Particle Acceleration and Magnetic Dissipation in Relativistic Current Sheet of Pair Plasmas

We study linear and nonlinear development of relativistic and ultrarelativistic current sheets of pair plasmas with antiparallel magnetic fields. Two types of two-dimensional problems are investigated by particle-in-cell simulations. First, we present the development of relativistic magnetic reconnection, whose outflow speed is an order of the light speed c. It is demonstrated that particles are strongly accelerated in and around the reconnection region, and that most of magnetic energy is converted into "nonthermal" part of plasma kinetic energy. Second, we present another two-dimensional problem of a current sheet in a cross-field plane. In this case, the relativistic drift kink instability (RDKI) occurs. Particle acceleration also takes place, but the RDKI fast dissipates the magnetic energy into plasma heat. We discuss the mechanism of particle acceleration and the theory of the RDKI in detail. It is important that properties of these two processes are similar in the relativistic regime of T > mc^2, as long as we consider the kinetics. Comparison of the two processes indicates that magnetic dissipation by the RDKI is more favorable process in the relativistic current sheet. Therefore the striped pulsar wind scenario should be reconsidered by the RDKI.Comment: To appear in ApJ vol. 670; 60 pages, 27 figures; References and typos are fixe

Human rotavirus strains bearing VP4 gene P[6] allele recovered from asymptomatic or symptomatic infections share similar, if not identical, VP4 neutralization specificities

AbstractA rotavirus VP4 gene P[6] allele has been documented in a number of countries to be characteristically associated with an endemic predominantly asymptomatic infection in neonates in maternity hospital nurseries. The mechanisms underlying the endemicity and asymptomatic nature of such neonatal infections remain unknown. Rotavirus strains sharing this same P genotype, however, have more recently been recovered from an increasing number of symptomatic diarrheal episodes in infants and young children in various parts of the world. Previously, we have shown that an asymptomatic P[6] rotavirus neonatal infection is not associated with a unique VP7 (G) serotype but may occur in conjunction with various G types. Although amino acid sequence comparisons of the VP4 gene between selected “asymptomatic” and “symptomatic” P[6] rotavirus strains have been reported and yielded information concerning their VP4 genotypes, serotypic comparisons of the outer capsid spike protein VP4 of such viruses have not been studied systematically by two-way cross-neutralizations. We determined the VP4 neutralization specificities of four asymptomatic and four symptomatic P[6] strains: two each of asymptomatic and symptomatic strains by two-way tests, and two each of additional asymptomatic and symptomatic strains by one-way tests. Both asymptomatic and symptomatic P[6] strains were shown to bear similar, if not identical, VP4 neutralization specificities. Thus, P[6] rotavirus strains causing asymptomatic or symptomatic infections did not appear to belong to unique P (VP4) serotypes. In addition, a close VP4 serotypic relationship between human P[6] rotavirus strains and the porcine P[6] rotavirus Gottfried strain was confirmed

X-ray Temperature and Mass Measurements to the Virial Radius of Abell 1413 with Suzaku

We present X-ray observations of the northern outskirts of the relaxed galaxy cluster A1413 with Suzaku, whose XIS instrument has the low intrinsic background needed to make measurements of these low surface brightness regions. We excise 15 point sources superimposed on the image above a flux of $1\times 10^{-14}$ \fluxunit (2--10keV) using XMM-Newton and Suzaku images of the cluster. We quantify all known systematic errors as part of our analysis, and show our statistical errors encompasses them for the most part. Our results extend previous measurements with Chandra and XMM-Newton, and show a significant temperature drop to about 3keV at the virial radius, $r_{200}$. Our entropy profile in the outer region ($> 0.5 r_{200}$) joins smoothly onto that of XMM-Newton, and shows a flatter slope compared with simple models, similar to a few other clusters observed at the virial radius. The integrated mass of the cluster at the virial radius is approximately $7.5\times10^{14}M_{\odot}$ and varies by about 30% depending on the particular method used to measure it.Comment: 32pages, 9 figures, accepted for publication in PAS

Dynamical mass generation of a two-component fermion in Maxwell-Chern-Simons QED_3: The lowest ladder approximation

Dynamical mass generation of a two-component fermion in $QED_3$ with a Chern-Simons term is investigated by solving the Schwinger-Dyson equation formulated in the lowest ladder approximation. Dependence of the dynamical fermion mass on a gauge-fixing parameter, a gauge coupling constant, and a topological mass is examined by approximated analytical and also numerical methods. The inclusion of the Chern-Simons term makes impossible to choose a peculiar gauge in which a wave function renormalization is absent. The numerical evaluation shows that the wave function renormalization is fairly close to 1 in the Landau gauge. It means that this gauge is still a specific gauge where the Ward-Takahashi identity is satisfied approximately. We also find that the dynamical mass is almost constant if the topological mass is larger than the coupling constant, while it decreases when the topological mass is comparable to or smaller than the coupling constant and tends to the value in $QED_3$ without the Chern-Simons term.Comment: 22 pages, 9 figures, Version to appear in Phys. Rev.

