Magnetoresistance oscillations of two-dimensional electron systems in lateral superlattices with structured unit cells

Science.gov (United States)

Gerhardts, Rolf R.

2015-11-01

Model calculations for commensurability oscillations of the low-field magnetoresistance of two-dimensional electron systems (2DES) in lateral superlattices, consisting of unit cells with an internal structure, are compared with recent experiments. The relevant harmonics of the effective modulation potential depend not only on the geometrical structure of the modulated unit cell, but also strongly on the nature of the modulation. While higher harmonics of an electrostatically generated surface modulation are exponentially damped at the position of the 2DES about 90 nm below the surface, no such damping appears for strain-induced modulation generated, e.g., by the deposition of stripes of calixarene resist on the surface before cooling down the sample.

Effects of different feeder layers on culture of bovine embryonic stem cell-like cells in vitro.

Science.gov (United States)

Cong, Shan; Cao, Guifang; Liu, Dongjun

2014-12-01

To find a suitable feeder layer is important for successful culture conditions of bovine embryonic stem cell-like cells. In this study, expression of pluripotency-related genes OCT4, SOX2 and NANOG in bovine embryonic stem cell-like cells on mouse embryonic fibroblast feeder layers at 1-5 passages were monitored in order to identify the possible reason that bovine embryonic stem cell-like cells could not continue growth and passage. Here, we developed two novel feeder layers, mixed embryonic fibroblast feeder layers of mouse and bovine embryonic fibroblast at different ratios and sources including mouse fibroblast cell lines. The bovine embryonic stem cell-like cells generated in our study displayed typical stem cell morphology and expressed specific markers such as OCT4, stage-specific embryonic antigen 1 and 4, alkaline phosphatase, SOX2, and NANOG mRNA levels. When feeder layers and cell growth factors were removed, the bovine embryonic stem cell-like cells formed embryoid bodies in a suspension culture. Furthermore, we compared the expression of the pluripotent markers during bovine embryonic stem cell-like cell in culture on mixed embryonic fibroblast feeder layers, including mouse fibroblast cell lines feeder layers and mouse embryonic fibroblast feeder layers by real-time quantitative polymerase chain reaction. Results suggested that mixed embryonic fibroblast and sources including mouse fibroblast cell lines feeder layers were more suitable for long-term culture and growth of bovine embryonic stem cell-like cells than mouse embryonic fibroblast feeder layers. The findings may provide useful experimental data for the establishment of an appropriate culture system for bovine embryonic stem cell lines.

A microfluidic galvanic cell on a single layer of paper

Science.gov (United States)

Purohit, Krutarth H.; Emrani, Saina; Rodriguez, Sandra; Liaw, Shi-Shen; Pham, Linda; Galvan, Vicente; Domalaon, Kryls; Gomez, Frank A.; Haan, John L.

2016-06-01

Paper microfluidics is used to produce single layer galvanic and hybrid cells to produce energy that could power paper-based analytical sensors. When two aqueous streams are absorbed onto paper to establish co-laminar flow, the streams stay in contact with each other with limited mixing. The interface at which mixing occurs acts as a charge-transfer region, eliminating the need for a salt bridge. We designed a Cusbnd Zn galvanic cell that powers an LED when two are placed in series. We also used more powerful redox couples (formate and silver, formate and permanganate) to produce higher power density (18 and 3.1 mW mg-1 Pd). These power densities are greater than previously reported paper microfluidic fuel cells using formate or methanol. The single layer design is much more simplified than previous reports of multi-layer galvanic cells on paper.

Multi-bits memory cell using degenerated magnetic states in a synthetic antiferromagnetic reference layer

International Nuclear Information System (INIS)

Fukushima, Akio; Yakushiji, Kay; Konoto, Makoto; Kubota, Hitoshi; Imamura, Hiroshi; Yuasa, Shinji

2016-01-01

We newly developed a magnetic memory cell having multi-bit function. The memory cell composed of a perpendicularly magnetized magnetic tunnel junction (MB-pMTJ) and a synthetic antiferromagnetic reference layer. The multi-bit function is realized by combining the freedom of states of the magnetic free layer and that in the antiferromagnetically coupled reference layer. The structure of the reference layer is (FeB/Ta/[Co/Pt]_3)/Ru/([Co/Pt]_6); the top and the bottom layers are coupled through Ru layer where the reference layer has two degrees of freedom of a head-to-head and a bottom-to-bottom magnetic configuration. A four-state memory cell is realized by combination of both degrees of freedom. The states in the reference layer however is hardly detected by the total resistance of MB-pMTJ, because the magnetoresistance effect in the reference layer is negligibly small. That implies that the resistance values for the different states in the reference layer are degenerated. On the other hand, the two different states in the reference layer bring different stray fields to the free layer, which generate two different minor loop with different switching fields. Therefore, the magnetic states in the reference layer can be differentiated by the two-step reading, before and after applying the appropriately pulsed magnetic field which can identify the initial state in the reference layer. This method is similar to distinguishing different magnetic states in an in-plane magnetized spin-valve element. We demonstrated that four different states in the MB-pMTJ can be distinguished by the two-step read-out. The important feature of the two-step reading is a practically large operation margins (large resistance change in reading) which is equal to that of a single MTJ. Even though the two-step reading is a destructive method by which 50% of the magnetic state is changed, this MB-pMTJ is promising for high density non-volatile memory cell with a minor cost of operation speed

In vitro evaluation of chondrosarcoma cells and canine chondrocytes on layer-by-layer (LbL) self-assembled multilayer nanofilms

International Nuclear Information System (INIS)

Shaik, J; Mohammed, J Shaikh; McShane, M J; Mills, D K

2013-01-01

Short-term cell–substrate interactions of two secondary chondrocyte cell lines (human chondrosarcoma cells, canine chondrocytes) with layer-by-layer self-assembled multilayer nanofilms were investigated for a better understanding of cellular-behaviour dependence on a number of nanofilm layers. Cell–substrate interactions were studied on polyelectrolyte multilayer nanofilms (PMNs) of eleven different biomaterials. Surface characterization of PMNs performed using AFM showed increasing surface roughness with increasing number of layers for most of the biomaterials. LDH-L and MTT assays were performed on chondrosarcoma cells and canine chondrocytes, respectively. A major observation was that 10-bilayer nanofilms exhibited lesser cytotoxicity towards human chondrosarcoma cells than their 5-bilayer counterparts. In the case of canine chondrocytes, BSA enhanced cell metabolic activity with increasing number of layers, underscoring the importance of the multilayer nanofilm architecture on cellular behaviour. (paper)

A Two-Layer Gene Circuit for Decoupling Cell Growth from Metabolite Production.

Science.gov (United States)

Lo, Tat-Ming; Chng, Si Hui; Teo, Wei Suong; Cho, Han-Saem; Chang, Matthew Wook

2016-08-01

We present a synthetic gene circuit for decoupling cell growth from metabolite production through autonomous regulation of enzymatic pathways by integrated modules that sense nutrient and substrate. The two-layer circuit allows Escherichia coli to selectively utilize target substrates in a mixed pool; channel metabolic resources to growth by delaying enzymatic conversion until nutrient depletion; and activate, terminate, and re-activate conversion upon substrate availability. We developed two versions of controller, both of which have glucose nutrient sensors but differ in their substrate-sensing modules. One controller is specific for hydroxycinnamic acid and the other for oleic acid. Our hydroxycinnamic acid controller lowered metabolic stress 2-fold and increased the growth rate 2-fold and productivity 5-fold, whereas our oleic acid controller lowered metabolic stress 2-fold and increased the growth rate 1.3-fold and productivity 2.4-fold. These results demonstrate the potential for engineering strategies that decouple growth and production to make bio-based production more economical and sustainable. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Unit-cell design for two-dimensional phase-field simulation of microstructure evolution in single-crystal Ni-based superalloys during solidification

Directory of Open Access Journals (Sweden)

Dongjia Cao

2017-12-01

Full Text Available Phase-field simulation serves as an effective tool for quantitative characterization of microstructure evolution in single-crystal Ni-based superalloys during solidification nowadays. The classic unit cell is either limited to γ dendrites along crystal orientation or too ideal to cover complex morphologies for γ dendrites. An attempt to design the unit cell for two-dimensional (2-D phase-field simulations of microstructure evolution in single-crystal Ni-based superalloys during solidification was thus performed by using the MICRESS (MICRostructure Evolution Simulation Software in the framework of the multi-phase-field (MPF model, and demonstrated in a commercial TMS-113 superalloy. The coupling to CALPHAD (CALculation of PHAse Diagram thermodynamic database was realized via the TQ interface and the experimental diffusion coefficients were utilized in the simulation. Firstly, the classic unit cell with a single γ dendrite along crystal orientation was employed for the phase-field simulation in order to reproduce the microstructure features. Then, such simple unit cell was extended into the cases with two other different crystal orientations, i.e., and . Thirdly, for crystal orientations, the effect of γ dendritic orientations and unit cell sizes on microstructure and microsegregation was comprehensively studied, from which a new unit cell with multiple γ dendrites was proposed. The phase-field simulation with the newly proposed unit cell was further performed in the TMS-113 superalloy, and the microstructure features including the competitive growth of γ dendrites, microsegregation of different solutes and distribution of γ′ grains, can be nicely reproduced.

Frequency distribution of the reduced unit cells of centred lattices from the Protein Data Bank.

Science.gov (United States)

Swaminathan, Kunchithapadam

2012-03-01

In crystallography, a centred conventional lattice unit cell has its corresponding reduced primitive unit cell. This study presents the frequency distribution of the reduced unit cells of all centred lattice entries of the Protein Data Bank (as of 23 August 2011) in four unit-cell-dimension-based groups and seven interaxial-angle-based subgroups. This frequency distribution is an added layer of support during space-group assignment in new crystals. In addition, some interesting patterns of distribution are discussed as well as how some reduced unit cells could be wrongly accepted as primitive lattices in a different crystal system.

Simulation of the catalyst layer in PEMFC based on a novel two-phase lattice model

Energy Technology Data Exchange (ETDEWEB)

Zhang Jiejing; Yang Wei; Xu Li [School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072 (China); Wang Yuxin, E-mail: yxwang@tju.edu.cn [School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin 300072 (China)

2011-08-01

Highlights: > We propose a novel two phase lattice model of catalyst layer in PEMFC. > The model features a catalyst phase and a mixed ionomer and pores phase. > Transport and electrochemical reaction in the lattice are simulated. > The model enables more accurate results than pore-solid two phase model. > Profiles of oxygen level and reaction rate across catalyst layer vary with cell current. - Abstract: A lattice model of catalyst layer in proton exchange membrane fuel cells (PEMFCs), consisting of randomly distributed catalyst phase (C phase) and mixed ionomer-pore phase (IP phase), was established by means of Monte Carlo method. Transport and electrochemical reactions in the model catalyst layer were calculated. The newly proposed C-IP model was compared with previously established pore-solid two phase model. The variation of oxygen level and reaction rate along the thickness of catalyst layer with cell current was discussed. The effect of ionomer distribution across catalyst layer was studied by comparing profiles of oxygen level, reaction rate and overpotential, as well as corresponding polarization curves.

Two-finger (TF) SPUDT cells.

Science.gov (United States)

Martin, Guenter; Biryukov, Sergey V; Schmidt, Hagen; Steiner, Bernd; Wall, Bert

2011-03-01

SPUDT cells including two fingers are only known thus far for so-called NSPUDT directions. In that case, usual solid-finger cells are used. The purpose of the present paper is to find SPUDT cell types consisting of two fingers only for pure mode directions. Two-finger (TF) cells for pure mode directions on substrates like 128°YX LiNbO(3) and YZ LiNbO(3) were found by means of an optimization procedure. The forward direction of a TF-cell SPUDT on 128°YX LiNbO(3) was determined experimentally. The properties of the new cells are compared with those of conventional SPUDT cells. The reflectivity of TF cells on 128°YX LiNbO(3) turns out to be two to three times larger than that of distributed acoustic reflection transducer (DART) and Hanma-Hunsinger cells at the same metal layer thickness.

Epitaxially grown polycrystalline silicon thin-film solar cells on solid-phase crystallised seed layers

Energy Technology Data Exchange (ETDEWEB)

Li, Wei, E-mail: weili.unsw@gmail.com; Varlamov, Sergey; Xue, Chaowei

2014-09-30

Highlights: • Crystallisation kinetic is used to analyse seed layer surface cleanliness. • Simplified RCA cleaning for the seed layer can shorten the epitaxy annealing duration. • RTA for the seed layer can improve the quality for both seed layer and epi-layer. • Epitaxial poly-Si solar cell performance is improved by RTA treated seed layer. - Abstract: This paper presents the fabrication of poly-Si thin film solar cells on glass substrates using seed layer approach. The solid-phase crystallised P-doped seed layer is not only used as the crystalline template for the epitaxial growth but also as the emitter for the solar cell structure. This paper investigates two important factors, surface cleaning and intragrain defects elimination for the seed layer, which can greatly influence the epitaxial grown solar cell performance. Shorter incubation and crystallisation time is observed using a simplified RCA cleaning than the other two wet chemical cleaning methods, indicating a cleaner seed layer surface is achieved. Cross sectional transmission microscope images confirm a crystallographic transferal of information from the simplified RCA cleaned seed layer into the epi-layer. RTA for the SPC seed layer can effectively eliminate the intragrain defects in the seed layer and improve structural quality of both of the seed layer and the epi-layer. Consequently, epitaxial grown poly-Si solar cell on the RTA treated seed layer shows better solar cell efficiency, V{sub oc} and J{sub sc} than the one on the seed layer without RTA treatment.

A two-layer linear piezoelectric micromotor.

Science.gov (United States)

Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

2015-03-01

A first bending (B1) mode two-layer piezoelectric ultrasonic linear micromotor has been developed for microoptics driving applications. The piezo-vibrator of the micromotor was composed of two small Pb(Zr,Ti)O3 (PZT-5) plates, with overall dimensions and mass of only 2.0 × 2.0 × 5.0 mm(3) and 0.2 g, respectively. The proposed micromotor could operate either in single-phase voltage (standing wave) mode or two-phase voltage (traveling wave) mode to drive a slider via friction force to provide bidirectional linear motion. A large thrust of up to 0.30 N, which corresponds to a high unit volume direct driving force of 15 mN/mm(3), and a linear movement velocity of up to 230 mm/s were obtained under an applied voltage of 80 Vpp at the B1 mode resonance frequency of 174 kHz.

One-unit versus two-unit cord-blood transplantation for hematologic cancers.

Science.gov (United States)

Wagner, John E; Eapen, Mary; Carter, Shelly; Wang, Yanli; Schultz, Kirk R; Wall, Donna A; Bunin, Nancy; Delaney, Colleen; Haut, Paul; Margolis, David; Peres, Edward; Verneris, Michael R; Walters, Mark; Horowitz, Mary M; Kurtzberg, Joanne

2014-10-30

Umbilical-cord blood has been used as the source of hematopoietic stem cells in an estimated 30,000 transplants. The limited number of hematopoietic cells in a single cord-blood unit prevents its use in recipients with larger body mass and results in delayed hematopoietic recovery and higher mortality. Therefore, we hypothesized that the greater numbers of hematopoietic cells in two units of cord blood would be associated with improved outcomes after transplantation. Between December 1, 2006, and February 24, 2012, a total of 224 patients 1 to 21 years of age with hematologic cancer were randomly assigned to undergo double-unit (111 patients) or single-unit (113 patients) cord-blood transplantation after a uniform myeloablative conditioning regimen and immunoprophylaxis for graft-versus-host disease (GVHD). The primary end point was 1-year overall survival. Treatment groups were matched for age, sex, self-reported race (white vs. nonwhite), performance status, degree of donor-recipient HLA matching, and disease type and status at transplantation. The 1-year overall survival rate was 65% (95% confidence interval [CI], 56 to 74) and 73% (95% CI, 63 to 80) among recipients of double and single cord-blood units, respectively (P=0.17). Similar outcomes in the two groups were also observed with respect to the rates of disease-free survival, neutrophil recovery, transplantation-related death, relapse, infections, immunologic reconstitution, and grade II-IV acute GVHD. However, improved platelet recovery and lower incidences of grade III and IV acute and extensive chronic GVHD were observed among recipients of a single cord-blood unit. We found that among children and adolescents with hematologic cancer, survival rates were similar after single-unit and double-unit cord-blood transplantation; however, a single-unit cord-blood transplant was associated with better platelet recovery and a lower risk of GVHD. (Funded by the National Heart, Lung, and Blood Institute and the

Movement of beta-irradiated epidermal basal cells to the spinous-granular layers in the absence of cell division

International Nuclear Information System (INIS)

Etoh, H.; Taguchi, Y.H.; Tabachnick, J.

1975-01-01

Guinea-pig epidermis was irradiated with 3000 rad of beta rays 1 hr after two injections of [ 3 H]thymidine 5 hr apart (labeled cells in S phase and G 2 phase) or 18 hr after injection (labeled early G 1 cells). In nonirradiated epidermis labeled basal cells divided within 24 hr with daughter cells remaining in the basal layer, and approximately 50 percent of the labeled cells moved into the spinal layer by the 3rd day. Cell division in nonirradiated epidermis diluted the number of silver grains/nucleus, and lightly labeled cells were found in the granular layer by day 7. Beta irradiation inhibited cell division but it did not slow the rate of transit (ca 8 days) of irradiated labeled cells from basal to granular layer, some of these remaining heavily labeled. Although cell division may play some role in upward movement of basal cells in normal epidermis detachment of a basal cell from the basement membrane and its transit to the granular layer is unimpaired in the absence of cell division. These findings suggest that some radioresistant metabolic function(s), not cell division, is responsible for upward movement of basal cells. (auth)

Layer-by-layer self-assembled active electrodes for hybrid photovoltaic cells

Energy Technology Data Exchange (ETDEWEB)

Kniprath, Rolf

2008-11-18

Solar cells based on thin organic/inorganic heterofilms are currently in the focus of research, since they represent promising candidates for cost-efficient photovoltaic energy conversion. In this type of cells, charges are separated at a heterointerface between dissimilar electrode materials. These materials either absorb light themselves, or they are sensitized by an additional absorber layer at the interface. The present work investigates photovoltaic cells which are composed of nanoporous TiO{sub 2} combined with conjugated polymers and semiconductor quantum dots (QDs). The method of layer-by-layer self-assembly of oppositely charged nanoparticles and polymers is used for the fabrication of such devices. This method allows to fabricate nanoporous films with controlled thicknesses in the range of a few hundred nanometers to several micrometers. Investigations with scanning electron (SEM) and atomic force microscopy (AFM) reveal that the surface morphology of the films depends only on the chemical structure of the polyions used in the production process, and not on their molecular weight or conformation. From dye adsorption at the internal surface of the electrodes one can estimate that the internal surface area of a 1 {mu}m thick film is up to 120 times larger than the projection plane. X-ray photoelectron spectroscopy (XPS) is used to demonstrate that during the layer-by-layer self-assembly at least 40% of the TiO{sub 2} surface is covered with polymers. This feature allows to incorporate polythiophene derivatives into the films and to use them as sensitizers for TiO{sub 2}. Further, electrodes containing CdSe or CdTe quantum dots (QDs) as sensitizers are fabricated. For the fabrication of photovoltaic cells the layer-by-layer grown films are coated with an additional polymer layer, and Au back electrodes are evaporated on top. The cells are illuminated through transparent doped SnO{sub 2} front electrodes. The I/V curves of all fabricated cells show diode

Layer-by-Layer Bioprinting of Stem Cells for Retinal Tissue Regeneration

Science.gov (United States)

2016-12-01

Precision Tissue Models”, Distinguished Seminar, Eli and Edythe Broad CIRM Center for Regenerative Medicine and Stem Cell Research, University of...in vitro drug screening and potential in vivo retinal neuron repair. The expansion of ganglion cells is tightly related to the spatial arrangement of...AWARD NUMBER: W81XWH-14-1-0522 TITLE: Layer-by-Layer Bioprinting of Stem Cells for Retinal Tissue Regeneration PRINCIPAL INVESTIGATOR

Uneven-Layered Coding Metamaterial Tile for Ultra-wideband RCS Reduction and Diffuse Scattering.

Science.gov (United States)

Su, Jianxun; He, Huan; Li, Zengrui; Yang, Yaoqing Lamar; Yin, Hongcheng; Wang, Junhong

2018-05-25

In this paper, a novel uneven-layered coding metamaterial tile is proposed for ultra-wideband radar cross section (RCS) reduction and diffuse scattering. The metamaterial tile is composed of two kinds of square ring unit cells with different layer thickness. The reflection phase difference of 180° (±37°) between two unit cells covers an ultra-wide frequency range. Due to the phase cancellation between two unit cells, the metamaterial tile has the scattering pattern of four strong lobes deviating from normal direction. The metamaterial tile and its 90-degree rotation can be encoded as the '0' and '1' elements to cover an object, and diffuse scattering pattern can be realized by optimizing phase distribution, leading to reductions of the monostatic and bi-static RCSs simultaneously. The metamaterial tile can achieve -10 dB RCS reduction from 6.2 GHz to 25.7 GHz with the ratio bandwidth of 4.15:1 at normal incidence. The measured and simulated results are in good agreement and validate the proposed uneven-layered coding metamaterial tile can greatly expanding the bandwidth for RCS reduction and diffuse scattering.

Two-layer anti-reflection strategies for implant applications

Science.gov (United States)

Guerrero, Douglas J.; Smith, Tamara; Kato, Masakazu; Kimura, Shigeo; Enomoto, Tomoyuki

2006-03-01

A two-layer bottom anti-reflective coating (BARC) concept in which a layer that develops slowly is coated on top of a bottom layer that develops more rapidly was demonstrated. Development rate control was achieved by selection of crosslinker amount and BARC curing conditions. A single-layer BARC was compared with the two-layer BARC concept. The single-layer BARC does not clear out of 200-nm deep vias. When the slower developing single-layer BARC was coated on top of the faster developing layer, the vias were cleared. Lithographic evaluation of the two-layer BARC concept shows the same resolution advantages as the single-layer system. Planarization properties of a two-layer BARC system are better than for a single-layer system, when comparing the same total nominal thicknesses.

Density of states and tunneling characteristics of layered superconductors

International Nuclear Information System (INIS)

Liu, S.H.; Klemm, R.A.

1993-04-01

We have studied the structure of the density-of-states (DOS) curves and tunneling characteristics of layered superconductors with two distinct layers in a unit cell. In general, the peaks of the DOS curves do not correspond to energy gaps of each layer, but depend on the gaps and the interlayer hopping strengths in a complex manner. This makes the interpretation of tunneling data of layered superconductors much less straightforward than isotropic superconductors. Our simulated tunneling characteristics bear certain resemblance to experimental results

An optimized multilayer structure of CdS layer for CdTe solar cells application

International Nuclear Information System (INIS)

Han Junfeng; Liao Cheng; Jiang Tao; Spanheimer, C.; Haindl, G.; Fu, Ganhua; Krishnakumar, V.; Zhao Kui; Klein, A.; Jaegermann, W.

2011-01-01

Research highlights: → Two different methods to prepare CdS films for CdTe solar cells. → A new multilayer structure of window layer for the CdTe solar cell. → Thinner CdS window layer for the solar cell than the standard CdS layer. → Higher performance of solar cells based on the new multilayer structure. - Abstract: CdS layers grown by 'dry' (close space sublimation) and 'wet' (chemical bath deposition) methods are deposited and analyzed. CdS prepared with close space sublimation (CSS) has better crystal quality, electrical and optical properties than that prepared with chemical bath deposition (CBD). The performance of CdTe solar cell based on the CSS CdS layer has higher efficiency than that based on CBD CdS layer. However, the CSS CdS suffers from the pinholes. And consequently it is necessary to prepare a 150 nm thin film for CdTe/CdS solar cell. To improve the performance of CdS/CdTe solar cells, a thin multilayer structure of CdS layer (∼80 nm) is applied, which is composed of a bottom layer (CSS CdS) and a top layer (CBD CdS). That bi-layer film can allow more photons to pass through it and significantly improve the short circuit current of the CdS/CdTe solar cells.

InP solar cell with window layer

Science.gov (United States)

Jain, Raj K. (Inventor); Landis, Geoffrey A. (Inventor)

1994-01-01

The invention features a thin light transmissive layer of the ternary semiconductor indium aluminum arsenide (InAlAs) as a front surface passivation or 'window' layer for p-on-n InP solar cells. The window layers of the invention effectively reduce front surface recombination of the object semiconductors thereby increasing the efficiency of the cells.

Intralayer and interlayer spin-singlet pairing and energy gap functions with different possible symmetries in high-Tc layered superconductors

International Nuclear Information System (INIS)

Jha, S.S.; Rajagopal, A.K.

1997-01-01

Anisotropy and the wave-vector dependence of the energy gap function determine many important properties of a superconductor. Starting from first principles, we present here a complete analysis of possible symmetries of the superconducting gap function E g (k) at the Fermi surface in high-T c layered superconductors with either a simple orthorhombic or a tetragonal unit cell. This is done within the framework of Gorkov close-quote s mean-field theory of superconductivity in the so-called open-quotes layer representationclose quotes introduced by us earlier. For N conducting cuprate layers, J=1,2,hor-ellipsis,N, in each unit cell, the spin-singlet order parameters Δ JJ (k) can be expanded in terms of possible basis functions of all the irreducible representations relevant to layered crystals, which are obtained here. In layered materials, the symmetry is restricted to the translational lattice periodicity in the direction perpendicular to the layers and the residual point group and translational symmetries for the two-dimensional unit cell in each layer of the three-dimensional unit cell. We derive an exact general relation to determine different branches of the energy gap function E g (k) at the Fermi surface in terms of Δ JJ (k), which include both intralayer and interlayer order parameters. For N=2, we also obtain an exact expression for quasiparticle energies E p (k), p=1,2, in the superconducting state in the presence of intralayer and complex interlayer order parameters as well as complex tunneling matrix elements between the two layers in the unit cell, which need not be equivalent. The form of the possible basis functions are also listed in terms of cylindrical coordinates k t ,φ,k z to take advantage of the orthogonality of functions with respect to φ integrations. (Abstract Truncated)

Stability of Armour Units in Flow Through a Layer

DEFF Research Database (Denmark)

Burcharth, Hans F.; C. Thompson, Alex

1984-01-01

As part of a program to study the hydraulics of wave attack on rubble mound breakwaters tests were made on model armour units in a steady flow through a layer laid on a slope. The flow angle has little effect on stability for dolosse or rock layers. The head drop at failure across each type...... of layer is similar but the dolosse layer is more permeable and fails as a whole. There was no viscous scale effect. These results and earlier tests in oscillating flow suggest a 'reservoir' effect is important in the stability in steep waves....

Unit Reynolds number, Mach number and pressure gradient effects on laminar-turbulent transition in two-dimensional boundary layers

Science.gov (United States)

Risius, Steffen; Costantini, Marco; Koch, Stefan; Hein, Stefan; Klein, Christian

2018-05-01

The influence of unit Reynolds number (Re_1=17.5× 106-80× 106 {m}^{-1}), Mach number (M= 0.35-0.77) and incompressible shape factor (H_{12} = 2.50-2.66) on laminar-turbulent boundary layer transition was systematically investigated in the Cryogenic Ludwieg-Tube Göttingen (DNW-KRG). For this investigation the existing two-dimensional wind tunnel model, PaLASTra, which offers a quasi-uniform streamwise pressure gradient, was modified to reduce the size of the flow separation region at its trailing edge. The streamwise temperature distribution and the location of laminar-turbulent transition were measured by means of temperature-sensitive paint (TSP) with a higher accuracy than attained in earlier measurements. It was found that for the modified PaLASTra model the transition Reynolds number (Re_{ {tr}}) exhibits a linear dependence on the pressure gradient, characterized by H_{12}. Due to this linear relation it was possible to quantify the so-called `unit Reynolds number effect', which is an increase of Re_{ {tr}} with Re_1. By a systematic variation of M, Re_1 and H_{12} in combination with a spectral analysis of freestream disturbances, a stabilizing effect of compressibility on boundary layer transition, as predicted by linear stability theory, was detected (`Mach number effect'). Furthermore, two expressions were derived which can be used to calculate the transition Reynolds number as a function of the amplitude of total pressure fluctuations, Re_1 and H_{12}. To determine critical N-factors, the measured transition locations were correlated with amplification rates, calculated by incompressible and compressible linear stability theory. By taking into account the spectral level of total pressure fluctuations at the frequency of the most amplified Tollmien-Schlichting wave at transition location, the scatter in the determined critical N-factors was reduced. Furthermore, the receptivity coefficients dependence on incidence angle of acoustic waves was used to

Two new layer structures of zinc(II) or strontium(II) diphosphonates based on N,N-dimethylaminomethane-1,1-diphosphonate ligand

Science.gov (United States)

Sun, Yu-Hui; Du, Zi-Yi; Zhou, Zhong-Gao; Zhang, Shi-Yong; Xu, Guo-Hai; Xie, Yong-Rong

2011-05-01

Hydrothermal reactions of Zn 2+ or Sr 2+ ion with N,N-dimethylaminomethane-1,1-diphosphonic acid (H 4L) afforded two new layered metal diphosphonates, namely, [Zn 2(H 2L) 2]·2H 2O ( 1) and [Sr 3(H 2L) 2(H 3L) 2(H 2O) 2]·2H 2O ( 2). The layer structure in 1 features a square-grid unit with Zn1O 6 octahedra acting as nodes, which tetradentately traps one Zn2 ion inside it. On the other hand, the layer architecture of 2 exhibits an unusual corner-sharing Sr 3O 17 tri-polyhedra unit; and such trimer unit is edge-shared with two neighboring trimers, which further chelate a third trimer to form a square-grid ring with two aqua molecules residing in it. The diphosphonate ligand in the two compounds manifests diversified coordination modes accompanying with a cooperative coordination effect of its two closely linked phosphonate moieties.

The effect of interfacial layers on charge transport in organic solar cell

Energy Technology Data Exchange (ETDEWEB)

Mbuyise, Xolani G.; Tonui, Patrick; Mola, Genene Tessema, E-mail: mola@ukzn.ac.za

2016-09-01

The effect of interfacial buffer layers in organic photovoltaic cell (OPV) whose active layer is composed of poly(3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend was studied. The electrical properties of OPV devices produced with and without interfacial layers are compared and discussed in terms of measured parameters of the cells. The charge transport properties showed significant difference on the mobility and activation factor between the two types of device structures. The life time measurements in the unprotected conditions are also presented and discussed.

A numerical two layer model for blood oxygenation in lungs

International Nuclear Information System (INIS)

Aminatai, A.

2001-01-01

In the modelling of the simultaneous transport of O 2 and CO 2 in the pulmonary circulation described in our earlier studies, the blood has been treated as a homogeneous layer of haemoglobin solution. Since the size of the erythrocyte is not negligible in comparison with that of the capillary, the blood can no longer be considered as a homogeneous fluid and hence, It is worthwhile to consider the blood flow as a two-phase flow consisting of cells and plasma. In the present study, the heterogeneous nature of blood has been proposed by considering the axial train model for the flow [whitmore (1967)], in order to analyze the effect of cell free plasma layer on the process of blood oxygenation in pulmonary capillaries. The proposed model consists of a core of suspended erythrocytes surrounded by a cell free plasma layer near the wall. The coupled system of convective diffusion equaions together with the physiologically relevant boundary, entrance and interface conditions is solved numerically by a four-point semi-implicit scheme to gether with a fixed point iterative technique. The distance traversed by the blood before getting fully oxygenated is computed. It is shown that the core haematocrit and the thickness of the cell depleted layer affect the oxygenation process significantly. It is found that (i) oxygen takes longest and carbondioxide is the fastest to attain equilibraton, (ii) the blood is completely oxygenated within one-fifth part of its transit and (iii) the rate of oxygenation is smaller in case of homogeneous model than that in heterogenous model in the capillary. Finally, the effect of various physiological parameters on the rate of oxygenation has been examined

Validity of two-phase polymer electrolyte membrane fuel cell models with respect to the gas diffusion layer

Science.gov (United States)

Ziegler, C.; Gerteisen, D.

A dynamic two-phase model of a proton exchange membrane fuel cell with respect to the gas diffusion layer (GDL) is presented and compared with chronoamperometric experiments. Very good agreement between experiment and simulation is achieved for potential step voltammetry (PSV) and sine wave testing (SWT). Homogenized two-phase models can be categorized in unsaturated flow theory (UFT) and multiphase mixture (M 2) models. Both model approaches use the continuum hypothesis as fundamental assumption. Cyclic voltammetry experiments show that there is a deterministic and a stochastic liquid transport mode depending on the fraction of hydrophilic pores of the GDL. ESEM imaging is used to investigate the morphology of the liquid water accumulation in the pores of two different media (unteflonated Toray-TGP-H-090 and hydrophobic Freudenberg H2315 I3). The morphology of the liquid water accumulation are related with the cell behavior. The results show that UFT and M 2 two-phase models are a valid approach for diffusion media with large fraction of hydrophilic pores such as unteflonated Toray-TGP-H paper. However, the use of the homgenized UFT and M 2 models appears to be invalid for GDLs with large fraction of hydrophobic pores that corresponds to a high average contact angle of the GDL.

Efficient organic photovoltaic cells on a single layer graphene transparent conductive electrode using MoOx as an interfacial layer.

Science.gov (United States)

Du, J H; Jin, H; Zhang, Z K; Zhang, D D; Jia, S; Ma, L P; Ren, W C; Cheng, H M; Burn, P L

2017-01-07

The large surface roughness, low work function and high cost of transparent electrodes using multilayer graphene films can limit their application in organic photovoltaic (OPV) cells. Here, we develop single layer graphene (SLG) films as transparent anodes for OPV cells that contain light-absorbing layers comprised of the evaporable molecular organic semiconductor materials, zinc phthalocyanine (ZnPc)/fullerene (C60), as well as a molybdenum oxide (MoO x ) interfacial layer. In addition to an increase in the optical transmittance, the SLG anodes had a significant decrease in surface roughness compared to two and four layer graphene (TLG and FLG) anodes fabricated by multiple transfer and stacking of SLGs. Importantly, the introduction of a MoO x interfacial layer not only reduced the energy barrier between the graphene anode and the active layer, but also decreased the resistance of the SLG by nearly ten times. The OPV cells with the structure of polyethylene terephthalate/SLG/MoO x /CuI/ZnPc/C60/bathocuproine/Al were flexible, and had a power conversion efficiency of up to 0.84%, which was only 17.6% lower than the devices with an equivalent structure but prepared on commercial indium tin oxide anodes. Furthermore, the devices with the SLG anode were 50% and 86.7% higher in efficiency than the cells with the TLG and FLG anodes. These results show the potential of SLG electrodes for flexible and wearable OPV cells as well as other organic optoelectronic devices.

Wounding coordinately induces cell wall protein, cell cycle and pectin methyl esterase genes involved in tuber closing layer and wound periderm development.

Science.gov (United States)

Neubauer, Jonathan D; Lulai, Edward C; Thompson, Asunta L; Suttle, Jeffrey C; Bolton, Melvin D

2012-04-15

Little is known about the coordinate induction of genes that may be involved in agriculturally important wound-healing events. In this study, wound-healing events were determined together with wound-induced expression profiles of selected cell cycle, cell wall protein, and pectin methyl esterase genes using two diverse potato genotypes and two harvests (NDTX4271-5R and Russet Burbank tubers; 2008 and 2009 harvests). By 5 d after wounding, the closing layer and a nascent phellogen had formed. Phellogen cell divisions generated phellem layers until cessation of cell division at 28 d after wounding for both genotypes and harvests. Cell cycle genes encoding epidermal growth factor binding protein (StEBP), cyclin-dependent kinase B (StCDKB) and cyclin-dependent kinase regulatory subunit (StCKS1At) were induced by 1 d after wounding; these expressions coordinated with related phellogen formation and the induction and cessation of phellem cell formation. Genes encoding the structural cell wall proteins extensin (StExt1) and extensin-like (StExtlk) were dramatically up-regulated by 1-5 d after wounding, suggesting involvement with closing layer and later phellem cell layer formation. Wounding up-regulated pectin methyl esterase genes (StPME and StPrePME); StPME expression increased during closing layer and phellem cell formation, whereas maximum expression of StPrePME occurred at 5-14 d after wounding, implicating involvement in later modifications for closing layer and phellem cell formation. The coordinate induction and expression profile of StTLRP, a gene encoding a cell wall strengthening "tyrosine-and lysine-rich protein," suggested a role in the formation of the closing layer followed by phellem cell generation and maturation. Collectively, the genes monitored were wound-inducible and their expression profiles markedly coordinated with closing layer formation and the index for phellogen layer meristematic activity during wound periderm development; results were more

Two stacked tandem white organic light-emitting diodes employing WO3 as a charge generation layer

Science.gov (United States)

Bin, Jong-Kwan; Lee, Na Yeon; Lee, SeungJae; Seo, Bomin; Yang, JoongHwan; Kim, Jinook; Yoon, Soo Young; Kang, InByeong

2016-09-01

Recently, many studies have been conducted to improve the electroluminescence (EL) performance of organic lightemitting diodes (OLEDs) by using appropriate organic or inorganic materials as charge generation layer (CGL) for their application such as full color displays, backlight units, and general lighting source. In a stacked tandem white organic light-emitting diodes (WOLEDs), a few emitting units are electrically interconnected by a CGL, which plays the role of generating charge carriers, and then facilitate the injection of it into adjacent emitting units. In the present study, twostacked WOLEDs were fabricated by using tungsten oxide (WO3) as inorganic charge generation layer and 1,4,5,8,9,11- hexaazatriphenylene hexacarbonitrile (HAT-CN) as organic charge generation layer (P-CGL). Organic P-CGL materials were used due to their ease of use in OLED fabrication as compared to their inorganic counterparts. To obtain high efficiency, we demonstrate two-stacked tandem WOLEDs as follows: ITO/HIL/HTL/HTL'/B-EML/ETL/N-CGL/P-CGL (WO3 or HAT-CN)/HTL″/YG-EML/ETL/LiF/Al. The tandem devices with blue- and yellow-green emitting layers were sensitive to the thickness of an adjacent layer, hole transporting layer for the YG emitting layer. The WOLEDs containing the WO3 as charge generation layer reach a higher power efficiency of 19.1 lm/W and the current efficiency of 51.2 cd/A with the white color coordinate of (0.316, 0.318) than the power efficiency of 13.9 lm/W, and the current efficiency of 43.7 cd/A for organic CGL, HAT-CN at 10 mA/cm2, respectively. This performance with inserting WO3 as CGL exhibited the highest performance with excellent CIE color coordinates in the two-stacked tandem OLEDs.

Scrape-off layer profile modifications by convective cells

International Nuclear Information System (INIS)

Myra, J.R.; DIppolito, D.A.

1996-01-01

Convective cells (CC close-quote s) are important in understanding density profile modifications induced by ion cyclotron range of frequencies (ICRF) antennas. This has motivated the present work in which the effect of CC close-quote s on transport in the scrape-off layer is studied, in the regime where the density gradient scale length L n and the cell size L are comparable. Monte Carlo simulations show that closed cell convection acts to flatten the density profile, and that open cells enhance the particle flow to the wall, depleting the density and yielding profiles similar to those measured near ICRF antennas. A new one-dimensional, two-branch model of CC transport is shown to agree well with the simulations. The model gives rise to two characteristic scale lengths, only one of which is retained in the enhanced diffusion models that are applicable for L n >L. The two-branch model is expected to be useful in analyzing ICRF experiments. copyright 1996 American Institute of Physics

Lipids from the nacreous and prismatic layers of two Pteriomorpha Mollusc shells

Science.gov (United States)

Farre, B.; Dauphin, Y.

2009-04-01

Mollusc shells are the best-known Ca-carbonate biominerals. They are commonly described as a mineralized two layered structure: an outer layer composed of calcite prismatic units, and an internal layer composed of tablets of aragonite: the nacreous layer. An external organic layer (periostracum) is present in most taxa. However, the most common structure in the Mollusc shell is the aragonite crossed lamellar layer, but aragonite prisms, calcite foliated layers and homogeneous layers have been also described by Boggild (1930) in all the Mollusc orders. Since, more detailed descriptions of Bivalve shells have been done (Taylor et al., 1969, 1973). Despite the nacroprismatic arrangement is rare, calcite prismatic and aragonite nacreous layers are the best studied because of their simple 3D structure and large units. Among these Molluscs, some Bivalve species composed of these two layers are of commercial interest, such as the pearl oyster, Pinctada margaritifera, cultivated in French Polynesia to produce black pearls. It is well established that Mollusc shells are composite structures of organic and inorganic components (Hatchett, 1799; Grégoire et al., 1955; Beedham, 1958; Simkiss, 1965; Mutvei, 1969; Cuif et al., 1980; Berman et al., 1993; Kobayashi and Samata, 2006). Numerous studies are concerned with the organic matrix of the shell. Organic components are commonly obtained after a strong or mild decalcification process. They are said to consist of both a soluble and insoluble fraction. The main part of studies is dedicated to the soluble components, and among them, proteins (Grégoire et al., 1955; Grégoire, 1961; Krampitz et al., 1976; Samata et al., 1980, 2004; Weiner, 1983; Miyamoto et al., 2006). Despite the pioneering work of Wada (1980) sugars are usually neglected despite their role in biomineralization. The third component of the organic matrix of calcareous biominerals is lipids. To date, there is a paucity of information concerning the presence

Evaluation of white matter hyperintensities and retinal fiber layer, ganglion cell layer, inner-plexiform layer, and choroidal layer in migraine patients.

Science.gov (United States)

Tak, Ali Zeynel Abidin; Sengul, Yıldızhan; Bilak, Şemsettin

2018-03-01

The aim of our study is to assess retinal nerve fiber layer (RNFL), the ganglion cell layer (GCL), inner-plexiform layer (IPL), and choroidal layer in migraine patients with white matter lesion (WML) or without WML, using spectral domain optical coherence tomography (OCT). To our study, 77 migraine patients who are diagnosed with migraine in accordance to the International Classification of Headache Disorders (ICHD)-3 beta and 43 healthy control are included. In accordance to cranial MRI, migraine patients are divided into two groups as those who have white matter lesions (39 patients), and those who do not have a lesion (38 patients). OCT was performed for participants. The average age of participants was comparable. The RNFL average thickness parameter in the migraine group was significantly lower than in the control group (p layer measuring scales. The proofs showing that affected retinal nerve fiber layer are increased in migraine patients. However, it is not known whether this may affect other layers of retina, or whether there is a correlation between affected retinal structures and white matter lesions. In our study, we found thinner RNFL in migraine patients when we compared with controls but IPL, GCL, and choroid layer values were similar between each patient groups and controls. Also, all parameters were similar between patients with WML and without WML. Studies in this regard are required.

Peclet number analysis of cross-flow in porous gas diffusion layer of polymer electrolyte membrane fuel cell (PEMFC).

Science.gov (United States)

Suresh, P V; Jayanti, Sreenivas

2016-10-01

Adoption of hydrogen economy by means of using hydrogen fuel cells is one possible solution for energy crisis and climate change issues. Polymer electrolyte membrane (PEM) fuel cell, which is an important type of fuel cells, suffers from the problem of water management. Cross-flow is induced in some flow field designs to enhance the water removal. The presence of cross-flow in the serpentine and interdigitated flow fields makes them more effective in proper distribution of the reactants on the reaction layer and evacuation of water from the reaction layer than diffusion-based conventional parallel flow fields. However, too much of cross-flow leads to flow maldistribution in the channels, higher pressure drop, and membrane dehydration. In this study, an attempt has been made to quantify the amount of cross-flow required for effective distribution of reactants and removal of water in the gas diffusion layer. Unit cells containing two adjacent channels with gas diffusion layer (GDL) and catalyst layer at the bottom have been considered for the parallel, interdigitated, and serpentine flow patterns. Computational fluid dynamics-based simulations are carried out to study the reactant transport in under-the-rib area with cross-flow in the GDL. A new criterion based on the Peclet number is presented as a quantitative measure of cross-flow in the GDL. The study shows that a cross-flow Peclet number of the order of 2 is required for effective removal of water from the GDL. Estimates show that this much of cross-flow is not usually produced in the U-bends of Serpentine flow fields, making these areas prone to flooding.

Area-Specific Cell Stimulation via Surface-Mediated Gene Transfer Using Apatite-Based Composite Layers

Directory of Open Access Journals (Sweden)

Yushin Yazaki

2015-04-01

Full Text Available Surface-mediated gene transfer systems using biocompatible calcium phosphate (CaP-based composite layers have attracted attention as a tool for controlling cell behaviors. In the present study we aimed to demonstrate the potential of CaP-based composite layers to mediate area-specific dual gene transfer and to stimulate cells on an area-by-area basis in the same well. For this purpose we prepared two pairs of DNA–fibronectin–apatite composite (DF-Ap layers using a pair of reporter genes and pair of differentiation factor genes. The results of the area-specific dual gene transfer successfully demonstrated that the cells cultured on a pair of DF-Ap layers that were adjacently placed in the same well showed specific gene expression patterns depending on the gene that was immobilized in theunderlying layer. Moreover, preliminary real-time PCR results indicated that multipotential C3H10T1/2 cells may have a potential to change into different types of cells depending on the differentiation factor gene that was immobilized in the underlying layer, even in the same well. Because DF-Ap layers have a potential to mediate area-specific cell stimulation on their surfaces, they could be useful in tissue engineering applications.

Bulk-heterojunction organic solar cells sandwiched by solution processed molybdenum oxide and titania nanosheet layers

Science.gov (United States)

Itoh, Eiji; Goto, Yoshinori; Fukuda, Katsutoshi

2014-02-01

The contributions of ultrathin titania nanosheet (TN) crystallites were studied in both an inverted bulk-heterojunction (BHJ) cell in an indium-tin oxide (ITO)/titania nanosheet (TN)/poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methylester (PCBM) active layer/MoOx/Ag multilayered photovoltaic device and a conventional BHJ cell in ITO/MoOx/P3HT:PCBM active layer/TN/Al multilayered photovoltaic device. The insertion of only one or two layers of poly(diallyldimethylammonium chloride) (PDDA) and TN multilayered film prepared by the layer-by-layer deposition technique effectively decreased the leakage current and increased the open circuit voltage (VOC), fill factor (FF), and power conversion efficiency (η). The conventional cell sandwiched between a solution-processed, partially crystallized molybdenum oxide hole-extracting buffer layer and a TN electron extracting buffer layer showed comparable cell performance to a device sandwiched between vacuum-deposited molybdenum oxide and TN layers, whereas the inverted cell with solution-processed molybdenum oxide showed a poorer performance probably owing to the increment in the leakage current across the film. The abnormal S-shaped curves observed in the inverted BHJ cell above VOC disappeared with the use of a polyfluorene-based cationic semiconducting polymer as a substitute for an insulating PDDA film, resulting in the improved cell performance.

Strength of the Three Layer Beam with Two Binding Layers

Directory of Open Access Journals (Sweden)

Smyczyński M. J.

2016-09-01

Full Text Available The paper is devoted to the strength analysis of a simply supported three layer beam. The sandwich beam consists of: two metal facings, the metal foam core and two binding layers between the faces and the core. In consequence, the beam is a five layer beam. The main goal of the study is to elaborate a mathematical model of this beam, analytical description and a solution of the three-point bending problem. The beam is subjected to a transverse load. The nonlinear hypothesis of the deformation of the cross section of the beam is formulated. Based on the principle of the stationary potential energy the system of four equations of equilibrium is derived. Then deflections and stresses are determined. The influence of the binding layers is considered. The results of the solutions of the bending problem analysis are shown in the tables and figures. The analytical model is verified numerically using the finite element analysis, as well as experimentally.

Multi-chamber and multi-layer thiol-ene microchip for cell culture

DEFF Research Database (Denmark)

Tan, H. Y.; Hemmingsen, Mette; Lafleur, Josiane P.

2014-01-01

We present a multi-layer and multi-chamber microfluidic chip fabricated using two different thiol-ene mixtures. Sandwiched between the thiol-ene chip layers is a commercially available membrane whose morphology has been altered with coatings of thiol-ene mixtures. Experiments have been conducted ...... with the microchip and shown that the fabricated microchip is suitable for long term cell culture....

Effect of duration and severity of migraine on retinal nerve fiber layer, ganglion cell layer, and choroidal thickness.

Science.gov (United States)

Abdellatif, Mona K; Fouad, Mohamed M

2018-03-01

To investigate the factors in migraine that have the highest significance on retinal and choroidal layers' thickness. Ninety patients with migraine and 40 age-matched healthy participants were enrolled in this observational, cross-sectional study. After full ophthalmological examination, spectral domain-optical coherence tomography was done for all patients measuring the thickness of ganglion cell layer and retinal nerve fiber layer. Enhanced depth imaging technique was used to measure the choroidal thickness. There was significant thinning in the superior and inferior ganglion cell layers, all retinal nerve fiber layer quadrants, and all choroidal quadrants (except for the central subfield) in migraineurs compared to controls. The duration of migraine was significantly correlated with ganglion cell layer, retinal nerve fiber layer, and all choroidal quadrants, while the severity of migraine was significantly correlated with ganglion cell layer and retinal nerve fiber layer only. Multiregression analysis showed that the duration of migraine is the most important determinant factor of the superior retinal nerve fiber layer quadrant (β = -0.375, p = 0.001) and in all the choroidal quadrants (β = -0.531, -0.692, -0.503, -0.461, -0.564, respectively, p  layer quadrants (β = -0.256, -0.335, -0.308; p  = 0.036, 0.005, 0.009, respectively) and the inferior ganglion cell layer hemisphere (β = -0.377 and p = 0.001). Ganglion cell layer, retinal nerve fiber layer, and choroidal thickness are significantly thinner in patients with migraine. The severity of migraine has more significant influence in the thinning of ganglion cell layer and retinal nerve fiber layer, while the duration of the disease affected the choroidal thickness more.

