THE DOUBLE-DEGENERATE NUCLEUS OF THE PLANETARY NEBULA TS 01: A CLOSE BINARY EVOLUTION SHOWCASE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tovmassian, Gagik; Richer, Michael G.; Yungelson, Lev

2010-05-01

We present a detailed investigation of SBS 1150+599A, a close binary star hosted by the planetary nebula PN G135.9+55.9 (TS 01). The nebula, located in the Galactic halo, is the most oxygen-poor known to date and is the only one known to harbor a double degenerate core. We present XMM-Newton observations of this object, which allowed the detection of the previously invisible component of the binary core, whose existence was inferred so far only from radial velocity (RV) and photometric variations. The parameters of the binary system were deduced from a wealth of information via three independent routes using themore » spectral energy distribution (from the infrared to X-rays), the light and RV curves, and a detailed model atmosphere fitting of the stellar absorption features of the optical/UV component. We find that the cool component must have a mass of 0.54 {+-} 0.2 M{sub sun}, an average effective temperature, T{sub eff}, of 58,000 {+-} 3000 K, a mean radius of 0.43 {+-} 0.3 R{sub sun}, a gravity, log g = 5.0 {+-} 0.3, and that it nearly fills its Roche lobe. Its surface elemental abundances are found to be: 12 + log He/H = 10.95 {+-} 0.04 dex, 12 + log C/H = 7.20 {+-} 0.3 dex, 12 + log N/H < 6.92, and 12 + log O/H < 6.80, in overall agreement with the chemical composition of the planetary nebula. The hot component has T{sub eff} = 160-180 kK, a luminosity of about {approx}10{sup 4} L{sub sun} and a radius slightly larger than that of a white dwarf. It is probably bloated and heated as a result of intense accretion and nuclear burning on its surface in the past. The total mass of the binary system is very close to the Chandrasekhar limit. This makes TS 01 one of the best Type Ia supernova progenitor candidates. We propose two possible scenarios for the evolution of the system up to its present stage.« less

The physical properties of double degenerate common proper motion binaries

NASA Technical Reports Server (NTRS)

Sion, Edward M.; Oswalt, Terry D.; Liebert, James; Hintzen, Paul

1991-01-01

Spectral types and spectrophotometry are presented for 21 double degenerate (DD) common proper motion binaries, along with estimates of their colors, absolute visual and bolometric magnitudes, and cooling ages. The oldest pairs in the sample are 9 x 10 to the 9th yr; the differential cooling ages range from 0.01 to 0.84. The median and mean separations of the DD pairs are 426 and 407 Au, respectively, both apparently smaller than the WD+MS values. The average UVW motions and velocity dispersions are significantly larger than the average velocities and dispersions associated with selected samples of single white dwarfs and MS+WD binaries when the latter are restricted to the same color/Mv range as the DD systems. This may be a result of the dynamical inflation of the velocity dispersion of DD systems due to their extremely ancient total stellar ages.

Formation Mechanisms for Helium White Dwarfs in Binaries

NASA Astrophysics Data System (ADS)

Sandquist, E. L.; Taam, R. E.; Burkert, A.

1999-05-01

We discuss the constraints that can be placed on formation mechanisms for helium degenerate stars in binary systems, as well as the orbital parameters of the progenitor binaries, by using observed systems and numerical simulations of common envelope evolution. For pre-cataclysmic variable stars having a helium white dwarf, common envelope simulations covering the range of observed companion masses indicate that the initial mass of the red giant (parent of the white dwarf) can be constrained by the final period of the system. The formation mechanisms for double helium degenerate systems are also restricted. Using energy arguments, we find that there are almost no parameter combinations for which such a system can be formed using two successive common envelope phases. Observed short-period systems appear to favor an Algol-like phase of stable mass transfer followed by a common envelope phase. However, theory predicts that the brighter component is also the most massive, which is not observed in at least one system. This may require that nuclear burning must have occurred on the white dwarf that formed first, but after its formation. Systems which instead go through a common envelope episode, followed by a phase of nonconservative mass transfer from secondary to primary, would tend to form double degenerates with low mass ratios, which have not been observed to date. Finally, we discuss a new mechanism for producing subdwarf B stars in binaries. This work was supported by NSF grants AST-9415423 and AST-9727875.

Dynamic mass exchange in doubly degenerate binaries. I - 0.9 and 1.2 solar mass stars

NASA Technical Reports Server (NTRS)

Benz, W.; Cameron, A. G. W.; Press, W. H.; Bowers, R. L.

1990-01-01

The dynamic mass exchange process in doubly degenerate binaries was investigated using a three-dimensional numerical simulation of the evolution of a doubly degenerate binary system in which the primary is a 1.2-solar-mass white dwarf and the Roche lobe filling secondary is a 0.9-solar-mass dwarf. The results show that, in a little more than two orbital periods, the secondary is completely destroyed and transformed into a thick disk orbiting about the primary. Since only a very small fraction of the mass (0.0063 solar mass) escapes the system, the evolution of the binary results in the formation of a massive object. This object is composed of three parts, the initial white dwarf primary, a very hot pressure-supported spherical envelope, and a rotationally supported outer disk. The evolution of the system can be understood in terms of a simple analytical model where it is shown that the angular momentum carried by the mass during the transfer and stored in the disk determines the evolution of the system.

The Post-merger Magnetized Evolution of White Dwarf Binaries: The Double-degenerate Channel of Sub-Chandrasekhar Type Ia Supernovae and the Formation of Magnetized White Dwarfs

NASA Astrophysics Data System (ADS)

Ji, Suoqing; Fisher, Robert T.; García-Berro, Enrique; Tzeferacos, Petros; Jordan, George; Lee, Dongwook; Lorén-Aguilar, Pablo; Cremer, Pascal; Behrends, Jan

2013-08-01

Type Ia supernovae (SNe Ia) play a crucial role as standardizable cosmological candles, though the nature of their progenitors is a subject of active investigation. Recent observational and theoretical work has pointed to merging white dwarf binaries, referred to as the double-degenerate channel, as the possible progenitor systems for some SNe Ia. Additionally, recent theoretical work suggests that mergers which fail to detonate may produce magnetized, rapidly rotating white dwarfs. In this paper, we present the first multidimensional simulations of the post-merger evolution of white dwarf binaries to include the effect of the magnetic field. In these systems, the two white dwarfs complete a final merger on a dynamical timescale, and are tidally disrupted, producing a rapidly rotating white dwarf merger surrounded by a hot corona and a thick, differentially rotating disk. The disk is strongly susceptible to the magnetorotational instability (MRI), and we demonstrate that this leads to the rapid growth of an initially dynamically weak magnetic field in the disk, the spin-down of the white dwarf merger, and to the subsequent central ignition of the white dwarf merger. Additionally, these magnetized models exhibit new features not present in prior hydrodynamic studies of white dwarf mergers, including the development of MRI turbulence in the hot disk, magnetized outflows carrying a significant fraction of the disk mass, and the magnetization of the white dwarf merger to field strengths ~2 × 108 G. We discuss the impact of our findings on the origins, circumstellar media, and observed properties of SNe Ia and magnetized white dwarfs.

Binary supersoft X-ray sources and the supernova Ia progenitor problem

NASA Astrophysics Data System (ADS)

Nelson, Thomas John

In this thesis I present a study of several binary supersoft X-ray sources in order to assess their properties and to determine whether they may be supernova Ia (SN Ia) progenitors. The first chapter is an introduction to the problem and the sources of interest. In the second and third chapters I present an X-ray spectroscopic study of the recurrent nova RS Ophiuchi (RS Oph) during and after its 2006 outburst, carried out with Chandra and XMM-Newton. I discuss the physical origins of the X-ray emission at each stage of the outburst and place the first direct constraints on the mass of the white dwarf, which is very close to the Chandrasekhar limit. I also show that the surface composition of the white dwarf during the supersoft phase is consistent with nuclear processed material, indicating that RS Oph retains mass after each outburst and is likely growing in mass with time, and is therefore a potential SN Ia progenitor. I discuss the lack of accretion signatures in the quiescent emission from RS Oph, which are at odds with the high frequency of nova outbursts, and explore the possibility that an alternative accretion model may account for the quiescent X-ray properties in the system. Finally, in the fourth chapter, I examine the supersoft X-ray source (SSS) population in the nearby galaxy M31 at X-ray, ultraviolet (UV) and optical wavelengths. I explore the long-term behavior of these objects, and find that a much smaller fraction are persistent or recurrent X-ray sources than in the Magellanic Clouds. I carry out a search for counterparts of the SSS using the Galactic Evolution Explorer (GALEX) satellite and the WIYN 3.5m telescope, and find that the majority of sources do not have any UV counterparts. For those that do, I find that the UV sources have properties consistent with young, massive stars in M31. I find indications that some SSS may be in high mass binaries. If these sources are nuclear burning white dwarfs, then they may be the progenitors of the SNe

Constraints on the Progenitor System of SN 2016gkg from a Comprehensive Statistical Analysis

NASA Astrophysics Data System (ADS)

Sravan, Niharika; Marchant, Pablo; Kalogera, Vassiliki; Margutti, Raffaella

2018-01-01

Type IIb supernovae (SNe) present a unique opportunity for understanding the progenitors of stripped-envelope SNe because the stellar progenitor of several SNe IIb have been identified in pre-explosion images. In this paper, we use Bayesian inference and a large grid of non-rotating solar-metallicity single and binary stellar models to derive the associated probability distributions of single and binary progenitors of the SN IIb 2016gkg using existing observational constraints. We find that potential binary star progenitors have smaller pre-SN hydrogen-envelope and helium-core masses than potential single-star progenitors typically by 0.1 M ⊙ and 2 M ⊙, respectively. We find that, a binary companion, if present, is a main-sequence or red-giant star. Apart from this, we do not find strong constraints on the nature of the companion star. We demonstrate that the range of progenitor helium-core mass inferred from observations could help improve constraints on the progenitor. We find that the probability that the progenitor of SN 2016gkg was a binary is 22% when we use constraints only on the progenitor luminosity and effective temperature. Imposing the range of pre-SN progenitor hydrogen-envelope mass and radius inferred from SN light curves, the probability that the progenitor is a binary increases to 44%. However, there is no clear preference for a binary progenitor. This is in contrast to binaries being the currently favored formation channel for SNe IIb. Our analysis demonstrates the importance of statistical inference methods to constrain progenitor channels.

THE POST-MERGER MAGNETIZED EVOLUTION OF WHITE DWARF BINARIES: THE DOUBLE-DEGENERATE CHANNEL OF SUB-CHANDRASEKHAR TYPE Ia SUPERNOVAE AND THE FORMATION OF MAGNETIZED WHITE DWARFS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji Suoqing; Fisher, Robert T.; Garcia-Berro, Enrique

2013-08-20

Type Ia supernovae (SNe Ia) play a crucial role as standardizable cosmological candles, though the nature of their progenitors is a subject of active investigation. Recent observational and theoretical work has pointed to merging white dwarf binaries, referred to as the double-degenerate channel, as the possible progenitor systems for some SNe Ia. Additionally, recent theoretical work suggests that mergers which fail to detonate may produce magnetized, rapidly rotating white dwarfs. In this paper, we present the first multidimensional simulations of the post-merger evolution of white dwarf binaries to include the effect of the magnetic field. In these systems, the twomore » white dwarfs complete a final merger on a dynamical timescale, and are tidally disrupted, producing a rapidly rotating white dwarf merger surrounded by a hot corona and a thick, differentially rotating disk. The disk is strongly susceptible to the magnetorotational instability (MRI), and we demonstrate that this leads to the rapid growth of an initially dynamically weak magnetic field in the disk, the spin-down of the white dwarf merger, and to the subsequent central ignition of the white dwarf merger. Additionally, these magnetized models exhibit new features not present in prior hydrodynamic studies of white dwarf mergers, including the development of MRI turbulence in the hot disk, magnetized outflows carrying a significant fraction of the disk mass, and the magnetization of the white dwarf merger to field strengths {approx}2 Multiplication-Sign 10{sup 8} G. We discuss the impact of our findings on the origins, circumstellar media, and observed properties of SNe Ia and magnetized white dwarfs.« less

Formation of Black Hole X-Ray Binaries with Non-degenerate Donors in Globular Clusters

NASA Astrophysics Data System (ADS)

Ivanova, Natalia; da Rocha, Cassio A.; Van, Kenny X.; Nandez, Jose L. A.

2017-07-01

In this Letter, we propose a formation channel for low-mass X-ray binaries with black hole accretors and non-degenerate donors via grazing tidal encounters with subgiants. We estimate that in a typically dense globular cluster with a core density of 105 stars pc-3, the formation rates are about one binary per Gyr per 50-100 retained black holes. The donors—stripped subgiants—will be strongly underluminous when compared to subgiant or giant branch stars of the same colors. The products of tidal stripping are underluminous by at least one magnitude for several hundred million years when compared to normal stars of the same color, and differ from underluminous red stars that could be produced by non-catastrophic mass transfer in an ordinary binary. The dynamically formed binaries become quiescent LMXBs, with lifetimes of about a Gyr. The expected number of X-ray binaries is one per 50-200 retained black holes, while the expected number of strongly underluminous subsubgiant is about half this. The presence of strongly underluminous stars in a GC may be indicative of the presence of black holes.

Formation of Black Hole X-Ray Binaries with Non-degenerate Donors in Globular Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanova, Natalia; Rocha, Cassio A. da; Van, Kenny X.

In this Letter, we propose a formation channel for low-mass X-ray binaries with black hole accretors and non-degenerate donors via grazing tidal encounters with subgiants. We estimate that in a typically dense globular cluster with a core density of 10{sup 5} stars pc{sup −3}, the formation rates are about one binary per Gyr per 50–100 retained black holes. The donors—stripped subgiants—will be strongly underluminous when compared to subgiant or giant branch stars of the same colors. The products of tidal stripping are underluminous by at least one magnitude for several hundred million years when compared to normal stars of themore » same color, and differ from underluminous red stars that could be produced by non-catastrophic mass transfer in an ordinary binary. The dynamically formed binaries become quiescent LMXBs, with lifetimes of about a Gyr. The expected number of X-ray binaries is one per 50–200 retained black holes, while the expected number of strongly underluminous subsubgiant is about half this. The presence of strongly underluminous stars in a GC may be indicative of the presence of black holes.« less

The white dwarf binary pathways survey - II. Radial velocities of 1453 FGK stars with white dwarf companions from LAMOST DR 4

NASA Astrophysics Data System (ADS)

Rebassa-Mansergas, A.; Ren, J. J.; Irawati, P.; García-Berro, E.; Parsons, S. G.; Schreiber, M. R.; Gänsicke, B. T.; Rodríguez-Gil, P.; Liu, X.; Manser, C.; Nevado, S. P.; Jiménez-Ibarra, F.; Costero, R.; Echevarría, J.; Michel, R.; Zorotovic, M.; Hollands, M.; Han, Z.; Luo, A.; Villaver, E.; Kong, X.

2017-12-01

We present the second paper of a series of publications aiming at obtaining a better understanding regarding the nature of type Ia supernovae (SN Ia) progenitors by studying a large sample of detached F, G and K main-sequence stars in close orbits with white dwarf companions (i.e. WD+FGK binaries). We employ the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) data release 4 spectroscopic data base together with Galaxy Evolution Explorer (GALEX) ultraviolet fluxes to identify 1549 WD+FGK binary candidates (1057 of which are new), thus doubling the number of known sources. We measure the radial velocities of 1453 of these binaries from the available LAMOST spectra and/or from spectra obtained by us at a wide variety of different telescopes around the globe. The analysis of the radial velocity data allows us to identify 24 systems displaying more than 3σ radial velocity variation that we classify as close binaries. We also discuss the fraction of close binaries among WD+FGK systems, which we find to be ∼10 per cent, and demonstrate that high-resolution spectroscopy is required to efficiently identify double-degenerate SN Ia progenitor candidates.

THE VERY EARLY LIGHT CURVE OF SN 2015F IN NGC 2442: A POSSIBLE DETECTION OF SHOCK-HEATED COOLING EMISSION AND CONSTRAINTS ON SN Ia PROGENITOR SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Im, Myungshin; Choi, Changsu; Kim, Jae-Woo

2015-11-15

The main progenitor candidates of Type Ia supernovae (SNe Ia) are white dwarfs in binary systems where the companion star is another white dwarf (double degenerate (DD) system) or a less-evolved, non-degenerate star with R{sub *} ≳ 0.1 R{sub ⊙} (single degenerate system). However, no direct observational evidence exists to tell us which progenitor system is more common. Recent studies suggest that the light curve of a supernova shortly after its explosion can be used to set a limit on the progenitor size, R{sub *}. Here, we report high-cadence monitoring observations of SN 2015F, a normal SN Ia in themore » galaxy NGC 2442, starting about 84 days before the first light time. Using our daily cadence data, we capture the emergence of the radioactively powered light curve; more importantly, with >97.4% confidence, we detect possible dim precursor emission that appears roughly 1.5 days before the rise of the radioactively powered emission. The signal is consistent with theoretical expectations for a progenitor system involving a companion star with R{sub *} ≃ 0.1–1 R{sub ⊙} or a prompt explosion of a DD system, but is inconsistent with the typically invoked size of a white dwarf progenitor of R{sub *} ∼ 0.01 R{sub ⊙}. Upper limits on the precursor emission also constrain the progenitor size to be R{sub *} ≲ 0.1 R{sub ⊙} with a companion star size of R{sub *} ≲ 1.0 R{sub ⊙}, excluding a very large companion star in the progenitor system. Additionally, we find that the distance to SN 2015F is 23.9 ± 0.4 Mpc.« less

SPIRAL INSTABILITY CAN DRIVE THERMONUCLEAR EXPLOSIONS IN BINARY WHITE DWARF MERGERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashyap, Rahul; Fisher, Robert; García-Berro, Enrique

2015-02-10

Thermonuclear, or Type Ia supernovae (SNe Ia), originate from the explosion of carbon–oxygen white dwarfs, and serve as standardizable cosmological candles. However, despite their importance, the nature of the progenitor systems that give rise to SNe Ia has not been hitherto elucidated. Observational evidence favors the double-degenerate channel in which merging white dwarf binaries lead to SNe Ia. Furthermore, significant discrepancies exist between observations and theory, and to date, there has been no self-consistent merger model that yields a SNe Ia. Here we show that a spiral mode instability in the accretion disk formed during a binary white dwarf mergermore » leads to a detonation on a dynamical timescale. This mechanism sheds light on how white dwarf mergers may frequently yield SNe Ia.« less

DKK1 mediated inhibition of Wnt signaling in postnatal mice leads to loss of TEC progenitors and thymic degeneration.

PubMed

Osada, Masako; Jardine, Logan; Misir, Ruth; Andl, Thomas; Millar, Sarah E; Pezzano, Mark

2010-02-08

Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T cell precursors from the bone marrow, as well as the subsequent expansion and selection of thymocytes resulting in a mature self-tolerant T cell repertoire. The molecular mechanisms, which control both the initial development and subsequent maintenance of these critical microenvironments, are poorly defined. Wnt signaling has been shown to be important to the development of several epithelial tissues and organs. Regulation of Wnt signaling has also been shown to impact both early thymocyte and thymic epithelial development. However, early blocks in thymic organogenesis or death of the mice have prevented analysis of a role of canonical Wnt signaling in the maintenance of TECs in the postnatal thymus. Here we demonstrate that tetracycline-regulated expression of the canonical Wnt inhibitor DKK1 in TECs localized in both the cortex and medulla of adult mice, results in rapid thymic degeneration characterized by a loss of DeltaNP63(+) Foxn1(+) and Aire(+) TECs, loss of K5K8DP TECs thought to represent or contain an immature TEC progenitor, decreased TEC proliferation and the development of cystic structures, similar to an aged thymus. Removal of DKK1 from DKK1-involuted mice results in full recovery, suggesting that canonical Wnt signaling is required for the differentiation or proliferation of TEC populations needed for maintenance of properly organized adult thymic epithelial microenvironments. Taken together, the results of this study demonstrate that canonical Wnt signaling within TECs is required for the maintenance of epithelial microenvironments in the postnatal thymus, possibly through effects on TEC progenitor/stem cell populations. Downstream targets of Wnt signaling, which are responsible for maintenance of these TEC progenitors may provide useful targets for therapies aimed at counteracting age associated thymic involution or the premature thymic degeneration associated

Signatures of progenitors of Type Ia supernovae

NASA Astrophysics Data System (ADS)

Hoeflich, P.; Chakraborty, S.; Comaskey, W.; Fisher, A.; Hristov, B.; Collins, D.; Diamond, T. R.; Dragulin, P.; Hsiao, E. Y.; Sadler, B.

Thermonuclear Supernovae (SNe Ia) are one of the building blocks of modern cosmology and laboratories for the explosion physics of White Dwarf star/s (WD) in close binary systems. The second star may be a WD (double degenerate systems, DD), or a non-degenerated star (SD) with a main sequence star, red giant or a helium star as companion \\citep{branch95,nomoto03,wang2012}. Light curves and spectra of the explosion look similar because a 'stellar amnesia' \\citep{h06}. Basic nuclear physics determines the progenitor structure and the explosion physics, breaking the link between progenitor evolution, and the explosion, resulting in three main classes of explosion scenarios: a) dynamical merging of two WD and a heating on time scales of seconds \\citep{webbink84,isern11}, b) surface helium detonations on top of a WD which ignite the central C/O by a detonation wave traveling inwards \\citep{n82,hk96,Kromer2010}; c) compressional heating in an accreting WD approaching the Chandrasekar mass on time of up to 108 years which may originated from SD and DD systems \\citep{WI73,Piersanti2004}. Simulations of the explosions depend on the inital conditions at the onset of the explosions, namely the mass and angular momentum of the WD(s). For all scenarios, diversity in SNe Ia must be expected because the WD originates from a range of Main Sequence masses (MMS < 8 M_⊙) and metallicities Z. Moreover, there is growing evidence that magnetic fields B may have to be added to the 'mix'. Only with recent advances in observations ranging from X-ray to radio, high precision spectroscopy, polarimetry and photometry and in the time-domain astronomy we obtain constraints for progenitor, on the explosion scenarios and links emerge between the progenitors and their environment with LCs and spectral signatures needed for high precision cosmology. It is too early to give final answers but we present our personal view. We will give some examples from the theory point of view and discuss

Uncovering the Putative B-Star Binary Companion of the SN 1993J Progenitor

NASA Technical Reports Server (NTRS)

Fox, Ori D.; Bostroem, K. Azalee; Van Dyk, Schuyler D.; Filippenko, Alexei V.; Fransson, Claes; Matheson, Thomas; Cenko, S. Bradley; Chandra, Poonam; Dwarkadas, Vikram; Li, Weidong;

IUE observations of long period eclipsing binaries - A study of accretion onto non-degenerate stars

NASA Technical Reports Server (NTRS)

Plavec, M. J.

1980-01-01

IUE observations made in 1978-1979 recorded a whole class of interacting long-period binaries similar to beta Lyrae, which includes RX Cas, SX Cas, V 367 Cyg, W Cru, beta Lyr, and W Ser, called the W Serpentis stars. These mass-transferring binaries with relatively high mass transfer rate show two prominent features in the far ultraviolet: a continuum with a color temperature higher than the one observed in the optical region (about 12,000 K), and a strong emission line spectrum with the N V doublet at 1240 A, C IV doublet at 1550 A and lines of Si II, Si III, Si IV, C II, Fe III, AI III, etc. These phenomena are discussed on the assumption that they are due to accretion onto non-degenerate stars.

Uncovering the cellular and molecular changes in tendon stem/progenitor cells attributed to tendon aging and degeneration.

PubMed

Kohler, Julia; Popov, Cvetan; Klotz, Barbara; Alberton, Paolo; Prall, Wolf Christian; Haasters, Florian; Müller-Deubert, Sigrid; Ebert, Regina; Klein-Hitpass, Ludger; Jakob, Franz; Schieker, Matthias; Docheva, Denitsa

2013-12-01

Although the link between altered stem cell properties and tissue aging has been recognized, the molecular and cellular processes of tendon aging have not been elucidated. As tendons contain stem/progenitor cells (TSPC), we investigated whether the molecular and cellular attributes of TSPC alter during tendon aging and degeneration. Comparing TSPC derived from young/healthy (Y-TSPC) and aged/degenerated human Achilles tendon biopsies (A-TSPC), we observed that A-TSPC exhibit a profound self-renewal and clonogenic deficits, while their multipotency was still retained. Senescence analysis showed a premature entry into senescence of the A-TSPC, a finding accompanied by an upregulation of p16(INK4A). To identify age-related molecular factors, we performed microarray and gene ontology analyses. These analyses revealed an intriguing transcriptomal shift in A-TSPC, where the most differentially expressed probesets encode for genes regulating cell adhesion, migration, and actin cytoskeleton. Time-lapse analysis showed that A-TSPC exhibit decelerated motion and delayed wound closure concomitant to a higher actin stress fiber content and a slower turnover of actin filaments. Lastly, based on the expression analyses of microarray candidates, we suggest that dysregulated cell-matrix interactions and the ROCK kinase pathway might be key players in TSPC aging. Taken together, we propose that during tendon aging and degeneration, the TSPC pool is becoming exhausted in terms of size and functional fitness. Thus, our study provides the first fundamental basis for further exploration into the molecular mechanisms behind tendon aging and degeneration as well as for the selection of novel tendon-specific therapeutical targets. © 2013 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

Gene expression changes in the retina following subretinal injection of human neural progenitor cells into a rodent model for retinal degeneration.

PubMed

Jones, Melissa K; Lu, Bin; Saghizadeh, Mehrnoosh; Wang, Shaomei

2016-01-01

Retinal degenerative diseases (RDDs) affect millions of people and are the leading cause of vision loss. Although treatment options for RDDs are limited, stem and progenitor cell-based therapies have great potential to halt or slow the progression of vision loss. Our previous studies have shown that a single subretinal injection of human forebrain derived neural progenitor cells (hNPCs) into the Royal College of Surgeons (RCS) retinal degenerate rat offers long-term preservation of photoreceptors and visual function. Furthermore, neural progenitor cells are currently in clinical trials for treating age-related macular degeneration; however, the molecular mechanisms of stem cell-based therapies are largely unknown. This is the first study to analyze gene expression changes in the retina of RCS rats following subretinal injection of hNPCs using high-throughput sequencing. RNA-seq data of retinas from RCS rats injected with hNPCs (RCS(hNPCs)) were compared to sham surgery in RCS (RCS(sham)) and wild-type Long Evans (LE(sham)) rats. Differential gene expression patterns were determined with in silico analysis and confirmed with qRT-PCR. Function, biologic, cellular component, and pathway analyses were performed on differentially expressed genes and investigated with immunofluorescent staining experiments. Analysis of the gene expression data sets identified 1,215 genes that were differentially expressed between RCS(sham) and LE(sham) samples. Additionally, 283 genes were differentially expressed between the RCS(hNPCs) and RCS(sham) samples. Comparison of these two gene sets identified 68 genes with inverse expression (termed rescue genes), including Pdc, Rp1, and Cdc42ep5. Functional, biologic, and cellular component analyses indicate that the immune response is enhanced in RCS(sham). Pathway analysis of the differential expression gene sets identified three affected pathways in RCS(hNPCs), which all play roles in phagocytosis signaling. Immunofluorescent staining

Blue supergiant progenitors from binary mergers for SN 1987A and other Type II-peculiar supernovae

NASA Astrophysics Data System (ADS)

Menon, Athira; Heger, Alexander

2017-11-01

We present results of a systematic and detailed stellar evolution study of binary mergers for blue supergiant (BSG) progenitors of Type II supernovae, particularly for SN 1987A. We are able to reproduce nearly all observational aspects of the progenitor of SN 1987A, Sk -69 °202, such as its position in the HR diagram, the enrichment of helium and nitrogen in the triple-ring nebula and its lifetime before its explosion. We build our evolutionary model based on the merger model of Podsiadlowski et al. (1992), Podsiadlowski et al. (2007) and empirically explore an initial parameter consisting of primary masses, secondary masses and different depths up to which the secondary penetrates the He core during the merger. The evolution of the post-merger star is continued until just before iron-core collapse. Of the 84 pre-supernova models (16 M⊙ - 23 M⊙) computed, the majority of the pre-supernova models are compact, hot BSGs with effective temperature >12 kK and 30 R⊙ - 70 R⊙ of which six match nearly all the observational properties of Sk -69 °202.

Formation of Thorne-Żytkow objects in close binaries

NASA Astrophysics Data System (ADS)

Hutilukejiang, Bumareyamu; Zhu, Chunhua; Wang, Zhaojun; Lü, Guoliang

2018-04-01

Thorne-Żytkow objects (TŻOs), originally proposed by Thorne and Żytkow, may form as a result of unstable mass transfer in a massive X-ray binary after a neutron star (NS) is engulfed in the envelope of its companion star. Using a rapid binary evolution program and the Monte Carlo method, we simulated the formation of TŻOs in close binary stars. The Galactic birth rate of TŻOs is about 1.5× 10^{-4} yr^{-1}. Their progenitors may be composed of a NS and a main-sequence star, a star in the Hertzsprung gap or a core-helium burning, or a naked helium star. The birth rates of TŻOs via the above different progenitors are 1.7× 10^{-5}, 1.2× 10^{-4}, 0.7× 10^{-5}, 0.6× 10^{-5} yr^{-1}, respectively. These progenitors may be massive X-ray binaries. We found that the observational properties of three massive X-ray binaries (SMC X-1, Cen X-3 and LMC X-4) in which the companions of NSs may fill their Roche robes were consistent with those of their progenitors.

Three very cool degenerate stars in Luyten common proper motion binaries - Implications for the age of the galactic disk

NASA Technical Reports Server (NTRS)

Hintzen, Paul; Oswalt, Terry D.; Liebert, James; Sion, Edward M.

1989-01-01

During the course of a spectroscopic study of Luyten common proper motion (CPM) stars, spectrophotometric observations have been obtained of three binaries containing degenerate stars with estimated absolute magnitudes M(V) of about 16. Each of the three pairs consists of a yellow degenerate star primary and a DC 13 + secondary 1.4-2.3 mag fainter. One of the primary stars is spectral class DC 7, another is a sharp-lined DA 8, and the third shows peculiar broad absorption features which we interpret as pressure-shifted C2 Swan bands. The LP 701 - 69/70 system has survived for over 8 billion years without disruption by passing stars, despite its 1500 a.u. orbital major axis. The three cool degenerate companions nearly double the available sample of stars at the low-luminosity terminus of the white dwarf cooling sequence. These findings appear consistent with the conclusion that degenerate stars in the old disk population have not had time to evolve to a luminosity fainter than M(V) about 16.2.

Merging black hole binaries: the effects of progenitor's metallicity, mass-loss rate and Eddington factor

NASA Astrophysics Data System (ADS)

Giacobbo, Nicola; Mapelli, Michela; Spera, Mario

2018-03-01

The first four gravitational wave events detected by LIGO were all interpreted as merging black hole binaries (BHBs), opening a new perspective on the study of such systems. Here we use our new population-synthesis code MOBSE, an upgraded version of BSE, to investigate the demography of merging BHBs. MOBSE includes metallicity-dependent prescriptions for mass-loss of massive hot stars. It also accounts for the impact of the electron-scattering Eddington factor on mass-loss. We perform >108 simulations of isolated massive binaries, with 12 different metallicities, to study the impact of mass-loss, core-collapse supernovae and common envelope on merging BHBs. Accounting for the dependence of stellar winds on the Eddington factor leads to the formation of black holes (BHs) with mass up to 65 M⊙ at metallicity Z ˜ 0.0002. However, most BHs in merging BHBs have masses ≲ 40 M⊙. We find merging BHBs with mass ratios in the 0.1-1.0 range, even if mass ratios >0.6 are more likely. We predict that systems like GW150914, GW170814 and GW170104 can form only from progenitors with metallicity Z ≤ 0.006, Z ≤ 0.008 and Z ≤ 0.012, respectively. Most merging BHBs have gone through a common envelope phase, but up to ˜17 per cent merging BHBs at low metallicity did not undergo any common envelope phase. We find a much higher number of mergers from metal-poor progenitors than from metal-rich ones: the number of BHB mergers per unit mass is ˜10-4 M_{⊙}^{-1} at low metallicity (Z = 0.0002-0.002) and drops to ˜10-7 M_{⊙}^{-1} at high metallicity (Z ˜ 0.02).

Inferences about binary stellar populations using gravitational wave observations

NASA Astrophysics Data System (ADS)

Wysocki, Daniel; Gerosa, Davide; O'Shaughnessy, Richard; Belczynski, Krzysztof; Gladysz, Wojciech; Berti, Emanuele; Kesden, Michael; Holz, Daniel

2018-01-01

With the dawn of gravitational wave astronomy, enabled by the LIGO and Virgo interferometers, we now have a new window into the Universe. In the short time these detectors have been in use, multiple confirmed detections of gravitational waves from compact binary coalescences have been made. Stellar binary systems are one of the likely progenitors of the observed compact binary sources. If this is indeed the case, then we can use measured properties of these binary systems to learn about their progenitors. We will discuss the Bayesian framework in which we make these inferences, and results which include mass and spin distributions.

Is black-hole ringdown a memory of its progenitor?

PubMed

Kamaretsos, Ioannis; Hannam, Mark; Sathyaprakash, B S

2012-10-05

We perform an extensive numerical study of coalescing black-hole binaries to understand the gravitational-wave spectrum of quasinormal modes excited in the merged black hole. Remarkably, we find that the masses and spins of the progenitor are clearly encoded in the mode spectrum of the ringdown signal. Some of the mode amplitudes carry the signature of the binary's mass ratio, while others depend critically on the spins. Simulations of precessing binaries suggest that our results carry over to generic systems. Using Bayesian inference, we demonstrate that it is possible to accurately measure the mass ratio and a proper combination of spins even when the binary is itself invisible to a detector. Using a mapping of the binary masses and spins to the final black-hole spin allows us to further extract the spin components of the progenitor. Our results could have tremendous implications for gravitational astronomy by facilitating novel tests of general relativity using merging black holes.

Planetary nebula progenitors that swallow binary systems

NASA Astrophysics Data System (ADS)

Soker, Noam

2016-01-01

I propose that some irregular messy planetary nebulae (PNe) owe their morphologies to triple-stellar evolution where tight binary systems evolve inside and/or on the outskirts of the envelope of asymptotic giant branch (AGB) stars. In some cases, the tight binary system can survive, in others, it is destroyed. The tight binary system might break up with one star leaving the system. In an alternative evolution, one of the stars of the broken-up tight binary system falls towards the AGB envelope with low specific angular momentum, and drowns in the envelope. In a different type of destruction process, the drag inside the AGB envelope causes the tight binary system to merge. This releases gravitational energy within the AGB envelope, leading to a very asymmetrical envelope ejection, with an irregular and messy PN as a descendant. The evolution of the triple-stellar system can be in a full common envelope evolution or in a grazing envelope evolution. Both before and after destruction (if destruction takes place), the system might launch pairs of opposite jets. One pronounced signature of triple-stellar evolution might be a large departure from axisymmetrical morphology of the descendant PN. I estimate that about one in eight non-spherical PNe is shaped by one of these triple-stellar evolutionary routes.

Probing massive stars around gamma-ray burst progenitors

NASA Astrophysics Data System (ADS)

Lu, Wenbin; Kumar, Pawan; Smoot, George F.

2015-10-01

Long gamma-ray bursts (GRBs) are produced by ultra-relativistic jets launched from core collapse of massive stars. Most massive stars form in binaries and/or in star clusters, which means that there may be a significant external photon field (EPF) around the GRB progenitor. We calculate the inverse-Compton scattering of EPF by the hot electrons in the GRB jet. Three possible cases of EPF are considered: the progenitor is (I) in a massive binary system, (II) surrounded by a Wolf-Rayet-star wind and (III) in a dense star cluster. Typical luminosities of 1046-1050 erg s-1 in the 1-100 GeV band are expected, depending on the stellar luminosity, binary separation (I), wind mass-loss rate (II), stellar number density (III), etc. We calculate the light curve and spectrum in each case, taking fully into account the equal-arrival time surfaces and possible pair-production absorption with the prompt γ-rays. Observations can put constraints on the existence of such EPFs (and hence on the nature of GRB progenitors) and on the radius where the jet internal dissipation process accelerates electrons.

The Changing Nature of QU Carinae: SN Ia Progenitor or a Hoax?

NASA Astrophysics Data System (ADS)

Kafka, Stella

2013-01-01

The race to the elusive Type Ia supernovae (SNe Ia) progenitors is at its zenith, with numerous clues from SNe Ia ejecta and a dearth of observational candidates. Still, the single degenerate channel is a viable route of mass accumulation onto a white dwarf to the Chandrasekhar limit. I present long-term high resolution spectroscopy of QU Carinae, one of the most promising single degenerate SNe Ia progenitors. I discuss its highly variable nature and compare it to current scenarios for mass accumulation onto high-mass white dwarfs, eventually leading to WD detonation and to a supernova explosion.

Common-envelope ejection in massive binary stars. Implications for the progenitors of GW150914 and GW151226

NASA Astrophysics Data System (ADS)

Kruckow, M. U.; Tauris, T. M.; Langer, N.; Szécsi, D.; Marchant, P.; Podsiadlowski, Ph.

2016-11-01

Context. The recently detected gravitational wave signals (GW150914 and GW151226) of the merger event of a pair of relatively massive stellar-mass black holes (BHs) calls for an investigation of the formation of such progenitor systems in general. Aims: We analyse the common-envelope (CE) stage of the traditional formation channel in binaries where the first-formed compact object undergoes an in-spiral inside the envelope of its evolved companion star and ejects the envelope in this process. Methods: We calculated envelope binding energies of donor stars with initial masses between 4 and 115M⊙ for metallicities of Z = ZMilky Way ≃ Z⊙/ 2 and Z = Z⊙/ 50, and derived minimum masses of in-spiralling objects needed to eject these envelopes. Results: In addition to producing double white dwarf and double neutron star binaries, CE evolution may also produce massive BH-BH systems with individual BH component masses of up to 50 - 60M⊙, in particular for donor stars evolved to giants beyond the Hertzsprung gap. However, the physics of envelope ejection of massive stars remains uncertain. We discuss the applicability of the energy-budget formalism, the location of the bifurcation point, the recombination energy, and the accretion energy during in-spiral as possible energy sources, and also comment on the effect of inflated helium cores. Conclusions: Massive stars in a wide range of metallicities and with initial masses of up to at least 115M⊙ may shed their envelopes and survive CE evolution, depending on their initial orbital parameters, similarly to the situation for intermediate- and low-mass stars with degenerate cores. In addition to being dependent on stellar radius, the envelope binding energies and λ-values also depend on the applied convective core-overshooting parameter, whereas these structure parameters are basically independent of metallicity for stars with initial masses below 60M⊙. Metal-rich stars ≳60M⊙ become luminous blue variables and do

A progenitor binary and an ejected mass donor remnant of faint type Ia supernovae

NASA Astrophysics Data System (ADS)

Geier, S.; Marsh, T. R.; Wang, B.; Dunlap, B.; Barlow, B. N.; Schaffenroth, V.; Chen, X.; Irrgang, A.; Maxted, P. F. L.; Ziegerer, E.; Kupfer, T.; Miszalski, B.; Heber, U.; Han, Z.; Shporer, A.; Telting, J. H.; Gänsicke, B. T.; Østensen, R. H.; O'Toole, S. J.; Napiwotzki, R.

2013-06-01

Type Ia supernovae (SN Ia) are the most important standard candles for measuring the expansion history of the universe. The thermonuclear explosion of a white dwarf can explain their observed properties, but neither the progenitor systems nor any stellar remnants have been conclusively identified. Underluminous SN Ia have been proposed to originate from a so-called double-detonation of a white dwarf. After a critical amount of helium is deposited on the surface through accretion from a close companion, the helium is ignited causing a detonation wave that triggers the explosion of the white dwarf itself. We have discovered both shallow transits and eclipses in the tight binary system CD-30°11223 composed of a carbon/oxygen white dwarf and a hot helium star, allowing us to determine its component masses and fundamental parameters. In the future the system will transfer mass from the helium star to the white dwarf. Modelling this process we find that the detonation in the accreted helium layer is sufficiently strong to trigger the explosion of the core. The helium star will then be ejected at such high velocity that it will escape the Galaxy. The predicted properties of this remnant are an excellent match to the so-called hypervelocity star US 708, a hot, helium-rich star moving at more than 750 km s-1, sufficient for it to leave the Galaxy. The identification of both progenitor and remnant provides a consistent picture of the formation and evolution of underluminous SNIa.

Mass-accreting white dwarfs and type Ia supernovae

NASA Astrophysics Data System (ADS)

Wang, Bo

2018-05-01

Type Ia supernovae (SNe Ia) play a prominent role in understanding the evolution of the Universe. They are thought to be thermonuclear explosions of mass-accreting carbon-oxygen white dwarfs (CO WDs) in binaries, although the mass donors of the accreting WDs are still not well determined. In this article, I review recent studies on mass-accreting WDs, including H- and He-accreting WDs. I also review currently most studied progenitor models of SNe Ia, i.e., the single-degenerate model (including the WD+MS channel, the WD+RG channel and the WD+He star channel), the double-degenerate model (including the violent merger scenario) and the sub-Chandrasekhar mass model. Recent progress on these progenitor models is discussed, including the initial parameter space for producing SNe Ia, the binary evolutionary paths to SNe Ia, the progenitor candidates for SNe Ia, the possible surviving companion stars of SNe Ia, some observational constraints, etc. Some other potential progenitor models of SNe Ia are also summarized, including the hybrid CONe WD model, the core-degenerate model, the double WD collision model, the spin-up/spin-down model and the model of WDs near black holes. To date, it seems that two or more progenitor models are needed to explain the observed diversity among SNe Ia.

No surviving evolved companions of the progenitor of SN 1006.

PubMed

González Hernández, Jonay I; Ruiz-Lapuente, Pilar; Tabernero, Hugo M; Montes, David; Canal, Ramon; Méndez, Javier; Bedin, Luigi R

2012-09-27

Type Ia supernovae are thought to occur when a white dwarf made of carbon and oxygen accretes sufficient mass to trigger a thermonuclear explosion. The accretion could be slow, from an unevolved (main-sequence) or evolved (subgiant or giant) star (the single-degenerate channel), or rapid, as the primary star breaks up a smaller orbiting white dwarf (the double-degenerate channel). A companion star will survive the explosion only in the single-degenerate channel. Both channels might contribute to the production of type Ia supernovae, but the relative proportions of their contributions remain a fundamental puzzle in astronomy. Previous searches for remnant companions have revealed one possible case for SN 1572 (refs 8, 9), although that has been questioned. More recently, observations have restricted surviving companions to be small, main-sequence stars, ruling out giant companions but still allowing the single-degenerate channel. Here we report the results of a search for surviving companions of the progenitor of SN 1006 (ref. 14). None of the stars within 4 arc minutes of the apparent site of the explosion is associated with the supernova remnant, and we can firmly exclude all giant and subgiant stars from being companions of the progenitor. In combination with previous results, our findings indicate that fewer than 20 per cent of type Ia supernovae occur through the single-degenerate channel.

Single progenitor model for GW150914 and GW170104

NASA Astrophysics Data System (ADS)

D'Orazio, Daniel J.; Loeb, Abraham

2018-04-01

The merger of stellar-mass black holes (BHs) is not expected to generate detectable electromagnetic (EM) emission. However, the gravitational wave (GW) events GW150914 and GW170104, detected by the Laser Interferometer Gravitational Wave Observatory to be the result of merging, ˜60 M⊙ binary black holes (BBHs), each have claimed coincident gamma-ray emission. Motivated by the intriguing possibility of an EM counterpart to BBH mergers, we construct a model that can reproduce the observed EM and GW signals for GW150914- and GW170104-like events, from a single-star progenitor. Following Loeb [Astrophys. J. Lett. 819, L21 (2016), 10.3847/2041-8205/819/2/L21], we envision a massive, rapidly rotating star within which a rotating-bar instability fractures the core into two overdensities that fragment into clumps which merge to form BHs in a tight binary with arbitrary spin-orbit alignment. Once formed, the BBH inspirals due to gas and gravitational-wave drag until tidal forces trigger strong feeding of the BHs with the surrounding stellar-density gas about 10 sec before merger. The resulting giga-Eddington accretion peak launches a jet that breaks out of the progenitor star and drives a powerful outflow that clears the gas from the orbit of the binary within 1 sec, preserving the vacuum GW waveform in the Laser Interferometer Gravitational Wave Observatory band. The single-progenitor scenario predicts the existence of variability of the gamma-ray burst, modulated at the ˜0.2 sec chirping period of the BBH due to relativistic Doppler boost. The jet breakout should be accompanied by a low-luminosity supernova. Finally, because the BBHs of the single-progenitor model do not exist at large separations, they will not be detectable in the low-frequency gravitational-wave band of the Laser Interferometer Space Antenna. Hence, the single-progenitor BBHs will be unambiguously discernible from BBHs formed through alternate, double-progenitor evolution scenarios.

Progenitor constraints for core-collapse supernovae from Chandra X-ray observations

NASA Astrophysics Data System (ADS)

Heikkilä, T.; Tsygankov, S.; Mattila, S.; Eldridge, J. J.; Fraser, M.; Poutanen, J.

2016-03-01

The progenitors of hydrogen-poor core-collapse supernovae (SNe) of Types Ib, Ic and IIb are believed to have shed their outer hydrogen envelopes either by extremely strong stellar winds, characteristic of classical Wolf-Rayet stars, or by binary interaction with a close companion star. The exact nature of the progenitors and the relative importance of these processes are still open questions. One relatively unexplored method to constrain the progenitors is to search for high-mass X-ray binaries (HMXBs) at SN locations in pre-explosion X-ray observations. In an HMXB, one star has already exploded as a core-collapse SN, producing a neutron star or a stellar mass black hole. It is likely that the second star in the system will also explode as an SN, which should cause a detectable long-term change in the system's X-ray luminosity. In particular, a pre-explosion detection of an HMXB coincident with an SN could be informative about the progenitor's nature. In this paper, we analyse pre-explosion ACIS observations of 18 nearby Type Ib, Ic and IIb SNe from the Chandra X-ray observatory public archive. Two sources that could potentially be associated with the SN are identified in the sample. Additionally we make similar post-explosion measurements for 46 SNe. Although our modelling indicates that progenitor systems with compact binary companions are probably quite rare, studies of this type can in the future provide more stringent constraints as the number of discovered nearby SNe and suitable pre-explosion X-ray data are both increasing.

Finally, the Progenitor of the Type Ib iPTF13bvn

NASA Astrophysics Data System (ADS)

Van Dyk, Schulyer

2017-08-01

Supernovae (SNe) are among the most powerful events in the Universe and have a profound influence on galaxy evolution. Whereas we have been able to identify the luminous red supergiant progenitor stars of the most common core-collapse explosions, the hydrogen-rich Type II, the progenitors of hydrogen-poor Type Ib and Type Ic have been far more elusive. To strip away a SN Ib/c progenitor's outer layers, theoretical models with either (a) a highly-massive star with prodigious winds during the Wolf-Rayet phase or (b) a somewhat lower-mass star in a close, mass-exchange binary system have been proposed. One example exists so far of a progenitor identification, for the SN Ib iPTF13bvn in NGC 5806. Both models have been invoked to explain this event, although most evidence to date points toward the binary model. Our combined team observed this SN with WFC3 in Cycle 22, about 2 years after explosion, to investigate whether the progenitor had disappeared. As a result, we were able to report that indeed it had. We also attempted to better characterize the nature of the progenitor by subtracting our images from the pre-explosion HST data. Unfortunately, the old SN was apparently still conspicuously present. We therefore propose to reimage the SN site, when the SN should then be well below detectability, to produce high-quality templates of the host galaxy for subtraction. We can then finally fully reveal the progenitor and understand its true nature. iPTF13bvn is one of the most important historical SNe and will most probably be the best available case of a SN Ib progenitor for HST's remaining lifetime. It is imperative to understand the nature of this SN and its progenitor object.

The direct identification of core-collapse supernova progenitors.

PubMed

Van Dyk, Schuyler D

2017-10-28

To place core-collapse supernovae (SNe) in context with the evolution of massive stars, it is necessary to determine their stellar origins. I describe the direct identification of SN progenitors in existing pre-explosion images, particularly those obtained through serendipitous imaging of nearby galaxies by the Hubble Space Telescope I comment on specific cases representing the various core-collapse SN types. Establishing the astrometric coincidence of a SN with its putative progenitor is relatively straightforward. One merely needs a comparably high-resolution image of the SN itself and its stellar environment to perform this matching. The interpretation of these results, though, is far more complicated and fraught with larger uncertainties, including assumptions of the distance to and the extinction of the SN, as well as the metallicity of the SN environment. Furthermore, existing theoretical stellar evolutionary tracks exhibit significant variations one from the next. Nonetheless, it appears fairly certain that Type II-P (plateau) SNe arise from massive stars in the red supergiant phase. Many of the known cases are associated with subluminous Type II-P events. The progenitors of Type II-L (linear) SNe are less established. Among the stripped-envelope SNe, there are now a number of examples of cool, but not red, supergiants (presumably in binaries) as Type IIb progenitors. We appear now finally to have an identified progenitor of a Type Ib SN, but no known example yet for a Type Ic. The connection has been made between some Type IIn SNe and progenitor stars in a luminous blue variable phase, but that link is still thin, based on direct identifications. Finally, I also describe the need to revisit the SN site, long after the SN has faded, to confirm the progenitor identification through the star's disappearance and potentially to detect a putative binary companion that may have survived the explosion.This article is part of the themed issue 'Bridging the gap: from

On the progenitors of Type Ia supernovae

NASA Astrophysics Data System (ADS)

Livio, Mario; Mazzali, Paolo

2018-03-01

We review all the models proposed for the progenitor systems of Type Ia supernovae and discuss the strengths and weaknesses of each scenario when confronted with observations. We show that all scenarios encounter at least a few serious difficulties, if taken to represent a comprehensive model for the progenitors of all Type Ia supernovae (SNe Ia). Consequently, we tentatively conclude that there is probably more than one channel leading SNe Ia. While the single-degenerate scenario (in which a single white dwarf accretes mass from a normal stellar companion) has been studied in some detail, the other scenarios will need a similar level of scrutiny before any firm conclusions can be drawn.

Time-series Spectroscopy of Two Candidate Double Degenerates in the Open Cluster NGC 6633

NASA Astrophysics Data System (ADS)

Williams, Kurtis A.; Serna-Grey, Donald; Chakraborty, Subho; Gianninas, A.; Canton, Paul A.

2015-12-01

SNe Ia are heavily used tools in precision cosmology, yet we still are not certain what the progenitor systems are. General plausibility arguments suggest there is potential for identifying double degenerate SN Ia progenitors in intermediate-age open star clusters. We present time-resolved high-resolution spectroscopy of two white dwarfs (WDs) in the field of the open cluster NGC 6633 that had previously been identified as candidate double degenerates in the cluster. However, three hours of continuous observations of each candidate failed to detect any significant radial velocity variations at the ≳10 km s-1 level, making it highly unlikely that either WD is a double degenerate that will merge within a Hubble Time. The WD LAWDS NGC 6633 4 has a radial velocity inconsistent with cluster membership at the 2.5σ level, while the radial velocity of LAWDS NGC 6633 7 is consistent with cluster membership. We conservatively conclude that LAWDS 7 is a viable massive double degenerate candidate, though unlikely to be a Type Ia progenitor. Astrometric data from GAIA will likely be needed to determine if either WD is truly a cluster member. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Detecting a Hot Companion to the Progenitor of the Type Ic Supernova 1994I in M51

NASA Astrophysics Data System (ADS)

Van Dyk, Schuyler

2013-10-01

Core-collapse supernovae {SNe} are the endpoints of the lives of massive stars {with initial mass > 8 solar masses}. We are reasonably confident that the progenitor stars for most hydrogen-rich Type II SNe are red supergiants, based in part on direct identifications with HST. However, the progenitors of the stripped-envelope He-rich Type Ib and He-poor Type Ic SNe have yet to be directly identified. These SNe are thought to arise from either single, high-mass stars in the Wolf-Rayet phase or, alternatively, from lower-mass stars in interacting binary systems. Both models can account for the required extensive envelope stripping. Until a progenitor is identified for these SN types, our best hope of testing these progenitor models is to detect the companion star to the progenitor, if the binary model holds. This star is predicted to be a hot supergiant. Therefore, it is best detected in the ultraviolet. The only SN which is sufficiently nearby and experienced low enough reddening to be a viable target for this detection is the SN Ic 1994I in M51. Furthermore, the SN was imaged by HST when it was still bright, so we can pinpoint its location. We therefore propose, as part of the UV Initiative in Cycle 21, to image the site in F275W and F336W to levels deep enough to significantly detect a putative progenitor companion, if it exists. The proposed observations will provide an important test of the binary progenitor hypothesis.

The double-degenerate model for the progenitors of Type Ia supernovae

NASA Astrophysics Data System (ADS)

Liu, D.; Wang, B.; Han, Z.

2018-02-01

The double-degenerate (DD) model, involving the merging of massive double carbon-oxygen white dwarfs (CO WDs) driven by gravitational wave radiation, is one of the classical pathways for the formation of Type Ia supernovae (SNe Ia). Recently, it has been proposed that the WD+He subgiant channel has a significant contribution to the production of massive double WDs, in which the primary WD accumulates mass by accreting He-rich matter from an He subgiant. We evolved about 1800 CO WD+He star systems and obtained a large and dense grid for producing SNe Ia through the DD model. We then performed a series of binary population synthesis simulations for the DD model, in which the WD+He subgiant channel is calculated by interpolations in the SN Ia production grid. According to our standard model, the Galactic birth rate of SNe Ia is about 2.4 × 10- 3 yr- 1 for the WD+He subgiant channel of the DD model; the total birth rate is about 3.7 × 10- 3 yr- 1 for all channels, reproducing that of observations. Previous theoretical models still have deficit with the observed SNe Ia with delay times < 1 Gyr and > 8 Gyr. After considering the WD+He subgiant channel, we found that the delay time distributions are comparable with the observed results. Additionally, some recent studies proposed that the violent WD mergers are more likely to produce SNe Ia based on the DD model. We estimated that the violent mergers through the DD model may contribute to at most 16 per cent of all SNe Ia.

Short gamma-ray bursts and gravitational-wave observations from eccentric compact binaries

NASA Astrophysics Data System (ADS)

Tan, Wei-Wei; Fan, Xi-Long; Wang, F. Y.

2018-03-01

Mergers of compact binaries, such as binary neutron stars (BNSs), neutron star-black hole binaries (NSBHs) and binary black holes (BBHs), are expected to be the best candidates for sources of gravitational waves (GWs) and the leading theoretical models for short gamma-ray bursts (SGRBs). Based on observations of SGRBs, we can derive the merger rates of these compact binaries and study stochastic GW backgrounds (SGWBs) or the co-detection rates of GWs associated with SGRBs (GW-SGRBs). Before that, however, the most important thing is to derive the GW spectrum from a single GW source. Usually, a GW spectrum from a circular-orbit binary is assumed. However, observations of the large spatial offsets of SGRBs from their host galaxies imply that SGRB progenitors may be formed by dynamical processes and will merge with residual eccentricities (er). The orbital eccentricity has an important effect on GW spectra and therefore on the SGWB and GW-SGRB co-detection rate. Our results show that the power spectra of SGWBs from eccentric compact binaries are greatly suppressed at low frequencies (e.g. f ≲ 1 Hz). In particular, SGWBs from binaries with high residual eccentricities (e.g. er ≳ 0.1 for BNSs) will be hard to detect (above the detection frequency of ˜ 100 Hz). Regarding the co-detection rates of GW-SGRB events, they could be ˜1.4 times higher than the circular case within some particular ranges of er (e.g. 0.01 ≲ er ≲ 0.1 for BBHs), but greatly reduced for high residual eccentricities (e.g. er > 0.1 for BNSs). In general, BBH progenitors produce 200 and 10 times higher GW-SGRB events than BNS and NSBH progenitors, respectively. Therefore, binaries with low residual eccentricities (e.g. 0.001 ≲ er ≲ 0.1) and high total masses will be easier to detect by Advanced LIGO (aLIGO). However, only a small fraction of BBHs can be SGRB progenitors (if they can produce SGRBs), because the predicted GW-SGRB event rate (60˜100 per year) is too high compared with recent

Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra

NASA Astrophysics Data System (ADS)

Leonard, Douglas

2006-02-01

The progenitor systems of Type Ia supernovae (SNe Ia) are observationally unconstrained. Prevailing theory invokes a carbon- oxygen white dwarf accreting matter from a companion until a thermonuclear runaway ensues that incinerates the white dwarf. While models of exploding carbon-oxygen white dwarfs faithfully reproduce the main characteristics of SNe Ia, we are ignorant about the nature of the proposed companion star. Simulations resulting from this single- degenerate binary channel, however, demand the presence of low-velocity, H(alpha) emission in spectra taken in the nebular phase (250 - 400 days after maximum light), since a portion of the companion's envelope becomes entrained in the ejecta. This hydrogen has never been detected, and only generally weak limits have heretofore been set from ~ 6 SNe Ia observed during the nebular phase at low resolution and often with a low signal-to-noise ratio (S/N). We propose to remedy this situation through high S/N observations of two nearby, nebular-phase SNe Ia, with sufficient sensitivity and resolution to detect ~ 0.01 Msun of solar abundance material in the ejecta. The detection of late- time H(alpha) emission would be considered a ``smoking gun'' for the binary scenario. If H(alpha) is not detected, the limits will effectively rule out sub-giant, red giant, and all but the most widely separated main-sequence companions.

Multidimensional Models of Type Ia Supernova Nebular Spectra: Strong Emission Lines from Stripped Companion Gas Rule Out Classic Single-degenerate Systems

NASA Astrophysics Data System (ADS)

Botyánszki, János; Kasen, Daniel; Plewa, Tomasz

2018-01-01

The classic single-degenerate model for the progenitors of Type Ia supernova (SN Ia) predicts that the supernova ejecta should be enriched with solar-like abundance material stripped from the companion star. Spectroscopic observations of normal SNe Ia at late times, however, have not resulted in definite detection of hydrogen. In this Letter, we study line formation in SNe Ia at nebular times using non-LTE spectral modeling. We present, for the first time, multidimensional radiative transfer calculations of SNe Ia with stripped material mixed in the ejecta core, based on hydrodynamical simulations of ejecta–companion interaction. We find that interaction models with main-sequence companions produce significant Hα emission at late times, ruling out these types of binaries being viable progenitors of SNe Ia. We also predict significant He I line emission at optical and near-infrared wavelengths for both hydrogen-rich or helium-rich material, providing an additional observational probe of stripped ejecta. We produce models with reduced stripped masses and find a more stringent mass limit of M st ≲ 1 × 10‑4 M ⊙ of stripped companion material for SN 2011fe.

On the merging rates of envelope-deprived components of binary systems which can give rise to supernova events

NASA Astrophysics Data System (ADS)

Tornambe, Amedeo

1989-08-01

Theoretical rates of mergings of envelope-deprived components of binary systems, which can give rise to supernova events are described. The effects of the various assumptions on the physical properties of the progenitor system and of its evolutionary behavior through common envelope phases are discussed. Four cases have been analyzed: CO-CO, He-CO, He-He double degenerate mergings and He star-CO dwarf merging. It is found that, above a critical efficiency of the common envelope action in system shrinkage, the rate of CO-CO mergings is not strongly sensitive to the efficiency. Below this critical value, no CO-CO systems will survive for times larger than a few Gyr. In contrast, He-CO dwarf systems will continue to merge at a reasonable rate up to 20 Gyr, and more, also under extreme conditions.

Constraints on core-collapse supernova progenitors from explosion site integral field spectroscopy

NASA Astrophysics Data System (ADS)

Kuncarayakti, H.; Anderson, J. P.; Galbany, L.; Maeda, K.; Hamuy, M.; Aldering, G.; Arimoto, N.; Doi, M.; Morokuma, T.; Usuda, T.

2018-05-01

Context. Observationally, supernovae (SNe) are divided into subclasses according to their distinct characteristics. This diversity naturally reflects the diversity in the progenitor stars. It is not entirely clear, however, how different evolutionary paths leading massive stars to become an SN are governed by fundamental parameters such as progenitor initial mass and metallicity. Aims: This paper places constraints on progenitor initial mass and metallicity in distinct core-collapse SN subclasses through a study of the parent stellar populations at the explosion sites. Methods: Integral field spectroscopy (IFS) of 83 nearby SN explosion sites with a median distance of 18 Mpc has been collected and analysed, enabling detection and spectral extraction of the parent stellar population of SN progenitors. From the parent stellar population spectrum, the initial mass and metallicity of the coeval progenitor are derived by means of comparison to simple stellar population models and strong-line methods. Additionally, near-infrared IFS was employed to characterise the star formation history at the explosion sites. Results: No significant metallicity differences are observed among distinct SN types. The typical progenitor mass is found to be highest for SN type Ic, followed by type Ib, then types IIb and II. Type IIn is the least associated with young stellar populations and thus massive progenitors. However, statistically significant differences in progenitor initial mass are observed only when comparing SNe IIn with other subclasses. Stripped-envelope SN progenitors with initial mass estimates lower than 25 M⊙ are found; they are thought to be the result of binary progenitors. Confirming previous studies, these results support the notion that core-collapse SN progenitors cannot arise from single-star channels only, and both single and binary channels are at play in the production of core-collapse SNe. Near-infrared IFS suggests that multiple stellar populations with

Single Degenerate Models for Type Ia Supernovae: Progenitor's Evolution and Nucleosynthesis Yields

NASA Astrophysics Data System (ADS)

Nomoto, Ken'ichi; Leung, Shing-Chi

2018-06-01

We review how the single degenerate models for Type Ia supernovae (SNe Ia) works. In the binary star system of a white dwarf (WD) and its non-degenerate companion star, the WD accretes either hydrogen-rich matter or helium and undergoes hydrogen and helium shell-burning. We summarize how the stability and non-linear behavior of such shell-burning depend on the accretion rate and the WD mass and how the WD blows strong wind. We identify the following evolutionary routes for the accreting WD to trigger a thermonuclear explosion. Typically, the accretion rate is quite high in the early stage and gradually decreases as a result of mass transfer. With decreasing rate, the WD evolves as follows: (1) At a rapid accretion phase, the WD increase its mass by stable H burning and blows a strong wind to keep its moderate radius. The wind is strong enough to strip a part of the companion star's envelope to control the accretion rate and forms circumstellar matter (CSM). If the WD explodes within CSM, it is observed as an "SN Ia-CSM". (X-rays emitted by the WD are absorbed by CSM.) (2) If the WD continues to accrete at a lower rate, the wind stops and an SN Ia is triggered under steady-stable H shell-burning, which is observed as a super-soft X-ray source: "SN Ia-SSXS". (3) If the accretion continues at a still lower rate, H shell-burning becomes unstable and many flashes recur. The WD undergoes recurrent nova (RN) whose mass ejection is smaller than the accreted matter. Then the WD evolves to an "SN Ia-RN". (4) If the companion is a He star (or a He WD), the accretion of He can trigger He and C double detonations at the sub-Chandrasekhar mass or the WD grows to the Chandrasekhar mass while producing a He-wind: "SN Ia-He CSM". (5) If the accreting WD rotates quite rapidly, the WD mass can exceed the Chandrasekhar mass of the spherical WD, which delays the trigger of an SN Ia. After angular momentum is lost from the WD, the (super-Chandra) WD contracts to become a delayed SN Ia

Electron Capture Supernovae from Close Binary Systems

NASA Astrophysics Data System (ADS)

Poelarends, Arend J. T.; Wurtz, Scott; Tarka, James; Cole Adams, L.; Hills, Spencer T.

2017-12-01

We present the first detailed study of the Electron Capture Supernova Channel (ECSN Channel) for a primary star in a close binary star system. Progenitors of ECSN occupy the lower end of the mass spectrum of supernova progenitors and are thought to form the transition between white dwarf progenitors and core-collapse progenitors. The mass range for ECSN from close binary systems is thought to be wider than the range for single stars, because of the effects of mass transfer on the helium core. Using the MESA stellar evolution code, we explored the parameter space of initial primary masses between 8 and 17 {M}⊙ , using a large grid of models. We find that the initial primary mass and the mass transfer evolution are important factors in the final fate of stars in this mass range. Mass transfer due to Roche lobe overflow during and after carbon burning causes the core to cool down so that it avoids neon ignition, even in helium-free cores with masses up to 1.52 {M}⊙ , which in single stars would ignite neon. If the core is able to contract to high enough densities for electron captures to commence, we find that, for the adopted Ledoux convection criterion, the initial mass range for the primary to evolve into an ECSN is between 13.5 and 17.6 {M}⊙ . The mass ratio, initial period, and mass-loss efficiency only marginally affect the predicted ranges.

The interacting binary white dwarf systems

NASA Astrophysics Data System (ADS)

Provencal, Judith Lucille

1994-01-01

Interacting binary white dwarfs are believed to contain two white dwarfs of extreme mass ratio, one of which is filling its Roche Lobe, transferring material to its companion via an accretion disk. The defining characteristic of an IBWD is the nondetection of hydrogen in the system. IBWD's represent the culmination of binary star evolution. In this final death dance, two degenerate objects are entangled, the massive white dwarf tidally stripping and devouring its helpless companion's outer layers. Because a white dwarf expands as it loses mass, the end result of this process is the complete absorption of one star by the other . My goal in the examination of these systems is to understand their photometric behavior and determine the best model of these objects. The IBWD's represent the endpoint of binary evolution. Knowledge of the physical properties of these objects will provide constraints on theories of binary evolution, white dwarf formation, the thermal and physical structure of accreting white dwarfs, and nucleosynthesis. To achieve this goal, I have analyzed the most comprehensive high speed photometric data sets available on 5 of the 6 known objects: AM CVn, PG1346+082, CP Eri, V803 Cen, and G61-29. AM CVn and PG1346+0S2 were targets of the Whole Earth Telescope in 1988 and 1990 respectively. We find a range of variation timescales, from minutes to days, and a range of physical behaviour. Most importantly, we measure a rate of period change of P = 1.68 +/- 0.03 x 10-11s/s for the dominant variation in AM CVn. We also find the differences in behavior can be attributed to a difference in mass transfer rate that may be evolutionary in origin. Finally, I discuss in detail the observational characteristics of each object, and overall properties of the IBWD family. In conclusion, I discuss past and future history of these objects, and touch on their possible influence on our knowledge of white dwarf evolution and formation. The IBWD's are possible progenitors of

THE LOCATIONS OF SHORT GAMMA-RAY BURSTS AS EVIDENCE FOR COMPACT OBJECT BINARY PROGENITORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fong, W.; Berger, E.

2013-10-10

We present a detailed investigation of Hubble Space Telescope rest-frame UV/optical observations of 22 short gamma-ray burst (GRB) host galaxies and sub-galactic environments. Utilizing the high angular resolution and depth of HST we characterize the host galaxy morphologies, measure precise projected physical and host-normalized offsets between the bursts and host centers, and calculate the locations of the bursts with respect to their host light distributions (rest-frame UV and optical). We calculate a median short GRB projected physical offset of 4.5 kpc, about 3.5 times larger than that for long GRBs, and find that ≈25% of short GRBs have offsets ofmore » ∼> 10 kpc. When compared to their host sizes, the median offset is 1.5 half-light radii (r{sub e} ), about 1.5 times larger than the values for long GRBs, core-collapse supernovae, and Type Ia supernovae. In addition, ≈20% of short GRBs having offsets of ∼> 5r{sub e} , and only ≈25% are located within 1r{sub e} . We further find that short GRBs severely under-represent their hosts' rest-frame optical and UV light, with ≈30%-45% of the bursts located in regions of their host galaxies that have no detectable stellar light, and ≈55% in the regions with no UV light. Therefore, short GRBs do not occur in regions of star formation or even stellar mass. This demonstrates that the progenitor systems of short GRBs must migrate from their birth sites to their eventual explosion sites, a signature of kicks in compact object binary systems. Utilizing the full sample of offsets, we estimate natal kick velocities of ≈20-140 km s{sup –1}. These independent lines of evidence provide the strongest support to date that short GRBs result from the merger of compact object binaries (NS-NS/NS-BH)« less

The Fate of Exploding White Dwarfs

NASA Astrophysics Data System (ADS)

Fisher, Robert

2018-01-01

Type Ia supernovae play an important role as standardizable candles for cosmology, providing one of the most important probes into the nature of dark energy. Yet, the nature of the stellar progenitors which give rise to Type Ia supernovae remains elusive. For decades, the leading model explaining Type Ia supernovae properties consisted of a white dwarf accreting to near the Chandrasekhar mass, in the single-degenerate channel. More recently, a variety of lines of evidence point instead towards merging binary white dwarfs, in the double-degenerate channel, as the progenitors of most Type Ia supernovae. In this talk, I will focus upon recent advances at the interface between observation and theory which will help crack the Type Ia progenitor problem. In particular, I will present new insights obtained from recent multidimensional numerical simulations of both the double-degenerate and single-degenerate channels which I have undertaken with my students and collaborators. I will discuss how new models and observations will help elucidate the long-standing mystery of Type supernovae.

Testing Common Envelopes on Double White Dwarf Binaries

NASA Astrophysics Data System (ADS)

Nandez, Jose L. A.; Ivanova, Natalia; Lombardi, James C., Jr.

2015-06-01

The formation of a double white dwarf binary likely involves a common envelope (CE) event between a red giant and a white dwarf (WD) during the most recent episode of Roche lobe overflow mass transfer. We study the role of recombination energy with hydrodynamic simulations of such stellar interactions. We find that the recombination energy helps to expel the common envelope entirely, while if recombination energy is not taken into account, a significant fraction of the common envelope remains bound. We apply our numerical methods to constrain the progenitor system for WD 1101+364 - a double WD binary that has well-measured mass ratio of q=0.87±0.03 and an orbital period of 0.145 days. Our best-fit progenitor for the pre-common envelope donor is a 1.5 ⊙ red giant.

