976 resultados para Fe-cr-b


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The metal-catalyzed autooxidation of S(IV) has been studied for more than a century without a consensus being obtained as to reaction rates, rate laws or mechanisms. The main objective in this work was to explore the reaction between Cu(II) and SO2 in the presence of M(II), paying special attention to the formation of double sulfites like Cu2SO3.M(II)SO3.2H 2O. The two principal aspects studied were: i) a new way to prepare double sulfites with high purity degree and the selectivity in the M(II) incorporation during the salt formation.

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Selectivity studies for the determination of Cr(VI) using the catalytic oxidation of the o-dianisidine by hydrogen peroxide showed two distincts situations. In the first, when interferents were studied by a univariate procedure, Cr(III) and Cu(II) cause serious interferences even at the 2:1 proportion, relative to Cr(VI), while Fe(III) interfered at the 15:1 ratio and EDTA at the 10:1 ratio. On the other hand, when a multivariate investigation was performed, Cr(III) did not present any significant principal effects and its significant interaction effects were negative, in contrast to EDTA, that presented positive interaction effects although, like Cr(III), did not show significant interaction effects. In view of the interferent's action it become necessary to separate Cr(VI) by extraction with methylisobutylketone in a chloridric acid medium before its determination in vegetals and in wastewater from a cellulose industry samples. Using this procedure, the method precision is ±0,5% at the 10 ng/mL Cr(VI) concentration level. The detection and quantification limits, calculated by means of absorbance measurements of ten replicates of blank reagents were 1,1 and 3,2 ng/mL, respectively. The results obtained with real samples showed a relative standard deviation between 1,2% and 3,0% relative to their reference values.

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In environmental studies it is necessary to know the adsorption behavior of metals by soils, since the unfavorable effects of heavy metals and even the micronutrients at high concentrations in the environment are related to these adsorbents' ability to immobilize them. A sample of a humic yellow red oxisol from Araponga region in the State of Minas Gerais, Brazil, was used to verify the adsorption behavior of Cu2+ ions in this substrate. The mathematical model described by Langmuir's adsorption equation in its linearized form was applied and the values of the maximum capacity b and those of the constant related to the bonding energy a were obtained. Aliquots of copper nitrate solutions containing several concentrations of this metal were added to soil samples, the pH being predetermined for developing the adsorption experiments. The chemical and physical characterization of soil sample were performed by determining the organic carbon, nitrogen and phosphorus concentrations, cation exchange capacity (CEC), pH, concentration of metals (Al, Fe, K, Mg, Ca, Zn, Cu, Ni, Cr, Co, Pb, and Cd), granulometric analysis and X-ray diffraction. Langmuir isotherms presented two distinct adsorption regions at both pH 4 and pH 5, showing that the adsorptive phenomenon occurs in two distinct stages. The adsorption sites for the lower part presented greater bonding energy and low adsorption capacity compared with the adsorption sites of the part of the curve corresponding to higher Cu concentrations in the equilibrating solution.

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There is no evidence of urban civilization in Brazilian prehistory; most inhabitants lived in tribal groupings, probably with regional economic integration among several independent tribes. There is little evidence of seasonal migrations between the coast and the inland of southern Brazil. Some specialized horticulturists competed among themselves but other groups lived more isolated and probably peacefully, in the upper interfluvial regions. Chemical analysis of artifacts is a means of documenting traffic in particular materials and intraregional production and distribution, development of craft specialization and typological refinement among other issues. In this study we tested some possibilities in two different cultural contexts using the parametric k0 neutron activation analysis technique, which allowed the determination of elements: Al, As, Au, Ce, Cl, Co, Cr, Cs, Cu, Fe, Ga, K, La, Na, Rb, Sc, Ta, Ti, V and Zn.

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We present studies involving metallic ions and the herbicide glyphosate. The metallic complexes of Cu(II), Zn(II), Mn(II), Ni(II), Cd(II), Pb(II), Cr(III), Fe(III), Co(III), ammonium, sodium, Ag(I), alkaline earth metals and of some lanthanides ions are described. The complexes are discussed in terms of their synthesis, identification, stability and structural properties, based on data from the current literature.

