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Sample records for chandra reveals twin

  1. Chandra Reveals Twin X-ray Jets in the Powerful FR-II Radio Galaxy 3C353

    Energy Technology Data Exchange (ETDEWEB)

    Kataoka, J.; Stawarz, L.; Harris, D.E.; Siemiginowska, A.; Ostrowski, M.; Swain, M.R.; Hardcastle, M.J.; Goodger, J.L.; Iwasawa, K.; Edwards, P.G.

    2008-06-13

    We report X-ray imaging of the powerful FR II radio galaxy 3C 353 using the Chandra X-ray Observatory. 3C 353's two 4-inch wide and 2-feet long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the sub-arcsecond spatial resolution provided by the VLA and Chandra instruments. In a 90 ks Chandra observation, we have detected X-ray emission from most radio structures in 3C 353, including the nucleus, the jet and the counterjet, the terminal jet regions (hotspots), and one radio lobe. We show that the detection of the X-ray emission associated with the radio knots and counterknots, which is most likely non-thermal in origin, puts several crucial constraints on the X-ray emission mechanisms in powerful large-scale jets of quasars and FR II sources. In particular, we show that this detection is inconsistent with the inverse-Compton model proposed in the literature, and instead implies a synchrotron origin of the X-ray jet photons. We also find that the width of the X-ray counterjet is possibly narrower than that measured in radio bands, that the radio-to-X-ray flux ratio decreases systematically downstream along the jets, and that there are substantial (kpc-scale) offsets between the positions of the X-ray and radio intensity maxima within each knot, whose magnitudes increase away from the nucleus. We discuss all these findings in the wider context of the physics of extragalactic jets, proposing some particular though not definitive solutions or interpretations for each problem. In general, we find that the synchrotron X-ray emission of extragalactic large-scale jets is not only shaped by the global hydrodynamical configuration of the outflows, but is also likely to be very sensitive to the microscopic parameters of the jet plasma. A complete, self-consistent model for the X-ray emission of extragalactic jets still remains elusive.

  2. The Young Stellar Population in M17 Revealed by Chandra

    Science.gov (United States)

    Broos, Patrick S.; Feigelson, Eric D.; Townsley, Leisa K.; Getman, Konstantin V.; Wang, Junfeng; Garmire, Gordon P.; Jiang, Zhibo; Tsuboi, Yohko

    2007-04-01

    We report here results from a Chandra ACIS observation of the stellar populations in and around the M17 H II region. The field reveals 886 sources with observed X-ray luminosities (uncorrected for absorption) between ˜29.3 ergs s-1tables of X-ray source properties, several results are presented: 1. The X-ray luminosity function is calibrated to that of the Orion Nebula Cluster population to infer a total population of roughly 8000-10,000 stars in M17, one-third lying in the central NGC 6618 cluster. 2. About 40% of the ACIS sources are heavily obscured with AV>10 mag. Some are concentrated around well-studied star-forming regions -- IRS 5/UC1, the Kleinmann-Wright Object, and M17-North -- but most are distributed across the field. As previously shown, star formation appears to be widely distributed in the molecular clouds. X-ray emission is detected from 64 of the hundreds of Class I protostar candidates that can be identified by near- and mid-infrared colors. These constitute the most likely protostar candidates known in M17. 3. The spatial distribution of X-ray stars is complex: in addition to the central NGC 6618 cluster and well-known embedded groups, we find a new embedded cluster (designated M17-X), a 2 pc long arc of young stars along the southwest edge of the M17 H II region, and 0.1 pc substructure within various populations. These structures may indicate that the populations are dynamically young. 4. All (14/14) of the known O stars but only about half (19/34) of the known B0-B3 stars in the M17 field are detected. These stars exhibit the long-reported correlation between X-ray and bolometric luminosities of LX˜10-7Lbol. While many O and early-B stars show the soft X-ray emission expected from microshocks in their winds or moderately hard emission that could be caused by magnetically channeled wind shocks, six of these stars exhibit very hard thermal plasma components (kT>4 keV) that may be due to colliding wind binaries. More than 100 candidate new OB

  3. Echoes of multiple outbursts of Sagittarius A* revealed by Chandra

    CERN Document Server

    Clavel, Maïca; Goldwurm, A; Morris, M R; Ponti, G; Soldi, S; Trap, G

    2013-01-01

    The relatively rapid spatial and temporal variability of the X-ray radiation from some molecular clouds near the Galactic center shows that this emission component is due to the reflection of X-rays generated by a source that was luminous in the past, most likely the central supermassive black hole, Sagittarius A*. Studying the evolution of the molecular cloud reflection features is therefore a key element to reconstruct Sgr A*'s past activity. The aim of the present work is to study this emission on small angular scales in order to characterize the source outburst on short time scales. We use Chandra high-resolution data collected from 1999 to 2011 to study the most rapid variations detected so far, those of clouds between 5' and 20' from Sgr A* towards positive longitudes. Our systematic spectral-imaging analysis of the reflection emission, notably of the Fe Kalpha line at 6.4 keV and its associated 4-8 keV continuum, allows us to characterize the variations down to 15" angular scale and 1-year time scale. ...

  4. What Virtual Twins Reveal About General Intelligence and Other Behaviors.

    Science.gov (United States)

    Segal, Nancy L; McGuire, Shirley A; Stohs, Joanne Hoven

    2012-09-01

    The Fullerton Virtual Twin Study has been assessing the behaviors of an unusual sibship since 1982. Virtual twins (VTs) are same-age, unrelated siblings reared together since infancy. They replicate the rearing situation of twins but without the genetic link, enabling direct assessment of shared environmental effects on behavior. An updated analysis of IQ data, based on an increased sample of 142 VT pairs (7.87 years, SD=8.22), is presented. Intraclass correlations of .28 (IQ) and .11 (subtest profile) indicated modest shared environmental influences on intelligence. Findings from the Twins, Adoptees, Peers and Siblings (TAPS) project that studies virtual twins and other kinships are described.

  5. What Virtual Twins Reveal About General Intelligence and Other Behaviors

    OpenAIRE

    2012-01-01

    The Fullerton Virtual Twin Study has been assessing the behaviors of an unusual sibship since 1982. Virtual twins (VTs) are same-age, unrelated siblings reared together since infancy. They replicate the rearing situation of twins but without the genetic link, enabling direct assessment of shared environmental effects on behavior. An updated analysis of IQ data, based on an increased sample of 142 VT pairs (7.87 years, SD=8.22), is presented. Intraclass correlations of .28 (IQ) and .11 (subtes...

  6. Chandra Reveals The X-Ray Glint In The Cat's Eye

    Science.gov (United States)

    2001-01-01

    SAN DIEGO -- Scientists have discovered a glowing bubble of hot gas and an unexpected X-ray bright central star within the planetary nebula known as the Cat's Eye using NASA's Chandra X-ray Observatory. The new results, presented today at the American Astronomical Society meeting, provide insight into the ways that stars like our Sun end their lives. Scientists believe they are witnessing the expulsion of material from a star that is in the last stages of its existence as a normal star. Material shed by the star is flying away at a speed of about 4 million miles per hour, and the star itself is expected to collapse to become a white dwarf star in a few million years. The X-ray data from the Cat's Eye Nebula, also known as NGC 6543, clearly show a bright central star surrounded by a cloud of multimillion-degree gas. By comparing the Chandra data with those from the Hubble Space Telescope, researchers are able to see where the hotter, X-ray emitting gas appears in relation to the cooler material seen in optical wavelengths by Hubble. "Despite the complex optical appearance of the nebula, the X-ray emission illustrates unambiguously that the hot gas in the central bubble is driving the expansion of the optical nebula," said You-Hua Chu of the University of Illinois and lead author of the paper submitted to the Astrophysical Journal. "The Chandra data will help us to better understand how stars similar to our Sun produce planetary nebulas and evolve into white dwarfs as they grow old." With Chandra, astronomers measured the temperature of the central bubble of X-ray emitting material, and this presents a new puzzle. Though still incredibly energetic and hot enough to emit X-rays, this hot gas is cooler than scientists would have expected from the stellar wind that has come to stagnation from the initial high speed of 4 million miles per hour. At first, the researchers thought that the cooler, outer shell might have mixed with the energetic material closer to the

  7. Revealing the Focused Companion Wind in Cygnus X-1 with Chandra

    CERN Document Server

    Miller, J M; Schulz, N S; Marshall, H L; Fabian, A C; Remillard, R A; Wijnands, R; Lewin, W H G

    2002-01-01

    We have analyzed a Chandra HETGS spectrum of the Galactic black hole Cygnus X-1, obtained at a source flux which is approximately twice that commonly observed in its persistent low-intensity, spectrally-hard state. We find a myriad of absorption lines in the spectrum, including Ly-alpha lines and helium-like resonance lines from Ne, Na, Mg, and Si. We calculate a flux-weighted mean red-shift of ~100 km/s and a flux-weighted mean velocity width of 800 km/s (FWHM) for lines from these elements. We also detect a number of transitions from Fe XVIII-XXIV and Ni XIX-XX in absorption; however, the identification of these lines is less certain and a greater range of shifts and breadth is measured. Our observation occurred at a binary phase of phi = 0.76; the lines observed are consistent with absorption in an ionized region of the supergiant O9.7 Iab companion wind. The spectrum is extremely complicated in that a range of temperatures and densities are implied. Prior Chandra HETGS spectra of Cygnus X-1 were obtained ...

  8. Chandra Reveals Heavy Obscuration and Circumnuclear Star Formation in Seyfert 2 Galaxy NGC 4968

    Science.gov (United States)

    LaMassa, Stephanie M.; Yaqoob, Tahir; Levenson, N. A.; Boorman, Peter; Heckman, Timothy M.; Gandhi, Poshak; Rigby, Jane R.; Urry, C. Megan; Ptak, Andrew F.

    2017-01-01

    We present the Chandra imaging and spectral analysis of NGC 4968, a nearby (z = 0.00986) Seyfert 2 galaxy. We discover extended (∼1 kpc) X-ray emission in the soft band (0.5–2 keV) that is neither coincident with the narrow line region nor the extended radio emission. Based on spectral modeling, it is linked to on-going star formation (∼2.6–4 M⊙ yr‑1). The soft emission at circumnuclear scales (inner ∼400 pc) originates from hot gas, with kT ∼ 0.7 keV, while the most extended thermal emission is cooler (kT ∼ 0.3 keV). We refine previous measurements of the extreme Fe Kα equivalent width in this source ({EW}={2.5}-1.0+2.6 {keV}), which suggests the central engine is completely embedded within Compton-thick levels of obscuration. Using physically motivated models fit to the Chandra spectrum, we derive a Compton-thick column density (NH > 1.25 × 1024 cm‑2) and an intrinsic hard (2–10 keV) X-ray luminosity of ∼3–8 × 1042 erg s‑1 (depending on the presumed geometry of the obscurer), which is over two orders of magnitude larger than that observed. The large Fe Kα EW suggests a spherical covering geometry, which could be confirmed with X-ray measurements above 10 keV. NGC 4968 is similar to other active galaxies that exhibit extreme Fe Kα EWs (i.e., >2 keV) in that they also contain on-going star formation. This work supports the idea that gas associated with nuclear star formation may increase the covering factor of the enshrouding gas and play a role in obscuring active galactic nuclei.

  9. Twin and family studies reveal strong environmental and weaker genetic cues explaining heritability of eosinophilic esophagitis

    Science.gov (United States)

    Alexander, Eileen S.; Martin, Lisa J.; Collins, Margaret H.; Kottyan, Leah; Sucharew, Heidi; He, Hua; Mukkada, Vincent A.; Succop, Paul A.; Abonia, J. Pablo; Foote, Heather; Eby, Michael D.; Grotjan, Tommie M.; Greenler, Alexandria J.; Dellon, Evan S.; Demain, Jeffrey G.; Furuta, Glenn T.; Gurian, Larry E.; Harley, John B.; Hopp, Russell J.; Kaul, Ajay; Nadeau, Kari C.; Noel, Richard J.; Putnam, Philip E.; von Tiehl, Karl F.; Rothenberg, Marc E.

    2014-01-01

    Background Eosinophilic esophagitis (EoE) is a chronic antigen-driven allergic inflammatory disease, likely involving the interplay of genetic and environmental factors, yet their respective contributions to heritability are unknown. Objective To quantify risk associated with genes and environment on familial clustering of EoE. Methods Family history was obtained from a hospital-based cohort of 914 EoE probands, (n=2192 first-degree “Nuclear-Family” relatives) and the new international registry of monozygotic and dizygotic twins/triplets (n=63 EoE “Twins” probands). Frequencies, recurrence risk ratios (RRRs), heritability and twin concordance were estimated. Environmental exposures were preliminarily examined. Results Analysis of the Nuclear-Family–based cohort revealed that the rate of EoE, in first-degree relatives of a proband, was 1.8% (unadjusted) and 2.3% (sex-adjusted). RRRs ranged from 10–64, depending on the family relationship, and were higher in brothers (64.0; p=0.04), fathers (42.9; p=0.004) and males (50.7; p<0.001) compared to sisters, mothers and females, respectively. Risk of EoE for other siblings was 2.4%. In the Nuclear-Families, combined gene and common environment heritability (hgc2) was 72.0±2.7% (p<0.001). In the Twins cohort, genetic heritability was 14.5±4.0% (p<0.001), and common family environment contributed 81.0±4% (p<0.001) to phenotypic variance. Proband-wise concordance in MZ co-twins was 57.9±9.5% compared to 36.4±9.3% in DZ (p=0.11). Greater birth-weight difference between twins (p=0.01), breastfeeding (p=0.15) and Fall birth season (p=0.02) were associated with twin discordance in disease status. Conclusions EoE recurrence risk ratios are increased 10–64-fold compared with the general population. EoE in relatives is 1.8–2.4%, depending upon relationship and sex. Nuclear-Family heritability appeared to be high (72.0%). However, Twins cohort analysis revealed a powerful role for common environment (81

  10. "Revealing a Population of Heavily Obscured Active Galactic Nuclei at z=0.5-1 in the Chandra Deep Field-South

    CERN Document Server

    Luo, B; Xue, Y Q; Alexander, D M; Brusa, M; Bauer, F E; Comastri, A; Fabian, A C; Gilli, R; Lehmer, B D; Rafferty, D A; Schneider, D P; Vignali, C

    2011-01-01

    (abridged) We identify a numerically significant population of heavily obscured AGNs at z~0.5-1 in the Chandra Deep Field-South (CDF-S) and Extended Chandra Deep Field-South by selecting 242 X-ray undetected objects with infrared-based star formation rates (SFRs) substantially higher (a factor of 3.2 or more) than their SFRs determined from the UV after correcting for dust extinction. An X-ray stacking analysis of 23 candidates in the central CDF-S region using the 4 Ms Chandra data reveals a hard X-ray signal with an effective power-law photon index of Gamma=0.6_{-0.4}^{+0.3}, indicating a significant contribution from obscured AGNs. Based on Monte Carlo simulations, we conclude that 74+-25% of the selected galaxies host obscured AGNs, within which ~95% are heavily obscured and ~80% are Compton-thick (CT; NH>1.5x10^{24} cm^{-2}). The heavily obscured objects in our sample are of moderate intrinsic X-ray luminosity [ ~ (0.9-4)x10^{42} erg/s in the 2-10 keV band]. The space density of the CT AGNs is (1.6+-0.5)...

  11. Deep Chandra Observations of NGC 1404: Cluster Plasma Physics Revealed by an Infalling Early-type Galaxy

    Science.gov (United States)

    Su, Yuanyuan; Kraft, Ralph P.; Roediger, Elke; Nulsen, Paul; Forman, William R.; Churazov, Eugene; Randall, Scott W.; Jones, Christine; Machacek, Marie E.

    2017-01-01

    The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics under extreme conditions that cannot be achieved on Earth. NGC 1404 is a bright elliptical galaxy that is being gas stripped as it falls through the ICM of the Fornax Cluster. We use the new Chandra X-ray observations of NGC 1404 to study ICM microphysics. The interstellar medium of NGC 1404 is characterized by a sharp leading edge, 8 kpc from the Galaxy center, and a short downstream gaseous tail. Contact discontinuities are resolved on unprecedented spatial scales (0.″5 = 45 pc) due to the combination of the proximity of NGC 1404, the superb spatial resolution of Chandra, and the very deep (670 ks) exposure. At the leading edge, we observe sub-kiloparsec-scale eddies generated by Kelvin–Helmholtz instability (KHI) and put an upper limit of 5% Spitzer on the isotropic viscosity of the hot cluster plasma. We also observe mixing between the hot cluster gas and the cooler galaxy gas in the downstream stripped tail, which provides further evidence of a low viscosity plasma. The assumed ordered magnetic fields in the ICM ought to be smaller than 5 μG to allow KHI to develop. The lack of an evident magnetic draping layer just outside the contact edge is consistent with such an upper limit.

  12. Chandra reveals a black-hole X-ray binary within the ultraluminous supernova remnant MF 16

    CERN Document Server

    Roberts, T P

    2003-01-01

    We present evidence, based on Chandra ACIS-S observations of the nearby spiral galaxy NGC 6946, that the extraodinary X-ray luminosity of the MF 16 supernova remnant actually arises in a black-hole X-ray binary. This conclusion is drawn from the point-like nature of the X-ray source, its X-ray spectrum closely resembling the spectrum of other ultraluminous X-ray sources thought to be black-hole X-ray binary systems, and the detection of rapid hard X-ray variability from the source. We briefly discuss the nature of the hard X-ray variability, and the origin of the extreme radio and optical luminosity of MF 16 in light of this identification.

  13. Revealing the heavily obscured AGN population of High Redshift 3CRR Sources with Chandra X-ray Observations

    CERN Document Server

    Wilkes, Belinda J; Haas, Martin; Barthel, Peter; Leipski, Christian; Willner, S P; Worrall, D M; Birkinshaw, Mark; Antonucci, Robert; Ashby, M L N; Chini, Rolf; Fazio, G G; Lawrence, Charles; Ogle, Patrick; Schulz, Bernhard

    2013-01-01

    Chandra observations of a complete, flux-limited sample of 38 high-redshift (10) indicating obscuration (log N_H ~ 22-24 cm^-2). These properties and the correlation between obscuration and radio core-fraction are consistent with orientation-dependent obscuration as in Unification models. About half the NLRGs have soft X-ray hardness ratios and/or high [OIII] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick (CT) material so that scattered nuclear or extended X-ray emission dominates (as in NGC1068). The ratios of unobscured to Compton-thin (10^{22} 1.5 x 10^{24} cm^-2) is 2.5:1.4:1 in this high luminosity, radio-selected sample. The obscured fraction is 0.5, higher than is typically reported for AGN at comparable luminosities from multi-wavelength surveys (0.1-0.3). Assuming random nuclear orientation, the unobscured half-opening angle of the disk/wind/torus structure is ~ 60deg and the obscuring material covers 30deg of which ~ 12deg is Compton thick. The multi-wavelength prope...

  14. The complex circumnuclear environment of the broad-line radio galaxy 3C 390.3 revealed by Chandra HETG

    CERN Document Server

    Tombesi, F; Kallman, T; Reynolds, C S; Mushotzky, R F; Braito, V; Behar, E; Leutenegger, M A; Cappi, M

    2016-01-01

    We present the first high spectral resolution X-ray observation of the broad-line radio galaxy 3C 390.3 obtained with the high energy transmission grating (HETG) spectrometer on board the Chandra X-ray Observatory. The spectrum shows complex emission and absorption features in both the soft X-rays and Fe K band. We detect emission and absorption lines in the energy range between E = 700-1000 eV associated with ionized Fe L transitions (Fe XVII-XX). An emission line at the energy of E=6.4 keV consistent with the Fe K\\alpha is also observed. Our best-fit model requires at least three different components: (i) a hot emission component likely associated with the hot interstellar medium in this elliptical galaxy with temperature kT=0.5+/-0.1 keV; (ii) a warm absorber with ionization parameter log\\xi=2.3+/-0.5 erg s^{-1} cm, column density logN_H=20.7+/-0.1 cm^{-2}, and outflow velocity of v_{out}<150 km s^{-1}; (iii) a lowly ionized reflection component in the Fe K band likely associated with the optical broad ...

  15. Shotgun metagenomics of 250 adult twins reveals genetic and environmental impacts on the gut microbiome

    DEFF Research Database (Denmark)

    Xie, Hailiang; Guo, Ruijin; Zhong, Huanzi

    2016-01-01

    associated with diseases. Moreover, we identified 8 million SNPs in the gut microbiome and observe a high similarity in microbiome SNPs between twins that slowly decreases after decades of living apart. The results shed new light on the genetic and environmental influences on the composition and function...... of the gut microbiome that could relate to risk of complex diseases.......The gut microbiota has been typically viewed as an environmental factor for human health. Twins are well suited for investigating the concordance of their gut microbiomes and decomposing genetic and environmental influences. However, existing twin studies utilizing metagenomic shotgun sequencing...

  16. Does the face of Venus reveal whether she is Earth's fraternal twin or identical twin separated at birth?

    Science.gov (United States)

    Smrekar, S. E.

    2015-12-01

    Venus has nearly the same diameter and bulk composition as Earth, yet lacks a dynamo and evidence for plate tectonics. Its dense CO2 greenhouse creates a surface T of 460°C. Orbital and landed spectroscopy indicate a basaltic crust, with possible analogs to terrestrial continents. Radar images and altimetry reveal a volcanic surface, with regions of intense tectonic deformation, including rifts, mountain belts and large, intensely deformed plateaus. The sparse impact craters give a resurfacing age of 0.3-1 b.y. Their distribution cannot be distinguished from a random one, and fit models with either a single, rapid resurfacing pulse or ongoing resurfacing. Incorporating geologic constraints favors ongoing resurfacing. Ar isotope data indicate less interior outgassing than Earth, assuming a similar volatile inventory. Gravity and topography data, along with geologic features, provide evidence for ~10 large mantle plumes, similar to the number on Earth. The gravity/topography data at these hotspots suggests no low viscosity zone, perhaps implying a dry interior. Positive thermal emissivity from the Venus Express mission correlate with volcanic flows at several hotspots and can be interpreted as unweathered basalt, implying geologically recent activity. In addition, there are ~500 coronae, which are unique to Venus and likely form via small-scale upwelling, downwelling, or a combination. Many of the larger coronae may be sites of plume-induced subduction (see Davaille abstract), although subduction does not appear to create plates. I will discuss possible reasons Venus and Earth may have evolved differently and supporting evidence from surface observations. Did early impact or magma ocean history modify interior volatile or radiogenic content? Does high surface T and its effect on rheology and mineralogy inhibit plate tectonics? What is the evidence for a wet or dry interior? What could new missions tell us about these questions?

  17. The First Chandra Field

    OpenAIRE

    Weisskopf, Martin C.; Aldcroft, Thomas L.; Cameron, Robert A.; Gandhi, Poshak; Foellmi, Cédric; Elsner, Ronald F.; Patel, Sandeep K.; Wu, Kinwah; O'Dell, Stephen L.

    2005-01-01

    Before the official first-light images, the Chandra X-Ray Observatory obtained an X-ray image of the field to which its focal plane was first exposed. We describe this historic observation and report our study of the first Chandra field. Chandra's Advanced CCD Imaging Spectrometer (ACIS) detected 15 X-ray sources, the brightest being dubbed ``Leon X-1'' to honor the Chandra Telescope Scientist, Leon Van Speybroeck. Based upon our analysis of the X-ray data and spectroscopy at the European Sou...

