Surface Area Parameters Research Articles

Synthesis, stereochemistry, antimicrobial evaluation and QSAR studies of 2,6-diaryltetrahydropyran-4-one thiosemicarbazones

A series of 2,6-diaryltetrahydropyran-4-one thiosemicarbazones ( 11–27) were synthesized and characterized for evaluation of potential antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Bacillus subtilis and Klebsiella pneumonia and antifungal activity against Cryptococcus neoformans, Candida albicans, Rhizopus sp., Aspergillus niger and Aspergillus flavus were evaluated. Compounds 21 and 22 showed maximum inhibition potency at low concentration (6.25 μg/ml) against P. aeruginosa. For antifungal activity, 20 and 21 were effective against C. neoformans and 22–24 against C. albicans at minimum concentration. Further, the results of QSAR studies of these synthesized compounds indicated the importance of weakly polar component of surface area, hydrophobicity and ionization potential parameters in defining their antimicrobial activity.

150 Immediate results of percutaneous mitral commissurotomy (Experience of Center of cardiology-University Hospital Ibn Rochd-Casablanca-Morocco)

In developing countries mitral stenosis is a frequent heart disease. The therapeutic management of mitral stenosis has been substantially improved through the development of percutaneous mitral commissurotomy, whose safety and efficacy have been demonstrated in many studies. The aim of this work is to study the immediate results of percutaneous mitral commissurotomy (PMC) in patients with severe mitral stenosis managed in Center of cardiology-University Hospital IBN Rochd-Casablanca. Of 150 patients there were 20 men and 130 women including 10 pregnant women (third trimester of pregnancy), their mean age was 35 ± 10 years. One hundred were in NYHA class II, 40 in class III and 10 in class IV. Eighty patients with atrial fibrillation. All patients had transthoracic echocardiography before and after the procedure and transesophageal echocardiography before the PMC. Wilkins score calculated in all patients with an average 7 ± 4. Grade 1+ mitral regurgitation was present in 70 and grade 2+ in 13. Mitral regurgitation grade I or II developed in 8 patients. The PMC was converted into a mitral replacement surgery in one patient. Tamponade occurred in one patient. No patient died. Mitral surface area and hemodynamic parameters improved significantly after PMC; mean left atrial pressure fell from 18.76 ± 6.18 to 10.65 ± 4.38 mmHg (P < 0.001), mean transmitral gradient from 14.03 ± 4.70 to 4.63 ± 2.05 mmHg (p < 0.001) and mitral valve area from 0.99 ± 0.22 to 1.88 ± 0.41 cm2 (p < 0.001). In conclusion, PMC is a safe and effective treatment in a wide range of patients with mitral stenosis.

Synthesis and Antiviral Activity of Novel 1,3,4-Thiadiazine Derivatives

A series of novel 1,3,4-thiadiazine derivatives were synthesized via chemical optimization on phthiobuzone. Their anti-herpes simplex virus (HSV) activities in vitro were also tested. Several compounds exhibited more highly potent anti-HSV activity and much higher selectivity index (SI) values than those of phthiobuzone. The most potent anti-HSV compound was 4f, which showed marked inhibition against HSV-1 (IC₅₀=77.04 µg/ml) and HSV-2 (IC₅₀=30.00 µg/ml). Meanwhile it had low cytotoxicity (CC₅₀=1000.00 µg/ml), resulting in high (SI(HSV-1)=12.98, SI(HSV-2)=33.33, respectively). Furthermore, a computational study for prediction of absorption, distribution, metabolism, excretion (ADME) properties of compound 4f was performed by determination of topological polar surface area, absorption and Lipinski parameters.

