at the time of the hurricane, higher generalized anxiety, and lack of insurance predicted resource barriers; and higher posttraumatic stress predicted stigma barriers. These findings suggest that postdisaster practices targeting subpopulations most likely to have barriers to service use may be indicated.

Emerging technologies in point-of-care molecular diagnostics for resource-limited settings.

Science.gov (United States)

Peeling, Rosanna W; McNerney, Ruth

2014-06-01

Emerging molecular technologies to diagnose infectious diseases at the point at which care is delivered have the potential to save many lives in developing countries where access to laboratories is poor. Molecular tests are needed to improve the specificity of syndromic management, monitor progress towards disease elimination and screen for asymptomatic infections with the goal of interrupting disease transmission and preventing long-term sequelae. In simplifying laboratory-based molecular assays for use at point-of-care, there are inevitable compromises between cost, ease of use and test performance. Despite significant technological advances, many challenges remain for the development of molecular diagnostics for resource-limited settings. There needs to be more advocacy for these technologies to be applied to infectious diseases, increased efforts to lower the barriers to market entry through streamlined and harmonized regulatory approaches, faster policy development for adoption of new technologies and novel financing mechanisms to enable countries to scale up implementation.

Electric Dipole Theory of Chemical Synaptic Transmission

Science.gov (United States)

Wei, Ling Y.

1968-01-01

In this paper we propose that chemicals such as acetylcholine are electric dipoles which when oriented and arranged in a large array could produce an electric field strong enough to drive positive ions over the junction barrier of the post-synaptic membrane and thus initiate excitation or produce depolarization. This theory is able to explain a great number of facts such as cleft size, synaptic delay, nonregeneration, subthreshold integration, facilitation with repetition, and the calcium and magnesium effects. It also shows why and how acetylcholine could act as excitatory or inhibitory transmitters under different circumstances. Our conclusion is that the nature of synaptic transmission is essentially electrical, be it mediated by electrical or chemical transmitters. PMID:4296121

Transfusion transmissible viral infections among potential blood ...

African Journals Online (AJOL)

effective approach for prevention and control of transfusion-transmissible infections (TTIs). Also, it has been documented that sub-standard test kits are mostly used in resource limited settings for transfusion related diagnosis. However, the role of ...

Removing the current-limit of vertical organic field effect transistors

Science.gov (United States)

Sheleg, Gil; Greenman, Michael; Lussem, Bjorn; Tessler, Nir

2017-11-01

The reported Vertical Organic Field Effect Transistors (VOFETs) show either superior current and switching speeds or well-behaved transistor performance, especially saturation in the output characteristics. Through the study of the relationship between the device architecture or dimensions and the device performance, we find that achieving a saturation regime in the output characteristics requires that the device operates in the injection limited regime. In current structures, the existence of the injection limited regime depends on the source's injection barrier as well as on the buried semiconductor layer thickness. To overcome the injection limit imposed by the necessity of injection barrier, we suggest a new architecture to realize VOFETs. This architecture shows better gate control and is independent of the injection barrier at the source, thus allowing for several A cm-2 for a semiconductor having a mobility value of 0.1 cm2 V-1 s-1.

The effect of desiccation on UMTRA Project radon barrier materials

International Nuclear Information System (INIS)

1990-11-01

The proposed US Environmental Protection Agency (EPA) groundwater standards (40 CFR 192) require that Uranium Mill Tailings Remedial Action (UMTRA) Project remedial action designs meet low numerical limits for contaminants contained in water or vapors exiting the disposal cell embankments. To meet the standards, a cover of compacted, fine-grained soil is placed over UMTRA Project embankments. One of the functions of this cover is to limit infiltration into the disposal cell . The hydraulic conductivity of this infiltration barrier must be low in order to reduce the resultant seepage from the base of the cell to the extent necessary to comply with the proposed EPA groundwater standards. Another function of this cover is to limit the emission of radon gas. The air permeability of the cover must be low in order to reduce radon emissions to comply with EPA standards. Fine-grained soils exposed to evaporation will dry. Continued exposure will cause shrinking that, if allowed to continue, will eventually result in the development of cracks. The results of the cracking could be an increase in the hydraulic conductivity and an increase in the air permeability. This could then allow additional infiltration and increased radon emissions. Cracking of the radon barrier has been noted at one UMTRA Project location. The potential for cracking of the radon barrier during construction has been addressed by requiring moistening of previously compacted surfaces prior to placing additional lifts. The efficacy of these treatments has not been verified. The potential for cracking after construction of the cover is completed has also not been examined. The purpose of this study is to evaluate the potential for cracking of the radon barrier both during construction and after completion of the cover. The effect of shrinkage cracking on the performance of the radon barrier will also be examined

Community Participation and Barriers in Rural Tourism: A Case Study in Kiulu, Sabah

Directory of Open Access Journals (Sweden)

Velnisa Paimin N. F.

2014-01-01

Full Text Available The paper presents an investigation on local community participation and barriers in rural tourism. It identifies two sides of community participation in tourism as identified by Timothy [5], which are; the benefits point of view and from the decision making process perspective. It also identifies the communities’ barriers in engaging in tourism and uses Tosun’s [18] approach in examining the barriers. A total of eighty-three questionnaire forms were completed by respondents from seven villages in Kiulu, Sabah, Malaysia. Respondents involved in tourism were mainly engaged as river guides, homestay operators and Tagal participants. Their involvement in the decision making process were limited to attending meetings and giving ideas and opinions only. The main barriers to participate in tourism were related to their limited knowledge about tourism, lack of capital, unable to communicate well in English, lack of information about tourism development in Kiulu, and limited incentives or support from the government for tourism development. The findings have significant implication to community participation in tourism especially in rural settings. More efforts should be made to ensure many more communities participate in tourism so as to share the benefits of tourism.

The corallivorous invertebrate Drupella aids in transmission of brown band disease on the Great Barrier Reef

Science.gov (United States)

Nicolet, K. J.; Hoogenboom, M. O.; Gardiner, N. M.; Pratchett, M. S.; Willis, B. L.

2013-06-01

Brown band disease (BrB) is an increasingly prevalent coral disease in the Indo-Pacific, but although the macroscopic signs of BrB have been associated with the ciliate Philaster guamensis, many aspects of its ecology remain unknown, particularly how the disease is transmitted among coral colonies. The aim of this study was to assess biotic factors affecting BrB transmission, explicitly testing whether corallivorous species contribute to disease spread. Several fish species were observed feeding on diseased tissue in the field, but did not influence either the progression or transmission rates of BrB on coral colonies in situ. In aquarium-based experiments, the butterflyfish Chaetodon aureofasciatus neither aided nor hindered the transmission of BrB from infected to uninfected corals. In contrast, the coral-feeding gastropod Drupella sp. was a highly effective vector of BrB, infecting more than 40 % of experimental colonies. This study also demonstrated the importance of injury in facilitating BrB infection, supporting the hypothesis that the BrB pathogen invades compromised coral tissue. In conclusion, disturbances and corallivorous activities that injure live corals are likely to contribute to increased occurrence of BrB provided that feeding scars create entry wounds sufficiently extensive to facilitate infection. These findings increase the understanding of the ecology of BrB, enabling better predictions of the prevalence and severity of this disease, and informing strategies for managing the impact of BrB on coral reefs.

Spin polarization of tunneling current in barriers with spin-orbit coupling

International Nuclear Information System (INIS)

Fujita, T; Jalil, M B A; Tan, S G

2008-01-01

We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons

Spin polarization of tunneling current in barriers with spin-orbit coupling.

Science.gov (United States)

Fujita, T; Jalil, M B A; Tan, S G

2008-03-19

We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons.

Phase characterization of Re-based diffusion barrier layer on Nb substrate

International Nuclear Information System (INIS)

Sugiarti, Eni; Wang, Youngmin; Hashimoto, Naoyuki; Ohnuki, Somei; Narita, Toshio

2011-01-01

An electron microscopy phase characterization was carried out for a Re-based diffusion barrier layer, which was deposited on the Nb substrate used as an ultra high temperature material. The coating process produced three layers; an outer Cr(Re) layer, an intermediate Cr-Nb-Re layer, and an inner Nb(Re) layer. The Cr-Nb-Re layer is considered to act as a diffusion barrier layer between the substrate and the outer Cr(Re) reservoir layer. The Cr(Re) and Nb(Re) layers are in single phase with a similar bcc structures, but they are different in structure from the intermediate layer, which is composed of a dual phase of Re 63 Cr 20 Nb 17 with a cubic structure and Nb 42 Re 33 Cr 25 with a hexagonal structure determined by transmission electron microscopy (TEM) in this study. (author)

Differences in perceived communication barriers among nurses and elderly patients in China.

Science.gov (United States)

Ruan, Jing; Lambert, Vickie A

2008-06-01

In China, limited information exists about nurses' and elderly patients' perceptions of barriers to the communication process. Therefore, the purposes of this study were to identify the major communication barriers (nurse-related, patient-related, and environment-related) perceived both by nurses and elderly patients and to determine the perceived differences in the level of importance of the communication barriers between nurses and elderly patients. The sample consisted of 84 nurses and 75 elderly patients who completed a demographic questionnaire and a communication barriers questionnaire. The findings suggested that the nurses and elderly patients often selected similar barriers related to the communication process. The nurses tended to assign higher values to the communication barriers that were found to be significantly different from those of the elderly patients. The study findings provide information about which type of barriers nurses need to address so as to facilitate effective communication with elderly patients.

Diamond and Diamond-Like Materials as Hydrogen Isotope Barriers

International Nuclear Information System (INIS)

Foreman, L.R.; Barbero, R.S.; Carroll, D.W.; Archuleta, T.; Baker, J.; Devlin, D.; Duke, J.; Loemier, D.; Trukla, M.

1999-01-01

This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The purpose of this project was to develop diamond and diamond-like thin-films as hydrogen isotope permeation barriers. Hydrogen embrittlement limits the life of boost systems which otherwise might be increased to 25 years with a successful non-reactive barrier. Applications in tritium processing such as bottle filling processes, tritium recovery processes, and target filling processes could benefit from an effective barrier. Diamond-like films used for low permeability shells for ICF and HEDP targets were also investigated. Unacceptable high permeabilities for hydrogen were obtained for plasma-CVD diamond-like-carbon films

Improvements in or relating to thermal barrier systems

International Nuclear Information System (INIS)

Birch, W.; Pearson, R.

1976-01-01

Reference is made to thermal barrier systems for the internal surface of gas cooled reactor prestressed concrete pressure vessels. Provision has to be made to anchor the thermal barrier system to a metal limit within the pressure vessel, and the object of the arrangement described is to provided a suitable attachment means. The thermal barrier may consist of a number of plates arranged in overlapped fashion or having flexible joint portions. A problem that arises concerns anchoring of the hot plates to the cold pressure vessel by a rigid attachment, and the design must be such as to ensure adequate bending and axial strength compatible with a minimum heat conduction area and allowable thermal stress. The arrangement must also allow easy installation. The arrangement described also provides for a 'fail-safe' structure. It comprises a metal stud with a hollow body; two or more helical channels are provided through the side walls of the body. The body portion expands or contracts to accommodate axial temperature gradient stress set up by the temperature difference between the pressure vessel and the thermal barrier. The space between the thermal barrier and the pressure vessel may contain solid insulating material. (U.K.)

Antimicrobial peptides in the female reproductive tract: a critical component of the mucosal immune barrier with physiological and clinical implications.

Science.gov (United States)

Yarbrough, Victoria L; Winkle, Sean; Herbst-Kralovetz, Melissa M

2015-01-01

At the interface of the external environment and the mucosal surface of the female reproductive tract (FRT) lies a first-line defense against pathogen invasion that includes antimicrobial peptides (AMP). Comprised of a unique class of multifunctional, amphipathic molecules, AMP employ a wide range of functions to limit microbial invasion and replication within host cells as well as independently modulate the immune system, dampen inflammation and maintain tissue homeostasis. The role of AMP in barrier defense at the level of the skin and gut has received much attention as of late. Given the far reaching implications for women's health, maternal and fetal morbidity and mortality, and sexually transmissible and polymicrobial diseases, we herein review the distribution and function of key AMP throughout the female reproductive mucosa and assess their role as an essential immunological barrier to microbial invasion throughout the reproductive cycle of a woman's lifetime. A comprehensive search in PubMed/Medline was conducted related to AMP general structure, function, signaling, expression, distribution and barrier function of AMP in the FRT, hormone regulation of AMP, the microbiome of the FRT, and AMP in relation to implantation, pregnancy, fertility, pelvic inflammatory disease, complications of pregnancy and assisted reproductive technology. AMP are amphipathic peptides that target microbes for destruction and have been conserved throughout all living organisms. In the FRT, several major classes of AMP are expressed constitutively and others are inducible at the mucosal epithelium and by immune cells. AMP expression is also under the influence of sex hormones, varying throughout the menstrual cycle, and dependent on the vaginal microbiome. AMP can prevent infection with sexually transmissible and opportunistic pathogens of the female reproductive tissues, although emerging understanding of vaginal dysbiosis suggests induction of a unique AMP profile with increased

Risk Factors for HIV Transmission and Barriers to HIV Disclosure: Metropolitan Atlanta Youth Perspectives

OpenAIRE

Camacho-Gonzalez, Andres F.; Wallins, Amy; Toledo, Lauren; Murray, Ashley; Gaul, Zaneta; Sutton, Madeline Y.; Gillespie, Scott; Leong, Traci; Graves, Chanda; Chakraborty, Rana

2016-01-01

Youth carry the highest incidence of HIV infection in the United States. Understanding adolescent and young adult (AYA) perspectives on HIV transmission risk is important for targeted HIV prevention. We conducted a mixed methods study with HIV-infected and uninfected youth, ages 18–24 years, from Atlanta, GA. We provided self-administered surveys to HIV-infected and HIV-uninfected AYAs to identify risk factors for HIV acquisition. By means of computer-assisted thematic analyses, we examined t...

Evaluation of DCS III Transmission Alternatives. Phase 1A report. Appendix B. Regulatory Barriers.

Science.gov (United States)

1980-05-26

Resolution DK). B.1.1.5 Importance of the RR in the DCS III Study. The ITU Radio Regulation offers a means to appraise viability of the alternatives to be...interference 466-1 483 Measurement of performance by means of signal 482 Measurement of noise in actual traffic 481 Table B.l-6. Communication Satellite...Economic and technical aspects of the choice of transmission systems GAS 5 Economic conditions and tel ecommunication development GAS 6 Economic and

Optical power limiting and transmitting properties of cadmium iodide single crystals: Temperature dependence

Energy Technology Data Exchange (ETDEWEB)

Miah, M. Idrish, E-mail: m.miah@griffith.edu.a [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)] [Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)] [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

2009-09-14

Optical limiting properties of the single crystals of cadmium iodide are investigated using ns laser pulses. It is found that the transmissions in the crystals increase with increasing temperature. However, they limit the transmissions at high input powers. The limiting power is found to be higher at higher temperature. From the measured transmission data, the photon absorption coefficients are estimated. The temperature dependence of the coefficients shows a decrease in magnitude with increasing temperature. This might be due to the temperature-dependent bandgap shift of the material. The results demonstrate that the cadmium iodide single crystals are promising materials for applications in optical power limiting devices.

