InAs/GaAs Quantum-Dot Lasers Monolithically Grown on on-axis Silicon (001)

Inversion boundaries (IBs) are charged planer defects that arise from the growth of polar III-V materials on non-polar Si (001) substrate. This paper demonstrates a novel technique to achieve all-MBE grown, IB-free GaAs on on-axis Si (001) substrates by employing periodic Si single-atomicheight steps to re-distribute the nucleation of IBs and promote IB self-annihilation in the subsequent GaAs growth. Furthermore, an electronically pumped quantum-dot (QD) laser has been demonstrated on this IB-free GaAs/Si platform with a maximum operating temperature of 120 °C. These results could be a significant step towards the monolithic integration of III-V materials and devices with mature CMOS technology

Comparison of model estimates of the effects of aviation emissions on atmospheric ozone and methane

One of the significant uncertainties in understanding the effects of aviation on climate is the effects of aviation emissions on ozone and atmospheric chemistry. In this study the effects of aviation emissions on atmospheric ozone for 2006 and two projections for 2050 are compared among seven models. The models range in complexity from a two-dimensional coupled model to three-dimensional offline and fully coupled three-dimensional chemistry-climate models. This study is the first step in a critical assessment and comparison among these model results. Changes in tropospheric O3 burdens range from 2.3 Tg-O3/Tg-N to 3.0 Tg-O3/Tg-N, ozone radiative forcings range from 6 to 37 mW/m2, and methane radiative forcings range from -8.3 to -12.5 mW/m2 for the 2006 aviation emissions. As a group, the chemistry transport models tend to have similar responses while the fully coupled models tend to separate from this group and do not show similar responses to each other. ©2013. American Geophysical Union. All Rights Reserved

Synchronized and Desynchronized Phases of Exciton-Polariton Condensates in the Presence of Disorder

Condensation of exciton-polaritons in semiconductor microcavities takes place despite in plane disorder. Below the critical density the inhomogeneity of the potential seen by the polaritons strongly limits the spatial extension of the ground state. Above the critical density, in presence of weak disorder, this limitation is spontaneously overcome by the non linear interaction, resulting in an extended synchronized phase. This mechanism is clearly evidenced by spatial and spectral studies, coupled to interferometric measurements. In case of strong disorder, several non phase-locked (independent) condensates can be evidenced. The transition from synchronized phase to desynchronized phase is addressed considering multiple realizations of the disorder.Comment: 11 pages, 4 figures,corrected typos, added figure

Critical temperature for quenching of pair correlations

The level density at low spin in the 161,162-Dy and 171,172-Yb nuclei has been extracted from primary gamma rays. The nuclear heat capacity is deduced within the framework of the canonical ensemble. The heat capacity exhibits an S-formed shape as a function of temperature, which is interpreted as a fingerprint of the phase transition from a strongly correlated to an uncorrelated phase. The critical temperature for the quenching of pair correlations is found at Tc=0.50(4) MeV.Comment: 8 pages including 4 figures, different method to extract Tc, different figures, text partly rewritte

Level density and gamma strength function in 162-Dy from inelastic 3-He scattering

Complementary measurements have been performed for the level density and gamma strength function in 162-Dy using inelastic 3-He scattering. Comparing these results to previous measurements using the 163-Dy(3-He,alpha) reaction, reveals that the measured quantities above 1.5 MeV do not depend significantly on the nuclear reaction chosen.Comment: 15 pages, including 7 figure

Properties and hydration behavior of blended clinker and portland-sediment cement pastes

In recent years, an increase of the interest in the use of secondary raw materials (sediment, sludge…) in construction has been observed.  This paper aims to contribute to the use of dredging sediments in the cement industry. Despite the literature on this subject, the available data on the aspects and phenomena related to the hydration process of such mixtures are incomplete. This paper aims to specify the calorimetric curves of hydration of mixtures made, from the sediment trapped at the site of Lyvet in the Brittany region of France. The mixtures are made ??using in one hand clinker and in the other hand Portland cement. Pastes with 8%, 16% and 33% of clinker or Portland cement substituted by sediment are used to determine the hydraulic properties of mixtures. The physico-chemical characterization of materials is made by different techniques to determine the chemical composition and physical properties. X-ray diffraction is used to determine the mineralogical compositions of samples before and after treatment. A  Tian-Calvet microcalorimeter is used to explore hydration behavior of the blended Sediment-Portland cement pastes. The addition of untreated sediment to both clinker or Portland cement increase the dormant period duration. On the contrary, this period becomes shorter when the sediment is thermally treated. The results show that 8% of treated sediment improve hydration of blended Sediment-Portland cement pastes. Mechanical properties of blended sediment-cements are also investigated. After 28 days of curing in water, the mortar containing 8% of treated sediment exhibits a compressive strength equal to 93.7% of the one of the reference mortar, maintaining it in the same cement class (52.5)

