Collisional Energy Loss of Fast Charged Particles in Relativistic Plasmas

Following an argument by Kirzhnits we rederive an exact expression for the energy loss of a fast charged particle in a relativistic plasma using the quantum field theoretical language. We compare this result to perturbative calculations of the collisional energy loss of an energetic electron or muon in an electron-positron plasma and of an energetic parton in the quark-gluon plasma.Comment: 9 pages, LATEX, 2 PostScript figure

Photon-Photon Interaction in a Photon Gas

Using the effective Lagrangian for the low energy photon-photon interaction the lowest order photon self energy at finite temperature and in non-equilibrium is calculated within the real time formalism. The Debye mass, the dispersion relation, the dielectric tensor, and the velocity of light following from the photon self energy are discussed. As an application we consider the interaction of photons with the cosmic microwave background radiation.Comment: REVTEX, 7 pages, 1 PostSrcipt figur

Mentalising and social problem solving in adults with Asperger's syndrome

It is well established that autistic spectrum disorder is linked to difficulties with mentalising, but the ways in which this affects everyday behaviour is less well understood. This study explored the nature and extent of difficulties in everyday social functioning in adults with Asperger's syndrome (AS), since increased understanding can enhance the development of more effective intervention strategies. Methods Individuals with AS (n=21) were compared with healthy control participants (n=21) on three tests of social cognition: the Mentalistic Interpretation task, which assesses interpretation of sarcasm and actions; the Social Problem Fluency task, which assesses ability to generate problem solutions; and the Social Problem Resolution task, which assesses judgement in selecting problem solutions. Results Comprehension of both sarcastic remarks and actions was impaired in those with AS on the mentalistic interpretation task. Participants with AS showed difficulties in identifying the awkward elements of everyday social scenarios, and they were also impaired in generating problem solutions but not in judging alternative solutions on the social problem fluency and resolution tasks. Conclusions These tasks potentially provide a means of profiling strengths and weaknesses in social processing, which in turn has implications for informing clinical evaluation and training. © 2013 Taylor & Francis

Field Theoretic Description of Ultrarelativistic Electron-Positron Plasmas

Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here we will use perturbative QED at finite temperature for calculating various important properties, such as the equation of state, dispersion relations of collective plasma modes of photons and electrons, Debye screening, damping rates, mean free paths, collision times, transport coefficients, and particle production rates, of ultrarelativistic electron-positron plasmas. In particular, we will focus on electron-positron plasmas produced with ultra-strong lasers.Comment: 13 pages, 7 figures, 1 table, published versio

The Quark-Gluon-Plasma Liquid

The quark-gluon plasma close to the critical temperature is a strongly interacting system. Using strongly coupled, classical, non-relativistic plasmas as an analogy, we argue that the quark-gluon plasma is in the liquid phase. This allows to understand experimental observations in ultrarelativistic heavy-ion collisions and to interpret lattice QCD results. It also supports the indications of the presence of a strongly coupled QGP in ultrarelativistic heavy-ion collisions.Comment: 8 pages, 2 figures, final version, to bepublished in J. Phys.

First Results from Viper: Detection of Small-Scale Anisotropy at 40 GHZ

Results of a search for small-scale anisotropy in the cosmic microwave background (CMB) are presented. Observations were made at the South Pole using the Viper telescope, with a .26 degree (FWHM) beam and a passband centered at 40 GHz. Anisotropy band-power measurements in bands centered at l = 108, 173, 237, 263, 422 and 589 are reported. Statistically significant anisotropy is detected in all bands.Comment: 5 pages, 4 figures, uses emulateapj.sty, submitted to ApJ Letter

Time efficiency and efficacy of a centralized computer-aided-design/computer-aided-manufacturing workflow for implant crown fabrication: A prospective controlled clinical study

OBJECTIVE To assess time efficiency and the efficacy of the prosthetic manufacturing for implant crown fabrication in a centralized workflow applying computer aided design and computer aided manufacturing (CAD-CAM). MATERIAL AND METHODS Fifty-nine patients with one posterior implant each, were randomly allocated to either a centralized digital workflow (c-DW, test) or a laboratory digital workflow (l-DW, control). Patients were excluded from efficiency and efficacy analyses, if any additional restoration than this single implant crown had to be fabricated. A customized titanium abutment and a monolithic zirconia crown were fabricated in the c-DW. In the l-DW, models were digitalized for CAD-CAM fabrication of a monolithic zirconia crown using a standardized titanium base abutment. Time for impression, laboratory operating and delivery time were recorded. The efficacy of the prosthetic manufacturing was evaluated at try-in and at delivery. Data was analyzed descriptively. Statistical analyses using student's unpaired t- and paired Wilcoxon were performed (p < 0.05). RESULTS At impression taking, 12 patients (c-DW) and 19 patients (l-DW) were included. The impression time was 9.4±3.5 min (c-DW) and 15.1 ± 4.6 min (l-DW) (p < 0.05). The laboratory operating time was 130 ± 31 min (c-DW) and 218.0±8 min (l-DW) (p < 0.05). The delivery time was significantly longer in the c-DW (5.9 ± 3.5 1 days) as compared to the l-DW (0.5±0.05 days). At try-in and at delivery, efficacy of prosthetic manufacturing was similar high in both workflows. CLINICAL RELEVANCE The c-DW was more time efficient compared to the lab-DW and rendered a similar efficacy of prosthetic manufacturing

Elliptic flow at large transverse momenta from quark coalescence

We show that hadronization via quark coalescence enhances hadron elliptic flow at large pT relative to that of partons at the same transverse momentum. Therefore, compared to earlier results based on covariant parton transport theory, more moderate initial parton densities dN/d\eta(b=0) ~ 1500-3000 can explain the differential elliptic flow v_2(pT) data for Au+Au reactions at s^1/2=130 and 200 AGeV from RHIC. In addition, v2(pT) could saturate at about 50% higher values for baryons than for mesons. If strange quarks have weaker flow than light quarks, hadron v_2 at high pT decreases with relative strangeness content.Comment: Minor changes, extended discussion. To appear in PR