5,073 research outputs found
The ultraviolet limit and sum rule for the shear correlator in hot Yang-Mills theory
We determine a next-to-leading order result for the correlator of the shear
stress operator in high-temperature Yang-Mills theory. The computation is
performed via an ultraviolet expansion, valid in the limit of small distances
or large momenta, and the result is used for writing operator product
expansions for the Euclidean momentum and coordinate space correlators as well
as for the Minkowskian spectral density. In addition, our results enable us to
confirm and refine a shear sum rule originally derived by Romatschke, Son and
Meyer.Comment: 16 pages, 2 figures. v2: small clarifications, one reference added,
published versio
Kinks in the dispersion of strongly correlated electrons
The properties of condensed matter are determined by single-particle and
collective excitations and their interactions. These quantum-mechanical
excitations are characterized by an energy E and a momentum \hbar k which are
related through their dispersion E_k. The coupling of two excitations may lead
to abrupt changes (kinks) in the slope of the dispersion. Such kinks thus carry
important information about interactions in a many-body system. For example,
kinks detected at 40-70 meV below the Fermi level in the electronic dispersion
of high-temperature superconductors are taken as evidence for phonon or
spin-fluctuation based pairing mechanisms. Kinks in the electronic dispersion
at binding energies ranging from 30 to 800 meV are also found in various other
metals posing questions about their origins. Here we report a novel, purely
electronic mechanism yielding kinks in the electron dispersions. It applies to
strongly correlated metals whose spectral function shows well separated Hubbard
subbands and central peak as, for example, in transition metal-oxides. The
position of the kinks and the energy range of validity of Fermi-liquid (FL)
theory is determined solely by the FL renormalization factor and the bare,
uncorrelated band structure. Angle-resolved photoemission spectroscopy (ARPES)
experiments at binding energies outside the FL regime can thus provide new,
previously unexpected information about strongly correlated electronic systems.Comment: 8 pages, 5 figure
SILAC-based phosphoproteomics reveals an inhibitory role of KSR1 in p53 transcriptional activity via modulation of DBC1
BACKGROUND
We have previously identified kinase suppressor of ras-1 (KSR1) as a potential regulatory gene in breast cancer. KSR1, originally described as a novel protein kinase, has a role in activation of mitogen-activated protein kinases. Emerging evidence has shown that KSR1 may have dual functions as an active kinase as well as a scaffold facilitating multiprotein complex assembly. Although efforts have been made to study the role of KSR1 in certain tumour types, its involvement in breast cancer remains unknown.
METHODS
A quantitative mass spectrometry analysis using stable isotope labelling of amino acids in cell culture (SILAC) was implemented to identify KSR1-regulated phosphoproteins in breast cancer. In vitro luciferase assays, co-immunoprecipitation as well as western blotting experiments were performed to further study the function of KSR1 in breast cancer.
RESULTS
Of significance, proteomic analysis reveals that KSR1 overexpression decreases deleted in breast cancer-1 (DBC1) phosphorylation. Furthermore, we show that KSR1 decreases the transcriptional activity of p53 by reducing the phosphorylation of DBC1, which leads to a reduced interaction of DBC1 with sirtuin-1 (SIRT1); this in turn enables SIRT1 to deacetylate p53.
CONCLUSION
Our findings integrate KSR1 into a network involving DBC1 and SIRT1, which results in the regulation of p53 acetylation and its transcriptional activity
Aharonov-Bohm interference in topological insulator nanoribbons
Topological insulators represent novel phases of quantum matter with an
insulating bulk gap and gapless edges or surface states. The two-dimensional
topological insulator phase was predicted in HgTe quantum wells and confirmed
by transport measurements. Recently, Bi2Se3 and related materials have been
proposed as three-dimensional topological insulators with a single Dirac cone
on the surface and verified by angle-resolved photoemission spectroscopy
experiments. Here, we show unambiguous transport evidence of topological
surface states through periodic quantum interference effects in layered
single-crystalline Bi2Se3 nanoribbons. Pronounced Aharonov-Bohm oscillations in
the magnetoresistance clearly demonstrate the coverage of two-dimensional
electrons on the entire surface, as expected from the topological nature of the
surface states. The dominance of the primary h/e oscillation and its
temperature dependence demonstrate the robustness of these electronic states.
Our results suggest that topological insulator nanoribbons afford novel
promising materials for future spintronic devices at room temperature.Comment: 5 pages, 4 figures, RevTex forma
Epidemiology and natural history of central venous access device use and infusion pump function in the NO16966 trial
Background: Central venous access devices in fluoropyrimidine therapy are associated with complications; however, reliable data are lacking regarding their natural history, associated complications and infusion pump performance in patients with metastatic colorectal cancer.<p></p>
Methods: We assessed device placement, use during treatment, associated clinical outcomes and infusion pump perfomance in the NO16966 trial.<p></p>
Results: Device replacement was more common with FOLFOX-4 (5-fluorouracil (5-FU)+oxaliplatin) than XELOX (capecitabine+oxaliplatin) (14.1% vs 5.1%). Baseline device-associated events and post-baseline removal-/placement-related events occurred more frequently with FOLFOX-4 than XELOX (11.5% vs 2.4% and 8.5% vs 2.1%). Pump malfunctions, primarily infusion accelerations in 16% of patients, occurred within 1.6–4.3% of cycles. Fluoropyrimidine-associated grade 3/4 toxicity was increased in FOLFOX-4-treated patients experiencing a malfunction compared with those who did not (97 out of 155 vs 452 out of 825 patients), predominantly with increased grade 3/4 neutropenia (53.5% vs 39.8%). Febrile neutropenia rates were comparable between patient cohorts±malfunction. Efficacy outcomes were similar in patient cohorts±malfunction.<p></p>
Conclusions: Central venous access device removal or replacement was common and more frequent in patients receiving FOLFOX-4. Pump malfunctions were also common and were associated with increased rates of grade 3/4 haematological adverse events. Oral fluoropyrimidine-based regimens may be preferable to infusional 5-FU based on these findings
Two Energy Scales and two Quasiparticle Dynamics in the Superconducting State of Underdoped Cuprates
The superconducting state of underdoped cuprates is often described in terms
of a single energy-scale, associated with the maximum of the (d-wave) gap.