SIC~POVMs and Clifford groups in prime dimensions

We show that in prime dimensions not equal to three, each group covariant symmetric informationally complete positive operator valued measure (SIC~POVM) is covariant with respect to a unique Heisenberg--Weyl (HW) group. Moreover, the symmetry group of the SIC~POVM is a subgroup of the Clifford group. Hence, two SIC~POVMs covariant with respect to the HW group are unitarily or antiunitarily equivalent if and only if they are on the same orbit of the extended Clifford group. In dimension three, each group covariant SIC~POVM may be covariant with respect to three or nine HW groups, and the symmetry group of the SIC~POVM is a subgroup of at least one of the Clifford groups of these HW groups respectively. There may exist two or three orbits of equivalent SIC~POVMs for each group covariant SIC~POVM, depending on the order of its symmetry group. We then establish a complete equivalence relation among group covariant SIC~POVMs in dimension three, and classify inequivalent ones according to the geometric phases associated with fiducial vectors. Finally, we uncover additional SIC~POVMs by regrouping of the fiducial vectors from different SIC~POVMs which may or may not be on the same orbit of the extended Clifford group.Comment: 30 pages, 1 figure, section 4 revised and extended, published in J. Phys. A: Math. Theor. 43, 305305 (2010

NLRC5 promotes transcription of BTN3A1-3 genes and Vγ9Vδ2 T cell-mediated killing

BTN3A molecules-BTN3A1 in particular-emerged as important mediators of Vγ9Vδ2 T cell activation by phosphoantigens. These metabolites can originate from infections, e.g. with Mycobacterium tuberculosis, or by alterations in cellular metabolism. Despite the growing interest in the BTN3A genes and their high expression in immune cells and various cancers, little is known about their transcriptional regulation. Here we show that these genes are induced by NLRC5, a regulator of MHC class I gene transcription, through an atypical regulatory motif found in their promoters. Accordingly, a robust correlation between NLRC5 and BTN3A gene expression was found in healthy, in M. tuberculosis-infected donors' blood cells, and in primary tumors. Moreover, forcing NLRC5 expression promoted Vγ9Vδ2 T-cell-mediated killing of tumor cells in a BTN3A-dependent manner. Altogether, these findings indicate that NLRC5 regulates the expression of BTN3A genes and hence open opportunities to modulate antimicrobial and anticancer immunity

Role of heavy-meson exchange in pion production near threshold

Recent calculations of $s$-wave pion production have severely underestimated the accurately known $pp\rightarrow pp\pi^0$\ total cross section near threshold. In these calculations, only the single-nucleon axial-charge operator is considered. We have calculated, in addition to the one-body term, the two-body contributions to this reaction that arise from the exchange of mesons. We find that the inclusion of the scalar $\sigma$-meson exchange current (and lesser contributions from other mesons) increases the cross section by about a factor of five, and leads to excellent agreement with the data. The results are neither very sensitive to changes in the distorting potential that generates the $NN$ wave function, nor to different choices for the meson-nucleon form factors. We argue that $pp\rightarrow pp\pi^0$\ data provide direct experimental evidence for meson-exchange contributions to the axial current.Comment: 28 Pages, IU-NTC #93-0

Continuous wave observation of massive polariton redistribution by stimulated scattering in semiconductor microcavities

A massive redistribution of the polariton occupancy to two specific wave vectors is observed under conditions of continuous wave excitation of a semiconductor microcavity. The “condensation” of the polaritons to the two specific states arises from stimulated scattering at final state occupancies of order unity. The stimulation phenomena, arising due to the bosonic character of the polariton quasiparticles, occur for conditions of resonant excitation of the lower polariton branch. High energy nonresonant excitation, as in most previous work, instead leads to conventional lasing in the vertical cavity structure