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1.
Neurologia (Engl Ed) ; 36(7): 525-530, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34537166

RESUMO

INTRODUCTION: According to most studies, the incidence of Guillain-Barré syndrome increases with age, with a peak incidence occurring between 70 and 80 years of age. The objective of this study is to describe the incidence (overall and by sex and age group) and clinical characteristics of Guillain-Barré syndrome in Osona (Barcelona, Spain). METHODS: We performed a retrospective, descriptive, population-based study covering the period 2003 to 2016. RESULTS: The global incidence of Guillain-Barré syndrome is 2.07 cases per 100000 person-years. Incidence increases with age, except for small peaks during childhood and between 40 and 50 years, and reaches a maximum of 6.26 cases per 100000 person-years above the age of 80. The incidences of the different variants were: AIDP, 72.1%; AMAN, 16.3%; ANSAN, 4.7%; and Miller Fisher syndrome, 4.7%. A total of 41.9% of patients had a history of respiratory tract infections, and 20.9% had a history of gastrointestinal infections. Protein in the cerebrospinal fluid was found in 76.7%. EMG findings suggested demyelination in 73.7% of the patients and axonal degeneration in 26.3%. A total of 20.9% of patients needed ventilatory support. Six-month mortality was 9.3%. Variables associated with worse prognosis were age over 80 years, delay in admission, previous gastrointestinal infection, and AMAN variant. CONCLUSIONS: The incidence observed in our study is in the upper range of estimated incidence rates reported in European and North American studies. The syndrome may be underdiagnosed in elderly patients; physicians must be vigilant to the possibility of the disease, which is associated with a high mortality rate if it is not treated early.


Assuntos
Síndrome de Guillain-Barré , Síndrome de Miller Fisher , Adulto , Idoso , Idoso de 80 Anos ou mais , Síndrome de Guillain-Barré/epidemiologia , Humanos , Incidência , Pessoa de Meia-Idade , Estudos Retrospectivos , Espanha/epidemiologia
2.
Neurología (Barc., Ed. impr.) ; 36(7): 525-530, septiembre 2021. tab, graf
Artigo em Espanhol | IBECS | ID: ibc-220088

RESUMO

Introducción: La mayoría de los estudios muestran que la incidencia del síndrome de Guillain-Barré aumenta con la edad, con un máximo entre los 70 y los 80 años y un descenso posterior. El objetivo del estudio es describir la incidencia global y específica por sexo y grupos de edad y las características clínicas del síndrome de Guillain-Barré en la comarca de Osona (Barcelona, España).MétodosEstudio descriptivo retrospectivo de base poblacional en el periodo 2003-2016.ResultadosLa incidencia global es de 2,07/100.000 habitantes-año. La incidencia aumenta con la edad, salvo un pequeño pico en la infancia y entre los 40 y los 50 años, alcanzando la máxima de 6,26/100.000 habitantes-año pasados los 80 años. Los porcentajes de las variantes fueron: AIDP (72,1%), AMAN (16,3%), ANSAN (4,7%) y síndrome de Miller-Fisher (4,7%). Presentaron infección previa de vías respiratorias el 41,9% e infección gastrointestinal el 20,9%. Se halló proteinorraquia en el 76,7%. El EMG mostraba un predominio desmielinizante en el 73,7% y axonal en el 26,3%. Necesitaron soporte ventilatorio el 20,9%. La mortalidad a los 6 meses fue del 9,3%. Las variables que se asociaron a un peor pronóstico fueron la edad superior a los 80 años, la demora en el ingreso, presentar infección gastrointestinal previa y la variante AMAN.ConclusionesLa incidencia descrita en nuestro estudio se encuentra en el rango más alto de las estimadas en Europa y Estados Unidos. En ancianos pudiera estar infradiagnosticado y se requeriría de una mayor alerta ante una enfermedad con alta mortalidad si no se trata de forma precoz. (AU)


