Suppression of the high pTp_T charged hadron RAAR_{AA} at the LHC

We present a parameter free postdiction of the high-$p_T$ charged-hadron nuclear modification factor ($R_{AA}$) in two centralities, measured by the CMS collaboration in $Pb$-$Pb$ collisions at the Large Hadron Collider (LHC). The evolution of the bulk medium is modeled using viscous fluid dynamics, with parameters adjusted to describe the soft hadron yields and elliptic flow. Assuming the dominance of radiative energy loss, we compute the medium modification of the $R_{AA}$ using a perturbative QCD based formalism, the higher twist scheme. The transverse momentum diffusion coefficient $\hat{q}$ is assumed to scale with the entropy density and normalized by fitting the $R_{AA}$ in the most central $Au$-$Au$ collisions at the Relativistic Heavy-Ion Collider (RHIC). This set up is validated in non-central $Au$-$Au$ collisions at RHIC and then extrapolated to $Pb$-$Pb$ collisions at the LHC, keeping the relation between $\hat{q}$ and entropy density unchanged. We obtain a satisfactory description of the CMS $R_{AA}$ over the $p_{T}$ range from 10-100 GeV.Comment: 4 pages, 3 figures, revtex4, new experimental data used, new calculations with systematic error bands, changed abstract and contents, conclusions unchange

Particle Production at Large Transverse Momentum with ALICE

We present transverse momentum distributions of inclusive charged particles and identified hadrons in $pp$ and Pb--Pb collisions at \rs= 2.76 TeV, measured by ALICE at the LHC. The Pb--Pb data are presented in intervals of collision centrality and cover transverse momenta up to 50 GeV/$c$. Nuclear medium effects are studied in terms of the nuclear modification factor \raa. The results indicate a strong suppression of high-$p_T$ particles in Pb--Pb collisions, consistent with a large energy loss of hard-scattered partons in the hot, dense and long-lived medium created at the LHC. We compare the preliminary results for inclusive charged particles to previous results from RHIC and calculations from energy loss models. Furthermore, we compare the nuclear modification factors of inclusive charged particles to those of identified $\pi^0$, $\pi^{\pm}$, K$^0_s$, and $\Lambda$.Comment: Talk given at Quark Matter 2011 conferenc

Charged Particle Production at Large Transverse Momentum in Pb−-Pb Collisions at sNN=2.76\sqrt{s_{NN}}=2.76 TeV Measured with ALICE at the LHC

Transverse momentum ($p_{T}$) spectra of charged particles are measured as a function of event centrality in Pb$-$Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV with ALICE at the LHC. The spectra are compared to those measured in pp collisions at the same collision energy in terms of the nuclear modification factor $R_{AA}$. The high-$p_{T}$ charge particle production in central Pb$-$Pb collisions ($0-5$) is strongly suppressed by a factor $\approx6$ at transverse momenta $p_{T}=6-7$ GeV/c as compared to expectation from independent superposition of nucleon-nucleon collisions. Above $p_{T}=7$ GeV/c there is a significant rise in the nuclear modification factor, which reaches $R_{AA} \approx 0.4$ at $p_{T}=50$ GeV/c. The measured suppression of high-$p_{T}$ particles is stronger than that measured at RHIC.Comment: 4 pages, 6 figures, Quark Matter 2011 Proceeding

How consistent are the transcriptome changes associated with cold acclimation in two species of the Drosophila virilis group?

This work was financially support by a Marie Curie Initial Training Network grant, “Understanding the evolutionary origin of biological diversity” (ITN-2008–213780 SPECIATION), grants from the Academy of Finland to A.H. (project 132619) and M.K. (projects 268214 and 272927), a grant from NERC, UK to M.G.R. (grant NE/J020818/1), and NERC, UK PhD studentship to D.J.P. (NE/I528634/1).For many organisms the ability to cold acclimate with the onset of seasonal cold has major implications for their fitness. In insects, where this ability is widespread, the physiological changes associated with increased cold tolerance have been well studied. Despite this, little work has been done to trace changes in gene expression during cold acclimation that lead to an increase in cold tolerance. We used an RNA-Seq approach to investigate this in two species of the Drosophila virilis group. We found that the majority of genes that are differentially expressed during cold acclimation differ between the two species. Despite this, the biological processes associated with the differentially expressed genes were broadly similar in the two species. These included: metabolism, cell membrane composition, and circadian rhythms, which are largely consistent with previous work on cold acclimation/cold tolerance. In addition, we also found evidence of the involvement of the rhodopsin pathway in cold acclimation, a pathway that has been recently linked to thermotaxis. Interestingly, we found no evidence of differential expression of stress genes implying that long-term cold acclimation and short-term stress response may have a different physiological basis.PostprintPeer reviewe

Multiple Oncogenic Pathway Signatures Show Coordinate Expression Patterns in Human Prostate Tumors

BACKGROUND: Gene transcription patterns associated with activation of oncogenes Myc, c-Src, beta-catenin, E2F3, H-Ras, HER2, EGFR, MEK, Raf, MAPK, Akt, and cyclin D1, as well as of the cell cycle and of androgen signaling have been generated in previous studies using experimental models. It was not clear whether genes in these "oncogenic signatures" would show coordinate expression patterns in human prostate tumors, particularly as most of the signatures were derived from cell types other than prostate. PRINCIPAL FINDINGS: The above oncogenic pathway signatures were examined in four different gene expression profile datasets of human prostate tumors (representing approximately 250 patients in all), using both Q1-Q2 and one-sided Fisher's exact enrichment analysis methods. A significant fraction (approximately 5%) of genes up-regulated experimentally by Myc, c-Src, HER2, Akt, or androgen were co-expressed in human tumors with the oncogene or biomarker corresponding to the pathway signature. Genes down-regulated experimentally, however, did not show anticipated patterns of anti-enrichment in the human tumors. CONCLUSIONS: Significant subsets of the genes in these experimentally-derived oncogenic signatures are relevant to the study of human prostate cancer. Both molecular biologists and clinical researchers could focus attention on the relatively small number of genes identified here as having coordinate patterns that arise from both the experimental system and the human disease system