Liquid–liquid equilibrium in ternary ionic liquid systems by UNIFAC: New volume, surface area and interaction parameters. Part II

Ionic liquids are potential solvents for liquid extraction processes; thermodynamic modeling of liquid–liquid equilibrium (LLE) data is essential for the optimization and operation of these processes. Therefore, ternary LLE data in systems involving ionic liquids have been investigated by several years. In most of the cases, the thermodynamic modeling of these systems has been made using the NRTL model; in some cases, the UNIQUAC model has also been used. The structural parameters of UNIQUAC for ionic liquids have been determined either by empirical correlations or, more recently, through quantum mechanics calculation. This work is a continuation of a recent paper, in which the structural group volume and area parameters for the group-contribution UNIFAC method have been calculated for five ionic liquids following the quantum mechanics approach. In order to optimize the molecular geometry and to calculate the area and volume, the Density Functional Theory (DFT) and the Polarizable Continuum Method (PCM) were used, respectively. The obtained parameters were used to correlate LLE data for fifteen ternary systems, totalizing 155 tie-lines. New interaction parameters were also estimated between the solvent and the ionic liquid functional groups. The results are very satisfactory, with root mean square deviations 0.0037 between experimental and calculated equilibrium mole fractions.

Effect of fine water droplets on extinguishment of diffusion flame stabilized in the forward stagnation region of a porous cylinder

The roles of the physical, thermal and chemical effects of fine water droplets on extinguishment of diffusion flame subjected to high strain are quantified experimentally using a methane counterflow diffusion flame. Water droplets were generated by twin-fluid atomizers and ultrasonic mist generators. The distributions of water droplet diameter were measured by a PDPA and found to be nearly normal, with the number mean diameter ranging typically from 15 to 25 μm and the Sauter mean diameter from 25 to 30 μm. The limit of extinguishment was determined by the velocity gradient and the non-dimensional fuel-ejection velocity. The critical velocity gradient at extinguishment without water droplets was found to be 423 s −1. Introduction of water droplets into air stream resulted in reduction of the velocity gradient at extinguishment due to evaporation which causes the cooling and depletion of oxygen in the flame zone. The critical velocity gradient at extinguishment decreases with the increase of the surface area parameter, Σ, which is expressed by the ratio of mass fraction of water droplets to Sauter mean diameter. By a simple analysis, the lifetime of a droplet was compared with the residence time and it was found that there exists threshold below which droplets can be evaporated within the flame zone. PDPA measurement also showed that the water droplets with diameters larger than the threshold pass through the flame zone towards the stagnation plane. The threshold was found to depend on the velocity gradient. The maximum temperature measured by a thermocouple decreases with the mass loading of water droplets as well as the velocity gradient. However, the maximum temperature at extinguishment is rather independent of mass loading of water droplets and also of velocity gradient and the thermal effect is predominant in the extinguishment of the counterflow diffusion flame.

Liquid–liquid equilibrium in ternary ionic liquid systems by UNIFAC: New volume, surface area and interaction parameters. Part I

Ternary liquid–liquid equilibria (LLE) data in systems involving ionic liquids has been investigated by several years, mainly due to the innovative role of ionic liquids as extraction solvents. The thermodynamic modeling of these systems has been performed almost invariably with the well-known NRTL model. In recent years, the UNIQUAC model has also been used, with structural parameters for ionic liquids determined either by empirical correlations or, more recently, through quantum mechanics calculations. In this work, the structural group volume and area parameters for the group-contribution UNIFAC method have been calculated for six ionic liquids following the quantum mechanics approach. The Density Functional Theory (DFT) was used to optimize the molecular geometry and the Polarizable Continuum Method (PCM) was used to calculate the area and volume. The obtained parameters were used to correlate LLE data for twenty-four ternary systems, totalizing 169 tie-lines. New interaction parameters were also estimated between the solvent and ionic liquid functional groups. The results are very satisfactory, with root mean square deviations between experimental and calculated compositions about 1.6%.

Effect of surface area parameters on the vapor–liquid equilibrium calculations using a lattice fluid equation of state with hydrogen bonding

Vapor–liquid equilibrium calculations at ambient and elevated pressures were performed using the lattice fluid equation of state with hydrogen bonding (NLF-HB EoS) proposed by You et al. [7,8] and Lee et al. [17]. Vapor–liquid equilibrium calculations composed of typical pure components were compared with electronic experimental database (Dortmund Data Bank). Special attention has been paid to the correction of surface area parameters. Bulkiness factors can be used to modify theoretical surface area parameters for molecules with nonlinear shapes. Empirical bulkiness factors were obtained from liquid density data and VLE data sets with n-hexane chosen as a reference component. Using empirical bulkiness factors, overall prediction performances without binary interaction parameters have been significantly improved. It is shown that the NLF-HB EoS have comparable prediction capability with UNIQUAC method or Peng–Robinson Equation of State only with pure component parameters and component-type-dependent hydrogen-bonding energy parameters for most systems considered in this study.

