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Sample records for suzorite mica flake

  1. Atomically Thin Mica Flakes and Their Application as Ultrathin Insulating Substrates for Graphene

    NARCIS (Netherlands)

    Castellanos-Gomez, Andres; Wojtaszek, Magdalena; Tombros, Nikolaos; Agrait, Nicolas; van Wees, Bart J.; Rubio-Bollinger, Gabino; Agraït, Nicolás

    2011-01-01

    By mechanical exfoliation, it is possible to deposit atomically thin mica flakes down to single-monolayer thickness on SiO(2)/Si wafers. The optical contrast of these mica flakes on top of a SiO(2)/Si substrate depends on their thickness, the illumination wavelength, and the SiO(2) substrate

  2. The reclamation of mica flakes from tailing disposal using gravity separators and flotation

    Directory of Open Access Journals (Sweden)

    Seied Mohammad Raoof Hoseini

    2016-06-01

    Full Text Available A sample from the small-sized tailing pile of an Iranian mica processing plant was subjected to a series of mica recovery experiments. Mineralogical and microscopic investigations indicated that the dominant mica mineral was phlogopite which was accompanied by plagioclase feldspars. Before beneficiation studies, the particle size distribution of the representative sample was obtained, and the specifications of each size fraction were investigated in detail. It was observed that the largest portion of mica (31% is accumulated in the size range of 0.3 to 2.0 mm. Afterward, gravity concentration and flotation experiments were carried out. Results proved that shaking table could produce a mica concentrate with grade of 74%. Also, according to the flotation tests, it seemed the best size fraction was -150+75, and after that, -100+150. Flotation in combination with attrition scrubbing produced a concentrate with 92% mica content and 70% recovery. Finally, with respect to the results of all implemented experiments, a processing flow sheet was proposed for mica reclamation from the mentioned waste disposal.

  3. Parimad Eesti Flakes toolid

    Index Scriptorium Estoniae

    2007-01-01

    ELKE Mööbli, Eesti Sisearhitektide Liidu ja Piiroinen OY korraldatud Flakes toolide Eesti kujunduskonkursi tulemused: I preemia - Heino Prunsvelt, II - Kadi Hektor, III - Andres Labi. Piironen OÜ eripreemiad - Andres Lember, Gerly Grünbaum, Kaarin Kokk

  4. Collective superlubricity of graphene flakes.

    Science.gov (United States)

    van Wijk, Merel M; de Wijn, Astrid S; Fasolino, Annalisa

    2016-04-06

    We investigate solid lubrication of graphene and graphene flakes using atomistic molecular-dynamics simulations. We find that graphene flakes yield lower friction than graphene as a result of a collective mechanism that emerges from the independent behaviour of the flakes. By freezing out different degrees of freedom of the flakes, we are able to attribute the low friction to non-simultaneous slipping of the individual flakes. We also compare the results of the atomistic simulations to those of a simplified two-dimensional model and find that the behaviour of the latter is strongly dependent on parameters, which emerge naturally from the atomistic simulations.

  5. Determining tensile properties of sweetgum veneer flakes

    Science.gov (United States)

    E.W. Price

    1976-01-01

    Rotary-cut 8weetgum veneer flakes measuring 3 inchee along the grain, 3/8 inch wide, and 0.015 inch thick, were stressed in tension parallel to the grain at gage lengths from 0.00 to 1.25 inchee for unpressed control and at 0.75 inch gage length for flakes pressed in a flakeboard mat. The control flakes had an average tensile strength of 9,400 psi for the smaller age...

  6. Optical alignment of oval graphene flakes

    Science.gov (United States)

    Mobini, E.; Rahimzadegan, A.; Alaee, R.; Rockstuhl, C.

    2017-03-01

    Patterned graphene, as an atomically thin layer, supports localized surface plasmon-polaritons (LSPPs) at mid-infrared or far-infrared frequencies. This provides a pronounced optical force/torque in addition to large optical cross sections and will make it an ideal candidate for optical manipulation. Here, we study the optical force and torque exerted by a linearly polarized plane wave on circular and oval graphene flakes. Whereas the torque vanishes for circular flakes, the finite torque allows rotating and orienting oval flakes relative to the electric field polarization. Depending on the wavelength, the alignment is either perpendicular or parallel. In our contribution, we rely on full-wave numerical simulation but also on an analytical model that treats the graphene flakes in dipole approximation. The presented results reveal a good level of control on the spatial alignment of graphene flakes subjected to far-infrared illumination.

  7. Variation in the Flaked Lines of Lathyrus Odoratus

    Indian Academy of Sciences (India)

    Somatic variation was also found in these forms. Flaked flower's bore at times dark-flaked sectors; the dark-flaked frequently had flaked parts. Rarely, bud variation occurred in the same way by Somatic mutation at the early stages of bud rudiments. More rarely the sport arose in the direction of self-coloured. We observed six.

  8. Optical alignment of oval graphene flakes

    OpenAIRE

    Mobini, E.; Rahimzadegan, A.; Alaee, R.; Rockstuhl, C.

    2016-01-01

    Patterned graphene, as an atomically thin layer, supports localized surface plasmon-polaritons (LSPPs) at mid-infrared or far-infrared frequencies. This provides a pronounced optical force/torque in addition to large optical cross sections and will make it an ideal candidate for optical manipulation. Here, we study the optical force and torque exerted by a linearly polarized plane wave on circular and oval graphene flakes. Whereas the torque vanishes for circular flakes, the finite torque all...

  9. Hot flakes in cold cases.

    Science.gov (United States)

    Schneider, Harald; Sommerer, Thomas; Rand, Steve; Wiegand, Peter

    2011-07-01

    In the past, it was almost impossible for forensic scientists to separate DNA from an undefined number of different individuals in mixed stains where, for example, two or more suspects had handled the same weapon. Such samples often contain complex mixtures with the consequence of ambiguous or inconclusive mixed DNA profiles. Using the method described of comprehensive and/or targeted screening of shed cells adhering to tapings of garments or objects enables such stains to be individualized. To evaluate the method, 500 microscopically selected single skin flakes were analyzed using two different commercial STR kits to compare the success rates for each PCR typing system. The method has been validated for use in routine casework and has been shown to be rapid, sensitive, and reproducible. It can be predicted that many cases in the archives with body tapings, which have not yet been examined will benefit from this new or perhaps more appropriate, reanimated, technical development, and of particular importance are serious crimes, the so-called cold cases. The remarkable forensic value of this simple but time-consuming technique is exemplified by 2 out of approximately 100 cases already successfully solved using this approach.

  10. Why Levallois? A morphometric comparison of experimental 'preferential' Levallois flakes versus debitage flakes.

    Directory of Open Access Journals (Sweden)

    Metin I Eren

    Full Text Available BACKGROUND: Middle Palaeolithic stone artefacts referred to as 'Levallois' have caused considerable debate regarding issues of technological predetermination, cognition and linguistic capacities in extinct hominins. Their association with both Neanderthals and early modern humans has, in particular, fuelled such debate. Yet, controversy exists regarding the extent of 'predetermination' and 'standardization' in so-called 'preferential Levallois flakes' (PLFs. METHODOLOGY/PRINCIPAL FINDINGS: Using an experimental and morphometric approach, we assess the degree of standardization in PLFs compared to the flakes produced during their manufacture. PLFs possess specific properties that unite them robustly as a group or 'category' of flake. The properties that do so, relate most strongly to relative flake thicknesses across their surface area. PLFs also exhibit significantly less variability than the flakes generated during their production. Again, this is most evident in flake thickness variables. A further aim of our study was to assess whether the particular PLF attributes identified during our analyses can be related to current knowledge regarding flake functionality and utility. CONCLUSIONS/SIGNIFICANCE: PLFs are standardized in such a manner that they may be considered 'predetermined' with regard to a specific set of properties that distinguishes them statistically from a majority of other flakes. Moreover, their attributes can be linked to factors that, based on current knowledge, are desirable features in flake tools (e.g. durability, capacity for retouch, and reduction of torque. As such, our results support the hypothesis that the lengthy, multi-phase, and hierarchically organized process of Levallois reduction was a deliberate, engineered strategy orientated toward specific goals. In turn, our results support suggestions that Levallois knapping relied on a cognitive capacity for long-term working memory. This is consistent with recent

  11. Fullerene growth from encapsulated graphene flakes.

    Science.gov (United States)

    Neng, Wan; Shuang-ying, Lei; Jun, Xu; Matteo, Martini; Yi-long, Zhou; Shu, Wan; Li-tao, Sun; Qing-an, Huang

    2014-10-07

    The direct in situ observation of fullerene formation encapsulated within a graphene ridge has been made possible using an aberration corrected transmission electron microscope (AC-TEM). An atom-by-atom mechanism was proposed based on in situ AC-TEM observations. First principle calculations found a continuous energy decrease upon the addition of carbon atoms to the edge of the graphene flakes, which mimics the fullerene growth steps and supports the atom-by-atom mechanism. The ridged graphene structure worked as a container for pinning small graphene flakes and capturing carbon atoms, which increased the growth probability of the fullerene structure within the small encapsulated space.

  12. Effects of flake size on mode-locking behavior for flake-graphene saturable absorber mirrors

    CERN Document Server

    Hussain, M I; Booth, L S; Petrasiunas, M J; Brown, C L; Kielpinski, D

    2016-01-01

    After advent of graphene as a saturable absorber many experiments have been conducted to produce short pulse duration pulses. Here, we have measured the properties of flake-graphene saturable absorber mirrors of various flake sizes dependent on fabrication technique. These mirrors enabled us to obtain a large mode-locking bandwidth of 16nm in an erbium-doped fiber laser. Mirrors with large flake size and multi-layered thickness induce strong pulse shaping and reflect mode-locked train of pulses with very large bandwidths.

  13. Electrically actuatable doped polymer flakes and electrically addressable optical devices using suspensions of doped polymer flakes in a fluid host

    Science.gov (United States)

    Trajkovska-Petkoska, Anka; Jacobs, Stephen D.; Marshall, Kenneth L.; Kosc, Tanya Z.

    2010-05-11

    Doped electrically actuatable (electrically addressable or switchable) polymer flakes have enhanced and controllable electric field induced motion by virtue of doping a polymer material that functions as the base flake matrix with either a distribution of insoluble dopant particles or a dopant material that is completely soluble in the base flake matrix. The base flake matrix may be a polymer liquid crystal material, and the dopants generally have higher dielectric permittivity and/or conductivity than the electrically actuatable polymer base flake matrix. The dopant distribution within the base flake matrix may be either homogeneous or non-homogeneous. In the latter case, the non-homogeneous distribution of dopant provides a dielectric permittivity and/or conductivity gradient within the body of the flakes. The dopant can also be a carbon-containing material (either soluble or insoluble in the base flake matrix) that absorbs light so as to reduce the unpolarized scattered light component reflected from the flakes, thereby enhancing the effective intensity of circularly polarized light reflected from the flakes when the flakes are oriented into a light reflecting state. Electro-optic devices contain these doped flakes suspended in a host fluid can be addressed with an applied electric field, thus controlling the orientation of the flakes between a bright reflecting state and a non-reflecting dark state.

  14. Sensitivity of graphene flakes and nanorings to impurities

    Energy Technology Data Exchange (ETDEWEB)

    Konobeeva, N.N., E-mail: yana_nn@volsu.ru [Volgograd State University, University Avenue 100, Volgograd 400062 (Russian Federation); Belonenko, M.B. [Volgograd State University, University Avenue 100, Volgograd 400062 (Russian Federation); Volgograd Institute of Business, Uzhno-Ukrainskaya Str., Volgograd 400048 (Russian Federation)

    2017-06-01

    In this paper, we consider the influence of impurity on the graphene flakes and nanorings conductance. Based on the jumping Hamiltonian for graphene electrons with its direct diagonalization, we obtain the density of states. Further, the tunneling current is calculated for the following contacts: graphene flake-metal, graphene flake-quantum dots, graphene nanoring-quantum dots. We analyze the effect of the flake dimensions and the positions of the adsorbed molecule of impurity on the characteristic properties of the tunneling current.

  15. PCLC flake-based apparatus and method

    Science.gov (United States)

    Cox, Gerald P; Fromen, Cathy A; Marshall, Kenneth L; Jacobs, Stephen D

    2012-10-23

    A PCLC flake/fluid host suspension that enables dual-frequency, reverse drive reorientation and relaxation of the PCLC flakes is composed of a fluid host that is a mixture of: 94 to 99.5 wt % of a non-aqueous fluid medium having a dielectric constant value .di-elect cons., where 1sigma., where 10.sup.-9>.sigma.>10.sup.-7 Siemens per meter (S/m), and a resistivity r, where 10.sup.7>r>10.sup.10 ohm-meters (.OMEGA.-m), and which is optically transparent in a selected wavelength range .DELTA..lamda.; 0.0025 to 0.25 wt % of an inorganic chloride salt; 0.0475 to 4.75 wt % water; and 0.25 to 2 wt % of an anionic surfactant; and 1 to 5 wt % of PCLC flakes suspended in the fluid host mixture. Various encapsulation forms and methods are disclosed including a Basic test cell, a Microwell, a Microcube, Direct encapsulation (I), Direct encapsulation (II), and Coacervation encapsulation. Applications to display devices are disclosed.

  16. Inkjet printing ultra-large graphene oxide flakes

    Science.gov (United States)

    He, Pei; Derby, Brian

    2017-06-01

    Graphene oxide 2D materials inks with mean flake diameter 36 µm can be inkjet printed, with no significant blockage of the printer or apparent damage to the flakes, despite the mean flake size being  >50% of the printer nozzle diameter and the ink containing individual flakes considerably larger than the nozzle. Printed flakes show a similar level of wrinkle and fold defects as observed in flakes deposited by drop casting. Polarised light imaging of the ink in the printhead prior to printing shows alignment of the flakes in the shear flow and this is believed to allow passage without agglomeration or blocking of the nozzle. The bulk electrical conductivity of these ultra-large flake printed films is 2.48  ×  104 Sm-1 after reduction, which is comparable to that reported with printed pristine graphene. The conductivity of the printed films increases slightly with increasing flake size indicating that there is no increase in damage to electrical properties as the flakes approach and exceed the nozzle diameter.

  17. Spintronic properties of zigzag-edged triangular graphene flakes

    OpenAIRE

    Şahin, Hasan; Senger, Ramazan Tuğrul; Çıracı, Salim

    2010-01-01

    We investigate quantum transport properties of triangular graphene flakes with zigzag edges by using first principles calculations. Triangular graphene flakes have large magnetic moments which vary with the number of hydrogen atoms terminating its edge atoms and scale with its size. Electronic transmission and current-voltage characteristics of these flakes, when contacted with metallic electrodes, reveal spin valve and remarkable rectification features. The transition from ferromagnetic to a...

  18. Ambipolar MoS2 Thin Flake Transistors

    NARCIS (Netherlands)

    Zhang, Yijin; Ye, Jianting; Matsuhashi, Yusuke; Iwasa, Yoshihiro

    Field effect transistors (FETs) made of thin flake single crystals isolated from layered materials have attracted growing interest since the success of graphene. Here, we report the fabrication of an electric double layer transistor (EDLT, a FET gated by ionic liquids) using a thin flake of MoS2, a

  19. Formulation of novel trehalose flakes for storage and delivery of ...

    African Journals Online (AJOL)

    PRECIOUS

    2009-12-01

    Dec 1, 2009 ... that the I-2 virus stored in trehalose flakes maintained its infectivity titre at 108.6 EID 50/0.1 mL for 4 weeks at ambient room ... with the flakes developed antiviral antibodies and resisted challenge with virulent strain of ND virus. The formulation of ..... Language Guide for Personal Computers. Version 6.

  20. Formulation of novel trehalose flakes for storage and delivery of ...

    African Journals Online (AJOL)

    Chickens vaccinated orally with the flakes developed antiviral antibodies and resisted challenge with virulent strain of ND virus. The formulation of trehalose vaccine flakes could be a useful way to store and deliver ND vaccines to village chicken flocks in rural areas, particularly in developing countries if it is optimised.

  1. Spatial design and control of graphene flake motion

    Science.gov (United States)

    Ghorbanfekr-Kalashami, H.; Peeters, F. M.; Novoselov, K. S.; Neek-Amal, M.

    2017-08-01

    The force between a sharp scanning probe tip and a surface can drive a graphene flake over crystalline substrates. The recent design of particular patterns of structural defects on a graphene surface allows us to propose an alternative approach for controlling the motion of a graphene flake over a graphene substrate. The thermally induced motion of a graphene flake is controlled by engineering topological defects in the substrate. Such defect regions lead to an inhomogeneous energy landscape and are energetically unfavorable for the motion of the flake, and will invert and scatter graphene flakes when they are moving toward the defect line. Engineering the distribution of these energy barriers results in a controllable trajectory for the thermal motion of the flake without using any external force. We predict superlubricity of the graphene flake for motion along and between particular defect lines. This Rapid Communication provides insights into the frictional forces of interfaces and opens a route to the engineering of the stochastic motion of a graphene flake over any crystalline substrate.

  2. Thermal activated rotation of graphene flake on graphene

    Science.gov (United States)

    Peymanirad, F.; Singh, Sandeep Kumar; Ghorbanfekr-Kalashami, H.; Novoselov, K. S.; Peeters, F. M.; Neek-Amal, M.

    2017-06-01

    The self rotation of a graphene flake over graphite is controlled by the size, initial misalignment and temperature. Using both ab initio calculations and molecular dynamics simulations, we investigate annealing effects on the self rotation of a graphene flake on a graphene substrate. The energy barriers for rotation and drift of a graphene flake over graphene is found to be smaller than 25 meV/atom which is comparable to thermal energy. We found that small flakes (of about  ∼4 nm) are more sensitive to temperature and initial misorientation angles than larger one (beyond 10 nm). The initial stacking configuration of the flake is found to be important for its dynamics and time evolution of misalignment. Large flakes, which are initially in the AA- or AB-stacking state with small misorientation angle, rotate and end up in the AB-stacking configuration. However small flakes can they stay in an incommensurate state specially when the initial misorientation angle is larger than {{2}\\circ} . Our results are in agreement with recent experiments.

  3. Very low energy electron microscopy of graphene flakes

    National Research Council Canada - National Science Library

    MIKMEKOVÁ, E; BOUYANFIF, H; LEJEUNE, M; MÜLLEROVÁ, I; HOVORKA, M; UNČOVSKÝ, M; FRANK, L

    2013-01-01

    .... Limited lateral resolution of Raman spectroscopy may produce a Raman spectrum corresponding to a single graphene layer even for flakes that can be identified by very low energy electron microscopy...

  4. Electronic shell and supershell structure in graphene flakes

    CERN Document Server

    Manninen, M; Akola, J

    2008-01-01

    We use a simple tight-binding (TB) model to study electronic properties of free graphene flakes. Valence electrons of triangular graphene flakes show a shell and supershell structure which follows an analytical expression derived from the solution of the wave equation for triangular cavity. However, the solution has different selection rules for triangles with armchair and zigzag edges, and roughly 40000 atoms are needed to see clearly the first supershell oscillation. In the case of spherical flakes, the edge states of the zigzag regions dominate the shell structure which is thus sensitive to the flake diameter and center. A potential well that is made with external gates cannot have true bound states in graphene due to the zero energy band gap. However, it can cause strong resonances in the conduction band.

  5. Particle size and kind of mica in synthesis of nontoxic bronze and gold pearlescent pigments based on nanoencapsulated hematite

    Directory of Open Access Journals (Sweden)

    Maryam Hosseini-Zori

    2015-12-01

    Full Text Available Nano-encapsulated iron oxide in Zirconium oxide-coated mica pigments are thermally stable,innocuous to human health, non-combustible, and they do not conduct electricity. They could beapplied in several industries such as thermoplastics, cosmetics, food packaging, children toys, paints,automobiles coating, security purposes, and banknotes. Nowadays, they are highly desirable inceramic decoration. In the present study, intensively dark gold to bronze colored mica clay pigments,which were based on mica flakes covered with a layer of nano-iron oxide-Zirconium oxide particles,were prepared by homogeneous precipitation of iron nitrate and Zirconium chloride ammonia in thepresence of mica flakes in two kinds of ore clay-based phlogopite and muscovite minerals. The finalcolor was obtained by thermal annealing of precipitates at a temperature of 800◦C. The pigments werecharacterized by X-Ray Diffraction, Particle size analysis, Scanning electron microscopy,Transmission electron microscopy, X-Ray fluorescence, and Simultaneous thermal analysis. Resultsindicate that nano-encapsulated iron oxide in zirconia particles have been formed on mica flakes andkinds of clay-mica can be related to obtained shade from dark gold to bronze pearl. Higher particlesize of mica flakes about phlogopite type of mica introduced pearl effects with higher L* changes indifferent angles. Muscovite performed higher hue and better pearl effect than phlogopite.

  6. Graphene-like carbon synthesized from popcorn flakes

    Science.gov (United States)

    Mendoza, D.; Flores, C. B.; Berrú, R. Y. Sato

    2015-01-01

    The synthesis of graphene-like carbon using popcorn kernels as a renewable resource is presented. In a first step popcorn kernels were heated to produce popcorn flakes with a spongy appearance consisting of a polygonal cellular structure. In a second step, the flakes were treated at high temperature in an inert atmosphere to produce carbonization. Raman spectroscopy shows graphene-like structure with a high degree of disorder.

  7. Unexpectedly strong anion-π interactions on the graphene flakes.

    Science.gov (United States)

    Shi, Guosheng; Ding, Yihong; Fang, Haiping

    2012-05-30

    Interactions of anions with simple aromatic compounds have received growing attention due to their relevancy in various fields. Yet, the anion-π interactions are generally very weak, for example, there is no favorable anion-π interaction for the halide anion F(-) on the simplest benzene surface unless the H-atoms are substituted by the highly negatively charged F. In this article, we report a type of particularly strong anion-π interactions by investigating the adsorptions of three halide anions, that is, F(-), Cl(-), and Br(-), on the hydrogenated-graphene flake using the density functional theory. The anion-π interactions on the graphene flake are shown to be unexpectedly strong compared to those on simple aromatic compounds, for example, the F(-)-adsorption energy is as large as 17.5 kcal/mol on a graphene flake (C(84) H(24)) and 23.5 kcal/mol in the periodic boundary condition model calculations on a graphene flake C(113) (the supercell containing a F(-) ion and 113 carbon atoms). The unexpectedly large adsorption energies of the halide anions on the graphene flake are ascribed to the effective donor-acceptor interactions between the halide anions and the graphene flake. These findings on the presence of very strong anion-π interactions between halide ions and the graphene flake, which are disclosed for the first time, are hoped to strengthen scientific understanding of the chemical and physical characteristics of the graphene in an electrolyte solution. These favorable interactions of anions with electron-deficient graphene flakes may be applicable to the design of a new family of neutral anion receptors and detectors. Copyright © 2012 Wiley Periodicals, Inc.

  8. Thermal conductivity of mass-graded graphene flakes

    OpenAIRE

    Cheh, Jigger; Zhao, Hong

    2011-01-01

    In this letter we study thermal conduction in mass-graded graphene flakes by nonequilibrium molecular dynamics simulations. It is found that mass-graded graphene flakes reveal no thermal rectification effect in thermal conduction process. The dependence of thermal conductivity upon the heat flux and the mass gradient are studied to confirm the generality of the result.The mechanism leading to the absence of thermal rectification effect is also discussed.

  9. Sorption isotherm characteristics of aonla flakes.

    Science.gov (United States)

    Alam, Md Shafiq; Singh, Amarjit

    2011-06-01

    The equilibrium moisture content was determined for un-osmosed and osmosed (salt osmosed and sugar osmosed) aonla flakes using the static method at temperatures of 25, 40,50, 60 and 70 °C over a range of relative humidities from 20 to 90%. The sorption capacity of aonla decreased with an increase in temperature at constant water activity. The sorption isotherms exhibited hysteresis, in which the equilibrium moisture content was higher at a particular equilibrium relative humidity for desorption curve than for adsorption. The hysteresis effect was more pertinent for un-osmosed and salt osmosed samples in comparison to sugar osmosed samples. Five models namely the modified Chung Pfost, modified Halsey, modified Henderson, modified Exponential and Guggenheim-Anderson-de Boer (GAB) were evaluated to determine the best fit for the experimental data. For both adsorption and desorption process of aonla fruit, the equilibrium moisture content of un-osmosed and osmosed aonla samples can be predicted well by GAB model as well as modified Exponential model. Moreover, the modified Exponential model was found to be the best for describing the sorption behaviour of un-osmosed and salt osmosed samples while, GAB model for sugar osmosed aonla samples.

  10. Ultralow friction of ink-jet printed graphene flakes.

    Science.gov (United States)

    Buzio, R; Gerbi, A; Uttiya, S; Bernini, C; Del Rio Castillo, A E; Palazon, F; Siri, A S; Pellegrini, V; Pellegrino, L; Bonaccorso, F

    2017-06-08

    We report the frictional response of few-layer graphene (FLG) flakes obtained by the liquid phase exfoliation (LPE) of pristine graphite. To this end, we inkjet print FLG on bare and hexamethyldisilazane-terminated SiO2 substrates, producing micrometric patterns with nanoscopic roughness that are investigated by atomic force microscopy. Normal force spectroscopy and atomically-resolved morphologies indicate reduced surface contamination by solvents after a vacuum annealing process. Notably, the printed FLG flakes show ultralow friction comparable to that of micromechanically exfoliated graphene flakes. Lubricity is retained on flakes with a lateral size of a few tens of nanometres, and with a thickness as small as ∼2 nm, confirming the high crystalline quality and low defects density in the FLG basal plane. Surface exposed step edges exhibit the highest friction values, representing the preferential sites for the origin of the secondary dissipative processes related to edge straining, wear or lateral displacement of the flakes. Our work demonstrates that LPE enables fundamental studies on graphene friction to the single-flake level. The capability to deliver ultralow-friction-graphene over technologically relevant substrates, using a scalable production route and a high-throughput, large-area printing technique, may also open up new opportunities in the lubrication of micro- and nano-electromechanical systems.

  11. Dating simple flakes: Early Bronze Age flake production technology on the Middle Euphrates Steppe, Syria

    Directory of Open Access Journals (Sweden)

    Yoshihiro Nishiaki

    2014-03-01

    Full Text Available Aceramic flint scatters, comprising very crude cores or flakes and no formalised tools, are frequently found on the Middle Euphrates steppe of northern Syria. Previous studies suggest that many of them are residues of short-term activities by the nomads or shepherds of the Early Bronze Age. In order to verify this interpretation, a more precise chronological framework needs to be established for the Early Bronze Age lithic industry. This paper analyses stratified flake assemblages of the Early Bronze Age at Tell Ghanem al-Ali, a securely radiocarbon-dated settlement on the Middle Euphrates, and examines which occupation level yields assemblages most similar to those of the steppe. Results demonstrate that the lithic industry of this period underwent significant diachronic changes in terms of core reduction technology. Based on the chronological framework developed at Tell Ghanem al-Ali, the steppe assemblages in question can be assigned to different phases of the Early Bronze Age. This finding will help identify processes at the beginning of the extensive exploitation of the steppe, which is regarded as one of the most important socioeconomic changes that occurred among Early Bronze Age communities of the Middle Euphrates.

  12. Graphene: powder, flakes, ribbons, and sheets.

    Science.gov (United States)

    James, Dustin K; Tour, James M

    2013-10-15

    Graphene's unique physical and electrical properties (high tensile strength, Young's modulus, electron mobility, and thermal conductivity) have led to its nickname of "super carbon." Graphene research involves the study of several different physical forms of the material: powders, flakes, ribbons, and sheets and others not yet named or imagined. Within those forms, graphene can include a single layer, two layers, or ≤10 sheets of sp² carbon atoms. The chemistry and applications available with graphene depend on both the physical form of the graphene and the number of layers in the material. Therefore the available permutations of graphene are numerous, and we will discuss a subset of this work, covering some of our research on the synthesis and use of many of the different physical and layered forms of graphene. Initially, we worked with commercially available graphite, with which we extended diazonium chemistry developed to functionalize single-walled carbon nanotubes to produce graphitic materials. These structures were soluble in common organic solvents and were better dispersed in composites. We developed an improved synthesis of graphene oxide (GO) and explored how the workup protocol for the synthesis of GO can change the electronic structure and chemical functionality of the GO product. We also developed a method to remove graphene layers one-by-one from flakes. These powders and sheets of GO can serve as fluid loss prevention additives in drilling fluids for the oil industry. Graphene nanoribbons (GNRs) combine small width with long length, producing valuable electronic and physical properties. We developed two complementary syntheses of GNRs from multiwalled carbon nanotubes: one simple oxidative method that produces GNRs with some defects and one reductive method that produces GNRs that are less defective and more electrically conductive. These GNRs can be used in low-loss, high permittivity composites, as conductive reinforcement coatings on Kevlar

  13. Star polymer unimicelles on graphene oxide flakes.

    Science.gov (United States)

    Choi, Ikjun; Kulkarni, Dhaval D; Xu, Weinan; Tsitsilianis, Constantinos; Tsukruk, Vladimir V

    2013-08-06

    We report the interfacial assembly of amphiphilic heteroarm star copolymers (PSnP2VPn and PSn(P2VP-b-PtBA)n (n = 28 arms)) on graphene oxide flakes at the air-water interface. Adsorption, spreading, and ordering of star polymer micelles on the surface of the basal plane and edge of monolayer graphene oxide sheets were investigated on a Langmuir trough. This interface-mediated assembly resulted in micelle-decorated graphene oxide sheets with uniform spacing and organized morphology. We found that the surface activity of solvated graphene oxide sheets enables star polymer surfactants to subsequently adsorb on the presuspended graphene oxide sheets, thereby producing a bilayer complex. The positively charged heterocyclic pyridine-containing star polymers exhibited strong affinity onto the basal plane and edge of graphene oxide, leading to a well-organized and long-range ordered discrete micelle assembly. The preferred binding can be related to the increased conformational entropy due to the reduction of interarm repulsion. The extent of coverage was tuned by controlling assembly parameters such as concentration and solvent polarity. The polymer micelles on the basal plane remained incompressible under lateral compression in contrast to ones on the water surface due to strongly repulsive confined arms on the polar surface of graphene oxide and a preventive barrier in the form of the sheet edges. The densely packed biphasic tile-like morphology was evident, suggesting the high interfacial stability and mechanically stiff nature of graphene oxide sheets decorated with star polymer micelles. This noncovalent assembly represents a facile route for the control and fabrication of graphene oxide-inclusive ultrathin hybrid films applicable for layered nanocomposites.

  14. Adhesive force between graphene nanoscale flakes and living biological cells.

    Science.gov (United States)

    Al Faouri, Radwan; Henry, Ralph; Biris, Alexandru S; Sleezer, Rob; Salamo, Gregory J

    2017-11-01

    We report on a measurement technique that quantifies the adhesive force between multi-layers of graphene flakes and the cell wall of live Escherichia coli cells using atomic force microscopy (AFM) in-fluid Peak Force- Quantitative Nanomechanical Mapping mode. To measure the adhesive force, we made use of the negative charge of E. coli cells to allow them to stick to positively charged surfaces, such as glass or silicon, that were covered by poly-L-Lysine. With this approach, cells were held in place for AFM characterization. Both pristine graphene (PG) flakes and functionalized graphene (FG) flakes were put on the E. coli cells and measurements of lateral size, flake thickness, and adhesion were made. Using this approach, the measured values of the adhesive force between multi-layers of graphene flakes (total thickness of 50 nm) and E. coli was determined to be equal or greater than 431 ± 65pN for (PG) and 694 ± 98pN for the (FG). More interestingly, the adhesive force of a graphene flake (thickness 1.3 nm) with the cell is determined to be equal or greater than 38.2 ± 16.4pN for the (PG) and 34.8 ± 15.3pN for the (FG). These interaction values can play an important role in determining and understanding the possible toxicity of graphene flakes. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  15. Tunable dynamics of a flake on graphene: Libration frequency

    Science.gov (United States)

    Aktürk, O. Üzengi; Aktürk, E.; Gürel, H. H.; Ciraci, S.

    2017-03-01

    In this paper we investigated the interaction between a graphene nanoflake anchored to the 2D graphene monolayer. This interaction is attractive but weak and is capable of setting a well defined registry in equilibrium. Rotational and linear displacements from equilibrium registry generate restoring forces, which can be controlled by external agents. Similar flakes can be self-assembled and can also execute simple harmonic motion as if a physical pendulum. Oscillation of a nanoflake about their equilibrium registries resulting in a characteristic libration frequency is predicted. This frequency depends on the size and geometry of the flake. Moreover, the libration frequency, as well as the electronic and magnetic properties of the flake+monolayer systems, can be tuned by a foreign molecule anchored to the flake, by electric charging and applied parallel and perpendicular electric and magnetic fields. When the sliding of the flake is combined with rotation, the friction force can be reduced dramatically. It is surprising that weak interaction can offer such features at nanoscale, which may offer potential applications. Our predictions are obtained by first-principles calculations based on density functional theory.

  16. Physicochemical properties of flakes made from three varieties of banana

    Science.gov (United States)

    Ratnawati, Lia; Afifah, Nok

    2017-11-01

    Ripe and unripe banana flour from three varieties of banana (Kepok, Raja and Ambon) were used to make a flake. This study aims to determine the physicochemical properties of flakes made from three types of banana varieties. The moisture, ash, protein, fat and carbohydrate content of flakes ranged from 1.01 to 4.40%, 2.40 to 2.99%, 7.38 to 9.19%, 4.71 to 8.32 % and 77.78 to 82.65%, respectively. WAI, WSI and TDF values of flakes ranged from 1.81 to 2.11 g/g, 34.54 to 52.64% and 8.64 to 10.04%, respectively. Values of hardness and fracturability were ranging from 346.65 to 563.50 g and 15.16 to 17.62 mm. The colour parameter values are lightness (L*), redness (a*) and yellowness (b*) of flakes ranged from 42.56 to 55.82, 3.34 to 6.60 and 3.99 to 13.09, respectively.

  17. High-yield production and transfer of graphene flakes obtained by anodic bonding

    OpenAIRE

    Moldt, Thomas; Eckmann, Axel; Klar, Philipp; Morozov, Sergey V.; Zhukov, Alexander A.; Novoselov, Kostya S.; CASIRAGHI, cinzia

    2011-01-01

    We report large-yield production of graphene flakes on glass by anodic bonding. Under optimum conditions, we counted several tens of flakes with lateral size around 20-30 {\\mu}m and few tens of flakes with larger size. 60-70% of the flakes have negligible D peak. We show that it is possible to easily transfer the flakes by wedging technique. The transfer on silicon does not damage graphene and lowers the doping. The charge mobility of the transferred flakes on silicon is of the order of 6000 ...

  18. Very low energy electron microscopy of graphene flakes.

    Science.gov (United States)

    Mikmeková, E; Bouyanfif, H; Lejeune, M; Müllerová, I; Hovorka, M; Unčovský, M; Frank, L

    2013-08-01

    Commercially available graphene samples are examined by Raman spectroscopy and very low energy scanning transmission electron microscopy. Limited lateral resolution of Raman spectroscopy may produce a Raman spectrum corresponding to a single graphene layer even for flakes that can be identified by very low energy electron microscopy as an aggregate of smaller flakes of various thicknesses. In addition to diagnostics of graphene samples at larger dimensions, their electron transmittance can also be measured at very low energies. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

  19. Simultaneous electrochemical synthesis of few-layer graphene flakes on both electrodes in protic ionic liquids.

    Science.gov (United States)

    Mao, Min; Wang, Mengmeng; Hu, Junyan; Lei, Gang; Chen, Shuzhen; Liu, Hongtao

    2013-06-11

    Here we illustrate a simple and moderate electrochemical strategy to simultaneously harvest high-quality few-layer graphene flakes (graphene flakes detached from cathodic graphite receive a defect healing.

  20. Fire effects on flaked stone, ground stone, and other stone artifacts [Chapter 4

    Science.gov (United States)

    Krista Deal

    2012-01-01

    Lithic artifacts can be divided into two broad classes, flaked stone and ground stone, that overlap depending on the defining criteria. For this discussion, flaked stone is used to describe objects that cut, scrape, pierce, saw, hack, etch, drill, or perforate, and the debris (debitage) created when these items are manufactured. Objects made of flaked stone include...

  1. Ag-catalyzed InAs nanowires grown on transferable graphite flakes

    DEFF Research Database (Denmark)

    Meyer-Holdt, Jakob; Kanne, Thomas; Sestoft, Joachim E.

    2016-01-01

    on exfoliated graphite flakes by molecular beam epitaxy. Ag catalyzes the InAs nanowire growth selectively on the graphite flakes and not on the underlying InAs substrates. This allows for easy transfer of the flexible graphite flakes with as-grown nanowire ensembles to arbitrary substrates by a micro-needle...

  2. Molecular dynamics simulation of the self-retracting motion of a graphene flake

    Science.gov (United States)

    Popov, Andrey M.; Lebedeva, Irina V.; Knizhnik, Andrey A.; Lozovik, Yurii E.; Potapkin, Boris V.

    2011-12-01

    The self-retracting motion of a graphene flake on a stack of graphene flakes is studied using molecular dynamics simulations. It is shown that in the case when the extended flake is initially rotated to an incommensurate state, there is no barrier to the self-retracting motion of the flake and the flake retracts as fast as possible. If the extended flake is initially commensurate with the other flakes, the self-retracting motion is hindered by potential energy barriers. However, in this case, rotation of the flake to incommensurate states is often observed. Such a rotation is found to be induced by the torque acting on the flake on hills of the potential relief of interaction energy between the flakes. Contrary to carbon nanotubes, telescopic oscillations of the graphene flake are suppressed because of high dynamic friction related to the excitation of flexural vibrations of the flake. This makes graphene promising for the use in fast-responding electromechanical memory cells.

  3. Flexural properties and impact strength of denture base resins reinforced with micronized glass flakes

    Directory of Open Access Journals (Sweden)

    Ronak H Choksi

    2016-01-01

    Conclusion: Flexural strength of unmodified PMMA denture base resin decreases with increase in the concentration of glass flakes. Impact strength does not show any significant change at 5% concentration of glass flakes and impact strength significantly reduces with the addition of glass flakes in 10% and 20%.

  4. Mechanical performance of cellulose nanofibril film-wood flake laminate

    Science.gov (United States)

    Jen-Chieh Liu; Robert J. Moon; Alan Rudie; Jeffrey P. Youngblood

    2014-01-01

    Homogeneous and transparent CNF films, fabricated from the (2,2,6,6- tetramethylpiperidin-1-yl) oxyl (TEMPO)-modified CNF suspension, were laminated onto wood flakes (WF) based on phenol-formaldehyde (PF) resin and the reinforcement potential of the material has been investigated. The focus was on the influence of CNF film lamination, relative humidity (RH), heat...

  5. 9 CFR 590.547 - Albumen flake process drying operations.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Albumen flake process drying operations. 590.547 Section 590.547 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE... free of flies, insects, and rodents. (b) Drying units, racks, and trucks shall be kept in a clean and...

  6. Microfocus infrared ellipsometry characterization of air-exposed graphene flakes

    NARCIS (Netherlands)

    Weber, J. W.; Hinrichs, K.; Gensch, M.; M. C. M. van de Sanden,; Oates, T. W. H.

    2011-01-01

    Graphene and ultrathin graphite flakes prepared by exfoliation were characterized by microfocus synchrotron infrared mapping ellipsometry. The dielectric function of graphene in a dry-air atmosphere is determined and compared to that of ultrathin graphite, bulk graphite, and gold. The imaginary part

  7. Moisture Barrier Composites Made of Non-Oxidized Graphene Flakes.

    Science.gov (United States)

    Kim, Jungmo; Song, Sung Ho; Im, Hyeon-Gyun; Yoon, Gabin; Lee, Dongju; Choi, Chanyong; Kim, Jin; Bae, Byeong-Soo; Kang, Kisuk; Jeon, Seokwoo

    2015-07-01

    Graphene flakes (GFs) with minimized defects and oxidation ratios are incorporated into polyethylene (PE) to enhance the moisture barrier. GFs produced involving solvothermal intercalation show extremely low oxidation rates (3.17%), and are noncovalently functionalized in situ, inducing strong hydrophobicity. The fabricated composite possesses the best moisture barrier performance reported for a polymer-graphene composite. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Interlayer repulsion and decoupling effects in stacked turbostratic graphene flakes

    OpenAIRE

    Berashevich, Julia; Chakraborty, Tapash

    2011-01-01

    We have explored the electronic properties of stacked graphene flakes with the help of the quantum chemistry methods. We found that the behavior of a bilayer system is governed by the strength of the repulsive interactions that arise between the layers as a result of the orthogonality of their $\\pi$ orbitals. The decoupling effect, seen experimentally in AA stacked layers is a result of the repulsion being dominant over the orbital interactions and the observed layer misorientation of 2$^{\\ci...

  9. Nutritional and technological characteristics of new broad bean flaked products.

    Science.gov (United States)

    Senesi, E; Duranti, M; Gervasini, M; Bertolo, G; Rizzolo, A

    1988-01-01

    The effects of the technological processes (soaking in water or alkaline solutions, drying, puree preparation) and the supplementation with maize flour on the nutritional value and on the organoleptic characteristics of broad bean (Vicia faba, L. major) flakes have been studied. Protein content was not affected by technological process. The addition of maize flour decreased the protein content of the final product depending on the amount of the maize flour added. Amino acid composition showed a decrease of tryptophan due to technological processing. Supplementation with maize flour improved the amino acid pattern and, except for tryptophan, the amount of essential amino acids in the flakes supplemented with 25% or more maize flour well compared with the provisional pattern by F.A.O. In vitro digestibility trials did not evidence significant changes due to technological processes or to integration of broad beans with maize flour. Broad bean toxic factors (vicine and convicine glycosides) were only slightly affected by the alkaline treatment of the flakes. Glycosides content decreased with the increasing supplementation with maize flour but the relationship was not linear. The organoleptic tests were positive for texture and taste, whereas the appearance of the products should be improved.

  10. Conductance of graphene flakes contacted at their corners.

    Science.gov (United States)

    Konôpka, Martin

    2015-11-04

    Linear conductance of junctions formed by graphene flakes with the order of the nanometer-thick electrodes attached at the corners of the flakes is studied. The explored structures have sizes up to 20,000 atoms and the conductance is studied as a function of applied gate voltage varied around the Fermi level. The finding, obtained computationally, is that junctions formed by armchair-edge flakes with the electrodes connected at the acute-angle corners block the electron transport while only junctions with such electrodes at the obtuse-angle corners tend to provide the high electrical conductance typical for metallic GNRs. The finding in the case of zig-zag edges is similar with the exception of a relatively narrow gate voltage interval in which each studied junction is highly conductive as mediated by the edge states. The contrast between the conductive and insulating setups is typically several orders of magnitude in terms of ratio of their conductances. The main results of the paper also remain to a large extent valid in the presence of edge disorder.

  11. Photon-assisted transport in bilayer graphene flakes

    Science.gov (United States)

    Zambrano, D.; Rosales, L.; Latgé, A.; Pacheco, M.; Orellana, P. A.

    2017-01-01

    The electronic conductance of graphene-based bilayer flake systems reveals different quantum interference effects, such as Fabry-Pérot resonances and sharp Fano antiresonances on account of competing electronic paths through the device. These properties may be exploited to obtain spin-polarized currents when the same nanostructure is deposited above a ferromagnetic insulator. Here, we study how the spin-dependent conductance is affected when a time-dependent gate potential is applied to the bilayer flake. Following a Tien-Gordon formalism, we explore how to modulate the transport properties of such systems via appropriate choices of the ac-field gate parameters. The presence of an oscillating field opens the possibility of tuning the original antiresonances for a large set of field parameters. We show that interference patterns can be partially or fully removed by the time-dependent gate voltage. The results are reflected in the corresponding weighted spin polarization, which can reach maximum values for a given spin component. We found that differential conductance maps as functions of bias and gate potentials show interference patterns for different ac-field parameter configurations. The proposed bilayer graphene flake systems may be used as a frequency detector in the THz range.

  12. Infrared Extinction Coefficients of Aerosolized Conductive Flake Powders and Flake Suspensions having a Zero-Truncated Poisson Size Distribution

    Science.gov (United States)

    2012-11-01

    image contrast without the cloud present. Contrast transmittance is a function of the extinction coefficient, single-scatter albedo , asymmetry parameter...scatter albedo and asymmetry parameter in controlling contrast transmittance. The metal flakes used in this study were exceptional because they possessed...it into a liquid jet or sheet . The liquid jet or sheet was then atomized through the 5 interaction with a high velocity gas. The velocity and

  13. High-yield production and transfer of graphene flakes obtained by anodic bonding.

    Science.gov (United States)

    Moldt, Thomas; Eckmann, Axel; Klar, Philipp; Morozov, Sergey V; Zhukov, Alexander A; Novoselov, Kostya S; Casiraghi, Cinzia

    2011-10-25

    We report large-yield production of graphene flakes on glass by anodic bonding. Under optimum conditions, we counted several tens of flakes with lateral size around 20-30 μm and a few tens of flakes with larger size. About 60-70% of the flakes have a negligible D peak. We show that it is possible to easily transfer the flakes by the wedging technique. The transfer on silicon does not damage graphene and lowers the doping. The charge mobility of the transferred flakes on silicon is on the order of 6000 cm(2)/V s (at a carrier concentration of 10(12) cm(-2)), which is typical for devices prepared on this substrate with exfoliated graphene.

  14. Use of Kelvin probe force microscopy for identification of CVD grown graphene flakes on copper foil

    Science.gov (United States)

    Kumar, Rakesh; Mehta, B. R.; Kanjilal, D.

    2017-05-01

    Graphene flakes have been grown by chemical vapour deposition (CVD) method on Cu foils. The obtained graphene flakes have been characterized by optical microscopy, field emission scanning electron microscopy, Kelvin probe force microscopy (KPFM) and Raman spectroscopy. The graphene flakes grown on Cu foil comprise mainly single layer graphene and confirm that the nucleation for graphene growth starts very quickly. Moreover, KPFM has been found to be a valuable technique to differentiate between covered and uncovered portion of Cu foil by graphene flakes deposited for shorter duration. The results show that KPFM can be a very useful technique in understanding the mechanism of graphene growth.

  15. Environmental and health effects review for obscurant graphite flakes. Final report, 1991 July--1993 May

    Energy Technology Data Exchange (ETDEWEB)

    Driver, C.J.; Ligotke, M.W.; Landis, W.G.; Downs, J.L.; Tiller, B.L.; Moore, E.B. Jr.; Cataldo, D.A.

    1993-07-01

    The health and environmental effects of obscurant graphite flakes were reviewed and compared to predicted levels of graphite flake material in the field during typical testing and training scenarios. Graphite flake dispersion and deposition for simulated mechanical and pyrotechnic releases were determined using a modified Gaussian atmospheric plume-dispersion model. The potential for wind resuspension of graphite flakes is controlled by weathering processes and incorporation rates in soil. Chemically, graphite flakes pose little risk to aquatic or terrestrial systems. Mechanical damage to plants and invertebrate and vertebrate organisms from the flakes is also minimal. In humans, the pathological and physiological response to inhaled graphite flake is similar to that induced by nuisance dusts and cause only transient pulmonary changes. Repeated exposure to very high concentrations (such as those near the source generator) may overwhelm the clearance mechanisms of the lung and result in pulmonary damage from the retained particles in unprotected individuals. However, these lesions either resolve with time or are of limited severity. Health effects of mixed aerosols of mixed aerosols of graphite and fog oil are similar to those produced by graphite flakes alone. Environmental impacts of fog oil-coated graphite flakes are not well known.

  16. Dynamic electro-optic response of graphene/graphitic flakes in nematic liquid crystals.

    Science.gov (United States)

    Tie, Weiwei; Bhattacharyya, Surjya Sarathi; Lim, Young Jin; Lee, Sang Won; Lee, Tae Hoon; Lee, Young Hee; Lee, Seung Hee

    2013-08-26

    Electric field induced dynamic reorientation phenomenon of graphene/graphitic flakes in homogeneously aligned nematic liquid crystal (NLC) medium has been demonstrated by optical microscopy. The flakes reorient from parallel to perpendicular configuration with respect to boundary plates of confining cells for an applied field strength of as low as tens of millivolt per micrometer. After field removal the reoriented flakes recover to their initial state with the help of relaxation of NLC. Considering flake reorientation phenomenon both in positive and negative dielectric anisotropy NLCs, the reorientation process depends on interfacial Maxwell-Wagner polarization and NLC director reorientation. We propose a phenomenological model based on electric field induced potential energy of graphitic flakes and coupling contribution of positive NLC to generate the rotational kinetic energy for flake reorientation. The model successfully explains the dependence of flake reorientation time over flake shape anisotropy, electric-field strength, and flake area. Using present operating scheme it is possible to generate dark field-off state and bright field-on state, having application potential for electro-optic light modulation devices.

  17. Long Spin Diffusion Length in Few-Layer Graphene Flakes

    Science.gov (United States)

    Yan, W.; Phillips, L. C.; Barbone, M.; Hämäläinen, S. J.; Lombardo, A.; Ghidini, M.; Moya, X.; Maccherozzi, F.; van Dijken, S.; Dhesi, S. S.; Ferrari, A. C.; Mathur, N. D.

    2016-09-01

    We report a spin valve with a few-layer graphene flake bridging highly spin-polarized La0.67Sr0.33MnO3 electrodes, whose surfaces are kept clean during lithographic definition. Sharp magnetic switching is verified using photoemission electron microscopy with x-ray magnetic circular dichroism contrast. A naturally occurring high interfacial resistance ˜12 M Ω facilitates spin injection, and a large resistive switching (0.8 M Ω at 10 K) implies a 70 - 130 μ m spin diffusion length that exceeds previous values obtained with sharp-switching electrodes.

  18. Microwave absorption properties of graphite flakes-phenolic resin composite

    Science.gov (United States)

    Gogoi, Jyoti P.; Gogoi, Pragyan J.; Bhattacharyya, Nidhi S.

    2013-01-01

    In the present investigation, microwave absorption properties of a conductor back single layer designed on graphite flakes (GF)-novolac phenolic resin (NPR) composites is studied. The complex permittivity of the developed composite enhance for higher GF percentages. The reflection loss(RL) measured using E8362C VNA shows a maximum RL values -25 dB at 9.8 GHz for 7 wt. % composition with -10 dB bandwidth of 0.3 GHz. The developed composites are being light weight and cost effective shows potential to be used as dielectric absorber.

  19. The extended growth of graphene oxide flakes using ethanol CVD.

    Science.gov (United States)

    Huang, Jingfeng; Larisika, Melanie; Fam, W H Derrick; He, Qiyuan; Nimmo, Myra A; Nowak, Christoph; Tok, I Y Alfred

    2013-04-07

    We report the extended growth of Graphene Oxide (GO) flakes using atmospheric pressure ethanol Chemical Vapor Deposition (CVD). GO was used to catalyze the deposition of carbon on a substrate in the ethanol CVD with Ar and H2 as carrier gases. Raman, SEM, XPS and AFM characterized the growth to be a reduced GO (RGO) of layers. This newly grown RGO possesses lower defect density with larger and increased distribution of sp(2) domains than chemically reduced RGO. Furthermore this method without optimization reduces the relative standard deviation of electrical conductivity between chips, from 80.5% to 16.5%, enabling RGO to be used in practical electronic devices.

  20. Cavity induced fluorescence enhancement of graphitic carbon nitride submicron flakes

    Science.gov (United States)

    Veluthandath, Aneesh Vincent; Reddy Bongu, Sudhakara; Ramaprabhu, Sundara; Ballabh Bisht, Prem

    2017-01-01

    Graphitic carbon nitride (g-C3N4), which is structurally analogous to graphene, shows excellent fluorescent yield. Sharp ripple structure is observed in the fluorescence spectra of g-C3N4 flakes grafted on the surface of single polymethyl methacrylate (PMMA) microspheres. The intensities and the number of modes of these structures nonlinearly vary with the size of micro-cavity and the coupled power. Theoretical simulations carried out with the help of Mie theory show that the ripple structure is due to modulation of the fluorescence by the whispering gallery modes (WGMs) of the spherical microcavity.

  1. Interlayer repulsion and decoupling effects in stacked turbostratic graphene flakes

    Science.gov (United States)

    Berashevich, Julia; Chakraborty, Tapash

    2011-07-01

    The behavior of stacked graphene flakes is found to be governed by the strength of the repulsive interactions that arise due to the orthogonality of interlayer π orbitals. Therefore, the decoupling effect in AA stacked layers is a result of the repulsion being dominant over the orbital interactions while misorientation of 2°-5° is an attempt by the system to suppress that repulsion. For misorientated graphene, in the regions of superposed lattices in the Moiré pattern, the repulsion between the layers manifest itself as lattice distortion by forming a bump.

  2. Sorption isotherms for oat flakes (Avena sativa L.

    Directory of Open Access Journals (Sweden)

    José Edgar Zapata M.

    2014-04-01

    Full Text Available Moisture sorption isotherms of oat flakes were determined at temperatures of 5, 25 and 37°C, using a gravimetric technique in an a w range of between 0.107 and 0.855. These curves were modeled using six equations commonly applied in food. The quality of the fit was assessed with the regression coefficient (r² and the mean relative percentage error (MRPE. The best fit were obtained with the Caurie model with r² of 0.996, 0.901 and 0.870, and MRPE of 7.190, 17.878 and 16.206, at 5, 25 and 37°C, respectively. The equilibrium moisture presented a dependence on temperature in the studied a w range, as did the security moisture (X S. These results suggest that the recommended storage conditions of oat flakes include: a relative air humidity of 50% between 5 and 25°C and of 38% up to 37°C.

  3. Design and characterization of biofunctional magnetic porous silicon flakes.

    Science.gov (United States)

    Muñoz Noval, A; García, R; Ruiz Casas, D; Losada Bayo, D; Sánchez Vaquero, V; Torres Costa, V; Martín Palma, R J; García, M A; García Ruiz, J P; Serrano Olmedo, J J; Muñoz Negrete, J F; del Pozo Guerrero, F; Manso Silván, M

    2013-04-01

    Magnetic porous silicon flakes (MPSF) were obtained from mesoporous silicon layers formed by multi-step anodization and subsequent composite formation with Fe oxide nanoparticles by thermal annealing. The magnetic nanoparticles adhered to the surface and penetrated inside the pores. Their structure evolved as a result of the annealing treatments derived from X-ray diffraction and X-ray absorption analyses. Moreover, by tailoring the magnetic load, the dynamic and hydrodynamic properties of the particles were controlled, as observed by the pressure displayed against a sensor probe. Preliminary functionality experiments were performed using an eye model, seeking potential use of MPSF as reinforcement for restored detached retina. It was observed that optimal flake immobilization is obtained when the MPSF reach values of magnetic saturation >10(-4)Am(2)g(-1). Furthermore, the MPSF were demonstrated to be preliminarily biocompatible in vitro. Moreover, New Zealand rabbit in vivo models demonstrated their short-term histocompatibility and their magnetic functionality as retina pressure actuators. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  4. Antibacterial Activity of Neat Chitosan Powder and Flakes.

    Science.gov (United States)

    Ardila, Nury; Daigle, France; Heuzey, Marie-Claude; Ajji, Abdellah

    2017-01-06

    This study investigates the antibacterial activity of neat chitosan powder and flakes against three different bacterial species, Escherichia coli , Listeria innocua and Staphylococcus aureus , which are frequent causes of food spoilage. The effect of chitosan concentration and purity, as well as the influence of temperature, ionic strength (salt) and impact of a solid physical support in the medium are examined. Results show that the antibacterial activity of neat chitosan: (i) requires partial solubilisation; (ii) can be promoted by environmental factors such as adequate temperature range, ionic strength and the presence of a solid physical support that may facilitate the attachment of bacteria; (iii) depends on bacterial species, with a sensitivity order of E. coli > L. innocua > S. aureus ; and (iv) increases with chitosan concentration, up to a critical point above which this effect decreases. The latter may be due to remaining proteins in chitosan acting as nutrients for bacteria therefore limiting its antibacterial activity. These results on the direct use of chitosan powder and flakes as potential antimicrobial agents for food protection at pH values lower than the chitosan p K a (6.2-6.7) are promising.

  5. Barium titanate flakes based composites for microwave absorbing applications

    Directory of Open Access Journals (Sweden)

    Raj Kumar Jain

    2013-12-01

    Full Text Available Barium titanate (BT has attained research focus in recent past owing to considering its high dielectric constant and stealth capabilities in microwave region. Shape effects of BT viz. powder, micron size flakes, nanoparticles and nanotubes have been studied vastly for its stealth capabilities. Present study aims at the preparation of millimetric size barium titanate flakes (BTFs via controlled sol-gel process followed by tape casting. BTFs were mixed in varied weight ratio (50–90 wt.% with polyurethane resin to fabricate composite laminates. Electromagnetic properties measurement in X and Ku band revealed high values of real and imaginary permittivity. Reflection loss measurements demonstrated more than 20 dB loss in wide frequency range (11.4–13.6 GHz. For single layer microwave absorber, reflection loss values have been calculated and it is observed that calculated and measured reflection loss values are in good agreement to each other. Developed material can find applications in broadband radar signature reduction.

  6. Investigation of transfer characteristics of high performance graphene flakes.

    Science.gov (United States)

    Venugopal, Gunasekaran; Krishnamoorthy, Karthikeyan; Kim, Sang-Jae

    2013-05-01

    In this article, we attempted a study on field effect transport characteristics of graphene flakes. These graphene flakes were exfoliated by mechanical peeling-off technique and the electrical contacts were patterned by photo-lithographic method. Graphene devices have shown better transfer characteristics which was obtained even in low-voltage (graphene transistors were patterned on oxidized silicon wafers. A clear n-type to p-type transition at Dirac point and higher electron drain-current modulation in positive back-gate field with current minimum (the Dirac point) were observed at V(GS) = -1.7 V. The carrier mobility was determined from the measured transconductance. The transconductance of the graphene transistors was observed as high as 18.6 microS with a channel length of 68 microm. A maximum electron mobility of 1870 +/- 143 cm2/V x s and hole mobility of 1050 +/- 35 cm2/V x s were achieved at a drain bias 2.1 V which are comparatively higher values among reported for mechanically exfoliated graphene using lithographic method. The fabricated devices also sustained with high-current density for 40 hr in continuous operation without any change in device resistance, which could be applied for robust wiring applications.

  7. 40 CFR 417.60 - Applicability; description of the manufacture of soap flakes and powders subcategory.

    Science.gov (United States)

    2010-07-01

    ... manufacture of soap flakes and powders subcategory. 417.60 Section 417.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS SOAP AND DETERGENT MANUFACTURING POINT SOURCE CATEGORY Manufacture of Soap Flakes and Powders Subcategory § 417.60 Applicability...

  8. Flake Orientation Effects On Physical and Mechanical Properties of Sweetgum Flakeboard

    Science.gov (United States)

    T.F. Shupe; Chung-Yun Hse; E.W. Price

    2001-01-01

    Research was initiated to determine the effect of flake orientation on the physical and mechanical properties offlakeboard. The panel fabrication techniques investigated were single-layer panels with random and oriented flake distribution, three-layer, five-layer, and seven-layer panels. Single-layer oriented panels had panel directional property ratios of 11.8 and 12....

  9. Inclusion of various amounts of steam-flaked soybeans in lactating dairy cattle diets

    Science.gov (United States)

    While most soybean feedstuffs have been extensively investigated for use in ruminant diets, there is a lack of information regarding steam-flaked soybeans. This research evaluated various inclusion rates of steam-flaked soybeans (SFSB) in lactating dairy cattle diets. Twelve multiparous Holstein cow...

  10. Formation of water-soluble soybean polysaccharides from spent flakes by hydrogen peroxide treatment

    DEFF Research Database (Denmark)

    Pierce, Brian; Wichmann, Jesper; Tran, Tam H.

    2016-01-01

    In this paper we propose a novel chemical process for the generation of water-soluble polysaccharides from soy spent flake, a by-product of the soy food industry. This process entails treatment of spent flake with hydrogen peroxide at an elevated temperature, resulting in the release of more than...

  11. Electronic structure of triangular, hexagonal and round graphene flakes near the Fermi level

    Energy Technology Data Exchange (ETDEWEB)

    Heiskanen, H P; Manninen, M; Akola, J [Nanoscience Center, Department of Physics, PO Box 35, FI-40014 University of Jyvaeskylae (Finland)], E-mail: matti.manninen@jyu.fi

    2008-10-15

    The electronic shell structure of triangular, hexagonal and round graphene quantum dots (flakes) near the Fermi level has been studied using a tight-binding method. The results show that close to the Fermi level the shell structure of a triangular flake is that of free massless particles, and that triangles with an armchair edge show an additional sequence of levels ('ghost states'). These levels result from the graphene band structure and the plane wave solution of the wave equation, and they are absent for triangles with a zigzag edge. All zigzag triangles exhibit a prominent edge state at {epsilon}{sub F}, and few low-energy conduction electron states occur both in triangular and hexagonal flakes due to symmetry reasons. Armchair triangles can be used as building blocks for other types of flakes that support the ghost states. Edge roughness has only a small effect on the level structure of the triangular flakes, but the effect is considerably enhanced in the other types of flakes. In round flakes, the states near the Fermi level depend strongly on the flake radius, and they are always localized on the zigzag parts of the edge.

  12. Optical manipulation of self-aligned graphene flakes in liquid crystals.

    Science.gov (United States)

    Twombly, Christopher W; Evans, Julian S; Smalyukh, Ivan I

    2013-01-14

    Graphene recently emerged as a new two-dimensional material platform with unique optical, thermal and electronic properties. Single- or few-atom-thick graphene flakes can potentially be utilized to form structured bulk composites that further enrich these properties and enable a broad range of new applications. Here we describe optical manipulation of self-aligned colloidal graphene flakes in thermotropic liquid crystals of nematic and cholesteric types. Three-dimensional rotational and translational manipulation of graphene flakes by means of holographic optical tweezers allows for non-contact spatial patterning of graphene, control of liquid crystal defects, and low-power optical realignment of the liquid crystal director using these flakes. Potential applications include optically- and electrically-controlled reconfigurable liquid crystalline dispersions of spontaneously aligning colloidal graphene flakes and new electro-optic devices with graphene-based interconnected transparent electrodes at surfaces and in the bulk of liquid crystals.

  13. Magnetostrain-driven quantum engine on a grapheme flake

    Science.gov (United States)

    Munoz, Enrique; Pena, Francisco

    The concept of a quantum heat engine (QHE) has been discussed as an alternative to efficiently recover, on a nanoscale device, thermal energy in the form of useful work. In a QHEN the working substance is in a mixed quantum state determined by a density matrix. Interesting examples of this concept are constituted by photosynthesis in plants as well as human-designed photocells. In this work, we propose a graphene-based quantum engine, driven by a superposition of mechanical strain and an external magnetic field. Engineering of strain in a nanoscale graphene flake creates a gauge field with an associated uniform pseudo-magnetic field. The combination leads to the emergence of discrete relativistic Landau levels. The inter-level distance and hence their statistical population can be modulated by quasi-statically tuning the imposed magnetic field along a sequence of reversible transformations that constitute a quantum mechanical analog of the classical Otto cycle. References Financial support from Fondecyt 1141146.

  14. Rapid identification of graphene flakes: alumina does it better

    Energy Technology Data Exchange (ETDEWEB)

    De Marco, P; Nardone, M; Santucci, S; Ottaviano, L [Dipartimento di Fisica, Universita dell' Aquila, Via Vetoio, 67100 Coppito-L' Aquila (Italy); Del Vitto, A; Alessandri, M, E-mail: patrizia.demarco@aquila.infn.it [Numonyx, Via C Olivetti 2, 20041 Agrate Brianza, Milano (Italy)

    2010-06-25

    We report a systematic investigation of the colour contrast (CC) of graphene (one, two and three layers) on 50, 72 and 80 nm thick Al{sub 2}O{sub 3}/Si(100) and 100 and 300 nm thick SiO{sub 2}/Si(100). The CC is determined by the analysis of optical microscopy images taken under white light illumination. A corresponding assignment of graphene in the single-layer, double-layer and trilayer phases is made using micro-Raman spectroscopy. A quantitative evaluation allows us to conclude that the colour contrast between 72 nm alumina and graphene is significantly larger than that between 300 nm silicon oxide and graphene (by factors of 2.2, 2.0 and 3.3 for the single-layer, double-layer and trilayer graphene flakes respectively). Moreover, data indicate that, to increase visibility, the use of a red or a green light is preferable.

  15. Transport through graphenelike flakes with intrinsic spin-orbit interactions

    Science.gov (United States)

    Weymann, I.; Barnaś, J.; Krompiewski, S.

    2015-07-01

    It was shown recently [J. L. Lado and J. Fernández-Rossier, Phys. Rev. Lett. 113, 027203 (2014), 10.1103/PhysRevLett.113.027203] that edge magnetic moments in graphene-like nanoribbons are strongly influenced by the intrinsic spin-orbit interaction. Due to this interaction an anisotropy comes about which makes the in-plane arrangement of magnetic moments energetically more favorable than that corresponding to the out-of-plane configuration. In this paper we raise both the edge magnetism problem and the differential conductance and shot noise Fano factor issues, in the context of finite-size flakes within the Coulomb blockade (CB) transport regime. Our findings elucidate the following problems: (i) modification of CB diamonds by the appearance of in-plane magnetic moments and (ii) modification of CB diamonds by the intrinsic spin-orbit interaction.

  16. Graphite structure and magnetic parameters of flake graphite cast iron

    Science.gov (United States)

    Vértesy, G.; Uchimoto, T.; Takagi, T.; Tomáš, I.; Kage, H.

    2017-11-01

    Different matrix and graphite morphologies were generated by a special heat treatment in three chemically different series of flake graphite cast iron samples. As cast, furnace cooled and air cooled samples were investigated. The length of graphite particles and the pearlite volume of samples were determined by metallographic examination and these parameters were compared with the nondestructively measured magnetic parameters. Magnetic measurements were performed by the method of Magnetic Adaptive Testing, which is based on systematic measurement and evaluation of minor magnetic hysteresis loops. It was shown that linear correlation existed between the magnetic quantities and the graphite length, and also between the magnetic quantities and the relative pearlite content in the investigated cast iron. A numerical expression was also determined between magnetic descriptors and relative pearlite content, which does not depend on the detailed experimental conditions.