Optical power limiting and transmitting properties of cadmium iodide single crystals: Temperature dependence

International Nuclear Information System (INIS)

Miah, M. Idrish

2009-01-01

Optical limiting properties of the single crystals of cadmium iodide are investigated using ns laser pulses. It is found that the transmissions in the crystals increase with increasing temperature. However, they limit the transmissions at high input powers. The limiting power is found to be higher at higher temperature. From the measured transmission data, the photon absorption coefficients are estimated. The temperature dependence of the coefficients shows a decrease in magnitude with increasing temperature. This might be due to the temperature-dependent bandgap shift of the material. The results demonstrate that the cadmium iodide single crystals are promising materials for applications in optical power limiting devices.

Protein kinase C-dependent signaling controls the midgut epithelial barrier to malaria parasite infection in anopheline mosquitoes.

Directory of Open Access Journals (Sweden)

Nazzy Pakpour

Full Text Available Anopheline mosquitoes are the primary vectors of parasites in the genus Plasmodium, the causative agents of malaria. Malaria parasites undergo a series of complex transformations upon ingestion by the mosquito host. During this process, the physical barrier of the midgut epithelium, along with innate immune defenses, functionally restrict parasite development. Although these defenses have been studied for some time, the regulatory factors that control them are poorly understood. The protein kinase C (PKC gene family consists of serine/threonine kinases that serve as central signaling molecules and regulators of a broad spectrum of cellular processes including epithelial barrier function and immunity. Indeed, PKCs are highly conserved, ranging from 7 isoforms in Drosophila to 16 isoforms in mammals, yet none have been identified in mosquitoes. Despite conservation of the PKC gene family and their potential as targets for transmission-blocking strategies for malaria, no direct connections between PKCs, the mosquito immune response or epithelial barrier integrity are known. Here, we identify and characterize six PKC gene family members--PKCδ, PKCε, PKCζ, PKD, PKN, and an indeterminate conventional PKC--in Anopheles gambiae and Anopheles stephensi. Sequence and phylogenetic analyses of the anopheline PKCs support most subfamily assignments. All six PKCs are expressed in the midgut epithelia of A. gambiae and A. stephensi post-blood feeding, indicating availability for signaling in a tissue that is critical for malaria parasite development. Although inhibition of PKC enzymatic activity decreased NF-κB-regulated anti-microbial peptide expression in mosquito cells in vitro, PKC inhibition had no effect on expression of a panel of immune genes in the midgut epithelium in vivo. PKC inhibition did, however, significantly increase midgut barrier integrity and decrease development of P. falciparum oocysts in A. stephensi, suggesting that PKC

Effects of Long-Term Static Bending Deformation on a Barrier Thin Film for Flexible Organic Optoelectronic Devices

Directory of Open Access Journals (Sweden)

Hung-I Lu

2018-03-01

Full Text Available The objective of this study is to investigate the effect of long-term static bending on the encapsulation properties of a commercial barrier thin film for flexible optoelectronic devices. Encapsulation properties of the barrier film are evaluated under long-term static bending at various radii of curvature. Experimental results reveal that no significantly detrimental effect on the water vapor transmission rate (WVTR at 40 °C and 90% RH is found for compressive bending up to 1000 h and for tensile bending up to 100 h with a radius of curvature of 5 mm or larger. However, WVTR of the barrier thin film is significantly increased and cracks are found in the barrier film when subjected to tensile bending of a radius of 10 mm or 5 mm for 1000 h. The expected WVTR of the given barrier thin film is numerically computed using a three-dimensional (3D finite element model. Numerical results indicate that, with the presence of cracks in the barrier thin film, the WVTR increases for an apparent increase in moisture entrances. The WVTR calculated by the 3D cracking model concurs with the experimental results.

Non-toxic poly(ethylene terephthalate)/clay nanocomposites with enhanced barrier properties

KAUST Repository

Hayrapetyan, Suren

2012-01-01

Motivated by the technological need for poly(ethylene terephthalate) materials with improved barrier properties together with the requirement for sustainability this study focuses on an eco-friendly sulfonated polyester as clay compatibilizer to facilitate polymer mixing during melt compounding. We demonstrate that the nanocomposites based on sulfonated polyester are a reliable alternative to their imidazolium counterparts, exhibiting enhanced properties (water vapor and UV transmission), without sacrificing the excellent transparency, clarity and mechanical strength of the matrix. © 2011 Elsevier Ltd. All rights reserved.

The global limits and population at risk of soil-transmitted helminth infections in 2010

Directory of Open Access Journals (Sweden)

Pullan Rachel L

2012-04-01

Full Text Available Abstract Background Understanding the global limits of transmission of soil-transmitted helminth (STH species is essential for quantifying the population at-risk and the burden of disease. This paper aims to define these limits on the basis of environmental and socioeconomic factors, and additionally seeks to investigate the effects of urbanisation and economic development on STH transmission, and estimate numbers at-risk of infection with Ascaris lumbricoides, Trichuris trichiura and hookworm in 2010. Methods A total of 4,840 geo-referenced estimates of infection prevalence were abstracted from the Global Atlas of Helminth Infection and related to a range of environmental factors to delineate the biological limits of transmission. The relationship between STH transmission and urbanisation and economic development was investigated using high resolution population surfaces and country-level socioeconomic indicators, respectively. Based on the identified limits, the global population at risk of STH transmission in 2010 was estimated. Results High and low land surface temperature and extremely arid environments were found to limit STH transmission, with differential limits identified for each species. There was evidence that the prevalence of A. lumbricoides and of T. trichiura infection was statistically greater in peri-urban areas compared to urban and rural areas, whilst the prevalence of hookworm was highest in rural areas. At national levels, no clear socioeconomic correlates of transmission were identified, with the exception that little or no infection was observed for countries with a per capita gross domestic product greater than US$ 20,000. Globally in 2010, an estimated 5.3 billion people, including 1.0 billion school-aged children, lived in areas stable for transmission of at least one STH species, with 69% of these individuals living in Asia. A further 143 million (31.1 million school-aged children lived in areas of unstable

Perception of barriers for expansion of electricity grids in the European Union

International Nuclear Information System (INIS)

Battaglini, Antonella; Komendantova, Nadejda; Brtnik, Patricia; Patt, Anthony

2012-01-01

Many of the scenarios for decarbonising the European energy system involve the integration of large-scale and decentralised renewable energy sources, such as wind and solar power. However, such integration requires substantial and rapid improvements to the existing transmission grids. Using a mix of qualitative and quantitative methods, we analysed the opinions and views of stakeholders concerning the main barriers and solutions to this problem. The results suggest two conclusions. The first is that primary barriers to the currently needed level of grid expansion are not technical or financial, but the lack of appropriate regulatory frameworks and public acceptance. The second is that major changes are needed in the overall regulatory process, rather than simply minor modifications or improved implementation of existing regulations. - Highlights: ► Estimations of perceptions on barriers for expansion of electricity grids in Europe. ► Recommendations on political process and level of acceptance among European population. ► Needs for better, simplified and standardized regulations. ► Strong and transparent consultation process in all stages.

Identification of barriers to medication adherence in a Latino population.

Science.gov (United States)

Compton, Sheryl; Haack, Sally; Phillips, Charles R

2010-12-01

Barriers to medication adherence may present differently in diverse patient populations. Because of changing U.S. demographics, health care providers will be required to identify alternative strategies for managing increasingly diverse patient populations. This pilot project identified barriers that may hinder medication adherence in a Latino population. The results of the survey may identify trends in barriers allowing for the development of interventions aimed at improving medication adherence. The study used a convenience sample of Spanish-labeled prescriptions that had not been picked up from a community pharmacy after a 2-week period to identify study subjects. Patients were contacted by phone and surveyed regarding reasons for not picking up their prescription medication. The 24-item survey instrument consisted of demographic and medication-related questions, reasons for, and associated barriers with failure to pick up medications. The most common classes of medications patients failed to pick up were chronic medications. More than 90% of the patients thought that the medication in question was helpful to them, and nearly 80% thought that the medicine was still needed. Patients cited communication issues (ie, content matter, such as when the prescription was ready), logistics, and limited hours of pharmacy operation as the primary barriers in picking up their medications, whereas nearly 40% failed to identify any barriers. Barriers identified by patients that could be improved included confusion regarding when their prescription was ready and limited hours of pharmacy operation. Most of the patients were comfortable using the American health care system. The barriers to medication adherence identified did not appear to be the result of cultural influences. This could be because the community pharmacy had bilingual staff and interpreters available for patient education and prescription processing. Alternative methods are needed to further identify reasons for

Knowledge Exchange and Management Research: Barriers and Potentials

DEFF Research Database (Denmark)

Bager, Torben

2018-01-01

Purpose: The growing involvement of management researchers in knowledge exchange activities and collaborative research does not seem to be reflected in a growing academic output. The purpose of this paper is to explore barriers for academic output from these activities as well as the potential...... for ‘interesting’ papers. Design/methodology/approach: The paper uses secondary data and statistics as well as an illustrative case study to trace knowledge exchange activities and barriers for academic output based on these activities. Findings: The paper identifies a number of barriers for the turning of data...... derived from knowledge exchange activities and Mode 2 research into academic papers such as low priority of case study research in leading management journals, a growing practice orientation in the research funding systems, methodological challenges due to limited researcher control, and disincentives...

Claudins, dietary milk proteins, and intestinal barrier regulation.

Science.gov (United States)

Kotler, Belinda M; Kerstetter, Jane E; Insogna, Karl L

2013-01-01

The family of claudin proteins plays an important role in regulating the intestinal barrier by modulating the permeability of tight junctions. The impact of dietary protein on claudin biology has not been studied extensively. Whey proteins have been reported to improve intestinal barrier function, but their mechanism of action is not clear. Recent studies, however, have demonstrated increased intestinal claudin expression in response to milk protein components. Reviewed here are new findings suggesting that whey-protein-derived transforming growth factor β transcriptionally upregulates claudin-4 expression via a Smad-4-dependent pathway. These and other data, including limited clinical studies, are summarized below and, in the aggregate, suggest a therapeutic role for whey protein in diseases of intestinal barrier dysfunction, perhaps, in part, by regulating claudin expression. © 2013 International Life Sciences Institute.

CORRELATION OF H-MODE BARRIER WIDTH AND NEUTRAL PENETRATION LENGTH

International Nuclear Information System (INIS)

GROEBNER, R.J.; MAHDAVI, M.A.; LEONARD, A.W.; OSBORNE, T.H.; WOLF, N.S.; PORTER, G.D.; STANGEBY, P.C.; BROOKS, N.H.; COLCHIN, R.J.; HEIDBRINK, W.W.; LUCE, T.C.; MCKEE, G.R.; OWEN, L.W.; WANG, G.; WHYTE, D.G.

2002-01-01

OAK A271 CORRELATION OF H-MODE BARRIER WIDTH AND NEUTRAL PENETRATION LENGTH. Pedestal studies in DIII-D find a good correlation between the width of the H-mode density barrier and the neutral penetration length. These results are obtained by comparing experimental density profiles to the predictions of an analytic model for the profile, obtained from the particle continuity equations for electrons and deuterium atoms. In its range of validity (edge temperature between 40-500 eV), the analytic model quantitatively predicts the observed decrease of the width as the pedestal density increases, the observed strong increase of the gradient of the density as the pedestal density increases and the observation that L-mode and H-mode profiles with the same pedestal density have very similar shapes. The width of the density barrier, measured from the edge of the electron temperature barrier, is the lower limit for the observed width of the temperature barrier. These results support the hypothesis that particle fueling provides the dominant control for the size of the H-mode transport barrier

The Schottky energy barrier dependence of charge injection in organic light-emitting diodes

Science.gov (United States)

Campbell, I. H.; Davids, P. S.; Smith, D. L.; Barashkov, N. N.; Ferraris, J. P.

1998-04-01

We present device model calculations of the current-voltage (I-V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. The I-V characteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the device I-V characteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited.

Tunable delay time and Hartman effect in graphene magnetic barriers

International Nuclear Information System (INIS)

Ban, Yue; Wang, Lin-Jun; Chen, Xi

2015-01-01

Tunable group delay and Hartman effect have been investigated for massless Dirac electrons in graphene magnetic barriers. In the presence of magnetic field, dwell time is found to be equal to net group delay plus the group delay contributing from the lateral shifts. The group delay times are discussed in both cases of normal and oblique incidence, to clarify the nature of Hartman effect. In addition, the group delay in transmission can be modulated from subluminality to superluminality by adjusting the magnetic field, which may also lead to potential applications in graphene-based microelectronics

Giant magnetoresistance effect in nanostructures consisting of magnetic-electric barriers

International Nuclear Information System (INIS)

Tang, Wei-Hua; Li, Chun-Shu; Kong, Yong-Hong; Zhang, Gui-Lian

2007-01-01

The GMR effect in magnetic-electric barrier nanostructure, which can be realized experimentally by depositing two parallel metallic ferromagnetic strips with an applied voltage on the top of heterostructure, is investigated theoretically. It is shown that a considerable GMR effect can be achieved in such nanosystems due to the significant transmission difference for electrons tunneling through parallel and antiparallel magnetization configurations. It is also shown that the magnetoresistance ratio is strongly dependent upon the applied voltage to metallic ferromagnetic strips in nanosystems, thus may leading to voltage-tunable GMR devices

Smart Transmission Grids - Benefits and Risks

Directory of Open Access Journals (Sweden)

Velasco-Ramírez E.

2013-01-01

Full Text Available Nowadays the Power Systems are working near their stability limits, for this reason it is necessary and essential a transition to new transmission systems that ensure efficient delivery of electrical energy, with the objective to prevent “blackouts” that causesignificant losses in the economy of any country in the world. This paper analyzes important elements to consider having a healthy and efficient transition from a power grid vertically integrated into a smart transmission grid. A comparative analysis in the model, development, benefits and risks of the implementation of these systems, between two of the main marc of references of smart grids, the EU and the USA is presented.

Efficacy of Tantalum Tungsten Alloys for Diffusion Barrier Applications

Science.gov (United States)

Smathers, D. B.; Aimone, P. R.

2017-12-01

Traditionally either Niobium, Tantalum or a combination of both have been used as diffusion barriers in Nb3Sn Multi-filament wire. Vanadium has also been used successfully but the ultimate RRR of the copper is limited unless an external shell of Niobium is included. Niobium is preferred over Tantalum when alternating current losses are not an issue as the Niobium will react to form Nb3Sn. Pure Tantalum tends to deform irregularly requiring extra starting thickness to ensure good barrier qualities. Our evaluations showed Tantalum lightly alloyed with 3 wt% Tungsten is compatible with the wire drawing process while deforming as well as or better than pure Niobium. Ta3wt%W has been processed as a single barrier and as a distributed barrier to fine dimensions. In addition, the higher modulus and strength of the Tantalum Tungsten alloy improves the overall tensile properties of the wire.