Introduction: According to most studies, the incidence of Guillain-Barré syndrome increases with age, with a peak incidence occurring between 70 and 80 years of age. The objective of this study is to describe the incidence (overall and by sex and age group) and clinical characteristics of Guillain-Barré syndrome in Osona (Barcelona, Spain).MethodsWe performed a retrospective, descriptive, population-based study covering the period 2003 to 2016.ResultsThe global incidence of Guillain-Barré syndrome is 2.07 cases per 100,000 person-years. Incidence increases with age, except for small peaks during childhood and between 40 and 50 years, and reaches a maximum of 6.26 cases per 100,000 person-years above the age of 80. The incidences of the different variants were: AIDP, 72.1%; AMAN, 16.3%; ANSAN, 4.7%; and Miller Fisher syndrome, 4.7%. A total of 41.9% of patients had a history of respiratory tract infections, and 20.9% had a history of gastrointestinal infections. Protein in the cerebrospinal fluid was found in 76.7%. EMG findings suggested demyelination in 73.7% of the patients and axonal degeneration in 26.3%. A total of 20.9% of patients needed ventilatory support. Six-month mortality was 9.3%. Variables associated with worse prognosis were age over 80 years, delay in admission, previous gastrointestinal infection, and AMAN variant.ConclusionsThe incidence observed in our study is in the upper range of estimated incidence rates reported in European and North American studies. The syndrome may be underdiagnosed in elderly patients; physicians must be vigilant to the possibility of the disease, which is associated with a high mortality rate if it is not treated early. (AU)


Assuntos
Humanos , Síndrome de Guillain-Barré/epidemiologia , Incidência , Síndrome de Miller Fisher , Espanha/epidemiologia , Estudos Retrospectivos
3.
Arch Prev Riesgos Labor ; 21(3): 128-157, 2018.
Artigo em Espanhol | MEDLINE | ID: mdl-30024116

RESUMO

The presence of formaldehyde at workplace remains significant. Exposure to it results in local irritation of the eye, nose and upper respiratory tract mucous membranes, and it has been chronically related to a higher risk of cancer development at the paranasal sinuses, naso-oropharynx and lungs. The aim of our work has been the updating of the bibliography and the categorization of the most up to date scientific evidence of formaldehyde effects on human body. Bibliographic search on the electronic database Medline / PubMed, restricted to the last 10 years through a combination of free and controlled language.Review of 185 scientific articles, finally including 54 due to duplicity, language, and inclusion criteria. We find among the main results a major evidence regarding genotoxicity; limited, inconsistent, and contradictory evidence regarding various neoplastic pathologies; and lack of evidence regarding bronchial asthma. Further studies have to be carried out, especially longitudinal studies and greater epidemiological power, to generate new knowledge about the behavior of this toxic.


La presencia del formaldehido en el ámbito laboral sigue siendo importante. La exposición produce irritación local de mucosas oculares, nasales y del tracto respiratorio superior, y crónicamente se ha asociado con mayor riesgo de desarrollar cáncer a nivel de senos paranasales, naso-orofaringe y pulmón. Esta revisión tiene por objetivo actualizar la bibliografía y categorizar la evidencia científica más actualizada de los efectos que el formaldehido produce sobre el organismo humano. Búsqueda bibliográfica en la base de datos electrónica Medline/PubMed, limitada a los últimos 10 años mediante combinación de lenguaje libre y controlado. Se revisaron 185 artículos con inclusión final de 54 tras descartar por duplicidad, idioma y criterios de inclusión. Se observa un elevado grado de evidencia respecto a la genotoxicidad, evidencia contradictoria, inconsistente o limitada respecto a patologías neoplásicas de origen hematopoyético, laringe, naso-sinusales o de pulmón y falta de evidencia sobre la relación con el asma bronquial. Es preciso efectuar nuevos estudios, especialmente con carácter longitudinal y mayor potencia epidemiológica, para generar nuevo conocimiento sobre el comportamiento de este tóxico.

4.
J Chem Phys ; 147(5): 054905, 2017 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-28789532

RESUMO

Stacking of disk-shaped organic molecules is a promising strategy to develop electronic and photovoltaic devices. Here, we investigate the capability of a soft block copolymer matrix that microphase separates into a cylindrical phase to direct the self-assembly of disk-shaped molecules by means of molecular simulations. We show that two disk molecules confined in the cylinder domain experience a depletion force, induced by the polymer chains, which results in the formation of stacks of disks. This entropic interaction and the soft confinement provided by the matrix are both responsible for the structures that can be self-assembled, which include slanted or columnar stacks. In addition, we evidence the transmission of stresses between the different minority domains of the microphase, which results in the establishment of a long-ranged interaction between disk molecules embedded in different domains; this interaction is of the order of the microphase periodicity and may be exploited to direct assembly of disks at larger scales.

