WorldWideScience

Sample records for two-dimensional thin layer

  1. Two-dimensional thin-layer chromatography in the analysis of secondary plant metabolites.

    Science.gov (United States)

    Cieśla, Lukasz; Waksmundzka-Hajnos, Monika

    2009-02-13

    Drugs, derived from medicinal plants, have been enjoying a renaissance in the last years. It is due to a great pharmacological potential of herbal drugs, as many natural compounds have been found to exhibit biological activity of wide spectrum. The introduction of whole plants, plant extracts, or isolated natural compounds has led to the need to create the analytical methods suitable for their analysis. The identification of isolated substances is relatively an easy task, but the analysis of plant extracts causes a lot of problems, as they are usually very complex mixtures. Chromatographic methods are one of the most popular techniques applied in the analysis of natural mixtures. Unfortunately the separation power of traditional, one-dimensional techniques, is usually inadequate for separation of more complex samples. In such a case the use of multidimensional chromatography is advised. Planar chromatography gives the possibility of performing two-dimensional separations with the use of one adsorbent with two different eluents or by using bilayer plates or graft thin-layer chromatography (TLC) technique; combinations of different multidimensional techniques are also possible. In this paper, multidimensional planar chromatographic methods, commonly applied in the analysis of natural compounds, were reviewed. A detailed information is given on the methodology of performing two-dimensional separations on one adsorbent, on bilayer plates, with the use of graft TLC and hyphenated methods. General aspects of multidimensionality in liquid chromatography are also described. Finally a reader will find a description of variable two-dimensional methods applied in the analysis of compounds, most commonly encountered in plant extracts. This paper is aimed to draw attention to the potential of two-dimensional planar chromatography in the field of phytochemistry. It may be useful for those who are interested in achieving successful separations of multicomponent mixtures by means

  2. Atomically thin two-dimensional materials as hole extraction layers in organolead halide perovskite photovoltaic cells

    Science.gov (United States)

    Kim, Yu Geun; Kwon, Ki Chang; Le, Quyet Van; Hong, Kootak; Jang, Ho Won; Kim, Soo Young

    2016-07-01

    Atomically thin two-dimensional materials such as MoS2, WS2, and graphene oxide (GO) are used as hole extraction layers (HEL) in organolead halide perovskites solar cells (PSCs) instead of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HEL. MoS2 and WS2 layers with a polycrystalline structure were synthesized by a chemical deposition method using a uniformly spin-coated (NH4)MoS4 and (NH4)WS4 precursor solution. GO was synthesized by the oxidation of natural graphite powder using Hummers' method. The work functions of MoS2, WS2, and GO are measured to be 5.0, 4.95, and 5.1 eV, respectively. The X-ray diffraction spectrum indicated that the synthesized perovskite material is CH3NH3PbI3-xClx. The PSCs with the p-n junction structure were fabricated based on the CH3NH3PbI3-xClx perovskite layer. The power conversion efficiencies of the MoS2, WS2, and GO-based PSCs were 9.53%, 8.02%, and 9.62%, respectively, which are comparable to those obtained from PEDOT:PSS-based devices (9.93%). These results suggest that two-dimensional materials such as MoS2, WS2, and GO can be promising candidates for the formation of HELs in the PSCs.

  3. Crystalline-crystalline phase transformation in two-dimensional In2Se3 thin layers.

    Science.gov (United States)

    Tao, Xin; Gu, Yi

    2013-08-14

    We report, for the first time, the fabrication of single-crystal In2Se3 thin layers using mechanical exfoliation and studies of crystalline-crystalline (α → β) phase transformations as well as the corresponding changes of the electrical properties in these thin layers. Particularly, using electron microscopy and correlative in situ micro-Raman and electrical measurements, we show that, in contrast to bulk single crystals, the β phase can persist in single-crystal thin layers at room temperature (RT). The single-crystal nature of the layers before and after the phase transition allows for unambiguous determination of changes in the electrical resistivity. Specifically, the β phase has an electrical resistivity about 1-2 orders of magnitude lower than the α phase. Furthermore, we find that the temperature of the α → β phase transformation increases by as much as 130 K with the layer thickness decreasing from ~87 nm to ~4 nm. These single-crystal thin layers are ideal for studying the scaling behavior of the phase transformations and associated changes of the electrical properties. For these In2Se3 thin layers, the accessibility of the β phase at RT, with distinct electrical properties than the α phase, provides the basis for multilevel phase-change memories in a single material system.

  4. Two-dimensional thin-layer chromatographic method for the analysis of ochratoxin A in green coffee.

    Science.gov (United States)

    Ventura, Meritxell; Anaya, Ivan; Broto-Puig, Francesc; Agut, Montserrat; Comellas, Lluís

    2005-09-01

    A low-cost thin-layer chromatographic method has been developed for the presumptive measurement of ochratoxin A (OTA) at 5 microg/kg in green coffee beans. The analytical method consisted of extracting OTA by shaking the beans with a mixture of methanol and aqueous sodium bicarbonate solution, which was then purified by liquid-liquid partition into toluene. OTA was separated by normal-phase two-dimensional thin-layer chromatography and detected by visual estimation of fluorescence intensity under a UV lamp at 365 nm. The chromatography solvents were toluene-methanol-formic acid (8:2:0.03) for the first development and petroleum ether-ethyl acetate-formic acid (8:10:1) for the second dimension development. This method was tested with uncontaminated green coffee bean samples spiked with an OTA standard at four different concentrations (5, 10, 20, and 30 microg/kg). The method is rapid, simple, and very easy to implement in coffee-producing countries. It is highly selective and does not involve the use of chlorinated solvents in the sample extraction step. This inexpensive method has been applied to different types of green coffee samples from various countries (Zimbabwe, Brazil, India, Uganda, Colombia, and Indonesia) and different manufacturers, and no OTA below the detection limit of 5 microg/kg was detected in any samples analyzed.

  5. Hydrophobic-hydrophilic monolithic dual-phase layer for two-dimensional thin-layer chromatography coupled with surface-enhanced Raman spectroscopy detection.

    Science.gov (United States)

    Zheng, Binxing; Liu, Yanhua; Li, Dan; Chai, Yifeng; Lu, Feng; Xu, Jiyang

    2015-08-01

    Hydrophobic-hydrophilic monolithic dual-phase plates have been prepared by a two-step polymerization method for two-dimensional thin-layer chromatography of low-molecular-weight compounds, namely, several dyes. The thin 200 μm poly(glycidyl methacrylate-co-ethylene dimethacrylate) layers attached to microscope glass plates were prepared using a UV-initiated polymerization method within a simple glass mold. After cutting and cleaning the specific area of the layer, the reassembled mold was filled with a polymerization mixture of butyl methacrylate and ethylene dimethacrylate and subsequently irradiated with UV light. During the second polymerization process, the former layer was protected from the UV light with a UV mask. After extracting the porogens and hydrolyzing the poly(glycidyl methacrylate-co-ethylene dimethacrylate) area, these two-dimensional layers were used to separate a mixture of dyes with great difference in their polarity using reversed-phase chromatography mode within the hydrophobic layer and then hydrophilic interaction chromatography mode along the hydrophilic area. In the latter dimension only the specific spot was developed further. Detection of the separated dyes could be achieved with surface-enhanced Raman spectroscopy.

  6. Optimized two-dimensional thin layer chromatography to monitor the intracellular concentration of acetyl phosphate and other small phosphorylated molecules

    Science.gov (United States)

    2008-01-01

    Acetyl phosphate (acetyl-P) serves critical roles in coenzyme A recycling and ATP synthesis. It is the intermediate of the Pta-AckA pathway that inter-converts acetyl-coenzyme A and acetate. Acetyl-P also can act as a global signal by donating its phosphoryl group to specific two-component response regulators. This ability derives from its capacity to store energy in the form of a high-energy phosphate bond. This bond, while critical to its function, also destabilizes acetyl-P in cell extracts. This lability has greatly complicated biochemical analysis, leading in part to widely varying acetyl-P measurements. We therefore developed an optimized protocol based on two-dimensional thin layer chromatography that includes metabolic labeling under aerated conditions and careful examination of the integrity of acetyl-P within extracts. This protocol results in greatly improved reproducibility, and thus permits precise measurements of the intracellular concentration of acetyl-P, as well as that of other small phosphorylated molecules. PMID:18385806

  7. Monolithic Superhydrophobic Polymer Layer with Photopatterned Virtual Channel for the Separation of Peptides Using Two-Dimensional Thin Layer Chromatography-Desorption Electrospray Ionization Mass Spectrometry

    Science.gov (United States)

    Han, Yehua; Levkin, Pavel; Abarientos, Irene; Liu, Huwei; Svec, Frantisek; Fréchet, Jean M.J.

    2010-01-01

    Superhydrophobic monolithic porous polymer layers with a photopatterned hydrophilic channel have been prepared. These layers were used for two-dimensional thin layer chromatography of peptides. The 50 μm thin poly(butyl methacrylate-co-ethylene dimethacrylate) layers supported onto 4.0 × 3.3 cm glass plates were prepared using UV-initiated polymerization in a simple glass mold. Photografting of a mixture of 2-acrylamido-2-methyl-1-propanesulfonic acid and 2-hydroxyethyl methacrylate carried out through a mask afforded a 600 μm wide virtual channel along one side of the layer. This channel, which contains ionizable functionalities, enabled the first dimension separation in ion exchange mode. The aqueous mobile phase migrates only through the channel due to the large difference in surface tension at the interface of the hydrophilic channel and the superhydrophobic monolith. The unmodified part of the layer featuring hydrophobic chemistry was then used for the reversed phase separation in the orthogonal second dimension. Practical application of our technique was demonstrated with a rapid 2D separation of a mixture of model peptides differing in hydrophobicity and isoelectric point using a combination of ion-exchange and reversed phase modes. In the former mode, the peptides migrated 11 mm in less than 1 min. Detection of fluorescently labeled peptides was achieved through UV light visualization. Separation of the native peptides was monitored directly using a desorption electrospray ionization (DESI) source coupled to a mass spectrometer. Unidirectional surface scanning with the DESI source was found suitable to determine both the location of each separated peptide and its molecular mass. PMID:20151661

  8. Two-dimensional high-performance thin-layer chromatography of tryptic bovine albumin digest using normal- and reverse-phase systems with silanized silica stationary phase.

    Science.gov (United States)

    Gwarda, Radosław Łukasz; Dzido, Tadeusz Henryk

    2013-10-18

    Among many advantages of planar techniques, two-dimensional (2D) separation seems to be the most important for analysis of complex samples. Here we present quick, simple and efficient two-dimensional high-performance thin-layer chromatography (2D HPTLC) of bovine albumin digest using commercial HPTLC RP-18W plates (silica based stationary phase with chemically bonded octadecyl ligands of coverage density 0.5μmol/m(2) from Merck, Darmstadt). We show, that at low or high concentration of water in the mobile phase comprised methanol and some additives the chromatographic systems with the plates mentioned demonstrate normal- or reversed-phase liquid chromatography properties, respectively, for separation of peptides obtained. These two systems show quite different separation selectivity and their combination into 2D HPTLC process provides excellent separation of peptides of the bovine albumin digest. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Qualitative and quantitative two-dimensional thin-layer chromatography/high performance liquid chromatography/diode-array/electrospray-ionization-time-of-flight mass spectrometry of cholinesterase inhibitors.

    Science.gov (United States)

    Mroczek, Tomasz

    2016-09-10

    Recently launched thin-layer chromatography-mass spectrometry (TLC-MS) interface enabling extraction of compounds directly from TLC plates into MS ion source was unusually extended into two-dimensional thin-layer chromatography/high performance liquid chromatography (2D, TLC/HPLC) system by its a direct connection to a rapid resolution 50×2.1mm, I.D. C18 column compartment followed by detection by diode array (DAD) and electrospray ionisation time-of-flight mass spectrometry (ESI-TOF-MS). In this way, even not separated bands of complicated mixtures of natural compounds could be analysed structurally, only within 1-2min after development of TLC plates. In comparison to typically applied TLC-MS interface, no ion suppression for acidic mobile phases was observed. Also, substantial increase in ESI-TOF-MS sensitivities and quality of spectra, were noticed. It has been utilised in combination with TLC- based bioautographic approaches of acetylcholinesterase (AChE) inhibitors, However, it can be also applied in any other procedures related to bioactivity (e.g. 2,2-Diphenyl-1-picryl-hydrazyl-DPPH screen test for radicals). This system has been also used for determination of half maximal inhibitory concentration (IC50 values) of the active inhibitor-galanthamine, as an example. Moreover, AChE inhibitory potencies of some of purified plant extracts, never studied before, have been quantitatively measured. This is first report of usage such the 2D TLC/HPLC/MS system both for qualitative and quantitative evaluation of cholinesterase inhibitors in biological matrices. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Monolithic polymer layer with gradient of hydrophobicity for separation of peptides using two-dimensional thin layer chromatography and MALDI-TOF-MS detection.

    Science.gov (United States)

    Urbanova, Iva; Svec, Frantisek

    2011-08-01

    Superhydrophobic monolithic porous polymer layers supported onto glass plates with a gradient of hydrophobicity have been prepared and used for 2-D thin layer chromatography of peptides. The 50 μm-thin poly(glycidyl methacrylate-co-ethylene dimethacrylate) layers prepared using UV-initiated polymerization in a simple mold were first hydrolyzed using dilute sulfuric acid and then hydrophilized via two-step grafting of poly(ethylene glycol) methacrylate to obtain superhydrophilic plates. The hydrophobicity was then formed by photografting of lauryl methacrylate. The exposure to UV light that initiates photografting was spatially controlled using moving shutter that enabled forming of the diagonal gradient of hydrophobicity. This new concept enables the solutes to encounter the gradient for each of the two sequential developments. Practical application of our novel plates was demonstrated with a rapid 2-D separation of a mixture of model peptides gly-tyr, val-tyr-val, leucine enkephalin, and oxytocin in dual reversed-phase mode using different mobile phases in each direction. Detection of fluorescent-labeled peptides was achieved through UV light visualization while separation of native leucine enkephalin and oxytocin was monitored directly using MALDI mass spectrometry. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers

    Science.gov (United States)

    2016-06-15

    polymers . 2. Introduction . Research objectives: This research aims to study the physical (van der Waals forces: crystal epitaxy and π-π...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

  12. Densitometric determination of catecholamine metabolites and 5-hydroxy-indoleacetic acid after two-dimensional thin-layer chromatography on cellulose

    NARCIS (Netherlands)

    Breebaart, K.; Haan, A.M.F.H.; Wadman, S.K.

    A quantitative two-dimensional chromatographic determination for the catecholamine metabolites vanilglycolic (vanilmandelic) acid, vanilacetic acid, vanillactic acid and vanilglycol is described. The method can also be used for the determination of 5-hydroxy-indoleacetic acid. The analytical

  13. Two-dimensional thin-layer chromatography with adsorbent gradient as a method of chromatographic fingerprinting of furanocoumarins for distinguishing selected varieties and forms of Heracleum spp.

    Science.gov (United States)

    Cieśla, Lukasz; Bogucka-Kocka, Anna; Hajnos, Michał; Petruczynik, Anna; Waksmundzka-Hajnos, Monika

    2008-10-17

    There are a lot of taxonomic classifications of the genus Heracleum, and many authors indicate they need revision. Morphological identification is difficult to perform, as there are only few characteristic differences between each Heracleum species, varieties and forms. Furanocoumarins are characteristic compounds for the Apiaceae family, and they can be found in the whole genus in large quantities. Despite this fact, it is difficult to use the furanocoumarin profiles of plants, for their discrimination, as furanocoumarins are difficult to separate, due to their similar chemical structures and physicochemical properties. In this paper, a new, simple method is proposed for the discrimination of selected species, varieties and forms of the genus Heracleum. Thin-layer chromatography (TLC) with an adsorbent gradient (unmodified silica gel+octadecylsilica wettable with water) enables complete separation of the structural analogues. The proposed method gives the possibility to distinguish selected species, varieties and forms of the Heracleum genus, as they produce distinctive furanocoumarin fingerprints. The method is characterised by high specificity, precision, reproducibility and stability values. It is for the first time that graft TLC is used for constructing fingerprints of herbs. The complete separation of ten structural analogues, by combining gradient TLC with the unidimensional multiple development technique, has not been reported yet.

  14. Optical modulators with two-dimensional layered materials

    CERN Document Server

    Sun, Zhipei; Wang, Feng

    2016-01-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that two-dimensional layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this review, we cover the state-of-the-art of optical modulators based on two-dimensional layered materials including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as two-dimensional heterostructures, plasmonic structures, and silicon/fibre integrated structures. We also take a look at future perspectives and discuss the potential of yet relatively unexplored mechanisms such as magneto-optic and acousto-optic modulation.

  15. How two-dimensional bending can extraordinarily stiffen thin sheets

    Science.gov (United States)

    Pini, V.; Ruz, J. J.; Kosaka, P. M.; Malvar, O.; Calleja, M.; Tamayo, J.

    2016-07-01

    Curved thin sheets are ubiquitously found in nature and manmade structures from macro- to nanoscale. Within the framework of classical thin plate theory, the stiffness of thin sheets is independent of its bending state for small deflections. This assumption, however, goes against intuition. Simple experiments with a cantilever sheet made of paper show that the cantilever stiffness largely increases with small amounts of transversal curvature. We here demonstrate by using simple geometric arguments that thin sheets subject to two-dimensional bending necessarily develop internal stresses. The coupling between the internal stresses and the bending moments can increase the stiffness of the plate by several times. We develop a theory that describes the stiffness of curved thin sheets with simple equations in terms of the longitudinal and transversal curvatures. The theory predicts experimental results with a macroscopic cantilever sheet as well as numerical simulations by the finite element method. The results shed new light on plant and insect wing biomechanics and provide an easy route to engineer micro- and nanomechanical structures based on thin materials with extraordinary stiffness tunability.

  16. Two-dimensional transport study of scrape off layer plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Nobuyuki [Interdisciplinary Graduate School of Advanced Energy Engineering Sciences, Kyushu University, Fukuoka (Japan); Yagi, Masatoshi; Itoh, Sanae-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    1999-09-01

    Two-dimensional transport code is developed to analyzed the heat pulse propagation in the scrape-off layer plasma. The classical and anomalous transport models are considered as a thermal diffusivity perpendicular to the magnetic field. On the other hand, the classical transport model is chosen as a thermal diffusivity parallel to the magnetic field. The heat deposition profiles are evaluated for various kinds of transport models. It is found that the heat pulse which arrives at the divertor plate due to the classical transport is largest compared with other models. The steady state temperate profiles of the electron and ion are also discussed. (author)

  17. Development of Novel Two-dimensional Layers, Alloys and Heterostructures

    Science.gov (United States)

    Liu, Zheng

    2015-03-01

    The one-atom-think graphene has fantastic properties and attracted tremendous interests in these years, which opens a window towards various two-dimensional (2D) atomic layers. However, making large-size and high-quality 2D layers is still a great challenge. Using chemical vapor deposition (CVD) method, we have successfully synthesized a wide varieties of highly crystalline and large scale 2D atomic layers, including h-BN, metal dichalcogenides e.g. MoS2, WS2, CdS, GaSe and MoSe2 which belong to the family of binary 2D materials. Ternary 2D alloys including BCN and MoS2xSe2 (1 - x) are also prepared and characterized. In addition, synthesis of 2D heterostructures such as vertical and lateral graphene/h-BN, vertical and lateral TMDs are also demonstrated. Complementary to CVD grown 2D layers, 2D single-crystal (bulk) such as Phosphorene (P), WTe2, SnSe2, PtS2, PtSe2, PdSe2, WSe2xTe2 (1 - x), Ta2NiS5andTa2NiSe5 are also prepared by solid reactions. There work provide a better understanding of the atomic layered materials in terms of the synthesis, atomic structure, alloying and their physical properties. Potential applications of these 2D layers e.g. optoelectronic devices, energy device and smart coating have been explored.

  18. Novel layered two-dimensional semiconductors as the building blocks for nano-electronic/photonic systems

    Science.gov (United States)

    Su, Guoxiong; De, Debtanu; Hadjiev, Viktor G.; Peng, Haibing

    2014-06-01

    Layered two-dimensional (2D) semiconductors beyond graphene have been emerging as potential building blocks for the next-generation electronic/photonic applications. Representative metal chalcogenides, including the widely studied MoS2, possess similar layered crystal structures with weak interaction between adjacent layers, thus allowing the formation of stable thin-layer crystals with thickness down to a few or even single atomic layer. Other important chalcogenides, involving earth-abundant and environment-friendly materials desirable for sustainable applications, include SnS2 (band gap: 2.1 eV) and SnS (band gap: 1.1 eV). So far, commonly adopted for research purpose are mechanical and liquid exfoliation methods for creating thin layers of such 2D semiconductors. Most recently, chemical vapor deposition (CVD) was attracting significant attention as a practical method for producing thin films or crystal grains of MoS2. However, critical yet still absent is an effective experimental approach for controlling the positions of thin crystal grains of layered 2D semiconductors during the CVD process. Here we report the controlled CVD synthesis of thin crystal arrays of representative layered semiconductors (including SnS2 and SnS) at designed locations on chip, promising large-scale optoelectronic applications. Our work opens a window for future practical applications of layered 2D semiconductors in integrated nano-electronic/photonic systems.

  19. The compressible Gortler problem in two-dimensional boundary layers

    Science.gov (United States)

    Dando, Andrew H.; Seddougui, Sharon O.

    1993-01-01

    In this paper the authors investigate the growth rates of Gortler vortices in a compressible flow in the inviscid limit of large Gortler number. Numerical solutions are obtained for O(1) wavenumbers. The further limits of (i) large Mach number and (ii) large wavenumber with O(1) Mach number are considered. It is shown that two different types of disturbance mode can appear in this problem. The first is a wall layer mode, so named as it has its eigenfunctions trapped in a thin layer near the wall. The other mode investigated is confined to a thin layer away from the wall and termed a trapped-layer mode for large wavenumbers and an adjustment-layer mode for large Mach numbers, since then this mode has its eigenfunctions concentrated in the temperature adjustment layer. It is possible to investigate the near crossing of the modes which occurs in each of the limits mentioned. The inviscid limit does not predict a fastest growing mode, but does enable a most dangerous mode to be identified for O(1) Mach number. For hypersonic flow the most dangerous mode depends on the size of the Gortler number.

  20. Vibrations of Thin Piezoelectric Shallow Shells: Two-Dimensional Approximation

    Indian Academy of Sciences (India)

    N Sabu

    2003-08-01

    In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two-dimensional eigenvalue problem.

  1. Transparent Conductive Two-Dimensional Titanium Carbide Epitaxial Thin Films.

    Science.gov (United States)

    Halim, Joseph; Lukatskaya, Maria R; Cook, Kevin M; Lu, Jun; Smith, Cole R; Näslund, Lars-Åke; May, Steven J; Hultman, Lars; Gogotsi, Yury; Eklund, Per; Barsoum, Michel W

    2014-04-08

    Since the discovery of graphene, the quest for two-dimensional (2D) materials has intensified greatly. Recently, a new family of 2D transition metal carbides and carbonitrides (MXenes) was discovered that is both conducting and hydrophilic, an uncommon combination. To date MXenes have been produced as powders, flakes, and colloidal solutions. Herein, we report on the fabrication of ∼1 × 1 cm(2) Ti3C2 films by selective etching of Al, from sputter-deposited epitaxial Ti3AlC2 films, in aqueous HF or NH4HF2. Films that were about 19 nm thick, etched with NH4HF2, transmit ∼90% of the light in the visible-to-infrared range and exhibit metallic conductivity down to ∼100 K. Below 100 K, the films' resistivity increases with decreasing temperature and they exhibit negative magnetoresistance-both observations consistent with a weak localization phenomenon characteristic of many 2D defective solids. This advance opens the door for the use of MXenes in electronic, photonic, and sensing applications.

  2. Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers

    Science.gov (United States)

    2016-06-15

    area electron diffraction (SAED) pattern of a MoSe2 nanosheet. (d) High resolution TEM (HR-TEM) image of the MoSe2 nanosheets. The digitally filtered ...nanosheets and end-functionalized polymers. 15.  SUBJECT TERMS 2D Materials, Nanosheets, Layered Materials, Nanocomposites 16.  SECURITY CLASSIFICATION OF...driving force for mixing between layers and the matrix. In addition, solution processes such as spin coating, dip coating and layer-by-layer coating are

  3. Two-dimensional wave propagation in layered periodic media

    KAUST Repository

    Quezada de Luna, Manuel

    2014-09-16

    We study two-dimensional wave propagation in materials whose properties vary periodically in one direction only. High order homogenization is carried out to derive a dispersive effective medium approximation. One-dimensional materials with constant impedance exhibit no effective dispersion. We show that a new kind of effective dispersion may arise in two dimensions, even in materials with constant impedance. This dispersion is a macroscopic effect of microscopic diffraction caused by spatial variation in the sound speed. We analyze this dispersive effect by using highorder homogenization to derive an anisotropic, dispersive effective medium. We generalize to two dimensions a homogenization approach that has been used previously for one-dimensional problems. Pseudospectral solutions of the effective medium equations agree to high accuracy with finite volume direct numerical simulations of the variable-coeffi cient equations.

  4. Review—Two-Dimensional Layered Materials for Energy Storage Applications

    KAUST Repository

    Kumar, Pushpendra

    2016-07-02

    Rechargeable batteries are most important energy storage devices in modern society with the rapid development and increasing demand for handy electronic devices and electric vehicles. The higher surface-to-volume ratio two-dimensional (2D) materials, especially transition metal dichalcogenides (TMDCs) and transition metal carbide/nitrite generally referred as MXene, have attracted intensive research activities due to their fascinating physical/chemical properties with extensive applications. One of the growing applications is to use these 2D materials as potential electrodes for rechargeable batteries and electrochemical capacitors. This review is an attempt to summarize the research and development of TMDCs, MXenes and their hybrid structures in energy storage systems. (C) The Author(s) 2016. Published by ECS. All rights reserved.

  5. Heterostructures based on two-dimensional layered materials and their potential applications

    KAUST Repository

    Li, Ming-yang

    2015-12-04

    The development of two-dimensional (2D) layered materials is driven by fundamental interest and their potential applications. Atomically thin 2D materials provide a wide range of basic building blocks with unique electrical, optical, and thermal properties which do not exist in their bulk counterparts. The van der Waals interlayer interaction enables the possibility to exfoliate and reassemble different 2D materials into arbitrarily and vertically stacked heterostructures. Recently developed vapor phase growth of 2D materials further paves the way of directly synthesizing vertical and lateral heterojunctions. This review provides insights into the layered 2D heterostructures, with a concise introduction to preparative approaches for 2D materials and heterostructures. These unique 2D heterostructures have abundant implications for many potential applications.

  6. Interfacial engineering of two-dimensional nano-structured materials by atomic layer deposition

    Science.gov (United States)

    Zhuiykov, Serge; Kawaguchi, Toshikazu; Hai, Zhenyin; Karbalaei Akbari, Mohammad; Heynderickx, Philippe M.

    2017-01-01

    Atomic Layer Deposition (ALD) is an enabling technology which provides coating and material features with significant advantages compared to other existing techniques for depositing precise nanometer-thin two-dimensional (2D) nanostructures. It is a cyclic process which relies on sequential self-terminating reactions between gas phase precursor molecules and a solid surface. ALD is especially advantageous when the film quality or thickness is critical, offering ultra-high aspect ratios. ALD provides digital thickness control to the atomic level by depositing film one atomic layer at a time, as well as pinhole-free films even over a very large and complex areas. Digital control extends to sandwiches, hetero-structures, nano-laminates, metal oxides, graded index layers and doping, and it is perfect for conformal coating and challenging 2D electrodes for various functional devices. The technique's capabilities are presented on the example of ALD-developed ultra-thin 2D tungsten oxide (WO3) over the large area of standard 4" Si substrates. The discussed advantages of ALD enable and endorse the employment of this technique for the development of hetero-nanostructure 2D semiconductors with unique properties.

  7. Two-dimensional coupled fluid and electrodynamic calculations for a MHD DCW channel with slag layers

    Science.gov (United States)

    Liu, B. L.

    1982-01-01

    A fully coupled, two dimensional numerical method of modeling linear, coal-fired MHD generators is developed for the case of a plasma flow bounded by a slag layer on the channel walls. The governing partial differential equations for the plasma flow, slag layer and electrodynamics are presented and their coupling discussed. An iterative, numerical procedure employing non-uniform computational meshes and appropriate tridiagonal matrix solution schemes for the equations is presented. The method permits the investigation of the mutual plasma flow-slag layer development for prescribed wall temperatures, electrode geometry, slag properties and channel loading. In particular, the slag layer-plasma interface properties which require prior specification in an uncoupled analysis comprise part of the solution in the present approach. Results are presented for a short diagonally connected generator channel and include contour plots of the electric potential and current stream function as well as transverse and axial profiles of pertinent plasma properties. The results indicate that a thin electrode slag layer can be maintained in the presence of reasonable current density levels.

  8. Nanofluidics in two-dimensional layered materials: inspirations from nature.

    Science.gov (United States)

    Gao, Jun; Feng, Yaping; Guo, Wei; Jiang, Lei

    2017-08-29

    With the advance of chemistry, materials science, and nanotechnology, significant progress has been achieved in the design and application of synthetic nanofluidic devices and materials, mimicking the gating, rectifying, and adaptive functions of biological ion channels. Fundamental physics and chemistry behind these novel transport phenomena on the nanoscale have been explored in depth on single-pore platforms. However, toward real-world applications, one major challenge is to extrapolate these single-pore devices into macroscopic materials. Recently, inspired partially by the layered microstructure of nacre, the material design and large-scale integration of artificial nanofluidic devices have stepped into a completely new stage, termed 2D nanofluidics. Unique advantages of the 2D layered materials have been found, such as facile and scalable fabrication, high flux, efficient chemical modification, tunable channel size, etc. These features enable wide applications in, for example, biomimetic ion transport manipulation, molecular sieving, water treatment, and nanofluidic energy conversion and storage. This review highlights the recent progress, current challenges, and future perspectives in this emerging research field of "2D nanofluidics", with emphasis on the thought of bio-inspiration.

  9. Electronic structure of boron based single and multi-layer two dimensional materials

    Science.gov (United States)

    Miyazato, Itsuki; Takahashi, Keisuke

    2017-09-01

    Two dimensional nanosheets based on boron and Group VA elements are designed and characterized using first principles calculations. B-N, B-P, B-As, B-Sb, and B-Bi are found to possess honeycomb structures where formation energies indicate exothermic reactions. Contrary to B-N, the cases of B-P, B-As, B-Sb, and B-Bi nanosheets are calculated to possess narrow band gaps. In addition, calculations reveal that the electronegativity difference between B and Group VA elements in the designed materials is a good indicator to predict the charge transfer and band gap of the two dimensional materials. Hydrogen adsorption over defect-free B-Sb and B-Bi results in exothermic reactions, while defect-free B-N, B-P, and B-As result in endothermic reactions. The layerability of the designed two dimensional materials is also investigated where the electronic structure of two-layered two dimensional materials is strongly coupled with how the two dimensional materials are layered. Thus, one can consider that the properties of two dimensional materials can be controlled by the composition of two dimensional materials and the structure of layers.

  10. Hexagonal boron nitride: Ubiquitous layered dielectric for two-dimensional electronics

    Science.gov (United States)

    Jain, Nikhil

    Hexagonal boron nitride (h-BN), a layer-structured dielectric with very similar crystalline lattice to that of graphene, has been studied as a ubiquitous dielectric for two-dimensional electronics. While 2D materials may lead to future platform for electronics, traditional thin-film dielectrics (e.g., various oxides) make highly invasive interface with graphene. Multiple key roles of h-BN in graphene electronics are explored in this thesis. 2D graphene/h-BN heterostructures are designed and implemented in diverse configurations in which h-BN is evaluated as a supporting substrate, a gate dielectric, a passivation layer, or an interposing barrier in "3D graphene" superlattice. First, CVD-grown graphene on h-BN substrate shows improved conductivity and resilience to thermally induced breakdown, as compared with graphene on SiO2, potentially useful for high-speed graphene devices and on-chip interconnects. h-BN is also explored as a gate dielectric for graphene field-effect transistor with 2D heterostructure design. The dielectric strength and tunneling behavior of h-BN are investigated, confirming its robust nature. Next, h-BN is studied as a passivation layer for graphene electronics. In addition to significant improvement in current density and breakdown threshold, fully encapsulated graphene exhibits minimal environmental sensitivity, a key benefit to 2D materials which have only surfaces. Lastly, reduction in interlayer carrier scattering is observed in a double-layered graphene setup with ultrathin h-BN multilayer as an interposing layer. The DFT simulation and Raman spectral analysis indicate reduction in interlayer scattering. The decoupling of the two graphene monolayers is further confirmed by electrical characterization, as compared with other referencing mono- and multilayer configurations. The heterostructure serves as the building element in "3D graphene", a versatile platform for future electronics.

  11. Flexural vibration band gaps in thin plates with two-dimensional binary locally resonant structures

    Institute of Scientific and Technical Information of China (English)

    Yu Dian-Long; Wang Gang; Liu Yao-Zong; Wen Ji-Hong; Qiu Jing

    2006-01-01

    The complete flexural vibration band gaps are studied in the thin plates with two-dimensional binary locally resonant structures, i.e. the composite plate consisting of soft rubber cylindrical inclusions periodically placed in a host material. Numerical simulations show that the low-frequency gaps of flexural wave exist in the thin plates. The width of the first gap decreases monotonically as the matrix density increases. The frequency response of the finite periodic thin plates is simulated by the finite element method, which provides attenuations of over 20dB in the frequency range of the band gaps. The findings will be significant in the application of phononic crystals.

  12. A Novel Synthesis of Two-dimensional Nanopatterned TiO2 Thin Film

    Institute of Scientific and Technical Information of China (English)

    Ming Xian LIU; Li Hua GAN; Gen CHEN; Zi Jie XU; Zhi Xian HAO; Long Wu CHEN

    2006-01-01

    A novel two-dimensional nanopatterned TiO2 thin film has been synthesized through the interaction between cationic Gemini surfactant molecules and the prepared TiO2 colloid nanoparticles with average diameters of 8 nm by controlling the surface pressure of the monolayer. TEM photographs from the formed Gemini-TiO2 composite monolayer confirm that the prepared TiO2 film is of a branch nanopattem.

  13. Scattering of Fexural Gravity Waves by a Two-Dimensional Thin Plate

    Directory of Open Access Journals (Sweden)

    Sudeshna Banerjee

    2017-01-01

    Full Text Available An approximate analysis based on standard perturbation technique together with an application of Green’s integral theorem is used in this paper to study the problem of scattering of water waves by a two dimensional thin plate submerged in deep ocean with ice cover. The reflection and transmission coefficients upto first order are obtained in terms of the shape function describing the plate and are studied graphically for different shapes of the plate.

  14. Epitaxial Growth of Two-Dimensional Layered Transition-Metal Dichalcogenides: Growth Mechanism, Controllability, and Scalability

    KAUST Repository

    Li, Henan

    2017-07-06

    Recently there have been many research breakthroughs in two-dimensional (2D) materials including graphene, boron nitride (h-BN), black phosphors (BPs), and transition-metal dichalcogenides (TMDCs). The unique electrical, optical, and thermal properties in 2D materials are associated with their strictly defined low dimensionalities. These materials provide a wide range of basic building blocks for next-generation electronics. The chemical vapor deposition (CVD) technique has shown great promise to generate high-quality TMDC layers with scalable size, controllable thickness, and excellent electronic properties suitable for both technological applications and fundamental sciences. The capability to precisely engineer 2D materials by chemical approaches has also given rise to fascinating new physics, which could lead to exciting new applications. In this Review, we introduce the latest development of TMDC synthesis by CVD approaches and provide further insight for the controllable and reliable synthesis of atomically thin TMDCs. Understanding of the vapor-phase growth mechanism of 2D TMDCs could benefit the formation of complicated heterostructures and novel artificial 2D lattices.

  15. Synthesis and characterization of pure mesoporous zirconia thin film with two-dimensional hexagonal framework

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Pure mesoporous ZrO2 thin film with two-dimensional hexagonal framework mesostructure has been successfully prepared by using a nonionic triblock copolymer as the structure-directing agent and ZrCl4 as the zirconia source through evaporation-induced self-assembly approach. The resulting materials were characterized by X-ray diffraction, scanning electron microscope, and nitrogen adsorption measurements. The obtained mesoporous ZrO2 thin film has a nanocrystalline inorganic framework (tetragonal zirconia) and narrowly distributed mesopore size (6. 7 nm in diameter).

  16. EFFECT OF SMALL CLUSTER DIFFUSION DURING TWO-DIMENSIONAL THIN FILM GROWTH ON METAL SURFACE

    Institute of Scientific and Technical Information of China (English)

    WU FENG-MIN; LI QIAO-WEN; WU ZI-QIN

    2000-01-01

    The diffusion of small clusters such as dimers and trimers on metal surface and the growth of two-dimensional thin films are studied by Monte Carlo simulation, using realistic growth model and physical parameters. It is found that small cluster diffusion plays an important role in the process of thin film growth at not very low temperature. It affects not only the island density and the size of islands but also the critical value of saturation occurring during growth of thin films. The effect of small cluster diffusion depends on both the size of critical nucleus and the growth temperature.The simulation results also show that the larger the cluster allowed to diffuse, the easier the saturation that takes place,giving rise to the lower critical coverage of saturation occurring. It is suggested that the effect of small cluster diffusion should be included in establishing the growth models of thin films.

  17. DISPLAY-2: a two-dimensional shallow layer model for dense gas dispersion including complex features.

    Science.gov (United States)

    Venetsanos, A G; Bartzis, J G; Würtz, J; Papailiou, D D

    2003-04-25

    A two-dimensional shallow layer model has been developed to predict dense gas dispersion, under realistic conditions, including complex features such as two-phase releases, obstacles and inclined ground. The model attempts to predict the time and space evolution of the cloud formed after a release of a two-phase pollutant into the atmosphere. The air-pollutant mixture is assumed ideal. The cloud evolution is described mathematically through the Cartesian, two-dimensional, shallow layer conservation equations for mixture mass, mixture momentum in two horizontal directions, total pollutant mass fraction (vapor and liquid) and mixture internal energy. Liquid mass fraction is obtained assuming phase equilibrium. Account is taken in the conservation equations for liquid slip and eventual liquid rainout through the ground. Entrainment of ambient air is modeled via an entrainment velocity model, which takes into account the effects of ground friction, ground heat transfer and relative motion between cloud and surrounding atmosphere. The model additionally accounts for thin obstacles effects in three ways. First a stepwise description of the obstacle is generated, following the grid cell faces, taking into account the corresponding area blockage. Then obstacle drag on the passing cloud is modeled by adding flow resistance terms in the momentum equations. Finally the effect of extra vorticity generation and entrainment enhancement behind obstacles is modeled by adding locally into the entrainment formula without obstacles, a characteristic velocity scale defined from the obstacle pressure drop and the local cloud height.The present model predictions have been compared against theoretical results for constant volume and constant flux gravity currents. It was found that deviations of the predicted cloud footprint area change with time from the theoretical were acceptably small, if one models the frictional forces between cloud and ambient air, neglecting the Richardson

  18. Prandtl's Boundary Layer Equation for Two-Dimensional Flow: Exact Solutions via the Simplest Equation Method

    Directory of Open Access Journals (Sweden)

    Taha Aziz

    2013-01-01

    Full Text Available The simplest equation method is employed to construct some new exact closed-form solutions of the general Prandtl's boundary layer equation for two-dimensional flow with vanishing or uniform mainstream velocity. We obtain solutions for the case when the simplest equation is the Bernoulli equation or the Riccati equation. Prandtl's boundary layer equation arises in the study of various physical models of fluid dynamics. Thus finding the exact solutions of this equation is of great importance and interest.

  19. Point Defects in Two-Dimensional Layered Semiconductors: Physics and Its Applications

    Science.gov (United States)

    Suh, Joonki

    Recent advances in material science and semiconductor processing have been achieved largely based on in-depth understanding, efficient management and advanced application of point defects in host semiconductors, thus finding the relevant techniques such as doping and defect engineering as a traditional scientific and technological solution. Meanwhile, two- dimensional (2D) layered semiconductors currently draw tremendous attentions due to industrial needs and their rich physics at the nanoscale; as we approach the end of critical device dimensions in silicon-based technology, ultra-thin semiconductors have the potential as next- generation channel materials, and new physics also emerges at such reduced dimensions where confinement of electrons, phonons, and other quasi-particles is significant. It is therefore rewarding and interesting to understand and redefine the impact of lattice defects by investigating their interactions with energy/charge carriers of the host matter. Potentially, the established understanding will provide unprecedented opportunities for realizing new functionalities and enhancing the performance of energy harvesting and optoelectronic devices. In this thesis, multiple novel 2D layered semiconductors, such as bismuth and transition- metal chalcogenides, are explored. Following an introduction of conventional effects induced by point defects in semiconductors, the related physics of electronically active amphoteric defects is revisited in greater details. This can elucidate the complication of a two-dimensional electron gas coexisting with the topological states on the surface of bismuth chalcogenides, recently suggested as topological insulators. Therefore, native point defects are still one of the keys to understand and exploit topological insulators. In addition to from a fundamental science point of view, the effects of point defects on the integrated thermal-electrical transport, as well as the entropy-transporting process in

  20. Analysis of Two-Layered Random Interfaces for Two Dimensional Widom-Rowlinson's Model

    Directory of Open Access Journals (Sweden)

    Jun Wang

    2011-01-01

    Full Text Available The statistical behaviors of two-layered random-phase interfaces in two-dimensional Widom-Rowlinson's model are investigated. The phase interfaces separate two coexisting phases of the lattice Widom-Rowlinson model; when the chemical potential μ of the model is large enough, the convergence of the probability distributions which describe the fluctuations of the phase interfaces is studied. In this paper, the backbones of interfaces are introduced in the model, and the corresponding polymer chains and cluster expansions are developed and analyzed for the polymer weights. And the existence of the free energy for two-layered random-phase interfaces of the two-dimensional Widom-Rowlinson model is given.

  1. Raman spectroscopy of atomically thin two-dimensional magnetic iron phosphorus trisulfide (FePS3) crystals

    Science.gov (United States)

    Wang, Xingzhi; Du, Kezhao; Liu, Yu Yang Fredrik; Hu, Peng; Zhang, Jun; Zhang, Qing; Owen, Man Hon Samuel; Lu, Xin; Gan, Chee Kwan; Sengupta, Pinaki; Kloc, Christian; Xiong, Qihua

    2016-09-01

    Metal phosphorous trichalcogenide is an important group of layered two-dimensional (2D) materials with potentially diverse applications in low-dimensional magnetic and spintronic devices. Herein we present a comprehensive investigation on the lattice dynamics and spin-phonon interactions of mechanically exfoliated atomically thin 2D magnetic material—iron phosphorus trisulfide (FePS3) by Raman spectroscopy and first principle calculations. Layer-number and temperature dependent Raman spectroscopy suggests a magnetic persistence in FePS3 even down to monolayer regime through the spin-phonon coupling, while the Néel temperature decreases from 117 K in bulk to 104 K in monolayer sample. Our studies advocate the intriguing magnetic properties in 2D crystals and suggest that FePS3 is a promising candidate material for future magnetic applications.

  2. Group classification of steady two-dimensional boundary-layer stagnation-point flow equations

    OpenAIRE

    Nadjafikhah, Mehdi; Hejazi, Seyed Reza

    2010-01-01

    Lie symmetry group method is applied to study the boundary-layer equations for two-dimensional steady flow of an incompressible, viscous fluid near a stagnation point at a heated stretching sheet placed in a porous medium equation. The symmetry group and its optimal system are given, and group invariant solutions associated to the symmetries are obtained. Finally the structure of the Lie algebra symmetries is determined.

  3. Thin catheter bending in the direction perpendicular to ultrasound propagation using two-dimensional array transducer

    Science.gov (United States)

    Suzuki, Toshiya; Mochizuki, Takashi; Ushimizu, Hidetaka; Miyazawa, Shinya; Tsurui, Nobuhiro; Masuda, Kohji

    2017-07-01

    Although we have already experimented on the bending of a thin catheter with acoustic radiation force using a single transducer, it is necessary to develop a method of bending a catheter in an arbitrary direction because the installation position of ultrasound transducers on a body surface is limited for application to various shapes of in vivo blood vessels. Therefore, we examined the bending of a thin catheter in the direction perpendicular to ultrasound propagation using a two-dimensional array transducer (1 MHz), which realizes not only the temporospatial design but also the dynamic variation of acoustic fields. Forming two focal points with opposite phases, where the amplitudes of the two points instantaneously have the positive and negative relationship, we confirmed the bending of a thin catheter in the direction perpendicular to ultrasound propagation. We used a thin catheter (diameter, 200 µm length, 50 mm) to obtain the maximum displacement of 220 µm, where the displacement was proportional to the square of the maximum sound pressure and the duty ratio. From these results, the acoustic energy densities observed in front of and behind the catheter are dominant for the bending of the thin catheter independent of ultrasound propagation. We also found that the distance between two focal points may improve the bending performance without requiring a precise position setting.

  4. Photodetectors Based on Two-Dimensional Layer-Structured Hybrid Lead Iodide Perovskite Semiconductors.

    Science.gov (United States)

    Zhou, Jiachen; Chu, Yingli; Huang, Jia

    2016-10-05

    Hybrid lead iodide perovskite semiconductors have attracted intense research interests recently because of their easy fabrication processes and high power conversion efficiencies in photovoltaic applications. Layer-structured materials have interesting properties such as quantum confinement effect and tunable band gap due to the unique two-dimensional crystalline structures. ⟨100⟩-oriented layer-structured perovskite materials are inherited from three-dimensional ABX3 perovskite materials with a generalized formula of (RNH3)2(CH3NH3)n-1MnX3n+1, and adopt the Ruddlesden-Popper type crystalline structure. Here we report the synthesis and investigation of three layer-structured perovskite materials with different layer numbers: (C4H9NH3)2PbI4 (n = 1, one-layered perovskite), (C4H9NH3)2(CH3NH3)Pb2I7 (n = 2, two-layered perovskite) and (C4H9NH3)2(CH3NH3)2Pb3I10 (n = 3, three-layered perovskite). Their photoelectronic properties were investigated in related to their molecular structures. Photodetectors based on these two-dimensional (2D) layer-structured perovskite materials showed tunable photoresponse with short response time in milliseconds. The photodetectors based on three-layered perovskite showed better performances than those of the other two devices, in terms of output current, responsivity, Ilight/Idark ratio, and response time, because of its smaller optical band gap and more condensed microstructure comparing the other two materials. These results revealed the relationship between the molecular structures, film microstructures and the photoresponse properties of 2D layer-structured hybrid perovskites, and demonstrated their potentials as flexible, functional, and tunable semiconductors in optoelectronic applications, by taking advantage of their tunable quantum well molecular structure.

  5. Facile Synthesis and Characterization of Two Dimensional Layered Tin Disulfide Nanowalls

    Science.gov (United States)

    Mutlu, Zafer; Shahrezaei, Sina; Temiz, Selcuk; Ozkan, Mihrimah; Ozkan, Cengiz S.

    2016-04-01

    Two dimensional layered metal chalcogenides, especially tin sulfides, have recently received great interest due to their enticing physical and chemical properties and hold promise for various applications. We report on synthesis of phase-pure two dimensional tin disulfide nanowalls by a facile vapor-phase synthesis method on insulator substrates such as silicon dioxide and magnesium oxide using tin dioxide and sulfur powders as precursors. The synthesized tin disulfide nanowalls have been characterized to study their fundamental properties by using various techniques such as scanning electron microscopy, x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. The synthesized films have an open network structure constituted of very uniform interconnected nanowalls with high crystallinity.

  6. Nonlinear incompressible finite element for simulating loading of cardiac tissue--Part I: Two dimensional formulation for thin myocardial strips.

    Science.gov (United States)

    Horowitz, A; Sheinman, I; Lanir, Y; Perl, M; Sideman, S

    1988-02-01

    A two-dimensional incompressible plane-stress finite element is formulated for the simulation of the passive-state mechanics of thin myocardial strips. The formulation employs a total Lagrangian and materially nonlinear approach, being based on a recently proposed structural material law, which is derived from the histological composition of the tissue. The ensuing finite element allows to demonstrate the mechanical properties of a single myocardial layer containing uniformly directed fibers by simulating various loading cases such as tension, compression and shear. The results of these cases show that the fiber direction is considerably stiffer than the cross-fiber direction, that there is significant coupling between these two directions, and that the shear stiffness of the tissue is lower than its tensile and compressive stiffness.

  7. Two-Dimensional Thermal Boundary Layer Corrections for Convective Heat Flux Gauges

    Science.gov (United States)

    Kandula, Max; Haddad, George

    2007-01-01

    This work presents a CFD (Computational Fluid Dynamics) study of two-dimensional thermal boundary layer correction factors for convective heat flux gauges mounted in flat plate subjected to a surface temperature discontinuity with variable properties taken into account. A two-equation k - omega turbulence model is considered. Results are obtained for a wide range of Mach numbers (1 to 5), gauge radius ratio, and wall temperature discontinuity. Comparisons are made for correction factors with constant properties and variable properties. It is shown that the variable-property effects on the heat flux correction factors become significant

  8. Simulation study of scalings in scrape-off layer plasma by two-dimensional transport code

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, S.-I.; Ueda, Noriaki; Itoh, Kimitaka (National Inst. for Fusion Science, Nagoya (Japan))

    1990-07-01

    Scrape-off Layer (SOL) plasma and divertor plasma in Tokamaks were numerically analyzed using a two-dimensional time-dependent transport code (UEDA code). Plasma transport in the SOL and the divertor region was studied for given particle and heat sources from the main plasma. A scaling study of the density, the temperature and their fall-off lengths was carried out for the JFT-2M Tokamak. The results show the inter-relations between the divertor plasma parameters and core plasma confinement. The operational conditions of the core necessary to guarantee the divertor performance are discussed. (author).

  9. Piezoelectric two-dimensional nanosheets/anionic layer heterojunction for efficient direct current power generation

    Science.gov (United States)

    Kim, Kwon-Ho; Kumar, Brijesh; Lee, Keun Young; Park, Hyun-Kyu; Lee, Ju-Hyuck; Lee, Hyun Hwi; Jun, Hoin; Lee, Dongyun; Kim, Sang-Woo

    2013-06-01

    Direct current (DC) piezoelectric power generator is promising for the miniaturization of a power package and self-powering of nanorobots and body-implanted devices. Hence, we report the first use of two-dimensional (2D) zinc oxide (ZnO) nanostructure and an anionic nanoclay layer to generate piezoelectric DC output power. The device, made from 2D nanosheets and an anionic nanoclay layer heterojunction, has potential to be the smallest size power package, and could be used to charge wireless nano/micro scale systems without the use of rectifier circuits to convert alternating current into DC to store the generated power. The combined effect of buckling behaviour of the ZnO nanosheets, a self-formed anionic nanoclay layer, and coupled semiconducting and piezoelectric properties of ZnO nanosheets contributes to efficient DC power generation. The networked ZnO nanosheets proved to be structurally stable under huge external mechanical loads.

  10. Piezoelectric two-dimensional nanosheets/anionic layer heterojunction for efficient direct current power generation.

    Science.gov (United States)

    Kim, Kwon-Ho; Kumar, Brijesh; Lee, Keun Young; Park, Hyun-Kyu; Lee, Ju-Hyuck; Lee, Hyun Hwi; Jun, Hoin; Lee, Dongyun; Kim, Sang-Woo

    2013-01-01

    Direct current (DC) piezoelectric power generator is promising for the miniaturization of a power package and self-powering of nanorobots and body-implanted devices. Hence, we report the first use of two-dimensional (2D) zinc oxide (ZnO) nanostructure and an anionic nanoclay layer to generate piezoelectric DC output power. The device, made from 2D nanosheets and an anionic nanoclay layer heterojunction, has potential to be the smallest size power package, and could be used to charge wireless nano/micro scale systems without the use of rectifier circuits to convert alternating current into DC to store the generated power. The combined effect of buckling behaviour of the ZnO nanosheets, a self-formed anionic nanoclay layer, and coupled semiconducting and piezoelectric properties of ZnO nanosheets contributes to efficient DC power generation. The networked ZnO nanosheets proved to be structurally stable under huge external mechanical loads.

  11. Spectroscopic studies of the electronic properties of regularly arrayed two-dimensional protein layers

    Energy Technology Data Exchange (ETDEWEB)

    Vyalikh, D V [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Kirchner, A [BioNanotechnology and Structure Formation Group, Max Bergmann Centre of Biomaterials, Dresden University of Technology, D-01062 Dresden (Germany); Kade, A [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Danzenbaecher, S [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Dedkov, Yu S [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany); Mertig, M [BioNanotechnology and Structure Formation Group, Max Bergmann Centre of Biomaterials, Dresden University of Technology, D-01062 Dresden (Germany); Molodtsov, S L [Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden (Germany)

    2006-04-05

    Photoemission (PE) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy were applied to characterize electronic properties of the regular two-dimensional bacterial surface protein layer (S layer) of Bacillus sphaericus NCTC 9602, which is widely used as a protein template for the bottom-up fabrication of advanced metallic and hybrid nanostructures. PE and NEXAFS at the C 1s, O 1s, and N 1s core levels show similar chemical states for each oxygen atom and also for each nitrogen atom, while carbon atoms exhibit a range of chemical environments in different functional groups of the amino acids. A series of characteristic NEXAFS peaks were assigned to particular molecular orbitals of the amino acids by applying a phenomenological building-block model. It was found that the {pi} clouds of aromatic rings make the main contribution to both the lowest unoccupied and highest occupied molecular orbitals. The two-dimensional protein crystal shows a semiconductor-like behaviour with a gap value of {approx}3.0 eV and the Fermi energy close to the bottom of the LUMO.

  12. Tuning Slow Magnetic Relaxation in a Two-Dimensional Dysprosium Layer Compound through Guest Molecules.

    Science.gov (United States)

    Chen, Qi; Li, Jian; Meng, Yin-Shan; Sun, Hao-Ling; Zhang, Yi-Quan; Sun, Jun-Liang; Gao, Song

    2016-08-15

    A novel two-dimensional dysprosium(III) complex, [Dy(L)(CH3COO)]·0.5DMF·H2O·2CH3OH (1), has been successfully synthesized from a new pyridine-N-oxide (PNO)-containing ligand, namely, N'-(2-hydroxy-3-methoxybenzylidene)pyridine-N-oxidecarbohydrazide (H2L). Single-crystal X-ray diffraction studies reveal that complex 1 is composed of a dinuclear dysprosium subunit, which is further extended by the PNO part of the ligand to form a two-dimensional layer. Magnetic studies indicate that complex 1 shows well-defined temperature- and frequency-dependent signals under a zero direct-current (dc) field, typical of slow magnetic relaxation with an effective energy barrier Ueff of 33.6 K under a zero dc field. Interestingly, powder X-ray diffraction and thermogravimetric analysis reveal that compound 1 undergoes a reversible phase transition that is induced by the desorption and absorption of methanol and water molecules. Moreover, the desolvated sample [Dy(L)(CH3COO)]·0.5DMF (1a) also exhibits slow magnetic relaxation but with a higher anisotropic barrier of 42.0 K, indicating the tuning effect of solvent molecules on slow magnetic relaxation.

  13. An investigation of two dimensional parallel and non-parallel steady mixing layers

    Energy Technology Data Exchange (ETDEWEB)

    Shabani, A. [Azad Islamic Univ., Faculty of Mechanical Engineering, School of Engineering, Research and Science Inst., Tehran (Iran, Islamic Republic of)]. E-mail: ario.shabani@cic.aut.ac.ir; Basirat Tabrizi, H. [Amirkabir Univ. of Technology, Dept. of Mechanical Engineering, Tehran (Iran, Islamic Republic of)

    2004-07-01

    A CFD code was generated to simulate the steady state behavior of two dimensional, parallel and nonparallel merging mixing layers. For the free stream velocity ratios of 0.7 and 0.9, the effect of the merging angle of free stream velocities of between 0.0 to 18.0 degrees on the mixing zone's velocity distribution, and on the physical spreading of the turbulent domain was numerically simulated and studied. The results were in good agreement with the available theoretical and experimental results, and indicated that increasing the angle of merging of the two free streams, or increasing their associated free stream velocity ratios increases the spatial growth rate and decreases the turbulent development distance. (author)

  14. New hybrid lead iodides: From one-dimensional chain to two-dimensional layered perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Kecai; Liu, Wei [Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854 (United States); Teat, Simon J. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); An, Litao; Wang, Hao; Emge, Thomas J. [Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854 (United States); Li, Jing, E-mail: jingli@rutgers.edu [Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854 (United States)

    2015-10-15

    Two new hybrid lead halides (H{sub 2}BDA)[PbI{sub 4}] (1) (H{sub 2}BDA=1,4-butanediammonium dication) and (HNPEIM)[PbI{sub 3}] (2) (HNPEIM=N-​phenyl-ethanimidamidine cation) have been synthesized and structurally characterized. X-ray diffraction analyses reveal that compound 1 features a two-dimensional corner-sharing perovskite layer whereas compound 2 contains one-dimensional edge-sharing double chains. The N-​phenyl-ethanimidamidine cation within compound 2 was generated in-situ under solvothermal conditions. The optical absorption spectra collected at room temperature suggest that both compounds are semiconductors having direct band gaps, with estimated values of 2.64 and 2.73 eV for 1 and 2, respectively. Results from the density functional theory (DFT) calculations are consistent with the experimental data. Density of states (DOS) analysis reveals that in both compounds 1 and 2, the energy states in the valence band maximum region are iodine 5p atomic orbitals with a small contribution from lead 6s, while in the region of conduction band minimum, the major contributions are from the inorganic (Pb 6p atomic orbitals) and organic components (C and N 2p atomic orbitals) in compound 1 and 2, respectively. - Graphical abstract: Two new hybrid lead halides built on one-dimensional edge-sharing double chains and two-dimensional corner-sharing perovskite layers are synthesized and their structural and electronic properties are analyzed. - Highlights: • Two new hybrid lead iodides are designed, synthesized, and characterized. • They are closely related to, but different from, perovskite structures. • The electronic properties of both compounds are analyzed by DFT calculations.

  15. Thickness Considerations of Two-Dimensional Layered Semiconductors for Transistor Applications

    Science.gov (United States)

    Zhang, Youwei; Li, Hui; Wang, Haomin; Xie, Hong; Liu, Ran; Zhang, Shi-Li; Qiu, Zhi-Jun

    2016-07-01

    Layered two-dimensional semiconductors have attracted tremendous attention owing to their demonstrated excellent transistor switching characteristics with a large ratio of on-state to off-state current, Ion/Ioff. However, the depletion-mode nature of the transistors sets a limit on the thickness of the layered semiconductor films primarily determined by a given Ion/Ioff as an acceptable specification. Identifying the optimum thickness range is of significance for material synthesis and device fabrication. Here, we systematically investigate the thickness-dependent switching behavior of transistors with a wide thickness range of multilayer-MoS2 films. A difference in Ion/Ioff by several orders of magnitude is observed when the film thickness, t, approaches a critical depletion width. The decrease in Ion/Ioff is exponential for t between 20 nm and 100 nm, by a factor of 10 for each additional 10 nm. For t larger than 100 nm, Ion/Ioff approaches unity. Simulation using technical computer-aided tools established for silicon technology faithfully reproduces the experimentally determined scaling behavior of Ion/Ioff with t. This excellent agreement confirms that multilayer-MoS2 films can be approximated as a homogeneous semiconductor with high surface conductivity that tends to deteriorate Ion/Ioff. Our findings are helpful in guiding material synthesis and designing advanced field-effect transistors based on the layered semiconductors.