Pharmacy-level barriers to implementing expedited partner therapy in Baltimore, Maryland.

Science.gov (United States)

Qin, Jennifer Z; Diniz, Clarissa P; Coleman, Jenell S

2018-05-01

Addressing record high rates of Chlamydia trachomatis incidence in the United States requires the utilization of effective strategies, such as expedited partner therapy, to reduce reinfection and further transmission. Expedited partner therapy, which can be given as a prescription or medication, is a strategy to treat the sexual partners of index patients diagnosed with a sexually transmitted infection without prior medical evaluation of the partners. There are multiple steps in the prescription-expedited partner therapy cascade, and we sought to identify pharmacy-level barriers to implementing prescription-expedited partner therapy for Chlamydia trachomatis treatment. We used spatial analysis and ArcGIS, a geographic information system, to map and assess geospatial access to pharmacies within Baltimore, MD, neighborhoods with the highest rates of Chlamydia trachomatis (1180.25-4255.31 per 100,000 persons). Expedited partner therapy knowledge and practices were collected via a telephone survey of pharmacists employed at retail pharmacies located in these same neighborhoods. Cost of antibiotic medication in US dollars was collected. Census tracts with the highest Chlamydia trachomatis incidence rates had lower median pharmacy density than other census tracts (26.9 per 100,000 vs 31.4 per 100,000, P barriers to implementing prescription-expedited partner therapy. Although most Baltimore pharmacists were unaware of expedited partner therapy, they were generally receptive to learning about and filling expedited partner therapy prescriptions. This finding suggests the need for wide dissemination of educational material targeted to pharmacists. In areas with limited geographic access to pharmacies, expedited partner therapy strategies that do not depend on partners physically accessing a pharmacy merit consideration. Copyright © 2018 Elsevier Inc. All rights reserved.

Optimizing The Organic/Inorganic Barrier Structure For Flexible Plastic Substrate Encapsulation

Directory of Open Access Journals (Sweden)

Yi-Chiuan Lin

2012-07-01

Full Text Available A multilayered barrier structure stacked with organosilicon and silicon oxide (SiOx films consecutively prepared using plasma-enhanced chemical vapor deposition (PECVD was developed to encapsulate flexible plastic substrate. The evolution on the residual internal stress, structural quality of the organosilicon/SiOx multilayered structure as well as its adhesion to the substrate were found to correlate closely with the thickness of the inset organosilicon layer. Due to the significant discrepancy in the thermal expansion coefficient between the substrate and SiOx film, the thickness of the organosilicon layer deposited onto the substrate and SiOx film thus was crucial to optimize the barrier property of the organosilicon/SiOx structure. The organosilicon/SiOx barrier structure possessed a lowest residual compressive stress and quality adhesion to the substrate was achieved from engineering the organosilicon layer thickness in the multilayered structure. The relaxation of the residual internal stress in the barrier structure led to a dense SiOx film as a consequence of the enhancement in the Si-O-Si networks and thereby resulted in the reduction of the water vapor permeation. Accordingly, a water vapor transmission rate (WVTR below 1 × 10-2 g/m2 /day being potential for the application on the flexible optoelectronic device packaging was achievable from the 3-pairs organosilicon/SiOx multilayered structure deposited onto the polyethylene terephthalate (PET substrate.

Transmission : roadway to a competitive electricity market

Energy Technology Data Exchange (ETDEWEB)

Thon, S. [AltaLink L.P., AB (Canada)

2002-07-01

Having a variety of suppliers, marketers and retailers is the key to developing a successful electricity market which is more competitive on pricing, with less price volatility, more innovative customer products and higher levels of customer services. Some areas of Alberta are developing their own power markets with limited capacity to interact. These include Pincher Creek, Empress, Calgary, Edmonton, and Fort McMurray. It was noted that increasing transmission capacity is the key to ensuring a bigger and more competitive electricity market. Transmission constraints only encourage a small number of suppliers to control the market. The current cost of transmission capacity accounts for less than 5 per cent of an average residential customer's bill, but it plays a major role in providing more choice to competitive electricity suppliers. Developing more transmission capacity will create an even more competitive market that benefits both consumers and suppliers. Prices in Alberta have been very volatile in the past couple of years because of supply and demand issues, and there is a need to increase market liquidity. Alberta's Transmission Administrator is looking to expand the transmission network to alleviate constraints and to lower the cost of power generation, regardless of location. These expansions are not expected to affect customers' bills by more than 2 to 3 per cent. Such transmission concerns are being felt all over North America. The Federal Energy Regulatory Commission (FERC) in the United States also recognizes the link between transmission and creating a competitive electricity market.

Correlation of H-mode barrier width and neutral penetration length

International Nuclear Information System (INIS)

Groebner, R.J.; Mahdavi, M.A.; Leonard, A.W.

2003-01-01

Pedestal studies in DIII-D find a good correlation between the width of the H-mode density barrier and the neutral penetration length. These results are obtained by comparing experimental density profiles to the predictions of an analytic model for the profile, obtained from the particle continuity equations for electrons and deuterium atoms. In its range of validity (edge temperature between 40-500 eV), the analytic model quantitatively predicts the observed decrease of the width as the pedestal density increases, the observed strong increase of the gradient of the density as the pedestal density increases and the observation that L-mode and H-mode profiles with the same pedestal density have very similar shapes. The width of the density barrier, measured from the edge of the electron temperature barrier, is the lower limit for the observed width of the temperature barrier. These results support the hypothesis that particle fueling provides the dominant control for the size of the H-mode transport barrier. (author)

Impedance-based cell monitoring: barrier properties and beyond

Directory of Open Access Journals (Sweden)

Benson Kathrin

2013-01-01

for barrier forming cells. Another impedance-based approach requires cells to be grown directly on solid, micro-structured electrodes. Here, we will discuss the physical background of the different techniques; advantages, disadvantages, and applications will be scrutinized. The aim is to give the reader a comprehensive understanding concerning the range and limits of the application, mainly focusing on endothelial cells.

Dynamics of a scrapie outbreak in a flock of Romanov sheep-estimation of transmission parameters

NARCIS (Netherlands)

Hagenaars, T.H.J.; Donelly, C.A.; Ferguson, N.M.; Anderson, R.M.

2003-01-01

Knowledge of epidemiological mechanisms and parameters underlying scrapie transmission in sheep flocks remains very limited at present. Here we introduce a method for fitting stochastic transmission models to outbreak data to estimate bounds on key transmission parameters. We apply this method to

Frequencies and Predictors of Barriers to Mental Health Service Use: A Longitudinal Study of Hurricane Ike Survivors

Science.gov (United States)

Lowe, Sarah R.; Fink, David S.; Norris, Fran H.; Galea, Sandro

2014-01-01

Background The majority of disaster survivors suffering from psychological symptoms do not receive mental health services. Research on barriers to service use among disaster survivors is limited by a lack of longitudinal studies of representative samples and investigations of predictors of barriers. The purpose of this study was to address these limitations through analysis of a three-wave population-based study of Hurricane Ike survivors (N = 658). Methods Frequencies of preference, outcome expectancy, resource, and stigma barriers among participants with unmet mental health needs were documented and logistic regression using a generalized estimating equations approach explored predisposing (e.g., age), illness-related (e.g., posttraumatic stress) and enabling (e.g., insurance coverage) factors as predictors of each type of barrier. Results Preference barriers were most frequently cited at each wave, whereas stigma barriers were least frequently cited. Older age and higher emotional support predicted preference barriers; being a parent of a child under 18-years old at the time of the hurricane, higher generalized anxiety, and lack of insurance predicted resource barriers; and higher posttraumatic stress predicted stigma barriers. Conclusions These findings suggest that postdisaster practices targeting subpopulations most likely to have barriers to service use may be indicated. PMID:24929355

Magnetic- and material-limiter discharges in Tokapole II

International Nuclear Information System (INIS)

Moyer, R.A.

1988-01-01

Disruptive instabilities were studied in Tokapole II, a small poloidal-divertor tokamak, in magnetic- and material-limiter configurations. In the magnetic limiter configuration, the divertor separatrix defines the tokamak current channel boundary. Limiters or neutralizer plate are not used to remove plasma in the scrape-off region. The relatively hot, dense plasma in the scrape-off region carries 5-20% of the current. In the material-limiter configuration, limiter plates are inserted to the separatrix to remove plasma and current in the scrape-off region. The plates vary the tokamak current-channel boundary condition in a controlled manner, and provide a benchmark for comparison with other tokamaks. Internal and external disruptions have been studied, and several unique features in the magnetic-limiter configuration were identified. The magnetic-limiter configuration enables routine passing of the stability barriers at q(a) = 2 and q(a) = 1, where q(a) is the edge safety factor, without a close-fitting wall, external windings, or detailed profile control techniques. Passing the q(a) = 1 barrier permits operation in the q < 1 regime where total reconnection of the sawtooth does not occur

Studies of the disruption prevention by ECRH at plasma current rise stage in limiter discharges/Possibility of an internal transport barrier producing under dominating electron transport in the T-10 tokamak

International Nuclear Information System (INIS)

Alikaev, V.V.; Borshegovskij, A.A.; Chistyakov, V.V.

2001-01-01

'Studies of the Disruption Prevention by ECRH at Plasma Current Rise Stage in Limiter Discharges' - Studies of disruption prevention by means of ECRH in T-10 at the plasma current rise phase in limiter discharges with circular plasma cross-section were performed. Reliable disruption prevention by ECRH at HF power (P HF ) min level equal to 20% of ohmic heating power P OH was demonstrated. m/n=2/1 mode MHD-activity developed before disruption (with characteristic time ∼ 120 ms) can be considered as disruption precursor and can be used in a feedback system. 'Possibility of an Internal Transport Barrier Producing under Dominating Electron Transport in the T-10 Tokamak' - The reversed shear experiments were carried out on T-10 at the HF power up to 1MW. The reversed shear in the core was produced by on-axis ECCD in direction opposite to the plasma current. There are no obvious signs of Internal Transport Barriers formation under condition when high-k turbulence determines the electron transport. (author)

Smart parking barrier

KAUST Repository

Alharbi, Abdulrazaq M.

2016-05-06

Various methods and systems are provided for smart parking barriers. In one example, among others, a smart parking barrier system includes a movable parking barrier located at one end of a parking space, a barrier drive configured to control positioning of the movable parking barrier, and a parking controller configured to initiate movement of the parking barrier, via the barrier drive. The movable parking barrier can be positioned between a first position that restricts access to the parking space and a second position that allows access to the parking space. The parking controller can initiate movement of the movable parking barrier in response to a positive identification of an individual allowed to use the parking space. The parking controller can identify the individual through, e.g., a RFID tag, a mobile device (e.g., a remote control, smartphone, tablet, etc.), an access card, biometric information, or other appropriate identifier.

Improvement of barrier properties of rotomolded PE containers with nanoclay

Energy Technology Data Exchange (ETDEWEB)

Jamshidi, Shadi; Sundararaj, Uttandaraman, E-mail: u.sundararaj@ucalgary.ca [Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta, T2N 1N4 (Canada)

2015-05-22

Polyethylene (PE) is widely used to make bulk containers in rotational molding process. The challenge in this study is to improve permeation resistance of PE to hydrocarbon solvents and gases. Adding organomodified clay improves the thermal, barrier and mechanical properties of PE. In fact, clay layers create a tortuous path against the permeant, yielding better barrier properties. Due to the non-polar hydrophobic nature of PE and polar hydrophilic structure of clay minerals, the compatibilizer plays a crucial role to enhance the dispersion level of clay in the matrix. In this study High Density Polyethylene (HDPE) and Linear Low Density Polyethylene (LLDPE) layered silicate nanocomposite were melt-compounded with two concentrations of organomodified clay (2 and 4 wt. %). The interaction between nanoclay, compatibilizer and rotomolding grade of PE were examined by using X-ray diffraction, transmission electron microscopy (TEM) and rheology test. Rheology was used to determine the performance of our material at low shear processing condition.

Immune Evasion Strategies of Pathogens in Macrophages: the Potential for Limiting Pathogen Transmission.

Science.gov (United States)

Ren, Yuwei; Khan, Faheem Ahmed; Pandupuspitasari, Nuruliarizki Shinta; Zhang, Shujun

2017-01-01

Preventing pathogen transmission to a new host is of major interest to the immunologist and could benefit from a detailed investigation of pathogen immune evasion strategies. The first line of defense against pathogen invasion is provided by macrophages. When they sense pathogens, macrophages initiate signals to inflammatory and pro-inflammatory cytokines through pattern recognition receptors (PRRs) subsequently mediating phagocytosis and inflammation. The macrophage immune machinery classically includes two subsets: the activated M1 and the activated M2 that respond accordingly in diverse immune challenges. The lipid and glycogen metabolic pathways work together with the lysosome to help the mature phagosome to degrade and eliminate intracellular pathogens in macrophages. The viral evasion strategies are even more complex due to the interplay between autophagy and apoptosis. However, pathogens evolve several strategies to camouflage themselves against immune responses in order to ensure their survival, replication and transmission. These strategies include the muting of PRRs initiated inflammatory responses, attenuation of M1 and/or induction of M2 macrophages, suppression of autophago-lysosomal formation, interference with lipid and glycogen metabolism, and viral mediation of autophagy and apoptosis cross-talk to enhance viral replication. This review focuses on pathogen immune evasion methods and on the strategies used by the host against camouflaged pathogens.

Barriers to condom use among women at risk of HIV/AIDS: a qualitative study from Iran

Directory of Open Access Journals (Sweden)

Lotfi Razieh

2012-05-01

Full Text Available Abstract Background The growing trend of women infected with HIV through sexual transmission is alarming. Factors influencing condom use have not yet been fully identified, especially in countries with conservative cultures and backgrounds. The present study aimed to explore the barriers of condom use in Iranian women at risk of HIV. Methods Using the grounded theory methodology, participants’ experiences and their perceptions regarding condom were collected during semi structured in depth interviews. Participants were 22 women, aged 21–49 years, considered to be at risk for HIV, due to their own or their partner’s sexual behaviors. Qualitative analysis of the data was conducted manually and was guided by constant comparative analysis. Results Two main barriers, personal and socio-environmental emerged from data analysis. Lack of perceived threat, absence of protective motivation, inadequate knowledge, perceived lack of control, negative attitudes towards condom and misperception were the major personal barriers, while unsupportive environments and cultural norms were the common socio-environmental barriers to condom use among these at risk women. Conclusions These critical barriers have to be addressed for implementing effective prevention programs against HIV among populations at risk for HIV.

