TRU decontamination of high-level Purex waste by solvent extraction using a mixed octyl(phenyl)-N,N-diisobutyl-carbamoylmethylphosphine oxide/TBP/NPH (TRUEX) solvent

International Nuclear Information System (INIS)

Horwitz, E.P.; Kalina, D.G.; Diamond, H.; Kaplan, L.; Vandegrift, G.F.; Leonard, R.A.; Steindler, M.J.; Schulz, W.W.

1984-01-01

The TRUEX (transuranium extraction) process was tested on a simulated high-level dissolved sludge waste (DSW). A batch counter-current extraction mode was used for seven extraction and three scrub stages. One additional extraction stage and two scrub stages and all strip stages were performed by batch extraction. The TRUEX solvent consisted of 0.20 M octyl(phenyl)-N,N-diisobutylcarbamoyl-methylphosphine oxide-1.4 M TBP in Conoco (C 12 -C 14 ). The feed solution was 1.0 M in HNO 3 , 0.3 M in H 2 C 2 O 4 and contained mixed (stable) fission products, U, Np, Pu, and Am, and a number of inert constituents, e.g., Fe and Al. The test showed that the process is capable of reducing the TRU concentration in the DSW by a factor of 4 x 10 4 (to <100 nCi/g of disposed form) and reducing the quantity of TRU waste by two orders of magnitude

Preparation of mesoporous MnO2/C catalyst for n-hexyl acetate synthesis

International Nuclear Information System (INIS)

Yang Zeheng; Pan Yanmei; Mei Zhousheng; Zhang Weixin

2012-01-01

A mesoporous MnO 2 /C composite was prepared by impregnating self-made porous carbon spheres with manganese nitrate aqueous solution and subsequently reacting with KMnO 4 aqueous solution. It was characterized with X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), the Brunauer-Emmett-Teller (BET) surface area and the Barrett-Joyner-Halenda (BJH) pore size distribution. The as-prepared mesoporous MnO 2 /C composite was used as catalyst for the synthesis of n-hexyl acetate, and the effects of MnO 2 loading and esterification reaction parameters on the esterification rate were investigated. The results prove that MnO 2 loading has a significant effect on the catalytic activity and that the mesoporous MnO 2 /C composite exhibits high catalytic activity with an esterification rate of 96.42% under the conditions below: MnO 2 loading (73.09 wt%), catalyst dosage (0.1% in total weight), acetic acid/n-hexanol molar ratio (2:1), reaction temperature (130 °C) and reaction time (5 h).

Thermal degradation of biocidal organic N-halamines and N-halamine polymers

Energy Technology Data Exchange (ETDEWEB)

Chylińska, Marta; Kaczmarek, Halina, E-mail: halina@chem.umk.pl

2014-05-01

Highlights: • Novel biocidal N-halamines have been substituted to poly(p-methyl styrene). • Thermal stability of all obtained compounds has been studied by thermogravimetry. • Stabilization of selected polymer has been achieved using octyl tin mercaptide. • The mechanism of thermal degradation of N-halamine polymers has been proposed. - Abstract: Novel biocidal organic N-halamines (based on imidazoline dione rings) were used as a substituents for poly(p-methyl styrene). The biocidal polymers and substituents have been investigated using thermogravimetric analysis. The thermal resistance of investigated compounds was compared to those of non-halogenated precursors. The introduction of chlorine atoms to polymers decreases their thermal resistance comparing to precursors but efficient stabilization is possible by using octyl tin mercaptide. The complex mechanism of thermal decomposition of polymers has been discussed.

Extraction of U(VI) with unsymmetrical N-methyl-N-octyl alkylamides in toluene

International Nuclear Information System (INIS)

Sun Guoxin; Li Yexin; Zhang Zhenwei; Cui Yu; Shandong University, Jinan; Sun Sixiu

2005-01-01

Extraction of U(VI) with three new unsymmetrical monoamides, N-methyl-N-octyloctylamide (MOOA), N-methyl-N-octyldecanamide (MODA), and N-methyl-N-octyldodecanamide (MODOA), from nitric acid solution employing toluene as diluent is discussed. The effects of nitric acid, sodium nitrate and extractant concentrations and also the temperature on the distribution ratio have been investigated. The extracted species were studied by IR spectrometry. (author)

Radiation effects on n-hexane-urea inclusion compound

International Nuclear Information System (INIS)

Ohta, Nobuaki; Ozasa, Senichi; Ichikawa, Takahisa

1987-01-01

n-hexane-urea inclusion compounds were γ-irradiated at room temperature and dimers from n-hexane were found to form. Additive effects of 1-hexene, 1-chloropentane, and n-hexylamine to the formation of the dimers have been studied. For the comparison liquid n-hexane systems were also γ-irradiated under the same conditions. The radiation-induced reactions in the inclusion compounds are discussed together with the reactions in the liquid n-hexane systems. The dimers from n-hexane in the inclusion compounds are presumably formed by dimerization of hexyl radicals; the hexyl radicals are possibly produced by hydrogen abstraction of hydrogen atom and/or urea radicals from n-hexane included in urea. (author)

Solvation of ionic liquids based on N-alkyl-N-methylmorpholinium cations in N,N-dimethylformamide and dimethyl sulfoxide – A volumetric and acoustic study

International Nuclear Information System (INIS)

Marcinkowski, Łukasz; Szepiński, Emil; Kloskowski, Adam; Namieśnik, Jacek; Warmińska, Dorota

2017-01-01

Highlights: • V ϕ of DMSO and DMF solutions of [Mor1,R][BF 4 ] increase with increasing IL concentration at all investigated temperatures. • Ion–ion interaction are stronger for DMF solutions than corresponding for DMSO. • DMSO interacts more effectively with ionic liquids studied than DMF. • Obtained results are the consequence of the cation size of the ionic liquid. - Abstract: Apparent molar volumes and molar isentropic compressibilities for N-ethyl-N-methylmorpholinium and N-decyl-N-methylmorpholinium tetrafluoroborates in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) have been determined from density and speed of sound measurements over the temperature range T = (298.15, 303.15, 308.15, 313.15, 318.15 and 328.15) K at experimental pressure p = 0.1 MPa. This data has been used to calculate partial molar volumes and partial molar isentropic compressibilities at infinite dilution. The partial molar expansion coefficients and their secondary derivative have been estimated as well. The obtained results indicate that dimethyl sulfoxide interacts more effectively with ionic liquids studied than N,N-dimetylformamide and ion–ion interaction are stronger for N,N-dimetylformamide solutions than corresponding in dimethyl sulfoxide. Moreover the temperature dependence of the limiting apparent molar volumes and compressibilities is a result of temperature influence on the electrostriction effect, the ordering of a bulk solvent and number solvent molecules in the nearest presence of the salt.

Identification of ftalates used as additives in the geo membrane of a la Florida reservoir through gas chromatography-mass spectrometry

International Nuclear Information System (INIS)

Blanco, M.; Rico, G.; Pargada, L.; Aguiar, E.; Castillo, F.

2009-01-01

This article studies the behaviour of the plastified poly (vinyl chloride) (PVC-P) applied as synthetic geo membrane for the waterproofing of the La Florida reservoir. We show the results of the initial examen of its properties and its most significant characteristics eighteen years after being applied. Furthermore we isolate and identify the quantitative and qualitative aspects of the plasticizers used in its formula through infrared spectroscopy, gas chromatography and mass spectrometry technic. We have identified as the said plasticizers di-n-octyl phthalate, di-n-decyl phthalate and n-decyl n-octyl phthalate, and we calculate the joint average molecular weight using Wilsons equation. The results found that the geo membranes we have studied has shown an excellent behaviour along through time. (Author) 53 refs

N,N-Dihexyl-4-[2-(4-nitrophenylvinyl]aniline

Directory of Open Access Journals (Sweden)

Dieter Schollmeyer

2011-06-01

Full Text Available The title compound, C26H36N2O2, was prepared by Horner olefination of p-dihexylaminobenzaldehyde and diethyl p-nitrobenzylphosphonate. It crystallizes with two independent molecules in the asymmetric unit. Both have similar geometries of the π-systems but the conformations of all hexyl chains are different. Whereas one hexyl chain of the first molecule shows the typical all-anti conformation, the second is arranged in a gauche-anti-gauche-anti conformation with N—C—C—C, C—C—C—C, C—C—C—C and C—C—C—C torsion angles of −65.1 (4, 167.3 (3, 63.3 (4, and 179.4 (3°. One of the hexyl chains in the other molecule has an anti-anti-gauche-anti conformation [N—C—C—C, C—C—C—C, C—C—C—C and C—C—C—C torsion angles = 179.6 (3, −179.8 (3, −68.7 (5 and −178.8 (4°], the other starts with an anti-gauche-gauche sequence. Molecules A and B are composed of five planar subunits. The angle sums around the N atoms are in the range 356 (2–360.0 (2°. Torsion angles between these segments do not exceed 4.9 (4°, except for one of the alkyl chains each [molecule A = 26.2 (4°; molecule B = −6.0 (4°]. The high planarity of the molecules and the short aniline C—N bonds [1.385 (3 Å in molecule A and 1.378 (3 Å in molecule B] indicate a strong electronic coupling through the stilbene unit. One methylene group is disordered over two positions with an occupancy ratio of 0.72:0.28.

Volumetric and surface properties of pure ionic liquid n-octyl-pyridinium nitrate and its binary mixture with alcohol

International Nuclear Information System (INIS)

Jiang Haichao; Wang Jianying; Zhao Fengyun; Qi Guodi; Hu Yongqi

2012-01-01

Highlights: ► Density and surface tension of [Ocpy][NO 3 ] were measured. ► Thermal expansion coefficient, molecular volume, and standard entropies were obtained. ► The critical temperature and enthalpy of vaporization were discussed. ► Density and surface tension were measured for (ionic liquid + alcohols) mixtures. ► Excess molar volumes and surface tension deviations were fitted to Redlich–Kister equation. - Abstract: The density and surface tension for pure ionic liquid N-octyl-pyridinium nitrate were measured from (293.15 to 328.15) K. The coefficient of thermal expansion, molecular volume, standard entropies, and lattice energy were calculated from the experimental density values. The critical temperature, surface entropy, surface enthalpy, and enthalpy of vaporization were also studied from the experimental surface tension results. Density and surface tension were also determined for binary mixtures of (N-octyl-pyridinium nitrate + alcohol) (methanol, ethanol, and 1-butanol) systems over the whole composition range at 298.15 K and atmospheric pressure. Excess molar volumes and surface tension deviations for the binary systems have been calculated and were fitted to a Redlich–Kister equation to determine the fitting parameters and the root mean square deviations. The partial molar volume, excess partial molar volume, and apparent molar volume of the component IL and alcohol in the binary mixtures were also discussed.

Crystal structure of bis[μ-S-hexyl 3-(2-oxidobenzylidenedithiocarbazato-κ4O,N3,S:O]dicopper(II

Directory of Open Access Journals (Sweden)

M. S. Begum

2015-12-01

Full Text Available The title compound, [Cu2(C14H18N2OS22], is a binuclear copper(II complex of an oxybenzylidenedithiocarbazate ligand. The ligand coordinates in a tridentate manner through N-, S- and O-donor atoms. Each O atom also bridges to a second CuII ion to form the binuclear species. It has a central Cu2O2 rhomboid moiety and a metal-to-metal separation of 2.9923 (6 Å. In the crystal, the binuclear complexes stack along the a axis with all the hexyl chains located side-by-side, forming a hydrophobic region. The complexes are linked via C—H...N hydrogen bonds, forming chains along the c-axis direction. One CuII atom has the S atom of a symmetry-related complex located approximately in the apical position at 2.9740 (11 Å. This weak interaction links the chains to form slabs parallel to the ac plane.

Atom transfer radical polymerization of n-butyl acrylate catalyzed by atom transfer radical polymerization of n-butyl acrylate catalyzed by

NARCIS (Netherlands)

Zhang, H.; Linde, van der R.

2002-01-01

The homogeneous atom transfer radical polymerization (ATRP) of n-butyl acrylate with CuBr/N-(n-hexyl)-2-pyridylmethanimine as a catalyst and ethyl 2-bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different

Structure-property relationships for n-alkyl-isocyanate-containing polymers

Science.gov (United States)

Aronson, Carl Lawrence

Poly(n-hexyl isocyanate) (PHIC), poly(n-butyl-isocyanate) (PBIC), poly(n-butyl-co-cyclohexyl isocyanate) (PBCHIC), poly(n-hexyl isocyanate-b-isoprene) (HI), poly(n-butyl isocyanate-b-isoprene) (BI) and poly(n-hexyl isocyanate-b-isoprene- b-styrene) (MS) were synthesized and characterized with respect to composition, molecular Weight and polydispersity. PHIC, HI and HIS were found to be lyotropic liquid crystalline whereas PBIC, PBCHIC and BI were found to be non-lyotropic. A lyotropic-nematic liquid crystalline phase diagram was determined for the PHIC/xylene system. A novel and reversible electric-field-induced biphasic-paranematic phase transition was found for the PHIC/xylene system from the dynamics of topological defects. The electric-field-induced phase diagram for PHIC/xylene agreed with the theoretically predicted field-induced phase diagram of Khokhlov and Semenov for semiflexible-persistent polymers. The dielectric characteristics, steady-state electrically induced birefringence and steady-state electroheological (ER) activity of PHIC, PBIC and PBCHIC solutions were compared as a function of polymer concentration. The role of lyotropic liquid crystalline ordering in the functional ER mechanism of poly( n-hexyl isocyanate) solutions is presented. PBCHIC was found to thermally decompose by a first-order rate process which became slower with increasing cyclohexyl isocyanate content from thermal gravimetric analysis. Competition between monomer dissociation and degradative trimerization as well as a non-alternating sequence distribution were determined for PBCHIC from direct pyrolysis/mass spectrometry. The Arrhenius activation energy, pre-exponential factor and entropy for diffusion and evaporation of xylene from PHIC, were found to be functions of initial polymer concentration whereas the intrinsic diffusion coefficient of the solvent was found to be independent of initial polymer concentration. The cross polarized/magic angle spinning solid state 13C

Study of extraction kinetics of lanthanides(III) and actinides(III) nitrates by the molecule N, N'-dimethyl-N, N'-dibutyl, tetradecylmalonamide

International Nuclear Information System (INIS)

Daldon, M.

1999-01-01

The kinetics of extraction of lanthanides (III) and actinides (III) nitrates by the molecule N, N'-dimethyl - N, N'-dibutyl tetra-decyl malonamide has been investigated. This study was realised with a new constant interfacial-area-stirred cell. During the qualification step of the device it appears that the reduction of the device can lead to hydrolytic perturbations. The main conclusions are: - after the determination of conditions which provide kinetics regime (diffusion of species neglectable), partial orders of the kinetics law have been obtained and lead to the establishment of the law J = k [Nd 3+ ] [NO 3 - ] 3 [diamide] 1 , - interfacial tension measurements and kinetics study in presence of surface-active compounds proved that the chemical limiting reaction for Nd(III) is interfacial, - the results allow to propose an adsorption-desorption reaction mechanism, - a comprehensive study of the extraction kinetics of the lanthanides(III) series and also Am(III) and Cm(III) nitrates has been realised. The lighter lanthanides (La, Ce and Pr) exhibit higher kinetics rate of extraction than the others, which differs from the tendency observed with distribution coefficients which exhibit tetrad effect. The kinetics rate of extraction of Am(III) and Cm(III) is closed to the value of Eu(III). (author)

Ortho-substituent correlated retention of polychlorinated biphenyls on a 50% n-octyl-methylpolysiloxane stationary phase by HRGC/MSD

Energy Technology Data Exchange (ETDEWEB)

Fischer, R.; Ballschmiter, K.

1988-11-01

Polychlorinated biphenyls (PCB) have been known as ubiquitous environmental pollutants since the late 60s. They are found partitioned between all environmental compartments according to their physico-chemical properties. Investigation of their partitioning, degradation, and transport behaviour demands sensitive and selective analytical methods for this complex mixture of up to 209 theoretically possible compounds. Congener-specific separation by high-resolution gas chromatography coupled with mass-selective detection would be a suitable approach to this multi-compound problem. In this paper, the separation of PCB congeners by capillary gas chromatography (HRGC) on a 50% n-octyl-methylpolysiloxane phase is presented.

Efficiency of n-octyl-acetate, 2-heptanone and citronellal in repelling bees from basil (Ocimum sellowii - Labiatae

Directory of Open Access Journals (Sweden)

Darclet Teresinha Malerbo-Souza

2004-03-01

Full Text Available The objective of this study was to test repellent substances for honey bees, Apis mellifera, for basil, Ocimum sellowii, and to study the most frequent insects in this crop as well as its behaviors. The frequency of honey bees did not decrease with the application of n.octyl.acetate, citronellal and 2.heptanone, used as repellents, in the concentrations 2.5, 5.0, 7.5 and 10.0% diluted in water. However, when the products (20% were diluted in water (75% and glycerine (5% were effective in repelling those bees of the basil flowers for a period of 20 minutes. The flower lasted, on average, 30 h from the bud phase until the flower withered. The flowers number opened by inflorescence was, on average, 5.65 flowers, and the inflorescence presented, on average, 160 flowers-buds. The basil was visited mainly for the honey bee (98.0%, followed by Augochloropsis electra bee - Halictidae (2.0% and visits sporadics of Diptera and Lepidoptera, collected only nectar. The honey bee frequency increased during the day to 14:00, decreasing soon after, accompanying the curve of the temperature sets registered in the experiment days.O objetivo do experimento foi estudar a polinização em manjericão (Ocimum sellowii, a fim de verificar sua atratividade para as abelhas Apis mellifera, os insetos mais freqüentes, bem como seus comportamentos e testar substâncias repelentes para as abelhas A. mellifera. A flor durou, em média, 30 horas, desde sua abertura até o murchamento. O número de flores abertas por inflorescência foi, em média, 5,65 flores, sendo que a inflorescência possuía, em média, 160 botões florais. O manjericão foi visitado quase que exclusivamente pela abelha A. mellifera africanizada (98,0%, seguida pela abelha Augochloropsis electra-Halictidae (2,0% e visitas esporádicas de dípteros e lepidópteros, sendo que todos coletavam apenas néctar. A freqüência da abelha africanizada aumentou no decorrer do dia até às 14 horas, diminuindo em

Study of extraction kinetics of lanthanides(III) and actinides(III) nitrates by the molecule N, N'-dimethyl-N, N'-dibutyl, tetradecylmalonamide; Etude des cinetiques d'extraction des nitrates de lanthanides (III) et d'actinides (III) par le malonamide N, N'-dimethyl-N, N'-dibutyl, tetradecylmalonamide

Energy Technology Data Exchange (ETDEWEB)

Daldon, M

1999-07-01

The kinetics of extraction of lanthanides (III) and actinides (III) nitrates by the molecule N, N'-dimethyl - N, N'-dibutyl tetra-decyl malonamide has been investigated. This study was realised with a new constant interfacial-area-stirred cell. During the qualification step of the device it appears that the reduction of the device can lead to hydrolytic perturbations. The main conclusions are: - after the determination of conditions which provide kinetics regime (diffusion of species neglectable), partial orders of the kinetics law have been obtained and lead to the establishment of the law J = k [Nd{sup 3+}] [NO{sub 3}{sup -}]{sup 3} [diamide]{sup 1}, - interfacial tension measurements and kinetics study in presence of surface-active compounds proved that the chemical limiting reaction for Nd(III) is interfacial, - the results allow to propose an adsorption-desorption reaction mechanism, - a comprehensive study of the extraction kinetics of the lanthanides(III) series and also Am(III) and Cm(III) nitrates has been realised. The lighter lanthanides (La, Ce and Pr) exhibit higher kinetics rate of extraction than the others, which differs from the tendency observed with distribution coefficients which exhibit tetrad effect. The kinetics rate of extraction of Am(III) and Cm(III) is closed to the value of Eu(III). (author)

Enhanced gas absorption in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) confined in silica slit pores: a molecular simulation study.

Science.gov (United States)

Shi, Wei; Luebke, David R

2013-05-07

Two-dimensional NPxyT and isostress-osmotic (N2PxyTf1) Monte Carlo simulations were used to compute the density and gas absorption properties of the ionic liquid (IL) 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) confined in silica slit pores (25-45 Å). Self-diffusivity values for both gas and IL were calculated from NVE molecular dynamics simulations using both smooth and atomistic potential models for silica. The simulations showed that the molar volume of [hmim][Tf2N] confined in 25-45-Å silica slit pores is 12-31% larger than that of the bulk IL at 313-573 K and 1 bar. The amounts of CO2, H2, and N2 absorbed in the confined IL are 1.1-3 times larger than those in the bulk IL because of the larger molar volume of the confined IL compared to the bulk IL. The CO2, N2, and H2 molecules are generally absorbed close to the silica wall where the IL density is very low. This arrangement causes the self-diffusivities of these gases in the confined IL to be 2-8 times larger than those in the bulk IL at 298-573 K. The solubilities of water in the confined and bulk ILs are similar, which is likely due to strong water interactions with [hmim][Tf2N] through hydrogen bonding, so that the molar volume of the confined IL plays a less important role in determining the H2O solubility. Water molecules are largely absorbed in the IL-rich region rather than close to the silica wall. The self-diffusivities of water correlate with those of the confined IL. The confined IL exhibits self-diffusivities larger than those of the bulk IL at lower temperatures, but smaller than those of the bulk IL at higher temperatures. The findings from our simulations are consistent with available experimental data for similar confined IL systems.

A contribution to the study of the extraction of mineral acids and of actinide (IV) and (VI) cations by N,N-dialkylamides

International Nuclear Information System (INIS)

Condamines, N.

1990-03-01

N,N-dialkylamides are alternate extractants to tributylphosphate, TBP, for the actinides separation in nuclear fuel reprocessing. N,N-di (2-ethyl hexyl) butyramide and N,N-di (2 ethyl hexyl) isobutyramide are selected for their sufficient extraction and partition ability towards actinides (IV) and (VI) without coextracting fission products. Mechanisms of HNO 3 , UO 2 2+ , Pu 4+ , Th 4+ are investigated. Nitric acid extraction is due to the competitive formation of the species (HNO 3 )L 2 , (HNO 3 )L, (HNO 3 ) 2 L (L: DOBA or DOiBA). An hydrogen bond is the driving force of the transfer. For low acidity media, amides are neutral extractants. Physical interactions, between free ligand and metallic complex, arise for high amide concentrations. Taking into account the non-ideality of the organic medium by a hard spheres mixture model, we estimate that such interactions are far from negligible and very specific to the amide group. Unlike TBP, when increasing acidity, amides behave as anionic extractants. DOBA and DOiBA appear to be satisfactory extractants for fuel reprocessing [fr

Resolution of D- and L-glucoses by chiral N-octyl-beta-D-glycoside-Cu(II) complex adsorbed at the gas/liquid interface of small bubbles

NARCIS (Netherlands)

Sakai, M.; Miyazawa, K.; Jitsumatsu, H.; Kamio, K.; Mitsuiki, S.; Toh, N.; Sugihara, G.; Norde, W.

2010-01-01

A new technique of the jet drop method (JDM) was applied to a chiral molecular discrimination of optically active D- or L-glucose (guest) by chiral N-octyl-beta-D-glycoside (O beta DG)-Cu(II) complex (host) at the gas/liquid interface of small bubbles. The discrimination of glucoses as the guests is

21 CFR 178.3480 - Fatty alcohols, synthetic.

Science.gov (United States)

2010-04-01

... derived lauryl alcohol permitted as an intermediate in the synthesis of sodium lauryl sulfate used in..._locations.html. (1) Synthetic fatty alcohols. (i) Hexyl, octyl, decyl, lauryl, myristyl, cetyl, and stearyl... they may contain not more than 0.8 weight percent total diols. (ii) Lauryl, myristyl, cetyl, and...

A contribution to the study of the extraction of mineral acids and of actinide (IV) and (VI) cations by N,N-dialkylamides; Contribution a l'etude de l'extraction d'acides mineraux et de cations actinides aux degres d'oxydation (IV) et (VI) par des N,N-dialkylamides

Energy Technology Data Exchange (ETDEWEB)

Condamines, N

1990-03-15

N,N-dialkylamides are alternate extractants to tributylphosphate, TBP, for the actinides separation in nuclear fuel reprocessing. N,N-di (2-ethyl hexyl) butyramide and N,N-di (2 ethyl hexyl) isobutyramide are selected for their sufficient extraction and partition ability towards actinides (IV) and (VI) without coextracting fission products. Mechanisms of HNO{sub 3}, UO{sub 2}{sup 2+}, Pu{sup 4+}, Th{sup 4+} are investigated. Nitric acid extraction is due to the competitive formation of the species (HNO{sub 3})L{sub 2}, (HNO{sub 3})L, (HNO{sub 3}){sub 2}L (L: DOBA or DOiBA). An hydrogen bond is the driving force of the transfer. For low acidity media, amides are neutral extractants. Physical interactions, between free ligand and metallic complex, arise for high amide concentrations. Taking into account the non-ideality of the organic medium by a hard spheres mixture model, we estimate that such interactions are far from negligible and very specific to the amide group. Unlike TBP, when increasing acidity, amides behave as anionic extractants. DOBA and DOiBA appear to be satisfactory extractants for fuel reprocessing.

100 keV 10-B+ implantation into poly-(di-n-hexyl silane), (PDHSi)

International Nuclear Information System (INIS)

Fink, D.; Mueller, M.; Behar, M.; Papaleo, R.M.

2006-01-01

100 keV 10 B + ions were implanted into poly-(di-n-hexyl silane) in different directions at a fluence of 1 x 10 14 cm -2 , and their depth distribution was determined by means of the neutron depth profiling technique. In no case were the projectile ions found to come to rest according to their predicted range profiles. Instead, they are always found to undergo considerable long-range migration. During the irradiation process this motion appears to be radiation-enhanced, and during the subsequent annealing steps one appears to deal with regular thermal diffusion. The implant redistribution is always found to be governed strongly by the self-created damage, insofar as both electronic and nuclear defects in the polymer act as trapping centers. Their population ratio is modified by thermal annealing. The as-implanted redistribution shows a pronounced directional dependence, which essentially is a consequence of the spatial distributions of the electronic and nuclear damage. The changes of the nuclear defect distribution during thermal annealing are studied by a specially developed tomographic method. It is found that boron is preferentially trapped along the irradiation direction, exhibiting quite pronounced prolate (i.e. cigar-like) distributions. This shape is almost unaffected by thermal annealing. (orig.)

Syntheses, Protonation Constants and Antimicrobial Activity of 2 ...

African Journals Online (AJOL)

carboxaldehyde and N-alkylimidazole-2-methanol derivatives [alkyl = benzyl, methyl, ethyl, propyl, butyl, heptyl, octyl and decyl] have been synthesized and the protonation constants determined. The antimicrobial properties of the compounds were tested ...

Dynamic adsorption properties of n-alkyl glucopyranosides determine their ability to inhibit cytolysis mediated by acoustic cavitation.

Science.gov (United States)

Sostaric, Joe Z; Miyoshi, Norio; Cheng, Jason Y; Riesz, Peter

2008-10-09

Suspensions of human leukemia (HL-60) cells readily undergo cytolysis when exposed to ultrasound above the acoustic cavitation threshold. However, n-alkyl glucopyranosides (hexyl, heptyl, and octyl) completely inhibit ultrasound-induced (1057 kHz) cytolysis (Sostaric, et al. Free Radical Biol. Med. 2005, 39, 1539-1548). The efficacy of protection from ultrasound-induced cytolysis was determined by the n-alkyl chain length of the glucopyranosides, indicating that protection efficacy depended on adsorption of n-alkyl glucopyranosides to the gas/solution interface of cavitation bubbles and/or the lipid membrane of cells. The current study tests the hypothesis that "sonoprotection" (i.e., protection of cells from ultrasound-induced cytolysis) in vitro depends on the adsorption of glucopyranosides at the gas/solution interface of cavitation bubbles. To test this hypothesis, the effect of ultrasound frequency (from 42 kHz to 1 MHz) on the ability of a homologous series of n-alkyl glucopyranosides to protect cells from ultrasound-induced cytolysis was investigated. It is expected that ultrasound frequency will affect sonoprotection ability since the nature of the cavitation bubble field will change. This will affect the relative importance of the possible mechanisms for ultrasound-induced cytolysis. Additionally, ultrasound frequency will affect the lifetime and rate of change of the surface area of cavitation bubbles, hence the dynamically controlled adsorption of glucopyranosides to their surface. The data support the hypothesis that sonoprotection efficiency depends on the ability of glucopyranosides to adsorb at the gas/solution interface of cavitation bubbles.

Pysico-chemical properties of hydrophobic ionic liquids containing1-octylpyridinium, 1-octyl-2-methylpyridinium or1-octyl-4-methylpyridinium cations

Energy Technology Data Exchange (ETDEWEB)

Papaiconomou, Nicolas; Salminen, Justin; Lee, Jong-Min; Prausnitz, John M.

2006-09-15

This paper reports synthesis of some ionic liquids based on cations 1-octylpyridinium, 1-octyl-2-methylpyridinium or 1-octyl-4-methylpyridinium and anions dicyanamide [N(CN)2]-, bis(trifluoromethylsulfonyl)imide [Tf2N]-, bis(pentafluoroethylsulfonyl)imide [BETI]-, trifluoromethyl sulfonate [TfO]-, nonafluorobutyl sulfonate [NfO]-, tetrafluoroborate [BF4]-, trifluorophenylborate [BF3Ph]- or hexafluoroarsenate [AsF6]-. Melting points, decomposition temperatures, densities, mutual solubilities with water, and viscosities have been measured. Unlike similar ionic liquids containing imidazolium cations, pyridinium ionic liquids studied here are nearly immiscible in water. Viscosities are similar and water content is slightly lower than those for ionic liquids containing imidazolium cations.

Large area, soft crystalline thin films of N,N' ,N'' -trialkyltriazatriangulenium salts with homeotropic alignment of the discotic cores in a lamellar lattice

DEFF Research Database (Denmark)

Just Sørensen, Thomas; Hildebrandt, Christoffer B.; Elm, Jonas

2012-01-01

techniques confirm that the 15–30 nm thick films maintain the lamellar structure of the bulk crystals, are flat on macroscopic length scales, and are completely ordered relative to the substrate. The triazatriangulenium molecules are electroactive dyes, and in the highly anisotropic polycrystalline thin film......N,N' ,N'' -Trialkyltriazatriangulenium (R-TATA+) tetrafluoroborate (BF4) salts form highly ordered thin films directly when spin-cast onto rotating substrates. The homogeneous and crystalline thin films show macroscopic order over centimetres. The crystal structures of the R-TATA$BF4 salts...... are investigated and compared for the propyl, 3-methylpentyl and octyl derivatives. In all cases the molecules pack in hexagonally ordered bilayers, with segregation of the ionic groups and the alkyl chains. This is a rare packing motif with the rigid discotic TATA+ cores organized co-planarly in sheets separated...

Gold recovery from acidic leach solutions using as extractants trialkylamines of N,N'-di-alkyl-aliphatic amides

Energy Technology Data Exchange (ETDEWEB)

Baroncelli, F.; Carlini, D.; Gasparini, G.M.; Simonetti, E.

1988-07-01

TriOctylAmine (TOA) and a di-substituted aliphatic amide, N,N-Di-N-ButylOctanamide (DBOA), were examined in batch and in mini mixer-settler experiments using leachates of Peruvian and Bolivian concentrates. With these minerals, very rich in sulfur (pyrites, stybine), 90-95% gold recovery in 12-24 hours was reached by leaching with 4M aqua regia (HCl 3M nitric acid 1M) at room temperature and with 1/3 solid/liquid ratio. With these leachate solutions (2-3M total acidity, 10-60 ppm ao Au), the two processes with TOA (GAMEX PROCESS) and with DBOA (AUMIDEX PROCESS) were tested and compared. Experimental results strongly support the possibility of using TOA and DBOA on an industrial scale.

All-Polymer Photovoltaic Devices of Poly(3-(4- n -octyl)-phenylthiophene) from Grignard Metathesis (GRIM) Polymerization

KAUST Repository

Holcombe, Thomas W.

2009-10-14

(Graph Presented) The synthesis of poly[3-(4-n-octyl)-phenylthiophene] (POPT) from Grignard Metathesis (GRIM) is reported. GRIM POPT is found to have favorable electronic, optical, and processing properties for organic photovoltaics (OPVs). Space-charge limited current and field effect transistor measurements for POPT yielded hole mobilities of 1 × 10-4 cm2/(V s) and 0.05 cm2/(V s), respectively. Spincasting GRIM POPT from chlorobenzene yields a thin film with a 1.8 eV band gap, and PC61BM:POPT bulk heterojection devices provide a peak performance of 3.1%. Additionally, an efficiency of 2.0% is achieved in an all-polymer, bilayer OPV using poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-(1-cyanovinylene) phenylene] (CNPPV) as an acceptor. This state-of-the-art all-polymer device is analyzed in comparison to the analogous poly(3-hexylthiophene) (P3HT)/CNPPV device. Counter to expectations based on more favorable energy level alignment, greater active layer light absorption, and similar hole mobility, P3HT/CNPPV devices perform less well than POPT/CNPPV devices with a peak efficiency of 0.93%. © 2009 American Chemical Society.

All-Polymer Photovoltaic Devices of Poly(3-(4- n -octyl)-phenylthiophene) from Grignard Metathesis (GRIM) Polymerization

KAUST Repository

Holcombe, Thomas W.; Woo, Claire H.; Kavulak, David F.J.; Thompson, Barry C.; Fréchet, Jean M. J.

2009-01-01

(Graph Presented) The synthesis of poly[3-(4-n-octyl)-phenylthiophene] (POPT) from Grignard Metathesis (GRIM) is reported. GRIM POPT is found to have favorable electronic, optical, and processing properties for organic photovoltaics (OPVs). Space-charge limited current and field effect transistor measurements for POPT yielded hole mobilities of 1 × 10-4 cm2/(V s) and 0.05 cm2/(V s), respectively. Spincasting GRIM POPT from chlorobenzene yields a thin film with a 1.8 eV band gap, and PC61BM:POPT bulk heterojection devices provide a peak performance of 3.1%. Additionally, an efficiency of 2.0% is achieved in an all-polymer, bilayer OPV using poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-(1-cyanovinylene) phenylene] (CNPPV) as an acceptor. This state-of-the-art all-polymer device is analyzed in comparison to the analogous poly(3-hexylthiophene) (P3HT)/CNPPV device. Counter to expectations based on more favorable energy level alignment, greater active layer light absorption, and similar hole mobility, P3HT/CNPPV devices perform less well than POPT/CNPPV devices with a peak efficiency of 0.93%. © 2009 American Chemical Society.

76 FR 6342 - n-Octyl Alcohol and n-Decyl Alcohol; Exemption From the Requirement of a Tolerance

Science.gov (United States)

2011-02-04

... produce sensitization in guinea pigs. A 90-day dermal toxicity study in rats with fatty alcohol blend (56... pesticide manufacturer. Potentially affected entities may include, but are not limited to: Crop production (NAICS code 111). Animal production (NAICS code 112). Food manufacturing (NAICS code 311). Pesticide...

N-Decyl-S-trityl-(R)-cysteine, a new chiral selector for "green" ligand-exchange chromatography applications.

Science.gov (United States)

Carotti, Andrea; Ianni, Federica; Camaioni, Emidio; Pucciarini, Lucia; Marinozzi, Maura; Sardella, Roccaldo; Natalini, Benedetto

2017-09-10

In search for new enantioselectivity profiles, the N-decyl-S-trityl-(R)-cysteine [C 10 -(R)-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for ligand-exchange chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C 10 -(R)-STC-based CSP, with resolution factor (R S ) values up to 8.86. Conformationally rigid and hydrophobic ligands often experienced the largest enantioselectivity effects. A high loadability emerged from the analysis of rac-NorVal (selected as prototype test compound): up to 20mg/mL were efficiently enantioseparated with the CLEC-CSP. Two in-line hand-made cartridges filled with a strong cation-exchange resin allowed the effective catching of Cu(II) ions after the semi-preparative enantioseparation. The quantitative recovery of the rac-NorVal enantiomers was made possible by flowing through the cartridge a 5% (v) ammonia solution. The CLEC phase proved successful in the enantioselective analysis of a commercially available (S)-Leu containing tablet. Furthermore, in order to understand the molecular basis for a successful use of the C 10 -(R)-STC-based CLEC system, a descriptive structure-separation relationship study was performed. As a result, all compounds with a MEAN-QPlogS (a hydrophilicity descriptor) value lower than 0.373 can be most likely enantioseparated with the CLEC system under investigation. In the work, the numerous aspects complying with the principles of green chromatography are highlighted and discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Solvent extraction of Pu(IV) with TODGA in C6mimTf2N

International Nuclear Information System (INIS)

Xiaohong Huang; Qiuyue Zhang; Jinping Liu; Hui He; Wenbin Zhu; Xiaorong Wang

2013-01-01

Studies on the solvent extraction of Plutonium(Pu(IV)) from aqueous nitric acid by N,N,N'N'tetraoctyl-diglycolamide (TODGA) in 1-hexyl-3-methylimidazolium-bis(trifluoromethylsulfonyl) imide (C 6 mimTf 2 N) room temperature ionic liquid (RTIL) were carried out. It was found that Pu(IV) is extracted into RTIL phase as [Pu(NO 3 )(TODGA)] 3+ through cation exchange mechanism. Extraction reaction equation is obtained by the influence of acidity and extractant concentration, and the parameters of thermodynamic equilibrium constant was calculated. (author)

Monosaccharides as Versatile Units for Water-Soluble Supramolecular Polymers.

Science.gov (United States)

Leenders, Christianus M A; Jansen, Gijs; Frissen, Martijn M M; Lafleur, René P M; Voets, Ilja K; Palmans, Anja R A; Meijer, E W

2016-03-18

We introduce monosaccharides as versatile water-soluble units to compatibilise supramolecular polymers based on the benzene-1,3,5-tricarboxamide (BTA) moiety with water. A library of monosaccharide-based BTAs is evaluated, varying the length of the alkyl chain (hexyl, octyl, decyl and dodecyl) separating the BTA and saccharide units, as well as the saccharide units (α-glucose, β-glucose, α-mannose and α-galactose). In all cases, the monosaccharides impart excellent water compatibility. The length of the alkyl chain is the determining factor to obtain either long, one-dimensional supramolecular polymers (dodecyl spacer), small aggregates (decyl spacer) or molecularly dissolved (octyl and hexyl) BTAs in water. For the BTAs comprising a dodecyl spacer, our results suggest that a cooperative self-assembly process is operative and that the introduction of different monosaccharides does not significantly change the self- assembly behaviour. Finally, we investigate the potential of post-assembly functionalisation of the formed supramolecular polymers by taking advantage of dynamic covalent bond formation between the monosaccharides and benzoxaboroles. We observe that the supramolecular polymers readily react with a fluorescent benzoxaborole derivative permitting imaging of these dynamic complexes by confocal fluorescence microscopy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and application of a macroporous silica-based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide composite for the chromatographic separation of high level liquid waste

International Nuclear Information System (INIS)

Zhang, A.

2006-01-01

The Minor Actinides Recovery from HLW by Extraction Chromatography (MAREC) process was used mainly for the separation of minor actinides (MAs) and some specific fission products (FPs) from highly active liquid waste (HLW) by the composite CMPO/SiO 2 -P of the macroporous silica based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) and others. In this study a cascade of chromatographic separation was performed on a 3.0M HNO 3 solution containing 5.0 x 10 -3 M of 13 elements, at 323 K. The cascade consisted of three columns the first and second ones were packed with CMPO/SiO 2 -P and the third with SiO 2 -P particles. The first column was employed to prepare various eluents containing saturated CMPO. The second column was used for separation into groups. The CMPO of CMPO/SiO2-P was recovered from the effluent by the third column and a CMPO-free effluent containing minor actinides was obtained. The elements contained in the simulated HLW of 3.0M HNO 3 were separated into (1) a non-adsorption group (Sr, Cs, and Ru etc.), (2) a MA-hRE (heavy rare earth)-Mo-Zr group, and (3) a lRE (light rare earth) group by eluting with 3.0M HNO 3 , 0.05M DTPA (diethylenetriaminepentaacetic acid) (pH 2.0) and HNO 3 (pH 3.5), respectively. The resultant MA-hRE-Mo-Zr mixture containing minor actinides was then separated into the groups (1) Pd-Ru, (2) MA-hRE, and (3) Mo-Zr by utilizing 3.0M HNO 3 , distilled water, and 0.05M DTPA (pH 2.0) as eluents. More than 92% of CMPO in the MA-hRE containing effluent was adsorbed by SiO 2 -P particles. The effectivity and technical feasibility of MAREC process were demonstrated. (author)

On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for InGaN/GaN light-emitting diodes.

Science.gov (United States)

Kyaw, Zabu; Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ju, Zhen Gang; Zhang, Xue Liang; Ji, Yun; Hasanov, Namig; Zhu, Binbin; Lu, Shunpeng; Zhang, Yiping; Sun, Xiao Wei; Demir, Hilmi Volkan

2014-01-13

N-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple quantum wells (MQWs) are systematically studied both experimentally and theoretically to increase the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN layer sandwiched in the NPNPN-GaN structure is completely depleted due to the built-in electric field in the NPNPN-GaN junctions, and the ionized acceptors in these P-GaN layers serve as the energy barriers for electrons from the n-GaN region, resulting in a reduced electron over flow and enhanced the current spreading horizontally in the n- GaN region. These lead to increased optical output power and external quantum efficiency (EQE) from the proposed device.

Effect of alkyl chain length on the rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imides.

Science.gov (United States)

Gangamallaiah, V; Dutt, G B

2013-10-10

Rotational diffusion of a nonpolar solute 9-phenylanthracene (9-PA) and a cationic solute rhodamine 110 (R110) has been examined in a series of 1-alkyl-3-methylimidazolium (alkyl = octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl) bis(trifluoromethylsulfonyl)imides to understand the influence of alkyl chain length on solute rotation. In this study, reorientation times (τr) have been measured as a function of viscosity (η) by varying the temperature (T) of the solvents. These results have been analyzed using the Stokes-Einstein-Debye (SED) hydrodynamic theory along with the ones obtained for the same solutes in 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides (Gangamallaiah and Dutt, J. Phys. Chem. B 2012, 116, 12819-12825). It has been noticed that the data for 9-PA and R110 follows the relation τr = A(η/T)(n) with A being the ratio of hydrodynamic volume of the solute to the Boltzmann constant and n = 1 as envisaged by the SED theory. However, upon increasing the alkyl chain length from methyl to octadecyl significant deviations from the SED theory have been observed especially from the octyl derivative onward. From methyl to octadecyl derivatives, the value of A decreases by a factor of 3 for both the solutes and n by a factor of 1.4 and 1.6 for 9-PA and R110, respectively. These observations have been rationalized by taking into consideration the organized structure of the ionic liquids, whose influence appears to be pronounced when the number of carbon atoms in the alkyl chain attached to the imidazolium cation exceeds eight.

Scientific contribution to the HYPAR 07 of the Europart contract

International Nuclear Information System (INIS)

Hill, C.; Meridiano, Y.; Sorel, C.; Berthon-Nigond, L.; Crozes, X.

2007-01-01

In the frame of the DIAMEX process, the self-association properties of the N,N'-dimethyl-N,N'-di-octyl-hexyl-ethoxy-malonamide (DMDOHEMA) were studied in order to establish a direct link between the structures of the extractant molecules in the organic phase and their extracting properties towards Ln(III) and An(III). Malonamides are amphiphilic molecules and diluted in n-alkane diluents, are organized in reverse aggregates with a polar core containing water and the extracted ions. (authors)

Human colon cancer targeted pro-apoptotic, anti-metastatic and cytostatic effects of binuclear Silver(I)-N-Heterocyclic carbene (NHC) complexes.