  17. Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

    Science.gov (United States)

    Kosc, Tanya Z [Rochester, NY; Marshall, Kenneth L [Rochester, NY; Jacobs, Stephen D [Pittsford, NY

    2006-05-09

    Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

  18. Changes on image texture features of breakfast flakes cereals during water absorption.

    Science.gov (United States)

    Medina, Wenceslao T; Quevedo, Roberto A; Aguilera, José M

    2013-02-01

    Normally breakfast cereal flakes are consumed by pouring them into a bowl and covering them with fresh or cold milk. During this process the liquid uptake causes changes in the surface and internal matrix of breakfast cereals that influence texture and integrity. Some breakfast cereal as flakes have a translucent structure that could provide information about the solid matrix and air cells and how they change during liquid absorption. The objective of the study was to assess the image texture changes of corn flakes and frosted flakes during water absorption at 5, 15 and 25 °C, employing 11 image feature textures extracted from grey-level co-occurrence matrix and grey-level run length matrix (at three directions) and to relate the fractal dimension (FD) of images with rupture force (RF) reduction during soaking of both flakes at 5 °C. The most relevant result from principal component analysis calculated with a matrix of 54 (soaking times) × 22 (texture features), shows that it was possible to distinguish an isolated group consisting of different soaking times at the same water temperature in each breakfast cereal flakes evaluated, corroborating that superficial liquid imbibition is important during the liquid absorption process when flakes are soaked. Furthermore, standardized FD could be related to RF in the period when samples tend to search for an equilibrium state.

  19. Flakes product supplemented with sunflower and dry residues of wild oregano

    Directory of Open Access Journals (Sweden)

    Košutić Milenko

    2017-01-01

    Full Text Available This paper investigates the effects of simultaneous addition of sunflower (3, 6 or 9 g/100 g of sample and dry residue of wild oregano (0.5 or 1 of sample, on the physical texture and chemical properties of corn flakes to obtain new products with altered nutritional properties. The chemometric analysis pointed at the versatile beneficial contributions of sunflower in corn flakes enriched with dry residue of wild oregano enabling the optimization of corn flakes formula. The presented data point that addition of milled sunflower in investigated corn flakes products improved nutritive properties while addition of dry residue of wild oregano improved physical characteristics of corn flakes products. Regarding quality (sample CF11, score value of 0.59 maximum scores have been obtained with the addition of 6 g/100 g of sunflower and 1 g/100 g of dry residue of wild oregano per 100 g of sample for corn flakes formulation. Production of corn flakes with addition of wild oregano residues contributed to the food waste valorisation in the food industry. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 46005 an Grant no. TR 31027

  20. Plasmonic-enhanced graphene flake counter electrodes for dye-sensitized solar cells

    Science.gov (United States)

    Kim, Hyun-Young; Lee, Myung Woo; Song, Da Hyun; Yoon, Hyeok Jin; Suh, Jung Sang

    2017-06-01

    A plasmonic-enhanced graphene flake counter electrode for dye-sensitized solar cells (DSSCs) was fabricated by immobilization of gold nanoparticles (NPs) on fluorine-doped tin oxide (FTO) glass and the deposition of a thin layer of graphene flakes. The graphene flakes, fabricated using a thermal plasma jet system, were very thin and pure and had good crystallinity. Even though their average size is larger than 100 nm, they had great dispersibility in common solvents. Their relatively large size and good crystallinity resulted in good conductivity, and their good dispersibility allowed us to fabricate relatively uniform films. The efficiency of the DSSC with a graphene flake/Au NP/FTO counter electrode was as much as 9.78%, which is higher than that with a conventional Pt/FTO (9.08%) or graphene flake/FTO (8.98%) counter electrode. Using cyclic voltammograms and electrochemical impedance spectroscopy and by measuring the incident photo-conversion efficiency, we proved that by the localized surface plasmon resonance effect of the Au NPs included between the graphene flakes and FTO, the charge-transfer resistance at the electrode/electrolyte interface was decreased. Consequently, the catalytic rate for I- regeneration improved, and the energy conversion efficiency of the DSSC with a graphene flake/Au NP/FTO counter electrode improved.

  1. Physical properties and microstructural changes during soaking of individual corn and quinoa breakfast flakes.

    Science.gov (United States)

    Medina, Wenceslao T; de la Llera, Andrés A; Condori, Juan L; Aguilera, José M

    2011-04-01

    The importance of breakfast cereal flakes (BCF) in Western diets deserves an understanding of changes in their mechanical properties and microstructure that occur during soaking in a liquid (that is, milk or water) prior to consumption. The maximum rupture force (RF) of 2 types of breakfast flaked products (BFP)--corn flakes (CF) and quinoa flakes (QF)--were measured directly while immersed in milk with 2% of fat content (milk 2%) or distilled water for different periods of time between 5 and 300 s. Under similar soaking conditions, QF presented higher RF values than CF. Soaked flakes were freeze-dried and their cross section and surface examined by scanning electron microscopy. Three consecutive periods (fast, gradual, and slow reduction of RF) were associated with changes in the microstructure of flakes. These changes were more pronounced in distilled water than in milk 2%, probably because the fat and other solids in milk become deposited on the flakes' surface hindering liquid infiltration. Structural and textural modifications were primarily ascribable to the plasticizing effect of water that softened the carbohydrate/protein matrix, inducing partial collapse of the porous structure and eventually disintegration of the whole piece through deep cracks.

  2. Effect of stray electric fields on cooling of center of mass motion of levitated graphite flakes

    Science.gov (United States)

    Nagornykh, Pavel; Coppock, Joyce; Kane, Bruce

    2015-03-01

    Levitation of charged multilayer graphene flakes in a quadrupole ion trap provides a unique way to study graphene in isolated conditions. Cooling of a flake in such a setup is necessary for high vacuum measurements of the flake and is achieved by using a parametric feedback scheme. We present data showing the strong dependence of the cooling of the flake's center of mass motion on the stray electric fields. We achieve this by using auxiliary electrodes to shift the position of the trap center in space. Once the point of minimum interaction between the stray fields and the particle is found (leading to cooling of the flake motion to temperatures below 20K at pressure of 10-7 Torr), we can estimate charge and mass of the flake by observing quantized discharge of the particle and measure transient dynamics of the center of mass motion by turning the cooling off and on. As an additional benefit, the behavior of the flake away from the optimum trap position can be used to quantify stray fields' effect on the particle motion by measuring its spinning orientation and frequency dependence on offset from the optimum position.

  3. Catalytically-etched hexagonal boron nitride flakes and their surface activity

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Do-Hyun, E-mail: nanotube@korea.ac.kr [School of Electrical Engineering, Korea University, 5-ga, Anam-dong, Seongbuk-gu, Seoul 136-713 (Korea, Republic of); Lee, Minwoo; Ye, Bora [Green Manufacturing 3Rs R& D Group, Korea Institute of Industrial Technology, Ulsan 681-310 (Korea, Republic of); Jang, Ho-Kyun; Kim, Gyu Tae [School of Electrical Engineering, Korea University, 5-ga, Anam-dong, Seongbuk-gu, Seoul 136-713 (Korea, Republic of); Lee, Dong-Jin [New Functional Components Research Team, Korea Institute of Footware & Leather Technology, 152 Danggamseo-ro, Busanjin-gu, Busan 614-100 (Korea, Republic of); Kim, Eok-Soo [Green Manufacturing 3Rs R& D Group, Korea Institute of Industrial Technology, Ulsan 681-310 (Korea, Republic of); Kim, Hong Dae, E-mail: hdkim@kitech.re.kr [Green Manufacturing 3Rs R& D Group, Korea Institute of Industrial Technology, Ulsan 681-310 (Korea, Republic of)

    2017-04-30

    Highlights: • Hexagonal boron nitride flakes are etched at low temperature in air by catalysts. • The presence of transition metal oxides produces an etched structure in the flakes. • Etched surfaces become highly active due to vacancy defects formed in the flakes. - Abstract: Hexagonal boron nitride (h-BN) is a ceramic compound which is thermally stable up to 1000 °C in air. Due to this, it is a very challenging task to etch h-BN under air atmosphere at low temperature. In this study, we report that h-BN flakes can be easily etched by oxidation at 350 °C under air atmosphere in the presence of transition metal (TM) oxide. After selecting Co, Cu, and Zn elements as TM precursors, we simply oxidized h-BN sheets impregnated with the TM precursors at 350 °C in air. As a result, microscopic analysis revealed that an etched structure was created on the surface of h-BN flakes regardless of catalyst type. And, X-ray diffraction patterns indicated that the air oxidation led to the formation of Co{sub 3}O{sub 4}, CuO, and ZnO from each precursor. Thermogravimetric analysis showed a gradual weight loss in the temperature range where the weight of h-BN flakes increased by air oxidation. As a result of etching, pore volume and pore area of h-BN flakes were increased after catalytic oxidation in all cases. In addition, the surface of h-BN flakes became highly active when the h-BN samples were etched by Co{sub 3}O{sub 4} and CuO catalysts. Based on these results, we report that h-BN flakes can be easily oxidized in the presence of a catalyst, resulting in an etched structure in the layered structure.

  4. Polymer Choleristic Liquid Crystal Flakes as New Candidates for Display and Sensor Applications

    Science.gov (United States)

    Petkoska, Anka Trajkovska

    In this paper polymer cholesteric liquid crystal (PCLC) flakes will be introduced as a novel form of particles for active applications, like electronic paper displays, as well as for sensors. The concept of electro-optic applications based on PCLC flakes is very attractive, because it offers a possibility for thin, reflective, lightweight, flexible devices that use little power. The uniqueness of PCLC flakes lies in their bright, saturated and full color capability, as well as their circular polarization effects, without the need of additional color filters and polarizers.

  5. Determination of the Test Methods Sensitive to Free Mica Content in Aggregate Fine Fractions

    Science.gov (United States)

    Kondelchuk, Dimitri; Miskovsky, Karel

    2009-04-01

    The detrimental influence of mica rich aggregates on structural deterioration of road pavement has been discussed in the literature for over a half century. This negative effect is of great importance especially for regions with crystalline, mica-rich bedrock and temperate, subarctic climates. Recent investigations reveal that elevated fractions of free mica particles in unbound granular materials, used in road constructions, greatly reduce bearing capacity and influence the hydraulic behavior of the road structure. Despite the awareness of mica’s potential harmful effect, the absence of properly adapted analytical methods is noticeable. The scope of the current study was to test two possible analytical methods which, are susceptible to mica content and could be used as an indicating technique for quantitative determination of free mica particles in unbound granular materials. Two standard methods: Sand equivalent test and methylene blue (MB) test were assumed as the most sensitive to mica presence. The rock samples used in the tests are representative for the common crushed rock aggregates for construction purposes with different contents of mica. Both methods showed susceptibility to mica content and gave strong correlation in terms of mica content. The result of the MB test can be explained by the schistose structure of mica particles and the ability of mica to absorb liquids. Another important explanation is the increased reaction surface of mica particles, which leads to an increase in the total reaction surface of the sample. The receptiveness of the sand equivalent test to mica content could be caused by the ability of mica to stay in suspension due to its flake-shaped grains.

  6. The different adsorption mechanism of methane molecule onto a boron nitride and a graphene flakes

    Energy Technology Data Exchange (ETDEWEB)

    Seyed-Talebi, Seyedeh Mozhgan [Shahid Chamran University, Golestan boulevard, Ahvaz, Khouzestan (Iran, Islamic Republic of); Neek-Amal, M., E-mail: neekamal@srttu.edu [Shahid Rajaee Teacher Training University, Lavizan, Tehran (Iran, Islamic Republic of)

    2014-10-21

    Graphene and single layer hexagonal boron-nitride are two newly discovered 2D materials with wonderful physical properties. Using density functional theory, we study the adsorption mechanism of a methane molecule over a hexagonal flake of single layer hexagonal boron-nitride (h-BN) and compare the results with those of graphene. We found that independent of the used functional in our ab-initio calculations, the adsorption energy in the h-BN flake is larger than that for graphene. Despite of the adsorption energy profile of methane over a graphene flake, we show that there is a long range behavior beyond minimum energy in the adsorption energy of methane over h-BN flake. This result reveals the higher sensitivity of h-BN sheet to the adsorption of a typical closed shell molecule with respect to graphene. The latter gives insight in the recent experiments of graphene over hexagonal boron nitride.

  7. Facile Hydrothermal Preparation and Photocatalytic Activity of Bismuth Tungstate Polycrystalline Flake-ball Particles

    OpenAIRE

    Amano, Fumiaki; Nogami, Kohei; Abe, Ryu; Ohtani, Bunsho

    2007-01-01

    Micrometer-sized spherical particles of bismuth tungstate (Bi2WO6) with hierarchical architecture were prepared by facile hydrothermal reaction without using any surfactants and polymers as structure-directing agents. The particles were assemblies of polycrystalline flakes composed of rectangular platelets. The hierarchical polycrystalline particles of “flake-ball” shape exhibited relatively high photocatalytic activity for oxidative decomposition of acetic acid in aqueous suspensions.

  8. First Principles Calculations of Spin-Dependent Conductance of Graphene Flakes

    OpenAIRE

    Sahin, Hasan; Senger, Ramazan Tugrul

    2008-01-01

    Using ab initio density functional theory and quantum transport calculations based on nonequilibrium Green's function formalism we study structural, electronic, and transport properties of hydrogen-terminated short graphene nanoribbons (graphene flakes) and their functionalization with vanadium atoms. Rectangular graphene flakes are stable, having geometric and electronic structures quite similar to that of extended graphene nanoribbons. We show that a spin-polarized current can be produced b...

  9. Orientation Control of Graphene Flakes by Magnetic Field: Broad Device Applications of Macroscopically Aligned Graphene.

    Science.gov (United States)

    Lin, Feng; Zhu, Zhuan; Zhou, Xufeng; Qiu, Wenlan; Niu, Chao; Hu, Jonathan; Dahal, Keshab; Wang, Yanan; Zhao, Zhenhuan; Ren, Zhifeng; Litvinov, Dimitri; Liu, Zhaoping; Wang, Zhiming M; Bao, Jiming

    2017-01-01

    Owing to a large diamagnetism, graphene flakes can respond and be aligned to magnetic field like a ferromagnetic material. Aligned graphene flakes exhibit emergent properties approaching single-layer graphene. Anisotropic optical properties also give rise to a magnetic writing board using graphene suspension and a bar magnet as a pen. This simple alignment technique opens up enormous applications of graphene. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Solar dryer for yam flakes and cassava chips

    Energy Technology Data Exchange (ETDEWEB)

    Onilude, M.A.; Oloso, O.A.

    1988-04-01

    A solar dryer was designed for drying yam (Dioscorea rotundata) flakes and cassava (Manihot utilissima) chips and constructed from locally available materials. The performance of the dryer was tested and yielded very promising results. One major factor considered in the design was to ensure ease of fabrication with readily available local materials. Details of the design features and construction are provided together with the diurnal variations in temperature and moisture content of the test samples. The sampled test specimen for cassava was dried from initial moisture content (M.C.) of 194% dry basis (d.b.) to about 25% M.C. within 3 days in the dryer while the control sample required 3 extra days to dry down to about 23% M.C. The yam specimen was dried to about 24% d.b. within 4 days in the dryer from an initial M.C. of 181% d.b. while the control sample took one extra day to attain a moisture content of 25% d.b. The highest average temperature recorded in the dryer was over 25 K above the average ambient temperature. The effectiveness of the dryer was further improved by increasing the area of the solar collector section.

  11. Dynamics of magnetic nano-flake vortices in Newtonian fluids

    Energy Technology Data Exchange (ETDEWEB)

    Bazazzadeh, Nasim, E-mail: n.bazazzadeh@gmail.com [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Mohseni, Seyed Majid, E-mail: m-mohseni@sbu.ac.ir [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Khavasi, Amin, E-mail: khavasi@sharif.edu [Department of Electrical Engineering, Sharif University of Technology, Tehran 11555-4363 (Iran, Islamic Republic of); Zibaii, Mohammad Ismail, E-mail: mizibaye@gmail.com [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Movahed, S.M.S., E-mail: m_movahed@sbu.ac.ir [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Jafari, G.R., E-mail: gjafari@gmail.com [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of)

    2016-12-01

    We study the rotational motion of nano-flake ferromagnetic disks suspended in a Newtonian fluid, as a potential material owing the vortex-like magnetic configuration. Using analytical expressions for hydrodynamic, magnetic and Brownian torques, the stochastic angular momentum equation is determined in the dilute limit conditions under applied magnetic field. Results are compared against experimental ones and excellent agreement is observed. We also estimate the uncertainty in the orientation of the disks due to the Brownian torque when an external magnetic field aligns them. Interestingly, this uncertainty is roughly proportional to the ratio of thermal energy of fluid to the magnetic energy stored in the disks. Our approach can be implemented in many practical applications including biotechnology and multi-functional fluidics. - Highlights: • The rotational motion of magnetic-vortex microdiscs in a Newtonian fluid is studied. • Results are compared against experimental ones and excellent agreement is observed. • The uncertainty in the orientation of the microdiscs is analytically derived.

  12. Reduced Drosophila suzukii Infestation in Berries Using Deterrent Compounds and Laminate Polymer Flakes.

    Science.gov (United States)

    Renkema, Justin M; Buitenhuis, Rosemarije; Hallett, Rebecca H

    2017-10-31

    Drosophila suzukii (Matsumura) is a recent invasive pest of soft fruits in North and South America and Europe. Control relies on frequent applications of synthetic insecticides. Additional tactics are needed for development of an effective integrated pest management program. Study objectives were to evaluate the repellency and oviposition deterrent capability of compounds in plant essential oils and the effect of select compounds on infestation rates in strawberries, using laminate polymer flakes as a carrier. Of 14 compounds from 5 essential oils, thymol was the most repellent to adult D. suzukii males and females for up to 24 h in the laboratory. Citronellol, geraniol and menthol were moderately repellent. In a choice assay, thymol on cotton wicks adjacent to ripe raspberries reduced female fly landings and larval infestation levels. In a no-choice assay, thymol reduced female fly landings by 60%, larval infestation by 50% and increased fly mortality compared to controls. Neither citronellol alone nor a blend of four repellent compounds was as effective as thymol alone at reducing fly landing, larval infestation, or increasing fly mortality. In a choice assay using polymer flakes, larval infestation was greater in raspberries near untreated flakes than in raspberries near flakes treated with thymol or peppermint oil. In the field, thymol and peppermint flakes reduced larval infestation levels by 25% in strawberries at 4, but not 7, days after application, compared to untreated flakes. With future improvements in application strategies, deterrent compounds may have a role in improving the management of D. suzukii.

  13. Glycemic index and quality evaluation of little millet (Panicum miliare) flakes with enhanced shelf life.

    Science.gov (United States)

    Patil, Kavita B; Chimmad, Bharati V; Itagi, Sunanda

    2015-09-01

    Little millet is a minor cereal crop contains several nutraceutical components. Ready To Cook (RTC) flakes of the millet exhibited higher total dietary fiber content (22.40 %) compared to dehulled grain (15.80 %). One serving (30 g) of RTC flakes provided 2.25 g of protein, 0.13 g of fat, 0.13 g of total minerals, 9.67 mg of iron and zero trans fats. The flakes possessed a medium Glycemic Index (GI) of 52.11 ranging from 41.57 to 61.80 among normal volunteers. Glycemic Load (GL) of the flakes was a low of 9.24. The RTC flakes exhibited an acceptability index of 81.11. The flakes possessed a shelf life of more than 6 months with an acceptability index of 67.55, moisture content of 11.82 per cent and Free fatty acid content of 18.02 per cent at the end of sixth month of storage period.

  14. In Situ Study of Li Intercalation into Highly Crystalline Graphitic Flakes of Varying Thicknesses.

    Science.gov (United States)

    Zou, Jianli; Sole, Christopher; Drewett, Nicholas E; Velický, Matěj; Hardwick, Laurence J

    2016-11-03

    An in situ Raman spectroelectrochemical study of Li intercalation into graphite flakes with different thicknesses ranging from 1.7 nm (3 graphene layers) to 61 nm (ca. 178 layers) is presented. The lithiation behavior of these flakes was compared to commercial microcrystalline graphite with a typical flake thickness of ∼100 nm. Li intercalation into the graphitic flakes was observed under potential control via in situ optical microscopy and Raman spectroscopy. As graphite flakes decreased in thickness, a Raman response indicative of increased tensile strain along the graphene sheet was observed during the early stages of intercalation. A progressively negative wavenumber shift of the interior and bounding modes of the split G band (E2g2(i) and E2g2(b)) is interpreted as a weakening of the C-C bonding. Raman spectra of Li intercalation into thin graphitic flakes are presented and discussed in the context of implications for Li ion battery applications, given that intercalation induced strain may accelerate carbon negative electrode aging and reduce long-term cycle life.

  15. Effect of processing techniques on color and active components amount of sweet potato (Ipomoea Batatas l) flakes

    Science.gov (United States)

    Rahmawati, Y.; Mahmudatussa'adah, A.; Yogha, S.

    2016-04-01

    Sweet potato processing is limited, such as flour, snacks, cystic, or chips. Flakes as pre-cooked meals are made through the stages of making pasta and drying. The purpose of this study was to optimize the production of sweet potato flakes at the stage of making pasta and drying. Making the pasta is done through techniques steamed or baked. Pasta drying using tools a drum dryer or cabinet dryer. As an indicator of optimization is the total of monomeric anthocyanins, β-carotene and color the resulting flakes. The results showed that the amount of anthocyanin monomeric flakes by using steam, and drum dryer (3.83 ± 0.03 mg CYE/g db), flakes by the technique of steam, and cabinet dryer (3.03 ± 0.02 mg CYE/g db), flakes with techniques bake, drum dryer (2.49 ± 0.05 CYE mg/g db), flakes with bake technique, cabinet dryer (1.98 ± 0.03 mg CYE/g db). The Color of purple sweet potato flakes produced through steamed techniques bright purple, while the color purple sweet potato flakes produced through techniques roast give a brownish purple color. The amount of β-carotene yellow flakes sweet potato with stages of cooking steamed, drum dryer (152±0.5 mg/Kg db), grilled drum dryer (136±0.4 mg/Kg db), flakes of yellow sweet potato with stages of roasted and cabinet dryer (140±0.8 mg/Kg db), and grilled stage with cabinet dryer (122±0.3 mg/Kg db). In conclusion sweet potato flakes production techniques through the stages of steam process, and used drum dryers have a number of anthocyanins or β-carotene bigger and brighter colors than the baked flakes techniques and used cabinet dryer.

  16. Quality Assessment of Solar Energy dried Tomato Flakes

    Directory of Open Access Journals (Sweden)

    M. Isiaka

    2013-08-01

    Full Text Available This study was carried out to assess the quality of solar dried tomato flakes by determining its safety, nutritive value and wholesomeness. In order to determine the safety of the dried tomato, the bacteria and mould loads were determined using three sliced thicknesses of solar energy dried samples. Two different types of agar culture media were used to culture the released bacteria and mould cells. Ascorbic acid and proximate tests were carried out to determine the nutritional value of the dried product as compared with the fresh products. To determine the wholesomeness of the dried product, the organoleptic properties in terms of colour (appearance and taste (flavour were examined and compared with those of three other tomato products. Results showed that the mean viable bacteria count ranged from 9 to 13 colonies/ml with the 25 mm thickness giving the highest value, followed by 20 mm thickness and the least value was from 15 mm thickness. The same pattern was observed for mould infection. The infection range for the three slice thicknesses was within the recommended safe limit of ≤30 colony forming unit/ml for bacteria and mould counts in food products. There was substantial drop in ascorbic acid content from 28.2 mg/100 g for fresh ripe tomato to as low as 13.6 mg/100 g for dried tomato of 25 mm slice thickness and highest value of 20.6 mg/100 g for 20 mm thickness. The results for organoleptic properties showed the tomato dried by solar energy dryer is superior to the other tomato products.

  17. Dynamic Response of Graphitic Flakes in Nematic Liquid Crystals: Confinement and Host Effect

    Directory of Open Access Journals (Sweden)

    Weiwei Tie

    2017-09-01

    Full Text Available Electric field-induced reorientation of suspended graphitic (GP flakes and its relaxation back to the original state in a nematic liquid crystal (NLC host are of interest not only in academia, but also in industrial applications, such as polarizer-free and optical film-free displays, and electro-optic light modulators. As the phenomenon has been demonstrated by thorough observation, the detailed study of the physical properties of the host NLC (the magnitude of dielectric anisotropy, elastic constants, and rotational viscosity, the size of the GP flakes, and cell thickness, are urgently required to be explored and investigated. Here, we demonstrate that the response time of GP flakes reorientation associated with an NLC host can be effectively enhanced by controlling the physical properties. In a vertical field-on state, higher dielectric anisotropy and higher elasticity of NLC give rise to quicker reorientation of the GP flakes (switching from planar to vertical alignment due to the field-induced coupling effect of interfacial Maxwell-Wagner polarization and NLC reorientation. In a field off-state, lower rotational viscosity of NLC and lower cell thickness can help to reduce the decay time of GP flakes reoriented from vertical to planar alignment. This is mainly attributed to strong coupling between GP flakes and NLC originating from the strong π-π interaction between benzene rings in the honeycomb-like graphene structure and in NLC molecules. The high-uniformity of reoriented GP flakes exhibits a possibility of new light modulation with a relatively faster response time in the switching process and, thus, it can show potential application in field-induced memory and modulation devices.

  18. Production and exchange during the Portuguese Chalcolitic: the case of bifacial flaked stone industries

    Directory of Open Access Journals (Sweden)

    Forenbaher, Stašo

    1998-12-01

    Full Text Available This study focuses on the economic organization of bifacial flaked stone industries of the Late Neolithic/Chalcolithic Portugal. It is often claimed that social hierarchies first appeared in Western Iberia during this period (ca. 3500-2500 BC. The specific research goals are: determining the production repertoire at lithic production sites, examining the possibility of craft specialization (with particular regard to artifact standardization, and investigating the geographic distribution of artifacts, in order to detect evidence of centralization. The analyses show that the organization of economy differed markedly between different artifact classes. Production of subsistence-related lithics was decentralized and they circulated through local exchange networks, although some of them could enter long-distance exchange. Prestige-related items were exchanged over large distances and apparently were produced by specialists. The level of specialization and its importance for the economy remained modest. There is no evidence for large-scale sociopolitical integration.

    Este estudio se centra en la organización económica de las industrias líticas de talla bifacial del Neolítico Final/ Calcolítico en Portugal. Se ha defendido a menudo que las jerarquías sociales aparecieron por primera vez en el occidente de la Península Ibérica durante este periodo (ca. 3500-2500 AC. Los objetivos específicos de la investigación son: determinar el repertorio de la producción en los talleres líticos, examinar la posibilidad de una especialización artesanal (prestando particular atención a la estandarización artefactual, e investigar la distribución geográfica de los artefactos para detectar las evidencias de centralización. Los análisis muestran que la organización de la economía difiere de forma notable entre las distintas clases de artefactos. La producción de los instrumentos conectados con la subsistencia era descentralizada. Los útiles

  19. Efficiency Analysis of Additions of Ice Flake in Cargo Hold Cooling System of Fishing Vessel

    Directory of Open Access Journals (Sweden)

    Amiadji Amiadji

    2017-06-01

    Full Text Available As a maritime nation, the majority of people's livelihood in Indonesia coast is as a fishermen. The process of preserving fish after being caught will determine how good the product quality. One of process on preserving fish that can be done is to perform the cooling process using a cooling machine on board. Refrigeration system certainly requires high electrical power consumption. That high power usage can be reduced as much as possible, one of which is to add chopped ice (ice flake on a fishing boat cargo space. So that the load for cooling can be reduced.The purpose of this thesis is to find out how the influence of the addition of ice flake on cooling load in the cargo hold of fishing vessels, and to know how much power is used when the cooling machine is combined with the addition of ice flake. In this analysis cooling load calculation refers to the standard ISO 7547.from the results of analysis found that the addition of ice flake on cargo space can reduce cooling load and can reduce electricity consumption day in the main vessel for the addition comparison flake ice and fish weight of 1: 1.

  20. Ex situ integration of iron oxide nanoparticles onto the exfoliated expanded graphite flakes in water suspension

    Directory of Open Access Journals (Sweden)

    Jović Nataša

    2014-01-01

    Full Text Available Hybrid structures composed of exfoliated expanded graphite (EG and iron oxide nanocrystals have been produced by an ex situ process. The iron oxide nanoparticles coated with meso-2,3-dimercaptosuccinic acid (DMSA, or poly(acrylic acid (PAA were integrated onto the exfoliated EG flakes by mixing their aqueous suspensions at room temperature under support of 1-ethyl-3-(3-dimethylaminopropylcarbodiimide (EDC and N-hydroxysuccin-nimide (NHS. EG flakes have been used both, naked and functionalized with branched polyethylenimine (PEI. Complete integration of two constituents has been achieved and mainteined stable for more than 12 months. No preferential spatial distribution of anchoring sites for attachement of iron oxide nanoparticles has been observed, regardless EG flakes have been used naked or functionalized with PEI molecules. The structural and physico-chemical characteristics of the exfoliated expanded graphite and its hybrids nanostructures has been investigated by SEM, TEM, FTIR and Raman techniques. [Projekat Ministarstva nauke Republike Srbije, br. 45015

  1. Supersonically blown nylon-6 nanofibers entangled with graphene flakes for water purification.

    Science.gov (United States)

    Lee, Jong-Gun; Kim, Do-Yeon; Mali, Mukund G; Al-Deyab, Salem S; Swihart, Mark T; Yoon, Sam S

    2015-12-07

    Water purification membranes, capable of purifying a few to tens of milliliters of aqueous methylene blue solution in a minute, were produced by supersonically blowing graphene flakes with a nylon-6 polymeric solution. The solution-blown nylon-6 nanofibers became entangled with graphene flakes thereby locking the graphene flakes within the frame of the bendable two-dimensional film structure. This method, which yielded a 5 × 7 cm(2)-sized membrane in less than 10 seconds, is commercially viable owing to fast fabrication and scalability. We show that our water purification device allows a flow rate range of 0.3-4 L h(-1) with a membrane area of just 5 cm(2), under a pressure difference of 0.5-3.5 bar. If the membrane were scaled up to 0.5 m(2), it could provide 300-4000 L h(-1) flow rate, an ample supply for home use.

  2. Transformation of graphene flakes into carbon nanostructures by γ-irradiation

    Science.gov (United States)

    Tiagulskyi, S. I.; Vasin, A. V.; Rusavsky, A. V.; Lytvyn, P. M.; Nikolenko, A. S.; Strelchuk, V. V.; Stubrov, Yu Yu; Gomeniuk, Yu Yu; Slobodian, O. M.; Lysenko, V. S.; Poroshin, V. N.; Povarchuk, V. Yu; Nazarov, A. N.

    2017-04-01

    In this paper the gamma irradiation effect on graphene layers is investigated. A simple method of synthesis from a solid-source bilayer (SiC/Ni) precursor has been used for the production of graphene flakes, both single-layer and multilayer. Samples with graphene flakes on the Ni surface were subjected to gamma irradiation in vacuum and in air under ambient atmospheric conditions. After a dose of 36 kGy, a variety of new carbon structures were observed on the surface of multilayer graphene flakes. This paper summarizes our thorough studies of the special features of these new carbon formations, including our study of the initial film morphology using optical and electron scanning microscopy, micro-Raman spectroscopy, atomic force microscopy and Kelvin probe force microscopy.

  3. Plasma treatment of thin film coated with graphene flakes for the reduction of sheet resistance.

    Science.gov (United States)

    Kim, Sung Hee; Oh, Jong Sik; Kim, Kyong Nam; Seo, Jin Seok; Jeon, Min Hwan; Yang, Kyung Chae; Yeom, Geun Young

    2013-12-01

    We investigated the effects of plasma treatment on the sheet resistance of thin films spray-coated with graphene flakes on polyethylene terephthalate (PET) substrates. Thin films coated with graphene flakes show high sheet resistance due to defects within graphene edges, domains, and residual oxygen content. Cl2 plasma treatment led to decreased sheet resistance when treatment time was increased, but when thin films were treated for too long the sheet resistance increased again. Optimum treatment time was related to film thickness. The reduction of sheet resistance may be explained by the donation of holes due to forming pi-type covalent bonds of Cl with carbon atoms on graphene surfaces, or by C--Cl bonding at the sites of graphene defects. However, due to radiation damage caused by plasma treatment, sheet resistance increased with increased treatment time. We found that the sheet resistance of PET film coated with graphene flakes could be decreased by 50% under optimum conditions.

  4. Physical and sensory properties of corn flakes with added dry residue of wild oregano distillation

    Directory of Open Access Journals (Sweden)

    Košutić Milenko

    2016-01-01

    Full Text Available According to the modern nutritionist opinions, cereal products such as flakes and snacks are the most common foods in the daily diet. Extrusion technology makes it possible to apply different sources of ingredients for the enrichment of cereal-based flakes or snack products. Substances with strong antioxidant properties such as wild oregano have a positive impact on human health. Therefore, they attract the attention of scientists, consumers and food industry experts. This paper investigates the effects of the simultaneous addition of dry residue from wild oregano distillation (0.5 g / 100g of sample and 1 g / 100g of sample, on the physical-textural and color properties of corn flakes in order to create a new product with improved nutritional properties. The addition of dry residue of wild oregano positively influenced physical characteristics (decreased bulk density 30.2 %, increased expansion rate 44.9 %, as well as texture hardness and the work of compression, 38.1 % and 40.3 %, respectively. Also, oregano significantly changed the color of flakes. Tukey’s HSD test showed statistically significant differences between most of the mean values of physical-textural, color and sensory attributes in the oregano-added corn flakes compared to the control sample. Principal component analysis has been applied to classify the samples according to differences in the studied parameters. The data pointed out that investigated corn flakes with the addition of wild oregano are new food products with good physical-textural and sensory properties due to a higher level of antioxidant activity. Moreover, it may contribute to the valorization of edible industrial waste in food production. [Projekat Ministarstva nauke Republike Srbije, br. III 46005 i br. TR 31027

  5. Chemically exfoliated large-area two-dimensional flakes of molybdenum disulfide for device applications

    Directory of Open Access Journals (Sweden)

    Vivek Pachauri

    2013-09-01

    Full Text Available A solution-based exfoliation method for obtaining large-area two-dimensional flakes of molybdenum disulfide, followed by the fabrication of electrical devices is presented in this manuscript. The exfoliation method is based on the use of an aprotic solvent, namely, acetonitrile under mild sonication steps. In order to fabricate devices, a dielectrophoresis technique is used for transferring MoS2 flakes site-specifically on to the electrode pairs pre-written on the glass chips. The devices fabricated thus can be operated as chemical sensor in liquids while investigations under photo illumination indicate that such devices can also efficiently function as photodetectors.

  6. Enhancement of thermoelectric efficiency by quantum interference effects in trilayer silicene flakes.

    Science.gov (United States)

    Cortés, Natalia; Rosales, L; Chico, Leonor; Pacheco, M; Orellana, P A

    2017-01-11

    In recent years, the enhancement of thermoelectric efficiencies has been accomplished in nanoscale systems by making use of quantum effects. We exploit the presence of quantum interference phenomena such as bound states in the continuum and Fano antiresonances in trilayer silicene flakes to produce sharp changes in the electronic transmission of the system. By applying symmetric gate voltages the thermoelectric properties can be tuned and, for particular flake lengths, a great enhancement of the figure of merit can be achieved. We show that the most favorable configurations are those in which the electronic transmission is dominated by the coupling of bound states to the continuum, tuned by an external gate.

  7. The effects of the metal temperature and wall thickness on flake graphite layer in ductile iron

    Directory of Open Access Journals (Sweden)

    M. Górny

    2015-01-01

    Full Text Available This article addresses the effect of mold filling and wall thickness on the flake graphite layer in ductile iron. The research was conducted for castings with different wall thickness (3-8 mm and using molding sand with furan resin. A thermal analysis has been performed along the length of the castings to determine the initial temperature of the metal in the mold cavity and the contact time of the liquid metal with the mold. Results demonstrated the strong influence of the temperature decrease of the metal in the mold cavity on the occurrence and the thickness of the flake graphite in the surface layer in ductile iron.

  8. Evidence of an embedded vortex translation mode in flake-shaped ferromagnetic particle composites

    Science.gov (United States)

    Neige, J.; Lepetit, T.; Malléjac, N.; Adenot-Engelvin, A.-L.; Thiaville, A.; Vukadinovic, N.

    2013-06-01

    A low-frequency resonance (sub-GHz) is observed in microwave permeability spectra of anisotropic flake-shaped ferromagnetic particle composites. The resonance frequency of this peak increases linearly with the saturation magnetization of flakes, their aspect ratio, and the amplitude of a perpendicular static magnetic field. In addition, this resonance becomes extinct for a perpendicular RF exciting magnetic field. These experimental features are reproduced by an analytical model of vortex dynamics which militates in favor of an assignment of this low-frequency signal as an embedded vortex translation mode within a multidomain magnetic structure.

  9. Determination of the lateral size and thickness of solution-processed graphene flakes

    Science.gov (United States)

    Lin, Li-Shang; Bin-Tay, Wei; Aslam, Zabeada; Westwood, A. V. K.; Brydson, R.

    2017-09-01

    We present a method to determine the lateral size distribution of solution…processed graphene via direct image analysis techniques. Initially transmission electron microscopy (TEM) and optical microscopy (OM) were correlated and used to provide a reliable benchmark. A rapid, automated OM method was then developed to obtain the distribution from thousands of flakes, avoiding statistical uncertainties and providing high accuracy. Dynamic light scattering (DLS) was further employed to develop an in-situ method to derive the number particle size distribution (PSD) for a dispersion, with a deviation lower than 22% in the sub-micron regime. Methods for determining flake thickness are also discussed.

  10. Electrically Addressable Optical Devices Using A System Of Composite Layered Flakes Suspended In A Fluid Host To Obtain Angularly Depende

    Science.gov (United States)

    Kosc, Tanya Z.; Marshall, Kenneth L.; Jacobs, Stephen D.

    2004-12-07

    Composite or layered flakes having a plurality of layers of different materials, which may be dielectric materials, conductive materials, or liquid crystalline materials suspended in a fluid host and subjected to an electric field, provide optical effects dependent upon the angle or orientation of the flakes in the applied electric field. The optical effects depend upon the composition and thickness of the layers, producing reflectance, interference, additive and/or subtractive color effects. The composition of layered flakes may also be selected to enhance and/or alter the dielectric properties of flakes, whereby flake motion in an electric field is also enhanced and/or altered. The devices are useful as active electro-optical displays, polarizers, filters, light modulators, and wherever controllable polarizing, reflecting and transmissive optical properties are desired.

  11. METABOLIC AND BIOCHEMICAL CHARACTERISTICS OF PROBIOTIC CULTURE IN MILK SUPPLEMENTED WITH RYE FLAKES AND MALT EXTRACT

    Directory of Open Access Journals (Sweden)

    Elena Bărăscu

    2010-01-01

    Full Text Available Rye flakes and malt extract were added to milk in order to stimulate growth and fermentative activity of probioticbacteria and to obtain a probiotic product with pleasant sensory attributes. Probiotic culture used in this study containsbifidobacteria, Lb. acidophilus, Lactobacilus lactis and Streptococcus thermophilus.Rye flakes have a stimulating effect more pronounced than malt extract on acidification capacity of the probioticculture, and to achieve an increase of the milk acidity of 7g lactic acid /dm3 (in 6h at 39oC the two ingredients must beadded in concentration of 2% and, respectively, 0.2%..The probiotic culture reach the greatest proteolytic activity when rye flakes are added in the proportion of 3% andmalt extract in the proportion of 0.1% and the amino acids released rate was 764.6 μg%. The lactose bioconversionrate was greater in the milk supplemented with rye flakes 3% and malt extract 0.1% and residual lactose was 3.84%.

  12. MODERN TECHNOLOGIES FOR APPLYING THE THERMAL INSULATIONS BASED ON CELLULOSE FLAKES

    Directory of Open Access Journals (Sweden)

    Daniela FIAT

    2013-05-01

    Full Text Available The paper presents cellulose thermal insulations based on cellulose flakes applied "in situ", by blowoutunder pressure. This mechanized method is using pneumatic systems with complex adjustments in order toobtain different densities and flow rates, when spraying the cellulose fibbers into the spaces to be insulated.

  13. Erosion and Soil Contamination Control Using Coconut Flakes And Plantation Of Centella Asiatica And Chrysopogon Zizanioides

    Science.gov (United States)

    Roslan, Rasyikin; Che Omar, Rohayu; Nor Zuliana Baharuddin, Intan; Zulkarnain, M. S.; Hanafiah, M. I. M.

    2016-11-01

    Land degradation in Malaysia due to water erosion and water logging cause of loss of organic matter, biodiversity and slope instability but also land are contaminated with heavy metals. Various alternative such as physical remediation are use but it not showing the sustainability in term of environmental sustainable. Due to that, erosion and soil contamination control using coconut flakes and plantation of Centella asiatica and Chrysopogon zizanioides are use as alternative approach for aid of sophisticated green technology known as phytoremediation and mycoremediation. Soil from cabonaceous phyllite located near to Equine Park, Sri Kembangan are use for monitoring the effect of phytoremediation and mycoremediation in reducing soil contamination and biotechnology for erosion control. Five laboratory scale prototypes were designed to monitor the effect of different proportion of coconut flakes i.e. 10%, 25%, 50% & 100% and plantation of Centella asiatica and Chrysopogon zizanioides to reduce the top soil from eroding and reduce the soil contamination. Prototype have been observe started from first week and ends after 12 weeks. Centella asiatica planted on 10% coconut flakes with 90% soil and Chrysopogon zizanioides planted on 25% coconut flakes with 75% soil are selected proportion to be used as phytoremediation and mycoremediation in reducing soil contamination and biotechnology for erosion control.

  14. Use of crude glycerin in steam-flaked corn-based growing diets

    Science.gov (United States)

    Three experiments were conducted to evaluate the use of crude glycerin in steam-flaked corn (SFC) based beef cattle growing diets. Experiment 1 utilized 50 crossbred steers (initial body weight (BW) = 282 +/- 2 kg) to determine the effects glycerin concentration (0.0, 2.5, 5.0, 7.5, and 10.0% dry ma...

  15. Direct Preparation of Few Layer Graphene Epoxy Nanocomposites from Untreated Flake Graphite.

    Science.gov (United States)

    Throckmorton, James; Palmese, Giuseppe

    2015-07-15

    The natural availability of flake graphite and the exceptional properties of graphene and graphene-polymer composites create a demand for simple, cost-effective, and scalable methods for top-down graphite exfoliation. This work presents a novel method of few layer graphite nanocomposite preparation directly from untreated flake graphite using a room temperature ionic liquid and laminar shear processing regimen. The ionic liquid serves both as a solvent and initiator for epoxy polymerization and is incorporated chemically into the matrix. This nanocomposite shows low electrical percolation (0.005 v/v) and low thickness (1-3 layers) graphite/graphene flakes by TEM. Additionally, the effect of processing conditions by rheometry and comparison with solvent-free conditions reveal the interactions between processing and matrix properties and provide insight into the theory of the chemical and physical exfoliation of graphite crystals and the resulting polymer matrix dispersion. An interaction model that correlates the interlayer shear physics of graphite flakes and processing parameters is proposed and tested.

  16. Self-assembly and continuous growth of hexagonal graphene flakes on liquid Cu.

    Science.gov (United States)

    Cho, Seong-Yong; Kim, Min-Sik; Kim, Minsu; Kim, Ki-Ju; Kim, Hyun-Mi; Lee, Do-Joong; Lee, Sang-Hoon; Kim, Ki-Bum

    2015-08-14

    Graphene growth on liquid Cu has received great interest, owing to the self-assembly behavior of hexagonal graphene flakes with aligned orientation and to the possibility of forming a single grain of graphene through a commensurate growth of these graphene flakes. Here, we propose and demonstrate a two-step growth process which allows the formation of self-assembled, completely continuous graphene on liquid Cu. After the formation of full coverage on the liquid Cu, grain boundaries were revealed via selective hydrogen etching and the original grain boundaries were clearly resolved. This result indicates that, while the flakes self-assembled with the same orientation, there still remain structural defects, gaps and voids that were not resolved by optical microscopy or scanning electron microscopy. To overcome this limitation, the two-step growth process was employed, consisting of a sequential process of a normal single-layer graphene growth and self-assembly process with a low carbon flux, followed by the final stage of graphene growth at a high degree of supersaturation with a high carbon flux. Continuity of the flakes was verified via hydrogen etching and a NaCl-assisted oxidation process, as well as by measuring the electrical properties of the graphene grown by the two-step process. Two-step growth can provide a continuous graphene layer, but commensurate stitching should be further studied.

  17. Graphene-Flakes Printed Wideband Elliptical Dipole Antenna for Low-Cost Wireless Communications Applications

    Science.gov (United States)

    Lamminen, Antti; Arapov, Kirill; de With, Gijsbertus; Haque, Samiul; Sandberg, Henrik G. O.; Friedrich, Heiner; Ermolov, Vladimir

    This letter presents the design, manufacturing and operational performance of a graphene-flakes based screenprinted wideband elliptical dipole antenna operating from 2 GHz up to 5 GHz for low cost wireless communications applications. To investigate radio frequency (RF) conductivity of the printed graphene, a coplanar waveguide (CPW) test structure was designed, fabricated and tested in the frequency range from 1 GHz to 20 GHz. Antenna and CPW were screen-printed on Kapton substrates using a graphene paste formulated with a graphene to binder ratio of 1:2. A combination of thermal treatment and subsequent compression rolling is utilized to further decrease the sheet resistance for printed graphene structures, ultimately reaching 4 Ohm/sq. at 10 {\\mu}m thicknesses. For the graphene-flakes printed antenna an antenna efficiency of 60% is obtained. The measured maximum antenna gain is 2.3 dBi at 4.8 GHz. Thus the graphene-flakes printed antenna adds a total loss of only 3.1 dB to an RF link when compared to the same structure screen-printed for reference with a commercial silver ink. This shows that the electrical performance of screen-printed graphene flakes, which also does not degrade after repeated bending, is suitable for realizing low-cost wearable RF wireless communication devices.

  18. Exfoliation of non-oxidized graphene flakes for scalable conductive film.

    Science.gov (United States)

    Park, Kwang Hyun; Kim, Bo Hyun; Song, Sung Ho; Kwon, Jiyoung; Kong, Byung Seon; Kang, Kisuk; Jeon, Seokwoo

    2012-06-13

    The increasing demand for graphene has required a new route for its mass production without causing extreme damages. Here we demonstrate a simple and cost-effective intercalation based exfoliation method for preparing high quality graphene flakes, which form a stable dispersion in organic solvents without any functionalization and surfactant. Successful intercalation of alkali metal between graphite interlayers through liquid-state diffusion from ternary KCl-NaCl-ZnCl(2) eutectic system is confirmed by X-ray diffraction and X-ray photoelectric spectroscopy. Chemical composition and morphology analyses prove that the graphene flakes preserve their intrinsic properties without any degradation. The graphene flakes remain dispersed in a mixture of pyridine and salts for more than 6 months. We apply these results to produce transparent conducting (∼930 Ω/□ at ∼75% transmission) graphene films using the modified Langmuir-Blodgett method. The overall results suggest that our method can be a scalable (>1 g/batch) and economical route for the synthesis of nonoxidized graphene flakes.

  19. Production of High-quality Few-layer Graphene Flakes by Intercalation and Exfoliation

    KAUST Repository

    Alzahrani, Areej A.

    2017-11-30

    Graphene, a two-dimensional nanomaterial, has been given much attention since it was first isolated in 2004. Driving this intensive research effort are the unique properties of this one atom thick sheet of carbon, in particular its electrical, thermal and mechanical properties. While the technological applications proposed for graphene abound, its low-cost production in large scales is still a matter of interrogation. Simple methods to obtain few-layered graphene flakes of high structural quality are being investigated with the exfoliation of graphite taking a prominent place in this arena. From the many suggested approaches, the most promising involve the use of liquid media assisted by intercalants and shear forces acting on the basal layers of graphite. In this thesis, it is discussed how a novel method was developed to produce flakes with consistent lateral dimensions that are also few-layered and retain the expected structural and chemical characteristics of graphene. Here, the source material was a commercially available graphiteintercalated compound, also known as expandable graphite. Several exfoliation-inducing tools were investigated including the use of blenders, homogenizers, and ultrasonic processors. To aid in this process, various solvents and intercalants were explored under different reactive conditions. The more efficient approach in yielding defect-free thin flakes was the use of thermally expanded graphite in boiling dimethylformamide followed by ultrasonic processing and centrifugation. In parallel, a method to fraction the flakes as a function of their lateral size was developed. Ultimately, it was possible to obtain samples of graphene flakes with a lateral dimension of a few micrometers (<5 μm) and thickness of 1-3 nm (i.e. <10 layers).

  20. Aerodinámica

    OpenAIRE

    Da Riva de la Cavada, Ignacio

    1991-01-01

    La Aerodinámica estudia las fuerzas que un viento relativo ejerce sobre un obstáculo sumergido en él. Desde este punto de vista tan general las aplicaciones de la Aerodinámica no se reducen exclusivamente al estudio de las fuerzas sobre aviones más o menos clásicos sino que trascienden a otros muchos campos por el efecto de arrastre que es característico de ciencias y técnicas avanzadas. La conferencia, dentro de un ciclo sobre Ingeniería Aeroespacial, se centra en la aerodinámica de...

  1. Vertically-aligned graphene flakes on nanoporous templates: morphology, thickness, and defect level control by pre-treatment.

    Science.gov (United States)

    Fang, Jinghua; Levchenko, Igor; Kumar, Shailesh; Seo, Donghan; Ostrikov, Kostya Ken

    2014-10-01

    Various morphologies of the vertically-aligned graphene flakes were fabricated on the nanoporous templates treated with metal ions in solutions, as well as coated with a thin gold layer and activated in the low-temperature Ar plasma. The thickness and level of structural defects in the graphene flakes could be effectively controlled by a proper selection of the pre-treatment method. We have also demonstrated that various combinations of the flake thickness and defect levels can be obtained, and the morphology and density of the graphene pattern can be effectively controlled. The result obtained could be of interest for various applications requiring fabrication of large graphene networks with controllable properties.

  2. [The value of glycemic index and glycemic load from selected corn flakes eaten with milk].

    Science.gov (United States)

    Mikołajczak, Jolanta; Bator, Ewa; Bronkowska, Monika; Piotrowska, Ewa; Orzeł, Dagmara; Wyka, Joanna; Biernat, Jadwiga

    2012-01-01

    Carbohydrates consumed with the daily diet are the cause of fluctuations in the concentrations of glucose in the blood, known as the glycemic effect. Glucose content in blood after eating any meal, and usually reaches its maximum after 20-30 min after ingestion of food and then gradually decreases to 1-2 hours to return to fasting levels. Knowing the GI along with information on their composition and nutrient content is important in terms of knowing the effect of carbohydrates on health. The glycemic indexes (GI) and the calculate values of the glycemic loads (GL) of the corn flakes eaten with milk (nesquik chocolate balls, cheerios, muesli tropical, fitness chocolate, oatmeal and instant flakes, corn flakes) were investigated. The relationship between IG and sex was calculated and examined. 67 young, healthy volunteers: 42 women and 25 men participated in the study. The average age of the participants was between 23.1 +/- 1.0 years, mean BMI- 22.4 +/- 3.1 kg/m2. Cereal with milk were given in 50 grams of digestible carbohydrates. The reference product was a solution in water (250 ml) containing 50 g glucose. In the morning, 7 times the blood was calleced - on an empty stomach and 15, 30, 45, 60, 90 and 120 minutes after eating. An average value GI and GL were calculated (for women and men), which were respectively: 48,6 and 25,5 - the milk soup with nesquik chocolate balls, 67,5 and 36,1 the milk soup with cheerios, 58,8 and 31,9 - the milk soup with muesli tropical, 66,7 and 34,9 - the milk soup with fitness chocolate, 42,5 and 23,4 - the milk soup with oatmeal flakes, 54,0 and 29,5 - the milk soup with oatmeal instant flakes, 54,4 i 27,9 - the milk soup with corn flakes. The results allowed the meal for the meals of low and medium GI. Showed statistically significant correlation between the glycemic index and gender of respondents.

  3. Creating high yield water soluble luminescent graphene quantum dots via exfoliating and disintegrating carbon nanotubes and graphite flakes.

    Science.gov (United States)

    Lin, Liangxu; Zhang, Shaowei

    2012-10-21

    We have developed an effective method to exfoliate and disintegrate multi-walled carbon nanotubes and graphite flakes. With this technique, high yield production of luminescent graphene quantum dots with high quantum yield and low oxidization can be achieved.

  4. Study on the giant positive magnetoresistance and Hall effect in ultrathin graphite flakes

    Energy Technology Data Exchange (ETDEWEB)

    Vansweevelt, Rob; Mortet, Vincent [Institute for Materials Research, Hasselt University, Diepenbeek (Belgium); Haen, Jan d' ; Ruttens, Bart; Wagner, Patrick [Institute for Materials Research, Hasselt University, Diepenbeek (Belgium); IMEC vzw, Division IMOMEC, Diepenbeek (Belgium); Haesendonck, Chris van [Laboratory of Solid State Physics and Magnetism, Katholieke Universiteit Leuven (Belgium); Partoens, Bart; Peeters, Francois M. [Physics Department - Condensed Matter Theory, Antwerp University (Belgium)

    2011-06-15

    In this paper, we report on the electronic transport properties of mesoscopic, ultrathin graphite flakes with a thickness corresponding to a stack of 150 graphene layers. The graphite flakes show an unexpectedly strong positive magnetoresistance (PMR) already at room temperature, which scales in good approximation with the square of the magnetic field. Furthermore, we show that the resistivity is unaffected by magnetic fields oriented in plane with the graphene layers. Hall effect measurements indicate that the charge carriers are p-type and their concentration increases with increasing temperature while the mobility is decreasing. The Hall voltage is non-linear in higher magnetic fields. Possible origins of the observed effects are discussed. Ball and stick model of the two topmost carbon layers of the hexagonal graphite structure. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Magnetisation oscillations, boundary conditions and the Hofstadter butterfly in graphene flakes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang; Brada, Matej; Kusmartsev, Feodor V. [Department of Physics, Loughborough University (United Kingdom); Mele, Eugene J. [Department of Physics, Loughborough University (United Kingdom); Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA (United States)

    2014-10-15

    New quantum oscillations in the magnetization of graphene flakes induced by magnetic fields, which depend on the shape of the flake, are described. At small values of the field they are due to the Aharonov-Bohm effect and with increasing field they are transformed into dHvA oscillations. The specific form of the dHvA oscillations is analyzed in terms of their energy spectrum, which has a form of Hofstadter's butterfly. Numerical results using a lattice tight-binding model and a continuum Dirac equation are presented and compared. Possible experiments to investigate the quantum oscillations in Moire and graphene anti-dot superlattices are discussed. (copyright 2014 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Electroluminescence of cubic boron nitride single crystal flakes with color-zoning

    Science.gov (United States)

    Liu, Xiuhuan; Wang, Shuang; Chen, Zhanguo; Jia, Gang; Bian, Tianliang; Hou, Lixin; Wang, Qi; Liu, Nian

    2015-04-01

    The current-voltage (I-V) characteristics and phenomena of electroluminescence of cubic boron nitride (cBN) single crystal flakes with color-zoning under extremely non-uniform electric fields (ENUEFs) induced by needle-plate electrodes were observed. When a cBN flake with sizes of 0.3×0.3×0.1 mm3 was tightly fixed between the tungsten needle and brass plate electrodes in the atmosphere, the I-V relationship exhibited nonlinearity, and peculiar phenomena of electroluminescence with bright blue-violet light appeared at the bias voltage in a range of 700-1200 V. The current-controlled differential negative resistance was synchronously observed. The electroluminescent phenomena were somewhat different for cases of the needle electrode respectively contacting to the amber and transparent zones. The electroluminescent radiations of cBN flakes biased at voltages with a range of 600-1550 V were also investigated in vacuum. In a vacuum chamber, the green emitting phosphor spread around the cBN flake might be excited by the vacuum ultraviolet (VUV) emission from the cBN crystal, and the green fluorescence was observed by naked eyes. The VUV radiation spectrum with a peak wavelength of 149 nm was measured. In the atmosphere, the blue-violet light emission may be the gas discharge resulted from the air ionization induced by the VUV emission from the cBN crystal under the ENUEF, and the ENUEF subsequently keeps the air discharging. The VUV emission from the cBN crystal under the ENUEF can be caused by the original interband transition and the subsequent intraband transfer for electrons, and the final electron-hole direct recombination.

  7. A Simple Transmission Electron Microscopy Method for Fast Thickness Characterization of Suspended Graphene and Graphite Flakes.

    Science.gov (United States)

    Rubino, Stefano; Akhtar, Sultan; Leifer, Klaus

    2016-02-01

    We present a simple, fast method for thickness characterization of suspended graphene/graphite flakes that is based on transmission electron microscopy (TEM). We derive an analytical expression for the intensity of the transmitted electron beam I 0(t), as a function of the specimen thickness t (tgraphene/graphite, the method we propose has the advantage of being simple and fast, requiring only the acquisition of bright-field images.

  8. Anisotropic etching of graphite flakes with water vapor to produce armchair-edged graphene.

    Science.gov (United States)

    Luo, Da; Yang, Feng; Wang, Xiao; Sun, Hao; Gao, Dongliang; Li, Ruoming; Yang, Juan; Li, Yan

    2014-07-23

    A one-step anisotropic etching method is developed to specifically obtain armchair-edged graphene directly from graphite flakes on various substrates. The armchair edge structure of the produced graphene is verified by the atomic resolution images obtained from the fluid mode peakforce tapping AFM and the relatively high intensity of D band in the Raman spectra. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Enhanced thermal conductivity of epoxy-graphene composites by using non-oxidized graphene flakes with non-covalent functionalization.

    Science.gov (United States)

    Song, Sung Ho; Park, Kwang Hyun; Kim, Bo Hyun; Choi, Yong Won; Jun, Gwang Hoon; Lee, Dong Ju; Kong, Byung-Seon; Paik, Kyung-Wook; Jeon, Seokwoo

    2013-02-06

    Homogeneous distribution of graphene flakes in a polymer matrix, still preserving intrinsic material properties, is key to successful composite applications. A novel approach is presented to disperse non-oxidized graphene flakes with non-covalent functionalization of 1-pyrenebutyric acid and to fabricate nanocomposites with outstanding thermal conductivity (∼1.53 W/mK) and mechanical properties (∼1.03 GPa). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Bioremediating Oil Spills in Nutrient Poor Ocean Waters Using Fertilized Clay Mineral Flakes: Some Experimental Constraints

    Directory of Open Access Journals (Sweden)

    Laurence N. Warr

    2013-01-01

    Full Text Available Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and P fertilizers, filming additives, and organoclay, clay flakes can be engineered to float on seawater, attach to the oil, and slowly release contained nutrients. Our laboratory experiments of microbial activity on weathered source oil from the Deepwater Horizon spill in the Gulf of Mexico show fertilized clay treatment significantly enhanced bacterial respiration and consumption of alkanes compared to untreated oil-in-water conditions and reacted faster than straight fertilization. Whereas a major portion (up to 98% of the alkane content was removed during the 1 month period of experimentation by fertilized clay flake interaction; the reduced concentration of polyaromatic hydrocarbons was not significantly different from the non-clay bearing samples. Such clay flake treatment could offer a way to more effectively apply the fertilizer to the spill in open nutrient poor waters and thus significantly reduce the extent and duration of marine oil spills, but this method is not expected to impact hydrocarbon toxicity.

  11. CEMS Study on Fe-Si-Al Alloy Flakes-Polymer Composites

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, K.; Suzuki, K.; Sawada, T.; Ujihira, Y. [University of Tokyo, School of Engineering (Japan); Yoshida, S. [NEC Tokin Co, Research Center (Japan)

    2003-06-15

    The composites of Fe-Si-Al alloy flakes and dielectric polymer fabricated for a new noise suppression filter in high-frequency bands were characterized by transmission and conversion electron Moessbauer spectrometry (TMS and CEMS). The Fe-Si-Al flakes were prepared by sand milling the atomized sendust powder (9.7 wt.% Si, 5.4 wt.% Al, and balance Fe) in n-hexane for several hours and days. The deformed structures were estimated by magnetic hyperfine field (H{sub in}) distributions, and the annealing effects were investigated. The composites of Fe-Si-Al alloy forged for less than 100 hours recovered the high permeability with production of D0{sub 3} structure after annealing at 650{sup o}C for 2 hours in Ar atmosphere. However, the Fe-Si-Al alloy flakes forged for 180 hours gave the broad H{sub in} with high magnetic fields, and were decomposed into {alpha}-Fe in the bulk and Fe species dispersed in the interface beneath the Si and Al oxides surface.

  12. Popcorn-Derived Porous Carbon Flakes with an Ultrahigh Specific Surface Area for Superior Performance Supercapacitors.

    Science.gov (United States)

    Hou, Jianhua; Jiang, Kun; Wei, Rui; Tahir, Muhammad; Wu, Xiaoge; Shen, Ming; Wang, Xiaozhi; Cao, Chuanbao

    2017-09-13

    Popcorn-derived porous carbon flakes have been successfully fabricated from the biomass of maize. Utilizing the "puffing effect", the nubby maize grain turned into materials with an interconnected honeycomb-like porous structure composed of carbon flakes. The following chemical activation method enabled the as-prepared products to possess optimized porous structures for electrochemical energy-storage devices, such as multilayer flake-like structures, ultrahigh specific surface area (SBET: 3301 m2 g-1), and a high content of micropores (microporous surface area of 95%, especially the optimized sub-nanopores with the size of 0.69 nm) that can increase the specific capacitance. The as-obtained sample displayed excellent specific capacitance of 286 F g-1 at 90 A g-1 for supercapacitors. Moreover, the unique porous structure demonstrated an ideal way to improve the volumetric energy density performance. A high energy density of 103 Wh kg-1 or 53 Wh L-1 has been obtained in the case of ionic liquid electrolyte, which is the highest among reported biomass-derived carbon materials and will satisfy the urgent requirements of a primary power source for electric vehicles. This work may prove to be a fast, green, and large-scale synthesis route by using the large nubby granular materials to synthesize applicable porous carbons in energy-storage devices.

  13. Bioremediating oil spills in nutrient poor ocean waters using fertilized clay mineral flakes: some experimental constraints.

    Science.gov (United States)

    Warr, Laurence N; Friese, André; Schwarz, Florian; Schauer, Frieder; Portier, Ralph J; Basirico, Laura M; Olson, Gregory M

    2013-01-01

    Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and P fertilizers, filming additives, and organoclay, clay flakes can be engineered to float on seawater, attach to the oil, and slowly release contained nutrients. Our laboratory experiments of microbial activity on weathered source oil from the Deepwater Horizon spill in the Gulf of Mexico show fertilized clay treatment significantly enhanced bacterial respiration and consumption of alkanes compared to untreated oil-in-water conditions and reacted faster than straight fertilization. Whereas a major portion (up to 98%) of the alkane content was removed during the 1 month period of experimentation by fertilized clay flake interaction; the reduced concentration of polyaromatic hydrocarbons was not significantly different from the non-clay bearing samples. Such clay flake treatment could offer a way to more effectively apply the fertilizer to the spill in open nutrient poor waters and thus significantly reduce the extent and duration of marine oil spills, but this method is not expected to impact hydrocarbon toxicity.

  14. How similar are nut-cracking and stone-flaking? A functional approach to percussive technology.

    Science.gov (United States)

    Bril, Blandine; Parry, Ross; Dietrich, Gilles

    2015-11-19

    Various authors have suggested similarities between tool use in early hominins and chimpanzees. This has been particularly evident in studies of nut-cracking which is considered to be the most complex skill exhibited by wild apes, and has also been interpreted as a precursor of more complex stone-flaking abilities. It has been argued that there is no major qualitative difference between what the chimpanzee does when he cracks a nut and what early hominins did when they detached a flake from a core. In this paper, similarities and differences between skills involved in stone-flaking and nut-cracking are explored through an experimental protocol with human subjects performing both tasks. We suggest that a 'functional' approach to percussive action, based on the distinction between functional parameters that characterize each task and parameters that characterize the agent's actions and movements, is a fruitful method for understanding those constraints which need to be mastered to perform each task successfully, and subsequently, the nature of skill involved in both tasks. © 2015 The Author(s).

  15. Experimental Demonstration of Printed Graphene Nano-flakes Enabled Flexible and Conformable Wideband Radar Absorbers

    Science.gov (United States)

    Huang, Xianjun; Pan, Kewen; Hu, Zhirun

    2016-12-01

    In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8-12 GHz) and Ku (12-18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene’s application to practical RCS reductions.

  16. Nacre-mimetic bulk lamellar composites reinforced with high aspect ratio glass flakes.

    Science.gov (United States)

    Guner, Selen N Gurbuz; Dericioglu, Arcan F

    2016-12-05

    Nacre-mimetic epoxy matrix composites reinforced with readily available micron-sized high aspect ratio C-glass flakes were fabricated by a relatively simple, single-step, scalable, time, cost and man-power effective processing strategy: hot-press assisted slip casting (HASC). HASC enables the fabrication of preferentially oriented two-dimensional inorganic reinforcement-polymer matrix bulk lamellar composites with a micro-scale structure resembling the brick-and-mortar architecture of nacre. By applying the micro-scale design guideline found in nacre and optimizing the relative volume fractions of the reinforcement and the matrix as well as by anchoring the brick-and-mortar architecture, and tailoring the interface between reinforcements and the matrix via silane coupling agents, strong, stiff and tough bio-inspired nacre-mimetic bulk composites were fabricated. As a result of high shear stress transfer lengths and effective stress transfer at the interface achieved through surface functionalization of the reinforcements, fabricated bulk composites exhibited enhanced mechanical performance as compared to neat epoxy. Furthermore, governed flake pull-out mode along with a highly torturous crack path, which resulted from extensive deflection and meandering of the advancing crack around well-aligned high aspect ratio C-glass flakes, have led to high work-of-fracture values similar to nacre.