Radioecological activity limits for radioactive waste disposal

International Nuclear Information System (INIS)

Ahmet, E. Osmanlioglu

2006-01-01

Full text: Near surface disposal is an option used by many countries for the disposal of radioactive waste containing mainly short lived radionuclides. Near surface disposal term includes broad range of facilities from simple trenches to concrete vaults. Principally, disposal of radioactive waste requires the implementation of measures that will provide safety for human health and environment now and in the future. For this reason preliminary activity limits should be determined to avoid radioecological problems. Radioactive waste has to be safely disposed in a regulated manner, consistent with internationally agreed principles and standards and with national legislations to avoid serious radioecological problems. The purpose of this study, presents a safety assessment approach to derive operational and post-closure radioecological activity limits for the disposal of radioactive waste. Disposal system has three components; the waste, the facility (incl. engineered barriers) and the site (natural barriers). Form of the waste (unconditioned or conditioned) is effective at the beginning of the migration scenerio. Existence of the engineered barriers in the facility will provide long term isolation of the waste from environment. The site characteristics (geology, groundwater, seismicity, climate etc.) are important for the safety of the system. Occupational exposure of a worker shall be controlled so that the following dose limits are not exceeded: an effective dose of 20mSv/y averaged over 5 consecutive years; and an effective dose of 50mSv in any single year. The effective dose limit for members of the public recommended by ICRP and IAEA is 1 mSv/y for exposures from all man-made sources [1,2]. Dose constraints are typically a fraction of the dose limit and ICRP recommendations (0.3 mSv/y) could be applied [3,4]. Radioecological activity concentration limits of each radionuclide in the waste (Bq/kg) were calculated. As a result of this study radioecological activity

Chaotic correlations in barrier billiards with arbitrary barriers

International Nuclear Information System (INIS)

Osbaldestin, A H; Adamson, L N C

2013-01-01

We study autocorrelation functions in symmetric barrier billiards for golden mean trajectories with arbitrary barriers. Renormalization analysis reveals the presence of a chaotic invariant set and thus that, for a typical barrier, there are chaotic correlations. The chaotic renormalization set is the analogue of the so-called orchid that arises in a generalized Harper equation. (paper)

Molecular Markers for Interspecies Transmission of Avian Influenza Viruses in Mammalian Hosts

Science.gov (United States)

Lee, Taehyung

2017-01-01

In the last decade, a wide range of avian influenza viruses (AIVs) have infected various mammalian hosts and continuously threaten both human and animal health. It is a result of overcoming the inter-species barrier which is mostly associated with gene reassortment and accumulation of mutations in their gene segments. Several recent studies have shed insights into the phenotypic and genetic changes that are involved in the interspecies transmission of AIVs. These studies have a major focus on transmission from avian to mammalian species due to the high zoonotic potential of the viruses. As more mammalian species have been infected with these viruses, there is higher risk of genetic evolution of these viruses that may lead to the next human pandemic which represents and raises public health concern. Thus, understanding the mechanism of interspecies transmission and molecular determinants through which the emerging AIVs can acquire the ability to transmit to humans and other mammals is an important key in evaluating the potential risk caused by AIVs among humans. Here, we summarize previous and recent studies on molecular markers that are specifically involved in the transmission of avian-derived influenza viruses to various mammalian hosts including humans, pigs, horses, dogs, and marine mammals. PMID:29236050

Refining the global spatial limits of dengue virus transmission by evidence-based consensus.

Directory of Open Access Journals (Sweden)

Oliver J Brady

Full Text Available Dengue is a growing problem both in its geographical spread and in its intensity, and yet current global distribution remains highly uncertain. Challenges in diagnosis and diagnostic methods as well as highly variable national health systems mean no single data source can reliably estimate the distribution of this disease. As such, there is a lack of agreement on national dengue status among international health organisations. Here we bring together all available information on dengue occurrence using a novel approach to produce an evidence consensus map of the disease range that highlights nations with an uncertain dengue status.A baseline methodology was used to assess a range of evidence for each country. In regions where dengue status was uncertain, additional evidence types were included to either clarify dengue status or confirm that it is unknown at this time. An algorithm was developed that assesses evidence quality and consistency, giving each country an evidence consensus score. Using this approach, we were able to generate a contemporary global map of national-level dengue status that assigns a relative measure of certainty and identifies gaps in the available evidence.The map produced here provides a list of 128 countries for which there is good evidence of dengue occurrence, including 36 countries that have previously been classified as dengue-free by the World Health Organization and/or the US Centers for Disease Control. It also identifies disease surveillance needs, which we list in full. The disease extents and limits determined here using evidence consensus, marks the beginning of a five-year study to advance the mapping of dengue virus transmission and disease risk. Completion of this first step has allowed us to produce a preliminary estimate of population at risk with an upper bound of 3.97 billion people. This figure will be refined in future work.

Resource-Constrained Low-Complexity Video Coding for Wireless Transmission

DEFF Research Database (Denmark)

Ukhanova, Ann

of video quality. We proposed a new metric for objective quality assessment that considers frame rate. As many applications deal with wireless video transmission, we performed an analysis of compression and transmission systems with a focus on power-distortion trade-off. We proposed an approach...... for ratedistortion-complexity optimization of upcoming video compression standard HEVC. We also provided a new method allowing decrease of power consumption on mobile devices in 3G networks. Finally, we proposed low-delay and low-power approaches for video transmission over wireless personal area networks, including......Constrained resources like memory, power, bandwidth and delay requirements in many mobile systems pose limitations for video applications. Standard approaches for video compression and transmission do not always satisfy system requirements. In this thesis we have shown that it is possible to modify...

Fabrication and characterization of Au/n-CdTe Schottky barrier under illumination and dark

Science.gov (United States)

Bera, Swades Ranjan; Saha, Satyajit

2018-04-01

CdTe nanoparticles have been grown by chemical reduction method using EDA as capping agent. These are used to fabricate Schottky barrier in a simple cost-effective way at room temperature. The grown nanoparticles are structurally characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM). The optical properties of nano CdTe is characterized by UV-Vis absorption spectra, PL spectra. The band gap of the CdTe nanoparticles is increased as compared to CdTe bulk form indicating there is blue shift. The increase of band gap is due to quantum confinement. Photoluminescence spectra shows peak which corresponds to emission from surface state. CdTe nanofilm is grown on ITO coated glass substrate by dipping it on toluene containing dispersed CdTe nanoparticles. Schottky barrier of Au/n-CdTe is fabricated on ITO coated glass by vacuum deposition of gold. I- V and C- V characteristics of Au/n-CdTe Schottky barrier junction have been studied under dark and light condition. It is found that these characteristics are influenced by surface or interface traps. The values of barrier height, ideality factor, donor concentration and series resistance are obtained from the reverse bias capacitance-voltage measurements.

Poster - 11: Radiation barrier thickness calculations for the GammaPod

International Nuclear Information System (INIS)

La Russa, Daniel; Vandervoort, Eric; Wilkins, David

2016-01-01

A consortium of radiotherapy centers in North America is in the process of evaluating a novel new 60 Co teletherapy device, called the GammaPod™ (Xcision Medical Systems, Columbia Maryland), designed specifically for breast SBRT. The GammaPod consists of 36 collimated 60 Co sources with a total activity of 4320 Ci. The sources are housed in a hemispherical source carrier that rotates during treatment to produce a cylindrically symmetric cone of primary beam spanning 16° – 54° degrees from the horizontal. This unique beam geometry presents challenges when designing or evaluating room shielding for the purposes of meeting regulatory requirements, and for ensuring the safety of staff and the public in surrounding areas. Conventional methods for calculating radiation barrier thicknesses have been adapted so that barrier transmission factors for the GammaPod can be determined from a few relevant distances and characteristics of the primary beam. Simple formalisms have been determined for estimating shielding requirements for primary radiation (with a rotating and non-rotating source carrier), patient-scattered radiation, and leakage radiation. When making worst case assumptions, it was found that conventional barrier thicknesses associated with linac treatment suites are sufficient for shielding all sources of radiation from the GammaPod.

Poster - 11: Radiation barrier thickness calculations for the GammaPod

Energy Technology Data Exchange (ETDEWEB)

La Russa, Daniel; Vandervoort, Eric; Wilkins, David [Radiation Medicine Program, The Ottawa Hospital (Canada)

2016-08-15

A consortium of radiotherapy centers in North America is in the process of evaluating a novel new {sup 60}Co teletherapy device, called the GammaPod™ (Xcision Medical Systems, Columbia Maryland), designed specifically for breast SBRT. The GammaPod consists of 36 collimated {sup 60}Co sources with a total activity of 4320 Ci. The sources are housed in a hemispherical source carrier that rotates during treatment to produce a cylindrically symmetric cone of primary beam spanning 16° – 54° degrees from the horizontal. This unique beam geometry presents challenges when designing or evaluating room shielding for the purposes of meeting regulatory requirements, and for ensuring the safety of staff and the public in surrounding areas. Conventional methods for calculating radiation barrier thicknesses have been adapted so that barrier transmission factors for the GammaPod can be determined from a few relevant distances and characteristics of the primary beam. Simple formalisms have been determined for estimating shielding requirements for primary radiation (with a rotating and non-rotating source carrier), patient-scattered radiation, and leakage radiation. When making worst case assumptions, it was found that conventional barrier thicknesses associated with linac treatment suites are sufficient for shielding all sources of radiation from the GammaPod.

Operational issues and barriers to implementation of prevention of mother-to-child transmission of HIV (PMTCT) interventions in Sub-Saharan Africa.

Science.gov (United States)

Aizire, Jim; Fowler, Mary G; Coovadia, Hoosen M

2013-03-01

Over the past 10 years substantial progress has been made in the implementation of prevention of mother-to-child transmission of HIV (PMTCT) interventions in Sub-Saharan Africa (SSA). In spite of this, new pediatric infections remain unacceptably high, contributing the majority (>90%) of the estimated 390,000 infections globally in 2010; and yet prolonged breastfeeding remains the norm and crucial to overall infant survival. However, there is reason for optimism given the 2010 World Health Organization PMTCT recommendations: to start HIV infected pregnant women with CD4 cell counts less than 350 cells/mm(3) on lifelong antiretroviral therapy (ART); and for mothers not eligible for ART to provide efficacious maternal and/or infant PMTCT antiretroviral (ARV) regimens to be taken during pregnancy, labor/delivery and through breastfeeding. Current attention is on whether to extend maternal ARVs for life once triple ARV PMTCT regimens are started. To dramatically reduce new pediatric infections, individual countries need to politically commit to rapid scale-up of a multi-pronged PMTCT effort: including primary prevention to reduce HIV incidence among women of reproductive age; increased access to family planning services; HIV screening of all pregnant and breastfeeding women followed by ART or ARVs for PMTCT; and comprehensive care for HIV affected families. Efforts to achieve population-level success in SSA need to critically address operational issues and challenges to implementation (health system) and utilization (social, economic and cultural barriers), at the country, health centre and client level that have led to the relatively slow progress in the scale-up of PMTCT strategies.

Barriers, motivators and enablers for dispensing multifocal contact lenses in Mumbai, India.

Science.gov (United States)

Thite, Nilesh; Shah, Ukti; Mehta, Jasmin; Jurkus, Janice

2015-01-01

To understand the potential barriers, motivators and enablers in dispensing multifocal contact lenses (MFCL). Two focus group discussions were conducted to design questionnaires regarding the prescribing habits for multifocal contact lenses (MFCL). Questions on potential barriers and motivators were included. The questionnaires were distributed among 133 eye care practitioners across Mumbai, India. Practitioners fitting one or less patient per month with MFCL completed the survey describing potential barriers, while those who prescribed more MFCL's per month completed the survey describing enablers and motivators. Responses from 102 practitioners were received. Most common potential barriers in prescribing MFCL were increased chair time (75%), lack of readily available trials (69%) and limitation in power range (63%). Lack of awareness among patients (90%) was the most common barrier from patients' outlook. Professional satisfaction (88%) and better business proposition (82%) were observed as main motivators while availability of the trials (84%) and correct patient selection (82%) were the major enablers. Graduate Optometrists felt dispensing MFCL did not offer a good business proposition (p=0.02). Experienced practitioners were observed to be least motivated (p=0.01) and believed that their patients found these lenses expensive (p=0.02). To enhance the MFCL practice, barriers like lack of awareness and limitations in power range must be addressed. Trial lens availability may motivate practitioners to prescribe MFCL. Further probing is required to understand lack of motivation among experienced practitioners. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Acoustic impact on the laminated plates placed between barriers

Science.gov (United States)

Paimushin, V. N.; Gazizullin, R. K.; Fedotenkov, G. V.

2016-11-01

On the basis of previously derived equations, analytical solutions are established on the forced vibrations of two-layer and three-layers rectangular plates hinged in an opening of absolutely rigid walls during the transmission of monoharmonic sound waves. It is assumed that the partition wall is situated between two absolutely rigid barriers, one of them by harmonic oscillation with a given displacements amplitude on the plate forms the incident sound wave, and the other is stationary and has a coating of deformable energy absorbing material with high damping properties. The behavior of acoustic environments in the spaces between the deformable plate and the barriers described by classical wave equation based on the ideal compressible fluid model. To describe the process of dynamic deformation of the energy absorbing coating of fixed barrier, two-dimensional equations of motion based on the use of models transversely soft layer are derived with a linear approximation of the displacement field in the thickness direction of the coating and taking into account the damping properties of the material and the hysteresis model for it. The influence of the physical and mechanical properties of the concerned mechanical system and the frequency of the incident sound wave on the parameters of its insulation properties of the plate, as well as on the parameters of the stress-strain state of the plate has been analyzed.

Small passenger car transmission test-Chevrolet 200 transmission

Science.gov (United States)

Bujold, M. P.

1980-01-01

The small passenger car transmission was tested to supply electric vehicle manufacturers with technical information regarding the performance of commerically available transmissions which would enable them to design a more energy efficient vehicle. With this information the manufacturers could estimate vehicle driving range as well as speed and torque requirements for specific road load performance characteristics. A 1979 Chevrolet Model 200 automatic transmission was tested per a passenger car automatic transmission test code (SAE J651b) which required drive performance, coast performance, and no load test conditions. The transmission attained maximum efficiencies in the mid-eighty percent range for both drive performance tests and coast performance tests. Torque, speed and efficiency curves map the complete performance characteristics for Chevrolet Model 200 transmission.

The Schottky energy barrier dependence of charge injection in organic light-emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Campbell, I.H.; Davids, P.S.; Smith, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico87545 (United States); Barashkov, N.N.; Ferraris, J.P. [The University of Texas at Dallas, Richardson, Texas75083 (United States)

1998-04-01

We present device model calculations of the current{endash}voltage (I{endash}V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. The I{endash}V characteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the device I{endash}V characteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited. {copyright} {ital 1998 American Institute of Physics.}

Composite Based EHV AC Overhead Transmission Lines

DEFF Research Database (Denmark)

Sørensen, Thomas Kjærsgaard

and analysed with regard to the possibilities, limitations and risks widespread application of composite materials on EHV AC overhead transmission lines may present. To form the basis for evaluation of the useability of composite materials, dierent overhead line projects aimed at reducing the environmental...

Smart parking barrier

KAUST Repository

Alharbi, Abdulrazaq M.

