Multi Response Optimization on Machinability of SiC Waste Fillers Reinforced Polymer Matrix Composite Using Taguchi’s Coupled Grey Relational Analysis

Silicon - Recycling and reutilization of industrial waste is one way to minimize land pollution to attain green environment. In this research waste SiC grinding wheel was ball milled to powder form...     

Issues and Requirements for Aluminum Alloys Used in Aircraft Components: State of the Art

Russian Journal of Non-Ferrous Metals - Aluminum alloys have always been the material of choice for the aircraft industry owing to their versatile attributes, such as excellent strength to weight...     

Studies of dielectric relaxation and a.c. conductivity in [(100−<Emphasis Type="Italic">x</Emphasis>)PEO + <Emphasis Type="Italic">x</Emphasis>NH<Subscript>4</Subscript>SCN]: Al-Zn ferrite nano composite polymer electrolyte

Present work deals with findings on dielectric behaviour and a.c. conduction in a ferrite doped polymer nano composite electrolyte system, namely [(100−x) PEO + xNH₄SCN]: ferrite. The formation of nano composite and structural behavior of electrolyte was studied by XRD and SEM images. The effect of salt and ferrite on conductivity behaviour of PEO based nano composite polymer electrolyte has been investigated by the impedance spectroscopy at room temperature. The variation of dielectric permittivity and dielectric loss with frequency was carried out at ambient temperature. The a.c. conductivity seems to follow the universal power law.     

Effect of Repetitive Lysine-Tryptophan Motifs on the Eukaryotic Membrane

In a previous study, we synthesized a series of peptides containing simple sequence repeats, (KW)_n–NH₂ (n = 2,3,4 and 5) and determined their antimicrobial and hemolytic activities, as well as their mechanism of antimicrobial action. However, (KW)₅ showed undesirable cytotoxicity against RBC cells. In order to identify the mechanisms behind the hemolytic and cytotoxic activities of (KW)₅, we measured the ability of these peptides to induce aggregation of liposomes. In addition, their binding and permeation activities were assessed by Trp fluorescence, calcein leakage and circular dichrorism using artificial phospholipids that mimic eukaryotic liposomes, including phosphatidylcholine (PC), PC/sphingomyelin (SM) (2:1, w/w) and PC/cholesterol (CH) (2:1, w/w). Experiments confirmed that only (KW)₅ induced aggregation of all liposomes; it formed much larger aggregates with PC:CH (2:1, w/w) than with PC or PC:SM (2:1, w/w). Longer peptide (KW)₅, but not (KW)₃ or (KW)₄, strongly bound and partially inserted into PC:CH compared to PC or PC:SM (2:1, w/w). Calcein release experiments showed that (KW)₅ induced calcein leakage from the eukaryotic membrane. Greater calcein leakage was induced by (KW)₅ from PC:CH than from PC:SM (2:1, w/w) or PC, whereas (KW)₄ did not induce calcein leakage from any of the liposomes. Circular dichroism measurements indicated that (KW)₅ showed higher conformational transition compared to (KW)₄ due to peptide-liposome interactions. Taken together, our results suggest that (KW)₅ reasonably mediates the aggregation and permeabilization of eukaryotic membranes, which could in turn explain why (KW)₅ displays efficient hemolytic activity.     

PG-2, a Potent AMP against Pathogenic Microbial Strains,from Potato (Solanum tuberosum L cv. Gogu Valley) Tubers Not Cytotoxic against Human Cells

In an earlier study, we isolated potamin-1 (PT-1), a 5.6-kDa trypsin-chymotrypsin protease inhibitor, from the tubers of a potato strain (Solanum tuberosum L cv. Gogu Valley). We established that PT-1 strongly inhibits pathogenic microbial strains, but not human bacterial strains, and that its sequence shows 62% homology with a serine protease inhibitor. In the present study, we isolated an antifungal and antibacterial peptide with no cytotoxicity from tubers of the same potato strain. The peptide (peptide-G2, PG-2) was isolated using salt-extraction, ultrafiltration and reverse-phase high performance liquid chromatography (RP-HPLC). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) showed the protein to have a molecular mass of 3228.5 Da, while automated Edman degradation showed the N-terminal sequence of PG-2 to be LVKDNPLDISPKQVQALCTDLVIRCMCCC-. PG-2 exhibited antimicrobial activity against Candida albicans, a human pathogenic yeast strain, and Clavibacter michiganensis subsp. michiganensis, a plant late blight strain. PG-2 also showed antibacterial activity against Staphylococcus aureus, but did not lyse human red blood cells and was thermostable. Overall, these results suggest PG-2 may be a good candidate to serve as a natural antimicrobial agent, agricultural pesticide and/or food additive.     

