Studies on structural transformation and magnetic properties in Sm2Co17 type alloys

Structural transformations and microstructural characterisation of Sm₂Co₁₇ alloys containing Fe, Cu and Zr at different stages of thermal processing have been investigated by X-ray diffraction, optical, scanning electron and transmission electron microscopes. Solution treated samples consist of a mixture of hexagonal TbCu₇ (1:7 H) and rhombohedral Th₂Zn₁₇ (2:17 R) structure types of 2:17 phase. After isothermal aging, TbCu₇ + Th₂Zn₁₇ structures transform into Th₂Zn₁₇ type structure with precipitation of Cu-rich hexagonal SmCo₅ (1:5 H) and Zr-rich platelet phases. In addition to the main phases, a soft magnetic phase of composition Zr₆(FeCo)₂₃ is formed in alloys containing higher Zr composition. Isothermal aging studies reveal that magnetic properties show a peak value when aged at 1108–1123 K for 10 h. TEM studies show cellular precipitate structure with cell interiors having 2:17 R structure, while the fully coherent cell boundaries have the 1:5 H structure. Zr-rich platelets which run across many cells and cell boundaries were found to have 1:7 H structure.     

Structure of poly d(AI).poly d(CT) in two different packing arrangements

X-ray diffraction analysis of poly d(AI).poly d(CT) in oriented and polycrystalline fibers has revealed the DNA structure to be a 10-fold, right-handed, antiparallel, Watson-Crick base paired double helix in two distinct packing arrangements corresponding to one and two helices, respectively, in the unit cell. The helix pitch is 32.1 A and 32.4 A in the two cases, almost 1.5 A shorter than in classical B-DNA. The resulting B'-DNA geometry, described in terms of a tetranucleotide repeat which is conformationally similar to B-DNA, has its minor groove closely shut and major groove correspondingly widened, thus striking a sharp morphological contrast to B-DNA. According to difference electron density maps, a spine of hydration along the minor groove connects both strands and provides structural stability; ordered sodium ions and water molecules are actively involved in bridging the phosphate groups of neighboring helices. The crystallographic R-values for these two allomorphs are 0.26 and 0.20, respectively, for data up to 3.0 A resolution.     

Molecular dynamics (MD) simulation of uniaxial tension of some single-crystal cubic metals at nanolevel

Molecular Dynamics (MD) simulations of uniaxial tension at nanolevel have been carried out at a constant rate of loading (500 ms⁻¹) on some single-crystal cubic metals, both FCC (Al, Cu, and Ni) and BCC (Fe, Cr, and W) to investigate the nature of deformation and fracture. Failure of the workmaterials due to void formation, their coalescence into nanocracks, and subsequent fracture or separation were observed similar to their behavior at macroscale. The engineering stress–strain diagrams obtained by the MD simulations of the tensile specimens of various materials show a rapid increase in stress up to a maximum followed by a gradual drop to zero when the specimen fails by ductile fracture. The radius of the neck is found to increase with an increase in the deformation of the specimen and to decrease as the ductility of the material decreases. In this investigation, the strain to fracture is observed to be lower with the BCC materials than FCC materials. In the case of BCC crystals, no distinct linear trend in the engineering stress–strain characteristics is observed. Instead, rapid fluctuations in the force values were observed. If the drop in the force curves can be attributed to the rearrangement of atoms to a new or modified crystalline structure, it appears that BCC materials undergo a significant change in their structure and subsequent realignment relative to the FCC materials, as previously reported in the literature. While good correlation is found between the D- and α-parameters of the Morse potential with the ultimate strength and the strain to failure for the FCC metals, no such correlation is found for the BCC metals. From this, it appears that Morse potentials may not represent the deformation behavior of BCC metals as accurately as FCC metals and alternate potentials may need to be considered.     

Innovative Methods for the Investigation of Tool-Chip Adhesion and Layer Formation during Machining

Tool-chip and tool-work adhesion often limit machinability, but quantitative methods to characterise adhesion are absent. Hence, a methodology based on interrupted turning was used and layer formation was quantified using a number of techniques. This included surface topography studies using 3D white light interferometry, element mapping and profiling using SEM-EDS and Laser ablation time of flight mass spectrometry (LA -TOFMS) along with temperature mapping using IR-CCD. Results from turning tests with stainless steel 316L indicate clearly that the above techniques compliment each other and provide valuable new insight on contact friction, adhesion and layer formation.     