5.
Neurologia ; 32(1): 1-5, 2017.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-25449965

RESUMO

INTRODUCTION: The reported prevalence of myasthenia gravis ranges between 5 and 24 cases per 100,000, and people over 65years account for less than 50% of all cases. The prevalence and clinical characteristics of myasthenia gravis in the county of Osona were studied in patients younger and older than 65. METHODS: The study draws from the county-based prospective myasthenia gravis register implemented by the Neurology Department at Hospital General de Vic in 1991. RESULTS: The prevalence of myasthenia gravis was 32.89×105 inhabitants (95%CI, 23.86-41.91). The standardized prevalence (European population) was 35.47×105 inhabitants (95%CI, 26.10-44.84). The ratio of women to men was 1.3. Overall, the group of patients older than 65 accounted for 62.75% of all cases. The prevalence of myasthenia gravis increased considerably in older age groups. No cases were registered among patients under 25years old, prevalence was 21.87×105 in the 25 to 64 age group, and prevalence in patients over 65 years increased to 122.35×105. The clinical characteristics prior to treatment and at the cut-off date are similar (P>.05) in patients younger than 65 and those aged 65 and older. CONCLUSIONS: These figures show the highest prevalence rate reported to date. This high prevalence is due to the rate observed among patients older than 65. These results provide a new warning that myasthenia gravis may be underdiagnosed in the elderly population.


Assuntos
Miastenia Gravis/epidemiologia , Adulto , Distribuição por Idade , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Prevalência , Estudos Prospectivos , Sistema de Registros , Distribuição por Sexo , Espanha/epidemiologia
6.
Semergen ; 43(5): 352-357, 2017.
Artigo em Espanhol | MEDLINE | ID: mdl-27449475

RESUMO

INTRODUCTION: Physical inactivity is the fourth leading risk factor for global mortality, and a significant percentage of the world population does not perform the necessary physical activity for health benefits. Certain professional groups are seen as an example for the general population with whom they interact. Prevalence of physical activity in health workers, one of these reference groups, is mainly unknown. The aim of this study has been to assess the prevalence of physical activity levels in Primary Health Care professionals. MATERIAL AND METHODS: A study was conducted on the physical activity levels in Primary Health Care workers who came voluntarily for a medical examination in 2014, and completed the short version of the International Physical Activity Questionnaire activity. RESULTS: A low level of physical activity was reported by 26.5% of those taking part, with 31.5% of the medical group indicating a low level of activity, followed by support staff (28.1%), nurses (24.7%), and finally the administrative staff (19.0%). CONCLUSIONS: The physical activity levels of Primary Health Care staff are significantly different from those of the general reference population. The latter has a higher percentage of physical activity of mild to moderate intensity, and below the level of physical activity of high intensity. Although there seems to be a tendency to significantly lower physical activity in other health groups, we do not have sufficiently reliable data to compare them.


Assuntos
Exercício Físico , Pessoal de Saúde/estatística & dados numéricos , Atenção Primária à Saúde , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Prevalência , Espanha , Inquéritos e Questionários , Adulto Jovem
7.
Rev. esp. pediatr. (Ed. impr.) ; 72(6): 338-345, nov.-dic. 2016. tab, ilus
Artigo em Espanhol | IBECS | ID: ibc-160649

RESUMO

La Unidad de Oncología y Hematología Infantil del Hospital Gregorio Marañón comenzó su andadura en los años 70, presentando desde entonces un crecimiento progresivo y una modernización acorde con la evolución de la propia especialidad. En esta monografía se describe la organización de la sección, así como los recursos estructurales, las características del trabajo asistencial, la actividad docente e investigadora y la participación en diversos grupos de trabajo colaborativos o multidisciplinares. Se destaca la capacidad de abordaje integral de este tipo de patologías en todas las fases de las mismas, desde el diagnóstico al tratamiento, sin Olvidar el aspecto psicosocial o la atención paliativa en su fase terminal, si fuera necesario. En conjunto, se dibuja un cuadro que es una obra coral de muchos profesionales sanitarios (personal médico, psicooncología, enfermería, auxiliares...) y no sanitarios, pero cuyo tema principal es proporcionar la mejor asistencia posible al niño y a su familia (AU)