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The overall purpose of this thesis was to increase the knowledge on the biogeochemistry of rural acid sulphate (AS) soil environments and urban forest ecosystems near small towns in Western Finland. In addition, the potential causal relationship between the distribution of AS soils and geographical occurence of multiple sclerosis (MS) disease was assessed based on a review of existing literature and data. Acid sulphate soils, which occupy an area of approximately 17–24 million hectare worldwide, are regarded as the nastiest soils in the world. Independent of the geographical locality of these soils, they pose a great threat to their surrounding environment if disturbed. The abundant metal-rich acid drainage from Finnish AS soils, which is a result of sulphide oxidation due to artificial farmland drainage, has significant but spatially and temporally variable ecotoxicological impacts on biodiversity and community structure of fish, benthic invertebrates and macrophytes. This has resulted in mass fish kills and even eradication of sensitive fish species in affected waters. Moreover, previous investigations demonstrated significantly enriched concentrations of Co, Ni, Mn and Al, metals which are abundantly mobilised in AS soils, in agricultural crops (timothy grass and oats) and approximately 50 times higher concentrations of Al in cow milk originating from AS soils in Western Finland. Nevertheless, the results presented here demonstrate, in general, relatively moderate metal concentrations in oats and cabbage grown on AS soils in Western Finland, although some of the studied fields showed anomalous values of metals (e.g. Co and Ni) in both the soil and target plants (especially oats), similar to that of the previous investigations. The results indicated that the concentrations of Co, Ni, Mn and Zn in oats and Co and Zn in cabbage were governed by soil geochemistry as these metals were correlated with corresponding concentrations extracted from the soil by NH4Ac-EDTA and NH4Ac, respectively. The concentrations of Cu and Fe in oats and cabbage were uncorrelated to that of the easily soluble concentrations in the soils, suggesting that biological processes (e.g. plant-root processes) overshadow geochemical variation. The concentrations of K and Mg in cabbage, which showed a low spread and were strongly correlated to the NH4Ac extractable contents in the soil, were governed by both the bioavailable fractions in the topsoil and plant-uptake mechanisms. The plant´s ability to regulate its uptake of Ca and P (e.g. through root exudates) seemed to be more important than the influence of soil geochemistry. The distribution of P, K, Ca, Mg, Mn and S within humus, moss and needles in and around small towns was to a high degree controlled by biological cycling, which was indicated by the low correlation coefficients for P, K, Ca, Mg and S between humus and moss, and the low spread of these nutrients in moss and needles. The concentration variations of elements in till are mainly due to natural processes (e.g. intrusions, weathering, mineralogical variations in the bedrock). There was a strong spatial pattern for B in humus, moss and needles, which was suggested to be associated with anthropogenic emissions from nearby town centres. Geogenic dust affected the spatial distribution of Fe and Cr in moss, while natural processes governed the Fe anomaly found in the needles. The spatial accumulation patterns of Zn, Cd, Cu, Ni and Pb in humus and moss were strong and diverse, and related to current industry, the former steel industry, coal combustion, and natural geochemical processes. An intriguing Cu anomaly was found in moss. Since it was located close to a main railway line and because the railway line´s electric cables are made of Cu, it was suggested that the reason for the Cu anomaly is corrosion of these cables. In Western Finland, where AS soils are particularly abundant and enrich the metal concentrations of stream waters, cow milk and to some extent crops, an environmental risk assessment would be motivated to elucidate if the metal dispersion affect human health. Within this context, a topic of concern is the distribution of multiple sclerosis as high MS prevalence rates are found in the main area of AS soils. Regionally, the AS soil type in the Seinäjoki area has been demonstrated to be very severe in terms of metal leaching, this area also shows one of the highest MS rates reported worldwide. On a local scale, these severe AS soil types coincide well with the corresponding MS clustering along the Kyrönjoki River in Seinäjoki. There are reasons to suspect that these spatial correlations are causal, as multiple sclerosis has been suggested to result from a combination of genetic and environmental factors.

