Reactive extraction and LSER model consideration of lactic acid with tripropylamine+organic solvent systems from aqueous solution at room temperature

The extraction of lactic acid was done by tripropylamine (TPA) dissolved in seven single solvents (isoamyl alcohol, heptan-1-ol, hexan-1-ol, octan-1-ol, nonan-1-ol, decan-1-ol, and dodecanol). All measurements were carried out at 298.15 K. The extent to which the organic phase may be loaded with lactic acid is expressed as loading ratio, Z, its value extraction efficiencies, E, and overall particular distribution coefficients, D, were calculated. Equilibrium complexation constants for (acid:amine) (1:1), (1:2) have been determined according to Bizek's approach. The maximum removal of lactic acid accomplished was about 81% with isoamyl alcohol having 1.935 mol dm^− 3 initial concentration of TPA. All of the obtained data have been correlated by linear solvation energy relationship (LSER) model. LSER model results were compared with the experimental results and well agreement between them was observed. Regression coefficient (R²) of LSER model is 0.972.     

Gingival involvement in mucous membrane pemphigoid

A 60-year-old woman with clinical features of desquamative gingivitis had a history of painful, blistering gingival lesions for more than 2 years. There were no other accompanying mucosal or skin lesions. Clinical examination revealed erythematous and edematous gingiva with ulcerated areas and evidence of intact and ruptured bullae. White plaquelike lesions were also noted. Gingival manipulation caused epithelial desquamation. Light microscopic examination of biopsy specimens from the perilesional gingival tissue showed separation of the oral gingival epithelium and connective tissue at the margin of the collapsed bulla. A moderately intense inflammatory infiltrate was present in the connective tissue. Direct immunofluorescent microscopy revealed a continuous linear deposition of immunoglobulin G and C3 at the basement membrane zone. On the basis of clinical, histopathologic, and immunofluorescent findings, the diagnosis of mucous membrane pemphigoid was made.     

Synthesis and proton conductivity studies of doped azole functional polymer electrolyte membranes

The development of anhydrous proton-conducting membranes is important for the operation of polymer electrolyte membrane fuel cell (PEMFC) at intermediate temperature (100-200 °C). In this work, poly(vinylbenzylchloride), PVBC was produced by free radical polymerization of 4-vinylbenzylchloride and then it was modified with 5-aminotetrazole (ATET) to obtain poly(vinylbenzylaminotetrazole), PVBC-ATET. The composition of the polymer was verified by elemental analysis (EA) and the structure was characterized by FT-IR and ¹³C NMR spectra. According to the elemental analysis result, PVBC was modified by ATET with 80% yield. The polymer was doped with trifluoromethanesulfonic acid (TA) at various molar ratios, x = 1.25, 2.5, 3.75 with respect to tetrazole unit. The proton transfer from TA to the tetrazole rings was proved with FT-IR spectroscopy. Thermogravimetry (TG) analysis showed that the samples are thermally stable up to approximately 200 °C. Differential scanning calorimetry (DSC) results illustrated the homogeneity of the materials. Cyclic voltammetry (CV) study illustrated that the electrochemical stability domain for PVBC-ATET-TA_2.5 extends over 3.0 V. The proton conductivity of these materials increased with dopant concentration and the temperature. Maximum proton conductivity of PVBC-ATET-TA_2.5 was found to be 0.01 S/cm at 150 °C in the anhydrous state.     

Developing of N‐(4‐methylpyrimidine‐2‐yl)methacrylamide Langmuir–Blodgett thin film chemical sensor via quartz crystal microbalance technique

In the present work, the characterization and gas sensing properties of newly synthesized N‐(4‐methylpyrimidine‐2‐yl)methacrylamide ( N‐MPMA ) monomer Langmuir–Blodgett (LB) thin films were investigated. The UV–visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy were utilized to characterize N‐MPMA LB thin films. The surface behavior of N‐MPMA monolayer was stable and allowed an effective transfer at a surface pressure of 14 mN/m. The mass change/unit area value of the N‐MPMA LB thin film deposited quartz crystal surfaces was investigated. The amount of N‐MPMA LB thin film deposited on the substrate for bilayer was calculated as 228.72 ng (86.31 ng/mm²) and 12.5 Hz frequency shift was observed for each layer of the N‐MPMA film. The kinetic responses of N‐MPMA LB film against chloroform, dichloromethane, benzene, and toluene were measured via QCM system at room temperature. N‐MPMA QCM sensor results displayed that chloroform has the largest frequency shifts compared with the other vapors used in the present work and these results can be illuminating in terms of physical properties of organic vapors.     

