für 71.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray La Tierra es el único planeta de nuestro sistema solar en el que la vida se ha abierto camino. En este sentido la atmósfera terrestre ha jugado un papel decisivo en modular las condiciones de habitabilidad del planeta. Pero las características de la atmósfera no son estables y los seres vivos interaccionan recíprocamente con ella. Así, desde que el hombre se desarrolla no hay actividad humana que no incida de una manera u otra sobre la atmósfera. El presente trabajo pretende realizar una evaluación de la compatibilidad medioambiental de algunos sustitutos de clorofluorocarbonos (CFCs) que se emplean actualmente o bien se prevé su empleo en un fututo próximo. Para ello, se obtendrán los tiempos de vida troposféricos de los mismos frente a radicales Cl y OH y se realizará un estudio radiativo obteniendo sus forzamientos radiativos (RF) y potenciales de calentamiento global (GWPs). Todos estos datos son necesarios para establecer el posible impacto de estas especies como posibles agentes de smog, destructores de la capa de ozono o gases invernadero. ····· 1036190932
für 53.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray Los mayores triunfos de la ciencia en el último siglo se debieron al desarrollo de técnicas capaces de estudiar el tamaño y forma de los objetos a niveles moleculares y atómicos. Esto permitió comprender la forma en que interactúan los átomos y moléculas y abrió las puertas al diseño , a estas escalas, de nuevos materiales, dando origen al nacimiento de las llamadas nanotecnologías. Una de las formas de describir a nivel molecular las interfases gas sólido, es a través de la adsorción desde sólidos porosos, superficies fractales y nanotubos de carbono. La adsorción de gases ha contribuido a brindar información de las estructuras presentes en materiales porosos inclusive poco cristalinos como son los carbones activados. Dado que los poros de carbones activados tienen forma de ranuras, algunos métodos resultan particularmente adecuados para determinar sus parámetros como son volúmen, superficie efectiva o ancho del poro. ····· 1036190902
für 35.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray Se estudió la reacción de isomerización de n-pentano sobre catalizadores Pt/MOR (1% p/p), con relaciones Si/Al desde 5 hasta 35. El platino fue incorporado a la zeolita mediante intercambio iónico en estado sólido. Los sólidos fueron caracterizados por energía dispersiva de rayos X (EDX), difracción de rayos X (XRD), termodesorción programada de amoníaco (TPD-NH3) y adsorción/desorción de N2 a 77K. Las reacciones fueron llevadas a cabo a diferentes temperaturas, observándose un aumento en la actividad del catalizador con el aumento de temperatura, pero también una disminución de la selectividad hacia iso-pentano. La conversión inicial es una función lineal de la concentración de sitios ácidos del catalizador, y está relacionada también con el volumen de poro de la zeolita. La selectividad de estos catalizadores depende de la distribución de la fuerza de los sitios ácidos, siendo los sitios ácidos débiles los que favorecen la isomerización. ····· 1036190806
für 53.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray La investigación sobre óxidos semiconductores transparentes (TCO) basada en sus propiedades físicas que les permiten ser utilizados en una amplia variedad de dispositivos electrónicos, ha generado una gran cantidad de publicaciones en la literatura científica internacional. Los materiales más estudiados en este campo son óxido de estaño, óxido de indio, óxido de zinc y óxido de tinanio. El óxido de zinc, ZnO, presenta las ventajas de ser un material no tóxico y estable ante plasmas moderados de hidrógeno. La formación de películas de ZnO con la técnica de Rocío Pirolítico presenta un alto potencial de aplicación industrial debido a su tecnología de control, su operación sencilla y reproducible. En esta investigación se presentan resultados originales obtenidos en el depósito de películas delgadas de ZnO empleando Flúor como inpurificante mediante la técnica de Rocío Pirolítico. La contribución principal es brindar una visión más amplia sobre las propiedades físicas de las películas de ZnO por medio de un estudio experimental completo y detallado. ····· 1036190087
für 62.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray Este libro contiene una versión revisada de la tesis doctoral presentada y defendida en la Universidad de Málaga por Francisco José Galindo Rosales en 2008. El uso del dióxido de silicio pirogénico como agente modificador de las propiedades reológicas es una práctica común en la búsqueda de sistemas materiales con comportamientos de flujo a la carta. La química superficial de la partículas de sílica fumada determina su carácter hidrofílico o hidrofóbico, haciendo que las interacciones con otras partículas y con el medio que las dispersa den lugar a suspensiones no floculadas, floculadas o geles coloidales. En este estudio se analizan las suspensiones de tres tipos de dióxido de silicio pirogénico, uno hidrofílico, uno parcialmente hidrofóbico y otro totalmente hidrofóbico, en polipropilenglicol de dos masas moleculares distintas, con el objeto de determinar la influencia en el comportamiento reológico tanto de la química superficial de la partícula como de la longitud de las moléculas de la matriz polimérica. También se define una ecuación constitutiva para condiciones de cizalla estacionaria y se resuelven distintos casos de flujo laminar estacionario en conductos. ····· 1036189492
