2,019 research outputs found
Ab initio prediction of the mechanical properties of alloys: The case of Ni/Mn-doped ferromagnetic Fe
First-principles alloy theory, formulated within the exact muffin-tin
orbitals method in combination with the coherent-potential approximation, is
used to study the mechanical properties of ferromagnetic body-centered cubic
(bcc) FeM alloys (M=Mn or Ni, ). We consider
several physical parameters accessible from \emph{ab initio} calculations and
their combinations in various phenomenological models to compare the effect of
Mn and Ni on the properties of Fe. Alloying is found to slightly alter the
lattice parameters and produce noticeable influence on elastic moduli. Both Mn
and Ni decrease the surface energy and the unstable stacking fault energy
associated with the surface facet and the
slip system, respectively. Nickel is found to produce larger effect on the
planar fault energies than Mn. The semi-empirical ductility criteria by Rice
and Pugh consistently predict that Ni enhances the ductility of Fe but give
contradictory results in the case of Mn doping. The origin of the discrepancy
between the two criteria is discussed and an alternative measure of the
ductile-brittle behavior based on the theoretical cleavage strength and
single-crystal shear modulus is proposed.Comment: 14 pages, 11 figure
A Spectral Line Survey from 138.3 to 150.7 GHZ toward Orion-KL
We present the results of a spectral line survey from 138.3 to 150.7 GHz
toward Orion-KL. The observations were made using the 14 m radio telescope of
Taeduk Radio Astronomy Observatory. Typical system temperatures were between
500 and 700 K, with the sensitivity between K in units of .
A total of 149 line spectra are detected in this survey. Fifty lines have
been previously reported, however we find 99 new detections. Among these new
lines, 32 are `unidentified', while 67 are from molecular transitions with
known identifications. There is no detection of H or He recombination lines.
The identified spectra are from a total of 16 molecular species and their
isotopic variants. In the range from 138.3 to 150.7 GHz, the strongest spectral
line is the J=3-2 transition of CS molecule, followed by transitions of the
, , , and . Spectral lines from
the large organic molecules such as , , , and are prominent; with 80 % of the
identified lines arising from transitions of these molecules. The rotational
temperatures and column densities are derived using the standard rotation
diagram analysis for (), , and with and . These estimates are fairly comparable to the values for the
same molecule in other frequency regions by other studies.Comment: 10 figures, 2 tex files for a manuscript and tables, accepted to Ap
Thermal surface free energy and stress of iron OPEN
Absolute values of surface energy and surface stress of solids are hardly accessible by experiment. Here, we investigate the temperature dependence of both parameters for the (001) and (110) surface facets of body-centered cubic Fe from first-principles modeling taking into account vibrational, electronic, and magnetic degrees of freedom. The monotonic decrease of the surface energies of both facets with increasing temperature is mostly due to lattice vibrations and magnetic disorder. The surface stresses exhibit nonmonotonic behaviors resulting in a strongly temperature dependent excess surface stress and surface stress anisotropy. Introduced by Gibbs, the surface free energy (γ) and the surface stress (σ), are the two essential macroscopic parameters that characterize the thermodynamic properties of crystalline surface
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Comparative prebiotic activity of mixtures of cereal grain polysaccharides
The main components of the non-starch polysaccharide (NSP) fraction of wheat flour are arabinoxylan (AX) and β-glucan. These are also present in other cereal grains, but their proportions vary with AX being the major component in wheat and rye and β-glucan in barley and oats. Therefore, it was hypothesised that these NSPs could act synergistically when fermented in vitro at the ratios present in the major foods consumed, resulting in increased prebiotic activity. AX and β-glucan were therefore tested in in vitro fermentation studies to assess their prebiotic activity when used individually and/or in different ratios. Short-chain fatty-acids (SCFAs) produced from in vitro fermentation were measured using HPLC and bacterial populations were measured using flow cytometry with fluorescence in situ hybridisation (Flow-FISH). Fermentation of AX alone resulted in a significant bifidogenic activity and increased concentrations of SCFAs, mainly acetate, after 8-24 h of fermentation, however β-glucan alone did not show prebiotic activity. The greatest prebiotic activity, based on concentration of total SCFAs and increases in total bacteria as well as beneficial Bifidobacterium and Clostridium coccoides/Eubacterium groups, was observed when AX and β-glucan were combined at a 3:1 ratio, which corresponds to their ratios in wheat flour which is major source of cereal fibre in the diet. This indicates that the population of bacteria in the human GI tract may be modulated by the composition of the fibre in the diet, to maximise the prebiotic potential
Expression of Matrix Metalloproteinases and Their Inhibitors in Squamous Cell Carcinoma of the Tonsil and Their Clinical Significance
ObjectivesTo investigate expressions of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in squamous cell carcinoma of the tonsil and to correlate expression profiles with clinicopathological characteristics.MethodsParaffin blocks were obtained from 45 tonsil squamous cell carcinoma (SCC) patients, who underwent surgery as an initial treatment between 1994 and 2004, and from 20 normal controls. Expressions of MMP-2, MMP-9, MMP-13, TIMP-1, and TIMP-2 were investigated immunohistochemically.ResultsThe expressions of MMPs (except MMP-2) and TIMPs were found to be significantly different in tonsil SCC and normal control tissues. Furthermore, MMP-13 expression was found to be correlated with tumor invasion (P=0.05), and the expressions of MMP-9 and TIMP-1 with nodal metastasis (P=0.048, 0.031). No relation was found between MMP or TIMP expression and recurrence. However, MMP-9 expression was found to be significantly associated with 5-year survival in tonsil SCC patients by multivariate analysis (hazard ratio, 3.853; P=0.013).ConclusionSignificant overexpressions of multiple MMPs and TIMPs were found in tonsil SCC tissues. Furthermore, our findings suggest that MMP-9 expression might be a useful prognostic factor
Resolution of Recalcitrant Uveitic Optic Disc Edema Following Administration of Methotrexate: Two Case Reports
A 13-year-old male and a 15-year-old female presented with optic disc edema associated with chronic recurrent uveitis. While the ocular inflammation responded to high doses of oral prednisolone, the disc edema showed little improvement. After oral administration of methotrexate, the disc edema and ocular inflammation were resolved, and the dose of oral corticosteroid could be reduced
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