Defect-Chemical Aspects in the Synthesis of Metallic Conductors La1–xBaxCuO3 (x= 0.0 to 0.5)

Compositions of La_{1- x} Ba _x CuO₃, where x ranges from 0.0 to 0.5, were fired in air, oxygen-enriched air, and oxygen. Studies show that BaO cannot make a solid solution with LaCuO₃ without changing the basic structure. The resulting phases, in all attempts, were the binary compounds La₂CuO₄, La_{1- x} Ba _x CuO_3-δ ( x = 0.2 to 0.5), or their mixtures. All samples showed metallic conductivity. Extra oxygen in the reaction atmosphere appeared to encourage the formation of the LaCuO₃-based phases of La_{1- x} Ba _x CuO_3-δ ( x = 0.2 or 0.5). We provide a defect-chemical and thermodynamical explanation for this observation.     

Numerical simulation and experimental investigation of gas–powder flow from radially symmetrical nozzles in laser-based direct metal deposition

Laser-based direct metal deposition (DMD) is a solid freeform fabrication process capable of fabricating fully dense and metallurgically sound parts. The process has been greatly enhanced toward multi-directional deposition by the use of discontinuous radially symmetrical powder nozzles to supply the build material. Since many operational parameters depend on the gas–powder stream characteristics between the nozzles and the deposition point, an extensive understanding of the gas–powder flow is necessary. Three-dimensional (3D) multi-phase gas–powder flow structures of radially symmetrical nozzles are modeled using computational fluid dynamics methods. The obtained results are in good agreement with the experimental ones, and they provide a good insight into the process phenomena.     

Contribution of dislocations to the zero-bias resistance-area product of LWIR HgCdTe photodiodes at low temperatures

Dislocations in the base material are shown to significantly influence zero-bias impedance of long wavelength infrared HgCdTe photodiodes by acting as a shunt, and by influencing their minority carrier lifetime. Consequently, temperature dependence of zero-bias resistance-area product (R/sub 0/A) of these photodiodes can be described very well over a broad temperature range, down to 25 K, after taking into account the temperature and dislocation dependence of the minority carrier lifetime in addition to the shunt resistance contribution of dislocations. Further, based on the theoretical prediction that the shunt resistance contribution of a dislocation is a sensitive function of the magnitude of the charge around its core, it is proposed that the scatter of the R/sub 0/A experimental data in diodes with dislocation densities of less than 1/spl times/10/sup 7/ cm/sup -2/ could be the result of statistical variations in the charge around the core of dislocations. Interaction of dislocations among themselves may be responsible for deviations above dislocation densities of 1/spl times/10/sup 7/ cm/sup -2/.     

Excipients in parenteral formulations: selection considerations and effective utilization with small molecules and biologics

Excipients form a major component of pharmaceutical formulations and are classified as any ingredient other than the active ingredient which is included within the product formulation to improve drug product performance. Functional uses of excipients include improving solubility and stability, safety and efficacy, as bulking agents in lyophilized formulations, tonicity agents, and aiding in controlled or prolonged drug delivery. Parenteral formulations are sterile, pyrogen-free; free of particulate matter and by-pass the body’s natural defense mechanisms. Excipients may demonstrate a synergistic effect when combined with an active ingredient but may also lead to unwanted reactions with the drugs and packaging components. Ideal excipients are required to be considered safe, inert and multifunctional. Contrary to the past, safety of excipients needs to be well established in order for their use in the pharmaceutical formulations. Therefore, careful consideration should be given while selecting an excipient. This review article provides an overview of the excipients used exclusively in small molecule and biological parenteral products including solutions, suspensions, and lyophilized formulations, information on the possible drug-excipient and drug-packaging interactions and the regulatory requirements for the use of pharmaceutical excipients. The readers will be able to have a comprehensive understanding of the excipients used in parenteral formulations.     

Dielectric relaxation studies on [PEO–SiO<Subscript>2</Subscript>]:NH<Subscript>4</Subscript>SCN nanocomposite polymer electrolyte films

Present work deals with findings on dielectric relaxation behaviour and a.c. conduction in a SiO₂-doped polymer nanocomposite electrolyte system, namely, [(100 − x)PEO + xSiO₂]:yNH₄SCN. The formation of nanocomposite has been ascertained by XRD measurements. The effect of salt and filler (SiO₂) on conductivity response of PEO-based nanocomposite polymer electrolyte has been investigated by impedance spectroscopy. The variation of dielectric permittivity, dielectric loss and modulus spectra with frequency and temperature was carried out from impedance spectroscopy data. The a.c. conductivity seems to follow the universal power law.