Effect of channel-to-channel cross-flow on local flooding in serpentine flow-fields

Serpentine flow-fields have long been used in polymer electrolyte membrane (PEM) fuel cells for effective transportation of reactants from the flow-field to the reaction sites. It has been observed in the literature that localized flooding near the U-bend region of serpentine flow-fields occurs at high current densities. This has been attributed to the boundary layer separation and recirculation of flow in the U-bend. In the present study, it is established, using computational fluid dynamics (CFD) simulations, that this is due to lower channel-to-channel cross-flow in the electrodes between consecutive serpentine channels rather than to the flow-field in the gas distribution channels.     

Role of Brown and Beige Adipose Tissues in Seasonal Adaptation in the Raccoon Dog (Nyctereutes procyonoides)

Brown adipose tissue (BAT) expresses uncoupling protein-1 (UCP1), which enables energy to be exerted towards needed thermogenesis. Beige adipocytes are precursor cells interspersed among white adipose tissue (WAT) that possess similar UCP1 activity and capacity for thermogenesis. The raccoon dog (Nyctereutes procyonoides) is a canid species that utilizes seasonal obesity to survive periods of food shortage in climate zones with cold winters. The potential to recruit a part of the abundant WAT storages as beige adipocytes for UCP1-dependent thermogenesis was investigated in vitro by treating raccoon dog adipocytes with different browning inducing factors. In vivo positron emission tomography/computed tomography (PET/CT) imaging with the glucose analog ¹⁸F-FDG showed that BAT was not detected in the adult raccoon dog during the winter season. In addition, UCP1 expression was not changed in response to chronic treatments with browning inducing factors in adipocyte cultures. Our results demonstrated that most likely the raccoon dog endures cold weather without the induction of BAT or recruitment of beige adipocytes for heat production. Its thick fur coat, insulating fat, and muscle shivering seem to provide the adequate heat needed for surviving the winter.     

X-Ray Diffraction Study of Plasma Exposed and Annealed AlSb Bilayer Thin Film

Aluminum antimony seems to be a promising semiconducting material for high temperature applications, especially for transistors and P-N junction diodes. Additionally, it is a highly efficient solar material. This paper discusses the plasma induced bilayer diffusion of AlSb bilayer thin films using X-ray diffractogram. AlSb bilayer thin films were prepared on a glass substrate by vacuum evaporation technique. The effect of plasma exposure time and annealing temperature on the micro-structural parameters were investigated. X-ray diffraction studies show that the cubic crystals of Al orient along the (111) plane and the hexagonal crystals of Sb orient along the (003) plane. Newly formed cubic crystals of AlSb are oriented along the (200) plane and they are formed due to the simultaneous growth of Al and Sb crystals during plasma exposure.     

Comprehensive one-dimensional,semi-analytical,mathematical model for liquid-feed polymer electrolyte membrane direct methanol fuel cells

Polymer electrolyte membrane direct methanol fuel cells (PEM-DMFCs) have several advantages over hydrogen-fuelled PEM fuel cells; but sluggish methanol electrochemical oxidation and methanol crossover from the anode to the cathode through the PEM are two major problems with these cells. In the present work, a comprehensive one-dimensional, single phase, isothermal mathematical model is developed for a liquid-feed PEM-DMFC, taking into account all the necessary mass transport and electrochemical phenomena. Diffusion and convective effects are considered for methanol transport on the anode side and in the PEM, whereas only diffusional transport of species is considered on the cathode side. A multi-step reaction mechanism is used to describe the electrochemical oxidation of methanol at the anode. Stefan–Maxwell equations are used to describe multi-component diffusion on the cathode side and Tafel type of kinetics is used to describe the simultaneous methanol oxidation and oxygen reduction reactions at the cathode. The model fully accounts for the mixed potential effect caused by methanol crossover at the cathode. It shows excellent agreement with literature data of the limiting current density for different low methanol feed concentrations at different operating temperatures. At high methanol feed concentrations, oxygen depletion on the cathode side, due to excessive methanol crossover, results in mass-transport limitations. The model can be used to optimize the geometric and physical parameters with a view to extracting the highest current density while still keeping a tolerably low methanol crossover.     

Assessing Multicomponent DNAPL Biostabilization Potential.?II: Aroclor 1242

Aroclors are dense nonaqueous-phase liquids (DNAPLs) composed of polychlorinated biphenyls, which are common subsurface contaminants. Because complete remediation of Aroclor is very difficult, biostabilization may offer an alternative where risk reduction can be achieved without destruction of the DNAPL mass. The potential for aerobic in situ biostabilization of Aroclor 1242 was evaluated using laboratory protocols similar to those described in the companion paper. Total microbial concentrations increased and stabilized in both mixed and unmixed systems, while the respiring cells did not stabilize in either system. After 100 days, the DNAPL in mixed biometers was depleted in dichlorobiphenyls; the DNAPL composition in unmixed biometers did not change significantly. The total aqueous polychlorinated biphenyl concentration was lower in the unmixed than mixed biometers; both were below the predicted equilibrium concentration. After 100 days, the chronic toxicity of the aqueous phase to Cerodaphnia was greater in the biotreated systems than in the unbiotreated systems. The results indicate that aerobic microbiological activity may be insufficient to fully stabilize Aroclor in the subsurface, in contrast to the clear biostabilization potential of coal tar.     

