A Stacking Fault Energy Perspective into the Uniaxial Tensile Deformation Behavior and Microstructure of a Cr-Mn Austenitic Steel

A Cr-Mn austenitic steel was tensile strained in the temperature range 273 K (0 °C) ≤ T ≤ 473 K (200 °C), to improve the understanding on the role of stacking fault energy (SFE) on the deformation behavior, associated microstructure, and mechanical properties of low-SFE alloys. The failed specimens were studied using X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The SFE of the steel was estimated to vary between ~ 10 to 40 mJ/m² at the lowest and highest deformation temperatures, respectively. At the ambient temperatures, the deformation involved martensite transformation (i.e., the TRIP effect), moderate deformation-induced twinning, and extended dislocations with wide stacking faults (SFs). The corresponding SF probability of austenite was very high (~10^?2). Deformation twinning was most prevalent at 323 K (50 °C), also resulting in the highest uniform elongation at this temperature. Above 323 K (50 °C), the TRIP effect was suppressed and the incidence of twinning decreased due to increasing SFE. At elevated temperatures, fine nano-sized SF ribbons were observed and the SF probability decreased by an order (~10^?3). High dislocation densities (~10¹⁵ m^?2) in austenite were estimated in the entire deformation temperature range. Dislocations had an increasingly screw character up to 323 K (50 °C), thereafter becoming mainly edge. The estimated dislocation and twin densities were found to explain approximately the measured flow stress on the basis of the Taylor equation.     

Biodistribution and gene expression of lipid/plasmid complexes after systemic administration

The objectives of this study were to investigate the influence of physicochemical properties of lipid/plasmid complexes on in vivo gene transfer and biodistribution characteristics. Formulations based on 1,2-di-O-octadecenyl-3-trimethylammonium propane (DOTMA) and novel biodegradable cationic lipids, such as ethyl dioleoyl phosphatidylcholine (EDOPC), ethyl palmitoyl myristyl phosphatidylcholine (EPMPC), myristyl myristoyl carnitine ester (MMCE), and oleyl oleoyl L-carnitine ester (DOLCE), were assessed for gene expression after tail vein injection of lipid/plasmid complexes in mice. Gene expression was influenced by cationic lipid structure, cationic lipid-to-colipid molar ratios, plasmid-to-lipid charge ratios, and precondensation liposome size. Detectable levels of human growth hormone (hGH) in serum, human factor IX (hFIX) in plasma, and chloramphenicol acetyltransferase (CAT) in the lung and liver were observed with positively charged lipid/plasmid complexes prepared from 400-nm extruded liposomes with a cationic lipid-to-colipid ratio of 4:1 (mol/mol). Intravenous administration of lipid/CAT plasmid complexes resulted in distribution of plasmid DNA mainly to the lung at 15 min after injection. Plasmid DNA accumulation in the liver increased with time up to 24 hr postinjection. There was a 10-fold decrease in the amount of plasmid DNA in the lung at 15 min after injection, when the lipid/plasmid complex charge ratio was decreased from 3:1 to 0.5:1 (+/-). Bright fluorescent aggregates were evident in in vivo-transfected lung with the positively charged pCMV-CAT/DOLCE:dioleyl phosphatidylethanolamine (DOPE) (1:1, mol/mol) complexes, while more discrete punctate fluorescence was observed with a 4:1 molar ratio of cationic lipid:colipid formulations. Preinjection of polyanions such as plasmid, dextran sulfate, polycytidic acid, and polyinosinic acid decreased hGH expression, whereas the preinjection of both positively charged and neutral liposomes had no effect on hGH serum levels. Of the cationic lipids tested, DOLCE was found to be the most effective potentially biodegradable cationic lipid. A correlation between gene expression and cationic lipid:colipid ratios and lipid-to-plasmid charge ratio was also observed for DOTMA- and DOLCE-based formulations.     

