965 research outputs found
Nonthermal Laser-Induced Formation of Crystalline Ge Quantum Dots on Si(100)
The effects of laser-induced electronic excitations on the self-assembly of Ge quantum dots on Si (100) - (2×1) grown by pulsed laser deposition are studied. Electronic excitations due to laser irradiation of the Si substrate and the Ge film during growth are shown to decrease the roughness of films grown at a substrate temperature of ∼120 °C. At this temperature, the grown films are nonepitaxial. Electronic excitation results in the formation of an epitaxial wetting layer and crystalline Ge quantum dots at ∼260 °C, a temperature at which no crystalline quantum dots form without excitation under the same deposition conditions.© 2008 American Institute of Physics. [DOI: 10.1063/1.3041493
Preventive effect of the flavonoid, quercetin, on hepatic cancer in rats via oxidant/antioxidant activity: molecular and histological evidences
<p>Abstract</p> <p>Background</p> <p>The incidence of hepatocellular carcinoma is increasing in many countries. The estimated number of new cases annually is over 500,000, and the yearly incidence comprises between 2.5 and 7% of patients with liver cirrhosis. The incidence varies between different geographic areas, being higher in developing areas; males are predominantly affected, with a 2:3 male/female ratio</p> <p>Methods</p> <p>Experiments were designed to examine the effect of <it>N</it>-Nitrosodiethylamine (NDEA) as cancer-inducer compound and to confirm the preventive effect of the flavonoid quercetin on hepatocellular carcinoma in rats. Briefly, thirty six male albino rats of Wistar strain were divided into 3 groups: the 1<sup>st </sup>group was administered NDEA alone (NDEA-treated), the 2<sup>nd </sup>group was treated simultaneously with NDEA and quercetin (NDEA+Q) and the 3<sup>rd </sup>group was used as control (CON). Randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) as well as <it>p53</it>-specifi PCR assays were employed to determine genomic difference between treated, and control animals. Histological confirmation as well as oxidant/antioxidant status of the liver tissue was done.</p> <p>Results</p> <p>RAPD analysis of liver samples generated 8 monomorphic bands and 22 polymorphic bands in a total of 30-banded RAPD patterns. Cluster analysis and statistical analyses of RAPD data resulted in grouping control and NDEA+Q samples in the same group with 80% similarity cut-off value. NDEA-treated samples were clustered in a separate group. Specific PCR assay for polymorphism of <it>P</it><sup>53 </sup>gene revealed a uniform pattern of allele separation in both control and NDEA+Q samples. Quercetin anticancer effect was exhibited in significant decrease of oxidative stress and significant decrease of antioxidant activity. Histopathological studies showed normal liver histology of the NDEA+Q samples. Meanwhile, several cancer-induced features were clearly observable in NDEA-treated samples.</p> <p>Conclusion</p> <p>This paper demonstrated that preventive effect of quercetin on hepatocarcinoma in rats by RAPD-PCR, tracing the effect on <it>p53 </it>gene and by histopathological evidence. Hereby, it was proved that quercetin exerted its preventive effect via decreased oxidative stress and decreased antioxidant activity.</p
First Results from Nb3Sn Coatings of 2.6 GHz Nb SRF Cavities Using DC Cylindrical Magnetron Sputtering System
A DC cylindrical magnetron sputtering system has been commissioned and
operated to deposit Nb3Sn onto 2.6 GHz Nb SRF cavities. After optimizing the
deposition conditions in a mock-up cavity, Nb-Sn films are deposited first on
flat samples by multilayer sequential sputtering of Nb and Sn, and later
annealed at 950 {\deg}C for 3 hours. X-ray diffraction of the films showed
multiple peaks for the Nb3Sn phase and Nb (substrate). No peaks from any Nb3Sn
compound other than Nb3Sn were detected. Later three 2.6 GHz Nb SRF cavities
are coated with ~1 m thick Nb3Sn. The first Nb3Sn coated cavity reached
close to Eacc = 8 MV/m, demonstrating a quality factor Q0 of 3.2 x 108 at Tbath
= 4.4 K and Eacc = 5 MV/m, about a factor of three higher than that of Nb at
this temperature. Q0 was close to 1.1 x 109, dominated by the residual
resistance, at 2 K and Eacc = 5 MV/m. The Nb3Sn coated cavities demonstrated Tc
in the range of 17.9 - 18 K. Here we present the commissioning experience,
system optimization, and the first results from the Nb3Sn fabrication on flat
samples and SRF cavities.Comment: 21st Intl Conf Radio Frequency Superconductivity (SRF 2023
Electron-lattice kinetics of metals heated by ultrashort laser pulses
We propose a kinetic model of transient nonequilibrium phenomena in metals
exposed to ultrashort laser pulses when heated electrons affect the lattice
through direct electron-phonon interaction. This model describes the
destruction of a metal under intense laser pumping. We derive the system of
equations for the metal, which consists of hot electrons and a cold lattice.