Neutron-Star-Black-Hole Binaries Produced by Binary-Driven Hypernovae

NASA Astrophysics Data System (ADS)

Fryer, Chris L.; Oliveira, F. G.; Rueda, J. A.; Ruffini, R.

2015-12-01

Binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (Eiso≳1052 erg ), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed "ultrastripped" binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differently than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs.

Implications of the Low Binary Black Hole Aligned Spins Observed by LIGO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hotokezaka, Kenta; Piran, Tsvi

We explore the implications of the low-spin components along the orbital axis observed in an Advanced LIGO O1 run on binary black hole (BBH) merger scenarios in which the merging BBHs have evolved from field binaries. The coalescence time determines the initial orbital separation of BBHs. This, in turn, determines whether the stars are synchronized before collapse, and hence determines their projected spins. Short coalescence times imply synchronization and large spins. Among known stellar objects, Wolf–Rayet (WR) stars seem to be the only progenitors consistent with the low aligned spins observed in LIGO’s O1, provided that the orbital axis maintainsmore » its direction during the collapse. We calculate the spin distribution of BBH mergers in the local universe, and its redshift evolution for WR progenitors. Assuming that the BBH formation rate peaks around a redshift of ∼2–3, we show that BBH mergers in the local universe are dominated by low-spin events. The high-spin population starts to dominate at a redshift of ∼0.5–1.5. WR stars are also progenitors of long gamma-ray bursts that take place at a comparable rate to BBH mergers. We discuss the possible connection between the two phenomena. Additionally, we show that hypothetical Population III star progenitors are also possible. Although WR and Population III progenitors are consistent with the current data, both models predict a non-vanishing fraction of high positive values of the BBHs’ aligned spin. If those are not detected within the coming LIGO/Virgo runs, it will be unlikely that the observed BBHs formed via field binaries.« less

The Evolution of Compact Binary Star Systems.

PubMed

Postnov, Konstantin A; Yungelson, Lev R

2014-01-01

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Mergings of compact-star binaries are expected to be the most important sources for forthcoming gravitational-wave (GW) astronomy. In the first part of the review, we discuss observational manifestations of close binaries with NS and/or BH components and their merger rate, crucial points in the formation and evolution of compact stars in binary systems, including the treatment of the natal kicks, which NSs and BHs acquire during the core collapse of massive stars and the common envelope phase of binary evolution, which are most relevant to the merging rates of NS-NS, NS-BH and BH-BH binaries. The second part of the review is devoted mainly to the formation and evolution of binary WDs and their observational manifestations, including their role as progenitors of cosmologically-important thermonuclear SN Ia. We also consider AM CVn-stars, which are thought to be the best verification binary GW sources for future low-frequency GW space interferometers.

Neutron-star–black-hole binaries produced by binary-driven hypernovae

DOE PAGES

Fryer, Chris L.; Oliveira, F. G.; Rueda, Jorge A.; ...

2015-12-04

Here, binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (E iso ≳10 52 erg), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed “ultrastripped” binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differentlymore » than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs.« less

Neutron-Star-Black-Hole Binaries Produced by Binary-Driven Hypernovae.

PubMed

Fryer, Chris L; Oliveira, F G; Rueda, J A; Ruffini, R

2015-12-04

Binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (E_{iso}≳10^{52}  erg), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed "ultrastripped" binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differently than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs.

Binary Population and Spectral Synthesis Version 2.1: Construction, Observational Verification, and New Results

NASA Astrophysics Data System (ADS)

Eldridge, J. J.; Stanway, E. R.; Xiao, L.; McClelland, L. A. S.; Taylor, G.; Ng, M.; Greis, S. M. L.; Bray, J. C.

2017-11-01

The Binary Population and Spectral Synthesis suite of binary stellar evolution models and synthetic stellar populations provides a framework for the physically motivated analysis of both the integrated light from distant stellar populations and the detailed properties of those nearby. We present a new version 2.1 data release of these models, detailing the methodology by which Binary Population and Spectral Synthesis incorporates binary mass transfer and its effect on stellar evolution pathways, as well as the construction of simple stellar populations. We demonstrate key tests of the latest Binary Population and Spectral Synthesis model suite demonstrating its ability to reproduce the colours and derived properties of resolved stellar populations, including well-constrained eclipsing binaries. We consider observational constraints on the ratio of massive star types and the distribution of stellar remnant masses. We describe the identification of supernova progenitors in our models, and demonstrate a good agreement to the properties of observed progenitors. We also test our models against photometric and spectroscopic observations of unresolved stellar populations, both in the local and distant Universe, finding that binary models provide a self-consistent explanation for observed galaxy properties across a broad redshift range. Finally, we carefully describe the limitations of our models, and areas where we expect to see significant improvement in future versions.

Neer Award 2018: Platelet-derived growth factor receptor α co-expression typifies a subset of platelet-derived growth factor receptor β-positive progenitor cells that contribute to fatty degeneration and fibrosis of the murine rotator cuff.

PubMed

Jensen, Andrew R; Kelley, Benjamin V; Mosich, Gina M; Ariniello, Allison; Eliasberg, Claire D; Vu, Brandon; Shah, Paras; Devana, Sai K; Murray, Iain R; Péault, Bruno; Dar, Ayelet; Petrigliano, Frank A

2018-04-10

After massive tears, rotator cuff muscle often undergoes atrophy, fibrosis, and fatty degeneration. These changes can lead to high surgical failure rates and poor patient outcomes. The identity of the progenitor cells involved in these processes has not been fully elucidated. Platelet-derived growth factor receptor β (PDGFRβ) and platelet-derived growth factor receptor α (PDGFRα) have previously been recognized as markers of cells involved in muscle fibroadipogenesis. We hypothesized that PDGFRα expression identifies a fibroadipogenic subset of PDGFRβ + progenitor cells that contribute to fibroadipogenesis of the rotator cuff. We created massive rotator cuff tears in a transgenic strain of mice that allows PDGFRβ + cells to be tracked via green fluorescent protein (GFP) fluorescence. We then harvested rotator cuff muscle tissues at multiple time points postoperatively and analyzed them for the presence and localization of GFP + PDGFRβ + PDGFRα + cells. We cultured, induced, and treated these cells with the molecular inhibitor CWHM-12 to assess fibrosis inhibition. GFP + PDGFRβ + PDGFRα + cells were present in rotator cuff muscle tissue and, after massive tears, localized to fibrotic and adipogenic tissues. The frequency of PDGFRβ + PDGFRα + cells increased at 5 days after massive cuff tears and decreased to basal levels within 2 weeks. PDGFRβ + PDGFRα + cells were highly adipogenic and significantly more fibrogenic than PDGFRβ + PDGFRα - cells in vitro and localized to adipogenic and fibrotic tissues in vivo. Treatment with CWHM-12 significantly decreased fibrogenesis from PDGFRβ + PDGFRα + cells. PDGFRβ + PDGFRα + cells directly contribute to fibrosis and fatty degeneration after massive rotator cuff tears in the mouse model. In addition, CWHM-12 treatment inhibits fibrogenesis from PDGFRβ + PDGFRα + cells in vitro. Clinically, perioperative PDGFRβ + PDGFRα + cell inhibition may limit rotator cuff tissue degeneration and, ultimately

Ex-companions of Supernovae Progenitors

NASA Astrophysics Data System (ADS)

Xue, Zinchao

Supernovae (SNe) are titanic explosions that end the life of stars. Fast expanding ejecta can create brightness that is comparable to the entire luminosity of the host galaxy for weeks. Eventually, the ejecta run into the ambient medium, creating the so-called supernova remnant (SNR) that fades away in 10,000 years. SNe come from two completely different mechanisms. The Type Ia SNe (SNIa) are powered by thermonuclear runaway when a white dwarf (WD) in a binary system accretes enough mass from a companion star. The Core Collapse supernovae (CCSNe) are massive stars that run out of fuel at the end of their lives and collapse. The basic scenario for SNIa is well established, but the type of the binary system containing the WD is the long-debated 'Type Ia Progenitor Problem'. (1) Searching for an ex-companion within a SNIa SNR would directly solve this problem as a binary system including two WDs should leave nothing behind, while others should leave a non-degenerate star near the site of the explosion. One of the results from this thesis is the determination of the explosion site of Tycho's SN (SN 1572). From this, I reject popular ex-companion candidates, e.g. Tycho star 'G' and a few other ones as they are too far away from the explosion site I determined. (2) Another attempt to address this problem is carried out by studying a rare kind of Type Ia SNe. Detailed photometric and spectral analysis indicates that ASASSN-14dc resembles features from the so-called SN Ia-CSM, in which, a SNIa explodes inside of dense Hydrogen-rich Circumstellar Material (CSM). The origin of the CSM brings serious questions to the traditional views of SNIa formation as none of them can comfortably explain the derived mass and distribution of the CSM. A recent realization of a particular model might solve a lot of puzzles around this rare class of SNIa. (3) CCSNe are known to be massive stars that rapidly evolve off the main sequence and soon explode. Nearly 80% of such stars have one or

Spectral types of four binaries based on photometric observations

NASA Astrophysics Data System (ADS)

Shimanskii, V. V.; Bikmaev, I. F.; Borisov, N. V.; Vlasyuk, V. V.; Galeev, A. I.; Sakhibullin, N. A.; Spiridonova, O. I.

2008-09-01

We present results of photometric and spectroscopic observations of four close binaries with subdwarf B components: PG 0918+029, PG 1000+408, PG 1116+301, PG 0001+275. We discovered that PG 1000+408 is a close binary, with the most probable orbital period being P orb = 1.041145 day. Based on a comparison of the observed light curves at selected orbital phases and theoretical predictions for their variations, all the systems are classified as doubly degenerate binaries with low-luminosity white-dwarf secondaries.

Polarized light curves illuminate wind geometries in Wolf-Rayet binary stars

NASA Astrophysics Data System (ADS)

Hoffman, Jennifer L.; Fullard, Andrew G.; Nordsieck, Kenneth H.

2018-01-01

Although the majority of massive stars are affected by a companion during the course of their evolution, the role of binary systems in creating supernova and GRB progenitors is not well understood. Binaries containing Wolf-Rayet stars are particularly interesting because they may provide a mechanism for producing the rapid rotation necessary for GRB formation. However, constraining the evolutionary fate of a Wolf-Rayet binary system requires characterizing its mass loss and mass transfer, a difficult prospect in systems whose colliding winds obscure the stars and produce complicated spectral signatures.The technique of spectropolarimetry is ideally suited to studying WR binary systems because it can disentangle spectral components that take different scattering paths through a complex distribution of circumstellar material. In particular, comparing the polarization behavior as a function of orbital phase of the continuum (which arises from the stars) with that of the emission lines (which arise from the interaction region) can provide a detailed view of the wind structures in a WR+O binary and constrain the system’s mass loss and mass transfer properties.We present new continuum and line polarization curves for three WR+O binaries (WR 30, WR 47, and WR 113) obtained with the RSS spectropolarimeter at the Southern African Large Telescope. We use radiative transfer simulations to analyze the polarization curves, and discuss our interpretations in light of current models for V444 Cygni, a well-studied related binary system. Accurately characterizing the structures of the wind collision regions in these massive binaries is key to understanding their evolution and properly accounting for their contribution to the supernova (and possible GRB) progenitor population.

The Evolution of Compact Binary Star Systems.

PubMed

Postnov, Konstantin A; Yungelson, Lev R

2006-01-01

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars - compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.

DISTINGUISHING COMPACT BINARY POPULATION SYNTHESIS MODELS USING GRAVITATIONAL WAVE OBSERVATIONS OF COALESCING BINARY BLACK HOLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevenson, Simon; Ohme, Frank; Fairhurst, Stephen, E-mail: simon.stevenson@ligo.org

2015-09-01

The coalescence of compact binaries containing neutron stars or black holes is one of the most promising signals for advanced ground-based laser interferometer gravitational-wave (GW) detectors, with the first direct detections expected over the next few years. The rate of binary coalescences and the distribution of component masses is highly uncertain, and population synthesis models predict a wide range of plausible values. Poorly constrained parameters in population synthesis models correspond to poorly understood astrophysics at various stages in the evolution of massive binary stars, the progenitors of binary neutron star and binary black hole systems. These include effects such asmore » supernova kick velocities, parameters governing the energetics of common envelope evolution and the strength of stellar winds. Observing multiple binary black hole systems through GWs will allow us to infer details of the astrophysical mechanisms that lead to their formation. Here we simulate GW observations from a series of population synthesis models including the effects of known selection biases, measurement errors and cosmology. We compare the predictions arising from different models and show that we will be able to distinguish between them with observations (or the lack of them) from the early runs of the advanced LIGO and Virgo detectors. This will allow us to narrow down the large parameter space for binary evolution models.« less

Constraining the Single-degenerate Channel of Type Ia Supernovae with Stable Iron-group Elements in SNR 3C 397

NASA Astrophysics Data System (ADS)

Dave, Pranav; Kashyap, Rahul; Fisher, Robert; Timmes, Frank; Townsley, Dean; Byrohl, Chris

2017-05-01

Recent Suzaku X-ray spectra of supernova remnant (SNR) 3C 397 indicate enhanced stable iron group element abundances of Ni, Mn, Cr, and Fe. Seeking to address key questions about the progenitor and explosion mechanism of 3C 397, we compute nucleosynthetic yields from a suite of multidimensional hydrodynamics models in the near-Chandrasekhar-mass, single-degenerate paradigm for Type Ia supernovae (SNe Ia). Varying the progenitor white dwarf (WD) internal structure, composition, ignition, and explosion mechanism, we find that the best match to the observed iron peak elements of 3C 397 are dense (central density ≥6 × 109 g cm-3), low-carbon WDs that undergo a weak, centrally ignited deflagration, followed by a subsequent detonation. The amount of 56Ni produced is consistent with a normal or bright normal SNe Ia. A pure deflagration of a centrally ignited, low central density (≃2 × 109 g cm-3) progenitor WD, frequently considered in the literature, is also found to produce good agreement with 3C 397 nucleosynthetic yields, but leads to a subluminous SN Ia event, in conflict with X-ray line width data. Additionally, in contrast to prior work that suggested a large supersolar metallicity for the WD progenitor for SNR 3C 397, we find satisfactory agreement for solar- and subsolar-metallicity progenitors. We discuss a range of implications our results have for the single-degenerate channel.

Formation of the first three gravitational-wave observations through isolated binary evolution

PubMed Central

Stevenson, Simon; Vigna-Gómez, Alejandro; Mandel, Ilya; Barrett, Jim W.; Neijssel, Coenraad J.; Perkins, David; de Mink, Selma E.

2017-01-01

During its first four months of taking data, Advanced LIGO has detected gravitational waves from two binary black hole mergers, GW150914 and GW151226, along with the statistically less significant binary black hole merger candidate LVT151012. Here we use the rapid binary population synthesis code COMPAS to show that all three events can be explained by a single evolutionary channel—classical isolated binary evolution via mass transfer including a common envelope phase. We show all three events could have formed in low-metallicity environments (Z=0.001) from progenitor binaries with typical total masses ≳160M⊙, ≳60M⊙ and ≳90M⊙, for GW150914, GW151226 and LVT151012, respectively. PMID:28378739

The helium star donor channel for the progenitors of Type Ia supernovae

NASA Astrophysics Data System (ADS)

Wang, B.; Meng, X.; Chen, X.; Han, Z.

2009-05-01

Type Ia supernovae (SNe Ia) play an important role in astrophysics, especially in the study of cosmic evolution. Several progenitor models for SNe Ia have been proposed in the past. In this paper we carry out a detailed study of the He star donor channel, in which a carbon-oxygen white dwarf (CO WD) accretes material from a He main-sequence star or a He subgiant to increase its mass to the Chandrasekhar mass. Employing Eggleton's stellar evolution code with an optically thick wind assumption, and adopting the prescription of Kato & Hachisu for the mass accumulation efficiency of the He-shell flashes on to the WDs, we performed binary evolution calculations for about 2600 close WD binary systems. According to these calculations, we mapped out the initial parameters for SNe Ia in the orbital period-secondary mass (logPi - Mi2) plane for various WD masses from this channel. The study shows that the He star donor channel is noteworthy for producing SNe Ia (~1.2 × 10-3yr-1 in our Galaxy), and that the progenitors from this channel may appear as supersoft X-ray sources. Importantly, this channel can explain SNe Ia with short delay times (<~108yr), which is consistent with the recent observational implications of young populations of SN Ia progenitors.

Dependence of corneal stem/progenitor cells on ocular surface innervation.

PubMed

Ueno, Hiroki; Ferrari, Giulio; Hattori, Takaaki; Saban, Daniel R; Katikireddy, Kishore R; Chauhan, Sunil K; Dana, Reza

2012-02-21

Neurotrophic keratopathy (NK) is a corneal degeneration associated with corneal nerve dysfunction. It can cause corneal epithelial defects, stromal thinning, and perforation. However, it is not clear if and to which extent epithelial stem cells are affected in NK. The purpose of this study was to identify the relationship between corneolimbal epithelial progenitor/stem cells and sensory nerves using a denervated mouse model of NK. NK was induced in mice by electrocoagulation of the ophthalmic branch of the trigeminal nerve. The absence of corneal nerves was confirmed with β-III tubulin immunostaining and blink reflex test after 7 days. ATP-binding cassette subfamily G member 2 (ABCG2), p63, and hairy enhancer of split 1 (Hes1) were chosen as corneolimbal stem/progenitor cell markers and assessed in denervated mice versus controls by immunofluorescent microscopy and real-time PCR. In addition, corneolimbal stem/progenitor cells were detected as side population cells using flow cytometry, and colony-forming efficiency assay was performed to assess their function. ABCG2, p63, and Hes1 immunostaining were significantly decreased in denervated eyes after 7 days. Similarly, the expression levels of ABCG2, p63, K15, Hes1, and N-cadherin transcripts were also significantly decreased in denervated eyes. Stem/progenitor cells measured as side population from NK mice were decreased by approximately 75% compared with normals. In addition, the authors found a significant (P = 0.038) reduction in colony-forming efficiency of stem/progenitor cells harvested from denervated eyes. Corneolimbal stem/progenitor cells are significantly reduced after depletion of sensory nerves. The data suggest a critical role of innervation in maintaining stem cells and/or the stem cell niche.

The Progenitor of Tycho’s Supernova was Not Hot and Luminous

NASA Astrophysics Data System (ADS)

Ghavamian, Parviz; Woods, T. E.; Gilfanov, M.; Badenes, C.; T. E. Woods, C. Badenes, M. Gilfanov

2018-01-01

Canonical accretion models of Type Ia supernovae predict that a hot and luminous progenitor will ionize the surrounding gas out to a radius of ∼10–100 pc for ∼100,000 years after the explosion. Tycho’s supernova of 1572 was a Type Ia explosion which produced a remnant that is currently interacting with neutral gas in the form of Balmer-dominated shocks. From analysis of these shocks and photoionization calculations, we have placed stringent upper limits on the temperature and luminosity of the progenitor of Tycho’s supernova. Hot, luminous progenitors that would have produced a greater hydrogen ionization fraction than that measured at the current SNR radius (∼3 parsecs) can thus be excluded. This rules out steadily nuclear-burning white dwarfs (i..e, supersoft X-ray sources), as well as disk emission from a Chandrasekhar-mass white dwarf accreting 1E-8 solar masses per year (recurrent novae). The lack of a Stromgren sphere around Tycho’s SNR is consistent with a double degenerate explosion, although other more exotic scenarios may be possible.

No hot and luminous progenitor for Tycho's supernova

NASA Astrophysics Data System (ADS)

Woods, T. E.; Ghavamian, P.; Badenes, C.; Gilfanov, M.

2017-11-01

Type Ia supernovae have proven vital to our understanding of cosmology, both as standard candles and for their role in galactic chemical evolution; however, their origin remains uncertain. The canonical accretion model implies a hot and luminous progenitor that would ionize the surrounding gas out to a radius of 10-100 pc for 100,000 years after the explosion. Here, we report stringent upper limits on the temperature and luminosity of the progenitor of Tycho's supernova (SN 1572), determined using the remnant itself as a probe of its environment. Hot, luminous progenitors that would have produced a greater hydrogen ionization fraction than that measured at the radius of the present remnant ( 3 pc) can thus be excluded. This conclusively rules out steadily nuclear-burning white dwarfs (supersoft X-ray sources), as well as disk emission from a Chandrasekhar-mass white dwarf accreting approximately greater than 10-8 M⊙ yr-1 (recurrent novae; M⊙ is equal to one solar mass). The lack of a surrounding Strömgren sphere is consistent with the merger of a double white dwarf binary, although other more exotic scenarios may be possible.

Constraining the Single-degenerate Channel of Type Ia Supernovae with Stable Iron-group Elements in SNR 3C 397

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dave, Pranav; Kashyap, Rahul; Fisher, Robert

Recent Suzaku X-ray spectra of supernova remnant (SNR) 3C 397 indicate enhanced stable iron group element abundances of Ni, Mn, Cr, and Fe. Seeking to address key questions about the progenitor and explosion mechanism of 3C 397, we compute nucleosynthetic yields from a suite of multidimensional hydrodynamics models in the near-Chandrasekhar-mass, single-degenerate paradigm for Type Ia supernovae (SNe Ia). Varying the progenitor white dwarf (WD) internal structure, composition, ignition, and explosion mechanism, we find that the best match to the observed iron peak elements of 3C 397 are dense (central density ≥6 × 10{sup 9} g cm{sup −3}), low-carbon WDsmore » that undergo a weak, centrally ignited deflagration, followed by a subsequent detonation. The amount of {sup 56}Ni produced is consistent with a normal or bright normal SNe Ia. A pure deflagration of a centrally ignited, low central density (≃2 × 10{sup 9} g cm{sup −3}) progenitor WD, frequently considered in the literature, is also found to produce good agreement with 3C 397 nucleosynthetic yields, but leads to a subluminous SN Ia event, in conflict with X-ray line width data. Additionally, in contrast to prior work that suggested a large supersolar metallicity for the WD progenitor for SNR 3C 397, we find satisfactory agreement for solar- and subsolar-metallicity progenitors. We discuss a range of implications our results have for the single-degenerate channel.« less

An Argument for Weakly Magnetized, Slowly Rotating Progenitors of Long Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Moreno Méndez, Enrique

2014-01-01

Using binary evolution with Case-C mass transfer, the spins of several black holes (BHs) in X-ray binaries (XBs) have been predicted and confirmed (three cases) by observations. The rotational energy of these BHs is sufficient to power up long gamma-ray bursts (GRBs) and hypernovae (HNe) and still leave a Kerr BH behind. However, strong magnetic fields and/or dynamo effects in the interior of such stars deplete their cores from angular momentum preventing the formation of collapsars. Thus, even though binaries can produce Kerr BHs, most of their rotation is acquired from the stellar mantle, with a long delay between BH formation and spin up. Such binaries would not form GRBs. We study whether the conditions required to produce GRBs can be met by the progenitors of such BHs. Tidal-synchronization and Alfvén timescales are compared for magnetic fields of different intensities threading He stars. A search is made for a magnetic field range that allows tidal spin up all the way in to the stellar core but prevents its slow down during differential rotation phases. The energetics for producing a strong magnetic field during core collapse, which may allow for a GRB central engine, are also estimated. An observationally reasonable choice of parameters is found (B <~ 102 G threading a slowly rotating He star) that allows Fe cores to retain substantial angular momentum. Thus, the Case-C mass-transfer binary channel is capable of explaining long GRBs. However, the progenitors must have low initial spin and low internal magnetic field throughout their H-burning and He-burning phases.

An argument for weakly magnetized, slowly rotating progenitors of long gamma-ray bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno Méndez, Enrique, E-mail: enriquemm@astro.unam.mx

2014-01-20

Using binary evolution with Case-C mass transfer, the spins of several black holes (BHs) in X-ray binaries (XBs) have been predicted and confirmed (three cases) by observations. The rotational energy of these BHs is sufficient to power up long gamma-ray bursts (GRBs) and hypernovae (HNe) and still leave a Kerr BH behind. However, strong magnetic fields and/or dynamo effects in the interior of such stars deplete their cores from angular momentum preventing the formation of collapsars. Thus, even though binaries can produce Kerr BHs, most of their rotation is acquired from the stellar mantle, with a long delay between BHmore » formation and spin up. Such binaries would not form GRBs. We study whether the conditions required to produce GRBs can be met by the progenitors of such BHs. Tidal-synchronization and Alfvén timescales are compared for magnetic fields of different intensities threading He stars. A search is made for a magnetic field range that allows tidal spin up all the way in to the stellar core but prevents its slow down during differential rotation phases. The energetics for producing a strong magnetic field during core collapse, which may allow for a GRB central engine, are also estimated. An observationally reasonable choice of parameters is found (B ≲ 10{sup 2} G threading a slowly rotating He star) that allows Fe cores to retain substantial angular momentum. Thus, the Case-C mass-transfer binary channel is capable of explaining long GRBs. However, the progenitors must have low initial spin and low internal magnetic field throughout their H-burning and He-burning phases.« less

The progenitors of Type Ia supernovae with long delay times

NASA Astrophysics Data System (ADS)

Wang, Bo; Li, Xiang-Dong; Han, Zhan-Wen

2010-02-01

The nature of the progenitors of Type Ia supernovae (SNe Ia) is still unclear. In this paper, by considering the effect of the instability of accretion disc on the evolution of white dwarf (WD) binaries, we performed binary evolution calculations for about 2400 close WD binaries, in which a carbon-oxygen WD accretes material from a main-sequence (MS) star or a slightly evolved subgiant star (WD + MS channel), or a red-giant star (WD + RG channel) to increase its mass to the Chandrasekhar (Ch) mass limit. According to these calculations, we mapped out the initial parameters for SNe Ia in the orbital period-secondary mass (logPi - Mi2) plane for various WD masses for these two channels, respectively. We confirm that WDs in the WD + MS channel with a mass as low as 0.61Msolar can accrete efficiently and reach the Ch limit, while the lowest WD mass for the WD + RG channel is 1.0Msolar. We have implemented these results in a binary population synthesis study to obtain the SN Ia birthrates and the evolution of SN Ia birthrates with time for both a constant star formation rate and a single starburst. We find that the Galactic SN Ia birthrate from the WD + MS channel is ~1.8 × 10-3yr-1 according to our standard model, which is higher than the previous results. However, similar to the previous studies, the birthrate from the WD + RG channel is still low (~3 × 10-5yr-1). We also find that about one-third of SNe Ia from the WD + MS channel and all SNe Ia from the WD + RG channel can contribute to the old populations (>~1Gyr) of SN Ia progenitors.

Discovery of the Closest Hot Subdwarf Binary with White Dwarf Companion

NASA Astrophysics Data System (ADS)

Geier, S.; Marsh, T. R.; Dunlap, B. H.; Barlow, B. N.; Schaffenroth, V.; Ziegerer, E.; Heber, U.; Kupfer, T.; Maxted, P. F. L.; Miszalski, B.; Shporer, A.; Telting, J. H.; Ostensen, R. H.; O'Toole, S. J.; Gänsicke, B. T.; Napiwotzki, R.

2013-01-01

We report the discovery of an extremely close, eclipsing binary system. A white dwarf is orbited by a core He-burning compact hot subdwarf star with a period as short as ≃ 0.04987 d making this system the most compact hot subdwarf binary discovered so far. The subdwarf will start to transfer helium-rich material on short timescales of less than 50 Myr. The ignition of He-burning at the surface may trigger carbon-burning in the core although the WD is less massive than the Chandrasekhar limit (> 0.74 M⊙) making this binary a possible progenitor candidate for a supernova type Ia event.

Dependence of Corneal Stem/Progenitor Cells on Ocular Surface Innervation

PubMed Central

Ueno, Hiroki; Ferrari, Giulio; Hattori, Takaaki; Saban, Daniel R.; Katikireddy, Kishore R.; Chauhan, Sunil K.

2012-01-01

Purpose. Neurotrophic keratopathy (NK) is a corneal degeneration associated with corneal nerve dysfunction. It can cause corneal epithelial defects, stromal thinning, and perforation. However, it is not clear if and to which extent epithelial stem cells are affected in NK. The purpose of this study was to identify the relationship between corneolimbal epithelial progenitor/stem cells and sensory nerves using a denervated mouse model of NK. Methods. NK was induced in mice by electrocoagulation of the ophthalmic branch of the trigeminal nerve. The absence of corneal nerves was confirmed with β-III tubulin immunostaining and blink reflex test after 7 days. ATP-binding cassette subfamily G member 2 (ABCG2), p63, and hairy enhancer of split 1 (Hes1) were chosen as corneolimbal stem/progenitor cell markers and assessed in denervated mice versus controls by immunofluorescent microscopy and real-time PCR. In addition, corneolimbal stem/progenitor cells were detected as side population cells using flow cytometry, and colony-forming efficiency assay was performed to assess their function. Results. ABCG2, p63, and Hes1 immunostaining were significantly decreased in denervated eyes after 7 days. Similarly, the expression levels of ABCG2, p63, K15, Hes1, and N-cadherin transcripts were also significantly decreased in denervated eyes. Stem/progenitor cells measured as side population from NK mice were decreased by approximately 75% compared with normals. In addition, the authors found a significant (P = 0.038) reduction in colony-forming efficiency of stem/progenitor cells harvested from denervated eyes. Conclusions. Corneolimbal stem/progenitor cells are significantly reduced after depletion of sensory nerves. The data suggest a critical role of innervation in maintaining stem cells and/or the stem cell niche. PMID:22232434

Bi-lobed Shape of Comet 67P from a Collapsed Binary

NASA Astrophysics Data System (ADS)

Nesvorný, David; Parker, Joel; Vokrouhlický, David

2018-06-01

The Rosetta spacecraft observations revealed that the nucleus of comet 67P/Churyumov–Gerasimenko consists of two similarly sized lobes connected by a narrow neck. Here, we evaluate the possibility that 67P is a collapsed binary. We assume that the progenitor of 67P was a binary and consider various physical mechanisms that could have brought the binary components together, including small-scale impacts and gravitational encounters with planets. We find that 67P could be a primordial body (i.e., not a collisional fragment) if the outer planetesimal disk lasted ≲10 Myr before it was dispersed by migrating Neptune. The probability of binary collapse by impact is ≃30% for tightly bound binaries. Most km-class binaries become collisionally dissolved. Roughly 10% of the surviving binaries later evolve to become contact binaries during the disk dispersal, when bodies suffer gravitational encounters with Neptune. Overall, the processes described in this work do not seem to be efficient enough to explain the large fraction (∼67%) of bi-lobed cometary nuclei inferred from spacecraft imaging.

PopCORN: Hunting down the differences between binary population synthesis codes

NASA Astrophysics Data System (ADS)

Toonen, S.; Claeys, J. S. W.; Mennekens, N.; Ruiter, A. J.

2014-02-01

Context. Binary population synthesis (BPS) modelling is a very effective tool to study the evolution and properties of various types of close binary systems. The uncertainty in the parameters of the model and their effect on a population can be tested in a statistical way, which then leads to a deeper understanding of the underlying (sometimes poorly understood) physical processes involved. Several BPS codes exist that have been developed with different philosophies and aims. Although BPS has been very successful for studies of many populations of binary stars, in the particular case of the study of the progenitors of supernovae Type Ia, the predicted rates and ZAMS progenitors vary substantially between different BPS codes. Aims: To understand the predictive power of BPS codes, we study the similarities and differences in the predictions of four different BPS codes for low- and intermediate-mass binaries. We investigate the differences in the characteristics of the predicted populations, and whether they are caused by different assumptions made in the BPS codes or by numerical effects, e.g. a lack of accuracy in BPS codes. Methods: We compare a large number of evolutionary sequences for binary stars, starting with the same initial conditions following the evolution until the first (and when applicable, the second) white dwarf (WD) is formed. To simplify the complex problem of comparing BPS codes that are based on many (often different) assumptions, we equalise the assumptions as much as possible to examine the inherent differences of the four BPS codes. Results: We find that the simulated populations are similar between the codes. Regarding the population of binaries with one WD, there is very good agreement between the physical characteristics, the evolutionary channels that lead to the birth of these systems, and their birthrates. Regarding the double WD population, there is a good agreement on which evolutionary channels exist to create double WDs and a rough

SECULAR EVOLUTION OF BINARIES NEAR MASSIVE BLACK HOLES: FORMATION OF COMPACT BINARIES, MERGER/COLLISION PRODUCTS AND G2-LIKE OBJECTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prodan, Snezana; Antonini, Fabio; Perets, Hagai B., E-mail: sprodan@cita.utoronto.ca, E-mail: antonini@cita.utoronto.ca

2015-02-01

Here we discuss the evolution of binaries around massive black holes (MBHs) in nuclear stellar clusters. We focus on their secular evolution due to the perturbation by the MBHs, while simplistically accounting for their collisional evolution. Binaries with highly inclined orbits with respect to their orbits around MBHs are strongly affected by secular processes, which periodically change their eccentricities and inclinations (e.g., Kozai-Lidov cycles). During periapsis approach, dissipative processes such as tidal friction may become highly efficient, and may lead to shrinkage of a binary orbit and even to its merger. Binaries in this environment can therefore significantly change theirmore » orbital evolution due to the MBH third-body perturbative effects. Such orbital evolution may impinge on their later stellar evolution. Here we follow the secular dynamics of such binaries and its coupling to tidal evolution, as well as the stellar evolution of such binaries on longer timescales. We find that stellar binaries in the central parts of nuclear stellar clusters (NSCs) are highly likely to evolve into eccentric and/or short-period binaries, and become strongly interacting binaries either on the main sequence (at which point they may even merge), or through their later binary stellar evolution. The central parts of NSCs therefore catalyze the formation and evolution of strongly interacting binaries, and lead to the enhanced formation of blue stragglers, X-ray binaries, gravitational wave sources, and possible supernova progenitors. Induced mergers/collisions may also lead to the formation of G2-like cloud-like objects such as the one recently observed in the Galactic center.« less

The binary progenitor of Tycho Brahe's 1572 supernova.

PubMed

Ruiz-Lapuente, Pilar; Comeron, Fernando; Méndez, Javier; Canal, Ramon; Smartt, Stephen J; Filippenko, Alexei V; Kurucz, Robert L; Chornock, Ryan; Foley, Ryan J; Stanishev, Vallery; Ibata, Rodrigo

2004-10-28

The brightness of type Ia supernovae, and their homogeneity as a class, makes them powerful tools in cosmology, yet little is known about the progenitor systems of these explosions. They are thought to arise when a white dwarf accretes matter from a companion star, is compressed and undergoes a thermonuclear explosion. Unless the companion star is another white dwarf (in which case it should be destroyed by the mass-transfer process itself), it should survive and show distinguishing properties. Tycho's supernova is one of only two type Ia supernovae observed in our Galaxy, and so provides an opportunity to address observationally the identification of the surviving companion. Here we report a survey of the central region of its remnant, around the position of the explosion, which excludes red giants as the mass donor of the exploding white dwarf. We found a type G0-G2 star, similar to our Sun in surface temperature and luminosity (but lower surface gravity), moving at more than three times the mean velocity of the stars at that distance, which appears to be the surviving companion of the supernova.

Poynting-Flux-Driven Bubbles and Shocks Around Merging Neutron Star Binaries

NASA Astrophysics Data System (ADS)

Medvedev, M. V.; Loeb, A.

2013-04-01

Merging binaries of compact relativistic objects are thought to be progenitors of short gamma-ray bursts. Because of the strong magnetic field of one or both binary members and high orbital frequencies, these binaries are strong sources of energy in the form of Poynting flux. The steady injection of energy by the binary forms a bubble filled with matter with the relativistic equation of state, which pushes on the surrounding plasma and can drive a shock wave in it. Unlike the Sedov-von Neumann-Taylor blast wave solution for a point-like explosion, the shock wave here is continuously driven by the ever-increasing pressure inside the bubble. We calculate from the first principles the dynamics and evolution of the bubble and the shock surrounding it, demonstrate that it exhibits finite time singularity and find the corresponding analytical solution. We predict that such binaries can be observed as radio sources a few hours before and after the merger.

MY Cam: can homogeneous evolution produce gravitational-wave progenitors?

NASA Astrophysics Data System (ADS)

Negueruela, Ignacio

2016-10-01

Besides opening the era of gravitational-wave astrophysics, GW150914 has revolutionized the field of massive stars. GW150914 proves the existence of stellar-mass black holes in a configuration that current models for stellar evolution can only reproduce in special conditions of homogeneous evolution and/or low metallicity.Only a handful of very-massive binaries that could lead to a binary black hole are known. We request UV spectroscopy of MY Cam (38Msun+32Msun), the best laboratory to test several predictions by current models, in order to derive stellar abundances and wind parameters that are inaccessible from the ground. Together with our previous photometric and spectroscopic exhaustive coverage, the STIS spectra will be key to characterize the pre-common envelope phase and test the homogeneous evolution hypothesis, critical ingredients of the different progenitor scenarios proposed to explain GW15091.

Efficacy and Safety of Human Retinal Progenitor Cells

PubMed Central

Semo, Ma'ayan; Haamedi, Nasrin; Stevanato, Lara; Carter, David; Brooke, Gary; Young, Michael; Coffey, Peter; Sinden, John; Patel, Sara; Vugler, Anthony

2016-01-01

Purpose We assessed the long-term efficacy and safety of human retinal progenitor cells (hRPC) using established rodent models. Methods Efficacy of hRPC was tested initially in Royal College of Surgeons (RCS) dystrophic rats immunosuppressed with cyclosporine/dexamethasone. Due to adverse effects of dexamethasone, this drug was omitted from a subsequent dose-ranging study, where different hRPC doses were tested for their ability to preserve visual function (measured by optokinetic head tracking) and retinal structure in RCS rats at 3 to 6 months after grafting. Safety of hRPC was assessed by subretinal transplantation into wild type (WT) rats and NIH-III nude mice, with analysis at 3 to 6 and 9 months after grafting, respectively. Results The optimal dose of hRPC for preserving visual function/retinal structure in dystrophic rats was 50,000 to 100,000 cells. Human retinal progenitor cells integrated/survived in dystrophic and WT rat retina up to 6 months after grafting and expressed nestin, vimentin, GFAP, and βIII tubulin. Vision and retinal structure remained normal in WT rats injected with hRPC and there was no evidence of tumors. A comparison between dexamethasone-treated and untreated dystrophic rats at 3 months after grafting revealed an unexpected reduction in the baseline visual acuity of dexamethasone-treated animals. Conclusions Human retinal progenitor cells appear safe and efficacious in the preclinical models used here. Translational Relevance Human retinal progenitor cells could be deployed during early stages of retinal degeneration or in regions of intact retina, without adverse effects on visual function. The ability of dexamethasone to reduce baseline visual acuity in RCS dystrophic rats has important implications for the interpretation of preclinical and clinical cell transplant studies. PMID:27486556

The double-degenerate, super-Chandrasekhar nucleus of the planetary nebula Henize 2-428.

PubMed

Santander-García, M; Rodríguez-Gil, P; Corradi, R L M; Jones, D; Miszalski, B; Boffin, H M J; Rubio-Díez, M M; Kotze, M M

2015-03-05

The planetary nebula stage is the ultimate fate of stars with masses one to eight times that of the Sun (M(⊙)). The origin of their complex morphologies is poorly understood, although several mechanisms involving binary interaction have been proposed. In close binary systems, the orbital separation is short enough for the primary star to overfill its Roche lobe as the star expands during the asymptotic giant branch phase. The excess gas eventually forms a common envelope surrounding both stars. Drag forces then result in the envelope being ejected into a bipolar planetary nebula whose equator is coincident with the orbital plane of the system. Systems in which both stars have ejected their envelopes and are evolving towards the white dwarf stage are said to be double degenerate. Here we report that Henize 2-428 has a double-degenerate core with a combined mass of ∼1.76M(⊙), which is above the Chandrasekhar limit (the maximum mass of a stable white dwarf) of 1.4M(⊙). This, together with its short orbital period (4.2 hours), suggests that the system should merge in 700 million years, triggering a type Ia supernova event. This supports the hypothesis of the double-degenerate, super-Chandrasekhar evolutionary pathway for the formation of type Ia supernovae.

Chemical Evolution of Binary Stars

NASA Astrophysics Data System (ADS)

Izzard, R. G.

2013-02-01

Energy generation by nuclear fusion is the fundamental process that prevents stars from collapsing under their own gravity. Fusion in the core of a star converts hydrogen to heavier elements from helium to uranium. The signature of this nucleosynthesis is often visible in a single star only for a very short time, for example while the star is a red giant or, in massive stars, when it explodes. Contrarily, in a binary system nuclear-processed matter can captured by a secondary star which remains chemically polluted long after its more massive companion star has evolved and died. By probing old, low-mass stars we gain vital insight into the complex nucleosynthesis that occurred when our Galaxy was much younger than it is today. Stellar evolution itself is also affected by the presence of a companion star. Thermonuclear novae and type Ia supernovae result from mass transfer in binary stars, but big questions still surround the nature of their progenitors. Stars may even merge and one of the challenges for the future of stellar astrophysics is to quantitatively understand what happens in such extreme systems. Binary stars offer unique insights into stellar, galactic and extragalactic astrophysics through their plethora of exciting phenomena. Understanding the chemical evolution of binary stars is thus of high priority in modern astrophysics.

SN 2017ein and the Possible First Identification of a Type Ic Supernova Progenitor

NASA Astrophysics Data System (ADS)

Van Dyk, Schuyler D.; Zheng, WeiKang; Brink, Thomas G.; Filippenko, Alexei V.; Milisavljevic, Dan; Andrews, Jennifer E.; Smith, Nathan; Cignoni, Michele; Fox, Ori D.; Kelly, Patrick L.; Adamo, Angela; Yunus, Sameen; Zhang, Keto; Kumar, Sahana

2018-06-01

We have identified a progenitor candidate in archival Hubble Space Telescope (HST) images for the Type Ic supernova (SN Ic) SN 2017ein in NGC 3938, pinpointing the candidate’s location via HST Target of Opportunity imaging of the SN itself. This would be the first identification of a stellar-like object as a progenitor candidate for any SN Ic to date. We also present observations of SN 2017ein during the first ∼49 days since explosion. We find that SN 2017ein most resembles the well-studied SN Ic SN 2007gr. We infer that SN 2017ein experienced a total visual extinction of A V ≈ 1.0–1.9 mag, predominantly because of dust within the host galaxy. Although the distance is not well known, if this object is the progenitor, it was likely of high initial mass, ∼47–48 M ⊙ if a single star, or ∼60–80 M ⊙ if in a binary system. However, we also find that the progenitor candidate could be a very blue and young compact cluster, further implying a very massive (>65 M ⊙) progenitor. Furthermore, the actual progenitor might not be associated with the candidate at all and could be far less massive. From the immediate stellar environment, we find possible evidence for three different populations; if the SN progenitor was a member of the youngest population, this would be consistent with an initial mass of ∼57 M ⊙. After it has faded, the SN should be reobserved at high spatial resolution and sensitivity, to determine whether the candidate is indeed the progenitor.

Magnetic Fields in Interacting Binaries

NASA Astrophysics Data System (ADS)

Briggs, G.; Ferrario, L.; Tout, C. A.; Wickramasinghe, D. T.

2018-01-01

Wickramasinghe et al. (2014) and Briggs et al. (2015) have proposed that the strong magnetic fields observed in some single white dwarfs (MWDs) are formed by an α—Ω dynamo driven by differential rotation when two stars, the more massive one with a degenerate core, merge during common envelope (CE) evolution (Ferrario et al., 2015b). We synthesise a population of binaries to investigate if fields in the magnetic cataclysmic variables (MCVs) may also originate during stellar interaction in the CE phase.

Retinal Remodeling in the Tg P347L Rabbit, a Large-Eye Model of Retinal Degeneration

PubMed Central

Jones, Bryan William; Kondo, Mineo; Terasaki, Hiroko; Watt, Carl Brock; Rapp, Kevin; Anderson, James; Lin, Yanhua; Shaw, Marguerite Victoria; Yang, Jia-Hui; Marc, Robert Edward

2013-01-01

Retinitis pigmentosa (RP) is an inherited blinding disease characterized by progressive loss of retinal photo-receptors. There are numerous rodent models of retinal degeneration, but most are poor platforms for interventions that will translate into clinical practice. The rabbit possesses a number of desirable qualities for a model of retinal disease including a large eye and an existing and substantial knowledge base in retinal circuitry, anatomy, and ophthalmology. We have analyzed degeneration, remodeling, and reprogramming in a rabbit model of retinal degeneration, expressing a rhodopsin proline 347 to leucine transgene in a TgP347L rabbit as a powerful model to study the pathophysiology and treatment of retinal degeneration. We show that disease progression in the TgP347L rabbit closely tracks human cone-sparing RP, including the cone-associated preservation of bipolar cell signaling and triggering of reprogramming. The relatively fast disease progression makes the TgP347L rabbit an excellent model for gene therapy, cell biological intervention, progenitor cell transplantation, surgical interventions, and bionic prosthetic studies. PMID:21681749

SN~2012cg: Evidence for Interaction Between a Normal Type Ia Supernova and a Non-degenerate Binary Companion

NASA Astrophysics Data System (ADS)

Marion, G. H.; Brown, Peter J.; Vinkó, Jozsef; Silverman, Jeffrey M.; Sand, David J.; Challis, Peter; Kirshner, Robert P.; Wheeler, J. Craig; Berlind, Perry; Brown, Warren R.; Calkins, Michael L.; Camacho, Yssavo; Dhungana, Govinda; Foley, Ryan J.; Friedman, Andrew S.; Graham, Melissa L.; Howell, D. Andrew; Hsiao, Eric Y.; Irwin, Jonathan M.; Jha, Saurabh W.; Kehoe, Robert; Macri, Lucas M.; Maeda, Keiichi; Mandel, Kaisey; McCully, Curtis; Pandya, Viraj; Rines, Kenneth J.; Wilhelmy, Steven; Zheng, Weikang

2016-04-01

We report evidence for excess blue light from the Type Ia supernova (Sn Ia) SN 2012cg at 15 and 16 days before maximum B-band brightness. The emission is consistent with predictions for the impact of the supernova on a non-degenerate binary companion. This is the first evidence for emission from a companion to a normal SN Ia. Sixteen days before maximum light, the B-V color of SN 2012cg is 0.2 mag bluer than for other normal SN Ia. At later times, this supernova has a typical SN Ia light curve, with extinction-corrected {M}B=-19.62+/- 0.02 mag and {{Δ }}{m}15(B)=0.86+/- 0.02. Our data set is extensive, with photometry in seven filters from five independent sources. Early spectra also show the effects of blue light, and high-velocity features are observed at early times. Near maximum, the spectra are normal with a silicon velocity vSi = -10,500 km s-1. Comparing the early data with models by Kasen favors a main-sequence companion of about six solar masses. It is possible that many other SN Ia have main-sequence companions that have eluded detection because the emission from the impact is fleeting and faint.

WFC3 Micro-arcsecond astrometry of the possible SNIa progenitor BPM 71214

NASA Astrophysics Data System (ADS)

Debes, John

2012-10-01

We propose to use the newly commissioned scanning mode on WFC3 to obtain astrometric measurements of the ~0.008 AU WD/M dwarf binary BPM 71214. This system is a fascinating mystery for post-common envelope binary evolution and may be a SN1a progenitor. COS spectra of the WD in the system shows that it is rapidly rotating with a vsin i of 200 km/s, implying that it has already accreted significant mass from its companion, but mass transfer has since stopped. The COS spectra imply a near Chandrasekar mass for the WD, while optical spectroscopy suggests a mass of 0.8 M_Sun. We propose to take four orbits of WFC3 observations in scanning mode to obtain astrometric measurements of this system at a per-measurement precision of ~30~micro-arcseconds. Such measurements will definitively constrain the mass of the WD and fully solve for both masses in the binary.

Further Evidence of a Brown Dwarf Orbiting the Post-Common Envelope Eclipsing Binary V470 Cam (HS 0705+6700)

NASA Astrophysics Data System (ADS)

Bogensberger, David; Clarke, Fraser; Lynas-Gray, Anthony Eugene

2017-12-01

Several post-common envelope binaries have slightly increasing, decreasing or oscillating orbital periods. One of several possible explanations is light travel-time changes, caused by the binary centre-of-mass being perturbed by the gravitational pull of a third body. Further studies are necessary because it is not clear how a third body could have survived subdwarf progenitor mass-loss at the tip of the Red Giant Branch, or formed subsequently. Thirty-nine primary eclipse times for V470 Cam were secured with the Philip Wetton Telescope during the period 2016 November 25th to 2017 January 27th. Available eclipse timings suggest a brown dwarf tertiary having a mass of at least 0.0236(40) M⊙, an elliptical orbit with an eccentricity of 0.376(98) and an orbital period of 11.77(67) years about the binary centreof- mass. The mass and orbit suggest a hybrid formation, in which some ejected material from the subdwarf progenitor was accreted on to a precursor tertiary component, although additional observations would be needed to confirm this interpretation and investigate other possible origins for the binary orbital period change.

A Gemini snapshot survey for double degenerates

NASA Astrophysics Data System (ADS)

Kilic, Mukremin; Brown, Warren R.; Gianninas, A.; Curd, Brandon; Bell, Keaton J.; Allende Prieto, Carlos

2017-11-01

We present the results from a Gemini snapshot radial-velocity survey of 44 low-mass white-dwarf candidates selected from the Sloan Digital Sky Survey (SDSS) spectroscopy. To find sub-hour orbital period binary systems, our time-series spectroscopy had cadences of 2-8 min over a period of 20-30 min. Through follow-up observations at Gemini and the MMT, we identify four double-degenerate binary systems with periods ranging from 53 min to 7 h. The shortest period system, SDSS J123549.88+154319.3, was recently identified as a sub-hour period detached binary by Breedt and collaborators. Here, we refine the orbital and physical parameters of this system. High-speed and time-domain survey photometry observations do not reveal eclipses or other photometric effects in any of our targets. We compare the period distribution of these four systems with the orbital period distribution of known double white dwarfs; the median period decreases from 0.64 to 0.24 d for M = 0.3-0.5 M⊙ to M < 0.3 M⊙ white dwarfs. However, we do not find a statistically significant correlation between the orbital period and white-dwarf mass.

The Tarantula Massive Binary Monitoring. I. Observational campaign and OB-type spectroscopic binaries

NASA Astrophysics Data System (ADS)

Almeida, L. A.; Sana, H.; Taylor, W.; Barbá, R.; Bonanos, A. Z.; Crowther, P.; Damineli, A.; de Koter, A.; de Mink, S. E.; Evans, C. J.; Gieles, M.; Grin, N. J.; Hénault-Brunet, V.; Langer, N.; Lennon, D.; Lockwood, S.; Maíz Apellániz, J.; Moffat, A. F. J.; Neijssel, C.; Norman, C.; Ramírez-Agudelo, O. H.; Richardson, N. D.; Schootemeijer, A.; Shenar, T.; Soszyński, I.; Tramper, F.; Vink, J. S.

2017-02-01

Context. Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way. Aims: The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region. Methods: In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries. Results: Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus's core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2-O7) tend to have shorter orbital periods than later spectral types (O9.2-O9.7). Conclusions: Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the

The Type IIb Supernova 2013df and its Cool Supergiant Progenitor

NASA Technical Reports Server (NTRS)

VanDyk, Schuyler D.; Zeng, Weikang; Fox, Ori D.; Cenko, S. Bradley; Clubb, Kelsey I.; Filippenko, Alexei; Foley, Ryan J.; Miller, Adam A.; Smith, Nathan; Kelly, Patrick L.;

PROBING ELECTRON-CAPTURE SUPERNOVAE: X-RAY BINARIES IN STARBURSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linden, T.; Sepinsky, J. F.; Kalogera, V.

We develop population models of high-mass X-ray binaries (HMXBs) formed after bursts of star formation and we investigate the effect of electron-capture supernovae (ECS) of massive ONeMg white dwarfs and the hypothesis that ECS events are associated with typically low supernova kicks imparted to the nascent neutron stars. We identify an interesting ECS bump in the time evolution of HMXB numbers; this bump is caused by significantly increased production of wind-fed HMXBs 20-60 Myr post-starburst. The amplitude and age extent of the ECS bump depend on the strength of ECS kicks and the mass range of ECS progenitors. We alsomore » find that ECS-HMXBs form through a specific evolutionary channel that is expected to lead to binaries with Be donors in wide orbits. These characteristics, along with their sensitivity to ECS properties, provide us with an intriguing opportunity to probe ECS physics and progenitors through studies of starbursts of different ages. Specifically, the case of the Small Magellanic Cloud, with a significant observed population of Be-HMXBs and starburst activity 30-60 Myr ago, arises as a promising laboratory for understanding the role of ECS in neutron star formation.« less

Ultra-stripped supernovae: progenitors and fate

NASA Astrophysics Data System (ADS)

Tauris, Thomas M.; Langer, Norbert; Podsiadlowski, Philipp

2015-08-01

The explosion of ultra-stripped stars in close binaries can lead to ejecta masses <0.1 M⊙ and may explain some of the recent discoveries of weak and fast optical transients. In Tauris et al., it was demonstrated that helium star companions to neutron stars (NSs) may experience mass transfer and evolve into naked ˜1.5 M⊙ metal cores, barely above the Chandrasekhar mass limit. Here, we elaborate on this work and present a systematic investigation of the progenitor evolution leading to ultra-stripped supernovae (SNe). In particular, we examine the binary parameter space leading to electron-capture (EC SNe) and iron core-collapse SNe (Fe CCSNe), respectively, and determine the amount of helium ejected with applications to their observational classification as Type Ib or Type Ic. We mainly evolve systems where the SN progenitors are helium star donors of initial mass MHe = 2.5-3.5 M⊙ in tight binaries with orbital periods of Porb = 0.06-2.0 d, and hosting an accreting NS, but we also discuss the evolution of wider systems and of both more massive and lighter - as well as single - helium stars. In some cases, we are able to follow the evolution until the onset of silicon burning, just a few days prior to the SN explosion. We find that ultra-stripped SNe are possible for both EC SNe and Fe CCSNe. EC SNe only occur for MHe = 2.60-2.95 M⊙ depending on Porb. The general outcome, however, is an Fe CCSN above this mass interval and an ONeMg or CO white dwarf for smaller masses. For the exploding stars, the amount of helium ejected is correlated with Porb - the tightest systems even having donors being stripped down to envelopes of less than 0.01 M⊙. We estimate the rise time of ultra-stripped SNe to be in the range 12 h-8 d, and light-curve decay times between 1 and 50 d. A number of fitting formulae for our models are provided with applications to population synthesis. Ultra-stripped SNe may produce NSs in the mass range 1.10-1.80 M⊙ and are highly relevant for

The quest for blue supergiants : The evolution of the progenitor of SN 1987A

NASA Astrophysics Data System (ADS)

Menon, Athira; Heger, Alexander

2015-08-01

SN 1987A is historically one of the most remarkable supernova explosions to be seen from Earth. Due to the proximity of its location in the LMC, it remains the most well-studied object outside the solar system. It was also the only supernova whose progenitor was observed prior to its explosion.SN 1987A however, was a unique and enigmatic core collapse supernova. It was the first Type II supernova to have been observed to have exploded while its progenitor was a blue supergiant (BSG). Until then Type II supernovae were expected to originate from explosions of red supergiants (RSGs). A spectacular triple-ring nebula structure, rich in helium and nitrogen, was observed around the remnant, indicating a recent RSG phase before becoming a BSG. Even today it is not entirely understood what the evolutionary history may have been to cause a BSG to explode. The most commonly accepted hypothesis for its origin is the merger of a massive binary star system.An evolutionary scenario for such a binary system, was proposed by Podsiadlowski (1992) (P92). Through SPH simulations of the merger and the stellar evolution of the post-merger remnant, Ivanova & Podsiadlowski (2002) and (2003) (I&M) could successfully obtain the RSG to BSG transition of the progenitor.The aim of the present work is to produce the evolutionary history of the progenitor of SN 1987A and its explosion. We construct our models based on the results of P92 and I&M. Here, the secondary (less massive) star is accreted on the primary, while being simultaneously mixed in its envelope over a period of 100 years. The merged star is evolved until the onset of core collapse. For this work we use the 1-dimensional, implicit, hydrodynamical stellar evolution code, KEPLER. A large parameter space is explored, consisting of primary (16-20 Ms) and secondary masses (5-8 Ms), mixing boundaries, and accreting timescales. Those models whose end states match the observed properties of the progenitor of SN 1987A are exploded. The

Core collapse supernovae from blue supergiant progenitors : The evolutionary history of SN 1987A

NASA Astrophysics Data System (ADS)

Menon, Athira

2015-08-01

SN 1987A is historically one of the most remarkable supernova explosions to be seen from Earth. Due to the proximity of its location in the LMC, it remains the most well-studied object outside the solar system. It was also the only supernova whose progenitor was observed prior to its explosion.SN 1987A however, was a unique and enigmatic core collapse supernova. It was the first Type II supernova to have been observed to have exploded while its progenitor was a blue supergiant (BSG). Until then Type II supernovae were expected to originate from explosions of red supergiants (RSGs). A spectacular triple-ring nebula structure, rich in helium and nitrogen, was observed around the remnant, indicating a recent RSG phase before becoming a BSG. Even today it is not entirely understood what the evolutionary history may have been to cause a BSG to explode. The most commonly accepted hypothesis for its origin is the merger of a massive binary star system.An evolutionary scenario for such a binary system, was proposed by Podsiadlowski (1992) (P92). Through SPH simulations of the merger and the stellar evolution of the post-merger remnant, Ivanova & Podsiadlowski (2002) and (2003) (I&M) could successfully obtain the RSG to BSG transition of the progenitor.The aim of the present work is to produce the evolutionary history of the progenitor of SN 1987A and its explosion. We construct our models based on the results of P92 and I&M. Here, the secondary (less massive) star is accreted on the primary, while being simultaneously mixed in its envelope over a period of 100 years. The merged star is evolved until the onset of core collapse. For this work we use the 1-dimensional, implicit, hydrodynamical stellar evolution code, KEPLER. A large parameter space is explored, consisting of primary (16-20 Ms) and secondary masses (5-8 Ms), mixing boundaries, and accreting timescales. Those models whose end states match the observed properties of the progenitor of SN 1987A are exploded. The

HYPERCRITICAL ACCRETION, INDUCED GRAVITATIONAL COLLAPSE, AND BINARY-DRIVEN HYPERNOVAE

DOE PAGES

Fryer, Chris L.; Rueda, Jorge A.; Ruffini, Remo

2014-09-16

We successfully, applied the induced gravitational collapse (IGC) paradigm to the explanation of GRB-SNe. The progenitor is a tight binary system composed of a CO core and a NS companion. Furthermore, the explosion of the SN leads to hypercritical accretion onto the NS companion, which reaches the critical mass, gravitationally collapsing to a BH with consequent emission of the GRB. The first estimates of this process were based on a simplified model of the binary parameters and the Bondi-Hoyle-Lyttleton accretion rate. We present the first full numerical simulations of the IGC process. We simulate the core-collapse, the SN explosion, andmore » the hydrodynamic evolution of the accreting material falling into the Bondi-Hoyle surface of the NS. For appropriate binary parameters, the IGC occurs in short timescale 102–103 s due to the combined action of photon trapping and neutrino cooling near the NS surface. We also address the observational features of this process.« less

Formation Timescales for High-Mass X-ray Binaries in M33

NASA Astrophysics Data System (ADS)

Garofali, Kristen; Williams, Benjamin F.; Hillis, Tristan; Gilbert, Karoline M.; Dolphin, Andrew E.; Eracleous, Michael; Binder, Breanna

2018-06-01

We have identified 55 candidate high-mass X-ray binaries (HMXBs) in M33 using available archival HST and Chandra imaging to find blue stars associated with X-ray positions. We use the HST photometric data to model the color-magnitude diagrams in the vicinity of each candidate HMXB to measure a resolved recent star formation history (SFH), and thus a formation timescale, or age for the source. Taken together, the SFHs for all candidate HMXBs in M33 yield an age distribution that suggests preferred formation timescales for HMXBs in M33 of < 5 Myr and ˜ 40 Myr after the initial star formation episode. The population at 40 Myr is seen in other Local Group galaxies, and can be attributed to a peak in formation efficiency of HMXBs with neutron stars as compact objects and B star secondary companions. This timescale is preferred as neutron stars should form in abundance from ˜ 8 M⊙ core-collapse progenitors on these timescales, and B stars are shown observationally to be most actively losing mass around this time. The young population at < 5 Myr has not be observed in other Local Group HMXB population studies, but may be attributed to a population of very massive progenitors forming black holes very early on. We discuss these results in the context of massive binary evolution, and the implications for compact object binaries and gravitational wave sources.

Morphological and genetical changes of endothelial progenitor cells after in-vitro conversion into photoreceptors.

PubMed

Qiang, Shi; Alsaeedi, Hiba Amer; Yuhong, Cheng; Yang, Hao; Tong, Li; Kumar, Suresh; Higuchi, Akon; Alarfaj, Abdullah A; Munisvaradass, Rusheni; Ling, Mok Pooi; Cheng, Pei

2018-06-01

Retinal degeneration is a condition ensued by various ocular disorders such as artery occlusion, diabetic retinopathy, retrolental fibroplasia and retinitis pigmentosa which cause abnormal loss of photoreceptor cells and lead to eventual vision impairment. No efficient treatment has yet been found, however, the use of stem cell therapy such as bone marrow and embryonic stem cells has opened a new treatment modality for retinal degenerative diseases. The major goal of this study is to analyze the potential of endothelial progenitor cells derived from bone marrow to differentiate into retinal neural cells for regenerative medicine purposes. In this study, endothelial progenitor cells were induced in-vitro with photoreceptor growth factor (taurine) for 21 days. Subsequently, the morphology and gene expression of CRX and RHO of the photoreceptors-induced EPCs were examined through immunostaining assay. The results indicated that the induced endothelial progenitor cells demonstrated positive gene expression of CRX and RHO. Our findings suggested that EPC cells may have a high advantage in cell replacement therapy for treating eye disease, in addition to other neural diseases, and may be a suitable cell source in regenerative medicine for eye disorders. Copyright © 2018 Elsevier B.V. All rights reserved.

A HST Search to Constrain the Binary Fraction of Stripped-Envelope Supernovae

NASA Astrophysics Data System (ADS)

Fox, Ori

2018-01-01

Stripped-envelope supernovae (e.g., SNe IIb, Ib, and Ic) refer to a subset of core-collapse explosions with progenitors that have lost some fraction of their outer envelopes in pre-SN mass loss. Mounting evidence over the past decade suggests that the mass loss in a large fraction of these systems occurs due to binary interaction. An unbiased, statistically significant sample of companion-star characteristics (including deep upper limits) can constrain the binary fraction, having direct implications on the theoretical physics of both single star and binary evolution. To date, however, only two detections have been made: SNe 1993J and 2011dh. Over the past year, we have improved this sample with an HST WFC3/NUV survey for binary companions of three additional nearby stripped-envelope SNe: 2002ap, 2001ig, and 2010br. I will present a review of previous companion searches and results from our current HST survey, which include one detection and two meaningful upper limits.

Panchromatic Observations of SN2011dh Point to a Compact Progenitor Star

NASA Technical Reports Server (NTRS)

Soderberg, A. M.; Margutti, R.; Zauerer, B. A.; Krauss, M.; Katz, B.; Chomiuk, L.; Dittmann, J. A.; Nakar, E.; Sakamoto, T.; Kawai, N.;

The population of single and binary white dwarfs of the Galactic bulge

NASA Astrophysics Data System (ADS)

Torres, S.; García-Berro, E.; Cojocaru, R.; Calamida, A.

2018-05-01

Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here, we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-discbulge stars is negligible.

The Growth of Stellar Mass Black Hole Binaries Trapped in the Accretion Disks of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Yi, Shu-Xu; Cheng, K. S.; Taam, Ronald E.

2018-06-01

Among the four black hole (BH) binary merger events detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), six progenitor BHs have masses greater than 20 M ⊙. The existence of such massive BHs suggests that extreme metal-poor stars are the progenitors. An alternative possibility, that a pair of stellar mass BHs each with mass ∼7 M ⊙ increases to >20 M ⊙ via accretion from a disk surrounding a supermassive BH (SMBH) in an active galactic nucleus (AGN), is considered. The growth of mass of the binary and the transfer of orbital angular momentum to the disk accelerates the merger. Based on the recent numerical work of Tang et al., it is found that, in the disk of a low-mass AGN with mass ∼106 M ⊙ and Eddington ratio >0.01, the mass of an individual BH in the binary can grow to >20 M ⊙ before coalescence, provided that accretion takes place at a rate more than 10 times the Eddington value. This mechanism predicts a new class of gravitational wave (GW) sources involving the merger of two extreme Kerr black holes associated with AGNs and a possible electromagnetic wave counterpart.

Quadrature demultiplexing using a degenerate vector parametric amplifier.

PubMed

Lorences-Riesgo, Abel; Liu, Lan; Olsson, Samuel L I; Malik, Rohit; Kumpera, Aleš; Lundström, Carl; Radic, Stojan; Karlsson, Magnus; Andrekson, Peter A

2014-12-01

We report on quadrature demultiplexing of a quadrature phase-shift keying (QPSK) signal into two cross-polarized binary phase-shift keying (BPSK) signals with negligible penalty at bit-error rate (BER) equal to 10(-9). The all-optical quadrature demultiplexing is achieved using a degenerate vector parametric amplifier operating in phase-insensitive mode. We also propose and demonstrate the use of a novel and simple phase-locked loop (PLL) scheme based on detecting the envelope of one of the signals after demultiplexing in order to achieve stable quadrature decomposition.

The first mass and angular momentum loss measurements for a CV-like binary

NASA Astrophysics Data System (ADS)

Drake, Jeremy

2015-10-01

The period distribution of close binaries, cataclysmic variables, novae and single-degenerate SN1a progenitor candidates is largely controlled by magnetically-driven mass and angular momentum loss (AML) from the M dwarf secondary. The mass loss rates for these spun-up stars remain essentially unknown and impossible to observe directly, with likely values in the range 1e-12 to 1e-15 Msun/yr. AML presciptions for CVs differ by orders of magnitude. One way to measure the mass loss rate is to observe the dM wind accrete onto its WD companion in a pre-CV very close to Roche Lobe overflow but lacking the obscuring complications and emission from an accretion disk. The measurement can be combined with realistic MHD models to understand the accretion fraction, the mass that escapes, and the AML. The best-studied nearby pre-CV is QS Vir (48pc, P=3.6hr). However, its wind accretion rates measured from 1999 HST UV spectra of the WD metal absorption lines and 2006 XMM-Newton CCD spectroscopy differ by a factor of a thousand, pointing to either a dominant CME stochastic component, or a magnetic switch found in MHD simulations and driven by cyclic activity on the M dwarf. HST COS spectra combined with XMM-Newton monitoring on timescales from weeks to years will tease out CME vs cyclic accretion variations. UV and X-ray measurements will provide the first consistency check of both accretion rate measurement methods. MHD models tailored to the system will enable the first quasi-direct measurements of the mass loss and AML from a CV-like binary. Our project requires 6 HST/COS orbits in Cycles 22-24, and 60ksec on XMM in Cycle 22

The first mass and angular momentum loss measurements for a CV-like binary

NASA Astrophysics Data System (ADS)

Drake, Jeremy

2014-10-01

The period distribution of close binaries, cataclysmic variables, novae and single-degenerate SN1a progenitor candidates is largely controlled by magnetically-driven mass and angular momentum loss (AML) from the M dwarf secondary. The mass loss rates for these spun-up stars remain essentially unknown and impossible to observe directly, with likely values in the range 1e-12 to 1e-15 Msun/yr. AML presciptions for CVs differ by orders of magnitude. One way to measure the mass loss rate is to observe the dM wind accrete onto its WD companion in a pre-CV very close to Roche Lobe overflow but lacking the obscuring complications and emission from an accretion disk. The measurement can be combined with realistic MHD models to understand the accretion fraction, the mass that escapes, and the AML. The best-studied nearby pre-CV is QS Vir (48pc, P=3.6hr). However, its wind accretion rates measured from 1999 HST UV spectra of the WD metal absorption lines and 2006 XMM-Newton CCD spectroscopy differ by a factor of a thousand, pointing to either a dominant CME stochastic component, or a "magnetic switch" found in MHD simulations and driven by cyclic activity on the M dwarf. HST COS spectra combined with XMM-Newton monitoring on timescales from weeks to years will tease out CME vs cyclic accretion variations. UV and X-ray measurements will provide the first consistency check of both accretion rate measurement methods. MHD models tailored to the system will enable the first quasi-direct measurements of the mass loss and AML from a CV-like binary. Our project requires 6 HST/COS orbits in Cycles 22-24, and 60ksec on XMM in Cycle 22

The first mass and angular momentum loss measurements for a CV-like binary

NASA Astrophysics Data System (ADS)

Drake, Jeremy

2016-10-01

The period distribution of close binaries, cataclysmic variables, novae and single-degenerate SN1a progenitor candidates is largely controlled by magnetically-driven mass and angular momentum loss (AML) from the M dwarf secondary. The mass loss rates for these spun-up stars remain essentially unknown and impossible to observe directly, with likely values in the range 1e-12 to 1e-15 Msun/yr. AML presciptions for CVs differ by orders of magnitude. One way to measure the mass loss rate is to observe the dM wind accrete onto its WD companion in a pre-CV very close to Roche Lobe overflow but lacking the obscuring complications and emission from an accretion disk. The measurement can be combined with realistic MHD models to understand the accretion fraction, the mass that escapes, and the AML. The best-studied nearby pre-CV is QS Vir (48pc, P=3.6hr). However, its wind accretion rates measured from 1999 HST UV spectra of the WD metal absorption lines and 2006 XMM-Newton CCD spectroscopy differ by a factor of a thousand, pointing to either a dominant CME stochastic component, or a magnetic switch found in MHD simulations and driven by cyclic activity on the M dwarf. HST COS spectra combined with XMM-Newton monitoring on timescales from weeks to years will tease out CME vs cyclic accretion variations. UV and X-ray measurements will provide the first consistency check of both accretion rate measurement methods. MHD models tailored to the system will enable the first quasi-direct measurements of the mass loss and AML from a CV-like binary. Our project requires 6 HST/COS orbits in Cycles 22-24, and 60ksec on XMM in Cycle 22

On the Peculiarities of Evolutionary History of EHB Objects in Binary Systems with Hot Subdwarf Companions

NASA Astrophysics Data System (ADS)

Pustynski, V.-V.; Pustylnik, I.