Here, we report on electronic Raman scattering results, which show that the gap
function in the underdoped regime is characterized by two energy scales,
depending on doping in opposite manners. Their ratios to the maximum critical
temperature are found to be universal in cuprates. Our experimental results
also reveal two different quasiparticle dynamics in the underdoped
superconducting state, associated with two regions of momentum space: nodal
regions near the zeros of the superconducting gap and antinodal regions. While
antinodal quasiparticles quickly loose coherence as doping is reduced, coherent
nodal quasiparticles persist down to low doping levels. A theoretical analysis
using a new sum-rule allows us to relate the low-frequency-dependence of the
Raman response to the temperature-dependence of the superfluid density, both
controlled by nodal excitations.Comment: 16 pages, 5 figure
Gated Diffusion-controlled Reactions
The binding and active sites of proteins are often dynamically occluded by motion of the nearby polypeptide. A variety of theoretical and computational methods have been developed to predict rates of ligand binding and reactivity in such cases. Two general approaches exist, "protein centric" approaches that explicitly treat only the protein target, and more detailed dynamical simulation approaches in which target and ligand are both treated explicitly. This mini-review describes recent work in this area and some of the biological implications
Anti-inflammatory recombinant TSG-6 stabilizes the progression of focal retinal degeneration in a murine model
<p>Abstract</p> <p>Background</p> <p>Inflammatory responses are detected in the retina of patients with age-related macular degeneration and <it>Ccl2<sup>-/-</sup>/Cx3cr1<sup>-/- </sup></it>mice on rd8 background,(<it>Ccl2<sup>-/-</sup>/Cx3cr1<sup>-/- </sup></it>mice) a model that develops progressive age-related macular degeneration-like retinal lesions including focal photoreceptor degeneration, abnormal retinal pigment epithelium and A2E accumulation. Tumor necrosis factor-inducible gene 6 protein is an anti-inflammatory protein and has been shown to improve myocardial infarction outcome and chemically injured cornea in mice by suppressing inflammation. In this study, we evaluated the effect of an intravitreous injection of recombinant TSG-6 on the retinal lesions of <it>Ccl2<sup>-/-</sup>/Cx3cr1<sup>-/- </sup></it>mice.</p> <p>Methods</p> <p>Recombinant TSG-6 (400 ng) was administered by intravitreous injection into the right eye of six-week-old C<it>cl2<sup>-/-</sup>/Cx3cr1<sup>-/- </sup></it>mice. Their left eye was injected with phosphate-buffered saline as a control. Funduscopic pictures were taken before injection and sequentially once a month after injection. The mice were killed two months after injection and the ocular histology examined. Retinal A2E, a major component of lipofuscin, was measured by high performance liquid chromatography. The microarray of ocular mRNA of 92 immunological genes was performed. The genes showing differentiated expression in microarray were further compared between the injected right eye and the contralateral (control) eye by [real-time quantitative reverse transcription polymerase chain reaction] qRT-PCR.</p> <p>Results</p> <p>The continuous monitoring of the fundus for two months showed a slower progression or alleviation of retinal lesions in the treated right eyes as compared with the untreated left eyes. Among 23 pairs of eyes, the lesion levels improved in 78.3%, stayed the same in 8.7% and progressed in 13.0%. Histology confirmed the clinical observation. Even though there was no difference in the level of A2E between the treated and the untreated eyes, microarray analysis of 92 immune genes showed that <it>IL-17a </it>was substantially decreased after the treatment. Expression of <it>TNF-α </it>showed a similar pattern to <it>IL-17a</it>. The results were consistent in duplicated arrays and confirmed by qRT-PCR.</p> <p>Conclusions</p> <p>We concluded that intravitreous administration of recombinant TSG-6 might stabilize retinal lesions in <it>Ccl2<sup>-/-</sup>/Cx3cr1<sup>-/- </sup></it>mice on rd8 background. Modulation of ocular immunological gene expressions, especially IL-17a, could be one of the mechanisms.</p
Quantum wave mixing and visualisation of coherent and superposed photonic states in a waveguide
Superconducting quantum systems (artificial atoms) have been recently
successfully used to demonstrate on-chip effects of quantum optics with single
atoms in the microwave range. In particular, a well-known effect of four-wave
mixing could reveal a series of features beyond classical physics, when a
non-linear medium is scaled down to a single quantum scatterer. Here we
demonstrate a phenomenon of the quantum wave mixing (QWM) on a single
superconducting artificial atom. In the QWM, the spectrum of elastically
scattered radiation is a direct map of the interacting superposed and coherent
photonic states. Moreover, the artificial atom visualises photon-state
statistics, distinguishing coherent, one- and two-photon superposed states with
the finite (quantized) number of peaks in the quantum regime. Our results may
give a new insight into nonlinear quantum effects in microwave optics with
artificial atoms.Comment: 6 pages, 5 figures; accepted versio
Clinical and prognostic analysis of 78 patients with human immuno-deficiency virus associated non-Hodgkin’s lymphoma in Chinese population
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