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Patients with diffuse large B-cell lymphoma treated in a University Hospital were studied from 1990 to 2001. Two treatment regimens were used: ProMACE-CytaBOM and then, from November 1996 on, the CHOP regimen. Complete remission (CR), disease-free survival (DFS), and overall survival (OS) rates were determined. Primary refractory patients and relapsed patients were also assessed. A total of 111 patients under 60 years of age were assessed and ranked according to the international prognostic index adjusted to age. Twenty (18%) of them were classified as low risk, 40 (36%) as intermediate risk, 33 (29.7%) as high intermediate risk, and 18 (16.3%) as high risk. Over a five-year period, OS and DFS rates were 71 and 59%, respectively, for all patients. For the same time period, OS and DFS rates were 72.8 and 61.3%, respectively, for 77 patients treated with CHOP chemotherapy and 71.3 and 60% for patients treated with the ProMACE-CytaBOM protocol. There was no significant difference in OS or DFS between the two groups. Eleven of 50 refractory and relapsed patients were consolidated with high doses of chemotherapy. Three received allogenic and 8 autologous bone marrow transplantation. For the latter, CR was 62.5% and mean OS was 41.1 months. The clinical behavior, CR, DFS, and OS of the present patients were similar to those reported in the literature. We conclude that both the CHOP and ProMACE-CytaBOM protocols can be used to treat diffuse large B-cell lymphoma patients, although the CHOP protocol is preferable because of its lower cost and lower toxicity.

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Dentro do contexto de assegurar à população dietas equilibradas em relação aos elementos essenciais e uma monitoração dos elementos tóxicos, este trabalho teve por objetivo a determinação dos níveis desses elementos, em refeições servidas no restaurante da Faculdade de Saúde Pública/USP freqüentada pelos estudantes universitários e funcionários, durante uma semana. Foram analisadas refeições servidas no almoço. Os alimentos foram recolhidos em bandejas completas em número de 3 por refeição, tomando-se por base as porções servidas, consideradas como análise em duplicata. Foram feitas análises para determinação da composição centesimal das refeições utilizando-se os métodos preconizados pela AOAC. As amostras foram submetidas também a análise multielementar utilizando-se a técnica de análise por ativação neutrônica, onde os seguintes elementos puderam ser determinados: Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Fe, K, Mg, Mn, Mo, Na, Rb, Sb, Sc, Se e Zn, níveis de m g/g a ng/g. Os resultados de ingestão por refeição obtidos no presente trabalho foram comparados com os valores diários recomendados pelo RDA, WHO e Homem Padrão. Salienta-se em relação aos macronutrientes, uma alta adequação protéica e excesso de lípides em algumas refeições, interferindo no valor calórico total. Dentre as causas de maior variação dos resultados a dieta entre os diferentes dias é a que mais contribui. Em relação à fração fibra alimentar, os valores obtidos foram adequados. Quanto aos micronutrientes, observa-se adequação quanto a Br, Ca, Fe, Mg, Mn, Rb, Se e Zn, entretanto, níveis acima do recomendado para K, Mo, Na, Cl e Cr. Para os elementos Ba, Co, Cs e Sb os níveis de ingestão foram comparados com os dados de ingestão diária para Homem Padrão. Os demais elementos traço determinados como Ce e Sc, observa-se que não existe recomendação, tendo-se observado grandes variações nos valores obtidos para estes elementos nos dias estudados.

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Os utensílios culinários podem liberar alguns componentes inorgânicos durante a cocção de alimentos. A migração destes pode ser interessante desde que ocorra em quantidades adequadas às necessidades nutricionais do usuário ou não existam implicações toxicológicas. Foi avaliada a migração de metais (Fe, Mg, Mn, Cr, Ni, Ca, Zn, Pb, Cd e Hg) por espectrometria de emissão óptica, utilizando ácidos láctico e acético como simulantes do alimento em panelas de aço inoxidável (304), ferro fundido (GG-10) e pedra-sabão (esteatito), durante 15 cocções seqüenciais. O comportamento da migração durante cinco ciclos de estocagem a 22ºC também foi estudado. Análise de regressão dos dados revelou que, em função do uso, as panelas de inox apresentam redução da migração de metais de forma rápida, enquanto as de pedra-sabão mostram um declínio suave na migração, contrastando com as de ferro, que apresentam aumento na migração de Fe e Mn com o uso contínuo. Em nenhum utensílio foi observada a liberação de metais pesados, como Pb, Cd ou Hg.

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The catalytic activity of some of the ABO3 (A = La, Pr and Sm, B= Cr, Mn, Fe, Co and Ni) perovskite-type oxides for the liquid phase reduction of ketone and oxidation of alcohol in 2-propanol medium has been studied. The data have been correlated with the surface electron donor properties of these oxides. The surface electron donor properties have been determined from the adsorption of electron acceptors of varying electron affinities on the oxide surface.

