Thermal analysis, X-ray diffraction, spectroscopy studies and magnetic properties of the new compound Tl2HAsO4.Te(OH)6

The Tl2HAsO4.Te(OH)6 (TlAsTe) compound crystallizes in the triclinic system P1 with unit cell parameters: a= 7.100(10) Å, b= 7.281(13) Å, c= 8.383(11) Å, α= 76.91(1)°, β= 87.16(1)°, γ= 66.96(2)°, Z= 2 and V= 388.19(1) Å3. This new structure can be described as a lamellar one with the atomic arrangement being built by planes of Te(OH)6 octahedra alterning with planes of arsenate tetrahedra. Raman and infrared spectra recorded at room temperature confirm the presence of As  and Te  groups and characterize the hydrogen bonds present in the crystal lattice. Differential scanning calorimerty shows the presence of three-phase transitions at 396 K, 408 K and 430 K present in the title compound. Typical thermal analyses, such as differential thermal analysis and thermogravimetry show that the decomposition of this material starts at about T= 445 K. Magnetization curve of Tl2HAsO4·Te(OH)6 substance have revealed a diamagnetic response overall temperature range studied

The effect of B and Si additions on the structural and magnetic behavior of Fe-Co-Ni alloy prepared by high-energy mechanical milling

Nanocrystalline Fe50Co25Ni15X10 (X = Bamorphous, Bcrystalline, and Si) powdered alloys were prepared by mechanical alloying process. Morphological, microstructural, and structural characterizations of the powders milled several times were investigated by scanning electron microscopy and X-ray diffraction. The final crystallographic state strongly depends on the chemical composition and the grinding time; it can be single-phase or two-phase. The crystallite size reduction down the nanometer scale is accompanied by the introduction of high level of lattice strains. The dissolution of Co, Ni, B (amorphous and crystalline), and Si into the α-Fe lattice leads to the formation of highly disordered Fe-based solid solutions. Coercivity (Hc) and the saturation magnetization (Ms) of alloyed powders were measured at room temperature by a vibration sample magnetization. The magnetic measurements show a contrasting Ms and (Hc) in all alloy compositions. Conclusively, soft magnetic properties of nanocrystalline alloys are related to various factors such as metalloid addition, formed phases, and chemical compositions

Crater formation by fast ions: comparison of experiment with Molecular Dynamics simulations

An incident fast ion in the electronic stopping regime produces a track of excitations which can lead to particle ejection and cratering. Molecular Dynamics simulations of the evolution of the deposited energy were used to study the resulting crater morphology as a function of the excitation density in a cylindrical track for large angle of incidence with respect to the surface normal. Surprisingly, the overall behavior is shown to be similar to that seen in the experimental data for crater formation in polymers. However, the simulations give greater insight into the cratering process. The threshold for crater formation occurs when the excitation density approaches the cohesive energy density, and a crater rim is formed at about six times that energy density. The crater length scales roughly as the square root of the electronic stopping power, and the crater width and depth seem to saturate for the largest energy densities considered here. The number of ejected particles, the sputtering yield, is shown to be much smaller than simple estimates based on crater size unless the full crater morphology is considered. Therefore, crater size can not easily be used to estimate the sputtering yield.Comment: LaTeX, 7 pages, 5 EPS figures. For related figures/movies, see: http://dirac.ms.virginia.edu/~emb3t/craters/craters.html New version uploaded 5/16/01, with minor text changes + new figure

Prognostic DNA methylation markers for sporadic colorectal cancer: a systematic review

Background Biomarkers that can predict the prognosis of colorectal cancer (CRC) patients and that can stratify high-risk early stage patients from low-risk early stage patients are urgently needed for better management of CRC. During the last decades, a large variety of prognostic DNA methylation markers has been published in the literature. However, to date, none of these markers are used in clinical practice. Methods To obtain an overview of the number of published prognostic methylation markers for CRC, the number of markers that was validated independently, and the current level of evidence (LoE), we conducted a systematic review of PubMed, EMBASE, and MEDLINE. In addition, we scored studies based on the REMARK guidelines that were established in order to attain more transparency and complete reporting of prognostic biomarker studies. Eighty-three studies reporting on 123 methylation markers fulfilled the study entry criteria and were scored according to REMARK. Results Sixty-three studies investigated single methylation markers, whereas 20 studies reported combinations of methylation markers. We observed substantial variation regarding the reporting of sample sizes and patient characteristics, statistical analyses, and methodology. The median (range) REMARK score for the studies was 10.7 points (4.5 to 17.5) out of a maximum of 20 possible points. The median REMARK score was lower in studies, which reported a p value below 0.05 versus those, which did not (p = 0.005). A borderline statistically significant association was observed between the reported p value of the survival analysis and the size of the study population (p = 0.051). Only 23 out of 123 markers (17%) were investigated in two or more study series. For 12 markers, and two multimarker panels, consistent results were reported in two or more study series. For four markers, the current LoE is level II, for all other markers, the LoE is lower. Conclusion This systematic review reflects that adequate reporting according to REMARK and validation of prognostic methylation markers is absent in the majority of CRC methylation marker studies. However, this systematic review provides a comprehensive overview of published prognostic methylation markers for CRC and highlights the most promising markers that have been published in the last two decades