  18. A complete developmental sequence of a Drosophila neuronal lineage as revealed by twin-spot MARCM.

    Directory of Open Access Journals (Sweden)

    Hung-Hsiang Yu

    Full Text Available Drosophila brains contain numerous neurons that form complex circuits. These neurons are derived in stereotyped patterns from a fixed number of progenitors, called neuroblasts, and identifying individual neurons made by a neuroblast facilitates the reconstruction of neural circuits. An improved MARCM (mosaic analysis with a repressible cell marker technique, called twin-spot MARCM, allows one to label the sister clones derived from a common progenitor simultaneously in different colors. It enables identification of every single neuron in an extended neuronal lineage based on the order of neuron birth. Here we report the first example, to our knowledge, of complete lineage analysis among neurons derived from a common neuroblast that relay olfactory information from the antennal lobe (AL to higher brain centers. By identifying the sequentially derived neurons, we found that the neuroblast serially makes 40 types of AL projection neurons (PNs. During embryogenesis, one PN with multi-glomerular innervation and 18 uniglomerular PNs targeting 17 glomeruli of the adult AL are born. Many more PNs of 22 additional types, including four types of polyglomerular PNs, derive after the neuroblast resumes dividing in early larvae. Although different offspring are generated in a rather arbitrary sequence, the birth order strictly dictates the fate of each post-mitotic neuron, including the fate of programmed cell death. Notably, the embryonic progenitor has an altered temporal identity following each self-renewing asymmetric cell division. After larval hatching, the same progenitor produces multiple neurons for each cell type, but the number of neurons for each type is tightly regulated. These observations substantiate the origin-dependent specification of neuron types. Sequencing neuronal lineages will not only unravel how a complex brain develops but also permit systematic identification of neuron types for detailed structure and function analysis of the

  19. ACARDIAC TWIN

    OpenAIRE

    Vinayachandran; Jyothi,; Bindu; Umadevi

    2014-01-01

    Acardiac twin is a very rare complication occurring in monozygotic twins in which one fetus develops normally (pump twin) and the other (recipient twin) demonstrate cardiac non development and othe r anomalies. This may represent an extreme form of TTTS, also referred to as TRAP sequence. 1,2,

  20. The unusual X-ray morphology of NGC4636 revealed by deep Chandra observations: cavities and shocks created by past AGN outbursts

    CERN Document Server

    Baldi, A; Jones, C; Kraft, R; Nulsen, P; Churazov, E; David, L; Giacintucci, S

    2009-01-01

    We present Chandra ACIS-I and ACIS-S observations ($\\sim$200 ks in total) of the X-ray luminous elliptical galaxy NGC 4636, located in the outskirts of the Virgo cluster. A soft band (0.5-2 keV) image shows the presence of a bright core in the center surrounded by an extended X-ray corona and two pronounced quasi-symmetric, 8 kpc long, arm-like features. Each of this features defines the rimof an ellipsoidal bubble. An additional bubble-like feature, whose northern rim is located $\\sim2$ kpc south of the north-eastern arm, is detected as well. We present surface brightness and temperature profiles across the rims of the bubbles, showing that their edges are sharp and characterized by temperature jumps of about 20-25%. Through a comparison of the observed profiles with theoretical shock models, we demonstrate that a scenario where the bubbles were produced by shocks, probably driven by energy deposited off-center by jets, is the most viable explanation to the X-ray morphology observed in the central part of NG...

  1. Chandra Observations of Starburst Galaxies

    Science.gov (United States)

    Prestwich, Andrea; Lavoie, Anthony R. (Technical Monitor)

    2000-01-01

    We present early X-ray results from Chandra for two starburst galaxies, M82 and NGC3256, obtained using AXAF CCD Imaging Spectrometer (ACIS-I) and the HRC. For M82 the arcsecond spatial resolution enables us to separate the point source component from the extended emission for the first time. Astrometry reveals that most of the X-ray sources are not coincident with the family of compact radio sources believed to be Super Nova Remnants (SNRs). In addition, based on three epoch Chandra observations, several of the X-ray sources are clearly variable indicating that they are binaries. When we deconvolve the extended and point source components detected in the hard X-ray band, we find that 50 percent arises from the extended component. This fact, together with its morphology, constrains the various models proposed to explain the hard X-ray emission. For NGC3256 we resolve two closely separated nuclei. These new data support a pure starburst origin for the total X-ray emission rather than a composite AGN/starburst, thereby making NGC3256 one of the most X-ray luminous starburst galaxies known.

  2. Recipient twin limb ischemia with postnatal onset.

    Science.gov (United States)

    Broadbent, Roland Spencer

    2007-02-01

    After the occurrence of 3 local cases of limb ischemia in newborn twins, we reviewed the literature to investigate this combination systematically. This review reveals a distinct condition: postnatal onset limb ischemia affecting recipient twins in twin-twin transfusion syndrome.

  3. Chandra Publication Statistics

    CERN Document Server

    Rots, Arnold H; Becker, Glenn

    2011-01-01

    In this study we develop and propose publication metrics, based on an analysis of data from the Chandra bibliographic database, that are more meaningful and less sensitive to observatory-specific characteristics than the traditional metrics. They fall in three main categories: speed of publication; fraction of observing time published; and archival usage. Citation of results is a fourth category, but lends itself less well to definite statements. For Chandra, the median time from observation to publication is 2.36 years; after about 7 years 90% of the observing time is published; and the total annual publication output of the mission is 60-70% of the cumulative observing time available, assuming a two year lag between data retrieval and publication.

  4. Ten Years of Chandra

    Science.gov (United States)

    Weisskopf, Martin C.

    2009-01-01

    We celebrated the 10-th anniversary of the Launch of the Chandra X-ray Observatory on July 13, 2009. During these 10 years data from this Great Observatory have had a profound impact on 21st century astrophysics. With its unrivaled capability to produce sub-arcsecond images, the Observatory has enabled astronomers to make new discoveries in topics as diverse as comets and cosmology. We shall review some of the highlights, discuss the current status, and future plans.

  5. The Chandra Bibliography Database

    Science.gov (United States)

    Rots, A. H.; Winkelman, S. L.; Paltani, S.; Blecksmith, S. E.; Bright, J. D.

    2004-07-01

    Early in the mission, the Chandra Data Archive started the development of a bibliography database, tracking publications in refereed journals and on-line conference proceedings that are based on Chandra observations, allowing our users to link directly to articles in the ADS from our archive, and to link to the relevant data in the archive from the ADS entries. Subsequently, we have been working closely with the ADS and other data centers, in the context of the ADEC-ITWG, on standardizing the literature-data linking. We have also extended our bibliography database to include all Chandra-related articles and we are also keeping track of the number of citations of each paper. Obviously, in addition to providing valuable services to our users, this database allows us to extract a wide variety of statistical information. The project comprises five components: the bibliography database-proper, a maintenance database, an interactive maintenance tool, a user browsing interface, and a web services component for exchanging information with the ADS. All of these elements are nearly mission-independent and we intend make the package as a whole available for use by other data centers. The capabilities thus provided represent support for an essential component of the Virtual Observatory.

  6. iPSC-Derived Dopamine Neurons Reveal Differences between Monozygotic Twins Discordant for Parkinson’s Disease

    Directory of Open Access Journals (Sweden)

    Chris M. Woodard

    2014-11-01

    Full Text Available Parkinson’s disease (PD has been attributed to a combination of genetic and nongenetic factors. We studied a set of monozygotic twins harboring the heterozygous glucocerebrosidase mutation (GBA N370S but clinically discordant for PD. We applied induced pluripotent stem cell (iPSC technology for PD disease modeling using the twins’ fibroblasts to evaluate and dissect the genetic and nongenetic contributions. Utilizing fluorescence-activated cell sorting, we obtained a homogenous population of “footprint-free” iPSC-derived midbrain dopaminergic (mDA neurons. The mDA neurons from both twins had ∼50% GBA enzymatic activity, ∼3-fold elevated α-synuclein protein levels, and a reduced capacity to synthesize and release dopamine. Interestingly, the affected twin’s neurons showed an even lower dopamine level, increased monoamine oxidase B (MAO-B expression, and impaired intrinsic network activity. Overexpression of wild-type GBA and treatment with MAO-B inhibitors normalized α-synuclein and dopamine levels, suggesting a combination therapy for the affected twin.

  7. Chandra Looks Back At The Earth

    Science.gov (United States)

    2005-12-01

    In an unusual observation, a team of scientists has scanned the northern polar region of Earth with NASA's Chandra X-ray Observatory. The results show that the aurora borealis, or "northern lights," also dance in X-ray light, creating changing bright arcs of X-ray energy above the Earth's surface. While other satellite observations had previously detected high-energy X-rays from the Earth auroras, the latest Chandra observations reveal low-energy X-rays generated during auroral activity for the first time. The researchers, led by Dr. Ron Elsner of NASA's Marshall Space Flight Center in Huntsville, Ala., used Chandra to observe the Earth 10 times over a four-month period in 2004. The images were created from approximately 20-minute scans during which Chandra was aimed at a fixed point in the sky and the Earth's motion carried the auroral regions through Chandra's field of view. From the ground, the aurora are well known to change dramatically over time and this is the case in X-ray light as well. The X-rays in this sample of the Chandra observations, which have been superimposed on a simulated image of the Earth, are seen here at four different epochs. Illlustration of Earth's Magnetosphere and Auroras Illlustration of Earth's Magnetosphere and Auroras Auroras are produced by solar storms that eject clouds of energetic charged particles. These particles are deflected when they encounter the Earth�s magnetic field, but in the process large electric voltages are created. Electrons trapped in the Earth�s magnetic field are accelerated by these voltages and spiral along the magnetic field into the polar regions. There they collide with atoms high in the atmosphere and emit X-rays. Chandra has also observed dramatic auroral activity on Jupiter. Dr. Anil Bhardwaj of Vikram Sarabhai Space Center in Trivandrum, India, is the lead author on a paper describing these results in the Journal of Atmospheric and Solar-Terrestrial Physics. Dr. Bhardwaj was a co

  8. Twin births

    DEFF Research Database (Denmark)

    Hoffmann, Elise; Oldenburg, Anna; Rode, Line;

    2012-01-01

    To assess morbidity and mortality in twin pregnancy deliveries, according to chorionicity and mode of delivery.......To assess morbidity and mortality in twin pregnancy deliveries, according to chorionicity and mode of delivery....

  9. Genesis of Twin Tropical Cyclones as Revealed by a Global Mesoscale Model: The Role of Mixed Rossby Gravity Waves

    Science.gov (United States)

    Shen, Bo-Wen; Tao, Wei-Kuo; Lin, Yuh-Lang; Laing, Arlene

    2012-01-01

    In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden-Julian Oscillation (MJO). This is shown by analyzing observational data, including NCEP reanalysis data and METEOSAT 7 IR satellite imagery, and performing numerical simulations using a global mesoscale model. A 10-day control run is initialized at 0000 UTC 1 May 2002 with grid-scale condensation but no sub-grid cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non-developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and thus the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8-10 day period. Five additional 10-day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres, leading to the formation of the TCs. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (1) wave deepening (intensification) associated with a reduction in wavelength and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with boundary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low- and mid-level cyclonic circulations associated with a specific gyre.

  10. Galaxy Clusters with Chandra

    CERN Document Server

    Forman, W; Markevitch, M L; Vikhlinin, A A; Churazov, E

    2002-01-01

    We discuss Chandra results related to 1) cluster mergers and cold fronts and 2) interactions between relativistic plasma and hot cluster atmospheres. We describe the properties of cold fronts using NGC1404 in the Fornax cluster and A3667 as examples. We discuss multiple surface brightness discontinuities in the cooling flow cluster ZW3146. We review the supersonic merger underway in CL0657. Finally, we summarize the interaction between plasma bubbles produced by AGN and hot gas using M87 and NGC507 as examples.

  11. Lunar Prospecting With Chandra

    Science.gov (United States)

    2003-09-01

    Observations of the bright side of the Moon with NASA's Chandra X-ray Observatory have detected oxygen, magnesium, aluminum and silicon over a large area of the lunar surface. The abundance and distribution of those elements will help to determine how the Moon was formed. "We see X-rays from these elements directly, independent of assumptions about the mineralogy and other complications," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., at a press conference at the "Four Years with Chandra" symposium in Huntsville, Alabama. "We have Moon samples from the six widely-space Apollo landing sites, but remote sensing with Chandra can cover a much wider area," continued Drake. "It's the next best thing to being there, and it's very fast and cost-effective." The lunar X-rays are caused by fluorescence, a process similar to the way that light is produced in fluorescent lamps. Solar X-rays bombard the surface of the Moon, knock electrons out of the inner parts of the atoms, putting them in a highly unstable state. Almost immediately, other electrons rush to fill the gaps, and in the process convert their energy into the fluorescent X-rays seen by Chandra. According to the currently popular "giant impact" theory for the formation of the Moon, a body about the size of Mars collided with the Earth about 4.5 billion years ago. This impact flung molten debris from the mantle of both the Earth and the impactor into orbit around the Earth. Over the course of tens of millions of years, the debris stuck together to form the Moon. By measuring the amounts of aluminum and other elements over a wide area of the Moon and comparing them to the Earth's mantle, Drake and his colleagues plan to help test the giant impact hypothesis. "One early result," quipped Drake, "is that there is no evidence for large amounts of calcium, so cheese is not a major constituent of the Moon." Illustration of Earth's Geocorona Illustration of Earth's Geocorona The same

  12. Chandra Discovers Cosmic Cannonball

    Science.gov (United States)

    2007-11-01

    One of the fastest moving stars ever seen has been discovered with NASA's Chandra X-ray Observatory. This cosmic cannonball is challenging theories to explain its blistering speed. Astronomers used Chandra to observe a neutron star, known as RX J0822-4300, over a period of about five years. During that span, three Chandra observations clearly show the neutron star moving away from the center of the Puppis A supernova remnant. This remnant is the stellar debris field created during the same explosion in which the neutron star was created about 3700 years ago. Chandra X-ray Image of RX J0822-4300 in Puppis A Chandra X-ray Image of RX J0822-4300 in Puppis A By combining how far it has moved across the sky with its distance from Earth, astronomers determined the neutron star is moving at over 3 million miles per hour. At this rate, RX J0822-4300 is destined to escape from the Milky Way after millions of years, even though it has only traveled about 20 light years so far. "This star is moving at 3 million miles an hour, but it's so far away that the apparent motion we see in five years is less than the height of the numerals in the date on a penny, seen from the length of a football field," said Frank Winkler of Middlebury College in Vermont. "It's remarkable, and a real testament to the power of Chandra, that such a tiny motion can be measured." Labeled Image of RX J0822-4300 in Puppis A Labeled Image of RX J0822-4300 in Puppis A "Just after it was born, this neutron star got a one-way ticket out of the Galaxy," said co-author Robert Petre of NASA's Goddard Space Flight Center in Greenbelt, Md. "Astronomers have seen other stars being flung out of the Milky Way, but few as fast as this." So-called hypervelocity stars have been previously discovered shooting out of the Milky Way with speeds around one million miles per hour. One key difference between RX J0822-4300 and these other reported galactic escapees is the source of their speed. The hypervelocity stars are

  13. Chandra Catches Cannibal Galaxy in the Act

    Science.gov (United States)

    2000-07-01

    quantities of energy as it falls into a giant black hole in the center of the galaxy. Closer in, the effects of a more recent explosion show up as dark twin cavities, each large enough to contain a galaxy half the diameter of our Milky Way galaxy. These cavities, which have been detected at lower resolution by previous X-ray satellites, appear to be buoyant, magnetized bubbles of energetic particles. The Chandra image shows that the gas that has piled up in the brilliant rims has "cooled" to a temperature of 30 million degrees. A long spiral of hot gas appears to be winding inward around the cavities toward the center of the galaxy. Fabian and his colleagues propose that the cooling of gas in this spiral can lead to the formation of a spiral structure of stars that has been detected in optical images of the galaxy. The observation was made on January 29, 2000 for 6.8 hours using the Advanced CCD Imaging Spectrometer (ACIS). The Advanced CCD X-ray Spectrometer (ACIS) X-ray camera was developed for NASA by Penn State University, University Park, and the Massachusetts Institute of Technology, Cambridge. NASA's Marshall Space Flight Center in Huntsville, Alabama, 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, Massachusetts. Images associated with this release are available on the World Wide Web at http://chandra.harvard.edu AND http://chandra.nasa.gov

  14. Chandra Catches Early Phase of Cosmic Assembly

    Science.gov (United States)

    2004-08-01

    A NASA Chandra X-ray Observatory image has revealed a complex of several intergalactic hot gas clouds in the process of merging. The superb Chandra spatial resolution made it possible to distinguish individual galaxies from the massive clouds of hot gas. One of the clouds, which that envelops hundreds of galaxies, has an extraordinarily low concentration of iron atoms, indicating that it is in the very early stages of cluster evolution. "We may be seeing hot intergalactic gas in a relatively pristine state before it has been polluted by gas from galaxies," said Q. Daniel Wang of the University of Massachusetts in Amherst, and lead author on an upcoming Astrophysical Journal article describing the study. "This discovery should provide valuable insight into how the most massive structures in the universe are assembled." 3-Panel Image of Abell 2125, Its Core & Galaxy C153 3-Panel Image of Abell 2125, Its Core & Galaxy C153 The complex, known as Abell 2125,is about 3 billion light years from Earth, and is seen at a time about 11 billion years after the Big Bang, when many galaxy clusters are believed to have formed. The Chandra Abell 2125 image shows several huge elongated clouds of multimillion degree gas coming together from different directions. These hot gas clouds, each of which contains hundreds of galaxies, appear to be in the process of merging to form a single massive galaxy cluster. Chandra, Hubble Space Telescope, and Very Large Array radio telescope data show that several galaxies in the Abell 2125 core cluster are being stripped of their gas as they fall through surrounding high-pressure hot gas. This stripping process has enriched the core cluster's gas in heavy elements such as iron. Abell 2125's Core & Galaxy C153 Abell 2125's Core & Galaxy C153 The gas in the pristine cloud, which is still several million light years away from the core cluster, is conspicuous for its lack of iron atoms. This anemic cloud must be in a very early evolutionary stage. The

  15. Twin studies reveal specific imbalances in the mucosa-associated microbiota of patients with ileal Crohn's disease

    Energy Technology Data Exchange (ETDEWEB)

    Willing, B.; Halfvarson, J.; Dicksved, J.; Rosenquist, M.; Jarnerot, G.; Engstrand, L.; Tysk, C.; Jansson, J. K

    2008-08-15

    Large inter-individual variation in the composition of the intestinal microbiota between unrelated individuals has made it challenging to identify specific aspects of dysbiosis that lead to Crohn's disease. To reduce variations in exposure during establishment of the gut flora and influence of genotype, we studied the mucosaassociated microbiota of monozygotic twin pairs that were discordant (n=6) or concordant (n=4) for Crohn's disease. DNA was extracted from biopsies collected from 5 locations between the ileum and rectum. Bacterial 16S ribosomal RNA genes were amplified and community composition assessed by terminal-restriction fragment length polymorphism, cloning and sequencing and quantitative real-time PCR. The microbial compositions at all biopsy locations for each individual were similar, regardless of disease state, but there were differences between individuals. In particular, individuals with predominantly ileal Crohn's had a dramatically lower abundance (P<0.001) of Faecalibacterium prausnitzii and increased abundance (P<0.03) of Escherichia coli compared to healthy co-twins and those with Crohn's localized in the colon. This dysbiosis was significantly correlated to the disease phenotype rather than genotype. The reduced abundance of F. prausnitzii and increased abundance of E. coli are indicative of an ileal Crohn's disease phenotype, distinct from colonic Crohn's disease and the relative abundances of these specific bacterial populations are promising biomarker candidates for differential diagnosis of Crohn's and eventually customized treatment.

  16. The Plerionic Supernova Remnant G21.5-0.9 Powered by PSR J1833-1034: New Spectroscopic and Imaging Results Revealed with the Chandra X-ray Observatory

    Science.gov (United States)

    Matheson, Heather; Safi-Harb, Samar

    2010-11-01

    In 1999, the Chandra X-ray Observatory revealed a 150'' radius halo surrounding the 40'' radius pulsar wind nebula (PWN) G21.5-0.9. A 2005 imaging study of G21.5-0.9 showed that the halo is limb-brightened and suggested that this feature is a candidate for the long-sought supernova remnant (SNR) shell. We present a spectral analysis of SNR G21.5-0.9, using the longest effective observation to date (578.6 ks with the Advanced CCD Imaging Spectrometer (ACIS) and 278.4 ks with the High-Resolution Camera (HRC)) to study unresolved questions about the spectral nature of remnant features, such as the limb brightening of the X-ray halo and the bright knot in the northern part of the halo. The Chandra analysis favors the non-thermal interpretation of the limb. Its spectrum is fit well with a power-law model with a photon index Γ = 2.13 (1.94-2.33) and a luminosity of Lx (0.5-8 keV) = (2.3 ± 0.6) × 1033 erg s-1 (at an assumed distance of 5.0 kpc). An srcut model was also used to fit the spectrum between the radio and X-ray energies. While the absence of a shell in the radio still prohibits constraining the spectrum at radio wavelengths, we assume a range of spectral indices to infer the 1 GHz flux density and the rolloff frequency of the synchrotron spectrum in X-rays and find that the maximum energy to which electrons are accelerated at the shock ranges from ~60 to 130 TeV (B/10 μG)-1/2, where B is the magnetic field in units of μG. For the northern knot, we constrain previous models and find that a two-component power-law (or srcut) + pshock model provides an adequate fit, with the pshock model requiring a very low ionization timescale and solar abundances for Mg and Si. Our spectroscopic study of PSR J1833-1034, the highly energetic pulsar powering G21.5-0.9, shows that its spectrum is dominated by hard non-thermal X-ray emission with some evidence of a thermal component that represents ~9% of the observed non-thermal emission and that suggests non-standard rapid

  17. New Results from Chandra

    CERN Document Server

    Forman, W; Jones, C; Vikhlinin, A A; Churazov, E

    2001-01-01

    We discuss two themes from Chandra observations of galaxies and clusters. First, we describe the effects of radio-emitting plasmas or ``bubbles'', inflated by active galactic nuclei, on the hot X-ray emitting gaseous atmospheres in galaxies and clusters. We describe the interaction of the ``bubbles'' and the X-ray emitting gas as the buoyant bubbles rise through the hot gas. Second, we describe sharp, edge-like surface brightness structures in clusters. Chandra observations show that these features are not shock fronts as was originally thought, but ``cold fronts'', most likely the boundaries of the remaining cores of merger components. Finally, we present recent observations of M86 and NGC507 which show similar sharp features around galaxies. For M86, the sharp edge is the boundary between the galaxy's X-ray corona and the Virgo cluster gas. The structures around NGC507, the central galaxy in a group, could be relics of galaxy formation or may reflect the motion of NGC507 in the larger potential of the group...

  18. The Chandra Source Catalog

    CERN Document Server

    Evans, Ian N; Glotfelty, Kenny J; Anderson, Craig S; Bonaventura, Nina R; Chen, Judy C; Davis, John E; Doe, Stephen M; Evans, Janet D; Fabbiano, Giuseppina; Galle, Elizabeth C; Gibbs, Danny G; Grier, John D; Hain, Roger M; Hall, Diane M; Harbo, Peter N; Xiangqun,; He,; Houck, John C; Karovska, Margarita; Kashyap, Vinay L; Lauer, Jennifer; McCollough, Michael L; McDowell, Jonathan C; Miller, Joseph B; Mitschang, Arik W; Morgan, Douglas L; Mossman, Amy E; Nichols, Joy S; Nowak, Michael A; Plummer, David A; Refsdal, Brian L; Rots, Arnold H; Siemiginowska, Aneta; Sundheim, Beth A; Tibbetts, Michael S; Van Stone, David W; Winkelman, Sherry L; Zografou, Panagoula

    2010-01-01

    The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public ACIS imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents <~ 30''. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to ...

  19. The Chandra HelpDesk

    Science.gov (United States)

    Galle, Elizabeth C.

    2008-03-01

    The Chandra X-ray Center (CXC) HelpDesk has answered hundreds of user questions over the course of the Chandra mission, ranging from basic syntax errors to advanced analysis questions. This talk gives an introduction to the HelpDesk system and staff, presents a sample of recent HelpDesk requests, and discusses how user-submitted questions improve the software and documentation.

  20. Dark Energy, Black Holes and Exploding Stars: NASA's Chandra Observatory Marks Five Years of Scientific Achievement

    Science.gov (United States)

    2004-08-01

    On Aug. 12, 1999, NASA's Chandra X-ray Observatory opened its sunshade doors for the first time, allowing celestial X-ray light to reach the observatory's mirrors. This one small step for the observatory proved to be a giant leap for science as Chandra began its mission to shed new light on a violent, mysterious universe invisible to the human eye. The Marshall Center manages the Chandra program. On August 12, 1999, NASA's Chandra X-ray Observatory opened its sunshade doors for the first time, allowing celestial X-ray light to reach the observatory's mirrors. This one small step for the observatory proved to be a giant leap for science as Chandra began its mission to shed new light on a violent, mysterious universe invisible to the human eye. "Humans cannot see X-rays, but Chandra can," said Chandra project scientist Dr. Martin C. Weisskopf of NASA's Marshall Space Flight Center in Huntsville, Ala. "And what the observatory has revealed in five short years has been nothing short of amazing. Thanks to Chandra, we've gleaned new information on dark energy, black holes, exploding stars and all other categories of astronomical objects." "Chandra's resolving power is equivalent to the ability to read a newspaper headline a half-mile away," said Chandra Program Manager Keith Hefner of the Marshall Center. "It's an engineering marvel that has performed nearly flawlessly and provided major science discoveries over the past five years." A Chandra timeline reveals some of its most noteworthy discoveries: * Chandra finds a ring around the Crab Nebula. After only two months in space, the observatory reveals a brilliant ring around the heart of the Crab Pulsar in the Crab Nebula - the remains of a stellar explosion - providing clues about how the nebula is energized by a pulsing neutron, or collapsed, star. (Sept. 28, 1999) * Chandra reveals a possible black hole in the Milky Way. Culminating 25 years of searching by astronomers, researchers say that a faint X-ray source, newly

  1. Postpartum Mental State of Mothers of Twins

    Science.gov (United States)

    Brantmüller, Éva; Gyúró, Mónika; Galgán, Kitti; Pakai, Annamária

    2016-01-01

    Twin birth is a relevant risk factor for postnatal depression (PND). The primary objective of our study is to reveal the prevalence of suspected cases of depression and to identify some background factors among mothers of twins. We applied convenience sampling method within a retrospective, quantitative study among mothers given birth to twins for…

  2. Diversity and evolution of bacterial twin arginine translocase protein, TatC, reveals a protein secretion system that is evolving to fit its environmental niche.