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Different aspects of the structure-magnetism and morphology-magnetism correlation in the ultrathin limit are studied in epitaxial Fe films grown on MgO(001). In the initial stages of growth the presence of substrate steps, intrinsically higher than an Fe atomic layer, prevent the connection between Fe islands and hence the formation of large volume magnetic regions. This is proposed as an explanation to the superparamagnetic nature of ultrathin Fe films grown on MgO in addition to the usually considered islanded, or Vollmer-Weber, growth. Using this model, we explain the observed transition from superparamagnetism to ferromagnetism for Fe coverages above 3 monolayers (ML). However, even though ferromagnetism and magnetocrystalline anisotropy are observed for 4 ML, complete coverage of the MgO substrate by the Fe ultrathin films only occurs around 6 ML as determined by polar Kerr spectra and simulations that consider different coverage situations. In annealed 3.5 ML Fe films, shape or configurational anisotropy dominates the intrinsic magnetocrystalline anisotropy, due to an annealing induced continuous to islanded morphological transition. A small interface anisotropy in thicker films is observed, probably due to dislocations observed at the Fe¿MgO(001) interface.

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Amorphous thin films of Fe/Sm, prepared by evaporation methods, have been magnetically characterized and the results were interpreted in terms of the random magnets theory. The samples behave as 2D and 3D random magnets depending on the total thickness of the film. From our data the existence of orientational order, which greatly influences the magnetic behavior of the films, is also clear.

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The ab initio periodic unrestricted Hartree-Fock method has been applied in the investigation of the ground-state structural, electronic, and magnetic properties of the rutile-type compounds MF2 (M=Mn, Fe, Co, and Ni). All electron Gaussian basis sets have been used. The systems turn out to be large band-gap antiferromagnetic insulators; the optimized geometrical parameters are in good agreement with experiment. The calculated most stable electronic state shows an antiferromagnetic order in agreement with that resulting from neutron scattering experiments. The magnetic coupling constants between nearest-neighbor magnetic ions along the [001], [111], and [100] (or [010]) directions have been calculated using several supercells. The resulting ab initio magnetic coupling constants are reasonably satisfactory when compared with available experimental data. The importance of the Jahn-Teller effect in FeF2 and CoF2 is also discussed.