  17. Automated sorting of polymer flakes: fluorescence labeling and development of a measurement system prototype.

    Science.gov (United States)

    Brunner, S; Fomin, P; Kargel, Ch

    2015-04-01

    The extensive demand and use of plastics in modern life is associated with a significant economical impact and a serious ecological footprint. The production of plastics involves a high energy consumption and CO2 emission as well as the large need for (limited) fossil resources. Due to the high durability of plastics, large amounts of plastic garbage is mounting in overflowing landfills (plus 9.6 million tons in Europe in the year 2012) and plastic debris is floating in the world oceans or waste-to-energy combustion releases even more CO2 plus toxic substances (dioxins, heavy metals) to the atmosphere. The recycling of plastic products after their life cycle can obviously contribute a great deal to the reduction of the environmental and economical impacts. In order to produce high-quality recycling products, mono-fractional compositions of waste polymers are required. However, existing measurement technologies such as near infrared spectroscopy show limitations in the sorting of complex mixtures and different grades of polymers, especially when black plastics are involved. More recently invented technologies based on mid-infrared, Raman spectroscopy or laser-aided spectroscopy are still under development and expected to be rather expensive. A promising approach to put high sorting purities into practice is to label plastic resins with unique combinations of fluorescence markers (tracers). These are incorporated into virgin resins during the manufacturing process at the ppm (or sub ppm) concentration level, just large enough that the fluorescence emissions can be detected with sensitive instrumentation but neither affect the visual appearance nor the mechanical properties of the polymers. In this paper we present the prototype of a measurement and classification system that identifies polymer flakes (mill material of a few millimeters size) located on a conveyor belt in real time based on the emitted fluorescence of incorporated markers. Classification performance

  18. Single-crystal and textured polycrystalline Nd2Fe14B flakes with a submicron or nanosize thickness

    Energy Technology Data Exchange (ETDEWEB)

    Cui, BZ; Zheng, LY; Li, WF; Liu, JF; Hadjipanayis, GC

    2012-02-01

    This paper reports on the fabrication, structure and magnetic property optimization of Nd2Fe14B single-crystal and [0 0 1] textured poly-nanocrystalline flakes prepared by surfactant-assisted high-energy ball milling (HEBM). Single-crystal Nd2Fe14B flakes first with micron and then with submicron thicknesses were formed via continuous basal cleavage along the (1 1 0) planes of the irregularly shaped single-crystal microparticles during the early stage of HEBM. With further milling, [0 0 1] textured polycrystalline submicron Nd2Fe14B flakes were formed. Finally, crystallographically anisotropic polycrystalline Nd2Fe14B nanoflakes were formed after milling for 5-6 h. Anisotropic magnetic behavior was found in all of the flake samples. Nd2Fe14B flakes prepared with either oleic acid (OA) or oleylamine (OY) as the surfactant exhibited similar morphology, structure and magnetic properties. Both the addition of some low-melting-point eutectic Nd70Cu30 alloy and an appropriate post-annealing can increase the coercivity of the Nd2Fe14B flakes. The coercivity of Nd2Fe14B nanoflakes with an addition of 16.7 wt.% Nd70Cu30 by milling for 5 h in heptane with 20 wt.% OY increased from 3.7 to 6.8 kOe after annealing at 450 degrees C for 0.5 h. The mechanism for formation and coercivity enhancement of Nd2Fe14B single-crystal and textured poly-nanocrystalline flakes with a submicron or nanosize thickness was discussed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  19. Consumers Preferences to Sweet Potato Flakes (Spf) From Sweet Potato Pasta as a Raw Material, with Enrichment Mung Bean Flour as Source Protein

    OpenAIRE

    Sjafrina, Noveria; Aminah, Syarifah

    2014-01-01

    Sweet potato flakes as an alternative food and a source of carbohydrates as breakfast cereals food. To meet the nutritional needs of sweet potato flakes contained in the primarily source of protein. The purpose of the research was a source of enrichment of protein contained in sweet potato flakes (SPF) with the addition of mung bean flour. And to get an optimal result of consumer preferences with the addition of mung bean flour optimal still be accepted by consumers based on organoleptic tes...

  20. Lead levels in paint flakes from buildings in Nigeria: a preliminary study.

    Science.gov (United States)

    Nduka, J K C; Orisakwe, O E; Maduawguna, C A

    2008-09-01

    Lead is a malleable metal previously used to improve the durability and color luster of paint applied in homes and on industrial structures such as bridges. Lead has deleterious effects on multiple organs in humans. There is paucity of information on the extent of the use of lead-based paint in Nigerian houses. This study has attempted to estimate the extent of use of lead-based paint in buildings in Eastern Nigeria using 168 buildings. Flaked paint samples were collected from residential, church, commercial, and school buildings from four most populous cities in Eastern Nigeria namely Enugu, Onitsha, Aba, and Port Harcourt, and they were digested using conc HNO(3):HCLO(4) (1:1) and analyzed using atomic absorption spectrophotometer. The lead levels from buildings in Enugu ranged from 39.385 +/- 1.111-69.843 +/- 4.886 mg/kg. The highest level of lead was found in Onitsha ranging from 49.503 +/- 0.000-74.352 +/- 0.571 mg/kg. Residential buildings, which mainly serve the under privileged populations, has the highest lead level in this study. In Aba, the highest lead level (66.432 +/- 0.013 mg/kg) was found in commercial buildings aged 5-10 years. The lead levels in paint flakes from buildings in the four cities tended to decrease with increasing age of the buildings. Taken together all the building paint flakes from the four cities had lead levels higher than the United States Environmental Protection Agency permissible level of 5 mg/kg. There is a need for primary intervention strategy to reduce the paint lead levels in Nigeria.

  1. Growth performance and nutrient composition of juvenile Nile tilapia (Oreochromis niloticus) fed Spirulina flakes, rice bran and mustard oil cake.

    Science.gov (United States)

    Sultana, N; Noor, P; Abdullah, A T M; Hasan, M R; Ahmed, K M; Naser, M N

    2012-08-01

    Tilapia (Oreochromis niloticus) is an important cultured fish that is widely distributed in Bangladesh. This study was conducted to improve the growth performance and nutrient contents of the fish using five different types of feeds. Tilapia fingerlings were fed two types of commercial fish feeds (Feed-1 and Feed-2), Spirulina flakes (Feed-3), Feed-2 mixed with Spirulina flakes (Feed-4) and manually mixed feed made from a mixture of mustard oil cake and rice bran (Feed-5). After 4 weeks of being fed with the diets, growth parameters and meat nutrient composition of the tilapia fingerlings were recorded. Significant growth in length and weight was observed in juvenile tilapia fish fed with commercial Feed-1 only, while growth performance varied significantly among fingerlings fed other types of feeds. Body tissue calcium (92.8 mg/100 g), iron (1.29 mg/100 g) was higher in fishes fed with dry Spirulina flakes (Feed 3), while the highest amount of zinc (2.09 mg/100 g) was recorded in fishes fed Feed-5. Protein (13.32%) content was highest in fish fed Feed-2 mixed with Spirulina flakes (Feed-4). Meat nutritional quality of tilapia can be improved by combining commercial feeds with Spirulina flakes, compared with feeding commercial feeds in isolation.

  2. Efficiency Analysis of Additions of Ice Flake in Cargo Hold Cooling System of Fishing Vessel

    OpenAIRE

    Amiadji Amiadji; Edi Djatmiko; Yosef Novian Prasetyo

    2017-01-01

    As a maritime nation, the majority of people's livelihood in Indonesia coast is as a fishermen. The process of preserving fish after being caught will determine how good the product quality. One of process on preserving fish that can be done is to perform the cooling process using a cooling machine on board. Refrigeration system certainly requires high electrical power consumption. That high power usage can be reduced as much as possible, one of which is to add chopped ice (ice flake) on a fi...

  3. Joining of graphene flakes by low energy N ion beam irradiation

    Science.gov (United States)

    Wu, Xin; Zhao, Haiyan; Pei, Jiayun; Yan, Dong

    2017-03-01

    An approach utilizing low energy N ion beam irradiation is applied in joining two monolayer graphene flakes. Raman spectrometry and atomic force microscopy show the joining signal under 40 eV and 1 × 1014 cm-2 N ion irradiation. Molecular dynamics simulations demonstrate that the joining phenomenon is attributed to the punch-down effect and the subsequent chemical bond generation between the two sheets. The generated chemical bonds are made up of inserted ions (embedded joining) and knocked-out carbon atoms (saturation joining). The electronic transport properties of the joint are also calculated for its applications.

  4. Robustness of the universal optical transmittance in monolayer and multilayer graphene flakes under Coulomb interactions

    Science.gov (United States)

    Yadav, Premlata; Srivastava, Pawan Kumar; Ray, Nirat; Ghosh, Subhasis

    2016-09-01

    We present an experimental investigation on the universality of the optical transmittance of mono- and multilayer chemically exfoliated graphene flakes. By varying the exfoliating solvent, and thereby modulating the strength of electron-electron interactions, we find that the universality is not impacted over the visible region. The impact of modulating the interaction strength is clearly seen as shifts in the M-point exciton spectra. These shifts can then lead to a reduction in the wavelength regime over which universal wavelength independent optical transmittance is observed. At the level of first-order perturbation theory, our results are consistent with existing theoretical predictions for interaction corrections in optical properties of monolayer graphene.

  5. In vitro fermentation characteristics of whole grain wheat flakes and the effect of toasting on prebiotic potential.

    Science.gov (United States)

    Connolly, Michael L; Lovegrove, Julie A; Tuohy, Kieran M

    2012-01-01

    Population studies have shown a positive correlation between diets rich in whole grains and a reduced risk of developing metabolic diseases, like diabetes, cardiovascular disease, and certain cancers. However, little is known about the mechanisms of action, particularly the impact different fermentable components of whole grains have on the human intestinal microbiota. The modulation of microbial populations by whole grain wheat flakes and the effects of toasting on digestion and subsequent fermentation profile were evaluated. Raw, partially toasted, and toasted wheat flakes were digested using simulated gastric and small intestinal conditions and then fermented using 24-hour, pH-controlled, anaerobic batch cultures inoculated with human feces. Major bacterial groups and production of short-chain fatty acids were compared with those for the prebiotic oligofructose and weakly fermented cellulose. Within treatments, a significant increase (PToasting appeared to have an effect on growth of lactobacilli as only fermentation of raw wheat flakes resulted in a significant increase in levels of this group.

  6. Reliable Exfoliation of Large-Area High-Quality Flakes of Graphene and Other Two-Dimensional Materials.

    Science.gov (United States)

    Huang, Yuan; Sutter, Eli; Shi, Norman N; Zheng, Jiabao; Yang, Tianzhong; Englund, Dirk; Gao, Hong-Jun; Sutter, Peter

    2015-11-24

    Mechanical exfoliation has been a key enabler of the exploration of the properties of two-dimensional materials, such as graphene, by providing routine access to high-quality material. The original exfoliation method, which remained largely unchanged during the past decade, provides relatively small flakes with moderate yield. Here, we report a modified approach for exfoliating thin monolayer and few-layer flakes from layered crystals. Our method introduces two process steps that enhance and homogenize the adhesion force between the outermost sheet in contact with a substrate: Prior to exfoliation, ambient adsorbates are effectively removed from the substrate by oxygen plasma cleaning, and an additional heat treatment maximizes the uniform contact area at the interface between the source crystal and the substrate. For graphene exfoliation, these simple process steps increased the yield and the area of the transferred flakes by more than 50 times compared to the established exfoliation methods. Raman and AFM characterization shows that the graphene flakes are of similar high quality as those obtained in previous reports. Graphene field-effect devices were fabricated and measured with back-gating and solution top-gating, yielding mobilities of ∼4000 and 12,000 cm(2)/(V s), respectively, and thus demonstrating excellent electrical properties. Experiments with other layered crystals, e.g., a bismuth strontium calcium copper oxide (BSCCO) superconductor, show enhancements in exfoliation yield and flake area similar to those for graphene, suggesting that our modified exfoliation method provides an effective way for producing large area, high-quality flakes of a wide range of 2D materials.

  7. Multiscale Hyperporous Silicon Flake Anodes for High Initial Coulombic Efficiency and Cycle Stability.

    Science.gov (United States)

    Ryu, Jaegeon; Hong, Dongki; Shin, Myoungsoo; Park, Soojin

    2016-11-22

    Three-dimensional (3D) hyperporous silicon flakes (HPSFs) are prepared via the chemical reduction of natural clay minerals bearing metal oxides. Natural clays generally have 2D flake-like structures with broad size distributions in the lateral dimension and varied thicknesses depending on the first processing condition from nature. They have repeating layers of silicate and metal oxides in various ratios. When the clay mineral is subjected to a reduction reaction, metal oxide layers can perform a negative catalyst for absorbing large amounts of exothermic heat from the reduction reaction of the silicate layers with metal reductant. Selectively etching out metal oxides shows a hyperporous nanoflake structure containing 100 nm macropores and meso-/micropores on its framework. The resultant HPSFs are demonstrated as anode materials for lithium-ion batteries. Compared to conventional micro-Si anodes, HPSFs exhibit exceptionally high initial Coulombic efficiency over 92%. Furthermore, HPSF anodes show outstanding cycling performance (reversible capacity of 1619 mAh g-1 at a rate of 0.5 C after 200 cycles, 95.2% retention) and rate performance (∼580 mAh g-1 at a rate of 10 C) owing to their distinctive structure.

  8. Functional energy nanocomposites surfaces based on mesoscopic microspheres, polymers and graphene flakes

    Science.gov (United States)

    Alekseev, S. A.; Dmitriev, A. S.; Dmitriev, A. A.; Makarov, P. G.; Mikhailova, I. A.

    2017-11-01

    In recent years, there has been a great interest in the development and creation of new functional energy materials, including for improving the energy efficiency of power equipment and for effectively removing heat from energy devices, microelectronics and optoelectronics (power micro electronics, supercapacitors, cooling of processors, servers and Data centers). In this paper, the technology of obtaining a new nanocomposite based on mesoscopic microspheres, polymers and graphene flakes is considered. The methods of sequential production of functional materials from graphite flakes of different volumetric concentration using polymers based on epoxy resins and polyimide, as well as the addition of a mesoscopic medium in the form of monodisperse microspheres are described. The data of optical and electron microscopy of such nanocomposites are presented, the main problems in the appearance of defects in such materials are described, the possibilities of their elimination by the selection of different concentrations and sizes of the components. Data are given on the measurement of the hysteresis of the contact angle and the evaporation of droplets on similar substrates. The results of studying the mechanical, electrophysical and thermal properties of such nanocomposites are presented. Particular attention is paid to the investigation of the thermal conductivity of these nanocomposites with respect to the creation of thermal interface materials for cooling devices of electronics, optoelectronics and power engineering.

  9. Combustion of Shock-Dispersed Flake Aluminum - High-Speed Visualization

    Energy Technology Data Exchange (ETDEWEB)

    Neuwald, P; Reichenbach, H; Kuhl, A

    2006-06-19

    Charges of 0.5 g PETN were used to disperse 1 g of flake aluminum in a rectangular test chamber of 4 liter inner volume and inner dimensions of approximately 10 cm x 10 cm x 40 cm. The subsequent combustion of the flake aluminum with the ambient air in the chamber gave rise to a highly luminous flame. The evolution of the luminous region was studied by means of high-speed cinematography. The high-speed camera is responsive to a broad spectral range in the visible and near infra-red. For a number of tests this response range was narrowed down by means of a band-pass filter with a center wavelength of 488 nm and a half-width of 23 nm. The corresponding images were expected to have a stronger temperature dependence than images obtained without the filter, thus providing better capability to highlight hot-spots. Emission in the range of the pass-band of the filter can be due to continuous thermal radiation from hot Al and Al{sub 2}O{sub 3} particles or to molecular band emission from gaseous AlO. A time-resolving spectrometer was improvised to inspect this topic. The results suggest that AlO emission occurs, but that the continuous spectrum is the dominating effect in our experiments.

  10. Low frequency and broadband metamaterial absorber with cross arrays and a flaked iron powder magnetic composite

    Directory of Open Access Journals (Sweden)

    Wangchang Li

    2018-01-01

    Full Text Available In this paper, we present a design, simulation and experimental measurement of a cross array metamaterial absorber (MMA based on the flaked Carbonyl iron powder (CIP filled rubber plate in the microwave regime. The metamaterial absorber is a layered structure consisting of multilayer periodic cross electric resonators, magnetic rubber plate and the ground metal plate. The MMA exhibits dual band absorbing property and the absorption can be tuned from 1∼8GHz in the same thickness depending on the dimension and position of the cross arrays. The obviously broadened absorbing band of the designed structure is a result of the synergistic effects of the electrical resonance of the cross arrays and intrinsic absorption of the magnetic layer. The polarization and oblique incident angle in TE and TM model are also investigated in detail to explore the absorbing mechanisms. The resonance current of the cross array can excite the enhanced local magnetic field and dielectric field which can promote the absorption. The measurement results are basically consistent with the simulations but the absorbing peaks move a little bit to higher frequency for the reason that the surface oxidation of the flaked CIP in the preparation process.

  11. Effect of edge plasmons on the optical properties of MoS2 monolayer flakes

    Science.gov (United States)

    Rossi, Tuomas P.; Winther, Kirsten T.; Jacobsen, Karsten W.; Nieminen, Risto M.; Puska, Martti J.; Thygesen, Kristian S.

    2017-10-01

    Finite MoS2 nanoparticles are known to support metallic edge states that are responsible for their catalytic activity. In this work we employ time-dependent density-functional theory (TDDFT) to study the influence of such edge states on the optical properties of triangular MoS2 monolayer flakes. We find that the edge states support collective plasmon-like excitations that couple strongly to the optical field leading to pronounced absorption peaks below the onset of interband transitions on the basal plane. Additionally, structural relaxation of the flakes can significantly distort the edge states. Thus, we observe that while an evenly-spaced edge configuration supports one-dimensional (1D) plasmon modes similar to those of an ideal 1D electron gas, the relaxed structures show mixed plasmon and single-electron excitations in the low-energy response. Our findings illustrate the sensitivity of the optical response of MoS2 nanostructures to the details of the edge configuration.

  12. Selected Area XPS Analysis for Identification of Pigment Compounds in Microscopic Paint Flakes

    Directory of Open Access Journals (Sweden)

    Camilla Baskcomb

    2008-05-01

    Full Text Available The application of X-ray photoelectron spectroscopy to the analysis of paint flakes from a painting by Henry Fuseli (1741–1825 is presented. Historically, the application of XPS to art conservation and restoration studies has been limited by the poor spatial resolution of the technique. Presented here is the successful analysis of paint flakes in the order of 100 μm using “imaging” XPS in conjunction with selected area analysis. Raman microscopy failed to satisfactorily identify the compounds present in this instance, and energy dispersive spectroscopy could not differentiate between lead and sulphur (two of the elements of interest due to the limited energy resolution inherent in that technique. Using XPS analysis of the lead 4f peak revealed that the pigment was a lead-based pigment, in this case comprising exclusively lead-sulphur compounds.

  13. Demulsification of oil-rich emulsion from enzyme-assisted aqueous extraction of extruded soybean flakes.

    Science.gov (United States)

    Wu, J; Johnson, L A; Jung, S

    2009-01-01

    Extraction of soybean oil from flaked and extruded soybeans using enzyme-assisted aqueous extraction processing (EAEP) is a promising alternative to conventional hexane extraction. The efficiencies of four proteases releasing oil from extruded material were compared. Protex 51FP, Protex 6L and Protex 7L each extracted 90% of the total oil available while Protex 50FP gave similar extraction yield as the control (without enzyme treatment). During EAEP, however, a stable emulsion forms that must be broken in order to recover free soybean oil. The potential of various proteases and phospholipases to destabilize the emulsion was determined. Two enzymes, a phospholipase A2 (LysoMax) and a protease (Protex 51FP) were selected to determine the effect of enzyme concentration on demulsification. Although at a 2% concentration (w/w, enzyme/(cream+free oil)), each enzyme tested was effective in totally destabilizing the cream; the protease released significantly more free oil than did the phospholipase at concentrations less than 2%. At 0.2% concentration, 88 and 48% of free oil were obtained with the protease and phospholipase, respectively. Reducing the pH of the cream also destabilized the cream with maximum demulsification at the isoelectric point of soy proteins. These results provide destabilization strategies for the oil-rich emulsion formed during aqueous extraction processing of extruded flakes and significantly contribute to the development of this environmentally-friendly technology.

  14. Determine Minimum Silver Flake Addition to GCM for Iodine Loaded AgZ

    Energy Technology Data Exchange (ETDEWEB)

    Garino, Terry J.; Nenoff, Tina M.; Rodriguez, Mark A.

    2014-04-01

    The minimum amount of silver flake required to prevent loss of I{sub 2} during sintering in air for a SNL Glass Composite Material (GCM) Waste Form containing AgI-MOR (ORNL, 8.7 wt%) was determined to be 1.1 wt% Ag. The final GCM composition prior to sintering was 20 wt% AgI-MOR, 1.1 wt% Ag, and 80 wt% Bi-Si oxide glass. The amount of silver flake needed to suppress iodine loss was determined using thermo gravimetric analysis with mass spectroscopic off-gas analysis. These studies found that the ratio of silver to AgI-MOR required is lower in the presence of the glass than without it. Therefore an additional benefit of the GCM is that it serves to inhibit some iodine loss during processing. Alternatively, heating the AgI-MOR in inert atmosphere instead of air allowed for densified GCM formation without I{sub 2} loss, and no necessity for the addition of Ag. The cause of this behavior is found to be related to the oxidation of the metallic Ag to Ag{sup +} when heated to above ~300{degrees}C in air. Heating rate, iodine loading levels and atmosphere are the important variables that determine AgI migration and results suggest that AgI may be completely incorporated into the mordenite structure by the 550{degrees}C sintering temperature.

  15. Synthesis, permeability resonance and microwave absorption of flake-assembled cobalt superstructure

    Science.gov (United States)

    Wen, S. L.; Liu, Y.; Zhao, X. C.; Fan, Z. Z.

    2015-07-01

    To meet the demands of high-efficient microwave absorption materials, cobalt superstructure was synthesized and characterized. As SEM confirmed, the cobalt superstructure was assembled by flakes. The size of cobalt superstructure was about 10 μm, and the thickness of the flake was about 500 nm. The permittivity and permeability were investigated as a function of frequency in the microwave range of 1-18 GHz. Based on the LLG equation and exchange resonance mode, three magnetic resonances, including one natural resonance and two exchange resonances were discussed. The calculated reflection loss (RL) indicated the cobalt superstructure indicated the cobalt superstructure has potential application as a promising candidate for microwave absorption. The maximum RL reached as high as -77.29 dB with a matching thickness of 1.5 mm, and the effective bandwidth with a reflection loss less than -10 dB was 3.6 GHz from 9.85 to 13.45 GHz. For cobalt superstructure, magnetic loss mainly contributed even more than dielectric loss to the microwave absorption.

  16. Synthesis, permeability resonance and microwave absorption of flake-assembled cobalt superstructure

    Energy Technology Data Exchange (ETDEWEB)

    Wen, S.L. [School of Materials Science and Engineering, Beijing Institute of Technology (China); Liu, Y., E-mail: yingliu@bit.edu.cn [School of Materials Science and Engineering, Beijing Institute of Technology (China); Zhao, X.C. [School of Materials Science and Engineering, Beijing Institute of Technology (China); Fan, Z.Z. [AVIC Beijing Institute of Aeronautical Materials, Beijing 100081 (China)

    2015-07-01

    To meet the demands of high-efficient microwave absorption materials, cobalt superstructure was synthesized and characterized. As SEM confirmed, the cobalt superstructure was assembled by flakes. The size of cobalt superstructure was about 10 μm, and the thickness of the flake was about 500 nm. The permittivity and permeability were investigated as a function of frequency in the microwave range of 1–18 GHz. Based on the LLG equation and exchange resonance mode, three magnetic resonances, including one natural resonance and two exchange resonances were discussed. The calculated reflection loss (RL) indicated the cobalt superstructure indicated the cobalt superstructure has potential application as a promising candidate for microwave absorption. The maximum RL reached as high as −77.29 dB with a matching thickness of 1.5 mm, and the effective bandwidth with a reflection loss less than −10 dB was 3.6 GHz from 9.85 to 13.45 GHz. For cobalt superstructure, magnetic loss mainly contributed even more than dielectric loss to the microwave absorption. - Highlights: • The cobalt superstructure were synthesized and characterized. • The multiple magnetic resonances were studied for cobalt superstructure based on the LLG equation and exchange resonance mode. • The maximum reflection loss of cobalt superstructure reaches to −77.29 dB.

  17. Lipoxygenase activity in different species of sweet lupin (Lupinus L.) seeds and flakes.

    Science.gov (United States)

    Stephany, Michael; Bader-Mittermaier, Stephanie; Schweiggert-Weisz, Ute; Carle, Reinhold

    2015-05-01

    Lipoxygenase (LOX)-catalysed degradation of polyunsaturated fatty acids is supposed to be a major cause of undesirable off-flavour development in legumes. In the present study, a photometric LOX assay including adequate sample workup was adapted to lupin seeds, kernels and flakes, respectively. Optimum reaction conditions were at pH 7.5 using a phosphate buffer concentration of 150 mmol l(-1) without the addition of sodium chloride. The LOX activities of different lupin species and varieties were compared. Significant variations among the species and varieties ranging from 50 to 1004 units mg(-1) protein were determined, being significantly lower than soybean LOX activity. Hulling and flaking of the seeds resulted in a 15% increase of LOX activity. In contrast to soy and other legumes, LOX from lupin only converted free fatty acids, whereas trilinolein and β-carotene were not oxidised. Consequently, according to the established classification, lupin LOX activity may be assigned to the LOX type-1, which, to the best of our knowledge, was demonstrated for the first time. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Low frequency and broadband metamaterial absorber with cross arrays and a flaked iron powder magnetic composite

    Science.gov (United States)

    Li, Wangchang; Liu, Qing; Wang, Liwei; Zhou, Zuzhi; Zheng, Jingwu; Ying, Yao; Qiao, Liang; Yu, Jing; Qiao, Xiaojing; Che, Shenglei

    2018-01-01

    In this paper, we present a design, simulation and experimental measurement of a cross array metamaterial absorber (MMA) based on the flaked Carbonyl iron powder (CIP) filled rubber plate in the microwave regime. The metamaterial absorber is a layered structure consisting of multilayer periodic cross electric resonators, magnetic rubber plate and the ground metal plate. The MMA exhibits dual band absorbing property and the absorption can be tuned from 1˜8GHz in the same thickness depending on the dimension and position of the cross arrays. The obviously broadened absorbing band of the designed structure is a result of the synergistic effects of the electrical resonance of the cross arrays and intrinsic absorption of the magnetic layer. The polarization and oblique incident angle in TE and TM model are also investigated in detail to explore the absorbing mechanisms. The resonance current of the cross array can excite the enhanced local magnetic field and dielectric field which can promote the absorption. The measurement results are basically consistent with the simulations but the absorbing peaks move a little bit to higher frequency for the reason that the surface oxidation of the flaked CIP in the preparation process.

  19. Large-area synthesis of high-quality monolayer 1T’-WTe2 flakes

    Science.gov (United States)

    Naylor, Carl H.; Parkin, William M.; Gao, Zhaoli; Kang, Hojin; Noyan, Mehmet; Wexler, Robert B.; Tan, Liang Z.; Kim, Youngkuk; Kehayias, Christopher E.; Streller, Frank; Zhou, Yu Ren; Carpick, Robert; Luo, Zhengtang; Park, Yung Woo; Rappe, Andrew M.; Drndić, Marija; Kikkawa, James M.; Johnson, A. T. Charlie

    2017-06-01

    Large-area growth of monolayer films of the transition metal dichalcogenides is of the utmost importance in this rapidly advancing research area. The mechanical exfoliation method offers high quality monolayer material but it is a problematic approach when applied to materials that are not air stable. One important example is 1T’-WTe2, which in multilayer form is reported to possess a large non saturating magnetoresistance, pressure induced superconductivity, and a weak antilocalization effect, but electrical data for the monolayer is yet to be reported due to its rapid degradation in air. Here we report a reliable and reproducible large-area growth process for obtaining many monolayer 1T’-WTe2 flakes. We confirmed the composition and structure of monolayer 1T’-WTe2 flakes using x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy and aberration corrected transmission electron microscopy. We studied the time dependent degradation of monolayer 1T’-WTe2 under ambient conditions, and we used first-principles calculations to identify reaction with oxygen as the degradation mechanism. Finally we investigated the electrical properties of monolayer 1T’-WTe2 and found metallic conduction at low temperature along with a weak antilocalization effect that is evidence for strong spin-orbit coupling.

  20. Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Sandeep Kumar, E-mail: SandeepKumar.Singh@uantwerpen.be; Peeters, F. M., E-mail: Francois.Peeters@uantwerpen.be [Department of Physics, University of Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Neek-Amal, M., E-mail: neekamal@srttu.edu [Department of Physics, University of Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16788 (Iran, Islamic Republic of)

    2014-02-21

    The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C{sub N{sub c}} X{sub N{sub x}} (X = F or H). We studied GNFs with 10 < N{sub c} < 56 and limit ourselves to the lowest energy configurations. We found that: (i) the energy difference Δ between the highest occupied molecular orbital and the lowest unoccupied molecular orbital decreases with N{sub c}, (ii) topological defects (pentagon and heptagon) break the symmetry of the GNFs and enhance the electric polarization, (iii) the mutual interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.

  1. Electronic properties of graphene nano-flakes: Energy gap, permanent dipole, termination effect, and Raman spectroscopy

    Science.gov (United States)

    Singh, Sandeep Kumar; Neek-Amal, M.; Peeters, F. M.

    2014-02-01

    The electronic properties of graphene nano-flakes (GNFs) with different edge passivation are investigated by using density functional theory. Passivation with F and H atoms is considered: C_{N_c} X_{N_x} (X = F or H). We studied GNFs with 10 interaction of bilayer GNFs can be understood by dipole-dipole interaction which were found sensitive to the relative orientation of the GNFs, (iv) the permanent dipoles depend on the edge terminated atom, while the energy gap is independent of it, and (v) the presence of heptagon and pentagon defects in the GNFs results in the largest difference between the energy of the spin-up and spin-down electrons which is larger for the H-passivated GNFs as compared to F-passivated GNFs. Our study shows clearly the effect of geometry, size, termination, and bilayer on the electronic properties of small GNFs. This study reveals important features of graphene nano-flakes which can be detected using Raman spectroscopy.

  2. Thermophysical and rheological properties of dulce de leche with and without coconut flakes as a function of temperature

    OpenAIRE

    Barbosa,Vanessa Camarinha; Garcia-Rojas,Edwin Elard; Coimbra,Jane Sélia dos Reis; Cipriano,Paula de Aguiar; Oliveira,Eduardo Basílio de; Telis-Romero,Javier

    2013-01-01

    Dulce de leche (DL), a dairy dessert highly appreciated in Brazil, is a concentrated product containing about 70% m/m of total solids. Thermophysical and rheological properties of two industrial Brazilian Dulce de leche formulations (classic Dulce de leche and Dulce de leche added with coconut flakes 1.5% m/m) were determined at temperatures comprised between 28.4 and 76.4 °C. In general, no significant differences (p < 0.05) were observed in the presence of coconut flakes in the two formulat...

  3. Structural, optical and compositional stability of MoS2 multi-layer flakes under high dose electron beam irradiation

    Science.gov (United States)

    Rotunno, E.; Fabbri, F.; Cinquanta, E.; Kaplan, D.; Longo, M.; Lazzarini, L.; Molle, A.; Swaminathan, V.; Salviati, G.

    2016-06-01

    MoS2 multi-layer flakes, exfoliated from geological molybdenite, have been exposed to high dose electron irradiation showing clear evidence of crystal lattice and stoichiometry modifications. A massive surface sulfur depletion is induced together with the consequent formation of molybdenum nanoislands. It is found that a nanometric amorphous carbon layer, unwillingly deposited during the transmission electron microscope experiments, prevents the formation of the nanoislands. In the absence of the carbon layer, the formation of molybdenum grains proceeds both on the top and bottom surfaces of the flake. If carbon is present on both the surfaces then the formation of Mo grains is completely prevented.

  4. Rapid growth of micron-sized graphene flakes using in-liquid plasma employing iron phthalocyanine-added ethanol

    Science.gov (United States)

    Amano, Tomoki; Kondo, Hiroki; Ishikawa, Kenji; Tsutsumi, Takayoshi; Takeda, Keigo; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

    2018-01-01

    Giant graphene flakes on the micron scale were synthesized and grown in plasmas in liquid-phase pure ethanol with added iron phthalocyanine (FePc) in a solvent. At atmospheric pressure, plasmas were generated in the gas phase filled with Ar and in the liquid phases comprising bubbles and liquid solutions. In the mixture of FePc in ethanol, nanographene sheets aggregated to form giant graphene flakes, as confirmed by the D, G, and 2D bands in the corresponding Raman spectra. Therefore, a bottom-up approach of graphite synthesis from pure ethanol with additives and a catalyst was realized by in-liquid plasma processing.

  5. Low-loss flake-graphene saturable absorber mirror for laser mode-locking at sub-200-fs pulse duration

    CERN Document Server

    Cunning, B V; Kielpinski, D

    2011-01-01

    Saturable absorbers are a key component for mode-locking femtosecond lasers. Polymer films containing graphene flakes have recently been used in transmission as laser mode-lockers, but suffer from high nonsaturable loss, limiting their application in low-gain lasers. Here we present a saturable absorber mirror based on a film of pure graphene flakes. The device is used to mode lock an erbium-doped fiber laser, generating pulses with state-of-the-art, sub-200-fs duration. The laser characteristic indicate that the film exhibits low nonsaturable loss (13% per pass) and large absorption modulation depth (45% of low-power absorption).

  6. Hypolipidaemic effects of oat flakes and β-glucans derived from four Chinese naked oat (Avena nuda) cultivars in Wistar-Lewis rats.

    Science.gov (United States)

    Zhou, Xianrong; Lin, Weijing; Tong, Litao; Liu, Xingxun; Zhong, Kui; Liu, Liya; Wang, Lili; Zhou, Sumei

    2016-01-30

    β-Glucan is widely considered to be the major ingredient responsible for the hypolipidaemic effects of oat. Determination of the β-glucan content in naked oat cultivars in China has been largely performed for breeding and food processing. Since oat is generally consumed as oat flakes in China, evaluation of the bioactivity of oat flakes might be more direct and comprehensive than determination of the internal β-glucan. However, the hypolipidaemic activity of oat flakes processed from Chinese oat cultivars has rarely been reported. The nutritional components of four naked oat cultivars were analysed before they were processed to oat flakes. The hypolipidaemic effects of oat flakes and the extracted β-glucans were tested on rats fed a high-fat diet for 30 days. Oat flakes and β-glucans of different origins showed different preventative effects on hyperlipidaemia. Among the four cultivars, β-glucan of 'Bayou-1' showed the greatest hypolipidaemic effect. However, oat flake processed from 'Dingyou-7' showed the best bioactivity to mediate the increase of serum lipid. The hypolipidaemic effect of oat might not only depend on β-glucan, but might also be related to other components. 'Dingyou-7' might be suitable for oat flake processing because of its superior bioactivity. © 2015 Society of Chemical Industry.

  7. Manufacture and characterization of a yogurt-like beverage made with oat flakes fermented by selected lactic acid bacteria.

    Science.gov (United States)

    Luana, Nionelli; Rossana, Coda; Curiel, José Antonio; Kaisa, Poutanen; Marco, Gobbetti; Rizzello, Carlo Giuseppe

    2014-08-18

    This study aimed at investigating the suitability of oat flakes for making functional beverages. Different technological options were assayed, including the amount of flakes, the inoculum of the starter and the addition of enzyme preparations. The beverage containing 25% (wt/wt) of oat flakes and fermented with L. plantarum LP09 was considered optimal on the basis of sensory and technological properties. The enzyme addition favored the growth of the starter, shortened the time needed to reach pH4.2 to ca. 8h, and favored a decrease of the quotient of fermentation. Fermentation increased the polyphenols availability and the antioxidant activity (25 and 70% higher, respectively) and decreased the hydrolysis index in vitro. Sensory analyses showed that fermented oat flakes beverage had the typical features of a yogurt-like beverage, enhancing the overall intensity of odor and flavor compared to the non-fermented control. Selection of proper processing and fermentation condition allowed the obtainment of a beverage with better nutritional and sensory properties. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Metamaterial composition comprising frequency-selective-surface resonant element disposed on/in a dielectric flake, methods, and applications

    Energy Technology Data Exchange (ETDEWEB)

    Shelton, David; Boreman, Glenn; D' Archangel, Jeffrey

    2015-11-10

    Infrared metamaterial arrays containing Au elements immersed in a medium of benzocyclobutene (BCB) were fabricated and selectively etched to produce small square flakes with edge dimensions of approximately 20 .mu.m. Two unit-cell designs were fabricated: one employed crossed-dipole elements while the other utilized square-loop elements.

  9. Nickel oxide crystalline nano flakes: synthesis, characterization and their use as anode in lithium-ion batteries

    DEFF Research Database (Denmark)

    Ahmadi, Majid; Younesi, Reza; Vegge, Tejs

    2014-01-01

    Nickel oxide crystalline nano flakes (NONFs)—only about 10 nm wide—were produced using a simple and inexpensive chemistry method followed by a short annealing in ambient air. In a first step, Ni(OH)2 sheets were synthesized by adding sodium hydroxide (NaOH) drop-wise in a Ni(NO3)2 aqueous solution...

  10. Alteration of biomacromolecule in corn by steam flaking in relation to biodegradation kinetics in ruminant, revealed with vibrational molecular spectroscopy.

    Science.gov (United States)

    Xu, Ningning; Liu, Jianxin; Yu, Peiqiang

    2017-10-12

    Large scale of steam flaked corn has been used in dairy ration to maintain high milk production level. This study aimed to determine effects of steam flaking on processing-induced intrinsic molecular structure changes that were associated with rumen degradation kinetics and nutrients supply. The advanced vibrational molecular spectroscopy was applied to reveal the processing-induced intrinsic structure changes on a molecular basis. The rumen degradation kinetics and nutrient supply were determined using in situ approach in ruminant livestock system. Raw corn grain (RC) and steam flaked corn grain (SFC) were obtained from two different processing plants. The results showed that (1) Compared to RC, SFC had greater truly digestible non-fiber carbohydrate [tdNFC: 86.8 versus 78.0% dry matter (DM)], but lower truly digestible crude protein [tdCP: 7.7 versus 9.0% DM]. (2) The steam flaking increased (PMolecular absorbance intensities of most carbohydrate biopolymers were greater in SFC (Pmolecular spectral intensities were lower (Pmolecular structure and nutrient interactive study showed that carbohydrate spectral intensities were positively (Pmolecular structure changes had an interactive relationship with rumen degradation kinetics. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Catalyst-Free Growth of Three-Dimensional Graphene Flakes and Graphene/g-C₃N₄ Composite for Hydrocarbon Oxidation.

    Science.gov (United States)

    Chen, Ke; Chai, Zhigang; Li, Cong; Shi, Liurong; Liu, Mengxi; Xie, Qin; Zhang, Yanfeng; Xu, Dongsheng; Manivannan, Ayyakkannu; Liu, Zhongfan

    2016-03-22

    Mass production of high-quality graphene flakes is important for commercial applications. Graphene microsheets have been produced on an industrial scale by chemical and liquid-phase exfoliation of graphite. However, strong-interaction-induced interlayer aggregation usually leads to the degradation of their intrinsic properties. Moreover, the crystallinity or layer-thickness controllability is not so perfect to fulfill the requirement for advanced technologies. Herein, we report a quartz-powder-derived chemical vapor deposition growth of three-dimensional (3D) high-quality graphene flakes and demonstrate the fabrication and application of graphene/g-C3N4 composites. The graphene flakes obtained after the removal of growth substrates exhibit the 3D curved microstructure, controllable layer thickness, good crystallinity, as well as weak interlayer interactions suitable for preventing the interlayer stacking. Benefiting from this, we achieved the direct synthesis of g-C3N4 on purified graphene flakes to form the uniform graphene/g-C3N4 composite, which provides efficient electron transfer interfaces to boost its catalytic oxidation activity of cycloalkane with relatively high yield, good selectivity, and reliable stability.

  12. Hydrothermal flake graphite mineralisation in Paleoproterozoic rocks of south-east Greenland

    DEFF Research Database (Denmark)

    Rosing-Schow, Nanna; Bagas, Leon; Kolb, Jochen

    2017-01-01

    , transporting carbon as CO2 and CH4, formed the mineralisation commonly hosted by shear zones, which acted as pathways for the mineralising fluids. The hydrothermal alteration assemblage is quartz-biotite-gruneriteedenite-pargasite-K-feldspar-titanite. The δ13C values of graphite, varying from −30 to −18‰ PDB......, indicate that the carbon was derived from organic matter most likely from metasedimentary sources. Devolatilisation of marble may have contributed a minor amount of carbon by fluid mixing. Precipitation of graphite involved retrograde hydration reactions, depleting the fluid in H2O and causing graphite......Flake graphite mineralisation is hosted in the Kuummiut Terrane of the Paleoproterozoic Nagssugtoqidian Orogen, south-east Greenland. Eclogite-facies peak-metamorphic assemblages record temperatures of 640–830 °C and pressures of 22–25 kbar, and are retrogressed in the high-pressure amphibolite...

  13. Direct laser planting of hybrid Au-Ag/C nanostructures - nanoparticles, flakes and flowers

    CERN Document Server

    Manshina, Alina; Bashouti, Muhammad; Povolotskiy, Alexey; Petrov, Yuriy; Koshevoy, Igor; Christiansen, Silke; Tunik, Sergey; Leuchs, Gerd

    2015-01-01

    We demonstrate a new approach for forming hybrid metal/carbonaceous nanostructures in a controlled direct laser planting process. Au-Ag nanoclusters in amorphous or crystalline carbonaceous matrices are formed with different morphology: nanoparticles, nanoflakes, and nanoflowers. In contrast to other generation techniques our approach is simple, involving only a single laser-induced process transforming supramolecular complexes dissolved in solvent such as acetone, acetophenone, or dichloroethane into hybrid nanostructures in the laser-affected area of the substrate. The morphology of the hybrid nanostructures can be steered by controlling the deposition parameters, the composition of the liquid phase and the type of substrate, amorphous or crystalline. The carbonaceous phase of the hybrid nanostructures consists of hydrogenated amorphous carbon in the case of nanoparticles and of crystalline orthorhombic graphite of nanoscale thickness in the case of flakes and flowers. To the best of our knowledge this is t...

  14. Pretreatment of cottonseed flakes with proteases and an amylase for higher oil yields

    Directory of Open Access Journals (Sweden)

    Hassanein, Minar M.

    2007-09-01

    Full Text Available The effect of enzymatic pretreatment of cottonseed flakes on oil extractability was studied. The enzymes investigated included bacterial protease (Bp, papain (Pa, savinase (S, termamyl (T, pectinase (Pe and cellulase (C. The variables studied during the enzymatic hydrolysis experiments were: enzyme concentration, moisture: cottonseed flakes ratio, and time of hydrolysis. Enzymatic hydrolysis experiments were first carried out with a single enzyme, then with enzyme mixtures formulated according to the results of single enzyme treatments. Results were evaluated based on the relative increase in oil extractability, and some oil characteristics in comparison with untreated cottonseed flakes (control. Pretreatment with enzyme mixtures resulted in a relative increase in oil extractability that was higher than single enzyme pretreatment and the control. Statistical analysis showed a significant difference (at 5% level between the control and all enzymatically treated oils as well as among different enzymatically treated oils. The relative increase in oil extractability due to pretreatment with enzyme mixtures were in the following order: S: Pe: Bp>S: P>S: C: Pe>S: Bp>S:T>S: C >S: Pa with values 44.9%, 38.9%, 37.1%, 34.9%, 30.1%, 28.9%, respectively. Enzymatic pretreatment of cottonseed flakes resulted in oils with fatty acid composition, acid value, iodine value and peroxide values that were generally comparable to the control.En este trabajo se estudió el efecto del pretratamiento con enzimas sobre la extractabilidad del aceite en hojuelas de semilla de algodón. Las enzimas que se investigaron fueron proteasa bacteriana (Bp, papaína (Pa, savinasa (S, temamil (T, pectinasa (Pe y celulasa (C. Las variables estudiadas durante los experimentos de hidrólisis enzimática fueron: concentración de la enzima, ratio humedad:cantidad de hojuelas y tiempo de hidrólisis. Estos experimentos se realizaron primeramente con una sola enzima y posteriormente con

  15. Geometries and Electronic States of Divacancy Defect in Finite-Size Hexagonal Graphene Flakes

    Directory of Open Access Journals (Sweden)

    Lili Liu

    2017-01-01

    Full Text Available The geometries and electronic properties of divacancies with two kinds of structures were investigated by the first-principles (U B3LYP/STO-3G and self-consistent-charge density-functional tight-binding (SCC-DFTB method. Different from the reported understanding of these properties of divacancy in graphene and carbon nanotubes, it was found that the ground state of the divacancy with 585 configurations is closed shell singlet state and much more stable than the 555777 configurations in the smaller graphene flakes, which is preferred to triplet state. But when the sizes of the graphene become larger, the 555777 defects will be more stable. In addition, the spin density properties of the both configurations are studied in this paper.

  16. An asymmetric dimer in a periodic potential: a minimal model for friction of graphene flakes

    Science.gov (United States)

    Hens, Remco; Fasolino, Annalisa

    2016-07-01

    We discuss the friction and motion of a model of a dimer with asymmetric interactions with a substrate potential. Starting from the consideration that a rigid dimer with spacing equal to half of the period of the potential has exactly zero static friction like the infinite incommensurate Frenkel Kontorova model, we show how stick-slip behaviour and friction arise as a function of asymmetry. We argue that this model can yield a simple yet insightful description of the frictional behaviour of graphene flakes on graphite and of superlubricity. The results can also be of interest for diatomic molecules on surfaces. Supplementary material in the form of three mp4 files available from the Journal web page at http://dx.doi.org/10.1140/epjb/e2016-70273-5

  17. Process Optimization for Solid Extraction, Flavor Improvement and Fat Removal in the Production of Soymilk From Full Fat Soy Flakes

    Energy Technology Data Exchange (ETDEWEB)

    Prawiradjaja, Stanley [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    Traditionally soymilk has been made with whole soybeans; however, there are other alternative raw ingredients for making soymilk, such as soy flour or full-fat soy flakes. US markets prefer soymilk with little or no beany flavor. modifying the process or using lipoxygenase-free soybeans can be used to achieve this. Unlike the dairy industry, fat reduction in soymilk has been done through formula modification instead of by conventional fat removal (skimming). This project reports the process optimization for solids and protein extraction, flavor improvement and fat removal in the production of 5, 8 and 12 °Brix soymilk from full fat soy flakes and whole soybeans using the Takai soymilk machine. Proximate analyses, and color measurement were conducted in 5, 8 and 12 °Brix soymilk. Descriptive analyses with trained panelists (n = 9) were conducted using 8 and 12 °Brix lipoxygenase-free and high protein blend soy flake soymilks. Rehydration of soy flakes is necessary to prevent agglomeration during processing and increase extractability. As the rehydration temperature increases from 15 to 50 to 85 C, the hexanal concentration was reduced. Enzyme inactivation in soy flakes milk production (measured by hexanal levels) is similar to previous reports with whole soybeans milk production; however, shorter rehydration times can be achieved with soy flakes (5 to 10 minutes) compared to whole beans (8 to 12 hours). Optimum rehydration conditions for a 5, 8 and 12 °Brix soymilk are 50 C for 5 minutes, 85 C for 5 minutes and 85 C for 10 minutes, respectively. In the flavor improvement study of soymilk, the hexanal date showed differences between undeodorized HPSF in contrast to triple null soymilk and no differences between deodorized HPSF in contrast to deodorized triple null. The panelists could not differentiate between the beany, cereal, and painty flavors. However, the panelists responded that the overall aroma of deodorized 8 °Brix triple null and HPSF soymilk are

  18. Synthesis of Carbon Nanotube-Reinforced Al2024 Matrix Nanocomposite Using Flake Powder Metallurgy Method

    Science.gov (United States)

    Rikhtegar, F.; Shabestari, S. G.; Saghafian, H.

    2016-12-01

    In current work, the flake powder metallurgy method was applied to achieve the uniform dispersion of carbon nanotubes (CNTs) within the Al2024 powder. For this purpose, the flake morphology of Al2024 powder with suitable diameter-to-thickness ratio ( D/ t = 85) was obtained after ball milling for 4 hours at 250 rpm and ball-to-powder ratio = 10. Then, the surface of matrix was modified by a hydrophilic polymer [polyvinyl alcohol (PVA)] to obtain the sufficient -OH group on its surface. Additionally, the refluxing of CNTs in nitric acid was performed at 393 K (120 °C) for 6 hours to functionalize the reinforcement by -COOH agent. After preparation of initial materials, the Al2024-1.5 wt pct CNTs suspension was stirred in a slurry at pH 3 until the color was changed in steady state from ink-like to transparent at pH 5. The hydrogen bonding was formed between the -OH groups of PVA coated Al2024 and -COOH groups of functionalized MWCNTs during the mixing step. Also, the temporary polarity could be considered between H+ and {{{C}}_{12}}{{{H}}_{25}}{{SO}}_4^ - ions on the surface of constituents, which led to improvement in the CNT distribution due to the changing of suspension pH. Consequently, the homogenous dispersion of CNTs in Al2024 flaky powders resulted in a chemical reaction of constituents without any destructive effects of mechanical forces. The morphological changes of Al2024 powders were studied by scanning electron microscopy (SEM), and surface treatments were evaluated by Fourier transform infrared and Raman spectroscopies. The dispersion of nanocomposite powder was investigated through field emission SEM. Also, X-ray diffraction analysis was used to investigate the initial Al2024 powder and formed phases after the ball milling process.

  19. Drought effect on biocrust resilience: High-speed winds result in crust burial and crust rupture and flaking.

    Science.gov (United States)

    Kidron, Giora J; Ying, Wang; Starinsky, Abraham; Herzberg, Moshe

    2017-02-01

    Once established, biocrusts (known also as biological soil crusts or microbiotic crusts) are thought to be relatively resilient to wind erosion, with crust burial being considered as the main mechanism responsible for crust death. Thus far, to the best of our knowledge, crust flaking and rupture under natural conditions were not reported. We report herein a two-year study during two severe drought years (2010-2012) in a dunefield in the Negev Desert during which in addition to crust burial, crust rupture and flaking also took place. As for crust burial, it took place under sand sheets or coppice dunes (mounds). Subsequent removal of the coppice dunes by wind resulted in crust disintegration and erosion of the formerly buried crust and the formation of patches devoid of crusts termed herein 'erosion cirques'. As for crust flaking and rupture, it is explained by a large change in the properties of the extracellular polymeric substances (EPS) composing the crust. The EPS adherence and viscoelastic properties were monitored using a quartz crystal microbalance with dissipation monitoring (QCD-M) technology. EPS adherence and viscoelastic properties deduced from the QCM-D experiments suggest that crust coherence and elasticity, mediated by the EPS, were affected by droughts. Although crust flaking affected up to 25% of the interdunal surface, it is suggested that with continuous rain shortage, further crust flaking is likely to take place under continuous drought-driven dry surface conditions. This positive feedback mechanism, during which initially eroded crusts trigger additional crust erosion, may have severe consequences on the structure and function of drought-prone ecosystems, and may endanger the stability of dunefields, causing dust storms, triggering dune encroachment and declining air quality. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Alteration of biomacromolecule in corn by steam flaking in relation to biodegradation kinetics in ruminant, revealed with vibrational molecular spectroscopy

    Science.gov (United States)

    Xu, Ningning; Liu, Jianxin; Yu, Peiqiang

    2018-02-01

    Large scale of steam flaked corn has been used in dairy ration to maintain high milk production level. This study aimed to determine effects of steam flaking on processing-induced intrinsic molecular structure changes that were associated with rumen degradation kinetics and nutrients supply. The advanced vibrational molecular spectroscopy was applied to reveal the processing-induced intrinsic structure changes on a molecular basis. The rumen degradation kinetics and nutrient supply were determined using in situ approach in ruminant livestock system. Raw corn grain (RC) and steam flaked corn grain (SFC) were obtained from two different processing plants. The results showed that (1) Compared to RC, SFC had greater truly digestible non-fiber carbohydrate [tdNFC: 86.8 versus 78.0% dry matter (DM)], but lower truly digestible crude protein [tdCP: 7.7 versus 9.0% DM]. (2) The steam flaking increased (P < 0.01) rumen degradable DM (RDDM) and starch (RDSt), but decreased (P < 0.01) rumen degradable protein (RDP). (3) Molecular absorbance intensities of most carbohydrate biopolymers were greater in SFC (P < 0.01), but protein amides associated molecular spectral intensities were lower (P < 0.01) in SFC. (4). The molecular structure and nutrient interactive study showed that carbohydrate spectral intensities were positively (P < 0.10) associated with RDDM and RDSt and protein amide spectral intensities were positively (P < 0.10) associated with RDP. This results indicated that the steam flaking induced molecular structure changes had an interactive relationship with rumen degradation kinetics.

  1. Electrolytic exfoliation of graphite in water with multifunctional electrolytes: en route towards high quality, oxide-free graphene flakes.

    Science.gov (United States)

    Munuera, J M; Paredes, J I; Villar-Rodil, S; Ayán-Varela, M; Martínez-Alonso, A; Tascón, J M D

    2016-02-07

    Electrolytic--usually referred to as electrochemical--exfoliation of graphite in water under anodic potential holds enormous promise as a simple, green and high-yield method for the mass production of graphene, but currently suffers from several drawbacks that hinder its widespread adoption, one of the most critical being the oxidation and subsequent structural degradation of the carbon lattice that is usually associated with such a production process. To overcome this and other limitations, we introduce and implement the concept of multifunctional electrolytes. The latter are amphiphilic anions (mostly polyaromatic hydrocarbons appended with sulfonate groups) that play different relevant roles as (1) an intercalating electrolyte to trigger exfoliation of graphite into graphene flakes, (2) a dispersant to afford stable aqueous colloidal suspensions of the flakes suitable for further use, (3) a sacrificial agent to prevent graphene oxidation during exfoliation and (4) a linker to promote nanoparticle anchoring on the graphene flakes, yielding functional hybrids. The implementation of this strategy with some selected amphiphiles even furnishes anodically exfoliated graphenes of a quality similar to that of flakes produced by direct, ultrasound- or shear-induced exfoliation of graphite in the liquid phase (i.e., almost oxide- and defect-free). These high quality materials were used for the preparation of catalytically efficient graphene-Pt nanoparticle hybrids, as demonstrated by model reactions (reduction of nitroarenes). The multifunctional performance of these electrolytes is also discussed and rationalized, and a mechanistic picture of their oxidation-preventing ability is proposed. Overall, the present results open the prospect of anodic exfoliation as a competitive method for the production of very high quality graphene flakes.

  2. Paleogenòmica

    OpenAIRE

    Lalueza-Fox, Carles

    2009-01-01

    Des que es va recuperar per primer cop DNA d'una espècie extingida, l'any 1984, la paleogenòmica ha experimentat una autèntica revolució, gràcies a les tècniques d'ultraseqüenciació desenvolupades en els dos darrers anys. Això ha permès per primer cop assolir projectes genòmics d'espècies extingides com els mamuts i els neandertals. Aquest treball fa un repàs històric dels principals estudis paleogenòmics i es discuteixen les possibles aplicacions, així com les problemàtiques m...

  3. macroeconômica

    Directory of Open Access Journals (Sweden)

    Eurilton Alves Araújo Júnior

    2011-01-01

    Full Text Available Este ensaio estuda políticas monetárias discricionárias otimizadas como extensão do novo modelo básico Keynesiano, o qual incorpora tributação da receita de juros, focando no efeito das mudanças na alíquota da receita de juros sobre volatilidade macroeconômica. Simulações mostram que altos níveis de tributação aumentam a volatilidade da inflação, do gap de produção, e a expectativas incondicionais da função de perda do banco central.

  4. Consumers Preferences to Sweet Potato Flakes (Spf) from Sweet Potato Pasta as A Raw Material, with Enrichment Mung Bean Flour as Source Protein

    OpenAIRE

    Noveria Sjafrina; Syarifah Aminah

    2014-01-01

    Sweet potato flakes as an alternative food and a source of carbohydrates as breakfast cereals food. To meet the nutritional needs of sweet potato flakes contained in the primarily source of protein. The purpose of the research was a source of enrichment of protein contained in sweet potato flakes (SPF) with the addition of mung bean flour.  And to get an optimal result of consumer preferences with the addition of mung bean flour optimal still be accepted by consumers based on organoleptic tes...

  5. Effect of commercial breakfast fibre cereals compared with corn flakes on postprandial blood glucose, gastric emptying and satiety in healthy subjects: a randomized blinded crossover trial

    Directory of Open Access Journals (Sweden)

    Almér Lars-Olof

    2007-09-01

    Full Text Available Abstract Background Dietary fibre food intake is related to a reduced risk of developing diabetes mellitus. However, the mechanism of this effect is still not clear. The aim of this study was to evaluate the effect of commercial fibre cereals on the rate of gastric emptying, postprandial glucose response and satiety in healthy subjects. Methods Gastric emptying rate (GER was measured by standardized real time ultrasonography. Twelve healthy subjects were assessed using a randomized crossover blinded trial. The subjects were examined after an 8 hour fast and after assessment of normal fasting blood glucose level. Satiety scores were estimated and blood glucose measurements were taken before and at 0, 20, 30, 40, 60, 80, 100 and 120 min after the end of the meal. GER was calculated as the percentage change in the antral cross-sectional area 15 and 90 min after ingestion of sour milk with corn flakes (GER1, cereal bran flakes (GER2 or wholemeal oat flakes (GER3. Results The median value was, respectively, 42% for GER1, 33 % for GER2 and 51% for GER3. The difference between the GER after ingestion of bran flakes compared to wholemeal oat flakes was statistically significant (p = 0.023. The postprandial delta blood glucose level was statistically significantly lower at 40 min (p = 0.045 and 120 min (p = 0.023 after the cereal bran flakes meal. There was no statistical significance between the areas under the curve (AUCs of the cereals as far as blood glucose and satiety were concerned. Conclusion The result of this study demonstrates that the intake of either bran flakes or wholemeal oat flakes has no effect on the total postprandial blood glucose response or satiety when compared to corn flakes. However, the study does show that the intake of cereal bran flakes slows the GER when compared to oat flakes and corn flakes, probably due to a higher fibre content. Since these products do not differ in terms of glucose response and satiety on healthy

  6. Versatile Wafer-Scale Technique for the Formation of Ultrasmooth and Thickness-Controlled Graphene Oxide Films Based on Very Large Flakes.

    Science.gov (United States)

    Azevedo, Joël; Campidelli, Stéphane; He, Delong; Cornut, Renaud; Bertucchi, Michael; Sorgues, Sébastien; Benattar, Jean-Jacques; Colbeau-Justin, Christophe; Derycke, Vincent

    2015-09-30

    We present a new strategy to form thickness-adjusted and ultrasmooth films of very large and unwrinkled graphene oxide (GO) flakes through the transfer of both hemispherical and vertical water films stabilized by surfactants. With its versatility in terms of substrate type (including flexible organic substrates) and in terms of flake density (from isolated flakes to continuous and multilayer films), this wafer-scale assembly technique is adapted to a broad range of experiments involving GO and rGO (reduced graphene oxide). We illustrate its use through the evaluation of transparent rGO electrodes.

  7. Magnetic decoupling of Fe coverage across atomic step of MoS2 flakes on SiO2 surface

    Science.gov (United States)

    Hsu, Chuan-Che; Lin, Zong-You; Chang, Po-Chun; Chiu, Hsiang-Chih; Chen, Hsiao-Wen; Liu, Hsiang-Lin; Bisio, Francesco; Lin, Wen-Chin

    2017-10-01

    In this study, we deposited Fe films on MoS2 flakes, and investigated the microscopic magnetic behavior on individual flakes. The MoS2 flakes were fabricated on SiO2/Si(1 0 0) substrates using chemical vapor deposition. Fe coverage was deposited on the MoS2 flakes by e-beam evaporation with a thin Pd capping for protection. Investigations by atomic force microscope and Raman spectroscopy confirmed that the MoS2 flakes had a mean lateral size of 10-20 μ m and mostly single layer thick. After depositing 3.6 and 7.0 nm Fe on MoS2/SiO2, clear hysteresis loops were observable with the in-plane magnetic field. From the investigation using a magneto-optical Kerr microscope, we measured the hysteresis curves within individual MoS2 flakes. Although the Fe coverage was much thicker than the MoS2 atomic step height (˜0.66 nm) and the direct connection and strong ferromagnetic coupling between Fe/MoS2 and Fe/SiO2 were expected, a magnetic decoupling between the magnetic domains of Fe/MoS2 and Fe/SiO2 was surprisingly observed. For 3.6 nm Fe/MoS2, the magnetic coercivity (H c ) was 28  ±  5 Oe, while in contrast, the H c of 3.6 nm Fe/SiO2 ranged 58  ±  5 Oe. With a thicker Fe coverage of 7.0 nm, the H c of Fe/MoS2 and Fe/SiO2 converged and the magnetic decoupling became too weak to observe. The distinct interface magnetic anisotropy of Fe on different substrates was held responsible for the observed magnetic decoupling across the MoS2 atomic step between Fe/MoS2 and Fe/SiO2 domains. These observations will be valuable in combining a magnetic coverage with a single layer MoS2 for future spintronic applications.

  8. IMNUNOHISTOQUÍMICA

    Directory of Open Access Journals (Sweden)

    AM Barbosa

    2005-01-01

    Full Text Available Con el propósito de diagnosticar en Colombia la bacteria conocida como Lawsonia intracellularis en cerdos se realizó un estudio retrospectivo de los casos diagnosticados por el Instituto Colombiano Agropecuario (ICA desde el año 1998 hasta el primer semestre del año 2004. Se evaluaron las lesiones con la coloración de H&E y se detectó la bacteria empleando las técnicas de coloración de plata e inmunohistoquímica. Adicionalmente, se realizó un estudio en plantas de sacrificio, tomando muestras de íleon, y se evaluó macroscópicamente la apariencia de los tejidos y el grado de engrosamiento de la pared intestinal por medio de la palpación, e histopatológicamente por medio de las técnicas mencionadas en el estudio retrospectivo. En los dos estudios se detectó la bacteria, con una alta presencia en la industria porcina desarrollada. También se observaron lesiones similares a las reportadas en la literatura, en su mayoría lesiones de tipo agudo y en menor grado de tipo crónico y subclínico.

  9. Transfer of an exfoliated monolayer graphene flake onto an optical fiber end face for erbium-doped fiber laser mode-locking

    Science.gov (United States)

    Guimaraes Rosa, Henrique; Viana Gomes, José Carlos; Thoroh de Souza, Eunézio A.

    2015-09-01

    This paper presents, for the first time, the successful transfer of exfoliated monolayer graphene flake to the optical fiber end face and alignment to its core. By fabricating and optimizing a polymeric poly(methyl methacrylate) (PMMA) and polyvinyl alcohol (PVA) substrate, it is possible to obtain a contrast of up to 11% for green light illumination, allowing the identification of monolayer graphene flakes that were transferred to optical fiber samples and aligned to its core. With Raman spectroscopy, it is demonstrated that graphene flake completely covers the optical fiber core, and its quality remains unaltered after the transfer. The generation of mode-locked erbium-doped fiber laser pulses, with a duration of 672 fs, with a single-monolayer graphene flake as a saturable absorber, is demonstrated for the first time. This transfer technique is of general applicability and can be used for other two-dimensional (2D) exfoliated materials.

  10. Large and flat graphene flakes produced by epoxy bonding and reverse exfoliation of highly oriented pyrolytic graphite

    Energy Technology Data Exchange (ETDEWEB)

    Huc, Vincent [ICMMO-CNRS, Universite Paris-Sud, F-91405 Orsay (France); Bendiab, Nedjma [Laboratoire de Spectrometrie Physique, Universite Joseph Fourier, F-38402 Saint Martin d' Heres (France); Rosman, Noel [LEPMI, ENSEEG, INPG, F-38402 Saint Martin d' Heres (France); Ebbesen, Thomas [ISIS, Universite Louis Pasteur, 8, Allee Gaspard Monge, BP 70028, F-67083 Strasbourg Cedex (France); Delacour, Cecile; Bouchiat, Vincent [Institut Neel, CNRS-Grenoble, 25 avenue des Martyrs, F-38042 Grenoble Cedex (France)

    2008-11-12

    We present a fabrication method producing large and flat graphene flakes that have a few layers down to a single layer based on substrate bonding of a thick sample of highly oriented pyrolytic graphite (HOPG), followed by its controlled exfoliation down to the few to single graphene atomic layers. As the graphite underlayer is intimately bonded to the substrate during the exfoliation process, the obtained graphene flakes are remarkably large and flat and present very few folds and pleats. The high occurrence of single-layered graphene sheets being tens of microns wide in lateral dimensions is assessed by complementary probes including spatially resolved micro-Raman spectroscopy, atomic force microscopy and electrostatic force microscopy. This versatile method opens the way for deposition of graphene on any substrates, including flexible ones.

  11. Large and flat graphene flakes produced by epoxy bonding and reverse exfoliation of highly oriented pyrolytic graphite

    Science.gov (United States)

    Huc, Vincent; Bendiab, Nedjma; Rosman, Noël; Ebbesen, Thomas; Delacour, Cécile; Bouchiat, Vincent

    2008-11-01

    We present a fabrication method producing large and flat graphene flakes that have a few layers down to a single layer based on substrate bonding of a thick sample of highly oriented pyrolytic graphite (HOPG), followed by its controlled exfoliation down to the few to single graphene atomic layers. As the graphite underlayer is intimately bonded to the substrate during the exfoliation process, the obtained graphene flakes are remarkably large and flat and present very few folds and pleats. The high occurrence of single-layered graphene sheets being tens of microns wide in lateral dimensions is assessed by complementary probes including spatially resolved micro-Raman spectroscopy, atomic force microscopy and electrostatic force microscopy. This versatile method opens the way for deposition of graphene on any substrates, including flexible ones.

  12. Spectroscopic imaging ellipsometry for automated search of flakes of mono- and n-layers of 2D-materials

    Science.gov (United States)

    Funke, S.; Wurstbauer, U.; Miller, B.; Matković, A.; Green, A.; Diebold, A.; Röling, C.; Thiesen, P. H.

    2017-11-01

    Spectroscopic imaging ellipsometry (SIE) is used to localize and characterize flakes of conducting, semi-conducting and insulating 2D-materials. Although the research in the field of monolayers of 2D-materials increased the last years, it is still challenging to look for small flakes and distinguish between different layer numbers. Special substrates are used to enhance optical contrast for the conventional light microscopy (LM). In case when other functional support from the substrate is essential, an additional transfer step needs to be employed, bringing the drawbacks as contamination, cracking and wrinkling of the 2D materials. Furthermore it is time-consuming and not yet fully automatically to search for monolayers by contrast with the LM. Here we present a method, that is able to automatically localize regions with desired thicknesses, e.g. monolayers, of the different materials on arbitrary substrates.

  13. High-yield synthesis of few-layer graphene flakes through electrochemical expansion of graphite in propylene carbonate electrolyte.