Two-layer membranes of calcium phosphate/collagen/PLGA nanofibres: in vitro biomineralisation and osteogenic differentiation of human mesenchymal stem cells

Science.gov (United States)

Hild, Nora; Schneider, Oliver D.; Mohn, Dirk; Luechinger, Norman A.; Koehler, Fabian M.; Hofmann, Sandra; Vetsch, Jolanda R.; Thimm, Benjamin W.; Müller, Ralph; Stark, Wendelin J.

2011-02-01

The present study evaluates the in vitro biomedical performance of an electrospun, flexible, anisotropic bilayer with one layer containing a collagen to mineral ratio similar to that in bone. The double membrane consists of a poly(lactide-co-glycolide) (PLGA) layer and an amorphous calcium phosphate (a-CaP)/collagen (Col)/PLGA layer. In vitro biomineralisation and a cell culture study with human mesenchymal stem cells (hMSC) were conducted to characterise such membranes for possible application as biomaterials. Nanofibres with different a-CaP/Col/PLGA compositions were synthesised by electrospinning to mimic the actual composition of bone tissue. Immersion in simulated body fluid and in cell culture medium resulted in the deposition of a hydroxyapatite layer. Incubation of hMSC for 4 weeks allowed for assessment of the proliferation and osteogenic differentiation of the cells on both sides of the double membrane. Confocal laser scanning microscopy was used to observe the proper adhesion of the cells. Calcium and collagen content was proven by Alizarin red S and Sirius red assays. Acute cytotoxic effects of the nanoparticles or the chemicals used in the scaffold preparation could be excluded based on viability assays (alamarBlue and alkaline phosphatase activity). The findings suggest possible application of such double membranes is in treatment of bone defects with complex geometries as wound dressing material.The present study evaluates the in vitro biomedical performance of an electrospun, flexible, anisotropic bilayer with one layer containing a collagen to mineral ratio similar to that in bone. The double membrane consists of a poly(lactide-co-glycolide) (PLGA) layer and an amorphous calcium phosphate (a-CaP)/collagen (Col)/PLGA layer. In vitro biomineralisation and a cell culture study with human mesenchymal stem cells (hMSC) were conducted to characterise such membranes for possible application as biomaterials. Nanofibres with different a

Failure mechanisms of additively manufactured porous biomaterials: Effects of porosity and type of unit cell.

Science.gov (United States)

Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Anaraki, A P; Ahmadi, S M; Zadpoor, A A; Schmauder, S

2015-10-01

Since the advent of additive manufacturing techniques, regular porous biomaterials have emerged as promising candidates for tissue engineering scaffolds owing to their controllable pore architecture and feasibility in producing scaffolds from a variety of biomaterials. The architecture of scaffolds could be designed to achieve similar mechanical properties as in the host bone tissue, thereby avoiding issues such as stress shielding in bone replacement procedure. In this paper, the deformation and failure mechanisms of porous titanium (Ti6Al4V) biomaterials manufactured by selective laser melting from two different types of repeating unit cells, namely cubic and diamond lattice structures, with four different porosities are studied. The mechanical behavior of the above-mentioned porous biomaterials was studied using finite element models. The computational results were compared with the experimental findings from a previous study of ours. The Johnson-Cook plasticity and damage model was implemented in the finite element models to simulate the failure of the additively manufactured scaffolds under compression. The computationally predicted stress-strain curves were compared with the experimental ones. The computational models incorporating the Johnson-Cook damage model could predict the plateau stress and maximum stress at the first peak with less than 18% error. Moreover, the computationally predicted deformation modes were in good agreement with the results of scaling law analysis. A layer-by-layer failure mechanism was found for the stretch-dominated structures, i.e. structures made from the cubic unit cell, while the failure of the bending-dominated structures, i.e. structures made from the diamond unit cells, was accompanied by the shearing bands of 45°. Copyright © 2015 Elsevier Ltd. All rights reserved.

Back contact buffer layer for thin-film solar cells

Science.gov (United States)

Compaan, Alvin D.; Plotnikov, Victor V.

2014-09-09

A photovoltaic cell structure is disclosed that includes a buffer/passivation layer at a CdTe/Back contact interface. The buffer/passivation layer is formed from the same material that forms the n-type semiconductor active layer. In one embodiment, the buffer layer and the n-type semiconductor active layer are formed from cadmium sulfide (CdS). A method of forming a photovoltaic cell includes the step of forming the semiconductor active layers and the buffer/passivation layer within the same deposition chamber and using the same material source.

Metasurface base on uneven layered fractal elements for ultra-wideband RCS reduction

Science.gov (United States)

Su, Jianxun; Cui, Yueyang; Li, Zengrui; Yang, Yaoqing Lamar; Che, Yongxing; Yin, Hongcheng

2018-03-01

A novel metasurface based on uneven layered fractal elements is designed and fabricated for ultra-wideband radar cross section (RCS) reduction in this paper. The proposed metasurface consists of two fractal subwavelength elements with different layer thickness. The reflection phase difference of 180° (±37°) between two unit cells covers an ultra-wide frequency range. Ultra-wideband RCS reduction results from the phase cancellation between two local waves produced by these two unit cells. The diffuse scattering of electromagnetic (EM) waves is caused by the randomized phase distribution, leading to a low monostatic and bistatic RCS simultaneously. This metasurface can achieve -10dB RCS reduction in an ultra-wide frequency range from 6.6 to 23.9 GHz with a ratio bandwidth (fH/fL) of 3.62:1 under normal incidences for both x- and y-polarized waves. Both the simulation and the measurement results are consistent to verify this excellent RCS reduction performance of the proposed metasurface.

The zebrafish tailbud contains two independent populations of midline progenitor cells that maintain long-term germ layer plasticity and differentiate in response to local signaling cues

Science.gov (United States)

Row, Richard H.; Tsotras, Steve R.; Goto, Hana; Martin, Benjamin L.

2016-01-01

Vertebrate body axis formation depends on a population of bipotential neuromesodermal cells along the posterior wall of the tailbud that make a germ layer decision after gastrulation to form spinal cord and mesoderm. Despite exhibiting germ layer plasticity, these cells never give rise to midline tissues of the notochord, floor plate and dorsal endoderm, raising the question of whether midline tissues also arise from basal posterior progenitors after gastrulation. We show in zebrafish that local posterior signals specify germ layer fate in two basal tailbud midline progenitor populations. Wnt signaling induces notochord within a population of notochord/floor plate bipotential cells through negative transcriptional regulation of sox2. Notch signaling, required for hypochord induction during gastrulation, continues to act in the tailbud to specify hypochord from a notochord/hypochord bipotential cell population. Our results lend strong support to a continuous allocation model of midline tissue formation in zebrafish, and provide an embryological basis for zebrafish and mouse bifurcated notochord phenotypes as well as the rare human congenital split notochord syndrome. We demonstrate developmental equivalency between the tailbud progenitor cell populations. Midline progenitors can be transfated from notochord to somite fate after gastrulation by ectopic expression of msgn1, a master regulator of paraxial mesoderm fate, or if transplanted into the bipotential progenitors that normally give rise to somites. Our results indicate that the entire non-epidermal posterior body is derived from discrete, basal tailbud cell populations. These cells remain receptive to extracellular cues after gastrulation and continue to make basic germ layer decisions. PMID:26674311

Hydrothermal synthesis of two layered indium oxalates with 12-membered apertures

International Nuclear Information System (INIS)

Chen Zhenxia; Zhou Yaming; Weng Linhong; Zhang Haoyu; Zhao Dongyuan

2003-01-01

Two layered indium oxalates, In(C 2 O 4 ) 2.5 (C 3 N 2 H 12 )(H 2 O) 3 , I, and In(C 2 O 4 ) 1.5 (H 2 O) 3 , II, have been hydrothermally synthesized. In I, the linkage between indium and oxalate units gives rise to a sheet with a rectangular 12-membered aperture (six indium atoms and six oxalate units). Indium atom of II has an unusual pentagonal bipyramidal coordination arrangement. The connectivity between indium and oxalate units forms a neutral puckered layer with 12- (along a-axis) and eight-membered (along b-axis) apertures. Crystal data for these two indium oxalates are as follows: I, triclinic, space group: P-1 (No. 2), a=8.725(3) A, b=9.170(3) A, c=9.901(3) A, α=98.101(4) deg. , β=97.068(4) deg. , γ=102.403(4) deg. , V=756.3(4) A 3 , Z=2, M=463.0(5), ρ calc =2.042 g/cm 3 , R 1 =0.0377, wR 2 =0.0834. II, monoclinic, space group: P2 1 /c (No. 14), a=10.203(5) A, b=6.638(1) A, c=11.152(7) A, β=95.649(4) deg. , V=751.7(4)A 3 , Z=4, M=300.9(0), ρ calc =2.659 g/cm 3 , R 1 =0.0229, wR 2 =0.0488. TG analyses indicate the water molecules of I can be removed at 150 deg. C. The dehydrated product retains structural integrity

Surface-Layer (S-Layer) Proteins Sap and EA1 Govern the Binding of the S-Layer-Associated Protein BslO at the Cell Septa of Bacillus anthracis

Science.gov (United States)

Kern, Valerie J.; Kern, Justin W.; Theriot, Julie A.; Schneewind, Olaf

2012-01-01

The Gram-positive pathogen Bacillus anthracis contains 24 genes whose products harbor the structurally conserved surface-layer (S-layer) homology (SLH) domain. Proteins endowed with the SLH domain associate with the secondary cell wall polysaccharide (SCWP) following secretion. Two such proteins, Sap and EA1, have the unique ability to self-assemble into a paracrystalline layer on the surface of bacilli and form S layers. Other SLH domain proteins can also be found within the S layer and have been designated Bacillus S-layer-associated protein (BSLs). While both S-layer proteins and BSLs bind the same SCWP, their deposition on the cell surface is not random. For example, BslO is targeted to septal peptidoglycan zones, where it catalyzes the separation of daughter cells. Here we show that an insertional lesion in the sap structural gene results in elongated chains of bacilli, as observed with a bslO mutant. The chain length of the sap mutant can be reduced by the addition of purified BslO in the culture medium. This complementation in trans can be explained by an increased deposition of BslO onto the surface of sap mutant bacilli that extends beyond chain septa. Using fluorescence microscopy, we observed that the Sap S layer does not overlap the EA1 S layer and slowly yields to the EA1 S layer in a growth-phase-dependent manner. Although present all over bacilli, Sap S-layer patches are not observed at septa. Thus, we propose that the dynamic Sap/EA1 S-layer coverage of the envelope restricts the deposition of BslO to the SCWP at septal rings. PMID:22609927

Analytical and experimental study of two delay-coupled excitable units.

Science.gov (United States)

Weicker, Lionel; Erneux, Thomas; Keuninckx, Lars; Danckaert, Jan

2014-01-01

We investigate the onset of time-periodic oscillations for a system of two identical delay-coupled excitable (nonoscillatory) units. We first analyze these solutions by using asymptotic methods. The oscillations are described as relaxation oscillations exhibiting successive slow and fast changes. The analysis highlights the determinant role of the delay during the fast transition layers. We then study experimentally a system of two coupled electronic circuits that is modeled mathematically by the same delay differential equations. We obtain quantitative agreements between analytical and experimental bifurcation diagrams.

Layer-by-Layer Heparinization of the Cell Surface by Using Heparin-Binding Peptide Functionalized Human Serum Albumin.

Science.gov (United States)

Song, Guowei; Hu, Yaning; Liu, Yusheng; Jiang, Rui

2018-05-20

Layer-by-layer heparinization of therapeutic cells prior to transplantation is an effective way to inhibit the instant blood-mediated inflammatory reactions (IBMIRs), which are the major cause of early cell graft loss during post-transplantation. Here, a conjugate of heparin-binding peptide (HBP) and human serum albumin (HSA), HBP-HSA, was synthesized by using heterobifunctional crosslinker. After the first heparin layer was coated on human umbilical vein endothelial cells (HUVECs) by means of the HBP-polyethylene glycol-phospholipid conjugate, HBP-HSA and heparin were then applied to the cell surface sequentially to form multiple layers. The immobilization and retention of heparin were analyzed by confocal microscopy and flow cytometry, respectively, and the cytotoxity of HBP-HSA was further evaluated by cell viability assay. Results indicated that heparin was successfully introduced to the cell surface in a layer-by-layer way and retained for at least 24 h, while the cytotoxity of HBP-HSA was negligible at the working concentration. Accordingly, this conjugate provides a promising method for co-immobilization of heparin and HSA to the cell surface under physiological conditions with improved biocompatibility.

Se interlayer in CIGS absorption layer for solar cell devices

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung-Kyu; Sim, Jae-Kwan [Semiconductor Materials Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development, Chonbuk National University, Deokjin-Dong 664-14, Jeonju 561-756 (Korea, Republic of); Kissinger, N.J. Suthan [Department of General Studies, Physics Group, Jubail University College, Royal Commission for Jubail, Jubail 10074 (Saudi Arabia); Song, Il-Seok; Kim, Jin-Soo; Baek, Byung-Joon [Semiconductor Materials Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development, Chonbuk National University, Deokjin-Dong 664-14, Jeonju 561-756 (Korea, Republic of); Lee, Cheul-Ro, E-mail: crlee7@jbnu.ac.kr [Semiconductor Materials Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development, Chonbuk National University, Deokjin-Dong 664-14, Jeonju 561-756 (Korea, Republic of)

2015-06-05

Highlights: • Se interlayer is deposited between the CuGa and CuIn/In/Mo/STS stacked layer. • Both CIG precursor layers were selenized at 500 °C for 1 h. • SIMS depth profile shows that Ga distribution is uniform by Se interlayer. • The efficiency was improved for the CIGS solar cell by Se interlayer. - Abstract: A CIGS absorber layer with high gallium contents in the space-charge region can reduce the carrier recombination and improve the open circuit voltage V{sub oc}. Therefore, controlling Ga grading on top of CIGS thin film solar cells is the main objective of this experiment. To reduce Selenium (Se) vacancy, it is important that the diffusion of Ga elements into Se vacancy between Mo back contact and CIGS absorption layer would be controlled. In order to reduce Se vacancy and confirm Ga inter-diffusion, two CIGS solar cells were fabricated by converting CIG precursor with and without Se interlayer. The copper-indium metallic precursors were fabricated corresponding to the sequence CuIn/In/Mo/STS on stainless steel (STS) substrates by sequential direct current magnetron sputtering while Se layer was evaporated by rapid thermal annealing (RTA) system to obtain a Se/CuIn/In/Mo/STS stack. CuGa precursor layer was also fabricated on the Se/CuIn/In/Mo/STS stack. Finally, both CuGa/Se/CuIn/In/Mo/STS and CuGa/CuIn/In/Mo/STS stacks were selenized at 500 °C for 1 h. It was clearly observed from the secondary ion mass spectroscopy (SIMS) and X-ray diffraction (XRD) that there was a change between the fabricated CIGS absorption layers and the amount of Ga elements. Furthermore, the Ga elements gradually decreased from the top to the bottom layer of the CIGS absorption layer. We also discussed the effect of Se interlayer in the CIGS absorption layer and its influence on the solar cell’s performance.

Se interlayer in CIGS absorption layer for solar cell devices

International Nuclear Information System (INIS)

Lee, Seung-Kyu; Sim, Jae-Kwan; Kissinger, N.J. Suthan; Song, Il-Seok; Kim, Jin-Soo; Baek, Byung-Joon; Lee, Cheul-Ro

2015-01-01

Highlights: • Se interlayer is deposited between the CuGa and CuIn/In/Mo/STS stacked layer. • Both CIG precursor layers were selenized at 500 °C for 1 h. • SIMS depth profile shows that Ga distribution is uniform by Se interlayer. • The efficiency was improved for the CIGS solar cell by Se interlayer. - Abstract: A CIGS absorber layer with high gallium contents in the space-charge region can reduce the carrier recombination and improve the open circuit voltage V oc . Therefore, controlling Ga grading on top of CIGS thin film solar cells is the main objective of this experiment. To reduce Selenium (Se) vacancy, it is important that the diffusion of Ga elements into Se vacancy between Mo back contact and CIGS absorption layer would be controlled. In order to reduce Se vacancy and confirm Ga inter-diffusion, two CIGS solar cells were fabricated by converting CIG precursor with and without Se interlayer. The copper-indium metallic precursors were fabricated corresponding to the sequence CuIn/In/Mo/STS on stainless steel (STS) substrates by sequential direct current magnetron sputtering while Se layer was evaporated by rapid thermal annealing (RTA) system to obtain a Se/CuIn/In/Mo/STS stack. CuGa precursor layer was also fabricated on the Se/CuIn/In/Mo/STS stack. Finally, both CuGa/Se/CuIn/In/Mo/STS and CuGa/CuIn/In/Mo/STS stacks were selenized at 500 °C for 1 h. It was clearly observed from the secondary ion mass spectroscopy (SIMS) and X-ray diffraction (XRD) that there was a change between the fabricated CIGS absorption layers and the amount of Ga elements. Furthermore, the Ga elements gradually decreased from the top to the bottom layer of the CIGS absorption layer. We also discussed the effect of Se interlayer in the CIGS absorption layer and its influence on the solar cell’s performance

Two-Layer Variable Infiltration Capacity Land Surface Representation for General Circulation Models

Science.gov (United States)

Xu, L.

1994-01-01

A simple two-layer variable infiltration capacity (VIC-2L) land surface model suitable for incorporation in general circulation models (GCMs) is described. The model consists of a two-layer characterization of the soil within a GCM grid cell, and uses an aerodynamic representation of latent and sensible heat fluxes at the land surface. The effects of GCM spatial subgrid variability of soil moisture and a hydrologically realistic runoff mechanism are represented in the soil layers. The model was tested using long-term hydrologic and climatalogical data for Kings Creek, Kansas to estimate and validate the hydrological parameters. Surface flux data from three First International Satellite Land Surface Climatology Project Field Experiments (FIFE) intensive field compaigns in the summer and fall of 1987 in central Kansas, and from the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS) in Brazil were used to validate the mode-simulated surface energy fluxes and surface temperature.

A Tri-Layer Proton-Conducting Electrolyte for Chemically Stable Operation in Solid Oxide Fuel Cells

KAUST Repository

Bi, Lei

2013-10-07

Two BaZr0.7Pr0.1Y0.2O3-δ (BZPY) layers were used to sandwich a BaCe0.8Y0.2O3-δ (BCY) layer to produce a tri-layer electrolyte consisting of BZPY/BCY/BZPY. The BZPY layers significantly improved the chemical stability of the BCY electrolyte layer, which was not stable when tested alone, suggesting that the BZPY layer effectively protected the BCY layer from CO2 reaction, which is the major problem of BCY-based materials. A fuel cell with this sandwiched electrolyte supported on a Ni-based composite anode showed a reasonable cell performance, reaching 185 mW cm-2 at 700 oC, in spite of the relatively large electrolyte thickness (about 65 µm).

A Tri-Layer Proton-Conducting Electrolyte for Chemically Stable Operation in Solid Oxide Fuel Cells

KAUST Repository

Bi, Lei; Traversa, Enrico

2013-01-01

Two BaZr0.7Pr0.1Y0.2O3-δ (BZPY) layers were used to sandwich a BaCe0.8Y0.2O3-δ (BCY) layer to produce a tri-layer electrolyte consisting of BZPY/BCY/BZPY. The BZPY layers significantly improved the chemical stability of the BCY electrolyte layer, which was not stable when tested alone, suggesting that the BZPY layer effectively protected the BCY layer from CO2 reaction, which is the major problem of BCY-based materials. A fuel cell with this sandwiched electrolyte supported on a Ni-based composite anode showed a reasonable cell performance, reaching 185 mW cm-2 at 700 oC, in spite of the relatively large electrolyte thickness (about 65 µm).

Effect of p-layer properties on nanocrystalline absorber layer and thin film silicon solar cells

International Nuclear Information System (INIS)

Chowdhury, Amartya; Adhikary, Koel; Mukhopadhyay, Sumita; Ray, Swati

2008-01-01

The influence of the p-layer on the crystallinity of the absorber layer and nanocrystalline silicon thin film solar cells has been studied. Boron doped Si : H p-layers of different crystallinities have been prepared under different power pressure conditions using the plasma enhanced chemical vapour deposition method. The crystalline volume fraction of p-layers increases with the increase in deposition power. Optical absorption of the p-layer reduces as the crystalline volume fraction increases. Structural studies at the p/i interface have been done by Raman scattering studies. The crystalline volume fraction of the i-layer increases as that of the p-layer increases, the effect being more prominent near the p/i interface. Grain sizes of the absorber layer decrease from 9.2 to 7.2 nm and the density of crystallites increases as the crystalline volume fraction of the p-layer increases and its grain size decreases. With increasing crystalline volume fraction of the p-layer solar cell efficiency increases

Advanced fuel cell development in the United States

International Nuclear Information System (INIS)

Ackerman, J.P.

1984-01-01

Both molten carbonate and solid oxide fuel cells are being developed in the United States to complement and/or supplant phosphoric acid cells for commercial and utility use. This paper described the two technologies and the programs for their development

Optimization of intrinsic layer thickness, dopant layer thickness and concentration for a-SiC/a-SiGe multilayer solar cell efficiency performance using Silvaco software

Directory of Open Access Journals (Sweden)

Wei Yuan Wong

2017-01-01

Full Text Available Solar cell is expanding as green renewable alternative to conventional fossil fuel electricity generation, but compared to other land-used electrical generators, it is a comparative beginner. Many applications covered by solar cells starting from low power mobile devices, terrestrial, satellites and many more. To date, the highest efficiency solar cell is given by GaAs based multilayer solar cell. However, this material is very expensive in fabrication and material costs compared to silicon which is cheaper due to the abundance of supply. Thus, this research is devoted to develop multilayer solar cell by combining two different layers of P-I-N structures with silicon carbide and silicon germanium. This research focused on optimising the intrinsic layer thickness, p-doped layer thickness and concentration, n-doped layer thickness and concentration in achieving the highest efficiency. As a result, both single layer a-SiC and a-SiGe showed positive efficiency improvement with the record of 27.19% and 9.07% respectively via parametric optimization. The optimized parameters is then applied on both SiC and SiGe P-I-N layers and resulted the convincing efficiency of 33.80%.

Optimization of intrinsic layer thickness, dopant layer thickness and concentration for a-SiC/a-SiGe multilayer solar cell efficiency performance using Silvaco software

Science.gov (United States)

Yuan, Wong Wei; Natashah Norizan, Mohd; Salwani Mohamad, Ili; Jamalullail, Nurnaeimah; Hidayah Saad, Nor

2017-11-01

Solar cell is expanding as green renewable alternative to conventional fossil fuel electricity generation, but compared to other land-used electrical generators, it is a comparative beginner. Many applications covered by solar cells starting from low power mobile devices, terrestrial, satellites and many more. To date, the highest efficiency solar cell is given by GaAs based multilayer solar cell. However, this material is very expensive in fabrication and material costs compared to silicon which is cheaper due to the abundance of supply. Thus, this research is devoted to develop multilayer solar cell by combining two different layers of P-I-N structures with silicon carbide and silicon germanium. This research focused on optimising the intrinsic layer thickness, p-doped layer thickness and concentration, n-doped layer thickness and concentration in achieving the highest efficiency. As a result, both single layer a-SiC and a-SiGe showed positive efficiency improvement with the record of 27.19% and 9.07% respectively via parametric optimization. The optimized parameters is then applied on both SiC and SiGe P-I-N layers and resulted the convincing efficiency of 33.80%.

The cell engineering construction and function evaluation of multi-layer biochip dialyzer.

Science.gov (United States)

Zhu, Wen; Li, Jiwei; Liu, Jianfeng

2013-10-01

We report the fabrication and function evaluation of multi-layer biochip dialyzer. Such device may potentially be applied to the wearable hemodialysis systems. By merging the advantages of microfluidic chip technology with cell engineering, both functions of glomerular filtration and renal tubule physiological activity are integrated in the same device. This device is designed into a laminated structure, in which the chip number of the superimposed layer can be arbitrarily tailored in accordance with the requirements of dialysis capacity. We propose that such structure can overcome the obstacles of large size and detached structure of the traditional hollow fiber dialyzer. To construct this multilayer biochips dialyzer, two types of dialyzer device with two-layered and six-layered chips are assembled, respectively. Cell adhesion and proliferation on three different dialysis membrane materials under static and dynamic conditions are investigated and compared. The filtration capability, re-absorption function and excrete ammonia function of the resulting multi-layer biochip dialyzer are evaluated. The results reveal that the constructed device can perform higher filtration efficiency and also play a role of renal tubule. This methodology may be useful in developing "scaling down" artificial kidneys that can act as wearable or even implantable hemodialysis systems.

Active unjamming of confluent cell layers

Science.gov (United States)

Marchetti, M. Cristina

Cell motion inside dense tissues governs many biological processes, including embryonic development and cancer metastasis, and recent experiments suggest that these tissues exhibit collective glassy behavior. Motivated by these observations, we have studied a model of dense tissues that combines self-propelled particle models and vertex models of confluent cell layers. In this model, referred to as self-propelled Voronoi (SPV), cells are described as polygons in a Voronoi tessellation with directed noisy cell motility and interactions governed by a shape energy that incorporates the effects of cell volume incompressibility, contractility and cell-cell adhesion. Using this model, we have demonstrated a new density-independent solid-liquid transition in confluent tissues controlled by cell motility and a cell-shape parameter measuring the interplay of cortical tension and cell-cell adhesion. An important insight of this work is that the rigidity and dynamics of cell layers depends sensitively on cell shape. We have also used the SPV model to test a new method developed by our group to determine cellular forces and tissue stresses from experimentally accessible cell shapes and traction forces, hence providing the spatio-temporal distribution of stresses in motile dense tissues. This work was done with Dapeng Bi, Lisa Manning and Xingbo Yang. MCM was supported by NSF-DMR-1305184 and by the Simons Foundation.

Effect of the prominent catalyst layer surface on reactant gas transport and cell performance at the cathodic side of a PEMFC

International Nuclear Information System (INIS)

Perng, Shiang-Wuu; Wu, Horng-Wen

2010-01-01

The cell performance enhancement of a proton exchange membrane fuel cell (PEMFC) has been numerically investigated with the prominence-like form catalyst layer surface of the same composition at the cathodic half-cell of a PEMFC. The geometries of the prominence-like form catalyst layer surface are assigned as one prominence, three prominences, and five prominences catalyst layer surfaces with constant distance between two prominences in the same gas diffusion layer (GDL) for the purpose of investigating the cell performance. To confine the current investigation to two-dimensional incompressible flows, we assume that the fluid flow is laminar with a low Reynolds number 15. The results indicate that the prominence-like form catalyst layer surface can effectively enhance the local cell performance of a PEMFC.

Buckling behavior of origami unit cell facets under compressive loads

Science.gov (United States)

Kshad, Mohamed Ali Emhmed; Naguib, Hani E.

2018-03-01

Origami structures as cores for sandwich structures are designed to withstand the compressive loads and to dissipate compressive energy. The deformation of the origami panels and the unit cell facets are the primary factors behind the compressive energy dissipation in origami structures. During the loading stage, the origami structures deform through the folding and unfolding process of the unit cell facets, and also through the plastic deformation of the facets. This work presents a numerical study of the buckling behavior of different origami unit cell elements under compressive loading. The studied origami configurations were Miura and Ron-Resch-like origami structures. Finite element package was used to model the origami structures. The study investigated the buckling behavior of the unit cell facets of two types of origami structures Miura origami and Ron-Resch-Like origami structures. The simulation was conducted using ANSYS finite element software, in which the model of the unit cell represented by shell elements, and the eigenvalues buckling solver was used to predict the theoretical buckling of the unit cell elements.

Ambient Layer-by-Layer ZnO Assembly for Highly Efficient Polymer Bulk Heterojunction Solar Cells

KAUST Repository

Eita, Mohamed Samir

2015-02-04

The use of metal oxide interlayers in polymer solar cells has great potential because metal oxides are abundant, thermally stable, and can be used in fl exible devices. Here, a layer-by-layer (LbL) protocol is reported as a facile, room-temperature, solution-processed method to prepare electron transport layers from commercial ZnO nanoparticles and polyacrylic acid (PAA) with a controlled and tunable porous structure, which provides large interfacial contacts with the active layer. Applying the LbL approach to bulk heterojunction polymer solar cells with an optimized ZnO layer thickness of H25 nm yields solar cell power-conversion effi ciencies (PCEs) of ≈6%, exceeding the effi ciency of amorphous ZnO interlayers formed by conventional sputtering methods. Interestingly, annealing the ZnO/PAA interlayers in nitrogen and air environments in the range of 60-300 ° C reduces the device PCEs by almost 20% to 50%, indicating the importance of conformational changes inherent to the PAA polymer in the LbL-deposited fi lms to solar cell performance. This protocol suggests a new fabrication method for solution-processed polymer solar cell devices that does not require postprocessing thermal annealing treatments and that is applicable to fl exible devices printed on plastic substrates.

Two luminescent frameworks constructed from lead(II) salts with carboxylate ligands containing dinuclear lead(II) units

International Nuclear Information System (INIS)

Zhu Xiandong; Li Xiaoju; Liu Qingyan; Lue Jian; Guo Zhengang; He Jinrun; Li Yafeng; Cao Rong

2007-01-01

Two luminescent Pb(II) coordination frameworks containing dinuclear lead(II) units, [Pb(PYDC)(H 2 O)] n (1) and [Pb(HPHT)] n (2) have been prepared by the self-assembly of lead(II) salts with pyridinecarboxylate and benzenecarboxylate. Single-crystal X-ray diffraction analyses reveal that compound 1 is a three-dimensional architecture consisting of Pb 2 O 2 dimeric building units, whereas compound 2 is a two-dimensional layer structure containing one-dimensional lead-oxide chains. The luminescent properties of 1 and 2 have been investigated in the solid state at room temperature, indicating structure-dependent photoluminescent properties of the coordination frameworks. - Graphical abstract: Two luminescent Pb(II) coordination frameworks, [Pb(PYDC)(H 2 O)] n (1) and [Pb(HPHT)] n (2) have been prepared. Single-crystal analyses reveal that compound 1 is a three-dimensional architecture consisting of Pb 2 O 2 dimeric building units, whereas compound 2 is a two-dimensional layer structure containing one-dimensional lead-oxide chains. The luminescent properties have been investigated, indicating structure-dependent photoluminescent properties of the coordination frameworks

Multi-layer thin-film electrolytes for metal supported solid oxide fuel cells

Science.gov (United States)

Haydn, Markus; Ortner, Kai; Franco, Thomas; Uhlenbruck, Sven; Menzler, Norbert H.; Stöver, Detlev; Bräuer, Günter; Venskutonis, Andreas; Sigl, Lorenz S.; Buchkremer, Hans-Peter; Vaßen, Robert

2014-06-01

A key to the development of metal-supported solid oxide fuel cells (MSCs) is the manufacturing of gas-tight thin-film electrolytes, which separate the cathode from the anode. This paper focuses the electrolyte manufacturing on the basis of 8YSZ (8 mol.-% Y2O3 stabilized ZrO2). The electrolyte layers are applied by a physical vapor deposition (PVD) gas flow sputtering (GFS) process. The gas-tightness of the electrolyte is significantly improved when sequential oxidic and metallic thin-film multi-layers are deposited, which interrupt the columnar grain structure of single-layer electrolytes. Such electrolytes with two or eight oxide/metal layers and a total thickness of about 4 μm obtain leakage rates of less than 3 × 10-4 hPa dm3 s-1 cm-2 (Δp: 100 hPa) at room temperature and therefore fulfill the gas tightness requirements. They are also highly tolerant with respect to surface flaws and particulate impurities which can be present on the graded anode underground. MSC cell tests with double-layer and multilayer electrolytes feature high power densities more than 1.4 W cm-2 at 850 °C and underline the high potential of MSC cells.

Hybrid Dye-Sensitized Solar Cells Consisting of Double Titania Layers for Harvesting Light with Wide Range of Wavelengths

Science.gov (United States)

Sadamasu, Kengo; Inoue, Takafumi; Ogomi, Yuhei; Pandey, Shyam S.; Hayase, Shuzi

2011-02-01

We report a hybrid dye-sensitized solar cell consisting of double titania layers (top and bottom layers) stained with two dyes. A top layer fabricated on a glass was mechanically pressed with a bottom layer fabricated on a glass cloth. The glass cloth acts as a supporter of a porous titania layer as well as a holder of electrolyte. The incident photon to current efficiency (IPCE) curve had two peaks corresponding to those of the two dyes, which demonstrates that electrons are collected from both the top and bottom layers.

Generation of organized germ layers from a single mouse embryonic stem cell.

Science.gov (United States)

Poh, Yeh-Chuin; Chen, Junwei; Hong, Ying; Yi, Haiying; Zhang, Shuang; Chen, Junjian; Wu, Douglas C; Wang, Lili; Jia, Qiong; Singh, Rishi; Yao, Wenting; Tan, Youhua; Tajik, Arash; Tanaka, Tetsuya S; Wang, Ning

2014-05-30

Mammalian inner cell mass cells undergo lineage-specific differentiation into germ layers of endoderm, mesoderm and ectoderm during gastrulation. It has been a long-standing challenge in developmental biology to replicate these organized germ layer patterns in culture. Here we present a method of generating organized germ layers from a single mouse embryonic stem cell cultured in a soft fibrin matrix. Spatial organization of germ layers is regulated by cortical tension of the colony, matrix dimensionality and softness, and cell-cell adhesion. Remarkably, anchorage of the embryoid colony from the 3D matrix to collagen-1-coated 2D substrates of ~1 kPa results in self-organization of all three germ layers: ectoderm on the outside layer, mesoderm in the middle and endoderm at the centre of the colony, reminiscent of generalized gastrulating chordate embryos. These results suggest that mechanical forces via cell-matrix and cell-cell interactions are crucial in spatial organization of germ layers during mammalian gastrulation. This new in vitro method could be used to gain insights on the mechanisms responsible for the regulation of germ layer formation.

Rhenium Dichalcogenides: Layered Semiconductors with Two Vertical Orientations.

Science.gov (United States)

Hart, Lewis; Dale, Sara; Hoye, Sarah; Webb, James L; Wolverson, Daniel

2016-02-10

The rhenium and technetium diselenides and disulfides are van der Waals layered semiconductors in some respects similar to more well-known transition metal dichalcogenides (TMD) such as molybdenum sulfide. However, their symmetry is lower, consisting only of an inversion center, so that turning a layer upside-down (that is, applying a C2 rotation about an in-plane axis) is not a symmetry operation, but reverses the sign of the angle between the two nonequivalent in-plane crystallographic axes. A given layer thus can be placed on a substrate in two symmetrically nonequivalent (but energetically similar) ways. This has consequences for the exploitation of the anisotropic properties of these materials in TMD heterostructures and is expected to lead to a new source of domain structure in large-area layer growth. We produced few-layer ReS2 and ReSe2 samples with controlled "up" or "down" orientations by micromechanical cleavage and we show how polarized Raman microscopy can be used to distinguish these two orientations, thus establishing Raman as an essential tool for the characterization of large-area layers.

Planar conjugated polymers containing 9,10-disubstituted phenanthrene units for efficient polymer solar cells.

Science.gov (United States)

Li, Guangwu; Kang, Chong; Li, Cuihong; Lu, Zhen; Zhang, Jicheng; Gong, Xue; Zhao, Guangyao; Dong, Huanli; Hu, Wenping; Bo, Zhishan

2014-06-01

Four novel conjugated polymers (P1-4) with 9,10-disubstituted phenanthrene (PhA) as the donor unit and 5,6-bis(octyloxy)benzothiadiazole as the acceptor unit are synthesized and characterized. These polymers are of medium bandgaps (2.0 eV), low-lying HOMO energy levels (below -5.3 eV), and high hole mobilities (in the range of 3.6 × 10(-3) to 0.02 cm(2) V(-1) s(-1) ). Bulk heterojunction (BHJ) polymer solar cells (PSCs) with P1-4:PC71 BM blends as the active layer and an alcohol-soluble fullerene derivative (FN-C60) as the interfacial layer between the active layer and cathode give the best power conversion efficiency (PCE) of 4.24%, indicating that 9,10-disubstituted PhA are potential donor materials for high-efficiency BHJ PSCs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modelling of fast jet formation under explosion collision of two-layer alumina/copper tubes

Directory of Open Access Journals (Sweden)

I Balagansky

2017-09-01

Full Text Available Under explosion collapse of two-layer tubes with an outer layer of high-modulus ceramics and an inner layer of copper, formation of a fast and dense copper jet is plausible. We have performed a numerical simulation of the explosion collapse of a two-layer alumina/copper tube using ANSYS AUTODYN software. The simulation was performed in a 2D-axis symmetry posting on an Eulerian mesh of 3900x1200 cells. The simulation results indicate two separate stages of the tube collapse process: the nonstationary and the stationary stage. At the initial stage, a non-stationary fragmented jet is moving with the velocity of leading elements up to 30 km/s. The collapse velocity of the tube to the symmetry axis is about 2 km/s, and the pressure in the contact zone exceeds 700 GPa. During the stationary stage, a dense jet is forming with the velocity of 20 km/s. Temperature of the dense jet is about 2000 K, jet failure occurs when the value of effective plastic deformation reaches 30.

Formation of double-layered TiO2 structures with selectively-positioned molecular dyes for efficient flexible dye-sensitized solar cells

International Nuclear Information System (INIS)

Kim, Eun Yi; Yu, Sora; Moon, Jeong Hoon; Yoo, Seon Mi; Kim, Chulhee; Kim, Hwan Kyu; Lee, Wan In

2013-01-01

Graphical abstract: A novel flexible tandem dye-sensitized solar cell, selectively loading different dyes in discrete layers, was successfully formed on a plastic substrate by transferring the high-temperature-processed N719/TiO 2 over an organic dye-adsorbed TiO 2 film by a typical compression process at room temperature. -- Highlights: • A novel flexible dye-sensitized solar cell, selectively loading two different dyes in discrete layers, was successfully formed on a plastic substrate. • η of the flexible tandem cell obtained by transferring the high-temperature-processed TiO 2 layer was enhanced from 2.91% to 6.86%. • Interface control between two TiO 2 layers is crucial for the efficient transport of photo-injected electrons from the top to bottom TiO 2 layer. -- Abstract: To fabricate flexible dye-sensitized solar cells (DSCs) utilizing full solar spectrum, the double-layered TiO 2 films, selectively loading two different dyes in discrete layers, were formed on a plastic substrate by transferring the high-temperature-processed N719/TiO 2 over an organic dye (TA-St-CA)-sensitized TiO 2 film by a typical compression process at room temperature. It was found that interface control between two TiO 2 layers is crucial for the efficient transport of photo-injected electrons from the N719/TiO 2 to the TA-St-CA/TiO 2 layer. Electron impedance spectra (EIS) and transient photoelectron spectroscopic analyses exhibited that introduction of a thin interfacial TiO 2 layer between the two TiO 2 layers remarkably decreased the resistance at the interface, while increasing the electron diffusion constant (D e ) by ∼10 times. As a result, the photovoltaic conversion efficiency (η) of the flexible tandem DSC was 6.64%, whereas that of the flexible cell derived from the single TA-St-CA/TiO 2 layer was only 2.98%. Another organic dye (HC-acid), absorbing a short wavelength region of solar spectrum, was also applied to fabricate flexible tandem DSC. The η of the cell

Enhanced photovoltaic performance of inverted pyramid-based nanostructured black-silicon solar cells passivated by an atomic-layer-deposited Al2O3 layer.

Science.gov (United States)

Chen, Hong-Yan; Lu, Hong-Liang; Ren, Qing-Hua; Zhang, Yuan; Yang, Xiao-Feng; Ding, Shi-Jin; Zhang, David Wei

2015-10-07

Inverted pyramid-based nanostructured black-silicon (BS) solar cells with an Al2O3 passivation layer grown by atomic layer deposition (ALD) have been demonstrated. A multi-scale textured BS surface combining silicon nanowires (SiNWs) and inverted pyramids was obtained for the first time by lithography and metal catalyzed wet etching. The reflectance of the as-prepared BS surface was about 2% lower than that of the more commonly reported upright pyramid-based SiNW BS surface over the whole of the visible light spectrum, which led to a 1.7 mA cm(-2) increase in short circuit current density. Moreover, the as-prepared solar cells were further passivated by an ALD-Al2O3 layer. The effect of annealing temperature on the photovoltaic performance of the solar cells was investigated. It was found that the values of all solar cell parameters including short circuit current, open circuit voltage, and fill factor exhibit a further increase under an optimized annealing temperature. Minority carrier lifetime measurements indicate that the enhanced cell performance is due to the improved passivation quality of the Al2O3 layer after thermal annealing treatments. By combining these two refinements, the optimized SiNW BS solar cells achieved a maximum conversion efficiency enhancement of 7.6% compared to the cells with an upright pyramid-based SiNWs surface and conventional SiNx passivation.

Evaluation of two thermal neutron detection units consisting of ZnS/{sup 6}LiF scintillating layers with embedded WLS fibers read out with a SiPM

Energy Technology Data Exchange (ETDEWEB)

Mosset, J.-B., E-mail: jean-baptiste.mosset@a3.epfl.ch [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Stoykov, A.; Greuter, U.; Hildebrandt, M.; Schlumpf, N. [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Van Swygenhoven, H. [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland)

2014-11-11

Two single channel detection units for thermal neutron detection are investigated in a neutron beam. They consist of two ZnS/{sup 6}LiF scintillating layers sandwiching an array of WLS fibers. The pattern of these units can be repeated laterally and vertically in order to build up a one-dimensional position sensitive multi-channel detector with the needed sensitive surface and with the required neutron absorption probability. The originality of this work arises from the fact that the WLS fibers are read out with SiPMs instead of the traditionally used PMTs or MaPMTs. The signal processing system is based on a photon counting approach. For SiPMs with a dark count rate as high as 0.7 MHz, a trigger efficiency of 80% is achieved together with a system background rate lower than 10{sup −3}Hz and a dead time of 30μs. No change of performance is observed for neutron count rates of up to 3.6 kHz.

Randomized trial of four-layer and two-layer bandage systems in the management of chronic venous ulceration.

Science.gov (United States)

Moffatt, Christine J; McCullagh, Lynn; O'Connor, Theresa; Doherty, Debra C; Hourican, Catherine; Stevens, Julie; Mole, Trevor; Franks, Peter J

2003-01-01

To compare a four-layer bandage system with a two-layer system in the management of chronic venous leg ulceration, a prospective randomized open parallel groups trial was undertaken. In total, 112 patients newly presenting to leg ulcer services with chronic leg ulceration, screened to exclude the presence of arterial disease (ankle brachial pressure index ulceration other than venous disease, were entered into the trial. Patients were randomized to receive either four-layer (Profore) or two-layer (Surepress) high-compression elastic bandage systems. In all, 109 out of 112 patients had at least one follow-up. After 24 weeks, 50 out of 57 (88%) patients randomized to the four-layer bandage system with follow-up had ulcer closure (full epithelialization) compared with 40 out of 52 (77%) on the two-layer bandage, hazard ratio = 1.18 (95% confidence interval 0.69-2.02), p = 0.55. After 12 weeks, 40 out of 57 (70%) patients randomized to the four-layer bandage system with follow-up had ulcer closure compared with 30 out of 52 (58%) on the two-layer bandage, odds ratio = 4.23 (95% confidence interval 1.29-13.86), p = 0.02. Withdrawal rates were significantly greater on the two-layer bandage (30 out of 54; 56%) compared with the four-layer bandage system (8 out of 58; 14%), p bandaging system (15 out of 54; 28%) compared with four-layer bandaging (5 out of 54; 9%), p = 0.01. The higher mean cost of treatment in the two-layer bandaging system arm over 24 weeks ($1374 [ pound 916] vs. $1314 [ pound 876]) was explained by the increased mean number of bandage changes (1.5 vs. 1.1 per week) with the two-layer system. In conclusion, the four-layer bandage offers advantages over the two-layer bandage in terms of reduced withdrawal from treatment, fewer adverse incidents, and lower treatment cost.

Fabrication and characterization of two-layered nanofibrous membrane for guided bone and tissue regeneration application.

Science.gov (United States)

Masoudi Rad, Maryam; Nouri Khorasani, Saied; Ghasemi-Mobarakeh, Laleh; Prabhakaran, Molamma P; Foroughi, Mohammad Reza; Kharaziha, Mahshid; Saadatkish, Niloufar; Ramakrishna, Seeram

2017-11-01

Membranes used in dentistry act as a barrier to prevent invasion of intruder cells to defected area and obtains spaces that are to be subsequently filled with new bone and provide required bone volume for implant therapy when there is insufficient volume of healthy bone at implant site. In this study a two-layered bioactive membrane were fabricated by electrospinning whereas one layer provides guided bone regeneration (GBR) and fabricated using poly glycerol sebacate (PGS)/polycaprolactone (PCL) and Beta tri-calcium phosphate (β-TCP) (5, 10 and 15%) and another one containing PCL/PGS and chitosan acts as guided tissue regeneration (GTR). The morphology, chemical, physical and mechanical characterizations of the membranes were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), tensile testing, then biodegradability and bioactivity properties were evaluated. In vitro cell culture study was also carried out to investigate proliferation and mineralization of cells on different membranes. Transmission electron microscope (TEM) and SEM results indicated agglomeration of β-TCP nanoparticles in the structure of nanofibers containing 15% β-TCP. Moreover by addition of β-TCP from 5% to 15%, contact angle decreased due to hydrophilicity of nanoparticles and bioactivity was found to increase. Mechanical properties of the membrane increased by incorporation of 5% and 10% of β-TCP in the structure of nanofibers, while addition of 15% of β-TCP was found to deteriorate mechanical properties of nanofibers. Although the presence of 5% and 10% of nanoparticles in the nanofibers increased proliferation of cells on GBR layer, cell proliferation was observed to decrease by addition of 15% β-TCP in the structure of nanofibers which is likely due to agglomeration of nanoparticles in the nanofiber structure. Our overall results revealed PCL/PGS containing 10% β-TCP could be selected as the optimum GBR membrane

Photobleachable Diazonium Salt-Phenolic Resin Two-Layer Resist System

Science.gov (United States)

Uchino, Shou-ichi; Iwayanagi, Takao; Hashimoto, Michiaki

1988-01-01

This article describes a new negative two-layer photoresist system formed by a simple, successive spin-coating method. An aqueous acetic acid solution of diazonium salt and poly(N-vinylpyrrolidone) is deposited so as to contact a phenolic resin film spin-coated on a silicon wafer. The diazonium salt diffuses into the phenolic resin layer after standing for several minutes. The residual solution on the phenolic resin film doped with diazonium salt is spun to form the diazonium salt-poly(N-vinylpyrrolidone) top layer. This forms a uniform two-layer resist without phase separation or striation. Upon UV exposure, the diazonium salt in the top layer bleaches to act as a CEL dye, while the diazonium salt in the bottom layer decomposes to cause insolubilization. Half μm line-and-space patterns are obtained with an i-line stepper using 4-diazo-N,N-dimethylaniline chloride zinc chloride double salt as the diazonium salt and a cresol novolac resin for the bottom polymer layer. The resist formation processes, insolubilization mechanism, and the resolution capability of the new two-layer resist are discussed.

Synchronization of coupled metronomes on two layers

Science.gov (United States)

Zhang, Jing; Yu, Yi-Zhen; Wang, Xin-Gang

2017-12-01

Coupled metronomes serve as a paradigmatic model for exploring the collective behaviors of complex dynamical systems, as well as a classical setup for classroom demonstrations of synchronization phenomena. Whereas previous studies of metronome synchronization have been concentrating on symmetric coupling schemes, here we consider the asymmetric case by adopting the scheme of layered metronomes. Specifically, we place two metronomes on each layer, and couple two layers by placing one on top of the other. By varying the initial conditions of the metronomes and adjusting the friction between the two layers, a variety of synchronous patterns are observed in experiment, including the splay synchronization (SS) state, the generalized splay synchronization (GSS) state, the anti-phase synchronization (APS) state, the in-phase delay synchronization (IPDS) state, and the in-phase synchronization (IPS) state. In particular, the IPDS state, in which the metronomes on each layer are synchronized in phase but are of a constant phase delay to metronomes on the other layer, is observed for the first time. In addition, a new technique based on audio signals is proposed for pattern detection, which is more convenient and easier to apply than the existing acquisition techniques. Furthermore, a theoretical model is developed to explain the experimental observations, and is employed to explore the dynamical properties of the patterns, including the basin distributions and the pattern transitions. Our study sheds new lights on the collective behaviors of coupled metronomes, and the developed setup can be used in the classroom for demonstration purposes.

