340 research outputs found
Back reaction effects on the dynamics of heavy probes in heavy quark cloud
We holographically study the effect of back reaction on the hydrodynamical
properties of strongly coupled super Yang-Mills (SYM) thermal
plasma. The back reaction we consider arises from the presence of static heavy
quarks uniformly distributed over SYM plasma. In order to
study the hydrodynamical properties, we use heavy quark as well as heavy
quark-antiquark bound state as probes and compute the jet quenching parameter,
screening length and binding energy. We also consider the rotational dynamics
of heavy probe quark in the back-reacted plasma and analyse associated energy
loss. We observe that the presence of back reaction enhances the energy-loss in
the thermal plasma. Finally, we show that there is no effect of angular drag on
the rotational motion of quark-antiquark bound state probing the back reacted
thermal plasma.Comment: 29 pages, 21 figure
Electrified plasma in AdS/CFT correspondence
We construct new gravity backgrounds holographic dual to neutral plasma with
U(1) global symmetry in the presence of constant electric field, considering
its full back-reactions to the metric. As the electric field and the induced
current cause a net energy in-flow to the system, the plasma is continually
heated up and the corresponding gravity solution has an expanding horizon.
After proposing a consistent late-time expansion scheme, we present analytic
solutions in the scheme up to next-leading order, and our solutions are new
time-dependent solutions of 5D asymptotic AdS Einstein-Maxwell(-Chern-Simons)
theory. To extract dual CFT stress tensor and U(1) current from the solutions,
we perform a rigorous holographic renormalization of
Einstein-Maxwell-Chern-Simons theory including full back-reactions, which can
in itself be an interesting addition to literatures. As by-products, we obtain
interesting modifications of energy-momentum/current Ward identities due to the
U(1) symmetry and its triangle anomaly.Comment: 27 pages, no figure, v3, minor typos fixed, matches with published
versio
Holographic RG flow of the shear viscosity to entropy density ratio in strongly coupled anisotropic plasma
We study holographic RG flow of the shear viscosity tensor of anisotropic,
strongly coupled N=4 super-Yang-Mills plasma by using its type IIB supergravity
dual in anisotropic bulk spacetime. We find that the shear viscosity tensor has
three independent components in the anisotropic bulk spacetime away from the
boundary, and one of the components has a non-trivial RG flow while the other
two have a trivial one. For the component of the shear viscosity tensor with
non-trivial RG flow, we derive its RG flow equation, and solve the equation
analytically to second order in the anisotropy parameter 'a'. We derive the RG
equation using the equation of motion, holographic Wilsonian RG method, and
Kubo's formula. All methods give the same result. Solving the equation, we find
that the ratio of the component of the shear viscosity tensor to entropy
density 'eta/s' flows from above '1/4pi' at the horizon (IR) to below '1/4pi'
at the boundary (UV) where it violates the holographic shear viscosity
(Kovtun-Son-Starinets) bound and where it agrees with the other longitudinal
component.Comment: 17 pages, 2 figures, slight change on the title, more background
material added, references added, accepted for publication in JHE
Diffractive Higgs Production by AdS Pomeron Fusion
The double diffractive Higgs production at central rapidity is formulated in
terms of the fusion of two AdS gravitons/Pomerons first introduced by Brower,
Polchinski, Strassler and Tan in elastic scattering. Here we propose a simple
self-consistent holographic framework capable of providing phenomenologically
compelling estimates of diffractive cross sections at the LHC. As in the
traditional weak coupling approach, we anticipate that several phenomenological
parameters must be tested and calibrated through factorization for a
self-consistent description of other diffractive process such as total cross
sections, deep inelastic scattering and heavy quark production in the central
region.Comment: 53 pages, 8 figure
Holographic Fermi and Non-Fermi Liquids with Transitions in Dilaton Gravity
We study the two-point function for fermionic operators in a class of