    Science.gov (United States)

    Wang, Junzhong; Manga, Kiran Kumar; Bao, Qiaoliang; Loh, Kian Ping

    2011-06-15

    High-yield production of few-layer graphene flakes from graphite is important for the scalable synthesis and industrial application of graphene. However, high-yield exfoliation of graphite to form graphene sheets without using any oxidation process or super-strong acid is challenging. Here we demonstrate a solution route inspired by the lithium rechargeable battery for the high-yield (>70%) exfoliation of graphite into highly conductive few-layer graphene flakes (average thickness graphene sheets with the aid of sonication. The dispersible graphene can be ink-brushed to form highly conformal coatings of conductive films (15 ohm/square at a graphene loading of <1 mg/cm(2)) on commercial paper. © 2011 American Chemical Society

  14. Large and flat graphene flakes produced by epoxy bonding and reverse exfoliation of highly oriented pyrolytic graphite.

    Science.gov (United States)

    Huc, Vincent; Bendiab, Nedjma; Rosman, Noël; Ebbesen, Thomas; Delacour, Cécile; Bouchiat, Vincent

    2008-11-12

    We present a fabrication method producing large and flat graphene flakes that have a few layers down to a single layer based on substrate bonding of a thick sample of highly oriented pyrolytic graphite (HOPG), followed by its controlled exfoliation down to the few to single graphene atomic layers. As the graphite underlayer is intimately bonded to the substrate during the exfoliation process, the obtained graphene flakes are remarkably large and flat and present very few folds and pleats. The high occurrence of single-layered graphene sheets being tens of microns wide in lateral dimensions is assessed by complementary probes including spatially resolved micro-Raman spectroscopy, atomic force microscopy and electrostatic force microscopy. This versatile method opens the way for deposition of graphene on any substrates, including flexible ones.

  15. Starch gelatinization and physical quality of pea flakes in canine dinners as affected by soaking, steam treatment and infrared radiation.

    Science.gov (United States)

    Yang, S C; Zandstra, T; van der Poel, A F B

    2008-06-01

    Cleaned, whole smooth green peas (Pisum sativum L.) were reconstituted by soaking in tap water of 40 degrees C (15, 20 or 25 min) and subsequently either toasted (100 degrees C during 1.5 min) and infrared (IR) radiated or just IR radiated. For IR radiation, a small-scale, propane-fired IR radiation plant was used with average residence times of 58 and 92 s respectively. After exiting the conveyor belt, peas were held for a pre-determined period (holding: 0, 15 or 30 min respectively) in a well-insulated container. Finally, all radiated peas were flaked (roll distance 0.75 mm) in a flaking mill located posterior to the IR plant and analysed for chemical and physical properties. Initial pea starch gelatinization degree (SGD) was 10.1% at a total starch content of 410.1 g/kg. Infrared processing during 92 s significantly improved the SGD (from 10.1% to 32.8%) of pea flakes compared to treatment during 58 s (SGD of 18.6%). The SGD was further improved with steam treatment of peas, prior to IR. For all determined parameters, no effect of holding time could be observed. Starch gelatinization degree can be improved by soaking, toasting and IR processing. The substantial improvement of SGD, however can be only obtained by a longer IR residence time as well as through toasting, prior to the IR processing. The improvements in SGD, however are paralleled by a lower durability of flakes (range 34.9% to 87.4%).

  16. Amperometric detection of carbohydrates based on the glassy carbon electrode modified with gold nano-flake layer

    OpenAIRE

    Huy Du Nguyen; T. Thuy Luyen Nguyen; Khac Manh Nguyen; Anh Mai Nguyen; Quoc Hien Nguyen

    2015-01-01

    An electro-deposition approach was established to incorporate the gold nano-flakes onto the glassy carbon electrode in electrochemical cells (nano-Au/GC/ECCs). Using pulsed amperometric detection (PAD) without any gold oxidation for cleaning (non-oxidative PAD), the nano-Au/GC/ECCs were able to maintain their activity for oxidizing of carbohydrates in a normal alkaline medium. The reproducibility of peak area was about 2 relative standard deviation (RSD,%) for 6 consecutive injections. A dyna...

  17. Effect of Flake Thickness on Coercivity of Nanocrystalline SmCo5 Bulk Prepared from Anisotropic Nanoflake Powder (Postprint)

    Science.gov (United States)

    2016-08-23

    flake thickness. 15. SUBJECT TERMS rare earth magnets , samarium cobalt magnets , permanent magnets 16. SECURITY CLASSIFICATION OF: 17...nanoflakes have attractive magnetic properties ; coercivity of up to 21 kOe and maximum energy product of up to 22 MGOe.9 Thus, the nanoflake powders...less reported on correlation between nanoflake morphology and final properties of the SmCo5 bulk magnets . In this study, we prepared SmCo5 nanoflakes

  18. Promoting power density by cleaving LiCoO2 into nano-flake structure for high performance supercapacitor.

    Science.gov (United States)

    Liu, Qipeng; Javed, Muhammad Sufyan; Zhang, Cuilin; Li, Yanrong; Hu, Chenguo; Zhang, Chengshuang; Lai, Meihui; Yang, Qi

    2017-05-04

    LiCoO2 (LCO) usually can deliver high energy density but low power density in Li-ion batteries (LIBs). Whether LCO could be used as electrode material for high-performance supercapacitors is dependent on promoting its power density. Owing to Faradaic redox reactions taking place on its surfaces or inside crystals through ion intercalation/deintercalation from the surfaces, increasing the specific area of LCO is a key factor to promote its rate capability. Herein, we report a facile strategy to prepare LCO nano-flakes with high specific area exceeding that of currently used micro-scale particles in LIBs. LCO as a nano-flake structure is expected to have a high fraction of Li atom exposure, which benefits fast redox reactions taking place on the surfaces. An LCO-based electrode exhibits an excellent specific capacitance of 581.3 F g-1 at 0.5 A g-1, high power density of 2262 W kg-1 at an energy density of 41.0 Wh kg-1, and good cycling stability (83.9% capacitance retention at 6 A g-1 after 2000 cycles) in LiCl aqueous electrolyte. Faradaic redox behaviors have been analyzed, indicating an ideal diffusion-controlled process. Moreover, a full solid-state symmetric supercapacitor is assembled using LCO nano-flake-based electrodes, which presents good performance with light weight and flexibility. Impressively, three charged supercapacitors in series can light 100 green light emitting diodes for 14 min. LCO in nano-flake structure form with high power density could be an excellent material for superior supercapacitors.

  19. Degradation mechanisms of organic rubber and glass flake/vinyl ester linings in flue gas desulphurization plants

    Energy Technology Data Exchange (ETDEWEB)

    Weber, R. [Allianz-Centre for Technology GmbH, Ismaning (Germany)

    1996-12-01

    In recent years, there have been reports in numerous publications about damage to rubber and glass flake coatings in flue gas desulphurization plants. The pattern of damage has been described and attempts have frequently been made to determine and explain the cause of the damage. Oxidation/hydrolytic changes were generally observed as the damage mechanisms. In addition, blistering occurs in both the chloroprene coatings in the absorbers and in the glass flake coatings in clean gas ducts. This blistering may be considered as the end of the useful life and leads to cost-intensive and time-intensive repair and restoration measures. The present state of knowledge suggests that the blistering is mainly due to osmotic processes preceded by permeation processes and with permeation processes superimposed on them. Among other things, the reports describe the permeation behaviour of water and other flue gas constituents; the blistering in chloroprene rubber coatings and glass flake coatings is explained by means of the knowledge gained. (au) 16 refs.

  20. Effects of oatmeal and corn flakes cereal breakfasts on satiety, gastric emptying, glucose, and appetite-related hormones.

    Science.gov (United States)

    Geliebter, Allan; Grillot, Charlotte L; Aviram-Friedman, Roni; Haq, Sakeena; Yahav, Eric; Hashim, Sami A

    2015-01-01

    The extent to which different types of breakfasts affect appetite and food intake is unclear. To assess the satiety effects of a high-fiber cereal, we compared oatmeal, isocaloric corn flakes, and water. Thirty-six subjects (18 lean, 18 overweight) were assigned to three conditions in a randomized sequence on different days. Ratings of hunger and fullness were obtained concurrently with blood samples for measuring concentrations of glucose, insulin, glucagon, leptin, and acetaminophen (gastric emptying tracer). Appetite was assessed by calculating the area under the curve (AUC) for fullness and hunger, and by measuring food intake of an ad libitum lunch meal at 180 min. Lunch meal intake was lowest after consuming oatmeal (p oatmeal. At 180 min, blood glucose was lowest after the corn flakes (p = 0.0001). Insulin AUC was greater for both cereals than water (p oatmeal (p = 0.046), reflecting slower gastric emptying. Satiety was greater and ad libitum test meal intake lower after consuming oatmeal than after corn flakes, especially in the overweight subjects. © 2015 S. Karger AG, Basel.

  1. Graphene oxide flakes as a cellular adhesive: prevention of reactive oxygen species mediated death of implanted cells for cardiac repair.

    Science.gov (United States)

    Park, Jooyeon; Kim, Bokyoung; Han, Jin; Oh, Jaewon; Park, Subeom; Ryu, Seungmi; Jung, Subin; Shin, Jung-Youn; Lee, Beom Seob; Hong, Byung Hee; Choi, Donghoon; Kim, Byung-Soo

    2015-05-26

    Mesenchymal stem cell (MSC) implantation has emerged as a potential therapy for myocardial infarction (MI). However, the poor survival of MSCs implanted to treat MI has significantly limited the therapeutic efficacy of this approach. This poor survival is primarily due to reactive oxygen species (ROS) generated in the ischemic myocardium after the restoration of blood flow. ROS primarily causes the death of implanted MSCs by inhibiting the adhesion of the MSCs to extracellular matrices at the lesion site (i.e., anoikis). In this study, we proposed the use of graphene oxide (GO) flakes to protect the implanted MSCs from ROS-mediated death and thereby improve the therapeutic efficacy of the MSCs. GO can adsorb extracellular matrix (ECM) proteins. The survival of MSCs, which had adhered to ECM protein-adsorbed GO flakes and were subsequently exposed to ROS in vitro or implanted into the ischemia-damaged and reperfused myocardium, significantly exceeded that of unmodified MSCs. Furthermore, the MSC engraftment improved by the adhesion of MSCs to GO flakes prior to implantation enhanced the paracrine secretion from the MSCs following MSC implantation, which in turn promoted cardiac tissue repair and cardiac function restoration. This study demonstrates that GO can effectively improve the engraftment and therapeutic efficacy of MSCs used to repair the injury of ROS-abundant ischemia and reperfusion by protecting implanted cells from anoikis.

  2. Effect of functionalization of boron nitride flakes by main group metal clusters on their optoelectronic properties

    Science.gov (United States)

    Chakraborty, Debdutta; Chattaraj, Pratim Kumar

    2017-10-01

    The possibility of functionalizing boron nitride flakes (BNFs) with some selected main group metal clusters, viz. OLi4, NLi5, CLi6, BLI7 and Al12Be, has been analyzed with the aid of density functional theory (DFT) based computations. Thermochemical as well as energetic considerations suggest that all the metal clusters interact with the BNF moiety in a favorable fashion. As a result of functionalization, the static (first) hyperpolarizability (β ) values of the metal cluster supported BNF moieties increase quite significantly as compared to that in the case of pristine BNF. Time dependent DFT analysis reveals that the metal clusters can lower the transition energies associated with the dominant electronic transitions quite significantly thereby enabling the metal cluster supported BNF moieties to exhibit significant non-linear optical activity. Moreover, the studied systems demonstrate broad band absorption capability spanning the UV-visible as well as infra-red domains. Energy decomposition analysis reveals that the electrostatic interactions principally stabilize the metal cluster supported BNF moieties.

  3. Introducing LIR (Lithotheque Ireland, a reference collection of flaked stone tool raw materials from Ireland

    Directory of Open Access Journals (Sweden)

    Killian Driscoll

    2016-09-01

    Full Text Available The LIR (Lithotheque Ireland reference collection of flaked stone tool raw materials from Ireland began in 2013, and is based on the geological prospection from two projects. The first (2013-2015 focused attention primarily on Carboniferous cherts from the northwest of Ireland, collecting 405 samples. The second (2015-2017 is currently collecting samples of the Cretaceous flint primarily from in situ contexts in the northeast of Ireland, but also includes beach surveys of Cretaceous flint from around the island; the first phase of geological prospection in Autumn 2015 collected 239 samples, with the geological prospection continuing in 2016. Therefore, to date the collection contains over 600 hand samples of chert and flint, along with a small number of other materials (siliceous limestone, tuff, mudstone. The physical reference collection is housed at the UCD School of Archaeology, University College Dublin and contains the geological hand samples along with the various thin sections of the samples that are used for petrographic analysis. The physical collection is complemented by an online database that is to be used alongside the physical collection, or can be used as a stand-alone resource. This paper provides an overview of the database’s metadata and the processes of data entry and editing, to serve as a reference point for the database and the fieldwork undertaken to date, and to serve as a template for other researchers undertaking similar work on lithic reference collections.

  4. Uniform hexagonal graphene flakes and films grown on liquid copper surface.

    Science.gov (United States)

    Geng, Dechao; Wu, Bin; Guo, Yunlong; Huang, Liping; Xue, Yunzhou; Chen, Jianyi; Yu, Gui; Jiang, Lang; Hu, Wenping; Liu, Yunqi

    2012-05-22

    Unresolved problems associated with the production of graphene materials include the need for greater control over layer number, crystallinity, size, edge structure and spatial orientation, and a better understanding of the underlying mechanisms. Here we report a chemical vapor deposition approach that allows the direct synthesis of uniform single-layered, large-size (up to 10,000 μm(2)), spatially self-aligned, and single-crystalline hexagonal graphene flakes (HGFs) and their continuous films on liquid Cu surfaces. Employing a liquid Cu surface completely eliminates the grain boundaries in solid polycrystalline Cu, resulting in a uniform nucleation distribution and low graphene nucleation density, but also enables self-assembly of HGFs into compact and ordered structures. These HGFs show an average two-dimensional resistivity of 609 ± 200 Ω and saturation current density of 0.96 ± 0.15 mA/μm, demonstrating their good conductivity and capability for carrying high current density.

  5. Inducing and Manipulating Heteroelectronic States in a Single MoS2 Thin Flake

    Science.gov (United States)

    Chen, Q. H.; Lu, J. M.; Liang, L.; Zheliuk, O.; Ali, A.; Sheng, P.; Ye, J. T.

    2017-10-01

    By dual gating a few-layer MoS2 flake, we induce spatially separated electronic states showing superconductivity and Shubnikov-de Haas (SdH) oscillations. While the highly confined superconductivity forms at the K /K' valleys of the topmost layer, the SdH oscillations are contributed by the electrons residing in the Q /Q' valleys of the rest of the bottom layers, which is confirmed by the extracted Landau level degeneracy of 3, electron effective mass of 0.6 me , and carrier density of 5 ×1012 cm-2 . Mimicking conventional heterostructures, the interaction between the heteroelectronic states can be electrically manipulated, which enables "bipolarlike" superconducting transistor operation. The off-on-off switching pattern can be continuously accessed at low temperatures by a field effect depletion of carriers with a negative back gate bias and the proximity effect between the top superconducting layer and the bottom metallic layers that quenches the superconductivity at a positive back gate bias.

  6. Facile Synthesis of High Quality Graphene Oxide from Graphite Flakes Using Improved Hummer's Technique.

    Science.gov (United States)

    Low, Foo Wah; Lai, Chin Wei; Abd Hamid, Sharifah Bee

    2015-09-01

    Graphene is a promising candidate for making next-generation nanotechnology devices due to its outstanding properties in terms of physical, chemical, mechanical aspects. Based on the theoretical point of view, graphene is a two-dimensional (2D) crystal structure with sp2 hybridized carbon atoms arrangement and has attracted extensive attention in a considerable number of applications such as solar energy, sensor and energy storage, naming a few. Herein, graphene oxide (GO) is synthesized from graphite flakes using the Improved Hummer's method. The results demonstrated the comparison of synthesized GO samples based on stirred duration of 6 h and 72 h. The FTIR results proved that the 72 h GO sample was well-bonded with the C-O functional group, signifying the successful synthesis of GO under an extended stirred duration. The FESEM images showed that the synthesized GO was well-arranged in crystal lattice of graphene sheets whereas the EDX result showed that higher atomic % of Oxygen, O2 was obtained with a longer stirred duration due to the high opportunity for oxygenated bonded to occur on the C-C functional group.

  7. Unsteady self-sustained detonation waves in flake aluminum dust/air mixtures

    CERN Document Server

    Liu, Qingming; Zhang, Yunming; Li, Shuzhuan

    2015-01-01

    Self-sustained detonation waves in flake aluminum dust/air mixtures have been studied in a tube of diameter 199 mm and length 32.4 m. A pressure sensor array of 32 sensors mounted around certain circumferences of the tube was used to measure the shape of the detonation front in the circumferential direction and pressure histories of the detonation wave. A two-head spin detonation wave front was observed for the aluminum dust/air mixtures, and the cellular structure resulting from the spinning movement of the triple point was analyzed. The variations in velocity and overpressure of the detonation wave with propagation distance in a cell were studied. The interactions of waves in triple-point configurations were analyzed and the flow-field parameters were calculated. Three types of triple-point configuration exist in the wave front of the detonation wave of an aluminum dust/air mixture. Both strong and weak transverse waves exist in the unstable self-sustained detonation wave.

  8. An Experimental Study on Heat Conduction and Thermal Contact Resistance for the AlN Flake

    Directory of Open Access Journals (Sweden)

    Huann-Ming Chou

    2013-01-01

    Full Text Available The electrical technology has been a fast development over the past decades. Moreover, the tendency of microelements and dense division multiplex is significantly for the electrical industries. Therefore, the high thermal conductible and electrical insulating device will be popular and important. It is well known that AlN still maintains stablility in the high temperature. This is quite attractive for the research and development department. Moreover, the thermal conduct coefficient of AlN is several times larger than the others. Therefore, it has been thought to play an important role for the radiator of heat source in the future. Therefore, this paper is focused on the studies of heat conduction and thermal contact resistance between the AlN flake and the copper specimens. The heating temperatures and the contact pressures were selected as the experimental parameters. According to the experimental results, the materials are soft and the real contact areas between the interfaces significantly increase under higher temperatures. As a result, the thermal contact resistance significantly decreases and the heat transfer rate increases with increasing the heating temperature or the contact pressures.

  9. Adsorption of ion pairs onto graphene flakes and impacts of counterions during the adsorption processes

    Science.gov (United States)

    Zhu, Chang; Yun, Jiena; Wang, Qian; Yang, Gang

    2018-03-01

    Although cations and anions are two integral constituents for all electrolytes, adsorption of ion pairs onto carbonaceous materials gains obviously less attention than adsorption of only cations or anions. Here DFT calculations are employed finding that four adsorption configurations emerge for KI onto graphene flakes (GF) instead of three for the other ion pairs. Reservation of ionic bonds is critical to their stabilities, and the bilateral configurations, where GFs couple with both cations and anions, are disfavored due to rupture of ionic bonds. Relative stabilities of two vertical configurations can be regulated and even reversed through edge-functionalization. Surprisingly, the horizontal adsorption configurations, which are global energy minima as long as present, are non-existent for a majority of ion pairs, and their existence or not is determined by the adsorption differences between halide ions and alkali ions (△Ead). Counterions effects for both cations and anions increase with the atomic electronegativities and cations correspond to stronger counterion effects; e.g., Li+ added on the other side of GFs promotes the adsorption of F- more pronouncedly than edge-functionalization. Mechanisms of electron transfers are also discussed, and three alteration patterns by counterions are observed for each type of adsorption configurations. Furthermore, addition of counterions causes band gaps to vary within a wider range that may be useful to design electronic devices.

  10. Current densities due to electron-hole puddles in graphene flakes at the charge neutrality point

    Science.gov (United States)

    Lima, Leandro; Lewenkopf, Caio

    2014-03-01

    Graphene flakes show a typical conductivity minimum of about e2 / h , almost independent of sample mobility, at the charge neutrality point. This is at odds with the notion that as the mobility increases, and graphene becomes more ballistic, its density of states (DOS) and conductivity at the charge neutrality point should vanish. The observed conductivity minimum is often attributed to the presence of electron-hole charge puddles, that give rise to an effective local-dependent chemical potential. In this way, the local chemical potential fluctuates creating p and n-doped regions and the electronic transport is facilitated by Klein tunneling through the p and n-doped domains. Although very attractive, there is little quantitative support for this this picture. We revisit this problem and analyze the transport properties using a self-consistent recursive Green's functions technique with spin resolution that includes the electronic interaction modeled by a mean field Hubbard term. We calculate electronic current densities between neighboring carbon sites near the p-n interface and relate the electronic propagation to the puddles charge, size and shapes.

  11. Unsteady self-sustained detonation in flake aluminum dust/air mixtures

    Science.gov (United States)

    Liu, Q.; Li, S.; Huang, J.; Zhang, Y.

    2017-07-01

    Self-sustained detonation waves in flake aluminum dust/air mixtures have been studied in a tube of diameter 199 mm and length 32.4 m. A pressure sensor array of 32 sensors mounted around certain circumferences of the tube was used to measure the shape of the detonation front in the circumferential direction and pressure histories of the detonation wave. A two-head spin detonation wave front was observed for the aluminum dust/air mixtures, and the cellular structure resulting from the spinning movement of the triple point was analyzed. The variations in velocity and overpressure of the detonation wave with propagation distance in a cell were studied. The interactions of waves in triple-point configurations were analyzed and the flow-field parameters were calculated. Three types of triple-point configuration have been found in the wave front of the detonation wave of an aluminum dust/air mixture. Both strong and weak transverse waves exist in the unstable self-sustained detonation wave.

  12. Electrochemical properties of graphene flakes as an air cathode material for Li-O2 batteries in an ether-based electrolyte.

    Science.gov (United States)

    Kim, Se Young; Lee, Ho-Taek; Kim, Kwang-Bum

    2013-12-14

    We employed graphene flakes as an air-cathode material for Li-O2 batteries and investigated their electrochemical properties in the dimethyl ether electrolyte. Graphene flakes were prepared by microwave-assisted reduction of graphene oxide, and their electrochemical properties were compared with those of Ketjen Black and carbon nanotubes. The catalytic effect of the prepared graphene flake-air cathode was demonstrated using cyclic voltammetry and discharge-charge testing performed under a limited discharge capacity. The catalytic effect of graphene flakes was also supported by morphological and spectroscopic analysis of the discharge-charge products formed on the graphene surface. Scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy revealed that Li2O2, Li2O, and Li2CO3 were the main discharge products on all carbon-air cathode surfaces. Raman spectroscopy revealed that LiRCO3 was additionally formed on Ketjen Black and carbon nanotubes during the first discharge; however, its formation was not observed on the graphene flakes. The catalytic effect of the graphene flakes and the absence of LiRCO3 in the discharge product could explain the higher Coulombic efficiency in the discharge-charge tests.

  13. Electrolytic exfoliation of graphite in water with multifunctional electrolytes: en route towards high quality, oxide-free graphene flakes

    Science.gov (United States)

    Munuera, J. M.; Paredes, J. I.; Villar-Rodil, S.; Ayán-Varela, M.; Martínez-Alonso, A.; Tascón, J. M. D.

    2016-01-01

    Electrolytic - usually referred to as electrochemical - exfoliation of graphite in water under anodic potential holds enormous promise as a simple, green and high-yield method for the mass production of graphene, but currently suffers from several drawbacks that hinder its widespread adoption, one of the most critical being the oxidation and subsequent structural degradation of the carbon lattice that is usually associated with such a production process. To overcome this and other limitations, we introduce and implement the concept of multifunctional electrolytes. The latter are amphiphilic anions (mostly polyaromatic hydrocarbons appended with sulfonate groups) that play different relevant roles as (1) an intercalating electrolyte to trigger exfoliation of graphite into graphene flakes, (2) a dispersant to afford stable aqueous colloidal suspensions of the flakes suitable for further use, (3) a sacrificial agent to prevent graphene oxidation during exfoliation and (4) a linker to promote nanoparticle anchoring on the graphene flakes, yielding functional hybrids. The implementation of this strategy with some selected amphiphiles even furnishes anodically exfoliated graphenes of a quality similar to that of flakes produced by direct, ultrasound- or shear-induced exfoliation of graphite in the liquid phase (i.e., almost oxide- and defect-free). These high quality materials were used for the preparation of catalytically efficient graphene-Pt nanoparticle hybrids, as demonstrated by model reactions (reduction of nitroarenes). The multifunctional performance of these electrolytes is also discussed and rationalized, and a mechanistic picture of their oxidation-preventing ability is proposed. Overall, the present results open the prospect of anodic exfoliation as a competitive method for the production of very high quality graphene flakes.Electrolytic - usually referred to as electrochemical - exfoliation of graphite in water under anodic potential holds enormous promise

  14. Mineral resource of the month: mica

    Science.gov (United States)

    Hedrick, J.B.

    2008-01-01

    Humans have been using mica for millennia. Mica was first mined in India about 4,000 years ago, where it was used primarily in medicines, and some Hindu physicians still incorporate biotite mica into medicines today. Early civilizations also used mica for decorations, as windows and as surfaces on which to draw or paint. Maya temples were decorated with mica pigments, which were incorporated into the stucco to make it sparkle in the sun. In North America, ancient inhabitants adorned gravesites and burial mounds with animal figures made of mica.

  15. Effect of Desiccation, Temperature and Storage on the Germination of Snow Flake (Leucojum aestivum L. Seeds

    Directory of Open Access Journals (Sweden)

    Emrah Çiçek

    2013-11-01

    Full Text Available Snowflake (Leucojum aestivum, Amaryllidaceae is one of the exported flower bulbs and it is the only natural species of Leucojum genus in Turkey. At present, the main habitats of snowflake are the narrow-leaved ash (Fraxinus angustifolia Vahl. forest ecosystems on low lands in Black Sea and Marmara regions where they have limited populations. Snowflake is collected from these populations as a non-wood forest product. It has been used as an ornamental and medicinal plant in the European countries for a long time. In this study, firstly, the effect of temperature on the germination of stratified snow flake seeds was investigated. After five weeks of warm stratification, the seeds were germinated at 20 and 25ºC constant and, 30/20ºC (8/16 h variable temperature regimes. Temperature significantly affected germination percentage (GP and the highest GP was determined both fresh and air dried seeds at 20oC constant temperature (53.2% and 50.9%. The seeds at 20ºC germination temperature were followed for further six months and total 90% GP was determined. This result shows that snowflake seeds have a long germination period. Later, air dried seeds were stored at 20, 4 and –5ºC temperatures for six months, and then germinated at 20ºC. Viability of the stored seeds was also determined. Results showed that the seeds stored at 4 and –5ºC had similar and higher GP than that of the seeds stored at 20ºC temperature. The initially 50.6% GP was decreased at 15.0% level after six months of storage. However, the viability of the seeds was similar in initially and after six months (%96.8 and %94.3.

  16. Characterization of Deposited Platinum Contacts onto Discrete Graphene Flakes for Electrical Devices

    KAUST Repository

    Holguin Lerma, Jorge A.

    2016-05-03

    For years, electron beam induced deposition has been used to fabricate electrical contacts for micro and nanostructures. The role of the contact resistance is key to achieve high performance and efficiency in electrical devices. The present thesis reports on the electrical, structural and chemical characterization of electron beam deposited platinum electrodes that are exposed to different steps of thermal annealing and how they are used in four-probe devices of ultrathin graphite (uG) flakes (<100nm thickness). The device integration of liquid phase exfoliated uG is demonstrated, and its performance compared to devices made with analogous mechanically exfoliated uG. For both devices, similar contact resistances of ~2kΩ were obtained. The electrical measurements confirm a 99.5% reduction in contact resistance after vacuum thermal annealing at 300 °C. Parallel to this, Raman characterization confirms the formation of a nanocrystalline carbon structure over the electrode. While this could suggest an enhancement of the electrical transport in the device, an additional thermal annealing step in air at 300 °C, promoted the oxidation and removal of the carbon shell and confirmed that the contact resistance remained the same. Overall this shows that the carbon shell along the electrode has no significant role in the contact resistance. Finally, the challenges based on topographical analysis of the deposited electrodes are discussed. Reduction of the electrode’s height down to one-third of the initial value, increased surface roughness, formation of voids along the electrodes and the onset of platinum nanoparticles near the area of deposition, represent a challenge for future work.

  17. Inclusion of various amounts of steam-flaked soybeans in lactating dairy cattle diets.

    Science.gov (United States)

    Bruns, H R; Hippen, A R; Kalscheur, K F; Schingoethe, D J

    2015-10-01

    Whereas most soybean feedstuffs have been extensively investigated for use in ruminant diets, a lack of information exists regarding steam-flaked soybeans (SFSB). This research evaluated various inclusion rates of SFSB in diets for lactating dairy cattle. Twelve multiparous Holstein cows (103 ± 39 d in milk) were used in a 4 × 4 Latin square experiment consisting of 28-d periods, 14 d for diet transitioning followed by a 14-d sampling period. Treatments were inclusion of SFSB at 0, 5, 10, and 15% of dietary dry matter (DM), replacing a mixture of soybean meal, soy hulls, calcium salts of fatty acids, and choice white grease. Animals were fed lactating dairy cow diets formulated to be isonitrogenous and isoenergetic, containing 60% of DM as forage and 40% of DM as concentrate. Dry matter intake (mean = 28.8 kg/d), milk production (42.2 kg/d), milk fat percentage (3.52%), and feed efficiency (1.43 kg of energy-corrected milk/kg of DM intake) were similar across all treatments. Milk protein (2.98%) and lactose (4.87%) were also unaffected by the amount of SFSB in the diet. Milk urea nitrogen concentration decreased linearly as the amount of SFSB in the diet increased. Unlike some other soybean supplements, feeding SFSB did not increase trans-11 C18:1 or cis-9,trans-11 conjugated linoleic acid, but instead resulted in increased cis-9,cis-12 C18:2 and α-C18:3. Body weights (752 kg) and body condition scores (3.17) were similar with all diets. This research demonstrated that SFSB can be substituted for soybean meal and commercial fat sources while maintaining milk and milk component production and decrease milk urea nitrogen concentration. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  18. Mica polytypes: Systematic description and identification

    Science.gov (United States)

    Ross, M.; Takeda, H.; Wones, D.R.

    1966-01-01

    X-ray studies of mica specimens from a variety of geological localities show that biotite and certain lithium-rich mica samples are composed of a mixture of different polytypes. Many of the biotite structures are new complex polytypes not before reported. A new method of designating mica polytypes is proposed. Techniques are described for the systematic generation of all the possible layer-stacking sequences of mica polytypes and for the verification of the stacking sequences in newly discovered forms.

  19. Facile Synthesis of Nitrogen Doped Graphene Oxide from Graphite Flakes and Powders: A Comparison of Their Surface Chemistry.

    Science.gov (United States)

    Yokwana, Kholiswa; Ray, Sekhar C; Khenfouch, Mohammad; Kuvarega, Alex T; Mamba, Bhekie B; Mhlanga, Sabelo D; Nxumalo, Edward N

    2018-08-01

    Nitrogen-doped graphene oxide (NGO) nanosheets were prepared via a facile one-pot modified Hummer's approach at low temperatures using graphite powder and flakes as starting materials in the presence of a nitrogen precursor. It was found that the morphology, structure, composition and surface chemistry of the NGO nanosheets depended on the nature of the graphite precursor used. GO nanosheets doped with nitrogen atoms exhibited a unique structure with few thin layers and wrinkled sheets, high porosity and structural defects. NGO sheets made from graphite powder (NGOp) exhibited excellent thermal stability and remarkably high surface area (up to 240.53 m2 ·g-1) compared to NGO sheets made from graphite flakes (NGOf) which degraded at low temperatures and had an average surface area of 24.70 m2 ·g-1. NGOf sheets had a size range of 850 to 2200 nm while NGOp sheets demonstrated obviously small sizes (460-1600 nm) even when exposed to different pH conditions. The NGO nanosheets exhibited negatively charged surfaces in a wide pH range (1 to 12) and were found to be stable above pH 6. In addition, graphite flakes were found to be more suitable for the production of NGO as they produced high N-doping levels (0.65 to 1.29 at.%) compared to graphite powders (0.30 to 0.35 at.%). This study further demonstrates that by adjusting the amount of N source in the host GO, one can tailor its thermal stability, surface morphology, surface chemistry and surface area.

  20. Enhanced and broadband microwave absorption of flake-shaped Fe and FeNi composite with Ba ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wangchang [Research Center of Magnetic and Electronic Materials, College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310000 (China); Lv, Junjun, E-mail: LyuJunJun@caep.cn [Institute of Chemical Material, CAEP, Mianyang 621900 (China); Zhou, Xiang; Zheng, Jingwu; Ying, Yao; Qiao, Liang; Yu, Jing [Research Center of Magnetic and Electronic Materials, College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310000 (China); Che, Shenglei, E-mail: cheshenglei@zjut.edu.cn [Research Center of Magnetic and Electronic Materials, College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310000 (China)

    2017-03-15

    In order to achieve a broad bandwidth absorber at high frequency, the composites of M-type ferrite BaCo{sub 1.0}Ti{sub 1.0}Fe{sub 10}O{sub 19} (BaM) with flaked carbonyl iron powders (CIP) and flaked Fe{sub 50}Ni{sub 50} were prepared to optimize the surface impedance in broadband frequency, respectively. The diameter of the flaked carbonyl iron powders (CIP) and Fe{sub 50}Ni{sub 50} is in the range of 5–10 µm and 10–20 µm and the thickness of the CIP and Fe{sub 50}Ni{sub 50} is close to 200 nm and 400 nm, respectively. The complex permeability and permittivity show that the addition of BaM obviously reduces the values of real part of permittivity and imaginary part of the permeability which can enhance the matched-wave-impedance. The absorption bands less than −10 dB of CIP-BaM and FeNi-BaM absorber approach to 5.5 GHz (5.7–11.2 GHz) and 7 GHz (11–18 GHz) at 1.5 mm. However, the bands of CIP and FeNi are only 1.9 GHz (4.7–6.6 GHz) and 2.1 GHz (4.0–6.1 GHz). Hence, the electromagnetic match property is greatly improved by BaM ferrites, and this composite shows a broaden absorption band. - Highlights: • In order to achieve a broad bandwidth absorber at high frequency, the composites of M-type ferrite with flaked carbonyl iron powdersand Fe{sub 50}Ni{sub 50} were prepared to optimize the surface impedance. • The complex permeability and permittivity show that the addition of BaM obviously reduces the real part of permittivity and imaginary part of the permeability enhancing the matched-wave-impedance. • The structure, morphology and electromagnetic properties are studied in detail. The optimized properties are ascribed to the strength of dipolar polarization and high frequency magnetic resonance.

  1. Methane dissociation process in inductively coupled Ar/H2/CH4 plasma for graphene nano-flakes production

    Science.gov (United States)

    Mohanta, Antaryami; Lanfant, Briac; Asfaha, Mehari; Leparoux, Marc

    2017-02-01

    The role of hydrogen and methane dissociation process in induction plasma synthesis of graphene nano-flakes (GNF) is studied by the optical emission spectroscopy of Ar/H2/CH4 plasma. The condensation of C2 species formed due to methane decomposition produces GNF, which depends on pressure. Electron impact and dehydrogenation processes dissociate methane, which promotes and hinders the GNF production, respectively. The effect of hydrogen is insignificant on quality, size and morphology of the GNF. The CH4 flow rate has no influence on particle temperature but has effect on cooling rate at the point of nucleation and, therefore, on production rate and thickness of GNF.

  2. Electrically-charged recyclable graphene flakes entangled with electrospun nanofibers for the adsorption of organics for water purification.

    Science.gov (United States)

    An, Seongpil; Jo, Hong Seok; Song, Kyo Yong; Mali, Mukund G; Al-Deyab, Salem S; Yoon, Sam S

    2015-12-07

    Graphene flakes were entrapped between nylon 6 nanofiber layers and the resulting assembly was used as a recyclable water purification membrane. Water purification was achieved via adsorption of the model organic pollutant (methylene blue; MB) on the surface of the graphene component. Desorption of these MB molecules was achieved by applying high voltage, which increased the removal efficiency of the recycled membrane. The adsorption and desorption mechanisms were evaluated in detail. The material characteristics of the membrane were analyzed by scanning electron microscopy, Raman, UV-visible, and Fourier transform infrared analyses.

  3. Flaked stones and old bones: biological and cultural evolution at the dawn of technology.

    Science.gov (United States)

    Plummer, Thomas

    2004-01-01

    The appearance of Oldowan sites ca. 2.6 million years ago (Ma) may reflect one of the most important adaptive shifts in human evolution. Stone artifact manufacture, large mammal butchery, and novel transport and discard behaviors led to the accumulation of the first recognized archaeological debris. The appearance of the Oldowan sites coincides with generally cooler, drier, and more variable climatic conditions across Africa, probably resulting in a net decrease in woodland foods and an increase in large mammal biomass compared to the early and middle Pliocene. Shifts in plant food resource availability may have provided the stimulus for incorporating new foods into the diet, including meat from scavenged carcasses butchered with stone tools. Oldowan artifact form varies with clast size, shape, raw material physical properties, and flaking intensity. Oldowan hominins preferred hard raw materials with good fracture characteristics. Habitual stone transport is evident from technological analysis, and raw material sourcing to date suggests that stone was rarely moved more than 2-3 km from source. Oldowan debris accumulation was spatially redundant, reflecting recurrent visitation of attractive points on the landscape. Thin archaeological horizons from Bed I Olduvai Gorge, Tanzania, were probably formed and buried in less than 10 years and document hominin processing of multiple carcasses per year. Transport beyond simple refuging behavior is suggested by faunal density at some site levels. By 2.0 Ma, hominin rank within the predatory guild may have been moderately high, as they probably accessed meaty carcasses through hunting and confrontational scavenging, and hominin-carnivore competition appears minimal at some sites. It is likely that both Homo habilis sensu stricto and early African H. erectus made Oldowan tools. H. habilis sensu stricto was more encephalized than Australopithecus and may foreshadow H. erectus in lower limb elongation and some thermoregulatory

  4. Milk production, nutrient digestibility and nitrogen balance in lactating cows fed total mixed ration silages containing steam-flaked brown rice as substitute for steam-flaked corn, and wet food by-products.

    Science.gov (United States)

    Miyaji, Makoto; Matsuyama, Hiroki; Hosoda, Kenji; Nonaka, Kazuhisa

    2013-06-01

    The objective of this study was to evaluate the effect of substituting brown rice grain for corn grain in total mixed ration (TMR) silage containing food by-products on the milk production, whole-tract nutrient digestibility and nitrogen balance in dairy cows. Six multiparous Holstein cows were used in a crossover design with two dietary treatments: a diet containing 30.9% steam-flaked corn (corn TMR) or 30.9% steam-flaked brown rice (rice TMR) with wet soybean curd residue and wet soy sauce cake. Dietary treatment did not affect the dry matter intake, milk yield and compositions in dairy cows. The dry matter and starch digestibility were higher, and the neutral detergent fiber digestibility was lower for rice TMR than for corn TMR. The urinary nitrogen (N) excretion as a proportion of the N intake was lower for rice TMR than for corn TMR with no dietary effect on N secretion in milk and fecal N excretion. These results indicated that the replacement of corn with brown rice in TMR silage relatively reduced urinary N loss without adverse effects on feed intake and milk production, when food by-products such as soybean curd residue were included in the TMR silage as dietary crude protein sources. © 2013 Japanese Society of Animal Science.

  5. X-ray absorption spectroscopy by full-field X-ray microscopy of a thin graphite flake: Imaging and electronic structure via the carbon K-edge

    Directory of Open Access Journals (Sweden)

    Carla Bittencourt

    2012-04-01

    Full Text Available We demonstrate that near-edge X-ray-absorption fine-structure spectra combined with full-field transmission X-ray microscopy can be used to study the electronic structure of graphite flakes consisting of a few graphene layers. The flake was produced by exfoliation using sodium cholate and then isolated by means of density-gradient ultracentrifugation. An image sequence around the carbon K-edge, analyzed by using reference spectra for the in-plane and out-of-plane regions of the sample, is used to map and spectrally characterize the flat and folded regions of the flake. Additional spectral features in both π and σ regions are observed, which may be related to the presence of topological defects. Doping by metal impurities that were present in the original exfoliated graphite is indicated by the presence of a pre-edge signal at 284.2 eV.

  6. Facile synthesis of flake-like TiO{sub 2}/C nano-composites for photocatalytic H{sub 2} evolution under visible-light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Baolin; Zhou, Juan; Liang, Xiaoyu; Song, Kainan; Su, Xintai, E-mail: suxintai827@163.com

    2017-01-15

    Highlights: • TiO{sub 2}/C nano-flakes were prepared by a facile phase-transfer strategy combined with salt-template calcination method. • The sub–10 nm of TiO{sub 2} NPs were uniformly dispersed on the carbon flakes. • The TiO{sub 2}/C nano-flakes showed a superior visible-light photocatalytic activity for H{sub 2} production. - Abstract: The production of H{sub 2} by photocatalytic water splitting has become a promising approach for clean, economical, and renewable evolution of H{sub 2} by using solar energy. In spite of tremendous efforts, the present challenge for materials scientists is to build a highly active photocatalytic system with high efficiency and low cost. Here we report a facile method for the preparation of TiO{sub 2}/C nano-flakes, which was used as an efficient visible-light photocatalyst for H{sub 2} evolution. This composite material was prepared by using a phase-transfer strategy combined with salt-template calcination treatment. The results showed that anatase TiO{sub 2} nanoparticles with the diameter of ∼10 nm were uniformly dispersed on the carbon nano-flakes. In addition, the samples prepared at 600 °C (denoted as T600) endowed a larger surface area of 196 m{sup 2} g{sup −1} and higher light absorption, resulting in enhanced photocatalytic activity. Further, the T600 product reached a high H{sub 2} production rate of 57.2 μmol h{sup −1} under visible-light irradiation. This unusual photocatalytic activity arose from the positive synergetic effect between the TiO{sub 2} and carbon in this hybrid catalyst. This work highlights the potential of TiO{sub 2}/C nano-flakes in the field of photocatalytic H{sub 2} evolution under visible-light irradiation.

  7. Q-switched double-clad Ytterbium-doped fiber laser using MoS2 flakes saturable absorber

    Science.gov (United States)

    Tey, K. L.; Rahman, M. F. A.; Rosol, A. H. A.; Rusdi, M. F. M.; Mahyuddin, M. B. H.; Harun, S. W.; Latiff, A. A.

    2017-06-01

    By sandwiching MoS2 thin flakes between two fiber ferrule connectors in the ring cavity, we successfully demonstrate the passive Q-switched fiber laser operation. The cavity consists of all-fiber double-clad ytterbium-doped fiber (YDF) as a gain medium and MoS2 tape as a saturable absorber (SA). The SA was prepared from a commercial MoS2 crystal (~ 99.8 % purity) through mechanical exfoliation process. A piece of 1 mm x 1 mm tape contains MoS2 thin flakes was sandwiched between two fiber connectors. By controlling loss and gain in the cavity, stable Q-switching operation were generated. The repetition rate was tunable from 4.8 kHz to 17.2 kHz as the pump power is varied from 753 mW to 1133 mW. The obtained pulse width is also narrowed from 21.3 µs to 10.44 µs with the same variation of pump power.

  8. Thermophysical and rheological properties of dulce de leche with and without coconut flakes as a function of temperature

    Directory of Open Access Journals (Sweden)

    Vanessa Camarinha Barbosa

    2013-03-01

    Full Text Available Dulce de leche (DL, a dairy dessert highly appreciated in Brazil, is a concentrated product containing about 70% m/m of total solids. Thermophysical and rheological properties of two industrial Brazilian Dulce de leche formulations (classic Dulce de leche and Dulce de leche added with coconut flakes 1.5% m/m were determined at temperatures comprised between 28.4 and 76.4 °C. In general, no significant differences (p < 0.05 were observed in the presence of coconut flakes in the two formulations. Heat capacity varied from 2633.2 to 3101.8 J/kg.°C; thermal conductivity from 0.383 to 0.452 W/m.°C; specific mass from 1350.7 to 1310.7 kg/m³; and, thermal diffusivity from (1.082 × 10-7 to 1.130 × 10-7 m²/s. The Bingham model was used to properly describe the non-Newtonian behavior of both formulations, with yielding stress values varying from 27.3 to 17.6 Pa and plastic viscosity from 19.9 to 5.9 Pa.s.

  9. Weak localization effect in topological insulator micro flakes grown on insulating ferrimagnet BaFe12O19

    Science.gov (United States)

    Zheng, Guolin; Wang, Ning; Yang, Jiyong; Wang, Weike; Du, Haifeng; Ning, Wei; Yang, Zhaorong; Lu, Hai-Zhou; Zhang, Yuheng; Tian, Mingliang

    2016-01-01

    Many exotic physics anticipated in topological insulators require a gap to be opened for their topological surface states by breaking time reversal symmetry. The gap opening has been achieved by doping magnetic impurities, which however inevitably create extra carriers and disorder that undermine the electronic transport. In contrast, the proximity to a ferromagnetic/ferrimagnetic insulator may improve the device quality, thus promises a better way to open the gap while minimizing the side-effects. Here, we grow thin single-crystal Sb1.9Bi0.1Te3 micro flakes on insulating ferrimagnet BaFe12O19 by using the van der Waals epitaxy technique. The micro flakes show a negative magnetoresistance in weak perpendicular fields below 50 K, which can be quenched by increasing temperature. The signature implies the weak localization effect as its origin, which is absent in intrinsic topological insulators, unless a surface state gap is opened. The surface state gap is estimated to be 10 meV by using the theory of the gap-induced weak localization effect. These results indicate that the magnetic proximity effect may open the gap for the topological surface attached to BaM insulating ferrimagnet. This heterostructure may pave the way for the realization of new physical effects as well as the potential applications of spintronics devices. PMID:26891682

  10. Out-of-plane Piezoelectricity and Ferroelectricity in Layered α-In2Se3 Nano-flakes

    KAUST Repository

    Zhou, Yu

    2017-08-25

    Piezoelectric and ferroelectric properties in the two dimensional (2D) limit are highly desired for nanoelectronic, electromechanical, and optoelectronic applications. Here we report the first experimental evidence of out-of-plane piezoelectricity and ferroelectricity in van der Waals layered α-In2Se3 nano-flakes. The non-centrosymmetric R3m symmetry of the α-In2Se3 samples is confirmed by scanning transmission electron microscopy, second-harmonic generation, and Raman spectroscopy measurements. Domains with opposite polarizations are visualized by piezo-response force microscopy. Single-point poling experiments suggest that the polarization is potentially switchable for α-In2Se3 nano-flakes with thicknesses down to ~ 10 nm. The piezotronic effect is demonstrated in two-terminal devices, where the Schottky barrier can be modulated by the strain-induced piezopotential. Our work on polar α-In2Se3, one of the model 2D piezoelectrics and ferroelectrics with simple crystal structures, shows its great potential in electronic and photonic applications.

  11. Effect of steam-flaked corn and soybeans on muscle and intramuscular fatty acid composition in Holstein calves.

    Science.gov (United States)

    Zhang, Y Q; He, D C; Meng, Q X; Wang, D C

    2015-12-01

    This study aimed to evaluate the effects of steam-flaked corn grains and soybeans on muscle fatty acid composition. Thirty Holstein bull calves (21 ± 3 d) were divided into 3 groups according to birth date and BW and were randomly assigned to receive fresh milk and a commercial pelleted starter diet containing extruded corn and soybean (ECS), steam-flaked corn and soybean (SFCS), or ground corn and raw soybean (GCS). The calves were fed the designated diet from 3 to 13 wk of age, after which they were slaughtered. The supraspinatus (CTM), longissimus lumborum (RLM), and spinalis dorsi (ERM) were analyzed to determine the chemical and intramuscular fatty acid composition. The fatty acid composition of muscle and its deposition differed among calves fed different starter feeds. Medium-chain fatty acid levels of the RLM and CTM were greater in GCS-fed calves than in ECS- and SFCS-fed calves ( 0.05). The levels of -3 and -6 fatty acids were similar among the 3 groups; a lower -6:-3 PUFA ratio was observed in GCS-fed calves ( soybean in calf starter feeds had no effect on the chemical composition of the RLM, CTM, or ERM but had a significant effect on the intramuscular fatty acid composition.

  12. Selective separation behavior of graphene flakes in interaction with halide anions in the presence of an external electric field.

    Science.gov (United States)

    Farajpour, E; Sohrabi, B; Beheshtian, J

    2016-03-14

    The adsorption of halide anions in the absence, and presence, of a perpendicularly external electric field on the C54H18 graphene surface has been investigated using M06-2X/6-31G(d,p) density functional theory (DFT). The structural characteristics, charge transfer, electric surface potential (ESP) maps, equilibrium distances between ions and the graphene surface and dipole moments of the ion-graphene complexes were investigated. The optimized structures show that halide anions (F(-) and Br(-)) adsorb on the graphene surface in contrast to the chloride anion that was stabilized on the edge area of the graphene flake. To clarify this unexpected behavior, diffusion of the chloride anion on the graphene surface was analyzed. The observations suggest that the moving of the chloride halide anion between barrier energies on the graphene flake has been facilitated as a result of the applied external electric field. In addition, an effective anion-π interaction between the fluoride anion and the graphene surface in the presence of an electric field holds out the capability of these anion-graphene complexes to design anion-selective nanoscale materials.

  13. Highly flexible and electroforming free resistive switching behavior of tungsten disulfide flakes fabricated through advanced printing technology

    Science.gov (United States)

    Muqeet Rehman, Muhammad; Uddin Siddiqui, Ghayas; Doh, Yang Hoi; Choi, Kyung Hyun

    2017-09-01

    Tungsten disulfide (WS2) is a transition metal dichalcogenide that differs from other 2D materials such as graphene owing to its distinctive semiconducting nature and tunable band gap. In this study, we have reported the structural, electrical, physical, and mechanical properties of exfoliated WS2 flakes and used them as the functional layer of a rewritable bipolar memory device. We demonstrate this concept by sandwiching few-layered WS2 flakes between two silver (Ag) electrodes on a flexible and transparent PET substrate. The entire device fabrication was carried out through all-printing technology such as reverse offset printing for patterning bottom electrodes, electrohydrodynamic (EHD) atomization for depositing functional thin film and EHD patterning for depositing the top electrode respectively. The memory device was further encapsulated with an atomically thin layer of aluminum oxide (Al2O3), deposited through a spatial atmospheric atomic layer deposition system to protect it against a humid environment. Remarkable resistive switching results were obtained, such as nonvolatile bipolar behavior, a high switching ratio (∼103), a long retention time (∼105 s), high endurance (1500 voltage sweeps), a low operating voltage (∼2 V), low current compliance (50 μA), mechanical robustness (1500 cycles) and unique repeatability at ambient conditions. Ag/WS2/Ag-based memory devices offer a new possibility for integration in flexible electronic devices.

  14. Effects of glycerin concentration in steam-flaked corn-based diets with supplemental yellow grease on performance and carcass characteristics of finishing beef steers

    Science.gov (United States)

    Forty-eight individually fed crossbred steers (initial BW = 381 ± 7.61 kg) were used to determine the effects of glycerin (GLY) concentration in steam-flaked corn (SFC)-based diets with added yellow grease on animal performance and carcass characteristics. Glycerin was included at 0, 2.5, 5, and 10...

  15. Influence of maturity of grass silage and flaked corn starch on the production and metabolism of volatile fatty acids in dairy cows

    NARCIS (Netherlands)

    Visser, de H.; Klop, A.; Meulen, van der J.; Vuuren, van A.M.

    1998-01-01

    An experiment employing a Latin square design was used to quantify the effects of two stages of maturity of grass silage (early cut and late cut) and three concentrations of flaked corn starch (0, 2, and 4 kg) on the molar proportion of rumen volatile fatty acids (VFA), the production of rumen VFA,

  16. Non-destructive analysis of flake properties in automotive paints with full-field optical coherence tomography and 3D segmentation.

    Science.gov (United States)

    Zhang, Jinke; Williams, Bryan M; Lawman, Samuel; Atkinson, David; Zhang, Zijian; Shen, Yaochun; Zheng, Yalin

    2017-08-07

    Automotive coating systems are designed to protect vehicle bodies from corrosion and enhance their aesthetic value. The number, size and orientation of small metallic flakes in the base coat of the paint has a significant effect on the appearance of automotive bodies. It is important for quality assurance (QA) to be able to measure the properties of these small flakes, which are approximately 10μm in radius, yet current QA techniques are limited to measuring layer thickness. We design and develop a time-domain (TD) full-field (FF) optical coherence tomography (OCT) system to scan automotive panels volumetrically, non-destructively and without contact. We develop and integrate a segmentation method to automatically distinguish flakes and allow measurement of their properties. We test our integrated system on nine sections of five panels and demonstrate that this integrated approach can characterise small flakes in automotive coating systems in 3D, calculating the number, size and orientation accurately and consistently. This has the potential to significantly impact QA testing in the automotive industry.

  17. Electrodeposition of flake-like Cu{sub 2}O on vertically aligned two-dimensional TiO{sub 2} nanosheet array films for enhanced photoelectrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Lei [School of Physics & Material Science, Anhui University, Hefei 230601 (China); Co-operative Innovation Research Center for Weak Signal-Detecting Materials and Devices Integration, Anhui University, Hefei 230601 (China); Institute of Applied Physics AOA, Hefei 230031 (China); Zhang, Miao; Zhu, Kerong [School of Physics & Material Science, Anhui University, Hefei 230601 (China); Lv, Jianguo [School of Electronic & Information Engineering, Hefei Normal University, Hefei 230601 (China); He, Gang [School of Physics & Material Science, Anhui University, Hefei 230601 (China); Sun, Zhaoqi, E-mail: szq@ahu.edu.cn [School of Physics & Material Science, Anhui University, Hefei 230601 (China)

    2017-01-01

    Highlights: • Flake-like Cu{sub 2}O/TNS with exposed {001} facets constructed p-n heterostructure. • The TNS arrays were used as starting substrates for Cu{sub 2}O growth. • The Cu{sub 2}O/TNS prepared at −0.4 V exhibits the best photoelectrochemical property. - Abstract: A novel Cu{sub 2}O/TNS composite structure of single crystal TiO{sub 2} nanosheet (TNS) arrays decorated with flake-like Cu{sub 2}O were synthesized by a facile hydrothermal reaction followed by the electrodeposition process. The effects of deposition potential on the microstructure, morphology, and optical property of the thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis spectrophotometer. When the deposition potential is higher than −0.4 V, peaks corresponding to Cu appear, meanwhile, flake-like Cu{sub 2}O become agglomerating, and transform into dense Cu{sub 2}O particles. Additionally, photoelectrochemical experiments indicate that the films deposited at −0.4 V show the lowest resistivity and highest exciton separation efficiency. This enhanced photoelectrochemical properties can be explained by synergistic effect of p-type flake-like Cu{sub 2}O and n-type TiO{sub 2} heterojunctions combined with two-dimensional TiO{sub 2} nanosheet with exposed highly reactive {001} facets.

  18. Hydrothermal synthesis of graphene flake embedded nanosheet-like molybdenum sulfide hybrids as counter electrode catalysts for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jeng-Yu, E-mail: jylin@ttu.edu.tw [Department of Chemical Engineering, Tatung University, No. 40, Sec. 3, ChungShan North Rd., Taipei City 104, Taiwan (China); Yue, Gentian [Department of Chemical Engineering, Tatung University, No. 40, Sec. 3, ChungShan North Rd., Taipei City 104, Taiwan (China); Institute of Materials Physical Chemistry, Huaqiao University, Quanzhou, Fujian 362021 (China); Tai, Sheng-Yen [Department of Chemical Engineering, Tatung University, No. 40, Sec. 3, ChungShan North Rd., Taipei City 104, Taiwan (China); Xiao, Yaoming [Department of Chemical Engineering, Tatung University, No. 40, Sec. 3, ChungShan North Rd., Taipei City 104, Taiwan (China); Institute of Molecular Science, Key Laboratory of Chemical Biology and Molecular Engineering of Education Ministry, Shanxi University, Taiyuan 030006 (China); Cheng, Ho-Ming; Wang, Fu-Ming [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei City 106, Taiwan (China); Wu, Jihuai [Institute of Materials Physical Chemistry, Huaqiao University, Quanzhou, Fujian 362021 (China)

    2013-12-16

    In this study, graphene flake (GF) was successfully embedded into a nanosheet-like molybdenum sulfide (MoS{sub 2}) matrix via an in situ hydrothermal route, and the resultant hybrid was employed as a counter electrode (CE) for Pt-free dye-sensitized solar cells (DSCs). It is confirmed from scanning electron microscopy, X-ray diffraction, Raman spectroscopy and transmission electron microscopy that GFs are successfully incorporated in the nanosheet-like MoS{sub 2} matrix and thus result in its surface evolution. The extensive electrochemical analyses reveal that the remarkably enhanced electrocatalytic activity can be demonstrated when GFs are incorporated in the MoS{sub 2} matrix. After the optimization, the nanosheet-like MoS{sub 2}/GF hybrid with 1.5 wt.% GF shows the best electrocatalytic activity. The DSC assembled with the novel nanosheet-like MoS{sub 2}/GF hybrid CE exhibits a high photovoltaic conversion efficiency of 6.07% under standard illumination, up to 95% of the level obtained using conventional Pt CE (6.41%). - Highlights: • Nanosheet-like MoS{sub 2}/graphene flake hybrid was prepared by a hydrothermal route. • The surface morphology of MoS{sub 2} changed with the incorporation of graphene flake. • The hybrid with 1.5 wt.% graphene flake showed the superior catalytic activity. • The cell efficiency of DSC with the hybrid CE reached 95% of that using Pt CE.

  19. Matrix interference-free method for the analysis of small molecules by using negative ion laser desorption/ionization on graphene flakes.

    Science.gov (United States)

    Lu, Minghua; Lai, Yongquan; Chen, Guonan; Cai, Zongwei

    2011-04-15

    This work presents a new approach for the analysis of small molecules with direct negative ion laser desorption/ionization (LDI) on graphene flakes. A series of matrix interference-free mass spectra were obtained for the analysis of a wide range of small molecules including peptides, amino acids, fatty acids, as well as nucleosides and nucleotides. The mixture of analytes and graphene flakes suspension were directly pipetted onto a sample plate for LDI-time-of-flight mass spectrometry (TOFMS) analysis. Deprotonated monomeric species [M-H](-) ions were homogeneously obtained on uniform graphene flakes film when negative ion mode was applied. In positive ion mode, the analytes were detected in form of multiple adduct ions such as sodium adduct [M+Na](+), potassium adduct [M+K](+), double sodium adduct [M+2Na-H](+), double potassium adduct [M+2K-H](+), as well as sodium and potassium mixed adduct [M+Na+K-H](+). Better sensitivity and reproducibility were achieved in negative ion mode compared to positive ion mode. It is believed that the new method of matrix interference-free negative ion LDI on graphene flakes may be expanded for LDI-MS analysis of various small molecules. © 2011 American Chemical Society

  20. Direct growth of graphene on in situ epitaxial hexagonal boron nitride flakes by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zuo, Zheng; Liu, Jianlin, E-mail: jianlin@ece.ucr.edu [Quantum Structures Laboratory, Department of Electrical and Computer Engineering, University of California, Riverside, California 92521 (United States)

    2015-11-23

    Hexagonal boron nitride (h-BN) single-crystal domains were grown on cobalt (Co) substrates at a substrate temperature of 850–900 °C using plasma-assisted molecular beam epitaxy. Three-point star shape h-BN domains were observed by scanning electron microscopy, and confirmed by Raman and X-ray photoelectron spectroscopy. The h-BN on Co template was used for in situ growth of multilayer graphene, leading to an h-BN/graphene heterostructure. Carbon atoms preferentially nucleate on Co substrate and edges of h-BN and then grow laterally to form continuous graphene. Further introduction of carbon atoms results in layer-by-layer growth of graphene on graphene and lateral growth of graphene on h-BN until it may cover entire h-BN flakes.

  1. Constitutive model for flake graphite cast iron automotive brake discs: from macroscopic multiscale models to a 1D rheological description

    Science.gov (United States)

    Augustins, L.; Billardon, R.; Hild, F.

    2016-07-01

    One of the critical points of the thermomechanical fatigue design process is the correct description of the cyclic behavior of the material. This work focuses on the material of automotive brake discs, namely flake graphite cast iron. The specificity of this material is its asymmetric behavior under tensile and compressive loadings, which is due to the shape of graphite that acts as small cracks. Multiscale models inspired from the literature are first presented. They lead to a good description of the material behavior under cyclic loadings. An elastoviscoplastic constitutive model is then proposed in a one-dimensional setting in order to accurately describe cyclic tests from room temperature up to {600^{circ}{C}}.

  2. Constitutive model for flake graphite cast iron automotive brake discs: induced anisotropic damage model under complex loadings

    Science.gov (United States)

    Augustins, L.; Billardon, R.; Hild, F.

    2016-09-01

    The present paper details an elasto-viscoplastic constitutive model for automotive brake discs made of flake graphite cast iron. In a companion paper (Augustins et al. in Contin Mech Thermodyn, 2015), the authors proposed a one-dimensional setting appropriate for representing the complex behavior of the material (i.e., asymmetry between tensile and compressive loadings) under anisothermal conditions. The generalization of this 1D model to 3D cases on a volume element and the associated challenges are addressed. A direct transposition is not possible, and an alternative solution without unilateral conditions is first proposed. Induced anisotropic damage and associated constitutive laws are then introduced. The transition from the volume element to the real structure and the numerical implementation require a specific basis change. Brake disc simulations with this constitutive model show that unilateral conditions are needed for the friction bands. A damage deactivation procedure is therefore defined.

  3. 21 CFR 73.1350 - Mica-based pearlescent pigments.

    Science.gov (United States)

    2010-04-01

    ... heating to produce one of the following combinations: Titanium dioxide on mica; iron oxide on mica; titanium dioxide and iron oxide on mica. Mica used to manufacture the color additive shall conform in... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Mica-based pearlescent pigments. 73.1350 Section...

  4. Flake structured SnSbCo/MCMB/C composite as high performance anodes for lithium ion battery

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiaoqiu [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006 (China); Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Guangdong Engineering Technology Research Center of Low Carbon and Advanced Energy Materials, Guangzhou 510631 (China); Ru, Qiang, E-mail: rq7702@yeah.net [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006 (China); Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Guangdong Engineering Technology Research Center of Low Carbon and Advanced Energy Materials, Guangzhou 510631 (China); Zhao, Doudou; Mo, Yudi; Hu, Shejun [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006 (China); Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Guangdong Engineering Technology Research Center of Low Carbon and Advanced Energy Materials, Guangzhou 510631 (China)

    2015-10-15

    SnSbCo/MCMB/C composite with flake structure were prepared by stepwise synthesis method. Firstly, SnSbCo nanoparticles were fabricated by co-precipitation, and then nanosized SnSbCo alloy were embedded in mesocarbon microbeads (MCMB) by ball-milling to synthesize primitive SnSbCo/MCMB hybrids, followed by carbonization of phenolic resin to produce an outer layer of carbon coating. The crystal structure, morphology and electrochemical properties of the SnSbCo/MCMB/C composite were evaluated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and galvanostatical cycling tests. Compared with bare SnSbCo alloy and SnSbCo/MCMB hybrids, the efficiently enhanced electrochemical performance of SnSbCo/MCMB/C composite were mainly ascribed to the improved electron conductivity and volume buffering effect provided by the amorphous carbon coating. The resultant SnSbCo/MCMB/C composite delivered an initial discharge capacity of 848 mAh g{sup −1} under 100 mA g{sup −1}, with a good capacity retention of 85.6% after 70 cycles. The composite also exhibited excellent rate capability of 603 mAh g{sup −1} and 405 mAh g{sup −1} at the current density of 200 mA g{sup −1} and 1000 mA g{sup −1}, respectively. - Highlights: • Flake structured SnSbCo/MCMB/C composite have been prepared by stepwise synthesis method. • SnSbCo/MCMB/C composite show good cycle performance and rate capability. • Using both MCMB and phenolic resin as dual carbon sources.

  5. Facile preparation and enhanced microwave absorption properties of flake carbonyl iron/Fe{sub 3}O{sub 4} composite

    Energy Technology Data Exchange (ETDEWEB)

    Min, Dandan, E-mail: mdd4776@126.com; Zhou, Wancheng; Luo, Fa; Zhu, Dongmei

    2017-08-01

    Highlights: • Flake carbonyl iron/Fe{sub 3}O{sub 4} composites were prepared by surface oxidation technique. • Lower permittivity and modest permeability was obtained by the FCI/Fe{sub 3}O{sub 4} composites. • Enhanced absorption efficiency and broader absorption band were obtained. - Abstract: Flake carbonyl iron/Fe{sub 3}O{sub 4} (FCI/Fe{sub 3}O{sub 4}) composites with enhanced microwave absorption properties were prepared by a direct and flexible surface oxidation technique. The phase structures, morphology, magnetic properties, frequency-dependent electromagnetic and microwave absorption properties of the composites were investigated. The measurement results showed that lower permittivity as well as modest permeability was obtained by the FCI/Fe{sub 3}O{sub 4} composites. The calculated microwave absorption properties indicated that enhanced absorption efficiency and broader absorption band were obtained by the FCI/Fe{sub 3}O{sub 4} composite comparing with the FCI composite. The absorption frequency range with reflection loss (RL) below −5 dB of FCI/Fe{sub 3}O{sub 4} composites at reaction time of 90 min at thickness of 1.5 mm is 13.3 GHz from 4.7 to 18 GHz, while the bandwidth of the FCI composite is only 5.9 GHz from 2.6 to 8.5 GHz at the same thickness. Thus, such absorbers could act as effective and wide broadband microwave absorbers in the GHz range.

  6. Resistance to impact of cross-linked denture base biopolymer materials: effect of relining, glass flakes reinforcement and cyclic loading.