    Directory of Open Access Journals (Sweden)

    Domenico Simone

    Full Text Available BACKGROUND: The twin-arginine translocation (Tat protein export system enables the transport of fully folded proteins across a membrane. This system is composed of two integral membrane proteins belonging to TatA and TatC protein families and in some systems a third component, TatB, a homolog of TatA. TatC participates in substrate protein recognition through its interaction with a twin arginine leader peptide sequence. METHODOLOGY/PRINCIPAL FINDINGS: The aim of this study was to explore TatC diversity, evolution and sequence conservation in bacteria to identify how TatC is evolving and diversifying in various bacterial phyla. Surveying bacterial genomes revealed that 77% of all species possess one or more tatC loci and half of these classes possessed only tatC and tatA genes. Phylogenetic analysis of diverse TatC homologues showed that they were primarily inherited but identified a small subset of taxonomically unrelated bacteria that exhibited evidence supporting lateral gene transfer within an ecological niche. Examination of bacilli tatCd/tatCy isoform operons identified a number of known and potentially new Tat substrate genes based on their frequent association to tatC loci. Evolutionary analysis of these Bacilli isoforms determined that TatCy was the progenitor of TatCd. A bacterial TatC consensus sequence was determined and highlighted conserved and variable regions within a three dimensional model of the Escherichia coli TatC protein. Comparative analysis between the TatC consensus sequence and Bacilli TatCd/y isoform consensus sequences revealed unique sites that may contribute to isoform substrate specificity or make TatA specific contacts. Synonymous to non-synonymous nucleotide substitution analyses of bacterial tatC homologues determined that tatC sequence variation differs dramatically between various classes and suggests TatC specialization in these species. CONCLUSIONS/SIGNIFICANCE: TatC proteins appear to be diversifying within

  3. Twin Baryogenesis

    CERN Document Server

    Farina, Marco; Shin, Chang Sub

    2016-01-01

    In the context of Twin Higgs models, we study a simple mechanism that simultaneously generates asymmetries in the dark and visible sector through the out-of-equilibrium decay of a TeV scale particle charged under a combination of baryon and twin baryon number. We predict the dark matter to be a 5 GeV twin baryon, which is easy to achieve because of the similarity between the two confinement scales. Dark matter is metastable and can decay to three quarks, yielding indirect detection signatures. The mechanism requires the introduction of a new colored particle, typically within the reach of the LHC, of which we study the rich collider phenomenology, including prompt and displaced dijets, multi-jets, monojets and monotops.

  4. The Chandra Galactic Bulge Survey

    NARCIS (Netherlands)

    Hynes, Robert I.; Jonker, P.G.; Bassa, C. G.; Dieball, A.; Greiss, S.; Maccarone, T. J.; Nelemans, G.; Steeghs, D.; Torres, M. A. P.; Britt, C. T.; Clem, J. L.; Gossen, L.; Grindlay, J. E.; Groot, P.J.; Kuiper, L.; Kuulkers, E.; Mendez, M.; Mikles, V. J.; Ratti, E. M.; Rea, N.; van Haaften, L.; Wijnands, R.; in't Zand, J. J. M.

    2011-01-01

    The Chandra Galactic Bulge Survey (CGBS) is a shallow but wide survey of two approximately 6x1 degree strips of the Galactic Bulge about a degree above and below the plane. The survey by design targets regions where extinction and crowding are manageable and optical counterparts are accessible to de

  5. The Chandra Galactic Bulge Survey

    NARCIS (Netherlands)

    Hynes, Robert I.; Jonker, P. G.; Bassa, C. G.; Nelemans, G.; Steeghs, D.; Torres, M. A. P.; Maccarone, T. J.; Greiss, S.; Clem, J.; Dieball, A.; Mikles, V. J.; Britt, C. T.; Gossen, L.; Collazzi, A. C.; Wijnands, R.; In't Zand, J. J. M.; Mendez, M.; Rea, N.; Kuulkers, E.; Ratti, E. M.; van Haaften, L. M.; Heinke, C.; Ozel, F.; Groot, P. J.; Verbunt, F.

    2012-01-01

    The Chandra Galactic Bulge Survey (GBS) is a shallow but wide survey of two approximately 6x1 degree strips of the Galactic Bulge about a degree above and below the plane. The survey by design targets regions where extinction and crowding are manageable and optical counterparts are accessible to det

  6. Global Analysis of DNA Methylation Variation in Adipose Tissue from Twins Reveals Links to Disease-Associated Variants in Distal Regulatory Elements

    Science.gov (United States)

    Grundberg, Elin; Meduri, Eshwar; Sandling, Johanna K.; Hedman, Åsa K.; Keildson, Sarah; Buil, Alfonso; Busche, Stephan; Yuan, Wei; Nisbet, James; Sekowska, Magdalena; Wilk, Alicja; Barrett, Amy; Small, Kerrin S.; Ge, Bing; Caron, Maxime; Shin, So-Youn; Ahmadi, Kourosh R.; Ainali, Chrysanthi; Barrett, Amy; Bataille, Veronique; Bell, Jordana T.; Buil, Alfonso; Deloukas, Panos; Dermitzakis, Emmanouil T.; Dimas, Antigone S.; Durbin, Richard; Glass, Daniel; Grundberg, Elin; Hassanali, Neelam; Hedman, Åsa K.; Ingle, Catherine; Knowles, David; Krestyaninova, Maria; Lindgren, Cecilia M.; Lowe, Christopher E.; McCarthy, Mark I.; Meduri, Eshwar; di Meglio, Paola; Min, Josine L.; Montgomery, Stephen B.; Nestle, Frank O.; Nica, Alexandra C.; Nisbet, James; O’Rahilly, Stephen; Parts, Leopold; Potter, Simon; Sandling, Johanna; Sekowska, Magdalena; Shin, So-Youn; Small, Kerrin S.; Soranzo, Nicole; Spector, Tim D.; Surdulescu, Gabriela; Travers, Mary E.; Tsaprouni, Loukia; Tsoka, Sophia; Wilk, Alicja; Yang, Tsun-Po; Zondervan, Krina T.; Lathrop, Mark; Dermitzakis, Emmanouil T.; McCarthy, Mark I.; Spector, Timothy D.; Bell, Jordana T.; Deloukas, Panos

    2013-01-01

    Epigenetic modifications such as DNA methylation play a key role in gene regulation and disease susceptibility. However, little is known about the genome-wide frequency, localization, and function of methylation variation and how it is regulated by genetic and environmental factors. We utilized the Multiple Tissue Human Expression Resource (MuTHER) and generated Illumina 450K adipose methylome data from 648 twins. We found that individual CpGs had low variance and that variability was suppressed in promoters. We noted that DNA methylation variation was highly heritable (h2median = 0.34) and that shared environmental effects correlated with metabolic phenotype-associated CpGs. Analysis of methylation quantitative-trait loci (metQTL) revealed that 28% of CpGs were associated with nearby SNPs, and when overlapping them with adipose expression quantitative-trait loci (eQTL) from the same individuals, we found that 6% of the loci played a role in regulating both gene expression and DNA methylation. These associations were bidirectional, but there were pronounced negative associations for promoter CpGs. Integration of metQTL with adipose reference epigenomes and disease associations revealed significant enrichment of metQTL overlapping metabolic-trait or disease loci in enhancers (the strongest effects were for high-density lipoprotein cholesterol and body mass index [BMI]). We followed up with the BMI SNP rs713586, a cg01884057 metQTL that overlaps an enhancer upstream of ADCY3, and used bisulphite sequencing to refine this region. Our results showed widespread population invariability yet sequence dependence on adipose DNA methylation but that incorporating maps of regulatory elements aid in linking CpG variation to gene regulation and disease risk in a tissue-dependent manner. PMID:24183450

  7. Twin pregnancy

    DEFF Research Database (Denmark)

    Sperling, Lene; Tabor, A

    2001-01-01

    Determination of chorionicity is one of the most important issues in the management of twin pregnancy. Modern ultrasound equipment has made it possible to accurately assess placentation already in the first trimester with the lambda sign. With regard to prenatal diagnosis, it is important to know...

  8. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties.

  9. A Deep Chandra Observation of A2052

    Science.gov (United States)

    Blanton, E. L.; Douglass, E. M.; Sarazin, C. L.; Clarke, T. E.; McNamara, B. R.

    We present initial results from a long (125 ksec) Chandra observation of Abell 2052. A2052 is a bright, nearby, cooling core cluster at a redshift of z=0.0348. It was previously observed for 36 ksec with Chandra [3,4]. The longer observation reveals ripples in the surface brightness, similar to what has been seen in e.g., the Perseus cluster [5] and M87/Virgo [6]. The southern cavity now appears to be split into two cavities with the southernmost cavity likely representing a ghost bubble from earlier radio activity. There also appears to be a ghost bubble present to the NW of the cluster center. Bright emission in the X-ray corresponds very well with optical line emission, and the correlated X-ray emission is seen to continue from the N bubble edge closer to the AGN in this longer exposure, tracking the H-α emission. The energy deposited by the radio source, as determined by measuring the pressure in the bright, X-ray shells, averaged over the repetition rate of the radio source (determined from either the ripple separation or the ghost cavity distances) can easily offset the cooling in the core of the cluster.

  10. Chandra Associates Pulsar and Historic Supernova

    Science.gov (United States)

    2001-01-01

    in the same area of the sky. Past attempts to identify the pulsar with G11.2-0.3, and hence the ancient Chinese observations, have been controversial. The location of the pulsar at the center of the remnant provides new evidence that it is associated with the remnant. Since pulsars are known to move rapidly away from where they are formed, a pulsar near the center of the remnant implies the system must be very young, since not enough time has elapsed for the pulsar to travel far from its birthplace. "We believe that the pulsar and the supernova remnant G11.2-0.3 are both likely to be left over from the explosion seen by the Chinese observers over 1600 years ago," said Roberts. "While this is exciting by itself, it also raises new questions about what we know about pulsars especially during their infancies." These questions follow from a discrepancy that arose when the ASCA team applied the present spin rate to current models to determine the pulsar’s estimated lifetime and compare it to the age of G11.2-0.3. The result was an age of roughly 24,000 years - far predating the birth year of 386 AD. To explain this contradiction, the Chandra team argues that this pulsar may have had approximately the same spin rate today as it did at its birth, as had been suggested by the ASCA data. If this is true, then it could have important implications for the conventional wisdom regarding pulsars, which, may be born spinning more slowly than has been thought. "We now have strong evidence that the standard age estimate for this pulsar is probably wrong, and it is much younger than previously believed," said Kaspi. "This, in turn, suggests that other standard pulsar age estimates may be wrong as well, and this has important implications for the population as a whole." In addition to these results, the Chandra observations of G11.2-0.3 have, for the first time, revealed the bizarre appearance of the pulsar wind nebula (also known as "plerions") at the center of the supernova remnant

  11. Chandra Images Provide New Vision of Cosmic Explosions

    Science.gov (United States)

    1999-09-01

    Images from NASA's Chandra X-ray Observatory released today reveal previously unobserved features in the remnants of three different supernova explosions. Two of the remnants G21.5-0.9 and PSR 0540-69 show dramatic details of the prodigious production of energetic particles by a rapidly rotating, highly magnetized neutron star, as well as the enormous shell structures produced by the explosions. The image of the third remnant, E0102-72, reveals puzzling spoke-like structures in its interior. G21.5-0.9, in the constellation of Scutum, is about 16,000 light years (1 light year = 6 trillion miles) from Earth. Chandra's image shows a bright nebula surrounded by a much larger diffuse cloud. Inside the inner nebula is a bright central source that is thought to be a rapidly rotating highly magnetized neutron star. A rotating neutron star acts like a powerful generator, creating intense electric voltages that accelerate electrons to speeds close to the speed of light. The total output of this generator is greater than a thousand suns. The fluffy appearance of the central nebula is thought to be due to magnetic field lines which constrain the motions of the high-energy electrons. "It's a remarkable image," said Dr. Patrick Slane of the Harvard-Smithsonian Center for Astrophysics. "Neither the inner core nor the outer shell has ever been seen before." "It is as though we have a set of Russian dolls, with structures embedded within structures," said Professor Gordon Garmire of Penn State University, and principal investigator of the Advanced CCD Imaging Spectrometer, the X-ray camera that was used to make two of the images. NASA's project scientist, Dr. Martin Weisskopf of the Marshall Space Flight Center said, "Chandra's capability to provide surprises and insights continues." PSR 0540-69 PSR 0540-69 The existence of a rotating neutron star, or pulsar, in the center of G21.5-0.9 is inferred from the appearance of the nebula and the energy distribution of X-rays and radio

  12. CIAO: Chandra's data analysis system

    Science.gov (United States)

    Fruscione, Antonella; McDowell, Jonathan C.; Allen, Glenn E.; Brickhouse, Nancy S.; Burke, Douglas J.; Davis, John E.; Durham, Nick; Elvis, Martin; Galle, Elizabeth C.; Harris, Daniel E.; Huenemoerder, David P.; Houck, John C.; Ishibashi, Bish; Karovska, Margarita; Nicastro, Fabrizio; Noble, Michael S.; Nowak, Michael A.; Primini, Frank A.; Siemiginowska, Aneta; Smith, Randall K.; Wise, Michael

    2006-06-01

    The CIAO (Chandra Interactive Analysis of Observations) software package was first released in 1999 following the launch of the Chandra X-ray Observatory and is used by astronomers across the world to analyze Chandra data as well as data from other telescopes. From the earliest design discussions, CIAO was planned as a general-purpose scientific data analysis system optimized for X-ray astronomy, and consists mainly of command line tools (allowing easy pipelining and scripting) with a parameter-based interface layered on a flexible data manipulation I/O library. The same code is used for the standard Chandra archive pipeline, allowing users to recalibrate their data in a consistent way. We will discuss the lessons learned from the first six years of the software's evolution. Our initial approach to documentation evolved to concentrate on recipe-based "threads" which have proved very successful. A multi-dimensional abstract approach to data analysis has allowed new capabilities to be added while retaining existing interfaces. A key requirement for our community was interoperability with other data analysis systems, leading us to adopt standard file formats and an architecture which was as robust as possible to the input of foreign data files, as well as re-using a number of external libraries. We support users who are comfortable with coding themselves via a flexible user scripting paradigm, while the availability of tightly constrained pipeline programs are of benefit to less computationally-advanced users. As with other analysis systems, we have found that infrastructure maintenance and re-engineering is a necessary and significant ongoing effort and needs to be planned in to any long-lived astronomy software.

  13. Chandra Independently Determines Hubble Constant

    Science.gov (United States)

    2006-08-01

    A critically important number that specifies the expansion rate of the Universe, the so-called Hubble constant, has been independently determined using NASA's Chandra X-ray Observatory. This new value matches recent measurements using other methods and extends their validity to greater distances, thus allowing astronomers to probe earlier epochs in the evolution of the Universe. "The reason this result is so significant is that we need the Hubble constant to tell us the size of the Universe, its age, and how much matter it contains," said Max Bonamente from the University of Alabama in Huntsville and NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., lead author on the paper describing the results. "Astronomers absolutely need to trust this number because we use it for countless calculations." Illustration of Sunyaev-Zeldovich Effect Illustration of Sunyaev-Zeldovich Effect The Hubble constant is calculated by measuring the speed at which objects are moving away from us and dividing by their distance. Most of the previous attempts to determine the Hubble constant have involved using a multi-step, or distance ladder, approach in which the distance to nearby galaxies is used as the basis for determining greater distances. The most common approach has been to use a well-studied type of pulsating star known as a Cepheid variable, in conjunction with more distant supernovae to trace distances across the Universe. Scientists using this method and observations from the Hubble Space Telescope were able to measure the Hubble constant to within 10%. However, only independent checks would give them the confidence they desired, considering that much of our understanding of the Universe hangs in the balance. Chandra X-ray Image of MACS J1149.5+223 Chandra X-ray Image of MACS J1149.5+223 By combining X-ray data from Chandra with radio observations of galaxy clusters, the team determined the distances to 38 galaxy clusters ranging from 1.4 billion to 9.3 billion

  14. Chandra's View of Tycho's Supernova Remnant

    Science.gov (United States)

    2000-01-01

    This Chandra image reveals, in detail, the turbulent debris created by a supernova explosion that was observed by the Danish Astronomer Tycho Brahe in the year 1572. The colors show different x-ray energies, with red, green, and blue representing low, medium, and high energies, respectively. Most likely caused by the destruction of a white dwarf star, a shock wave produced by the expanding debris is outlined by the sharp blue circular arcs of 20 million degree Celsius gas seen on the outer rim. The stellar debris, visible only by x-ray, has a temperature of about 10 million degrees, and shows up as mottled yellow, green, and red fingers of gas.

  15. Maximising the mileage from the Chandra podcasts

    Science.gov (United States)

    Arcand, K. K.; Watzke, M.

    2008-06-01

    NASA's Chandra X-ray Observatory captures X-ray images and measures spectra of many highenergy cosmic phenomena. There is a constant challenge to devise new and appropriate means to bring these potentially esoteric science results and concepts in a digestible way to the public. One of the ideas to address this challenge became the Chandra podcast.

  16. Aragonite twinning in gastropod nacre

    Science.gov (United States)

    Mukai, Hiroki; Saruwatari, Kazuko; Nagasawa, Hiromichi; Kogure, Toshihiro

    2010-10-01

    Aragonite twinning in gastropod nacre has been investigated using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), and transmission electron microscopy (TEM) with the focused ion beam (FIB) sample preparation technique. At the growth front of nacre, Haliotis discus hannai and Omphalius rusticus form a "stack-of-coins" structures, which consist of pseudo-hexagonal and elliptical aragonite tablets, respectively. SEM, EBSD, and TEM analyses revealed that these tablets are monolithic single crystal and almost free of the {1 1 0} twins that are common in aragonite of biotic or abiotic origin. The longest diagonal of the hexagon and the longer axis of the ellipse are parallel to the a-axis of aragonite. The crystal orientation of each tablet in a stack, measured by TEM-Kikuchi pattern analysis, is almost the same but there is occasionally {1 1 0} twin-like relationship between adjacent tablets along the stacking. On the other hand, the fibrous aragonite layer formed prior to the nacreous structure is composed of polycrystalline aragonite with high density of {1 1 0} twins. TEM observation suggests that the interlamellar organic sheet prevents the inheritance of the twins, by selecting only single domain of the twins, through the mineral bridge.

  17. Fingerprinting stress: Stylolite and calcite twinning paleopiezometry revealing the complexity of progressive stress patterns during folding—The case of the Monte Nero anticline in the Apennines, Italy

    Science.gov (United States)

    Beaudoin, Nicolas; Koehn, Daniel; Lacombe, Olivier; Lecouty, Alexandre; Billi, Andrea; Aharonov, Einat; Parlangeau, Camille

    2016-07-01

    In this study we show for the first time how quantitative stress estimates can be derived by combining calcite twinning and stylolite roughness stress fingerprinting techniques in a fold-and-thrust belt. First, we present a new method that gives access to stress inversion using tectonic stylolites without access to the stylolite surface and compare results with calcite twin inversion. Second, we use our new approach to present a high-resolution deformation and stress history that affected Meso-Cenozoic limestone strata in the Monte Nero Anticline during its late Miocene-Pliocene growth in the Umbria-Marche Arcuate Ridge (northern Apennines, Italy). In this area an extensive stylolite-joint/vein network developed during layer-parallel shortening (LPS), as well as during and after folding. Stress fingerprinting illustrates how stress in the sedimentary strata did build up prior to folding during LPS. The stress regime oscillated between strike slip and compressional during LPS before ultimately becoming strike slip again during late stage fold tightening. Our case study shows that high-resolution stress fingerprinting is possible and that this novel method can be used to unravel temporal relationships that relate to local variations of regional orogenic stresses. Beyond regional implications, this study validates our approach as a new powerful toolbox to high-resolution stress fingerprinting in basins and orogens combining joint and vein analysis with sedimentary and tectonic stylolite and calcite twin inversion techniques.

  18. Hardening by twin boundary during nanoindentation in nanocrystals.

    Science.gov (United States)

    Qu, Shaoxing; Zhou, Haofei

    2010-08-20

    The atomistic deformation processes of nanocrystals embedded with nanoscale twin boundaries during nanoindentation are studied by molecular dynamics simulations. Load-displacement curves are obtained and the hardening mechanisms associated with the nanoscale twin boundaries are revealed. Johnson's theoretical indentation model is adopted to estimate the elastic stage of the nanoindentation. In addition, twin boundary-mediated dislocation nucleation is observed and analyzed.

  19. The Qingdao Twin Registry

    DEFF Research Database (Denmark)

    Duan, Haiping; Ning, Feng; Zhang, Dongfeng;

    2013-01-01

    In 1998, the Qingdao Twin Registry was initiated as the main part of the Chinese National Twin Registry. By 2005, a total of 10,655 twin pairs had been recruited. Since then new twin cohorts have been sampled, with one longitudinal cohort of adolescent twins selected to explore determinants...... of metabolic disorders and health behaviors during puberty and young adulthood. Adult twins have been sampled for studying heritability of multiple phenotypes associated with metabolic disorders. In addition, an elderly twin cohort has been recruited with a focus on genetic studies of aging-related phenotypes...

  20. Twin Jet

    Science.gov (United States)

    Henderson, Brenda; Bozak, Rick

    2010-01-01

    Many subsonic and supersonic vehicles in the current fleet have multiple engines mounted near one another. Some future vehicle concepts may use innovative propulsion systems such as distributed propulsion which will result in multiple jets mounted in close proximity. Engine configurations with multiple jets have the ability to exploit jet-by-jet shielding which may significantly reduce noise. Jet-by-jet shielding is the ability of one jet to shield noise that is emitted by another jet. The sensitivity of jet-by-jet shielding to jet spacing and simulated flight stream Mach number are not well understood. The current experiment investigates the impact of jet spacing, jet operating condition, and flight stream Mach number on the noise radiated from subsonic and supersonic twin jets.

  1. Chandra and Swift Observations of Unidentified Fermi-LAT Objects

    Science.gov (United States)

    Donato, Davide; Cheung, T.; Gehrels, N.

    2010-03-01

    In the last year we targeted some of the unidentified Fermi-LAT objects (UFOs) at high Galactic latitude with Chandra and Swift in order to determine the basic properties (positions, fluxes, hardness ratios) of all X-ray sources within the Fermi-LAT localization circles. These satellites enable us to detect the X-ray conterparts with a flux limit that is at least an order of magnitude lower than achieved in extant RASS data and to further follow-up at other wavelengths, with the ultimate goal to reveal the nature of these enigmatic gamma-ray sources. Here we present the results obtained with 5 Chandra pointings of high Galactic latitude UFOs in the Fermi-LAT 3-months bright source list. The association of detected X-ray sources within the improved 11-months Fermi-LAT localization circles with available optical and radio observations is discussed.

  2. Myocardial hypertrophy in the recipient with twin-to-twin transfusion syndrome

    DEFF Research Database (Denmark)

    Jeppesen, D.L.; Jorgensen, F.S.; Pryds, O.A.

    2008-01-01

    In a set of monochorionic-diamniotic twins with twin-to-twin transfusion syndrome, systemic hypertension and biventricular myocardial hypertrophy were found in the recipient. The infant developed mild respiratory distress. A partial exchange transfusion was performed because of polycytaemia. Blood...... pressure measurements revealed persistent systemic hypertension. Biventricular hypertrophy was demonstrated by echocardiography. Blood pressure normalised after treatment with Nifedipine and the cardiac hypertrophy subsided over the following weeks. A potential contributing mechanism is intrauterine...