strongly coupled systems using the gauge-gravity correspondence. The gravity
description includes a gauge field and a dilaton which determines the gauge
coupling and the potential energy. Extremal black brane solutions in this
system typically have vanishing entropy. By analyzing a charged fermion in
these extremal black brane backgrounds we calculate the two-point function of
the corresponding boundary fermionic operator. We find that in some region of
parameter space it is of Fermi liquid type. Outside this region no well-defined
quasi-particles exist, with the excitations acquiring a non-vanishing width at
zero frequency. At the transition, the two-point function can exhibit non-Fermi
liquid behaviour.Comment: 52 pages, 6 figures. v3: Appendix F added showing numerical
interpolation between the near-horizon region and AdS4. Additional minor
comments also adde
Calcium electroporation and electrochemotherapy for cancer treatment:Importance of cell membrane composition investigated by lipidomics, calorimetry and in vitro efficacy
Abstract Calcium electroporation is a novel anti-cancer treatment investigated in clinical trials. We explored cell sensitivity to calcium electroporation and electroporation with bleomycin, using viability assays at different time and temperature points, as well as heat calorimetry, lipidomics, and flow cytometry. Three cell lines: HT29 (colon cancer), MDA-MB231 (breast cancer), and HDF-n (normal fibroblasts) were investigated for; (a) cell survival dependent on time of addition of drug relative to electroporation (1.2 kV/cm, 8 pulses, 99 µs, 1 Hz), at different temperatures (37 °C, 27 °C, 17 °C); (b) heat capacity profiles obtained by differential scanning calorimetry without added calcium; (c) lipid composition by mass spectrometry; (d) phosphatidylserine in the plasma membrane outer leaflet using flow cytometry. Temperature as well as time of drug administration affected treatment efficacy in HT29 and HDF-n cells, but not MDA-MB231 cells. Interestingly the HT29 cell line displayed a higher phase transition temperature (approximately 20 °C) versus 14 °C (HDF-n) and 15 °C (MDA-MB231). Furthermore the HT29 cell membranes had a higher ratio of ethers to esters, and a higher expression of phosphatidylserine in the outer leaflet. In conclusion, lipid composition and heat capacity of the membrane might influence permeabilisation of cells and thereby the effect of calcium electroporation and electrochemotherapy
Lung Cancer in Pulmonary Fibrosis: Tales of Epithelial Cell Plasticity
Lung epithelial cells exhibit a high degree of plasticity. Alterations to lung epithelial cell function are critically involved in several chronic lung diseases such as pulmonary fibrosis. Pulmonary fibrosis is characterized by repetitive injury and subsequent impaired repair of epithelial cells, which leads to aberrant growth factor activation and fibroblast accumulation. Increased proliferation and hyper- and metaplasia of epithelial cells upon injury have also been observed in pulmonary fibrosis; this epithelial cell activation might represent the basis for lung cancer development. Indeed, several studies have provided histopathological evidence of an increased incidence of lung cancer in pulmonary fibrosis. The mechanisms involved in the development of cancer in pulmonary fibrosis, however, remain poorly understood. This review highlights recently uncovered molecular mechanisms shared between lung cancer and fibrosis, which extend the current evidence of a common trait of cancer and fibrosis, as provided by histopathological observations. Copyright (C) 2011 S. Karger AG, Base
Epithelial ovarian cancer relapsing as isolated lymph node disease: natural history and clinical outcome
