The Geometry of an Electron Scale Magnetic Cavity in the Plasma Sheet

Electron scale magnetic cavities are electron vortex structures formed in turbulent plasma, while the evolution and electron dynamics of these structures have not been fully understood. Recently, highâ energy, angular, and temporal electron measurements from Magnetospheric Multiscale have enabled the application of an energetic particle sounding technique to these structures. This study analyzes an electron scale magnetic cavity observed by Magnetospheric Multiscale on 7 May 2015 in the plasma sheet. A comprehensive sounding technique is applied to obtain the geometry and propagation velocities of the boundaries. The result shows that the scale size of the structure is â ¼90 km, and the leading and trailing boundaries are moving in the same direction but with different speeds (â ¼11.5 ± 2.2 and â ¼18.1 ± 3.4 km/s, respectively). The speed difference suggests a shrinking of the structure that may play a significant role in magnetic energy dissipation and electron energization of electron scale magnetic cavities.Plain Language SummaryElectron scale magnetic cavities are extremely small vortices frequently found in space plasma environments, where a cavity of the depressed magnetic field contains energetic electrons forming a ringâ like current at electron scale. The formation of these structures is thought to be linked to energy cascade in plasma turbulence, while the mechanism and process of the energy transformation are not clear. In this paper we discuss an electron scale magnetic cavity in the terrestrial plasma sheet with a modified particle sounding technique proposed and applied to the boundaries, suggesting that the structure is shrinking. This analysis may provide new insight into understanding the evolution and electron energization of these structures.Key PointsA comprehensive energetic particle sounding technique is applied to detect the geometry of an electron scale magnetic cavityThe boundary loss plays a significant role in forming electron nonâ gyrotropic distributions in the cavityMoving speed obtained by the technique is higher for the trailing boundary than the leading boundary suggesting a shrinkage of the cavityPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151894/1/grl59390.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151894/2/grl59390_am.pd

Chemistry of hydrogen oxide radicals (HO_x) in the Arctic troposphere in spring

We use observations from the April 2008 NASA ARCTAS aircraft campaign to the North American Arctic, interpreted with a global 3-D chemical transport model (GEOS-Chem), to better understand the sources and cycling of hydrogen oxide radicals (HO_x≡H+OH+peroxy radicals) and their reservoirs (HO_y≡HO_x+peroxides) in the springtime Arctic atmosphere. We find that a standard gas-phase chemical mechanism overestimates the observed HO_2 and H_2O_2 concentrations. Computation of HO_x and HO_y gas-phase chemical budgets on the basis of the aircraft observations also indicates a large missing sink for both. We hypothesize that this could reflect HO_2 uptake by aerosols, favored by low temperatures and relatively high aerosol loadings, through a mechanism that does not produce H_2O_2. We implemented such an uptake of HO_2 by aerosol in the model using a standard reactive uptake coefficient parameterization with γ(HO_2) values ranging from 0.02 at 275 K to 0.5 at 220 K. This successfully reproduces the concentrations and vertical distributions of the different HO_x species and HO_y reservoirs. HO_2 uptake by aerosol is then a major HO_x and HO_y sink, decreasing mean OH and HO_2 concentrations in the Arctic troposphere by 32% and 31% respectively. Better rate and product data for HO_2 uptake by aerosol are needed to understand this role of aerosols in limiting the oxidizing power of the Arctic atmosphere

Signal pathways underlying homocysteine-induced production of MCP-1 and IL-8 in cultured human whole blood

Aim : To elucidate the mechanisms underlying homocysteine (Hcy)-induced chemokine production. Methods : Human whole blood was pretreated with inhibitors of calmodulin (CaM), protein kinase C (PKC), protein tyrosine kinase (PTK), mitogen-activated protein kinase (MAPK), and NF-ΚB and activators of PPARΓ for 60 min followed by incubation with Hcy 100 Μmol/L for 32 h. The levels of mitogen chemokine protein (MCP)-1 and interleukin-8 (IL-8) were determined by enzyme-linked immunosorbant assay (ELISA). Results : Inhibitors of PKC (calphostin C, 50-500 nmol/L and RO-31-8220, 10–100 nmol/L), CaM (W7, 28–280 Μmol/L), ERK1/2 MAPK (PD 98059, 2–20 Μmol/L), p38 MAPK (SB 203580, 0.6–6 Μmol/L), JNK MAPK (curcumin, 2–10 Μmol/L), and NF-ΚB (PDTC, 10-100 nmol/L) markedly reduced Hcy 100 Μmol/L-induced production of MCP-1 and IL-8 in human cultured whole blood, but the inhibitors of PTK (genistein, 2.6–26 Μmol/L and tyrphostin, 0.5-5 Μmol/L) had no obvious effect on MCP-1 and IL-8 production. PPARΓ activators (ciglitazone 30 Μmol/L and troglitazone 10 Μmol/L) depressed the Hcy-induced MCP-1 production but not IL-8 production in the cultured whole blood. Conclusion : Hcy-induced MCP-1 and IL-8 production is mediated by activated signaling pathways such as PKC, CaM, MAPK, and NF-ΚB. Our results not only provide clues for the signal transduction pathways mediating Hcy-induced chemokine production, but also offer a plausible explanation for a pathogenic role of hyperhomocysteinemia in these diseases.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75644/1/j.1745-7254.2005.00005.x.pd

