713 research outputs found
Spectral Analysis of Solar Radio Type III Bursts from 20 kHz to 410 MHz
We present the statistical analysis of the spectral response of solar radio type III bursts over the wide frequency range between 20 kHz and 410 MHz. For this purpose, we have used observations that were carried out using both spaced-based (Wind/Waves) and ground-based (Nançay Decameter Array and Nançay Radioheliograph) facilities. In order to compare the flux densities observed by the different instruments, we have carefully calibrated the data and displayed them in solar flux units. The main result of our study is that type III bursts, in the metric to hectometric wavelength range, statistically exhibit a clear maximum of their median radio flux density around 2 MHz. Although this result was already reported by inspecting the spectral profiles of type III bursts in the frequency range 20 kHz–20 MHz, our study extends such analysis for the first time to metric radio frequencies (i.e., from 20 kHz to 410 MHz) and confirms the maximum spectral response around 2 MHz. In addition, using a simple empirical model we show that the median radio flux S of the studied data set obeys the polynomial form Y = 0.04X3 − 1.63X2 + 16.30X − 41.24, with and with . Using the Sittler and Guhathakurtha model for coronal streamers, we have found that the maximum of radio power therefore falls in the range 4 to 10 R⊙, depending on whether the type III emissions are assumed to be at the fundamental or the harmonic
Correlation Induced Inhomogeneity in Circular Quantum Dots
Properties of the "electron gas" - in which conduction electrons interact by
means of Coulomb forces but ionic potentials are neglected - change
dramatically depending on the balance between kinetic energy and Coulomb
repulsion. The limits are well understood. For very weak interactions (high
density), the system behaves as a Fermi liquid, with delocalized electrons. In
contrast, in the strongly interacting limit (low density), the electrons
localize and order into a Wigner crystal phase. The physics at intermediate
densities, however, remains a subject of fundamental research. Here, we study
the intermediate-density electron gas confined to a circular disc, where the
degree of confinement can be tuned to control the density. Using accurate
quantum Monte Carlo techniques, we show that the electron-electron correlation
induced by an increase of the interaction first smoothly causes rings, and then
angular modulation, without any signature of a sharp transition in this density
range. This suggests that inhomogeneities in a confined system, which exist
even without interactions, are significantly enhanced by correlations.Comment: final version, modified introduction and clarifications, 4 page
Nitrogenated holey two-dimensional structures
Recent graphene research has triggered enormous interest in new two-dimensional ordered crystals constructed by the inclusion of elements other than carbon for bandgap opening. The design of new multifunctional two-dimensional materials with proper bandgap has become an important challenge. Here we report a layered two-dimensional network structure that possesses evenly distributed holes and nitrogen atoms and a C 2 N stoichiometry in its basal plane. The two-dimensional structure can be efficiently synthesized via a simple wet-chemical reaction and confirmed with various characterization techniques, including scanning tunnelling microscopy. Furthermore, a field-effect transistor device fabricated using the material exhibits an on/off ratio of 10 7, with calculated and experimental bandgaps of approximately 1.70 and 1.96eV, respectively. In view of the simplicity of the production method and the advantages of the solution processability, the C 2 N-h2D crystal has potential for use in practical applications.open111
Collagen II antibody-induced arthritis in Tg1278TNFko mice: optimization of a novel model to assess treatments targeting human TNFα in rheumatoid arthritis
Phellinus linteus sensitises apoptosis induced by doxorubicin in prostate cancer
It has been demonstrated that the Phellinus linteus (PL) mushroom, which mainly consists of polysaccharides, possesses antitumour activity. The mechanisms of PL against malignant growth remain unknown. The anticancer drug doxorubicin (Dox) has been shown to induce apoptosis via initiating a caspase cascade. In this investigation, we tested the effect of PL on Dox-induced apoptosis in prostate cancer LNCaP cells. We showed that PL or Dox, at relatively low doses, does not induce apoptosis in the cells. However, combination treatment with low doses of PL and Dox results in a synergistic effect on the induction of apoptosis. In this apoptotic process, caspases 8, 3 and BID are cleaved, and the addition of caspase inhibitor z-VADfmk completely blocks apoptosis. In addition, JNK is activated in response to PL or the combination treatment in LNCaP cells. The suppression of JNK partially inhibits the induction of apoptosis elicited by the co-treatment. These findings indicate that PL has a synergistic effect with Dox to activate caspases in prostate cancer LNCaP cells. Our study also suggests that PL has therapeutic potential to augment the magnitude of apoptosis induced by antiprostate cancer drugs
Long-term outcome and patterns of failure in patients with advanced head and neck cancer