  16. Synthesis, characterization and application of two-dimensional layered metal hydroxides for environmental remediation purposes

    Science.gov (United States)

    Machingauta, Cleopas

    Two-dimensional layered nano composites, which include layered double hydroxides (LDHs), hydroxy double salts (HDSs) and layered hydroxide salts (LHSs) are able to intercalate different molecular species within their gallery space. These materials have a tunable structural composition which has made them applicable as fire retardants, adsorbents, catalysts, catalyst support materials, and ion exchangers. Thermal treatment of these materials results in destruction of the layers and formation of mixed metal oxides (MMOs) and spinels. MMOs have the ability to adsorb anions from solution and may also regenerate layered structures through a phenomenon known as memory effect. Zinc-nickel hydroxy nitrate was used for the uptake of a series of halogenated acetates (HAs). HAs are pollutants introduced into water systems as by-products of water chlorination and pesticide degradation; their sequestration from water is thus crucial. Optimization of layered materials for controlled uptake requires an understanding of their ion-exchange kinetics and thermodynamics. Exchange kinetics of these anions was monitored using ex-situ PXRD, UV-vis, HPLC and FTIR. It was revealed that exchange rates and uptake efficiencies are related to electronic spatial extents and the charge on carboxyl-oxygen atoms. In addition, acetate and nitrate-based HDSs were used to explore how altering the hydroxide layer affects uptake of acetate/nitrate ions. Changing the metal identities affects the interaction of the anions with the layers. From FTIR, we observed that nitrates coordinate in a D3h and Cs/C 2v symmetry; the nitrates in D3h symmetry were easily exchangeable. Interlayer hydrogen bonding was also revealed to be dependent on metal identity. Substituting divalent cations with trivalent cations produces materials with a higher charge density than HDSs and LHSs. A comparison of the uptake efficiency of zinc-aluminum, zinc-gallium and zinc-nickel hydroxy nitrates was performed using trichloroacetic

  17. Critical properties of XY model on two-dimensional layered magnetic films

    Institute of Scientific and Technical Information of China (English)

    Wang Yi; Liu Xiao-Yan; Sun Lei; Zhang Xing; Han Ru-Qi

    2006-01-01

    Using Monte Carlo simulations, we have investigated the classical XY model on triangular lattices of ultra-thin film structures with middle ferromagnetic layers sandwiched between two antiferromagnetic layers. The internal energy,the specific heat, the chirality and the chiral susceptibility are calculated in order to clarify phase transitions and critical phenomena. From the finite-size scaling analyses, the values of critical exponents are determined. In a range of interaction parameters, we find that the chirality steeply goes up as temperature increases in a temperature range;correspondingly the value of a critical exponent for this change is estimated.

  18. Graphene-like two-dimensional layered nanomaterials: applications in biosensors and nanomedicine

    Science.gov (United States)

    Yang, Guohai; Zhu, Chengzhou; Du, Dan; Zhu, Junjie; Lin, Yuehe

    2015-08-01

    The development of nanotechnology provides promising opportunities for various important applications. The recent discovery of atomically-thick two-dimensional (2D) nanomaterials can offer manifold perspectives to construct versatile devices with high-performance to satisfy multiple requirements. Many studies directed at graphene have stimulated renewed interest on graphene-like 2D layered nanomaterials (GLNs). GLNs including boron nitride nanosheets, graphitic-carbon nitride nanosheets and transition metal dichalcogenides (e.g. MoS2 and WS2) have attracted significant interest in numerous research fields from physics and chemistry to biology and engineering, which has led to numerous interdisciplinary advances in nano science. Benefiting from the unique physical and chemical properties (e.g. strong mechanical strength, high surface area, unparalleled thermal conductivity, remarkable biocompatibility and ease of functionalization), these 2D layered nanomaterials have shown great potential in biochemistry and biomedicine. This review summarizes recent advances of GLNs in applications of biosensors and nanomedicine, including electrochemical biosensors, optical biosensors, bioimaging, drug delivery and cancer therapy. Current challenges and future perspectives in these rapidly developing areas are also outlined. It is expected that they will have great practical foundation in biomedical applications with future efforts.

  19. Universal equations of unsteady two-dimensional MHD boundary layer whose temperature varies with time

    Directory of Open Access Journals (Sweden)

    Boričić Zoran

    2009-01-01

    Full Text Available This paper concerns with unsteady two-dimensional temperature laminar magnetohydrodynamic (MHD boundary layer of incompressible fluid. It is assumed that induction of outer magnetic field is function of longitudinal coordinate with force lines perpendicular to the body surface on which boundary layer forms. Outer electric filed is neglected and magnetic Reynolds number is significantly lower then one i.e. considered problem is in inductionless approximation. Characteristic properties of fluid are constant because velocity of flow is much lower than speed of light and temperature difference is small enough (under 50ºC . Introduced assumptions simplify considered problem in sake of mathematical solving, but adopted physical model is interesting from practical point of view, because its relation with large number of technically significant MHD flows. Obtained partial differential equations can be solved with modern numerical methods for every particular problem. Conclusions based on these solutions are related only with specific temperature MHD boundary layer problem. In this paper, quite different approach is used. First new variables are introduced and then sets of similarity parameters which transform equations on the form which don't contain inside and in corresponding boundary conditions characteristics of particular problems and in that sense equations are considered as universal. Obtained universal equations in appropriate approximation can be solved numerically once for all. So-called universal solutions of equations can be used to carry out general conclusions about temperature MHD boundary layer and for calculation of arbitrary particular problems. To calculate any particular problem it is necessary also to solve corresponding momentum integral equation.

  20. Evaporation, Heat Transfer, and Velocity Distribution in Two-Dimensional and Rotationally Symmetrical Laminar Boundary-Layer Flow

    Science.gov (United States)

    Froessling, Nils

    1958-01-01

    The fundamental boundary layer equations for the flow, temperature and concentration fields are presented. Two dimensional symmetrical and unsymmetrical and rotationally symmetrical steady boundary layer flows are treated as well as the transfer boundary layer. Approximation methods for the calculation of the transfer layer are discussed and a brief survey of an investigation into the validity of the law that the Nusselt number is proportional to the cube root of the Prandtl number is presented.

  1. Two-dimensional energy spectra in a high Reynolds number turbulent boundary layer

    Science.gov (United States)

    Chandran, Dileep; Baidya, Rio; Monty, Jason; Marusic, Ivan

    2016-11-01

    The current study measures the two-dimensional (2D) spectra of streamwise velocity component (u) in a high Reynolds number turbulent boundary layer for the first time. A 2D spectra shows the contribution of streamwise (λx) and spanwise (λy) length scales to the streamwise variance at a given wall height (z). 2D spectra could be a better tool to analyse spectral scaling laws as it is devoid of energy aliasing errors that could be present in one-dimensional spectra. A novel method is used to calculate the 2D spectra from the 2D correlation of u which is obtained by measuring velocity time series at various spanwise locations using hot-wire anemometry. At low Reynolds number, the shape of the 2D spectra at a constant energy level shows λy √{ zλx } behaviour at larger scales which is in agreement with the literature. However, at high Reynolds number, it is observed that the square-root relationship gradually transforms into a linear relationship (λy λx) which could be caused by the large packets of eddies whose length grows proportionately to the growth of its width. Additionally, we will show that this linear relationship observed at high Reynolds number is consistent with attached eddy predictions. The authors gratefully acknowledge the support from the Australian Research Council.

  2. Coupled two-dimensional edge plasma and neutral gas modeling of tokamak scrape-off-layers

    Energy Technology Data Exchange (ETDEWEB)

    Maingi, R. [North Carolina State Univ., Raleigh, NC (United States)

    1992-08-01

    The objective of this study is to devise a detailed description of the tokamak scrape-off-layer (SOL), which includes the best available models of both the plasma and neutral species and the strong coupling between the two in many SOL regimes. A good estimate of both particle flux and heat flux profiles at the limiter/divertor target plates is desired. Peak heat flux is one of the limiting factors in determining the survival probability of plasma-facing-components at high power levels. Plate particle flux affects the neutral flux to the pump, which determines the particle exhaust rate. A technique which couples a two-dimensional (2-D) plasma and a 2-D neutral transport code has been developed (coupled code technique), but this procedure requires large amounts of computer time. Relevant physics has been added to an existing two-neutral-species model which takes the SOL plasma/neutral coupling into account in a simple manner (molecular physics model), and this model is compared with the coupled code technique mentioned above. The molecular physics model is benchmarked against experimental data from a divertor tokamak (DIII-D), and a similar model (single-species model) is benchmarked against data from a pump-limiter tokamak (Tore Supra). The models are then used to examine two key issues: free-streaming-limits (ion energy conduction and momentum flux) and the effects of the non-orthogonal geometry of magnetic flux surfaces and target plates on edge plasma parameter profiles.

  3. Direct-referencing Two-dimensional-array Digital Microfluidics Using Multi-layer Printed Circuit Board

    Science.gov (United States)

    Gong, Jian; Kim, Chang-Jin “CJ”

    2008-01-01

    Digital (i.e. droplet-based) microfluidics, by the electrowetting-on-dielectric (EWOD) mechanism, has shown great potential for a wide range of applications, such as lab-on-a-chip. While most reported EWOD chips use a series of electrode pads essentially in one-dimensional line pattern designed for specific tasks, the desired universal chips allowing user-reconfigurable paths would require the electrode pads in two-dimensional pattern. However, to electrically access the electrode pads independently, conductive lines need to be fabricated underneath the pads in multiple layers, raising a cost issue especially for disposable chip applications. In this article, we report the building of digital microfluidic plates based on a printed-circuit-board (PCB), in which multilayer electrical access lines were created inexpensively using mature PCB technology. However, due to its surface topography and roughness and resulting high resistance against droplet movement, as-fabricated PCB surfaces require unacceptably high (~500 V) voltages unless coated with or immersed in oil. Our goal is EWOD operations of aqueous droplets not only on oil-covered but also on dry surfaces. To meet varying levels of performances, three types of gradually complex post-PCB microfabrication processes are developed and evaluated. By introducing land-grid-array (LGA) sockets in the packaging, a scalable digital microfluidics system with reconfigurable and low-cost chip is also demonstrated. PMID:19234613

  4. Two-dimensional point spread matrix of layered metal-dielectric imaging elements

    CERN Document Server

    Kotynski, Rafal; Krol, Karol; Panajotov, Krassimir

    2010-01-01

    We describe the change of the spatial distribution of the state of polarisation occurring during two-dimensional imaging through a multilayer and in particular through a layered metallic flat lens. Linear or circular polarisation of incident light is not preserved due to the difference in the amplitude transfer functions for the TM and TE polarisations. In effect, the transfer function and the point spread function that characterize 2D imaging through a multilayer both have a matrix form and cross-polarisation coupling is observed for spatially modulated beams with a linear or circular incident polarisation. The point spread function in a matrix form is used to characterise the resolution of the superlens for different polarisation states. We demonstrate how the 2D PSF may be used to design a simple diffractive nanoelement consisting of two radial slits. The structure assures the separation of non-diffracting radial beams originating from two slits in the mask and exhibits an interesting property of a backwar...

  5. Movement dependence and layer specificity of entorhinal phase precession in two-dimensional environments.

    Directory of Open Access Journals (Sweden)

    Eric Reifenstein

    Full Text Available As a rat moves, grid cells in its entorhinal cortex (EC discharge at multiple locations of the external world, and the firing fields of each grid cell span a hexagonal lattice. For movements on linear tracks, spikes tend to occur at successively earlier phases of the theta-band filtered local field potential during the traversal of a firing field - a phenomenon termed phase precession. The complex movement patterns observed in two-dimensional (2D open-field environments may fundamentally alter phase precession. To study this question at the behaviorally relevant single-run level, we analyzed EC spike patterns as a function of the distance traveled by the rat along each trajectory. This analysis revealed that cells across all EC layers fire spikes that phase-precess; indeed, the rate and extent of phase precession were the same, only the correlation between spike phase and path length was weaker in EC layer III. Both slope and correlation of phase precession were surprisingly similar on linear tracks and in 2D open-field environments despite strong differences in the movement statistics, including running speed. While the phase-precession slope did not correlate with the average running speed, it did depend on specific properties of the animal's path. The longer a curving path through a grid-field in a 2D environment, the shallower was the rate of phase precession, while runs that grazed a grid field tangentially led to a steeper phase-precession slope than runs through the field center. Oscillatory interference models for grid cells do not reproduce the observed phenomena.

  6. Experimental and Theoretical Research on the Vibrational Gaps in Two-Dimensional Three-Component Composite Thin Plates

    Institute of Scientific and Technical Information of China (English)

    YU Dian-Long; LIU Yao-Zong; QIU Jing; ZHAO Hong-Gang; LIU Zhi-Ming

    2005-01-01

    @@ We investigate the vibrational band gaps in a thin plate of two-dimensional phononic crystals with the locally resonant structure in theory and experiment. The experimental sample is optimized based on the simple analytical model. The experimental results are in good agreement with the theoretical calculation by the finite element method. The findings will be significant for applications of phononic crystals in the field of vibration isolation.

  7. Onset of two-dimensional superconductivity in space charge doped few-layer molybdenum disulfide.

    Science.gov (United States)

    Biscaras, Johan; Chen, Zhesheng; Paradisi, Andrea; Shukla, Abhay

    2015-11-03

    Atomically thin films of layered materials such as molybdenum disulfide (MoS2) are of growing interest for the study of phase transitions in two-dimensions through electrostatic doping. Electrostatic doping techniques giving access to high carrier densities are needed to achieve such phase transitions. Here we develop a method of electrostatic doping which allows us to reach a maximum n-doping density of 4 × 10(14) cm(-2) in few-layer MoS2 on glass substrates. With increasing carrier density we first induce an insulator to metal transition and subsequently an incomplete metal to superconductor transition in MoS2 with critical temperature ≈10 K. Contrary to earlier reports, after the onset of superconductivity, the superconducting transition temperature does not depend on the carrier density. Our doping method and the results we obtain in MoS2 for samples as thin as bilayers indicates the potential of this approach.

  8. Stabilized lithium-ion battery anode performance by calcium-bridging of two dimensional siloxene layers.

    Science.gov (United States)

    Imagawa, Haruo; Itahara, Hiroshi

    2017-03-14

    A Ca-bridged siloxene (Ca-siloxene) composed of two-dimensional siloxene planes with Ca bridging was synthesized via a solid state metathesis reaction using TaCl5 to extract Ca from CaSi2. Three different Ca-siloxenes synthesized at Cl2/Ca molar ratios of 0.25, 1.25 and 2.5 (CS0.25, CS1.25 and CS2.5, respectively) were fabricated and investigated as anode active materials for lithium-ion batteries. Both secondary and primary Ca-siloxene particles, which serve to increase the contact interfaces with conductive materials and to generate accessible sites for lithium ions, respectively, were found to become smaller and to have increased pore volumes as the Cl2/Ca molar ratio was increased. These Ca-siloxenes exhibited stable charge/discharge performance as anode materials, with 69-99% capacity retention after 50 charge/discharge cycles (compared with 36% retention for a conventional Kautsky-type siloxene). The charge capacity also increased with increases in the Cl2/Ca molar ratio, such that the CS2.5 showed the highest capacity after 50 charge/discharge cycles. This may reflect the formation of Si6Li6 rather than SiLi4.4 and suggests the maintenance of layered Si planes for large capacity retention after charge/discharge cycling. The increase of contact interfaces between acetylene black (as a conductive material) and Ca-siloxenes was found to effectively increase the lithium-ion capacity of Ca-siloxene during high rate charge/discharge cycling.

  9. Exciton Migration and Amplified Quenching on Two-Dimensional Metal–Organic Layers

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Lingyun; Lin, Zekai; Shi, Wenjie; Wang, Zi; Zhang, Cankun; Hu, Xuefu; Wang, Cheng; Lin, Wenbin

    2017-05-10

    The dimensionality dependency of resonance energy transfer is of great interest due to its importance in understanding energy transfer on cell membranes and in low-dimension nanostructures. Light harvesting two-dimensional metal–organic layers (2D-MOLs) and three-dimensional metal–organic frameworks (3D-MOFs) provide comparative models to study such dimensionality dependence with molecular accuracy. Here we report the construction of 2D-MOLs and 3D-MOFs from a donor ligand 4,4',4''-(benzene-1,3,5-triyl-tris(ethyne-2,1-diyl))tribenzoate (BTE) and a doped acceptor ligand 3,3',3''-nitro-4,4',4''-(benzene-1,3,5-triyl-tris(ethyne-2,1-diyl))tribenzoate (BTE-NO2). These 2D-MOLs and 3D-MOFs are connected by similar hafnium clusters, with key differences in the topology and dimensionality of the metal–ligand connection. Energy transfer from donors to acceptors through the 2D-MOL or 3D-MOF skeletons is revealed by measuring and modeling the fluorescence quenching of the donors. We found that energy transfer in 3D-MOFs is more efficient than that in 2D-MOLs, but excitons on 2D-MOLs are more accessible to external quenchers as compared with those in 3D-MOFs. These results not only provide support to theoretical analysis of energy transfer in low dimensions, but also present opportunities to use efficient exciton migration in 2D materials for light-harvesting and fluorescence sensing.

  10. How two-dimensional brick layer J-aggregates differ from linear ones: excitonic properties and line broadening mechanisms

    CERN Document Server

    Dijkstra, Arend G; Knoester, Jasper; Nelson, Keith A; Cao, Jianshu

    2016-01-01

    We study the excitonic coupling and homogeneous spectral line width of brick layer J-aggregate films. We begin by analysing the structural information revealed by the two-exciton states probed in two-dimensional spectra. Our first main result is that the relation between the excitonic couplings and the spectral shift in a two-dimensional structure is different (larger shift for the same nearest neighbour coupling) from that in a one-dimensional structure, which leads to an estimation of dipolar coupling in two-dimensional lattices. We next investigate the mechanisms of homogeneous broadening - population relaxation and pure dephasing - and evaluate their relative importance in linear and two-dimensional aggregates. Our second main result is that pure dephasing dominates the line width in two-dimensional systems up to a crossover temperature, which explains the linear temperature dependence of the homogeneous line width. This is directly related to the decreased density of states at the band edge when compared...

  11. Two-dimensional coupled electron-hole layers in high magnetic fields

    NARCIS (Netherlands)

    Parlangeli, Andrea

    2000-01-01

    In solids, it is nowadays possible to create structures in which electrons are confined into a two-dimensional (2D) plane. The physics of a 2D electron gas (2DEG) has proved to be very rich, in particular in the presence of a transverse magnetic field. The Quantum Hall Effect, i.e. the quantization

  12. Modern Thin-Layer Chromatography.

    Science.gov (United States)

    Poole, Colin F.; Poole, Salwa K.

    1989-01-01

    Some of the important modern developments of thin-layer chromatography are introduced. Discussed are the theory and instrumentation of thin-layer chromatography including multidimensional and multimodal techniques. Lists 53 references. (CW)

  13. Modern Thin-Layer Chromatography.

    Science.gov (United States)

    Poole, Colin F.; Poole, Salwa K.

    1989-01-01

    Some of the important modern developments of thin-layer chromatography are introduced. Discussed are the theory and instrumentation of thin-layer chromatography including multidimensional and multimodal techniques. Lists 53 references. (CW)

  14. Lateral Versus Vertical Growth of Two-Dimensional Layered Transition-Metal Dichalcogenides: Thermodynamic Insight into MoS2.

    Science.gov (United States)

    Shang, Shun-Li; Lindwall, Greta; Wang, Yi; Redwing, Joan M; Anderson, Tim; Liu, Zi-Kui

    2016-09-14

    Unprecedented interest has been spurred recently in two-dimensional (2D) layered transition metal dichalcogenides (TMDs) that possess tunable electronic and optical properties. However, synthesis of a wafer-scale TMD thin film with controlled layers and homogeneity remains highly challenging due mainly to the lack of thermodynamic and diffusion knowledge, which can be used to understand and design process conditions, but falls far behind the rapidly growing TMD field. Here, an integrated density functional theory (DFT) and calculation of phase diagram (CALPHAD) modeling approach is employed to provide thermodynamic insight into lateral versus vertical growth of the prototypical 2D material MoS2. Various DFT energies are predicted from the layer-dependent MoS2, 2D flake-size related mono- and bilayer MoS2, to Mo and S migrations with and without graphene and sapphire substrates, thus shedding light on the factors that control lateral versus vertical growth of 2D islands. For example, the monolayer MoS2 flake in a small 2D lateral size is thermodynamically favorable with respect to the bilayer counterpart, indicating the monolayer preference during the initial stage of nucleation; while the bilayer MoS2 flake becomes stable with increasing 2D lateral size. The critical 2D flake-size of phase stability between mono- and bilayer MoS2 is adjustable via the choice of substrate. In terms of DFT energies and CALPHAD modeling, the size dependent pressure-temperature-composition (P-T-x) growth windows are predicted for MoS2, indicating that the formation of MoS2 flake with reduced size appears in the middle but close to the lower T and higher P "Gas + MoS2" phase region. It further suggests that Mo diffusion is a controlling factor for MoS2 growth owing to its extremely low diffusivity compared to that of sulfur. Calculated MoS2 energies, Mo and S diffusivities, and size-dependent P-T-x growth windows are in good accord with available experiments, and the present data

  15. Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping

    Science.gov (United States)

    Ming, Fangfei; Mulugeta, Daniel; Tu, Weisong; Smith, Tyler S.; Vilmercati, Paolo; Lee, Geunseop; Huang, Ying-Tzu; Diehl, Renee D.; Snijders, Paul C.; Weitering, Hanno H.

    2017-03-01

    Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Its formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform.

  16. On t-local solvability of inverse scattering problems in two-dimensional layered media

    Science.gov (United States)

    Baev, A. V.

    2015-06-01

    The solvability of two-dimensional inverse scattering problems for the Klein-Gordon equation and the Dirac system in a time-local formulation is analyzed in the framework of the Galerkin method. A necessary and sufficient condition for the unique solvability of these problems is obtained in the form of an energy conservation law. It is shown that the inverse problems are solvable only in the class of potentials for which the stationary Navier-Stokes equation is solvable.

  17. Two-dimensional patterning of thin coatings for the control of tissue outgrowth

    DEFF Research Database (Denmark)

    Thissen, H.; Johnson, G.; Hartley, P.G.

    2006-01-01

    were used to provide evidence of successful surface modifications. Adsorption of the extracellular matrix protein collagen I followed by tissue outgrowth experiments with bovine corneal epithelial tissue for up to 21 days showed that two-dimensional control over tissue outgrowth is achievable with our......Control of the precise location and extent of cellular attachment and proliferation, and of tissue outgrowth is important in a number of biomedical applications, including biomaterials and tissue engineered medical devices. Here we describe a method to control and direct the location and define...... boundaries of tissue growth on surfaces in two dimensions. The method relies on the generation of a spatially defined surface chemistry comprising protein adsorbing and non-adsorbing areas that allow control over the adsorption of cell-adhesive glycoproteins. Surface modification was carried out...

  18. Recent Advancement on the Optical Properties of Two-Dimensional Molybdenum Disulfide (MoS2 Thin Films

    Directory of Open Access Journals (Sweden)

    Mingxiao Ye

    2015-03-01

    Full Text Available The emergence of two-dimensional (2D materials has led to tremendous interest in the study of graphene and a series of mono- and few-layered transition metal dichalcogenides (TMDCs. Among these TMDCs, the study of molybdenum disulfide (MoS2 has gained increasing attention due to its promising optical, electronic, and optoelectronic properties. Of particular interest is the indirect to direct band-gap transition from bulk and few-layered structures to mono-layered MoS2, respectively. In this review, the study of these properties is summarized. The use of Raman and Photoluminescence (PL spectroscopy of MoS2 has become a reliable technique for differentiating the number of molecular layers in 2D MoS2.

  19. A Two-Dimensional Landau-Lifshitz Model in Studying Thin Film Micromagnetics

    Directory of Open Access Journals (Sweden)

    Jingna Li

    2009-01-01

    equation which was first raised by A. DeSimone and F. Otto, and so fourth, when studying thin film micromagnetics. We get the existence of a local weak solution by approximating it with a higher-order equation. Penalty approximation and semigroup theory are employed to deal with the higher-order equation.

  20. Characteristic length of phonon transport within periodic nanoporous thin films and two-dimensional materials

    Science.gov (United States)

    Hao, Qing; Xiao, Yue; Zhao, Hongbo

    2016-08-01

    In the past two decades, phonon transport within nanoporous thin films has attracted enormous attention for their potential applications in thermoelectrics and thermal insulation. Various computational studies have been carried out to explain the thermal conductivity reduction within these thin films. Considering classical phonon size effects, the lattice thermal conductivity can be predicted assuming diffusive pore-edge scattering of phonons and bulk phonon mean free paths. Following this, detailed phonon transport can be simulated for a given porous structure to find the lattice thermal conductivity [Hao et al., J. Appl. Phys. 106, 114321 (2009)]. However, such simulations are intrinsically complicated and cannot be used for the data analysis of general samples. In this work, the characteristic length Λ P o r e of periodic nanoporous thin films is extracted by comparing the predictions of phonon Monte Carlo simulations and the kinetic relationship using bulk phonon mean free paths modified by Λ P o r e . Under strong ballistic phonon transport, Λ P o r e is also extracted by the Monte Carlo ray-tracing method for graphene with periodic nanopores. The presented model can be widely used to analyze the measured thermal conductivities of such nanoporous structures.

  1. Numerical Investigation on Two-dimensional Boundary Layer Flow with Transition

    Institute of Scientific and Technical Information of China (English)

    Yong Zhao; Tianlin Wang; Zhi Zong

    2014-01-01

    As a basic problem in many engineering applications, transition from laminar to turbulence still remains a difficult problem in computational fluid dynamics (CFD). A numerical study of one transitional flow in two-dimensional is conducted by Reynolds averaged numerical simulation (RANS) in this paper. Turbulence model plays a significant role in the complex flows’ simulation, and four advanced turbulence models are evaluated. Numerical solution of frictional resistance coefficient is compared with the measured one in the transitional zone, which indicates that Wilcox (2006) k-ω model with correction is the best candidate. Comparisons of numerical and analytical solutions for dimensionless velocity show that averaged streamwise dimensionless velocity profiles correct the shape rapidly in transitional region. Furthermore, turbulence quantities such as turbulence kinetic energy, eddy viscosity, and Reynolds stress are also studied, which are helpful to learn the transition’s behavior.

  2. Unsteady two-dimensional potential-flow model for thin variable geometry airfoils

    DEFF Research Database (Denmark)

    Gaunaa, Mac

    2010-01-01

    as in classic thin-airfoil theory, and the deflection of the airfoil is given by superposition of chord-wise deflection mode shapes. It is shown from the expressions for the forces that the influence from the shed vorticity in the wake is described by the same time lag for all chord-wise positions...... on the airfoil. This time-lag term can be approximated using an indicial function approach, making the practical calculation of the aerodynamic response numerically very efficient by use of Duhamel superposition. Furthermore, the indicial function expressions for the time-lag terms are formulated...

  3. Defects detection in thin components using two-dimensional ultrasonic arrays

    Science.gov (United States)

    Velichko, A.; Wilcox, P. D.; Drinkwater, B. W.

    2013-01-01

    The use of 2D ultrasonic arrays provides great flexibility, as one array probe allows a given defect to be illuminated from a wide range of angles. However there are a number of challenges in the application of 2D arrays to detection and characterization of 3D defects. In the current paper the problem of finding the optimal array configuration for defects detection in thin sections is investigated. The efficient FE scattering model is used to simulate an ultrasonic array response for different 3D defects. The data provided by this model is then used to analyze the influence of different parameters on the array performance (signal to noise ratio, sensitivity, resolution). Finally, experimental results are shown that illustrate the imaging performance of optimal 2D array configuration.

  4. Band Gap Tuning and Defect Tolerance of Atomically Thin Two- Dimensional Organic-Inorganic Halide Perovskites

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2016-01-01

    Organic−inorganic halide perovskites have proven highly successful for photovoltaics but suffer from low stability, which deteriorates their performance over time. Recent experiments have demonstrated that low dimensional phases of the hybrid perovskites may exhibit improved stability. Here we...... report first-principles calculations for isolated monolayers of the organometallic halide perovskites (C4H9NH3)2MX2Y2, where M = Pb, Ge, Sn and X,Y = Cl, Br, I. The band gaps computed using the GLLB-SC functional are found to be in excellent agreement with experimental photoluminescence data...... for the already synthesized perovskites. Finally, we study the effect of different defects on the band structure. We find that the most common defects only introduce shallow or no states in the band gap, indicating that these atomically thin 2D perovskites are likely to be defect tolerant....

  5. A humidity sensitive two-dimensional tunable amorphous photonic structure in the outer layer of bivalve ligament from Sunset Siliqua

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Weigang, E-mail: abczwg15@163.com [College of Materials and Chemical Engineering, Chuzhou University, Chuzhou 239000 (China); Zhang, Gangsheng [College of Material Science and Technology, Guangxi University, Nanning 530004 (China)

    2015-07-01

    A humidity sensitive two-dimensional tunable amorphous photonic structure (2D TAPS) in the outer layer of bivalve ligament from Sunset Siliqua (OLLS) was reported in this paper. The structural color and microstructure of OLLS were investigated by reflection spectra and scanning electron microscopy, respectively. The results indicate that the reflection peak wavelength of the wet OLLS blue-shifts from 454 nm to 392 nm with the increasing of air drying time from 0 to 40 min, while the reflectivity decreases gradually and vanishes at last, relevant color changes from blue to black background color. The structural color in the OLLS is produced by a two-dimensional amorphous photonic structure consisting of aligned protein fibers, in which the diameter of protein fiber and the inter-fiber spacing are 101 ± 12 nm. Water can reversibly tune the reflection peak wavelength and reflectivity of this photonic structure, and the regulation achieved through dynamically tuning the interaction between inter-fiber spacing and average refractive index. - Highlights: • A humidity sensitive two-dimensional tunable amorphous photonic structure • Water can reversibly tune the reflection peak wavelength and reflectivity of this photonic structure. • This photonic structure may yield very useful template for artificial structures.

  6. Nonlinear chemoconvection in the methylene-blue-glucose system: Two-dimensional shallow layers

    Science.gov (United States)

    Pons, A. J.; Batiste, O.; Bees, M. A.

    2008-07-01

    Interfacial hydrodynamic instabilities arise in a range of chemical systems. One mechanism for instability is the occurrence of unstable density gradients due to the accumulation of reaction products. In this paper we conduct two-dimensional nonlinear numerical simulations for a member of this class of system: the methylene-blue-glucose reaction. The result of these reactions is the oxidation of glucose to a relatively, but marginally, dense product, gluconic acid, that accumulates at oxygen permeable interfaces, such as the surface open to the atmosphere. The reaction is catalyzed by methylene-blue. We show that simulations help to disassemble the mechanisms responsible for the onset of instability and evolution of patterns, and we demonstrate that some of the results are remarkably consistent with experiments. We probe the impact of the upper oxygen boundary condition, for fixed flux, fixed concentration, or mixed boundary conditions, and find significant qualitative differences in solution behavior; structures either attract or repel one another depending on the boundary condition imposed. We suggest that measurement of the form of the boundary condition is possible via observation of oxygen penetration, and improved product yields may be obtained via proper control of boundary conditions in an engineering setting. We also investigate the dependence on parameters such as the Rayleigh number and depth. Finally, we find that pseudo-steady linear and weakly nonlinear techniques described elsewhere are useful tools for predicting the behavior of instabilities beyond their formal range of validity, as good agreement is obtained with the simulations.

  7. Evidence of molecular hydrogen trapped in two-dimensional layered titanium carbide-based MXene

    Science.gov (United States)

    Osti, Naresh C.; Naguib, Michael; Tyagi, Madhusudan; Gogotsi, Yury; Kolesnikov, Alexander I.; Mamontov, Eugene

    2017-07-01

    Two-dimensional transition metal carbides and nitrides (MXenes) are one of the largest and fastest growing families of materials. The presence of molecular hydrogen at ambient conditions in a MXene (T i3C2Tx , where Tx represents a surface terminating species, including O, OH, and F) material is revealed here by inelastic and elastic neutron scatterings. The inelastic neutron-scattering spectrum measured at 5 K shows a peak at 14.6 meV, presenting a clear indication of the presence of parahydrogen in the MXene synthesized using 48 % hydrofluoric acid and annealed at 110 ∘C in vacuum prior to the measurement. An increase in the measurement temperature gradually reduces the peak intensity and increases the peak width due to the mobility of the molecular hydrogen in confinement. The presence of molecular hydrogen is confirmed further from the observed elastic intensity drop in a fixed energy-window scan of elastic intensity measurements in the temperature range of 10-35 K. Using milder etching conditions, ion intercalation, or an increase in the annealing temperature all result in the absence of the trapped hydrogen molecules in MXene. The results of this paper can guide the development of MXene materials with desired properties and improve our understanding of the behavior of MXenes in applications ranging from supercapacitors to hydrogen evolution reaction catalysis and hydrogen storage.

  8. Two-Dimensional Atomic-Layered Alloy Junctions for High-Performance Wearable Chemical Sensor.

    Science.gov (United States)

    Cho, Byungjin; Kim, Ah Ra; Kim, Dong Jae; Chung, Hee-Suk; Choi, Sun Young; Kwon, Jung-Dae; Park, Sang Won; Kim, Yonghun; Lee, Byoung Hun; Lee, Kyu Hwan; Kim, Dong-Ho; Nam, Jaewook; Hahm, Myung Gwan

    2016-08-03

    We first report that two-dimensional (2D) metal (NbSe2)-semiconductor (WSe2)-based flexible, wearable, and launderable gas sensors can be prepared through simple one-step chemical vapor deposition of prepatterned WO3 and Nb2O5. Compared to a control device with a Au/WSe2 junction, gas-sensing performance of the 2D NbSe2/WSe2 device was significantly enhanced, which might have resulted from the formation of a NbxW1-xSe2 transition alloy junction lowering the Schottky barrier height. This would make it easier to collect charges of channels induced by molecule adsorption, improving gas response characteristics toward chemical species including NO2 and NH3. 2D NbSe2/WSe2 devices on a flexible substrate provide gas-sensing properties with excellent durability under harsh bending. Furthermore, the device stitched on a T-shirt still performed well even after conventional cleaning with a laundry machine, enabling wearable and launderable chemical sensors. These results could pave a road toward futuristic gas-sensing platforms based on only 2D materials.

  9. Real-Time Two-Dimensional Mapping of Relative Local Surface Temperatures with a Thin-Film Sensor Array

    Directory of Open Access Journals (Sweden)

    Gang Li

    2016-06-01

    Full Text Available Dynamic mapping of an object’s local temperature distribution may offer valuable information for failure analysis, system control and improvement. In this letter we present a computerized measurement system which is equipped with a hybrid, low-noise mechanical-electrical multiplexer for real-time two-dimensional (2D mapping of surface temperatures. We demonstrate the performance of the system on a device embedded with 32 pieces of built-in Cr-Pt thin-film thermocouples arranged in a 4 × 8 matrix. The system can display a continuous 2D mapping movie of relative temperatures with a time interval around 1 s. This technique may find applications in a variety of practical devices and systems.

  10. Ultra-thin two-dimensional transmissive anisotropic metasurfaces for polarization filter and beam steering application

    Science.gov (United States)

    Guo, Wen-Long; Wang, Guang-Ming; Li, Hai-Peng; Zhang, Kun; Cai, Tong

    2016-10-01

    We propose an anisotropic planar transmitting metasurface, which has the ability to manipulate orthogonally-polarized electromagnetic waves in the reflection and refraction modes respectively. The metasurface is composed of four layered rectangular patches spaced by three layered dielectric isolators each with a thickness of 0.15λ 0 at 15 GHz. By tailoring the sizes of the patches, the metasurface functions as a band-stop filter for the y-polarzied wave and a band-pass filter for the x-polarized wave operating from 14 GHz to 16 GHz. Moreover the phases of the transmitting x-polarized wave can be modulated at about 15 GHz, which contributes to beam steering according to the general refraction law. Experimental results are in good accordance with the simulated ones, in which the reflection efficiency is almost 100% while the transmission efficiency of the x-polarized wave reaches 80% at 15 GHz. Besides, the transmitted x-polarized wave is effectively manipulated from 14 GHz to 16 GHz. Project supported by the National Natural Science Foundation of China (Grant No. 61372034).

  11. Thin layer chromatography.

    Science.gov (United States)

    Santiago, Marina; Strobel, Scott

    2013-01-01

    In many experiments, it is important to be able to separate a mixture into its chemical components in order to isolate one compound or to assess the purity of the mixture. Thin layer chromatography (TLC) is one of the easiest and most versatile methods of doing this because of its low cost, simplicity, quick development time, high sensitivity, and good reproducibility. TLC is used by many industries and fields of research, including pharmaceutical production, clinical analysis, industrial chemistry, environmental toxicology, food chemistry, water, inorganic, and pesticide analysis, dye purity, cosmetics, plant materials, and herbal analysis. In its simplest form, glass plates are coated with a uniform layer of silica gel (SiO2). The dissolved sample is placed on the plate, and the plate is inserted into a screw-top jar containing the developing solvent and a piece of filter paper. When the solvent has risen to near the top of the plate, the plate is removed, dried, and visualized using UV light. Variations on this protocol are used for different purposes, including pretreating the sample, changing the sorbent, plate material, the solvent system, the development techniques, and method of detection and visualization or by coupling TLC to other techniques. © 2013 Elsevier Inc. All rights reserved.

  12. Normal range of myocardial layer-specific strain using two-dimensional speckle tracking echocardiography

    Science.gov (United States)

    Wu, Victor Chien-Chia; Otsuji, Yutaka; Takeuchi, Masaaki

    2017-01-01

    Background Newer 2D strain software has a potential to assess layer-specific strain. However, normal reference values for layer-specific strain have not been established. We aimed to establish the normal ranges of layer-specific longitudinal and circumferential strain (endocardial global longitudinal strain (GLS), transmural GLS, epicardial GLS, endocardial global circumferential strain (GCS), transmural GCS, and epicardial GCS). Methods and results We retrospectively analyzed longitudinal and circumferential strain parameters in 235 healthy subjects, with use of layer-specific 2D speckle tracking software (GE). The endocardial strain/epicardial strain (Endo/Epi) ratio was also measured to assess the strain gradient across the myocardium. The endocardial, transmural, and epicardial GLS values and the Endo/Epi ratio in the normal subjects were -23.1±2.3, -20.0±2.0, -17.6±1.9, and 1.31±0.07, respectively. The corresponding values of GCS were -28.5±3.0, -20.8±2.3, -15.3±2.0, and 1.88±0.17, respectively. The layer-specific global strain parameters exhibited no age dependency but did exhibit gender dependency except for endocardial GCS. A subgroup analysis revealed that basal and middle levels of endocardial LS was decreased in the middle and elderly aged group. However, apical endocardial LS was preserved even in the elderly subjects. Conclusions We proposed normal reference values for layer-specific strain based on both age and gender. This detailed strain analysis provides layer-oriented information with the potential to characterize abnormal findings in various cardiovascular diseases. PMID:28662186

  13. Fundamental interactions of vortical structures with boundary layers in two-dimensional flows

    DEFF Research Database (Denmark)

    Coutsias, E.A.; Lynov, Jens-Peter

    1991-01-01

    in the vorticity-stream function representation for bounded geometries. Fundamental processes connected to vorticity detachment from the boundary layers caused by the proximity of vortical structures are described. These processes include enstrophy enhancement of the main flow during bursting events, and pinning...

  14. Two-dimensional linear variation displacement discontinuity method for three-layered elastic media

    CSIR Research Space (South Africa)

    Shou, KJ

    1999-09-01

    Full Text Available bonded half-planes. A three-layered elastic region is obtained by superposing two sets of bonded half-planes and subtracting one infinite plane. The advantages of this approach are: (1) it is not necessary to introduce elements at the interface, (2...

  15. Boundary-Value Problem for Two-Dimensional Fluctuations in Boundary Layers

    Science.gov (United States)

    1985-07-01

    inviscid analysis by P. Durbin "Distortion of turbulence by a constant-shear layer adjacent to a wall," private communication (1977). (l.2e) 2-D...vortices near a boundary," ~ of the Americ~ p ~ ~ , Volume 20, Number 9 (November 1975). 21. Hultgren, Lennart S. and Gustavsson, L. Hakan, " Algebraic

  16. DESIGN OF TWO-DIMENSIONAL SUPERSONIC TURBINE ROTOR BLADES WITH BOUNDARY-LAYER CORRECTION

    Science.gov (United States)

    Goldman, L. J.

    1994-01-01

    A computer program has been developed for the design of supersonic rotor blades where losses are accounted for by correcting the ideal blade geometry for boundary layer displacement thickness. The ideal blade passage is designed by the method of characteristics and is based on establishing vortex flow within the passage. Boundary-layer parameters (displacement and momentum thicknesses) are calculated for the ideal passage, and the final blade geometry is obtained by adding the displacement thicknesses to the ideal nozzle coordinates. The boundary-layer parameters are also used to calculate the aftermixing conditions downstream of the rotor blades assuming the flow mixes to a uniform state. The computer program input consists essentially of the rotor inlet and outlet Mach numbers, upper- and lower-surface Mach numbers, inlet flow angle, specific heat ratio, and total flow conditions. The program gas properties are set up for air. Additional gases require changes to be made to the program. The computer output consists of the corrected rotor blade coordinates, the principal boundary-layer parameters, and the aftermixing conditions. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 7094. This program was developed in 1971.

  17. A two-dimensional particle simulation of the magnetopause current layer

    Energy Technology Data Exchange (ETDEWEB)

    Berchem, J.; Okuda, H.

    1988-11-01

    We have developed a 2/1/2/-D (x, y, v/sub x/, v/sub y/, v/sub z/) electromagnetic code to study the formation and the stability of the magnetopause current layer. This code computes the trajectories of ion and electron particles in their self-consistently generated electromagnetic field and an externally imposed 2-D vacuum dipolar magnetic field. The results presented here are obtained for the simulation of the solar wind-magnetosphere interaction in the subsolar region of the equatorial plane. We observe the self-consistent establishment of a current layer resulting from both diamagnetic drift and E /times/ B drift due to the charge separation. The simulation results show that during the establishment of the current layer, its thickness is of the order of the hybrid gyroradius /rho//sub H/ = ..sqrt../rho//sub i//rho//sub e/ predicted by the Ferraro-Rosenbluth model. However, diagnostics indicate that the current sheet is subject to an instability which broadens the width of the current layer. Ripples with amplitudes of the order of the ion gyroradius appear at the interface between the field and the particles. These pertubations are observed both on the electrostatic field and on the compressional component of the magnetic field. This instability has a frequency of the order of the local ion cyclotron frequency. However, the modulation propagates in the same direction as the electron diamagnetic drift which indicates that the instability is not a classical gradient-driven instability, such as the lower hybrid or ion drift cyclotron instabilities. The nonlinear phase of the instability is characterized by the filamentation of the current layer which causes anomalous diffusion inside the central current sheet. 79 refs., 7 figs.

  18. A novel two-dimensional MgB6 crystal: metal-layer stabilized boron kagome lattice.

    Science.gov (United States)

    Xie, Sheng-Yi; Li, Xian-Bin; Tian, Wei Quan; Chen, Nian-Ke; Wang, Yeliang; Zhang, Shengbai; Sun, Hong-Bo

    2015-01-14

    Based on first-principles calculations, we designed for the first time a boron-kagome-based two-dimensional MgB6 crystal, in which two boron kagome layers sandwich a triangular magnesium layer. The two-dimensional lattice is metallic with several bands across the Fermi level, and among them a Dirac point appears at the K point of the first Brillouin zone. This metal-stabilized boron kagome system displays electron-phonon coupling, with a superconductivity critical transition temperature of 4.7 K, and thus it is another possible superconducting Mg-B compound besides MgB2. Furthermore, the proposed 2D MgB6 can also be used for hydrogen storage after decoration with Ca. Up to five H2 molecules can be attracted by one Ca with an average binding energy of 0.225 eV. The unique properties of 2D MgB6 will spur broad interest in nanoscience and technology.

  19. Two-dimensional versus three-dimensional post-deposition grain growth in epitaxial oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bachelet, R. [Science des Procedes Ceramiques et de Traitements de Surface - CNRS UMR 6638, ENSCI, 47-73 Avenue Albert Thomas 87065 Limoges Cedex (France); Boulle, A. [Science des Procedes Ceramiques et de Traitements de Surface - CNRS UMR 6638, ENSCI, 47-73 Avenue Albert Thomas 87065 Limoges Cedex (France); Soulestin, B. [Science des Procedes Ceramiques et de Traitements de Surface - CNRS UMR 6638, ENSCI, 47-73 Avenue Albert Thomas 87065 Limoges Cedex (France); Rossignol, F. [Science des Procedes Ceramiques et de Traitements de Surface - CNRS UMR 6638, ENSCI, 47-73 Avenue Albert Thomas 87065 Limoges Cedex (France); Guinebretiere, R. [Science des Procedes Ceramiques et de Traitements de Surface - CNRS UMR 6638, ENSCI, 47-73 Avenue Albert Thomas 87065 Limoges Cedex (France)]. E-mail: r_guinebretiere@ensci.fr; Dauger, A. [Science des Procedes Ceramiques et de Traitements de Surface - CNRS UMR 6638, ENSCI, 47-73 Avenue Albert Thomas 87065 Limoges Cedex (France)

    2007-06-25

    Epitaxial thin films made of nanosized yttria-stabilized zirconia islands deposited on (0001) sapphire substrates are synthesized by sol-gel dip-coating followed by a high-temperature post-deposition thermal annealing procedure. At high temperatures, a competitive growth process takes place that allows to obtain thin films made of atomically flat islands with an in-plane diameter typically ten times higher than the thickness or on the contrary inducing the formation of dome-shaped islands. Apart from having a different shape, these islands are also characterized by a different crystallographic orientation with respect to the substrates respectively (001) and (111). In this paper, we investigate the influence of the substrate surface roughness on this competitive grain growth process. The deposition on epi-polished substrates results in a two-dimensional (2D) island growth, whereas the deposition on rough substrates results in a three-dimensional (3D) growth of dome-shaped nanosized islands. The films have been characterized by atomic force microscopy and high-resolution X-ray diffraction using the reciprocal space mapping technique.

  20. Data set for fabrication of conformal two-dimensional TiO2 by atomic layer deposition using tetrakis (dimethylamino) titanium (TDMAT) and H2O precursors.

    Science.gov (United States)

    Zhuiykov, Serge; Akbari, Mohammad Karbalaei; Hai, Zhenyin; Xue, Chenyang; Xu, Hongyan; Hyde, Lachlan

    2017-08-01

    The data and complementary information presented hare are related to the research article of "http://dx.doi.org/10.1016/j.matdes.2017.02.016; Materials and Design 120 (2017) 99-108" [1]. The article provides data and information on the case of atomic layer deposition (ALD) of ultra-thin two-dimensional TiO2 film. The chemical structure of precursors, and the fabrication process were illustrated. The data of spectral ellipsometric measurements and the methods of calculations were presented. Data of root mean square roughness and the average roughness of the ADL TiO2 film are presented. The method of bandgap measurements and the bandgap calculation are also explained in the present data article.

  1. Data set for fabrication of conformal two-dimensional TiO2 by atomic layer deposition using tetrakis (dimethylamino titanium (TDMAT and H2O precursors

    Directory of Open Access Journals (Sweden)

    Serge Zhuiykov

    2017-08-01

    Full Text Available The data and complementary information presented hare are related to the research article of “http://dx.doi.org/10.1016/j.matdes.2017.02.016; Materials and Design 120 (2017 99–108” [1]. The article provides data and information on the case of atomic layer deposition (ALD of ultra-thin two-dimensional TiO2 film. The chemical structure of precursors, and the fabrication process were illustrated. The data of spectral ellipsometric measurements and the methods of calculations were presented. Data of root mean square roughness and the average roughness of the ADL TiO2 film are presented. The method of bandgap measurements and the bandgap calculation are also explained in the present data article.

  2. Emerging Energy Applications of Two-Dimensional Layered Transition Metal Dichalcogenides

    KAUST Repository

    Li, Henan

    2015-10-31

    Transition metal dichalcogenides (TMDCs) have attracted significant attention for their great potential in nano energy. TMDC layered materials represent a diverse and largely untapped source of 2D systems. High-quality TMDC layers with an appropriate size, variable thickness, superior electronic and optical properties can be produced by the exfoliation or vapour phase deposition method. Semiconducting TMDC monolayers have been demonstrated feasible for various energy related applications, where their electronic properties and uniquely high surface areas offer opportunities for various applications such as nano generators, green electronics, electrocatalytic hydrogen generation and energy storage. In this review, we start from the structure, properties and preparation, followed by detailed discussions on the development of TMDC-based nano energy applications. Graphical abstract The structure characterizations and preparative methods of 2D TMDCs have obtained significant progresses. Their recent advances for nano energy generation, solar harvesting, conversion and storage, and green electronics are reviewed.

  3. Dense Carbon Monoxide to 160 GPa: Stepwise Polymerization to Two-Dimensional Layered Solid

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Young-Jay; Kim, Minseob; Lim, Jinhyuk; Dias, Ranga; Klug, Dennis; Yoo, Choong-Shik

    2016-11-14

    Carbon monoxide (CO) is the first molecular system found to transform into a nonmolecular “polymeric” solid above 5.5 GPa, yet been studied beyond 10 GPa. Here, we show a series of pressure-induced phase transformations in CO to 160 GPa: from a molecular solid to a highly colored, low-density polymeric phase I to translucent, high-density phase II to transparent, layered phase III. The properties of these phases are consistent with those expected from recently predicted 1D P21/m, 3D I212121, and 2D Cmcm structures, respectively. Thus, the present results advocate a stepwise polymerization of CO triple bonds to ultimately a 2D singly bonded layer structure with an enhanced ionic character.

  4. Bio-inspired two-dimensional nanofluidic generators based on a layered graphene hydrogel membrane.

    Science.gov (United States)

    Guo, Wei; Cheng, Chi; Wu, Yanzhe; Jiang, Yanan; Gao, Jun; Li, Dan; Jiang, Lei

    2013-11-13

    An electrogenetic layered graphene hydrogel membrane (GHM) possesses ultra-large interlayer spacing of about 10 nm, forming charged 2D nanocapillaries between graphene sheets that selectively permeate counter-ions and exclude co-ions. When an electrolyte flow goes through the GHM, it functions as an integrated 2D nanofluidic generator converting hydraulic motion into electricity. The maximum streaming conductance density approaches 16.8 μA cm(-2) bar(-1) .

  5. Molecular-scale dynamics of light-induced spin cross-over in a two-dimensional layer

    Science.gov (United States)

    Bairagi, Kaushik; Iasco, Olga; Bellec, Amandine; Kartsev, Alexey; Li, Dongzhe; Lagoute, Jérôme; Chacon, Cyril; Girard, Yann; Rousset, Sylvie; Miserque, Frédéric; Dappe, Yannick J; Smogunov, Alexander; Barreteau, Cyrille; Boillot, Marie-Laure; Mallah, Talal; Repain, Vincent

    2016-01-01

    Spin cross-over molecules show the unique ability to switch between two spin states when submitted to external stimuli such as temperature, light or voltage. If controlled at the molecular scale, such switches would be of great interest for the development of genuine molecular devices in spintronics, sensing and for nanomechanics. Unfortunately, up to now, little is known on the behaviour of spin cross-over molecules organized in two dimensions and their ability to show cooperative transformation. Here we demonstrate that a combination of scanning tunnelling microscopy measurements and ab initio calculations allows discriminating unambiguously between both states by local vibrational spectroscopy. We also show that a single layer of spin cross-over molecules in contact with a metallic surface displays light-induced collective processes between two ordered mixed spin-state phases with two distinct timescale dynamics. These results open a way to molecular scale control of two-dimensional spin cross-over layers. PMID:27425776

  6. Layer-dependent anisotropic electronic structure of freestanding quasi-two-dimensional Mo S 2

    KAUST Repository

    Hong, Jinhua

    2016-02-29

    The anisotropy of the electronic transition is a well-known characteristic of low-dimensional transition-metal dichalcogenides, but their layer-thickness dependence has not been properly investigated experimentally until now. Yet, it not only determines the optical properties of these low-dimensional materials, but also holds the key in revealing the underlying character of the electronic states involved. Here we used both angle-resolved electron energy-loss spectroscopy and spectral analysis of angle-integrated spectra to study the evolution of the anisotropic electronic transition involving the low-energy valence electrons in the freestanding MoS2 layers with different thicknesses. We are able to demonstrate that the well-known direct gap at 1.8 eV is only excited by the in-plane polarized field while the out-of-plane polarized optical gap is 2.4 ± 0.2 eV in monolayer MoS2. This contrasts with the much smaller anisotropic response found for the indirect gap in the few-layer MoS2 systems. In addition, we determined that the joint density of states associated with the indirect gap transition in the multilayer systems and the corresponding indirect transition in the monolayer case has a characteristic three-dimensional-like character. We attribute this to the soft-edge behavior of the confining potential and it is an important factor when considering the dynamical screening of the electric field at the relevant excitation energies. Our result provides a logical explanation for the large sensitivity of the indirect transition to thickness variation compared with that for the direct transition, in terms of quantum confinement effect.

  7. Nonparallel stability of two-dimensional nonuniformly heated boundary-layer flows

    Science.gov (United States)

    Nayfeh, A. H.; El-Hady, N. M.

    1979-01-01

    An analysis is presented for the linear stability of water boundary-layer flows over nonuniformly flat plates. Included in the analysis are disturbances due to velocity, pressure, temperatures, density, and transport properties as well as variations of the liquid properties with temperature. The method of multiple scales is used to account for the nonparallelism of the mean flow. In contrast with previous analyses, the nonsimilarity of the mean flow is taken into account. No analysis agrees, even qualitatively, with the experimental data when similar profiles are used. However, both the parallel and nonparallel results qualitatively agree with the experimental results of Strazisar and Reshotko when nonsimilar profiles are used.

  8. Two-dimensional modeling of thermal inversion layers in the middle atmosphere of Mars

    Science.gov (United States)

    Theodore, B.; Chassefiere, E.

    1993-01-01

    There is some evidence that the thermal structure of the martian middle atmosphere may be altered in a significant way by the general circulation motions. Indeed, while it is well known that the circulation in the meridional plane is responsible for the reversal of the latitudinal thermal gradient at the solstice through the adiabatic heating due to sinking motions above the winter pole, here we want to emphasize that a likely by-product effect could be the formation of warm layers, mainly located in the winter hemisphere, and exhibiting an inversion of the vertical thermal gradient.

  9. Excitation of instability waves in a two-dimensional shear layer by sound

    Science.gov (United States)

    Tam, C. K. W.

    1978-01-01

    The excitation of instability waves in a plane compressible shear layer by sound waves is studied. The problem is formulated mathematically as an inhomogeneous boundary-value problem. A general solution for abitrary incident sound wave is found by first constructing the Green's function of the problem. Numerical values of the coupling constants between incident sound waves and excited instability waves for a range of flow Mach number are calculated. The effect of the angle of incidence in the case of a beam of acoustic waves is analyzed. It is found that for moderate subsonic Mach numbers a narrow beam aiming at an angle between 50 to 80 deg to the flow direction is most effective in exciting instability waves.

  10. Layered double hydroxide nanosheet as a two-dimensional support of dense platinum nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hyo Gyoung; Cho, Se Hee; Ji, Hong Geun [H and A PharmaChem, R and D center, Bucheon (Korea, Republic of); Lee, Jong Hyeon [Dept. of Chemistry, The Catholic University of Korea, Bucheon (Korea, Republic of)

    2017-02-15

    Transition metal nanoparticles (NPs) with a narrow size distribution have been intensively synthesized on various solid supports for anti-agglomeration, and high catalytic activity and selectivity. Layered double hydroxides (LDH) are currently attracting intense interest in the field of heterogeneous catalysis as catalyst supports. In order to obtain a well-crystallized LDH nanosheet, the as-synthesize d carbonate form of LDH was hydrothermally treated according to a reported procedure, and further reacted by anion-exchange with an aqueous solution of NaNO{sub 3} and acetate buffer to give the nitrate form of LDH. Dense and uniform Pt NPs were synthesized on the exfoliated LDH nanosheets through precursor exchange and thermal reduction of the precursor ions. In this nanocomposite, the Pt Nps were uniformly grown on the surface of the LDH nano sheet and the average size of Pt Nps was 2nm.

  11. Two-dimensional Oxygen Distribution in a Surface Sediment Layer Measured Using an RGB Color Ratiometric Oxygen Planar Optode

    Directory of Open Access Journals (Sweden)

    Jae Seong Lee

    2013-09-01

    Full Text Available We measured two-dimensional (2-D oxygen distribution in the surface sediment layer of intertidal sediment using a simple and inexpensive planar oxygen optode, which is based on a color ratiometric image approach. The recorded emission intensity of red color luminophore light significantly changed with oxygen concentration by O2 quenching of platinum(IIoctaethylporphyrin (PtOEP. The ratios between the intensity of red and green emissions with oxygen concentration variation demonstrated the Stern-Volmer relationship. The 2-D oxygen distribution image showed microtopographic structure, diffusivity boundary layer and burrow in surface sediment layer. The oxygen penetration depth (OPD was about 2 mm and the one-dimensional vertical diffusive oxygen uptake (DOU was 12.6 mmol m−2 d−1 in the undisturbed surface sediment layer. However, those were enhanced near burrow by benthic fauna, and the OPD was two times deeper and DOU was increased by 34%. The simple and inexpensive oxygen planar optode has great application potential in the study of oxygen dynamics with high spatiotemporal resolution, in benthic boundary layers.

  12. Two-dimensional superconductivity in the cuprates revealed by atomic-layer-by-layer molecular beam epitaxy

    Science.gov (United States)

    Bollinger, A. T.; Božović, I.

    2016-10-01

    Various electronic phases displayed by cuprates that exhibit high temperature superconductivity continue to attract much interest. We provide a short review of several experiments that we have performed aimed at investigating the superconducting state in these compounds. Measurements on single-phase films, bilayers, and superlattices all point to the conclusion that the high-temperature superconductivity (HTS) in these materials is an essentially quasi-two dimensional phenomenon. With proper control over the film growth, HTS can exist in a single copper oxide plane with the critical temperatures as high as that achieved in the bulk samples.

  13. A humidity sensitive two-dimensional tunable amorphous photonic structure in the outer layer of bivalve ligament from Sunset Siliqua.

    Science.gov (United States)

    Zhang, Weigang; Zhang, Gangsheng

    2015-01-01

    A humidity sensitive two-dimensional tunable amorphous photonic structure (2D TAPS) in the outer layer of bivalve ligament from Sunset Siliqua (OLLS) was reported in this paper. The structural color and microstructure of OLLS were investigated by reflection spectra and scanning electron microscopy, respectively. The results indicate that the reflection peak wavelength of the wet OLLS blue-shifts from 454 nm to 392 nm with the increasing of air drying time from 0 to 40 min, while the reflectivity decreases gradually and vanishes at last, relevant color changes from blue to black background color. The structural color in the OLLS is produced by a two-dimensional amorphous photonic structure consisting of aligned protein fibers, in which the diameter of protein fiber and the inter-fiber spacing are 101 ± 12 nm. Water can reversibly tune the reflection peak wavelength and reflectivity of this photonic structure, and the regulation achieved through dynamically tuning the interaction between inter-fiber spacing and average refractive index.