2006-03-01

It has been shown quite recently (Maxted etal 2001, Morales-Rueda etal 2003) that dB stars, extreme horizontal branch (EHB) objects, likely all belong to binary systems. We study in detail the mass and angular momentum loss in the giant progenitors of sdB stars in an attempt to clarify why binarity must be a crucial factor in producing EHB objects. Assuming that the progenitors of EHB objects belong to the binaries with initial separations of 100-150 R_odot and fill in their critical Roche lobes while being close to the RGB tip we have found that considerable shrinkage of the orbit can be achieved due to the combined effect of angular momentum loss from the red giant and appreciable accretion on its low mass companion on the hydrodynamical time scale of the donor resulting in formation of helium white dwarfs with masses about 0.5 M_odot and thus evading the common envelope stage.

Soman poisoning increases neural progenitor proliferation and induces long-term glial activation in mouse brain.

PubMed

Collombet, Jean-Marc; Four, Elise; Bernabé, Denis; Masqueliez, Catherine; Burckhart, Marie-France; Baille, Valérie; Baubichon, Dominique; Lallement, Guy

2005-03-30

To date, only short-term glial reaction has been extensively studied following soman or other warfare neurotoxicant poisoning. In a context of cell therapy by neural progenitor engraftment to repair brain damage, the long-term effect of soman on glial reaction and neural progenitor division was analyzed in the present study. The effect of soman poisoning was estimated in mouse brains at various times ranging from 1 to 90 days post-poisoning. Using immunochemistry and dye staining techniques (hemalun-eosin staining), the number of degenerating neurons, the number of dividing neural progenitors, and microglial, astroglial or oligodendroglial cell activation were studied. Soman poisoning led to rapid and massive (post-soman day 1) death of mature neurons as assessed by hemalun-eosin staining. Following this acute poisoning phase, a weak toxicity effect on mature neurons was still observed for a period of 1 month after poisoning. A massive short-termed microgliosis peaked on day 3 post-poisoning. Delayed astrogliosis was observed from 3 to 90 days after soman poisoning, contributing to glial scar formation. On the other hand, oligodendroglial cells or their precursors were practically unaffected by soman poisoning. Interestingly, neural progenitors located in the subgranular zone of the dentate gyrus (SGZ) or in the subventricular zone (SVZ) of the brain survived soman poisoning. Furthermore, soman poisoning significantly increased neural progenitor proliferation in both SGZ and SVZ brain areas on post-soman day 3 or day 8, respectively. This increased proliferation rate was detected up to 1 month after poisoning.

Equilibrium, stability, and orbital evolution of close binary systems

NASA Technical Reports Server (NTRS)

Lai, Dong; Rasio, Frederic A.; Shapiro, Stuart L.

1994-01-01

We present a new analytic study of the equilibrium and stability properties of close binary systems containing polytropic components. Our method is based on the use of ellipsoidal trial functions in an energy variational principle. We consider both synchronized and nonsynchronized systems, constructing the compressible generalizations of the classical Darwin and Darwin-Riemann configurations. Our method can be applied to a wide variety of binary models where the stellar masses, radii, spins, entropies, and polytropic indices are all allowed to vary over wide ranges and independently for each component. We find that both secular and dynamical instabilities can develop before a Roche limit or contact is reached along a sequence of models with decreasing binary separation. High incompressibility always makes a given binary system more susceptible to these instabilities, but the dependence on the mass ratio is more complicated. As simple applications, we construct models of double degenerate systems and of low-mass main-sequence star binaries. We also discuss the orbital evoltuion of close binary systems under the combined influence of fluid viscosity and secular angular momentum losses from processes like gravitational radiation. We show that the existence of global fluid instabilities can have a profound effect on the terminal evolution of coalescing binaries. The validity of our analytic solutions is examined by means of detailed comparisons with the results of recent numerical fluid calculations in three dimensions.

Stripped Red Giants - Helium Core White Dwarf Progenitors and their sdB Siblings

NASA Astrophysics Data System (ADS)

Heber, U.

2017-03-01

Some gaps in the mosaic of binary star evolution have recently been filled by the discoveries of helium-core white dwarf progenitors (often called extremely low mass (ELM) white dwarfs) as stripped cores of first-giant branch objects. Two varieties can be distinguished. One class is made up by SB1 binaries, companions being white dwarfs as well. Another class, the so-called EL CVn stars, are composite spectrum binaries, with A-Type companions. Pulsating stars are found among both classes. A riddle is posed by the apparently single objects. There is a one-to-one correspondence of the phenomena found for these new classes of star to those observed for sdB stars. In fact, standard evolutionary scenarios explain the origin of sdB stars as red giants that have been stripped close to the tip of first red giant branch. A subgroup of subluminous B stars can also be identified as stripped helium-cores of red giants. They form an extension of the ELM sequence to higher temperatures. Hence low mass white dwarfs of helium cores and sdB stars in binaries are close relatives in terms of stellar evolution.

Thermonuclear Explosions from Hybrid C/O/Ne White Dwarf Progenitors Ignited Centrally After Interior Mixing

NASA Astrophysics Data System (ADS)

Augustine, Carlyn

2018-01-01

Type Ia Supernovae are thermonuclear explosions of white dwarf (WD) stars. Past studies predict the existence of "hybrid" white dwarfs, made of a C/O/Ne core with a O/Ne shell, and that these are viable progenitors for supernovae. More recent work found that the C/O core is mixed with the surrounding O/Ne while the WD cools. Inspired by this scenario, we performed simulations of thermonuclear supernovae in the single degenerate paradigm from these hybrid progenitors. Our investigation began by constructing a hybrid white dwarf model with the one-dimensional stellar evolution code MESA. The model was allowed to go through unstable interior mixing ignite carbon burning centrally. The MESA model was then mapped to a two-dimensional initial condition and an explosion simulated from that with FLASH. For comparison, a similar simulation of an explosion was performed from a traditional C/O progenitor WD. Comparing the yields produced by explosion simulations allows us to determine which model produces more 56Ni, and therefore brighter events, and how explosions from these models differ from explosions from previous models without the mixing during the WD cooling.

A Microfabricated Scaffold for Retinal Progenitor Cell Grafting

PubMed Central

Neeley, William L.; Redenti, Stephen; Klassen, Henry; Tao, Sarah; Desai, Tejal; Young, Michael J.; Langer, Robert

2007-01-01

Diseases that cause photoreceptor cell degeneration afflict millions of people, yet no restorative treatment exists for these blinding disorders. Replacement of photoreceptors using retinal progenitor cells (RPCs) represents a promising therapy for the treatment of retinal degeneration. Previous studies have demonstrated the ability of polymer scaffolds to increase significantly both the survival and differentiation of RPCs. We report the microfabrication of a poly(glycerol-sebacate) scaffold with superior mechanical properties for the delivery of RPCs to the subretinal space. Using a replica molding technique, a porous poly(glycerol-sebacate) scaffold with a thickness of 45 μm was fabricated. Evaluation of the mechanical properties of this scaffold showed that the Young’s modulus is about 5-fold lower and the maximum elongation at failure is about 10-fold higher than the previously reported RPC scaffolds. RPCs strongly adhered to the poly(glycerol-sebacate) scaffold, and endogenous fluorescence nearly doubled over a 2 day period before leveling off after 3 days. Immunohistochemistry revealed that cells grown on the scaffold for 7 days expressed a mixture of immature and mature markers, suggesting a tendency towards differentiation. We conclude that microfabricated poly(glycerol-sebacate) exhibits a number of novel properties for use as a scaffold for RPC delivery. PMID:17961646

Low-mass X-ray binary evolution and the origin of millisecond pulsars

NASA Technical Reports Server (NTRS)

Frank, Juhan; King, Andrew R.; Lasota, Jean-Pierre

1992-01-01

The evolution of low-mass X-ray binaries (LMXBs) is considered. It is shown that X-ray irradiation of the companion stars causes these systems to undergo episodes of rapid mass transfer followed by detached phases. The systems are visible as bright X-ray binaries only for a short part of each cycle, so that their space density must be considerably larger than previously estimated. This removes the difficulty in regarding LMXBs as the progenitors of low-mass binary pulsars. The low-accretion-rate phase of the cycle with the soft X-ray transients is identified. It is shown that 3 hr is likely to be the minimum orbital period for LMXBs with main-sequence companions and it is suggested that the evolutionary endpoint for many LMXBs may be systems which are the sites of gamma-ray bursts.

Constraints for the Progenitor Masses of Historic Core-collapse Supernovae

NASA Astrophysics Data System (ADS)

Williams, Benjamin F.; Hillis, Tristan J.; Murphy, Jeremiah W.; Gilbert, Karoline; Dalcanton, Julianne J.; Dolphin, Andrew E.

2018-06-01

We age-date the stellar populations associated with 12 historic nearby core-collapse supernovae (CCSNe) and two supernova impostors; from these ages, we infer their initial masses and associated uncertainties. To do this, we have obtained new Hubble Space Telescope imaging covering these CCSNe. Using these images, we measure resolved stellar photometry for the stars surrounding the locations of the SNe. We then fit the color–magnitude distributions of this photometry with stellar evolution models to determine the ages of any young existing populations present. From these age distributions, we infer the most likely progenitor masses for all of the SNe in our sample. We find ages between 4 and 50 Myr, corresponding to masses from 7.5 to 59 solar masses. There were no SNe that lacked a local young population. Our sample contains four SNe Ib/c; their masses have a wide range of values, suggesting that the progenitors of stripped-envelope SNe are binary systems. Both impostors have masses constrained to be ≲7.5 solar masses. In cases with precursor imaging measurements, we find that age-dating and precursor imaging give consistent progenitor masses. This consistency implies that, although the uncertainties for each technique are significantly different, the results of both are reliable to the measured uncertainties. We combine these new measurements with those from our previous work and find that the distribution of 25 core-collapse SNe progenitor masses is consistent with a standard Salpeter power-law mass function, no upper mass cutoff, and an assumed minimum mass for core-collapse of 7.5 M⊙. The distribution is consistent with a minimum mass <9.5 M⊙.

A Chandrasekhar mass progenitor for the Type Ia supernova remnant 3C 397 from the enhanced abundances of nickel and manganese

DOE PAGES

Yamaguchi, Hiroya; Badenes, Carles; Foster, Adam R.; ...

2015-03-12

Despite decades of intense efforts, many fundamental aspects of Type Ia supernovae (SNe Ia) remain elusive. One of the major open questions is whether the mass of an exploding white dwarf (WD) is close to the Chandrasekhar limit. Here, we report the detection of strong K-shell emission from stable Fe-peak elements in the Suzaku X-ray spectrum of the Type Ia supernova remnant (SNR) 3C 397. The high Ni/Fe and Mn/Fe mass ratios (0.11–0.24 and 0.018–0.033, respectively) in the hot plasma component that dominates the K-shell emission lines indicate a degree of neutronization in the supernova ejecta that can only bemore » achieved by electron capture in the dense cores of exploding WDs with a near-Chandrasekhar mass. This suggests a single-degenerate origin for 3C 397, since Chandrasekhar mass progenitors are expected naturally if the WD accretes mass slowly from a companion. Altogether with other results supporting the double-degenerate scenario, our work adds to the mounting evidence that both progenitor channels make a significant contribution to the SN Ia rate in star-forming galaxies.« less

A Chandrasekhar Mass Progenitor for the Type Ia Supernova Remnant 3C 397 from the Enhanced Abundances of Nickel and Manganese

NASA Technical Reports Server (NTRS)

Yamaguchi, Hiroya; Badenes, Carles; Foster, Adam R.; Bravo, Eduardo; Williams, Brian J.; Maeda, Keiichi; Nobukawa, Masayoshi; Eriksen, Kristoffer A.; Brickhouse, Nancy S.; Petre, Robert;

Use of antidementia drugs in frontotemporal lobar degeneration.

PubMed

López-Pousa, Secundino; Calvó-Perxas, Laia; Lejarreta, Saioa; Cullell, Marta; Meléndez, Rosa; Hernández, Erélido; Bisbe, Josep; Perkal, Héctor; Manzano, Anna; Roig, Anna Maria; Turró-Garriga, Oriol; Vilalta-Franch, Joan; Garre-Olmo, Josep

2012-06-01

Clinical evidence indicates that acetylcholinesterase inhibitors (AChEIs) are not efficacious to treat frontotemporal lobar degeneration (FTLD). The British Association for Psychopharmacology recommends avoiding the use of AChEI and memantine in patients with FTLD. Cross-sectional design using 1092 cases with Alzheimer's disease (AD) and 64 cases with FTLD registered by the Registry of Dementias of Girona. Bivariate analyses were performed, and binary logistic regressions were used to detect variables associated with antidementia drugs consumption. The AChEIs were consumed by 57.6% and 42.2% of the patients with AD and FTLD, respectively. Memantine was used by 17.2% and 10.9% of patients with AD and FTLD, respectively. Binary logistic regressions yielded no associations with antidementia drugs consumption. There is a discrepancy regarding clinical practice and the recommendations based upon clinical evidence. The increased central nervous system drug use detected in FTLD requires multicentric studies aiming at finding the best means to treat these patients.

The binary white dwarf LHS 3236

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise

2013-12-10

The white dwarf LHS 3236 (WD1639+153) is shown to be a double-degenerate binary, with each component having a high mass. Astrometry at the U.S. Naval Observatory gives a parallax and distance of 30.86 ± 0.25 pc and a tangential velocity of 98 km s{sup –1}, and reveals binary orbital motion. The orbital parameters are determined from astrometry of the photocenter over more than three orbits of the 4.0 yr period. High-resolution imaging at the Keck Observatory resolves the pair with a separation of 31 and 124 mas at two epochs. Optical and near-IR photometry give a set of possible binarymore » components. Consistency of all data indicates that the binary is a pair of DA stars with temperatures near 8000 and 7400 K and with masses of 0.93 and 0.91 M {sub ☉}; also possible is a DA primary and a helium DC secondary with temperatures near 8800 and 6000 K and with masses of 0.98 and 0.69 M {sub ☉}. In either case, the cooling ages of the stars are ∼3 Gyr and the total ages are <4 Gyr. The combined mass of the binary (1.66-1.84 M {sub ☉}) is well above the Chandrasekhar limit; however, the timescale for coalescence is long.« less

In vitro culture of stress erythroid progenitors identifies distinct progenitor populations and analogous human progenitors.

PubMed

Xiang, Jie; Wu, Dai-Chen; Chen, Yuanting; Paulson, Robert F

2015-03-12

Tissue hypoxia induces a systemic response designed to increase oxygen delivery to tissues. One component of this response is increased erythropoiesis. Steady-state erythropoiesis is primarily homeostatic, producing new erythrocytes to replace old erythrocytes removed from circulation by the spleen. In response to anemia, the situation is different. New erythrocytes must be rapidly made to increase hemoglobin levels. At these times, stress erythropoiesis predominates. Stress erythropoiesis is best characterized in the mouse, where it is extramedullary and utilizes progenitors and signals that are distinct from steady-state erythropoiesis. In this report, we use an in vitro culture system that recapitulates the in vivo development of stress erythroid progenitors. We identify cell-surface markers that delineate a series of stress erythroid progenitors with increasing maturity. In addition, we use this in vitro culture system to expand human stress erythroid progenitor cells that express analogous cell-surface markers. Consistent with previous suggestions that human stress erythropoiesis is similar to fetal erythropoiesis, we demonstrate that human stress erythroid progenitors express fetal hemoglobin upon differentiation. These data demonstrate that similar to murine bone marrow, human bone marrow contains cells that can generate BMP4-dependent stress erythroid burst-forming units when cultured under stress erythropoiesis conditions. © 2015 by The American Society of Hematology.

Is the Link Between the Observed Velocities of Neutron Stars and their Progenitors a Simple Mass Relationship?

NASA Astrophysics Data System (ADS)

Bray, J. C.

2017-11-01

While the imparting of velocity `kicks' to compact remnants from supernovae is widely accepted, the relationship of the `kick' to the progenitor is not. We propose the `kick' is predominantly a result of conservation of momentum between the ejected and compact remnant masses. We propose the `kick' velocity is given by v kick = α(M ejecta/M remnant)+β, where α and β are constants we wish to determine. To test this we use the BPASS v2 (Binary Population and Spectral Synthesis) code to create stellar populations from both single star and binary star evolutionary pathways. We then use our Remnant Ejecta and Progenitor Explosion Relationship (REAPER) code to apply `kicks' to neutron stars from supernovae in these models using a grid of α and β values, (from 0 to 200 km s-1 in steps of 10 km s-1), in three different `kick' orientations, (isotropic, spin-axis aligned and orthogonal to spin-axis) and weighted by three different Salpeter initial mass functions (IMF's), with slopes of -2.0, -2.35 and -2.70. We compare our synthetic 2D and 3D velocity probability distributions to the distributions provided by Hobbs et al. (1995).

SALT HRS discovery of a long-period double-degenerate binary in the planetary nebula NGC 1360

NASA Astrophysics Data System (ADS)

Miszalski, B.; Manick, R.; Mikołajewska, J.; Iłkiewicz, K.; Kamath, D.; Van Winckel, H.

2018-01-01

Whether planetary nebulae (PNe) are predominantly the product of binary stellar evolution as some population synthesis models (PSM) suggest remains an open question. Around 50 short-period binary central stars (P ∼ 1 d) are known, but with only four with measured orbital periods over 10 d, our knowledge is severely incomplete. Here we report on the first discovery from a systematic Southern African Large Telescope (SALT) High Resolution Spectrograph (HRS) survey for long-period binary central stars. We find a 142 d orbital period from radial velocities of the central star of NGC 1360, HIP 16566. NGC 1360 appears to be the product of common-envelope (CE) evolution, with nebula features similar to post-CE PNe, albeit with an orbital period considerably longer than expected to be typical of post-CE PSM. The most striking feature is a newly identified ring of candidate low-ionization structures. Previous spatiokinematic modelling of the nebula gives a nebula inclination of 30° ± 10°, and assuming the binary nucleus is coplanar with the nebula, multiwavelength observations best fit a more massive, evolved white dwarf (WD) companion. A WD companion in a 142 d orbit is not the focus of many PSM, making NGC 1360 a valuable system with which to improve future PSM work. HIP 16566 is amongst many central stars in which large radial velocity variability was found by low-resolution surveys. The discovery of its binary nature may indicate long-period binaries may be more common than PSM models predict.

Observational properties of SNe Ia progenitors close to the explosion

NASA Astrophysics Data System (ADS)

Tornambé, A.; Piersanti, L.; Raimondo, G.; Delgrande, R.

2018-04-01

We determine the expected signal in various observational bands of supernovae Ia progenitors just before the explosion by assuming the rotating double-degenerate scenario. Our results are valid also for all the evolutionary scenarios invoking rotation as the driving mechanism of the accretion process as well as the evolution up to the explosion. We find that the observational properties depend mainly on the mass of the exploding object, even if the angular momentum evolution after the end of the mass accretion phase and before the onset of C-burning plays a non-negligible role. Just before the explosion, the magnitude MV ranges between 9 and 11 mag, while the colour (F225W - F555W) is about -1.64 mag. The photometric properties remain constant for a few decades before the explosion. During the last few months, the luminosity decreases very rapidly. The corresponding decline in the optical bands varies from a few hundredths up to one magnitude, the exact value depending on both the white dwarf total mass and the braking efficiency at the end of the mass transfer. This feature is related to the exponentially increasing energy production, which drives the formation of a convective core rapidly extending over a large part of the exploding object. Also, a drop in the angular velocity occurs. We find that observations in the soft X band (0.5-2 keV) may be used to check if the evolution of the SNe Ia progenitors up to the explosion is driven by rotation and, hence, to discriminate among different progenitor scenarios.

Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra

NASA Astrophysics Data System (ADS)

Leonard, Douglas C.

2007-12-01

Despite intense scrutiny, the progenitor system(s) that gives rise to Type Ia supernovae remains unknown. The favored theory invokes a carbon-oxygen white dwarf accreting hydrogen-rich material from a close companion until a thermonuclear runaway ensues that incinerates the white dwarf. However, simulations resulting from this single-degenerate, binary channel demand the presence of low-velocity Hα emission in spectra taken during the late nebular phase, since a portion of the companion's envelope becomes entrained in the ejecta. This hydrogen has never been detected, but has only rarely been sought. Here we present results from a campaign to obtain deep, nebular-phase spectroscopy of nearby Type Ia supernovae, and include multiepoch observations of two events: SN 2005am (slightly subluminous) and SN 2005cf (normally bright). No Hα emission is detected in the spectra of either object. An upper limit of 0.01 Msolar of solar abundance material in the ejecta is established from the models of Mattila et al., which, when coupled with the mass-stripping simulations of Marietta et al. and Meng et al., effectively rules out progenitor systems for these supernovae with secondaries close enough to the white dwarf to be experiencing Roche lobe overflow at the time of explosion. Alternative explanations for the absence of Hα emission, along with suggestions for future investigations necessary to confidently exclude them as possibilities, are critically evaluated. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Additional observations were obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a

Accreting neutron stars, black holes, and degenerate dwarf stars.

PubMed

Pines, D

1980-02-08

During the past 8 years, extended temporal and broadband spectroscopic studies carried out by x-ray astronomical satellites have led to the identification of specific compact x-ray sources as accreting neutron stars, black holes, and degenerate dwarf stars in close binary systems. Such sources provide a unique opportunity to study matter under extreme conditions not accessible in the terrestrial laboratory. Quantitative theoretical models have been developed which demonstrate that detailed studies of these sources will lead to a greatly increased understanding of dense and superdense hadron matter, hadron superfluidity, high-temperature plasma in superstrong magnetic fields, and physical processes in strong gravitational fields. Through a combination of theory and observation such studies will make possible the determination of the mass, radius, magnetic field, and structure of neutron stars and degenerate dwarf stars and the identification of further candidate black holes, and will contribute appreciably to our understanding of the physics of accretion by compact astronomical objects.

The Primordial Binary Fraction in Trumpler 14: Frequency and Multiplicity Parameters

NASA Astrophysics Data System (ADS)

Sabbi, Elena

2017-08-01

This is an astrometric proposal designed to identify and characterize the properties of medium- and long-period (orbital periods ranging from 1.8 to 100 years) visual binaries in the mass range between 4 and 20 Mo in the young compact cluster Trumpler 14 in the Carina Nebula. We aim to probe the virtually unexplored population of intermediate- and high-mass binaries that will experience a Roche-lobe overflow during their post-main-sequence evolution. These binaries are of particular interest because they are expected to be the progenitors of supernovae Type Ia, b, and c, X-ray binaries, double neutron stars and double black holes. Multiplicity properties of young stars can be further used to constrain the outcome of the star-formation process and hence distinguish between various formation scenarios. The medium- and long-period binaries (P> 0.5 yr) are hard to detect and expensive to characterize with traditional ground-based spectroscopy. Knowledge of their orbital properties is however crucial to properly estimate the overall fraction of OB stars whose evolution is affected by binary interaction and to predict the outcome of such interaction. Because of the well characterized PSF of WFC3/UVIS and its temporal stability, HST is the only facility able to characterize the properties of OB-type medium-period binaries in Tr14, and Tr14 is the only nearby high-density OB-type young cluster.

Engineering retinal progenitor cell and scrollable poly(glycerol-sebacate) composites for expansion and subretinal transplantation

PubMed Central

Redenti, Stephen; Neeley, William L.; Rompani, Santiago; Saigal, Sunita; Yang, Jing; Klassen, Henry; Langer, Robert; Young, Michael J.

2014-01-01

Retinal degenerations cause permanent visual loss and affect millions world-wide. Presently, a novel treatment highlights the potential of using biodegradable polymer scaffolds to induce differentiation and deliver retinal progenitor cells for cell replacement therapy. In this study, we engineered and analyzed a micro-fabricated polymer, poly(glycerol sebacate) (PGS) scaffold, whose useful properties include biocompatibility, elasticity, porosity, and a microtopology conducive to mouse retinal progenitor cell (mRPC) differentiation. In vitro proliferation assays revealed that PGS held up to 86,610 (±9993) mRPCs per square millimeter, which were retained through simulated transplantations. mRPCs adherent to PGS differentiated toward mature phenotypes as evidenced by changes in mRNA, protein levels, and enhanced sensitivity to glutamate. Transplanted composites demonstrated long-term mRPC survival and migrated cells exhibited mature marker expression in host retina. These results suggest that combining mRPCs with PGS scaffolds for subretinal transplantation is a practical strategy for advancing retinal tissue engineering as a restorative therapy. PMID:19361860

X-ray Binaries in the Galaxy and the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Cowley, Anne P.

1993-05-01

For more than two decades astronomers have been aware that the most X-ray luminous stellar sources (L_x > 10(35) erg s(-1) ) are interacting binaries where one component is a neutron star or black hole. While other types of single and multiple stars are known X-ray sources, none compare in X-ray luminosity with the ``classical" X-ray binaries. In these systems X-ray emission results from accretion of material from a non-degenerate companion onto the compact star through several alternate mechanisms including Roche lobe overflow, stellar winds, or periastron effects in non-circular orbits. It has been recognized for many years that X-ray binaries divide into two broad groups, characterized primarily by the mass of the non-degenerate star: 1) massive X-ray binaries (MXRB), in which the optical primary is a bright, early-type star, and 2) low-mass X-ray binaries (LMXB), where a lower main-sequence or subgiant star is the mass donor. A broad variety of observational characteristics further subdivide these classes. In the Galaxy these two groups appear to be spatially and kinematically associated with the disk and the halo populations, respectively. A few dozen MXRB are known in the Galaxy. A great deal of information about their physical properties has been learned from observational study. Their optical primaries can be investigated by conventional techniques. Furthermore, most MXRB contain X-ray pulsars, allowing accurate determination of their orbital parameters. From these data masses have been determined for the neutron stars, all of which are ~ 1.4 Msun, within measurement errors. By contrast, the LMXB have been much more difficult to study. Although there are ~ 150 LMXB in the Galaxy, most are distant and faint, requiring use of large telescopes for their study. Their optical light is almost always dominated by an accretion disk, rather than the mass-losing star, making interpretation of their spectral and photometric properties difficult. Their often uncertain

Dust in a Type Ia Supernova Progenitor: Spitzer Spectroscopy of Kepler's Supernova Remnant

NASA Technical Reports Server (NTRS)

Williams, Brian J.; Borkowski, Kazimierz; Reynolds, Stephen P.; Ghavamian, Parviz; Blair, William P.; Long, Knox S.; Sankrit, Ravi

2012-01-01

Characterization of the relatively poorly-understood progenitor systems of Type Ia supernovae is of great importance in astrophysics, particularly given the important cosmological role that these supernovae play. Kepler's Supernova Remnant, the result of a Type Ia supernova, shows evidence for an interaction with a dense circumstellar medium (CSM), suggesting a single-degenerate progenitor system. We present 7.5-38 micron IR spectra of the remnant, obtained with the Spitzer Space Telescope, dominated by emission from warm dust. Broad spectral features at 10 and 18 micron, consistent with various silicate particles, are seen throughout. These silicates were likely formed in the stellar outflow from the progenitor system during the AGB stage of evolution, and imply an oxygen-rich chemistry. In addition to silicate dust, a second component, possibly carbonaceous dust, is necessary to account for the short-wavelength IRS and IRAC data. This could imply a mixed chemistry in the atmosphere of the progenitor system. However, non-spherical metallic iron inclusions within silicate grains provide an alternative solution. Models of collisionally-heated dust emission from fast shocks (> 1000 km/s) propagating into the CSM can reproduce the majority of the emission associated with non-radiative filaments, where dust temperatures are approx 80-100 K, but fail to account for the highest temperatures detected, in excess of 150 K. We find that slower shocks (a few hundred km/s) into moderate density material (n(sub o) approx 50-100 / cubic cm) are the only viable source of heating for this hottest dust. We confirm the finding of an overall density gradient, with densities in the north being an order of magnitude greater than those in the south.

A strange dwarf scenario for the formation of the peculiar double white dwarf binary SDSS J125733.63+542850.5

NASA Astrophysics Data System (ADS)

Jiang, Long; Chen, Wen-Cong; Li, Xiang-Dong

2018-05-01

The Hubble Space Telescope observation of the double white dwarf (WD) binary SDSS J125733.63+542850.5 reveals that the massive WD has a surface gravity log g1 ˜ 8.7 (which implies a mass of M1 ˜ 1.06 M⊙) and an effective temperature T1 ˜ 13 000 K, while the effective temperature of the low-mass WD (M2 < 0.24 M⊙) is T2 ˜ 6400K. Therefore, the massive and the low-mass WDs have a cooling age τ1 ˜ 1 Gyr and τ2 ≥ 5 Gyr, respectively. This is in contradiction with traditional binary evolution theory. In this paper, we propose a strange dwarf (SD) scenario to explain the formation of this double WD binary. We assume that the massive WD is a SD originating from a phase transition (PT) in a ˜1.1 M⊙ WD, which has experienced accretion and spin-down processes. Its high effective temperature could arise from the heating process during the PT. Our simulations suggest that the progenitor of SDSS J125733.63+542850.5 can be a binary system consisting of a 0.65 M⊙ WD and a 1.5 M⊙ main-sequence star in a 1.492 d orbit. Especially, the secondary star (i.e. the progenitor of the low-mass WD) is likely to have an ultra-low metallicity of Z = 0.0001.

High-mass X-ray binary populations. 1: Galactic modeling

NASA Technical Reports Server (NTRS)

Dalton, William W.; Sarazin, Craig L.

1995-01-01

Modern stellar evolutionary tracks are used to calculate the evolution of a very large number of massive binary star systems (M(sub tot) greater than or = 15 solar mass) which cover a wide range of total masses, mass ratios, and starting separations. Each binary is evolved accounting for mass and angular momentum loss through the supernova of the primary to the X-ray binary phase. Using the observed rate of star formation in our Galaxy and the properties of massive binaries, we calculate the expected high-mass X-ray binary (HMXRB) population in the Galaxy. We test various massive binary evolutionary scenarios by comparing the resulting HMXRB predictions with the X-ray observations. A major goal of this study is the determination of the fraction of matter lost from the system during the Roche lobe overflow phase. Curiously, we find that the total numbers of observable HMXRBs are nearly independent of this assumed mass-loss fraction, with any of the values tested here giving acceptable agreement between predicted and observed numbers. However, comparison of the period distribution of our HMXRB models with the observed period distribution does reveal a distinction among the various models. As a result of this comparison, we conclude that approximately 70% of the overflow matter is lost from a massive binary system during mass transfer in the Roche lobe overflow phase. We compare models constructed assuming that all X-ray emission is due to accretion onto the compact object from the donor star's wind with models that incorporate a simplified disk accretion scheme. By comparing the results of these models with observations, we conclude that the formation of disks in HMXRBs must be relatively common. We also calculate the rate of formation of double degenerate binaries, high velocity detached compact objects, and Thorne-Zytkow objects.

Black holes, disks, and jets following binary mergers and stellar collapse: The narrow range of electromagnetic luminosities and accretion rates.

PubMed

Shapiro, Stuart L

2017-05-15

We have performed magnetohydrodynamic simulations in general relativity of binary neutron star and binary black hole-neutron star mergers, as well as the magnetorotational collapse of supermassive stars. In many cases the outcome is a spinnng black hole (BH) immersed in a magnetized disk, with a jet emanating from the poles of the BH. While their formation scenarios differ and their BH masses, as well as their disk masses, densities, and magnetic field strengths, vary by orders of magnitude, these features conspire to generate jet Poynting luminosities that all lie in the same, narrow range of ~10 52±1 erg s -1 . A similar result applies to their BH accretion rates upon jet launch, which is ~0.1-10 M ⊙ s -1 . We provide a simple model that explains these unanticipated findings. Interestingly, these luminosities reside in the same narrow range characterizing the observed luminosity distributions of over 400 short and long GRBs with distances inferred from spectroscopic redshifts or host galaxies. This result, together with the GRB lifetimes predicted by the model, supports the belief that a compact binary merger is the progenitor of an SGRB, while a massive, stellar magnetorotational collapse is the progenitor of an LGRB.

Black holes, disks, and jets following binary mergers and stellar collapse: The narrow range of electromagnetic luminosities and accretion rates

PubMed Central

Shapiro, Stuart L.

2018-01-01

We have performed magnetohydrodynamic simulations in general relativity of binary neutron star and binary black hole-neutron star mergers, as well as the magnetorotational collapse of supermassive stars. In many cases the outcome is a spinnng black hole (BH) immersed in a magnetized disk, with a jet emanating from the poles of the BH. While their formation scenarios differ and their BH masses, as well as their disk masses, densities, and magnetic field strengths, vary by orders of magnitude, these features conspire to generate jet Poynting luminosities that all lie in the same, narrow range of ~1052±1 erg s−1. A similar result applies to their BH accretion rates upon jet launch, which is ~0.1–10 M⊙ s−1. We provide a simple model that explains these unanticipated findings. Interestingly, these luminosities reside in the same narrow range characterizing the observed luminosity distributions of over 400 short and long GRBs with distances inferred from spectroscopic redshifts or host galaxies. This result, together with the GRB lifetimes predicted by the model, supports the belief that a compact binary merger is the progenitor of an SGRB, while a massive, stellar magnetorotational collapse is the progenitor of an LGRB. PMID:29881790

Compact Objects In Binary Systems: Formation and Evolution of X-ray Binaries and Tides in Double White Dwarfs

NASA Astrophysics Data System (ADS)

Valsecchi, Francesca

Binary star systems hosting black holes, neutron stars, and white dwarfs are unique laboratories for investigating both extreme physical conditions, and stellar and binary evolution. Black holes and neutron stars are observed in X-ray binaries, where mass accretion from a stellar companion renders them X-ray bright. Although instruments like Chandra have revolutionized the field of X-ray binaries, our theoretical understanding of their origin and formation lags behind. Progress can be made by unravelling the evolutionary history of observed systems. As part of my thesis work, I have developed an analysis method that uses detailed stellar models and all the observational constraints of a system to reconstruct its evolutionary path. This analysis models the orbital evolution from compact-object formation to the present time, the binary orbital dynamics due to explosive mass loss and a possible kick at core collapse, and the evolution from the progenitor's Zero Age Main Sequence to compact-object formation. This method led to a theoretical model for M33 X-7, one of the most massive X-ray binaries known and originally marked as an evolutionary challenge. Compact objects are also expected gravitational wave (GW) sources. In particular, double white dwarfs are both guaranteed GW sources and observed electromagnetically. Although known systems show evidence of tidal deformation and a successful GW astronomy requires realistic models of the sources, detached double white dwarfs are generally approximated to point masses. For the first time, I used realistic models to study tidally-driven periastron precession in eccentric binaries. I demonstrated that its imprint on the GW signal yields constrains on the components' masses and that the source would be misclassified if tides are neglected. Beyond this adiabatic precession, tidal dissipation creates a sink of orbital angular momentum. Its efficiency is strongest when tides are dynamic and excite the components' free

THE FINAL SPIN FROM BINARY BLACK HOLES IN QUASI-CIRCULAR ORBITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hofmann, Fabian; Rezzolla, Luciano; Barausse, Enrico

2016-07-10

We revisit the problem of predicting the spin magnitude and direction of the black hole (BH) resulting from the merger of two BHs with arbitrary masses and spins inspiraling in quasi-circular orbits. We do this by analyzing a catalog of 619 recent numerical-relativity simulations collected from the literature and spanning a large variety of initial conditions. By combining information from the post-Newtonian approximation, the extreme mass-ratio limit, and perturbative calculations, we improve our previously proposed phenomenological formulae for the final remnant spin. In contrast with alternative suggestions in the literature, and in analogy with our previous expressions, the new formulamore » is a simple algebraic function of the initial system parameters and is not restricted to binaries with spins aligned/anti-aligned with the orbital angular momentum but can be employed for fully generic binaries. The accuracy of the new expression is significantly improved, especially for almost extremal progenitor spins and for small mass ratios, yielding an rms error σ ≈ 0.002 for aligned/anti-aligned binaries and σ ≈ 0.006 for generic binaries. Our new formula is suitable for cosmological applications and can be employed robustly in the analysis of the gravitational waveforms from advanced interferometric detectors.« less

Neural Progenitors Adopt Specific Identities by Directly Repressing All Alternative Progenitor Transcriptional Programs.

PubMed

Kutejova, Eva; Sasai, Noriaki; Shah, Ankita; Gouti, Mina; Briscoe, James

2016-03-21

In the vertebrate neural tube, a morphogen-induced transcriptional network produces multiple molecularly distinct progenitor domains, each generating different neuronal subtypes. Using an in vitro differentiation system, we defined gene expression signatures of distinct progenitor populations and identified direct gene-regulatory inputs corresponding to locations of specific transcription factor binding. Combined with targeted perturbations of the network, this revealed a mechanism in which a progenitor identity is installed by active repression of the entire transcriptional programs of other neural progenitor fates. In the ventral neural tube, sonic hedgehog (Shh) signaling, together with broadly expressed transcriptional activators, concurrently activates the gene expression programs of several domains. The specific outcome is selected by repressive input provided by Shh-induced transcription factors that act as the key nodes in the network, enabling progenitors to adopt a single definitive identity from several initially permitted options. Together, the data suggest design principles relevant to many developing tissues. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Constraints on the Progenitor System of the Type Ia Supernova 2014J from Pre-Explosion Hubble Space Telescope Imaging

NASA Technical Reports Server (NTRS)

Kelly, Patrick L.; Fox, Ori D.; Filippenko, Alexei V.; Cenko, S. Bradley; Prato, Lisa; Schaefer, Gail; Shen, Ken J.; Zheng, WeiKang; Graham, Melissa L.; Tucker, Brad E.

2014-01-01

We constrain the properties of the progenitor system of the highly reddened Type Ia supernova (SN Ia) 2014J in Messier 82 (M82; d (is) approx. 3.5 Mpc). We determine the supernova (SN) location using Keck-II K-band adaptive optics images, and we find no evidence for flux from a progenitor system in pre-explosion near-ultraviolet through near-infrared Hubble Space Telescope (HST) images. Our upper limits exclude systems having a bright red giant companion, including symbiotic novae with luminosities comparable to that of RS Ophiuchi. While the flux constraints are also inconsistent with predictions for comparatively cool He-donor systems (T (is) approximately 35,000 K), we cannot preclude a system similar to V445 Puppis. The progenitor constraints are robust across a wide range of RV and AV values, but significantly greater values than those inferred from the SN light curve and spectrum would yield proportionally brighter luminosity limits. The comparatively faint flux expected from a binary progenitor system consisting of white dwarf stars would not have been detected in the pre-explosion HST imaging. Infrared HST exposures yield more stringent constraints on the luminosities of very cool (T (is) less than 3000 K) companion stars than was possible in the case of SN Ia 2011fe.

Is supernova 1987A a stripped asymptotic-branch giant in a binary system?

NASA Technical Reports Server (NTRS)

Joss, P. C.; Podsiadlowski, PH.; Hsu, J. J. L.; Rappaport, S.

1988-01-01

It is proposed that the progenitor of supernova 1987A was a previously undetected red star in orbit about a blue supergiant. The progenitor was the remnant of an asymptotic-branch giant that had lost most of its hydrogen-rich envelope to its blue companion by type C mass transfer. A detailed evolutionary model strongly supports the feasibility of this proposition. It is found that the original mass of the supernova precursor was 10-15 solar (unless a large fraction of the mass was ejected from the binary sytem), and its final mass, just before the supernova event, was 3-6 solar. The system remained bound, with a new orbital period of 3-10 yr and an eccentricity of 0.1-0.4. This picture can provide plausible qualitative explanations for several anomalies in the observational properties of this supernova.

Light Echoes and the Progenitor of SN 2016adj in Cen A

NASA Astrophysics Data System (ADS)

Sugerman, Ben; Lawrence, Stephen

2016-02-01

The Type Ib/IIb supernova (SN) 2016adj is the fifth closest SN to be discovered during the lifetime of HST. This event offers us a rich variety of rare and unique opportunities, including: (1) identifying the progenitor; (2) mapping the three-dimensional structure and chemical composition of the progenitor's circumstellar and the host galaxy's interstellar environments; and (3) testing models of stellar mass loss and high-mass stellar evolution. The progenitor field of the SN has been observed from the near-UV to the mid-IR with HST and Spitzer, which will immediately allow us to accomplish the first science goal by identifying the progenitor (or establishing its upper limits) once new image with the SN present are taken with both observatories. Preliminary analyses of early-time spectra of SN 2016adj indicate its light is being extinguished by at least A(V)=2-4 magnitudes, meaning it is buried deep within the dust lane of Cen A. Echoes of the SN light off of this dust will allow us to produce high-resolution, three-dimensional maps of the structure and composition of the dust in and around the line-of-sight to the SN, which we will use to accomplish science goals (2)-(3) listed above. In particular, we will directly test the hypothesis that Type Ib/IIb SNe come not from very-high mass stars but from only moderately-massive stars that lost their envelopes to close binary companions. Please note that since echoes pass through a given point in space only once, data are permanently lost for each epoch that is not observed. While we will propose for continued observations in the Cycle 13 call for proposals, most of the science we propose cannot be achieved if the observations in this proposal are not taken before Cycle 13 begins.

Strong Evidence against a Non-degenerate Companion in SN 2012cg

NASA Astrophysics Data System (ADS)

Shappee, B. J.; Piro, A. L.; Stanek, K. Z.; Patel, S. G.; Margutti, R. A.; Lipunov, V. M.; Pogge, R. W.

2018-03-01

Even though SN 2012cg is one of the best-studied Type Ia supernovae to date, the nature of its progenitor system has been debated in numerous studies. Specifically, it is difficult to reconcile recent claims of the detection of a ∼6 {M}ȯ MS companion with recent deep, late-time {{H}}α flux limits. In this study we add three new constraints. (1) We analyze a new high-signal-to-noise, nebular-phase, Large Binocular Telescope/MODS spectrum of SN 2012cg and place an upper limit on the amount of low-velocity, solar-abundance material removed from a possible companion of < 7.8× {10}-3 {M}ȯ . (2) We use Swift X-ray observations to constrain the pre-explosion mass-loss rate to be \\dot{M}< {10}-6 {M}ȯ {yr}}-1 for {v}{{w}}=100 {km} {{{s}}}-1. (3) We carefully reanalyze a prediscovery MASTER image, and with published light curves of SN 2012cg we estimate the time of first light and conservatively constrain the radius of a Roche-lobe overflowing companion to be < 0.24 {R}ȯ . These observations disagree with a large nearby companion, and when considered with other studies of SN 2012cg’s progenitor system, essentially rule out a non-degenerate companion.

WD+RG systems as the progenitors of type Ia supernovae

NASA Astrophysics Data System (ADS)

Wang, Bo; Han, Zhan-Wen

2010-03-01

Type Ia supernovae (SNe Ia) play an important role in the study of cosmic evolution, especially in cosmology. There are several progenitor models for SNe Ia proposed in the past years. By considering the effect of accretion disk instability on the evolution of white dwarf (WD) binaries, we performed detailed binary evolution calculations for the WD + red-giant (RG) channel of SNe Ia, in which a carbon-oxygen WD accretes material from a RG star to increase its mass to the Chandrasekhar mass limit. According to these calculations, we mapped out the initial and final parameters for SNe Ia in the orbital period-secondary mass (log Pi - Mi2) plane for various WD masses for this channel. We discussed the influence of the variation of the duty cycle value on the regions for producing SNe Ia. Similar to previous studies, this work also indicates that the long-period dwarf novae offer possible ways for producing SNe Ia. Meanwhile, we find that the surviving companion stars from this channel have a low mass after the SN explosion, which may provide a means for the formation of the population of single low-mass WDs (<0.45 Modot).

Type Ia supernovae: explosions and progenitors

NASA Astrophysics Data System (ADS)

Kerzendorf, Wolfgang Eitel

2011-08-01

that they somehow need to acquire mass if they are to explode as SN Ia. Currently there are two major scenarios for this mass acquisition. In the favoured single degenerate scenario the white dwarf accretes matter from a companion star which is much younger in its evolutionary state. The less favoured double degenerate scenario sees the merger of two white dwarfs (with a total combined mass of more than 1.38 Msun). This thesis has tried to answer the question about the mass acquisition in two ways. First the single degenerate scenario predicts a surviving companion post-explosion. We undertook an observational campaign to find this companion in two ancient supernovae (SN 1572 and SN 1006). Secondly, we have extended an existing code to extract the elemental and energy yields of SNe Ia spectra by automating spectra fitting to specific SNe Ia. This type of analysis, in turn, help diagnose to which of the two major progenitor scenarios is right.

SN Ia archaeology: Searching for the relics of progenitors past

NASA Astrophysics Data System (ADS)

Woods, Tyrone E.; Gilfanov, Marat; Clocchiatti, Alejandro; Rest, Armin

2016-06-01

Despite the critical role that SNe Ia play in the chemical enrichment of the Universe and their great importance in measuring cosmological distances, we still don't know for certain how they arise. In the canonical form of the ``single-degenerate'' scenario, a white dwarf grows through the nuclear burning of matter accreted at its surface from some companion star. This renders it a hot, luminous object (a supersoft X-ray source or SSS, 10^5-10^6K, 10^{38} erg/s) for up to a million years prior to explosion. Past efforts to directly detect the progenitors of very recent, nearby SNe Ia in archival soft X-ray images have produced only upper limits, and are only constraining assuming progenitors with much higher temperatures than known SSSs. In this talk, I will outline an alternative approach: given that such objects should be strong sources of ionizing radiation, one may instead search the environment surrounding nearby SN Ia remnants for interstellar matter ionized by the progenitor. Such fossil nebulae should extend out to tens of parsecs and linger for roughly the recombination timescale in the ISM, of order 10,000 — 100,000 years. Progress on this front has been hampered by the failure to detect nebulae surrounding most known SSSs using 1m class telescopes in the early 1990s. I will present new benchmark calculations for the emission-line nebulae expected to surround such objects, demonstrating that previous non-detections are entirely consistent with the low ISM densities expected in the vicinity of most SN Ia progenitors (Woods & Gilfanov, 2016). Modern large optical telescopes are now well able to reach the required limiting surface brightness needed to find such faint emission. With this in mind, I will introduce our new narrow-band survey for fossil nebulae surrounding young Magellanic SN Ia remnants and SSSs, already underway using the Magellan Baade telescope (PI: Alejandro Clocchiatti). In addition to opening a new era of SN Ia archaeology, I will show

Macular degeneration (image)

MedlinePlus

Macular degeneration is a disease of the retina that affects the macula in the back of the eye. ... see fine details. There are two types of macular degeneration, dry and wet. Dry macular degeneration is more ...

Mesenchymal progenitor cells for the osteogenic lineage.

PubMed

Ono, Noriaki; Kronenberg, Henry M

2015-09-01

Mesenchymal progenitors of the osteogenic lineage provide the flexibility for bone to grow, maintain its function and homeostasis. Traditionally, colony-forming-unit fibroblasts (CFU-Fs) have been regarded as surrogates for mesenchymal progenitors; however, this definition cannot address the function of these progenitors in their native setting. Transgenic murine models including lineage-tracing technologies based on the cre-lox system have proven to be useful in delineating mesenchymal progenitors in their native environment. Although heterogeneity of cell populations of interest marked by a promoter-based approach complicates overall interpretation, an emerging complexity of mesenchymal progenitors has been revealed. Current literatures suggest two distinct types of bone progenitor cells; growth-associated mesenchymal progenitors contribute to explosive growth of bone in early life, whereas bone marrow mesenchymal progenitors contribute to the much slower remodeling process and response to injury that occurs mainly in adulthood. More detailed relationships of these progenitors need to be studied through further experimentation.

On the Afterglow and Progenitor of FRB 150418

NASA Astrophysics Data System (ADS)

Zhang, Bing

2016-05-01

Keane et al. recently detected a fading radio source following FRB 150418, leading to the identification of a putative host galaxy at z = 0.492 ± 0.008. Assuming that the fading source is the afterglow of FRB 150418, I model the afterglow and constrain the isotropic energy of the explosion to be a few 1050 erg, comparable to that of a short-duration gamma-ray burst (GRB). The outflow may have a jet opening angle of ˜0.22 rad, so that the beaming-corrected energy is below 1049 erg. The results rule out most fast radio burst (FRB) progenitor models for this FRB, but may be consistent with either of the following two scenarios. The first scenario invokes a merger of an NS-NS binary, which produced an undetected short GRB and a supra-massive neutron star, which subsequently collapsed into a black hole, probably hundreds of seconds after the short GRB. The second scenario invokes a merger of a compact star binary (BH-BH, NS-NS, or BH-NS) system whose pre-merger dynamical magnetospheric activities made the FRB, which is followed by an undetected short GRB-like transient. The gravitational-wave (GW) event GW 150914 would be a sister of FRB 150418 in this second scenario. In both cases, one expects an exciting prospect of GW/FRB/GRB associations.

The hot subdwarf in the eclipsing binary HD 185510

NASA Technical Reports Server (NTRS)

Jeffery, C. S.; Simon, Theodore; Evans, T. L.

1992-01-01

High-resolution spectroscopic measurements of radial velocity are employed to characterize the eclipsing binary HD 185510 in terms of masses and evolutionary status. The IUE is used to obtain the radial velocities which indicate a large mass ratio Mp/Ms of 7.45 +/- 0.15, and Teff is given at 25,000 +/- 1000 K based on Ly alpha and UV spectrophotometry. Photometric observations are used to give an orbital inclination of between 90 and 70 deg inclusive, leading to masses of 0.31-0.37 and 2.3-2.8 solar mass for the hot star and the K star, respectively. The surface gravity of HD 185510B is shown to be higher than those values for sdB stars suggesting that the object is a low-mass white dwarf that has not reached its fully degenerate configuration. The object is theorized to be a low-mass helium main-sequence star or a nascent helium degenerate in a post-Algol system.

Astronomy in Denver: Spectropolarimetric Observations of 5 Wolf-Rayet Binary Stars with SALT/RSS

NASA Astrophysics Data System (ADS)

Fullard, Andrew; Ansary, Zyed; Azancot Luchtan, Daniel; Gallegos, Hunter; Luepker, Martin; Hoffman, Jennifer L.; Nordsieck, Kenneth H.; SALT observation team

2018-06-01

Mass loss from massive stars is an important yet poorly understood factor in shaping their evolution. Wolf-Rayet (WR) stars are of particular interest due to their stellar winds, which create large regions of circumstellar material (CSM). They are also supernova and possible gamma-ray burst (GRB) progenitors. Like other massive stars, WR stars often occur in binaries, where interaction can affect their mass loss rates and provide the rapid rotation thought to be required for GRB production. The diagnostic tool of spectropolarimetry, along with the potentially eclipsing nature of a binary system, helps us to better characterize the CSM created by the stars’ colliding winds. Thus, we can determine mass loss rates and infer rapid rotation. We present spectropolarimetric results for five WR+O eclipsing binary systems, obtained with the Robert Stobie Spectrograph at the South African Large Telescope, between April 2017 and April 2018. The data allow us to map both continuum and emission line polarization variations with phase, which constrains where different CSM components scatter light in the systems. We discuss our initial findings and interpretations of the polarimetric variability in each binary system, and compare the systems.

Neuronal expression of pathological tau accelerates oligodendrocyte progenitor cell differentiation

PubMed Central

Ossola, Bernardino; Zhao, Chao; Compston, Alastair; Pluchino, Stefano; Franklin, Robin J. M.

2015-01-01

Oligodendrocyte progenitor cell (OPC) differentiation is an important therapeutic target to promote remyelination in multiple sclerosis (MS). We previously reported hyperphosphorylated and aggregated microtubule‐associated protein tau in MS lesions, suggesting its involvement in axonal degeneration. However, the influence of pathological tau‐induced axonal damage on the potential for remyelination is unknown. Therefore, we investigated OPC differentiation in human P301S tau (P301S‐htau) transgenic mice, both in vitro and in vivo following focal demyelination. In 2‐month‐old P301S‐htau mice, which show hyperphosphorylated tau in neurons, we found atrophic axons in the spinal cord in the absence of prominent axonal degeneration. These signs of early axonal damage were associated with microgliosis and an upregulation of IL‐1β and TNFα. Following in vivo focal white matter demyelination we found that OPCs differentiated more efficiently in P301S‐htau mice than wild type (Wt) mice. We also found an increased level of myelin basic protein within the lesions, which however did not translate into increased remyelination due to higher susceptibility of P301S‐htau axons to demyelination‐induced degeneration compared to Wt axons. In vitro experiments confirmed higher differentiation capacity of OPCs from P301S‐htau mice compared with Wt mice‐derived OPCs. Because the OPCs from P301S‐htau mice do not ectopically express the transgene, and when isolated from newborn mice behave like Wt mice‐derived OPCs, we infer that their enhanced differentiation capacity must have been acquired through microenvironmental priming. Our data suggest the intriguing concept that damaged axons may signal to OPCs and promote their differentiation in the attempt at rescue by remyelination. GLIA 2016;64:457–471 PMID:26576485

Macular degeneration

MedlinePlus Videos and Cool Tools

... center of the field of vision. Macular degeneration results from a partial breakdown of the insulating layer ... of blood vessels behind the retina. Macular degeneration results in the loss of central vision only.

A 15.65-solar-mass black hole in an eclipsing binary in the nearby spiral galaxy M 33.

PubMed

Orosz, Jerome A; McClintock, Jeffrey E; Narayan, Ramesh; Bailyn, Charles D; Hartman, Joel D; Macri, Lucas; Liu, Jiefeng; Pietsch, Wolfgang; Remillard, Ronald A; Shporer, Avi; Mazeh, Tsevi

2007-10-18

Stellar-mass black holes are found in X-ray-emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses more than ten times that of the Sun (>10; ref. 4), which is consistent with the fact that the most massive stellar black holes known so far all have masses within one standard deviation of 10. Here we report a mass of (15.65 +/- 1.45) for the black hole in the recently discovered system M 33 X-7, which is located in the nearby galaxy Messier 33 (M 33) and is the only known black hole that is in an eclipsing binary. To produce such a massive black hole, the progenitor star must have retained much of its outer envelope until after helium fusion in the core was completed. On the other hand, in order for the black hole to be in its present 3.45-day orbit about its (70.0 +/- 6.9) companion, there must have been a 'common envelope' phase of evolution in which a significant amount of mass was lost from the system. We find that the common envelope phase could not have occurred in M 33 X-7 unless the amount of mass lost from the progenitor during its evolution was an order of magnitude less than what is usually assumed in evolutionary models of massive stars.

The Progenitor and Remnant of the Helium Nova V445 Puppis

NASA Astrophysics Data System (ADS)

Goranskij, V.; Shugarov, S.; Zharova, A.; Kroll, P.; Barsukova, E. A.

2010-10-01

V445 Pup was a peculiar nova with no hydrogen spectral lines during the outburst. The spectrum contained strong emission lines of carbon, oxygen, calcium, sodium, and iron. We have performed digital processing of photographic images of the V445 Pup progenitor using astronomical plate archives. The brightness of the progenitor in the B band was 14.3m. It was a periodic variable star, its most probable period being 0.650654+/-0.000011 days. The light curve shape suggests that the progenitor was a common-envelope binary with a spot on the surface and variable surface brightness. The spectral energy distribution of the progenitor between 0.44 and 2.2 microns was similar to that of an A0V type star. After the explosion in 2001, the dust was formed in the ejecta, and the star became a strong infrared source. This resulted in the star's fading below 20m in the V band. Our CCD BVR observations acquired between 2003 and 2009 suggest that the dust absorption minimum finished in 2004, and the remnant reappeared at the level of 18.5m V. The dust dispersed but a star-like object was absent in frames taken in the K band with the VLT adaptive optics. Only expanding ejecta of the explosion were seen in these frames till March 2007. No reddened A0V type star reappeared in the spectral energy distribution. The explosion of V445 Pup in 2000 was a helium flash on the surface of a CO-type white dwarf. Taking into account the results of modern dynamic calculations, we discuss the possibility of a white-dwarf core detonation triggered by the helium flash and the observational evidence for it. Additionally, the common envelope of the system was lost in the explosion. Destruction in the system and mass loss from its components exclude the future SN Ia scenario for V445 Pup.

Spectral analysis of the binary nucleus of the planetary nebula Hen 2-428 - first results

NASA Astrophysics Data System (ADS)

Finch, Nicolle L.; Reindl, Nicole; Barstow, Martin A.; Casewell, Sarah L.; Geier, Stephan; Bertolami, Marcelo M. Miller; Taubenberger, Stefan

2018-04-01

Identifying progenitor systems for the double-degenerate scenario is crucial to check the reliability of type Ia supernovae as cosmological standard candles. Santander-Garcia et al. (2015) claimed that Hen 2-428 has a doubledegenerate core whose combined mass significantly exceeds the Chandrasekhar limit. Together with the short orbital period (4.2 hours), the authors concluded that the system should merge within a Hubble time triggering a type Ia supernova event. Garcia-Berro et al. (2016) explored alternative scenarios to explain the observational evidence, as the high mass conclusion is highly unlikely within predictions from stellar evolution theory. They conclude that the evidence supporting the supernova progenitor status of the system is premature. Here we present the first quantitative spectral analysis of Hen 2-428which allows us to derive the effective temperatures, surface gravities and helium abundance of the two CSPNe based on state-of-the-art, non-LTE model atmospheres. These results provide constrains for further studies of this particularly interesting system.

Astrophysical Implications of the Binary Black-hole Merger GW150914

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Belczynski, C.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M., Jr.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Phelps, M.; Piccinni, O.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stevenson, S. P.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; van den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; White, D. J.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; and; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2016-02-01

The discovery of the gravitational-wave (GW) source GW150914 with the Advanced LIGO detectors provides the first observational evidence for the existence of binary black hole (BH) systems that inspiral and merge within the age of the universe. Such BH mergers have been predicted in two main types of formation models, involving isolated binaries in galactic fields or dynamical interactions in young and old dense stellar environments. The measured masses robustly demonstrate that relatively “heavy” BHs (≳ 25 {M}⊙ ) can form in nature. This discovery implies relatively weak massive-star winds and thus the formation of GW150914 in an environment with a metallicity lower than about 1/2 of the solar value. The rate of binary-BH (BBH) mergers inferred from the observation of GW150914 is consistent with the higher end of rate predictions (≳ 1 Gpc-3 yr-1) from both types of formation models. The low measured redshift (z≃ 0.1) of GW150914 and the low inferred metallicity of the stellar progenitor imply either BBH formation in a low-mass galaxy in the local universe and a prompt merger, or formation at high redshift with a time delay between formation and merger of several Gyr. This discovery motivates further studies of binary-BH formation astrophysics. It also has implications for future detections and studies by Advanced LIGO and Advanced Virgo, and GW detectors in space.

Astrophysical Implications of the Binary Black Hole Merger GW150914

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.;

Binary dislocation junction formation and strength in hexagonal close-packed crystals

DOE PAGES

Wu, Chi -Chin; Aubry, Sylvie; Arsenlis, Athanasios; ...

2015-12-17

This work examines binary dislocation interactions, junction formation and junction strengths in hexagonal close-packed ( hcp ) crystals. Through a line-tension model and dislocation dynamics (DD) simulations, the interaction and dissociation of different sets of binary junctions are investigated involving one dislocation on the (011¯0) prismatic plane and a second dislocation on one of the following planes: (0001) basal, (11¯00) prismatic, (11¯01) primary pyramidal, or (2¯112) secondary pyramidal. Varying pairs of Burgers vectors are chosen from among the common types the basal type < a > 1/3 < 112¯0 >, prismatic type < c > <0001>, and pyramidal type 1/3 < 112¯3¯ >. For binary interaction due to dislocation intersection, both the analytical results and DD-simulations indicate a relationship between symmetry of interaction maps and the relative magnitude of the Burgers vectors that constitute the junction. Using analytical formulae, a simple regressive model is also developed to represent the junction yield surface. The equation is treated as a degenerated super elliptical equation to quantify the aspect ratio and tilting angle. Lastly, the results provide analytical insights on binary dislocation interactions that may occur in general hcp metals.« less

A search for X-ray binary stars in their quiescent phase

NASA Technical Reports Server (NTRS)

Helfand, D. J.

1980-01-01

Fourteen early-type stars representative of systems which may be harboring a neutron star companion and are thus potential progenitors of massive X-ray binaries have been examined for X-ray emission with the HEAO A-1 experiment. Limits on the 0.5-20 keV luminosity for these objects lie in the range 10 to the 31-33 erg/sec. In several cases, the hypothesis of a collapsed companion, in combination with the X-ray limit, places a serious constraint on the mass-loss rate of the primary star. In one instance, an X-ray source was discovered coincident with a candidate star, although the luminosity of 5 x 10 to the 31 is consistent with that expected from a single star of the same spectral type. The prospects for directly observing the quiescent phase of a binary X-ray source with the Einstein Observatory are discussed in the context of these results.

Understanding the Progenitors of Short Gamma-Ray Bursts via their Host Galaxies: A Pilot Study

NASA Astrophysics Data System (ADS)

Cenko, S. Brad

2014-08-01

While massive star core-collapse is known to power long-duration gamma-ray bursts (GRBs), the origin of short GRBs remains unconfirmed. Studies of the host galaxies of short GRBs provide critical constraints on their progenitors, particularly if (as expected) short GRBs result from the neutron star mergers. Here we request deep Keck/LRIS imaging of short GRBs lacking securely identified hosts. By constraining the fraction of events that appear to have been 'kicked' out of their host galaxy in a more unbiased manner than past efforts, we aim to infer fundamental properties about the formation and evolution of binary neutron star systems.

Gravitational Wave Astrophysics in the Mid-band: progenitors and advanced localizations of Advanced LIGO/Virgo binary-merger events

NASA Astrophysics Data System (ADS)

Cheung, Chi C. Teddy; Hogan, Jason; Graham, Peter; Kasevich, Mark; Rajendran, Surjeet; Saif, Babak; Kerr, Matthew T.; Lovellette, Michael; Wood, Kent S.; Michelson, Peter; MAGIS Team

2018-01-01

We consider the scientific potential of gravitational wave (GW) observations in the ~30 mHz to 3 Hz frequency range with the Mid-band Atomic Gravitational-wave Interferometric Sensor (MAGIS). MAGIS is a probe-class space-mission concept, using an atom-based gravitational wave detector, that will provide all-sky strain sensitivities of ~10^-21 sqrt(Hz) and better (1-year) in the GW-frequency mid-band between the LISA/L3 detector (planned 2034 launch) and ground-based Advanced LIGO/Virgo interferometers. Primary gravitational wave astrophysics science in the mid-band include GW observations of the binary black hole population discovered by Advanced LIGO/Virgo at higher-frequencies, prior to their merger stage. For such systems, MAGIS will observe the binaries in their inspiral phase, where system parameters such as eccentricities are most easily constrained, and will provide advanced, degree-scale localizations that would enable electromagnetic observations of possible precursor emission 1-week to 1-month prior to their mergers as well as prompt post-merger transient emission. Joint GW-observations with MAGIS and Advanced LIGO/Virgo covering all stages of binary coalescence will further reduce uncertainties in the GW- localizations and distances, and will be powerful paired with galaxy catalogs, to enable unique galaxy counterpart identifications in the case black hole binary mergers are completely absent of detectable electromagnetic precursor or transient signals. These possibilities for MAGIS extend to neutron star binary systems (black hole - neutron star, neutron star - neutron star), and mid-band prospects for such systems will also be considered.The MAGIS team is a collaboration between institutes in the U.S. including Stanford, AOSense, Harvard, NASA/GSFC, NASA/JPL, NIST, NRL, and UC Berkeley, and international partners at Birmingham, Bordeaux, CNRS, Dusseldorf, Ecole Normale Superieure, Florence, Hannover, and Ulm University.

LBT Discovery of a Yellow Supergiant Eclipsing Binary in the Dwarf Galaxy Holmberg IX

NASA Astrophysics Data System (ADS)

Prieto, J. L.; Stanek, K. Z.; Kochanek, C. S.; Weisz, D. R.; Baruffolo, A.; Bechtold, J.; Burwitz, V.; De Santis, C.; Gallozzi, S.; Garnavich, P. M.; Giallongo, E.; Hill, J. M.; Pogge, R. W.; Ragazzoni, R.; Speziali, R.; Thompson, D. J.; Wagner, R. M.

2008-01-01

In a variability survey of M81 using the Large Binocular Telescope we have discovered a peculiar eclipsing binary (MV ~ - 7.1) in the field of the dwarf galaxy Holmberg IX. It has a period of 271 days, and the light curve is well fit by an overcontact model in which both stars are overflowing their Roche lobes. It is composed of two yellow supergiants (V - Isimeq 1 mag, Teffsimeq 4800 K), rather than the far more common red or blue supergiants. Such systems must be rare. While we failed to find any similar systems in the literature, we did, however, note a second example. The SMC F0 supergiant R47 is a bright (MV ~ - 7.5) periodic variable whose All Sky Automated Survey (ASAS) light curve is well fit as a contact binary with a 181 day period. We propose that these systems are the progenitors of supernovae like SN 2004et and SN 2006ov, which appeared to have yellow progenitors. The binary interactions (mass transfer, mass loss) limit the size of the supergiant to give it a higher surface temperature than an isolated star at the same core evolutionary stage. We also discuss the possibility of this variable being a long-period Cepheid. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia.

Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction

NASA Astrophysics Data System (ADS)

Zapartas, E.; de Mink, S. E.; Izzard, R. G.; Yoon, S.-C.; Badenes, C.; Götberg, Y.; de Koter, A.; Neijssel, C. J.; Renzo, M.; Schootemeijer, A.; Shrotriya, T. S.

2017-05-01

Most massive stars, the progenitors of core-collapse supernovae, are in close binary systems and may interact with their companion through mass transfer or merging. We undertake a population synthesis study to compute the delay-time distribution of core-collapse supernovae, that is, the supernova rate versus time following a starburst, taking into account binary interactions. We test the systematic robustness of our results by running various simulations to account for the uncertainties in our standard assumptions. We find that a significant fraction, %, of core-collapse supernovae are "late", that is, they occur 50-200 Myr after birth, when all massive single stars have already exploded. These late events originate predominantly from binary systems with at least one, or, in most cases, with both stars initially being of intermediate mass (4-8 M⊙). The main evolutionary channels that contribute often involve either the merging of the initially more massive primary star with its companion or the engulfment of the remaining core of the primary by the expanding secondary that has accreted mass at an earlier evolutionary stage. Also, the total number of core-collapse supernovae increases by % because of binarity for the same initial stellar mass. The high rate implies that we should have already observed such late core-collapse supernovae, but have not recognized them as such. We argue that φ Persei is a likely progenitor and that eccentric neutron star - white dwarf systems are likely descendants. Late events can help explain the discrepancy in the delay-time distributions derived from supernova remnants in the Magellanic Clouds and extragalactic type Ia events, lowering the contribution of prompt Ia events. We discuss ways to test these predictions and speculate on the implications for supernova feedback in simulations of galaxy evolution.

Why Are Peculiar Type Ia Supernovae More Likely to Show the Signature of a Single-degenerate Model?

NASA Astrophysics Data System (ADS)

Meng, Xiang-Cun; Han, Zhan-Wen

2018-03-01

Although type Ia supernovae (SNe Ia) are very useful in many astrophysical fields, their exact progenitor nature is still unclear. A basic method to distinguish the different progenitor models is to search the signal from the single-degenerate (SD) model, e.g., the signal for the existence of a nondegenerate companion before or after supernova explosion. Observationally, some SNe Ia show such signals, while the others do not. Here, we propose a universal model to explain these observations based on the spin-up/spin-down model, in which a white dwarf (WD) will experience a spin-down phase before supernova explosion, and the spin-down timescale is determined by its initial mass, i.e., the more massive the initial WD, the shorter the spin-down timescale and then the more likely the SN Ia is to show the SD signature. Therefore, our model predicts that the SNe Ia from hybrid carbon–oxygen–neon WDs are more likely to show the SD signature observationally, as some peculiar SNe Ia showed.

TWO STARS TWO WAYS: CONFIRMING A MICROLENSING BINARY LENS SOLUTION WITH A SPECTROSCOPIC MEASUREMENT OF THE ORBIT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yee, Jennifer C.; Johnson, John Asher; Eastman, Jason

Light curves of microlensing events involving stellar binaries and planetary systems can provide information about the orbital elements of the system due to orbital modulations of the caustic structure. Accurately measuring the orbit in either the stellar or planetary case requires detailed modeling of subtle deviations in the light curve. At the same time, the natural, Cartesian parameterization of a microlensing binary is partially degenerate with the microlens parallax. Hence, it is desirable to perform independent tests of the predictions of microlens orbit models using radial velocity (RV) time series of the lens binary system. To this end, we presentmore » 3.5 years of RV monitoring of the binary lens system OGLE-2009-BLG-020 L, for which Skowron et al. constrained all internal parameters of the 200–700 day orbit. Our RV measurements reveal an orbit that is consistent with the predictions of the microlens light curve analysis, thereby providing the first confirmation of orbital elements inferred from microlensing events.« less

Turbulent Nuclear Burning of Carbon Fuel in Double-Degenerate White Dwarfs

NASA Astrophysics Data System (ADS)

Mozumdar, Pritom; Fisher, Robert

2018-01-01

Type Ia supernovae (SNe Ia) are of interest as standardizable cosmological candles, though their stellar progenitors are still poorly understood. The double-degenerate (DD) channel is promising, but the mechanism for the explosion remains a matter of active investigation. A long-standing problem in modeling SNe Ia is the fact that 3D simulations leave the length scales crucial for a possible detonation unresolved. In this work, we have performed local 3D hydrodynamical adaptive mesh refinement simulations of driven turbulence for various initial conditions characteristic of the DD scenario, which are capable of capturing length scales relevant to the Zel’dovich gradient mechanism. Because the carbon burning rate is highly sensitive to temperature in this regime, we demonstrate that turbulence can dramatically enhance the nuclear burning rate, and we investigate the connection to a possible detonation.

