1,911 research outputs found

    The 1995-1996 Decline of R Coronae Borealis - High Resolution Optical Spectroscopy

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    A set of high-resolution optical spectra of RCrB acquired before, during, and after its 1995-1996 decline is discussed. All of the components reported from earlier declines are seen. This novel dataset provides new information on these components including several aspects not previously seen in declines of RCrB and other RCBs. In the latter category is the discovery that the decline's onset is marked by distortions of absorption lines of high-excitation lines, and quickly followed by emission in these and in low excitation lines. This 'photospheric trigger' implies that dust causing the decline is formed close to the star. These emission lines fade quickly. After 1995 November 2, low excitation narrow (FWHM ~12 km s-1) emission lines remain. These appear to be a permanent feature, slightly blue-shifted from the systemic velocity, and unaffected by the decline except for a late and slight decrease of flux at minimum light. The location of the warm, dense gas providing these lines is uncertain. Absorption lines unaffected by overlying sharp emission are greatly broadened, weakened, and red-shifted at the faintest magnitudes when scattered light from the star is a greater contributor than direct light transmitted through the fresh soot cloud. A few broad lines are seen at and near minimum light with approxiamately constant flux: prominent among these are the He I triplet series, Na I D, and [N II] lines. These lines are blue-shifted by about 30 km s(-1) relative to the systemic velocity with no change in velocity over the several months for whicht he lines were seen. It is suggested that these lines, especially the He I lines, arise from an accretion disk around an unseen compact companion, which may be a low-mass white dwarf. If so, R CrB is similar to the unusual post-AGB star 89 Her.Comment: 31 pages, 26 figure

    Prostatic trypsin-like kallikrein-related peptidases (KLKs) and other prostate-expressed tryptic proteinases as regulators of signalling via proteinase-activated receptors (PARs)

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    The prostate is a site of high expression of serine proteinases including members of the kallikrein-related peptidase (KLK) family, as well as other secreted and membrane-anchored serine proteinases. It has been known for some time that members of this enzyme family elicit cellular responses by acting directly on cells. More recently, it has been recognised that for serine proteinases with specificity for cleavage after arginine and lysine residues (trypsin-like or tryptic enzymes) these cellular responses are often mediated by cleavage of members of the proteinase-activated receptor (PAR) family - a four member sub-family of G protein-coupled receptors. Here, we review the expression of PARs in prostate, the ability of prostatic trypsin-like KLKs and other prostate-expressed tryptic enzymes to cleave PARs, as well as the prostate cancer-associated consequences of PAR activation. In addition, we explore the dysregulation of trypsin-like serine proteinase activity through the loss of normal inhibitory mechanisms and potential interactions between these dysregulated enzymes leading to aberrant PAR activation, intracellular signalling and cancer-promoting cellular changes

    FGFR2-activating mutations disrupt cell polarity to potentiate migration and invasion in endometrial cancer cell models

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    Fibroblast growth factor receptors (FGFRs) are a family of receptor tyrosine kinases that control a diverse range of biological processes during development and in adult tissues. We recently reported that somatic FGFR2 mutations are associated with shorter survival in endometrial cancer. However, little is known about how these FGFR2 mutations contribute to endometrial cancer metastasis. Here, we report that expression of the activating mutations FGFR2N550K and FGFR2Y376C in an endometrial cancer cell model induce Golgi fragmentation, and loss of polarity and directional migration. In mutant FGFR2-expressing cells, this was associated with an inability to polarise intracellular pools of FGFR2 towards the front of migrating cells. Such polarization defects were exacerbated in three-dimensional culture, where FGFR2 mutant cells were unable to form well-organised acini, instead undergoing exogenous ligand-independent invasion. Our findings uncover collective cell polarity and invasion as common targets of disease-associated FGFR2 mutations that lead to poor outcome in endometrial cancer patients

    Hadronic properties of the S_{11}(1535) studied by electroproduction off the deuteron

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    Properties of excited baryonic states are investigated in the context of electroproduction of baryon resonances off the deuteron. In particular, the hadronic radii and the compositeness of baryon resonances are studied for kinematic situations in which their hadronic reinteraction is the dominant contribution. Specifically, we study the reaction d(e,e′S11)Nd(e,e'S_{11})N at Q2≥1GeV2Q^2\ge 1 GeV^2 for kinematics in which the produced hadronic state reinteracts predominantly with the spectator nucleon. A comparison of constituent quark model and effective chiral Lagrangian calculations of the S11S_{11} shows substantial sensitivity to the structure of the produced resonance.Comment: 24 pages, 5 figure