  3. The Chandra Galactic Bulge Survey

    Science.gov (United States)

    Britt, C. T.; Hynes, R. I.; Jonker, P. G.; Maccarone, T.; Torres, M. A. P.; Steeghs, D.; Nelemans, G.; Johnson, C.; Greiss, S.

    2015-05-01

    The Chandra Galactic Bulge Survey (GBS) is a multi-wavelength survey of two 6×1 degree strips above and below the Galactic plane, including deep r' and i' imaging and time domain photometry from CTIO and shallow, wide-field X-ray imaging with Chandra. Targeting fields above |b|=1 avoids most of the copious extinction along the Galactic plane while maintaining high source density. This results in targets that are accessible to follow up in optical and NIR wavelengths. The X-ray observations are shallow to maximize the number of quiescent Low Mass X-ray Binaries (LMXBs) relative to Cataclysmic Variables (CVs). The goals of the GBS are to conduct a census of Low Mass X-ray Binaries in the Milky Way in order to constrain models of binary evolution, the common envelope phase in particular, and to expand the number of known LMXBs for optical follow up. Mass measurements in particular will help constrain the black hole (BH) mass distribution and the equation of state for neutron stars (NS). Constraining the BH mass distribution will constrain models of their formation in supernovae. The current population of Galactic BHs suffers from selection effects, which the GBS avoids by finding new objects while still in quiescence. We expect to find qLMXBs, magnetic CVs, RS CVn stars, and smaller numbers of other types of sources. After removing duplicates, there are 1640 unique X-ray sources in the 12 square degree survey area, which closely matches the predicted number of 1648. We are currently matching X-ray sources to counterparts in other wavelengths using new photometric and spectroscopic observations as well as in archival data where it exists, and searching for variability and periodicity in the counterparts in photometric data. So far, we have spectroscopically identified 27 interacting binaries including promising candidates for quiescent black holes.

  4. Deformation twinning in monazite

    Energy Technology Data Exchange (ETDEWEB)

    Hay, R.S.; Marshall, D.B

    2003-10-20

    Polycrystalline monazite (LaPO{sub 4}) was deformed at room temperature by a spherical indenter. Deformation twins were identified by TEM in 70 grains. Five twin planes were found: (100) was by far the most common; (001) and (120) were less common; (122-bar)was rare, and kinks in (120) twins were identified as irrational '(483)' twin planes. The twinning modes on these planes were inferred from the expression of twinning shear at free surfaces, predictions of classical deformation twinning theory, and various considerations of twin morphology and crystal structure. Atomic shuffle calculations that allow formation of either a glide plane or a mirror plane at the twin interface were used to analyze twin modes. The inferred twin modes all have small atomic shuffles. For (001) twins, the smallest shuffles were obtained with a glide plane at the interface, with displacement vector R=((1)/(2))[010]. The results do not uniquely define a twin mode on (100), leaving open the possibility of more than one mode operating on this plane. Factors that may determine the operative deformation twinning modes are discussed. Crystal structure considerations suggest that the relative abundance of twinning modes may correlate with low shear modulus on the twin plane in the direction of twinning shear, and with a possible low-energy interface structure consisting of a layer of xenotime of one half-unit-cell thickness that could form at (100) and (001) twins. The three most common twins have low strains to low {sigma} coincidence site lattices (CSLs)

  5. The Norwegian Twin Registry.

    Science.gov (United States)

    Nilsen, Thomas S; Brandt, Ingunn; Magnus, Per; Harris, Jennifer R

    2012-12-01

    Norway has a long-standing tradition in twin research, but the data collected in several population-based twin studies were not coordinated centrally or easily accessible to the scientific community. In 2009, the Norwegian Twin Registry was established at the Norwegian Institute of Public Health (NIPH) in Oslo with the purpose of creating a single research resource for Norwegian twin data. As of today, the Norwegian Twin Registry contains 47,989 twins covering birth years 1895-1960 and 1967-1979; 31,440 of these twins consented to participate in health-related research. In addition, DNA from approximately 4,800 of the twins is banked at the NIPH biobank and new studies are continually adding new data to the registry. The value of the Norwegian twin data is greatly enhanced by the linkage opportunities offered by Norway's many nationwide registries, spanning a broad array of medical, demographic, and socioeconomic information.

  6. Chandra Observations of Tycho’s Supernova Remnant

    Indian Academy of Sciences (India)

    U. Hwang; R. Petre; A. E. Szymkowiak; S. S. Holt

    2002-03-01

    We present a new Chandra observation of Tycho’s supernova remnant with the Advanced CCD Imaging Spectrometer. Multicolor X-ray imaging reveals new details of the outer shock and ejecta. At energies between 4 and 6 keV, the outline of the outer shock is clearly revealed in X-rays for the first time. The distribution of the emission from lines of Si and Fe are confirmed to have a different morphology from each other, and the Si ejecta are shown to extend to the blast shock at several locations. Characteristic spectra of the outer shock and ejecta are also presented.

  7. The Danish Twin Register

    DEFF Research Database (Denmark)

    Kyvik, K O; Christensen, Kaare; Skytthe, A;

    1996-01-01

    BACKGROUND: Population based twin registers represent a valuable tool for genetic epidemiological research, since twin studies aim at separating the effect of genes and environment for complex traits. The Danish Twin Register's history, size, ascertainment and completeness of data, as well as data...... accessibility and availability are described. RESULTS: The Danish Twin Register comprises 14,051 twin pairs born 1870-1930, representing all twins surviving to age six years, and 20,888 twin pairs born 1953-1982, representing 75% of those born 1953-1967 and 95% of those born 1968-1982. The birth cohorts 1931......-1952 og 1983-1993 are being ascertained at the moment. The register is available for research given certain conditions are fulfilled. CONCLUSION: This register will in a few years be the most comprehensive twin register in the world. It is a very valuable Danish research resource....

  8. Monochorionic twin pregnancies

    NARCIS (Netherlands)

    Hack, K.E.A.

    2008-01-01

    Following widespread application of assisted reproductive technology modalities and the increased age of motherhood, the incidence of twin gestations has increased markedly. Twins are either monozygotic or dizygotic. Dizygotic (i.e. fraternal) twins result from the fertilization of two different egg

  9. Chandra Grating Spectroscopy of Three Hot White Dwarfs

    Science.gov (United States)

    Adamczak, J.; Werner, K.; Rauch, T.; Schuh, S.; Drake, J. J.; Kruk, J. W.

    2013-01-01

    High-resolution soft X-ray spectroscopic observations of single hot white dwarfs are scarce. With the Chandra Low-Energy Transmission Grating, we have observed two white dwarfs, one is of spectral type DA (LB1919) and the other is a non-DA of spectral type PG1159 (PG1520+525). The spectra of both stars are analyzed, together with an archival Chandra spectrum of another DA white dwarf (GD246). Aims. The soft X-ray spectra of the two DA white dwarfs are investigated in order to study the effect of gravitational settling and radiative levitation of metals in their photospheres. LB1919 is of interest because it has a significantly lower metallicity than DAs with otherwise similar atmospheric parameters. GD246 is the only white dwarf known that shows identifiable individual iron lines in the soft X-ray range. For the PG1159 star, a precise effective temperature determination is performed in order to confine the position of the blue edge of the GW Vir instability region in the HRD. Methods. The Chandra spectra are analyzed with chemically homogeneous as well as stratified NLTE model atmospheres that assume equilibrium between gravitational settling and radiative acceleration of chemical elements. Archival EUV and UV spectra obtained with EUVE, FUSE, and HST are utilized to support the analysis. Results. No metals could be identified in LB1919. All observations are compatible with a pure hydrogen atmosphere. This is in stark contrast to the vast majority of hot DA white dwarfs that exhibit light and heavy metals and to the stratified models that predict significant metal abundances in the atmosphere. For GD246 we find that neither stratified nor homogeneous models can fit the Chandra spectrum. The Chandra spectrum of PG1520+525 constrains the effective temperature to T(sub eff) = 150 000 +/- 10 000 K. Therefore, this nonpulsating star together with the pulsating prototype of the GWVir class (PG1159-035) defines the location of the blue edge of the GWVir instability region

  10. [Hereditary phaeochromocytoma in twins].

    Science.gov (United States)

    Tóth, Géza; Patócs, Attila; Tóth, Miklós

    2016-08-01

    Phaeochromocytoma is a tumor of the catecholamine-producing cells of the adrenal gland. Extraadrenal phaeochromocytomas are frequently called paragangliomas. The majority of phaeochromocytomas are sporadic, however, about 25-30% are caused by genetic mutation. These tumor are frequently referred as hereditary phaeochromocytomas/paragangliomas. Their incidence increases continuously which can be attributed to availability of genetic examination and to the discovery of novel genes. The 47-year-old female patient underwent abdominal computed tomography which revealed bilateral adrenal gland enlargement. Abdominal magnetic resonance imaging, the 131-I- metaiodobenzylguanidine scintigraphy, urinary catecholamines and serum chomogranin A measurements confirmed the diagnosis of bilateral phaeochromocytomas. The genetically identical twin sister of the patient was also diagnosed with hormonally active bilateral phaechromocytoma, suggesting the genetic origin of phaeochromocytoma. Mutation screening confirmed a germline mutation of the transmembrane protein 127 tumorsupressor gene in both patients. Both patients underwent cortical-sparing adrenalectomy. The adrenal gland with the larger tumor was totally resected, while in the opposite side only the tumor was resected and a small part of the cortex was saved. After the operation urinary catecholamines and serum chromogranin A returned to normal in both patients. Adrenocortical deficiency was absent in the first patient, but her sister developed adrenal insufficiency requiring glucocorticoid replacement. To the best of the authors' knowledge phaeochromocytoma affecting twins has never been described earlier. Genetic examination performed in siblings confirmed the presence of the mutant gene through four generations. Orv. Hetil., 2016, 157(33), 1326-1330.

  11. Fingerprinting stress: stylolite and calcite twinning paleopiezometry reveal the complexity of stress distribution during the growth of the Monte Nero anticline (Apennines, Italy).

    Science.gov (United States)

    Beaudoin, Nicolas; Koehn, Daniel; Lacombe, Olivier; Lecouty, Alexandre; Billi, Andrea; Aharonov, Einat; Parlangeau, Camille

    2016-04-01

    This contribution presents for the first time how quantitative stress estimates can be derived by combining calcite twinning and stylolite roughness stress fingerprinting techniques in a structure part of a complex fold and thrust belts. We report a high-resolution deformation and stress history that was experienced by Meso-Cenozoic limestone strata in the overturned Monte Nero Anticline during its late Miocene-Pliocene growth in the Umbria-Marche Arcuate Ridge (northern Apennines, Italy). New methodological development enables an easier use for the inversion technique of sedimentary and tectonic stylolite roughness. A stylolite-fracture network developed during layer-parallel shortening (LPS), as well as syn- and post-folding. Stress fingerprinting shows how stress builds up in the sedimentary strata during LPS with variations of differential stress before folding around a value of 50 MPa. The stress regime oscillated between strike-slip and compressional during LPS and became transiently extensional in limbs of developing fold due to a coeval increase of vertical stress related to local burial and decrease of maximum horizontal stress related to hinge development, before ultimately becoming strike-slip again during late stage fold tightening. Our case study shows that stress fingerprinting is possible and that this novel method can be used to unravel complex temporal relationships that relate to local variations within evolving regional orogenic stresses. Beyond regional implication, this study validates our approach as a new exciting toolbox to high-resolution stress fingerprinting in basins and orogens.

  12. Gene expression profiling of lymphoblastoid cell lines from monozygotic twins discordant in severity of autism reveals differential regulation of neurologically relevant genes

    Directory of Open Access Journals (Sweden)

    Lee Norman H

    2006-05-01

    Full Text Available Abstract Background The autism spectrum encompasses a set of complex multigenic developmental disorders that severely impact the development of language, non-verbal communication, and social skills, and are associated with odd, stereotyped, repetitive behavior and restricted interests. To date, diagnosis of these neurologically based disorders relies predominantly upon behavioral observations often prompted by delayed speech or aberrant behavior, and there are no known genes that can serve as definitive biomarkers for the disorders. Results Here we demonstrate, for the first time, that lymphoblastoid cell lines from monozygotic twins discordant with respect to severity of autism and/or language impairment exhibit differential gene expression patterns on DNA microarrays. Furthermore, we show that genes important to the development, structure, and/or function of the nervous system are among the most differentially expressed genes, and that many of these genes map closely in silico to chromosomal regions containing previously reported autism candidate genes or quantitative trait loci. Conclusion Our results provide evidence that novel candidate genes for autism may be differentially expressed in lymphoid cell lines from individuals with autism spectrum disorders. This finding further suggests the possibility of developing a molecular screen for autism based on expressed biomarkers in peripheral blood lymphocytes, an easily accessible tissue. In addition, gene networks are identified that may play a role in the pathophysiology of autism.

  13. The Danish Twin Registry

    DEFF Research Database (Denmark)

    Skytthe, Axel; Ohm Kyvik, Kirsten; Vilstrup Holm, Niels;

    2011-01-01

    Introduction: The Danish Twin Registry is a unique source for studies of genetic, familial and environmental factors on life events, health conditions and diseases. Content: More than 85,000 twin pairs born 1870-2008 in Denmark. Validity and coverage: Four main ascertainment methods have been...... employed. Completeness of ascertainment varies according to birth cohorts. For birth cohorts 1870-1930 both twins should survive to age 6 years. From 1931-1968 72% of all twin pairs has been ascertained, with complete ascertainment of all live born twins since 1968. CONCLUSION: Because twins have been...... identified independent of traits and on a population basis, the Danish Twin Registry is well suited for studies to understand the influence of genetic and environmental factors for a wide variety of diseases and traits....

  14. Thoracopagus conjoined twin: an unusual presentation

    Directory of Open Access Journals (Sweden)

    Rajesh Kumari

    2014-02-01

    Full Text Available Conjoined twins are among rare clinical conditions observed by obstetricians. Due to rare incidence of this condition there is general lack of knowledge among obstetricians, especially at primary care level which leads to missed diagnosis during antenatal period. The management of this condition is complex especially in cases where the diagnosis is not known before onset of labour. A 30 - year old Hindu lady was referred to us from other hospital with diagnosis of twin pregnancy and prolonged second stage of labour. Clinical examination revealed findings of ruptured uterus and foetal head of one baby and feet of second baby were outside the introitus. Emergency laparotomy was done which revealed conjoined twins. This article report clinical course of a thoracopagus conjoined twin. The relevant literature is also reviewed. [Int J Reprod Contracept Obstet Gynecol 2014; 3(1.000: 245-247

  15. Beyond Chandra - the X-ray Surveyor

    CERN Document Server

    Weisskopf, Martin C; Tananbaum, Harvey; Vikhlinin, Alexey

    2015-01-01

    Over the past 16 years, NASA's Chandra X-ray Observatory has provided an unparalleled means for exploring the universe with its half-arcsecond angular resolution. Chandra studies have deepened our understanding of galaxy clusters, active galactic nuclei, galaxies, supernova remnants, planets, and solar system objects addressing almost all areas of current interest in astronomy and astrophysics. As we look beyond Chandra, it is clear that comparable or even better angular resolution with greatly increased photon throughput is essential to address even more demanding science questions, such as the formation and subsequent growth of black hole seeds at very high redshift; the emergence of the first galaxy groups; and details of feedback over a large range of scales from galaxies to galaxy clusters. Recently, NASA Marshall Space Flight Center, together with the Smithsonian Astrophysical Observatory, has initiated a concept study for such a mission named the X-ray Surveyor. This study starts with a baseline payloa...

  16. NASA's Chandra Finds Black Holes Are "Green"

    Science.gov (United States)

    2006-04-01

    Black holes are the most fuel efficient engines in the Universe, according to a new study using NASA's Chandra X-ray Observatory. By making the first direct estimate of how efficient or "green" black holes are, this work gives insight into how black holes generate energy and affect their environment. The new Chandra finding shows that most of the energy released by matter falling toward a supermassive black hole is in the form of high-energy jets traveling at near the speed of light away from the black hole. This is an important step in understanding how such jets can be launched from magnetized disks of gas near the event horizon of a black hole. Illustration of Fuel for a Black Hole Engine Illustration of Fuel for a Black Hole Engine "Just as with cars, it's critical to know the fuel efficiency of black holes," said lead author Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and the Stanford Linear Accelerator Center. "Without this information, we cannot figure out what is going on under the hood, so to speak, or what the engine can do." Allen and his team used Chandra to study nine supermassive black holes at the centers of elliptical galaxies. These black holes are relatively old and generate much less radiation than quasars, rapidly growing supermassive black holes seen in the early Universe. The surprise came when the Chandra results showed that these "quiet" black holes are all producing much more energy in jets of high-energy particles than in visible light or X-rays. These jets create huge bubbles, or cavities, in the hot gas in the galaxies. Animation of Black Hole in Elliptical Galaxy Animation of Black Hole in Elliptical Galaxy The efficiency of the black hole energy-production was calculated in two steps: first Chandra images of the inner regions of the galaxies were used to estimate how much fuel is available for the black hole; then Chandra images were used to estimate the power required to produce

  17. 15 Years of Chandra Observations of Capella

    Science.gov (United States)

    Kashyap, Vinay

    2014-11-01

    Capella is the strongest coronal line source accessible to Chandra. It has been cumulatively observed with gratings for over 1.2 Ms. The accumulated spectrum represents astrophysical ground truth for atomic physics calculations that is unprecedented in quality. We analyze co-added spectra to generate a comprehensive list of detectable lines and their locations, spanning two orders of magnitude in photon energy. We compare the locations of identifiable lines with locations from atomic databases ATOMDB and Chianti and characterize the uncertainties in the databases. The full line lists and comparisons will be made available at the Dataverse at http://dx.doi.org/10.7910/DVN/27084 This work is supported by Chandra grant AR0-11001X and NASA Contract NAS8-03060 to the Chandra X-Ray Center.

  18. Evidence for Time-Reversal Symmetry Breaking of the Superconducting State near Twin-Boundary Interfaces in FeSe Revealed by Scanning Tunneling Spectroscopy

    Science.gov (United States)

    Watashige, T.; Tsutsumi, Y.; Hanaguri, T.; Kohsaka, Y.; Kasahara, S.; Furusaki, A.; Sigrist, M.; Meingast, C.; Wolf, T.; Löhneysen, H. v.; Shibauchi, T.; Matsuda, Y.

    2015-07-01

    Junctions and interfaces consisting of unconventional superconductors provide an excellent experimental playground to study exotic phenomena related to the phase of the order parameter. Not only does the complex structure of unconventional order parameters have an impact on the Josephson effects, but it also may profoundly alter the quasiparticle excitation spectrum near a junction. Here, by using spectroscopic-imaging scanning tunneling microscopy, we visualize the spatial evolution of the LDOS near twin boundaries (TBs) of the nodal superconductor FeSe. The π /2 rotation of the crystallographic orientation across the TB twists the structure of the unconventional order parameter, which may, in principle, bring about a zero-energy LDOS peak at the TB. The LDOS at the TB observed in our study, in contrast, does not exhibit any signature of a zero-energy peak, and an apparent gap amplitude remains finite all the way across the TB. The low-energy quasiparticle excitations associated with the gap nodes are affected by the TB over a distance more than an order of magnitude larger than the coherence length ξa b. The modification of the low-energy states is even more prominent in the region between two neighboring TBs separated by a distance ≈7 ξa b . In this region, the spectral weight near the Fermi level (≈±0.2 meV ) due to the nodal quasiparticle spectrum is almost completely removed. These behaviors suggest that the TB induces a fully gapped state, invoking a possible twist of the order parameter structure, which breaks time-reversal symmetry.

  19. In situ nanoindentation study on plasticity and work hardening in aluminium with incoherent twin boundaries.

    Science.gov (United States)

    Bufford, D; Liu, Y; Wang, J; Wang, H; Zhang, X

    2014-09-10

    Nanotwinned metals have been the focus of intense research recently, as twin boundaries may greatly enhance mechanical strength, while maintaining good ductility, electrical conductivity and thermal stability. Most prior studies have focused on low stacking-fault energy nanotwinned metals with coherent twin boundaries. In contrast, the plasticity of twinned high stacking-fault energy metals, such as aluminium with incoherent twin boundaries, has not been investigated. Here we report high work hardening capacity and plasticity in highly twinned aluminium containing abundant Σ3{112} incoherent twin boundaries based on in situ nanoindentation studies in a transmission electron microscope and corresponding molecular dynamics simulations. The simulations also reveal drastic differences in deformation mechanisms between nanotwinned copper and twinned aluminium ascribed to stacking-fault energy controlled dislocation-incoherent twin boundary interactions. This study provides new insight into incoherent twin boundary-dominated plasticity in high stacking-fault energy twinned metals.

  20. Local structural variations near twins in YBa2Cu3O7–δ

    NARCIS (Netherlands)

    Bakel, G.P.E.M. van; Hof, P.A.; Engelen, J.P.M. van; Bronsveld, P.M.; Hosson, J.Th.M. De

    1990-01-01

    Field-ion microscopic images of twinned high-Tc YBa2Cu3O7–δ revealed the characteristic fingerprint pattern combined with planar defects crossing the tip apex. The orientation and location of the twin boundaries was examined by transmission electron microscopy. Computed images revealed little twin-b

  1. Malaysian Twin Registry.

    Science.gov (United States)

    Jahanfar, Shayesteh; Jaffar, Sharifah Halimah

    2013-02-01

    The National Malaysian Twin Registry was established in Royal College of Medicine, Perak, University Kuala Lumpur (UniKL) in June 2008 through a grant provided by UniKL. The general objective is to facilitate scientific research involving participation of twins and their family members in order to answer questions of health and wellbeing relevant to Malaysians. Recruitment is done via mass media, poster, and pamphlets. We now have 266 adult and 204 children twins registered. Several research projects including reproductive health study of twins and the role of co-bedding on growth and development of children are carried out. Registry holds annual activities for twins and seeks to provide health-related information for twins. We seek international collaboration.

  2. Perinatal hepatic infarction in twin-twin transfusion.

    LENUS (Irish Health Repository)

    O'Sullivan, M J

    2012-02-03

    We report a case of a twin pregnancy which was complicated by a twin-twin transfusion in which the recipient twin was noted to have an intra-abdominal echogenic mass. This twin died at two days of age of hepatic infarction. The donor twin was healthy at birth, at thirty weeks\\' gestation, and did not have any subsequent problems. Fetal intra-abdominal echogenicity may be a marker of hepatic infarction.

  3. Chandra Imaging of Gamma-Ray Binaries

    CERN Document Server

    Kargaltsev, Oleg; Hare, Jeremy; Pavlov, George G

    2013-01-01

    We review the multiwavelength properties of the few known gamma-ray binaries, focusing on extended emission recently resolved with Chandra. We discuss the implications of these findings for the nature of compact objects and for physical processes operating in these systems.

  4. The Chandra Source Catalog: Processing and Infrastructure

    Science.gov (United States)

    Evans, Janet; Evans, Ian N.; Glotfelty, Kenny J.; Hain, Roger; Hall, Diane M.; Miller, Joseph B.; Plummer, David A.; Zografou, Panagoula; Primini, Francis A.; Anderson, Craig S.; Bonaventura, Nina R.; Chen, Judy C.; Davis, John E.; Doe, Stephen M.; Fabbiano, Giuseppina; Galle, Elizabeth C.; Gibbs, Danny G., II; Grier, John D.; Harbo, Peter N.; He, Xiang Qun (Helen); Houck, John C.; Karovska, Margarita; Kashyap, Vinay L.; Lauer, Jennifer; McCollough, Michael L.; McDowell, Jonathan C.; Mitschang, Arik W.; Morgan, Douglas L.; Mossman, Amy E.; Nichols, Joy S.; Nowak, Michael A.; Refsdal, Brian L.; Rots, Arnold H.; Siemiginowska, Aneta L.; Sundheim, Beth A.; Tibbetts, Michael S.; van Stone, David W.; Winkelman, Sherry L.