Ge-rich graded-index Si_1-xGex waveguides with broadband tight mode confinement and flat anomalous dispersion for nonlinear mid-infrared photonics

This work explores the use of Ge-rich graded-index Si1-xGex rib waveguides as building blocks to develop integrated nonlinear optical devices for broadband operation in the mid-IR. The vertical Ge gradient concentration in the waveguide core renders unique properties to the guided optical mode, providing tight mode confinement over a broadband mid-IR wavelength range from λ = 3 µm to 8 µm. Additionally, the gradual vertical confinement pulls the optical mode upwards in the waveguide core, overlapping with the Ge-rich area where the nonlinear refractive index is larger. Moreover, the Ge-rich graded-index Si1-xGex waveguides allow efficient tailoring of the chromatic dispersion curves, achieving flat anomalous dispersion for the quasi-TM optical mode with D ≤ 14 ps/nm/km over a ~1.4 octave span while retaining an optimum third-order nonlinear parameter, γeff. These results confirm the potential of Ge-rich graded-index Si1-xGex waveguides as an attractive platform to develop mid-IR nonlinear approaches requiring broadband dispersion engineering

High-Redshift Starbursting Dwarf Galaxies Revealed by GRB Afterglows

We present a study of 15 long-duration gamma-ray burst (GRB) host galaxies at z>2. The GRBs are selected with available early-time afterglow spectra in order to compare interstellar medium (ISM) absorption-line properties with stellar properties of the host galaxies. In addition to five previously studied hosts, we consider new detections for the host galaxies of GRB050820 and GRB060206 and place 2-sigma upper limits to the luminosities of the remaining unidentified hosts. We examine the nature of the host galaxy population and find that (1) the UV luminosity distribution of GRB host galaxies is consistent with expectations from a UV luminosity weighted random galaxy population with a median luminosity of =0.1 L*; (2) there exists a moderate correlation between UV luminosity and SiII 1526 absorption width, which together with the observed large line widths of W(1526)>1.5 Ang for a large fraction of the objects suggests a galactic outflow driven velocity field in the host galaxies; (3) there is tentative evidence for a trend of declining ISM metallicity with decreasing galaxy luminosity in the star-forming galaxy population at z=2-4; (4) the interstellar UV radiation field is found ~ 35-350 times higher in GRB hosts than the Galactic mean value; and (5) additional galaxies are found at < 2" from the GRB host in all fields with known presence of strong MgII absorbers, but no additional faint galaxies are found at < 2" in fields without strong MgII absorbers. Our study confirms that the GRB host galaxies (with known optical afterglows) are representative of unobscured star-forming galaxies at z>2, and demonstrates that high spatial resolution images are necessary for an accurate identification of GRB host galaxies in the presence of strong intervening absorbers.Comment: 24 emulateapj pages, 24 figures, ApJ in press; full-resolution version available at http://lambda.uchicago.edu/public/tmp/ghost.pd

Achieving a robust grassy-ELM operation regime in CFETR

We have identified a robust grassy-edge localized mode (ELM) operation regime for future tokamak reactors. The regime exists within a pedestal top electron collisionality (ν *) window at high global poloidal beta (β p). The existence of an upper ν * limit for grassy-ELMs is consistent with results previously reported in experiments (Oyama et al 2010 Nucl. Fusion 50 064014), while the existence of a lower ν * limit has not been reported previously. Using EPED and BOUT  +  +, a theoretical model that quantitatively explains the physics of the grassy-ELMs within the window, which distinguishes them from the small mixed-ELMs at lower ν *, is presented for the first time. A peeling-ballooning stability boundary is obtained by scanning the operating density space. The change in density corresponds to a change in ν * that affects the pedestal bootstrap current. High β p leads to a strong Shafranov shift, which affects the flux surface averaged pressure drive. The two effects combine to create a peeling-dominated window in intermediate ν * buffered by ballooning-dominated regimes. Only the peeling-dominated regime shows a cyclic behavior in the perturbed pressure during the nonlinear simulation of an ELM crash, reminiscent of grassy-ELM dynamics. Similarly, the energy released across the separatrix is demonstrated to be significantly smaller. The quick recovery of the ELM crash is explainable by the rapid rise of a low n kink-peeling instability when the pedestal current Iped exceeds a threshold at high β p. It minimizes the excursion beyond marginal stability and is absent in the ballooning-dominated regime. Comparison with recent experiments over a range of β p and ν * strongly supports the physical picture proposed by the modeling