2016-01-01

positioning of the movable parking barrier, and a parking controller configured to initiate movement of the parking barrier, via the barrier drive. The movable parking barrier can be positioned between a first position that restricts access to the parking

A new alternative in vertical barrier wall construction

International Nuclear Information System (INIS)

Rawl, G.F.

1997-01-01

A new proprietary vertical barrier wall system has been developed to revolutionize the construction process by eliminating many of the concerns of conventional installation method's with respect to performance, installation constraints and costs. Vertical barrier walls have been used in the environmental and construction industries for a variety of purposes, usually for cut-off or containment. The typical scenario involves a groundwater contamination problem, in which a vertical barrier wall is utilized to contain or confine the spread of contaminants below the ground surface. Conventional construction techniques have been adequate in many applications, but often fall short of their intended purposes due to physical constraints. In many instances, the economics of these conventional methods have limited the utilization of physical barrier walls. Polywall, the trade name for this new barrier wall technology, was subsequently developed to meet these needs and offer a number of distinct advantages in a variety of scenarios by maximizing confinement and minimizing installation costs. Polywall is constructed from chemically resistant high density polyethylene (HDPE) plastic. It has proven in a half-dozen projects to date to be the most cost-effective and technically sound approach to many containment situations. This paper will cover the development of the technology and will provide a brief synopsis of several installations

Transmission Electron Microscopy Physics of Image Formation

CERN Document Server

Kohl, Helmut

2008-01-01

Transmission Electron Microscopy: Physics of Image Formation presents the theory of image and contrast formation, and the analytical modes in transmission electron microscopy. The principles of particle and wave optics of electrons are described. Electron-specimen interactions are discussed for evaluating the theory of scattering and phase contrast. Also discussed are the kinematical and dynamical theories of electron diffraction and their applications for crystal-structure analysis and imaging of lattices and their defects. X-ray microanalysis and electron energy-loss spectroscopy are treated as analytical methods. Specimen damage and contamination by electron irradiation limits the resolution for biological and some inorganic specimens. This fifth edition includes discussion of recent progress, especially in the area of aberration correction and energy filtering; moreover, the topics introduced in the fourth edition have been updated. Transmission Electron Microscopy: Physics of Image Formation is written f...

Enhancement of seeding for electroless Cu plating of metallic barrier layers by using alkyl self-assembled monolayers

Energy Technology Data Exchange (ETDEWEB)

Chen, Sung-Te [Department of Electronic Engineering, Hsiuping University of Science and Technology, Dali 412, Taichung, Taiwan (China); Chung, Yu-Cheng [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Fang, Jau-Shiung [Department of Materials Science and Engineering, National Formosa University, Huwei 632, Taiwan (China); Cheng, Yi-Lung [Department of Electrical Engineering, National Chi-Nan University, Puli, Nantou 545, Taiwan (China); Chen, Giin-Shan, E-mail: gschen@fcu.edu.tw [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China)

2017-05-31

Highlights: • Ta barrier layers are used as model substrates for seeding of electroless plating. • Ta layers seeded with Ta-OH yield seeds with limited density and large size (>10 nm). • Substantial improvement of seeding is obtained with functionalized SAMs. • The mechanism of seeding improvement by functionalized SAMs is clearly clarified. - Abstract: Tethering a self-assembled monolayer (SAM) on ultralow-k (porous) dielectric materials as a seed-trapping layer for electroless Cu plating has been extensively studied. By contrast, literature on direct electroless Cu plating of metallic barrier layers assisted by SAMs is scarce. Therefore, Ta, a crucial component of barrier materials for Cu interconnect metallization, was investigated as a model substrate for a new seeding (Ni catalyst formation) process of electroless Cu plating. Transmission and scanning electron microscopies indicated that catalytic particles formed on Ta films through Ta−OH groups tend to become aggregates with an average size of 14 nm and density of 2 × 10{sup 15} m{sup −2}. By contrast, Ta films with a plasma-functionalized SAM tightly bound catalytic particles without agglomeration, thus yielding a markedly smaller size (3 nm) and higher density (3 × 10{sup 16} m{sup −2}; one order greater than those formed by other novel methods). X-ray photoelectron spectroscopy clearly identified the types of material species and functional groups induced at each step of the seeding process. Moreover, the phase of the catalytic particles, either nickel alkoxide, Ni(OH){sub 2}, or metallic Ni, along with the seed-bonding mechanism, was also unambiguously distinguished. The enhancement of film-formation quality of Cu by the new seeding process was thus demonstrated.

Congruent biogeographical disjunctions at a continent-wide scale: Quantifying and clarifying the role of biogeographic barriers in the Australian tropics

Science.gov (United States)

Crisp, Michael D.; Cook, Dianne H.; Cook, Lyn G.

2017-01-01

Aim To test whether novel and previously hypothesized biogeogaphic barriers in the Australian Tropics represent significant disjunction points or hard barriers, or both, to the distribution of plants. Location Australian tropics: Australian Monsoon Tropics and Australian Wet Tropics. Methods The presence or absence of 6,861 plant species was scored across 13 putative biogeographic barriers in the Australian Tropics, including two that have not previously been recognised. Randomizations of these data were used to test whether more species showed disjunctions (gaps in distribution) or likely barriers (range limits) at these points than expected by chance. Results Two novel disjunctions in the Australian Tropics flora are identified in addition to eleven putative barriers previously recognized for animals. Of these, eleven disjunction points (all within the Australian Monsoon Tropics) were found to correspond to range-ending barriers to a significant number of species, while neither of the two disjunctions found within the Australian Wet Tropics limited a significant number of species’ ranges. Main conclusions Biogeographic barriers present significant distributional limits to native plant species in the Australian Monsoon Tropics but not in the Australian Wet Tropics. PMID:28376094

Electron microscopy characterization of a molybdenum diffusion barrier in metallizations for chip carriers

International Nuclear Information System (INIS)

He Anqiang; Ivey, Douglas G.

2004-01-01

Mo layers have been studied as potential diffusion barriers for Au-Sn solder bonds in micro/optoelectronic device packaging. Solder was electroplated as alternating AuSn and Au 5 Sn multi-layers on wafers covered with Ti as an adhesion layer, followed by Mo as the diffusion barrier and Au as a capping layer. Samples were annealed at 340-420 deg. C for as long as 20 min. Scanning and transmission electron microscopy (SEM and TEM) were utilized to characterize interfacial reactions. Mo was found to be metallurgically stable, relative to the Au-Sn solder and the other metallization components, at temperatures up to at least 420 deg. C. However, the effectiveness of Mo as a barrier can be compromised by two factors. One of these is related to surface roughness associated with AlN or Al 2 O 3 carriers. Non-uniform metallization coverage can lead to breaks in the Mo barrier, resulting in contact between the carrier and molten solder during bonding applications. In addition, thermal stresses generated during heating and cooling can lead to cracking and spalling of the Mo and adhesion layers, exposing the carrier material to molten solder. Pre-annealing can help to relieve the thermal stresses and prevent spalling

Reactive barriers for 137Cs retention

International Nuclear Information System (INIS)

Krumhansl, James L.; Brady, Patrick V.; Anderson, Howard L.

2000-01-01

137 Cs was dispersed globally by cold war activities and, more recently, by the Chernobyl accident. Engineered extraction of 137 Cs from soils and groundwaters is exceedingly difficult. Because the half life of 137 Cs is only 30.2 years, remediation might be more effective (and less costly) if 137 Cs bioavailability could be demonstrably limited for even a few decades by use of a reactive barrier. Essentially permanent isolation must be demonstrated in those few settings where high nuclear level wastes contaminated the environment with 135 Cs (half life 2.3x10 6 years) in addition to 137 Cs. Clays are potentially a low-cost barrier to Cs movement, though their long-term effectiveness remains untested. To identify optimal clays for Cs retention Cs resorption was measured for five common clays: Wyoming Montmorillonite (SWy-1), Georgia Kaolinites (KGa-1 and KGa-2), Fithian Illite (F-Ill), and K-Metabentonite (K-Mbt). Exchange sites were pre-saturated with 0.16 M CsCl for 14 days and readily exchangeable Cs was removed by a series of LiNO 3 and LiCl washes. Washed clay were then placed into dialysis bags and the Cs release to the deionized water outside the bags measured. Release rates from 75 to 139 days for SWy-1, K-Mbt and F- 111 were similar; 0.017 to 0.021% sorbed Cs released per day. Both kaolinites released Cs more rapidly (0.12 to 0.05% of the sorbed Cs per day). In a second set of experiments, clays were doped for 110 days and subjected to an extreme and prolonged rinsing process. All the clays exhibited some capacity for irreversible Cs uptake so most soils have some limited ability to act as a natural barrier to Cs migration. However, the residual loading was greatest on K-Mbt (∼ 0.33 wt% Cs). Thus, this clay would be the optimal material for constructing artificial reactive barriers

Gate-Controlled Transmission of Quantum Hall Edge States in Bilayer Graphene.

Science.gov (United States)

Li, Jing; Wen, Hua; Watanabe, Kenji; Taniguchi, Takashi; Zhu, Jun

2018-02-02

The edge states of the quantum Hall and fractional quantum Hall effect of a two-dimensional electron gas carry key information of the bulk excitations. Here we demonstrate gate-controlled transmission of edge states in bilayer graphene through a potential barrier with tunable height. The backscattering rate is continuously varied from 0 to close to 1, with fractional quantized values corresponding to the sequential complete backscattering of individual modes. Our experiments demonstrate the feasibility to controllably manipulate edge states in bilayer graphene, thus opening the door to more complex experiments.

Gate-Controlled Transmission of Quantum Hall Edge States in Bilayer Graphene

Science.gov (United States)

Li, Jing; Wen, Hua; Watanabe, Kenji; Taniguchi, Takashi; Zhu, Jun

2018-02-01

The edge states of the quantum Hall and fractional quantum Hall effect of a two-dimensional electron gas carry key information of the bulk excitations. Here we demonstrate gate-controlled transmission of edge states in bilayer graphene through a potential barrier with tunable height. The backscattering rate is continuously varied from 0 to close to 1, with fractional quantized values corresponding to the sequential complete backscattering of individual modes. Our experiments demonstrate the feasibility to controllably manipulate edge states in bilayer graphene, thus opening the door to more complex experiments.

Barriers and facilitators of mental health screening in pregnancy.

Science.gov (United States)

Kingston, Dawn; Austin, Marie-Paule; Heaman, Maureen; McDonald, Sheila; Lasiuk, Gerri; Sword, Wendy; Giallo, Rebecca; Hegadoren, Kathy; Vermeyden, Lydia; van Zanten, Sander Veldhuyzen; Kingston, Joshua; Jarema, Karly; Biringer, Anne

2015-11-01

Access to mental health services during pregnancy is most commonly mobilized through formal mental health screening. However, few studies to date have identified barriers and facilitators that affect pregnant women's responses to mental health screening. The objective was to identify barriers and facilitators that influence pregnant women's responses to the screening process and factors associated with their identification. This multi-site, cross-sectional survey recruited pregnant women >16 years of age who spoke/read English in Alberta, Canada. Main outcomes were barriers and facilitators of mental health screening. Descriptive statistics were generated to identify the most common barriers and facilitators and multivariable logistic regression models were conducted to determine factors associated with barriers and facilitators. Study participation rate was 92% (460/500). Women's most common barriers were: significant others normalizing their emotional difficulties; desiring to handle mental health problems on their own; preferring to discuss feelings with significant others; and not knowing what emotions were 'normal'. Women who identified these barriers were more likely not to have been treated previously for mental illness, were primiparous, and could not be completely honest with their provider. Main facilitators were provider characteristics (sensitive, interested), reassurance that mental healthcare is a part of routine prenatal care, hearing that other women have emotional problems during pregnancy and knowing that help was available. The sample comprised largely Caucasian, well-educated, and partnered women, which limits generalizability of the findings. Personal and stigma-related barriers influence pregnant women's responses to mental health screening. Efforts to minimize barriers and enhance facilitators should be explored as potential strategies for optimizing prenatal mental health screening. Copyright © 2015 Elsevier B.V. All rights reserved.

Method of estimating the leakage of multiple barriers in a radioactive materials shipping package

International Nuclear Information System (INIS)

Towell, R.H.; Kapoor, A.; Oras, J.J.

1997-01-01

This paper presents the results of a theoretical study of the performance of multiple leaky barriers in containing radioactive materials in a shipping package. The methods used are reasoned analysis and finite element modeling barriers. The finite element model is developed and evaluated with parameters set to bracket 6M configurations with three to six nested plastic jars, food-pack cans, and plastic bags inside Department of Transportation (DOT) Specification 2R inner containers with pipe thread closures. The results show that nested barriers reach the regulatory limit of 1x10 -6 A 2 /hr in 11 to 52 days, even though individually the barriers would exceed the regulatory limit by a factor of as much as 370 instantaneously. These times are within normal shipping times. The finite element model is conservative because it does not consider the deposition and sticking of the leaking radioactive material on the surfaces inside each boundary

Microstability of TMX-U during initial thermal barrier operation

International Nuclear Information System (INIS)

Casper, T.A.; Berzins, L.V.; Ellis, R.F.; James, R.A.; Lasnier, C.

1984-03-01

During the initial thermal barrier experiments on the Tandem Mirror Experiment-Upgrade (TMX-U), we successfully demonstrated the principle of improved axial tandem mirror confinement achieved by establishment of both the thermal barrier and the ion confining potential peak. During this operation, we created both hot (100-keV) mirror-confined electron and hot (8-keV) mirror-confined ion populations in the end cells. In certain parameter ranges, we observed these species to be weakly unstable to various microinstabilities, but we did not observe clear evidence for an absolute limit to confinement

An extraordinary transmission analogue for enhancing microwave antenna performance

Directory of Open Access Journals (Sweden)

Sarin V. Pushpakaran

2015-10-01

Full Text Available The theory of diffraction limit proposed by H.A Bethe limits the total power transfer through a subwavelength hole. Researchers all over the world have gone through different techniques for boosting the transmission through subwavelength holes resulting in the Extraordinary Transmission (EOT behavior. We examine computationally and experimentally the concept of EOT nature in the microwave range for enhancing radiation performance of a stacked dipole antenna working in the S band. It is shown that the front to back ratio of the antenna is considerably enhanced without affecting the impedance matching performance of the design. The computational analysis based on Finite Difference Time Domain (FDTD method reveals that the excitation of Fabry-Perot resonant modes on the slots is responsible for performance enhancement.

Survey of Transmission Cost Allocation Methodologies for Regional Transmission Organizations

Energy Technology Data Exchange (ETDEWEB)

Fink, S.; Porter, K.; Mudd, C.; Rogers, J.

2011-02-01

The report presents transmission cost allocation methodologies for reliability transmission projects, generation interconnection, and economic transmission projects for all Regional Transmission Organizations.

North-east transmission networks : organization and operations

International Nuclear Information System (INIS)

Roberge, F.