    2009-09-01

    Chandra Source Catalog processing recalibrates each observation using the latest available calibration data, and employs a wavelet-based source detection algorithm to identify all the X-ray sources in the field of view. Source properties are then extracted from each detected source that is a candidate for inclusion in the catalog. Catalog processing is completed by matching sources across multiple observations, merging common detections, and applying quality assurance checks. The Chandra Source Catalog processing system shares a common processing infrastructure and utilizes much of the functionality that is built into the Standard Data Processing (SDP) pipeline system that provides calibrated Chandra data to end-users. Other key components of the catalog processing system have been assembled from the portable CIAO data analysis package. Minimal new software tool development has been required to support the science algorithms needed for catalog production. Since processing pipelines must be instantiated for each detected source, the number of pipelines that are run during catalog construction is a factor of order 100 times larger than for SDP. The increased computational load, and inherent parallel nature of the processing, is handled by distributing the workload across a multi-node Beowulf cluster. Modifications to the SDP automated processing application to support catalog processing, and extensions to Chandra Data Archive software to ingest and retrieve catalog products, complete the upgrades to the infrastructure to support catalog processing.

  5. Spectral analysis of the Chandra comet survey

    NARCIS (Netherlands)

    Bodewits, D.; Christian, D. J.; Torney, M.; Dryer, M.; Lisse, C. M.; Dennerl, K.; Zurbuchen, T. H.; Wolk, S. J.; Tielens, A. G. G. M.; Hoekstra, R.

    2007-01-01

    Aims. We present results of the analysis of cometary X-ray spectra with an extended version of our charge exchange emission model (Bodewits et al. 2006). We have applied this model to the sample of 8 comets thus far observed with the Chandra X-ray observatory and acis spectrometer in the 300 - 1000

  6. The Brazilian Twin Registry.

    Science.gov (United States)

    Ferreira, Paulo H; Oliveira, Vinicius C; Junqueira, Daniela R; Cisneros, Lígia C; Ferreira, Lucas C; Murphy, Kate; Ordoñana, Juan R; Hopper, John L; Teixeira-Salmela, Luci F

    2016-12-01

    The Brazilian Twin Registry (BTR) was established in 2013 and has impelled twin research in South America. The main aim of the initiative was to create a resource that would be accessible to the Brazilian scientific community as well as international researchers interested in the investigation of the contribution of genetic and environmental factors in the development of common diseases, phenotypes, and human behavior traits. The BTR is a joint effort between academic and governmental institutions from Brazil and Australia. The collaboration includes the Federal University of Minas Gerais (UFMG) in Brazil, the University of Sydney and University of Melbourne in Australia, the Australian Twin Registry, as well as the research foundations CNPq and CAPES in Brazil. The BTR is a member of the International Network of Twin Registries. Recruitment strategies used to register twins have been through participation in a longitudinal study investigating genetic and environmental factors for low back pain occurrence, and from a variety of sources including media campaigns and social networking. Currently, 291 twins are registered in the BTR, with data on demographics, zygosity, anthropometrics, and health history having been collected from 151 twins using a standardized self-reported questionnaire. Future BTR plans include the registration of thousands of Brazilian twins identified from different sources and collaborate nationally and internationally with other research groups interested on twin studies.

  7. Delivery in Twin Gestation

    Directory of Open Access Journals (Sweden)

    Mark T. Peters

    1995-01-01

    Full Text Available Objective: The objective of this study was to determine whether prophylactic treatment with oral broad-spectrum antimicrobial therapy improves pregnancy outcomes in twin gestations.

  8. Acoustic Emission of Deformation Twinning in Magnesium

    Directory of Open Access Journals (Sweden)

    Chengyang Mo

    2016-08-01

    Full Text Available The Acoustic Emission of deformation twinning in Magnesium is investigated in this article. Single crystal testing with combined full field deformation measurements, as well as polycrystalline testing inside the scanning electron microscope with simultaneous monitoring of texture evolution and twin nucleation were compared to testing at the laboratory scale with respect to recordings of Acoustic Emission activity. Single crystal testing revealed the formation of layered twin boundaries in areas of strain localization which was accompanied by distinct changes in the acoustic data. Testing inside the microscope directly showed twin nucleation, proliferation and growth as well as associated crystallographic reorientations. A post processing approach of the Acoustic Emission activity revealed the existence of a class of signals that appears in a strain range in which twinning is profuse, as validated by the in situ and ex situ microscopy observations. Features extracted from such activity were cross-correlated both with the available mechanical and microscopy data, as well as with the Acoustic Emission activity recorded at the laboratory scale for similarly prepared specimens. The overall approach demonstrates that the method of Acoustic Emission could provide real time volumetric information related to the activation of deformation twinning in Magnesium alloys, in spite of the complexity of the propagation phenomena, the possible activation of several deformation modes and the challenges posed by the sensing approach itself when applied in this type of materials evaluation approach.

  9. Chandra Examines a Quadrillion-Volt Pulsar

    Science.gov (United States)

    2001-09-01

    The high-voltage environment of one of the most energetic and strongly magnetized pulsars known has been surveyed by NASA's Chandra X-ray Observatory. A team of astronomers found a powerful jet of high-energy particles extending over a distance of 20 light years and bright arcs believed to be due to particles of matter and anti-matter generated by the pulsar. The team of US, Canadian, and Japanese scientists pointed Chandra at the rapidly spinning neutron star B1509-58, located 19,000 light years away in the constellation of Circinus, for over five hours. These results were announced at the "Two Years of Science with Chandra" symposium in Washington, DC. "Jets and arcs on this vast scale have never been seen in any other pulsar," said Bryan Gaensler of the Smithsonian Astrophysical Observatory. "The spectacular images we have obtained of this source are letting us test theories as to how pulsars unleash so much energy." The features seen with Chandra give the scientists insight into the process by which voltages of more than 7000 trillion volts are created around rotating neutron stars (the dense remnants of supernova explosions) and how these extreme voltages affect their environment. B1509-58 is of particular interest because it has a much stronger magnetic field than the Crab Nebula pulsar, which exhibits similar features on a much smaller scale. The general picture emerging from these results is that high-energy particles of matter and antimatter are streaming away from the neutron star along its poles and near its equator. The particles leaving the poles produce the jets; astronomers speculate that only one side of the jet is apparent in B1509-58, indicating that this one side is beamed in our direction, while the other is rushing away. "Until this observation, no one knew for sure whether such tremendous voltages and energy outputs were a trademark of all pulsars, or if the Crab was an oddball," said Vicky Kaspi of McGill University in Montreal. "Now thanks

  10. Chandra X-ray Observatory Optical Axis and Aimpoint

    Science.gov (United States)

    Zhao, Ping

    2016-01-01

    Chandra X-ray Observatory revolutionized the X-ray astronomy as being the first, and so far the only, X-ray telescope achieving sub-arcsecond resolution. Chandra comprises of three principal elements: the High Resolution Mirror Assembly (HRMA), Pointing Control and Aspect Determination (PCAD) system, and the Science Instrument Module (SIM). To achieve and retain the unprecedented imaging quality, it is critical that these three principal elements stay rigid and stable for the entire life time of the Chandra operation. Tracking the Chandra optical axis and aimpoint with respect to detector positions is the most relevant measurement for understanding telescope stability. The study shows that both the optical axis and the aimpoint has been drifting since Chandra launch. I will discuss the telescope focal-point, optical axis, aimpoint, their positiondrifts during the mission, the impact to Chandra operations, and the permanent default aimpoint, to be implemented in Chandra cycle 18.

  11. The Chandra Deep Field South the 1 Million Second

    CERN Document Server

    Rosati, P; Giacconi, R; Gilli, R; Hasinger, G; Kewley, L J; Mainieri, V; Nonino, M; Norman, C; Szokoly, G; Wang, J X; Zirm, A W; Bergeron, J; Borgani, S; Gilmozzi, R; Grogin, N A; Koekemoer, A M; Schreier, E J; Zheng, W

    2002-01-01

    We present the main results from our 940 ksec observation of the Chandra Deep Field South (CDFS), using the source catalog described in an accompanying paper (Giacconi et al. 2001). We extend the measurement of source number counts to 5.5e-17 erg/cm^2/s in the soft 0.5-2 keV band and 4.5e-16 erg/cm^2/s in the hard 2-10 keV band. The hard band LogN-LogS shows a significant flattening (slope~=0.6) below ~1e-14 erg/cm^2/s, leaving at most 10-15% of the X-ray background (XRB) to be resolved, the main uncertainty lying in the measurement of the total flux of the XRB. On the other hand, the analysis in the very hard 5-10 keV band reveals a relatively steep LogN-LogS (slope ~=1.3) down to 1e-15 erg/cm^2/s. Together with the evidence of a progressive flattening of the average X-ray spectrum near the flux limit, this indicates that there is still a non negligible population of faint hard sources to be discovered at energies not well probed by Chandra, which possibly contribute to the 30 keV bump in the spectrum of the...

  12. Twin anemia polycythemia sequence

    NARCIS (Netherlands)

    Slaghekke, Femke

    2014-01-01

    In this thesis we describe that Twin Anemia Polycythemia Sequence (TAPS) is a form of chronic feto-fetal transfusion in monochorionic (identical) twins based on a small amount of blood transfusion through very small anastomoses. For the antenatal diagnosis of TAPS, Middle Cerebral Artery – Peak Syst

  13. Orientation-dependent mechanical behaviour of electrodeposited copper with nanoscale twins.

    Science.gov (United States)

    Mieszala, Maxime; Guillonneau, Gaylord; Hasegawa, Madoka; Raghavan, Rejin; Wheeler, Jeffrey M; Mischler, Stefano; Michler, Johann; Philippe, Laetitia

    2016-09-21

    The mechanical properties of electrodeposited copper with highly-oriented nanoscale twins were investigated by micropillar compression. Uniform nanotwinned copper films with preferred twin orientations, either vertical or horizontal, were obtained by controlling the plating conditions. In addition, an ultrafine grained copper film was synthesized to be used as a reference sample. The mechanical properties were assessed by in situ SEM microcompression of micropillars fabricated with a focused ion beam. Results show that the mechanical properties are highly sensitive to the twin orientation. When compared to the ultrafine grained sample, an increase of 44% and 130% in stress at 5% offset strain was observed in quasi-static tests for vertically and horizontally aligned twins, respectively. Inversely strain rate jump microcompression testing reveals higher strain sensitivity for vertical twins. These observations are attributed to a change in deformation mechanism from dislocation pile-ups at the twin boundary for horizontal twins to dislocations threading inside the twin lamella for vertical twins.

  14. Atomistic observation of a crack tip approaching coherent twin boundaries.

    Science.gov (United States)

    Liu, L; Wang, J; Gong, S K; Mao, S X

    2014-03-18

    Coherent twin boundaries (CTBs) in nano-twinned materials could improve crack resistance. However, the role of the CTBs during crack penetration has never been explored at atomic scale. Our in situ observation on nano-twinned Ag under a high resolution transmission electron microscope (HRTEM) reveals the dynamic processes of a crack penetration across the CTBs, which involve alternated crack tip blunting, crack deflection, twinning/detwinning and slip transmission across the CTBs. The alternated blunting processes are related to the emission of different types of dislocations at the crack tip and vary with the distance of the crack tip from the CTBs.

  15. Chandra Discovers Eruption and Pulsation in Nova Outburst

    Science.gov (United States)

    2001-09-01

    ,000 light years, it could be seen with the naked eye for about a month, during which it was about 100,000 times brighter than our own Sun," said R. Mark Wagner of the University of Arizona. Nova Aquilae Chandra observed the nova, so-called because early astronomers believed they heralded the appearance of a new star, four times from April 2000 through October 2000. "Our first Chandra observations showed that the expanding gas around Nova Aquilae was hot and nearly opaque," said Joachim Krautter of the State Observatory in Heidelberg, Germany. "When we looked months later with Chandra, the expanding gases cleared enough for us to see through them to the underlying star on which the explosion occurred." The latter Chandra X-ray data revealed the cyclical changes in brightness are due to the white dwarf expanding and shrinking over a 40-minute period. They also showed that the temperature on the surface of the white dwarf was 300,000 degrees Celsius, making Nova Aquilae one of the hottest stars ever observed to undergo such pulsations. "The observations told us that thermonuclear fusion reactions were still occurring on the surface layers of the white dwarf - more than eight months after the explosion first began!" said Robert Gehrz of the University of Minnesota. Other members of the team are Howard Bond (Space Telescope Science Institute), Yousaf Butt (Harvard-Smithsonian Center for Astrophysics), Koji Mukai (Goddard Space Flight Center), Peter Hauschildt (University of Georgia), Margarida Hernanz (Institute for Space Studies, Catalonia, Spain), Marina Orio (University of Wisconsin and the Torino Observatory in Italy), and Charles Woodward (University of Minnesota). Chandra observed Nova Aquilae for a total of 10 hours with the High Resolution Camera (HRC) and the Advanced CCD Imaging Spectrometer (ACIS). The HRC was built for NASA by the Smithsonian Astrophysical Observatory, Cambridge, MA. The ACIS instrument was built for NASA by the Massachusetts Institute of Technology

  16. Unilateral primary pulmonary agenesis and hypoplasia in monozygotic twins.

    Science.gov (United States)

    Alsaadi, Muslim; Al Muqhem, Badr; Boukai, A; Iqbal, Shaikh M

    2012-01-01

    We describe 10-month-old identical female twin infants, one with primary left-sided pulmonary agenesis and the other with primary left-sided pulmonary hypoplasia. They came to our outpatient clinic complaining of persistent dry cough. The clinical examination revealed decreased air entry over the left hemithorax. Chest x-rays showed complete left-sided radio-opacity in both the twins. The chest computed tomography scan with contrast confirmed the diagnoses of left-sided pulmonary agenesis (twin A) and left-sided hypoplasia (twin B). No other associated congenital anomaly was noted in either of the twins. To our knowledge, such a condition in live monozygotic twins has not been previously reported in published studies.

  17. Chandra hardware and systems: keeping things running

    Science.gov (United States)

    Paton, Lisa

    2006-06-01

    System management for any organization can be a challenge, but satellite projects present their own issues. I will be presenting the network and system architecture chosen to support the scientists in the Chandra X-ray Center. My group provides the infrastructure for science data processing, mission planning, user support, archive support and software development. Our challenge is to create a stable environment with enough flexibility to roll with the changes during the mission. I'll discuss system and network choices, web service, backups, security and systems monitoring. Also, how to build infrastructure that's flexible, how to support a large group of scientists with a relatively small staff, what challenges we faced (anticipated and unanticipated) and what lessons we learned over the past 6 years since the launch of Chandra. Finally I'll outline our plans for the future including beowulf cluster support, an improved helpdesk system, methods for dealing with the explosive amount of data that needs to be managed.

  18. Statistical Characterization of the Chandra Source Catalog

    CERN Document Server

    Primini, Francis A; Davis, John E; Nowak, Michael A; Evans, Ian N; Glotfelty, Kenny J; Anderson, Craig S; Bonaventura, Nina R; Chen, Judy C; Doe, Stephen M; Evans, Janet D; Fabbiano, Giuseppina; Galle, Elizabeth C; Gibbs, Danny G; Grier, John D; Hain, Roger M; Hall, Diane M; Harbo, Peter N; Xiangqun,; He,; Karovska, Margarita; Kashyap, Vinay L; Lauer, Jennifer; McCollough, Michael L; McDowell, Jonathan C; Miller, Joseph B; Mitschang, Arik W; Morgan, Douglas L; Mossman, Amy E; Nichols, Joy S; Plummer, David A; Refsdal, Brian L; Rots, Arnold H; Siemiginowska, Aneta; Sundheim, Beth A; Tibbetts, Michael S; Van Stone, David W; Winkelman, Sherry L; Zografou, Panagoula

    2011-01-01

    The first release of the Chandra Source Catalog (CSC) contains ~95,000 X-ray sources in a total area of ~0.75% of the entire sky, using data from ~3,900 separate ACIS observations of a multitude of different types of X-ray sources. In order to maximize the scientific benefit of such a large, heterogeneous data-set, careful characterization of the statistical properties of the catalog, i.e., completeness, sensitivity, false source rate, and accuracy of source properties, is required. Characterization efforts of other, large Chandra catalogs, such as the ChaMP Point Source Catalog (Kim et al. 2007) or the 2 Mega-second Deep Field Surveys (Alexander et al. 2003), while informative, cannot serve this purpose, since the CSC analysis procedures are significantly different and the range of allowable data is much less restrictive. We describe here the characterization process for the CSC. This process includes both a comparison of real CSC results with those of other, deeper Chandra catalogs of the same targets and e...

  19. SUSY Meets Her Twin

    CERN Document Server

    Katz, Andrey; Pokorski, Stefan; Redigolo, Diego; Ziegler, Robert

    2017-01-01

    We investigate the general structure of mirror symmetry breaking in the Twin Higgs scenario. We show, using the IR effective theory, that a significant gain in fine tuning can be achieved if the symmetry is broken hardly. We emphasize that weakly coupled UV completions can naturally accommodate this scenario. We analyze SUSY UV completions and present a simple Twin SUSY model with a tuning of around 10% and colored superpartners as heavy as 2 TeV. The collider signatures of general Twin SUSY models are discussed with a focus on the extended Higgs sectors.

  20. SUSY Meets Her Twin

    CERN Document Server

    Katz, Andrey; Pokorski, Stefan; Redigolo, Diego; Ziegler, Robert

    2016-01-01

    We investigate the general structure of mirror symmetry breaking in the Twin Higgs scenario. We show, using the IR effective theory, that a significant gain in fine tuning can be achieved if the symmetry is broken hardly. We emphasize that weakly coupled UV completions can naturally accommodate this scenario. We analyze SUSY UV completions and present a simple Twin SUSY model with a tuning of around 10% and colored superpartners as heavy as 2 TeV. The collider signatures of general Twin SUSY models are discussed with a focus on the extended Higgs sectors.

  1. Intrinsic Absorption in the Spectrum of Mrk 279: Simultaneous Chandra, FUSE, and STIS Observations

    CERN Document Server

    Scott, J E; Lee, J C; Arav, N; Ogle, P M; Roraback, K; Weaver, K; Alexander, T; Brotherton, M; Green, R F; Hutchings, J B; Kaiser, M E; Marshall, H; Oegerle, W; Zheng, W; Scott, Jennifer E.; Kriss, Gerard A.; Lee, Julia C.; Arav, Nahum; Ogle, Patrick; Roraback, Kenneth; Weaver, Kimberly; Alexander, Tal; Brotherton, Michael; Green, Richard F.; Hutchings, John; Kaiser, Mary Elizabeth; Marshall, Herman; Oegerle, William; Zheng, Wei

    2004-01-01

    We present a study of the intrinsic X-ray and far-ultraviolet absorption in the Seyfert 1.5 galaxy Markarian 279 using simultaneous observations from the Chandra X-ray Observatory, the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope, and the Far Ultraviolet Spectroscopic Explorer (FUSE). We also present FUSE observations made at three additional epochs. We detect the Fe K-alpha emission line in the Chandra spectrum, and its flux is consistent with the low X-ray continuum flux level of Mrk 279 at the time of the observation. Due to low signal-to-noise ratios in the Chandra spectrum, no O VII or O VIII absorption features are observable in the Chandra data, but the UV spectra reveal strong and complex absorption from HI and high-ionization species such as O VI, N V, and C IV, as well as from low-ionization species such as C III, N III, C II, and N II in some velocity components. The far-UV spectral coverage of the FUSE data provides information on high-order Lyman series absorption, which...

  2. Twin Reversed Arterial Perfusion Sequence: A Rare Entity

    Science.gov (United States)

    Khanduri, Sachin; Chhabra, Saakshi; Raja, Anshul; Bhagat, Saurav

    2015-01-01

    Twin reversed arterial perfusion (TRAP) sequence is an extremely rare complication of monochorionic multi-fetal pregnancy, occurring once in 35,000 births. This condition is characterized by a malformed fetus without a cardiac pump being perfused by a structurally normal (pump) twin via an artery-to-artery anastomosis in a reverse direction. We report a case of a primigravida, who came for routine antenatal checkup to our hospital at 31 weeks gestational age. Ultrasound imaging and magnetic resonance imaging revealed twin monochorionic intrauterine pregnancy with a viable, normal-appearing first twin and amorphous structured second twin connected by umbilical vessels. The patient was monitored with weekly ultrasonography, echocardiography, and Doppler ultrasound examination to ascertain the well-being of the pump twin. She delivered successfully at term a normal live baby and an acardius acephalus fetus. Plain X-ray of the acardius acephalus fetus confirmed the absence of cephalic structures. The perinatal mortality of the pump twin ranges from 35 to 55%; hence, it is essential to diagnose the presence of a pump twin at an early gestational age through improved imaging techniques, so that intervention can be planned early in the pregnancy for a better outcome of the pump twin. PMID:25861543

  3. Twin-twin Transfusion Syndrome with a Single Ectopic Kidney in a Twin Donor. Case Presentation

    Directory of Open Access Journals (Sweden)

    Gerardo Rogelio Robaina Castellanos

    2016-10-01

    Full Text Available Twin-twin Transfusion Syndrome presents more frequently in diamniotic monochromic twins. In advanced stages and without prenatal intervention, is associated to high rates of peri natal mortality and neurological sequel in the survivors. It is presented a case of a pair of twins with severe depression at birth in which it was diagnosed a Twin-twin Transfusion Syndrome, later confirmed with the presence of anemia in the donor twin and polycythemia in the receptor twin. Both twins had an unfavourable evolution with an early neonatal death. Necropsy findings were comparable with secondary damage to the syndrome, with the particularity that both had evidences of pulmonary infection and a renal malformation in the donor twin which is not included in the proper malformations of this syndrome. The objective of this work is to point out the essential elements for the diagnosis and antenatal treatment for this disease through the peculiarities of the presented case.

  4. Fullerton Virtual Twin Study.

    Science.gov (United States)

    Segal, Nancy L

    2006-12-01

    Virtual twins (VTs; same-age unrelated siblings reared together from early infancy) have been studied at California State University (CSU), Fullerton since 1991. The current sample includes over 130 pairs. Past and current research have research have focused on siblings' similarities and differences in general intelligence and body size. Future research in these areas will continue as new pairs continue to be identified. These studies will be supplemented by analyses of personality, social relations and adjustment using monozygotic (MZ) twins, dizygotic (DZ) twins, full siblings and friends, as well as new VTs, who have participated in Twins, Adoptees, Peers and Siblings (TAPS), a collaborative project conducted between CSU Fullerton and the University of San Francisco, from 2002 to 2006.