    Science.gov (United States)

    da Cruz Perez, Luciano Elias; Lucia Machado, Ana; Eduardo Vergani, Carlos; Andrade Zamperini, Camila; Cláudia Pavarina, Ana; Vicente Canevarolo, Sebastião

    2014-09-01

    The effect of reinforcement and cyclic loading on the resistance to impact (RI) of denture base biopolymer materials was evaluated using Charpy (C) and falling-weight (FW) impact tests. Bar-shaped (60×6×2mm(3)) and denture-shaped specimens (2mm) for the C and FD tests, respectively, were prepared with Lucitone 550 (L) and Vipi Wave (V) and relined (2mm) using the same material or the autopolymerizing relining resins Tokuyama Rebase II (T) and Ufi Gel Hard (U). Bulk specimens (60×6×4mm(3)) of all materials (L, V, T and U) were also prepared and tested. To evaluate the effect of reinforcement, glass flakes were added to the powder of the relining resins T and U (5% by weight). Half of bar-shaped (n=320) and half of the denture-shaped specimens (n=480) were subjected to cyclic loading (10,000 cycles) before the impact tests. Data were analyzed by one-way ANOVAs (α=0.05) and revealed that the RI of L and V were comparable and higher than those of U and T. Compared to L and V, the RI was increased by relining with T and decreased by relining with U. When relining was made using the same material (L and V) the RI was maintained. Flexural cyclic loading and the incorporation of glass flakes into the resins T and U did not cause any significant alteration in the RI. A high correlation between results from C and FW tests was observed (r=0.8854). Relining may exert effects on the RI of L and V denture base resins, which vary according to the relining material used. The high correlation between C and FW, suggests that the Charpy test, using bar-shaped specimens, can be a simple and reliable method for evaluating factors that may influence the RI of denture base polymers. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction.

    Science.gov (United States)

    Flyunt, Roman; Knolle, Wolfgang; Kahnt, Axel; Halbig, Christian E; Lotnyk, Andriy; Häupl, Tilmann; Prager, Andrea; Eigler, Siegfried; Abel, Bernd

    2016-04-14

    This work highlights a surprisingly simple and kinetically controlled highly efficient indirect method for the production of high quality reduced graphene oxide (rGO) flakes via UV irradiation of aqueous dispersions of graphene oxide (GO), in which the GO is not excited directly. While the direct photoexcitation of aqueous GO (when GO is the only light-absorbing component) takes several hours of reaction time at ambient temperature (4 h) leading only to a partial GO reduction, the addition of small amounts of isopropanol and acetone (2% and 1%) leads to a dramatically shortened reaction time by more than two orders of magnitude (2 min) and a very efficient and soft reduction of graphene oxide. This method avoids the formation of non-volatile species and in turn contamination of the produced rGO and it is based on the highly efficient generation of reducing carbon centered isopropanol radicals via the reaction of triplet acetone with isopropanol. While the direct photolysis of GO dispersions easily leads to degradation of the carbon lattice of GO and thus to a relatively low electric conductivity of the films of flakes, our indirect photoreduction of GO instead largely avoids the formation of defects, keeping the carbon lattice intact. Mechanisms of the direct and indirect photoreduction of GO have been elucidated and compared. Raman spectroscopy, XPS and conductivity measurements prove the efficiency of the indirect photoreduction in comparison with the state-of-the-art reduction method for GO (hydriodic acid/trifluoroacetic acid). The rapid reduction times and water solvent containing only small amounts of isopropanol and acetone may allow easy process up-scaling for technical applications and low-energy consumption.

  8. Possible origin of life between mica sheets: does life imitate mica?

    Science.gov (United States)

    Hansma, Helen Greenwood

    2013-01-01

    The mica hypothesis for the origin of life proposes that life originated between the sheets of muscovite mica. This paper elaborates on two ways that life resembles what might have originated between mica sheets. First, enzymes: The configurations and dynamics of enzymes, with their substrates, cofactors, and sometimes transition metal ions, often resemble mica sheets, with their open-and-shut motions, acting on small molecules between them, sometimes assisted by transition metal ions. Second, organisms: Mica world had the potential to be a community or ecosystem of prebiotic organisms in a way unlike other models for the origin of life.

  9. 21 CFR 73.2496 - Mica.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Mica. 73.2496 Section 73.2496 Food and Drugs FOOD...) Uses and restrictions. Mica is safe for use in coloring cosmetics generally, including cosmetics... color additive and any mixture prepared therefrom intended solely or in part for coloring purposes shall...

  10. INVESTIGATION OF THE INFLUENCE OF PROCESS CONDITIONS AND PROPERTIES OF THE MEDIUM ON THE KINETICS OF THE SWELLING OF GREEN BUCKWHEAT FLAKES

    Directory of Open Access Journals (Sweden)

    L. E. Glagoleva

    2015-01-01

    Full Text Available The chemical composition of green buckwheat flakes, especially swelling of the flakes at different process conditions. The process of swelling depends on the nature of the high molecular compound, temperature, composition and pH of the absorbing liquid and can flow unrestricted and restricted. With a limited degree of swelling of the swelling reaches the limit and is no longer changing. As a result of limited swelling formed jelly. If the limit value of the degree of swelling in contact with a further high-molecular compound and a solvent is reduced, there is an unlimited swelling. In this case, the swelling of the first stage of dissolution. Unlimited swell polymers with weak intermolecular bonds. Character of the process has an impact on quality indicators and semi-finished products. The resulting kinetic curves indicate limited swelling main components of green buckwheat flakes in all test solutions. In the alkaline pH range, partial dissolution occurred certain components, but the general nature of the process is not appreciably affected. The paper identified the maximum degree and the rate constant swelling green buckwheat flakes in solutions with different pH. To quantify the extent and limit of the rate constant swelling high-molecular compound at different process conditions (type of solvent, temperature, pH determine the degree of swelling at specified intervals and construct the kinetic curve swelling. The acidity of the medium affects mainly on swelling polyampholytes, which are the proteins that make up most of the swell components flakes green buckwheat. Depending on the pH of the protein macromolecule adopt different conformations. The minimum degree of swelling of the protein corresponds to its isoelectric point at which stipulates equality of positive and negative charges in the macromolecule and it rolled into a ball or globule, which hinders the penetration of solvent molecules into the matrix of high-molecular compound

  11. Field measurement of erosion rates: time-lapse monitoring of rapid stone flaking at Howden Minster, UK

    Science.gov (United States)

    Doehne, E.; Pinchin, S.

    2012-04-01

    The use of a solar-powered, field time-lapse camera and environmental monitoring system enabled measurements of the pattern and rate of loss of stone from the surface of Howden Minster, an abandoned monastery in Yorkshire dating to 1380 AD. Acquiring a photograph every 1-3 hours allowed the stone damage to be correlated with local environmental conditions. Image comparison techniques borrowed from observational astronomy, such as blink comparison, were used to determine what elements had changed from image to image. Results indicate that loss is episodic rather than continuous and in several cases is related to specific environmental conditions, such as condensation/dew formation or high winds. Damage was found also to be synchronous, with surface change (flaking, granular disintegration, and loss of flakes) occurring at the same time on different stone blocks. Crystallization pressure from magnesium sulfate phase transitions appear to be the main cause of the loss of stone surfaces. Significant variation in surface loss rates was observed and appears to be related to variations in salt concentration. An examination of stone texture by ESEM/EDS revealed signification variations and suggests that salt concentrations are controlled in part by stone micromorphology. Quantitative data on rates of surface loss are not available from most monuments. Time-lapse methods permit the relatively inexpensive acquisition of this type of data, which is needed to aid conservation decision-making and the evaluation of interventions. Such tools should also prove useful to geomorphologists studying honeycomb weathering, the moving rocks on Death Valley's Racetrack Playa, and other phenomena that are otherwise difficult to study. Context: The rapid deterioration of magnesian limestone structures in the north of England has been a serious problem for more than one hundred years. While air quality in England has improved during this period, the rate of stone loss in these carved stone

  12. Fresh steam-flaked corn in cattle feedlots is an important site for fecal coliform contamination by house flies.

    Science.gov (United States)

    Ghosh, Anuradha; Zurek, Ludek

    2015-03-01

    House flies are a common pest at food animal facilities, including cattle feedlots. Previously, house flies were shown to play an important role in the ecology of Escherichia coli O157:H7; house flies in cattle feedlots carried this zoonotic pathogen and were able to contaminate cattle through direct contact and/or by contamination of drinking water and feed. Because house flies aggregate in large numbers on fresh ( # 6 h) steam-flaked corn (FSFC) used in cattle feed, the aim of this study was to assess FSFC in a cattle feedlot as a potentially important site of fecal coliform contamination by house flies. House flies and FSFC samples were collected, homogenized, and processed for culturing of fecal coliforms on membrane fecal coliform agar. Selected isolates were identified by 16S rRNA gene sequencing, and representative isolates from each phylogenetic group were genotyped by pulsed-field gel electrophoresis. Fecal coliforms were undetectable in FSFC shortly (0 h) after flaking; however, in summer, after 4 to 6 h, the concentrations of fecal coliforms ranged from 1.9 × 10(3) to 3.7 × 10(4) CFU/g FSFC (mean, 1.1 ± 3.0 × 10(4) CFU/g). House flies from FSFC carried between 7.6 × 10(2) and 4.1 × 10(6) CFU of fecal coliforms per fly (mean, 6.0 ± 2.3 × 10(5) CFU per fly). Fecal coliforms were represented by E. coli (85.1%), Klebsiella spp. (10.6%), and Citrobacter spp. (4.3%). Pulsed-field gel electrophoresis demonstrated clonal matches of E. coli and Klebsiella spp. between house flies and FSFC. In contrast, in winter and in the absence of house flies, the contamination of corn by fecal coliforms was significantly (∼10-fold) lower. These results indicate that FSFC is an important site for bacterial contamination by flies and possible exchange of E. coli and other bacteria among house flies. Further research is needed to evaluate the potential use of screens or blowers to limit the access of house flies to FSFC and therefore their effectiveness in preventing

  13. Controllable synthesis of flake-like Al-doped ZnO nanostructures and its application in inverted organic solar cells

    Directory of Open Access Journals (Sweden)

    Fan Xi

    2011-01-01

    Full Text Available Abstract Flake-like Al-doped ZnO (AZO nanostructures including dense AZO nanorods were obtained via a low-temperature (100°C hydrothermal process. By doping and varying Al concentrations, the electrical conductivity (σ and morphology of the AZO nanostructures can be readily controlled. The effect of σ and morphology of the AZO nanostructures on the performance of the inverted organic solar cells (IOSCs was studied. It presents that the optimized power conversion efficiency of the AZO-based IOSCs is improved by approximately 58.7% compared with that of un-doped ZnO-based IOSCs. This is attributed to that the flake-like AZO nanostructures of high σ and tunable morphology not only provide a high-conduction pathway to facilitate electron transport but also lead to a large interfacial area for exciton dissociation and charge collection by electrodes.

  14. Microwave properties of sphere-, flake-, and disc-shaped BaFe12O19 nanoparticle inks for high-frequency applications on printed electronics

    Science.gov (United States)

    Myllymäki, S.; Maček Kržmanc, M.; Sloma, M.; Juuti, J.; Nelo, M.; Teirikangas, M.; Jakubowska, M.; Suvorov, D.; Jantunen, H.

    2016-12-01

    Spherical (diameter 50-200 nm), flake- (diameter 40-200 nm), and disc-shaped (diameter 10-20 nm) BaFe12O19 nanoparticles were synthesized with a wet chemical method, and their permittivity, electric loss tangent, permeability, and magnetic loss tangent were measured in the 0.045-10 GHz range. The materials were prepared using a solution of 12% PMMA resin in a butyldiglycol solvent for 10-50 wt% filling content. Microstrip transmission-line perturbation was used to measure complex permeability and the split post dielectric resonator method was employed to measure dielectric properties. The frequency dependence of the permeability and permittivity spectra of the composites was affected by their shape and filling fraction. The composites made with spherical particles had higher permeability values (1.4-1.75) at 1 GHz than the composites made with flake (1.25-1.6) or disc particles (1.1-1.3), but the spherical particles caused more losses. The flake particle composite provided permeability and magnetic loss characteristics at both 1 GHz and 7 GHz superior to those of the sphere particle composite in low-loss RF applications. The magnetic loss tangent of PMMA/BaFe12O19 was 0.2-0.3 at 1 GHz, being lower than that of state-of-the-art PANI/BaFe12O19 composites. The sphere composite inks showed permeability values less than 1 at 1-4 GHz ferromagnetic resonance (FMR); they could be used as a tunable material in microwave applications. The sphere and flake composite inks also had sufficient printing quality for the screen-printing fabrication method.

  15. Studying physisorption processes and molecular friction of cycloparaphenylene molecules on graphene nano-sized flakes: role of π⋯π and CH⋯π interactions

    OpenAIRE

    Pérez-Guardiola, Andrés; Pérez-Jiménez, Ángel J.; Sancho-Garcia, Juan-Carlos

    2017-01-01

    We theoretically study, by means of dispersion-corrected and cost-effective methods, the strength of non-covalent interactions between cyclic organic nanorings (i.e. [8]cycloparaphenylene molecule) and nano-sized (e.g. C96H24) graphene flakes acting as substrates. Both CH⋯π and π⋯π driven interactions are investigated, according to the relative orientation between the two weakly interacting monomers, whose potential energy profiles are accurately calculated in both cases. These configurations...

  16. breve panorámica

    Directory of Open Access Journals (Sweden)

    Sandra M. Camelo Roa

    2005-01-01

    Full Text Available Desde los terrenos de la psicoinmunología, la presente revisión se propone una mirada panorámica a sus principales postulados, líneas de investigación, resultados y perspectivas. Para ello, inicialmente se abordaron algunos aspectos históricos de la relación entre la vida psíquica y la salud; posteriormente, se revisaron aspectos como la fisiología del sistema inmune especificando los tipos de inmunidad adquirida e inmunidad natural. Temas como las interacciones entre el sistema inmune y cerebro fueron revisados desde la evidencia experimental y resumidos en cuatro grupos: condicionamiento de la respuesta inmune, lesiones cerebrales, estrés e inmunidad y emociones e inmunidad. Finalmente, se contemplaron algunos métodos para el estudio del sistema inmune como los ensayos in vitro, citometría de flujo y ensayos in vivo. Como observaciones finales, toda la literatura sugiere que existe relación entre el sistema inmune y diversos estados psíquicos. Pero aún surgen preguntas de esta indiscutible relación sin tener una respuesta satisfactoria.

  17. Magnetoresistance studies of MeV ranged {sup 1}H{sup +} and {sup 12}C{sup +} ion irradiated HOPG flakes

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Neeraj; Bose, Saurabh K.; Choudhary, Shyam K.; Pandey, Himanshu; Sarkar, Mihir; Banerji, Nobin; Gupta, Anjan K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Verma, Harish C., E-mail: hcverma@iitk.ac.in [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

    2012-11-15

    2 MeV protons and 1 MeV carbon ions are bombarded on highly oriented pyrolytic graphite (HOPG) samples and their electronic transport measurements are carried out in the presence of magnetic field. The Magneto-Resistance (MR) measurements show measurable hysteresis in the resistance value after ion beam irradiation for the in-plane magnetic field direction as well as for the out-of-plane field direction. The MR depends on the thickness of the flake and the method of its separation from the bulk HOPG. The results substantiate that the ferromagnetic coupling between the magnetic moments at the vacancy defect sites in HOPG sensitively depends on the average defect separation. The average defect separation range of 1.7-0.5 nm allows only a part of the 40 {mu}m thick proton beam irradiated sample to go for ferromagnetic ordering. Similar conclusions are drawn from carbon ion irradiated HOPG flake. The irradiation increases the resistance of the flake as well. - Highlights: Black-Right-Pointing-Pointer Magnetoresistance (MR) studies of MeV ranged H and C ion irradiated Graphite. Black-Right-Pointing-Pointer Hysteresis in the MR data and lowering of MR post ion irradiation. Black-Right-Pointing-Pointer Large MR value in the case of thinner sample for B field along the c axis. Black-Right-Pointing-Pointer MR results substantiate ferromagnetic coupling between ion induced defects. Black-Right-Pointing-Pointer The defect separation range has a preferred window for ferromagnetic coupling.

  18. Tuning the LUMO level of organic photovoltaic solar cells by conjugately fusing graphene flake: A DFT-B3LYP study

    Science.gov (United States)

    Ganji, M. Darvish; Tajbakhsh, M.; Kariminasab, M.; Alinezhad, H.

    2016-07-01

    The efficiency of polymer solar cells can be essentially enhanced by improving the performance of electron acceptor materials especially by increasing its lowest unoccupied molecular orbital (LUMO) level. To this aim, the electronic properties of an extremely π-extended system, graphene flake and functionalized graphene flake with phenyl-C-butyric methyl ester (PCBM) group, were investigated and compared with those of C60 ones. Several properties of phenyl-C61-butyric methyl ester ([C60]PCBM) derivatives have been calculated and compared against the experimental and other theoretical results. All geometrical and electronic structures calculations were carried out by using the density functional theory (DFT) method at the B3LYP level of theory. The results show that the phenyl ring of [C60]PCBM was substituted with the methoxy groups to increase the LUMO level of the respective system which is in agreement with other studies. We found that graphene flake functionalized by methoxy-PCBM group offer significant increase in the value of the LUMO energy level in comparison with C60 counterpart. Furthermore, the electrophilicity of this compound is lower than that of the other counterparts, which results in higher open circuit voltage (Voc) value in the photovoltaic device. These findings could provide fundamental insights in improving the Voc value as well as raising the LUMO levels of electron acceptor materials and may also serve as an alternative strategy to increase open circuit voltage in polymer solar cells.

  19. Fast sintering of silver nanoparticle and flake layers by infrared module assistance in large area roll-to-roll gravure printing system

    Science.gov (United States)

    Park, Janghoon; Kang, Hyi Jae; Shin, Kee-Hyun; Kang, Hyunkyoo

    2016-01-01

    We present fast sintering for silver (Ag) nanoparticle (NP) and flake layers printed using roll-to-roll (R2R) gravure printing. An infrared (IR) sintering module was applied to an R2R system to shorten the sintering duration of an R2R gravure-printed Ag layer. IR sintering of the conductive layer was improved by optimising the process condition. After printing of the Ag NP and Ag flake layers, additional IR sintering was performed in the R2R system. The lowest sheet resistance obtained in the Ag NP layer was 0.294 Ω/□, the distance between the substrate and lamp was 50-mm long, the IR lamp power was 500 W, and the sintering time was 5.4 s. The fastest sintering of 0.34 Ω/□ was achieved with 50-mm distance, 1,000-W IR lamp power, and 1.08-s sintering time. In the Ag flake layer, the lowest sheet resistance obtained was 0.288 Ω/□ with a 20-mm distance, 1,000-W IR lamp power, and 10.8-s sintering time. Meanwhile, the fastest sintering was obtained with a 3.83 Ω/□ sheet resistance, 20-mm distance, 1000-W IR lamp, and 1.08-s sintering time. Thus, the IR sintering module can easily be employed in an R2R system to obtain excellent layer sheet resistance. PMID:27713469

  20. Mesoporous MnCo2O4 with a flake-like structure as advanced electrode materials for lithium-ion batteries and supercapacitors.

    Science.gov (United States)

    Mondal, Anjon Kumar; Su, Dawei; Chen, Shuangqiang; Ung, Alison; Kim, Hyun-Soo; Wang, Guoxiu

    2015-01-19

    A mesoporous flake-like manganese-cobalt composite oxide (MnCo2O4) is synthesized successfully through the hydrothermal method. The crystalline phase and morphology of the materials are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller methods. The flake-like MnCo2O4 is evaluated as the anode material for lithium-ion batteries. Owing to its mesoporous nature, it exhibits a high reversible capacity of 1066 mA h g(-1), good rate capability, and superior cycling stability. As an electrode material for supercapacitors, the flake-like MnCo2O4 also demonstrates a high supercapacitance of 1487 F g(-1) at a current density of 1 A g(-1), and an exceptional cycling performance over 2000 charge/discharge cycles. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Lateral assembly of oxidized graphene flakes into large-scale transparent conductive thin films with a three-dimensional surfactant 4-sulfocalix[4]arene.

    Science.gov (United States)

    Sundramoorthy, Ashok K; Wang, Yilei; Wang, Jing; Che, Jianfei; Thong, Ya Xuan; Lu, Albert Chee W; Chan-Park, Mary B

    2015-06-04

    Graphene is a promising candidate material for transparent conductive films because of its excellent conductivity and one-carbon-atom thickness. Graphene oxide flakes prepared by Hummers method are typically several microns in size and must be pieced together in order to create macroscopic films. We report a macro-scale thin film fabrication method which employs a three-dimensional (3-D) surfactant, 4-sulfocalix[4]arene (SCX), as a lateral aggregating agent. After electrochemical exfoliation, the partially oxidized graphene (oGr) flakes are dispersed with SCX. The SCX forms micelles, which adsorb on the oGr flakes to enhance their dispersion, also promote aggregation into large-scale thin films under vacuum filtration. A thin oGr/SCX film can be shaved off from the aggregated oGr/SCX cake by immersing the cake in water. The oGr/SCX thin-film floating on the water can be subsequently lifted from the water surface with a substrate. The reduced oGr (red-oGr) films can be as thin as 10-20 nm with a transparency of >90% and sheet resistance of 890 ± 47 kΩ/sq. This method of electrochemical exfoliation followed by SCX-assisted suspension and hydrazine reduction, avoids using large amounts of strong acid (unlike Hummers method), is relatively simple and can easily form a large scale conductive and transparent film from oGr/SCX suspension.

  2. Facile synthesis of flake-like TiO2/C nano-composites for photocatalytic H2 evolution under visible-light irradiation

    Science.gov (United States)

    Yan, Baolin; Zhou, Juan; Liang, Xiaoyu; Song, Kainan; Su, Xintai

    2017-01-01

    The production of H2 by photocatalytic water splitting has become a promising approach for clean, economical, and renewable evolution of H2 by using solar energy. In spite of tremendous efforts, the present challenge for materials scientists is to build a highly active photocatalytic system with high efficiency and low cost. Here we report a facile method for the preparation of TiO2/C nano-flakes, which was used as an efficient visible-light photocatalyst for H2 evolution. This composite material was prepared by using a phase-transfer strategy combined with salt-template calcination treatment. The results showed that anatase TiO2 nanoparticles with the diameter of ∼10 nm were uniformly dispersed on the carbon nano-flakes. In addition, the samples prepared at 600 °C (denoted as T600) endowed a larger surface area of 196 m2 g-1 and higher light absorption, resulting in enhanced photocatalytic activity. Further, the T600 product reached a high H2 production rate of 57.2 μmol h-1 under visible-light irradiation. This unusual photocatalytic activity arose from the positive synergetic effect between the TiO2 and carbon in this hybrid catalyst. This work highlights the potential of TiO2/C nano-flakes in the field of photocatalytic H2 evolution under visible-light irradiation.

  3. Simultaneous reduction and adsorption for immobilization of uranium from aqueous solution by nano-flake Fe-SC

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Lingjun, E-mail: kongl_jun@163.com [School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of radioactive contamination control and resources, Guangzhou University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275 (China); Zhu, Yuting; Wang, Min; Li, Zhixuan; Tan, Zhicong; Xu, Ruibin; Tang, Hongmei; Chang, Xiangyang [School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of radioactive contamination control and resources, Guangzhou University, Guangzhou, 510275 (China); Xiong, Ya [Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275 (China); Chen, Diyun, E-mail: cdy@gzhu.edu.cn [School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of radioactive contamination control and resources, Guangzhou University, Guangzhou, 510275 (China)

    2016-12-15

    Uranium containing radioactive wastewater is seriously hazardous to the natural environment if it is being discharged directly. Herein, nano-flake like Fe loaded sludge carbon (Fe-SC) is synthesized by carbothermal process from Fe-rich sludge waste and applied in the immobilization of uranium in aqueous. Batch isotherm and kinetic adsorption experiments are adopted to investigate the adsorption behavior of Fe-SC to uranium in aqueous. XPS analyses were conducted to evaluate the immobilized mechanism. It was found that the carbonized temperature played significant role in the characteristics and immobilization ability of the resulted Fe-SC. The Fe-SC-800 carbonized at 800 °C takes more advantageous ability in immobilization of uranium from aqueous than the commercial available AC and powder zero valent iron. The adsorption behavior could be fitted well with the Langmuir isotherm adsorption model and pseudo-second order model. The equilibrium adsorption amount and rate for Fe-SC-800 is high to 148.99 mg g{sup -1} and 0.015 g mg{sup -1} min{sup -1}, respectively. Both reductive precipitation and physical adsorption are the main mechanisms of immobilization of uranium from aqueous by Fe-SC-800.

  4. Production of biofunctionalized MoS2 flakes with rationally modified lysozyme: a biocompatible 2D hybrid material

    Science.gov (United States)

    Siepi, Marialuisa; Morales-Narváez, Eden; Domingo, Neus; Monti, Daria Maria; Notomista, Eugenio; Merkoçi, Arben

    2017-09-01

    Bioapplications of 2D materials embrace demanding features in terms of environmental impact, toxicity and biocompatibility. Here we report on the use of a rationally modified lysozyme to assist the exfoliation of MoS2 bulk crystals suspended in water through ultrasonic exfoliation. The design of the proposed lysozyme derivative provides this exfoliated 2D-materail with both, hydrophobic groups that interact with the surface of MoS2 and hydrophilic groups exposed to the aqueous medium, which hinders its re-aggregation. This approach, clarified also by molecular docking studies, leads to a stable material (ζ-potential, 27  ±  1 mV) with a yield of up to 430 µg ml-1. The bio-hybrid material was characterized in terms of number of layers and optical properties according to different slots separated by diverse centrifugal forces. Furthermore the obtained material was proved to be biocompatible using human normal keratinocytes and human cancer epithelial cells, whereas the method was demonstrated to be applicable to produce other 2D materials such as graphene. This approach is appealing for the advantageous production of high quality MoS2 flakes and their application in biomedicine and biosensing. Moreover, this method can be applied to different starting materials, making the denatured lysozyme a promising bio-tool for surface functionalization of 2D materials.

  5. Simultaneous reduction and adsorption for immobilization of uranium from aqueous solution by nano-flake Fe-SC.

    Science.gov (United States)

    Kong, Lingjun; Zhu, Yuting; Wang, Min; Li, Zhixuan; Tan, Zhicong; Xu, Ruibin; Tang, Hongmei; Chang, Xiangyang; Xiong, Ya; Chen, Diyun

    2016-12-15

    Uranium containing radioactive wastewater is seriously hazardous to the natural environment if it is being discharged directly. Herein, nano-flake like Fe loaded sludge carbon (Fe-SC) is synthesized by carbothermal process from Fe-rich sludge waste and applied in the immobilization of uranium in aqueous. Batch isotherm and kinetic adsorption experiments are adopted to investigate the adsorption behavior of Fe-SC to uranium in aqueous. XPS analyses were conducted to evaluate the immobilized mechanism. It was found that the carbonized temperature played significant role in the characteristics and immobilization ability of the resulted Fe-SC. The Fe-SC-800 carbonized at 800°C takes more advantageous ability in immobilization of uranium from aqueous than the commercial available AC and powder zero valent iron. The adsorption behavior could be fitted well with the Langmuir isotherm adsorption model and pseudo-second order model. The equilibrium adsorption amount and rate for Fe-SC-800 is high to 148.99mgg(-1) and 0.015gmg(-1)min(-1), respectively. Both reductive precipitation and physical adsorption are the main mechanisms of immobilization of uranium from aqueous by Fe-SC-800. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. The structural, magnetic and microwave properties of spherical and flake shaped carbonyl iron particles as thin multilayer microwave absorbers

    Science.gov (United States)

    Khani, Omid; Shoushtari, Morteza Zargar; Ackland, Karl; Stamenov, Plamen

    2017-04-01

    An increase in microwave permeability is a prerequisite for reducing the thickness of radar absorber coatings. The aim of this paper is to increase the magnetic loss of commercial carbonyl iron particles for fabricating wideband microwave absorbers with a multilayer structure. For this purpose, carbonyl iron particles were milled and their static and dynamic magnetic properties were studied before and after milling. A distinct morphological change from spherical to flake-like particles is measured with increased milling time, whereas no distinct changes in magnetic properties are measured with increased milling time. The imaginary part of the permeability (μ״) of the milled carbonyl iron particles increased from 1.23 to 1.88 and showed a very broad peak over the entire frequency range 1-18 GHz. The experimental results were modeled using the Rousselle effective medium theory (EMT) in the Neo formulation. The theoretical predictions showed good agreement with the experimental results. Two layer absorbers were designed according to the measured microwave parameters and the multilayer design. The results revealed that a thin multilayer with a thickness of 1.75 mm can effectively absorb microwaves in both the entire X and Ku frequency bands. The results suggest that microwave absorbers with excellent absorption properties could be mass-produced, using commercial carbonyl iron particles.

  7. A method to transfer an individual graphene flake to a target position with a precision of sub-micrometer

    Science.gov (United States)

    Wang, Yubing; Yin, Weihong; Han, Qin; Yang, Xiaohong; Ye, Han; Lü, Qianqian; Yin, Dongdong

    2017-04-01

    Graphene field-effect transistors have been intensively studied. However, in order to fabricate devices with more complicated structures, such as the integration with waveguide and other two-dimensional materials, we need to transfer the exfoliated graphene samples to a target position. Due to the small area of exfoliated graphene and its random distribution, the transfer method requires rather high precision. In this paper, we systematically study a method to selectively transfer mechanically exfoliated graphene samples to a target position with a precision of sub-micrometer. To characterize the doping level of this method, we transfer graphene flakes to pre-patterned metal electrodes, forming graphene field-effect transistors. The hole doping of graphene is calculated to be 2.16 × {10}12{{{cm}}}-2. In addition, we fabricate a waveguide-integrated multilayer graphene photodetector to demonstrate the viability and accuracy of this method. A photocurrent as high as 0.4 μA is obtained, corresponding to a photoresponsivity of 0.48 mA/W. The device performs uniformly in nine illumination cycles. Project supported by the National Key Research and Development Program of China (No. 2016YFB0402404), the High-Tech Research and Development Program of China (Nos. 2013AA031401, 2015AA016902, 2015AA016904), and the National Natural Foundation of China (Nos. 61674136, 61176053, 61274069, 61435002).

  8. Few-Flakes Reduced Graphene Oxide Sensors for Organic Vapors with a High Signal-to-Noise Ratio.

    Science.gov (United States)

    Hasan, Nowzesh; Zhang, Wenli; Radadia, Adarsh D

    2017-10-21

    This paper reports our findings on how to prepare a graphene oxide-based gas sensor for sensing fast pulses of volatile organic compounds with a better signal-to-noise ratio. We use rapid acetone pulses of varying concentrations to test the sensors. First, we compare the effect of graphene oxide deposition method (dielectrophoresis versus solvent evaporation) on the sensor's response. We find that dielectrophoresis yields films with uniform coverage and better sensor response. Second, we examine the effect of chemical reduction. Contrary to prior reports, we find that graphene oxide reduction leads to a reduction in sensor response and current noise, thus keeping the signal-to-noise ratio the same. We found that if we sonicated the sensor in acetone, we created a sensor with a few flakes of reduced graphene oxide. Such sensors provided a higher signal-to-noise ratio that could be correlated to the vapor concentration of acetone with better repeatability. Modeling shows that the sensor's response is due to one-site Langmuir adsorption or an overall single exponent process. Further, the desorption of acetone as deduced from the sensor recovery signal follows a single exponent process. Thus, we show a simple way to improve the signal-to-noise ratio in reduced graphene oxide sensors.

  9. One-Pot Synthesis of Hydrophilic and Hydrophobic N-Doped Graphene Quantum Dots via Exfoliating and Disintegrating Graphite Flakes.

    Science.gov (United States)

    Kuo, Na-Jung; Chen, Yu-Syuan; Wu, Chien-Wei; Huang, Chun-Yuan; Chan, Yang-Hsiang; Chen, I-Wen Peter

    2016-07-25

    Graphene quantum dots (GQDs) have drawn tremendous attention on account of their numerous alluring properties and a wide range of application potentials. Here, we report that hydrophilic and hydrophobic N-doped GQDs can be prepared via exfoliating and disintegrating graphite flakes. Various spectroscopic characterizations including TEM, AFM, FTIR, PL, XPS, and Raman spectroscopy demonstrated that the hydrophilic N-doped GQDs (IN-GQDs) and the hydrophobic N-doped GQDs (ON-GQDs) are mono-layered and multi-layered, respectively. In terms of practical aspects, the supercapacitor of an ON-GQDs/SWCNTs composite paper electrode was fabricated and exhibited an areal capacitance of 114 mF/cm(2), which is more than 250% higher than the best reported value to date for a GQDs/carbon nanotube hybrid composite. For IN-GQDs applications, bio-memristor devices of IN-GQDs-albumen combination exhibited on/off current ratios in excess of 10(4) accompanied by stable switching endurance of over 250 cycles. The resistance stability of the high resistance state and the low resistance state could be maintained for over 10(4) s. Moreover, the IN-GQDs exhibited a superior quantum yield (34%), excellent stability of cellular imaging, and no cytotoxicity. Hence, the solution-based method for synchronized production of IN-GQDs and ON-GQDs is a facile and processable route that will bring GQDs-based electronics and composites closer to actualization.

  10. Few-Flakes Reduced Graphene Oxide Sensors for Organic Vapors with a High Signal-to-Noise Ratio

    Directory of Open Access Journals (Sweden)

    Nowzesh Hasan

    2017-10-01

    Full Text Available This paper reports our findings on how to prepare a graphene oxide-based gas sensor for sensing fast pulses of volatile organic compounds with a better signal-to-noise ratio. We use rapid acetone pulses of varying concentrations to test the sensors. First, we compare the effect of graphene oxide deposition method (dielectrophoresis versus solvent evaporation on the sensor’s response. We find that dielectrophoresis yields films with uniform coverage and better sensor response. Second, we examine the effect of chemical reduction. Contrary to prior reports, we find that graphene oxide reduction leads to a reduction in sensor response and current noise, thus keeping the signal-to-noise ratio the same. We found that if we sonicated the sensor in acetone, we created a sensor with a few flakes of reduced graphene oxide. Such sensors provided a higher signal-to-noise ratio that could be correlated to the vapor concentration of acetone with better repeatability. Modeling shows that the sensor’s response is due to one-site Langmuir adsorption or an overall single exponent process. Further, the desorption of acetone as deduced from the sensor recovery signal follows a single exponent process. Thus, we show a simple way to improve the signal-to-noise ratio in reduced graphene oxide sensors.

  11. One-Pot Synthesis of Hydrophilic and Hydrophobic N-Doped Graphene Quantum Dots via Exfoliating and Disintegrating Graphite Flakes

    Science.gov (United States)

    Kuo, Na-Jung; Chen, Yu-Syuan; Wu, Chien-Wei; Huang, Chun-Yuan; Chan, Yang-Hsiang; Chen, I-Wen Peter

    2016-01-01

    Graphene quantum dots (GQDs) have drawn tremendous attention on account of their numerous alluring properties and a wide range of application potentials. Here, we report that hydrophilic and hydrophobic N-doped GQDs can be prepared via exfoliating and disintegrating graphite flakes. Various spectroscopic characterizations including TEM, AFM, FTIR, PL, XPS, and Raman spectroscopy demonstrated that the hydrophilic N-doped GQDs (IN-GQDs) and the hydrophobic N-doped GQDs (ON-GQDs) are mono-layered and multi-layered, respectively. In terms of practical aspects, the supercapacitor of an ON-GQDs/SWCNTs composite paper electrode was fabricated and exhibited an areal capacitance of 114 mF/cm2, which is more than 250% higher than the best reported value to date for a GQDs/carbon nanotube hybrid composite. For IN-GQDs applications, bio-memristor devices of IN-GQDs-albumen combination exhibited on/off current ratios in excess of 104 accompanied by stable switching endurance of over 250 cycles. The resistance stability of the high resistance state and the low resistance state could be maintained for over 104 s. Moreover, the IN-GQDs exhibited a superior quantum yield (34%), excellent stability of cellular imaging, and no cytotoxicity. Hence, the solution-based method for synchronized production of IN-GQDs and ON-GQDs is a facile and processable route that will bring GQDs-based electronics and composites closer to actualization. PMID:27452118

  12. La coyuntura económica nacional

    Directory of Open Access Journals (Sweden)

    Arturo Huerta González

    2003-01-01

    Full Text Available El objetivo de este artículo es analizar los problemas de contracción económica que enfrenta nuestro país como resultado de la política económica predominante, que lo ha llevado a depender de la economía estadounidense. Cuando ésta enfrentó problemas de crecimiento también frenó el crecimiento de la economía nacional. El gobierno mexicano no instrumenta política fiscal anticíclica (expansión del gasto para contrarrestar la caída de exportaciones y recuperar la dinámica económica por considerar que ello originaría presiones sobre precios y el sector externo y pudiera llevar a un contexto de especulación y crisis. Es por esto que se opta por seguir priorizando políticas contraccionistas para evitar la inflación, como si éste fuese el principal problema del país. Asimismo, el gobierno insiste en las reformas estructurales (apertura eléctrica, petrolera, reforma fiscal y laboral para ampliar la esfera de influencia del sector privado nacional y extranjero y para consolidar el saneamiento fiscal y abaratar el costo de la fuerza de trabajo, impulsando así la dinámica económica. Sin embargo, tales reformas ya las hemos vivido —desde el gobierno de Salinas de Gortari a la fecha— y sus resultados han sido crecimientos espurios que han desembocado en crisis y en el actual estancamiento. Mientras prosiga la actual política económica seguirá deteriorándose la esfera productiva y aumentando el desempleo, sin que se logre un crecimiento sostenido y menos vulnerable de la economía

  13. Effects of crude glycerin in steam-flaked corn-based diets fed to growing feedlot cattle.

    Science.gov (United States)

    Hales, K E; Bondurant, R G; Luebbe, M K; Cole, N A; MacDonald, J C

    2013-08-01

    Crude glycerin is a by-product of biodiesel production and has recently become more available as a livestock feed with the growth of the biofuel industry. Two experiments were conducted to evaluate the use of crude glycerin (GLY) as a feed ingredient in steam-flaked corn (SFC)-based growing diets fed to beef cattle. In Exp. 1, crossbred steers (n = 50; initial BW = 282 ± 2 kg) were used to determine the effects of GLY when included at 0, 2.5, 5, 7.5, and 10% of DM in a growing diet on cattle performance. In Exp. 2, crossbred steers (n = 54; initial BW = 283 ± 1 kg) were used to determine the effects of replacing SFC (REPSFC) or alfalfa hay (REPAH) with 7.5% GLY or a control diet without GLY (CON) on growing steer performance. In Exp. 1, final BW tended to respond in a quadratic manner (P = 0.09) in which it increased from 0 to 7.5% GLY and decreased from 7.5 to 10% GLY. Dry matter intake did not differ (P > 0.23), yet ADG responded quadratically (P = 0.04), where it increased from 0 to 7.5% GLY and decreased from 7.5 to 10% GLY. Feed efficiency (G:F) decreased linearly (P = 0.05) with increasing GLY concentration. In Exp. 2, final BW was greater for steers fed REPAH than CON or REPSFC (P = 0.04). Steers fed REPAH had a greater ADG than CON or REPSFC (P = 0.04). When GLY replaced SFC, ADG increased from 0 to 7.5% GLY where it was maximized before decreasing from 7.5 to 10% GLY inclusion. Replacing 7.5% of alfalfa hay (AH) in a growing diet with GLY can be beneficial to animal performance, which is likely the result of GLY being greater in energy than AH.

  14. Pressure flaking to serrate bifacial points for the hunt during the MIS5 at Sibudu Cave (South Africa)

    Science.gov (United States)

    Lentfer, Carol; Schmid, Viola C.; Porraz, Guillaume; Conard, Nicholas J.

    2017-01-01

    Projectile technology is considered to appear early in the southern African Middle Stone Age (MSA) and the rich and high resolution MSA sequence of Sibudu Cave in KwaZulu-Natal has provided many new insights about the use and hafting of various projectile forms. We present the results of a functional and technological analysis on a series of unpublished serrated bifacial points recently recovered from the basal deposits of Sibudu Cave. These serrated tools, which only find equivalents in the neighbouring site of Umhlatuzana, precede the Still Bay techno-complex and are older than 77 ka BP. Independent residue and use-wear analyses were performed in a phased procedure involving two separate analysts, which allowed the engagement between two separate lines of functional evidence. Thanks to the excellent preservation at Sibudu Cave, a wide range of animal, plant and mineral residues were observed in direct relation with diagnostic wear patterns. The combination of technological, wear and residue evidence allowed us to confirm that the serration was manufactured with bone compressors and that the serrated points were mounted with a composite adhesive as the tips of projectiles used in hunting activities. The suite of technological and functional data pushes back the evidence for the use of pressure flaking during the MSA and highlights the diversity of the technical innovations adopted by southern African MSA populations. We suggest the serrated points from the stratigraphic units Adam to Darya of Sibudu illustrate one important technological adaptation of the southern African MSA and provide another example of the variability of MSA bifacial technologies. PMID:28445544

  15. Biodegradability Study of the Blend Film of High Density Polyethylene and Poly(lactic acid Disposable Packages Flake

    Directory of Open Access Journals (Sweden)

    Elahe Baghi Neirizi

    2016-03-01

    Full Text Available One of the major concerns of using a non-biodegradable polymer product is its disposal at the end of its life cycle. Development of biodegradable plastics promises an alternative solution to combat this problem. Blending of poly(lactic acid with non-biodegradable polymers is a practical and economical method for modifying the biodegradability properties of non-biodegradable polymers. In this study, soil biodegradability of the blends of high density polyethylene (HDPE and variable amounts of recycled poly(lactic acid (r-PLA plastic flakes at 0, 5, 10, 20, 30, 40 and 50 wt% was studied. The behavior of the force-elongation profile of the blends having r-PLA content of lower than 30 wt% was approximately the same as that of pure HDPE while, it was completely different for the other blends. Tearing force and elongation-at-yield-point of the blends films with the 20 to 50 wt% r-PLA were decreased significantly after 60 days of soil biodegradability test. Morphological study showed that biodegradability of the blend films at surface of the samples (deep pores and grooves was increased with extended biodegradability time and higher r-PLA content, while, this variation was significant for the blend films of more than 20 wt% r-PLA content. Thermal properties evaluation by differential scanning calorimetry (DSC curves indicated that the glass transition temperature and enthalpy peaks during the heating stage were eliminated with increasing the biodegradability testing time. Also, reduction in the crystallinity degree of the r-PLA component with increasing the biodegradability testing time coincided with the earlier results.

  16. Pressure flaking to serrate bifacial points for the hunt during the MIS5 at Sibudu Cave (South Africa.

    Directory of Open Access Journals (Sweden)

    Veerle Rots

    Full Text Available Projectile technology is considered to appear early in the southern African Middle Stone Age (MSA and the rich and high resolution MSA sequence of Sibudu Cave in KwaZulu-Natal has provided many new insights about the use and hafting of various projectile forms. We present the results of a functional and technological analysis on a series of unpublished serrated bifacial points recently recovered from the basal deposits of Sibudu Cave. These serrated tools, which only find equivalents in the neighbouring site of Umhlatuzana, precede the Still Bay techno-complex and are older than 77 ka BP. Independent residue and use-wear analyses were performed in a phased procedure involving two separate analysts, which allowed the engagement between two separate lines of functional evidence. Thanks to the excellent preservation at Sibudu Cave, a wide range of animal, plant and mineral residues were observed in direct relation with diagnostic wear patterns. The combination of technological, wear and residue evidence allowed us to confirm that the serration was manufactured with bone compressors and that the serrated points were mounted with a composite adhesive as the tips of projectiles used in hunting activities. The suite of technological and functional data pushes back the evidence for the use of pressure flaking during the MSA and highlights the diversity of the technical innovations adopted by southern African MSA populations. We suggest the serrated points from the stratigraphic units Adam to Darya of Sibudu illustrate one important technological adaptation of the southern African MSA and provide another example of the variability of MSA bifacial technologies.

  17. Magnesium sulfate salts and historic building materials: experimental simulation of limestone flaking by relative humidity cycling and crystallization of salts

    Directory of Open Access Journals (Sweden)

    Pinchin, S.

    2008-06-01

    Full Text Available Magnesium sulfate salts often result from the combination of incompatible construction materials, such as stone or mortar with high magnesium content and sulfates from adjacent mortars or polluted air. When combined with a source of moisture, these materials react to form soluble salts, often leading to significant damage by flaking of the stone, as the magnesium sulfate responds to fluctuating environmental conditions. Several laboratory experiments were performed to reproduce surface flaking on different types of limestone from Spain and the UK to evaluate the effects of humidity cycling on the damage of stone by salt crystallization. The two salt solutions used for the experiments were a single salt of magnesium sulfate and a mixture of magnesium sulfate, calcium sulfate and sodium chloride, a typical salt mixture found in damaged stone at the site of Howden Minster (UK. A climate chamber with precise and programmable temperature and humidity control was used to test the hypothesis that salt damage in the stone can be readily caused by humidity fluctuations. Damage was monitored using Linear Variable Differential Transformer (LVDT, which measure transducers displacement by dimensional change on the order of microns. In addition, Ion Chromatography, Environmental Scanning Electron Microscopy with energy dispersive X-ray spectroscopy (ESEM-EDX and X-ray Diffraction analyses (XRD were also carried out to analyze salt behavior. Damage by flaking took place in two types of magnesian limestone cubes impregnated with the salt mixture, from Cadeby quarry and York Minster, apparently by deliquescent salts of low equilibrium relative humidity (RHeq, while the rest of the samples developed a salt crust over the surface, but no damage was observed in the stone. It is important to verify hypotheses developed from field observations with laboratory experiments. By combining both field and laboratory data, a clearer understanding the different mechanisms of

  18. QUÍMICA VERDE: UN NUEVO RETO

    Directory of Open Access Journals (Sweden)

    Nerlis Paola Pájaro Castro

    2011-01-01

    Full Text Available En la actualidad, existe un enorme deterioro del medio ambiente que ha generado la necesidad de buscar alternativas que conduzcan a la sostenibilidad ambiental. Una de estas herramientas es la ¿química verde¿, concepto que contempla el diseño de productos y procesos que reduzcan la generación de sustancias peligrosas y maximicen la eficiencia en la utilización de recursos materiales y energéticos. El empleo de tecnologías menos contaminantes, permitirá a las empresas químicas mitigar los efectos ambientales asociados a su actividad, reduciendo el consumo de materiales e incrementando la participación de recursos renovables. Para alcanzar estas metas, se han propuesto 12 principios básicos de química verde, aplicables en diferentes campos, tales como la medicina, la agricultura, la industria química y farmacéutica. Esta revisión detalla los principios y usos principales de la química verde, y su aplicación como una filosofía de trabajo para avanzar hacia un verdadero desarrollo sostenible.

  19. Optical emission spectroscopic study of Ar/H2/CH4 plasma during the production of graphene nano-flakes by induction plasma synthesis

    Science.gov (United States)

    Mohanta, Antaryami; Lanfant, Briac; Asfaha, Mehari; Leparoux, Marc

    2017-04-01

    Graphene nano-flakes using CH4 precursor were synthesized in a radio frequency inductively coupled plasma reactor with in-situ investigation of Ar/H2/CH4 plasma by optical emission spectroscopy at fixed H2 and Ar flow rates of 4 and 75 slpm, respectively, and at different plate powers (12 to 18 kW), pressures (400 to 700 mbar) and CH4 flow rates (0.3 to 2 slpm). Emissions from C2 Swan band, C3, CH and H2 are observed in the optical emission spectra of Ar/H2/CH4 plasma. Plasma temperature estimated analyzing the C2 Swan band emission intensities is found to be decreased with increasing pressure and decreasing plate power. The decreasing plasma temperature gives rise to increase in production rate due to increase in condensation process. The production rate is observed to be increased from 0 to 0.3 g/h at 18 kW and from 0 to 1 g/h at 15 kW with increase in pressure from 400 to 700 mbar at fixed CH4 flow rate of 0.7 slpm. Broad band continuum emission appears in the emission spectra at specific growth conditions in which the formation of vapor phase nanoparticles due to condensation of supersaturated vapor is facilitated. The production rate at 12 kW, 700 mbar, and 0.7 slpm of CH4 flow rate is found to be 1.7 g/h which is more than that at 15 and 18 kW. Thus, the broadband continuum emission dominates the optical emission spectra at 12 kW due to lower temperature and higher production rate, and is attributed to the emission from suspended nanoparticles formed in vapor phase. The synthesized nanoparticles exhibit flake like structures having average length and width about 200 and 100 nm, respectively, irrespective of the growth conditions. Nano-flakes have thickness between 3.7 to 7.5 nm and are composed of 11 to 22 graphene layers depending on the growth conditions. The intensity ratio (ID/IG) of D and G band observed in the Raman spectra is less than 0.33 which indicates good quality of the synthesized graphene nano-flakes.

  20. Contribution of Portuguese two-mica granites to stone built heritage

    Science.gov (United States)

    Almeida, Angela; Begonha, Arlindo

    2013-04-01

    The present study deals with the importance of the application of natural stone in monuments in urban setting, both as the main building material during the historical evolution of a city and as a means to increase the public awareness of the social role of geological resources of a specific region. The City of Oporto, World Heritage of the Humanity , has been selected to illustrate the use of the local granite since ancient times to the present day, a two-mica peraluminous granite ,classified as syn-tectonic relatively to the third tectonic deformation phase of the Hercynian orogeny, included in an expressive group that occurs extensively in northern Portugal . The Oporto granite has been the object of several geochemical, structural and geotechnical approaches. Despite the urban development, outcrops of this granite can be observed in different areas of the city, side by side with the urban constructions, and particularly in the imposing and intensely fractured escarpments carved by the river Douro. Oporto monumental heritage goes back to Roman occupation and the profile has been developed by the construction of granite buildings, following history and the social evolution, of an impressive grey architecture according to different styles of granite work that characterize the city in all its aspects, namely the old city wall, the medieval and baroque churches, the neoclassic houses but also the small humble habitations. The Oporto granite is always affected by weathering processes and the buildings exhibit various aspects of stone decay such as granular desintegration, plates, flakes, black crusts, thin black layers, efflorescences and biological colonization. The description of selected sites within the historical centre , where it is possible to recognize the importance of the granite in the character of the city, aims to call the attention to the inextricable role of geology in built heritage and in the culture, as well as to diagnose the deterioration

  1. APRENDIENDO ELECTROQUÍMICA. UN ESTUDIO COMPARATIVO

    Directory of Open Access Journals (Sweden)

    Maria I. Vera

    2011-01-01

    Full Text Available Se realizó un seguimiento del proceso de enseñanza y aprendizaje de Electroquímica y se compararon los resultados obtenidos en evaluaciones parciales, con el objetivo de analizar si existen diferencias significativas en la apropiación de contenidos entre alumnos de carreras con diferentes perfiles. Se trabajó en los años 2009 y 2010 con dos grupos de alumnos en cada año, pertenecientes a carreras químicas y no químicas respectivamente. En ambos grupos se desarrollaron, con la misma carga horaria, contenidos conceptuales y procedimentales en clases teóricas con prácticas de resolución de problemas y de laboratorio. Para la evaluación se presentaron idénticas situaciones problemáticas, cuyos resultados muestran diferencias no significativas entre ambos grupos en la identificación del cátodo y del ánodo y cálculo de la fem estándar de la celda; en cambio en la aplicación de la Ecuación de Nernst y la identificación de especies químicas que reaccionan en los electrodos, hay diferencias significativas en las respuestas dadas.

  2. mica – music information center austria

    OpenAIRE

    2011-01-01

    1994 wurde das österreichische Musikinformationszentrum (mica) im Auftrag des österreichischen Bundesministers für Unterricht und Kunst (Rudolf Scholten) von den Bundeskuratoren für Musik (L. Knessl, Christian Scheib) gegründet (Geschäftsführer 1994–99 Matthias Finkentey, 1999–09 Peter Rantasa, ab 2009 Sabine Reiter).

  3. MeV fullerene impacts on mica

    Energy Technology Data Exchange (ETDEWEB)

    Doebeli, M.; Scandella, L. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Ames, F. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Hillock heights on mica irradiated with MeV C{sub 60} ions have been investigated systematically. Results show that the small range of secondary particles along the track plays a crucial role in defect production. (author) figs., tab., refs.

  4. The Relationship of Anti-MICA Antibodies and MICA Expression with Heart Allograft Rejection

    National Research Council Canada - National Science Library

    Suarez-Alvarez, B; Lopez-Vazquez, A; Gonzalez, M. Zapico; Fdez-Morera, J. L; Diaz-Molina, B; Blanco-Gelaz, M. A; Pascual, D; Martinez-Borra, J; Muro, M; Alvarez-Lopez, M. R; Lopez-Larrea, C

    2007-01-01

    The role of MICA antibodies in acute heart allograft rejection was examined utilizing 190 pre- and post-transplant serum samples from 44 patients collected during the first year after transplantation...

  5. Nitrogen determination in micas of metamorphic rocks

    Energy Technology Data Exchange (ETDEWEB)

    Ager, F.J. [Depto. Fisica Aplicada I, Escuela Universitaria Politecnica, Universidad de Sevilla, C. Virgen de Africa 7, E-41011 Sevilla (Spain) and Centro Nacional de Aceleradores, Av. Thomas A. Edison, E-41092 Sevilla (Spain)]. E-mail: fjager@us.es; Mata, M.P. [Depto. Geologia, Fac. Ciencias del Mar y Ambientales, Campus Rio San Pedro, s/n, E-11510 Puerto Real, Cadiz (Spain); Ynsa, M.D. [Centre d' Etudes Nucleaires de Bordeaux-Gradignan, IN2P3-CNRS, BP 120, 33175 Gradignan Cedex (France); Respaldiza, M.A. [Centro Nacional de Aceleradores, Av. Thomas A. Edison, E-41092 Sevilla (Spain); Goffe, B. [UMR 8538, Lb. Geologie, ENS, 24, Rue Lhomond, F-75231 Paris Cedex 05 (France); Nieto, F. [Dpto. Mineralogia y Petrologia, Fac. Ciencias, Av. Fuentenueva s/n, E-18002 Granada (Spain)

    2006-08-15

    Micas are minerals that provide large amounts of information regarding geological processes, because of the sensitivity of their chemical composition to temperature, pressure and deformation of rocks in which they form. Rocks under analysis are formed of different minerals with variable grain size. Mica grain size may vary between 5 and 10 {mu}m and approximately correspond to the chemical formula (Si{sub 3.2}Al{sub 0.8})O{sub 10}(Al{sub 1.9}Fe{sub 0.05}Mg{sub 0.1})(OH){sub 2}(K{sub 0.75}Na{sub 0.05}), being distinguishable from other minerals because of their composition and their morphology in secondary electron images and specially backscattered electron (BSE) images. NH{sub 4}, when present, would partially substitute K in the previous formula. In some cases NH{sub 4}-rich micas (tobelites) have been described coexisting with the corresponding K-rich micas, but the actual NH{sub 4} content of normal K-rich micas is still unknown. Low N content makes necessary to use nuclear reactions such as {sup 14}N(d, p{gamma}){sup 15}N at 1.4 MeV and its cascade of intense {gamma}-rays. For the quantification and localization of nitrogen on the surface of the samples, PIGE analysis was carried out in the vacuum microprobe line of the CNA, together with simultaneous micro-RBS and micro-PIXE analyses, giving a more comprehensive picture of sample structure and composition.

  6. Cinética Química

    OpenAIRE

    Peirano, Silvana

    2014-01-01

    Documento sobre los conceptos básicos acerca de la cinética química, que es una rama de la química que estudia las velocidades de las reacciones químicas y los factores que afectan a esas velocidades.

  7. Electromagnetic properties of core–shell particles by way of electroless Ni–Fe–P alloy plating on flake-shaped diatomite

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Deyuan [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China); Yuan, Liming, E-mail: lming_y@163.com [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China); Lan, Mingming; Hu, Yanyan; Cai, Jun [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China); Zhang, Wenqiang [College of Engineering, China Agricultural University, Beijing 100083 (China); Li, Haiyang [China Aerospace Science and Technology Corporation, Beijing 100854 (China)

    2013-11-15

    Flake-shaped diatomite particles coated by Ni–Fe–P alloy were prepared by electroless plating technique and processed by heat treatment. The samples were characterized by SEM, EDS and XRD. The results indicated that the magnetic diatomite particles had continuous and homogeneous Ni–Fe–P coating, and the phase constitution of the Ni–Fe–P coating was transformed from an amorphous structure to a crystalline structure during heat treatment. The measured electromagnetic parameters and the calculated reflection loss suggested that heat treatment was able to enhance the microwave absorption performance of the paraffin wax based composites. In a word, the Ni–Fe–P coated diatomite particle obtained in this paper is a promising candidate for lightweight microwave absorbing inclusions. - Highlights: • We used the flake-shaped diatomite particles as forming template to fabricate the core–shell ferromagnetic particles. • The diatomite particles were deposited Ni–Fe–P alloy by way of electroless plating methods. • The coated diatomite particles were lightweight ferromagnetic fillers. • The composites containing coated diatomite particles with heat treatment exhibited great potential in the field of electromagnetic absorbing.

  8. TAPHONOMIC ANALYSIS ON FOSSIL REMAINS FROM THE CIOTA CIARA CAVE (PIEDMONT, ITALY AND NEW EVIDENCE OF CAVE BEAR AND WOLF EXPLOITATION WITH SIMPLE QUARTZ FLAKES BY NEANDERTHAL

    Directory of Open Access Journals (Sweden)

    FABIO BUCCHERI

    2016-10-01

    Full Text Available The Ciota Ciara cave is located in the karst area of Monte Fenera (Borgosesia - VC and, with the Ciotarun cave, it is the only Middle Palaeolithic site in Piedmont where the presence of Homo neanderthalensis has been confirmed by discoveries of human remains. Preliminary taphonomic and archaeozoological studies have been performed on a portion of the palaeontological remains from the Stratigraphic Unit 14 (1144 bones. The studies confirmed the presence of cut-marks on Ursus spelaeus and Canis lupus, made by lithic instruments. The position of the cut marks on the bones can be related to skinning and butchery. An experimental butchery has been performed to test the efficiency of the tools made by local quartz during slaughtering activities. The archaeozoological analysis of the faunal remains of S.U. 14, identified cut-marks with weak peculiarities, probably due to the use of quartz tools. The analysis of the experimental collection allowed distinguishing between cut-marks made by quartz tools from those made by flint tools. A preliminary experimentation, conducted on more than 50 different cut-marks made with flakes of three different raw materials (vein quartz, quartzite and flint, allow us to hypothesize that it is possible to distinguish cut-marks made with unretouched flakes of different raw materials.

  9. Electrochemical Properties of Porous Co(OH){sub 2} Nano-flake Thin Film Prepared by Electro-deposition for Supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeon Jeong; Jin, En Mei; Jeong, Sang Mun [Chungbuk National University, Cheongju (Korea, Republic of)

    2016-04-15

    Porous Co(OH){sub 2} nano-flake thin films were prepared by a potential-controlled electro-deposition technique at various deposition voltage (−0.75, −1.0, −1.2, and −1.4 V) on Ti-mesh substrates for supercapacitor application. The potential of electrode was controlled to regulate the film thickness and the amount of Co(OH){sub 2} nano-flake on the titanium substrate. The film thickness was shown to reach the maximum value of 34 μm at −1.4 V of electrode potential, where 17.2 g of Co(OH){sub 2} was deposited on the substrate. The specific discharge capacitances were measured to be 226, 370, 720, and 1008 mF cm{sup -2} in the 1st cycle corresponding to the films which were formed at −0.75, −1.0, −1.2, and −1.4 V of electrode potentials, respectively. Then the discharge capacities were decreased to be 206, 349, 586 and 866 mF/cm{sup 2}, where the persistency rates were 91, 94, 81, and 86%, respectively.

  10. Farmacogenómica: Aplicaciones cardiovasculares

    Directory of Open Access Journals (Sweden)

    Luis Quiñones S., PH.D.

    2015-03-01

    Este trabajo pretende dar una visión general acerca de farmacogenómica cardiovascular y la posibilidad de utilizar, en la consulta clínica, herramientas genéticas para apoyar la decisión farmacoterapéutica, con el objeto de mejorar la respuesta al tratamiento de enfermedades cardiovasculares, un paso hacia la medicina personalizada en Chile.

  11. Influence of substituting steam-flaked corn for dry rolled corn on feedlot cattle growth performance when cattle are allowed either or restricted access to the finishing diet

    Directory of Open Access Journals (Sweden)

    Víctor Manuel González-Vizcarra

    2017-11-01

    Full Text Available Objective The influence of substituting steam-flaked corn (SFC for dry rolled corn (DRC on feedlot cattle growth performance and dietary net energy when cattle are allowed either ad libitum or 2-h restricted access to the finishing diet was evaluated. Methods Treatment effects were tested using 96 crossbred steers (251±2 kg during the initial 56 d of the finishing phase. Cattle were blocked by weight and randomly assigned within blocks to 16 pens (4 pens/treatment. Bunk space was sufficient (41 cm/head to allow all steers access to the feed bunk at the same time. Treatments consisted of two finishing diets containing (dry matter basis 77.1% corn grain processed by dry rolling (density = 0.50 kg/L or steam flaking (density = 0.36 kg/L. Cattle were fed twice daily at 06:00 and 14:00 h, allowing for approximately 5% residual. In the case of restricted feeding, steers were allowed access to feeders for 1 h following each feeding, after which residual feed was withdrawn. Results There were no treatment interactions on dry matter intake (DMI, average daily gain (ADG, gain efficiency (G:F, or dietary net energy (NE. Restricting feed access time reduced (p <0.01 feed intake, and hence, ADG. Substitution of SFC for DRC increased (p<0.01 ADG, feed efficiency (G:F, and estimated dietary NE, without affecting DMI. Based on tabular net energy of maintenance (NEm value (2.18 Mcal/kg for DRC, the estimated NEm value for SFC using the replacement technique, averaged 2.44 Mcal/kg; an improvement of 10.7%. The ratio of observed-to-expected dietary NE was not affected by feed access time. Conclusion Substitution of SFC for DRC in finishing diets for feedlot cattle enhanced ADG, gain efficiency, and the NE value of the diet. Although restriction of feed access time depressed DMI and ADG, it did not affect the comparative benefit of steam flaking toward enhancement of ADG, G:F, and dietary NE.

  12. Effect of a mixture of steam-flaked corn and soybeans on health, growth, and selected blood metabolism of Holstein calves.

    Science.gov (United States)

    Zhang, Y Q; He, D Ch; Meng, Q X

    2010-05-01

    The objective of the experiment was to evaluate the effects of steam-flaked corn grains and soybeans on calf health, growth, and selected blood parameters. Holstein bull calves (n=30, approximately 7+/-3 d of age) were purchased from local dairy farms and offered milk, starter diets, and hay, and were then assigned to the experiment at 21+/-3 d of age. Calves were blocked into 3 treatments by birth date and body weight and randomly assigned to receive fresh milk and a commercial pelleted starter containing extruded corn and soybeans (ECS), steam-flaked corn and soybeans (SFCS), or ground corn and soybeans (GCS). The experiment was conducted with calves from 3 to 13 wk of age. Body weight, calf starter intake, milk intake, total dry matter intake, and body structural growth were not significantly influenced by corn and soybean processing during the study; however, feed efficiency was significantly improved by the SFCS treatment. Average daily gain generally decreased during the weaning week for all treatments, but did not differ significantly among treatments. Health incidences for calves fed the SFCS starter were lower than those fed the other 2 treatments. The blood hematocrit was higher for calves fed the SFCS starter than for those fed the GCS and ECS starters during wk 6 to 11. The concentration of plasma beta-hydroxybutyrate was higher for the calves fed the GCS and SFCS treatments than for those fed the ECS treatment during wk 6 to 13, but lower during wk 4 and 5. Plasma glucose concentrations decreased remarkably with increasing calf age but were not affected by corn and soybean processing. Plasma nonesterified fatty acids were influenced by calf age, and higher NEFA concentration was observed in the SFCS treatment than in the other 2 treatments during wk 5 to 9. Calves consuming the SFCS starter had similar average daily gain, milk intake, starter intake, total dry matter intake, and body structure, but had improved feed efficiency when compared with

  13. Insight into interactions of amyloid beta sheets with graphene flakes: Scrutinizing the role of aromatic residues in amyloids interacting with graphene.

    Science.gov (United States)

    Zarić, Snežana D; Bozinovski, Dragana; Petrovic, Predrag; Belic, Mililvoj

    2017-09-26

    The interaction of amyloid β-sheet segments with graphene flake models is investigated using the density functional theory (DFT). The structure of β-sheets of selected amyloid segments is based on the crystal structures obtained from the Protein Data Bank. Our study, based on the DFT calculations on model systems, indicates that the interaction in amyloid-graphene aggregates can be stronger than the interactions for respective amyloid-amyloid aggregates. The results also indicate an important specific role of aromatic side chains in amyloid-graphene interactions. This work confirms recent experimental evidence that graphene and its modifications inhibit the aggregation of β-amyloid peptides. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Highly Efficient Electronic Sensitization of Non-oxidized Graphene Flakes on Controlled Pore-loaded WO3 Nanofibers for Selective Detection of H2S Molecules

    Science.gov (United States)

    Choi, Seon–Jin; Choi, Chanyong; Kim, Sang-Joon; Cho, Hee-Jin; Hakim, Meggie; Jeon, Seokwoo; Kim, Il–Doo

    2015-01-01

    Tailoring of semiconducting metal oxide nanostructures, which possess controlled pore size and concentration, is of great value to accurately detect various volatile organic compounds in exhaled breath, which act as potential biomarkers for many health conditions. In this work, we have developed a very simple and robust route for controlling both the size and distribution of spherical pores in electrospun WO3 nanofibers (NFs) via a sacrificial templating route using polystyrene colloids with different diameters (200 nm and 500 nm). A tentacle-like structure with randomly distributed pores on the surface of electrospun WO3 NFs were achieved, which exhibited improved surface area as well as porosity. Porous WO3 NFs with enhanced surface area exhibited high gas response (Rair/Rgas = 43.1 at 5 ppm) towards small and light H2S molecules. In contrast, porous WO3 NFs with maximized pore diameter showed a high response (Rair/Rgas = 2.8 at 5 ppm) towards large and heavy acetone molecules. Further enhanced sensing performance (Rair/Rgas = 65.6 at 5 ppm H2S) was achieved by functionalizing porous WO3 NFs with 0.1 wt% non-oxidized graphene (NOGR) flakes by forming a Schottky barrier (ΔΦ = 0.11) at the junction between the WO3 NFs (Φ = 4.56 eV) and NOGR flakes (Φ = 4.67 eV), which showed high potential for the diagnosis of halitosis. PMID:25626399

  15. Achieving extremely concentrated aqueous dispersions of graphene flakes and catalytically efficient graphene-metal nanoparticle hybrids with flavin mononucleotide as a high-performance stabilizer.