Gamma rays and neutrinos from the Crab Nebula produced by pulsar accelerated nuclei

We investigate the consequences of the acceleration of heavy nuclei (e.g. iron nuclei) by the Crab pulsar. Accelerated nuclei can photodisintegrate in collisions with soft photons produced in the pulsar's outer gap, injecting energetic neutrons which decay either inside or outside the Crab Nebula. The protons from neutron decay inside the nebula are trapped by the Crab Nebula magnetic field, and accumulate inside the nebula producing gamma-rays and neutrinos in collisions with the matter in the nebula. Neutrons decaying outside the Crab Nebula contribute to the Galactic cosmic rays. We compute the expected fluxes of gamma-rays and neutrinos, and find that our model could account for the observed emission at high energies and may be tested by searching for high energy neutrinos with future neutrino telescopes currently in the design stage.Comment: 8 pages, 4 figures, LaTeX uses revtex.sty, submitted to Phys. Rev. Let

Neutrinos from the pulsar wind nebulae

In the recent paper we calculated the $\gamma$-ray spectra from pulsar wind nebulae (PWNe), assuming that a significant amount of the pulsar rotational energy is converted into relativistic nuclei. These nuclei accelerate leptons which are responsible for most of the observed electromagnetic emission from PWNe. Small part of nuclei also interact with the matter of the supernova producing $\gamma$-rays, which can also contribute to the observed spectra of young nebulae. Here we calculate the spectra of neutrinos from the interaction of nuclei inside the nebula and the expected neutrino event rates in the 1 km$^2$ neutrino detector from: the Crab Nebula (PSR 0531+21), the Vela SNR (PSR 0833-45), G 343.1-2.3 (PSR 1706-44), MSH15-52 (PSR 1509-58), 3C58 (PSR J0205+6449), and CTB80 (PSR 1951+32). It is shown that only the Crab Nebula can produce the neutrino event rate above the sensitivity limit of the 1 km$^2$ neutrino detector, provided that nuclei take most of the rotational energy lost by the pulsar. The neutrino event rate expected from the Vela SNR is comparable to that from the Crab Nebula but these neutrinos are less energetic and emitted from a much larger region on the sky. Therefore it may be difficult to subtract the Vela SNR signal from the higher background of the atmospheric neutrinos.Comment: 7 pages, 3 figures, A&A style, accepted to A&

Broad Efficacy of a Computationally Designed ACE2 Decoy Against SARS-CoV-2 Omicron Variants and Related Viruses In Vitro and In Vivo

Background: The SARS-CoV-2 omicron variant (B.1.1.529) and its sublineages are currently the dominant variants in the United States accounting for 100% of COVID-19 cases. Problem: The S protein receptor-binding domain (RBD), located in the S1 subunit of the S protein, binds the human angiotensin-converting enzyme 2 (hACE2) leading to S1 shedding and proteolytic processing of S2 that is important for membrane fusion and release of viral RNA. Various neutralizing therapeutics including protein minibinders, peptides, monoclonal antibodies, and nanobodies have been developed to block the critical interaction between the RBD and hACE2. However, these therapeutics are often developed against the S protein of wildtype or a specific variant of SARSCoV- 2, making them highly susceptible to mutational escape.1 Solution: A strategy employed by our group includes using sACE2 (soluble dimeric ACE2 that contains both the protease and dimerization domains) with enhanced S RBD affinity to outcompete native ACE2 expressed on host cells, acting as a ‘decoy’ to block the interaction between the RBD and hACE2 (Figure 1). sACE2 has moderate affinity for the S protein (~20 nM)2. Therefore, sACE2 must be engineered (by introducing affinity enhancing mutations) to bind with tighter affinity to outcompete membrane bound ACE2-S interaction and rival the potency of mAbs. These sACE2 derivatives maintain close similarity to the native ACE2 receptor making them extremely resistant to virus escape. Any mutation in the RBD that limits binding to the sACE2 derivative will likely have reduced binding towards native ACE2 receptors potentially making the virus unfit to propagate.https://jdc.jefferson.edu/aoa_research_symposium_posters/1000/thumbnail.jp

Optimizing the vertebrate vestibular semicircular canal: could we balance any better?

The fluid-filled semicircular canals (SCCs) of the vestibular system are used by all vertebrates to sense angular rotation. Despite masses spanning seven decades, all mammalian SCCs are nearly the same size. We propose that the SCC represents a sensory organ that evolution has `optimally designed'. Four geometric parameters are used to characterize the SCC, and `building materials' of given physical properties are assumed. Identifying physical and physiological constraints on SCC operation, we find that the most sensitive SCC has dimensions consistent with available data.Comment: 4 pages, 3 figure