Progenitor Epithelium

PubMed Central

Marty-Santos, Leilani

2015-01-01

Insulin-producing β cells within the vertebrate fetal pancreas acquire their fate in a step-wise manner. Whereas the intrinsic factors dictating the transcriptional or epigenetic status of pancreatic lineages have been intensely examined, less is known about cell–cell interactions that might constitute a niche for the developing β cell lineage. It is becoming increasingly clear that understanding and recapitulating these steps may instruct in vitro differentiation of embryonic stem cells and/or therapeutic regeneration. Indeed, directed differentiation techniques have improved since transitioning from 2D to 3D cultures, suggesting that the 3D microenvironment in which β cells are born is critical. However, to date, it remains unknown whether the changing architecture of the pancreatic epithelium impacts the fate of cells therein. An emerging challenge in the field is to elucidate how progenitors are allocated during key events, such as the stratification and subsequent resolution of the pre-pancreatic epithelium, as well as the formation of lumens and branches. Here, we assess the progenitor epithelium and examine how it might influence the emergence of pancreatic multipotent progenitors (MPCs), which give rise to β cells and other pancreatic lineages. PMID:26216134

Dynamics of stellar black holes in young star clusters with different metallicities - II. Black hole-black hole binaries

NASA Astrophysics Data System (ADS)

Ziosi, Brunetto Marco; Mapelli, Michela; Branchesi, Marica; Tormen, Giuseppe

2014-07-01

In this paper, we study the formation and dynamical evolution of black hole-black hole (BH-BH) binaries in young star clusters (YSCs), by means of N-body simulations. The simulations include metallicity-dependent recipes for stellar evolution and stellar winds, and have been run for three different metallicities (Z = 0.01, 0.1 and 1 Z⊙). Following recent theoretical models of wind mass-loss and core-collapse supernovae, we assume that the mass of the stellar remnants depends on the metallicity of the progenitor stars. We find that BH-BH binaries form efficiently because of dynamical exchanges: in our simulations, we find about 10 times more BH-BH binaries than double neutron star binaries. The simulated BH-BH binaries form earlier in metal-poor YSCs, which host more massive black holes (BHs) than in metal-rich YSCs. The simulated BH-BH binaries have very large chirp masses (up to 80 M⊙), because the BH mass is assumed to depend on metallicity, and because BHs can grow in mass due to the merger with stars. The simulated BH-BH binaries span a wide range of orbital periods (10-3-107 yr), and only a small fraction of them (0.3 per cent) is expected to merge within a Hubble time. We discuss the estimated merger rate from our simulations and the implications for Advanced VIRGO and LIGO.

ON THE RARITY OF X-RAY BINARIES WITH NAKED HELIUM DONORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linden, T.; Valsecchi, F.; Kalogera, V.

The paucity of known high-mass X-ray binaries (HMXBs) with naked He donor stars (hereafter He star) in the Galaxy has been noted over the years as a surprising fact, given the significant number of Galactic HMXBs containing H-rich donors, which are expected to be their progenitors. This contrast has further sharpened in light of recent observations uncovering a preponderance of HMXBs hosting loosely bound Be donors orbiting neutron stars (NSs), which would be expected to naturally evolve into He-HMXBs through dynamical mass transfer onto the NS and a common-envelope (CE) phase. Hence, reconciling the large population of Be-HMXBs with themore » observation of only one He-HMXB can help constrain the dynamics of CE physics. Here, we use detailed stellar structure and evolution models and show that binary mergers of HMXBs during CE events must be common in order to resolve the tension between these observed populations. We find that, quantitatively, this scenario remains consistent with the typically adopted energy parameterization of CE evolution, yielding expected populations which are not at odds with current observations. However, future observations which better constrain the underlying population of loosely bound O/B-NS binaries are likely to place significant constraints on the efficiency of CE ejection.« less

The Oligodendrocyte Progenitor Response to Demyelination

DTIC Science & Technology

2006-01-01

DATE 2006 2. REPORT TYPE 3. DATES COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE The Oligodendrocyte Progenitor Response to Demyelination...material in the thesis manuscript entitled: “The Oligodendrocyte Progenitor Response to Demyelination” is appropriately acknowledged and, beyond... oligodendrocyte progenitor (OP) amplification prior to remyelination. Myelin transcription factor 1 (Myt1) influences OP proliferation, differentiation, and

The core mass-radius relation for giants - A new test of stellar evolution theory

NASA Technical Reports Server (NTRS)

Joss, P. C.; Rappaport, S.; Lewis, W.

1987-01-01

It is demonstrated here that the measurable properties of systems containing degenerate dwarfs can be used as a direct test of the core mass-radius relation for moderate-mass giants if the final stages of the loss of the envelope of the progenitor giant occurred via stable critical lobe overflow. This relation directly probes the internal structure of stars at a relatively advanced evolutionary state and is only modestly influenced by adjustable parameters. The measured properties of six binary systems, including such diverse systems as Sirius and Procyon and two millisecond pulsars, are utilized to derive constraints on the empirical core mass-radius relation, and the constraints are compared to the theoretical relation. The possibility that the final stages of envelope ejection of the giant progenitor of Sirius B occurred via critical lobe overflow in historical times is considered.

Finding binaries from phase modulation of pulsating stars with Kepler: V. Orbital parameters, with eccentricity and mass-ratio distributions of 341 new binaries

NASA Astrophysics Data System (ADS)

Murphy, Simon J.; Moe, Maxwell; Kurtz, Donald W.; Bedding, Timothy R.; Shibahashi, Hiromoto; Boffin, Henri M. J.

2018-03-01

The orbital parameters of binaries at intermediate periods (102-103 d) are difficult to measure with conventional methods and are very incomplete. We have undertaken a new survey, applying our pulsation timing method to Kepler light curves of 2224 main-sequence A/F stars and found 341 non-eclipsing binaries. We calculate the orbital parameters for 317 PB1 systems (single-pulsator binaries) and 24 PB2s (double-pulsators), tripling the number of intermediate-mass binaries with full orbital solutions. The method reaches down to small mass ratios q ≈ 0.02 and yields a highly homogeneous sample. We parametrize the mass-ratio distribution using both inversion and Markov-Chain Monte Carlo forward-modelling techniques, and find it to be skewed towards low-mass companions, peaking at q ≈ 0.2. While solar-type primaries exhibit a brown dwarf desert across short and intermediate periods, we find a small but statistically significant (2.6σ) population of extreme-mass-ratio companions (q < 0.1) to our intermediate-mass primaries. Across periods of 100-1500 d and at q > 0.1, we measure the binary fraction of current A/F primaries to be 15.4 per cent ± 1.4 per cent, though we find that a large fraction of the companions (21 per cent ± 6 per cent) are white dwarfs in post-mass-transfer systems with primaries that are now blue stragglers, some of which are the progenitors of Type Ia supernovae, barium stars, symbiotics, and related phenomena. Excluding these white dwarfs, we determine the binary fraction of original A/F primaries to be 13.9 per cent ± 2.1 per cent over the same parameter space. Combining our measurements with those in the literature, we find the binary fraction across these periods is a constant 5 per cent for primaries M1 < 0.8 M⊙, but then increases linearly with log M1, demonstrating that natal discs around more massive protostars M1 ≳ 1 M⊙ become increasingly more prone to fragmentation. Finally, we find the eccentricity distribution of the main

Yap is essential for retinal progenitor cell cycle progression and RPE cell fate acquisition in the developing mouse eye.

PubMed

Kim, Jin Young; Park, Raehee; Lee, Jin Hwan J; Shin, Jinyeon; Nickas, Jenna; Kim, Seonhee; Cho, Seo-Hee

2016-11-15

Yap functions as a transcriptional regulator by acting together with sequence-specific DNA binding factors and transcription cofactors to mediate cell proliferation in developing epithelial tissues and tumors. An upstream kinase cascade controls nuclear localization and function in response to partially identified exogenous signals, including cell-to-cell contact. Nevertheless, its role in CNS development is poorly understood. In order to investigate Yap function in developing CNS, we characterized the cellular outcomes after selective Yap gene ablation in developing ocular tissues. When Yap was lost, presumptive retinal pigment epithelium acquired anatomical and molecular characteristics resembling those of the retinal epithelium rather than of RPE, including loss of pigmentation, pseudostratified epithelial morphology and ectopic induction of markers for retinal progenitor cells, like Chx10, and neurons, like β-Tubulin III. In addition, developing retina showed signs of progressive degeneration, including laminar folding, thinning and cell loss, which resulted from multiple defects in cell proliferation and survival, and in junction integrity. Furthermore, Yap-deficient retinal progenitors displayed decreased S-phase cells and altered cell cycle progression. Altogether, our studies not only illustrate the canonical function of Yap in promoting the proliferation of progenitors, but also shed new light on its evolutionarily conserved, instructive role in regional specification, maintenance of junctional integrity and precise regulation of cell proliferation during neuroepithelial development. Copyright © 2016 Elsevier Inc. All rights reserved.

Evolution of Cataclysmic Variables and Related Binaries Containing a White Dwarf

NASA Astrophysics Data System (ADS)

Kalomeni, B.; Nelson, L.; Rappaport, S.; Molnar, M.; Quintin, J.; Yakut, K.

2016-12-01

We present a binary evolution study of cataclysmic variables (CVs) and related systems with white dwarf (WD) accretors, including for example, AM CVn systems, classical novae, supersoft X-ray sources (SXSs), and systems with giant donor stars. Our approach intentionally avoids the complications associated with population synthesis algorithms, thereby allowing us to present the first truly comprehensive exploration of all of the subsequent binary evolution pathways that zero-age CVs might follow (assuming fully non-conservative, Roche-lobe overflow onto an accreting WD) using the sophisticated binary stellar evolution code MESA. The grid consists of 56,000 initial models, including 14 WD accretor masses, 43 donor-star masses (0.1-4.7 M ⊙), and 100 orbital periods. We explore evolution tracks in the orbital period and donor-mass (P orb-M don) plane in terms of evolution dwell times, masses of the WD accretor, accretion rate, and chemical composition of the center and surface of the donor star. We report on the differences among the standard CV tracks, those with giant donor stars, and ultrashort period systems. We show where in parameter space one can expect to find SXSs, present a diagnostic to distinguish among different evolutionary paths to forming AM CVn binaries, quantify how the minimum orbital period in CVs depends on the chemical composition of the donor star, and update the P orb(M wd) relation for binaries containing WDs whose progenitors lost their envelopes via stable Roche-lobe overflow. Finally, we indicate where in the P orb-M don the accretion disks will tend to be stable against the thermal-viscous instability, and where gravitational radiation signatures may be found with LISA.

Testing the Formation Scenarios of Binary Neutron Star Systems with Measurements of the Neutron Star Moment of Inertia

NASA Astrophysics Data System (ADS)

Newton, William G.; Steiner, Andrew W.; Yagi, Kent

2018-03-01

Two low-mass (M < 1.4 M ⊙) neutron stars, J0737-3039B and the companion to J1756-2251, show strong evidence of being formed in an ultra-stripped supernova explosion (US-SN) with a ONeMg or Fe progenitor. Using systematically generated sets of equations of state we map out the relationship between the moment of inertia of J0737-3039A, a candidate for a moment of inertia measurement within a decade, and the binding energy of the two low-mass neutron stars. This relationship, similar to the I-Love-Q relations, is more robust than a previously explored correlation between the binding energy and the slope of the nuclear symmetry energy L. We find that, if either J0737-3039B or the J1756-2251 companion were formed in a US-SN, no more than 0.06 M ⊙ could have been lost from the progenitor core. Furthermore, a measurement of the moment of inertia of J0737-3039A to within 10% accuracy can discriminate between formation scenarios and, given current constraints on the predicted core mass loss, potentially rule them out. Advanced LIGO can potentially measure the neutron star tidal polarizability to equivalent accuracy which, using the I-Love-Q relations, would obtain similar constraints on the formation scenarios. Such information would help constrain important aspects of binary evolution used for population synthesis predictions of the rate of binary neutron star mergers and resulting electromagnetic and gravitational wave signals. Further progress needs to be made in modeling the core-collapse process that leads to low-mass neutron stars, particularly in making robust predictions for the mass loss from the progenitor core.

The progenitors of stripped-envelope supernovae

NASA Astrophysics Data System (ADS)

Elias-Rosa, N.

2013-05-01

The type Ib/c SNe are those explosions which come from massive star populations, but lack hydrogen and helium. These have been proposed to originate in the explosions of massive Wolf-Rayet stars, and we should easily be able to detect the very luminous, young progenitors if they exist. However, there has not been any detection of progenitors so far. I present the study of two extinguished Type Ic SNe 2003jg and 2004cc. In both cases there is no clear evidence of a direct detection of their progenitors in deep pre-explosion images. Upper limits derived by inserting artificial stars of known brightness at random positions around the progenitor positions (M_v>-8.8 and M_v>-9 magnitudes for the progenitors of SN 2003jg and SN 2004cc, respectively) are brighter than those expected for a massive WC (Wolf-Rayet, carbon-rich) or WO (Wolf-Rayet, oxygen-rich) (e.g., approximately between -3 and -6 in the LMC). Therefore, this is perhaps further evidence that the most massive stars may give rise to black-holes forming SNe, or it is an undetected, compact massive star hidden by a thick dust lane. However the extinction toward these SNe is currently one of the largest known. Even if these results do not directly reveal the nature of the type Ic SN progenitors, they can help to characterize the dusty environment which surrounded the progenitor of the stripped-envelope CC-SNe.

Macular Degeneration: An Overview.

ERIC Educational Resources Information Center

Chalifoux, L. M.

1991-01-01

This article presents information on macular degeneration for professionals helping persons with this disease adjust to their visual loss. It covers types of macular degeneration, the etiology of the disease, and its treatment. Also considered are psychosocial problems and other difficulties that persons with age-related macular degeneration face.…

Coordinated temporal and spatial control of motor neuron and serotonergic neuron generation from a common pool of CNS progenitors.

PubMed

Pattyn, Alexandre; Vallstedt, Anna; Dias, José M; Samad, Omar Abdel; Krumlauf, Robb; Rijli, Filippo M; Brunet, Jean-Francois; Ericson, Johan

2003-03-15

Neural progenitor cells often produce distinct types of neurons in a specific order, but the determinants that control the sequential generation of distinct neuronal subclasses in the vertebrate CNS remain poorly defined. We examined the sequential generation of visceral motor neurons and serotonergic neurons from a common pool of neural progenitors located in the ventral hindbrain. We found that the temporal specification of these neurons varies along the anterior-posterior axis of the hindbrain, and that the timing of their generation critically depends on the integrated activities of Nkx- and Hox-class homeodomain proteins. A primary function of these proteins is to coordinate the spatial and temporal activation of the homeodomain protein Phox2b, which in turn acts as a binary switch in the selection of motor neuron or serotonergic neuronal fate. These findings assign new roles for Nkx, Hox, and Phox2 proteins in the control of temporal neuronal fate determination, and link spatial and temporal patterning of CNS neuronal fates.

Coordinated temporal and spatial control of motor neuron and serotonergic neuron generation from a common pool of CNS progenitors

PubMed Central

Pattyn, Alexandre; Vallstedt, Anna; Dias, José M.; Samad, Omar Abdel; Krumlauf, Robb; Rijli, Filippo M.; Brunet, Jean-Francois; Ericson, Johan

2003-01-01

Neural progenitor cells often produce distinct types of neurons in a specific order, but the determinants that control the sequential generation of distinct neuronal subclasses in the vertebrate CNS remain poorly defined. We examined the sequential generation of visceral motor neurons and serotonergic neurons from a common pool of neural progenitors located in the ventral hindbrain. We found that the temporal specification of these neurons varies along the anterior-posterior axis of the hindbrain, and that the timing of their generation critically depends on the integrated activities of Nkx- and Hox-class homeodomain proteins. A primary function of these proteins is to coordinate the spatial and temporal activation of the homeodomain protein Phox2b, which in turn acts as a binary switch in the selection of motor neuron or serotonergic neuronal fate. These findings assign new roles for Nkx, Hox, and Phox2 proteins in the control of temporal neuronal fate determination, and link spatial and temporal patterning of CNS neuronal fates. PMID:12651891

Dry Macular Degeneration

MedlinePlus

... developing macular degeneration. Include fish in your diet. Omega-3 fatty acids, which are found in fish, may ... macular degeneration. Nuts, such as walnuts, also contain omega-3 fatty acids. By Mayo Clinic Staff . Mayo Clinic ...

The 1.17 Day Orbit of the Double-degenerate (DA+DQ) NLTT 16249

NASA Astrophysics Data System (ADS)

Vennes, S.; Kawka, A.; O'Toole, S. J.; Thorstensen, J. R.

2012-09-01

New spectroscopic observations show that the double-degenerate system NLTT 16249 is in a close orbit (a = 5.6 ± 0.3 R ⊙) with a period of 1.17 days. The total mass of the system is estimated between 1.47 and 2.04 M ⊙ but it is not expected to merge within a Hubble timescale (t merge ≈ 1011 yr). Vennes & Kawka originally identified the system because of the peculiar composite hydrogen (DA class) and molecular (C2-DQ class and CN) spectra and the new observations establish this system as the first DA plus DQ close double degenerate. Also, the DQ component was the first of its class to show nitrogen dredged up from the core in its atmosphere. The star may be viewed as the first known DQ descendant of the born-again PG1159 stars. Alternatively, the presence of nitrogen may be the result of past interactions and truncated evolution in a close binary system. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under program ID 86.D-0562.

HST FUV/NUV Photometry of the Putative Binary Companion to the SN 1993J Progenitor

NASA Astrophysics Data System (ADS)

Miles, Nathan; Fox, Ori; Azalee Bostroem, K.; Zheng, WeiKang; Graham, Melissa; Van Dyk, Schuyler D.; Filippenko, Alexei V.; Matheson, Thomas; Dwarkadas, Vikram; Fransson, Claes; Smith, Nathan; Brink, Thomas

2018-06-01

A previous analysis of HST/COS spectra from 2012 revealed an FUV excess consistent with the presence of the hypothetical B-star companion to the SN 1993J progenitor. The spectrum, however, had low signal-to-noise and was blended with several other nearby stars within the 2.5 arcsec COS aperture. Since that time, the SN has sufficiently faded allowing for more accurate photometry to be performed. Here we present follow-up HST FUV/NUV imaging using the F140LP filter on ACS/SBC and the F218W, F275W, and F336W filters on WFC3/UVIS. This photometry isolates the UV flux from only the putative companion. We will discuss whether this new evidence removes all ambiguity about the nature of the companion once and for all.

Orbital variability in the eclipsing pulsar binary PSR B1957+20

NASA Technical Reports Server (NTRS)

Arzoumanian, Z.; Fruchter, A. S.; Taylor, J. H.

1994-01-01

We have conducted timing observations of the eclipsing millisecond binary pulsar PSR B1957+20, extending the span of data on this pulsar to more than five years. During this time the orbital period of the system has varied by roughly Delta P(sub b)/P(sub b) = 1.6 x 10(exp -7), changing quardratically with time and displaying with time and displaying an orbital period second derivative of P(sub b) = (1.43 +/- 0.08) x 10(exp -18)/sec. The previous measurement of a large negative orbital period derivative reflected only the short-term behavior of the system during the early observations; the orbital period derivative is now positive. If, as we suspect, the PSR B1957+20 system is undergoing quasi-cyclic orbital period variations similar to those found in other close binaries such as Algol and RS CVn, then the 0.025 solar mass companion to PSR B1957+20 is most likely non-degenerate, convective, and magnetically active.

EVOLUTION OF CATACLYSMIC VARIABLES AND RELATED BINARIES CONTAINING A WHITE DWARF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalomeni, B.; Rappaport, S.; Molnar, M.

We present a binary evolution study of cataclysmic variables (CVs) and related systems with white dwarf (WD) accretors, including for example, AM CVn systems, classical novae, supersoft X-ray sources (SXSs), and systems with giant donor stars. Our approach intentionally avoids the complications associated with population synthesis algorithms, thereby allowing us to present the first truly comprehensive exploration of all of the subsequent binary evolution pathways that zero-age CVs might follow (assuming fully non-conservative, Roche-lobe overflow onto an accreting WD) using the sophisticated binary stellar evolution code MESA. The grid consists of 56,000 initial models, including 14 WD accretor masses, 43more » donor-star masses (0.1–4.7 M {sub ⊙}), and 100 orbital periods. We explore evolution tracks in the orbital period and donor-mass ( P {sub orb}– M {sub don}) plane in terms of evolution dwell times, masses of the WD accretor, accretion rate, and chemical composition of the center and surface of the donor star. We report on the differences among the standard CV tracks, those with giant donor stars, and ultrashort period systems. We show where in parameter space one can expect to find SXSs, present a diagnostic to distinguish among different evolutionary paths to forming AM CVn binaries, quantify how the minimum orbital period in CVs depends on the chemical composition of the donor star, and update the P {sub orb}( M {sub wd}) relation for binaries containing WDs whose progenitors lost their envelopes via stable Roche-lobe overflow. Finally, we indicate where in the P {sub orb}– M {sub don} the accretion disks will tend to be stable against the thermal-viscous instability, and where gravitational radiation signatures may be found with LISA.« less

A survey of the Local Group of galaxies for symbiotic binary stars - I. First detection of symbiotic stars in M33

NASA Astrophysics Data System (ADS)

Mikołajewska, Joanna; Shara, Michael M.; Caldwell, Nelson; Iłkiewicz, Krystian; Zurek, David

2017-02-01

We present and discuss initial selection criteria and first results in M33 from a systematic search for extragalactic symbiotic stars. We show that the presence of diffuse ionized gas (DIG) emission can significantly contaminate the spectra of symbiotic star candidates. This important effect forces upon us a more stringent working definition of an extragalactic symbiotic star. We report the first detections and spectroscopic characterization of 12 symbiotic binaries in M33. We found that four of our systems contain carbon-rich giants. In another two of them, the giant seems to be a Zr-enhanced MS star, while the remaining six objects host M-type giants. The high number ratio of C to M giants in these binaries is consistent with the low metallicity of M33. The spatial and radial velocity distributions of these new symbiotic binaries are consistent with a wide range of progenitor star ages.

Angular momentum exchange in white dwarf binaries accreting through direct impact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepinsky, J. F.; Kalogera, V., E-mail: jeremy.sepinsky@scranton.edu, E-mail: vicky@northwestern.edu

We examine the exchange of angular momentum between the component spins and the orbit in semi-detached double white dwarf binaries undergoing mass transfer through direct impact of the transfer stream. We approximate the stream as a series of discrete massive particles ejected in the ballistic limit at the inner Lagrangian point of the donor toward the accretor. This work improves upon similar earlier studies in a number of ways. First, we self-consistently calculate the total angular momentum of the orbit at all times. This includes changes in the orbital angular momentum during the ballistic trajectory of the ejected mass, asmore » well as changes during the ejection/accretion due to the radial component of the particle's velocity. Second, we calculate the particle's ballistic trajectory for each system, which allows us to determine the precise position and velocity of the particle upon accretion. We can then include specific information about the radius of the accretor as well as the angle of impact. Finally, we ensure that the total angular momentum is conserved, which requires the donor star spin to vary self-consistently. With these improvements, we calculate the angular momentum change of the orbit and each binary component across the entire parameter space of direct impact double white dwarf binary systems. We find a significant decrease in the amount of angular momentum removed from the orbit during mass transfer, as well as cases where this process increases the angular momentum of the orbit at the expense of the spin angular momentum of the donor. We conclude that, unlike earlier claims in the literature, mass transfer through direct impact need not destabilize the binary and that the quantity and sign of the orbital angular momentum transfer depends on the binary properties, particularly the masses of the double white dwarf binary component stars. This stabilization may significantly impact the population synthesis calculations of the expected numbers

Loss of the tumor suppressor p15Ink4b enhances myeloid progenitor formation from common myeloid progenitors.

PubMed

Rosu-Myles, Michael; Taylor, Barbara J; Wolff, Linda

2007-03-01

The tumor suppressor p15Ink4b (Ink4b) is a cell-cycle inhibitor that is inactivated in a high percentage of acute myeloid leukemia and myeloid dysplasia syndrome cases. Despite this, the role of Ink4b in hematopoiesis remains unclear. Here we examined the role of Ink4b in blood cell formation using Ink4b-deficient (Ink4b(-/-)) mice. We compared the bone marrow (BM) of Ink4b(-/-) and wild-type mice using flow cytometric, colony-forming unit and competitive repopulating assays (CRA). The proliferation, differentiation, self-renewal, and apoptosis of progenitor cells were further compared by in vitro and in vivo methods. BM from Ink4b(-/-) mice contained increased numbers of granulocyte-monocyte progenitors and Gr-1(+) cells and showed a competitive advantage over wild-type cells in myeloid cell formation by CRA. Ink4b(-/-) progenitors did not demonstrate increased proliferation, self-renewing potential, or reduced apoptosis. Instead, Ink4b(-/-) common myeloid progenitors (CMPs) showed increased myeloid progenitor formation concomitant with reduced erythroid potential. This work establishes a role for Ink4b in regulating the differentiation of CMPs and indicates that loss of Ink4b enhances the formation of myeloid progenitors.

Long-lasting X-ray emission from type IIb supernova 2011dh and mass-loss history of the yellow supergiant progenitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maeda, Keiichi; Katsuda, Satoru; Bamba, Aya

2014-04-20

Type IIb supernova (SN) 2011dh, with conclusive detection of an unprecedented yellow supergiant (YSG) progenitor, provides an excellent opportunity to deepen our understanding on the massive star evolution in the final centuries toward the SN explosion. In this paper, we report on detection and analyses of thermal X-ray emission from SN IIb 2011dh at ∼500 days after the explosion on Chandra archival data, providing a solidly derived mass-loss rate of a YSG progenitor for the first time. We find that the circumstellar media should be dense, more than that expected from a Wolf-Rayet (W-R) star by one order of magnitude.more » The emission is powered by a reverse shock penetrating into an outer envelope, fully consistent with the YSG progenitor but not with a W-R progenitor. The density distribution at the outermost ejecta is much steeper than that expected from a compact W-R star, and this finding must be taken into account in modeling the early UV/optical emission from SNe IIb. The derived mass-loss rate is ∼3 × 10{sup –6} M {sub ☉} yr{sup –1} for the mass-loss velocity of ∼20 km s{sup –1} in the final ∼1300 yr before the explosion. The derived mass-loss properties are largely consistent with the standard wind mass-loss expected for a giant star. This is not sufficient to be a main driver to expel nearly all the hydrogen envelope. Therefore, the binary interaction, with a huge mass transfer having taken place at ≳ 1300 yr before the explosion, is a likely scenario to produce the YSG progenitor.« less

The Progenitor Dependence of Core-collapse Supernovae from Three-dimensional Simulations with Progenitor Models of 12–40 M ⊙

NASA Astrophysics Data System (ADS)

Ott, Christian D.; Roberts, Luke F.; da Silva Schneider, André; Fedrow, Joseph M.; Haas, Roland; Schnetter, Erik

2018-03-01

We present a first study of the progenitor star dependence of the three-dimensional (3D) neutrino mechanism of core-collapse supernovae. We employ full 3D general-relativistic multi-group neutrino radiation-hydrodynamics and simulate the postbounce evolutions of progenitors with zero-age main sequence masses of 12, 15, 20, 27, and 40 M ⊙. All progenitors, with the exception of the 12 M ⊙ star, experience shock runaway by the end of their simulations. In most cases, a strongly asymmetric explosion will result. We find three qualitatively distinct evolutions that suggest a complex dependence of explosion dynamics on progenitor density structure, neutrino heating, and 3D flow. (1) Progenitors with massive cores, shallow density profiles, and high post-core-bounce accretion rates experience very strong neutrino heating and neutrino-driven turbulent convection, leading to early shock runaway. Accretion continues at a high rate, likely leading to black hole formation. (2) Intermediate progenitors experience neutrino-driven, turbulence-aided explosions triggered by the arrival of density discontinuities at the shock. These occur typically at the silicon/silicon–oxygen shell boundary. (3) Progenitors with small cores and density profiles without strong discontinuities experience shock recession and develop the 3D standing-accretion shock instability (SASI). Shock runaway ensues late, once declining accretion rate, SASI, and neutrino-driven convection create favorable conditions. These differences in explosion times and dynamics result in a non-monotonic relationship between progenitor and compact remnant mass.

The binary fraction of planetary nebula central stars - III. the promise of VPHAS+

NASA Astrophysics Data System (ADS)

Barker, Helen; Zijlstra, Albert; De Marco, Orsola; Frew, David J.; Drew, Janet E.; Corradi, Romano L. M.; Eislöffel, Jochen; Parker, Quentin A.

2018-04-01

The majority of planetary nebulae (PNe) are not spherical, and current single-star models cannot adequately explain all the morphologies we observe. This has led to the Binary Hypothesis, which states that PNe are preferentially formed by binary systems. This hypothesis can be corroborated or disproved by comparing the estimated binary fraction of all PNe central stars (CS) to that of the supposed progenitor population. One way to quantify the rate of CS binarity is to detect near infrared excess indicative of a low-mass main-sequence companion. In this paper, a sample of known PNe within data release 2 of the ongoing VPHAS+ is investigated. We give details of the method used to calibrate VPHAS+ photometry, and present the expected colours of CS and main-sequence stars within the survey. Objects were scrutinized to remove PN mimics from our sample and identify true CS. Within our final sample of seven CS, six had previously either not been identified or confirmed. We detected an i-band excess indicative of a low-mass companion star in three CS, including one known binary, leading us to conclude that VPHAS+ provides the precise photometry required for the IR excess method presented here, and will likely improve as the survey completes and the calibration process finalized. Given the promising results from this trial sample, the entire VPHAS+ catalogue should be used to study PNe and extend the IR excess-tested CS sample.

The planetary nebula IC 4776 and its post-common-envelope binary central star

NASA Astrophysics Data System (ADS)

Sowicka, Paulina; Jones, David; Corradi, Romano L. M.; Wesson, Roger; García-Rojas, Jorge; Santander-García, Miguel; Boffin, Henri M. J.; Rodríguez-Gil, Pablo

2017-11-01

We present a detailed analysis of IC 4776, a planetary nebula displaying a morphology believed to be typical of central star binarity. The nebula is shown to comprise a compact hourglass-shaped central region and a pair of precessing jet-like structures. Time-resolved spectroscopy of its central star reveals a periodic radial velocity variability consistent with a binary system. Whilst the data are insufficient to accurately determine the parameters of the binary, the most likely solutions indicate that the secondary is probably a low-mass main-sequence star. An empirical analysis of the chemical abundances in IC 4776 indicates that the common-envelope phase may have cut short the asymptotic giant branch evolution of the progenitor. Abundances calculated from recombination lines are found to be discrepant by a factor of approximately 2 relative to those calculated using collisionally excited lines, suggesting a possible correlation between low-abundance discrepancy factors and intermediate-period post-common-envelope central stars and/or Wolf-Rayet central stars. The detection of a radial velocity variability associated with the binarity of the central star of IC 4776 may be indicative of a significant population of (intermediate-period) post-common-envelope binary central stars that would be undetected by classic photometric monitoring techniques.

Circulating endothelial progenitor cells and cardiovascular outcomes.

PubMed

Werner, Nikos; Kosiol, Sonja; Schiegl, Tobias; Ahlers, Patrick; Walenta, Katrin; Link, Andreas; Böhm, Michael; Nickenig, Georg

2005-09-08

Endothelial progenitor cells derived from bone marrow are believed to support the integrity of the vascular endothelium. The number and function of endothelial progenitor cells correlate inversely with cardiovascular risk factors, but the prognostic value associated with circulating endothelial progenitor cells has not been defined. The number of endothelial progenitor cells positive for CD34 and kinase insert domain receptor (KDR) was determined with the use of flow cytometry in 519 patients with coronary artery disease as confirmed on angiography. After 12 months, we evaluated the association between baseline levels of endothelial progenitor cells and death from cardiovascular causes, the occurrence of a first major cardiovascular event (myocardial infarction, hospitalization, revascularization, or death from cardiovascular causes), revascularization, hospitalization, and death from all causes. A total of 43 participants died, 23 from cardiovascular causes. A first major cardiovascular event occurred in 214 patients. The cumulative event-free survival rate increased stepwise across three increasing baseline levels of endothelial progenitor cells in an analysis of death from cardiovascular causes, a first major cardiovascular event, revascularization, and hospitalization. After adjustment for age, sex, vascular risk factors, and other relevant variables, increased levels of endothelial progenitor cells were associated with a reduced risk of death from cardiovascular causes (hazard ratio, 0.31; 95 percent confidence interval, 0.16 to 0.63; P=0.001), a first major cardiovascular event (hazard ratio, 0.74; 95 percent confidence interval, 0.62 to 0.89; P=0.002), revascularization (hazard ratio, 0.77; 95 percent confidence interval, 0.62 to 0.95; P=0.02), and hospitalization (hazard ratio, 0.76; 95 percent confidence interval, 0.63 to 0.94; P=0.01). Endothelial progenitor-cell levels were not predictive of myocardial infarction or of death from all causes. The level of

Degenerate pressure driven modified nucleus-acoustic waves in degenerate plasmas

NASA Astrophysics Data System (ADS)

Mamun, A. A.

2018-02-01

The existence of degenerate pressure driven modified nucleus-acoustic (DPDMNA) waves propagating in a cold degenerate quantum plasma (DQP) system [containing cold inertialess degenerate electron species (DES), cold inertial non-degenerate light nucleus species (LNS), and stationary heavy nucleus species (HNS)] is predicted for the first time. The DPDMNA waves (in which the mass density of the cold LNS provides the inertia and the cold inertialess DES gives rise to the restoring force) are new since they completely disappear if the degenerate pressure of the cold DES is neglected. It is found that the phase speed (Vp) of the DPDMNA waves decreases with the rise of the charge number density of the stationary HNS for both non-relativistic and ultra-relativistic DES, and that the ultra-relativistic DES does not have any effect on Vp when β = 1, where β = Λc/Λe with Λ e = ne 0 - 1 / 3 being the average inter-electron distance in the DQP system and Λc being the constant (˜10-10 cm) for the DES. However, the ultra-relativistic DES does have quite a significant effect on Vp for β ≫ 1 and β ≪ 1, and the ultra-relativistic effect significantly enhances (reduces) Vp for β ≫ 1 (β ≪ 1). The DPDMNA waves and their dispersion properties are expected to be useful in understanding the basic features of the electrostatic perturbation mode in space and laboratory DQP systems.

Possible Progenitor of Special Supernova Type Detected

NASA Astrophysics Data System (ADS)

2008-04-01

Using data from NASA's Chandra X-ray Observatory, scientists have reported the possible detection of a binary star system that was later destroyed in a supernova explosion. The new method they used provides great future promise for finding the detailed origin of these important cosmic events. In an article appearing in the February 14th issue of the journal Nature, Rasmus Voss of the Max Planck Institute for Extraterrestrial Physics in Germany and Gijs Nelemans of Radboud University in the Netherlands searched Chandra images for evidence of a much sought after, but as yet unobserved binary system - one that was about to go supernova. Near the position of a recently detected supernova, they discovered an object in Chandra images taken more than four years before the explosion. Optical image of SN 2007on Optical image of SN 2007on The supernova, known as SN 2007on, was identified as a Type Ia supernova. Astronomers generally agree that Type Ia supernovas are produced by the explosion of a white dwarf star in a binary star system. However, the exact configuration and trigger for the explosion is unclear. Is the explosion caused by a collision between two white dwarfs, or because a white dwarf became unstable by pulling too much material off a companion star? Answering such questions is a high priority because Type Ia supernovas are major sources of iron in the Universe. Also, because of their nearly uniform intrinsic brightness, Type Ia supernova are used as important tools by scientists to study the nature of dark energy and other cosmological issues. People Who Read This Also Read... Oldest Known Objects Are Surprisingly Immature Black Holes Have Simple Feeding Habits Discovery of Most Recent Supernova in Our Galaxy Geriatric Pulsar Still Kicking "Right now these supernovas are used as black boxes to measure distances and derive the rate of expansion of the universe," said Nelemans. "What we're trying to do is look inside the box." If the supernova explosion is

The True Ultracool Binary Fraction Using Spectral Binaries

NASA Astrophysics Data System (ADS)

Bardalez Gagliuffi, Daniella; Burgasser, Adam J.; Schmidt, Sarah J.; Gagné, Jonathan; Faherty, Jacqueline K.; Cruz, Kelle; Gelino, Chris

2018-01-01

Brown dwarfs bridge the gap between stars and giant planets. While the essential mechanisms governing their formation are not well constrained, binary statistics are a direct outcome of the formation process, and thus provide a means to test formation theories. Observational constraints on the brown dwarf binary fraction place it at 10 ‑ 20%, dominated by imaging studies (85% of systems) with the most common separation at 4 AU. This coincides with the resolution limit of state-of-the-art imaging techniques, suggesting that the binary fraction is underestimated. We have developed a separation-independent method to identify and characterize tightly-separated (< 5 AU) binary systems of brown dwarfs as spectral binaries by identifying traces of methane in the spectra of late-M and early-L dwarfs. Imaging follow-up of 17 spectral binaries yielded 3 (18%) resolved systems, corroborating the observed binary fraction, but 5 (29%) known binaries were missed, reinforcing the hypothesis that the short-separation systems are undercounted. In order to find the true binary fraction of brown dwarfs, we have compiled a volume-limited, spectroscopic sample of M7-L5 dwarfs and searched for T dwarf companions. In the 25 pc volume, 4 candidates were found, three of which are already confirmed, leading to a spectral binary fraction of 0.95 ± 0.50%, albeit for a specific combination of spectral types. To extract the true binary fraction and determine the biases of the spectral binary method, we have produced a binary population simulation based on different assumptions of the mass function, age distribution, evolutionary models and mass ratio distribution. Applying the correction fraction resulting from this method to the observed spectral binary fraction yields a true binary fraction of 27 ± 4%, which is roughly within 1σ of the binary fraction obtained from high resolution imaging studies, radial velocity and astrometric monitoring. This method can be extended to identify giant

Embryonic Heart Progenitors and Cardiogenesis

PubMed Central

Brade, Thomas; Pane, Luna S.; Moretti, Alessandra; Chien, Kenneth R.; Laugwitz, Karl-Ludwig

2013-01-01

The mammalian heart is a highly specialized organ, comprised of many different cell types arising from distinct embryonic progenitor populations during cardiogenesis. Three precursor populations have been identified to contribute to different myocytic and nonmyocytic cell lineages of the heart: cardiogenic mesoderm cells (CMC), the proepicardium (PE), and cardiac neural crest cells (CNCCs). This review will focus on molecular cues necessary for proper induction, expansion, and lineage-specific differentiation of these progenitor populations during cardiac development in vivo. Moreover, we will briefly discuss how the knowledge gained on embryonic heart progenitor biology can be used to develop novel therapeutic strategies for the management of congenital heart disease as well as for improvement of cardiac function in ischemic heart disease. PMID:24086063

Molecular and cell-based therapies for muscle degenerations: a road under construction.

PubMed

Berardi, Emanuele; Annibali, Daniela; Cassano, Marco; Crippa, Stefania; Sampaolesi, Maurilio

2014-01-01

Despite the advances achieved in understanding the molecular biology of muscle cells in the past decades, there is still need for effective treatments of muscular degeneration caused by muscular dystrophies and for counteracting the muscle wasting caused by cachexia or sarcopenia. The corticosteroid medications currently in use for dystrophic patients merely help to control the inflammatory state and only slightly delay the progression of the disease. Unfortunately, walkers and wheel chairs are the only options for such patients to maintain independence and walking capabilities until the respiratory muscles become weak and the mechanical ventilation is needed. On the other hand, myostatin inhibition, IL-6 antagonism and synthetic ghrelin administration are examples of promising treatments in cachexia animal models. In both dystrophies and cachectic syndrome the muscular degeneration is extremely relevant and the translational therapeutic attempts to find a possible cure are well defined. In particular, molecular-based therapies are common options to be explored in order to exploit beneficial treatments for cachexia, while gene/cell therapies are mostly used in the attempt to induce a substantial improvement of the dystrophic muscular phenotype. This review focuses on the description of the use of molecular administrations and gene/stem cell therapy to treat muscular degenerations. It reviews previous trials using cell delivery protocols in mice and patients starting with the use of donor myoblasts, outlining the likely causes for their poor results and briefly focusing on satellite cell studies that raise new hope. Then it proceeds to describe recently identified stem/progenitor cells, including pluripotent stem cells and in relationship to their ability to home within a dystrophic muscle and to differentiate into skeletal muscle cells. Different known features of various stem cells are compared in this perspective, and the few available examples of their use in

[An in vivo study of basic fibroblast growth factor on activation and proliferation of retinal progenitor cell in RCS rats].

PubMed

Xia, Xiaoping; Song, Guoxiang; Liu, Xiangfu; Tang, Xiangchen; Ye, Hui

2010-11-01

To investigate the effect of intravitreal basic fibroblast growth factor(bFGF) on activation and proliferation of endogenous retinal progenitor cells in the Royal College of Surgeons(RCS) rats. Twenty-four rats were studied after the 30th postnatal day(≥30). Eighteen affected rats were randomly divided into 3 groups: bFGF-treated, vehicle-treated and untreated group, and 6 unaffected rats were used as normal controls. Six μl of bFGF (5μg/10 μl) or vehicle was injected into the vitreous on days 31, 33 and 35 after birth (P31, P33, P35) in the bFGF group and vehicle group, and no injection was administered in the untreated and control groups. All the rats were euthanized, and their eyes were enucleated, hemisected and fixed at 50 d after birth for immunohistochemistry and measurement of outer nuclear layer thickness. Nestin and Chx10 were positively expressed in all retinal layers, intravitreous injection of bFGF in retina-dystrophic RCS(RCS-p+/Lav) rats induced intense labeling for the retinal progenitor cell markers Chx10 and Nestin, which were highly colocalized. Fluorescence intensity for both labels was slightly less in the control rats, and much less in the vehicle-injected rats as well as in the untreated RCS rats. The outer nuclear layer (ONL) was significantly thicker in bFGF group than that of vehicle-treated or untreated group(p<0.01), but thinner than that of the control group(p<0.01). No significant difference was observed in the ONL thicknesses between the vehicle group and untreated group(P>0.05). bFGF may contribute to the activation of retinal progenitor cells in RCS rats, thus counteract degeneration by promoting the proliferation of the progenitor cells.

Evolution of an electron-positron plasma produced by induced gravitational collapse in binary-driven hypernovae

NASA Astrophysics Data System (ADS)

Melon Fuksman, J. D.; Becerra, L.; Bianco, C. L.; Karlica, M.; Kovacevic, M.; Moradi, R.; Muccino, M.; Pisani, G. B.; Primorac, D.; Rueda, J. A.; Ruffini, R.; Vereshchagin, G. V.; Wang, Y.

2018-01-01

The binary-driven hypernova (BdHN) model has been introduced in the past years, to explain a subfamily of gamma-ray bursts (GRBs) with energies Eiso ≥ 1052 erg associated with type Ic supernovae. Such BdHNe have as progenitor a tight binary system composed of a carbon-oxigen (CO) core and a neutron star undergoing an induced gravitational collapse to a black hole, triggered by the CO core explosion as a supernova (SN). This collapse produces an optically-thick e+e- plasma, which expands and impacts onto the SN ejecta. This process is here considered as a candidate for the production of X-ray flares, which are frequently observed following the prompt emission of GRBs. In this work we follow the evolution of the e+e- plasma as it interacts with the SN ejecta, by solving the equations of relativistic hydrodynamics numerically. Our results are compatible with the Lorentz factors estimated for the sources that produce the flares, of typically Γ ≲ 4.

X-82 to Treat Age-related Macular Degeneration

ClinicalTrials.gov

2018-05-30

Age-Related Macular Degeneration (AMD); Macular Degeneration; Exudative Age-related Macular Degeneration; AMD; Macular Degeneration, Age-related, 10; Eye Diseases; Retinal Degeneration; Retinal Diseases

Accelerated cellular senescence in degenerate intervertebral discs: a possible role in the pathogenesis of intervertebral disc degeneration

PubMed Central

Le Maitre, Christine Lyn; Freemont, Anthony John; Hoyland, Judith Alison

2007-01-01

Current evidence implicates intervertebral disc degeneration as a major cause of low back pain, although its pathogenesis is poorly understood. Numerous characteristic features of disc degeneration mimic those seen during ageing but appear to occur at an accelerated rate. We hypothesised that this is due to accelerated cellular senescence, which causes fundamental changes in the ability of disc cells to maintain the intervertebral disc (IVD) matrix, thus leading to IVD degeneration. Cells isolated from non-degenerate and degenerate human tissue were assessed for mean telomere length, senescence-associated β-galactosidase (SA-β-gal), and replicative potential. Expression of P16INK4A (increased in cellular senescence) was also investigated in IVD tissue by means of immunohistochemistry. RNA from tissue and cultured cells was used for real-time polymerase chain reaction analysis for matrix metalloproteinase-13, ADAMTS 5 (a disintegrin and metalloprotease with thrombospondin motifs 5), and P16INK4A. Mean telomere length decreased with age in cells from non-degenerate tissue and also decreased with progressive stages of degeneration. In non-degenerate discs, there was an age-related increase in cellular expression of P16INK4A. Cells from degenerate discs (even from young patients) exhibited increased expression of P16INK4A, increased SA-β-gal staining, and a decrease in replicative potential. Importantly, there was a positive correlation between P16INK4A and matrix-degrading enzyme gene expression. Our findings indicate that disc cell senescence occurs in vivo and is accelerated in IVD degeneration. Furthermore, the senescent phenotype is associated with increased catabolism, implicating cellular senescence in the pathogenesis of IVD degeneration. PMID:17498290

Learning to assign binary weights to binary descriptor

NASA Astrophysics Data System (ADS)

Huang, Zhoudi; Wei, Zhenzhong; Zhang, Guangjun

2016-10-01

Constructing robust binary local feature descriptors are receiving increasing interest due to their binary nature, which can enable fast processing while requiring significantly less memory than their floating-point competitors. To bridge the performance gap between the binary and floating-point descriptors without increasing the computational cost of computing and matching, optimal binary weights are learning to assign to binary descriptor for considering each bit might contribute differently to the distinctiveness and robustness. Technically, a large-scale regularized optimization method is applied to learn float weights for each bit of the binary descriptor. Furthermore, binary approximation for the float weights is performed by utilizing an efficient alternatively greedy strategy, which can significantly improve the discriminative power while preserve fast matching advantage. Extensive experimental results on two challenging datasets (Brown dataset and Oxford dataset) demonstrate the effectiveness and efficiency of the proposed method.

A catalogue of potentially bright close binary gravitational wave sources

NASA Technical Reports Server (NTRS)

Webbink, Ronald F.

1985-01-01

This is a current print-out of results of a survey, undertaken in the spring of 1985, to identify those known binary stars which might produce significant gravitational wave amplitudes at earth, either dimensionless strain amplitudes exceeding a threshold h = 10(exp -21), or energy fluxes exceeding F = 10(exp -12) erg cm(exp -2) s(exp -1). All real or putative binaries brighter than a certain limiting magnitude (calculated as a function of primary spectral type, orbital period, orbital eccentricity, and bandpass) are included. All double degenerate binaries and Wolf-Rayet binaries with known or suspected orbital periods have also been included. The catalog consists of two parts: a listing of objects in ascending order of Right Ascension (Equinox B1950), followed by an index, listing of objects by identification number according to all major stellar catalogs. The object listing is a print-out of the spreadsheets on which the catalog is currently maintained. It should be noted that the use of this spreadsheet program imposes some limitations on the display of entries. Text entries which exceed the cell size may appear in truncated form, or may run into adjacent columns. Greek characters are not available; they are represented here by the first two or three letters of their Roman names, the first letter appearing as a capital or lower-case letter according to whether the capital or lower-case Greek character is represented. Neither superscripts nor subscripts are available; they appear here in normal position and type-face. The index provides the Right Ascension and Declination of objects sorted by catalogue number.

Identification and isolation of adult liver stem/progenitor cells.

PubMed

Tanaka, Minoru; Miyajima, Atsushi

2012-01-01

Hepatoblasts are considered to be liver stem/progenitor cells in the fetus because they propagate and differentiate into two types of liver epithelial cells, hepatocytes and cholangiocytes. In adults, oval cells that emerge in severely injured liver are considered facultative hepatic stem/progenitor cells. However, the nature of oval cells has remained unclear for long time due to the lack of a method to isolate them. It has also been unclear whether liver stem/progenitor cells exist in normal adult liver. Recently, we and others have successfully identified oval cells and adult liver stem/progenitor cells. Here, we describe the identification and isolation of mouse liver stem/progenitor cells by utilizing antibodies against specific cell surface marker molecules.

Comparative analysis of circulating endothelial progenitor cells in age-related macular degeneration patients using automated rare cell analysis (ARCA) and fluorescence activated cell sorting (FACS).

PubMed

Say, Emil Anthony T; Melamud, Alex; Esserman, Denise Ann; Povsic, Thomas J; Chavala, Sai H

2013-01-01

Patients with age-related macular degeneration (ARMD) begin with non-neovascular (NNV) phenotypes usually associated with good vision. Approximately 20% of NNV-ARMD patients will convert to vision debilitating neovascular (NV) ARMD, but precise timing of this event is unknown. Developing a clinical test predicting impending conversion to NV-ARMD is necessary to prevent vision loss. Endothelial progenitor cells (EPCs), defined as CD34(+)VEGR2(+) using traditional fluorescence activated cell sorting (FACS), are rare cell populations known to be elevated in patients with NV-ARMD compared to NNV-ARMD. FACS has high inter-observer variability and subjectivity when measuring rare cell populations precluding development into a diagnostic test. We hypothesized that automated rare cell analysis (ARCA), a validated and FDA-approved technology for reproducible rare cell identification, can enumerate EPCs in ARMD patients more reliably. This pilot study serves as the first step in developing methods for reproducibly predicting ARMD phenotype conversion. We obtained peripheral venous blood samples in 23 subjects with NNV-ARMD or treatment naïve NV-ARMD. Strict criteria were used to exclude subjects with known angiogenic diseases to minimize confounding results. Blood samples were analyzed in masked fashion in two separate laboratories. EPCs were independently enumerated using ARCA and FACS within 24 hours of blood sample collection, and p<0.2 was considered indicative of a trend for this proof of concept study, while statistical significance was established at 0.05. We measured levels of CD34(+)VEGFR2(+) EPCs suggestive of a trend with higher values in patients with NV compared to NNV-ARMD (p = 0.17) using ARCA. Interestingly, CD34(+)VEGR2(+) EPC analysis using FACS did not produce similar results (p = 0.94). CD34(+)VEGR2(+) may have predictive value for EPC enumeration in future ARCA studies. EPC measurements in a small sample size were suggestive of a trend in ARMD using

Comparative Analysis of Circulating Endothelial Progenitor Cells in Age-Related Macular Degeneration Patients Using Automated Rare Cell Analysis (ARCA) and Fluorescence Activated Cell Sorting (FACS)

PubMed Central

Say, Emil Anthony T.; Melamud, Alex; Esserman, Denise Ann; Povsic, Thomas J.; Chavala, Sai H.

2013-01-01

Background Patients with age-related macular degeneration (ARMD) begin with non-neovascular (NNV) phenotypes usually associated with good vision. Approximately 20% of NNV-ARMD patients will convert to vision debilitating neovascular (NV) ARMD, but precise timing of this event is unknown. Developing a clinical test predicting impending conversion to NV-ARMD is necessary to prevent vision loss. Endothelial progenitor cells (EPCs), defined as CD34+VEGR2+ using traditional fluorescence activated cell sorting (FACS), are rare cell populations known to be elevated in patients with NV-ARMD compared to NNV-ARMD. FACS has high inter-observer variability and subjectivity when measuring rare cell populations precluding development into a diagnostic test. We hypothesized that automated rare cell analysis (ARCA), a validated and FDA-approved technology for reproducible rare cell identification, can enumerate EPCs in ARMD patients more reliably. This pilot study serves as the first step in developing methods for reproducibly predicting ARMD phenotype conversion. Methods We obtained peripheral venous blood samples in 23 subjects with NNV-ARMD or treatment naïve NV-ARMD. Strict criteria were used to exclude subjects with known angiogenic diseases to minimize confounding results. Blood samples were analyzed in masked fashion in two separate laboratories. EPCs were independently enumerated using ARCA and FACS within 24 hours of blood sample collection, and p<0.2 was considered indicative of a trend for this proof of concept study, while statistical significance was established at 0.05. Results We measured levels of CD34+VEGFR2+ EPCs suggestive of a trend with higher values in patients with NV compared to NNV-ARMD (p = 0.17) using ARCA. Interestingly, CD34+VEGR2+ EPC analysis using FACS did not produce similar results (p = 0.94). Conclusions CD34+VEGR2+ may have predictive value for EPC enumeration in future ARCA studies. EPC measurements in a small sample size were

Parallaxes and Distance Estimates for Eleven Cataclysmic Binary Stars

NASA Astrophysics Data System (ADS)

Thorstensen, John R.; Lepine, S.; Shara, M.; Peters, C. S.

2007-12-01

We will present new distance estimates for eleven cataclysmic binary stars, based on trigonometric parallaxes measured with the 2.4m Hiltner telescope at MDM Observatory. The MDM parallaxes have typical uncertainties of 1 mas. A Bayesian formalism is used to find the most likely distance given the parallax, proper motion, and prior information. Results will be reported for the eclipsing dwarf nova HT Cas, for which our parallax favors a relatively short distance; KT Per, which proves to have a K-dwarf physical companion; the 65-minute double-degenerate system V396 Hya (CE 315); and the low accretion rate-polar MQ Dra (SDSS 1553). We gratefully acknowledge funding from the NSF through grants AST-9987334, AST-0307413, and AST-0708810.

Reduction of Endoplasmic Reticulum Stress Improves Angiogenic Progenitor Cell function in a Mouse Model of Type 1 Diabetes.

PubMed

Bhatta, Maulasri; Chatpar, Krishna; Hu, Zihua; Wang, Joshua J; Zhang, Sarah X

2018-04-27

Persistent vascular injury and degeneration in diabetes are attributed in part to defective reparatory function of angiogenic cells. Our recent work implicates endoplasmic reticulum (ER) stress in high-glucose-induced bone marrow (BM) progenitor dysfunction. Herein, we investigated the in vivo role of ER stress in angiogenic abnormalities of streptozotocin-induced diabetic mice. Our data demonstrate that ER stress markers and inflammatory gene expression in BM mononuclear cells and hematopoietic progenitor cells increase dynamically with disease progression. Increased CHOP and cleaved caspase- 3 levels were observed in BM--derived early outgrowth cells (EOCs) after 3 months of diabetes. Inhibition of ER stress by ex vivo or in vivo chemical chaperone treatment significantly improved the generation and migration of diabetic EOCs while reducing apoptosis of these cells. Chemical chaperone treatment also increased the number of circulating angiogenic cells in peripheral blood, alleviated BM pathology, and enhanced retinal vascular repair following ischemia/reperfusion in diabetic mice. Mechanistically, knockdown of CHOP alleviated high-glucose-induced EOC dysfunction and mitigated apoptosis, suggesting a pivotal role of CHOP in mediating ER stress-associated angiogenic cell injury in diabetes. Together, our study suggests that targeting ER signaling may provide a promising and novel approach to enhancing angiogenic function in diabetes.

Binary black hole mergers within the LIGO horizon: statistical properties and prospects for detecting electromagnetic counterparts

NASA Astrophysics Data System (ADS)

Perna, Rosalba; Chruslinska, Martyna; Corsi, Alessandra; Belczynski, Krzysztof

2018-07-01

Binary black holes (BBHs) are one of the endpoints of isolated binary evolution, and their mergers a leading channel for gravitational wave events. Here, using the evolutionary code STARTRACK, we study the statistical properties of the BBH population from isolated binary evolution for a range of progenitor star metallicities and BH natal kicks. We compute the mass function and the distribution of the primary BH spin a as a result of mass accretion during the binary evolution, and find that this is not an efficient process to spin-up BHs, producing an increase by at most a ˜ 0.2-0.3 for very low natal BH spins. We further compute the distribution of merger sites within the host galaxy, after tracking the motion of the binaries in the potentials of a massive spiral, a massive elliptical, and a dwarf galaxy. We find that a fraction of 70-90 per cent of mergers in massive galaxies and of 40-60 per cent in dwarfs (range mostly sensitive to the natal kicks) are expected to occur inside of their hosts. The number density distribution at the merger sites further allows us to estimate the broad-band luminosity distribution that BBH mergers would produce, if associated with a kinetic energy release in an outflow, which, as a reference, we assume at the level inferred for the Fermi GBM counterpart to GW150914, with the understanding that current limits from the O1 and O2 runs would require such emission to be produced within a jet of angular size within ≲50°.

Binary Black Hole Mergers within the LIGO Horizon: Statistical Properties and prospects for detecting Electromagnetic Counterparts

NASA Astrophysics Data System (ADS)

Perna, Rosalba; Chruslinska, Martyna; Corsi, Alessandra; Belczynski, Krzysztof

2018-03-01

Binary black holes (BBHs) are one of the endpoints of isolated binary evolution, and their mergers a leading channel for gravitational wave events. Here, using the evolutionary code STARTRACK, we study the statistical properties of the BBH population from isolated binary evolution for a range of progenitor star metallicities and BH natal kicks. We compute the mass function and the distribution of the primary BH spin a as a result of mass accretion during the binary evolution, and find that this is not an efficient process to spin up BHs, producing an increase by at most a ˜ 0.2-0.3 for very low natal BH spins. We further compute the distribution of merger sites within the host galaxy, after tracking the motion of the binaries in the potentials of a massive spiral, a massive elliptical, and a dwarf galaxy. We find that a fraction of 70-90% of mergers in massive galaxies and of 40-60% in dwarfs (range mostly sensitive to the natal kicks) is expected to occur inside of their hosts. The number density distribution at the merger sites further allows us to estimate the broadband luminosity distribution that BBH mergers would produce, if associated with a kinetic energy release in an outflow, which, as a reference, we assume at the level inferred for the Fermi GBM counterpart to GW150914, with the understanding that current limits from the O1 and O2 runs would require such emission to be produced within a jet of angular size within ≲ 50°.

Black-hole binaries as relics of gamma-ray burst/hypernova explosions

NASA Astrophysics Data System (ADS)

Moreno Mendez, Enrique

The Collapsar model, in which a fast-spinning massive star collapses into a Kerr black hole, has become the standard model to explain long-soft gamma-ray bursts and hypernova explosions (GRB/HN). However, stars massive enough (those with ZAMS mass ≳ (18--20) M⊙ ) to produce these events evolve through a path that loses too much angular momentum to produce a central engine capable of delivering the necessary energy. In this work I suggest that the soft X-ray transient sources are the remnants of GRBs/HNe. Binaries in which the massive primary star evolves a carbon-oxygen burning core, then start to transfer material to the secondary star (Case C mass transfer), causing the orbit to decay until a common-envelope phase sets in. The secondary spirals in, further narrowing the orbit of the binary and removing the hydrogen envelope of the primary star. Eventually the primary star becomes tidally locked and spins up, acquiring enough rotational energy to power up a GRB/HN explosion. The central engine producing the GRB/HN event is the Kerr black hole acting through the Blandford-Znajek mechanism. This model can explain not only the long-soft GRBs, but also the subluminous bursts (which comprise ˜ 97% of the total), the long-soft bursts and the short-hard bursts (in a neutron star, black hole merger). Because of our binary evolution through Case C mass transfer, it turns out that for the subluminous and cosmological bursts, the angular momentum O is proportional to m3/2D , where mD is the mass of the donor (secondary star). This binary evolution model has a great advantage over the Woosley Collapsar model; one can "dial" the donor mass in order to obtain whatever angular momentum is needed to drive the explosion. Population syntheses show that there are enough binaries to account for the progenitors of all known classes of GRBs.

PRS J0045-7319: A massive SMC binary

NASA Astrophysics Data System (ADS)

Bell, J. F.

1994-04-01

The existence of X-ray binary systems shows that neutron stars are found in orbit around massive stars. Before these systems enter the mass accretion phase, one would expect the neutron star might be detectable as a radio pulsar. The discovery of PSR B1259-63 by Johnston et al. (1992, Astrophys. J. Lett, 387, L37), which is in orbit around the Be star SS2883, provided the first evidence for such systems. PSR J0045-7319 was discovered in a systematic search of the Magellanic Clouds for radio pulsars by McConnell et al. (1991, Mon. Not. R. Astron. Soc., 249, 645). Its dispersion measure of 105 pc/cu cm assures its association with the Small Magellanic Cloud making it the only known pulsar in the SMC. The discovery of regular Doppler shifts of the pulse period of PSR J0045-7319 implies that the pulsar is in a highly eccentric 51-day binary orbit, making it the most luminous binary pulsar known (Kaspi et al., 1993, submitted to Astrophys. J.). The observed Keplerian orbital parameters show that the companion mass is greater the 4 solar mass. Optical observations of the field reveal a 16th magnitude, 11 solar mass, B1 main-sequence star, which we conclude is the pulsar's companion. The timing observations imply that this pulsar has not been spun up by accretion from the companion. This suggests that, like the PSR B1259-63 binary system, the PSR J0045-7319 system is a progenitor of an X-ray binary system. At periastron the pulsar approaches to within six stellar radii of the companion.

Thyroid hormone accelerates the differentiation of adult hippocampal progenitors.

PubMed

Kapoor, R; Desouza, L A; Nanavaty, I N; Kernie, S G; Vaidya, V A

2012-09-01

Disrupted thyroid hormone function evokes severe physiological consequences in the immature brain. In adulthood, although clinical reports document an effect of thyroid hormone status on mood and cognition, the molecular and cellular changes underlying these behavioural effects are poorly understood. More recently, the subtle effects of thyroid hormone on structural plasticity in the mature brain, in particular on adult hippocampal neurogenesis, have come to be appreciated. However, the specific stages of adult hippocampal progenitor development that are sensitive to thyroid hormone are not defined. Using nestin-green fluorescent protein reporter mice, we demonstrate that thyroid hormone mediates its effects on hippocampal neurogenesis by influencing Type 2b and Type 3 progenitors, although it does not alter proliferation of either the Type 1 quiescent progenitor or the Type 2a amplifying neural progenitor. Thyroid hormone increases the number of doublecortin (DCX)-positive Type 3 progenitors, and accelerates neuronal differentiation into both DCX-positive immature neurones and neuronal nuclei-positive granule cell neurones. Furthermore, we show that this increase in neuronal differentiation is accompanied by a significant induction of specific transcription factors involved in hippocampal progenitor differentiation. In vitro studies using the neurosphere assay support a direct effect of thyroid hormone on progenitor development because neurospheres treated with thyroid hormone are shifted to a more differentiated state. Taken together, our results indicate that thyroid hormone mediates its neurogenic effects via targeting Type 2b and Type 3 hippocampal progenitors, and suggests a role for proneural transcription factors in contributing to the effects of thyroid hormone on neuronal differentiation of adult hippocampal progenitors. © 2012 The Authors. Journal of Neuroendocrinology © 2012 British Society for Neuroendocrinology.

Stability of binaries. Part 1: Rigid binaries

NASA Astrophysics Data System (ADS)

Sharma, Ishan

2015-09-01

We consider the stability of binary asteroids whose members are possibly granular aggregates held together by self-gravity alone. A binary is said to be stable whenever each member is orbitally and structurally stable to both orbital and structural perturbations. To this end, we extend the stability test for rotating granular aggregates introduced by Sharma (Sharma, I. [2012]. J. Fluid Mech., 708, 71-99; Sharma, I. [2013]. Icarus, 223, 367-382; Sharma, I. [2014]. Icarus, 229, 278-294) to the case of binary systems comprised of rubble members. In part I, we specialize to the case of a binary with rigid members subjected to full three-dimensional perturbations. Finally, we employ the stability test to critically appraise shape models of four suspected binary systems, viz., 216 Kleopatra, 25143 Itokawa, 624 Hektor and 90 Antiope.

Indian hedgehog contributes to human cartilage endplate degeneration.

PubMed

Wang, Shaowei; Yang, Kun; Chen, Shuai; Wang, Jiying; Du, Guoqing; Fan, Shunwu; Wei, Lei

2015-08-01

To determine the role of Indian hedgehog (Ihh) signaling in human cartilage endplate (CEP) degeneration. CEP-degenerated tissues from patients with Modic I or II changes (n = 9 and 45, respectively) and normal tissues from vertebral burst fracture patients (n = 17) were collected. Specimens were either cut into slices for organ culture ex vivo or digested to isolate chondrocytes for cell culture in vitro. Ihh expression and the effect of Ihh on cartilage degeneration were determined by investigating degeneration markers in this study. Ihh expression and cartilage degeneration markers significantly increased in the Modic I and II groups. The expression of cartilage degeneration markers was positively correlated with degeneration severity. Gain-of-function for Ihh promoted expression of cartilage degeneration markers in vitro, while loss-of-function for Ihh inhibited their expression both in vitro and ex vivo. These findings demonstrated that Ihh promotes CEP degeneration. Blocking Ihh pathway has potential clinical usage for attenuating CEP degeneration.

Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers

NASA Technical Reports Server (NTRS)

Teng, Stacy H.; Schawinski, Kevin; Urry, C. Megan; Darg, Dan W.; Kaviraj, Sugata; Oh, Kyuseok; Bonning, Erin W.; Cardamone, Carolin N.; Keel, William C.; Lintott, Chris J.;

Spectral thresholds in macular degeneration.

PubMed Central

Alvarez, S L; King-Smith, P E; Bhargava, S K

1983-01-01

Spectral sensitivities were measured in 18 normal eyes, 9 eyes in patients with senile macular degeneration, 4 patients with Stargardt's juvenile macular degeneration (JMD), and 2 patients without conclusive signs--that is, genetic or morphological abnormalities--to indicate the cause of loss of central vision. Spectral sensitivity, testing for which included measurements on white, yellow, purple, and blue backgrounds, is here used as an aid in differential diagnosis for cases of macular degeneration. PMID:6871142

PDL Progenitor-Mediated PDL Recovery Contributes to Orthodontic Relapse.

PubMed

Feng, L; Yang, R; Liu, D; Wang, X; Song, Y; Cao, H; He, D; Gan, Y; Kou, X; Zhou, Y

2016-08-01

Periodontal ligament (PDL) is subjected to mechanical force during physiologic activities. PDL stem /: progenitor cells are the main mesenchymal stem cells in PDL. However, how PDL progenitors participate in PDL homeostasis upon and after mechanical force is largely unknown. In this study, force-triggered orthodontic tooth movement and the following relapse were used as models to demonstrate the response of PDL progenitors and their role in PDL remodeling upon and after mechanical force. Upon orthodontic force, PDL collagen on the compression side significantly degraded, showing a broken and disorganized pattern. After force withdrawal, the degraded PDL collagen recovered during the early stage of relapse. Correspondingly, increased CD90(+) PDL progenitors with suppressed expression of type I collagen (Col-I) were observed upon orthodontic force, whereas these cells accumulated at the degradation regions and regained Col-I expression after force withdrawal during early relapse. Our results further showed that compressive force altered cell morphology and repressed collagen expression in cultured PDL progenitors, which both recovered after force withdrawal. Force withdrawal-induced recovery of collagen expression in cultured PDL progenitors could be regulated by transforming growth factor-β (TGF-β), a key molecule for tissue homeostasis and extracellular matrix remodeling. More interesting, inhibiting the regained Col-I expression in CD90(+) PDL progenitors by blocking TGF-β interrupted PDL collagen recovery and partially inhibited the early relapse. These data suggest that PDL progenitors can respond to mechanical force and may process intrinsic stability to recover to original status after force withdrawal. PDL progenitors with intrinsic stability are required for PDL recovery and consequently contribute to early orthodontic relapse, which can be regulated by TGF-β signaling. © International & American Associations for Dental Research 2016.

Biology and flow cytometry of proangiogenic hematopoietic progenitors cells.

PubMed

Rose, Jonathan A; Erzurum, Serpil; Asosingh, Kewal

2015-01-01

During development, hematopoiesis and neovascularization are closely linked to each other via a common bipotent stem cell called the hemangioblast that gives rise to both hematopoietic cells and endothelial cells. In postnatal life, this functional connection between the vasculature and hematopoiesis is maintained by a subset of hematopoietic progenitor cells endowed with the capacity to differentiate into potent proangiogenic cells. These proangiogenic hematopoietic progenitors comprise a specific subset of bone marrow (BM)-derived cells that homes to sites of neovascularization and possess potent paracrine angiogenic activity. There is emerging evidence that this subpopulation of hematopoietic progenitors plays a critical role in vascular health and disease. Their angiogenic activity is distinct from putative "endothelial progenitor cells" that become structural cells of the endothelium by differentiation into endothelial cells. Proangiogenic hematopoietic progenitor cell research requires multidisciplinary expertise in flow cytometry, hematology, and vascular biology. This review provides a comprehensive overview of proangiogenic hematopoietic progenitor cell biology and flow cytometric methods to detect these cells in the peripheral blood circulation and BM. © 2014 International Society for Advancement of Cytometry.

Transfusion Support for ABO-Incompatible Progenitor Cell Transplantation

PubMed Central

Kopko, Patricia M.

2016-01-01

Summary ABO-incompatible transplants comprise up to 50% of allogeneic progenitor cell transplants. Major, minor and bidirectional ABO-incompatible transplants each have unique complications that can occur, including hemolysis at the time of progenitor cell infusion, hemolysis during donor engraftment, passenger lymphocyte syndrome, delayed red blood cell engraftment, and pure red cell aplasia. Appropriate transfusion support during the different phases of the allogeneic progenitor cell transplant process is an important part of ABO-incompatible transplantation. PMID:27022318

Binary Plutinos

NASA Astrophysics Data System (ADS)

Noll, Keith S.

