Enhancement of low-mass dileptons in heavy-ion collisions

Using a relativistic transport model for the expansion stage of S+Au collisions at 200 GeV/nucleon, we show that the recently observed enhancement of low-mass dileptons by the CERES collaboration can be explained by the decrease of vector meson masses in hot and dense hadronic matter.Comment: 12 pages, RevTeX, 3 figures available from [email protected]

Dilepton production in proton-nucleus and nucleus-nucleus collisions at SPS energies

Dilepton production in proton- and nucleus-induced reactions is studied in relativistic transport model using initial conditions determined by the string dynamics from RQMD. It is found that both the CERES and HELIOS-3 data for dilepton spectra in proton-nucleus reactions can be well described by the `conventional' mechanism of Dalitz decay and direct vector meson decay. However, to provide a quantitative explanation of the observed dilepton spectra in central S+Au and S+W collisions requires contributions other than these direct decays. Introducing a decrease of vector meson masses in hot and dense medium, we find that these heavy-ion data can also be satisfactorily explained. This agrees with our earlier conclusions based on a fire cylinder model. We also give predictions for Pb+Au collisions at 160 GeV/nucleon using current CERES mass resolution and acceptance.Comment: RevTeX, 45 pages, including 21 postscript figures, to be published in Nuclear Physics

Competition of Superconductivity and Antiferromagnetism in a d-Wave Vortex Lattice

The d-wave vortex lattice state is studied within the framework of Bogoliubov-de Gennes (BdG) mean field theory. We allow antiferromagnetic (AFM) order to develop self-consistently along with d-wave singlet superconducting (dSC) order in response to an external magnetic field that generates vortices. The resulting AFM order has strong peaks at the vortex centers, and changes sign, creating domain walls along lines where $\nabla \times j_s \approx 0$. The length scale for decay of this AFM order is found to be much larger than the bare d-wave coherence length, $\xi$. Coexistence of dSC and AFM order in this system is shown to induce $\pi$-triplet superconducting order. Competition between different orders is found to suppress the local density of states at the vortex center and comparison to recent experimental findings is discussed.Comment: 10 pages, 7 figure

Effects of in-medium vector meson masses on low-mass dileptons from SPS heavy-ion collisions

Using a relativistic transport model to describe the expansion of the fire-cylinder formed in the initial stage of heavy-ion collisions at SPS/CERN energies, we study the production of dileptons with mass below about 1 GeV from these collisions. The initial hadron abundance and their momentum distributions in the fire-cylinder are determined by following the general features of the results from microscopic models based on the string dynamics and further requiring that the final proton and pion spectra and rapidity distributions are in agreement with available experimental data. For dilepton production, we include the Dalitz decay of $\pi ^0$, $\eta$, $\eta^\prime$, $\omega$ and $a_1$ mesons, the direct decay of primary $\rho ^0$, $\omega$ and $\phi$ mesons, and the pion-pion annihilation that proceeds through the $\rho^0$ meson, the pion-rho annihilation that proceeds through the $a_1$ meson, and the kaon-antikaon annihilation that proceeds through the $\phi$ meson. We find that the modification of vector meson properties, especially the decrease of their mass due to the partial restoration of chiral symmetry, in hot and dense hadronic matter, provides a quantitative explanation of the recently observed enhancement of low-mass dileptons by the CERES collaboration in central S+Au collisions and by the HELIOS-3 collaboration in central S+W collisions.Comment: 46 pages, LaTeX, figures available from [email protected], to appear in Nucl. Phys.

Molecular epidemiological analysis of Mycoplasma genitalium shows low prevalence of azithromycin resistance and a well-established epidemic in South Africa