für 35.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray En este trabajo se realizó la producción de cintas amorfas de composición Co80-xFexB10Si10 con x= 10, 8 y 6, Fe78B13Si9 y Fe80B10Si10, por medio del método de solidificación rápida de la rueda fría Melt Spinning y se llevó a cabo la caracterización térmica, termomagnética y magnética de las mismas. Por medio de la técnica de Calorimetría Diferencial de Barrido (DSC) se realizó el análisis de la cinética de cristalización de las aleaciones y se obtuvo la energía de activación (Ea) y el coeficiente de Avrami n de las mismas. La Temperatura de Curie y el comportamiento termomagnético de las cintas, se estudiaron por medio de Análisis Termogravimétrico (TGA), el lazo de histéresis y la magnetización de saturación (Ms) para cada aleación se obtuvieron con Magnetometría de Muestra Vibrante (VSM). También se llevó a cabo un estudio del fenómeno de Magnetoimpedancia gigante (MIG) éste consiste en el cambio de la impedancia de un material magnético blando cuando a través de él se hace pasar una corriente eléctrica ac en presencia de un campo magnético dc, H0. Tal efecto se ha presentado en materiales magnéticamente blandos en forma cintas, hilos, películas y multicapas. ····· 1036189414
für 35.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray En este trabajo de Tesis, se logró encontrar las condiciones para la síntesis de nanopartículas semiconductoras de CdS, con propiedades fotofísicas diferentes. Se realizó un estudio de sus propiedades fotofísicas, proponiéndose un esquema de recombinación de cargas. Además se estudió la interacción con detergentes y derivados de los mismos, se propusieron mecanismos de interacción de los detergentes con las nanopartículas. Se encontró la posibilidad de que los detergentes sean utilizados para disolver sustancias orgánicas de manera tal de aumentar su interacción con la superficie de las nanopartículas. Finalmente, se estudió la interacción de las nanopartículas con donantes y aceptores de electrones, se encontraron efectos considerables sobre la fluorescencia de las nanopartículas, abriendo la posibilidad de utilizar estos sistemas como degradantes de contaminantes orgánicos, en combinación con detergentes en el caso que, por la baja solubilidad del compuesto orgánico sea necesario la utilización de detergentes. ····· 1036189373
für 44.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray The book described catalytic systems for living polymerization of 1,3-butadiene by CoX2 ( X = Halogens ) combined with MAO as a cocatalyst at 0, 10 and 18 C. The uni-modal molecular weight distribution curves of the resulting polymers shifted toward higher molecular weight regions and became narrower with the increasing of the polymerization time. The number-average molecular weight increased linearly against polymerization time, while the polymer yield exponentially increased in the initial stage. As a consequence, the number of polymer chains calculated from the polymer yield and Mn value increased gradually with polymerization time to reach a steady value. These phenomena were interpreted based on a slow initiation system without any termination and chain transfer reaction. The kinetic analysis indicated that the rates of initiation were significantly influenced by the nature of the halides and descended in the following order, CoCl2 CoBr2CoI2CoF2 = 0, while the rates of propagation were independent on variation of halogen ligands. The effects of other cocatalysts and additive on livingness were also analyzed systematically. ····· 1036189269
für 53.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray The purpose of this work is to utilize atmospheric plasma to increase coating adhesion between textile substrate and a surface which is repellent to liquid water, formed using electrospun nanofibers (NFs). Atmospheric pressure plasma and electrospinning can be scaled to industrial levels and promise cost and energy savings relative to many current textile finishing methods. A quick, simple and durable hydrophobic finishing process for woven military Nylon 6,6/cotton fabric is demonstrated, maintaining similar bulk garment characteristics like moisture vapor transmission to promote necessary dissipation of heat. The promotion of necessary heat transfer while providing protection against chemical and thermal hazards using a multilayered garment approach has become important for many textile applications including military and industrial uses for Chemical-Biological hazard protection, as well as medical and activewear textiles. Incorporation of a NF coating with a fabric imparts composite multifunctional properties, while demonstrating the potential for greatly decreased processing time and uses less water, energy, and hazardous chemicals than traditional finishing techniques. ····· 1036189064