Forced phase-locked states and information retrieval in a two-layer network of oscillatory neurons with directional connectivity

International Nuclear Information System (INIS)

Kazantsev, Victor; Pimashkin, Alexey

2007-01-01

We propose two-layer architecture of associative memory oscillatory network with directional interlayer connectivity. The network is capable to store information in the form of phase-locked (in-phase and antiphase) oscillatory patterns. The first (input) layer takes an input pattern to be recognized and their units are unidirectionally connected with all units of the second (control) layer. The connection strengths are weighted using the Hebbian rule. The output (retrieved) patterns appear as forced-phase locked states of the control layer. The conditions are found and analytically expressed for pattern retrieval in response on incoming stimulus. It is shown that the system is capable to recover patterns with a certain level of distortions or noises in their profiles. The architecture is implemented with the Kuramoto phase model and using synaptically coupled neural oscillators with spikes. It is found that the spiking model is capable to retrieve patterns using the spiking phase that translates memorized patterns into the spiking phase shifts at different time scales

TFB:TPDSi2 interfacial layer usable in organic photovoltaic cells

Science.gov (United States)

Marks, Iobin J [Evanston, IL; Hains, Alexander W [Evanston, IL

2011-02-15

The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode; an active organic layer comprising an electron-donating organic material and an electron-accepting organic material; and an interfacial layer formed between the anode and active organic layer, where the interfacial layer comprises a hole-transporting polymer characterized with a hole-mobility higher than that of the electron-donating organic material in the active organic layer, and a small molecule that has a high hole-mobility and is capable of crosslinking on contact with air.

Atomic-Layer-Deposited Transparent Electrodes for Silicon Heterojunction Solar Cells

International Nuclear Information System (INIS)

Demaurex, Benedicte; Seif, Johannes P.; Smit, Sjoerd; Macco, Bart; Kessels, W. M.; Geissbuhler, Jonas; De Wolf, Stefaan; Ballif, Christophe

2014-01-01

We examine damage-free transparent-electrode deposition to fabricate high-efficiency amorphous silicon/crystalline silicon heterojunction solar cells. Such solar cells usually feature sputtered transparent electrodes, the deposition of which may damage the layers underneath. Using atomic layer deposition, we insert thin protective films between the amorphous silicon layers and sputtered contacts and investigate their effect on device operation. We find that a 20-nm-thick protective layer suffices to preserve, unchanged, the amorphous silicon layers beneath. Insertion of such protective atomic-layer-deposited layers yields slightly higher internal voltages at low carrier injection levels. However, we identify the presence of a silicon oxide layer, formed during processing, between the amorphous silicon and the atomic-layer-deposited transparent electrode that acts as a barrier, impeding hole and electron collection

A comparative study on the performance of hybrid solar cells containing ZnSTe QDs in hole transporting layer and photoactive layer

Energy Technology Data Exchange (ETDEWEB)

Najeeb, Mansoor Ani [Qatar University, Center for Advanced Materials (CAM) (Qatar); Abdullah, Shahino Mah; Aziz, Fakhra [University of Malaya, Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science (Malaysia); Ahmad, Zubair, E-mail: zubairtarar@qu.edu.qa; Shakoor, R. A. [Qatar University, Center for Advanced Materials (CAM) (Qatar); Mohamed, A. M. A. [Suez University, Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering (Egypt); Khalil, Uzma [University of Peshawar, Department of Electronics, Jinnah College for Women (Pakistan); Swelm, Wageh; Al-Ghamdi, Ahmed A. [King Abdulaziz University, Department of Physics, Faculty of Science (Saudi Arabia); Sulaiman, Khaulah [University of Malaya, Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science (Malaysia)

2016-12-15

In this paper, ZnSTe quantum dots-based hybrid solar cells (HSC) with two different device architectures have been investigated. The improved performance of the poly(3-hexylthiophene) (P3HT) and [6,6]phenyl C{sub 71} butyric acid methyl ester (PC{sub 71}BM)-based bulk heterojunction (BHJ) solar cells by the incorporation of ZnSTe quantum dots (QDs) with an average size of 2.96 nm in PEDOT:PSS layer and active layer that have been demonstrated. Although the efficiency of both types of devices is almost the same, a close comparison reveals different reasons behind their improved performance. The device prepared with QDs in the HTL has shown reduced series resistance, increased shunt resistance, and improved mobility. On the other hand, QDs in the photoactive layer demonstrates increased photo-generation leading to improved efficiency.

Mass transfer model for two-layer TBP oxidation reactions

International Nuclear Information System (INIS)

Laurinat, J.E.

1994-01-01

To prove that two-layer, TBP-nitric acid mixtures can be safely stored in the canyon evaporators, it must be demonstrated that a runaway reaction between TBP and nitric acid will not occur. Previous bench-scale experiments showed that, at typical evaporator temperatures, this reaction is endothermic and therefore cannot run away, due to the loss of heat from evaporation of water in the organic layer. However, the reaction would be exothermic and could run away if the small amount of water in the organic layer evaporates before the nitric acid in this layer is consumed by the reaction. Provided that there is enough water in the aqueous layer, this would occur if the organic layer is sufficiently thick so that the rate of loss of water by evaporation exceeds the rate of replenishment due to mixing with the aqueous layer. This report presents measurements of mass transfer rates for the mixing of water and butanol in two-layer, TBP-aqueous mixtures, where the top layer is primarily TBP and the bottom layer is comprised of water or aqueous salt solution. Mass transfer coefficients are derived for use in the modeling of two-layer TBP-nitric acid oxidation experiments. Three cases were investigated: (1) transfer of water into the TBP layer with sparging of both the aqueous and TBP layers, (2) transfer of water into the TBP layer with sparging of just the TBP layer, and (3) transfer of butanol into the aqueous layer with sparging of both layers. The TBP layer was comprised of 99% pure TBP (spiked with butanol for the butanol transfer experiments), and the aqueous layer was comprised of either water or an aluminum nitrate solution. The liquid layers were air sparged to simulate the mixing due to the evolution of gases generated by oxidation reactions. A plastic tube and a glass frit sparger were used to provide different size bubbles. Rates of mass transfer were measured using infrared spectrophotometers provided by SRTC/Analytical Development

Surface and Interface Properties of 10–12 Unit Cells Thick Sputter Deposited Epitaxial CeO2 Films

Directory of Open Access Journals (Sweden)

L. V. Saraf

2008-01-01

Full Text Available Ultrathin and continuous epitaxial films with relaxed lattice strain can potentially maintain more of its bulk physical and chemical properties and are useful as buffer layers. We study surface, interface, and microstructural properties of ultrathin (∼10–12 unit cells thick epitaxial ceria films grown on single crystal YSZ substrates. The out-of -plane and in-plane lattice parameters indicate relaxation in the continuous film due to misfit dislocations seen by high-resolution transmission electron microscopy (HRTEM and substrate roughness of ∼1-2 unit cells, confirmed by atomic force microscopy and HRTEM. A combination of secondary sputtering, lattice mismatch, substrate roughness, and surface reduction creating secondary phase was likely the cause of surface roughness which should be reduced to a minimum level for effective use of it as buffer layers.

Enhanced photocurrent density in graphene/Si based solar cell (GSSC) by optimizing active layer thickness

International Nuclear Information System (INIS)

Rosikhin, Ahmad; Hidayat, Aulia Fikri; Syuhada, Ibnu; Winata, Toto

2015-01-01

Thickness dependent photocurrent density in active layer of graphene/Si based solar cell has been investigated via analytical – simulation study. This report is a preliminary comparison of experimental and analytical investigation of graphene/Si based solar cell. Graphene sheet was interfaced with Si thin film forming heterojunction solar cell that was treated as a device model for photocurrent generator. Such current can be enhanced by optimizing active layer thickness and involving metal oxide as supporting layer to shift photons absorption. In this case there are two type of devices model with and without TiO 2 in which the silicon thickness varied at 20 – 100 nm. All of them have examined and also compared with each other to obtain an optimum value. From this calculation it found that generated currents almost linear with thickness but there are saturated conditions that no more enhancements will be achieved. Furthermore TiO 2 layer is effectively increases photon absorption but reducing device stability, maximum current is fluctuates enough. This may caused by the disturbance of excitons diffusion and resistivity inside each layer. Finally by controlling active layer thickness, it is quite useful to estimate optimization in order to develop the next solar cell devices

Enhanced photocurrent density in graphene/Si based solar cell (GSSC) by optimizing active layer thickness

Energy Technology Data Exchange (ETDEWEB)

Rosikhin, Ahmad, E-mail: a.rosikhin86@yahoo.co.id; Hidayat, Aulia Fikri; Syuhada, Ibnu; Winata, Toto, E-mail: toto@fi.itb.ac.id [Department of physics, physics of electronic materials research division Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung Jl. Ganesha 10, Bandung 40132, Jawa Barat – Indonesia (Indonesia)

2015-12-29

Thickness dependent photocurrent density in active layer of graphene/Si based solar cell has been investigated via analytical – simulation study. This report is a preliminary comparison of experimental and analytical investigation of graphene/Si based solar cell. Graphene sheet was interfaced with Si thin film forming heterojunction solar cell that was treated as a device model for photocurrent generator. Such current can be enhanced by optimizing active layer thickness and involving metal oxide as supporting layer to shift photons absorption. In this case there are two type of devices model with and without TiO{sub 2} in which the silicon thickness varied at 20 – 100 nm. All of them have examined and also compared with each other to obtain an optimum value. From this calculation it found that generated currents almost linear with thickness but there are saturated conditions that no more enhancements will be achieved. Furthermore TiO{sub 2} layer is effectively increases photon absorption but reducing device stability, maximum current is fluctuates enough. This may caused by the disturbance of excitons diffusion and resistivity inside each layer. Finally by controlling active layer thickness, it is quite useful to estimate optimization in order to develop the next solar cell devices.

In vitro proliferation of haemopoietic cells in the presence of adherent cell layers. II. Differential effect of adherent cell layers derived from various organs

NARCIS (Netherlands)

Reimann, J.; Burger, H.

1979-01-01

Mouse bone marrow-derived adherent cell populations promoted proliferation of haemopoietic cells in vitro in a liquid culture system for at least 4 weeks. Adherent cell layers derived from other haemopoietic organs (foetal liver, adult spleen) and fibroblasts from embryonic tissues did not maintain

Difluorobenzothiadiazole based two-dimensional conjugated polymers with triphenylamine substituted moieties as pendants for bulk heterojunction solar cells

Directory of Open Access Journals (Sweden)

W. H. Lee

2017-11-01

Full Text Available Three donor/acceptor (D/A-type two-dimensional polythiophenes (PTs; PBTFA13, PBTFA12, PBTFA11 featuring difluorobenzothiadiazole (DFBT derivatives as the conjugated (acceptor units in the polymer backbone and tertbutyl–substituted triphenylamine (tTPA-containing moieties as (donor pendants have been synthesized and characterized. These PTs exhibited good thermal stabilities, broad absorption spectra, and narrow optical band gaps. The cutoff wavelength of the UV–Vis absorption band was red-shifted upon increasing the content of the DFBT units in the PTs. Bulk heterojunction solar cells having an active layer comprising blends of the PTs and fullerene derivatives [6,6] phenyl-C61/71-butyric acid methyl ester (PC61BM/PC71BM were fabricated; their photovoltaic performance was strongly dependent on the content of the DFBT derivative in the PT. Incorporating a suitable content of the DFBT derivative in the polymer backbone enhanced the solar absorption ability and conjugation length of the PTs. The photovoltaic properties of the PBTFA13-based solar cells were superior to those of the PBTFA11- and PBTFA12-based solar cells.

Interfacial Layer Engineering for Performance Enhancement in Polymer Solar Cells

Directory of Open Access Journals (Sweden)

Hao Zeng

2015-02-01

Full Text Available Improving power conversion efficiency and device performance stability is the most critical challenge in polymer solar cells for fulfilling their applications in industry at large scale. Various methodologies have been developed for realizing this goal, among them interfacial layer engineering has shown great success, which can optimize the electrical contacts between active layers and electrodes and lead to enhanced charge transport and collection. Interfacial layers also show profound impacts on light absorption and optical distribution of solar irradiation in the active layer and film morphology of the subsequently deposited active layer due to the accompanied surface energy change. Interfacial layer engineering enables the use of high work function metal electrodes without sacrificing device performance, which in combination with the favored kinetic barriers against water and oxygen penetration leads to polymer solar cells with enhanced performance stability. This review provides an overview of the recent progress of different types of interfacial layer materials, including polymers, small molecules, graphene oxides, fullerene derivatives, and metal oxides. Device performance enhancement of the resulting solar cells will be elucidated and the function and operation mechanism of the interfacial layers will be discussed.

Exposure buildup factors for a cobalt-60 point isotropic source for single and two layer slabs

International Nuclear Information System (INIS)

Chakarova, R.

1992-01-01

Exposure buildup factors for point isotropic cobalt-60 sources are calculated by the Monte Carlo method with statistical errors ranging from 1.5 to 7% for 1-5 mean free paths (mfp) thick water and iron single slabs and for 1 and 2 mfp iron layers followed by water layers 1-5 mfp thick. The computations take into account Compton scattering. The Monte Carlo data for single slab geometries are approximated by Geometric Progression formula. Kalos's formula using the calculated single slab buildup factors may be applied to reproduce the data for two-layered slabs. The presented results and discussion may help when choosing the manner in which the radiation field gamma irradiation units will be described. (author)

Isostructural exclusion of elements between aragonite and calcite layers in the shell of the Pacific oyster Crassostrea gigas

International Nuclear Information System (INIS)

Markwitz, A.; Gauldie, R.W.; Trompetter, W.J.; Pithie, J.; Jamieson, D.N.; Sharma, S.K.

1999-01-01

Sections of the shell of the farmed Pacific oyster 'Crassostrea gigas' that are available commercially in Wellington, New Zealand, showed a distinct alternating pattern in the shell mineral when observed by reflected light. The layers were identified by Raman scattering as alternating bands of the calcite and aragonite mineral forms of calcium carbonate using the micro-Raman facility at the Hawaii Institute of Geophysics and Planetology. The differences in the unit cell structure of calcite and aragonite favour different trace elements in the two minerals. Aragonite is isostructural with Strontianite SrCO 3 , and calcite is isostructural with Smithsonite ZnCO 3 . As a result, Sr deposition should be favoured in the aragonite layer and is excluded from the calcite layer; and, conversely, Zn deposition should be favoured in the calcite layer and is excluded from the aragonite layer. However, up to today, significant differences in the pattern of Sr and Zn in microprobe scans are not discovered. By ion microprobe analysis, it was shown that differences in the unit cell structure of calcite and aragonite favor different trace elements in the two minerals

Flexible bactericidal graphene oxide–chitosan layers for stem cell proliferation

International Nuclear Information System (INIS)

Mazaheri, M.; Akhavan, O.; Simchi, A.

2014-01-01

Highlights: • Fabrication of flexible graphene oxide–chitosan nanocomposite layers was reported. • The flexibility of the chitosan layers were improved by adding graphene oxide sheets. • The nanocomposite layers with 1.5 wt% graphene oxide content showed yielded flexible and antibacterial surfaces for stem cell proliferation. - Abstract: Graphene oxide (GO)–chitosan composite layers with stacked layer structures were synthesized using chemically exfoliated GO sheets (with lateral dimensions of ∼1 μm and thickness of ∼1 nm), and applied as antibacterial and flexible nanostructured templates for stem cell proliferation. By increasing the GO content from zero to 6 wt%, the strength and elastic modulus of the layers increased ∼80% and 45%, respectively. Similar to the chitosan layer, the GO–chitosan composite layers showed significant antibacterial activity (>77% inactivation after only 3 h) against Staphylococcus aureus bacteria. Surface density of the actin cytoskeleton fibers of human mesenchymal stem cells (hMSCs) cultured on the chitosan and GO(1.5 wt%)–chitosan composite layers was found nearly the same, while it significantly decreased by increasing the GO content to 3 and 6 wt%. Our results indicated that although a high concentration of GO in the chitosan layer (here, 6 wt%) could decelerate the proliferation of the hMSCs on the flexible layer, a low concentration of GO (i.e., 1.5 wt%) not only resulted in biocompatibility but also kept the mechanical flexibility of the self-sterilized layers for high proliferation of hMSCs

Flexible bactericidal graphene oxide–chitosan layers for stem cell proliferation

Energy Technology Data Exchange (ETDEWEB)

Mazaheri, M. [Department of Materials Science and Engineering, Sharif University of Technology, PO Box 11365-9466, Tehran (Iran, Islamic Republic of); Akhavan, O., E-mail: oakhavan@sharif.edu [Department of Physics, Sharif University of Technology, PO Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, PO Box 14588-89694, Tehran (Iran, Islamic Republic of); Simchi, A. [Department of Materials Science and Engineering, Sharif University of Technology, PO Box 11365-9466, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, PO Box 14588-89694, Tehran (Iran, Islamic Republic of)

2014-05-01

Highlights: • Fabrication of flexible graphene oxide–chitosan nanocomposite layers was reported. • The flexibility of the chitosan layers were improved by adding graphene oxide sheets. • The nanocomposite layers with 1.5 wt% graphene oxide content showed yielded flexible and antibacterial surfaces for stem cell proliferation. - Abstract: Graphene oxide (GO)–chitosan composite layers with stacked layer structures were synthesized using chemically exfoliated GO sheets (with lateral dimensions of ∼1 μm and thickness of ∼1 nm), and applied as antibacterial and flexible nanostructured templates for stem cell proliferation. By increasing the GO content from zero to 6 wt%, the strength and elastic modulus of the layers increased ∼80% and 45%, respectively. Similar to the chitosan layer, the GO–chitosan composite layers showed significant antibacterial activity (>77% inactivation after only 3 h) against Staphylococcus aureus bacteria. Surface density of the actin cytoskeleton fibers of human mesenchymal stem cells (hMSCs) cultured on the chitosan and GO(1.5 wt%)–chitosan composite layers was found nearly the same, while it significantly decreased by increasing the GO content to 3 and 6 wt%. Our results indicated that although a high concentration of GO in the chitosan layer (here, 6 wt%) could decelerate the proliferation of the hMSCs on the flexible layer, a low concentration of GO (i.e., 1.5 wt%) not only resulted in biocompatibility but also kept the mechanical flexibility of the self-sterilized layers for high proliferation of hMSCs.

A new backpropagation learning algorithm for layered neural networks with nondifferentiable units.

Science.gov (United States)

Oohori, Takahumi; Naganuma, Hidenori; Watanabe, Kazuhisa

2007-05-01

We propose a digital version of the backpropagation algorithm (DBP) for three-layered neural networks with nondifferentiable binary units. This approach feeds teacher signals to both the middle and output layers, whereas with a simple perceptron, they are given only to the output layer. The additional teacher signals enable the DBP to update the coupling weights not only between the middle and output layers but also between the input and middle layers. A neural network based on DBP learning is fast and easy to implement in hardware. Simulation results for several linearly nonseparable problems such as XOR demonstrate that the DBP performs favorably when compared to the conventional approaches. Furthermore, in large-scale networks, simulation results indicate that the DBP provides high performance.

Layered vanadyl (IV) nitroprusside: Magnetic interaction through a network of hydrogen bonds

Energy Technology Data Exchange (ETDEWEB)

Gil, D.M. [Instituto de Química Física, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, San Lorenzo 456, T4000CAN San Miguel de Tucumán (Argentina); Osiry, H. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, México (Mexico); Pomiro, F.; Varetti, E.L. [CEQUINOR (CONICET-UNLP), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 and 115, 1900, La Plata (Argentina); Carbonio, R.E. [INFIQC – CONICET, Departamento de Físico Química, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre esq, Medina Allende, Ciudad Universitaria, X5000HUA Córdoba (Argentina); Alejandro, R.R. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, México (Mexico); Ben Altabef, A. [INQUINOA-UNT-CONICET, Instituto de Química Física, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, San Lorenzo 456, T4000CAN San Miguel de Tucumán (Argentina); and others

2016-07-15

The hydrogen bond and π-π stacking are two non-covalent interactions able to support cooperative magnetic ordering between paramagnetic centers. This contribution reports the crystal structure and related magnetic properties for VO[Fe(CN){sub 5}NO]·2H{sub 2}O, which has a layered structure. This solid crystallizes with an orthorhombic unit cell, in the Pna2{sub 1} space group, with cell parameters a=14.1804(2), b=10.4935(1), c=7.1722(8) Å and four molecules per unit cell (Z=4). Its crystal structure was solved and refined from powder X-ray diffraction data. Neighboring layers remain linked through a network of hydrogen bonds involving a water molecule coordinated to the axial position for the V atom and the unbridged axial NO and CN ligands. An uncoordinated water molecule is found forming a triple bridge between these last two ligands and the coordinated water molecule. The magnetic measurements, recorded down to 2 K, shows a ferromagnetic interaction between V atoms located at neighboring layers, with a Curie-Weiss constant of 3.14 K. Such ferromagnetic behavior was interpreted as resulting from a superexchange interaction through the network of strong OH····O{sub H2O}, OH····N{sub CN}, and OH····O{sub NO} hydrogen bonds that connects neighboring layers. The interaction within the layer must be of antiferromagnetic nature and it was detected close to 2 K. - Graphical abstract: Coordination environment for the metals in vanadyl (II) nitroprusside dihydrate. Display Omitted - Highlights: • Crystal structure of vanadyl nitroprusside dehydrate. • Network of hydrogen bonds. • Magnetic interactions through a network of hydrogen bonds. • Layered transition metal nitroprussides.

A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection

KAUST Repository

Eita, Mohamed Samir; Usman, Anwar; El-Ballouli, AlA'A O.; Alarousu, Erkki Antero; Bakr, Osman; Mohammed, Omar F.

2014-01-01

solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by

Layer-by-layer buildup of polysaccharide-containing films: Physico-chemical properties and mesenchymal stem cells adhesion.

Science.gov (United States)

Kulikouskaya, Viktoryia I; Pinchuk, Sergei V; Hileuskaya, Kseniya S; Kraskouski, Aliaksandr N; Vasilevich, Irina B; Matievski, Kirill A; Agabekov, Vladimir E; Volotovski, Igor D

2018-03-22

Layer-by-Layer assembled polyelectrolyte films offer the opportunity to control cell attachment and behavior on solid surfaces. In the present study, multilayer films based on negatively charged biopolymers (pectin, dextran sulfate, carboxymethylcellulose) and positively charged polysaccharide chitosan or synthetic polyelectrolyte polyethyleneimine has been prepared and evaluated. Physico-chemical properties of the formed multilayer films, including their growth, morphology, wettability, stability, and mechanical properties, have been studied. We demonstrated that chitosan-containing films are characterized by the linear growth, the defect-free surface, and predominantly viscoelastic properties. When chitosan is substituted for the polyethyleneimine in the multilayer system, the properties of the formed films are significantly altered: the rigidity and surface roughness increases, the film growth acquires the exponential character. The multilayer films were subsequently used for culturing mesenchymal stem cells. It has been determined that stem cells effectively adhered to chitosan-containing films and formed on them the monolayer culture of fibroblast-like cells with high viability. Our results show that cell attachment is a complex process which is not only governed by the surface functionality because one of the key parameter effects on cell adhesion is the stiffness of polyelectrolyte multilayer films. We therefore propose our Layer-by-Layer films for applications in tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2018. © 2018 Wiley Periodicals, Inc.

S-layer and cytoplasmic membrane – exceptions from the typical archaeal cell wall with a focus on double membranes

Directory of Open Access Journals (Sweden)

Andreas eKlingl

2014-11-01

Full Text Available The common idea of typical cell wall architecture in archaea consists of a pseudo-crystalline proteinaceous surface layer (S-layer, situated upon the cytoplasmic membrane. This is true for the majority of described archaea, hitherto. Within the crenarchaea, the S-layer often represents the only cell wall component, but there are various exceptions from this wall architecture. Beside (glycosylated S-layers in (hyperthermophilic cren- and euryarchaea as well as halophilic archaea, one can find a great variety of other cell wall structures like proteoglycan-like S-layers (Halobacteria, glutaminylglycan (Natronococci, methanochondroitin (Methanosarcina or double layered cell walls with pseudomurein (Methanothermus and Methanopyrus. The presence of an outermost cellular membrane in the crenarchaeal species Ignicoccus hospitalis already gave indications for an outer membrane similar to Gram-negative bacteria. Although there is just limited data concerning their biochemistry and ultrastructure, recent studies on the euryarchaeal methanogen Methanomassiliicoccus luminyensis, cells of the ARMAN group, and the SM1 euryarchaeon delivered further examples for this exceptional cell envelope type consisting of two membranes.

Impact of Interfacial Layers in Perovskite Solar Cells.

Science.gov (United States)

Cho, An-Na; Park, Nam-Gyu

2017-10-09

Perovskite solar cells (PCSs) are composed of organic-inorganic lead halide perovskite as the light harvester. Since the first report on a long-term-durable, 9.7 % efficient, solid-state perovskite solar cell, organic-inorganic halide perovskites have received considerable attention because of their excellent optoelectronic properties. As a result, a power conversion efficiency (PCE) exceeding 22 % was certified. Controlling the grain size, grain boundary, morphology, and defects of the perovskite layer is important for achieving high efficiency. In addition, interfacial engineering is equally or more important to further improve the PCE through better charge collection and a reduction in charge recombination. In this Review, the type of interfacial layers and their impact on photovoltaic performance are investigated for both the normal and the inverted cell architectures. Four different interfaces of fluorine-doped tin oxide (FTO)/electron-transport layer (ETL), ETL/perovskite, perovskite/hole-transport layer (HTL), and HTL/metal are classified, and their roles are investigated. The effects of interfacial engineering with organic or inorganic materials on photovoltaic performance are described in detail. Grain-boundary engineering is also included because it is related to interfacial engineering and the grain boundary in the perovskite layer plays an important role in charge conduction, recombination, and chargecarrier life time. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A three-layer distributed RC network with two transmission zeros

Science.gov (United States)

Huelsman, L. P.

1974-01-01

This report describes the properties of a three-layer distributed RC network consisting of two resistive layers separated by a dielectric which may be used to realize two zeros of transmission on the j-omega axis of the complex frequency plane. The relative location of the two zeros is controlled by the location of a contact placed on one of the resistive layers.

Low temperature fabrication of perovskite solar cells with TiO2 nanoparticle layers

International Nuclear Information System (INIS)

Kanayama, Masato; Oku, Takeo; Suzuki, Atsushi; Yamada, Masahiro; Sakamoto, Hiroki; Minami, Satoshi; Kohno, Kazufumi

2016-01-01

TiO 2 /CH 3 NH 3 PbI 3 -based photovoltaic devices were fabricated by a spin-coating method using a mixture solution. TiO 2 require high-temperature processing to achieve suitably high carrier mobility. TiO 2 electron transport layers and TiO 2 scaffold layers for the perovskite were fabricated from TiO 2 nanoparticles with different grain sizes. The photovoltaic properties and microstructures of solar cells were characterized. Nanoparticle sizes of these TiO 2 were 23 nm and 3 nm and the performance of solar cells was improved by combination of two TiO 2 nanoparticles

Dislocation Coupling-Induced Transition of Synchronization in Two-Layer Neuronal Networks

International Nuclear Information System (INIS)

Qin Hui-Xin; Ma Jun; Wang Chun-Ni; Jin Wu-Yin

2014-01-01

The mutual coupling between neurons in a realistic neuronal system is much complex, and a two-layer neuronal network is designed to investigate the transition of electric activities of neurons. The Hindmarsh—Rose neuron model is used to describe the local dynamics of each neuron, and neurons in the two-layer networks are coupled in dislocated type. The coupling intensity between two-layer networks, and the coupling ratio (Pro), which defines the percentage involved in the coupling in each layer, are changed to observe the synchronization transition of collective behaviors in the two-layer networks. It is found that the two-layer networks of neurons becomes synchronized with increasing the coupling intensity and coupling ratio (Pro) beyond certain thresholds. An ordered wave in the first layer is useful to wake up the rest state in the second layer, or suppress the spatiotemporal state in the second layer under coupling by generating target wave or spiral waves. And the scheme of dislocation coupling can be used to suppress spatiotemporal chaos and excite quiescent neurons. (interdisciplinary physics and related areas of science and technology)

Successive reactive liquid flow episodes in a layered intrusion (Unit 9, Rum Eastern Layered Intrusion, Scotland)

Science.gov (United States)

Leuthold, Julien; Blundy, Jon; Holness, Marian

2014-05-01

We will present a detailed microstructural and geochemical study of reactive liquid flow in Unit 9 of the Rum Eastern Layered Intrusion. In the study region, Unit 9 comprises an underlying lens-like body of peridotite overlain by a sequence of troctolite and gabbro (termed allivalite), with some local and minor anorthosite. The troctolite is separated from the overlying gabbro by a distinct, sub-horizontal, undulose horizon (the major wavy horizon). Higher in the stratigraphy is another, similar, horizon (the minor wavy horizon) that separates relatively clinopyroxene-poor gabbro from an overlying gabbro. To the north of the peridotite lens, both troctolite and gabbro grade into poikilitic gabbro. Clinopyroxene habit in the allivalite varies from thin rims around olivine in troctolite, to equigranular crystals in gabbro, to oikocrysts in the poikilitic gabbro. The poikilitic gabbros contain multiple generations of clinopyroxene, with Cr-rich (~1.1 wt.% Cr2O3), anhedral cores with moderate REE concentrations (core1) overgrown by an anhedral REE-depleted second generation with moderate Cr (~0.7 wt.% Cr2O3) (core2). These composite cores are rimmed by Cr-poor (~0.2 wt.% Cr2O3) and REE-poor to moderate clinopyroxene. We interpret these microstructures as a consequence of two separate episodes of partial melting triggered by the intrusion of hot olivine-phyric picrite to form the discontinuous lenses that comprise the Unit 9 peridotite. Loss of clinopyroxene-saturated partial melt from the lower part of the allivalite immediately following the early stages of sill intrusion resulted in the formation of clinopyroxene-poor gabbro. The spatial extent of clinopyroxene loss is marked by the minor wavy horizon. A further partial melting event stripped out almost all clinopyroxene from the lowest allivalite, to form a troctolite, with the major wavy horizon marking the extent of melting during this second episode. The poikilitic gabbro formed from clinopyroxene-saturated melt

Surface passivation of InP solar cells with InAlAs layers

Science.gov (United States)

Jain, Raj K.; Flood, Dennis J.; Landis, Geoffrey A.

1993-01-01

The efficiency of indium phosphide solar cells is limited by high values of surface recombination. The effect of a lattice-matched In(0.52)Al(0.48)As window layer material for InP solar cells, using the numerical code PC-1D is investigated. It was found that the use of InAlAs layer significantly enhances the p(+)n cell efficiency, while no appreciable improvement is seen for n(+)p cells. The conduction band energy discontinuity at the heterojunction helps in improving the surface recombination. An optimally designed InP cell efficiency improves from 15.4 percent to 23 percent AMO for a 10 nm thick InAlAs layer. The efficiency improvement reduces with increase in InAlAs layer thickness, due to light absorption in the window layer.

Learning about the Unit Cell and Crystal Lattice with Computerized Simulations and Games: A Pilot Study

Science.gov (United States)

Luealamai, Sutha; Panijpan, Bhinyo

2012-01-01

The authors have developed a computer-based learning module on the unit cell of various types of crystal. The module has two components: the virtual unit cell (VUC) part and the subsequent unit cell hunter part. The VUC is a virtual reality simulation for students to actively arrive at the unit cell from exploring, from a broad view, the crystal…

Modeling a two-layer flow system at the subarctic, subalpine tree line during snowmelt

Science.gov (United States)

Leenders, Erica E.; Woo, Ming-Ko

2002-10-01

In the subarctic it is common to encounter a two-layer flow system consisting of a porous organic cover overlying frozen or unfrozen mineral soils with much lower hydraulic conductivities. The "simple lumped reservoir parametric," or "semidistributed land-use-based runoff processes" (SLURP), model was adapted to simulate runoff generated by such a flow system from an upland shrub land to an open woodland downslope. A subalpine site in Wolf Creek, Yukon, Canada, was subdivided into two aggregated simulation areas (ASA), each being a unit characterized by a set of parameters. The model computes the vertical water balance and flow generation from several storages, and then routes the water out of the ASA. When applied to the 1999 snowmelt season, the model simulated the very low lateral flow and a large increase in storage in the mineral soil, as was observed in the field. The model was used to assess the sensitivity of the two-layer flow system under a range of temperature, snow cover, and frost conditions. Results show that within the range of possible climatic conditions, the hydrologic system is unlikely to yield significant runoff across the subalpine tree line, but if ground ice is abundant in the soil pores, percolation will be limited and fast flow from the surface layer is enhanced.

Lithium-Ion Cell Charge Control Unit

Science.gov (United States)

Reid, Concha; Button, Robert; Manzo, Michelle; McKissock, Barbara; Miller, Thomas; Gemeiner, Russel; Bennett, William; Hand, Evan

2006-01-01

Life-test data of Lithium-Ion battery cells is critical in order to establish their performance capabilities for NASA missions and Exploration goals. Lithium-ion cells have the potential to replace rechargeable alkaline cells in aerospace applications, but they require a more complex charging scheme than is typically required for alkaline cells. To address these requirements in our Lithium-Ion Cell Test Verification Program, a Lithium-Ion Cell Charge Control Unit was developed by NASA Glenn Research Center (GRC). This unit gives researchers the ability to test cells together as a pack, while allowing each cell to charge individually. This allows the inherent cell-to-cell variations to be addressed on a series string of cells and results in a substantial reduction in test costs as compared to individual cell testing. The Naval Surface Warfare Center at Crane, Indiana developed a power reduction scheme that works in conjunction with the Lithium-Ion Cell Charge Control Unit. This scheme minimizes the power dissipation required by the circuitry to prolong circuit life and improve its reliability.

A proposed agglomerate model for oxygen reduction in the catalyst layer of proton exchange membrane fuel cells

International Nuclear Information System (INIS)

Zhang, Xiaoxian; Gao, Yuan; Ostadi, Hossein; Jiang, Kyle; Chen, Rui

2014-01-01

Highlights: • We developed a new agglomerate model to describe oxygen reduction reaction. • We showed how to calculate the model parameters from catalyst layer structure. • We verified the agglomerate model. - Abstract: Oxygen diffusion and reduction in the catalyst layer of PEM fuel cell is an important process in fuel cell modelling, but models able to link the reduction rate to catalyst-layer structure are lack; this paper makes such an effort. We first link the average reduction rate over the agglomerate within a catalyst layer to a probability that an oxygen molecule, which is initially on the agglomerate surface, will enter and remain in the agglomerate at any time in the absence of any electrochemical reaction. We then propose a method to directly calculate distribution function of this probability and apply it to two catalyst layers with contrasting structures. A formula is proposed to describe these calculated distribution functions, from which the agglomerate model is derived. The model has two parameters and both can be independently calculated from catalyst layer structures. We verify the model by first showing that it is an improvement and able to reproduce what the spherical model describes, and then testing it against the average oxygen reductions directly calculated from pore-scale simulations of oxygen diffusion and reaction in the two catalyst layers. The proposed model is simple, but significant as it links the average oxygen reduction to catalyst layer structures, and its two parameters can be directly calculated rather than by calibration

Strong and reversible modulation of carbon nanotube-silicon heterojunction solar cells by an interfacial oxide layer.

Science.gov (United States)

Jia, Yi; Cao, Anyuan; Kang, Feiyu; Li, Peixu; Gui, Xuchun; Zhang, Luhui; Shi, Enzheng; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai

2012-06-21

Deposition of nanostructures such as carbon nanotubes on Si wafers to make heterojunction structures is a promising route toward high efficiency solar cells with reduced cost. Here, we show a significant enhancement in the cell characteristics and power conversion efficiency by growing a silicon oxide layer at the interface between the nanotube film and Si substrate. The cell efficiency increases steadily from 0.5% without interfacial oxide to 8.8% with an optimal oxide thickness of about 1 nm. This systematic study reveals that formation of an oxide layer switches charge transport from thermionic emission to a mixture of thermionic emission and tunneling and improves overall diode properties, which are critical factors for tailoring the cell behavior. By controlled formation and removal of interfacial oxide, we demonstrate oscillation of the cell parameters between two extreme states, where the cell efficiency can be reversibly altered by a factor of 500. Our results suggest that the oxide layer plays an important role in Si-based photovoltaics, and it might be utilized to tune the cell performance in various nanostructure-Si heterojunction structures.

One-dimensional conduction through supporting electrolytes: two-scale cathodic Debye layer.

Science.gov (United States)

Almog, Yaniv; Yariv, Ehud

2011-10-01

Supporting-electrolyte solutions comprise chemically inert cations and anions, produced by salt dissolution, together with a reactive ionic species that may be consumed and generated on bounding ion-selective surfaces (e.g., electrodes or membranes). Upon application of an external voltage, a Faraday current is thereby established. It is natural to analyze this ternary-system process through a one-dimensional transport problem, employing the thin Debye-layer limit. Using a simple model of ideal ion-selective membranes, we have recently addressed this problem for moderate voltages [Yariv and Almog, Phys. Rev. Lett. 105, 176101 (2010)], predicting currents that scale as a fractional power of Debye thickness. We address herein the complementary problem of moderate currents. We employ matched asymptotic expansions, separately analyzing the two inner thin Debye layers adjacent to the ion-selective surfaces and the outer electroneutral region outside them. A straightforward calculation following comparable singular-perturbation analyses of binary systems is frustrated by the prediction of negative ionic concentrations near the cathode. Accompanying numerical simulations, performed for small values of Debye thickness, indicate a number unconventional features occurring at that region, such as inert-cation concentration amplification and electric-field intensification. The current-voltage correlation data of the electrochemical cell, obtained from compilation of these simulations, does not approach a limit as the Debye thickness vanishes. Resolution of these puzzles reveals a transformation of the asymptotic structure of the cathodic Debye layer. This reflects the emergence of an internal boundary layer, adjacent to the cathode, wherein field and concentration scaling differs from those of the Gouy-Chapman theory. The two-scale feature of the cathodic Debye layer is manifested through a logarithmic voltage scaling with Debye thickness. Accounting for this scaling, the

Ambient Layer-by-Layer ZnO Assembly for Highly Efficient Polymer Bulk Heterojunction Solar Cells

KAUST Repository

Eita, Mohamed Samir; El Labban, Abdulrahman; Cruciani, Federico; Usman, Anwar; Beaujuge, Pierre; Mohammed, Omar F.

2015-01-01

The use of metal oxide interlayers in polymer solar cells has great potential because metal oxides are abundant, thermally stable, and can be used in fl exible devices. Here, a layer-by-layer (LbL) protocol is reported as a facile, room

Reassembly of S-layer proteins

International Nuclear Information System (INIS)

Pum, Dietmar; Sleytr, Uwe B

2014-01-01

Crystalline bacterial cell surface layers (S-layers) represent the outermost cell envelope component in a broad range of bacteria and archaea. They are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. They are highly porous protein mesh works with unit cell sizes in the range of 3 to 30 nm, and pore sizes of 2 to 8 nm. S-layers are usually 5 to 20 nm thick (in archaea, up to 70 nm). S-layer proteins are one of the most abundant biopolymers on earth. One of their key features, and the focus of this review, is the intrinsic capability of isolated native and recombinant S-layer proteins to form self-assembled mono- or double layers in suspension, at solid supports, the air-water interface, planar lipid films, liposomes, nanocapsules, and nanoparticles. The reassembly is entropy-driven and a fascinating example of matrix assembly following a multistage, non-classical pathway in which the process of S-layer protein folding is directly linked with assembly into extended clusters. Moreover, basic research on the structure, synthesis, genetics, assembly, and function of S-layer proteins laid the foundation for their application in novel approaches in biotechnology, biomimetics, synthetic biology, and nanotechnology. (topical review)

The Transient Intermediate Plexiform Layer, a Plexiform Layer-like Structure Temporarily Existing in the Inner Nuclear Layer in Developing Rat Retina.

Science.gov (United States)

Park, Hyung Wook; Kim, Hong-Lim; Park, Yong Soo; Kim, In-Beom

2018-02-01

The retina is a highly specialised part of the brain responsible for visual processing. It is well-laminated; three layers containing five different types of neurons are compartmentalised by two synaptic layers. Among the retinal layers, the inner nuclear layer (INL) is composed of horizontal, bipolar, and amacrine cell types. Bipolar cells form one sublayer in the distal half of the IPL, while amacrine cells form another sublayer in the proximal half, without any border-like structure. Here, we report that a plexiform layer-like structure exists temporarily in the border between the bipolar and amacrine sublayers in the INL in the rat retina during retinal development. This transient intermediate plexiform layer (TIPL) appeared at postnatal day (PD) 7 and then disappeared around PD 12. Most apoptotic cells in the INL were found near the TIPL. These results suggest that the TIPL may contribute to the formation of sublayers and the cell number limit in the INL.

Microfluidically supported biochip design for culture of endothelial cell layers with improved perfusion conditions.

Science.gov (United States)

Raasch, Martin; Rennert, Knut; Jahn, Tobias; Peters, Sven; Henkel, Thomas; Huber, Otmar; Schulz, Ingo; Becker, Holger; Lorkowski, Stefan; Funke, Harald; Mosig, Alexander

2015-03-02

Hemodynamic forces generated by the blood flow are of central importance for the function of endothelial cells (ECs), which form a biologically active cellular monolayer in blood vessels and serve as a selective barrier for macromolecular permeability. Mechanical stimulation of the endothelial monolayer induces morphological remodeling in its cytoskeleton. For in vitro studies on EC biology culture devices are desirable that simulate conditions of flow in blood vessels and allow flow-based adhesion/permeability assays under optimal perfusion conditions. With this aim we designed a biochip comprising a perfusable membrane that serves as cell culture platform multi-organ-tissue-flow (MOTiF biochip). This biochip allows an effective supply with nutrition medium, discharge of catabolic cell metabolites and defined application of shear stress to ECs under laminar flow conditions. To characterize EC layers cultured in the MOTiF biochip we investigated cell viability, expression of EC marker proteins and cell adhesion molecules of ECs dynamically cultured under low and high shear stress, and compared them with an endothelial culture in established two-dimensionally perfused flow chambers and under static conditions. We show that ECs cultured in the MOTiF biochip form a tight EC monolayer with increased cellular density, enhanced cell layer thickness, presumably as the result of a rapid and effective adaption to shear stress by remodeling of the cytoskeleton. Moreover, endothelial layers in the MOTiF biochip express higher amounts of EC marker proteins von-Willebrand-factor and PECAM-1. EC layers were highly responsive to stimulation with TNFα as detected at the level of ICAM-1, VCAM-1 and E-selectin expression and modulation of endothelial permeability in response to TNFα/IFNγ treatment under flow conditions. Compared to static and two-dimensionally perfused cell culture condition we consider MOTiF biochips as a valuable tool for studying EC biology in vitro under

Two-dimensional analytical model of a proton exchange membrane fuel cell

International Nuclear Information System (INIS)

Liu, Jia Xing; Guo, Hang; Ye, Fang; Ma, Chong Fang

2017-01-01

In this study, a two-dimensional full cell analytical model of a proton exchange membrane fuel cell is developed. The analytical model describes electrochemical reactions on the anode and cathode catalyst layer, reactants diffusion in the gas diffusion layer, and gases flow in the gas channel, etc. The analytical solution is derived according to the basic physical equations. The performance predicted by the model is in good agreement with the experimental data. The results show that the polarization mainly occurs in the cathode side of the proton exchange membrane fuel cell. The anodic overpotential cannot be neglected. The hydrogen and oxygen concentrations decrease along the channel flow direction. The hydrogen and oxygen concentrations in the catalyst layer decrease with the current density. As predicted by the model, concentration polarization mainly occurs in the cathode side. - Highlights: • A 2D full cell analytical model of a proton exchange membrane fuel cell is developed. • The analytical solution is deduced according to the basic equations. • The anode overpotential is not so small that it cannot be neglected. • Species concentration distributions in the fuel cell is obtained and analyzed.

Double-layered ZnO nanostructures for efficient perovskite solar cells

KAUST Repository

Mahmood, Khalid; S. Swain, Bhabani; Amassian, Aram

2014-01-01

To date, a single layer of TiO2 or ZnO has been the most successful implementations of any electron transport layer (ETL) in solution-processed perovskite solar cells. In a quest to improve the ETL, we explore a new nanostructured double-layer ZnO film for mesoscopic perovskite-based thin film photovoltaics. This approach yields a maximum power conversion efficiency of 10.35%, which we attribute to the morphology of oxide layer and to faster electron transport. The successful implementation of the low-temperature hydrothermally processed double-layer ZnO film as ETL in perovskite solar cells highlights the opportunities to further improve the efficiencies by focusing on the ETL in this rapidly developing field. This journal is

Solid oxide fuel cells with bi-layered electrolyte structure

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xinge; Robertson, Mark; Deces-Petit, Cyrille; Xie, Yongsong; Hui, Rob; Qu, Wei; Kesler, Olivera; Maric, Radenka; Ghosh, Dave [Institute for Fuel Cell Innovation, National Research Council Canada, 4250 Wesbrook Mall, Vancouver, B.C. V6T 1W5 (Canada)

2008-01-10

In this work, we have developed solid oxide fuel cells with a bi-layered electrolyte of 2 {mu}m SSZ and 4 {mu}m SDC using tape casting, screen printing, and co-firing processes. The cell reached power densities of 0.54 W cm{sup -2} at 650 C and 0.85 W cm{sup -2} at 700 C, with open circuit voltage (OCV) values larger than 1.02 V. The electrical leaking between anode and cathode through an SDC electrolyte has been blocked in the bi-layered electrolyte structure. However, both the electrolyte resistance (R{sub el}) and electrode polarization resistance (R{sub p,a+c}) increased in comparison to cells with single-layered SDC electrolytes. The formation of a solid solution of (Ce, Zr)O{sub 2-x} during sintering process and the flaws in the bi-layered electrolyte structure seem to be the main causes for the increase in the R{sub el} value (0.32 {omega} cm{sup 2}) at 650 C, which is almost one order of magnitude higher than the calculated value. (author)

Solar cells with perovskite-based light sensitization layers

Science.gov (United States)

Kanatzidis, Mercouri G.; Chang, Robert P.H.; Stoumpos, Konstantinos; Lee, Byunghong

2018-05-08

Solar cells are provided which comprise an electron transporting layer and a light sensitizing layer of perovskite disposed over the surface of the electron transporting layer. The perovskite may have a formula selected from the group consisting of A2MX6, Z2MX6 or YMX6, wherein A is an alkali metal, M is a metal or a metalloid, X is a halide, Z is selected from the group consisting of a primary ammonium, an iminium, a secondary ammonium, a tertiary ammonium, and a quaternary ammonium, and Y has formula Mb(L)3, wherein Mb is a transition metal in the 2+ oxidation state L is an N--N neutral chelating ligand. Methods of making the solar cells are also provided, including methods based on electrospray deposition.

Photonic intermediate layer for silicon tandem solar cells

Energy Technology Data Exchange (ETDEWEB)

Bielawny, Andreas; Miclea, Paul-Tiberiu; Wehrspohn, Ralf [Martin-Luther Universitaet Halle-Wittenberg (Germany). Inst. fuer Physik, Mikro-MD; Lee, Seuong-Mo; Knez, Mato [Max-Planck-Inst. fuer Mikrostrukturphysik, Halle (Germany); Carius, Reinhard [Forschungszentrum Juelich (DE). Inst. fuer Photovoltaik (IEF-5); Lisca, Marian; Rockstuhl, Carsten; Lederer, Falk [Universitaet Jena (Germany). Dept. Physik

2008-07-01

The concept of incorporation of a 3D photonic crystal as diffractive spectral filter within a-Si/mc-Si tandem solar cells has been investigated as a promising application. Our intermediate reflective filter enhances the pathway of spectrally selected light within an amorphous silicon top cell in its spectral region of low absorption. From our previous work, we expect a significant improvement of the tandem's efficiency of about 1.2%(absolute). This increases efficiency for a typical silicon tandem cell from 11.2% to 12.4%, as a result of the optical current-matching of the two junctions. Our wavelength-selective optical element is a 3D-structured optical thin-film - prepared by self-organized artificial opal templates and finalized with atomic layer deposition techniques. The resulting samples are highly periodical thin-film inverted opals made of zinc-oxide. We compare recent experimental data on the optical properties with our simulations and photonic bandstructure calculations.

Improved Efficiency of Polymer Solar Cells by means of Coating Hole Transporting Layer as Double Layer Deposition

Science.gov (United States)

Chonsut, T.; Kayunkid, N.; Rahong, S.; Rangkasikorn, A.; Wirunchit, S.; Kaewprajak, A.; Kumnorkaew, P.; Nukeaw, J.

2017-09-01

Polymer solar cells is one of the promising technologies that gain tremendous attentions in the field of renewable energy. Optimization of thickness for each layer is an important factor determining the efficiency of the solar cells. In this work, the optimum thickness of Poly(3,4-ethylenedioxythione): poly(styrenesulfonate) (PEDOT:PSS), a famous polymer widely used as hole transporting layer in polymer solar cells, is determined through the analyzing of device’s photovoltaic parameters, e.g. short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) as well as power conversion efficiency (PCE). The solar cells were prepared with multilayer of ITO/PEDOT:PSS/PCDTBT:PC70BM/TiOx/Al by rapid convective deposition. In such preparation technique, the thickness of the thin film is controlled by the deposition speed. The faster deposition speed is used, the thicker film is obtained. Furthermore, double layer deposition of PEDOT:PSS was introduced as an approach to improve solar cell efficiency. The results obviously reveal that, with the increase of PEDOT:PSS thickness, the increments of Jsc and FF play the important role to improve PCE from 3.21% to 4.03%. Interestingly, using double layer deposition of PEDOT:PSS shows the ability to enhance the performance of the solar cells to 6.12% under simulated AM 1.5G illumination of 100 mW/cm2.