  14. Two-dimensional layered MoS₂ biosensors enable highly sensitive detection of biomolecules.

    Science.gov (United States)

    Lee, Joonhyung; Dak, Piyush; Lee, Yeonsung; Park, Heekyeong; Choi, Woong; Alam, Muhammad A; Kim, Sunkook

    2014-01-01

    We present a MoS2 biosensor to electrically detect prostate specific antigen (PSA) in a highly sensitive and label-free manner. Unlike previous MoS2-FET-based biosensors, the device configuration of our biosensors does not require a dielectric layer such as HfO2 due to the hydrophobicity of MoS2. Such an oxide-free operation improves sensitivity and simplifies sensor design. For a quantitative and selective detection of PSA antigen, anti-PSA antibody was immobilized on the sensor surface. Then, introduction of PSA antigen, into the anti-PSA immobilized sensor surface resulted in a lable-free immunoassary format. Measured off-state current of the device showed a significant decrease as the applied PSA concentration was increased. The minimum detectable concentration of PSA is 1 pg/mL, which is several orders of magnitude below the clinical cut-off level of ~4 ng/mL. In addition, we also provide a systematic theoretical analysis of the sensor platform - including the charge state of protein at the specific pH level, and self-consistent channel transport. Taken together, the experimental demonstration and the theoretical framework provide a comprehensive description of the performance potential of dielectric-free MoS2-based biosensor technology.

  15. Two-dimensional Layered MoS2 Biosensors Enable Highly Sensitive Detection of Biomolecules

    Science.gov (United States)

    Lee, Joonhyung; Dak, Piyush; Lee, Yeonsung; Park, Heekyeong; Choi, Woong; Alam, Muhammad A.; Kim, Sunkook

    2014-12-01

    We present a MoS2 biosensor to electrically detect prostate specific antigen (PSA) in a highly sensitive and label-free manner. Unlike previous MoS2-FET-based biosensors, the device configuration of our biosensors does not require a dielectric layer such as HfO2 due to the hydrophobicity of MoS2. Such an oxide-free operation improves sensitivity and simplifies sensor design. For a quantitative and selective detection of PSA antigen, anti-PSA antibody was immobilized on the sensor surface. Then, introduction of PSA antigen, into the anti-PSA immobilized sensor surface resulted in a lable-free immunoassary format. Measured off-state current of the device showed a significant decrease as the applied PSA concentration was increased. The minimum detectable concentration of PSA is 1 pg/mL, which is several orders of magnitude below the clinical cut-off level of ~4 ng/mL. In addition, we also provide a systematic theoretical analysis of the sensor platform - including the charge state of protein at the specific pH level, and self-consistent channel transport. Taken together, the experimental demonstration and the theoretical framework provide a comprehensive description of the performance potential of dielectric-free MoS2-based biosensor technology.

  16. The effect of thin filament activation on the attachment of weak binding cross-bridges: A two-dimensional x-ray diffraction study on single muscle fibers.

    Science.gov (United States)

    Kraft, T; Xu, S; Brenner, B; Yu, L C

    1999-03-01

    To study possible structural changes in weak cross-bridge attachment to actin upon activation of the thin filament, two-dimensional (2D) x-ray diffraction patterns of skinned fibers from rabbit psoas muscle were recorded at low and high calcium concentration in the presence of saturating concentrations of MgATPgammaS, a nucleotide analog for weak binding states. We also studied 2D x-ray diffraction patterns recorded under relaxing conditions at an ionic strength above and below 50 mM, because it had been proposed from solution studies that reducing ionic strength below 50 mM also induces activation of the thin filament. For this project a novel preparation had to be established that allows recording of 2D x-ray diffraction patterns from single muscle fibers instead of natural fiber bundles. This was required to minimize substrate depletion or product accumulation within the fibers. When the calcium concentration was raised, the diffraction patterns recorded with MgATPgammaS revealed small changes in meridional reflections and layer line intensities that could be attributed in part to the effects of calcium binding to the thin filament (increase in I380, decrease in first actin layer line intensity, increase in I59) and in part to small structural changes of weakly attached cross-bridges (e.g., increase in I143 and I72). Calcium-induced small-scale structural rearrangements of cross-bridges weakly attached to actin in the presence of MgATPgammaS are consistent with our previous observation of reduced rate constants for attachment and detachment of cross-bridges with MgATPgammaS at high calcium. Yet, no evidence was found that weakly attached cross-bridges change their mode of attachment toward a stereospecific conformation when the actin filament is activated by adding calcium. Similarly, reducing ionic strength to less than 50 mM does not induce a transition from nonstereospecific to stereospecific attachment.

  17. Scaling analysis of field-tuned superconductor-insulator transition in two-dimensional tantalum thin films.

    Science.gov (United States)

    Park, Sungyu; Shin, Junghyun; Kim, Eunseong

    2017-02-20

    The superconductor-insulator (SI) transition in two-dimensional Ta thin films is investigated by controlling both film thickness and magnetic field. An intriguing metallic phase appears between a superconducting and an insulating phase within a range of film thickness and magnetic field. The temperature and electric field scaling analyses are performed to investigate the nature of the SI transition in the thickness-tuned metallic and superconducting samples. The critical exponents product of νz obtained from the temperature scaling analysis is found to be approximately 0.67 in the entire range of film thickness. On the other hand, an apparent discrepancy is measured in the product of ν(z + 1) by the electric filed analysis. The product values are found to be about 1.37 for the superconducting films and about 1.86 for the metallic films respectively. We find that the discrepancy is the direct consequence of electron heating that introduces additional dissipation channels in the metallic Ta films.

  18. Scaling analysis of field-tuned superconductor–insulator transition in two-dimensional tantalum thin films

    Science.gov (United States)

    Park, Sungyu; Shin, Junghyun; Kim, Eunseong

    2017-02-01

    The superconductor–insulator (SI) transition in two-dimensional Ta thin films is investigated by controlling both film thickness and magnetic field. An intriguing metallic phase appears between a superconducting and an insulating phase within a range of film thickness and magnetic field. The temperature and electric field scaling analyses are performed to investigate the nature of the SI transition in the thickness-tuned metallic and superconducting samples. The critical exponents product of νz obtained from the temperature scaling analysis is found to be approximately 0.67 in the entire range of film thickness. On the other hand, an apparent discrepancy is measured in the product of ν(z + 1) by the electric filed analysis. The product values are found to be about 1.37 for the superconducting films and about 1.86 for the metallic films respectively. We find that the discrepancy is the direct consequence of electron heating that introduces additional dissipation channels in the metallic Ta films.

  19. Scaling analysis of field-tuned superconductor–insulator transition in two-dimensional tantalum thin films

    Science.gov (United States)

    Park, Sungyu; Shin, Junghyun; Kim, Eunseong

    2017-01-01

    The superconductor–insulator (SI) transition in two-dimensional Ta thin films is investigated by controlling both film thickness and magnetic field. An intriguing metallic phase appears between a superconducting and an insulating phase within a range of film thickness and magnetic field. The temperature and electric field scaling analyses are performed to investigate the nature of the SI transition in the thickness-tuned metallic and superconducting samples. The critical exponents product of νz obtained from the temperature scaling analysis is found to be approximately 0.67 in the entire range of film thickness. On the other hand, an apparent discrepancy is measured in the product of ν(z + 1) by the electric filed analysis. The product values are found to be about 1.37 for the superconducting films and about 1.86 for the metallic films respectively. We find that the discrepancy is the direct consequence of electron heating that introduces additional dissipation channels in the metallic Ta films. PMID:28218296

  20. Sound generated by instability waves of supersonic flows. I Two-dimensional mixing layers. II - Axisymmetric jets

    Science.gov (United States)

    Tam, C. K. W.; Burton, D. E.

    1984-01-01

    An investigation is conducted of the phenomenon of sound generation by spatially growing instability waves in high-speed flows. It is pointed out that this process of noise generation is most effective when the flow is supersonic relative to the ambient speed of sound. The inner and outer asymptotic expansions corresponding to an excited instability wave in a two-dimensional mixing layer and its associated acoustic fields are constructed in terms of the inner and outer spatial variables. In matching the solutions, the intermediate matching principle of Van Dyke and Cole is followed. The validity of the theory is tested by applying it to an axisymmetric supersonic jet and comparing the calculated results with experimental measurements. Very favorable agreements are found both in the calculated instability-wave amplitude distribution (the inner solution) and the near pressure field level contours (the outer solution) in each case.

  1. Two dimensional finite element method for metabolic effect in thermoregulation on human males and females skin layers

    Directory of Open Access Journals (Sweden)

    Saraswati Acharya

    2015-08-01

    Full Text Available Objective: To deal the implication of metabolic reaction relying on dermal thicknesses of males and females for temperature distribution on the layers of dermal part at various atmospheric temperatures. Methods: The mathematical model involving bioheat equation has been solved using finite element method and Crank-Nicolson technique to numerically investigate two dimensional temperature distributions. Initially, human dermal region under consideration is divided into six parts: stratum corneum, stratum germinativum, papillary region, reticular region, fatty layer and muscle part of subcutaneous tissue. Pennes bioheat equation is used considering the suitable physical and physiological parameters that affect the heat regulation in the layers. Computer simulation has been used for numerical results and graph of the temperatures profiles. Results: Lower percentage of muscle mass and higher percentage of adipose tissue in subcutaneous part of females result lower metabolic rate compared to males. Metabolism is considered as a heat source within the body tissue. The study delineates that when the metabolic heat generation S increases, body temperature rises and when S decreases, it goes down. In higher ambient temperature T∞ effect of S is lower as compared to lower T∞. Conclusions: Males and females would differ in their physiological responses in temperature distribution due to differences in metabolic heat production between genders. The thinner layers of males lead to higher values of skin temperature than thicker layer of females. Thickness plays a significant role in temperature distributions in human males and females body. Current understanding of human thermoregulation is based on male patterns; studies on women are still relatively rare and involve only small number of subjects. So it is still necessary for micro level study for temperature distribution model on the dermal layers of males and females.

  2. Two dimensional finite element method for metabolic effect in thermoregulation on human males and females skin layers

    Institute of Scientific and Technical Information of China (English)

    SaraswatiAcharya; Dil Bahadur Gurung; Vinod Prakash Saxena

    2015-01-01

    Objective: To deal the implication of metabolic reaction relying on dermal thicknesses of males and females for temperature distribution on the layers of dermal part at various atmospheric temperatures. Methods: The mathematical model involving bioheat equation has been solved using finite element method and Crank-Nicolson technique to numerically investigate two dimensional temperature distributions. Initially, human dermal region under consideration is divided into six parts: stratum corneum, stratum germinativum, papillary region, reticular region, fatty layer and muscle part of subcutaneous tissue. Pennes bioheat equation is used considering the suitable physical and physiological parameters that affect the heat regulation in the layers. Computer simulation has been used for numerical results and graph of the temperatures profiles. Results: Lower percentage of muscle mass and higher percentage of adipose tissue in subcutaneous part of females result lower metabolic rate compared to males. Metabolism is considered as a heat source within the body tissue. The study delineates that when the metabolic heat generation S increases, body temperature rises and when S decreases, it goes down. In higher ambient temperature T∞ effect of S is lower as compared to lower T∞. Conclusions: Males and females would differ in their physiological responses in temperature distribution due to differences in metabolic heat production between genders. The thinner layers of males lead to higher values of skin temperature than thicker layer of females. Thickness plays a significant role in temperature distributions in human males and females body. Current understanding of human thermoregulation is based on male patterns; studies on women are still relatively rare and involve only small number of subjects. So it is still necessary for micro level study for temperature distribution model on the dermal layers of males and females.

  3. Two-dimensionally stacked heterometallic layers hosting a discrete chair dodecameric ring of water clusters: synthesis and structural study.

    Science.gov (United States)

    Kenfack Tsobnang, Patrice; Wenger, Emmanuel; Biache, Coralie; Lambi Ngolui, John; Ponou, Siméon; Dahaoui, Slimane; Lecomte, Claude

    2014-10-01

    The stacked two-dimensional supramolecular compound catena-{Co(amp)3Cr(ox)3·6H2O} (amp = 2-picolylamine, ox = oxalate) has been synthesized from the bimolecular approach using hydrogen bonds. It is built from layers in which both Co(amp)(3+) (D) and Cr(ox)(3-) (A) ions are bonded in a repeating DADADA… pattern along the a and c axes by multiple hydrogen bonds. These layers host a well resolved R12 dodecameric discrete ring of water clusters built by six independent molecules located around the 2c centrosymmetric Wyckoff positions of the P21/n space group in which the compound crystallizes. These clusters are ranged along the [001] direction, occupy 733.5 Å(3) (22.0%) of the unit cell and have a chair conformation via 12 hydrogen bonds. The water molecules of the cluster are linked with stronger hydrogen bonds than those between the cluster and its host, which explains the single continuous step of the dehydration process of the compound.

  4. Two-Dimensional Electron Gas at SrTiO3-Based Oxide Heterostructures via Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Sang Woon Lee

    2016-01-01

    Full Text Available Two-dimensional electron gas (2DEG at an oxide interface has been attracting considerable attention for physics research and nanoelectronic applications. Early studies reported the formation of 2DEG at semiconductor interfaces (e.g., AlGaAs/GaAs heterostructures with interesting electrical properties such as high electron mobility. Besides 2DEG formation at semiconductor junctions, 2DEG was realized at the interface of an oxide heterostructure such as the LaAlO3/SrTiO3 (LAO/STO heterojunction. The origin of 2DEG was attributed to the well-known “polar catastrophe” mechanism in oxide heterostructures, which consist of an epitaxial LAO layer on a single crystalline STO substrate among proposed mechanisms. Recently, it was reported that the creation of 2DEG was achieved using the atomic layer deposition (ALD technique, which opens new functionality of ALD in emerging nanoelectronics. This review is focused on the origin of 2DEG at oxide heterostructures using the ALD process. In particular, it addresses the origin of 2DEG at oxide interfaces based on an alternative mechanism (i.e., oxygen vacancies.

  5. Theory of substrate-directed heat dissipation for single-layer graphene and other two-dimensional crystals

    Science.gov (United States)

    Ong, Zhun-Yong; Cai, Yongqing; Zhang, Gang

    2016-10-01

    We present a theory of the phononic thermal (Kapitza) resistance at the interface between graphene or another single-layer two-dimensional (2D) crystal (e.g., MoS2) and a flat substrate, based on a modified version of the cross-plane heat transfer model by Persson, Volokitin, and Ueba [J. Phys.: Condens. Matter 23, 045009 (2011), 10.1088/0953-8984/23/4/045009]. We show how intrinsic flexural phonon damping is necessary for obtaining a finite Kapitza resistance and also generalize the theory to encased single-layer 2D crystals with a superstrate. We illustrate our model by computing the thermal boundary conductance (TBC) for bare and SiO2-encased single-layer graphene and MoS2 on a SiO2 substrate, using input parameters from first-principles calculation. The estimated room temperatures TBC for bare (encased) graphene and MoS2 on SiO2 are 34.6 (105) and 3.10 (5.07) MWK -1m-2 , respectively. The theory predicts the existence of a phonon frequency crossover point, below which the low-frequency flexural phonons in the bare 2D crystal do not dissipate energy efficiently to the substrate. We explain within the framework of our theory how the encasement of graphene with a top SiO2 layer introduces new low-frequency transmission channels, which significantly reduce the graphene-substrate Kapitza resistance. We emphasize that the distinction between bare and encased 2D crystals must be made in the analysis of cross-plane heat dissipation to the substrate.

  6. [A comment on chiral thin layer chromatography].

    Science.gov (United States)

    Chen, Xuexian; Yuan, Liming

    2016-01-01

    In recent eight years, authors' group has repeated a lot of experiments of chiral thin layer chromatography coming from literature. From the practical opinion, we summarized that there are nine characteristics for chiral thin layer chromatography. Some progresses of chiral thin layer chromatography are reviewed, and the enantioselectivity of a commercial chiral thin layer plate is introduced. The study of vancomycin as the chiral selector in thin layer chromatography is also reported.

  7. Turbulent Friction in the Boundary Layer of a Flat Plate in a Two-Dimensional Compressible Flow at High Speeds

    Science.gov (United States)

    Frankl, F.; Voishel, V.

    1943-01-01

    In the present report an investigation is made on a flat plate in a two-dimensional compressible flow of the effect of compressibility and heating on the turbulent frictional drag coefficient in the boundary layer of an airfoil or wing radiator. The analysis is based on the Prandtl-Karman theory of the turbulent boundary later and the Stodola-Crocco, theorem on the linear relation between the total energy of the flow and its velocity. Formulas are obtained for the velocity distribution and the frictional drag law in a turbulent boundary later with the compressibility effect and heat transfer taken into account. It is found that with increase of compressibility and temperature at full retardation of the flow (the temperature when the velocity of the flow at a given point is reduced to zero in case of an adiabatic process in the gas) at a constant R (sub x), the frictional drag coefficient C (sub f) decreased, both of these factors acting in the same sense.

  8. Two-Dimensional Superconductor with a Giant Rashba Effect: One-Atom-Layer Tl-Pb Compound on Si(111)

    Science.gov (United States)

    Matetskiy, A. V.; Ichinokura, S.; Bondarenko, L. V.; Tupchaya, A. Y.; Gruznev, D. V.; Zotov, A. V.; Saranin, A. A.; Hobara, R.; Takayama, A.; Hasegawa, S.

    2015-10-01

    A one-atom-layer compound made of one monolayer of Tl and one-third monolayer of Pb on a Si(111) surface having √{3 }×√{3 } periodicity was found to exhibit a giant Rashba-type spin splitting of metallic surface-state bands together with two-dimensional superconducting transport properties. Temperature-dependent angle-resolved photoelectron spectroscopy revealed an enhanced electron-phonon coupling for one of the spin-split bands. In situ micro-four-point-probe conductivity measurements with and without magnetic field demonstrated that the (Tl, Pb)/Si(111) system transformed into the superconducting state at 2.25 K, followed by the Berezinskii-Kosterlitz-Thouless mechanism. The 2D Tl-Pb compound on Si(111) is believed to be the prototypical object for prospective studies of intriguing properties of the superconducting 2D system with lifted spin degeneracy, bearing in mind that its composition, atomic and electron band structures, and spin texture are already well established.

  9. BEM/FDM Conjugate Heat Transfer Analysis of a Two-dimensional Air-cooled Turbine Blade Boundary Layer

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A coupled boundary element method (BEM) and finite difference method (FDM) are applied to solve conjugate heat transfer problem of a two-dimensional air-cooled turbine blade boundary layer. A loosely coupled strategy is adopted, in which each set of field equations is solved to provide boundary conditions for the other. The Navier-Stokes equations are solved by HIT-NS code. In this code, the FDM is adopted and is used to resolve the convective heat transfer in the fluid region. The BEM code is used to resolve the conduction heat transfer in the solid region. An iterated convergence criterion is the continuity of temperature and heat flux at the fluid-solid interface. The numerical results from the BEM adopted in this paper are in good agreement with the results of analyrical solution and the results of commercial code, such as Fluent 6.2. The BEM avoids the complicated mesh needed in other computation method and saves the computation time. The results prove that the BEM adopted in this paper can give the same precision in numerical results with less boundary points. Comparing the conjugate results with the numerical results of an adiabatic wall flow solution, it reveals a significant difference in the distribution of metal temperatures. The results from conjugate heat transfer analysis are more accurate and they are closer to realistic thermal environment of turbines.

  10. High-resolution structural studies of ultra-thin magnetic, transition metal overlayers and two-dimensional transition metal oxides using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kellar, S.A. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Advanced Light Source Div.

    1997-05-01

    This thesis report the surface-structure determination of three, ultra-thin magnetic transition-metal films, Fe/Au(100), Mn/Ni(100), and Mn/Cu(100) using Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) and photoelectron holography. These structural studies are the first to use non-s initial states in the ARPEFS procedure. This thesis also reports an ARPEFS surface-structure determination of a two-dimensional transition-metal oxide, [(1 x 1)O/W(110)] x 12. The authors have analyzed the ARPFES signal from the Au 4f{sub 7/5} core level of the Au(1 ML)/Fe(15 ML)/Au(100) system. The analysis shows that the Fe grows layer by layer with one monolayer of gold, acting as a surfactant, remaining on top of the growing Fe layers. These surface gold atoms sit in the four-fold hollow site, 1.67 {+-} 0.02 A above the iron surface. The grown Fe layer is very much like the bulk, bcc iron, with an interlayer spacing of 1.43 {+-} 0.03 A. Analysis of the Mn 3p ARPEFS signals from c(2 x 2)Mn/Ni(100) and c(2 x 2)Mn/Cu(100) shows that the Mn forms highly corrugated surface alloys. The corrugation of the Mn/Ni(100) and Mn/Cu(100) systems are 0.24 {+-} 0.02 A and 0.30 {+-} 0.04 A respectively. In both cases the Mn is sticking above the plane of the surface substrate atoms. For the Mn/Ni(100) system the first layer Ni is contracted 4% from the bulk value. The Mn/Cu(100) system shows bulk spacing for the substrate Cu. Photoelectron holography shows that the Mn/Ni interface is very abrupt with very little Mn leaking into the second layer, while the Mn/Cu(100) case has a significant amount of Mn leaking into the second layer. A new, five-element electrostatic electron lens was developed for hemispherical electron-energy analyzers. This lens system can be operated at constant transverse or constants angular magnification, and has been optimized for use with the very small photon-spot sizes. Improvements to the hemispherical electron-energy analyzer are also discussed.

  11. Two-Dimensional Layered Double Hydroxide Derived from Vermiculite Waste Water Supported Highly Dispersed Ni Nanoparticles for CO Methanation

    Directory of Open Access Journals (Sweden)

    Panpan Li

    2017-03-01

    Full Text Available Expanded multilayered vermiculite (VMT was successfully used as catalyst support and Ni/VMT synthesized by microwave irradiation assisted synthesis (MIAS exhibited excellent performance in our previous work. We also developed a two-dimensional porous SiO2 nanomesh (2D VMT-SiO2 by mixed-acid etching of VMT. Compared with three-dimensional (3D MCM-41, 2D VMT-SiO2 as a catalyst support provided a superior position for implantation of NiO species and the as-obtained catalyst exhibited excellent performance. In this paper, we successfully synthesized a layered double hydroxide (LDH using the spent liquor after mixed-acid etching of VMT, which mainly contained Mg2+ and Al3+. The as-calcined layered double oxide (LDO was used as a catalyst support for CO methanation. Compared with Ni/MgAl-LDO, Ni/VMT-LDO had smaller active component particles; therefore, in this study, it exhibited excellent catalytic performance over the whole temperature range of 250–500 °C. Ni/VMT-LDO achieved the best activity with 87.88% CO conversion, 89.97% CH4 selectivity, and 12.47 × 10−2·s−1 turn over frequency (TOF at 400 °C under a gas hourly space velocity of 20,000 mL/g/h. This study demonstrated that VMT-LDO as a catalyst support provided an efficient way to develop high-performance catalysts for synthetic natural gas (SNG from syngas.

  12. Structure of two-dimensional and three-dimensional turbulent boundary layers with sparsely distributed roughness elements

    Science.gov (United States)

    George, Jacob

    The present study deals with the effects of sparsely distributed three-dimensional elements on two-dimensional (2-D) and three-dimensional (3-D) turbulent boundary layers (TBL) such as those that occur on submarines, ship hulls, etc. This study was achieved in three parts: Part 1 dealt with the cylinders when placed individually in the turbulent boundary layers, thereby considering the effect of a single perturbation on the TBL; Part 2 considered the effects when the same individual elements were placed in a sparse and regular distribution, thus studying the response of the flow to a sequence of perturbations; and in Part 3, the distributions were subjected to 3-D turbulent boundary layers, thus examining the effects of streamwise and spanwise pressure gradients on the same perturbed flows as considered in Part 2. The 3-D turbulent boundary layers were generated by an idealized wing-body junction flow. Detailed 3-velocity-component Laser-Doppler Velocimetry (LDV) and other measurements were carried out to understand and describe the rough-wall flow structure. The measurements include mean velocities, turbulence quantities (Reynolds stresses and triple products), skin friction, surface pressure and oil flow visualizations in 2-D and 3-D rough-wall flows for Reynolds numbers, based on momentum thickness, greater than 7000. Very uniform circular cylindrical roughness elements of 0.38mm, 0.76mm and 1.52mm height (k) were used in square and diagonal patterns, yielding six different roughness geometries of rough-wall surface. For the 2-D rough-wall flows, the roughness Reynolds numbers, k +, based on the element height (k) and the friction velocity (Utau), range from 26 to 131. Results for the 2-D rough-wall flows reveal that the velocity-defect law is similar for both smooth and rough surfaces, and the semi-logarithmic velocity-distribution curve is shifted by an amount DeltaU/U, depending on the height of the roughness element, showing that Delta U/Utau is a function

  13. Photoluminescence Properties of Two-dimensional Planar Layer and Three-dimensional Island Layer for ZnO Films Grown Using MOCVD

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    ZnO(002) films with different thicknesses ranging from 7 to 300 nm were grown on sapphire(006) substrates via metal-organic chemical vapor deposition(MOCVD). The two-dimensional(2D) planar layer and the three-dimensional(3D) island layer were studied by using of X-ray diffraction(XRD) rocking curves and atomic force microscopy(AFM). The room temperature photoluminescence(PL) spectra show a blue shift of the peak positions of the ultraviolet(UV) emission with increasing film thickness. The blue shift is remarkably high(393-380 nm) when an increase in film thickness(7-15 nm) is accompanied by the change of structure from a2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a2D planar layer to a 3D island layer near the2D layer region.

  14. Three-Dimensional Porous Particles Composed of Curved, Two-Dimensional, Nano-Sized Layers for Li-Ion Batteries

    Science.gov (United States)

    Yushin, Gleb; Evanoff, Kara; Magasinski, Alexander

    2012-01-01

    Thin Si films coated on porous 3D particles composed of curved 2D graphene sheets have been synthesized utilizing techniques that allow for tunable properties. Since graphene exhibits specific surface area up to 100 times higher than carbon black or graphite, the deposition of the same mass of Si on graphene is much faster in comparison -- a factor which is important for practical applications. In addition, the distance between graphene layers is tunable and variation in the thickness of the deposited Si film is feasible. Both of these characteristics allow for optimization of the energy and power characteristics. Thicker films will allow higher capacity, but slower rate capabilities. Thinner films will allow more rapid charging, or higher power performance. In this innovation, uniform deposition of Si and C layers on high-surface area graphene produced granules with specific surface area (SSA) of 5 sq. m/g.

  15. High Performance Thin Layer Chromatography.

    Science.gov (United States)

    Costanzo, Samuel J.

    1984-01-01

    Clarifies where in the scheme of modern chromatography high performance thin layer chromatography (TLC) fits and why in some situations it is a viable alternative to gas and high performance liquid chromatography. New TLC plates, sample applications, plate development, and instrumental techniques are considered. (JN)

  16. High Performance Thin Layer Chromatography.

    Science.gov (United States)

    Costanzo, Samuel J.

    1984-01-01

    Clarifies where in the scheme of modern chromatography high performance thin layer chromatography (TLC) fits and why in some situations it is a viable alternative to gas and high performance liquid chromatography. New TLC plates, sample applications, plate development, and instrumental techniques are considered. (JN)

  17. Slow relaxation of the magnetization observed in an antiferromagnetically ordered phase for SCM-based two-dimensional layered compounds.

    Science.gov (United States)

    Kagesawa, Koichi; Nishimura, Yuki; Yoshida, Hiroki; Breedlove, Brian K; Yamashita, Masahiro; Miyasaka, Hitoshi

    2017-03-07

    Two-dimensional layered compounds with different counteranions, [{Mn(salen)}4C6](BF4)2·2(CH3OH) (1) and [{Mn(salen)}4C6](PF6)2·2(CH3OH) (2) (salen(2-) = N,N'-bis(salicylideneiminato), C6(2-) = C6H12(COO)2(2-)), were synthesized by assembling [Mn(salen)(H2O)]X (X(-) = BF4(-) and PF6(-)) and C6H12(CO2(-))2 (C6(2-)) in a methanol/2-propanol medium. The compounds have similar structures, which are composed of Mn(salen) out-of-plane dimers bridged by μ(4)-type C6(2-) ions, forming a brick-wall-type network of [-{Mn2}-OCO-] chains alternately connected via C6H12 linkers of C6(2-) moieties. The counteranions for 1 and 2, i.e., BF4(-) and PF6(-), respectively, are located between layers. Since the size of BF4(-) is smaller than that of PF6(-), intra-layer inter-chain and inter-plane nearest-neighbor MnMn distances are shorter in 1 than in 2. The zigzag chain moiety of [-{Mn2}-OCO-] leads to a canted S = 2 spin arrangement with ferromagnetic coupling in the Mn(III) out-of-plane dimer moiety and antiferromagnetic coupling through -OCO- bridges. Due to strong uniaxial anisotropy of the Mn(III) ion, the [-{Mn2}-OCO-] chains could behave as a single-chain magnet (SCM), which exhibits slow relaxation of magnetization at low temperatures. Nevertheless, these compounds fall into an antiferromagnetic ground state at higher temperatures of TN = 4.6 and 3.8 K for 1 and 2, respectively, than active temperatures for SCM behavior. The spin flip field at 1.8 K is 2.7 and 1.8 kOe for 1 and 2, respectively, which is attributed to the inter-chain interactions tuned by the size of the counteranions. The relaxation times of magnetization become longer at the boundary between the antiferromagnetic phase and the paramagnetic phase.

  18. Atomic layer deposition of two dimensional MoS{sub 2} on 150 mm substrates

    Energy Technology Data Exchange (ETDEWEB)

    Valdivia, Arturo; Conley, John F., E-mail: jconley@eecs.oregonstate.edu [School of EECS, Oregon State University, Corvallis, Oregon 97331 (United States); Tweet, Douglas J. [Sharp Labs of America, Camas, Washington 98607 (United States)

    2016-03-15

    Low temperature atomic layer deposition (ALD) of monolayer to few layer MoS{sub 2} uniformly across 150 mm diameter SiO{sub 2}/Si and quartz substrates is demonstrated. Purge separated cycles of MoCl{sub 5} and H{sub 2}S precursors are used at reactor temperatures of up to 475 °C. Raman scattering studies show clearly the in-plane (E{sup 1}{sub 2g}) and out-of-plane (A{sub 1g}) modes of MoS{sub 2}. The separation of the E{sup 1}{sub 2g} and A{sub 1g} peaks is a function of the number of ALD cycles, shifting closer together with fewer layers. X-ray photoelectron spectroscopy indicates that stoichiometry is improved by postdeposition annealing in a sulfur ambient. High resolution transmission electron microscopy confirms the atomic spacing of monolayer MoS{sub 2} thin films.

  19. Raman enhancement effect on two-dimensional layered materials: graphene, h-BN and MoS2.

    Science.gov (United States)

    Ling, Xi; Fang, Wenjing; Lee, Yi-Hsien; Araujo, Paulo T; Zhang, Xu; Rodriguez-Nieva, Joaquin F; Lin, Yuxuan; Zhang, Jin; Kong, Jing; Dresselhaus, Mildred S

    2014-06-11

    Realizing Raman enhancement on a flat surface has become increasingly attractive after the discovery of graphene-enhanced Raman scattering (GERS). Two-dimensional (2D) layered materials, exhibiting a flat surface without dangling bonds, were thought to be strong candidates for both fundamental studies of this Raman enhancement effect and its extension to meet practical applications requirements. Here, we study the Raman enhancement effect on graphene, hexagonal boron nitride (h-BN), and molybdenum disulfide (MoS2), by using the copper phthalocyanine (CuPc) molecule as a probe. This molecule can sit on these layered materials in a face-on configuration. However, it is found that the Raman enhancement effect, which is observable on graphene, hBN, and MoS2, has different enhancement factors for the different vibrational modes of CuPc, depending strongly on the surfaces. Higher-frequency phonon modes of CuPc (such as those at 1342, 1452, 1531 cm(-1)) are enhanced more strongly on graphene than that on h-BN, while the lower frequency phonon modes of CuPc (such as those at 682, 749, 1142, 1185 cm(-1)) are enhanced more strongly on h-BN than that on graphene. MoS2 demonstrated the weakest Raman enhancement effect as a substrate among these three 2D materials. These differences are attributed to the different enhancement mechanisms related to the different electronic properties and chemical bonds exhibited by the three substrates: (1) graphene is zero-gap semiconductor and has a nonpolar C-C bond, which induces charge transfer (2) h-BN is insulating and has a strong B-N bond, while (3) MoS2 is semiconducting with the sulfur atoms on the surface and has a polar covalent bond (Mo-S) with the polarity in the vertical direction to the surface. Therefore, the different Raman enhancement mechanisms differ for each material: (1) charge transfer may occur for graphene; (2) strong dipole-dipole coupling may occur for h-BN, and (3) both charge transfer and dipole-dipole coupling may

  20. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

    Science.gov (United States)

    Wang, Qing Hua; Kalantar-Zadeh, Kourosh; Kis, Andras; Coleman, Jonathan N; Strano, Michael S

    2012-11-01

    The remarkable properties of graphene have renewed interest in inorganic, two-dimensional materials with unique electronic and optical attributes. Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickness. Although TMDCs have been studied for decades, recent advances in nanoscale materials characterization and device fabrication have opened up new opportunities for two-dimensional layers of thin TMDCs in nanoelectronics and optoelectronics. TMDCs such as MoS(2), MoSe(2), WS(2) and WSe(2) have sizable bandgaps that change from indirect to direct in single layers, allowing applications such as transistors, photodetectors and electroluminescent devices. We review the historical development of TMDCs, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.

  1. Microstructure of bidisperse ferrofluids in a thin layer

    Energy Technology Data Exchange (ETDEWEB)

    Minina, E. S., E-mail: alla2307@gmail.com; Muratova, A. B. [Ural Federal University, Department of Mathematical Physics (Russian Federation); Cerda, J. J. [Campus University de les Illes Balears, Institute for Cross-Disciplinary Physics and Complex Systems (Spain); Kantorovich, S. S., E-mail: sue.kantorovich@usu.ru [Ural Federal University, Department of Mathematical Physics (Russian Federation)

    2013-03-15

    In this work we present a characterization of the bidisperse ferrofluid microstructures that appear in thin layers of ferrofluid. These layers have been studied by a combination of Langevin dynamics simulations and density functional theory. Our results allow us to compare the microstructures that exist in quasi-two-dimensional ferrofluid nanolayers with the microstructures found in three-dimensional bidisperse ferrofluids. Furthermore, our results allow us to explain the influence of the geometry of the sample on the topology and size-distribution of the observed aggregates of magnetic nanoparticles.

  2. Two-Dimensional Superconductivity Emerged at Monatomic Bi(2-) Square Net in Layered Y2O2Bi via Oxygen Incorporation.

    Science.gov (United States)

    Sei, Ryosuke; Kitani, Suguru; Fukumura, Tomoteru; Kawaji, Hitoshi; Hasegawa, Tetsuya

    2016-09-07

    Discovery of layered superconductors such as cuprates and iron-based compounds has unveiled new science and compounds. In these superconductors, quasi-two-dimensional layers including transition metal cations play principal role in the superconductivity via carrier doping by means of aliovalent-ion substitution. Here, we report on a two-dimensional superconductivity at 2 K in ThCr2Si2-type layered oxide Y2O2Bi possessing conducting monatomic Bi(2-) square net, possibly associated with an exotic superconductivity. The superconductivity emerges only in excessively oxygen-incorporated Y2O2Bi with expanded inter-net distance, in stark contrast to nonsuperconducting pristine Y2O2Bi reported previously. This result suggests that the element incorporation into hidden interstitial site could be an alternative approach to conventional substitution and intercalation methods for search of novel superconductors.

  3. Phase and Texture of Solution-Processed Copper Phthalocyanine Thin Films Investigated by Two-Dimensional Grazing Incidence X-Ray Diffraction

    Directory of Open Access Journals (Sweden)

    Lulu Deng

    2011-07-01

    Full Text Available The phase and texture of a newly developed solution-processed copper phthalocyanine (CuPc thin film have been investigated by two-dimensional grazing incidence X-ray diffraction. The results show that it has β phase crystalline structure, with crystallinity greater than 80%. The average size of the crystallites is found to be about 24 nm. There are two different arrangements of crystallites, with one dominating the diffraction pattern. Both of them have preferred orientation along the thin film normal. Based on the similarities to the vacuum deposited CuPc thin films, the new solution processing method is verified to offer a good alternative to vacuum process, for the fabrication of low cost small molecule based organic photovoltaics.

  4. The effect of thin filament activation on the attachment of weak binding cross-bridges: A two-dimensional x-ray diffraction study on single muscle fibers.

    OpenAIRE

    Kraft, T; Xu, S.; Brenner, B; Yu, L C

    1999-01-01

    To study possible structural changes in weak cross-bridge attachment to actin upon activation of the thin filament, two-dimensional (2D) x-ray diffraction patterns of skinned fibers from rabbit psoas muscle were recorded at low and high calcium concentration in the presence of saturating concentrations of MgATPgammaS, a nucleotide analog for weak binding states. We also studied 2D x-ray diffraction patterns recorded under relaxing conditions at an ionic strength above and below 50 mM, because...

  5. A direct time measurements technique for the two-dimensional precision coordinate detectors based on thin-walled drift tubes

    CERN Document Server

    Makankin, A M; Peshekhonov, V D; Ritt, S; Vasilyev, S E

    2013-01-01

    This article presents the results of a study of the longitudinal spatial resolution of 2 m long straw tubes by means of the direct timing method (DTM). The feasibility of achieving a coordinate resolution (r.m.s.) better than 2 cm over full length of the straw is demonstrated. The spatial resolution insignificantly changes when measured by detecting gammas from a Fe-55 gamma ray source or minimum ionizing particles from a Ru-106 source. The use of the same type of FEE for data taking both for measuring the drift time of ionization electrons and propagation of a signal along the anode wire allows one to construct a two-dimensional detector for precision coordinate measurements.

  6. A direct time measurement technique for the two-dimensional precision coordinate detectors based on thin-walled drift tubes

    Energy Technology Data Exchange (ETDEWEB)

    Makankin, A.M.; Myalkovskiy, V.V. [Joint Institute for Nuclear Research (JINR), Dubna (Russian Federation); Peshekhonov, V.D., E-mail: Vladimir.Peshekhonov@sunse.jinr.ru [Joint Institute for Nuclear Research (JINR), Dubna (Russian Federation); Ritt, S. [Paul Scherrer Institute (PSI), Villigen (Switzerland); Vasilyev, S.E. [Joint Institute for Nuclear Research (JINR), Dubna (Russian Federation)

    2014-01-21

    This article presents the results of a study of the longitudinal spatial resolution by means of the direct timing method (DTM) using 2 m long and 9.53 mm diameter straw tubes. The feasibility of achieving the spatial resolution (r.m.s.) better than 2 cm over full length of the straw is demonstrated. The spatial resolution changes little when measured by detecting gammas from a Fe-55 gamma ray source or minimum ionizing electrons from a Ru-106 source. The use of the same type of front end electronics (FEE) both for measuring the drift time of ionization electrons and propagation time of a signal along the anode wire allows one to construct a detector capable for measuring the two dimensional coordinates of charged particles.

  7. Effects of rapid thermal annealing on two-dimensional delocalized electronic states of the epitaxial N δ-doped layer in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Yasuhiro; Harada, Yukihiro; Baba, Takeshi; Kaizu, Toshiyuki; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

    2016-03-14

    We have conducted rapid thermal annealing (RTA) for improving the two-dimensional (2D) arrangement of electronic states in the epitaxial nitrogen (N) δ-doped layer in GaAs. RTA rearranged the N-pair configurations in the GaAs (001) plane and reduced the number of non-radiative recombination centers. Furthermore, a Landau shift, representing the 2D delocalized electronic states in the (001) plane, was observed at around zero magnetic field intensity in the Faraday configuration.

  8. Recent progress of two-dimensional layered molyb denum disulfide%层状二硫化钼研究进展∗

    Institute of Scientific and Technical Information of China (English)

    顾品超; 张楷亮; 冯玉林; 王芳; 苗银萍; 韩叶梅; 张韩霞

    2016-01-01

    Recently, two-dimensional (2D) layered molybdenum disulfide (MoS2) has attracted great attention because of its graphene-like structure and unique physical and chemical properties. In this paper, physical structure, band gap structure, and optical properties of MoS2 are summarized. MoS2 is semiconducting and composed of covalently bonded sheets held together by weak van der Waals force. In each MoS2 layer, a layer of molybdenum (Mo) atoms is sandwiched between two layers of sulfur (S) atoms. There are three types of MoS2 compounds, including 1T MoS2, 2H MoS2, and 3R MoS2. As the number of layers decreases, the bad gap becomes larger. The bad gap transforms from indirect to direct as MoS2 is thinned to a monolayer. Changes of band gap show a great potential in photoelectron. Preparation methods of 2D MoS2 are reviewed, including growth methods and exfoliation methods. Ammonium thiomolybdate (NH4)2MoS4, elemental molybdenum Mo and molybdenum trioxide MoO3 are used to synthesize 2D MoS2 by growth methods. (NH4)2MoS4 is dissolved in a solution and then coated on a substrate. (NH4)2MoS4 is decomposed into MoS2 after annealing at a high temperature. Mo is evaporated onto a substrate, and then sulfurized into MoS2. MoO3 is most used to synthesize MoS2 on different substrates by a chemical vapor deposition or plasma-enhanced chemical vapor deposition. Other precursors like Mo(CO)6, MoS2 and MoCl5 are also used for MoS2 growth. For the graphene-like structure, monolayer MoS2 can be exfoliated from bulk MoS2. Exfoliation methods include micromechanical exfoliation, liquid exfoliation, lithium-based intercalation and electrochemistry lithium-based intercalation. For micromechanical exfoliation, the efficiency is low and the sizes of MoS2 flakes are small. For liquid exfoliation, it is convenient for operation to obtain mass production, but the concentration of monolayer MoS2 is low. For lithium-based intercalation, the yield of monolayer MoS2 is high while it takes a long

  9. Band Gap Tuning and Defect Tolerance of Atomically Thin Two-Dimensional Organic-Inorganic Halide Perovskites.

    Science.gov (United States)

    Pandey, Mohnish; Jacobsen, Karsten W; Thygesen, Kristian S

    2016-11-03

    Organic-inorganic halide perovskites have proven highly successful for photovoltaics but suffer from low stability, which deteriorates their performance over time. Recent experiments have demonstrated that low dimensional phases of the hybrid perovskites may exhibit improved stability. Here we report first-principles calculations for isolated monolayers of the organometallic halide perovskites (C4H9NH3)2MX2Y2, where M = Pb, Ge, Sn and X,Y = Cl, Br, I. The band gaps computed using the GLLB-SC functional are found to be in excellent agreement with experimental photoluminescence data for the already synthesized perovskites. Finally, we study the effect of different defects on the band structure. We find that the most common defects only introduce shallow or no states in the band gap, indicating that these atomically thin 2D perovskites are likely to be defect tolerant.

  10. Two-dimensional differential deposition: figure correction of thin-shell mirror substrates for x-ray astronomy

    Science.gov (United States)

    Windt, David L.; Conley, Ray

    2015-09-01

    This paper describes a new variation of the differential deposition/differential erosion technique for mid-frequency surface-height error correction. In our approach, the technique is extended to two dimensions in order to correct surfaceheight errors in thin-shell cylindrical mirror segments with high throughput. We describe the new infrastructure currently being developed to realize this technique, including an LTP system for surface metrology of mid-frequency surfaceheight errors, a new UHV linear stage for precise substrate motion during deposition or erosion, and most crucially, the development of electronically-actuated aperture arrays that are mounted in front of a rectangular magnetron cathode, or a rectangular ion source, in order to modulate the deposition/erosion rate of material in two dimensions, in real-time.

  11. Quasi-two-dimensional superconductivity in FeSe0.3Te0.7 thin films and electric-field modulation of superconducting transition.

    Science.gov (United States)

    Lin, Zhu; Mei, Chenguang; Wei, Linlin; Sun, Zhangao; Wu, Shilong; Huang, Haoliang; Zhang, Shu; Liu, Chang; Feng, Yang; Tian, Huanfang; Yang, Huaixin; Li, Jianqi; Wang, Yayu; Zhang, Guangming; Lu, Yalin; Zhao, Yonggang

    2015-09-18

    We report the structural and superconducting properties of FeSe0.3Te0.7 (FST) thin films with different thicknesses grown on ferroelectric Pb(Mg1/3Nb2/3)0.7Ti0.3O3 substrates. It was shown that the FST films undergo biaxial tensile strains which are fully relaxed for films with thicknesses above 200 nm. Electrical transport measurements reveal that the ultrathin films exhibit an insulating behavior and superconductivity appears for thicker films with Tc saturated above 200 nm. The current-voltage curves around the superconducting transition follow the Berezinskii-Kosterlitz-Thouless (BKT) transition behavior and the resistance-temperature curves can be described by the Halperin-Nelson relation, revealing quasi-two-dimensional phase fluctuation in FST thin films. The Ginzburg number decreases with increasing film thickness indicating the decrease of the strength of thermal fluctuations. Upon applying electric field to the heterostructure, Tc of FST thin film increases due to the reduction of the tensile strain in FST. This work sheds light on the superconductivity, strain effect as well as electric-field modulation of superconductivity in FST films.

  12. Split-step finite-difference time-domain method with perfectly matched layers for efficient analysis of two-dimensional photonic crystals with anisotropic media.

    Science.gov (United States)

    Singh, Gurpreet; Tan, Eng Leong; Chen, Zhi Ning

    2012-02-01

    This Letter presents a split-step (SS) finite-difference time-domain (FDTD) method for the efficient analysis of two-dimensional (2-D) photonic crystals (PhCs) with anisotropic media. The proposed SS FDTD method is formulated with perfectly matched layer boundary conditions and caters for inhomogeneous anisotropic media. Furthermore, the proposed method is derived using the efficient SS1 splitting formulas with simpler right-hand sides that are more efficient and easier to implement. A 2-D PhC cavity with anisotropic media is used as an example to validate the efficiency of the proposed method.

  13. Bolometric detection of magnetoplasma resonances in microwave absorption by two-dimensional electron systems based on doping layer conductivity measurements in GaAs/AlGaAs heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Dorozhkin, S. I., E-mail: dorozh@issp.ac.ru; Sychev, D. V.; Kapustin, A. A. [Institute of Solid State Physics RAS, 142432 Chernogolovka, Moscow district (Russian Federation)

    2014-11-28

    We have implemented a new bolometric method to detect resonances in magneto-absorption of microwave radiation by two-dimensional electron systems (2DES) in selectively doped GaAs/AlGaAs heterostructures. Radiation is absorbed by the 2DES and the thermally activated conductivity of the doping layer supplying electrons to the 2DES serves as a thermometer. The resonant absorption brought about by excitation of the confined magnetoplasma modes appears as peaks in the magnetic field dependence of the low-frequency impedance measured between the Schottky gate and 2DES.

  14. A theoretical model for the evolution of two-dimensional large-scale coherent structures in a mixing layer

    Institute of Scientific and Technical Information of China (English)

    周恒; 马良

    1995-01-01

    By a proper combination of the modified weakly nonlinear theory of hydrodynamic stability and the energy method, the spatial evolution of the large-scale coherent structures in a mixing layer has been calculated. The results are satisfactory.

  15. Piezoelectric-paint-based two-dimensional phased sensor arrays for structural health monitoring of thin panels

    Science.gov (United States)

    Yoo, B.; Purekar, A. S.; Zhang, Y.; Pines, D. J.

    2010-07-01

    A damage detection method based on an innovative 2D phased sensor array made of piezoelectric paint is proposed for in situ damage detection of a thin isotropic panel using guided Lamb waves. A design analysis of candidate 2D arrays based on spiral, cruciform and circular element layouts is performed. In this study, a 2D phased sensor array with a spiral configuration is fabricated using a piezoelectric composite (piezopaint) patch and used for detecting damages in an aluminum panel. Steered array responses are generated from the raw sensor signals using a directional filtering algorithm based on phased array signal processing. The fundamental flexural (or transverse), A0 mode, of the guided Lamb waves is used though the sensing and analysis technique is not limited to the mode used in this work. To enhance the proposed analysis technique, empirical mode decomposition (EMD) and a Hilbert-Huang transform (HHT) are applied. A new damage detection algorithm including threshold setting and damage index (DI) calculation is developed and implemented for detecting damages in the form of holes and a simulated crack. The characteristic damage indices consistently increase as damage size grows.

  16. Depth profiling of SBS/PET layered materials using step-scan phase modulation Fourier transform infrared photoacoustic spectroscopy and two-dimensional correlation analysis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper demonstrates the application of step-scan phase modulation Fourier transform infrared photoacoustic spectroscopy(FTIR-PAS) in non-destructively depth profiling of styrene-butadiene-styrene block copolymer/polyethylene terephthalate(SBS/PET) layered materials.The surface thicknesses of three layered samples were determined to be 1.2,4.3 and 9.4μm by using phase difference analysis,overcoming the spatial detection limits of FTIR.Combined with generalized two-dimensional(G2D) FTIR correlation analysis,the spatial origins of peaks in the SBS/PET spectrum are identified with those having overlapping peaks between different layers are resolved.

  17. Two-dimensional simulation of interdigitated back contact silicon heterojunction solar cells having overlapped p/i and n/i a-Si:H layers

    Science.gov (United States)

    Noge, Hiroshi; Saito, Kimihiko; Sato, Aiko; Kaneko, Tetsuya; Kondo, Michio

    2015-08-01

    The performance of interdigitated back contact silicon heterojunction solar cells having overlapped p/i and n/i a-Si:H layers on the back has been investigated by two-dimensional simulation in comparison with the conventional cell structure having a gap between p/i and n/i layers. The results show that narrower overlap width leads to higher short circuit current and conversion efficiency, especially for poor heterojunction interface and thinner silicon substrate of the cells in addition to narrower uncovered width of p/i layer by a metal electrode. This is similar to the gap width dependence in the conventional cells, since both overlap and gap act as dead area for diffused excess carriers in the back contacts.

  18. Delamination of Compressed Thin Layers at Corners

    DEFF Research Database (Denmark)

    Sørensen, Kim D.; Jensen, Henrik Myhre; Clausen, Johan

    2008-01-01

    An analysis of delamination for a thin elastic layer under compression, attached to a substrate at a corner is carried out. The analysis is performed by combining results from interface fracture mechanics and the theory of thin shells. In contrast with earlier results for delamination on a flat...... layers, Fracture mechanics, Crack closure, Steady state crack propagation....

  19. Existence of shocklets in a two-dimensional supersonic mixing layer and its influence on the flow structure

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The spatial evolution of a T-S wave and its subharmonic wave, introduced at the inlet in a 2-D supersonic mixing layer, was investigated by using DNS. The relationship between the amplitude of the disturbance wave and the strength of the shocklet caused by the disturbance was investigated. We analyzed the shape of the disturbance velocity profile on both sides of the shocklet, and found that the existence of shocklet affected appreciably the disturbance velocity. The effects on the high speed side and low speed side of the mixing layer were found to be different.

  20. Atomic force microscopy imaging of transition metal layered compounds : A two-dimensional stick–slip system

    NARCIS (Netherlands)

    Kerssemakers, J.; Hosson, J.Th.M. De

    1995-01-01

    Various layered transition metal dichalcogenides were scanned with an optical-lever atomic force microscope (AFM). The microscopic images indicate the occurrence of strong lateral stick–slip effects. In this letter, two models are presented to describe the observations due to stick–slip, i.e., eithe

  1. Energy-efficient optical line terminal for WDM-OFDM-PON based on two-dimensional subcarrier and layer allocation.

    Science.gov (United States)

    Hu, Xiaofeng; Cao, Pan; Zhuang, Zhiming; Zhang, Liang; Yang, Qi; Su, Yikai

    2012-11-05

    We propose and experimentally demonstrate a scheme to reduce the energy consumption of optical line terminal (OLT) in wavelength division multiplexing - orthogonal frequency division multiplexing - passive optical networks (WDM-OFDM-PONs). In our scheme, a wireless communication technique, termed layered modulation, is introduced to maximize the transmission capacity of OFDM modulation module in the OLT by multiplexing data from different ONU groups with signal-to-noise ratio (SNR) margins onto the same subcarriers. With adaptive and dynamic subcarrier and layer allocation, several ONU groups with low traffic demands can share one OFDM modulation module to deliver their data during non-peak hours of a day, thus greatly reducing the number of running devices and minimizing the energy consumption of the OLT. Numerical calculation shows that an energy efficiency improvement of 28.3% in the OLT can be achieved by using proposed scheme compared to the conventional WDM-OFDM-PON.

  2. GaN: From three- to two-dimensional single-layer crystal and its multilayer van der Waals solids

    Science.gov (United States)

    Onen, A.; Kecik, D.; Durgun, E.; Ciraci, S.

    2016-02-01

    Three-dimensional (3D) GaN is a III-V compound semiconductor with potential optoelectronic applications. In this paper, starting from 3D GaN in wurtzite and zinc-blende structures, we investigated the mechanical, electronic, and optical properties of the 2D single-layer honeycomb structure of GaN (g -GaN ) and its bilayer, trilayer, and multilayer van der Waals solids using density-functional theory. Based on high-temperature ab initio molecular-dynamics calculations, we first showed that g -GaN can remain stable at high temperature. Then we performed a comparative study to reveal how the physical properties vary with dimensionality. While 3D GaN is a direct-band-gap semiconductor, g -GaN in two dimensions has a relatively wider indirect band gap. Moreover, 2D g -GaN displays a higher Poisson ratio and slightly less charge transfer from cation to anion. In two dimensions, the optical-absorption spectra of 3D crystalline phases are modified dramatically, and their absorption onset energy is blueshifted. We also showed that the physical properties predicted for freestanding g -GaN are preserved when g -GaN is grown on metallic as well as semiconducting substrates. In particular, 3D layered blue phosphorus, being nearly lattice-matched to g -GaN , is found to be an excellent substrate for growing g -GaN . Bilayer, trilayer, and van der Waals crystals can be constructed by a special stacking sequence of g -GaN , and they can display electronic and optical properties that can be controlled by the number of g -GaN layers. In particular, their fundamental band gap decreases and changes from indirect to direct with an increasing number of g -GaN layers.

  3. Two-Dimensional SnO Anodes with a Tunable Number of Atomic Layers for Sodium Ion Batteries

    KAUST Repository

    Zhang, Fan

    2017-01-18

    We have systematically changed the number of atomic layers stacked in 2D SnO nanosheet anodes and studied their sodium ion battery (SIB) performance. The results indicate that as the number of atomic SnO layers in a sheet decreases, both the capacity and cycling stability of the Na ion battery improve. The thinnest SnO nanosheet anodes (two to six SnO monolayers) exhibited the best performance. Specifically, an initial discharge and charge capacity of 1072 and 848 mAh g-1 were observed, respectively, at 0.1 A g-1. In addition, an impressive reversible capacity of 665 mAh g-1 after 100 cycles at 0.1 A g-1 and 452 mAh g-1 after 1000 cycles at a high current density of 1.0 A g-1 was observed, with excellent rate performance. As the average number of atomic layers in the anode sheets increased, the battery performance degraded significantly. For example, for the anode sheets with 10-20 atomic layers, only a reversible capacity of 389 mAh g-1 could be obtained after 100 cycles at 0.1 A g-1. Density functional theory calculations coupled with experimental results were used to elucidate the sodiation mechanism of the SnO nanosheets. This systematic study of monolayer-dependent physical and electrochemical properties of 2D anodes shows a promising pathway to engineering and mitigating volume changes in 2D anode materials for sodium ion batteries. It also demonstrates that ultrathin SnO nanosheets are promising SIB anode materials with high specific capacity, stable cyclability, and excellent rate performance.

  4. Modeling of Lamb wave propagation in plate with two-dimensional phononic crystal layer coated on uniform substrate using plane-wave-expansion method

    Energy Technology Data Exchange (ETDEWEB)

    Hou Zhilin [Laboratoire de Physique des Milieux Ionises et Applications (LPMIA), Nancy University, CNRS Boulevard des Aiguillettes, BP 239 F-54506, Vandoeuvre-les-Nancy (France)], E-mail: zhilin.hou@lpmi.uhp-nancy.fr; Assouar, Badreddine M. [Laboratoire de Physique des Milieux Ionises et Applications (LPMIA), Nancy University, CNRS Boulevard des Aiguillettes, BP 239 F-54506, Vandoeuvre-les-Nancy (France)

    2008-03-17

    We show that the conversional three-dimensional plane wave expansion method can be revised to investigate the lamb wave propagation in the plate with two-dimensional phononic crystal layer coated on uniform substrate. We find that an imaginary three-dimensional periodic system can be constructed by stacking the studied plates and vacuum layers alternately, and then the Fourier series expansion can be performed. The difference between our imaginary periodic system and the true three-dimensional one is that, in our system, the Bloch feature of the wave along the thickness direction is broken. Three different systems are investigated by the proposed method as examples. The principle and reliability of the method are also discussed.

  5. Quantum transport in two dimensional electron gas/p-wave superconductor junction with Rashba spin–orbit coupling at the interface and in the normal layer

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadkhani, R., E-mail: rmkhani@znu.ac.ir; Hassanloo, Gh.

    2014-11-01

    We have studied the tunneling conductance of a clean two dimensional electron gas/p- wave superconductor junction with Rashba spin–orbit coupling (RSOC) which is present in the normal layer and at the interface. Using the extended Blonder–Tinkham–Klapwijk formalism we have found that the subgap conductance peaks are shifted to a nonzero bias by RSOC at the interface which are the same as Ref. [1]. It is shown that for low insulating barrier and in the absence of the interface RSOC, the tunneling conductance decreases within energy gap with increasing of the RSOC in the normal layer while for high insulating barrier it enhances by increase of the RSOC. We have also shown that the RSOC inside the normal cannot affect the location of the subgap conductance peaks shifted by the interface RSOC.

  6. Design strategy of two-dimensional material field-effect transistors: Engineering the number of layers in phosphorene FETs

    Science.gov (United States)

    Yin, Demin; Yoon, Youngki

    2016-06-01

    Thickness or the number of layers in 2D semiconductors is a key parameter to determine the material's electronic properties and the overall device performance of 2D material electronics. Here, we discuss the engineering practice of optimizing material and device parameters of phosphorene field-effect transistors (FETs) by means of self-consistent atomistic quantum transport simulations, where the impacts of different numbers of phosphorene layers on various device characteristics are explored in particular, considering two specific target applications of high-performance and low-power devices. Our results suggest that, for high-performance applications, monolayer phosphorene should be utilized in a conventional FET structure since it can provide the equally large on current as other multilayer phosphorenes (Ion > 1 mA/μm) without showing a penalty of relatively lower density of states, along with favorableness for steep switching and large immunity to gate-induced drain leakage. On the other hand, more comprehensive approach is required for low-power applications, where operating voltage, doping concentration, and channel length should be carefully engineered along with the thickness of phosphorene in tunnel FET (TFET) structure to achieve ultra-low leakage current without sacrificing on current significantly. Our extensive simulation results revealed that either bilayer or trilayer phosphorene can provide the best performance in TFET with the maximum Ion/Ioff of ˜2 × 1011 and the subthreshold swing as low as 13 mV/dec. In addition, our comparative study of phosphorene-based conventional FET and TFET clearly shows the feasibility and the limitation of each device for different target applications, providing irreplaceable insights into the design strategy of phosphorene FETs that can be also extended to other similar layered material electronic devices.