    Science.gov (United States)

    Ayán-Varela, M; Paredes, J I; Guardia, L; Villar-Rodil, S; Munuera, J M; Díaz-González, M; Fernández-Sánchez, C; Martínez-Alonso, A; Tascón, J M D

    2015-05-20

    The stable dispersion of graphene flakes in an aqueous medium is highly desirable for the development of materials based on this two-dimensional carbon structure, but current production protocols that make use of a number of surfactants typically suffer from limitations regarding graphene concentration or the amount of surfactant required to colloidally stabilize the sheets. Here, we demonstrate that an innocuous and readily available derivative of vitamin B2, namely the sodium salt of flavin mononucleotide (FMNS), is a highly efficient dispersant in the preparation of aqueous dispersions of defect-free, few-layer graphene flakes. Most notably, graphene concentrations in water as high as ∼50 mg mL(-1) using low amounts of FMNS (FMNS/graphene mass ratios of about 0.04) could be attained, which facilitated the formation of free-standing graphene films displaying high electrical conductivity (∼52000 S m(-1)) without the need of carrying out thermal annealing or other types of post-treatment. The excellent performance of FMNS as a graphene dispersant could be attributed to the combined effect of strong adsorption on the sheets through the isoalloxazine moiety of the molecule and efficient colloidal stabilization provided by its negatively charged phosphate group. The FMNS-stabilized graphene sheets could be decorated with nanoparticles of several noble metals (Ag, Pd, and Pt), and the resulting hybrids exhibited a high catalytic activity in the reduction of nitroarenes and electroreduction of oxygen. Overall, the present results should expedite the processing and implementation of graphene in, e.g., conductive inks, composites, and hybrid materials with practical utility in a wide range of applications.

  16. Electronic structure and field emission properties of nitrogen doped graphene nano-flakes (GNFs:N) and carbon nanotubes (CNTs:N)

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Sekhar C., E-mail: Raysc@unisa.ac.za [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Private Bag X6, Florida, 1710, Science Campus, Christiaan de Wet and Pioneer Avenue, Florida Park, Johannesburg (South Africa); Pong, W.F. [Department of Physics, Tamkang University, Tamsui 251, New Taipei City, Taiwan (China); Papakonstantinou, P. [Nanotechnology and Integrated Bio-Engineering Centre, University of Ulster, Shore Road, Newtownabbey BT37 0QB (United Kingdom)

    2016-09-01

    Highlights: • Nitrogen doped graphene nano-flakes (GNFs:N) and carbon nano-tubes (CNTs:N) are used to study the electronic/bonding structure along with their defects state. • The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy used for the study of the defects states of CNTs:N than GNFs:N. • The electron field emission result shows that the turn on electric field is lower in case of CNTs:N than GNFs:N. • All results are good agreement with XANES and the results obtained from Raman spectra. - Abstract: Substitution of hetero-atom doping is a promising route to modulate the outstanding material properties of carbon nanotubes and graphene for customized applications. Nitrogen-doping has been introduced to ensure tunable work-function, enhanced n-type carrier concentration, diminished surface energy, and manageable polarization. Along with the promising assessment of N-doping effects, research on the N-doped carbon based composite structures is emerging for the synergistic integration with various functional materials. Nitrogen undoped/doped graphene nano-flakes (GNFs/GNFs:N) and multiwall carbon nano-tubes (MWCNTs/MWCNTs:N) are used for comparative study of their electronic/bonding structure along with their defects state. X-ray absorption near edge structure (XANES) spectroscopy shows that the GNFs:N produce mainly pyridine like structure; whereas MWCNTs:N shows graphitic nitrogen atoms are attached with the carbon lattice. The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy shows that the defects is higher in MWCNTs:N than GNFs:N. The electron field emission result shows that the turn on electric field is lower (higher electron emission current) in case of MWCNTs:N than GNFs:N and are good agreement with XANES and the results obtained from Raman spectra.

  17. Preparation of cast aluminum alloy-mica particle composites

    Science.gov (United States)

    Deonath, MR.; Bhat, R. T.; Rohatgi, P. K.

    1980-01-01

    A method for making aluminum-mica particle composites is presented in which mica particles are stirred in molten aluminum alloys followed by casting in permanent molds. Magnesium is added either as an alloying element or in the form of pieces to the surface of the alloy melts to disperse up to 3 wt% mica powders in the melts and to obtain high recoveries of mica in the castings. The mechanical properties of the aluminum alloy-mica composite decrease with increasing mica content; however, even at 2.2% it has a tensile strength of 14.22 kg/sq mm with 1.1% elongation, a compression strength of 42.61 kg/sq mm, and an impact strength of 0.30 kgm/sq cm. Cryogenic and self-lubricating bearing are mentioned applications.

  18. Aprendiendo química con golosinas

    OpenAIRE

    José Manuel Rodríguez Rodríguez; Navarro de Tuero Bonán, Juan A.

    2011-01-01

    Las golosinas (caramelos, chicles, nubes, palotes, papas fritas, etc.) nos gustan a casi todos y gozan de una imagen positiva, a pesar de sus efectos secundarios si no se consumen con moderación. Aprovechándonos de esa buena imagen y de la gran variedad de golosinas que existen en el mercado, hemos diseñado una serie de experimentos con los que podemos explicar distintos tipos de reacciones químicas (ácido-base, oxidación reducción, endotérmicas¿), la actuación de un indicador e, incluso, pod...

  19. Aprendiendo química con golosinas

    OpenAIRE

    Rodríguez Rodríguez, José Manuel; Navarro de Tuero Bonán, Juan A.

    2011-01-01

    Las golosinas (caramelos, chicles, nubes, palotes, papas fritas, etc.) nos gustan a casi todos y gozan de una imagen positiva, a pesar de sus efectos secundarios si no se consumen con moderación. Aprovechándonos de esa buena imagen y de la gran variedad de golosinas que existen en el mercado, hemos diseñado una serie de experimentos con los que podemos explicar distintos tipos de reacciones químicas (acido-base, oxidación-reducción, endotérmicas…), la actuación de un indicador e, incluso, pod...

  20. La delincuencia económica

    OpenAIRE

    Ismael Aráuz Ulloa; María Asunción Moreno Castillo

    2001-01-01

    Este estudio tiene como objetivo presentar algunas Consideraciones especiales sobre la llamada "criminalidad económica", los factores que Contribuyen a Su desarrollo y las diferentes teorías doctrinales que tratan de explicar su naturaleza desde distintos puntos de vista -psicológico, social. Se presentan, además, algunos conceptos sobre la nueva rama del derecho denominada "Derecho Penal Económico", manejados tanto en la doctrina alemana como en la española, y los criterios diferenciador...

  1. Constelaciones sistémicas en organizaciones

    OpenAIRE

    Gómez Gómez, Francisco

    2010-01-01

    Han sido muchos los ríos de tinta que han corrido sobre el comportamiento y la gestión de los recursos humanos, en artículos periodísticos, académicos de diferentes campos, así como en libros divulgativos y académicos. Roevens, el autor de este estudio, se apoyó en su experiencia en gestión académica y de los recursos humanos, en la labor desarrollada en más de diez organizaciones, como consultor sobre asesoramiento de personal, como investigador participante en talleres con nuevas tendencia...

  2. La polémica del nacionalismo

    Directory of Open Access Journals (Sweden)

    Germán Posada

    1961-10-01

    Full Text Available La polémica empezó con el artículo de Hernando Téllez, hace veinte días. Con el pretexto de defender a los escritores de su propia generación, a quienes, según él, se viene acusando sistemáticamente de producir una literatura desarraigada y ausente de la vida nacional, Téllez se lanzó a combatir las teorías de " nacionalismo literario'' que actualmente se agitan en Colombia.

  3. Aprendiendo química con golosinas

    Directory of Open Access Journals (Sweden)

    José Manuel Rodríguez Rodríguez

    2011-01-01

    Full Text Available Las golosinas (caramelos, chicles, nubes, palotes, papas fritas, etc. nos gustan a casi todos y gozan de una imagen positiva, a pesar de sus efectos secundarios si no se consumen con moderación. Aprovechándonos de esa buena imagen y de la gran variedad de golosinas que existen en el mercado, hemos diseñado una serie de experimentos con los que podemos explicar distintos tipos de reacciones químicas (ácido-base, oxidación reducción, endotérmicas¿, la actuación de un indicador e, incluso, podemos comparar cantidades de vitamina C. En todas las actividades se persigue explicar algún aspecto de la Química que, en general, el público desconoce, captando su atención, por ejemplo, mediante cambios de color espectaculares y con las golosinas como protagonistas. Así mismo, estas experiencias pueden emplearse como recursos didácticos para alumnos de 4º E.S.O. y Bachillerato, apoyando los contenidos teóricos del currículum.

  4. 21 CFR 73.3128 - Mica-based pearlescent pigments.

    Science.gov (United States)

    2010-04-01

    ... pigments. (a) Identity and specifications. The color additive is formed by depositing titanium or iron salts from a basic solution onto mica, followed by calcination to produce titanium dioxide or iron... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Mica-based pearlescent pigments. 73.3128 Section...

  5. Mechanical properties of Al-mica particulate composite material

    Science.gov (United States)

    Nath, D.; Bhatt, R. T.; Rohatgi, P. K.; Biswas, S. K.

    1980-01-01

    Cast aluminum alloy mica particle composites of varying mica content were tested in tension, compression, and impact. With 2.2 percent mica (size range 40-120 microns) the tensile and compression strengths of aluminum alloy decreased by 56 and 22 percent, respectively. The corresponding decreases in percent elongation and percent reduction are 49 and 39 percent. Previous work shows that despite this decrease in strength the composite with 2.5 percent mica and having an UTS of 15 kg/sq mm and compression strength of 28 kg/sq mm performs well as a bearing material under severe running conditions. The differences in strength characteristics of cast aluminum-mica particle composites between tension and compression suggests that, as in cast iron, expansion of voids at the matrix particle interface may be the guiding mechanism of the deformation. SEM studies show that on the tensile fractured specimen surface, there are large voids at the particle matrix interface.

  6. Effects of a mixture of steam-flaked corn and extruded soybeans on performance, ruminal development, ruminal fermentation, and intestinal absorptive capability in veal calves.

    Science.gov (United States)

    Xie, X X; Meng, Q X; Liu, P; Wu, H; Li, S R; Ren, L P; Li, X Z

    2013-09-01

    This study investigated the effects of a mixture of steam-flaked corn and extruded soybeans on performance, ruminal development, ruminal fermentation variables, and intestinal absorptive capability in Holstein male calves (n = 39). Calves were assigned to 1 of 3 treatments (13 calves per treatment): 1) milk replacer (MR), 2) one-half of the amount of MR in treatment 1, plus a mixture of 62.1% steam-flaked corn and 30.5% extruded soybeans provided ad libitum (HMCS), or 3) a mixture of 62.1% steam-flaked corn and 30.5% extruded soybeans provided ad libitum (CS). All the calves were started at 2 ± 1 d of age and studied for 150 d. Each 30 d was defined as 1 period. Dry matter intake and growth were measured daily and monthly, respectively. All calves were harvested at 150 d of age, after which rumen fluid was collected. Rumen and intestine samples were gathered. Calves fed MR exhibited greater BW (P = 0.001) and ADG (P < 0.001), compared with calves fed HMCS and CS from period 2 to 3; however, from period 4 to 5, CS calves had greater (P < 0.04) ADG than MR calves. The treatments did not differ in final BW (P = 0.72) and ADG (P = 0.20) from period 2 to 5. Compared with HMCS and MR calves, CS calves had the greatest DMI (P < 0.001) and the least feed efficiency (P < 0.001) from period 2 to 5. For ruminal fermentation parameters, CS calves had decreased (P = 0.04) rumen pH than MR calves. The NH3 concentrations were greater (P = 0.03) in calves fed HMCS than calves fed MR and CS. Total VFA concentrations were greatest in CS calves (P = 0.02). Calves fed CS had the greatest molar concentrations of propionate, butyrate, and valerate (P < 0.002), and calves fed HMCS had the greatest molar concentrations of isobutyrate (P = 0.001) and isovalerate (P = 0.001). The CS calves exhibited greater empty rumen weight (P = 0.001), papillae length (P < 0.001), papillae width (P < 0.001), rumen wall thickness (P = 0.012), and papillae density (P = 0.003). The greatest villus heights

  7. La delincuencia económica

    Directory of Open Access Journals (Sweden)

    Ismael Aráuz Ulloa

    2001-06-01

    Full Text Available Este estudio tiene como objetivo presentar algunas Consideraciones especiales sobre la llamada "criminalidad económica", los factores que Contribuyen a Su desarrollo y las diferentes teorías doctrinales que tratan de explicar su naturaleza desde distintos puntos de vista -psicológico, social. Se presentan, además, algunos conceptos sobre la nueva rama del derecho denominada "Derecho Penal Económico", manejados tanto en la doctrina alemana como en la española, y los criterios diferenciadores entre delitos patrimoniales y delitos económicos. Finalmente se muestran algunas consideraciones criminológicas y de política criminal.

  8. Kinetic Analysis of Mica Tape Curing Process

    Directory of Open Access Journals (Sweden)

    Radek Polansky

    2008-01-01

    Full Text Available Curing program of thermoset insulating materials and its responsible setting has the key importance for assurance of high quality and reliability of electrical devices. It is possible to determine parameters of this program (temperature and time of curing by several ways in practise. There is mostly focused on methods based on kinetic analysis. The result comparison of selected methods of kinetic analysis and residual enthalpy measurement is the main aim of the paper. Two insulating tapes were chosen for the purpose of this study. These tapes correspond in their composition (glass fabric, mica and epoxy binder, but they differ in curing agent type. Simultaneous thermal analysis (STA was used during the measurements. Monitored results demonstrate the advantages and disadvantages of particular methods.

  9. Aumentando la realidad química

    Directory of Open Access Journals (Sweden)

    Mª Luisa Roqueta Buj

    2017-08-01

    Full Text Available El uso de nuevas tecnologías como la Realidad Aumentada en la enseñanza de la Química permite manejar información virtual y asociarla a elementos de la vida real. Se accede a la misma a través de un dispositivo tecnológico con un software específico. Esta herramienta tecnológica recibe el nombre de Realidad Aumentada y permite añadir contenido digital a nuestro mundo real aumentando la percepción que tenemos del mismo. Nos permite incorporar contenido en forma de texto, imagen, audio o vídeo.

  10. LA CRISIS ECONÓMICA MUNDIAL

    Directory of Open Access Journals (Sweden)

    Julián Sabogal Tamayo

    2008-07-01

    Full Text Available Se argumenta el contenido de la actual crisis mundial, entendida como propia del movimiento cíclico del sistema capitalista y no como una crisis particularmente financiera. Se sostiene que las crisis económicas son propias del sistema, mas no de la economía perse. Se sustenta su diferencia con respecto a la crisis cíclica de 1929-1933 con base los ciclos sistémicos y las características diferentes de los inicios y el final del ciclo; al final del ciclo el capital es en su mayor parte financiero. Finalmente se sostiene la tesis que las crisis cíclicas, por tener causas objetivas, son inevitables, la única alternativa es buscar otra forma de organizar la sociedad y la producción: pasar de la búsqueda de rentabilidad a la satisfacción de las necesidades de toda la comunidad.

  11. de la química

    Directory of Open Access Journals (Sweden)

    Gregorio Jiménez-Valverde

    2006-01-01

    Full Text Available En la presente comunicación se detalla una innovadora experiencia llevada a cabo durante los cursos 2001-02 y 2002-03 consistente en el uso del BSCW, un entorno telemático para el trabajo cooperativo, en el Ciclo Formativo de Grado Superior de Química Ambiental. En el artículo se detallan las principales características del entorno, cómo fue aplicado y los resultados que se obtuvieron, presentados en páginas web creadas por los propios estudiantes sobre diferentes aspectos de metales en aguas. El alumnado, a través de una encuesta, respaldó esta experiencia y mostró una actitud muy positiva en la creación de materiales hipermedia.

  12. Fabrication of TiO{sub 2} nanorod assembly grafted rGO (rGO@TiO{sub 2}-NR) hybridized flake-like photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Kangle, E-mail: lvkangle@mail.scuec.edu.cn [Department of Science and Environmental Studies, The Hong Kong Institute of Education, Taipo, N.T., Hong Kong (China); Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan 430074 (China); Fang, Shun; Si, Lingling; Xia, Yang [Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan 430074 (China); Ho, Wingkei, E-mail: keithho@ied.edu.hk [Department of Science and Environmental Studies, The Hong Kong Institute of Education, Taipo, N.T., Hong Kong (China); Li, Mei [Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan 430074 (China)

    2017-01-01

    Highlights: • TiO{sub 2} nanorod assembly grafted with GO hybrid was successfully fabricated. • TiO{sub 2} nanorods can reduce the aggregation of TiO{sub 2} nanoparticles on graphene. • This unique structure facilitates the injection of electron from TiO{sub 2} to graphene. - Abstract: To efficiently separate the photo-generated electron–hole pairs of TiO{sub 2} hybrid, anatase TiO{sub 2} nanorod assembly grafted reduced graphene oxides (rGO@TiO{sub 2}-NR) hybrid was successfully fabricated using potassium titanium oxalate (PTO) and graphene oxides (GO) as starting materials and diethylene glycol (DEG) as reductant. The effect of GO content on the structure and photocatalytic activity of rGO@TiO{sub 2}-NR composite was systematically studied. Results show that, in the absence of GO, only TiO{sub 2} microsphere assembly is obtained from TiO{sub 2} nanorods. The presence of GO results in the formation of a flake-like TiO{sub 2}-nanorod-assembled grafted rGO hybrid. The photocatalytic activity of rGO@TiO{sub 2}-NR composite increases first and then decreases with increase in the amount of GO from 0 wt.% to 10 wt.%. The hybridized S4 sample prepared with 4 wt.% GO possesses the highest photocatalytic activity with a constant rate of 0.039 min{sup −1} in the photocataytic degradation of Brilliant X-3B dye (X3B); this sample was enhanced more than three times when compared with pure TiO{sub 2} sample (0.012 min{sup −1}). The enhanced photocatalytic activity of the rGO@TiO{sub 2}-NR hybrid was attributed to the strong interaction between TiO{sub 2} nanorods and rGO. The unique hierarchical structure of 1D nanorod assembly TiO{sub 2}–rGO flakes facilitates the injection and transfer of photo-generated electrons from TiO{sub 2} to graphene, thus retarding the recombination of electron–hole pairs and enhancing the photocatalytic activity. The enlarged BET surface areas, not only increasing the number of active sites, but also facilitating the adsorption of

  13. Fabrication of TiO2 nanorod assembly grafted rGO (rGO@TiO2-NR) hybridized flake-like photocatalyst

    Science.gov (United States)

    Lv, Kangle; Fang, Shun; Si, Lingling; Xia, Yang; Ho, Wingkei; Li, Mei

    2017-01-01

    To efficiently separate the photo-generated electron-hole pairs of TiO2 hybrid, anatase TiO2 nanorod assembly grafted reduced graphene oxides (rGO@TiO2-NR) hybrid was successfully fabricated using potassium titanium oxalate (PTO) and graphene oxides (GO) as starting materials and diethylene glycol (DEG) as reductant. The effect of GO content on the structure and photocatalytic activity of rGO@TiO2-NR composite was systematically studied. Results show that, in the absence of GO, only TiO2 microsphere assembly is obtained from TiO2 nanorods. The presence of GO results in the formation of a flake-like TiO2-nanorod-assembled grafted rGO hybrid. The photocatalytic activity of rGO@TiO2-NR composite increases first and then decreases with increase in the amount of GO from 0 wt.% to 10 wt.%. The hybridized S4 sample prepared with 4 wt.% GO possesses the highest photocatalytic activity with a constant rate of 0.039 min-1 in the photocataytic degradation of Brilliant X-3B dye (X3B); this sample was enhanced more than three times when compared with pure TiO2 sample (0.012 min-1). The enhanced photocatalytic activity of the rGO@TiO2-NR hybrid was attributed to the strong interaction between TiO2 nanorods and rGO. The unique hierarchical structure of 1D nanorod assembly TiO2-rGO flakes facilitates the injection and transfer of photo-generated electrons from TiO2 to graphene, thus retarding the recombination of electron-hole pairs and enhancing the photocatalytic activity. The enlarged BET surface areas, not only increasing the number of active sites, but also facilitating the adsorption of the dye, and improved light-harvesting ability also contribute to the enhanced photoreactivity of rGO@TiO2-NR hybrid.

  14. Recovery from Iridium-192 flakes of a radioactive source for industrial use after a radiation incident; Recuperacion de hojuelas de Iridio-192 provenientes de una fuente radiactivas de uso industrial despues de un incidente radiologico

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, W.H.; Zapata, L.A., E-mail: wcruz@ipen.gob.pe, E-mail: lzapata@ipen.gob.pe [Instituto Peruano de Energia Nuclear (GRRA/IPEN), Lima (Peru). Division de Gestion de Residuos Radiactivos

    2013-07-01

    The Iridium-192 ({sup 192}Ir) is the most used and ideal for industrial radiography applications, especially in petrochemical plants and pipelines and provides better contrast sensitivity for thick (25.4 mm). This source has constructive sealed double encapsulation, the internal capsule containing stainless steel to radioactive material in the form of flakes and welded with TIG process. The radiological incident happened at a gas station fuel sales in circumstances in which there was a homogeneity test welds a tank, the flakes or Ir-192 fell off his ponytail and left scattered over an area of 2 m{sup 2}, some fell flat areas and other land so collected in lead shielding and metal container and ground source. Full recovery of the leaflets was performed at the Division of radioactive waste management (GRRA) gaining a total of 22 flakes with no radiation risk to staff performance and installation and the conclusion was reached that the misapplicaion of TIG welding was the main cause the incident. (author)

  15. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials

    Energy Technology Data Exchange (ETDEWEB)

    Das, Saptarshi; Bera, Mrinal K.; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P.; Antonio, Mark R.; Sankaranarayanan, Subramanian K. R. S.; Roelofs, Andreas K.

    2016-06-21

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well.

  16. Genesis of flake-like morphology and dye-sensitized solar cell performance of Al-doped ZnO particles: a study

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, D.; Mondal, B.; Mukherjee, K., E-mail: kalisadhanm@yahoo.com [CSIR-Central Mechanical Engineering Research Institute, Centre for Advanced Materials Processing (India)

    2017-03-15

    In dye-sensitized solar cell (DSSC) application, the particulate morphologies of photo-anode facilitate efficient dye loading and thus lead to better photo-conversion efficiency than their thin film counterpart. However, till date, the electronic and optical properties as well as the DSSC application of Al-doped ZnO (AZO) particles as photo-anode material is studied less than thin films. Herein, phase formation behavior, morphology evolution, optical properties, and dye-sensitized solar cell performance of wet chemically prepared ZnO and AZO (dopant level: 1–4 mol%) particles are studied. It is found that Al doping modulates significantly the ZnO morphology which in turn results the maximum dye adsorption as well as best photo-conversion efficiency at optimum dopant concentration. Specifically, the nanoparticle of ZnO turns predominantly to flake-like morphology with a higher surface area when 2 mol% Al is doped. Such morphology modulation is expected, since the crystallinity, lattice parameters, and lattice strain of ZnO changes appreciably with Al doping. The variations of optical properties (absorbance, diffused reflectance, and band gap) of AZO materials as compared to primitive ZnO are also identified through UV-vis studies. An attempt is made here to correlate the structural features with the photovoltaic performances of ZnO and AZO.

  17. Bio-corrosion behavior and mechanical characteristics of magnesium-titania-hydroxyapatite nanocomposites coated by magnesium-oxide flakes and silicon for use as resorbable bone fixation material.

    Science.gov (United States)

    Khalajabadi, Shahrouz Zamani; Abu, Aminudin Bin Haji; Ahmad, Norhayati; Yajid, Muhammad Azizi Mat; Hj Redzuan, Norizah Bt; Nasiri, Rozita; Haider, Waseem; Noshadi, Iman

    2018-01-01

    This study was aimed to improve of the corrosion resistance and mechanical properties of Mg/15TiO2/5HA nanocomposite by silicon and magnesium oxide coatings prepared using a powder metallurgy method. The phase evolution, chemical composition, microstructure and mechanical properties of uncoated and coated samples were characterized. Electrochemical and immersion tests used to investigate the in vitro corrosion behavior of the fabricated samples. The adhesion strength of ~36MPa for MgO and ~32MPa for Si/MgO coatings to substrate was measured by adhesion test. Fabrication a homogenous double layer coating with uniform thicknesses consisting micro-sized particles of Si as outer layer and flake-like particles of MgO as the inner layer on the surface of Mg/15TiO2/5HA nanocomposite caused the corrosion resistance and ductility increased whereas the ultimate compressive stress decreased. However, after immersion in SBF solution, Si/MgO-coated sample indicates the best mechanical properties compared to those of the uncoated and MgO-coated samples. The increase of cell viability percentage of the normal human osteoblast (NHOst) cells indicates the improvement in biocompatibility of Mg/15TiO2/5HA nanocomposite by Si/MgO coating. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Mesoporous-activated carbon prepared from chitosan flakes via single-step sodium hydroxide activation for the adsorption of methylene blue.

    Science.gov (United States)

    Marrakchi, F; Ahmed, M J; Khanday, W A; Asif, M; Hameed, B H

    2017-05-01

    In this work, mesoporous-activated carbon (CSAC) was prepared from chitosan flakes (CS) via single-step sodium hydroxide activation for the adsorption of methylene blue (MB). CSAC was prepared using different impregnation ratios of NaOH:CS (1:1, 2:1, 3:1, and 4:1) at 800°C for 90min. The adsorption performance of CSAC was evaluated for MB at different adsorption variables, such MB initial concentrations (25-400mg/L), solution pH (3-11), and temperature (30-50°C). The adsorption isotherm data of CSAC-MB were well fitted to Langmuir model with a maximum adsorption capacity 143.53mg/g at 50°C. Best representation of kinetic data was obtained by the pseudo-second order model. CSAC exhibited excellent adsorption uptake for MB and can potentially be used for other cationic dyes. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Measurements of current-induced spin polarizations in topological insulators Bi2Te2Se and Bi2Se3 thin flakes

    Science.gov (United States)

    Tian, Jifa; Miotkowski, Ireneusz; Hong, Seokmin; Datta, Supriyo; Chen, Yong

    Topological insulators (TIs) possess nontrivial spin-momentum-locked topological surface states (TSS). Real TI can also host trivial surface 2DEG with strong Rashba spin-orbit coupling derived from the bulk states. Both TSS and Rashba 2DEG can generate current induced spin polarization, although the dominant helicities of their spin-momentum locking (SML) are expected to be opposite. Here, we report spin potentiometric measurements in exfoliated bulk-insulating Bi2Te2Se and bulk-metallic Bi2Se3 thin flakes. In both materials, the voltage measured by a FM electrode shows a hysteretic step-like change when the FM magnetization is switched by an in-plane magnetic field. The trend of the voltage change can be reversed by reversing the direction of the dc current, and the amplitude of the spin signal increases linearly with increasing bias current. Such a spin signal is consistent with a current induced spin polarization arising from a helical SML. However, the observed trend of the voltage change is opposite between Bi2Te2Se and Bi2Se3, suggesting opposite signs of dominant spin helicity that we attribute to TSS and Rashba 2DEG respectively.

  20. Functional mastery of percussive technology in nut-cracking and stone-flaking actions: experimental comparison and implications for the evolution of the human brain

    Science.gov (United States)

    Bril, Blandine; Smaers, Jeroen; Steele, James; Rein, Robert; Nonaka, Tetsushi; Dietrich, Gilles; Biryukova, Elena; Hirata, Satoshi; Roux, Valentine

    2012-01-01

    Various authors have suggested behavioural similarities between tool use in early hominins and chimpanzee nut cracking, where nut cracking might be interpreted as a precursor of more complex stone flaking. In this paper, we bring together and review two separate strands of research on chimpanzee and human tool use and cognitive abilities. Firstly, and in the greatest detail, we review our recent experimental work on behavioural organization and skill acquisition in nut-cracking and stone-knapping tasks, highlighting similarities and differences between the two tasks that may be informative for the interpretation of stone tools in the early archaeological record. Secondly, and more briefly, we outline a model of the comparative neuropsychology of primate tool use and discuss recent descriptive anatomical and statistical analyses of anthropoid primate brain evolution, focusing on cortico-cerebellar systems. By juxtaposing these two strands of research, we are able to identify unsolved problems that can usefully be addressed by future research in each of these two research areas. PMID:22106427

  1. Exploring the main function of reduced graphene oxide nano-flakes in a nickel cobalt sulfide counter electrode for dye-sensitized solar cell

    Science.gov (United States)

    Lu, Man-Ning; Lin, Jeng-Yu; Wei, Tzu-Chien

    2016-11-01

    Addition of carbonaceous materials into transition metal sulfide counter electrode (CE) of a dye-sensitized solar cell (DSSC) is a common method to improve the performance of the CE and consequent photovoltaic performance. This improvement is almost without exception attributed to the improvement of overall conductivity after the carbonaceous material addition; however, the root function of these carbonaceous materials in promoting the solar cell efficiency is seldom discussed. In this study, highly crystallized nickel cobalt sulfide (NCS) micro-particles were mixed with a small portion of home-made reduced graphene oxide (rGO) nano-flakes. This NCS/rGO hybrid is subjected to extensive characterizations including X-ray diffraction, Raman spectroscopy, field emission scanning microscopy and electrochemical impedance spectroscopy. It is found that the rGO acts bi-functionally including a co-catalyst in accelerating the tri-iodide reduction for the main NCS catalysts, conductivity promotor to decrease the series resistance of the CE. Proved by electrochemical impedance spectroscopy, it is confirmed that the decrease in series resistance is less insignificant than that in charge transfer resistance, indicating rGO functions more profoundly as a co-catalyst than as a conductivity promotor. Moreover, an argument to highlight the requirement of a CE in a dim-light optimized DSSC is also proposed.

  2. Growth and survival of Octopus vulgaris (Cuvier 1797 paralarvae fed on three Artemia-based diets complemented with frozen fish flakes, crushed zooplankton and marine microalgae

    Directory of Open Access Journals (Sweden)

    Lidia Fuentes

    2011-07-01

    Full Text Available During one month, paralarvae of common octopus (Octopus vulgaris were fed 3 different diets: (1 Artemia sp. enriched with Isochrysis galbana (AI complemented with sand eel (Hyperoplus lanceolatus flakes (AH; (2 Artemia sp. enriched with crushed marine zooplankton (AZ; and (3 Artemia sp. cultured with Isochrysis galbana and further enriched with the microalga Nannochloropsis sp. (AN. The highest dry weight (1.6179±0.3861 mg was registered with the AN diet and the best average survival (67.0% with the AZ diet. Considering the highest dry weight obtained, the moderate high survival and the fact that with this diet it was possible to attain the adult stage, the AN diet was the most appropriate. The reasons for the best result in growth observed with AN are discussed as: (1 the combination of docosahexaenoic acid (DHA provided by Isochrysis galbana and the high eicosapentaenoic acid (EPA content present in Nannochloropsis sp.; (2 the fact that the higher protein/lipid ratio of this diet improves the final dry weight of the paralarvae; and (3 the fact that Nannochloropsis sp. could inhibit the harmful microflora growth in the rearing tank. Regarding nutritional aspects, DHA content per se is not the only determinant factor for growth and survival of O. vulgaris paralarvae, but the presence of a high protein/lipid ratio and a high phospholipid content in the diet could possibly explain the better quality and strength of the paralarvae.

  3. Study of the effect of solidification on graphite flakes microstructure and mechanical properties of an ASTM a-48 gray cast iron using steel molds

    Directory of Open Access Journals (Sweden)

    Ganwarich Pluphrach

    2010-12-01

    Full Text Available The analysis of heat conduction is a widely used technique for control of metallurgical process and solidified eutecticalloy investigation. The objectives of this research are studies about the effect of solidification on graphite flakes microstructureand mechanical properties of an ASTM A-48 gray cast iron using SKD 11 tool steel, S45C medium carbon steel andSS400 hot-rolled steel molds. These three steel molds are important for heat conduction and different from other works. Thisanalysis involving thermocouples immersed in the molten cast alloy is convenient to quickly obtain solidified ingot data onthe behavior of solidification processing. This research intends to describe the thermal analysis using thermocouples, shapeof thermal field and the experimental boundary conditions. The Newtonian thermal analysis and the Fourier thermal analysisdiffer because of the number of used thermocouples. Mechanical properties of structural ASTM A-48 gray cast iron materialsstrongly depend on their microstructure. Metallographic sections are observed to quantitatively measure the relevant microstructuralparameters, as graphite lamellas morphology, eutectic cell size and inclusions content. Results are correlated tothe measured mechanical properties: reduced graphite content increases the tensile strength.

  4. Genesis of flake-like morphology and dye-sensitized solar cell performance of Al-doped ZnO particles: a study

    Science.gov (United States)

    Sengupta, D.; Mondal, B.; Mukherjee, K.

    2017-03-01

    In dye-sensitized solar cell (DSSC) application, the particulate morphologies of photo-anode facilitate efficient dye loading and thus lead to better photo-conversion efficiency than their thin film counterpart. However, till date, the electronic and optical properties as well as the DSSC application of Al-doped ZnO (AZO) particles as photo-anode material is studied less than thin films. Herein, phase formation behavior, morphology evolution, optical properties, and dye-sensitized solar cell performance of wet chemically prepared ZnO and AZO (dopant level: 1-4 mol%) particles are studied. It is found that Al doping modulates significantly the ZnO morphology which in turn results the maximum dye adsorption as well as best photo-conversion efficiency at optimum dopant concentration. Specifically, the nanoparticle of ZnO turns predominantly to flake-like morphology with a higher surface area when 2 mol% Al is doped. Such morphology modulation is expected, since the crystallinity, lattice parameters, and lattice strain of ZnO changes appreciably with Al doping. The variations of optical properties (absorbance, diffused reflectance, and band gap) of AZO materials as compared to primitive ZnO are also identified through UV-vis studies. An attempt is made here to correlate the structural features with the photovoltaic performances of ZnO and AZO.

  5. Actas de Bioquímica: Contractilidade muscular

    OpenAIRE

    Silva, João Alcindo Martins e, 1942-; Ribeiro, Carlos

    1989-01-01

    1.º Curso avançado de Bioquímica aplicada à Medicina: Contractilidade muscular. Lisboa, 15 e 16 de Dezembro de 1986. As actas do Instituto de Bioquímica destinam-se fundamentalmente à publicação dos textos completos, lições, conferências e outros trabalhos apresentados em Cursos Avançados de Pós-Graduação ou Simpósios Científicos organizados, no todo ou em parte, pelo Instituto de Bioquímica da Faculdade de Medicina da Universidade de Lisboa. Adicionalmente, poderão incluir artigos orig...

  6. Vochysiaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Vochysiaceae es reconocida en el Perú por presentar cuatro géneros y 32 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, todas árboles. En este trabajo reconocemos dos especies endémicas en el género Qualea. Estas especies endémicas han sido encontradas en la región Bosques Húmedos Amazónicos, entre los 100 y 160 m de altitud. Ninguna especie endémica se encuentra representada dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  7. Rosaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Wilfredo Mendoza

    2013-10-01

    Full Text Available La familia Rosaceae es reconocida en el Perú por presentar 24 géneros y 113 especies (Brako & Zarucchi, 1993; Mendoza, 2005; Ulloa Ulloa et al., 2004, entre hierbas, arbustos y árboles. En este trabajo reconocemos 14 especies endémicas en cuatro géneros. Las especies endémicas se encuentran principalmente en las regiones Bosques Pluviales Montanos, Bosques Muy Húmedos Montanos y Páramo, entre los 1900 y 3800 m de altitud. Seis especies endémicas se encuentran representadas dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  8. Hepatitis isquémica Ischemic hepatitis

    Directory of Open Access Journals (Sweden)

    Marcos Amuchástegui (h

    2006-10-01

    Full Text Available La hepatitis isquémica es una complicación sumamente infrecuente de cirugía cardiovascular. Las biopsias muestran necrosis centrolobulillar. El término de "hepatitis" fue propuesto debido al aumento de transaminasas similar a aquellas de origen infeccioso, e "isquémica" por falla en la perfusión hepática. Posteriormente se definió el término de hepatitis isquémica como cuadro de elevación aguda y reversible (dentro de las 72 horas de transaminasas de hasta 20 veces el valor normal, asociado a trastornos en la perfusión hepática, luego de haber excluido otras causas de hepatitis aguda o daño hepatocelular. Se describe el caso de un paciente de 53 años que consulta por dolor epigástrico de 12 h de evolución sin fiebre, náuseas ni vómitos, resistente a la medicación. Tenía antecedentes inmediatos de reemplazo de válvula aórtica, y estaba anticoagulado. Evolucionó con shock y fallo multiorgánico. El examen evidenció marcada ictericia y signos de taponamiento pericárdico, asociado a un aumento considerable de enzimas hepáticas. Un ecocardiograma informó signos de taponamiento cardíaco y ausencia de disección aórtica. Se decidió pericardiocentesis, extrayéndose 970 cc. de líquido sanguinolento, y hemodiálisis, con notable mejoría de su estado hemodinámico. Los valores enzimáticos disminuyeron. Los marcadores virales fueron negativos.Ischemic hepatitis is an uncommon cardiovascular surgery complication. Hepatic biopsies show centrolobulillar necrosis. The term "hepatitis" was proposed because of a raise in hepatic enzymes similar with infectious disease, and "ischemic" because of failure in hepatic perfusion. Ischemic hepatitis was then defined as an acute and reversible elevation of hepatic enzymes (within 72 h, associated with disturbance in hepatic perfusion after excluding other causes of acute hepatitis. A 53 year-old male presented complaining of a 12 h epigastric pain, without nausea or vomiting, resistant

  9. Electrical Conductivity of Micas at High Temperatures

    Science.gov (United States)

    Watanabe, T.

    2008-12-01

    Electrical conductivity, along with seismic velocity, gives us clues to infer constituent materials and temperatures in the Earth's interior. Dry rocks have been considered to be electrically insulating at crustal temperatures. Observed high conductivity has been ascribed to the existence of fluids. However, Fuji-ta et al. (2007) recently reported that a dry gneiss shows relatively high conductivity (10-4-10-3 S/m) at the temperature of 300-400°C, and that it is strongly anisotropic in conductivity. They suggested that the alignment of biotite grains governs conductivity of the gneiss sample. Electrical properties of rock forming minerals are still poorly understood. We thus have measured electrical properties of biotite single crystals up to 700°C. In order to get a good understanding of conduction mechanisms, measurements have been also made on phlogopite and muscovite, which are common micas with similar crystallographic structures. Thin plates parallel to cleavages (thickness~0.1mm) were prepared from mica single crystals. Electrical impedance was measured by 2-electrode method. The specimen was kept in nitrogen or argon atmosphere. The conductivity measured parallel to cleavages is higher than that measured perpendicular to cleavages by 3-4 orders of magnitude. However, no significant difference in the activation energy of conductivity was observed between two directions. The activation energy of conductivity is ~50 kJ/mol for biotite and ~100 kJ/mol for phlogopite and muscovite. The conductivity of biotite is higher than those of phlogopite and muscovite by several orders of magnitude at the same temperature. The conductivity of biotite parallel to cleavages is ~10-1 S/m at 400°C. The conductivity of biotite increases irreversibly by heating. The irreversible change was not significant below 450°C. Remarkable increase is observed at the temperature of 450-550°C. No significant change was observed in the second heating. Such an increase in conductivity

  10. Mechanistic Indicators of Childhood Asthma (MICA): piloting ...

    Science.gov (United States)

    Background: Modem methods in molecular biology and advanced computational tools show promise in elucidating complex interactions that occur between genes and environmental factors in diseases such as asthma; however appropriately designed studies are critical for these methods to reach their full potential. Objective: We used a case-control study to investigate whether genomic data (blood gene expression), viewed together with a spectrum of exposure effects and susceptibility markers (blood, urine and nail), can provide a mechanistic explanation for the increased susceptibility of asthmatics to ambient air pollutants. Methods: We studied 205 non-asthmatic and asthmatic children, (9-12 years of age) who participated in a clinical study in Detroit, Michigan. The study combines a traditional epidemiological design with an integrative approach to investigate the environmental exposure of children to indoor-outdoor air. The study includes measurements of internal dose (metals, allergen specific IgE, PAH and VOC metabolites) and clinical measures of health outcome (immunological, cardiovascular and respiratory). Results: Expected immunological indications of asthma have been obtained. In addition, initial results from our analyses point to the complex nature of childhood health and risk factors linked to metabolic syndrome (obesity, blood pressure and dyslipidemia). For example, 31% and 34% of the asthmatic MICA subjects were either overweight (BMI > 25) o

  11. CONFLICTO, VIOLENCIA SOCIOECONÓMICA Y DESPLAZAMIENTO FORZADO EN COLOMBIA

    Directory of Open Access Journals (Sweden)

    Andrés Felipe Mora Cortés

    2013-12-01

    Full Text Available Este artículo introduce el concepto de violencia socioeconómica, que se refiere a mecanismos de regulación de conflictos distributivos y prácticas gubernamentales que eliminan las condiciones base para la reproducción de la vida. Se identifican tres expresiones clave de la violencia socioeconómica: el despojo, la inseguridad económica y la no generación de oportunidades. El artículo insiste en el efecto desproporcionado que dichas expresiones de violencia socioeconómica tienen sobre la población desplazada; también defiende la necesidad de una agenda mínima que erradique la violencia como lógica reguladora de los conflictos distributivos y que sirva de base para la construcción de paz con justicia social en Colombia.

  12. Malvaceae endémicas del Perú

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    Magda Chanco

    2013-10-01

    Full Text Available La familia Malvaceae es reconocida en el Perú con 38 géneros y 264 especies (Brako & Zarucchi 1993, Ulloa et al. 2004, mayormente arbustos y hierbas. En este trabajo reconocemos 87 especies endémicas en 16 géneros. El género más rico en especies endémicas es Nototriche. Las especies endémicas se encuentran en varias regiones ecológicas, entre ellas Altoandina, Mesoandina y Puna Húmeda y Seca, por encima de los 2500 m, hasta alcanzar los límites de la vegetación a 5100 m de altitud. Se aplicaron las categorías y criterios de la UICN a 84 especies. Once especies endémicas se encuentran presentes en el Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  13. Fotoquímica de sistemas Areno/Olefina

    OpenAIRE

    LEO BLASCO, EDGAR ABRAHAM

    2011-01-01

    La presente tesis doctoral, con el título "Fotoquímica de Sistemas Areno/Olefina", se centra en el campo de la fotoquímica dentro de la disciplina de la Química Orgánica. Más concretamente, el objetivo de la misma ha sido el estudio de la fotoquímica y la fotofísica de sistemas bicromofóricos que contienen un fenol y/o una anilina, junto con una olefina. Esto se ha llevado a cabo mediante la síntesis y caracterización de los sustratos a estudiar. Tras la irradiación de los mismos, se identifi...

  14. Cerámica pretensada, su fabricación

    OpenAIRE

    Equipo Editorial

    2017-01-01

    El pretensado puede aplicarse, además del hormigón, a otros muchos materiales, entre ellos, en particular, a las piezas cerámicas. El desarrollo que va cobrando en los países vecinos el procedimiento de la cerámica pretensada nos ha inducido a presentar este breve resumen, en el cual se compendian todas las fases características del proceso de su fabricación.

  15. La industria cerámica turca

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    Cetinov, F.

    2001-02-01

    Full Text Available The Turkish Ceramic Industry has developed a rapid growth, after industrialisation from early fifties. The influence of the public companies was at the beginning critical, but the privatisation process launched during the last years promotes changes to private companies decisions. Most relevant figures for production, foreign trade and employment for ceramic sectors like tiles, roof, refractories, tableware, electroporcelain and red building brick are showed. Trends and prospective for different sectors are very differents. Tile and roofing products show specially relevant figures. Today, Turkey with 250 million square meters tiles produced in 2000, is located in the third position among European countries. Sanitary ware production is also relevant and with 10 million pieces/year, Turkey leading European production. For refractories area, the excess in production capacity, nearly 60% reveals strong problems, in spite of some good basic raw materials. Tableware shows also critical prospective due to the East Asian low production costs. Electroceramics production shows a sustained development for conventional materials. Data for R&D institutions, professional and teaching ceramic network was also described.

    La industria cerámica turca ha experimentado un gran crecimiento, tras el período de reindustrialización que se inicia en todo el país a principio de los años 50. El peso de la empresa pública fue relevante en el surgimiento de la mayor parte de los sectores cerámicos. En los últimos años, los procesos de privatización y el cierre de algunas grandes factorías han hecho que predomine el sector privado. Se ofrecen las cifras más significativas de producción, empleo y comercio exterior de los sectores de pavimentos y revestimientos, sanitarios, vajilla, electrocerámica y refractarios. El crecimiento y las expectativas es muy diferenciado según los diferentes sectores. Los pavimentos y revestimientos se muestran especialmente

  16. Graphene flakes enhance the detection of TiO2-enriched catechins by SALDI-MS after microwave-assisted enrichment.

    Science.gov (United States)

    Juang, Yu-Min; Chien, Han-Ju; Chen, Chao-Jung; Lai, Chien-Chen

    2016-06-01

    In this study, we describe a novel method for the rapid detection of catechins in tea leaves using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). The method involves incubating catechins in a mixture of titanium dioxide (TiO2) nanoparticles and graphene flakes (GF) and then subjecting the mixture to microwave irradiation to facilitate the enrichment of analytes. In this approach, TiO2 nanoparticles serve as probes to enrich catechins while GF serve to increase the desorption/ionization efficiency. The use of the TiO2-GF mixture as matrix provides a number of advantages over TiO2 nanoparticles alone, including higher desorption/ionization efficiency, enhanced analyte enrichment and reduced run time (less 10min). We demonstrate that the addition of GF to nanoparticles of TiO2 improves the detection of catechins by SALDI-MS. At a signal-to-noise ratio of 3, the limits of detection were 0.04pmole for (+)-catechin (C), 0.17pmole for (-)-epigallocatechin (EGC), 0.35pmole for (-)-epicatechin gallate (ECG), and 0.50pmole for (-)-epigallocatechin gallate (EGCG). This method was further applied to determine the catechin content in several tea samples and the results showed good shot-to-shot and sample-to-sample reproducibility (less than 10% and 13%, respectively) as well as good quantitative linearity for the four analytes (R(2)>0.995). The precision calculated as percent relative standard derivation (%RSD), ranged from 3.6% to 12.4%. Overall, we show that this method is a sensitive, simple and high-throughput technique for the detection of catechins in tea. Copyright © 2016. Published by Elsevier B.V.

  17. Análisis de la avería de un generador de escamas de hielo. // Analysis of the failure of ice flake generator.

    Directory of Open Access Journals (Sweden)

    R. Goytisolo Espinosa

    2008-05-01

    Full Text Available En el trabajo se realizó una investigación para esclarecer las causas de la avería del generador de escamas de hielo No.1 dela empresa EPICIEN de Cienfuegos el cual fue instalado recientemente y fue suministrado por la firma Frigofrance S.A.Desde su puesta a punto dicho generador presentó dificultades hasta que se produjo la deformación del cuerpo delgenerador, lo cual lo puso fuera de servicio. La investigación arrojó que la causa de la avería fue la pérdida de la estabilidaddel equilibrio provocada por las elevadas tensiones de compresión que surgen en la pared del cuerpo producto de lasuperposición de los efectos de la presión exterior, la temperatura y una pequeña ovalidad de fabricación en el mismo.Palabras claves: Estabilidad del equilibrio, tensión crítica, generador de escamas de hielo._______________________________________________________________________________Abstract.This research paper was carried to determine the causes of the failure of the Company EPICIEN geneglace No.1 of theFishing Port of Cienfuegos, which was installed recently by the Frigofrance Corporation. Since the generator was installed,it presented several difficulties until the deformation of the body of the generator took place, which put it out of service.The investigation showed that the cause of the failure was the collapse of the wall due to the loss of the stability caused byhigh compression tensions. These stresses arise in the body wall due to the overlapping of the effects of the externalpressure, the temperature and a small geometric imperfection of construction found in the wall.Key words: Ice flake generator, loss of stability, critical stress.

  18. Effects of glycerin concentration in steam-flaked corn-based diets with supplemental yellow grease on performance and carcass characteristics of finishing beef steers.

    Science.gov (United States)

    Buttrey, E K; Luebbe, M K; McCollum, F T; Cole, N A; MacDonald, J C; Hales, K E

    2015-07-01

    Forty-eight individually fed crossbred steers (initial BW = 381 ± 7.61 kg) were used to determine the effects of glycerin (GLY) concentration in steam-flaked corn (SFC)-based diets with added yellow grease on animal performance and carcass characteristics. Glycerin was included at 0, 2.5, 5, and 10% dietary DM replacing SFC. A completely randomized design was used with steers as the experimental unit, and the model included the fixed effects of diet. Contrast statements were used to determine linear and quadratic effects of GLY inclusion. Final BW and DMI were not affected (P > 0.27) by GLY concentration. Average daily gain and G:F based on live BW did not differ as GLY level increased in the diet from 0 to 10% of DM (P > 0.33). Carcass-adjusted final BW and carcass-adjusted G:F were also not affected by GLY concentration (P > 0.22); however, carcass-adjusted ADG tended to respond quadratically by decreasing from 2.5 to 5% GLY inclusion and increasing thereafter (P = 0.10). Calculated dietary NEm and NEg did not differ as GLY increased in the diet (P > 0.37). Hot carcass weight tended to respond quadratically, decreasing from 2.5 to 5% GLY and increasing thereafter (P = 0.10). Likewise, dressing percentage tended to respond quadratically by decreasing from 2.5 to 5% GLY inclusion and increasing to 10% GLY inclusion (P = 0.09). Fat thickness decreased linearly as GLY inclusion increased in the diet (P 0.21). Calculated yield grade (YG) decreased linearly as GLY increased in the diet from 0 to 10% of DM (P = 0.04). Based on our results, there was no animal performance benefit for replacing SFC with GLY in diets containing yellow grease, and the only change in carcass merit was a slight improvement in YG.

  19. La Proteómica, otra cara de la genómica

    OpenAIRE

    Mojica, Tobías; Sánchez, Oscar; Bobadilla, Leonardo

    2003-01-01

    Las proteínas son lo que uno podría llamar los arquitectos de la vida, pues son cruciales en los procesos celulares de todos los seres vivos. Las proteínas están implicadas en la catálisis de las reacciones químicas celulares, el transporte de moléculas, la transducción de señales, la segregación del material genético, la producción y el manejo de la energía. El programa celular vital necesita del trabajo coordinado de muchos tipos diferentes de proteínas (1). La mayor parte del peso seco de ...

  20. La Industria Química: Importancia y Retos

    Directory of Open Access Journals (Sweden)

    Nancy Montes-Valencia

    2015-06-01

    Full Text Available La química siempre ha estado presente en la vida del hombre para satisfacer sus necesidades y mejorar su calidad de vida. Hoy en día la industria química es un importante sector industrial presente en la mayoría de países, que dinamiza el crecimiento económico, genera empleo y ofrece diversidad de productos, no obstante produce contaminación al medio ambiente y utiliza recursos naturales no renovables. Por lo tanto surge el concepto de química verde como respuesta a la problemática ambiental cuya estructura es la sostenibilidad, siendo su principal objetivo prevenir la generación de emisiones y armonizar la química con los recursos naturales. Existe un gran reto para la industria química y es encontrar fuentes alternativas de energía para no seguir dependiendo del petróleo, el gas natural y el carbón, una de estas es el uso de la biomasa para la obtención de combustibles líquidos.

  1. Processing and Characterization of Nanocrystalline Mica Glass-Ceramics

    Directory of Open Access Journals (Sweden)

    V. Khani

    2012-10-01

    Full Text Available In order to fabrication of transparent glass-ceramics with Li-mica nano crystals, the glasses with chemical composition of 94.9 mass% Li(1+xMg3AlSi3(1+xF2 (x=0.5 with 5.1 mass% MgF2 were crystallized. The glasses were fabricated via the conventional melt-quenching technique. Mica crystals were precipitated in the glass phase by later heat treatment. Glass samples had glass transition temperature (Tg, 557 ?C, softening temperature (Ts, 603 ?C, and crystallization peak temperature (Tp, 655 ?C. The fine mica crystals with size of separation. It’s confirmed that both as-quenched and heat-treated samples are transparent in the visible wave length.

  2. Moraceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Pamela Cáceres

    2013-10-01

    Full Text Available La familia Moraceae es reconocida en el Perú por presentar 19 géneros y 128 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, la mayoría arbóreas y/o hemiepífitos. En este trabajo reconocemos dos especies endémicas en igual número de géneros. Las especies endémicas se encuentran en la región Bosques Húmedos Amazónicos, entre los 115 y 220 m de altitud. Ambas especies endémicas se encuentran dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  3. CFD e a Defesa Química

    OpenAIRE

    Ardson S. Vianna Jr.; Universidade de São Paulo; Fábio C. S. de Siqueira; Universidade de São Paulo; Leandro R. Quintal; Instituto Militar de Engenharia; Antônio Luis S. Lima; Instituto Militar de Engenharia

    2014-01-01

    A fluidodinâmica computacional é uma ferramenta de modelagem e simulação que pode ser utilizada para compreender fluxos tridimensionais, por exemplo, distribuições de concentrações de substâncias químicas. Este trabalho apresenta diversos conceitos relacionados com a fluidodinâmica computacional de forma a assinalar sua importância. São apresentados dois estudos de caso, a dispersão de gás cloro de uma fonte transiente e de uma fonte contínua, onde isosuperfícies de concentração são analisada...

  4. Mejora aerodinámica de un turismo

    OpenAIRE

    Martin Morillo, Daniel

    2016-01-01

    L’objectiu principal d’aquest projecte és estudiar l’aerodinàmica d’un Volkswagen Golf MK1, aportant, a través de l’anàlisi realitzada y mitjançant canvis a la carrosseria del vehicle en qüestió, una millora aerodinàmica per a l’automòbil seleccionat. Al mateix temps, aprofitant la presentació explícita de la millora aerodinàmica del vehicle, es vol fer èmfasi en el fet que els afegits en el xassís de l’automòbil no són una acció únicament estètica, sinó que permeten una millora aerodinàmi...

  5. Onagraceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Susy Castillo

    2013-10-01

    Full Text Available Esta es la familia de las «fucsias», la cual es reconocida en el Perú por presentar seis géneros y 76 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, principalmente arbustos y hierbas. En este trabajo reconocemos 24 especies endémicas, la mayoría en el género Fuchsia. Las especies endémicas se encuentran mayormente en la región Bosques Muy Húmedos Montanos, entre los 1600 y 2500 m de altitud. Diez especies endémicas se encuentran representados dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  6. Gentianaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Susy Castillo

    2013-10-01

    Full Text Available La familia Gentianaceae es reconocida en el Perú por presentar alrededor de 15 géneros y aproximadamente de 170 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004; S. Castillo, com.pers., mayormente hierbas y arbustos. En este trabajo se reconoce 103 especies endémicas en siete géneros. Los géneros con mayor número de especies endemicas son Gentianella y Macrocarpaea. Las especies endémicas ocupan principalmente las regiones de la Puna Húmeda y Seca, Páramo y Bosque Muy Húmedo Montano, entre los 1000 y 5100 m de altitud. Se aplicaron las categorías y criterios de la UICN a 99 especies. Treinta y tres especies endémicas se encuentran representadas dentro de un área protegida.

  7. Effects of altering alfalfa hay quality when feeding steam-flaked versus high-moisture corn grain on ruminal fermentation and lactational performance of dairy cows.

    Science.gov (United States)

    Eun, J-S; Kelley, A W; Neal, K; Young, A J; Hall, J O

    2014-12-01

    This experiment was performed to test a hypothesis that nutritive benefits of feeding high-moisture corn (HMC) would be different when fed with different qualities of alfalfa hay (AH) due to associative effects on ruminal fermentation and nutrient utilization efficiency. Eight multiparous lactating Holstein cows were used; 4 were surgically fitted with ruminal cannulas. Days in milk averaged 184 ± 10.7 at the start of the experiment. The experiment was performed in a duplicate 4 × 4 Latin square design. Within each square, cows were randomly assigned to a sequence of 4 diets during each of the four 21-d periods (14 d of treatment adaptation and 7 d of data collection and sampling). A 2 × 2 factorial arrangement was used; fair-quality AH [FAH; 39.6% neutral detergent fiber (NDF) and 17.9% crude protein (CP)] or high-quality AH (HAH; 33.6% NDF and 21.9% CP) was combined with steam-flaked corn (SFC) or HMC to form 4 treatments: FAH with SFC, FAH with HMC, HAH with SFC, and HAH with HMC. The AH was fed at 32% dry matter (DM) content, whereas SFC or HMC was included at 17% DM content. Quality of AH did not affect DM intake, whereas feeding HMC decreased DM intake, regardless of quality of AH. Digestibility of DM was greater for cows fed HAH compared with those fed FAH (70.1 vs. 67.6%). Digestibility of NDF increased by feeding HMC (67.6 vs. 58.4%), but not by quality of AH. Under FAH, starch digestibility decreased by feeding HMC compared with SFC (85.7 vs. 95.0%), but it was similar under HAH, resulting in an interaction between quality of AH and type of corn grain (CG). Feeding different qualities of AH did not affect milk yield; however, feeding HMC decreased milk yield in FAH diet, causing an AH × CG interaction. Efficiency of milk yield/DM intake was improved due to feeding HMC, regardless of the quality of the AH. In addition, dietary N utilization for milk N tended to increase by feeding HMC, but it was not influenced by quality of AH. Yield of microbial

  8. Fabrication of conducting composite sheets using cost-effective graphite flakes and amorphous styrene acrylonitrile for enhanced thermistor, dielectric, and electromagnetic interference shielding properties

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, Varij, E-mail: varijpanwarcertain@gmail.com [Electronics and Communication Engineering, Graphic Era University, Dehradun, Uttarakhand (India); Gill, Fateh Singh; Rathi, Vikas; Tewari, V.K. [Electronics and Communication Engineering, Graphic Era University, Dehradun, Uttarakhand (India); Mehra, R.M. [Sharda University, Greater Noida (India); Park, Jong-Oh, E-mail: jop@jnu.ac.kr [School of Mechanical Engineering, Chonnam National University, Gwangju (Korea, Republic of); Park, Sukho, E-mail: shpark12@dgist.ac.kr [Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu (Korea, Republic of)

    2017-06-01

    The fabrication of strong conducting composite sheets (CCSs) using a simple technique with cost-effective materials is desirable for capacitor, decoupling capacitor, and electromagnetic interference (EMI) shielding applications. Here, we used cost-effective graphite flakes (GFs) as a conducting filler and amorphous poly (styrene-co-acrylonitrile) (PSAN) as an insulating polymer to fabricate a CCS via a simple mechanical mixing and hot compression molding process in 2.5 h, with the aim to save time and avoid the use of toxic reagents, which are generally used in chemical methods. In the present method, the GFs are connected in diffusively adhere polymer matrix, controlled by temperature and pressure that generate the conduction in the CCSs. The resulting PSAN/GF CCSs were characterized by using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and hardness tests. The GFs penetrated the interfacial region of PSAN, thus improving the thermistor and dielectric properties (dielectric constant, AC conductivity, and dissipation factor) of the PSAN/GF CCSs. Furthermore, the PSAN/GF CCSs showed enhanced hardness and EMI shielding effectiveness (SE) properties in the X-band frequency range (8.5–12.5 GHz). The percolation theory was implemented to DC and AC conductivity. To detect the transition of the dielectric properties, the dielectric constant of the CCSs was analyzed with increasing volume fraction of GFs in the radio frequency region. The improved dielectric constant, AC conductivity, and dissipation factor of the PSAN/GF CCS, indicated a significant improvement in their EMI shielding properties in the X-band frequency range, which were measured using the waveguide method. The ac conductivity of PSAN/GF CCS shows stable behavior in the higher frequency ranges. The EMISE of PSAN/GF CCS were found to increase with increasing GF content due to the absorbance mechanism. - Highlights: • Enhanced hardness and

  9. Tuberculose multissistémica

    Directory of Open Access Journals (Sweden)

    S. Saldanha Coelho

    1999-07-01

    computer tomogram (CT revealed a right pleural effusion and a nodular cavitated lesion in the posterior segment of the upper right lung lobe. A pleural biopsy was performed and acid fast bacilii (AFB were seen. Specific treatment for tuberculosis was started. The lung findings resolved but fever and abdominal pain persisted. After several diagnostic procedures a laparotomy was required. A terminal ileitis with a fistulous comunication to the sigmoid colon was confirmed and a partial colectomy was done. There was mesenteric lymph node enlargement and AFB ewere identified on biopsy material. The patient remains free of disease after 10 months.REV PORT PNEUMOL 1999; V (4: 427-434 Key-words: Terminal ileitis, Crohn’s disease, intestinal tuberculosis: multisistemic tuberculosis, : Palavras-chave, Ileite terminal, doença de Crohn, tuberculose intestinal, tuberculose multissistémica

  10. Guía astronómica

    OpenAIRE

    Duque Escobar, Gonzalo

    2003-01-01

    Esta Guía Astronómica es una versión de mis conferencias en el Taller de Astronomía desde 1985 y en el curso de Contexto en Astronomía desde 2000, dos actividades ofrecidas por la Universidad Nacional de Colombia en Manizales, como espacios disponibles para la comunidad académica y para los aficionados a la astronomía. Por esa razón, este texto propio de la vida universitaria, ha evolucionado hasta encontrar el lenguaje sencillo y la medida adecuada en la extensión y profundidad de los tem...

  11. El desarrollo sostenible desde una prespectiva sistémica

    OpenAIRE

    Gallopín, Gilberto C.

    2010-01-01

    En aquest treball es presenta una visió sistèmica del concepte de desenvolupament sostenible, i es diferencia del concepte de sostenibilitat amb què sovint es confon. Aquesta mirada sistèmica permet ressaltar les fonts de les ambigüitats que apareixen en les diferents discussions sobre el desenvolupament sostenible. El treball comença amb una breu recapitulació sobre l’origen i l’evolució del concepte i una breu discussió sobre la pertinença de la distinció que alguns proposen entre desenv...

  12. Diplopia aguda postlaberintectomía química

    OpenAIRE

    Santos Gorjón, Pablo; Collado Lorduy, Teresa; Sánchez Terradillos, Elena; Sánchez-Jara Sánchez, Juan Luis; Velasco García, María Jesús; Martín Hernández, Gonzalo

    2012-01-01

    [ES]Introducción: La laberintectomía química con gentamicina es un procedimiento ambulatorio considerado seguro y eficaz y que provoca poca iatrogenia. Presentamos un caso clínico de una rara complicación de la técnica y se revisa la literatura. Caso clínico: Paciente diagnosticada de enfermedad de Ménière izquierda que no responde a esquema de tratamiento conservador. Se propone realizar terapia intratimpánica con corticoide y después una laberintectomía química. Aparece de forma aguda u...

  13. Cetoacidosis normoglucémica en una embarazada

    OpenAIRE

    Maure, Gabriela; Dromi, Carolina; Lavandaio, Hugo; Marcucci, Guillermo; Santolín, Laura; Carena, José Alberto

    2012-01-01

    La cetoacidosis normoglucémica se define como un cuadro de cetoacidosis diabética, con niveles de bicarbonato menores a 10 mEq/l, cetonemia o cetonuria y niveles de glucosa inferiores a 200 mg/dl. Representa hasta el 30% de las formas de presentación de cetoacidosis diabética. Se comunica un caso de cetoacidosis normoglucémica en una embarazada con el objeto de destacar esta inusual asociación y forma de presentación y realizar comentarios res...

  14. Resurgimiento comunitario ante la nueva realidad socioeconómica

    OpenAIRE

    Barrera Algarín, Evaristo; SARASOLA SÁNCHEZ SERRANO, José Luis; Malagón Siria, José Carlos

    2017-01-01

    Este estudio analizó las características de los movimientos comunitarios que han cobrado fuerza tras el inicio de la crisis económica en estos últimos años. El trabajo de campo se realizó en cuatro contextos específicos de experiencias comunitarias: Dos de Monedas Sociales, uno de Huertos Urbanos, y otro de Bancos del Tiempo. Hipótesis: Los movimientos de base comunitaria que suponen una ayuda a aspectos económicos de las familias e individuos, toman fuerza en situaciones de crisis económicas...

  15. Voloshinite, a new rubidium mica from granitic pegmatite of Voron'i Tundras, Kola Peninsula, Russia

    Science.gov (United States)

    Pekov, I. V.; Kononkova, N. N.; Agakhanov, A. A.; Belakovsky, D. I.; Kazantsev, S. S.; Zubkova, N. V.

    2010-12-01

    Voloshinite, a new mineral of the mica group, a rubidium analogue of lepidolite, has been found from the rare-element granitic pegmatite at Mt. Vasin-Myl'k, Voron'i Tundras, Kola Peninsula, Russia. It is closely associated with pollucite and lepidolite and commonly with muscovite, albite, and quartz; K,Rb-feldspar, rubicline, spodumene, montebrasite, and elbaite are among associated minerals as well. Voloshinite, a late mineral that formed after pollucite, commonly fills polymineralic veinlets and pods within the pollucite aggregates. It occurs as rims up to 0.05 mm thick around lepidolite, as intergrowths of tabular crystals up to 0.25 mm in size, and occasionally replaces lepidolite. The new mineral is colorless, transparent, with vitreous luster. Cleavage is eminent parallel to {001}; flakes are flexible. The calculated density is 2.95 g/cm3. The new mineral is biaxial (-), with 2 V = 25°, α calc = 1.511, β = 1.586, and γ = 1.590. The optical orientation is Y = b, Z = a. The chemical composition of the type material determined by electron microprobe (average of five point analyses; Li has been determined with ICP-OES) is as follows (wt %): 0.03 Na2O, 3.70 K2O, 12.18 Rb2O, 2.02 Cs2O, 4.0 Li2O, 0.03 CaO, 0.02 MgO, 0.14 MnO, 21.33 Al2O3, 53.14 SiO2, 6.41 F, -O = F2 2.70, total is 100.30. The empirical formula is: (Rb0.54K0.33Cs0.06)Σ0.93(Al1.42Li1.11Mn0.01)Σ2.54(Si3.68Al0.32)Σ4O10 (F1.40(OH)0.60)Σ2. The idealized formula is as follows: Rb(LiAl1.5□0.5)[Al0.5Si3.5O10]F2. Voloshinite forms a continuous solid solution with lepidolite. According to X-ray single crystal study, voloshinite is monoclinic, space group C2/ c. The unit-cell dimensions are: a = 5.191, b = 9.025, c = 20.40 Å, β = 95.37°, V= 951.5 Å3, Z = 4. Polytype is 2 M 1. The strongest reflections in the X-ray powder diffraction pattern ( d, Å- I[ hkl]) are: 10.1-60[001]; 4.55-80[020, 110, 11 bar 1 ]; 3.49-50[11 bar 4 ]; 3.35-60[024, 006]; 3.02-45[025]; 2.575-100[11 bar 6 , 131, 20 bar 2 , 13

  16. Jackfruit (Artocarpus heterophyllus Lam.) peel: A better source of antioxidants and a-glucosidase inhibitors than pulp, flake and seed, and phytochemical profile by HPLC-QTOF-MS/MS.