2015-08-01

The Pluto-Charon binary was the first trans-neptunian binary to be identified in 1978. Pluto-Charon is a true binary with both components orbiting a barycenter located between them. The Pluto system is also the first, and to date only, known binary with a satellite system consisting of four small satellites in near-resonant orbits around the common center of mass. Seven other Plutinos, objects in 3:2 mean motion resonance with Neptune, have orbital companions including 2004 KB19 reported here for the first time. Compared to the Cold Classical population, the Plutinos differ in the frequency of binaries, the relative sizes of the components, and their inclination distribution. These differences point to distinct dynamical histories and binary formation processes encountered by Plutinos.

Reporter-Based Isolation of Developmental Myogenic Progenitors

PubMed Central

Kheir, Eyemen; Cusella, Gabriella; Messina, Graziella; Cossu, Giulio; Biressi, Stefano

2018-01-01

The formation and activity of mammalian tissues entail finely regulated processes, involving the concerted organization and interaction of multiple cell types. In recent years the prospective isolation of distinct progenitor and stem cell populations has become a powerful tool in the hands of developmental biologists and has rendered the investigation of their intrinsic properties possible. In this protocol, we describe how to purify progenitors with different lineage history and degree of differentiation from embryonic and fetal skeletal muscle by fluorescence-activated cell sorting (FACS). The approach takes advantage of a panel of murine strains expressing fluorescent reporter genes specifically in the myogenic progenitors. We provide a detailed description of the dissection procedures and of the enzymatic dissociation required to maximize the yield of mononucleated cells for subsequent FACS-based purification. The procedure takes ~6–7 h to complete and allows for the isolation and the subsequent molecular and phenotypic characterization of developmental myogenic progenitors. PMID:29674978

Counting Patterns in Degenerated Sequences

NASA Astrophysics Data System (ADS)

Nuel, Grégory

Biological sequences like DNA or proteins, are always obtained through a sequencing process which might produce some uncertainty. As a result, such sequences are usually written in a degenerated alphabet where some symbols may correspond to several possible letters (ex: IUPAC DNA alphabet). When counting patterns in such degenerated sequences, the question that naturally arises is: how to deal with degenerated positions ? Since most (usually 99%) of the positions are not degenerated, it is considered harmless to discard the degenerated positions in order to get an observation, but the exact consequences of such a practice are unclear. In this paper, we introduce a rigorous method to take into account the uncertainty of sequencing for biological sequences (DNA, Proteins). We first introduce a Forward-Backward approach to compute the marginal distribution of the constrained sequence and use it both to perform a Expectation-Maximization estimation of parameters, as well as deriving a heterogeneous Markov distribution for the constrained sequence. This distribution is hence used along with known DFA-based pattern approaches to obtain the exact distribution of the pattern count under the constraints. As an illustration, we consider a EST dataset from the EMBL database. Despite the fact that only 1% of the positions in this dataset are degenerated, we show that not taking into account these positions might lead to erroneous observations, further proving the interest of our approach.

Neural stem/progenitor cell properties of glial cells in the adult mouse auditory nerve

PubMed Central

Lang, Hainan; Xing, Yazhi; Brown, LaShardai N.; Samuvel, Devadoss J.; Panganiban, Clarisse H.; Havens, Luke T.; Balasubramanian, Sundaravadivel; Wegner, Michael; Krug, Edward L.; Barth, Jeremy L.

2015-01-01

The auditory nerve is the primary conveyor of hearing information from sensory hair cells to the brain. It has been believed that loss of the auditory nerve is irreversible in the adult mammalian ear, resulting in sensorineural hearing loss. We examined the regenerative potential of the auditory nerve in a mouse model of auditory neuropathy. Following neuronal degeneration, quiescent glial cells converted to an activated state showing a decrease in nuclear chromatin condensation, altered histone deacetylase expression and up-regulation of numerous genes associated with neurogenesis or development. Neurosphere formation assays showed that adult auditory nerves contain neural stem/progenitor cells (NSPs) that were within a Sox2-positive glial population. Production of neurospheres from auditory nerve cells was stimulated by acute neuronal injury and hypoxic conditioning. These results demonstrate that a subset of glial cells in the adult auditory nerve exhibit several characteristics of NSPs and are therefore potential targets for promoting auditory nerve regeneration. PMID:26307538

Identifying the progenitors of present-day early-type galaxies in observational surveys: correcting `progenitor bias' using the Horizon-AGN simulation

NASA Astrophysics Data System (ADS)

Martin, G.; Kaviraj, S.; Devriendt, J. E. G.; Dubois, Y.; Pichon, C.; Laigle, C.

2018-03-01

As endpoints of the hierarchical mass-assembly process, the stellar populations of local early-type galaxies encode the assembly history of galaxies over cosmic time. We use Horizon-AGN, a cosmological hydrodynamical simulation, to study the merger histories of local early-type galaxies and track how the morphological mix of their progenitors evolves over time. We provide a framework for alleviating `progenitor bias' - the bias that occurs if one uses only early-type galaxies to study the progenitor population. Early types attain their final morphology at relatively early epochs - by z ˜ 1, around 60 per cent of today's early types have had their last significant merger. At all redshifts, the majority of mergers have one late-type progenitor, with late-late mergers dominating at z > 1.5 and early-early mergers becoming significant only at z < 0.5. Progenitor bias is severe at all but the lowest redshifts - e.g. at z ˜ 0.6, less than 50 per cent of the stellar mass in today's early types is actually in progenitors with early-type morphology, while, at z ˜ 2, studying only early types misses almost all (80 per cent) of the stellar mass that eventually ends up in local early-type systems. At high redshift, almost all massive late-type galaxies, regardless of their local environment or star formation rate, are progenitors of local early-type galaxies, as are lower mass (M⋆ < 1010.5 M_{⊙}) late-types as long as they reside in high-density environments. In this new era of large observational surveys (e.g. LSST, JWST), this study provides a framework for studying how today's early-type galaxies have been built up over cosmic time.

Degenerate Cauchy numbers of the third kind.

PubMed

Pyo, Sung-Soo; Kim, Taekyun; Rim, Seog-Hoon

2018-01-01

Since Cauchy numbers were introduced, various types of Cauchy numbers have been presented. In this paper, we define degenerate Cauchy numbers of the third kind and give some identities for the degenerate Cauchy numbers of the third kind. In addition, we give some relations between four kinds of the degenerate Cauchy numbers, the Daehee numbers and the degenerate Bernoulli numbers.

Long-term safety of human retinal progenitor cell transplantation in retinitis pigmentosa patients.

PubMed

Liu, Yong; Chen, Shao Jun; Li, Shi Ying; Qu, Ling Hui; Meng, Xiao Hong; Wang, Yi; Xu, Hai Wei; Liang, Zhi Qing; Yin, Zheng Qin

2017-09-29

Retinitis pigmentosa is a common genetic disease that causes retinal degeneration and blindness for which there is currently no curable treatment available. Vision preservation was observed in retinitis pigmentosa animal models after retinal stem cell transplantation. However, long-term safety studies and visual assessment have not been thoroughly tested in retinitis pigmentosa patients. In our pre-clinical study, purified human fetal-derived retinal progenitor cells (RPCs) were transplanted into the diseased retina of Royal College of Surgeons (RCS) rats, a model of retinal degeneration. Based on these results, we conducted a phase I clinical trial to establish the safety and tolerability of transplantation of RPCs in eight patients with advanced retinitis pigmentosa. Patients were studied for 24 months. After RPC transplantation in RCS rats, we observed moderate recovery of vision and maintenance of the outer nuclear layer thickness. Most importantly, we did not find tumor formation or immune rejection. In the retinis pigmentosa patients given RPC injections, we also did not observe immunological rejection or tumorigenesis when immunosuppressive agents were not administered. We observed a significant improvement in visual acuity (P < 0.05) in five patients and an increase in retinal sensitivity of pupillary responses in three of the eight patients between 2 and 6 months after the transplant, but this improvement did not appear by 12 months. Our study for the first time confirmed the long-term safety and feasibility of vision repair by stem cell therapy in patients blinded by retinitis pigmentosa. WHO Trial Registration, ChiCTR-TNRC-08000193 . Retrospectively registered on 5 December 2008.

Evolution of Degenerate Space-Time from Non-Degenerate Initial Value in Ashtekar's Formalism

NASA Astrophysics Data System (ADS)

Ma, Yongge; Liang, Canbin

1998-09-01

The possibility of evolving a degenerate space-time from non-degenerate initial value in Ashtekar's formalism is considered in a constructed example. It is found that this possibility could be realized in the time evolution given by Ashtekar's equations, but the topology change of space makes it fail to be a Cauchy evolution.

Binary progenitors of supernovae

NASA Astrophysics Data System (ADS)

Trimble, V.

1984-12-01

Among the massive stars that are expected to produce Type II, hydrogen-rich supernovae, the presence of a close companion can increase the main sequence mass needed to yield a collapsing core. In addition, due to mass transfer from the primary to the secondary, the companion enhances the stripping of the stellar hydrogen envelope produced by single star winds and thereby makes it harder for the star to give rise to a typical SN II light curve. Among the less massive stars that may be the basis for Type I, hydrogen-free supernovae, a close companion could be an innocent bystander to carbon detonation/deflagration in the primary. It may alternatively be a vital participant which transfers material to a white dwarf primary and drives it to explosive conditions.

Stem cells in clinical trials for treatment of retinal degeneration.

PubMed

Klassen, Henry

2016-01-01

After decades of basic science research involving the testing of regenerative strategies in animal models of retinal degenerative diseases, a number of clinical trials are now underway, with additional trials set to begin shortly. These efforts will evaluate the safety and preliminary efficacy of cell-based products in the eyes of patients with a number of retinal conditions, notably including age-related macular degeneration, retinitis pigmentosa and Stargardt's disease. This review considers the scientific work and early trials with fetal cells and tissues that set the stage for the current clinical investigatory work, as well the trials themselves, specifically those either now completed, underway or close to initiation. The cells of interest include retinal pigment epithelial cells derived from embryonic stem or induced pluripotent stem cells, undifferentiated neural or retinal progenitors or cells from the vascular/bone marrow compartment or umbilical cord tissue. Degenerative diseases of the retina represent a popular target for emerging cell-based therapeutics and initial data from early stage clinical trials suggest that short-term safety objectives can be met in at least some cases. The question of efficacy will require additional time and testing to be adequately resolved.

The Formation of Rapidly Rotating Black Holes in High-mass X-Ray Binaries

NASA Astrophysics Data System (ADS)

Batta, Aldo; Ramirez-Ruiz, Enrico; Fryer, Chris

2017-09-01

High-mass X-ray binaries (HMXRBs), such as Cygnus X-1, host some of the most rapidly spinning black holes (BHs) known to date, reaching spin parameters a≳ 0.84. However, there are several effects that can severely limit the maximum BH spin parameter that could be obtained from direct collapse, such as tidal synchronization, magnetic core-envelope coupling, and mass loss. Here, we propose an alternative scenario where the BH is produced by a failed supernova (SN) explosion that is unable to unbind the stellar progenitor. A large amount of fallback material ensues, whose interaction with the secondary naturally increases its overall angular momentum content, and therefore the spin of the BH when accreted. Through SPH hydrodynamic simulations, we studied the unsuccessful explosion of an 8 {M}⊙ pre-SN star in a close binary with a 12 {M}⊙ companion with an orbital period of ≈1.2 days, finding that it is possible to obtain a BH with a high spin parameter a≳ 0.8 even when the expected spin parameter from direct collapse is a≲ 0.3. This scenario also naturally explains the atmospheric metal pollution observed in HMXRB stellar companions.

SHADOWS OF OUR FORMER COMPANIONS: HOW THE SINGLE-DEGENERATE BINARY TYPE IA SUPERNOVA SCENARIO AFFECTS REMNANTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, William J.; Raskin, Cody; Owen, J. Michael

2016-12-10

Here we present three-dimensional high-resolution simulations of Type Ia supernova in the presence of a non-degenerate companion. We find that the presence of a nearby companion leaves a long-lived hole in the supernova ejecta. In particular, we aim to study the long-term evolution of this hole as the supernova ejecta interacts with the surrounding interstellar medium (ISM). Using estimates for the X-ray emission, we find that the hole generated by the companion remains for many centuries after the interaction between the ejecta and the ISM. We also show that the hole is discernible over a wide range of viewing anglesmore » and companion masses.« less

Stability of binaries. Part II: Rubble-pile binaries

NASA Astrophysics Data System (ADS)

Sharma, Ishan

2016-10-01

We consider the stability of the binary asteroids whose members are granular aggregates held together by self-gravity alone. A binary is said to be stable whenever both its members are orbitally and structurally stable to both orbital and structural perturbations. To this end, we extend the stability analysis of Sharma (Sharma [2015] Icarus, 258, 438-453), that is applicable to binaries with rigid members, to the case of binary systems with rubble members. We employ volume averaging (Sharma et al. [2009] Icarus, 200, 304-322), which was inspired by past work on elastic/fluid, rotating and gravitating ellipsoids. This technique has shown promise when applied to rubble-pile ellipsoids, but requires further work to settle some of its underlying assumptions. The stability test is finally applied to some suspected binary systems, viz., 216 Kleopatra, 624 Hektor and 90 Antiope. We also see that equilibrated binaries that are close to mobilizing their maximum friction can sustain only a narrow range of shapes and, generally, congruent shapes are preferred.

Strategies to reverse endothelial progenitor cell dysfunction in diabetes.

PubMed

Petrelli, Alessandra; Di Fenza, Raffaele; Carvello, Michele; Gatti, Francesca; Secchi, Antonio; Fiorina, Paolo

2012-01-01

Bone-marrow-derived cells-mediated postnatal vasculogenesis has been reported as the main responsible for the regulation of vascular homeostasis in adults. Since their discovery, endothelial progenitor cells have been depicted as mediators of postnatal vasculogenesis for their peculiar phenotype (partially staminal and partially endothelial), their ability to differentiate in endothelial cell line and to be incorporated into the vessels wall during ischemia/damage. Diabetes mellitus, a condition characterized by cardiovascular disease, nephropathy, and micro- and macroangiopathy, showed a dysfunction of endothelial progenitor cells. Herein, we review the mechanisms involved in diabetes-related dysfunction of endothelial progenitor cells, highlighting how hyperglycemia affects the different steps of endothelial progenitor cells lifetime (i.e., bone marrow mobilization, trafficking into the bloodstream, differentiation in endothelial cells, and homing in damaged tissues/organs). Finally, we review preclinical and clinical strategies that aim to revert diabetes-induced dysfunction of endothelial progenitor cells as a means of finding new strategies to prevent diabetic complications.

The cosmic merger rate of stellar black hole binaries from the Illustris simulation

NASA Astrophysics Data System (ADS)

Mapelli, Michela; Giacobbo, Nicola; Ripamonti, Emanuele; Spera, Mario

2017-12-01

The cosmic merger rate density of black hole binaries (BHBs) can give us an essential clue to constraining the formation channels of BHBs, in light of current and forthcoming gravitational wave detections. Following a Monte Carlo approach, we couple new population-synthesis models of BHBs with the Illustris cosmological simulation, to study the cosmic history of BHB mergers. We explore six population-synthesis models, varying the prescriptions for supernovae, common envelope and natal kicks. In most considered models, the cosmic BHB merger rate follows the same trend as the cosmic star formation rate. The normalization of the cosmic BHB merger rate strongly depends on the treatment of common envelope and on the distribution of natal kicks. We find that most BHBs merging within LIGO's instrumental horizon come from relatively metal-poor progenitors (<0.2 Z⊙). The total masses of merging BHBs span a large range of values, from ∼6 to ∼82 M⊙. In our fiducial model, merging BHBs consistent with GW150914, GW151226 and GW170104 represent ∼6, 3 and 12 per cent of all BHBs merging within the LIGO horizon, respectively. The heavy systems, like GW150914, come from metal-poor progenitors (<0.15 Z⊙). Most GW150914-like systems merging in the local Universe appear to have formed at high redshift, with a long delay time. In contrast, GW151226-like systems form and merge all the way through the cosmic history, from progenitors with a broad range of metallicities. Future detections will be crucial to put constraints on common envelope, on natal kicks, and on the BHB mass function.

Constraining Core-collapse Supernova Theory Predictions with 400 Progenitor Masses

NASA Astrophysics Data System (ADS)

Murphy, Jeremiah

2017-08-01

A new era is emerging in which we will have hundreds of progenitor masses for supernovae (SNe) and supernova remnants (SNRs); we propose to develop the statistical and theoretical tools needed to interpret this data. Two of the fundamental predictions of stellar evolution theory are that stars more massive than about 8 solar masses will explode and that some of these stars will not explode and form black holes. These statements are clear and simple, yet constraining them with observations has remained elusive until recently. For many years, the rate of progenitor discovery was steady but slow; each progenitor discovery required rare serendipitous pre-cursor imaging. With this steady drip of direct imaging, the number of progenitor masses numbered no more than 20. Recently, we developed a technique that increased the number of progenitor masses by a factor of 10 or more. In this new technique, we use HST photometry to age-date the stellar populations surrounding SNRs. From this age, we derive a progenitor mass for each SNR. We currently have progenitor masses for 115 SNRs in M31 and M33, soon we will have 300 more from M83, and there are hundreds more SNRs that could be analyzed in other nearby galaxies. To prepare for this watershed, we propose to develop the Bayesian framework needed to properly infer the progenitor mass distribution. This work will culminate in a direct constraint on the predictions of core-collapse supernova theory.

R144: a very massive binary likely ejected from R136 through a binary-binary encounter

NASA Astrophysics Data System (ADS)

Oh, Seungkyung; Kroupa, Pavel; Banerjee, Sambaran

2014-02-01

R144 is a recently confirmed very massive, spectroscopic binary which appears isolated from the core of the massive young star cluster R136. The dynamical ejection hypothesis as an origin for its location is claimed improbable by Sana et al. due to its binary nature and high mass. We demonstrate here by means of direct N-body calculations that a very massive binary system can be readily dynamically ejected from an R136-like cluster, through a close encounter with a very massive system. One out of four N-body cluster models produces a dynamically ejected very massive binary system with a mass comparable to R144. The system has a system mass of ≈355 M⊙ and is located at 36.8 pc from the centre of its parent cluster, moving away from the cluster with a velocity of 57 km s-1 at 2 Myr as a result of a binary-binary interaction. This implies that R144 could have been ejected from R136 through a strong encounter with another massive binary or single star. In addition, we discuss all massive binaries and single stars which are ejected dynamically from their parent cluster in the N-body models.

Premyogenic progenitors derived from human pluripotent stem cells expand in floating culture and differentiate into transplantable myogenic progenitors.

PubMed

Sakai-Takemura, Fusako; Narita, Asako; Masuda, Satoru; Wakamatsu, Toshifumi; Watanabe, Nobuharu; Nishiyama, Takashi; Nogami, Ken'ichiro; Blanc, Matthias; Takeda, Shin'ichi; Miyagoe-Suzuki, Yuko

2018-04-26

Human induced pluripotent stem cells (hiPSCs) are a potential source for cell therapy of Duchenne muscular dystrophy. To reliably obtain skeletal muscle progenitors from hiPSCs, we treated hiPS cells with a Wnt activator, CHIR-99021 and a BMP receptor inhibitor, LDN-193189, and then induced skeletal muscle cells using a previously reported sphere-based culture. This protocol greatly improved sphere formation efficiency and stably induced the differentiation of myogenic cells from hiPS cells generated from both healthy donors and a patient with congenital myasthenic syndrome. hiPSC-derived myogenic progenitors were enriched in the CD57(-) CD108(-) CD271(+) ERBB3(+) cell fraction, and their differentiation was greatly promoted by TGF-β inhibitors. TGF-β inhibitors down-regulated the NFIX transcription factor, and NFIX short hairpin RNA (shRNA) improved the differentiation of iPS cell-derived myogenic progenitors. These results suggest that NFIX inhibited differentiation of myogenic progenitors. hiPSC-derived myogenic cells differentiated into myofibers in muscles of NSG-mdx 4Cv mice after direct transplantation. Our results indicate that our new muscle induction protocol is useful for cell therapy of muscular dystrophies.

The Merger Rate of Binary White Dwarfs in the Galactic Disk

NASA Astrophysics Data System (ADS)

Badenes, Carles; Maoz, Dan

2012-04-01

We use multi-epoch spectroscopy of ~4000 white dwarfs in the Sloan Digital Sky Survey to constrain the properties of the Galactic population of binary white dwarf systems and calculate their merger rate. With a Monte Carlo code, we model the distribution of ΔRVmax, the maximum radial velocity shift between exposures of the same star, as a function of the binary fraction within 0.05 AU, f bin, and the power-law index in the separation distribution at the end of the common-envelope phase, α. Although there is some degeneracy between f bin and α, the 15 high-ΔRVmax systems that we find constrain the combination of these parameters, which determines a white dwarf merger rate per unit stellar mass of 1.4+3.4 -1.0 × 10-13 yr-1 M -1 ⊙ (1σ limits). This is remarkably similar to the measured rate of Type Ia supernovae (SNe Ia) per unit stellar mass in Milky-Way-like Sbc galaxies. The rate of super-Chandrasekhar mergers is only 1.0+1.6 -0.6 × 10-14 yr-1 M -1 ⊙. We conclude that there are not enough close binary white dwarf systems to reproduce the observed SN Ia rate in the "classic" double degenerate super-Chandrasekhar scenario. On the other hand, if sub-Chandrasekhar mergers can lead to SNe Ia, as has been recently suggested by some studies, they could make a major contribution to the overall SN Ia rate. Although unlikely, we cannot rule out contamination of our sample by M-dwarf binaries or non-Gaussian errors. These issues will be clarified in the near future by completing the follow-up of all 15 high-ΔRVmax systems.

Muscle: a source of progenitor cells for bone fracture healing.

PubMed

Henrotin, Yves

2011-12-22

Bone repair failure is a major complication of open fracture, leading to non-union of broken bone extremities and movement at the fracture site. This results in a serious disability for patients. The role played by the periosteum and bone marrow progenitors in bone repair is now well documented. In contrast, limited information is available on the role played by myogenic progenitor cells in bone repair. In a recent article published in BMC Musculoskeletal Disorders, Liu et al. compared the presence of myogenic progenitor (MyoD lineage cells) in closed and open fractures. They showed that myogenic progenitors are present in open, but not closed fractures, suggesting that muscle satellite cells may colonize the fracture site in the absence of intact periosteum. Interestingly, these progenitors sequentially expressed a chondrogenic and, thereafter, an osteoblastic phenotype, suggestive of a functional role in the repair process. This finding opens up new perspectives for the research of orthopedic surgical methods, which could maximize myogenic progenitor access and mobilization to augment bone repair. Please see related article: http://www.biomedcentral.com/1471-2474/12/288.

Heterogeneity and Fgf dependence of adult neural progenitors in the zebrafish telencephalon.

PubMed

Ganz, Julia; Kaslin, Jan; Hochmann, Sarah; Freudenreich, Dorian; Brand, Michael

2010-08-15

Adult telencephalic neurogenesis is a conserved trait of all vertebrates studied. It has been investigated in detail in rodents, but very little is known about the composition of neurogenic niches and the cellular nature of progenitors in nonmammalian vertebrates. To understand the components of the progenitor zones in the adult zebrafish telencephalon and the link between glial characteristics and progenitor state, we examined whether canonical glial markers are colocalized with proliferation markers. In the adult zebrafish telencephalon, we identify heterogeneous progenitors that reside in two distinct glial domains. We find that the glial composition of the progenitor zone is linked to its proliferative behavior. Analyzing both fast-cycling proliferating cells as well as slowly cycling progenitors, we find four distinct progenitor types characterized by differential expression of glial markers. Importantly, a significant proportion of progenitors do not display typical radial glia characteristics. By blocking or activating Fgf signaling by misexpression of a dominant negative Fgf-receptor 1 or Fgf8a, respectively, we find that ventral and dorsal progenitors in the telencephalon also differ in their requirement for Fgf signaling. Together with data on the expression of Fgf signaling components in the ventricular zone of the telencephalon, this suggests that Fgf signaling directly regulates proliferation of specific subsets of adult telencephalic progenitors in vivo. Taken together our results show that adult neural progenitor cells are heterogeneous with their respect to distribution into two distinct glial domains and their dependence upon Fgf signaling as a proliferative cue in the zebrafish telencephalon.

Planetary Nebulae that Cannot Be Explained by Binary Systems

NASA Astrophysics Data System (ADS)

Bear, Ealeal; Soker, Noam

2017-03-01

We examine the images of hundreds of planetary nebulae (PNe) and find that for about one in six PNe the morphology is too “messy” to be accounted for by models of stellar binary interaction. We speculate that interacting triple stellar systems shaped these PNe. In this preliminary study, we qualitatively classify PNe by one of four categories. (1) PNe that show no need for a tertiary star to account for their morphology. (2) PNe whose structure possesses a pronounced departure from axial-symmetry and/or mirror-symmetry. We classify these, according to our speculation, as “having a triple stellar progenitor.” (3) PNe whose morphology possesses departure from axial-symmetry and/or mirror-symmetry, but not as pronounced as in the previous class, and are classified as “likely shaped by triple stellar system.” (4) PNe with minor departure from axial-symmetry and/or mirror-symmetry that could have been also caused by an eccentric binary system or the interstellar medium. These are classified as “maybe shaped by a triple stellar system.” Given a weight η t = 1, η l = 0.67, and η m = 0.33 to classes 2, 3, and 4, respectively, we find that according to our assumption about 13%-21% of PNe have been shaped by triple stellar systems. Although in some evolutionary scenarios not all three stars survive the evolution, we encourage the search for a triple stellar systems at the center of some PNe.

New binaries among UV-selected, hot subdwarf stars and population properties

NASA Astrophysics Data System (ADS)

Kawka, A.; Vennes, S.; O'Toole, S.; Németh, P.; Burton, D.; Kotze, E.; Buckley, D. A. H.

2015-07-01

We have measured the orbital parameters of seven close binaries, including six new objects, in a radial velocity survey of 38 objects comprising a hot subdwarf star with orbital periods ranging from ˜0.17 to 3 d. One new system, GALEX J2205-3141, shows reflection on an M dwarf companion. Three other objects show significant short-period variations, but their orbital parameters could not be constrained. Two systems comprising a hot subdwarf paired with a bright main-sequence/giant companion display short-period photometric variations possibly due to irradiation or stellar activity and are also short-period candidates. All except two candidates were drawn from a selection of subluminous stars in the Galaxy Evolution Explorer ultraviolet sky survey. Our new identifications also include a low-mass subdwarf B star and likely progenitor of a low-mass white dwarf (GALEX J0805-1058) paired with an unseen, possibly substellar, companion. The mass functions of the newly identified binaries imply minimum secondary masses ranging from 0.03 to 0.39 M⊙. Photometric time series suggest that, apart from GALEX J0805-1058 and J2205-3141, the companions are most likely white dwarfs. We update the binary population statistics: close to 40 per cent of hot subdwarfs have a companion. Also, we found that the secondary mass distribution shows a low-mass peak attributed to late-type dwarfs, and a higher mass peak and tail distribution attributed to white dwarfs and a few spectroscopic composites. Also, we found that the population kinematics imply an old age and include a few likely halo population members.

Conversion of immortal liver progenitor cells into pancreatic endocrine progenitor cells by persistent expression of Pdx-1.

PubMed

Jin, Cai-Xia; Li, Wen-Lin; Xu, Fang; Geng, Zhen H; He, Zhi-Ying; Su, Juan; Tao, Xin-Rong; Ding, Xiao-Yan; Wang, Xin; Hu, Yi-Ping

2008-05-01

The conversion of expandable liver progenitor cells into pancreatic beta cells would provide a renewable cell source for diabetes cell therapy. Previously, we reported the establishment of liver epithelial progenitor cells (LEPCs). In this work, LEPCs were modified into EGFP/Pdx-1 LEPCs, cells with stable expression of both Pdx-1 and EGFP. Unlike previous work, with persistent expression of Pdx-1, EGFP/Pdx-1 LEPCs acquired the phenotype of pancreatic endocrine progenitor cells rather than giving rise to insulin-producing cells directly. EGFP/Pdx-1 LEPCs proliferated vigorously and expressed the crucial transcription factors involved in beta cell development, including Ngn3, NeuroD, Nkx2.2, Nkx6.1, Pax4, Pax6, Isl1, MafA and endogenous Pdx-1, but did not secrete insulin. When cultured in high glucose/low serum medium supplemented with cytokines, EGFP/Pdx-1 LEPCs stopped proliferating and gave rise to functional beta cells without any evidence of exocrine or other islet cell lineage differentiation. When transplanted into diabetic SCID mice, EGFP/Pdx-1 LEPCs ameliorated hyperglycemia by secreting insulin in a glucose regulated manner. Considering the limited availability of beta cells, we propose that our experiments will provide a framework for utilizing the immortal liver progenitor cells as a renewable cell source for the generation of functional pancreatic beta cells.

CHANDRA OBSERVATIONS OF GALAXY ZOO MERGERS: FREQUENCY OF BINARY ACTIVE NUCLEI IN MASSIVE MERGERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teng, Stacy H.; Schawinski, Kevin; Urry, C. Megan

We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 10{sup 11} M{sub Sun} that already have optical active galactic nucleus (AGN) signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (N{sub H} {approx}< 1.1 Multiplication-Sign 10{sup 22} cm{sup -2}) X-ray nuclei are relatively common (8/12), but the detections are too faint (<40 counts per nucleus; f{sub 2-10keV} {approx}< 1.2 Multiplication-Sign 10{sup -13} erg s{sup -1} cm{sup -2})more » to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGNs in these mergers are rare (0%-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.« less

Phase-coexisting patterns, horizontal segregation, and controlled convection in vertically vibrated binary granular mixtures

NASA Astrophysics Data System (ADS)

Ansari, Istafaul Haque; Rivas, Nicolas; Alam, Meheboob

2018-01-01

We report patterns consisting of coexistence of synchronous and asynchronous states [for example, a granular gas co-existing with (i) bouncing bed, (ii) undulatory subharmonic waves, and (iii) Leidenfrost-like states] in experiments on vertically vibrated binary granular mixtures in a Hele-Shaw cell. Most experiments have been carried out with equimolar binary mixtures of glass and steel balls of same diameter by varying the total layer height (F ) for a range of shaking acceleration (Γ ). All patterns as well as the related phase diagram in the (Γ ,F ) plane have been reproduced via molecular dynamics simulations of the same system. The segregation of heavier and lighter particles along the horizontal direction is shown to be the progenitor of such phase-coexisting patterns as confirmed in both experiment and simulation. At strong shaking we uncover a partial convection state in which a pair of convection rolls is found to coexist with a Leidenfrost-like state. The crucial role of the relative number density of two species on controlling the buoyancy-driven granular convection is demonstrated. The onset of horizontal segregation can be explained in terms of an anisotropic diffusion tensor.

Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers

NASA Technical Reports Server (NTRS)

Teng, Stacy H.; Schwainski, Kevin; Urry, C. Megan; Darg, Dan W.; Kaviraj, Sugata; Oh, Kyuseok; Bonning, Erin W.; Cardamone, Carolin N.; Keel, William C.; Lintott, Chris J.;

Kraepelin and degeneration theory.

PubMed

Hoff, Paul

2008-06-01

Emil Kraepelin's contribution to the clinical and scientific field of psychiatry is recognized world-wide. In recent years, however, there have been a number of critical remarks on his acceptance of degeneration theory in particular and on his political opinion in general, which was said to have carried "overtones of proto-fascism" by Michael Shepherd [28]. The present paper discusses the theoretical cornerstones of Kraepelinian psychiatry with regard to their relevance for Kraepelin's attitude towards degeneration theory. This theory had gained wide influence not only in scientific, but also in philosophical and political circles in the last decades of the nineteenth century. There is no doubt that Kraepelin, on the one hand, accepted and implemented degeneration theory into the debate on etiology and pathogenesis of mental disorders. On the other hand, it is not appropriate to draw a simple and direct line from early versions of degeneration theory to the crimes of psychiatrists and politicians during the rule of national socialism. What we need, is a differentiated view, since this will be the only scientific one. Much research needs to be done here in the future, and such research will surely have a significant impact not only on the historical field, but also on the continuous debate about psychiatry, neuroscience and neurophilosophy.

Huntingtin interacting protein 1 Is a clathrin coat binding protein required for differentiation of late spermatogenic progenitors.

PubMed

Rao, D S; Chang, J C; Kumar, P D; Mizukami, I; Smithson, G M; Bradley, S V; Parlow, A F; Ross, T S

2001-11-01

Huntingtin-interacting protein 1 (HIP1) interacts with huntingtin, the protein whose gene is mutated in Huntington's disease. In addition, a fusion between HIP1 and platelet-derived growth factor beta receptor causes chronic myelomonocytic leukemia. The HIP1 proteins, including HIP1 and HIP1-related (HIP1r), have an N-terminal polyphosphoinositide-interacting epsin N-terminal homology, domain, which is found in proteins involved in clathrin-mediated endocytosis. HIP1 and HIP1r also share a central leucine zipper and an actin binding TALIN homology domain. Here we show that HIP1, like HIP1r, colocalizes with clathrin coat components. We also show that HIP1 physically associates with clathrin and AP-2, the major components of the clathrin coat. To further understand the putative biological role(s) of HIP1, we have generated a targeted deletion of murine HIP1. HIP1(-/-) mice developed into adulthood, did not develop overt neurologic symptoms in the first year of life, and had normal peripheral blood counts. However, HIP1-deficient mice exhibited testicular degeneration with increased apoptosis of postmeiotic spermatids. Postmeiotic spermatids are the only cells of the seminiferous tubules that express HIP1. These findings indicate that HIP1 is required for differentiation, proliferation, and/or survival of spermatogenic progenitors. The association of HIP1 with clathrin coats and the requirement of HIP1 for progenitor survival suggest a role for HIP1 in the regulation of endocytosis.

Huntingtin Interacting Protein 1 Is a Clathrin Coat Binding Protein Required for Differentiation of late Spermatogenic Progenitors

PubMed Central

Rao, Dinesh S.; Chang, Jenny C.; Kumar, Priti D.; Mizukami, Ikuko; Smithson, Glennda M.; Bradley, Sarah V.; Parlow, A. F.; Ross, Theodora S.

2001-01-01

Huntingtin-interacting protein 1 (HIP1) interacts with huntingtin, the protein whose gene is mutated in Huntington's disease. In addition, a fusion between HIP1 and platelet-derived growth factor β receptor causes chronic myelomonocytic leukemia. The HIP1 proteins, including HIP1 and HIP1-related (HIP1r), have an N-terminal polyphosphoinositide-interacting epsin N-terminal homology, domain, which is found in proteins involved in clathrin-mediated endocytosis. HIP1 and HIP1r also share a central leucine zipper and an actin binding TALIN homology domain. Here we show that HIP1, like HIP1r, colocalizes with clathrin coat components. We also show that HIP1 physically associates with clathrin and AP-2, the major components of the clathrin coat. To further understand the putative biological role(s) of HIP1, we have generated a targeted deletion of murine HIP1. HIP1−/− mice developed into adulthood, did not develop overt neurologic symptoms in the first year of life, and had normal peripheral blood counts. However, HIP1-deficient mice exhibited testicular degeneration with increased apoptosis of postmeiotic spermatids. Postmeiotic spermatids are the only cells of the seminiferous tubules that express HIP1. These findings indicate that HIP1 is required for differentiation, proliferation, and/or survival of spermatogenic progenitors. The association of HIP1 with clathrin coats and the requirement of HIP1 for progenitor survival suggest a role for HIP1 in the regulation of endocytosis. PMID:11604514

Endothelial progenitor cells in chronic obstructive pulmonary disease and emphysema

PubMed Central

Tracy, Russell P.; Parikh, Megha A.; Hoffman, Eric A.; Shimbo, Daichi; Austin, John H. M.; Smith, Benjamin M.; Hueper, Katja; Vogel-Claussen, Jens; Lima, Joao; Gomes, Antoinette; Watson, Karol; Kawut, Steven; Barr, R. Graham

2017-01-01

Endothelial injury is implicated in the pathogenesis of COPD and emphysema; however the role of endothelial progenitor cells (EPCs), a marker of endothelial cell repair, and circulating endothelial cells (CECs), a marker of endothelial cell injury, in COPD and its subphenotypes is unresolved. We hypothesized that endothelial progenitor cell populations would be decreased in COPD and emphysema and that circulating endothelial cells would be increased. Associations with other subphenotypes were examined. The Multi-Ethnic Study of Atherosclerosis COPD Study recruited smokers with COPD and controls age 50–79 years without clinical cardiovascular disease. Endothelial progenitor cell populations (CD34+KDR+ and CD34+KDR+CD133+ cells) and circulating endothelial cells (CD45dimCD31+CD146+CD133-) were measured by flow cytometry. COPD was defined by standard spirometric criteria. Emphysema was assessed qualitatively and quantitatively on CT. Full pulmonary function testing and expiratory CTs were measured in a subset. Among 257 participants, both endothelial progenitor cell populations, and particularly CD34+KDR+ endothelial progenitor cells, were reduced in COPD. The CD34+KDR+CD133+ endothelial progenitor cells were associated inversely with emphysema extent. Both endothelial progenitor cell populations were associated inversely with extent of panlobular emphysema and positively with diffusing capacity. Circulating endothelial cells were not significantly altered in COPD but were inversely associated with pulmonary microvascular blood flow on MRI. There was no consistent association of endothelial progenitor cells or circulating endothelial cells with measures of gas trapping. These data provide evidence that endothelial repair is impaired in COPD and suggest that this pathological process is specific to emphysema. PMID:28291826

Reprogramming the metabolome rescues retinal degeneration.

PubMed

Park, Karen Sophia; Xu, Christine L; Cui, Xuan; Tsang, Stephen H

2018-05-01

Metabolomics studies in the context of ophthalmology have largely focused on identifying metabolite concentrations that characterize specific retinal diseases. Studies involving mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy have shown that individuals suffering from retinal diseases exhibit metabolic profiles that markedly differ from those of control individuals, supporting the notion that metabolites may serve as easily identifiable biomarkers for specific conditions. An emerging branch of metabolomics resulting from biomarker studies, however, involves the study of retinal metabolic dysfunction as causes of degeneration. Recent publications have identified a number of metabolic processes-including but not limited to glucose and oxygen metabolism-that, when perturbed, play a role in the degeneration of photoreceptor cells. As a result, such studies have led to further research elucidating methods for prolonging photoreceptor survival in an effort to halt degeneration in its early stages. This review will explore the ways in which metabolomics has deepened our understanding of the causes of retinal degeneration and discuss how metabolomics can be used to prevent retinal degeneration from progressing to its later disease stages.

Lipofuscin accumulation, abnormal electrophysiology, and photoreceptor degeneration in mutant ELOVL4 transgenic mice: a model for macular degeneration.

PubMed

Karan, G; Lillo, C; Yang, Z; Cameron, D J; Locke, K G; Zhao, Y; Thirumalaichary, S; Li, C; Birch, D G; Vollmer-Snarr, H R; Williams, D S; Zhang, K

2005-03-15

Macular degeneration is a heterogeneous group of disorders characterized by photoreceptor degeneration and atrophy of the retinal pigment epithelium (RPE) in the central retina. An autosomal dominant form of Stargardt macular degeneration (STGD) is caused by mutations in ELOVL4, which is predicted to encode an enzyme involved in the elongation of long-chain fatty acids. We generated transgenic mice expressing a mutant form of human ELOVL4 that causes STGD. In these mice, we show that accumulation by the RPE of undigested phagosomes and lipofuscin, including the fluorophore, 2-[2,6-dimethyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-1E,3E,5E,7E-octatetraenyl]-1-(2-hyydroxyethyl)-4-[4-methyl-6-(2,6,6,-trimethyl-1-cyclohexen-1-yl)-1E,3E,5E-hexatrienyl]-pyridinium (A2E) is followed by RPE atrophy. Subsequently, photoreceptor degeneration occurs in the central retina in a pattern closely resembling that of human STGD and age-related macular degeneration. The ELOVL4 transgenic mice thus provide a good model for both STGD and dry age-related macular degeneration, and represent a valuable tool for studies on therapeutic intervention in these forms of blindness.

Motor neurons and oligodendrocytes arise from distinct cell lineages by progenitor recruitment

PubMed Central

Ravanelli, Andrew M.; Appel, Bruce

2015-01-01

During spinal cord development, ventral neural progenitor cells that express the transcription factors Olig1 and Olig2, called pMN progenitors, produce motor neurons and then oligodendrocytes. Whether motor neurons and oligodendrocytes arise from common or distinct progenitors in vivo is not known. Using zebrafish, we found that motor neurons and oligodendrocytes are produced sequentially by distinct progenitors that have distinct origins. When olig2+ cells were tracked during the peak period of motor neuron formation, most differentiated as motor neurons without further cell division. Using time-lapse imaging, we found that, as motor neurons differentiated, more dorsally positioned neuroepithelial progenitors descended to the pMN domain and initiated olig2 expression. Inhibition of Hedgehog signaling during motor neuron differentiation blocked the ventral movement of progenitors, the progressive initiation of olig2 expression, and oligodendrocyte formation. We therefore propose that the motor neuron-to-oligodendrocyte switch results from Hedgehog-mediated recruitment of glial-fated progenitors to the pMN domain subsequent to neurogenesis. PMID:26584621

Neuropeptides: Developmental Signals in Placode Progenitor Formation

PubMed Central

Lleras-Forero, Laura; Tambalo, Monica; Christophorou, Nicolas; Chambers, David; Houart, Corinne; Streit, Andrea

2013-01-01

Summary Few families of signaling factors have been implicated in the control of development. Here, we identify the neuropeptides nociceptin and somatostatin, a neurotransmitter and neuroendocrine hormone, as a class of developmental signals in both chick and zebrafish. We show that signals from the anterior mesendoderm are required for the formation of anterior placode progenitors, with one of the signals being somatostatin. Somatostatin controls ectodermal expression of nociceptin, and both peptides regulate Pax6 in lens and olfactory progenitors. Consequently, loss of somatostatin and nociceptin signaling leads to severe reduction of lens formation. Our findings not only uncover these neuropeptides as developmental signals but also identify a long-sought-after mechanism that initiates Pax6 in placode progenitors and may explain the ancient evolutionary origin of neuropeptides, predating a complex nervous system. PMID:23906067

A Comparison of Grid-based and SPH Binary Mass-transfer and Merger Simulations

DOE PAGES

Motl, Patrick M.; Frank, Juhan; Staff, Jan; ...

2017-03-29

There is currently a great amount of interest in the outcomes and astrophysical implications of mergers of double degenerate binaries. In a commonly adopted approximation, the components of such binaries are represented by polytropes with an index of n = 3/2. We present detailed comparisons of stellar mass-transfer and merger simulations of polytropic binaries that have been carried out using two very different numerical algorithms—a finite-volume "grid" code and a smoothed-particle hydrodynamics (SPH) code. We find that there is agreement in both the ultimate outcomes of the evolutions and the intermediate stages if the initial conditions for each code aremore » chosen to match as closely as possible. We find that even with closely matching initial setups, the time it takes to reach a concordant evolution differs between the two codes because the initial depth of contact cannot be matched exactly. There is a general tendency for SPH to yield higher mass transfer rates and faster evolution to the final outcome. Here, we also present comparisons of simulations calculated from two different energy equations: in one series, we assume a polytropic equation of state and in the other series an ideal gas equation of state. In the latter series of simulations, an atmosphere forms around the accretor, which can exchange angular momentum and cause a more rapid loss of orbital angular momentum. In the simulations presented here, the effect of the ideal equation of state is to de-stabilize the binary in both SPH and grid simulations, but the effect is more pronounced in the grid code.« less

A Comparison of Grid-based and SPH Binary Mass-transfer and Merger Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Motl, Patrick M.; Frank, Juhan; Clayton, Geoffrey C.

2017-04-01

There is currently a great amount of interest in the outcomes and astrophysical implications of mergers of double degenerate binaries. In a commonly adopted approximation, the components of such binaries are represented by polytropes with an index of n  = 3/2. We present detailed comparisons of stellar mass-transfer and merger simulations of polytropic binaries that have been carried out using two very different numerical algorithms—a finite-volume “grid” code and a smoothed-particle hydrodynamics (SPH) code. We find that there is agreement in both the ultimate outcomes of the evolutions and the intermediate stages if the initial conditions for each code are chosen to matchmore » as closely as possible. We find that even with closely matching initial setups, the time it takes to reach a concordant evolution differs between the two codes because the initial depth of contact cannot be matched exactly. There is a general tendency for SPH to yield higher mass transfer rates and faster evolution to the final outcome. We also present comparisons of simulations calculated from two different energy equations: in one series, we assume a polytropic equation of state and in the other series an ideal gas equation of state. In the latter series of simulations, an atmosphere forms around the accretor, which can exchange angular momentum and cause a more rapid loss of orbital angular momentum. In the simulations presented here, the effect of the ideal equation of state is to de-stabilize the binary in both SPH and grid simulations, but the effect is more pronounced in the grid code.« less

Physical Properties and Evolutionary States of EA-type Eclipsing Binaries Observed by LAMOST

NASA Astrophysics Data System (ADS)

Qian, S.-B.; Zhang, J.; He, J.-J.; Zhu, L.-Y.; Zhao, E.-G.; Shi, X.-D.; Zhou, X.; Han, Z.-T.

2018-03-01

About 3196 EA-type binaries (EAs) were observed by LAMOST by 2017 June 16 and their spectral types were derived. Meanwhile, the stellar atmospheric parameters of 2020 EAs were determined. In this paper, those EAs are cataloged and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EW-type binaries (EWs), indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs (0.4< P< 1 days) are the same as those of EAs with the same periods, while their values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may have formed through a combination of these mechanisms.

Nucleic Acid Encoding A Lectin-Derived Progenitor Cell Preservation Factor

DOEpatents

Colucci, M. Gabriella; Chrispeels, Maarten J.; Moore, Jeffrey G.

2001-10-30

The invention relates to an isolated nucleic acid molecule that encodes a protein that is effective to preserve progenitor cells, such as hematopoietic progenitor cells. The nucleic acid comprises a sequence defined by SEQ ID NO:1, a homolog thereof, or a fragment thereof. The encoded protein has an amino acid sequence that comprises a sequence defined by SEQ ID NO:2, a homolog thereof, or a fragment thereof that contains an amino acid sequence TNNVLQVT. Methods of using the encoded protein for preserving progenitor cells in vitro, ex vivo, and in vivo are also described. The invention, therefore, include methods such as myeloablation therapies for cancer treatment wherein myeloid reconstitution is facilitated by means of the specified protein. Other therapeutic utilities are also enabled through the invention, for example, expanding progenitor cell populations ex vivo to increase chances of engraftation, improving conditions for transporting and storing progenitor cells, and facilitating gene therapy to treat and cure a broad range of life-threatening hematologic diseases.

An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5.

PubMed

Schaefer, Bradley E; Pagnotta, Ashley

2012-01-11

A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a 'double-degenerate' origin), or by mass transfer from a companion star (the 'single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin has been widely rejected. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified, but that claim is still controversial. Here we report that the central region of the supernova remnant SNR 0509-67.5 (the site of a type Ia supernova 400 ± 50 years ago, based on its light echo) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of M(V) = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been 'kicked' by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system.

Noninvasive Imaging of Administered Progenitor Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steven R Bergmann, M.D., Ph.D.

The objective of this research grant was to develop an approach for labeling progenitor cells, specifically those that we had identified as being able to replace ischemic heart cells, so that the distribution could be followed non-invasively. In addition, the research was aimed at determining whether administration of progenitor cells resulted in improved myocardial perfusion and function. The efficiency and toxicity of radiolabeling of progenitor cells was to be evaluated. For the proposed clinical protocol, subjects with end-stage ischemic coronary artery disease were to undergo a screening cardiac positron emission tomography (PET) scan using N-13 ammonia to delineate myocardial perfusionmore » and function. If they qualified based on their PET scan, they would undergo an in-hospital protocol whereby CD34+ cells were stimulated by the administration of granulocytes-colony stimulating factor (G-CSF). CD34+ cells would then be isolated by apharesis, and labeled with indium-111 oxine. Cells were to be re-infused and subjects were to undergo single photon emission computed tomography (SPECT) scanning to evaluate uptake and distribution of labeled progenitor cells. Three months after administration of progenitor cells, a cardiac PET scan was to be repeated to evaluate changes in myocardial perfusion and/or function. Indium oxine is a radiopharmaceutical for labeling of autologous lymphocytes. Indium-111 (In-111) decays by electron capture with a t{sub ½} of 67.2 hours (2.8 days). Indium forms a saturated complex that is neutral, lipid soluble, and permeates the cell membrane. Within the cell, the indium-oxyquinolone complex labels via indium intracellular chelation. Following leukocyte labeling, ~77% of the In-111 is incorporated in the cell pellet. The presence of red cells and /or plasma reduces the labeling efficacy. Therefore, the product needed to be washed to eliminate plasma proteins. This repeated washing can damage cells. The CD34 selected product was a

Neuronal Progenitor Maintenance Requires Lactate Metabolism and PEPCK-M-Directed Cataplerosis.

PubMed

Álvarez, Zaida; Hyroššová, Petra; Perales, José Carlos; Alcántara, Soledad

2016-03-01

This study investigated the metabolic requirements for neuronal progenitor maintenance in vitro and in vivo by examining the metabolic adaptations that support neuronal progenitors and neural stem cells (NSCs) in their undifferentiated state. We demonstrate that neuronal progenitors are strictly dependent on lactate metabolism, while glucose induces their neuronal differentiation. Lactate signaling is not by itself capable of maintaining the progenitor phenotype. The consequences of lactate metabolism include increased mitochondrial and oxidative metabolism, with a strict reliance on cataplerosis through the mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M) pathway to support anabolic functions, such as the production of extracellular matrix. In vivo, lactate maintains/induces populations of postnatal neuronal progenitors/NSCs in a PEPCK-M-dependent manner. Taken together, our data demonstrate that, lactate alone or together with other physical/biochemical cues maintain NSCs/progenitors with a metabolic signature that is classically found in tissues with high anabolic capacity. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

The Formation of Rapidly Rotating Black Holes in High-mass X-Ray Binaries

DOE PAGES

Batta, Aldo; Ramirez-Ruiz, Enrico; Fryer, Chris Lee

2017-09-01

In this paper, high-mass X-ray binaries (HMXRBs), such as Cygnus X-1, host some of the most rapidly spinning black holes (BHs) known to date, reaching spin parametersmore » $$a\\gtrsim 0.84$$. However, there are several effects that can severely limit the maximum BH spin parameter that could be obtained from direct collapse, such as tidal synchronization, magnetic core-envelope coupling, and mass loss. Here, we propose an alternative scenario where the BH is produced by a failed supernova (SN) explosion that is unable to unbind the stellar progenitor. A large amount of fallback material ensues, whose interaction with the secondary naturally increases its overall angular momentum content, and therefore the spin of the BH when accreted. Through SPH hydrodynamic simulations, we studied the unsuccessful explosion of an $$8\\,{M}_{\\odot }$$ pre-SN star in a close binary with a $$12\\,{M}_{\\odot }$$ companion with an orbital period of ≈1.2 days, finding that it is possible to obtain a BH with a high spin parameter $$a\\gtrsim 0.8$$ even when the expected spin parameter from direct collapse is $$a\\lesssim 0.3$$. This scenario also naturally explains the atmospheric metal pollution observed in HMXRB stellar companions.« less

The Formation of Rapidly Rotating Black Holes in High-mass X-Ray Binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batta, Aldo; Ramirez-Ruiz, Enrico; Fryer, Chris Lee

In this paper, high-mass X-ray binaries (HMXRBs), such as Cygnus X-1, host some of the most rapidly spinning black holes (BHs) known to date, reaching spin parametersmore » $$a\\gtrsim 0.84$$. However, there are several effects that can severely limit the maximum BH spin parameter that could be obtained from direct collapse, such as tidal synchronization, magnetic core-envelope coupling, and mass loss. Here, we propose an alternative scenario where the BH is produced by a failed supernova (SN) explosion that is unable to unbind the stellar progenitor. A large amount of fallback material ensues, whose interaction with the secondary naturally increases its overall angular momentum content, and therefore the spin of the BH when accreted. Through SPH hydrodynamic simulations, we studied the unsuccessful explosion of an $$8\\,{M}_{\\odot }$$ pre-SN star in a close binary with a $$12\\,{M}_{\\odot }$$ companion with an orbital period of ≈1.2 days, finding that it is possible to obtain a BH with a high spin parameter $$a\\gtrsim 0.8$$ even when the expected spin parameter from direct collapse is $$a\\lesssim 0.3$$. This scenario also naturally explains the atmospheric metal pollution observed in HMXRB stellar companions.« less

Prospects for joint observations of gravitational waves and gamma rays from merging neutron star binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patricelli, B.; Razzano, M.; Fidecaro, F.

The detection of the events GW150914 and GW151226, both consistent with the merger of a binary black hole system (BBH), opened the era of gravitational wave (GW) astronomy. Besides BBHs, the most promising GW sources are the coalescences of binary systems formed by two neutron stars or a neutron star and a black hole. These mergers are thought to be connected with short Gamma Ray Bursts (GRBs), therefore combined observations of GW and electromagnetic (EM) signals could definitively probe this association. We present a detailed study on the expectations for joint GW and high-energy EM observations of coalescences of binarymore » systems of neutron stars with Advanced Virgo and LIGO and with the Fermi gamma-ray telescope. To this scope, we designed a dedicated Montecarlo simulation pipeline for the multimessenger emission and detection by GW and gamma-ray instruments, considering the evolution of the GW detector sensitivities. We show that the expected rate of joint detection is low during the Advanced Virgo and Advanced LIGO 2016–2017 run; however, as the interferometers approach their final design sensitivities, the rate will increase by ∼ a factor of ten. Future joint observations will help to constrain the association between short GRBs and binary systems and to solve the puzzle of the progenitors of GWs. Comparison of the joint detection rate with the ones predicted in this paper will help to constrain the geometry of the GRB jet.« less

Outflow-driven Transients from the Birth of Binary Black Holes. II. Primary-induced Accretion Transients

NASA Astrophysics Data System (ADS)

Kimura, Shigeo S.; Murase, Kohta; Mészáros, Peter

2017-12-01

We discuss the electromagnetic radiation from newborn binary black holes (BBHs). As a consequence of the evolution of massive stellar binaries, a binary consisting of a primary black hole (BH) and a secondary Wolf–Rayet star is expected as a BBH progenitor system. We investigate optical transients from the birth of BBHs powered by the Bondi–Hoyle–Lyttleton accretion onto the primary BH, which occur ∼1–10 Gyr earlier than gravitational-wave signals at the BH–BH merger. When the secondary massive star collapses into a BH, it may eject a fraction of its outer material and may form a disk around the primary BH and induces a powerful disk wind. These primary-induced winds can lead to optical transients with a kinetic energy of ∼1047–3 × 1048 erg, an ejecta velocity of 108–109 cm s‑1, a duration of a few days, and an absolute magnitude ranging from about ‑11 to ‑14. The light curves and late-time spectra of these transients are distinctive from those of ordinary supernovae, and detection of this type of transient is possible by future optical transient surveys if the event rate of this transient is comparable to the merger rate of BBHs. This paper focuses on the emissions from disk-driven transients induced by the primary BH, different from Paper I, which focuses on wind-driven transients from the tidally locked secondary massive star.

Light-curve and spectral properties of ultrastripped core-collapse supernovae leading to binary neutron stars

NASA Astrophysics Data System (ADS)

Moriya, Takashi J.; Mazzali, Paolo A.; Tominaga, Nozomu; Hachinger, Stephan; Blinnikov, Sergei I.; Tauris, Thomas M.; Takahashi, Koh; Tanaka, Masaomi; Langer, Norbert; Podsiadlowski, Philipp

2017-04-01

We investigate light-curve and spectral properties of ultrastripped core-collapse supernovae. Ultrastripped supernovae are the explosions of heavily stripped massive stars that lost their envelopes via binary interactions with a compact companion star. They eject only ˜0.1 M⊙ and may be the main way to form double neutron-star systems that eventually merge emitting strong gravitational waves. We follow the evolution of an ultrastripped supernova progenitor until iron core collapse and perform explosive nucleosynthesis calculations. We then synthesize light curves and spectra of ultrastripped supernovae using the nucleosynthesis results and present their expected properties. Ultrastripped supernovae synthesize ˜0.01 M⊙ of radioactive 56Ni, and their typical peak luminosity is around 1042 erg s-1 or -16 mag. Their typical rise time is 5-10 d. Comparing synthesized and observed spectra, we find that SN 2005ek, some of the so-called calcium-rich gap transients, and SN 2010X may be related to ultrastripped supernovae. If these supernovae are actually ultrastripped supernovae, their event rate is expected to be about 1 per cent of core-collapse supernovae. Comparing the double neutron-star merger rate obtained by future gravitational-wave observations and the ultrastripped supernova rate obtained by optical transient surveys identified with our synthesized light-curve and spectral models, we will be able to judge whether ultrastripped supernovae are actually a major contributor to the binary neutron-star population and provide constraints on binary stellar evolution.

Stanniocalcin-1 Rescued Photoreceptor Degeneration in Two Rat Models of Inherited Retinal Degeneration

PubMed Central

Roddy, Gavin W; Rosa Jr, Robert H; Youn Oh, Joo; Ylostalo, Joni H; Bartosh, Thomas J; Choi, Hosoon; Lee, Ryang Hwa; Yasumura, Douglas; Ahern, Kelly; Nielsen, Gregory; Matthes, Michael T; LaVail, Matthew M; Prockop, Darwin J

2012-01-01

Oxidative stress and photoreceptor apoptosis are prominent features of many forms of retinal degeneration (RD) for which there are currently no effective therapies. We previously observed that mesenchymal stem/stromal cells reduce apoptosis by being activated to secrete stanniocalcin-1 (STC-1), a multifunctional protein that reduces oxidative stress by upregulating mitochondrial uncoupling protein-2 (UCP-2). Therefore, we tested the hypothesis that intravitreal injection of STC-1 can rescue photoreceptors. We first tested STC-1 in the rhodopsin transgenic rat characterized by rapid photoreceptor loss. Intravitreal STC-1 decreased the loss of photoreceptor nuclei and transcripts and resulted in measurable retinal function when none is otherwise present in this rapid degeneration. We then tested STC-1 in the Royal College of Surgeons (RCS) rat characterized by a slower photoreceptor degeneration. Intravitreal STC-1 reduced the number of pyknotic nuclei in photoreceptors, delayed the loss of photoreceptor transcripts, and improved function of rod photoreceptors. Additionally, STC-1 upregulated UCP-2 and decreased levels of two protein adducts generated by reactive oxygen species (ROS). Microarrays from the two models demonstrated that STC-1 upregulated expression of a similar profile of genes for retinal development and function. The results suggested that intravitreal STC-1 is a promising therapy for various forms of RD including retinitis pigmentosa and atrophic age-related macular degeneration (AMD). PMID:22294148

Cortical-basal ganglionic degeneration.

PubMed

Riley, D E; Lang, A E; Lewis, A; Resch, L; Ashby, P; Hornykiewicz, O; Black, S

1990-08-01

We report our experience with 15 patients believed to have cortical-basal ganglionic degeneration. The clinical picture is distinctive, comprising features referable to both cortical and basal ganglionic dysfunction. Characteristic manifestations include cortical sensory loss, focal reflex myoclonus, "alien limb" phenomena, apraxia, rigidity and akinesia, a postural-action tremor, limb dystonia, hyperreflexia, and postural instability. The asymmetry of symptoms and signs is often striking. Brain imaging may demonstrate greater abnormalities contralateral to the more affected side. Postmortem studies in 2 patients revealed the characteristic pathologic features of swollen, poorly staining (achromatic) neurons and degeneration of cerebral cortex and substantia nigra. Biochemical analysis of 1 brain showed a severe, diffuse loss of dopamine in the striatum. This condition is more frequent than previously believed, and the diagnosis can be predicted during life on the basis of clinical findings. However, as with other "degenerative" diseases of the nervous system, a definitive diagnosis of cortical-basal ganglionic degeneration requires confirmation by autopsy.

Pulsars in binary systems: probing binary stellar evolution and general relativity.

PubMed

Stairs, Ingrid H

2004-04-23

Radio pulsars in binary orbits often have short millisecond spin periods as a result of mass transfer from their companion stars. They therefore act as very precise, stable, moving clocks that allow us to investigate a large set of otherwise inaccessible astrophysical problems. The orbital parameters derived from high-precision binary pulsar timing provide constraints on binary evolution, characteristics of the binary pulsar population, and the masses of neutron stars with different mass-transfer histories. These binary systems also test gravitational theories, setting strong limits on deviations from general relativity. Surveys for new pulsars yield new binary systems that increase our understanding of all these fields and may open up whole new areas of physics, as most spectacularly evidenced by the recent discovery of an extremely relativistic double-pulsar system.

Vascular wall progenitor cells in health and disease.

PubMed

Psaltis, Peter J; Simari, Robert D

2015-04-10

The vasculature plays an indispensible role in organ development and maintenance of tissue homeostasis, such that disturbances to it impact greatly on developmental and postnatal health. Although cell turnover in healthy blood vessels is low, it increases considerably under pathological conditions. The principle sources for this phenomenon have long been considered to be the recruitment of cells from the peripheral circulation and the re-entry of mature cells in the vessel wall back into cell cycle. However, recent discoveries have also uncovered the presence of a range of multipotent and lineage-restricted progenitor cells in the mural layers of postnatal blood vessels, possessing high proliferative capacity and potential to generate endothelial, smooth muscle, hematopoietic or mesenchymal cell progeny. In particular, the tunica adventitia has emerged as a progenitor-rich compartment with niche-like characteristics that support and regulate vascular wall progenitor cells. Preliminary data indicate the involvement of some of these vascular wall progenitor cells in vascular disease states, adding weight to the notion that the adventitia is integral to vascular wall pathogenesis, and raising potential implications for clinical therapies. This review discusses the current body of evidence for the existence of vascular wall progenitor cell subpopulations from development to adulthood and addresses the gains made and significant challenges that lie ahead in trying to accurately delineate their identities, origins, regulatory pathways, and relevance to normal vascular structure and function, as well as disease. © 2015 American Heart Association, Inc.

Frontotemporal Lobar Degeneration

PubMed Central

Rabinovici, Gil D.; Miller, Bruce L.

2010-01-01

Frontotemporal lobar degeneration (FTLD) is a clinically and pathologically heterogeneous syndrome, characterized by progressive decline in behaviour or language associated with degeneration of the frontal and anterior temporal lobes. While the seminal cases were described at the turn of the 20th century, FTLD has only recently been appreciated as a leading cause of dementia, particularly in patients presenting before the age of 65 years. Three distinct clinical variants of FTLD have been described: (i) behavioural-variant frontotemporal dementia, characterized by changes in behaviour and personality in association with frontal-predominant cortical degeneration; (ii) semantic dementia, a syndrome of progressive loss of knowledge about words and objects associated with anterior temporal neuronal loss; and (iii) progressive nonfluent aphasia, characterized by effortful language output, loss of grammar and motor speech deficits in the setting of left perisylvian cortical atrophy. The majority of pathologies associated with FTLD clinical syndromes include either tau-positive (FTLD-TAU) or TAR DNA-binding protein 43 (TDP-43)-positive (FTLD-TDP) inclusion bodies. FTLD overlaps clinically and pathologically with the atypical parkinsonian disorders corticobasal degeneration and progressive supranuclear palsy, and with amyotrophic lateral sclerosis. The majority of familial FTLD cases are caused by mutations in the genes encoding microtubule-associated protein tau (leading to FTLD-TAU) or progranulin (leading to FTLD-TDP). The clinical and pathologic heterogeneity of FTLD poses a significant diagnostic challenge, and in vivo prediction of underlying histopathology can be significantly improved by supplementing the clinical evaluation with genetic tests and emerging biological markers. Current pharmacotherapy for FTLD focuses on manipulating serotonergic or dopaminergic neurotransmitter systems to ameliorate behavioural or motor symptoms. However, recent advances in FTLD

Ionizing spectra of stars that lose their envelope through interaction with a binary companion: role of metallicity

NASA Astrophysics Data System (ADS)

Götberg, Y.; de Mink, S. E.; Groh, J. H.

2017-11-01

Understanding ionizing fluxes of stellar populations is crucial for various astrophysical problems including the epoch of reionization. Short-lived massive stars are generally considered as the main stellar sources. We examine the potential role of less massive stars that lose their envelope through interaction with a binary companion. Here, we focus on the role of metallicity (Z). For this purpose we used the evolutionary code MESA and created tailored atmosphere models with the radiative transfer code CMFGEN. We show that typical progenitors, with initial masses of 12 M⊙, produce hot and compact stars ( 4 M⊙, 60-80 kK, 1 R⊙). These stripped stars copiously produce ionizing photons, emitting 60-85% and 30-60% of their energy as HI and HeI ionizing radiation, for Z = 0.0001-0.02, respectively. Their output is comparable to what massive stars emit during their Wolf-Rayet phase, if we account for their longer lifetimes and the favorable slope of the initial mass function. Their relative importance for reionization may be further favored since they emit their photons with a time delay ( 20 Myr after birth in our fiducial model). This allows time for the dispersal of the birth clouds, allowing the ionizing photons to escape into the intergalactic medium. At low Z, we find that Roche stripping fails to fully remove the H-rich envelope, because of the reduced opacity in the subsurface layers. This is in sharp contrast with the assumption of complete stripping that is made in rapid population synthesis simulations, which are widely used to simulate the binary progenitors of supernovae and gravitational waves. Finally, we discuss the urgency to increase the observed sample of stripped stars to test these models and we discuss how our predictions can help to design efficient observational campaigns.

VEGF is a chemoattractant for FGF-2–stimulated neural progenitors

PubMed Central

Zhang, Huanxiang; Vutskits, Laszlo; Pepper, Michael S.; Kiss, Jozsef Z.

2003-01-01

Mmigration of undifferentiated neural progenitors is critical for the development and repair of the nervous system. However, the mechanisms and factors that regulate migration are not well understood. Here, we show that vascular endothelial growth factor (VEGF)-A, a major angiogenic factor, guides the directed migration of neural progenitors that do not display antigenic markers for neuron- or glia-restricted precursor cells. We demonstrate that progenitor cells express both VEGF receptor (VEGFR) 1 and VEGFR2, but signaling through VEGFR2 specifically mediates the chemotactic effect of VEGF. The expression of VEGFRs and the chemotaxis of progenitors in response to VEGF require the presence of fibroblast growth factor 2. These results demonstrate that VEGF is an attractive guidance cue for the migration of undifferentiated neural progenitors and offer a mechanistic link between neurogenesis and angiogenesis in the nervous system. PMID:14691144

Transcriptome Profiles of Isolated Murine Achilles Tendon Proper- and Peritenon- Derived Progenitor Cells.

PubMed

Mienaltowski, Michael J; Cánovas, Angela; Fates, Valerie A; Hampton, Angela R; Pechanec, Monica Y; Islas-Trejo, Alma; Medrano, Juan F

2018-06-21

Progenitor cells of the tendon proper and peritenon have unique properties that could impact their utilization in tendon repair strategies. While a few markers have been found to aid in distinguishing progenitors cells from each region, there is great value in identifying more markers. In this study, we hypothesized that RNAseq could be used to improve our understanding of those markers that define these cell types. Transcriptome profiles were generated for pools of mouse Achilles tendon progenitor cells from both regions and catalogues of potential markers were generated. Moreover, common (e.g., glycoprotein, signaling, and proteinaceous extracellular matrix) and unique (e.g., cartilage development versus angiogenesis and muscle contraction) biological processes and molecular functions were described for progenitors from each region. Real-time quantitative PCR of a subset of genes was used to gain insight into the heterogeneity amongst individual progenitor colonies from each region. Markers like Scx, Mkx, Thbs4, and Wnt10a were consistently able to distinguish tendon proper progenitors from peritenon progenitors; expression variability for other genes suggested greater cell type complexity for potential peritenon progenitor markers. This is the first effort to define Achilles tendon progenitor markers by region. Further efforts to investigate the value of these catalogued markers are required by screening more individual colonies of progenitors for more markers. Findings from this study advance efforts in the discernment of cell type specific markers for tendon proper and peritenon progenitor cells; insight into marker sets could improve tracking and sorting strategies for these cells for future therapeutic strategies. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Thymus-autonomous T cell development in the absence of progenitor import.

PubMed

Martins, Vera C; Ruggiero, Eliana; Schlenner, Susan M; Madan, Vikas; Schmidt, Manfred; Fink, Pamela J; von Kalle, Christof; Rodewald, Hans-Reimer

2012-07-30

Thymus function is thought to depend on a steady supply of T cell progenitors from the bone marrow. The notion that the thymus lacks progenitors with self-renewal capacity is based on thymus transplantation experiments in which host-derived thymocytes replaced thymus-resident cells within 4 wk. Thymus grafting into T cell-deficient mice resulted in a wave of T cell export from the thymus, followed by colonization of the thymus by host-derived progenitors, and cessation of T cell development. Compound Rag2(-/-)γ(c)(-/-)Kit(W/Wv) mutants lack competitive hematopoietic stem cells (HSCs) and are devoid of T cell progenitors. In this study, using this strain as recipients for wild-type thymus grafts, we noticed thymus-autonomous T cell development lasting several months. However, we found no evidence for export of donor HSCs from thymus to bone marrow. A diverse T cell antigen receptor repertoire in progenitor-deprived thymus grafts implied that many thymocytes were capable of self-renewal. Although the process was most efficient in Rag2(-/-)γ(c)(-/-)Kit(W/Wv) hosts, γ(c)-mediated signals alone played a key role in the competition between thymus-resident and bone marrow-derived progenitors. Hence, the turnover of each generation of thymocytes is not only based on short life span but is also driven via expulsion of resident thymocytes by fresh progenitors entering the thymus.