  7. Instrument platforms for thin-layer chromatography.

    Science.gov (United States)

    Bernard-Savary, Pierre; Poole, Colin F

    2015-11-20

    High performance column and thin-layer chromatography are both instrumental techniques but differ in that column chromatography requires a fully integrated instrument platform with high pressure capability while for thin-layer chromatography separate devices are used for each unit operation, usually at or close to atmospheric pressure, and afford higher flexibility supporting on-line or off-line operation. The unit operations of thin-layer chromatography are defined as sample application, development and evaluation with derivatization as an optional step. The diversity of equipment for each operation contributes to the flexibility of analysis by thin-layer chromatography and supports manual, semi-automated or full-automation of the separation process. Instrument platforms are more than a convenience as they affect performance, repeatability, sample detectability, and time management. The current trend in thin-layer chromatography is to make the unit operations independent of the user so that analysts can perform other tasks while each step is performed. In addition, in thin-layer chromatography it is general practice to separate several samples simultaneously, and instrument platforms are required to accommodate this feature. In this article, we review contemporary instrumentation employed in thin-layer chromatography for sample application, development, derivatization, photodocumentation, densitometric evaluation, and hyphenation with spectroscopic detectors with an emphasis on the variety and performance of commercially available systems. Some suggestions for best practices and avoidance of common mistakes are included. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Separation of Gases Using Ultra-Thin Porous Layers of Monodisperse Nanoparticles

    Directory of Open Access Journals (Sweden)

    Bubenchikov Mikhail A

    2016-01-01

    Full Text Available The present paper deals with a numerical solution of the two-dimensional problem of helium and methane molecules motion through an ultra-thin layer of a porous material composed of spherical nanoparticles of the same size. The interaction potential “nanoparticle-molecule” is obtained by integrating paired molecular interactions over the nanoparticle volume. Using the method of classical molecular dynamics, permeability of a layer having the size of about 10−8 m is studied.

  9. Three-dimensional structural damage localization system and method using layered two-dimensional array of capacitance sensors

    Science.gov (United States)

    Curry, Mark A (Inventor); Senibi, Simon D (Inventor); Banks, David L (Inventor)

    2010-01-01

    A system and method for detecting damage to a structure is provided. The system includes a voltage source and at least one capacitor formed as a layer within the structure and responsive to the voltage source. The system also includes at least one sensor responsive to the capacitor to sense a voltage of the capacitor. A controller responsive to the sensor determines if damage to the structure has occurred based on the variance of the voltage of the capacitor from a known reference value. A method for sensing damage to a structure involves providing a plurality of capacitors and a controller, and coupling the capacitors to at least one surface of the structure. A voltage of the capacitors is sensed using the controller, and the controller calculates a change in the voltage of the capacitors. The method can include signaling a display system if a change in the voltage occurs.

  10. Two-dimensional inorganic–organic hybrid semiconductors composed of double-layered ZnS and monoamines with aromatic and heterocyclic aliphatic rings: Syntheses, structures, and properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Sujing; Li, Jing, E-mail: jingli@rutgers.edu

    2015-04-15

    As an addition to the II–VI based inorganic–organic hybrid semiconductor family, five new two-dimensional (2D) double-layered structures have been synthesized employing monoamines with different aromatic or heterocyclic aliphatic rings. Zn{sub 2}S{sub 2}(bza) (1), Zn{sub 2}S{sub 2}(mbza) (2), Zn{sub 2}S{sub 2}(fbza) (3), Zn{sub 2}S{sub 2}(pca) (4), and Zn{sub 2}S{sub 2}(thfa) (5) (bza=benzylamine, mbza=4-methoxybenzylamine, fbza=4-flurobenzylamine, pca=3-picolylamine, and thfa=tetrahydrofurfurylamine) are prepared by solvothermal reactions and characterized by different analytical methods, including powder X-ray diffraction, optical diffuse reflection, thermogravimetric analysis and photoluminescence spectroscopy. The powder X-ray diffraction patterns show that all five compounds adopt 2D double-layered structures. Optical diffuse reflectance spectra of these compounds suggest that they have notably lower band gaps than those of the similar compounds composed of aliphatic alkyl amines. Their photoluminescence properties and thermal stability are also analyzed. - Graphical abstract: Five new members of two-dimensional double-layered 2D-Zn{sub 2}S{sub 2}(L) (L=Ligand) structures employing monoamines with different aromatic or heterocyclic aliphatic rings have been designed, synthesized, and characterized. - Highlights: • A new sub-family of II-VI based hybrid semiconductors are designed, synthesized, and structurally characterized using amines with aromatic or aliphatic cyclic rings. • These compounds have notably lower band gaps than those made of aliphatic alkyl amines, greatly broadening the range of band gaps of this material family. • They emit strongly with systematically tunable emission intensity and energy.

  11. A two-dimensional iterative panel method and boundary layer model for bio-inspired multi-body wings

    Science.gov (United States)

    Blower, Christopher J.; Dhruv, Akash; Wickenheiser, Adam M.

    2014-03-01

    The increased use of Unmanned Aerial Vehicles (UAVs) has created a continuous demand for improved flight capabilities and range of use. During the last decade, engineers have turned to bio-inspiration for new and innovative flow control methods for gust alleviation, maneuverability, and stability improvement using morphing aircraft wings. The bio-inspired wing design considered in this study mimics the flow manipulation techniques performed by birds to extend the operating envelope of UAVs through the installation of an array of feather-like panels across the airfoil's upper and lower surfaces while replacing the trailing edge flap. Each flap has the ability to deflect into both the airfoil and the inbound airflow using hinge points with a single degree-of-freedom, situated at 20%, 40%, 60% and 80% of the chord. The installation of the surface flaps offers configurations that enable advantageous maneuvers while alleviating gust disturbances. Due to the number of possible permutations available for the flap configurations, an iterative constant-strength doublet/source panel method has been developed with an integrated boundary layer model to calculate the pressure distribution and viscous drag over the wing's surface. As a result, the lift, drag and moment coefficients for each airfoil configuration can be calculated. The flight coefficients of this numerical method are validated using experimental data from a low speed suction wind tunnel operating at a Reynolds Number 300,000. This method enables the aerodynamic assessment of a morphing wing profile to be performed accurately and efficiently in comparison to Computational Fluid Dynamics methods and experiments as discussed herein.

  12. Redox Active Cation Intercalation/Deintercalation in Two-Dimensional Layered MnO2 Nanostructures for High-Rate Electrochemical Energy Storage.

    Science.gov (United States)

    Xiong, Pan; Ma, Renzhi; Sakai, Nobuyuki; Bai, Xueyin; Li, Shen; Sasaki, Takayoshi

    2017-02-22

    Two-dimensional (2D) layered materials with a high intercalation pseudocapacitance have long been investigated for Li(+)-ion-based electrochemical energy storage. By contrast, the exploration of guest ions other than Li(+) has been limited, although promising. The present study investigates intercalation/deintercalation behaviors of various metal ions in 2D layered MnO2 with various interlayer distances, K-birnessite nanobelt (K-MnO2), its protonated form (H-MnO2), and a freeze-dried sample of exfoliated nanosheets. Series of metal ions, such as monovalent Li(+), Na(+), and K(+) and divalent Mg(2+), exhibit reversible intercalation during charge/discharge cycling, delivering high-rate pseudocapacitances. In particular, the freeze-dried MnO2 of exfoliated nanosheets restacked with the largest interlayer spacing and a less compact 3D network exhibits the best rate capability and a stable cyclability over 5000 cycles. Both theoretical calculation and kinetic analysis reveal that the increased interlayer distance facilitates the fast diffusion of cations in layered MnO2 hosts. The results presented herein provide a basis for the controllable synthesis of layered nanostructures for high-rate electrochemical energy storage using various single- and multivalent ions.

  13. Christhin: Quantitative Analysis of Thin Layer Chromatography

    CERN Document Server

    Barchiesi, Maximiliano; Renaudo, Carlos; Rossi, Pablo; Pramparo, María de Carmen; Nepote, Valeria; Grosso, Nelson Ruben; Gayol, María Fernanda

    2012-01-01

    Manual for Christhin 0.1.36 Christhin (Chromatography Riser Thin) is software developed for the quantitative analysis of data obtained from thin-layer chromatographic techniques (TLC). Once installed on your computer, the program is very easy to use, and provides data quickly and accurately. This manual describes the program, and reading should be enough to use it properly.

  14. Delamination of Compressed Thin Layers at Corners

    DEFF Research Database (Denmark)

    Sørensen, Kim Dalsten; Jensen, Henrik Myhre; Clausen, Johan

    2008-01-01

    An analysis of delamination for a thin elastic layer under compression, attached to a substrate at a corner is carried out. The analysis is performed by combining results from interface fracture mechanics and the theory of thin shells. In contrast with earlier results for delamination on a flat...

  15. Two-dimensional percolation transition at finite temperature: Phase boundary for in-plane magnetism in films with two atomic layers of Fe on W(110)

    Science.gov (United States)

    Belanger, R.; Venus, D.

    2017-02-01

    A two-dimensional (2D) percolation transition in Fe/W(110) ultrathin magnetic films occurs when islands in the second atomic layer percolate and resolve a frustrated magnetic state to produce long-range in-plane ferromagnetic order. Novel measurements of percolation using the magnetic susceptibility χ (θ ) as the films are deposited at a constant temperature, allow the long-range percolation transition to be observed as a sharp peak consistent with a critical phase transition. The measurements are used to trace the paramagnetic-to-ferromagnetic phase boundary between the T =0 percolation magnetic transition and the thermal Curie magnetic transition of the undiluted film. A quantitative comparison to critical scaling theory is made by fitting the functional form of the phase boundary. The fitted parameters are then used in theoretical expressions for χ (T ) in the critical region of the paramagnetic state to provide an excellent, independent representation of the experimental measurements.

  16. Proton transfer through hydrogen bonds in two-dimensional water layers: A theoretical study based on ab initio and quantum-classical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Bankura, Arindam; Chandra, Amalendu, E-mail: amalen@iitk.ac.in [Department of Chemistry, Indian Institute of Technology, Kanpur 208016 (India)

    2015-01-28

    The dynamics of proton transfer (PT) through hydrogen bonds in a two-dimensional water layer confined between two graphene sheets at room temperature are investigated through ab initio and quantum-classical simulations. The excess proton is found to be mostly solvated as an Eigen cation where the hydronium ion donates three hydrogen bonds to the neighboring water molecules. In the solvation shell of the hydronium ion, the three coordinated water molecules with two donor hydrogen bonds are found to be properly presolvated to accept a proton. Although no hydrogen bond needs to be broken for transfer of a proton to such presolvated water molecules from the hydronium ion, the PT rate is still found to be not as fast as it is for one-dimensional chains. Here, the PT is slowed down as the probability of finding a water with two donor hydrogen bonds in the solvation shell of the hydronium ion is found to be only 25%-30%. The hydroxide ion is found to be solvated mainly as a complex anion where it accepts four H-bonds through its oxygen atom and the hydrogen atom of the hydroxide ion remains free all the time. Here, the presolvation of the hydroxide ion to accept a proton requires that one of its hydrogen bonds is broken and the proton comes from a neighboring water molecule with two acceptor and one donor hydrogen bonds. The coordination number reduction by breaking of a hydrogen bond is a slow process, and also the population of water molecules with two acceptor and one donor hydrogen bonds is only 20%-25% of the total number of water molecules. All these factors together tend to slow down the hydroxide ion migration rate in two-dimensional water layers compared to that in three-dimensional bulk water.

  17. Proton transfer through hydrogen bonds in two-dimensional water layers: A theoretical study based on ab initio and quantum-classical simulations

    Science.gov (United States)

    Bankura, Arindam; Chandra, Amalendu

    2015-01-01

    The dynamics of proton transfer (PT) through hydrogen bonds in a two-dimensional water layer confined between two graphene sheets at room temperature are investigated through ab initio and quantum-classical simulations. The excess proton is found to be mostly solvated as an Eigen cation where the hydronium ion donates three hydrogen bonds to the neighboring water molecules. In the solvation shell of the hydronium ion, the three coordinated water molecules with two donor hydrogen bonds are found to be properly presolvated to accept a proton. Although no hydrogen bond needs to be broken for transfer of a proton to such presolvated water molecules from the hydronium ion, the PT rate is still found to be not as fast as it is for one-dimensional chains. Here, the PT is slowed down as the probability of finding a water with two donor hydrogen bonds in the solvation shell of the hydronium ion is found to be only 25%-30%. The hydroxide ion is found to be solvated mainly as a complex anion where it accepts four H-bonds through its oxygen atom and the hydrogen atom of the hydroxide ion remains free all the time. Here, the presolvation of the hydroxide ion to accept a proton requires that one of its hydrogen bonds is broken and the proton comes from a neighboring water molecule with two acceptor and one donor hydrogen bonds. The coordination number reduction by breaking of a hydrogen bond is a slow process, and also the population of water molecules with two acceptor and one donor hydrogen bonds is only 20%-25% of the total number of water molecules. All these factors together tend to slow down the hydroxide ion migration rate in two-dimensional water layers compared to that in three-dimensional bulk water.

  18. Two-dimensional hybrid layered materials: strain engineering on the band structure of MoS2/WSe2 hetero-multilayers

    Science.gov (United States)

    Gu, Kunming; Yu, Sheng; Eshun, Kwesi; Yuan, Haiwen; Ye, Huixian; Tang, Jiaoning; Ioannou, Dimitris E.; Xiao, Changshi; Wang, Hui; Li, Qiliang

    2017-09-01

    In this paper, we report a comprehensive modeling and simulation study of constructing hybrid layered materials by alternately stacking MoS2 and WSe2 monolayers. Such hybrid MoS2/WSe2 hetero-multilayers exhibited direct bandgap semiconductor characteristics with bandgap energy (E g) in a range of 0.45-0.55 eV at room temperature, very attractive for optoelectronics (wavelength range 2.5-2.75 μm) based on thicker two-dimensional (2D) materials. It was also found that the interlayer distance has a significant impact on the electronic properties of the hetero-multilayers, for example a five orders of magnitude change in the conductance was observed. Three material phases, direct bandgap semiconductor, indirect bandgap semiconductor, and metal were observed in MoS2/WSe2 hetero-multilayers, as the interlayer distance decreased from its relaxed (i.e., equilibrium) value of about 6.73 Å down to 5.50 Å, representing a vertical pressure of about 0.8 GPa for the bilayer and 1.5 GPa for the trilayer. Such new hybrid layered materials are very interesting for future nanoelectronic pressure sensor and nanophotonic applications. This study describes a new approach to explore and engineer the construction and application of tunable 2D semiconductors.

  19. H-T phase diagram and the nature of vortex-glass phase in a quasi-two-dimensional superconductor: Sn-metal layer sandwiched between graphene sheets

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Masatsugu; Suzuki, Itsuko S.; Walter, Juergen

    2004-02-15

    The magnetic properties of a quasi-two-dimensional (2D) superconductor, Sn-metal graphite (MG), are studied using DC and AC magnetic susceptibility. Sn-MG has a unique layered structure where Sn metal layer is sandwiched between adjacent graphene sheets. This compound undergoes a superconducting transition at T{sub c}=3.75 K at H=0. The H-T diagram of Sn-MG is similar to that of a quasi-2D superconductors. The phase boundaries of vortex liquid, vortex glass, and vortex lattice phase merge into a multicritical point located at T*=3.4 K and H*=40 Oe. There are two irreversibility lines denoted by H{sub gl} (de Almeida-Thouless type) and H{sub gl{sup '}} (Gabay-Toulouse type), intersecting at T{sub 0}{sup '}=2.5 K and H{sub 0}{sup '}=160 Oe. The nature of slow dynamic and nonlinearity of the vortex glass phase is studied.

  20. Screw-dislocation-driven growth of two-dimensional few-layer and pyramid-like WSe₂ by sulfur-assisted chemical vapor deposition.

    Science.gov (United States)

    Chen, Liang; Liu, Bilu; Abbas, Ahmad N; Ma, Yuqiang; Fang, Xin; Liu, Yihang; Zhou, Chongwu

    2014-11-25

    Two-dimensional (2D) layered tungsten diselenides (WSe2) material has recently drawn a lot of attention due to its unique optoelectronic properties and ambipolar transport behavior. However, direct chemical vapor deposition (CVD) synthesis of 2D WSe2 is not as straightforward as other 2D materials due to the low reactivity between reactants in WSe2 synthesis. In addition, the growth mechanism of WSe2 in such CVD process remains unclear. Here we report the observation of a screw-dislocation-driven (SDD) spiral growth of 2D WSe2 flakes and pyramid-like structures using a sulfur-assisted CVD method. Few-layer and pyramid-like WSe2 flakes instead of monolayer were synthesized by introducing a small amount of sulfur as a reducer to help the selenization of WO3, which is the precursor of tungsten. Clear observations of steps, helical fringes, and herringbone contours under atomic force microscope characterization reveal the existence of screw dislocations in the as-grown WSe2. The generation and propagation mechanisms of screw dislocations during the growth of WSe2 were discussed. Back-gated field-effect transistors were made on these 2D WSe2 materials, which show on/off current ratios of 10(6) and mobility up to 44 cm(2)/(V·s).

  1. Layer-by-layer thinning of MoSe2 by soft and reactive plasma etching

    Science.gov (United States)

    Sha, Yunfei; Xiao, Shaoqing; Zhang, Xiumei; Qin, Fang; Gu, Xiaofeng

    2017-07-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) like molybdenum diselenide (MoSe2) have recently gained considerable interest since their properties are complementary to those of graphene. Unlike gapless graphene, the band structure of MoSe2 can be changed from the indirect band gap to the direct band gap when MoSe2 changed from bulk material to monolayer. This transition from multilayer to monolayer requires atomic-layer-precision thining of thick MoSe2 layers without damaging the remaining layers. Here, we present atomic-layer-precision thinning of MoSe2 nanaosheets down to monolayer by using SF6 + N2 plasmas, which has been demonstrated to be soft, selective and high-throughput. Optical microscopy, atomic force microscopy, Raman and photoluminescence spectra suggest that equal numbers of MoSe2 layers can be removed uniformly regardless of their initial thickness, without affecting the underlying SiO2 substrate and the remaining MoSe2 layers. By adjusting the etching rates we can achieve complete MoSe2 removal and any disired number of MoSe2 layers including monolayer. This soft plasma etching method is highly reliable and compatible with the semiconductor manufacturing processes, thereby holding great promise for various 2D materials and TMD-based devices.

  2. Universal Strategy to Fabricate a Two-Dimensional Layered Mesoporous Mo2C Electrocatalyst Hybridized on Graphene Sheets with High Activity and Durability for Hydrogen Generation.

    Science.gov (United States)

    Huo, Lili; Liu, Baocang; Zhang, Geng; Zhang, Jun

    2016-07-20

    A universal strategy was developed for fabrication of a highly active and durable precious-metal-free mesoporous Mo2C/graphene (m-Mo2C/G) electrocatalyst with a two-dimensional layered structural feature via a nanocasting method using glucose as a carbon source and an in-stiu assembled mesoporous KIT-6/graphene (KIT-6/G) as a template. The m-Mo2C/G catalyst exhibits high catalytic activity and excellent durability for hydrogen evolution reaction (HER) over a wide pH range, which displays a small onset potential of 8 mV, owerpotential (η10) for driving a cathodic current density of 10 mA·cm(-2) of 135 mV, a Tafel slope of 58 mV·dec(-1), and an exchange current density of 6.31 × 10(-2) mA·cm(-2) in acidic media and an onset potential of of 41 mV, η10 of 128 mV, Tafel slope of 56 mV·dec(-1), and an exchange current density of 4.09 × 10(-2) mA·cm(-2) in alkaline media, respectively. Furthermore, such an m-Mo2C/G electrocatalyst also gives about 100% Faradaic yield and shows excellent durability during 3000 cycles of a long-term test, and the catalytic current remains stable over 20 h at fixed overpotentials, making it a great potential application prospect for energy issues.

  3. Perovskite Thin Films via Atomic Layer Deposition

    KAUST Repository

    Sutherland, Brandon R.

    2014-10-30

    © 2014 Wiley-VCH Verlag GmbH & Co. KGaA. (Graph Presented) A new method to deposit perovskite thin films that benefit from the thickness control and conformality of atomic layer deposition (ALD) is detailed. A seed layer of ALD PbS is place-exchanged with PbI2 and subsequently CH3NH3PbI3 perovskite. These films show promising optical properties, with gain coefficients of 3200 ± 830 cm-1.

  4. Perovskite thin films via atomic layer deposition.

    Science.gov (United States)

    Sutherland, Brandon R; Hoogland, Sjoerd; Adachi, Michael M; Kanjanaboos, Pongsakorn; Wong, Chris T O; McDowell, Jeffrey J; Xu, Jixian; Voznyy, Oleksandr; Ning, Zhijun; Houtepen, Arjan J; Sargent, Edward H

    2015-01-01

    A new method to deposit perovskite thin films that benefit from the thickness control and conformality of atomic layer deposition (ALD) is detailed. A seed layer of ALD PbS is place-exchanged with PbI2 and subsequently CH3 NH3 PbI3 perovskite. These films show promising optical properties, with gain coefficients of 3200 ± 830 cm(-1) .

  5. Thin-Layer Solutions of the Helmholtz and Related Equations

    KAUST Repository

    Ockendon, J. R.

    2012-01-01

    This paper concerns a certain class of two-dimensional solutions to four generic partial differential equations-the Helmholtz, modified Helmholtz, and convection-diffusion equations, and the heat conduction equation in the frequency domain-and the connections between these equations for this particular class of solutions.S pecifically, we consider thin-layer solutions, valid in narrow regions across which there is rapid variation, in the singularly perturbed limit as the coefficient of the Laplacian tends to zero.F or the wellstudied Helmholtz equation, this is the high-frequency limit and the solutions in question underpin the conventional ray theory/WKB approach in that they provide descriptions valid in some of the regions where these classical techniques fail.E xamples are caustics, shadow boundaries, whispering gallery, and creeping waves and focusing and bouncing ball modes.It transpires that virtually all such thin-layer models reduce to a class of generalized parabolic wave equations, of which the heat conduction equation is a special case. Moreover, in most situations, we will find that the appropriate parabolic wave equation solutions can be derived as limits of exact solutions of the Helmholtz equation.W e also show how reasonably well-understood thin-layer phenomena associated with any one of the four generic equations may translate into less well-known effects associated with the others.In addition, our considerations also shed some light on the relationship between the methods of matched asymptotic, WKB, and multiple-scales expansions. © 2012 Society for Industrial and Applied Mathematics.

  6. Modulated two-dimensional charge-carrier density in LaTiO3-layer-doped LaAlO3/SrTiO3 heterostructure.

    Science.gov (United States)

    Nazir, Safdar; Bernal, Camille; Yang, Kesong

    2015-03-11

    The highly mobile two-dimensional electron gas (2DEG) formed at the polar/nonpolar LaAlO3/SrTiO3 (LAO/STO) heterostructure (HS) is a matter of great interest because of its potential applications in nanoscale solid-state devices. To realize practical implementation of the 2DEG in device design, desired physical properties such as tuned charge carrier density and mobility are necessary. In this regard, polar perovskite-based transition metal oxides can act as doping layers at the interface and are expected to tune the electronic properties of 2DEG of STO-based HS systems dramatically. Herein, we investigated the doping effects of LaTiO3(LTO) layers on the electronic properties of 2DEG at n-type (LaO)(+1)/(TiO2)(0) interface in the LAO/STO HS using spin-polarized density functional theory calculations. Our results indicate an enhancement of orbital occupation near the Fermi energy, which increases with respect to the number of LTO unit cells, resulting in a higher charge carrier density of 2DEG than that of undoped system. The enhanced charge carrier density is attributed to an extra electron introduced by the Ti 3d(1) orbitals from the LTO dopant unit cells. This conclusion is consistent with the recent experimental findings (Appl. Phys. Lett. 2013, 102, 091601). Detailed charge density and partial density of states analysis suggests that the 2DEG in the LTO-doped HS systems primarily comes from partially occupied dyz and dxz orbitals.

  7. Rationally synthesized two-dimensional polymers.

    Science.gov (United States)

    Colson, John W; Dichtel, William R

    2013-06-01

    Synthetic polymers exhibit diverse and useful properties and influence most aspects of modern life. Many polymerization methods provide linear or branched macromolecules, frequently with outstanding functional-group tolerance and molecular weight control. In contrast, extending polymerization strategies to two-dimensional periodic structures is in its infancy, and successful examples have emerged only recently through molecular framework, surface science and crystal engineering approaches. In this Review, we describe successful 2D polymerization strategies, as well as seminal research that inspired their development. These methods include the synthesis of 2D covalent organic frameworks as layered crystals and thin films, surface-mediated polymerization of polyfunctional monomers, and solid-state topochemical polymerizations. Early application targets of 2D polymers include gas separation and storage, optoelectronic devices and membranes, each of which might benefit from predictable long-range molecular organization inherent to this macromolecular architecture.

  8. Thin Layer Chromatography (TLC) of Chlorophyll Pigments.

    Science.gov (United States)

    Foote, Jerry

    1984-01-01

    Background information, list of materials needed, procedures used, and discussion of typical results are provided for an experiment on the thin layer chromatography of chlorophyll pigments. The experiment works well in high school, since the chemicals used are the same as those used in paper chromatography of plant pigments. (JN)

  9. Carbon nanofiber growth on thin rhodium layers

    NARCIS (Netherlands)

    Chinthaginjala, J.K.; Unnikrishnan, S.; Smithers, M.A.; Kip, G.A.M.; Lefferts, L.

    2012-01-01

    A thinlayer of carbon nanofibers (CNFs) was synthesized on a thin polycrystalline rhodium (Rh) metal layer by decomposing ethylene in the presence of hydrogen. Interaction of Rh crystals with carbon results in fragmentation and formation of Rh-nanoparticles, facilitating CNF growth. CNFs are immobil

  10. Thin Layer Chromatography (TLC) of Chlorophyll Pigments.

    Science.gov (United States)

    Foote, Jerry

    1984-01-01

    Background information, list of materials needed, procedures used, and discussion of typical results are provided for an experiment on the thin layer chromatography of chlorophyll pigments. The experiment works well in high school, since the chemicals used are the same as those used in paper chromatography of plant pigments. (JN)

  11. Diverse effects of two-dimensional and step flow growth mode induced microstructures on the magnetic anisotropies of SrRuO[subscript3] thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Y.Z.; Chmaissem, O.; Kolesnik, S.; Ullah, A.; Lurio, L.B.; Brown, D.E.; Brady, J.; Dabrowski, B.; Kimball, C.W.; Haji-Sheikh, M.; Genis, A.P. (NIU)

    2010-12-03

    Geometrical anisotropy axes of diverse SrRuO{sub 3} (SRO) films grown by random and directional two-dimensional and step flow modes are determined and their characteristic angular magnetizations are understood in terms of growth mode induced structural effects. Two-dimensional SRO films possess single-crystal-like structural qualities. Angular magnetization measurements show sharp minima and indicate the films easy axis to be in the [310] direction. In contrast, examination of step flow SRO films shows the presence of degenerate multiple in-plane domains and the anisotropy axis in a direction close to [110] even though directional surface steps are clearly visible.

  12. Subsurface Raman analysis of thin painted layers.

    Science.gov (United States)

    Conti, Claudia; Colombo, Chiara; Realini, Marco; Zerbi, Giuseppe; Matousek, Pavel

    2014-01-01

    Here we present, for the first time, an extension of spatially offset Raman spectroscopy to thin (tens of micrometers thick), highly turbid stratified media such as those encountered in paintings. The method permits the non-destructive interrogation of painted layers in situations where conventional Raman microscopy is not applicable due to high turbidity of the top layer(s). The concept is demonstrated by recovering the pure Raman spectra of paint sub-layers that are completely obscured by paint over-layers. Potential application areas include the analysis of paintings in art preservation and restoration avoiding the cross-sectional analysis used currently with this type of samples. The technique also holds promise for the development as a non-destructive subsurface tool for in situ analysis using portable instruments.

  13. An Electrochemical Experiment Using an Optically Transparent Thin Layer Electrode

    Science.gov (United States)

    DeAngelis, Thomas P.; Heineman, William R.

    1976-01-01

    Describes a unified experiment in which an optically transparent thin layer electrode is used to illustrate the techniques of thin layer electrochemistry, cyclic voltammetry, controlled potential coulometry, and spectroelectrochemistry. (MLH)

  14. Silver buffer layers for YBCO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, J. [Tel Aviv Univ. (Israel). Center for Technol. Education Holon

    1999-09-01

    A simple economical conventional vacuum system was used for evaporation of YBCO thin films on as-deposited unbuffered Ag layers on MgO substrates. The subsequent heat treatment was carried out in low oxygen partial pressure at a relative low temperature and short dwelling time. The films thus obtained were characterized for electrical properties using dc four probe electrical measurements and inspected for structural properties and chemical composition by scanning electron microscopy (SEM). (orig.)

  15. Note: Automatic layer-by-layer spraying system for functional thin film coatings

    Science.gov (United States)

    Seo, Seongmin; Lee, Sangmin; Park, Yong Tae

    2016-03-01

    In this study, we have constructed an automatic spray machine for producing polyelectrolyte multilayer films containing various functional materials on wide substrates via the layer-by-layer (LbL) assembly technique. The proposed machine exhibits advantages in terms of automation, process speed, and versatility. Furthermore, it has several features that allow a fully automated spraying operation, such as various two-dimensional spraying paths, control of the flow rate and operating speed, air-assist fan-shaped twin-fluid nozzles, and an optical display. The robot uniformly sprays aqueous mixtures containing complementary (e.g., oppositely charged, capable of hydrogen bonding, or capable of covalent bonding) species onto a large-area substrate. Between each deposition of opposite species, samples are spray-rinsed with deionized water and blow-dried with air. The spraying, rinsing, and drying areas and times are adjustable by a computer program. Twenty-bilayer flame-retardant thin films were prepared in order to compare the performance of the spray-assisted LbL assembly with a sample produced by conventional dipping. The spray-coated film exhibited a reduction of afterglow time in vertical flame tests, indicating that the spray-LbL technique is a simple method to produce functional thin film coatings.

  16. Method of transferring a thin crystalline semiconductor layer

    Science.gov (United States)

    Nastasi, Michael A.; Shao, Lin; Theodore, N. David

    2006-12-26

    A method for transferring a thin semiconductor layer from one substrate to another substrate involves depositing a thin epitaxial monocrystalline semiconductor layer on a substrate having surface contaminants. An interface that includes the contaminants is formed in between the deposited layer and the substrate. Hydrogen atoms are introduced into the structure and allowed to diffuse to the interface. Afterward, the thin semiconductor layer is bonded to a second substrate and the thin layer is separated away at the interface, which results in transferring the thin epitaxial semiconductor layer from one substrate to the other substrate.

  17. Thickness gauging of thin layers by laser ultrasonics and neural network

    Energy Technology Data Exchange (ETDEWEB)

    Lefevre, F; Jenot, F; Ouaftouh, M; Duquennoy, M; Ourak, M, E-mail: Fabien.lefevre@univ-valenciennes.fr [Institut d' Electronique de Microelectronique et de Nanotechnologie Departement Opto-Acousto-Electronique (UMR CNRS 8520), Universite de Valenciennes, Le Mont Houy, 59313 Valenciennes Cedex 09 (France)

    2011-01-01

    Non destructive testing has been performed on a thin indium layer deposited on a two inches silicon wafer. Guided waves were generated and studied using a laser ultrasonic setup, and a two-dimensional Fourier transform technique was employed to obtain the dispersion curves. The inverse problem, in other words the determination of the layer thickness and the elastic constants of the substrate, has been solved by means of a feedforward neural network. These parameters were then evaluated simultaneously, the dispersion curves being entirely fitted. The experimental results show a good agreement with the theoretical model. This inversion method was found to be prompt and easy to automate.

  18. Two-dimensional calculus

    CERN Document Server

    Osserman, Robert

    2011-01-01

    The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o

  19. Two dimensional vernier

    Science.gov (United States)

    Juday, Richard D. (Inventor)

    1992-01-01

    A two-dimensional vernier scale is disclosed utilizing a cartesian grid on one plate member with a polar grid on an overlying transparent plate member. The polar grid has multiple concentric circles at a fractional spacing of the spacing of the cartesian grid lines. By locating the center of the polar grid on a location on the cartesian grid, interpolation can be made of both the X and Y fractional relationship to the cartesian grid by noting which circles coincide with a cartesian grid line for the X and Y direction.

  20. Metallic ground state in an ion-gated two-dimensional superconductor

    NARCIS (Netherlands)

    Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu

    2015-01-01

    Recently emerging two-dimensional (2D) superconductors in atomically thin layers and at heterogeneous interfaces are attracting growing interest in condensed matter physics. Here, we report that an ion-gated zirconium nitride chloride surface, exhibiting a dome-shaped phase diagram with a maximum cr

  1. Energy spectrum and specific heat of two-dimensional electron systems with spin-orbit interaction in a magnetic field parallel to the conducting layer

    Science.gov (United States)

    Shevchenko, O. S.; Kopeliovich, A. I.

    2016-03-01

    The energy spectrum of a quasi-two-dimensional electron gas in an in-plane magnetic field is studied using the perturbation theory and quasiclassical approach in the presence of the Rashba and Dresselhaus spin-orbit coupling. The existence of the intersection of energy sublevels in electron spectrum is demonstrated. The reciprocal mass tensor of electrons is analyzed. The heat capacity of the degenerate electron gas is examined, and its relations with the key features of the spectrum are shown.

  2. Thermal analysis of thin layer boilover

    Energy Technology Data Exchange (ETDEWEB)

    Kozanoglu, Bulent [Universidad de las Americas, Puebla (Mexico); Mechanical Engineering Department, Cholula, Puebla (Mexico); Ferrero, Fabio; Munoz, Miguel; Arnaldos, Josep; Casal, Joaquim [Universitat Politecnica de Catalunya, Barcelona (Spain)

    2008-10-15

    A mathematical model is developed to simulate the thin layer boilover phenomenon. This model takes into account convective currents as well as conduction and radiation absorption through the fuel layer and is resolved numerically employing a scheme of Runge-Kutta, combined with the numerical method of lines. Solutions of the model showed a good agreement with the experimental data, both from this work and by other authors, demonstrating the importance of the convective currents. The model provided velocities of these currents, of the same order of magnitude as the values reported in the technical literature. Thickness of the remaining fuel and the interface temperature are correctly calculated by the model, allowing the prediction of the time required for the boilover to start. (orig.)

  3. Two-dimensional optical spectroscopy

    CERN Document Server

    Cho, Minhaeng

    2009-01-01

    Discusses the principles and applications of two-dimensional vibrational and optical spectroscopy techniques. This book provides an account of basic theory required for an understanding of two-dimensional vibrational and electronic spectroscopy.

  4. RF screening by thin resistive layers

    CERN Document Server

    Caspers, Friedhelm; González, C; Jensen, E; Keil, Eberhard; Morvillo, M; Ruggiero, F; Schröder, G; Zotter, Bruno W; Dyachkov, M

    1999-01-01

    We discuss the results of recent impedance measurements for an LHC dump kicker prototype, performed at CERN using the coaxial wire method. The kicker design includes a vacuum barrier consisting of a ceramic chamber internally coated with a thin metallic layer having good electric contact with the external beam pipe. For the bench test the coated ceramic tube was replaced by a kapton foil with a 0.2 \\mu\\m copper layer having the same DC resistance of 0.7 Ømega\\m. The measurements show that this resistive coating provides a very effective RF screening down to frequencies below 1 MHz, where the skin depth is two orders of magnitude larger than the layer thickness and one could expect full penetration of the electromagnetic fields. We also present simulation results and analytic considerations in agreement with the measurements, showing that the return currents almost entirely flow through the copper layer down to frequencies where the reactive impedance of the kicker elements located behind it becomes comparabl...

  5. Limits on the validity of the thin-layer model of the ionosphere for radio interferometric calibration

    CERN Document Server

    Martin, Poppy L; Scaife, Anna M M

    2016-01-01

    For a ground-based radio interferometer observing at low frequencies, the ionosphere causes propagation delays and refraction of cosmic radio waves which result in phase errors in the received signal. These phase errors can be corrected using a calibration method that assumes a two-dimensional phase screen at a fixed altitude above the surface of the Earth, known as the thin-layer model. Here we investigate the validity of the thin-layer model and provide a simple equation with which users can check when this approximation can be applied to observations for varying time of day, zenith angle, interferometer latitude, baseline length, ionospheric electron content and observing frequency.

  6. Limits on the validity of the thin-layer model of the ionosphere for radio interferometric calibration

    Science.gov (United States)

    Martin, Poppy L.; Bray, Justin D.; Scaife, Anna M. M.

    2016-07-01

    For a ground-based radio interferometer observing at low frequencies, the ionosphere causes propagation delays and refraction of cosmic radio waves which result in phase errors in the received signal. These phase errors can be corrected using a calibration method that assumes a two-dimensional phase screen at a fixed altitude above the surface of the Earth, known as the thin-layer model. Here, we investigate the validity of the thin-layer model and provide a simple equation with which users can check when this approximation can be applied to observations for varying time of day, zenith angle, interferometer latitude, baseline length, ionospheric electron content and observing frequency.

  7. Fullerenes as adhesive layers for mechanical peeling of metallic, molecular and polymer thin films.

    Science.gov (United States)

    Wieland, Maria B; Slater, Anna G; Mangham, Barry; Champness, Neil R; Beton, Peter H

    2014-01-01

    We show that thin films of C60 with a thickness ranging from 10 to 100 nm can promote adhesion between a Au thin film deposited on mica and a solution-deposited layer of the elastomer polymethyldisolaxane (PDMS). This molecular adhesion facilitates the removal of the gold film from the mica support by peeling and provides a new approach to template stripping which avoids the use of conventional adhesive layers. The fullerene adhesion layers may also be used to remove organic monolayers and thin films as well as two-dimensional polymers which are pre-formed on the gold surface and have monolayer thickness. Following the removal from the mica support the monolayers may be isolated and transferred to a dielectric surface by etching of the gold thin film, mechanical transfer and removal of the fullerene layer by annealing/dissolution. The use of this molecular adhesive layer provides a new route to transfer polymeric films from metal substrates to other surfaces as we demonstrate for an assembly of covalently-coupled porphyrins.

  8. Two Dimensional Plasmonic Cavities on Moire Surfaces

    Science.gov (United States)

    Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla

    2010-03-01

    We investigate surface plasmon polariton (SPP) cavitiy modes on two dimensional Moire surfaces in the visible spectrum. Two dimensional hexagonal Moire surface can be recorded on a photoresist layer using Interference lithography (IL). Two sequential exposures at slightly different angles in IL generate one dimensional Moire surfaces. Further sequential exposure for the same sample at slightly different angles after turning the sample 60 degrees around its own axis generates two dimensional hexagonal Moire cavity. Spectroscopic reflection measurements have shown plasmonic band gaps and cavity states at all the azimuthal angles (omnidirectional cavity and band gap formation) investigated. The plasmonic band gap edge and the cavity states energies show six fold symmetry on the two dimensional Moire surface as measured in reflection measurements.

  9. Flexible Quasi-Two-Dimensional CoFe2O4 Epitaxial Thin Films for Continuous Strain Tuning of Magnetic Properties.

    Science.gov (United States)

    Zhang, Yong; Shen, Lvkang; Liu, Ming; Li, Xin; Lu, Xiaoli; Lu, Lu; Ma, Chunrui; You, Caiyin; Chen, Aiping; Huang, Chuanwei; Chen, Lang; Alexe, Marin; Jia, Chun-Lin

    2017-08-22

    Epitaxial thin films of CoFe2O4 (CFO) have successfully been transferred from a SrTiO3 substrate onto a flexible polyimide substrate. By bending the flexible polyimide, different levels of uniaxial strain are continuously introduced into the CFO epitaxial thin films. Unlike traditional epitaxial strain induced by substrates, the strain from bending will not suffer from critical thickness limitation, crystalline quality variation, and substrate clamping, and more importantly, it provides a more intrinsic and reliable way to study strain-controlled behaviors in functional oxide systems. It is found that both the saturation magnetization and coercivity of the transferred films can be changed over the bending status and show a high accord with the movement of the curvature bending radius of the polyimide substrate. This reveals that the mechanical strain plays a critical role in tuning the magnetic properties of CFO thin films parallel and perpendicular to the film plane direction.

  10. Suppression of conductivity deterioration of copper thin films by coating with atomic-layer materials

    Science.gov (United States)

    Cuong, Nguyen Thanh; Okada, Susumu

    2017-03-01

    Theoretical calculations are performed to explore the electronic structures and electron conducting properties of copper (Cu) thin films coated with graphene or h-boron-nitride (h-BN) layers. The Shockley surface states of Cu surfaces are preserved by the graphene and h-BN coatings which prevent the surface oxidation of Cu because of the weak interaction between the Cu surface and graphene or the h-BN layers. Furthermore, the Shockley surface states in Cu thin films possess quasi-two dimensional free-electron characteristics and exhibit a high conductivity of 1.62 × 107 (Ωm)-1 at room temperature. These hybrid structures may be suitable as interconnects in memory devices that can stably store data for long periods.

  11. Low-Dimensional Nanomaterials as Active Layer Components in Thin-Film Photovoltaics

    Science.gov (United States)

    Shastry, Tejas Attreya

    Thin-film photovoltaics offer the promise of cost-effective and scalable solar energy conversion, particularly for applications of semi-transparent solar cells where the poor absorption of commercially-available silicon is inadequate. Applications ranging from roof coatings that capture solar energy to semi-transparent windows that harvest the immense amount of incident sunlight on buildings could be realized with efficient and stable thin-film solar cells. However, the lifetime and efficiency of thin-film solar cells continue to trail their inorganic silicon counterparts. Low-dimensional nanomaterials, such as carbon nanotubes and two-dimensional metal dichalcogenides, have recently been explored as materials in thin-film solar cells due to their exceptional optoelectronic properties, solution-processability, and chemical inertness. Thus far, issues with the processing of these materials has held back their implementation in efficient photovoltaics. This dissertation reports processing advances that enable demonstrations of low-dimensional nanomaterials in thin-film solar cells. These low-dimensional photovoltaics show enhanced photovoltaic efficiency and environmental stability in comparison to previous devices, with a focus on semiconducting single-walled carbon nanotubes as an active layer component. The introduction summarizes recent advances in the processing of carbon nanotubes and their implementation through the thin-film photovoltaic architecture, as well as the use of two-dimensional metal dichalcogenides in photovoltaic applications and potential future directions for all-nanomaterial solar cells. The following chapter reports a study of the interaction between carbon nanotubes and surfactants that enables them to be sorted by electronic type via density gradient ultracentrifugation. These insights are utilized to construct of a broad distribution of carbon nanotubes that absorb throughout the solar spectrum. This polychiral distribution is then shown

  12. Two-dimensional x-ray diffraction

    CERN Document Server

    He, Bob B

    2009-01-01

    Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea

  13. Crystalline thin films: The electrochemical atomic layer deposition (ECALD) view

    CSIR Research Space (South Africa)

    Modibedi, M

    2011-09-01

    Full Text Available Electrochemical atomic layer deposition technique is selected as one of the methods to prepare thin films for various applications, including electrocatalytic materials and compound....

  14. Plant thin cell layers: update and perspectives

    Directory of Open Access Journals (Sweden)

    Teixeira da Silva Jaime A.

    2015-12-01

    Full Text Available Thin cell layers (TCLs are small and versatile explants for the in vitro culture of plants. At face value, their morphogenic productivity may appear to be less than conventional explants, but once the plant growth correction factor and geometric factor have been applied, the true (potential productivity exceeds that of a conventional explant. It is for this reason that for almost 45 years, TCLs have been applied to the in vitro culture of almost 90 species or hybrids, mainly ornamentals and orchids, but also to field and vegetable crops and medicinal plants. Focusing on 12 new studies that have emerged in the recent past (2013-2015, this paper brings promise to other horticultural species that could benefit from the use of TCLs.

  15. Thin layer chromatography in drug discovery process.

    Science.gov (United States)

    Ciura, Krzesimir; Dziomba, Szymon; Nowakowska, Joanna; Markuszewski, Michał J

    2017-10-20

    The review is mainly focused on application of thin layer chromatography (TLC) as simple, rapid and inexpensive method for lipophilicity assessment. Among separation techniques, TLC is still one of the most popular for lipophilicity measurement. The principles and methodology of Quantitative Structure Retention Relationship (QSRR) employed to lipophilicity prediction from retention data are presented. Moreover, applications of TLC retention constants in Quantitative Structure Activity Relationship (QSAR) studies were critically overviewed. The paper concerns also bioautography as a TLC method complementary to QSAR studies. In the article, the advantages and limitations of well established and less common planar chromatography modes applied for drug discovery process were discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Thin layer convection-drying of mushrooms

    Energy Technology Data Exchange (ETDEWEB)

    Pal, U.S.; Chakraverty, A. [Indian Inst. of Tech., Kharagpur (India). Dept. of Agricultural Engineering

    1997-06-01

    Dehydration characteristics of the Oyster Pleurotus variety of mushroom were studied. Both untreated and treated (steam blanching followed by sulphiting and citric acid pretreatment before drying) mushrooms were dried in the thin layer experimental equipment at each of the drying air temperatures of 45, 50 and 60{sup o}C with air velocities of 0.9 and 1.6 m/s. Studies on the equilibrium moisture content (EMC) of both untreated and treated dehydrated mushrooms were performed at different relative humidities ranging from 11.2 to 86.3% at 30{sup o}C. Taking drying time and quality of the dehydrated product into account, a combination of a drying air temperature of 50{sup o}C and an air velocity of 0.9 m/s appears to be suitable for drying of both untreated and treated mushrooms for a good dehydrated product. (author)

  17. Scaling percolation in thin porous layers

    Science.gov (United States)

    Médici, E. F.; Allen, J. S.

    2011-12-01

    Percolation in porous media is a complex process that depends on the flow rate, material, and fluids properties as well as the boundary conditions. Traditional methods of characterizing percolation rely upon visual observation of a flow pattern or a pressure-saturation relation valid only in the limit of no flow. In this paper, the dynamics of fluid percolation in thin porous media is approached through a new scaling. This new scaling in conjunction with the capillary number and the viscosity ratio has resulted in a linear non-dimensional correlation of the percolation pressure and wetted area in time unique to each porous media. The effect of different percolation flow patterns on the dynamic pressure-saturation relation can be condensed into a linear correlation using this scaling. The general trend and implications of the scaling have been analyzed using an analytical model of a fluid percolating between two parallel plates and by experimental testing on thin porous media. Cathode porous transport layers (PTLs), also known as gas diffusion layers, of a proton exchange membrane (PEM) fuel cell having different morphological and wetting properties were tested under drainage conditions. Images of the fluid percolation evolution and the percolation pressure in the PTLs were simultaneously recorded. A unique linear correlation is obtained for each type of PTL samples using the new scaling. The correlation derived from this new scaling can be used to quantitatively characterize porous media with respect to percolation. While the characterization method discussed herein was developed for the study of porous materials used in PEM fuel cells, the method and scaling are applicable to any porous media.

  18. Enhancement of band-to-band tunneling in mono-layer transition metal dichalcogenides two-dimensional materials by vacancy defects

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Xiang-Wei; Li, Shu-Shen [State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Gong, Jian [School of Physics Science and Technology, Inner Mongolia University, Hohhot 010021 (China); Xu, Nuo [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States); Zhang, Jinfeng; Hao, Yue [Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); Wang, Lin-Wang, E-mail: lwwang@lbl.gov [Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2014-01-13

    The band-to-band tunneling of monolayer transition metal dichalcogenides nano-junction is investigated using atomistic ab initio quantum transport simulations. From the simulation, it is found that the transition metal vacancy defect in the two-dimensional MX{sub 2} (M = Mo,W; X = S,Se) band-to-band tunneling diode can dramatically boost the on-state current up to 10 times while maintaining the device sub-threshold swing. The performance enhancement mechanism is discussed in detail by examining partial density of states of the system. It is found that the transition metal vacancy induces band-gap states, which reduce the effective length of the tunneling transition region.

  19. Thin layer Characterization by ZGV Lamb modes

    Energy Technology Data Exchange (ETDEWEB)

    Ces, Maximin; Clorennec, Dominique; Royer, Daniel; Prada, Claire, E-mail: maximin.ces@espci.fr [Laboratoire Ondes et Acoustique, ESPCI- Universite Paris 7- CNRS UMR 7587, 10 rue Vauquelin, 75231 Paris Cedex 05- France (France)

    2011-01-01

    Ultrasonic non-destructive testing of plates can be performed with Lamb modes guided by the structure. Non contact generation and detection of the elastic waves can be achieved with optical means such as a pulsed laser source and an interferometer. With this setup, we propose a method using zero group velocity (ZGV) Lamb modes rather than propagating modes. These ZGV modes have noteworthy properties, in particular their group velocity vanishes, whereas their phase velocity remains finite. Thus, a significant part of the energy deposited by the pulsed laser can be trapped in the source area. For example, in a homogeneous isotropic plate and at the minimum frequency of the S{sub 1}-Lamb mode a very sharp resonance can be observed, the frequency of which only depends on the plate thickness, for a given material. In fact, other ZGV modes exist and the set of ZGV resonance frequencies provide a local and absolute measurement of Poisson's ratio. These non-propagating modes can also be used to characterize multi-layered structures. Experimentally, we observed that a thin (500 nm) gold layer deposited on a thick (1.5 mm) Duralumin plate induces a sensitive down-shift of the set of ZGV resonance frequencies. This shift, which is typically 5 kHz for the S{sub 1}-Lamb mode at 1.924 MHz, can be approximated by a formula providing the layer thickness. Thickness down to 100 nm can be estimated by this method. Such a sensitivity with conventional ultrasound inspection by acoustic microscopy would require an operating frequency in the GHz range.

  20. Piezoelectricity in Two-Dimensional Materials

    KAUST Repository

    Wu, Tao

    2015-02-25

    Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

  1. Energy Transfer Between Coherently Delocalized States in Thin Films of the Explosive Pentaerythritol Tetranitrate (PETN) Revealed by Two-Dimensional Infrared Spectroscopy.

    Science.gov (United States)

    Ostrander, Joshua S; Knepper, Robert; Tappan, Alexander S; Kay, Jeffrey J; Zanni, Martin T; Farrow, Darcie A

    2017-02-16

    Pentaerythritol tetranitrate (PETN) is a common secondary explosive and has been used extensively to study shock initiation and energy propagation in energetic materials. We report 2D IR measurements of PETN thin films that resolve vibrational energy transfer and relaxation mechanisms. Ultrafast anisotropy measurements reveal a sub-500 fs reorientation of transition dipoles in thin films of vapor-deposited PETN that is absent in solution measurements, consistent with intermolecular energy transfer. The anisotropy is frequency dependent, suggesting spectrally heterogeneous vibrational relaxation. Cross peaks are observed in 2D IR spectra that resolve a specific energy transfer pathway with a 2 ps time scale. Transition dipole coupling calculations of the nitrate ester groups in the crystal lattice predict that the intermolecular couplings are as large or larger than the intramolecular couplings. The calculations match well with the experimental frequencies and the anisotropy, leading us to conclude that the observed cross peak is measuring energy transfer between two eigenstates that are extended over multiple PETN molecules. Measurements of the transition dipole strength indicate that these vibrational modes are coherently delocalized over at least 15-30 molecules. We discuss the implications of vibrational relaxation between coherently delocalized eigenstates for mechanisms relevant to explosives.

  2. Exploring Two-Dimensional Transport Phenomena in Metal Oxide Heterointerfaces for Next-Generation, High-Performance, Thin-Film Transistor Technologies.

    Science.gov (United States)

    Labram, John G; Lin, Yen-Hung; Anthopoulos, Thomas D

    2015-11-04

    In the last decade, metal oxides have emerged as a fascinating class of electronic material, exhibiting a wide range of unique and technologically relevant characteristics. For example, thin-film transistors formed from amorphous or polycrystalline metal oxide semiconductors offer the promise of low-cost, large-area, and flexible electronics, exhibiting performances comparable to or in excess of incumbent silicon-based technologies. Atomically flat interfaces between otherwise insulating or semiconducting complex oxides, are also found to be highly conducting, displaying 2-dimensional (2D) charge transport properties, strong correlations, and even superconductivity. Field-effect devices employing such carefully engineered interfaces are hoped to one day compete with traditional group IV or III-V semiconductors for use in the next-generation of high-performance electronics. In this Concept article we provide an overview of the different metal oxide transistor technologies and potential future research directions. In particular, we look at the recent reports of multilayer oxide thin-film transistors and the possibility of 2D electron transport in these disordered/polycrystalline systems and discuss the potential of the technology for applications in large-area electronics.

  3. Thin-Layer Chromatography: Four Simple Activities for Undergraduate Students.

    Science.gov (United States)

    Anwar, Jamil; And Others

    1996-01-01

    Presents activities that can be used to introduce thin-layer chromatography at the undergraduate level in relatively less developed countries and that can be performed with very simple and commonly available apparati in high schools and colleges. Activities include thin-layer chromatography with a test-tube, capillary feeder, burette, and rotating…

  4. Thin-Layer Fuel Cell for Teaching and Classroom Demonstrations

    Science.gov (United States)

    Shirkhanzadeh, M.

    2009-01-01

    A thin-layer fuel cell is described that is simple and easy to set up and is particularly useful for teaching and classroom demonstrations. The cell is both an electrolyzer and a fuel cell and operates using a thin layer of electrolyte with a thickness of approximately 127 micrometers and a volume of approximately 40 microliters. As an…

  5. Thin-Layer Chromatography: Four Simple Activities for Undergraduate Students.

    Science.gov (United States)

    Anwar, Jamil; And Others

    1996-01-01

    Presents activities that can be used to introduce thin-layer chromatography at the undergraduate level in relatively less developed countries and that can be performed with very simple and commonly available apparati in high schools and colleges. Activities include thin-layer chromatography with a test-tube, capillary feeder, burette, and rotating…

  6. Seeing Many-Body Effects in Single- and Few-Layer Graphene: Observation of Two-Dimensional Saddle-Point Excitons

    Science.gov (United States)

    2010-01-01

    manifested by recent reports of broken symmetry states in the quantum Hall regime [1], of the fractional quantum Hall effect [2], of a renormalization ...normalized change in reflectance of the bare substrate induced by the presence of the sample. For a sufficiently thin sample supported on a transparent

  7. Significantly Dense Two-Dimensional Hydrogen-Bond Network in a Layered Zirconium Phosphate Leading to High Proton Conductivities in Both Water-Assisted Low-Temperature and Anhydrous Intermediate-Temperature Regions.

    Science.gov (United States)

    Gui, Daxiang; Zheng, Tao; Xie, Jian; Cai, Yawen; Wang, Yaxing; Chen, Lanhua; Diwu, Juan; Chai, Zhifang; Wang, Shuao

    2016-12-19

    A highly stable layered zirconium phosphate, (NH4)2[ZrF2(HPO4)2] (ZrP-1), was synthesized by an ionothermal method and contains an extremely dense two-dimensional hydrogen-bond network that is thermally stable up to 573 K, leading to combined ultrahigh water-assisted proton conductivities of 1.45 × 10(-2) S cm(-1) at 363 K/95% relative humidity and sustainable anhydrous proton conductivity of 1.1 × 10(-5) S cm(-1) at 503 K.

  8. Development of optimized mobile phases for protein separation by high performance thin layer chromatography.

    Science.gov (United States)

    Biller, Julia; Morschheuser, Lena; Riedner, Maria; Rohn, Sascha

    2015-10-09

    In recent years, protein chemistry tends inexorably toward the analysis of more complex proteins, proteoforms, and posttranslational protein modifications. Although mass spectrometry developed quite fast correspondingly, sample preparation and separation of these analytes is still a major issue and quite challenging. For many years, electrophoresis seemed to be the method of choice; nonetheless its variance is limited to parameters such as size and charge. When taking a look at traditional (thin-layer) chromatography, further parameters such as polarity and different mobile and stationary phases can be utilized. Further, possibilities of detection are manifold compared to electrophoresis. Similarly, two-dimensional separation can be also performed with thin-layer chromatography (TLC). As the revival of TLC developed enormously in the last decade, it seems to be also an alternative to use high performance thin-layer chromatography (HPTLC) for the separation of proteins. The aim of this study was to establish an HPTLC separation system that allows a separation of protein mixtures over a broad polarity range, or if necessary allowing to modify the separation with only few steps to improve the separation for a specific scope. Several layers and solvent systems have been evaluated to reach a fully utilized and optimized separation system. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Chemical Gated Field Effect Transistor by Hybrid Integration of One-Dimensional Silicon Nanowire and Two-Dimensional Tin Oxide Thin Film for Low Power Gas Sensor.

    Science.gov (United States)

    Han, Jin-Woo; Rim, Taiuk; Baek, Chang-Ki; Meyyappan, M

    2015-09-30

    Gas sensors based on metal-oxide-semiconductor transistor with the polysilicon gate replaced by a gas sensitive thin film have been around for over 50 years. These are not suitable for the emerging mobile and wearable sensor platforms due to operating voltages and powers far exceeding the supply capability of batteries. Here we present a novel approach to decouple the chemically sensitive region from the conducting channel for reducing the drive voltage and increasing reliability. This chemically gated field effect transistor uses silicon nanowire for the current conduction channel with a tin oxide film on top of the nanowire serving as the gas sensitive medium. The potential change induced by the molecular adsorption and desorption allows the electrically floating tin oxide film to gate the silicon channel. As the device is designed to be normally off, the power is consumed only during the gas sensing event. This feature is attractive for the battery operated sensor and wearable electronics. In addition, the decoupling of the chemical reaction and the current conduction regions allows the gas sensitive material to be free from electrical stress, thus increasing reliability. The device shows excellent gas sensitivity to the tested analytes relative to conventional metal oxide transistors and resistive sensors.