  5. Craniofacial anomalies in twins.

    Science.gov (United States)

    Keusch, C F; Mulliken, J B; Kaplan, L C

    1991-01-01

    Studies of twins provide insight into the relative contribution of genetic and environmental factors in the causality of structural anomalies. Thirty-five affected twin pairs were identified from a group of 1114 patients with congenital craniofacial deformities evaluated from 1972 to 1989. Forty-three of these 70 twins exhibited one or more craniofacial anomalies; these were analyzed for dysmorphic characteristics, zygosity, concordance, and family history. The anomalies were categorized into two groups: malformations and deformations. The malformations (n = 36) included hemifacial microsomia (n = 10), cleft lip and palate (n = 8), cleft palate (n = 4), rare facial cleft (n = 2), craniosynostosis (n = 2), Binder syndrome (n = 2), Treacher Collins syndrome (n = 2), craniopagus (n = 2), CHARGE association (n = 1), frontonasal dysplasia (n = 2), and constricted ears (n = 1). The deformations (n = 7) included plagiocephaly (n = 5), hemifacial hypoplasia (n = 1), and micrognathia (n = 1). Twenty-one monozygotic and 14 dizygotic twin pairs were identified. The concordance rate was 33 percent for monozygotic twins and 7 percent for dizygotic twins.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Chandra Detects Halo Of Hot Gas Around Milky Way-Like Galaxy

    Science.gov (United States)

    2001-07-01

    The first unambiguous evidence for a giant halo of hot gas around a nearby, spiral galaxy much like our own Milky Way was found by astronomers using NASA's Chandra X-ray Observatory. This discovery may lead to a better understanding of our own Galaxy, as well the structure and evolution of galaxies in general. A team of astronomers, led by Professor Daniel Wang of the University of Massachusetts, Amherst, observed NGC 4631, a spiral galaxy approximately 25 million light years from Earth with both Chandra and NASA's Hubble Space Telescope. While previous X-ray satellites have detected extended X-ray emission from this and other spiral galaxies, because of Chandra's exceptional resolution this is the first time that astronomers were able to separate the individual X-ray sources from the diffuse halo. Chandra found the diffuse halo of X-ray gas to be radiating at a temperature of almost 3 million degrees and extending some 25,000 light years from the galactic plane. "Scientists have debated for over 40 years whether the Milky Way has an extended corona, or halo, of hot gas," said Wang, lead author of the paper which appeared this month in The Astrophysical Journal Letters. "Of course since we are within the Milky Way, we can't get outside and take a picture. However, by studying similar galaxies like NGC 4631, we can get an idea of what's going on within our own Galaxy." The Chandra image reveals a halo of hot gas that extends for approximately 25,000 light years above the disk of the galaxy. One important feature of the X-ray emission from NGC 4631 is that it closely resembles the overall size and shape seen in the radio emission from the galaxy. This indicates that there may be a close connection between the outflows of hot gas, seen in X-rays, and the galaxy's magnetic field, revealed by radio emission. The Hubble image of NGC 4631 shows filamentary, loop-like structures enclosing enhanced X-ray-emitting gas and emanating from regions of recent star formation in

  7. ASA's Chandra Neon Discovery Solves Solar Paradox

    Science.gov (United States)

    2005-07-01

    NASA's Chandra X-ray Observatory survey of nearby sun-like stars suggests there is nearly three times more neon in the sun and local universe than previously believed. If true, this would solve a critical problem with understanding how the sun works. "We use the sun to test how well we understand stars and, to some extent, the rest of the universe," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "But in order to understand the sun, we need to know exactly what it is made of," he added. It is not well known how much neon the sun contains. This is critical information for creating theoretical models of the sun. Neon atoms, along with carbon, oxygen and nitrogen, play an important role in how quickly energy flows from nuclear reactions in the sun's core to its edge, where it then radiates into space. Chandra X-ray Spectrum of II Pegasi Chandra X-ray Spectrum of II Pegasi The rate of this energy flow determines the location and size of a crucial stellar region called the convection zone. The zone extends from near the sun's surface inward approximately 125,000 miles. The zone is where the gas undergoes a rolling, convective motion much like the unstable air in a thunderstorm. "This turbulent gas has an extremely important job, because nearly all of the energy emitted at the surface of the sun is transported there by convection," Drake said. The accepted amount of neon in the sun has led to a paradox. The predicted location and size of the solar convection zone disagree with those deduced from solar oscillations. Solar oscillations is a technique astronomers previously relied on to probe the sun's interior. Several scientists have noted the problem could be fixed if the abundance of neon is in fact about three times larger than currently accepted. Attempts to measure the precise amount of neon in the Sun have been frustrated by a quirk of nature; neon atoms in the Sun give off no signatures in visible light. However, in a gas

  8. Twin delivery: how should the second twin be delivered?

    Science.gov (United States)

    Olofsson, P; Rydhström, H

    1985-11-01

    In a series of 803 pairs of twins born between 1973 and 1982, 0.33% of second twins were delivered by cesarean section after vaginal delivery of the first twin. During the last year the frequency has increased to 7%, calling attention to the problem of declining obstetric skills and experience. This has caused us to update the routines of intrapartum management of twin gestations. In the present program only commonly available obstetric techniques are used. The potentially hazardous twin delivery is excluded from a trial of vaginal delivery. Hopefully, the program will help other obstetricians to decide in favor of vaginal delivery in selected twin gestations.

  9. Deformation twinning and the role of amino acids and magnesium in calcite hardness from molecular simulation.

    Science.gov (United States)

    Côté, A S; Darkins, R; Duffy, D M

    2015-08-21

    We employ classical molecular dynamics to calculate elastic properties and to model the nucleation and propagation of deformation twins in calcite, both as a pure crystal and with magnesium and aspartate inclusions. The twinning is induced by applying uniaxial strain to the crystal and relaxing all stress components except the uniaxial component. A detailed analysis of the atomistic processes reveal that the twinning mechanism involves small displacements of the Ca ions and cooperative rotations of the CO3 ions. The volume of the twinned region expands under increased uniaxial strain via the propagation of steps along the twin boundaries. The energy cost of the twin boundaries is compensated by the reduced hydrostatic stress and strain energy. The presence of biogenic impurities is shown to decrease the strain required to induce twin formation in calcite and, thus, the yield stress. This increased propensity for twinning provides a possible explanation for the increased hardness and penetration resistance observed experimentally in biominerals.

  10. Dependency of deformation twinning on grain orientation in an FCC and a HCP metal

    Institute of Scientific and Technical Information of China (English)

    YANG Ping

    2007-01-01

    Twinning plays important roles in HCP metals and those FCC metals with low stacking fault energy.The structural difierence of two types of metals makes quite different contributions of twinning to plasticity The variety of grain orientation in polycrystalline metals causes the inhomogeneous occurrence of twinning and further distinct transformation kinetics of twinning as strain increases and texture develops.This changes finally the work hardening behavior and mechanical properties.This Paper reveals the dependency of twinning on grain orientation in an FCC TWIP(twinning induced plasticity)steel with high Mn content and in a magnesium alloy using electron-backscatter-difiraction(EBSD) technique,and analyzes the characteristies of twinning in the two types of metals by Schmid factor calculation.In addition,the relation of twinning and shear banding, as well as their influence on properties are discussed.

  11. Twin and grain boundary in InP: A synchrotron radiation study

    Energy Technology Data Exchange (ETDEWEB)

    Han, Y.; Liu, X.; Jiao, J.; Lin, L. [Chinese Academy of Sciences, Beijing (China). Inst. of Semiconductors; Jiang, J.; Wang, Z.; Tian, Y. [Chinese Academy of Sciences, Beijing (China). Beijing Synchrotron Radiation Lab.

    1998-12-31

    Experimentally observed X-ray reflectivity curves show bi-crystal(twin) characteristics. The study revealed that there was defect segregation at the twin boundary. Stress was relaxed at the edge of the boundary. Relaxation of the stress resulted in formation of twin and other defects. As a result of formation of such defects, a defect-free and stress-free zone or low defect density and small stress zone is created around the defects. So a twin model was proposed to explain the experimental results. Stress(mainly thermal stress), chemical stoichiometry deviation and impurities nonhomogeneous distributions are the key factors that cause twins in LEC InP crystal growth. Twins on (111) face in LEC InP crystal were studied. Experimental evidence of above mentioned twin model and suggestions on how to get twin-free LEC InP single crystals will be discussed.

  12. The BMW-Chandra Serendipitous Source Catalog

    Science.gov (United States)

    Romano, P.; Campana, S.; Mignani, R. P.; Moretti, A.; Mottini, M.; Panzera, M. R.; Tagliaferri, G.

    2004-08-01

    We present the BMW-Chandra source catalog drawn from all Chandra ACIS-I pointed observations with an exposure time in excess of 10 ks public as of March 2003 (136 observations). Using the wavelet detection algorithm developed by Lazzati et al. (1999) and Campana et al. (1999), which can characterize point-like as well as extended sources, we identified 21325 sources. Among them, 16758 are serendipitous, i.e. not associated with the targets of the pointings, and do not require a non-automated analysis. This makes our catalog the largest compilation of Chandra sources to date. The 0.5--10 keV absorption corrected fluxes of these sources range from ˜ 3× 10-16 to 9×10-12 erg cm-2 s-1 with a median of 7× 10-15 erg cm-2 s-1. The catalog consists of count rates and relative errors in three energy bands (total, 0.5--7 keV; soft, 0.5--2 keV; and hard band, 2--7 keV), and source positions relative to the highest signal-to-noise detection among the three bands. The wavelet algorithm also provides an estimate of the extension of the source which we refined with a σ -clipping method. We report on the main properties of the sources in our catalog, such as sky coverage ( ˜ 8 deg2 at a limiting flux of ˜ 10-13 erg cm-2 s-1) and cosmological log N--log S for a subset at high Galactic latitude (∣ b ∣ > 20o) for a flux as low as ˜ 1.5 × 10-15 erg cm-2 s-1. Support for this work was provided by the Italian MIUR.

  13. Chandra Observations of Embedded Young Stellar Objects

    CERN Document Server

    Koyama, K

    2001-01-01

    This paper reviews the Chandra deep exposure observations of star forming regions, rho-Ophiuchi, Orion Molecular Clouds 2 and 3, Sagittarius B2 and Monoceros R2. The results are; (1) class I protostars are found to exhibit higher temperature plasma than those of T Tauri stars, (2) heavily absorbed X-rays are discovered from the candidates of class 0 protostars, (3) hard and highly variable X-rays are observed from high-mass young stars, and (4) young brown dwarfs emit X-rays similar to those of low-mass young stars.

  14. Chandra Locates Mother Lode of Planetary Ore in Colliding Galaxies

    Science.gov (United States)

    2004-01-01

    NASA's Chandra X-ray Observatory has discovered rich deposits of neon, magnesium, and silicon in a pair of colliding galaxies known as The Antennae. When the clouds in which these elements are present cool, an exceptionally high number of stars with planets should form. These results may foreshadow the fate of the Milky Way and its future collision with the Andromeda Galaxy. "The amount of enrichment of elements in The Antennae is phenomenal," said Giuseppina Fabbiano of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. at a press conference at a meeting of the American Astronomical Society in Atlanta, Ga. "This must be due to a very high rate of supernova explosions in these colliding galaxies." Fabbiano is lead author of a paper on this discovery by a team of U.S. and U.K. scientists that will appear in an upcoming issue of The Astrophysical Journal Letters. When galaxies collide, direct hits between stars are extremely rare, but collisions between huge gas clouds in the galaxies can trigger a stellar baby boom. The most massive of these stars race through their evolution in a few million years and explode as supernovas. Heavy elements manufactured inside these stars are blown away by the explosions and enrich the surrounding gas for thousands of light years. "The amount of heavy elements supports earlier studies that indicate there was a very high rate of relatively recent supernovas, 30 times that of the Milky Way," according to collaborator Andreas Zezas of the CfA. Animation of Colliding Galaxies Animation of Colliding Galaxies The supernova violence also heats the gas to millions of degrees Celsius. This makes much of the matter in the clouds invisible to optical telescopes, but it can be observed by an X-ray telescope. Chandra data revealed for the first time regions of varying enrichment in the galaxies – in one cloud magnesium and silicon are 16 and 24 times as abundant as in the Sun. "These are the kinds of elements that

  15. X-ray Mass Profiles from Chandra Galaxy Atlas

    Science.gov (United States)

    Paggi, Alessandro; Kim, Dong-Woo; Anderson, Craig; Burke, Douglas J.; Fabbiano, Giuseppina; Fruscione, Antonella; Lauer, Jennifer L.; McCollough, Michael L.; Morgan, Douglas; Mossman, Amy; O'Sullivan, Ewan; Trinchieri, Ginevra

    2016-04-01

    We present preliminary results of a Chandra/XMM-Newton joint analysis on a sample of three Early Type Galaxies (ETGs, namely NGC4649, NGC4636 and NGC5846). X-ray observations of the hot ISM is used to measure the total enclosed mass assuming hydrostatic equilibrium, and compasion with mass distributions obtained through optical kinematics data of globular clusters and planetary nebulae yields informations about disturbances in the ISM distribution due to nuclear activity, merging history, etc. Our analysis makes use of the Chandra Galaxy Atlas (CGA) data products - exploiting the unmatched spatial resolution of the ACIS detectors to reveal fine ISM features and disturbances in the inner galactic regions - and XMM-Newton data - relying on the large field of view of EPIC detector to extend the mass profiles to larger radii. We then measured the mass profiles in various pie sectors to separate different gas features (e.g., discontinuity and extended tail) and compared them with GCs/PNe based mass profiles. The X-ray mass profiles of NGC4649 show a generally relaxed morphology and, in agreement with previous analysis, the comparison with the optical mass profiles shows a significant deviations on parsec scale likely due to non-thermal pressure linked to nuclear activity. In significantly disturbed cases (NGC4648 and NGC5846) where we found discontinuities and extended tails, we found that the mass profiles are over-estimated toward the compressed discontinuity and under-estimated toward the extended tails, similar to inflow and outflow cases. These preliminary results are promising toward an extended analysis of the whole CGA sample in order to study the distribution of gas temperature and metal abundances in the ISM, and to investigate scaling relations between ETG global quantities like ISM temperature, luminosity and total mass.

  16. Simultaneous NuSTAR/Chandra Observations of The Bursting Pulsar GRO J1744-28 During Its Third Reactivation

    DEFF Research Database (Denmark)

    Younes, G.; Kouveliotou, C.; Grefenstette, B. W.;

    2015-01-01

    keV with an Eddington persistent flux level. Seven bursts, followed by dips, are seen with Chandra, three of which are also detected with NuSTAR. Timing analysis reveals a slight increase in the persistent emission pulsed fraction with energy (from 10% to 15%) up to 10 keV, above which it remains......We report on a 10 ks simultaneous Chandra/High Energy Transmission Grating (HETG)-Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the Bursting Pulsar, GRO J1744-28, during its third detected outburst since discovery and after nearly 18 yr of quiescence. The source is detected up to 60...

  17. Twinning in muskox and the cytogenetic investigation of a freemartin

    Directory of Open Access Journals (Sweden)

    N. J. Reindl

    1993-12-01

    Full Text Available The occurrence of twinning has been documented for muskox in both wild and captive populations. Of two known captive twin births only one set survived beyond 120 days. In both cases the twins were male-female pairs and both females showed abnormal sexual development. Two sets of stillborn twins have also been recorded. All four stillborn fetuses were female and none showed anomalies of the reproductive tract upon post-mortem examination. Blood cultures from the surviving male and female twins revealed that both were chimeric, indicating the admixture of fetal blood. Fibroblast cultures were normal for the respective sex of each individual. The freemartin heifer had anatomical abnormalities of the clitoris as well as the secondary sex characteristics of a male.

  18. Nustar and Chandra insight into the nature of the 3-40 kev nuclear emission in NGC 253

    DEFF Research Database (Denmark)

    Lehmer, B. D.; Wik, D. R.; Hornschemeier, A. E.;

    2013-01-01

    We present results from three nearly simultaneous Nuclear Spectroscopic Telescope Array ( NuSTAR ) and Chandra monitoring observations between 2012 September 2 and 2012 November 16 of the local star-forming galaxy NGC 253. The 3-40 keV intensity of the inner ~ 20 arcsec ( ~ 400 pc) nuclear region......, as measured by NuSTAR , varied by a factor of ~ 2 across the three monitoring observations. The Chandra data reveal that the nuclear region contains three bright X-ray sources, including a luminous ( L2-10 keV ~ few × 1039 erg s-1 ) point source located ~ 1 arcsec from the dynamical center of the galaxy...... nature for this source. Future NuSTAR and Chandra monitoring would be well equipped to break the degeneracy between the AGN and ULX nature of the 2003 source, if again caught in a high state....

  19. Chandra Observations of SNR RCW 103

    CERN Document Server

    Frank, Kari A; Park, Sangwook

    2015-01-01

    We analyze three Chandra observations, with a combined exposure time of 99 ks, of the Galactic supernova remnant RCW 103, a young supernova remnant, previously with no clear detection of metal-rich ejecta. Based on our imaging and spectral analyses of these deep Chandra data, we find evidence for metal-rich ejecta emission scattered throughout the remnant. X-ray emission from the shocked ejecta is generally weak, and the shocked circumstellar medium (CSM) is a largely dominant component across the entire remnant. The CSM component shows abundances of ~0.5 solar, while Ne, Mg, Si, S, and Fe abundances of the ejecta are up to a few times solar. Comparison of these ejecta abundances with yields from supernova nucleosynthesis models suggests, together with the existence of a central neutron star, a progenitor mass of ~18-20 M$_\\odot$, though the Fe/Si ratios are larger than predicted. The shocked CSM emission suggests a progenitor with high mass-loss rate and subsolar metallicity.

  20. Stellar Forensics with Striking Image from Chandra

    Science.gov (United States)

    2007-10-01

    A spectacular new image shows how complex a star's afterlife can be. By studying the details of this image made from a long observation by NASA's Chandra X-ray Observatory, astronomers can better understand how some stars die and disperse elements like oxygen into the next generation of stars and planets. At a distance of about 20,000 light years, G292.0+1.8 is one of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. The image shows a rapidly expanding, intricately structured, debris field that contains, along with oxygen, other elements such as neon and silicon that were forged in the star before it exploded. Hard X-ray Image of G292.0+1.8 Hard X-ray Image of G292.0+1.8 "We are finding that, just like snowflakes, each supernova remnant is complicated and beautiful in its own way," said Sangwook Park of Penn State who led the work, released in conjunction with the "8 Years of Chandra" symposium in Huntsville, Ala. The new, deep Chandra image - equaling nearly 6 days worth of observing time - shows an incredibly complex structure. Understanding the details of G292.0+1.8 is especially important because astronomers have considered it to be a "textbook" case of a supernova created by the death of a massive star. Chandra X-ray Image of G292.0+1.8 Chandra X-ray Image of G292.0+1.8 By mapping the distribution of X-rays in different energy bands, the Chandra image traces the distribution of chemical elements ejected in the supernova. The results imply that the explosion was not symmetrical. For example, blue (silicon and sulfur) and green (magnesium) are seen strongly in the upper right, while yellow and orange (oxygen) dominate the lower left. These elements light up at different temperatures, indicating that the temperature is higher in the upper right portion of G292.0+1.8. Slightly below and to the left of the center of G292.0+1.8 is a pulsar, a dense, rapidly rotating neutron star that remained behind after the original star

  1. X-raying Galaxies: A Chandra Legacy

    CERN Document Server

    Wang, Q Daniel

    2010-01-01

    This presentation reviews Chandra's major contribution to the understanding of nearby galaxies. After a brief summary on significant advances in characterizing various types of discrete X-ray sources, the presentation focuses on the global hot gas in and around galaxies, especially normal ones like our own. The hot gas is a product of stellar and AGN feedback -- the least understood part in theories of galaxy formation and evolution. Chandra observations have led to the first characterization of the spatial, thermal, chemical, and kinetic properties of the gas in our Galaxy. The gas is concentrated around the Galactic bulge and disk on scales of a few kpc. The column density of chemically-enriched hot gas on larger scales is at least an order magnitude smaller, indicating that it may not account for the bulk of the missing baryon matter predicted for the Galactic halo according to the standard cosmology. Similar results have also been obtained for other nearby galaxies. The X-ray emission from hot gas is well...

  2. Hypoalbuminemia in Donors with Twin-Twin Transfusion Syndrome

    NARCIS (Netherlands)

    Verbeek, L.; Middeldorp, J. M.; Hulzebos, C. V.; Oepkes, D.; Walther, F. J.; Lopriore, E.

    2013-01-01

    Objective: To estimate the differences in albumin levels between donors and recipients with twin-twin transfusion syndrome (TTTS). Methods: We performed a matched case-control study including twin pairs with TTTS treated conservatively (conservative group) or with fetoscopic laser surgery (laser gro

  3. The Danish Twin Registry

    DEFF Research Database (Denmark)

    Skytthe, Axel; Christiansen, Lene; Kyvik, Kirsten Ohm;

    2013-01-01

    decade of combining questionnaire and survey data with national demographic, social, and health registers in Statistics Denmark. Second, we describe our most recent data collection effort, which was conducted during the period 2008-2011 and included both in-person assessments of 14,000+ twins born 1931......Over the last 60 years, the resources and the research in the Danish Twin Registry (DTR) have periodically been summarized. Here, we give a short overview of the DTR and a more comprehensive description of new developments in the twenty-first century. First, we outline our experience over the last......-1969 and sampling of biological material, hereby expanding and consolidating the DTR biobank. Third, two examples of intensively studied twin cohorts are given. The new developments in the DTR in the last decade have facilitated the ongoing research and laid the groundwork for new research directions....

  4. Dialysis for twins

    DEFF Research Database (Denmark)

    Gramkow, Ann-Maria; Aarup, Michael; Andersen, L. L. T.

    2014-01-01

    A 32-year-old woman with known stage-4 chronic kidney disease due to lupus nephritis presented with twin pregnancy after in vitro fertilization at a gestational age of 24 weeks + 3 days because of imminent preterm labour. Repeated ultrasound evaluations confirmed intrauterine growth restriction...... in both twins and polyhydramnios as the cause of imminent preterm labour. After initiation of haemodialysis treatment, ultrasound evaluation showed a significant decrease in amniotic fluids, and also reduction in blood urea nitrogen and in clinical complaints could be observed. At a gestational age of 28...... weeks + 4 days, delivery was performed by Caesarean section. This case study shows that effective treatment of elevated uraemic toxins significantly reduced the morbidity risks of the twins....

  5. Ischiopagus tripus conjoined twins in a western lowland gorilla (Gorilla gorilla).

    Science.gov (United States)

    Langer, S; Jurczynski, K; Gessler, A; Kaup, F-J; Bleyer, M; Mätz-Rensing, K

    2014-05-01

    Conjoined twinning is rare in man and non-human primates. The current report describes a case of ischiopagus tripus conjoined Western Lowland gorilla (Gorilla gorilla) twins. The female twins were joined at the umbilical and pelvic region, involving the liver, xiphoid, umbilicus, body wall and skin. Computed tomography revealed two complete spines. The combined pelvic space was formed by two sacra, each connected with two iliac bones. The twins were only conjoined by a common pubis. Cause of death was attributed to cardiac and circulatory collapse resulting from a large patent foramen ovale (8 mm in diameter) of one twin and neonatal asphyxia.

  6. Maternal nutrition in twin pregnancy.

    Science.gov (United States)

    Campbell, D M; MacGillivray, I; Tuttle, S

    1982-01-01

    Energy and protein intake as measured by 24-hour urinary nitrogen values are similar in twin and singleton pregnancies. The relationship between urinary nitrogen and nitrogen intake is equally significant in twin and singleton pregnancies. Dietary zinc, copper, and iron are not different in women with twins, nor are the levels of these elements in plasma. These observations are surprising in view of the extra fetal demands on the mother and the different adaptation of twin pregnancies.

  7. Imaging of conjoined twins

    Energy Technology Data Exchange (ETDEWEB)

    McHugh, Kieran [Great Ormond Street Hospital for Children, Department of Radiology, London (United Kingdom); Kiely, Edward M.; Spitz, Lewis [Great Ormond Street Hospital for Children, Department of Surgery, London (United Kingdom)

    2006-09-15

    The incidence of conjoined twins is estimated to be around 1 in 250,000 live births. There is a distinct female predominance. In this paper the imaging of conjoined twins both antenatally and postnatally is reviewed, in particular taking into consideration recent advances with multidetector CT. Accurate counselling of parents regarding the likely outcome of the pregnancy and the likelihood of successful separation is dependent on good prenatal imaging with ultrasound and MRI. Planning of postnatal surgical separation is aided by accurate preoperative imaging which, depending on the conjoined area, will encompass many imaging modalities, but often relies heavily on CT scanning. (orig.)

  8. Chandra Resolves Cosmic X-ray Glow and Finds Mysterious New Sources

    Science.gov (United States)

    2000-01-01

    While taking a giant leap towards solving one of the greatest mysteries of X-ray astronomy, NASA's Chandra X-ray Observatory also may have revealed the most distant objects ever seen in the universe and discovered two puzzling new types of cosmic objects. Not bad for being on the job only five months. Chandra has resolved most of the X-ray background, a pervasive glow of X-rays throughout the universe, first discovered in the early days of space exploration. Before now, scientists have not been able to discern the background's origin, because no X-ray telescope until Chandra has had both the angular resolution and sensitivity to resolve it. "This is a major discovery," said Dr. Alan Bunner, Director of NASA's Structure andEvolution of the universe science theme. "Since it was first observed thirty-seven years ago, understanding the source of the X-ray background has been aHoly Grail of X-ray astronomy. Now, it is within reach." The results of the observation will be discussed today at the 195th national meeting of the American Astronomical Society in Atlanta, Georgia. An article describing this work has been submitted to the journal Nature by Dr. Richard Mushotzky, of NASA Goddard Space Flight Center, Greenbelt, Md., Drs. Lennox Cowie and Amy Barger at the University of Hawaii, Honolulu, and Dr. Keith Arnaud of the University of Maryland, College Park. "We are all very excited by this finding," said Mushotzky. "The resolution of most of the hard X-ray background during the first few months of the Chandra mission is a tribute to the power of this observatory and bodes extremely well for its scientific future," Scientists have known about the X-ray glow, called the X-ray background, since the dawn of X-ray astronomy in the early 1960s. They have been unable to discern its origin, however, for no X-ray telescope until Chandra has had both the angular resolution and sensitivity to resolve it. The German-led ROSAT mission, now completed, resolved much of the lower

  9. Prenatal Sonographic Diagnosis of Acardiac Twins

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Ah; Song, Mi Jin [Cheil General Hospital, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2006-09-15

    This study was performed to present the prenatal sonographic findings and the associated abnormalities of acardiac twins. Seven cases of acardiac twins were reviewed retrospectively. Prenatal ultrasonography was performed in all patients at a gestational age between 12 and 27 weeks (mean 17.6 weeks). Autopsy was performed in four cases. The sonographic and autopsy findings were reviewed to report the associated abnormalities of the acardiac and donor fetuses. The diagnosis of acardiac twins was made on the basis of ultrasonography (n=6) or autopsy (n=1). The associated abnormalities of the acardiac fetuses were single umbilical artery (SUA) (n=5), abdominal wall defect (n=4), club feet (n=4), scoliosis (n=1), cleft lip and palate (n=1), digital anomaly (n=1), and umbilical cord cyst (n=1). In four of the donor fetuses, sonographic abnormalities were found. Autopsy was performed in three of the four cases to reveal hydropic change (n=2), diaphragmatic hernia (n=1) and multiple structural abnormalities of interventricular septal defect, polydactyly, club feet and SUA (n=1). Intrauterine fetal death occurred in five donors and follow-up was lost in the remaining two. Meticulous sonography enables the diagnosis of acardiac twins at an early gestational age and can reveal the associated abnormalities of the donor fetus as well as the acardiac fetus

  10. Applying the Background-Source separation algorithm to Chandra Deep Field South data

    CERN Document Server

    Guglielmetti, F; Fischer, R; Rosati, P; Tozzi, P

    2012-01-01

    A probabilistic two-component mixture model allows one to separate the diffuse background from the celestial sources within a one-step algorithm without data censoring. The background is modeled with a thin-plate spline combined with the satellite's exposure time. Source probability maps are created in a multi-resolution analysis for revealing faint and extended sources. All detected sources are automatically parametrized to produce a list of source positions, fluxes and morphological parameters. The present analysis is applied to the Chandra Deep Field South 2 Ms public released data. Within its 1.884 ks of exposure time and its angular resolution (0.984 arcsec), the Chandra Deep Field South data are particularly suited for testing the Background-Source separation algorithm.

