In-Situ Nuclear Magnetic Resonance Investigation of Strain, Temperature, and Strain-Rate Variations of Deformation-Induced Vacancy Concentration in Aluminum

Critical strain to serrated flow in solid solution alloys exhibiting dynamic strain aging (DSA) or Portevin–LeChatelier effect is due to the strain-induced vacancy production. Nuclear magnetic resonance (NMR) techniques can be used to monitor in situ the dynamical behavior of point and line defects in materials during deformation, and these techniques are nondestructive and noninvasive. The new CUT-sequence pulse method allowed an accurate evaluation of the strain-enhanced vacancy diffusion and, thus, the excess vacancy concentration during deformation as a function of strain, strain rate, and temperature. Due to skin effect problems in metals at high frequencies, thin foils of Al were used and experimental results correlated with models based on vacancy production through mechanical work (vs thermal jogs), while in situ annealing of excess vacancies is noted at high temperatures. These correlations made it feasible to obtain explicit dependencies of the strain-induced vacancy concentration on test variables such as the strain, strain rate, and temperature. These studies clearly reveal the power and utility of these NMR techniques in the determination of deformation-induced vacancies in situ in a noninvasive fashion.

केंद्रीय समुद्री मात्स्यिकी अनुसंधान संस्थान मुख्यालय कोचीन

केंद्रीय समुद्री मात्स्यिकी अनुसंधान संस्थान मुख्यालय कोची

Variant translocation with a deletion of derivative (9q) in a case of Philadelphia chromosome positive (Ph +) essential thrombocythemia (ET), a variant of Chronic Myelogenous Leukemia (CML) with a poor prognosis

Patients presenting with thrombocytosis require thorough clinical and laboratory evaluation to determine whether they suffer from essential thrombocythemia or another myeloproliferative disorder. This distinction becomes increasingly relevant as targeted agents become available to treat specific myeloproliferative diseases. Cytogenetic testing plays a major role in this analysis. This study presents a patient with Philadelphia chromosome positive (Ph+) thrombocytosis and a cryptic der(9q)t(5;9)t(9;22) not found by conventional cytogenetics, whose disease progressed within 2 years to typical myeloblastic crisis of CML. It discusses the entity of Ph + ET, the utility of molecular cytogenetic testing in the diagnosis of this unusual disease entity and the importance of cytogenetic testing in the prognosis of ET

On amorphization and nanocomposite formation in Al-Ni-Ti system by mechanical alloying

Amorphous structure generated by mechanical alloying (MA) is often used as a precursor for generating nanocomposites through controlled devitrification. The amorphous forming composition range of ternary Al-Ni-Ti system was calculated using the extended Miedema's semi-empirical model. Eleven compositions of this system showing a wide range of negative enthalpy of mixing (-ΔH mix) and amorphization (-ΔH amor) of the constituent elements were selected for synthesis by MA. The Al88Ni6Ti6 alloy with relatively small negative ΔH mix (-0.4 kJ/mol) and ΔHamor (-14.8 kJ/mol) became completely amorphous after 120 h of milling, which is possibly the first report of complete amorphization of an Al-based rare earth element free Al-TM-TM system (TM = transition metal) by MA. The alloys of other compositions selected had much more negative ΔHmix and Hamor; but they yielded either nanocomposites of partial amorphous and crystalline structure or no amorphous phase at all in the as-milled condition, evidencing a high degree of stability of the intermetallic phases under the MA environment. Hence, the negative ΔH mix and ΔH amor are not so reliable for predicting the amorphization in the present system by MA

Beneficiation of Indian Heavy Mineral Sands- Some New Possibilities Identified by Tata Steel

Titanium, the 9th most abundant element on the earth's crust, is available mostly (90%)in the form of ilmenite (FeO.TiO2) and leucoxene (weathered ilmenite). These titanium bearing minerals occur either as placer minerals or some times, as rock deposits (e.g. in canada and Norway

A localised chlorophyll deficiency associated with male sterility in Nicotiana tabacum L.