    Science.gov (United States)

    Zhang, Lu; Tu, Zong-Cai; Xie, Xing; Wang, Hui; Wang, Hao; Wang, Zhen-Xing; Sha, Xiao-Mei; Lu, Yu

    2017-11-01

    Jackfruit (Artocarpus heterophyllus Lam.) peel is an underutilized by-product in both, the production and processing of jackfruit. This research compared the antioxidant and hypoglycemic potential of jackfruit peel with jackfruit pulp, flake and seed for the first time. The phytochemical profile of peel extract was characterized with HPLC-QTOF-MS/MS. Results revealed that peel extract exhibited the highest total phenolic and total flavonoid content, and the phenolics was 4.65, 4.12 and 4.95 times higher than that of pulp, flake and seed extract, respectively. The strongest DPPH and ABTS + scavenging ability, α-glucosidase inhibition were also found in peel extract, and the α-glucosidase inhibition was about 11.8-fold of that of acarbose. The HPLC-QTOF-MS/MS analysis led to the tentative identification of 53 compounds, prenylflavonoids, hydroxycinnamic acids and glycosides are the predominant bioactive compounds. Above results reveal promising potential of jackfruit peel as a new source of natural antioxidants and hypoglycemic agents. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. El etanol como materia prima petroquímica

    Directory of Open Access Journals (Sweden)

    Luis M. Carballo

    1981-07-01

    Full Text Available En este trabajo se presentan los aspectos relevantes de un programa a de investigación, aprobado por el CINDEC y COLCIENCIAS, sobre el desarrollo y estudio cinético de catalizadores para algunas reacciones químicas en las que el etanol está involucrado como reactante.

  18. Un buen comienzo para la historia económica

    Directory of Open Access Journals (Sweden)

    José Eduardo Rueda Enciso

    2012-06-01

    Full Text Available Economía colombiana del siglo XIX. Adolfo Meisel Roca y María Teresa Ramírez (EDS.. Banco de la República, Fondo de Cultura Económica, Bogotá, 2010, 723 págs., il., + 1 CD-ROM.

  19. El etanol como materia prima petroquímica

    Directory of Open Access Journals (Sweden)

    Luis M. Carballo

    2011-10-01

    Full Text Available En este trabajo se presentan los aspectos relevantes de un programa a de investigación, aprobado por el CINDEC y COLCIENCIAS, sobre el desarrollo y estudio cinético de catalizadores para algunas reacciones químicas en las que el etanol está involucrado como reactante.

  20. Dinámica de las psicosis delirantes

    OpenAIRE

    Santos Ramírez, Mario

    2014-01-01

    El delirio es un trastorno del contenido del pensamiento, pero también es el síntoma principal de los trastornos psicóticos y uno de los temas más estudiados en la psiquiatría y psicopatología dinámica a lo largo de la historia.

  1. 21 CFR 73.350 - Mica-based pearlescent pigments.

    Science.gov (United States)

    2010-04-01

    ... foods: (i) Cereals. (ii) Confections and frostings. (iii) Gelatin desserts. (iv) Hard and soft candies... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Mica-based pearlescent pigments. 73.350 Section 73.350 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL...

  2. Synthesis of nanocomposites using glasses and mica as templates

    Indian Academy of Sciences (India)

    Nanoparticles of silver and silver oxide could be aligned in a polymethylmethacrylate film by an a.c. electric field of 1 MHz frequency. The composites showed large sensitivity to relative humidity. Lead sulfide nanowires of diameter, 1.2 nm, were grown within the nanochannels of Na-4 mica. These exhibited a semiconductor ...

  3. Laboratori de Química Orgànica. Manual de Pràctiques

    OpenAIRE

    Verdaguer i Espaulella, Xavier

    2016-01-01

    Manual d'experiències de Laboratori de Química Orgànica (LQO) del Grau de Química de la Univesitat de Barcelona. La primera part conté informació general d'actuació en laboratori de química orgànica. La segona part descriu com dur a terme 10 experiments de química orgànica.

  4. 78 FR 54758 - Listing of Color Additives Exempt From Certification; Mica-Based Pearlescent Pigments...

    Science.gov (United States)

    2013-09-06

    ... regulations to provide for the safe use of mica-based pearlescent pigments prepared from titanium dioxide and... titanium dioxide and mica as color additives in distilled spirits containing not less than 18 percent and... Certification; Mica-Based Pearlescent Pigments; Confirmation of Effective Date AGENCY: Food and Drug...

  5. APEC 2004: "viejas" y nuevas dinámicas de apertura económica transpacífica

    National Research Council Canada - National Science Library

    Hernán Gutiérrez B

    2004-01-01

    En 2004, el foro de Cooperación Económica de Asia-Pacífico o APEC, según su sigla en inglés, cumplirá 15 años desde que fue creado en Canberra, como resultado de los esfuerzos de australianos y japoneses por impedir el quiebre...

  6. Sobre la enseñanza de la termoquímica en la Química del nivel bachillerato

    OpenAIRE

    Trejo Candelas, L.

    2009-01-01

    La termoquímica de nivel bachillerato no ha podido integrar la termodinámica con la química general. El modelo central que se pretende aprender de energía de enlace (se libera energía cuando un enlace químico se forma) es contrario a lo que piensan muchos profesores y estudiantes, y se necesitan experimentos y tiempo para su construcción en el aula. Para estudiar este problema revisamos algunas dificultades relacionadas al aprendizaje de la termoquímica. Identificamos el qué conviene enseñar ...

  7. Highly charged swelling mica reduces Cu bioavailability in Cu-contaminated soils

    Energy Technology Data Exchange (ETDEWEB)

    Stuckey, Jason W. [Department of Crop and Soil Sciences, Pennsylvania State University, 116 ASI Building, University Park, PA 16802 (United States); Neaman, Alexander [Facultad de Agronomia, P. Universidad Catolica de Valparaiso, Centro Regional de Estudios en Alimentos Saludables (Chile); Ravella, Ramesh; Komarneni, Sridhar [Department of Crop and Soil Sciences, Pennsylvania State University, 116 ASI Building, University Park, PA 16802 (United States); Martinez, Carmen Enid [Department of Crop and Soil Sciences, Pennsylvania State University, 116 ASI Building, University Park, PA 16802 (United States)], E-mail: cem17@psu.edu

    2009-01-15

    This is the first test of a highly charged swelling mica's (Na-2-mica) ability to reduce the plant-absorbed Cu in Cu-contaminated soils from Chile. Perennial ryegrass (Lolium perenne L.) was grown in two acid soils (Sector 2: pH 4.2, total Cu = 172 mg Cu kg{sup -1} and Sector 3: pH 4.2, total Cu = 112 mg Cu kg{sup -1}) amended with 0.5% and 1% (w/w) mica, and 1% (w/w) montmorillonite. At 10 weeks of growth, both mica treatments decreased the shoot Cu of ryegrass grown in Sector 2 producing shoot Cu concentrations above 21-22 mg Cu kg{sup -1} (the phytotoxicity threshold for that species), yet the mica treatments did not reduce shoot Cu concentrations when grown in Sector 3, which were at a typical level. The mica treatments improved shoot growth in Sector 3 by reducing free and extractable Cu to low enough levels where other nutrients could compete for plant absorption and translocation. In addition, the mica treatments improved root growth in both soils, and the 1% mica treatment reduced root Cu in both soils. This swelling mica warrants further testing of its ability to assist re-vegetation and reduce Cu bioavailability in Cu-contaminated surface soils. - In situ remediation of Cu-contaminated soils with a synthetic mica (Na-2-mica) will aid in re-vegetative efforts.

  8. Química ambiental e química verde : como se integram às áreas tradicionais da química na visão de graduandos

    OpenAIRE

    Porto Alves, P.

    2009-01-01

    Este trabalho investiga as concepções de alunos de graduação em química da Universidade de São Paulo (USP) a respeito do status da Química Ambiental e da Química Verde em relação ao conjunto do conhecimento químico. O estudo foi feito através da análise de quatorze mapas conceituais produzidos por alunos do terceiro ano de graduação considerando-se as concepções manifestadas a respeito da química ambiental e da química verde, bem como as relações estabelecidas entre elas e as cinco áreas trad...

  9. Química de condensaciones moleculares iluminadas por objetos

    Science.gov (United States)

    Girart Medina, J. M.

    La fuerte radiación generada por los objetos Herbig-Haro (HH) impregna las nubes moleculares en las cuáles están embebidas, alterando significativamente la composición química de las regiones más cercanas a estos objetos. Así pues, condensaciones moleculares densas originalmente ``oscuras'' (es decir con la mayor parte de moléculas trazadoras de gas denso observacionalmente invisibles) pasan a ser molecularmente ``iluminadas'' por los objetos HH. El estudio de estas condensaciones ``iluminadas'' por los objetos HH no sólo nos permite conocer cuáles son sus propiedades químicas y físicas, sino que también nos proporciona información valiosa de las nubes moleculares oscuras.

  10. Genômica comparativa em gramíneas.

    OpenAIRE

    Bervald, Clauber Mateus Priebe

    2009-01-01

    O uso de seqüências de DNA tem sido à base da genômica comparativa para estudos evolucionários e a transferência de informações de espécies modelo para espécies agrícolas tem revolucionado a genética molecular e estratégias de melhoramento das culturas. A combinação de métodos clássicos de genética e melhoramento com tecnologias moleculares de análise genômica abre uma nova perspectiva para a ampliação do conhecimento das bases genéticas e aceleração de programas de melhoram...

  11. Análise proteômica da esquizofrenia

    Directory of Open Access Journals (Sweden)

    Bruno M. Oliveira

    2013-01-01

    Full Text Available Valioso conhecimento a respeito de esquizofrenia tem sido gerado recentemente para decifrar sua patobiologia e revelar biomarcadores. Entretanto, esforços ainda são necessários, especialmente se levarmos em conta que essa debilitante desordem mental afeta aproximadamente 30 milhões de pessoas ao redor do mundo. Considerando que esquizofrenia é resultado de uma complexa interação entre fatores ambientais, função genética alterada e expressão proteica diferencial sistemática, a proteômica é provavelmente uma ferramenta adequada ao estudo dessa desordem. Aqui sintetizamos os principais achados em estudos proteômicos e posteriores direções a serem tomadas de forma a melhor compreender a bioquímica da esquizofrenia, bem como revelar biomarcadores.

  12. Dilleniaceae endémicas del Perú

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    Blanca León

    2013-10-01

    Full Text Available La familia Dilleniaceae es una adición reciente a la flora endémica peruana; los endemismos han sido recolectados y reconocidos hacia fines de los 1990. Está representada en el Perú por seis géneros y 23 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, la mayoría lianas. En este trabajo reconocemos tres endemismos en dos géneros. Las especies endémicas ocupan la región Bosques Húmedos Amazónicos, entre los 100 y 125 m de altitud. No se encuentra representada en el Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  13. Crassulaceae endémicas del Perú

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    Blanca León

    2013-10-01

    Full Text Available La familia Crassulaceae es reconocida en el Perú por presentar cinco géneros y 29 especies (Brako & Zarucchi, 1993, mayormente arbustos y hierbas. En este trabajo reconocemos 13 especies y dos variedades como endemismos peruanos en tres géneros. Echeveria es el género con el mayor número de especies endémicas. Los taxones endémicos ocupan principalmente las regiones Mesoandina y Puna Húmeda y Seca, entre los 1700 y 4500 m de altitud. Se aplicaron las categorías y criterios de la UICN a nueve taxones. Dos Crassulaceae endémicas están representados dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  14. Perspectivas de futuro en historia económica

    OpenAIRE

    Sebastián COLL MARTÍN

    2000-01-01

    Editada en la Fundación Empresa Pública Este artículo explora posibles vías de evolución de la historia económica en un futuro próximo. El autor pasa revista a la trayectoria de la disciplina durante las últimas décadas, con especial atención a la influencia de la revolución cliométrica, y argumenta que la historia económica pasa actualmente por una situación crítica. Para salir de ella, aboga por una mayor atención al cambio tecnológico y al cambio institucional, como temas distintivos de...

  15. Variantes anatómicas del septum pellucidum

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    P. Sartori

    2015-04-01

    Durante la vida embrionaria existen variantes anatómicas del septum pellucidum que se disponen en sentido rostro-dorsal. Estas son el cavum del septum pellucidum, el cavum vergae y el cavum velum interpositum. Su presencia o ausencia puede estar relacionada con alteraciones del desarrollo del sistema nervioso y trastornos cognitivo-psiquiátricos, por lo que deben conocerse bien para evitar diagnósticos erróneos.

  16. Variedades químicas de Hyptis mutabilis

    OpenAIRE

    Luz,Α. I. Reis; Zoghbi,Μ. G. Bichara; Silva,M. L. da; L. S. Ramos; Soares Maia,J. G.

    1989-01-01

    RESUMODuas variedades químicas de Hyptis mutabilis foram estudadas. Uma delas, a variedade A, contém α e β-pineno, α e β-feladreno e β-cariofileno como os principais constituintes de seu óleo essencial. A outra variedade B, apresentou α-cimeno , 1,8-cineol, timol, β-cariofileno e β-elemeno como os seus principais componentes.

  17. Premio Nobel de Ciencias Económicas 1999

    Directory of Open Access Journals (Sweden)

    Academia Real de Ciencias de Suecia

    1999-12-01

    Full Text Available La Academia Real de Ciencias de Suecia concedió el Premio Banco de Suecia en Ciencias Económicas en memoria a Alfred Nobel, 1999, al Profesor Robert A. Mundell, Universidad de Culumbia, Nueva York, por su analisis de la politica monetaria y fiscal en diferentes regimenes de la tasa de cambio, y por su analisis de las areas monetarias optimas.

  18. La elite económica Argentina, 1810-1914

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    Roy Hora

    2014-12-01

    Full Text Available Este artículo analiza los principales rasgos del sector más poderoso de la elite económica argentina del período 1810-1914. El trabajo discute las principales interpretaciones sobre las características y naturaleza de este grupo, pone de relieve algunas de limitaciones de los enfoques más habituales sobre el tema, y sugiere de qué manera conceptualizarlo de forma productiva. Aunque el objeto de este trabajo es la elite económica, todo análisis de este actor supone a la vez una manera de concebir las características del sistema de poder y del entorno económico en el que se desenvuelve la acción de los hombres de fortuna. Por este motivo, este trabajo formula algunas consideraciones generales sobre las características del Estado (argentino y el capitalismo (pampeano, con el fin de precisar mejor qué tipo de elite económica dominó la producción rural y la economía argentina en el período de crecimiento exportador que se extendió desde la Independencia hasta la Primera Guerra Mundial. El trabajo toma distancia de los estudios que enfatizan la importancia de la dimensión política para explicar el proceso de constitución y reproducción de esta elite económica, enfatizando en cambio los determinantes económicos de este proceso. El ensayo no aporta nueva evidencia empírica, sino una reflexión a partir de la literatura existente.

  19. Premio Nobel de ciencias Económicas 1998

    Directory of Open Access Journals (Sweden)

    Sen Amartya

    1998-12-01

    Full Text Available

    La Academia Real de Ciencias de Suecia ha decidido otorgar el premio Banco de Suecia 1998 en Ciencias Económicas, en Memoria de Alfred Nobel, al Profesor Amartya Sen, del Trinity College, Reino Unido, y ciudadano indio, por sus contribuciones a la economía del bienestar.

     

     

     

  20. MICA: desktop software for comprehensive searching of DNA databases

    Directory of Open Access Journals (Sweden)

    Glick Benjamin S

    2006-10-01

    Full Text Available Abstract Background Molecular biologists work with DNA databases that often include entire genomes. A common requirement is to search a DNA database to find exact matches for a nondegenerate or partially degenerate query. The software programs available for such purposes are normally designed to run on remote servers, but an appealing alternative is to work with DNA databases stored on local computers. We describe a desktop software program termed MICA (K-Mer Indexing with Compact Arrays that allows large DNA databases to be searched efficiently using very little memory. Results MICA rapidly indexes a DNA database. On a Macintosh G5 computer, the complete human genome could be indexed in about 5 minutes. The indexing algorithm recognizes all 15 characters of the DNA alphabet and fully captures the information in any DNA sequence, yet for a typical sequence of length L, the index occupies only about 2L bytes. The index can be searched to return a complete list of exact matches for a nondegenerate or partially degenerate query of any length. A typical search of a long DNA sequence involves reading only a small fraction of the index into memory. As a result, searches are fast even when the available RAM is limited. Conclusion MICA is suitable as a search engine for desktop DNA analysis software.

  1. LA PROTEOMICA EN LA ERA POSTGENÓMICA

    Directory of Open Access Journals (Sweden)

    MARÍA CLAUDIA SANDOVAL-USME

    2009-01-01

    Full Text Available El principal desafío de la biología moderna es entender la expresión, función y regulación del conjunto completo de proteínas codificadas por un organismo, lo cual describe el objetivo del nuevo campo de la proteómica. Las proteínas son las efectoras del trabajo celular, por ello el estudio de sus perfiles globales de expresión y de sus cambios bajo determinadas condiciones fisiológicas o patológicas, permite entender la red compleja de interacciones en que se basa el funcionamiento de una célula. La electroforesis en dos dimensiones (2D-PAGE es la técnica central de la proteómica. En la actualidad no existe otro método con la capacidad para resolver simultáneamente miles de proteínas en un solo procedimiento y para detectar modificaciones post y co-traduccionales imposibles de predecir a partir de la secuencia genómica. Sus aplicaciones incluyen el análisis de proteomas, señalización, detección de marcadores de enfermedades y cáncer.

  2. Mujeres y dinámica emprendedora: un estudio exploratorio.

    Directory of Open Access Journals (Sweden)

    José Ernesto Amorós Espinosa

    2010-05-01

    Full Text Available El avance cualitativo y cuantitativo de las mujeres en la actividad emprendedora alrededor del mundo, representa un interesante factor a considerar dentro del desarrollo económico y el progreso social (Minniti et ál., 2005, 2006a. Este trabajo analiza de forma exploratoria los indicadores de la dinámica emprendedora de las mujeres en el ámbito latinoamericano, tomando como caso de estudio una muestra de mujeres en Chile. Los indicadores de la dinámica emprendedora son tomados de los datos proporcionados por el Global Entrepreneurship Monitor, GEM (2005, y una serie de entrevistas que nos proporcionan información de índole cualitativa. Los principales resultados nos indican que no hay diferencias significativas en cuanto a la percepción de la dinámica emprendedora entre mujeres y hombres que ya se encuentran involucrados en algún tipo de emprendimiento, no así para las mujeres que no están en algún tipo de actividad emprendedora, quienes perciben mayores dificultades para emprender. Esto se confirma con los resultados de las entrevistas que indican que aun cuando es socialmente aceptado que las mujeres inicien nuevos negocios, están más alejadas de las oportunidades y no existen los incentivos suficientes para iniciarlos. Se discuten implicaciones y conclusiones sobre ver el fenómeno del emprendimiento en mujeres como un buen indicador de desarrollo social.

  3. Graphene Visualizes the Ion Distribution on Air-Cleaved Mica

    Science.gov (United States)

    Bampoulis, Pantelis; Sotthewes, Kai; Siekman, Martin H.; Zandvliet, Harold J. W.; Poelsema, Bene

    2017-03-01

    The distribution of potassium (K+) ions on air-cleaved mica is important in many interfacial phenomena such as crystal growth, self-assembly and charge transfer on mica. However, due to experimental limitations to nondestructively probe single ions and ionic domains, their exact lateral organization is yet unknown. We show, by the use of graphene as an ultra-thin protective coating and scanning probe microscopies, that single potassium ions form ordered structures that are covered by an ice layer. The K+ ions prefer to minimize the number of nearest neighbour K+ ions by forming row-like structures as well as small domains. This trend is a result of repulsive ionic forces between adjacent ions, weakened due to screening by the surrounding water molecules. Using high resolution conductive atomic force microscopy maps, the local conductance of the graphene is measured, revealing a direct correlation between the K+ distribution and the structure of the ice layer. Our results shed light on the local distribution of ions on the air-cleaved mica, solving a long-standing enigma. They also provide a detailed understanding of charge transfer from the ionic domains towards graphene.

  4. Nutrigenómica, obesidad y salud pública.

    Directory of Open Access Journals (Sweden)

    Manuela Belén Silveira

    2007-01-01

    Full Text Available El desarrollo de la genómica funcional en los próximos años condicionará cambios en el conocimiento teórico y la práctica clínica de la nutrición. La posibilidad de determinar el perfil genético de un individuo (variaciones genéticas y modificaciones epigenéticas y de conseguir la integración de estos datos en una compleja red de interacciones metabólicas constituye un desafío sin precedentes en la nutrición humana. La aplicación práctica del conocimiento científico puro derivado de la nutrigenómica, en términos de prevención y tratamiento de la obesidad, la DM2 y las enfermedades cardiovasculares, y sus implicaciones en la salud pública, son en este momento todavía indeterminadas. La posibilidad de una intervención nutricional en periodos críticos del desarrollo y la capacidad de modificar la susceptibilidad genética a ciertas enfermedades a través de la alimentación es el gran reto de la nutrigenómica, más allá del diseño de dietas o alimentos funcionales “personalizados”.

  5. El sector inmobiliario y las crisis económicas

    Directory of Open Access Journals (Sweden)

    Antonio Daher

    2013-09-01

    Full Text Available La creciente urbanización de la economía y la doble concentración -económica y territorial- de los sectores inmobiliario y financiero en las metrópolis, fundamentan la relación entre los ciclos inmobiliarios y las crisis económicas detonadas por sus burbujas, la alta incidencia macroeconómica del sector inmobiliario y su rol articulador entre el sector financiero y la economía real. Antes de la última crisis (2008, las instituciones financieras y fondos de inversión inmobiliaria transnacionales encontraron en la financiarización y titulización una vía eficaz para su diversificación geográfica y distribución del riesgo hipotecario. Fue también la vía expedita del contagio de una crisis con ubicuidad financiera, aunque no social ni territorial. Las hipotecas subprime fueron para las minorías marginadas en los barrios con más hispanos, negros, inmigrantes y pobres: la vivienda social estadounidense, financiarizada, "inmobiliarizó" al sector financiero y desfinanciarizó la banca internacional, en una crisis global con dramáticas consecuencias sociales y políticas.

  6. Fabaceae endémicas del Perú

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    Severo Baldeón

    2013-10-01

    Full Text Available La familia Fabaceae es reconocida en el Perú por presentar alrededor de 145 géneros y 1000 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, mayormente árboles y arbustos. En este trabajo reconocemos 234 especies y 40 variedades como endémicas en 47 géneros. Un género, Weberbauerella, es endémico del Perú. Sin lugar a dudas, el género con mayor número de especies endémicas es Lupinus, siendo al mismo tiempo el que mayor necesidad tiene de estudios taxonómicos detallados y mayor recolección. Las Fabaceae endémicas ocupan la mayoría de regiones, principalmente la Mesoandina, Puna Húmeda y Seca y Bosques Muy Húmedos Montanos, entre los 1100 y 4800 m de altitud. Se aplicaron las categorías y criterios de la UICN a 203 taxones. Diecisiete taxones endémicos se encuentran representados dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  7. van der Waals epitaxy of Ge films on mica

    Science.gov (United States)

    Littlejohn, A. J.; Xiang, Y.; Rauch, E.; Lu, T.-M.; Wang, G.-C.

    2017-11-01

    To date, many materials have been successfully grown on substrates through van der Waals epitaxy without adhering to the constraint of lattice matching as is required for traditional chemical epitaxy. However, for elemental semiconductors such as Ge, this has been challenging and therefore it has not been achieved thus far. In this paper, we report the observation of Ge epitaxially grown on mica at a narrow substrate temperature range around 425 °C. Despite the large lattice mismatch (23%) and the lack of high in-plane symmetry in the mica surface, an epitaxial Ge film with [111] out-of-plane orientation is observed. Crystallinity and electrical properties degrade upon deviation from the ideal growth temperature, as shown by Raman spectroscopy, X-ray diffraction, and Hall effect measurements. X-ray pole figure analysis reveals that there exist multiple rotational domains in the epitaxial Ge film with dominant in-plane orientations between Ge [" separators="|1 ¯10 ] and mica[100] of (20 n )°, where n = 0, 1, 2, 3, 4, 5. A superlattice area mismatch model was used to account for the likelihood of the in-plane orientation formation and was found to be qualitatively consistent with the observed dominant orientations. Our observation of Ge epitaxy with one out-of-plane growth direction through van der Waals forces is a step toward the growth of single crystal Ge films without the constraint in the lattice and symmetry matches with the substrates.

  8. La debacle peruana: ¿dinámica económica o causas políticas?

    OpenAIRE

    Schydlowsky, Daniel

    2014-01-01

    El gobierno de Alan García se inició con grandes esperanzas. La política económica implementada en los primeros dos años se basó en una evaluación pragmática de las circunstancias del país. La activación económica perseguida fue exitosa pero olvidó una oportuna promoción de exportaciones; ello comenzó a causar problemas a partir de fines de 1986. La situación todavía era salvable a mediados de 1987 pero Alan García decidió estatizar la banca. Con ello rompió el pacto social de fondo del país ...

  9. BIOÉTICA Y GENÓMICA BIOÉTICA E GENÔMICA BIOETHICS AND GENOMICS

    Directory of Open Access Journals (Sweden)

    José Alberto Mainetti

    2003-01-01

    Full Text Available Los avances científicos en el campo de la genómica abren las puertas a los fantasmas de la humanidad. Por esto, el Proyecto Genoma Humano (PGH ha sido el primer gran proyecto de investigación internacional que ha tenido un subproyecto sobre la problemática ética, legal y social asociada al mismo: Ethical, Legal, and Social Issues (ELSI. Esta preocupación bioética surgió como espacio de dilucidación de las diferentes preocupaciones éticas y sociales que nacían a la par de los avances de la genómica. La genómica, expresada como la clave que revelará el misterio del ser (la lámpara de Aladino o como la herramienta de destrucción ecológica, el determinismo genético, el reduccionismo genético y la eugenesia, es decir, como la caja de Pandora. El PGH posee un incalculable valor para el diagnóstico de nuevas enfermedades, nuevos fármacos y nuevas terapias, pero abre también riesgos y temores que han de ser estudiados y analizados desde una perspectiva más amplia que la científicotécnica, es decir, como una reflexión bioética sobre la genómicaOs avanços científicos no campo da genômica abrem as portas aos fantasmas da humanidade. Por isso, o Projeto Genoma Humano (PGH foi o primeiro grande projeto de pesquisa internacional que teve um subprojeto sobre a problemática ética, legal e social associada ao mesmo. Esta preocupação bioética surgiu como espaço de elucidação das diferentes preocupações éticas e sociais que surgiam ao par dos avanços da genômica. A genômica, expressa como a chave que revelará o mistério do ser ( a lâmpada de Aladim ou como a ferramenta de destruição ecológica, o determinismo gen´tico, o reducionismo genético e a eugenésia, isto é, como a caixa de Pandora. O PGH possui um incalculável valor para o diagnóstico de novas enfermidades, novos fármacos e novas terapias, porém abrem também riscos e temores que devem ser estudados e analisados numa perspectiva mais ampla que a

  10. Recubrimientos por PVD decorativos sobre cerámicas

    Directory of Open Access Journals (Sweden)

    García, J. A.

    2006-08-01

    Full Text Available During the last years PVD coatings has been used for decorative purposes on ceramics and other substrates. Standards layers like TiN, CrN, TiCN, etc, give us the possibly of obtaining a wide range of colours, with a good mechanical, chemical properties. This paper gathers the works carried out in the Center of Advance Surface engineering of AIN during the three last years in the field of the decorative coatings. Different layer have been deposited by means of a METAPLAS 232 PVD equipment. A complete chemical and mechanical characterisation have been carried out on the different deposited layers like ultramicroindentation, scratch tests, wear resistance and GDOES.

    En los últimos años se ha venido estudiado la aplicabilidad de las técnicas de depósitos mediante métodos físicos en fase vapor (PVD, para la realización de recubrimientos sobre cerámicas y otros substratos con fines decorativos. Los recubrimientos estándar por PVD como el TiN, CrN, TiCN, etc, ofrecen la posibilidad de conseguir acabados de apariencia metálica, de una amplia gama de colores, y con buenas propiedades mecánicas y químicas, como resistencia a la abrasión, estabilidad térmica, o resistencia a la corrosión. En este trabajo se recogen las experiencias realizadas en el recubrimiento y caracterización de cerámicas decorativas, durante los tres últimos años, en el Centro de Ingeniería de Superficies de la Asociación de la Industria Navarra. Los distintos tipos de recubrimientos se han realizado mediante un equipo de PVD modelo METAPLAS 232, con seis evaporadores de arco eléctrico y sistema de limpieza iónica patentado AEGD. Los recubrimientos han sido caracterizados, tanto química como mecánicamente, empleando las más modernas técnicas tribológicas (ultramicrodureza, scrascth tests, resistencia al desgaste... y espectroscópicas óptica por descarga luminiscente (GDOES. Los resultados obtenidos muestran que las técnicas de PVD son una

  11. Sumérgete en la Bioquímica

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    Josep M. Fernández Novell

    2013-11-01

    Full Text Available Hace ya dos años que el Departamento de Bioquímica y Biología Molecular de la Universidad de Barcelona con la colaboración de la SEBBM viene realizando anualmente unas sesiones prácticas de Bioquímica “Sumérgete en la Bioquímica”. Sesiones de mañana o de tarde dirigidas a los jóvenes de tercero y cuarto de la Enseñanza Secundaria Obligatoria (ESO. Estos jóvenes han recibido una información exhaustiva sobre qué es y de qué trata la Bioquímica, al mismo tiempo, han realizado una serie de experimentos en el laboratorio. En éstos, además de aprender las normas de seguridad, cómo utilizar el material volumétrico y las pipetas automáticas, han experimentado sobre: la obtención de ADN de vegetales, cómo medir la concentración de glucosa o de proteína de una muestra utilizando un espectrofotómetro, la producción de una proteína como la GFP en bacterias y las condiciones de precipitación de la caseína de la leche. También, desde Internet, han trabajado sobre cómo extraer el ADN humano y cómo clonar un ratón. Al finalizar cada sesión se recogieron dos tipos de encuestas, una dirigida al alumnado y la otra al profesorado de secundaria para saber el grado de aceptación de dicha actividad. El resultado de unas y otras indica que para todos ellos han sido unas actividades muy apreciadas e interesantes que sirven para aumentar el interés de los estudiantes hacia las ciencias y hacia la Bioquímica en particular. Esta experiencia se ha desarrollado en los laboratorios del Departamento de Bioquímica y Biología Molecular de la UB durante dos semanas entre el mes de Enero y el de Febrero época en que no están ocupados por la enseñanza habitual del Departamento. Este último curso han participado más de 750 estudiantes, la demanda ha superado nuestras previsiones obligándonos a preparar una tercera semana para el curso 2013-2014.

  12. Não-linearidades: da dinâmica do simples à dinâmica do complexo

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    José Roberto Castilho Piqueira

    1994-01-01

    Full Text Available Foram apresentados alguns conceitos relativos à utilização da Teoria dos Sistemas Dinâmicos em problemas de sistemas complexos. A apresentação destes conceitos centra-se no estabelecimento de duas dinâmicas: uma de curto termo e outra de longo termo, relacionando-as com os processos de organização dos sistemas.

  13. Dinámica ambiental y económica en la localidad de Puente Aranda en Bogotá

    Directory of Open Access Journals (Sweden)

    Carlos Fernando Parra Moreno

    2014-01-01

    Full Text Available Este documento muestra los resultados parciales de la investigación “Responsabilidad social y ambiental de la industria manufacturera en la localidad de Puente Aranda en la ciudad de Bogotá como alternativa al desarrollo humano integral sustentable”, realizados dentro del marco de trabajo del grupo de investigación Girsa. El estudio se basó en el análisis de la dinámica poblacional, ambiental y económica de la dicha localidad, a través de la metodología de la matriz de Vester. Con este instrumento se logró identificar las relaciones e interacciones dinámicas de todos los actores locales en el tiempo y en el espacio. Dentro de los problemas críticos que se encontraron en la localidad de Puente Aranda se encontró el agotamiento de fuentes hídricas, poca conciencia y educación ambiental de la población, una mala disposición de basuras, la no disponibilidad de servicios públicos para los nuevos asentamientos y altos niveles de emisión de partículas contaminantes.

  14. Algunas reflexiones sobre la distancia entre "hablar química" y "comprender química"

    Directory of Open Access Journals (Sweden)

    Lydia Raquel Galagovsky

    2014-12-01

    Full Text Available Una clase de química puede ser considerada como un espacio de comunicación entre el docente experto y los estudiantes novatos, donde los lenguajes utilizados son la interfase explícita y observable del intercambio comunicativo. En el presente trabajo se muestra con dos ejemplos cómo la diversidad de lenguajes químicos en lugar de favorecer la comprensión de los estudiantes, puede actuar como fuente de obstáculos que dificultan la comunicación en el aula. Así mismo, se analizará con otros dos ejemplos cómo el discurso con el que se enseña la disciplina también es potencial generador de errores en los estudiantes, cuando ellos construyen sus modelos mentales idiosincrásicos a partir de un discurso recortado y simplificado, desde las mejores intenciones de realizar buenas transposiciones didácticas. Se plantea que un enfoque de análisis de la situación de aula como un encuentro comunicativo entre experto y novato conduce a una necesaria diferenciación entre "hablar química" y "comprender química".

  15. Temas de Física para Ingeniería: Primer principio de la termodinámica

    OpenAIRE

    Beléndez Vázquez, Augusto

    1992-01-01

    Acústica, fluidos y termodinámica: "Primer principio de la termodinámica". Objetivos y caracteres generales de la termodinámica. Conceptos fundamentales de la termodinámica. Capacidad calorífica, calor específico y calor latente. Trabajo. Primer principio de la termodinámica: energía interna. Algunas aplicaciones del primer principio.

  16. La industria cerámica brasileña

    Directory of Open Access Journals (Sweden)

    Pacheco Jordao, M. A.

    2001-02-01

    Full Text Available Ceramics play an important role in the Brazilian economy, with a participation estimated in 1% of the GNP ( Gross National Product, corresponding to about 6 billion dollars. The abundance of natural raw-materials, alternative energy sources, and the availability of practical technologies within the industrial equipments, caused a rapid evolution of the Brazilian industries, and several types of products from the various ceramic segments attained international quality levels, with significative exportation. He ceramic sector is very diverse and can be divided into the following classes: heavy clay ceramics, wall and floor tiles, refractory materials, sanitary ware, porcelain electric insulators, tableware, decorative china, ceramic filters and reservoirs for domestic use, technical ceramics, and thermal insulators. All these segments exist in Brazil, in a higher or lower stage of development and production capacity. Moreover, there are also manufacturers of synthetic glazes and colorants, plaster of paris, equipments and some auxiliary chemicals. In this paper, an overview of the main Brazilian ceramic segments is presented, excluding the glass, cement, and lime sectors, which, despite being ceramic, are generally treated in separate.

    La cerámica juega un papel muy importante para la economía del país brasileño con una participación en el P.I.B (Producto Interior Bruto estimado en el 1%, correspondiendo a cerca de 6 millones de dólares. La abundancia de materias primas naturales, fuentes alternativas de energía y una amplia tecnología incorporada a los equipos industriales, han hecho que las industrias brasileñas evolucionasen rápidamente de forma que muchos tipos de productos de diferentes segmentos de la actividad cerámica alcanzasen niveles de calidad mundial, con cifras apreciables destinadas a la exportación. El sector industrial de la cerámica incluye producciones muy diversificados y puede ser dividido en los siguientes

  17. Probing the structure of the cold dark matter halo using ancient mica

    Science.gov (United States)

    Baltz, Edward A.; Westphal, Andrew J.; Snowden-Ifft, Daniel P.

    1999-01-01

    Mica can store (for >1 Gyr) etchable tracks caused by atoms recoiling from WIMPs. Ancient mica is a directional detector despite the complex motions it makes with respect to the WIMP ``wind.'' We can exploit the properties of directionality and long integration time to probe for structure in the dark matter halo of our galaxy. We compute a sample of possible signals in mica for a plausible model of halo structure.

  18. Las cooperativas: Una alternativa económica y social frente a la crisis

    Directory of Open Access Journals (Sweden)

    Javier Divar Garteiz-Aurrecoa

    2013-12-01

    Full Text Available El Cooperativismo nació como alternativa económica y social, impulsado por la piedad religiosa y reglado bajo los principios democráticos. La solidaridad y la democracia económica hacen de las cooperativas  sociedades especialmente resistentes frente a las dificultades económicas.Recibido: 29.05.2013Aceptado: 26.06.2013

  19. Plagio e integridad académica en Alemania

    Directory of Open Access Journals (Sweden)

    2016-07-01

    Full Text Available Alemania es quizá uno de los países europeos que, ya desde el siglo XVIII, ha mantenido un debate público más intenso sobre prácticas científicas y académicas deshonestas, relacionadas especialmente con tesis doctorales. Este debate fue especialmente productivo a finales del siglo XIX, dando lugar desde entonces, para evitar estas prácticas inaceptables, a la obligatoriedad de publicar todas las tesis doctorales, como requisito previo a la expedición del título de doctor por cualquier universidad alemana. Este trabajo analiza los avances más importantes en plagio e integridad académica en Alemania, especialmente después del escándalo surgido en 2011 a raíz del plagio de la tesis doctoral del Ministro de Defensa Guttenberg, como son la creación de una eficaz metodología colaborativa de investigación del plagio en trabajos científicos o académicos utilizando Internet y las redes sociales, materializada en la Wiki «VroniPlag». También se describe someramente en este trabajo la consolidación definitiva de la figura del «Defensor de la Ciencia», como instrumento de ámbito nacional para prevenir, gestionar y combatir la deshonestidad científica, aparte de la publicación en 2013 de una nueva versión del manual de referencia al respecto «Sicherung guter wissenschaftlicher Praxis». Por último se analizan las conclusiones de la experiencia alemana relacionada con la ética académica, también desde una perspectiva histórica, pues sus recientes logros y avances pueden servir de referencia a otros países europeos.

  20. Resinas quelantes amidoxímicas Amidoxime chelating resins

    Directory of Open Access Journals (Sweden)

    Fernanda M. B. Coutinho

    1999-12-01

    Full Text Available Resinas quelantes com grupos amidoxima foram sintetizadas por copolimerização em suspensão de acrilonitrila (AN e divinilbenzeno (DVB e subsequente modificação química dos grupos ciano por reação com hidroxilamina. Na copolimerização, a proporção de divinilbenzeno e o grau de diluição foram variados. Gelatina e carbonato de cálcio foram usados como estabilizadores de suspensão e sulfato de sódio foi adicionado para reduzir a solubilidade da acrilonitrila em água, por meio do efeito salting out. Os copolímeros de AN/DVB e as resinas amidoxímicas obtidos foram caracterizados por meio de densidade aparente, área específica, volume de poros e teor de nitrogênio. As resinas amidoxímicas foram também avaliadas em relação a capacidade de complexação de íons cobre.Chelating resins with amidoxime groups were synthesized by suspension copolymerization of acrylonitrile (AN and divinylbenzene (DVB and subsequent chemical modification of cyano groups by reaction with hydroxylamine. In the copolymerization, the proportion of divinylbenzene and the dilution degree were varied. Gelatin and calcium carbonate were used as suspension stabilizers and sodium sulphate was added in order to reduce acrylonitrile solubility in water, by salting out effect. The AN/DVB copolymers and amidoxime resins obtained were characterized by apparent density, surface area, pore volume and by the content of nitrogen. The amidoxime resins were also evaluated in relation to the complexation capacity of copper ion.

  1. Acute Antibody-Mediated Rejection in Presence of MICA-DSA and Successful Renal Re-Transplant with Negative-MICA Virtual Crossmatch.

    Directory of Open Access Journals (Sweden)

    Yingzi Ming

    Full Text Available The presence of donor-specific alloantibodies (DSAs against the MICA antigen results in high risk for antibody-mediated rejection (AMR of a transplanted kidney, especially in patients receiving a re-transplant. We describe the incidence of acute C4d+ AMR in a patient who had received a first kidney transplant with a zero HLA antigen mismatch. Retrospective analysis of post-transplant T and B cell crossmatches were negative, but a high level of MICA alloantibody was detected in sera collected both before and after transplant. The DSA against the first allograft mismatched MICA*018 was in the recipient. Flow cytometry and cytotoxicity tests with five samples of freshly isolated human umbilical vein endothelial cells demonstrated the alloantibody nature of patient's MICA-DSA. Prior to the second transplant, a MICA virtual crossmatch and T and B cell crossmatches were used to identify a suitable donor. The patient received a second kidney transplant, and allograft was functioning well at one-year follow-up. Our study indicates that MICA virtual crossmatch is important in selection of a kidney donor if the recipient has been sensitized with MICA antigens.

  2. Abundancias químicas de ψ Octantis

    Science.gov (United States)

    Medina, M. C.; Pintado, O. I.

    Se determinan las abundancias químicas de ψ Oct usando espectros obtenidos con EBASIM en CASLEO. Los valores iniciales de temperatura efectiva y gravedad superficial se calculan con la fotometría uvbyβ. Esta estrella fue estudiada por Pintado y Adelman (1996) usando espectros REOSC y Adelman y otros (1993), este último basado en espectros echelle obtenidos con el Telescopio Anglo Australiano. Comparamos nuestros resultados con los de los trabajos anteriormente mencionados, pudiéndose realizar una evaluación de la calidad de los espectros EBASIM.

  3. Nanotecnología y nanoquímica

    OpenAIRE

    Aguayo-González, Francisco; Zarzuela Roldán, Elías; Lama-Ruiz, Juan Ramón

    2011-01-01

    Ejemplar dedicado a: Ingeniería química y medioambiental La creciente mejora de los productos en los últimos tiempos es consecuencia de la investigación y el desarrollo de nuevas técnicas que permiten el desarrollo de innovaciones complementarias a las obtenidas por el diseño. La nanotecnología constituye un ámbito de conocimiento que permite desarrollar nuevos productos derivados del conocimiento de las propiedades y los procesos a escala nanométrica. En el present...

  4. Mechanics of anisotropic inclusions applied to mica fish populations

    Science.gov (United States)

    Mulchrone, K.

    2009-04-01

    An analytical solution is derived for the mechanical behaviour of a linear viscous anisotropic elliptical inclusion immersed in a linear viscous isotropic fluid. By assuming that the internal anisotropy deforms passively a system of three differential equations describe the rate of change of ellipse long axis orientation, anisotropy orientation and ellipse aspect ratio. Taking appropriate limits, the model can be adapted to represent the behaviour of mica fish which deform only by glide along the basal plane. Simulation studies indicate that ellipse long axes tend towards a stable orientation of approximately 15 degrees, whereas anisotropy orientations tend to show a fatter and more asymmetric distribution. This is consistent with published natural data.

  5. Carrera Académica, Una Alternativa Posible?

    OpenAIRE

    González, José María

    2004-01-01

    La legislación argentina que regula la educación superior universitaria ha establecido la necesidad de implementar la carrera académica en las universidades como un mecanismo regulatorio del ingreso y promoción de los docentes. Las universidades han reaccionado de diversa forma ante este requisito replicando la heterogeneidad que caracteriza a la educación superior en la Argentina. En el presente documento se realiza el análisis de los requerimientos exigidos por la legislación para abo...

  6. Flacourtiaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Flacourtiaceae es reconocida en el Perú por presentar 19 géneros y 65 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, mayormente arbustos y árboles. En este trabajo reconocemos tres especies endémicas en dos géneros, las cuales ocupan la región de los Bosques Muy Húmedos Montanos, entre los 2300 y 3600 m de altitud. Solamente una de estas especies se encuentra representada en el Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  7. Psiconeuroinmunología: breve panorámica

    OpenAIRE

    Sandra M. Camelo Roa

    2005-01-01

    Desde los terrenos de la psicoinmunología, la presente revisión se propone una mirada panorámica a sus principales postulados, líneas de investigación, resultados y perspectivas. Para ello, inicialmente se abordaron algunos aspectos históricos de la relación entre la vida psíquica y la salud; posteriormente, se revisaron aspectos como la fisiología del sistema inmune especificando los tipos de inmunidad adquirida e inmunidad natural. Temas como las interacciones entre ...

  8. Implicações macroeconômicas do BNDES

    OpenAIRE

    Rosa, Rafael Mouallem

    2015-01-01

    Este trabalho se propõe a estudar as implicações macroeconômicas da existência do BNDES na economia. Construímos aqui um modelo DSGE contemplando as características do BNDES e realizamos exercícios sobre o mesmo. Este é o primeiro trabalho a analisar o impacto de curto prazo do BNDES, sendo essa sua contribuição central. Constatamos aqui que o BNDES atua de forma a amplificar os choques de produtividade sobre a economia e reduz a eficácia da política monetária. This paper pu...

  9. Rare earth ion controlled crystallization of mica glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Garai, Mrinmoy; Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in

    2016-09-05

    In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO{sub 2}, Nd{sub 2}O{sub 3}, Sm{sub 2}O{sub 3} and Gd{sub 2}O{sub 3} doped K{sub 2}O−MgO−B{sub 2}O{sub 3}−Al{sub 2}O{sub 3}−SiO{sub 2}−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm{sup −3}) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T{sub g}) and crystallization temperature (T{sub c}). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg{sub 3}(AlSi{sub 3}O{sub 10})F{sub 2} by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10{sup −6}/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque

  10. LOS PROFESORES UNIVERSITARIOS Y LA ESCRITURA ACADÉMICA

    OpenAIRE

    Carrera Moreno, Germán

    2017-01-01

    El objetivo de este artículo es presentar una descripción de las principales falencias encontradas en la redacción artículos científicos escritos por profesores universitarios. Se realizó un estudio diagnóstico que corresponde a la primera etapa del proyecto de investigación denominado Comprensión Lectora y Escritura Académica. A través de este proyecto se trata encontrar alternativas que permitan el incremento de la producción científica de la Universidad Laica Eloy Alfaro de Manabí, la mism...

  11. Ecuaciones polinómicas de tercer y cuarto grado

    OpenAIRE

    Allan, Nelo; Pérez, Hernando

    2012-01-01

    Los primeros problemas de ecuación es lineales y  polinómicas se plantearon a los geómetras  y matemáticos de los primeros tiempos como necesarios en la comprensión de otros temas de mayor interés para ellos, y aun que en la actualidad, la teoría de ecuaciones tiene interés por si misma (Teoría de Galois) también se hace necesaria en el estudio de otros tópicos matemáticos.

  12. Farmacoquímica molecular, 2010-11

    OpenAIRE

    López Pérez, José Luis

    2010-01-01

    I. Materiales de clase: Tema 1 Introducción a la Farmacoquímica molecular; Tema 2 Dianas de los fármacos; Tema 3 Enzimas como catalizadores; Tema 4 Receptores y neurotransmisores; Tema 5 Complejos fármaco-receptor; Tema 6 Ácidos nucleicos; Tema 7 Estructura tridimensional de los fármacos; Tema 8 Grupos funcionales en los fármacos; Tema 9 Fases en la acción de los fármacos; Tema 10 Investigación planificada y aproximaciones racionales. II. Bibliografía Los objetivos de esta asignatura son l...

  13. Burmanniaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Burmanniaceae es reconocida en el Perú por presentar ocho géneros y 16 especies (Brako & Zarucchi, 1993, principalmente hierbas saprófitas. En este trabajo reconocemos un endemismo en el genero Burmannia. Esta especie endémica posee un amplio grado de adaptación ambiental, habiéndosele localizado en las vertientes occidentales, valles interandinos, páramos y bosques montanos orientales, entre los 1200 y 4100 m de altitud. Esta especie se encuentra representada en un área natural protegida.

  14. Chloranthaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Chloranthaceae es reconocida en el Perú por presentar un género, Hedyosmum, y 14 especies (Brako & Zarucchi, 1993, todos ellas árboles y/o arbustos. En este trabajo reconocemos una especie endémica, la cual ocupa la región Bosques Muy Húmedos Montanos, entre los 1900 y 2650 m de altitud, y está representada dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  15. Dinámica de columnas líquidas

    OpenAIRE

    Perales Perales, José Manuel

    2011-01-01

    En esta tesis se analiza la dinámica de puentes líquidos entre apoyos sólidos circulares y concéntricos sometida a la oscilación de estos. El problema se ha resuelto aplicando un modelo unidimensional de Cosserat que permite incluir los efectos de la viscosidad en el análisis. Previamente se ha desarrollado un método para determinar numéricamente el mínimo volumen para el cual un puente líquido es estable. Los límites obtenidos se han comprobado experimentalmente, habiéndose encontrado un muy...

  16. Dinámica de columnas líquidas

    OpenAIRE

    Perales Perales, José Manuel

    1990-01-01

    En esta tesis se analiza la dinámica de puentes líquidos entre apoyos sólidos circulares y concéntricos sometida a la oscilación de estos. El problema se ha resuelto aplicando un modelo unidimensional de Cosserat que permite incluir los efectos de la viscosidad en el análisis. Previamente se ha desarrollado un método para determinar numéricamente el mínimo volumen para el cual un puente líquido es estable. Los límites obtenidos se han comprobado experimentalmente, habiéndose encontrado un muy...

  17. Jung, mandala e arquitetura Islâmica

    OpenAIRE

    Rafael Raffaelli

    2009-01-01

    Este artigo se propõe a refletir sobre as origens do conceito junguiano de mandala. Utiliza-se o relato autobiográfico de Jung, Memórias, Sonhos e Reflexões, e sua obra Psicologia e Alquimia para traçar essa origem. Segundo Barbara Hannah, biógrafa de Jung, uma mesquita no Cairo (Egito) foi de importância capital para a formulação desse conceito. Provavelmente esse templo é a Mesquita Ahmad Ibn Tulun. É analisada a relação entre a simbologia arquitetônica islâmica inspirada pelo sufismo e as ...

  18. Buxaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Buxaceae es reconocida en el Perú por presentar un género, Styloceras, y tres especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, todos arbustos. En este trabajo reconocemos un endemismo. Esta especie endémica se encuentra en la región Bosques Muy Húmedos Montanos, entre los 1800 y 1850 m de altitud. No está representada en el Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  19. Dichapetalaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Dichapetalaceae es una adición reciente a la flora endémica peruana. Incluye plantas leñosas como árboles y lianas, siendo reconocida en la flora peruana por presentar tres géneros y 16 especies (Brako & Zarucchi, 1993. En este trabajo reconocemos un endemismo en el género Tapura. Este taxón endémico ocupa la región Bosques Húmedos Amazónicos, a 250 m de altitud. No se encuentra representada en el Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  20. Buddlejaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Buddlejaceae es reconocida en el Perú por presentar dos géneros y 16 especies (Norman, 2000; Ulloa Ulloa et al., 2004, principalmente arbustos. En este trabajo reconocemos dos especies endémicas en el género Buddleja. Estos taxones endémicos se encuentran en las regiones Mesoandina, Puna Húmeda y Seca y Páramo, entre los 2650 y 3900 m de altitud. Una de estas dos especies se encuentra representada dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  1. Termodinámica básica : ejercicios

    OpenAIRE

    Barrio Casado, María del

    2006-01-01

    Este libro pretende ser una introducción a la termodinámica básica del equilibrio y se dirige especialmente a los alumnos de primer ciclo de ciencias y enseñanzas técnicas universitarias. La obra consta de un total de diez capítulos, cada uno de los cuales se compone de tres partes. En la primera, se expone un resumen de los conceptos teóricos más relevantes; en la segunda, se resuelven minuciosamente un conjunto significativo de problemas con la finalidad de facilitar la consolidación de...

  2. Tropaeolaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available Esta es la familia de la «mashua». La familia Tropaeolaceae es reconocida en el Perú por presentar un género, Tropaeolum, y 24 especies (Brako & Zarucchi, 1993, todas herbáceas y bejucos. En este trabajo reconocemos 10 especies endémicas, las cuales se encuentran principalmente en las regiones Bosques Muy Húmedos Montanos y Mesoandina, entre los 1800 y 3200 m de altitud. Una especie, aparentemente, se encuentra representada dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  3. Rigidez dinámica de estribos y puentes

    OpenAIRE

    Martínez Cutillas, Antonio; Alarcón Álvarez, Enrique

    1994-01-01

    Los datos obtenidos de puentes instrumentados en zonas sísmicas, demuestran la importancia que tienen los estribos en la respuesta dinámica de la estructura. Si bien existen modelos que permiten estudiar la incidencia de las cimentaciones de las pilas, no existe ningún modelo analítico un numérico que permita acotar la incidencia d e los estribos. En este trabajo se presentan modelos de Elementos de Contorno en el dominio de la frecuencia, tanto en dos como en tres dimensiones, así como el cá...

  4. ISLAMOFOBIA EPISTÉMICA Y CIENCIAS SOCIALES COLONIALES

    OpenAIRE

    Ramón Grosfoguel

    2011-01-01

    Este artículo investiga la manera en que el racismo epistémico modela las discusiones contemporáneas sobre islamofobia. El racismo epistémico es un aspecto subestimado del racismo. En la primera parte, se presenta una discusión sobre el racismo epistémico a nivel del sistema mundial. En la segunda, se introduce la política de identidad hegemónica del varón occidental y las respuestas fundamentalistas que motivó. La tercera parte trata de la islamofobia epistémica y las ciencias sociales. ...

  5. ISLAMOFOBIA EPISTÉMICA Y CIENCIAS SOCIALES COLONIALES

    Directory of Open Access Journals (Sweden)

    Ramón Grosfoguel

    2011-06-01

    Full Text Available Este artículo investiga la manera en que el racismo epistémico modela las discusiones contemporáneas sobre islamofobia. El racismo epistémico es un aspecto subestimado del racismo. En la primera parte, se presenta una discusión sobre el racismo epistémico a nivel del sistema mundial. En la segunda, se introduce la política de identidad hegemónica del varón occidental y las respuestas fundamentalistas que motivó. La tercera parte trata de la islamofobia epistémica y las ciencias sociales.

  6. Termodinámica de la atmósfera

    OpenAIRE

    Martínez Herranz, Isidoro

    2010-01-01

    Se dice que el planeta Tierra debería llamarse planeta Agua, pues más del 70% de su superficie es acuosa, pero el aire aún ocupa más, y nos es más preciado si cabe a los animales terrestres (si falta el aire, es cuestión de vida o muerte en unos minutos), y particularmente a los ingenieros aeroespaciales. Cuando se diseñan sistemas de soporte de vida (aeroespaciales, submarinos u otros) las prioridades son: aire, agua, y alimento. La termodiná- mica es una de las ciencias básicas para ...

  7. física y química

    Directory of Open Access Journals (Sweden)

    Cristina Díez-Rodríguez

    2005-01-01

    Full Text Available La experiencia que se plantea a continuación recoge el desarrollo de una estrategia de comunicación entre un grupo de alumnos de Bachillerato y su profesora de Física y Química, basada en el uso de Internet como medio de expresión y comunicación. Se trata de una experiencia piloto, diseñada como paso previo a la integración definitiva de varias herramientas de comunicación en el desarrollo del próximo curso escolar

  8. Quantifying the molecular-scale aqueous response to the mica surface

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Arushi; Pfaendtner, Jim; Chun, Jaehun; Mundy, Christopher J.

    2017-08-31

    Modeling assembly at surfaces requires a multi-scale understanding of the interactions between solutes, solvents, and surfaces. We investigated the solvent response (water structure and orientation) to a dielectric surface (mica) using density functional theory. A different water structure is engendered by replacing naturally-occurring surface ions (K+) with H3O+ and validates classical models for the mica surface (CLAYFF). The detailed microscopic response of water to mica can be used as input into continuum models for the total interactions between two mica surfaces supporting a strong correlation between physicochemical phenomena at different scales.

  9. “Nadie es profeta en su tierra”: Etnografía económica de las dinámicas comerciales de los Kichwa-Otavalo en San Victorino, Bogotá

    OpenAIRE

    López Ávila, Diego Felipe

    2015-01-01

    La presente monografía describe las dinámicas económicas de los Kichwas Otavalo en la zona comercial de San Victorino, Bogotá. Dichas dinámicas son examinadas a partir de la Nueva Sociología Económica (Smelser & Swedberg, 2005) y la Etnografía Económica (Dufy & Weber, 2009) para mostrar las divergentes racionalidades que surgen al interior del mercado. Esto nos lleva a debatir con la ciencia económica ortodoxa y los supuestos que manejan frente a la racionalidad, el mercado y la competencia....

  10. Alfabetización económica y actitudes hacia la compra en universitarios posterior a un programa de educación económica

    Directory of Open Access Journals (Sweden)

    Marianela Denegri Coria

    2016-01-01

    después de participar en el programa de Educación Económica se les aplicó la Escala de Actitudes hacia la Compra y el Consumo y el Test de Alfabetización Económica para adultos (TAE-A. Los resultados indican una menor tendencia hacia la impulsividad en la compra y el consumo en los estudiantes después de participar en la intervención. Las implicancias de este estudio enfatizan la necesidad de crear tempranamente programas de formación económica para favorecer el cambio actitudinal y el consumo reflexivo.

  11. sensibilizando enfermeiros com a dinâmica musical

    Directory of Open Access Journals (Sweden)

    Leila Brito Bergold

    2006-01-01

    Full Text Available Las influencias de la música en el cuerpo, fueron objeto de este estudio conducido junto a un grupo de enfermeros participantes de una disciplina del Posgrado. El estudio tuvo como objetivo, analizar la aplicabilidad de la Dinámica de Creatividad y Sensibilidad Cuerpo-Musical como una forma de sensibilización del enfermero respecto al uso de la música en su práctica de cuidar. Se utilizó el Método Creativo-Sensible y el desarrollo del DCS en la producción de datos de investigación. La influencia holística, lúdica, y mecánica de la música sobre el cuerpo, fueron los temas generados en la discusión. El grupo concluye que la música reacciona sobre todo el cuerpo pero influye según el estilo musical para una determinada región gusto del oyente. La investigación reveló el potencial de la dinámica como un rico espacio de la educación dialógica, constituyéndose como una estrategia importante en la sensibilización de los enfermeros, sobre las posibilidades de la música como un recurso terapéutico.

  12. RACIONALIDADE ECONÔMICA, TRABALHO E ECOLOGIA EM ANDRÉ GORZ

    Directory of Open Access Journals (Sweden)

    André Langer

    Full Text Available O presente artigo tem por objetivo apresentar a análise crítica de André Gorz sobre o trabalho e a ecologia política a partir da centralidade que o conceito de racionalidade econômica no capitalismo adquire em seu pensamento. Para ele, a extensão ilimitada da racionalidade econômica ao trabalho e à natureza é considerada sem futuro do ponto de vista da sociedade. Gorz reconhece a íntima relação entre a crítica do capitalismo e a tarefa da ecologia política. Outro aspecto presente em sua obra, menos explorado, é a relação entre trabalho e crise ecológica. O capitalismo apropria-se do trabalho ou emprego não apenas para os seus interesses, mas também os transforma em instrumentos de destruição da natureza. Este paper objetiva também, fiel ao espírito do próprio Gorz, embora de maneira sucinta, indicar alguns horizontes alternativos.

  13. Crisis global, económica, social y ambiental

    Directory of Open Access Journals (Sweden)

    Araceli Damián

    2015-01-01

    Full Text Available El presente artículo tiene la finalidad de explorar la compleja crisis del sistema capita - lista actual retomando diversos ángulos de su manifestación: económica, social y am - biental. El trabajo está dirigido a examinar las crisis del capitalismo actual a partir de la crisis inmobiliaria y financiera de 2008, que fue considerada como la más grave en el ámbito mundial después de la de 1929. Para ello se examinan, en primer término, las explicaciones que desde la teoría marxista y keynesiana se han ofrecido en torno a las crisis económicas propias del capitalismo. En segundo lugar se analizan algunas de las consecuencias de las crisis padecidas en los últimos cincuenta años, sobre todo en relación con los cambios en las relaciones de poder entre capital y trabajo; ello ha producido un deterioro en las condiciones de vida de la mayoría de la población, que se manifiesta en una creciente pobreza, desigualdad, persistencia del hambre y deterioro ambiental en el mundo.

  14. Angeitis necrotizante sistémica no supurativa

    Directory of Open Access Journals (Sweden)

    Gabriel Toro G.

    1972-04-01

    Full Text Available 1. Se estudian 3 casos de angeítis necrotizante sistémica no supurativa: un hombre de 36 y una mujer de 58 años con granulomatosis de Wegener y un hombre de 30 años con granulomatosis alérgica del tipo descrito por Churg y Strauss. 2. Se prefiere el hombre de angeítis necrotizante sistémica no supurativa como lo ha hecho Paronetto cuando trata este capítulo desde el punto de vista inmunopatológico. 3. Consideran los autores que la lesión renal es la periglomerulitis granulomatosa parahiliar y que su presencia ya en la biopsia tiene gran valor diagnóstico. 4. Se subraya que el cuadro clínico, la marcada eosinofilia tisular y la presencia de imágenes micromultinodulares en el ganglio linfático, apoyan sólidamente un diagnóstico de granulomatosis alérgica de la forma descrita por Churg y Strauss. 5. Se hace una amplia revisión bibliográfica.

  15. Role of HLA, KIR, MICA, and Cytokines Genes in Leprosy

    Science.gov (United States)

    Jarduli, Luciana Ribeiro; Sell, Ana Maria; Reis, Pâmela Guimarães; Ayo, Christiane Maria; Mazini, Priscila Saamara; Alves, Hugo Vicentin; Teixeira, Jorge Juarez Vieira; Visentainer, Jeane Eliete Laguila

    2013-01-01

    Many genes including HLA, KIR, and MICA genes, as well as polymorphisms in cytokines have been investigated for their role in infectious disease. HLA alleles may influence not only susceptibility or resistance to leprosy, but also the course of the disease. Some combinations of HLA and KIR may result in negative as well as positive interactions between NK cells and infected host cells with M. leprae, resulting in activation or inhibition of NK cells and, consequently, in death of bacillus. In addition, studies have demonstrated the influence of MICA genes in the pathogenesis of leprosy. Specifically, they may play a role in the interaction between NK cells and infected cells. Finally, pro- and anti-inflammatory cytokines have been influencing the clinical course of leprosy. Data from a wide variety of sources support the existence of genetic factors influencing the leprosy pathogenesis. These sources include twin studies, segregation analyses, family-based linkage and association studies, candidate gene association studies, and, most recently, genome-wide association studies (GWAS). The purpose of this brief review was to highlight the importance of some immune response genes and their correlation with the clinical forms of leprosy, as well as their implications for disease resistance and susceptibility. PMID:23936864

  16. CULTURAS ACADÉMICAS: ENTRE REINVENCIÓN Y CONTRABANDO

    Directory of Open Access Journals (Sweden)

    Kathya Araujo

    2015-01-01

    Full Text Available Sobre la base del análisis de una historia personal de desplazamiento entre academias (peruana y chilena, y la reinvención y el contrabando que toda migración supone, este artículo argumenta de qué manera frente a las nuevas modalidades de evaluación (los rankings, la búsqueda de isomorfismo de las estructuras argumentativas y las formas lingüísticas o incluso la ficción de sociologías globales, se mantienen vivas culturas académicas particulares. En este marco, la reflexión se organiza mostrando que detrás de la singularidad de los estilos intelectuales, formas de sociabilidad profesionales e incluso formas lingüísticas de cada una de ellas, lo que se revela es la manera en la que cada cultura académica local responde desde tradiciones diversas a desafíos político sociales distintos y con ello su rol de compromiso público y crítico.

  17. Effects of compositional defects on small polaron hopping in micas.

    Science.gov (United States)

    Rosso, Kevin M; Ilton, Eugene S

    2005-06-22

    Hartree-Fock calculations and electron transfer (ET) theory were used to model the effects of compositional defects on ET in the brucite-like octahedral sheet of mica. ET was modeled as an Fe(IIIII) valence interchange reaction across shared octahedral edges of the M2-M2 iron sublattice. The model entails the hopping of localized electrons and small polaron behavior. Hartree-Fock calculations indicate that substitution of F for structural OH bridges increases the reorganization energy lambda, decreases the electronic coupling matrix element V(AB), and thereby substantially decreases the hopping rate. The lambda increase arises from modification of the metal-ligand bond force constants, and the V(AB) decrease arises from reduction of superexchange interaction through anion bridges. Deprotonation of an OH bridge, consistent with a possible mechanism of maintaining charge neutrality during net oxidation, yields a net increase in the ET rate. Although substitution of Al or Mg for Fe in M1 sites distorts the structure of adjacent Fe-occupied M2 sites, the distortion has little net impact on ET rates through these M2 sites. Hence the main effect of Al or Mg substitution for Fe, should it occur in the M2 sublattice, is to block ET pathways. Collectively, these findings pave the way for larger-scale oxidation/reduction models to be constructed for realistic, compositionally diverse micas.

  18. LA RACIONALIDAD ECONÓMICA EN NUEVA PERSPECTIVA

    Directory of Open Access Journals (Sweden)

    Jorge Arturo Chaves

    2002-08-01

    Full Text Available Las amenazas a la vida en el planeta, los hechos que han “asaltado al dogma económico” (Daly y Cobb, 1993 tienen mucho que ver con una doble toma de conciencia en la sociedad contemporánea. La primera, sobre lo restringida y esterilizante que resulta una visión economicista para enfrentar los problemas que más preocupan al ser humano hoy: las heridas infligidas al ecosistema, el aumento de la pobreza y la desigualdad, y el crecimiento desproporcionado de la actividad humana en relación a las posibilidades de la biosfera.La segunda, implicada en la anterior, la de darse cuenta que esa limitación está asociada al concepto de suyo estrecho y parcial de racionalidad económica. Enfrentamos aquí el problema del reduccionismo transmitido en el discurso y en la práctica misma de la disciplina económica que, sin embargo, no es exclusivo de ésta ni es atribuible sólo a deficiencias internas de los profesionales que la practican. Existe toda una larga tradición dentro de la cual se ha ido reduciendo de manera progresiva el concepto de razón humana y se ha ido produciendo ese concepto estrecho de racionalidad del que ahora la humanidad realiza esfuerzos por librarse.