Atomic Analysis of Protein-Protein Interfaces with Known Inhibitors: The 2P2I Database

BackgroundIn the last decade, the inhibition of protein-protein interactions (PPIs) has emerged from both academic and private research as a new way to modulate the activity of proteins. Inhibitors of these original interactions are certainly the next generation of highly innovative drugs that will reach the market in the next decade. However, in silico design of such compounds still remains challenging.Methodology/Principal FindingsHere we describe this particular PPI chemical space through the presentation of 2P2IDB, a hand-curated database dedicated to the structure of PPIs with known inhibitors. We have analyzed protein/protein and protein/inhibitor interfaces in terms of geometrical parameters, atom and residue properties, buried accessible surface area and other biophysical parameters. The interfaces found in 2P2IDB were then compared to those of representative datasets of heterodimeric complexes. We propose a new classification of PPIs with known inhibitors into two classes depending on the number of segments present at the interface and corresponding to either a single secondary structure element or to a more globular interacting domain. 2P2IDB complexes share global shape properties with standard transient heterodimer complexes, but their accessible surface areas are significantly smaller. No major conformational changes are seen between the different states of the proteins. The interfaces are more hydrophobic than general PPI's interfaces, with less charged residues and more non-polar atoms. Finally, fifty percent of the complexes in the 2P2IDB dataset possess more hydrogen bonds than typical protein-protein complexes. Potential areas of study for the future are proposed, which include a new classification system consisting of specific families and the identification of PPI targets with high druggability potential based on key descriptors of the interaction.Conclusions2P2I database stores structural information about PPIs with known inhibitors and provides a useful tool for biologists to assess the potential druggability of their interfaces. The database can be accessed at http://2p2idb.cnrs-mrs.fr.

Modification of Pellet Materials by Low Temperature Plasma

Low temperature plasma made some modifications of pellet materials (activated alumina and haydite) placed between electrodes. It altered the characteristics of pellets after discharge, such as the pellet surface element proportion, binding energy, specific surface area, pore volume and pore size. The activated alumina surface parameters of specific surface area, pore volume and pore size increased after discharge, which was good for catalytic activity. The original pores on haydite surface were destroyed, and bigger holes were formed. Activated alumina would be polarized when placed between discharge electrodes, which enhanced the electric field intensity. Due to the effect of plasma, the solid pellet surface was modified, which was useful for pellet catalysis in application.

The relation of physical properties of native starch granules to the kinetics of amylolysis catalysed by porcine pancreatic α-amylase

Various native starch granules were tested as substrates for porcine pancreatic α-amylase and enzyme kinetic parameters obtained from initial rate studies. Surface area per kg weight values and gelatinisation enthalpies (Δ H gel ) for the different granules were measured. Δ H gel was used as an indication of the degree of disorder within the starch granules. K m values, that are indicative of starch availability, decreased with the particle size but not in a linear fashion. The catalytic efficiency of amylase and the initial rate of catalysed hydrolysis were both significantly correlated with the surface area. Also, K m , catalytic efficiency ( k cat / K m ) and initial hydrolysis rate were all significantly correlated with Δ H gel . Thus the surface area of granules and the degree of order of starch have important influences on the initial rate at which native starch is digested by amylase. We believe that this is the first systematic report linking kinetic data with surface area and gelatinisation parameters of native starch.

