Pore size distributions derived from adsorption isotherms, immersion calorimetry, and isosteric heats: A comparative study

We compare the pore size distribution of a well-characterized activated carbon derived from model-dependent, adsorption integral equation (AIE) methods with those from model-independent, immersion calorimetry and isosteric heat analyses. The AIE approach applied to nitrogen gave a mean pore width of 0.57 nm; the CO2 distribution exhibited wider dispersion. Spherical model application to CO2 and diffusion limitations for nitrogen and argon were proposed as primary reasons for inconsistency. Immersion enthalpy revealed a sharp decrease in available area equivalent to a cut-off due to molecular exclusion when the accessible surface was assessed against probe kinetic diameter. Mean pore width was identified as 0.58 ± 0.02 nm, endorsing the underlying assumptions for the nitrogen-based AIE approach. A comparison of the zero-coverage isosteric heat of adsorption for various non-polar adsorptives by the porous test sample was compared with the same adsorptives in contact with a non-porous reference adsorbent, leading to an energy ratio or adsorption enhancement factor. A linear relationship between the energy ratio and probe kinetic diameter indicated a primary pore size at 0.59 nm. The advantage of this enthalpy, model-independent methods over AIE were due to no assumptions regarding probe molecular shape, and no assumptions for pore shape and/or connectivity.

High-sensitivity differential scanning calorimetry for measurement of steroid entrapment in nebulised liposomes generated from proliposomes

A novel approach to the determination of steroid entrapment in the bilayers of aerosolised liposomes has been introduced using high-sensitivity differential scanning calorimetry (DSC). Proliposomes were dispersed in water within an air-jet nebuliser and the energy produced during atomisation was used to hydrate the proliposomes and generate liposome aerosols. Proliposomes that included the steroid beclometasone dipropionate (BDP) produced lower aerosol and lipid outputs than steroid-free proliposomes. Size analysis and transmission electron microscopy showed an evidence of liposome formation within the nebuliser, which was followed by deaggregation and size reduction of multilamellar liposomes on nebulisation to a two-stage impinger. For each formulation, no difference in thermal transitions was observed between delivered liposomes and those remaining in the nebuliser. However, steroid (5 mole%) lowered the onset temperature and the enthalpy of the pretransition, and produced a similar onset temperature and larger enthalpy of the main transition, with broadened pretransition and main transitions. This indicates that BDP was entrapped and exhibited an interaction with the liposome phospholipid membranes. Since the pretransition was depressed but not completely removed and no phase separation occurred, it is suggested that the bilayers of the multilamellar liposomes can entrap more than 5 mole% BDP. Overall, liposomes were generated from proliposomes and DSC investigations indicated that the steroid was entrapped in the bilayers of aerosolised multilamellar vesicles.

Assessment of resting energy expenditure in pediatric mitochondrial diseases with indirect calorimetry

Mitochondrial diseases (MD) are the most frequent inborn errors of metabolism. In affected tissues, MD can alter cellular oxygen consumption rate leading to potential decreases in whole-body resting energy expenditure (REE), but data on pediatric children are absent. We determined, using indirect calorimetry (IC), whole-body oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ) and REE in pediatric patients with MD and healthy controls. Another goal was to assess the accuracy of available predictive equations for REE estimation in this patient population. IC data were obtained under fasting and resting conditions in 20 MD patients and 27 age and gender-matched healthy peers. We determined the agreement between REE measured with IC and REE estimated with Schofield weight and FAO/WHO/UNU equations. Mean values of VO2, VCO2 (mL·min-1·kg-1) or RQ did not differ significantly between patients and controls (P = 0.085, P = 0.055 and P = 0.626 respectively). Accordingly, no significant differences (P = 0.086) were found for REE (kcal·day-1 kg-1) either. On the other hand, although we found no significant differences between IC-measured REE and Schofield or FAO/WHO/UNU-estimated REE, Bland-Altman analysis revealed wide limits of agreement and there were some important individual differences between IC and equation-derived REE. VO2, VCO2, RQ and REE are not significantly altered in pediatric patients with MD compared with healthy controls. The energy demands of pediatric patients with MD should be determined based on IC data in order to provide the best possible personalized nutritional management for these children.