2003-01-01

A review of Quebec's electric power industry was presented along with an outline of non-regulated activity and regulated activities in terms of power generation, transmission, distribution and customer service. Both the transmission and distribution components of Quebec's electric power industry are regulated by the Regie de l'energie. Transmission networks offer access to all wholesalers. Hydro-Quebec TransEnergie was created in 1997 as a functionally independent open access transmission provider with high reliability standards. TransEnergie can address seams issues with neighbouring networks. The three types of services offered in terms of tariffs were also discussed along with data regarding Hydro-Quebec assets, revenue and net income. Hydro-Quebec's relation with the New Brunswick, Ontario, New York and New England were presented along with the issue of congestion and congestion costs. Congestion was defined as an incapacity to deliver energy at low cost because of a limited grid capacity, which results in a need to use more expensive energy. Solutions to decrease congestion include: building new transmission lines; using specialized equipment at existing distribution points; constructing strategically placed power generating stations; reducing the power load; and, increasing network control. The factors that influence investments in transport were also discussed. 1 tab., 9 figs

Asbestos exposure among transmission mechanics in automotive repair shops.

Science.gov (United States)

Salazar, Natalia; Cely-García, María Fernanda; Breysse, Patrick N; Ramos-Bonilla, Juan Pablo

2015-04-01

Asbestos has been used in a broad variety of industrial products, including clutch discs of the transmission system of vehicles. Studies conducted in high-income countries that have analyzed personal asbestos exposures of transmission mechanics have concluded that these workers are exposed to asbestos concentrations in compliance with the US Occupational Safety and Health Administration (US OSHA) occupational standards. Clutch facings are the friction component of clutch discs. If clutch facings are sold separated from the support, they require manipulation before installation in the vehicle. The manipulation of asbestos containing clutch facings is performed by a group of mechanics known as riveters, and includes drilling, countersinking, riveting, sanding, and occasionally grinding, tasks that can potentially release asbestos fibers, exposing the mechanics. These manipulation activities are not reported in studies conducted in high-income countries. This study analyzes personal asbestos exposures of transmission mechanics that manipulate clutch facings. Air sampling campaigns in two transmission repair shops (TRS) were conducted in November 2012 and July 2013 in Bogotá, Colombia. Four workers employed in these TRS were sampled (i.e. three riveters and one supervisor). Personal samples (n = 39), short-term personal samples (n = 49), area samples (n = 52), blank samples (n = 8), and background samples (n = 2) were collected in both TRS during 3-5 consecutive days, following US National Institute for Occupational Safety and Health (US NIOSH) methods 7400 and 7402. Asbestos samples were analyzed by an American Industrial Hygiene Association accredited laboratory. On at least one of the days sampled, all riveters were exposed to asbestos concentrations that exceeded the US OSHA permissible exposure limit or the Colombian permissible limit value. Additionally, from the forty-seven 30-min short-term personal samples collected, two (4.3%) exceeded the US OSHA excursion

New approaches to the design and economics of EHV transmission plant

CERN Document Server

Jones, Brian

1972-01-01

New Approaches to the Design and Economics of EHV Transmission Plant examines the limitations of EHV transmission plant. Analysis is also covered in the book to correct these limitations. The concept behind EHV is that allowable transfer of electricity is related to the square of the voltage. Factors such as the expense of supplying a certain volume of electricity over a given distance and creations of power stations are examined. The book provides economic studies of alternative design policies based on estimation of costs and benefits of the design parameters. The text also focuses on the pr

Transmission of climate risks across sectors and borders

Science.gov (United States)

Challinor, Andy J.; Adger, W. Neil; Benton, Tim G.; Conway, Declan; Joshi, Manoj; Frame, Dave

2018-06-01

Systemic climate risks, which result from the potential for cascading impacts through inter-related systems, pose particular challenges to risk assessment, especially when risks are transmitted across sectors and international boundaries. Most impacts of climate variability and change affect regions and jurisdictions in complex ways, and techniques for assessing this transmission of risk are still somewhat limited. Here, we begin to define new approaches to risk assessment that can account for transboundary and trans-sector risk transmission, by presenting: (i) a typology of risk transmission that distinguishes clearly the role of climate versus the role of the social and economic systems that distribute resources; (ii) a review of existing modelling, qualitative and systems-based methods of assessing risk and risk transmission; and (iii) case studies that examine risk transmission in human displacement, food, water and energy security. The case studies show that policies and institutions can attenuate risks significantly through cooperation that can be mutually beneficial to all parties. We conclude with some suggestions for assessment of complex risk transmission mechanisms: use of expert judgement; interactive scenario building; global systems science and big data; innovative use of climate and integrated assessment models; and methods to understand societal responses to climate risk. These approaches aim to inform both research and national-level risk assessment.

Pharmacists’ Attitudes and Perceived Barriers about Community Pharmacy-Based Cardiovascular Risk Screening Services

Directory of Open Access Journals (Sweden)

Zahra Jahangard-Rafsanjani

2015-10-01

Full Text Available  Background: Community pharmacies are considered as ideal settings to provide cardiovascular risk screening (CRS. However, little is known about pharmacists’ views on providing such services in developing countries including Iran. In the present study, we evaluated the pharmacists’ attitudes and perceived barriers to providing CRS services. Methods:In a cross-sectional study, a questionnaire in three sections was developed by the investigators (attitudes, perceived barriers, and demographics. Five likert items (5 points bipolar scale were designed to evaluate pharmacists’ attitudes about their professional role in providing CRS services in community pharmacies. Seven likert items were designed to assess the pharmacists’ perceived importance of possible barriers to providing the services. The study tool was distributed among a convenient sample of 500 pharmacists, who had participated in a national continuing education event. Results:The response rate was 44% and descriptive statistics and Chi squared test were used to analyze data. Results showed that 70.4% participants had an overall positive attitude to providing CRS services. Pharmacists who were pharmacy owner and pharmacist-in-charge simultaneously were more positive about providing CRS services. Lack of regulatory policy and compensation mechanism, limited physical space in pharmacy and time limitation were reported to be the most important barriers to providing CRS services (> 50% rated as highly important. Low human resource and time limitation were significantly associated with negative attitudes (P: 0.02 and 0.001, respectively.Conclusion:The Iranian pharmacists’ attitudes seem to be positive about providing CRS services; however, their perceived barriers should be addressed prior to CRS service implementation.

Alternating space charge and ambiguity of quantum states in double-barrier structure

International Nuclear Information System (INIS)

Pashkovskij, A.B.

2000-01-01

Solution for nonstationary self-consistent Schroedinger and Poisson equations describing resonance interaction of electrons tunneled through asymmetric double-barrier structures with a high-frequency electric field was obtained by summing perturbation theory series. In case of uniform distribution of electrons by energy the solution is obtained analytically, whereas in case of monoenergy beam, it is reduced to finding the roots of power five algebraic polynomial. It is shown that in some cases the influence of spatial charge gives rise to quite a new effect for the systems: several different electron wave functions will correspond to the same amplitude of high-frequency voltage applied to the structure and, accordingly, the values of high-frequency conductivity, transmission and reflection factors may differ by several times. As a result, instability of current transmission and hysteresis of volt-ampere characteristics may be observed in the structures [ru

Transmission coefficents in strongly deformed nuclei

International Nuclear Information System (INIS)

Aleshin, V.P.

1996-01-01

By using our semiclassical approach to particle evaporation from deformed nuclei developed earlier, we analyze here the heuristic methods of taking into account the effects of shape deformations on particle emission. These methods are based on the 'local' transmission coefficients in which the effective barrier depends on the angle with respect to the symmetry axis. The calculations revealed that the heuristic models are reasonable for particle energy spectra but fail, at large deformations, to describe the angular distributions. In A∼160 nuclei with axis ratio in the vicinity of 2:1 at temperatures of 2-3 MeV, the W (90 )/W(0 ) anisotropies of α particles with respect to the nuclear spin are 1.5 to 3 times larger than our approach predicts. The influence of spin alignment on particle energy spectra is discussed shortly. (orig.)

Natural and Human-Induced Variability in Barrier-Island Response to Sea Level Rise

Science.gov (United States)

Miselis, Jennifer L.; Lorenzo-Trueba, Jorge

2017-12-01

Storm-driven sediment fluxes onto and behind barrier islands help coastal barrier systems keep pace with sea level rise (SLR). Understanding what controls cross-shore sediment flux magnitudes is critical for making accurate forecasts of barrier response to increased SLR rates. Here, using an existing morphodynamic model for barrier island evolution, observations are used to constrain model parameters and explore potential variability in future barrier behavior. Using modeled drowning outcomes as a proxy for vulnerability to SLR, 0%, 28%, and 100% of the barrier is vulnerable to SLR rates of 4, 7, and 10 mm/yr, respectively. When only overwash fluxes are increased in the model, drowning vulnerability increases for the same rates of SLR, suggesting that future increases in storminess may increase island vulnerability particularly where sediment resources are limited. Developed sites are more vulnerable to SLR, indicating that anthropogenic changes to overwash fluxes and estuary depths could profoundly affect future barrier response to SLR.

Atmospheric plasma assisted PLA/microfibrillated cellulose (MFC) multilayer biocomposite for sustainable barrier application

DEFF Research Database (Denmark)

Meriçer, Çağlar; Minelli, Matteo; Angelis, Maria G De

2016-01-01

Fully bio-based and biodegradable materials, such as polylactic acid (PLA) and microfibrillated cellulose (MFC), are considered in order to produce a completely renewable packaging solution for oxygen barrier applications, even at medium-high relative humidity (R.H.). Thin layers of MFC were coated...... on different PLA substrates by activating film surface with an atmospheric plasma treatment, leading to the fabrication of robust and transparent multilayer composite films, which were then characterized by different experimental techniques. UV transmission measurements confirmed the transparency of multilayer...... films (60% of UV transmission rate), while SEM micrographs showed the presence of a continuous, dense and defect free layer of MFC on PLA surface. Concerning the mechanical behavior of the samples, tensile tests revealed that the multilayer films significantly improved the stress at break value of neat...

Understanding barriers to glycaemic control from the patient's perspective

Directory of Open Access Journals (Sweden)

Janes R

2013-06-01

Full Text Available INTRODUCTION: To better understand barriers to glycaemic control from the patient's perspective. METHODS: An interpretative phenomenological approach was used to study the experiences of 15 adults with Type 2 diabetes. Participants each gave a semi-structured interview of their experiences of living with diabetes. Interviews were transcribed, and themes extracted and organised using a patientcentred framework. FINDINGS: Participants' stories confirmed many of the barriers in the literature, particularly those related to context, such as family, finances, work. Barriers also related to negative emotional reactions to diabetes: fear of new events (diagnosis, starting pills/insulin; guilt about getting diabetes and not controlling it; and shame about having diabetes. Barriers also related to unscientific beliefs and personal beliefs. There were additional barriers related to poor clinician-patient relationships. Overall, participants had a poor understanding of diabetes, and complained that their clinician simply 'told them what to do'. CONCLUSION: Using a patient-centred approach, this study identified many barriers to glycaemic control. We suggest that a key barrier is clinician ignorance of their patients' fears, beliefs, expectations, context; of what constitutes a positive therapeutic relationship; and of the limitations of a biomedical approach to patient non-adherence. Faced with both a worsening diabetes epidemic and increasing health care workforce shortages, clinicians urgently need to understand that it is they, not their patients, who must change their approach if diabetes care is to be improved.

CORRELATION OF H-MODE BARRIER WIDTH AND NEUTRAL PENTRATION LENGTH

International Nuclear Information System (INIS)

GROEBNER, R.J.; MAHDAVI, M.A.; LEONARD, A.W.; OSBORNE, T.H.; WOLF, N.S.; PORTER, G.D.; STANGEBY, P.C.; BROOKS, N.H.; COLCHIN, R.J.; HEIDBRINK, W.W.; LUCE, T.C.; MCKEE, G.R.; OWEN, L.W.; WANG, G.; WHYTE, D.G.

2002-01-01

OAK A271 CORRELATION OF H-MODE BARRIER WIDTH AND NEUTRAL PENTRATION LENGTH. Pedestal studies in DIII-D find a good correlation between the width of the region of steep gradient in the H-mode density and the neutral penetration length. These results are obtained by comparing experimental density profiles to the predictions of an analytic model for the profile, obtained from the particle continuity equations for electrons and deuterium atoms. In its range of validity (edge temperature between 40-500 eV), the analytic model quantitatively predicts the observed decrease of the width as the pedestal density increases, the observed strong increase of the gradient of the density as the pedestal density increases and the observation that L-mode and H-mode profiles with the same pedestal density have very similar shapes. The width of the density barrier, measured from the edge of the electron temperature barrier, is the lower limit for the observed width of the temperature barrier. These results support the hypothesis that particle fueling provides a dominant control for the size of the H-mode transport barrier

Stability of barrier buckets with zero RF-barrier separations

Energy Technology Data Exchange (ETDEWEB)

Ng, K.Y.; /Fermilab

2005-03-01

A barrier bucket with very small separation between the rf barriers (relative to the barrier widths) or even zero separation has its synchrotron tune decreasing rather slowly from a large value towards the boundary of the bucket. As a result, large area at the bucket edges can become unstable under the modulation of rf voltage and/or rf phase. In addition, chaotic regions may form near the bucket center and extend outward under increasing modulation. Application is made to those barrier buckets used in the process of momentum mining at the Fermilab Recycler Ring.

Trends in drug delivery through tissue barriers containing tight junctions.

Science.gov (United States)

Tscheik, Christian; Blasig, Ingolf E; Winkler, Lars

2013-04-01

A limitation in the uptake of many drugs is the restricted permeation through tissue barriers. There are two general ways to cross barriers formed by cell layers: by transcytosis or by diffusion through the intercellular space. In the latter, tight junctions (TJs) play the decisive role in the regulation of the barrier permeability. Thus, transient modulation of TJs is a potent strategy to improve drug delivery. There have been extensive studies on surfactant-like absorption enhancers. One of the most effective enhancers found is sodium caprate. However, this modulates TJs in an unspecific fashion. A novel approach would be the specific modulation of TJ-associated marvel proteins and claudins, which are the main structural components of the TJs. Recent studies have identified synthetic peptidomimetics and RNA interference techniques to downregulate the expression of targeted TJ proteins. This review summarizes current progress and discusses the impact on TJs' barrier function.

Barriers to Asthma Management for School Nurses: An Integrative Review.

Science.gov (United States)

Hanley Nadeau, Ellen; Toronto, Coleen E

2016-04-01

Childhood asthma is a growing health concern. Asthma is the most common chronic illness of childhood and a leading cause of emergency room visits, hospitalizations, and school absenteeism. School nurses play a valuable role in asthma management. The purpose of this integrative review is to examine barriers to asthma management for school nurses in the school setting. Findings revealed multiple barriers school nurses encounter in managing asthma. Six themes emerged that included lack of resources and support, insufficient time, communication challenges, limited knowledge, and lack of awareness of school nurses' expertise. Students, parents, primary care physicians, school administration, staff, and school nurses themselves all play a role in constructing barriers to asthma management. There is a need for school nurses and school nurse leaders to focus efforts to develop strategies to overcome barriers to ensure evidence-based, best practice management of asthma in the school setting. © The Author(s) 2015.