Science.gov (United States)

Asif, Muhammad; Iqbal, Muhammad Adnan; Hussein, Mouayed A; Oon, Chern Ein; Haque, Rosenani A; Khadeer Ahamed, Mohamed B; Abdul Majid, Aman Shah; Abdul Majid, Amin Malik Shah

2016-01-27

The current mechanistic study was conducted to explore the effects of increased lipophilicity of binuclear silver(I)-NHC complexes on cytotoxicity. Two new silver(I)-N-Heterocyclic Carbene (NHC) complexes (3 and 4), having lypophilic terminal alkyl chains (Octyl and Decyl), were derived from meta-xylyl linked bis-benzimidazolium salts (1 and 2). Each of the synthesized compounds was characterized by microanalysis and spectroscopic techniques. The complexes were tested for their cytotoxicity against a panel of human cancer c as well normal cell lines using MTT assay. Based on MTT assay results, complex 4 was found to be selectively toxic towards human colorectal carcinoma cell line (HCT 116). Complex 4 was further studied in detail to explore the mechanism of cell death and findings of the study revealed that complex 4 has promising pro-apoptotic and anti-metastatic activities against HCT 116 cells. Furthermore, it showed pronounced cytostatic effects in HCT 116 multicellular spheroid model. Hence, binuclear silver(I)-NHC complexes with longer terminal aliphatic chains have worth to be further studied against human colon cancer for the purpose of drug development. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

One-pot Synthesis of Substituted Pyrroles with N,N,N',N'

African Journals Online (AJOL)

In this research, N,N,N'N'-tetrachlorobenzene-1,3-disulphonamide as novel catalytic reagent and N,N'-diiodo-N,N'-1,2-ethanediylbis(p-toluenesulphonamide) as new catalyst were used for the synthesis of N-substituted pyrroles in good to excellent yields under mild conditions. These reusable reagents were compared with ...

Iron halide mediated atom transfer radical polymerization of methyl methacrylate with N-Alkyl-2-pyridylmethanimine as the ligand

NARCIS (Netherlands)

Zhang, H.; Schubert, U.S.

2004-01-01

The controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) catalyzed by iron halide/N-(n-hexyl)-2-pyridylmethanimine (NHPMI) is described. The ethyl 2-bromoisobutyrate (EBIB)-initiated ATRP with [MMA]0/[EBIB]0/[iron halide]0/[NHPMI]0 = 150/1/1/2 was better controlled in

Self-Assembly, Surface Activity and Structure of n-Octyl-β-D-thioglucopyranoside in Ethylene Glycol-Water Mixtures

Directory of Open Access Journals (Sweden)

Cristóbal Carnero Ruiz

2013-02-01

Full Text Available The effect of the addition of ethylene glycol (EG on the interfacial adsorption and micellar properties of the alkylglucoside surfactant n-octyl-β-D-thioglucopyranoside (OTG has been investigated. Critical micelle concentrations (cmc upon EG addition were obtained by both surface tension measurements and the pyrene 1:3 ratio method. A systematic increase in the cmc induced by the presence of the co-solvent was observed. This behavior was attributed to a reduction in the cohesive energy of the mixed solvent with respect to pure water, which favors an increase in the solubility of the surfactant with EG content. Static light scattering measurements revealed a decrease in the mean aggregation number of the OTG micelles with EG addition. Moreover, dynamic light scattering data showed that the effect of the surfactant concentration on micellar size is also controlled by the content of the co-solvent in the system. Finally, the effect of EG addition on the microstructure of OTG micelles was investigated using the hydrophobic probe Coumarin 153 (C153. Time-resolved fluorescence anisotropy decay curves of the probe solubilized in micelles were analyzed using the two-step model. The results indicate a slight reduction of the average reorientation time of the probe molecule with increasing EG in the mixed solvent system, thereby suggesting a lesser compactness induced by the presence of the co-solvent.

Separation of Cu, In, Fe and Sn from nuclear grade thorium by tri-n-octyl amine-5 M HCI and their determination by atomic absorption spectrophotometry

International Nuclear Information System (INIS)

Moraes, S. de; Cipriani, M.; Abrao, A.

1976-01-01

The results of solvent extraction separation of a group of metal traces in high pure thorium with the aid of tri-n-octyl amine-benzene from ThCL 4 HCI are summarized. ThCl 4 HCI-KI solutions Cu,In,Fe and Sn are extracted together and determined by atomic absoprtion spectrophotometry, burning directly the organic phase. The behavior of Cu,In,Fe and Sn toward direct burn of the organic phase using hydrogen-air mixture was studied, and an absorption enhancement was observed. The procedure is being used ot perform the quality control of nuclear grade thorium and its compounds. The calibration curves have provided precisions in the range 1 to 10% in analysis of thorium

Concentration determination of urinary metabolites of N,N-dimethylacetamide by high-performance liquid chromatography-tandem mass spectrometry.

Science.gov (United States)

Yamamoto, Shinobu; Matsumoto, Akiko; Yui, Yuko; Miyazaki, Shota; Kumagai, Shinji; Hori, Hajime; Ichiba, Masayoshi

2018-03-27

N,N-Dimethylacetamide (DMAC) is widely used in industry as a solvent. It can be absorbed through human skin. Therefore, it is necessary to determine exposure to DMAC via biological monitoring. However, the precision of traditional gas chromatography (GC) is low due to the thermal decomposition of metabolites in the high-temperature GC injection port. To overcome this problem, we have developed a new method for the simultaneous separation and quantification of urinary DMAC metabolites using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Urine samples were diluted 10-fold in formic acid, and 1-μl aliquots were injected into the LC-MS/MS equipment. A C18 reverse-phase Octa Decyl Silyl (ODS) column was used as the analytical column, and the mobile phase consisted of a mixture of methanol and aqueous formic acid solution. Urinary concentrations of DMAC and its known metabolites (N-hydroxymethyl-N-methylacetamide (DMAC-OH), N-methylacetamide (NMAC), and S- (acetamidomethyl) mercapturic acid (AMMA) ) were determined in a single run. The dynamic ranges of the calibration curves were 0.05-5 mg/l (r≥0.999) for all four compounds. The limits of detection for DMAC, DMAC-OH, NMAC, and AMMA in urine were 0.04, 0.02, 0.05, and 0.02 mg/l, respectively. Within-run accuracies were 96.5%-109.6% with relative standard deviations of precision being 3.43%-10.31%. The results demonstrated that the proposed method could successfully quantify low concentrations of DMAC and its metabolites with high precision. Hence, this method is useful for evaluating DMAC exposure. In addition, this method can be used to examine metabolite behaviors in human bodies after exposure and to select appropriate biomarkers.

Concentration determination of urinary metabolites of N,N-dimethylacetamide by high-performance liquid chromatography-tandem mass spectrometry

Science.gov (United States)

Yamamoto, Shinobu; Matsumoto, Akiko; Yui, Yuko; Miyazaki, Shota; Kumagai, Shinji; Hori, Hajime; Ichiba, Masayoshi

2017-01-01

Objectives: N,N-Dimethylacetamide (DMAC) is widely used in industry as a solvent. It can be absorbed through human skin. Therefore, it is necessary to determine exposure to DMAC via biological monitoring. However, the precision of traditional gas chromatography (GC) is low due to the thermal decomposition of metabolites in the high-temperature GC injection port. To overcome this problem, we have developed a new method for the simultaneous separation and quantification of urinary DMAC metabolites using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Methods: Urine samples were diluted 10-fold in formic acid, and 1-μl aliquots were injected into the LC-MS/MS equipment. A C18 reverse-phase Octa Decyl Silyl (ODS) column was used as the analytical column, and the mobile phase consisted of a mixture of methanol and aqueous formic acid solution. Results: Urinary concentrations of DMAC and its known metabolites (N-hydroxymethyl-N-methylacetamide (DMAC-OH), N-methylacetamide (NMAC), and S- (acetamidomethyl) mercapturic acid (AMMA) ) were determined in a single run. The dynamic ranges of the calibration curves were 0.05-5 mg/l (r≥0.999) for all four compounds. The limits of detection for DMAC, DMAC-OH, NMAC, and AMMA in urine were 0.04, 0.02, 0.05, and 0.02 mg/l, respectively. Within-run accuracies were 96.5%-109.6% with relative standard deviations of precision being 3.43%-10.31%. Conclusions: The results demonstrated that the proposed method could successfully quantify low concentrations of DMAC and its metabolites with high precision. Hence, this method is useful for evaluating DMAC exposure. In addition, this method can be used to examine metabolite behaviors in human bodies after exposure and to select appropriate biomarkers. PMID:29213009

Synthesis and characterization of n-alkylamino derivatives of vitamin K3: Molecular structure of 2-propylamino-3-methyl-1,4-naphthoquinone and antibacterial activities

Science.gov (United States)

Chadar, Dattatray; Camilles, Maria; Patil, Rishikesh; Khan, Ayesha; Weyhermüller, Thomas; Salunke-Gawali, Sunita

2015-04-01

We would like to introduce eight analogues of n-alkylamino derivatives of vitamin K3 (2-methyl-1,4-naphthoquinone) viz, 2-(n-alkylamino)-3-methyl-1,4-naphthoquinone (where n-alkyl is methyl; LM-1, ethyl; LM-2, propyl; LM-3, butyl; LM-4, pentyl; LM-5, hexyl; LM-6, heptyl; LM-7, octyl; LM-8). All the above analogues have been successfully synthesized from vitamin K3 and characterized using different analytical techniques. Furthermore, in order to understand the mechanistic aspects of formation of LM-1 to LM-8 compounds, we could propose the mechanism. The FT-IR analysis of LM-1 to LM-8 indicate the presence of characteristic band of Nsbnd H group ∼3287-3364 cm-1, the variation was attributed to extensive intramolecular hydrogen bonding interaction. The molecular structure of LM-3 compound has been confirmed by single crystal X-ray diffraction analysis. LM-3 compound crystallises in triclinic space group P1. There were four independent molecules in asymmetric unit cell and their molecular interactions observed via Nsbnd H⋯O, Csbnd H⋯O and π-π stacking of quinonoid rings. Pharmacological potential of all compounds has been evaluated in terms of their antibacterial activities against Pseudomonas aeruginosa and Staphylococcus aureus. All the compounds were active against both the strains while LM-2 was found to be more effective with a minimum inhibition concentration of 0.3125 μg/mL and 0.156 μg/mL respectively.

N,N'-Diethyl-N,N'-diphenylpyridine-2,6-dicarboxamide

Czech Academy of Sciences Publication Activity Database

Klepetářová, Blanka; Makrlík, E.; Babain, V.A.; Kašička, Václav

2012-01-01

Roč. 68, č. 4 (2012), o1099-o1100 ISSN 1600-5368 Grant - others:GA ČZU(CZ) 42900/1312/3114 Institutional research plan: CEZ:AV0Z40550506 Keywords : N,N'-Diethyl-N,N'-diphenylpyridine-2,6-dicarboxamide * crystal structure * amide nitrogen Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.347, year: 2011

Separation of Cu, In, Fe and Sn from nuclear grade thorium by tri-n-octyl amine--5 M HCI and their determination by atomic absorption spectrophotometry

Energy Technology Data Exchange (ETDEWEB)

de Moraes, S; Cipriani, M; Abrao, A

1976-03-01

The results of solvent extraction separation of a group of metal traces in high pure thorium with the aid of tri-n-octyl amine-benzene from ThCl/sub 4/HCl are summarized. ThCl/sub 4/HCl-KI solutions of Cu, In, Fe and Sn are extracted together and determined by atomic absoprtion spectrophotometry and burning directly the organic phase. The behavior of Cu, In, Fe and Sn toward direct burn of the organic phase using hydrogen-air mixture was studied, and an absorption enhancement was observed. The procedure is being used to perform the quality control of nuclear grade thorium and its compounds. The calibration curves have provided precisions in the range 1 to 10% in analysis of thorium.

Ultrasonic velocities, densities, and excess molar volumes of binary mixtures of N,N-dimethyl formamide with methyl acrylate, or ethyl acrylate, or butyl acrylate, or 2-ethyl hexyl acrylate at T = 308.15 K

Energy Technology Data Exchange (ETDEWEB)

Kondaiah, M. [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522510, Andhra Pradesh (India); Sravana Kumar, D. [Dr. V.S. Krishna Govt. Degree College, Visakhapatnam, Andhra Pradesh (India); Sreekanth, K. [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522510, Andhra Pradesh (India); Krishna Rao, D., E-mail: krdhanekula@yahoo.co.in [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522510, Andhra Pradesh (India)

2011-12-15

Highlights: > Positive values of V{sub m}{sup E}, indicate dispersion forces between acrylic esters and DMF. > V{sub m}{sup E} values compared with Redlich-Kister polynomial. > Partial molar volumes data conclude that weak interactions exist in the systems. > Measured velocity values compared with theoretical values obtained by polynomials. - Abstract: Ultrasonic velocities, u, densities, {rho}, of binary mixtures of N,N-dimethyl formamide (DMF) with methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), and 2-ethyl hexyl acrylate (EHA), including pure liquids, over the entire composition range have been measured at T = 308.15 K. Using the experimental results, the excess molar volume, V{sub m}{sup E}, partial molar volumes, V-bar {sub m,1}, V-bar{sub m,2}, and excess partial molar volumes, V-bar{sub m,1}{sup E}, V-bar{sub m,2}{sup E} have been calculated. Molecular interactions in the systems have been studied in the light of variation of excess values of calculated properties. The excess properties have been fitted to Redlich-Kister type polynomial and the corresponding standard deviations have been calculated. The positive values of V{sub m}{sup E} indicate the presence of dispersion forces between the DMF and acrylic ester molecules. Further theoretical values of sound velocity in the mixtures have been evaluated using various theories and have been compared with experimental sound velocities to verify the applicability of such theories to the systems studied. Theoretical ultrasonic velocity data have been used to study molecular interactions in the binary systems investigated.

Microbial corrosion resistance of galvanized coatings with 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one as a biocidal ingredient in electrolytes

International Nuclear Information System (INIS)

Zhai, Xiaofan; Myamina, Maria; Duan, Jizhou; Hou, Baorong

2013-01-01

Highlights: •Addition of DCOIT to zinc electrolyte increases current efficiency. •Zn deposited from electrolytes with DCOIT inhibits growth and metabolism of SRB. •DCOIT on coating surfaces influences the coating structure and morphology. •EIS and polarization results show good microbial-corrosion resistance in SRB. -- Abstract: Electrodeposition of galvanized coatings from electrolyte containing 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) can increase microbial corrosion resistance. Coatings were found to inhibit the growth and metabolism of sulphate-reducing bacteria (SRB). Open circuit potentials and corrosion rates of coupons revealed DCOIT effectively influences the coating property. Energy diffraction spectrum and infrared absorption spectra were used to detect DCOIT on the coating surface. Scanning electron microscopy and X-ray diffraction revealed morphological and structural modifications. Electrochemical impedance spectroscopy and polarization techniques determined the corrosion behaviour of coatings in SRB. Results showed coatings formed from electrolytes with DCOIT have improved microbial corrosion resistance and bactericidal action

Amide and Ester-Functionalized Humic Acid for Fuel Combustion Enhancement

Science.gov (United States)

Riggs, Mark

Humic acid is a class of naturally occurring molecules composed of large sheet-like regions of cyclic aromatic hydrocarbon networks with surface and edge functional groups including phenols, carboxylic acids, and epoxides. These naturally occurring molecules are found in brown coal deposits near lignite formations. Humic acid has gained attention from the scientific community as a precursor for graphene. Graphene is a 2-dimensional honeycomb structure of fully unsaturated carbon atoms that has exceptional material properties and inherent aromaticity. Graphene's incredible properties are matched by the difficulty associated with reproducibly manufacturing it on a large scale. This issue has limited the use of graphene for commercial applications. The polar functional groups of humic acid contribute to the hydrophilic nature of the molecule, limiting its miscibility in any alkyl-based solvent. Surfactants containing long alkyl chains can affect the miscibility of the molecule in an organic solvent. Surfactants are often difficult to remove from the system. It is theorized that alkylation of the functional sites of humic acid can affect the hydrophilic nature of the molecule, and effectively enable its dispersion into organic solvents without simultaneous incorporation of surfactants. This dissertation investigated the amidation and esterification of humic acid molecules extracted from leonardite. The resulting change in the modified humic acid dispersibility in organic solvents and its potential usage as a fuel additive were evaluated. Butyl, hexyl, octyl, and decyl amide-modified and ester-modified humic acids were synthesized. These products were characterized to confirm successful chemical reaction through thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The decyl-modified humic acids remained suspended in kerosene mixtures for longer than 1 week. Other organo-humic acids showed varying degrees of flocculation

Impact of gate engineering in enhancement mode n++GaN/InAlN/AlN/GaN HEMTs

Science.gov (United States)

Adak, Sarosij; Swain, Sanjit Kumar; Rahaman, Hafizur; Sarkar, Chandan Kumar

2016-12-01

This paper illustrate the effect of gate material engineering on the performance of enhancement mode n++GaN/InAlN/AlN/GaN high electron mobility transistors (HEMTs). A comparative analysis of key device parameters is discussed for the Triple Material Gate (TMG), Dual Material Gate (DMG) and the Single Material Gate (SMG) structure HEMTs by considering the same device dimensions. The simulation results shows that an significant improvement is noticed in the key analysis parameters such as drain current (Id), transconductance (gm), cut off frequency (fT), RF current gain, maximum cut off frequency (fmax) and RF power gain of the gate material engineered devices with respect to SMG normally off n++GaN/InAlN/AlN/GaN HEMTs. This improvement is due to the existence of the perceivable step in the surface potential along the channel which successfully screens the drain potential variation in the source side of the channel for the gate engineering devices. The analysis suggested that the proposed TMG and DMG engineered structure enhancement mode n++GaN/InAlN/AlN/GaN HEMTs can be considered as a potential device for future high speed, microwave and digital application.

N,N,N-Tris(diphenylphosphorylmethylamine

Directory of Open Access Journals (Sweden)

Olaf Walter

2017-10-01

Full Text Available The structure of N,N,N-tris(diphenylphosphorylmethylamine, C39H36NO3P3, at 103 K has monoclinic (P21/c symmetry. Two molecules, each with pseudo-threefold rotation symmetry, crystallize in the asymmetric unit of the monoclinic unit cell. The compound acts as ligand for the stabilization of metal ions with flexible coordination enabling three- or fourfold coordination.

Evaluation of Some (n,n'), (n,γ), (n,p), (n,2n) and (n,3n) Reaction Excitation Functions for Fission and Fusion Reactor Dosimetry Applications; Evaluation of the Excitation Functions for the 54Fe(n,p)54Mn, 58Ni(n,2n)57Ni, 67Zn(n,p)67Cu, 92Mo(n,p)92mNb, 93Nb(n,γ)94Nb, 113In(n,n')113mIn, 115In(n,γ) 116mIn, and 169Tm(n,3n)167Tm Reactions. Progress Report on Research Contract No 16242

International Nuclear Information System (INIS)

Zolotarev, K.I.; Zolotarev, P.K.

2013-12-01

Cross section data for the 54 Fe(n,p) 54 Mn, 58 Ni(n,2n) 57 Ni, 67 Zn(n,p) 67 Cu, 92 Mo(n,p) 92m Nb, 93 Nb(n,γ) 94 Nb, 113 In(n,n') 113m In, 115 In(n,γ) 116m In, 169 Tm(n,3n) 167 Tm reactions are needed to solve a wide spectrum of scientific and technical tasks. Activation detectors based on these reactions may be used in the field of reactor dosimetry. Furthermore, the 54 Fe(n,p) 54 Mn reaction is often used in experimental nuclear physics as a monitor reaction for measurements of unknown cross sections by means of the activation method over the neutron energy range from 5 to 15 MeV. The 93 Nb(n,γ) 94 Nb reaction is also very promising for using in retrospective neutron dosimetry for determination of total neutron fluence during a campaign of a reactor. In the existing version of the International Reactor Dosimetry File and the new extended version named as IRDFF data for excitation functions of 67 Zn(n,p) 67 Cu, 92 Mo(n,p) 92m Nb, 113 In(n,n') 113m In, and 169 Tm(n,3n) 167 Tm reactions are absent. Data for these reactions are also absent in the JENDL/D-99 dosimetry file. Excitation functions of 67 Zn(n,p) 67 Cu and 169 Tm(n,3n) 167 Tm are presented in the TENDL-2012, EAF-2010, JENDL-4.0, JEFF-3.1/A, MENDL-2 libraries. Cross section data for the 67 Zn(n,p) 67 Cu reaction up to 20 MeV are given also in the JENDL/HE-2007 library. Excitation functions of the 92 Mo(n,p) 92m Nb and 113 In(n,n') 113m In reactions are evaluated in the EAF-2010 and JEFF-3.1/A libraries. Cross section data for the 113 In(n,n') 113m In reaction are given also in the TENDL-2010 library. It is necessary to note that neutron data in the JEFF-3.1/A and JENDL-4.0 libraries were evaluated up to 20 MeV. Neutron data in the TENDL-2012, EAF-2010, MENDL-2 and TENDL-2010 libraries had been evaluated up to 30 MeV, 60 MeV, 100 MeV and 200 MeV, respectively. Neutron cross sections in the MENDL-2, TENDL-2010 and TENDL-2012 libraries had been obtained on the basis of pure theoretical model calculations

Ohmic contacts to n+-GaN capped AlGaN/AlN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Wang Liang; Mohammed, Fitih M.; Ofuonye, Benedict; Adesida, Ilesanmi

2007-01-01

Investigations of Ti/Al/Mo/Au Ohmic contact formation, premetallization plasma treatment effects, and interfacial reactions for n + -GaN capped AlGaN/AlN/GaN heterostructures are presented. Ti thickness played an important role in determining contact performance. Transmission electron microscopy studies confirmed that thick Ti layer was necessary to fully consume the GaN cap and the top of AlGaN to enable a higher tunneling current flow. A direct correlation of plasma treatment conditions with I-V linearity, current level, and contact performance was established. The plasma-affected region is believed to extend over 20 nm into the AlGaN and GaN

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

Kinetics of the transformation of n-propyl gallate and structural analogs in the perfused rat liver

International Nuclear Information System (INIS)

Eler, Gabrielle Jacklin; Santos, Israel Souza; Giaretta de Moraes, Amarilis; Mito, Márcio Shigueaki; Comar, Jurandir Fernando; Peralta, Rosane Marina; Bracht, Adelar

2013-01-01

n-Propyl gallate and its analogs are used in foods and other products to prevent oxidation. In the liver the compound exerts several harmful effects, especially gluconeogenesis inhibition. The mode of transport and distribution of n-propyl gallate and its kinetics of biotransformation have not yet been investigated. To fill this gap the transformation, transport and distribution of n-propyl gallate and two analogs were investigated in the rat liver. Isolated perfused rat liver was used. n-Propyl gallate, methyl gallate, n-octyl gallate and transformation products were quantified by high pressure-liquid chromatography coupled to fluorescence detection. The interactions of n-propyl gallate and analogs with the liver presented three main characteristics: (1) the hydrolytic release of gallic acid from n-propyl gallate and methyl gallate was very fast compared with the subsequent transformations of the gallic acid moiety; (2) transport of the esters was very fast and flow-limited in contrast to the slow and barrier-limited transport of gallic acid; (3) the apparent distribution volume of n-propyl gallate, but probably also of methyl gallate and n-octyl gallate, greatly exceeded the water space in the liver, contrary to the gallic acid space which is smaller than the water space. It can be concluded that at low portal concentrations (< 50 μM) the gallic acid esters are 100% extracted during a single passage through the liver, releasing mainly gallic acid into the systemic circulation. For the latter a considerable time is required until complete biotransformation. The exposure of the liver to the esters, however, is quite prolonged due to extensive intracellular binding. - Highlights: • The liver binds very strongly n-propyl gallate and releases basically gallic acid. • n-propyl gallate and analogs undergo concentrative flow-limited distribution. • Gallic acid undergoes barrier-limited distribution and is slowly transformed. • The long residence time of n

Kinetics of the transformation of n-propyl gallate and structural analogs in the perfused rat liver

Energy Technology Data Exchange (ETDEWEB)

Eler, Gabrielle Jacklin; Santos, Israel Souza; Giaretta de Moraes, Amarilis; Mito, Márcio Shigueaki; Comar, Jurandir Fernando; Peralta, Rosane Marina; Bracht, Adelar, E-mail: adebracht@uol.com.br

2013-11-15

n-Propyl gallate and its analogs are used in foods and other products to prevent oxidation. In the liver the compound exerts several harmful effects, especially gluconeogenesis inhibition. The mode of transport and distribution of n-propyl gallate and its kinetics of biotransformation have not yet been investigated. To fill this gap the transformation, transport and distribution of n-propyl gallate and two analogs were investigated in the rat liver. Isolated perfused rat liver was used. n-Propyl gallate, methyl gallate, n-octyl gallate and transformation products were quantified by high pressure-liquid chromatography coupled to fluorescence detection. The interactions of n-propyl gallate and analogs with the liver presented three main characteristics: (1) the hydrolytic release of gallic acid from n-propyl gallate and methyl gallate was very fast compared with the subsequent transformations of the gallic acid moiety; (2) transport of the esters was very fast and flow-limited in contrast to the slow and barrier-limited transport of gallic acid; (3) the apparent distribution volume of n-propyl gallate, but probably also of methyl gallate and n-octyl gallate, greatly exceeded the water space in the liver, contrary to the gallic acid space which is smaller than the water space. It can be concluded that at low portal concentrations (< 50 μM) the gallic acid esters are 100% extracted during a single passage through the liver, releasing mainly gallic acid into the systemic circulation. For the latter a considerable time is required until complete biotransformation. The exposure of the liver to the esters, however, is quite prolonged due to extensive intracellular binding. - Highlights: • The liver binds very strongly n-propyl gallate and releases basically gallic acid. • n-propyl gallate and analogs undergo concentrative flow-limited distribution. • Gallic acid undergoes barrier-limited distribution and is slowly transformed. • The long residence time of n

On Positive Solutions for the Rational Difference Equation Systems x n+1 = A/x n y n (2), and y n+1 = By n /x n-1 y n-1.

Science.gov (United States)

Ma, Hui-Li; Feng, Hui

2014-01-01

Our aim in this paper is to investigate the behavior of positive solutions for the following systems of rational difference equations: x n+1 = A/x n y n (2), and y n+1 = By n /x n-1 y n-1, n = 0,1,…, where x -1, x 0, y -1, and y 0 are positive real numbers and A and B are positive constants.

Evasión remisión de V. duración de la evasión.

OpenAIRE

2011-01-01

[ES] Definición del término Evasión remisión de V. duración de la evasión. en el diccionario Dicter. [EN] Definition of the word Evasión remisión de V. duración de la evasión. in the dictionary Dicter.

Thermal stability study of Cr/Au contact formed on n-type Ga-polar GaN, N-polar GaN, and wet-etched N-polar GaN surfaces

International Nuclear Information System (INIS)

Choi, Yunju; Kim, Yangsoo; Ahn, Kwang-Soon; Kim, Hyunsoo

2014-01-01

Highlights: • The Cr/Au contact on n-type Ga-polar (0 0 0 1) GaN, N-polar (0 0 0 −1) GaN, and wet-etched N-polar GaN were investigated. • Thermal annealing led to a significant degradation of contact formed on N-polar n-GaN samples. • Contact degradation was shown to be closely related to the increase in the electrical resistivity of n-GaN. • Out-diffusion of Ga and N atoms was clearly observed in N-polar samples. - Abstract: The electrical characteristics and thermal stability of a Cr/Au contact formed on n-type Ga-polar (0 0 0 1) GaN, N-polar GaN, and wet-etched N-polar GaN were investigated. As-deposited Cr/Au showed a nearly ohmic contact behavior for all samples, i.e., the specific contact resistance was 3.2 × 10 −3 , 4.3 × 10 −4 , and 1.1 × 10 −3 Ω cm 2 for the Ga-polar, flat N-polar, and roughened N-polar samples, respectively. However, thermal annealing performed at 250 °C for 1 min in a N 2 ambient led to a significant degradation of contact, i.e., the contact resistance increased by 186, 3260, and 2030% after annealing for Ga-polar, flat N-polar, and roughened N-polar samples, respectively. This could be due to the different disruption degree of Cr/Au and GaN interface after annealing, i.e., the insignificant interfacial reaction occurred in the Ga-polar sample, while out-diffusion of Ga and N atoms was clearly observed in N-polar samples

Thermal stability study of Cr/Au contact formed on n-type Ga-polar GaN, N-polar GaN, and wet-etched N-polar GaN surfaces

Energy Technology Data Exchange (ETDEWEB)

Choi, Yunju [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Suncheon Center, Korea Basic Science Institute, Suncheon 540-742 (Korea, Republic of); Kim, Yangsoo [Suncheon Center, Korea Basic Science Institute, Suncheon 540-742 (Korea, Republic of); Ahn, Kwang-Soon, E-mail: kstheory@ynu.ac.kr [School of Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 712-749 (Korea, Republic of); Kim, Hyunsoo, E-mail: hskim7@jbnu.ac.kr [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

2014-10-30

Highlights: • The Cr/Au contact on n-type Ga-polar (0 0 0 1) GaN, N-polar (0 0 0 −1) GaN, and wet-etched N-polar GaN were investigated. • Thermal annealing led to a significant degradation of contact formed on N-polar n-GaN samples. • Contact degradation was shown to be closely related to the increase in the electrical resistivity of n-GaN. • Out-diffusion of Ga and N atoms was clearly observed in N-polar samples. - Abstract: The electrical characteristics and thermal stability of a Cr/Au contact formed on n-type Ga-polar (0 0 0 1) GaN, N-polar GaN, and wet-etched N-polar GaN were investigated. As-deposited Cr/Au showed a nearly ohmic contact behavior for all samples, i.e., the specific contact resistance was 3.2 × 10{sup −3}, 4.3 × 10{sup −4}, and 1.1 × 10{sup −3} Ω cm{sup 2} for the Ga-polar, flat N-polar, and roughened N-polar samples, respectively. However, thermal annealing performed at 250 °C for 1 min in a N{sub 2} ambient led to a significant degradation of contact, i.e., the contact resistance increased by 186, 3260, and 2030% after annealing for Ga-polar, flat N-polar, and roughened N-polar samples, respectively. This could be due to the different disruption degree of Cr/Au and GaN interface after annealing, i.e., the insignificant interfacial reaction occurred in the Ga-polar sample, while out-diffusion of Ga and N atoms was clearly observed in N-polar samples.

Noncompetitive inhibition of indolethylamine-N-methyltransferase by N,N-dimethyltryptamine and N,N-dimethylaminopropyltryptamine.

Science.gov (United States)

Chu, Uyen B; Vorperian, Sevahn K; Satyshur, Kenneth; Eickstaedt, Kelsey; Cozzi, Nicholas V; Mavlyutov, Timur; Hajipour, Abdol R; Ruoho, Arnold E

2014-05-13

Indolethylamine-N-methyltransferase (INMT) is a Class 1 transmethylation enzyme known for its production of N,N-dimethyltryptamine (DMT), a hallucinogen with affinity for various serotonergic, adrenergic, histaminergic, dopaminergic, and sigma-1 receptors. DMT is produced via the action of INMT on the endogenous substrates tryptamine and S-adenosyl-l-methionine (SAM). The biological, biochemical, and selective small molecule regulation of INMT enzyme activity remain largely unknown. Kinetic mechanisms for inhibition of rabbit lung INMT (rabINMT) by the product, DMT, and by a new novel tryptamine derivative were determined. After Michaelis-Menten and Lineweaver-Burk analyses had been applied to study inhibition, DMT was found to be a mixed competitive and noncompetitive inhibitor when measured against tryptamine. The novel tryptamine derivative, N-[2-(1H-indol-3-yl)ethyl]-N',N'-dimethylpropane-1,3-diamine (propyl dimethyl amino tryptamine or PDAT), was shown to inhibit rabINMT by a pure noncompetitive mechanism when measured against tryptamine with a Ki of 84 μM. No inhibition by PDAT was observed at 2 mM when it was tested against structurally similar Class 1 methyltransferases, such as human phenylethanolamine-N-methyltransferase (hPNMT) and human nicotinamide-N-methyltransferase (hNNMT), indicating selectivity for INMT. The demonstration of noncompetitive mechanisms for INMT inhibition implies the presence of an inhibitory allosteric site. In silico analyses using the computer modeling software Autodock and the rabINMT sequence threaded onto the human INMT (hINMT) structure (Protein Data Bank entry 2A14 ) identified an N-terminal helix-loop-helix non-active site binding region of the enzyme. The energies for binding of DMT and PDAT to this region of rabINMT, as determined by Autodock, were -6.34 and -7.58 kcal/mol, respectively. Assessment of the allosteric control of INMT may illuminate new biochemical pathway(s) underlying the biology of INMT.

Cross sections for the (n,p), (n,α) and (n,2n) threshold reactions

International Nuclear Information System (INIS)

Bychkov, V.M.; Manokhin, V.N.; Pashchenko, A.B.; Plyaskin, V.I.

1980-07-01

The (n,p), (n,α), (n,2n) threshold reactions are reviewed for nuclei with Z>=20 in the neutron energy range from the threshold up to 20MeV. The review consists of four parts. In the first part the theoretical methods of cross-section calculations and the empirical or semi-empirical systematics are considered. In the second, third and fourth parts the experimental data compilations on the (n,p), (n,α) and (n,2n) excitation functions are given. The recommended values of cross-sections at 14.5MeV neutron energy are given in tables. For some isotopes the recommended curves of excitation functions also are given in graphs. (author)

Characterization of N-polar AlN in GaN/AlN/(Al,Ga)N heterostructures grown by metal-organic chemical vapor deposition

Science.gov (United States)

Li, Haoran; Mazumder, Baishakhi; Bonef, Bastien; Keller, Stacia; Wienecke, Steven; Speck, James S.; Denbaars, Steven P.; Mishra, Umesh K.

2017-11-01

In GaN/(Al,Ga)N high-electron-mobility transistors (HEMT), AlN interlayer between GaN channel and AlGaN barrier suppresses alloy scattering and significantly improves the electron mobility of the two-dimensional electron gas. While high concentrations of gallium were previously observed in Al-polar AlN interlayers grown by metal-organic chemical vapor deposition, the N-polar AlN (Al x Ga1-x N) films examined by atom probe tomography in this study exhibited aluminum compositions (x) equal to or higher than 95% over a wide range of growth conditions. The also investigated AlN interlayer in a N-polar GaN/AlN/AlGaN/ S.I. GaN HEMT structure possessed a similarly high x content.

Equilibrium constant and nitrogen activity and the parameters of interaction eN(N), rN(N,Cr), rN(N,Mn) in high nitrogen steels of Fe-Cr-Mn-N type

International Nuclear Information System (INIS)

Svyazhin, A.G.; Siwka, J.; Rashev, T.

1999-01-01

In the paper a description of a thermodynamic of liquid solutions of Fe-Cr-Mn-N type with using a concept of parameters of an interaction has been presented. A temperature relationship of the equilibrium constant K N(Fe) and values of self interaction parameters e N (N) , r N (N,Cr) , r N (N,Mn) and t N (N,Cr,Cr) has been determined for mean values of temperatures of liquid metal equal 1990 K and 2090 K. By application of a theory of regular solutions those values were recalculated for a temperature 1873 K. (orig.)

Simulación, Optimización y Gestión

OpenAIRE

Momparler Pechuám, Juan

2005-01-01

En este trabajo divulgativo pretendemos mostrar como La Teoría de Colas, la Simulación de Eventos Discretos y la Optimización utilizadas conjuntamente, pueden ser una poderosa herramienta, de fácil aplicación, en la resolución de algunos problemas de gestión muy habituales en las empresas. Veremos sobre diferentes problemas de gestión como podemos utilizar para modelarlos las técnicas de Optimización y de Teoría de Colas. Para resolver los modelos planteados utilizaremos la programación...

ADSORCIÓN DE RESORCINOL DESDE SOLUCIÓN ACUOSA SOBRE CARBÓN ACTIVADO. RELACIÓN ISOTERMAS DE ADSORCIÓN Y ENTALPÍA DE INMERSIÓN RESORCINOL

OpenAIRE

Blanco, Diego A; Giraldo, Liliana; JuanC, Moreno

2008-01-01

Se estudia la adsorción de resorcinol sobre carbones activados modificados, obtenidos a partir de un carbón activado granular comercial CarbochemTM –PS30, (CAG), por medio de tratamiento químico con HNO37M, carbón activado oxidado (CAO) y tratamiento térmico bajo flujo de H2, carbón activado reducido (CAR). Se analiza la influencia del pH de la solución, la reducción y oxidación de la superficie del carbón y se determina la entalpía de inmersión de los carbones activados en soluciones acuosas...

40 CFR 721.10056 - Benzenemethanaminium, N-(3-aminopropyl)-N,N-dimethyl-, N-soya acyl derivs., chlorides.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Benzenemethanaminium, N-(3-aminopropyl...-aminopropyl)-N,N-dimethyl-, N-soya acyl derivs., chlorides. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as benzenemethanaminium, N-(3-aminopropyl)-N,N...

Simulación, Optimización y Gestión

Directory of Open Access Journals (Sweden)

Momparler Pechuám, Juan

2005-01-01

Full Text Available En este trabajo divulgativo pretendemos mostrar como La Teoría de Colas, la Simulación de Eventos Discretos y la Optimización utilizadas conjuntamente, pueden ser una poderosa herramienta, de fácil aplicación, en la resolución de algunos problemas de gestión muy habituales en las empresas. Veremos sobre diferentes problemas de gestión como podemos utilizar para modelarlos las técnicas de Optimización y de Teoría de Colas. Para resolver los modelos planteados utilizaremos la programación en MATLAB y LINGO, Comentaremos también una bibliografía especializada sobre estos temas que sirva de referencia.

Studies on the structure and thermal behaviour of poly(N-alkyl sesqui oxanes) base silicon resins; Estudos da estrutura e do comportamento termico de resinas de silicona a base de poli(N-alquilsilsesquioxanos)

Energy Technology Data Exchange (ETDEWEB)

Prado, Luis Antonio Sanchez de Almeida; Yoshida, Inez Valeria Pagotto [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica], e-mail: valeria@iqm.unicamp.br

2000-07-01

In this work, T, T{sup A}D{sup L} and T{sup A}D{sup C} silicone resins were obtained by the sol-gel process. Poly(dimethylsiloxane) and tetramethyl diethoxydisiloxane were used as sources of D{sup L} and D{sup C} units, respectively, while n-octyltriethoxysilane and n-dodecyltriethoxysilane were employed as precursors for T{sup A} units. The molecular structure and the composition were investigated by FT-IR and {sup 29}Si MAS NMR spectra. A partial loss of TMDES was observed during the curing of the resins. TGA traces indicated good thermal stability for all resins prepared. DSC curves showed the presence of a glass-transition and first-order transition for the resins containing n-octyl and n-dodecyl groups, respectively. The presence of the last transition could be attributed to the fusion of nano domains constituted by n-dodecyl groups. (author)

Crystal structure of bis{S-hexyl 3-[4-(dimethylaminobenzylidene]dithiocarbazato-κ2N3,S}copper(II

Directory of Open Access Journals (Sweden)

E. Zangrando

2015-06-01

Full Text Available In the title complex, [Cu(C16H24N3S22], the CuII atom is coordinated by two azomethine N and two thiolate S atoms of the chelating Schiff base ligands, resulting in a distorted square-planar coordination environment. The S—Cu—N chelating angle is of 84.41 (5°. The CuII atom is located on a crystallographic inversion centre, leading to a trans configuration of the N,S-chelating ligands.

ERRADICACIÓN Y POSTERRADICACIÓN

Directory of Open Access Journals (Sweden)

Francisco Salmerón García

2013-01-01

Full Text Available La vacunación antipoliomielítica genera inmunidad de grupo (con vacunas atenuadas (VPO e inactivadas (VPI y ello permitirá la erradica- ción de la enfermedad. La VPO produce de 2-4 casos de poliomielitis por cohorte de un millón de niños y por ello los países que pueden hacer frente al coste de la VPI (unas 15 veces más cara la utilizan. En 1988 la Asamblea de la Organización Mundial de la Salud aprobó el objetivo de la erradicación como “la interrupción de la transmisión de poliovirus salvajes”. Si se conseguía su eliminación, el mantenimiento de la VPO produciría al año entre 250 y 500 casos de poliomielitis en el mundo. Desde 1999 era evidente que la erradicación requeriría la cesación de la vacunación con VPO. El 25 de enero del 2013 se aprobó el plan para la erradicación y la contención de todos los virus de la polio, salvajes o no, para que ningún niño sufra una poliomielitis paralítica. Los hitos más importantes incluyen, la no aparición de casos de polio saducción de al menos una dosis de VPI en todos los programas de vacunación y que se suspenda la vacunación con VPO tipo 2 al final del 2016 y que en 2019 se pueda cesar de utilizar la vacuna bivalente oral. Para todo ello será preciso un trabajo científico complejo y solidaridad financiera.

ADSORCIÓN DE RESORCINOL DESDE SOLUCIÓN ACUOSA SOBRE CARBÓN ACTIVADO. RELACIÓN ISOTERMAS DE ADSORCIÓN Y ENTALPÍA DE INMERSIÓN

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Diego Blanco

2009-04-01

Full Text Available Se estudia la adsorción de resorcinol, sobre carbones activados modificados, obtenidos a partir de un carbón activado comercial CarbochemTM –PS30, CAG, por medio de tratamiento químico con HNO3 7M, CAO y tratamiento térmico bajo flujo de H2, CAR; se analiza la influencia del pH de la solución, la reducción y oxidación de la superficie del carbón y se determina la entalpía de inmersión de los carbones activados en soluciones acuosas de resorcinol.La interacción sólido-solución se caracteriza por el análisis de las isotermas de adsorción a 298 K a los pHs de 7, 9 y 11 con el propósito de evaluar el sistema sobre y por debajo del valor de las pKa del resorcinol. La capacidad de adsorción de los carbones aumenta al disminuir el pH de la solución. La cantidad retenida aumenta en el carbón reducido al pH de máxima adsorción y disminuye en el carbón oxidado. Los resultados experimentales de las isotermas de adsorción se ajustaron a los modelos de Freundlich y Langmuir, obteniendo valores para el parámetro Qmáx del modelo de Langmuir en el CAG de 179, 156 y 44 mgg-1, para valores de pH de 7, 9 y 11 respectivamente. En el caso de los carbones modificados se obtienen valores de 233, 179 y 164 mgg-1, para el CAR, CAG y CAO a pH 7 respectivamente. Como tendencia general la adsorción de resorcinol aumenta en el siguiente orden CAR > CAG > CAO Similares conclusiones se obtienen de las entalpías de inmersión, cuyos valores se incrementan con la cantidad de soluto retenido. En el caso del CAG se obtienen entalpías de inmersión entre 25,8 a 40,9 Jg-1 para soluciones acuosas de resorcinol en un rango de 20 a 1500 mgL-1.

Lattice thermal expansions of NpN, PuN and AmN

International Nuclear Information System (INIS)

Takano, Masahide; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo

2008-01-01

Lattice parameters of NpN, PuN and AmN were measured by a high temperature X-ray diffraction method from room temperature up to 1478 K. Linear thermal expansions of these TRU nitrides were determined as a function of temperature. The average coefficients of linear thermal expansion from 293 to 1273 K were 8.8, 11.1 and 11.2 x 10 -6 K -1 for NpN, PuN and AmN, respectively. The instantaneous coefficient of thermal expansion either at 293 or at 1273 K against the reciprocal decomposition temperature under 1 atm of nitrogen showed a linear relationship for TiN, ZrN, HfN, UN, NpN and PuN. Based on this relationship, the decomposition temperature of AmN was roughly predicted to be 2700 K

GaN-based ultraviolet light-emitting diodes with AlN/GaN/InGaN multiple quantum wells.

Science.gov (United States)

Chang, Hung-Ming; Lai, Wei-Chih; Chen, Wei-Shou; Chang, Shoou-Jinn

2015-04-06

We demonstrate indium gallium nitride/gallium nitride/aluminum nitride (AlN/GaN/InGaN) multi-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) to improve light output power. Similar to conventional UV LEDs with AlGaN/InGaN MQWs, UV LEDs with AlN/GaN/InGaN MQWs have forward voltages (V(f)'s) ranging from 3.21 V to 3.29 V at 350 mA. Each emission peak wavelength of AlN/GaN/InGaN MQW UV LEDs presents 350 mA output power greater than that of the corresponding emission peak wavelength of AlGaN/InGaN MQW UV LEDs. The light output power at 350mA of AlN/GaN/InGaN MQWs UV LEDs with 375 nm emission wavelength can reach around 26.7% light output power enhancement in magnitude compared to the AlGaN/InGaN MQWs UV LEDs with same emission wavelength. But 350mA light output power of AlN/GaN/InGaN MQWs UV LEDs with emission wavelength of 395nm could only have light output power enhancement of 2.43% in magnitude compared with the same emission wavelength AlGaN/InGaN MQWs UV LEDs. Moreover, AlN/GaN/InGaN MQWs present better InGaN thickness uniformity, well/barrier interface quality and less large size pits than AlGaN/InGaN MQWs, causing AlN/GaN/InGaN MQW UV LEDs to have less reverse leakage currents at -20 V. Furthermore, AlN/GaN/InGaN MQW UV LEDs have the 2-kV human body mode (HBM) electrostatic discharge (ESD) pass yield of 85%, which is 15% more than the 2-kV HBM ESD pass yield of AlGaN/InGaN MQW UV LEDs of 70%.

