1,461 research outputs found
Quench cooling under reduced gravity
We report the quench cooling experiments performed with liquid O2 under
different levels of gravity simulated with the magnetic gravity compensation. A
copper disk is quenched from 270K to 90K. It is found that the cooling time in
microgravity is very long in comparison with any other gravity level. This
phenomenon is explained by the isolation effect of the gas surrounding the
disk. The liquid subcooling is shown to drastically improuve the heat exchange
thus reducing the cooling time (about 20 times). The effect of subcooling on
the heat transfer is analyzed at different gravity levels. It is shown that
such type of experiments cannot be used for the analysis of the critical heat
flux (CHF) of the boiling crisis. The minimum heat flux (MHF) of boiling is
analyzed instead
Ferromagnetic (Ga,Mn)N epilayers versus antiferromagnetic GaMnN clusters
Mn-doped wurtzite GaN epilayers have been grown by nitrogen plasma-assisted
molecular beam epitaxy. Correlated SIMS, structural and magnetic measurements
show that the incorporation of Mn strongly depends on the conditions of the
growth. Hysteresis loops which persist at high temperature do not appear to be
correlated to the presence of Mn. Samples with up to 2% Mn are purely
substitutional GaMnN epilayers, and exhibit paramagnetic
properties. At higher Mn contents, precipitates are formed which are identified
as GaMnN clusters by x-ray diffraction and absorption: this induces a
decrease of the paramagnetic magnetisation. Samples co-doped with enough Mg
exhibit a new feature: a ferromagnetic component is observed up to
K, which cannot be related to superparamagnetism of unresolved magnetic
precipitates.Comment: Revised versio
Remote optical addressing of single nano-objects
We present a scheme for remotely addressing single nano-objects by means of
near-field optical microscopy that makes only use of one of the most
fundamental properties of electromagnetic radiation: its polarization. A medium
containing optically active nano-objects is covered with a thin metallic film
presenting sub-wavelength holes. When the optical tip is positioned some
distance away from a hole, surface plasmons in the metal coating are generated
which, by turning the polarization plane of the excitation light, transfer the
excitation towards a chosen hole and induce emission from the underlying
nano-objects. The method, easily applicable to other systems, is demonstrated
for single quantum dots (QDs) at low temperature. It may become a valuable tool
for future optical applications in the nanoworld
Correlated Photon Emission from a Single II-VI Quantum Dot
We report correlation and cross-correlation measurements of photons emitted
under continuous wave excitation by a single II-VI quantum dot (QD) grown by
molecular-beam epitaxy. A standard technique of microphotoluminescence combined
with an ultrafast photon correlation set-up allowed us to see an antibunching
effect on photons emitted by excitons recombining in a single CdTe/ZnTe QD, as
well as cross-correlation within the biexciton ()-exciton ()
radiative cascade from the same dot. Fast microchannel plate photomultipliers
and a time-correlated single photon module gave us an overall temporal
resolution of 140 ps better than the typical exciton lifetime in II-VI QDs of
about 250ps.Comment: 4 pages, 3 figures, to appear in Appl. Phys. Let
Sub-nanosecond delay of light in (Cd,Zn)Te crystal
We study excitonic polariton relaxation and propagation in bulk CdZnTe using
time- resolved photoluminescence and time-of-flight techniques. Propagation of
picosecond optical pulses through 0.745 mm thick crystal results in time delays
up to 350 ps, depending on the photon energy. Optical pulses with 150 fs
duration become strongly stretched. The spectral dependence of group velocity
is consistent with the dispersion of the lower excitonic polariton branch. The
lifetimes of excitonic polariton in the upper and lower branches are 1.5 and 3
ns, respectively.Comment: 5 pages, 4 figure
Excitonic giant Zeeman effect in GaN:Mn^3+
We describe a direct observation of the excitonic giant Zeeman splitting in
(Ga,Mn)N, a wide-gap III-V diluted magnetic semiconductor. Reflectivity and
absorption spectra measured at low temperatures display the A and B excitons,
with a shift under magnetic field due to s,p-d exchange interactions. Using an
excitonic model, we determine the difference of exchange integrals between
Mn^3+ and free carriers in GaN, N_0(alpha-beta)=-1.2 +/- 0.2 eV. Assuming a
reasonable value of alpha, this implies a positive sign of beta which
corresponds to a rarely observed ferromagnetic interaction between the magnetic
ions and the holes.Comment: 4 pages, 4 figure
Implications of a newly discovered DR5 specific antagonistic peptide for neurodegenerative disorders
Most neurodegenerative disorders are the result of inflammation and neuronal cell death. Although many cytokines have been implied to be involved in the pathogenesis, recent studies have shown TRAIL to be responsible for neuronal apoptosis.TRAIL is best known for its ability to induce apoptosis in many cancer cells. Normally TRAIL is not present in the CNS. However, it is induced by β‐amyloid protein and up regulated on infected macrophages which can infiltrate the CNS. TRAIL is able to induce apoptosis via death receptors DR4 and DR5. DR5 is shown to be expressed on neuronal cells. The identification of an antagonistic peptide that specifically binds DR5 provides us with a useful investigative tool. Small peptides can bind their targets with high affinity and specificity.In addition, they are easily modified and further developed for clinical application. So the peptide R2C16 might even be used as a lead peptide for the development of therapeutic agents in neurodegenerative disorders
Safety and effectiveness of adalimumab in patients with rheumatoid arthritis over 5 years of therapy in a phase 3b and subsequent postmarketing observational study.