NFIX Regulates Neural Progenitor Cell Differentiation During Hippocampal Morphogenesis

PubMed Central

Heng, Yee Hsieh Evelyn; McLeay, Robert C.; Harvey, Tracey J.; Smith, Aaron G.; Barry, Guy; Cato, Kathleen; Plachez, Céline; Little, Erica; Mason, Sharon; Dixon, Chantelle; Gronostajski, Richard M.; Bailey, Timothy L.; Richards, Linda J.; Piper, Michael

2014-01-01

Neural progenitor cells have the ability to give rise to neurons and glia in the embryonic, postnatal and adult brain. During development, the program regulating whether these cells divide and self-renew or exit the cell cycle and differentiate is tightly controlled, and imbalances to the normal trajectory of this process can lead to severe functional consequences. However, our understanding of the molecular regulation of these fundamental events remains limited. Moreover, processes underpinning development of the postnatal neurogenic niches within the cortex remain poorly defined. Here, we demonstrate that Nuclear factor one X (NFIX) is expressed by neural progenitor cells within the embryonic hippocampus, and that progenitor cell differentiation is delayed within Nfix−/− mice. Moreover, we reveal that the morphology of the dentate gyrus in postnatal Nfix−/− mice is abnormal, with fewer subgranular zone neural progenitor cells being generated in the absence of this transcription factor. Mechanistically, we demonstrate that the progenitor cell maintenance factor Sry-related HMG box 9 (SOX9) is upregulated in the hippocampus of Nfix−/− mice and demonstrate that NFIX can repress Sox9 promoter-driven transcription. Collectively, our findings demonstrate that NFIX plays a central role in hippocampal morphogenesis, regulating the formation of neuronal and glial populations within this structure. PMID:23042739

Direct Reprogramming of Mouse Fibroblasts into Functional Skeletal Muscle Progenitors.

PubMed

Bar-Nur, Ori; Gerli, Mattia F M; Di Stefano, Bruno; Almada, Albert E; Galvin, Amy; Coffey, Amy; Huebner, Aaron J; Feige, Peter; Verheul, Cassandra; Cheung, Priscilla; Payzin-Dogru, Duygu; Paisant, Sylvain; Anselmo, Anthony; Sadreyev, Ruslan I; Ott, Harald C; Tajbakhsh, Shahragim; Rudnicki, Michael A; Wagers, Amy J; Hochedlinger, Konrad

2018-05-08

Skeletal muscle harbors quiescent stem cells termed satellite cells and proliferative progenitors termed myoblasts, which play pivotal roles during muscle regeneration. However, current technology does not allow permanent capture of these cell populations in vitro. Here, we show that ectopic expression of the myogenic transcription factor MyoD, combined with exposure to small molecules, reprograms mouse fibroblasts into expandable induced myogenic progenitor cells (iMPCs). iMPCs express key skeletal muscle stem and progenitor cell markers including Pax7 and Myf5 and give rise to dystrophin-expressing myofibers upon transplantation in vivo. Notably, a subset of transplanted iMPCs maintain Pax7 expression and sustain serial regenerative responses. Similar to satellite cells, iMPCs originate from Pax7 + cells and require Pax7 itself for maintenance. Finally, we show that myogenic progenitor cell lines can be established from muscle tissue following small-molecule exposure alone. This study thus reports on a robust approach to derive expandable myogenic stem/progenitor-like cells from multiple cell types. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Trojan Binaries

NASA Astrophysics Data System (ADS)

Noll, K. S.

2017-12-01

The Jupiter Trojans, in the context of giant planet migration models, can be thought of as an extension of the small body populations found beyond Neptune in the Kuiper Belt. Binaries are a distinctive feature of small body populations in the Kuiper Belt with an especially high fraction apparent among the brightest Cold Classicals. The binary fraction, relative sizes, and separations in the dynamically excited populations (Scattered, Resonant) reflects processes that may have eroded a more abundant initial population. This trend continues in the Centaurs and Trojans where few binaries have been found. We review new evidence including a third resolved Trojan binary and lightcurve studies to understand how the Trojans are related to the small body populations that originated in the outer protoplanetary disk.

Characterization of Proliferating Neural Progenitors after Spinal Cord Injury in Adult Zebrafish

PubMed Central

Hui, Subhra Prakash; Nag, Tapas Chandra; Ghosh, Sukla

2015-01-01

Zebrafish can repair their injured brain and spinal cord after injury unlike adult mammalian central nervous system. Any injury to zebrafish spinal cord would lead to increased proliferation and neurogenesis. There are presences of proliferating progenitors from which both neuronal and glial loss can be reversed by appropriately generating new neurons and glia. We have demonstrated the presence of multiple progenitors, which are different types of proliferating populations like Sox2+ neural progenitor, A2B5+ astrocyte/ glial progenitor, NG2+ oligodendrocyte progenitor, radial glia and Schwann cell like progenitor. We analyzed the expression levels of two common markers of dedifferentiation like msx-b and vimentin during regeneration along with some of the pluripotency associated factors to explore the possible role of these two processes. Among the several key factors related to pluripotency, pou5f1 and sox2 are upregulated during regeneration and associated with activation of neural progenitor cells. Uncovering the molecular mechanism for endogenous regeneration of adult zebrafish spinal cord would give us more clues on important targets for future therapeutic approach in mammalian spinal cord repair and regeneration. PMID:26630262

Macular Degeneration

MedlinePlus

... happens when the light-sensitive cells in the macula slowly break down. Your gradually lose your central vision. A common early symptom is that straight lines appear crooked. Regular comprehensive eye exams can detect macular degeneration before the disease causes vision loss. Treatment can ...

The lowest-metallicity type II supernova from the highest-mass red supergiant progenitor

NASA Astrophysics Data System (ADS)

Anderson, J. P.; Dessart, L.; Gutiérrez, C. P.; Krühler, T.; Galbany, L.; Jerkstrand, A.; Smartt, S. J.; Contreras, C.; Morrell, N.; Phillips, M. M.; Stritzinger, M. D.; Hsiao, E. Y.; González-Gaitán, S.; Agliozzo, C.; Castellón, S.; Chambers, K. C.; Chen, T.-W.; Flewelling, H.; Gonzalez, C.; Hosseinzadeh, G.; Huber, M.; Fraser, M.; Inserra, C.; Kankare, E.; Mattila, S.; Magnier, E.; Maguire, K.; Lowe, T. B.; Sollerman, J.; Sullivan, M.; Young, D. R.; Valenti, S.

2018-05-01

Red supergiants have been confirmed as the progenitor stars of the majority of hydrogen-rich type II supernovae1. However, while such stars are observed with masses >25 M⊙ (ref. 2), detections of >18 M⊙ progenitors remain elusive1. Red supergiants are also expected to form at all metallicities, but discoveries of explosions from low-metallicity progenitors are scarce. Here, we report observations of the type II supernova, SN 2015bs, for which we infer a progenitor metallicity of ≤0.1 Z⊙ from comparison to photospheric-phase spectral models3, and a zero-age main-sequence mass of 17–25 M⊙ through comparison to nebular-phase spectral models4,5. SN 2015bs displays a normal ‘plateau’ light-curve morphology, and typical spectral properties, implying a red supergiant progenitor. This is the first example of such a high-mass progenitor for a ‘normal’ type II supernova, suggesting a link between high-mass red supergiant explosions and low-metallicity progenitors.

Formation of Degenerate Band Gaps in Layered Systems

PubMed Central

Ignatov, Anton I.; Merzlikin, Alexander M.; Levy, Miguel; Vinogradov, Alexey P.

2012-01-01

In the review, peculiarities of spectra of one-dimensional photonic crystals made of anisotropic and/or magnetooptic materials are considered. The attention is focused on band gaps of a special type—the so called degenerate band gaps which are degenerate with respect to polarization. Mechanisms of formation and properties of these band gaps are analyzed. Peculiarities of spectra of photonic crystals that arise due to the linkage between band gaps are discussed. Particularly, it is shown that formation of a frozen mode is caused by linkage between Brillouin and degenerate band gaps. Also, existence of the optical Borrmann effect at the boundaries of degenerate band gaps and optical Tamm states at the frequencies of degenerate band gaps are analyzed. PMID:28817024

Circulating hematopoietic progenitor cells in patients affected by Chornobyl accident.

PubMed

Bilko, N M; Dyagil, I S; Russu, I Z; Bilko, D I

2016-12-01

High radiation sensitivity of stem cells and their ability to accumulate sublethal radiation damage provides the basis for investigation of hematopoietic progenitors using in vivo culture methodology. Unique samples of peripheral blood and bone marrow were derived from the patients affected by Chornobyl accident during liquidation campaign. To investigate functional activity of circulating hematopoietic progenitor cells from peripheral blood and bone marrow of cleanup workers in early and remote periods after the accident at Chornobyl nuclear power plant (CNPP). The assessment of the functional activity of circulating hematopoietic progenitor cells was performed in samples of peripheral blood and bone marrow of 46 cleanup workers, who were treated in the National Scientific Center for Radiation Medicine of the Academy of Medical Sciences of Ukraine alongside with 35 non radiated patients, who served as a control. Work was performed by culturing peripheral blood and bone marrow mononuclear cells in the original gel diffusion capsules, implanted into the peritoneal cavity of CBA mice. It was shown that hematopoietic progenitor cells could be identified in the peripheral blood of liquidators of CNPP accident. At the same time the number of functionally active progenitor cells of the bone marrow was significantly decreased and during the next 10 years after the accident, counts of circulating progenitor cells in the peripheral blood as well as functionally active hematopoietic cells in bone marrow returned to normal levels. It was shown that hematopoietic progenitor cells are detected not only in the bone marrow but also in the peripheral blood of liquidators as a consequence of radiation exposure associated with CNPP accident. This article is a part of a Special Issue entitled "The Chornobyl Nuclear Accident: Thirty Years After".

Inter-progenitor pool wiring: An evolutionarily conserved strategy that expands neural circuit diversity.

PubMed

Suzuki, Takumi; Sato, Makoto

2017-11-15

Diversification of neuronal types is key to establishing functional variations in neural circuits. The first critical step to generate neuronal diversity is to organize the compartmental domains of developing brains into spatially distinct neural progenitor pools. Neural progenitors in each pool then generate a unique set of diverse neurons through specific spatiotemporal specification processes. In this review article, we focus on an additional mechanism, 'inter-progenitor pool wiring', that further expands the diversity of neural circuits. After diverse types of neurons are generated in one progenitor pool, a fraction of these neurons start migrating toward a remote brain region containing neurons that originate from another progenitor pool. Finally, neurons of different origins are intermingled and eventually form complex but precise neural circuits. The developing cerebral cortex of mammalian brains is one of the best examples of inter-progenitor pool wiring. However, Drosophila visual system development has revealed similar mechanisms in invertebrate brains, suggesting that inter-progenitor pool wiring is an evolutionarily conserved strategy that expands neural circuit diversity. Here, we will discuss how inter-progenitor pool wiring is accomplished in mammalian and fly brain systems. Copyright © 2017 Elsevier Inc. All rights reserved.

Combined KIT and FGFR2b Signaling Regulates Epithelial Progenitor Expansion during Organogenesis

PubMed Central

Lombaert, Isabelle M.A.; Abrams, Shaun R.; Li, Li; Eswarakumar, Veraragavan P.; Sethi, Aditya J.; Witt, Robert L.; Hoffman, Matthew P.

2013-01-01

Summary Organ formation and regeneration require epithelial progenitor expansion to engineer, maintain, and repair the branched tissue architecture. Identifying the mechanisms that control progenitor expansion will inform therapeutic organ (re)generation. Here, we discover that combined KIT and fibroblast growth factor receptor 2b (FGFR2b) signaling specifically increases distal progenitor expansion during salivary gland organogenesis. FGFR2b signaling upregulates the epithelial KIT pathway so that combined KIT/FGFR2b signaling, via separate AKT and mitogen-activated protein kinase (MAPK) pathways, amplifies FGFR2b-dependent transcription. Combined KIT/FGFR2b signaling selectively expands the number of KIT+K14+SOX10+ distal progenitors, and a genetic loss of KIT signaling depletes the distal progenitors but also unexpectedly depletes the K5+ proximal progenitors. This occurs because the distal progenitors produce neurotrophic factors that support gland innervation, which maintains the proximal progenitors. Furthermore, a rare population of KIT+FGFR2b+ cells is present in adult glands, in which KIT signaling also regulates epithelial-neuronal communication during homeostasis. Our findings provide a framework to direct regeneration of branched epithelial organs. PMID:24371813

Targeting human oligodendrocyte progenitors for myelin repair☆

PubMed Central

Dietz, Karen C.; Polanco, Jessie J.; Pol, Suyog U.; Sim, Fraser J.

2017-01-01

Oligodendrocyte development has been studied for several decades, and has served as a model system for both neurodevelopmental and stem/progenitor cell biology. Until recently, the vast majority of studies have been conducted in lower species, especially those focused on rodent development and remyelination. In humans, the process of myelination requires the generation of vastly more myelinating glia, occurring over a period of years rather than weeks. Furthermore, as evidenced by the presence of chronic demyelination in a variety of human neurologic diseases, it appears likely that the mechanisms that regulate development and become dysfunctional in disease may be, in key ways, divergent across species. Improvements in isolation techniques, applied to primary human neural and oligodendrocyte progenitors from both fetal and adult brain, as well as advancements in the derivation of defined progenitors from human pluripotent stem cells, have begun to reveal the extent of both species-conserved signaling pathways and potential key differences at cellular and molecular levels. In this article, we will review the commonalities and differences in myelin development between rodents and man, describing the approaches used to study human oligodendrocyte differentiation and myelination, as well as heterogeneity within targetable progenitor pools, and discuss the advances made in determining which conserved pathways may be both modeled in rodents and translate into viable therapeutic strategies to promote myelin repair. PMID:27001544

Prolonged Mitosis of Neural Progenitors Alters Cell Fate in the Developing Brain.

PubMed

Pilaz, Louis-Jan; McMahon, John J; Miller, Emily E; Lennox, Ashley L; Suzuki, Aussie; Salmon, Edward; Silver, Debra L

2016-01-06

Embryonic neocortical development depends on balanced production of progenitors and neurons. Genetic mutations disrupting progenitor mitosis frequently impair neurogenesis; however, the link between altered mitosis and cell fate remains poorly understood. Here we demonstrate that prolonged mitosis of radial glial progenitors directly alters neuronal fate specification and progeny viability. Live imaging of progenitors from a neurogenesis mutant, Magoh(+/-), reveals that mitotic delay significantly correlates with preferential production of neurons instead of progenitors, as well as apoptotic progeny. Independently, two pharmacological approaches reveal a causal relationship between mitotic delay and progeny fate. As mitotic duration increases, progenitors produce substantially more apoptotic progeny or neurons. We show that apoptosis, but not differentiation, is p53 dependent, demonstrating that these are distinct outcomes of mitotic delay. Together our findings reveal that prolonged mitosis is sufficient to alter fates of radial glia progeny and define a new paradigm to understand how mitosis perturbations underlie brain size disorders such as microcephaly. Copyright © 2016 Elsevier Inc. All rights reserved.

APC sets the Wnt tone necessary for cerebral cortical progenitor development.

PubMed

Nakagawa, Naoki; Li, Jingjun; Yabuno-Nakagawa, Keiko; Eom, Tae-Yeon; Cowles, Martis; Mapp, Tavien; Taylor, Robin; Anton, E S

2017-08-15

Adenomatous polyposis coli (APC) regulates the activity of β-catenin, an integral component of Wnt signaling. However, the selective role of the APC-β-catenin pathway in cerebral cortical development is unknown. Here we genetically dissected the relative contributions of APC-regulated β-catenin signaling in cortical progenitor development, a necessary early step in cerebral cortical formation. Radial progenitor-specific inactivation of the APC-β-catenin pathway indicates that the maintenance of appropriate β-catenin-mediated Wnt tone is necessary for the orderly differentiation of cortical progenitors and the resultant formation of the cerebral cortex. APC deletion deregulates β-catenin, leads to high Wnt tone, and disrupts Notch1 signaling and primary cilium maintenance necessary for radial progenitor functions. β-Catenin deregulation directly disrupts cilium maintenance and signaling via Tulp3, essential for intraflagellar transport of ciliary signaling receptors. Surprisingly, deletion of β-catenin or inhibition of β-catenin activity in APC-null progenitors rescues the APC-null phenotype. These results reveal that APC-regulated β-catenin activity in cortical progenitors sets the appropriate Wnt tone necessary for normal cerebral cortical development. © 2017 Nakagawa et al.; Published by Cold Spring Harbor Laboratory Press.

APC sets the Wnt tone necessary for cerebral cortical progenitor development

PubMed Central

Nakagawa, Naoki; Li, Jingjun; Yabuno-Nakagawa, Keiko; Eom, Tae-Yeon; Cowles, Martis; Mapp, Tavien; Taylor, Robin; Anton, E.S.

2017-01-01

Adenomatous polyposis coli (APC) regulates the activity of β-catenin, an integral component of Wnt signaling. However, the selective role of the APC–β-catenin pathway in cerebral cortical development is unknown. Here we genetically dissected the relative contributions of APC-regulated β-catenin signaling in cortical progenitor development, a necessary early step in cerebral cortical formation. Radial progenitor-specific inactivation of the APC–β-catenin pathway indicates that the maintenance of appropriate β-catenin-mediated Wnt tone is necessary for the orderly differentiation of cortical progenitors and the resultant formation of the cerebral cortex. APC deletion deregulates β-catenin, leads to high Wnt tone, and disrupts Notch1 signaling and primary cilium maintenance necessary for radial progenitor functions. β-Catenin deregulation directly disrupts cilium maintenance and signaling via Tulp3, essential for intraflagellar transport of ciliary signaling receptors. Surprisingly, deletion of β-catenin or inhibition of β-catenin activity in APC-null progenitors rescues the APC-null phenotype. These results reveal that APC-regulated β-catenin activity in cortical progenitors sets the appropriate Wnt tone necessary for normal cerebral cortical development. PMID:28916710

Hmga2 regulates self-renewal of retinal progenitors.

PubMed

Parameswaran, Sowmya; Xia, Xiaohuan; Hegde, Ganapati; Ahmad, Iqbal

2014-11-01

In vertebrate retina, histogenesis occurs over an extended period. To sustain the temporal generation of diverse cell types, retinal progenitor cells (RPCs) must self-renew. However, self-renewal and regulation of RPCs remain poorly understood. Here, we demonstrate that cell-extrinsic factors coordinate with the epigenetic regulator high-mobility group AT-hook 2 (Hmga2) to regulate self-renewal of late retinal progenitor cells (RPCs). We observed that a small subset of RPCs was capable of clonal propagation and retained multipotentiality of parents in the presence of endothelial cells (ECs), known self-renewal regulators in various stem cell niches. The self-renewing effects, also observed in vivo, involve multiple intercellular signaling pathways, engaging Hmga2. As progenitors exhaust during retinal development, expression of Hmga2 progressively decreases. Analyses of Hmga2-expression perturbation, in vitro and in vivo, revealed that Hmga2 functionally helps to mediate cell-extrinsic influences on late-retinal progenitor self-renewal. Our results provide a framework for integrating the diverse intercellular influences elicited by epigenetic regulators for self-renewal in a dynamic stem cell niche: the developing vertebrate retina. © 2014. Published by The Company of Biologists Ltd.

Does corticobasal degeneration exist? A clinicopathological re-evaluation.

PubMed

Ling, Helen; O'Sullivan, Sean S; Holton, Janice L; Revesz, Tamas; Massey, Luke A; Williams, David R; Paviour, Dominic C; Lees, Andrew J

2010-07-01

The pathological findings of corticobasal degeneration are associated with several distinct clinical syndromes, and the corticobasal syndrome has been linked with a number of diverse pathologies. We have reviewed all the archival cases in the Queen Square Brain Bank for Neurological Disorders over a 20-year period with either a clinical diagnosis of corticobasal syndrome or pathological diagnosis of corticobasal degeneration in an attempt to identify the main diagnostic pitfalls. Of 19 pathologically confirmed corticobasal degeneration cases, only five had been diagnosed correctly in life (sensitivity=26.3%) and four of these had received an alternative earlier diagnosis. All five of these had a unilateral presentation, clumsy useless limb, limb apraxia and myoclonus, four had cortical sensory impairment and focal limb dystonia and three had an alien limb. Eight cases of corticobasal degeneration had been clinically diagnosed as progressive supranuclear palsy, all of whom had vertical supranuclear palsy and seven had falls within the first 2 years. On the other hand, of 21 cases with a clinical diagnosis of corticobasal syndrome, only five had corticobasal degeneration pathology, giving a positive predictive value of 23.8%; six others had progressive supranuclear palsy pathology, five had Alzheimer's disease and the remaining five had other non-tau pathologies. Corticobasal degeneration can present very commonly with a clinical picture closely resembling classical progressive supranuclear palsy or Richardson's syndrome, and we propose the term corticobasal degeneration-Richardson's syndrome for this subgroup. Cases of corticobasal degeneration-Richardson's syndrome have delayed onset of vertical supranuclear gaze palsy (>3 years after onset of first symptom) and the infrequent occurrence of predominant downgaze abnormalities, both of which can be helpful pointers to their underlying corticobasal degeneration pathology. Fourty-two per cent of corticobasal

Chandra Reveals Nest of Tight Binaries in Dense Cluster

NASA Astrophysics Data System (ADS)

2001-05-01

than we would expect based on the number of their likely progenitors we found," said co-author Peter Edmonds, also of the CfA. "While there is a general consensus on how some of the millisecond pulsars form, these new data suggest that there need to be other methods to create them." In addition to the millisecond pulsars, Chandra also detected other important populations of binary systems, including those with white dwarf stars and normal stars, and others where pairs of normal stars undergo large flares induced by their close proximity. The Chandra data also indicate an apparent absence of a central black hole. Stellar-sized mass black holes -- those about five to ten times as massive as the Sun -- have apparently not coalesced to the center of the star cluster. All or most stellar-sized black holes that formed over the lifetime of the cluster have likely been ejected by their slingshot encounters with binaries deep in the cluster core. "These results show that binary star systems are a source of gravitational energy which ejects stellar mass black holes and prevents the collapse of the cluster’s core to a more massive, central black hole," said the CfA's Craig Heinke. "In other words, binary systems - not black holes - are the dynamical heat engines that drive the evolution of globular clusters." Chandra observed 47 Tucanae on March 16-17, 2000, for a period of 74,000 seconds with the Advanced CCD Imaging Spectrometer (ACIS). The ACIS X-ray camera was developed for NASA by Penn State and the Massachusetts Institute of Technology. The High Energy Transmission Grating Spectrometer was built by MIT. NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program. TRW, Inc., Redondo Beach, California, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, MA. Images associated with this release are available on the World Wide Web at: http://chandra.harvard.edu AND http://chandra.nasa.gov

Testing the Binary Black Hole Nature of a Compact Binary Coalescence

NASA Astrophysics Data System (ADS)

Krishnendu, N. V.; Arun, K. G.; Mishra, Chandra Kant

2017-09-01

We propose a novel method to test the binary black hole nature of compact binaries detectable by gravitational wave (GW) interferometers and, hence, constrain the parameter space of other exotic compact objects. The spirit of the test lies in the "no-hair" conjecture for black holes where all properties of a Kerr black hole are characterized by its mass and spin. The method relies on observationally measuring the quadrupole moments of the compact binary constituents induced due to their spins. If the compact object is a Kerr black hole (BH), its quadrupole moment is expressible solely in terms of its mass and spin. Otherwise, the quadrupole moment can depend on additional parameters (such as the equation of state of the object). The higher order spin effects in phase and amplitude of a gravitational waveform, which explicitly contains the spin-induced quadrupole moments of compact objects, hence, uniquely encode the nature of the compact binary. Thus, we argue that an independent measurement of the spin-induced quadrupole moment of the compact binaries from GW observations can provide a unique way to distinguish binary BH systems from binaries consisting of exotic compact objects.

Testing the Binary Black Hole Nature of a Compact Binary Coalescence.

PubMed

Krishnendu, N V; Arun, K G; Mishra, Chandra Kant

2017-09-01

We propose a novel method to test the binary black hole nature of compact binaries detectable by gravitational wave (GW) interferometers and, hence, constrain the parameter space of other exotic compact objects. The spirit of the test lies in the "no-hair" conjecture for black holes where all properties of a Kerr black hole are characterized by its mass and spin. The method relies on observationally measuring the quadrupole moments of the compact binary constituents induced due to their spins. If the compact object is a Kerr black hole (BH), its quadrupole moment is expressible solely in terms of its mass and spin. Otherwise, the quadrupole moment can depend on additional parameters (such as the equation of state of the object). The higher order spin effects in phase and amplitude of a gravitational waveform, which explicitly contains the spin-induced quadrupole moments of compact objects, hence, uniquely encode the nature of the compact binary. Thus, we argue that an independent measurement of the spin-induced quadrupole moment of the compact binaries from GW observations can provide a unique way to distinguish binary BH systems from binaries consisting of exotic compact objects.

Advances in hepatic stem/progenitor cell biology

PubMed Central

Verhulst, Stefaan; Best, Jan; van Grunsven, Leo A.; Dollé, Laurent

2015-01-01

The liver is famous for its strong regenerative capacity, employing different modes of regeneration according to type and extent of injury. Mature liver cells are able to proliferate in order to replace the damaged tissue allowing the recovery of the parenchymal function. In more severe scenarios hepatocytes are believed to arise also from a facultative liver progenitor cell compartment. In human, severe acute liver failure and liver cirrhosis are also both important clinical targets in which regeneration is impaired, where the role of this stem cell compartment seems more convincing. In animal models, the current state of ambiguity regarding the identity and role of liver progenitor cells in liver physiology dampens the enthusiasm for the potential use of these cells in regenerative medicine. The aim of this review is to give the basics of liver progenitor cell biology and discuss recent results vis-à-vis their identity and contribution to liver regeneration. PMID:26600740

Differentiation of Inflammation-Responsive Astrocytes from Glial Progenitors Generated from Human Induced Pluripotent Stem Cells.

PubMed

Santos, Renata; Vadodaria, Krishna C; Jaeger, Baptiste N; Mei, Arianna; Lefcochilos-Fogelquist, Sabrina; Mendes, Ana P D; Erikson, Galina; Shokhirev, Maxim; Randolph-Moore, Lynne; Fredlender, Callie; Dave, Sonia; Oefner, Ruth; Fitzpatrick, Conor; Pena, Monique; Barron, Jerika J; Ku, Manching; Denli, Ahmet M; Kerman, Bilal E; Charnay, Patrick; Kelsoe, John R; Marchetto, Maria C; Gage, Fred H

2017-06-06

Astrocyte dysfunction and neuroinflammation are detrimental features in multiple pathologies of the CNS. Therefore, the development of methods that produce functional human astrocytes represents an advance in the study of neurological diseases. Here we report an efficient method for inflammation-responsive astrocyte generation from induced pluripotent stem cells (iPSCs) and embryonic stem cells. This protocol uses an intermediate glial progenitor stage and generates functional astrocytes that show levels of glutamate uptake and calcium activation comparable with those observed in human primary astrocytes. Stimulation of stem cell-derived astrocytes with interleukin-1β or tumor necrosis factor α elicits a strong and rapid pro-inflammatory response. RNA-sequencing transcriptome profiling confirmed that similar gene expression changes occurred in iPSC-derived and primary astrocytes upon stimulation with interleukin-1β. This protocol represents an important tool for modeling in-a-dish neurological diseases with an inflammatory component, allowing for the investigation of the role of diseased astrocytes in neuronal degeneration. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Identification of oocyte progenitor cells in the zebrafish ovary.

PubMed

Draper, Bruce W

2012-01-01

Zebrafish breed year round and females are capable of producing thousands of eggs during their lifetime. This amazing fecundity is due to the fact that the adult ovary, contains premeiotic oocyte progenitor cells, called oogonia, which produce a continuous supply of new oocytes throughout adult life. Oocyte progenitor cells can be easily identified based on their expression of Vasa, and their characteristic nuclear morphology. Thus, the zebrafish ovary provides a unique and powerful system to study the genetic regulation of oocyte production in a vertebrate animal. A method is presented here for identifying oocyte progenitor cells in the zebrafish ovary using whole-mount confocal immunofluorescence that is simple and accurate.

Wnt Signaling Specifies Anteroposterior Progenitor Zone Identity in the Drosophila Visual Center.

PubMed

Suzuki, Takumi; Trush, Olena; Yasugi, Tetsuo; Takayama, Rie; Sato, Makoto

2016-06-15

During brain development, various types of neuronal populations are produced from different progenitor pools to produce neuronal diversity that is sufficient to establish functional neuronal circuits. However, the molecular mechanisms that specify the identity of each progenitor pool remain obscure. Here, we show that Wnt signaling is essential for the specification of the identity of posterior progenitor pools in the Drosophila visual center. In the medulla, the largest component of the visual center, different types of neurons are produced from two progenitor pools: the outer proliferation center (OPC) and glial precursor cells (GPCs; also known as tips of the OPC). We found that OPC-type neurons are produced from the GPCs at the expense of GPC-type neurons when Wnt signaling is suppressed in the GPCs. In contrast, GPC-type neurons are ectopically induced when Wnt signaling is ectopically activated in the OPC. These results suggest that Wnt signaling is necessary and sufficient for the specification of the progenitor pool identity. We also found that Homothorax (Hth), which is temporally expressed in the OPC, is ectopically induced in the GPCs by suppression of Wnt signaling and that ectopic induction of Hth phenocopies the suppression of Wnt signaling in the GPCs. Thus, Wnt signaling is involved in regionalization of the fly visual center through the specification of the progenitor pool located posterior to the medulla by suppressing Hth expression. Brain consists of considerably diverse neurons of different origins. In mammalian brain, excitatory and inhibitory neurons derive from the dorsal and ventral telencephalon, respectively. Multiple progenitor pools also contribute to the neuronal diversity in fly brain. However, it has been unclear how differences between these progenitor pools are established. Here, we show that Wnt signaling, an evolutionarily conserved signaling, is involved in the process that establishes the differences between these progenitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Kuo-Chuan; Ricker, Paul M.; Taam, Ronald E., E-mail: kpan2@illinois.edu, E-mail: pmricker@illinois.edu, E-mail: r-taam@northwestern.edu

The progenitor systems of Type Ia supernovae (SNe Ia) are still under debate. Based on recent hydrodynamics simulations, non-degenerate companions in the single-degenerate scenario (SDS) should survive the supernova (SN) impact. One way to distinguish between the SDS and the double-degenerate scenario is to search for the post-impact remnant stars (PIRSs) in SN Ia remnants. Using a technique that combines multi-dimensional hydrodynamics simulations with one-dimensional stellar evolution simulations, we have examined the post-impact evolution of helium-rich binary companions in the SDS. It is found that these helium-rich PIRSs (He PIRSs) dramatically expand and evolve to a luminous phase (L {approx}more » 10{sup 4} L{sub Sun }) about 10 yr after an SN explosion. Subsequently, they contract and evolve to become hot blue-subdwarf-like (sdO-like) stars by releasing gravitational energy, persisting as sdO-like stars for several million years before evolving to the helium red-giant phase. We therefore predict that a luminous OB-like star should be detectable within {approx}30 yr after the SN explosion. Thereafter, it will shrink and become an sdO-like star in the central regions of SN Ia remnants within star-forming regions for SN Ia progenitors evolved via the helium-star channel in the SDS. These He PIRSs are predicted to be rapidly rotating (v{sub rot} {approx}> 50 km s{sup -1}) and to have high spatial velocities (v{sub linear} {approx}> 500 km s{sup -1}). Furthermore, if SN remnants have diffused away and are not recognizable at a later stage, He PIRSs could be an additional source of single sdO stars and/or hypervelocity stars.« less

Self-organization and progenitor targeting generate stable patterns in planarian regeneration.

PubMed

Atabay, Kutay Deniz; LoCascio, Samuel A; de Hoog, Thom; Reddien, Peter W

2018-04-27

During animal regeneration, cells must organize into discrete and functional systems. We show that self-organization, along with patterning cues, govern progenitor behavior in planarian regeneration. Surgical paradigms allowed the manipulation of planarian eye regeneration in predictable locations and numbers, generating alternative stable neuroanatomical states for wild-type animals with multiple functional ectopic eyes. We used animals with multiple ectopic eyes and eye transplantation to demonstrate that broad progenitor specification, combined with self-organization, allows anatomy maintenance during regeneration. We propose a model for regenerative progenitors involving (i) migratory targeting cues, (ii) self-organization into existing or regenerating eyes, and (iii) a broad zone, associated with coarse progenitor specification, in which eyes can be targeted by progenitors. These three properties help explain how tissues can be organized during regeneration. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Bipotential adult liver progenitors are derived from chronically injured mature hepatocytes

PubMed Central

Tarlow, Branden D.; Pelz, Carl; Naugler, Willscott E.; Wakefield, Leslie; Wilson, Elizabeth M.; Finegold, Milton J.; Grompe, Markus

2014-01-01

Summary Adult liver progenitor cells are biliary-like epithelial cells that emerge only under injury conditions in the periportal region of the liver. They exhibit phenotypes of both hepatocytes and bile ducts. However, their origin and their significance to injury repair remain unclear. Here, we used a chimeric lineage tracing system to demonstrate that hepatocytes contribute to the progenitor pool. RNA-sequencing, ultrastructural analysis, and in vitro progenitor assays revealed that hepatocyte-derived progenitors were distinct from their biliary-derived counterparts. In vivo lineage tracing and serial transplantation assays showed that hepatocyte-derived proliferative ducts retained a memory of their origin and differentiated back into hepatocytes upon cessation of injury. Similarly, human hepatocytes in chimeric mice also gave rise to biliary progenitors in vivo. We conclude that human and mouse hepatocytes can undergo reversible ductal metaplasia in response to injury, expand as ducts and subsequently contribute to restoration of the hepatocyte mass. PMID:25312494

Renal blood flow and oxygenation drive nephron progenitor differentiation.

PubMed

Rymer, Christopher; Paredes, Jose; Halt, Kimmo; Schaefer, Caitlin; Wiersch, John; Zhang, Guangfeng; Potoka, Douglas; Vainio, Seppo; Gittes, George K; Bates, Carlton M; Sims-Lucas, Sunder

2014-08-01

During kidney development, the vasculature develops via both angiogenesis (branching from major vessels) and vasculogenesis (de novo vessel formation). The formation and perfusion of renal blood vessels are vastly understudied. In the present study, we investigated the regulatory role of renal blood flow and O2 concentration on nephron progenitor differentiation during ontogeny. To elucidate the presence of blood flow, ultrasound-guided intracardiac microinjection was performed, and FITC-tagged tomato lectin was perfused through the embryo. Kidneys were costained for the vasculature, ureteric epithelium, nephron progenitors, and nephron structures. We also analyzed nephron differentiation in normoxia compared with hypoxia. At embryonic day 13.5 (E13.5), the major vascular branches were perfused; however, smaller-caliber peripheral vessels remained unperfused. By E15.5, peripheral vessels started to be perfused as well as glomeruli. While the interior kidney vessels were perfused, the peripheral vessels (nephrogenic zone) remained unperfused. Directly adjacent and internal to the nephrogenic zone, we found differentiated nephron structures surrounded and infiltrated by perfused vessels. Furthermore, we determined that at low O2 concentration, little nephron progenitor differentiation was observed; at higher O2 concentrations, more differentiation of the nephron progenitors was induced. The formation of the developing renal vessels occurs before the onset of blood flow. Furthermore, renal blood flow and oxygenation are critical for nephron progenitor differentiation. Copyright © 2014 the American Physiological Society.

FGF/EGF signaling regulates the renewal of early nephron progenitors during embryonic development.

PubMed

Brown, Aaron C; Adams, Derek; de Caestecker, Mark; Yang, Xuehui; Friesel, Robert; Oxburgh, Leif

2011-12-01

Recent studies indicate that nephron progenitor cells of the embryonic kidney are arranged in a series of compartments of an increasing state of differentiation. The earliest progenitor compartment, distinguished by expression of CITED1, possesses greater capacity for renewal and differentiation than later compartments. Signaling events governing progression of nephron progenitor cells through stages of increasing differentiation are poorly understood, and their elucidation will provide key insights into normal and dysregulated nephrogenesis, as well as into regenerative processes that follow kidney injury. In this study, we found that the mouse CITED1(+) progenitor compartment is maintained in response to receptor tyrosine kinase (RTK) ligands that activate both FGF and EGF receptors. This RTK signaling function is dependent on RAS and PI3K signaling but not ERK. In vivo, RAS inactivation by expression of sprouty 1 (Spry1) in CITED1(+) nephron progenitors results in loss of characteristic molecular marker expression and in increased death of progenitor cells. Lineage tracing shows that surviving Spry1-expressing progenitor cells are impaired in their subsequent epithelial differentiation, infrequently contributing to epithelial structures. These findings demonstrate that the survival and developmental potential of cells in the earliest embryonic nephron progenitor cell compartment are dependent on FGF/EGF signaling through RAS.

DNMT1 maintains progenitor function in self-renewing somatic tissue.

PubMed

Sen, George L; Reuter, Jason A; Webster, Daniel E; Zhu, Lilly; Khavari, Paul A

2010-01-28

Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation. DNA methylation provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1) maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance, the role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is unclear. Here we show that DNMT1 is essential for epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. Genome-wide analysis showed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Furthermore, UHRF1 (refs 9, 10), a component of the DNA methylation machinery that targets DNMT1 to hemi-methylated DNA, is also necessary to suppress premature differentiation and sustain proliferation. In contrast, Gadd45A and B, which promote active DNA demethylation, are required for full epidermal differentiation gene induction. These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue.

Invited review: mesenchymal progenitor cells in intramuscular connective tissue development.

PubMed

Miao, Z G; Zhang, L P; Fu, X; Yang, Q Y; Zhu, M J; Dodson, M V; Du, M

2016-01-01

The abundance and cross-linking of intramuscular connective tissue contributes to the background toughness of meat, and is thus undesirable. Connective tissue is mainly synthesized by intramuscular fibroblasts. Myocytes, adipocytes and fibroblasts are derived from a common pool of progenitor cells during the early embryonic development. It appears that multipotent mesenchymal stem cells first diverge into either myogenic or non-myogenic lineages; non-myogenic mesenchymal progenitors then develop into the stromal-vascular fraction of skeletal muscle wherein adipocytes, fibroblasts and derived mesenchymal progenitors reside. Because non-myogenic mesenchymal progenitors mainly undergo adipogenic or fibrogenic differentiation during muscle development, strengthening progenitor proliferation enhances the potential for both intramuscular adipogenesis and fibrogenesis, leading to the elevation of both marbling and connective tissue content in the resulting meat product. Furthermore, given the bipotent developmental potential of progenitor cells, enhancing their conversion to adipogenesis reduces fibrogenesis, which likely results in the overall improvement of marbling (more intramuscular adipocytes) and tenderness (less connective tissue) of meat. Fibrogenesis is mainly regulated by the transforming growth factor (TGF) β signaling pathway and its regulatory cascade. In addition, extracellular matrix, a part of the intramuscular connective tissue, provides a niche environment for regulating myogenic differentiation of satellite cells and muscle growth. Despite rapid progress, many questions remain in the role of extracellular matrix on muscle development, and factors determining the early differentiation of myogenic, adipogenic and fibrogenic cells, which warrant further studies.

Degenerate r-Stirling Numbers and r-Bell Polynomials

NASA Astrophysics Data System (ADS)

Kim, T.; Yao, Y.; Kim, D. S.; Jang, G.-W.

2018-01-01

The purpose of this paper is to exploit umbral calculus in order to derive some properties, recurrence relations, and identities related to the degenerate r-Stirling numbers of the second kind and the degenerate r-Bell polynomials. Especially, we will express the degenerate r-Bell polynomials as linear combinations of many well-known families of special polynomials.

Endothelial progenitor cells--an evolving story.

PubMed

Pearson, Jeremy D

2010-05-01

The first description of endothelial progenitor cells (EPC) in 1997 led rapidly to substantial changes in our understanding of angiogenesis, and within 5 years to the first clinical studies in humans using bone marrow derived EPC to enhance coronary neovascularisation and cardiac function after myocardial ischemia. However, to improve the success of this therapy a clearer understanding of the biology of EPC is needed. This article summarises recent data indicating that most EPC are not, in fact, endothelial progenitors but can be better described as angiogenic monocytes, and explores the implications this has for their future therapeutic use. Copyright 2009 Elsevier Inc. All rights reserved.

Ultraviolet Detection of the Binary Companion to the Type IIb SN 2001ig

NASA Astrophysics Data System (ADS)

Ryder, Stuart D.; Van Dyk, Schuyler D.; Fox, Ori D.; Zapartas, Emmanouil; de Mink, Selma E.; Smith, Nathan; Brunsden, Emily; Azalee Bostroem, K.; Filippenko, Alexei V.; Shivvers, Isaac; Zheng, WeiKang

2018-03-01

We present HST/WFC3 ultraviolet imaging in the F275W and F336W bands of the Type IIb SN 2001ig at an age of more than 14 years. A clear point source is detected at the site of the explosion, with m F275W = 25.39 ± 0.10 and m F336W = 25.88 ± 0.13 mag. Despite weak constraints on both the distance to the host galaxy NGC 7424 and the line-of-sight reddening to the supernova, this source matches the characteristics of an early B-type main-sequence star with 19,000 < T eff < 22,000 K and {log}({L}bol}/{L}ȯ )=3.92+/- 0.14. A BPASS v2.1 binary evolution model, with primary and secondary masses of 13 M ⊙ and 9 M ⊙, respectively, is found to simultaneously resemble, in the Hertzsprung–Russell diagram, both the observed location of this surviving companion, and the primary star evolutionary endpoints for other Type IIb supernovae. This same model exhibits highly variable late-stage mass loss, as expected from the behavior of the radio light curves. A Gemini/GMOS optical spectrum at an age of 6 years reveals a narrow He II λ4686 emission line, indicative of continuing interaction with a dense circumstellar medium at large radii from the progenitor. We review our findings on SN 2001ig in the context of binary evolution channels for stripped-envelope supernovae. Owing to the uncrowded nature of its environment in the ultraviolet, this study of SN 2001ig represents one of the cleanest detections to date of a surviving binary companion to a Type IIb supernova.

SOX2 expression levels distinguish between neural progenitor populations of the developing dorsal telencephalon.

PubMed

Hutton, Scott R; Pevny, Larysa H

2011-04-01

The HMG-Box transcription factor SOX2 is expressed in neural progenitor populations throughout the developing and adult central nervous system and is necessary to maintain their progenitor identity. However, it is unclear whether SOX2 levels are uniformly expressed across all neural progenitor populations. In the developing dorsal telencephalon, two distinct populations of neural progenitors, radial glia and intermediate progenitor cells, are responsible for generating a majority of excitatory neurons found in the adult neocortex. Here we demonstrate, using both cellular and molecular analyses, that SOX2 is differentially expressed between radial glial and intermediate progenitor populations. Moreover, utilizing a SOX2(EGFP) mouse line, we show that this differential expression can be used to prospectively isolate distinct, viable populations of radial glia and intermediate cells for in vitro analysis. Given the limited repertoire of cell-surface markers currently available for neural progenitor cells, this provides an invaluable tool for prospectively identifying and isolating distinct classes of neural progenitor cells from the central nervous system. Copyright © 2011 Elsevier Inc. All rights reserved.

Metallicity Differences in Type Ia Supernova Progenitors Inferred from Ultraviolet Spectra

NASA Astrophysics Data System (ADS)

Foley, Ryan J.; Kirshner, Robert P.

2013-05-01

Two "twin" Type Ia supernovae (SNe Ia), SNe 2011by and 2011fe, have extremely similar optical light-curve shapes, colors, and spectra, yet have different ultraviolet (UV) continua as measured in Hubble Space Telescope spectra and measurably different peak luminosities. We attribute the difference in the UV continua to significantly different progenitor metallicities. This is the first robust detection of different metallicities for SN Ia progenitors. Theoretical reasoning suggests that differences in metallicity also lead to differences in luminosity. SNe Ia with higher progenitor metallicities have lower 56Ni yields and lower luminosities for the same light-curve shape. SNe 2011by and 2011fe have different peak luminosities (ΔMV ≈ 0.6 mag), which correspond to different 56Ni yields: M_11fe(^{56}Ni) / M_11by(^{56}Ni) = 1.7^{+0.7}_{-0.5}. From theoretical models that account for different neutron-to-proton ratios in progenitors, the differences in 56Ni yields for SNe 2011by and 2011fe imply that their progenitor stars were above and below solar metallicity, respectively. Although we can distinguish progenitor metallicities in a qualitative way from UV data, the quantitative interpretation in terms of abundances is limited by the present state of theoretical models.

Multiple prethymic defects underlie age-related loss of T progenitor competence

PubMed Central

Zediak, Valerie P.; Maillard, Ivan

2007-01-01

Aging in mice and humans is characterized by declining T-lymphocyte production in the thymus, yet it is unclear whether aging impacts the T-lineage potential of hematopoietic progenitors. Although alterations in the lymphoid progenitor content of aged mouse bone marrow (BM) have been described, irradiation-reconstitution experiments have failed to reveal defects in T-lineage potential of BM hematopoietic progenitors or purified hematopoietic stem cells (HSCs) from aged mice. Here, we assessed T-progenitor potential in unmanipulated recipient mice without conditioning irradiation. T-progenitor potential was reduced in aged BM compared with young BM, and this reduction was apparent at the earliest stages of intrathymic differentiation. Further, enriched populations of aged HSCs or multipotent progenitors (MPPs) gave rise to fewer T-lineage cells than their young counterparts. Whereas the T-precursor frequency within the MPP pool was unchanged, there was a 4-fold decline in T-precursor frequency within the HSC pool. In addition, among the T-competent HSC clones, there were fewer highly proliferative clones in the aged HSC pool than in the young HSC pool. These results identify T-compromised aged HSCs and define the nature and cellular sites of prethymic, age-related defects in T-lineage differentiation potential. PMID:17456721

Collision Tomography: Physical Properties of Possible Progenitors of the Andromeda Stellar Stream

NASA Astrophysics Data System (ADS)

Miki, Yohei; Mori, Masao; Rich, R. Michael

2016-08-01

To unveil a progenitor of the Andromeda Giant Stellar Stream, we investigate the interaction between an accreting satellite galaxy and the Andromeda Galaxy using an N-body simulation. We perform a comprehensive exploration of the properties of the progenitor dwarf galaxy, using 247 models of varying mass, mass distribution, and size. We show that the binding energy of the progenitor is the crucial parameter in reproducing the Andromeda Giant Stellar Stream and the shell-like structures surrounding the Andromeda Galaxy. As a result of the simulations, the progenitor must satisfy a simple scaling relation between the core radius, the total mass and the tidal radius. Using this relation, we successfully constrain the physical properties of the progenitors to have masses ranging from 5× {10}8{M}⊙ to 5× {10}9{M}⊙ and central surface densities around {10}3 {M}⊙ {{pc}}-2. A detailed comparison between our result and the nearby observed galaxies indicates that possible progenitors of the Andromeda Giant Stellar Stream include a dwarf elliptical galaxy, a dwarf irregular galaxy, and a small spiral galaxy.

Angular momentum role in the hypercritical accretion of binary-driven hypernovae

DOE PAGES

Becerra, L.; Cipolletta, F.; Fryer, Chris L.; ...

2015-10-12

Here, the induced gravitational collapse paradigm explains a class of energetic,more » $${E}_{{\\rm{iso}}}\\gtrsim {10}^{52}$$ erg, long-duration gamma-ray bursts (GRBs) associated with Ic supernovae, recently named binary-driven hypernovae. The progenitor is a tight binary system formed of a carbon–oxygen (CO) core and a neutron star (NS) companion. The supernova ejecta of the exploding CO core trigger a hypercritical accretion process onto the NS, which reaches the critical mass in a few seconds, and gravitationally collapses to a black hole, emitting a GRB. In our previous simulations of this process, we adopted a spherically symmetric approximation to compute the features of the hypercritical accretion process. We here present the first estimates of the angular momentum transported by the supernova ejecta, $${L}_{{\\rm{acc}}},$$ and perform numerical simulations of the angular momentum transfer to the NS during the hyperaccretion process in full general relativity. We show that the NS (1) reaches either the mass-shedding limit or the secular axisymmetric instability in a few seconds depending on its initial mass, (2) reaches a maximum dimensionless angular momentum value, $${[{cJ}/({{GM}}^{2})]}_{{\\rm{max}}}\\approx 0.7$$, and (3) can support less angular momentum than the one transported by supernova ejecta, $${L}_{{\\rm{acc}}}\\gt {J}_{{\\rm{NS,max}}},$$ hence there is an angular momentum excess that necessarily leads to jetted emission.« less

Angular momentum role in the hypercritical accretion of binary-driven hypernovae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becerra, L.; Cipolletta, F.; Fryer, Chris L.

Here, the induced gravitational collapse paradigm explains a class of energetic,more » $${E}_{{\\rm{iso}}}\\gtrsim {10}^{52}$$ erg, long-duration gamma-ray bursts (GRBs) associated with Ic supernovae, recently named binary-driven hypernovae. The progenitor is a tight binary system formed of a carbon–oxygen (CO) core and a neutron star (NS) companion. The supernova ejecta of the exploding CO core trigger a hypercritical accretion process onto the NS, which reaches the critical mass in a few seconds, and gravitationally collapses to a black hole, emitting a GRB. In our previous simulations of this process, we adopted a spherically symmetric approximation to compute the features of the hypercritical accretion process. We here present the first estimates of the angular momentum transported by the supernova ejecta, $${L}_{{\\rm{acc}}},$$ and perform numerical simulations of the angular momentum transfer to the NS during the hyperaccretion process in full general relativity. We show that the NS (1) reaches either the mass-shedding limit or the secular axisymmetric instability in a few seconds depending on its initial mass, (2) reaches a maximum dimensionless angular momentum value, $${[{cJ}/({{GM}}^{2})]}_{{\\rm{max}}}\\approx 0.7$$, and (3) can support less angular momentum than the one transported by supernova ejecta, $${L}_{{\\rm{acc}}}\\gt {J}_{{\\rm{NS,max}}},$$ hence there is an angular momentum excess that necessarily leads to jetted emission.« less

Full Ionisation In Binary-Binary Encounters With Small Positive Energies

NASA Astrophysics Data System (ADS)

Sweatman, W. L.

2006-08-01

Interactions between binary stars and single stars and binary stars and other binary stars play a key role in the dynamics of a dense stellar system. Energy can be transferred between the internal dynamics of a binary and the larger scale dynamics of the interacting objects. Binaries can be destroyed and created by the interaction. In a binary-binary encounter, full ionisation occurs when both of the binary stars are destroyed in the interaction to create four single stars. This is only possible when the total energy of the system is positive. For very small energies the probability of this occurring is very low and it tends towards zero as the total energy tends towards zero. Here the case is considered for which all the stars have equal masses. An asymptotic power law is predicted relating the probability of full ionisation with the total energy when this latter quantity is small. The exponent, which is approximately 2.31, is compared with the results from numerical scattering experiments. The theoretical approach taken is similar to one used previously in the three-body problem. It makes use of the fact that the most dramatic changes in scale and energies of a few-body system occur when its components pass near to a central configuration. The position, and number, of these configurations is not known for the general four-body problem, however, with equal masses there are known to be exactly five different cases. Separate consideration and comparison of the properties of orbits close to each of these five central configurations enables the prediction of the form of the cross-section for full ionisation for the case of small positive total energy. This is the relation between total energy and the probability of total ionisation described above.

DNA damage tolerance in hematopoietic stem and progenitor cells in mice

PubMed Central

Pilzecker, Bas; Buoninfante, Olimpia Alessandra; van den Berk, Paul; Lancini, Cesare; Song, Ji-Ying; Citterio, Elisabetta

2017-01-01

DNA damage tolerance (DDT) enables bypassing of DNA lesions during replication, thereby preventing fork stalling, replication stress, and secondary DNA damage related to fork stalling. Three modes of DDT have been documented: translesion synthesis (TLS), template switching (TS), and repriming. TLS and TS depend on site-specific PCNA K164 monoubiquitination and polyubiquitination, respectively. To investigate the role of DDT in maintaining hematopoietic stem cells (HSCs) and progenitors, we used PcnaK164R/K164R mice as a unique DDT-defective mouse model. Analysis of the composition of HSCs and HSC-derived multipotent progenitors (MPPs) revealed a significantly reduced number of HSCs, likely owing to increased differentiation of HSCs toward myeloid/erythroid-associated MPP2s. This skewing came at the expense of the number of lymphoid-primed MPP4s, which appeared to be compensated for by increased MPP4 proliferation. Furthermore, defective DDT decreased the numbers of MPP-derived common lymphoid progenitor (CLP), common myeloid progenitor (CMP), megakaryocyte-erythroid progenitor (MEP), and granulocyte-macrophage progenitor (GMP) cells, accompanied by increased cell cycle arrest in CMPs. The HSC and MPP phenotypes are reminiscent of premature aging and stressed hematopoiesis, and indeed progressed with age and were exacerbated on cisplatin exposure. Bone marrow transplantations revealed a strong cell intrinsic defect of DDT-deficient HSCs in reconstituting lethally irradiated mice and a strong competitive disadvantage when cotransplanted with wild-type HSCs. These findings indicate a critical role of DDT in maintaining HSCs and progenitor cells, and in preventing premature aging. PMID:28761001

The afterglow of GRB 050709 and the nature of the short-hard gamma-ray bursts.

PubMed

Fox, D B; Frail, D A; Price, P A; Kulkarni, S R; Berger, E; Piran, T; Soderberg, A M; Cenko, S B; Cameron, P B; Gal-Yam, A; Kasliwal, M M; Moon, D-S; Harrison, F A; Nakar, E; Schmidt, B P; Penprase, B; Chevalier, R A; Kumar, P; Roth, K; Watson, D; Lee, B L; Shectman, S; Phillips, M M; Roth, M; McCarthy, P J; Rauch, M; Cowie, L; Peterson, B A; Rich, J; Kawai, N; Aoki, K; Kosugi, G; Totani, T; Park, H-S; MacFadyen, A; Hurley, K C

2005-10-06

The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the coalescence of neutron-star or black-hole binary systems. Numerous searches for the afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.

Phagocyte dysfunction, tissue aging and degeneration

PubMed Central

2013-01-01

Immunologically-silent phagocytosis of apoptotic cells is critical to maintaining tissue homeostasis and innate immune balance. Aged phagocytes reduce their functional activity, leading to accumulation of unphagocytosed debris, chronic sterile inflammation and exacerbation of tissue aging and damage. Macrophage dysfunction plays an important role in immunosenescence. Microglial dysfunction has been linked to age-dependent neurodegenerations. Retinal pigment epithelial (RPE) cell dysfunction has been implicated in the pathogenesis of age-related macular degeneration (AMD). Despite several reports on the characterization of aged phagocytes, the role of phagocyte dysfunction in tissue aging and degeneration is yet to be fully appreciated. Lack of knowledge of molecular mechanisms by which aging reduces phagocyte function has hindered our capability to exploit the therapeutic potentials of phagocytosis for prevention or delay of tissue degeneration. This review summarizes our current knowledge of phagocyte dysfunction in aged tissues and discusses possible links to age-related diseases. We highlight the challenges to decipher the molecular mechanisms, present new research approaches and envisage future strategies to prevent phagocyte dysfunction, tissue aging and degeneration. PMID:23748186

Phagocyte dysfunction, tissue aging and degeneration.

PubMed

Li, Wei

2013-09-01

Immunologically-silent phagocytosis of apoptotic cells is critical to maintaining tissue homeostasis and innate immune balance. Aged phagocytes reduce their functional activity, leading to accumulation of unphagocytosed debris, chronic sterile inflammation and exacerbation of tissue aging and damage. Macrophage dysfunction plays an important role in immunosenescence. Microglial dysfunction has been linked to age-dependent neurodegenerations. Retinal pigment epithelial (RPE) cell dysfunction has been implicated in the pathogenesis of age-related macular degeneration (AMD). Despite several reports on the characterization of aged phagocytes, the role of phagocyte dysfunction in tissue aging and degeneration is yet to be fully appreciated. Lack of knowledge of molecular mechanisms by which aging reduces phagocyte function has hindered our capability to exploit the therapeutic potentials of phagocytosis for prevention or delay of tissue degeneration. This review summarizes our current knowledge of phagocyte dysfunction in aged tissues and discusses possible links to age-related diseases. We highlight the challenges to decipher the molecular mechanisms, present new research approaches and envisage future strategies to prevent phagocyte dysfunction, tissue aging and degeneration. Copyright © 2013 Elsevier B.V. All rights reserved.

Degenerate pressure driven self-gravito-acoustic solitary waves in a self-gravitating degenerate quantum plasma system

NASA Astrophysics Data System (ADS)

Mamun, A. A.

2018-02-01

A general (but realistic) self-gravitating degenerate quantum plasma system (SG-DQPS) containing inertialess degenerate electron species, inertial degenerate light, and heavy ion/nucleus species is considered to examine the possibility for the existence of degenerate pressure driven self-gravito-acoustic (DPD-SGA) solitary waves (SWs) formed in such a SG-DQPS. The pseudo-potential approach, which is valid for the arbitrary amplitude DPD-SGA SWs, is employed. It is found that depending on the value of the number density of heavy ion/nucleus species, the SG-DQPS under consideration supports the existence of positive or the coexistence of positive and negative DPD-SGA SWs. The basic features (polarity, amplitude, and width) of both positive and negative DPD-SGA SWs are found to be significantly modified by the dynamics of heavy ion/nucleus species. The theoretical investigation presented here is so general that it can be applied not only in astrophysical SG-DQPSs (such as white dwarf and neutron star SG-DQPSs), but also in laboratory SG-DQPSs (viz., solid density and laser-produced SG-DQPSs) to identify the salient features of the DPD-SGA SWs formed in them.

DNMT1 Maintains Progenitor Function in Self-Renewing Somatic Tissue

PubMed Central

Sen, George L.; Reuter, Jason A.; Webster, Daniel E.; Zhu, Lilly; Khavari, Paul A.

2010-01-01

Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation1,2. DNA methylation3,4,5 provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1)6,7 maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance,8 a clear role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is unknown. Here we show that DNMT1 is essential for epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. Genome-wide analysis revealed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Furthermore, we show that UHRF1,9,10 a component of the DNA methylation machinery that targets DNMT1 to hemi-methylated DNA, is also necessary to suppress premature differentiation and sustain proliferation. In contrast, Gadd45A11,12 and B13, which promote active DNA demethylation, are required for full epidermal differentiation gene induction. These data demonstrate that proteins involved in the dynamic regulation of DNA methylation patterns are required for progenitor maintenance and self-renewal in mammalian somatic tissue. PMID:20081831

PSR J0538+2817 As The Remnant Of The First Supernova Explosion in a Massive Binary

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

2006-08-01

It is generally accepted that the radio pulsar PSR J0538+2817 is associated with the supernova remnant (SNR) S147. The only problem for the association is the obvious discrepancy (Kramer et al. 2003) between the kinematic age of the system of ~30 kyr (estimated from the angular offset of the pulsar from the geometric center of the SNR and pulsar's proper motion) and the characteristic age of the pulsar of ~600 kyr. To reconcile these ages one can assume that the pulsar was born with a spin period close to the present one (Kramer et al. 2003; Romani & Ng 2003). We propose an alternative explanation of the age discrepancy based on the fact that PSR J0538+2817 could be the stellar remnant of the first supernova explosion in a massive binary system and therefore could be as old as indicated by its characteristic age. Our proposal implies that S147 is the diffuse remnant of the second supernova explosion (that disrupted the binary system) and that a much younger second neutron star (not necessarily manifesting itself as a radio pulsar) should be associated with S147. We use the existing observational data on the system PSR J0538+2817/SNR S147 to suggest that the progenitor of the supernova that formed S147 was a Wolf-Rayet star (so that the supernova explosion occurred within a wind bubble surrounded by a massive shell) and to constrain the parameters of the binary system. We also restrict the magnitude and direction of the kick velocity received by the young neutron star at birth and find that the kick vector should not strongly deviate from the orbital plane of the binary system.

Differences and similarities between human and chimpanzee neural progenitors during cerebral cortex development

PubMed Central

Mora-Bermúdez, Felipe; Badsha, Farhath; Kanton, Sabina; Camp, J Gray; Vernot, Benjamin; Köhler, Kathrin; Voigt, Birger; Okita, Keisuke; Maricic, Tomislav; He, Zhisong; Lachmann, Robert; Pääbo, Svante; Treutlein, Barbara; Huttner, Wieland B

2016-01-01

Human neocortex expansion likely contributed to the remarkable cognitive abilities of humans. This expansion is thought to primarily reflect differences in proliferation versus differentiation of neural progenitors during cortical development. Here, we have searched for such differences by analysing cerebral organoids from human and chimpanzees using immunohistofluorescence, live imaging, and single-cell transcriptomics. We find that the cytoarchitecture, cell type composition, and neurogenic gene expression programs of humans and chimpanzees are remarkably similar. Notably, however, live imaging of apical progenitor mitosis uncovered a lengthening of prometaphase-metaphase in humans compared to chimpanzees that is specific to proliferating progenitors and not observed in non-neural cells. Consistent with this, the small set of genes more highly expressed in human apical progenitors points to increased proliferative capacity, and the proportion of neurogenic basal progenitors is lower in humans. These subtle differences in cortical progenitors between humans and chimpanzees may have consequences for human neocortex evolution. DOI: http://dx.doi.org/10.7554/eLife.18683.001 PMID:27669147

Adaptable Binary Programs

DTIC Science & Technology

1994-04-01

a variation of Ziv - Lempel compression [ZL77]. We found that using a standard compression algorithm rather than semantic compression allowed simplified...mentation. In Proceedings of the Conference on Programming Language Design and Implementation, 1993. (ZL77] J. Ziv and A. Lempel . A universal algorithm ...required by adaptable binaries. Our ABS stores adaptable binary information using the conventional binary symbol table and compresses this data using

Human disc degeneration is associated with increased MMP 7 expression.

PubMed

Le Maitre, C L; Freemont, A J; Hoyland, J A

2006-01-01

During intervertebral disc (IVD) degeneration, normal matrix synthesis decreases and degradation of disc matrix increases. A number of proteases that are increased during disc degeneration are thought to be involved in its pathogenesis. Matrix metalloproteinase 7 (MMP 7) (Matrilysin, PUMP-1) is known to cleave the major matrix molecules found within the IVD, i.e., the proteoglycan aggrecan and collagen type II. To date, however, it is not known how its expression changes with degeneration or its exact location. We investigated the localization of MMP 7 in human, histologically graded, nondegenerate, degenerated and prolapsed discs to ascertain whether MMP 7 is up-regulated during disc degeneration. Samples of human IVD tissue were fixed in neutral buffered formalin, embedded in paraffin, and sections stained with hematoxylin and eosin to score the degree of morphological degeneration. Immunohistochemistry was performed to localize MMP 7 in 41 human IVDs with varying degrees of degeneration. We found that the chondrocyte-like cells of the nucleus pulposus and inner annulus fibrosus were MMP 7 immunopositive; little immunopositivity was observed in the outer annulus. Nondegenerate discs showed few immunopositive cells. A significant increase in the proportion of MMP 7 immunopositive cells was seen in the nucleus pulposus of discs classified as showing intermediate levels of degeneration and a further increase was seen in discs with severe degeneration. Prolapsed discs showed more MMP 7 immunopositive cells compared to nondegenerated discs, but fewer than those seen in cases of severe degeneration.

Notochord Cells in Intervertebral Disc Development and Degeneration

PubMed Central

McCann, Matthew R.; Séguin, Cheryle A.

2016-01-01

The intervertebral disc is a complex structure responsible for flexibility, multi-axial motion, and load transmission throughout the spine. Importantly, degeneration of the intervertebral disc is thought to be an initiating factor for back pain. Due to a lack of understanding of the pathways that govern disc degeneration, there are currently no disease-modifying treatments to delay or prevent degenerative disc disease. This review presents an overview of our current understanding of the developmental processes that regulate intervertebral disc formation, with particular emphasis on the role of the notochord and notochord-derived cells in disc homeostasis and how their loss can result in degeneration. We then describe the role of small animal models in understanding the development of the disc and their use to interrogate disc degeneration and associated pathologies. Finally, we highlight essential development pathways that are associated with disc degeneration and/or implicated in the reparative response of the tissue that might serve as targets for future therapeutic approaches. PMID:27252900

Mechanisms of Distal Axonal Degeneration in Peripheral Neuropathies

PubMed Central

Cashman, Christopher R.; Höke, Ahmet

2015-01-01

Peripheral neuropathy is a common complication of a variety of diseases and treatments, including diabetes, cancer chemotherapy, and infectious causes (HIV, hepatitis C, and Campylobacter jejuni). Despite the fundamental difference between these insults, peripheral neuropathy develops as a combination of just six primary mechanisms: altered metabolism, covalent modification, altered organelle function and reactive oxygen species formation, altered intracellular and inflammatory signaling, slowed axonal transport, and altered ion channel dynamics and expression. All of these pathways converge to lead to axon dysfunction and symptoms of neuropathy. The detailed mechanisms of axon degeneration itself have begun to be elucidated with studies of animal models with altered degeneration kinetics, including the slowed Wallerian degeneration (Wlds) and Sarmknockout animal models. These studies have shown axonal degeneration to occur througha programmed pathway of injury signaling and cytoskeletal degradation. Insights into the common disease insults that converge on the axonal degeneration pathway promise to facilitate the development of therapeutics that may be effective against other mechanisms of neurodegeneration. PMID:25617478

Identification, Characterization, and Utilization of Adult Meniscal Progenitor Cells

DTIC Science & Technology

2015-09-01

the development of knee osteoarthritis (OA). New treatments centered on the stem/progenitor cell population resident within the adult meniscus will be...cells, stem cells, progenitor cells, meniscus healing, meniscus repair, osteoarthritis 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT...changes that occur after injury. As a result, meniscal injuries are a common underlying cause of post-traumatic osteoarthritis . This is particularly

Identification, Characterization, and Utilization of Adult Meniscal Progenitor Cells

DTIC Science & Technology

2016-09-01

development of knee osteoarthritis (OA). New treatments centered on the stem/progenitor cell population resident within the adult meniscus will be key to...cells, progenitor cells, meniscus healing, meniscus repair, osteoarthritis 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER...common underlying cause of post- traumatic osteoarthritis . This is particularly striking in young, healthy individuals such as military personnel

Luminal Progenitors Restrict Their Lineage Potential during Mammary Gland Development

PubMed Central

Rodilla, Veronica; Dasti, Alessandro; Huyghe, Mathilde; Lafkas, Daniel; Laurent, Cécile; Reyal, Fabien; Fre, Silvia

2015-01-01

The hierarchical relationships between stem cells and progenitors that guide mammary gland morphogenesis are still poorly defined. While multipotent basal stem cells have been found within the myoepithelial compartment, the in vivo lineage potential of luminal progenitors is unclear. Here we used the expression of the Notch1 receptor, previously implicated in mammary gland development and tumorigenesis, to elucidate the hierarchical organization of mammary stem/progenitor cells by lineage tracing. We found that Notch1 expression identifies multipotent stem cells in the embryonic mammary bud, which progressively restrict their lineage potential during mammary ductal morphogenesis to exclusively generate an ERαneg luminal lineage postnatally. Importantly, our results show that Notch1-labelled cells represent the alveolar progenitors that expand during pregnancy and survive multiple successive involutions. This study reveals that postnatal luminal epithelial cells derive from distinct self-sustained lineages that may represent the cells of origin of different breast cancer subtypes. PMID:25688859

Luminal progenitors restrict their lineage potential during mammary gland development.

PubMed

Rodilla, Veronica; Dasti, Alessandro; Huyghe, Mathilde; Lafkas, Daniel; Laurent, Cécile; Reyal, Fabien; Fre, Silvia

2015-02-01

The hierarchical relationships between stem cells and progenitors that guide mammary gland morphogenesis are still poorly defined. While multipotent basal stem cells have been found within the myoepithelial compartment, the in vivo lineage potential of luminal progenitors is unclear. Here we used the expression of the Notch1 receptor, previously implicated in mammary gland development and tumorigenesis, to elucidate the hierarchical organization of mammary stem/progenitor cells by lineage tracing. We found that Notch1 expression identifies multipotent stem cells in the embryonic mammary bud, which progressively restrict their lineage potential during mammary ductal morphogenesis to exclusively generate an ERαneg luminal lineage postnatally. Importantly, our results show that Notch1-labelled cells represent the alveolar progenitors that expand during pregnancy and survive multiple successive involutions. This study reveals that postnatal luminal epithelial cells derive from distinct self-sustained lineages that may represent the cells of origin of different breast cancer subtypes.

Drug discovery for Diamond-Blackfan anemia using reprogrammed hematopoietic progenitors

PubMed Central

Doulatov, Sergei; Vo, Linda T.; Macari, Elizabeth R.; Wahlster, Lara; Kinney, Melissa A.; Taylor, Alison M.; Barragan, Jessica; Gupta, Manav; McGrath, Katherine; Lee, Hsiang-Ying; Humphries, Jessica M.; DeVine, Alex; Narla, Anupama; Alter, Blanche P.; Beggs, Alan H.; Agarwal, Suneet; Ebert, Benjamin L.; Gazda, Hanna T.; Lodish, Harvey F.; Sieff, Colin A.; Schlaeger, Thorsten M.; Zon, Leonard I.; Daley, George Q.