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Magnetism and magnetic materials have been playing a lead role in improving the quality of life. They are increasingly being used in a wide variety of applications ranging from compasses to modern technological devices. Metallic glasses occupy an important position among magnetic materials. They assume importance both from a scientific and an application point of view since they represent an amorphous form of condensed matter with significant deviation from thermodynamic equilibrium. Metallic glasses having good soft magnetic properties are widely used in tape recorder heads, cores of high-power transformers and metallic shields. Superconducting metallic glasses are being used to produce high magnetic fields and magnetic levitation effect. Upon heat treatment, they undergo structural relaxation leading to subtle rearrangements of constituent atoms. This leads to densification of amorphous phase and subsequent nanocrystallisation. The short-range structural relaxation phenomenon gives rise to significant variations in physical, mechanical and magnetic properties. Magnetic amorphous alloys of Co-Fe exhibit excellent soft magnetic properties which make them promising candidates for applications as transformer cores, sensors, and actuators. With the advent of microminiaturization and nanotechnology, thin film forms of these alloys are sought after for soft under layers for perpendicular recording media. The thin film forms of these alloys can also be used for fabrication of magnetic micro electro mechanical systems (magnetic MEMS). In bulk, they are drawn in the form of ribbons, often by melt spinning. The main constituents of these alloys are Co, Fe, Ni, Si, Mo and B. Mo acts as the grain growth inhibitor and Si and B facilitate the amorphous nature in the alloy structure. The ferromagnetic phases such as Co-Fe and Fe-Ni in the alloy composition determine the soft magnetic properties. The grain correlation length, a measure of the grain size, often determines the soft magnetic properties of these alloys. Amorphous alloys could be restructured in to their nanocrystalline counterparts by different techniques. The structure of nanocrystalline material consists of nanosized ferromagnetic crystallites embedded in an amorphous matrix. When the amorphous phase is ferromagnetic, they facilitate exchange coupling between nanocrystallites. This exchange coupling results in the vanishing of magnetocrystalline anisotropy which improves the soft magnetic properties. From a fundamental perspective, exchange correlation length and grain size are the deciding factors that determine the magnetic properties of these nanocrystalline materials. In thin films, surfaces and interfaces predominantly decides the bulk property and hence tailoring the surface roughness and morphology of the film could result in modified magnetic properties. Surface modifications can be achieved by thermal annealing at various temperatures. Ion irradiation is an alternative tool to modify the surface/structural properties. The surface evolution of a thin film under swift heavy ion (SHI) irradiation is an outcome of different competing mechanism. It could be sputtering induced by SHI followed by surface roughening process and the material transport induced smoothening process. The impingement of ions with different fluence on the alloy is bound to produce systematic microstructural changes and this could effectively be used for tailoring magnetic parameters namely coercivity, saturation magnetization, magnetic permeability and remanence of these materials. Swift heavy ion irradiation is a novel and an ingenious tool for surface modification which eventually will lead to changes in the bulk as well as surface magnetic property. SHI has been widely used as a method for the creation of latent tracks in thin films. The bombardment of SHI modifies the surfaces or interfaces or creates defects, which induces strain in the film. These changes will have profound influence on the magnetic anisotropy and the magnetisation of the specimen. Thus inducing structural and morphological changes by thermal annealing and swift heavy ion irradiation, which in turn induce changes in the magnetic properties of these alloys, is one of the motivation of this study. Multiferroic and magneto-electrics is a class of functional materials with wide application potential and are of great interest to material scientists and engineers. Magnetoelectric materials combine both magnetic as well as ferroelectric properties in a single specimen. The dielectric properties of such materials can be controlled by the application of an external magnetic field and the magnetic properties by an electric field. Composites with magnetic and piezo/ferroelectric individual phases are found to have strong magnetoelectric (ME) response at room temperature and hence are preferred to single phasic multiferroic materials. Currently research in this class of materials is towards optimization of the ME coupling by tailoring the piezoelectric and magnetostrictive properties of the two individual components of ME composites. The magnetoelectric coupling constant (MECC) (_ ME) is the parameter that decides the extent of interdependence of magnetic and electric response of the composite structure. Extensive investigates have been carried out in bulk composites possessing on giant ME coupling. These materials are fabricated by either gluing the individual components to each other or mixing the magnetic material to a piezoelectric matrix. The most extensively investigated material combinations are Lead Zirconate Titanate (PZT) or Lead Magnesium Niobate-Lead Titanate (PMNPT) as the piezoelectric, and Terfenol-D as the magnetostrictive phase and the coupling is measured in different configurations like transverse, longitudinal and inplane longitudinal. Fabrication of a lead free multiferroic composite with a strong ME response is the need of the hour from a device application point of view. The multilayer structure is expected to be far superior to bulk composites in terms of ME coupling since the piezoelectric (PE) layer can easily be poled electrically to enhance the piezoelectricity and hence the ME effect. The giant magnetostriction reported in the Co-Fe thin films makes it an ideal candidate for the ferromagnetic component and BaTiO3 which is a well known ferroelectric material with improved piezoelectric properties as the ferroelectric component. The multilayer structure of BaTiO3- CoFe- BaTiO3 is an ideal system to understand the underlying fundamental physics behind the ME coupling mechanism. Giant magnetoelectric coupling coefficient is anticipated for these multilayer structures of BaTiO3-CoFe-BaTiO3. This makes it an ideal candidate for cantilever applications in magnetic MEMS/NEMS devices. SrTiO3 is an incipient ferroelectric material which is paraelectric up to 0K in its pure unstressed form. Recently few studies showed that ferroelectricity can be induced by application of stress or by chemical / isotopic substitution. The search for room temperature magnetoelectric coupling in SrTiO3-CoFe-SrTiO3 multilayer structures is of fundamental interest. Yet another motivation of the present work is to fabricate multilayer structures consisting of CoFe/ BaTiO3 and CoFe/ SrTiO3 for possible giant ME coupling coefficient (MECC) values. These are lead free and hence promising candidates for MEMS applications. The elucidation of mechanism for the giant MECC also will be the part of the objective of this investigation.