<p>Abstract</p> <p>Background</p> <p>Several evidences suggested that ovarian cancer (OC) patients showing isolated lymph node recurrence (ILNR) have an indolent evolution. The aim of the study was to retrospectively review ILNR observed in our Institution over the past 11 years in order to investigate: the pattern of disease progression after the first diagnosis of ILNR, and their clinical outcome.</p> <p>Methods</p> <p>Between September 1995 and September 2006, 523 epithelial OC were diagnosed in our centers, and 301 of these relapsed. Cases with a diagnosis of ILNR, and at least 12 months of follow up after the diagnosis of ILNR were included. Post-relapse survival (PRS) was recorded from the date of the diagnosis of ILNR to the date of death or date last seen. Survival probabilities were estimated according to the method of Kaplan and Meier and compared by the log rank test. Cox's regression model with stepwise variable selection was used to analyse the role of clinico-pathological parameters as prognostic factors for PRS.</p> <p>Results</p> <p>Thirty-two cases were identified as ILNR (10.6% of the recurrences, and 6.1% of the OC population). Most of the patients continued to exhibit the same pattern of progression during follow up, with 75% of the patients free from peritoneal disease after 2 years from the diagnosis of ILNR. Median Post-Relapse Survival (PRS) was 37 months, and median Overall Survival (OS) was 109 months, with all patients surviving more than 2 years after the initial diagnosis. In multivariate analysis only Platinum-Free Interval (PFI) retained a prognostic role for PRS (p value = 0.033).</p> <p>Conclusion</p> <p>ILNR represents a less aggressive pattern of OC relapse which keeps progressing in the lymph nodes in a relatively high percentage of cases. On the other hand, the occurrence of peritoneal spreading after ILNR is associated with a rapidly fatal outcome.</p
Complicated skin, skin structure and soft tissue infections - are we threatened by multi-resistant pathogens?
Tissue infections or skin, skin structure, and deep seated soft tissue infections are general terms for infections of the entire skin layer including the subcutaneous and muscle tissue layers and their respective fascia structures. Infections of the different mediastinal fascias (mediastinitis) and retroperitoneal fascia infections also belong to this category. Due to the variability of their clinical presentation, skin and soft tissue infections can be classified according to different features. The following aspects can be used for classification
Altered monocyte and fibrocyte phenotype and function in scleroderma interstitial lung disease: reversal by caveolin-1 scaffolding domain peptide
Interstitial lung disease (ILD) is a major cause of morbidity and mortality in scleroderma (systemic sclerosis, or SSc). Fibrocytes are a monocyte-derived cell population implicated in the pathogenesis of fibrosing disorders. Given the recently recognized importance of caveolin-1 in regulating function and signaling in SSc monocytes, in the present study we examined the role of caveolin-1 in the migration and/or trafficking and phenotype of monocytes and fibrocytes in fibrotic lung disease in human patients and an animal model. These studies fill a gap in our understanding of how monocytes and fibrocytes contribute to SSc-ILD pathology. We found that C-X-C chemokine receptor type 4-positive (CXCR4+)/collagen I-positive (ColI+), CD34+/ColI+ and CD45+/ColI+ cells are present in SSc-ILD lungs, but not in control lungs, with CXCR4+ cells being most prevalent. Expression of CXCR4 and its ligand, stromal cell-derived factor 1 (CXCL12), are also highly upregulated in SSc-ILD lung tissue. SSc monocytes, which lack caveolin-1 and therefore overexpress CXCR4, exhibit almost sevenfold increased migration toward CXCL12 compared to control monocytes. Restoration of caveolin-1 function by administering the caveolin scaffolding domain (CSD) peptide reverses this hypermigration. Similarly, transforming growth factor β-treated normal monocytes lose caveolin-1, overexpress CXCR4 and exhibit 15-fold increased monocyte migration that is CSD peptide-sensitive. SSc monocytes exhibit a different phenotype than normal monocytes, expressing high levels of ColI, CD14 and CD34. Because ColI+/CD14+ cells are prevalent in SSc blood, we looked for such cells in lung tissue and confirmed their presence in SSc-ILD lungs but not in normal lungs. Finally, in the bleomycin model of lung fibrosis, we show that CSD peptide diminishes fibrocyte accumulation in the lungs. Our results suggest that low caveolin-1 in SSc monocytes contributes to ILD via effects on cell migration and phenotype and that the hyperaccumulation of fibrocytes in SSc-ILD may result from the altered phenotype and migratory activity of their monocyte precursors
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