Use of zirconium diboride-copper as an electrode in plasma applications

Frequent replacement of electrodes, due to their high wear rate, is an undesired feature of most thermal plasma processes. Hence, the discovery of a high spark-resistive tool, ZrB2-Cu, is of interest. Performance evaluation of this metal matrix ceramic (MMC) employed electrical discharge machining (EDM), where steel is used as the cathode workpiece and the MMC is used as the anode tool. Compared with the performance of copper and graphite tools, ZrB2-Cu yields the highest workpiece removal rate,; and the lowest tool wear rate at high plasma heat flux conditions, resulting in an extremely low wear ratio. Energy dispersive spectroscopy shows deposition of workpiece materials (Fe, Cr, Ni and S) on the ZrB2-Cu surface after EDM. This is due to the difference between the surface temperature of the tool and the workpiece. Scanning electron microscopy and elemental mapping analysis reveal that the composite electrode erodes by a combination of dominant evaporation and melting of the metal phase, negligible melting and thermal spalling in the ceramic phase, quick refreezing of the metal phase back to the surface, and deposition of the workpiece (steel) on the tool surface. Most of the heat is conducted through the Cu phase, reducing thermal stress in the ceramic phase. This causes lower surface temperatures for the molten ZrB2 matrix; hence, the Cu tends to refreeze quickly near the surrounding ceramic matrix.     

Enhancing the Anhydrous Proton Conductivity of Boronic and Phosphonic Acid Functional Copolymers by Grafting With Flexible Spacers

Polymers comprised of phosphonic acid units are generally preferred for proton conducting membranes due to their high proton conductivity in humidified and anhydrous state. Polymers based on 4-vinylbenzene boronic acid and diisopropyl-p-vinylbenzyl phosphonate were synthesized and the phosphonate group was hydrolyzed. Boronic acid groups were grafted with polyethyleneglycol methyl ether (PEGME) to produce more flexible copolymers. The copolymerization and grafting reactions were verified by Fourier Transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry (DSC). The P content of the samples was analyzed with SEM–EDS. Thermograms indicate that the copolymers are thermally stable to 200 °C. In addition, grafting resulted in the inhibition of condensation of the acidic units. DSC results show that after grafting the copolymers have distinct melting temperatures corresponding to PEGME units, which are bound to the polymer. The ion exchange capacity and cyclic voltammetry of the copolymers results were measured. The proton conductivity of the copolymers was investigated in the anhydrous state. Although the copolymers have low proton conductivity (<10^?10 S/cm), they reached a value of 1.6 × 10^?6 S/cm after grafting with PEGME units. This demonstrated that the presence of flexible side units increased the proton conductivity at least five orders of magnitude. This idea can be used for designing the novel membranes for fuel cells.     

Distraction of lumbar vertebrae in gravitational traction

STUDY DESIGN: Experimental study of 30 patients diagnosed with low back pain resulting from lumbar disc herniation, disc degeneration, and segmental instability. Patients underwent gravitational traction, and widening of the intervertebral space and posterior facets was measured on radiographs. This same procedure was performed with a group of 30 healthy individuals. OBJECTIVES: To determine the effect of gravitational traction on the widening of the intervertebral space and the other vertebral structures in patients with low back pain and in healthy individuals. SUMMARY OF BACKGROUND DATA: Gravitational traction is performed by suspending the patient in a hanging, upright position for an extended period of time. In spite of disagreement among authors about the effect of lumbar traction, recent innovations have enabled the distraction of vertebrae. METHODS: A specially designed apparatus was used to apply gravitational traction. Pre- and post-traction radiographs were obtained to study the changes in the L2-L3, L3-L4, L4-L5, and L5-S1 intervertebral spaces; Ferguson's angle; L1-S1 total distance; and blood pressure. RESULTS: Distraction was more than approximately 3 mm in each intervertebral space in both groups. CONCLUSION: Gravitational traction had a very apparent effect on intervertebral space and was found to be an effective method to distract lumbar vertebrae. Discomfort experienced by the patient during suspension may be overcome by making biomedical changes to the suspension corset.     

Measurement and estimation of species distribution in a direct methanol fuel cell

Determination of methanol concentration in a direct methanol fuel cell is crucial for design improvement and performance enhancement. Methanol and water concentrations in a direct methanol fuel cell are experimentally and numerically investigated. In the experimental program, a single cell direct methanol fuel cell is developed and an experimental setup is devised to measure methanol and water concentrations and performance of the cell depending on operating conditions. In theoretical program a mathematical model which includes fluid flow, species distribution, electric field and electrochemistry is adapted and numerically solved. The results showed that the performance of a Direct Methanol Fuel Cell (DMFC) is mainly influenced by operating temperature. A large drop in methanol concentration methanol is measured at the inlet section of cell. The mathematical model is found to satisfactorily capture main physics involved in a DMFC.     

Investigation of luminescence centers inside InGaN/GaN multiple quantum well over a wide range of temperature and injection currents

Journal of Materials Science: Materials in Electronics - InGaN/GaN multiple quantum well-based light-emitting diode LEDs were investigated over a wide range of injection currents (0.04 mA–0.1...