für 53.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray The project covers the preparation and characterization of new series of macrocycle compounds derived from phosphinic acid namely, bis-[1,5-diphenylcarbazide-dimethyl phosphinic acid], bis-[1,5-diphenylthiocarbazide-dimethyl phosphinic acid] and bis-[1,6-diphenyl-oxaloyldihaydrazine dimethyl phosphinic acid. These compounds were prepared from the reaction of paraformaldehyde, phosphinic acid with(1,5-diphenylcarbazide),(1,5-diphenylthiocarbazide) and (1,6-diphenyloxoloyldihydrazine) respectively, at the reflux temperature in presence of 6N HCl. The prepared compounds were characterized by elemental microanalysis, melting point, FTIR, 1H, 13C, 31P, 2D 1H-1H, NMR, and Mass spectroscopy. The prepared compounds were used for adsorption from solution of phenol, p-chlorophenol, copper (II), and nickel (II) at different conditions of temperature and ionic strengths. Shapes of the isotherms obtained from the adsorption studies of phenol, p-chlorophenol, copper (II), and nickel (II) on surfaces of these compounds were found to be combatable to the Freundlich equation and were similar to (S Type) according to Giles classification. ····· 1036188339
für 71.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray From many years of teaching experience, I know the difficulties students face as they begin to acquire a chemist s view of the world. I strongly believe that a textbook must connect observation- in the everyday world and in the laboratory- to the principles of chemistry. My approach is anchored in a student s experience and then goes beyond the perceived, to help students visualize entities they cannot directly see. This book is written primarily for undergraduate science and allied science students who in the beginning of their university studies receive education in basic general chemical principles. The aim of this book is to introduce, explain and clarify important terms and concepts which the students are supposed to be familiar with. The book gives a great supplement to the education within chemistry. Many assignments, self-study questions and worked examples are given in the book. The book is divided into fourteen chapters covering the introductory parts of the education within chemistry at universities. One of the aims of this book is to lighten the shift from senior high school to the university. ····· 1036188226
für 44.10€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray It`s often a problem that the measurement of reaction rate constant is influenced by the clustering of foreign molecule to one of the reactant partners especially in Atmospheric Physics and Physical Chemistry. The presence of such clustering also hinders to extract sufficient information pertaining to a reaction like Gibb`s free energy which is important thermodynamic variable. Even though the problem is inevitable in such areas, no much and sound work is done to understand it. The task of this book is then devoted to examine such effects particularly focused on water clustering effect on reaction rate constants and their corresponding thermodynamic variables. A computer simulation was made to compute this effect. The computation was based on the Average Dipole Orientation and the Hard Sphere Average Dipole Orientation theories. The reactions considered were the NI-PTRs. Such reactions are of great importance in enormous field of studies, environmental science to mention the most common one. These computed results facilitate the use of NI-PTR Mass Spectrometry technique in the application of laboratory investigation and field research of environmentally important VOCs. ····· 1036188181
für 61.20€ kaufen ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray This book handles, presents, and discusses very important and attractive experimental data concerning the formation of highly ordered and orientated self-assembled monolayers of aromaticthiols on Au(111). These SAMs are generated from conjugated molecules that are useful for future molecular electronics application because they are considered to be electrically conductive. The resulting SAMs are characterized by means of different surface techniques such as STM, LEED, XPS, and FTIR. The results demonstrate that the packing of the biphenyl (BP) and terphenyl (TP) moieties in BPn and TPn (n=0-6) films exhibit a periodical `odd-even` variation with the length of the aliphatic part. For an odd number of CH2 group in the alkyl chain of BPn and TPn a higher density was found. In the opposite case, the biphenyl and terphenyl moieties adopt a lower density. ····· 1036187242