  11. Supernova Remnant 1987A: High Resolution Images and Spectrum from Chandra Observations

    CERN Document Server

    Park, S; Burrows, D N; Racusin, J L; McCray, R; Borkowski, K J; Park, Sangwook; Zhekov, Svetozar A.; Burrows, David N.; Racusin, Judith L.; Cray, Richard Mc; Borkowski, Kazimierz J.

    2005-01-01

    We report on the morphological and spectral evolution of SNR 1987A from the monitoring observations with the Chandra/ACIS. As of 2005, the X-ray-bright lobes are continuously brightening and expanding all around the ring. The softening of the overall X-ray spectrum also continues. The X-ray lightcurve is particularly remarkable: i.e., the recent soft X-ray flux increase rate is significantly deviating from the model which successfully fits the earlier data, indicating even faster flux increase rate since early 2004 (day ~6200). We also report results from high resolution spectral analysis with deep Chandra/LETG observations. The high resolution X-ray line emission features unambiguously reveal that the X-ray emission of SNR 1987A is originating primarily from a "disk" along the inner ring rather than from a spherical shell. We present the ionization structures, elemental abundances, and the shock velocities of the X-ray emitting plasma.

  12. Chandra and XMM Observations of the Composite Supernova Remnant G327.1-1.1

    CERN Document Server

    Temim, Tea; Gaensler, B M; Hughes, John P; van der Swaluw, Eric

    2008-01-01

    We present new X-ray imaging and spectroscopy of a composite supernova remnant G327.1-1.1 using the Chandra and XMM-Newton X-ray observatories. G327.1-1.1 has an unusual morphology consisting of a symmetric radio shell and an off center nonthermal component that indicates the presence of a pulsar wind nebula (PWN). Radio observations show a narrow finger of emission extending from the PWN structure towards the northwest. X-ray studies with ASCA, ROSAT, and BeppoSAX revealed elongated extended emission and a compact source at the tip of the finger that may be coincident with the actual pulsar. The high resolution Chandra observations provide new insight into the structure of the inner region of the remnant. The images show a compact source embedded in a cometary structure, from which a trail of X-ray emission extends in the southeast direction. The Chandra images also reveal two prong-like structures that appear to originate from the vicinity of the compact source and extend into a large bubble that is oriente...

  13. An X-ray Tour of Massive Star-forming Regions with Chandra

    CERN Document Server

    Townsley, L K

    2006-01-01

    The Chandra X-ray Observatory is providing fascinating new views of massive star-forming regions, revealing all stages in the life cycles of massive stars and their effects on their surroundings. I present a Chandra tour of some of the most famous of these regions: M17, NGC 3576, W3, Tr14 in Carina, and 30 Doradus. Chandra highlights the physical processes that characterize the lives of these clusters, from the ionizing sources of ultracompact HII regions (W3) to superbubbles so large that they shape our views of galaxies (30 Dor). X-ray observations usually reveal hundreds of pre-main sequence (lower-mass) stars accompanying the OB stars that power these great HII region complexes, although in one case (W3 North) this population is mysteriously absent. The most massive stars themselves are often anomalously hard X-ray emitters; this may be a new indicator of close binarity. These complexes are sometimes suffused by soft diffuse X-rays (M17, NGC 3576), signatures of multi-million-degree plasmas created by fas...

  14. NASA'S Chandra Finds New Evidence on Origin of Supernovas

    Science.gov (United States)

    2011-04-01

    CAMBRIDGE, Ma. -- Astronomers may now know the cause of an historic supernova explosion that is an important type of object for investigating dark energy in the universe. The discovery, made using NASA's Chandra X-ray Observatory, also provides strong evidence that a star can survive the explosive impact generated when a companion star goes supernova. The new study examined the remnant of a supernova observed by the Danish astronomer Tycho Brahe in 1572. The object, dubbed Tycho for short, was formed by a Type Ia supernova, a category of stellar explosion useful in measuring astronomical distances because of their reliable brightness. Type Ia supernovas have been used to determine that the universe is expanding at an accelerating rate, an effect attributed to the prevalence of an invisible, repulsive force throughout space called dark energy. A team of researchers analyzed a deep Chandra observation of Tycho and found an arc of X-ray emission in the supernova remnant. Evidence supports the conclusion that a shock wave created the arc when a white dwarf exploded and blew material off the surface of a nearby companion star. "There has been a long-standing question about what causes Type Ia supernovas," said Fangjun Lu of the Institute of High Energy Physics, Chinese Academy of Sciences in Beijing. "Because they are used as steady beacons of light across vast distances, it is critical to understand what triggers them." One popular scenario for Type Ia supernovas involves the merger of two white dwarfs. In this case, no companion star or evidence for material blasted off a companion should exist. In the other main competing theory, a white dwarf pulls material from a "normal," or sun-like, companion star until a thermonuclear explosion occurs. Both scenarios may actually occur under different conditions, but the latest Chandra result from Tycho supports the latter one. n addition, the Tycho study seems to show the remarkable resiliency of stars, as the supernova

  15. Chandra Finds Well-Established Black Holes In Distant Quasars

    Science.gov (United States)

    2002-03-01

    Pushing further back toward the first generation of objects to form in the universe, NASA's Chandra X-ray Observatory has observed the three most distant known quasars and found them to be prodigious producers of X-rays. This indicates that the supermassive black holes powering them were already in place when the Universe was only about one billion years old. "Chandra's superb sensitivity has allowed the detection of X-rays from the dawn of the modern universe, when the first massive black holes and galaxies were forming," said Niel Brandt of Penn State University, leader of one the teams involved. "These results indicate that future X-ray surveys should be able to detect the first black holes to form in the Universe." The three quasars were recently discovered at optical wavelengths by the Sloan Digital Sky Survey and are 13 billion light years from Earth, making them the most distant known quasars. The X-rays Chandra detected were emitted when the universe was only a billion years old, about 7 percent of the present age of the Universe. Since X-rays reveal conditions in the immediate vicinity of supermassive black holes, Brandt proposed that Chandra look at these objects in three snapshots of about two hours each to see if they were different from their older counterparts. The observations on January 29, 2002 were made public immediately and the four different teams quickly went to work on them. Brandt's team concluded that the quasars looked similar to ones that were at least twice as old, so the conditions around the central black hole had not changed much in that time, contrary to some theoretical expectations. A team led by Smita Mathur of Ohio State University reached a similar conclusion. "These young quasars do not appear to be any different from their older cousins, based upon our current understanding and assumptions," said Mathur. "Perhaps the most remarkable thing about them may be that they are so absolutely unremarkable." Jill Bechtold of the

  16. Amelia in Twin Pregnancy

    Directory of Open Access Journals (Sweden)

    Davari Tanha Fatemeh

    2009-04-01

    Full Text Available Limb bud first appears during the third week of gestation with the upper limb buds appearing a few days before the lower limb buds. Complete absence of one or more limbs, called Amelia, occurs prior to the eighth week of gestation. We report a case of Amelia in a twin gestation.

  17. Identical Twins Raised Apart

    Science.gov (United States)

    Farnsworth, David L.

    2015-01-01

    This article describes a bivariate data set that is interesting to students. Indeed, this particular data set, which involves twins and IQ, has sparked more student interest than any other set that I have presented. Specific uses of the data set are presented.

  18. Sleep Terrors in Twins

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2008-12-01

    Full Text Available In an attempt to clarify the genetic and environmental causes of sleep terrors in childhood, reasearchers in Canada followed 390 pairs of monozygotic and dizygotic twins by assessing the frequency of sleep terrors at 18 and 30 months of age using a questionnaire administered to the biological mothers.

  19. Twin Hub Network (poster)

    NARCIS (Netherlands)

    Kreutzberger, E.D.; Konings, J.W.

    2014-01-01

    Twin hub network, a European Interreg IVB project, aims at making intermodal rail transport within, to and from North West Europe more competitive, in particular between seaports and inland terminals. Improving rail competitiveness enables to shift freight flows from road to rail, providing a more s

  20. Twin-twin transfusion syndrome - diagnosis and prognosis

    Directory of Open Access Journals (Sweden)

    Hajrić-Egić Amira

    2003-01-01

    Full Text Available Twin-twin transfusion syndrome is a serious complication of monozygotic, monochorionic, diamniotic twins resulting from transplacental vascular communications. In this syndrome blood is thought to be shunted from one twin - donor,who develops anaemia,growth retardation and oligoamnios, to the other twin - recipient,who becomes plethoric,macrosomic and develops polyhydroamnios. The incidence of twin-twin transfusion syndrome ranges from 5-15% of all twin pregnancies. If this condition develops in the second trimester, it is usually associated with spontaneous abortion and death of one or both fetuses before viability. Developing the syndrome in the third trimester has better perinatal outcome. Mortality rates ranging from 56%-100%, depending on gestational age and severity of the syndrome. The ultrasound criterias for diagnosis, in this study,were the presence of twins of the same sex with discordant growth, with oligohydroamnios in one twin sac and polyhydroamnios in the other one, one placenta and thin membrane between twins. The present study shows clinical course of 14 cases and value of Doppler ultrasound to analyze the usefulness of umbilical artery blood flow velocimetry for predicting the risk of twin-twin transfusion syndrome. 14 twin pregnancies with twin-twin transfusion syndrome were diagnosed during the last four years period and prospectivelly followed. 9 cases were diagnosed before the completion od 28 weeks of gestation.The mean gestational age was 21,6_+4,2 weeks at diagnosis and 23,2+_3,6 weeks at delivery. 5 cases were diagnosed after 28 weeks of gestation. The mean gestational age in this group was 29,6+_2,1 weeks at diagnosis and 33+_3,3 weeks at delivery. The survival rate in this study was 29%(8/28.9 cases ended in spontaneous abortion between 18th and 27th weeks of pregnancy (table 1 and 5 in premature labor (table 2.There were 7 intrauterine death (5 at admission and 2 few days after admission and 13 neonatal deaths

  1. Chandra data archive operations: lessons learned

    Science.gov (United States)

    McCollough, Michael L.; Rots, Arnold H.; Winkelman, Sherry L.

    2006-06-01

    We present a discussion of the lessons learned from establishing and operating the Chandra Data Archive (CDA). We offer an overview of the archive, what preparations were done before launch, the transition to operations, actual operations, and some of the unexpected developments that had to be addressed in running the archive. From this experience we highlight some of the important issues that need to be addressed in the creation and running of an archive for a major project. Among these are the importance of data format standards; the integration of the archive with the rest of the mission; requirements throughout all phases of the mission; operational requirements; what to expect at launch; the user interfaces; how to anticipate new tasks; and overall importance of team management and organization.

  2. The BMW-Chandra Serendipitous Source Catalogue

    Science.gov (United States)

    Romano, P.; Campana, S.; Mignani, R. P.; Moretti, A.; Panzera, M. R.; Tagliaferri, G.

    We present the BMW-Chandra Source Catalogue drawn from all Chandra ACIS-I pointed observations with an exposure time in excess of 10 ks public as of March 2003 (136 observations). Using the wavelet detection algorithm developed by \\citep{Lazzatiea99} and \\citep{Campanaea99}, which can characterize point-like as well as extended sources, we identified 21325 sources which were visually inspected and verified. Among them, 16758 are not associated with the targets of the pointings and are considered certain; they have a 0.5-10 keV absorption corrected flux distribution median of ˜ 7 × 10-15 erg cm-2 s-1. The catalogue consists of source positions, count rates, extensions and relative errors in three energy bands (total, 0.5-7 keV; soft, 0.5-2 keV; and hard band, 2-7 keV), as well as the additional information drawn from the headers of the original files. We also extracted source counts in four additional energy bands, (0.5-1.0 keV, 1.0-2.0 keV, 2.0-4.0 keV and 4.0-7.0 keV). We compute the sky coverage in the soft and hard bands. The complete catalogue provides a sky coverage in the soft band (0.5-2 keV, S/N =3) of ˜ 8 deg2 at a limiting flux of ˜ 10-13 erg cm-2 s-1, and ˜ 2 deg2 at a limiting flux of ˜ 10-15 erg cm-2 s-1. http://www.merate.mi.astro.it/~xanadu/BMC/bmc_home.html

  3. Chandra Survey of Nearby Galaxies: The Catalog

    Science.gov (United States)

    She, Rui; Ho, Luis C.; Feng, Hua

    2017-02-01

    We searched the public archive of the Chandra X-ray Observatory as of 2016 March and assembled a sample of 719 galaxies within 50 Mpc with available Advanced CCD Imaging Spectrometer observations. By cross-correlation with the optical or near-infrared nuclei of these galaxies, 314 of them are identified to have an X-ray active galactic nucleus (AGN). The majority of them are low-luminosity AGNs and are unlikely X-ray binaries based upon their spatial distribution and luminosity functions. The AGN fraction is around 60% for elliptical galaxies and early-type spirals, but drops to roughly 20% for Sc and later types, consistent with previous findings in the optical. However, the X-ray survey is more powerful in finding weak AGNs, especially from regions with active star formation that may mask the optical AGN signature. For example, 31% of the H ii nuclei are found to harbor an X-ray AGN. For most objects, a single power-law model subject to interstellar absorption is adequate to fit the spectrum, and the typical photon index is found to be around 1.8. For galaxies with a non-detection, their stacked Chandra image shows an X-ray excess with a luminosity of a few times 1037 erg s‑1 on average around the nuclear region, possibly composed of faint X-ray binaries. This paper reports on the technique and results of the survey; in-depth analysis and discussion of the results will be reported in forthcoming papers.

  4. Mitral valve regurgitation in twins

    DEFF Research Database (Denmark)

    Bakkestrøm, Rine; Larsen, Lisbeth Aagaard; Møller, Jacob Eifer

    2016-01-01

    BACKGROUND: Smaller observational studies have suggested familial clustering of mitral regurgitation (MR). Using a large twin cohort, the aims were to assess MR concordance rates and assess mortality in MR twins and unaffected cotwins. METHODS: Through the Danish Twin Registry, twins...... with an International Classification of Diseases, Eighth Revision and Tenth Revision diagnosis code of MR born 1880-1989 were identified and proband-wise concordance rates were calculated. To assess whether having a cotwin with MR affected survival, 10 matched twins without MR (n = 5,575) were selected for each MR twin...... (n = 562), and all-cause mortality rates were assessed. RESULTS: Among the 87,432 twins alive January 1, 1977, or later, 494 (0.57%) MR individuals were identified. Six MR concordant pairs were found, of which 3 were monozygotic. Proband-wise concordance rate when accounting for right censoring...

  5. Chandra Discovers X-Ray Ring Around Cosmic Powerhouse in Crab Nebula

    Science.gov (United States)

    1999-09-01

    After barely two months in space, NASA's Chandra X-ray Observatory has taken a stunning image of the Crab Nebula, the spectacular remains of a stellar explosion, and has revealed something never seen before: a brilliant ring around the nebula's heart. Combined with observations from the Hubble Space Telescope, the image provides important clues to the puzzle of how the cosmic "generator," a pulsing neutron star, energizes the nebula, which still glows brightly almost 1,000 years after the explosion. "The inner ring is unique," said Professor Jeff Hester of Arizona State University, Tempe, AZ. "It has never been seen before, and it should tell us a lot about how the energy from the pulsar gets into the nebula. It's like finding the transmission lines between the power plant and the light bulb." Professor Mal Ruderman of Columbia University, New York, NY, agreed. "The X-rays Chandra sees are the best tracer of where the energy is. With images such as these, we can directly diagnose what is going on." What is going on, according to Dr. Martin Weisskopf, Chandra Project Scientist from NASA's Marshall Space Flight Center, Huntsville, AL, is awesome. "The Crab pulsar is accelerating particles up to the speed of light and flinging them out into interstellar space at an incredible rate." The image shows tilted rings or waves of high-energy particles that appear to have been flung outward over the distance of a light year from the central star, and high-energy jets of particles blasting away from the neutron star in a direction perpendicular to the spiral. Hubble Space Telescope images have shown moving knots and wisps around the neutron star, and previous X-ray images have shown the outer parts of the jet and hinted at the ring structure. With Chandra's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears. The image was made with Chandra's Advanced CCD Imaging Spectrometer and High Energy Transmission

  6. Incidence of hand eczema in a population-based twin cohort

    DEFF Research Database (Denmark)

    Lerbaek, A; Kyvik, Kirsten Ohm; Ravn, H;

    2007-01-01

    BACKGROUND: Population-based studies on the incidence of hand eczema are sparse. OBJECTIVES: The aim of this prospective follow-up study was to determine the incidence rate of hand eczema in a population-based twin cohort. Secondly, the role of genetic factors and other potential risk factors...... for hand eczema was investigated. METHODS: A questionnaire on self-reported hand eczema was answered by 5610 and 4128 twin individuals in 1996 and 2005, respectively. Data were analysed in a Poisson regression analysis. RESULTS: The crude incidence rate was 8.8 cases per 1000 person-years (95% confidence...... interval, [CI] 7.7-9.9). Incidence rate ratios (IRRs) dependent on the co-twin's hand eczema status revealed a significant, doubled risk for monozygotic twin individuals with a co-twin affected by hand eczema, compared with dizygotic twin individuals with a co-twin affected by hand eczema (IRR 2.4, 95% CI...

  7. Brazilian Twin Registry: A Bright Future for Twin Studies/Twin Research: Twin Study of Alcohol Consumption and Mortality; Oxygen Uptake in Adolescent Twins/In the News: Superfecundated Twins In Vietnam; Adolescent Twin Relations; Twin and Triplet Co-Workers; A Special Twin Ultrasound; Monozygotic Twins With Different Skin Color; Identical Twin Returns from Space.

    Science.gov (United States)

    Segal, Nancy L

    2016-06-01

    The establishment of the Brazilian Twin Registry for the study of genetic, social, and cultural influences on behavior is one of eleven newly funded projects in the Department of Psychology at the University of São Paulo. These 11 interrelated projects form the core of the university's Center for Applied Research on Well-Being and Human Behavior. An overview of the planned twin research and activities to date is presented. Next, two recent twin studies are reviewed, one on the relationship between alcohol consumption and mortality, and the other on factors affecting maximal oxygen uptake. Twins cited in the media include the first identified superfecundated twins in Vietnam, adolescent twin relations, twins and triplets who work together, monozygotic twins with different skin tones and a co-twin control study that addresses the effects of space travel.

  8. Hydropic Placenta as a First Manifestation of Twin-Twin Transfusion in a Monochorionic Diamniotic Twin Pregnancy

    NARCIS (Netherlands)

    de Laat, Monique W. M.; Manten, Gwendoline T. R.; Nikkels, Peter G. J.; Stoutenbeek, Philip

    2009-01-01

    Monochorionic twin pregnancies are at a 10% to 1.5% risk of developing twin-twin transfusion syndrome (TTTS).(1) Monitoring such pregnancies is aimed at evaluating the fetal condition by measuring the amount of amniotic fluid, Doppler parameters, and fetal growth. Twin-twin transfusion syndrome may

  9. Intrinsic Absorption in the Spectrum of NGC 7469: Simultaneous Chandra, FUSE, and STIS Observations

    CERN Document Server

    Scott, J E; Lee, J C; Quijano, J K; Brotherton, M; Canizares, C R; Green, R F; Hutchings, J B; Kaiser, M E; Marshall, H; Oegerle, W; Ogle, P; Zheng, W; Scott, Jennifer E.; Kriss, Gerard A.; Lee, Julia C.; Quijano, Jessica Kim; Brotherton, Michael; Canizares, Claude R.; Green, Richard F.; Hutchings, John; Kaiser, Mary Elizabeth; Marshall, Herman; Oegerle, William; Ogle, Patrick; Zheng, Wei

    2005-01-01

    We present simultaneous X-ray, far-ultraviolet, and near-ultraviolet spectra of the Seyfert 1 galaxy NGC 7469 obtained with the Chandra X-Ray Observatory, the Far Ultraviolet Spectroscopic Explorer, and the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. Previous non-simultaneous observations of this galaxy found two distinct UV absorption components, at -560 and -1900 km/s, with the former as the likely counterpart of the X-ray absorber. We confirm these two absorption components in our new UV observations, in which we detect prominent O VI, Ly alpha, N V, and C IV absorption. In our Chandra spectrum we detect O VIII emission, but no significant O VIII or O VII absorption. We also detect a prominent Fe K alpha emission line in the Chandra spectrum, as well as absorption due to hydrogen-like and helium-like neon, magnesium, and silicon at velocities consistent with the -560 km/s UV absorber. The FUSE data reveal that the H I and C IV column densities in this UV- and X-ray- absorbing compon...

  10. Reared-Apart Chinese Twins: Chance Discovery/Twin-Based Research: Twin Study of Media Use; Twin Relations Over the Life Span; Breast-Feeding Opposite-Sex Twins/Print and Online Media: Twins in Fashion; Second Twin Pair Born to Tennis Star; Twin Primes; Twin Pandas.

    Science.gov (United States)

    Segal, Nancy L

    2017-04-01

    A January 2017 reunion of 10-year-old reared-apart Chinese twin girls was captured live on ABC's morning talk show Good Morning America, and rebroadcast on their evening news program Nightline. The twins' similarities and differences, and their participation in ongoing research will be described. This story is followed by reviews of twin research concerning genetic and environmental influences on media use, twin relations across the lifespan and the breast-feeding of opposite-sex twins. Popular interest items include twins in fashion, the second twin pair born to an internationally renowned tennis star, twin primes and twin pandas.

  11. Minimal Mirror Twin Higgs

    CERN Document Server

    Barbieri, Riccardo; Harigaya, Keisuke

    2016-01-01

    In a Mirror Twin World with a maximally symmetric Higgs sector the little hierarchy of the Standard Model can be significantly mitigated, perhaps displacing the cutoff scale above the LHC reach. We show that consistency with observations requires that the Z2 parity exchanging the Standard Model with its mirror be broken in the Yukawa couplings. A minimal such effective field theory, with this sole Z2 breaking, can generate the Z2 breaking in the Higgs sector necessary for the Twin Higgs mechanism, and has constrained and correlated signals in invisible Higgs decays, direct Dark Matter Detection and Dark Radiation, all within reach of foreseen experiments. For dark matter, both mirror neutrons and a variety of self-interacting mirror atoms are considered. Neutrino mass signals and the effects of a possible additional Z2 breaking from the vacuum expectation values of B-L breaking fields are also discussed.

  12. In Brief: Chandra Observatory marks 10 years in space

    Science.gov (United States)

    Showstack, Randy

    2009-08-01

    NASA's Chandra X-ray Observatory, originally envisioned as a 5-year mission, was deployed into an elliptical orbit around Earth 10 years ago, on 23 July 1999. The most powerful X-ray telescope yet, Chandra has provided a peak into the high-energy universe and has independently confirmed the existence of dark energy. Martin Weisskopf, Chandra project scientist at NASA's Marshall Space Flight Center, Huntsville, Ala., said discoveries made possible by the observatory “have made dramatic changes to our understanding of the universe and its constituents.” “The Great Observatories program—of which Chandra is a major part—shows how astronomers need as many tools as possible to tackle the big questions out there,” said Ed Weiler, associate administrator of NASA's Science Mission Directorate at NASA Headquarters in Washington. The Hubble Space Telescope, Compton Gamma Ray Observatory, and Spitzer Space Telescope are NASA's other Great Observatories. For more information, visit http://chandra.harvard.edu/ten/ and http://chandra.nasa.gov.