2017-01-01

Diamond-Blackfan anemia (DBA) is a congenital disorder characterized by the failure of erythroid progenitor differentiation, severely curtailing red blood cell production. Because many DBA patients fail to respond to corticosteroid therapy, there is considerable need for therapeutics for this disorder. Identifying therapeutics for DBA requires circumventing the paucity of primary patient blood stem and progenitor cells. To this end, we adopted a reprogramming strategy to generate expandable hematopoietic progenitor cells from induced pluripotent stem cells (iPSCs) from DBA patients. Reprogrammed DBA progenitors recapitulate defects in erythroid differentiation, which were rescued by gene complementation. Unbiased chemical screens identified SMER28, a small-molecule inducer of autophagy, which enhanced erythropoiesis in a range of in vitro and in vivo models of DBA. SMER28 acted through autophagy factor ATG5 to stimulate erythropoiesis and up-regulate expression of globin genes. These findings present an unbiased drug screen for hematological disease using iPSCs and identify autophagy as a therapeutic pathway in DBA. PMID:28179501

Early patterning and specification of cardiac progenitors in gastrulating mesoderm

PubMed Central

Devine, W Patrick; Wythe, Joshua D; George, Matthew; Koshiba-Takeuchi, Kazuko; Bruneau, Benoit G

2014-01-01

Mammalian heart development requires precise allocation of cardiac progenitors. The existence of a multipotent progenitor for all anatomic and cellular components of the heart has been predicted but its identity and contribution to the two cardiac progenitor ‘fields’ has remained undefined. Here we show, using clonal genetic fate mapping, that Mesp1+ cells in gastrulating mesoderm are rapidly specified into committed cardiac precursors fated for distinct anatomic regions of the heart. We identify Smarcd3 as a marker of early specified cardiac precursors and identify within these precursors a compartment boundary at the future junction of the left and right ventricles that arises prior to morphogenesis. Our studies define the timing and hierarchy of cardiac progenitor specification and demonstrate that the cellular and anatomical fate of mesoderm-derived cardiac cells is specified very early. These findings will be important to understand the basis of congenital heart defects and to derive cardiac regeneration strategies. DOI: http://dx.doi.org/10.7554/eLife.03848.001 PMID:25296024

Arbitrary electron acoustic waves in degenerate dense plasmas

NASA Astrophysics Data System (ADS)

Rahman, Ata-ur; Mushtaq, A.; Qamar, A.; Neelam, S.

2017-05-01

A theoretical investigation is carried out of the nonlinear dynamics of electron-acoustic waves in a collisionless and unmagnetized plasma whose constituents are non-degenerate cold electrons, ultra-relativistic degenerate electrons, and stationary ions. A dispersion relation is derived for linear EAWs. An energy integral equation involving the Sagdeev potential is derived, and basic properties of the large amplitude solitary structures are investigated in such a degenerate dense plasma. It is shown that only negative large amplitude EA solitary waves can exist in such a plasma system. The present analysis may be important to understand the collective interactions in degenerate dense plasmas, occurring in dense astrophysical environments as well as in laser-solid density plasma interaction experiments.

Accretion onto CO White Dwarfs using MESA

NASA Astrophysics Data System (ADS)

Feng, Wanda; Starrfield, Sumner

2018-06-01

The nature of type Ia Supernovae (SNe Ia) progenitor systems and their underlying mechanism are not well understood. There are two competing progenitor scenarios: the single-degenerate scenario wherein a white dwarf (WD) star accretes material from a companion star, reaching the Chandrasekhar mass limit; and, the double-degenerate scenario wherein two WDs merge. In this study, we investigate the single-degenerate scenario by accretion onto carbon-oxygen (CO) WDs using the Modules for Experiments in Stellar Astrophysics (MESA). We vary the WD mass, composition of the accreting material, and accretion rate in our models. Mixing between the accreted material and the WD core is informed by multidimensional studies that suggest occurance after thermonuclear runaway (TNR) ensues. We compare the accretion of solar composition material onto CO WDs with the accretion of mixed solar and core material after TNR. As many of our models eject less material than accreted, our study supports that accretion onto CO WDs is a feasible channel for SNe I progenitors.

Binary Sources and Binary Lenses in Microlensing Surveys of MACHOs

NASA Astrophysics Data System (ADS)

Petrovic, N.; Di Stefano, R.; Perna, R.

2003-12-01

Microlensing is an intriguing phenomenon which may yield information about the nature of dark matter. Early observational searches identified hundreds of microlensing light curves. The data set consisted mainly of point-lens light curves and binary-lens events in which the light curves exhibit caustic crossings. Very few mildly perturbed light curves were observed, although this latter type should constitute the majority of binary lens light curves. Di Stefano (2001) has suggested that the failure to take binary effects into account may have influenced the estimates of optical depth derived from microlensing surveys. The work we report on here is the first step in a systematic analysis of binary lenses and binary sources and their impact on the results of statistical microlensing surveys. In order to asses the problem, we ran Monte-Carlo simulations of various microlensing events involving binary stars (both as the source and as the lens). For each event with peak magnification > 1.34, we sampled the characteristic light curve and recorded the chi squared value when fitting the curve with a point lens model; we used this to asses the perturbation rate. We also recorded the parameters of each system, the maximum magnification, the times at which each light curve started and ended and the number of caustic crossings. We found that both the binarity of sources and the binarity of lenses increased the lensing rate. While the binarity of sources had a negligible effect on the perturbation rates of the light curves, the binarity of lenses had a notable effect. The combination of binary sources and binary lenses produces an observable rate of interesting events exhibiting multiple "repeats" in which the magnification rises above and dips below 1.34 several times. Finally, the binarity of lenses impacted both the durations of the events and the maximum magnifications. This work was supported in part by the SAO intern program (NSF grant AST-9731923) and NASA contracts NAS8

Fibroblast growth factor receptor-Frs2α signaling is critical for nephron progenitors.

PubMed

Di Giovanni, Valeria; Walker, Kenneth A; Bushnell, Daniel; Schaefer, Caitlin; Sims-Lucas, Sunder; Puri, Pawan; Bates, Carlton M

2015-04-01

Previous studies using transgenic Pax3cre mice have revealed roles for fibroblast growth factor receptors (Fgfrs) and Fgfr substrate 2α (Frs2α) signaling in early metanephric mesenchyme patterning and in ureteric morphogenesis. The role of Fgfr/Frs2α signaling in nephron progenitors is unknown. Thus, we generated mouse models using BAC transgenic Six2EGFPcre (Six2cre) mediated deletion of Fgfrs and/or Frs2α in nephron progenitors. Six2cre mediated deletion of Fgfr1 or Fgfr2 alone led to no obvious kidney defects. Six2creFgfr1(flox/flox)Fgfr2(flox/flox) (Fgfr1/2(NP-/-)) mice generate a discernable kidney; however, they develop nephron progenitor depletion starting at embryonic day 12.5 (E12.5) and later demonstrate severe cystic dysplasia. To determine the role of Frs2α signaling downstream of Fgfr2 in Fgfr1/2(NP-/-) mice, we generated Six2cre(,)Fgfr1(flox/flox)Fgfr2(LR/LR) (Fgfr1(NP-/-)Fgfr2(LR/LR)) mice that have point mutations in the Frs2α binding site of Fgfr2. Like Fgfr1/2(NP-/-) mice, Fgfr1(NP-/-)Fgfr2(LR/LR) develop nephron progenitor depletion, but it does not start until E14.5 and older mice have less severe cystic dysplasia than Fgfr1/2(NP-/-) To determine the role of Frs2α alone in nephron progenitors, we generated Six2creFrs2'A(flox/flox) (Frs2a(NP-/-)) mice. Frs2a(NP-/-)mice also develop nephron progenitor depletion and renal cysts, although these occurred later and were less severe than in the other Six2cre mutant mice. The nephron progenitor loss in all Six2cre mutant lines was associated with decreased Cited1 expression and increased apoptosis versus controls. FAC-sorted nephron progenitors in Six2cre Frs2'A(flox/flox) mice demonstrated evidence of increased Notch activity versus controls, which likely drives the progenitor defects. Thus, Fgfr1 and Fgfr2 have synergistic roles in maintaining nephron progenitors; furthermore, Fgfr signaling in nephron progenitors appears to be mediated predominantly by Frs2α. Copyright © 2015 Elsevier Inc

Oocyte Degeneration Associated with Follicle Cells in Female Mactra chinensis (Bivalvia: Mactridae)

PubMed Central

Kim, Sung Han; Chung, Ee-Yung; Lee, Ki-Young

2014-01-01

Ultrastructural studies of oocyte degeneration in the oocyte, and the functions of follicle cells during oocyte degeneration are described to clarify the reproductive mechanism on oocyte degeneration of Mactra chinensis using cytological methods. Commonly, the follicle cells are attached to the oocyte. Follicle cells play an important role in oocyte degeneration. In particular, the functions of follicle cells during oocyte degeneration are associated with phagocytosis and the intracellular digestion of products. In this study, morphologically similar degenerated phagosomes (various lysosomes), which were observed in the degenerated oocytes, appeared in the follicle cells. After the spawning of the oocytes, the follicle cells were involved in oocyte degeneration through phagocytosis by phagolysosomes. Therefore, it can be assumed that follicle cells reabsorb phagosomes from degenerated oocytes. In this study, the presence of lipid granules, which occurred from degenerating yolk granules, gradually increased in degenerating oocytes. The function of follicle cells can accumulate reserves of lipid granules and glycogen in the cytoplasm, which can be employed by the vitellogenic oocyte. Based on observations of follicle cells attached to degenerating oocytes after spawning, the follicle cells of this species are involved in the lysosomal induction of oocyte degeneration for the reabsorption of phagosomes (phagolysosomes) in the cytoplasm for nutrient storage, as seen in other bivalves. PMID:25949203

Low- and high-LET radiation drives clonal expansion of lung progenitor cells in vivo

PubMed Central

Farin, Alicia M.; Manzo, Nicholas D.; Kirsch, David G.; Stripp, Barry R.

2015-01-01

Abundant populations of epithelial progenitor cells maintain the epithelium along the proximal-to-distal axis of the airway. Exposure of lung tissue to ionizing radiation leads to tissue remodeling and potential cancer initiation or progression. However, little is known about the effects of ionizing radiation on airway epithelial progenitor cells. We hypothesized that ionizing radiation exposure will alter the behavior of airway epithelial progenitor cells in a radiation dose- and quality-dependent manner. To address this hypothesis, we cultured primary airway epithelial cells isolated from mice exposed to various doses of 320 kVp X-ray or 600 MeV/nucleon 56Fe ions in a 3D epithelial-fibroblast co-culture system. Colony-forming efficiency of the airway epithelial progenitor cells was assessed at culture day 14. In vivo clonogenic and proliferative potentials of airway epithelial progenitor cells were measured after exposure to ionizing radiation by lineage tracing and IdU incorporation. Exposure to both X-rays and 56Fe resulted in a dose dependent decrease in the ability of epithelial progenitors to form colonies in vitro. In vivo evidence for increased clonogenic expansion of epithelial progenitors was observed after exposure to both X-rays and 56Fe. Interestingly, we found no significant increase in the epithelial proliferative index, indicating that ionizing radiation does not promote increased turnover of the airway epithelium. Therefore, we propose a model in which radiation induces a dose-dependent decrease in the pool of available progenitor cells, leaving fewer progenitors able to maintain the airway long-term. This work provides novel insights into the effects of ionizing radiation exposure on airway epithelial progenitor cell behavior. PMID:25564721

Wet Macular Degeneration

MedlinePlus

... has a hereditary component. Researchers have identified several genes related to developing the condition. Smoking. Smoking cigarettes or being regularly exposed to smoke significantly increases your risk of macular degeneration. Obesity. Research indicates that being obese increases the chance ...

Selective In Vitro Propagation of Nephron Progenitors Derived from Embryos and Pluripotent Stem Cells.

PubMed

Tanigawa, Shunsuke; Taguchi, Atsuhiro; Sharma, Nirmala; Perantoni, Alan O; Nishinakamura, Ryuichi

2016-04-26

Nephron progenitors in the embryonic kidney propagate while generating differentiated nephrons. However, in mice, the progenitors terminally differentiate shortly after birth. Here, we report a method for selectively expanding nephron progenitors in vitro in an undifferentiated state. Combinatorial and concentration-dependent stimulation with LIF, FGF2/9, BMP7, and a WNT agonist is critical for expansion. The purified progenitors proliferated beyond the physiological limits observed in vivo, both for cell numbers and lifespan. Neonatal progenitors were maintained for a week, while progenitors from embryonic day 11.5 expanded 1,800-fold for nearly 20 days and still reconstituted 3D nephrons containing glomeruli and renal tubules. Furthermore, progenitors generated from mouse embryonic stem cells and human induced pluripotent cells could be expanded with retained nephron-forming potential. Thus, we have established in vitro conditions for promoting the propagation of nephron progenitors, which will be essential for dissecting the mechanisms of kidney organogenesis and for regenerative medicine. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

TEAD and YAP regulate the enhancer network of human embryonic pancreatic progenitors.

PubMed

Cebola, Inês; Rodríguez-Seguí, Santiago A; Cho, Candy H-H; Bessa, José; Rovira, Meritxell; Luengo, Mario; Chhatriwala, Mariya; Berry, Andrew; Ponsa-Cobas, Joan; Maestro, Miguel Angel; Jennings, Rachel E; Pasquali, Lorenzo; Morán, Ignasi; Castro, Natalia; Hanley, Neil A; Gomez-Skarmeta, Jose Luis; Vallier, Ludovic; Ferrer, Jorge

2015-05-01

The genomic regulatory programmes that underlie human organogenesis are poorly understood. Pancreas development, in particular, has pivotal implications for pancreatic regeneration, cancer and diabetes. We have now characterized the regulatory landscape of embryonic multipotent progenitor cells that give rise to all pancreatic epithelial lineages. Using human embryonic pancreas and embryonic-stem-cell-derived progenitors we identify stage-specific transcripts and associated enhancers, many of which are co-occupied by transcription factors that are essential for pancreas development. We further show that TEAD1, a Hippo signalling effector, is an integral component of the transcription factor combinatorial code of pancreatic progenitor enhancers. TEAD and its coactivator YAP activate key pancreatic signalling mediators and transcription factors, and regulate the expansion of pancreatic progenitors. This work therefore uncovers a central role for TEAD and YAP as signal-responsive regulators of multipotent pancreatic progenitors, and provides a resource for the study of embryonic development of the human pancreas.

Cerebellar Granule Cell Replenishment Post-Injury by Adaptive Reprogramming of Nestin+ Progenitors

PubMed Central

Wojcinski, Alexandre; Lawton, Andrew K.; Bayin, N Sumru.; Lao, Zhimin; Stephen, Daniel N.; Joyner, Alexandra L.

2017-01-01

Regeneration of several organs involves adaptive reprogramming of progenitors, however, the intrinsic capacity of the developing brain to replenish lost cells remains largely unknown. In this study, we discovered that the developing cerebellum has unappreciated progenitor plasticity, since it undergoes near full growth and functional recovery following acute depletion of granule cells, the most plentiful neuron population in the brain. We demonstrate that following postnatal ablation of granule cell progenitors, Nestin-expressing progenitors (NEPs) specified during mid-embryogenesis to produce astroglia and interneurons, switch their fate and generate granule neurons in mice. Moreover, Hedgehog-signaling in two NEP populations is crucial not only for the compensatory replenishment of granule neurons but also to scale interneuron and astrocyte numbers. Thus we provide insights into the mechanisms underlying robustness of circuit formation in the cerebellum, and speculate that adaptive reprogramming of progenitors in other brain regions plays a greater role than appreciated in developmental regeneration. PMID:28805814

Prospectives for Gene Therapy of Retinal Degenerations

PubMed Central

Thumann, Gabriele

2012-01-01

Retinal degenerations encompass a large number of diseases in which the retina and associated retinal pigment epithelial (RPE) cells progressively degenerate leading to severe visual disorders or blindness. Retinal degenerations can be divided into two groups, a group in which the defect has been linked to a specific gene and a second group that has a complex etiology that includes environmental and genetic influences. The first group encompasses a number of relatively rare diseases with the most prevalent being Retinitis pigmentosa that affects approximately 1 million individuals worldwide. Attempts have been made to correct the defective gene by transfecting the appropriate cells with the wild-type gene and while these attempts have been successful in animal models, human gene therapy for these inherited retinal degenerations has only begun recently and the results are promising. To the second group belong glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy (DR). These retinal degenerations have a genetic component since they occur more often in families with affected probands but they are also linked to environmental factors, specifically elevated intraocular pressure, age and high blood sugar levels respectively. The economic and medical impact of these three diseases can be assessed by the number of individuals affected; AMD affects over 30 million, DR over 40 million and glaucoma over 65 million individuals worldwide. The basic defect in these diseases appears to be the relative lack of a neurogenic environment; the neovascularization that often accompanies these diseases has suggested that a decrease in pigment epithelium-derived factor (PEDF), at least in part, may be responsible for the neurodegeneration since PEDF is not only an effective neurogenic and neuroprotective agent but also a potent inhibitor of neovascularization. In the last few years inhibitors of vascularization, especially antibodies against vascular endothelial cell

Adaptive remodeling of the biliary tree: the essence of liver progenitor cell expansion.

PubMed

Kok, Cindy Yuet-Yin; Miyajima, Atsushi; Itoh, Tohru

2015-07-01

The liver progenitor cell population has long been thought to exist within the liver. However, there are no standardized criteria for defining the liver progenitor cells, and there has been intense debate about the origin of these cells in the adult liver. The characteristics of such cells vary depending on the disease model used and also on the method of analysis. Visualization of three-dimensional biliary structures has revealed that the emergence of liver progenitor cells essentially reflects the adaptive remodeling of the hepatic biliary network in response to liver injury. We propose that the progenitor cell exists as a subpopulation in the biliary tree and show that the appearance of liver progenitor cells in injured parenchyma is reflective of extensive remodeling of the biliary structure. © 2015 Japanese Society of Hepato-Biliary-Pancreatic Surgery.

Bone marrow niche-inspired, multiphase expansion of megakaryocytic progenitors with high polyploidization potential.

PubMed

Panuganti, Swapna; Papoutsakis, Eleftherios T; Miller, William M

2010-10-01

Megakaryopoiesis encompasses hematopoietic stem and progenitor cell (HSPC) commitment to the megakaryocytic cell (Mk) lineage, expansion of Mk progenitors and mature Mks, polyploidization and platelet release. pH and pO2 increase from the endosteum to sinuses, and different cytokines are important for various stages of differentiation. We hypothesized that mimicking the changing conditions during Mk differentiation in the bone marrow would facilitate expansion of progenitors that could generate many high-ploidy Mks. CD34+ HSPCs were cultured at pH 7.2 and 5% O2 with stem cell factor (SCF), thrombopoietin (Tpo) and all combinations of Interleukin (IL)-3, IL-6, IL-11 and Flt-3 ligand to promote Mk progenitor expansion. Cells cultured with selected cytokines were shifted to pH 7.4 and 20% O2 to generate mature Mks, and treated with nicotinamide (NIC) to enhance polyploidization. Using Tpo + SCF + IL-3 + IL-11, we obtained 3.5 CD34+ CD41+ Mk progenitors per input HSPC, while increasing purity from 1% to 17%. Cytokine cocktails with IL-3 yielded more progenitors and mature Mks, although the purities were lower. Mk production was much greater at higher pH and pO2. Although fewer progenitors were present, shifting to 20% O2 /pH 7.4 at day 5 (versus days 7 or 9) yielded the greatest mature Mk production, 14 per input HSPC. NIC more than doubled the percentage of high-ploidy Mks to 40%. We obtained extensive Mk progenitor expansion, while ensuring that the progenitors could produce high-ploidy Mks. We anticipate that subsequent optimization of cytokines for mature Mk production and delayed NIC addition will greatly increase high-ploidy Mk production.

Mutually exclusive signaling signatures define the hepatic and pancreatic progenitor cell lineage divergence

PubMed Central

Rodríguez-Seguel, Elisa; Mah, Nancy; Naumann, Heike; Pongrac, Igor M.; Cerdá-Esteban, Nuria; Fontaine, Jean-Fred; Wang, Yongbo; Chen, Wei; Andrade-Navarro, Miguel A.; Spagnoli, Francesca M.

2013-01-01

Understanding how distinct cell types arise from multipotent progenitor cells is a major quest in stem cell biology. The liver and pancreas share many aspects of their early development and possibly originate from a common progenitor. However, how liver and pancreas cells diverge from a common endoderm progenitor population and adopt specific fates remains elusive. Using RNA sequencing (RNA-seq), we defined the molecular identity of liver and pancreas progenitors that were isolated from the mouse embryo at two time points, spanning the period when the lineage decision is made. The integration of temporal and spatial gene expression profiles unveiled mutually exclusive signaling signatures in hepatic and pancreatic progenitors. Importantly, we identified the noncanonical Wnt pathway as a potential developmental regulator of this fate decision and capable of inducing the pancreas program in endoderm and liver cells. Our study offers an unprecedented view of gene expression programs in liver and pancreas progenitors and forms the basis for formulating lineage-reprogramming strategies to convert adult hepatic cells into pancreatic cells. PMID:24013505

Distribution and Characterization of Progenitor Cells within the Human Filum Terminale

PubMed Central

Jaff, Nasren; Ossoinak, Amina; Jansson, Katarina; Hägerstrand, Anders; Johansson, Clas B.; Brundin, Lou; Svensson, Mikael

2011-01-01

Background Filum terminale (FT) is a structure that is intimately associated with conus medullaris, the most caudal part of the spinal cord. It is well documented that certain regions of the adult human central nervous system contains undifferentiated, progenitor cells or multipotent precursors. The primary objective of this study was to describe the distribution and progenitor features of this cell population in humans, and to confirm their ability to differentiate within the neuroectodermal lineage. Methodology/Principal Findings We demonstrate that neural stem/progenitor cells are present in FT obtained from patients treated for tethered cord. When human or rat FT-derived cells were cultured in defined medium, they proliferated and formed neurospheres in 13 out of 21 individuals. Cells expressing Sox2 and Musashi-1 were found to outline the central canal, and also to be distributed in islets throughout the whole FT. Following plating, the cells developed antigen profiles characteristic of astrocytes (GFAP) and neurons (β-III-tubulin). Addition of PDGF-BB directed the cells towards a neuronal fate. Moreover, the cells obtained from young donors shows higher capacity for proliferation and are easier to expand than cells derived from older donors. Conclusion/Significance The identification of bona fide neural progenitor cells in FT suggests a possible role for progenitor cells in this extension of conus medullaris and may provide an additional source of such cells for possible therapeutic purposes. Filum terminale, human, progenitor cells, neuron, astrocytes, spinal cord. PMID:22096566

Role of medullary progenitor cells in epithelial cell migration and proliferation

PubMed Central

Chen, Dong; Chen, Zhiyong; Zhang, Yuning; Park, Chanyoung; Al-Omari, Ahmed

2014-01-01

This study is aimed at characterizing medullary interstitial progenitor cells and to examine their capacity to induce tubular epithelial cell migration and proliferation. We have isolated a progenitor cell side population from a primary medullary interstitial cell line. We show that the medullary progenitor cells (MPCs) express CD24, CD44, CXCR7, CXCR4, nestin, and PAX7. MPCs are CD34 negative, which indicates that they are not bone marrow-derived stem cells. MPCs survive >50 passages, and when grown in epithelial differentiation medium develop phenotypic characteristics of epithelial cells. Inner medulla collecting duct (IMCD3) cells treated with conditioned medium from MPCs show significantly accelerated cell proliferation and migration. Conditioned medium from PGE2-treated MPCs induce tubule formation in IMCD3 cells grown in 3D Matrigel. Moreover, most of the MPCs express the pericyte marker PDGFR-b. Our study shows that the medullary interstitium harbors a side population of progenitor cells that can differentiate to epithelial cells and can stimulate tubular epithelial cell migration and proliferation. The findings of this study suggest that medullary pericyte/progenitor cells may play a critical role in collecting duct cell injury repair. PMID:24808539

Inhibition of cyclooxygenase (COX)-2 affects endothelial progenitor cell proliferation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colleselli, Daniela; Bijuklic, Klaudija; Mosheimer, Birgit A.

2006-09-10

Growing evidence indicates that inducible cyclooxygenase-2 (COX-2) is involved in the pathogenesis of inflammatory disorders and various types of cancer. Endothelial progenitor cells recruited from the bone marrow have been shown to be involved in the formation of new vessels in malignancies and discussed for being a key point in tumour progression and metastasis. However, until now, nothing is known about an interaction between COX and endothelial progenitor cells (EPC). Expression of COX-1 and COX-2 was detected by semiquantitative RT-PCR and Western blot. Proliferation kinetics, cell cycle distribution and rate of apoptosis were analysed by MTT test and FACS analysis.more » Further analyses revealed an implication of Akt phosphorylation and caspase-3 activation. Both COX-1 and COX-2 expression can be found in bone-marrow-derived endothelial progenitor cells in vitro. COX-2 inhibition leads to a significant reduction in proliferation of endothelial progenitor cells by an increase in apoptosis and cell cycle arrest. COX-2 inhibition leads further to an increased cleavage of caspase-3 protein and inversely to inhibition of Akt activation. Highly proliferating endothelial progenitor cells can be targeted by selective COX-2 inhibition in vitro. These results indicate that upcoming therapy strategies in cancer patients targeting COX-2 may be effective in inhibiting tumour vasculogenesis as well as angiogenic processes.« less

Spectroscopic observations of cool degenerate star candidates

NASA Technical Reports Server (NTRS)

Hintzen, P.

1986-01-01

Spectroscopic observations are reported for 23 Luyten Half-Second degenerate star candidates and for 13 Luyten-Palomar common proper-motion pairs containing possible degenerate star components. Twenty-five degenerate stars are identified, 20 of which lack previous spectroscopy. Most of these stars are cool - Luyten color class g or later. One star, LP 77-57, shows broad continuum depressions similar to those in LHS 1126, which Liebert and Dahn attributed to pressure-shifted C2. A second degenerate star, LHS 290, exhibits apparent strong Swan bands which are blueshifted about 75 A. Further observations, including polarimetry and photometry, are required to appraise the spectroscopic peculiarities of these stars. Finally, five cool, sharp-lined DA white dwarfs have been observed to detect lines of metals and to determine line strengths. None of these DAs show signs of Mg b or the G band, and four show no evidence of Ca II K. The attempt to detect Ca MI in the fifth star, G199-71, was inconclusive.

Electromagnetic transients as triggers in searches for gravitational waves from compact binary mergers

NASA Astrophysics Data System (ADS)

Kelley, Luke Zoltan; Mandel, Ilya; Ramirez-Ruiz, Enrico

2013-06-01

The detection of an electromagnetic transient which may originate from a binary neutron star merger can increase the probability that a given segment of data from the LIGO-Virgo ground-based gravitational-wave detector network contains a signal from a binary coalescence. Additional information contained in the electromagnetic signal, such as the sky location or distance to the source, can help rule out false alarms and thus lower the necessary threshold for a detection. Here, we develop a framework for determining how much sensitivity is added to a gravitational-wave search by triggering on an electromagnetic transient. We apply this framework to a variety of relevant electromagnetic transients, from short gamma-ray bursts (GRBs) to signatures of r-process heating to optical and radio orphan afterglows. We compute the expected rates of multimessenger observations in the advanced detector era and find that searches triggered on short GRBs—with current high-energy instruments, such as Fermi—and nucleosynthetic “kilonovae”—with future optical surveys, like the Large Synoptic Survey Telescope—can boost the number of multimessenger detections by 15% and 40%, respectively, for a binary neutron star progenitor model. Short GRB triggers offer precise merger timing but suffer from detection rates decreased by beaming and the high a priori probability that the source is outside the LIGO-Virgo sensitive volume. Isotropic kilonovae, on the other hand, could be commonly observed within the LIGO-Virgo sensitive volume with an instrument roughly an order of magnitude more sensitive than current optical surveys. We propose that the most productive strategy for making multimessenger gravitational-wave observations is using triggers from future deep, optical all-sky surveys, with characteristics comparable to the Large Synoptic Survey Telescope, which could make as many as ten such coincident observations a year.

Orbital period variability in the eclipsing pulsar binary PSR B1957+20: Evidence for a tidally powered star

NASA Technical Reports Server (NTRS)

Applegate, James H.; Shaham, Jacob

1994-01-01

Recent observations indicate that the eclipsing pulsar binary PSR B1957+20 undergoes alternating epochs of orbital period increase and decrease. We apply a model developed to explain orbital period changes of alternating sign in other binaries to the PSR B1957+20 system and find that it fits the pulsars observations well. The novel feature of the PSR B1957+20 system is that the energy flow in the companion needed to power the orbital period change mechanism can be supplied by tidal dissipation, making the companion the first identified tidally powered star. The flow of energy in the companion drives magnetic activity, which underlies the observed orbital period variations. The magnetic activity and the wind driven by the pulsar irradiation results in a torque on the spin of the companion. This torque holds the companion out of synchronous rotation, causing tidal dissipation of energy. We propose that the progenitor had a approximately 2 hr orbital period and a companion mass of 0.1-0.2 solar mass, and the system is evolving to longer orbital periods by mass and angular momentum loss on a timescale of 10(exp 8) yr.

Role of progenitor cell producing normal vagina by metaplasia in laparoscopic peritoneal vaginoplasty

PubMed Central

Mhatre, Pravin N.; Narkhede, Hemraj R.; Pawar, P. Amol; Mhatre, P. Jyoti; Kumar, Das Dhanjit

2016-01-01

CONTEXT: Host of vaginoplasty techniques have been described. None has been successful in developing normal vagina. Laparoscopic peritoneal vaginoplasty (LPV) is performed in Mayer–Rokitansky–Küster–Hauser syndrome (MRKHS) culminating in normal vagina. AIMS: This study aims to confirm normal development of neovagina by anatomical and functional parameters of histology, cytology, and ultrasonography (USG) in LPV. To identify peritoneal progenitor cell by OCT4/SOX2 markers. To demonstrate the metaplastic conversion of peritoneum to neovagina and the progenitor cell concentration, distribution pattern. SETTINGS AND DESIGN: This is prospective experimental study, conducted at teaching hospital and private hospital. SUBJECTS AND METHODS: Fifteen women of MRKHS underwent LPV followed by histology, cytology, two-/three-dimensional USG of neovagina. Four women underwent peritoneal biopsy for identification of progenitor cells with OCT4/SOX2 markers. One patient underwent serial biopsies for 4 weeks for histology and progenitor cell immunohistochemistry. RESULTS: Normal vaginal histology and cytology were apparent. USG of neovagina showed normal appearance and blood flow. Two peritoneal samples confirmed the presence of progenitor cells. Serial biopsies demonstrated the epithelial change from single to multilayer with stromal compaction and neoangiogenesis. The progenitor cells concentration and different distribution patterns were described using SOX2/OCT4 markers. CONCLUSIONS: We have shown successful peritoneal metaplastic conversion to normal vagina in LPV. The progenitor cell was identified in normal peritoneum using SOX2/OCT4 markers. The progenitor cell concentration and pattern were demonstrated at various stages of neovaginal development. PMID:28216908

Death Receptor 6 Promotes Wallerian Degeneration in Peripheral Axons.

PubMed

Gamage, Kanchana K; Cheng, Irene; Park, Rachel E; Karim, Mardeen S; Edamura, Kazusa; Hughes, Christopher; Spano, Anthony J; Erisir, Alev; Deppmann, Christopher D

2017-03-20

Axon degeneration during development is required to sculpt a functional nervous system and is also a hallmark of pathological insult, such as injury [1, 2]. Despite similar morphological characteristics, very little overlap in molecular mechanisms has been reported between pathological and developmental degeneration [3-5]. In the peripheral nervous system (PNS), developmental axon pruning relies on receptor-mediated extrinsic degeneration mechanisms to determine which axons are maintained or degenerated [5-7]. Receptors have not been implicated in Wallerian axon degeneration; instead, axon autonomous, intrinsic mechanisms are thought to be the primary driver for this type of axon disintegration [8-10]. Here we survey the role of neuronally expressed, paralogous tumor necrosis factor receptor super family (TNFRSF) members in Wallerian degeneration. We find that an orphan receptor, death receptor 6 (DR6), is required to drive axon degeneration after axotomy in sympathetic and sensory neurons cultured in microfluidic devices. We sought to validate these in vitro findings in vivo using a transected sciatic nerve model. Consistent with the in vitro findings, DR6 -/- animals displayed preserved axons up to 4 weeks after injury. In contrast to phenotypes observed in Wld s and Sarm1 -/- mice, preserved axons in DR6 -/- animals display profound myelin remodeling. This indicates that deterioration of axons and myelin after axotomy are mechanistically distinct processes. Finally, we find that JNK signaling after injury requires DR6, suggesting a link between this novel extrinsic pathway and the axon autonomous, intrinsic pathways that have become established for Wallerian degeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

PRMT5 is essential for the maintenance of chondrogenic progenitor cells in the limb bud

PubMed Central

Norrie, Jacqueline L.; Li, Qiang; Co, Swanie; Huang, Bau-Lin; Ding, Ding; Uy, Jann C.; Ji, Zhicheng; Mackem, Susan; Bedford, Mark T.; Galli, Antonella; Ji, Hongkai

2016-01-01

During embryonic development, undifferentiated progenitor cells balance the generation of additional progenitor cells with differentiation. Within the developing limb, cartilage cells differentiate from mesodermal progenitors in an ordered process that results in the specification of the correct number of appropriately sized skeletal elements. The internal pathways by which these cells maintain an undifferentiated state while preserving their capacity to differentiate is unknown. Here, we report that the arginine methyltransferase PRMT5 has a crucial role in maintaining progenitor cells. Mouse embryonic buds lacking PRMT5 have severely truncated bones with wispy digits lacking joints. This novel phenotype is caused by widespread cell death that includes mesodermal progenitor cells that have begun to precociously differentiate into cartilage cells. We propose that PRMT5 maintains progenitor cells through its regulation of Bmp4. Intriguingly, adult and embryonic stem cells also require PRMT5 for maintaining pluripotency, suggesting that similar mechanisms might regulate lineage-restricted progenitor cells during organogenesis. PMID:27827819

PRMT5 is essential for the maintenance of chondrogenic progenitor cells in the limb bud.

PubMed

Norrie, Jacqueline L; Li, Qiang; Co, Swanie; Huang, Bau-Lin; Ding, Ding; Uy, Jann C; Ji, Zhicheng; Mackem, Susan; Bedford, Mark T; Galli, Antonella; Ji, Hongkai; Vokes, Steven A

2016-12-15

During embryonic development, undifferentiated progenitor cells balance the generation of additional progenitor cells with differentiation. Within the developing limb, cartilage cells differentiate from mesodermal progenitors in an ordered process that results in the specification of the correct number of appropriately sized skeletal elements. The internal pathways by which these cells maintain an undifferentiated state while preserving their capacity to differentiate is unknown. Here, we report that the arginine methyltransferase PRMT5 has a crucial role in maintaining progenitor cells. Mouse embryonic buds lacking PRMT5 have severely truncated bones with wispy digits lacking joints. This novel phenotype is caused by widespread cell death that includes mesodermal progenitor cells that have begun to precociously differentiate into cartilage cells. We propose that PRMT5 maintains progenitor cells through its regulation of Bmp4 Intriguingly, adult and embryonic stem cells also require PRMT5 for maintaining pluripotency, suggesting that similar mechanisms might regulate lineage-restricted progenitor cells during organogenesis. © 2016. Published by The Company of Biologists Ltd.

Analyses of cell surface molecules on hepatic stem/progenitor cells in mouse fetal liver.

PubMed

Kakinuma, Sei; Ohta, Haruhiko; Kamiya, Akihide; Yamazaki, Yuji; Oikawa, Tsunekazu; Okada, Ken; Nakauchi, Hiromitsu

2009-07-01

Hepatic stem/progenitor cells possess active proliferative ability and the capacity for differentiation into hepatic and cholangiocytic lineages. Our group and others have shown that a prospectively defined population in mid-gestational fetal liver contains hepatic stem/progenitor cells. However, the phenotypes of such cells are incompletely elucidated. We analyzed the profile of cell-surface molecules on primary hepatic stem/progenitor cells. Expression of cell surface molecules on primary hepatic stem/progenitor cells in mouse mid-gestational fetal liver was analyzed using flow cytometric multicolor analyses and colony-formation assays. The potential of the cells for liver repopulation was examined by transplantation assay. We found that CD13 (aminopeptidase N) was detected on the cells of the previously reported (Dlk/Pref-1(+)) hepatic stem/progenitor fraction. Colony-formation assays revealed that the CD13(+) fraction, compared with the Dlk(+) fraction, of non-hematopoietic cells in fetal liver was enriched in hepatic stem/progenitor cells. Transplantation assay showed the former fraction exhibited repopulating potential in regenerating liver. Moreover, flow cytometric analysis for over 90 antigens demonstrated enrichment of hepatic stem/progenitor cells using several positive selection markers, including (hitherto unknown) CD13, CD73, CD106, and CD133. Our data indicated that CD13 is a positive selection marker for hepatic stem/progenitor cells in mid-gestational fetal liver.

Mutations in ABCR (ABCA4) in patients with Stargardt macular degeneration or cone-rod degeneration.

PubMed

Briggs, C E; Rucinski, D; Rosenfeld, P J; Hirose, T; Berson, E L; Dryja, T P

2001-09-01

To determine the spectrum of ABCR mutations associated with Stargardt macular degeneration and cone-rod degeneration (CRD). One hundred eighteen unrelated patients with recessive Stargardt macular degeneration and eight with recessive CRD were screened for mutations in ABCR (ABCA4) by single-strand conformation polymorphism analysis. Variants were characterized by direct genomic sequencing. Segregation analysis was performed on the families of 20 patients in whom at least two or more likely pathogenic sequence changes were identified. The authors found 77 sequence changes likely to be pathogenic: 21 null mutations (15 novel), 55 missense changes (26 novel), and one deletion of a consensus glycosylation site (also novel). Fifty-two patients with Stargardt macular degeneration (44% of those screened) and five with CRD each had two of these sequence changes or were homozygous for one of them. Segregation analyses in the families of 19 of these patients were informative and revealed that the index cases and all available affected siblings were compound heterozygotes or homozygotes. The authors found one instance of an apparently de novo mutation, Ile824Thr, in a patient. Thirty-seven (31%) of the 118 patients with Stargardt disease and one with CRD had only one likely pathogenic sequence change. Twenty-nine patients with Stargardt disease (25%) and two with CRD had no identified sequence changes. This report of 42 novel mutations brings the growing number of identified likely pathogenic sequence changes in ABCR to approximately 250.

Identification, Characterization, and Utilization of Adult Meniscal Progenitor Cells

DTIC Science & Technology

2015-09-01

pluripotent stem cells for osteoarthritis drug screening . Arthritis Rheumatol. 66, 3062–3072. Xia, Y., Zheng, S., Bidthanapally, A., 2008. Depth-dependent...the development of knee osteoarthritis (OA). New treatments centered on the stem /progenitor cell population resident within the adult meniscus will be...biology to develop a profile of repair cells in the adult meniscus, track meniscal stem /progenitor cell (MSPC) behavior within meniscus as function of

TOX3 regulates neural progenitor identity.

PubMed

Sahu, Sanjeeb Kumar; Fritz, Alina; Tiwari, Neha; Kovacs, Zsuzsa; Pouya, Alireza; Wüllner, Verena; Bora, Pablo; Schacht, Teresa; Baumgart, Jan; Peron, Sophie; Berninger, Benedikt; Tiwari, Vijay K; Methner, Axel

2016-07-01

The human genomic locus for the transcription factor TOX3 has been implicated in susceptibility to restless legs syndrome and breast cancer in genome-wide association studies, but the physiological role of TOX3 remains largely unknown. We found Tox3 to be predominantly expressed in the developing mouse brain with a peak at embryonic day E14 where it co-localizes with the neural stem and progenitor markers Nestin and Sox2 in radial glia of the ventricular zone and intermediate progenitors of the subventricular zone. Tox3 is also expressed in neural progenitor cells obtained from the ganglionic eminence of E15 mice that express Nestin, and it specifically binds the Nestin promoter in chromatin immunoprecipitation assays. In line with this, over-expression of Tox3 increased Nestin promoter activity, which was cooperatively enhanced by treatment with the stem cell self-renewal promoting Notch ligand Jagged and repressed by pharmacological inhibition of Notch signaling. Knockdown of Tox3 in the subventricular zone of E12.5 mouse embryos by in utero electroporation of Tox3 shRNA revealed a reduced Nestin expression and decreased proliferation at E14 and a reduced migration to the cortical plate in E16 embryos in electroporated cells. Together, these results argue for a role of Tox3 in the development of the nervous system. Copyright © 2016 Elsevier B.V. All rights reserved.

Hans A. Bethe Prize: Cosmic Collisions Online - Compact Binary Mergers, Gravitational Waves and Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Shapiro, Stuart

2017-01-01

Hans A. Bethe elucidated our understanding of the fundamental forces of Nature by exploring and explaining countless phenomena occurring in nuclear laboratories and in stars. With the dawn of gravitational wave astronomy we now can probe compact binary mergers - Nature's cosmic collision experiments - to deepen our understanding, especially where strong-field gravitation is involved. In addition to gravitational waves, some mergers are likely to generate observable electromagnetic and/or neutrino radiation, heralding a new era of multimessenger astronomy. Robust numerical algorithms now allow us to simulate these events in full general relativity on supercomputers. We will describe some recent magnetohydrodynamic simulations that show how binary black hole-neutron star and neutron star-neutron star mergers can launch jets, lending support to the idea that such mergers could be the engines that power short gamma-ray bursts. We will also show how the magnetorotational collapse of very massive stars to spinning black holes immersed in magnetized accretion disks can launch jets as well, reinforcing the belief that such ``collapsars'' are the progenitors of long gamma-ray bursts. Computer-generated movies highlighting some of these simulations will be shown. We gratefully acknowledge support from NSF Grants 1300903 and 1602536 and NASA Grant NNX13AH44G.

Effects of transplanted circulating endothelial progenitor cells and platelet microparticles in atherosclerosis development.

PubMed

Georgescu, Adriana; Alexandru, Nicoleta; Andrei, Eugen; Dragan, Emanuel; Cochior, Daniel; Dias, Sérgio

2016-08-01

Atherosclerosis is an inflammatory disease, in which risk factors such as hyperlipidemia and hypertension affect the arterial endothelium, resulting in dysfunction, cell damage or both. The number of circulating endothelial progenitor cells and microparticles provides invaluable outcome prediction for atherosclerosis disease. However, evidence for the therapeutic potential of endothelial progenitor cells and microparticles in atherosclerosis development is limited. Our study was designed to investigate the possible protective role of a cell therapy-based approach, using endothelial progenitor cells and the dual behaviour of circulating platelet microparticles, on atherosclerosis development in hypertensive-hypercholesterolemic hamster model. Consequently, control hamsters received four intravenous inoculations of: (1) 1×10(5) endothelial progenitor cells of healthy origins in one dose per month, during four months of diet-induced atherosclerosis, and after hypertensive-hypercholesterolemic diet for further four months; (2) in a second set of experiments, 1×10(5) endothelial progenitor cells of healthy origins or/and 1×10(5) platelet microparticles of atherosclerotic origins were inoculated every other month during hypertensive-hypercholesterolemic diet. Endothelial progenitor cell treatment had the following effects: (1) re-established plasmatic parameters: cholesterol and triglyceride concentrations, blood pressure, heart rate, cytokine and chemokine profiles, platelet microparticle pro-thrombotic activity and endothelial progenitor cell paracrine activity reflected by cytokine/chemokine detection; (2) reduced lipid, macrophage and microparticle accumulation in liver; (3) reduced atherosclerosis development, revealed by decreased lipid, macrophage and microparticle content of arterial wall; (4) induced the recruitment and incorporation of endothelial progenitor cells into liver and arterial wall; (5) improved arterial dysfunction by increasing contraction and

Intersections of lung progenitor cells, lung disease and lung cancer.

PubMed

Kim, Carla F

2017-06-30

The use of stem cell biology approaches to study adult lung progenitor cells and lung cancer has brought a variety of new techniques to the field of lung biology and has elucidated new pathways that may be therapeutic targets in lung cancer. Recent results have begun to identify the ways in which different cell populations interact to regulate progenitor activity, and this has implications for the interventions that are possible in cancer and in a variety of lung diseases. Today's better understanding of the mechanisms that regulate lung progenitor cell self-renewal and differentiation, including understanding how multiple epigenetic factors affect lung injury repair, holds the promise for future better treatments for lung cancer and for optimising the response to therapy in lung cancer. Working between platforms in sophisticated organoid culture techniques, genetically engineered mouse models of injury and cancer, and human cell lines and specimens, lung progenitor cell studies can begin with basic biology, progress to translational research and finally lead to the beginnings of clinical trials. Copyright ©ERS 2017.

Corticobasal degeneration.

PubMed

Stover, N P; Watts, R L

2001-01-01

Corticobasal degeneration (CBG) is an increasingly recognized neurodegenerative disease with both motor and cognitive dysfunction. The diagnosis is probably underestimated because of the heterogeneity of clinical features, overlap with symptoms, and pathologic findings of other neurodegenerative diseases. The most characteristic initial motor symptoms are akinesia, rigidity, and apraxia. Dystonia and alien limb phenomena are frequently observed. There is often a parkinsonian picture with failure or lack of efficacy of dopaminergic medical therapy. Cognitive decline, prompting the diagnosis of dementia, may be the most common presentation of CBD that is misdiagnosed. Pathology is characterized by an asymmetric frontoparietal neuronal loss and gliosis with ballooned, achromatic cortical neurons, nigral degeneration, and variable subcortical involvement. Neuroimaging and electrophysiologic studies may help with the diagnosis but are not specific. Treatment is primarily symptomatic and minimally effective, especially after the first several years of symptoms. CBD should be considered in the differential diagnosis of patients with motor and cognitive dysfunction presenting with cortical and subcortical features. Further studies to elucidate molecular abnormalities and biological markers associated with CBD are needed to improve clinical diagnosis and treatment of patients with this disorder.

On the Evolution of Low-Mass X-Ray Binaries under the Influence of a Donor Stellar Wind Induced by X-Rays from the Accretor

NASA Astrophysics Data System (ADS)

Iben, Icko, Jr.; Tutukov, Alexander V.; Fedorova, Alexandra V.

1997-09-01

the influence of a magnetic stellar wind (MSW) when the donor is a main-sequence star (CV-like LMXBs), or under the influence of nuclear evolution when the donor is a subgiant or giant with a degenerate helium core (Algol-like LMXBs) of mass in the range MHe = 0.13-0.45 M⊙. The observed concentration of LMXBs in the 3-24 hr orbital period range corresponds to a similar concentration in the CV distribution and could be interpreted as evidence that the MSW in LMXBs operates at a strength not too different from its strength in CVs. For 0.3-1 M⊙ main-sequence donors, if the radius of the donor is larger than ~70% of the Roche lobe radius, the tendency of the ISW to force orbital expansion can balance the braking influence of the MSW and prevent an LMXB with a main-sequence donor from evolving to periods less than ~3 hr. When a main-sequence donor becomes completely convective (donor mass ~0.1-0.3 M⊙, depending on the mass-loss rate) and the MSW shuts off, orbital angular momentum loss due to gravitational wave radiation (GWR) is unable to counter the tendency toward expansion, and this may explain the apparent absence of short-period (Porb < 3 hr) LMXBs with main-sequence donors. This contrasts with the CV family in which the number of systems in the Galaxy with Porb ~ 1.3-2 hr (with donor mass <=0.3 M⊙ and with evolution driven only by GWR) is larger by a factor of ~100 than the number of systems with Porb > 3 hr. In Algol-like LMXBs in the Galactic disk, the timescale for the evaporation (caused by the ISW) of the donor with a low-mass, degenerate helium core can be smaller than the timescale for the radial expansion of the donor owing to nuclear evolution, and the donor may never fill its Roche lobe. However, if progenitor binaries are initially wide enough, the donor may escape evaporation as a main-sequence star, and significant mass transfer may not occur until the secondary evolves into a giant with a degenerate helium core of large mass and fills its Roche

Increased Cardiac Myocyte Progenitors in Failing Human Hearts

PubMed Central

Kubo, Hajime; Jaleel, Naser; Kumarapeli, Asangi; Berretta, Remus M.; Bratinov, George; Shan, Xiaoyin; Wang, Hongmei; Houser, Steven R.; Margulies, Kenneth B.

2009-01-01

Background Increasing evidence, derived mainly from animal models, supports the existence of endogenous cardiac renewal and repair mechanisms in adult mammalian hearts that could contribute to normal homeostasis and the responses to pathological insults. Methods and Results Translating these results, we isolated small c-kit+ cells from 36 of 37 human hearts using primary cell isolation techniques and magnetic cell sorting techniques. The abundance of these cardiac progenitor cells was increased nearly 4-fold in patients with heart failure requiring transplantation compared with nonfailing controls. Polychromatic flow cytometry of primary cell isolates (<30 μm) without antecedent c-kit enrichment confirmed the increased abundance of c-kit+ cells in failing hearts and demonstrated frequent coexpression of CD45 in these cells. Immunocytochemical characterization of freshly isolated, c-kit–enriched human cardiac progenitor cells confirmed frequent coexpression of c-kit and CD45. Primary cardiac progenitor cells formed new human cardiac myocytes at a relatively high frequency after coculture with neonatal rat ventricular myocytes. These contracting new cardiac myocytes exhibited an immature phenotype and frequent electric coupling with the rat myocytes that induced their myogenic differentiation. Conclusions Despite the increased abundance and cardiac myogenic capacity of cardiac progenitor cells in failing human hearts, the need to replace these organs via transplantation implies that adverse features of the local myocardial environment overwhelm endogenous cardiac repair capacity. Developing strategies to improve the success of endogenous cardiac regenerative processes may permit therapeutic myocardial repair without cell delivery per se. PMID:18645055

Observations of Core-Collapse Supernovae with Candidate Progenitor Identifications.

NASA Astrophysics Data System (ADS)

Elias-Rosa, Nancy; van Dyk, Schuyler D.

2010-02-01

Supernovae (SNe) have a profound effect on galaxies. They are clearly very important events deserving of intense study. Yet, even with nearly 4000 historical SNe, we know relatively little about the stars which give rise to these powerful explosions. The main limitation has been the lack of spatial resolution in pre-SN imaging data. However, since 1999 our team has been at the vanguard of directly identifying the progenitor stars of Core-Collapse (CC-) SNe in Hubble Space Telescope (HST) images. From this exciting new line of study, the emerging trend from a growing number of detections for Type II-Plateau SNe is that their progenitors appear to be relatively low mass (8-20 M_⊙) red supergiants, although more cases are needed. The nature of the progenitors of Type Ib/c SNe, a subset of which are associated with the amazing gamma-ray bursts, remains ambiguous. In HST Cycle 17 we are expecting to trigger our ToO observations using ACS/HRC (GO-11575) on 4 nearby (within 17 Mpc) CC-SNe, to determine the identities of the progenitors. It is conceivable that at least half of these will be discovered in the southern hemisphere. To fully characterize the progenitor star, we require detailed light curves and spectral evolution for the SNe, starting soon after discovery, to estimate the reddening to the SNe, characterize the overall luminosity and obtain a better understanding of the physics of the event. Therefore, to support the HST work, we are requesting up to 2 ToO triggers during semester 2010A, where we will monitor the SNe in BVRI with ANDICAM, and the 300 l/mm grating with the Goodman.

Embryonic mescencephalon derived neurospheres contain progenitors as well as differentiated neurons and glia.

PubMed

Khaing, Zin Z; Roberts, James L

2009-01-01

Stem cells and progenitor cells in the central nervous system may have potential for therapeutic use in patients with degenerative diseases or after injury. Neural precursor cells can be grown in culture in the presence of mitogens as aggregates termed neurospheres (NSs), as a source of proliferating progenitor cells. Withdrawal of mitogen and allowing the NSs to adhere to a substrate is the conventional way to study the differentiation potential of the progenitor cells propagated in NSs form. Here we asked if differentiation occurs within NSs cultured in the normal manner, in the presence of mitogen. We used non-passaged NSs derived from E13.5 mouse ventral mesencephalon. The NSs contained not only progenitor cells but also phenotypically-differentiated neurons and glia, in the presence of mitogen. Extracellular matrix molecules (fibronectin, laminin and collagen type IV) were also detected within these NSs, which may aid in the differentiation of progenitors inside the NSs. The cell types within NSs were also organized in a way that the differentiated cells were found in the inner cell mass while progenitors were found in the outer region. Additionally, the proportion of differentiated cell types within the NSs was also affected by exposure to different mitogens. Moreover, when placed together in to co-culture, dissociated embryonic striatal and mesencephalic cells aggregated spontaneously to form mixed NSs, enhancing the eventual differentiation into dopaminergic neurons from progenitors within these NSs. Therefore, the NSs contained progenitor cells and differentiated neurons and glial cells. In addition, NS culture system can be used to study cellular differentiation in vitro in non-adherent conditions.

Binary-disk interaction. II. Gap-opening criteria for unequal-mass binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Del Valle, Luciano; Escala, Andrés, E-mail: ldelvalleb@gmail.com

We study the interaction of an unequal-mass binary with an isothermal circumbinary disk, motivated by the theoretical and observational evidence that after a major merger of gas-rich galaxies, a massive gaseous disk with a supermassive black hole binary will be formed in the nuclear region. We focus on the gravitational torques that the binary exerts on the disk and how these torques can drive the formation of a gap in the disk. This exchange of angular momentum between the binary and the disk is mainly driven by the gravitational interaction between the binary and a strong nonaxisymmetric density perturbation thatmore » is produced in the disk, in response to the presence of the binary. Using smoothed particle hydrodynamics numerical simulations, we test two gap-opening criteria, one that assumes the geometry of the density perturbation is an ellipsoid/thick spiral and another that assumes a flat spiral geometry for the density perturbation. We find that the flat spiral gap-opening criterion successfully predicts which simulations will have a gap in the disk and which will not. We also study the limiting cases predicted by the gap-opening criteria. Since the viscosity in our simulations is considerably smaller than the expected value in the nuclear regions of gas-rich merging galaxies, we conclude that in such environments the formation of a circumbinary gap is unlikely.« less

Progenitor Masses for Every Nearby Historic Core-Collapse Supernova

NASA Astrophysics Data System (ADS)

Williams, Benjamin

2016-10-01

Some of the most energetic explosions in the Universe are the core-collapse supernovae (CCSNe) that arise from the death of massive stars. They herald the birth of neutron stars and black holes, are prodigious emitters of neutrinos and gravitational waves, influence galactic hydrodynamics, trigger further star formation, and are a major site for nucleosynthesis, yet even the most basic elements of CCSN theory are poorly constrained by observations. Specifically, there are too few observations to constrain the progenitor mass distribution and fewer observations still to constrain the mapping between progenitor mass and explosion type (e.g. IIP IIL, IIb, Ib/c, etc.). Combining previous measurements with 9 proposed HST pointings covering 13 historic CCSNe, we plan to obtain progenitor mass measurements for all cataloged historic CCSNe within 8 Mpc, optimizing observational mass constraints for CCSN theory.

[Tauopathy and Alzheimer disease: a full degenerating process].

PubMed

Buée, Luc; Delacourte, André

2006-12-01

Neurofibrillary degeneration is well correlated to the clinical signs of Alzheimer disease. However, the amyloid cascade is so well established in the scientific and medical community that the role of neurofibrillary degeneration in Alzheimer's disease etiopathogenesis is often underestimated. However, neuronal vulnerability is clearly a key factor for facilitating the amyloid pathology which allows the propagation of the degenerating process. In the present work, the role of tau pathology as both diagnostic marker and therapeutic target is highlighted in Alzheimer disease and related disorders.

Osteoclast fusion is initiated by a small subset of RANKL-stimulated monocyte progenitors, which can fuse to RANKL-unstimulated progenitors.

PubMed

Levaot, Noam; Ottolenghi, Aner; Mann, Mati; Guterman-Ram, Gali; Kam, Zvi; Geiger, Benjamin

2015-10-01

Osteoclasts are multinucleated, bone-resorbing cells formed via fusion of monocyte progenitors, a process triggered by prolonged stimulation with RANKL, the osteoclast master regulator cytokine. Monocyte fusion into osteoclasts has been shown to play a key role in bone remodeling and homeostasis; therefore, aberrant fusion may be involved in a variety of bone diseases. Indeed, research in the last decade has led to the discovery of genes regulating osteoclast fusion; yet the basic cellular regulatory mechanism underlying the fusion process is poorly understood. Here, we applied a novel approach for tracking the fusion processes, using live-cell imaging of RANKL-stimulated and non-stimulated progenitor monocytes differentially expressing dsRED or GFP, respectively. We show that osteoclast fusion is initiated by a small (~2.4%) subset of precursors, termed "fusion founders", capable of fusing either with other founders or with non-stimulated progenitors (fusion followers), which alone, are unable to initiate fusion. Careful examination indicates that the fusion between a founder and a follower cell consists of two distinct phases: an initial pairing of the two cells, typically lasting 5-35 min, during which the cells nevertheless maintain their initial morphology; and the fusion event itself. Interestingly, during the initial pre-fusion phase, a transfer of the fluorescent reporter proteins from nucleus to nucleus was noticed, suggesting crosstalk between the founder and follower progenitors via the cytoplasm that might directly affect the fusion process, as well as overall transcriptional regulation in the developing heterokaryon. Copyright © 2015 Elsevier Inc. All rights reserved.

Derivation and characterization of hepatic progenitor cells from human embryonic stem cells.

PubMed

Zhao, Dongxin; Chen, Song; Cai, Jun; Guo, Yushan; Song, Zhihua; Che, Jie; Liu, Chun; Wu, Chen; Ding, Mingxiao; Deng, Hongkui

2009-07-31

The derivation of hepatic progenitor cells from human embryonic stem (hES) cells is of value both in the study of early human liver organogenesis and in the creation of an unlimited source of donor cells for hepatocyte transplantation therapy. Here, we report for the first time the generation of hepatic progenitor cells derived from hES cells. Hepatic endoderm cells were generated by activating FGF and BMP pathways and were then purified by fluorescence activated cell sorting using a newly identified surface marker, N-cadherin. After co-culture with STO feeder cells, these purified hepatic endoderm cells yielded hepatic progenitor colonies, which possessed the proliferation potential to be cultured for an extended period of more than 100 days. With extensive expansion, they co-expressed the hepatic marker AFP and the biliary lineage marker KRT7 and maintained bipotential differentiation capacity. They were able to differentiate into hepatocyte-like cells, which expressed ALB and AAT, and into cholangiocyte-like cells, which formed duct-like cyst structures, expressed KRT19 and KRT7, and acquired epithelial polarity. In conclusion, this is the first report of the generation of proliferative and bipotential hepatic progenitor cells from hES cells. These hES cell-derived hepatic progenitor cells could be effectively used as an in vitro model for studying the mechanisms of hepatic stem/progenitor cell origin, self-renewal and differentiation.

Compensatory Response by Late Embryonic Tubular Epithelium to the Reduction in Pancreatic Progenitors

PubMed Central

Nishimura, Wataru; Kapoor, Archana; El Khattabi, Ilham; Jin, Wanzhu; Yasuda, Kazuki; Bonner-Weir, Susan; Sharma, Arun

2015-01-01

Early in pancreatic development, epithelial cells of pancreatic buds function as primary multipotent progenitor cells (1°MPC) that specify all three pancreatic cell lineages, i.e., endocrine, acinar and duct. Bipotent "Trunk" progenitors derived from 1°MPC are implicated in directly regulating the specification of endocrine progenitors. It is unclear if this specification process is initiated in the 1°MPC where some 1°MPC become competent for later specification of endocrine progenitors. Previously we reported that in Pdx1 tTA/+ ;tetO MafA (bigenic) mice inducing expression of transcription factor MafA in Pdx1-expressing (Pdx1+) cells throughout embryonic development inhibited the proliferation and differentiation of 1°MPC cells, resulting in reduced pancreatic mass and endocrine cells by embryonic day (E) 17.5. Induction of the transgene only until E12.5 in Pdx1+ 1°MPC was sufficient for this inhibition of endocrine cells and pancreatic mass at E17.5. However, by birth (P0), as we now report, such bigenic pups had significantly increased pancreatic and endocrine volumes with endocrine clusters containing all pancreatic endocrine cell types. The increase in endocrine cells resulted from a higher proliferation of tubular epithelial cells expressing the progenitor marker Glut2 in E17.5 bigenic embryos and increased number of Neurog3-expressing cells at E19.5. A BrdU-labeling study demonstrated that inhibiting proliferation of 1°MPC by forced MafA-expression did not lead to retention of those progenitors in E17.5 tubular epithelium. Our data suggest that the forced MafA expression in the 1°MPC inhibits their competency to specify endocrine progenitors only until E17.5, and after that compensatory proliferation of tubular epithelium gives rise to a distinct pool of endocrine progenitors. Thus, these bigenic mice provide a novel way to characterize the competency of 1°MPC for their ability to specify endocrine progenitors, a critical limitation in our

Haploinsufficiency for the Six2 gene increases nephron progenitor proliferation promoting branching and nephron number.

PubMed

Combes, Alexander N; Wilson, Sean; Phipson, Belinda; Binnie, Brandon B; Ju, Adler; Lawlor, Kynan T; Cebrian, Cristina; Walton, Sarah L; Smyth, Ian M; Moritz, Karen M; Kopan, Raphael; Oshlack, Alicia; Little, Melissa H

2018-03-01

The regulation of final nephron number in the kidney is poorly understood. Cessation of nephron formation occurs when the self-renewing nephron progenitor population commits to differentiation. Transcription factors within this progenitor population, such as SIX2, are assumed to control expression of genes promoting self-renewal such that homozygous Six2 deletion results in premature commitment and an early halt to kidney development. In contrast, Six2 heterozygotes were assumed to be unaffected. Using quantitative morphometry, we found a paradoxical 18% increase in ureteric branching and final nephron number in Six2 heterozygotes, despite evidence for reduced levels of SIX2 protein and transcript. This was accompanied by a clear shift in nephron progenitor identity with a distinct subset of downregulated progenitor genes such as Cited1 and Meox1 while other genes were unaffected. The net result was an increase in nephron progenitor proliferation, as assessed by elevated EdU (5-ethynyl-2'-deoxyuridine) labeling, an increase in MYC protein, and transcriptional upregulation of MYC target genes. Heterozygosity for Six2 on an Fgf20-/- background resulted in premature differentiation of the progenitor population, confirming that progenitor regulation is compromised in Six2 heterozygotes. Overall, our studies reveal a unique dose response of nephron progenitors to the level of SIX2 protein in which the role of SIX2 in progenitor proliferation versus self-renewal is separable. Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Commission 42: Close Binary Stars

NASA Astrophysics Data System (ADS)

Rucinski, Slavek M.; Ribas, Ignasi; Giménez, Alvaro; Harmanec, Petr; Hilditch, Ronald W.; Kaluzny, Janusz; Niarchos, Panayiotis; Nordström, Birgitta; Oláh, Katalin; Richards, Mercedes T.; Scarfe, Colin D.; Sion, Edward M.; Torres, Guillermo; Vrielmann, Sonja

Two meetings of interest to close binaries took place during the reporting period: A full day session on short-period binary stars mostly CV's (Milone et al. 2008) during the 2006 AAS Spring meeting in Calgary and the very broadly designed IAU Symposium No. 240 on Binary Stars as Critical Tools and Tests in Contemporary Astrophysics in Prague, 2006, with many papers on close binaries [Hartkopf et al. 2007]. In addition, the book by Eggleton (2006), which is a comprehensive summary of evolutionary processes in binary and multiple stars, was published.

The fate of close encounters between binary stars and binary supermassive black holes

NASA Astrophysics Data System (ADS)

Wang, Yi-Han; Leigh, Nathan; Yuan, Ye-Fei; Perna, Rosalba

2018-04-01

The evolution of main-sequence binaries that reside in the Galactic Centre can be heavily influenced by the central supermassive black hole (SMBH). Due to these perturbative effects, the stellar binaries in dense environments are likely to experience mergers, collisions, or ejections through secular and/or non-secular interactions. More direct interactions with the central SMBH are thought to produce hypervelocity stars (HVSs) and tidal disruption events (TDEs). In this paper, we use N-body simulations to study the dynamics of stellar binaries orbiting a central SMBH primary with an outer SMBH secondary orbiting this inner triple. The effects of the secondary SMBH on the event rates of HVSs, TDEs, and stellar mergers are investigated, as a function of the SMBH-SMBH binary mass ratio. Our numerical experiments reveal that, relative to the isolated SMBH case, the TDE and HVS rates are enhanced for, respectively, the smallest and largest mass ratio SMBH-SMBH binaries. This suggests that the observed event rates of TDEs and HVSs have the potential to serve as a diagnostic of the mass ratio of a central SMBH-SMBH binary. The presence of a secondary SMBH also allows for the creation of hypervelocity binaries. Observations of these systems could thus constrain the presence of a secondary SMBH in the Galactic Centre.

Insm1 promotes the transition of olfactory progenitors from apical and proliferative to basal, terminally dividing and neuronogenic.

PubMed

Rosenbaum, Jason N; Duggan, Anne; García-Añoveros, Jaime

2011-02-01

Insm1 is a zinc-finger transcription factor transiently expressed throughout the developing nervous system in late progenitors and nascent neurons. Insm1 is also highly expressed in medulloblastomas and other neuroendocrine tumors. We generated mice lacking the Insm1 gene and used them to elucidate its role in neurogenic proliferation of the embryonic olfactory epithelium. We found that deletion of Insm1 results in more apical cells and fewer nascent and mature neurons. In the embryonic olfactory epithelium of Insm1 mutants we detect fewer basal progenitors, which produce neurons, and more apical progenitors, which at this stage produce additional progenitors. Furthermore, in the mutants we detect fewer progenitors expressing NEUROD1, a marker of terminally dividing, neuronogenic (neuron-producing) progenitors (immediate neuronal precursors), and more progenitors expressing ASCL1, a marker of the transit amplifying progenitors that migrate from the apical to the basal edges of the epithelium while dividing to generate the terminal, neuronogenic progenitors. Finally, with timed administration of nucleoside analogs we demonstrate that the Insm1 mutants contain fewer terminally dividing progenitors at embryonic day 12.5. Altogether, these results suggest a role for Insm1 in promoting the transition of progenitors from apical and proliferative to basal, terminal and neuronogenic. This role appears partially conserved with that of its nematode ortholog, egl-46. The similar effects of Insm1 deletion on progenitors of embryonic olfactory epithelium and cortex point to striking parallels in the development of these neuroepithelia, and particularly between the basal progenitors of olfactory epithelium and the subventricular zone progenitors of cortex.

Retinoid-signaling in progenitors controls specification and regeneration of the urothelium

PubMed Central

Reiley, Maia; Laufer, Ed; Metzger, Daniel; Liang, Fengxia; Liao, Yi; Sun, Tung-Tien; Aronow, Bruce; Rosen, Roni; Mauney, Josh; Adam, Rosalyn; Rosselot, Carolina; Van Batavia, Jason; McMahon, Andrew; McMahon, Jill; Guo, Jin-Jin; Mendelsohn, Cathy

2013-01-01

The urothelium is a stratified epithelium that prevents exchange of water and toxic substances between the urinary tract and blood. It is composed of Keratin-5-expressing-basal-cells (K5-BCs), intermediate cells and superficial cells specialized for synthesis and transport of uroplakins that assemble into the apical barrier. K5-BCs are considered to be a progenitor cell type in the urothelium and other stratified epithelia. Fate mapping studies however, reveal that P-cells, a transient population, are urothelial progenitors in the embryo, intermediate cells are superficial cell progenitors in the adult regenerating urothelium, and K5-BCs are a distinct lineage. Our studies indicate that retinoids, potent regulators of ES cells and other progenitors, are also required in P-cells and intermediate cells for their specification. These observations have important implications for tissue engineering and repair, and ultimately, may lead to treatments that prevent loss of the urothelial barrier, a major cause of voiding dysfunction and bladder pain syndrome. PMID:23993789

Culture and Characterization of Circulating Endothelial Progenitor Cells in Patients with Renal Cell Carcinoma.

PubMed

Gu, Wenyu; Sun, Wei; Guo, Changcheng; Yan, Yang; Liu, Min; Yao, Xudong; Yang, Bin; Zheng, Junhua

2015-07-01

Although emerging evidence demonstrates increased circulating endothelial progenitor cells in patients with solid tumors, to our knowledge it is still unknown whether such cells can be cultured from patients with highly angiogenic renal cell carcinoma. We cultured and characterized circulating endothelial progenitor cells from patients with renal cell carcinoma. The circulating endothelial progenitor cell level (percent of CD45(-)CD34(+) VEGF-R2(+) cells in total peripheral blood mononuclear cells) was quantified in 47 patients with renal cell carcinoma and 40 healthy controls. Peripheral blood mononuclear cells were then isolated from 33 patients with renal cell carcinoma and 30 healthy controls to culture and characterize circulating endothelial progenitor cells. The circulating endothelial progenitor cell level was significantly higher in patients with renal cell carcinoma than in healthy controls (0.276% vs 0.086%, p <0.001). A colony of circulating endothelial progenitor cells first emerged significantly earlier in patient than in control preparations (6.72 vs 14.67 days, p <0.001). The culture success rate (87.8% vs 40.0% of participants) and the number of colonies (10.06 vs 1.83) were significantly greater for patients than for controls (each p <0.001). The circulating endothelial progenitor cell level correlated positively with the number of patient colonies (r = 0.762, p <0.001). Cells cultured from patients and controls showed a similar growth pattern, immunophenotype, ability to uptake Ac-LDL and bind lectin, and form capillary tubes in vitro. However, significantly more VEGF-R2(+) circulating endothelial progenitor cells were found in preparations from patients with renal cell carcinoma than from healthy controls (21.1% vs 13.4%, p <0.001). Earlier emergence of circulating endothelial progenitor cell colonies, a higher cell culture success rate and more colonies were found for patients with renal cell carcinoma than for healthy controls. Results

A progenitor model of SN 1987A based on the slow-merger scenario

NASA Astrophysics Data System (ADS)

Urushibata, Takaki; Takahashi, Koh; Umeda, Hideyuki; Yoshida, Takashi

2018-01-01

Even after elaborate investigations spanning 30 years, it is still not understand how the progenitor of SN 1987A has evolved. In order to explain the unusual red-to-blue evolution, previous studies have suggested that in the red giant stage an increase either in the surface helium abundance or in the envelope mass was necessary. It is usually supposed that the helium enhancement is caused by rotational mixing, and that the mass increase is the result of a binary merger. We have thus investigated these scenarios thoroughly. We found that rotating single-star models do not satisfy all the observational constraints and that the enhancement of the envelope mass alone does not explain the observations. Here, we consider a slow-merger scenario in which both the helium abundance and the envelope mass enhancements are expected to occur. We show that most of the observational constraints, such as the red-to-blue evolution, lifetime, total mass and position in the Hertzsprung-Russell diagram at collapse, and the chemical anomalies are well reproduced by a merger model with 14 and 9 M⊙ stars. We also discuss the effects of the added envelope spin in the merger scenarios.