Novel manufacturing process for direct methanol fuel cells (DMFC) by defined layer structures; Neuartiges Herstellungsverfahren fuer Direkt-Methanol-Brennstoffzellen (DMFC) durch definierte Schichtstrukturen

Energy Technology Data Exchange (ETDEWEB)

Frey, Thomas

2007-07-17

A novel method to prepare membrane electrode assemblies (MEA) for direct methanol fuel cells (DMFC) by a layer-upon-layer fabrication onto a porous substrate is presented. The novel preparation technique is based on a single method for the fabrication of the whole MEA, e.g. spraying one functional layer onto the other, and therefore simplifies its preparation considerably. It also permits new fuel cell designs with in-plane serial connection of single cells. The new concept offers high flexibility in the choice of cell geometry as well as superior control of the structural parameters. Layer thickness, composition, catalyst and ionomer loadings can easily be varied and adapted. Cells fabricated with the new concept are especially suited for low power micro fuel cells operated at ambient conditions. In this work, process parameters enabling such a layer-upon-layer MEA preparation have been developed. Advanced catalyst inks and electrolyte solutions were formulated as precursors for each functional layer. Nafion {sup registered} as well as polyaryl-based polymers were investigated for the fabrication of dense electrolyte layers. Catalyst layers were prepared from inks containing Pt and PtRu-black catalysts which were suspended in suitable solvents with diluted proton-conducting electrolytes. The critical parameters for the layer build-up were identified and optimized afterwards. Various candidate materials for the porous substrate were characterized and selected for further investigation. Experiments and calculation models led to a concept and an advanced design for a serially connected multi-cells unit on the substrate. The inplane conductivity of the electrodes turned out to be the critical parameter resulting in high ohmic losses especially when the electrodes were applied on non-conductive substrates. Various conductive coatings were tested to selectively increase the conductivity of non-conductive substrates, which are prerequisite for serial connection. Only

A vertically integrated dynamic RAM-cell: Buried bit line memory cell with floating transfer layer

NARCIS (Netherlands)

Mouthaan, A.J.; Vertregt, Maarten

1986-01-01

A charge injection device has been realized in which charge can be injected on to an MOS-capacitor from a buried layer via an isolated transfer layer. The cell is positioned vertically between word and bit line. LOCOS (local oxidation) is used to isolate the cells and (deep) ion implantation to

Two-Step Physical Deposition of a Compact CuI Hole-Transport Layer and the Formation of an Interfacial Species in Perovskite Solar Cells.

Science.gov (United States)

Gharibzadeh, Saba; Nejand, Bahram Abdollahi; Moshaii, Ahmad; Mohammadian, Nasim; Alizadeh, Amir Hossein; Mohammadpour, Rahele; Ahmadi, Vahid; Alizadeh, Abdolali

2016-08-09

A simple and practical approach is introduced for the deposition of CuI as an inexpensive inorganic hole-transport material (HTM) for the fabrication of low cost perovskite solar cells (PSCs) by gas-solid phase transformation of Cu to CuI. The method provides a uniform and well-controlled CuI layer with large grains and good compactness that prevents the direct connection between the contact electrodes. Solar cells prepared with CuI as the HTM with Au electrodes displays an exceptionally high short-circuit current density of 32 mA cm(-2) , owing to an interfacial species formed between the perovskite and the Cu resulting in a long wavelength contribution to the incident photon-to-electron conversion efficiency (IPCE), and an overall power conversion efficiency (PCE) of 7.4 %. The growth of crystalline and uniform CuI on a low roughness perovskite layer leads to remarkably high charge extraction in the cells, which originates from the high hole mobility of CuI in addition to a large number of contact points between CuI and the perovskite layer. In addition, the solvent-free method has no damaging side effect on the perovskite layer, which makes it an appropriate method for large scale applications of CuI in perovskite solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Single-layer colonic anastomoses using polyglyconate (Maxon) vs. two-layer anastomoses using chromic catgut and silk. Experimental study].

Science.gov (United States)

García-Osogobio, Sandra Minerva; Takahashi-Monroy, Takeshi; Velasco, Liliana; Gaxiola, Miguel; Sotres-Vega, Avelina; Santillán-Doherty, Patricio

2006-01-01

The safety of an intestinal anastomosis is usually measured by its complication rate, especially the incidence of anastomotic leakage. A wide variety of methods have been described to reestablish intestinal continuity including single-layer continuous or two-layer interrupted anastomosis. To evaluate if the single-layer continuous anastomosis using polygluconate is safer and reliable than two-layer interrupted anastomosis with chromic catgut and silk. A prospective, experimental, randomized and comparative analysis was conducted in 20 dogs. They were divided in two groups; group 1 underwent two-layer interrupted anastomosis and group 2 underwent sigle-layer continuous technique. Anastomoses were timed. Both groups were under observation. Anastomotic leakage, and other complications were evaluated. The animals were sacrified and the anastomosis was taken out together with 10 cm of colon on both sides of the anastomosis. Breaking strength, histologic evaluation and hydroxyproline determination were performed. Ten two-layer anastomosis and ten single-layer anastomosis were performed. A median of 25 minutes (range: 20-30 minutes) was required to construct the anastomoses in group 1 versus 20 minutes (range: 12-25 minutes) in group 2. All animals survived and no leakage was observed. Wound infection ocurred in four dogs (20%). Median breaking strength was 230 mm Hg in group 1 and 210 mm Hg in group 2. Hydroxyproline concentration was 8.94 mg/g in group 1 (range: 5.33-16.71) and 9.94 mg/g in group 2 (range: 2.96-21.87). There was no difference among groups about the inflammatory response evaluated by pathology. There was no statistical significance in any variable evaluated. CONCLUIONS: This study demonstrates that a single-layer continuous is similar in terms of safety to the two-layer technique, but because of its facility to perform, the single-layer technique could be superior.

Novel building units with bimetallic rings in inorganic/organic hybrid chains and layers

International Nuclear Information System (INIS)

Mahenthirarajah, Thushitha; Li Yang; Lightfoot, Philip

2009-01-01

Hydrothermal synthesis has produced three new compounds constructed from novel building units containing vanadium-oxide (or oxyfluoride) subunits linked together via covalently bound cationic copper complexes. Each new compound exhibits novel structural features: [Cu(dipa)][VOF 4 ] (1) incorporates a corner-sharing octahedral vanadium(IV) oxyfluoride chain decorated by copper-(2,2'-dipyridyl amine) complexes which form intra-chain bridges. Within a similar reactant system [Cu(dipa)] 2 [V 6 O 17 ] (2) is produced, the structure of which exhibits edge-sharing trigonal bipyramidal vanadium(V) 'ladder-like' double chains which are bridged into layers by tetrahedral pyrovanadate dimers together with the copper-(2,2'-dipyridyl amine) complexes. [Cu(py) 4 ] 2 [V 4 O 12 ] (3), is a 2-D structure featuring exclusively tetrahedral vanadium(V) in four-membered ring building blocks, linked through octahedral copper-pyridine complexes to form two crystallographically different bimetallic layers. - Graphical abstract: Hydrothermal synthesis is used to prepare hybrid mixed metal oxides and oxyfluorides with novel extended connectivities

Characterization and use of crystalline bacterial cell surface layers

Science.gov (United States)

Sleytr, Uwe B.; Sára, Margit; Pum, Dietmar; Schuster, Bernhard

2001-10-01

Crystalline bacterial cell surface layers (S-layers) are one of the most common outermost cell envelope components of prokaryotic organisms (archaea and bacteria). S-layers are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. S-layers as the most abundant of prokaryotic cellular proteins are appealing model systems for studying the structure, synthesis, genetics, assembly and function of proteinaceous supramolecular structures. The wealth of information existing on the general principle of S-layers have revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for chemical modifications and binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from a variety of organisms are capable of recrystallizing as closed monolayers onto solid supports (e.g., metals, polymers, silicon wafers) at the air-water interface, on lipid films or onto the surface of liposomes; (iv) functional domains can be incorporated in S-layer proteins by genetic engineering. Thus, S-layer technologies particularly provide new approaches for biotechnology, biomimetics, molecular nanotechnology, nanopatterning of surfaces and formation of ordered arrays of metal clusters or nanoparticles as required for nanoelectronics.

Layer-by-layer assembled cell instructive nanocoatings containing platelet lysate.

Science.gov (United States)

Oliveira, Sara M; Santo, Vítor E; Gomes, Manuela E; Reis, Rui L; Mano, João F

2015-04-01

Great efforts have been made to introduce growth factors (GFs) onto 2D/3D constructs in order to control cell behavior. Platelet lysate (PL) presents itself as a cost-effective source of multiple GFs and other proteins. The instruction given by a construct-PL combination will depend on how its instructive cues are presented to the cells. The content, stability and conformation of the GFs affect their instruction. Strategies for a controlled incorporation of PL are needed. Herein, PL was incorporated into nanocoatings by layer-by-layer assembling with polysaccharides presenting different sulfation degrees (SD) and charges. Heparin and several marine polysaccharides were tested to evaluate their PL and GF incorporation capability. The consequent effects of those multilayers on human adipose derived stem cells (hASCs) were assessed in short-term cultures. Both nature of the polysaccharide and SD were important properties that influenced the adsorption of PL, vascular endothelial growth factor (VEGF), fibroblast growth factor b (FGFb) and platelet derived growth factor (PDGF). The sulfated polysaccharides-PL multilayers showed to be efficient in the promotion of morphological changes, serum-free adhesion and proliferation of high passage hASCs (P > 5). These biomimetic multilayers promise to be versatile platforms to fabricate instructive devices allowing a tunable incorporation of PL. Copyright © 2015 Elsevier Ltd. All rights reserved.

Substrate and p-layer effects on polymorphous silicon solar cells

Directory of Open Access Journals (Sweden)

Abolmasov S.N.

2014-07-01

Full Text Available The influence of textured transparent conducting oxide (TCO substrate and p-layer on the performance of single-junction hydrogenated polymorphous silicon (pm-Si:H solar cells has been addressed. Comparative studies were performed using p-i-n devices with identical i/n-layers and back reflectors fabricated on textured Asahi U-type fluorine-doped SnO2, low-pressure chemical vapor deposited (LPCVD boron-doped ZnO and sputtered/etched aluminum-doped ZnO substrates. The p-layers were hydrogenated amorphous silicon carbon and microcrystalline silicon oxide. As expected, the type of TCO and p-layer both have a great influence on the initial conversion efficiency of the solar cells. However they have no effect on the defect density of the pm-Si:H absorber layer.

Efficient small-molecule organic solar cells incorporating a doped buffer layer

Energy Technology Data Exchange (ETDEWEB)

Chou, Dei-Wei [Department of aviation and Communication Electronics, Air Force Institute of Technology, Kaohsiung 820, Taiwan (China); Chen, Kan-Lin [Department of Electronic Engineering, Fortune Institute of Technology, Kaohsiung 831, Taiwan (China); Huang, Chien-Jung, E-mail: chien@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Nanzih, Kaohsiung 811, Taiwan (China); Tsao, Yao-Jen [Department of Applied Physics, National University of Kaohsiung, Nanzih, Kaohsiung 811, Taiwan (China); Chen, Wen-Ray; Meen, Teen-Hang [Department of Electronic Engineering, National Formosa University, Hu-Wei, Yunlin 632, Taiwan (China)

2013-06-01

Small-molecule organic solar cells (OSCs) with an optimized structure of indium tin oxide/poly (3,4-ethylenedioxythioxythiophene):poly(styrenesulfonate)/copper phthalocyanine (CuPc) (10 nm)/CuPc: fullerene (C{sub 60}) mixed (20 nm)/C{sub 60} (20 nm)/4,7-diphenyl-1,10-phenanthroline (BPhen) (5 nm)/Ag were fabricated. In this study, the cesium carbonate-doped BPhen (Cs{sub 2}CO{sub 3}:BPhen) was adopted as the buffer layer to enhance the efficiency of the OSCs. The photovoltaic parameters of the OSCs, such as the short-circuit current density and fill factor, depend on the doping concentration of Cs{sub 2}CO{sub 3} in the BPhen layer. The cell with a Cs{sub 2}CO{sub 3}:BPhen (1:4) cathode buffer layer exhibits a power conversion efficiency (PCE) of 3.51%, compared to 3.37% for the device with the pristine BPhen layer. The enhancement of PCE was attributed to the energy-level alignment between the C{sub 60} layer and the Cs{sub 2}CO{sub 3}:BPhen layer. In addition, the characterization measured using atomic force microscopy shows that the Cs{sub 2}CO{sub 3}:BPhen layers have smoother surfaces. - Highlight: • Cs2CO3-doped 4,7-diphenyl-1,10-phenanthroline (BPhen) cathode buffer layer. • Cs2CO3:BPhen layer with different ratios affects organic solar cells performance. • Cell with 1:4 (Cs2CO3:BPhen) ratio shows 3.51% power conversion efficiency.

Flexible bactericidal graphene oxide-chitosan layers for stem cell proliferation

Science.gov (United States)

Mazaheri, M.; Akhavan, O.; Simchi, A.

2014-05-01

Graphene oxide (GO)-chitosan composite layers with stacked layer structures were synthesized using chemically exfoliated GO sheets (with lateral dimensions of ˜1 μm and thickness of ˜1 nm), and applied as antibacterial and flexible nanostructured templates for stem cell proliferation. By increasing the GO content from zero to 6 wt%, the strength and elastic modulus of the layers increased ˜80% and 45%, respectively. Similar to the chitosan layer, the GO-chitosan composite layers showed significant antibacterial activity (>77% inactivation after only 3 h) against Staphylococcus aureus bacteria. Surface density of the actin cytoskeleton fibers of human mesenchymal stem cells (hMSCs) cultured on the chitosan and GO(1.5 wt%)-chitosan composite layers was found nearly the same, while it significantly decreased by increasing the GO content to 3 and 6 wt%. Our results indicated that although a high concentration of GO in the chitosan layer (here, 6 wt%) could decelerate the proliferation of the hMSCs on the flexible layer, a low concentration of GO (i.e., 1.5 wt%) not only resulted in biocompatibility but also kept the mechanical flexibility of the self-sterilized layers for high proliferation of hMSCs.

Organic photovoltaic cells utilizing ultrathin sensitizing layer

Science.gov (United States)

Rand, Barry P [Princeton, NJ; Forrest, Stephen R [Princeton, NJ

2011-05-24

A photosensitive device includes a series of organic photoactive layers disposed between two electrodes. Each layer in the series is in direct contact with a next layer in the series. The series is arranged to form at least one donor-acceptor heterojunction, and includes a first organic photoactive layer comprising a first host material serving as a donor, a thin second organic photoactive layer comprising a second host material disposed between the first and a third organic photoactive layer, and the third organic photoactive layer comprising a third host material serving as an acceptor. The first, second, and third host materials are different. The thin second layer serves as an acceptor relative to the first layer or as a donor relative to the third layer.

Testing water pollution in a two layer aquifer

OpenAIRE

García León, Manuel; Lin Ye, Jue

2011-01-01

Water bodies around urban areas may be polluted with chemical elements from urban or industrial activities. We study the case of underground water pollution. This is a serious problem, since under- ground water is high qualified drinkable water in a world where this natural resource is increasingly reduced. This study is focused on a two-layer aquifer. If the superficial layer is contaminated, the deeper layer could be spoiled as well. This contribution checks the equality of the mean or c...

Optical measurements of absorption changes in two-layered diffusive media

International Nuclear Information System (INIS)

Fabbri, Francesco; Sassaroli, Angelo; Henry, Michael E; Fantini, Sergio

2004-01-01

We have used Monte Carlo simulations for a two-layered diffusive medium to investigate the effect of a superficial layer on the measurement of absorption variations from optical diffuse reflectance data processed by using: (a) a multidistance, frequency-domain method based on diffusion theory for a semi-infinite homogeneous medium; (b) a differential-pathlength-factor method based on a modified Lambert-Beer law for a homogeneous medium and (c) a two-distance, partial-pathlength method based on a modified Lambert-Beer law for a two-layered medium. Methods (a) and (b) lead to a single value for the absorption variation, whereas method (c) yields absorption variations for each layer. In the simulations, the optical coefficients of the medium were representative of those of biological tissue in the near-infrared. The thickness of the first layer was in the range 0.3-1.4 cm, and the source-detector distances were in the range 1-5 cm, which is typical of near-infrared diffuse reflectance measurements in tissue. The simulations have shown that (1) method (a) is mostly sensitive to absorption changes in the underlying layer, provided that the thickness of the superficial layer is ∼0.6 cm or less; (2) method (b) is significantly affected by absorption changes in the superficial layer and (3) method (c) yields the absorption changes for both layers with a relatively good accuracy of ∼4% for the superficial layer and ∼10% for the underlying layer (provided that the absorption changes are less than 20-30% of the baseline value). We have applied all three methods of data analysis to near-infrared data collected on the forehead of a human subject during electroconvulsive therapy. Our results suggest that the multidistance method (a) and the two-distance partial-pathlength method (c) may better decouple the contributions to the optical signals that originate in deeper tissue (brain) from those that originate in more superficial tissue layers

Lithium-Ion Cell Charge-Control Unit Developed

Science.gov (United States)

Reid, Concha M.; Manzo, Michelle A.; Buton, Robert M.; Gemeiner, Russel

2005-01-01

A lithium-ion (Li-ion) cell charge-control unit was developed as part of a Li-ion cell verification program. This unit manages the complex charging scheme that is required when Li-ion cells are charged in series. It enables researchers to test cells together as a pack, while allowing each cell to charge individually. This allows the inherent cell-to-cell variations to be addressed on a series string of cells and reduces test costs substantially in comparison to individual cell testing.

Two cases of seborrheic keratosis with basal clear cells.

Science.gov (United States)

Anan, Takashi; Fukumoto, Takaya; Kimura, Tetsunori

2017-03-01

Seborrheic keratosis with basal clear cells (SKBCC) is an extremely rare histopathological variant of seborrheic keratosis that has histological similarities to melanoma in situ. We herein report two cases of SKBCC and provide the first description of the dermoscopic features of this condition, in addition to the histopathological findings. Both of the two lesions showed typical histological architectures of seborrheic keratosis with rows or focal clusters of monomorphic clear cells with abundant pale cytoplasm and small round nucleus in the basal layer. Immunohistochemical examination revealed that most clear cells were positive for high molecular weight cytokeratin (34βE12) in a peripheral pattern but were negative tor Melan-A. Dermoscopy revealed typical features of ordinary seborrheic keratosis, while unfortunately did not reflect the presence of basal clear cells. © 2016 Japanese Dermatological Association.

Study of two-phase boundary layer phenomena in boiling water by means of photographic techniques

International Nuclear Information System (INIS)

Molen, S.B. van der

1976-01-01

The behaviour of bubbles in the boundary layer of a two-phase flow is important for the heat exchange between the heat production unit and the cooling medium. Theoretical knowledge of the forces on a bubble and the interaction between molecules of different kind are essential for understanding the phenomena. The photographic techniques are needed for the investigation of the bubble pattern which exists where we find Departure from Nucleate Boiling. (orig.) [de

Importance of unit cells in accurate evaluation of the characteristics of graphene

Energy Technology Data Exchange (ETDEWEB)

Sabzyan, Hassan; Sadeghpour, Narges [Isfahan Univ. (Iran, Islamic Republic of). Dept. of Chemistry

2016-08-01

Effects of the size of the unit cell on energy, atomic charges, and phonon frequencies of graphene at the Γ point of the Brillouin zone are studied in the absence and presence of an electric field using density functional theory (DFT) methods (LDA and DFT-PBE functionals with Goedecker-Teter-Hutter (GTH) and Troullier-Martins (TM) norm-conserving pseudopotentials). Two types of unit cells containing n{sub c}=4-28 carbon atoms are considered. Results show that stability of graphene increases with increasing size of the unit cell. Energy, atomic charges, and phonon frequencies all converge above n{sub c}=24 for all functional-pseudopotentials used. Except for the LDA-GTH calculations, application of an electric field of 0.4 and 0.9 V/nm strengths does not change the trends with the size of the unit cell but instead slightly decreases the binding energy of graphene. Results of this study show that the choice of unit cell size and type is critical for calculation of reliable characteristics of graphene.

Scattering-layer-induced energy storage function in polymer-based quasi-solid-state dye-sensitized solar cells.

Science.gov (United States)

Zhang, Xi; Jiang, Hongrui

2015-03-09

Photo-self-charging cells (PSCs) are compact devices with dual functions of photoelectric conversion and energy storage. By introducing a scattering layer in polymer-based quasi-solid-state dye-sensitized solar cells, two-electrode PSCs with highly compact structure were obtained. The charge storage function stems from the formed ion channel network in the scattering layer/polymer electrolyte system. Both the photoelectric conversion and the energy storage functions are integrated in only the photoelectrode of such PSCs. This design of PSC could continuously output power as a solar cell with considerable efficiency after being photo-charged. Such PSCs could be applied in highly-compact mini power devices.

Cellular interaction of a layer-by-layer based drug delivery system depending on material properties and cell types.

Science.gov (United States)

Brueckner, Mandy; Jankuhn, Steffen; Jülke, Eva-Maria; Reibetanz, Uta

2018-01-01

Drug delivery systems (DDS) and their interaction with cells are a controversial topic in the development of therapeutic concepts and approaches. On one hand, DDS are very useful for protected and targeted transport of defined dosages of active agents. On the other hand, their physicochemical properties such as material, size, shape, charge, or stiffness have a huge impact on cellular uptake and intracellular processing. Additionally, even identical DDS can undergo a completely diverse interaction with different cell types. However, quite often in in vitro DDS/cell interaction experiments, those aspects are not considered and DDS and cells are randomly chosen. Hence, our investigations provide an insight into layer-by-layer designed microcarriers with modifications of only some of the most important parameters (surface charge, stiffness, and applied microcarrier/cell ratio) and their influence on cellular uptake and viability. We also considered the interaction of these differently equipped DDS with several cell types and investigated professional phagocytes (neutrophil granulocytes; macrophages) as well as non-professional phagocytes (epithelial cells) under comparable conditions. We found that even small modifications such as layer-by-layer (LbL)-microcarriers with positive or negative surface charge, or LbL-microcarriers with solid core or as hollow capsules but equipped with the same surface properties, show significant differences in interaction and viability, and several cell types react very differently to the offered DDS. As a consequence, the properties of the DDS have to be carefully chosen with respect to the addressed cell type with the aim to efficiently transport a desired agent.

Assembly of 1D nanofibers into a 2D bi-layered composite nanofibrous film with different functionalities at the two layers via layer-by-layer electrospinning.

Science.gov (United States)

Wang, Zijiao; Ma, Qianli; Dong, Xiangting; Li, Dan; Xi, Xue; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

2016-12-21

A two-dimensional (2D) bi-layered composite nanofibrous film assembled by one-dimensional (1D) nanofibers with trifunctionality of electrical conduction, magnetism and photoluminescence has been successfully fabricated by layer-by-layer electrospinning. The composite film consists of a polyaniline (PANI)/Fe 3 O 4 nanoparticle (NP)/polyacrylonitrile (PAN) tuned electrical-magnetic bifunctional layer on one side and a Tb(TTA) 3 (TPPO) 2 /polyvinylpyrrolidone (PVP) photoluminescent layer on the other side, and the two layers are tightly combined face-to-face together into the novel bi-layered composite film of trifunctionality. The brand-new film has totally different characteristics at the double layers. The electrical conductivity and magnetism of the electrical-magnetic bifunctional layer can be, respectively, tunable via modulating the PANI and Fe 3 O 4 NP contents, and the highest electrical conductivity can reach up to the order of 10 -2 S cm -1 , and predominant intense green emission at 545 nm is obviously observed in the photoluminescent layer under the excitation of 357 nm single-wavelength ultraviolet light. More importantly, the luminescence intensity of the photoluminescent layer remains almost unaffected by the electrical-magnetic bifunctional layer because the photoluminescent materials have been successfully isolated from dark-colored PANI and Fe 3 O 4 NPs. By comparing with the counterpart single-layered composite nanofibrous film, it is found that the bi-layered composite nanofibrous film has better performance. The novel bi-layered composite nanofibrous film with trifunctionality has potential in the fields of nanodevices, molecular electronics and biomedicine. Furthermore, the design conception and fabrication technique for the bi-layered multifunctional film provide a new and facile strategy towards other films of multifunctionality.

Band splitting and relative spin alignment in two-layer systems

CERN Document Server

Ovchinnikov, A A

2002-01-01

It is shown that the single-particle spectra of the low Hubbard zone in the two-layer correlated 2D-systems sharply differ in the case of different relative alignment of the layers spin systems. The behavior of the two-layer splitting in the Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 sub + subdelta gives all reasons for the hypothesis on the possible rearrangement of the F sub z -> AF sub z alignment configuration, occurring simultaneously with the superconducting transition. The effects of the spin alignment on the magnetic excitations spectrum, as the way for studying the spin structure of the two-layer systems, are discussed by the example of homogenous solutions for the effective spin models

Mechanical behaviour of PEM fuel cell catalyst layers during regular cell operation

OpenAIRE

Maher A.R. Sadiq Al-Baghdadi

2010-01-01

Damage mechanisms in a proton exchange membrane fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling), and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the mechanical behaviour of the catalyst layers during regular cell operation, mechanical response under steady-state hygro-thermal stresses s...

TWO-LAYER PHASE COMPENSATING INTERFERENCE SYSTEMS

Directory of Open Access Journals (Sweden)

Georgiy V. Nikandrov

2014-09-01

Full Text Available The paper deals with creation of optical interferential coatings, giving the possibility to form the wave front without the change of energy characteristics of the incident and reflected radiation. Correction is achieved due to the layer, which thickness is a function of coordinate of an optical element surface. Selection technique is suggested for refractive index materials, forming two-layer interference coating that creates a coating with a constant coefficient of reflection on the surface of the optical element. By this procedure the change of coefficient of reflection for the optical element surface, arising because of the variable thickness is eliminated. Magnesium oxide and zirconium dioxide were used as the film-forming materials. The paper presents experimentally obtained thickness distribution of the layer, which is a part of the phase compensating coating. A new class of optical coatings proposed in the paper can find its application for correcting the form of a wave front.

Two Outer Membrane Proteins Contribute to Caulobacter crescentus Cellular Fitness by Preventing Intracellular S-Layer Protein Accumulation

Energy Technology Data Exchange (ETDEWEB)

Overton, K. Wesley; Park, Dan M.; Yung, Mimi C.; Dohnalkova, Alice; Smit, John; Jiao, Yongqin

2016-09-23

Surface layers, or S-layers, are two-dimensional protein arrays that form the outermost layer of many bacteria and archaea. They serve several functions, including physical protection of the cell from environmental threats. The high abundance of S-layer proteins necessitates a highly efficient export mechanism to transport the S-layer protein from the cytoplasm to the cell exterior.Caulobacter crescentusis unique in that it has two homologous, seemingly redundant outer membrane proteins, RsaF_aand RsaF_b, which together with other components form a type I protein translocation pathway for S-layer export. These proteins have homology toEscherichia coliTolC, the outer membrane channel of multidrug efflux pumps. Here we provide evidence that, unlike TolC, RsaF_aand RsaF_bare not involved in either the maintenance of membrane stability or the active export of antimicrobial compounds. Rather, RsaF_aand RsaF_bare required to prevent intracellular accumulation and aggregation of the S-layer protein RsaA; deletion of RsaF_aand RsaF_bled to a general growth defect and lowered cellular fitness. Using Western blotting, transmission electron microscopy, and transcriptome sequencing (RNA-seq), we show that loss of both RsaF_aand RsaF_bled to accumulation of insoluble RsaA in the cytoplasm, which in turn caused upregulation of a number of genes involved in protein misfolding and degradation pathways. These findings provide new insight into the requirement for RsaF_aand RsaF_bin cellular fitness and tolerance to antimicrobial agents and further our understanding of the S-layer export mechanism on both the transcriptional and translational levels in

UV radiation hardness of silicon inversion layer solar cells

International Nuclear Information System (INIS)

Hezel, R.

1990-01-01

For full utilization of the high spectral response of inversion layer solar cells in the very-short-wavelength range of the solar spectrum sufficient ultraviolet-radiation hardness is required. In addition to the charge-induced passivation achieved by cesium incorporation into the silicon nitride AR coating, in this paper the following means for further drastic reduction of UV light-induced effects in inversion layer solar cells without encapsulation are introduced and interpretations are given: increasing the nitride deposition temperature, silicon surface oxidation at low temperatures, and texture etching and using higher substrate resistivities. High UV radiation tolerance and improvement of the cell efficiency could be obtained simultaneously

Efficiency limit of solar cells with index-near-zero photon management layers

Energy Technology Data Exchange (ETDEWEB)

Kirk, A.P.

2017-05-15

As single-junction solar cells saturate in efficiency, the topic of photon management has generated interest in the long running quest to exceed the Shockley-Queisser efficiency limit. While a mirror applied to the backside of a solar cell has proven its benefit as a photon management layer in record setting devices that fall within the Shockley-Queisser limit, it has been proposed that a new type of photon management layer – a transparent index-near-zero (INZ) material – applied to the top surface of a solar cell will allow it to finally exceed the Shockley-Queisser limit. INZ layers – and their influence on solar cell current density, open circuit voltage, and power conversion efficiency – are analyzed. By considering the principle of detailed balance, Snell's law, and the role that entropy plays, it is shown that INZ layers do not allow a solar cell to exceed the Shockley-Queisser efficiency limit. At best, a solar cell with an INZ layer would have the same Shockley-Queisser limiting efficiency as a conventional solar cell tracked under a direct solar spectrum (direct beam radiation only), yet would suffer diminished efficiency under a global solar spectrum (direct beam plus diffuse light) due to the presence of an external critical acceptance angle.

Efficiency limit of solar cells with index-near-zero photon management layers

International Nuclear Information System (INIS)

Kirk, A.P.

2017-01-01

As single-junction solar cells saturate in efficiency, the topic of photon management has generated interest in the long running quest to exceed the Shockley-Queisser efficiency limit. While a mirror applied to the backside of a solar cell has proven its benefit as a photon management layer in record setting devices that fall within the Shockley-Queisser limit, it has been proposed that a new type of photon management layer – a transparent index-near-zero (INZ) material – applied to the top surface of a solar cell will allow it to finally exceed the Shockley-Queisser limit. INZ layers – and their influence on solar cell current density, open circuit voltage, and power conversion efficiency – are analyzed. By considering the principle of detailed balance, Snell's law, and the role that entropy plays, it is shown that INZ layers do not allow a solar cell to exceed the Shockley-Queisser efficiency limit. At best, a solar cell with an INZ layer would have the same Shockley-Queisser limiting efficiency as a conventional solar cell tracked under a direct solar spectrum (direct beam radiation only), yet would suffer diminished efficiency under a global solar spectrum (direct beam plus diffuse light) due to the presence of an external critical acceptance angle.

Efficiency limit of solar cells with index-near-zero photon management layers

Science.gov (United States)

Kirk, A. P.

2017-05-01

As single-junction solar cells saturate in efficiency, the topic of photon management has generated interest in the long running quest to exceed the Shockley-Queisser efficiency limit. While a mirror applied to the backside of a solar cell has proven its benefit as a photon management layer in record setting devices that fall within the Shockley-Queisser limit, it has been proposed that a new type of photon management layer - a transparent index-near-zero (INZ) material - applied to the top surface of a solar cell will allow it to finally exceed the Shockley-Queisser limit. INZ layers - and their influence on solar cell current density, open circuit voltage, and power conversion efficiency - are analyzed. By considering the principle of detailed balance, Snell's law, and the role that entropy plays, it is shown that INZ layers do not allow a solar cell to exceed the Shockley-Queisser efficiency limit. At best, a solar cell with an INZ layer would have the same Shockley-Queisser limiting efficiency as a conventional solar cell tracked under a direct solar spectrum (direct beam radiation only), yet would suffer diminished efficiency under a global solar spectrum (direct beam plus diffuse light) due to the presence of an external critical acceptance angle.

Atomic layer deposition for photovoltaics: applications and prospects for solar cell manufacturing

International Nuclear Information System (INIS)

Van Delft, J A; Garcia-Alonso, D; Kessels, W M M

2012-01-01

Atomic layer deposition (ALD) is a vapour-phase deposition technique capable of depositing high quality, uniform and conformal thin films at relatively low temperatures. These outstanding properties can be employed to face processing challenges for various types of next-generation solar cells; hence, ALD for photovoltaics (PV) has attracted great interest in academic and industrial research in recent years. In this review, the recent progress of ALD layers applied to various solar cell concepts and their future prospects are discussed. Crystalline silicon (c-Si), copper indium gallium selenide (CIGS) and dye-sensitized solar cells (DSSCs) benefit from the application of ALD surface passivation layers, buffer layers and barrier layers, respectively. ALD films are also excellent moisture permeation barriers that have been successfully used to encapsulate flexible CIGS and organic photovoltaic (OPV) cells. Furthermore, some emerging applications of the ALD method in solar cell research are reviewed. The potential of ALD for solar cells manufacturing is discussed, and the current status of high-throughput ALD equipment development is presented. ALD is on the verge of being introduced in the PV industry and it is expected that it will be part of the standard solar cell manufacturing equipment in the near future. (paper)

Fabrication of Inverted Bulk-Heterojunction Organic Solar Cell with Ultrathin Titanium Oxide Nanosheet as an Electron-Extracting Buffer Layer

Science.gov (United States)

Itoh, Eiji; Maruyama, Yasutake; Fukuda, Katsutoshi

2012-02-01

The contributions and deposition conditions of ultrathin titania nanosheet (TN) crystallites were studied in an inverted bulk-heterojunction (BHJ) cell in indium tin oxide (ITO)/titania nanosheet/poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methylester (PCBM) active layer/MoOx/Ag multilayered photovoltaic devices. Only one or two layers of poly(diallyldimethylammonium chloride) (PDDA) and TN multilayered film deposited by the layer-by-layer deposition technique effectively decreased the leakage current and increased both open circuit voltage (VOC) and fill factor (FF), and power conversion efficiency (η) was increased nearly twofold by the insertion of two TN layers. The deposition of additional TN layers caused the reduction in FF, and the abnormal S-shaped curves above VOC for the devices with three and four TN layers were ascribed to the interfacial potential barrier at the ITO/TN interface and the series resistance across the multilayers of TN and PDDA. The performance of the BHJ cell with TN was markedly improved, and the S-shaped curves were eliminated following the the insertion of anatase-phase titanium dioxide between the ITO and TN layers owing to the decrease in the interfacial potential barrier.

Effect of multi-layered bottom electrodes on the orientation of strontium-doped lead zirconate titanate thin films

Energy Technology Data Exchange (ETDEWEB)

Bhaskaran, M. [Microelectronics and Materials Technology Centre, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001 (Australia)], E-mail: madhu.bhaskaran@gmail.com; Sriram, S. [Microelectronics and Materials Technology Centre, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001 (Australia); Mitchell, D.R.G.; Short, K.T. [Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation (ANSTO), PMB 1, Menai, New South Wales 2234 (Australia); Holland, A.S. [Microelectronics and Materials Technology Centre, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001 (Australia)

2008-09-30

This article discusses the results from X-ray diffraction (XRD) analysis of piezoelectric strontium-doped lead zirconate titanate (PSZT) thin films deposited on multi-layer coatings on silicon. The films were deposited by RF magnetron sputtering on a metal coated substrate. The aim was to exploit the pronounced piezoelectric effect that is theoretically expected normal to the substrate. This work highlighted the influence that the bottom electrode architecture exerts on the final crystalline orientation of the deposited thin films. A number of bottom electrode architectures were used, with the uppermost metal layer on which PSZT was deposited being gold or platinum. The XRD analysis revealed that the unit cell of the PSZT thin films deposited on gold and on platinum were deformed, relative to expected unit cell dimensions. Experimental results have been used to estimate the unit cell parameters. The XRD results were then indexed based on these unit cell parameters. The choice and the thickness of the intermediate adhesion layers influenced the relative intensity, and in some cases, the presence of perovskite peaks. In some cases, undesirable reactions between the bottom electrode layers were observed, and layer architectures to overcome these reactions are also discussed.

Modified Back Contact Interface of CZTSe Thin Film Solar Cells: Elimination of Double Layer Distribution in Absorber Layer.

Science.gov (United States)

Zhang, Zhaojing; Yao, Liyong; Zhang, Yi; Ao, Jianping; Bi, Jinlian; Gao, Shoushuai; Gao, Qing; Jeng, Ming-Jer; Sun, Guozhong; Zhou, Zhiqiang; He, Qing; Sun, Yun

2018-02-01

Double layer distribution exists in Cu 2 SnZnSe 4 (CZTSe) thin films prepared by selenizing the metallic precursors, which will degrade the back contact of Mo substrate to absorber layer and thus suppressing the performance of solar cell. In this work, the double-layer distribution of CZTSe film is eliminated entirely and the formation of MoSe 2 interfacial layer is inhibited successfully. CZTSe film is prepared by selenizing the precursor deposited by electrodeposition method under Se and SnSe x mixed atmosphere. It is found that the insufficient reaction between ZnSe and Cu-Sn-Se phases in the bottom of the film is the reason why the double layer distribution of CZTSe film is formed. By increasing Sn content in the metallic precursor, thus making up the loss of Sn because of the decomposition of CZTSe and facilitate the diffusion of liquid Cu 2 Se, the double layer distribution is eliminated entirely. The crystallization of the formed thin film is dense and the grains go through the entire film without voids. And there is no obvious MoSe 2 layer formed between CZTSe and Mo. As a consequence, the series resistance of the solar cell reduces significantly to 0.14 Ω cm 2 and a CZTSe solar cell with efficiency of 7.2% is fabricated.

Mass transfer model for two-layer TBP oxidation reactions: Revision 1

International Nuclear Information System (INIS)

Laurinat, J.E.

1994-01-01

To prove that two-layer, TBP-nitric acid mixtures can be safely stored in the Canyon evaporators, it must be demonstrated that a runaway reaction between TBP and nitric acid will not occur. Previous bench-scale experiments showed that, at typical evaporator temperatures, this reaction is endothermic and therefore cannot run away, due to the loss of heat from evaporation of water in the organic layer. However, the reaction would be exothermic and could run away if the small amount of water in the organic layer evaporates before the nitric acid in this layer is consumed by the reaction. Provided that there is enough water in the aqueous layer, this would occur if the organic layer is sufficiently thick so that the rate of loss of water by evaporation exceeds the rate of replenishment due to mixing with the aqueous layer. Bubbles containing reaction products enhance the rate of transfer of water from the aqueous layer to the organic layer. These bubbles are generated by the oxidation of TBP and its reaction products in the organic layer and by the oxidation of butanol in the aqueous layer. Butanol is formed by the hydrolysis of TBP in the organic layer. For aqueous-layer bubbling to occur, butanol must transfer into the aqueous layer. Consequently, the rate of oxidation and bubble generation in the aqueous layer strongly depends on the rate of transfer of butanol from the organic to the aqueous layer. This report presents measurements of mass transfer rates for the mixing of water and butanol in two-layer, TBP-aqueous mixtures, where the top layer is primarily TBP and the bottom layer is comprised of water or aqueous salt solution. Mass transfer coefficients are derived for use in the modeling of two-layer TBP-nitric acid oxidation experiments

Recombination barrier layers in solid-state quantum dot-sensitized solar cells

KAUST Repository

Roelofs, Katherine E.

2012-06-01

By replacing the dye in the dye-sensitized solar cell design with semiconductor quantum dots as the light-absorbing material, solid-state quantum dot-sensitized solar cells (ss-QDSSCs) were fabricated. Cadmium sulfide quantum dots (QDs) were grown in situ by successive ion layer adsorption and reaction (SILAR). Aluminum oxide recombination barrier layers were deposited by atomic layer deposition (ALD) at the TiO2/hole-conductor interface. For low numbers of ALD cycles, the Al2O3 barrier layer increased open circuit voltage, causing an increase in device efficiency. For thicker Al2O3 barrier layers, photocurrent decreased substantially, leading to a decrease in device efficiency. © 2012 IEEE.

Two-dimensional condensation of physi-sorbed methane on layer-like halides

International Nuclear Information System (INIS)

Nardon, Yves

1972-01-01

Two-dimensional condensation of methane in physi-sorbed layers has been studied from sets of stepped isotherms of methane on the cleavage plane of layer-like halides (FeCl 2 , CdCl 2 , NiBr 2 , CdBr 2 , FeI 2 , CaI 2 , CaI 2 and PbI 2 ) in most cases prepared by sublimation in a rapid current of inert gas. The vertical parts of the steps of adsorption isotherms correspond to the formation of successive monomolecular layers by two-dimensional condensation. Thermodynamic analysis of experimental results, has mainly emphasized the important effect of the potential relief of adsorbent surfaces, on both the structure of the physi-sorbed layers and the two-dimensional critical temperature. From its entropy, we conclude that the first layer is a (111) plane of f.c.c.: methane which becomes more loosely packed as the dimensional compatibility of the lattices of the adsorbent and adsorbate becomes poorer. Experimental values of the two-dimensional critical temperatures in the first, second and third layers have been determined, and interpreted on the following basis. An expansion of the layer induces a lowering of the two-dimensional critical temperature by decreasing the lateral interaction energy, while a localisation of the adsorbed molecules in potential wells, when possible, induces a rise of the two-dimensional critical temperature. (author) [fr

1:250,000-scale Hydrologic Units of the United States

Science.gov (United States)

Steeves, Peter; Nebert, Douglas

1994-01-01

The Geographic Information Retrieval and Analysis System (GIRAS) was developed in the mid 70s to put into digital form a numberof data layers which were of interest to the USGS. One of these data layers was the Hydrologic Units. The map is based on the Hydrologic Unit Maps published by the U.S. Geological Survey Office of Water Data Coordination, together with the list descriptions and name of region, subregion, accounting units, and cataloging unit. The hydrologic units are encoded with an eight-digit number that indicates the hydrologic region (first two digits), hydrologic subregion (second two digits), accounting unit (third two digits), and cataloging unit (fourth two digits). The data produced by GIRAS was originally collected at a scale of 1:250K. Some areas, notably major cities in the west, were recompiled at a scale of 1:100K. In order to join the data together and use the data in a geographic information system (GIS) the data were processed in the ARC/INFO GUS software package. Within the GIS, the data were edgematched and the neatline boundaries between maps were removed to create a single data set for the conterminous

Biometrics encryption combining palmprint with two-layer error correction codes

Science.gov (United States)

Li, Hengjian; Qiu, Jian; Dong, Jiwen; Feng, Guang

2017-07-01

To bridge the gap between the fuzziness of biometrics and the exactitude of cryptography, based on combining palmprint with two-layer error correction codes, a novel biometrics encryption method is proposed. Firstly, the randomly generated original keys are encoded by convolutional and cyclic two-layer coding. The first layer uses a convolution code to correct burst errors. The second layer uses cyclic code to correct random errors. Then, the palmprint features are extracted from the palmprint images. Next, they are fused together by XORing operation. The information is stored in a smart card. Finally, the original keys extraction process is the information in the smart card XOR the user's palmprint features and then decoded with convolutional and cyclic two-layer code. The experimental results and security analysis show that it can recover the original keys completely. The proposed method is more secure than a single password factor, and has higher accuracy than a single biometric factor.

Superlattice doped layers for amorphous silicon photovoltaic cells

Science.gov (United States)

Arya, Rajeewa R.

1988-01-12

Superlattice doped layers for amorphous silicon photovoltaic cells comprise a plurality of first and second lattices of amorphous silicon alternatingly formed on one another. Each of the first lattices has a first optical bandgap and each of the second lattices has a second optical bandgap different from the first optical bandgap. A method of fabricating the superlattice doped layers also is disclosed.

Microstructures of tribologically modified surface layers in two-phase alloys

International Nuclear Information System (INIS)

Figueroa, C G; Ortega, I; Jacobo, V H; Ortiz, A; Bravo, A E; Schouwenaars, R

2014-01-01

When ductile alloys are subject to sliding wear, small increments of plastic strain accumulate into severe plastic deformation and mechanical alloying of the surface layer. The authors constructed a simple coaxial tribometer, which was used to study this phenomenon in wrought Al-Sn and cast Cu-Mg-Sn alloys. The first class of materials is ductile and consists of two immiscible phases. Tribological modification is observed in the form of a transition zone from virgin material to severely deformed grains. At the surface, mechanical mixing of both phases competes with diffusional unmixing. Vortex flow patterns are typically observed. The experimental Cu-Mg-Sn alloys are ductile for Mg-contents up to 2 wt% and consist of a- dendrites with a eutectic consisting of a brittle Cu 2 Mg-matrix with α-particles. In these, the observations are similar to the Al-Sn Alloys. Alloys with 5 wt% Mg are brittle due to the contiguity of the eutectic compound. Nonetheless, under sliding contact, this compound behaves in a ductile manner, showing mechanical mixing of a and Cu 2 Mg in the top layers and a remarkable transition from a eutectic to cellular microstructure just below, due to severe shear deformation. AFM-observations allow identifying the mechanically homogenized surface layers as a nanocrystalline material with a cell structure associated to the sliding direction

Observations of the atmospheric boundary layer height over Abu Dhabi, United Arab Emirates: Investigating boundary layer climatology in arid regions

Science.gov (United States)

Marzooqi, Mohamed Al; Basha, Ghouse; Ouarda, Taha B. M. J.; Armstrong, Peter; Molini, Annalisa

2014-05-01

Strong sensible heat fluxes and deep turbulent mixing - together with marked dustiness and a low substrate water content - represent a characteristic signature in the boundary layer over hot deserts, resulting in "thicker" mixing layers and peculiar optical properties. Beside these main features however, desert ABLs present extremely complex local structures that have been scarcely addressed in the literature, and whose understanding is essential in modeling processes such as the transport of dust and pollutants, and turbulent fluxes of momentum, heat and water vapor in hyper-arid regions. In this study, we analyze a continuous record of observations of the atmospheric boundary layer (ABL) height from a single lens LiDAR ceilometer operated at Masdar Institute Field Station (24.4oN, 54.6o E, Abu Dhabi, United Arab Emirates), starting March 2013. We compare different methods for the estimation of the ABL height from Ceilometer data such as, classic variance-, gradient-, log gradient- and second derivation-methods as well as recently developed techniques such as the Bayesian Method and Wavelet covariance transform. Our goal is to select the most suited technique for describing the climatology of the ABL in desert environments. Comparison of our results with radiosonde observations collected at the nearby airport of Abu Dhabi indicate that the WCT and the Bayesian method are the most suitable tools to accurately identify the ABL height in all weather conditions. These two methods are used for the definition of diurnal and seasonal climatologies of the boundary layer conditional to different atmospheric stability classes.

In situ monitoring of structure formation in the active layer of polymer solar cells during roll-to-roll coating

DEFF Research Database (Denmark)

Rossander, Lea Hildebrandt; Zawacka, Natalia Klaudia; Dam, Henrik Friis

2014-01-01

The active layer crystallization during roll-to-roll coating of organic solar cells is studied in situ. We developed an X-ray setup where the coater unit is an integrated part of the small angle X-ray scattering instrument, making it possible to control the coating process while recording...

Low temperature fabrication of perovskite solar cells with TiO{sub 2} nanoparticle layers

Energy Technology Data Exchange (ETDEWEB)

Kanayama, Masato; Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Suzuki, Atsushi [Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga 522-8533 (Japan); Yamada, Masahiro; Sakamoto, Hiroki [Energy Technology Laboratories, Osaka Gas Co., Ltd., Osaka 554-0051 (Japan); Minami, Satoshi; Kohno, Kazufumi [Frontier Materials Laboratories, Osaka Gas Chemicals Co., Ltd., Osaka 554-0051 (Japan)

2016-02-01

TiO{sub 2}/CH{sub 3}NH{sub 3}PbI{sub 3}-based photovoltaic devices were fabricated by a spin-coating method using a mixture solution. TiO{sub 2} require high-temperature processing to achieve suitably high carrier mobility. TiO{sub 2} electron transport layers and TiO{sub 2} scaffold layers for the perovskite were fabricated from TiO{sub 2} nanoparticles with different grain sizes. The photovoltaic properties and microstructures of solar cells were characterized. Nanoparticle sizes of these TiO{sub 2} were 23 nm and 3 nm and the performance of solar cells was improved by combination of two TiO{sub 2} nanoparticles.