Barriers to cross--institutional health information exchange: a literature review.

Science.gov (United States)

Edwards, Ashley; Hollin, Ilene; Barry, Jeffrey; Kachnowski, Stan

2010-01-01

While the development of health information technology, particularly electronic health records (EHR), is a triumph for the advancement of healthcare, non-interoperable clinical data systems lead to fragmented communication and incomplete records. If interoperable HIT systems could be achieved integrated HIT could be leveraged to lessen medical errors, improve patient care and optimize epidemiological research. To understand the barriers to interoperability or health information exchange (HIE), we reviewed the literature on HIT and barriers to HIE. Our search yielded 492 articles, 25 meeting our inclusion criteria. In general, we found that the predominant barriers to HIE are need for standards, security concerns, economic loss to competitors, and federated systems. Research on interoperability is limited because most HIE programs are still in formative stages. More research is needed to fully understand interoperability of HIT, how to overcome the barriers to interoperability, and how to design HIT to better facilitate HIE.

Potential barrier heights at metal on oxygen-terminated diamond interfaces

Energy Technology Data Exchange (ETDEWEB)

Muret, P., E-mail: pierre.muret@neel.cnrs.fr; Traoré, A.; Maréchal, A.; Eon, D. [Inst. NEEL, Univ. Grenoble Alpes, F-38042 Grenoble, France and CNRS, Inst. NEEL, F-38042 Grenoble (France); Pernot, J. [Univ. Grenoble Alpes, Inst. NEEL, F-38042 Grenoble, (France); CNRS, Inst. NEEL, F-38042 Grenoble, (France); Institut Universitaire de France, 103 Boulevard Saint-Michel, F-75005 Paris (France); Pinero, J. C.; Villar, M. P.; Araujo, D., E-mail: daniel.araujo@uca.es [Dpto. Ciencias de los Materiales, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain)

2015-11-28

Electrical properties of metal-semiconductor (M/SC) and metal/oxide/SC structures built with Zr or ZrO{sub 2} deposited on oxygen-terminated surfaces of (001)-oriented diamond films, comprised of a stack of lightly p-doped diamond on a heavily doped layer itself homoepitaxially grown on an Ib substrate, are investigated experimentally and compared to different models. In Schottky barrier diodes, the interfacial oxide layer evidenced by high resolution transmission electron microscopy and electron energy losses spectroscopy before and after annealing, and barrier height inhomogeneities accounts for the measured electrical characteristics until flat bands are reached, in accordance with a model which generalizes that by Tung [Phys. Rev. B 45, 13509 (1992)] and permits to extract physically meaningful parameters of the three kinds of interface: (a) unannealed ones, (b) annealed at 350 °C, (c) annealed at 450 °C with the characteristic barrier heights of 2.2–2.5 V in case (a) while as low as 0.96 V in case (c). Possible models of potential barriers for several metals deposited on well defined oxygen-terminated diamond surfaces are discussed and compared to experimental data. It is concluded that interface dipoles of several kinds present at these compound interfaces and their chemical evolution due to annealing are the suitable ingredients that are able to account for the Mott-Schottky behavior when the effect of the metal work function is ignored, and to justify the reverted slope observed regarding metal work function, in contrast to the trend always reported for all other metal-semiconductor interfaces.

Data analysis strategies for the characterization of normal: superconductor point contacts by barrier strength parameter

Science.gov (United States)

Smith, Charles W.; Reinertson, Randal C.; Dolan, P. J., Jr.

1993-05-01

The theoretical description by Blonder, Tinkham, and Klapwijk [Phys. Rev. B 25, 4515 (1982)] of the I-V curves of normal: superconductor point contacts encompasses a broad range of experimental behavior, from the tunnel junction case, on the one hand, to the clean metallic microconstriction limit on the other. The theory characterizes point contacts in terms of a single parameter, the barrier strength. The differential conductance of a point contact, at zero bias, as a function of temperature, offers a direct experimental method by which the barrier strength parameter can be evaluated. In view of the full range of phenomena incorporated by this theory, we suggest several different strategies for the evaluation of the barrier strength parameter from data in the low and intermediate barrier strength regimes and for measurements in the low temperature (near T=0 K) and high temperature (near T=Tc) limits.

Role of structural barriers in the in vitro bioaccessibility of anthocyanins in comparison with carotenoids.

Science.gov (United States)

Carrillo, Celia; Buvé, Carolien; Panozzo, Agnese; Grauwet, Tara; Hendrickx, Marc

2017-07-15

Although natural structural barriers are factors limiting nutrient bioaccessibility, their specific role in anthocyanin bioaccessibility is still unknown. To better understand how natural barriers govern bioactive compound bioaccessibility, an experimental approach comparing anthocyanins and carotenoids was designed, using a single plant matrix. Initial results revealed increased anthocyanin bioaccessibility in masticated black carrot. To explain this observation, samples with increasing levels of bioencapsulation (free-compound, homogenized-puree, puree) were examined. While carotenoid bioaccessibility was inversely proportional to the level of bioencapsulation, barrier disruption did not increase anthocyanin bioaccessibility. This means that mechanical processing is of particular importance in the case of carotenoid bioaccessibility. While micelle incorporation is the limiting factor for carotenoid bioaccessibility, anthocyanin degradation under alkaline conditions in the gastrointestinal tract dominates. In the absence of structural barriers, anthocyanin bioaccessibility is greater than that of carotenoids. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hepatitis C Virus Sensing by Human Trophoblasts Induces Innate Immune Responses and Recruitment of Maternal NK Cells: Potential Implications for Limiting Vertical Transmission.

Science.gov (United States)

Giugliano, Silvia; Petroff, Margaret G; Warren, Bryce D; Jasti, Susmita; Linscheid, Caitlin; Ward, Ashley; Kramer, Anita; Dobrinskikh, Evgenia; Sheiko, Melissa A; Gale, Michael; Golden-Mason, Lucy; Winn, Virginia D; Rosen, Hugo R

2015-10-15

Hepatitis C virus (HCV) is the world's most common blood-borne viral infection for which there is no vaccine. The rates of vertical transmission range between 3 and 6% with odds 90% higher in the presence of HIV coinfection. Prevention of vertical transmission is not possible because of lack of an approved therapy for use in pregnancy or an effective vaccine. Recently, HCV has been identified as an independent risk factor for preterm delivery, perinatal mortality, and other complications. In this study, we characterized the immune responses that contribute to the control of viral infection at the maternal-fetal interface (MFI) in the early gestational stages. In this study, we show that primary human trophoblast cells and an extravillous trophoblast cell line (HTR8), from first and second trimester of pregnancy, express receptors relevant for HCV binding/entry and are permissive for HCV uptake. We found that HCV-RNA sensing by human trophoblast cells induces robust upregulation of type I/III IFNs and secretion of multiple chemokines that elicit recruitment and activation of decidual NK cells. Furthermore, we observed that HCV-RNA transfection induces a proapoptotic response within HTR8 that could affect the morphology of the placenta. To our knowledge, for the first time, we demonstrate that HCV-RNA sensing by human trophoblast cells elicits a strong antiviral response that alters the recruitment and activation of innate immune cells at the MFI. This work provides a paradigm shift in our understanding of HCV-specific immunity at the MFI as well as novel insights into mechanisms that limit vertical transmission but may paradoxically lead to virus-related pregnancy complications. Copyright © 2015 by The American Association of Immunologists, Inc.

Barriers and promoters of home-based pasteurization of breastmilk among HIV-infected mothers in greater Dar es Salaam, Tanzania.

Science.gov (United States)

Young, Sera; Leshabari, Sebalda; Arkfeld, Chaele; Singler, Jennifer; Dantzer, Emily; Israel-Ballard, Kiersten; Mashio, Clara; Maternowska, Catherine; Chantry, Caroline

2013-06-01

For the past decade, heat-treating breastmilk has been an infant feeding option recommended by the World Health Organization as a strategy to reduce vertical transmission. However, little is known about field experiences with it. Our primary objective was to explore the barriers and promoters of the implementation of breastmilk pasteurization, "flash-heating" (FH), in the real-world setting of Dar es Salaam, Tanzania. Nineteen in-depth interviews were conducted with participants in a home-based infant feeding counseling intervention in which FH was promoted after 6 months of exclusive breastfeeding. Additionally, three focus group discussions were conducted with peer counselors. Interviews were transcribed, translated, and coded independently using NVivo 8 software (QSR International). Data were analyzed using the socioecological framework. Information and support provided by peer counselors were the most important promoters of initiation and continuation of FH; this impacted individual-, interpersonal-, and institutional-level promoters of success. Other promoters included perceived successful breastmilk expression, infant health after initiation of FH, and the inability to pay for replacement milks. Stigma was the most important barrier and cut across all levels of the framework. Other barriers included doubt about the safety or importance of pasteurized breastmilk, difficulties with expressing milk (often attributed to poor diet), and competing responsibilities. The most common suggestion for improving the uptake and duration of FH was community education. Given the acknowledged role of breastmilk pasteurization in the prevention of vertical transmission, further implementation research is needed. A multilevel intervention addressing barriers to FH would likely improve uptake.

Transmission investment problems in Europe: Going beyond standard solutions

International Nuclear Information System (INIS)

Buijs, Patrik; Bekaert, David; Cole, Stijn; Van Hertem, Dirk; Belmans, Ronnie

2011-01-01

The European transmission grid is facing an investment challenge. There is a strong call for more transmission capacity. At the same time, the investment climate is fierce and troubled by public opposition, a complex regulatory framework, etc. Many transmission capacity expansion projects are delayed or canceled. In this paper different technology options suitable for increasing transmission capacity are discussed. The aim is to provide policy-makers with information on technologies without going too much into technical details. The focus is on opportunities and limitations to implement various technological alternatives in practice, including technical solutions that go beyond constructing new connection lines. The criteria used in this technology assessment are based on the obstacles reported in the European Priority Interconnection Plan. This ensures a realistic approach based on problems encountered in real projects. Although AC overhead lines (OHL) will remain the standard solution for grid expansion, it is argued that different technology options can overcome many obstacles that OHL face. Additionally, it is illustrated that the higher investment costs for some solutions can be offset with an increased benefit, e.g. by accomplishing investments with smaller delays due to fewer obstacles encountered. - Research highlights: → Assessment of real problems encountered in transmission investments. → Comparison of transmission technologies. → Techno-economic evaluation of transmission technologies.

47 CFR 27.50 - Power limits and duty cycle.

Science.gov (United States)

2010-10-01

... MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.50 Power limits and duty cycle. (a) The.... In measuring transmissions in this band using an average power technique, the peak-to-average ratio (PAR) of the transmission may not exceed 13 dB. (6) Peak transmit power must be measured over any...

The Manitoba-Ontario intertie : perspectives of a merchant transmission developer

International Nuclear Information System (INIS)

Van Beers, R.

2006-01-01

This presentation discussed merchant transmission models for the Manitoba-Ontario intertie. Merchant transmission involves the reallocation of risk from rate payers to investors and facility users. Merchant transmission is now a niche market due to the fact that the power industry is now more centrally planned. However, merchant transmission structures limit the ability to fully assess congestion and nodal values, and governments continue to retain control of the power sector. Power generation and contracting trends are now changing as a result of market liberalization. In order to be successful, power merchants require financial markets that possess an understanding of the electricity sector. In a merchant transmission scenario, the sizing, timing, connection points, and tariffs will be determined by demonstrated commercial value, and not by central planning principles. The presentation included consideration of government block contracts and reverse block contracts. Details of the Montana-Alberta intertie project were also provided. tabs., figs

Perceived barriers to communication between hospital and nursing home at time of patient transfer.

Science.gov (United States)

Shah, Faraaz; Burack, Orah; Boockvar, Kenneth S

2010-05-01

To identify perceived barriers to communication between hospital and nursing home at the time of patient transfer and examine associations between perceived barriers and hospital and nursing home characteristics. Mailed survey. Medicare- or Medicaid-certified nursing homes in New York State. Nursing home administrators, with input from other nursing home staff. Respondents rated the importance as a barrier to hospital-nursing home communication of (1) hospital providers' attitude, time, effort, training, payment, and familiarity with nursing home patients; (2) unplanned and off-hours transfers; (3) HIPAA privacy regulations; and (4) lost or failed information transmission. Associations were determined between barriers and the following organizational characteristics: (1) hospital-nursing home affiliations, pharmacy or laboratory agreements, cross-site staff visits, and cross-site physician care; (2) hospital size, teaching status, and frequency of geriatrics specialty care; (3) nursing home size, location, type, staffing, and Medicare quality indicators; and (4) hospital-to-nursing home communication, consistency of hospital care with health care goals, and communication quality improvement efforts. Of 647 questionnaires sent, 229 were returned (35.4%). The most frequently reported perceived barriers to communication were sudden or unplanned transfers (44.4%), transfers that occur at night or on the weekend (41.4%), and hospital providers' lack of effort (51.0%), lack of familiarity with patients (45.0%), and lack of time (43.5%). Increased hospital size, teaching hospitals, and urban nursing home location were associated with greater perceived importance of these barriers, and cross-site staff visits and hospital provision of laboratory and pharmacy services to the nursing home were associated with lower perceived importance of these barriers. Hospital and nursing home characteristics and interorganizational relationships were associated with nursing home

Transmission eigenvalues

Science.gov (United States)

Cakoni, Fioralba; Haddar, Houssem

2013-10-01

In inverse scattering theory, transmission eigenvalues can be seen as the extension of the notion of resonant frequencies for impenetrable objects to the case of penetrable dielectrics. The transmission eigenvalue problem is a relatively late arrival to the spectral theory of partial differential equations. Its first appearance was in 1986 in a paper by Kirsch who was investigating the denseness of far-field patterns for scattering solutions of the Helmholtz equation or, in more modern terminology, the injectivity of the far-field operator [1]. The paper of Kirsch was soon followed by a more systematic study by Colton and Monk in the context of developing the dual space method for solving the inverse scattering problem for acoustic waves in an inhomogeneous medium [2]. In this paper they showed that for a spherically stratified media transmission eigenvalues existed and formed a discrete set. Numerical examples were also given showing that in principle transmission eigenvalues could be determined from the far-field data. This first period of interest in transmission eigenvalues was concluded with papers by Colton et al in 1989 [3] and Rynne and Sleeman in 1991 [4] showing that for an inhomogeneous medium (not necessarily spherically stratified) transmission eigenvalues, if they existed, formed a discrete set. For the next seventeen years transmission eigenvalues were ignored. This was mainly due to the fact that, with the introduction of various sampling methods to determine the shape of an inhomogeneous medium from far-field data, transmission eigenvalues were something to be avoided and hence the fact that transmission eigenvalues formed at most a discrete set was deemed to be sufficient. In addition, questions related to the existence of transmission eigenvalues or the structure of associated eigenvectors were recognized as being particularly difficult due to the nonlinearity of the eigenvalue problem and the special structure of the associated transmission

Reinforcement of the Gas Barrier Properties of Polyethylene and Polyamide Through the Nanocomposite Approach: Key Factors and Limitations

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Picard E.