    Revisiting Event Horizon Finders

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    Event horizons are the defining physical features of black hole spacetimes, and are of considerable interest in studying black hole dynamics. Here, we reconsider three techniques to localise event horizons in numerical spacetimes: integrating geodesics, integrating a surface, and integrating a level-set of surfaces over a volume. We implement the first two techniques and find that straightforward integration of geodesics backward in time to be most robust. We find that the exponential rate of approach of a null surface towards the event horizon of a spinning black hole equals the surface gravity of the black hole. In head-on mergers we are able to track quasi-normal ringing of the merged black hole through seven oscillations, covering a dynamic range of about 10^5. Both at late times (when the final black hole has settled down) and at early times (before the merger), the apparent horizon is found to be an excellent approximation of the event horizon. In the head-on binary black hole merger, only {\em some} of the future null generators of the horizon are found to start from past null infinity; the others approach the event horizons of the individual black holes at times far before merger.Comment: 30 pages, 15 figures, revision

    Lyman Alpha Blobs as an Observational Signature of Cold Accretion Streams into Galaxies

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    Recent hydrodynamic simulations of galaxy formation reveal streams of cold (T ~ 1e4 K) gas flowing into the centers of dark matter halos as massive as 1e12-1e13.5 M_sun at redshifts z~1-3. In this paper we show that if > 20% of the gravitational binding energy of the gas is radiated away, then the simulated cold flows are spatially extended Lyman Alpha (Lya) sources with luminosities, Lya line widths, and number densities that are comparable to those of observed Lya blobs. Furthermore, the filamentary structure of the cold flows can explain the wide range of observed Lya blob morphologies. Since the most massive halos form in dense environments, the association of Lya blobs with overdense regions arise naturally. We argue that Lya blobs - even those which are clearly associated with starburst galaxies or quasars - provide direct observational support for the cold accretion mode of galaxies. We discuss various testable predictions of this association.Comment: MNRAS in press. 13 pages, 6 figures. Discussion + references added. Main conclusions unaffecte

    hSSB1 (NABP2/OBFC2B) is regulated by oxidative stress

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    The maintenance of genome stability is an essential cellular process to prevent the development of diseases including cancer. hSSB1 (NABP2/ OBFC2A) is a critical component of the DNA damage response where it participates in the repair of double-strand DNA breaks and in base excision repair of oxidized guanine residues (8-oxoguanine) by aiding the localization of the human 8-oxoguanine glycosylase (hOGG1) to damaged DNA. Here we demonstrate that following oxidative stress, hSSB1 is stabilized as an oligomer which is required for hSSB1 to function in the removal of 8-oxoguanine. Monomeric hSSB1 shows a decreased affinity for oxidized DNA resulting in a cellular 8-oxoguanine-repair defect and in the absence of ATM signaling initiation. While hSSB1 oligomerization is important for the removal of 8-oxoguanine from the genome, it is not required for the repair of double-strand DNA-breaks by homologous recombination. These findings demonstrate a novel hSSB1 regulatory mechanism for the repair of damaged DNA.Publisher PDFPeer reviewe

    Interviewer: 'Are women and girls ever responsible for the domestic violence they encounter?' Student: 'No, well, unless they did something really, really bad …'

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    Research shows the ‘gendered nature’ of domestic violence, with Women’s Aid (a UK-based charity) estimating that 1 in 4 women are affected (2014). This paper reports on a project - funded by Comic Relief, completed by Nottinghamshire Domestic Violence Forum (now known as Equation) and evaluated by Nottingham Trent University. The project adopts a Whole School Approach in seeking to prevent domestic violence. Students at three secondary schools attended between one and five blocks of work, and special events. There is evidence of positive developments - with young people showing understanding of domestic violence as well as the margins between healthy and unhealthy relationships. However, not all students could reply ‘never’ to the question of ‘are women and girls to blame for the domestic violence they experience?’, remarking that if the woman had done something ‘really, really bad’ then violence might be justified. We argue that young people’s uncertainties need to be situated within the gender-unequal socio-contexts of contemporary society, and further call for a WSA to domestic violence prevention to be a compulsory part of the UK national curriculum
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