First-principles study on the intermediate compounds of LiBH4_4

We report the results of the first-principles calculation on the intermediate compounds of LiBH$_4$. The stability of LiB$_3$H$_8$ and Li$_2$B$_n$H$_n (n=5-12)$ has been examined with the ultrasoft pseudopotential method based on the density functional theory. Theoretical prediction has suggested that monoclinic Li$_2$B$_{12}$H$_{12}$ is the most stable among the candidate materials. We propose the following hydriding/dehydriding process of LiBH$_4$ via this intermediate compound : LiBH$_4 \leftrightarrow {1/12}$Li$_{2}$B$_{12}$H$_{12} + {5/6}$ LiH $+ {13/12}$H$_2 \leftrightarrow$LiH $+$ B $+ {3/2}$H$_2$. The hydrogen content and enthalpy of the first reaction are estimated to be 10 mass% and 56 kJ/mol H$_2$, respectively, and those of the second reaction are 4 mass% and 125 kJ/mol H$_2$. They are in good agreement with experimental results of the thermal desorption spectra of LiBH$_4$. Our calculation has predicted that the bending modes for the $\Gamma$-phonon frequencies of monoclinic Li$_2$B$_{12}$H$_{12}$ are lower than that of LiBH$_4$, while stretching modes are higher. These results are very useful for the experimental search and identification of possible intermediate compounds.Comment: 7 pages, 5 figures, submitted to PR

Thermodynamic and Transport Properties of CeMg2Cu9 under Pressure

We report the transport and thermodynamic properties under hydrostatic pressure in the antiferromagnetic Kondo compound CeMg2Cu9 with a two-dimensional arrangement of Ce atoms. Magnetic specific heat Cmag(T) shows a Schottky-type anomaly around 30 K originating from the crystal electric field (CEF) splitting of the 4f state with the first excited level at \Delta_{1}/kB = 58 K and the second excited level at \Delta_{2}/kB = 136 K from the ground state. Electric resistivity shows a two-peaks structure due to the Kondo effect on each CEF level around T_{1}^{max} = 3 K and T_{2}^{max} = 40 K. These peaks merge around 1.9 GPa with compression. With increasing pressure, Neel temperature TN initially increases and then change to decrease. TN finally disappears at the quantum critical point Pc = 2.4 GPa.Comment: 10 pages, 6 figure

CANGAROO-III Observation of TeV Gamma Rays from the vicinity of PSR B1 706-44

Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov Telescope has detected extended emission of TeV gamma rays in the vicinity of the pulsar PSR B1706$-$44. The strength of the signal observed as gamma-ray-like events varies when we apply different ways of emulating background events. The reason for such uncertainties is argued in relevance to gamma-rays embedded in the "off-source data", that is, unknown sources and diffuse emission in the Galactic plane, namely, the existence of a complex structure of TeV gamma-ray emission around PSR B1706$-$44.Comment: 10 pages, 13 figures, to be published in Ap

CANGAROO-III observation of TeV gamma rays from the unidentified gamma-ray source HESS J1614-518

We report the detection, with the CANGAROO-III imaging atmospheric Cherenkov telescope array, of a very high energy gamma-ray signal from the unidentified gamma-ray source HESS J1614-518, which was discovered in the H.E.S.S. Galactic plane survey. Diffuse gamma-ray emission was detected above 760 GeV at the 8.9 sigma level during an effective exposure of 54 hr from 2008 May to August. The spectrum can be represented by a power-law: 8.2+-2.2_{stat}+-2.5_{sys}x10^{-12}x (E/1TeV)^{-Gamma} cm^{-2} s^{-1} TeV^{-1} with a photon index Gamma of 2.4+-0.3_{stat}+-0.2_{sys}, which is compatible with that of the H.E.S.S. observations. By combining our result with multi-wavelength data, we discuss the possible counterparts for HESS J1614-518 and consider radiation mechanisms based on hadronic and leptonic processes for a supernova remnant, stellar winds from massive stars, and a pulsar wind nebula. Although a leptonic origin from a pulsar wind nebula driven by an unknown pulsar remains possible, hadronic-origin emission from an unknown supernova remnant is preferred.Comment: 9 pages, 7 figures, accepted for publication in Ap

Improved Unsteady RANS Models Applied to Jet Transverse to a Pipe Flow

An unsteady RANS model is developed in order to simulate the complex situations involving both free and bounded flows. This model tuned to catch coherent flow structures is developed both in the k-ε and k-l approaches. The full 3D geometry of a round jet exiting from a reservoir into a pipe has been computed. Periodic conditions are applied in order to compare with an experiments consisting of eight jets exiting in a cross pipe flow. Improvement has been obtained with this URANS turbulence model compared to RANS and good agreement compared with experiments has been obtained. Unsteady phenomena are reproduced by the model and provide more insight into the physical properties of the flow and of the transport of a passive scalar

Invasive behavior of ulcerative colitis-associated carcinoma is related to reduced expression of CD44 extracellular domain: comparison with sporadic colon carcinoma