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a) Conocer el estado y situaci??n actual de las familias con un miembro afectado de una enfermedad mental cr??nica en el Principado de Asturias; b) Establecer una comparativa entre los distintos territorios del Principado de Asturias (Oviedo, Gij??n, Avil??s, Cuenca del Nal??n, Cuenca del Caudal, Oriente y Occidente) en base a los objetivos espec??ficos del estudio; c) Se??alar pautas para la mejora de su situaci??n y orientar sobre las diferentes l??neas o proyectos de investigaci??n a desarrollar a partir de las conclusiones de este estudio. La hip??tesis global de este estudio es que la familia sufre un cambio total ante la enfermedad mental de uno de sus integrantes. La composici??n de la muestra se hizo en base a criterios estrat??gicos y estad??sticos de tal manera que resultara representativa de las familias que tienen una persona con enfermedad mental severa o grave en el Principado de Asturias. Para ello, se cont?? con la colaboraci??n de la Asociaci??n de Familiares de Enfermos Mentales de Asturias (AFESA). La muestra final la componen 213 personas. Desarrollo de un marco te??rico donde se hace un recorrido hist??rico sobre la 'locura' en Espa??a hasta llegar a la situaci??n actual y se analiza cu??l es la situaci??n de las familias que tienen a su cargo a personas afectadas por una enfermedad mental severa o grave. Al mismo tiempo, se realiza un estudio de car??cter descriptivo cuyo proceso de investigaci??n se divide en varias etapas: la elaboraci??n y planificaci??n del estudio, la recogida y an??lisis de los datos a trav??s del correo postal y, por ??ltimo, la comunicaci??n de los resultados y conclusiones. Utilizaci??n de la encuesta postal como procedimiento de recogida de informaci??n. Elaboraci??n de un cuestionario con 58 ??tems estructurados en 11 grandes bloques: datos de identificaci??n; actividades de la vida diaria; contenci??n de comportamientos alterados; gasto econ??mico extra; cambios en la rutina diaria; repercusi??n en la salud, sentimiento y sobrecarga; satisfacci??n del servicio de Salud Mental; repercusi??n global sobre el n??cleo familiar; preocupaciones, demandas y actuaciones; ayuda recibida y satisfacci??n. El tratamiento de los datos se lleva a cabo a trav??s del programa inform??tico SPSS versi??n 12.0. Dado el car??cter descriptivo, exploratorio y explicativo del mismo, se utilizan t??cnicas descriptivas e inferenciales de car??cter tanto param??trico como no param??trico. A) La madre es la cuidadora del enfermo esquizofr??nico por antonomasia mientras que el padre es quien trabaja fuera del hogar y reporta el sustento econ??mico a la familia. B) Sin atender a su parentesco, el cuidador principal del enfermo es una mujer. C) Los hombres cuidadores son, mayoritariamente, los padres que se encuentran jubilados o viudos. D) Las mujeres cuidadoras presentan una configuraci??n distinta entre ellas, especialmente las esposas de las personas enfermas. E) Las esposas que persisten al lado de la persona esquizofr??nica o afectada de otra enfermedad mental cr??nica representan un grupo de cuidadores distintivos al del resto de las mujeres. La esposa presenta una mayor intensidad de la carga subjetiva, manifiesta carecer de vida propia y ven c??mo su proyecto de vida, su proyecto de familia se derrumba y desaparece. F) Gran parte de las personas cuya enfermedad se inicia ya dentro del matrimonio est??n separados o divorciados. G) La forma de afrontar la enfermad es diferente en la madre y en la esposa del paciente. La madre ejerce el rol de cuidador como una obligaci??n, la esposa ve truncado su futuro al lado de la persona con la que se caso. H) Las hermanas cuidadoras se encuentran en una situaci??n similar al de las esposas del enfermo, por cuanto intentan mantener una vida propia al margen del cuidado de su familiar. I) El principal cuidador debe estar pendiente con gran frecuencia de que el enfermo tome correctamente la medicaci??n. J) Hay un alto porcentaje de hombres afectados de una enfermedad mental cr??nica, fundamentalmente la esquizofrenia. K) Las necesidades asistenciales y existenciales de la familia del enfermo mental est??n directamente relacionadas con la posibilidad y demanda de mejora de la asistencia de los Servicios Sociales y de Salud Mental.