TeV Cherenkov Events as Bose-Einstein Gamma Condensations

The recent detection of gamma radiation from Mkn 501 at energies as high as 25 TeV suggests stringent upper bounds on the diffuse, far infrared, extragalactic radiation density. The production of electron-positron pairs through photon-photon collisions would prevent gamma photons of substantially higher energies from reaching us across distances of order 100 Mpc. However, coherently arriving TeV or sub-TeV gammas - Bose-Einstein condensations of photons at these energies - could mimic the Cherenkov shower signatures of extremely energetic gammas. To better understand such events, we describe their observational traits and discuss how they might be generated.Comment: 12 pages, 2 figures, accepted for publication in Ap.J.(Lett.

Competing itinerant and localized states in strongly correlated BaVS3_3

The electronic structure of the quasi-lowdimensional vanadium sulfide \bavs3 is investigated for the different phases above the magnetic ordering temperature. By means of density functional theory and its combination with dynamical-mean field theory, we follow the evolution of the relevant low-energy electronic states on cooling. Hence we go in the metallic regime from the room temperature hexagonal phase to the orthorhombic phase after the first structural transition, and close with the monoclinic insulating phase below the metal-insulator transition. Due to the low symmetry and expected intersite correlations, the latter phase is treated within cellular dynamical mean-field theory. It is generally discussed how the intriguing interplay between band-structure and strong-correlation effects leads to the stabilization of the various electronic phases with decreasing temperature.Comment: 12 pages, submitted to PR

Links between electrophilic stress and antifungal resistance in pathogenic Candida species

Collectively, Candida species are the most prevalent cause of both superficial and invasive fungal infections worldwide. Invasive Candida infections have a high mortality rate and predominantly affect individuals with underlying diseases, such as diabetes, HIV, or cancer. Unfortunately, many invasive Candida infections are recalcitrant to antifungal treatment, while intrinsically multidrug-resistant pathogens, like Candida auris, are increasing in prevalence. Although the canonical mechanisms of antifungal resistance in Candida species are well established, i.e., overexpression of efflux pumps and overexpression of or mutations in genes encoding drug targets, factors affecting the natural evolution and regulation of resistance mechanisms remain poorly understood. One cause of antifungal resistance in Candida species is the acquisition of gain-of-function mutations in the transcription factor Mrr1, resulting in overexpression of the multidrug transporter Mdr1. However, little is known about the functions of other genes regulated by Mrr1 or how Mrr1 activity is modulated in vivo. In this work, we demonstrate in Candida lusitaniae and in C. auris that Mrr1 contributes to resistance against methylglyoxal (MG), a toxic, electrophilic dicarbonyl derived from natural metabolic processes, and that Mrr1-mediated MG resistance is driven in part by expression of the methylglyoxal reductase genes MGD1 and MGD2 in C. lusitaniae and MGD1 in C. auris. Furthermore, we show that a sublethal concentration of MG induces expression of MDR1 and MG reductase genes in C. lusitaniae and C. auris, and consequently increases fluconazole (FLZ) resistance in C. lusitaniae. Finally, we characterize the complete Mrr1- dependent and independent transcriptional response of C. auris to MG and to the known inducer of Mrr1-regulated gene expression, benomyl, and show that both compounds cause the differential expression of a multitude of genes involved in metabolism and stress response, which could contribute to pathogen survival while colonizing and infecting a mammalian host. Together, the work presented herein provides valuable insight into a potential mechanism for the regulation of Mrr1-dependent transcription in vivo as well as a possible selective pressure for gain-of-function mutations in the MRR1 gene. This is particularly noteworthy because MG is elevated in many of the same human diseases that are considered risk factors for Candida infection, and MG is also produced by activated phagocytes in response to pathogens. Thus, it is conceivable that Candida would encounter biologically significant levels of MG in the context of infection. We propose that MG-mediated induction of Mrr1-dependent transcription in Candida species is one factor that plays a role in antifungal treatment failure

Correlation between Compact Radio Quasars and Ultra-High Energy Cosmic Rays

Some proposals to account for the highest energy cosmic rays predict that they should point to their sources. We study the five highest energy events (E>10^20 eV) and find they are all aligned with compact, radio-loud quasars. The probability that these alignments are coincidental is 0.005, given the accuracy of the position measurements and the rarity of such sources. The source quasars have redshifts between 0.3 and 2.2. If the correlation pointed out here is confirmed by further data, the primary must be a new hadron or one produced by a novel mechanism.Comment: 8 pages, 3 tables, revtex. with some versions of latex it's necessary to break out the tables and latex them separately using article.sty rather than revtex.st

The Origin of Galactic Cosmic Rays

Motivated by recent measurements of the major components of the cosmic radiation around 10 TeV/nucleon and above, we discuss the phenomenology of a model in which there are two distinct kinds of cosmic ray accelerators in the galaxy. Comparison of the spectra of hydrogen and helium up to 100 TeV per nucleon suggests that these two elements do not have the same spectrum of magnetic rigidity over this entire region and that these two dominant elements therefore receive contributions from different sources.Comment: To be published in Physical Review D, 13 pages, with 3 figures, uuencode

Cluster magnetic fields from large-scale-structure and galaxy-cluster shocks

The origin of the micro-Gauss magnetic fields in galaxy clusters is one of the outstanding problem of modern cosmology. We have performed three-dimensional particle-in-cell simulations of the nonrelativistic Weibel instability in an electron-proton plasma, in conditions typical of cosmological shocks. These simulations indicate that cluster fields could have been produced by shocks propagating through the intergalactic medium during the formation of large-scale structure or by shocks within the cluster. The strengths of the shock-generated fields range from tens of nano-Gauss in the intercluster medium to a few micro-Gauss inside galaxy clusters.Comment: 4 pages, 2 color figure