  10. Thin layer joining by gas adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Taga, Yasunori, E-mail: y-taga@isc.chubu.ac.jp; Fukumura, Toshio

    2014-10-01

    Highlights: • We report thin layer molecular joining between glass and COP by gas adsorption. Thickness of joining layer is 1–2 nm and joining process was carried out at low temperature at about 100 °C. • Adhesion strength measured by 180 degree peel test revealed to be 1–10 N/25 mm and the joined stack showed high durability for practical use. - Abstract: Attempt has been made to join borosilicate glass and cycloolefin (COP) polymer film by using gas adsorption method. After corona plasma treat, COP was exposed to (3-glycidoxypropyl) trimethoxysilane (GPS) and glass to (3-aminopropyl) triethoxysilane (APS) both in air atmosphere, resulting in co-adsorption of water vapor in the atmosphere and organosilane gases. Surface characterization of plasma treated and gas adsorbed surfaces was carried out by X-ray photoelectron spectroscopy (XPS) using Mg Kα X-ray source. Joining was carried out by a roll laminator after contact of both surfaces at room temperature, followed by annealing at 130 °C for 10 min. Adhesion strength was evaluated by 180 degree peel test based on ASTM D-903 and durability was examined under the conditions of 60 °C and 95% RH. It was found that after plasma treatment, complex functional groups such as C-H, C-O, C=O, O-C=O and CO{sub 3} were found on COP and O-H on glass. Thickness of GPS gas adsorption layer on COP was evaluated by the XPS to be at least 1.1 nm by taking inelastic mean free path of Si{sub 2p} photoelectron into consideration. Joining force was found to be more than 5 N/25 mm corresponding to almost equal to COP bulk tensile strength. In addition, durability of this adhesion strength remained unchanged over 2000 h even after exposure to the durability test conditions of 60 °C and 95% RH. The results can be explained in terms of formation of H-H hydrogen bonding and Si-O covalent bonding via silanols will be made at the interface as a result of lamination and annealing processes. In conclusion, ultrathin joining method

  11. Exploration and exploitation of homologous series of bis(acrylamidoalkanes containing pyridyl and phenyl groups: β-sheet versus two-dimensional layers in solid-state photochemical [2 + 2] reactions

    Directory of Open Access Journals (Sweden)

    Mousumi Garai

    2015-09-01

    Full Text Available The homologous series of phenyl and pyridyl substituted bis(acrylamidoalkanes have been synthesized with the aim of systematic analysis of their crystal structures and their solid-state [2 + 2] reactivities. The changes in the crystal structures with respect to a small change in the molecular structure, that is by varying alkyl spacers between acrylamides and/or by varying the end groups (phenyl, 2-pyridyl, 3-pyridyl, 4-pyridyl on the C-terminal of the amide, were analyzed in terms of hydrogen-bonding interference (N—H...Npy versus N—H...O=C and network geometries. In this series, a greater tendency towards the formation of N—H...O hydrogen bonds (β-sheets and two-dimensional networks over N—H...N hydrogen bonds was observed. Among all the structures seven structures were found to have the required alignments of double bonds for the [2 + 2] reaction such that the formations of single dimer, double dimer and polymer are facilitated. However, only four structures were found to exhibit such a solid-state [2 + 2] reaction to form a single dimer and polymers. The two-dimensional hydrogen-bonding layer via N—H...O hydrogen bonds was found to promote solid-state [2 + 2] photo-polymerization in a single-crystal-to-single-crystal manner. Such two-dimensional layers were encountered only when the spacer between acryl amide moieties is butyl. Only four out of the 16 derivatives were found to form hydrates, two each from 2-pyridyl and 4-pyridyl derivatives. The water molecules in these structures govern the hydrogen-bonding networks by the formation of an octameric water cluster and one-dimensional zigzag water chains. The trends in the melting points and densities were also analyzed.

  12. A nanoporous two-dimensional polymer by single-crystal-to-single-crystal photopolymerization.

    Science.gov (United States)

    Kissel, Patrick; Murray, Daniel J; Wulftange, William J; Catalano, Vincent J; King, Benjamin T

    2014-09-01

    In contrast to the wide number and variety of available synthetic routes to conventional linear polymers, the synthesis of two-dimensional polymers and unambiguous proof of their structure remains a challenge. Two-dimensional polymers-single-layered polymers that form a tiling network in exactly two dimensions-have potential for use in nanoporous membranes and other applications. Here, we report the preparation of a fluorinated hydrocarbon two-dimensional polymer that can be exfoliated into single sheets, and its characterization by high-resolution single-crystal X-ray diffraction analysis. The procedure involves three steps: preorganization in a lamellar crystal of a rigid monomer bearing three photoreactive arms, photopolymerization of the crystalline monomers by [4 + 4] cycloaddition, and isolation of individual two-dimensional polymer sheets. This polymer is a molecularly thin (~1 nm) material that combines precisely defined monodisperse pores of ~9 Å with a high pore density of 3.3 × 10(13) pores cm(-2). Atomic-resolution single-crystal X-ray structures of the monomer, an intermediate dimer and the final crystalline two-dimensional polymer were obtained and prove the single-crystal-to-single-crystal nature and molecular precision of the two-dimensional photopolymerization.

  13. Second-harmonic generation in quaternary atomically thin layered AgInP2S6 crystals

    Science.gov (United States)

    Wang, Xingzhi; Du, Kezhao; Liu, Weiwei; Hu, Peng; Lu, Xin; Xu, Weigao; Kloc, Christian; Xiong, Qihua

    2016-09-01

    Nonlinear effects in two-dimensional (2D) atomic layered materials have attracted increasing interest. Here, we report the observation of optical second-harmonic generation (SHG) in two-dimensional atomically thin silver indium phosphorus sulfide (AgInP2S6) crystals, with odd layer thickness. The nonlinear signal facilitates the use of thickness-dependent SHG intensity to investigate the stacking type of this material, while the crystal-orientation dependent SHG intensity of the monolayer sample reveals the rotational symmetry of the AgInP2S6 lattice in plane. Our studies expand the 2D crystal family in nonlinear effect field, which opened considerable promise to the functionalities and potential applications of 2D materials.

  14. Quantum creep in a highly crystalline two-dimensional superconductor

    Science.gov (United States)

    Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu

    Conventional studies on quantum phase transitions, especially on superconductor-insulator or superconductor-metal-insulator transitions have been performed in deposited metallic thin films such as Bismuth or MoGe. Although the techniques of thin films deposition have been considerably improved, unintentional disorder such as impurities and deficiencies, generating the pinning centers, seems to still exist in such systems. The mechanical exfoliated highly crystalline two-dimensional material can be a good candidate to realize a less-disordered 2D superconductor with extremely weak pinning, combined with transfer method or ionic-liquid gating. We report on the quantum metal, namely, magnetic-field-induced metallic state observed in an ion-gated two-dimensional superconductor based on an ultra-highly crystalline layered band insulator, ZrNCl. We found that the superconducting state is extremely fragile against external magnetic fields; that is, zero resistance state immediately disappears, once an external magnetic field switches on. This is because the present system is relatively clean and the pinning potential is extremely weak, which cause quantum tunneling and flux flow of vortices, resulting in metallic ground state.

  15. Thin layer drying of tomato slices.

    Science.gov (United States)

    Das Purkayastha, Manashi; Nath, Amit; Deka, Bidyut Chandra; Mahanta, Charu Lata

    2013-08-01

    The hot air convective drying characteristics of blanched tomato (Lycopersicon esculantum L.) slices have been investigated. Drying experiments were carried out at four different temperatures (50, 60, 65 and 70 °C). The effect of drying temperatures on the drying behavior of the tomato slices was evaluated. All drying experiments had only falling rate period. The average effective diffusivity values varied from 0.5453 × 10(-9) to 2.3871 × 10(-9) m(2)/s over the temperature range studied and the activation energy was estimated to be 61.004 kJ/mol. In order to select a suitable form of the drying curve, six different thin layer drying models (Henderson-Pabis, Page, Diamante et al., Wang and Singh, Logarithmic and Newton models) were fitted to the experimental data. The goodness of fit tests indicated that the Logarithmic model gave the best fit to experimental results, which was closely followed by the Henderson-Pabis model. The influence of varied drying temperatures on quality attributes of the tomato slices viz. Hunter color parameters, ascorbic acid, lycopene, titratable acidity, total sugars, reducing sugars and sugar/acid ratio of dried slices was also studied. Slices dried at 50 and 60 °C had high amount of total sugars, lycopene, sugar/acid ratio, Hunter L- and a-values. Drying of slices at 50 °C revealed optimum retention of ascorbic acid, sugar/acid ratio and red hue, whereas, drying at higher temperature (65 and 70 °C) resulted in a considerable decrease in nutrients and colour quality of the slices.

  16. Thickness and dielectric constant determination of thin dielectric layers

    NARCIS (Netherlands)

    Bruijn, de Helene E.; Minor, Marcel; Kooyman, Rob P.H.; Greve, Jan

    1993-01-01

    We derive a method for the determination of the dielectric constant and thickness of a thin dielectric layer, deposited on top of a thick dielectric layer which is in turn present on a metal film. Reflection of p- and s-polarized light from the metal layer yields minima for certain angles of inciden

  17. A new family of two-dimensional zeolites prepared from the intermediate layered precursor IPC-3P obtained during the synthesis of TUN zeolite.

    Science.gov (United States)

    Kubů, Martin; Roth, Wieslaw J; Greer, Heather F; Zhou, Wuzong; Morris, Russell E; Přech, Jan; Čejka, Jiří

    2013-10-04

    The crystallization of zeolite TUN with 1,4-bis(N-methylpyrrolidinium)butane as template proceeds through an intermediate, designated IPC-3P, following the Ostwald rule of successive transformations. This apparently layered transient product has been thoroughly investigated and found to consist of MWW monolayers stacked without alignment in register, that is, disordered compared with MCM-22P. The structure was confirmed based on X-ray diffraction and high-resolution (HR)TEM analysis. The layered zeolite precursor IPC-3P can be swollen and pillared affording a combined micro- and mesoporous material with enhanced Brunauer-Emmett-Teller (BET) surface area (685 m(2) g(-1) ) and greater accessibility of Brønsted acid sites for bulky molecules. This mesoporous material was probed with 2,6-di-tert-butylpyridine (DTBP). IPC-3P and its modification create a new layered zeolite sub-family belonging to the MWW family. FTIR data indicate that (Al)MWW materials MCM-22 and IPC-3 with Si/Al ratios greater than 20 exhibit a lower relative ratio of Brønsted to Lewis acid sites than MCM-22 (with Si/Al ratios of around 13), that is, less than 2 versus more than 3, respectively. This is maintained even upon pillaring and warrants further exploration of materials like IPC-3P with a higher Al content. The unique XRD features of IPC-3P indicating misaligned stacking of layers and distinct from MCM-22P, are also seen in other MWW materials such as EMM-10P, hexamethonium-templated (HM)-MCM-22, ITQ-30, and UZM-8 suggesting the need for more detailed study of their identity and properties.

  18. Thin-Layer Spectroelectrochemistry on an Aqueous Micro-drop

    Energy Technology Data Exchange (ETDEWEB)

    Schroll, Cynthia A.; Chatterjee, Sayandev; Heineman, William R.; Bryan, Samuel A.

    2012-05-01

    Here we report the ability to perform thin-layer spectroelectrochemistry using an aqueous micro-drop. The thin-layer setup was evaluated using [Fe(CN){sub 6}]{sup 3-/4-} as a absorbance based model analyte and [Ru(bpy){sub 3}]{sup 3+/2+} as an emission based model analyte. The thin-layer capability of the electrochemical cell was validated with these two chemical systems using cyclic voltammetry, and UV-visible absorbance and luminescence spectroscopies. This work supports our FCRD process monitoring work and is a direct result of the collaboration under subcontract with University of Cincinnati.

  19. Spectroscopic investigations on thin adhesive layers in multi-material laminates.

    Science.gov (United States)

    Voronko, Yuliya; Chernev, Boril S; Eder, Gabriele C

    2014-01-01

    Three different spectroscopic approaches, Raman linescans, Raman imaging, and attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) imaging were evaluated for the visualization of the thin adhesive layers (3-6 μm) present in polymeric photovoltaic backsheets. The cross-sections of the multilayer laminates in the original, weathered, and artificially aged samples were investigated spectroscopically in order to describe the impact of the environmental factors on the evenness and thickness of the adhesive layers. All three methods were found to be suitable tools to detect and visualize these thin layers within the original and aged polymeric laminates. However, as the adhesive layer is not very uniform in thickness and partly disintegrates upon weathering and/or artificial aging, Raman linescans yield only qualitative information and do not allow for an estimation of the layer thickness. Upon increasing the measuring area by moving from one-dimensional linescans to two-dimensional Raman images, a much better result could be achieved. Even though a longer measuring time has to be taken into account, the information on the uniformity and evenness of the adhesive layer obtainable using the imaging technique is much more comprehensive. Although Raman spectroscopy is known to have the superior lateral resolution as compared with ATR FT-IR spectroscopy, the adhesive layers of the samples used within this study (layer thickness 3-6 μm) could also be detected and visualized by applying the ATR FT-IR spectroscopic imaging method. However, the analysis of the images was quite a demanding task, as the thickness of the adhesive layer was in the region of the resolution limit of this method. The information obtained for the impact of artificial aging and weathering on the adhesive layer obtained using Raman imaging and ATR FT-IR imaging was in good accordance.

  20. Buffer layer for thin film structures

    Science.gov (United States)

    Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Wang, Haiyan

    2006-10-31

    A composite structure including a base substrate and a layer of a mixture of strontium titanate and strontium ruthenate is provided. A superconducting article can include a composite structure including an outermost layer of magnesium oxide, a buffer layer of strontium titanate or a mixture of strontium titanate and strontium ruthenate and a top-layer of a superconducting material such as YBCO upon the buffer layer.

  1. Delamination of Compressed thin Layers at Corners

    DEFF Research Database (Denmark)

    Clausen, Johan; Jensen, Henrik Myhre; Sørensen, Kim Dalsten

    2008-01-01

    An analysis of delamination for a thin elastic film, attached to a substrate with a corner, is carried out. The film is in compression and the analysis is performed by combining results from fracture mechanics and the theory of thin shells. The results show a very strong dependency of the angle...

  2. Optimisation of interdigitated back contacts solar cells by two-dimensional numerical simulation

    Energy Technology Data Exchange (ETDEWEB)

    Nichiporuk, O.; Kaminski, A.; Lemiti, M.; Fave, A. [Instituit National des Sciences Appliquees Lyon, Villeurbanne (France). Lab. de Physique de la Matiere; Skryshevsky, V. [National Taras Shevchenko Univ., Kiev (Ukraine). Radiophysics Dept.

    2005-04-01

    In this paper we present the results of the simulation of interdigitated back contacts solar cell on thin-film ({approx}{mu}m) silicon layer. The influence of several parameters (surface recombination rate, substrate thickness and type, diffusion length, device geometry, doping levels) on device characteristics are simulated using the accurate two-dimensional numerical simulator DESSIS that allows to optimise the cell design. (Author)

  3. Directional interlayer spin-valley transfer in two-dimensional heterostructures

    Science.gov (United States)

    Schaibley, John R.; Rivera, Pasqual; Yu, Hongyi; Seyler, Kyle L.; Yan, Jiaqiang; Mandrus, David G.; Taniguchi, Takashi; Watanabe, Kenji; Yao, Wang; Xu, Xiaodong

    2016-12-01

    Van der Waals heterostructures formed by two different monolayer semiconductors have emerged as a promising platform for new optoelectronic and spin/valleytronic applications. In addition to its atomically thin nature, a two-dimensional semiconductor heterostructure is distinct from its three-dimensional counterparts due to the unique coupled spin-valley physics of its constituent monolayers. Here, we report the direct observation that an optically generated spin-valley polarization in one monolayer can be transferred between layers of a two-dimensional MoSe2-WSe2 heterostructure. Using non-degenerate optical circular dichroism spectroscopy, we show that charge transfer between two monolayers conserves spin-valley polarization and is only weakly dependent on the twist angle between layers. Our work points to a new spin-valley pumping scheme in nanoscale devices, provides a fundamental understanding of spin-valley transfer across the two-dimensional interface, and shows the potential use of two-dimensional semiconductors as a spin-valley generator in two-dimensional spin/valleytronic devices for storing and processing information.

  4. Crystal Structure And Magnetic Property of the Complex of Hydrogen-bonded Two-dimensional Layer Copper(Ⅱ) Acrylate with Trimethyl Phosphate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@ Copper carboxylate complexes play an important role in catalysing the enzymatic activities[1-4], and the phosphate has an especial use in DNA recognition[5]. Indeed the report about copper carboxylate complexes with phosphate ligands is rare. A chain structure supramolecule [Cu2(CH2CH-COO)4(H2O)2]n has been reported recently[6], in which a Cu2(CH2CH-COO)4(H2O)2 unit is linked by four O(water)-H...O(carboxyl) hydrogen bonds with two adjacent units(Fig.1). In this work a layer structure complex {Cu2(CH2CH-COO)4(H2O)2[OP(OCH3)3]}n was synthesized by means of hydrogen-bonded assembly approach between complex [Cu2(CH2CH-COO)4(H2O)2]n with trimethyl phosphate(TMP).

  5. Polytypism in LaOBi S2 -type compounds based on different three-dimensional stacking sequences of two-dimensional Bi S2 layers

    Science.gov (United States)

    Liu, Qihang; Zhang, Xiuwen; Zunger, Alex

    2016-05-01

    LaOBi S2 -type materials have drawn much attention recently because of various interesting physical properties, such as low-temperature superconductivity, hidden spin polarization, and electrically tunable Dirac cones. However, it was generally assumed that each LaOBi S2 -type compound has a unique and specific crystallographic structure (with a space group P 4 /nmm) separated from other phases. Using first-principles total energy and stability calculations we confirm that the previous assignment of the P 4 /nmm structure to LaOBi S2 is incorrect. Furthermore, we find that the unstable structure is replaced by a family of energetically closely spaced modifications (polytypes) differing by the layer sequences and orientations. We find that the local Bi-S distortion leads to three polytypes of LaOBi S2 with different stacking patterns of the distorted Bi S2 layers. The energy difference between the polytypes of LaOBi S2 is merely ˜1 meV/u.c., indicating the possible coexistence of all polytypes in the real sample and that the particular distribution of polytypes may be growth induced. The in-plane distortion can be suppressed by pressure, leading to a phase transition from polytypes to the high-symmetry P 4 /nmm structure with a pressure larger than 2.5 GPa. In addition, different choices of the intermediate atoms (replacing La) or active atoms (Bi S2 ) could also manifest different ground-state structures. One can thus tune the distortion and the ground state by pressure or by substituting covalence atoms in the LaOBi S2 family.

  6. Thin Layer Chromatography for the Analysis of Glycosaminoglycan Oligosaccharides

    OpenAIRE

    Zhang, Zhenqing; Xie, Jin; Zhang, Fuming; Linhardt, Robert J.

    2007-01-01

    Thin layer chromatography was used to analyze glycosaminoglycan oligosaccharides obtained through the use of polysaccharide lyases. This method allows for the rapid, semi-quantitative analysis of a wide variety of glycosaminoglycan oligosaccharides.

  7. Diamond nucleation on surface of C60 thin layers

    Institute of Scientific and Technical Information of China (English)

    杨国伟; 袁放成; 刘大军; 何金田; 张兵临

    1997-01-01

    Diamond nucleation on the surface of C60 thin layers and intermediate layer of Si substrates are studied by scanning electron microscopy (SEM). The cross-section SEM images of diamond films show that diamond grains really nucleate on the surface of C60 thin layers. The SEM images of diamond nucleating sites show the nucleating aggregation of diamond on C60 surfaces. The preferential oriented diamond films are observed. The plasma pre-treatment of C60 sublimating layers is a key factor for diamond nucleation.

  8. Two-dimensional supramolecular electron spin arrays.

    Science.gov (United States)

    Wäckerlin, Christian; Nowakowski, Jan; Liu, Shi-Xia; Jaggi, Michael; Siewert, Dorota; Girovsky, Jan; Shchyrba, Aneliia; Hählen, Tatjana; Kleibert, Armin; Oppeneer, Peter M; Nolting, Frithjof; Decurtins, Silvio; Jung, Thomas A; Ballav, Nirmalya

    2013-05-07

    A bottom-up approach is introduced to fabricate two-dimensional self-assembled layers of molecular spin-systems containing Mn and Fe ions arranged in a chessboard lattice. We demonstrate that the Mn and Fe spin states can be reversibly operated by their selective response to coordination/decoordination of volatile ligands like ammonia (NH3). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Thin layer structure of dissipation rate of scalar turbulence

    Institute of Scientific and Technical Information of China (English)

    ZHOU; Haibing; (周海兵); CUI; Guixiang; (崔桂香); XU; Chunxiao; (许春晓); ZHANG; Zhaoshun; (张兆顺)

    2003-01-01

    The structure of scalar turbulence dissipation is studied by means of direct numerical simulation. It has been discovered that the scalar turbulence dissipation exhibits thin layer structure. Based on the analysis of transportation equation of scalar turbulence dissipation, we have investigated the effect of turbulent strains on the generation of scalar turbulence dissipation and found that fluctuating scalar gradients trend to the third principal direction of turbulent strains. Therefore the generation of the thin layer structure of scalar turbulence dissipation is well interpreted.

  10. The Physical Context for Thin Layers in the Coastal Ocean

    Science.gov (United States)

    2010-03-01

    their statistics is in preparation. This latter article will be co-authored by MIT/WHOI Joint Program student Nick Woods who was partially supported...Abstract OS34M-05. Fratantoni, D. M., B. A. Hodges , and J. M. Lund, Autonomous Investigation of Thin Phytoplankton Layers and Their Physical Context...Poster presented at AGU Ocean Sciences Meeting, March 2008, Orlando, FL. Hodges , B. A., Fratantoni, D. M, and J. M. Lund, Propagation of a thin layer

  11. Layer-by-Layer Assembly of a pH-Responsive and Electrochromic Thin Film

    Science.gov (United States)

    Schmidt, Daniel J.; Pridgen, Eric M.; Hammond, Paula T.; Love, J. Christopher

    2010-01-01

    This article summarizes an experiment on thin-film fabrication with layer-by-layer assembly that is appropriate for undergraduate laboratory courses. The purpose of this experiment is to teach students about self-assembly in the context of thin films and to expose students to the concepts of functional polymeric coatings. Students dip coat…

  12. (CH3 NH3 )2 PdCl4 : A Compound with Two-Dimensional Organic-Inorganic Layered Perovskite Structure.

    Science.gov (United States)

    Huang, Tang Jiao; Thiang, Zhang Xian; Yin, Xuesong; Tang, Chunhua; Qi, Guojun; Gong, Hao

    2016-02-01

    The synthesis of previously unknown perovskite (CH3 NH3 )2 PdCl4 is reported. Despite using an organic cation with the smallest possible alkyl group, a 2D organic-inorganic layered Pd-based perovskites was still formed. This demonstrates that Pd-based 2D perovskites can be obtained even if the size of the organic cation is below the size limit predicted by the Goldschmidt tolerance-factor formula. The (CH3 NH3 )2 PdCl4 phase has a bulk resistivity of 1.4 Ω cm, a direct optical gap of 2.22 eV, and an absorption coefficient on the order of 10(4)  cm(-1) . XRD measurements suggest that the compound is moderately stable in air, an important advantage over several existing organic-inorganic perovskites that are prone to phase degradation problems when exposed to the atmosphere. Given the recent interest in organic-inorganic perovskites, the synthesis of this new Pd-based organic-inorganic perovskite may be helpful in the preparation and understanding of other organic-inorganic perovskites. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Engineering one-dimensional and two-dimensional birnessite manganese dioxides on nickel foam-supported cobalt–aluminum layered double hydroxides for advanced binder-free supercapacitors

    KAUST Repository

    Hao, Xiaodong

    2014-11-19

    © The Royal Society of Chemistry. We report a facile decoration of the hierarchical nickel foam-supported CoAl layered double hydroxides (CoAl LDHs) with MnO2 nanowires and nanosheets by a chemical bath method and a hydrothermal approach for high-performance supercapacitors. We demonstrate that owing to the sophisticated configuration of binder-free LDH@MnO2 on the conductive Ni foam (NF), the designed NF/LDH@MnO2 nanowire composites exhibit a highly boosted specific capacitance of 1837.8 F g-1 at a current density of 1 A g-1, a good rate capability, and an excellent cycling stability (91.8% retention after 5000 cycles). By applying the hierarchical NF/LDH@MnO2 nanowires as the positive electrode and activated microwave exfoliated graphite oxide activated graphene as the negative electrode, the fabricated asymmetric supercapacitor produces an energy density of 34.2 Wh kg-1 with a maximum power density of 9 kW kg-1. Such strategies with controllable assembly capability could open up a new and facile avenue in fabricating advanced binder-free energy storage electrodes. This journal is

  14. Buffer layers for high-Tc thin films on sapphire

    Science.gov (United States)

    Wu, X. D.; Foltyn, S. R.; Muenchausen, R. E.; Cooke, D. W.; Pique, A.; Kalokitis, D.; Pendrick, V.; Belohoubek, E.

    1992-01-01

    Buffer layers of various oxides including CeO2 and yttrium-stabilized zirconia (YSZ) have been deposited on R-plane sapphire. The orientation and crystallinity of the layers were optimized to promote epitaxial growth of YBa2Cu3O(7-delta) (YBCO) thin films. An ion beam channeling minimum yield of about 3 percent was obtained in the CeO2 layer on sapphire, indicating excellent crystallinity of the buffer layer. Among the buffer materials used, CeO2 was found to be the best one for YBCO thin films on R-plane sapphire. High Tc and Jc were obtained in YBCO thin films on sapphire with buffer layers. Surface resistances of the YBCO films were about 4 mOmega at 77 K and 25 GHz.

  15. Buffer layers for high-Tc thin films on sapphire

    Science.gov (United States)

    Wu, X. D.; Foltyn, S. R.; Muenchausen, R. E.; Cooke, D. W.; Pique, A.; Kalokitis, D.; Pendrick, V.; Belohoubek, E.

    1992-01-01

    Buffer layers of various oxides including CeO2 and yttrium-stabilized zirconia (YSZ) have been deposited on R-plane sapphire. The orientation and crystallinity of the layers were optimized to promote epitaxial growth of YBa2Cu3O(7-delta) (YBCO) thin films. An ion beam channeling minimum yield of about 3 percent was obtained in the CeO2 layer on sapphire, indicating excellent crystallinity of the buffer layer. Among the buffer materials used, CeO2 was found to be the best one for YBCO thin films on R-plane sapphire. High Tc and Jc were obtained in YBCO thin films on sapphire with buffer layers. Surface resistances of the YBCO films were about 4 mOmega at 77 K and 25 GHz.

  16. Predictive two-dimensional scrape-off layer plasma transport modeling of phase-I operations of tokamak SST-1 using SOLPS5

    Science.gov (United States)

    Himabindu, M.; Tyagi, Anil; Sharma, Devendra; Deshpande, Shishir P.; Bonnin, Xavier

    2014-02-01

    Computational analysis of coupled plasma and neutral transport in the Scrape-Off Layer (SOL) region of the Steady-State Superconducting Tokamak (SST-1) is done using SOLPS for Phase-I of double-null divertor plasma operations. An optimum set of plasma parameters is explored computationally for the first phase operations with the central objective of achieving an effective control over particle and power exhaust. While the transport of plasma species is treated using a fluid model in the B2.5 code, a full kinetic description is provided by the EIRENE code for the neutral particle transport in a realistic geometry. Cases with and without external gas puffing are analyzed for finding regimes where an effective control of plasma operations can be exercised by controlling the SOL plasma conditions over a range of heating powers. In the desired parameter range, a reasonable neutral penetration across the SOL is observed, capable of causing a variation of up to 15% of the total input power, in the power deposited on the divertors. Our computational characterization of the SOL plasma with input power 1 MW and lower hybrid current drive, for the separatrix density up to 1019 m-3, indicates that there will be access to high recycling operations producing reduction in the temperature and the peak heat flux at the divertor targets. This indicates that a control of the core plasma density and temperature would be achievable. A power balance analysis done using the kinetic neutral transport code EIRENE indicates about 60%-75% of the total power diverted to the targets, providing quantitative estimates for the relative power loading of the targets and the rest of the plasma facing components.

  17. Thin-film organic photonics molecular layer deposition and applications

    CERN Document Server

    Yoshimura, Tetsuzo

    2011-01-01

    Among the many atomic/molecular assembling techniques used to develop artificial materials, molecular layer deposition (MLD) continues to receive special attention as the next-generation growth technique for organic thin-film materials used in photonics and electronics. Thin-Film Organic Photonics: Molecular Layer Deposition and Applications describes how photonic/electronic properties of thin films can be improved through MLD, which enables precise control of atomic and molecular arrangements to construct a wire network that achieves ""three-dimensional growth"". MLD facilitates dot-by-dot--o

  18. A General Method for Constructing Two-Dimensional Layered Mesoporous Mono- and Binary-Transition-Metal Nitride/Graphene as an Ultra-Efficient Support to Enhance Its Catalytic Activity and Durability for Electrocatalytic Application.

    Science.gov (United States)

    Liu, Baocang; Huo, Lili; Si, Rui; Liu, Jian; Zhang, Jun

    2016-07-27

    We constructed a series of two-dimensional (2D) layered mesoporous mono- and binary-transition-metal nitride/graphene nanocomposites (TMN/G, TM = Ti, Cr, W, Mo, TiCr, TiW, and TiMo) via an efficient and versatile nanocasting strategy for the first time. The 2D layered mesoporous TMN/G is constituted of small TMN nanoparticles composited with graphene nanosheets and has a large surface area with high porosity. Through decoration with well-dispersed Pt nanoparticles, 2D layered mesoporous Pt/TMN/G catalysts can be obtained that display excellent catalytic activity and stability for methanol electro-oxidation reactions (MOR) and oxygen reduction reactions (ORR) in both acidic and alkaline media. The 2D layered mesoporous binary-Pt/TMN/G catalysts possess catalytic activity superior to that of mono-Pt/TMN/G, graphene free Pt/TMN, Pt/G, and Pt/C catalysts. Encouragingly, the 2D layered mesoporous Pt/Ti0.5Cr0.5N/G catalyst exhibits the best electrocatalytic performance for both MOR and ORR. The outstanding electrocatalytic performance of the Pt/Ti0.5Cr0.5N/G catalyst is rooted in its large surface area, high porosity, strong interaction among Pt, Ti0.5Cr0.5N, and graphene, an excellent electron transfer property facilitated by N-doped graphene, and the small size of Pt and Ti0.5Cr0.5N nanocrystals. The outstanding catalytic performance provides the 2D layered mesoporous Pt/Ti0.5Cr0.5N/G catalyst with a wide range of application prospects in direct methanol fuel cells in both acidic and alkaline media. The synthetic method may be available for constructing other 2D layered mesoporous metal nitrides, carbides, and phosphides.

  19. Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals

    Science.gov (United States)

    Carey, Benjamin J.; Ou, Jian Zhen; Clark, Rhiannon M.; Berean, Kyle J.; Zavabeti, Ali; Chesman, Anthony S. R.; Russo, Salvy P.; Lau, Desmond W. M.; Xu, Zai-Quan; Bao, Qiaoliang; Kevehei, Omid; Gibson, Brant C.; Dickey, Michael D.; Kaner, Richard B.; Daeneke, Torben; Kalantar-Zadeh, Kourosh

    2017-02-01

    A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (~1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes.

  20. Hydrogen in magnesium palladium thin layer structures

    OpenAIRE

    Kruijtzer, G. L.

    2008-01-01

    In this thesis, the study of hydrogen storage, absorption and desorption in magnesium layers is described. The magnesium layers have a thickness of 50-500 nm and are covered by a palladium layer which acts as a hydrogen dissociation/association catalyst. The study was preformed under ultra high vacuum conditions to avoid oxygen contamination. The main analysis techniques were RBS, ERD and TDS.

  1. Two-dimensional heterospectral correlation analysis of the redox-induced conformational transition in cytochrome c using surface-enhanced Raman and infrared absorption spectroscopies on a two-layer gold surface.

    Science.gov (United States)

    Zou, Changji; Larisika, Melanie; Nagy, Gabor; Srajer, Johannes; Oostenbrink, Chris; Chen, Xiaodong; Knoll, Wolfgang; Liedberg, Bo; Nowak, Christoph

    2013-08-22

    The heme protein cytochrome c adsorbed to a two-layer gold surface modified with a self-assembled monolayer of 2-mercaptoethanol was analyzed using a two-dimensional (2D) heterospectral correlation analysis that combined surface-enhanced infrared absorption spectroscopy (SEIRAS) and surface-enhanced Raman spectroscopy (SERS). Stepwise increasing electric potentials were applied to alter the redox state of the protein and to induce conformational changes within the protein backbone. We demonstrate herein that 2D heterospectral correlation analysis is a particularly suitable and useful technique for the study of heme-containing proteins as the two spectroscopies address different portions of the protein. Thus, by correlating SERS and SEIRAS data in a 2D plot, we can obtain a deeper understanding of the conformational changes occurring at the redox center and in the supporting protein backbone during the electron transfer process. The correlation analyses are complemented by molecular dynamics calculations to explore the intramolecular interactions.

  2. The effect of the interlayer element on the exfoliation of layered Mo2AC (A = Al, Si, P, Ga, Ge, As or In) MAX phases into two-dimensional Mo2C nanosheets

    Science.gov (United States)

    Khazaei, Mohammad; Arai, Masao; Sasaki, Taizo; Estili, Mehdi; Sakka, Yoshio

    2014-02-01

    The experimental exfoliation of layered, ternary transition-metal carbide and nitride compounds, known as MAX phases, into two-dimensional (2D) nanosheets, is a great development in the synthesis of novel low-dimensional inorganic systems. Among the MAX phases, Mo-containing ones might be considered as the source for obtaining Mo2C nanosheets with potentially unique properties, if they could be exfoliated. Here, by using a set of first-principles calculations, we discuss the effect of the interlayer ‘A’ element on the exfoliation of Mo2AC (A = Al, Si, P, Ga, Ge, As or In) MAX phases into the 2D Mo2C nanosheets. Based on the calculated exfoliation energies and the elastic constants, we propose that Mo2InC with the lowest exfoliation energy and the highest elastic constant anisotropy between C11 and C33 might be a suitable compound for exfoliation into 2D Mo2C nanosheets.

  3. Surface and Interface Engineering of Organometallic and Two Dimensional Semiconductor

    Science.gov (United States)

    Park, Jun Hong

    For over half a century, inorganic Si and III-V materials have led the modern semiconductor industry, expanding to logic transistor and optoelectronic applications. However, these inorganic materials have faced two different fundamental limitations, flexibility for wearable applications and scaling limitation as logic transistors. As a result, the organic and two dimensional have been studied intentionally for various fields. In the present dissertation, three different studies will be presented with followed order; (1) the chemical response of organic semiconductor in NO2 exposure. (2) The surface and stability of WSe2 in ambient air. (3) Deposition of dielectric on two dimensional materials using organometallic seeding layer. The organic molecules rely on the van der Waals interaction during growth of thin films, contrast to covalent bond inorganic semiconductors. Therefore, the morphology and electronic property at surface of organic semiconductor in micro scale is more sensitive to change in gaseous conditions. In addition, metal phthalocyanine, which is one of organic semiconductor materials, change their electronic property as reaction with gaseous analytes, suggesting as potential chemical sensing platforms. In the present part, the growth behavior of metal phthalocyanine and surface response to gaseous condition will be elucidated using scanning tunneling microscopy (STM). In second part, the surface of layered transition metal dichalcogenides and their chemical response to exposure ambient air will be investigated, using STM. Layered transition metal dichalcogenides (TMDs) have attracted widespread attention in the scientific community for electronic device applications because improved electrostatic gate control and suppression of short channel leakage resulted from their atomic thin body. To fabricate the transistor based on TMDs, TMDs should be exposed to ambient conditions, while the effect of air exposure has not been understood fully. In this part

  4. Thin tungsten telluride layer preparation by thermal annealing

    Science.gov (United States)

    Lu, Wei; Zhang, Yudao; Zhu, Zusong; Lai, Jiawei; Zhao, Chuan; Liu, Xuefeng; Liu, Jing; Sun, Dong

    2016-10-01

    We report a simple method to prepare a thin Tungsten Telluride (WTe2) flake with accurate thickness control, which allows preparing and studying this two dimensional material conveniently. First, the WTe2 flake, which is relatively thick due to its strong interlayer van der Waals forces, is obtained by a conventional mechanical exfoliation method. Then, the exfoliated flake is annealed at 600 °C under a constant Ar protecting flow. Raman and atomic force spectroscopy characterizations demonstrate that thermal annealing can effectively thin down the WTe2 flake and retain its original lattice structure, though its surface smoothness is slightly deteriorated. Additionally, systematical study indicates that the thinning process strongly depends on the initial thickness of the WTe2 flake before annealing: the thinning rate increases from 0.12 nm min-1 to 0.36 nm min-1 as the initial thickness increases from 10 nm to 45 nm, while the roughness of the final product also increases with the increase of its initial thickness. However, the method fails when it is applied to WTe2 flakes thicker than 100 nm, resulting in uneven or burnt surface, which is possibly caused by big cavities formed by a large amount of defects gathered at the top surface.

  5. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    of this thesis is on online comprehensive two-dimensional liquid chromatography (online LC×LC) with reverse phase in both dimensions (online RP×RP). Since online RP×RP has not been attempted before within this research group, a significant part of this thesis consists of knowledge and experience gained...

  6. Singular layers for transmission problems in thin shallow shell theory: Elastic junction case

    Science.gov (United States)

    Merabet, Ismail; Chacha, D. A.; Nicaise, Serge

    2010-05-01

    In this Note we study two-dimensional transmission problems for the linear Koiter's model of an elastic multi-structure composed of two thin shallow shells with the same thickness ɛ≪1, in the elastic junction case. We suppose that the loading is singular, that the elastic coefficients are of different order on each part ( O(ɛ) and O(1) respectively) and that the elastic stiffness coefficient of the hinge is k=O(ɛ). The formal limit problem fails to give a solution satisfying all boundary and transmission conditions; it gives only the outer solution. We derive the inner limit problem which allows us to describe the transmission layer.

  7. The spin-wave spectrum of layered magnetic thin films

    Science.gov (United States)

    van Stapele, R. P.; Greidanus, F. J. A. M.; Smits, J. W.

    1985-02-01

    The ferromagnetic resonance spectrum of a layered magnetic thin film is expected to show a number of standing spin-wave resonances with a wavelength that matches the thickness of the film. For the case of perpendicular resonance such spectra were calculated for some typical films in which magnetic layers are alternated with weaker magnetic layers. Some useful approximations are discussed. The results of the calculations are compared with experimental perpendicular spectra measured on films in which fifty Permalloy layers alternate with Ni layers.

  8. NMR of thin layers using a meanderline surface coil

    Science.gov (United States)

    Cowgill, Donald F.

    2001-01-01

    A miniature meanderline sensor coil which extends the capabilities of nuclear magnetic resonance (NMR) to provide analysis of thin planar samples and surface layer geometries. The sensor coil allows standard NMR techniques to be used to examine thin planar (or curved) layers, extending NMRs utility to many problems of modern interest. This technique can be used to examine contact layers, non-destructively depth profile into films, or image multiple layers in a 3-dimensional sense. It lends itself to high resolution NMR techniques of magic angle spinning and thus can be used to examine the bonding and electronic structure in layered materials or to observe the chemistry associated with aging coatings. Coupling this sensor coil technology with an arrangement of small magnets will produce a penetrator probe for remote in-situ chemical analysis of groundwater or contaminant sediments. Alternatively, the sensor coil can be further miniaturized to provide sub-micron depth resolution within thin films or to orthoscopically examine living tissue. This thin-layer NMR technique using a stationary meanderline coil in a series-resonant circuit has been demonstrated and it has been determined that the flat meanderline geometry has about he same detection sensitivity as a solenoidal coil, but is specifically tailored to examine planar material layers, while avoiding signals from the bulk.

  9. 21 CFR 862.2270 - Thin-layer chromatography system for clinical use.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Thin-layer chromatography system for clinical use... Instruments § 862.2270 Thin-layer chromatography system for clinical use. (a) Identification. A thin-layer... a mixture. The mixture of compounds is absorbed onto a stationary phase or thin layer of...

  10. A simplified method for rapid quantification of intracellular nucleoside triphosphates by one-dimensional thin-layer chromatography

    DEFF Research Database (Denmark)

    Jendresen, Christian Bille; Kilstrup, Mogens; Martinussen, Jan

    2011-01-01

    -pyrophosphate (PRPP), and inorganic pyrophosphate (PPi) in cell extracts. The method uses one-dimensional thin-layer chromatography (TLC) and radiolabeled biological samples. Nucleotides are resolved at the level of ionic charge in an optimized acidic ammonium formate and chloride solvent, permitting...... quantification of NTPs. The method is significantly simpler and faster than both current two-dimensional methods and high-performance liquid chromatography (HPLC)-based procedures, allowing a higher throughput while common sources of inaccuracies and technical problems are avoided. For determination of PPi...

  11. A low-power all-optical bistable device based on a liquid crystal layer embedded in thin gold films

    Science.gov (United States)

    Takase, Yuki; Tien Thanh, Pham; Fujimura, Ryushi; Kajikawa, Kotaro

    2014-04-01

    An all-optical bistable (AOB) resonator device composed of a 430-nm-thick liquid crystal (LC) layer embedded in two thin gold films (MLM) is reported in this paper. This device allows the use of the incident illumination at normal incidence, whereas the previous AOB devices based on twisted nematic (TN)-LC function only for illumination at oblique incidence. The fastest switching time was measured to be 1.8 ms, which is significantly faster than that of TN-LC. Because the MLM device operates free from electronic circuits, it is promising for two-dimensional optical data processing, random access optical memories, and spatial light modulators.

  12. Thin film photovoltaic devices with a minimally conductive buffer layer

    Science.gov (United States)

    Barnes, Teresa M.; Burst, James

    2016-11-15

    A thin film photovoltaic device (100) with a tunable, minimally conductive buffer (128) layer is provided. The photovoltaic device (100) may include a back contact (150), a transparent front contact stack (120), and an absorber (140) positioned between the front contact stack (120) and the back contact (150). The front contact stack (120) may include a low resistivity transparent conductive oxide (TCO) layer (124) and a buffer layer (128) that is proximate to the absorber layer (140). The photovoltaic device (100) may also include a window layer (130) between the buffer layer (128) and the absorber (140). In some cases, the buffer layer (128) is minimally conductive, with its resistivity being tunable, and the buffer layer (128) may be formed as an alloy from a host oxide and a high-permittivity oxide. The high-permittivity oxide may further be chosen to have a bandgap greater than the host oxide.

  13. Preparation of Thin Metal Layers on Polymers

    Directory of Open Access Journals (Sweden)

    J. Siegel

    2007-01-01

    Full Text Available Continuous gold layers of increasing thickness were prepared by the vacuum deposition method on pristine and plasma modified sheets of  PE, PET and PTFE. Various surface profiles were obtained. The surface morphology was studied using atomic force microscopy (AFM. The continuity of the metal layer on the polymer surface was validated by measuring its electrical resistance. Changes in the wettability of the plasma treated polymers were evaluated by measuring the aging curves. These were obtained as the dependence of contact angle on ageing time. 

  14. Epitaxy of layered semiconductor thin films

    Science.gov (United States)

    Brahim Otsmane, L.; Emery, J. Y.; Jouanne, M.; Balkanski, M.

    1993-03-01

    Epilayers of InSe on InSe(00.1) and GaSe(00.1) have been grown by the molecular beam epitaxy (MBE) technique. Raman spectroscopy was used for a characterization of the structure and crystallinity in InSe/InSe(00.1) (homoepitaxy) and InSe/GaSe(00.1) (heteroepitaxy). The Raman spectra of the InSe thin films are identical to those of polytype γ-InSe. An activation of the E(LO) mode at 211 cm -1 is observed in these films here. Scanning electron microscopy (SEM) is also used to investigate surfaces of these films.

  15. Two dimensional unstable scar statistics.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)

    2006-12-01

    This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.

  16. Two-Dimensional Vernier Scale

    Science.gov (United States)

    Juday, Richard D.

    1992-01-01

    Modified vernier scale gives accurate two-dimensional coordinates from maps, drawings, or cathode-ray-tube displays. Movable circular overlay rests on fixed rectangular-grid overlay. Pitch of circles nine-tenths that of grid and, for greatest accuracy, radii of circles large compared with pitch of grid. Scale enables user to interpolate between finest divisions of regularly spaced rule simply by observing which mark on auxiliary vernier rule aligns with mark on primary rule.

  17. Atomically thin semiconducting layers and nanomembranes: a review

    Science.gov (United States)

    Dragoman, Mircea; Dragoman, Daniela; Tiginyanu, Ion

    2017-03-01

    This article reviews the main physical properties of atomically thin semiconductors and the electronic devices based on them. We start with graphene, describing its physical properties and growth methods, followed by a discussion of its electronic device applications. Then, transition metal dichalcogenides (TMDs) are analyzed as a prototype of atomically thin semiconductors, their physical properties, growth methods, and electronic devices are discussed in detail. Finally, non-layered semiconducting membranes with thicknesses ranging from a few nanometers to about 50 nm, and considered as counterparts of atomically thin semiconductors, are analyzed, and their applications presented.

  18. Separation of zirconium by thin-layer chromatography.

    Science.gov (United States)

    Oguma, K

    1969-03-01

    The thin-layer Chromatographie separation of a number of metal ions [Sc, Y, Zr, La, Sm, Th, U(VI), etc.] with solvent mixtures of mesityl oxide, ethanol and 5M nitric acid on silica gel-cellulose (5:1) thin-layer plates is reported. Zirconium remains stationary whilst the other metal ions move with the solvent, thus allowing a selective separation of zirconium from about 20 metal ions in ratios ranging from 100:1 to 1:100. Mixtures of various metal ions can also be separated.

  19. Ultra-thin Metal and Dielectric Layers for Nanophotonic Applications

    DEFF Research Database (Denmark)

    Shkondin, Evgeniy; Leandro, Lorenzo; Malureanu, Radu;

    2015-01-01

    In our talk we first give an overview of the various thin films used in the field of nanophotonics. Then we describe our own activity in fabrication and characterization of ultra-thin films of high quality. We particularly focus on uniform gold layers having thicknesses down to 6 nm fabricated by......-beam deposition on dielectric substrates and Al-oxides/Ti-oxides multilayers prepared by atomic layer deposition in high aspect ratio trenches. In the latter case we show more than 1:20 aspect ratio structures can be achieved....

  20. Optimal excitation of two dimensional Holmboe instabilities

    CERN Document Server

    Constantinou, Navid C

    2010-01-01

    Highly stratified shear layers are rendered unstable even at high stratifications by Holmboe instabilities when the density stratification is concentrated in a small region of the shear layer. These instabilities may cause mixing in highly stratified environments. However these instabilities occur in tongues for a limited range of parameters. We perform Generalized Stability analysis of the two dimensional perturbation dynamics of an inviscid Boussinesq stratified shear layer and show that Holmboe instabilities at high Richardson numbers can be excited by their adjoints at amplitudes that are orders of magnitude larger than by introducing initially the unstable mode itself. We also determine the optimal growth that obtains for parameters for which there is no instability. We find that there is potential for large transient growth regardless of whether the background flow is exponentially stable or not and that the characteristic structure of the Holmboe instability asymptotically emerges for parameter values ...

  1. Peculiarities of neutron waveguides with thin Gd layer

    CERN Document Server

    Khaydukov, Yu; Progliado, V; Ustinov, V; Nikitenko, Yu; Keller, T; Aksenov, V; Keimer, B

    2015-01-01

    Peculiarities of the formation of a neutron enhanced standing wave in the structure with a thin highly absorbing layer of gadolinium are considered in the article. An analogue of the poisoning effect well known in reactor physics was found. The effect is stronger for the Nb/Gd/Nb system. Despite of this effect, for a Nb/Gd bilayer and a Nb/Gd/Nb trilayer placed between Al2O3 substrate and Cu layer, it is shown theoretically and experimentally that one order of magnitude enhancement of neutron density is possible in the vicinity of the Gd layer. This enhancement makes it possible to study domain formation in the Gd layer under transition of the Nb layer(s) into the superconducting state (cryptoferromagnetic phase).

  2. ANTIREFLECTION MULTILAYER COATINGS WITH THIN METAL LAYERS

    OpenAIRE

    L. A. Gubanova

    2016-01-01

    The design of anti-reflective coatings for metal surfaces of Al, Ti, N,i Cr is proposed. The coatings have the form of alternating layers of dielectric/metal/dielectric with the number of cells up to15. The method of calculation of such coatings is proposed. We have calculated the coatings of the type [HfO2/Cr/HfO2]15, [ZrO2/Ti/Al2O3]15, [ZrO2/Cr/ZrO2]15. It is shown that the proposed interference coatings provide reduction of the residual reflectance of the metal several times (from 3.5 to 6...

  3. ANTIREFLECTION MULTILAYER COATINGS WITH THIN METAL LAYERS

    Directory of Open Access Journals (Sweden)

    L. A. Gubanova

    2016-03-01

    Full Text Available The design of anti-reflective coatings for metal surfaces of Al, Ti, N,i Cr is proposed. The coatings have the form of alternating layers of dielectric/metal/dielectric with the number of cells up to15. The method of calculation of such coatings is proposed. We have calculated the coatings of the type [HfO2/Cr/HfO2]15, [ZrO2/Ti/Al2O3]15, [ZrO2/Cr/ZrO2]15. It is shown that the proposed interference coatings provide reduction of the residual reflectance of the metal several times (from 3.5 to 6.0 in a wide spectral range (300-1000 nm. The proposed coatings can be recommended as anti-reflective coatings for energy saving solar systems and batteries, and photovoltaic cells.

  4. A Thin Layer Chromatography Laboratory Experiment of Medical Importance

    Science.gov (United States)

    Sharma, Loretta; Desai, Ankur; Sharma, Ajit

    2006-01-01

    A thin layer chromatography experiment of medical importance is described. The experiment involves extraction of lipids from simulated amniotic fluid samples followed by separation, detection, and scanning of the lecithin and sphingomyelin bands on TLC plates. The lecithin-to-sphingomyelin ratio is calculated. The clinical significance of this…

  5. Transparent conducting oxide layers for thin film silicon solar cells

    NARCIS (Netherlands)

    Rath, J.K.|info:eu-repo/dai/nl/304830585; Liu, Y.|info:eu-repo/dai/nl/304831743; de Jong, M.M.|info:eu-repo/dai/nl/325844208; de Wild, J.|info:eu-repo/dai/nl/314641378; Schuttauf, J.A.|info:eu-repo/dai/nl/314118039; Brinza, M.|info:eu-repo/dai/nl/304823325; Schropp, R.E.I.|info:eu-repo/dai/nl/072502584

    2009-01-01

    Texture etching of ZnO:1%Al layers using diluted HCl solution provides excellent TCOs with crater type surface features for the front contact of superstrate type of thin film silicon solar cells. The texture etched ZnO:Al definitely gives superior performance than Asahi SnO2:F TCO in case of nanocry

  6. A Thin Layer Chromatography Laboratory Experiment of Medical Importance

    Science.gov (United States)

    Sharma, Loretta; Desai, Ankur; Sharma, Ajit

    2006-01-01

    A thin layer chromatography experiment of medical importance is described. The experiment involves extraction of lipids from simulated amniotic fluid samples followed by separation, detection, and scanning of the lecithin and sphingomyelin bands on TLC plates. The lecithin-to-sphingomyelin ratio is calculated. The clinical significance of this…

  7. Thin-Layer Chromatography: The "Eyes" of the Organic Chemist

    Science.gov (United States)

    Dickson, Hamilton; Kittredge, Kevin W.; Sarquis, Arlyne

    2004-01-01

    Thin-layer chromatography (TLC) methods are successfully used in many areas of research and development such as clinical medicine, forensic chemistry, biochemistry, and pharmaceutical analysis as TLC is relatively inexpensive and has found widespread application as an easy to use, reliable, and quick analytic tool. The usefulness of TLC in organic…

  8. An Undergraduate Organic Experiment Using Thin-Layer Chromatography.

    Science.gov (United States)

    Jones, Taylor B.; Jones, Tappey H.

    1985-01-01

    The separation of derivatives of aliphatic compounds (2,4-dinitrophenylhydrazones) is used to introduce methods and techniques typically employed in thin layer chromatography and to provide a clear illustration of chromatographic principles in general. Procedures used in the separation are presented. (JN)

  9. Spatial atomic layer deposition of zinc oxide thin films

    NARCIS (Netherlands)

    Illiberi, A.; Roozeboom, F.; Poodt, P.W.G.

    2012-01-01

    Zinc oxide thin films have been deposited at high growth rates (up to ~1 nm/s) by spatial atomic layer deposition technique at atmospheric pressure. Water has been used as oxidant for diethylzinc (DEZ) at deposition temperatures between 75 and 250 °C. The electrical, structural (crystallinity and mo

  10. Thin-Layer Chromatography: The "Eyes" of the Organic Chemist

    Science.gov (United States)

    Dickson, Hamilton; Kittredge, Kevin W.; Sarquis, Arlyne

    2004-01-01

    Thin-layer chromatography (TLC) methods are successfully used in many areas of research and development such as clinical medicine, forensic chemistry, biochemistry, and pharmaceutical analysis as TLC is relatively inexpensive and has found widespread application as an easy to use, reliable, and quick analytic tool. The usefulness of TLC in organic…

  11. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    Two-dimensional liquid chromatography has received increasing interest due to the rise in demand for analysis of complex chemical mixtures. Separation of complex mixtures is hard to achieve as a simple consequence of the sheer number of analytes, as these samples might contain hundreds or even...... dimensions. As a consequence of the conclusions made within this thesis, the research group has, for the time being, decided against further development of online LC×LC systems, since it was not deemed ideal for the intended application, the analysis of the polar fraction of oil. Trap-and...

  12. Layered Organization in the Coastal Ocean: 4-D Assessment of Thin Layer Structure, Dynamics and Impacts

    Science.gov (United States)

    2008-01-01

    Donaghay, in press. Spatial characteristics of thin scattering layers observed by airborn LIDAR. ICES Journal of Marine Systems [in press, refereed...scattering layers observed by airborne LIDAR. ICES Journal of Marine Systems [in press, refereed]. Holliday, D.V., P.L. Donaghay, C.F. Greenlaw, J.M. Napp

  13. The effect of the interlayer element on the exfoliation of layered Mo2AC (A = Al, Si, P, Ga, Ge, As or In MAX phases into two-dimensional Mo2C nanosheets

    Directory of Open Access Journals (Sweden)

    Mohammad Khazaei

    2014-01-01

    Full Text Available The experimental exfoliation of layered, ternary transition-metal carbide and nitride compounds, known as MAX phases, into two-dimensional (2D nanosheets, is a great development in the synthesis of novel low-dimensional inorganic systems. Among the MAX phases, Mo-containing ones might be considered as the source for obtaining Mo2C nanosheets with potentially unique properties, if they could be exfoliated. Here, by using a set of first-principles calculations, we discuss the effect of the interlayer 'A' element on the exfoliation of Mo2AC (A = Al, Si, P, Ga, Ge, As or In MAX phases into the 2D Mo2C nanosheets. Based on the calculated exfoliation energies and the elastic constants, we propose that Mo2InC with the lowest exfoliation energy and the highest elastic constant anisotropy between C11 and C33 might be a suitable compound for exfoliation into 2D Mo2C nanosheets.

  14. Effective material parameter retrieval for thin sheets: theory and application to graphene, thin silver films, and single-layer metamaterials

    CERN Document Server

    Tassin, Philippe; Soukoulis, Costas M; 10.1016/j.physb.2012.01.119

    2012-01-01

    An important tool in the field of metamaterials is the extraction of effective material parameters from simulated or measured scattering parameters of a sample. Here we discuss a retrieval method for thin-film structures that can be approximated by a two-dimensional scattering sheet. We determine the effective sheet conductivity from the scattering parameters and we point out the importance of the magnetic sheet current to avoid an overdetermined inversion problem. Subsequently, we present two applications of the sheet retrieval method. First, we determine the effective sheet conductivity of thin silver films and we compare the resulting conductivities with the sheet conductivity of graphene. Second, we apply the method to a cut-wire metamaterial with an electric dipole resonance. The method is valid for thin-film structures such as two-dimensional metamaterials and frequency-selective surfaces and can be easily generalized for anisotropic or chiral media.

  15. Effective material parameter retrieval for thin sheets: theory and application to graphene, thin silver films, and single-layer metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas

    2012-01-30

    An important tool in the field of metamaterials is the extraction of effective material parameters from simulated or measured scattering parameters of a sample. Here we discuss a retrieval method for thin-film structures that can be approximated by a two-dimensional scattering sheet. We determine the effective sheet conductivity from the scattering parameters and we point out the importance of the magnetic sheet current to avoid an overdetermined inversion problem. Subsequently, we present two applications of the sheet retrieval method. First, we determine the effective sheet conductivity of thin silver films and we compare the resulting conductivities with the sheet conductivity of graphene. Second, we apply the method to a cut-wire metamaterial with an electric dipole resonance. The method is valid for thin-film structures such as two-dimensional metamaterials and frequency-selective surfaces and can be easily generalized for anisotropic or chiral media.

  16. Effective material parameter retrieval for thin sheets: Theory and application to graphene, thin silver films, and single-layer metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Tassin, Philippe, E-mail: tassin@ameslab.gov [Ames Laboratory - U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Koschny, Thomas, E-mail: koschny@ameslab.gov [Ames Laboratory - U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Soukoulis, Costas M., E-mail: soukoulis@ameslab.gov [Ames Laboratory - U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Institute of Electronic Structure and Lasers (IESL), FORTH, 71110 Heraklion, Crete (Greece)

    2012-10-15

    An important tool in the field of metamaterials is the extraction of effective material parameters from simulated or measured scattering parameters of a sample. Here we discuss a retrieval method for thin-film structures that can be approximated by a two-dimensional scattering sheet. We determine the effective sheet conductivity from the scattering parameters and we point out the importance of the magnetic sheet current to avoid an overdetermined inversion problem. Subsequently, we present two applications of the sheet retrieval method. First, we determine the effective sheet conductivity of thin silver films and we compare the resulting conductivities with the sheet conductivity of graphene. Second, we apply the method to a cut-wire metamaterial with an electric dipole resonance. The method is valid for thin-film structures such as two-dimensional metamaterials and frequency-selective surfaces and can be easily generalized for anisotropic or chiral media.

  17. The dynamics of thin vibrated granular layers

    Energy Technology Data Exchange (ETDEWEB)

    Melby, P [Department of Physics, Georgetown University, Washington, DC 20057 (United States); Vega Reyes, F [Department of Physics, Georgetown University, Washington, DC 20057 (United States); Prevost, A [Laboratoire de Physique Statistique de l' Ecole Normale Superieure, CNRS-UMR 8550, 24 rue Lhomond, 75231 Paris cedex 05 (France); Robertson, R [Department of Physics, Georgetown University, Washington, DC 20057 (United States); Kumar, P [Department of Physics, Georgetown University, Washington, DC 20057 (United States); Egolf, D A [Department of Physics, Georgetown University, Washington, DC 20057 (United States); Urbach, J S [Department of Physics, Georgetown University, Washington, DC 20057 (United States)

    2005-06-22

    We describe a series of experiments and computer simulations on vibrated granular media in a geometry chosen to eliminate gravitationally induced settling. The system consists of a collection of identical spherical particles on a horizontal plate vibrating vertically, with or without a confining lid. Previously reported results are reviewed, including the observation of homogeneous, disordered liquid-like states, an instability to a 'collapse' of motionless spheres on a perfect hexagonal lattice, and a fluctuating, hexagonally ordered state. In the presence of a confining lid we see a variety of solid phases at high densities and relatively high vibration amplitudes, several of which are reported for the first time in this article. The phase behaviour of the system is closely related to that observed in confined hard-sphere colloidal suspensions in equilibrium, but with modifications due to the effects of the forcing and dissipation. We also review measurements of velocity distributions, which range from Maxwellian to strongly non-Maxwellian depending on the experimental parameter values. We describe measurements of spatial velocity correlations that show a clear dependence on the mechanism of energy injection. We also report new measurements of the velocity autocorrelation function in the granular layer and show that increased inelasticity leads to enhanced particle self-diffusion.