Progress on lead-free metal halide perovskites for photovoltaic applications: a review

ABSTRACT: Metal halide perovskites have revolutionized the field of solution-processable photovoltaics. Within just a few years, the power conversion efficiencies of perovskite-based solar cells have been improved significantly to over 20%, which makes them now already comparably efficient to silicon-based photovoltaics. This breakthrough in solution-based photovoltaics, however, has the drawback that these high efficiencies can only be obtained with lead-based perovskites and this will arguably be a substantial hurdle for various applications of perovskite-based photovoltaics and their acceptance in society, even though the amounts of lead in the solar cells are low. This fact opened up a new research field on lead-free metal halide perovskites, which is currently remarkably vivid. We took this as incentive to review this emerging research field and discuss possible alternative elements to replace lead in metal halide perovskites and the properties of the corresponding perovskite materials based on recent theoretical and experimental studies. Up to now, tin-based perovskites turned out to be most promising in terms of power conversion efficiency; however, also the toxicity of these tin-based perovskites is argued. In the focus of the research community are other elements as well including germanium, copper, antimony, or bismuth, and the corresponding perovskite compounds are already showing promising properties. GRAPHICAL ABSTRACT: [Image: see text

Energy levels and crystal-field analysis of Tm3+ in YAl3(BO3)4 crystals

The electronic structure of the Tm3+ in YAl3(BO3)(4) crystals has been investigated by means of low temperature absorption and emission spectroscopy in the 5000-30,000 cm(-1) range. The assignment of the lines composing the observed manifolds to transitions between the Stark levels of Tm3+ is complicated by the presence of extra features having different origins. The energy levels scheme of the doping ion has been compiled after a careful analysis of the spectra by reproducing the observed transitions by means of theoretical calculations based on a Hamiltonian, including the free ion and the crystal field (CF) terms. The agreement between experimental and calculated energy values was reasonably good, the overall r.m.s. deviation being 16 cm(-1). The resulting CF parameters have been tabulated and compared with those reported in literature for other rare earth ions doped in YAB. The analysis of trends observed along the lanthanide series evidences some inconsistencies and the necessity of a systematic investigation of these systems. (C) 2011 Elsevier B.V. All rights reserved

Effects of impurities on oxygen transfer rate in the electroflotation process

513-518In this work, three different types of impurities: soybean oil, surfactant and diatomaceous earth were doped to simulate the impurities in wastewaters issued from edible oil refinery plant. The effects of the impurities on the oxygen transfer rate were investigated in an electroflotation cell. The volumetric mass transfer coefficient was studied for a batch mode involving different values of the current density for different impurities concentrations. The capacity of oxygenation and the corrective alpha factor were also studied. Models which relate the volumetric mass transfer coefficient to the current density and the concentration of the impurities were established. The results showed that the presence of impurities significantly reduce the volumetric mass transfer coefficient KLa

The cubic-to-rhombohedral phase transition of Pb(Zn1/3Nb2/3)O3: a high-resolution x-ray diffraction study on single crystals

The cubic-to-rhombohedral (C-R) phase transition of the ferroelectric relaxor Pb(Zn1/3Nb2/3O3) is investigated by means of a high-resolution x-ray diffraction study on single crystals. The phase transition is diffuse and spreads over the temperature range T-CR = 385 +/- 5 K to T-R = 325 +/- 5 K. Below T-CR, the cubic phase transforms progressively into rhombohedral domains whose average size, about 60-70 nm in the [111] direction, remains unchanged as temperature is lowered, so no growth of the R-domains is observed. At TR, the nanometric R-domains fully pave the crystal but structural mismatches between adjacent domains generate stresses; which increase as temperature is lowered. The anomalous broadening of diffraction peaks of the R-phase, which originates from size and strain effects, can be suppressed by applying a do electric field, along the [111] direction, which transforms the polydomain state into a rhombohedral quasi-monodomain state