Morphology and structural properties of pH-responsive amphiphilic peptides

Protein nanomaterials at the peptide level have shown great potential for medical applications. Peptides change their morphological conformation because of changes in self-assembly properties when they are exposed to changes in solvent composition or pH. Two 15-residue peptide sequences, KhK (KKKFLIVIGSIIKKK) and Alternating Kh (KFLKKIVKIGKKSII), were designed for the purpose of determining the role of peptide sequence on solution morphology and conformation. KhK solutions exhibited a random coil to helical transition when solvent conditions were changed from water to a trifluorethanol/water solution at acidic pH. Alternating Kh solutions, however, demonstrated primarily random coil character under similar solvent and pH conditions as determined by circular dichroism spectroscopy and 2D-1H-1H nuclear magnetic resonance spectroscopy. At basic pH, circular dichroism spectroscopy and nuclear magnetic resonance spectroscopy analysis demonstrated that random coil character increased at basic pH for KhK, whereas Alternating Kh exhibited an increase in beta-sheet character. Further analysis by transmission electron microscopy showed marked differences in the peptide solution morphology. Peptide particle aggregation and fiber formation were significantly affected by solvent composition and pH values for both peptide sequences.     

Prevalence and toxin type of Clostridium perfringens in beef from four different types of meat markets in Seoul,Korea

Food Science and Biotechnology - Beef is the primary source of foodborne poisoning caused by Clostridium perfringens. We investigated the prevalence of C. perfringens in retail beef from four...     

Electrical conduction behavior and immittance analysis of Gd and Mn substituted strontium titanate

Various compositions in the system Sr_1−x Gd _x Ti_1−x Mn _x O₃ (x ≤ 0.50) were synthesized by solid-state ceramic route. Solid solution forms in all the compositions investigated. Crystal structure remains cubic up to x = 0.10 similar to SrTiO₃, while for compositions with x ≥ 0.30, it becomes orthorhombic, similar to GdMnO₃. Average grain size is small in all the compositions investigated, and it decreases with increasing x. For compositions with x ≤ 0.30, Seebeck coefficient is initially positive. It becomes negative at higher temperatures. For x = 0.50, it is negative over the entire temperature range of measurements. Immittance analysis shows the presence of two polarization processes, one due to grains and other due to grain boundaries. Results of DC resistivity, ρ_dc and Seebeck coefficient, α as a function of temperature show that in the samples with x ≤ 0.30, in the lowest temperature range conduction occurs due to hopping of holes among Mn⁺³ and Mn⁴⁺ ions, and for x = 0.50 it occurs due to hopping of electrons among Mn²⁺ and Mn³⁺ ions over the entire temperature range. In the intermediate temperature range, for x ≤ 0.30 the conduction occurs by hopping of electrons among Mn²⁺ and Mn³⁺ ions. For x = 0.01 and 0.05 conduction occurs due to diffusion of oxygen ions through doubly positively charged oxygen vacancies in the highest temperature range.     

Exceptionally High Dielectric Constant in Ceramic Pr2CuO4

The pristine layered cuprate Pr₂CuO₄ samples of >95% density were fabricated as thin disks. The samples, analyzed by X‐ray diffraction and Scanning electron microscopy, showed clean T′‐type phase with Rietveld refined lattice parameters a = b = 3.95805(±5) Å and c = 12.2262(±5) Å. The measured dielectric properties of the Pr₂CuO₄ ceramics, in the temperature range ?100°C–150°C and frequencies (ν) 0.1 Hz–1 MHz, showed extremely high ε_r′ > 10⁴ (above ?30°C), and dissipation (tan δ = ε_r′′/ε_r′) between 0.1 and 5 (for 500 Hz ≤ ν ≤ 1 MHz, and ?100 ≤ T ≤ 150°C). The ac conductivity of Pr₂CuO₄ ceramics ranged between 10^?6 and 10^?3 Scm^?1 for the measured frequencies and temperatures, and showed frequency‐dependent double power law behavior akin to a modified Jonscher's power law.     

Influence of Soret and Dufour on mixed convection flow across a vertical cone

This contribution examines the influence of Soret and Dufour on an incompressible viscous fluid flow across a vertical cone. The flow model is framed in the form of mathematical governing equations and a nondimensionalization is performed on them for ease of the numerical computations' examination; the obtained nonsimilarity equations are solved numerically through the bivariate Chebyshev spectral collocation quasi-linearization method. Outcomes of the flow characteristics, velocity, temperature, concentration, skin friction rate, heat, and mass transfer rates are analyzed with the variations of governing parameters, Prandtl number, buoyancy parameter, Schmidt number, buoyancy ratio, Soret and Dufour parameters at various stream-wise spots of the flow. To certify the exactness of the listed computations, we performed a comparison with prior published computations, which were found with great agreement, and the residual analysis study was also portrayed to reflect the convergence and stability of the adopted numerical technique.     

Overall efficiency enhancement and cost optimization of semitransparent photovoltaic thermal air collector

A semitransparent photovoltaic‐thermal (PV/T) air collector can produce electricity and heat simultaneously. To maximize the thermal and overall efficiency of the semitransparent PV/T air collector, its availability should be maximum; this can be determined through a Markov analysis. In this paper, a Markov model is developed to select an optimized number of semitransparent PV modules in service with five states and two states by considering two parameters, namely failure rate ( λ ) and repair rate (µ). Three artificial neural network (ANN) models are developed to obtain the minimum cost, minimum temperature, and maximum thermal efficiency of the semitransparent PV/T air collector by setting its type appropriately and optimizing the number of photovoltaic modules and cost. An attempt is also made to achieve maximum thermal and overall efficiency for the semitransparent PV/T air collector by using ANN after obtaining its minimum temperature and available solar radiation.     

Neutralization of Acid Mine Drainage Contaminated Water and Ecorestoration of Stream in a Coal Mining Area of East Jaintia Hills,Meghalaya

Mine Water and the Environment - The unscientific mining of coal without environmental safeguards in Jaintia Hills, Meghalaya has adversely affected the water resources of the area, leading to...     

Currents Induced in a Human Being for Plane-Wave Exposure Conditions 0-50 MHz and for RF Sealers

The currents induced in a human being were measured for plane-wave exposure conditions 0-50 MHz. These are used to point out that very large SAR's may be set up in the wet tissues for the cross section of the ankle for standing human beings exposed to electric fields suggested in the ANSI C95.1-1982 RF safety guide. For these exposure conditions, foot currents on the order of 627 mA are projected for a human adult of height 1.75 m for the frequency band 3-30 MHz with the value increasing to 780 mA for 40 MHz. The corresponding ankle-section SAR's are 182 and 243 W/kg. Using electromagnetic scaling concepts, SAR's as high as 371 and 534 W/kg are projected for ten- and five-year old children, respectively, for f = 50.7 and 62.5 MHz, E = 61.4 V/m (1 mW/cm2) recommended by the ANSI C95.1-1982 RF safety guide. The paper also gives currents induced by two sealer models and three industrial RF sealers for a human being under grounded and insulated conditions. Though smaller than those for plane-wave irradiation conditions, these currents may be substantial for high leakage fields that are quite typical.