  18. Two-dimensional capillary origami

    Energy Technology Data Exchange (ETDEWEB)

    Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu

    2016-01-08

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

  19. Quasi-two-dimensional electron gas at the interface of γ-Al{sub 2}O{sub 3}/SrTiO{sub 3} heterostructures grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, Thong Q.; McDaniel, Martin D.; Ekerdt, John G., E-mail: ekerdt@che.utexas.edu [Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States); Goble, Nicholas J.; Gao, Xuan P. A. [Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106 (United States); Posadas, Agham; Kormondy, Kristy J.; Demkov, Alexander A. [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Lu, Sirong [School of Engineering for Matter, Transport and Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Jordan-Sweet, Jean [IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

    2015-09-21

    We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al{sub 2}O{sub 3}/TiO{sub 2}-terminated SrTiO{sub 3} (STO) grown by atomic layer deposition (ALD). The ALD growth of Al{sub 2}O{sub 3} on STO(001) single crystal substrates was performed at temperatures in the range of 200–345 °C. Trimethylaluminum and water were used as co-reactants. In situ reflection high energy electron diffraction, ex situ x-ray diffraction, and ex situ cross-sectional transmission electron microscopy were used to determine the crystallinity of the Al{sub 2}O{sub 3} films. As-deposited Al{sub 2}O{sub 3} films grown above 300 °C were crystalline with the γ-Al{sub 2}O{sub 3} phase. In situ x-ray photoelectron spectroscopy was used to characterize the Al{sub 2}O{sub 3}/STO interface, indicating that a Ti{sup 3+} feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al{sub 2}O{sub 3} at 345 °C and even after the exposure to trimethylaluminum alone at 300 and 345 °C. The interface quasi-2-DEG is metallic and exhibits mobility values of ∼4 and 3000 cm{sup 2} V{sup −1} s{sup −1} at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al{sub 2}O{sub 3} layer. The Ti{sup 3+} signal originated from the near-interfacial region and vanished after annealing in an oxygen environment.

  20. Two-dimensional shape memory graphene oxide

    Science.gov (United States)

    Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe

    2016-06-01

    Driven by the increasing demand for micro-/nano-technologies, stimuli-responsive shape memory materials at nanoscale have recently attracted great research interests. However, by reducing the size of conventional shape memory materials down to approximately nanometre range, the shape memory effect diminishes. Here, using density functional theory calculations, we report the discovery of a shape memory effect in a two-dimensional atomically thin graphene oxide crystal with ordered epoxy groups, namely C8O. A maximum recoverable strain of 14.5% is achieved as a result of reversible phase transition between two intrinsically stable phases. Our calculations conclude co-existence of the two stable phases in a coherent crystal lattice, giving rise to the possibility of constructing multiple temporary shapes in a single material, thus, enabling highly desirable programmability. With an atomic thickness, excellent shape memory mechanical properties and electric field stimulus, the discovery of a two-dimensional shape memory graphene oxide opens a path for the development of exceptional micro-/nano-electromechanical devices.

  1. Thin layer joining by gas adsorption

    Science.gov (United States)

    Taga, Yasunori; Fukumura, Toshio

    2014-10-01

    Attempt has been made to join borosilicate glass and cycloolefin (COP) polymer film by using gas adsorption method. After corona plasma treat, COP was exposed to (3-glycidoxypropyl) trimethoxysilane (GPS) and glass to (3-aminopropyl) triethoxysilane (APS) both in air atmosphere, resulting in co-adsorption of water vapor in the atmosphere and organosilane gases. Surface characterization of plasma treated and gas adsorbed surfaces was carried out by X-ray photoelectron spectroscopy (XPS) using Mg Kα X-ray source. Joining was carried out by a roll laminator after contact of both surfaces at room temperature, followed by annealing at 130 °C for 10 min. Adhesion strength was evaluated by 180 degree peel test based on ASTM D-903 and durability was examined under the conditions of 60 °C and 95% RH. It was found that after plasma treatment, complex functional groups such as Csbnd H, Csbnd O, Cdbnd O, Osbnd Cdbnd O and CO3 were found on COP and Osbnd H on glass. Thickness of GPS gas adsorption layer on COP was evaluated by the XPS to be at least 1.1 nm by taking inelastic mean free path of Si2p photoelectron into consideration. Joining force was found to be more than 5 N/25 mm corresponding to almost equal to COP bulk tensile strength. In addition, durability of this adhesion strength remained unchanged over 2000 h even after exposure to the durability test conditions of 60 °C and 95% RH. The results can be explained in terms of formation of Hsbnd H hydrogen bonding and Sisbnd O covalent bonding via silanols will be made at the interface as a result of lamination and annealing processes. In conclusion, ultrathin joining method by gas adsorption was established by the formation of hydrogen and covalent bonds at the interface by low temperature reaction process.

  2. Laser powder coating by multi-thin-layer technics

    Science.gov (United States)

    Sepold, Gerd; Becker, Reinhard

    1990-10-01

    The laser beam is an interesting tool for production of thin surface layers. The energy input is locally limited thus leading to a snall heat loading of the substrate. The geometric dinensions of the coatings are small as compared to conventional thermal technics like surface melting and coating. In the following the multithin-layer technique is introduced. By this process coatings of small dimensions could be produced. Due to high processing speeds high cooling rates up to lO K/s are achieved by heat conduction into the substrate. This process results in fine microcrystalline structures of the deposit. Using NiCrBSi as coating material it will be shown how and to which extent different parameters influence structure and geometry of the coating. 2. MULTI-THIN-LAYER TECHNIQUE The multi-pass thin layer technique is in principle a powder feed process. Under an oblique angle a powder is blown by an inert gas stream into the laser beam. On their way to the surface the powder particles are partially heated. The surface itself is melted by the laser beam. So a good adherence is ensured between the molten surface and the impinging melting particles. This process can be repeated several times thus forming a coating by a multithinlayer technique see fig. 2. In principle the powder feed process is a well known " thick coating " process for conventional coatings like turbine blades dyes etc. /1/. In this however very small dimensions are desired which may be used for reasons of wear or corrosion resistance or for conductive or insolating layers in micro technics. In this work we investigated the influence of some processing parameters in order to achieve layers or traces of small geometries. 3. MULTIPLE THIN LAYER COATING OF NiCrBSi NiCrBSi had been used as a coating material to produce thin layers or traces. These alloys are hard and wear resistant materials which are usually applied by conventional powder spraying methods followed by arc- or flame-fusing of the sprayed layer

  3. Two-Dimensional Gel Electrophoresis Analyses of pH-Dependent Protein Expression in Facultatively Alkaliphilic Bacillus pseudofirmus OF4 Lead to Characterization of an S-Layer Protein with a Role in Alkaliphily

    Science.gov (United States)

    Gilmour, Raymond; Messner, Paul; Guffanti, Arthur A.; Kent, Rebecca; Scheberl, Andrea; Kendrick, Nancy; Krulwich, Terry Ann

    2000-01-01

    The large majority of proteins of alkaliphilic Bacillus pseudofirmus OF4 grown at pH 7.5 and 10.5, as studied by two-dimensional gel electrophoresis analyses, did not exhibit significant pH-dependent variation. A new surface layer protein (SlpA) was identified in these studies. Although the prominence of some apparent breakdown products of SlpA in gels from pH 10.5-grown cells led to discovery of the alkaliphile S-layer, the largest and major SlpA forms were present in large amounts in gels from pH 7.5-grown cells as well. slpA RNA abundance was, moreover, unchanged by growth pH. SlpA was similar in size to homologues from nonalkaliphiles but contained fewer Arg and Lys residues. An slpA mutant strain (RG21) lacked an exterior S-layer that was identified in the wild type by electron microscopy. Electrophoretic analysis of whole-cell extracts further indicated the absence of a 90-kDa band in the mutant. This band was prominent in wild-type extracts from both pH 7.5- and 10.5-grown cells. The wild type grew with a shorter lag phase than RG21 at either pH 10.5 or 11 and under either Na+-replete or suboptimal Na+ concentrations. The extent of the adaptation deficit increased with pH elevation and suboptimal Na+. By contrast, the mutant grew with a shorter lag and faster growth rate than the wild type at pH 7.5 under Na+-replete and suboptimal Na+ conditions, respectively. Logarithmically growing cells of the two strains exhibited no significant differences in growth rate, cytoplasmic pH regulation, starch utilization, motility, Na+-dependent transport of α-aminoisobutyric acid, or H+-dependent synthesis of ATP. However, the capacity for Na+-dependent pH homeostasis was diminished in RG21 upon a sudden upward shift of external pH from 8.5 to 10.5. The energy cost of retaining the SlpA layer at near-neutral pH is apparently adverse, but the constitutive presence of SlpA enhances the capacity of the extremophile to adjust to high pH. PMID:11029415

  4. Guest-Induced Two-Way Structural Transformation in a Layered Metal-Organic Framework Thin Film.

    Science.gov (United States)

    Haraguchi, Tomoyuki; Otsubo, Kazuya; Sakata, Osami; Fujiwara, Akihiko; Kitagawa, Hiroshi

    2016-12-28

    Fabrication of thin films made of metal-organic frameworks (MOFs) has been intensively pursued for practical applications that use the structural response of MOFs. However, to date, only physisorption-induced structural response has been studied in these films. Chemisorption can be expected to provide a remarkable structural response because of the formation of bonds between guest molecules and reactive metal sites in host MOFs. Here, we report that chemisorption-induced two-way structural transformation in a nanometer-sized MOF thin film. We prepared a two-dimensional layered-type MOF Fe[Pt(CN)4] thin film using a step-by-step approach. Although the as-synthesized film showed poor crystallinity, the dehydrated form of this thin film had a highly oriented crystalline nature (Film-D) as confirmed by synchrotron X-ray diffraction (XRD). Surprisingly, under water and pyridine vapors, Film-D showed chemisorption-induced dynamic structural transformations to Fe(L)2[Pt(CN)4] thin films [L = H2O (Film-H), pyridine (Film-P)], where water and pyridine coordinated to the open Fe(2+) site. Dynamic structural transformations were also confirmed by in situ XRD, sorption measurement, and infrared reflection absorption spectroscopy. This is the first report of chemisorption-induced dynamic structural response in a MOF thin film, and it provides useful insights, which would lead to future practical applications of MOFs utilizing chemisorption-induced structural responses.

  5. Two-dimensional quantum repeaters

    Science.gov (United States)

    Wallnöfer, J.; Zwerger, M.; Muschik, C.; Sangouard, N.; Dür, W.

    2016-11-01

    The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.

  6. Two-dimensional capillary origami

    Science.gov (United States)

    Brubaker, N. D.; Lega, J.

    2016-01-01

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid.

  7. Two-dimensional cubic convolution.

    Science.gov (United States)

    Reichenbach, Stephen E; Geng, Frank

    2003-01-01

    The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.

  8. Thin hybrid pixel assembly fabrication development with backside compensation layer

    Science.gov (United States)

    Bates, R.; Buttar, C.; McMullen, T.; Cunningham, L.; Ashby, J.; Doherty, F.; Pares, G.; Vignoud, L.; Kholti, B.; Vahanen, S.

    2017-02-01

    The ATLAS and CMS experiments will both replace their entire tracking systems for operation at the HL-LHC in 2026. This will include a significantly larger pixel systems, for example, for ATLAS approximately 15 m2. To keep the tracker material budget low it is crucial to minimize the mass of the pixel modules via thinning both the sensor and readout chip to about 150 μm each. The bump yield of thin module assemblies using solder based bump bonding can be problematic due to wafer bowing during solder reflow at high temperature. A new bump-bonding process using backside compensation on the readout chip to address the issue of low yield will be presented. The objective is to compensate dynamically the stress of the front side stack by adding a compensating layer to the backside of the wafer. A SiN and Al:Si stack has been chosen for the backside layer. The bow reducing effect of applying a backside compensation layer will be demonstrated using the FE-I4 wafer. The world's first results from assemblies produced from readout wafers thinned to 100 μm with a stress compensation layer are presented with bond yields close to 100% measured using the FE-I4 readout chip.

  9. Metal Nanoparticle-Decorated Two-Dimensional Molybdenum Sulfide for Plasmonic-Enhanced Polymer Photovoltaic Devices

    Directory of Open Access Journals (Sweden)

    Ming-Kai Chuang

    2015-08-01

    Full Text Available Atomically thin two-dimensional (2D transition metal dichalcogenides have also attracted immense interest because they exhibit appealing electronic, optical and mechanical properties. In this work, we prepared gold nanoparticle-decorated molybdenum sulfide (AuNP@MoS2 through a simple spontaneous redox reaction. Transmission electron microscopy, UV-Vis spectroscopy, and Raman spectroscopy were used to characterize the properties of the AuNP@MoS2 nanomaterials. Then we employed such nanocomposites as the cathode buffer layers of organic photovoltaic devices (OPVs to trigger surface plasmonic resonance, leading to noticeable enhancements in overall device efficiencies. We attribute the primary origin of the improvement in device performance to local field enhancement induced by the effects of localized surface plasmonic resonance. Our results suggest that the metal nanoparticle-decorated two-dimensional materials appear to have great potential for use in high-performance OPVs.

  10. Effect of pirfenidone delivered using layer-by-layer thin film on excisional wound healing.

    Science.gov (United States)

    Mandapalli, Praveen Kumar; Labala, Suman; Bojja, Jagadeesh; Venuganti, Venkata Vamsi Krishna

    2016-02-15

    The aim of this study was to evaluate the effect of a new anti-fibrotic agent, pirfenidone (PFD), delivered using polyelectrolyte multilayer films on excisional wound healing. Polyelectrolyte multilayer films were prepared by layer-by-layer (LbL) sequential adsorption of chitosan and sodium alginate. The UV-spectrophotometer, FTIR and differential scanning calorimeter were used to characterize the LbL thin films. The PFD was entrapped within the LbL thin films and its effect on excisional wound healing was studied in C57BL/6. The total protein, collagen content and TGF-β expression within the wound tissue were determined after application of PFD using LbL thin films, chitosan hydrogel and polyethylene glycol hydrogel. UV-spectrophotometer and FTIR studies showed a sequential adsorption of chitosan and alginate polymer layers to form LbL thin films. The thickness of LbL thin films with 15 bilayers was found to be 15 ± 2 μm. HPLC analysis showed a PFD loading efficiency of 1.0 ± 0.1mg in 1cm(2) area of LbL thin film. In vivo wound healing studies in C57BL/6 mice showed an accelerated (healing.

  11. A new one-dimensional Cd(II) coordination polymer with a two-dimensional layered structure incorporating 2-[(1H-imidazol-1-yl)methyl]-1H-benzimidazole and benzene-1,2-dicarboxylate ligands.

    Science.gov (United States)

    Huang, Qiu Ying; Lin, Xiao Yi; Meng, Xiang Ru

    2016-06-01

    The N-heterocyclic ligand 2-[(1H-imidazol-1-yl)methyl]-1H-benzimidazole (imb) has a rich variety of coordination modes and can lead to polymers with intriguing structures and interesting properties. In the coordination polymer catena-poly[[cadmium(II)-bis[μ-benzene-1,2-dicarboxylato-κ(4)O(1),O(1'):O(2),O(2')]-cadmium(II)-bis{μ-2-[(1H-imidazol-1-yl)methyl]-1H-benzimidazole}-κ(2)N(2):N(3);κ(2)N(3):N(2)] dimethylformamide disolvate], {[Cd(C8H4O4)(C11H10N4)]·C3H7NO}n, (I), each Cd(II) ion exhibits an irregular octahedral CdO4N2 coordination geometry and is coordinated by four O atoms from two symmetry-related benzene-1,2-dicarboxylate (1,2-bdic(2-)) ligands and two N atoms from two symmetry-related imb ligands. Two Cd(II) ions are connected by two benzene-1,2-dicarboxylate ligands to generate a binuclear [Cd2(1,2-bdic)2] unit. The binuclear units are further connected into a one-dimensional chain by pairs of bridging imb ligands. These one-dimensional chains are further connected through N-H...O hydrogen bonds and π-π interactions, leading to a two-dimensional layered structure. The dimethylformamide solvent molecules are organized in dimeric pairs via weak interactions. In addition, the title polymer exhibits good fluorescence properties in the solid state at room temperature.

  12. The Theoretical Investigation and Analysis of High-Performance ZnO Double-Gate Double-Layer Insulator Thin-Film Transistors

    Institute of Scientific and Technical Information of China (English)

    GAO Hai-Xia; HU Rong; YANG Yin-Tang

    2012-01-01

    A novel structure of a ZnO thin-film transistor with a double-gate and double-layer insulator is proposed to improve device performance.Compared with the conventional ZnO thin-film transistor structure,the novel thinfilm transistor has a higher on-state current,steeper sub-threshold characteristics and a lower threshold voltage,owing to the double-gate and high-k dielectric.Based on two-dimensional simulation,the potential channel distribution and the reasons for the improvement in performance are investigated.%A novei structure of a ZnO thin-film transistor with a double-gate and double-layer insulator is proposed to improve device performance. Compared with the conventional ZnO thin-Rim transistor structure, the novel thin-Sim transistor has a higher on-state current, steeper sub-threshold characteristics and a lower threshold voltage, owing to the double-gate and high-k dielectric. Based on two-dimensional simulation, the potential channel distribution and the reasons for the improvement in performance are investigated.

  13. Dislocation climb in two-dimensional discrete dislocation dynamics

    NARCIS (Netherlands)

    Davoudi, K.M.; Nicola, L.; Vlassak, J.J.

    2012-01-01

    In this paper, dislocation climb is incorporated in a two-dimensional discrete dislocation dynamics model. Calculations are carried out for polycrystalline thin films, passivated on one or both surfaces. Climb allows dislocations to escape from dislocation pile-ups and reduces the strain-hardening r

  14. Thin layer laser bonding using spin-on-glass materials

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Joohan [Department of Mechanical Engineering, Seoul National University of Technology, Seoul, Zip: 139-743 (Korea, Republic of)], E-mail: joohankim@snut.ac.kr; Kim, Hyangtae [Department of Mechanical Engineering, Seoul National University of Technology, Seoul, Zip: 139-743 (Korea, Republic of); Lee, Jae-Hoon [Korea Institute of Machinery and Materials, Daejun, Zip: 305-343 (Korea, Republic of)

    2008-08-30

    We developed and characterized a new laser bonding process with a nano adhesive layer for transparent materials. The adhesive is spin-coated on a glass substrate and cured locally with a focused laser beam. The minimum viscosity of the adhesive is very low, so that a thin layer only a few hundred nanometers thick can be coated on a cover substrate. Laser irradiation from a Nd:YAG laser system with a wavelength of 1064 nm is employed as the curing source for the localized nano layer bonding process. The measured thickness of the bonding layer is in the range of 400 nm to 3 {mu}m. This process can be applied to the nano or micro bonding of various transparent systems such as flat panel displays, biochips, and heat-sensitive microelectronics. We present experimental results and discuss the process characteristics.

  15. Thin-Layer Drying Characteristics and Modeling of Chinese Jujubes

    Directory of Open Access Journals (Sweden)

    Xiao-Kang Yi

    2012-01-01

    Full Text Available A mathematical modeling of thin-layer drying of jujubes in a convective dryer was established under controlled conditions of temperature and velocity. The drying process took place both in the accelerating rate and falling rate period. We observed that higher temperature reduced the drying time, indicating higher drying rates of jujubes. The experimental drying data of jujubes were used to fit ten different thin-layer models, then drying rate constants and coefficients of models tested were determined by nonlinear regression analysis using the Statistical Computer Program. As for all the drying models, the Weibull distribution model was superior and best predicted the experimental values. Therefore, this model can be used to facilitate dryer design and promote efficient dryer operation by simulation and optimization of the drying processes. The volumetric shrinkable coefficient of jujubes decreased as the drying air temperature increased.

  16. Investigation of multi-layer thin films for energy storage.

    Energy Technology Data Exchange (ETDEWEB)

    Renk, Timothy Jerome; Monson, Todd

    2009-01-01

    We investigate here the feasibility of increasing the energy density of thin-film capacitors by construction of a multi-layer capacitor device through ablation and redeposition of the capacitor materials using a high-power pulsed ion beam. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laboratories. The dielectric capacitor filler material was a composition of Lead-Lanthanum-Zirconium-Titanium oxide (PLZT). The energy storage can be increased by using material of intrinsically high dielectric constant, and constructing many thin layers of this material. For successful device construction, there are a number of challenging requirements including correct stoichiometric and crystallographic composition of the deposited PLZT. This report details some success in satisfying these requirements, even though the attempt at device manufacture was unsuccessful. The conclusion that 900 C temperatures are necessary to reconstitute the deposited PLZT has implications for future manufacturing capability.

  17. Transmittance jump in a thin aluminium layer during laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Bykovsky, N E; Senatsky, Yu V [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Pershin, S M; Samokhin, A A [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2016-02-28

    A jump in the transmittance (from ∼0.1% to ∼50% for ∼1 ns) of an optical gate on a Mylar film (a thin aluminium layer on a Lavsan substrate) irradiated by nanosecond (10{sup -7} – 10{sup -8} s) pulses of a neodymium laser with an intensity up to 0.1 GW cm{sup -2} has been recorded. The mechanism of a fast (10{sup -10} – 10{sup -11} s) increase in the transmittance of the aluminium layer upon its overheating (without boiling) to the metal – insulator phase-transition temperature is discussed. (interaction of laser radiation with matter. laser plasma)

  18. Numerical simulation of thin layer coffee drying by control volumes

    OpenAIRE

    CIRO-VELÁSQUEZ, HÉCTOR J.; ABUD-CANO, LUIS C.; PÉREZ-ALEGRÍA, LUIS. R.

    2011-01-01

    The thin layer drying model proposed by Sokhansanj and Bruce (1987) was implemented to model the drying process of parchment coffee beans. A computational model based on a control volume approach was developed to simulate the drying process of parchment coffee. A one dimensional transient analysis was implemented in the radial direction applied to a spherical coffee bean of equivalent radius. The results found that, even though the numerical value for the mass transfer coefficient is a small ...

  19. Metal-Organic Frameworks for Thin-Layer Chromatographic Applications.

    Science.gov (United States)

    Schenk, Claudia; Kutzscher, Christel; Drache, Franziska; Helten, Stella; Senkovska, Irena; Kaskel, Stefan

    2017-01-25

    Preparation of thin-layer chromatographic (TLC) plates based on metal-organic frameworks (MOFs) as porous stationary phases is described. DUT-67 (DUT = Dresden University of Technology), a zirconium based MOF, was used in combination with a fluorescent indicator as stationary phase for analyzing a small selection of a wide spectrum of relevant analytes. The successful separation of benzaldehyde from trans-cinnamaldehyde and 4-aminophenol from 2-aminotoluene is reported as a model system using optimized eluent mixtures containing acetic acid.

  20. LOCO: Characterization of Phytoplankton in Thin Optical Layers

    Science.gov (United States)

    2008-01-01

    this process is that compatible gametes must be successful in finding each other in a dilute, watery environment. We have hypothesized that the...close proximity of cells in a dense thin layer should facilitate this process. Consistent with these ideas, male gamete formation, as well as auxospores...various stages of male gamete formation. CytoSense Evaluation. Our CytoSense scanning, in-line flow cytometer was specifically designed to study the

  1. Ultra-thin, single-layer polarization rotator

    Energy Technology Data Exchange (ETDEWEB)

    Son, T. V.; Truong, V. V., E-mail: Truong.Vo-Van@Concordia.Ca [Department of Physics, Concordia University, Montreal, Quebec, H4B 1R6 (Canada); Do, P. A.; Haché, A. [Département de Physique et d’Astronomie, Université de Moncton, Moncton, New Brunswick, E1A 3E9 (Canada)

    2016-08-15

    We demonstrate light polarization control over a broad spectral range by a uniform layer of vanadium dioxide as it undergoes a phase transition from insulator to metal. Changes in refractive indices create unequal phase shifts on s- and p-polarization components of incident light, and rotation of linear polarization shows intensity modulation by a factor of 10{sup 3} when transmitted through polarizers. This makes possible polarization rotation devices as thin as 50 nm that would be activated thermally, optically or electrically.

  2. Characterizing Mixing in a Quasi-Two-Dimensional Flow using Persistent Homology

    Science.gov (United States)

    Tithof, Jeffrey; Kelley, Douglas

    2016-11-01

    Fluid mixing is a tremendously important phenomenon present in numerous physical systems, both natural and human-made. Describing, understanding, and predicting the mixing behavior of fluid flows poses an immense challenge. In this work, we explore the utility of topological data analysis in quantifying fluid mixing. We analyze Eulerian and Lagrangian quantities obtained from a quasi-two-dimensional flow realized by driving a thin layer of fluid with electromagnetic forces. Our analysis employs persistent homology, which offers a unique framework for quantifying topological features associated with connectivity in the fluid flow. Preliminary results suggest that this topological approach offers new physical insight, complementing existing methods for quantifying fluid mixing.

  3. Characterization of metal contacts for two-dimensional MoS{sub 2} nanoflakes

    Energy Technology Data Exchange (ETDEWEB)

    Walia, Sumeet, E-mail: madhu.bhaskaran@rmit.edu.au, E-mail: kourosh.kalantar@rmit.edu.au, E-mail: sumeet.walia@rmit.edu.au; Balendhran, Sivacarendran; Sriram, Sharath; Bhaskaran, Madhu, E-mail: madhu.bhaskaran@rmit.edu.au, E-mail: kourosh.kalantar@rmit.edu.au, E-mail: sumeet.walia@rmit.edu.au [Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Victoria 3000 (Australia); School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3000 (Australia); Wang, Yichao; Ab Kadir, Rosmalini; Sabirin Zoolfakar, Ahmad; Atkin, Paul; Zhen Ou, Jian; Kalantar-zadeh, Kourosh, E-mail: madhu.bhaskaran@rmit.edu.au, E-mail: kourosh.kalantar@rmit.edu.au, E-mail: sumeet.walia@rmit.edu.au [School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria 3000 (Australia)

    2013-12-02

    While layered materials are increasingly investigated for their potential in nanoelectronics, their functionality and efficiency depend on charge injection into the materials via metallic contacts. This work explores the characteristics of different metals (aluminium, tungsten, gold, and platinum) deposited on to nanostructured thin films made of two-dimensional (2D) MoS{sub 2} flakes. Metals are chosen based on their work functions relative to the electron affinity of MoS{sub 2}. It is observed, and analytically verified that lower work functions of the contact metals lead to smaller Schottky barrier heights and consequently higher charge carrier injection through the contacts.

  4. Specimen charging on thin films with one conducting layer:Discussion of physical principles

    Energy Technology Data Exchange (ETDEWEB)

    Glaeser, Robert M.; Downing, Kenneth H.

    2003-04-15

    While the most familiar consequences of specimen charging in transmission electron microscopy can be eliminated by evaporating a thin conducting film (such as a carbon film) onto an insulating specimen, or by preparing samples directly on such a conducting film to begin with, a more subtle charging effect still remains. We argue here that specimen charging is in this case likely to produce a dipole sheet rather than a layer of positive charge at the surface of the specimen. A simple model of the factors that control the kinetics of specimen charging, and its neutralization, is discussed as a guide for experiments that attempt to minimize the amount of specimen charging. Believable estimates of the electrostatic forces and the electron optical disturbances that are likely to occur suggest that specimen bending and warping may have the biggest impact on degrading the image quality at high resolution. Electron optical effects are likely to be negligible except in the case of a specimen that is tilted to high angle. A model is proposed to explain how both the mechanical and electron-optical effects of forming a dipole layer would have much greater impact on the image resolution in a direction perpendicular to the tilt axis, a well-known effect in electron microscopy of two-dimensional crystals.

  5. The collective motion of nematodes in a thin liquid layer

    CERN Document Server

    Gart, Sean; Jung, Sunghwan

    2010-01-01

    Many organisms live in confined fluidic environments such as the thin liquid layers on the skin of host organisms or in partially- saturated soil. We investigate the collective behaviour of nematodes in a thin liquid layer, which was first observed by Gray and Lissmann, [J. Exp. Biol. 41, 135 (1964)]. We show experimentally that nematodes confined by a thin liquid film come into contact and only separate again after some intervention. We attribute this collective motion to an attractive force between them arising from the surface tension of the layer and show that for nearby nematodes this force is typically stronger than the force that may be exerted by the nematodes' muscles. We believe this to be the first demonstration of the "Cheerios effect" acting on a living organism. However, we find that being grouped together does not significantly alter the body stroke and kinematic performance of the nematode: there are no statistically significant changes of the Strouhal number and the ratio of amplitude to wave...

  6. Spray Layer-by-Layer Assembled Clay Composite Thin Films as Selective Layers in Reverse Osmosis Membranes.

    Science.gov (United States)

    Kovacs, Jason R; Liu, Chaoyang; Hammond, Paula T

    2015-06-24

    Spray layer-by-layer assembled thin films containing laponite (LAP) clay exhibit effective salt barrier and water permeability properties when applied as selective layers in reverse osmosis (RO) membranes. Negatively charged LAP platelets were layered with poly(diallyldimethylammonium) (PDAC), poly(allylamine) (PAH), and poly(acrylic acid) (PAA) in bilayer and tetralayer film architectures to generate uniform films on the order of 100 nm thick that bridge a porous poly(ether sulfone) support to form novel RO membranes. Nanostructures were formed of clay layers intercalated in a polymeric matrix that introduced size-exclusion transport mechanisms into the selective layer. Thermal cross-linking of the polymeric matrix was used to increase the mechanical stability of the films and improve salt rejection by constraining swelling during operation. Maximum salt rejection of 89% was observed for the tetralayer film architecture, with an order of magnitude increase in water permeability compared to commercially available TFC-HR membranes. These clay composite thin films could serve as a high-flux alternative to current polymeric RO membranes for wastewater and brackish water treatment as well as potentially for forward osmosis applications. In general, we illustrate that by investigating the composite systems accessed using alternating layer-by-layer assembly in conjunction with complementary covalent cross-linking, it is possible to design thin film membranes with tunable transport properties for water purification applications.

  7. Synthesis and structure of two-dimensional transition-metal dichalcogenides

    KAUST Repository

    Shi, Yumeng

    2015-07-13

    Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) exhibit unique electrical, optical, thermal, and mechanical properties, which enable them to be used as building blocks in compact and lightweight integrated electronic systems. The controllable and reliable synthesis of atomically thin TMDCs is essential for their practical application. Recent progress in large-area synthesis of monolayer TMDCs paves the way for practical production of various 2D TMDC layers. The intrinsic optical and electrical properties of monolayer TMDCs can be defined by stoichiometry during synthesis. By manipulating the lattice structure or layer stacking manner, it is possible to create atomically thin van der Waals materials with unique and unexplored physical properties. In this article, we review recent developments in the synthesis of TMDC monolayers, alloys, and heterostructures, which shine light on the design of novel TMDCs with desired functional properties.

  8. Classifying Two-dimensional Hyporeductive Triple Algebras

    CERN Document Server

    Issa, A Nourou

    2010-01-01

    Two-dimensional real hyporeductive triple algebras (h.t.a.) are investigated. A classification of such algebras is presented. As a consequence, a classification of two-dimensional real Lie triple algebras (i.e. generalized Lie triple systems) and two-dimensional real Bol algebras is given.

  9. A two-dimensional polymer prepared by organic synthesis.

    Science.gov (United States)

    Kissel, Patrick; Erni, Rolf; Schweizer, W Bernd; Rossell, Marta D; King, Benjamin T; Bauer, Thomas; Götzinger, Stephan; Schlüter, A Dieter; Sakamoto, Junji

    2012-02-05

    Synthetic polymers are widely used materials, as attested by a production of more than 200 millions of tons per year, and are typically composed of linear repeat units. They may also be branched or irregularly crosslinked. Here, we introduce a two-dimensional polymer with internal periodicity composed of areal repeat units. This is an extension of Staudinger's polymerization concept (to form macromolecules by covalently linking repeat units together), but in two dimensions. A well-known example of such a two-dimensional polymer is graphene, but its thermolytic synthesis precludes molecular design on demand. Here, we have rationally synthesized an ordered, non-equilibrium two-dimensional polymer far beyond molecular dimensions. The procedure includes the crystallization of a specifically designed photoreactive monomer into a layered structure, a photo-polymerization step within the crystal and a solvent-induced delamination step that isolates individual two-dimensional polymers as free-standing, monolayered molecular sheets.

  10. Thin-layer chromatography analysis and scavenging activity of marigold (Calendula officinalis L extracts

    Directory of Open Access Journals (Sweden)

    Ćetković Gordana S.

    2003-01-01

    Full Text Available The methanol, petroleum ether, chloroform, ethyl acetate, n-butanol and water extracts were obtained by extraction of marigold flower (Calendula officinalis L. The content of total phenolic compounds, determined by UV spectrophotometric method using the Folin-Ciocalteu reagent, was 15.12 mg/g. The content of total flavonoids, determined by UV spectrophotometric method according to Markham, was 5.13 mg/g. Qualitative determination of phenolic compounds in the extracts was performed by one- and two-dimensional thin-layer chromatography (TLC procedures. The results of one- and two-dimensional TLC analyses showed that different flavonoids and phenolic acids were present in the investigated extracts. The greatest number of flavonoids (rutin, quercetin and some unidentified flavonoid glycosides and phenolic acids (chlorogenic, caffeic, coumaric and vanillic acid were deteminated in methanol extract. The influence of marigold extracts, in concentration range 0.6-1.2 mg/mL, on 2,2’-diphenyl-1-picrylhydrazyl (DPPH free radicals was investigated by electron spin resonance (ESR spectroscopy. All extracts showed scavenging activity (SA in the following order: ethyl acetate > n-butanol > methanol > water > chloroform > petroleum ether. The SA increased with increasing concentration of extracts. The ethyl acetate and n-butanol extracts exibited the most significant SA. These extracts in concentration of 1.2 mg/mL eliminated completely DPPH radicals. The lowest SA had chloroform and petroleum ether extracts (in concentration of 0.6 mg/mL SA=0%. The SA of marigold extracts is attributed to its hydrogen-donating ability and scavenging effect.

  11. Measured Two-Dimensional Ice-Wedge Polygon Thermal Dynamics

    Science.gov (United States)

    Cable, William; Romanovsky, Vladimir; Busey, Robert

    2016-04-01

    necessarily found in areas of higher MAGT. Active layer thickness does not appear to be correlated to mean annual air temperature but rather is a function of summer air temperature or thawing degree-days. While the refreezing of the active layer initiated at nearly the same time for all locations and polygons, we find differences in the proportion of top-down versus bottom-up freezing and the length of time required to complete the refreezing process. Examination of the daily temperature dynamics using interpolated two-dimensional temperature fields reveal that during the summer, the predominate temperature gradient is vertical while the isotherms tend to follow the topography. However, as the active layer begins to refreeze and snow accumulates, the thermal regime diverges. The fall shows an increased temperature gradient horizontally with landscape positions containing higher soil moisture and/or snow depth (low centers and troughs) cooling more slowly than the adjacent ground (rims and high centers). This two-dimensional effect is greatest as the active layer refreezes and persists until mid-winter, by which time the temperature gradients are again mostly vertical and the isotherms follow the topography. Our findings demonstrate the complexity and two-dimensionality of the temperature dynamics in these landscapes.

  12. Infrared analysis of thin layers by attenuated total reflection spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rochat, N.; Chabli, A.; Bertin, F.; Vergnaud, C.; Mur, P.; Petitdidier, S.; Besson, P

    2003-09-15

    Interests in infrared spectroscopy (IRS) have been stimulated by the increasing need for non-destructive surface characterization providing structural and chemical informations about the new materials used in microelectronic devices. Standard infrared spectroscopy of thin layers is limited because of its lack of sensitivity. The use of optical configurations such as the attenuated total reflection (ATR) allows to characterize nanometric layers. This paper will present the results of a study conducted for a better understanding of the capabilities and limitations of this technique. A theoretical analysis based on a perturbation method is used to elucidate the results of ATR measurements performed on silicon oxide layers of different thickness on silicon substrates. This analysis shows that the absorbance ATR spectrum in p polarization is the image of the layer energy loss function, under specific conditions. The exact ATR spectrum simulation using a matrix formalism showed that the straightforward interpretation in terms of the layer dielectric function is limited to a very narrow layer thickness range. The fitting process of the ATR spectrum is evaluated for the interpretation of experimental spectra obtained for the growth of chemical silicon oxide layers.

  13. Two-dimensional function photonic crystals

    CERN Document Server

    Wu, Xiang-Yao; Liu, Xiao-Jing; Liang, Yu

    2016-01-01

    In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed into the appropriate band gaps structures by the two-dimensional function photonic crystals.

  14. Two-dimensional superconductors with atomic-scale thickness

    Science.gov (United States)

    Uchihashi, Takashi

    2017-01-01

    Recent progress in two-dimensional superconductors with atomic-scale thickness is reviewed mainly from the experimental point of view. The superconducting systems treated here involve a variety of materials and forms: elemental metal ultrathin films and atomic layers on semiconductor surfaces; interfaces and superlattices of heterostructures made of cuprates, perovskite oxides, and rare-earth metal heavy-fermion compounds; interfaces of electric-double-layer transistors; graphene and atomic sheets of transition metal dichalcogenide; iron selenide and organic conductors on oxide and metal surfaces, respectively. Unique phenomena arising from the ultimate two dimensionality of the system and the physics behind them are discussed.

  15. Reflection of infrared radiation from thin aluminium layers

    CERN Document Server

    Calatroni, Sergio

    2001-01-01

    The thermal shielding of the LHC magnets cryostats will make use of Multi-Layer Insulation. This is a sandwich of several Mylar (polyester) foils 6 µm thick coated with a thin film of aluminium, having a thickness of some 30 nm. The thickness of the aluminium film must be kept at a minimum to minimise lateral thermal conduction. The outer layer of this sandwich stays at a temperature of 20 K or below, and receives IR radiation from surfaces at 77 K (wavelength of 37.6 µm at the peak of blackbody radiation), which should be reflected with the highest efficiency. The minimum thickness for the aluminium layer to avoid transmission of the radiation can be calculated by making use of the skin effect theory, taking into account the changes in electrical properties that are due to the extremely low thickness of the film.

  16. Thermomagnetic writing in thin Co/Pt layered structures

    Science.gov (United States)

    Greidanus, F. J. A. M.; Zeper, W. B.; den Broeder, F. J. A.; Godlieb, W. F.; Carcia, P. F.

    1989-06-01

    In this letter we demonstrate thermomagnetic writing in a Co/Pt thin-film layered structure or multilayer: 25×(4.1 Å Co+19 Å Pt). This film exhibits perpendicular magnetic anisotropy, 100% remanence, and a coercive field of 76 kA/m at room temperature. The coercive field is a strong function of temperature and decreases to zero at 250 °C. In this layered film regular domains can be written with low applied fields (below 50 kA/m) and the writing threshold is about 4 mW. Their good magnetic and magneto-optical properties together with their high corrosion resistance make these layers promising candidates for magneto-optical recording.

  17. Fracture Patterns Induced by Desiccation in a Thin Layer

    CERN Document Server

    Kitsunezaki, S

    1999-01-01

    We study a theoretical model of mud cracks, that is, the fracture patterns resulting from the contraction with drying in a thin layer of a mixture of granules and water. In this model, we consider the slip on the bottom of this layer and the relaxation of the elastic field that represents deformation of the layer. Analysis of the one-dimensional model gives results for the crack size that are consistent with experiments. We propose an analytical method of estimation for the growth velocity of a simple straight crack to explain the very slow propagation observed in actual experiments. Numerical simulations reveal the dependence of qualitative nature of the formation of crack patterns on material properties.

  18. Properties of Ultra-Thin Hafnium Oxide and Interfacial Layer Deposited by Atomic Layer Deposition

    Institute of Scientific and Technical Information of China (English)

    Taeho Lee; Young-Bae Kim; Kyung-Il Hong; Duck-Kyun Choi; Jinho Ahn

    2004-01-01

    Ultra-thin hafnium-oxide gate dielectric films deposited by atomic layer deposition technique using HfCl4 and H2O precursor on a hydrogen-terminated Si substrate were investigated. X-ray photoelectron spectroscopy indicates that the interface layer is Hf-silicate rather than phase separated Hf-silicide and silicon oxide structure. The Hf-silicate interfacial layer partially changes into SiOx after high temperature annealing, resulting in a complex HfO2-silicate-SiOx dielectric structure. Electrical measurements confirms that HfO2 on Si is stable up to 700 ℃ for 30 s under N2 ambient.

  19. Effects of different wetting layers on the growth of smooth ultra-thin silver thin films

    Science.gov (United States)

    Ni, Chuan; Shah, Piyush; Sarangan, Andrew M.

    2014-09-01

    Ultrathin silver films (thickness below 10 nm) are of great interest as optical coatings on windows and plasmonic devices. However, producing these films has been a continuing challenge because of their tendency to form clusters or islands rather than smooth contiguous thin films. In this work we have studied the effect of Cu, Ge and ZnS as wetting layers (1.0 nm) to achieve ultrasmooth thin silver films. The silver films (5 nm) were grown by RF sputter deposition on silicon and glass substrates using a few monolayers of the different wetting materials. SEM imaging was used to characterize the surface properties such as island formation and roughness. Also the optical properties were measured to identify the optical impact of the different wetting layers. Finally, a multi-layer silver based structure is designed and fabricated, and its performance is evaluated. The comparison between the samples with different wetting layers show that the designs with wetting layers which have similar optical properties to silver produce the best overall performance. In the absence of a wetting layer, the measured optical spectra show a significant departure from the model predictions, which we attribute primarily to the formation of clusters.

  20. Growth and electronic properties of two-dimensional systems on (110) oriented GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, F.

    2005-07-01

    As the only non-polar plane the (110) surface has a unique role in GaAs. Together with Silicon as a dopant it is an important substrate orientation for the growth of n-type or p-type heterostructures. As a consequence, this thesis will concentrate on growth and research on that surface. In the course of this work we were able to realize two-dimensional electron systems with the highest mobilities reported so far on this orientation. Therefore, we review the necessary growth conditions and the accompanying molecular process. The two-dimensional electron systems allowed the study of a new, intriguing transport anisotropy not explained by current theory. Moreover, we were the first growing a two-dimensional hole gas on (110) GaAs with Si as dopant. For this purpose we invented a new growth modulation technique necessary to retrieve high mobility systems. In addition, we discovered and studied the metal-insulator transition in thin bulk p-type layers on (110) GaAs. Besides we investigated the activation process related to the conduction in the valence band and a parallelly conducting hopping band. The new two-dimensional hole gases revealed interesting physics. We studied the zero B-field spin splitting in these systems and compared it with the known theory. Furthermore, we investigated the anisotropy of the mobility. As opposed to the expectations we observed a strong persistent photoconductivity in our samples. Landau levels for two dimensional hole systems are non-linear and can show anticrossings. For the first time we were able to resolve anticrossings in a transport experiment and study the corresponding activation process. Finally, we compared these striking results with theoretical calculations. (orig.)

  1. Two approaches for enhancing the hydrogenation properties of palladium: Metal nanoparticle and thin film over layers

    Indian Academy of Sciences (India)

    Manika Khanuja; B R Mehta; S M Shivaprasad

    2008-11-01

    In the present study, two approaches have been used for enhancing the hydrogenation properties of Pd. In the first approach, metal thin film (Cu, Ag) has been deposited over Pd and hydrogenation properties of bimetal layer Cu (thin film)/Pd(thin film) and Ag(thin film)/Pd(thin film) have been studied. In the second approach, Ag metal nanoparticles have been deposited over Pd and hydrogenation properties of Ag (nanoparticle)/Pd (thin film) have been studied and compared with Ag(thin film)/Pd(thin film) bimetal layer system. The observed hydrogen sensing response is stable and reversible over a number of hydrogen loading and deloading cycles in both bimetallic systems. Alloying between Ag and Pd is suppressed in case of Ag(nanoparticle)/Pd(thin film) bimetallic layer on annealing as compared to Ag (thin film)/Pd(thin film).

  2. Two-dimensional recrystallisation processes of nanometric vanadium oxide thin films grown by atomic layer chemical vapor deposition (ALCVD) evidenced by AFM

    Energy Technology Data Exchange (ETDEWEB)

    Groult, H. [Laboratoire Liquides Ioniques et Interfaces Chargees (CNRS-UMR 7612), Universite P and M Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France)]. E-mail: groult@ccr.jussieu.fr; Balnois, E. [Laboratoire Liquides Ioniques et Interfaces Chargees (CNRS-UMR 7612), Universite P and M Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Laboratoire Polymeres, Proprietes aux Interfaces et Composites, Universite de Bretagne Sud, rue de St. Maude, BP92116, 56321 Lorient Cedex (France); Mantoux, A. [Laboratoire Liquides Ioniques et Interfaces Chargees (CNRS-UMR 7612), Universite P and M Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Le Van, K. [Laboratoire Liquides Ioniques et Interfaces Chargees (CNRS-UMR 7612), Universite P and M Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Lincot, D. [Laboratoire d' Electrochimie et de Chimie Analytique (UMR CNRS 7575), ENSCP, 11 rue P and M Curie, 75231 Paris Cedex 05 (France)

    2006-06-15

    The influence of thermal annealing on the morphology and structure of nanometer range thickness vanadium oxide films deposited by ALCVD on silicon substrate was investigated by AFM. The appearance of crystalline centres with typical rectangular V{sub 2}O{sub 5} plates was clearly observed from 400 deg. C. Furthermore, spectacular 2D-reorganisation phenomenon with increasing temperature was pointed out since, initial circular particles change to elongated ones with a rectangular shape with increasing temperature. This reorganisation process results from an increase in the high surface atomic mobilities with increasing temperature. The growth of V{sub 2}O{sub 5} particles in the ab-plane occurs preferentially along the b-direction for which the atoms density is higher, in good agreement with results previously deduced from XRD analyses. The latter show limitation of the coherence domains values along the a-axis for temperatures higher than 450 deg. C.

  3. Obtaining shape memory alloy thin layer using PLD technique

    Directory of Open Access Journals (Sweden)

    Cimpoeşu N.

    2014-01-01

    Full Text Available Copper-based shape memory alloy (SMA was obtained through a classic melting method. The material was analyzed in heat treated and deformed states using scanning electrons microscopy (SEM, dilatometry (DIL, differential scanning calorimetry (DSC, dynamic mechanical analyzer (DMA and energy dispersive X-ray analyze (EDAX to establish the material microstructure, memory properties like martensitic transformation domain and rate or damping capacity. The material exhibits a good shape memory effect and high internal friction and it is proposed as target in a pulsed laser deposition (PLD process for obtaining thin films. The deposition process is described in this paper through presented experimental results on the layer.

  4. Active Constrained Layer Damping of Thin Cylindrical Shells

    Science.gov (United States)

    RAY, M. C.; OH, J.; BAZ, A.

    2001-03-01

    The effectiveness of the active constrained layer damping (ACLD) treatments in enhancing the damping characteristics of thin cylindrical shells is presented. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. Experiments are performed to verify the numerical predictions. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  5. Gravitational instability of thin gas layer between two thick liquid layers

    Science.gov (United States)

    Pimenova, A. V.; Goldobin, D. S.

    2016-12-01

    We consider the problem of gravitational instability (Rayleigh-Taylor instability) of a horizontal thin gas layer between two liquid half-spaces (or thick layers), where the light liquid overlies the heavy one. This study is motivated by the phenomenon of boiling at the surface of direct contact between two immiscible liquids, where the rate of the "break-away" of the vapor layer growing at the contact interface due to development of the Rayleigh-Taylor instability on the upper liquid-gas interface is of interest. The problem is solved analytically under the assumptions of inviscid liquids and viscous weightless vapor. These assumptions correspond well to the processes in real systems, e.g., they are relevant for the case of interfacial boiling in the system water- n-heptane. In order to verify the results, the limiting cases of infinitely thin and infinitely thick gas layers were considered, for which the results can be obviously deduced from the classical problem of the Rayleigh-Taylor instability. These limiting cases are completely identical to the well-studied cases of gravity waves at the liquidliquid and liquid-gas interfaces. When the horizontal extent of the system is long enough, the wavenumber of perturbations is not limited from below, and the system is always unstable. The wavelength of the most dangerous perturbations and the rate of their exponential growth are derived as a function of the layer thickness. The dependence of the exponential growth rate on the gas layer thickness is cubic.

  6. Indirect fluorometric detection techniques on thin layer chromatography and effect of ultrasound on gel electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Yinfa, Ma.

    1990-12-10

    Thin-layer chromatography (TLC) is a broadly applicable separation technique. It offers many advantages over high performance liquid chromatography (HPLC), such as easily adapted for two-dimensional separation, for whole-column'' detection and for handling multiple samples, etc. However, due to its draggy development of detection techniques comparing with HPLC, TLC has not received the attention it deserves. Therefore, exploring new detection techniques is very important to the development of TLC. It is the principal of this dissertation to present a new detection method for TLC -- indirect fluorometric detection method. This detection technique is universal sensitive, nondestructive, and simple. This will be described in detail from Sections 1 through Section 5. Section 1 and 3 describe the indirect fluorometric detection of anions and nonelectrolytes in TLC. In Section 2, a detection method for cations based on fluorescence quenching of ethidium bromide is presented. In Section 4, a simple and interesting TLC experiment is designed, three different fluorescence detection principles are used for the determination of caffeine, saccharin and sodium benzoate in beverages. A laser-based indirect fluorometric detection technique in TLC is developed in Section 5. Section 6 is totally different from Sections 1 through 5. An ultrasonic effect on the separation of DNA fragments in agarose gel electrophoresis is investigated. 262 refs.

  7. Electrochemical Thin Layers in Nanostructures for Energy Storage.

    Science.gov (United States)

    Noked, Malachi; Liu, Chanyuan; Hu, Junkai; Gregorczyk, Keith; Rubloff, Gary W; Lee, Sang Bok

    2016-10-18

    Conventional electrical energy storage (EES) electrodes, such as rechargeable batteries, are mostly based on composites of monolithic micrometer sized particles bound together with polymeric and conductive carbon additives and binders. The kinetic limitations of these monolithic chunks of material are inherently linked to their electrical properties, the kinetics of ion insertion through their interface and ion migration in and through the composite phase. Redox chemistry of nanostructured materials in EES systems offer vast gains in power and energy. Furthermore, due to their thin nature, ion and electron transport is dramatically increased, especially when thin heterogeneous conducting layers are employed synergistically. However, since the stability of the electrode material is dictated by the nature of the electrochemical reaction and the accompanying volumetric and interfacial changes from the perspective of overall system lifetime, research with nanostructured materials has shown often indefinite conclusions: in some cases, an increase in unwanted side-reactions due to the high surface area (bad). In other cases, results have shown significantly better handling of mechanical stress that results from lithiation/delithiation (good). Despite these mixed results, scientifically informed design of thin electrode materials, with carefully chosen architectures, is considered a promising route to address many limitations witnessed in EES systems by reducing and protecting electrodes from parasitic reactions, accommodating mechanical stress due to volumetric changes from electrochemical reactions, and optimizing charge carrier mobilities from both the "ionic" and "electronic" points of view. Furthermore, precise nanoscale control over the electrode structure can enable accurate measurement through advanced spectroscopy and microscopy techniques. This Account summarizes recent findings related to thin electrode materials synthesized by atomic layer deposition (ALD) and

  8. Process for the production of thin layers, preferably for a photovoltaic cell

    NARCIS (Netherlands)

    Nanu, M.; Meester, B.; Goossens, A.; Schoonman, J.

    2006-01-01

    The invention is directed to a process for the production of a thin layer, preferably for a photovoltaic cell, which cell has at least a first contact layer, a p-type semiconductor layer, an n-type semiconductor layer, or a combined p-type/n-type semiconductor layer, and a second contact layer, said

  9. Photodetectors based on two dimensional materials

    Science.gov (United States)

    Zheng, Lou; Zhongzhu, Liang; Guozhen, Shen

    2016-09-01

    Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on. Project supported by the National Natural Science Foundation of China (Nos. 61377033, 61574132, 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.

  10. Hadamard States and Two-dimensional Gravity

    CERN Document Server

    Salehi, H

    2001-01-01

    We have used a two-dimensional analog of the Hadamard state-condition to study the local constraints on the two-point function of a linear quantum field conformally coupled to a two-dimensional gravitational background. We develop a dynamical model in which the determination of the state of the quantum field is essentially related to the determination of a conformal frame. A particular conformal frame is then introduced in which a two-dimensional gravitational equation is established.

  11. Topological defects in two-dimensional crystals

    OpenAIRE

    Chen, Yong; Qi, Wei-Kai

    2008-01-01

    By using topological current theory, we study the inner topological structure of the topological defects in two-dimensional (2D) crystal. We find that there are two elementary point defects topological current in two-dimensional crystal, one for dislocations and the other for disclinations. The topological quantization and evolution of topological defects in two-dimensional crystals are discussed. Finally, We compare our theory with Brownian-dynamics simulations in 2D Yukawa systems.

  12. Light scattering of thin azobenzene side-chain polyester layers

    DEFF Research Database (Denmark)

    Kerekes, Á.; Lörincz, E.; Ramanujam, P.S.

    2002-01-01

    characteristics than the liquid crystalline polyester. The amorphous samples have negligible polarization part orthogonal to the incident beam. the liquid crystalline samples have relative high orthogonal polarization part in light scattering, The light scattering results can be used to give a lower limit...... for the domain size in thin liquid crystalline polyester layers being responsible for the dominant light scattering. The characteristic domain Sizes obtained from the Fourier transformation of polarization microscopic Pictures confirm these values.......Light scattering properties of liquid crystalline and amorphous azobenzene side-chain polyester layers used for optical data storage were examined by means of transmissive scatterometry. Comparative experiments show that the amorphous polyester has significantly lower light scattering...

  13. Optimum high temperature strength of two-dimensional nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Monclús, M. A.; Molina-Aldareguía, J. M., E-mail: jon.molina@imdea.org [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Zheng, S. J.; Mayeur, J. R.; Beyerlein, I. J.; Mara, N. A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Polcar, T. [Czech Technical University in Prague, Technická 2, Prague 6 (Czech Republic); Llorca, J. [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science, Polytechnic University of Madrid, E. T. S. de Ingenieros de Caminos, 28040 Madrid (Spain)

    2013-11-01

    High-temperature nanoindentation was used to reveal nano-layer size effects on the hardness of two-dimensional metallic nanocomposites. We report the existence of a critical layer thickness at which strength achieves optimal thermal stability. Transmission electron microscopy and theoretical bicrystal calculations show that this optimum arises due to a transition from thermally activated glide within the layers to dislocation transmission across the layers. We demonstrate experimentally that the atomic-scale properties of the interfaces profoundly affect this critical transition. The strong implications are that interfaces can be tuned to achieve an optimum in high temperature strength in layered nanocomposite structures.

  14. Optimum high temperature strength of two-dimensional nanocomposites

    Directory of Open Access Journals (Sweden)

    M. A. Monclús

    2013-11-01

    Full Text Available High-temperature nanoindentation was used to reveal nano-layer size effects on the hardness of two-dimensional metallic nanocomposites. We report the existence of a critical layer thickness at which strength achieves optimal thermal stability. Transmission electron microscopy and theoretical bicrystal calculations show that this optimum arises due to a transition from thermally activated glide within the layers to dislocation transmission across the layers. We demonstrate experimentally that the atomic-scale properties of the interfaces profoundly affect this critical transition. The strong implications are that interfaces can be tuned to achieve an optimum in high temperature strength in layered nanocomposite structures.

  15. Underpotential deposition-mediated layer-by-layer growth of thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jia Xu; Adzic, Radoslav R.

    2017-06-27

    A method of depositing contiguous, conformal submonolayer-to-multilayer thin films with atomic-level control is described. The process involves electrochemically exchanging a mediating element on a substrate with a noble metal film by alternatingly sweeping potential in forward and reverse directions for a predetermined number of times in an electrochemical cell. By cycling the applied voltage between the bulk deposition potential for the mediating element and the material to be deposited, repeated desorption/adsorption of the mediating element during each potential cycle can be used to precisely control film growth on a layer-by-layer basis.

  16. Descriptions of membrane mechanics from microscopic and effective two-dimensional perspectives

    DEFF Research Database (Denmark)

    Lomholt, Michael Andersen; Miao, L.

    2006-01-01

    Mechanics of fluid membranes may be described in terms of the concepts of mechanical deformations and stresses or in terms of mechanical free-energy functions. In this paper, each of the two descriptions is developed by viewing a membrane from two perspectives: a microscopic perspective, in which...... the membrane appears as a thin layer of finite thickness and with highly inhomogeneous material and force distributions in its transverse direction, and an effective, two-dimensional perspective, in which the membrane is treated as an infinitely thin surface, with effective material and mechanical properties....... A connection between these two perspectives is then established. Moreover, the functional dependence of the variation in the mechanical free energy of the membrane on its mechanical deformations is first studied in the microscopic perspective. The result is then used to examine to what extent different...

  17. Numerical Modeling of Thermocapillary Deformation and Film Breakdown in a Locally Heated Thin Horizontal Volatile Liquid Layer

    Directory of Open Access Journals (Sweden)

    Barakhovskaya Ella

    2016-01-01

    Full Text Available The problem of thermocapillary deformation and film breakdown in a thin horizontal layer of viscous incompressible liquid with a free surface is considered. The deformable liquid layer is locally heated. The problem of thermocapillary deformation of the locally heated horizontal liquid layer has been solved numerically for two-dimensional unsteady case. The lubrication approximation theory is used. Capillary pressure, viscosity and gravity are taken into account. Evaporating rate is supposed to be proportional to the temperature difference between the liquid and ambient. Heat transfer in the substrate is also simulated. The numerical algorithm for the joint solution of the energy equation and the evolution equation for the thickness of liquid layer has been developed. The model predicts the thermocapillary deformation of the liquid surface and the formation of dry spots. The dynamics of liquid surface, the dry spots formation and the velocity of the contact line have been calculated. The deformation of the free surface has been calculated for different values of the heating power and thickness of the liquid layer. The effect of surface tension coefficient and wetting contact angle on the velocity of the contact line motion has been analyzed. It has been obtained that the velocity of the contact line increases with the increase of the wetting contact angle value and of the surface tension coefficient.

  18. Strongly interacting two-dimensional Dirac fermions

    NARCIS (Netherlands)

    Lim, L.K.; Lazarides, A.; Hemmerich, Andreas; de Morais Smith, C.

    2009-01-01

    We show how strongly interacting two-dimensional Dirac fermions can be realized with ultracold atoms in a two-dimensional optical square lattice with an experimentally realistic, inherent gauge field, which breaks time reversal and inversion symmetries. We find remarkable phenomena in a temperature

  19. Topology optimization of two-dimensional waveguides

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard; Sigmund, Ole

    2003-01-01

    In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....

  20. Structural properties of dopping metallic impurities on CdS thin layers

    Directory of Open Access Journals (Sweden)

    S. Ghasemzadeh

    2016-12-01

    Full Text Available (Cu,Zn-dopped CdS thin layers were deposited on glass substrates by chemical bath deposition technique. The effects of the doping on the structural properties of CdS thin layers were studied by SEM and EDAX analysis. Hetero junction layers were produced with different nano structures and different fraction of voids and metallic ions.

  1. Structural properties of dopping metallic impurities on CdS thin layers

    OpenAIRE

    S. Ghasemzadeh; H. kangarlou

    2016-01-01

    (Cu,Zn)-dopped CdS thin layers were deposited on glass substrates by chemical bath deposition technique. The effects of the doping on the structural properties of CdS thin layers were studied by SEM and EDAX analysis. Hetero junction layers were produced with different nano structures and different fraction of voids and metallic ions.

  2. Fabrication of organic thin-film transistors using layer-by-layer assembly.

    Science.gov (United States)

    Stricker, Jeffery T; Gudmundsdóttir, Anna D; Smith, Adam P; Taylor, Barney E; Durstock, Michael F

    2007-06-14

    Layer-by-layer assembly is presented as a deposition technique for the incorporation of ultrathin gate dielectric layers into thin-film transistors utilizing a highly doped organic active layer. This deposition technique enables the fabrication of device structures with a controllable gate dielectric thickness. In particular, devices with a dielectric layer comprised of poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) bilayer films were fabricated to examine the properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as the transistor active layer. The transistor Ion/off ratio and switching speed are shown to be controlled by the gate bias, which is dependent upon the voltage applied and the number of bilayers deposited for the gate dielectric. The devices operate in the depletion mode as a result of dedoping of the active layer with the application of a positive gate bias. The depletion and recovery rate are highly dependent on the level of hydration in the film and the environment under which the device is operated. These observations are consistent with an electrochemical dedoping of the conducting polymer during operation.