Characterization of stem/progenitor cell cycle using murine circumvallate papilla taste bud organoid.

PubMed

Aihara, Eitaro; Mahe, Maxime M; Schumacher, Michael A; Matthis, Andrea L; Feng, Rui; Ren, Wenwen; Noah, Taeko K; Matsu-ura, Toru; Moore, Sean R; Hong, Christian I; Zavros, Yana; Herness, Scott; Shroyer, Noah F; Iwatsuki, Ken; Jiang, Peihua; Helmrath, Michael A; Montrose, Marshall H

2015-11-24

Leucine-rich repeat-containing G-protein coupled receptor 5-expressing (Lgr5(+)) cells have been identified as stem/progenitor cells in the circumvallate papillae, and single cultured Lgr5(+) cells give rise to taste cells. Here we use circumvallate papilla tissue to establish a three-dimensional culture system (taste bud organoids) that develops phenotypic characteristics similar to native tissue, including a multilayered epithelium containing stem/progenitor in the outer layers and taste cells in the inner layers. Furthermore, characterization of the cell cycle of the taste bud progenitor niche reveals striking dynamics of taste bud development and regeneration. Using this taste bud organoid culture system and FUCCI2 transgenic mice, we identify the stem/progenitor cells have at least 5 distinct cell cycle populations by tracking within 24-hour synchronized oscillations of proliferation. Additionally, we demonstrate that stem/progenitor cells have motility to form taste bud organoids. Taste bud organoids provides a system for elucidating mechanisms of taste signaling, disease modeling, and taste tissue regeneration.

Characterization of stem/progenitor cell cycle using murine circumvallate papilla taste bud organoid

PubMed Central

Aihara, Eitaro; Mahe, Maxime M.; Schumacher, Michael A.; Matthis, Andrea L.; Feng, Rui; Ren, Wenwen; Noah, Taeko K.; Matsu-ura, Toru; Moore, Sean R.; Hong, Christian I.; Zavros, Yana; Herness, Scott; Shroyer, Noah F.; Iwatsuki, Ken; Jiang, Peihua; Helmrath, Michael A.; Montrose, Marshall H.

2015-01-01

Leucine-rich repeat-containing G-protein coupled receptor 5-expressing (Lgr5+) cells have been identified as stem/progenitor cells in the circumvallate papillae, and single cultured Lgr5+ cells give rise to taste cells. Here we use circumvallate papilla tissue to establish a three-dimensional culture system (taste bud organoids) that develops phenotypic characteristics similar to native tissue, including a multilayered epithelium containing stem/progenitor in the outer layers and taste cells in the inner layers. Furthermore, characterization of the cell cycle of the taste bud progenitor niche reveals striking dynamics of taste bud development and regeneration. Using this taste bud organoid culture system and FUCCI2 transgenic mice, we identify the stem/progenitor cells have at least 5 distinct cell cycle populations by tracking within 24-hour synchronized oscillations of proliferation. Additionally, we demonstrate that stem/progenitor cells have motility to form taste bud organoids. Taste bud organoids provides a system for elucidating mechanisms of taste signaling, disease modeling, and taste tissue regeneration. PMID:26597788

Absolute Parameters and Physical Nature of the Low-amplitude Contact Binary HI Draconis

NASA Astrophysics Data System (ADS)

Papageorgiou, A.; Christopoulou, P.-E.

2015-05-01

We present a detailed investigation of the low-amplitude contact binary HI Dra based on the new VRcIc CCD photometric light curves (LCs) combined with published radial velocity (RV) curves. Our completely covered LCs were analyzed using PHOEBE and revealed that HI Dra is an overcontact binary with low fill-out factor f = 24 ± 4(%) and temperature difference between the components of 330 K. Two spotted models are proposed to explain the LC asymmetry, between which the A subtype of W UMa type eclipsing systems, with a cool spot on the less massive and cooler component, proves to be more plausible on evolutionary grounds. The results and stability of the solutions were explored by heuristic scan and parameter perturbation to provide a consistent and reliable set of parameters and their errors. Our photometric modeling and RV curve solution give the following absolute parameters of the hot and cool components, respectively: Mh = 1.72 ± 0.08 {{M}⊙ } and Mc = 0.43 ± 0.02 {{M}⊙ }, Rh = 1.98 ± 0.03 {{R}⊙ } and Rc = 1.08 ± 0.02 {{R}⊙ }, and Lh = 9.6 ± 0.1 {{L}⊙ } and Lc = 2.4 ± 0.1 {{L}⊙ }. Based on these results the initial masses of the progenitors (1.11 ± 0.03 {{M}⊙ } and 2.25 ± 0.07 {{M}⊙ }, respectively) and a rough estimate of the age of the system of 2.4 Gyr are discussed.

The double helium-white dwarf channel for the formation of AM CVn binaries

NASA Astrophysics Data System (ADS)

Zhang, Xian-Fei; Liu, Jin-Zhong; Jeffery, C. Simon; Hall, Philip D.; Bi, Shao-Lan

2018-01-01

Most close double helium white dwarfs will merge within a Hubble time due to orbital decay by gravitational wave radiation. However, a significant fraction with low mass ratios will survive for a long time as a consequence of stable mass transfer. Such stable mass transfer between two helium white dwarfs (HeWDs) provides one channel for the production of AM CVn binary stars. In previous calculations of double HeWD progenitors, the accreting HeWD was treated as a point mass. We have computed the evolution of 16 double HeWD models in order to investigate the consequences of treating the evolution of both components in detail. We find that the boundary between binaries having stable and unstable mass transfer is slightly modified by this approach. By comparing with observed periods and mass ratios, we redetermine masses of eight known AM CVn stars by our double HeWDs channel, i.e. HM Cnc, AM CVn, V406 Hya, J0926, J1240, GP Com, Gaia14aae and V396 Hya.We propose that central spikes in the triple-peaked emission spectra of J1240, GP Com and V396 Hya and the surface abundance ratios of N/C/O in GP Com can be explained by the stable double HeWD channel. The mass estimates derived from our calculations are used to discuss the predicted gravitational wave signal in the context of the Laser Interferometer Space Antenna (LISA) project.

Endothelial Progenitor Cells as Shuttle of Anticancer Agents.

PubMed

Laurenzana, Anna; Margheri, Francesca; Chillà, Anastasia; Biagioni, Alessio; Margheri, Giancarlo; Calorini, Lido; Fibbi, Gabriella; Del Rosso, Mario

2016-10-01

Cell therapies are treatments in which stem or progenitor cells are stimulated to differentiate into specialized cells able to home to and repair damaged tissues. After their discovery, endothelial progenitor cells (EPCs) stimulated worldwide interest as possible vehicles to perform autologous cell therapy of tumors. Taking into account the tumor-homing properties of EPCs, two different approaches to control cancer progression have been pursued by combining cell-based therapy with gene therapy or with nanomedicine. The first approach is based on the possibility of engineering EPCs to express different transgenes, and the second is based on the capacity of EPCs to take up nanomaterials. Here we review the most important progress covering the following issues: the characterization of bona fide endothelial progenitor cells, their role in tumor vascularization and metastasis, and preclinical data about their use in cell-based tumor therapy, considering antiangiogenic, suicide, immune-stimulating, and oncolytic virus gene therapy. The mixed approach of EPC cell therapy and nanomedicine is discussed in terms of plasmonic-dependent thermoablation and molecular imaging.

Bone marrow niche-inspired, multi-phase expansion of megakaryocytic progenitors with high polyploidization potential

PubMed Central

Panuganti, Swapna; Papoutsakis, Eleftherios T.; Miller, William M.

2010-01-01

Background Megakaryopoiesis encompasses hematopoietic stem and progenitor cell (HSPC) commitment to the megakaryocytic cell (Mk) lineage, expansion of Mk progenitors and mature Mks, polyploidization, and platelet release. pH and pO2 increase from the endosteum to sinuses, and different cytokines are important for various stages of differentiation. We hypothesized that mimicking the changing conditions during Mk differentiation in the bone marrow would facilitate expansion of progenitors that could generate many high-ploidy Mks. Methods CD34+ HSPCs were cultured at pH 7.2 and 5% O2 with stem cell factor (SCF), thrombopoietin (Tpo), and all combinations of Interleukin (IL)-3, IL-6, IL-11, and Flt-3 ligand to promote Mk progenitor expansion. Cells cultured with selected cytokines were shifted to pH 7.4 and 20% O2 to generate mature Mks, and treated with nicotinamide to enhance polyploidization. Results Using Tpo+SCF+IL-3+IL-11, we obtained 3.5 CD34+CD41+ Mk progenitors per input HSPC, while increasing purity from 1% to 17%. Cytokine cocktails with IL-3 yielded more progenitors and mature Mks, although the purities were lower. Mk production was much greater at higher pH and pO2. Although fewer progenitors were present, shifting to 20% O2/pH 7.4 at day 5 (versus days 7 or 9) yielded the greatest mature Mk production, 14 per input HSPC. Nicotinamide more than doubled the percentage of high-ploidy Mks to 40%. Discussion We obtained extensive Mk progenitor expansion, while ensuring that the progenitors could produce high-ploidy Mks. We anticipate that subsequent optimization of cytokines for mature Mk production and delayed nicotinamide addition will greatly increase high-ploidy Mk production. PMID:20482285

Mature Hepatocytes Exhibit Unexpected Plasticity by Direct Dedifferentiation into Liver Progenitor Cells in Culture

PubMed Central

Chen, Yixin; Wong, Philip P.; Sjeklocha, Lucas; Steer, Clifford J.; Sahin, M. Behnan

2011-01-01

Although there have been numerous reports describing the isolation of liver progenitor cells from adult liver, their exact origin has not been clearly defined; and the role played by mature hepatocytes as direct contributors to the hepatic progenitor cell pool has remained largely unknown. Here we report strong evidence that mature hepatocytes in culture have the capacity to dedifferentiate into a population of adult liver progenitors without genetic or epigenetic manipulations. By using highly-purified mature hepatocytes, which were obtained from untreated, healthy rat liver and labeled with fluorescent dye PKH2, we found that hepatocytes in culture gave rise to a population of PKH2-positive liver progenitor cells. These cells, Liver Derived Progenitor Cells or LDPCS, which share phenotypic similarities with oval cells, were previously reported to be capable of forming mature hepatocytes both in culture and in animals. Studies done at various time points during the course of dedifferentiation cultures revealed that hepatocytes rapidly transformed into liver progenitors within one week through a transient oval cell-like stage. This finding was supported by lineage-tracing studies involving double-transgenic AlbuminCreXRosa26 mice expressing β-galactosidase exclusively in hepatocytes. Cultures set up with hepatocytes obtained from these mice resulted in generation of β-galactosidase-positive liver progenitor cells demonstrating that they were a direct dedifferentiation product of mature hepatocytes. Additionally, these progenitors differentiated into hepatocytes in vivo when transplanted into rats that had undergone retrorsine pretreatment and partial hepatectomy. Conclusion Our studies provide strong evidence for the unexpected plasticity of mature hepatocytes to dedifferentiate into progenitor cells in culture; and this may potentially have a significant impact on the treatment of liver diseases requiring liver or hepatocyte transplantation. PMID:21953633

Learning Rotation-Invariant Local Binary Descriptor.

PubMed

Duan, Yueqi; Lu, Jiwen; Feng, Jianjiang; Zhou, Jie

2017-08-01

In this paper, we propose a rotation-invariant local binary descriptor (RI-LBD) learning method for visual recognition. Compared with hand-crafted local binary descriptors, such as local binary pattern and its variants, which require strong prior knowledge, local binary feature learning methods are more efficient and data-adaptive. Unlike existing learning-based local binary descriptors, such as compact binary face descriptor and simultaneous local binary feature learning and encoding, which are susceptible to rotations, our RI-LBD first categorizes each local patch into a rotational binary pattern (RBP), and then jointly learns the orientation for each pattern and the projection matrix to obtain RI-LBDs. As all the rotation variants of a patch belong to the same RBP, they are rotated into the same orientation and projected into the same binary descriptor. Then, we construct a codebook by a clustering method on the learned binary codes, and obtain a histogram feature for each image as the final representation. In order to exploit higher order statistical information, we extend our RI-LBD to the triple rotation-invariant co-occurrence local binary descriptor (TRICo-LBD) learning method, which learns a triple co-occurrence binary code for each local patch. Extensive experimental results on four different visual recognition tasks, including image patch matching, texture classification, face recognition, and scene classification, show that our RI-LBD and TRICo-LBD outperform most existing local descriptors.

Binary YORP Effect and Evolution of Binary Asteroids

NASA Astrophysics Data System (ADS)

Steinberg, Elad; Sari, Re'em

2011-02-01

The rotation states of kilometer-sized near-Earth asteroids are known to be affected by the Yarkevsky O'Keefe-Radzievskii-Paddack (YORP) effect. In a related effect, binary YORP (BYORP), the orbital properties of a binary asteroid evolve under a radiation effect mostly acting on a tidally locked secondary. The BYORP effect can alter the orbital elements over ~104-105 years for a Dp = 2 km primary with a Ds = 0.4 km secondary at 1 AU. It can either separate the binary components or cause them to collide. In this paper, we devise a simple approach to calculate the YORP effect on asteroids and the BYORP effect on binaries including J 2 effects due to primary oblateness and the Sun. We apply this to asteroids with known shapes as well as a set of randomly generated bodies with various degrees of smoothness. We find a strong correlation between the strengths of an asteroid's YORP and BYORP effects. Therefore, statistical knowledge of one could be used to estimate the effect of the other. We show that the action of BYORP preferentially shrinks rather than expands the binary orbit and that YORP preferentially slows down asteroids. This conclusion holds for the two extremes of thermal conductivities studied in this work and the assumption that the asteroid reaches a stable point, but may break down for moderate thermal conductivity. The YORP and BYORP effects are shown to be smaller than could be naively expected due to near cancellation of the effects at small scales. Taking this near cancellation into account, a simple order-of-magnitude estimate of the YORP and BYORP effects as a function of the sizes and smoothness of the bodies is calculated. Finally, we provide a simple proof showing that there is no secular effect due to absorption of radiation in BYORP.

New spectroscopic binary companions of giant stars and updated metallicity distribution for binary systems

NASA Astrophysics Data System (ADS)

Bluhm, P.; Jones, M. I.; Vanzi, L.; Soto, M. G.; Vos, J.; Wittenmyer, R. A.; Drass, H.; Jenkins, J. S.; Olivares, F.; Mennickent, R. E.; Vučković, M.; Rojo, P.; Melo, C. H. F.

2016-10-01

We report the discovery of 24 spectroscopic binary companions to giant stars. We fully constrain the orbital solution for 6 of these systems. We cannot unambiguously derive the orbital elements for the remaining stars because the phase coverage is incomplete. Of these stars, 6 present radial velocity trends that are compatible with long-period brown dwarf companions. The orbital solutions of the 24 binary systems indicate that these giant binary systems have a wide range in orbital periods, eccentricities, and companion masses. For the binaries with restricted orbital solutions, we find a range of orbital periods of between ~97-1600 days and eccentricities of between ~0.1-0.4. In addition, we studied the metallicity distribution of single and binary giant stars. We computed the metallicity of a total of 395 evolved stars, 59 of wich are in binary systems. We find a flat distribution for these binary stars and therefore conclude that stellar binary systems, and potentially brown dwarfs, have a different formation mechanism than planets. This result is confirmed by recent works showing that extrasolar planets orbiting giants are more frequent around metal-rich stars. Finally, we investigate the eccentricity as a function of the orbital period. We analyzed a total of 130 spectroscopic binaries, including those presented here and systems from the literature. We find that most of the binary stars with periods ≲30 days have circular orbits, while at longer orbital periods we observe a wide spread in their eccentricities. Based on observations collected at La Silla - Paranal Observatory under programs IDs IDs 085.C-0557, 087.C.0476, 089.C-0524, 090.C-0345, 096.A-9020 and through the Chilean Telescope Time under programs IDs CN2012A-73, CN2012B-47, CN2013A-111, CN2013B-51, CN2014A-52 and CN2015A-48.

Oxygen-induced retinopathy in mice with retinal photoreceptor cell degeneration.

PubMed

Zhang, Qian; Zhang, Zuo-Ming

2014-04-25

It is reported that retinal neovascularization seems to rarely co-exist with retinitis pigmentosa in patients and in some mouse models; however, it is not widely acknowledged as a universal phenomenon in all strains of all animal species. We aimed to further explore this phenomenon with an oxygen-induced retinopathy model in mice with retinal photoreceptor cell degeneration. Oxygen-induced retinopathy of colored and albino mice with rapid retinal degeneration were compared to homologous wild-type mice. The retinas were analyzed using high-molecular-weight FITC-dextran stained flat-mount preparation, hematoxylin and eosin (H&E) stained cross-sections, an immunohistochemical test for vascular endothelial growth factor (VEGF) distribution and Western blotting for VEGF expression after exposure to hyperoxia between postnatal days 17 (P17) and 21. Leakage and areas of non-perfusion of the retinal blood vessels were alleviated in the retinal degeneration mice. The number of preretinal vascular endothelial cell nuclei in the retinal degeneration mice was smaller than that in the homologous wild-type mice after exposure to hyperoxia (P<0.01). The degree of oxygen-induced retinopathy was positively correlated with the VEGF expression level. However, the VEGF expression level was lower in the retinal degeneration mice. Proliferative retinopathy occurred in mice with rapid retinal degeneration, but retinal photoreceptor cell degeneration could partially restrain the retinal neovascularization in this rapid retinal degeneration mouse model. Copyright © 2014 Elsevier Inc. All rights reserved.

Using SN 1987A light echoes to determine mass loss from the progenitor

NASA Technical Reports Server (NTRS)

Crotts, Arlin P. S.; Kunkel, William E.

1991-01-01

The hypothesis that the blue progenitor of SN 1987A passed through a blue supergiant phase ending with the expulsion of the outer envelope is tested. The many light echoes seen near SN 1987A were used to search for a mass flow from the progenitor and for abrupt density changes at the limits of this smooth mass flow. The progenitor needed roughly a million yr to create these structures, assuming a constant mass loss at 15 km/s. The dust in the region is small-grained and isotropically scattering. Interaction between the progenitor blue supergiant and red supergiant winds is probably contained within a roughly spherical structure 1.5 pc in diameter.

Heber Binary Project. Binary Cycle Geothermal Demonstration Power Plant (RP1900-1)

NASA Astrophysics Data System (ADS)

Lacy, R. G.; Nelson, T. T.

1982-12-01

The Heber Binary Project (1) demonstrates the potential of moderate temperature (below 410 F) geothermal energy to produce economic electric power with binary cycle conversion technology; (2) allows the scaling up and evaluation of the performance of binary cycle technology in geothermal service; (3) establishes schedule, cost and equipment performance, reservoir performance, and the environmental acceptability of such plants; and (4) resolves uncertainties associated with the reservoir performance, plant operation, and economics.

New Results on Contact Binary Stars

NASA Astrophysics Data System (ADS)

He, J.; Qian, S.; Zhu, L.; Liu, L.; Liao, W.

2014-08-01

Contact binary star is a kind of close binary with the strongest interaction binary system. Their formations and evolutions are unsolved problems in astrophysics. Since 2000, our groups have observed and studied more than half a hundred of contact binaries. In this report, I will summarize our new results of some contact binary stars (e.g. UZ CMi, GSC 03526-01995, FU Dra, GSC 0763-0572, V524 Mon, MR Com, etc.). They are as follow: (1) We discovered that V524 Mon and MR Com are shallow-contact binaries with their period decreasing; (2) GSC 03526-01995 is middle-contact binary without a period increasing or decreasing continuously; (3) UZ CMi, GSC 0763-0572 and FU Dra are middle-contact binaries with the period increasing continuously; (4) UZ CMi, GSC 03526-01995, FU Dra and V524 Mon show period oscillation which may imply the presence of additional components in these contact binaries.

The prevalence of sacroiliac joint degeneration in asymptomatic adults.

PubMed

Eno, Jonathan-James T; Boone, Christopher R; Bellino, Michael J; Bishop, Julius A

2015-06-03

Degenerative changes of the sacroiliac joint have been implicated as a cause of lower back pain in adults. The purpose of this study was to determine the prevalence of sacroiliac joint degeneration in asymptomatic patients. Five hundred consecutive pelvic computed tomography (CT) scans, made at a tertiary-care medical center, of patients with no history of pain in the lower back or pelvic girdle were retrospectively reviewed and analyzed for degenerative changes of the sacroiliac joint. After exclusion criteria were applied, 373 CT scans (746 sacroiliac joints) were evaluated for degenerative changes. Regression analysis was used to determine the association between age and the degree of sacroiliac joint degeneration. The prevalence of sacroiliac joint degeneration was 65.1%, with substantial degeneration occurring in 30.5% of asymptomatic subjects. The prevalence steadily increased with age, with 91% of subjects in the ninth decade of life displaying degenerative changes. Radiographic evidence of sacroiliac joint degeneration is highly prevalent in the asymptomatic population and is associated with age. Caution must be exercised when attributing lower back or pelvic girdle pain to sacroiliac joint degeneration seen on imaging. Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence. Copyright © 2015 by The Journal of Bone and Joint Surgery, Incorporated.

Aging-associated inflammation promotes selection for adaptive oncogenic events in B cell progenitors.

PubMed

Henry, Curtis J; Casás-Selves, Matias; Kim, Jihye; Zaberezhnyy, Vadym; Aghili, Leila; Daniel, Ashley E; Jimenez, Linda; Azam, Tania; McNamee, Eoin N; Clambey, Eric T; Klawitter, Jelena; Serkova, Natalie J; Tan, Aik Choon; Dinarello, Charles A; DeGregori, James

2015-12-01

The incidence of cancer is higher in the elderly; however, many of the underlying mechanisms for this association remain unexplored. Here, we have shown that B cell progenitors in old mice exhibit marked signaling, gene expression, and metabolic defects. Moreover, B cell progenitors that developed from hematopoietic stem cells (HSCs) transferred from young mice into aged animals exhibited similar fitness defects. We further demonstrated that ectopic expression of the oncogenes BCR-ABL, NRAS(V12), or Myc restored B cell progenitor fitness, leading to selection for oncogenically initiated cells and leukemogenesis specifically in the context of an aged hematopoietic system. Aging was associated with increased inflammation in the BM microenvironment, and induction of inflammation in young mice phenocopied aging-associated B lymphopoiesis. Conversely, a reduction of inflammation in aged mice via transgenic expression of α-1-antitrypsin or IL-37 preserved the function of B cell progenitors and prevented NRAS(V12)-mediated oncogenesis. We conclude that chronic inflammatory microenvironments in old age lead to reductions in the fitness of B cell progenitor populations. This reduced progenitor pool fitness engenders selection for cells harboring oncogenic mutations, in part due to their ability to correct aging-associated functional defects. Thus, modulation of inflammation--a common feature of aging--has the potential to limit aging-associated oncogenesis.

Declining lymphoid progenitor fitness promotes aging-associated leukemogenesis.

PubMed

Henry, Curtis J; Marusyk, Andriy; Zaberezhnyy, Vadym; Adane, Biniam; DeGregori, James

2010-12-14

Aging is associated with the functional decline of cells, tissues, and organs. At the same time, age is the single most important prognostic factor in the development of most human cancers, including chronic myelogenous and acute lymphoblastic leukemias initiated by Bcr-Abl oncogenic translocations. Prevailing paradigms attribute the association between aging and cancers to the accumulation of oncogenic mutations over time, because the accrual of oncogenic events is thought to be the rate-limiting step in initiation and progression of cancers. Conversely, aging-associated functional decline caused by both cell-autonomous and non-cell-autonomous mechanisms is likely to reduce the fitness of stem and progenitor cell populations. This reduction in fitness should be conducive for increased selection of oncogenic mutations that can at least partially alleviate fitness defects, thereby promoting the initiation of cancers. We tested this hypothesis using mouse hematopoietic models. Our studies indicate that the dramatic decline in the fitness of aged B-lymphopoiesis coincides with altered receptor-associated kinase signaling. We further show that Bcr-Abl provides a much greater competitive advantage to old B-lymphoid progenitors compared with young progenitors, coinciding with restored kinase signaling pathways, and that this enhanced competitive advantage translates into increased promotion of Bcr-Abl-driven leukemias. Moreover, impairing IL-7-mediated signaling is sufficient to promote selection for Bcr-Abl-expressing B progenitors. These studies support an unappreciated causative link between aging and cancer: increased selection of oncogenic mutations as a result of age-dependent alterations of the fitness landscape.

Basal Cells Are a Multipotent Progenitor Capable of Renewing the Bronchial Epithelium

PubMed Central

Hong, Kyung U.; Reynolds, Susan D.; Watkins, Simon; Fuchs, Elaine; Stripp, Barry R.

2004-01-01

Commitment of the pulmonary epithelium to bronchial and bronchiolar airway lineages occurs during the transition from pseudoglandular to cannalicular phases of lung development, suggesting that regional differences exist with respect to the identity of stem and progenitor cells that contribute to epithelial maintenance in adulthood. We previously defined a critical role for Clara cell secretory protein-expressing (CE) cells in renewal of bronchiolar airway epithelium following injury. Even though CE cells are also the principal progenitor for maintenance of the bronchial airway epithelium, CE cell injury is resolved through a mechanism involving recruitment of a second progenitor cell population that we now identify as a GSI-B4 reactive, cytokeratin-14-expressing basal cell. These cells exhibit multipotent differentiation capacity as assessed by analysis of cellular phenotype within clones of LacZ-tagged cells. Clones were derived from K14-expressing cells tagged in a cell-type-specific fashion by ligand-regulable Cre recombinase-mediated genomic rearrangement of the ROSA26 recombination substrate allele. We conclude that basal cells represent an alternative multipotent progenitor cell population of bronchial airways and that progenitor cell selection is dictated by the type of airway injury. PMID:14742263

[Pharmacological therapy of age-related macular degeneration based on etiopathogenesis].

PubMed

Fischer, Tamás

2015-11-15

It is of great therapeutic significance that disordered function of the vascular endothelium which supply the affected ocular structures plays a major role in the pathogenesis and development of age-related macular degeneration. Chronic inflammation is closely linked to diseases associated with endothelial dysfunction, and age-related macular degeneration is accompanied by a general inflammatory response. According to current concept, age-related macular degeneration is a local manifestation of systemic vascular disease. This recognition could have therapeutic implications because restoration of endothelial dysfunction can restabilize the condition of chronic vascular disease including age-related macular degeneration as well. Restoration of endothelial dysfunction by pharmaacological or non pharmacological interventions may prevent the development or improve endothelial dysfunction, which result in prevention or improvement of age related macular degeneration as well. Medicines including inhibitors of the renin-angiotensin system (converting enzyme inhibitors, angiotensin-receptor blockers and renin inhibitors), statins, acetylsalicylic acid, trimetazidin, third generation beta-blockers, peroxisome proliferator-activated receptor gamma agonists, folate, vitamin D, melatonin, advanced glycation end-product crosslink breaker alagebrium, endothelin-receptor antagonist bosentan, coenzyme Q10; "causal" antioxidant vitamins, N-acetyl-cysteine, resveratrol, L-arginine, serotonin receptor agonists, tumor necrosis factor-alpha blockers, specific inhibitor of the complement alternative pathway, curcumin and doxycyclin all have beneficial effects on endothelial dysfunction. Restoration of endothelial dysfunction can restabilize chronic vascular disease including age-related macular degeneration as well. Considering that the human vascular system is consubstantial, medicines listed above should be given to patients (1) who have no macular degeneration but have risk factors

LFsGRB: Binary neutron star merger rate via the luminosity function of short gamma-ray bursts

NASA Astrophysics Data System (ADS)

Paul, Debdutta

2018-04-01

LFsGRB models the luminosity function (LF) of short Gamma Ray Bursts (sGRBs) by using the available catalog data of all short GRBs (sGRBs) detected till 2017 October, estimating the luminosities via pseudo-redshifts obtained from the Yonetoku correlation, and then assuming a standard delay distribution between the cosmic star formation rate and the production rate of their progenitors. The data are fit well both by exponential cutoff powerlaw and broken powerlaw models. Using the derived parameters of these models along with conservative values in the jet opening angles seen from afterglow observations, the true rate of short GRBs is derived. Assuming a short GRB is produced from each binary neutron star merger (BNSM), the rate of gravitational wave (GW) detections from these mergers are derived for the past, present and future configurations of the GW detector networks.

The long-period binary central stars of the planetary nebulae NGC 1514 and LoTr 5

NASA Astrophysics Data System (ADS)

Jones, D.; Van Winckel, H.; Aller, A.; Exter, K.; De Marco, O.

2017-04-01

The importance of long-period binaries for the formation and evolution of planetary nebulae is still rather poorly understood, which in part is due to the lack of central star systems that are known to comprise such long-period binaries. Here, we report on the latest results from the on-going Mercator-HERMES survey for variability in the central stars of planetary nebulae. We present a study of the central stars of NGC 1514, BD+30°623, the spectrum of which shows features associated with a hot nebular progenitor as well as a possible A-type companion. Cross-correlation of high-resolution HERMES spectra against synthetic spectra shows the system to be a highly eccentric (e 0.5) double-lined binary with a period of 3300 days. Previous studies indicated that the cool component might be a horizontal branch star of mass 0.55 M⊙, but the observed radial velocity amplitudes rule out such a low mass. If we assume that the nebular symmetry axis and binary orbital plane are perpendicular, then the data are more consistent with a post-main-sequence star ascending towards the giant branch. We also present the continued monitoring of the central star of LoTr 5, HD 112313, which has now completed one full cycle, allowing the orbital period (P 2700 days) and eccentricity (e 0.3) to be derived. To date, the orbital periods of BD+30°623 and HD 112313 are the longest to have been measured spectroscopically in the central stars of planetary nebulae. Furthermore, these systems, along with BD+33°2642, comprise the only spectroscopic wide-binary central stars currently known. Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.The radial velocity data for both objects are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http

Dynamic collapses of relativistic degenerate stellar cores and radiation pressure dominated stellar interiors

NASA Astrophysics Data System (ADS)

Shi, Chun-Hui; Lou, Yu-Qing

2018-04-01

We investigate and explore self-similar dynamic radial collapses of relativistic degenerate stellar cores (RDSCs) and radiation pressure dominated stellar interiors (RPDSIs) of spherical symmetry by invoking a conventional polytropic (CP) equation of state (EoS) with a constant polytropic index γ = 4 / 3 and by allowing free-fall non-zero RDSC or RPDSI surface mass density and pressure due to their sustained physical contact with the outer surrounding stellar envelopes also in contraction. Irrespective of the physical triggering mechanisms (including, e.g., photodissociation, electron-positron pair instability, general relativistic instability etc.) for initiating such a self-similar dynamically collapsing RDSC or RPDSI embedded within a massive star, a very massive star (VMS) or a supermassive star (SMS) in contraction and by comparing with the Schwarzschild radii associated with their corresponding RDSC/RPDSI masses, the emergence of central black holes in a wide mass range appears inevitable during such RDSC/RPDSI dynamic collapses inside massive stars, VMSs, and SMSs, respectively. Radial pulsations of progenitor cores or during a stellar core collapse may well leave imprints onto collapsing RDSCs/RPDSIs towards their self-similar dynamic evolution. Massive neutron stars may form during dynamic collapses of RDSC inside massive stars in contraction under proper conditions.

Biochemistry and biology: heart-to-heart to investigate cardiac progenitor cells.

PubMed

Chimenti, Isotta; Forte, Elvira; Angelini, Francesco; Messina, Elisa; Giacomello, Alessandro

2013-02-01

Cardiac regenerative medicine is a rapidly evolving field, with promising future developments for effective personalized treatments. Several stem/progenitor cells are candidates for cardiac cell therapy, and emerging evidence suggests how multiple metabolic and biochemical pathways strictly regulate their fate and renewal. In this review, we will explore a selection of areas of common interest for biology and biochemistry concerning stem/progenitor cells, and in particular cardiac progenitor cells. Numerous regulatory mechanisms have been identified that link stem cell signaling and functions to the modulation of metabolic pathways, and vice versa. Pharmacological treatments and culture requirements may be exploited to modulate stem cell pluripotency and self-renewal, possibly boosting their regenerative potential for cell therapy. Mitochondria and their many related metabolites and messengers, such as oxygen, ROS, calcium and glucose, have a crucial role in regulating stem cell fate and the balance of their functions, together with many metabolic enzymes. Furthermore, protein biochemistry and proteomics can provide precious clues on the definition of different progenitor cell populations, their physiology and their autocrine/paracrine regulatory/signaling networks. Interdisciplinary approaches between biology and biochemistry can provide productive insights on stem/progenitor cells, allowing the development of novel strategies and protocols for effective cardiac cell therapy clinical translation. This article is part of a Special Issue entitled Biochemistry of Stem Cells. Copyright © 2012 Elsevier B.V. All rights reserved.

Characterization of hepatic progenitors from human fetal liver during second trimester.

PubMed

Rao, Mekala-Subba; Khan, Aleem-Ahmed; Parveen, Nyamath; Habeeb, Mohammed-Aejaz; Habibullah, Chittoor-Mohammed; Pande, Gopal

2008-10-07

To enrich hepatic progenitors using epithelial cell adhesion molecule (EpCAM) as a marker from human fetal liver and investigate the expression of human leukocyte antigen (HLA) and their markers associated with hepatic progenitor cells. EpCAM +ve cells were isolated using magnetic cell sorting (MACS) from human fetuses (n = 10) at 15-25 wk gestation. Expression of markers for hepatic progenitors such as albumin, alpha-fetoprotein (AFP), CD29 (integrin beta1), CD49f (integrin alpha6) and CD90 (Thy 1) was studied by using flow cytometry, immunocytochemistry and RT-PCR; HLA class I (A, B, C) and class II (DR) expression was studied by flow cytometry only. FACS analysis indicated that EpCAM +ve cells were positive for CD29, CD49f, CD90, CD34, HLA class I, albumin and AFP but negative for HLA class II (DR) and CD45. RT PCR showed that EpCAM +ve cells expressed liver epithelial markers (CK18), biliary specific marker (CK19) and hepatic markers (albumin, AFP). On immunocytochemical staining, EpCAM +ve cells were shown positive signals for CK18 and albumin. Our study suggests that these EpCAM +ve cells can be used as hepatic progenitors for cell transplantation with a minimum risk of alloreactivity and these cells may serve as a potential source for enrichment of hepatic progenitor.

Comparison of culture media for ex vivo cultivation of limbal epithelial progenitor cells

PubMed Central

Loureiro, Renata Ruoco; Cristovam, Priscila Cardoso; Martins, Caio Marques; Covre, Joyce Luciana; Sobrinho, Juliana Aparecida; Ricardo, José Reinaldo da Silva; Hazarbassanov, Rossen Myhailov; Höfling-Lima, Ana Luisa; Belfort, Rubens; Nishi, Mauro

2013-01-01

Purpose To compare the effectiveness of three culture media for growth, proliferation, differentiation, and viability of ex vivo cultured limbal epithelial progenitor cells. Methods Limbal epithelial progenitor cell cultures were established from ten human corneal rims and grew on plastic wells in three culture media: supplemental hormonal epithelial medium (SHEM), keratinocyte serum-free medium (KSFM), and Epilife. The performance of culturing limbal epithelial progenitor cells in each medium was evaluated according to the following parameters: growth area of epithelial migration; immunocytochemistry for adenosine 5′-triphosphate-binding cassette member 2 (ABCG2), p63, Ki67, cytokeratin 3 (CK3), and vimentin (VMT) and real-time reverse transcription polymerase chain reaction (RT–PCR) for CK3, ABCG2, and p63, and cell viability using Hoechst staining. Results Limbal epithelial progenitor cells cultivated in SHEM showed a tendency to faster migration, compared to KSFM and Epilife. Immunocytochemical analysis showed that proliferated cells in the SHEM had lower expression for markers related to progenitor epithelial cells (ABCG2) and putative progenitor cells (p63), and a higher percentage of positive cells for differentiated epithelium (CK3) when compared to KSFM and Epilife. In PCR analysis, ABCG2 expression was statistically higher for Epilife compared to SHEM. Expression of p63 was statistically higher for Epilife compared to SHEM and KSFM. However, CK3 expression was statistically lower for KSFM compared to SHEM. Conclusions Based on our findings, we concluded that cells cultured in KSFM and Epilife media presented a higher percentage of limbal epithelial progenitor cells, compared to SHEM. PMID:23378720

Osteogenic differentiation capacity of human skeletal muscle-derived progenitor cells.

PubMed

Oishi, Teruyo; Uezumi, Akiyoshi; Kanaji, Arihiko; Yamamoto, Naoki; Yamaguchi, Asami; Yamada, Harumoto; Tsuchida, Kunihiro

2013-01-01

Heterotopic ossification (HO) is defined as the formation of ectopic bone in soft tissue outside the skeletal tissue. HO is thought to result from aberrant differentiation of osteogenic progenitors within skeletal muscle. However, the precise origin of HO is still unclear. Skeletal muscle contains two kinds of progenitor cells, myogenic progenitors and mesenchymal progenitors. Myogenic and mesenchymal progenitors in human skeletal muscle can be identified as CD56(+) and PDGFRα(+) cells, respectively. The purpose of this study was to investigate the osteogenic differentiation potential of human skeletal muscle-derived progenitors. Both CD56(+) cells and PDGFRα(+) cells showed comparable osteogenic differentiation potential in vitro. However, in an in vivo ectopic bone formation model, PDGFRα(+) cells formed bone-like tissue and showed successful engraftment, while CD56(+) cells did not form bone-like tissue and did not adapt to an osteogenic environment. Immunohistological analysis of human HO sample revealed that many PDGFRα(+) cells were localized in proximity to ectopic bone formed in skeletal muscle. MicroRNAs (miRNAs) are known to regulate many biological processes including osteogenic differentiation. We investigated the participation of miRNAs in the osteogenic differentiation of PDGFRα(+) cells by using microarray. We identified miRNAs that had not been known to be involved in osteogenesis but showed dramatic changes during osteogenic differentiation of PDGFRα(+) cells. Upregulation of miR-146b-5p and -424 and downregulation of miR-7 during osteogenic differentiation of PDGFRα(+) cells were confirmed by quantitative real-time RT-PCR. Inhibition of upregulated miRNAs, miR-146b-5p and -424, resulted in the suppression of osteocyte maturation, suggesting that these two miRNAs have the positive role in the osteogenesis of PDGFRα(+) cells. Our results suggest that PDGFRα(+) cells may be the major source of HO and that the newly identified miRNAs may

Bilateral aniridia lenticular coloboma and snowflake retinal degeneration.

PubMed

Doganay, Selim; Emre, Sinan; Firat, Penpegül

2009-01-01

A 6-year-old boy presented with bilateral aniridia associated with lens coloboma and snowflake retinal degeneration. Ophthalmologic examination revealed bilateral corneal peripheral epithelial thickening and aniridia. Additionally, the patient had lenticular coloboma and snowflake retinal degeneration in both eyes. Intraocular pressure was 22 mm Hg bilaterally. The patient also had pendular nystagmus. Uncorrected visual acuity was counting fingers at 2 meters for both eyes, but improved to 0.2 and 0.05, respectively, with correction. Congenital aniridia has been reported with various ophthalmic pathologies, but this is the first case to display bilateral lenticular coloboma and snowflake retinal degeneration associated with aniridia.

PSR J0538+2817 as the remnant of the first supernova explosion in a massive binary

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

It is generally accepted that the radio pulsar PSR J 0538 2817 is associated with the supernova remnant SNR S 147 The only problem for the association is the obvious discrepancy Kramer et al 2003 between the kinematic age of the system of sim 30 kyr estimated from the angular offset of the pulsar from the geometric center of the SNR and pulsar s proper motion and the characteristic age of the pulsar of sim 600 kyr To reconcile these ages one can assume that the pulsar was born with a spin period close to the present one Kramer et al 2003 Romani Ng 2003 We propose an alternative explanation of the age discrepancy based on the fact that PSR J 0538 2817 could be the stellar remnant of the first supernova explosion in a massive binary system and therefore could be as old as indicated by its characteristic age Our proposal implies that S 147 is the diffuse remnant of the second supernova explosion that disrupted the binary system and that a much younger second neutron star not necessarily manifesting itself as a radio pulsar should be associated with S 147 We use the existing observational data on the system PSR J 0538 2817 SNR S 147 to suggest that the progenitor of the supernova that formed S 147 was a Wolf-Rayet star so that the supernova explosion occurred within a wind bubble surrounded by a massive shell and to constrain the parameters of the binary system We also restrict the magnitude and direction of the kick velocity received by the young neutron star at birth and find that the kick vector

Sall1 Maintains Nephron Progenitors and Nascent Nephrons by Acting as Both an Activator and a Repressor

PubMed Central

Kanda, Shoichiro; Tanigawa, Shunsuke; Ohmori, Tomoko; Taguchi, Atsuhiro; Kudo, Kuniko; Suzuki, Yutaka; Sato, Yuki; Hino, Shinjiro; Sander, Maike; Perantoni, Alan O.; Sugano, Sumio; Nakao, Mitsuyoshi

2014-01-01

The balanced self-renewal and differentiation of nephron progenitors are critical for kidney development and controlled, in part, by the transcription factor Six2, which antagonizes canonical Wnt signaling-mediated differentiation. A nuclear factor, Sall1, is expressed in Six2-positive progenitors as well as differentiating nascent nephrons, and it is essential for kidney formation. However, the molecular functions and targets of Sall1, especially the functions and targets in the nephron progenitors, remain unknown. Here, we report that Sall1 deletion in Six2-positive nephron progenitors results in severe progenitor depletion and apoptosis of the differentiating nephrons in mice. Analysis of mice with an inducible Sall1 deletion revealed that Sall1 activates genes expressed in progenitors while repressing genes expressed in differentiating nephrons. Sall1 and Six2 co-occupied many progenitor-related gene loci, and Sall1 bound to Six2 biochemically. In contrast, Sall1 did not bind to the Wnt4 locus suppressed by Six2. Sall1-mediated repression was also independent of its binding to DNA. Thus, Sall1 maintains nephron progenitors and their derivatives by a unique mechanism, which partly overlaps but is distinct from that of Six2: Sall1 activates progenitor-related genes in Six2-positive nephron progenitors and represses gene expression in Six2-negative differentiating nascent nephrons. PMID:24744442

The burden of age-related macular degeneration: a value-based analysis.

PubMed

Brown, Melissa M; Brown, Gary C; Sharma, Sanjay; Stein, Joshua D; Roth, Zachary; Campanella, Joseph; Beauchamp, George R

2006-06-01

The quality-of-life loss and the financial consequences associated with age-related macular degeneration are assessed. The quality-of-life loss associated with macular degeneration is markedly underestimated by the general public, nonophthalmic physicians, and ophthalmologists who treat patients with this condition. Mild age-related macular degeneration causes a 17% decrement in the quality of life of the average patient, similar to that encountered with moderate cardiac angina or symptomatic human immunodeficiency virus syndrome. Moderate age-related macular degeneration causes a 40% decrease in the average patient's quality of life, similar to that associated with severe cardiac angina or renal dialysis. Very severe age-related macular degeneration causes a large 63% decrease in the average patient's quality of life, similar to that encountered with end-stage prostatic cancer or a catastrophic stroke that leaves a person bedridden, incontinent and requiring constant nursing care. The return on investment is high for both treatment with current age-related macular degeneration therapies and the research costs invested in the development of age-related macular degeneration treatment modalities. Age-related macular degeneration is a major public health problem that has a devastating effect upon patients and marked adverse financial consequences for the economy.

Reprogramming mouse fibroblasts into engraftable myeloerythroid and lymphoid progenitors

PubMed Central

Cheng, Hui; Ang, Heather Yin-Kuan; A. EL Farran, Chadi; Li, Pin; Fang, Hai Tong; Liu, Tong Ming; Kong, Say Li; Chin, Michael Lingzi; Ling, Wei Yin; Lim, Edwin Kok Hao; Li, Hu; Huber, Tara; Loh, Kyle M.; Loh, Yuin-Han; Lim, Bing

2016-01-01

Recent efforts have attempted to convert non-blood cells into hematopoietic stem cells (HSCs) with the goal of generating blood lineages de novo. Here we show that hematopoietic transcription factors Scl, Lmo2, Runx1 and Bmi1 can convert a developmentally distant lineage (fibroblasts) into ‘induced hematopoietic progenitors' (iHPs). Functionally, iHPs generate acetylcholinesterase+ megakaryocytes and phagocytic myeloid cells in vitro and can also engraft immunodeficient mice, generating myeloerythoid and B-lymphoid cells for up to 4 months in vivo. Molecularly, iHPs transcriptionally resemble native Kit+ hematopoietic progenitors. Mechanistically, reprogramming factor Lmo2 implements a hematopoietic programme in fibroblasts by rapidly binding to and upregulating the Hhex and Gfi1 genes within days. Moreover the reprogramming transcription factors also require extracellular BMP and MEK signalling to cooperatively effectuate reprogramming. Thus, the transcription factors that orchestrate embryonic hematopoiesis can artificially reconstitute this programme in developmentally distant fibroblasts, converting them into engraftable blood progenitors. PMID:27869129

Coupled modes in magnetized dense plasma with relativistic-degenerate electrons

NASA Astrophysics Data System (ADS)

Khan, S. A.

2012-01-01

Low frequency electrostatic and electromagnetic waves are investigated in ultra-dense quantum magnetoplasma with relativistic-degenerate electron and non-degenerate ion fluids. The dispersion relation is derived for mobile as well as immobile ions by employing hydrodynamic equations for such plasma under the influence of electromagnetic forces and pressure gradient of relativistic-degenerate Fermi gas of electrons. The result shows the coexistence of shear Alfven and ion modes with relativistically modified dispersive properties. The relevance of results to the dense degenerate plasmas of astrophysical origin (for instance, white dwarf stars) is pointed out with brief discussion on ultra-relativistic and non-relativistic limits.

Periodontal Bioengineering: A Discourse in Surface Topographies, Progenitor Cells and Molecular Profiles

NASA Astrophysics Data System (ADS)

Dangaria, Smit J.

2011-12-01

Stem/progenitor cells are a population of cells capable of providing replacement cells for a given differentiated cell type. We have applied progenitor cell-based technologies to generate novel tissue-engineered implants that use biomimetic strategies with the ultimate goal of achieving full regeneration of lost periodontal tissues. Mesenchymal periodontal tissues such as cementum, alveolar bone (AB), and periodontal ligament (PDL) are neural crest-derived entities that emerge from the dental follicle (DF) at the onset of tooth root formation. Using a systems biology approach we have identified key differences between these periodontal progenitors on the basis of global gene expression profiles, gene cohort expression levels, and epigenetic modifications, in addition to differences in cellular morphologies. On an epigenetic level, DF progenitors featured high levels of the euchromatin marker H3K4me3, whereas PDL cells, AB osteoblasts, and cementoblasts contained high levels of the transcriptional repressor H3K9me3. Secondly, we have tested the influence of natural extracellular hydroxyapatite matrices on periodontal progenitor differentiation. Dimension and structure of extracellular matrix surfaces have powerful influences on cell shape, adhesion, and gene expression. Here we show that natural tooth root topographies induce integrin-mediated extracellular matrix signaling cascades in tandem with cell elongation and polarization to generate physiological periodontium-like tissues. In this study we replanted surface topography instructed periodontal ligament progenitors (PDLPs) into rat alveolar bone sockets for 8 and 16 weeks, resulting in complete attachment of tooth roots to the surrounding alveolar bone with a periodontal ligament fiber apparatus closely matching physiological controls along the entire root surface. Displacement studies and biochemical analyses confirmed that progenitor-based engineered periodontal tissues were similar to control teeth and

An interacting O + O supergiant close binary system: Cygnus OB2-5 (V729 Cyg)

NASA Astrophysics Data System (ADS)

Yaşarsoy, B.; Yakut, K.

2014-08-01

The massive interacting close binary system V729 Cyg (OIa + O/WN9), plausibly progenitor of a Wolf-Rayet system, is studied using new observations gathered over 65 nights and earlier published data. Radial velocity and five color light curves are analysed simultaneously. Estimated physical parameters of the components are M1=36±3 M, M2=10±1 M, R1=27±1 R, R2=15±0.6 R, log(L1/L⊙)=5.59±0.06, and log(L2/L⊙)=4.65±0.07. We give only the formal 1σ scatter, but we believe systematic errors in the luminosities, of uncertain origin as discussed in the text, are likely to be much bigger. The distance of the Cygnus OB2 association is estimated as 967±48 pc by using our newly obtained parameters.

Anomalous skin effects in a weakly magnetized degenerate electron plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbas, G., E-mail: gohar.abbas@gcu.edu.pk; Sarfraz, M.; Shah, H. A.

2014-09-15

Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring themore » ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].« less

The degenerate parametric oscillator and Ince's equation

NASA Astrophysics Data System (ADS)

Cordero-Soto, Ricardo; Suslov, Sergei K.

2011-01-01

We construct Green's function for the quantum degenerate parametric oscillator in the coordinate representation in terms of standard solutions of Ince's equation in a framework of a general approach to variable quadratic Hamiltonians. Exact time-dependent wavefunctions and their connections with dynamical invariants and SU(1, 1) group are also discussed. An extension to the degenerate parametric oscillator with time-dependent amplitude and phase is also mentioned.

A massive hypergiant star as the progenitor of the supernova SN 2005gl.

PubMed

Gal-Yam, A; Leonard, D C

2009-04-16

Our understanding of the evolution of massive stars before their final explosions as supernovae is incomplete, from both an observational and a theoretical standpoint. A key missing piece in the supernova puzzle is the difficulty of identifying and studying progenitor stars. In only a single case-that of supernova SN 1987A in the Large Magellanic Cloud-has a star been detected at the supernova location before the explosion, and been subsequently shown to have vanished after the supernova event. The progenitor of SN 1987A was a blue supergiant, which required a rethink of stellar evolution models. The progenitor of supernova SN 2005gl was proposed to be an extremely luminous object, but the association was not robustly established (it was not even clear that the putative progenitor was a single luminous star). Here we report that the previously proposed object was indeed the progenitor star of SN 2005gl. This very massive star was likely a luminous blue variable that standard stellar evolution predicts should not have exploded in that state.

Iron homeostasis and toxicity in retinal degeneration.

PubMed

He, Xining; Hahn, Paul; Iacovelli, Jared; Wong, Robert; King, Chih; Bhisitkul, Robert; Massaro-Giordano, Mina; Dunaief, Joshua L

2007-11-01

Iron is essential for many metabolic processes but can also cause damage. As a potent generator of hydroxyl radical, the most reactive of the free radicals, iron can cause considerable oxidative stress. Since iron is absorbed through diet but not excreted except through menstruation, total body iron levels buildup with age. Macular iron levels increase with age, in both men and women. This iron has the potential to contribute to retinal degeneration. Here we present an overview of the evidence suggesting that iron may contribute to retinal degenerations. Intraocular iron foreign bodies cause retinal degeneration. Retinal iron buildup resulting from hereditary iron homeostasis disorders aceruloplasminemia, Friedreich's ataxia, and panthothenate kinase-associated neurodegeneration cause retinal degeneration. Mice with targeted mutation of the iron exporter ceruloplasmin have age-dependent retinal iron overload and a resulting retinal degeneration with features of age-related macular degeneration (AMD). Post mortem retinas from patients with AMD have more iron and the iron carrier transferrin than age-matched controls. Over the past 10 years much has been learned about the intricate network of proteins involved in iron handling. Many of these, including transferrin, transferrin receptor, divalent metal transporter-1, ferritin, ferroportin, ceruloplasmin, hephaestin, iron-regulatory protein, and histocompatibility leukocyte antigen class I-like protein involved in iron homeostasis (HFE) have been found in the retina. Some of these proteins have been found in the cornea and lens as well. Levels of the iron carrier transferrin are high in the aqueous and vitreous humors. The functions of these proteins in other tissues, combined with studies on cultured ocular tissues, genetically engineered mice, and eye exams on patients with hereditary iron diseases provide clues regarding their ocular functions. Iron may play a role in a broad range of ocular diseases, including

Iron homeostasis and toxicity in retinal degeneration

PubMed Central

He, Xining; Hahn, Paul; Iacovelli, Jared; Wong, Robert; King, Chih; Bhisitkul, Robert; Massaro-Giordano, Mina; Dunaief, Joshua L.

2007-01-01

Iron is essential for many metabolic processes but can also cause damage. As a potent generator of hydroxyl radical, the most reactive of the free radicals, iron can cause considerable oxidative stress. Since iron is absorbed through diet but not excreted except through menstruation, total body iron levels build up with age. Macular iron levels increase with age, in both men and women. This iron has the potential to contribute to retinal degeneration. Here we present an overview of the evidence suggesting that iron may contribute to retinal degenerations. Intraocular iron foreign bodies cause retinal degeneration. Retinal iron buildup resulting from hereditary iron homeostasis disorders aceruloplasminemia, Friedreich’s Ataxia, and panthothenate kinase associated neurodegeneration cause retinal degeneration. Mice with targeted mutation of the iron exporter ceruloplasmin have age-dependent retinal iron overload and a resulting retinal degeneration with features of age-related macular degeneration (AMD). Post mortem retinas from patients with AMD have more iron and the iron carrier transferrin than age- matched controls. Over the past ten years much has been learned about the intricate network of proteins involved in iron handling. Many of these, including transferrin, transferrin receptor, divalent metal transporter 1, ferritin, ferroportin, ceruloplasmin, hephaestin, iron regulatory protein, and histocompatibility leukocyte antigen class I-like protein involved in iron homeostasis (HFE) have been found in the retina. Some of these proteins have been found in the cornea and lens as well. Levels of the iron carrier transferrin are high in the aqueous and vitreous humors. The functions of these proteins in other tissues, combined with studies on cultured ocular tissues, genetically engineered mice, and eye exams on patients with hereditary iron diseases provide clues regarding their ocular functions. Iron may play a role in a broad range of ocular diseases, including

Dynamics of quadruple systems composed of two binaries: stars, white dwarfs, and implications for Ia supernovae

NASA Astrophysics Data System (ADS)

Fang, Xiao; Thompson, Todd A.; Hirata, Christopher M.

2018-05-01

We investigate the long-term secular dynamics and Lidov-Kozai (LK) eccentricity oscillations of quadruple systems composed of two binaries at quadrupole and octupole orders in the perturbing Hamiltonian. We show that the fraction of systems reaching high eccentricities is enhanced relative to triple systems, over a broader range of parameter space. We show that this fraction grows with time, unlike triple systems evolved at quadrupole order. This is fundamentally because with their additional degrees of freedom, quadruple systems do not have a maximal set of commuting constants of the motion, even in secular theory at quadrupole order. We discuss these results in the context of star-star and white dwarf-white dwarf (WD) binaries, with emphasis on WD-WD mergers and collisions relevant to the Type Ia supernova problem. For star-star systems, we find that more than 30 per cent of systems reach high eccentricity within a Hubble time, potentially forming triple systems via stellar mergers or close binaries. For WD-WD systems, taking into account general relativistic and tidal precession and dissipation, we show that the merger rate is enhanced in quadruple systems relative to triple systems by a factor of 3.5-10, and that the long-term evolution of quadruple systems leads to a delay-time distribution ˜1/t for mergers and collisions. In gravitational wave-driven mergers of compact objects, we classify the mergers by their evolutionary patterns in phase space and identify a regime in about 8 per cent of orbital shrinking mergers, where eccentricity oscillations occur on the general relativistic precession time-scale, rather than the much longer LK time-scale. Finally, we generalize previous treatments of oscillations in the inner binary eccentricity (evection) to eccentric mutual orbits. We assess the merger rate in quadruple and triple systems and the implications for their viability as progenitors of stellar mergers and Type Ia supernovae.

Progress toward the maintenance and repair of degenerating retinal circuitry.

PubMed

Vugler, Anthony A

2010-01-01

Retinal diseases such as age-related macular degeneration and retinitis pigmentosa remain major causes of severe vision loss in humans. Clinical trials for treatment of retinal degenerations are underway and advancements in our understanding of retinal biology in health/disease have implications for novel therapies. A review of retinal biology is used to inform a discussion of current strategies to maintain/repair neural circuitry in age-related macular degeneration, retinitis pigmentosa, and Type 2 Leber congenital amaurosis. In age-related macular degeneration/retinitis pigmentosa, a progressive loss of rods/cones results in corruption of bipolar cell circuitry, although retinal output neurons/photoreceptive melanopsin cells survive. Visual function can be stabilized/enhanced after treatment in age-related macular degeneration, but in advanced degenerations, reorganization of retinal circuitry may preclude attempts to restore cone function. In Type 2 Leber congenital amaurosis, useful vision can be restored by gene therapy where central cones survive. Remarkable progress has been made in restoring vision to rodents using light-responsive ion channels inserted into bipolar cells/retinal ganglion cells. Advances in genetic, cellular, and prosthetic therapies show varying degrees of promise for treating retinal degenerations. While functional benefits can be obtained after early therapeutic interventions, efforts should be made to minimize circuitry changes as soon as possible after rod/cone loss. Advances in retinal anatomy/physiology and genetic technologies should allow refinement of future reparative strategies.

Binary optics: Trends and limitations

NASA Technical Reports Server (NTRS)

Farn, Michael W.; Veldkamp, Wilfrid B.

1993-01-01

We describe the current state of binary optics, addressing both the technology and the industry (i.e., marketplace). With respect to the technology, the two dominant aspects are optical design methods and fabrication capabilities, with the optical design problem being limited by human innovation in the search for new applications and the fabrication issue being limited by the availability of resources required to improve fabrication capabilities. With respect to the industry, the current marketplace does not favor binary optics as a separate product line and so we expect that companies whose primary purpose is the production of binary optics will not represent the bulk of binary optics production. Rather, binary optics' more natural role is as an enabling technology - a technology which will directly result in a competitive advantage in a company's other business areas - and so we expect that the majority of binary optics will be produced for internal use.

Photometric binary stars in Praesepe and the search for globular cluster binaries

NASA Technical Reports Server (NTRS)

Bolte, Michael

1991-01-01

A radial velocity study of the stars which are located on a second sequence above the single-star zero-age main sequence at a given color in the color-magnitude diagram of the open cluster Praesepe, (NGC 2632) shows that 10, and possibly 11, of 17 are binary systems. Of the binary systems, five have full amplitudes for their velocity variations that are greater than 50 km/s. To the extent that they can be applied to globular clusters, these results suggests that (1) observations of 'second-sequence' stars in globular clusters would be an efficient way of finding main-sequence binary systems in globulars, and (2) current instrumentation on large telescopes is sufficient for establishing unambiguously the existence of main-sequence binary systems in nearby globular clusters.

Subretinal transplantation of bone marrow mesenchymal stem cells delays retinal degeneration in the RCS rat model of retinal degeneration.

PubMed

Inoue, Yuji; Iriyama, Aya; Ueno, Shuji; Takahashi, Hidenori; Kondo, Mineo; Tamaki, Yasuhiro; Araie, Makoto; Yanagi, Yasuo

2007-08-01

Because there is no effective treatment for this retinal degeneration, potential application of cell-based therapy has attracted considerable attention. Several investigations support that bone marrow mesenchymal stem cells (MSCs) can be used for a broad spectrum of indications. Bone marrow MSCs exert their therapeutic effect in part by secreting trophic factors to promote cell survival. The current study investigates whether bone marrow MSCs secrete factor(s) to promote photoreceptor cell survival and whether subretinal transplantation of bone marrow MSCs promotes photoreceptor survival in a retinal degeneration model using Royal College of Surgeons (RCS) rats. In vitro, using mouse retinal cell culture, it was demonstrated that the conditioned medium of the MSCs delays photoreceptor cell apoptosis, suggesting that the secreted factor(s) from the MSCs promote photoreceptor cell survival. In vivo, the MSCs were injected into the subretinal space of the RCS rats and histological analysis, real-time RT-PCR and electrophysiological analysis demonstrated that the subretinal transplantation of MSCs delays retinal degeneration and preserves retinal function in the RCS rats. These results suggest that MSC is a useful cell source for cell-replacement therapy for some forms of retinal degeneration.

BINARY ASTROMETRIC MICROLENSING WITH GAIA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sajadian, Sedighe, E-mail: sajadian@ipm.ir; Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran

2015-04-15

We investigate whether or not Gaia can specify the binary fractions of massive stellar populations in the Galactic disk through astrometric microlensing. Furthermore, we study whether or not some information about their mass distributions can be inferred via this method. In this regard, we simulate the binary astrometric microlensing events due to massive stellar populations according to the Gaia observing strategy by considering (i) stellar-mass black holes, (ii) neutron stars, (iii) white dwarfs, and (iv) main-sequence stars as microlenses. The Gaia efficiency for detecting the binary signatures in binary astrometric microlensing events is ∼10%–20%. By calculating the optical depth duemore » to the mentioned stellar populations, the numbers of the binary astrometric microlensing events being observed with Gaia with detectable binary signatures, for the binary fraction of about 0.1, are estimated to be 6, 11, 77, and 1316, respectively. Consequently, Gaia can potentially specify the binary fractions of these massive stellar populations. However, the binary fraction of black holes measured with this method has a large uncertainty owing to a low number of the estimated events. Knowing the binary fractions in massive stellar populations helps with studying the gravitational waves. Moreover, we investigate the number of massive microlenses for which Gaia specifies masses through astrometric microlensing of single lenses toward the Galactic bulge. The resulting efficiencies of measuring the mass of mentioned populations are 9.8%, 2.9%, 1.2%, and 0.8%, respectively. The numbers of their astrometric microlensing events being observed in the Gaia era in which the lens mass can be inferred with the relative error less than 0.5 toward the Galactic bulge are estimated as 45, 34, 76, and 786, respectively. Hence, Gaia potentially gives us some information about the mass distribution of these massive stellar populations.« less

[CORRELATION OF LUMBAR FACET JOINT DEGENERATION AND SPINE-PELVIC SAGITTAL BALANCE].

PubMed

Lo, Xin; Zhang, Bin; Liu, Yuan; Dai, Min

2015-08-01

To investigate the relationship between lumbar facet joint degeneration of each segment and spine-pelvic sagittal balance parameters. A retrospective analysis was made the clinical data of 120 patients with lumbar degenerative disease, who accorded with the inclusion criteria between June and November 2014. There were 58 males and 62 females with an average age of 53 years (range, 24-77 years). The disease duration ranged from 3 to 96 months (mean, 6.6 months). Affected segments included L3,4 in 32 cases, L4,5 in 47 cases, and L5, S1 in 52 cases. The CT and X-ray films of the lumbar vertebrae were taken. The facet joint degeneration was graded based on the grading system of Pathria. The spine-pelvic sagittal balance parameters were measured, including lumbar lordosis (LL), upper lumbar lordosis (ULL), lower lumbar lordosis (LLL), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). According to normal range of PI, the patients were divided into 3 groups: group A (PI was less than normal range), group B (PI was within normal range), and group C (PI was more than normal range). The facet joint degeneration was compared; according to the facet joint degeneration degree, the patients were divided into group N (mild degeneration group) and group M (serious degeneration group) to observe the relationship of lumbar facet joint degeneration of each segment and spine-pelvic sagittal balance parameters. At L4,5 and L5, S1, facet joint degeneration showed significant difference among groups A, B, and C (P < 0.05), more serious facet joint degeneration was observed in group C; no significant difference was found in facet joint degeneration at L3,4 (P > 0.05). There was no significant difference in the other spine-pelvic sagittal balance parameters between groups N and M at each segment (P > 0.05) except for PT (P < 0.05). PI of more than normal range may lead to or aggravate lumbar facet joint degeneration at L4,5 and L5, Si; PT and PI are significantly associated

Agmatine inhibits chronic morphine exposure-induced impairment of hippocampal neural progenitor proliferation in adult rats.

PubMed

Liu, Ying; Lu, Guan-Yi; Chen, Wen-Qiang; Li, Yun-Feng; Wu, Ning; Li, Jin

2018-01-05

Our previous studies have shown that agmatine inhibited opioid dependence, yet the neural mechanism remains unclear. Growing evidence showed that opioids decrease neurogenesis in the adult hippocampal subgranular zone by inhibiting neural progenitor proliferation. However, whether agmatine affects chronic opioid exposure-induced impairment to hippocampal neural progenitor cell proliferation remains unknown. In the present study, we investigated the role of agmatine in hippocampal neural progenitors in morphine dependence rats. We found that chronic administration of morphine for 12 days induced morphine dependence in rats. This treatment not only decreased the proliferation of hippocampal neural progenitors in the granule cell layer, but also decreased the levels of hippocampal cAMP, pCREB and BDNF. However, these alterations can be restored to normal levels by co-treatment of agmatine (10mg/kg, s.c.). In vitro treatment with agmatine (10µM) for two days significantly increased proliferation of the cultured hippocampal neural progenitors. Concurrent treatment of agmatine (10µM) with morphine (10 or 50µM) reversed the supression of morphine-induced neural progenitor proliferation. In conclusion, we found that agmatine abolished chronic morphine-induced decrease in proliferation of hippocampal progenitors in vivo and in vitro, which may be due to the increase in cAMP-CREB-BDNF signaling. The enhancement of agmatine to proliferation of hippocampal progenitors may be one of the important mechanisms involved in the inhibition of morphine dependence by agmatine. Copyright © 2017. Published by Elsevier B.V.

Relationship of Tear Size and Location to Fatty Degeneration of the Rotator Cuff

PubMed Central

Kim, H. Mike; Dahiya, Nirvikar; Teefey, Sharlene A.; Keener, Jay D.; Galatz, Leesa M.; Yamaguchi, Ken

2010-01-01

Background: Fatty degeneration of the rotator cuff muscles may have detrimental effects on both anatomical and functional outcomes following shoulder surgery. The purpose of this study was to investigate the relationship between tear geometry and muscle fatty degeneration in shoulders with a deficient rotator cuff. Methods: Ultrasonograms of both shoulders of 262 patients were reviewed to assess the type of rotator cuff tear and fatty degeneration in the supraspinatus and infraspinatus muscles. The 251 shoulders with a full-thickness tear underwent further evaluation for tear size and location. The relationship of tear size and location to fatty degeneration of the supraspinatus and infraspinatus muscles was investigated with use of statistical comparisons and regression models. Results: Fatty degeneration was found almost exclusively in shoulders with a full-thickness rotator cuff tear. Of the 251 shoulders with a full-thickness tear, eighty-seven (34.7%) had fatty degeneration in either the supraspinatus or infraspinatus, or both. Eighty-two (32.7%) of the 251 full-thickness tears had a distance of 0 mm between the biceps tendon and anterior margin of the tear. Ninety percent of the full-thickness tears with fatty degeneration in both muscles had a distance of 0 mm posterior from the biceps, whereas only 9% of those without fatty degeneration had a distance of 0 mm. Tears with fatty degeneration had significantly greater width and length than those without fatty degeneration (p < 0.0001). Tears with fatty degeneration had a significantly shorter distance posterior from the biceps than those without fatty degeneration (p < 0.0001). The distance posterior from the biceps was found to be the most important predictor for supraspinatus fatty degeneration, whereas tear width and length were found to be the most important predictors for infraspinatus fatty degeneration. Conclusions: Fatty degeneration of the rotator cuff muscles is closely associated with tear size and

A disease-specific metabolic brain network associated with corticobasal degeneration

PubMed Central

Niethammer, Martin; Tang, Chris C.; Feigin, Andrew; Allen, Patricia J.; Heinen, Lisette; Hellwig, Sabine; Amtage, Florian; Hanspal, Era; Vonsattel, Jean Paul; Poston, Kathleen L.; Meyer, Philipp T.; Leenders, Klaus L.

2014-01-01

Corticobasal degeneration is an uncommon parkinsonian variant condition that is diagnosed mainly on clinical examination. To facilitate the differential diagnosis of this disorder, we used metabolic brain imaging to characterize a specific network that can be used to discriminate corticobasal degeneration from other atypical parkinsonian syndromes. Ten non-demented patients (eight females/two males; age 73.9 ± 5.7 years) underwent metabolic brain imaging with 18F-fluorodeoxyglucose positron emission tomography for atypical parkinsonism. These individuals were diagnosed clinically with probable corticobasal degeneration. This diagnosis was confirmed in the three subjects who additionally underwent post-mortem examination. Ten age-matched healthy subjects (five females/five males; age 71.7 ± 6.7 years) served as controls for the imaging studies. Spatial covariance analysis was applied to scan data from the combined group to identify a significant corticobasal degeneration-related metabolic pattern that discriminated (P < 0.001) the patients from the healthy control group. This pattern was characterized by bilateral, asymmetric metabolic reductions involving frontal and parietal cortex, thalamus, and caudate nucleus. These pattern-related changes were greater in magnitude in the cerebral hemisphere opposite the more clinically affected body side. The presence of this corticobasal degeneration-related metabolic topography was confirmed in two independent testing sets of patient and control scans, with elevated pattern expression (P < 0.001) in both disease groups relative to corresponding normal values. We next determined whether prospectively computed expression values for this pattern accurately discriminated corticobasal degeneration from multiple system atrophy and progressive supranuclear palsy (the two most common atypical parkinsonian syndromes) on a single case basis. Based upon this measure, corticobasal degeneration was successfully distinguished from