Estructuración de mantenimiento, gestión, administración y planeación

OpenAIRE

García Tamayo, Juan Luis

2010-01-01

Mediante esta propuesta de investigación se presenta un modelo para la estructuración del área de mantenimiento de Fábrica de Calcetines Crystal en cuanto a su gestión, administración y planeación. Adicionalmente, se incluye un esquema básico como iniciativa para una oficina o departamento de proyectos con un enfoque hacia dicha área. 58 p. Contenido parcial: ¿Qué es Mantenimiento? -- Mantenimiento basado en el tiempo -- Mantenimiento basado en la condición -- Estructuración de mantenim...

Fabrication of TiN/AlN/TiN tunnel junctions

Energy Technology Data Exchange (ETDEWEB)

Nakayama, Takeru; Naruse, Masato; Myoren, Hiroaki; Taino, Tohru, E-mail: taino@mail.saitama-u.ac.jp

2016-11-15

Highlights: • We have fabricated TiN/AlN/TiN tunnel junctions with an epitaxial layer. • TiN and AlN films were deposited by dc and rf magnetron sputtering at ambient substrate temperatures. • The junctions have a V{sub g} = 1.1 mV, J{sub c} = 0.24 A/cm{sup 2}, R{sub sg}/R{sub n} of 7.2, and low subgap leakage current of 180 nA. - Abstract: We have fabricated TiN/AlN/TiN tunnel junctions with an epitaxial layer. The critical temperature of TiN can be changed in the range from 0.5 to 5.0 K. Therefore, it is easy to set 5.0 K as the target critical temperature. When a Superconducting Tunnel Junction (STJ) is operated as a photon detector, it is necessary to cool it to within 0.1 K of the critical temperature in consideration of the noise of the thermally stimulated currents. Because 0.3 K was desirable, as for the manufacture of general purpose photon detectors, the critical temperature 5.0 K. TiN and AlN films were deposited by dc and rf magnetron sputtering in a load-lock sputtering system at ambient substrate temperatures. The junctions have a gap voltage of V{sub g} = 1.1 mV, and critical current density of J{sub c} = 0.24 A/cm{sup 2}, and R{sub sg}/R{sub n} of 7.2, and low subgap leakage current (I{sub sub}@ 500 µV = 180 nA). We report our experiment system, the manufacture method and the junction properties in this paper.

Ruthenium (3) coordination compounds with ethylenediamine-N,N,N',N'-tetramethylphosphonic acid

International Nuclear Information System (INIS)

Ezerskaya, N.A.; Buj Kuang Ki; Shubochkin, L.K.

1987-01-01

In the process of interaction of K 2 Ru(H 2 O)Cl 5 with ethylenediamine-N,N,N',N'-tetramethylphosphonic acid (H 8 EDTP) Ru 3 mono-, bi- and trinuclear complexonates are synthesized. On the basis of IR and X-ray electron spectroscopy and potentiometry suppositions are made on the way of ligand (EDTP, Cl - , H 2 O) coordination. Ru 3 complexonates are characterized using spectrophotometry, polarography, conductometry. Thermal decomposition of the complexonates is studied

Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

Energy Technology Data Exchange (ETDEWEB)

Sun, Rui [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Makise, Kazumasa; Terai, Hirotaka [Advanced ICT Research Institute, National Institute of Information and Communications Technology (Japan); Zhang, Lu [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Wang, Zhen, E-mail: zwang@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Shanghai Tech University, Shanghai 201210 (China)

2016-06-15

We have developed epitaxial NbN/AlN/NbN tunnel junctions on Si (100) substrates with a TiN buffer layer. A 50-nm-thick (200)-oriented TiN thin film was introduced as the buffer layer for epitaxial growth of NbN/AlN/NbN trilayers on Si substrates. The fabricated NbN/AlN/NbN junctions demonstrated excellent tunneling properties with a high gap voltage of 5.5 mV, a large I{sub c}R{sub N} product of 3.8 mV, a sharp quasiparticle current rise with a ΔV{sub g} of 0.4 mV, and a small subgap leakage current. The junction quality factor R{sub sg}/R{sub N} was about 23 for the junction with a J{sub c} of 47 A/cm{sup 2} and was about 6 for the junction with a J{sub c} of 3.0 kA/cm{sup 2}. X-ray diffraction and transmission electron microscopy observations showed that the NbN/AlN/NbN trilayers were grown epitaxially on the (200)-orientated TiN buffer layer and had a highly crystalline structure with the (200) orientation.

Walls of massive K\\"ahler sigma models on SO(2N)/U(N) and Sp(N)/U(N)

OpenAIRE

Arai, Masato; Shin, Sunyoung

2011-01-01

We study the Bogomol'nyi-Prasad-Sommerfield wall solutions in massive K\\"ahler nonlinear sigma models on SO(2N)/U(N) and Sp(N)/U(N) in three-dimensional spacetime. We show that SO(2N)/U(N) and Sp(N)/U(N) models have 2^{N-1} and 2^N discrete vacua, respectively. We explicitly construct the exact BPS multiwall solutions for N\\le 3.

Ruthenium (3) coordination compounds with ethylenediamine-N,N,N',N'-tetramethylphosphonic acid

Energy Technology Data Exchange (ETDEWEB)

Ezerskaya, N A; Ki, Buj Kuang; Shubochkin, L K

1987-12-01

In the process of interaction of K/sub 2/Ru(H/sub 2/O)Cl/sub 5/ with ethylenediamine-N,N,N',N'-tetramethylphosphonic acid (H/sub 8/EDTP) Ru/sup 3/ mono-, bi- and trinuclear complexonates are synthesized. On the basis of IR and X-ray electron spectroscopy and potentiometry suppositions are made on the way of ligand (EDTP, Cl/sup -/, H/sub 2/O) coordination. Ru/sup 3/ complexonates are characterized using spectrophotometry, polarography, conductometry. Thermal decomposition of the complexonates is studied.

Comparison of electrical characteristic between AlN/GaN and AlGaN/GaN heterostructure Schottky diodes

International Nuclear Information System (INIS)

Lü Yuan-Jie; Feng Zhi-Hong; Gu Guo-Dong; Dun Shao-Bo; Yin Jia-Yun; Han Ting-Ting; Cai Shu-Jun; Lin Zhao-Jun

2014-01-01

Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current—voltage and capacitance—voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an AlGaN/GaN diode by self-consistently solving Schrödinger's and Poisson's equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostructure results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an AlGaN/GaN diode. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Addition compounds between lanthanide trifluoromethane sulphonates and N,N,N',N' - tetrametilmalonamida (TMMA)

International Nuclear Information System (INIS)

Bellis, V.M. de.

1984-01-01

The preparation and characterization of the addiction compounds between lanthanide trifluoromethanesulphonates with the N,N,N',N' - tetramethylmodomamide (TMMA) are reported. The characterization of the compounds obtained by microanalytical procedures, infrared spectra, conductance measurements, X-ray powder patterns, absorption spectra of the praseodymium, neodymium, holmium and erbium and the emission spectra of the europium and the europium-doped lanthanum and lutetium adducts were made. (M.J.C.) [pt

Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

Directory of Open Access Journals (Sweden)

Rui Sun

2016-06-01

Full Text Available We have developed epitaxial NbN/AlN/NbN tunnel junctions on Si (100 substrates with a TiN buffer layer. A 50-nm-thick (200-oriented TiN thin film was introduced as the buffer layer for epitaxial growth of NbN/AlN/NbN trilayers on Si substrates. The fabricated NbN/AlN/NbN junctions demonstrated excellent tunneling properties with a high gap voltage of 5.5 mV, a large IcRN product of 3.8 mV, a sharp quasiparticle current rise with a ΔVg of 0.4 mV, and a small subgap leakage current. The junction quality factor Rsg/RN was about 23 for the junction with a Jc of 47 A/cm2 and was about 6 for the junction with a Jc of 3.0 kA/cm2. X-ray diffraction and transmission electron microscopy observations showed that the NbN/AlN/NbN trilayers were grown epitaxially on the (200-orientated TiN buffer layer and had a highly crystalline structure with the (200 orientation.

Preparation, composition, and solid state investigations of TiN, ZrN, NbN, and compounds from the pseudobinary systems NbN-NbC, NbN-TiC, and NbN-TiN

International Nuclear Information System (INIS)

Christensen, A.N.; Fregerslev, S.

1977-01-01

Single crystals of the cubic phases TiN, ZrN, delta-NbN and of compounds from the pseudobinary systems NbN-NbC, NbN-TiC, and NbN-TiN were obtained by zone melting, zone annealing and annealing of the metal carbides in nitrogen gas of 2 MPa. Single crystals of the tetragonal phase gamma-NbN were obtained in a similar way by annealing of niobium. The nitrides are non-stochiometric. TiN was obtained in the composition range TiNsub(0.99) to TiNsub(0.50), ZrN in the range ZrNsub(1.00) to ZrNsub(0.63), and in niobium nitrides were obtained in the composition range NbNsub(0.90) to NbNsub(0.69). The compounds from the pseudobinary systems have up to 35% vacant sites in the nitrogen-carbon sublattice. TiN and ZrN have only vacant sites in the nitrogen sublattice. A correlation is found between the unit cell parameters for titanium nitride and zirconium nitride and the nitrogen-metal ratios. (orig.) [de

PROPUESTA PARA LA FORMULACIÓN E IMPLEMENTACIÓN DE UNA ESTRATEGIA DE INNOVACIÓN EN GRUPOS DE INVESTIGACIÓN. APLICACIÓN EN UN GRUPO DE INVESTIGACIÓN EN AGROINDUSTRIA

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GINA LIA OROZCO-MENDOZA

Full Text Available Este artículo describe los resultados de una investigación cuyo propósito era la formulación y generación de un plan de implementación de una estrategia de innovación mediante la aplicación de la metodología de Melissa Schilling, 2010 para un grupo de investigación en agroindustria de una universidad de la ciudad de Medellín- Colombia. Como resultado, se obtuvo: a la identificación de brechas de innovación y tecnología, la definición de elementos claves para su orientación estratégica, b la clasificación de sus proyectos en derivativos, de plataforma, de ruptura y de avanzada, dentro de la herramienta Mapa de proyectos de I+D+i, c el análisis y establecimiento de formas de colaboración para cada proyecto, d el establecimiento de mecanismos de protección de la innovación y, por último, se aplicaron metodologías para determinar un plan de implementación de la estrategia de innovación tales como: herramientas para la generación de nuevos servicios y productos, elección de formas de organización de sus equipos de proyectos y la identificación de parámetros de desempeño de curvas en S para analizar y comprender la difusión de futuras innovaciones. Los resultados de éste proyecto permitieron al grupo generar un plan estratégico coherente con sus capacidades.

Gas chromatography-mass spectrometry analysis of di-n-octyl disulfide in a straight oil metalworking fluid: application of differential permeation and Box-Cox transformation.

Science.gov (United States)

Xu, Wenhai; Que Hee, Shane S

2006-01-06

The aim of this study was to identify and quantify an unknown peak in the chromatogram of a very complex mixture, a straight oil metalworking fluid (MWF). The fraction that permeated through a thin nitrile polymer membrane had less mineral oil background than the original MWF did at the retention time of the unknown peak, thus facilitating identification by total ion current (TIC) gas chromatography-mass spectrometry (GC-MS). The peak proved to be di-n-octyl disulfide (DOD) through retention time and mass spectral comparisons. Quantitation of DOD was by extracted ion chromatogram analysis of the DOD molecular ion (mass-to-charge ratio (m/z) 290), and of the m/z 71 ion for the internal standard, n-triacontane. Linear models of the area ratio (y) of these two ions versus DOD concentration showed a systematic negative bias at low concentrations, a common occurrence in analysis. The linear model of y(0.8) (from Box-Cox power transformation) versus DOD concentration showed negligible bias from the lowest measured standard of 1.51 mg/L to the highest concentration tested at 75.5 mg/L. The intercept did not differ statistically from zero. The concentration of DOD in the MWF was then calculated to be 0.398+/-0.034% (w/w) by the internal standard method, and 0.387+/-0.036% (w/w) by the method of standard additions. These two results were not significantly different at p Box-Cox transformation is therefore recommended when the data for standards are non-linear.

Barrier height and interface effect of Pt-n-GaN and Pd-n-GaN Schottky diodes

International Nuclear Information System (INIS)

Khan, M.R.H.; Saha, S.L.; Sawaki, N.

1999-01-01

Schottky barriers on n-type GaN films by Pt and Pd are fabricated and characterized. A thin Pt or Pd layer is deposited on n-GaN layers to form Schottky contacts in a vacuum below 1x10/sup -6/ Torr. The area of all diodes is 3.46 x 10-4 cm/sup 2/. Several samples of Pt-n GaN and Pd-n GaN were studied. The ideality factor of Pt-n-GaN diode is 1.26 and of Pd-n-GaN is 1.17. The breakdown voltage of Pt-n-GaN and Pd-n-GaN diodes is 21 V and 26 V respectively. In both the cases the leakage current varies between 1x10-9 A and 5x 10-9 A. The Schottky barrier heights (phi/sub B/ ) of Pt-GaN diode is been determined to be 1.02 eV by current voltage (I-V) and 1.07 eV by capacitance (C-V) measurements Also, phi/sub B/ of Pd-GaN diode is determined to be 0.91 eV by I-V and 0.98 eV, by C-V measurements. The departure of the values of the ideality factor is considered to be due to spatial inhomogeneities at the meal semiconductor interface. The difference in the values of phi/sub B/ determined by I-V and C-V measurements is attributed to the deformation of the spatial barrier distribution. (author)

INCLUSIÓN SOCIAL DE LA POBLACIÓN CON LIMITACIÓN AUDITIVA EN LA EDUCACIÓN SUPERIOR COLOMBIANA

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Daniel Francisco Ochoa Morón

2017-07-01

Full Text Available El presente artículo contiene políticas y conceptos, con el fin de generar reflexión y debate que conlleven a gestar propuestas y soluciones entorno a la problemática de inclusión educativa de las poblaciones en situación de discapacidad. Inicialmente, se realiza la descripción los derechos que definen a la educación como una institución de formación imprescindible y un estudio documental de conceptos establecidos por distintos autores. Posteriormente, se expone la actual problemática de inclusión educativa de las poblaciones en situación de discapacidad desde un aspecto cualitativo, centrando principal atención en los procesos de acceso, permanecía y promoción de Sordos en el sistema educativo de Nivel Superior Colombiano; de igual forma se citan algunas políticas establecidas y llevadas a cabo por diferentes instituciones de Educación Superior en Colombia, en aras de erigir soluciones al problema en debate. A modo de resultado, se propone la construcción de un modelo de inclusión educativa para Sordos, haciendo énfasis en la proyección laboral de los individuos como fin último de su inclusión en la sociedad.

40 CFR 721.10055 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts.

Science.gov (United States)

2010-07-01

...-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts. 721.10055 Section 721.10055 Protection of...-amino-N-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts. (a) Chemical substance and...-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts (PMN P-03-46; CAS No. 136504-87-5) is subject to...

N-barN interaction theoretical models

International Nuclear Information System (INIS)

Loiseau, B.

1991-12-01

In the framework of antinucleon-nucleon interaction theoretical models, our present understanding on the N-barN interaction is discussed, either from quark- or/and meson- and baryon-degrees of freedom, by considering the N-barN annihilation into mesons and the N-barN elastic and charge-exchange scattering. (author) 52 refs., 11 figs., 2 tabs

Phase Diagrams of the n-Decane- n-Hexadecane-Cyclododecane, n-Decane-Cyclododecane, and n-Hexadecane-Cyclododecane Systems

Science.gov (United States)

Shamitov, A. A.; Garkushin, I. K.; Kolyado, A. V.; Petrov, E. P.

2018-02-01

The n-decane- n-hexadecane-cyclododecane, n-decane-cyclododecane, and n-hexadecane-cyclododecane systems are studied by means of low-temperature differential thermal analysis using a differential scanning heat flow calorimeter. It is noted that all studied systems belong to the eutectic type. It is concluded that in the n-decane- n-hexadecane-cyclododecane system, the eutectic composition contains 85.0 wt % n-C10H22, 4.0 wt % n-C16H34, and 11.0 wt % C12H24. It has a melting point of -35.0°C.

Ternary Mixtures of N-Docosane, N-Tricosane and N-Tetracosane Mélanges ternaires de n-docosane, n-tricosane et n-tétracosane

Directory of Open Access Journals (Sweden)

Nouar H.

2006-11-01

Full Text Available Binary phase diagrams of the systems: n-docosane: n-tricosane (C22H46 : C23H48, n-tricosane: n-tetracosane (C23H48: C24H50 and n-docosane: n-tetracosane (C22H46: C24H50 have been established by means of structural and differential scanning calorimetry analyses. On the basis of these results and of X-ray examination of forty one ternary mixtures, it is proposed the ternary phase diagram (C22H46: C23H48: C24H50 at room temperature. This work has indicated the existence of limited terminal solid solutions near the three pure n-alkanes and three domains of orthorhombic intermediate phases (noted ß' 1, ß'' 1, ß' 2 identical to those observed in the binary systems. X-ray experiments have showed that the phases ß' 1, ß'' 2 situated on the both sides of the middle intermediate phase ß' 1, are isostructural as in the binary systems. Les diagrammes de phases des systèmes binaires : n-docosane : n-tricosane (C22H46 : C23H48, n-tricosane : n-tétracosane (C23H48 : C24H50 et n-docosane : n-tétracosane (C22H46 : C24H50 ont été établis à partir d'analyses thermiques différentielles (ATD et structurales. Sur la base de ces résultats, ainsi que de l'examen aux rayons X de 41 mélanges ternaires, le diagramme de phases du ternaire (C22H46 : C23H48 : C24H50 à température ambiante est proposé. Ce travail a indiqué l'existence de domaines limités de solutions solides au voisinage des trois n-alcanes purs, ainsi que de trois régions de phases intermédiaires orthorhombiques (notées ß' 1, ß 1, ß' 2 identiques à celles observées avec les systèmes binaires. Les analyses aux rayons X ont montré que les phases ß' 1 et ß' 2 situées de part et d'autre de la phase médiane intermédiaire ß1 sont isostructurales, tout comme dans le cas des systèmes binaires.

Thermal stability of TaN Schottky contacts on n-GaN

Energy Technology Data Exchange (ETDEWEB)

Hayes, J.R.; Kim, D-W.; Meidia, H.; Mahajan, S

2003-02-07

The thermal stability and electrical characteristics of tantalum-nitrogen alloy Schottky contacts on n-GaN were investigated. Non-stoichiometric {delta}-phase (40 atomic percent nitrogen) tantalum nitride contacts exhibited good electrical properties up to an annealing temperature of 600 deg. C. However, they degrade rapidly above this temperature due to outward diffusion of Ga and presumably nitrogen into the {delta}-phase tantalum nitride. It is surmised that excess Ta reacts with N at the GaN surface, freeing Ga which then diffuses into the TaN layer. Stoichiometric TaN Schottky contacts were stable at temperatures as high as 800 deg. C and had far superior electrical performance. This stems from the thermodynamic stability of the stoichiometric TaN/GaN interface. {delta}-phase TaN had I-V and C-V barrier heights of 0.55 eV and 0.8 eV respectively. On the other hand, TaN had an I-V barrier height near 0.7 eV and a C-V barrier height near 1.2 eV. The ideality factors for both {delta}-phase TaN and TaN were above 1.8 at all annealing temperatures, suggesting tunneling contributes significantly to current transport.

Iodide, azide, and cyanide complexes of (N,C), (N,N), and (N,O) metallacycles of tetra- and pentavalent uranium

International Nuclear Information System (INIS)

Benaud, Olivier; Berthet, Jean-Claude; Thuery, Pierre; Ephritikhine, Michel

2011-01-01

In contrast to the neutral macrocycle [UN* 2 (N,C)] (1) [N* = N(SiMe 3 ) 3 ; N,C = CH 2 SiMe 2 N-(SiMe 3 )] which was quite inert toward I 2 , the anionic bismetallacycle [NaUN*(N,C) 2 ] (2) was readily transformed into the enlarged monometallacycle [UN*(N,N)I] (4) [N,N = (Me 3 Si)NSiMe 2 CH 2 CH 2 SiMe 2 N(SiMe 3 )] resulting from C-C coupling of the two CH 2 groups, and [NaUN*(N,O) 2 ] (3) [N,O = OC(=CH 2 )SiMe 2 N(SiMe 3 )], which is devoid of any U-C bond, was oxidized into the UV bismetallacycle [Na{UN*(N,O) 2 }2(μ-I)] (5). Sodium amalgam reduction of 4 gave the U(III) compound [UN*(N,N)] (6). Addition of MN 3 or MCN to the (N,C), (N,N), and (N,O) metallacycles 1, 4, and 5 led to the formation of the anionic azide or cyanide derivatives M[UN* 2 (N,C)(N 3 )] [M = Na, 7a or Na(15-crown-5), 7b], M[UN* 2 (N,C)(CN)] [M = NEt 4 , 8a or Na(15-crown-5), 8b or K(18-crown-6), 8c], M[UN*(N,N)(N 3 ) 2 ] [M = Na, 9a or Na(THF)4, 9b], [NEt 4 ][UN*(N,N)(CN) 2 ] (10), M[UN*(N,O) 2 (N 3 )] [M = Na, 11a or Na(15-crown-5), 11b], M[UN*(N,O) 2 (CN)] [M = NEt 4 , 12a or Na(15-crown-5), 12b]. In the presence of excess iodine in THF, the cyanide 12a was converted back into the iodide 5, while the azide 11a was transformed into the neutral UV complex [U(N{SiMe 3 }-SiMe 2 C{CHI}O) 2 I(THF)] (13). The X-ray crystal structures of 4, 7b, 8a-c, 9b, 10, 12b, and 13 were determined. (authors)

Growth of high quality GaN epilayer on AlInN/GaN/AlInN/GaN multilayer buffer and its device characteristics

International Nuclear Information System (INIS)

Lee, Suk-Hun; Lee, Hyun-Hwi; Jung, Jong-Jae; Moon, Young-Bu; Kim, Tae Hoon; Baek, Jong Hyeob; Yu, Young Moon

2004-01-01

The role of AlInN 1st /GaN/AlInN 2nd /GaN multi-layer buffer (MLB) on the growth of the high quality GaN epilayers was demonstrated by atomic force microscope (AFM), X-ray diffraction (XRD), photoluminescence, and Hall measurement. The surface morphology and crystalline quality of GaN epilayers were considerably dependent on AlInN layers thicknesses rather than those of GaN inter layers. With optimal thickness of 2 nd AlInN layer, the pit density of GaN epilayers was substantially reduced. Also, the RMS roughness of the well ordered terraces generated on the GaN surface was 1.8 A at 5 x 5 μm 2 . The omega-rocking width of GaN(0002) Bragg peak and Hall mobility of GaN epilayers grown on AlInN 1st /GaN/AlInN 2nd /GaN MLB were 190 arcsec and 500 cm 2 /Vs, while those values of GaN epilayers on single GaN buffer layer were 250 arcsec and 250 cm 2 /Vs, respectively. Especially, the light output power and operating voltage of the fabricated light emitting diodes with this new buffer layer was about 5 mW and 3.1 V (dominant luminous wavelength ∝460 nm) at 20 mA, respectively. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

239Pu(n, 2n) and 241Pu(n, 2n) surrogate cross section measurements using NeutronSTARS

Energy Technology Data Exchange (ETDEWEB)

Burke, J. T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Alan, B. S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Akindele, O. A. [Univ. of California, Berkeley, CA (United States); Casperson, R. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hughes, R. O. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Koglin, J. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tamashiro, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Oregon State Univ., Corvallis, OR (United States); Kolos, K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Norman, E. B. [Univ. of California, Berkeley, CA (United States); Saastamoinen, A. [Univ. of California, Los Angeles, CA (United States); Padilla, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Los Angeles, CA (United States); Fisher, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-12-08

The goal of this project was to develop a new approach to measuring (n,2n) reactions for isotopes of interest. We set out to measure the ²³⁹Pu(n,2n) and ²⁴¹Pu(n,2n) cross sections by directly detecting the 2n neutrons that are emitted. With the goal of improving the ²³⁹Pu(n,2n) cross section and to measure the ²⁴¹Pu(n,2n) cross section for the first time. To that end, we have constructed a new neutron-charged-particle detector array called NeutronSTARS. It has been described extensively in Casperson et al. [1] and in Akindele et al. [2]. We have used this new neutron-charged-particle array to measure the ²⁴¹Pu and ²³⁹Pu fission neutron multiplicity as a function of equivalent incident-neutron energy from 100 keV to 20 MeV. We have made a preliminary determination of the ²³⁹Pu(n,2n) and ²⁴¹Pu(n,2n) cross sections from the surrogate ²⁴⁰Pu(α,α’2n) and ²⁴²Pu(α,α’2n) reactions respectively. The experimental approach, detector array, data analysis, and results to date are summarized in the following sections.

Polarization-engineered GaN/InGaN/GaN tunnel diodes

International Nuclear Information System (INIS)

Krishnamoorthy, Sriram; Nath, Digbijoy N.; Akyol, Fatih; Park, Pil Sung; Esposto, Michele; Rajan, Siddharth

2010-01-01

We report on the design and demonstration of polarization-engineered GaN/InGaN/GaN tunnel junction diodes with high current density and low tunneling turn-on voltage. Wentzel-Kramers-Brillouin calculations were used to model and design tunnel junctions with narrow band gap InGaN-based barrier layers. N-polar p-GaN/In 0.33 Ga 0.67 N/n-GaN heterostructure tunnel diodes were grown using molecular beam epitaxy. Efficient interband tunneling was achieved close to zero bias with a high current density of 118 A/cm 2 at a reverse bias of 1 V, reaching a maximum current density up to 9.2 kA/cm 2 . These results represent the highest current density reported in III-nitride tunnel junctions and demonstrate the potential of III-nitride tunnel devices for a broad range of optoelectronic and electronic applications.

[ital N][sub [ital p]N[ital n

Energy Technology Data Exchange (ETDEWEB)

Saha, M.; Sen, S. (Saha Institute of Nuclear Physics, Calcutta 700 064 (India))

1993-02-01

It is shown that the well known phenomenon of the saturation in the [ital B]([ital E]2;0[sub 1][sup +][r arrow]2[sub 1][sup +]), as well as the [ital E][sub 21][sup +] values near midshell in the even rare-earth and actinide nuclei, can be reproduced in the [ital N][sub [ital p]N[ital n

Iniciación a número natural en Educación Infantil

OpenAIRE

Muñoz Millán, Vanesa

2013-01-01

En este Trabajo de Fin de Grado (TFG) hemos querido mostrar la evolución en la adquisición del número natural en el niño de Educación Infantil, haciendo una recopilación de modelos de aprendizaje para escoger cuál sería el más adecuado para trabajar en estas primeras edades. Posteriormente, ofrecemos una propuesta con ejemplos de actividades para trabajar la iniciación a los números naturales y algunas pinceladas sobre la iniciación a la posterior representación simbólica en niños de 3-4 años...

Re-evaluation of microscopic and integral cross-section data for important dosimetry reactions. Re-evaluation of the excitation functions for the 24Mg(n,p)24Na, 32S(n,p)32P, 60Ni(n,p)60m+gCo, 63Cu(n,2n)62Cu, 65Cu(n,2n)64Cu, 64Zn(n,p)64Cu, 115In(n,2n)114mIn, 127I(n,2n)126I, 197Au(n,2n)196Au and 199Hg(n,n')199mHg reactions

International Nuclear Information System (INIS)

Zolotarev, K.I.

2008-08-01

Re-evaluations of cross sections and their associated covariance matrices have been carried out for ten dosimetry reactions: - excitation functions for the 63 Cu(n,2n) 62 Cu, 65 Cu(n,2n) 64 Cu, 64 Zn(n,p) 64 Cu, 115 In(n,2n) 114m In and 199 Hg(n,n') 199m Hg reactions were re-evaluated over the neutron energy range from threshold to 20 MeV; - excitation functions for the 24 Mg(n,p) 24 Na, 32 S(n,p) 32 P and 60 Ni(n,p) 60m+g Co were reevaluated in the energy range from threshold to 21 MeV; - excitation functions for the 127 I(n,2n) 126 I and 197 Au(n,2n) 196 Au reactions were reevaluated in the energy range from threshold to 32 and 40 MeV, respectively. Benchmark calculations performed for 235 U thermal fission and 252 Cf spontaneous fission neutron spectra show that the integral cross sections derived from the newly evaluated excitation functions exhibit improved agreement with related experimental data when compared with the equivalent data from the IRDF-2002 library. (author)

ADMINISTRACIÓN DE LA PRODUCCIÓN

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Ana Urquiaga Rodríguez

2004-11-01

Full Text Available

Este artículo presenta los resultados de una investigación descriptiva realizada durante el año 2003, al 57 % de las empresas de más de diez personas ocupadas en la agrupación 381 de la ciudad de Manizales. El objetivo de dicha investigación es establecer algunas de las principales características de la administración de la producción y los inventarios en estas empresas, siguiendo el enfoque jerárquico de la planificación, programación y control de la producción.

Comparison of trap characteristics between AlGaN/GaN and AlGaN/InGaN/GaN heterostructure by frequency dependent conductance measurement

International Nuclear Information System (INIS)

Chakraborty, Apurba; Biswas, Dhrubes

2015-01-01

Frequency dependent conductance measurement is carried out to observe the trapping effect in AlGaN/InGaN/GaN double heterostructure and compared that with conventional AlGaN/GaN single heterostructure. It is found that the AlGaN/InGaN/GaN diode structure does not show any trapping effect, whereas single heterostructure AlGaN/GaN diode suffers from two kinds of trap energy states in near depletion to higher negative voltage bias region. This conductance behaviour of AlGaN/InGaN/GaN heterostructure is owing to more Fermi energy level shift from trap energy states at AlGaN/InGaN junction compare to single AlGaN/GaN heterostructure and eliminates the trapping effects. Analysis yielded interface trap energy state in AlGaN/GaN is to be with time constant of (33.8–76.5) μs and trap density of (2.38–0.656) × 10 12  eV −1  cm −2 in −3.2 to −4.8 V bias region, whereas for AlGaN/InGaN/GaN structure no interface energy states are found and the extracted surface trap energy concentrations and time constants are (5.87–4.39) ×10 10  eV −1  cm −2 and (17.8–11.3) μs, respectively, in bias range of −0.8–0.0 V

Relativistic scalar-vector models of the N-N and N-nuclear interactions

International Nuclear Information System (INIS)

Green, A.E.S.

1985-01-01

This paper for the Proceedings of Conference an Anti-Nucleon and Nucleon-Nucleus Interactions summarizes work by the principal investigator and his collaborators on the nucleon-nucleon (N-N) and nucleon-nuclear (N-eta) interactions. It draws heavily on a paper presented at the Many Body Conference in Rome in 1972 but also includes a brief review of our phenomenological N-eta interaction studies. We first summarize our 48-49 generalized scalar-vector meson field theory model of the N-N interactions. This is followed by a brief description of our phenomenological work in the 50's on the N-eta interaction sponsored by the Atomic Energy Commission (the present DOE). This work finally led to strong velocity dependent potentials with spin orbit and isospin terms for shell and optical model applications. This is followed by a section on the Emergence of One-Boson Exchange Models describing developments in the 60's of quantitative generalized one boson exchange potentials (GOBEP) including our purely relativistic N-N analyses. Then follows a section on the application of this meson field model to the N-eta interaction, in particular to spherical closed shell nuclei. This work was sponsored by AFOSR but funding was halted with the Mansfield amendment. We conclude with a discussion of subsequent collateral work by former colleagues and by others who have converged upon scalar-vector relativistic models of N-N, antiN-N, N-eta and antiN-eta interactions and some lessons learned from this extended endeavor. 61 refs

Bipolar characteristics of AlGaN/AlN/GaN/AlGaN double heterojunction structure with AlGaN as buffer layer

International Nuclear Information System (INIS)

Peng, Enchao; Wang, Xiaoliang; Xiao, Hongling; Wang, Cuimei; Yin, Haibo; Chen, Hong; Feng, Chun; Jiang, Lijuan; Hou, Xun; Wang, Zhanguo

2013-01-01

Highlights: •2DEG and 2DHG coexist in the AlGaN/AlN/GaN/AlGaN DH-structure. •The sheet densities of 2DEG and 2DHG vary with buffer Al content and GaN thickness. •The conditions for the disappearance of 2DHG are discussed. •Increasing buffer Al content provides better electron confinement. •Dislocation scattering is reduced in the DH-structure. -- Abstract: This is a theoretical study of AlGaN/AlN/GaN/AlGaN double heterojunction (DH) structure with AlGaN as buffer layer. Our calculation shows that as the buffer Al content increases, though two-dimensional electron gas (2DEG) sheet density decreases, the channel back-barrier caused by polarization-induced electric field in GaN provides better electron confinement. And under certain conditions the DH-structure shows bipolar characteristics, with an additional two-dimensional hole gas (2DHG) formed at GaN/AlGaN interface. The influence of the buffer Al content and GaN channel thickness on the 2DEG and 2DHG sheet densities are investigated, and the conditions for the disappearance of 2DHG are discussed. Also, the mobility inhibited by dislocation scattering is enhanced in DH-structure due to the enhancement of screening effect of the 2DEG

Gate length scaling effect on high-electron mobility transistors devices using AlGaN/GaN and AlInN/AlN/GaN heterostructures.

Science.gov (United States)

Liao, S Y; Lu, C C; Chang, T; Huang, C F; Cheng, C H; Chang, L B

2014-08-01

Compared to AlGaN/GaN HEMT with 0.15 μm T-gate length, the AlInN/AlN/GaN one exhibits much higher current density and transconductance of 1558 mA/mm at Vd = 2 V and 330 mS/mm, respectively. The high extrinsic ft and fmax of 82 GHz and 70 GHz are extracted from AlInN/AlN/GaN HEMT. Besides, we find that the transconductance roll-off is significant in AlGaN/GaN, but largely improved in AlInN/AlN/GaN HEMT, suggesting that the high carrier density and lattice-matched epitaxial heterostructure is important to reach both large RF output power and high operation frequency, especially for an aggressively gate length scaling.

CALIDAD, AUTOEVALUACIÓN Y ACREDITACIÓN UNIVERSITARIA

OpenAIRE

Maraví, Doris

2014-01-01

La Comisión Nacional de Rectores para la Acreditación Universitaria promueve la cultura de autoevaluación y la mejora continua de la institución, determina los lineamientos y estándares de autoevaluación con fines de acreditación, asesora y apoya a las universidades en sus procesos de autoevaluación, y promueve la capacitación de evaluadores La Comisión Nacional de Rectores para la Acreditación Universitaria inicia sus labores en abril de 2002, cumple las siguientes funciones: • Apoya a la Of...

Evaluación de la dimensión vertical de oclusión, perfil blando y maloclusión en dentición mixta

Directory of Open Access Journals (Sweden)

María Laura Hermida Bruno

2016-01-01

Full Text Available Objetivo: Verificar la relación entre dimensión vertical de oclusión, perfil blando y maloclusión en dentición mixta. Métodos: Se realizó un estudio observacional, transversal, analítico. El protocolo fue aprobado por el Comité de Ética de la Universidad Católica del Uruguay. Participaron 79 niños entre 6 y 12 años, con una media de edad de 8,66 ±1,41, alumnos del Colegio San José del Cerro, Montevideo, Uruguay. El 57,5% (n=45 correspondió al sexo masculino y 42,5% (n=34 al sexo femenino. Un observador calibrado (CCI=0,76 realizó un examen clínico y físico, medición de la dimensión vertical de oclusión (DVO y registró la clasificación de Angle. Se tomaron fotografías de perfil y se realizó el análisis de convexidad facial de Legan y Burstone (CCI=0,84. Se aplicó el test comparativo ANOVA, el de comparaciones múltiples de TUKEY y el test de Pearson (p ≤ 0,05. Resultados: La media de la DVO fue 59,16 ± 4,02. El 56,3% (n=45 fueron clasificados como Clase I de Angle; 22,5% (n=18 Clase II y 21,3% (n=17 Clase III. No hubo diferencia significativa en la media de DVO entre ambos sexos (p=0,217 ni entre los diferentes tipos de oclusión (p=0,568. La media del ángulo de la convexidad facial fue 14,57°± 3,80. Se encontró asociación estadísticamente significativa entre perfil convexo/relación molar clase II (p=0,003317, perfil recto/relación molar clase I (p=0,015887, perfil recto/relación molar clase III (p=0,003268. Conclusión: En la muestra estudiada no se encontró relación entre DVO y maloclusión, pero sí se encontró entre perfil blando y maloclusión.

LA FORMACIÓN INTEGRAL: UNA APROXIMACIÓN DESDE LA INVESTIGACIÓN

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Ana Elsy Díaz Monsalve

2013-12-01

Full Text Available En este artículo se exponen los resultados de la investigación en la que se indagó acerca de las representaciones que tienen los docentes de inglés de educación básica primaria, en algunas instituciones públicas de Medellín, Colombia, acerca del ideal de formación integral. A partir de un enfoque de investigación cualitativa, se implementó una encuesta con preguntas abiertas aplicadas a diecinueve docentes y, posteriormente, se realizó una entrevista a profundidad a cinco de los encuestados. La información recogida fue sometida a la técnica del análisis crítico del discurso propuesta por Teun Van Dijk (2003. Los principales hallazgos permiten reconocer que dichas representaciones reflejan cinco líneas temáticas principales: (1 Formación integral de un ser humano multidimensional; (2 Formación de un ser humano valioso; (3 Formación integral, aprendizaje de una lengua extranjera y acercamiento a diferentes culturas; (4 Formación integral, enseñanza de las lenguas extranjeras y personas autónomas; (5 Formación integral y competencia comunicativa en lengua extranjera. Se encontró que las representaciones de los docentes, sobre la formación integral, poseen un marcado énfasis ético -moral, valores y normas- y que esta, analizada desde la enseñanza de la lengua extranjera, no debe reducirse al uso de estructuras lingüísticas básicas, en contextos de comunicación inmediatos y cotidianos.

COMUNICACIÓN Y CONVERSACIÓN. UNA APROXIMACIÓN A SU RE-DEFINICIÓN DESDE LA INFANCIA TEMPRANA

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Teresita Virgen García Espinosa

2016-04-01

Full Text Available En el artículo se analiza la conversación desde la infancia temprana, con énfasis en las peculiaridades que distinguen su desarrollo en el tercer año de vida, de otras etapas de la ontogenia en la comunicación, que no siempre son tenidas en cuenta para la estimulación de su proceso educativo, a partir de lo cual se arriba a una definición operativa del término comunicación y la reconceptualización de la categoría conversación.

Investigación en Educación

Directory of Open Access Journals (Sweden)

Lígia Inés Moncada

2006-10-01

Full Text Available Se hace un análisis del proceso de investigación como estrategia didáctica y como método científico para la producción de conocimiento, a su vez como pilar para el desarrollo del profesor tanto en el ámbito de la disciplina o profesión como en su quehacer como educador. Se argumenta sobre la importancia de la formación docente y la renovación del modelo pedagógico tradicional. Se presentan diferentes estrategias de aprendizaje y enseñanza en la búsqueda de la creación de una cultura de investigación: ensayo-error, razonamiento lógico, repetición de conocimientos tradicionales, investigación, líneas o áreas de investigación, líneas de profundización, seminario investigativo. Finalmente, se describen las posibilidades de la investigación educativa con el enfoque cuantitativo y cualitativo, la investigación acción participativa, la etnografía y la fenomenología.

Improved InGaN/GaN quantum wells on treated GaN template with a Ga-rich GaN interlayer

International Nuclear Information System (INIS)

Fang, Zhilai; Shen, Xiyang; Wu, Zhengyuan; Zhang, Tong-Yi

2015-01-01

Treated GaN template was achieved by in situ droplet epitaxy of a Ga-rich GaN interlayer on the conventional GaN template. InGaN/GaN quantum wells (QWs) were grown on the conventional and treated GaN templates under the same growth conditions and then comprehensively characterized. The indium homogeneity in the InGaN layers and the interface sharpness between InGaN and GaN layers of the InGaN/GaN QWs on the treated GaN template were significantly improved. The emission intensity from the InGaN/GaN QWs on the treated GaN template was enhanced by 20% than that on the conventional GaN template, which was attributed to the strain reduction and the improvement in crystalline quality. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

"Zhizneopisanie" astronomia N. N. Pavlova, im samim napisannoe %t Astronomer N. N. Pavlov's autobiography

Science.gov (United States)

Zhukov, V. Yu.

This document called by the author "the life story" is written for the human resources department. It is a document intended for the official departmental purposes. At the same time there is something facinating about this documentary testimony about the epoch and the man. This short autobiography describes the early years of the Pulkovo astronomer N. N. Pavlov that fell on hard times of the Civil War. In the years between the World War I and the World War II he was awarded Mendeleyev Prize. He defended his doctorate dissertation after the evacuation from Leningrad. He was one fo the first Pulkovo astronomers to return to Leningrad in order to start reconstruction of the observatory that had been completely ruined during the war. Astronomer N. N. Pavlov renewed the Time Service in the city. N. N. Pavlov was a successful scientist and an outstanding person, all his life was devoted to science.

Self-consistent simulation of carrier confinement characteristics in (AlyGa1−yN/AlN)SLs/GaN/(InxGa1−xN/GaN)MQW/GaN heterostructures

International Nuclear Information System (INIS)

Ding Jieqin; Wang Xiaoliang; Xiao Hongling; Wang Cuimei; Yin Haibo; Chen Hong; Feng Chun; Jiang Lijuan

2012-01-01

Highlights: ► We present calculations of carrier confinement characteristics. ► An optimization of In x Ga 1−x N/GaN multiquantum-well (MQW) was made. ► 2DEG sheet carrier density in designed heterostructure is greatly increased. ► Interface roughness and alloy disorder scattering reduced. ► Carrier mobility will be improved in designed heterostructure. - Abstract: We present calculations of carrier confinement characteristics in (Al y Ga 1−y N/AlN)SLs/GaN/(In x Ga 1−x N/GaN)MQW/GaN heterojunction structure in the presence of spontaneous and piezoelectrically induced polarization effects. The calculations were made using a self-consistent solution of the Schrödinger, Poisson, potential and charge balance equations. An optimization of In x Ga 1−x N/GaN multiquantum-well (MQW) was made firstly including thickness of GaN channel, InGaN, and indium composition of In x Ga 1−x N in order to increase carrier density and mobility, and the influence of pairs of AlGaN/AlN superlattices (SLs) and InGaN/GaN MQWs on structure was discussed. Theoretical calculations clearly indicate that the two-dimensional electron gas (2DEG) sheet carrier density in designed heterostructure is greatly increased due to the enhancing of carrier confinement compared to those in conventional AlGaN/GaN one at the similar Al composition. Furthermore, the calculated carrier distribution shows that carrier mobility will be improved by reducing interface roughness and alloy disorder scattering in designed heterostructure.

N/sub p/.N/sub n/ systematics and their implications

International Nuclear Information System (INIS)

Casten, R.F.

