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The isothermal-isobaric Monte Carlo simulation technique was used to study the behavior of residual heat capacity of compressed supercritical methanol was studied. Further, the experimentally observed maximum of the heat capacity of some sterically hindered alcohols are elucidated.

On the basis of NpT Monte Carlo simulations, a detailed analysis on the microscopic origins of some specific features of thermodynamic response functions of fluids is performed. Specifically, the residual isobaric heat capacity Cpres, the isobaric thermal expansivity αp, and the isothermal compressibility κT for Lennard–Jones methane and optimized potential for liquid simulations (OPLS) methanol have been determined via standard techniques. For the former, data along the liquid, gas, and supercritical regions are presented, while a wide temperature range at a single supercritical pressure is covered for the latter. They have been obtained by computing the various pairwise fluctuations contributing to each property. Attention is mainly focused on isothermal and isobaric maxima found for both Cpres and αp, which have been rationalized at a molecular level using qualitative arguments. It is encountered that maxima emerge as a natural consequence of the destruction of fluid structure as temperature is increased or as pressure is decreased. The results for Lennard–Jones methane reveal the competition of energetic and volumetric effects, while those for OPLS methanol evidence that hydrogen-bonding is dominant as energetic effects are concerned. Further discussion on previous results and alternative approaches using equations of state as well as on closely related topics such as “maxima and critical phenomena” is included. [ABSTRACT FROM AUTHOR]

A study shows that the two-state association model (TSAM) is capable of describing satisfactorily the thermodynamic behavior of associated liquid systems. TSAM is found to provide an adequate rendering of the experimentally determined temperature and pressure dependence of the isobaric heat capacities of pure liquids.

A Gibbs ensemble Monte Carlo calculation of the properties of water using the four point transferable intermolecular potential with fluctuating charges model (TIP4Pfq) is presented. The model yields very good results for the thermodynamic properties, comparable with the ones obtained with fixed charges models and with the experimental data. Remarkable results for the liquid phase chemical potential at room temperature are obtained. The dielectric constant calculation is improved with respect to the model with fixed charges, and gives similar results when compared with a molecular dynamics simulation for the same water model. The intermolecular potential model used here seems to be a promising one for studying the properties of aqueous solutions, where the dielectric behavior of the solvent makes a direct and substantial contribution to the solution properties. © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: An extension of the Cubic-Two-State (CTS) equation of state was employed to evaluate the fugacities of ionic species in solution. The equation contains three terms relating to the various intermolecular interactions occurring in electrolyte solutions: a short range non-specific term represented by the Soave–Redlich–Kwong equation of state, a specific association term described by the two-state association model and a Debye–Hückel primitive model term for long range ion–ion interactions. The resulting equation, named eCTS, has six adjustable parameters: three for the non-specific part, two for the association term and one for the ionic term. Then, the eCTS EoS was used to describe both chemical and phase equilibria for systems including acid gases (H2S and CO2), alkanolamines (monoethanolamine, diethanolamine and methyldiethanolamine) and water. Measured saturation pressures, liquid densities and binary and ternary vapor–liquid equilibria data were used to estimate the model''s pure and binary parameters. Low deviations from experimental data were observed for pure, binary and ternary systems. Finally, the eCTS was employed to predict the behavior of quaternary VLE with mixtures containing CO2–H2S and alkanolamine blends. Except for the prediction of CO2 partial pressures over aqueous alkanolamine blends, the eCTS gave good predictions of experimental quaternary data over a broad range of temperatures and alkanolamine concentrations. [Copyright &y& Elsevier]

Previous studies have shown that inflammatory and metabolic biomarkers may be associated with demyelinating diseases of the central nervous system. The aim of this study was to evaluate inflammatory and metabolic biomarkers in patients with neuromyelitis optica (NMO), and multiple sclerosis (MS). Demographic and clinical data were obtained from 16 NMO and 41 MS patients, and 50 healthy controls. The disability of the NMO and MS patients was evaluated using the Expanded Disability Status Scale (EDSS). Peripheral blood samples were collected to measure C-reactive protein (CRP), total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL), triglycerides (TG), glucose, and insulin. The homeostasis model assessment for insulin resistance (HOMA-IR) was calculated. All NMO patients were female and, therefore, the MS patients and controls were gender-matched. Characteristics such as age, ethnicity, body mass index, and smoking history were also controlled (p≥0.05). No difference was found in CRP levels between the groups (p≥0.05). MS patients presented higher total cholesterol levels compared with controls (p=0.0021). NMO and MS patients presented higher triglycerides levels (p=0.0044), insulin (p= 0.0070), and HOMA-IR (p= 0.0055) compared with controls. NMO patients presented higher EDSS than MS patients (p=0.0052). High insulin levels (p= 0.0206) and HOMA-IR (p= 0.0607) were independently associated with NMO, while none of the variables were independently associated with MS. Among the NMO patients, a negative correlation was observed between EDSS and glucose levels (r=-0.6349, p= 0.0147) and a positive correlation was observed between EDSS and insulin levels (r= 0.5858, p= 0.0354). The results suggest that metabolic biomarkers may be associated with NMO, with insulin and HOMA-IR independently associated with the disease. Moreover, low levels of glucose and hyperinsulinemia were associated with disability of NMO patients. [ABSTRACT FROM AUTHOR]

Neuromyelitis optica (NMO) is a severe demyelinating disease of the central nervous system that has a worldwide distribution. The aim of this study was to report demographic and clinical features of patients with NMO from Southern Brazil. Demographic and clinical data were obtained from 16 patients with NMO using a standard questionnaire and from medical records. All patients were female: 5 (31.3%) Caucasian; 9 (14.4%) Mullato (mixed race); and 2 (12.5%) Black. The median age was 44.5 years, the median age at disease onset was 36 years, and the median disease duration was 7 years. Fifteen (93.8%) patients presented a relapsing course and 1 (6.2%) a monophasic course. The initial event was myelitis in 6 (37.5%) women, bilateral optic neuritis in 3 (18.8%) and unilateral optic neuritis in 4 (25.0%) women, simultaneous myelitis and bilateral optic neuritis in 1 (6.2%), and simultaneous myelitis and unilateral optic neuritis in 2 (12.5%) women. The second event was myelitis in 7 (43.8%), bilateral optic neuritis in 1 (6.2%), and unilateral neuritis in 4 (25.0%) patients, with 4 (25.0%) not presenting this data. According to magnetic resonance imaging data of the first myelitis, 4 (25.0%) presented cervical lesions, 5 (31.4%) presented thoracic lesions, 4 (25.0%) presented cervical and thoracic lesions, 2 (12.4%) presented cervical lesions extending into the medulla oblongata, and 1 (6.2%) presented lesions in all spinal segments. Four (25.0%) of the women presented associated autoimmune diseases (juvenile rheumatoid arthritis, hypothyroidism, systemic lupus erythematosus and scleroderma), 1 (6.2%) presented arterial hypertension, 1 (6.2%) presented depression, and 10 (62.6%) had no associated disease. Five (31.3%) patients presented positive NMO-IgG, 6 (37.4%) negative NMO-IgG, and 5 (31.3%) were not evaluated for this marker. Demographic and clinical characteristics of NMO patients from Southern Brazil are in agreement with previous studies worldwide reported in the scientific literature. [ABSTRACT FROM AUTHOR]