Initiating sacubitril/valsartan (LCZ696) in heart failure: results of TITRATION, a double-blind, randomized comparison of two uptitration regimens

The aim is tassess the tolerability of initiating/uptitrating sacubitril/valsartan (LCZ696) from 50 to 200 mg twice daily (target dose) over 3 and 6 weeks in heart failure (HF) patients (ejection fraction ≤35%). A 5-day open-label run-in (sacubitril/valsartan 50 mg twice daily) preceded an 11-week, double-blind, randomization period [100 mg twice daily for 2 weeks followed by 200 mg twice daily (‘condensed’ regimen) vs. 50 mg twice daily for 2 weeks, 100 mg twice daily for 3 weeks, followed by 200 mg twice daily (‘conservative’ regimen)]. Patients were stratified by pre-study dose of angiotensin-converting enzyme inhibitor/angiotensin-receptor blocker (ACEI/ARB; low-dose stratum included ACEI/ARB-naïve patients). Of 540 patients entering run-in, 498 (92%) were randomized and 429 (86.1% of randomized) completed the study. Pre-defined tolerability criteria were hypotension, renal dysfunction and hyperkalaemia; and adjudicated angioedema, which occurred in (‘condensed’ vs. ‘conservative’) 9.7% vs. 8.4% (P = 0.570), 7.3% vs. 7.6% (P = 0.990), 7.7% vs. 4.4% (P = 0.114), and 0.0% vs. 0.8% of patients, respectively. Corresponding proportions for pre-defined systolic blood pressure <95 mmHg, serum potassium >5.5 mmol/L, and serum creatinine >3.0 mg/dL were 8.9% vs. 5.2% (P = 0.102), 7.3% vs. 4.0% (P = 0.097), and 0.4% vs. 0%, respectively. In total, 378 (76%) patients achieved and maintained sacubitril/valsartan 200 mg twice daily without dose interruption/down-titration over 12 weeks (77.8% vs. 84.3% for ‘condensed’ vs. ‘conservative’; P = 0.078). Rates by ACEI/ARB pre-study dose stratification were 82.6% vs. 83.8% (P = 0.783) for high-dose/‘condensed’ vs. high-dose/‘conservative’ and 84.9% vs. 73.6% (P = 0.030) for low-dose/‘conservative’ vs. low-dose/‘condensed’. Initiation/uptitration of sacubitril/valsartan from 50 to 200 mg twice daily over 3 or 6 weeks had a tolerability profile in line with other HF treatments. More gradual initiation/uptitration maximized attainment of target dose in the low-dose ACEI/ARB group.

Solid Lipid Nanoparticles For Hydrophilic Biotech Drugs: Optimization And Cell Viability Studies (caco-2 & Hepg-2 Cell Lines).

Insulin was used as model protein to developed innovative Solid Lipid Nanoparticles (SLNs) for the delivery of hydrophilic biotech drugs, with potential use in medicinal chemistry. SLNs were prepared by double emulsion with the purpose of promoting stability and enhancing the protein bioavailability. Softisan(®)100 was selected as solid lipid matrix. The surfactants (Tween(®)80, Span(®)80 and Lipoid(®)S75) and insulin were chosen applying a 2(2) factorial design with triplicate of central point, evaluating the influence of dependents variables as polydispersity index (PI), mean particle size (z-AVE), zeta potential (ZP) and encapsulation efficiency (EE) by factorial design using the ANOVA test. Therefore, thermodynamic stability, polymorphism and matrix crystallinity were checked by Differential Scanning Calorimetry (DSC) and Wide Angle X-ray Diffraction (WAXD), whereas the effect of toxicity of SLNs was check in HepG2 and Caco-2 cells. Results showed a mean particle size (z-AVE) width between 294.6 nm and 627.0 nm, a PI in the range of 0.425-0.750, ZP about -3 mV, and the EE between 38.39% and 81.20%. After tempering the bulk lipid (mimicking the end process of production), the lipid showed amorphous characteristics, with a melting point of ca. 30 °C. The toxicity of SLNs was evaluated in two distinct cell lines (HEPG-2 and Caco-2), showing to be dependent on the concentration of particles in HEPG-2 cells, while no toxicity in was reported in Caco-2 cells. SLNs were stable for 24 h in in vitro human serum albumin (HSA) solution. The resulting SLNs fabricated by double emulsion may provide a promising approach for administration of protein therapeutics and antigens.

Nitric Oxide-releasing Poly(vinyl Alcohol) Film For Increasing Dermal Vasodilation.