1985-01-01

A substantial simplification of the systematics in nuclear phase transition regions is obtained if the data are plotted against the product, N/sub p/.N/sub n/, of the number of valence protons and neutrons instead of against N, Z, or A as is usually done. Such a scheme leads to a unified view of nuclear transition regions and to a simplified scheme for collective model calculations. 7 refs., 5 figs

Growth and properties of InN, InGaN, and InN/InGaN quantum wells

Energy Technology Data Exchange (ETDEWEB)

Naoi, H.; Na, H. [Center for Promotion of the COE Program, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577 (Japan); Kurouchi, M.; Muto, D.; Takado, S.; Araki, T.; Nanishi, Y. [Dept. of Photonics, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577 (Japan); Miyajima, T. [Optoelectronics Laboratory, Materials Laboratories, Sony Corporation, 4-14-1 Asahi, Atsugi, Kanagawa 243-0014 (Japan)

2006-01-01

This paper describes our recent progress on InN, In-rich In{sub x}Ga{sub 1-x}N, and InN/In{sub x}Ga{sub 1-x}N quantum wells (QWs) grown by radio-frequency plasma-assisted molecular-beam epitaxy. Among the essential growth sequences to obtain high-quality InN, the nitridation process of (0001) sapphire substrates was reexamined. It was found that the lower-temperature and longer-period nitridation-process was very effective in improving crystalline quality of InN films. We succeeded in dramatically improving c -axis orientation of InN films without deteriorating their a -axis orientation by nitridating the substrates at a relatively low-temperature of 300 C for a relatively long period of 2 h. The full widths at half maximum (FWHMs) of (0002) X-ray rocking curves as narrow as 1 arcmin were obtained from only 400 nm thick InN films. These FWHMs are the narrowest value ever reported for InN and moreover approximately a twentieth part of the values obtained from our conventional InN films with a similar thickness, which were grown via the conventional nitridation process carried out at 550 C for 1 h. Furthermore interference fringes in X-ray diffraction ({omega}-2{theta} scan) were observed from these improved InN films. These high crystalline quality InN layers have been employed as a template for the growth of In-rich In{sub x}Ga{sub 1-x}N layers (0.70{<=}x{<=}0.94). The resultant In{sub x}Ga{sub 1-x}N layers have shown dramatic improvements in not only the surface morphology but also both the a- and c-axis orientations. By employing In{sub 0.8}Ga{sub 0.2}N layers of improved quality as the bottom barrier layer, InN/In{sub 0.8}Ga{sub 0.2}N multiple quantum well (MQW) and single quantum well (SQW) structures with different well widths were fabricated. Clear satellite peaks of X-ray diffraction were observed from these MQW structures. Both of these SQW and MQW structures have exhibited a blue shift of the photoluminescence peak energy with decreasing well width

40 CFR 721.10193 - 1-Butanaminium, N-(3-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 1-Butanaminium, N-(3-aminopropyl)-N...-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts. (a) Chemical substance and...-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts (PMN P-06-263, Chemical B; CAS No...

Azobenzene Pd(II) complexes with N^N- and N^O-type ligands

Science.gov (United States)

Nikolaeva, M. V.; Puzyk, An. M.; Puzyk, M. V.

2017-05-01

Methods of synthesis of cyclometalated azobenzene palladium(II) complexes of [Pd(N^N)Azb]ClO4 and [Pd(N^O)Azb]ClO4 types (where Azb- is the deprotonated form of azobenzene; N^N is 2NH3, ethylenediamine, or 2,2'-bipyridine; and (N^O)- is the deprotonated form of amino acid (glycine, α-alanine, β-alanine, tyrosine, or tryptophan)) are developed. The electronic absorption and the electrochemical properties of these complexes are studied.

La investigación acción y la comunicación en la formación docente

Directory of Open Access Journals (Sweden)

MSc. Ingrid Zumba Vera

2016-04-01

Full Text Available En el artículo se presenta los fundamentos teóricos y prác­ticos a tener en cuenta para la formación del docente des­de la comunicación, utilizando la investigación acción. Los resultados que se presentan se organizaron en torno a un proceso de intervención investigadora, donde los docentes se implicaron de manera directa, y cuyo eje principal fue­ron los procesos de intercambio, reflexión y enriquecimiento profesional. Los resultados obtenidos evidenciaron que es posible conjugar la teoría y la práctica en la formación per­manente del docente y que se puede organizar y desarrollar dicha formación a partir de su propia practica por lo que constituye una aportación a dichos estudios en el panorama de la formación del docente.

Un sistema de indicadores para la medición, evaluación, innovación y participación orientado a la Administración Pública

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César Alfaro

2016-11-01

Full Text Available Durante los últimos años la sociedad está demandando que las Administraciones Públicas trabajen con eficiencia y transparencia y que afronten sus actuaciones con un enfoque de gestión abierto a la evaluación y a la rendición de cuentas. El avance de las nuevas tecnologías posibilita la aparición de novedosos canales de participación ciudadana más dinámicos, abiertos y transparentes. En este artículo presentamos una aproximación a un sistema de indicadores para la medición, evaluación, innovación y participación orientado a la Administración Pública. El sistema está enfocado a un modelo colaborativo que fomente la participación ciudadana y promueva la innovación social.

Comparative analysis of oxidative synthesis of N-alkyl, N,N-dialkyl and N-cykloalkyl-O-isobutyl thioncarbamate

Directory of Open Access Journals (Sweden)

Sovrlić Milica Ž.

2011-01-01

Full Text Available A optimized synthesis of N-alkyl, N,N-dialkyl- and N-cycloalkyl-O-isobutyl thioncarbamates by aminolysis of sodium isobutylxanthogenic acid (NaiBXAc and primary, secondary and cycloalkyl amines was developed at laboratory scale and applied at semi-industrial level. Studies on dependence of N-n-propyl-O-isopropylthiocarbamate yield and purity with respect to reaction parameters: reaction time and molar ratio of n-propylamine and NaiBXAc, were performed. In such way, optimal reaction conditions for synthesis of N-alkyl, N,N-dialkyl- and N-cycloalkyl-O-isobutyl thioncarbamates, by aminolysis of NaiBXAc, were established. Also, comparative results of thioncarbamates synthesis starting from potassium isobutyl xanthate (KiBX and corresponding amines in presence of different oxidants: hydrogen peroxide, sodium hypochlorite and new oxidative agent potassium peroxodisulfate were evaluated. Synthesized compounds have been fully characterized by FTIR, 1H and 13C NMR and MS data, elemental analysis and purity have been determined by gas chromatographic method (GC. According to our knowledge, ten synthesized thioncarbamates are for the first time characterized. Synthesized compounds could be used as selective reagents for flotation of copper and zinc ores. The presented methods offer several benefits, namely, high product yields and purity, simple operation, mild reaction conditions without use of hazardous organic solvents, while some of them could be implemented on industrial scale production.

Enthalpies of solution of N,N,N',N'-tetramethylurea in amides, dimethylsulphoxide, and acetone at 298.15 K

International Nuclear Information System (INIS)

Ivanov, Evgeniy V.; Smirnov, Valeriy I.

2008-01-01

The enthalpies of solution Δ sol H m m were determined for N,N,N',N'-tetramethylurea in formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, and acetone. Measurements were made at 298.15 K and molalities m = (0.004 to 0.031) mol . kg -1 with a precise isoperibol ampoule-type calorimeter. Standard enthalpies of solution Δ sol H m 0 and transfer Δ tr H m 0 from one solvent to another were computed. The enthalpies of solution of the solute in the hydrogen-non-bonding media were found to be endothermic and weak depending on the nature of methylation in a solvent molecule. It was concluded that the solvent proton-donor ability and existing steric hindrances for hydrogen bonding and other intermolecular interactions play the key role in solvation of tetramethylurea

RELACIÓN DE LA INTENCIÓN E IDEACIÓN SUICIDA CON ALGUNAS VARIABLES

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Paola Valderrama

2006-06-01

Full Text Available El objetivo de este estudio fue hallar la relación de la intención e ideación suicida con algunas variables sociodemográficas, las características de la enfermedad, el tratamiento antirretroviral y los aspectos piscoafectivos en personas con el VIH/SIDA que residen en Bogotá (Colombia y pertenecientes a una fundación. Para ello, se tomó una muestra de 75 pacientes con VIH positivo a quienes se evaluó a través de una entrevista semiestructurada y dos instrumentos: el inventario de depresión de Beck (IBD y la escala de Ideación Suicida (SSI. Los resultados mostraron que solo 29 personas tenían ideación suicida y 10 intención suicida: De los 10 solo 2 sujetos tenían intención después del diagnóstico. Se encontró una relación estadística significativa para ideación suicida e intención suicida con edad, estrato socioeconómico, estado civil, orientación sexual, las características de la enfermedad, el tratamiento antirretroviral y los aspectos piscoafectivos.

InN/GaN short-period superlattices as ordered InGaN ternary alloys

International Nuclear Information System (INIS)

Kusakabe, Kazuhide; Imai, Daichi; Wang, Ke; Yoshikawa, Akihiko

2016-01-01

Coherent (InN) 1 /(GaN) n short-period superlattices (SPSs) were successfully grown through dynamic atomic layer epitaxy (D-ALEp) mode by RF-plasma molecular beam epitaxy (MBE), where GaN layer thicknesses n were thinned down to 4 monolayer (ML). After this achievement, we demonstrated quasi-ternary InGaN behavior in their photoluminescence (PL) spectra for the first time. It was found interestingly that GaN layer thickness of n = 4 ML was the criterion both for structural control and continuum-band formation. Although highly lattice-mismatched InN/GaN interfaces easily introduce relaxation in (InN) 1 /(GaN) 4 SPSs during growth depending on the dynamic surface stoichiometry condition, this problem was overcome by precise control/removal of fluid-like residual In/Ga metals on the growth front with in-situ monitoring method. The (InN) 1 /(GaN) n SPSs with n ≥ 7 ML showed a constant PL peak energy around 3.2 eV at 12 K, reflecting discrete electron/hole wavefunctions. On the other hand, the (InN) 1 /(GaN) 4 SPSs indicated the red-shifted PL peak at 2.93 eV at 12 K, which was attributed to the continuum-band state with increasing in the overlap of electrons/hole wavefunctions. This result is concluded that the (InN) 1 /(GaN) 4 SPSs can be considered as ordered InGaN alloys. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Extracting properties of N,N,N'N'-tetraalkyl-2 alkyl propane -1,3 diamides

International Nuclear Information System (INIS)

Nigond, L.

1992-01-01

N,N,N',N'-tetraalkyl -2 alkyl propane -1,3 diamides (RR'NCO) 2 CHR'' are investigated in the aim to separate actinides from nuclear wastes. N,N'-dimethyl N,N'-dibutyl tetradecylmalonamide (DMDBTDMA) was selected. This molecule can extract trivalent actinides in aliphatic diluents. Americium extraction is faster than iron extraction, hydrolytic degradation and solubility in aqueous phase are satisfactory. In non acidic media, diamides form aggregates, the size of which is function of diluent and diamide concentration. Extraction equilibria of HNO 3 , UO 2 2+ , Pu 4+ , Am 3+ and Fe 3+ are investigated.Four complexes are formed with nitric acid: L 2 HNO 3 , LHNO 3 , L 2 (HNO 3 ) 2 and L(HNO 3 ) 3 with L=DMDBTDMA. UO 2 2+ and Pu 4+ extraction takes place via the formation of neutral complexes: LUO 2 (NO 3 ) 2 , LPu(NO 3 ) 4 and L 2 Pu(NO 3 ) 4 for any nitric acid concentration. Am 3+ extraction takes place via the formation of LAm(NO 3 ) 3 and L 2 Am(NO 3 ) 3 for low nitric acid concentration and L x H y Am(NO 3 ) 3+y at higher acidity. Fe 3+ extraction involves anionic complexes L x HFe(NO 3 ) 4 for any acid concentration. In the presence of metallic cations, two kinds of interactions are observed: in the inner sphere of the metal diamide-metal ion complexation and in the outer sphere diamide-metallic complex interaction. The malonamide DMDBTDMA can be used to separate (III), (IV) and (VI) actinides from radioactive wastes

DE ACUMULACIÓN POR DESPOSESIÓN

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Sebastián Gómez Lende

2015-01-01

Full Text Available Omnipresente, la acumulación por desposesión es uno de los elementos centrales del orden global contemporáneo. Observados desde una perspectiva crítica, los usos extractivos del territorio constituyen una de las principales expresiones de ese proceso. A la luz de ese sistema de ideas, este artículo procura demostrar que el modelo sojero actualmente vigente en la Argentina es una de las formas más completas, exhaustivas, actuales y sofisticadas, de acumulación por desposesión en el país. En ese sentido, el artículo analiza el boom de la soja transgénica y sus vínculos con las formas tanto seculares (endeudamiento financiero, concentración de la propiedad rural, usurpación de la tierra y actuales de desposesión (degradación de la naturaleza, despojo del derecho a la salud, pillaje de recursos genéticos efectuadas por los grandes agricultores, el capital financiero, las agroindustrias y las corporaciones biotecnológicas, en detrimento de los pequeños productores, los campesinos, los pueblos aborígenes y la población en general.

EVALUACIÓN DE UN CARBÓN SULFONADO COMO CATALIZADOR EN DESTILACIÓN REACTIVA

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Álvaro Orjuela

2008-03-01

Full Text Available A partir de la sulfonación de un carbón antracítico de origen colombiano, se prepararon pastillas catalíticas con las cuales se empacó una columna de destilación semi-continua,  a la cual se alimentaron ácido acético y etanol, con el fin de evaluar experimentalmente la factibilidad de la destilación reactiva para la producción de acetato de etilo. El empaque-catalizador  se caracterizó mediante la determinación de la capacidad total de intercambio, titulación potenciométrica, área BET. Se realizaron ensayos con tres relaciones ácido/etanol para obtener los valores de conversión, concentración de destilado y fondos. El empaque de carbón sulfonado demostró capacidad tanto catalítica, con conversiones entre 29 y 45%, como de separación.

Modelación y simulación de un pervaporador acoplado a un proceso de sacarificación-fermentación para la producción de etanol

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Jairo Antonio Cubillos-Lobo

2015-09-01

Full Text Available Actualmente, la integración de procesos es considerada una opción viable para reducir costos en la producción de etanol a partir de biomasa. Simulaciones y resultados experimentales han demostrado los beneficios de la integración de las etapas de sacarificación y fermentación y del acoplamiento del proceso de fermentación a la recuperación in-situ de etanol por pervaporación en la producción de bioetanol; sin embargo, no se han publicado estudios de la integración del proceso de sacarificación-fermentación simultánea con membranas de separación, para la remoción insitu de etanol a partir del caldo de fermentación. En este trabajo se aborda esta necesidad, mediante la modelación y simulación de la producción de etanol a partir de almidón de yuca por sacarificación-fermentación simultánea, acopladas a un sistema de remoción in-situ de etanol por pervaporación, con membranas a base de polidimetilsiloxano (PDMS, silicalita y PDMS-Silicalita. La membrana de PDMS se modeló usando el mecanismo de solución-difusión, mientras que para la membrana de silicalita se utilizó el modelo de adsorción-difusión. Para el modelo del proceso de sacarificación-fermentación simultánea (SSF se utilizó una fusión del modelo multicadena (Michaelis–Menten, junto con un modelo tipo Monod. El ajuste del modelo de SSF a los datos experimentales reportados, así como de los modelos de membranas de PDMS y silicalita a los valores reportados en la literatura es bueno: la máxima desviación encontrada es del orden de 3%. El modelo integrado se utilizó para predecir la concentración de etanol en función del tiempo durante la sacarificación-fermentación simultánea.

Metalorganic chemical vapor deposition growth of high-mobility AlGaN/AlN/GaN heterostructures on GaN templates and native GaN substrates

Energy Technology Data Exchange (ETDEWEB)

Chen, Jr-Tai, E-mail: jrche@ifm.liu.se; Hsu, Chih-Wei; Forsberg, Urban; Janzén, Erik [Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE 581 83 Linköping (Sweden)

2015-02-28

Severe surface decomposition of semi-insulating (SI) GaN templates occurred in high-temperature H{sub 2} atmosphere prior to epitaxial growth in a metalorganic chemical vapor deposition system. A two-step heating process with a surface stabilization technique was developed to preserve the GaN template surface. Utilizing the optimized heating process, a high two-dimensional electron gas mobility ∼2000 cm{sup 2}/V·s was obtained in a thin AlGaN/AlN/GaN heterostructure with an only 100-nm-thick GaN spacer layer homoepitaxially grown on the GaN template. This technique was also demonstrated viable for native GaN substrates to stabilize the surface facilitating two-dimensional growth of GaN layers. Very high residual silicon and oxygen concentrations were found up to ∼1 × 10{sup 20 }cm{sup −3} at the interface between the GaN epilayer and the native GaN substrate. Capacitance-voltage measurements confirmed that the residual carbon doping controlled by growth conditions of the GaN epilayer can be used to successfully compensate the donor-like impurities. State-of-the-art structural properties of a high-mobility AlGaN/AlN/GaN heterostructure was then realized on a 1 × 1 cm{sup 2} SI native GaN substrate; the full width at half maximum of the X-ray rocking curves of the GaN (002) and (102) peaks are only 21 and 14 arc sec, respectively. The surface morphology of the heterostructure shows uniform parallel bilayer steps, and no morphological defects were noticeable over the entire epi-wafer.

Adsorción de resorcinol desde solución acuosa sobre carbón activado. relación isotermas de adsorción y entalpía de inmersión

OpenAIRE

Blanco, Diego; Moreno, Juan; Giraldo, Liliana

2009-01-01

Se estudia la adsorción de resorcinol, sobre carbones activados modificados, obtenidos a partir de un carbón activado comercial CarbochemTM –PS30, CAG, por medio de tratamiento químico con HNO3 7M, CAO y tratamiento térmico bajo flujo de H2, CAR; se analiza la influencia del pH de la solución, la reducción y oxidación de la superficie del carbón y se determina la entalpía de inmersión de los carbones activados en soluciones acuosas de resorcinol.La interacción sólido-solución se caracteriza...

EVOLUCIÓN O CREACIÓN, GENOMAS Y CLONACIÓN

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Emilio Yunis

2001-01-01

Full Text Available El texto -siguiendo el proceso histórico-científico-, muestra la importancia de los estudios referidos a la creación y evolución, tanto del genoma humano como de la clonación, los temores que se generaron alrededor de los avances propuestos por la Ingeniería genética y sus implicaciones políticoéticas.

Información incompleta y regulación: una introducción.

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Carlos Pombo

2010-05-01

Full Text Available Este artículo describe el modelo de regulación de costos con información completa para monopolios naturales, y lo compara con modelo con modelos que presentan asimetrías e información incompleta como el modelo de regulación de monopolios naturales con selección adversa de Baron y Myerson y el modelo de gestión con riesgo moral De Laffont y Tirole. El enfoque básico sigue el marco de trabajo de principal agente para el caso de dos tipos, en el cual la distorsión causada por las rentas provenientes de la información se consideran más importantes debido al hecho de que el regulador no conoce el costo marginal de la firma por el esfuerzo efectivo de la firma en reducir los costos operativos.

A Mesopore-Dependent Catalytic Cracking of n-Hexane Over Mesoporous Nanostructured ZSM-5.

Science.gov (United States)

Qamar, M; Ahmed, M I; Qamaruddin, M; Asif, M; Sanhoob, M; Muraza, O; Khan, M Y

2018-08-01

Herein, pore size, crystalinity, and Si/Al ratio of mesoporous ZSM-5 (MFI) nanocrystals was controlled by synthesis parameters, such as surfactant concentration ([3-(trimethoxysilyl)propyl] hexa-decyl dimethyl ammonium chloride), sodium hydroxide concentrations, synthesis temperature and time. The morphology, surface structure and composition of the MFI particles was systematically investigated. More notably, the mesopore-dependent catalytic activity of ZSM-5 was evaluated by studying the cracking of n-hexane. The findings suggest the porosity has pronounced impact on the catalytic activity, selectivity and stability of ZSM-5 nanocrystals. Critical surface attributes such as nature of acid sites (Brønsted and Lewis), concentration, and strength are obtained by the infrared study of adsorbed probe molecules (pyridine) and the temperature programmed desorption. In spite of being weaker in Si/Al ratio or acidic strength, mesoporous catalysts showed more stable and efficient cracking of n-hexane suggesting that acidity seems not the predominant factor operative in the activity, selectivity and stability.

Síntesis de la N,N-diisopropiletanoamida y N,N-dibutiletanoamida mediante métodos de activación no convencionales: microondas y ultrasonido

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Joel O. Ovalle Rodríguez

2010-12-01

Full Text Available In the present investigation two amides were synthesized: N, N-diisopropiletanoamida and N, N-dibutyletano-amide, using two different non-conventional sources of activation: microwave and ultrasound. It was shown that the use of microwaves in this type of synthesis greatly increases yields and decreases reaction times. In the synthesis of N, N-diisopropyletanoamide yields were about 75% for the synthesis assisted by microwaves (SAM and 35% in the ultrasound-assisted synthesis (SAUS. The yields for the N, N-dibutiletanoamida were 73% (SAM and 45% (SAUS. The reaction times employed were 15 min. (SAM and 7 hours (SAUS. It is noteworthy that all reactions were carried out in a single step and in the absence of solvent.

Living Polycondensation: Synthesis of Well-Defined Aromatic Polyamide-Based Polymeric Materials

KAUST Repository

Alyami, Mram Z.

2016-11-01

Chain growth condensation polymerization is a powerful tool towards the synthesis of well-defined polyamides. This thesis focuses on one hand, on the synthesis of well-defined aromatic polyamides with different aminoalkyl pendant groups with low polydispersity and controlled molecular weights, and on the other hand, on studying their thermal properties. In the first project, well-defined poly (N-octyl-p-aminobenzoate) and poly (N-butyl-p-aminobenzoate) were synthesized, and for the first time, their thermal properties were studied. In the second project, ethyl4-aminobenzoate, ethyl 4-octyl aminobenzoate and 4-(hydroxymethyl) benzoic acid were used as novel efficient initiators of ε-caprolactone with t-BuP2 as a catalyst. Macroinitiator and Macromonomer of poly (ε-caprolactone) were synthesized with ethyl 4-octyl aminobenzoate and ethyl 4-aminobenzoate as initiators to afford polyamide-block-poly (ε-caprolactone) and polyamide-graft-poly (ε-caprolactone) by chain growth condensation polymerization (CGCP). In the third project, a new study has been done on chain growth condensation polymerization to discover the probability to synthesize new polymers and studied their thermal properties. For this purpose, poly (N-cyclohexyl-p-aminobenzoate) and poly (N-hexyl-p-aminobenzoate) were synthesized with low polydispersity and controlled molecular weights.

Globalización y transmigración

OpenAIRE

Rodas Martínez, Hernán

2001-01-01

No cabe duda que el proceso de globalización ha transformado profundamente el carácter de la migración internacional. Las teorías clásicas de emigración, inmigración, remigración ya no explican los procesos que viven hoy millones de personas. Las nuevas trayectorias laborables, diversas residencias, secuencias y formas de movilización, identidades y redes que controlan, catalogan, expulsan o seleccionan la aceptación de los inmigrantes, ha puesto en crisis conceptos como comunidad de residen...

"Creación y Salvación": La creación como fundamento de la salvación cristiana. La salvación como plenificación de la creación de Dios

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Andrés Arteaga M.

2001-01-01

Full Text Available RESUMEN El artículo intenta profundizar, de manera inicial, en el carácter de las relaciones entre la creación y la salvación. Una vez planteada la pregunta por el lugar de la creación en el misterio cristiano, en el contexto de la teología actual, se muestra en algunos ejemplos la complejidad de la relación entre creación y salvación. Se analiza el origen de la doctrina de la creación en el Antiguo Testamento, su evolución en la teología paulina, su perspectiva en algunos escritos de Rahner, y finalmente, en los textos del Concilio Vaticano II. Termina proponiendo algunas observaciones conclusivas acerca de la luz que trae el misterio de la creación sobre las mediaciones de la salvación. La salvación es un "aspecto de la totalidad" del plan divino. Soteriología y protología se implican mutuamente. De tal manera que la salvación desde la óptica de la creación, es "de Dios", pero también "de la persona humana en el mundo y en la historia". "Mundanidad", "historicidad" y "humanidad" de la salvación son características inextirpables y coordenadas fundamentales para cualquier reflexión teológica acerca de las mediaciones de la salvación. La salvación cristiana es toda de Dios y a la vez toda mediada.ABSTRACT The article attempts to look in depth, the character of the relations between creation and salvation. It first poses the question of the role of creation on salvation, in the context of the current theology, and then shows some examples of the complexity of the relation between creation and salvation. It analyses the origin of the doctrine of creation in the Old Testament, its evolution in Paul’s doctrine, its perspective in some of Ranner’s works, and finally, in the Vatican Council II texts. It finishes offering some conclusive observation on the light that the mystery of creation brings over the mediations of salvation. Salvation is "an aspect of the fullness" of the divine plan. Soteriology and protology imply

Fitorremediación en la recuperación de suelos: una visión general

OpenAIRE

Andrea Angélica Bernal Figueroa

2014-01-01

En esta investigación se revisan aspectos fundamentales de la fitorremediación como técnica en la recuperación de suelos, la cual se emplea para eliminar o disminuir la contaminación o degradación de los mismos, por medio de la utilización de especies vegetales. Se encontró que técnicas tales como la fitoextracción, rizofiltración, fitoestabilización, fitodegradación, rizodegradación y fitovolatilización, están determinadas principalmente por el tipo de contaminante, diversidad microbiana y p...

Strain Balanced AlGaN/GaN/AlGaN nanomembrane HEMTs.

Science.gov (United States)

Chang, Tzu-Hsuan; Xiong, Kanglin; Park, Sung Hyun; Yuan, Ge; Ma, Zhenqiang; Han, Jung

2017-07-25

Single crystal semiconductor nanomembranes (NM) are important in various applications such as heterogeneous integration and flexible devices. This paper reports the fabrication of AlGaN/GaN NMs and NM high electron mobility transistors (HEMT). Electrochemical etching is used to slice off single-crystalline AlGaN/GaN layers while preserving their microstructural quality. A double heterostructure design with a symmetric strain profile is employed to ensure minimal residual strain in freestanding NMs after release. The mobility of the two-dimensional electron gas (2DEG), formed by the AlGaN/GaN heterostructure, is noticeably superior to previously reported values of many other NMs. AlGaN/GaN nanomembrane HEMTs are fabricated on SiO 2 and flexible polymeric substrates. Excellent electrical characteristics, including a high ON/OFF ratio and transconductance, suggest that III-Nitrides nanomembranes are capable of supporting high performance applications.

Televisión: Muerte y resurrección de la televisión venezolana

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Jenny Bustamante Newball

2015-01-01

Full Text Available El desarrollo acelerado de la autopista de la información y la tecnología digital se suman a la polémica para anunciar la muerte de la televisión analógica venezolana. "Vamos hacia una e-volución que incluye la transformación del concepto de televisión y de los estilos de los programas, el paso de una caja tonta a un interfaz inteligente, la reivindicación de los contenidos, la pacificación espontánea entre la televisión y la educación se está perfilando en el sentido de una "conciliación necesaria". Topa también el tema de las franquicias.

Globalización e integración latinoamericana

OpenAIRE

Salgado Peñaherrera, Germánico

1998-01-01

SUMARIO: 1. Las características de la globalización: sus alcances. 2. La globalización económica. 2.1. Concepciones de la globalización. 2.2. Orígenes y elementos impulsores. 2.3. Manifestaciones de la globalización. 3. Los efectos de la globalización económica. 4. Globalización y regionalización. 5. ¿Qué clase de regionalización? 6. Conclusiones aplicables a nuestras políticas de integración. Instituto de Integración Latinoamericana

Televisión: Muerte y resurrección de la televisión venezolana

OpenAIRE

Jenny Bustamante Newball

2015-01-01

El desarrollo acelerado de la autopista de la información y la tecnología digital se suman a la polémica para anunciar la muerte de la televisión analógica venezolana. "Vamos hacia una e-volución que incluye la transformación del concepto de televisión y de los estilos de los programas, el paso de una caja tonta a un interfaz inteligente, la reivindicación de los contenidos, la pacificación espontánea entre la televisión y la educación se está perfilando en el sentido de una "conciliación nec...

Electron states at electrolyte/n-GaN and electrolyte/n-InGaN interfaces

Energy Technology Data Exchange (ETDEWEB)

Rudinsky, M. E., E-mail: rudinskym@mail.ru; Gutkin, A. A.; Brunkov, P. N. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2012-06-15

The differential capacitance and differential active conductance of rectifying contacts of n-GaN and n-In{sub x}Ga{sub 1-x}N (x Almost-Equal-To 0.15) with an electrolyte (0.2 M aqueous solutions of NaOH, NaCl, or HCl) have been studied. It was found that electron states with energies corresponding to the upper half of the energy gap of a semiconductor exist at the interface between these semiconductors and a NaOH solution. The density and characteristic recharging time of states noticeably contributing to the differential capacitance and differential active conductance at probe-voltage frequencies of 0.3-1 kHz grow with their binding energy and, for states lying at 0.15-0.3 eV below the conduction-band bottom of n-GaN, fall within the ranges 10{sup 12}-2 Multiplication-Sign 10{sup 13} cm{sup -2} eV{sup -1} and 10{sup -4}-10{sup -2} s, respectively. For contacts with NaCl and HCl solutions, there are no states of this kind. It is assumed that the observed states are related to the adsorption of hydroxyl groups.

Novel quinazoline ring synthesis by cycloaddition of N-arylketenimines with N,N-disubstituted cyanamides.

Science.gov (United States)

Shimizu, Masao; Oishi, Akihiro; Taguchi, Yoichi; Gama, Yasuo; Shibuya, Isao

2002-03-01

The reaction of N-aryl-substituted ketenimines with N,N-disubstituted cyanamides or (MeS)2C=N-CN under high pressure afforded 4-(N,N-disubstituted amino) or 4-(MeS)2C=N-substituted quinazoline derivatives, respectively. These products were formed by [4+2] cycloaddition between the aza-diene moieties of the N-arylsubstituted ketenimines and cyano groups. A 4-(unsubstituted amino)quinazoline derivative was synthesized by hydrolysis of the latter product.

DETECCIÓN DE RADIACIÓN NO IONIZANTE

Directory of Open Access Journals (Sweden)

GUSTAVO NAVAS

2009-01-01

Full Text Available Se diseñó y construyó una red de sensores para detección de radiación no ionizante en la banda comprendida entre 800MHz y 2.5GHz. El sistema se basa en el sensor que muestra a la salida una tensión DC proporcional a la potencia de la señal RF a su entrada, sin importar el tipo de modulación. Esta red comprende cuatro antenas banda ancha, cuatro tarjetas sensoras, una tarjeta central y un software de visualización de datos. El comportamiento del sistema se analizó con diferentes configuraciones y con múltiples fuentes de radiación. Igualmente, se muestran los resultados de la simulación de una antena espiral de Arquímedes utilizando CST STUDIOTM y los experimentos realizados para caracterizar la antena banda ancha HG2404CU. Los resultados mostraron un eficiente sistema de detección de radiación electromagnética en la banda estudiada. Una aplicación inmediata de este trabajo, para la cual se están haciendo pruebas de campo, es la detección de llamadas de celulares en lugares no permitidos como centros carcelarios, bancos, entre otros.

Simulación numérica : ecuación de difusión

OpenAIRE

Millán, Zulma; Torre, Leonor de la; Oliva, Laura; Berenguer, María del Carmen

2011-01-01

La simulación numérica es una herramienta eficaz en las ciencias aplicadas, para la determinación de soluciones y la predicción del comportamiento de las mismas, sin recurrir a la experimentación. Permite la recreación matemática de procesos físicos que aparecen con frecuencia en el área de Ingeniería. El uso de simulaciones numéricas para estudiar ecuaciones diferenciales en derivadas parciales, en particular la ecuación de difusión, requiere normalmente de un cuidadoso estudio d...

Prevención del sarampión

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Revista Biomédica

1982-09-01

Full Text Available Esta revisión de las recomendaciones del ACIP sobre la prevención del Sarampión hace continuidad con las anteriores [MMWE 1978; 27: 427 y 4351, para actualizar la información sobre la efectividad de la vacuna y los esfuerzos que se hacen para eliminar el Sarampión. No hay cambios básicos en los fundamentos trazados. Se incluyen nuevas discusiones respecto al síndrome de sarampión atípico y a la revacunación de los primovacunados con vacuna de virus muertos. Se revisan las recomendaciones para la vacunación de personas alérgicas. La confirmación serológica ha alcanzado mayor importancia ante el declinar de las tasas de incidencia. Se incluyen nuevas recomendaciones para los viajeros internacionales.

Obtención de carbón activado a partir de aserrín y carbón mineral

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Gloria E. Cardona

2009-06-01

Full Text Available Siendo el carbón activado un material extensamente utilizado en el control de la contaminación de las aguas, la purificación de azúcares, la recuperación de solventes, la manufactura de llantas, la elaboración de productos farmacéuticos, la refinación de productos alimenticios y aún como antítodo en casos de envenenamiento, y siendo demás un producto que se Importa en nuestro país, decidimos emprender la labor de preparar carbón activado a partir de materias primas baratas como aserrín, desechos de carbón mineral y CaCl2 y ZnCL2 (activantes. Fue así como preparamos varios carbones activados en polvo y granulares.

Molecular simulations and experimental studies of solubility and diffusivity for pure and mixed gases of H2, CO2, and Ar absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]).

Science.gov (United States)

Shi, Wei; Sorescu, Dan C; Luebke, David R; Keller, Murphy J; Wickramanayake, Shan

2010-05-20

Classical molecular dynamics and Monte Carlo simulations are used to calculate the self-diffusivity and solubility of pure and mixed CO(2), H(2), and Ar gases absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf(2)N]). Overall, the computed absorption isotherms, Henry's law constants, and partial molar enthalpies for pure H(2) agree well with the experimental data obtained by Maurer et al. [J. Chem. Eng. Data 2006, 51, 1364] and the experimental values determined in this work. However, the agreement is poor between the simulations and the experimental data by Noble et al. [Ind. Eng. Chem. Res. 2008, 47, 3453] and Costa Gomes [J. Chem. Eng. Data 2007, 52, 472] at high temperatures. The computed H(2) permeability values are in good agreement with the experimental data at 313 K obtained by Luebke et al. [J. Membr. Sci. 2007, 298, 41; ibid, 2008, 322, 28], but about three times larger than the experimental value at 573 K from the same group. Our computed H(2) solubilities using different H(2) potential models have similar values and solute polarizations were found to have a negligible effect on the predicted gas solubilities for both the H(2) and Ar. The interaction between H(2) and the ionic liquid is weak, about three times smaller than between the ionic liquid and Ar and six times smaller than that of CO(2) with the ionic liquid, results that are consistent with a decreasing solubility from CO(2) to Ar and to H(2). The molar volume of the ionic liquid was found to be the determining factor for the H(2) solubility. For mixed H(2) and Ar gases, the solubilities for both solutes decrease compared to the respective pure gas solubilities. For mixed gases of CO(2) and H(2), the solubility selectivity of CO(2) over H(2) decreases from about 30 at 313 K to about 3 at 573 K. For the permeability, the simulated values for CO(2) in [hmim][Tf(2)N] are about 20-60% different than the experimental data by Luebke et al. [J. Membr

COMPORTAMIENTO DE CORROSIÓN-EROSIÓN EN RECUBRIMIENTOS DE TiN/ZrN DEPOSITADOS SOBRE ACERO AISI 4140

OpenAIRE

Aperador, Willian; Mejía, Aura S; Caicedo, Julio

2014-01-01

Se depositaron películas delgadas de nitruro de titanio/nitruro de zirconio sobre acero AISI 4140 mediante un sistema multi-blanco magnetrón pulverización (sputtering) con radiofrecuencia. El proceso se desarrolló bajo el sistema de rotación del sustrato que permitió situar el sustrato de frente a los blancos de titanio y zirconio, generando la super-red con periodos de 1, 50, 100 y 200 bicapas. Las multicapas fueron evaluadas frente a la sinergia corrosión-erosión en una solución compuesta p...

Step-flow growth mode instability of N-polar GaN under N-excess

International Nuclear Information System (INIS)

Chèze, C.; Sawicka, M.; Siekacz, M.; Łucznik, B.; Boćkowski, M.; Skierbiszewski, C.; Turski, H.; Cywiński, G.; Smalc-Koziorowska, J.; Weyher, J. L.; Kryśko, M.

2013-01-01

GaN layers were grown on N-polar GaN substrates by plasma-assisted molecular beam epitaxy under different III/V ratios. Ga-rich conditions assure step-flow growth with atomically flat surface covered by doubly-bunched steps, as for Ga-polar GaN. Growth under N-excess however leads to an unstable step-flow morphology. Particularly, for substrates slightly miscut towards , interlacing fingers are covered by atomic steps pinned on both sides by small hexagonal pits. In contrast, a three-dimensional island morphology is observed on the Ga-polar equivalent sample. We attribute this result to lower diffusion barriers on N-polar compared to Ga-polar GaN under N-rich conditions

Metal chelates of phosphonate-containing ligands-III Analytical applications of N,N,N',N'-ethylenediaminetetra(methylenephosphonic) acid.

Science.gov (United States)

Zaki, M T; Rizkalla, E N

1980-05-01

N,N*,N',N'-Ethylenediaminetetra(methylenephosphonic) acid is used as a titrant for the direct determination of Cu, Co and Ni, with murexide as indicator. Indirect titrimetric procedures are suggested for the determination of silver, mercury, zinc and cyanide and both direct and indirect methods are applied for the analysis of binary mixtures of silver (or mercury) and copper (cobalt or nickel). The stoichiometry of the reaction, interferences of some metal ions and the pH effects on the complexation reactions are discussed. The values of the equilibrium constants of the protonated CuH(n)L (n = 1, 2, 3 and 4) as well as the unprotonated CuL chelates have been measured.

Boletín Oficial núm. 53

OpenAIRE

Universidad Carlos III de Madrid

2014-01-01

Contiene: Modificación de la normativa sobre el nombramiento de profesores eméritos en la Universidad Carlos III de Madrid, aprobado por el Consejo de Gobierno en su sesión de 10 de julio de 2014. (p. 3) . -- Modificación de la normativa reguladora de los estudios con docencia en inglés y de matriculación y evaluación de los estudiantes en dichos estudios, aprobado por el Consejo de Gobierno en su sesión de 10 de julio de 2014. (pp. 3-4) . -- Reglamento del fondo de cooperación al desarrollo ...

Properties of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters

Energy Technology Data Exchange (ETDEWEB)

Dong, Yi; Rehman, Habib ur; Springborg, Michael [Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrücken (Germany)

2015-01-22

The structures of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters with up to 44 atoms have been determined theoretically using an unbiased structure-optimization method in combination with a parametrized, density-functional description of the total energy for a given structure. By analyzing the total energy in detail, particularly stable clusters are identified. Moreover, general trends in the structures are identified with the help of specifically constructed descriptors.

InGaN/GaN quantum well improved by in situ SiN{sub x} pretreatment of GaN template

Energy Technology Data Exchange (ETDEWEB)

Huang, Demeng; Wu, Zhengyuan; Fang, Zhilai [Department of Physics, Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Xiamen University (China)

2016-12-15

In situ SiN{sub x} pretreatment was employed to modify the growth behavior and optical properties of InGaN/GaN quantum wells (QWs). With moderate SiN{sub x} pretreatment surface smoothness of InGaN/GaN QWs was improved and attributed to enhanced layer growth by Ga surfactant effect. Significant increase of photoluminescence peak intensity and relatively uniform and bright cathodoluminescence images were observed, which were attributed to the improvement in crystalline quality and strain reduction for the InGaN/GaN QWs with moderate SiN{sub x} pretreatment. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Probabilistic n-normed spaces, D-n-compact sets and D-n-bounded sets

International Nuclear Information System (INIS)

Pourmoslemi, A.; Salimi, M.

2009-01-01

In this paper, first we define and study the probabilistic n-normed spaces and D-n-compactness, also we prove some theorems and inequalities. In the next section we define D-n-boundedness and prove some results in relation between D-n-compact and D-n-bounded sets in these spaces.

De números y más números: identificación, control y representación documental

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Victor Julián Cid Carmona

2015-06-01

Full Text Available El uso de números en los documentos, independientemente de utilizarse como parte del contenido propiamente dicho de las obras —para expresar cantidades, fórmulas, medidas, posiciones, valores, etc.— tiene un variado conjunto de aplicaciones según propósitos claramente definidos. El presente texto tiene como finalidad hacer una breve descripción de la manera en que se emplean diversos códigos numéricos en los procesos de producción, control e identificación de impresos. Para especificar el tipo de datos a que nos referiremos, se incluye en primer lugar una propuesta de tipificación en razón del origen de los números. A continuación, se abordan los casos de números que van impresos en los libros y después, aquellos que se anotan por los poseedores de los mismos. En tercer lugar, se incluyen códigos numéricos que permiten identificar a los documentos en repertorios impresos o en catálogos bibliográficos en línea.

Thermal expansion and magnetostriction in Pr(n+2)(n+1)Nin(n-1)+2Sin(n+1) compounds

International Nuclear Information System (INIS)

Jiles, D.C.; Song, S.H.; Snyder, J.E.; Pecharsky, V.K.; Lograsso, T.A.; Wu, D.; Pecharsky, A.O.; Mudryk, Ya.; Dennis, K.W.; McCallum, R.W.

2006-01-01

Thermal expansion and magnetostriction of members of a homologous series of compounds based on the alloy series Pr (n+2)(n+1) Ni n(n-1)+2 Si n(n+1) have been measured. The crystal structures of these compounds are closely interrelated because they form trigonal prismatic columns in which the number of trigonal prisms that form the base of the trigonal columns is determined by the value of n in the chemical formula. Two compositions were investigated, Pr 5 Ni 2 Si 3 and Pr 15 Ni 7 Si 10 , corresponding to n=3 and n=4, respectively. The results were analyzed and used to determine the location of magnetic phase transitions by calculating the magnetic contribution to thermal expansion using the Gruneisen-Debye theory. This allowed more precise determination of the magnetic transition temperatures than could be achieved using the total thermal expansion. The results show two phase transitions in each material, one corresponding to the Curie temperature and the other at a lower temperature exhibiting characteristics of a spin reorientation transition

Control e información directiva: evaluación de la gestión

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Guillermo Vázquez Ávila

2016-02-01

Full Text Available Este trabajo de investigación tiene como principal interés evidenciar avances en la gestión directiva y en la evaluación del desempeño, describiendo ésta como la búsqueda disciplinada de conocimiento, donde el juicio resultante presupone la analogía entre la información obtenida y el criterio de búsqueda para constatar, rectificar y perfeccionar el objeto o realidad evaluados y, por otra parte, la relevancia que tiene la alineación de una estrategia de negocio con un sistema de retribución para lograr la ejecución satisfactoria de la misma. Losresultados de la investigación, en su oportunidad, permiten plantear la posibilidad de desarrollo de un esquema sistémico que no solamente considere el control directivo y la revisión del plan de retribución, sino que atienda también la forma en que el mismo cambio organizacional deseado influye en el diseño de la visión, la misión y los valores de una empresa.

DISFUNCIÓN TIROIDEA Y CORAZÓN

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Dr. Juan Ramón Soto S.

2015-03-01

Full Text Available Los trastornos de la función tiroidea afectan profundamente al sistema cardiovascular. En esta revisión se presentan algunos aspectos fisiológicos de la interrelación entre tiroides y corazón, como tambiècn las consecuencias de la tirotoxicosis e hipotiroidismo sobre el aparato cardiovascular. Se analiza la influencia del hipertiroidismo en la gècnesis de la fibrilación auricular y del hipotiroidismo en el metabolismo de las lipoproteínas. Adicionalmente, el artículo se referirá a los potenciales efectos adversos del antiarrítmico amiodarona sobre la función tiroidea y cómo se investigan y tratan. Finalmente, se expone un caso clínico real para ilustrar con mayor claridad la enorme importancia que pueden alcanzar las relaciones fisiopatológicas entre el corazón y las afecciones de esta glándula endocrina.

Transición de la ruralidad: resignificación y refuncionalización.

Directory of Open Access Journals (Sweden)

Zuluaga Sánchez Gloria Patricia

1999-12-01

Full Text Available Este artículo es una continuación de la tesis de maestría en Paisaje, Territorio y Medio ambiente y busca reflexionar sobre la nueva ruralidad colombiana, su resignificación y refuncionalización. La pregunta central del presente trabajo es: ¿La creciente consciencia ciudadana sobre el medio ambiente podrá generar una neorruralízación o llevará sólo a una diversificación de las actividades y funcionales de lo rural? Debemos recordar que estamos frente a un cambio fundamental de visión en la ciencia y la sociedad; un cambio de paradigma del modelo de desarrollo industrial hacia el denominado paradigma ambiental. Esta nueva visión ha empezado a transformar la percepción y la manera como pensamos el mundo y actuamos sobre él. No estamos pues, presenciando una simple propuesta de reformulación de nuestra gestión, que llama al cuidado de los bosques, estamos frente a un nuevo contrato social que determinará la concepción futura de la humanidad.

