TLR Signaling and DNA Repair: Are They Associated?

Toll-like receptor (TLR) signaling is a well-characterized, innate immune cellular defense mechanism used to detect and respond to pathogen-associated molecular patterns (PAMPs). TLR signaling is highly conserved and has evolved to have both extracellular and endosomal receptors that recognize PAMPs from a wide range of microbial pathogens. Recent literature has emerged to show that activation of TLRs not only leads to the upregulation of cellular defense mechanisms, but also results in upregulation of DNA repair genes and increased functional DNA repair. Endosomal TLR agonists result in increased survival and repair after both ionizing and UV radiation, suggesting that the repair pathways for single- and double-strand breaks are affected. This review brings together these and other experimental findings to examine how DNA repair pathways may be linked to TLR signaling. Also discussed are the varied outcomes and related physiological implications that increased DNA repair after injury might have

Differential neuropsychological profiles in Parkinsonian patients with or without vascular lesions.

The purpose of this study is to compare the neuropsychological profile of patients affected by parkinsonism and vascular lesions to that in patients with PD alone (PD) and to evaluate whether the brain vascular lesion load is associated with neuropsychological variables. Thirty-six nondemented patients with parkinsonism were divided into 3 groups of 12 patients each, according to both clinical history and the presence of brain vascular lesions and/or dopaminergic denervation as revealed by magnetic resonance and dopamine transporter imaging, respectively. The first group had vascular lesions without dopaminergic denervation (VP group); the second group had vascular lesions and dopaminergic denervation (DD) (VP+DD group); and the third group consisted of patients with dopaminergic denervation (PD group) without vascular lesions. All patients underwent neurological and neuropsychological assessments. The groups differed in disease duration, age at onset, and cerebrovascular risk factors. The VP and VP+DD groups performed worse than the PD group on frontal/executive tasks. Regardless of the presence of dopaminergic denervation, cerebrovascular lesions in hemispheric white matter, basal ganglia, and cerebellum have an important effect in determining early onset and severity of cognitive impairment in patients with parkinsonism

On the connection between turbulent motions and particle acceleration in galaxy clusters

Giant radio halos are Mpc-scale diffuse radio sources associated with the central regions of galaxy clusters. The most promising scenario to explain the origin of these sources is that of turbulent re-acceleration, in which MeV electrons injected throughout the formation history of galaxy clusters are accelerated to higher energies by turbulent motions mostly induced by cluster mergers. In this Letter, we use the amplitude of density fluctuations in the intracluster medium as a proxy for the turbulent velocity and apply this technique to a sample of 51 clusters with available radio data. Our results indicate a segregation in the turbulent velocity of radio halo and radio quiet clusters, with the turbulent velocity of the former being on average higher by about a factor of two. The velocity dispersion recovered with this technique correlates with the measured radio power through the relation $P_{\rm radio}\propto\sigma_v^{3.3\pm0.7}$, which implies that the radio power is nearly proportional to the turbulent energy rate. Our results provide an observational confirmation of a key prediction of the turbulent re-acceleration model and possibly shed light on the origin of radio halos.Comment: Submitted to ApJ Letter

Superconductivity in Compressed Potassium and Rubidium

Calculations of the electron-phonon interaction in the alkali metals, Potassium and Rubidium, using the results of band theory and BCS theory-based techniques suggest that at high pressures K and Rb would be superconductors with transition temperatures approaching 10 K.Comment: three figure

The relation between gas density and velocity power spectra in galaxy clusters: qualitative treatment and cosmological simulations

We address the problem of evaluating the power spectrum of the velocity field of the ICM using only information on the plasma density fluctuations, which can be measured today by Chandra and XMM-Newton observatories. We argue that for relaxed clusters there is a linear relation between the rms density and velocity fluctuations across a range of scales, from the largest ones, where motions are dominated by buoyancy, down to small, turbulent scales: $(\delta\rho_k/\rho)^2 = \eta_1^2 (V_{1,k}/c_s)^2$, where $\delta\rho_k/\rho$ is the spectral amplitude of the density perturbations at wave number $k$, $V_{1,k}^2=V_k^2/3$ is the mean square component of the velocity field, $c_s$ is the sound speed, and $\eta_1$ is a dimensionless constant of order unity. Using cosmological simulations of relaxed galaxy clusters, we calibrate this relation and find $\eta_1\approx 1 \pm 0.3$. We argue that this value is set at large scales by buoyancy physics, while at small scales the density and velocity power spectra are proportional because the former are a passive scalar advected by the latter. This opens an interesting possibility to use gas density power spectra as a proxy for the velocity power spectra in relaxed clusters, across a wide range of scales.Comment: 6 pages, 3 figures, submitted to ApJ Letter

Colloidal CuFeS2 Nanocrystals: Intermediate Fe d-Band Leads to High Photothermal Conversion Efficiency

We describe the colloidal hot-injection synthesis of phase-pure nanocrystals (NCs) of a highly abundant mineral, chalcopyrite (CuFeS2). Absorption bands centered at around 480 and 950 nm, spanning almost the entire visible and near infrared regions, encompass their optical extinction characteristics. These peaks are ascribable to electronic transitions from the valence band (VB) to the empty intermediate band (IB), located in the fundamental gap and mainly composed of Fe 3d orbitals. Laser-irradiation (at 808 nm) of an aqueous suspension of CuFeS2 NCs exhibited significant heating, with a photothermal conversion efficiency of 49%. Such efficient heating is ascribable to the carrier relaxation within the broad IB band (owing to the indirect VB-IB gap), as corroborated by transient absorption measurements. The intense absorption and high photothermal transduction efficiency (PTE) of these NCs in the so-called biological window (650-900 nm) makes them suitable for photothermal therapy as demonstrated by tumor cell annihilation upon laser irradiation. The otherwise harmless nature of these NCs in dark conditions was confirmed by in vitro toxicity tests on two different cell lines. The presence of the deep Fe levels constituting the IB is the origin of such enhanced PTE, which can be used to design other high performing NC photothermal agents.Comment: 12 pages, Chemistry of Materials, 31-May-201

3D Numerical Simulations of AGN Outflows in Clusters and Groups

We compute 3D gasdynamical models of jet outflows from the central AGN, that carry mass as well as energy to the hot gas in galaxy clusters and groups. These flows have many attractive attributes for solving the cooling flow problem: why the hot gas temperature and density profiles resemble cooling flows but show no spectral evidence of cooling to low temperatures. Subrelativistic jets, described by a few parameters, are assumed to be activated when gas flows toward or cools near a central SMBH. Using approximate models for a rich cluster (A1795), a poor cluster (2A 0336+096) and a group (NGC 5044), we show that mass-carrying jets with intermediate mechanical efficiencies ($\sim10^{-3}$) can reduce for many Gyr the global cooling rate to or below the low values implied by X-spectra, while maintaining $T$ and $\rho$ profiles similar to those observed, at least in clusters. Groups are much more sensitive to AGN heating and present extreme time variability in both profiles. Finally, the intermittency of the feedback generates multiple generations of X-ray cavities similar to those observed in Perseus cluster and elsewhere. Thus we also study the formation of buoyant bubbles and weak shocks in the ICM, along with the injection of metals by SNIa and stellar winds.Comment: 4 pages, 2 figures, to appear in proceedings of the conference "The Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters", June 2009, Madison Wisconsi