Pathological conditions associated with the impairment of nitric oxide (NO) production in the vasculature, such as Raynaud's syndrome and diabetic angiopathy, have stimulated the development of new biomaterials capable of delivering NO topically. With this purpose, we modified poly(vinyl-alcohol) (PVA) by chemically crosslinking it via esterification with mercaptosuccinic acid. This reaction allowed the casting of sulfhydrylated PVA (PVA-SH) films. Differential scanning calorimetry and X-ray diffractometry showed that the crosslinking reaction completely suppressed the crystallization of PVA, leading to a non-porous film with a homogeneous distribution of -SH groups. The remaining free hydroxyl groups in the PVA-SH network conferred partial hydrophylicity to the material, which was responsible for a swelling degree of ca. 110%. The PVA-SH films were subjected to an S-nitrosation reaction of the -SH groups, yielding a PVA containing S-nitrosothiol groups (PVA-SNO). Amperometric and chemiluminescence measurements showed that the PVA-SNO films were capable of releasing NO spontaneously after immersion in physiological medium. Laser Doppler-flowmetry, used to assess the blood flow in the dermal microcirculation, showed that the topical application of hydrated PVA-SNO films on the health skin led to a dose- and time-dependent increase of more than 5-fold in the dermal baseline blood flow in less than 10min, with a prolonged action of more than 4h during continuous application. These results show that PVA-SNO films might emerge as a new material with potential for the topical treatment of microvascular skin disorders.

Determination Of Tetrakis(hydroxymethyl)phosphonium Sulfate In Commercial Formulations And Cooling Water By Capillary Electrophoresis With Contactless Conductivity Detection.

A novel capillary electrophoresis method using capacitively coupled contactless conductivity detection is proposed for the determination of the biocide tetrakis(hydroxymethyl)phosphonium sulfate. The feasibility of the electrophoretic separation of this biocide was attributed to the formation of an anionic complex between the biocide and borate ions in the background electrolyte. Evidence of this complex formation was provided by (11) B NMR spectroscopy. A linear relationship (R(2) = 0.9990) between the peak area of the complex and the biocide concentration (50-900 μmol/L) was found. The limit of detection and limit of quantification were 15.0 and 50.1 μmol/L, respectively. The proposed method was applied to the determination of tetrakis(hydroxymethyl)phosphonium sulfate in commercial formulations, and the results were in good agreement with those obtained by the standard iodometric titration method. The method was also evaluated for the analysis of tap water and cooling water samples treated with the biocide. The results of the recovery tests at three concentration levels (300, 400, and 600 μmol/L) varied from 75 to 99%, with a relative standard deviation no higher than 9%.

O emprego de quitosana quimicamente modificada com anidrido succínico na adsorção de azul de metileno

The adsorption capacity of alpha-chitosan and its modified form with succinic anhydride was compared with the traditional adsorbent active carbon by using the dye methylene blue, employed in the textile industry. The isotherms for both biopolymers were classified as SSA systems in the Giles model, more specifically in L class and subgroup 3. The dye concentration in the supernatant in the adsorption assay was determined through electronic spectroscopy. By calorimetric titration thermodynamic data of the interaction between methyene blue and the chemically modified chitosan at the solid/liquid interface were obtained. The enthalpy of the dye/chitosan interaction gave 2.47 ± 0.02 kJ mol-1 with an equilibrium constant of 7350 ± 10 and for the carbon/dye interaction this constant gave 5951 ± 8. The spontaneity of these adsorptions are reflected by the free Gibbs energies of -22.1 ± 0.4 and -21.5 ± 0.2 kJ mol-1, respectively, found for these systems. This new adsorbent derived from a natural polysaccharide is as efficient as activated carbon. However 97% of the bonded dye can be eluted by sodium chloride solution, while this same operation elutes only 42% from carbon. Chitosan is efficient in dye removal with the additional advantage of being cheap, non-toxic, biocompatible and biodegradable.

Titulação potenciométrica aplicada na determinação de ácidos graxos livres de óleos e gorduras comestíveis

Free fatty acids are a measure of evaluating fats and oils, submitted to abusive conditions, besides being a quality characteristic of edible vegetable oils. The official method of determination (AOCS Ca 5a-40, 2004) is based on titration, using phenolphthalein as an indicator. For crude and degummed oils, the titration end point is difficult to be observed due to the high level of pigments, resulting in dark solutions. In this case and others, such as self-life studies, in which sample quantities are limited, potentiometric titration may be a very good alternative.

Construção de um calorímetro isotérmico diferencial de alta sensibilidade e baixo custo

The high cost of sensitivity commercial calorimeters may represent an obstacle for many calorimetric research groups. This work describes the construction and calibration of a batch differential heat conduction calorimeter with sample cells volumes of about 400 μL. The calorimeter was built using two small high sensibility square Peltier thermoelectric sensors and the total cost was estimated to be about US$ 500. The calorimeter was used to study the excess enthalpy of solution of binary mixtures of liquids, as a function of composition, for the following binary systems of solvents: water + 1,4-dioxane or + dimethylsulfoxide at 298,2 ± 0,5 K.