  19. Los nuevos dominios de la ciencia económica

    Directory of Open Access Journals (Sweden)

    Bejarano Jesús Antonio

    1999-12-01

    Full Text Available Hace algo más de diez años, siendo Decano de la Facultad de Ciencias Económicas de la Universidad Nacional, tuve el honor de ser el primer expositor en el primer congreso de estudiantes de economía del país. Once años después, recae de nuevo en mí ese honor, y por ello debo expresar mi gratitud a los estudiantes organizadores de este cuento. Entre aquel primer congreso y éste se transformó no sólo el panorama del quehacer profesional sino también el panorama global de la ciencia económica, y creo que en forma radical. En poco más de veinte años, desde comienzos de los años setenta, se abrieron nuevos rumbos que, sin duda, quienes hoy son estudiantes seguirán en el futuro.

  20. A crise econômica de 2014/2017

    Directory of Open Access Journals (Sweden)

    Fernando de Holanda Barbosa Filho

    Full Text Available Resumo Este artigo mostra que a crise de 2014/2017 é fruto de uma combinação de choques de oferta e demanda resultado de erros de política econômica. Esses choques produziram uma redução da capacidade de crescimento da economia brasileira e risco de insolvência das finanças públicas. A solução da crise fiscal, através da PEC do teto dos gastos, fará que o país retome o crescimento econômico a partir de 2017, utilizando a capacidade ociosa da economia. No entanto, a taxa de crescimento do produto potencial não recuperará o ritmo anterior devido aos efeitos duradouros das políticas da Nova Matriz Econômica (NME que reduziram o produto potencial nacional. Recomenda-se, portanto, a adoção de políticas que induzam uma recuperação da produtividade da economia brasileira.

  1. La dinámica vincular celos-infidelidad

    Directory of Open Access Journals (Sweden)

    Jorge Humberto Vanegas Osorio

    2011-01-01

    Full Text Available En el conflicto celos-infidelidad subyacen motivaciones intrapsíquicas tan fuertes como el temor de pérdida del objeto, necesidades de satisfacciones narcisistas, búsqueda de la diferenciación y relaciones de poder. Lo que comparten, tanto el celoso como el infiel, son sentimientos tales como: dolor, odio, tristeza, miedo, desconcierto, desconfianza, arrepentimiento, comportamiento errático, dudas, disociación constante y culpa. Los significados de la infidelidad tienen que ver con escapar del objeto invasivo, obligarse a la reparación, negar la desidealización del objeto de amor o salvaguardarse del abandono. La frecuencia de este conflicto en las parejas y su recurrencia como motivo de consulta obliga a los psicoterapeutas una mayor profundización de la complejidad que subyace a la dinámica del vínculo. La orientación teórica para presentar este tema lo integran básicamente la dinámica inconsciente de las relaciones objetales, la identificación proyectiva y la colusión.

  2. TICs en la enseñanza de la Química: Propuesta de evaluación de Laboratorios Virtuales de Química (LVQs)

    OpenAIRE

    Cataldi, Zulma; Dominighini, Claudio; Chiarenza, Diego; Lage, Fernando Javier

    2012-01-01

    Los LVQs son unas nuevas formas de enseñanza de la química a través del uso de TICs. En este contexto se presenta el relevamiento de los laboratorios virtuales de química (LVQs) más apropiados para la enseñanza de la química. Se analizan las ventajas de su aplicación en química básica y se delinean las pautas para su evaluación y selección de acuerdo a los indicadores propuestos, articulados con el marco teórico y con las dimensiones de análisis. Se propone una evaluación centrada en tres eje...

  3. A ANÁLISE ECONÔMICA DO DIREITO COMO INSTRUMENTO PARA A ABORDAGEM SISTÊMICA

    Directory of Open Access Journals (Sweden)

    Luciano Vaz Ferreira

    2009-01-01

    Full Text Available No estudo da epistemologia, duas vertentes opostas encontram-se em conflito. De um lado, a proposta cartesiana, que vê o mundo como um objeto preciso e previsível, capaz de ser dissecado em partes totalmente independentes, sem comunicação entre elas, de modo a facilitar sua compreensão. Como contraponto, tem-se a abordagem sistêmica, a qual prega que a interação entre as diversas partes é fundamental para o funcionamento do objeto como um todo. Dessa maneira, pode-se concluir que enquanto o fundamento para a primeira está na separação das diversas disciplinas, a segunda prima pela interdisciplinaridade. A realidade é rica em demonstrar variados exemplos de influências mútuas entre direito, economia e administração. Nesse cenário, a abordagem da “Análise Econômica do Direito” revela-se ser um interessante mecanismo para a solução das controvérsias jurídicas, por meio da superação do paradigma cartesiano. Palavras-chave: Cartesianismo. Teoria dos Sistemas. Análise Econômica do Direito.

  4. DINÁMICA MACROECONÓMICA CON METAS DE INFLACIÓN Y DÉFICIT FISCAL

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    Waldo Mendoza Bellido

    2011-01-01

    Full Text Available En este modelo la política monetaria se basa en un sistema de metas explícitas de inflación, con la tasa de interés interbancaria como instrumento de política y la cantidad de dinero endógena; mientras que la política fiscal opera con un límite en el déficit fiscal como porcentaje del PIB, y el gasto público es endógeno. En la regla de política monetaria, el parámetro de suavizamiento de la tasa de interés se infiere del comportamiento optimador del banco central.El modelo muestra la dinámica macroeconómica que se produce en dos panora-mas extremos, de credibilidad completa en la meta de inflación del banco central, y de credibilidad nula, y se encuentra que i puede haber convergencia hacia el equilibrio estacionario, incluso si no se cumple el principio de Taylor, y ii si hay completa credibilidad en el banco central, una política monetaria contractiva puede producir un reajuste insuficiente (undershooting de la inflación.

  5. Electrical Trees in a Composite Insulating System Consisted of Epoxy Resin and Mica: The Case of Multiple Mica Sheets For Machine Insulation

    Directory of Open Access Journals (Sweden)

    V. A. Kioussis

    2014-08-01

    Full Text Available Epoxy resin and mica sheets consist the essential insulation of rotating machine stator bars. Such an insulation, although very resistant to partial discharges, is subjected to considerable electrical stresses and consequently electrical trees may ensue. In this paper, an effort is made to simulate electrical tree propagation in multiple epoxy resin/mica sheets with the aid of Cellular Automata (CA. An attempt to compare the simulation results with experimental results is also made.

  6. Catalizadores Organometálicos en la Industria Química

    National Research Council Canada - National Science Library

    Alfonso Enrique Ramírez Sanabria; Johny Roberto Rodríguez Pérez

    2015-01-01

    ... química, debido a la participación de una especie química denominada catalizador. El presente trabajo recopila cinco procesos industriales en los cuales son empleados catalizadores organometálicos en fase homogénea...

  7. Bioquímica clínica i hematologia. Curs 2008-2009

    OpenAIRE

    Universitat de Barcelona. Facultat de Farmàcia

    2008-01-01

    Pla docent de l'assignatura Bioquímica Clínica i Hematologia de l'Ensenyament de Farmàcia, Facultat de Farmàcia. Curs acadèmic 2008-2009. Departament de Bioquímica i Biologia Molecular (Farmàcia)

  8. RECIFE, DINÂMICA URBANA E CENA MANGUEBEAT

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    Cristiano Nunes Alves

    2016-04-01

    Full Text Available Cidade marcada a um só tempo pela desigualdade socioterritorial e pelo seu caráter cosmopolita, o Recife fora o lugar de surgimento do manguebeat ou manguebit, movimentação artística difundida alhures no início dos anos 1990. Sinalizando para a fusão entre a música elétrica e os ritmos negros de matriz brasileira, o manguebeat contribuiu decisivamente para a constituição de um olhar especial sobre a cultura do Recife e de Pernambuco. Operacionalizando a noção de “cena musical”, objetiva-se analisar os nexos entre a dinâmica urbana do Recife e o manguebeat. Abordam-se os contornos da Cena Manguebeat durante o seu período de formação, dinamizada por sujeitos oriundos de diversos lugares e classes sociais da capital pernambucana, pensando e agindo sobre a cidade como abrigo. Discute-se a relação entre a dinâmica da urbe recifense e o manifesto “Caranguejos com Cérebro”, portador de uma crítica ao crescimento desordenado sofrido pela metrópole e anteato para a difusão da Cena Mangue alhures. Tecem-se reflexões sobre os vínculos entre a Cena Mangue, a cultura popular erigida nos lugares e a concepção de vanguarda nas artes. Observam-se assim, as associações e os conflitos entre os sujeitos da Cena e agentes da indústria cultural. Reflete-se sobre a repercussão espaço temporal do Manguebeat, destacando-se a dinâmica dessa Cena no período contemporâneo, presente na urbe recifense e fora dela, aportando em diversos lugares da rede urbana brasileira. Trata-se, o manguebeat, de rica empiria, para, a partir da dimensão cultural, melhor entender o funcionamento da metrópole contemporânea.

  9. Espaço, Diplomacia Económica e Políticas Públicas

    OpenAIRE

    Neto, Paulo

    2013-01-01

    Em Espaço, Diplomacia Económica e Políticas Públicas defende-se que cada território constrói o seu próprio modelo relacional, o qual resulta, entre outros fatores, da história económica e social, da natureza das práticas e dos processos de tomada de decisão, das opções pela localização de infraestruturas, da dinâmica no apoio e sucesso registado na atracão de empresas, ou da acumulação de dinâmica empresarial e económica que o território tenha podido assegurar. Neste sentido, a especifi...

  10. Association of MICA gene polymorphisms with liver fibrosis in schistosomiasis patients in the Dongting Lake region

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Zheng; Luo, Qi-Zhi; Lin, Lin [Department of Immunology, College of Basic Medical Sciences, Central South University, Changsha, Hunan Province (China); Su, Yu-Ping; Peng, Hai-Bo [Central Blood Bank in Yueyang, Yueyang, Hunan Province (China); Du, Kun; Yu, Ping [Department of Immunology, College of Basic Medical Sciences, Central South University, Changsha, Hunan Province (China); Wang, Shi-Ping [Key Laboratory of Schistosomiasis in Hunan, Department of Parasitology, College of Basic Medical Sciences, Central South University, Changsha, Hunan Province (China)

    2012-03-02

    Major histocompatibility complex class I chain-related A (MICA) is a highly polymorphic gene located within the MHC class I region of the human genome. Expressed as a cell surface glycoprotein, MICA modulates immune surveillance by binding to its cognate receptor on natural killer cells, NKG2D, and its genetic polymorphisms have been recently associated with susceptibility to some infectious diseases. We determined whether MICA polymorphisms were associated with the high rate of Schistosoma parasitic worm infection or severity of disease outcome in the Dongting Lake region of Hunan Province, China. Polymerase chain reaction-sequence specific priming (PCR-SSP) and sequencing-based typing (SBT) were applied for high-resolution allele typing of schistosomiasis cases (N = 103, age range = 36.2-80.5 years, 64 males and 39 females) and healthy controls (N = 141, age range = 28.6-73.3 years, 73 males and 68 females). Fourteen MICA alleles and five short-tandem repeat (STR) alleles were identified among the two populations. Three (MICA*012:01/02, MICA*017 and MICA*027) showed a higher frequency in healthy controls than in schistosomiasis patients, but the difference was not significantly correlated with susceptibility to S. japonicum infection (Pc > 0.05). In contrast, higher MICA*A5 allele frequency was significantly correlated with advanced liver fibrosis (Pc < 0.05). Furthermore, the distribution profile of MICA alleles in this Hunan Han population was significantly different from those published for Korean, Thai, American-Caucasian, and Afro-American populations (P < 0.01), but similar to other Han populations within China (P > 0.05). This study provides the initial evidence that MICA genetic polymorphisms may underlie the severity of liver fibrosis occurring in schistosomiasis patients from the Dongting Lake region.

  11. DINÁMICA DEL COMPLEJO DEL PORO NUCLEAR

    Directory of Open Access Journals (Sweden)

    TD GEYDAN

    2010-01-01

    Full Text Available El complejo del poro nuclear (CPN es un conjunto supra-molecular compuesto de múltiples copias de 30 familias de proteínas diferentes, siendo 456 nucleoporinas (Nups en total, que atraviesan la envoltura nuclear de todos los organismos pertenecientes al dominio Eukaria. El CPN es la compuerta del núcleo; por lo tanto, todas las macromo- léculas deben atravesarla para transitar del núcleo al citoplasma y viceversa. Durante los últimos años, se han propuesto varios modelos para explicar la regulación y el transporte de macromoléculas a través del CPN. En esta nota se describe la estructura, los meca- nismos y procesos involucrados durante el transporte a través del CPN, y cómo estos procesos son regulados por interacciones macromoleculares altamente dinámicas.

  12. Solanaceae endémicas del Perú

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    Sandra Knapp

    2013-10-01

    Full Text Available La familia Solanaceae es una de las más ricas en especies en la flora peruana, siendo reconocida con alrededor de 42 géneros y 600 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, principalmente hierbas y arbustos. En este trabajo reconocemos 208 especies y seis variedades como endémicos, en 16 géneros. Esta familia ocupa el sexto lugar por su diversidad en especies endémicas, siendo Solanum, Nolana y Jaltomata los géneros más ricos en especies. Los taxones endémicos se encuentran en la mayoría de las regiones, principalmente en Mesoandina, Desierto Semicálido Tropical y Bosques Muy Húmedos Montanos, desde el nivel del mar hasta los 3800 m de altitud. Treinta y seis taxones se encuentran representados dentro del Sistema Nacional de Áreas Naturales Protegidas por el Estado.

  13. Úvea y enfermedades sistémicas

    OpenAIRE

    Pablo Sabat, O.; Víctor Velásquez, R.

    2010-01-01

    El ojo, además de entregarnos el sentido de la visión, también nos permite conocer la salud general del organismo. Muchas enfermedades sistémicas se manifiestan en el órgano visual antes, durante o después del debut de ellas a nivel sistémico. Este compromiso visual es variado y depende de la enfermedad en cuestión, destacando la escleritis, uveítis y vasculitis retinales. Conocer el estado ocular permitirá al clínico realizar diagnósticos más asertivos y oportunos, realizar el tratamiento má...

  14. Nutrigenómica, obesidad y salud pública.

    OpenAIRE

    Manuela Belén Silveira; Lourdes Martínez-Piñeiro Muñoz; Raffaele Carraro Casieri

    2007-01-01

    El desarrollo de la genómica funcional en los próximos años condicionará cambios en el conocimiento teórico y la práctica clínica de la nutrición. La posibilidad de determinar el perfil genético de un individuo (variaciones genéticas y modificaciones epigenéticas) y de conseguir la integración de estos datos en una compleja red de interacciones metabólicas constituye un desafío sin precedentes en la nutrición humana. La aplicación práctica del conocimiento científico puro...

  15. Las cooperativas ante la crisis económica

    Directory of Open Access Journals (Sweden)

    Javier Divar Garteiz-Aurrecoa

    2010-12-01

    Full Text Available Las Cooperativas están especialmente preparadas ante las crisis económicas, puesto que su estructura participativa permite el esfuerzo común de sus partícipes para afrontar las adversidades e incentivar la innovación, a más de que las uniones tradicionales entre ellas facilitan las sinergias colectivas de sus grupos societarios. Complementariamente su falta de lucrativismo permite los sacrificios laborales de sus socios, que además radican a estas sociedades con su entorno y les imponen la operatividad ante cualquier situación política.Recibido: 02.06.10Aceptado: 28.06.10

  16. Liliaceae endémicas del Perú

    Directory of Open Access Journals (Sweden)

    Blanca León

    2013-10-01

    Full Text Available La familia Liliaceae es reconocida en el Perú con 15 géneros (excepto Alstroemeria y Bomarea y aproximadamente 29 especies (Brako & Zarucchi, 1993; Ulloa Ulloa et al., 2004, todas ellas hierbas. Esta familia incluye tres géneros endémicos, Diamena, Diora y Trichlora. En este trabajo reconocemos 11 especies endémicas en cinco géneros. Se asignó las categorías de amenaza de la UICN a seis especies. La mitad de los endemismos es conocido solamente de una localidad. Los taxones endémicos ocupan las regiones del Desierto Semicálido Costero y Mesoandina, entre los 600 y 3600 m de altitud. Solamente una especie está representada en un área natural protegida.

  17. ARTE ISLÂMICA: UMA FENOMENOLOGIA DO SAGRADO

    Directory of Open Access Journals (Sweden)

    Cláudia Felicia Falluh Balduino Ferreira

    2011-09-01

    Full Text Available Considerando as artes do arabesco e da caligrafia islâmicas como compositoras de um sítio místico e sagrado representado pelo Alcorão, estudaremos o modo pelo qual o artífice se apropria dos elementos do mundo da experiência para ilustrar o Livro santo dos muçulmanos criando assim uma geografia mística que é devolvida ao mundo e nele gera expressões artísticas (arquitetônicas, literárias e pictóricas. Para tal tomaremos os conceitos da fenomenologia e da história das religiões e comparações oriundas das artes citadas e da literatura.

  18. Venezuela 1983. Impacto de la crisis económica

    Directory of Open Access Journals (Sweden)

    Alfredo Keller R.

    2015-01-01

    Full Text Available La revista se centra en el rol que desempeñan los medios en las campañas electorales,se publica la función política de éstos en Escandinavia,(1983La campaña electoral en una transición política en Argentina, (1986Una democracia amenazada en Costa Rica, (1985 Rescate de la memoria colectiva desde el Perú, (1983 Impacto de la crisis económica en Venezuela,(1986 Impresiones del periodismo político en Austria, (1984Propaganda electoral en la prensa de Quito, (1984 En DOCUMENTOS se publica sobre Innovación tecnológica en Educación, el Informe de proyectos 1985, la Primera reunión de Jamaica.

  19. Proyecto gestor de actividades académicas extracurriculares

    OpenAIRE

    Pérez Campo, Juan Carlos

    2016-01-01

    Proyecto final de carrera en Ingeniería del Software que consiste en la elaboración de las fases de análisis y diseño técnico de un software que permita realizar la gestión de las actividades académicas extracurriculares que se ofrecen en una universidad. Projecte final de carrera en Enginyeria del Programari que consisteix en l'elaboració de les fases d'anàlisi i disseny tècnic d'un programari que permeti realitzar la gestió de les activitats acadèmiques extracurriculars que s'ofereixen e...

  20. Las teorías sistémicas

    OpenAIRE

    Urteaga, Eguzki

    2010-01-01

    A partir de los años 1970, diversas teorías (teorías de los sistemas abiertos, teoría cibernética, teoría del sistema general, teoría de la organización) han tenido cierta tendencia a reunirse en una perspectiva autónoma denominada la sistémica que es, de hecho, un pensamiento interdisciplinar y multidisciplinar. Esta ciencia de los sistemas, aplicada a las ciencias sociales, propone una nueva visión de los fenómenos sociales y un método de modelización de las relaciones sociales. A ...

  1. L'Aerodinàmica en el DTM

    OpenAIRE

    Gallostra Cuberes, Albert

    2017-01-01

    En aquest projecte s’estudiarà el recorregut històric del món de l’aerodinàmica així com els principals elements relacionats amb el món de l’automoció. Es realitzaran els models de l’automòbil escollit amb el suport de les eines de disseny 3D Solidworks i Catia a partir de la modelització de superfícies, així com els dissenys individuals dels seus apèndixs aerodinàmics i posteriorment es procedirà als seus estudis amb les eines de simulació escollides. Les simulacions d’elem...

  2. Jung, mandala e arquitetura Islâmica

    Directory of Open Access Journals (Sweden)

    Rafael Raffaelli

    2009-03-01

    Full Text Available Este artigo se propõe a refletir sobre as origens do conceito junguiano de mandala. Utiliza-se o relato autobiográfico de Jung, Memórias, Sonhos e Reflexões, e sua obra Psicologia e Alquimia para traçar essa origem. Segundo Barbara Hannah, biógrafa de Jung, uma mesquita no Cairo (Egito foi de importância capital para a formulação desse conceito. Provavelmente esse templo é a Mesquita Ahmad Ibn Tulun. É analisada a relação entre a simbologia arquitetônica islâmica inspirada pelo sufismo e as concepções psicológicas de Jung.

  3. Resistive switching effect in the planar structure of all-printed, flexible and rewritable memory device based on advanced 2D nanocomposite of graphene quantum dots and white graphene flakes

    Science.gov (United States)

    Muqeet Rehman, Muhammad; Uddin Siddiqui, Ghayas; Kim, Sowon; Choi, Kyung Hyun

    2017-08-01

    Pursuit of the most appropriate materials and fabrication methods is essential for developing a reliable, rewritable and flexible memory device. In this study, we have proposed an advanced 2D nanocomposite of white graphene (hBN) flakes embedded with graphene quantum dots (GQDs) as the functional layer of a flexible memory device owing to their unique electrical, chemical and mechanical properties. Unlike the typical sandwich type structure of a memory device, we developed a cost effective planar structure, to simplify device fabrication and prevent sneak current. The entire device fabrication was carried out using printing technology followed by encapsulation in an atomically thin layer of aluminum oxide (Al2O3) for protection against environmental humidity. The proposed memory device exhibited attractive bipolar switching characteristics of high switching ratio, large electrical endurance and enhanced lifetime, without any crosstalk between adjacent memory cells. The as-fabricated device showed excellent durability for several bending cycles at various bending diameters without any degradation in bistable resistive states. The memory mechanism was deduced to be conductive filamentary; this was validated by illustrating the temperature dependence of bistable resistive states. Our obtained results pave the way for the execution of promising 2D material based next generation flexible and non-volatile memory (NVM) applications.

  4. Desigualdades socioeconômicas na saúde

    Directory of Open Access Journals (Sweden)

    Diaz Maria Dolores M.

    2003-01-01

    Full Text Available Este artigo analisa as desigualdades socioeconômicas na área da saúde no Brasil, por meio da mensuração de índice de concentração para a variável autoavaliação do estado de saúde. Utilizou-se a base de dados originada pela Pesquisa Domiciliar sobre Padrões de Vida - PPV - realizada pelo IBGE no período de março/1996 a março/1997, em convênio com o Banco Mundial. Entre os principais resultados, deve-se destacar a constatação de que existem diferenças estatisticamente significativas entre índices calculados a partir de distintas variáveis caracterizadoras do nível socioeconômico dos indivíduos. Neste caso, em particular, os indicadores calculados a partir da classificação baseada na variável renda indicou, sistematicamente, a presença de desigualdades na saúde ligeiramente superiores àquelas identificadas a partir da utilização das despesas familiares. Constatou-se, ainda, que os resultados obtidos são bastante robustos em relação às distintas ponderações utilizadas na construção das escalas de equivalência entre os indivíduos. Todas as simulações realizadas revelaram a presença de desigualdades que favorecem os indivíduos pertencentes às camadas mais elevadas das escalas socioeconômicas adotadas.

  5. La historia económica en Internet

    Directory of Open Access Journals (Sweden)

    Donato Gómez Díaz

    2008-12-01

    Full Text Available La conexión de Instituciones, Universidades, centros científicos, empresas e incluso páginas personales en una única red mundial, ha conferido al acto de investigar una nueva dimensión. El artículo que presentamos pretende ayudar a conocer las herramientas y lugares más interesantes donde buscar información en Internet. Para eso hemos dividido nuestra exposición en tres partes, una primera donde se narra la evolución de los ordenadores y el desarrollo de Internet. Otra segunda en la que definimos la Historia económica, a la búsqueda de los temas que le son propios. Finalmente, hemos recopilado las direcciones más interesantes en Internet, tanto para la Historia económica como para muchas de las subáreas en las que participa. Otras direcciones imprescindibles como working papers, bases de datos y bibliotecas, también se incluyen en beneficio de nuestros intereses investigadores o pedagógicos.______________________ABSTRACT:The connection among the Institutions, Universities, scientific centres, companies, and even personal pages in one worlwide net has converted the act of research into a new dimension. The paper we present tries to know the tools and places more interesting where to find information in the net. For that reason we have divided our presentation in three parts; a first where we narrate the evolution of computers and the development of the net; a second one, where we define the Economic History, trying to look for the topics of their own. Finally, we have collected the more interesting sites in the net, for Economic History and for the different sub-areas pending on it. Other interesting addresses like data bases, working papers and libraries, are as well included to benefit our research and pedagogic interests.

  6. CARACTERIZAÇÃO ANATÔMICA E HISTOQUÍMICA DAS FOLHAS DE EUGENIA UNIFLORA L.

    Directory of Open Access Journals (Sweden)

    Rafaela Damasceno Sá

    2016-10-01

    Full Text Available Eugenia uniflora L., popularmente conhecida como pitangueira, é uma importante frutífera muito utilizada na medicina tradicional brasileira para o tratamento de diarreia e disenteria, gripe, parasitas intestinais, febre, hipertensão e como calmante e diurético. Devido ao seu amplo interesse popular e com o intuito de ampliar as informações farmacobotânicas da espécie, este trabalho tem como objetivo realizar a caracterização anatômica e histoquímica das folhas de E. uniflora. Foram confeccionadas e analisadas em microscópico de luz lâminas semipermanentes contendo secções transversais de pecíolo e lâmina foliar, além de secções paradérmicas de lâmina foliar. Realizou-se também testes histoquímicos em secções transversais de lâmina foliar A análise microscópica permitiu a identificação de estruturas importantes na diagnose da espécie: cavidades secretoras no pecíolo e na lâmina foliar; cristais prismáticos no floema do pecíolo e da lâmina foliar, bem como no mesofilo e nas células parenquimáticas e colenquimáticas da nervura central; drusas estão presentes apenas no parênquima do pecíolo e no mesofilo, parênquima e colênquima da lâmina foliar; presença de cutícula espessa no pecíolo e na lâmina foliar; feixes vasculares bicolaterais e mesofilo dorsiventral, com parênquima paliçádico bisseriado. Através da histoquímica evidenciou-se na lâmina foliar a presença de compostos fenólicos, taninos, lignina, compostos lipofílicos, óleos essenciais, triterpenos e esteroides e cristais de oxalato de cálcio. Os resultados apresentados são úteis para a identificação correta da espécie.

  7. La práctica docente universitaria en Ciencias Económicas y el rol de las TICS

    OpenAIRE

    Casparri, María Teresa; Garnica Hervas, Juan Ramón; Castegnaro de Pasarin, Aída Beatriz

    2012-01-01

    Fil: Casparri, María Teresa. Universidad de Buenos Aires. Facultad de Ciencias Económicas Fil: Garnica Hervas, Juan Ramón. Universidad de Buenos Aires. Facultad de Ciencias Económicas Fil: Castegnaro de Pasarin, Aída Beatriz. Universidad de Buenos Aires. Facultad de Ciencias Económicas

  8. Major histocompatibility complex class I-related chain A/B (MICA/B expression in tumor tissue and serum of pancreatic cancer: Role of uric acid accumulation in gemcitabine-induced MICA/B expression

    Directory of Open Access Journals (Sweden)

    Kaufman Howard L

    2011-05-01

    Full Text Available Abstract Background Major histocompatibility complex class I-related chain A and B (MICA/B are two stress-inducible ligands that bind the immunoreceptor NKG2D and play an important role in mediating the cyotoxicity of NK and T cells. In this study, we sought to study MICA/B expression in pancreatic cancer and to determine whether and how genotoxic drugs such as gemcitabine can affect MICA/B expression and natural killer cytotoxity. Methods Seven pancreatic cancer cell lines were analyzed for MICA/B expression by flow cytometry and for their sensitivity to NK-92 cell killing by a 51Cr release assay. MICA/B expression in tumor tissues and sera of pancreatic cancer was analyzed by immunohistochemical staining (IHC and ELISA, respectively. Results Two MICA/B-positive cell lines were sensitive to the cytotoxic activity of NK-92 cells. Other two MICA/B-positive cell lines and three MICA/B-negative cell lines were resistant to NK-92 cell killing. MICA/B expression was positive in 17 of 25 (68% pancreatic ductal adenocarcinomas but not in normal pancreatic ductal epithelial cells. Serum MICA/B levels were significantly elevated in patients with pancreatic adenocarcinomas but did not correlate with the stage of pancreatic cancer and patient survival. Gemcitabine therapy led to increased serum MICA levels in 6 of 10 patients with detectable serum MICA. Allopurinol, an inhibitor of xanthine oxidoreductase that converts xanthine to uric acid, blocked uric acid production, MICA/B expression, and sensitivity to NK-92 cell killing toward a PANC-1 cancer cell line exposed to radiation and two genotoxic drugs, gemcitabine and 5-fluorouracil. Conclusions The levels of MICA/B expression in serum and tissue of pancreatic cancer are elevated. DNA damage-induced MICA/B expression is mediated through increased uric acid production.

  9. Reacciones fotoquímicas en Química Analítica Determinación de peroxodisulfatos.

    OpenAIRE

    García García, María Soledad; Sánchez-Pedreño, C.; Sierra Hernández, María Isabel

    1983-01-01

    Se presenta un nuevo método de determinación de peroxidisulfatos basado en su precipitación homogénea bajo la forma de SOéBa. El paso de S208^ a S04^ es producido por la acción reductora del anión ioduro engendrado «in situ» en la reacción fotoquímica entre el ácido etilenodiaminotetracético y el iodo. Se han estudiado las variables que afectan al proceso analítico pH, temperatura, iluminación, concentración de reactivos y presencia de iones extraños, para establec...

  10. Pseudotumor tras cirugía de revisión por rotura de cabeza cerámica en una artroplastia total de cadera con par cerámica-cerámica: caso clínico

    OpenAIRE

    Sangüesa, M. J.; Cabanes, F.; Fernández Gabarda, Rafael; Valverde,C.

    2011-01-01

    Se presenta un caso clínico con una importante y precoz metalosis, tan solo tres meses después de la revisión de una artroplastia total de cadera primaria par cerámica-cerámica, en la que se había roto la cabeza cerámica, y en la revisión se sustituyó por un par metal-polietileno. Catorce meses después apareció un pseudotumor causado por la metalosis por rotura de la cabeza metálica, por lo que se realizó una nueva revisión utilizando un par metal-metal preservando el vástago femo...

  11. Effect of Mica and Hematite (001 Surfaces on the Precipitation of Calcite

    Directory of Open Access Journals (Sweden)

    Huifang Xu

    2018-01-01

    Full Text Available The substrate effect of mica and hematite on the nucleation and crystallization of calcite was investigated using scanning electron microscope (SEM, X-ray diffraction (XRD, and electron backscatter diffraction (EBSD methods. On mica, we found, in the absence of Mg2+, the substrates’ (001 surfaces with hexagonal and pseudo-hexagonal two-dimensional (2-D structure can affect the orientation of calcite nucleation with calcite (001 ~// mica (001 and calcite (010 ~// mica (010 to be the major interfacial relationship. On hematite, we did not observe frequent twinning relationship between adjacent calcite gains, but often saw preferentially nucleation of calcite at surface steps on hematite substrate. We suggest that calcite crystals initially nucleate from the Ca2+ layers adsorbed on the surfaces. The pseudo-hexagonal symmetry on mica (001 surface also leads to the observed calcite (001 twinning. A second and less common orientation between calcite {104} and mica (001 was detected but could be due to local structure damage of the mica surface. Results in the presence of Mg2+ show that the substrate surfaces can weaken Mg toxicity to calcite nucleation and lead to a higher level of Mg incorporation into calcite lattice.

  12. CEACAM1 and MICA as novel serum biomarkers in patients with acute and recurrent pericarditis.

    Science.gov (United States)

    Markel, Gal; Imazio, Massimo; Koren-Morag, Nira; Galore-Haskel, Gilli; Schachter, Jacob; Besser, Michal; Cumetti, Davide; Maestroni, Silvia; Altman, Arie; Shoenfeld, Yehuda; Brucato, Antonio; Adler, Yehuda

    2016-04-05

    The immune response plays a significant role in pericarditis, but the mechanisms of disease are poorly defined. Further, efficient monitoring and predictive clinical tools are unavailable. Carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is an immune-inhibitory protein, while MHC class I chain related protein A (MICA) and B (MICB) have an immune-stimulating function. Serum CEACAM1, MICA and MICB concentrations were measured by ELISA in ~50 subjects of each group: acute pericarditis (AP), recurrent pericarditis (RP) and lupus (SLE) patients, metastatic melanoma patients as well as healthy donors. Serum CEACAM1 was dramatically elevated in AP and RP patients, but not in SLE patients, and displayed a highly accurate profile in ROC curve analyses. MICA and MICB were elevated in some pericarditis patients. All markers were enhanced in metastatic melanoma patients irrespective of neoplastic pericardial involvement. Etiology-guided analysis of RP patients showed that very low MICA levels were associated with idiopathic RP, while high MICA was associated with autoimmune and post-operative RP. Importantly, MICA was significantly associated with recurrences, independently of other potentially confounding parameters such as age, time of follow up or treatment modality. Here we report for the first time on CEACAM1 as a potentially novel biomarker for pericarditis, as well as on MICA as an innovative prognostic marker in these patients. Determination of the roles of these immune factors, as well as their diagnostic and prognostic values should be determined in future prospective studies.

  13. TICs en la enseñanza de la Química: Propuesta de evaluación de Laboratorios Virtuales de Química (LVQs

    Directory of Open Access Journals (Sweden)

    Cataldi, Zulma

    2012-01-01

    Full Text Available Los LVQs son unas nuevas formas de enseñanza de la química a través del uso de TICs. En este contexto se presenta el relevamiento de los laboratorios virtuales de química (LVQs más apropiados para la enseñanza de la química. Se analizan las ventajas de su aplicación en química básica y se delinean las pautas para su evaluación y selección de acuerdo a los indicadores propuestos, articulados con el marco teórico y con las dimensiones de análisis. Se propone una evaluación centrada en tres ejes: a dimensiones tecnológicas y técnicas, b dimensiones pedagógicas y c otras dimensiones como costo y comercialización. Se realizan pruebas de ajuste y aplicación del instrumento según los siguientes objetivos: a Analizar las estrategias didácticas docentes y la percepción en el uso de las TICs y b Delinear acciones formativas en didáctica de la química con uso de TICs.

  14. Sobre el enfoque estocástico de la dinámica de poblaciones marinas

    OpenAIRE

    Eduardo Ferrandis

    2007-01-01

    dinámica de poblaciones marinas, evaluación de recursos marinos, análisis de supervivencia, modelos deEl presente trabajo trata de profundizar y estructurar el fundamento estadístico de la dinámica de poblaciones marinas. El punto de partida es la relación entre los conceptos de mortalidad, supervivencia y distribución del tiempo de vida. Este triángulo constituye un nido de posibilidades que las técnicas de análisis de supervivencia ofrecen a la dinámica de poblaciones marinas. Se citan...

  15. Measurement of friction force between two mica surfaces with multiple beam interferometry

    Directory of Open Access Journals (Sweden)

    Jung J.C.

    2010-06-01

    Full Text Available Friction forces play a crucial role in the tribological behaviour of microcomponents and the application of MEMS products. It is necessary to develop a measurement system to understand and control the material characteristics. In this study, a microscopic measurement system based on multiple beam interferometry is developed to measure the friction force between two mica thin films. Some frictional behaviour between the two mica sheets in contact are reported. The evaluated shear strength of mica agrees well to the existing data. It is possible to use the developed system for micro-tribology study.

  16. The growth of sodium rough films on mica (0001) as determined by Helium Atom Scattering

    DEFF Research Database (Denmark)

    Gerlach, Rolf; Balzer, Frank; Rubahn, Horst-Günter

    2001-01-01

    Elastic helium atom scattering (HAS) and linear optical extinction measurements are used to investigate the growth of sodium (Na) films on mica substrates in the surface temperature range between 90 and 300 K. At half a monolayer (ML) surface coverage we observe a maximum of scattered He intensity......, which is addressed to Na atoms that fill cleavage-induced holes in the mica surface. It provides a convenient means of calibrating the coverage of the surface. With increasing surface coverage Na clusters are formed on the mica surface. A broad angular distribution of the scattered Helium intensity...

  17. CD56+ immune cell infiltration and MICA are decreased in breast lobules with fibrocystic changes.

    Science.gov (United States)

    Kerekes, Daniel; Visscher, Daniel W; Hoskin, Tanya L; Radisky, Derek C; Brahmbhatt, Rushin D; Pena, Alvaro; Frost, Marlene H; Arshad, Muhammad; Stallings-Mann, Melody; Winham, Stacey J; Murphy, Linda; Denison, Lori; Carter, Jodi M; Knutson, Keith L; Degnim, Amy C

    2017-11-01

    While the role of natural killer (NK) cells in breast cancer therapy has been investigated, little information is known about NK cell function and presence in nonmalignant and premalignant breast tissue. Here, we investigate and quantify NK cell marker CD56 and activating ligand MICA in breast tissue with benign breast disease. Serial tissue sections from 88 subjects, 44 with benign breast disease (BBD) who remained cancer-free, and 44 with BBD who later developed cancer, were stained with H&E, anti-MICA, and anti-CD56. Up to ten representative lobules were identified on each section. Using digital image analysis, MICA and CD56 densities were determined for each lobule, reported as percent of pixels in the lobule that registered as stained by each antibody. Analyses were performed on a per-subject and per-lobule basis. Per-subject multivariate analyses showed associations of CD56 and MICA with age: CD56 was increased in older subjects (p = 0.03), while MICA was increased in younger subjects (p = 0.005). Per-lobule analyses showed that CD56 and MICA levels were both decreased in lobules with fibrocystic change, with median levels of CD56 and MICA staining, respectively, at 0.31 and 7.0% in fibrocystic lobules compared to 0.76 and 12.2% in lobules without fibrocystic change (p fibrocystic lobules, proliferative/atypical lobules showed significantly lower expression compared to nonproliferative lobules for MICA (p = 0.02) but not for CD56 (p = 0.80). Levels of CD56+ NK cells and activating ligand MICA were decreased in breast lobules with fibrocystic change, and MICA levels showed a significant stepwise decrease with increasing histopathologic abnormality. MICA levels were also significantly decreased in older subjects, who generally have higher risk of developing cancer. These findings advance a model in which MICA promotes cytotoxic activity in CD56+ NK cells to protect against tumorigenesis in breast lobules, and suggest further research is warranted.

  18. A empresa e o meio nas teorias económicas da empresa: uma leitura longitudinal

    OpenAIRE

    Santos, João; Ferreira, Manuel Portugal; Reis, Nuno

    2010-01-01

    A teoria económica tem tentado compreender e explicar o comportamento das empresas nos mercados. Contudo, persistem grandes divergências acerca do papel das diferentes forças que influenciam o crescimento e os objectivos das empresas. Sintetizar os principais contributos dos autores mais relevantes das diferentes teorias económicas parece útil. Assim, neste artigo fazemos uma breve revisão das teorias da empresa desde a teoria neoclássica até ao conceito de capacidades dinâmicas e o impacto n...

  19. Consideraciones anatómicas durante la cirugía periodontal

    OpenAIRE

    P. Solano Mendoza; A. Bascones Martínez

    2014-01-01

    En el presente trabajo hemos realizado una revisión bibliográfica de la literatura con el objetivo de esclarecer las consideraciones anatómicas que deben tenerse en cuenta a la hora de realizar cirugía periodontal, que posibles estructuras anatómicas podemos encontrarnos al elevar un colgajo y cómo podemos evitar la lesión de las mismas. También aportamos un breve repaso sobre conceptos y referencias anatómicas que los especialistas debemos tener presentes durante el manejo de los tejidos bla...

  20. Efecto acaricida de una mezcla química

    Directory of Open Access Journals (Sweden)

    E. Egea

    2000-02-01

    Full Text Available

    Introducción: Se investiga el efecto de una nueva mezcla química (ATLASAC para el control de ácaros del polvo doméstico, microorganismos cosmopolitas que conviven con el hombre, reconocidos como importante fuente de alergenos y la principal causa de exacerbación de las enfermedades alérgicas. En el medio ambiente de los hogares colombianos se conoce por reportes científicos la prevalencia de varias especies comunes en otros países: Dermatophagoides pteronyssinus, D. Farinae, Blomia tropicales, etc, asociados con asma y/o rinitis. Por todo ello, en el medio ambiente residencial del paciente es importante establecer medidas locativas tendientes a evitar la exposición y el control químico para reducir o eliminar la fuente de alergenos, en especial, los ácaros. Un recurso fácil de aplicar son los acaricidas, los cuales varían en el grado de efectividad y tiempo de protección. En nuestro medio no se tienen productos aprobados como acaricidas. Por tal motivo, esta investigación pretende llenar un vacío en el medio colombiano con una mezcla química con efecto acaricida, en especial sobre aquellos implicados con las enfermedades alérgicas.

    Metodología: Se seleccionaron 25 pacientes definidos por historia clínica como alérgicos y 50 voluntarios que por pruebas cutáneas se descartó sensibilización a ácaros. Inmediatamente después del ingreso se hicieron muestreos para determinar la presencia de ácaros del polvo doméstico y fundamentalmente para obtener cultivos puros.

    Resultados preliminares: 100 ácaros de

  1. Manifestaciones sistémicas del brote dentario

    Directory of Open Access Journals (Sweden)

    Juana María Abreu Correa

    1997-12-01

    Full Text Available Se realizó un estudio para comprobar la presencia de manifestaciones sistémicas asociadas con el brote dentario, aspecto que ha sido motivo de discrepancias entre médicos y estomatólogos durante mucho tiempo. Para la obtención de los datos se entrevistaron a las madres de 121 infantes, cuyas edades oscilaron entre 6 y 12 meses, por considerarse las edades más propensas a estas manifestaciones. Se aplicó el método estadístico de prueba de contraste de hipótesis. No hubo diferencias en relación con el sexo. Las madres refirieron los síntomas y signos que se presentan durante la erupción dentaria y que se expresan en por cientos; otro grupo planteó que la erupción fue asintomática. Entre las manifestaciones o patologías asociadas, las diarreas tuvieron una mayor incidencia, seguidas de la fiebre, el estado catarral y los vómitos. También estuvieron presentes, aunque con menos incidencia, la irritabilidad y la dermatitis. Según las pruebas estadísticas los resultados fueron altamente significativos, lo que demuestra la relación existente entre manifestaciones sistémicas y el brote dentario.It was conducted a study to prove the presence of systemic manifestations associated with tooth eruption, an aspect that has been the cause of differences between doctors and stomatologists for a long time. In order to obtain information the mothers of 121 infants aged 6-12 months were interviewed as they had more possibilities to present these manifestations. The statistical method of hypothesis contrast test was applied. There were no differences in connection with sex. Mothers explained the symptoms and signs appearing during tooth eruption that are expressed in percents. The other group said that the eruption was asymptomatic. Among the associated manifestations or pathologies, diarrheas had the greatest incidence, followed by fever, cold, and vomits. Irritability and dermatitis were also present but with less incidence. According to the

  2. Peasant economic rationality Racionalidad económica campesina

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    Fernando Pablo Landini

    2011-01-01

    Full Text Available It is undoubtedly true that the logic through which peasants make decisions in the area of production, commercialization, investment and consumption is not the same as that the one used by businessmen, who organize their activities following other rules. Now, despite the importance of properly understanding peasant economic rationality, the papers aimed at this end tend to be disseminated in multiple publications, being difficult to find articles that synthesize its core features.Thus, this paper, after presenting useful concepts such as 'strategies', 'rationalities' and 'worldviews', aims at overcoming this limitation synthesizing different scholars' contributions to the understanding of peasant economic rationality. Finally, with the objective of enriching this paper, I will add some interesting results of a case study conducted in the province of Formosa, Argentina.Resulta indudable que la lógica a partir de la cual los campesinos toman decisiones en el ámbito de la producción, la comercialización, la inversión y el consumo, no se identifica con la que utilizan los empresarios capitalistas, los cuales organizan su actividad según otros parámetros. Ahora bien, no obstante la importancia de contar con una comprensión lo más acabada posible de la racionalidad económica campesina, se observa que los trabajos que contribuyen a este fin tienden a encontrarse dispersos en múltiples publicaciones, siendo difícil encontrar escritos que se ocupen de sintetizar sus aspectos más relevantes. Por esta razón, el presente artículo, luego de desarrollar conceptos de fundamental importancia como 'estrategias', 'racionalidades' y 'cosmovisiones', se propone resolver esta limitación sistematizando las contribuciones realizadas por diferentes autores a la comprensión de la racionalidad económica campesina. Finalmente, con el objetivo de enriquecer los resultados del trabajo, se incorporan una serie de propuestas e ideas fuerza surgidas a partir

  3. Hemodinâmica glomerular renal no roedor Calomys callosus

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    Mirian A. Boim

    1989-03-01

    Full Text Available A função renal do roedor Calomys callosus, envolvido no ciclo de transmissão de diversos agentes patogênicos para o homem foi avaliada no animal intacto, através da técnica de depuração e micropunção renal. Os resultados mostraram que este roedor apresenta níveis pressóricos, hematócrito e proteinas plasmáticas semelhantes aos dos ratos submetidos ao mesmo procedimento experimental. Os pesos corporal e renal, bem como a filtração glomerular global e por nefro assemelham-se aos do camundongo. Surpreendentemente estes roedores apresentaram significante número de glomérulos superficiais por rim, permitindo a avaliação da hemodinàmica glomerular. Apesar da pressão arterial semelhante à dos ratos Munich-Wistar (MW, a pressão hidráulica intraglomerular no Calomys callosus foi inferior. Esta redução foi conseqüente à menor resistência pós-glomerular quando comparada à dos ratos MW. O fluxo plasmático glomerular atingiu valor bastante elevado em relação à filtração glomerular por nefro, fato que não só compensaria a reduzida pressão intraglomerular, como também seria suficiente para elevar a filtração (por g/rim a níveis superiores neste roedor, pois o coeficiente de ultrafiltração glomerular (Kj foi semelhante ao do rato MW. O presente trabalho sugere que apesar das dificuldades técnicas que este animal impõe devido ao seu reduzido tamanho, o estudo da função renal global bem como da hemodinàmica glomerular é factível, podendo portanto ser utilizado como modelo para estudo da função renal em doenças tropicais.

  4. Cerámicas Estampilladas de Salvatierra de Tormes (Salamanca. Contribución al Estudio de las Cerámicas Tardorromanas del Valle del Duero

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    Enrique CERRILLO MARTÍN DE CÁCERES

    2009-10-01

    Full Text Available Dentro del conjunto de yacimientos del Valle del Duero han sido exhaustivamente analizados diversos materiales en bloque (cuchillos, bronces, vidrios, adornos de uso personal, etc. que ponen de manifiesto una indudable unidad cultural de esta zona en un momento determinado, concretamente en los siglos iv y v d. de C. Sin embargo, y a pesar de que el Prof. Palol promete un estudio sobre las cerámicas tardorromanas de estos yacimientos, añadimos a las ya conocidas un lote bastante homogéneo de cerámicas de factura local, pero que a pesar de ello observan unos caracteres muy concretos e interesantes para el estudio de la cerámica del Duero en estos momentos que siempre han quedado vacíos al clasificar cronológicamente los hallazgos, bien de época romana, o bien de época visigoda.

  5. Dinámica económica y migración en el centro de México: impronta territorial de dos procesos convergentes

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    Guillermo Olivera-Lozano

    2013-01-01

    Full Text Available Esta investigación aborda la base económica de municipios y estados del centro del país, y su influencia sobre los flujos migratorios internos. Primero se hace una síntesis de estudios recientes en Latinoamérica y México sobre migración y desarrollo; después se analiza la estructura y dinámica económica por municipio y aglomeraciones metropolitanas, por gran sector económico; posteriormente, se muestran los destinos interregionales de la migración y algunas características de los migrantes, para ilustrar la faceta predominantemente laboral de la migración que otros análisis hacen evidente, y que aquí se reafirma, sin desconocer otros factores. Finalmente se especifican las conclusiones a las que se llegaron con este análisis.

  6. La enseñanza de la química desde la perspectiva de la Química Verde

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    Pía José González García

    2016-06-01

    Full Text Available La Química Verde, como área de investigación, se comprende como el desarrollo de metodologías para modificar los productos o procesos con la finalidad de reducir o eliminar los riesgos que existen para el medio ambiente y la salud. De este modo, permite proyectar líneas de investigación en la construcción de un conocimiento y enfoques didácticos de las ciencias, y  para ser considerada como parte de los programas Ministeriales. El objetivo del estudio fue conocer y comprender el significado que le otorgan los(as docentes del área a la Química Verde como perspectiva para su enseñanza. A partir de los discursos emanados por los docentes participantes del estudio, se construyeron 4 categorías, las cuales son: la Química Verde como: contexto para la enseñanza de la química, medio de apropiación significativo del aprendizaje de la química, motivadora de la conciencia ambiental y reflejo de la Institución y su relación con los docentes. The teaching of chemistry from the Green Chemistry perspective Green Chemistry (GC, as a research area, understood as the development of methodologies to modify products or processes in order to reduce or eliminate the risks posed to the environment and human health. Thus it is allowing research project lines in building knowledge and didactic approaches of the sciences, and to be considered as part of the ministerial programs. The objective of this study was to know and understand the significance given by teachers in the area to GC as a perspective for education. From the speeches issued by teachers participating in the study, four categories, was built. GC as: context for teaching chemistry, through significant learning chemistry appropriation, motivating environmental awareness and reflection of the institution and its relationship with teachers.  O ensino de química, na perspectiva da Química verde A Química verde, como área de investigação, é compreendida como o desenvolvimento de

  7. El Área de Ciencia y Tecnologías Químicas del CSIC: ¿Un Área de químicas?

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    García-López, María Teresa

    2002-08-01

    Full Text Available Not available

    El artículo titulado "El Area de Ciencia y Tecnologías Químicas del CSIC: ¿un Area de químicas?» pretende mostrar una breve panorámica del lugar que ocupa el género femenino dentro de la citada Area. En la primera parte se aportan las estadísticas que reflejan el número y porcentaje de científicas totales en los distintos Institutos del Area, así como su distribución entre las tres escalas de personal científico del Organismo. Una segunda parte está dedicada a recoger las aportaciones personales de varias científicas del Area acerca del tema, visto desde sus propias experiencias.

  8. High performance of macro-flexible piezoelectric energy harvester using a 0.3PIN-0.4Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 flake array

    Science.gov (United States)

    Zeng, Zhou; Xia, Rongyu; Gai, Linlin; Wang, Xian; Lin, Di; Luo, Haosu; Li, Faxin; Wang, Dong

    2016-12-01

    Harvesting energy from human motion to power wearable devices using flexible piezoelectric energy harvesters is becoming a hot research topic, since this approach could fix the charging problem related to batteries and would do no harm to the environment. Unlike nano-generators, which have a piezoelectric material thickness at the level of a few nm to a few μm, we present a high-performance macro-flexible piezoelectric energy harvester (MF-PEH) with a piezoelectric material thickness of 45 μm, based on a 0.3PIN-0.4PMN-0.3PT (PIMNT) long flake array with an optimized cut. The piezoelectric properties of (110)-oriented PIMNT were studied as a function of thickness and compared to those of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNT). The electrical properties of this device under different strain and load resistances are studied systematically. The results of our experiment show that under a strain of 0.225%, the open-circuit voltage and short-circuit current of MF-PEH reach levels as high as 23.2 V and 0.105 mA (at an excitation frequency of 1.1 Hz), respectively, with a maximum electric output power of 245 μW across a piezoelectric materials area of 400 mm2. We have also used the device to harvest mechanical energy from the motion of human knees and charge a battery successfully. Efficient conversion from mechanical energy to electric energy and large output power demonstrate that our MF-PEH is an important complement to flexible energy harvesters and a potential candidate as a self-powered source for wearable low-power electronics.

  9. Comparative feeding value of distillers dried grains plus solubles as a partial replacement for steam-flaked corn in diets for calf-fed Holstein steers: characteristics of digestion, growth performance, and dietary energetics.

    Science.gov (United States)

    Carrasco, R; Arrizon, A A; Plascencia, A; Torrentera, N G; Zinn, R A

    2013-04-01

    Two experiments were conducted to examine the effect of level of dried distillers grains plus solubles (DDGS) supplementation (0, 10, 20, and 30%; DM basis), replacing steam-flaked (SF) corn in finishing diets, on characteristics of digestion (Exp. 1) and growth performance (Exp. 2) in calf-fed Holstein steers. In Exp.1, 4 cannulated Holstein steers (349 ± 12 kg) were used to evaluate treatment effects on characteristics of digestion. Ruminal NDF digestion tended to increase (quadratic effect, P = 0.09) and ruminal OM digestion decreased (linear effect, P = 0.01) with DDGS substitution. There were no treatment effects on duodenal flow of microbial N (MN). Substitution with DDGS increased (linear effect, P growth performance and carcass characteristics. During the initial 126 d, DDGS substitution increased ADG (linear effect, P = 0.03), G:F (quadratic effect, P = 0.03), and dietary NE (quadratic effect, P = 0.02), maximal for both at 20% DDGS inclusion rate. Based on estimated indispensable AA supply to the small intestine as a percentage of requirements during the initial 126-d period, histidine was first limiting followed by methionine. During the final 179-d period and overall (305-d feeding period), treatment effects on ADG and G:F were small (P ≥ 0.22). Compared with the other treatments, HCW was greater (3.4; P = 0.03) at the 20% level of DDGS substitution. The NE value for DDGS in SF corn-based diets for the calf-fed Holstein are consistent with current tabular standards. Extra-caloric value of DDGS as a metabolizable AA source is apparent during the initial growing phase. The UIP value of DDGS used in this study (35%) was considerably less than current tabular estimates (52%; NRC, 2000).

  10. Immobilization of bilirubin oxidase on graphene oxide flakes with different negative charge density for oxygen reduction. The effect of GO charge density on enzyme coverage, electron transfer rate and current density.

    Science.gov (United States)

    Filip, Jaroslav; Andicsová-Eckstein, Anita; Vikartovská, Alica; Tkac, Jan

    2017-03-15

    Previously we showed that an effective bilirubin oxidase (BOD)-based biocathode using graphene oxide (GO) could be prepared in 2 steps: 1. electrostatic adsorption of BOD on GO; 2. electrochemical reduction of the BOD-GO composite to form a BOD-ErGO (electrochemically reduced GO) film on the electrode. In order to identify an optimal charge density of GO for BOD-ErGO composite preparation, several GO fractions differing in an average flake size and ζ-potential were prepared using centrifugation and consequently employed for BOD-ErGO biocathode preparation. A simple way to express surface charge density of these particular GO nanosheets was developed. The values obtained were then correlated with biocatalytic and electrochemical parameters of the prepared biocathodes, i.e. electrocatalytically active BOD surface coverage (Γ), heterogeneous electron transfer rate (kS) and a maximum biocatalytic current density. The highest bioelectrocatalytic current density of (597±25)μAcm(-2) and the highest Γ of (23.6±0.9)pmolcm(-2) were obtained on BOD-GO composite having the same moderate negative charge density, but the highest kS of (79.4±4.6)s(-1) was observed on BOD-GO composite having different negative charge density. This study is a solid foundation for others to consider the influence of a charge density of GO on direct bioelectrochemistry/bioelectrocatalysis of other redox enzymes applicable for construction of biosensors, bioanodes, biocathodes or biofuel cells. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Química recreativa con agua oxigenada

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    Mª Luisa Aguilar Muñoz

    2011-01-01

    Full Text Available Con el objeto de despertar el interés por la química así como de tratar diversos conceptos químicos y biológicos, presentamos la reacción de descomposición catalítica del agua oxigenada (H2O2 en tres experiencias diferentes y con distintos catalizadores. Esta reacción es muy exotérmica, produciendo agua y oxígeno. En la primera experiencia, se mezclan en una probeta la disolución de agua oxigenada y un poco de lavavajillas. Al añadir yoduro de potasio, éste actúa como catalizador y aparece gran cantidad de espuma debido al oxígeno desprendido en la reacción. En la segunda, se utiliza como catalizador un óxido de manganeso finamente dividido, que al dejarlo caer en el recipiente que contiene agua oxigenada, produce un espectacular chorro de vapor de agua. En la última, se produce una llamativa reacción luminiscente entre el peróxido de hidrógeno y el luminol utilizando como catalizador el ión hierro contenido en el hexacianoferrato (III de potasio (ferricianuro de potasio.

  12. Cinética Química: el laboratorio

    Science.gov (United States)

    Cabañas Galán, B.

    La interpretación de las transformaciones químicas que se producen en la atmósfera requiere un profundo conocimiento de la cinética, productos y mecanismos de reacción de las posibles interacciones que pueden ocurrir entre las distintas especies presentes en ella. Información cuantitativa de este tipo es un prerrequisito para la construcción de modelos numéricos adecuados que expliquen el comportamiento químico-físico de la atmósfera. Esta información se obtiene a partir de experimentos realizados en laboratorios y por tanto independiente de medidas atmosféricas, por lo que los modelos atmosféricos derivados de ellos, pueden usarse para diagnosticar y predecir adecuadamente el comportamiento atmosférico. En esta exposición se recogen las técnicas experimentales más extendidas para la obtención de datos cinéticos así como los métodos de análisis de datos más utilizados en el estudio de las distintas reacciones de interés atmosférico. Se analizan sus características generales así como su adecuación a los distintos tipos de reacciones.

  13. Psicodinâmica do adolescente envolvido com drogas

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    Kessler Felix

    2003-01-01

    Full Text Available O uso e o abuso de drogas pelos adolescentes é cada vez mais prevalente e traz desdobramentos sérios nos vários níveis de seu desenvolvimento e na sua família. O presente trabalho aborda as pesquisas no campo epidemiológico sobre fatores de proteção e de risco para o uso de drogas entre os jovens, que demonstram que fracassos tanto pessoais como familiares, além de eventos estressores durante a vida, estão mais associados com o uso de drogas. No entanto, a presença dos pais, a motivação pessoal e o monitoramento do adolescente, estão associados com o não uso. São descritos os principais estudos prospectivos já realizados nessa área. Em seguida, à luz do pensamento de diversos autores como H. Kohut, J. McDougall, H. Rosenfeld, C. Olievenstein, Khantzian, entre outros, apresentam-se teorias psicodinâmicas relacionadas ao problema das adições e sua evolução ao longo dos anos dentro do paradigma psicanalítico. A aplicação das técnicas baseadas nos modelos psicoterápicos de orientação analítica, em dependentes químicos, é também discutida.

  14. Simulaciones hidrodinámicas de flujos complejos

    Science.gov (United States)

    María Ibáñez Cabanell, José

    Son muchos los escenarios astrofísicos en que los procesos hidrodinámicos juegan un papel clave. En la complejidad que encierra la descripción de dichos procesos destaca el de la correcta simulación de flujos complejos donde la presencia de ondas de choque fuertes que, eventualmente, interaccionan entre ellas o también la presencia de inestabilidades (Kelvin-Helmholtz, Rayleigh-Taylor, etc.) suponen un verdadero desafío numérico. Los códigos hidrodinámicos basados en la solución de un problema de valores iniciales discontinuo (problema de Riemann) son, en la actualidad, los más robustos en el campo de la dinámica de fluidos computacional. En esta charla se dará un resumen de los fundamentos de dichas técnicas numéricas (esquemas de alta resolución de captura de choques) y se ilustrará su potencialidad mostrando una amplia gama de resultados en diferentes aplicaciones astrofísicas.

  15. DINÂMICA DAS QUEIMADAS NA BAIXADA MARANHENSE

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    Celso Henrique Leite Silva Junior

    2016-08-01

    Incendios se producen de forma natural y por la influencia humana, pueden tener sus impactos negativos maximizan los efectos del cambio climático. En el Maranhão, debido a sus características históricas de uso y ocupación del suelo y su amplio territorio, hay un predominio de las actividades agrícolas con el uso predominante del sistema de “tala” y “quema”. En este contexto, el presente estudio tuvo como objetivo evaluar la dinámica de los incendios en el Baixada Maranhense, lugar de potencial social y ambiental complejo y que es vulnerable al fuego. Los datos utilizados son intervalo de tiempo desde 2000 hasta 2013, y se utilizan los siguientes datos: base de datos de incendios del Instituto Nacional de Investigaciones Espaciales (INPE, datos de precipitación de la Tropical Rainfall Measuring Mission (TRMM y datos de altimetría de la Banco de Dados Geomorfométricos del Brasil (TOPODATA. Los resultados muestran un patrón espacial, donde los incendios ocurren en períodos de lluvias más bajo, y en áreas con alta influencia humana. Otro factor importante observado fue la altimetría, para lugares expuestos a las inundaciones más bajo y, eran menos susceptibles a la quema. Palabras clave: Llanuras Inundadas; Sequías; Cambio de Uso y Cobertura de la Tierra.

  16. Dinámica de planetas extrasolares resonantes

    Science.gov (United States)

    Beauge, C.

    Actualmente se han detectado 117 planetas alrededor de estrellas de Secuencia Principal, incluyendo 12 sistemas planetarios, cada uno con dos o tres miembros. De estos últimos, ocho poseen planetas en órbitas próximas y sus perturbaciones gravitacionales se convierten en un factor fundamental para la estabilidad orbital del sistema. Todos se encuentran en configuraciones resonantes, desde la conmensurabilidad de movimientos 2/1 de Gliese 876, hasta la resonancia secular de Ups And. En esta presentación analizamos varios aspectos de la dinámica resonante de los planetas extrasolares, incluyendo la existencia de soluciones de equilibrio, construcción de modelos analógicos y métodos para la determinación de masas individuales. También discutimos por qué las resonancias son tan frecuentes en estos sistemas, comparado con nuestro propio Sistema Solar. Por último, intentamos relacionar estos modelos con la hipótesis de migración planetaria, buscando límites en su extensión y en los posibles mecanismos que le dieron origen.

  17. Redes económicas y desigualdades sociales

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    MARIANO FERNÁNDEZ ENGUITA

    1993-01-01

    Full Text Available Se propone un marco general para la interpretación de las desigualdades sociales según el cual éstas, o las más relevantes de éstas, se configuran en torno a redes económicas de carácter inclusivo (hogares y estados o voluntario (organizaciones y mercados. Organizaciones y mercados movilizan los medios de producción, la fuerza de trabajo y la ciencia y la técnica, y el control diferencial sobre estos factores toma respectivamente la forma de propiedad, autoridad y cualificación. Hogares y estados son el origen de las diferencias genéricas y generacionales, los primeros, y comunitarias y étnicas, los segundos. En la economía abierta, formada por organizaciones y mercados, la propiedad, la autoridad y la cualificación sirven de base a relaciones de explotación (transferencia de excedente y dividen a la sociedad en clases, mientras que el género, la generación y la etnia sirven de base a relaciones de privilegio (oportunidades desiguales y la dividen en categorías.

  18. Dinámicas de la violencia guerrillera en Colombia

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    Jerónimo Ríos Sierra

    2016-01-01

    Full Text Available El propósito de este artículo es analizar las dinámicas de la violencia directa derivada de los dos principales grupos guerrilleros que alimentan el conflicto armado interno colombiano, las Fuerzas Armadas Revolucionarias de Colombia (FARC y el Ejército de Liberación Nacional (ELN. Se utiliza un diseño cuantitativo, de carácter descriptivo y explicativo, donde, de acuerdo a una lógica deductiva, se compara la información disponible del año 2015 con la información del año 2012 y anteriores. Se recurre a las bases de datos que fueron facilitadas por el Observatorio de Derechos Humanos y Derecho Internacional Humanitario (ODHDIH, s.f., adscrito a la Presidencia de la República, y por la Oficina de Naciones Unidas contra la Droga y el Delito, conocida por sus siglas en inglés (UNODC, 2016. Se muestra cómo la tendencia que explica el activismo armado de las guerrillas colombianas responde a un doble proceso de periferialización y narcotización. Una doble tendencia que puede definir los paradigmas a los que deberá enfrentar la política de seguridad colombiana en el marco transformador que representan tanto los acuerdos de paz con las FARC como las negociaciones exploratorias con el ELN.

  19. Peptides@mica: from affinity to adhesion mechanism.

    Science.gov (United States)

    Gladytz, A; John, T; Gladytz, T; Hassert, R; Pagel, M; Risselada, H J; Naumov, S; Beck-Sickinger, A G; Abel, B

    2016-09-14

    Investigating the adsorption of peptides on inorganic surfaces, on the molecular level, is fundamental for medicinal and analytical applications. Peptides can be potent as linkers between surfaces and living cells in biochips or in implantation medicine. Here, we studied the adsorption process of the positively charged pentapeptide RTHRK, a recently identified binding sequence for surface oxidized silicon, and novel analogues thereof to negatively charged mica surfaces. Homogeneous formation of monolayers in the nano- and low micromolar peptide concentration range was observed. We propose an alternative and efficient method to both quantify binding affinity and follow adhesion behavior. This method makes use of the thermodynamic relationship between surface coverage, measured by atomic force microscopy (AFM), and the concomitant free energy of adhesion. A knowledge-based fit to the autocorrelation of the AFM images was used to correct for a biased surface coverage introduced by the finite lateral resolution of the AFM. Binding affinities and mechanisms were further explored by large scale molecular dynamics (MD) simulations. The combination of well validated MD simulations with topological data from AFM revealed a better understanding of peptide adsorption processes on the atomistic scale. We demonstrate that binding affinity is strongly determined by a peptide's ability to form salt bridges and hydrogen bonds with the surface lattice. Consequently, differences in hydrogen bond formation lead to substantial differences in binding affinity despite conservation of the peptide's overall charge. Further, MD simulations give access to relative changes in binding energy of peptide variations in comparison to a lead compound.

  20. Amiloidosis sistémica y linfoma no Hodgkin

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    Daniel V. Drake Sosa

    2014-08-01

    Full Text Available La amiloidosis sistémica se caracteriza por el depósito extracelular de proteína amiloide en uno o más órganos. Se presenta el caso de un hombre de 62 años de edad, con antecedentes de lesiones papulosas, amarillentas y brillantes, fundamentalmente en el tronco y las extremidades; con formación de placas profundas y dolorosas de más de un año de evolución, así como lesiones papulosas purpúricas en el abdomen y muslos. El paciente también refirió dolores abdominales y articulares. Los exámenes complementarios demostraron anemia, una eritrosedimentación acelerada, eosinofilia y trastornos de la función hepática. El ultrasonido abdominal informó hepatomegalia, mientras que el medulograma reveló una médula ósea infiltrada por linfocitos pequeños, con depresión del sistema eritropoyético y ligero aumento de mielocitos eosinófilos del sistema granulopoyético, sugestivos de un Linfoma No Hodgking. La biopsia cutánea demostró el depósito de sustancia amiloide en la dermis superior y en las paredes vasculares. El paciente fue tratado con prednisona y ciclofosfamida, obteniéndose una mejoría de su cuadro clínico