Study of the feasibility of involving male student volunteers in case holding in an urban tuberculosis programme

AIMS: To investigate the effect of the angiotensin converting enzyme inhibitor, benazepril, on pulmonary function. METHODS: We investigated the influence of benazepril, on lung function and the interaction with inhaled salbutamol (0.1 to 6.6 mg) and histamine (0.03 to 30.69 g l-1) in normal subjects. Benazepril 20 mg, salbutamol 8 mg, propranolol 160 mg, and placebo were given orally once daily over 10 days. RESULTS: On day 8, there was no difference in the area under the salbutamol dose-response curves between benazepril, placebo and oral salbutamol (P > 0.05), propranolol shifted the curves to the right (P < 0.05). On day 10, histamine challenge resulted in following PD35sGaw values (geometric mean and 95% CI): with placebo 1.02 (0.95-1.09) g l-1, benazepril 1.04 (0.99-1.08), salbutamol 1.19 (1.13-1.25), propranolol 0.57 (0.50-0.65). CONCLUSIONS: Benazepril had no influence on baseline lung function, caused no interaction with inhaled salbutamol and the bronchial response to histamine was similar to placebo. However, our findings in normal subjects cannot be extrapolated automatically to asthmatics.     

X-ray and conformational analysis of arabinan

Fibers prepared from the enzymically debranched plant polysaccharide arabinan, containing (1-->5)-linked alpha-L-arabinofuranose residues, produce X-ray diffraction patterns containing concentric rings indicative of a high degree of structural organization. The measured unit cell dimensions and fiber density are consistent with a 2-fold helix passing through each unit cell. According to model-building techniques and energy calculations, a total of seven molecular structures (three with C2'-endo and four with C3'-endo sugars), all of pitch 8.74 A, and hence seven different crystal-packing arrangements are the most probable. While intrachain hydrogen bonds are only present in three cases, interhelix association is facilitated by hydrogen bonds in all allomorphs. Small energy differences between them suggest that easy conformational transitions may be made from one form to another. This polymorphism and the tendency to form microcrystals in the solid state might confer upon arabinan the observed fat mimetic properties.     

Polyaniline Salts and Complexes as Catalyst in Bisindole Synthesis

Polyaniline salts are prepared by doping of polyaniline base with different Bronsted acids (H₂SO₄, HNO₃ and H₃PO₄), organic acid — p-toluene sulfonic acid (PTSA) and Iodine (I₂). Polyaniline complexes are also prepared using Lewis acids (BF₃, AlCl₃ and SnCl₂). Polyaniline salts and polyaniline complexes are characterized by physical, electrical and spectral methods. Polyaniline salts and polyaniline complexes are used as catalyst for the first time in bisindole synthesis. Bisindole (3,3′-bis(indolyl)phenylmethane) is obtained in excellent yields with simple and more environmental benign procedure. The use of polyaniline catalysts are feasible because of their easy preparation, easy handling, stability, easy recovery, reusability, good activity and eco-friendly.     

Microenvironment of Tumor-Draining Lymph Nodes: Opportunities for Liposome-Based Targeted Therapy

The World Health Organization (WHO) recently reported that the total number of global cancer cases in 2013 reached 14 million, a 10% rise since 2008, while the total number of cancer deaths reached 8.2 million, a 5.2% increase since 2008. Metastasis is the major cause of death from cancer, accounting for 90% of all cancer related deaths. Tumor-draining lymph nodes (TDLN), the sentinel nodes, are the first organs of metastasis in several types of cancers. The extent of metastasis in the TDLN is often used in disease staging and prognosis evaluation in cancer patients. Here, we describe the microenvironment of the TDLN and review the recent literature on liposome-based therapies directed to immune cells within the TDLN with the intent to target cancer cells.     

Growth and characterization of hexamethylenetetramine crystals grown from solution

Organic nonlinear optical single crystals of hexamethylenetetramine (HMT; 10 × 10 × 5 mm³) were prepared by crystallization from methanol solution. The grown crystals were subjected to various characterization techniques such as single crystal XRD, powder XRD, UV-Vis and electrical studies. Single crystal XRD analysis confirmed the crystalline structure of the grown crystals. Their crystalline nature was also confirmed by powder XRD technique. The optical transmittance property was identified from UV-Vis spectrum. Dielectric measurements were performed as a function of frequency at different temperatures. DC conductivity and photoconductivity studies were also carried out for the crystal. The powder second harmonic generation efficiency (SHG) of the crystal was measured using Nd:YAG laser and the efficiency was found to be two times greater than that of potassium dihydrogen phosphate (KDP).     

Experimental study and modelling of tool temperature distribution in orthogonal cutting of AISI 316L and AISI 3115 steels

Cutting tool temperature distribution was mapped using the IR-CCD technique during machining of carbon steel AISI 3115 and stainless steel AISI 316L under orthogonal cutting conditions using flat-face geometry inserts. The effect of work material treatment on tool temperature was investigated, and the results showed that AISI 3115 in heat-treated state displayed higher tool temperature than the as-rolled state. Stainless steel 316L with high sulphur content (0.027?wt.%) and calcium treatment displayed lower cutting tool temperature than the variant with low sulphur (0.009?wt.%). The experimental results were compared with theoretical tool temperature distributions based on a modified version of Komanduri and Hou??s analytical model. In particular, variable frictional heat source and secondary shear were introduced and modelling of the tool stress distribution on rake surface was also considered.