Expression of recombinant {alpha}Ains-crystallin and not {alpha}A-crystallin inhibits bacterial growth

A-Crystallin and A^ins-crystallin are derived from the A-crystallingene via alternative splicing. They are identical except forthe presence of a polypeptide, 23 amino acids long, encodedby the ‘insert’ exon. Evolutionary logic would suggestthat the insertion of a 23 amino acid peptide in the middleof A-crystallin, a protein evolving more slowly than eitherhistone H1, cytochrome c or hemoglobin, would lead to appreciablestructural and functional changes. However, based on physico-chemicalstudies, it is presently believed that A-crystallin and A^ins-crystallinare functionally equivalent and that the presence of the ‘insert’peptide in A^Ins-crystallin is inconsequential. We report herethat the independent expression of recombinant A^Ins-crystallin,and not A-crystallin, inhibits growth of the bacterial host.These observations were confirmed in co-expression experiments,wherein both the proteins were expressed in the same cell. Interestingly,growth inhibition is reversible. Importantly, the data demonstratethat it is catalytic amounts and not the gross accumulationof A^Ins-crystalline which causes growth inhibition. Given theprior knowledge that A-crystallin and A^Ins-crystallin differby a peptide of 23 amino acids, these data suggest that the‘insert peptide’ in A^Ins-crystallin imparts propertieson this protein that are different from A-crystallin.     

Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization

A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (μAPPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different μAPPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in μAPPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production.     

Self-emulsifying drug delivery system for enhanced solubility of asenapine maleate: design,characterization, in vitro,ex vivo and in vivo appraisal

Self-emulsifying drug delivery systems (SES) were developed to improve oral bioavailability of asenapine maleate (ASM), an antipsychotic drug with challenging amphiphobic nature and extensive pre-systemic metabolism. ASM-SES was prepared by choosing the proportion of oil, surfactant, co-surfactant from constructed phase diagram. The in vitro and ex vivo evaluation was done. In vivo evaluation was done through pharmacokinetic and pharmacodynamic studies. Role of lymphatic absorption was studied by lymphatic absorption inhibition study. A formulation consisting of 9.9%, 59.4%, 29.7% and 1% of oil, surfactant, co-surfactant, and drug respectively was considered as optimized formulation. After various evaluation test, the globule size and zeta potential for optimized formulation (SES₄) were found to be 137.9?nm and ?28.8?mV respectively. A maximum of 99.64?±?0.16% of ASM was released from SES₄ in 60?minutes of time. The flux (ex vivo study) increased by 2.33 folds, which prove the enhanced release and permeation of ASM when loaded into SES. The animals administered with SES₄ showed higher activity and good pharmacodynamic response than the control and ASM-Suspension, which may be due to the greater availability of the drug. The maximum pharmacodynamic response was observed at the t_max determined by Pharmacokinetic studies. The bioavailability increased by 1.64 folds with 16.55?±?3.11% as extend of lymphatic absorption (r?=?0.9732). Good in vitro in vivo correlation was observed. ASM-SES is a novel approach to effectively deliver ASM and improve the oral bioavailability.     

The impacts of the sulphur emission regulation on the sulphur emission abatement innovation system in the Baltic Sea region

Clean Technologies and Environmental Policy - According to the Porter hypothesis, regulations on environmental emissions under certain conditions can promote eco-innovation. This is why the...     

Structural and electrical properties of Gd3+ ion substituted CoGdxFe(2-x)O4 nano-ferrites

Nano particles of CoGdxFe(2-x)O4, with x = 0.0, 0.1, 0.3, 0.5 have been prepared by chemical co-precipitation method. The as synthesized particles are annealed at 300 degrees C for two hours to improve crystallinity. The X-ray diffraction patterns reveal the single cobalt ferrite phase formation and the average crystallite size decreases to 7 nm in the Gd3+ ion doped sample (with x = 0.5) compared to 27 nm in case of un-doped cobalt ferrite sample. The electrical properties for the different compositions of Gd3+ ion substituted cobalt ferrite material were studied in the frequency range 100 Hz to 10 MHz at room temperature using WK impedance analyzer. It is found that the electrical conductivity of the samples increases with increasing Gd3+ ion concentration. The results of our investigations reveal a strong dependence of material properties on Gd3+ ion doping.