Orientación psicopedagógica, educación y televisión

OpenAIRE

Monescillo Palomo, Manuel

2005-01-01

En esta comunicación se pretende resaltar la importancia que tiene la acción orientadora dentro del proceso formativo de las personas -tanto formal como informal- y su contribución al logro de la formación integral y la capacitación para poder tomar decisiones autónomas, acertadas y responsables en cada momento y faceta de la vida personal, familiar, académica y/o laboral. En concreto se pone de relieve la relación entre la tutoría orientadora y la televisión, considerando a ésta com...

Evaluation of the cross-sections for the reactions 19F(n,2n)18F, 31P(n,p)31Si, 93Nb(n,n')sup(93m)Nb and 103Rh(n,n')sup(103m)Rh

International Nuclear Information System (INIS)

Strohmaier, B.; Tagesen, S.; Vonach, H.

1980-01-01

The cross-sections for the four important neutron dosimetry reactions 19 F(n,2n) 18 F, 31 P(n,p) 31 Si, 93 Nb(n,n')sup(93m)Nb and 103 Rh(n,n')sup(103m)Rh were evaluated in the neutron energy range from threshold to 20 MeV. For the 19 F(n,2n) reaction the evaluation could be based entirely on experimental data; for the reactions 31 P(n,p) 31 Si and 103 Rh(n,n')sup(103m)Rh large gaps in the experimental excitation functions and large discrepancies between the existing data made it necessary to supplement the experimental data by cross-section calculations and to give about equal weight to the experimental and calculated cross-sections. For the 93 Nb(n,n')sup(93m)Nb reaction the evaluation had to be based entirely on the theoretically calculated cross-sections. All data sets were critically reviewed and obviously erroneous data sets were disregarded. If necessary, the data were renormalized in order to take into account adjustments in corresponding standard cross-sections and decay schemes. For each evaluated cross-sections also an uncertainty (on a 1sigma confidence level) was derived taking into account the errors given by the experimentalists, the general consistency of the experimental data and the estimated errors of the theoretically calculated cross-sections. (orig.) [de

Modelación y simulación de un pervaporador acoplado a un proceso de sacarificación-fermentación para la producción de etanol

OpenAIRE

Jairo Antonio Cubillos-Lobo; Felipe Bustamante-Londoño; Alejandro Acosta-Cárdenas

2015-01-01

Actualmente, la integración de procesos es considerada una opción viable para reducir costos en la producción de etanol a partir de biomasa. Simulaciones y resultados experimentales han demostrado los beneficios de la integración de las etapas de sacarificación y fermentación y del acoplamiento del proceso de fermentación a la recuperación in-situ de etanol por pervaporación en la producción de bioetanol; sin embargo, no se han publicado estudios de la integración del proceso de sacarificació...

SO(2N) and SU(N) gauge theories

OpenAIRE

Lau, Richard; Teper, Michael

2013-01-01

We present our preliminary results of SO(2N) gauge theories, approaching the large-N limit. SO(2N) theories may help us to understand QCD at finite chemical potential since there is an orbifold equivalence between SO(2N) and SU(N) gauge theories at large-N and SO(2N) theories do not have the sign problem present in QCD. We consider the string tensions, mass spectra, and deconfinement temperatures in the SO(2N) pure gauge theories in 2+1 dimensions, comparing them to their corresponding SU(N) ...

Global behavior of the difference equation $x_{n+1}=\\frac{Ax_{n-1}} {B-Cx_{n}x_{n-2}}$

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R. Abo-Zeid

2013-11-01

Full Text Available The aim of this work is to investigate the global stability, periodic nature, oscillation and the boundedness of all admissible solutions of the difference equation $x_{n+1}=\\frac{Ax_{n-1}} {B-Cx_{n}x_{n-2}}$, n=0,1,2,... where A, B, C are positive real numbers.

LA CONCERTACIÓN CON LA ADMINISTRACIÓN ESPECIAL REFERENCIA A LA CONCERTACIÓN INFORMAL

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Jorge Agudo González

2011-12-01

Full Text Available La concertación con la Administración constituye un fenómeno jurídico habitual en el moderno Estado cooperativo, donde el derecho administrativo se concibe como ciencia de dirección, y cuyo objetivo es dirigir los procesos sociales con eficacia. Así pues, el derecho interioriza un enfoque basado en la capacidad inductora de lo jurídico, creando un clima propicio para la efectividad del derecho. Desde esta perspectiva, la concertación con la Administración tiene una importancia especial. El fenómeno de la concertación es variable, pero en todo caso debe encuadrarse entre la denominada actuación material de la Administración. El análisis de esta forma de actuación administrativa se aborda ofreciendo una unidad sistemática que facilita la integración de las diferentes cuestiones dogmáticas planteadas, para lo cual se trata el tema desde la perspectiva de la teoría de las relaciones jurídico-administrativas, debido a la insuficiencia de la doctrina de las formas jurídicas de la actuación administrativa para aprehender dogmáticamente la actuación material de la Administración. Del mismo modo, se afronta el tema clave de la concertación informal y la vinculación de la Administración a la Ley, y se finaliza con el planteamiento de los importantes problemas de tutela jurídica que este tipo de actuación material puede dar lugar.

Fundamental Characterization of the Micellar Self-Assembly of Sophorolipid Esters.

Science.gov (United States)

Koh, Amanda; Todd, Katherine; Sherbourne, Ezekiel; Gross, Richard A

2017-06-13

Surfactants are ubiquitous constituents of commercial and biological systems that function based on complex structure-dependent interactions. Sophorolipid (SL) n-alkyl esters (SL-esters) comprise a group of modified naturally derived glycolipids from Candida bombicola. Herein, micellar self-assembly behavior as a function of SL-ester chain length was studied. Surface tensions as low as 31.2 mN/m and critical micelle concentrations (CMCs) as low as 1.1 μM were attained for diacetylated SL-decyl ester (dASL-DE) and SL-octyl ester, respectively. For deacetylated SL-esters, CMC values reach a lower limit at SL-ester chains above n-butyl (SL-BE, 1-3 μM). This behavior of SL-esters with increasing hydrophobic tail length is unlike other known surfactants. Diffusion-ordered spectroscopy (DOSY) and T 1 relaxation NMR experiments indicate this behavior is due to a change in intramolecular interactions, which impedes the self-assembly of SL-esters with chain lengths above SL-BE. This hypothesis is supported by micellar thermodynamics where a disruption in trends occurs at n-alkyl ester chain lengths above those of SL-BE and SL-hexyl ester (SL-HE). Diacetylated (dA) SL-esters exhibit an even more unusual trend in that CMC increases from 1.75 to 815 μM for SL-ester chain lengths of dASL-BE and dASL-DE, respectively. Foaming studies, performed to reveal the macroscopic implications of SL-ester micellar behavior, show that the observed instability in foams formed using SL-esters are due to coalescence, which highlights the importance of understanding intermicellar interactions. This work reveals that SL-esters are an important new family of green high-performing surfactants with unique structure-property relationships that can be tuned to optimize micellar characteristics.

n-Type Azaacenes Containing B←N Units.

Science.gov (United States)

Min, Yang; Dou, Chuandong; Tian, Hongkun; Geng, Yanhou; Liu, Jun; Wang, Lixiang

2018-02-12

We disclose a novel strategy to design n-type acenes through the introduction of boron-nitrogen coordination bonds (B←N). We synthesized two azaacenes composed of two B←N units and six/eight linearly annelated rings. The B←N unit significantly perturbed the electronic structures of the azaacenes: Unique LUMOs delocalized over the entire acene skeletons and decreased aromaticity of the B←N-adjacent rings. Most importantly, these B←N-containing azaacenes exhibited low-lying LUMO energy levels and high electron affinities, thus leading to n-type character. The solution-processed organic field-effect transistor based on one such azaacene exhibited unipolar n-type characteristics with an electron mobility of 0.21 cm 2  V -1  s -1 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Promoción de derechos y sanción. La regulación de la comunicación en Ecuador

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Abel Suing

2017-10-01

Full Text Available Acorde al espíritu de la UNESCO de procurar sistemas reguladores de la comunicación que conduzcan a la libertad de expresión, el pluralismo y la diversidad de los medios la investigación presenta los argumentos que justifican la instauración de autoridades de regulación para luego exponer la génesis de la Superintendencia de Información y Comunicación de Ecuador (Supercom y su capacidad sancionadora. El propósito de la investigación es determinar el perfil de la Supercom en relación a la promoción de derechos y el control de medios, se evalúan los resultados de sus tres primeros años de gestión. Las hipótesis son: 1 La Supercom promueve derechos en mayor proporción que ejecuta sanciones; 2 Los procesos administrativos surgen por denuncias más que “de oficio; y, 3 Los procesos se resuelven a través de amonestaciones escritas y réplicas. La metodología es cualitativa, los instrumentos son análisis de contenidos y entrevistas semi estructuradas. Se concluye que la Supercom ha avanzado poco en la promoción de derechos pero se destaca como órgano sancionador. Hay condiciones para el abuso a través de actuaciones “de oficio”. La regulación en comunicación se ha convertido en un instrumento político, además no hay proporcionalidad en la aplicación de sanciones.

Presentación. Globalización e inmigración:los debates actuales.

Directory of Open Access Journals (Sweden)

Carlota Solé

2006-01-01

Full Text Available Este artículo sirve de presentación al monográfico de la Revista Española de Investigaciones Sociológicas sobre "Globalización e inmigración". Comienza poniendo de relieve algunos de los cambios que se están produciendo en los flujos migratorios (como su feminización y en las políticas de regulación de las migraciones (como las políticas europeas. A continuación apunta brevemente algunos de los debates teóricos y políticos actuales en torno a la inmigración en el marco de la globalización: transnacionalidad, ciudadanía e integración, identidad europea y multiculturalidad. La segunda parte del artículo presenta el desarrollo académico de las teorías de las migraciones a través de la comparación del contenido del Handbook of International Migration de 1999 y los artículos recogidos en el monográfico de la International Migration Review de 2004. Por último, sintetiza los artículos y notas de investigación de este monográfico de la Revista Española de Investigaciones Sociológicas, ubicándolos en esos desarrollos teóricos.

Relación de parejas : ¿Satisfacción o insatisfacción conyugal?

OpenAIRE

Vélez Mejía, Luz Estela

2017-01-01

La actual investigación tuvo como objetivo general, comprender las dinámicas relacionales en cuanto a comunicación, expresión del afecto, solución de problemas, sexualidad, tiempo libre compartido y manejo del dinero que establecen las parejas y su influencia en la percepción de satisfacción o insatisfacción conyugal. Se abordó bajo la perspectiva teórica del enfoque sistémico. En ella se utilizaron los siguientes instrumentos: Inventario de Satisfacción Marital – R, Test del Dibujo Proyect...

Innovación, investigación y educación interdisciplinaria en México

OpenAIRE

Esqueda Villegas, María Fernanda; León Duarte, Gustavo Adolfo

2017-01-01

La interdisciplina, siendo un modo innovador, tanto de formación como de investigación, permite la integración de información, datos, técnicas, herramientas, perspectivas, conceptos y/o teorías de dos o más disciplinas. En el presente texto se analizan y discuten los procesos de innovación, investigación y formación interdisciplinaria en educación superior. Particularmente, en las y los estudiantes del Posgrado Integral en Ciencias Sociales (PICS) de la Universidad de Sonora en México. El par...

Characterization of the N-deacetylase domain from the heparan sulfate N-deacetylase/N-sulfotransferase 2

International Nuclear Information System (INIS)

Duncan, Michael B.; Liu, May; Fox, Courtney; Liu, Jian

2006-01-01

Heparin and heparan sulfate are linear sulfated polysaccharides that exert a multitude of biological functions. Heparan sulfate glucosaminyl N-deacetylase/N-sulfotransferase isoform 2 (NDST-2), a key enzyme in the biosynthesis of heparin, contains two distinct activities. This bifunctional enzyme removes the acetyl group from N-acetylated glucosamine (N-deacetylase activity) and transfers a sulfuryl group to the unsubstituted amino position (N-sulfotransferase activity). The N-sulfotransferase activity of NDST has been unambiguously localized to the C-terminal domain of NDST. Here, we report that the N-terminal domain of NDST-2 retains N-deacetylase activity. The N-terminal domain (A66-P604) of human NDST-2, designated as N-deacetylase (NDase), was cloned as a (His) 6 -fusion protein, and protein expression was carried out in Escherichia coli. Heparosan treated with NDase contains N-unsubstituted glucosamine and is highly susceptible to N-sulfation by N-sulfotransferase. Our results conclude that the N-terminal domain of NDST-2 contains functional N-deacetylase activity. This finding helps further elucidate the mechanism of action of heparan sulfate N-deacetylase/N-sulfotransferases and the biosynthesis of heparan sulfate in general

N = 4 super KdV hierarchy in N = 4 and N = 2 superspaces

International Nuclear Information System (INIS)

Delduc, F.

1995-10-01

The results of further analysis of the integrability properties of the N = 4 supersymmetric KdV equation deduced earlier as a Hamiltonian flow on N 4 SU(2) superconformal algebra in the harmonic N = 4 superspace are presented. To make this equation and the relevant Hamiltonian structures more tractable, it is reformulated in the ordinary N = 4 and further in N = 2 superspaces. These results provide a strong evidence that the unique N = 4 SU(2) super KdV hierarchy exists. (author)

EVALUACIÓN DE LA DEGRADACIÓN Y MINERALIZACIÓN DEL MALATIÓN USANDO FOTOCATÁLISIS MEDIANTE UN COLECTOR SOLAR

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Diana Catalina Rodriguez

2010-02-01

Full Text Available Se empleó un colector solar para evaluar la degradación del malatión en una solución acuosa de 15 _g/L del plaguicida, usando tres concentraciones diferentes de dióxido de titanio (100, 200 y 250 mg/L y peróxido de hidrógeno (H2O2 al 30% como agente oxidante. La disminución de la concentración del malatión se determinó por cromatografía de gases con detector de microcaptura de electrones (CG-_ECD, previa extracción de las muestras con discos C18, y la mineralización se determinó mediante análisis de carbono orgánico total (COT. El proceso de degradación se evaluó durante 16 horas, durante las cuales, se registró la energía solar incidente mediante un radiómetro (Kipp & Zonen, modelo CUV 3. En la fotolisis se alcanzó un porcentaje de degradación de 58,8% y en la fotocatálisis, con 250 mg/L de TiO2 y 10 mL/h de H2O2, se obtuvo 98,7% de degradación. El porcentaje de mineralización alcanzado durante la fotocatálisis fue de 73%.

Features of the Thermodynamics of Trivalent Lanthanide/Actinide Distribution Reactions by Tri-n-Octylphosphine Oxide and Bis(2-EthylHexyl) Phosphoric Acid

Energy Technology Data Exchange (ETDEWEB)

Travis S. Grimes; Peter R. Zalupski

2014-11-01

A new methodology has been developed to study the thermochemical features of the biphasic transfer reactions of trisnitrato complexes of lanthanides and americium by a mono-functional solvating ligand (tri-n-octyl phosphine oxide - TOPO). Stability constants for successive nitrato complexes (M(NO3)x3-x (aq) where M is Eu3+, Am3+ or Cm3+) were determined to assist in the calculation of the extraction constant, Kex, for the metal ions under study. Enthalpies of extraction (?Hextr) for the lanthanide series (excluding Pm3+) and Am3+ by TOPO have been measured using isothermal titration calorimetry. The observed ?Hextr were found to be constant at ~29 kJ mol-1across the series from La3+-Er3+, with a slight decrease observed from Tm3+-Lu3+. These heats were found to be consistent with enthalpies determined using van ’t Hoff analysis of temperature dependent extraction studies. A complete set of thermodynamic parameters (?G, ?H, ?S) was calculated for Eu(NO3)3, Am(NO3)3 and Cm(NO3)3 extraction by TOPO and Am3+ and Cm3+ extraction by bis(2-ethylhexyl) phosphoric acid (HDEHP). A discussion comparing the energetics of these systems is offered. The measured biphasic extraction heats for the transplutonium elements, ?Hextr, presented in these studies are the first ever direct measurements offered using two-phase calorimetric techniques.

A new family of N dimensional superintegrable double singular oscillators and quadratic algebra Q(3) ⨁ so(n) ⨁ so(N-n)

Science.gov (United States)

Fazlul Hoque, Md; Marquette, Ian; Zhang, Yao-Zhong

2015-11-01

We introduce a new family of N dimensional quantum superintegrable models consisting of double singular oscillators of type (n, N-n). The special cases (2,2) and (4,4) have previously been identified as the duals of 3- and 5-dimensional deformed Kepler-Coulomb systems with u(1) and su(2) monopoles, respectively. The models are multiseparable and their wave functions are obtained in (n, N-n) double-hyperspherical coordinates. We obtain the integrals of motion and construct the finitely generated polynomial algebra that is the direct sum of a quadratic algebra Q(3) involving three generators, so(n), so(N-n) (i.e. Q(3) ⨁ so(n) ⨁ so(N-n)). The structure constants of the quadratic algebra itself involve the Casimir operators of the two Lie algebras so(n) and so(N-n). Moreover, we obtain the finite dimensional unitary representations (unirreps) of the quadratic algebra and present an algebraic derivation of the degenerate energy spectrum of the superintegrable model.

La noción patrón de reproducción del capital

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Jaime Osorio

2014-10-01

Full Text Available El escrito se propone fundamentar teóricamente la noción patrón de reproducción del capital, tras asumir que cubre un espacio no desarrollado por la teoría marxista en el análisis de totalidades concretas. Tras establecer el tejido conceptual para estos objetivos, apoyado particularmente en la obra de Marx, y en la de Marini sobre las particularidades del capitalismo dependiente, el autor ofrece a su vez una propuesta para el análisis de los patrones de reproducción. De esta forma emerge una formulación que rompe con la dispersión y la fragmentación imperantes, justificadas por la especialización, y que permite retomar el sentido que asume la vida en común.

LA ALFABETIZACIÓN Y FORMACIÓN EN MEDIOS DE COMUNICACIÓN EN LA FORMACIÓN INICIAL DEL PROFESORADO

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Julio Cabero Almenara

2011-01-01

Full Text Available Este artículo muestra los resultados obtenidos en un estudio centrado en averiguar el grado de alfabetización y formación didáctica en Alfabetización en Medios que mantienen los futuros educadores en formación inicial de las diferentes etapas educativas de Infantil, Primaria, Secundaria y Psicopedagogía de la Facultad de Educación de la Universidad de Cantabria, a los que se les impartió una formación en Alfabetización en Medios. En este estudio mantenemos la premisa, que si formamos a los agentes educativos en una Educación en Medios, podemos lograr que estas personas desarrollen una serie de competencias útiles y necesarias en nuestra actual sociedad, algunas de ellas como: mantener una actitud crítica con los medios, reconocer y valorar su realidad y entorno en el que viven, ser menos vulnerables e influenciables, comprender mejor los mensajes, desarrollar técnicas, herramientas, estrategias, etc. de los Medios de Comunicación, practicar una ciudadanía participativa y responsable y experimentar un consumo responsable.

Performance Analysis of GaN Capping Layer Thickness on GaN/AlGaN/GaN High Electron Mobility Transistors.

Science.gov (United States)

Sharma, N; Periasamy, C; Chaturvedi, N

2018-07-01

In this paper, we present an investigation of the impact of GaN capping layer and AlGaN layer thickness on the two-dimensional (2D)-electron mobility and the carrier concentration which was formed close to the AlGaN/GaN buffer layer for Al0.25Ga0.75N/GaN and GaN/Al0.25Ga0.75N/GaN heterostructures deposited on sapphire substrates. The results of our analysis clearly indicate that expanding the GaN capping layer thickness from 1 nm to 100 nm prompts an increment in the electron concentration at hetero interface. As consequence of which drain current was additionally increments with GaN cap layer thicknesses, and eventually saturates at approximately 1.85 A/mm for capping layer thickness greater than 40 nm. Interestingly, for the same structure, the 2D-electron mobility, decrease monotonically with GaN capping layer thickness, and saturate at approximately 830 cm2/Vs for capping layer thickness greater than 50 nm. A device with a GaN cap layer didn't exhibit gate leakage current. Furthermore, it was observed that the carrier concentration was first decrease 1.03 × 1019/cm3 to 6.65 × 1018/cm3 with AlGaN Layer thickness from 5 to 10 nm and after that it increases with the AlGaN layer thickness from 10 to 30 nm. The same trend was followed for electric field distributions. Electron mobility decreases monotonically with AlGaN layer thickness. Highest electron mobility 1354 cm2/Vs were recorded for the AlGaN layer thickness of 5 nm. Results obtained are in good agreement with published experimental data.

INTERNACIONALIZACIÓN Y CONTROL INTERORGANIZATIVO: REVISIÓN TEÓRICA Y PROPUESTAS DE INVESTIGACIÓN

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Araújo Pinzón, P.

2010-01-01

Full Text Available Dentro de los desafíos que los procesos de internacionalización presentan a las empresas, la gestión de los canales de exportación externalizados ha ido adquiriendo una mayor relevancia. Analizando las conclusiones de los trabajos que han estudiado el papel del Control Interorganizativo (CI en el contexto de las relaciones interorganizativas, este trabajo argumenta que el CI podría permitir una mayor integración y coordinación de las relaciones entre socios domésticos e internacionales, diferente a la propiedad. Como aproximación exploratoria a ambos tópicos de investigación, este trabajo realiza una revisión de la literatura con un enfoque meta-analítico. Sobre esta revisión de la literatura, se han evaluado los principales autores y trabajos, sugiriendo nuevas vías en la investigación del papel del CI en la internacionalización de las empresas.

Revisión sedación paliativa

OpenAIRE

González Calabaza, Marta; González Arnáiz, Elena

2016-01-01

Los Cuidados Paliativos en su acepción moderna surgen en Reino Unido en 1967, pero las primeras publicaciones sobre sedación paliativa no aparecen hasta 1990. La sedación paliativa es la disminución intencional del nivel de conciencia del paciente por medio de fármacos, con el fin de aliviar el sufrimiento físico o psíquico refractario a otras medidas terapéuticas. La diferencia entre sedación paliativa y eutanasia es clara. Divergen en la intención, procedimiento y resultado. Es vital conoce...

Chemistry of organogold compounds I. Syntheses and properties of dihalogold(III) N,N-dialkyldithiocarbamates and dialkylgold(III) N,N-dialkyldithiocarbamates

NARCIS (Netherlands)

Blaauw, H.J.A.; Nivard, R.J.F.; Kerk, G.J.M. van der

Monomeric dialkylgold(III) N,N-dialkyldithiocarbamates (R2AuSSCNR'2) can be prepared in good yields from monomeric dibromogold(III) N,N-dialkyldithiocarbamates (Br2AuSSCNR'2) and alkylmagnesium halides or dialkylcadmium compounds. In addition N-ethylpiperidinium tetrachloroaurate can be converted

PRESENTACIÓN: EL SANGRADO CORAZÓN

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Marco Julián Martínez y Carlos José Suárez

2008-07-01

Full Text Available La actual sociedad colombiana es descrita como una donde el uso de la violencia en la transformación de los conflictos es recurrente y privilegiada. Ello ocurre tanto en el plano estatal como en la intimidad familiar, incluyendo variadas relaciones personales y del día a día. Lo anterior constituye un objeto de preocupación pública y académica, que comúnmente equipara la violencia con la maldad. Algunos estudios asumen la violencia como corruptora del orden social, señalando el deber de algunas agencias por controlar aquel flagelo. Los agentes estatales buscan domesticar al perpetrador a través de intervenciones racionales, que suponen utopías justificadas en nombre del derecho, la ciencia y la religión. Otros estudios abordan la violencia como una expresión indeseada de los conflictos, que contribuye a la ruptura del paradigma social de la convivencia, que debe ser restablecido mediante acciones no-violentas. Hay acercamientos que resaltan las emociones y sensaciones que envuelven la teatralidad del momento disruptivo y sus huellas en la memoria, resaltando el drama humano y los testimonios. Por último, existen interpretaciones centradas en la relación víctima-victimario, reduciendo problemáticas sociales a responsabilidades individuales enmarcadas en la resiliencia y la reparación. Estas posturas han tenido incidencia en los discursos sociales y políticos sobre la opresión, la vulneración y la desigualdad, así como en la construcción y aplicación de políticas públicas para la paz y la seguridad.

Formación para la información: información para la innovación / Training information: information for innovation

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Noel Angulo

2010-07-01

Full Text Available Se aborda el concepto de búsqueda de información y sus alcances, así como las herramientas comunes a la búsqueda de información en Internet; se describen los diferentes tipos de búsqueda, los diferentes tipos de buscadores de información así como las técnicas básicas de información en Internet. Se asume que los docentes interesados en la innovación educativa tendrán mejores posibilidades de éxito si se ocupan de mejorar sus competencias en la búsqueda, recuperación, registro y organización de información y su conversión en conocimiento.

Músculo esquelético y lesión por reperfusión. Ultraestructura, alteración y regeneración: Revisión sistemática

OpenAIRE

Rosero Salazar, Doris Haydee; Tovar, María Ana

2015-01-01

La función tisular se basa en la asociación celular y la comunicación mediante uniones intercelulares o la matriz extracelular, que compone el tejido conectivo. La isquemia conlleva a cambios de lesión a los cuales las células responden según duración e intensidad del estímulo de lesión. En periodos cortos de isquemia y prolongados de reperfusión, el tejido muscular estriado esquelético presenta cambios en la predominancia de los tipos de fibras musculares y en los component...

Adsorción de resorcinol desde solución acuosa sobre carbón activado

OpenAIRE

BLANCO, DIEGO A.; GIRALDO, LILIANA; MORENO, JUAN C.

2009-01-01

Se analiza el comportamiento de adsorción de resorcinol, un fenol monohidroxilado débilmente ácido a 298 K sobre carbón activado, estudiando la influencia del pH de la solución en el proceso de adsorción y la influencia de la reducción de la superficie del carbón. Para ello se utiliza un carbón activado de origen lignocelulósico y un material que resulta de la reducción del mismo. La interacción sólido­solución se caracteriza por el análisis de sus isotermas de adsorción a 298 K a valore...

Air stability and magnetic properties of GdN, TiN, and (Gd,Ti)N nanoparticles

International Nuclear Information System (INIS)

Si Pingzhan; Choi, C. J.; Tegus, O.; Brueck, E.; Geng, D. Y.; Zhang, Z. D.

2008-01-01

GdN, TiN, and (Gd,Ti)N nanoparticles were prepared by arc evaporating Gd, Ti, and Gd-Ti alloys in N 2 , respectively. Most of these nanoparticles show narrow size distribution with average diameter of 20 nm. Shell/core structure was observed in the (Gd,Ti)N nanoparticles, in which the shell was formed by surface reaction with air. (Gd,Ti)N nanoparticles are more stable than GdN nanoparticles in air due partially to the formation of the protective shell. The Curie temperature of GdN nanoparticles is lower than that of the bulk GdN. Both GdN and (Gd, Ti)N nanoparticles are difficult to reach magnetic saturation and show zero coercivity

Traducción comentada : transcripción y traducción forenses

OpenAIRE

Benito Vega, Mª del Pilar

2016-01-01

El documento objeto de esta investigación y traducción es un texto sobre la transcripción y traducción forenses. En él se abordan los problemas más habituales a los que se tienen que enfrentar los profesionales de este campo, tales como: 1. falta de concienciación social y del sistema jurídico estadounidense sobre la importancia de tener transcriptores y traductores forenses cualificados, 2. los problemas judiciales que una persona con bajo nivel de inglés padece como consecuencia...

Educación Ambiental: de la sensibilización a la acción

OpenAIRE

Donato-Calderón, Fiorella

2012-01-01

En las últimas décadas, la Educación Ambiental ha estado sometida a un proceso de evolución histórico, conceptual y metodológico, que ha favorecido su planteamiento como estrategia intencionada hacia la construcción de conocimientos, la formación de valores, el desarrollo de actitudes y aptitudes, en busca de un cambio de comportamiento para la acción y la participación en la resolución de problemas ambientales.

Neutron cross section measurements using the ORELA: 86Kr(n,x), 40Ca(n,x), 22Ne(n,γ), 189Os(n,n'), 186187188189Os(n,x), 189Os(n,γ), 148149150Sm(n,γ), 179Ta(n,γ), 868788Sr(n,x), 40Ar(n,x), the stable tellurium isotopes (n,γ) and 205Tl(n,x). Progress report, September 1, 1983-August 31, 1984

International Nuclear Information System (INIS)

Winters, R.R.

1984-09-01

The research performed during this reporting period has resulted in (1) publication of two papers dealing with the optical model and with 187 Os(n,n') for astrophysics; (2) preparation and submission of two papers describing measurements of 148 149 150 Sm(n,γ) and 60 Ni(n,x) cross sections; (3) mesurement of the 189 Os(n,n') cross sections at energies of astrophysical interest; (4) measurement of the 189 Os(n,γ) cross sections over a range of energies pertinent to astrophysical interest; (5) extraction of the tantalum target from an ORELA target assembly and arranging shipment of the radioactive tantalum to Kernforschungszentrum, West Germany, in preparation for a measurement of the 179 Ta(n,γ) cross sections; and (6) acquistion of a smart terminal computer workstation. Preliminary results from our 189 Os measurements are consistent with the cross sections calculated using the same optical model reported by Hershberger et al. for 187 Os. Hence the effect of the first excited state in 187 Os on the use of the Re/Os beta decay as a stellar nucleosynthesis chronometer is very nearly as estimated by Woosley and Fowler. The duration of galactic nucleosynthesis is now estimated from the Re/Os chronmeter as approx. 11.3 byr. and the age of the universe as approx. 17 byr. 19 references

Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111

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J. Hennig

2015-07-01

Full Text Available We report on GaN based field-effect transistor (FET structures exhibiting sheet carrier densities of n = 2.9 1013 cm−2 for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally xIn = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the InxGa1−xN/GaN/AlN/Al0.87In0.13N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of ISD = 1300 mA/mm (560 mA/mm. In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents.

Effects of GaN/AlGaN/Sputtered AlN nucleation layers on performance of GaN-based ultraviolet light-emitting diodes

Science.gov (United States)

Hu, Hongpo; Zhou, Shengjun; Liu, Xingtong; Gao, Yilin; Gui, Chengqun; Liu, Sheng

2017-03-01

We report on the demonstration of GaN-based ultraviolet light-emitting diodes (UV LEDs) emitting at 375 nm grown on patterned sapphire substrate (PSS) with in-situ low temperature GaN/AlGaN nucleation layers (NLs) and ex-situ sputtered AlN NL. The threading dislocation (TD) densities in GaN-based UV LEDs with GaN/AlGaN/sputtered AlN NLs were determined by high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM), which revealed that the TD density in UV LED with AlGaN NL was the highest, whereas that in UV LED with sputtered AlN NL was the lowest. The light output power (LOP) of UV LED with AlGaN NL was 18.2% higher than that of UV LED with GaN NL owing to a decrease in the absorption of 375 nm UV light in the AlGaN NL with a larger bandgap. Using a sputtered AlN NL instead of the AlGaN NL, the LOP of UV LED was further enhanced by 11.3%, which is attributed to reduced TD density in InGaN/AlInGaN active region. In the sputtered AlN thickness range of 10-25 nm, the LOP of UV LED with 15-nm-thick sputtered AlN NL was the highest, revealing that optimum thickness of the sputtered AlN NL is around 15 nm.

La Fusión, la Escisión, la Transformación y la Extinción de las Cooperativas

OpenAIRE

Eva Alonso

2005-01-01

Se estudia la fusión de sociedades cooperativas. Son de especial interés las formas de colaboración económica entre cooperativas, por lo que se ha abordado su regulación procurando su ampliación y facilitando su integración.

Protección contra la contaminación acústica de Aragón.

OpenAIRE

Aragón.

2011-01-01

Contiene: la Ley 7/2010 de 18 de noviembre de Protección Contra la Contaminación Acústica de Aragón. Incluye (p. [111]-152): Ordenanza municipal tipo de Aragón en materia de contaminación acústica.

Band offsets of non-polar A-plane GaN/AlN and AlN/GaN heterostructures measured by X-ray photoemission spectroscopy.

Science.gov (United States)

Sang, Ling; Zhu, Qin Sheng; Yang, Shao Yan; Liu, Gui Peng; Li, Hui Jie; Wei, Hong Yuan; Jiao, Chun Mei; Liu, Shu Man; Wang, Zhan Guo; Zhou, Xiao Wei; Mao, Wei; Hao, Yue; Shen, Bo

2014-01-01

The band offsets of non-polar A-plane GaN/AlN and AlN/GaN heterojunctions are measured by X-ray photoemission spectroscopy. A large forward-backward asymmetry is observed in the non-polar GaN/AlN and AlN/GaN heterojunctions. The valence-band offsets in the non-polar A-plane GaN/AlN and AlN/GaN heterojunctions are determined to be 1.33 ± 0.16 and 0.73 ± 0.16 eV, respectively. The large valence-band offset difference of 0.6 eV between the non-polar GaN/AlN and AlN/GaN heterojunctions is considered to be due to piezoelectric strain effect in the non-polar heterojunction overlayers.

Compounds of addition between yttrium and rare-earths (III) nitrates and the N,N,N'N'-tetramethyladipamide (TMAA)

International Nuclear Information System (INIS)

Lima, W.N. de.

1974-01-01

The synthesis of addition compounds between hydrated rare-earths and yttrium nitrates with the diamine N,N,N',N'-tetramethyladipamide (TMAA) in ethanol, is described. The compounds were characterized by elemental analisys, infrared, Raman, visible and near infrared spectra, molar conductance and molecular weight measurements, conductometric titrations and X-ray powder patterns. (Author) [pt

Improved AlGaN/GaN HEMTs Grown on Si Substrates Using Stacked AlGaN/AlN Interlayer by MOCVD

International Nuclear Information System (INIS)

Wang Yong; Yu Nai-Sen; Li Ming; Lau Kei-May

2011-01-01

AlGaN/GaN high electron mobility transistors (HEMTs) are grown on 2-inch Si (111) substrates by MOCVD. The stacked AlGaN/AlN interlayer with different AlGaN thickness and indium surfactant doped is designed and optimized to relieve the tensile stress during GaN epitaxial growth. The top 1.0μm GaN buffer layer grown on the optimized AlGaN/AlN interlayer shows a crack-free and shining surface. The XRD results show that GaN(002) FWHM is 480 arcsec and GaN(102) FWHM is 900 arcsec. The AGaN/GaN HEMTs with optimized and non-optimized AlGaN/AlN interlayer are grown and processed for comparison and the dc and rf characteristics are characterized. For the dc characteristics of the device with optimized AlGaN/AlN interlayer, maximum drain current density I dss of 737mA/mm, peak transconductance G m of 185mS/mm, drain leakage current density I ds of 1.7μA/mm, gate leakage current density I gs of 24.8 μA/mm and off-state breakdown voltage V BR of 67 V are achieved with L g /W g /L gs /L gd = 1/10/1/1 μm. For the small signal rf characteristics of the device with optimized AlGaN/AlN interlayer, current gain cutoff frequency f T of 8.3 GHz and power gain cutoff frequency f max of 19.9 GHz are achieved with L g /W g /L gs /L gd = 1/100/1/1 μm. Furthermore, the best rf performance with f T of 14.5 GHz and f max of 37.3 GHz is achieved with a reduced gate length of 0.7μm. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

EDUCACIÓN EN VALORES Y EDUCACIÓN EMOCIONAL: PROPUESTAS PARA LA ACCIÓN PEDAGÓGICA

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María Rosa Buxarrais Estrada

2010-12-01

Full Text Available Relacionar la educación en valores con la educación emocional supone enfatizar la idea de que la educación consiste en ofrecer respuestas desde la institución escolar a todas las dimensiones de la persona: cognitivas, conductuales y afectivas -el pensar, el hacer y el sentir-. Respuestas que parece no se han dado en sistemas educativos anteriores. En este artículo planteamos la necesidad de rescatar una educación en valores que no sólo no olvide la educación emocional, sino que la explicite a través de programas de acción pedagógica cuyos objetivos se concreten en la construcción de la personalidad ética, la educación de los sentimientos y la competencia comunicacional, la adquisición de competencias éticas, la aceptación de límites y normas de convivencia, así como la gestión de las emociones y su consecuencia conductual: la autorregulación del comportamiento. La sensibilización y formación del profesorado resultará indispensable para se plantee y desarrolle en las instituciones educativas esta innovación.

Propuesta de integración de los sistemas de información de una institución de compensación y liquidación de valores

OpenAIRE

Lescano Blanco, Mack Paul; Lescano Blanco, Mack Paul; Lescano Blanco, Mack Paul

2011-01-01

El presente trabajo trata sobre situación de la integración de información de los sistemas informáticos de una empresa de Compensación y Liquidación de Valores (ICLV). Actualmente el sistema de administración de valores de la empresa ICLV (la cual llamaremos sistema Core) tiene una arquitectura que integra todo sus módulos principales, sin embargo hay otros sistemas externos que necesitan extraer información del sistema Core, tales como el sistemas ERP-07 la cual necesita información de los m...

RESIDUOS DE LA CONSTRUCCIÓN: UNA OPCIÓN PARA LA RECUPERACIÓN DE SUELOS

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Erica Mejía Restrepo

2015-06-01

Full Text Available La disposición final de residuos de la construcción y demolición (RCD puede generar impactos ambientales negativos como la degradación y erosión de suelos, destrucción de la vegetación y pérdida de servicios ambientales. Los procesos de restauración buscan la integridad ecológica de estas zonas, lo cual incluye el reacondicionamiento físico, químico y biológico de estos terrenos degradados. El objetivo de este trabajo fue caracterizar química y mineralógicamente los RCD generados en la ciudad de Medellín y determinar su uso potencial en la biorremediación de suelos degradados por la minería. A través de las técnicas de difracción de rayos X y microscopia óptica de luz plana polarizada se ha encontrado en los RCD minerales tales como cuarzo, calcita, wallostonita, albita, anatasa, actinolita. Estos minerales al aplicarse a suelos degradados pueden mejorar las propiedades físicas de estos (aireación, infiltración, así como aportar nutrientes esenciales (Ca, Mg, Fe, Mn, Cu, Zn, Ni o benéficos para las plantas (Na, Si, Cu. Los resultados obtenidos sugieren que los RCD tienen un alto potencial para ser usados en la bioremediación de terrenos degradados por minería.

Moderately inhibitory effects of N-dodecyloxymethylene-N-methylpiperidinium and N-dodecyloxymethylene-N-methylmorpholinium chlorides on seed germination

Directory of Open Access Journals (Sweden)

Stanisław J. Knypl

2014-01-01

Full Text Available N-Dodecyloxymethylene-N-methylpiperidinium chloride (DMMP and N-dodecyloxyme-thylene-N-methylmorpholinium chloride (DMMM retarded germination of seeds of 9 cultivated plant species when applied at a concentration of 10-3 M, and inhibited germination at a concentration of 10-2 M. The exceptions were represented by Lepidium sativum L. and Linum usitatissimum L. seeds which germinated well even in 10-2 M solutions of either DMMP or DMMM.

INTEGRACIÓN Y COLABORACIÓN EN EL CIBERESPACIO

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Wander M. Paes

2011-08-01

Full Text Available El concepto de compartir recursos computacionales entre participantes WEB, ha sidogradualmente extendido para apoyar escenarios en el mundo  wireless que introduce unavariedad posible de integración y colaboración. El concepto de “servicios” deviene en unaclave del compartir información dentro del mundo de la tecnología de información. En estepunto de vista se presenta la relación entre los movimientos dentro del entorno de informacióndigital enfocado en conceptos socio-tecnológico: tecnología persuasiva/ubicua, Arquitecturade Servicios/Sistema, Colaboración e Integración en aplicaciones WEB como un recurso delsistema e interoperabilidad de la información. La idea acerca del punto de vistainterdisciplinario, como un instrumento de sabiduría, producción de conocimiento, ycolaboración de información esparcida dentro del entorno digital, es un factor que se adapta alcontexto contemporáneo, alcanzando a los dispositivos móviles usando los serviciosdistribuidos en Internet. Este aproximamiento queda en la necesidad de un estudio relacionadoa la interoperabilidad que refiere a la comunicación y al intercambio de información entre lagente. Este fenómeno muestra una tendencia de las soluciones de sistemas en entornoswireless   y tecnología de Internet debido a una variedad de protocolos y a la popularidad de losdispositivos móviles (celular, PDAs, Smartphone, Tablets y Pocket PC. La consolidación deInternet como un entorno de colaboración así como también la aparición de las aplicacionsmóviles habiendo influenciado directamente en las solucions comerciales y en la arquitecturade sistemas en la sociedad contemporánea. Este renueva el mapa digital cartográfico de losservicios decentralizados en el ciberespacio. Deviene en un fértil entorno para el estudio de lasaplicaciones móviles, los componentes computacionales (como un servicio y su usabilidadentre accionistas en el ciberespacio. Una escena que representa el

Cocreación: una propuesta para la recolección, sistematización y análisis de la información en la investigación cualitativa

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Rubén Nanclares

2014-04-01

Full Text Available El investigador debe hacer un tipo de investigación abierta, interdisciplinaria, multidimensional, plurivalente y solo sujeta a las restricciones determinadas por la consistencia y coherencia del proceso investigativo desarrollado (Cerda 1996:100. Este planteamiento hace posible pensar en la reflexión que se propone desarrollar en este artículo, el cual surge en el campo de la investigación cualitativa en educación. Se parte de la investigación de maestríala Hipermedia Educativa: una estrategia para la gestión del conocimiento (GC en procesos formativos de la educación superior, en donde se emplearon de manera experimental técnicas para la cocreación como instrumento soporte para la recolección, sistematización y análisis de la información al servicio de la investigación cualitativa. Para el desarrollo, se empleó la investigación acción desde un enfoque crítico, estos métodos permitieron plantear la ruta metodológica que propicio los resultados obtenidos en la investigación, a su vez facilitó crear y validar una matriz que soporta la producción de Hipermedia Educativa, para propiciarla GCen los procesos formativos. En los resultados, se evidencia como se retroalimentan los procesos formativos considerando aportes y experiencias de los participantes, así como la generación de valor agregado a la propuesta formativa, lo que genera un impacto positivo en el desarrollo del proceso de enseñanza y aprendizaje. En conclusión, se evidencia que las técnicas para la cocreación fueron clave para llegar a los resultados de la investigación realizada.

REMOCIÓN DE SÓLIDOS TOTALES DE VINAZAS POR ELECTROCOAGULACIÓN - ELECTROFLOTACIÓN

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JAVIER DÁVILA RINCÓN

2009-01-01

Full Text Available El presente artículo presenta los resultados obtenidos en el tratamiento de vinaza proveniente una destilería de alcohol por medio de un proceso de electrocoagulación - electroflotación. Se evaluaron diferentes variables de operación como pH inicial de la solución, densidad de corriente y concentración de NaCl, como soporte electrolítico, en un diseño factorial 23 usando electrodos de aluminio en un arreglo monopolar. Los resultados indican que esta técnica podría ser usada en el proceso de concentración de vinazas. Se obtuvo remoción de sólidos totales de 37% sin utilizar un soporte electrolítico.

Investigación e investigación formativa

OpenAIRE

Carlos Augusto Hernández

2003-01-01

Este artículo hace una distinción entre investigación e investigación formativa. También señala los peligros de confundir estas dos formas de trabajo académico e insiste en la necesidad de desarrollarlas simultáneamente para enfrentar los nuevos retos de la educación superior. Igualmente habla de la importancia de intensificar los vínculos entre investigación y docencia y hace la diferencia entre investigación pedagógica e investigación formativa. Finalmente cuestiona la posibilidad de una fo...

Density, viscosity and excess molar volume of binary mixtures of tri-n-octylamine + diluents (n-heptane, n-octane, n-nonane, and n-decane) at various temperatures

International Nuclear Information System (INIS)

Fang, Sheng; Zuo, Xiao-Bo; Xu, Xue-Jiao; Ren, Da-Hai

2014-01-01

Highlights: • Densities and viscosities of tri-n-octylamine + n-heptane, +n-octane, +n-nonane, or +n-decane are determined. • The excess molar volume is calculated. • The Grunberg and Nissan equation and Fang and He equation are used to correlate the binary viscosities. -- Abstract: Densities (ρ) and viscosities (η) for binary mixtures of tri-n-octylamine (TOA) + n-heptane, TOA + n-octane, TOA + n-nonane, and TOA + n-decane are determined at T (283.15, 293.15, and 303.15) K and atmospheric pressure. The excess molar volume is calculated from the density data and is correlated by a Redlich–Kister type equation. The excess molar volume is negative for all the four systems. The results show that the volume accommodation effect is predominant in these systems. The Grunberg and Nissan equation and Fang and He equation for binary mixtures are used to correlate the experimental viscosity data. The Fang and He equation gives an average absolute deviation (AAD%) of 0.8% for TOA with alkane mixtures, better than that of 3.8% given by the Grunberg and Nissan equation

Theoretical study of the interaction of N2 with water molecules. (H2O)/sub n/:N2, n = 1--8

International Nuclear Information System (INIS)

Curtiss, L.A.; Eisgruber, C.L.