Centrifugal Separation Device Based on Two-Layer Laminar Flow in Microchannels for High-Throughput and Continuous Blood Cell/Plasma Separation

Science.gov (United States)

Taizo Kobayashi,; Taisuke Funamoto,; Makoto Hosaka,; Satoshi Konishi,

2010-07-01

This paper presents a novel type of centrifugation device that is based on the two-layer laminar flow in micro flow channels for continuous blood cell/plasma separation. We propose to rotate the flow channels which are arranged along the circumference around the rotational axis. Downsizing the channel width reduced both the cell sedimentation time and the required centrifugal force, because the channel width corresponds to the centrifugal sedimentation length. First, plasma and cells were continuously extracted from pig blood in each of the branch channels using a milled acrylic prototype device (channel width = 800 μm, volume = 150 μl). Next, the relationship between the channel width (125, 250, and 500 μm) and the sedimentation time taken for various centrifugal forces (2.3, 9, 36, and 145 G) was evaluated using the downsized microchannels fabricated by hot-embossing and thermal bonding technologies. Using downsized microchannels with a width of 125 μm successfully reduced the sedimentation time to 85 s as compared to the sedimentation time of 270 s for a channel of a width of 500 μm, when a centrifugal force of 2.3 G was applied. The use of the proposed device did not result in obvious hemolysis at the centrifugal forces lower than 335 G.

Enhanced Performance of Nanowire-Based All-TiO2 Solar Cells using Subnanometer-Thick Atomic Layer Deposited ZnO Embedded Layer

International Nuclear Information System (INIS)

Ghobadi, Amir; Yavuz, Halil I.; Ulusoy, T. Gamze; Icli, K. Cagatay; Ozenbas, Macit; Okyay, Ali K.

2015-01-01

In this paper, the effect of angstrom-thick atomic layer deposited (ALD) ZnO embedded layer on photovoltaic (PV) performance of Nanowire-Based All-TiO 2 solar cells has been systematically investigated. Our results indicate that by varying the thickness of ZnO layer the efficiency of the solar cell can be significantly changed. It is shown that the efficiency has its maximum for optimal thickness of 1 ALD cycle in which this ultrathin ZnO layer improves device performance through passivation of surface traps without hampering injection efficiency of photogenerated electrons. The mechanisms contributing to this unprecedented change in PV performance of the cell have been scrutinized and discussed

S-layer fusion protein as a tool functionalizing emulsomes and CurcuEmulsomes for antibody binding and targeting.

Science.gov (United States)

Ucisik, Mehmet H; Küpcü, Seta; Breitwieser, Andreas; Gelbmann, Nicola; Schuster, Bernhard; Sleytr, Uwe B

2015-04-01

Selective targeting of tumor cells by nanoparticle-based drug delivery systems is highly desirable because it maximizes the drug concentration at the desired target while simultaneously protecting the surrounding healthy tissues. Here, we show a design for smart nanocarriers based on a biomimetic approach that utilizes the building principle of virus envelope structures. Emulsomes and CurcuEmulsomes comprising a tripalmitin solid core surrounded by phospholipid layers are modified by S-layer proteins that self-assemble into a two-dimensional array to form a surface layer. One significant advantage of this nanoformulation is that it increases the solubility of the lipophilic anti-cancer agent curcumin in the CurcuEmulsomes by a factor of 2700. In order to make the emulsomes specific for IgG, the S-layer protein is fused with two protein G domains. This S-layer fusion protein preserves its recrystallization characteristics, forming an ordered surface layer (square lattice with 13 nm unit-by-unit distance). The GG domains are presented in a predicted orientation and exhibit a selective binding affinity for IgG. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Influence of layer-by-layer assembled electrospun poly (L-lactic acid) nanofiber mats on the bioactivity of endothelial cells

Energy Technology Data Exchange (ETDEWEB)

Wu, Keke; Zhang, Xiazhi; Yang, Wufeng; Liu, Xiaoyan; Jiao, Yanpeng, E-mail: tjiaoyp@jnu.edu.cn; Zhou, Changren

2016-12-30

Highlights: • Layer-by-layer assembled PLLA nanofiber mats were successfully prepared. • The modified PLLA nanofiber mats enhanced the adhesion, proliferation of endothelial cells. • The modified PLLA nanofiber mats had inhibited the inflammatory response to some extent. - Abstract: Electrospun poly(L-lactic acid) (PLLA) nanofiber mats were successfully modified by deposition of multilayers with chitosan (CS), heparin (Hep) and graphene oxide (GO) through electrostatic layer-by-layer (LBL) self-assembly method. In this study, the surface properties of PLLA nanofiber mats before and after modification were investigated via scanning electron microscope (SEM), atomic force microscopy (AFM), attenuated total reflectance fourier transformation infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. In addition, the cytocompatibility of the modified PLLA nanofiber mats were investigated by testing endothelial cells compatibility, including cell attachment, cell proliferation and cell cycle. The results revealed that the surfaces of modified PLLA nanofiber mats become much rougher, stifiness and the hydrophilicity of the LBL modified PLLA nanofiber mats were improved compared to original PLLA one. Moreover, the modified PLLA nanofiber mats had promoted the endothelial cells viability attachment significantly. Besides, we studied the PLLA nanofiber mats on the expression of necrosis factor (TNF-α), interleukine-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells. The results showed that modified PLLA nanofiber mats had inhibited the inflammatory response to some extent.

Central-Upwind Schemes for Two-Layer Shallow Water Equations

KAUST Repository

Kurganov, Alexander

2009-01-01

We derive a second-order semidiscrete central-upwind scheme for one- and two-dimensional systems of two-layer shallow water equations. We prove that the presented scheme is well-balanced in the sense that stationary steady-state solutions are exactly preserved by the scheme and positivity preserving; that is, the depth of each fluid layer is guaranteed to be nonnegative. We also propose a new technique for the treatment of the nonconservative products describing the momentum exchange between the layers. The performance of the proposed method is illustrated on a number of numerical examples, in which we successfully capture (quasi) steady-state solutions and propagating interfaces. © 2009 Society for Industrial and Applied Mathematics.

Organic solar cells with graded absorber layers processed from nanoparticle dispersions.

Science.gov (United States)

Gärtner, Stefan; Reich, Stefan; Bruns, Michael; Czolk, Jens; Colsmann, Alexander

2016-03-28

The fabrication of organic solar cells with advanced multi-layer architectures from solution is often limited by the choice of solvents since most organic semiconductors dissolve in the same aromatic agents. In this work, we investigate multi-pass deposition of organic semiconductors from eco-friendly ethanol dispersion. Once applied, the nanoparticles are insoluble in the deposition agent, allowing for the application of further nanoparticulate layers and hence for building poly(3-hexylthiophene-2,5-diyl):indene-C60 bisadduct absorber layers with vertically graded polymer and conversely graded fullerene concentration. Upon thermal annealing, we observe some degrees of polymer/fullerene interdiffusion by means of X-ray photoelectron spectroscopy and Kelvin probe force microscopy. Replacing the common bulk-heterojunction by such a graded photo-active layer yields an enhanced fill factor of the solar cell due to an improved charge carrier extraction, and consequently an overall power conversion efficiency beyond 4%. Wet processing of such advanced device architectures paves the way for a versatile, eco-friendly and industrially feasible future fabrication of organic solar cells with advanced multi-layer architectures.

Charge-Control Unit for Testing Lithium-Ion Cells

Science.gov (United States)

Reid, Concha M.; Mazo, Michelle A.; Button, Robert M.

2008-01-01

A charge-control unit was developed as part of a program to validate Li-ion cells packaged together in batteries for aerospace use. The lithium-ion cell charge-control unit will be useful to anyone who performs testing of battery cells for aerospace and non-aerospace uses and to anyone who manufacturers battery test equipment. This technology reduces the quantity of costly power supplies and independent channels that are needed for test programs in which multiple cells are tested. Battery test equipment manufacturers can integrate the technology into their battery test equipment as a method to manage charging of multiple cells in series. The unit manages a complex scheme that is required for charging Li-ion cells electrically connected in series. The unit makes it possible to evaluate cells together as a pack using a single primary test channel, while also making it possible to charge each cell individually. Hence, inherent cell-to-cell variations in a series string of cells can be addressed, and yet the cost of testing is reduced substantially below the cost of testing each cell as a separate entity. The unit consists of electronic circuits and thermal-management devices housed in a common package. It also includes isolated annunciators to signal when the cells are being actively bypassed. These annunciators can be used by external charge managers or can be connected in series to signal that all cells have reached maximum charge. The charge-control circuitry for each cell amounts to regulator circuitry and is powered by that cell, eliminating the need for an external power source or controller. A 110-VAC source of electricity is required to power the thermal-management portion of the unit. A small direct-current source can be used to supply power for an annunciator signal, if desired.

Steady ablation on the surface of a two-layer composite

Energy Technology Data Exchange (ETDEWEB)

Lin, Wen-Shan [Chung Shan Institute of Science and Technology, P.O. Box 90008-15-3, Lung-Tan, Tao-Yuan, 32526 Taiwan (China)

2005-12-01

Discovered is a quasi-steady ablation phenomenon on the surface of a two-layer composite which is formed by a layer of ablative material and another layer of non-ablative substrate. Theoretical exact solutions of quasi-steady ablation rate, the associated temperature distribution and end-of-ablation time of this two-layer composite are derived. A criterion for the occurrence of quasi-steady ablation is presented also. A one-dimensional transient numerical model is developed to perform a number of numerical experiments and hence to verify the correctness of the above theoretical solutions for the current quasi-steady ablation phenomenon. Based on the current results, a new method of measuring the ablation (or sublimation) heat is also proposed. (author)

Conductive polymer layers to limit transfer of fuel reactants to catalysts of fuel cells to reduce reactant crossover

Science.gov (United States)

Stanis, Ronald J.; Lambert, Timothy N.

2016-12-06

An apparatus of an aspect includes a fuel cell catalyst layer. The fuel cell catalyst layer is operable to catalyze a reaction involving a fuel reactant. A fuel cell gas diffusion layer is coupled with the fuel cell catalyst layer. The fuel cell gas diffusion layer includes a porous electrically conductive material. The porous electrically conductive material is operable to allow the fuel reactant to transfer through the fuel cell gas diffusion layer to reach the fuel cell catalyst layer. The porous electrically conductive material is also operable to conduct electrons associated with the reaction through the fuel cell gas diffusion layer. An electrically conductive polymer material is coupled with the fuel cell gas diffusion layer. The electrically conductive polymer material is operable to limit transfer of the fuel reactant to the fuel cell catalyst layer.

Plasma-assisted atomic layer deposition of TiO2 compact layers for flexible mesostructured perovskite solar cells

NARCIS (Netherlands)

Zardetto, V.; Di Giacomo, F.; Lucarelli, G.; Kessels, W.M.M.; Brown, T.M.; Creatore, M.

2017-01-01

In mesostructured perovskite solar cell devices, charge recombination processes at the interface between the transparent conductive oxide, perovskite and hole transport layer are suppressed by depositing an efficient compact TiO2 blocking layer. In this contribution we investigate the role of the

Experimental and numerical studies on pressure drop in reverse electrodialysis: Effect of unit cell configuration

Energy Technology Data Exchange (ETDEWEB)

Hong, Sung Kook; Choi, Kyung Soo [Advanced Combustion Laboratory, Korea Institute of Energy Research, Daejeon (Korea, Republic of); Kim, Chan Soo; Hwang, Kyo Sik; Han, Ji Hyung; Kim, Han Ki; Jeong, Nam Jo [Jeju Global Research Center, Korea Institute of Energy Research, Jeju (Korea, Republic of)

2016-11-15

Experimental and numerical studies on pressure drop in Reverse electrodialysis (RED) were performed. In this study, a module with 200 unit cells is considered for the demonstration of bench-scale RED module and two different unit cell configurations are utilized. Pressure drop through the module is measured by varying flow rates. For evaluating the hydrodynamic characteristics in the unit cell, a numerical simulation is also conducted and the simplified method using a porous media model is employed to simulate the channel filled with spacer. Due to the insertion of spacer and narrow channel, great pressure loss occurs along the unit cell. Based on estimated pressure data, high pressure difference between seawater and fresh water channel takes place locally in the unit cell configuration with crossflow direction, leading to a leakage problem through the membrane and finally degradation in the output power. Consequently, it is confirmed that the unit cell configuration is one of the important design parameters in a RED module.

Pluripotency Factors in Embryonic Stem Cells Regulate Differentiation into Germ Layers

OpenAIRE

Thomson, Matt; Liu, Siyuan John; Zou, Ling-Nan; Smith, Zack; Meissner, Alexander; Ramanathan, Sharad

2011-01-01

Cell fate decisions are fundamental for development, but we do not know how transcriptional networks reorganize during the transition from a pluripotent to a differentiated cell state. Here, we asked how mouse embryonic stem cells (ESCs) leave the pluripotent state and choose between germ layer fates. By analyzing the dynamics of the transcriptional circuit that maintains pluripotency, we found that Oct4 and Sox2, proteins that maintain ESC identity, also orchestrate germ layer fate selection...

Non-destructive lateral mapping of the thickness of the photoactive layer in polymer-based solar cells

DEFF Research Database (Denmark)

Sylvester-Hvid, Kristian O.; Tromholt, Thomas; Jørgensen, Mikkel

2013-01-01

Non-destructive lateral mapping of the thickness of the photoactive layer in poly(3-hexyl-thiophene) : 1-(3-methoxy-carbonyl)propyl-1-phenyl-(6,6)C61 (P3HT : PCBM) solar cells is demonstrated. The method employs a spatially resolved (XY) recording of ultraviolet-visible spectra in reflection...... geometry at normal incidence, using a dense raster defined by a circular probe spot of 800-µm diameter. The evaluation of the thickness of the photoactive layer at each raster point employs an algorithm-driven comparison of the measured absorption spectrum with spectral features, as compiled from......-coated float glass substrates. After this, two application examples for solar cells processed either by spin coating or slot die coating of the P3HT : PCBM layer follow. The spin-coated solar cells have glass as the substrate with the P3HT : PCBM spun at different spinning speeds. The slot die-coated solar...

Thermal diffusivity measurements of molten salts using a three-layered cell by the laser flash method

Science.gov (United States)

Ohta, Hiromichi; Ogura, Gaku; Waseda, Yoshio; Suzuki, Mustumi

1990-10-01

A simple cell and easy data processing are described for measuring the thermal diffusivity of a liquid sample at high temperatures using the laser flash method. A cell consists of a liquid sample sandwiched by two metallic plates. The front surface of one metallic plate is exposed to a single pulse of beam laser and the resulting temperature rise of the back surface of the other metallic plate is measured. The logarithmic analysis proposed by James using the initial time region of the temperature response curve of a two layered cell system has been extended to apply to the present three layered cell system in order to estimate the thermal diffusivity value of a liquid sample. Measurements of distilled water and methanol were made first and the results were found to be in good agreement with the reference data. Then, the thermal diffusivities of molten NaNO3 at 593-660 K and of molten KNO3 at 621-694 K were determined and the results also appear to agree reasonably well with those reported in the literature.

Enhanced Charge Collection with Passivation Layers in Perovskite Solar Cells.

Science.gov (United States)

Lee, Yong Hui; Luo, Jingshan; Son, Min-Kyu; Gao, Peng; Cho, Kyung Taek; Seo, Jiyoun; Zakeeruddin, Shaik M; Grätzel, Michael; Nazeeruddin, Mohammad Khaja

2016-05-01

The Al2 O3 passivation layer is beneficial for mesoporous TiO2 -based perovskite solar cells when it is deposited selectively on the compact TiO2 surface. Such a passivation layer suppressing surface recombination can be formed by thermal decomposition of the perovskite layer during post-annealing. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Clustering Approaches for Pragmatic Two-Layer IoT Architecture

Directory of Open Access Journals (Sweden)

J. Sathish Kumar

2018-01-01

Full Text Available Connecting all devices through Internet is now practical due to Internet of Things. IoT assures numerous applications in everyday life of common people, government bodies, business, and society as a whole. Collaboration among the devices in IoT to bring various applications in the real world is a challenging task. In this context, we introduce an application-based two-layer architectural framework for IoT which consists of sensing layer and IoT layer. For any real-time application, sensing devices play an important role. Both these layers are required for accomplishing IoT-based applications. The success of any IoT-based application relies on efficient communication and utilization of the devices and data acquired by the devices at both layers. The grouping of these devices helps to achieve the same, which leads to formation of cluster of devices at various levels. The clustering helps not only in collaboration but also in prolonging overall network lifetime. In this paper, we propose two clustering algorithms based on heuristic and graph, respectively. The proposed clustering approaches are evaluated on IoT platform using standard parameters and compared with different approaches reported in literature.

Two dimensional layered materials: First-principle investigation

Science.gov (United States)

Tang, Youjian

Two-dimensional layered materials have emerged as a fascinating research area due to their unique physical and chemical properties, which differ from those of their bulk counterparts. Some of these unique properties are due to carriers and transport being confined to 2 dimensions, some are due to lattice symmetry, and some arise from their large surface area, gateability, stackability, high mobility, spin transport, or optical accessibility. How to modify the electronic and magnetic properties of two-dimensional layered materials for desirable long-term applications or fundamental physics is the main focus of this thesis. We explored the methods of adsorption, intercalation, and doping as ways to modify two-dimensional layered materials, using density functional theory as the main computational methodology. Chapter 1 gives a brief review of density functional theory. Due to the difficulty of solving the many-particle Schrodinger equation, density functional theory was developed to find the ground-state properties of many-electron systems through an examination of their charge density, rather than their wavefunction. This method has great application throughout the chemical and material sciences, such as modeling nano-scale systems, analyzing electronic, mechanical, thermal, optical and magnetic properties, and predicting reaction mechanisms. Graphene and transition metal dichalcogenides are arguably the two most important two-dimensional layered materials in terms of the scope and interest of their physical properties. Thus they are the main focus of this thesis. In chapter 2, the structure and electronic properties of graphene and transition metal dichalcogenides are described. Alkali adsorption onto the surface of bulk graphite and metal intecalation into transition metal dichalcogenides -- two methods of modifying properties through the introduction of metallic atoms into layered systems -- are described in chapter 2. Chapter 3 presents a new method of tuning

Full coverage of perovskite layer onto ZnO nanorods via a modified sequential two-step deposition method for efficiency enhancement in perovskite solar cells

Science.gov (United States)

Ruankham, Pipat; Wongratanaphisan, Duangmanee; Gardchareon, Atcharawon; Phadungdhitidhada, Surachet; Choopun, Supab; Sagawa, Takashi

2017-07-01

Full coverage of perovskite layer onto ZnO nanorod substrates with less pinholes is crucial for achieving high-efficiency perovskite solar cells. In this work, a two-step sequential deposition method is modified to achieve an appropriate property of perovskite (MAPbI3) film. Surface treatment of perovskite layer and its precursor have been systematically performed and their morphologies have been investigated. By pre-wetting of lead iodide (PbI2) and letting it dry before reacting with methylammonium iodide (MAI) provide better coverage of perovskite film onto ZnO nanorod substrate than one without any treatment. An additional MAI deposition followed with toluene drop-casting technique on the perovskite film is also found to increase the coverage and enhance the transformation of PbI2 to MAPbI3. These lead to longer charge carrier lifetime, resulting in an enhanced power conversion efficiency (PCE) from 1.21% to 3.05%. The modified method could been applied to a complex ZnO nanorods/TiO2 nanoparticles substrate. The enhancement in PCE to 3.41% is observed. These imply that our introduced method provides a simple way to obtain the full coverage and better transformation to MAPbI3 phase for enhancement in performances of perovskite solar cells.

Estimation of apparent soil resistivity for two-layer soil structure

Energy Technology Data Exchange (ETDEWEB)

Nassereddine, M.; Rizk, J.; Nagrial, M.; Hellany, A. [School of Computing, Engineering and Mathematics, University of Western Sydney (Australia)

2013-07-01

High voltage (HV) earthing design is one of the key elements when it comes to safety compliance of a system. High voltage infrastructure exposes workers and people to unsafe conditions. The soil structure plays a vital role in determining the allowable and actual step/touch voltage. This paper presents vital information when working with two-layer soil structure. It shows the process as to when it is acceptable to use a single layer instead of a two-layer structure. It also discusses the simplification of the soil structure approach depending on the reflection coefficient. It introduces the reflection coefficient K interval which determines if single layer approach is acceptable. Multiple case studies are presented to address the new approach and its accuracy.

Cyclotron resonance study of the two-dimensional electron layers and double layers in tilted magnetic fields

Czech Academy of Sciences Publication Activity Database

Goncharuk, Natalya; Smrčka, Ludvík; Kučera, Jan

2004-01-01

Roč. 22, - (2004), s. 590-593 ISSN 1386-9477. [International Conference on Electronic Properties of Two-Dimensional Systems /15./. Nara, 14.07.2003-18.07.2003] R&D Projects: GA ČR GA202/01/0754 Institutional research plan: CEZ:AV0Z1010914 Keywords : single layer * double layer * two-dimensional electron system * cyclotron resonance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.898, year: 2004

Improved Reliability of Small Molecule Organic Solar Cells by Double Anode Buffer Layers

Directory of Open Access Journals (Sweden)

Pao-Hsun Huang

2014-01-01

Full Text Available An optimized hybrid planar heterojunction (PHJ of small molecule organic solar cells (SM-OSCs based on copper phthalocyanine (CuPc as donor and fullerene (C60 as acceptor was fabricated, which obviously enhanced the performance of device by sequentially using both MoO3 and pentacene as double anode buffer layers (ABL, also known as hole extraction layer (HEL. A series of the vacuum-deposited ABL, acting as an electron and exciton blocking layer, were examined for their characteristics in SM-OSCs. The performance and reliability were compared between conventional ITO/ABL/CuPc/C60/BCP/Ag cells and the new ITO/double ABL/CuPc/C60/BCP/Ag cells. The effect on the electrical properties of these materials was also investigated to obtain the optimal thickness of ABL. The comparison shows that the modified cell has an enhanced reliability compared to traditional cells. The improvement of lifetime was attributed to the idea of double layers to prevent humidity and oxygen from diffusing into the active layer. We demonstrated that the interfacial extraction layers are necessary to avoid degradation of device. That is to say, in normal temperature and pressure, a new avenue for the device within double buffer layers has exhibited the highest values of open circuit voltage (Voc, fill factor (FF, and lifetime in this work compared to monolayer of ABL.

High throughput two-step ultrasonic spray deposited CH3NH3PbI3 thin film layer for solar cell application

Science.gov (United States)

Lan, Ding-Hung; Hong, Shao-Huan; Chou, Li-Hui; Wang, Xiao-Feng; Liu, Cheng-Liang

2018-06-01

Organometal halide perovskite materials have demonstrated tremendous advances in the photovoltaic field recently because of their advantageous features of simple fabrication and high power conversion efficiency. To meet the high demand for high throughput and cost-effective, we present a wet process method that enables the probing of the parameters for perovskite layer deposition through two-step sequential ultrasonic spray-coating. This paper describes a detailed investigation on the effects of modification of spray precursor solution (PbI2 and CH3NH3I precursor concentration and solvents used) and post-annealing condition (temperature and time), which can be performed to create optimal film quality as well as improve device efficiency. Through the systematic optimization, the inverted planar perovskite solar cells show the reproducible photovoltaic properties with best power conversion efficiency (PCE) of 10.40% and average PCE of 9.70 ± 0.40%. A continuous spray-coating technique for rapid fabrication of total 16 pieces of perovskite films was demonstrated for providing a viable alternative for the high throughput production of the perovskite solar cells.

Fe gettering by p+ layer in bifacial Si solar cell fabrication

International Nuclear Information System (INIS)

Terakawa, T.; Wang, D.; Nakashima, H.

2006-01-01

Gettering behaviors of Fe into solar cell grade Si are investigated by deep level transient spectroscopy. The samples contaminated with Fe in the range of the concentration of 1.5x10 12 -2.0x10 14 cm -3 were annealed at 600 deg. C to induce gettering. It is shown that the surface layer gettering behaviors of Fe for the sample without p + layer strongly depend on the Fe contamination level, in which the surface layer gettering is not effective for the sample with low level contamination 13 cm -3 but effective for the sample with middle level contamination of 1-5x10 13 cm -3 . In contrast, the samples with p + layer show effective gettering for low and middle level contaminations. The gettering mechanisms in solar cell grade Si without and with p + layer are discussed in details

Simulation on the Performance of Dye Solar Cell Incorporated with TiO2 Passivation Layer

Directory of Open Access Journals (Sweden)

Unan Yusmaniar Oktiawati

2016-01-01

Full Text Available Dye Solar Cell (DSC has started to gain interest in the recent years for practical application because of its ecofriendly, low cost, and easy fabrication. However, its efficiency is still not as competitive as the conventional silicon based solar cell. One of the research efforts to improve the efficiency of DSC is to use the passivation layer in between the photoelectrode material and the conductive oxide substrate. Thus, the objective of this simulation study is to investigate the effect of passivation layer on the performance of DSC. Properties from literatures which are based on physical work were captured as the input for the simulation using process, ATHENA, and device, ATLAS, simulator. Results have shown that the addition of two-20 nm TiO2 passivation layers on DSC can enhance the efficiency by 11% as the result of less recombination, higher electron mobility, and longer electron lifetime.

Forced Vibrations of a Two-Layer Orthotropic Shell with an Incomplete Contact Between Layers

Science.gov (United States)

Ghulghazaryan, L. G.; Khachatryan, L. V.

2018-01-01

Forced vibrations of a two-layer orthotropic shell, with incomplete contact conditions between layers, when the upper face of the shell is free and the lower one is subjected to a dynamic action are considered. By an asymptotic method, the solution of the corresponding dynamic equations and correlations of a 3D problem of elasticity theory is obtained. The amplitudes of forced vibrations are determined, and resonance conditions are established.

Four-parametric two-layer algebraic model of transition boundary layer at a planar plate

International Nuclear Information System (INIS)

Labusov, A.N.; Lapin, Yu.V.

1996-01-01

Consideration is given to four-parametric two-layer algebraic model of transition boundary layer on a plane plate, based on generalization of one-parametric algebraic Prandtl-Loitsjansky-Klauzer-3 model. The algebraic model uses Prandtl formulas for mixing path with Loitsjansky damping multiplier in the internal region and the relation for turbulent viscosity, based on universal scales of external region and named the Klauzer-3 formula. 12 refs., 10 figs

Fabrication of contacts for silicon solar cells including printing burn through layers

Science.gov (United States)

Ginley, David S; Kaydanova, Tatiana; Miedaner, Alexander; Curtis, Calvin J; Van Hest, Marinus Franciscus Antonius Maria

2014-06-24

A method for fabricating a contact (240) for a solar cell (200). The method includes providing a solar cell substrate (210) with a surface that is covered or includes an antireflective coating (220). For example, the substrate (210) may be positioned adjacent or proximate to an outlet of an inkjet printer (712) or other deposition device. The method continues with forming a burn through layer (230) on the coating (220) by depositing a metal oxide precursor (e.g., using an inkjet or other non-contact printing method to print or apply a volume of liquid or solution containing the precursor). The method includes forming a contact layer (240) comprising silver over or on the burn through layer (230), and then annealing is performed to electrically connect the contact layer (240) to the surface of the solar cell substrate (210) through a portion of the burn through layer (230) and the coating (220).

Modeling Low-Platinum-Loading Effects in Fuel-Cell Catalyst Layers

Energy Technology Data Exchange (ETDEWEB)

Yoon, Wonseok; Weber, Adam Z.

2011-01-01

The cathode catalyst layer within a proton-exchange-membrane fuel cell is the most complex and critical, yet least understood, layer within the cell. The exact method and equations for modeling this layer are still being revised and will be discussed in this paper, including a 0.8 reaction order, existence of Pt oxides, possible non-isopotential agglomerates, and the impact of a film resistance towards oxygen transport. While the former assumptions are relatively straightforward to understand and implement, the latter film resistance is shown to be critically important in explaining increased mass-transport limitations with low Pt-loading catalyst layers. Model results demonstrate agreement with experimental data that the increased oxygen flux and/or diffusion pathway through the film can substantially decrease performance. Also, some scale-up concepts from the agglomerate scale to the more macroscopic porous-electrode scale are discussed and the resulting optimization scenarios investigated.

Quasi-three dimensional dynamic modeling of a proton exchange membrane fuel cell with consideration of two-phase water transport through a gas diffusion layer

International Nuclear Information System (INIS)

Kang, Sanggyu

2015-01-01

Water management is one of the challenging issues for low-temperature PEMFCs (proton exchange membrane fuel cells). When liquid water is formed at the GDL (gas diffusion layer), the pathway of reactant gas can be blocked, which inhibits the electrochemical reaction of PEMFC. Thus, liquid water transport through GDL is a critical factor determining the performance of a PEMFC. In present study, quasi-three dimensional dynamic modeling of PEMFC with consideration of two-phase water transport through GDL is developed. To investigate the distributions of PEMFC characteristics, including current density, species mole fraction, and membrane hydration, the PEMFC was discretized into twenty control volumes along the anode channel. To resolve the mass and energy conservation, the PEMFC is discretized into eleven and fifteen control volumes in the perpendicular direction, respectively. The dynamic variation of PEMFC characteristics of cell voltage, overvoltage of activation and ohmic, liquid water saturation through a GDL, and oxygen concentration were captured during transient behavior. - Highlights: • A quasi-three dimensional two-phase dynamic model of PEMFC is developed. • Presented model is validated by comparison with experimental data. • Two-phase model is compared with one-phase model at steady-states and transients.

Data layer integration for the national map of the united states

Science.gov (United States)

Usery, E.L.; Finn, M.P.; Starbuck, M.

2009-01-01

The integration of geographic data layers in multiple raster and vector formats, from many different organizations and at a variety of resolutions and scales, is a significant problem for The National Map of the United States being developed by the U.S. Geological Survey. Our research has examined data integration from a layer-based approach for five of The National Map data layers: digital orthoimages, elevation, land cover, hydrography, and transportation. An empirical approach has included visual assessment by a set of respondents with statistical analysis to establish the meaning of various types of integration. A separate theoretical approach with established hypotheses tested against actual data sets has resulted in an automated procedure for integration of specific layers and is being tested. The empirical analysis has established resolution bounds on meanings of integration with raster datasets and distance bounds for vector data. The theoretical approach has used a combination of theories on cartographic transformation and generalization, such as T??pfer's radical law, and additional research concerning optimum viewing scales for digital images to establish a set of guiding principles for integrating data of different resolutions.

Tandem colloidal quantum dot solar cells employing a graded recombination layer

KAUST Repository

Wang, Xihua; Koleilat, Ghada I.; Tang, Jiang; Liu, Huan; Kramer, Illan J.; Debnath, Ratan; Brzozowski, Lukasz; Barkhouse, D. Aaron R.; Levina, Larissa; Hoogland, Sjoerd; Sargent, Edward H.

2011-01-01

Tuning of the electronic bandgap in colloidal quantum dots (CQDs) by changing their size enables the spectral response of CQD-based photodetectors and photovoltaic devices to be tailored. Multi-junction solar cells made from a combination of CQDs of differing sizes and thus bandgaps are a promising means by which to increase the energy harvested from the Sun's broad spectrum. Here, we report the first CQD tandem solar cells using the size-effect tuning of a single CQD material, PbS. We use a graded recombination layer to provide a progression of work functions from the hole-accepting electrode in the bottom cell to the electron-accepting electrode in the top cell, allowing matched electron and hole currents to meet and recombine. Our tandem solar cell has an open-circuit voltage of 1.06Â V, equal to the sum of the two constituent single-junction devices, and a solar power conversion efficiency of up to 4.2%. © 2011 Macmillan Publishers Limited. All rights reserved.

Tandem colloidal quantum dot solar cells employing a graded recombination layer

KAUST Repository

Wang, Xihua

2011-06-26

Tuning of the electronic bandgap in colloidal quantum dots (CQDs) by changing their size enables the spectral response of CQD-based photodetectors and photovoltaic devices to be tailored. Multi-junction solar cells made from a combination of CQDs of differing sizes and thus bandgaps are a promising means by which to increase the energy harvested from the Sun\\'s broad spectrum. Here, we report the first CQD tandem solar cells using the size-effect tuning of a single CQD material, PbS. We use a graded recombination layer to provide a progression of work functions from the hole-accepting electrode in the bottom cell to the electron-accepting electrode in the top cell, allowing matched electron and hole currents to meet and recombine. Our tandem solar cell has an open-circuit voltage of 1.06Â V, equal to the sum of the two constituent single-junction devices, and a solar power conversion efficiency of up to 4.2%. © 2011 Macmillan Publishers Limited. All rights reserved.

Irradiated murine fibroblasts as feeder layer used in human cell culture

International Nuclear Information System (INIS)

Almeida, Tiago L.; Klingbeil, Fatima G.; Yoshito, Daniele; Caproni, Priscila; Mathor, Monica B.; Herson, Marisa R.

2007-01-01

In 1975, Rheinwald and Green published an in vitro model for keratinocyte cell cultures in which the use of murine fibroblasts, as a feeder layer was introduced. These cells are modified fibroblasts, which presence render keratinocyte cells to remain proliferative for longer periods of time. This optimization of culture outputs has allowed for several clinical applications of confluent keratinocyte cultures as skin substitutes or wound dressings in situations such as post burn extensive skin loss, loss of oral mucosa, and other skin disorders. Nevertheless, proliferation of fibroblast in co-culture with keratinocytes must be controlled by anti-proliferative measures such as irradiation; at the same time, keratinocytes require specific nutrients in the culture medium, which may interfere with the fibroblast feeder layer viability. Therefore, the thorough understanding of the impact of different issues such as culture media composition, irradiation dose and pre-plating storage conditions of irradiated fibroblast to be used as feeder layer in these co-culture systems is important. In this work, changes as far as viability and proliferative rates of irradiated fibroblasts in culture were evaluated in relation to the type of culture medium used, dose of gamma radiation exposure, storage and timing of cell plating post irradiation. Results indicate that the type of culture medium used and time-lag between irradiation, refrigeration and plating of irradiated cells do not have significant impact in culture outcomes. However, the dose of gamma radiation administered to the cells may influence the final quality of these cells if to be used as a feeder layer. (author)

The Application of Load-cell Technique in the Study of Armour Unit Responses to Impact Loads Tests

DEFF Research Database (Denmark)

Burcharth, H. F.; Liu, Z.

1995-01-01

The slender, complex types of armour units, such as Tetrapods and Dolosse are widely used for rubble mound breakwaters. Many of the recent failures of such structures were caused by unforeseen early breakage of the units, thus revealing an in balance between the strength (structural integrity......) of the units and the hydraulic stability (resistance to displacements) of the armour layers. Breakage is caused by stresses from static, pulsating and impact loads. Impact load generated stresses are difficult to investigate due to non-linear scaling laws. The paper describes a method by which impact loads on....... slender armour units can be studied. by load-cell technique. Moreover, the paper presents DoJos design diagrams for the prediction of both breakage and hydraulic stability...

A buffer-layer/a-SiO{sub x}:H(p) window-layer optimization for thin film amorphous silicon based solar cells

Energy Technology Data Exchange (ETDEWEB)

Park, Jinjoo; Dao, Vinh Ai [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Shin, Chonghoon [Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Hyeongsik [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Minbum; Jung, Junhee [Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Doyoung [School of Electricity and Electronics, Ulsan College West Campus, Ulsan 680-749 (Korea, Republic of); Yi, Junsin, E-mail: yi@yurim.skku.ac.kr [College of Information and Communication Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Department of Energy Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

2013-11-01

Amorphous silicon based (a-Si:H-based) solar cells with a buffer-layer/boron doped hydrogenated amorphous silicon oxide (a-SiO{sub x}:H(p)) window-layer were fabricated and investigated. In the first part, in order to reduce the Schottky barrier height at the fluorine doped tin oxide (FTO)/a-SiO{sub x}:H(p) window-layer heterointerface, we have used buffer-layer/a-SiO{sub x}:H(p) for the window-layer, in which boron doped hydrogenated amorphous silicon (a-Si:H(p)) or boron doped microcrystalline silicon (μc-Si:H(p)) is introduced as a buffer layer between the a-SiO{sub x}:H(p) and FTO of the a-Si:H-based solar cells. The a-Si:H-based solar cell using a μc-Si:H(p) buffer-layer shows the highest efficiency compared to the optimized bufferless, and a-Si:H(p) buffer-layer in the a-Si:H-based solar cells. This highest performance was attributed not only to the lower absorption of the μc-Si:H(p) buffer-layer but also to the lower Schottky barrier height at the FTO/window-layer interface. Then, we present the dependence of the built-in potential (V{sub bi}) and blue response of the devices on the inversion of activation energy (ξ) of the a-SiO{sub x}:H(p), in the μc-Si:H(p)/a-SiO{sub x}:H(p) window-layer. The enhancement of both V{sub bi} and blue response is observed, by increasing the value of ξ. The improvement of V{sub bi} and blue response can be ascribed to the enlargement of the optical gap of a-SiO{sub x}:H(p) films in the μc-Si:H(p)/a-SiO{sub x}:H(p) window-layer. Finally, the conversion efficiency was increased by 22.0%, by employing μc-Si:H(p) as a buffer-layer and raising the ξ of the a-SiO{sub x}:H(p), compared to the optimized bufferless case, with a 10 nm-thick a-SiO{sub x}:H(p) window-layer. - Highlights: • Low Schottky barrier height benefits fill factor, and open-circuit voltage (V{sub oc}). • High band gap is beneficial for short-circuit current density (J{sub sc}). • Boron doped microcrystalline silicon is a suitable buffer-layer for

Spin transport in two-layer-CVD-hBN/graphene/hBN heterostructures

Science.gov (United States)

Gurram, M.; Omar, S.; Zihlmann, S.; Makk, P.; Li, Q. C.; Zhang, Y. F.; Schönenberger, C.; van Wees, B. J.

2018-01-01

We study room-temperature spin transport in graphene devices encapsulated between a layer-by-layer-stacked two-layer-thick chemical vapor deposition (CVD) grown hexagonal boron nitride (hBN) tunnel barrier, and a few-layer-thick exfoliated-hBN substrate. We find mobilities and spin-relaxation times comparable to that of SiO2 substrate-based graphene devices, and we obtain a similar order of magnitude of spin relaxation rates for both the Elliott-Yafet and D'Yakonov-Perel' mechanisms. The behavior of ferromagnet/two-layer-CVD-hBN/graphene/hBN contacts ranges from transparent to tunneling due to inhomogeneities in the CVD-hBN barriers. Surprisingly, we find both positive and negative spin polarizations for high-resistance two-layer-CVD-hBN barrier contacts with respect to the low-resistance contacts. Furthermore, we find that the differential spin-injection polarization of the high-resistance contacts can be modulated by dc bias from -0.3 to +0.3 V with no change in its sign, while its magnitude increases at higher negative bias. These features point to the distinctive spin-injection nature of the two-layer-CVD-hBN compared to the bilayer-exfoliated-hBN tunnel barriers.

Graphene Quantum Dot Layers with Energy-Down-Shift Effect on Crystalline-Silicon Solar Cells.

Science.gov (United States)

Lee, Kyung D; Park, Myung J; Kim, Do-Yeon; Kim, Soo M; Kang, Byungjun; Kim, Seongtak; Kim, Hyunho; Lee, Hae-Seok; Kang, Yoonmook; Yoon, Sam S; Hong, Byung H; Kim, Donghwan

2015-09-02

Graphene quantum dot (GQD) layers were deposited as an energy-down-shift layer on crystalline-silicon solar cell surfaces by kinetic spraying of GQD suspensions. A supersonic air jet was used to accelerate the GQDs onto the surfaces. Here, we report the coating results on a silicon substrate and the GQDs' application as an energy-down-shift layer in crystalline-silicon solar cells, which enhanced the power conversion efficiency (PCE). GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density was enhanced by about 2.94% (0.9 mA/cm(2)) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).

Experimental investigations of superconductivity in quasi-two-dimensional epitaxial copper oxide superlattices and trilayers

International Nuclear Information System (INIS)

Lowndes, D.H.; Norton, D.P.

1993-01-01

Epitaxial trilayer and superlattice structures grown by pulsed laser ablation have been used to study the superconducting-to-normal transition of ultrathin (one and two c-axis unit cells) YBa 2 Cu 3 O 7-x layers. The normalized flux-flow resistances for several epitaxial structures containing two-cell-thick YBa 2 Cu 3 O 7-x films collapse onto the ''universal'' curve of the Ginzburg-Landau Coulomb Gas (GLCG) model. Analysis of normalized resistance data for a series of superlattices containing one-cell-thick YBa 2 Cu 3 O 7-x layers also is consistent with the behavior expected for quasi-two-dimensional layers in a highly anisotropic, layered three-dimensional superconductor. Current-voltage measurements for one of the trilayer structures also are consistent with the normalized resistance data, and with the GLCG model. Scanning tunneling microscopy, transmission electron microscopy, and electrical transport studies show that growth-related steps in ultrathin YBa 2 Cu 3 O 7-x layers affect electrical continuity over macroscopic distances, acting as weak links. However , the perturbation of the superconducting order parameter can be minimized by utilizing hole-doped buffer and cap layers, on both sides of the YBa 2 Cu 3 O 7-x layer, in trilayers and superlattices. These results demonstrate the usefulness of epitaxial trilayer and superlattice structures as tools for systematic, fundamental studies of high-temperature superconductivity

Flow Generated by a Partially Penetrating Well in a Leaky Two-Aquifer System with a Storative Semiconfining Layer

Science.gov (United States)

Sepulveda, N.; Rohrer, K.

2008-05-01

The permeability of the semiconfining layers of the highly productive Floridan Aquifer System may be large enough to invalidate the assumptions of the leaky aquifer theory. These layers are the intermediate confining and the middle semiconfining units. The analysis of aquifer-test data with analytical solutions of the ground-water flow equation developed with the approximation of a low hydraulic conductivity ratio between the semiconfining layer and the aquifer may lead to inaccurate hydraulic parameters. An analytical solution is presented here for the flow in a confined leaky aquifer, the overlying storative semiconfining layer, and the unconfined aquifer, generated by a partially penetrating well in a two-aquifer system, and allowing vertical and lateral flow components to occur in the semiconfining layer. The equations describing flow caused by a partially penetrating production well are solved analytically to provide a method to accurately determine the hydraulic parameters in the confined aquifer, semiconfining layer, and unconfined aquifer from aquifer-test data. Analysis of the drawdown data from an aquifer test performed in central Florida showed that the flow solution presented here for the semiconfining layer provides a better match and a more unique identification of the hydraulic parameters than an analytical solution that considers only vertical flow in the semiconfining layer.

Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

Science.gov (United States)

Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

2016-07-06

Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

Protective layer formation on magnesium in cell culture medium.

Science.gov (United States)

Wagener, V; Virtanen, S

2016-06-01

In the past, different studies showed that hydroxyapatite (HA) or similar calcium phosphates can be precipitated on Mg during immersion in simulated body fluids. However, at the same time, in most cases a dark grey or black layer is built under the white HA crystals. This layer seems to consist as well of calcium phosphates. Until now, neither the morphology nor its influence on Mg corrosion have been investigated in detail. In this work commercially pure magnesium (cp) was immersed in cell culture medium for one, three and five days at room temperature and in the incubator (37 °C, 5% CO2). In addition, the influence of proteins on the formation of a corrosion layer was investigated by adding 20% of fetal calf serum (FCS) to the cell culture medium in the incubator. In order to analyze the formed layers, SEM images of cross sections, X-ray Photoelectron Spectroscopy (XPS), X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier Transformed Infrared Spectroscopy (FTIR) measurements were carried out. Characterization of the corrosion behavior was achieved by electrochemical impedance spectroscopy (EIS) and by potentio-dynamic polarization in Dulbecco's Modified Eagle's Medium (DMEM) at 37°C. Surface analysis showed that all formed layers consist mainly of amorphous calcium phosphate compounds. For the immersion at room temperature the Ca/P ratio indicates the formation of HA, while in the incubator probably pre-stages to HA are formed. The different immersion conditions lead to a variation in layer thicknesses. However, electrochemical characterization shows that the layer thickness does not influence the corrosion resistance of magnesium. The main influencing factor for the corrosion behavior is the layer morphology. Thus, immersion at room temperature leads to the highest corrosion protection due to the formation of a compact outer layer. Layers formed in the incubator show much worse performances due to completely porous structures. The

Paired single cell co-culture microenvironments isolated by two-phase flow with continuous nutrient renewal.

Science.gov (United States)

Chen, Yu-Chih; Cheng, Yu-Heng; Kim, Hong Sun; Ingram, Patrick N; Nor, Jacques E; Yoon, Euisik

2014-08-21

Cancer-stromal cell interactions are a critical process in tumorigenesis. Conventional dish-based assays, which simply mix two cell types, have limitations in three aspects: 1) limited control of the cell microenvironment; 2) inability to study cell behavior in a single-cell manner; and 3) have difficulties in characterizing single cell behavior within a highly heterogeneous cell population (e.g. tumor). An innovative use of microfluidic technology is for improving the spatial resolution for single cell assays. However, it is challenging to isolate the paired interacting cells while maintaining nutrient renewal. In this work, two-phase flow was used as a simple isolation method, separating the microenvironment of each individual chamber. As nutrients in an isolated chamber are consumed by cells, media exchange is required. To connect the cell culture chamber to the media exchange layer, we demonstrated a 3D microsystem integration technique using vertical connections fabricated by deep reactive-ion etching (DRIE). Compared to previous approaches, the presented process allows area reduction of vertical connections by an order of magnitude, enabling compact 3D integration. A semi-permeable membrane was sandwiched between the cell culture layer and the media exchange layer. The selectivity of the semi-permeable membrane results in the retention of the signaling proteins within the chamber while allowing free diffusion of nutrients (e.g., glucose and amino acids). Thus, paracrine signals are accumulated inside the chamber without cross-talk between cells in other chambers. Utilizing these innovations, we co-cultured UM-SCC-1 (head and neck squamous cell carcinoma) cells and endothelial cells to simulate tumor proliferation enhancement in the vascular endothelial niche.

Photoluminescence of epitactical and polycrystalline CuInS2 layers for thin-film solar cells

International Nuclear Information System (INIS)

Eberhardt, J.

2007-01-01

The present thesis deals with one- and polycrystalline CuInS 2 absorber layers for thin-film solar cells and especially with their optical and structural characterization. By means of detailed temperature- and power-dependent photoluminescence measurements in epitactical and polycrystalline absorber layers different radiative transitions could be analyzed and identified. The spectra were dominated by broad luminescence bands of deep perturbing levels. The implantation of hydrogen at low energies led to a passivation of these perturbing levels. On the base of the optical studies on epitactical and polycrystalline absorber layers a new improved defect model for CuInS 2 could be developed. The model contains two donor and two acceptor levels with following ionization energies: D-1=46 meV, D-2=87 meV, A-1=70 meV, and A-2=119 meV

The silicon-silicon oxide multilayers utilization as intrinsic layer on pin solar cells

International Nuclear Information System (INIS)

Colder, H.; Marie, P.; Gourbilleau, F.

2008-01-01

Silicon nanostructures are promising candidate for the intrinsic layer on pin solar cells. In this work we report on new material: silicon-rich silicon oxide (SRSO) deposited by reactive magnetron sputtering of a pure silica target and an interesting structure: multilayers consisting of a stack of SRSO and pure silicon oxide layers. Two thicknesses of the SRSO sublayer, t SRSO , are studied 3 nm and 5 nm whereas the thickness of silica sublayer is maintaining at 3 nm. The presence of nanocrystallites of silicon, evidenced by X-Ray diffraction (XRD), leads to photoluminescence (PL) emission at room temperature due to the quantum confinement of the carriers. The PL peak shifts from 1.3 eV to 1.5 eV is correlated to the decreasing of t SRSO from 5 nm down to 3 nm. In the purpose of their potential utilization for i-layer, the optical properties are studied by absorption spectroscopy. The achievement a such structures at promising absorption properties. Moreover by favouring the carriers injection by the tunnel effect between silicon nanograins and silica sublayers, the multilayers seem to be interesting for solar cells

Respiration Gates Sensory Input Responses in the Mitral Cell Layer of the Olfactory Bulb

Science.gov (United States)

Short, Shaina M.; Morse, Thomas M.; McTavish, Thomas S.; Shepherd, Gordon M.; Verhagen, Justus V.

2016-01-01

Respiration plays an essential role in odor processing. Even in the absence of odors, oscillating excitatory and inhibitory activity in the olfactory bulb synchronizes with respiration, commonly resulting in a burst of action potentials in mammalian mitral/tufted cells (MTCs) during the transition from inhalation to exhalation. This excitation is followed by inhibition that quiets MTC activity in both the glomerular and granule cell layers. Odor processing is hypothesized to be modulated by and may even rely on respiration-mediated activity, yet exactly how respiration influences sensory processing by MTCs is still not well understood. By using optogenetics to stimulate discrete sensory inputs in vivo, it was possible to temporally vary the stimulus to occur at unique phases of each respiration. Single unit recordings obtained from the mitral cell layer were used to map spatiotemporal patterns of glomerular evoked responses that were unique to stimulations occurring during periods of inhalation or exhalation. Sensory evoked activity in MTCs was gated to periods outside phasic respiratory mediated firing, causing net shifts in MTC activity across the cycle. In contrast, odor evoked inhibitory responses appear to be permitted throughout the respiratory cycle. Computational models were used to further explore mechanisms of inhibition that can be activated by respiratory activity and influence MTC responses. In silico results indicate that both periglomerular and granule cell inhibition can be activated by respiration to internally gate sensory responses in the olfactory bulb. Both the respiration rate and strength of lateral connectivity influenced inhibitory mechanisms that gate sensory evoked responses. PMID:28005923

Device and performance parameters of Cu(In,Ga)(Se,S)2-based solar cells with varying i-ZnO layer thickness

International Nuclear Information System (INIS)

Macabebe, E.Q.B.; Sheppard, C.J.; Dyk, E.E. van

2009-01-01

In pursuit of low-cost and highly efficient thin film solar cells, Cu(In,Ga)(Se,S) 2 /CdS/i-ZnO/ZnO:Al (CIGSS) solar cells were fabricated using a two-step process. The thickness of i-ZnO layer was varied from 0 to 454 nm. The current density-voltage (J-V) characteristics of the devices were measured, and the device and performance parameters of the solar cells were obtained from the J-V curves to analyze the effect of varying i-ZnO layer thickness. The device parameters were determined using a parameter extraction method that utilized particle swarm optimization. The method is a curve-fitting routine that employed the two-diode model. The J-V curves of the solar cells were fitted with the model and the parameters were determined. Results show that as the thickness of i-ZnO was increased, the average efficiency and the fill factor (FF) of the solar cells increase. Device parameters reveal that although the series resistance increased with thicker i-ZnO layer, the solar cells absorbed more photons resulting in higher short-circuit current density (J sc ) and, consequently, higher photo-generated current density (J L ). For solar cells with 303-454 nm-thick i-ZnO layer, the best devices achieved efficiency between 15.24% and 15.73% and the fill factor varied between 0.65 and 0.67.