OBJECTIVES: Macrolide resistance in Mycoplasma genitalium is emerging globally. There is paucity of data from sub-Saharan Africa where syndromic management is used to treat sexually transmitted infections (STIs). We conducted a molecular epidemiological study to determine the prevalence of azithromycin resistance and epidemic diversity of M. genitalium infections in South Africa. METHODS : We analysed 90 M. genitalium-positive specimens that had been collected consecutively from men and women (50% symptomatic) from geographically diverse communities across the northern part of South Africa between 2015 and 2019. Melting curve analysis followed by targeted sequencing of the 23S rRNA gene was performed to detect azithromycin resistance. Molecular typing was done through single nucleotide polymorphism (SNP) analysis of the MG191 gene and short tandem repeats (STR) assessment of the MG309 gene. An overview of all published M. genitalium sequence types was generated and novel sequence types identified in this study were allocated numbers accordingly. RESULTS : Azithromycin resistance was detected in 1/90 M. genitalium-positive specimens (1.1%; 95% CI 0% to 3.3%) as conferred by A2071G mutation; this strain also harboured a C234T mutation in the parC gene with wild type gyrA gene. SNP typing and STR assessment was successful in 38/90 specimens (42%) and showed a genetically diverse epidemic, without geographic clustering, with eight novel sequence types identified. CONCLUSION : This is the first study that determines resistance in M. genitalium infection since introduction of azithromycin in the syndromic management regimen for STIs in South Africa in 2015. Despite a well-established epidemic, azithromycin-resistant M. genitalium infection is still uncommon in the public healthcare sector. However, it has the potential to undermine the effectiveness of syndromic management. Introduction of molecular diagnostics and continuous surveillance are warranted for early detection emergence of resistance.The Netherlands Enterprise Agency (Rijksdienst voor Ondernemend Nederland) and by the Eunice Kennedy Shriver National Institute of Child Health & Human Development, U.S. National Institute of Health.http://sti.bmj.comhj2022Medical Microbiolog

QED3 theory of underdoped high temperature superconductors

Low-energy theory of d-wave quasiparticles coupled to fluctuating vortex loops that describes the loss of phase coherence in a two dimensional d-wave superconductor at T=0 is derived. The theory has the form of 2+1 dimensional quantum electrodynamics (QED3), and is proposed as an effective description of the T=0 superconductor-insulator transition in underdoped cuprates. The coupling constant ("charge") in this theory is proportional to the dual order parameter of the XY model, which is assumed to be describing the quantum fluctuations of the phase of the superconducting order parameter. The principal result is that the destruction of phase coherence in d-wave superconductors typically, and immediately, leads to antiferromagnetism. The transition can be understood in terms of the spontaneous breaking of an approximate "chiral" SU(2) symmetry, which may be discerned at low enough energies in the standard d-wave superconductor. The mechanism of the symmetry breaking is analogous to the dynamical mass generation in the QED3, with the "mass" here being proportional to staggered magnetization. Other insulating phases that break chiral symmetry include the translationally invariant "d+ip" and "d+is" insulators, and various one dimensional charge-density and spin-density waves. The theory offers an explanation for the rounded d-wave-like dispersion seen in ARPES experiments on Ca2CuO2Cl2 (F. Ronning et. al., Science 282, 2067 (1998)).Comment: Revtex, 20 pages, 5 figures; this is a much extended follow-up to the Phys. Rev. Lett. vol.88, 047006 (2002) (cond-mat/0110188); improved presentation, many additional explanations, comments, and references added, sec. IV rewritten. Final version, to appear in Phys. Rev.

Collective cancer invasion forms an integrin-dependent radioresistant niche

Contains fulltext : 219833.pdf (Publisher’s version ) (Open Access)Cancer fatalities result from metastatic dissemination and therapy resistance, both processes that depend on signals from the tumor microenvironment. To identify how invasion and resistance programs cooperate, we used intravital microscopy of orthotopic sarcoma and melanoma xenografts. We demonstrate that these tumors invade collectively and that, specifically, cells within the invasion zone acquire increased resistance to radiotherapy, rapidly normalize DNA damage, and preferentially survive. Using a candidate-based approach to identify effectors of invasion-associated resistance, we targeted beta1 and alphaVbeta3/beta5 integrins, essential extracellular matrix receptors in mesenchymal tumors, which mediate cancer progression and resistance. Combining radiotherapy with beta1 or alphaV integrin monotargeting in invading tumors led to relapse and metastasis in 40-60% of the cohort, in line with recently failed clinical trials individually targeting integrins. However, when combined, anti-beta1/alphaV integrin dual targeting achieved relapse-free radiosensitization and prevented metastatic escape. Collectively, invading cancer cells thus withstand radiotherapy and DNA damage by beta1/alphaVbeta3/beta5 integrin cross-talk, but efficient radiosensitization can be achieved by multiple integrin targeting