2015-02-01

Full Text Available In this study, polyamide 6 (PA6 and polyethylene (PE nanocomposites were prepared from melt blending and a detailed characterization of the nanocomposite morphology and gas barrier properties was performed. The choice of the organoclay was adapted to each polymer matrix. Exfoliated morphology and improved gas transport properties were obtained by melt mixing the polar PA6 matrix and the organoclay, whereas a microcomposite with poor barrier properties was formed from the binary PE/organomodified clay mixture. Different modified polyethylenes were examined as compatibilizers for the polyethylene/organoclay system. The effect of compatibilizer molar mass, polarity and content was investigated on the clay dispersion and on the gas barrier properties. The optimal compatibilizer to clay weight ratio was found to be equal to 4 whatever the compatibilizer. However, a high degree of clay delamination was obtained with the high molar mass compatibilizer whereas highly swollen clay aggregates resulted from the incorporation of the low molar mass interfacial agents. Contrary to the PA based system, the barrier properties of PE nanocomposites were not directly related to the clay dispersion state but resulted also from the matrix/clay interfacial interactions. Oxidized wax was identified as a very promising interfacial agent and a step by step study was performed to optimize the gas transport properties of the systems based on PE, oxidized wax and organoclay. In particular, an interesting combination of oxidized wax and high molar mass maleic anhydride grafted polyethylene allowing dividing the gas permeability by a factor 2 in comparison with neat PE was proposed.

Microbial diversity and structure are drivers of the biological barrier effect against Listeria monocytogenes in soil.

Science.gov (United States)

Vivant, Anne-Laure; Garmyn, Dominique; Maron, Pierre-Alain; Nowak, Virginie; Piveteau, Pascal

2013-01-01

Understanding the ecology of pathogenic organisms is important in order to monitor their transmission in the environment and the related health hazards. We investigated the relationship between soil microbial diversity and the barrier effect against Listeria monocytogenes invasion. By using a dilution-to-extinction approach, we analysed the consequence of eroding microbial diversity on L. monocytogenes population dynamics under standardised conditions of abiotic parameters and microbial abundance in soil microcosms. We demonstrated that highly diverse soil microbial communities act as a biological barrier against L. monocytogenes invasion and that phylogenetic composition of the community also has to be considered. This suggests that erosion of diversity may have damaging effects regarding circulation of pathogenic microorganisms in the environment.

Project Guarantee 1985. Final repository for low- and intermediate-level radioactive wastes: The system of safety barriers

International Nuclear Information System (INIS)

Anon.

1985-01-01

The safety barrier system for the type B repository for low- and intermediate-level waste is described. The barrier parameters which are relevant for safety analysis are quantified and associated error limits and data scatter are given. The aim of the report is to give a summary documentation of the safety analysis input data and their scientific background. For secure containment of radioactive waste safety barriers are used which effectively limit the release of radioactive material from the repository (release barriers) and effectively retard the entry of the original radioactive material into the biosphere (time barriers). In the case of low- and intermediate-level waste the technical safety barrier system comprises: waste solidification matrix (cement, bitumen and resin), immobilisation of the waste packages in containers using liquid cement, concrete repository containers, backfilling of remaining vacant storage space with special concrete, concrete lining of the repository caverns, sealing of access tunnels on final closure of the repository. Natural geological safety barriers - host rock and overlying formations - have the following important functions. Because of its stability, the host rock in the repository zone protects the technical safety barrier system from destruction caused by climatic effects and erosion for a sufficient length of time. It also provides for low water flow and favourable chemistry (reducing conditions)

Transmission dose estimation algorithm for in vivo dosimetry

International Nuclear Information System (INIS)

Yun, Hyong Geun; Shin, Kyo Chul; Huh, Soon Nyung; Woo, Hong Gyun; Ha, Sung Whan; Lee, Hyoung Koo

2002-01-01

Measurement of transmission dose is useful for in vivo dosimetry of QA purpose. The objective of this study is to develope an algorithm for estimation of tumor dose using measured transmission dose for open radiation field. Transmission dose was measured with various field size (FS), phantom thickness (Tp), and phantom chamber distance (PCD) with an acrylic phantom for 6 MV and 10 MV X-ray. Source to chamber distance (SCD) was set to 150 cm. Measurement was conducted with a 0.6 cc Farmer type ion chamber. Using measured data and regression analysis, an algorithm was developed for estimation of expected reading of transmission dose. Accuracy of the algorithm was tested with flat solid phantom with various settings. The algorithm consisted of quadratic function of log(A/P) (where A/P is area-perimeter ratio) and tertiary function of PCD. The algorithm could estimate dose with very high accuracy for open square field, with errors within ±0.5%. For elongated radiation field, the errors were limited to ±1.0%. The developed algorithm can accurately estimate the transmission dose in open radiation fields with various treatment settings

Transmission dose estimation algorithm for in vivo dosimetry

Energy Technology Data Exchange (ETDEWEB)

Yun, Hyong Geun; Shin, Kyo Chul [Dankook Univ., Seoul (Korea, Republic of); Huh, Soon Nyung; Woo, Hong Gyun; Ha, Sung Whan [Seoul National Univ., Seoul (Korea, Republic of); Lee, Hyoung Koo [Catholic Univ., Seoul (Korea, Republic of)

2002-07-01

Measurement of transmission dose is useful for in vivo dosimetry of QA purpose. The objective of this study is to develope an algorithm for estimation of tumor dose using measured transmission dose for open radiation field. Transmission dose was measured with various field size (FS), phantom thickness (Tp), and phantom chamber distance (PCD) with an acrylic phantom for 6 MV and 10 MV X-ray. Source to chamber distance (SCD) was set to 150 cm. Measurement was conducted with a 0.6 cc Farmer type ion chamber. Using measured data and regression analysis, an algorithm was developed for estimation of expected reading of transmission dose. Accuracy of the algorithm was tested with flat solid phantom with various settings. The algorithm consisted of quadratic function of log(A/P) (where A/P is area-perimeter ratio) and tertiary function of PCD. The algorithm could estimate dose with very high accuracy for open square field, with errors within {+-}0.5%. For elongated radiation field, the errors were limited to {+-}1.0%. The developed algorithm can accurately estimate the transmission dose in open radiation fields with various treatment settings.

Influenza A virus transmission via respiratory aerosols or droplets as it relates to pandemic potential

Science.gov (United States)

Richard, Mathilde; Fouchier, Ron A.M.

2015-01-01

Many respiratory viruses of humans originate from animals. For instance, there are now eight paramyxoviruses, four coronaviruses and four orthomxoviruses that cause recurrent epidemics in humans but were once confined to other hosts. In the last decade, several members of the same virus families have jumped the species barrier from animals to humans. Fortunately, these viruses have not become established in humans, because they lacked the ability of sustained transmission between humans. However, these outbreaks highlighted the lack of understanding of what makes a virus transmissible. In part triggered by the relatively high frequency of occurrence of influenza A virus zoonoses and pandemics, the influenza research community has started to investigate the viral genetic and biological traits that drive virus transmission via aerosols or respiratory droplets between mammals. Here we summarize recent discoveries on the genetic and phenotypic traits required for airborne transmission of zoonotic influenza viruses of subtypes H5, H7 and H9 and pandemic viruses of subtypes H1, H2 and H3. Increased understanding of the determinants and mechanisms of respiratory virus transmission is not only key from a basic scientific perspective, but may also aid in assessing the risks posed by zoonotic viruses to human health, and preparedness for such risks. PMID:26385895

Through-Metal-Wall Power Delivery and Data Transmission for Enclosed Sensors: A Review

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Ding-Xin Yang

2015-12-01

Full Text Available The aim of this review was to assess the current viable technologies for wireless power delivery and data transmission through metal barriers. Using such technologies sensors enclosed in hermetical metal containers can be powered and communicate through exterior power sources without penetration of the metal wall for wire feed-throughs. In this review, we first discuss the significant and essential requirements for through-metal-wall power delivery and data transmission and then we: (1 describe three electromagnetic coupling based techniques reported in the literature, which include inductive coupling, capacitive coupling, and magnetic resonance coupling; (2 present a detailed review of wireless ultrasonic through-metal-wall power delivery and/or data transmission methods; (3 compare various ultrasonic through-metal-wall systems in modeling, transducer configuration and communication mode with sensors; (4 summarize the characteristics of electromagnetic-based and ultrasound-based systems, evaluate the challenges and development trends. We conclude that electromagnetic coupling methods are suitable for through thin non-ferromagnetic metal wall power delivery and data transmission at a relatively low data rate; piezoelectric transducer-based ultrasonic systems are particularly advantageous in achieving high power transfer efficiency and high data rates; the combination of more than one single technique may provide a more practical and reliable solution for long term operation.

Theoretical modeling of transport barriers in helical plasmas

International Nuclear Information System (INIS)

Toda, S.; Itoh, K.; Ohyabu, N.

2008-10-01

A unified transport modelling to explain electron Internal Transport Barriers (e-ITB) in helical plasmas and Internal Diffusion Barriers (IDB) observed in Large Helical Device (LHD) is proposed. The e-ITB can be predicted with the effect of zonal flows to obtain the e-ITB in the low collisional regime when the radial variation of the particle anomalous diffusivity is included. Transport analysis in this article can newly show that the particle fuelling induces the IDB formation when this unified transport modelling is used in the high collisional regime. The density limit for the IDB in helical plasmas is also examined including the effect of the radiation loss. (author)

Inner ear barriers to nanomedicine-augmented drug delivery and imaging

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Jing Zou

2016-12-01

Full Text Available There are several challenges to inner ear drug delivery and imaging due to the existence of tight biological barriers to the target structure and the dense bone surrounding it. Advances in imaging and nanomedicine may provide knowledge for overcoming the existing limitations to both the diagnosis and treatment of inner ear diseases. Novel techniques have improved the efficacy of drug delivery and targeting to the inner ear, as well as the quality and accuracy of imaging this structure. In this review, we will describe the pathways and biological barriers of the inner ear regarding drug delivery, the beneficial applications and limitations of the imaging techniques available for inner ear research, the behavior of engineered nanomaterials in inner ear applications, and future perspectives for nanomedicine-based inner ear imaging.

Small passenger car transmission test; Chevrolet LUV transmission

Science.gov (United States)

Bujold, M. P.

1980-01-01

A 1978 Chevrolet LUV manual transmission tested per the applicable portions of a passenger car automatic transmission test code (SAE J65lb) which required drive performance, coast performance, and no load test conditions. Under these test conditions, the transmission attained maximum efficiencies in the upper ninety percent range for both drive performance tests and coast performance tests. The major results of this test (torque, speed, and efficiency curves) are presented. Graphs map the complete performance characteristics for the Chevrolet LUV transmission.

Emergence of the virulence-associated PB2 E627K substitution in a fatal human case of highly pathogenic avian influenza virus A(H7N7) infection as determined by Illumina ultra-deep sequencing

NARCIS (Netherlands)

Jonges, Marcel; Welkers, Matthijs R. A.; Jeeninga, Rienk E.; Meijer, Adam; Schneeberger, Peter; Fouchier, Ron A. M.; de Jong, Menno D.; Koopmans, Marion

2014-01-01

Avian influenza viruses are capable of crossing the species barrier and infecting humans. Although evidence of human-to-human transmission of avian influenza viruses to date is limited, evolution of variants toward more-efficient human-to-human transmission could result in a new influenza virus

Normal Incidence of Sound Transmission Loss of a Double-Leaf Partition Inserted with a Microperforated Panel

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A. Putra

2013-01-01

Full Text Available A double-leaf partition in engineering structures has been widely applied for its advantages, that is, in terms of its mechanical strength as well as its lightweight property. In noise control, the double-leaf also serves as an effective noise barrier. Unfortunately at low frequency, the sound transmission loss reduces significantly due to the coupling between the panels and the air between them. This paper studies the effect of a microperforated panel (MPP inserted inside a double-leaf partition on the sound transmission loss performance of the system. The MPP insertion is proposed to provide a hygienic double-leaf noise insulator replacing the classical abrasive porous materials between the panels. It is found that the transmission loss improves at the troublesome mass-air-mass resonant frequency if the MPP is located closer to the solid panel. The mathematical model is derived for normal incidence of acoustic loading.

[Do organizational barriers to pneumococcal and influenza vaccine access exist?].

Science.gov (United States)

Rousseau, Louise; Guay, Maryse; Archambault, Denis; El m'ala, Zahra; Abdelaziz, Nadia

2007-01-01

Despite the implementation of a Quebec immunization program against influenza and pneumococcal disease (PQIIP), vaccine coverage has remained low. There have been many studies on personal barriers to vaccination, but few have explored other kinds of barriers. To explore the presence of barriers in relation to the organization of the health care system and to propose recommendations for increasing vaccine coverage. Within a mixed protocol, a phone survey of 996 people in the target population and a case study implicating the follow-up of the PQIIP with all the site and actor categories via 43 semistructured interviews and 4 focus groups were realized. Survey data underwent a descriptive statistical analysis. Qualitative analysis followed the Miles and Huberman approach. The results indicate the presence of barriers with regard to information accessibility. These include access to: the physicians' recommendation, knowledge of the efficacy or the security of vaccines, and admissibility of clients to the PQIIP. Organizational barriers were also found to limit access to vaccination, especially in terms of restricted choices of time and location. Coordination and incentives mechanisms are not optimal. Removal of organizational barriers depends more on strategic rather than structural factors. Addressing organizational barriers should be an important component of strategies aimed at improving vaccine coverage. Public health authorities should focus on strategic management of the information and inter-organizational environment.

Transmission issues

International Nuclear Information System (INIS)

Bradford, J.; Wilson, L.; Thon, S.; Millar, N.

2005-01-01

This session on transmission issues focused on the role that transmission plays in electricity markets and the importance of getting the market structure right in terms of generation divestiture with buy back contracts, demand side responsive programs, transmission upgrades and long term contracts. The difficulties of distinguishing between market power and scarcity were examined along with some of the complications that ensue if transmission experiences congestion, as exemplified by the August 2003 blackout in eastern North America. The presentations described the best ways to handle transmission issues, and debated whether transmission should be deregulated or follow market forces. Issues of interconnections and reliability of connections were also debated along with the attempt to integrate renewables into the grid. Some presentations identified what new transmission must be built and what must be done to ensure that transmission gets built. The challenges and business opportunities for transmission in Alberta were discussed with reference to plans to invest in new infrastructure, where it is going outside of the province and how it works with other jurisdictions. Manitoba's Conawapa Hydro Project and its 2000 MW tie line to Ontario was also discussed. Some examples of non-optimal use of interconnections in Europe were also discussed in an effort to learn from these mistakes and avoid them in Canada. tabs., figs

105K West Isolation Barrier Acceptance Test results