Hydrophobic Polystyrene Passivation Layer for Simultaneously Improved Efficiency and Stability in Perovskite Solar Cells.

Science.gov (United States)

Li, Minghua; Yan, Xiaoqin; Kang, Zhuo; Huan, Yahuan; Li, Yong; Zhang, Ruxiao; Zhang, Yue

2018-06-06

The major restraint for the commercialization of the high-performance hybrid metal halide perovskite solar cells is the long-term stability, especially at the infirm interface between the perovskite film and organic charge-transfer layer. Recently, engineering the interface between the perovskite and spiro-OMeTAD becomes an effective strategy to simultaneously improve the efficiency and stability in the perovskite solar cells. In this work, we demonstrated that introducing an interfacial polystyrene layer between the perovskite film and spiro-OMeTAD layer can effectively improve the perovskite solar cells photovoltaic performance. The inserted polystyrene layer can passivate the interface traps and defects effectively and decrease the nonradiative recombination, leading to enhanced photoluminescence intensity and carrier lifetime, without compromising the carrier extraction and transfer. Under the optimized condition, the perovskite solar cells with the polystyrene layer achieve an enhanced average power efficiency of about 19.61% (20.46% of the best efficiency) from about 17.63% with negligible current density-voltage hysteresis. Moreover, the optimized perovskite solar cells with the hydrophobic polystyrene layer can maintain about 85% initial efficiency after 2 months storage in open air conditions without encapsulation.

A two-layer architecture for force-reflecting bilateral teleoperation with time delays

NARCIS (Netherlands)

Heck, D.J.F.; Saccon, A.; Nijmeijer, H.

2015-01-01

We propose a two-layer control architecture for bilateral teleoperation with communication delays. The controller is structured with an (outer) performance layer and an (inner) passivity layer. In the performance layer, any traditional controller for bilateral teleoperation can be implemented. In

Cross-Layer Design for Two-Way Relaying Networks with Multiple Antennas

Directory of Open Access Journals (Sweden)

zhuo wu

2015-10-01

Full Text Available In this paper, we developed a cross-layer design for two-way relaying (TWR networks with multiple antennas, where two single antenna source nodes exchange information with the aid of one multiple antenna relay node. The proposed cross-layer design considers adaptive modulation (AM and space-time block coding (STBC at the physical layer with an automatic repeat request (ARQ protocol at the data link layer, in order to maximize the spectral efficiency under specific delay and packet error ratio (PER constraints. An MMSE-interference cancellation (IC receiver is employed at the relay node, to remove the interference in the fist phase of the TWR transmission. The transmission mode is updated for each phase of the TWR transmission on a frame-by-frame basis, to match the time-varying channel conditions and exploit the system performance and throughput gain. Simulation results show that retransmission at the data link layer could alleviate rigorous error-control requirements at the physical layer, and thereby allows higher data transmission. As a result, cross-layer design helps to achieve considerable system spectral efficiency gain for TWR networks, compared to those without cross-layer design.

Effect of primary and secondary parameters on analytical estimation of effective thermal conductivity of two phase materials using unit cell approach

Science.gov (United States)

S, Chidambara Raja; P, Karthikeyan; Kumaraswamidhas, L. A.; M, Ramu

2018-05-01

Most of the thermal design systems involve two phase materials and analysis of such systems requires detailed understanding of the thermal characteristics of the two phase material. This article aimed to develop geometry dependent unit cell approach model by considering the effects of all primary parameters (conductivity ratio and concentration) and secondary parameters (geometry, contact resistance, natural convection, Knudsen and radiation) for the estimation of effective thermal conductivity of two-phase materials. The analytical equations have been formulated based on isotherm approach for 2-D and 3-D spatially periodic medium. The developed models are validated with standard models and suited for all kind of operating conditions. The results have shown substantial improvement compared to the existing models and are in good agreement with the experimental data.

Exactly solvable model of the two-dimensional electrical double layer.

Science.gov (United States)

Samaj, L; Bajnok, Z

2005-12-01

We consider equilibrium statistical mechanics of a simplified model for the ideal conductor electrode in an interface contact with a classical semi-infinite electrolyte, modeled by the two-dimensional Coulomb gas of pointlike unit charges in the stability-against-collapse regime of reduced inverse temperatures 0layer) carries some nonzero surface charge density. The model is mappable onto an integrable semi-infinite sine-Gordon theory with Dirichlet boundary conditions. The exact form-factor and boundary state information gained from the mapping provide asymptotic forms of the charge and number density profiles of electrolyte particles at large distances from the interface. The result for the asymptotic behavior of the induced electric potential, related to the charge density via the Poisson equation, confirms the validity of the concept of renormalized charge and the corresponding saturation hypothesis. It is documented on the nonperturbative result for the asymptotic density profile at a strictly nonzero beta that the Debye-Hückel beta-->0 limit is a delicate issue.

Electrochemical Characterization of TiO 2 Blocking Layers for Dye-Sensitized Solar Cells

KAUST Repository

Kavan, Ladislav

2014-07-31

Thin compact layers of TiO2 are grown by thermal oxidation of Ti, by spray pyrolysis, by electrochemical deposition, and by atomic layer deposition. These layers are used in dye-sensitized solar cells to prevent recombination of electrons from the substrate (FTO or Ti) with the hole-conducting medium at this interface. The quality of blocking is evaluated electrochemically by methylviologen, ferro/ferricyanide, and spiro-OMeTAD as the model redox probes. Two types of pinholes in the blocking layers are classified, and their effective area is quantified. Frequency-independent Mott-Schottky plots are fitted from electrochemical impedance spectroscopy. Certain films of the thicknesses of several nanometers allow distinguishing the depletion layer formation both in the TiO2 film and in the FTO substrate underneath the titania film. The excellent blocking function of thermally oxidized Ti, electrodeposited film (60 nm), and atomic-layer-deposited films (>6 nm) is documented by the relative pinhole area of less than 1%. However, the blocking behavior of electrodeposited and atomic-layer-deposited films is strongly reduced upon calcination at 500 °C. The blocking function of spray-pyrolyzed films is less good but also less sensitive to calcination. The thermally oxidized Ti is well blocking and insensitive to calcination. © 2014 American Chemical Society.

Convection Cells in the Atmospheric Boundary Layer

Science.gov (United States)

Fodor, Katherine; Mellado, Juan-Pedro

2017-04-01

In dry, shear-free convective boundary layers (CBLs), the turbulent flow of air is known to organise itself on large scales into coherent, cellular patterns, or superstructures, consisting of fast, narrow updraughts and slow, wide downdraughts which together form circulations. Superstructures act as transport mechanisms from the surface to the top of the boundary layer and vice-versa, as opposed to small-scale turbulence, which only modifies conditions locally. This suggests that a thorough investigation into superstructure properties may help us better understand transport across the atmospheric boundary layer as a whole. Whilst their existence has been noted, detailed studies into superstructures in the CBL have been scarce. By applying methods which are known to successfully isolate similar large-scale patterns in turbulent Rayleigh-Bénard convection, we can assess the efficacy of those detection techniques in the CBL. In addition, through non-dimensional analysis, we can systematically compare superstructures in various convective regimes. We use direct numerical simulation of four different cases for intercomparison: Rayleigh-Bénard convection (steady), Rayleigh-Bénard convection with an adiabatic top lid (quasi-steady), a stably-stratified CBL (quasi-steady) and a neutrally-stratified CBL (unsteady). The first two are non-penetrative and the latter two penetrative. We find that although superstructures clearly emerge from the time-mean flow in the non-penetrative cases, they become obscured by temporal averaging in the CBL. This is because a rigid lid acts to direct the flow into counter-rotating circulation cells whose axis of rotation remains stationary, whereas a boundary layer that grows in time and is able to entrain fluid from above causes the circulations to not only grow in vertical extent, but also to move horizontally and merge with neighbouring circulations. Spatial filtering is a useful comparative technique as it can be performed on boundary

Au Nanoparticles as Interfacial Layer for CdS Quantum Dot-sensitized Solar Cells

Directory of Open Access Journals (Sweden)

Zhu Guang

2010-01-01

Full Text Available Abstract Quantum dot-sensitized solar cells based on fluorine-doped tin oxide (FTO/Au/TiO2/CdS photoanode and polysulfide electrolyte are fabricated. Au nanoparticles (NPs as interfacial layer between FTO and TiO2 layer are dip-coated on FTO surface. The structure, morphology and impedance of the photoanodes and the photovoltaic performance of the cells are investigated. A power conversion efficiency of 1.62% has been obtained for FTO/Au/TiO2/CdS cell, which is about 88% higher than that for FTO/TiO2/CdS cell (0.86%. The easier transport of excited electron and the suppression of charge recombination in the photoanode due to the introduction of Au NP layer should be responsible for the performance enhancement of the cell.

Silver nanoparticles-incorporated Nb2O5 surface passivation layer for efficiency enhancement in dye-sensitized solar cells.

Science.gov (United States)

Suresh, S; Unni, Gautam E; Satyanarayana, M; Sreekumaran Nair, A; Mahadevan Pillai, V P

2018-08-15

Guiding and capturing photons at the nanoscale by means of metal nanoparticles and interfacial engineering for preventing back-electron transfer are well documented techniques for performance enhancement in excitonic solar cells. Drifting from the conventional route, we propose a simple one-step process to integrate both metal nanoparticles and surface passivation layer in the porous photoanode matrix of a dye-sensitized solar cell. Silver nanoparticles and Nb 2 O 5 surface passivation layer are simultaneously deposited on the surface of a highly porous nanocrystalline TiO 2 photoanode, facilitating an absorption enhancement in the 465 nm and 570 nm wavelength region and a reduction in back-electron transfer in the fabricated dye-sensitized solar cells together. The TiO 2 photoanodes were prepared by spray pyrolysis deposition method from a colloidal solution of TiO 2 nanoparticles. An impressive 43% enhancement in device performance was accomplished in photoanodes having an Ag-incorporated Nb 2 O 5 passivation layer as against a cell without Ag nanoparticles. By introducing this idea, we were able to record two benefits - the metal nanoparticles function as the absorption enhancement agent, and the Nb 2 O 5 layer as surface passivation for TiO 2 nanoparticles and as an energy barrier layer for preventing back-electron transfer - in a single step. Copyright © 2018 Elsevier Inc. All rights reserved.

The cerebellar Golgi cell and spatiotemporal organization of granular layer activity

Directory of Open Access Journals (Sweden)

Egidio eD‘Angelo

2013-05-01

Full Text Available The cerebellar granular layer has been suggested to perform a complex spatiotemporal reconfiguration of incoming mossy fiber signals. Central to this role is the inhibitory action exerted by Golgi cells over granule cells: Golgi cells inhibit granule cells through double feedforward and feedback inhibitory loops and generate a broad lateral inhibition that extends beyond the afferent synaptic field. This characteristic connectivity has recently been investigated in great detail and been correlated with specific functional properties of the neuron. These include theta-frequency pacemaking, network entrainment into coherent oscillations and phase resetting. Important advances have also been made in terms of determining the membrane and synaptic properties of the neuron, and clarifying the mechanisms of activation by input bursts. Moreover, voltage sensitive dye imaging and multi-electrode array recordings, combined with mathematical simulations based on realistic computational models, have improved our understanding of the impact of Golgi cell activity on granular layer circuit computations. These investigations have highlighted the critical role of Golgi cells in: generating dense clusters of granule cell activity organized in center-surround structures, implementing combinatorial operations on multiple mossy fiber inputs, regulating transmission gain and cut-off frequency, controlling spike timing and burst transmission, and determining the sign, intensity and extension of long-term synaptic plasticity at the mossy fiber-granule cell relay. This review considers recent advances in the field, highlighting the functional implications of Golgi cells for granular layer network computation and indicating new challenges for cerebellar research.

Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers

Science.gov (United States)

2016-06-15

AFRL-AFOSR-JP-TR-2016-0071 Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers Cheolmin Park YONSEI UNIVERSITY...Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-14-1-4054 5c.  PROGRAM ELEMENT...prospects for a variety of emerging applications in a broad range of fields, such as electronics, energy conversion and storage, catalysis and polymer

Influence of intermediate layers on the surface condition of laser crystallized silicon thin films and solar cell performance

Energy Technology Data Exchange (ETDEWEB)

Höger, Ingmar, E-mail: ingmar.hoeger@ipht-jena.de; Gawlik, Annett; Brückner, Uwe; Andrä, Gudrun [Leibniz-Institut für Photonische Technologien, PF 100239, 07702 Jena (Germany); Himmerlich, Marcel; Krischok, Stefan [Institut für Mikro-und Nanotechnologien, Technische Universität Ilmenau, PF 100565, 98684 Ilmenau (Germany)

2016-01-28

The intermediate layer (IL) between glass substrate and silicon plays a significant role in the optimization of multicrystalline liquid phase crystallized silicon thin film solar cells on glass. This study deals with the influence of the IL on the surface condition and the required chemical surface treatment of the crystallized silicon (mc-Si), which is of particular interest for a-Si:H heterojunction thin film solar cells. Two types of IL were investigated: sputtered silicon nitride (SiN) and a layer stack consisting of silicon nitride and silicon oxide (SiN/SiO). X-ray photoelectron spectroscopy measurements revealed the formation of silicon oxynitride (SiO{sub x}N{sub y}) or silicon oxide (SiO{sub 2}) layers at the surface of the mc-Si after liquid phase crystallization on SiN or SiN/SiO, respectively. We propose that SiO{sub x}N{sub y} formation is governed by dissolving nitrogen from the SiN layer in the silicon melt, which segregates at the crystallization front during crystallization. This process is successfully hindered, when additional SiO layers are introduced into the IL. In order to achieve solar cell open circuit voltages above 500 mV, a removal of the formed SiO{sub x}N{sub y} top layer is required using sophisticated cleaning of the crystallized silicon prior to a-Si:H deposition. However, solar cells crystallized on SiN/SiO yield high open circuit voltage even when a simple wet chemical surface treatment is applied. The implementation of SiN/SiO intermediate layers facilitates the production of mesa type solar cells with open circuit voltages above 600 mV and a power conversion efficiency of 10%.

Barium: An Efficient Cathode Layer for Bulk-heterojunction Solar Cells

Science.gov (United States)

Gupta, Vinay; Kyaw, Aung Ko Ko; Wang, Dong Hwan; Chand, Suresh; Bazan, Guillermo C.; Heeger, Alan J.

2013-01-01

We report Barium (Ba) cathode layer for bulk-heterojunction solar cells which enhanced the fill factor (FF) of p-DTS(FBTTh2)2/PC71BM BHJ solar cell up to 75.1%, one of the highest value reported for an organic solar cell. The external quantum efficiency exceeds 80%. Analysis of recombination mechanisms using the current-voltage (J–V) characteristics at various light intensities in the BHJ solar cell layer reveals that Ba prevents trap assisted Shockley-Read-Hall (SRH) recombination at the interface and with different thicknesses of the Ba, the recombination shifts towards bimolecular from monomolecular. Moreover, Ba increases shunt resistance and decreases the series resistance significantly. This results in an increase in the charge collection probability leading to high FF. This work identifies a new cathode interlayer which outclasses the all the reported interlayers in increasing FF leading to high power conversion efficiency and have significant implications in improving the performance of BHJ solar cells. PMID:23752562

Protective layer formation on magnesium in cell culture medium

Energy Technology Data Exchange (ETDEWEB)

Wagener, V.; Virtanen, S., E-mail: virtanen@ww.uni-erlangen.de

2016-06-01

In the past, different studies showed that hydroxyapatite (HA) or similar calcium phosphates can be precipitated on Mg during immersion in simulated body fluids. However, at the same time, in most cases a dark grey or black layer is built under the white HA crystals. This layer seems to consist as well of calcium phosphates. Until now, neither the morphology nor its influence on Mg corrosion have been investigated in detail. In this work commercially pure magnesium (cp) was immersed in cell culture medium for one, three and five days at room temperature and in the incubator (37 °C, 5% CO{sub 2}). In addition, the influence of proteins on the formation of a corrosion layer was investigated by adding 20% of fetal calf serum (FCS) to the cell culture medium in the incubator. In order to analyze the formed layers, SEM images of cross sections, X-ray Photoelectron Spectroscopy (XPS), X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier Transformed Infrared Spectroscopy (FTIR) measurements were carried out. Characterization of the corrosion behavior was achieved by electrochemical impedance spectroscopy (EIS) and by potentio-dynamic polarization in Dulbecco's Modified Eagle's Medium (DMEM) at 37 °C. Surface analysis showed that all formed layers consist mainly of amorphous calcium phosphate compounds. For the immersion at room temperature the Ca/P ratio indicates the formation of HA, while in the incubator probably pre-stages to HA are formed. The different immersion conditions lead to a variation in layer thicknesses. However, electrochemical characterization shows that the layer thickness does not influence the corrosion resistance of magnesium. The main influencing factor for the corrosion behavior is the layer morphology. Thus, immersion at room temperature leads to the highest corrosion protection due to the formation of a compact outer layer. Layers formed in the incubator show much worse performances due to completely porous

Protective layer formation on magnesium in cell culture medium

International Nuclear Information System (INIS)

Wagener, V.; Virtanen, S.

2016-01-01

In the past, different studies showed that hydroxyapatite (HA) or similar calcium phosphates can be precipitated on Mg during immersion in simulated body fluids. However, at the same time, in most cases a dark grey or black layer is built under the white HA crystals. This layer seems to consist as well of calcium phosphates. Until now, neither the morphology nor its influence on Mg corrosion have been investigated in detail. In this work commercially pure magnesium (cp) was immersed in cell culture medium for one, three and five days at room temperature and in the incubator (37 °C, 5% CO_2). In addition, the influence of proteins on the formation of a corrosion layer was investigated by adding 20% of fetal calf serum (FCS) to the cell culture medium in the incubator. In order to analyze the formed layers, SEM images of cross sections, X-ray Photoelectron Spectroscopy (XPS), X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier Transformed Infrared Spectroscopy (FTIR) measurements were carried out. Characterization of the corrosion behavior was achieved by electrochemical impedance spectroscopy (EIS) and by potentio-dynamic polarization in Dulbecco's Modified Eagle's Medium (DMEM) at 37 °C. Surface analysis showed that all formed layers consist mainly of amorphous calcium phosphate compounds. For the immersion at room temperature the Ca/P ratio indicates the formation of HA, while in the incubator probably pre-stages to HA are formed. The different immersion conditions lead to a variation in layer thicknesses. However, electrochemical characterization shows that the layer thickness does not influence the corrosion resistance of magnesium. The main influencing factor for the corrosion behavior is the layer morphology. Thus, immersion at room temperature leads to the highest corrosion protection due to the formation of a compact outer layer. Layers formed in the incubator show much worse performances due to completely porous structures. The

Implementation of a Comprehensive On-Line Closed-Loop Diagnostic System for Roll-to-Roll Amorphous Silicon Solar Cell Production: Annual Report, Year Two; 1 September 2003--31 August 2004

Energy Technology Data Exchange (ETDEWEB)

Ellison, T.

2005-02-01

Energy Conversion Devices, Inc. (ECD) has developed and built 7 generations of roll-to-roll amorphous silicon PV production equipment. In the ECD/United Solar Ovonic production process, we deposit about a 1-mm-thick, 12-layer coating consisting of a metal/oxide backreflector, a - layer a-Si/a-SiGe alloy triple-junction solar cell, and a top transparent conductive oxide coating onto 125-mm-thick, 35.5-cm-wide stainless steel webs in a series of three roll-to-roll deposition machines. ECD has now completed the Phase II work for this program. In the following report, we summarize the Phase II work in each of these tasks. We have involved United Solar production personnel in each of these Tasks. This is important for two reasons: Firstly, the collaboration of ECD and United Solar personnel keeps the projects responsive to the developing needs at United Solar. Secondly, most of the tasks affect operations and consequently need the support of United Solar production and QA/QC managers. In the process, we have developed a good working relationship between the production personnel and good balance between optimizing production, while also ''adiabatically'' improving the manufacturing equipment.

Dynamic properties of sensory stimulation evoked responses in mouse cerebellar granule cell layer and molecular layer.

Science.gov (United States)

Bing, Yan-Hua; Zhang, Guang-Jian; Sun, Lei; Chu, Chun-Ping; Qiu, De-Lai

2015-01-12

Sensory information coming from climbing fiber and mossy fiber-granule cell pathways, generates motor-related outputs according to internal rules of integration and computation in the cerebellar cortex. However, the dynamic properties of sensory information processing in mouse cerebellar cortex are less understood. Here, we studied the dynamic properties of sensory stimulation-evoked responses in the cerebellar granule cell layer (GCL) and molecular layer (ML) by electrophysiological recordings method. Our data showed that air-puff stimulation (5-10 ms in duration) of the ipsilateral whisker pad evoked single-peak responses in the GCL and ML; whereas a duration of stimulation ≥30 ms in GCL and ≥60 ms in ML, evoked double-peak responses that corresponded with stimulation-on and -off responses via mossy fiber pathway. The highest frequency of stimulation train for evoking GCL responses was 33 Hz. In contrast, the highest frequency of stimulation train for evoking ML responses was 4 Hz. These results indicate that the cerebellar granule cells transfer the high-fidelity sensory information from mossy fibers, which is cut-off by molecular layer interneurons (MLIs). Our results suggest that the MLIs network acts as a low-pass filter during the processing of high-frequency sensory information. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

A general analytical equation for phase diagrams of an N-layer ferroelectric thin film with two surface layers

Energy Technology Data Exchange (ETDEWEB)

Lu, Z X; Teng, B H; Rong, Y H; Lu, X H; Yang, X [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)], E-mail: phytbh@163.com

2010-03-15

Within the framework of effective-field theory with correlations, the phase diagrams of an N-layer ferroelectric thin film with two surface layers are studied by the differential operator technique based on the spin-1/2 transverse Ising model. A general analytical equation for the phase diagram of a ferroelectric thin film with arbitrary layer number as well as exchange interactions and transverse fields is derived, and then the effects of exchange interactions and transverse fields on phase diagrams are discussed for an arbitrary layer number N. Meanwhile, the crossover features, from the ferroelectric-dominant phase diagram (FPD) to the paraelectric-dominant phase diagram (PPD), for various parameters of an N-layer ferroelectric thin film with two surface layers are investigated. As a result, an N-independent common intersection point equation is obtained, and the three-dimensional curved surfaces for the crossover values are constructed. In comparison with the usual mean-field approximation, the differential operator technique with correlations reduces to some extent the ferroelectric features of a ferroelectric thin film.

Characterization of up-converter layers on bifacial silicon solar cells

International Nuclear Information System (INIS)

Pan, A.C.; Canizo, C. del; Luque, A.

2009-01-01

Photon converters can enhance the performance of solar cells as they have the ability to condition the solar spectrum, thus suiting the semiconductor bandgap better. This paper analyzes the implementation and characterization of rare earth-doped up-converters on bifacial silicon solar cells. The bifacial structures considered absorb the light emitted by the up-converter layer located at the rear of the cell. Two different ways of attaching the up-converter to the bifacial solar cell have been implemented: by dissolving the powder in a spin-on oxide and by dissolving it in a silicone gel. The characterization of this system through measurements of quantum efficiency and photocurrent is described. The measurement setup has been adapted to detect the device response in the NIR (near-infrared) range. A key aspect is the light power impinging on the cell; the system has a quartz-tungsten-halogen lamp as a source, and is capable of giving 240 mW m -2 . As the signals we want to detect are very small, an effort has been made to enhance the signal-to-noise ratio by using a low noise pre-amplifier, optimizing the power of the lamp and reducing the chopper frequency. The characterization of two commercial up-converter materials shows the functioning of the approach, as an increase in the photocurrent when illuminated in the 1500 nm wavelength range is detected in some of the cases.

Central-Upwind Schemes for Two-Layer Shallow Water Equations

KAUST Repository

Kurganov, Alexander; Petrova, Guergana

2009-01-01

We derive a second-order semidiscrete central-upwind scheme for one- and two-dimensional systems of two-layer shallow water equations. We prove that the presented scheme is well-balanced in the sense that stationary steady-state solutions

Silicotungstate, a Potential Electron Transporting Layer for Low-Temperature Perovskite Solar Cells.

Science.gov (United States)

Choi, Yoon Ho; Kim, Hyun Bin; Yang, In Seok; Sung, Sang Do; Choi, Young Sik; Kim, Jeongho; Lee, Wan In

2017-08-02

Thin films of a heteropolytungstate, lithium silicotungstate (Li 4 SiW 12 O 40 , termed Li-ST), prepared by a solution process at low temperature, were successfully applied as electron transporting layer (ETL) of planar-type perovskite solar cells (PSCs). Dense and uniform Li-ST films were prepared on FTO glass by depositing a thin Li-ST buffer layer, followed by coating of a main Li-ST layer. The film thickness was controlled by varying the number of coating cycles, consisting of spin-coating and thermal treatment at 150 °C. In particular, by employing 60 nm-thick Li-ST layer obtained by two cycles of coating, the fabricated CH 3 NH 3 PbI 3 PSC device demonstrates the photovoltaic conversion efficiency (PCE) of 14.26% with J SC of 22.16 mA cm -2 , V OC of 0.993 mV and FF of 64.81%. The obtained PCE is significantly higher than that of the PSC employing a TiO 2 layer processed at the same temperature (PCE = 12.27%). Spectroscopic analyses by time-resolved photoluminescence and pulsed light-induced transient measurement of photocurrent indicate that the Li-ST layer collects electrons from CH 3 NH 3 PbI 3 more efficiently and also exhibits longer electron lifetime than the TiO 2 layer thermally treated at 150 °C. Thus, Li-ST is considered to be a promising ETL material that can be applied for the fabrication of flexible PSC devices.

Conformal bi-layered perovskite/spinel coating on a metallic wire network for solid oxide fuel cells via an electrodeposition-based route

Science.gov (United States)

Park, Beom-Kyeong; Song, Rak-Hyun; Lee, Seung-Bok; Lim, Tak-Hyoung; Park, Seok-Joo; Jung, WooChul; Lee, Jong-Won

2017-04-01

Solid oxide fuel cells (SOFCs) require low-cost metallic components for current collection from electrodes as well as electrical connection between unit cells; however, the degradation of their electrical properties and surface stability associated with high-temperature oxidation is of great concern. It is thus important to develop protective conducting oxide coatings capable of mitigating the degradation of metallic components under SOFC operating conditions. Here, we report a conformal bi-layered coating composed of perovskite and spinel oxides on a metallic wire network fabricated by a facile electrodeposition-based route. A highly dense, crack-free, and adhesive bi-layered LaMnO3/Co3O4 coating of ∼1.2 μm thickness is conformally formed on the surfaces of wires with ∼100 μm diameter. We demonstrate that the bi-layered LaMnO3/Co3O4 coating plays a key role in improving the power density and durability of a tubular SOFC by stabilizing the surface of the metallic wire network used as a cathode current collector. The electrodeposition-based technique presented in this study offers a low-cost and scalable process to fabricate conformal multi-layered coatings on various metallic structures.

Flexible inverted polymer solar cells with an indium-free tri-layer cathode

International Nuclear Information System (INIS)

El Hajj, Ahmad; Lucas, Bruno; Schirr-Bonnans, Martin; Ratier, Bernard; Kraft, Thomas M.; Torchio, Philippe

2014-01-01

Indium tin oxide (ITO)-free inverted polymer solar cells (PSCs) have been fabricated without the need of an additional electron transport layer. The indium-free transparent electrode consists of a tri-layer stack ZnO (30 nm)/Ag (14 nm)/ZnO (30 nm) deposited on glass and plastic substrates via ion-beam sputtering. The tri-layer electrodes exhibit similar physical properties to its ITO counterpart, specifically yielding high transmittance and low resistivity (76.5% T at 550 nm, R sq of 8 Ω/◻) on plastic substrates. The novel tri-layer electrode allows for the fabrication of inverted PSCs without the additional ZnO interfacial layer commonly deposited between ITO and the photoactive layer. This allows for the preparation of thinner plastic solar cells using less material than conventional architectures. Initial studies involving the newly realized architecture (tri-layer electrode/P3HT:PCBM/PEDOT:PSS/Ag) have shown great promise for the transition from ITO to other viable electrodes in organic electronics

Layer-by-layer cell membrane assembly

Science.gov (United States)

Matosevic, Sandro; Paegel, Brian M.

2013-11-01

Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

Nucleosome organizations in induced pluripotent stem cells reprogrammed from somatic cells belonging to three different germ layers.

Science.gov (United States)

Tao, Yu; Zheng, Weisheng; Jiang, Yonghua; Ding, Guitao; Hou, Xinfeng; Tang, Yitao; Li, Yueying; Gao, Shuai; Chang, Gang; Zhang, Xiaobai; Liu, Wenqiang; Kou, Xiaochen; Wang, Hong; Jiang, Cizhong; Gao, Shaorong

2014-12-21

Nucleosome organization determines the chromatin state, which in turn controls gene expression or silencing. Nucleosome remodeling occurs during somatic cell reprogramming, but it is still unclear to what degree the re-established nucleosome organization of induced pluripotent stem cells (iPSCs) resembles embryonic stem cells (ESCs), and whether the iPSCs inherit some residual gene expression from the parental fibroblast cells. We generated genome-wide nucleosome maps in mouse ESCs and in iPSCs reprogrammed from somatic cells belonging to three different germ layers using a secondary reprogramming system. Pairwise comparisons showed that the nucleosome organizations in the iPSCs, regardless of the iPSCs' tissue of origin, were nearly identical to the ESCs, but distinct from mouse embryonic fibroblasts (MEF). There is a canonical nucleosome arrangement of -1, nucleosome depletion region, +1, +2, +3, and so on nucleosomes around the transcription start sites of active genes whereas only a nucleosome occupies silent transcriptional units. Transcription factor binding sites possessed characteristic nucleosomal architecture, such that their access was governed by the rotational and translational settings of the nucleosome. Interestingly, the tissue-specific genes were highly expressed only in the parental somatic cells of the corresponding iPS cell line before reprogramming, but had a similar expression level in all the resultant iPSCs and ESCs. The re-established nucleosome landscape during nuclear reprogramming provides a conserved setting for accessibility of DNA sequences in mouse pluripotent stem cells. No persistent residual expression program or nucleosome positioning of the parental somatic cells that reflected their tissue of origin was passed on to the resulting mouse iPSCs.

Programming voltage reduction in phase change memory cells with tungsten trioxide bottom heating layer/electrode

International Nuclear Information System (INIS)

Rao Feng; Song Zhitang; Gong Yuefeng; Wu Liangcai; Feng Songlin; Chen, Bomy

2008-01-01

A phase change memory cell with tungsten trioxide bottom heating layer/electrode is investigated. The crystalline tungsten trioxide heating layer promotes the temperature rise in the Ge 2 Sb 2 Te 5 layer which causes the reduction in the reset voltage compared to a conventional phase change memory cell. Theoretical thermal simulation and calculation for the reset process are applied to understand the thermal effect of the tungsten trioxide heating layer/electrode. The improvement in thermal efficiency of the PCM cell mainly originates from the low thermal conductivity of the crystalline tungsten trioxide material.

Plated copper front side metallization on printed seed-layers for silicon solar cells

OpenAIRE

Kraft, Achim

2015-01-01

A novel copper front side metallization architecture for silicon solar cells based on a fine printed silver seed-layer, plated with nickel, copper and silver, is investigated. The work focuses on the printing of fine seed-layers with low silver consumption, the corrosion of the printed seed-layers by the interaction with electrolyte solutions and the encapsulation material on module level and on the long term stability of the cells due to copper migration. The investigation of the correlation...

Device and performance parameters of Cu(In,Ga)(Se,S){sub 2}-based solar cells with varying i-ZnO layer thickness

Energy Technology Data Exchange (ETDEWEB)

Macabebe, E.Q.B. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Sheppard, C.J. [Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park 2006 (South Africa); Dyk, E.E. van, E-mail: ernest.vandyk@nmmu.ac.z [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

2009-12-01

In pursuit of low-cost and highly efficient thin film solar cells, Cu(In,Ga)(Se,S){sub 2}/CdS/i-ZnO/ZnO:Al (CIGSS) solar cells were fabricated using a two-step process. The thickness of i-ZnO layer was varied from 0 to 454 nm. The current density-voltage (J-V) characteristics of the devices were measured, and the device and performance parameters of the solar cells were obtained from the J-V curves to analyze the effect of varying i-ZnO layer thickness. The device parameters were determined using a parameter extraction method that utilized particle swarm optimization. The method is a curve-fitting routine that employed the two-diode model. The J-V curves of the solar cells were fitted with the model and the parameters were determined. Results show that as the thickness of i-ZnO was increased, the average efficiency and the fill factor (FF) of the solar cells increase. Device parameters reveal that although the series resistance increased with thicker i-ZnO layer, the solar cells absorbed more photons resulting in higher short-circuit current density (J{sub sc}) and, consequently, higher photo-generated current density (J{sub L}). For solar cells with 303-454 nm-thick i-ZnO layer, the best devices achieved efficiency between 15.24% and 15.73% and the fill factor varied between 0.65 and 0.67.

Low cost fuel cell diffusion layer configured for optimized anode water management

Science.gov (United States)

Owejan, Jon P; Nicotera, Paul D; Mench, Matthew M; Evans, Robert E

2013-08-27

A fuel cell comprises a cathode gas diffusion layer, a cathode catalyst layer, an anode gas diffusion layer, an anode catalyst layer and an electrolyte. The diffusion resistance of the anode gas diffusion layer when operated with anode fuel is higher than the diffusion resistance of the cathode gas diffusion layer. The anode gas diffusion layer may comprise filler particles having in-plane platelet geometries and be made of lower cost materials and manufacturing processes than currently available commercial carbon fiber substrates. The diffusion resistance difference between the anode gas diffusion layer and the cathode gas diffusion layer may allow for passive water balance control.

Fabrication and characterization of contact layers in amorphous silicon solar cells

International Nuclear Information System (INIS)

Kolter, M.

1993-04-01

The production and characterisation of amorphous and microcrystalline n-doped layers (a-Si:H(n) and c-Si:H(n)) for thin film solar cells is described together contact investigations. The layers were produced in a plasma CVD. The electric conductivity was measured

Reverse-feeding effect of epidemic by propagators in two-layered networks

International Nuclear Information System (INIS)

Wu Dayu; Zhao Yanping; Zheng Muhua; Zhou Jie; Liu Zonghua

2016-01-01

Epidemic spreading has been studied for a long time and is currently focused on the spreading of multiple pathogens, especially in multiplex networks. However, little attention has been paid to the case where the mutual influence between different pathogens comes from a fraction of epidemic propagators, such as bisexual people in two separated groups of heterosexual and homosexual people. We here study this topic by presenting a network model of two layers connected by impulsive links, in contrast to the persistent links in each layer. We let each layer have a distinct pathogen and their interactive infection is implemented by a fraction of propagators jumping between the corresponding pairs of nodes in the two layers. By this model we show that (i) the propagators take the key role to transmit pathogens from one layer to the other, which significantly influences the stabilized epidemics; (ii) the epidemic thresholds will be changed by the propagators; and (iii) a reverse-feeding effect can be expected when the infective rate is smaller than its threshold of isolated spreading. A theoretical analysis is presented to explain the numerical results. (paper)

Magnetooptic effects and Auger electron spectroscopy of two-layer NiFe-Dy and Fe-Dy films with nonuniform layers

International Nuclear Information System (INIS)

Ehdel'man, I.S.; Markov, V.V.; Khudyakov, A.E.; Ivantsov, R.D.; Bondarenko, G.V.; Ovchinnikov, S.G.; Kesler, V.G.; Parshin, A.S.; Ronzhin, I.P.

2001-01-01

Magneto-optical effects (magnetic circular dichroism and meridional Kerr effect) and element distribution with layer thickness in two-layer NiFe-Dy and Fe-Dy films, prepared by thermal sputtering of component in ultrahigh vacuum, are investigated. It is shown, that Dy in a two-layer film in the temperature range of 80-300 K makes constant contributions to both effects investigated which are approximately equal to the values of the effects observed in an isolated Dy film only at temperatures below the temperature T c of Dy transition into a ferromagnetic state (T c ∼ 100 K for the films under study). This behaviour of magneto-optical effects is assumed to be due to the influence of a NiFe layer spin system on magnetic state of a Dy layer, this influence is enhanced by the deep penetration of Ni and Fe ions into Dy layer as it follows from the data obtained using Auger electron spectroscopy [ru

Filaggrin 2 deficiency results in abnormal cell-cell adhesion in the cornified cell layers and causes peeling skin syndrome type A.

Science.gov (United States)

Mohamad, Janan; Sarig, Ofer; Godsel, Lisa M; Peled, Alon; Malchin, Natalia; Bochner, Ron; Vodo, Dan; Rabinowitz, Tom; Pavlovsky, Mor; Taiber, Shahar; Fried, Maya; Eskin-Schwartz, Marina; Assi, Siwar; Shomron, Noam; Uitto, Jouni; Koetsier, Jennifer L; Bergman, Reuven; Green, Kathleen J; Sprecher, Eli

2018-05-11

Peeling skin syndromes form a large and heterogeneous group of inherited disorders characterized by superficial detachment of the epidermal cornified cell layers, often associated with inflammatory features. Here we report on a consanguineous family featuring non-inflammatory peeling of the skin exacerbated by exposure to heat and mechanical stress. Whole exome sequencing revealed a homozygous nonsense mutation in FLG2, encoding filaggrin 2, which co-segregated with the disease phenotype in the family. The mutation was found to result in decreased FLG2 RNA levels as well almost total absence of filaggrin 2 in the patient epidermis. Filaggrin 2 was found to be expressed throughout the cornified cell layers and to co-localize with corneodesmosin which plays a crucial role in maintaining cell-cell adhesion in this region of the epidermis. Absence of filaggrin 2 in the patient skin was associated with markedly decreased corneodesmosin expression, which may contribute to the peeling phenotype displayed by the patients. Accordingly, using the dispase dissociation assay, we showed that FLG2 down-regulation interferes with keratinocyte cell-cell adhesion. Of particular interest, this effect was aggravated by temperature elevation, consistent with the clinical phenotype. Restoration of CDSN levels by ectopic expression rescued cell-cell adhesion.Taken together, the present data suggest that filaggrin 2 is essential for normal cell-cell adhesion in the cornified cell layers. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Nano-crystalline thin and nano-particulate thick TiO2 layer: Cost effective sequential deposition and study on dye sensitized solar cell characteristics

International Nuclear Information System (INIS)

Das, P.; Sengupta, D.; Kasinadhuni, U.; Mondal, B.; Mukherjee, K.

2015-01-01

Highlights: • Thin TiO 2 layer is deposited on conducting substrate using sol–gel based dip coating. • TiO 2 nano-particles are synthesized using hydrothermal route. • Thick TiO 2 particulate layer is deposited on prepared thin layer. • Dye sensitized solar cells are made using thin and thick layer based photo-anode. • Introduction of thin layer in particulate photo-anode improves the cell efficiency. - Abstract: A compact thin TiO 2 passivation layer is introduced between the mesoporous TiO 2 nano-particulate layer and the conducting glass substrate to prepare photo-anode for dye-sensitized solar cell (DSSC). In order to understand the effect of passivation layer, other two DSSCs are also developed separately using TiO 2 nano-particulate and compact thin film based photo-anodes. Nano-particles are prepared using hydrothermal synthesis route and the compact passivation layer is prepared by simply dip coating the precursor sol prepared through wet chemical route. The TiO 2 compact layer and the nano-particles are characterised in terms of their micro-structural features and phase formation behavior. It is found that introduction of a compact TiO 2 layer in between the mesoporous TiO 2 nano-particulate layer and the conducting substrate improves the solar to electric conversion efficiency of the fabricated cell. The dense thin passivation layer is supposed to enhance the photo-excited electron transfer and prevent the recombination of photo-excited electrons

Layer- and Cell Type-Specific Modulation of Excitatory Neuronal Activity in the Neocortex

Directory of Open Access Journals (Sweden)

Gabriele Radnikow

2018-01-01

Full Text Available From an anatomical point of view the neocortex is subdivided into up to six layers depending on the cortical area. This subdivision has been described already by Meynert and Brodmann in the late 19/early 20. century and is mainly based on cytoarchitectonic features such as the size and location of the pyramidal cell bodies. Hence, cortical lamination is originally an anatomical concept based on the distribution of excitatory neuron. However, it has become apparent in recent years that apart from the layer-specific differences in morphological features, many functional properties of neurons are also dependent on cortical layer or cell type. Such functional differences include changes in neuronal excitability and synaptic activity by neuromodulatory transmitters. Many of these neuromodulators are released from axonal afferents from subcortical brain regions while others are released intrinsically. In this review we aim to describe layer- and cell-type specific differences in the effects of neuromodulator receptors in excitatory neurons in layers 2–6 of different cortical areas. We will focus on the neuromodulator systems using adenosine, acetylcholine, dopamine, and orexin/hypocretin as examples because these neuromodulator systems show important differences in receptor type and distribution, mode of release and functional mechanisms and effects. We try to summarize how layer- and cell type-specific neuromodulation may affect synaptic signaling in cortical microcircuits.

Distribution of electrode elements near contacts and junction layers in amorphous silicon solar cell

Energy Technology Data Exchange (ETDEWEB)

Imura, T; Hiraki, A; Okamoto, H

1982-01-01

Auger electron spectroscopy with the ion sputter-etching technique and secondary ion mass spectroscopy have been utilized to investigate the depth distribution of Sn and In electrode elements in amorphous silicon layers of the photovoltaic device. The comparison of the depth profiles with the cell performances has indicated that the presence of the reduced state of In in both the p and i-layers affects the solar cell performance, but that of Sn does not. It was also shown that layered structure of In-Sn oxide (ITO)/SnO2 effectively prevents the diffusion of In and achieves high cell performances, having the thickness of the SnO2 layer about 200 A. 8 references.

A study on the dissymmetrical microporous layer structure of a direct methanol fuel cell

International Nuclear Information System (INIS)

Wang Tongtao; Lin Caishun; Fang Yong; Ye Feng; Miao Ruiying; Wang Xindong

2008-01-01

The effect of carbon type, carbon loading and microporous layer structure in the microporous layer on the performance of a direct methanol fuel cell (DMFC) at low temperature was investigated using electrochemical polarization techniques, electrochemical impedance spectroscopy, scanning electron microscope and other methods. Vulcan XC-72 carbon was found to be most suitable as a microporous layer for low temperature DMFC. Maximum fuel cell performance was obtained utilizing a microporous layer with carbon loading of 1.0 mg cm -2 when air was used as an oxidant. A membrane electrode assembly with 1.0 mg cm -2 Vulcan XC-72 carbon with 20 wt.% Teflon in the cathode and no microporous layer in the anode showed a maximum power density of 36.7 mW cm -2 at 35 deg. C under atmospheric pressure. The AC impedance study proved that a cell with a dissymmetrical microporous layer structure had lower internal resistance and mass transfer resistance, thus obtaining better performance

Anti-reflecting and passivating coatings for silicon solar cells on a basis of SO2 and TiO2 layers

International Nuclear Information System (INIS)

Taurbaev, T.I.; Nikulin, V.Eh.; Shorin, V.F.; Topanov, B.G.; Dikhanbaev, K.K.

2002-01-01

An analysis of influence of passivating layer on performance of anti-reflection coating of solar cells is carried out. The introduction of passivating SiO 2 layer between a frontal surface of the solar cell and TiO 2 +SiO 2 anti-reflection coating increase total reflection. If a thickness of a passivating layer no more than 20 Angstrom an increase of reflection does not exceed 0.5 %. However, for effective passivation the thickness of the passivating layer has to be within 100-1000 Angstrom region, thus the interference contribution of the passivating layer becomes essential and the AC is necessary to calculate as triple system SiO 2 -TiO 2 -SiO 2 . Such the three layers system ensuring average coefficient of reflection less of 3.5 % in a range 0.4-1.1 μm if the thickness of passivating SiO 2 layer no more 200 Angstrom. For solar cells with passivating SiO 2 layer thickness of 100 Angstrom and protective glass of non-interference thickness the single layer AC from TiO 2 allows to receive average value of reflection coefficient for a spectral range 0.4-1.1 μm no more than 9.5 %. The introduction of two additional layers SiO 2 and TiO 2 allows to reduce this value on 2.0-3.0 %. The comparison of calculation and experimental results is given. (author)

YKL-40 is differentially expressed in human embryonic stem cells and in cell progeny of the three germ layers.

Science.gov (United States)

Brøchner, Christian B; Johansen, Julia S; Larsen, Lars A; Bak, Mads; Mikkelsen, Hanne B; Byskov, Anne Grete; Andersen, Claus Yding; Møllgård, Kjeld

2012-03-01

The secreted glycoprotein YKL-40 participates in cell differentiation, inflammation, and cancer progression. High YKL-40 expression is reported during early human development, but its functions are unknown. Six human embryonic stem cell (hESC) lines were cultured in an atmosphere of low or high oxygen tension, in culture medium with or without basic fibroblast growth factor, and on feeder layers comprising mouse embryonic fibroblasts or human foreskin fibroblasts to evaluate whether hESCs and their progeny produced YKL-40 and to characterize YKL-40 expression during differentiation. Secreted YKL-40 protein and YKL-40 mRNA expression were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative RT-PCR. Serial-sectioned colonies were stained for YKL-40 protein and for pluripotent hESC (OCT4, NANOG) and germ layer (HNF-3β, PDX1, CD34, p63, nestin, PAX6) markers. Double-labeling showed YKL-40 expression in OCT4-positive hESCs, PAX6-positive neuroectodermal cells, and HNF-3β-positive endodermal cells. The differentiating progeny showed strong YKL-40 expression. Abrupt transition between YKL-40 and OCT4-positive hESCs and YKL-40-positive ecto- and neuroectodermal lineages was observed within the same epithelial-like layer. YKL-40-positive cells within deeper layers lacked contact with OCT4-positive cells. YKL-40 may be important in initial cell differentiation from hESCs toward ectoderm and neuroectoderm, with retained epithelial morphology, whereas later differentiation into endoderm and mesoderm involves a transition into the deeper layers of the colony.

Three-dimensional flow in electromagnetically driven shallow two-layer fluids

NARCIS (Netherlands)

Akkermans, R.A.D.; Kamp, L.P.J.; Clercx, H.J.H.; van Heijst, G.J.F.

2010-01-01

Recent experiments on a freely evolving dipolar vortex in a homogeneous shallow fluid layer have clearly shown the existence and evolution of complex three-dimensional 3D flow structures. The present contribution focuses on the 3D structures of a dipolar vortex evolving in a stable shallow two-layer

Plume Splitting in a Two-layer Stratified Ambient Fluid

Science.gov (United States)

Ma, Yongxing; Flynn, Morris; Sutherland, Bruce

2017-11-01

A line-source plume descending into a two-layer stratified ambient fluid in a finite sized tank is studied experimentally. Although the total volume of ambient fluid is fixed, lower- and upper-layer fluids are respectively removed and added at a constant rate mimicking marine outfall through diffusers and natural and hybrid ventilated buildings. The influence of the plume on the ambient depends on the value of λ, defined as the ratio of the plume buoyancy to the buoyancy loss of the plume as it crosses the ambient interface. Similar to classical filling-box experiments, the plume can always reach the bottom of the tank if λ > 1 . By contrast, if λ < 1 , an intermediate layer eventually forms as a result of plume splitting. Eventually all of the plume fluid spreads within the intermediate layer. The starting time, tv, and the ending time, tt, of the transition process measured from experiments correlate with the value of λ. A three-layer ambient fluid is observed after transition, and the mean value of the measured densities of the intermediate layer fluid is well predicted using plume theory. Acknowledgments: Funding for this study was provided by NSERC.

Solution-processed In2S3 buffer layer for chalcopyrite thin film solar cells

Science.gov (United States)

Wang, Lan; Lin, Xianzhong; Ennaoui, Ahmed; Wolf, Christian; Lux-Steiner, Martha Ch.; Klenk, Reiner

2016-02-01

We report a route to deposit In2S3 thin films from air-stable, low-cost molecular precursor inks for Cd-free buffer layers in chalcopyrite-based thin film solar cells. Different precursor compositions and processing conditions were studied to define a reproducible and robust process. By adjusting the ink properties, this method can be applied in different printing and coating techniques. Here we report on two techniques, namely spin-coating and inkjet printing. Active area efficiencies of 12.8% and 12.2% have been achieved for In2S3-buffered solar cells respectively, matching the performance of CdS-buffered cells prepared with the same batch of absorbers.