Prediction of Partial Molar Volumes of Amino Acids and Small Peptides: Counting Atoms versus Topological Indices

Experimental data of partial molar volumes of amino acids and small peptides were compiled from several publications and enabled us to perform a predicative analysis based on quantitative structure-property relationships (QSPR). Based on the simplest level of the descriptors, the new method has high accuracy and was found to be more reliable when compared to the latter QSPR method based on topological indexes. Incorporation of isoelectric pH and 3-D solvent-accessible surface area parameters increased the predictability of the equation to a small extent. Cross-validation studies show that this method is successful in predicting the partial molar volumes of other noncoded amino acids, dipeptides, and diketopiperazine derivatives. This method is the beginning of new studies for larger peptides and proteins. It also can be suggested to be used for molecules that contain the same type of atoms as an amino acid.

Impact of Air Convection on H3PO4-Activated Biomass for Sequestration of Cu (II) and Cd (II) Ions

Crushed, depitted peach stones were impregnated activated with 50% <TEX>$H_3PO_4$</TEX> followed by pyrolysis at <TEX>$500^{\circ}C$</TEX>. Two activated carbons were produced, one under its own evolved gases during pyrolysis, and the second conducted with air flow throughout the carbonization stage. Physicochemical properties were investigated by several procedures; carbon yield, ash content, elemental chemical analysis, TG/DTG and FTIR spectra. Porosity characteristics were determined by the conventional <TEX>$N_2$</TEX> adsorption at 77 K, and data analyzed to get the major texture parameters of surface area and pore volume. Highly developed activated carbons were obtained, essentially microporous, with slight effect of air on the porous structure. Oxygen was observed to be markedly incorporated in the carbon matrix during the air treatment process. Cation exchange capacity towards Cu (II) and Cd (II) was tested in batch single ion experimental mode, which proved to be slow and a function of carbon dose, time and initial ion concentration. Copper was up taken more favorably than cadmium, under same conditions, and adsorption of both cations was remarkably enhanced as a consequence of the air treatment procedure. Sequestration of the metal ions was explained on basis of the combined effect of the oxygen functional groups and the phosphorous-containing compounds; both contributing to the total surface acidity character.

Multiple functions of the paranodal junction of myelinated nerve fibers

Myelin sheaths include an extraordinary structure, the "paranodal axoglial junction" (PNJ), which attaches the sheath to the axon at each end of each myelin segment. Its size is enormous and its structure unique. Here we review past and current studies showing that this junction can serve multiple functions in maintaining reliable saltatory conduction. The present evidence points to three functions in particular. 1) It seals the myelin sheath to the axon to prevent major shunting of nodal action currents beneath the myelin sheath while still leaving a narrow channel interconnecting the internodal periaxonal space with the perinodal space. This pathway represents a potential route through which juxtaparanodal and internodal channels can influence nodal activity and through which nutrients, such as glucose, and other metabolites can diffuse to and from the internodal periaxonal space. 2) It serves as a mechanism for maintaining discrete, differentiated axolemmal domains at and around the node of Ranvier by acting as a barrier to the lateral movement of ion channel complexes within the axolemma, thus concentrating voltage-gated sodium channels at the node and segregating fast voltage-gated potassium channels to the juxtaparanode under the myelin sheath. 3) It attaches the myelin sheath to the axon on either side of the node and can thus maintain nodal dimensions in the face of mechanical stresses associated with stretch or other local factors that might cause disjunction. It is therefore the likely means for maintaining constancy of nodal surface area and electrical parameters essential for consistency in conduction.

Modeling Thermal Conductivity of Concentrated and Mixed-Solvent Electrolyte Systems

A comprehensive model has been developed for calculating the thermal conductivity of aqueous, nonaqueous, and mixed-solvent electrolyte systems ranging from dilute solutions to fused salts or pure solutes. The model consists of a correlation for calculating the thermal conductivity of solvent mixtures and a method for predicting the effect of electrolyte components. The thermal conductivity of multicomponent solvent mixtures can be represented using surface area parameters and thermal conductivities of pure solvents in conjunction with a single binary parameter per solvent pair. The effect of electrolytes is modeled by accounting for a contribution of individual ions, which is quantified by the Riedel coefficients, and a contribution of specific interactions between ions or neutral species. Formulations have been developed for the contributions of individual ions and species−species interactions to represent the effect of multiple solvents. In addition to solvent composition, the species−species interacti...