The Pediatric Oncology and Hematology Unit at the Gregorio Marañón Children's Hospital began its activity in the 705, presenting since then a progressive growth and modernization in accordance with the evolution of the specialty itself… In this paper we describe the organization of the section, our structural resources, the characteristics of care work, teaching and research activities and our participation in various collaborative or multidisciplinary work groups. It is remarkable the ability to comprehensively address this type of pathologies in its different phases, from diagnosis to treatment, without forgetting to mention the psychosocial aspect or palliative care in its terminal phase, if necessary. Altogether, a choral picture is drawn with the work of many health professionals (medical, psycho-oncology, nursing, assistants …) and non—health, but the main theme is to provide the best care for the child and his family (AU)


Assuntos
Humanos , Masculino , Feminino , Criança , Cuidado da Criança/métodos , Cuidado da Criança/organização & administração , Saúde da Criança/normas , Saúde da Criança/tendências , Oncologia/classificação , Oncologia/normas , Serviço Hospitalar de Oncologia/organização & administração , Hematologia/métodos , Hematologia/tendências , Neoplasias/epidemiologia , Neoplasias/prevenção & controle , Cuidados Paliativos/métodos
8.
J Chem Phys ; 144(12): 124504, 2016 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-27036458

RESUMO

The solubility of NaCl in water is evaluated by using three force field models: Joung-Cheatham for NaCl dissolved in two different water models (SPC/E and TIP4P/2005) and Smith Dang NaCl model in SPC/E water. The methodology based on free-energy calculations [E. Sanz and C. Vega, J. Chem. Phys. 126, 014507 (2007)] and [J. L. Aragones et al., J. Chem. Phys. 136, 244508 (2012)] has been used, except, that all calculations for the NaCl in solution were obtained by using molecular dynamics simulations with the GROMACS package instead of homemade MC programs. We have explored new lower molalities and made longer runs to improve the accuracy of the calculations. Exploring the low molality region allowed us to obtain an analytical expression for the chemical potential of the ions in solution as a function of molality valid for a wider range of molalities, including the infinite dilute case. These new results are in better agreement with recent estimations of the solubility obtained with other methodologies. Besides, two empirical simple rules have been obtained to have a rough estimate of the solubility of a certain model, by analyzing the ionic pairs formation as a function of molality and/or by calculating the difference between the NaCl solid chemical potential and the standard chemical potential of the salt in solution.

9.
Nat Commun ; 7: 11325, 2016 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-27112961

RESUMO

The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between the active stresses and elasticity of the system. This discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium.

11.
Occup Med (Lond) ; 66(3): 202-7, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26590956

RESUMO

BACKGROUND: The effects of long-term occupational exposure to small concentrations of volatile anaesthetics on health professionals are still uncertain despite the research literature available on this subject. AIMS: To analyse the existing literature on the health effects of volatile anaesthetics on exposed health professionals. METHODS: We performed a systematic review from March 2013 to January 2014. The literature was searched in the Medline and Cochrane libraries using the following keywords: 'Anaesthetics AND occupational health', 'Volatile anaesthetics AND occupational health', 'Sevoflurane AND occupational health' and 'Occupational surveillance AND anaesthetics', with no time limit. We used the Scottish Intercollegiate Guidelines Network to evaluate the quality of studies and to grade the recommendations. RESULTS: From 1429 articles retrieved from the databases and an additional 20 obtained from secondary sources, we excluded 1391 (95.9%). After excluding duplicate publications, we finally included 17 articles in the review. CONCLUSIONS: Evidence for adverse effects of volatile anaesthetics on exposed personnel is scarce and inconsistent, but there is no evidence of adverse effects when environmental levels are kept within legal threshold values. Further studies are needed to improve our knowledge of the effects of occupational exposure to volatile anaesthetics. New surveillance methods that include systematic data collection, clinical signs and biomarkers of exposure are required to formulate consistent and reproducible surveillance criteria for exposed personnel.