  3. Manipulation of surface plasmon polariton propagation on isotropic and anisotropic two-dimensional materials coupled to boron nitride heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Inampudi, Sandeep; Nazari, Mina; Forouzmand, Ali; Mosallaei, Hossein, E-mail: hosseinm@coe.neu.edu [Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 (United States)

    2016-01-14

    We present a comprehensive analysis of surface plasmon polariton dispersion characteristics associated with isotropic and anisotropic two-dimensional atomically thin layered materials (2D sheets) coupled to h-BN heterostructures. A scattering matrix based approach is presented to compute the electromagnetic fields and related dispersion characteristics of stacked layered systems composed of anisotropic 2D sheets and uniaxial bulk materials. We analyze specifically the surface plasmon polariton (SPP) dispersion characteristics in case of isolated and coupled two-dimensional layers with isotropic and anisotropic conductivities. An analysis based on residue theorem is utilized to identify optimum optical parameters (surface conductivity) and geometrical parameters (separation between layers) to maximize the SPP field at a given position. The effect of type and degree of anisotropy on the shapes of iso-frequency curves and propagation characteristics is discussed in detail. The analysis presented in this paper gives an insight to identify optimum setup to enhance the SPP field at a given position and in a given direction on the surface of two-dimensional materials.

  4. Microstructural properties of multi-nano-layered YSZ thin films

    Energy Technology Data Exchange (ETDEWEB)

    Amezaga-Madrid, P.; Antunez-Flores, W.; Gonzalez-Hernandez, J.; Saenz-Hernandez, J.; Campos-Venegas, K.; Solis-Canto, O.; Ornelas-Gutierrez, C.; Vega-Becerra, O.; Martinez-Sanchez, R. [Centro de Investigacion en Materiales Avanzados S.C., Miguel de Cervantes 120, Chihuahua, Chih, CP. 31109 (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.m [Centro de Investigacion en Materiales Avanzados S.C., Miguel de Cervantes 120, Chihuahua, Chih, CP. 31109 (Mexico)

    2010-04-16

    We report the fabrication of submicron, multi-nano-layered, yttria-stabilized zirconia (YSZ) thin films by aerosol assisted CVD. The film consisted of a periodic stack of several layers, a few nanometers thick, of the same composition but different density; formation of voids during synthesis originate the low-density layer. Grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry, high-resolution transmission electron microscopy (HRTEM) and high angle annular dark field (HAADF) images were employed to analyze the microstructure of the films. GIXRD pattern showed characteristic peaks of cubic zirconia. Peak broadening in the pattern comes from a microstructure composed of nanocrystals, but principally due to the multilayered structure, that cause satellite peaks around the Bragg reflections. Lattice fringes measurement in HRTEM and HAADF images was consistent with the interplanar distance of the YSZ cubic phase. Additionally, lattice parameter obtained from selected area electron diffraction and GIXRD patterns was around 0.513 nm, in agreement to values reported in the literature for YSZ.

  5. Approximate reflection coefficients for a thin VTI layer

    KAUST Repository

    Hao, Qi

    2017-09-18

    We present an approximate method to derive simple expressions for the reflection coefficients of P- and SV-waves for a thin transversely isotropic layer with a vertical symmetry axis (VTI) embedded in a homogeneous VTI background. The layer thickness is assumed to be much smaller than the wavelengths of P- and SV-waves inside. The exact reflection and transmission coefficients are derived by the propagator matrix method. In the case of normal incidence, the exact reflection and transmission coefficients are expressed in terms of the impedances of vertically propagating P- and S-waves. For subcritical incidence, the approximate reflection coefficients are expressed in terms of the contrast in the VTI parameters between the layer and the background. Numerical examples are designed to analyze the reflection coefficients at normal and oblique incidence, and investigate the influence of transverse isotropy on the reflection coefficients. Despite giving numerical errors, the approximate formulae are sufficiently simple to qualitatively analyze the variation of the reflection coefficients with the angle of incidence.

  6. Polymer Thin Films and Interfaces; a Layer-by-Layer Approach

    Science.gov (United States)

    White, Ronald; Lipson, Jane

    2013-03-01

    In this talk we discuss new ways to model polymer films and interfaces, including properties such as density and concentration gradients, interfacial tension, and surface enrichment. We build on recent work where we developed a very simple equation of state approach for polymer thin films, and successfully applied it to determine thermodynamic properties and even to make predictions for the thickness-dependent depression of the thin film glass transition temperature. In that very simplified mean field model, the film properties across the entire interface region were treated as a ``whole sample'' average. Here, we take the next step, and develop a layer-by-layer equation of state model wherein details of the interface region are captured by allowing properties to vary from one discretized layer (within which properties are uniform) to the next. The model can be solved by imposing hydrostatic equilibrium in each layer, which then leads to predictions for the corresponding density gradient and other key interface properties. Work supported by the National Science Foundation.

  7. On two-dimensional magnetic reconnection with nonuniform resistivity

    Science.gov (United States)

    Malyshkin, Leonid M.; Kulsrud, Russell M.

    2010-12-01

    In this paper, two theoretical approaches for the calculation of the rate of quasi-stationary, two-dimensional magnetic reconnection with nonuniform anomalous resistivity are considered in the framework of incompressible magnetohydrodynamics (MHD). In the first, 'global' equations approach, the MHD equations are approximately solved for a whole reconnection layer, including the upstream and downstream regions and the layer center. In the second, 'local' equations approach, the equations are solved across the reconnection layer, including only the upstream region and the layer center. Both approaches give the same approximate answer for the reconnection rate. Our theoretical model is in agreement with the results of recent simulations of reconnection with spatially nonuniform resistivity.

  8. Transport parameters of thin, supported cathode layers in solid oxide fuel cells (SOFCs); Transportparameter duenner, getraegerter Kathodenschichten der oxidkeramischen Brennstoffzelle

    Energy Technology Data Exchange (ETDEWEB)

    Wedershoven, Christian

    2010-12-22

    The aim of this work was to determine the transport properties of thin cathode layers, which are part of the composite layer of a fabricated anode-supported solid oxide fuel cell (SOFC). The transport properties of the anode and cathode have a significant influence on the electrochemical performance of a fuel cell stack and therefore represent an important parameter when designing fuel cell stacks. In order to determine the transport parameters of the cathode layers in a fabricated SOFC, it is necessary to permeate the thin cathode layer deposited on the gas-tight electrolyte with a defined gas transport. These thin cathode layers cannot be fabricated as mechanically stable single layers and cannot therefore be investigated in the diffusion and permeation experiments usually used to determine transport parameters. The setup of these experiments - particularly the sample holder - was therefore altered in this work. The result of this altered setup was a three-dimensional flow configuration. Compared to the conventional setup, it was no longer possible to describe the gas transport in the experiments with an analytical one-dimensional solution. A numerical solution process had to be used to evaluate the measurements. The new setup permitted a sufficiently symmetrical gas distribution and thus allowed the description of the transport to be reduced to a two-dimensional description, which significantly reduced the computational effort required to evaluate the measurements. For pressure-induced transport, a parametrized coherent expression of transport could be derived. This expression is equivalent to the analytical description of the transport in conventional measurement setups, with the exception of parameters that describe the geometry of the gas diffusion. In this case, a numerical process is not necessary for the evaluation. Using the transport parameters of mechanically stable anode substrates, which can be measured both in the old and the new setups, the old and

  9. Structural properties of produced CuO/NiO/glass thin layers Produced by chemical method

    Directory of Open Access Journals (Sweden)

    A. Ramezani

    2016-12-01

    Full Text Available Nickel Oxide and Copper oxide on Nickel Oxide thin layers were produced by chemical bath deposition method. There nano structures were investigated by SEM and EDAX analysis. By producing CuO/NiO/glass sandwich layers nano structure of NiO/glass layer changed and fraction of voids decreases. In sandwich layer physical property of outer layer was dominant

  10. Redox cycling for electrolysis of pure water in a thin layer cell

    OpenAIRE

    李, 春艳

    2013-01-01

    The redox cycling can achieve in thin layer cell because products of electrode reactions diffuse in opposite directions across the thin layer to the electrodes where they can react again. This redox cycling can enhance the current, and hence improve the sensitivity and selectivity. The redox cycling can make the current be under steady state in thin layer electrolysis. The aim of this thesis is to get controlling factors of redox cycling in electrolysis of water. the factors include not only ...

  11. Underpotential deposition-mediated layer-by-layer growth of thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jia Xu; Adzic, Radoslav R.

    2015-05-19

    A method of depositing contiguous, conformal submonolayer-to-multilayer thin films with atomic-level control is described. The process involves the use of underpotential deposition of a first element to mediate the growth of a second material by overpotential deposition. Deposition occurs between a potential positive to the bulk deposition potential for the mediating element where a full monolayer of mediating element forms, and a potential which is less than, or only slightly greater than, the bulk deposition potential of the material to be deposited. By cycling the applied voltage between the bulk deposition potential for the mediating element and the material to be deposited, repeated desorption/adsorption of the mediating element during each potential cycle can be used to precisely control film growth on a layer-by-layer basis. This process is especially suitable for the formation of a catalytically active layer on core-shell particles for use in energy conversion devices such as fuel cells.

  12. Drift modes of a quasi-two-dimensional current sheet

    Energy Technology Data Exchange (ETDEWEB)

    Artemyev, A. V.; Malova, Kh. V.; Popov, V. Yu.; Zelenyi, L. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation)

    2012-03-15

    Stability of a plasma configuration consisting of a thin one-dimensional current sheet embedded into a two-dimensional background current sheet is studied. Drift modes developing in plasma as unstable waves along the current direction are considered. Dispersion relations for kink and sausage perturbation modes are obtained depending on the ratio of parameters of thin and background current sheets. It is shown that the existence of the background sheet results in a decrease in the instability growth rates and a significant increase in the perturbation wavelengths. The role of drift modes in the excitation of oscillations observed in the current sheet of the Earth's magnetotail is discussed.

  13. Preparations and Characterizations of Luminescent Two Dimensional Organic-inorganic Perovskite Semiconductors

    Directory of Open Access Journals (Sweden)

    Sanjun Zhang

    2010-05-01

    Full Text Available This article reviews the synthesis, structural and optical characterizations of some novel luminescent two dimensional organic-inorganic perovskite (2DOIP semiconductors. These 2DOIP semiconductors show a self-assembled nano-layered structure, having the electronic structure of multi-quantum wells. 2DOIP thin layers and nanoparticles have been prepared through different methods. The structures of the 2DOIP semiconductors are characterized by atomic force microscopy and X-ray diffraction. The optical properties of theb DOIP semiconductors are characterized from absorption and photoluminescence spectra measured at room and low temperatures. Influences of different components, in particular the organic parts, on the structural and optical properties of the 2DOIP semiconductors are discussed.

  14. Deterministic strain-induced arrays of quantum emitters in a two-dimensional semiconductor

    Science.gov (United States)

    Branny, Artur; Kumar, Santosh; Proux, Raphaël; Gerardot, Brian D

    2017-01-01

    An outstanding challenge in quantum photonics is scalability, which requires positioning of single quantum emitters in a deterministic fashion. Site positioning progress has been made in established platforms including defects in diamond and self-assembled quantum dots, albeit often with compromised coherence and optical quality. The emergence of single quantum emitters in layered transition metal dichalcogenide semiconductors offers new opportunities to construct a scalable quantum architecture. Here, using nanoscale strain engineering, we deterministically achieve a two-dimensional lattice of quantum emitters in an atomically thin semiconductor. We create point-like strain perturbations in mono- and bi-layer WSe2 which locally modify the band-gap, leading to efficient funnelling of excitons towards isolated strain-tuned quantum emitters that exhibit high-purity single photon emission. We achieve near unity emitter creation probability and a mean positioning accuracy of 120±32 nm, which may be improved with further optimization of the nanopillar dimensions. PMID:28530219

  15. Deterministic strain-induced arrays of quantum emitters in a two-dimensional semiconductor

    Science.gov (United States)

    Branny, Artur; Kumar, Santosh; Proux, Raphaël; Gerardot, Brian D.

    2017-05-01

    An outstanding challenge in quantum photonics is scalability, which requires positioning of single quantum emitters in a deterministic fashion. Site positioning progress has been made in established platforms including defects in diamond and self-assembled quantum dots, albeit often with compromised coherence and optical quality. The emergence of single quantum emitters in layered transition metal dichalcogenide semiconductors offers new opportunities to construct a scalable quantum architecture. Here, using nanoscale strain engineering, we deterministically achieve a two-dimensional lattice of quantum emitters in an atomically thin semiconductor. We create point-like strain perturbations in mono- and bi-layer WSe2 which locally modify the band-gap, leading to efficient funnelling of excitons towards isolated strain-tuned quantum emitters that exhibit high-purity single photon emission. We achieve near unity emitter creation probability and a mean positioning accuracy of 120+/-32 nm, which may be improved with further optimization of the nanopillar dimensions.

  16. Measurement of a thin layers thickness using independent component analysis of ground penetrating radar data

    Institute of Scientific and Technical Information of China (English)

    LI Xiang-tang; ZHANG Xiao-ning; WANG Duan-yi

    2008-01-01

    To detect overlapped echoes due to the thin pavement layers, we present a thickness measurement approach for the very thin layer of pavement structures. The term "thin" is relative to the incident wavelength or pulse. By means of independent component analysis of noisy signals received by a single radar sensor, the over-lapped echoes can be successfully separated. Once the echoes from the top and bottom side of a thin layer have been separated, the time delay and the layer thickness determination follow immediately. Results of the simula-tion and real data re fy the feasibility of the presented method.

  17. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    OpenAIRE

    2012-01-01

    The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis o...

  18. Tensile strength of thin resin composite layers as a function of layer thickness.

    Science.gov (United States)

    Alster, D; Feilzer, A J; De Gee, A J; Davidson, C L

    1995-11-01

    As a rule, cast restorations do not allow for free curing contraction of the resin composite luting cement. In a rigid situation, the resulting contraction stress is inversely proportional to the resin layer thickness. Adhesive technology has demonstrated, however, that thin joints may be considerably stronger than thicker ones. To investigate the effects of layer thickness and contraction stress on the tensile strength of resin composite joints, we cured cylindrical samples of a chemically initiated resin composite (Clearfil F2) in restrained conditions and subsequently loaded them in tension. The samples had a diameter of 5.35 mm and thicknesses of 50, 100, 200, 300, 400, 500, 600, and 700 microns, 1.4 mm, or 2.7 mm. None of the samples fractured due to contraction stress prior to tensile loading. Tensile strength decreased gradually from 62 +/- 2 MPa for the 50-microns layer to 31 +/- 4 MPa for the 2.7-mm layer. The failures were exclusively cohesive in resin for layers between 50 and 400 microns thick. Between 500 and 700 microns, the failures were cohesive or mixed adhesive/cohesive, while the 1.4- and 2.7-mm layers always failed in a mixed adhesive/cohesive mode. For the resin composite tested, the contraction stress did not endanger the cohesive strength. It was concluded that if adhesion to tooth structure were improved, thinner adhesive joints might enhance the clinical success of luted restorations.

  19. Multilayered gold-nanoparticle/polyimide composite thin film through layer-by-layer assembly.

    Science.gov (United States)

    Zhang, Fengxiang; Srinivasan, M P

    2007-09-25

    A novel type of composite thin film consisting of gold nanoparticles (AuNPs) and polymide (PI) was fabricated through layer-by-layer (LBL) assembly. To fabricate such films, bare AuNPs and a poly (amic acid) bearing pendant amine groups, namely, amino poly (amic acid) or APAA, were synthesized and assembled in an LBL fashion. Without any organic encapsulation layer on their surface, AuNPs were bound directly to APAA chains at the amine sites; X-ray photoelectron spectroscopy study suggested that the binding was based on a combined effect of metal-ligand coordination and electrostatic interaction, with the former dominating over the latter. An approximately linear growth of the film started from the second layer of AuNP as revealed by the UV-vis spectroscopy, and the degree of particle aggregation was higher in the first AuNP layer than in the subsequent layers due to the differences in the density of binding sites. The resultant assembly was heated to imidize the APAA, thereby creating a robust composite structure.

  20. The Untapped Potential Of Plant Thin Cell Layers

    Directory of Open Access Journals (Sweden)

    Teixeira da Silva Jaime

    2015-12-01

    Full Text Available Thin cell layers (TCLs, which contain a small number of cells or tissues, are explants excised from different organs (stems, leaves, roots, inflorescences, flowers, cotyledons, hypocotyls/epicotyls, and embryos. After almost 45 years of research, this culture system has been used for several monocotyledonous and dicotyledonous plants of commercial importance, and for model plants. The limited amount of cells in a TCL is of paramount importance because marker molecules/genes of differentiation can be easily localized in situ in the target/responsive cells. Thus, the use of TCLs has allowed, and continues to allow, for the expansion of knowledge in plant research in a practical and applied manner into the fields of tissue culture and micropropagation, cell and organ genetics, molecular biology, biochemistry, and development. Starting from a brief historical background, the actual and potential uses of the TCL system are briefly reviewed.

  1. Thin layer modelling of Gelidium sesquipedale solar drying process

    Energy Technology Data Exchange (ETDEWEB)

    Ait Mohamed, L. [Laboratoire d' Energie Solaire et des Plantes Aromatiques et Medicinales, Ecole Normale Superieure, BP 2400, Marrakech (Morocco); Faculte des Sciences Semlalia, BP 2390, Marrakech (Morocco); Ethmane Kane, C.S. [Faculte des Sciences de Tetouan, BP 2121, Tetouan (Morocco); Kouhila, M.; Jamali, A. [Laboratoire d' Energie Solaire et des Plantes Aromatiques et Medicinales, Ecole Normale Superieure, BP 2400, Marrakech (Morocco); Mahrouz, M. [Faculte des Sciences Semlalia, BP 2390, Marrakech (Morocco); Kechaou, N. [Ecole Nationale d' Ingenieurs de Sfax, BPW 3038 (Tunisia)

    2008-05-15

    The effect of air temperature and air flow rate on the drying kinetics of Gelidium sesquipedale was investigated in convective solar drying. Drying was conducted at 40, 50 and 60 C. The relative humidity was varied from 50% to 57%, and the drying air flow rate was varied from 0.0277 to 0.0833 m{sup 3}/s. The expression for the drying rate equation is determined empirically from the characteristic drying curve. Thirteen mathematical models of thin layer drying are selected in order to estimate the suitable model for describing the drying curves. The two term model gives the best prediction of the drying curves and satisfactorily describes the drying characteristics of G. sesquipedale with a correlation coefficient R of 0.9999 and chi-square ({chi}{sup 2}) of 3.381 x 10{sup -6}. (author)

  2. Thin Layer Chromatographic Analysis of Beta-Lactam Antibiotics

    Directory of Open Access Journals (Sweden)

    Gabriel Hancu

    2013-08-01

    Full Text Available Purpose: The paper describes some thin layer chromatographic procedures that allow simple and rapid separation and identification of penicillins and cephalosporins from complex mixtures. Methods: Using silicagel GF254 as stationary phase and selecting different mobile phases we succeeded in the separation of the studied beta-lactamins. Our aim was not only to develop a simple, rapid and efficient method for their separation but also the optimization of the analytical conditions. Results: No system will separate all the beta-lactams, but they could be identified when supplementary information is used from color reactions and/or by using additional chromatographic systems. Conclusions: The right combination of solvent system and detection method allows the identification of the studied penicillins and cephalosporins and can be successfully used in the preliminary analysis beta-lactam antibiotics.

  3. An improved method for thin layer chromatographic analysis of saponins.

    Science.gov (United States)

    Sharma, Om P; Kumar, Neeraj; Singh, Bikram; Bhat, Tej K

    2012-05-01

    Analysis of saponins by thin layer chromatography (TLC) is reported. The solvent system was n-butanol:water:acetic acid (84:14:7). Detection of saponins on the TLC plates after development and air-drying was done by immersion in a suspension of sheep erythrocytes, followed by washing off the excess blood on the plate surface. Saponins appeared as white spots against a pink background. The protocol provided specific detection of saponins in the saponins enriched extracts from Aesculusindica (Wall. ex Camb.) Hook.f., Lonicera japonica Thunb., Silene inflata Sm., Sapindusmukorossi Gaertn., Chlorophytum borivilianum Santapau & Fernandes, Asparagusadscendens Roxb., Asparagus racemosus Willd., Agave americana L., Camellia sinensis [L.] O. Kuntze. The protocol is convenient, inexpensive, does not require any corrosive chemicals and provides specific detection of saponins.

  4. High performance thin layer chromatography profile of Cassytha filiformis

    Institute of Scientific and Technical Information of China (English)

    Mythili Sathiavelu; Sathiavelu Arunachalam

    2012-01-01

    Objective: To study the phenols, flavonoids, saponin profile of the medicinal plant Cassytha filiformis (C. filiformis) using high performance thin layer chromatography (HPTLC). Methods:The extracts were tested to determine the presence of various phytochmeicals like alkaloids, phenolic compounds, flavonoids, carbohydrates, glycosides, saponins, terpenoids, tannins, fixed oils, fats and protein and aminoacids (Harborne and Harborne, 1998). HPTLC studies were carried out by Harborne and Wagner et al method. Different compositions of the mobile phase for HPTLC analysis were tested in order to obtain high resolution and reproducible peaks. Results: The results of the preliminary phytochemical studies confirm the presence of phenols, alkaloids, carbohydrates, saponins, flavanoids, terpenoids and tannins in the methanolic extracts of C. filiformis. The methanolic extracts of C. filiformis displayed the presence of 13 types of phenolic substances with 13 different Rf values ranging from 0.01 to 0.96. The results illustrated the presence of 9 different types of flavonoides with 9 different Rf values ranging from 0.01 to 0.97. The results of HPTLC analysis of saponins demonstrated the presence of 11 different types of saponins with 11 different Rf values ranging from 0.04 to 0.92. Conclusions: In the present study we observed the phenols, flavonoids, saponin profile of the medicinal plant C. filiformis using high performance thin layer chromatography (HPTLC). Hence it was concluded that the phenolic compounds present in the methonolic extract could be responsible for antioxidant activities. Plant derived antioxidants, especially phenols and flavonoids, have been described to have various properties like anticancer, antiaging and prevention of cardiovascular diseases. Furthur, separation and characterization of the bioactive compound from the plant is to be evaluated and reported in near future.

  5. KINETICS OF THIN LAYER DRYING OF POULTRY MANURE

    Directory of Open Access Journals (Sweden)

    A. E. Ghaly

    2012-01-01

    Full Text Available The poultry industry is one of the largest and fastest growing sectors of livestock production in the world. The estimated 2010 world flock was over 18 billion birds with a yearly manure output of 22 million tonnes. Storage and disposal of raw poultry manure has become an environmental problem because of the associated air, water and soil pollution. Environmental and health problems such as odor and pathogens that may arise during and after land application of raw manure can be eliminated by drying. Dried manure can be utilized as a soil conditioner to improve soil tilth and reduce the problems associated with soil compaction and as a feed for ruminants because of its high nitrogen content. The aim of this study was to investigate the kinetics of thin layer drying of poultry manure and evaluate the effects of drying with heated air on the chemical and biological properties of manure. The effects of temperature and depth of manure layer were evaluated. The profile of the moisture content of poultry manure followed an exponential decay curve. The moisture decay constant was affected by the drying temperature and the depth of the manure layer. At the three temperature levels studied, the time required to dry poultry manure in 1 cm-deep layer was the least, followed by 2 and 3 cm-deep layers, respectively. The diffusion coefficient increased with both temperature and depth of drying layer, but did not show a linear increase with either variable. The optimum depth for drying manure (at which the highest drying effectiveness occurred was 3 cm. Drying manure at 40-60°C resulted in the loss of 44-55% of the total Kjeldahl nitrogen, with losses increasing with both the temperature and depth of manure. The pH of the manure decreased from the initial value of 8.4 before drying to about 6.6 after drying. The odor analysis indicated that dried poultry manure did not have an offensive odor. Drying achieved 65.3 and 69.3% reductions in odor intensity and

  6. Symmetrical periods used as matching layers in multilayer thin film design

    Institute of Scientific and Technical Information of China (English)

    Dan Wang; Zhengxiu Fan; Jianbing Huang; Jun Bi; Yingjian Wang

    2006-01-01

    Properties of symmetrical layers as matching layers in multilayer thin film design were analyzed. Acalculation method was presented to derive parameters of desired equivalent refractive index. A harmonicbeam splitter was designed and fabricated to test this matching method.

  7. Thin hybrid pixel assembly with backside compensation layer on ROIC

    Science.gov (United States)

    Bates, R.; Buttar, C.; McMullen, T.; Cunningham, L.; Ashby, J.; Doherty, F.; Gray, C.; Pares, G.; Vignoud, L.; Kholti, B.; Vahanen, S.

    2017-01-01

    The entire ATLAS inner tracking system will be replaced for operation at the HL-LHC . This will include a significantly larger pixel detector of approximately 15 m2. For this project, it is critical to reduce the mass of the hybrid pixel modules and this requires thinning both the sensor and readout chips to about 150 micrometres each. The thinning of the silicon chips leads to low bump yield for SnAg bumps due to bad co-planarity of the two chips at the solder reflow stage creating dead zones within the pixel array. In the case of the ATLAS FEI4 pixel readout chip thinned to 100 micrometres, the chip is concave, with the front side in compression, with a bow of +100 micrometres at room temperature which varies to a bow of -175 micrometres at the SnAg solder reflow temperature, caused by the CTE mismatch between the materials in the CMOS stack and the silicon substrate. A new wafer level process to address the issue of low bump yield be controlling the chip bow has been developed. A back-side dielectric and metal stack of SiN and Al:Si has been deposited on the readout chip wafer to dynamically compensate the stress of the front side stack. In keeping with a 3D process the materials used are compatible with Through Silicon Via (TSV) technology with a TSV last approach which is under development for this chip. It is demonstrated that the amplitude of the correction can be manipulated by the deposition conditions and thickness of the SiN/Al:Si stack. The bow magnitude over the temperature range for the best sample to date is reduced by almost a factor of 4 and the sign of the bow (shape of the die) remains constant. Further development of the backside deposition conditions is on-going with the target of close to zero bow at the solder reflow temperature and a minimal bow magnitude throughout the temperature range. Assemblies produced from FEI4 readout wafers thinned to 100 micrometres with the backside compensation layer have been made for the first time and

  8. Thin Layer Sensory Cues Affect Antarctic Krill Swimming Kinematics

    Science.gov (United States)

    True, A. C.; Webster, D. R.; Weissburg, M. J.; Yen, J.

    2013-11-01

    A Bickley jet (laminar, planar free jet) is employed in a recirculating flume system to replicate thin shear and phytoplankton layers for krill behavioral assays. Planar laser-induced fluorescence (LIF) and particle image velocimetry (PIV) measurements quantify the spatiotemporal structure of the chemical and free shear layers, respectively, ensuring a close match to in situ hydrodynamic and biochemical conditions. Path kinematics from digitized trajectories of free-swimming Euphausia superba examine the effects of hydrodynamic sensory cues (deformation rate) and bloom level phytoplankton patches (~1000 cells/mL, Tetraselamis spp.) on krill behavior (body orientation, swimming modes and kinematics, path fracticality). Krill morphology is finely tuned for receiving and deciphering both hydrodynamic and chemical information that is vital for basic life processes such as schooling behaviors, predator/prey, and mate interactions. Changes in individual krill behavior in response to ecologically-relevant sensory cues have the potential to produce population-scale phenomena with significant ecological implications. Krill are a vital trophic link between primary producers (phytoplankton) and larger animals (seabirds, whales, fish, penguins, seals) as well as the subjects of a valuable commercial fishery in the Southern Ocean; thus quantifying krill behavioral responses to relevant sensory cues is an important step towards accurately modeling Antarctic ecosystems.

  9. Two-dimensional function photonic crystals

    Science.gov (United States)

    Liu, Xiao-Jing; Liang, Yu; Ma, Ji; Zhang, Si-Qi; Li, Hong; Wu, Xiang-Yao; Wu, Yi-Heng

    2017-01-01

    In this paper, we have studied two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , that can become true easily by electro-optical effect and optical kerr effect. We calculated the band gap structures of TE and TM waves, and found the TE (TM) wave band gaps of function photonic crystals are wider (narrower) than the conventional photonic crystals. For the two-dimensional function photonic crystals, when the dielectric constant functions change, the band gaps numbers, width and position should be changed, and the band gap structures of two-dimensional function photonic crystals can be adjusted flexibly, the needed band gap structures can be designed by the two-dimensional function photonic crystals, and it can be of help to design optical devices.

  10. Two-Dimensional Planetary Surface Lander

    Science.gov (United States)

    Hemmati, H.; Sengupta, A.; Castillo, J.; McElrath, T.; Roberts, T.; Willis, P.

    2014-06-01

    A systems engineering study was conducted to leverage a new two-dimensional (2D) lander concept with a low per unit cost to enable scientific study at multiple locations with a single entry system as the delivery vehicle.

  11. Modeling the influence of the seeding layer on the transition behavior of a ferroelectric thin film

    Energy Technology Data Exchange (ETDEWEB)

    Oubelkacem, A.; Essaoudi, I. [Laboratoire de Physique des Materiaux et Modelisation des Systemes, Unite Associee au CNRST, URAC: 08, University of Moulay Ismail, Faculty of Sciences, Physics Department, B.P. 11201, Meknes (Morocco); Ainane, A., E-mail: ainane@pks.mpg.de [Laboratoire de Physique des Materiaux et Modelisation des Systemes, Unite Associee au CNRST, URAC: 08, University of Moulay Ismail, Faculty of Sciences, Physics Department, B.P. 11201, Meknes (Morocco); Max-Planck-Institut fuer Physik Complexer Systeme, Noethnitzer Str. 38 D-01187 Dresden (Germany); Laboratoire de Physique des Milieux Denses (LPMD) Institut de Chimie, Physique et Materiaux (ICPM), 1 Bd. Arago, 57070, Metz (France); INFM-Dip. Fisica. Univ. Padova, via Marzolo 8, 54124 Padova (Italy); Saber, M. [Laboratoire de Physique des Materiaux et Modelisation des Systemes, Unite Associee au CNRST, URAC: 08, University of Moulay Ismail, Faculty of Sciences, Physics Department, B.P. 11201, Meknes (Morocco); Max-Planck-Institut fuer Physik Complexer Systeme, Noethnitzer Str. 38 D-01187 Dresden (Germany); Dujardin, F. [Laboratoire de Physique des Milieux Denses (LPMD) Institut de Chimie, Physique et Materiaux (ICPM), 1 Bd. Arago, 57070, Metz (France)

    2011-10-31

    The transition properties of a ferroelectric thin film with seeding layers were studied using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions. The effect of interaction parameters for the seeding layer on the phase diagram was also examined. We calculated the critical temperature and the polarization of the ferroelectric thin film for different seeding layer structures. We found that the seeding layer can greatly increase the Curie temperature and the polarization.

  12. Graphene oxide monolayers as atomically thin seeding layers for atomic layer deposition of metal oxides

    Science.gov (United States)

    Nourbakhsh, Amirhasan; Adelmann, Christoph; Song, Yi; Lee, Chang Seung; Asselberghs, Inge; Huyghebaert, Cedric; Brizzi, Simone; Tallarida, Massimo; Schmeißer, Dieter; van Elshocht, Sven; Heyns, Marc; Kong, Jing; Palacios, Tomás; de Gendt, Stefan

    2015-06-01

    Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the capacitive properties of GO with its electronic structure. Capacitance-voltage measurements showed that the capacitive behavior of Al2O3/GO depends on the oxidation level of GO. Finally, GO was successfully used as an ALD seed layer for the deposition of Al2O3 on chemically inert single layer graphene, resulting in high performance top-gated field-effect transistors.Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the

  13. The micro-cavity of the two dimensional plasmonic photonic crystal

    Science.gov (United States)

    Tong, Kai; Zhang, Zhenguo; Yang, Qing

    2015-02-01

    In this manuscript, we proposed a novel and effective two dimensional hybrid plasmonic photonic crystal micro-cavity structure to confine the surface plasmon to a sub-wavelength scale mode volume and obtain a relatively high quality factor. By introducing a single-cell defect at the two dimensional triangular lattice photonic crystal layer, the defect cavity has been established to provide sub-wavelength scale plasmonic mode localization within the hybrid plasmonic photonic crystal structure TM band gap. Comprehensive analysis methods of three-dimensional finite difference time domain method (3D-FDTD) have been used to analyze the characteristics of the micro-cavity of this hybrid structure, including the effects of the radius of the nearest neighbor air holes around the defect, the cavity length of the defect and the thickness of the gain medium on the features of the micro-cavity. By using a quantum dots (QDs)-polymer as a gain medium for the low index thin layer, a gain threshold as low as gth = 534 cm-1 can be achieved with such structures, and deep sub-wavelength mode volume of 0.00201 (λ/n)3 is also obtained.

  14. Comparison of cytotoxicity and thin-layer chromatography methods for detection of mycotoxins.

    OpenAIRE

    Robb, J; Norval, M

    1983-01-01

    Thirty-three standard mycotoxins were assayed by thin-layer chromatography and by cytotoxicity in HEp-2 and Chang cells. Various levels of detection were found. The cytotoxicity test was significantly more sensitive than thin-layer chromatography for the trichothecenes and should be useful for screening extracts from animal feedstuffs for the presence of unknown mycotoxins.

  15. Using thin metal layers on composite structures for shielding the electromagnetic pulse caused by nearby lightning

    NARCIS (Netherlands)

    Blaj, M.A.; Buesink, F.J.K.; Damstra, G.C.; Leferink, F.B.J.

    2011-01-01

    Electronic systems in composite structures could be vulnerable to the (dominant magnetic) field caused by a lightning strike, because only thin layers of metal can be used on composite structures. Thin layers result in a very low shielding effectiveness against magnetic fields. Many experiments usin

  16. Proteins at fluid interfaces: adsorption layers and thin liquid films.

    Science.gov (United States)

    Yampolskaya, Galina; Platikanov, Dimo

    2006-12-21

    A review in which many original published results of the authors as well as many other papers are discussed. The structure and some properties of the globular proteins are shortly presented, special accent being put on the alpha-chymotrypsin (alpha-ChT), lysozyme (LZ), human serum albumin (HSA), and bovine serum albumin (BSA) which have been used in the experiments with thin liquid films. The behaviour of protein adsorption layers (PAL) is extensively discussed. The dynamics of PAL formation, including the kinetics of adsorption as well as the time evolution of the surface tension of protein aqueous solutions, are considered. A considerable place is devoted to the surface tension and adsorption isotherms of the globular protein solutions, the simulation of PAL by interacting hard spheres, the experimental surface tension isotherms of the above mentioned proteins, and the interfacial tension isotherms for the protein aqueous solution/oil interface. The rheological properties of PAL at fluid interfaces are shortly reviewed. After a brief information about the experimental methods for investigation of protein thin liquid (foam or emulsion) films, the properties of the protein black foam films are extensively discussed: the conditions for their formation, the influence of the electrolytes and pH on the film type and stability, the thermodynamic properties of the black foam films, the contact angles film/bulk and their dynamic hysteresis. The next center of attention concerns some properties of the protein emulsion films: the conditions for formation of emulsion black films, the formation and development of a dimpling in microscopic, circular films. The protein-phospholipid mixed foam films are also briefly considered.

  17. Phase separation under two-dimensional Poiseuille flow.

    Science.gov (United States)

    Kiwata, H

    2001-05-01

    The spinodal decomposition of a two-dimensional binary fluid under Poiseuille flow is studied by numerical simulation. We investigated time dependence of domain sizes in directions parallel and perpendicular to the flow. In an effective region of the flow, the power-law growth of a characteristic length in the direction parallel to the flow changes from the diffusive regime with the growth exponent alpha=1/3 to a new regime. The scaling invariance of the growth in the perpendicular direction is destroyed after the diffusive regime. A recurrent prevalence of thick and thin domains which determines log-time periodic oscillations has not been observed in our model. The growth exponents in the infinite system under two-dimensional Poiseuille flow are obtained by the renormalization group.

  18. Design of step composition gradient thin film transistor channel layers grown by atomic layer deposition

    Science.gov (United States)

    Ahn, Cheol Hyoun; Hee Kim, So; Gu Yun, Myeong; Koun Cho, Hyung

    2014-12-01

    In this study, we proposed the artificially designed channel structure in oxide thin-film transistors (TFTs) called a "step-composition gradient channel." We demonstrated Al step-composition gradient Al-Zn-O (AZO) channel structures consisting of three AZO layers with different Al contents. The effects of stacking sequence in the step-composition gradient channel on performance and electrical stability of bottom-gate TFT devices were investigated with two channels of inverse stacking order (ascending/descending step-composition). The TFT with ascending step-composition channel structure (5 → 10 → 14 at. % Al composition) showed relatively negative threshold voltage (-3.7 V) and good instability characteristics with a reduced threshold voltage shift ( Δ 1.4 V), which was related to the alignment of the conduction band off-set within the channel layer depending on the Al contents. Finally, the reduced Al composition in the initial layer of ascending step-composition channel resulted in the best field effect mobility of 4.5 cm2/V s. We presented a unique active layer of the "step-composition gradient channel" in the oxide TFTs and explained the mechanism of adequate channel design.

  19. Graphene oxide monolayers as atomically thin seeding layers for atomic layer deposition of metal oxides.

    Science.gov (United States)

    Nourbakhsh, Amirhasan; Adelmann, Christoph; Song, Yi; Lee, Chang Seung; Asselberghs, Inge; Huyghebaert, Cedric; Brizzi, Simone; Tallarida, Massimo; Schmeisser, Dieter; Van Elshocht, Sven; Heyns, Marc; Kong, Jing; Palacios, Tomás; De Gendt, Stefan

    2015-06-28

    Graphene oxide (GO) was explored as an atomically-thin transferable seed layer for the atomic layer deposition (ALD) of dielectric materials on any substrate of choice. This approach does not require specific chemical groups on the target surface to initiate ALD. This establishes GO as a unique interface which enables the growth of dielectric materials on a wide range of substrate materials and opens up numerous prospects for applications. In this work, a mild oxygen plasma treatment was used to oxidize graphene monolayers with well-controlled and tunable density of epoxide functional groups. This was confirmed by synchrotron-radiation photoelectron spectroscopy. In addition, density functional theory calculations were carried out on representative epoxidized graphene monolayer models to correlate the capacitive properties of GO with its electronic structure. Capacitance-voltage measurements showed that the capacitive behavior of Al2O3/GO depends on the oxidation level of GO. Finally, GO was successfully used as an ALD seed layer for the deposition of Al2O3 on chemically inert single layer graphene, resulting in high performance top-gated field-effect transistors.

  20. Atomic layer deposition of copper sulfide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Nathanaelle, E-mail: n.schneider@chimie-paristech.fr; Lincot, Daniel; Donsanti, Frédérique

    2016-02-01

    Atomic Layer Deposition (ALD) of copper sulfide (Cu{sub x}S) thin films from Cu(acac){sub 2} (acac = acetylacetonate = 2,4-pentanedionate) and H{sub 2}S as Cu and S precursors is reported. Typical self-saturated reactions (“ALD window”) are obtained in the temperature range T{sub dep} = 130–200 °C for an average growth per cycle (GR) = 0.25 Å/cycle. The morphology, crystallographic structure, chemical composition, electrical properties and optical band gap of thin films were investigated using scanning electronic microscopy (SEM), X-ray diffraction under Grazing Incidence conditions (GI-XRD), X-ray reflectivity (XRR), energy dispersive spectrometry (EDS), Hall effect measurements, and UV–vis spectroscopy. The obtained copper sulfide films are heavily p-doped (charge carrier concentration ~ 10{sup 21} –10{sup 22} cm{sup −3}) with optical band gaps in the range of 2.2–2.5 eV for direct and 1.6–1.8 eV for indirect band gaps. Depending on the number of ALD cycles, multiphase compounds (made of digenite Cu{sub 1.8}S, chalcocite Cu{sub 2}S, djurleite Cu{sub 31}S{sub 16} and covellite CuS) or single-phase digenite Cu{sub 1.8}S films are obtained via a growth mechanism that involves in-situ copper reduction and loss of sulfur by evaporation. - Highlights: • Cu{sub x}S films were synthesized by atomic layer deposition from Cu(acac){sub 2} and H{sub 2}S. • Self-saturated reactions at T{sub dep} = 130–200 °C for growth = 0.25 Å/cycle • Multi- or single- phase films are obtained depending on the number of cycles. • Growth mechanism involves copper reduction and loss of sulfur by evaporation.

  1. Layer-by-layer thin film of reduced graphene oxide and gold nanoparticles as an effective sample plate in laser-induced desorption/ionization mass spectrometry.

    Science.gov (United States)

    Kuo, Tsung-Rong; Wang, Di-Yan; Chiu, Yu-Chen; Yeh, Yun-Chieh; Chen, Wei-Ting; Chen, Ching-Hui; Chen, Chun-Wei; Chang, Huan-Cheng; Hu, Cho-Chun; Chen, Chia-Chun

    2014-01-27

    This work demonstrated a simple platform for rapid and effective surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) measurements based on the layer structure of reduced graphene oxide (rGO) and gold nanoparticles. A multi-layer thin film was fabricated by alternate layer-by-layer depositions of rGO and gold nanoparticles (LBL rGO/AuNP). The flat and clean two-dimensional film was served as the sample plate and also functioned as the matrix in SALDI-TOF MS. By simply one-step deposition of analytes onto the LBL rGO/AuNP sample plate, the MS measurements of various homogeneous samples were ready to execute. The optimization of MS signal was reached by the variation of the layer numbers of rGO and gold nanoparticles. Also, the small molecules including amino acids, carbohydrates and peptides were successfully analyzed in SALDI-TOF MS using the LBL rGO/AuNP sample plate. The results showed that the signal intensity, S N(-1) ratio and reproducibility of SALDI-TOF spectra have been significantly improved in comparison to the uses of gold nanoparticles or α-cyano-4-hydroxy-cinnamic acid (CHCA) as the assisted matrixes. Taking the advantages of the unique properties of rGO and gold nanoparticles, the ready-to-use MS sample plate, which could absorb and dissipate laser energy to analytes quite efficiently and homogeneously, has shown great commercial potentials for MS applications.

  2. Percolative behavior of an anisotropic two-dimensional network:Growth of tellurium onto an oriented polymer film

    Science.gov (United States)

    Hoffmann, T.; Martínez-Salazar, J.; Herrero, P.; Petermann, J.

    1997-01-01

    In situ transport measurements during the growth of a thin layer of thermally evaporated tellurium onto an oriented polymer film are presented. The system, which resembles the characteristics of a two-dimensional anisotropic network, is analyzed in terms of the current percolation theory. Parameters such as the percolation threshold and the critical exponents are calculated for the perpendicular and the parallel orientation. Within the limits of the experiments the values of t∥ and t⊥ are estimated to be 1.15 and 1.46, respectively.

  3. Molecular assembly on two-dimensional materials

    Science.gov (United States)

    Kumar, Avijit; Banerjee, Kaustuv; Liljeroth, Peter

    2017-02-01

    Molecular self-assembly is a well-known technique to create highly functional nanostructures on surfaces. Self-assembly on two-dimensional (2D) materials is a developing field driven by the interest in functionalization of 2D materials in order to tune their electronic properties. This has resulted in the discovery of several rich and interesting phenomena. Here, we review this progress with an emphasis on the electronic properties of the adsorbates and the substrate in well-defined systems, as unveiled by scanning tunneling microscopy. The review covers three aspects of the self-assembly. The first one focuses on non-covalent self-assembly dealing with site-selectivity due to inherent moiré pattern present on 2D materials grown on substrates. We also see that modification of intermolecular interactions and molecule–substrate interactions influences the assembly drastically and that 2D materials can also be used as a platform to carry out covalent and metal-coordinated assembly. The second part deals with the electronic properties of molecules adsorbed on 2D materials. By virtue of being inert and possessing low density of states near the Fermi level, 2D materials decouple molecules electronically from the underlying metal substrate and allow high-resolution spectroscopy and imaging of molecular orbitals. The moiré pattern on the 2D materials causes site-selective gating and charging of molecules in some cases. The last section covers the effects of self-assembled, acceptor and donor type, organic molecules on the electronic properties of graphene as revealed by spectroscopy and electrical transport measurements. Non-covalent functionalization of 2D materials has already been applied for their application as catalysts and sensors. With the current surge of activity on building van der Waals heterostructures from atomically thin crystals, molecular self-assembly has the potential to add an extra level of flexibility and functionality for applications ranging

  4. Interpolation by two-dimensional cubic convolution

    Science.gov (United States)

    Shi, Jiazheng; Reichenbach, Stephen E.

    2003-08-01

    This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.

  5. Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Nurhandoko, Bagus Endar B., E-mail: bagusnur@bdg.centrin.net.id, E-mail: bagusnur@rock-fluid.com [Wave Inversion and Subsurface Fluid Imaging Research Laboratory (WISFIR), Basic Science Center A 4" t" hfloor, Physics Dept., FMIPA, Institut Teknologi Bandung (Indonesia); Rock Fluid Imaging Lab., Bandung (Indonesia); Susilowati, E-mail: bagusnur@bdg.centrin.net.id, E-mail: bagusnur@rock-fluid.com [Rock Fluid Imaging Lab., Bandung (Indonesia)

    2015-04-16

    Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir’s layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied about the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir’s character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia.

  6. Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs

    Science.gov (United States)

    Nurhandoko, Bagus Endar B.; Susilowati

    2015-04-01

    Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir's layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied about the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir's character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia.

  7. Thin layer chromatography-ion mobility spectrometry (TLC-IMS).

    Science.gov (United States)

    Ilbeigi, Vahideh; Tabrizchi, Mahmoud

    2015-01-06

    Ion mobility spectrometry (IMS) is a fast and sensitive analytical method which operates at the atmospheric pressure. To enhance the capability of IMS for the analysis of mixtures, it is often used with preseparation techniques, such as GC or HPLC. Here, we report for the first time the coupling of the thin-layer chromatography and IMS. A variety of coupling schemes were tried that included direct electrospray from the TLC strip tip, indirect electrospray from a needle connected to the TLC strip, introducing the moving solvent into the injection port, and, the simplest way, offline introduction of scratched or cut pieces of strips into the IMS injection port. In this study a special solvent tank was designed and the TLC strip was mounted horizontally where the solvent would flow down. A very small funnel right below the TLC tip collected the solvent and transferred it to a needle via a capillary tubing. Using the TLC-ESI-IMS technique, acceptable separations were achieved for two component mixtures of morphine-papaverine and acridine-papaverine. A special injection port was designed to host the pieces cut off the TLC. The method was successfully used to identify each spot on the TLC by IMS in a few seconds.

  8. Junction conditions in quadratic gravity: thin shells and double layers

    CERN Document Server

    Reina, Borja; Vera, Raül

    2015-01-01

    The junction conditions for the most general gravitational theory with a Lagrangian containing terms quadratic in the curvature are derived. We include the cases with a possible concentration of matter on the joining hypersurface -termed as thin shells, domain walls or braneworlds in the literature- as well as the proper matching conditions where only finite jumps of the energy-momentum tensor are allowed. In the latter case we prove that the matching conditions are more demanding than in General Relativity. In the former case, we show that generically the shells/domain walls are of a new kind because they possess, in addition to the standard energy-momentum tensor, a double layer energy-momentum contribution which actually induces an external energy flux vector and an external scalar pressure/tension on the shell. We prove that all these contributions are necessary to make the entire energy-momentum tensor divergence-free, and we present the field equations satisfied by these energy-momentum quantities. The ...

  9. Somatic Embryogenesis of Lilium from Microbulb Transverse Thin Cell Layers.

    Science.gov (United States)

    Marinangeli, Pablo

    2016-01-01

    A reliable somatic embryogenesis protocol is a prerequisite for application of other plant biotechniques. Several protocols were reported for genus Lilium, with variable success. Between them, transverse Thin Cell Layers (tTCL) were used efficiently to induce indirect somatic embryogenesis of Lilium. Somatic embryogenesis potential is dependent on the genotype, explant, and culture medium composition, especially as for plant growth regulators and environmental conditions. Usually, the process comprises three phases: embryogenic callus induction, embryogenic callus proliferation and somatic embryo germination. Somatic embryo germination can be achieved in light or dark. In the first case, complete plantlets are formed, with green leaves and pseudobulb in the base. In darkness, microbulbs are formed from single somatic embryos or clusters. A last phase of microbulb enlargement allows plantlets or microbulbs to increase their biomass. These enlarged microbulbs do not need special acclimatization conditions when transferred to soil and quickly produce sturdy plants. This chapter describes a protocol for somatic embryogenesis of Lilium using tTCL from microbulbs.

  10. Mathematical analogies in physics. Thin-layer wave theory

    Directory of Open Access Journals (Sweden)

    José M. Carcione

    2014-03-01

    Full Text Available Field theory applies to elastodynamics, electromagnetism, quantum mechanics, gravitation and other similar fields of physics, where the basic equations describing the phenomenon are based on constitutive relations and balance equations. For instance, in elastodynamics, these are the stress-strain relations and the equations of momentum conservation (Euler-Newton law. In these cases, the same mathematical theory can be used, by establishing appropriate mathematical equivalences (or analogies between material properties and field variables. For instance, the wave equation and the related mathematical developments can be used to describe anelastic and electromagnetic wave propagation, and are extensively used in quantum mechanics. In this work, we obtain the mathematical analogy for the reflection/refraction (transmission problem of a thin layer embedded between dissimilar media, considering the presence of anisotropy and attenuation/viscosity in the viscoelastic case, conductivity in the electromagnetic case and a potential barrier in quantum physics (the tunnel effect. The analogy is mainly illustrated with geophysical examples of propagation of S (shear, P (compressional, TM (transverse-magnetic and TE (transverse-electric waves. The tunnel effect is obtained as a special case of viscoelastic waves at normal incidence.

  11. Characterization of Thin Layer Hot Air Drying of Celery Root

    Directory of Open Access Journals (Sweden)

    Xiaohong Wei

    2015-08-01

    Full Text Available The hot air drying characteristics of celery root were evaluated in a laboratory scale dryer at the drying temperatures of 50, 60, 70 and 80°C. The effect of hot air drying on drying time, drying rate, moisture content, moisture ratio and effective moisture diffusivity of celery root was investigated. Fifteen thin layer drying models were fitted by using experimental drying data. The fitting effect of model predictions was evaluated by using the values of coefficient of determination, sum squared error, root mean square error and chi-square. The results showed fitting accuracy of model 15 (Hii et al.,2009 gave a better fit for all drying conditions applied. The average values of effective moisture diffusivities of celery root ranged from 1.957×10-9 to 9.016×10-9 within the given drying temperature range. With in a certain temperature range (50-70°C, the average effective moisture diffusivities of celery root increased with increased temperature. The activation energy was estimated as 21.817 KJ/mol using an exponential expression based on the Arrhenius equation.

  12. Junction conditions in quadratic gravity: thin shells and double layers

    Science.gov (United States)

    Reina, Borja; Senovilla, José M. M.; Vera, Raül

    2016-05-01

    The junction conditions for the most general gravitational theory with a Lagrangian containing terms quadratic in the curvature are derived. We include the cases with a possible concentration of matter on the joining hypersurface—termed as thin shells, domain walls or braneworlds in the literature—as well as the proper matching conditions where only finite jumps of the energy-momentum tensor are allowed. In the latter case we prove that the matching conditions are more demanding than in general relativity. In the former case, we show that generically the shells/domain walls are of a new kind because they possess, in addition to the standard energy-momentum tensor, a double layer energy-momentum contribution which actually induces an external energy flux vector and an external scalar pressure/tension on the shell. We prove that all these contributions are necessary to make the entire energy-momentum tensor divergence-free, and we present the field equations satisfied by these energy-momentum quantities. The consequences of all these results are briefly analyzed.

  13. TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yougang; Xu, Yidong; Chen, Xuelei [Key Laboratory of Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 China (China); Park, Changbom [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); Kim, Juhan, E-mail: wangyg@bao.ac.cn, E-mail: cbp@kias.re.kr [Center for Advanced Computation, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of)

    2015-11-20

    We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array.

  14. Two dimensional topology of cosmological reionization

    CERN Document Server

    Wang, Yougang; Xu, Yidong; Chen, Xuelei; Kim, Juhan

    2015-01-01

    We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two dimensional genus curve for the early, middle and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometer Array.

  15. Fibromyalgia Is Correlated with Retinal Nerve Fiber Layer Thinning

    Science.gov (United States)

    Garcia-Martin, Elena; Garcia-Campayo, Javier; Puebla-Guedea, Marta; Ascaso, Francisco J.; Roca, Miguel; Gutierrez-Ruiz, Fernando; Vilades, Elisa; Polo, Vicente; Larrosa, Jose M.; Pablo, Luis E.; Satue, Maria

    2016-01-01

    Objective To investigate whether fibromyalgia induces axonal damage in the optic nerve that can be detected using optical coherence tomography (OCT), as the retinal nerve fiber layer (RNFL) is atrophied in patients with fibromyalgia compared with controls. Methods Fibromyalgia patients (n = 116) and age-matched healthy controls (n = 144) were included in this observational and prospective cohort study. All subjects underwent visual acuity measurement and structural analysis of the RNFL using two OCT devices (Cirrus and Spectralis). Fibromyalgia patients were evaluated according to Giesecke’s fibromyalgia subgroups, the Fibromyalgia Impact Questionnaire (FIQ), and the European Quality of Life-5 Dimensions (EQ5D) scale. We compared the differences between fibromyalgia patients and controls, and analyzed the correlations between OCT measurements, disease duration, fibromyalgia subgroups, severity, and quality of life. The impact on quality of life in fibromyalgia subgroups and in patients with different disease severity was also analyzed. Results A significant decrease in the RNFL was detected in fibromyalgia patients compared with controls using the two OCT devices: Cirrus OCT ganglion cell layer analysis registered a significant decrease in the minimum thickness of the inner plexiform layer (74.99±16.63 vs 79.36±3.38 μm, respectively; p = 0.023), nasal inferior, temporal inferior and temporal superior sectors (p = 0.040; 0.011 and 0.046 respectively). The Glaucoma application of the Spectralis OCT revealed thinning in the nasal, temporal inferior and temporal superior sectors (p = 0.009, 0.006, and 0.002 respectively) of fibromyalgia patients and the Axonal application in all sectors, except the nasal superior and temporal sectors. The odds ratio (OR) to estimate the size effect of FM in RNFL thickness was 1.39. RNFL atrophy was detected in patients with FIQ scores fibromyalgia (FIQ≥60) compared with patients with mild fibromyalgia (FIQfibromyalgia exhibited

  16. Instrumentation in Support of Research on Bio-optical Thin Layers in Coastal Waters

    Science.gov (United States)

    1997-09-30

    INSTRUMENTATION IN SUPPORT OF RESEARCH ON BIO -OPTICAL THIN LAYERS IN COASTAL WATERS Dian J. Gifford Graduate School of Oceanography University of...SUBTITLE Instrumentation in Support of Research on Bio -optical Thin Layers in Coastal Waters 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...Because the layers scatter both sound and light, they are important in a number of other disciplinary areas in ocean including bio -optics and acoustics

  17. Matching Two-dimensional Gel Electrophoresis' Spots

    DEFF Research Database (Denmark)

    Dos Anjos, António; AL-Tam, Faroq; Shahbazkia, Hamid Reza

    2012-01-01

    This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches. This ar......This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches...

  18. Mobility anisotropy of two-dimensional semiconductors

    Science.gov (United States)

    Lang, Haifeng; Zhang, Shuqing; Liu, Zhirong

    2016-12-01

    The carrier mobility of anisotropic two-dimensional semiconductors under longitudinal acoustic phonon scattering was theoretically studied using deformation potential theory. Based on the Boltzmann equation with the relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was derived, showing that the influence of effective mass on mobility anisotropy is larger than those of deformation potential constant or elastic modulus. Parameters were collected for various anisotropic two-dimensional materials (black phosphorus, Hittorf's phosphorus, BC2N , MXene, TiS3, and GeCH3) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio is overestimated by the previously described method.

  19. Towards two-dimensional search engines

    OpenAIRE

    Ermann, Leonardo; Chepelianskii, Alexei D.; Shepelyansky, Dima L.

    2011-01-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Statistical properties of inf...

  20. Authors' reply to Discussion by E. Siebrits and S. L. Crouch regarding the paper "A two-dimensional linear variation displacement discontinuity method for three-layered elastic media", International Journal of Rock Mechanics and Mining Sciences, Vol. 36, No. 6, pp. 719-729, 1999

    CSIR Research Space (South Africa)

    Shou, KJ

    2000-07-01

    Full Text Available to Discussion by E. Siebrits and S. L. Crouch regarding the paper ``A two-dimensional linear variation displacement discontinuity method for three-layered elastic media'', International Journal of Rock Mechanics and Mining Sciences, Vol. 36, No. 6, pp. 719... of judging the accuracy of their ``highly accurate semi-analytic simulator'' which is International Journal of Rock Mechanics and Mining Sciences 37 (2000) 877±878 1365-1609/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S...

  1. Improvement of the electrical contact resistance at rough interfaces using two dimensional materials

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jianchen; Pan, Chengbin; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano & Soft Materials (FUNSOM), Collaborative Innovation Center of Suzhou Nanoscience and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Li, Heng [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); CAPT, HEDPS and IFSA Collaborative Innovation Center of MoE, Peking University, Beijing 100871 (China); Shen, Panpan; Sun, Hui; Duan, Huiling [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, CAPT, College of Engineering, Peking University, Beijing 100871 (China)

    2015-12-07

    Reducing the electronic contact resistance at the interfaces of nanostructured materials is a major goal for many kinds of planar and three dimensional devices. In this work, we develop a method to enhance the electronic transport at rough interfaces by inserting a two dimensional flexible and conductive graphene sheet. We observe that an ultra-thin graphene layer with a thickness of 0.35 nm can remarkably reduce the roughness of a sample in a factor of 40%, avoiding the use of thick coatings, leading to a more homogeneous current flow, and extraordinarily increasing the total current compared to the graphene-free counterpart. Due to its simplicity and performance enhancement, this methodology can be of interest to many interface and device designers.

  2. Metallic ground state in an ion-gated two-dimensional superconductor.

    Science.gov (United States)

    Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu

    2015-10-23

    Recently emerging two-dimensional (2D) superconductors in atomically thin layers and at heterogeneous interfaces are attracting growing interest in condensed matter physics. Here, we report that an ion-gated zirconium nitride chloride surface, exhibiting a dome-shaped phase diagram with a maximum critical temperature of 14.8 kelvin, behaves as a superconductor persisting to the 2D limit. The superconducting thickness estimated from the upper critical fields is ≅ 1.8 nanometers, which is thinner than one unit-cell. The majority of the vortex phase diagram down to 2 kelvin is occupied by a metallic state with a finite resistance, owing to the quantum creep of vortices caused by extremely weak pinning and disorder. Our findings highlight the potential of electric-field-induced superconductivity, establishing a new platform for accessing quantum phases in clean 2D superconductors.