<p>Abstract</p> <p>Purpose</p> <p>To access the long-time outcome and patterns of failure in patients with advanced head and neck squamous cell carcinoma (HNSCC).</p> <p>Methods and materials</p> <p>Between 1992 and 2005 127 patients (median age 55 years, UICC stage III n = 6, stage IV n = 121) with primarily inoperable, advanced HNSCC were treated with definite platinum-based radiochemotherapy (median dose 66.4 Gy). Analysed end-points were overall survival (OS), disease-free survival (DFS), loco-regional progression-free survival (LPFS), development of distant metastases (DM), prognostic factors and causes of death.</p> <p>Results</p> <p>The mean follow-up time was 34 months (range, 3-156 months), the 3-, 5- and 10-year OS rates were 39%, 28% and 14%, respectively. The median OS was 23 months. Forty-seven patients achieved a complete remission and 78 patients a partial remission. The median LPFS was 17 months, the 3-, 5- and 10-year LPFS rates were 41%, 33% and 30%, respectively. The LPFS was dependent on the nodal stage (p = 0.029). The median DFS was 11 months (range, 2-156 months), the 3-, 5- and 10-year DFS rates were 30%, 24% and 22%, respectively. Prognostic factors in univariate analyses were alcohol abuse (n = 102, p = 0.015), complete remission (n = 47, p < 0.001), local recurrence (n = 71, p < 0.001), development of DM (n = 45, p < 0.001; median OS 16 months) and borderline significance in nodal stage N2 versus N3 (p = 0.06). Median OS was 26 months with lung metastases (n = 17). Nodal stage was a predictive factor for the development of DM (p = 0.025). Cause of death was most commonly tumor progression.</p> <p>Conclusions</p> <p>In stage IV HNSCC long-term survival is rare and DM is a significant predictor for mortality. If patients developed DM, lung metastases had the most favourable prognosis, so intensified palliative treatment might be justified in DM limited to the lungs.</p
Double Diffraction Dissociation at the Fermilab Tevatron Collider
We present results from a measurement of double diffraction dissociation in
collisions at the Fermilab Tevatron collider. The production cross
section for events with a central pseudorapidity gap of width
(overlapping ) is found to be [] at [630]
GeV. Our results are compared with previous measurements and with predictions
based on Regge theory and factorization.Comment: 10 pages, 4 figures, using RevTeX. Submitted to Physical Review
Letter
Search for Kaluza-Klein Graviton Emission in Collisions at TeV using the Missing Energy Signature
We report on a search for direct Kaluza-Klein graviton production in a data
sample of 84 of \ppb collisions at = 1.8 TeV, recorded
by the Collider Detector at Fermilab. We investigate the final state of large
missing transverse energy and one or two high energy jets. We compare the data
with the predictions from a -dimensional Kaluza-Klein scenario in which
gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for
=2, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71
TeV, respectively.Comment: Submitted to PRL, 7 pages 4 figures/Revision includes 5 figure
Search for Gluinos and Scalar Quarks in Collisions at TeV using the Missing Energy plus Multijets Signature
We have performed a search for gluinos (\gls) and squarks (\sq) in a data
sample of 84 pb of \ppb collisions at = 1.8 TeV, recorded by
the Collider Detector at Fermilab, by investigating the final state of large
missing transverse energy and 3 or more jets, a characteristic signature in
R-parity-conserving supersymmetric models. The analysis has been performed
`blind', in that the inspection of the signal region is made only after the
predictions from Standard Model backgrounds have been calculated. Comparing the
data with predictions of constrained supersymmetric models, we exclude gluino
masses below 195 \gev (95% C.L.), independent of the squark mass. For the case
\msq \approx \mgls, gluino masses below 300 \gev are excluded.Comment: 7 pages, 3 figure
Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron
We study the underlying event in proton-antiproton collisions by examining
the behavior of charged particles (transverse momentum pT > 0.5 GeV/c,
pseudorapidity |\eta| < 1) produced in association with large transverse
momentum jets (~2.2 fb-1) or with Drell-Yan lepton-pairs (~2.7 fb-1) in the
Z-boson mass region (70 < M(pair) < 110 GeV/c2) as measured by CDF at 1.96 TeV
center-of-mass energy. We use the direction of the lepton-pair (in Drell-Yan
production) or the leading jet (in high-pT jet production) in each event to
define three regions of \eta-\phi space; toward, away, and transverse, where
\phi is the azimuthal scattering angle. For Drell-Yan production (excluding the
leptons) both the toward and transverse regions are very sensitive to the
underlying event. In high-pT jet production the transverse region is very
sensitive to the underlying event and is separated into a MAX and MIN
transverse region, which helps separate the hard component (initial and
final-state radiation) from the beam-beam remnant and multiple parton
interaction components of the scattering. The data are corrected to the
particle level to remove detector effects and are then compared with several
QCD Monte-Carlo models. The goal of this analysis is to provide data that can
be used to test and improve the QCD Monte-Carlo models of the underlying event
that are used to simulate hadron-hadron collisions.Comment: Submitted to Phys.Rev.
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