Thermodynamic modeling of vapor–liquid equilibrium of binary systems ionic liquid + supercritical {CO 2 or CHF 3} and ionic liquid + hydrocarbons using Peng–Robinson equation of state

Vapor–liquid equilibrium (VLE) data from literature for binary systems involving several ionic liquids were correlated. The Peng–Robinson equation of state, coupled with the van der Waals and Wong–Sandler mixing rules, was used as the thermodynamic model to evaluate the fugacity coefficients. The UNIQUAC and NRTL models were used to calculate the excess Gibbs free energy in the Wong–Sandler mixing rule. A molecular modeling strategy using the software ChemOffice was used to calculate the volume and surface area parameters of ionic liquids for UNIQUAC, while the binary interaction energy parameters for UNIQUAC and NRTL models, as well as the binary interaction parameter of the van der Waals and Wong–Sandler mixing rules were estimated through a method based on the genetic algorithm. The results show that, as expected, the Wong–Sandler mixing rules represented better the data, with both activity coefficient models showing high accuracy. However, in one case, NRTL predicted an erroneous azeotropic condition, while UNIQUAC was able to correlate the data without this error.

The clinical anatomy of the triangle of Grynfeltt

Dorsal lumbar hernias are rare pathologies of the abdominal wall. Such hernias may manifest within the superior lumbar triangle of Grynfeltt (TG) or the triangle of Petit. The aim of our study was to identify and describe variations in the size and anatomy of the TG. The triangle was studied in 50 adult human cadavers, and dimensions and surface area were measured. The TG was identified in 82% of cases. Based on surface area parameters, we were able to classify the triangles into four distinct types. Type I (50%), or small triangles, had a surface area of <5 cm(2). Type II (22%, n=22) were defined as triangles intermediate in size with surface areas of 5-15 cm(2). Type III (10%, 10) were large triangles with surface areas of >15 cm(2). Finally, Type 0 (18%, 18) did not exhibit a triangle; instead, the aponeurosis of the transversus abdominis was enclosed by the external abdominal oblique muscle and the sacrospinalis muscle. We present these data with the hope that after further investigation in a clinical setting, they may serve practitioners in predicting which morphometric variations of the TG most predispose patients to posterior wall herniation.

Advanced computational tools for PEM fuel cell design: Part 2. Detailed experimental validation and parametric study

This paper reports on the systematic experimental validation of a comprehensive 3D CFD-based computational model presented and documented in Part 1. Simulations for unit cells with straight channels, similar to the Ballard Mk902 hardware, are performed and analyzed in conjunction with detailed current mapping measurements and water mass distributions in the membrane-electrode assembly. The experiments were designed to display sensitivity of the cell over a range of operating parameters including current density, humidification, and coolant temperature, making the data particularly well suited for systematic validation. Based on the validation and analysis of the predictions, values of model parameters, including the electro-osmotic drag coefficient, capillary diffusion coefficient, and catalyst specific surface area are determined adjusted to fit experimental data of current density and MEA water content. The predicted net water flux out of the anode (normalized by the total water generated) increases as anode humidification water flow rate is increased, in agreement with experimental results. A modification of the constitutive equation for the capillary diffusivity of water in the porous electrodes that attempts to incorporate the experimentally observed immobile (or irreducible) saturation yields a better fit of the predicted MEA water mass with experimental data. The specific surface area parameter used in the catalyst layer model is found to be effective in tuning the simulations to predict the correct cell voltage over a range of stoichiometries.

Preliminary study of Lead (Pb) immobilization by meat and bone meal combustion residues (MBMCR) in soil: Assessment of Pb toxicity (phytotoxicity and genotoxicity) using the tobacco model (Nicotiana tabacum var. xanthi Dulieu)