INTRODUCTION: Patients with active rheumatoid arthritis who had failed at least one disease-modifying anti-rheumatic drug (DMARD) were treated with adalimumab (ADA) in the ReAct study with the option to continue treatment for 5 years in ReAlise. The purpose of this study was to evaluate the long-term safety and effectiveness of ADA as prescribed from the first injection in ReAct to the last observation in ReAlise. METHODS: Patients received ADA alone or in combination with DMARDs according to usual clinical care practices. Adverse events (AEs) were tabulated by five time windows after the first ADA injection. Effectiveness measures included achievement of low disease activity (LDA), defined as Simplified Disease Activity Index (SDAI) ≤11, or remission, (REM), defined as SDAI ≤3.3. RESULTS: Of the 6,610 ReAct patients, 3,435 (52%) continued in ReAlise. At baseline in ReAct, mean age was 54 years, mean DAS28 was 6.0 and mean HAQ DI was 1.64. The mean treatment duration was 1,016 days, representing 18,272 patient-years (PYs) of ADA exposure. Overall incidence rates of serious AEs and serious infections were 13.8 and 2.8 events (E)/100 PYs, respectively. Serious AEs occurred most frequently in the first 6 months and deceased thereafter. Standardised mortality ratio was 0.71 (95% CI 0.57 to 0.87) and standardised incidence ratio for malignancies was 0.64 (95% CI 0.53 to 0.76). LDA was achieved by 50% and REM by 21% of patients at last observation. CONCLUSIONS: Results of this large observational study of ADA in routine clinical practice were consistent with controlled trials, with no new safety concerns during a follow-up of more than 5 years. Effectiveness of ADA was maintained during long-term observation. TRIAL REGISTRATION: NCT00448383, NCT0023488
The creation of modulated monoclinic aperiodic composites in n-alkane/urea compounds
Citation: Mariette, C., Guerin, L., Rabiller, P., Chen, Y. S., Bosak, A., Popov, A., . . . Toudic, B. (2015). The creation of modulated monoclinic aperiodic composites in n-alkane/urea compounds. Zeitschrift Fur Kristallographie, 230(1), 5-11. doi:10.1515/zkri-2014-1773n-Dodecane/urea is a member of the prototype series of n-alkane/urea inclusion compounds. At room temperature, it presents a quasi-one dimensional liquid-like state for the confined guest molecules within the rigid, hexagonal framework of the urea host. At lower temperatures, we report the existence of two other phases. Below T-c=248 K there appears a phase with rank four superspace group P6(1)22(00 gamma), the one typically observed at room temperature in n-alkane/urea compounds with longer guest molecules. A misfit parameter, defined by the ratio gamma=C-h/C-g (C-host/C-guest), is found to be 0.632 +/- 0.005. Below T-c1=123 K, a monoclinic modulated phase is created with a constant shift along c of the guest molecules in adjacent channels. The maximal monoclinic space group for this structure is P12(1)1(alpha 0 gamma). Analogies and differences with n-heptane/urea, which also presents a monoclinic, modulated low-temperature phase, are discussed
Phase diagrams of magnetopolariton gases
The magnetic field effect on phase transitions in electrically neutral
bosonic systems is much less studied than those in fermionic systems, such as
superconducting or ferromagnetic phase transitions. Nevertheless, composite
bosons are strongly sensitive to magnetic fields: both their internal structure
and motion as whole particles may be affected. A joint effort of ten
laboratories has been focused on studies of polariton lasers, where
non-equilibrium Bose-Einstein condensates of bosonic quasiparticles,
exciton-polaritons, may appear or disappear under an effect of applied magnetic
fields. Polariton lasers based on pillar or planar microcavities were excited
both optically and electrically. In all cases a pronounced dependence of the
onset to lasing on the magnetic field has been observed. For the sake of
comparison, photon lasing (lasing by an electron-hole plasma) in the presence
of a magnetic field has been studied on the same samples as polariton lasing.
The threshold to photon lasing is essentially governed by the excitonic Mott
transition which appears to be sensitive to magnetic fields too. All the
observed experimental features are qualitatively described within a uniform
model based on coupled diffusion equations for electrons, holes and excitons
and the Gross-Pitaevskii equation for exciton-polariton condensates. Our
research sheds more light on the physics of non-equilibrium Bose-Einstein
condensates and the results manifest high potentiality of polariton lasers for
spin-based quantum logic applications.Comment: 21 pages, 11 figure
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