1984-01-01

Ab initio molecular orbital calculations including correlation energy have been carried out on the interaction of a single H 2 O molecule with N 2 . The potential energy surface for H 2 O:N 2 is found to have a minimum corresponding to a HOH xxx N 2 structure with a weak ( -1 ) hydrogen bond. A second, less stable, configuration corresponding to a H 2 O xxx N 2 structure with N 2 bonded side on to the oxygen of H 2 O was found to be either a minimum or a saddle point in the potential energy surface depending on the level of calculation. The minimal STO-3G basis set was used to investigate the interaction of up to eight H 2 O molecules with N 2 . Two types of clusters, one containing only HOH xxx N 2 interactions and the other containing both HOH xxxN 2 and H 2 O xxx N 2 interactions, were investigated for [N 2 :(H 2 O)/sub n/, n = 2--8

EN DIRECCIÓN A LA POSTCOMUNICACIÓN

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Luis Rodolfo Rojas Vera

1999-01-01

Full Text Available El artículo desarrolla bajo el estilo de ensayo la idea de una teoría de la Postcomunicación. Centra la atención en los cambios acelerados del mundo comunicacional y los retos de entendimiento de la cultura postcomunicacional bajo los esquemas de los actuales modelos de comunicación. Señala que la sinergía de las comunicaciones será la clave que explicará el mundo postcomunicacional del Siglo XXI. Anuncia que la Postcomunicación cambiará las reglas de la Dirección y plantea la necesidad de enfoques transdisciplinarios para el estudio de la postcomunicación. Ofrece un conjunto de reflexiones que pueden ser útiles para los científicos de la Comunicación.

HIFK:n sponsoriyhteistyön kehittäminen

OpenAIRE

Leppälahti, Jussi

2012-01-01

HIFK Jalkapallo on urheiluseura HIFK:n jalkapallojaos. Seuran miesten edustusjoukkue pelaa Suomen toiseksi korkeimmalla sarjatasolla miesten Ykkösessä. Seitsemän Suomen mestaruuden seuran aikeissa on tulevaisuudessa selkeä urheilullinen sekä taloudellinen kasvu. Tämän tulee mahdollistamaan yritysten kanssa tehtävän sponsorointiyhteistyön kehittäminen ja siitä saatavien varojen kasvu. Tämän opinnäytetyön tarkoituksena oli tutkia, miten HIFK Jalkapallon sponsorointiyhteistyötä voisi kehittä...

Molecular and component volumes of N,N-dimethyl-N-alkylamine N-oxides in DOPC bilayers

DEFF Research Database (Denmark)

Belicka, Michal; Klacsova, Maria; Karlovska, Janka

2014-01-01

The volumetric properties of fluid bilayers formed of dioleoylphosphatidylcholine (DOPC) with incorporated N ,N -dimethyl-N -alkylamine N -oxides (Cn NO, n = 6, 10–18 is the even number of carbons in alkyl chain) were studied by vibrating tube densitometry in the temperature interval from 20 °C...... to 50 °C. It was found that the DOPC and Cn NO mixed ideally in the investigated composition range and hence the molecular volumes of DOPC (V DOPC) and incorporated Cn NO (V CnNO) were constant and additive within error limits. From the temperature dependencies of the molecular volumes of DOPC and Cn...... NO their coefficients of isobaric thermal expansivities in the investigated temperature interval were obtained. The V CnNO volumes of Cn NO incorporated into DOPC bilayers showed linear dependencies on the Cn NO alkyl chain length at all measured temperatures. This allowed to calculate the component volume of the Cn...

Fitorremediación en la recuperación de suelos: una visión general

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Andrea Angélica Bernal Figueroa

2014-12-01

Full Text Available En esta investigación se revisan aspectos fundamentales de la fitorremediación como técnica en la recuperación de suelos, la cual se emplea para eliminar o disminuir la contaminación o degradación de los mismos, por medio de la utilización de especies vegetales. Se encontró que técnicas tales como la fitoextracción, rizofiltración, fitoestabilización, fitodegradación, rizodegradación y fitovolatilización, están determinadas principalmente por el tipo de contaminante, diversidad microbiana y propiedades del suelo. Se mencionan algunos  spectos en cuanto a la nutrición mineral y la tolerancia de las plantas, las principales ventajas y desventajas que ofrece esta técnica, algunas especies empleadas para su implementación y unos estudios de caso. Se concluye que el conocimiento de los procesos fisiológicos en la planta y los compuestos tóxicos, permite que se puedan seleccionar especies vegetales con mayores niveles de tolerancia hacia contaminantes específicos; y adicionalmente, por medio de modificaciones genéticas se puede incrementar la biomasa vegetal, su morfología, densidad radicular o penetración en profundidad, así como favorecer la existencia de asociaciones específicas entre microorganismos y raíces.

Neuroeducación, ansiedad y atención en alumnos de Educación Primaria

OpenAIRE

Betegón Blanca, Elena

2017-01-01

El Trabajo de Fin de Máster que se expone a continuación constituye una iniciación a la investigación educativa. El tema principal que se aborda está centrado en la búsqueda de metodologías adaptables, en niveles de Educación Primaria, que ayuden a resolver el reciente aumento de trastornos del aprendizaje y la aparición de conductas disruptivas en la población infanto-juvenil en el medio escolar. Partiendo de la fundamentación teórica sobre Neuroeducación se instalan una serie de estímulos n...

Thermophysical properties of N, N-dimethylacetamide mixtures with n-butanol

Science.gov (United States)

Maharolkar, Aruna P.; Murugkar, A. G.; Khirade, P. W.; Mehrotra, S. C.

2017-09-01

The refraction, dielectric, viscosity, density, data of the binary mixtures of N, N-dimethylacetamide (DMA) with n-butanol at 308.15 and 313.15 K. The measured parameters used to obtain derived properties like Bruggeman factor, molar refraction and excess static dielectric constant, excess inverse relaxation time, excess molar volume and excess viscosity, excess molar refraction. The variation in magnitude with composition and temperature of these quantities has been used to discuss the type, strength and nature of binary interactions. Results confirm that there are strong hydrogen-bond interactions between unlike molecules of DMA+ n-butanol mixtures and that 1: 1 complexes are formed and strength of intermolecular interaction increases with temperature.

VALORACIÓN SOCIOECONÓMICA DE LA EXTRACCIÓN DE GAS MEDIANTE FRACTURACIÓN HIDRÁULICA EN LA REGIÓN DE MURCIA

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José M. Martínez-Paz

2015-01-01

Full Text Available La extracción de gas no convencional mediante fracturación hidráulica (fracking es una técnica controvertida, ya que a sus beneficios sociales y económicos se contraponen sus potenciales riesgos ambientales y sobre la salud humana. En el norte de la Región de Murcia, al igual que en otras zonas de España, se han concedido recientemente permisos de investigación y prospección para la posible explotación de yacimientos de gas mediante fracking, lo que ha originado la aparición de movimientos ciudadanos que abogan por su prohibición. El objetivo central de este trabajo es estudiar el conocimiento, la percepción y la aceptabilidad que tienen los ciudadanos de la Región de Murcia sobre la explotación de esta fuente de energía. Con este fin se realiza una encuesta en la que se implementa el método de la Valoración Contingente. Los resultados informan, entre otros, que algo más de dos tercios de la población estarían a favor de su implementación, condicionado a que salud y el medioambiente sean salvaguardados. A su vez cada familia murciana se muestra dispuesta a contribuir, en media, con 15 €/año como sobrecoste en el recibo eléctrico para fijar una moratoria en la explotación.

Analysis of the auger recombination rate in P+N-n-N-N HgCdTe detectors for HOT applications

Science.gov (United States)

Schuster, J.; Tennant, W. E.; Bellotti, E.; Wijewarnasuriya, P. S.

2016-05-01

Infrared (IR) photon detectors must be cryogenically cooled to provide the highest possible performance, usually to temperatures at or below ~ 150K. Such low operating temperatures (Top) impose very stringent requirements on cryogenic coolers. As such, there is a constant push in the industry to engineer new detector architectures that operate at higher temperatures, so called higher operating temperature (HOT) detectors. The ultimate goal for HOT detectors is room temperature operation. While this is not currently possibly for photon detectors, significant increases in Top are nonetheless beneficial in terms of reduced size, weight, power and cost (SWAP-C). The most common HgCdTe IR detector architecture is the P+n heterostructure photodiode (where a capital letter indicates a wide band gap relative to the active layer or "AL"). A variant of this architecture, the P+N-n-N-N heterostructure photodiode, should have a near identical photo-response to the P+n heterostructure, but with significantly lower dark diffusion current. The P+N-n-N-N heterostructure utilizes a very low doped AL, surrounded on both sides by wide-gap layers. The low doping in the AL, allows the AL to be fully depleted, which drastically reduces the Auger recombination rate in that layer. Minimizing the Auger recombination rate reduces the intrinsic dark diffusion current, thereby increasing Top. Note when we use the term "recombination rate" for photodiodes, we are actually referring to the net generation and recombination of minority carriers (and corresponding dark currents) by the Auger process. For these benefits to be realized, these devices must be intrinsically limited and well passivated. The focus of this proceeding is on studying the fundamental physics of the intrinsic dark currents in ideal P+N-n-N-N heterostructures, namely Auger recombination. Due to the complexity of these devices, specifically the presence of multiple heterojunctions, numerical device modeling techniques must be

Estimación de la corrosión intergranular en la aleación de magnesio AZ31B soldada por fricción - agitación

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Willian Aperador Chaparro

2013-12-01

Full Text Available En este trabajo se evalúa la corrosión intergranular, que se presenta en las soldaduras de la aleación de magnesio AZ31B unidas por los procesos de fricción-agitación y comparada con la soldadura con arco de tungsteno y gas, con el fin de evaluar y comparar el comportamiento a la corrosión de ambas soldaduras por medio la técnica de Espectroscopia de Impedancias Electroquímica. Adicionalmente se realizaron análisis microestructurales de los límites de grano por medio del microscopio. Los resultados obtenidos en esta investigación muestran una mayor resistencia a la corrosión de las muestras obtenidas con el proceso de fricción-agitación.

Polarization-enhanced InGaN/GaN-based hybrid tunnel junction contacts to GaN p-n diodes and InGaN LEDs

Science.gov (United States)

Mughal, Asad J.; Young, Erin C.; Alhassan, Abdullah I.; Back, Joonho; Nakamura, Shuji; Speck, James S.; DenBaars, Steven P.

2017-12-01

Improved turn-on voltages and reduced series resistances were realized by depositing highly Si-doped n-type GaN using molecular beam epitaxy on polarization-enhanced p-type InGaN contact layers grown using metal-organic chemical vapor deposition. We compared the effects of different Si doping concentrations and the addition of p-type InGaN on the forward voltages of p-n diodes and light-emitting diodes, and found that increasing the Si concentrations from 1.9 × 1020 to 4.6 × 1020 cm-3 and including a highly doped p-type InGaN at the junction both contributed to reductions in the depletion width, the series resistance of 4.2 × 10-3-3.4 × 10-3 Ω·cm2, and the turn-on voltages of the diodes.

Polarization-enhanced InGaN/GaN-based hybrid tunnel junction contacts to GaN p–n diodes and InGaN LEDs

KAUST Repository

Mughal, Asad J.

2017-11-27

Improved turn-on voltages and reduced series resistances were realized by depositing highly Si-doped n-type GaN using molecular beam epitaxy on polarization-enhanced p-type InGaN contact layers grown using metal–organic chemical vapor deposition. We compared the effects of different Si doping concentrations and the addition of p-type InGaN on the forward voltages of p–n diodes and light-emitting diodes, and found that increasing the Si concentrations from 1.9 × 1020 to 4.6 × 1020 cm−3 and including a highly doped p-type InGaN at the junction both contributed to reductions in the depletion width, the series resistance of 4.2 × 10−3–3.4 × 10−3 Ωcenterdotcm2, and the turn-on voltages of the diodes.

Polarization-enhanced InGaN/GaN-based hybrid tunnel junction contacts to GaN p–n diodes and InGaN LEDs

KAUST Repository

Mughal, Asad J.; Young, Erin C.; Alhassan, Abdullah I.; Back, Joonho; Nakamura, Shuji; Speck, James S.; DenBaars, Steven P.

2017-01-01

Improved turn-on voltages and reduced series resistances were realized by depositing highly Si-doped n-type GaN using molecular beam epitaxy on polarization-enhanced p-type InGaN contact layers grown using metal–organic chemical vapor deposition. We compared the effects of different Si doping concentrations and the addition of p-type InGaN on the forward voltages of p–n diodes and light-emitting diodes, and found that increasing the Si concentrations from 1.9 × 1020 to 4.6 × 1020 cm−3 and including a highly doped p-type InGaN at the junction both contributed to reductions in the depletion width, the series resistance of 4.2 × 10−3–3.4 × 10−3 Ωcenterdotcm2, and the turn-on voltages of the diodes.

Educación y sensibilización en alergias alimentarias en Educación Primaria

OpenAIRE

Orenes Muñoz, Elena

2016-01-01

El presente Trabajo Final de Grado (TFG) fomenta la sensibilización y la educación de la alergia alimentaria en el alumnado del ciclo de Educación Primaria. El presente TFG presenta un programa de actividades educativas para la adquisición de hábitos saludables rutinarios para fomentar la prevención y la creación de un entorno seguro para educandos alérgicos en la comunidad educativa. Ciencias de la Alimentación Educación

Oxidation resistance of TiN, CrN, TiAlN and CrAlN coatings deposited by lateral rotating cathode arc

International Nuclear Information System (INIS)

Chim, Y.C.; Ding, X.Z.; Zeng, X.T.; Zhang, S.

2009-01-01

In this paper, four kinds of hard coatings, TiN, CrN, TiAlN and CrAlN (with Al/Ti or Al/Cr atomic ratio around 1:1), were deposited on stainless steel substrates by a lateral rotating cathode arc technique. The as-deposited coatings were annealed in ambient atmosphere at different temperatures (500-1000 o C) for 1 h. The evolution of chemical composition, microstructure, and microhardness of these coatings after annealing at different temperatures was systematically analyzed by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and nanoindentation experiments. The oxidation behaviour and its influence on overall hardness of these four coatings were compared. It was found that the ternary TiAlN and CrAlN coatings have better oxidation resistance than their binary counterparts, TiN and CrN coatings. The Cr-based coatings (CrN and CrAlN) exhibited evidently better oxidation resistance than the Ti-based coatings (TiN and TiAlN). TiN coating started to oxidize at 500 o C. After annealing at 700 o C no N could be detected by EDX, indicating that the coating was almost fully oxidized. After annealed at 800 o C, the coating completely delaminated from the substrate. TiAlN started to oxidize at 600 o C. It was nearly fully oxidized (with little residual nitrogen detected in the coating by EDX) and partially delaminated at 1000 o C. Both CrN and CrAlN started to oxidize at 700 o C. CrN was almost fully oxidized (with little residual nitrogen detected in the coating by EDX) and partially delaminated at 900 o C. The oxidation rate of the CrAlN coating is quite slow. After annealing at 1000 o C, only about 19 at.% oxygen was detected and the coating showed no delamination. The Ti-based (TiN and TiAlN) coatings were not able to retain their hardness at higher temperatures (≥ 700 o C). On the other hand, the hardness of CrAlN was stable at a high level between 33 and 35 GPa up to an annealing temperature of 800 o C and still kept at a comparative high value of

Gümüşhanevî’de Tanrı’nın Varlığının Bilinmesi Meselesi

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Hasan Tanrıverdi

2013-12-01

Full Text Available Ahmed Ziyaüddin Gümüşhanevî (1813-1893 19. yüzyılda yaşamış önemli mutasavvıflardan biridir. Biz bu çalışmada onun, Allah’ın varlığının bilinmesiyle ilgili görüşlerini incelemeye çalışacağız. İlahî dinlere göre, insanların Tanrı’nın varlığını bilmeleri mümkündür; zira Tanrı insanı bu kabiliyette yaratmıştır. Bu nedenle Tanrı’nın varlığı ve varlığının temellendirilmesi meselesi gerek filozofların gerekse teolog ve mutasavvıfların düşünce sistemlerinde önemli bir yere sahiptir. Onlar, Tanrı’nın varlığının, duyu, akıl ve sezgi gibi bilgi yetileriyle bilinebileceği iddia etmişler ve bu yetilerle Tanrı’nın varlığını temellendirmeye çalışmışlardır. Gümüşhanevî, Allah’ın varlığının akıl ile âlemde onun varlığına delalet eden işaretlerden hareketle bilinebileceğini iddia etmiştir. Ancak Allah’ın akıl ile tam olarak bilinmesi mümkün değildir. O, altıncı his denilen kalbin devreye girmesiyle bilinebilir

Coulomb dissociation of N-20,N-21

NARCIS (Netherlands)

Roeder, Marko; Adachi, Tatsuya; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M.; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J. G.; Burgunder, G.; Caamano, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkall, Joakim; Chakraborty, S.; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Pramanik, Ushasi Datta; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A.; Farinon, F.; Fraile, Luis M.; Freer, Martin; Freudenberger, M.; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhaeuser, Roman; Goebel, Kathrin; Kalantar-Nayestanaki, Nasser; Najafi, Mohammad Ali; Rigollet, Catherine; Stoica, V.; Streicher, Branislav; Van de Walle, J.

2016-01-01

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N-20,N-21 are reported. Relativistic N-20,N-21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a

Investigación educativa e investigación en educación matemática

Directory of Open Access Journals (Sweden)

Mario Castillo Sánchez

2013-07-01

Full Text Available El presente artículo teórico tiene como propósitos exponer el punto de vista de distintos autores sobre el concepto de educación; establecer la relación entre ciencias de la educación, pedagogía y educación; así como mostrar el papel que posee la filosofía de la educación en este proceso, y analizar el rol de la investigación en el campo de la educación y en la educación matemática. Se concibe la educación como un proceso permanente y dinámico que le brinda al individuo herramientas para su realización personal, el perfeccionamiento de este y su inserción en la sociedad al inculcarle reglas, comportamientos, conocimientos, contenidos escolares y valores, entre otros; acordes con el entorno cultural en cual se encuentra inmerso. Después de analizar la investigación en educación, se puede concluir que la investigación en educación matemática asume un rol preponderante para comprender el proceso de enseñanza y aprendizaje de la disciplina, el papel de las matemáticas en el desarrollo de los individuos y en el desarrollo científico de la sociedad. Se destaca, además, la importancia de una integración de los métodos cuantitativos y cualitativos para la comprensión del proceso de enseñanza y aprendizaje de las matemáticas.

La formación de recursos humanos en alimentación y nutrición

OpenAIRE

Quintana, Ibrahin; Gómez, Amarilis; Rodríguez, Leandro; Rodríguez-Ojea, Arturo; Fernández, Rebeca

2008-01-01

OBJETIVO: hacer una breve historia de la formación de recursos humanos en alimentación y nutrición, y describir cómo se ha comportado la formación de recursos humanos en el instituto, así como algunos elementos que la caracterizan, enfatizando en el proceso de formación del Maestro en Ciencias en Nutrición en Salud Pública. MÉTODOS: se realizó una revisión del diseño curricular de la maestría y otras maneras de formación de recursos humanos, haciéndose una descripción de los resultados alcanz...

Evaluación de la investigación

OpenAIRE

Tamayo y Tamayo, Mario

2010-01-01

La universidad ha desarrollado modelos en torno a la investigación evaluativa, pero es poco lo que ha realizado sobre la evaluación de la investigación, pues es bien diferente de la anterior, ya que la evaluación de la investigación está presente en todo proyecto, pues en último caso es ésta la que decidirá la realización o no del proyecto, mientras que algunos proyectos en diferentes áreas podrían presentarse como investigación evaluativa.

SIMULACIÓN DE MECANISMOS COMPLEJOS DE REACCIÓN.

Directory of Open Access Journals (Sweden)

Daniel A Barragán R.

2010-10-01

Full Text Available Se propone un método para la interpretación de mecanismos complejos de reacción, el cual es aplicado a la simulación del mecanismo de Gyórgyi-Field, (GF desarrollado para la reacción química oscilante de Belousov-Zhabotinsky (BZ. El método basado en la ley de acción de masas y en el principio de independencia y coexistencia de los pasos elementales, reproduce el comportamiento oscilatorio en la concentración de los intermediarios de reacción.

Una introducción a los números complejos

OpenAIRE

Rivero, Francisco

2004-01-01

Una introducción a los números complejos (Rivero, Francisco) Historia de los números complejos 1.1 Los inicios del álgebra 1.2 Cardano 1.3 Bombelli 1.4 Números imaginarios Álgebra de los números complejos 2.1 Definición de número complejo 2.2 Suma de números complejos 2.3 Producto de números complejos 2.4 Representación geométrica 2.5 La forma polar 2.6 Potencias y raíces de números complejos 44 ciens-004 Primera Nivel monográ...

ORGANIZACIÓN Y PLANIFICACIÓN EN NIÑOS CON TDAH: EVALUACIÓN Y PROPUESTA DE UN PROGRAMA DE ESTIMULACIÓN

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Josefina Rubiales

2011-01-01

Full Text Available El Trastorno por Déficit de Atención e Hiperactividad (TDAH es un tra storno de origen neurobiológico complejo y heterogéneo que se caracteriza por un patrón persistente de desatención, hiperactividad y/o impulsividad. Es una de las alteraciones neuroconductuales mas frecuentes en la infancia y la adolescencia, y uno de los principales motivos de consulta debido a sus dificultades en el rendimiento e scolar, problemas de conducta, dificultades de convivencia en el hogar y con pares, afectación de la autoestima y agresividad . El déficit primario está asociado a una disfunción e jecutiva, entre las cuales se encuentra la organización y planificación. El objetivo del presente trabajo fue comparar el desempeño en organización y planificación de niños con y sin diagnóstico de TDAH y presentar una propuesta de estimulación acorde a su s necesidades . MATERIALES Y METODOS: L a muestra clínica conformada por 16 niños con diagnóstico de TDAH y la muestra control por 32 niños sin el diagnóstico, en ambos casos de 8 a 14 años de edad y de la ciudad de Mar del Plata (Argentina . Los instrumento s utilizados para evaluar la organización y planificación han sido el subtest Torres de México de la Batería Neuropsicológica Infantil (ENI, y las subp ruebas Construcción con cubos, Completamiento de Objetos y Ordenamiento de Historias del Test de Intelig encia de Weschler para niños y adolescentes. La propuesta de tratamiento incluye 8 sesiones de estimulación . RESULTADOS Y CONCLUSIONES: L os niños con diagnóstico de TDAH presentan mayor dificultad en la capacidad de organización y planificación que los niñ os de la muestra control; a partir de lo cual se establece una propuesta de estimulación, cuya ventaja y originalidad está acentuada en la validez ecológica del proce

Gestión del talento humano, satisfacción laboral y calidad de gestión en la Institución Educativa 20189

OpenAIRE

Castillo Calvo, Fedra Marisol

2016-01-01

El presente estudio titulado “Gestión del talento humano, satisfacción laboral y calidad de gestión en la Institución Educativa 20189”, tiene como objetivo “Determinar la relación entre la gestión del talento humano, satisfacción laboral y calidad de gestión en la Institución Educativa 20189”, el objetivo del estudio fue conocer los factores que determinan la satisfacción laboral asociado a la gestión de calidad y del talento humano para contribuir con la escuela. El enfoque...

Reaction theories for N* excitations in πN and γN reactions

International Nuclear Information System (INIS)

Lee, T.S.H.

1996-01-01

The importance of developing reaction theories for investigating N* physics is illustrated in an analysis of pion photoproduction on the nucleon. It is shown that the γN ↔ Δ transition amplitudes predicted by the constituent quark model are in agreement with the values extracted from the γN → πN data only when the contributions from the reaction mechanisms calculated using a dynamical approach are taken into account in the analysis

Low-threshold pure UV electroluminescence from n-ZnO:Al/i-layer/n-GaN heterojunction

International Nuclear Information System (INIS)

Li Songzhan; Fang Guojia; Long Hao; Wang Haoning; Huang Huihui; Mo Xiaoming; Zhao Xingzhong

2012-01-01

Ultraviolet (UV) electroluminescence (EL) of n-ZnO:Al (AZO)/i-layer/n-GaN heterojunctions with different intrinsic layers has been obtained. Rectifying behavior and EL spectra of the heterojunctions are investigated at room temperature. Under positive voltage, a dominant UV emission peak around ∼370 nm is observed for both AZO/i-ZnO/n-GaN and AZO/i-MgO/n-GaN heterojunctions. Nevertheless, the UV emission peak intensity of AZO/i-MgO/n-GaN heterojunction is much stronger than that of AZO/i-ZnO/n-GaN heterojunction at the same voltage. The threshold voltage of AZO/i-MgO/n-GaN heterostructured device is as low as 2.3 V. The difference of EL spectra and the emission mechanism in these devices are discussed. - Highlights: ► UV electroluminescence of n-ZnO:Al/i-layer/n-GaN heterojunctions has been obtained. ► Under positive voltage, a dominant UV emission peak around ∼370 nm is observed for both heterojunctions. ► The UV emission peak intensity of the heterojunction with i-MgO layer is much stronger than that with i-ZnO layer at the same voltage. ► The threshold voltage of n-ZnO:Al/i-MgO/n-GaN heterostructured device is as low as 2.3 V.

Investigation of the fabrication processes of AlGaN/AlN/GaN HEMTs with in situ Si3N4 passivation

International Nuclear Information System (INIS)

Tomosh, K. N.; Pavlov, A. Yu.; Pavlov, V. Yu.; Khabibullin, R. A.; Arutyunyan, S. S.; Maltsev, P. P.

2016-01-01

The optimum mode of the in situ plasma-chemical etching of a Si 3 N 4 passivating layer in C 3 F 8 /O 2 medium is chosen for the case of fabricating AlGaN/AlN/GaN HEMTs. It is found that a bias of 40–50 V at a high-frequency electrode provides anisotropic etching of the insulator through a resist mask and introduces no appreciable radiation-induced defects upon overetching of the insulator films in the region of gate-metallization formation. To estimate the effect of in situ Si 3 N 4 growth together with the heterostructure in one process on the AlGaN/AlN/GaN HEMT characteristics, transistors with gates without the insulator and with gates through Si 3 N 4 slits are fabricated. The highest drain current of the AlGaN/AlN/GaN HEMT at 0 V at the gate is shown to be 1.5 times higher in the presence of Si 3 N 4 than without it.

Spectroscopic ellipsometry analysis of InGaN/GaN and AlGaN/GaN heterostructures using a parametric dielectric function model

International Nuclear Information System (INIS)

Wagner, J.; Ramakrishnan, A.; Obloh, H.; Kunzer, M.; Koehler, K.; Johs, B.

2000-01-01

Spectroscopic ellipsometry (SE) has been used for the characterization of AlGaN/GaN and InGaN/GaN heterostructures. The resulting pseudodielectric function spectra were analyzed using a multilayer approach, describing the dielectric functions of the individual layers by a parametric oscillator model. From this analysis, the dielectric function spectra of GaN, Al x Ga 1-x N (x le 0.16), and In 0.13 Ga 0.87 N were deduced. Further, the dependence of the Al x Ga 1-x N band gap energy on the Al mole fraction was derived and compared with photoluminescence data recorded on the same material. The SE band gap data are compatible with a bowing parameter close to 1 eV for the composition dependence of the Al x Ga 1-x N gap energy. Finally, the parametric dielectric functions have been used to model the pseudodielectric function spectrum of a complete GaN/AlGaN/InGaN LED structure

Religión, educación y subjetividades

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Juan Illicachi Guzñay

2014-12-01

Full Text Available El trabajo examina el papel de la religión en la educación y en la sociedad, y la relación entre religión, educación y la producción de subjetividades en los grupos subalternos, particularmente en los indígenas y la población estudiantil, pero antes justifica la vigencia del presente tema en el escenario geopolítico de Riobamba. Para abordar lo planteado, las preguntas que guían el desarrollo del presente artículo son: ¿cuál es el rol de la religión en la sociedad y, específicamente, en la educación? ¿Existen incidencias del “campo” religioso en el “campo” educativo? ¿Qué tipo de subjetividad construye tanto el campo educativo como el religioso?

Introducción a Japón: historia

OpenAIRE

Pelegrín Solé, Ángeles

2008-01-01

Análisis del marco histórico de Japón, con una breve introducción sobre los orígenes del pueblo japonés y su cultura, la época aristocrática (Nara), la hegemonía samurai (Kamakura-Ashikaga), el periodo Tokugawa, y por último la apertura de Japón, la restauración Meiji y la aparición del Japón imperial.

Materiales sostenibles en la edificación : residuos de construcción y demolición, hormigón reciclado

OpenAIRE

MIÑAN ARENAS, MARÍA DEL CARMEN

2012-01-01

PFG de Intercambios académicos. Università Politecnica delle Marche, Ancona (Italia). Este Proyecto Final de Grado trata sobre la reutilización y el reciclaje de los residuos de la construcción como una de las estrategias fundamentales para alcanzar la sostenibilidad en el sector de la construcción. En primer lugar se aportan las definiciones de residuos de construcción y demolición según las diferentes normativas. Después se indica el proceso de producción de áridos reciclados. Finalmente, s...

La investigación-acción en la formación del profesorado

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Romera-Iruela, María Jesús

2011-12-01

Full Text Available Action research by teachers allows for continuous improvement in education and the bridging of theory and practice. This research, while traditionally used in teacher education, is currently becoming enormously important since it should be carried out both before and after educational reforms. The purpose of this study is to map the development of action research in teacher education through articles published in Spanish education journals. The research uses a survey approach and applies a documentary methodology. The results show how productive this line of research has been throughout its evolution, provide a database of all the articles, and offer a view of the personal, social and cognitive dimensions of this line of research: collaboration in publications, the most productive authors, research teams, main institutions performing the studies, specific journals dedicated to this line of research, main topics studied, and epistemological approaches, among others.

La investigación en la acción del profesor posibilita la mejora continua de la educación y la vinculación entre la teoría y la práctica. Esta investigación, si bien tiene tradición en la formación del profesorado, adquiere, en estos momentos, una gran relevancia, puesto que ha de preceder y seguir a las reformas educativas. El objetivo de esta investigación es identificar la trayectoria de la investigación-acción en la formación del profesorado, a través de los artículos publicados en las revistas españolas de educación. El diseño de la misma es de examen y utiliza la metodología documental. Los resultados dan a conocer la productividad de esta línea de investigación duran te todo su desarrollo, aportando una base de datos con todos los artículos, y muestran sus dimensiones personales, sociales y cognitivas: grado de colaboración en las publicaciones, autores más productivos, grupos de investigación, principales instituciones en la realización de

La reinvención de Medellín

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Andres Sanchez Jabba

2013-01-01

Full Text Available Resumen: Con la adopción del modelo de industrialización por sustitución de importaciones, Medellín se convirtió en el centro industrial más importante de Colombia. Esto se debió al surgimiento de su aglomerado textil, el cual fue la fuente de crecimiento económico urbano durante gran parte del siglo XX. Sin embargo, el excesivo grado de especialización en la producción textil generó una profunda crisis industrial cuando inició el proceso de liberalización comercial en la década de 1990. Adicionalmente, el surgimiento del narcotráfico incrementó considerablemente los niveles de violencia. La combinación de estos dos factores dejó a la ciudad sumida en una profunda crisis urbana caracterizada por una gran inestabilidad institucional. Sin embargo, Medellín supo reinventarse: los niveles de violencia disminuyeron, los indicadores sociales y económicos mejoraron y la ciudad buscó el resurgimiento urbano orientando su economía hacia la generación de conocimiento apalancado en la innovación y el uso intensivo de la tecnología.

La reinvención de Medellín

Directory of Open Access Journals (Sweden)

Andrés Sánchez Jabba

2013-06-01

Full Text Available Con la adopción del modelo de industrialización por sustitución de importaciones, Medellín se convirtió en el centro industrial más importante de Colombia. Esto se debió al surgimiento de su aglomerado textil, el cual fue la fuente de crecimiento económico urbano durante gran parte del siglo XX. Sin embargo, el excesivo grado de especialización en la producción textil generó una profunda crisis industrial cuando inició el proceso de liberalización comercial en la década de 1990. Adicionalmente, el surgimiento del narcotráfico incrementó considerablemente los niveles de violencia. La combinación de estos dos factores dejó a la ciudad sumida en una profunda crisis urbana caracterizada por una gran inestabilidad institucional. Sin embargo, Medellín supo reinventarse: los niveles de violencia disminuyeron, los indicadores sociales y económicos mejoraron y la ciudad buscó el resurgimiento urbano orientando su economía hacia la generación de conocimiento apalancado en la innovación y el uso intensivo de la tecnología.

Aproximación teórica a la relación entre los términos gestión documental, gestión de información y gestión del conocimiento

Directory of Open Access Journals (Sweden)

Gauchi Risso, Verónica

2012-12-01

Full Text Available The purpose of this paper is to offer a theoretical approach to the terms «record management», «information management» and «knowledge management», as well as to the relationships among them. This work consists of a descriptive review of the pertinent literature in which the chosen terms are described individually. It aims to transmit scientifically valid information in order to establish a relationship among the three. Three aspects are drawn together in the conceptualization: documents, communication technologies, and people, the combination of which gives rise to a number of strengths that constitute the capital of any organization. This process provides evidence of a strong relationship among record management, information management and knowledge management, which together represent a complementary and indispensable grouping in any organization.

El objeto de esta exposición consiste en el abordaje teórico de los términos gestión documental, gestión de información y gestión del conocimiento y las relaciones existentes entre ellos. Este trabajo corresponde a un estudio de revisión o compilación de tipo descriptivo, en el que los términos seleccionados son descritos uno a uno en sus características y que tiene por finalidad transmitir informaciones válidas científicamente con el objeto de establecer una relación entre los términos propuestos. Tres aspectos confluyen en la conceptualización: documentos, tecnologías de la comunicación y personas; la combinación de todas ellas da lugar a una serie de capacidades que son lo que constituye el capital de toda organización; este proceso evidencia una relación estrecha entre la gestión documental, de información y del conocimiento que conforman un equipo complementario e imprescindible en toda organización.

Lanthanide and actinide extractions with anionic ligands based on cobalt bis(dicarbollide) ions with covalently bonded CMPO functions

Energy Technology Data Exchange (ETDEWEB)

Selucky, P.; Rais, J.; Lucanikova, M. [Nuclear Research Inst. plc., Rez near Prague (Czech Republic); Gruener, B.; Kvicalova, M. [Inst. of Inorganic Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Husinec-Rez near Prague (Czech Republic); Fejfarova, K. [Inst. of Physics, Academy of Sciences of the Czech Republic, Prague (Czech Republic); Cisarova, I. [Charles Univ., Prague (Czech Republic). Dept. of Chemistry

2008-07-01

Compounds were synthesized with the aim to develop efficient extraction agents for liquid-liquid extraction of polyvalent cations, i.e. lanthanides and actinides from high-level activity nuclear waste. Compounds of general formulation [(8-CMPO-(CH{sub 2}-CH{sub 2}O){sub 2}-1,2-C{sub 2}B{sub 9}H{sub 10})(1',2'-C{sub 2}B{sub 9}H{sub 11})-3.3'-Co(III)] with different phosphorus and nitrogen substitution (CMPO={sup 2}R,{sup 3}R P(O)-(CH{sub 2}){sub n}C(O)N{sup 1}R, {sup 1}R = t-octyl, H, Ph, {sup 2}R=Ph, n-octyl, {sup 3}R=Ph, n = 1,2)-(4a to 4e), were prepared and characterized by combination of {sup 11}B NMR, {sup 1}H high field NMR, ESI-M.S., HPLC and other techniques. Molecular structure of the sodium complex of ligand 4a ({sup 1}R = t-octyl, {sup 2}R = {sup 3}R = Ph, n = 1) was determined by single crystal X-ray diffraction analysis. Effect of several modifications in the structure of 4a-4e on the extraction properties was outlined. The study resulted in the definition of ionic ligand with enhanced extraction efficiency for 4a,b (t-octyl and H on the amidic nitrogen atom) and a better solubility of 4a and 4d ({sup 1}R = t-octyl, {sup 2}R = n-Oct, {sup 1}R=Ph, n = 1) in less polar solvents. Low polar mixtures of hydrogenated tetrapropylene (TPH) hexyl methyl ketone (HMK) can be applied as an auxiliary solvent for 4a, selected for detailed studies, replacing thus the polar and less environmentally friendly nitro-, fluoro- and chloro- solvents used in the current dicarbollide liquid-liquid extraction process. Results of the fission products separation from the simulated PUREX feed using 4a are presented inclusive procedures for Eu{sup 3+} stripping. (orig.)

Gestión del tiempo y procrastinación en la educación superior

OpenAIRE

Garzón Umerenkova, Angélica; Universidad El Bosque; Gil Flores, Javier; Universidad de Sevilla (Espala)

2017-01-01

La procrastinación constituye un fallo de las conductas autorregulatorias que conlleva efectos negativos a nivel académico. Analizamos el valor de la gestión del tiempo como variable predictora de la procrastinación, estudiando una muestra de 494 estudiantes universitarios colombianos de primer año, que fueron clasificados en dos grupos en función de su grado de procrastinación académica. Hemos recogido información sobre sus conductas de gestión del tiempo, medidas a través de una versión es...

Operación a corazón abierto

OpenAIRE

Camezzana, María Daniela

2013-01-01

Corazón de nuestro tango, el bandoneón es un instrumento en vías de extinción, de fabricación luthier. Sólo entre 1910 y 1933 entraron unos 60.000 bandoneones a la Argentina, pero conseguir uno hoy es tan complicado que ya hay cosecha en films y libros al respecto. En la Universidad Nacional de Lanús y a partir de la inquietud de su rectora, Ana Jaramillo, se desarrolló Pichuco, el primer bandoneón de fabricación seriada. Facultad de Periodismo y Comunicación Social

La gestión de los números internacionales de identificación de documentos:estado de la cuestión

Directory of Open Access Journals (Sweden)

Pilar Beltran Orenes

2011-04-01

Full Text Available La gestión de los estándares de los números internacionales de identificación de documentos está teniendo una serie de consecuencias derivadas directamente del carácter público o privado de la gestión realizada y de los intereses comerciales. En este texto se hace un análisis del estado actual de las gestiones de los principales números de identificación de documentos, de cara a establecer las bases de la, a nuestro juicio, necesaria reflexión que deberían hacer las instituciones públicas para poder llevar a cabo el control bibliográfico de la producción a escala mundial.

First-principles molecular dynamics investigation of thermal and mechanical stability of the TiN(001)/AlN and ZrN(001)/AlN heterostructures

International Nuclear Information System (INIS)

Ivashchenko, V.I.; Veprek, S.; Turchi, P.E.A.; Shevchenko, V.I.; Leszczynski, J.; Gorb, L.; Hill, F.

2014-01-01

First-principles quantum molecular dynamics investigations of TiN(001)/AlN and ZrN(001)/AlN heterostructures with one and two monolayers (1 ML and 2 ML) of AlN interfacial layers were carried out in the temperature range of 0–1400 K with subsequent static relaxation. It is shown that the epitaxially stabilized cubic B1-AlN interfacial layers are preserved in all TiN(001)/AlN heterostructures over the whole temperature range. In the ZrN(001)/AlN heterostructures, the B1-AlN(001) interfacial layer exists at 0 K, but it transforms into a distorted one at 10 K consisting of tetrahedral AlN 4 , octahedral AlN 6 , and AlN 5 units. The thermal stability of the interfaces was investigated by studying the phonon dynamic stability of the B1-AlN phase with different lattice parameters. The calculations showed that the B1-AlN interface should be unstable in ZrN(001)/AlN heterostructures and nanocomposites, and in those based on transition metal nitrides with lattice parameters larger than 4.4 Å. Electronic band structure calculations showed that energy gap forms around the Fermi energy for all interfaces. The formation of the interfacial AlN layer in TiN and ZrN crystals reduces their ideal tensile and shear strengths. Upon tensile load, decohesion occurs between Ti (Zr) and N atoms adjacent to the 1 ML AlN interfacial layer, whereas in the case of 2 ML AlN it occurs inside the TiN and ZrN slabs. The experimentally reported strength enhancement in the TiN/AlN and ZrN/AlN heterostructures is attributed to impeding effect of the interfacial layer on the plastic flow. - Highlights: • First-principles quantum molecular dynamics studies were conducted. • TiN- and ZrN-based heterostructures with one and two AlN interfacial layers. • Stability and structural transformation between 0 and 1400 K have been calculated. • Stress–strain relationships and ideal strengths determined. • Systems which may form stable superhard heterostructures are identified

First-principles molecular dynamics investigation of thermal and mechanical stability of the TiN(001)/AlN and ZrN(001)/AlN heterostructures

Energy Technology Data Exchange (ETDEWEB)

Ivashchenko, V.I., E-mail: ivash@ipms.kiev.ua [Institute of Problems of Material Science, National Academy of Science of Ukraine, Krzhyzhanosky str. 3, 03142 Kyiv (Ukraine); Veprek, S., E-mail: stan.veprek@lrz.tum.de [Department of Chemistry, Technical University Munich, Lichtenbergstrasse 4, D-85747 Garching (Germany); Turchi, P.E.A. [Lawrence Livermore National Laboratory (L-352), P.O. Box 808, Livermore, CA 94551 (United States); Shevchenko, V.I. [Institute of Problems of Material Science, National Academy of Science of Ukraine, Krzhyzhanosky str. 3, 03142 Kyiv (Ukraine); Leszczynski, J. [Department of Chemistry and Biochemistry, Interdisciplinary Center for Nanotoxicity, Jackson State University, Jackson, MS 39217 (United States); Gorb, L. [Department of Chemistry and Biochemistry, Interdisciplinary Center for Nanotoxicity, Jackson State University, Jackson, MS 39217 (United States); U.S. Army ERDC, Vicksburg, MS 39180 (United States); Hill, F. [U.S. Army ERDC, Vicksburg, MS 39180 (United States)

2014-08-01

First-principles quantum molecular dynamics investigations of TiN(001)/AlN and ZrN(001)/AlN heterostructures with one and two monolayers (1 ML and 2 ML) of AlN interfacial layers were carried out in the temperature range of 0–1400 K with subsequent static relaxation. It is shown that the epitaxially stabilized cubic B1-AlN interfacial layers are preserved in all TiN(001)/AlN heterostructures over the whole temperature range. In the ZrN(001)/AlN heterostructures, the B1-AlN(001) interfacial layer exists at 0 K, but it transforms into a distorted one at 10 K consisting of tetrahedral AlN{sub 4}, octahedral AlN{sub 6}, and AlN{sub 5} units. The thermal stability of the interfaces was investigated by studying the phonon dynamic stability of the B1-AlN phase with different lattice parameters. The calculations showed that the B1-AlN interface should be unstable in ZrN(001)/AlN heterostructures and nanocomposites, and in those based on transition metal nitrides with lattice parameters larger than 4.4 Å. Electronic band structure calculations showed that energy gap forms around the Fermi energy for all interfaces. The formation of the interfacial AlN layer in TiN and ZrN crystals reduces their ideal tensile and shear strengths. Upon tensile load, decohesion occurs between Ti (Zr) and N atoms adjacent to the 1 ML AlN interfacial layer, whereas in the case of 2 ML AlN it occurs inside the TiN and ZrN slabs. The experimentally reported strength enhancement in the TiN/AlN and ZrN/AlN heterostructures is attributed to impeding effect of the interfacial layer on the plastic flow. - Highlights: • First-principles quantum molecular dynamics studies were conducted. • TiN- and ZrN-based heterostructures with one and two AlN interfacial layers. • Stability and structural transformation between 0 and 1400 K have been calculated. • Stress–strain relationships and ideal strengths determined. • Systems which may form stable superhard heterostructures are identified.