Cell clusters overlying focally disrupted mammary myoepithelial cell layers and adjacent cells within the same duct display different immunohistochemical and genetic features: implications for tumor progression and invasion

International Nuclear Information System (INIS)

Man, Yan-gao; Vinh, Tuyethoa N; Strauss, Brian L; Tai, Lisa; Barner, Ross; Vang, Russell; Saenger, Jeffrey S; Shekitka, Kris M; Bratthauer, Gary L; Wheeler, Darren T; Liang, Chang Y

2003-01-01

Our previous studies detected focal disruptions in myoepithelial cell layers of several ducts with carcinoma in situ. The cell cluster overlying each of the myoepithelial disruptions showed a marked reduction in or a total loss of immunoreactivity for the estrogen receptor (ER). This is in contrast to the adjacent cells within the same duct, which were strongly immunoreactive for the ER. The current study attempts to confirm and expand previous observations on a larger scale. Paraffin sections from 220 patients with ER-positive intraductal breast tumors were double immunostained with the same protocol previously used. Cross-sections of ducts lined by ≥ 40 epithelial cells were examined for myoepithelial cell layer disruptions and for ER expression. In five selected cases, ER-negative cells overlying the disrupted myoepithelial cell layer and adjacent ER-positive cells within the same duct were separately microdissected and assessed for loss of heterozygosity and microsatellite instability. Of the 220 cases with 5698 duct cross-sections examined, 94 showed disrupted myoepithelial cell layers with 405 focal disruptions. Of the 94 cases, 79 (84%) contained only ER-negative cell clusters, nine (9.6%) contained both ER-negative and ER-positive cell clusters, and six (6.4%) contained only ER-positive cell clusters overlying disrupted myoepithelial cell layers. Of the 405 disruptions, 350 (86.4%) were overlain by ER-negative cell clusters and 55 (13.6%) were overlain by ER-positive cell clusters (P < 0.01). Microdissected ER-negative and ER-positive cells within the same duct from all five selected cases displayed a different frequency or pattern of loss of heterozygosity and/or microsatellite instability at 10 of the 15 DNA markers. Cells overlying focally disrupted myoepithelial layers and their adjacent counterparts within the same duct displayed different immunohistochemical and molecular features. These features potentially represent an early sign of the formation

Additively Manufactured Open-Cell Porous Biomaterials Made from Six Different Space-Filling Unit Cells: The Mechanical and Morphological Properties

Directory of Open Access Journals (Sweden)

Seyed Mohammad Ahmadi

2015-04-01

Full Text Available It is known that the mechanical properties of bone-mimicking porous biomaterials are a function of the morphological properties of the porous structure, including the configuration and size of the repeating unit cell from which they are made. However, the literature on this topic is limited, primarily because of the challenge in fabricating porous biomaterials with arbitrarily complex morphological designs. In the present work, we studied the relationship between relative density (RD of porous Ti6Al4V EFI alloy and five compressive properties of the material, namely elastic gradient or modulus (Es20–70, first maximum stress, plateau stress, yield stress, and energy absorption. Porous structures with different RD and six different unit cell configurations (cubic (C, diamond (D, truncated cube (TC, truncated cuboctahedron (TCO, rhombic dodecahedron (RD, and rhombicuboctahedron (RCO were fabricated using selective laser melting. Each of the compressive properties increased with increase in RD, the relationship being of a power law type. Clear trends were seen in the influence of unit cell configuration and porosity on each of the compressive properties. For example, in terms of Es20–70, the structures may be divided into two groups: those that are stiff (comprising those made using C, TC, TCO, and RCO unit cell and those that are compliant (comprising those made using D and RD unit cell.

Mitigation of Unwanted Forward Narrow-band Radiation from PCBs with a Metamaterial Unit Cell

DEFF Research Database (Denmark)

Ruaro, Andrea; Thaysen, Jesper; Jakobsen, Kaj Bjarne

2013-01-01

Mitigation of EMI from a PCB is obtained through the use of a metamaterial unit cell. The focus is on the reduction of narrow-band radiation in the forward hemisphere when the resonant element is etched on a layer located between the source of radiation and the ground plane. As opposed to previous...... publications in the literature, the aim of this work is the application of a filter to scattered radiation, generalizing the former characterizations based solely upon transmission lines’ insertion loss. The radiating area accounts for traces and components placed on the top layer of a PCB and is simulated via...... a patch antenna. The study exhibits how the radiation pattern and the electric field on the patch antenna change within and outside the resonance bandwidth of the parasitic element. An EMC assessment provides experimental verification of the operating principle....

Comparison of two detection methods in thin layer chromatographic ...

African Journals Online (AJOL)

o-tolidine plus potassium iodide and photosynthesis inhibition detection methods were investigated for the analysis of three triazine herbicides (atrazine, ametryne, simazine) and two urea herbicides (diuron, metobromuron) in a coastal savanna soil using thin layer chromatography to compare the suitability of the two ...

Unit cell geometry of 3-D braided structures

Science.gov (United States)

Du, Guang-Wu; Ko, Frank K.

1993-01-01

The traditional approach used in modeling of composites reinforced by three-dimensional (3-D) braids is to assume a simple unit cell geometry of a 3-D braided structure with known fiber volume fraction and orientation. In this article, we first examine 3-D braiding methods in the light of braid structures, followed by the development of geometric models for 3-D braids using a unit cell approach. The unit cell geometry of 3-D braids is identified and the relationship of structural parameters such as yarn orientation angle and fiber volume fraction with the key processing parameters established. The limiting geometry has been computed by establishing the point at which yarns jam against each other. Using this factor makes it possible to identify the complete range of allowable geometric arrangements for 3-D braided preforms. This identified unit cell geometry can be translated to mechanical models which relate the geometrical properties of fabric preforms to the mechanical responses of composite systems.

Pluripotency factors in embryonic stem cells regulate differentiation into germ layers.

Science.gov (United States)

Thomson, Matt; Liu, Siyuan John; Zou, Ling-Nan; Smith, Zack; Meissner, Alexander; Ramanathan, Sharad

2011-06-10

Cell fate decisions are fundamental for development, but we do not know how transcriptional networks reorganize during the transition from a pluripotent to a differentiated cell state. Here, we asked how mouse embryonic stem cells (ESCs) leave the pluripotent state and choose between germ layer fates. By analyzing the dynamics of the transcriptional circuit that maintains pluripotency, we found that Oct4 and Sox2, proteins that maintain ESC identity, also orchestrate germ layer fate selection. Oct4 suppresses neural ectodermal differentiation and promotes mesendodermal differentiation; Sox2 inhibits mesendodermal differentiation and promotes neural ectodermal differentiation. Differentiation signals continuously and asymmetrically modulate Oct4 and Sox2 protein levels, altering their binding pattern in the genome, and leading to cell fate choice. The same factors that maintain pluripotency thus also integrate external signals and control lineage selection. Our study provides a framework for understanding how complex transcription factor networks control cell fate decisions in progenitor cells. Copyright © 2011 Elsevier Inc. All rights reserved.

Electrochemical Characterization of TiO 2 Blocking Layers for Dye-Sensitized Solar Cells

KAUST Repository

Kavan, Ladislav; Té treault, Nicolas; Moehl, Thomas; Grä tzel, Michael

2014-01-01

Thin compact layers of TiO2 are grown by thermal oxidation of Ti, by spray pyrolysis, by electrochemical deposition, and by atomic layer deposition. These layers are used in dye-sensitized solar cells to prevent recombination of electrons from

Inter-layer Cooper pairing of two-dimensional electrons

International Nuclear Information System (INIS)

Inoue, Masahiro; Takemori, Tadashi; Yoshizaki, Ryozo; Sakudo, Tunetaro; Ohtaka, Kazuo

1987-01-01

The authors point out the possibility that the high transition temperatures of the recently discovered oxide superconductors are dominantly caused by the inter-layer Cooper pairing of two-dimensional electrons that are coupled through the exchange of three-dimensional phonons. (author)

Free surface simulation of a two-layer fluid by boundary element method

Directory of Open Access Journals (Sweden)

Weoncheol Koo

2010-09-01

Full Text Available A two-layer fluid with free surface is simulated in the time domain by a two-dimensional potential-based Numerical Wave Tank (NWT. The developed NWT is based on the boundary element method and a leap-frog time integration scheme. A whole domain scheme including interaction terms between two layers is applied to solve the boundary integral equation. The time histories of surface elevations on both fluid layers in the respective wave modes are verified with analytic results. The amplitude ratios of upper to lower elevation for various density ratios and water depths are also compared.

Improvement in IBC-silicon solar cell performance by insertion of highly doped crystalline layer at heterojunction interfaces

International Nuclear Information System (INIS)

Bashiri, Hadi; Azim Karami, Mohammad; Mohammadnejad, Shahramm

2017-01-01

By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact (IBC) silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters (doping concentration and thickness) is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of 2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si:H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density. (paper)

New approaches for the analysis of confluent cell layers with quantitative phase digital holographic microscopy

Science.gov (United States)

Pohl, L.; Kaiser, M.; Ketelhut, S.; Pereira, S.; Goycoolea, F.; Kemper, Björn

2016-03-01

Digital holographic microscopy (DHM) enables high resolution non-destructive inspection of technical surfaces and minimally-invasive label-free live cell imaging. However, the analysis of confluent cell layers represents a challenge as quantitative DHM phase images in this case do not provide sufficient information for image segmentation, determination of the cellular dry mass or calculation of the cell thickness. We present novel strategies for the analysis of confluent cell layers with quantitative DHM phase contrast utilizing a histogram based-evaluation procedure. The applicability of our approach is illustrated by quantification of drug induced cell morphology changes and it is shown that the method is capable to quantify reliable global morphology changes of confluent cell layers.

Intra- and inter-layer charge redistribution in biased bilayer graphene

Directory of Open Access Journals (Sweden)

Rui-Ning Wang

2016-03-01

Full Text Available We investigate the spatial redistribution of the electron density in bilayer graphene in the presence of an interlayer bias within density functional theory. It is found that the interlayer charge redistribution is inhomogeneous between the upper and bottom layers and the transferred charge from the upper layer to the bottom layer linearly increases with the external voltage which further makes the gap at K point linearly increase. However, the band gap will saturate to 0.29 eV in the strong-field regime, but it displays a linear field dependence at the weak-field limit. Due to the AB-stacked way, two carbon atoms per unit cell in the same layer are different and there is also a charge transfer between them, making the widths of π valence bands reduced. In the bottom layer, the charge transfers from the direct atoms which directly face another carbon atom to the indirect atoms facing the center of the hexagon on the opposite layer, while the charge transfers from the indirect atoms to the direct atoms in the upper layer. Furthermore, there is a diploe between the upper and bottom layers which results in the reduction of the interlayer hopping interaction.

Thin Cell Layer technology in ornamental plant micropropagation ...

African Journals Online (AJOL)

Thin cell layer (TCL) technology originated almost 30 years ago with the controlled development of flowers, roots, shoots and somatic embryos on tobacco pedicel longitudinal TCLs. Since then TCLs have been successfully used in the micropropagation of many ornamental plant species whose previous in vitro ...

Spatial Atmospheric Pressure Atomic Layer Deposition of Tin Oxide as an Impermeable Electron Extraction Layer for Perovskite Solar Cells with Enhanced Thermal Stability.

Science.gov (United States)

Hoffmann, Lukas; Brinkmann, Kai O; Malerczyk, Jessica; Rogalla, Detlef; Becker, Tim; Theirich, Detlef; Shutsko, Ivan; Görrn, Patrick; Riedl, Thomas

2018-02-14

Despite the notable success of hybrid halide perovskite-based solar cells, their long-term stability is still a key-issue. Aside from optimizing the photoactive perovskite, the cell design states a powerful lever to improve stability under various stress conditions. Dedicated electrically conductive diffusion barriers inside the cell stack, that counteract the ingress of moisture and prevent the migration of corrosive halogen species, can substantially improve ambient and thermal stability. Although atomic layer deposition (ALD) is excellently suited to prepare such functional layers, ALD suffers from the requirement of vacuum and only allows for a very limited throughput. Here, we demonstrate for the first time spatial ALD-grown SnO x at atmospheric pressure as impermeable electron extraction layers for perovskite solar cells. We achieve optical transmittance and electrical conductivity similar to those in SnO x grown by conventional vacuum-based ALD. A low deposition temperature of 80 °C and a high substrate speed of 2.4 m min -1 yield SnO x layers with a low water vapor transmission rate of ∼10 -4 gm -2 day -1 (at 60 °C/60% RH). Thereby, in perovskite solar cells, dense hybrid Al:ZnO/SnO x electron extraction layers are created that are the key for stable cell characteristics beyond 1000 h in ambient air and over 3000 h at 60 °C. Most notably, our work of introducing spatial ALD at atmospheric pressure paves the way to the future roll-to-roll manufacturing of stable perovskite solar cells.

Multifunctional MgO Layer in Perovskite Solar Cells.

Science.gov (United States)

Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

2015-06-08

A multifunctional magnesium oxide (MgO) layer was successfully introduced into perovskite solar cells (PSCs) to enhance their performance. MgO was coated onto the surface of mesoporous TiO(2) by the decomposition of magnesium acetate and, therefore, could block contact between the perovskite and TiO(2). X-ray photoelectron spectroscopy and infrared spectroscopy showed that the amount of H(2)O/hydroxyl absorbed on the TiO(2) decreased after MgO modification. The UV/Vis absorption spectra of the perovskite with MgO modification revealed an enhanced photoelectric performance compared with that of unmodified perovskite after UV illumination. In addition to the photocurrent, the photovoltage and fill factor also showed an enhancement after modification, which resulted in an increase in the overall efficiency of the cell from 9.6 to 13.9 %. Electrochemical impedance spectroscopy (EIS) confirmed that MgO acts as an insulating layer to reduce charge recombination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solution-Processed rGO/AgNPs/rGO Sandwich Structure as a Hole Extraction Layer for Polymer Solar Cells

Directory of Open Access Journals (Sweden)

Quang Trung Tran

2015-01-01

Full Text Available We found that inserting silver nanoparticles (AgNPs between two layers of reduced grapheme oxide (rGO has an effect on tailoring the work function of rGO. The utilization of rGO/AgNPs/rGO sandwich structure as the hole extraction layer in polymer solar cells is demonstrated. Solution-processable fabrication of this sandwich structure at the ITO/active layer interface facilitates the extraction of hole from active layer into ITO anode because of lowering the barrier level alignment at the interface. It results in an improvement of the short circuit current density and the overall photovoltaic performance.

Structure optimization of cathode microporous layer for direct methanol fuel cells

International Nuclear Information System (INIS)

Liu, Guicheng; Ding, Xianan; Zhou, Hongwei; Chen, Ming; Wang, Manxiang; Zhao, Zhenxuan; Yin, Zhuang; Wang, Xindong

2015-01-01

Highlights: • Pore-forming technology was introduced to optimize microporous layer microstructure. • The water removal and gas mass transfer property of diffusion layer were improved. • The optimum DMFC performance reached 292 mW cm −2 at 80 °C. - Abstract: To obtain the cathode microporous layer (CML) with high mass transfer performance and high electronic conductivity, a pore-forming technology was introduced to optimize CML microstructure for direct methanol fuel cells. In this paper, the effects of carbon material type, carbon material loading and pore-forming agent loading in CML on fuel cell performance were discussed systematically. The results indicated that the optimized CML consisted of carbon nanotubes and ammonium oxalate with the loading of 1.5 and 3.5 mg cm −2 respectively. The fuel cell performance was improved by 30.3%, from 224 to 292 mW cm −2 at 80 °C under 0.3 MPa O 2 . Carbon nanotube was found to be the most suitable carbon material for the CML due to its great specific surface area and small particle size, resulting in increasing the number of the hydrophobic sites and the contact area between the support and the catalyst layer. The carbon material and pore-forming agent loading directly influenced the pore distribution and the contact resistance of membrane electrode assembly. The water removal capacity and the gas mass transfer property of diffusion layer were improved by optimizing the amount of micropore and macropore structures

Reverse-feeding effect of epidemic by propagators in two-layered networks

Science.gov (United States)

Dayu, Wu; Yanping, Zhao; Muhua, Zheng; Jie, Zhou; Zonghua, Liu

2016-02-01

Epidemic spreading has been studied for a long time and is currently focused on the spreading of multiple pathogens, especially in multiplex networks. However, little attention has been paid to the case where the mutual influence between different pathogens comes from a fraction of epidemic propagators, such as bisexual people in two separated groups of heterosexual and homosexual people. We here study this topic by presenting a network model of two layers connected by impulsive links, in contrast to the persistent links in each layer. We let each layer have a distinct pathogen and their interactive infection is implemented by a fraction of propagators jumping between the corresponding pairs of nodes in the two layers. By this model we show that (i) the propagators take the key role to transmit pathogens from one layer to the other, which significantly influences the stabilized epidemics; (ii) the epidemic thresholds will be changed by the propagators; and (iii) a reverse-feeding effect can be expected when the infective rate is smaller than its threshold of isolated spreading. A theoretical analysis is presented to explain the numerical results. Project supported by the National Natural Science Foundation of China (Grant Nos. 11135001, 11375066, and 11405059) and the National Basic Key Program of China (Grant No. 2013CB834100).

Direct force-reflecting two-layer approach for passive bilateral teleoperation with time delays

NARCIS (Netherlands)

Heck, D.; Saccon, A.; Beerens, R.; Nijmeijer, H.

2018-01-01

We propose a two-layer control architecture for bilateral teleoperation with communication delays. The controller is structured with an (inner) performance layer and an (outer) passivity layer. In the performance layer, any traditional controller for bilateral teleoperation can be implemented. The

Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers

Science.gov (United States)

Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

2015-02-01

Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers.

Science.gov (United States)

Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

2015-02-18

Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

Temperature-dependent layer breathing modes in two-dimensional materials

Science.gov (United States)

Maity, Indrajit; Maiti, Prabal K.; Jain, Manish

2018-04-01

Relative out-of-plane displacements of the constituent layers of two-dimensional materials give rise to unique low-frequency breathing modes. By computing the height-height correlation functions from molecular dynamics simulations, we show that the layer breathing modes (LBMs) can be mapped consistently to vibrations of a simple linear chain model. Our calculated thickness dependence of LBM frequencies for few-layer (FL) graphene and molybdenum disulfide (MoS2) are in excellent agreement with available experiments. Our results show a redshift of LBM frequency with an increase in temperature, which is a direct consequence of anharmonicities present in the interlayer interaction. We also predict the thickness and temperature dependence of LBM frequencies for FL hexagonal boron nitride. Our Rapid Communication provides a simple and efficient way to probe the interlayer interaction for layered materials and their heterostructures with the inclusion of anharmonic effects.

The double layers in the plasma sheet boundary layer during magnetic reconnection

Science.gov (United States)

Guo, J.; Yu, B.

2014-11-01

We studied the evolutions of double layers which appear after the magnetic reconnection through two-dimensional electromagnetic particle-in-cell simulation. The simulation results show that the double layers are formed in the plasma sheet boundary layer after magnetic reconnection. At first, the double layers which have unipolar structures are formed. And then the double layers turn into bipolar structures, which will couple with another new weak bipolar structure. Thus a new double layer or tripolar structure comes into being. The double layers found in our work are about several ten Debye lengths, which accords with the observation results. It is suggested that the electron beam formed during the magnetic reconnection is responsible for the production of the double layers.

Effect of Mesostructured Layer upon Crystalline Properties and Device Performance on Perovskite Solar Cells.

Science.gov (United States)

Listorti, Andrea; Juarez-Perez, Emilio J; Frontera, Carlos; Roiati, Vittoria; Garcia-Andrade, Laura; Colella, Silvia; Rizzo, Aurora; Ortiz, Pablo; Mora-Sero, Ivan

2015-05-07

One of the most fascinating characteristics of perovskite solar cells (PSCs) is the retrieved obtainment of outstanding photovoltaic (PV) performances withstanding important device configuration variations. Here we have analyzed CH3NH3PbI3-xClx in planar or in mesostructured (MS) configurations, employing both titania and alumina scaffolds, fully infiltrated with perovskite material or presenting an overstanding layer. The use of the MS scaffold induces to the perovskite different structural properties, in terms of grain size, preferential orientation, and unit cell volume, in comparison to the ones of the material grown with no constraints, as we have found out by X-ray diffraction analyses. We have studied the effect of the PSC configuration on photoinduced absorption and time-resolved photoluminescence, complementary techniques that allow studying charge photogeneration and recombination. We have estimated electron diffusion length in the considered configurations observing a decrease when the material is confined in the MS scaffold with respect to a planar architecture. However, the presence of perovskite overlayer allows an overall recovering of long diffusion lengths explaining the record PV performances obtained with a device configuration bearing both the mesostructure and a perovskite overlayer. Our results suggest that performance in devices with perovskite overlayer is mainly ruled by the overlayer, whereas the mesoporous layer influences the contact properties.

Using stochastic cell division and death to probe minimal units of cellular replication

Science.gov (United States)

Chib, Savita; Das, Suman; Venkatesan, Soumya; Sai Narain Seshasayee, Aswin; Thattai, Mukund

2018-03-01

The invariant cell initiation mass measured in bacterial growth experiments has been interpreted as a minimal unit of cellular replication. Here we argue that the existence of such minimal units induces a coupling between the rates of stochastic cell division and death. To probe this coupling we tracked live and dead cells in Escherichia coli populations treated with a ribosome-targeting antibiotic. We find that the growth exponent from macroscopic cell growth or decay measurements can be represented as the difference of microscopic first-order cell division and death rates. The boundary between cell growth and decay, at which the number of live cells remains constant over time, occurs at the minimal inhibitory concentration (MIC) of the antibiotic. This state appears macroscopically static but is microscopically dynamic: division and death rates exactly cancel at MIC but each is remarkably high, reaching 60% of the antibiotic-free division rate. A stochastic model of cells as collections of minimal replicating units we term ‘widgets’ reproduces both steady-state and transient features of our experiments. Sub-cellular fluctuations of widget numbers stochastically drive each new daughter cell to one of two alternate fates, division or death. First-order division or death rates emerge as eigenvalues of a stationary Markov process, and can be expressed in terms of the widget’s molecular properties. High division and death rates at MIC arise due to low mean and high relative fluctuations of widget number. Isolating cells at the threshold of irreversible death might allow molecular characterization of this minimal replication unit.

Low-dimensional analysis, using POD, for two mixing layer-wake interactions

International Nuclear Information System (INIS)

Braud, Caroline; Heitz, Dominique; Arroyo, Georges; Perret, Laurent; Delville, Joeel; Bonnet, Jean-Paul

2004-01-01

The mixing layer-wake interaction is studied experimentally in the framework of two flow configurations. For the first one, the initial conditions of the mixing layer are modified by using a thick trailing edge, a wake effect is therefore superimposed to the mixing layer from its beginning (blunt trailing edge). In the second flow configuration, a canonical mixing layer is perturbed in its asymptotic region by the wake of a cylinder arranged perpendicular to the plane of the mixing layer. These interactions are analyzed mainly by using two-point velocity correlations and the proper orthogonal decomposition (POD). These two flow configurations differ by the degree of complexity they involve: the former is mainly 2D while the latter is highly 3D. The blunt trailing edge configuration is analyzed by using rakes of hot wire probes. This flow configuration is found to be considerably different when compared to a conventional mixing layer. It appears in particular that the scale of the large structures depends only on the trailing edge thickness and does not grow in its downstream evolution. A criterion, based on POD, is proposed in order to separate wake-mixing layer dominant areas of the downstream evolution of the flow. The complex 3D dynamical behaviour resulting from the interaction between the canonical plane mixing layer and the wake of a cylinder is investigated using data arising from particle image velocimetry measurements. An analysis of the velocity correlations shows different length scales in the regions dominated by wake like structures and shear layer type structures. In order to characterize the particular organization in the plane of symmetry, a POD-Galerkin projection of the Navier-Stokes equations is performed in this plane. This leads to a low-dimensional dynamical system that allows the analysis of the relationship between the dominant frequencies to be performed. A reconstruction of the dominant periodic motion suspected from previous studies is

Reduction of bonding resistance of two-terminal III-V/Si tandem solar cells fabricated using smart-stack technology

Science.gov (United States)

Baba, Masaaki; Makita, Kikuo; Mizuno, Hidenori; Takato, Hidetaka; Sugaya, Takeyoshi; Yamada, Noboru

2017-12-01

This paper describes a method that remarkably reduces the bonding resistance of mechanically stacked two-terminal GaAs/Si and InGaP/Si tandem solar cells, where the top and bottom cells are bonded using a Pd nanoparticle array. A transparent conductive oxide (TCO) layer, which partially covers the surface of the Si bottom cell below the electrodes of the III-V top cell, significantly enhances the fill factor (FF) and cell conversion efficiency. The partial TCO layer reduces the bonding resistance and thus, increases the FF and efficiency of InGaP/Si by factors of 1.20 and 1.11, respectively. Eventually, the efficiency exceeds 15%. Minimizing the optical losses at the bonding interfaces of the TCO layer is important in the fabrication of high-efficiency solar cells. To help facilitate this, the optical losses in the tandem solar cells are thoroughly characterized through optical simulations and experimental verifications.

Label-free electrochemical aptasensor constructed by layer-by-layer technology for sensitive and selective detection of cancer cells.

Science.gov (United States)

Wang, Tianshu; Liu, Jiyang; Gu, Xiaoxiao; Li, Dan; Wang, Jin; Wang, Erkang

2015-07-02

Here, a cytosensor was constructed with ferrocene-appended poly(allylamine hydrochloride) (Fc-PAH) functionalized graphene (Fc-PAH-G), poly(sodium-p-styrenesulfonate) (PSS) and aptamer (AS1411) by layer-by-layer assembly technology. The hybrid nanocomposite Fc-PAH-G not only brings probes on the electrode and also promotes electron transfer between the probes and the substrate electrode. Meanwhile, LBL technology provides more effective probes to enhance amplified signal for improving the sensitivity of the detection. While AS1411 forming G-quardruplex structure and binding cancer cells, the current response of the sensing electrode decreased due to the insulating properties of cellular membrane. Differential pulse voltammetry (DPV) was performed to investigate the electrochemical detection of HeLa cells attributing to its sensitivity of the current signal change. The as-prepared aptasensor showed a high sensitivity and good stability, a widely detection range from 10 to 10(6) cells/mL with a detection limit as low as 10 cells/mL for the detection of cancer cells. Copyright © 2015. Published by Elsevier B.V.

Preparation, structures and magnetic properties of Dy/Zr and Ho/Zr two-layers and multi-layers

International Nuclear Information System (INIS)

Luche, M.C.

1993-01-01

The first part of the report is devoted to the description of the ultra-vacuum evaporation equipment, to the sample preparation conditions and to the characterization of the two-layers and multi-layers through reflection and glancing incidence X diffraction and transmission electron microscopy. In the second part, the magnetic properties of the samples are studied and relations between properties and structures are examined. 37 fig., 35 ref

Neocortical layers I and II of the hedgehog (Erinaceus europaeus). I. Intrinsic organization.

Science.gov (United States)

Valverde, F; Facal-Valverde, M V

1986-01-01

The intrinsic organization and interlaminar connections in neocortical layers I and II have been studied in adult hedgehogs (Erinaceus europaeus) using the Golgi method. Layer I contains a dense plexus of horizontal fibers, the terminal dendritic bouquets of pyramidal cells of layer II and of underlying layers, and varieties of intrinsic neurons. Four main types of cells were found in layer I. Small horizontal cells represent most probably persisting foetal horizontal cells described for other mammals. Large horizontal cells, tufted cells, and spinous horizontal cells were also found in this layer. Layer II contains primitive pyramidal cells representing the most outstanding feature of the neocortex of the hedgehog. Most pyramidal cells in layer II have two, three or more apical dendrites, richly covered by spines predominating over the basal dendrites. These cells resemble pyramidal cells found in the piriform cortex, hippocampus and other olfactory areas. It is suggested that the presence of these neurons reflects the retention of a primitive character in neocortical evolution. Cells with intrinsic axons were found among pyramidal cells in layer II. These have smooth dendrites penetrating layer I and local axons forming extremely complex terminal arborizations around the bodies and proximal dendritic portions of pyramidal cells. They most probably effect numerous axo-somatic contacts resembling basket cells. The similarity of some axonal terminals with the chandelier type of axonal arborization is discussed. Other varieties of cells located in deep cortical layers and having ascending axons for layers I and II were also studied. It is concluded that the two first neocortical layers represent a level of important integration in this primitive mammal.

Modeling and performance analysis dataset of a CIGS solar cell with ZnS buffer layer

Directory of Open Access Journals (Sweden)

Md. Billal Hosen

2017-10-01

Full Text Available This article represents the baseline data of the several semiconductor materials used in the model of a CIGS thin film solar cell with an inclusion of ZnS buffer layer. As well, input parameters, contact layer data and operating conditions for CIGS solar cell simulation with ZnS buffer layer have been described. The schematic diagram of photovoltaic solar cell has been depicted. Moreover, the most important performance measurement graph, J-V characteristic curve, resulting from CIGS solar cell simulation has been analyzed to estimate the optimum values of fill factor and cell efficiency. These optimum results have been obtained from the open circuit voltage, short circuit current density, and the maximum points of voltage and current density generated from the cell.

Layer-by-layer self-assembled two-dimensional MXene/layered double hydroxide composites as cathode for alkaline hybrid batteries

Science.gov (United States)

Dong, Xiaowan; Zhang, Yadi; Ding, Bing; Hao, Xiaodong; Dou, Hui; Zhang, Xiaogang

2018-06-01

Multifarious layered materials have received extensive concern in the field of energy storage due to their distinctive two-dimensional (2D) structure. However, the natural tendency to be re-superimposed and the inherent disadvantages of a single 2D material significantly limit their performance. In this work, the delaminated Ti3C2Tx (d-Ti3C2Tx)/cobalt-aluminum layered double hydroxide (Ti3C2Tx/CoAl-LDH) composites are prepared by layer-by-layer self-assembly driven by electrostatic interaction. The alternate Ti3C2Tx and CoAl-LDH layers prevent each other from restacking and the obtained Ti3C2Tx/CoAl-LDH heterostructure combine the advantages of high electron conductivity of Ti3C2Tx and high electrochemical activity of CoAl-LDH, thus effectively improving the electrochemical reactivity of electrode materials and accelerating the kinetics of Faraday reaction. As a consequence, as a cathode for alkaline hybrid battery, the Ti3C2Tx/CoAl-LDH electrode exhibits a high specific capacity of 106 mAh g-1 at a current density of 0.5 A g-1 and excellent rate capability (78% at 10 A g-1), with an excellent cycling stability of 90% retention after 5000 cycles at 4 A g-1. This work provides an alternative route to design advanced 2D electrode materials, thus exploiting their full potentials for alkaline hybrid batteries.

Atmospheric spatial atomic layer deposition of Zn(O,S) buffer layer for Cu(In,Ga)Se2 solar cells

NARCIS (Netherlands)

Frijters, C.H.; Poodt, P.; Illeberi, A.

2016-01-01

Zinc oxysulfide has been grown by spatial atomic layer deposition (S-ALD) and successfully applied as buffer layer in Cu(In, Ga)Se2 (CIGS) solar cells. S-ALD combines high deposition rates (up to nm/s) with the advantages of conventional ALD, i.e. excellent control of film composition and superior

Fabrication of dye sensitized solar cells with a double layer photoanode

Directory of Open Access Journals (Sweden)

M. Pirhadi

2016-01-01

Full Text Available Dye sensitized solar cell was fabricated from a double layer photoanode. First, TiO2 nanoparticles  were synthesized by hydrothermal method. These TiO2 NPs were deposited on FTO glasses by electrophoretic deposition  method in applied voltage of 5 V and EPD time of 2.5-10 min. Then TiO2 hollow spheres (HSs were synthesized by sacrificed template method with Carbon Spheres as template and TTIP as precursor. Then these template scarified and the hollow structures found. Since the HSs paste was prepared as same method of prepared TiO2 nano particles and this paste was deposited on last layer by Dr. Blade method. The prepared photoanodes was soaped in N-719 dye after sintering in 500 ÚC. The dye sensitized solar cells  were fabricated with the finalized double layer photoanodes. The best photovoltaic characteristics of the optimized cell were 734 mV, 13.16 mA/cm2, 62% and 5.96% for Voc, Jsc, F.F. and efficiency respectively.

Solution-processed In2S3 buffer layer for chalcopyrite thin film solar cells

Directory of Open Access Journals (Sweden)

Wang Lan

2016-01-01

Full Text Available We report a route to deposit In2S3 thin films from air-stable, low-cost molecular precursor inks for Cd-free buffer layers in chalcopyrite-based thin film solar cells. Different precursor compositions and processing conditions were studied to define a reproducible and robust process. By adjusting the ink properties, this method can be applied in different printing and coating techniques. Here we report on two techniques, namely spin-coating and inkjet printing. Active area efficiencies of 12.8% and 12.2% have been achieved for In2S3-buffered solar cells respectively, matching the performance of CdS-buffered cells prepared with the same batch of absorbers.

A Novel, Diazonium-Phenolic Resin Two-Layer Resist System Utilizing Photoinduced Interfacial Insolubilization

Science.gov (United States)

Uchino, Shou-ichi; Iwayanagi, Takao; Ueno, Takumi; Hashimoto, Michiaki; Nonogaki, Saburo

1987-08-01

This paper deals with a negative two-layer photoresist system utilizing a photoinduced insolubilization process at the interface. The bottom layer is a phenolic resin either with or without aromatic azide and the top layer is a photosensitive layer comprised of an aromatic diazonium compound and a water soluble polymer. Upon exposure to light, the diazo compound decomposes to cause insolubilization at the interface between the two layers. The system exhibits high contrast due to the combination of interfacial insolubilization and contrast enhancement by photobleaching of the diazonium compound. Patterns of 0.5 um lines and spaces are obtained using an i-line stepper and a resist system containing 4-diazo-N,N-dimethylaniline chloride zinc chloride in the top layer and 3-(4-azidostyry1)- 5,5-dimethyl- 2-cyclohexen-1-one in the bottom layer. Resists with varying spectral responses from mid-UV to g-line can be designed by selecting the kind of diazo compound used in the top layer.

Particle-bearing currents in uniform density and two-layer fluids

Science.gov (United States)

Sutherland, Bruce R.; Gingras, Murray K.; Knudson, Calla; Steverango, Luke; Surma, Christopher

2018-02-01

Lock-release gravity current experiments are performed to examine the evolution of a particle bearing flow that propagates either in a uniform-density fluid or in a two-layer fluid. In all cases, the current is composed of fresh water plus micrometer-scale particles, the ambient fluid is saline, and the current advances initially either over the surface as a hypopycnal current or at the interface of the two-layer fluid as a mesopycnal current. In most cases the tank is tilted so that the ambient fluid becomes deeper with distance from the lock. For hypopycnal currents advancing in a uniform density fluid, the current typically slows as particles rain out of the current. While the loss of particles alone from the current should increase the current's buoyancy and speed, in practice the current's speed decreases because the particles carry with them interstitial fluid from the current. Meanwhile, rather than settling on the sloping bottom of the tank, the particles form a hyperpycnal (turbidity) current that advances until enough particles rain out that the relatively less dense interstitial fluid returns to the surface, carrying some particles back upward. When a hypopycnal current runs over the surface of a two-layer fluid, the particles that rain out temporarily halt their descent as they reach the interface, eventually passing through it and again forming a hyperpycnal current. Dramatically, a mesopycnal current in a two-layer fluid first advances along the interface and then reverses direction as particles rain out below and fresh interstitial fluid rises above.

Diffusion of single Au, Ag and Cu atoms inside Si(111)-(7 × 7) half unit cells: A comparative study

Energy Technology Data Exchange (ETDEWEB)

Liu, Qin [Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055 (China); Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong (China); Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang, Sichuan 621908 (China); Fu, Qiang [Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Zum Großen Windkanal 6, 12489 Berlin (Germany); Shao, Xiji; Ma, Xuhang; Wu, Xuefeng [Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055 (China); Wang, Kedong, E-mail: wangkd@sustc.edu.cn [Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055 (China); Xiao, Xudong, E-mail: xdxiao@phy.cuhk.edu.hk [Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong (China)

2017-04-15

Highlights: • Diffusions of Au, Ag and Cu atoms in the half unit cells of Si(111)-(7×7) have been studied by using a STM-based I-t method. • Despite their similar absorption sites, the diffusion dynamics show obvious differences between Ag and the other two. • Theoretical calculations suggest that different potential energy profiles are responsible for the observed differences. - Abstract: The diffusion behaviors of single Au, Ag and Cu atoms on Si(111)-(7 × 7) half unit cells have been investigated via combining scanning tunneling microscopy and first-principles calculations. Despite the similar adsorption sites between both half unit cells among these elements, the diffusion dynamics show obvious differences between Ag and the other two. Although obvious asymmetry has been found in the diffusion behaviors of Au and Cu atoms in two half unit cells of Si(111)-(7 × 7), the asymmetry behaves in a way different from that of Ag atoms and no dual-time character has been observed for the diffusions of Au and Cu in both half unit cells. Theoretical calculations suggest a different potential energy profile caused by the stronger hybridization between d states of Au (Cu) and Si states make the concept of basin useless for the diffusion of Au and Cu atoms inside the half unit cells of Si(111)-(7 × 7).

Low-Temperature Process for Atomic Layer Chemical Vapor Deposition of an Al2O3 Passivation Layer for Organic Photovoltaic Cells.

Science.gov (United States)

Kim, Hoonbae; Lee, Jihye; Sohn, Sunyoung; Jung, Donggeun

2016-05-01

Flexible organic photovoltaic (OPV) cells have drawn extensive attention due to their light weight, cost efficiency, portability, and so on. However, OPV cells degrade quickly due to organic damage by water vapor or oxygen penetration when the devices are driven in the atmosphere without a passivation layer. In order to prevent damage due to water vapor or oxygen permeation into the devices, passivation layers have been introduced through methods such as sputtering, plasma enhanced chemical vapor deposition, and atomic layer chemical vapor deposition (ALCVD). In this work, the structural and chemical properties of Al2O3 films, deposited via ALCVD at relatively low temperatures of 109 degrees C, 200 degrees C, and 300 degrees C, are analyzed. In our experiment, trimethylaluminum (TMA) and H2O were used as precursors for Al2O3 film deposition via ALCVD. All of the Al2O3 films showed very smooth, featureless surfaces without notable defects. However, we found that the plastic flexible substrate of an OPV device passivated with 300 degrees C deposition temperature was partially bended and melted, indicating that passivation layers for OPV cells on plastic flexible substrates need to be formed at temperatures lower than 300 degrees C. The OPV cells on plastic flexible substrates were passivated by the Al2O3 film deposited at the temperature of 109 degrees C. Thereafter, the photovoltaic properties of passivated OPV cells were investigated as a function of exposure time under the atmosphere.

Enhanced performance of proton exchange membrane fuel cell by introducing nitrogen-doped CNTs in both catalyst layer and gas diffusion layer

CSIR Research Space (South Africa)

Hou, S

2017-11-01

Full Text Available The performance of the proton exchange membrane fuel cell (PEMFC) is significantly improved through introducing nitrogen-doped carbon nanotubes (NCNTs) into the catalyst layer (CL) and microporous layer (MPL) of the membrane electrode assembly (MEA...

Effect of Nafion ionometer content on proton conductivity in the catalyst layer of proton exchange fuel cell

Energy Technology Data Exchange (ETDEWEB)

Ozalevlia, Cihan Cemil; Jian Xie; Xu, Fan [METU MS Mechanical Engineering (United States)], email: cihan.ozalevli@metu.edu.tr, email: jianxie@iupui.edu, email: fanxu@iupui.edu

2011-07-01

In the energy conversion sector, proton exchange fuel cells (PEFC's) are among the most promising technologies for the future. The Nafion ionometer is the most important part of the membrane electrode assembly (MEA) which is the core technology of the system. The Nafion ionometer is both a proton conductor and a binder for the catalyst layer in the technology. The aim of this study is to assess the effect of the Nafion content in the cathode catalyst layer on the proton conductivity of the MEA. Two MEAs with different Nafion content were prepared following the LANL process and the proton conductivity of the catalyst layer was measured. Results showed a much higher performance of the 28wt. % Nafion MEA than the 10wt. %. This study demonstrated that when the Nafion ionometer content decreases, the performance of the fuel cell decreases; further investigations should be undertaken with Nafion ionometer amounts of 15wt. % to 20wt. %.

Method for manufacturing a solar cell with a surface-passivating dielectric double layer, and corresponding solar cell

NARCIS (Netherlands)

2014-01-01

We will describe a solar cell with a Dielektrikumdoppelschicht and a method for their preparation. It comprises a first dielectric layer (3) containing aluminum oxide or consisting of alumina, and a second, hydrogen-containing dielectric layer (5) is produced by sequential vapor deposition, whereby

Tuning cell adhesion and growth on biomimetic polyelectrolyte multilayers by variation of pH during layer-by-layer assembly.

Science.gov (United States)

Aggarwal, Neha; Altgärde, Noomi; Svedhem, Sofia; Michanetzis, Georgios; Missirlis, Yannis; Groth, Thomas

2013-10-01

Polyelectrolyte multilayers of chitosan and heparin are assembled on glass where heparin is applied at pH = 4, 9 and 4 during the formation of the first layers followed by pH = 9 at the last steps (denoted pH 4 + 9). Measurements of wetting properties, layer mass, and topography show that multilayers formed at pH = 4 are thicker, contain more water and have a smoother surface compared to those prepared at pH = 9 while the pH = 4 + 9 multilayers expressed intermediate properties. pH = 9 multilayers are more cell adhesive and support growth of C2C12 cells better than pH = 4 ones. However, pH 4 + 9 conditions improve the bioactivity to a similar level of pH = 9 layers. Multilayers prepared using pH 4 + 9 conditions form thick enough layers that may allow efficient loading of bioactive molecules. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a unit cell model for interim performance assessment of vitrified low level waste disposal

International Nuclear Information System (INIS)

Kline, N.W.

1995-09-01

The unit cell modeling approach has been developed and used in analysis of some design options for a vitrified low level waste disposal facility. The unit cell modeling approach is likely to be useful in interim performance assessment for the facility. The present unit cell model will probably need to be refitted in terms of some model parameters for the latter purpose. Two present disposal facility concepts differ in the length of a capillary barrier proposed to limit effective recharge through the top of the facility. Results of the study summarized herein suggest design of a capillary barrier which can reduce a recharge rate of 0.1 cm/yr by one or two orders of magnitude seems feasible for both concepts. A benchmark comparison of the unit cell model against a full facility model shows comparable predictive accuracy in less than one percent of the computer time. Results suggest that model parameters include capillary barrier performance, inter-canister spacing, rate of moisture withdrawal due to glass corrosion, contaminant inventory, and the well interceptor factor. It is also important that variations of waste form hydraulic parameters suggest that transport through the waste form is dominated by diffusion

Photoacoustic investigation of the effective diffusivity of two-layer semiconductors

Energy Technology Data Exchange (ETDEWEB)

Medina, J; Gurevich, Yu. G; Logvinov G, N; Rodriguez, P; Gonzalez de la Cruz, G. [Instituto Mexicano del Petroleo, Mexico, D.F. (Mexico)

2001-08-01

In this work, the problem of the effective thermal diffusivity of two-layer systems is investigated using the photoacoustic spectroscopy. The experimental results are examined in terms of the effective thermal parameters of the composite system determined from an homogeneous material which produces the same physical response under an external perturbation in the detector device. It is shown, that the effective thermal conductivity is not symmetric under exchange of the two layers of the composite; i.e., the effective thermal parameters depend upon which layer is illuminated in the photoacoustic experiments. Particular emphasis is given to the characterization of the interface thermal conductivity between the layer-system. [Spanish] En el presente trabajo se utiliza la espectroscopia fotoacustica para medir la difusividad termica de un sistema de dos capas. Los resultados experimentales son analizados en terminos de los parametros termicos efectivos determinados a partir de un material homogeneo, el cual produce la misma respuesta fisica bajo una perturbacion externa. Se puso particular enfasis en la caracterizacion de los efectos de interfase en el flujo de calor en el sistema de dos capas. Los resultados experimentales se comparan con el modelo teorico propuesto en este trabajo.

SiNx layers on nanostructured Si solar cells: Effective for optical absorption and carrier collection

International Nuclear Information System (INIS)

Cho, Yunae; Kim, Eunah; Gwon, Minji; Kim, Dong-Wook; Park, Hyeong-Ho; Kim, Joondong

2015-01-01

We compared nanopatterned Si solar cells with and without SiN x layers. The SiN x layer coating significantly improved the internal quantum efficiency of the nanopatterned cells at long wavelengths as well as short wavelengths, whereas the surface passivation helped carrier collection of flat cells mainly at short wavelengths. The surface nanostructured array enhanced the optical absorption and also concentrated incoming light near the surface in broad wavelength range. Resulting high density of the photo-excited carriers near the surface could lead to significant recombination loss and the SiN x layer played a crucial role in the improved carrier collection of the nanostructured solar cells

Hole-doping of mechanically exfoliated graphene by confined hydration layers

Institute of Scientific and Technical Information of China (English)

Tjeerd R. J. Bollmann[1,2; Liubov Yu. Antipina[3,4; Matthias Temmen[2; Michael Reichling[2; Pavel B. Sorokin[5

2015-01-01

By the use of non-contact atomic force microscopy （NC-AFM） and Kelvin probe force microscopy （KPFM）, we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CAF2（111）. Hydration layers confined between the graphene and the CaF2 substrate, resulting from the graphene＇s preparation under ambient conditions on the hydrophilic substrate surface, are found to electronically modify the graphene as the material＇s electron density transfers from graphene to the hydration layer. Density functional theory （DFT） calculations predict that the first 2 to 3 water layers adjacent to the graphene hole-dope the graphene by several percent of a unit charge per unit cell.

Non-Toxic Buffer Layers in Flexible Cu(In,GaSe2 Photovoltaic Cell Applications with Optimized Absorber Thickness

Directory of Open Access Journals (Sweden)

Md. Asaduzzaman

2017-01-01

Full Text Available Absorber layer thickness gradient in Cu(In1−xGaxSe2 (CIGS based solar cells and several substitutes for typical cadmium sulfide (CdS buffer layers, such as ZnS, ZnO, ZnS(O,OH, Zn1−xSnxOy (ZTO, ZnSe, and In2S3, have been analyzed by a device emulation program and tool (ADEPT 2.1 to determine optimum efficiency. As a reference type, the CIGS cell with CdS buffer provides a theoretical efficiency of 23.23% when the optimum absorber layer thickness was determined as 1.6 μm. It is also observed that this highly efficient CIGS cell would have an absorber layer thickness between 1 μm and 2 μm whereas the optimum buffer layer thickness would be within the range of 0.04–0.06 μm. Among all the cells with various buffer layers, the best energy conversion efficiency of 24.62% has been achieved for the ZnO buffer layer based cell. The simulation results with ZnS and ZnO based buffer layer materials instead of using CdS indicate that the cell performance would be better than that of the CdS buffer layer based cell. Although the cells with ZnS(O,OH, ZTO, ZnSe, and In2S3 buffer layers provide slightly lower efficiencies than that of the CdS buffer based cell, the use of these materials would not be deleterious for the environment because of their non-carcinogenic and non-toxic nature.

Rapid fabricating technique for multi-layered human hepatic cell sheets by forceful contraction of the fibroblast monolayer.

Directory of Open Access Journals (Sweden)

Yusuke Sakai

Full Text Available Cell sheet engineering is attracting attention from investigators in various fields, from basic research scientists to clinicians focused on regenerative medicine. However, hepatocytes have a limited proliferation potential in vitro, and it generally takes a several days to form a sheet morphology and multi-layered sheets. We herein report our rapid and efficient technique for generating multi-layered human hepatic cell (HepaRG® cell sheets using pre-cultured fibroblast monolayers derived from human skin (TIG-118 cells as a feeder layer on a temperature-responsive culture dish. Multi-layered TIG-118/HepaRG cell sheets with a thick morphology were harvested on day 4 of culturing HepaRG cells by forceful contraction of the TIG-118 cells, and the resulting sheet could be easily handled. In addition, the human albumin and alpha 1-antitrypsin synthesis activities of TIG-118/HepaRG cells were approximately 1.2 and 1.3 times higher than those of HepaRG cells, respectively. Therefore, this technique is considered to be a promising modality for rapidly fabricating multi-layered human hepatocyte sheets from cells with limited proliferation potential, and the engineered cell sheet could be used for cell transplantation with highly specific functions.