Lead (Pb) is a major chemical pollutant in the environment. The present investigation evaluates the possible use of Meat and Bone Meal Combustion Residues (MBMCR), to sequester Pb from the soil compartment using the heterozygous tobacco model (Nicotiana tabacum var. xanthi Dulieu) characterized by the a1+ /a1 a2+ /a2 system. The toxic potential of Pb-contaminations (50, 100, 1,000, 2,000 and 10,000 mg Pb kg(-1)) as Pb(NO3) in standard soil was investigated in lab conditions according to three endpoints: (i) acute toxicity of plants (mortality, height and surface area parameters), (ii) Pb-accumulation in roots, stems and leaves, and (iii) genetic effects as the expression of reversion in the leaf of plants. Moreover, chemical investigations of Pb interactions with soil were realized to complete the toxicity evaluation. The results demonstrated that: (i) MBMCR were not acutely toxic or genotoxic to tobacco plants, (ii) Pb is acutely toxic to tobacco plants at 10,000 mg Pb kg(-1) of soil, (ii) but is not genotoxic, and (iii) Pb-bioaccumulation is significant in leaves, stems and roots (from 1,000, 2,000, and 50 mg Pb kg(-1) of soil, respectively). In contrast, in the presence of MBMCR, the toxic impacts of Pb were inhibited and Pb-accumulation in tobacco plants was reduced. In complement, chemical analyses highlighted the high capacity of the standard soil to immobilize Pb. The results suggest that even if Pb is bioavailable from soils to plants, complex mechanisms could occur in plants protecting them from the toxic impact of Pb.

Physico-chemical properties and healing capacity of potentially bioactive titanium surface

The aim of this study was to evaluate physico-chemical properties and the healing capacity of surface treated titanium. Surface treatment combining sand-blasting, acid etching and alkaline etching (BIO surface) was evaluated together with machined titanium as a reference surface. Hydration, wetting angle, surface area and roughness parameters were evaluated for both surfaces. Stability of dental implants with both surfaces implanted in the tibia of dog was measured during the healing of twelve weeks. BIO surface exhibited lower wetting angle, larger surface area, higher degree of hydration and higher average roughness compared to machined titanium. Implants with the BIO surface maintained their stability during the whole healing period in contrast to those with machined titanium surface, which showed a statistically significant decrease in stability three and nine weeks after implantation.

Specific and non-specific interactions on non-porous carbon black surfaces

The interactions which occur between methanol, ethanol or propanol and the surfaces of non-porous carbon blacks with increasing levels of oxygen chemistry have been studied using adsorption isotherm analysis and immersion calorimetry. Surface oxygen has been controlled by ozone treatment and characterised using X-ray photoelectron spectroscopy, which gives a direct and quantitative measure of surface composition from first-principles, and has not yet been extensively employed in detailed carbon adsorption studies. Nitrogen adsorption at 77 K and heat of immersion − h i (mJ m −2) data for toluene, show that the physical structure of the carbon blacks is not modified by ozone treatment. A systematic shift to higher adsorption values, due to increasing specific hydrogen bonding interactions between the alcohol –OH groups and surface oxygen, is observed in all of the alcohol isotherms as the total oxygen content of the carbon surfaces ([O] T/at.%) increases. This effect is most significant for methanol confirming that the mechanism of adsorption is dominated by hydrogen bonding and therefore dependant on the surface concentration of oxygen sites. It is also observed for ethanol and propanol but is less marked due to the increasing non-specific, dispersion, interactions of the alkyl chain with the non-polar carbon surface. This description is in agreement with the data obtained for the specific enthalpies of immersion − h i (mJ m −2) into the alcohols and into water or toluene which allow a semi-quantitative assessment off the relative polar and dispersion contributions to the overall interactions as functions of both carbon surface oxygen composition and the molecular structure of the alcohols. An overall correlation is observed between adsorption behaviour, [O] T/at.%, the resulting − h i values and the characteristic energy E (kJ mol −1) of the DRK equation. It is also observed that the values of the affinity coefficient β DRK increase directly as a function of [O] T indicating that this latter parameter may provide a basis for predicting the adsorption isotherms of certain polar vapours on non-porous carbon surfaces. The effects of carbon surface chemistry on the character of adsorption isotherms, which change from Type III for the base N330 (and for a graphitized carbon black N234G) to Type II for the oxidised N330 materials, is discussed and the resulting effects on the surface area parameters S DRK and S BET (m 2 g −1) are considered.