This article does not have an abstract

High prevalence of subclinical hypothyroidism in pregnant women in South India

Background: Thyroid dysfunction is one of the commonest endocrinopathies seen in pregnancy and affects both maternal and fetal outcomes. There is little data available on its prevalence in Indian pregnant women. This study was conducted at Bhaskar medical college and hospital situated in a rural/suburban area near Hyderabad, Telengana, India. The aim of the study was to find out the prevalence of thyroid disease among pregnant women.  Methods: All consecutive pregnant women registered from January 2014 to December 2014 were included in the study. Morning samples of serum were tested for T3, T4 and TSH.  Results: A total of 1340 women were included in the study. 260 pregnant women (19.41%) had TSH values more than 3.0 mIU/L, the cut-off value used for upper limit of normal in this study. Out of these, 216 had normal T4 value, hence labeled as subclinical hypothyroidism and 44 had low T4, hence termed overt hypothyroidism. Three pregnant women had overt hyperthyroidism and 11 had subclinical hyperthyroidism. Nine women had low T4 values-Isolated hypothyroidism.Conclusions: Prevalence of thyroid disease in pregnancy was found to be higher in our patients, more so the sub clinical hypothyroidism

In situ nuclear magnetic resonance study of defect dynamics during deformation of materials

Nuclear magnetic resonance techniques can be used to monitor in situ the dynamical behaviour of point and line defects in materials during deformation. These techniques are non-destructive and non-invasive. We report here the atomic transport, in particular the enhanced diffusion during deformation by evaluating the spin lattice relaxation time in the rotating frame, T-1p, in pure NaCl single crystals as a function of temperature (from ambient to about 900 K) and strain-rate (to approximate to 1.0s(-1)) in situ during deformation. The strain-induced excess vacancy concentration increased with the strain-rate while in situ annealing of these excess defects is noted at high temperatures. Contributions due to phonons or paramagnetic impurities dominated at lower temperatures in the undeformed material. During deformation, however, the dislocation contribution became predominant at these low temperatures. The dislocation jump distances were noted to decrease with increase in temperature leading to a reduced contribution to the overall spin relaxation as temperature is increased. Similar tests with an improved pulse sequence (CUT-sequence), performed on ultra-pure NaCl and NaF single crystals revealed slightly different results; however, strain-enhanced vacancy concentrations were observed. The applicability of these techniques to metallic systems will be outlined taking thin aluminium foils as an example

Formation of a nickel hydroxide monolayer on Au through a self-assembled monolayer of 5,5'-dithiobis(2-nitrobenzoic acid): voltammetric, SERS and XPS investigations of the modified electrodes

The formation of self-assembled monolayers (SAM) of 5,5'-dithiobis (2-nitrobenzoic acid), DNBA on gold has enabled further derivatization of the electrode surface with functional moieties anchored to the surface bound molecules. A SAM of DNBA was formed on the Au surface. Nickel ions tethered to the SAM-covered Au surface, were subsequently derivatized electrochemically to yield nickel hydroxide overlayers, thereby showing the possibility of preparing ultra-thin films of metal oxides through solution chemistry. The nickel hydroxide surface coverage obtained on bare and SAM-covered electrodes was estimated from voltammetric peaks and it varied from one monolayer to about 300 monolayers. The formation of a monolayer of nickel hydroxide has been achieved for the first time by electrochemical modification. Further, the modified electrodes were subjected to SERS and XPS studies to understand their surface characteristics. Modified electrodes provide a catalytic pathway involving nickel hydroxide for the electro-oxidation of glucose in alkaline solutions

Radioactive isotopes reveal a non sluggish kinetics of grain boundary diffusion in high entropy alloys

High entropy alloys (HEAs) have emerged as a new class of multicomponent materials, which have potential for high temperature applications. Phase stability and creep deformation, two key selection criteria for high temperature materials, are predominantly influenced by the diffusion of constituent elements along the grain boundaries (GBs). For the first time, GB diffusion of Ni in chemically homogeneous CoCrFeNi and CoCrFeMnNi HEAs is measured by radiotracer analysis using the $^{63}$Ni isotope. Atom probe tomography confirmed the absence of elemental segregation at GBs that allowed reliable estimation of the GB width to be about 0.5 nm. Our GB diffusion measurements prove that a mere increase in number of constituent elements does not lower the diffusion rates in HEAs, but the nature of added constituents plays a more decisive role. The GB energies in both HEAs are estimated at about 0.8-0.9 J/m$^2$, they are found to increase significantly with temperature and the effect is more pronounced for the CoCrFeMnNi alloy.Comment: 11 pages, 9 figure