Hot electrons are described with the help of the Boltzmann equation and
equation of thermoconductivity. We use the equations of motion for lattice
displacements with the electron force included. The lattice deformation is
estimated immediately after the laser pulse up to the time of electron
temperature relaxation. An estimate shows that the ablation regime can be
achieved.Comment: 7 pages; Revtex. to appear in JETP 88, #1 (1999
Stimulated perturbation on the neutron flux distribution in the mutually-dependent source-to-absorber geometry
The complexity of the neutron transport phenomenon throws its shadows on
every physical system wherever neutron is produced or absorbed. The Monte Carlo
N-Particle Transport Code (MCNP) was used to investigate the flux perturbations
in the neutron field caused by an absorber. The geometry of the present
experiment was designed to reach a simulation of an isotopic neutron field. The
neutron source was a AmBe with the production physics of neutrons is
dependent only on alpha-beryllium interaction and is independent of what
happened to the neutron after it was generated. The geometries have been
designed to get a volume of uniform neutron densities within a spherical volume
of radius 15 cm in every neutron energy group up to 10 MeV. Absorbers of
different dimensions were placed within the volume to investigate the field
perturbation. Different neutron absorbers were used to correlate the phenomenon
to the integral cross-section of the absorber. Flux density inside and outside
the absorber samples was determined, while the spatial neutron flux
distribution produced by the AmBe source without an absorber was taken as a
reference. This study displayed that absorbers of various dimensions perturb
the neutron field in a way that is dependent on the absorption and scattering
cross-sections, particularly in the neutron resonance region. Unlike the simple
picture of reducing the number density of neutrons, the perturbation was found
to influence the moderation of neutrons in the medium, significantly above 1
MeV.Comment: 10 pages, 13 figures, 26 reference
One-stage lingual augmented urethroplasty in repair of distal penile hypospadias
AbstractObjectivesTo evaluate the outcome of augmentation of shallow urethral plate by lingual graft in repair of distal penile hypospadias.Patients and methodsBetween June 2008 and May 2011, the procedure was performed on 23 patients with mean age 2.3 years (range 1–3). All patients had distal penile hypospadias; 11 sub coronal and 12 coronal. The urethral plate was less than 8mm in all patients and 3 of them had history of previous hypospadias surgery. All procedures were carried out under general anesthesia using 4× magnifying loupe. After penile degloving and dorsal incision of the urethral plate, the lingual graft was harvested and sutured to the edges of the incised urethral plate from the hypospadias opening to the tip of the penis. The neourethra was closed and an intervening flap was fixed over the neourethra as a barrier against fistula formation.ResultsSuccess rate was 87% as 20/23 patients were cured without any permanent complication throughout the follow up period. None of patients suffered meatal stenosis or required regular urethral dilatation. Three patients developed urethrocutaneous fistula, of which two closed spontaneously and one required surgical repair 6 months later. Two patients had failed procedures and delayed re-intervention was performed due to complete loss of the graft in one of them and repair disruption following infection in the other. Two patients had post-operative pain in the graft harvesting site which disappeared within days.ConclusionThe one-stage lingual augmented urethral plate urethroplasty offers promising outcomes for repair of distal penile hypospadias with narrow urethral plate
Enhancing lepton flavour violation in the supersymmetric inverse seesaw beyond the dipole contribution
In minimal supersymmetric models the -penguin usually provides
sub-dominant contributions to charged lepton flavour violating observables. In
this study, we consider the supersymmetric inverse seesaw in which the
non-minimal particle content allows for dominant contributions of the
-penguin to several lepton flavour violating observables. In particular, and
due to the low-scale (TeV) seesaw, the penguin contribution to, for instance,
\Br(\mu \to 3e) and conversion in nuclei, allows to render some of
these observables within future sensitivity reach. Moreover, we show that in
this framework, the -penguin exhibits the same non-decoupling behaviour
which had previously been identified in flavour violating Higgs decays in the
Minimal Supersymmetric Standard Model.Comment: 29 pages, 9 figures, 4 tables; v2: minor corrections, version to
appear in JHE
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