Unsteady state mass transfer coefficients controlling steel pipe corrosion under isothermal flow conditions

Corrosion tests of commercial steel pipe in aerated natural water under variable flow isothermal conditions were made by weight loss determinations over periods up to 210 days. The porosity, density, and the average thickness of the corrosion product layer were determined. Friction coefficients were evaluated through precise pressure drop measurements as a function of exposure time for the various flow rates (Reynolds number range 4000–25,000).The corrosion mechanism was analysed as a mass transfer operation by considering all the plausible unsteady state process characteristics, involving growth of corrosion product on the metal surface and change of surface roughness. The general mathematical model postulated from that analysis fitted the experimental data with acceptable precision. The model permitted, using corrosion data only, the prediction of values for the porosity and friction coefficient which were in good agreement with the experimental data. The average thickness of the damped turbulence layer for the smooth pipe was also calculated from the corrosion data, using the same model, and showed an excellent agreement with values estimated from usual hydrodynamic relationships.The effect of the surface roughness on the mass transfer coefficients in the damped turbulence layer, K_L, and in the corrosion product layer, K_s, were examined in detail. It was found that K_L controls the overall mass transfer process for the time range and flow rate range examined.     

Synthesis and characterization of some PLNZT ceramics

Powder of sodium doped polycrystalline samples of PLZT with composition Pb_0.98(La_{_1–x/3}Na _x )_0.02(Zr_0.53 Ti_0.47)_0.9950·O₃ (PLNZT) with x=0.5 was systematically prepared using spray drying technique. Rhombohedral phase of PLNZT compound has been confirmed after being calcined at 800 °C. DTA–TGA and XRD studies were used to characterize the compound synthesized. SEM was used for micro-structural evaluation. The dielectric constant () and loss tangent (tan ) of the compound were studied at different temperatures at 10 kHz frequency, which suggests that the compound undergoes a ferro-electric phase transition of diffuse type.     

Osteoradionecrosis (ORN) of the mandible: a laser Raman spectroscopic study

Laser Raman spectroscopy has been used in this study to characterize mandibular bone samples from patients who had undergone radiation therapy for oral cancer. The paper discusses spectral changes resulting in osteoradionecrosis (ORN) of the mandibular bone, a serious complication that may occur after radiation therapy. Histopathological studies normally reveal the radiation damage on vascular canals and loss in bone cells, but will not reveal any structural or biochemical changes. All radiation-induced side effects are attributed to this hypovascularity and hypocellularity caused by early- and/or late-delayed effects. Our Raman studies on normal and ORN bone and on bone exposed to radiation, but not in the ORN state, show that irradiation produces immediate structural changes in the inorganic bone matrix with a slight loss in cells. ORN bone, in addition to the structural changes that had already occurred on radiation exposure, shows almost complete loss of cellular components. Since bone tissue is continuously being remodeled (dissolved and rebuilt) under normal conditions, our results suggest that the immediate structural changes in the calcium hydroxy apatite mineral part is not repaired in ORN, due to loss of the highly transient osteoblasts and osteoclasts resulting from destruction of stem cells. The spectral studies also show changes in the organic matrix, which is mostly type I collagen.     

Dielectric,Impedance and Conduction Behavior of Double Perovskite Pr<Subscript>2</Subscript>CuTiO<Subscript>6</Subscript> Ceramics

Polycrystalline Pr₂CuTiO₆ (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz–1 MHz) and temperature (303–593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole–Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance (Z″) and the normalized imaginary part of modulus (M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed.     

Fractal dimension of synthesized and natural color images in Lab space

Pattern Analysis and Applications - Fractal dimension (FD) is a useful metric for the analysis of natural images that exhibit a high degree of complexity, randomness and irregularity in color and...     

Synthesis and characterization of novel silicone acrylate–soya alkyd resin as binder for long life exterior coatings

A polymeric binder on soya alkyd, silicone intermediate and 2-hydroxyethyl metacrylate has been synthesized for formulation of long life exterior coating. Initially silicone acrylate monomer (SAM) was prepared by reacting hydroxyl-terminated silicone and 2-hydroxyl ethyl methacrylate (HEMA) and characterized by Fourier transformer infrared spectroscopy (FTIR) and carbon nuclear magnetic resonance spectroscopy (¹³C NMR). SAM was used in varying concentrations to synthesize novel soya alkyd resin. The unpigmented polymer film obtained from silicone acrylate–soya alkyd resin exhibits excellent mechanical properties and good exterior durability compared to silicone modified alkyd resin.     

Measuring the robustness of neighbourhood business districts

A key component of vibrant urban neighbourhoods is the neighbourhood business district (NBD) – the place for amenities, shopping, social engagement and recreation. In order to provide these advantages and be competitive with big box and online retailers, the NBD must be easily accessible and provide a basic range of goods and services. Yet few tools exist that measure both the access and completeness of amenities on NBDs. This paper presents a systematic analysis and provides cities with a tool to assess NBDs and create policies and programmes to support more complete, robust and useful neighbourhood business districts.