La modernización del Japón

Directory of Open Access Journals (Sweden)

rikiwo Shikama

1988-04-01

Full Text Available RESUMEN El autor presenta de forma general una visión del proceso de modernización del Japón. El significado importante de la Revolución Meiji, haciendo alusión al contexto en el cual ésta se desarrolló. Hace un análisis comparativo de la China y Japón derivado de las tesis del doctor Reischaver, catedrático de la universidad de Harvard. Resalta la importancia que tuvo en el proceso de modernización las características específicas del régimen Feudad Japonés, y el alto nivel de alfabetización, que supuso una mayor capacidad  para absorber y asimilar la cultura occidental.

Observations of HC3N, HC5N, and HC7N in molecular clouds

International Nuclear Information System (INIS)

Snell, R.L.; Schloerb, F.P.; Young, J.S.; Hjalmarson, A.; Friberg, P.

1981-01-01

We present observations of HC 3 N, HC 5 N, and HC 7 N in five molecular clouds. Statistical equilibrium calculations have been performed for HC 5 N and HC 7 N and compared with our data and data on other transitions of these molecules reported in the literature to derive the densities and the column densities of the cyanopolyynes in these clouds. We derive densities for TMC 1, TMC 2, and L1544 of between 1 and 4 x 10 4 cm -3 . We have found that the ratios of the cyanopolyynes in these three clouds are the following: HC 3 N/HC 5 Nroughly-equal1.4 and HC 5 N/HC 7 Nroughly-equal3. In L134 N and DR 21(OH) we have measured limits on the HC 5 N emission and find the HC 3 N/HC 5 N ratio to be substantially greater than in the three Taurus clouds. We have also compared the cyanopolyyne column densities with those of 13 CO and find that the abundance of HC 3 N in L134 N and DR 21(OH) is an order of magnitude smaller than that found in the Taurus clouds. The chemical differences between L134 N and the Taurus clouds are particularly interesting in view of their similar physical properties

Mixed complexes of uranium(IV) and thorium(IV) with N,N'-ethylenebis(salicylideneimine) and N,N'-propylenebis(salicylideneimine)

Energy Technology Data Exchange (ETDEWEB)

Doretti, L; Madalosso, F; Sitran, S; Faleschini, S [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi

1976-01-01

Recently some uranium tetrachloride adducts with N-(hydroxyphenyl)-salicylaldimine and N-(methoxyphenyl)salicylaldimine have been prepared (Doretti et al., J. Inorg. Nucl. Chem., (in press)): the study has now extended to the complexes of Uranium(IV) and Thorium(IV) with N,N'-Ethylenebis(salicylideneimine), H/sub 2/salen, and N,N'-Propylenebis(salicylideneimine), H/sub 2/salpropen, with the aim to prepare fully substituted complexes, mixed complexes containing both chloride and Schiff base groups and adducts of tetrachlorides with free Schiff bases. This paper reports the preparation and properties of the compounds MCl/sub 4/(H/sub 2/salen), MCl/sub 4/(H/sub 2/salpropen), M(salen)Cl/sub 2/, M(salen)/sub 2/ and M(salpropen)/sub 2/, where M = U or Th. These compounds have been characterized by elemental analyses and their IR spectra are reported and discussed.

PRODUCCIÓN DE UNA ALEACIÓN NANOESTRUCTURADA FeAl MEDIANTE ALEACIÓN MECÁNICA Y SU CARACTERIZACIÓN MICROESTRUCTURAL

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Roberto. A. Rodríguez-Díaz

2013-01-01

Full Text Available En este trabajo se elaboró la aleación Fe40Al mediante la técnica de aleación mecánica (AM a partir de una mezcla de polvos elementales de Fe y Al, empleando distintos tiempos de molienda. Se caracterizó la evolución en tamaño y morfología de los polvos empleados en el proceso de AM en función del tiempo de molienda mediante la técnica de Microscopía Electrónica de Barrido (MEB. Se empleó la técnica de Difracción de Rayos X (DRX para caracterizar la evolución de la estructura cristalina de las fases obtenidas en función del tiempo de molienda. La aleación Fe40Al con estructura cristalina desordenada del tipo cúbico centrado en el cuerpo se formó a las 20 h de molienda. El tamaño nano-métrico de grano correspondiente a la aleación desordenada Fe40Al se redujo con el transcurso del tiempo mientras que su parámetro de red se incrementó con el transcurso del tiempo de molienda.

High-quality InN grown on KOH wet etched N-polar InN template by RF-MBE

International Nuclear Information System (INIS)

Muto, D.; Araki, T.; Kitagawa, S.; Kurouchi, M.; Nanishi, Y.; Naoi, H.; Na, H.

2006-01-01

We have succeeded in dramatically decreasing the density of dislocations in InN by regrowing InN films on micro-facetted N-polar InN templates. The micro-facetted N-polar InN templates were formed by wet etching in a 10 mol/l KOH solution. InN films were regrown on the micro-facetted N-polar InN templates and on flat surface N-polar InN templates for comparison by radio-frequency plasma-assisted molecular beam epitaxy. InN regrown on micro-facetted InN had considerably smaller twist distribution than that grown on the flat InN templates. From transmission electron microscopy observation, it was confirmed that the InN grown on the micro-facetted InN template had much lower density of dislocations than that grown on the flat InN template, and moreover the propagation of edge dislocations was almost completely terminated at the interface between the regrown InN and the micro-facetted InN template. Based on the results, we propose that regrowth of InN on micro-facetted InN templates is an effective way to obtain high-quality InN films. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Mindfulness e investigación-acción en educación secundaria. Gestación del Programa TREVA​​

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Luis López-González

2016-01-01

Full Text Available Investigación-acción (IA llevada a cabo por ocho docentes más el investigador principal (IP en un instituto de secundaria con todo su alumnado (n = 420. Su objetivo es el diseño, desarrollo y evaluación de 12 Lesson Study de relajaciónmindfulness, que darían lugar al Programa TREVA. El proceso tuvo 6 fases: diagnóstico, hipótesis-acción, diseño del programa, realización del programa (10 semanas de formación y 12 de lessons study, presentación de resultados y evaluación- seguimiento. El Programa TREVA se compone de 12 Lesson Study semanales (9 básicas y 3 especiales. Se usaron técnicas de recogida y de análisis cualitativas y cuantitativas. Se evaluó con el modelo CIPP (contexto, input, proceso y producto y los criterios de Stufflebeam. Tuvo un impacto considerable y efectos individuales y grupales positivos. Es sostenible y transportable.

Characteristics in AlN/AlGaN/GaN Multilayer-Structured High-Electron-Mobility Transistors

International Nuclear Information System (INIS)

Gui-Zhou, Hu; Ling, Yang; Li-Yuan, Yang; Si, Quan; Shou-Gao, Jiang; Ji-Gang, Ma; Xiao-Hua, Ma; Yue, Hao

2010-01-01

A new multilayer-structured AlN/AlGaN/GaN heterostructure high-electron-mobility transistor (HEMT) is demonstrated. The AlN/AlGaN/GaN HEMT exhibits the maximum drain current density of 800 mA/mm and the maximum extrinsic transconductance of 170 mS/mm. Due to the increase of the distance between the gate and the two-dimensional electron-gas channel, the threshold voltage shifts slightly to the negative. The reduced drain current collapse and higher breakdown voltage are observed on this AlN/AlGaN/GaN HEMT. The current gain cut-off frequency and the maximum frequency of oscillation are 18.5 GHz and 29.0 GHz, respectively. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

60Co gamma radiation effect on AlGaN//AlN/GaN HEMT devices

International Nuclear Information System (INIS)

Wang Yanping; Luo Yinhong; Wang Wei; Zhang Keying; Guo Hongxia; Guo Xiaoqiang; Wang Yuanming

2013-01-01

The testing techniques and experimental methods of the 60 Co gamma irradiation effect on AlGaN/AlN/GaN high electron mobility transistors (HEMTs) are established. The degradation of the electrical properties of the device under the actual radiation environment are analyzed theoretically, and studies of the total dose effects of gamma radiation on AlGaN/AlN/GaN HEMTs at three different radiation bias conditions are carried out. The degradation patterns of the main parameters of the AlGaN/AlN/GaN HEMTs at different doses are then investigated, and the device parameters that were sensitive to the gamma radiation induced damage and the total dose level induced device damage are obtained. (authors)

EVALUACIÓN DE LA SATISFACCIÓN DEL PROFESORADO DE CIENCIAS CON LA ADAPTACIÓN AL ESPACIO EUROPEO DE EDUCACIÓN SUPERIOR

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Raúl Quevedo-Blasco

2015-01-01

Full Text Available La implantación del Espacio Europeo de Educación Superior (EEES ha supuesto una transformación de la educación superior en España. Sin embargo, se desconoce cuál es la actitud del profesorado universitario hacia el proceso y cómo ha afectado esta reforma a sus funciones docentes y como investigador. Por ello, se evalúa el grado de satisfacción hacia distintos aspectos relacionados con el EEES. Los participantes fueron 1.958 profesores que imparten docencia en titulaciones de la rama de Ciencias, pertenecientes a universidades públicas españolas. Se trata de un estudio descriptivo de poblaciones mediante encuesta con muestra probabilística, de tipo transversal. En primer lugar, se realizó la selección de la muestra con un nivel de confianza del 97%. Posteriormente, se elaboró un cuestionario ad hoc, aplicado vía online y compuesto por preguntas relacionadas con: información personal y profesional; aspectos generales e institucionales del EEES; docencia, investigación y gestión; metodología y proceso de enseñanza-aprendizaje; evaluación al alumnado; formación del profesorado; coordinación, organización y recursos del centro; comentarios adicionales y propuestas de mejora. El coeficiente alfa de Cronbach fue de 0,80. Los resultados ponen de manifiesto la insatisfacción de la mayor parte del profesorado con la forma en la que se ha realizado la adaptación de las titulaciones de Ciencias al EEES (46,4%, seguido del 44% que piensa que podría mejorar. También se proponen posibles soluciones que pueden tenerse en cuenta a la hora de establecer políticas educativas eficaces para mejorar la educación su¬perior en España. Finalmente, se reflexiona sobre la influencia del proceso de convergencia europea en el desarrollo profesional del profesorado de esta rama y las consecuencias producidas en el ámbito educativo y científico.

Intervención para la racionalización del uso de losartán

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Alfredo Portilla

2017-01-01

Conclusiones: Se logró reducir la prescripción del losartán en dosis superiores a las estimadas como efectivas, lo que implica una reducción en el riesgo de la hiperkalemia y de los costos por dosificación mayor a la recomendada. Es importante reforzar las actividades de educación médica continuada para promover el uso apropiado de los medicamentos.

40 CFR 721.10175 - 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18 and C18-unsatd...

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 1-Propanaminium, N-(3-aminopropyl)-2... 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18 and C18-unsatd. acyl... chemical substance identified as 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12...

SIMULACIÓN DE FLUJOS PIROCLÁSTICOS DEL VOLCÁN CERRO MACHÍN, COLOMBIA, MEDIANTE LA APLICACIÓN DE HERRAMIENTAS DE ARCGIS©

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Elsa Adriana Cárdenas Quiroga

2012-01-01

Full Text Available Cerro Machín es un volcán activo, caracterizado en el pasado por erupciones explosivas de tipo pliniano y ubicado en un sector de gran importancia económica. Desde la década de los noventa se han desarrollado varios modelos de simulación para determinar el área que podría resultar afectada en una nueva erupción, pero estos modelos se basan en programas con variables predeterminadas que no son fácilmente modificables. Por tanto, se diseñó una aplicación del modelo de simulación Model Builder de las herramientas del software ArcGIS© para facilitar el proceso de análisis de los flujos piroclásticos expulsados por ese volcán en tres eventos eruptivos identificados y modelados previamente, con el objetivo de crear una aplicación fácilmente adaptable a cambios en las variables de simulación y que pudiera ser empleada también para modelar otros volcanes. Los resultados obtenidos resultan compatibles y similares a los obtenidos en simulaciones previas, lo que indica que la aplicación desarrollada es funcional.

La gestión de los números internacionales de identificación de documentos:estado de la cuestión

OpenAIRE

Orenes, Pilar Beltran; Universidad Rey Juan Carlos; Usero, José Ángel Martínez

2011-01-01

La gestión de los estándares de los números internacionales de identificación de documentos está teniendo una serie de consecuencias derivadas directamente del carácter público o privado de la gestión realizada y de los intereses comerciales. En este texto se hace un análisis del estado actual de las gestiones de los principales números de identificación de documentos, de cara a establecer las bases de la, a nuestro juicio, necesaria reflexión que deberían hacer las insti...

La separación del almidón de yuca: Evaluación de la sedimentación por gravedad en canales

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Patricia Torres Lozada

2014-01-01

Full Text Available La producción de almidón de yuca en Colombia proviene principalmente del norte del departamento del Cauca, en pequeñas industrias agrícolas llamadas "rallanderías", en las cuales la sedimentación de las partículas suspendidas ocurre en canales. Puesto que el proceso de sedimentación determina la capacidad de la industria del almidón, razón por la cual, se consideró importante evaluar el proceso de sedimentación en los canales rectangulares (0.3x0.4 x 165 m, utilizados generalmente en la región. Se evaluaron dos componentes principales en la zona de decantación: el cambio en la concentración de la suspensión afluente y la distribución del tamaño de la partícula. Con relación al afluente de los canales, se encontró que la concentración de la suspensión durante el funcionamiento del filtro, la mayor parte del tiempo fue entre 0.1 a 6%, predominando la sedimentación de partículas discretas para las cuales aplica la ley de Stokes. En la sedimentación, el flujo varió entre 0.82 a 1.44 L/s con predominio de flujo laminar yTRH> 150 minutos. En los primeros 104 m del canal, las partículas con tamaños> 10 µm fueron retenidas eficientemente; las partículas con tamaños entre 6.7 a 8.8 μm no fueron retenidas, siendo vertidas a los cuerpos de agua y generando así, problemas ambientales.

COMUNICACIÓN GLOBAL Y CAPACIDAD COMPETITIVA EN LAS MICRO EMPRESAS DE COMUNICACIÓN E INFORMACIÓN

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Ángel Páez

2001-01-01

Full Text Available La presente investigación ahonda en la caracterización de las micro empresas de comunicación e información (MECI, empresas que han aparecido en el ámbito mundial a raíz del crecimiento y expansión de las tecnologías de información y comunicación. Se explica en esta investigación la relación entre la comunicación global y la competitividad de las MECI de Maracaibo. Es una investigación de tipo correlacional. Para la recolección de datos se utilizó la técnica de la entrevista estruturada, efectuándola al personal gerencial, administrativo y operativo de las MECI. Los resultados obtenidos comprueban la hipótesis de que existe una relación entre la comunicación global y la capacidad competitiva. El trabajo constituye una contribución para las MECI, debido a que su estudio sistemático proporciona una serie de criterios teóricos y prácticos que podrían ser utilizados por sus gerentes para generar competitividad en el futuro.

Cerebro, números y educación

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Diego ALONSO CÁNOVAS

2013-06-01

Full Text Available En este artículo se aborda el tema de las posibles contribuciones que la Neurociencia Cognitiva puede realizar a la Educación Matemática. En particular, se analizan las bases cerebrales del llamado sentido numérico, y la diferencia entre el cálculo rutinario y el que requiere la comprensión de los números como magnitud. El estudio del cerebro también aporta explicaciones plausibles a algunas de las dificultades en el aprendizaje de las matemáticas que aparecen en nuestras aulas. Se expone, de forma breve, una posible relación entre la inmadurez del lóbulo frontal en el proceso de desarrollo y algunos errores debidos a respuestas impulsivas. Aunque algunas hipótesis son muy especulativas, hacemos referencia a la posible relación entre el talento para las matemáticas y la biología. Finalmente citamos algunos resultados provenientes desde la Psicología Cognitiva sobre la importancia del desarrollo de la intuición matemática en la Educación Primaria y Secundaria.

Statistical model calculation of fission isomer excitation functions in (n,n') and (n,γ) reactions

International Nuclear Information System (INIS)

Chatterjee, A.; Athougies, A.L.; Mehta, M.K.

1977-01-01

A statistical model developed by Britt and others (1971, 1973) to analyze isomer excitation functions in spallation type reactions like (α,2n) has been adopted in fission isomer calculations for (n,n') and (n,γ) reactions. Calculations done for 235 U(n,n')sup(238m)U and 235 U(n,γ)sup(236m)U reactions have been compared with experimental measurements. A listing of the computer program ISOMER using FORTRAN IV to calculate the isomer to prompt ratios is given. (M.G.B.)

Enhancement of indium incorporation to InGaN MQWs on AlN/GaN periodic multilayers

Science.gov (United States)

Monavarian, Morteza; Hafiz, Shopan; Das, Saikat; Izyumskaya, Natalia; Özgür, Ümit; Morkoç, Hadis; Avrutin, Vitaliy

2016-02-01

The effect of compressive strain in buffer layer on strain relaxation and indium incorporation in InGaN multi-quantum wells (MQWs) is studied for two sets of samples grown side by side on both relaxed GaN layers and strained 10-pairs of AlN/GaN periodic multilayers. The 14-nm AlN layers were utilized in both multilayers, while GaN thickness was 4.5 and 2.5 nm in the first and the second set, respectively. The obtained results for the InGaN active layers on relaxed GaN and AlN/GaN periodic multilayers indicate enhanced indium incorporation for more relaxed InGaN active layers providing a variety of emission colors from purple to green.

Effect of GaN buffer polarization on electron distribution of AlGaN/GaN heterostructure

International Nuclear Information System (INIS)

He, Xiaoguang; Zhao, Degang; Liu, Wei; Yang, Jing; Li, Xiaojing; Li, Xiang

2016-01-01

The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. A misunderstanding about the 2DEG sheet density expression is clarified. It is predicted by theoretical analysis and validated by self-consistent Schrodinger–Poisson numerical simulation that under the force of GaN polarization, large amounts of electrons will accumulate at the GaN/substrate interface in AlGaN/GaN/substrate HEMT structure. - Highlights: • The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. • Self-consistent Schrodinger–Poisson numerical simulation is used to modulate the AlGaN/GaN/substrate structure. • It is predicted by that large amounts of electrons will accumulate at the GaN/substrate interface.

Effect of GaN buffer polarization on electron distribution of AlGaN/GaN heterostructure

Energy Technology Data Exchange (ETDEWEB)

He, Xiaoguang; Zhao, Degang, E-mail: dgzhao@red.semi.ac.cn; Liu, Wei; Yang, Jing; Li, Xiaojing; Li, Xiang

2016-06-15

The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. A misunderstanding about the 2DEG sheet density expression is clarified. It is predicted by theoretical analysis and validated by self-consistent Schrodinger–Poisson numerical simulation that under the force of GaN polarization, large amounts of electrons will accumulate at the GaN/substrate interface in AlGaN/GaN/substrate HEMT structure. - Highlights: • The formation of 2DEG in AlGaN/GaN heterostructure is discussed in detail. • Self-consistent Schrodinger–Poisson numerical simulation is used to modulate the AlGaN/GaN/substrate structure. • It is predicted by that large amounts of electrons will accumulate at the GaN/substrate interface.

La modernización del Japón

OpenAIRE

rikiwo Shikama

1988-01-01

RESUMEN El autor presenta de forma general una visión del proceso de modernización del Japón. El significado importante de la Revolución Meiji, haciendo alusión al contexto en el cual ésta se desarrolló. Hace un análisis comparativo de la China y Japón derivado de las tesis del doctor Reischaver, catedrático de la universidad de Harvard. Resalta la importancia que tuvo en el proceso de modernización las características específicas del régimen Feudad Japonés, y el alto nivel de alfabet...

Fibromialgia: ¿exageración o simulación?

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Pilar Capilla Ramírez

2013-01-01

Full Text Available Se presenta un estudio multidimensional de la exageración de síntomas en pacientes con fibromialgia. El objetivo principal es detectar patrones discriminantes de simulación de discapacidad relacionada con el dolor con el fin de desarrollar un protocolo detallado para la evaluación de sospecha de simulación en los casos con síntomas físicos o psicológicos falsos o exagerados motivados por incentivos externos. La muestra total (N=113 estuvo compuesta por cuatro grupos: pacientes con fibromialgia no litigantes (n= 36, pacientes con fibromialgia en situación de litigancia (n = 26, participantes análogos (n = 21 y grupo control (n = 30. Se administraron diferentes pruebas médicas y psicológicas a los participantes, incluyendo pruebas médicas complementarias, la adaptación española de la Escala de Auto-Eficacia (Baessler y Schwarzer, 1996, la Escala de Satisfacción Personal Vital (González Ordi, Santamaría y Casado Morales, 2012, la adaptación española del Cuestionario de Impacto de Fibromialgia (FIQ, Monterde, Salvat, Montull y Fernández-Ballart, 2004, la versión española de la Encuesta de Salud SF-36 (Alonso, Prieto y Antó, 1995, la adaptación española del Inventario Estructurado de Simulación de Síntomas (SIMS, González Ordi y Santamaría, 2009 y la adaptación española del Inventario de Personalidad de Minnesota- 2- Formulario Reestructurado (MMPI-2-RF, Ben-Porath y Tellegen, 2008a. Se presentan datos sobre las diferencias entre grupos y la precisión de predicción instrumentos utilizados. También se aborda un protocolo para la detección de la simulación en base a los resultados del perfil diferencial entre la fibromialgia no litigante y litigantes.

In-situ SiN{sub x}/InN structures for InN field-effect transistors

Energy Technology Data Exchange (ETDEWEB)

Zervos, Ch., E-mail: hzervos@physics.uoc.gr; Georgakilas, A. [Microelectronics Research Group (MRG), Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas - FORTH, P.O. Box 1385, GR-70013 Heraklion, Crete (Greece); Department of Physics, University of Crete, P.O. Box 2208, GR-71003 Heraklion, Crete (Greece); Adikimenakis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G. [Microelectronics Research Group (MRG), Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas - FORTH, P.O. Box 1385, GR-70013 Heraklion, Crete (Greece); Beleniotis, P. [Department of Physics, University of Crete, P.O. Box 2208, GR-71003 Heraklion, Crete (Greece)

2016-04-04

Critical aspects of InN channel field-effect transistors (FETs) have been investigated. SiN{sub x} dielectric layers were deposited in-situ, in the molecular beam epitaxy system, on the surface of 2 nm InN layers grown on GaN (0001) buffer layers. Metal-insulator-semiconductor Ni/SiN{sub x}/InN capacitors were analyzed by capacitance-voltage (C-V) and current-voltage measurements and were used as gates in InN FET transistors (MISFETs). Comparison of the experimental C-V results with self-consistent Schrödinger-Poisson calculations indicates the presence of a positive charge at the SiN{sub x}/InN interface of Q{sub if} ≈ 4.4 – 4.8 × 10{sup 13 }cm{sup −2}, assuming complete InN strain relaxation. Operation of InN MISFETs was demonstrated, but their performance was limited by a catastrophic breakdown at drain-source voltages above 2.5–3.0 V, the low electron mobility, and high series resistances of the structures.

Electron density and currents of AlN/GaN high electron mobility transistors with thin GaN/AlN buffer layer

Energy Technology Data Exchange (ETDEWEB)

Bairamis, A.; Zervos, Ch.; Georgakilas, A., E-mail: alexandr@physics.uoc.gr [Microelectronics Research Group, IESL, Foundation for Research and Technology-Hellas (FORTH), P.O. Box 1385, GR-71110 Heraklion, Crete (Greece); Department of Physics, University of Crete, P.O. Box 2208, GR-71003 Heraklion, Crete (Greece); Adikimenakis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G. [Microelectronics Research Group, IESL, Foundation for Research and Technology-Hellas (FORTH), P.O. Box 1385, GR-71110 Heraklion, Crete (Greece)

2014-09-15

AlN/GaN high electron mobility transistor (HEMT) structures with thin GaN/AlN buffer layer have been analyzed theoretically and experimentally, and the effects of the AlN barrier and GaN buffer layer thicknesses on two-dimensional electron gas (2DEG) density and transport properties have been evaluated. HEMT structures consisting of [300 nm GaN/ 200 nm AlN] buffer layer on sapphire were grown by plasma-assisted molecular beam epitaxy and exhibited a remarkable agreement with the theoretical calculations, suggesting a negligible influence of the crystalline defects that increase near the heteroepitaxial interface. The 2DEG density varied from 6.8 × 10{sup 12} to 2.1 × 10{sup 13} cm{sup −2} as the AlN barrier thickness increased from 2.2 to 4.5 nm, while a 4.5 nm AlN barrier would result to 3.1 × 10{sup 13} cm{sup −2} on a GaN buffer layer. The 3.0 nm AlN barrier structure exhibited the highest 2DEG mobility of 900 cm{sup 2}/Vs for a density of 1.3 × 10{sup 13} cm{sup −2}. The results were also confirmed by the performance of 1 μm gate-length transistors. The scaling of AlN barrier thickness from 1.5 nm to 4.5 nm could modify the drain-source saturation current, for zero gate-source voltage, from zero (normally off condition) to 0.63 A/mm. The maximum drain-source current was 1.1 A/mm for AlN barrier thickness of 3.0 nm and 3.7 nm, and the maximum extrinsic transconductance was 320 mS/mm for 3.0 nm AlN barrier.

Electron density and currents of AlN/GaN high electron mobility transistors with thin GaN/AlN buffer layer

International Nuclear Information System (INIS)

Bairamis, A.; Zervos, Ch.; Georgakilas, A.; Adikimenakis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G.

2014-01-01

AlN/GaN high electron mobility transistor (HEMT) structures with thin GaN/AlN buffer layer have been analyzed theoretically and experimentally, and the effects of the AlN barrier and GaN buffer layer thicknesses on two-dimensional electron gas (2DEG) density and transport properties have been evaluated. HEMT structures consisting of [300 nm GaN/ 200 nm AlN] buffer layer on sapphire were grown by plasma-assisted molecular beam epitaxy and exhibited a remarkable agreement with the theoretical calculations, suggesting a negligible influence of the crystalline defects that increase near the heteroepitaxial interface. The 2DEG density varied from 6.8 × 10 12 to 2.1 × 10 13 cm −2 as the AlN barrier thickness increased from 2.2 to 4.5 nm, while a 4.5 nm AlN barrier would result to 3.1 × 10 13 cm −2 on a GaN buffer layer. The 3.0 nm AlN barrier structure exhibited the highest 2DEG mobility of 900 cm 2 /Vs for a density of 1.3 × 10 13 cm −2 . The results were also confirmed by the performance of 1 μm gate-length transistors. The scaling of AlN barrier thickness from 1.5 nm to 4.5 nm could modify the drain-source saturation current, for zero gate-source voltage, from zero (normally off condition) to 0.63 A/mm. The maximum drain-source current was 1.1 A/mm for AlN barrier thickness of 3.0 nm and 3.7 nm, and the maximum extrinsic transconductance was 320 mS/mm for 3.0 nm AlN barrier.

High breakdown voltage in AlGaN/GaN HEMTs using AlGaN/GaN/AlGaN quantum-well electron-blocking layers.

Science.gov (United States)

Lee, Ya-Ju; Yao, Yung-Chi; Huang, Chun-Ying; Lin, Tai-Yuan; Cheng, Li-Lien; Liu, Ching-Yun; Wang, Mei-Tan; Hwang, Jung-Min

2014-01-01

In this paper, we numerically study an enhancement of breakdown voltage in AlGaN/GaN high-electron-mobility transistors (HEMTs) by using the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. This concept is based on the superior confinement of two-dimensional electron gases (2-DEGs) provided by the QW EBL, resulting in a significant improvement of breakdown voltage and a remarkable suppression of spilling electrons. The electron mobility of 2-DEG is hence enhanced as well. The dependence of thickness and composition of QW EBL on the device breakdown is also evaluated and discussed.

Aristoteles Ve İbn Sînâ’nın Reenkarnasyonu Reddi

Directory of Open Access Journals (Sweden)

Hasan Özalp

2013-06-01

Full Text Available Bu makalede düşünce tarihinin iki önemli düşünürü Aristoteles ve İbn Sînâ’nın reenkarnasyon/tenasüh hakkındaki görüşlerini inceledik. Her iki düşünürde reenkar-nasyonu reddetmektedir. Konuyu ele almadan önce kaynak olmaları bakımından Aristoteles ve İbn Sînâ’dan önceki bazı filozofların ruh ve reenkarnasyon hakkındaki görüşlerini araştırdık. Daha sonra da her iki filozofun ruh tanımlarım belirledikten sonra reenkarnasyone niçin reddettiklerini ortaya koymaya çalıştık. Nihayetinde görüşlerinde ki benzer ve farklı noktaları tespit için bir karşılaştırma yaptık

Influence of InGaN sub-quantum-well on performance of InAlN/GaN/InAlN resonant tunneling diodes

International Nuclear Information System (INIS)

Chen, Haoran; Yang, Lin'an; Hao, Yue

2014-01-01

The resonant tunneling mechanism of the GaN based resonant tunneling diode (RTD) with an InGaN sub-quantum-well has been investigated by means of numerical simulation. At resonant-state, Electrons in the InGaN/InAlN/GaN/InAlN RTD tunnel from the emitter region through the aligned discrete energy levels in the InGaN sub-quantum-well and GaN main-quantum-well into the collector region. The implantation of the InGaN sub-quantum-well alters the dominant transport mechanism, increase the transmission coefficient and give rise to the peak current and peak-to-valley current ratio. We also demonstrate that the most pronounced negative-differential-resistance characteristic can be achieved by choosing appropriately the In composition of In x Ga 1−x N at around x = 0.06

Gestión de la integración social

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Carolina García Tobón

2013-07-01

Full Text Available El artículo presenta los resultados de la investigación cualitativa –estudio de casos–, “Gestión de la Integración Social de la Investigación de la Universidad de Antioquia”, proyecto que formó parte de la investigación nacional, Gestión de la Integración Social de la Investigación en Instituciones de Educación Superior – IES colombianas, terminada por la red GISI4 en diciembre de 2003, red conformada en principio por nueve universidades y el SENA.

Enhancement of TE polarized light extraction efficiency in nanoscale (AlN)m /(GaN)n (m>n) superlattice substitution for Al-rich AlGaN disorder alloy: ultra-thin GaN layer modulation

International Nuclear Information System (INIS)

Jiang, Xin-he; Shi, Jun-jie; Zhong, Hong-xia; Huang, Pu; Ding, Yi-min; Yu, Tong-jun; Shen, Bo; Lu, Jing; Zhang, Min; Wang, Xihua

2014-01-01

The problem of achieving high light extraction efficiency in Al-rich Al x Ga 1−x N is of paramount importance for the realization of AlGaN-based deep ultraviolet (DUV) optoelectronic devices. To solve this problem, we investigate the microscopic mechanism of valence band inversion and light polarization, a crucial factor for enhancing light extraction efficiency, in Al-rich Al x Ga 1−x N alloy using the Heyd–Scuseria–Ernzerhof hybrid functional, local-density approximation with 1/2 occupation, and the Perdew–Burke–Ernzerhof functional, in which the spin–orbit coupling effect is included. We find that the microscopic Ga-atom distribution can effectively modulate the valence band structure of Al-rich Al x Ga 1−x N. Moreover, we prove that the valence band arrangement in the decreasing order of heavy hole, light hole, and crystal-field split-off hole can be realized by using nanoscale (AlN) m /(GaN) n (m>n) superlattice (SL) substituting for Al-rich Al x Ga 1−x N disorder alloy as the active layer of optoelectronic devices due to the ultra-thin GaN layer modulation. The valence band maximum, i.e., the heavy hole band, has p x - and p y -like characteristics and is highly localized in the SL structure, which leads to the desired transverse electric (TE) polarized (E⊥c) light emission with improved light extraction efficiency in the DUV spectral region. Some important band-structure parameters and electron/hole effective masses are also given. The physical origin for the valence band inversion and TE polarization in (AlN) m /(GaN) n SL is analyzed in depth. (paper)

Using the N-15 method to determine N-soil, N-green manure, and N-urea availability after six seasons in an alley cropping system

International Nuclear Information System (INIS)

Elsje L Sisworo; Haryanto and Ania Citraresmini

2006-01-01

Nitrogen (N) is the most important nutrient for crop growth and production. This study was conducted to determine whether in each of six seasons and after these seasons the N-soil, N-green manure, N-green manure + urea, and N-urea is still available for crops. Upland rice and corn were planted successively for six seasons. In each season upland rice and corn were planted and applied with N-fertilizers at rate of: control (0N), N1 (100% green manure), N2 (50% green manure + 50% urea), N3 (100% urea). N-15 labelled urea was added at each season to determine the A-value of the crops. In each seasons it was shown that crops used N-soil as well as N-fertilizer. With the increase of the availability of N-fertilizers the use of N-soil decrease and so could preserve N-soil. With preservation of N-soil it could be assumed that soil quality has increased. The N-15 method could be used to determine the availability at each fertilizer rate’s in each season and at the end of the sixth season. (author)

Yaygın Gelişimsel Bozukluk Tanılı Çocukların Anne-Babalarının Yas Tepkilerinin, Evlilik Uyumlarının ve Sosyal Destek Algılarının Đncelenmesi

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Deniz Karpat

2012-07-01

Full Text Available Bu çalışma, yaygın gelişimsel bozukluk tanılı çocukların anne babalarının bu tanı nedeniyle yaşadıkları yas sürecini, evlilik uyumlarını ve algıladıkları sosyal desteği etkileyen faktörleri incelemek amacıyla gerçekleştirilmiştir. Veriler, 3-18 yaş aralığında yaygın gelişimsel bozukluk (YGB tanılı çocuğu olan gönüllü 103 anne-babaya uygulanan Hogan Yas Tepkileri Tarama Listesi, Çiftler Uyum Ölçeği, Çok Boyutlu Algılanan Sosyal Destek Ölçeği ve Kişisel Bilgi Formu kullanılarak toplanmıştır. Yaş, evlilik uyumu ve algılanan sosyal desteğin çeşitli demografik değişkenler açısından farklılaştığı bulunmuştur. YGB tanılı çocukların anne-babalarında yasın olumsuz yanını yordayan değişkenlerin annebabaların cinsiyet ve eğitim düzeyi, evlilik süresi, özel insan kategorisinden algılanan sosyal destek, arkadaş kategorisinden algılanan sosyal destek ve çift bağlılığı olduğu görülmüştür. Yasın olumlu yanını yordayan değişkenlerin ise anne-babanın cinsiyeti ve eğitim düzeyi, tanıdan sonra geçen süre ve çift uyumu olduğu belirlenmiştir. Sonuçlar ilgili alanyazın verileri ışığında tartışılmıştır. The aim of this study is to examine the factors effecting grief, marital adjustment and social support and relationship between grief, marital adjustment and social support of the parents of children with pervasive development disorder. Hogan Grief Reaction Checklist, Multidimensional Scale of Perceived Social Support, Dyadic Adjustment Scale and Personal Information Form which was developed by the researcher were used for this purpose. The sample of the study consists of 103 parents of the children between 3 and 18 years old with PDD. The results showed that the grief, marital adjustment and social support differentiated among the demographic variables. The variables that predict the grief of the parents of the children with PDD in a negative

Religión y Educación Pública

OpenAIRE

Palomino Lozano, Rafael

2009-01-01

Relación general sobre la presencia de la religión como materia docente en la educación reglada: actores implicados, derechos educativos, modelos educativos y enseñanza de la religión, modalidades de enseñanza de la religión como asignatura. Breve apunte sobre lo símbolos religiosos en la escuela. Versión parcial. Keynote speech. General account concerning the presence of religion in public education: social actors, educational rights, educational models, religion as a school subject. Bri...

Activated N-nitrosocarbamates for regioselective synthesis of N-nitrosoureas.

Science.gov (United States)

Martinez, J; Oiry, J; Imbach, J L; Winternitz, F

1982-02-01

A practical and convenient method for synthesizing antitumor compounds, N-alkyl-N-nitrosoureas, regioselectively nitrosated on the nitrogen atom bearing the alkyl group is proposed. N-Alkyl-N-nitrosocarbamates are interesting intermediates in these syntheses and yield, by reaction with amino compounds, the regioselectively nitrosated N-alkyl-N-nitrosoureas. As an interesting example, N,N'-bis[(2-chloroethyl)nitrosocarbamoyl]cystamine, a new attractive oncostatic derivative, has been prepared. The cytotoxic activity of these various compounds were tested on L1210 leukemia.

High energy ion irradiated III-N semiconductors (AlN, GaN, InN): study of point defect and extended defect creation

International Nuclear Information System (INIS)

Sall, Mamour

2013-01-01

Nitride semiconductors III N (AlN, GaN, InN) have interesting properties for micro-and opto-electronic applications. In use, they may be subjected to different types of radiation in a wide range of energy. In AlN, initially considered insensitive to electronic excitations (Se), we have demonstrated a novel type of synergy between Se and nuclear collisions (Sn) for the creation of defects absorbing at 4.7 eV. In addition, another effect of Se is highlighted in AlN: climb of screw dislocations under the influence of Se, at high fluence. In GaN, two mechanisms can explain the creation of defects absorbing at 2.8 eV: a synergy between Se and Sn, or a creation only due to Sn but with a strong effect of the size of displacement cascades. The study, by TEM, of the effects of Se in the three materials, exhibits behaviors highly dependent on the material while they all belong to the same family with the same atomic structure. Under monoatomic ion irradiations (velocity between 0.4 and 5 MeV/u), while discontinuous tracks are observed in GaN and InN, no track is observed in AlN with the highest electronic stopping power (33 keV/nm). Only fullerene clusters produce tracks in AlN. The inelastic thermal spike model was used to calculate the energies required to produce track in AlN, GaN and InN, they are 4.2 eV/atom, 1.5 eV/atom and 0.8 eV/atom, respectively. This sensitivity difference according to Se, also occurs at high fluence. (author)

Impermeabilización del hormigón

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Gete-Alonso de Ylera, Antonio

1977-03-01

Full Text Available This article refers to concrete water-proofing, and the different sealing systems used. After a brief study of the different types of pores and air and water capillaries, the various kinds of water penetration —penetrability and hygroscopicity— are analyzed. The origin of the water is studied: natural moisture, construction humidity, moisture coming from absorption and condensation, rain, accumulated water pressure and miscellaneous moisture and the damaging effects they have on permeability and on hygroscopicity; losses in reservoirs, sub-pressure, Chemical reactions and oxidation. The different forms of measuring permeability are also studied: DIN Standard, by means of test tubes in the form of plates; ASTM Standard, by freezing and permeability tests, by means of a permeability meter, etc. After analyzing the basic conditions for decreasing water penetration in the concrete the following is considered. a Means of additives or treatments which improve the quality of same in order to obtain optimum conditions for waterproofing; b using products which avoid water penetration inside the concrete mass, without altering its basic properti.es. These two forms refer to different waterproofing systems: mass, hydrofugous, joints, sheets and continuous lining. These systems are studied in detail as far as their effects, characteristics and applications are concerned.Se trata en este artículo la impermeabilidad del hormigón y los diferentes sistemas de impermeabilización. Después de un breve estudio de las diversas clases de poros: capilares, de aire y de agua, se analizan los diversos modos de penetración del agua —penetrabilidad e higroscopicidad—, resaltando la mayor importancia de la permeabilidad, y su aumento en función del diámetro de los poros capilares mientras la higroscopicidad disminuye al aumentar el diámetro de aquéllos. Se estudia la procedencia del agua: humedad natural, humedad de construcción, humedad

La reconversión de la formación en comunicación desde el EEES

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Miguel Ortiz Sobrino

2012-04-01

Full Text Available "La adaptación de los estudios universitarios al nuevo Espacio Europeo de Educación Superior es una oportunidad para reorientar y actualizar la formación en materia de Comunicación desde el ámbito universitario. Es el momento de dar una respuesta desde la Universidad al nuevo contexto comunicativo, a la abundancia informativa, a la incidencia de la tecnología en los procesos de producción de la Comunicación o a los nuevos modelos de consumo mediático, si se quiere conseguir un sector de la Comunicación que esté en consonancia con los nuevos tiempos.La adaptación de los estudios de Comunicación a este nuevo marco educativo se está realizando sobre la base de un cambio de metodologías y herramientas educativas, sobre un nuevo modelo de relación entre el profesor y el alumno, y sobre un diseño formativo fundamentado en la adquisición de competencias, tanto profesionales como académicas, por parte los futuros profesionales de la Comunicación. La justificación de los estudios de la Comunicación en la Universidad, los cambios en el modelo educativo, y algunas incógnitas sobre los resultados de este proceso de adaptación de los estudios de Comunicación al Espacio Europeo de Educación Superior, son los aspectos que se abordan a lo largo de esta contribución."

Evaluation of cross sections for 197Au(n,3n) and 197Au(n,4n) reactions from threshold to 50 MeV

International Nuclear Information System (INIS)

Yu Baosheng; Shen Qingbiao; Cai Dunjiu

1994-01-01

The measured data of cross sections for 197 Au(n,3n) and 197 Au(n,4n) reactions were collected and analysed. The theoretical calculations of above mentioned reactions were carried out to predict the data in higher energy region. The sets of cross sections for 197 Au(n,3n) and 197 Au(n,4n) reactions from threshold to 50 MeV were recommended on the basis of the experimental and calculated data. (2 figs)

Gestión de residuos de construcción y demolición

OpenAIRE

Matallana Matallana, Carlos

2010-01-01

La concienciación social de la necesidad de llevar a cabo un Desarrollo Sostenible obliga en el campo de la construcción a potenciar el reciclaje de los materiales que han cumplido ya su vida útil, procedentes de las propias actividades constructivas así como de diversos procesos industriales. La ventaja más destacada de este reciclaje es la solución, a un mismo tiempo, de la problemática originada por la eliminación de unos subproductos de desecho así como la obtención de una nueva materia p...

Definición, etiopatogenia, clasificación y formas de presentación

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Xavier Mas Garriga

2014-01-01

La artrosis de rodilla tiene una prevalencia del 10,2% en España y muestra una importante disociación clinicorradiológica. La artrosis de manos, con una prevalencia de afectación sintomática de alrededor del 6,2% puede adoptar diferentes formas de presentación (artrosis nodal, artrosis generalizada, rizartrosis y artrosis erosiva. La artrosis sintomática de cadera afecta entre el 3,5 y 5,6% de los mayores de 50 años y tiene diferentes patrones radiológicos en función de la migración de la cabeza femoral.

Educación intercultural y educación visual: una reunión desafiante para la educación argentina

OpenAIRE

Osorio, Griselda

2012-01-01

La conformación de la modalidad de la Ecuación Intercultural Bilingüe dentro del Sistema Educativo argentino se pensó conforme a la Constitución Nacional en tanto garantiza el derecho constitucional de los pueblos indígena (…) a recibir una educación que contribuya a preservar y fortalecer sus pautas culturales, su lengua, su cosmovisión e identidad étnica; a mejorar su calidad de vida . Art. 75 inc.17.

Narrow n anti n resonances

International Nuclear Information System (INIS)

Bogdanova, L.N.; Dalkarov, O.D.; Kerbikov, B.O.; Shapiro, I.S.

1975-01-01

The present status of the problem of quasinuclear states in systems of nucleons and antinucleons is reviewed. The theoretical predictions are compared with experimental data on narrow meson resonances near N anti N threshold which appeared in 1971-74

Influence of InGaN sub-quantum-well on performance of InAlN/GaN/InAlN resonant tunneling diodes

Energy Technology Data Exchange (ETDEWEB)

Chen, Haoran; Yang, Lin' an, E-mail: layang@xidian.edu.cn; Hao, Yue [State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology, School of Microelectronics, Xidian University, Xi' an 710071 (China)

2014-08-21

The resonant tunneling mechanism of the GaN based resonant tunneling diode (RTD) with an InGaN sub-quantum-well has been investigated by means of numerical simulation. At resonant-state, Electrons in the InGaN/InAlN/GaN/InAlN RTD tunnel from the emitter region through the aligned discrete energy levels in the InGaN sub-quantum-well and GaN main-quantum-well into the collector region. The implantation of the InGaN sub-quantum-well alters the dominant transport mechanism, increase the transmission coefficient and give rise to the peak current and peak-to-valley current ratio. We also demonstrate that the most pronounced negative-differential-resistance characteristic can be achieved by choosing appropriately the In composition of In{sub x}Ga{sub 1−x}N at around x = 0.06.

Producción cepalina sobre educación

OpenAIRE

Fernando Díaz Ortega

2005-01-01

El siguiente trabajo presenta una visión global del conjunto de la producción de la Comisión Económica para América Latina y el Caribe (CEPAL) sobre educación, mediante la clasificación y análisis de las publicaciones cepalinas relacionadas con el tema educativo desde 1949 hasta 2002. Para dar esa visión dividí los documentos bajo tres criterios temporales y bajo cuatro clasificaciones. Los criterios temporales fueron: anualmente, en dos periodos (1949-1976 y 1977-2002) y en seis etapas (1949...