Efeitos do treinamento com pesos sobre a densidade mineral ossea, força muscular e variaveis funcionais na menopausa

Universidade Estadual de Campinas . Faculdade de Educação Física

Dental caries and related factors in Brazilian children from fluoridated and non-fluoridated areas

PURPOSE: To compare the caries prevalence, saliva buffering capacity (SBC), oral hygiene (OH), dietary habits, family income (FI) and frequency of visits to a dental office (Do) between Brazilian children living in areas with and without fluoridated public water supply. METHODS: Forty-six 5-7-year-old preschoolers were selected in Itatiba, SP, Brazil; 19 were from a fluoridated area, and 27 were from a non-fluoridated area. The caries index was determined according to the World Health Organization criteria, and the SBC was assessed by titration with hydrochloric acid. The FI, frequency of OH and visits to Do were estimated by questionnaire. The dietary habits were assessed with a diet chart. The differences between the groups were analyzed with Mann-Whitney-U tests (α=0.05). RESULTS: Children from the non-fluoridated area showed significantly higher dmft/DMFT than those from the fluoridated area, but they showed significantly lower SBC, OH frequency and FI. No significant differences were observed between the areas for dietary habits and visits to Do. CONCLUSION: Children from fluoridated areas showed higher salivary buffering capacity, family income and oral hygiene frequency as well as lower caries prevalence, supporting the beneficial effect of fluoride in the tap water for caries prevention.

Shelf-life of a 2.5% sodium hypochlorite solution as determined by arrhenius equation

Accelerated stability tests are indicated to assess, within a short time, the degree of chemical degradation that may affect an active substance, either alone or in a formula, under normal storage conditions. This method is based on increased stress conditions to accelerate the rate of chemical degradation. Based on the equation of the straight line obtained as a function of the reaction order (at 50 and 70 ºC) and using Arrhenius equation, the speed of the reaction was calculated for the temperature of 20 ºC (normal storage conditions). This model of accelerated stability test makes it possible to predict the chemical stability of any active substance at any given moment, as long as the method to quantify the chemical substance is available. As an example of the applicability of Arrhenius equation in accelerated stability tests, a 2.5% sodium hypochlorite solution was analyzed due to its chemical instability. Iodometric titration was used to quantify free residual chlorine in the solutions. Based on data obtained keeping this solution at 50 and 70 ºC, using Arrhenius equation and considering 2.0% of free residual chlorine as the minimum acceptable threshold, the shelf-life was equal to 166 days at 20 ºC. This model, however, makes it possible to calculate shelf-life at any other given temperature.

Heat treatment of a direct composite resin: influence on flexural strength

The purpose of this study was to evaluate the flexural strength of a direct composite, for indirect application, that received heat treatment, with or without investment. One indirect composite was used for comparison. For determination of the heat treatment temperature, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed, considering the initial weight loss temperature and glass transition temperature (Tg). Then, after photoactivation (600 mW/cm² - 40 s), the specimens (10 x 2 x 2 mm) were heat-treated following these conditions: 170ºC for 5, 10 or 15 min, embedded or not embedded in investment. Flexural strength was assessed as a means to evaluate the influence of different heat treatment periods and investment embedding on mechanical properties. The data were analyzed by ANOVA and Tukey's test (α = 0.05). TGA showed an initial weight loss temperature of 180ºC and DSC showed a Tg value of 157°C. Heat treatment was conducted in an oven (Flli Manfredi, Italy), after 37°C storage for 48 h. Flexural strength was evaluated after 120 h at 37°C storage. The results showed that different periods and investment embedding presented similar statistical values. Nevertheless, the direct composite resin with treatments presented higher values (178.7 MPa) compared to the indirect composite resin (146.0 MPa) and the same direct composite submitted to photoactivation only (151.7 MPa). Within the limitations of this study, it could be concluded that the heat treatment increased the flexural strength of the direct composite studied, leading to higher mechanical strength compared to the indirect composite.

Phase transitions in biodegradable films based on blends of gelatin and poly (vinyl alcohol)

The aim of this work was to study the effect of the hydrolysis degree (HD) and the concentration (C PVA) of two types of poly (vinyl alcohol) (PVA) and the effect of the type and the concentration of plasticizers on the phase properties of biodegradable films based on blends of gelatin and PVA, using a response-surface methodology. The films were made by casting and the studied properties were their glass (Tg) and melting (Tm) transition temperatures, which were determined by diferential scanning calorimetry (DSC). For the data obtained on the first scan, the fitting of the linear model was statistically significant and predictive only for the second melting temperature. In this case, the most important effect on the second Tm of the first scan was due to the HD of the PVA. In relation to the second scan, the linear model could be fit to Tg data with only two statistically significant parameters. Both the PVA and plasticizer concentrations had an important effect on Tg. Concerning the second Tm of the second scan, the linear model was fit to data with two statistically significant parameters, namely the HD and the plasticizer concentration. But, the most important effect was provoked by the HD of the PVA.