Assuntos
Anestésicos Inalatórios/efeitos adversos , Ambiente Controlado , Doenças do Sistema Nervoso/induzido quimicamente , Doenças Profissionais/induzido quimicamente , Exposição Ocupacional/efeitos adversos , Salas Cirúrgicas , Feminino , Pessoal de Saúde , Humanos , Masculino , Doenças do Sistema Nervoso/fisiopatologia , Doenças do Sistema Nervoso/prevenção & controle , Doenças Profissionais/fisiopatologia , Doenças Profissionais/prevenção & controle , Exposição Ocupacional/prevenção & controle , Saúde Ocupacional , Guias de Prática Clínica como Assunto , Medição de Risco
12.
Oncogene ; 35(5): 587-94, 2016 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-25915846

RESUMO

Inactivation of the von Hippel-Lindau (VHL) tumor suppressor drives the development of clear-cell renal cell carcinoma (ccRCC) through hypoxia-inducible factors (HIFs). Although ccRCC cells exhibit constitutive normoxic HIF signaling, the potential role of hypoxia in this setting is not fully understood. We show here that the ccRCC cell lines RCC4 and RCC10, which express mutant versions of VHL, have reduced HIF1α expression in hypoxia, whereas HIF2α expression is increased or not affected. Similar findings were observed in normoxia after abrogation of prolyl hydroxylase activity by siRNA or pharmacological inhibition, and by siRNA inhibition of mutant VHL. This reduction of HIF1α protein is due to proteasome-dependent degradation and is mediated by the E3 ubiquitin ligase SART1. HIF1α degradation favors ccRCC proliferation, in line with the previously recognized tumor suppressor capability of HIF1α. Our data indicate that mutant VHL can protect HIF1α from SART1-dependent degradation in normoxic conditions, but this protection is lost in hypoxic settings, favoring hypoxia-dependent ccRCC proliferation. This mechanism of HIF1α degradation might operate in some VHL-related clear-cell renal carcinomas in which the deletion of HIF1α locus does not occur.


Assuntos
Antígenos de Neoplasias/metabolismo , Carcinoma de Células Renais/genética , Carcinoma de Células Renais/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Neoplasias Renais/genética , Neoplasias Renais/metabolismo , Ribonucleoproteínas Nucleares Pequenas/metabolismo , Proteína Supressora de Tumor Von Hippel-Lindau/genética , Antígenos de Neoplasias/genética , Carcinoma de Células Renais/patologia , Hipóxia Celular/genética , Hipóxia Celular/fisiologia , Linhagem Celular Tumoral , Proliferação de Células/genética , Proliferação de Células/fisiologia , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Neoplasias Renais/patologia , Ribonucleoproteínas Nucleares Pequenas/genética , Proteína Supressora de Tumor Von Hippel-Lindau/metabolismo
13.
Oncogene ; 34(20): 2609-20, 2015 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-25023702

RESUMO

The presence of hypoxic regions in solid tumors is an adverse prognostic factor for patient outcome. Here, we show that hypoxia induces the expression of Ephrin-A3 through a novel hypoxia-inducible factor (HIF)-mediated mechanism. In response to hypoxia, the coding EFNA3 mRNA levels remained relatively stable, but HIFs drove the expression of previously unknown long noncoding (lnc) RNAs from EFNA3 locus and these lncRNA caused Ephrin-A3 protein accumulation. Ephrins are cell surface proteins that regulate diverse biological processes by modulating cellular adhesion and repulsion. Mounting evidence implicates deregulated ephrin function in multiple aspects of tumor biology. We demonstrate that sustained expression of both Ephrin-A3 and novel EFNA3 lncRNAs increased the metastatic potential of human breast cancer cells, possibly by increasing the ability of tumor cells to extravasate from the blood vessels into surrounding tissue. In agreement, we found a strong correlation between high EFNA3 expression and shorter metastasis-free survival in breast cancer patients. Taken together, our results suggest that hypoxia could contribute to metastatic spread of breast cancer via HIF-mediated induction of EFNA3 lncRNAs and subsequent Ephrin-A3 protein accumulation.