  3. High-efficiency two-dimensional Ruddlesden-Popper perovskite solar cells

    Science.gov (United States)

    Tsai, Hsinhan; Nie, Wanyi; Blancon, Jean-Christophe; Stoumpos, Constantinos C.; Asadpour, Reza; Harutyunyan, Boris; Neukirch, Amanda J.; Verduzco, Rafael; Crochet, Jared J.; Tretiak, Sergei; Pedesseau, Laurent; Even, Jacky; Alam, Muhammad A.; Gupta, Gautam; Lou, Jun; Ajayan, Pulickel M.; Bedzyk, Michael J.; Kanatzidis, Mercouri G.; Mohite, Aditya D.

    2016-08-01

    Three-dimensional organic-inorganic perovskites have emerged as one of the most promising thin-film solar cell materials owing to their remarkable photophysical properties, which have led to power conversion efficiencies exceeding 20 per cent, with the prospect of further improvements towards the Shockley-Queisser limit for a single-junction solar cell (33.5 per cent). Besides efficiency, another critical factor for photovoltaics and other optoelectronic applications is environmental stability and photostability under operating conditions. In contrast to their three-dimensional counterparts, Ruddlesden-Popper phases—layered two-dimensional perovskite films—have shown promising stability, but poor efficiency at only 4.73 per cent. This relatively poor efficiency is attributed to the inhibition of out-of-plane charge transport by the organic cations, which act like insulating spacing layers between the conducting inorganic slabs. Here we overcome this issue in layered perovskites by producing thin films of near-single-crystalline quality, in which the crystallographic planes of the inorganic perovskite component have a strongly preferential out-of-plane alignment with respect to the contacts in planar solar cells to facilitate efficient charge transport. We report a photovoltaic efficiency of 12.52 per cent with no hysteresis, and the devices exhibit greatly improved stability in comparison to their three-dimensional counterparts when subjected to light, humidity and heat stress tests. Unencapsulated two-dimensional perovskite devices retain over 60 per cent of their efficiency for over 2,250 hours under constant, standard (AM1.5G) illumination, and exhibit greater tolerance to 65 per cent relative humidity than do three-dimensional equivalents. When the devices are encapsulated, the layered devices do not show any degradation under constant AM1.5G illumination or humidity. We anticipate that these results will lead to the growth of single-crystalline, solution

  4. Fermi level de-pinning of aluminium contacts to n-type germanium using thin atomic layer deposited layers

    Energy Technology Data Exchange (ETDEWEB)

    Gajula, D. R., E-mail: dgajula01@qub.ac.uk; Baine, P.; Armstrong, B. M.; McNeill, D. W. [School of Electronics, Electrical Engineering and Computer Science, Queen' s University Belfast, Ashby Building, Stranmillis Road, Belfast BT9 5AH (United Kingdom); Modreanu, M.; Hurley, P. K. [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland)

    2014-01-06

    Fermi-level pinning of aluminium on n-type germanium (n-Ge) was reduced by insertion of a thin interfacial dielectric by atomic layer deposition. The barrier height for aluminium contacts on n-Ge was reduced from 0.7 eV to a value of 0.28 eV for a thin Al{sub 2}O{sub 3} interfacial layer (∼2.8 nm). For diodes with an Al{sub 2}O{sub 3} interfacial layer, the contact resistance started to increase for layer thicknesses above 2.8 nm. For diodes with a HfO{sub 2} interfacial layer, the barrier height was also reduced but the contact resistance increased dramatically for layer thicknesses above 1.5 nm.

  5. a First Cryptosystem for Security of Two-Dimensional Data

    Science.gov (United States)

    Mishra, D. C.; Sharma, Himani; Sharma, R. K.; Kumar, Naveen

    In this paper, we present a novel technique for security of two-dimensional data with the help of cryptography and steganography. The presented approach provides multilayered security of two-dimensional data. First layer security was developed by cryptography and second layer by steganography. The advantage of steganography is that the intended secret message does not attract attention to itself as an object of scrutiny. This paper proposes a novel approach for encryption and decryption of information in the form of Word Data (.doc file), PDF document (.pdf file), Text document, Gray-scale images, and RGB images, etc. by using Vigenere Cipher (VC) associated with Discrete Fourier Transform (DFT) and then hiding the data behind the RGB image (i.e. steganography). Earlier developed techniques provide security of either PDF data, doc data, text data or image data, but not for all types of two-dimensional data and existing techniques used either cryptography or steganography for security. But proposed approach is suitable for all types of data and designed for security of information by cryptography and steganography. The experimental results for Word Data, PDF document, Text document, Gray-scale images and RGB images support the robustness and appropriateness for secure transmission of these data. The security analysis shows that the presented technique is immune from cryptanalytic. This technique further provides security while decryption as a check on behind which RGB color the information is hidden.

  6. Investigation of crystallization behavior of CIG-Se bi-layer thin films.

    Science.gov (United States)

    Park, Mi Sun; Sung, Shi-Joon; Kim, Dae-Hwan; Kang, Jin-Kyu

    2012-04-01

    Copper indium gallium diselenide (CIGSe) thin film was fabricated via a thermal treatment of GIG-Se bi-layer thin films. A CIG layer was prepared first, by a chemical solution deposition (CSD) process. The Se layer was deposited separately on the CIG layer by evaporation. The GIG-Se bi-layer then underwent a thermal treatment to cause a reaction between the two layers. In order to investigate the mechanism of CIG-Se bi-layer crystallization, the thermal treatment temperature was varied. The properties of the prepared CIGSe2 thin films were analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), and UV-visible spectrophotometry.

  7. Photoluminescence-based quality control for thin film absorber layers of photovoltaic devices

    Energy Technology Data Exchange (ETDEWEB)

    Repins, Ingrid L.; Kuciauskas, Darius

    2015-07-07

    A time-resolved photoluminescence-based system providing quality control during manufacture of thin film absorber layers for photovoltaic devices. The system includes a laser generating excitation beams and an optical fiber with an end used both for directing each excitation beam onto a thin film absorber layer and for collecting photoluminescence from the absorber layer. The system includes a processor determining a quality control parameter such as minority carrier lifetime of the thin film absorber layer based on the collected photoluminescence. In some implementations, the laser is a low power, pulsed diode laser having photon energy at least great enough to excite electron hole pairs in the thin film absorber layer. The scattered light may be filterable from the collected photoluminescence, and the system may include a dichroic beam splitter and a filter that transmit the photoluminescence and remove scattered laser light prior to delivery to a photodetector and a digital oscilloscope.

  8. Photoluminescence-based quality control for thin film absorber layers of photovoltaic devices

    Science.gov (United States)

    Repins, Ingrid L.; Kuciauskas, Darius

    2015-07-07

    A time-resolved photoluminescence-based system providing quality control during manufacture of thin film absorber layers for photovoltaic devices. The system includes a laser generating excitation beams and an optical fiber with an end used both for directing each excitation beam onto a thin film absorber layer and for collecting photoluminescence from the absorber layer. The system includes a processor determining a quality control parameter such as minority carrier lifetime of the thin film absorber layer based on the collected photoluminescence. In some implementations, the laser is a low power, pulsed diode laser having photon energy at least great enough to excite electron hole pairs in the thin film absorber layer. The scattered light may be filterable from the collected photoluminescence, and the system may include a dichroic beam splitter and a filter that transmit the photoluminescence and remove scattered laser light prior to delivery to a photodetector and a digital oscilloscope.

  9. Kronecker Product of Two-dimensional Arrays

    Institute of Scientific and Technical Information of China (English)

    Lei Hu

    2006-01-01

    Kronecker sequences constructed from short sequences are good sequences for spread spectrum communication systems. In this paper we study a similar problem for two-dimensional arrays, and we determine the linear complexity of the Kronecker product of two arrays. Our result shows that similar good property on linear complexity holds for Kronecker product of arrays.

  10. Two-Dimensional Toda-Heisenberg Lattice

    Directory of Open Access Journals (Sweden)

    Vadim E. Vekslerchik

    2013-06-01

    Full Text Available We consider a nonlinear model that is a combination of the anisotropic two-dimensional classical Heisenberg and Toda-like lattices. In the framework of the Hirota direct approach, we present the field equations of this model as a bilinear system, which is closely related to the Ablowitz-Ladik hierarchy, and derive its N-soliton solutions.

  11. A novel two dimensional particle velocity sensor

    NARCIS (Netherlands)

    Pjetri, Olti; Wiegerink, Remco J.; Lammerink, Theo S.; Krijnen, Gijs J.

    2013-01-01

    In this paper we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0x2.5x0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to fabrica

  12. Two-dimensional microstrip detector for neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Oed, A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.

  13. Two-dimensional magma-repository interactions

    NARCIS (Netherlands)

    Bokhove, O.

    2001-01-01

    Two-dimensional simulations of magma-repository interactions reveal that the three phases --a shock tube, shock reflection and amplification, and shock attenuation and decay phase-- in a one-dimensional flow tube model have a precursor. This newly identified phase ``zero'' consists of the impact of

  14. Two-dimensional subwavelength plasmonic lattice solitons

    CERN Document Server

    Ye, F; Hu, B; Panoiu, N C

    2010-01-01

    We present a theoretical study of plasmonic lattice solitons (PLSs) formed in two-dimensional (2D) arrays of metallic nanowires embedded into a nonlinear medium with Kerr nonlinearity. We analyze two classes of 2D PLSs families, namely, fundamental and vortical PLSs in both focusing and defocusing media. Their existence, stability, and subwavelength spatial confinement are studied in detai

  15. A two-dimensional Dirac fermion microscope

    DEFF Research Database (Denmark)

    Bøggild, Peter; Caridad, Jose; Stampfer, Christoph

    2017-01-01

    in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2...

  16. Advanced germanium layer transfer for ultra thin body on insulator structure

    Science.gov (United States)

    Maeda, Tatsuro; Chang, Wen-Hsin; Irisawa, Toshifumi; Ishii, Hiroyuki; Hattori, Hiroyuki; Poborchii, Vladimir; Kurashima, Yuuichi; Takagi, Hideki; Uchida, Noriyuki

    2016-12-01

    We present the HEtero-Layer Lift-Off (HELLO) technique to obtain ultra thin body (UTB) Ge on insulator (GeOI) substrates. The transferred ultra thin Ge layers are characterized by the Raman spectroscopy measurements down to the thickness of ˜1 nm, observing a strong Raman intensity enhancement for high quality GeOI structure in ultra thin regime due to quantum size effect. This advanced Ge layer transfer technique enabled us to demonstrate UTB-GeOI nMOSFETs with the body thickness of only 4 nm.

  17. Singular layers for transmission problems in thin shallow shell theory: Rigid junction case

    Science.gov (United States)

    Merabet, Ismail; Chacha, D. A.; Nicaise, S.

    2010-02-01

    In this Note we study two-dimensional transmission problems for the linear Koiter's model of an elastic multi-structure composed of two thin shallow shells. This work enters in the framework of singular perturbation of problems depending on a small parameter ɛ. The formal limit problem fails to give a solution satisfying all boundary and transmission conditions; it gives only the outer solution. Both in the case of regular or singular loadings, we derive a limit problem which allows us to determine the inner solution explicitly.

  18. 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.

  19. Back contact buffer layer for thin-film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. The photoluminescent lifetime of polyelectrolytes in thin films formed via layer by layer self-assembly.

    Science.gov (United States)

    Reilly, Roseanne S; Smyth, Ciarán A; Rakovich, Yury P; McCabe, Eithne M

    2009-03-04

    We present results on luminescence lifetime studies of thin multilayer films of polyelectrolyte molecules produced via layer by layer (LbL) electrostatic assembly. We found that, in contrast to common assumptions, LbL films show measurable photoluminescent lifetimes with an average value of 6 ns. Scanning fluorescence lifetime imaging microscopy studies combined with steady-state photoluminescence measurements imply that this lifetime may be due to aggregation of polyelectrolyte molecules during preparation of LbL films. This conclusion has been further confirmed by atomic force microscopy (AFM). AFM images clearly show the presence of 100-200 nm high aggregates on the surface of these films. This aggregation of polyelectrolyte molecules contributes significantly to the experimentally detected luminescence decays of any light-emitting samples attached to LbL film, especially in a single molecule detection regime. To demonstrate this effect we compare photoluminescence lifetime results for CdTe quantum dots deposited on the surface of LbL polyelectrolyte films.

  1. A model for thin layer formation by delayed particle settling at sharp density gradients

    Science.gov (United States)

    Prairie, Jennifer C.; White, Brian L.

    2017-02-01

    Thin layers - regions where plankton or particles accumulate vertically on scales of a few meters or less - are common in coastal waters, and have important implications for both trophic dynamics and carbon cycling. These features can form by a variety of biological and physical mechanisms, including localized growth, shear-thinning, and directed swimming. An additional mechanism may result in the formation of thin layers of marine aggregates, which have been shown to decrease their settling velocity when passing through sharp density gradients, a behavior termed delayed settling. Here, we apply a simple vertical advection-diffusion model to predict the properties of aggregate thin layers formed by this process. We assume a constant vertical flux of particles from the surface, which is parameterized by observations from laboratory experiments with marine aggregates. The formation, maintenance, and shape of the layers are described in relation to non-dimensional numbers that depend on environmental conditions and particle settling properties. In particular, model results demonstrate layer intensity and sharpness both increase with higher Péclet number (Pe), that is, under conditions with weaker mixing relative to layer formation. Similarly, more intense and sharper layers are found when the delayed settling behavior of aggregates is characterized by a lower velocity minimum. The model also predicts layers that are vertically asymmetric and highly "peaky" when compared with a Gaussian distribution, features often seen in thin layers in natural environments. Lastly, by comparing model predictions with observations of thin layers in the field, we are able to gain some insight into the applicability of delayed settling as a thin layer formation mechanism in different environmental conditions.

  2. Wafer-scale controlled exfoliation of metal organic vapor phase epitaxy grown InGaN/GaN multi quantum well structures using low-tack two-dimensional layered h-BN

    Energy Technology Data Exchange (ETDEWEB)

    Ayari, Taha; Li, Xin; Voss, Paul L.; Ougazzaden, Abdallah, E-mail: aougazza@georgiatech-metz.fr [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Georgia Tech Lorraine, UMI 2958, Georgia Tech-CNRS, 57070 Metz (France); Sundaram, Suresh; El Gmili, Youssef [Georgia Tech Lorraine, UMI 2958, Georgia Tech-CNRS, 57070 Metz (France); Salvestrini, Jean Paul [Georgia Tech Lorraine, UMI 2958, Georgia Tech-CNRS, 57070 Metz (France); Université de Lorraine, LMOPS, EA 4423, 57070 Metz (France)

    2016-04-25

    Recent advances in epitaxial growth have led to the growth of III-nitride devices on 2D layered h-BN. This advance has the potential for wafer-scale transfer to arbitrary substrates, which could improve the thermal management and would allow III-N devices to be used more flexibly in a broader range of applications. We report wafer scale exfoliation of a metal organic vapor phase epitaxy grown InGaN/GaN Multi Quantum Well (MQW) structure from a 5 nm thick h-BN layer that was grown on a 2-inch sapphire substrate. The weak van der Waals bonds between h-BN atomic layers break easily, allowing the MQW structure to be mechanically lifted off from the sapphire substrate using a commercial adhesive tape. This results in the surface roughness of only 1.14 nm on the separated surface. Structural characterizations performed before and after the lift-off confirm the conservation of structural properties after lift-off. Cathodoluminescence at 454 nm was present before lift-off and 458 nm was present after. Electroluminescence near 450 nm from the lifted-off structure has also been observed. These results show that the high crystalline quality ultrathin h-BN serves as an effective sacrificial layer—it maintains performance, while also reducing the GaN buffer thickness and temperature ramps as compared to a conventional two-step growth method. These results support the use of h-BN as a low-tack sacrificial underlying layer for GaN-based device structures and demonstrate the feasibility of large area lift-off and transfer to any template, which is important for industrial scale production.

  3. Electronics based on two-dimensional materials.

    Science.gov (United States)

    Fiori, Gianluca; Bonaccorso, Francesco; Iannaccone, Giuseppe; Palacios, Tomás; Neumaier, Daniel; Seabaugh, Alan; Banerjee, Sanjay K; Colombo, Luigi

    2014-10-01

    The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

  4. Two-dimensional ranking of Wikipedia articles

    Science.gov (United States)

    Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.

    2010-10-01

    The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.

  5. Two-Dimensional NMR Lineshape Analysis

    Science.gov (United States)

    Waudby, Christopher A.; Ramos, Andres; Cabrita, Lisa D.; Christodoulou, John

    2016-04-01

    NMR titration experiments are a rich source of structural, mechanistic, thermodynamic and kinetic information on biomolecular interactions, which can be extracted through the quantitative analysis of resonance lineshapes. However, applications of such analyses are frequently limited by peak overlap inherent to complex biomolecular systems. Moreover, systematic errors may arise due to the analysis of two-dimensional data using theoretical frameworks developed for one-dimensional experiments. Here we introduce a more accurate and convenient method for the analysis of such data, based on the direct quantum mechanical simulation and fitting of entire two-dimensional experiments, which we implement in a new software tool, TITAN (TITration ANalysis). We expect the approach, which we demonstrate for a variety of protein-protein and protein-ligand interactions, to be particularly useful in providing information on multi-step or multi-component interactions.

  6. Towards two-dimensional search engines

    CERN Document Server

    Ermann, Leonardo; Shepelyansky, Dima L

    2011-01-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Information flow properties on PageRank-CheiRank plane are analyzed for networks of British, French and Italian Universities, Wikipedia, Linux Kernel, gene regulation and other networks. Methods of spam links control are also analyzed.

  7. Toward two-dimensional search engines

    Science.gov (United States)

    Ermann, L.; Chepelianskii, A. D.; Shepelyansky, D. L.

    2012-07-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank-CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed.

  8. A two-dimensional Dirac fermion microscope

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M.; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-01

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  9. A two-dimensional Dirac fermion microscope.

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-09

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  10. Isolation of Three Components from Spearmint Oil: An Exercise in Column and Thin-Layer Chromatography

    Science.gov (United States)

    Davies, Don R.; Johnson, Todd M.

    2007-01-01

    A simple experiment for undergraduate organic chemistry students to separate a colorless mixture using column chromatography and then monitor the outcome of the separation using thin-layer chromatography (TLC) and infrared spectroscopy(IR) is described. The experiment teaches students the principle and techniques of column and thin-layer…

  11. Optimization of optical absorption in thin layers of amorphous silicon enhanced by silver nanospheres

    CERN Document Server

    Omelyanovich, Mikhail; Simovski, Constantin

    2015-01-01

    We study a highly controllable perfect plasmonic absorber -- a thin metamaterial layer which possess balanced electric and magnetic responses in some frequency range. We show that this regime is compatible with both metal-backed variant of the structure or its semitransparent variant. This regime can be implemented in a prospective thin-film photovoltaic cell with negligible parasitic losses.

  12. Detection of Phenolic and Flavonoid Compounds Using High Performance Thin Layer Chromatography (HPTLC).

    Science.gov (United States)

    2016-01-01

    High performance thin layer chromatography (HPTLC) is a sophisticated instrumental technique based on the full capabilities of thin layerchromatography. The advantages of automation, scanning, full optimization, selective detection principle, minimum sample preparation,hyphenation, etc., enable it to be a powerful analytical tool for chromatographic information of complex mixtures of inorganic, organic andbiomolecules which are characterized in this chapter.

  13. Isolation of Three Components from Spearmint Oil: An Exercise in Column and Thin-Layer Chromatography

    Science.gov (United States)

    Davies, Don R.; Johnson, Todd M.

    2007-01-01

    A simple experiment for undergraduate organic chemistry students to separate a colorless mixture using column chromatography and then monitor the outcome of the separation using thin-layer chromatography (TLC) and infrared spectroscopy(IR) is described. The experiment teaches students the principle and techniques of column and thin-layer…

  14. Two-Dimensional Scheduling: A Review

    Directory of Open Access Journals (Sweden)

    Zhuolei Xiao

    2013-07-01

    Full Text Available In this study, we present a literature review, classification schemes and analysis of methodology for scheduling problems on Batch Processing machine (BP with both processing time and job size constraints which is also regarded as Two-Dimensional (TD scheduling. Special attention is given to scheduling problems with non-identical job sizes and processing times, with details of the basic algorithms and other significant results.

  15. Two dimensional fermions in four dimensional YM

    CERN Document Server

    Narayanan, R

    2009-01-01

    Dirac fermions in the fundamental representation of SU(N) live on a two dimensional torus flatly embedded in $R^4$. They interact with a four dimensional SU(N) Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the size of the torus in units of $\\frac{1}{\\Lambda_{SU(N)}}$ is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit.

  16. Two-dimensional Kagome photonic bandgap waveguide

    DEFF Research Database (Denmark)

    Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou;

    2000-01-01

    The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....

  17. String breaking in two-dimensional QCD

    CERN Document Server

    Hornbostel, K J

    1999-01-01

    I present results of a numerical calculation of the effects of light quark-antiquark pairs on the linear heavy-quark potential in light-cone quantized two-dimensional QCD. I extract the potential from the Q-Qbar component of the ground-state wavefunction, and observe string breaking at the heavy-light meson pair threshold. I briefly comment on the states responsible for the breaking.

  18. In situ Validation of the Source of Thin Layers Detected by NOAA Airborne Fish Lidar

    Science.gov (United States)

    2010-09-30

    2009, doi:10.1093/icesjms/fsp029. Donaghay, P.L., Osborn, T.R., 1997. Toward a theory of biological-physical control of harmful algal bloom ...DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited. In situ Validation of the Source of Thin Layers Detected by...resulting thin layers impact in situ and remote sensing technologies of critical interest to the Navy. We are also interested in improving our ability

  19. [Use of column and thin layer chromatography for detection of vanillyl mandelic acid in urine].

    Science.gov (United States)

    Riabichenko, V V; Barchukov, V G; Chernyĭ, A V; Salenko, Iu A

    2002-03-01

    The excretion of vanillylmandelic acid was measured by column chromatography of urinary samples on aluminum oxide with subsequent thin-layer chromatography on silica gel. Use of aluminum oxide allowed application of greater urine samples (up to 0.1% of 24-h diuresis) onto chromatographic plates and essentially improved the quality of separation of vanillylmandelic acid from other phenylcarbonic acids by thin-layer chromatography, as well as the specificity and reproducibility of measurements.

  20. Two-dimensional oxides: multifunctional materials for advanced technologies.

    Science.gov (United States)

    Pacchioni, Gianfranco

    2012-08-13

    The last decade has seen spectacular progress in the design, preparation, and characterization down to the atomic scale of oxide ultrathin films of few nanometers thickness grown on a different material. This has paved the way towards several sophisticated applications in advanced technologies. By playing around with the low-dimensionality of the oxide layer, which sometimes leads to truly two-dimensional systems, one can exploit new properties and functionalities that are not present in the corresponding bulk materials or thick films. In this review we provide some clues about the most recent advances in the design of these systems based on modern electronic structure theory and on their preparation and characterization with specifically developed growth techniques and analytical methods. We show how two-dimensional oxides can be used in mature technologies by providing added value to existing materials, or in new technologies based on completely new paradigms. The fields in which two-dimensional oxides are used are classified based on the properties that are exploited, chemical or physical. With respect to chemical properties we discuss use of oxide ultrathin films in catalysis, solid oxide fuel cells, gas sensors, corrosion protection, and biocompatible materials; regarding the physical properties we discuss metal-oxide field effect transistors and memristors, spintronic devices, ferroelectrics and thermoelectrics, and solar energy materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Layered ternary M n+1AX n phases and their 2D derivative MXene: an overview from a thin-film perspective

    Science.gov (United States)

    Eklund, Per; Rosen, Johanna; Persson, Per O. Å.

    2017-03-01

    Inherently and artificially layered materials are commonly investigated both for fundamental scientific purposes and for technological application. When a layered material is thinned or delaminated to its physical limits, a two-dimensional (2D) material is formed and exhibits novel properties compared to its bulk parent phase. The complex layered phases known as ‘MAX phases’ (where M  =  early transition metal, A  =  A-group element, e.g. Al or Si, and X  =  C or N) are an exciting model system for materials design and the understanding of process-structure-property relationships. When the A layers are selectively etched from the MAX phases, a new type of 2D material is formed, named MXene to emphasize the relation to the MAX phases and the parallel with graphene. Since their discovery in 2011, MXenes have rapidly become established as a novel class of 2D materials with remarkable possibilities for composition variations and property tuning. This article gives a brief overview of MAX phases and MXene from a thin-film perspective, reviewing theory, characterization by electron microscopy, properties and how these are affected by the change in dimensionality, and outstanding challenges.

  2. Two dimensional echocardiographic detection of intraatrial masses.

    Science.gov (United States)

    DePace, N L; Soulen, R L; Kotler, M N; Mintz, G S

    1981-11-01

    With two dimensional echocardiography, a left atrial mass was detected in 19 patients. Of these, 10 patients with rheumatic mitral stenosis had a left atrial thrombus. The distinctive two dimensional echocardiographic features of left atrial thrombus included a mass of irregular nonmobile laminated echos within an enlarged atrial cavity, usually with a broad base of attachment to the posterior left atrial wall. Seven patients had a left atrial myxoma. Usually, the myxoma appeared as a mottled ovoid, sharply demarcated mobile mass attached to the interatrial septum. One patient had a right atrial angiosarcoma that appeared as a nonmobile mass extending from the inferior vena caval-right atrial junction into the right atrial cavity. One patient had a left atrial leiomyosarcoma producing a highly mobile mass attached to the lateral wall of the left atrium. M mode echocardiography detected six of the seven myxomas, one thrombus and neither of the other tumors. Thus, two dimensional echocardiography appears to be the technique of choice in the detection, localization and differentiation of intraatrial masses.

  3. Crystallinity Improvement of ZnO Thin Film on Different Buffer Layers Grown by MBE

    Directory of Open Access Journals (Sweden)

    Shao-Ying Ting

    2012-01-01

    Full Text Available The material and optical properties of ZnO thin film samples grown on different buffer layers on sapphire substrates through a two-step temperature variation growth by molecular beam epitaxy were investigated. The thin buffer layer between the ZnO layer and the sapphire substrate decreased the lattice mismatch to achieve higher quality ZnO thin film growth. A GaN buffer layer slightly increased the quality of the ZnO thin film, but the threading dislocations still stretched along the c-axis of the GaN layer. The use of MgO as the buffer layer decreased the surface roughness of the ZnO thin film by 58.8% due to the suppression of surface cracks through strain transfer of the sample. From deep level emission and rocking curve measurements it was found that the threading dislocations play a more important role than oxygen vacancies for high-quality ZnO thin film growth.

  4. Two-Dimensional Micro-TLC Phenolic Fingerprints of Selected Mentha sp. on Cyano-Bonded Polar Stationary Phase.

    Science.gov (United States)

    Hawrył, Mirosław A; Niemiec, Małgorzata A; Słomka, Kamil; Waksmundzka-Hajnos, Monika; Szymczak, Grażyna

    2016-01-01

    Micro-thin-layer chromatography in two-dimensional (2D-mTLC) mode in normal- (NP) and reversed-phase (RP) systems by use of cyanopropyl-bonded stationary phases was applied to make fingerprints of 11 species of Mentha genus and two finished pharmaceutical products. Non-aqueous eluents were used in the NP systems. Mixtures of acetonitrile with water and methanol with water were used in the RP chromatographic systems. Optimization of one-dimensional systems was performed by determining RM vs. composition of mobile phase dependencies for standards occurring in various Mentha sp. On the basis of these dependencies, the most selective chromatographic systems for each run were chosen. Then most selective eluents were applied to optimize two-dimensional systems by creating RF in NP systems vs. RF in RP systems correlations. The best two-dimensional systems were chosen on the basis of R(2) values for RF vs. RF correlations (the lowest values of R(2) coefficients). The 2D-mTLC optimized systems were applied to separate phenolic compounds and make fingerprints of the examined plant materials.

  5. Breakdown voltage model and structure realization of a thin silicon layer with linear variable doping on a silicon on insulator high voltage device with multiple step field plates

    Institute of Scientific and Technical Information of China (English)

    Qiao Ming; Zhuang Xiang; Wu Li-Juan; Zhang Wen-Tong; Wen Heng-Juan; Zhang Bo; Li Zhao-Ji

    2012-01-01

    Based on the theoretical and experimental investigation of a thin silicon layer (TSL) with linear variable doping (LVD) and further research on the TSL LVD with a multiple step field plate (MSFP),a breakdown voltage (BV) model is proposed and experimentally verified in this paper.With the two-dimensional Poisson equation of the silicon on insulator (SOI) device,the lateral electric field in drift region of the thin silicon layer is assumed to be constant.For the SOI device with LVD in the thin silicon layer,the dependence of the BV on impurity concentration under the drain is investigated by an enhanced dielectric layer field (ENDIF),from which the reduced surface field (RESURF) condition is deduced.The drain in the centre of the device has a good self-isolation effect but the problem of the high voltage interconnection (HVI) line will become serious.The two step field plates including the source field plate and gate field plate can be adopted to shield the HVI adverse effect on the device.Based on this model,the TSL LVD SOI n-channel lateral double-diffused MOSFET (nLDMOS) with MSFP is realized.The experimental breakdown voltage (BV) and specific on-resistance (Ron,sp) of the TSL LVD SOI device are 694 V and 21.3 Ω.mm2 with a drift region length of 60 μm,buried oxide layer of 3 μm,and silicon layer of 0.15 μm,respectively.

  6. Theories on Frustrated Electrons in Two-Dimensional Organic Solids

    Directory of Open Access Journals (Sweden)

    Chisa Hotta

    2012-08-01

    Full Text Available Two-dimensional quarter-filled organic solids are a promising class of materials to realize the strongly correlated insulating states called dimer Mott insulator and charge order. In their conducting layer, the molecules form anisotropic triangular lattices, harboring geometrical frustration effect, which could give rise to many interesting states of matter in the two insulators and in the metals adjacent to them. This review is concerned with the theoretical studies on such issue over the past ten years, and provides the systematic understanding on exotic metals, dielectrics, and spin liquids, which are the consequences of the competing correlation and fluctuation under frustration.

  7. Mean flow generation in rotating anelastic two-dimensional convection

    CERN Document Server

    Currie, Laura K

    2016-01-01

    We investigate the processes that lead to the generation of mean flows in two-dimensional anelastic convection. The simple model consists of a plane layer that is rotating about an axis inclined to gravity. The results are two-fold: firstly we numerically investigate the onset of convection in three-dimensions, paying particular attention to the role of stratification and highlight a curious symmetry. Secondly, we investigate the mechanisms that drive both zonal and meridional flows in two dimensions. We find that, in general, non-trivial Reynolds stresses can lead to systematic flows and, using statistical measures, we quantify the role of stratification in modifying the coherence of these flows.

  8. Two-dimensional carbon fundamental properties, synthesis, characterization, and applications

    CERN Document Server

    Yihong, Wu; Ting, Yu

    2013-01-01

    After a brief introduction to the fundamental properties of graphene, this book focuses on synthesis, characterization and application of various types of two-dimensional (2D) nanocarbons ranging from single/few layer graphene to carbon nanowalls and graphene oxides. Three major synthesis techniques are covered: epitaxial growth of graphene on SiC, chemical synthesis of graphene on metal, and chemical vapor deposition of vertically aligned carbon nanosheets or nanowalls. One chapter is dedicated to characterization of 2D nanocarbon using Raman spectroscopy. It provides extensive coverage for a

  9. Magnetization of two-dimensional superconductors with defects

    CERN Document Server

    Kashurnikov, V A; Zyubin, M V

    2002-01-01

    The new method for modeling the layered high-temperature superconductors magnetization with defects, based on the Monte-Carlo algorithm, is developed. Minimization of the free energy functional of the vortex two-dimensional system made it possible to obtain the equilibrium vortex density configurations and calculate the magnetization of the superconductor with the arbitrary defects distribution in the wide range of temperatures. The magnetic induction profiles and magnetic flux distribution inside the superconductor, proving the applicability of the Bean model, are calculated

  10. Conduction mechanisms in thin atomic layer deposited Al{sub 2}O{sub 3} layers

    Energy Technology Data Exchange (ETDEWEB)

    Spahr, Holger; Montzka, Sebastian; Reinker, Johannes; Hirschberg, Felix; Kowalsky, Wolfgang; Johannes, Hans-Hermann, E-mail: h2.johannes@ihf.tu-bs.de [Institut für Hochfrequenztechnik, Technische Universität Braunschweig, Schleinitzstraße 22, 38106 Braunschweig (Germany)

    2013-11-14

    Thin Al{sub 2}O{sub 3} layers of 2–135 nm thickness deposited by thermal atomic layer deposition at 80 °C were characterized regarding the current limiting mechanisms by increasing voltage ramp stress. By analyzing the j(U)-characteristics regarding ohmic injection, space charge limited current (SCLC), Schottky-emission, Fowler-Nordheim-tunneling, and Poole-Frenkel-emission, the limiting mechanisms were identified. This was performed by rearranging and plotting the data in a linear scale, such as Schottky-plot, Poole-Frenkel-plot, and Fowler-Nordheim-plot. Linear regression then was applied to the data to extract the values of relative permittivity from Schottky-plot slope and Poole-Frenkel-plot slope. From Fowler-Nordheim-plot slope, the Fowler-Nordheim-energy-barrier was extracted. Example measurements in addition to a statistical overview of the results of all investigated samples are provided. Linear regression was applied to the region of the data that matches the realistic values most. It is concluded that ohmic injection and therefore SCLC only occurs at thicknesses below 12 nm and that the Poole-Frenkel-effect is no significant current limiting process. The extracted Fowler-Nordheim-barriers vary in the range of up to approximately 4 eV but do not show a specific trend. It is discussed whether the negative slope in the Fowler-Nordheim-plot could in some cases be a misinterpreted trap filled limit in the case of space charge limited current.

  11. Cross-Field Current Instabilities in Thin Ionization Layers and the Enhanced Aurora

    Energy Technology Data Exchange (ETDEWEB)

    Jay R. Johnson and Hideo Okuda

    2008-05-20

    Nearly half of the time, auroral displays exhibit thin, bright layers known as \\enhanced aurora." There is a substantial body of evidence that connects these displays with thin, dense, heavy ion layers in the E-region. Based on the spectral characteristics of the enhanced layers, it is believed that they result when wave-particle interaction heats ambient electrons to energies at or just above the 17 eV ionization energy of N2. While there are several possible instabilities that could produce suprathermal electrons in thin layers, there has been no clear theoretical investigation which examines in detail how wave instabilities in the thin ionization layers could develop and produce the suprathermal electrons. We examine instabilities which would occur in thin, dense, heavy ion layers using extensive analytical analysis combined with particle simulations. We analyze a cross field current instability that is found to be strongly unstable in the heavy ion layers. Electrostatic simulations show that substantial heating of the ambient electrons occurs with energization at or above the N2 ionization energy.

  12. Studies of oxide-based thin-layered heterostructures by X-ray scattering methods

    Energy Technology Data Exchange (ETDEWEB)

    Durand, O. [Thales Research and Technology France, Route Departementale 128, F-91767 Palaiseau Cedex (France)]. E-mail: olivier.durand@thalesgroup.com; Rogers, D. [Nanovation SARL, 103 bis rue de Versailles 91400 Orsay (France); Universite de Technologie de Troyes, 10-12 rue Marie Curie, 10010 (France); Teherani, F. Hosseini [Nanovation SARL, 103 bis rue de Versailles 91400 Orsay (France); Andrieux, M. [LEMHE, ICMMOCNRS-UMR 8182, Universite d' Orsay, Batiment 410, 91410 Orsay (France); Modreanu, M. [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland)

    2007-06-04

    Some X-ray scattering methods (X-ray reflectometry and Diffractometry) dedicated to the study of thin-layered heterostructures are presented with a particular focus, for practical purposes, on the description of fast, accurate and robust techniques. The use of X-ray scattering metrology as a routinely working non-destructive testing method, particularly by using procedures simplifying the data-evaluation, is emphasized. The model-independent Fourier-inversion method applied to a reflectivity curve allows a fast determination of the individual layer thicknesses. We demonstrate the capability of this method by reporting X-ray reflectometry study on multilayered oxide structures, even when the number of the layers constitutive of the stack is not known a-priori. Fast Fourier transform-based procedure has also been employed successfully on high resolution X-ray diffraction profiles. A study of the reliability of the integral-breadth methods in diffraction line-broadening analysis applied to thin layers, in order to determine coherent domain sizes, is also reported. Examples from studies of oxides-based thin-layers heterostructures will illustrate these methods. In particular, X-ray scattering studies performed on high-k HfO{sub 2} and SrZrO{sub 3} thin-layers, a (GaAs/AlOx) waveguide, and a ZnO thin-layer are reported.

  13. Preparation and characterization of polymeric thin films containing gold nanoshells via electrostatic layer-by-layer self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Ho; Jamison, Andrew C.; Hoffman, David M., E-mail: hoffman@uh.edu; Jacobson, Allan J., E-mail: ajjacob@uh.edu; Lee, T. Randall, E-mail: trlee@uh.edu

    2014-05-02

    As an initial step in the development of surfaces for collecting thermal energy, gold shell/silica core particles (∼ 200 nm in diameter with shells ∼ 25 nm thick) were synthesized and incorporated into organic polymeric thin films. The morphologies of these nanoshells were characterized with scanning and transmission electron microscopy. Powder X-ray diffraction demonstrated that the gold layers were highly crystalline. Thin films containing the gold nanoshells and polyethyleneimine were generated using dip-coating techniques based on electrostatic layer-by-layer self-assembly methods. Scanning electron microscopy was used to image the resultant composite films, which contained uniformly distributed gold nanoshells with limited aggregation. The optical properties were analyzed by absorption spectroscopy, revealing broad extinctions ranging from the visible to the near-IR spectral regions. X-ray photoelectron spectroscopy spectra were also obtained to determine the elements present and the oxidation states of these elements. - Highlights: • Prepared gold nanoshells with broad light absorption from visible to near IR. • Added the gold nanoshells to polyethyleneimine films via layer-by-layer assembly. • The resulting layered thin films exhibited minimal gold nanoshell aggregation.

  14. Cracks in nano-ceramic thin layers produced by laser treatments

    NARCIS (Netherlands)

    De Hosson, JTM; Teeuw, DHJ; Beltz, GE; Selinger, RLB; Kim, KS; Marder, MP

    1999-01-01

    Sol-gel derived thin nano-ceramic layers of TiO2 and Al2O3 are studied using scanning electron microscopy to reveal the microstructure and morphologies of the layers. The low-voltage scanning electron microscope with a field emission gun is equipped with an especially designed lens, where the specim

  15. Solution processed metal oxide thin film hole transport layers for high performance organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.

    2017-01-10

    A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.

  16. Two-dimensional MoS2: A promising building block for biosensors.

    Science.gov (United States)

    Gan, Xiaorong; Zhao, Huimin; Quan, Xie

    2017-03-15

    Recently, two-dimensional (2D) layered nanomaterials have trigged intensive interest due to the intriguing physicochemical properties that stem from a quantum size effect connected with their ultra-thin structure. In particular, 2D molybdenum disulfide (MoS2), as an emerging class of stable inorganic graphene analogs with intrinsic finite bandgap, would possibly complement or even surpass graphene in electronics and optoelectronics fields. In this review, we first discuss the historical development of ultrathin 2D nanomaterials. Then, we are concerned with 2D MoS2 including its structure-property relationships, synthesis methods, characterization for the layer thickness, and biosensor applications over the past five years. Thereinto, we are highlighting recent advances in 2D MoS2-based biosensors, especially emphasize the preparation of sensing elements, roles of 2D MoS2, and assay strategies. Finally, on the basis of the current achievements on 2D MoS2 and other ultrathin layered nanomaterials, perspectives on the challenges and opportunities for the exploration of 2D MoS2-based biosensors are put forward.

  17. Two dimensional heat transfer problem in flow boiling in a rectangular minichannel

    Directory of Open Access Journals (Sweden)

    Hożejowska Sylwia

    2015-01-01

    Full Text Available The paper presents mathematical modelling of flow boiling heat transfer in a rectangular minichannel asymmetrically heated by a thin and one-sided enhanced foil. Both surfaces are available for observations due to the openings covered with glass sheets. Thus, changes in the colour of the plain foil surface can be registered and then processed. Plain side of the heating foil is covered with a base coat and liquid crystal paint. Observation of the opposite, enhanced surface of the minichannel allows for identification of the gas-liquid two-phase flow patterns and vapour quality. A two-dimensional mathematical model of heat transfer in three subsequent layers (sheet glass, heating foil, liquid was proposed. Heat transfer in all these layers was described with the respective equations: Laplace equation, Poisson equation and energy equation, subject to boundary conditions corresponding to the observed physical process. The solutions (temperature distributions in all three layers were obtained by Trefftz method. Additionally, the temperature of the boiling liquid was obtained by homotopy perturbation method (HPM combined with Trefftz method. The heat transfer coefficient, derived from Robin boundary condition, was estimated in both approaches. In comparison, the results by both methods show very good agreement especially when restricted to the thermal sublayer.

  18. Thin TaC layer produced by ion mixing

    DEFF Research Database (Denmark)

    Barna, Árpád; Kotis, László; Pécz, Béla

    2012-01-01

    Ion-beam mixing in C/Ta layered systems was investigated. C 8nm/Ta 12nm and C 20nm/Ta 19nm/C 20nm layer systems were irradiated by Ga+ ions of energy in the range of 2–30keV. In case of the 8nm and 20nm thick C cover layers applying 5–8keV and 20–30keV Ga+ ion energy, respectively resulted...... in strongly asymmetric ion mixing; the carbon was readily transported to the Ta layer, while the reverse process was much weaker. Because of the asymmetrical transport the C/TaC interface remained sharp independently from the applied fluence. The carbon transported to the Ta layer formed Ta......Cx. The stoichiometry of the carbide produced varied along the depth. The TaCx layer contained implanted Ga, the concentration of which decreased with increasing depth. The thickness of the TaCx layer could be tailored by the ion fluence and energy making possible to produce coating layer of desired thickness....

  19. Weakly disordered two-dimensional Frenkel excitons

    Science.gov (United States)

    Boukahil, A.; Zettili, Nouredine

    2004-03-01

    We report the results of studies of the optical properties of weakly disordered two- dimensional Frenkel excitons in the Coherent Potential Approximation (CPA). An approximate complex Green's function for a square lattice with nearest neighbor interactions is used in the self-consistent equation to determine the coherent potential. It is shown that the Density of States is very much affected by the logarithmic singularities in the Green's function. Our CPA results are in excellent agreement with previous investigations by Schreiber and Toyozawa using the Monte Carlo simulation.

  20. Two-dimensional photonic crystal surfactant detection.

    Science.gov (United States)

    Zhang, Jian-Tao; Smith, Natasha; Asher, Sanford A

    2012-08-07

    We developed a novel two-dimensional (2-D) crystalline colloidal array photonic crystal sensing material for the visual detection of amphiphilic molecules in water. A close-packed polystyrene 2-D array monolayer was embedded in a poly(N-isopropylacrylamide) (PNIPAAm)-based hydrogel film. These 2-D photonic crystals placed on a mirror show intense diffraction that enables them to be used for visual determination of analytes. Binding of surfactant molecules attaches ions to the sensor that swells the PNIPAAm-based hydrogel. The resulting increase in particle spacing red shifts the 2-D diffracted light. Incorporation of more hydrophobic monomers increases the sensitivity to surfactants.

  1. Theory of two-dimensional transformations

    OpenAIRE

    Kanayama, Yutaka J.; Krahn, Gary W.

    1998-01-01

    The article of record may be found at http://dx.doi.org/10.1109/70.720359 Robotics and Automation, IEEE Transactions on This paper proposes a new "heterogeneous" two-dimensional (2D) transformation group ___ to solve motion analysis/planning problems in robotics. In this theory, we use a 3×1 matrix to represent a transformation as opposed to a 3×3 matrix in the homogeneous formulation. First, this theory is as capable as the homogeneous theory, Because of the minimal size, its implement...

  2. Two-dimensional ranking of Wikipedia articles

    CERN Document Server

    Zhirov, A O; Shepelyansky, D L

    2010-01-01

    The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists {\\it ab aeterno}. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. We analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.

  3. Mobility anisotropy of two-dimensional semiconductors

    CERN Document Server

    Lang, Haifeng; Liu, Zhirong

    2016-01-01

    The carrier mobility of anisotropic two-dimensional (2D) semiconductors under longitudinal acoustic (LA) phonon scattering was theoretically studied with the deformation potential theory. Based on Boltzmann equation with relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was deduced, which shows that the influence of effective mass to the mobility anisotropy is larger than that of deformation potential constant and elastic modulus. Parameters were collected for various anisotropic 2D materials (black phosphorus, Hittorf's phosphorus, BC$_2$N, MXene, TiS$_3$, GeCH$_3$) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio was overestimated in the past.

  4. Sums of two-dimensional spectral triples

    DEFF Research Database (Denmark)

    Christensen, Erik; Ivan, Cristina

    2007-01-01

    construct a sum of two dimensional modules which reflects some aspects of the topological dimensions of the compact metric space, but this will only give the metric back approximately. At the end we make an explicit computation of the last module for the unit interval in. The metric is recovered exactly......, the Dixmier trace induces a multiple of the Lebesgue integral but the growth of the number of eigenvalues is different from the one found for the standard differential operator on the unit interval....

  5. Binding energy of two-dimensional biexcitons

    DEFF Research Database (Denmark)

    Singh, Jai; Birkedal, Dan; Vadim, Lyssenko;

    1996-01-01

    Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....

  6. Dynamics of film. [two dimensional continua theory

    Science.gov (United States)

    Zak, M.

    1979-01-01

    The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets. The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles. The theory is illustrated by examples.

  7. TWO-LAYER MODEL DESCRIPTION OF POLYMER THIN FILM DYNAMICS

    Institute of Scientific and Technical Information of China (English)

    Dong-dong Peng; Ran-xing Nancy Li; Chi-hang Lam; Ophelia K.C.Tsui

    2013-01-01

    Experiments in the past two decades have shown that the glass transition temperature of polymer films can become noticeably different from that of the bulk when the film thickness is decreased below ca.100 nm.It is broadly believed that these observations are caused by a nanometer interfacial layer with dynamics faster or slower than that of the bulk.In this paper,we examine how this idea may be realized by using a two-layer model assuming a hydrodynamic coupling between the interfacial layer and the remaining,bulk-like layer in the film.Illustrative examples will be given showing how the two-layer model is applied to the viscosity measurements of polystyrene and polymethylmethacrylate films supported by silicon oxide,where divergent thickness dependences are observed.

  8. Thin films flowing down inverted substrates: two dimensional flow

    CERN Document Server

    Lin, Te-sheng

    2009-01-01

    We consider free surface instabilities of films flowing on inverted substrates within the framework of lubrication approximation. We allow for the presence of fronts and related contact lines, and explore the role which they play in instability development. It is found that a contact line, modeled by a commonly used precursor film model, leads to free surface instabilities of convective type without any additional natural or excited perturbations. A single parameter D=(3Ca)^{1/3}cot\\alpha, where Ca is the capillary number and \\alpha is the inclination angle, is identified as a governing parameter in the problem. This parameter may be interpreted to reflect the combined effect of inclination angle, film thickness, Reynolds number and the fluid flux. Variation of D leads to change of the wave-like properties of the instabilities, allowing to observe traveling wave behavior, mixed waves, and the waves resembling solitary ones.

  9. Thin-layer voltammetry of soluble species on screen-printed electrodes: proof of concept.

    Science.gov (United States)

    Botasini, S; Martí, A C; Méndez, E

    2016-10-17

    Thin-layer diffusion conditions were accomplished on screen-printed electrodes by placing a controlled-weight onto the cast solution and allowing for its natural spreading. The restricted diffusive conditions were assessed by cyclic voltammetry at low voltage scan rates and electrochemical impedance spectroscopy. The relationship between the weight exerted over the drop and the thin-layer thickness achieved was determined, in such a way that the simple experimental set-up designed for this work could be developed into a commercial device with variable control of the thin-layer conditions. The experimental results obtained resemble those reported for the voltammetric features of electroactive soluble species employing electrodes modified with carbon nanotubes or graphene layers, suggesting that the attainment of the benefits reported for these nanomaterials could be done simply by forcing the solution to spread over the screen-printed electrodic system to form a thin layer solution. The advantages of thin-layer voltammetry in the kinetic characterization of quasi-reversible and irreversible processes are highlighted.

  10. Microstructure and mechanical behavior of a shape memory Ni-Ti bi-layer thin film

    Energy Technology Data Exchange (ETDEWEB)

    Mohri, Maryam [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Nili-Ahmadabadi, Mahmoud, E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Ivanisenko, Julia [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Schwaiger, Ruth [Karlsruhe Institute of Technology, Institute for Applied Materials, 76021 Karlsruhe (Germany); Hahn, Horst; Chakravadhanula, Venkata Sai Kiran [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany)

    2015-05-29

    Two different single-layers and a bi-layer Ni-Ti thin films with chemical compositions of Ni{sub 45}Ti{sub 50}Cu{sub 5}, Ni{sub 50.8}Ti{sub 49.2} and Ni{sub 50.8}Ti{sub 49.2}/Ni{sub 45}Ti{sub 50}Cu{sub 5} (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy were deposited on Si (111) substrates using DC magnetron sputtering. The structures, surface morphology and transformation temperatures of annealed thin films at 500 °C for 15 min and 1 h were studied using grazing incidence X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy and differential scanning calorimetry (DSC), respectively. Nanoindentation was used to characterize the mechanical properties. The DSC and X-ray diffraction results indicated the austenitic structure of the Ni{sub 50.8}Ti{sub 49.2} and martensitic structure of the Ni{sub 45}Ti{sub 50}Cu{sub 5} thin films while the bi-layer was composed of austenitic and martensitic thin films. TEM study revealed that copper encourages crystallization in the bi-layer such that crystal structure containing nano-precipitates in the Ni{sub 45}Ti{sub 50}Cu{sub 5} layer was detected after 15 min annealing while the Ni{sub 50.8}Ti{sub 49.2} layer crystallized after 60 min at 500 °C. Furthermore, after annealing at 500 °C for 15 min, a precipitate free zone and thin layer amorphous were observed closely to the interface in the top layer. The bi-layer was completely crystallized at 500 °C for 1 h and the orientation of the Ni-rich precipitates indicated a stress gradient in the bi-layer. The bi-layer thin film showed different transformation temperatures and mechanical behavior from the single-layers. The developed bi-layer has different phase transformation temperatures, the higher temperatures of shape memory effect and lower temperature of pseudo-elastic behavior compared to the single-layers. Also, the bi-layer thin film exhibited a combined pseudo-elastic behavior and shape memory effect with a reduced

  11. Erosion of thin carbon layer on metal surface by hydrogen ion bombardment at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ohno, Hirotaka, Morita, Kenji, Horino, Yuji, Itoh, Noriaki

    1985-10-01

    In this letter, we report experimental results on the erosion of thin carbon layers segregated on nickel surfaces caused by hydrogen ion bombardements at elevated temperatures. The erosion yield of the segregated carbon layers at temperatures of around 900 K was found to depend on their thickness and for the layers with a thicknes less than 20 A the yield near the 900 K was found to be nearly the same as the physical sputtering yield. (orig./RK).

  12. Mechanical Failure of Thin Ta and Cu/Ta Layers on Polyimide Substrates: A Synchrotron-Based Technique for In Situ Characterization

    Science.gov (United States)

    Frank, Stephan; Handge, Ulrich A.; Olliges, Sven; Spolenak, Ralph

    2009-06-01

    In situ synchrotron radiation diffraction and confocal light microscopy is used to study fragmentation and buckling of thin brittle Ta layers with thicknesses of 50 nm, 100 nm and 200 nm on polyimide substrates. Synchrotron-based stress measurements confirm that cracking leads to relaxation of tensile stress. Simultaneously, compressive stress arises in transverse direction, which finally leads to buckling. This behavior can be explained quantitatively by a two-dimensional shear lag model. It is well established that the properties of the coating-substrate interface determine the processes of coating fragmentation and delamination. A possible approach for influencing and controlling these processes is given by the incorporation of a ductile interlayer. It can be observed that the presence of Cu interlayers with thicknesses of 5 nm, 20 nm and 50 nm reduces the fracture strength of brittle Ta coatings on polyimide substrates, whereas the resistance to buckling is increased significantly.

  13. Two-dimensional gauge theoretic supergravities

    Science.gov (United States)

    Cangemi, D.; Leblanc, M.

    1994-05-01

    We investigate two-dimensional supergravity theories, which can be built from a topological and gauge invariant action defined on an ordinary surface. One is the N = 1 supersymmetric extension of the Jackiw-Teitelboim model presented by Chamseddine in a superspace formalism. We complement the proof of Montano, Aoaki and Sonnenschein that this extension is topological and gauge invariant, based on the graded de Sitter algebra. Not only do the equations of motion correspond to the supergravity ones and do gauge transformations encompass local supersymmetries, but we also identify the ∫-theory with the superfield formalism action written by Chamseddine. Next, we show that the N = 1 supersymmetric extension of string-inspired two-dimensional dilaton gravity put forward by Park and Strominger cannot be written as a ∫-theory. As an alternative, we propose two topological and gauge theories that are based on a graded extension of the extended Poincaré algebra and satisfy a vanishing-curvature condition. Both models are supersymmetric extensions of the string-inspired dilaton gravity.

  14. Two-Dimensional Theory of Scientific Representation

    Directory of Open Access Journals (Sweden)

    A Yaghmaie

    2013-03-01

    Full Text Available Scientific representation is an interesting topic for philosophers of science, many of whom have recently explored it from different points of view. There are currently two competing approaches to the issue: cognitive and non-cognitive, and each of them claims its own merits over the other. This article tries to provide a hybrid theory of scientific representation, called Two-Dimensional Theory of Scientific Representation, which has the merits of the two accounts and is free of their shortcomings. To do this, we will argue that although scientific representation needs to use the notion of intentionality, such a notion is defined and realized in a simply structural form contrary to what cognitive approach says about intentionality. After a short introduction, the second part of the paper is devoted to introducing theories of scientific representation briefly. In the third part, the structural accounts of representation will be criticized. The next step is to introduce the two-dimensional theory which involves two key components: fixing and structural fitness. It will be argued that fitness is an objective and non-intentional relation, while fixing is intentional.

  15. Nonclassical Symmetry Analysis of Heated Two-Dimensional Flow Problems

    Science.gov (United States)

    Naeem, Imran; Naz, Rehana; Khan, Muhammad Danish

    2015-12-01

    This article analyses the nonclassical symmetries and group invariant solution of boundary layer equations for two-dimensional heated flows. First, we derive the nonclassical symmetry determining equations with the aid of the computer package SADE. We solve these equations directly to obtain nonclassical symmetries. We follow standard procedure of computing nonclassical symmetries and consider two different scenarios, ξ1≠0 and ξ1=0, ξ2≠0. Several nonclassical symmetries are reported for both scenarios. Furthermore, numerous group invariant solutions for nonclassical symmetries are derived. The similarity variables associated with each nonclassical symmetry are computed. The similarity variables reduce the system of partial differential equations (PDEs) to a system of ordinary differential equations (ODEs) in terms of similarity variables. The reduced system of ODEs are solved to obtain group invariant solution for governing boundary layer equations for two-dimensional heated flow problems. We successfully formulate a physical problem of heat transfer analysis for fluid flow over a linearly stretching porous plat and, with suitable boundary conditions, we solve this problem.

  16. Peeling process of thin-film solar cells using graphene layers

    Science.gov (United States)

    Ishikawa, Ryousuke; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Konagai, Makoto

    2017-08-01

    A novel peeling process for thin-film solar cells using graphene layers was demonstrated. We fabricated amorphous silicon (a-Si) solar cells as substitutes for the undeveloped nanostructured silicon solar cells on graphene layers in order to investigate the solar cell performance after peeling for the first time. The graphene layers functioned as transparent electrodes after the peeling process, even though the series resistance increased after the peeling. Next, we fabricated a silicon nanowire (SiNW) array on graphene layers by a combination of chemical etching and thermal crystallization. Finally, we successfully peeled a SiNW array using graphene layers.

  17. Visualising the strain distribution in suspended two-dimensional materials under local deformation

    Science.gov (United States)

    Elibol, Kenan; Bayer, Bernhard C.; Hummel, Stefan; Kotakoski, Jani; Argentero, Giacomo; Meyer, Jannik C.

    2016-06-01

    We demonstrate the use of combined simultaneous atomic force microscopy (AFM) and laterally resolved Raman spectroscopy to study the strain distribution around highly localised deformations in suspended two-dimensional materials. Using the AFM tip as a nanoindentation probe, we induce localised strain in suspended few-layer graphene, which we adopt as a two-dimensional membrane model system. Concurrently, we visualise the strain distribution under and around the AFM tip in situ using hyperspectral Raman mapping via the strain-dependent frequency shifts of the few-layer graphene’s G and 2D Raman bands. Thereby we show how the contact of the nm-sized scanning probe tip results in a two-dimensional strain field with μm dimensions in the suspended membrane. Our combined AFM/Raman approach thus adds to the critically required instrumental toolbox towards nanoscale strain engineering of two-dimensional materials.

  18. Single-borehole measuring method for broken rock zone in gently inclined thin layer weakness structure

    Institute of Scientific and Technical Information of China (English)

    CHEN Qing-fa; ZHOU Ke-ping; LONG Teng-teng; GAO Feng

    2008-01-01

    According to the structural characteristics of gently inclined thin layer rock mass in which lots of weak interlayer existed, the concept of gently inclined thin layer weakness structure was proposed. If single-borehole measuring method of the acoustic along the conventional arrangement mode was used in measuring the broken rock zone in this structure, the change of the relationship curves (Vp-L) between acoustic p-wave velocity (Vp) and borehole depth (L) would present the irregular feature due to the mechanical characteristics of layered rock mass and harmful effects of weak interlayers, and the scope of broken rock zone couldn't be defined quickly. Based on the analysis of the mechanical characteristics of layered rock mass, the propagation rule of acoustic and distributions characteristics of plastic zone and slip zone in layered rock mass, new arrangement mode of acoustic measuring boreholes for broken rock zone in gently inclined thin layer weakness structure was proposed. Namely, the measuring boreholes in two sides were parallel to the strata, the measuring boreholes in the roof and floor perpendicular to the strata. Besides the controlling depth of the measuring boreholes in the scope of the large plastic zones or the large slip zones should be increased. Engineering exampleshowed that new acoustic measuring boreholes arrangement mode had the better applicability and could determine the scope of the broken rock zone in the gently inclined thin layer weakness structure quickly.

  19. Existence and Stability of Two-Dimensional Compact-Like Discrete Breathers in Discrete Two-Dimensional Monatomic Square Lattices

    Institute of Scientific and Technical Information of China (English)

    XU Quan; TIAN Qiang

    2007-01-01

    Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generafized discrete two-dimensional monatomic model.It is proven that the twodimensional compact-like discrete breathers exist not only in two-dimensional soft Ф4 potentials but also in hard two-dimensional Ф4 potentials and pure two-dimensional K4 lattices.The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Ф4 potential are determined by coupling parameter K4,while those in pure two-dimensional K4 lattices have no coupling with parameter K4.The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.

  20. X-Ray Diffractometry of Thin Layers - Possibilities and Problems

    Directory of Open Access Journals (Sweden)

    Vladimir Zucha

    2005-01-01

    Full Text Available Efficieney of two deconvolution methods used in X-ray powder diffraction analysis is compared for thin films of Pd and Pt. The first method is the classical Stokes method and the second one is method of indirect deconvolution. But calculated integral breadth of Gauss and Cauchy components of Voigt function which describe the physical broadening are different. The analysis of the all found pheromones show that the method of indirect deconvolution gives more accurate results.