····· lezzter Preis 79.00€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray The aim of the present work includes the prepration of 5-sulfo-7-(p-substituated phenyl azo)-8-hydroxyquinoline ligands. The formed ligands were reacted with UO2(NO3)2 and VO22+ to form their corresponding complexes. All prepared comounds were characterized by elemental analyses and various physico-chemical techniques. The azo quinoline compounds act as a monobasic bidentate chelates through the nitrogen of azo group and alcholic oxygen of 8-hydroxyquinoline moiety. As a matter of fact, the transition metal ion complexes of hydrazone and/or azo compounds have applications as catalyst in various chemical and photochemical reactions as well as in biological systems. The 8-hydroxyquinoline applications of such metal complexes to any system depends to a great extent on its molecular structure. Thus, it is of importance to get an idea about the structure of the formed complexes. The DC electrical behaviour of 5-sulfo-7-(p-substituated phenyl azo) -8-hydroxyquinoline compounds and their uranyl complexes are investigated in the temperature range 290-410 K. The conductivities are found to depend on the structure of the compounds and the metal. ····· 1036125802
····· lezzter Preis 61.20€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray Rapid and sensitive detection of chemical and biological analytes becomes increasingly important in areas such as medical diagnostics, food control and environmental monitoring. Optical biosensors based on surface plasmon resonance (SPR) and optical waveguide spectroscopy have been extensively pushed forward in these fields. In this book, we combine long range surface plasmons (LRSPs), surface plasmon-enhanced fluorescence spectroscopy (SPFS) and optical waveguide spectroscopy with hydrogel thin film for highly sensitive detection of molecular analytes. LRSPs are special surface plasmon waves propagating along thin metal films with orders of magnitude higher electromagnetic field intensity and lower damping than conventional SPs. Therefore, their excitation on the sensor surface provides higher fluorescence signal for molecules detection. The hydrogel thin film attached on a sensor surface served both as a binding matrix and as an optical waveguide for probing molecules interactions. The higher binding capacity of hydrogel and low damping of optical waveguide provide higher sensitivity for molecules detection as compared to regular SPR. ····· 1036125747
····· lezzter Preis 53.10€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray This book, Removal of Heavy Metals from aqueous Systems, is a complete, up-to-date book on different methods employed to remove metal ions from aqueous solution. The topics in this book are properly treated and presented in such a way that facilitate easy comprehension. The chapters are attractively arranged and emphasis has been placed on the use of immobilized bacterial cells such as Escherichia coli and Bacillus subtilis on agarose to remove heavy metals from aqueous solution in a phenomenon known as biosorption. What makes this book unique is its practical approach through experiment and the use of various mathematical relation(isotherms) to explain the adsorption process. Chemistry and chemical engineering student at BSc. and MSc. level will find this book handy in the same ways teacher will benefit from it ····· 1036125535
····· lezzter Preis 71.10€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray Wood of Prunus persica was utilized for the preparation of activated carbon. The carbon was characterized by pH, moisture content, ash content, bulk density, surface area (BET), FTIR and EDS. The BET (m2/g) surface area analysis of the carbon samples activated at 800 oC showed high surface area. FTIR analysis showed that the carbon surface carried the oxygen containing functional groups, which disappeared at high activation temperatures. The EDS analysis showed high carbon contents in the sample activated at high temperature as compared to Raw and 300 oC activated samples while the contents of oxygen was found to decrease with the increase in activation temperature. The equilibrium for the aliphatic mono carboxylic acids adsorption on the carbon samples was achieved after 3 hours. Freundlich and Langmuir models were used to know the adsorption parameters. The best fit of the isotherms, found from the correlation coefficients were in the sequence: Langmuir Freundlich. ····· 1036125105
····· lezzter Preis 61.20€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray To investigate the effect of non-ionic polymers polyvinyl pyrrolidone (PVP), polyethylene oxide and polyvinyl alcohol on critical micelle concentration of an anionic surfactant, sodium dodecyl sulfate and a cationic surfactant, cetyltrimethyl ammonium bromide at different temperatures by conductivity and surface tension techniques. The CMC of SDS decreased in presence of the polymers. The degree of this decrease in CMC of SDS was greater for PVP than for PEO and PVA. Increase in the micellar ionization degree was observed for SDS-polymer mixtures. Gcomp values for SDS-polymer mixtures were higher, more negative for SDS-polymer mixtures than pure SDS. These results showed that as compared to PEO and PVA, PVP interacts more strongly with SDS. The critical aggregation concentration of SDS-PVP, SDS-PEO and SDS-PVA mixtures slightly decreased with rise in temperature. and Gcomp of SDS-polymer mixtures increased with increase in temperature reflecting that complexation is favored at high temperatures. The krafft temperature of CTAB did not show any dependence on the concentration of the polymers. ····· 1036124659