Assuntos
Neoplasias da Mama/metabolismo , Loci Gênicos , Fator 1 Induzível por Hipóxia/metabolismo , Proteínas de Neoplasias/metabolismo , RNA Longo não Codificante/biossíntese , RNA Neoplásico/biossíntese , Animais , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Hipóxia Celular/genética , Linhagem Celular Tumoral , Efrina-A3/genética , Efrina-A3/metabolismo , Feminino , Células Endoteliais da Veia Umbilical Humana , Humanos , Fator 1 Induzível por Hipóxia/genética , Camundongos , Camundongos Nus , Metástase Neoplásica , Proteínas de Neoplasias/genética , RNA Longo não Codificante/genética , RNA Neoplásico/genética , Peixe-Zebra
15.
J Chem Phys ; 139(3): 034104, 2013 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-23883007

RESUMO

In this work, we describe a procedure to evaluate the free energy of molecular solids with the GROMACS molecular dynamics package. The free energy is calculated using the Einstein molecule method that can be regarded as a small modification of the Einstein crystal method. Here, the position and orientation of the molecules is fixed by using an Einstein field that binds with harmonic springs at least three non-collinear atoms (or points of the molecule) to their reference positions. The validity of the Einstein field is tested by performing free-energy calculations of methanol, water (ice), and patchy colloids molecular solids. The free energies calculated with GROMACS show a very good agreement with those obtained using Monte Carlo and with previously published results.

17.
J Chem Phys ; 137(10): 104507, 2012 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-22979874

RESUMO

In this paper, we study the liquid-solid coexistence of NaCl-type alkali halides, described by interaction potentials such as Tosi-Fumi (TF), Smith-Dang (SD), and Joung-Cheatham (JC), and compute their melting temperature (T(m)) at 1 bar via three independent routes: (1) liquid/solid direct coexistence, (2) free-energy calculations, and (3) Hamiltonian Gibbs-Duhem integration. The melting points obtained by the three routes are consistent with each other. The calculated T(m) of the Tosi-Fumi model of NaCl is in good agreement with the experimental value as well as with other numerical calculations. However, the other two models considered for NaCl, SD and JC, overestimate the melting temperature of NaCl by more than 200 K. We have also computed the melting temperature of other alkali halides using the Tosi-Fumi interaction potential and observed that the predictions are not always as close to the experimental values as they are for NaCl. It seems that there is still room for improvement in the area of force-fields for alkaline halides, given that so far most models are still unable to describe a simple yet important property such as the melting point.

18.
J Chem Phys ; 136(24): 244508, 2012 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-22755588

RESUMO

In this paper, the solubility of NaCl in water is evaluated by using computer simulations for three different force fields. The condition of chemical equilibrium (i.e., equal chemical potential of the salt in the solid and in the solution) is obtained at room temperature and pressure to determine the solubility of the salt. We used the same methodology that was described in our previous work [E. Sanz and C. Vega, J. Chem. Phys. 126, 014507 (2007)] although several modifications were introduced to improve the accuracy of the calculations. It is found that the predictions of the solubility are quite sensitive to the details of the force field used. Certain force fields underestimate the experimental solubility of NaCl in water by a factor of four, whereas the predictions of other force fields are within 20% of the experimental value. Direct coexistence molecular dynamic simulations were also performed to determine the solubility of the salt. Reasonable agreement was found between the solubility obtained from free energy calculations and that obtained from direct coexistence simulations. This work shows that the evaluation of the solubility of salts in water can now be performed in computer simulations. The solubility depends on the ion-ion, ion-water, and water-water interactions. For this reason, the prediction of the solubility can be quite useful in future work to develop force fields for ions in water.

19.
Phys Rev Lett ; 107(15): 155702, 2011 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-22107302

RESUMO

Simulations are used to investigate for the first time the anisotropy of the dielectric response and the effects of an applied electric field E(ex) on the phase diagram of water. In the presence of electric fields ice II disappears from the phase diagram. When E(ex) is applied in the direction perpendicular to the ac crystallographic plane the melting temperatures of ices III and V increase whereas that of ice Ih is hardly affected. Ice III also disappears as a stable phase when E(ex) is applied in the direction perpendicular to the ab plane. E(ex) increases by a small amount the critical temperature and reduces slightly the temperature of the maximum density of liquid water. The presence E(ex) modifies all phase transitions of water but its effect on solid-solid and solid-fluid transitions seems to be more important and different depending on the direction of E(ex).

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