The nuclear receptors of Biomphalaria glabrata and Lottia gigantea: Implications for developing new model organisms

© 2015 Kaur et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedNuclear receptors (NRs) are transcription regulators involved in an array of diverse physiological functions including key roles in endocrine and metabolic function. The aim of this study was to identify nuclear receptors in the fully sequenced genome of the gastropod snail, Biomphalaria glabrata, intermediate host for Schistosoma mansoni and compare these to known vertebrate NRs, with a view to assessing the snail's potential as a invertebrate model organism for endocrine function, both as a prospective new test organism and to elucidate the fundamental genetic and mechanistic causes of disease. For comparative purposes, the genome of a second gastropod, the owl limpet, Lottia gigantea was also investigated for nuclear receptors. Thirty-nine and thirty-three putative NRs were identified from the B. glabrata and L. gigantea genomes respectively, based on the presence of a conserved DNA-binding domain and/or ligand-binding domain. Nuclear receptor transcript expression was confirmed and sequences were subjected to a comparative phylogenetic analysis, which demonstrated that these molluscs have representatives of all the major NR subfamilies (1-6). Many of the identified NRs are conserved between vertebrates and invertebrates, however differences exist, most notably, the absence of receptors of Group 3C, which includes some of the vertebrate endocrine hormone targets. The mollusc genomes also contain NR homologues that are present in insects and nematodes but not in vertebrates, such as Group 1J (HR48/DAF12/HR96). The identification of many shared receptors between humans and molluscs indicates the potential for molluscs as model organisms; however the absence of several steroid hormone receptors indicates snail endocrine systems are fundamentally different.The National Centre for the Replacement, Refinement and Reduction of Animals in Research, Grant Ref:G0900802 to CSJ, LRN, SJ & EJR [www.nc3rs.org.uk]

Mathematical model of a telomerase transcriptional regulatory network developed by cell-based screening: analysis of inhibitor effects and telomerase expression mechanisms

Cancer cells depend on transcription of telomerase reverse transcriptase (TERT). Many transcription factors affect TERT, though regulation occurs in context of a broader network. Network effects on telomerase regulation have not been investigated, though deeper understanding of TERT transcription requires a systems view. However, control over individual interactions in complex networks is not easily achievable. Mathematical modelling provides an attractive approach for analysis of complex systems and some models may prove useful in systems pharmacology approaches to drug discovery. In this report, we used transfection screening to test interactions among 14 TERT regulatory transcription factors and their respective promoters in ovarian cancer cells. The results were used to generate a network model of TERT transcription and to implement a dynamic Boolean model whose steady states were analysed. Modelled effects of signal transduction inhibitors successfully predicted TERT repression by Src-family inhibitor SU6656 and lack of repression by ERK inhibitor FR180204, results confirmed by RT-QPCR analysis of endogenous TERT expression in treated cells. Modelled effects of GSK3 inhibitor 6-bromoindirubin-3′-oxime (BIO) predicted unstable TERT repression dependent on noise and expression of JUN, corresponding with observations from a previous study. MYC expression is critical in TERT activation in the model, consistent with its well known function in endogenous TERT regulation. Loss of MYC caused complete TERT suppression in our model, substantially rescued only by co-suppression of AR. Interestingly expression was easily rescued under modelled Ets-factor gain of function, as occurs in TERT promoter mutation. RNAi targeting AR, JUN, MXD1, SP3, or TP53, showed that AR suppression does rescue endogenous TERT expression following MYC knockdown in these cells and SP3 or TP53 siRNA also cause partial recovery. The model therefore successfully predicted several aspects of TERT regulation including previously unknown mechanisms. An extrapolation suggests that a dominant stimulatory system may programme TERT for transcriptional stability

Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes

We review the different excitation processes in the interstellar mediumComment: Accepted in Chem. Re