<p>Abstract</p> <p>Background</p> <p>To elucidate relations of invasion of ulcerative colitis (UC)-associated carcinoma with its prognosis, the characteristics of invasive fronts were analyzed in comparison with sporadic colonic carcinomas.</p> <p>Methods</p> <p>Prognoses of 15 cases of UC-associated colonic carcinoma were compared with those of sporadic colon carcinoma cases, after which 75 cases of sporadic invasive adenocarcinoma were collected. Tumor budding was examined histologically at invasive fronts using immunohistochemistry (IHC) of pancytokeratin. Expressions of beta-catenin with mutation analysis, CD44 extracellular domain, Zo-1, occludin, matrix matalloproteinase-7, laminin-5γ2, and sialyl Lewis X (Le^X) were immunohistochemically evaluated.</p> <p>Results</p> <p>UC-associated carcinoma showed worse prognosis than sporadic colon carcinoma in all the cases, and exhibited a tendency to become more poorly differentiated when carcinoma invaded the submucosa or deeper layers than sporadic carcinoma. When the lesions were compared with sporadic carcinomas considering differentiation grade, reduced expression of CD44 extracellular domain in UC-associated carcinoma was apparent. Laminin-5γ2 and sialyl-Le^Xexpression showed a lower tendency in UC-associated carcinomas than in their sporadic counterparts. There were no differences in the numbers of tumor budding foci between the two lesion types, with no apparent relation to nuclear beta-catenin levels in IHC.</p> <p>Conclusions</p> <p>UC-associated carcinoma showed poorer differentiation when the carcinoma invaded submucosa or deeper parts, which may influence the poorer prognosis. The invasive behavior of UC-associated carcinoma is more associated with CD44 cleavage than with basement membrane disruption or sialyl-Lewis-antigen alteration.</p

Observation of an extended VHE gamma-ray emission from MSH 15-52 with CANGAROO-III

We have observed the supernova remnant MSH 15-52 (G320.4-1.2), which contains the gamma-ray pulsar PSR B1509-58, using the CANGAROO-III imaging atmospheric Cherenkov telescope array from April to June in 2006. We detected gamma rays above 810 GeV at the 7 sigma level during a total effective exposure of 48.4 hours. We obtained a differential gamma-ray flux at 2.35 TeV of (7.9+/-1.5_{stat}+/-1.7_{sys}) \times 10^{-13} cm^{-2}s^{-1}TeV^{-1} with a photon index of 2.21+/-0.39_{stat}+/-0.40_{sys}, which is compatible with that of the H.E.S.S. observation in 2004. The morphology shows extended emission compared to our Point Spread Function. We consider the plausible origin of the high energy emission based on a multi-wavelength spectral analysis and energetics arguments.Comment: 9 pages, 9 figures, Accepted in Ap

Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)

We present detailed analysis of the two gamma-ray sources,1FGL J1801.3-2322c and 1FGL J1800.5-2359c,that have been found toward the supernova remnant(SNR) W28 with the Large Area Telescope(LAT) on board the Fermi Gamma-ray Space Telescope.1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28,and to extensively overlap with the TeV gamma-ray source HESS J1801-233,which is associated with a dense molecular cloud interacting with the supernova remnant.The gamma-ray spectrum measured with LAT from 0.2--100 GeV can be described by a broken power-law function with a break of ~1GeV,and photon indices of 2.09$\pm$0.08(stat)$\pm$0.28(sys) below the break and 2.74$\pm$0.06(stat)$\pm$0.09(sys) above the break.Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV--TeV band,we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud.The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provide a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved.An upper limit on the size of the gamma-ray emission was estimated to be ~16$'$ using events above ~2GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B,which is considered to be associated with a dense molecular cloud that contains the ultra compact HII region W28A2(G5.89-0.39).We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C.The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10GeV and 100GeV.Comment: 23 pages, 6 figures. Accepted for publication in the Astrophysical Journal. Corresponding authors: H. Katagiri, H. Tajima, T. Tanaka, and Y. Uchiyam

Detection of the energetic pulsar PSR B1509-58 and its pulsar wind nebula in MSH 15-52 using the Fermi-Large Area Telescope

We report the detection of high energy gamma-ray emission from the young and energetic pulsar PSR B1509$-$58 and its pulsar wind nebula (PWN) in the composite supernova remnant SNR G320.4-1.2 (aka MSH 15-52). Using 1 year of survey data with the Fermi-Large Area Telescope (LAT), we detected pulsations from PSR B1509-58 up to 1 GeV and extended gamma-ray emission above 1 GeV spatially coincident with the PWN. The pulsar light curve presents two peaks offset from the radio peak by phases 0.96 $\pm$ 0.01 and 0.33 $\pm$ 0.02. New constraining upper limits on the pulsar emission are derived below 1 GeV and confirm a severe spectral break at a few tens of MeV. The nebular spectrum in the 1 - 100 GeV energy range is well described by a power-law with a spectral index of (1.57 $\pm$ 0.17 $\pm$ 0.13) and a flux above 1 GeV of (2.91 $\pm$ 0.79 $\pm$ 1.35) 10^{-9} cm^{-2} s^{-1}. The first errors represent the statistical errors on the fit parameters, while the second ones are the systematic uncertainties. The LAT spectrum of the nebula connects nicely with Cherenkov observations, and indicates a spectral break between GeV and TeV energies.Comment: 14 pages, 6 figures, accepted for publication by Ap

Fermi observations of high-energy gamma-ray emission from GRB 090217A

The Fermi observatory is advancing our knowledge of Gamma-Ray Bursts (GRBs) through pioneering observations at high energies, covering more than 7 decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9 sigma. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to 1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.Comment: 17 pages, 4 figures. Contact Authors: Fred, Piron; Sara, Cutini; Andreas, von Kienli