Effects of ZnS layer on the performance improvement of the photosensitive ZnO nanowire arrays solar cells

Energy Technology Data Exchange (ETDEWEB)

Javed, Hafiz Muhammad Asif [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Gao, Yanping; Xing, Yonglei [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Kong, Ling Bing, E-mail: ELBKong@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 (Singapore)

2016-08-01

The impact of ZnS layer as an interface modification on the photosensitive ZnO nanowire arrays solar cells was studied. CdS, CdSe and ZnS were deposited on ZnO nanowire arrays by SILAR method. When a ZnS layer was deposited, the quantum dot barrier was indirectly become in contact with the electrolyte, which thus restrained the flow of electrons. The CdS sensitized solar cells has an efficiency of 0.55% with the deposition of the ZnS(3) layer, that is, with a deposition of three times, whereas the CdS/CdSe co-sensitized solar cells has an efficiency of 2.03% with the deposition of the ZnS(1) layer. It was also noted that as the thickness of the of ZnS layer was increased, V{sub oc}, I{sub sc} and efficiencies of both the solar cells were first increased and then decreased. In addition, the CdS/N719 solar cells has an efficiency of 0.75% with the deposition of the ZnS(2) layer. - Highlights: • The impact of ZnS layer on the photosensitive ZnO nanowire solar cells was studied. • ZnS layer restrained the flow of electrons to the electrolyte. • CdS/CdSe co-sensitized solar cells have higher efficiency than CdS solar cells. • When ZnS layer was increased, V{sub oc} and I{sub sc} firstly increased and then decreased.

Fabrication and characteristics of unit cell for SOFC

Energy Technology Data Exchange (ETDEWEB)

Kim, Gwi-Yeol; Eom, Seung-Wook; Moon, Seong-In [Korea Electrotechnology Research Institute, Kyongnam (Korea, Republic of)] [and others

1996-12-31

Research and development on solid oxide fuel cells in Korea have been mainly focused on unit cell and small stack. Fuel cell system is called clean generation system which not cause NOx or SOx. It is generation efficiency come to 50-60% in contrast to 40% of combustion generation system. Among the fuel cell system, solid oxide fuel cell is constructed of ceramics, so stack construction is simple, power density is very high, and there are no corrosion problems. The object of this study is to develop various composing material for SOFC generation system, and to test unit cell performance manufactured. So we try to present a guidance for developing mass power generation system. We concentrated on development of manufacturing process for cathode, anode and electrolyte.

AFFORDABLE MULTI-LAYER CERAMIC (MLC) MANUFACTURING FOR POWER SYSTEMS (AMPS)

Energy Technology Data Exchange (ETDEWEB)

E.A. Barringer, Ph.D.

2002-11-27

McDermott Technology, Inc. (MTI) is attempting to develop high-performance, cost-competitive solid oxide fuel cell (SOFC) power systems. Recognizing the challenges and limitations facing the development of SOFC stacks comprised of electrode-supported cells and metallic interconnects, McDermott Technology, Inc. (MTI) has chosen to pursue an alternate path to commercialization. MTI is developing a multi-layer, co-fired, planar SOFC stack that will provide superior performance and reliability at reduced costs relative to competing designs. The MTI approach combines state-of-the-art SOFC materials with the manufacturing technology and infrastructure established for multi-layer ceramic (MLC) packages for the microelectronics industry. The rationale for using MLC packaging technology is that high quality, low-cost manufacturing has been demonstrated at high volumes. With the proper selection of SOFC materials, implementation of MLC fabrication methods offers unique designs for stacks (cells and interconnects) that are not possible through traditional fabrication methods. The MTI approach eliminates use of metal interconnects and ceramic-metal seals, which are primary sources of stack performance degradation. Co-fired cells are less susceptible to thermal cycling stresses by using material compositions that have closely matched coefficients of thermal expansion between the cell and the interconnect. The development of this SOFC stack technology was initiated in October 1999 under the DOE cosponsored program entitled ''Affordable Multi-layer Ceramic Manufacturing for Power Systems (AMPS)''. The AMPS Program was conducted as a two-phase program: Phase I--Feasibility Assessment (10/99--9/00); and Phase II--Process Development for Co-fired Stacks (10/00-3/02). This report provides a summary of the results from Phase I and a more detailed review of the results for Phase II. Phase I demonstrated the feasibility for fabricating multi-layer, co-fired cells and

2D layered insulator hexagonal boron nitride enabled surface passivation in dye sensitized solar cells.

Science.gov (United States)

Shanmugam, Mariyappan; Jacobs-Gedrim, Robin; Durcan, Chris; Yu, Bin

2013-11-21

A two-dimensional layered insulator, hexagonal boron nitride (h-BN), is demonstrated as a new class of surface passivation materials in dye-sensitized solar cells (DSSCs) to reduce interfacial carrier recombination. We observe ~57% enhancement in the photo-conversion efficiency of the DSSC utilizing h-BN coated semiconductor TiO2 as compared with the device without surface passivation. The h-BN coated TiO2 is characterized by Raman spectroscopy to confirm the presence of highly crystalline, mixed monolayer/few-layer h-BN nanoflakes on the surface of TiO2. The passivation helps to minimize electron-hole recombination at the TiO2/dye/electrolyte interfaces. The DSSC with h-BN passivation exhibits significantly lower dark saturation current in the low forward bias region and higher saturation in the high forward bias region, respectively, suggesting that the interface quality is largely improved without impeding carrier transport at the material interface. The experimental results reveal that the emerging 2D layered insulator could be used for effective surface passivation in solar cell applications attributed to desirable material features such as high crystallinity and self-terminated/dangling-bond-free atomic planes as compared with high-k thin-film dielectrics.

Preparation of ultra-thin and high-quality WO{sub 3} compact layers and comparision of WO{sub 3} and TiO{sub 2} compact layer thickness in planar perovskite solar cells

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jincheng; Shi, Chengwu, E-mail: shicw506@foxmail.com; Chen, Junjun; Wang, Yanqing; Li, Mingqian

2016-06-15

In this paper, the ultra-thin and high-quality WO{sub 3} compact layers were successfully prepared by spin-coating-pyrolysis method using the tungsten isopropoxide solution in isopropanol. The influence of WO{sub 3} and TiO{sub 2} compact layer thickness on the photovoltaic performance of planar perovskite solar cells was systematically compared, and the interface charge transfer and recombination in planar perovskite solar cells with TiO{sub 2} compact layer was analyzed by electrochemical impedance spectroscopy. The results revealed that the optimum thickness of WO{sub 3} and TiO{sub 2} compact layer was 15 nm and 60 nm. The planar perovskite solar cell with 15 nm WO{sub 3} compact layer gave a 9.69% average and 10.14% maximum photoelectric conversion efficiency, whereas the planar perovskite solar cell with 60 nm TiO{sub 2} compact layer achieved a 11.79% average and 12.64% maximum photoelectric conversion efficiency. - Graphical abstract: The planar perovskite solar cell with 15 nm WO{sub 3} compact layer gave a 9.69% average and 10.14% maximum photoelectric conversion efficiency, whereas the planar perovskite solar cell with 60 nm TiO{sub 2} compact layer achieved a 11.79% average and 12.64% maximum photoelectric conversion efficiency. Display Omitted - Highlights: • Preparation of ultra-thin and high-quality WO{sub 3} compact layers. • Perovskite solar cell with 15 nm-thick WO{sub 3} compact layer achieved PCE of 10.14%. • Perovskite solar cell with 60 nm-thick TiO{sub 2} compact layer achieved PCE of 12.64%.

Nano-crystalline thin and nano-particulate thick TiO{sub 2} layer: Cost effective sequential deposition and study on dye sensitized solar cell characteristics

Energy Technology Data Exchange (ETDEWEB)

Das, P.; Sengupta, D. [Centre for Advanced Materials Processing, CSIR-Central Mechanical Engineering Research Institute, Durgapur, 713209 West Bengal (India); CSIR-Central Mechanical Engineering Research Institute, Academy of Scientific and Innovative Research (AcSIR), Durgapur, 713209 West Bengal (India); Kasinadhuni, U. [Department of Engineering Physics, Bengal College of Engineering and Technology, Durgapur, West Bengal (India); Mondal, B. [Centre for Advanced Materials Processing, CSIR-Central Mechanical Engineering Research Institute, Durgapur, 713209 West Bengal (India); Mukherjee, K., E-mail: kalisadhanm@yahoo.com [Centre for Advanced Materials Processing, CSIR-Central Mechanical Engineering Research Institute, Durgapur, 713209 West Bengal (India)

2015-06-15

Highlights: • Thin TiO{sub 2} layer is deposited on conducting substrate using sol–gel based dip coating. • TiO{sub 2} nano-particles are synthesized using hydrothermal route. • Thick TiO{sub 2} particulate layer is deposited on prepared thin layer. • Dye sensitized solar cells are made using thin and thick layer based photo-anode. • Introduction of thin layer in particulate photo-anode improves the cell efficiency. - Abstract: A compact thin TiO{sub 2} passivation layer is introduced between the mesoporous TiO{sub 2} nano-particulate layer and the conducting glass substrate to prepare photo-anode for dye-sensitized solar cell (DSSC). In order to understand the effect of passivation layer, other two DSSCs are also developed separately using TiO{sub 2} nano-particulate and compact thin film based photo-anodes. Nano-particles are prepared using hydrothermal synthesis route and the compact passivation layer is prepared by simply dip coating the precursor sol prepared through wet chemical route. The TiO{sub 2} compact layer and the nano-particles are characterised in terms of their micro-structural features and phase formation behavior. It is found that introduction of a compact TiO{sub 2} layer in between the mesoporous TiO{sub 2} nano-particulate layer and the conducting substrate improves the solar to electric conversion efficiency of the fabricated cell. The dense thin passivation layer is supposed to enhance the photo-excited electron transfer and prevent the recombination of photo-excited electrons.

Many layers of embryonic hematopoiesis: new insights into B-cell ontogeny and the origin of hematopoietic stem cells.

Science.gov (United States)

Hadland, Brandon; Yoshimoto, Momoko

2018-04-01

In adult hematopoiesis, the hematopoietic stem cell (HSC) sits at the top of a hierarchy of hematopoietic progenitors responsible for generating the diverse repertoire of blood and immune cells. During embryonic development, however, the initial waves of hematopoiesis provide the first functioning blood cells of the developing embryo, such as primitive erythrocytes arising in the yolk sac, independently of HSCs. In the field of developmental immunology, it has been recognized that some components of the immune system, such as B-1a lymphocytes, are uniquely produced during the embryonic and neonatal period, suggesting a "layered" development of immunity. Several recent studies have shed new light on the developmental origin of the layered immune system, suggesting complex and sometimes multiple contributions to unique populations of innate-like immune cells from both fetal HSCs and earlier HSC-independent progenitors. In this review, we will attempt to synthesize these studies to provide an integrated model of developmental hematopoiesis and layered immunity that may offer new insights into the origin of HSCs. Copyright © 2018 ISEH – Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.

CURING EFFICIENCY OF DUAL-CURE RESIN CEMENT UNDER ZIRCONIA WITH TWO DIFFERENT LIGHT CURING UNITS

Directory of Open Access Journals (Sweden)

Pınar GÜLTEKİN

2015-04-01

Full Text Available Purpose: Adequate polymerization is a crucial factor in obtaining optimal physical properties and a satisfying clinical performance from composite resin materials. The aim of this study was to evaluate the polymerization efficiency of dual-cure resin cement cured with two different light curing units under zirconia structures having differing thicknesses. Materials and Methods: 4 zirconia discs framework in 4 mm diameter and in 0.5 mm, 1 mm and 1.5 mm thickness were prepared using computer-aided design system. One of the 0.5 mm-thick substructures was left as mono-layered whereas others were layered with feldspathic porcelain of same thickness and ceramic samples with 4 different thicknesses (0.5, 1, 1.5 and 2.0 mm were prepared. For each group (n=12 resin cement was light cured in polytetrafluoroethylene molds using Light Emitting Diode (LED or Quartz-Tungsten Halogen (QHT light curing units under each of 4 zirconia based discs (n=96. The values of depth of cure (in mm and the Vickers Hardness Number values (VHN were evaluated for each specimen. Results: The use of LED curing unit produced a greater depth of cure compared to QTH under ceramic discs with 0.5 and 1 mm thickness (p<0.05.At 100μm and 300 μm depth, the LED unit produced significantly greater VHN values compared to the QTH unit (p<0.05. At 500 μm depth, the difference between the VHN values of LED and QTH groups were not statistically significant. Conclusion: Light curing may not result in adequate resin cement polymerization under thick zirconia structures. LED light sources should be preferred over QTH for curing dual-cure resin cements, especially for those under thicker zirconia restorations.

Modulation of the androgenetic response in diverse skin cell types: the pilosebaceous unit

International Nuclear Information System (INIS)

Zurvarra, F.; Kerner, N.; Hagelin, K.

2009-01-01

Androgens play a central role in diverse morphogenetic processes of the skin. Hair growth and follicular cycle are regulated in part by androgens. Androgens also play a key function, together with other receptors such as the PPARs receptors family, on the proliferation and differentiation of the sebaceous gland that forms part of the pilosebaceous unit and influences hair growth and skin well-being. UV radiation may affect androgens regulation of skin homeostasis. Objectives: to study the modulation of androgenetic response related to UV radiation on the pilosebaceous unit, in two skin conditions: androgenetic alopecia and acne, both affecting skin and constituting major concerns for affected individuals. Methods: primary cultures of cells and established cell lines from the pilosebaceous unit: dermal papillae cells, keratinocytes and sebocytes. Analysis of lipid content, inflammatory response and proliferation of cells under the influence of androgens, PPARs ligands and UVR. Results: sebocytes primary cultures were obtained from human sebaceous glands. Proliferation and differentiation, as well as the expression of proinflammatory molecules (IL-1, TNF alpha, iNOs) and lipogenic enzymes (FASN) under androgens and UV treatment were assessed. The response to androgens under UV exposure was also analyzed in dermal papillae cells in culture. (authors)

Anti corrosion layer for stainless steel in molten carbonate fuel cell - comprises phase vapour deposition of titanium nitride, aluminium nitride or chromium nitride layer then oxidising layer in molten carbonate electrolyte

DEFF Research Database (Denmark)

2000-01-01

Forming an anticorrosion protective layer on a stainless steel surface used in a molten carbonate fuel cell (MCFC) - comprises the phase vapour deposition (PVD) of a layer comprising at least one of titanium nitride, aluminium nitride or chromium nitride and then forming a protective layer in situ...

Effect of incorporation of silver nanoparticles in PEDOT:PSS layer on performance of organic solar cell

Science.gov (United States)

Singh, Joginder; Nirwal, Varun Singh; Bhatnagar, P. K.; Peta, Koteswara Rao

2018-05-01

Solution processable organic solar cells have attracted significant interest in scientific community due to their easy processability, flexibility and eco friendly fabrication. In these organic solar cells structure, PEDOT:PSS layer has major importance as it used as hole transporting layer. In the present work, we have analyzed the effect of incorporation of silver nanoparticles (AgNPs) in PEDOT:PSS layer for P3HT:PCBM based organic solar cells. The presence of Ag nanoparticles in PEDOT:PSS film is confirmed by atomic force microscopy (AFM) images. It has been observed that PEDOT:PSS layer with AgNPs has ˜5.4% more transmittance than PEDOT:PSS layer in most of the visible region, which helps in reaching more light on active layer. Finally, solar cell with structure ITO/PEDOT:PSS:AgNPs/Al is fabricated and J-V characteristics are plotted under illumination. It is observed that there is a significant (˜10%) enhancement in short circuit current and slight increment in open circuit voltage with addition of AgNPs in PEDOT:PSS layer. The calculated value of power conversion efficiency (PCE) of fabricated device without AgNPs in PEDOT:PSS was 1.67%, which increased to 2.02% after addition of AgNPs in PEDOT:PSS layer.

Preparation of TiO{sub 2} films by layer-by-layer assembly and their application in solar cell

Energy Technology Data Exchange (ETDEWEB)

Zhang, L. [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Anhui Key Laboratory of Spin Electron and Nanomaterials (Cultivating Base), Suzhou University, Suzhou 234000 (China); Xie, A.J. [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Shen, Y.H., E-mail: s_yuhua@163.co [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Li, S.K. [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China)

2010-09-03

Polyacrylate sodium (PAAS)/titania (TiO{sub 2}) multilayers have been fabricated through the electrostatic layer-by-layer assembly technique. The composite films display an excellent photovoltaic performance after sintering and sensitization by cyanine dye (CD), which can be applied in dye-sensitized solar cells. The properties of PAAS/TiO{sub 2} multilayers are investigated by ultraviolet-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD), Thermogravimetric analysis (TGA), and photovoltaic measurements. The results indicate that the thermal stability of the PAAS has a direct influence on the performance of dye-sensitized solar cells. The energy conversion efficiency of approximately 1.29% was obtained for dye-sensitized solar cell with TiO{sub 2}/PAAS (40 bilayers) as precursor film. In addition, the composite films also show a good self-cleaning property for photocatalytic degradation of methylene blue.

p-Type semiconducting nickel oxide as an efficiency-enhancing anodal interfacial layer in bulk heterojunction solar cells

Science.gov (United States)

Irwin, Michael D; Buchholz, Donald B; Marks, Tobin J; Chang, Robert P. H.

2014-11-25

The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode, a p-type semiconductor layer formed on the anode, and an active organic layer formed on the p-type semiconductor layer, where the active organic layer has an electron-donating organic material and an electron-accepting organic material.

Surface pressure drag for hydrostatic two-layer flow over axisymmetric mountains

Energy Technology Data Exchange (ETDEWEB)

Leutbecher, M.

2000-07-01

The effect of partial reflections on surface pressure drag is investigated for hydrostatic gravity waves in two-layer flow with piecewise constant buoyancy frequency. The variation of normalized surface pressure drag with interface height is analyzed for axisymmetric mountains. The results are compared with the familiar solution for infinitely long ridges. The drag for the two-layer flow is normalized with the drag of one-layer flow, which has the buoyancy frequency of the lower layer. An analytical expression for the normalized drag of axisymmetric mountains is derived from linear theory of steady flow. Additionally, two-layer flow over finite-height axisymmetric mountains is simulated numerically for flow with higher stability in the upper layer. The temporal evolution of the surface pressure drag is examined in a series of experiments with different interface and mountain heights. The focus is on the linear regime and the nonlinear regime of nonbreaking gravity waves. The dispersion of gravity waves in flow over isolated mountains prevents that the entire wave spectrum is in resonance at the same interface height, which is the case in hydrostatic flow over infinitely long ridges. In consequence, the oscillation of the normalized drag with interface height is smaller for axisymmetric mountains than for infinitely long ridges. However, even for a reflection coefficient as low as 1/3 the drag of an axisymmetric mountain can be amplified by 50% and reduced by 40%. The nonlinear drag becomes steady in the numerical experiments in which no wave breaking occurs. The steady state nonlinear drag agrees quite well with the prediction of linear theory if the linear drag is computed for a slightly lowered interface. (orig.)

Process analysis of two-layered tube hydroforming with analytical and experimental verification

International Nuclear Information System (INIS)

Seyedkashi, S. M. Hossein; Panahizadeh R, Valiollah; Xu, Haibin; Kim, Sang Yun; Moon, Young Hoon

2013-01-01

Two-layered tubular joints are suitable for special applications. Designing and manufacturing of two layered components require enough knowledge about the tube material behavior during the hydroforming process. In this paper, hydroforming of two-layered tubes is investigated analytically, and the results are verified experimentally. The aim of this study is to derive an analytical model which can be used in the process design. Fundamental equations are written for both of the outer and inner tubes, and the total forming pressure is obtained from these equations. Hydroforming experiments are carried out on two different combinations of materials for inner and outer tubes; case 1: copper/aluminum and case 2: carbon steel/stainless steel. It is observed that experimental results are in good agreement with the theoretical model obtained for estimation of forming pressure able to avoid wrinkling.

Two-phase gas bubble-liquid boundary layer flow along vertical and inclined surfaces

International Nuclear Information System (INIS)

Cheung, F.B.; Epstein, M.

1985-01-01

The behavior of a two-phase gas bubble-liquid boundary layer along vertical and inclined porous surfaces with uniform gas injection is investigated experimentally and analytically. Using argon gas and water as the working fluids, a photographical study of the two-phase boundary layer flow has been performed for various angles of inclination ranging from 45 0 to 135 0 and gas injection rates ranging from 0.01 to 0.1 m/s. An integral method has been employed to solve the system of equations governing the two-phase motion. The effects of the gas injection rate and the angle of inclination on the growth of the boundary layer have been determined. The predicted boundary layer thickness is found to be in good agreement with the experimental results. The calculated axial liquid velocity and the void fraction in the two-phase region are also presented along with the observed flow behavior

Voc enhancement of a solar cell with doped Li+-PbS as the active layer

Science.gov (United States)

Chávez Portillo, M.; Alvarado Pulido, J.; Gallardo Hernández, S.; Soto Cruz, B. S.; Alcántara Iniesta, S.; Gutiérrez Pérez, R.; Portillo Moreno, O.

2018-06-01

In this report, we investigate the fabrication of solar cells obtained by chemical bath technique, based on CdS as window layer and PbS and PbS-Li+-doped as the active layer. We report open-circuit-voltage Voc values of ∼392 meV for PbS and ∼630 meV for PbSLi+-doped, a remarkable enhanced in the open circuit voltage is shown for solar cells with doped active layer. Li+ ion passivate the dangling bonds in PbS-metal layer interface in consequence reducing the recombination centers.

Status epilepticus increases mature granule cells in the molecular layer of the dentate gyrus in rats★

Science.gov (United States)

Liang, Zhaoliang; Gao, Fei; Wang, Fajun; Wang, Xiaochen; Song, Xinyu; Liu, Kejing; Zhan, Ren-Zhi

2013-01-01

Enhanced neurogenesis in the dentate gyrus of the hippocampus following seizure activity, especially status epilepticus, is associated with ectopic residence and aberrant integration of newborn granule cells. Hilar ectopic granule cells may be detrimental to the stability of dentate circuitry by means of their electrophysiological properties and synaptic connectivity. We hypothesized that status epilepticus also increases ectopic granule cells in the molecular layer. Status epilepticus was induced in male Sprague-Dawley rats by intraperitoneal injection of pilocarpine. Immunostaining showed that many doublecortin-positive cells were present in the molecular layer and the hilus 7 days after the induction of status epilepticus. At least 10 weeks after status epilepticus, the estimated number of cells positive for both prospero homeobox protein 1 and neuron-specific nuclear protein in the hilus was significantly increased. A similar trend was also found in the molecular layer. These findings indicate that status epilepticus can increase the numbers of mature and ectopic newborn granule cells in the molecular layer. PMID:25206705

High-velocity DC-VPS for diffusion and protecting barrier layers in solid oxide fuel cells (SOFCs)

Science.gov (United States)

Henne, R. H.; Franco, T.; Ruckdäschel, R.

2006-12-01

High-temperature fuel cells of the solid oxide fuel cell (SOFC) type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced lightweight planar cells for electricity supply units in cars and other mobile systems. Such cells, in one new design, consist mainly of metallic parts, for example, of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of chromium species from the interconnect or the cell containment into the electrolyte/cathode interface forming insulating phases and by the mutual diffusion of substrate and anode material, for example, iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite, which in both cases reduces performance and system lifetime. Additional intermediate layers of perovskite-type material, (e.g., doped LaCrO3) applied with high-velocity direct-current vacuum plasma spraying (DC-VPS) can reduce such effects considerably if they are stable and of high electronic conductivity.

Quantification of the specific yield in a two-layer hard-rock aquifer model

Science.gov (United States)

Durand, Véronique; Léonardi, Véronique; de Marsily, Ghislain; Lachassagne, Patrick

2017-08-01

Hard rock aquifers (HRA) have long been considered to be two-layer systems, with a mostly capacitive layer just below the surface, the saprolite layer, and a mainly transmissive layer underneath, the fractured layer. Although this hydrogeological conceptual model is widely accepted today within the scientific community, it is difficult to quantify the respective storage properties of each layer with an equivalent porous medium model. Based on an HRA field site, this paper attempts to quantify in a distinct manner the respective values of the specific yield (Sy) in the saprolite and the fractured layer, with the help of a deterministic hydrogeological model. The study site is the Plancoët migmatitic aquifer located in north-western Brittany, France, with piezometric data from 36 observation wells surveyed every two weeks for eight years. Whereas most of the piezometers (26) are located where the water table lies within the saprolite, thus representing the specific yield of the unconfined layer (Sy1), 10 of them are representative of the unconfined fractured layer (Sy2), due to their position where the saprolite is eroded or unsaturated. The two-layer model, based on field observations of the layer geometry, runs with the MODFLOW code. 81 values of the Sy1/Sy2 parameter sets were tested manually, as an inverse calibration was not able to calibrate these parameters. In order to calibrate the storage properties, a new quality-of-fit criterion called ;AdVar; was also developed, equal to the mean squared deviation of the seasonal piezometric amplitude variation. Contrary to the variance, AdVar is able to select the best values for the specific yield in each layer. It is demonstrated that the saprolite layer is about 2.5 times more capacitive than the fractured layer, with Sy1 = 10% (7% < Sy1 < 15%) against Sy2 = 2% (1% < Sy2 < 3%), in this particular example.

Migration and distribution of two populations of hippocampal granule cell precursors during the perinatal and postnatal periods

International Nuclear Information System (INIS)

Altman, J.; Bayer, S.A.

1990-01-01

Methacrylate-embedded sections and short-survival thymidine radiograms of the hippocampal dentate gyrus were examined in perinatal and postnatal rats in order to trace the site of origin and migration of the precursors of granule cells and study the morphogenesis of the granular layer. The densely packed, spindle-shaped cells of the secondary dentate matrix (a derivative of the primary dentate neuroepithelium) stream in a subpial position towards the granular layer of the internal dentate limb during the perinatal and early postnatal periods. By an accretionary process, the crest of the granular layer forms on day E21 and on the subsequent days the granular layer of the internal dentate limb expands progressively in a lateral direction. Granule cells differentiation, as judged by the transformation of polymorph, darkly staining small cells into rounder, lightly staining larger granule cells, follows the same gradient from the external dentate limb to the internal dentate limb. The secondary dentate matrix is in a process of dissolution by day P5. This matrix is the source of what will later become the outer shell of the granular layer composed of early generated granule cells. The thicker inner shell of the granular layer, formed during the infantile and juvenile periods, derives from an intrinsic, tertiary germinal matrix. On day E22, the dentate migration of the secondary dentate matrix becomes partitioned into two components: (a) the subpial component of extradentate origin, referred to in this context as the first dentate migration, and (b) the second dentate migration. The latter is distributed in the basal polymorph layer throughout the entire dentate gyrus and is henceforth recognized as the tertiary dentate matrix. The tertiary dentate matrix is prominent between days P3 and P10

The different influence of the residual layer on the development of the summer convective boundary layer in two deserts in northwest China

Science.gov (United States)

Lin, Zhao; Bo, Han; Shihua, Lv; Lijuan, Wen; Xianhong, Meng; Zhaoguo, Li

2018-02-01

The development of the atmospheric boundary layer is closely connected with the exchange of momentum, heat, and mass near the Earth's surface, especially for a convective boundary layer (CBL). Besides being modulated by the buoyancy flux near the Earth's surface, some studies point out that a neutrally stratified residual layer is also crucial for the appearance of a deep CBL. To verify the importance of the residual layer, the CBLs over two deserts in northwest China (Badan Jaran and Taklimakan) were investigated. The summer CBL mean depth over the Taklimakan Desert is shallower than that over the Badan Jaran Desert, even when the sensible heat flux of the former is stronger. Meanwhile, the climatological mean residual layer in the Badan Jaran Desert is much deeper and neutrally stratified in summer. Moreover, we found a significant and negative correlation between the lapse rate of the residual layer and the CBL depth over the Badan Jaran Desert. The different lapse rates of the residual layer in the two regions are partly connected with the advection heating from large-scale atmospheric circulation. The advection heating tends to reduce the temperature difference in the 700 to 500-hPa layer over the Badan Jaran Desert, and it increases the stability in the same atmospheric layer over the Taklimakan Desert. The advection due to climatological mean atmospheric circulation is more effective at modulating the lapse rate of the residual layer than from varied circulation. Also, the interannual variation of planetary boundary layer (PBL) height over two deserts was found to covary with the wave train.

Buffer layer between a planar optical concentrator and a solar cell

Energy Technology Data Exchange (ETDEWEB)

Solano, Manuel E. [Departamento de Ingeniería Matemática and CI" 2 MA, Universidad de Concepción, Concepción, Casilla 160-C (Chile); Barber, Greg D. [Penn State Institute of Energy and the Environment, Pennsylvania State University, University Park, PA 16802 (United States); Department of Chemistry, Pennsylvania State University, University Park, PA 16802 (United States); Lakhtakia, Akhlesh [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802 (United States); Faryad, Muhammad [Department of Physics, Lahore University of Management Sciences, Lahore 54792 (Pakistan); Monk, Peter B. [Department of Mathematical Sciences, University of Delaware, Newark, DE 19716 (United States); Mallouk, Thomas E. [Department of Chemistry, Pennsylvania State University, University Park, PA 16802 (United States)

2015-09-15

The effect of inserting a buffer layer between a periodically multilayered isotropic dielectric (PMLID) material acting as a planar optical concentrator and a photovoltaic solar cell was theoretically investigated. The substitution of the photovoltaic material by a cheaper dielectric material in a large area of the structure could reduce the fabrication costs without significantly reducing the efficiency of the solar cell. Both crystalline silicon (c-Si) and gallium arsenide (GaAs) were considered as the photovoltaic material. We found that the buffer layer can act as an antireflection coating at the interface of the PMLID and the photovoltaic materials, and the structure increases the spectrally averaged electron-hole pair density by 36% for c-Si and 38% for GaAs compared to the structure without buffer layer. Numerical evidence indicates that the optimal structure is robust with respect to small changes in the grating profile.

Conserved S-Layer-Associated Proteins Revealed by Exoproteomic Survey of S-Layer-Forming Lactobacilli

Science.gov (United States)

Johnson, Brant R.; Hymes, Jeffrey; Sanozky-Dawes, Rosemary; Henriksen, Emily DeCrescenzo

2015-01-01

The Lactobacillus acidophilus homology group comprises Gram-positive species that include L. acidophilus, L. helveticus, L. crispatus, L. amylovorus, L. gallinarum, L. delbrueckii subsp. bulgaricus, L. gasseri, and L. johnsonii. While these bacteria are closely related, they have varied ecological lifestyles as dairy and food fermenters, allochthonous probiotics, or autochthonous commensals of the host gastrointestinal tract. Bacterial cell surface components play a critical role in the molecular dialogue between bacteria and interaction signaling with the intestinal mucosa. Notably, the L. acidophilus complex is distinguished in two clades by the presence or absence of S-layers, which are semiporous crystalline arrays of self-assembling proteinaceous subunits found as the outermost layer of the bacterial cell wall. In this study, S-layer-associated proteins (SLAPs) in the exoproteomes of various S-layer-forming Lactobacillus species were proteomically identified, genomically compared, and transcriptionally analyzed. Four gene regions encoding six putative SLAPs were conserved in the S-layer-forming Lactobacillus species but not identified in the extracts of the closely related progenitor, L. delbrueckii subsp. bulgaricus, which does not produce an S-layer. Therefore, the presence or absence of an S-layer has a clear impact on the exoproteomic composition of Lactobacillus species. This proteomic complexity and differences in the cell surface properties between S-layer- and non-S-layer-forming lactobacilli reveal the potential for SLAPs to mediate intimate probiotic interactions and signaling with the host intestinal mucosa. PMID:26475115

Study of buffer layer thickness on bulk heterojunction solar cell.

Science.gov (United States)

Noh, Seunguk; Suman, C K; Lee, Donggu; Kim, Seohee; Lee, Changhee

2010-10-01

We studied the effect of the buffer layer (molybdenum-oxide (MoO3)) thickness on the performance of organic solar cell based on blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester fullerene derivative (PCBM). The thickness of MoO3 was varied from 1 nm to 30 nm for optimization of device performance. The photocurrent-voltage and impedance spectroscopy were measured under dark and AM1.5G solar simulated illumination of 100 mW/cm2 for exploring the role of the buffer layer thickness on carrier collection at an anode. The MoO3 thickness of the optimized device (efficiency approximately 3.7%) was found to be in the range of 5 approximately 10 nm. The short-circuit current and the shunt resistance decrease gradually for thicker MoO3 layer over 5 nm. The device can be modeled as the combination of three RC parallel circuits (each one for the active layer, buffer layer and interface between the buffer layer and the active layer) in series with contact resistance (Rs approximately 60 ohm).

Phase transitions in two dimensions: The case of Sn adsorbed on Ge (111) surfaces

DEFF Research Database (Denmark)

Bunk, O.; Zeysing, J.H.; Falkenberg, G.

1999-01-01

. In the low-temperature phase one of the three Sn atoms per ( 3×3) unit cell is displaced outwards by 0.26±0.04Å relative to the other two. This displacement is accompanied by an increase in the first to second double-layer spacing in the Ge substrate. © 1999 The American Physical Society...

Ti–Al–O nanocrystal charge trapping memory cells fabricated by atomic layer deposition

International Nuclear Information System (INIS)

Cao, Zheng-Yi; Li, Ai-Dong; Li, Xin; Cao, Yan-Qiang; Wu, Di

2014-01-01

Charge trapping memory cells using Ti–Al–O (TAO) film as charge trapping layer and amorphous Al 2 O 3 as the tunneling and blocking layers were fabricated on Si substrates by atomic layer deposition method. As-deposited TAO films were annealed at 700 °C, 800 °C and 900 °C for 3 min in N 2 with a rapid thermal annealing process to form nanocrystals. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were used to characterize the microstructure and band diagram of the heterostructures. The electrical characteristics and charge storage properties of the Al 2 O 3 /TAO/Al 2 O 3 /Si stack structures were also evaluated. Compared to 700 °C and 900 °C samples, the memory cells annealed at 800 °C exhibit better memory performance with larger memory window of 4.8 V at ± 6 V sweeping, higher program/erase speed and excellent endurance. - Highlights: • The charge trapping memory cells were fabricated by atomic layer deposition method. • The anneal temperature plays a key role in forming nanocrystals. • The memory cells annealed at 800 °C exhibit better memory performance. • The band alignment is beneficial to enhance the retention characteristics

A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection

KAUST Repository

Eita, Mohamed Samir

2014-08-28

Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by-layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Copper variation in Cu(In,Ga)Se{sub 2} solar cells with indium sulphide buffer layer

Energy Technology Data Exchange (ETDEWEB)

Spiering, S., E-mail: stefanie.spiering@zsw-bw.de [Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW) Baden-Wuerttemberg, Industriestrasse 6, 70565 Stuttgart (Germany); Paetel, S.; Kessler, F. [Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW) Baden-Wuerttemberg, Industriestrasse 6, 70565 Stuttgart (Germany); Igalson, M.; Abdel Maksoud, H. [Warsaw University of Technology (WUT), Faculty of Physics, Koszykowa 75, 00-662 Warszawa (Poland)

2015-05-01

In the manufacturing of Cu(In,Ga)Se{sub 2} (CIGS) thin film solar cells the application of a buffer layer on top of the absorber is essential to obtain high efficiency devices. Regarding the roll-to-roll production of CIGS cells and modules a vacuum deposition process for the buffer is preferable to the conventional cadmium sulphide buffer deposited in a chemical bath. Promising results have already been achieved for the deposition of indium sulphide buffer by different vacuum techniques. The solar device performance is very sensitive to the conditions at the absorber-buffer heterojunction. In view of optimization we investigated the influence of the Cu content in the absorber on the current-voltage characteristics. In this work the integral copper content was varied between 19 and 23 at.% in CIGS on glass substrates. An improvement of the cell performance by enhanced open circuit voltage was observed for a reduction to ~ 21 at.% when thermally evaporated indium sulphide was applied as the buffer layer. The influence of stoichiometry deviations on the transport mechanism and secondary barriers in the device was studied using detailed dark and light current-voltage analysis and admittance spectroscopy and compared to the reference CdS-buffered cells. We conclude that the composition of the absorber in the interface region affects current transport in In{sub x}S{sub y}-buffered and CdS-buffered cells in different ways hence optimal Cu content in those two types of devices is different. - Highlights: • Influence of Cu-variation in CIGS cells with In{sub x}S{sub y} buffer layer on cell performance • Enhanced efficiency by slight reduction of Cu-content to 21 at.% • Contribution of tunnelling-enhanced interface recombination for higher Cu-content.

Solution-processed In2S3 buffer layer for chalcopyrite thin film solar cells

OpenAIRE

Wang Lan; Lin Xianzhong; Ennaoui Ahmed; Wolf Christian; Lux-Steiner Martha Ch.; Klenk Reiner

2016-01-01

We report a route to deposit In2S3 thin films from air-stable, low-cost molecular precursor inks for Cd-free buffer layers in chalcopyrite-based thin film solar cells. Different precursor compositions and processing conditions were studied to define a reproducible and robust process. By adjusting the ink properties, this method can be applied in different printing and coating techniques. Here we report on two techniques, namely spin-coating ...

Hydrothermal growth of double-layer TiO{sub 2} nanostructure film for quantum dot sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Feng Shuanglong; Yang Junyou, E-mail: jyyang@mail.hust.edu.cn; Liu Ming; Zhu Hu; Zhang Jiansheng; Li Gen; Peng Jiangying; Liu Qiongzhen

2012-01-31

A double-layer (DL) film with a TiO{sub 2} nanosheet-layer on a layer of TiO{sub 2} nanorod-array, was synthesized on a transparent conductive fluorine-doped tin oxide substrate by a two-step hydrothermal method. Starting from the precursors of NaSeSO{sub 3}, CdSO{sub 4} and the complex of N(CH{sub 2}COOK){sub 3}, CdSe quantum dots (QDs) were grown on the DL-TiO{sub 2} substrate by chemical bath deposition method. The samples were characterized by X-ray diffraction, Scanning electron microscopy, Energy dispersion spectroscopy, and their optical scattering property was measured by light reflection spectrometry. Some CdSe QDs sensitized DL-TiO{sub 2} films serve as the photoanodes, were assembled into solar cell devices and their photovoltaic performance were also characterized. The short circuit current and open-circuit voltage of the solar cells range from 0.75 to 4.05 mA/cm{sup 2} and 0.20 - 0.42 V under the illumination of one sun (AM1.5, 100 mW/cm{sup 2}), respectively. The photocurrent density of the DL-TiO{sub 2} film is five times higher than that of a bare TiO{sub 2} nanorod array photoelectrode cell. - Highlights: Black-Right-Pointing-Pointer A two-step hydrothermal deposition method was used to deposit TiO{sub 2} films. Black-Right-Pointing-Pointer Double-layer TiO{sub 2} films were synthesized on transparent FTO substrate. Black-Right-Pointing-Pointer The bi-functional character of the electrode were confirmed. Black-Right-Pointing-Pointer Photocurrent density of DL-film electrode was enhanced 5 times than a single film.

Two-dimensional diffusion limited system for cell growth

International Nuclear Information System (INIS)

Hlatky, L.

1985-11-01

A new cell system, the ''sandwich'' system, was developed to supplement multicellular spheroids as tumor analogues. Sandwiches allow new experimental approaches to questions of diffusion, cell cycle effects and radiation resistance in tumors. In this thesis the method for setting up sandwiches is described both theoretically and experimentally followed by its use in x-ray irradiation studies. In the sandwich system, cells are grown in a narrow gap between two glass slides. Where nutrients and waste products can move into or out of the local environment of the cells only by diffusing through the narrow gap between the slides. Due to the competition between cells, self-created gradients of nutrients and metabolic products are set up resulting in a layer of cells which resembles a living spheroid cross section. Unlike the cells of the spheroid, however, cells in all regions of the sandwich are visible. Therefore, the relative sizes of the regions and their time-dependent growth can be monitored visually without fixation or sectioning. The oxygen and nutrient gradients can be ''turned off'' at any time without disrupting the spatial arrangement of the cells by removing the top slide of the assembly and subsequently turned back on if desired. Removal of the top slide also provides access to all the cells, including those near the necrotic center, of the sandwich. The cells can then be removed for analysis outside the sandwich system. 61 refs., 17 figs

Pore-Network Modeling of Water and Vapor Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

NARCIS (Netherlands)

Qin, C.; Hassanizadeh, S.M.; van Oosterhout, L.M.

2016-01-01

In the cathode side of a polymer electrolyte fuel cell (PEFC), a micro porous layer (MPL) added between the catalyst layer (CL) and the gas diffusion layer (GDL) plays an important role in water management. In this work, by using both quasi-static and dynamic pore-network models, water and vapor

On nonlinear dynamics of a dipolar exciton BEC in two-layer graphene

International Nuclear Information System (INIS)

Berman, O.L.; Kezerashvili, R.Ya.; Kolmakov, G.V.

2012-01-01

The nonlinear dynamics of a Bose–Einstein condensate (BEC) of dipolar excitons in two-layer graphene is studied. It is demonstrated that a steady turbulent state is formed in this system. A comparison between the dynamics of the exciton BEC in two-layer graphene and those in GaAs/AlGaAs coupled quantum wells shows that turbulence is a general effect in a BEC.

Layering of confined water between two graphene sheets and its liquid–liquid transition

International Nuclear Information System (INIS)

Zhou Xuyan; Duan Yunrui; Wang Long; Liu Sida; Li Tao; Li Yifan; Li Hui

2017-01-01

Molecular dynamics (MD) simulations are performed to explore the layering structure and liquid–liquid transition of liquid water confined between two graphene sheets with a varied distance at different pressures. Both the size of nanoslit and pressure could cause the layering and liquid–liquid transition of the confined water. With increase of pressure and the nanoslit’s size, the confined water could have a more obvious layering. In addition, the neighboring water molecules firstly form chain structure, then will transform into square structure, and finally become triangle with increase of pressure. These results throw light on layering and liquid–liquid transition of water confined between two graphene sheets. (paper)

First passage time in a two-layer system

International Nuclear Information System (INIS)

Lee, J.; Koplik, J.

1995-01-01

As a first step in the first passage problem for passive tracer in stratified porous media, we consider the case of a two-dimensional system consisting of two layers with different convection velocities. Using a lattice generating function formalism and a variety of analytic and numerical techniques, we calculate the asymptotic behavior of the first passage time probability distribution. We show analytically that the asymptotic distribution is a simple exponential in time for any choice of the velocities. The decay constant is given in terms of the largest eigenvalue of an operator related to a half-space Green's function. For the anti-symmetric case of opposite velocities in the layers, we show that the decay constant for system length L crosses over from L -2 behavior in the diffusive limit to L -1 behavior in the convective regime, where the crossover length L* is given in terms of the velocities. We also have formulated a general self-consistency relation, from which we have developed a recursive approach which is useful for studying the short-time behavior

Influence of layer-by-layer assembled electrospun poly (L-lactic acid) nanofiber mats on the bioactivity of endothelial cells

Science.gov (United States)

Wu, Keke; Zhang, Xiazhi; Yang, Wufeng; Liu, Xiaoyan; Jiao, Yanpeng; Zhou, Changren

2016-12-01

Electrospun poly(L-lactic acid) (PLLA) nanofiber mats were successfully modified by deposition of multilayers with chitosan (CS), heparin (Hep) and graphene oxide (GO) through electrostatic layer-by-layer (LBL) self-assembly method. In this study, the surface properties of PLLA nanofiber mats before and after modification were investigated via scanning electron microscope (SEM), atomic force microscopy (AFM), attenuated total reflectance fourier transformation infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. In addition, the cytocompatibility of the modified PLLA nanofiber mats were investigated by testing endothelial cells compatibility, including cell attachment, cell proliferation and cell cycle. The results revealed that the surfaces of modified PLLA nanofiber mats become much rougher, stifiness and the hydrophilicity of the LBL modified PLLA nanofiber mats were improved compared to original PLLA one. Moreover, the modified PLLA nanofiber mats had promoted the endothelial cells viability attachment significantly. Besides, we studied the PLLA nanofiber mats on the expression of necrosis factor (TNF-α), interleukine-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells. The results showed that modified PLLA nanofiber mats had inhibited the inflammatory response to some extent.

Separation prediction in two dimensional boundary layer flows using artificial neural networks

International Nuclear Information System (INIS)

Sabetghadam, F.; Ghomi, H.A.

2003-01-01

In this article, the ability of artificial neural networks in prediction of separation in steady two dimensional boundary layer flows is studied. Data for network training is extracted from numerical solution of an ODE obtained from Von Karman integral equation with approximate one parameter Pohlhousen velocity profile. As an appropriate neural network, a two layer radial basis generalized regression artificial neural network is used. The results shows good agreements between the overall behavior of the flow fields predicted by the artificial neural network and the actual flow fields for some cases. The method easily can be extended to unsteady separation and turbulent as well as compressible boundary layer flows. (author)

Experimental analysis of two-layered dissimilar metals by roll bonding

Science.gov (United States)

Zhao, Guanghui; Li, Yugui; Li, Juan; Huang, Qingxue; Ma, Lifeng

2018-02-01

Rolling reduction and base layers thickness have important implications for rolling compounding. A two-layered 304 stainless steel/Q345R low alloyed steel was roll bonded. The roll bonding was performed at the three thickness reductions of 25%, 40% and 55% with base layers of various thicknesses (Q345R). The microstructures of the composite were investigated by the ultra-deep microscope (OM) and scanning electron microscope (SEM) and Transmission electron microscope (TEM). Simultaneously, the mechanical properties of the composite were experimentally measured and the tensile fracture surfaces were observed by SEM. The interfaces were successfully bonded without any cracking or voids, which indicated a good fabrication of the 304/Q345R composite. The rolling reduction rate and thinning increase of the substrate contributed to the bonding effects appearance of the roll bonded sheet. The Cr and Ni enriched diffusion layer was formed by the interface elements diffusion. The Cr and Ni diffusion led to the formation of ˜10 μm wide Cr and Ni layers on the carbon steel side.

Two-dimensional steady unsaturated flow through embedded elliptical layers

Science.gov (United States)

Bakker, Mark; Nieber, John L.

2004-12-01

New analytic element solutions are presented for unsaturated, two-dimensional steady flow in vertical planes that include nonoverlapping impermeable elliptical layers and elliptical inhomogeneities. The hydraulic conductivity, which is represented by an exponential function of the pressure head, differs between the inside and outside of an elliptical inhomogeneity; both the saturated hydraulic conductivity and water retention parameters are allowed to differ between the inside and outside. The Richards equation is transformed, through the Kirchhoff transformation and a second standard transformation, into the modified Helmholtz equation. Analytic element solutions are obtained through separation of variables in elliptical coordinates. The resulting equations for the Kirchhoff potential consist of infinite sums of products of exponentials and modified Mathieu functions. In practical applications the series are truncated but still fulfill the differential equation exactly; boundary conditions are met approximately but up to machine accuracy, provided that enough terms are used. The pressure head, saturation, and flow may be computed analytically at any point in the vadose zone. Examples are given of the shadowing effect of an impermeable elliptical layer in a uniform flow field and funnel-type flow between two elliptical inhomogeneities. The presented solutions may be applied to study transport processes in vadose zones containing many impermeable elliptical layers or elliptical inhomogeneities.

Highly efficient polymer solar cells with printed photoactive layer: rational process transfer from spin-coating

KAUST Repository

Zhao, Kui

2016-09-05

Scalable and continuous roll-to-roll manufacturing is at the heart of the promise of low-cost and high throughput manufacturing of solution-processed photovoltaics. Yet, to date the vast majority of champion organic solar cells reported in the literature rely on spin-coating of the photoactive bulk heterojunction (BHJ) layer, with the performance of printed solar cells lagging behind in most instances. Here, we investigate the performance gap between polymer solar cells prepared by spin-coating and blade-coating the BHJ layer for the important class of modern polymers exhibiting no long range crystalline order. We find that thickness parity does not always yield performance parity even when using identical formulations. Significant differences in the drying kinetics between the processes are found to be responsible for BHJ nanomorphology differences. We propose an approach which benchmarks the film drying kinetics and associated BHJ nanomorphology development against those of the champion laboratory devices prepared by spin-coating the BHJ layer by adjusting the process temperature. If the optimization requires the solution concentration to be changed, then it is crucial to maintain the additive-to-solute volume ratio. Emulating the drying kinetics of spin-coating is also shown to help achieve morphological and performance parities. We put this approach to the test and demonstrate printed PTB7:PC71BM polymer solar cells with efficiency of 9% and 6.5% PCEs on glass and flexible PET substrates, respectively. We further demonstrate performance parity for two other popular donor polymer systems exhibiting rigid backbones and absence of a long range crystalline order, achieving a PCE of 9.7%, the highest efficiency reported to date for a blade coated organic solar cell. The rational process transfer illustrated in this study should help the broader and successful adoption of scalable printing methods for these material systems.

Ultrasound evaluation of the cesarean scar: comparison between one- and two layer uterotomy closure

DEFF Research Database (Denmark)

Glavind, Julie; Madsen, Lene Duch; Uldbjerg, Niels

Objectives: To compare the residual myometrial thickness and the size of the cesarean scar defect after one- and two layer uterotomy closure. Methods: From July 2010 a continuous two-layer uterotomy closure technique replaced a continuous one-layer technique after cesarean delivery...... at the Department of Obstetrics and Gynecology at Aarhus University Hospital. A total of 149 consecutively invited women (68 women with one-layer and 81 women with two-layer closure) had their cesarean scar examined with 2D transvaginal sonography (TVS) 6-16 months post partum. Inclusion criteria were non......-pregnant women with one previous elective cesarean, no post-partum uterine infection or uterine re-operation, and no type 1 diabetes. Scar defect width, depth, and residual myometrial thickness were measured on the sagittal plane, and scar defect length was measured on the transverse plane. Results: The median...