Administración del agua. - Introducción

OpenAIRE

Fernández Morales, Juan Carlos

2008-01-01

ÍNDICE Créditos Dedicatoria Agradecimiento Notas del autor Introducción Capítulo I: Marco jurídico conceptual de la gestión del agua. Capítulo II: Organización administrativa del agua. Capítulo III: Las confederaciones hidrográficas en la legislación española. Capítulo IV: Los usuarios y la gestión del agua. Capítulo V: Administración del agua y competencias sectoriales en las comunidades autonómas españolas. Capítulo VI: Abastecimien...

Evaluation of the 175Lu(n,2n)174Lu, 175Lu(n,2n/sup 174m/Lu, and 175Lu(n,3n)173Lu cross sections from threshold to 20 MeV

International Nuclear Information System (INIS)

Philis, C.; Young, P.G.; Arthur, E.D.

1978-04-01

An evaluation of the 175 Lu(n,2n) 174 Lu, 175 Lu(n,2n)/sup 174m/Lu, and 175 Lu(n,3n) 173 Lu reactions from threshold to 20 MeV is presented. Available experimental data were renormalized to a consistent set of standards and were used along with results from statistical-preequilibrium model calculations to produce recommended curves for each of these reactions

Coordinación de las protecciones de la subestación de distribución en el sistema Durán norte

OpenAIRE

Tinoco Tinoco, Misael Patricio; Sanchez Yela, Darwin Horacio

2016-01-01

El presente trabajo desarrolla el estudio de la coordinación de protecciones aplicados a la subestación de distribución “DURÁN NORTE”, ubicada en el cantón Durán en la parte norte de la cuidad del mismo nombre. Partiendo primero desde la descripción de las instalaciones, para conocer los elementos que la componen; posteriormente, se realiza un estudio de flujo de carga en condiciones de máxima y mínima carga y un estudio de cortocircuito de la subestación aplicados a la barra de 69kV y 13.8kV...

La investigación - acción en el contexto de la Educación Musical

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Jimeno, María Manuela

2000-05-01

Full Text Available Investigación que propone un marco para adecuar, organizar, estructurar e interrelacionar los "Curriculum" de Escuelas de Música (3-12 años y Educación Musical en: Educación Infantil y Primaria (3-12 años, analizando convergencias y divergencias, fundamentando la música en su dualidad de Ciencia y Arte. Dicha investigación dirigida por Mª Manuela Jimeno, ha sido realizada con la participación de un equipo de profesores de Educación Infantil y Primaria así como de Escuelas de Música.La investigación que presentamos se está llevando a cabo en estos momentos en varios Centros de la Comunidad Foral de Navarra bajo el Patrocinio del Gobierno de Navarra, Departamento de Educación y Cultura. El planteamiento Teórico y Análisis de las propuestas se lleva a cabo en la Universidad Pública de Navarra, desde 1995 hasta la fecha.La finalidad de este proyecto pedagógico-musical es conseguir para los niños/as entre 3 y 12 años una cultura y formación musical equilibradas, el acercamiento más profundo al hecho musical, apostando por la unidad y convergencia de los "Currículos" como eje vertebrador, con la doble finalidad de servir de formación básica para unos, y como formación y preparación más específica, para aquellos otros que posean aptitudes para optar a las pruebas de grado medio de las Enseñanzas regladas de Música, o servir de fundamento para la apertura hacia otros itinerarios de expresión ARTÍSTICA.El planteamiento de la investigación que presentamos nos brinda la oportunidad de reflexionar y analizar sobre:Nuestra concepción del alumno/a. Nuestra concepción de Investigación Ecológica y la situación de la Investigación en la Acción. Las hipótesis de Trabajo. Como realizamos una sesión práctica. El Modelo creado que se sigue en la Investigación. Valoración de Datos y Conclusiones obtenidas hasta la fecha.

La reutilización de la información en el sector público: aplicación en la Unión Europea

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Vicent Giménez Chornet

2014-01-01

Full Text Available En este artículo se analiza la reutilización de la información en la Unión Europea tras la aplicación de la Directiva de 2003. Se estudia la forma en que los seis Estados europeos con mayor Producto Interior Bruto ponen a disposición de los ciudadanos dicha información en sus portales web. El objetivo es evaluar cómo ha incidido su aplicación en estos países. La metodología ha consistido, por una parte, en analizar la normativa para identificar su alcance y, por otra, en realizar un test de recuperación de la información para comparar los resultados de las búsquedas. En conclusión, se demuestra que hay una gran disparidad en cuanto al volumen de datos ofrecidos entre los Estados, diferencias en los sistemas de clasificación, carencias en cuanto a la descripción formal y grandes diferencias en cuanto al número de resultados en la recuperación de la información, por lo que se propone avanzar en la interoperabilidad de datos, con un mayor control del lenguaje documental.

Divulgación de información sobre corrupción: empresas del IBEX 35

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Maider Aldaz Odriozola

2012-01-01

Full Text Available El interés por la relación existente entre la corrupción y el sector privado se ha incrementado en los últimos tiempos. El presente trabajo pretende estudiar este asunto con efectos sociales desde una doble perspectiva; por una parte, conocer la realidad actual de la divulgación sobre corrupción en las empresas españolas del Ibex 35 para, posteriormente, tratar de analizar cuáles son las motivaciones subyacentes de tales prácticas y las posibles implicaciones en la gestión interna. Para alcanzar este objetivo, inicialmente realizamos un análisis exploratorio de la información relativa a la corrupción emitida por las empresas del Ibex 35 en sus memorias de sostenibilidad y, posteriormente, –basándonos en la Teoría de la Legitimidad– realizamos una entrevista en profundidad con un ejecutivo responsable de la RSC, con el objetivo de detectar las motivaciones y las implicaciones en la gestión. Las conclusiones alcanzadas son: en primer lugar, la información sobre corrupción aportada por las empresas se puede concretar en tres aspectos generales (política contra la corrupción, auditorías y sistemas de control, y los mecanismos de implementación. En segundo lugar, hemos identificado tres clusters en las empresas, destacando en este agrupamiento por su particular comportamiento, la compañía Telefónica. Por último, al analizar el caso de esta compañía, hemos observado cómo pretende mantener un nivel alto de legitimidad; para ello, intenta cumplir con las normas socialmente establecidas, y emplea la divulgación para continuar con su estatus de “empresa legítima”, e intenta generar valor y confianza. Sin embargo, los procedimientos en relación a la gestión de la corrupción parecen no haber alcanzado el nivel de concreción que en la actualidad se les exige.

Growth of InGaN multiple quantum wells and GaN eplilayer on GaN substrate

International Nuclear Information System (INIS)

Lee, Sung-Nam; Paek, H.S.; Son, J.K.; Sakong, T.; Yoon, E.; Nam, O.H.; Park, Y.

2006-01-01

We investigated that the surface morphology of GaN epilayers was significantly affected by the surface tilt orientation of GaN substrate. Surface morphologies of GaN epilayers on GaN substrates show three types: mirror, wavy, and hillock. These surface morphologies are dependent on the surface orientation of GaN substrates. It is found that the hillock morphology of GaN epilayer was formed on the GaN substrate with surface tilt orientation less than 0.1 o . As the surface tilt angle increased to 0.35 o , the surface morphology varied from hillock to wavy morphology. Above a surface tilt angle of 0.4 o , surface morphology changed to the mirror-like type morphology. Additionally, these three types of GaN surface morphology also affected the optical quality of GaN epilayers as well as InGaN multiple quantum wells on GaN substrates by non-uniform In incorporation on the different surface morphologies of GaN epilayers

Local lattice environment of indium in GaN, AlN, and InN; Lokale Gitterumgebung von Indium in GaN, AlN und InN

Energy Technology Data Exchange (ETDEWEB)

Penner, J

2007-12-20

After an introduction to the physical properties of the nitrides, their preparation, and the state of studies on the implantation in the nitrides the experimental method (PAC) applied in this thesis and the data analysis are presented. The next chapter describes then the applied materials and the sample preparation. The following chapters contain the PAC measurements on the annealing behaviout of GaN, AlN, and InN after the implantation as well as dose- and temperature dependent PAC studies. Finally the most important results are summarized.

Resonance particle production in inelastic N-N and π-N interactions

International Nuclear Information System (INIS)

Amelin, N.S.; Barashenkov, V.S.; Slavin, N.V.

1984-01-01

Using the considerations connected with the scaling hypothesis and the Regge pole model the phenomenological expressions are obtained for differential single-particle inclusive production cross sections (Δ + , Δ 0 , Δ ++ ) and (p +- , p 0 , ω) resonances in inelastic π-N and N-N collisions at high energies. These expressions describe the known experimental data in a wide region of kinematic variables from 10 to several thousand GeV

MODELACIÓN DE LA SEPARACIÓN DE PARTÍCULAS NO RETENIDAS EN LA ETAPA DE SEDIMENTACIÓN EN CANALES: PROCESO DE EXTRACCIÓN DE ALMIDÓN DE YUCA

Directory of Open Access Journals (Sweden)

PATRICIA TORRES-LOZADA

Full Text Available En la etapa de sedimentación en canales del proceso de extracción de almidón de yuca se genera alrededor del 80% del total del agua residual del proceso. Este estudio tuvo como objetivo realizar la modelación teórica de la separación de las partículas no retenidas en los canales de sedimentación, basándose en el análisis de sedimentación de partículas discretas entre 2 y 8 µm y usando el principio de la Ley de Stockes. La modelación teórica mostró que la velocidad de sedimentación oscila entre 0,007 y 0,112 cm/min. Con este rango de velocidad y un caudal crítico de 1,5 L/s, para la remoción total de las partículas se requeriría una estructura con un área superficial de 1.288 m2, altura de 1 m y TRH de 10 días aproximadamente. Este estudio demuestra que no es económica ni técnicamente viable la sedimentación convencional ni la de alta tasa para la retención de estas partículas, siendo recomendable evaluar mecanismos diferentes para mejorar la eficiencia de separación de las mismas que pueda potencializar su aprovechamiento y evitar contaminar los cuerpos receptores de estos efluentes.

AlGaN nanocolumns and AlGaN/GaN/AlGaN nanostructures grown by molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Ristic, J.; Sanchez-Garcia, M.A.; Ulloa, J.M.; Calleja, E. [Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Sanchez-Paramo, J.; Calleja, J.M. [Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Jahn, U.; Trampert, A.; Ploog, K.H. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2002-12-01

This work reports on the characterization of hexagonal, single crystal AlGaN nanocolumns with diameters in the range of 30 to 100 nm grown by molecular beam epitaxy on Si(111) substrates. The change of the flux ratio between the Al and the total III-element controls the alloy composition. The Al composition trend versus the Al flux is consistent both with the E{sub 2} phonon energy values measured by inelastic light scattering and the luminescence emission peaks position. High quality low dimensional AlGaN/GaN/AlGaN heterostructures with five GaN quantum discs, 2 and 4 nm thick, embedded into the AlGaN columns, were designed in order to study the quantum confinement effects. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

New series of Tc-99m-labeled hepatobiliary tracers: N'-acyl- and N'-sulfonyl ethylenediamine-N,N-diacetic acids

International Nuclear Information System (INIS)

Karube, Y.; Kono, A.; Maeda, T.; Ohya, M.; Matsushima, Y.

1981-01-01

Various Tc-99m-labeled N'-substituted derivatives of ethylenediamine-N,N-diacetic acid (EDDA) are evaluated as hepatobiliary imaging agents. N-substituted aromatic acyl and aromatic sulfonyl derivatives of EDDA, labeled with Tc-99m, were administered to rabbits and golden hamsters, and the distribution indicated clearance by the hepatobiliary system. N'-aromatic sulfonyl EDDAs were labeled with Tc-99m by the SnCl 2 method with more than 99% yield. Clearance of Tc-99m-p-toluenesulfonyl EDDA from the blood and the liver was as rapid as that of TC-99m N-(2,6-diethylphenylcarbamoylmethyl)iminodiacetic acid (Tc-99m benzenesulfonyl EDDA lowered urinary excretion. It is concluded that the sulfonyl EDDAs provide a fruitful source for Tc-99m-labeled hepatobiliary radiopharmaceuticals

Electronic structure and optical properties of N vacancy and O filling on n-GaN (0001) surface

Science.gov (United States)

Lu, Feifei; Liu, Lei; Xia, Sihao; Diao, Yu; Feng, Shu

2018-06-01

In the X-ray photoelectron spectroscopy experiment, we observed that the valence band spectrum of the n-GaN (0001) surface appeared a bump near 1.9 eV after Ar etching and the N/Ga ratio became smaller, while the bump disappeared upon exposure to air. In order to analyze this phenomenon theoretically, we mainly study the electronic structure and optical properties of n-GaN (0001) surface with N vacancy and filled with O atom based on the first principles of density functional theory. The results suggest that the n-GaN (0001) surface exhibits semi-metallic property. The introduction of N vacancy reduces the n-type conductivity, whereas the filling of O atom enhances conductivity. The density of state near -1.9eV shows a good agreement between the clean n-type surface and the O-atom-filled surface, while the N vacancy surface has a higher density of states, which is similar to the experimentally observed phenomenon. It is also found that the existence of N vacancy reduces the photoemission properties of the n-GaN (0001) surface and the filling of O atom alleviates the defect caused by vacancy. This study shows that N vacancy increases the doping difficulty of n-type GaN films, however, the filling of O atom may compensate for the diminished photoelectric properties induced by N vacancy and be conducive to prepare high-performance optoelectronic devices with the contact of n-GaN and metal.

Deserción y retención universitaria: una discusión bibliográfica

OpenAIRE

Fernández-Hileman, María Del Rosario; Corengia, Ángela; Durand, Julio

2014-01-01

El objetivo de este artículo es presentar una discusión bibliográfica acerca del fenómeno de la deserción y retención en la universidad. Para ello, se realizó una revisión y síntesis de los principales estudios empíricos y perspectivas teóricas que abordan esta temática en Argentina y otros países. Para comenzar, se muestra el problema de la deserción en números, algunas precisiones terminológicas y su contextualización nacional (Argentina) e internacional. Posteriormente se desarrollan tanto...

Asociación entre desnutrición y depresión en el adulto mayor

OpenAIRE

Elizabeth Pérez Cruz; Diana Cecilia Lizárraga Sánchez; María del Rosario Martínez Esteves

2014-01-01

Antecedentes: La desnutrición y la depresión son trastornos geriátricos comunes. Nuestro objetivo fue determinar la prevalencia de desnutrición y depresión en adultos mayores, así como evaluar su asociación. Métodos: Estudio transversal que se realizó en población geriátrica de la consulta externa de un Hospital Público de referencia de Alta Especialidad de la Ciudad de México. El estado nutricional se clasifico mediante la Evaluación Mínima Nutricional (MNA), el Índice de Quetelet se clasifi...

Caracterización de la utilización de innovación en el sector bancario: Una aproximación hacia la adquisición de ventajas competitivas

OpenAIRE

Herazo Villa, Jesús Alejandro; Restrepo Ramírez, Susana; Yi Forero, Alex Daniel

2013-01-01

Investigación exploratoria mixta siguiendo un método deductivo con la que se logró caracterizar el grado de utilización de innovación en el sector bancario y su utilidad en la adquisición de ventajas competitivas con la ayuda de del modelo del Radar de Innovación.

Compound list: N-methyl-N-nitrosourea [Open TG-GATEs

Lifescience Database Archive (English)

Full Text Available N-methyl-N-nitrosourea MNU 00164 ftp://ftp.biosciencedbc.jp/archive/open-tggates/LA...TEST/Human/in_vitro/N-methyl-N-nitrosourea.Human.in_vitro.Liver.zip ftp://ftp.biosciencedbc.jp/archive/open-...tggates/LATEST/Rat/in_vivo/Liver/Single/N-methyl-N-nitrosourea.Rat.in_vivo.Liver.Single.zip ...

INTERPRETACIÓN E INTEGRACIÓN NORMATIVA

Directory of Open Access Journals (Sweden)

Eleonora del Pilar Salazar Londoño

2012-01-01

Full Text Available El objetivo del presente artículo es reflexionar sobre el fenómeno de la interpretación en la norma jurídica. Por esta razón, se construye un diálogo con diversos horizontes teóricos que se sitúan entre los teóricos del derecho de un pensamiento iuspositivista e iusnaturalista, dentro de teorías constructivistas, como Dworkin y Hart, teoría argumentativa como Alexy y Habermas, positivistas puros como Kelsen, entre otros. Todos alimentan el discurso hermenéutico con nuevos conceptos de interpretación, como nuevas tendencias de interpretaciones jurídicas. El diálogo entre los teóricos se direcciona a través de preguntas para resolver el problema de la interpretación en el tema de los principios y la integración normativa.

Compressed liquid densities for the (n-heptane + n-decane) and (n-octane + n-decane) systems from T = (313 to 363) K

Energy Technology Data Exchange (ETDEWEB)

Quevedo-Nolasco, Rodolfo [Laboratorio de Termodinamica, SEPI-ESIQIE, Instituto Politecnico Nacional, UPALM, Ed. Z, Secc. 6, 1ER piso, Lindavista, C.P. 07738 Mexico D.F. (Mexico); Galicia-Luna, Luis A., E-mail: lgalicial@ipn.mx [Laboratorio de Termodinamica, SEPI-ESIQIE, Instituto Politecnico Nacional, UPALM, Ed. Z, Secc. 6, 1ER piso, Lindavista, C.P. 07738 Mexico D.F. (Mexico); Elizalde-Solis, Octavio [Departamento de Ingenieria Quimica Petrolera, ESIQIE, Instituto Politecnico Nacional, UPALM, Edif. 8, 2o piso, Lindavista, C.P. 07738 Mexico D.F. (Mexico)

2012-01-15

Highlights: > We built an equipment which consists of a variable volume cell and a VTD Anton Paar DMA-HPM. > Compressed liquid densities are reported for n-heptane and n-decane. > Binary (n-heptane or n-octane + n-decane) systems were studied in the whole range of composition. > Derived properties were calculated from experimental data. - Abstract: Densities (p, {rho}, T, x{sub 1}) of two binary n-alkane systems are reported from T = (313 to 363) K in the compressed liquid phase up to 25 MPa over the whole range of composition. The binary mixtures {l_brace}x{sub 1}n-heptane + (1 - x{sub 1})n-decane{r_brace} and {l_brace}x{sub 1}n-octane + (1 - x{sub 1})n-decane{r_brace} were prepared at compositions of (x{sub 1} = 0.0531, 0.2594, 0.5219, 0.777, 0.952), and (x{sub 1} = 0.0616, 0.2801, 0.5314, 0.7736, 0.9623), respectively. A measuring system based on a vibrating tube densimeter, DMA HPM from Anton Paar with data acquisition system was developed in order to obtain experimental densities. Water and nitrogen were used as reference fluids to calibrate the densimeter. Experimental methodology was checked by comparing the n-heptane and n-decane densities against multi-parameter equations proposed in the literature. Differences between both sets of data show a maximum deviation of 0.07%. Excess molar volumes, isothermal compressibility and isobaric thermal expansivity were computed from experimental densities.

Compressed liquid densities for the (n-heptane + n-decane) and (n-octane + n-decane) systems from T = (313 to 363) K

International Nuclear Information System (INIS)

Quevedo-Nolasco, Rodolfo; Galicia-Luna, Luis A.; Elizalde-Solis, Octavio

2012-01-01

Highlights: → We built an equipment which consists of a variable volume cell and a VTD Anton Paar DMA-HPM. → Compressed liquid densities are reported for n-heptane and n-decane. → Binary (n-heptane or n-octane + n-decane) systems were studied in the whole range of composition. → Derived properties were calculated from experimental data. - Abstract: Densities (p, ρ, T, x 1 ) of two binary n-alkane systems are reported from T = (313 to 363) K in the compressed liquid phase up to 25 MPa over the whole range of composition. The binary mixtures {x 1 n-heptane + (1 - x 1 )n-decane} and {x 1 n-octane + (1 - x 1 )n-decane} were prepared at compositions of (x 1 = 0.0531, 0.2594, 0.5219, 0.777, 0.952), and (x 1 = 0.0616, 0.2801, 0.5314, 0.7736, 0.9623), respectively. A measuring system based on a vibrating tube densimeter, DMA HPM from Anton Paar with data acquisition system was developed in order to obtain experimental densities. Water and nitrogen were used as reference fluids to calibrate the densimeter. Experimental methodology was checked by comparing the n-heptane and n-decane densities against multi-parameter equations proposed in the literature. Differences between both sets of data show a maximum deviation of 0.07%. Excess molar volumes, isothermal compressibility and isobaric thermal expansivity were computed from experimental densities.

Gestión de la formación permanente del docente: reflexión y propuesta

Directory of Open Access Journals (Sweden)

MSc. Silvia M. Sarmiento-Berrezueta

2015-11-01

Full Text Available La práctica educativa actual exige implementar un nuevo Modelode Gestión de la formación permanente de los docentes basado en los estándares de calidad. Este artículo se centra en cómo alcanzar la calidad de la gestión formativa profesional mediante una propuesta de autoformación y co-formación basada sobre la reflexión, valoración y motivación, normada desde el Código de Convivencia, que conlleva a aprender y desaprender en los colectivos de docentes de educación básica superior en el Ecuador.

The investigation of Al0.29Ga0.71N/GaN/AlN and AlN/GaN/AlN thin films grown on Si (111) by RF plasma-assisted MBE

Science.gov (United States)

Yusoff, Mohd Zaki Mohd; Mahyuddin, Azzafeerah; Hassan, Zainuriah; Hassan, Haslan Abu; Abdullah, Mat Johar

2012-06-01

Recently, gallium nitride (GaN) and its related compounds involving Al and In have attracted much attention because of their potential to be used as high-efficiency UV light emitting devices, and as high frequency and high power electronic devices. Consequently, the growth and physics of GaN-based materials have attracted remarkable scientific attention. In this work, the growth and characterization of epitaxial Al0.29Ga0.71N and AlN layers grown on Si (111) by RF-plasma assisted molecular beam epitaxy (MBE) are described. The Al mole fraction was derived from the HR-XRD symmetric rocking curve (RC) ω/2θ scans of (0002) plane as x = 0.29. For AlN/GaN/AlN sample, the maximum Raman intensity at 521.53 cm-1 is attributed to crystalline silicon. It was found that the allowed Raman optical phonon mode of GaN, the E1 (high) is clearly visible, which is located at 570.74 cm-1. Photoluminscence (PL) spectrums of both samples have shown sharp and intense band edge emission of GaN without the existence of yellow emission band, showing good crystal quality of the samples have been successfully grown on Si substrate.

Gestión de nóminas

OpenAIRE

Sánchez González, Cristina

2015-01-01

El objetivo de este trabajo es el de realizar una aplicación EXCEL con su respectivo manual para la gestión de nóminas en una pequeña o mediana empresa (PYME). Desde el ámbito global de la política salarial en el que se desarrolla cada parte, se va acotando cada nivel hasta el tema principal del trabajo que es la nómina. Una vez descrito el concepto de nómina, se explica, junto con sus características, los tipos y partes, así como los cálculos a realizar a la hora de determinar las cantidades...

Evaluación del cuesco de palma africana y del carbón del cerrejón para producir carbón activado

Directory of Open Access Journals (Sweden)

Anundo Polanía León

2010-05-01

Full Text Available Se produjeron carbones activados a partir de carbón de El Cerrejón y del Cuesco de Palma Africana mediante activación con vapor de agua y KOH, a 700 y 800 ó 900°C variando la relación activante/carbonizado y el tiempo de activación. Los tiempos de activación a los que se desarrolla mayor área superficial son mucho más cortos con el vapor de agua que con el KOH. Al activar con este último se obtienen valores de área superficial similares errlas dos materias primas, según la temperatura de trabajo, mientras que la activación con vapor de agua, presenta características totalmente diferentes. La activación del Cuesco de Palma Africana con KOH, produce carbones esencialmente microporosos, mientras que con vapor de agua, produce carbones activados con una apreciable mesoporosidad favorecida por el incremento de la temperatura. La activación del carbón de El Cerrejón con KOH o vapor de agua produce carbones activados microporosos. En líneas generales se puede decir que el tipo de textura porosa obtenida en la producción de un carbón activado, es función no sólo de los agentes activantes utilizados, sino también del tipo u origen de la materia prima, mientras que la calidad del carbón activado, (área superficial total, es función del tiempo y de la temperatura de activación, al menos con los materiales de partida usados en este trabajo.

Study on radiolysis products of N,N,N',N'-tetrabutyl-3-oxa-pentanediamide. Pt.1: Qualitative and quantitative analysis of dibutylamine

International Nuclear Information System (INIS)

Zhang Xiaolan; Shanghai Univ., Shanghai; Bao Borong; Shanghai Univ., Shanghai; Yang Yanqin; Ye Guoan; Zhang Xianye

2005-01-01

The study on radiolysis products of gamma-irradiated N,N,N',N'-tetrabutyl-3-oxa-pentane-diamide (TBOPDA) is very useful towards the extractant stability. IR and headspace solid-phase microextraction combined with gas chromatography/mass spectrometry (SPME-GC/MS) are used in the research. By comparisons with standard substances, dibutylamine and N,N-dibutylformamide are comfirmed to be the major radiolysis products. The influences of irradiation on TBOPDA and dibutylamine are quantitated by using headspace SPME-GC and HPLC. According to the experiment results, the possible ways of degradation are also proposed. (authors)

Vapor Pressure of N,N’-Diisopropylcarbodiimide (DICDI)

Science.gov (United States)

2016-02-01

11. Furumoto, S. The Synthesis of Carbodiimides from N,N-Disubstituted Thioureas and 2- Chloro-4,6-dimethylpyrimidine, 2,4-Dichloropyrimidine or...N-Phenylbenzimidoyl Chloride . Journal of Synthetic Organic Chemistry, Japan 1975, 33, 748–752. 12. Kagami, H.; Hanzawa, N.; Suzuki, N.; Yamaguchi...25. Brozena, A.; Buchanan, J.H.; Miles, R.W., Jr.; Williams, B.R.; Hulet, M.S. Vapor Pressure of Triethyl and Tri-n- Propyl Phosphates and Diethyl

Modulación Contextual en la Extinción: Recuperación de una Aversión Condicionada al Sabor en un Tercer Contexto

Directory of Open Access Journals (Sweden)

Rodolfo Bernal-Gamboa

2011-01-01

Full Text Available Este experimento se diseñó para evaluar la renovación ABC con un procedimiento de condicionamiento de aversión al sabor (CAS en tres fases: adquisición, extinción y prueba. Durante la adquisición, 15 ratas Wistar, asignadas a los grupos ABC y ABB, tuvieron acceso a una solución con sacarosa y posteriormente recibieron una inyección de cloruro de litio (LiCl en el Contexto A. En la extinción, ambos grupos bebieron la solución con sacarosa sin la administración del LiCl en el Contexto B. En la prueba, los grupos tuvieron acceso a la solución con sacarosa sin administrarles LiCl en el contexto de extinción para el grupo ABB, y en un tercer contexto para el grupo ABC. Los resultados mostraron la recuperación de la aversión condicionada al sabor únicamente en el grupo ABC.

Ventilación manométrica controlada, con relación inspiración/espiración inversa: una opción de tratamiento en catástrofes pulmonares

Directory of Open Access Journals (Sweden)

Enrique Guzmán Rubín

1998-03-01

Full Text Available Se realizó un estudio prospectivo y longitudinal con el fin de conocer los beneficios de la ventilación manométrica controlada, con inversión de la relación inspiración espiración. Se estudiaron 42 pacientes con una edad media de 1 1/2 años, que durante un síndrome de respuesta inflamatoria sistémica, desarrollaron distress respiratorio agudo, y fueron ventilados volumétricamente, y en una segunda fase se les asoció la inversión de la relación inspiración/espiración, para finalmente pasarlos a una ventilación manométrica con inversión de la relación inspiración/espiración. Los resultados óptimos de distintos parámetros ventilatorios, gasométricos y hemodinámicos al compararlos estadísticamente, correspondieron al último tipo de ventilación empleada.A prospective longitudinal study for finding out the benefits of controlled manometric ventilation with reversed inspiration-expiration ratio was performed. 42 patients with average age of one-year six months were studied, who suffered an acute respiratory distress in a systemic inflammatory syndrome and were finally volumetrically ventilated. In a second phase, a reversed inspiration-expiration ratio was put into practice and finally the patients were applied manometric ventilation with reversed inspiration-expiration ratio. In a statistical comparison, the controlled manometric ventilation obtained the best results in several ventilatory, gasometric and hemodynamic parameters.

El sistema de gestión en laboratorios de calibración para su acreditación

Directory of Open Access Journals (Sweden)

Elia I. Guevara-Guerrero

2014-01-01

Full Text Available La experiencia práctica y evidencias obtenidas por los autores, a partir de la realización de diagnósticos permitieron puntualizar aspectos de interés en la preparación de los laboratorios para cumplir con los requisitos de competencia exigidos en busca de lograr un servicio de calibración eficiente y eficaz y el reconocimiento que representa su acreditación. Para su realización se requirió de la aplicación de diversos métodos de la investigación que incluyeron entre otros la observación del desempeño de procesos, actividades y áreas, revisión de documentos, aplicación de entrevistas y listas de verificación, revisión de documentos, así como elementos básicos de estadística descriptiva. Se ofrecieron sugerencias o recomendaciones que facilitan la interpretación y aplicación de algunos de estos requisitos con énfasis en la definición del alcance de la acreditación, la documentación del sistema de gestión para el laboratorio, los ensayos de aptitud y el servicio al cliente incluyendo las quejas.

Gestión gerencial del docente directivo en las funciones: planificación, organización y dirección

Directory of Open Access Journals (Sweden)

Carlos Santana Soteldo

2015-10-01

Full Text Available El presente estudio tuvo como propósito analizar la gestión gerencial del docente directivo en cuanto a las funciones de planificación, organización y dirección. Se trata de una investigación de campo de carácter descriptivo y para obtener la información se aplicó un cuestionario con preguntas dicotómicas. El instrumento que se utilizó fue validado a través de la técnica de juicio de expertos y su confiabilidad se determinó mediante la aplicación de la fórmula de Kuder-Richardson (K-R20, obteniéndose la muy alta confiabilidad de 0.90. Los resultados permitieron conocer que la gestión gerencial del docente directivo en cuanto a la planificación, organización y dirección no es ejercida eficientemente, lo cual afecta a la institución y a todos sus actores. AbstractThe purpose of this research was to analyze the administrative management of the teacher director in terms of planning, organization and direction. It is about a field research of descriptive character in which a dichotomous questionnaire was applied in order to obtain the information. The instrument used was validated through the technique of experts’ opinion, and its reliability was determined by applying the Kuder-Richardson formula (K-R20 resulting in high reliability 0.90. The results revealed that the teacher director’s administrative management in terms of planning, organization and direction is not performed efficiently; this fact affects the institution and all the actors involved in it.

Ternary nitrides for hydrogen storage: Li-B-N, Li-Al-N and Li-Ga-N systems

International Nuclear Information System (INIS)

Langmi, Henrietta W.; McGrady, G. Sean

2008-01-01

This paper reports an investigation of hydrogen storage performance of ternary nitrides based on lithium and the Group 13 elements boron, aluminum and gallium. These were prepared by ball milling Li 3 N together with the appropriate Group 13 nitride-BN, AlN or GaN. Powder X-ray diffraction of the products revealed that the ternary nitrides obtained are not the known Li 3 BN 2 , Li 3 AlN 2 and Li 3 GaN 2 phases. At 260 deg. C and 30 bar hydrogen pressure, the Li-Al-N ternary system initially absorbed 3.7 wt.% hydrogen, although this is not fully reversible. We observed, for the first time, hydrogen uptake by a pristine ternary nitride of Li and Al synthesized from the binary nitrides of the metals. While the Li-Ga-N ternary system also stored a significant amount of hydrogen, the storage capacity for the Li-B-N system was near zero. The hydrogenation reaction is believed to be similar to that of Li 3 N, and the enthalpies of hydrogen absorption for Li-Al-N and Li-Ga-N provide evidence that AlN and GaN, as well as the ball milling process, play a significant role in altering the thermodynamics of Li 3 N

AlGaN/GaN HEMT structures on ammono bulk GaN substrate

International Nuclear Information System (INIS)

Kruszewski, P; Prystawko, P; Krysko, M; Smalc-Koziorowska, J; Leszczynski, M; Kasalynas, I; Nowakowska-Siwinska, A; Plesiewicz, J; Dwilinski, R; Zajac, M; Kucharski, R

2014-01-01

The work shows a successful fabrication of AlGaN/GaN high electron mobility transistor (HEMT) structures on the bulk GaN substrate grown by ammonothermal method providing an ultralow dislocation density of 10 4  cm −2  and wafers of size up to 2 inches in diameter. The AlGaN layers grown by metalorganic chemical vapor phase epitaxy method demonstrate atomically smooth surface, flat interfaces with reproduced low dislocation density as in the substrate. The test electronic devices—Schottky diodes and transistors—were designed without surface passivation and were successfully fabricated using mask-less laser-based photolithography procedures. The Schottky barrier devices demonstrate exceptionally low reverse currents smaller by a few orders of magnitude in comparison to the Schottky diodes made of AlGaN/GaN HEMT on sapphire substrate. (paper)

AlGaN/GaN double-channel HEMT

International Nuclear Information System (INIS)

Quan Si; Hao Yue; Ma Xiaohua; Zheng Pengtian; Xie Yuanbin

2010-01-01

The fabrication of AlGaN/GaN double-channel high electron mobility transistors on sapphire substrates is reported. Two carrier channels are formed in an AlGaN/GaN/AlGaN/GaN multilayer structure. The DC performance of the resulting double-channel HEMT shows a wider high transconductance region compared with single-channel HEMT. Simulations provide an explanation for the influence of the double-channel on the high transconductance region. The buffer trap is suggested to be related to the wide region of high transconductance. The RF characteristics are also studied. (semiconductor devices)

Digital growth of thick N-polar InGaN films on relaxed InGaN pseudosubstrates

Science.gov (United States)

Lund, Cory; Hestroffer, Karine; Hatui, Nirupam; Nakamura, Shuji; DenBaars, Steven P.; Mishra, Umesh K.; Keller, Stacia

2017-11-01

Smooth relaxed N-polar InGaN films were grown by metal-organic CVD (MOCVD) on N-polar InGaN pseudosubstrates (PSs) using a novel digital approach consisting of a constant In precursor flow with the pulsed injection of H2 carrier gas. InGaN layers grown on PSs exhibited an In composition of about 50% higher than those of the layers grown on N-polar GaN templates, assuming the in-plane lattice constant of the relaxed PSs, corresponding to In0.11Ga0.89N. Additionally, the luminescence recorded from InGaN layers grown on PSs at 490 nm was twice as intense as that obtained from the layers deposited on coloaded GaN-on-sapphire templates, which emitted at 430 nm.

Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

Energy Technology Data Exchange (ETDEWEB)

Liu, Chao; Cai, Yuefei; Liu, Zhaojun; Ma, Jun; Lau, Kei May, E-mail: eekmlau@ust.hk [Photonics Technology Center, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2015-05-04

We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme.

Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Liu, Chao; Cai, Yuefei; Liu, Zhaojun; Ma, Jun; Lau, Kei May

2015-01-01

We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme

Determinantes de la divulgación de información financiera: aplicación de una propuesta para su clasificación

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Saitua Iriba, Ainhoa

2008-11-01

Full Text Available En este trabajo reflexionamos acerca del papel que desempeña el campo de la investigación sobre los factores determinantes del nivel de divulgación de las empresas, para tratar de contribuir a la búsqueda de soluciones que promuevan las mejores condiciones de divulgación por parte de las empresas. Para ello, en el apartado segundo realizamos una propuesta teórica en relación con la dirección que a nuestro juicio debería seguir la investigación sobre los factores determinantes del nivel de divulgación de información. En el apartado tres aplicamos dicha propuesta a un trabajo de revisión de los estudios que se han publicado sobre la materia, y en el último plasmamos nuestras reflexiones finales.

Percepción del alumnado de Educación Secundaria sobre la mediación escolar en Castellón y Valencia

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Laura García Raga

2017-04-01

Full Text Available La realidad social, en constante proceso de cambio, exige al sistema educativo un esfuerzo por actualizar las respuestas educativas frente a la mejora de la convivencia. Es en este contexto en el que la mediación ha dejado ver sus potencialidades educativas, ya que influye sobre la mejora del individuo, de las relaciones interpersonales y del clima escolar. No obstante, son escasas las investigaciones orientadas a conocer el impacto de la misma. En este artículo presentamos un estudio dirigido a conocer la valoración de la mediación atendiendo a las opiniones del alumnado de cinco centros educativos de secundaria de Valencia y cuatro de Castellón. Asimismo, se pretende detectar si existen diferencias significativas entre las valoraciones ofrecidas en ambas provincias. Para el logro de estos objetivos se ha recogido información de 1043 estudiantes a través de un cuestionario elaborado ad hoc. Mediante un estudio descriptivo-inferencial destacamos como resultado el gran acuerdo que existe por parte del alumnado participante en valorar de forma muy positiva la mediación. Como aspectos mejorables, se detecta la necesidad de difundir en los centros la información sobre sus servicios de mediación, formar en mediación a todo el alumnado y ampliar las funciones de la mediación a aquellos conflictos más relacionados con las tareas de enseñanza y aprendizaje y con las relaciones entre el alumnado y el profesorado. Finamente, se observa que, en general, la satisfacción sobre la mediación es menor en Valencia que en Castellón. En conclusión, el estudio refleja que la mediación escolar es considerada como ventajosa para el alumnado y como una oportunidad que le facilita la gestión de sus propios conflictos, si bien hay aspectos en los que se debe trabajar para la mejora de la convivencia y la configuración de una ciudadanía democrática.

EL REORDENAMIENTO URBANO CON PARTICIPACIÓN COMUNITARIA. UNA ESTRATEGIA PARA LA PREVENCIÓN Y MITIGACIÓN INTEGRAL DEL RIESGO POR FENÓMENOS GEOLÓGICOS: CASO DE APLICACIÓN EN MEDELLÍN, COLOMBIA

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Rendón R. Albeiro de J.

2008-07-01

Full Text Available En este artículo mostramos una experiencia de prevención y mitigación del riesgo por caída de rocas en Medellín, Colombia. La participación de la comunidad fue el componente trasversal a la planeación- gestión, prevención- mitigación del riesgo, legalización de la tierra, mejoramiento- reubicación de vivienda e infraestructura urbana. Los resultados más importantes fueron: a mejoramiento de la calidad de vida directamente a 2.500 personas e indirectamente a 24.000, con una inversión de 3.6 millones de dólares; b construcción de tejido social y sentido de pertenencia; c mejor gobernabilidad y relación estado-comunidad y d reducción del riesgo geológico. Finalmente, la participación de la comunidad en todas las fases del proyecto y el concepción del riesgo como un problema no resuelto del desarrollo fueron dos elementos determinantes para que el reordenamiento urbano fuera la mejor alternativa para la prevención y mitigación del riesgo geológico frente a la reubicación masiva de la población, en este sector de desarrollo informal de la ciudad.

Photoluminescence and pressure effects in short period InN/nGaN superlattices

DEFF Research Database (Denmark)

Staszczak, G.; Gorczyca, I.; Suski, T.

2013-01-01

Measurements of photoluminescence and its dependence on hydrostatic pressure are performed on a set of InN/nGaN superlattices with one InN monolayer and with different numbers of GaN monolayers. The emission energies, EPL, measured at ambient pressure, are close to the value of the band gap, Eg......, in bulk GaN, in agreement with other experimental findings. The pressure dependence of the emission energies, dEPL/dp, however, resembles that of the InN energy gap. Further, the magnitudes of both EPL and dEPL/dp are significantly higher than those obtained from ab-initio calculations for 1In...

A comparative study on MOVPE InN grown on Ga- and N-polarity bulk GaN

International Nuclear Information System (INIS)

Wang, W.J.; Miwa, H.; Hashimoto, A.; Yamamoto, A.

2006-01-01

The influence of substrate polarity on the growth of InN film by MOVPE was investigated using bulk GaN as a substrate. Single-crystalline In- and N-polarity InN films were obtained on Ga- and N-polarity GaN substrate, respectively. Significant difference of the morphologies between the In- and N-polarity InN films was found. For the In-polarity InN film, the morphology was similar to that grown on sapphire substrate. The film surface was consisted of grains with small facets. In contrast, for the N-polarity InN film, the surface was consisted of large hexagonal shape crystal grains with flat surface. The grain size was about 2 μm in diameter on the average, and two-dimensional growth was enhanced obviously for each crystal grain. The influence of the growth temperature on the morphology, polarity, and optical property was also investigated. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Investigación cualitativa e imaginación epidemiológica, una relación vital

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Popay J.

2003-01-01

Full Text Available Este artículo presume que la «imaginación epidemiológica» tiene un papel relevante en el futuro desarrollo e implementación de políticas cuya finalidad sea mejorar la salud de la población y reducir las desigualdades de salud entre países y dentro de ellos. Sin embargo, si obviamos la contribución de la investigación cualitativa a la epidemiología fracasaremos en el desarrollo de ese potencial. Este artículo brevemente describe qué es la investigación cualitativa desde un punto de vista epidemiológico -qué tipo de «conocimiento» genera- y aborda cuestiones metodológicas (aproximaciones sobre recogida de datos, análisis e interpretación de resultados. Se presentan dos modelos diferentes sobre la relación entre la investigación cualitativa y cuantitativa. El primer modelo, denominado de intensificación, asume que los resultados de la investigación cualitativa enriquecen los resultados obtenidos mediante investigación cuantitativa y sugiere 3 roles para la investigación cualitativa: generar hipótesis que se podrán probar en la investigación cuantitativa, ayudar a construir medidas más sofisticadas de fenómenos sociales y explicar resultados sorprendentes obtenidos mediante una aproximación cuantitativa. Por el contrario, el modelo epistemológico sugiere que la investigación cualitativa es diferente de la cuantitativa en el sentido de que realiza una contribución única: estudia aspectos que otras aproximaciones no pueden analizar; mejora y amplía el conocimiento al profundizar en aspectos conceptuales y teóricos; cambia el equilibrio de poder entre los investigadores y el objeto de investigación, y por último desafía los métodos que utiliza la epidemiología tradicional para conocer el mundo social. Este artículo ilustra los diferentes tipos de contribuciones con ejemplos de la investigación cualitativa y finalmente discute cómo la investigación cualitativa "digna de confianza" puede evaluarse.

Measurements and systematics studies of the (n,p), (n,α) and (n,2n) reactions cross-sections at 14.5 MeV neutrons

International Nuclear Information System (INIS)

Osman, Khalda

2000-01-01

Accurate knowledge of the cross-sections for fast neutron-induced reactions utilizing the D-T reaction is important not only because of the wide spread of data observed in the literature, but also because of the world wide demand and requests for such data, in view of the increasing interest in the fusion reactor technology, which is based on the same reactions. Cross-sections are needed also for various practical purposes, including neutron activation analysis and dosimetry. In this work the (n.p), (n,2n) and (n,α) reactions cross-sections were measured at 14.5 MeV for isotopes of the elements: Cr, Ti, Ni, Co, Zr, and Mo using the activation method. The measured cross-sections were compared with recently published data. Good agreement was observed for most of the measurements. The discrepancies observed were attributed to difficulties related to the long half-life of the product nuclei and small abundances of the target isotopes. Attempts were also made to study the dependence of the (n,p), (n,2n) and (n,α) reactions cross-sections on the on the asymmetry parameter (N-Z)/A. The results confirmed the trend theoretically suggested by Levkovskii and experimentally realized by Qaim and co-workers. The isotopic dependence of (n,p) reaction cross-sections and the variation of the ration σ n ,p/σ n ,α with Z-number of the target isotopes were also studied in this work and the results obtained were found to be in agreement with theoretical predictions. In this work studies carried out for the systematics of the (n,p), (n,2n) and (n,α) reactions cross-sections at 14 MeV neutrons and formula based on the statistical model presented, with the aim of improving the systematics of these cross-sections. Comparison of present proposed systematics were for the (n,p), (n,2n) and (n,α) reactions cross-sections with the cross-section values measured in this work was made. Good agreement was generally noted, but some discrepancies were also observed. These discrepancies were