····· lezzter Preis 71.10€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray Some halogenated hydrocarbons and their substituted derivatives are stable compounds and show markedly low chemical reactivity. These properties make them long lasting and non-biodegradable. These compounds are passed on to the aquatic plants and animals by different ways, which are consumed as food by human beings and other animals and become a part of food chain. In the present time, photochemistry is one of the most rapidly expanding and challenging fields for the chemists. The photochemistry of aromatic halo-substituted compounds has been studied with considerable interest in recent years due to the toxic impact of these species on the environment, by developing special techniques for their degradation like UV irradiation, photosensitized sun simulated light irradiation and photo-catalysis. Different categories of halogenated organic compounds have been degraded using the photosensitized reaction and the effect of different parameters affecting the rate of degradation has been studied. ····· 1036124641
····· lezzter Preis 61.20€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray This work deals with the preparation, characterization and kinetic studies on base hydrolysis of some Fe(II) Schiff base amino acid complexes.The prepared complexes were found to be of 1:2 or 1:1 stoichiometry and non electrolytic character, solubility measurements of these complexes showed them as hydrophobic in nature. The base hydrolysis reaction of the prepared complexes was carried out in aqueous, co-organic media and in the presence of added salts. The kinetic measurements confirmed the pseudo 1st order rate dependence in [complex] and 2nd order in [OH-]. A relevant mechanism was suggested in which the parallel attack of OH- ion on the central Fe(II) atom and the dissociation of the first ligand is provided as rate determining step. The observed decrease of base hydrolysis rate constant kobs. with increasing the mole fraction of co-organic solvent indicates solute solvent interaction between delocalized charge in complex and dispersion centers on solvent molecules. ····· 1036124598
····· lezzter Preis 79.00€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray Chitosan is a natural carbohydrate biopolymer derived by deacetylation of chitin. Reaction of chitosan with carbonyl compounds leading to formation of Schiff bases have been reported in the older literatures and their importance has not yet fully realized. The present work involves modification of chitosan by benzophenone, acetophenone, cinnamic acid or phenylacetic acid. The thermal stabilities of the prepared polymers were compared with chitosan polymer. Thermal degradation of the modified polymers has been studied in order to determine the nature of the degradation products and the activation energies of the degradation were calculated. ····· 1036124514
····· lezzter Preis 26.10€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray El oxido de zinc (ZnO) es un mineral complejo con propiedades fisicoquímicas unicas que lo hacen fascinante desde un punto de vista científico, en película delgada presentan una baja resistividad y una transmitancia en el visible alrededor de un 80 %. Esto se debe a la microestructura de la película, la cual esta restringida por los procesos termodinámicos que se llevan a cabo durante su fabricación, su impurificación y la importancia de la concentración del ácido acético glacial en su fabricación para controlar las propiedades eléctricas, ópticas y morfológicas. Este libro describe las técnicas que se utilizan para caracterizar las películas delgadas de ZnO:In. con el propósito de conocer la variación de las propiedades físicas en función de los parámetros de deposito ····· 1036124071
····· lezzter Preis 53.10€ ···· Rheinberg-Buch.de - Bücher, eBooks, DVD & Blu-ray La fotocatálisis heterogénea, que pertenece al grupo de las denominadas Técnicas Avanzadas de Oxidación (TAOs), es muy utilizada en el tratamiento de aguas contaminadas donde es muy reconocido el uso del óxido de titanio, fase anatasa, semiconductor que ha dado buenos resultados en la fotodegradación de moléculas orgánicas. Entre otros sistemas que, según la literatura, pueden presentar las propiedades de fotocatálisis heterogénea se encuentran los óxidos de cinc (ZnO con energía de gap Egap=3,2 eV y longitud de onda =388nm) y de estaño (SnO2). En este documento se indican los principales resultados que se obtuvieron de la síntesis y caracterización de los polvos nanométricos de óxido de cinc (ZnO), y del óxido de cinc dopado con óxido de estaño (ZnO/SnOx), obtenidos por precipitación controlada, y su posterior empleo para propiciar reacciones de fotodegradación, a una solución de azul de metileno, con el fin de determinar su capacidad fotodegradante. ····· 1036123810· 1 ·· 2 ·· 3 ·· 4 ·· 5 ·· 6 ·· 7 ·· 8 ·· 9 ·
Affiliate Marketing
AdHoc MeldungenAffiliate & PublisherAdvertiser & MerchantAcademyAntwortenArtikelsucheAdventskalender
AffilitivProduktdatenPreisvergleich