  13. Nutrition in twin pregnancy.

    Science.gov (United States)

    MacGillivray, I

    1979-01-01

    The urinary nitrogen output appears to be related to both protein and energy intake, so that women having heavier babies probably eat more, although this may simply mean that they are larger women. Women with twin pregnancies have been found to have a lesser urinary nitrogen output, but it seems unlikely that this be due to lower intakes. They might simply utilize their diet more efficiently--a hypothesis that is now being tested.

  14. Emergence of Digital Twins

    OpenAIRE

    Datta, Shoumen Palit Austin

    2016-01-01

    Multiple forms of digital transformation are imminent. Digital Twins represent one concept. It is gaining momentum because it may offer real-time transparency. Rapid diffusion of digital duplicates faces hurdles due to lack of semantic interoperability between architectures, standards and ontologies. The technologies necessary for automated discovery are in short supply. Progression of the field depends on convergence of information technology, operational technology and protocol-agnostic tel...

  15. Chandra X-Ray Observatory Image of Crab Nebula

    Science.gov (United States)

    1999-01-01

    After barely 2 months in space, the Chandra X-Ray Observatory (CXO) took this sturning image of the Crab Nebula, the spectacular remains of a stellar explosion, revealing something never seen before, a brilliant ring around the nebula's heart. The image shows the central pulsar surrounded by tilted rings of high-energy particles that appear to have been flung outward over a distance of more than a light-year from the pulsar. Perpendicular to the rings, jet-like structures produced by high-energy particles blast away from the pulsar. Hubble Space Telescope images have shown moving knots and wisps around the neutron star, and previous x-ray images have shown the outer parts of the jet and hinted at the ring structure. With CXO's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears. The image was made with CXO's Advanced Charge-Coupled Device (CCD) Imaging Spectrometer (ACIS) and High Energy Transmission Grating. The Crab Nebula, easily the most intensively studied object beyond our solar system, has been observed using virtually every astronomical instrument that could see that part of the sky

  16. Chandra Observations of Outflows from PSR J1509-5850

    CERN Document Server

    Klingler, Noel; Rangelov, Blagoy; Pavlov, George G; Posselt, Bettina; Ng, C -Y

    2016-01-01

    PSR J1509-5850 is a middle-aged pulsar with the period P ~ 89 ms, spin-down power Edot = 5.1 x 10^35 erg/s, at a distance of about 3.8 kpc. We report on deep Chandra X-ray Observatory observations of this pulsar and its pulsar wind nebula (PWN). In addition to the previously detected tail extending up to 7' southwest from the pulsar (the southern outflow), the deep images reveal a similarly long, faint diffuse emission stretched toward the north (the northern outflow) and the fine structure of the compact nebula (CN) in the pulsar vicinity. The CN is resolved into two lateral tails and one axial tail pointing southwest (a morphology remarkably similar to that of the Geminga PWN), which supports the assumption that the pulsar moves towards the northeast. The luminosities of the southern and northern outflows are about 1 x 10^33 and 4 x 10^32 erg/s, respectively. The spectra extracted from four regions of the southern outflow do not show any softening with increasing distance from the pulsar. The lack of synchr...

  17. Socioeconomic position and twins' health

    DEFF Research Database (Denmark)

    Osler, Merete; McGue, Matt; Christensen, Kaare

    2007-01-01

    of middle-aged Danish twins was conducted in 1998-99. The study population included 1266 like-sex twin pairs [52.5% monozygotic (MZ) and 47.6% dizygotic (DZ)]. Data were obtained on childhood and adult social class and on height, BMI, grip strength, depression symptoms, self-rated health, cognitive function......, prenatal and rearing environmental factors from environmental factor later in life, we compared the health status among male and female twin pairs who lived together during childhood and were discordant or concordant on adult socioeconomic position. METHODS: A cross-sectional survey among a random sample......, physical activity, smoking, alcohol and food intake. RESULTS: The expected associations between the individual twins' adult social class and health measures were observed. Among DZ male twins discordant on adult social class, the higher social class twin was on average significantly taller and had higher...

  18. Tribute to dr louis keith: twin and physician extraordinaire/twin research reports: influences on asthma severity; chimerism revisited; DNA strand break repair/media reports: twins born apart; elevated twin frequencies; celebrity father of twins; conjoined twinning.

    Science.gov (United States)

    Segal, Nancy L

    2014-10-01

    The International Society for Twin Studies has lost a valued friend and colleague. Dr Louis Keith, Emeritus Professor of Obstetrics and Gynecology at Northwestern University, in Chicago, passed away on Sunday, July 6, 2014. His life and work with twins will be acknowledged at the November 2014 International Twin Congress in Budapest, Hungary. Next, twin research reports on the severity of asthma symptoms, a case of chimerism, and factors affecting DNA breakage and repair mechanisms are reviewed. Media reports cover twins born apart, elevated twin frequencies, a celebrity father of twins, and a family's decision to keep conjoined twins together.

  19. A polynomial chaos expansion based molecular dynamics study for probabilistic strength analysis of nano-twinned copper

    Science.gov (United States)

    Mahata, Avik; Mukhopadhyay, Tanmoy; Adhikari, Sondipon

    2016-03-01

    Nano-twinned structures are mechanically stronger, ductile and stable than its non-twinned form. We have investigated the effect of varying twin spacing and twin boundary width (TBW) on the yield strength of the nano-twinned copper in a probabilistic framework. An efficient surrogate modelling approach based on polynomial chaos expansion has been proposed for the analysis. Effectively utilising 15 sets of expensive molecular dynamics simulations, thousands of outputs have been obtained corresponding to different sets of twin spacing and twin width using virtual experiments based on the surrogates. One of the major outcomes of this work is that there exists an optimal combination of twin boundary spacing and twin width until which the strength can be increased and after that critical point the nanowires weaken. This study also reveals that the yield strength of nano-twinned copper is more sensitive to TBW than twin spacing. Such robust inferences have been possible to be drawn only because of applying the surrogate modelling approach, which makes it feasible to obtain results corresponding to 40 000 combinations of different twin boundary spacing and twin width in a computationally efficient framework.

  20. The 'Planemo' Twins

    Science.gov (United States)

    2006-08-01

    Photo 29b/06 ESO PR Photo 29b/06 The System Oph 1622 (ISAAC/VLT) By comparing to widely used theoretical models, Jayawardhana and Ivanov estimate that the companion is about seven times the mass of Jupiter, while the more massive object comes in at about 14 times Jupiter's mass. The newborn pair, barely a million years old, is separated by about six times the distance between the Sun and Pluto, and is located in the Ophiuchus star-forming region approximately 400 light years away. Planets are thought to form out of discs of gas and dust that surround stars, brown dwarfs, and even some free-floating planetary mass objects (see ESO 19/06). But, "it is likely that these planemo twins formed together out of a contracting gas cloud that fragmented, like a miniature stellar binary," said Jayawardhana. "We are resisting the temptation to call it a 'double planet' because this pair probably didn't form the way that planets in our Solar system did," added Ivanov. Oph1622B is only the second or third directly imaged planetary mass companion to be confirmed spectroscopically (see ESO 23/04 [1]), and the first one around a primary that is itself a planetary mass object. What's more, its existence poses a challenge to a popular theoretical scenario, which suggests that brown dwarfs and free-floating planetary mass objects are embryos ejected from multiple proto-star systems. Since the two objects in Oph1622 are so far apart, and only weakly bound to each other by gravity, they would not have survived such a chaotic birth. "Recent discoveries have revealed an amazing diversity of worlds out there. Still, the Oph1622 pair stands out as one of the most intriguing, if not peculiar," said Jayawardhana. "Now we're curious to find out whether such pairs are common or rare. The answer could shed light on how free-floating planetary-mass objects form," added Ivanov.

  1. Trojan twin planets

    Science.gov (United States)

    Dvorak, R.; Loibnegger, B.; Schwarz, R.

    2017-03-01

    The Trojan asteroids are moving in the vicinity of the stable Lagrange points L_4 and L_5 of the gas giants Jupiter, Uranus and Neptune. Their motion can be described and understood with the aid of the restricted three-body problem. As an extension of this problem we investigate how stable motion close to the Lagrange points of two massive bodies can exist. This configuration can be described as the Trojan Twin Problem when we regard the two additional bodies as having a mass significantly smaller than the the two primary bodies: a star in the center (m_1) and an additional Jupiter-like mass (m_2). Using this 4-body problem we have undertaken numerical investigations concerning possible stable "twin orbits". However, these two bodies (m_3 and m_4) in Trojan-like orbits may have quite different masses. We decided to choose 6 different scenaria for this problem: as primary body, m2, we have taken a Jupiter-like planet, a Saturn-like one, and a super-Earth with 10 Earthmasses (m_{Earth}) respectively. As quasi twin planets, we have used different mass ratios namely objects for m3 and m4 from 10m_{Earth} to Moon like ones. We found different stable configurations depending on the involved masses and the initial distances between the twins (always close to the Lagrange point). Although the formation of such a configuration seems to be not very probable we should not exclude that it exists regarding the huge number of planets even in our own galaxy. This model is of special interest when the most massive planet (m_2) is moving on an orbit in the habitable zone around a main sequence star. One can use our results of stable orbits of Trojan Twin Planets (or asteroids) for extrasolar systems having as second primary a Jupiter-like, a Saturn-like or a super-Earth like planet around a star similar to our Sun.

  2. Twin tubal pregnancy: A large unruptured ectopic pregnancy.

    Science.gov (United States)

    Goswami, Deepti; Agrawal, Nidhi; Arora, Vrinda

    2015-11-01

    Twin ectopic pregnancy is a rare occurrence, with an estimated incidence of 1 in 20 000 spontaneous pregnancies. We describe a case of unilateral twin ectopic pregnancy in which the gravid fallopian tube showed no signs of tubal rupture despite marked tubal distension. A 25-year-old woman presented with clinical features suggestive of large right-sided tubal ectopic pregnancy. Serum β-human chorionic gonadotropin was 10 800 IU/mL. Laparotomy revealed markedly distended right fallopian tube. There was no hemoperitoneum. The tube contained twin gestational sacs. The crown-rump length of the embryos was 2 cm. The ectopic gestation was thus unique, in that despite marked tubal distension, the trophoblastic invasion was not significant to cause tubal rupture. There may be a role for medical management based on individual gestational sac size in selected cases of twin tubal pregnancy in which there is no evidence of hemoperitoneum.

  3. Deep Chandra observations of Pictor A

    CERN Document Server

    Hardcastle, M J; Birkinshaw, M; Croston, J H; Goodger, J L; Marshall, H L; Perlman, E S; Siemiginowska, A; Stawarz, L; Worrall, D M

    2015-01-01

    We report on deep Chandra observations of the nearby broad-line radio galaxy Pictor A, which we combine with new Australia Telescope Compact Array (ATCA) observations. The new X-ray data have a factor 4 more exposure than observations previously presented and span a 15-year time baseline, allowing a detailed study of the spatial, temporal and spectral properties of the AGN, jet, hotspot and lobes. We present evidence for further time variation of the jet, though the flare that we reported in previous work remains the most significantly detected time-varying feature. We also confirm previous tentative evidence for a faint counterjet. Based on the radio through X-ray spectrum of the jet and its detailed spatial structure, and on the properties of the counterjet, we argue that inverse-Compton models can be conclusively rejected, and propose that the X-ray emission from the jet is synchrotron emission from particles accelerated in the boundary layer of a relativistic jet. For the first time, we find evidence that...

  4. Chandra observations of Cygnus OB2

    CERN Document Server

    Wright, Nicholas J; Drew, Janet E; Vink, Jorick S

    2011-01-01

    Cygnus OB2 is the nearest example of a massive star forming region, containing over 50 O-type stars and hundreds of B-type stars. We have analyzed two Chandra pointings in Cyg OB2, detecting ~1700 X-ray sources, of which ~1450 are thought to be members of the association. Optical and near-IR photometry has been obtained for ~90% of these sources from recent deep Galactic plane surveys. We have performed isochrone fits to the near-IR color-magnitude diagram, deriving ages of 3.5(+0.75,-1.0) and 5.25(+1.5,-1.0) Myrs for sources in the two fields, both with considerable spreads around the pre-MS isochrones. The presence of a second population in the region, somewhat older than the present-day O-type stars, has been suggested by other authors and fits with the ages derived here. The fraction of sources with inner circumstellar disks (as traced by the K-band excess) is found to be very low, but appropriate for a population of age ~5 Myrs. We measure the stellar mass functions and find a power-law slope of Gamma = ...

  5. Intracranial aneurysms in twins: case report and review of the literature.

    Science.gov (United States)

    Leung, H K; Lam, Y; Cheng, K M; Chan, C M; Cheung, Y L

    2011-04-01

    Intracranial aneurysm in twins is a rare clinical disease entity. Only 15 cases have been described in the literature. We report on a pair of identical twins with intracranial aneurysms. One presented with subarachnoid haemorrhage; digital subtraction angiography showed a left posterior communicating artery aneurysm, which was treated by coiling. The patient's twin sister was called for screening, whereupon digital subtraction angiography revealed a right ophthalmic internal carotid artery aneurysm that was treated conservatively.

  6. Chandra and Swift observations of the quasi-persistent neutron star transient EXO 0748-676 in quiescence

    CERN Document Server

    Degenaar, N; Wolff, M T; Ray, P S; Wood, K S; Homan, J; Lewin, W H G; Jonker, P G; Cackett, E M; Miller, J M; Brown, E F

    2008-01-01

    The quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 recently returned to quiescence following an accretion outburst that lasted more than 24 years. We report on 2 Chandra and 5 Swift observations performed approximately one to two months after the transition from outburst to quiescence. The Chandra observations detect the source at a bolometric thermal luminosity of ~9.8E33 (d/7.4 kpc) erg/s. The spectrum is composed of a soft, thermal component that fits to a neutron star atmosphere model with kT^inf~0.11 keV, combined with a hard powerlaw tail that contributes ~20% of the total 0.5-10 keV quiescent flux. Several Swift observations were obtained 1-2 weeks before the Chandra observations and another series was taken approximately 2 weeks thereafter. The combined Chandra/Swift data set reveals a relatively hot and luminous quiescent system with a temperature of kT^inf~0.11-0.13 keV and a bolometric thermal luminosity that slightly decreased from ~1.6E34 to ~8.3E33 (d/7.4 kpc) er...

  7. Cataclysmic Variables and Other Compact Binaries in the Globular Cluster NGC 362: Candidates from Chandra and HST

    CERN Document Server

    Margon, Bruce; Homer, L; Pooley, D; Bassa, C G; Anderson, S F; Lewin, W H G; Verbunt, F; Kong, A K H; Plotkin, R M

    2010-01-01

    Highly sensitive and precise X-ray imaging from Chandra, combined with the superb spatial resolution of HST optical images, dramatically enhances our empirical understanding of compact binaries such as cataclysmic variables and low mass X-ray binaries, their progeny, and other stellar X-ray source populations deep into the cores of globular clusters. Our Chandra X-ray images of the globular cluster NGC 362 reveal 100 X-ray sources, the bulk of which are likely cluster members. Using HST color-magnitude and color-color diagrams, we quantitatively consider the optical content of the NGC 362 Chandra X-ray error circles, especially to assess and identify the compact binary population in this condensed-core globular cluster. Despite residual significant crowding in both X-rays and optical, we identify an excess population of H{\\alpha}-emitting objects that is statistically associated with the Chandra X-ray sources. The X-ray and optical characteristics suggest that these are mainly cataclysmic variables, but we al...

  8. Study of the twinned dendrite tip shape II: Experimental assessment

    Energy Technology Data Exchange (ETDEWEB)

    Salgado-Ordorica, M.A., E-mail: mario.salgado@novelis.com [Laboratoire de Simulation des Materiaux LSMX, Ecole Polytechnique Federale de Lausanne, Station 12, 1015 Lausanne (Switzerland); Burdet, P.; Cantoni, M. [Centre Interdisciplinaire de Microscopie Electronique CIME, Ecole Polytechnique Federale de Lausanne, Station 12, 1015 Lausanne (Switzerland); Rappaz, M. [Laboratoire de Simulation des Materiaux LSMX, Ecole Polytechnique Federale de Lausanne, Station 12, 1015 Lausanne (Switzerland)

    2011-08-15

    The favorable growth kinetics of twinned dendrites can be explained by their complex morphology, multiple side branching mechanisms, growth undercooling and tip morphology. Three models were proposed for the twinned dendrite tip shape: (i) a grooved tip satisfying the Smith condition at the triple line; (ii) a doublon , i.e. a double-tip dendrite that grows with a narrow and deep liquid channel in its center; and (iii) a pointed (or edgy) tip, with consideration of the solid-liquid interfacial energy anisotropy. In the first part of this work, phase field simulations of half a twinned dendrite with an appropriate boundary condition to reproduce the Smith condition supported the doublon conjecture, with a narrow liquid channel ending its solidification with the formation of small liquid droplets. In this part, experimental observations of twinned dendrite tips reveal the presence of a small, but well-defined, groove, thus definitely eliminating the edged tip hypothesis. Focused ion beam nanotomography and energy-dispersive spectroscopy chemical analysis in a transmission electron microscope reveal the existence of a positive solute gradient in a region localized within 2 {mu}m around the twin plane. In Al-Zn specimens, small particles aligned within the twin plane further support the doublon conjecture and the predicted formation of small liquid droplets below the doublon root.

  9. When You Are a Twin or Triplet

    Science.gov (United States)

    ... be a twin? Are you a twin and wonder why everyone thinks it's so special? It's fascinating ... the way the egg is fertilized when a woman becomes pregnant . In fraternal twins, two different eggs ...

  10. A Full Year's Chandra Exposure on SDSS Quasars from the Chandra Multiwavelength Project

    CERN Document Server

    Green, Paul J; Richards, G T; Barkhouse, W A; Constantin, A; Haggard, D; Karovska, M; Kim, D -W; Kim, M; Vikhlinin, A; Mossman, A; Silverman, J D; Anderson, S F; Kashyap, V; Wilkes, B J; Tananbaum, H

    2008-01-01

    We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey (SDSS) that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project (ChaMP). Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.23 QSOs detected, we find no evidence for evolution out to z~5 for either the X-ray photon index Gamma or for the ratio of optical/UV to X-ray flux alpha_ox. About 10% of detected QSOs are obscured (Nh>1E22), but the fraction might reach ~1/3 if most non-detections are absorbed. We confirm a significant correlation between alpha_ox and optical luminosity, but it flattens or disappears for fainter AGN alone. Gamma hardens significantly both towards higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in non-thermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and ...

  11. Twinning across the Developing World.

    Directory of Open Access Journals (Sweden)

    Jeroen Smits

    Full Text Available BACKGROUND: Until now, little was known about the variation in incidence of twin births across developing countries, because national representative data was lacking. This study provides the first comprehensive overview of national twinning rates across the developing world on the basis of reliable survey data. METHODS: Data on incidence of twinning was extracted from birth histories of women aged 15-49 interviewed in 150 Demographic and Health Surveys, held between 1987 and 2010 in 75 low and middle income countries. During the interview, information on all live births experienced by the women was recorded, including whether it was a singleton or multiple birth. Information was available for 2.47 million births experienced by 1.38 million women in a period of ten years before the interview. Twinning incidence was measured as the number of twin births per thousand births. Data for China were computed on the basis of published figures from the 1990 census. Both natural and age-standardized twinning rates are presented. RESULTS/CONCLUSIONS: The very low natural twinning rates of 6-9 per thousand births previously observed in some East Asian countries turn out to be the dominant pattern in the whole South and South-East Asian region. Very high twinning rates of above 18 per thousand are not restricted to Nigeria (until now seen as the world's twinning champion but found in most Central-African countries. Twinning rates in Latin America turn out to be as low as those in Asia. Changes over time are small and not in a specific direction. SIGNIFICANCE: We provide the most complete and comparable overview of twinning rates across the developing world currently possible.

  12. Twinning and heteropaternity in chimpanzees (Pan troglodytes).

    Science.gov (United States)

    Ely, John J; Frels, William I; Howell, Sue; Izard, M Kay; Keeling, Michale E; Lee, D Rick

    2006-05-01

    Unlike monozygotic (MZ) twins, dizygotic (DZ) twins develop from separate ova. The resulting twins can have different sires if the fertilizing sperm comes from different males. Routine paternity testing of a pair of same-sexed chimpanzee twins born to a female housed with two males indicated that the twins were sired by two different males. DNA typing of 22 short-tandem repeat (STR) loci demonstrated that these twins were not MZ twins but heteropaternal DZ twins. Reproductive data from 1926-2002 at five domestic chimpanzee colonies, including 52 twins and two triplets in 1,865 maternities, were used to estimate total twinning rates and the MZ and DZ components. The average chimpanzee MZ twinning rate (0.43%) equaled the average human MZ rate (0.48%). However, the chimpanzee DZ twinning rate (2.36%) was over twice the human average, and higher than all but the fertility-enhanced human populations of Nigeria. Similarly high twinning rates among African chimpanzees indicated that these estimates were not artifacts of captivity. Log-linear analyses of maternal and paternal effects on recurrent twinning indicated that females who twinned previously had recurrence risks five times greater than average, while evidence for a paternal twinning effect was weak. Chimpanzee twinning rates appear to be elevated relative to corresponding estimated human rates, making twinning and possibly heteropaternity more important features of chimpanzee reproductive biology than previously recognized.

  13. Twin Legacies: Victor and Vincent McKusick/Twin Studies: Twinning Rates I; Twinning Rates II; MZ Twin Discordance for Russell-Silver Syndrome; Twins' Language Skills/Headlines: Babies Born to Identical Twin Couples; Identity Exchange; Death of Princess Ashraf (Twin); Yahoo CEO Delivers Identical Twins.

    Science.gov (United States)

    Segal, Nancy L

    2016-04-01

    The lives of the illustrious monozygotic (MZ) twins, Victor A. and Vincent L. McKusick, are described. Victor earned the distinction as the 'Father of Medical Genetics', while Vincent was a legendary Chief Justice of the Maine Supreme Court. This dual biographical account is followed by two timely reports of twinning rates, a study of MZ twin discordance for Russell-Silver Syndrome (RSS) and a study of twins' language skills. Twin stories in the news include babies born to identical twin couples, a case of switched identity, the death of Princess Ashraf (Twin) and a new mother of twins who is also Yahoo's CEO.

  14. Estimating twin concordance for bivariate competing risks twin data

    DEFF Research Database (Denmark)

    Scheike, Thomas Harder; Holst, Klaus Kähler; von Bornemann Hjelmborg, Jacob

    2014-01-01

    For twin time-to-event data, we consider different concordance probabilities, such as the casewise concordance that are routinely computed as a measure of the lifetime dependence/correlation for specific diseases. The concordance probability here is the probability that both twins have experienced...... over time, and covariates may be further influential on the marginal risk and dependence structure. We establish the estimators large sample properties and suggest various tests, for example, for inferring familial influence. The method is demonstrated and motivated by specific twin data on cancer...... the event of interest. Under the assumption that both twins are censored at the same time, we show how to estimate this probability in the presence of right censoring, and as a consequence, we can then estimate the casewise twin concordance. In addition, we can model the magnitude of within pair dependence...

  15. Deeper Chandra Follow-up of Cygnus TeV Source Perpetuates Mystery

    CERN Document Server

    Butt, Y; Benaglia, P; Combi, J; Dame, T; Miniati, F; Romero, G; Butt, Yousaf; Drake, Jeremy; Benaglia, Paula; Combi, Jorge; Dame, Thomas; Miniati, Francesco; Romero, Gustavo

    2005-01-01

    A 50 ksec Chandra observation of the unidentified TeV source in Cygnus reported by the HEGRA collaboration reveals no obvious X-ray counterpart(s). 220 Point-like X-ray sources are detected within or nearby the extended TeV J2032+4130 source region, of which at least 30 are massive stars and 6 are known radio emitters. Based on the low X-ray and radio emissivity we favor a nucleonic rather than electronic origin of the very high energy gamma-ray flux and suspect it is related to the very massive and extremely powerful Cygnus OB2 stellar association.

  16. Confronting Twin Paradox Acceleration

    Science.gov (United States)

    Murphy, Thomas W.

    2016-05-01

    The resolution to the classic twin paradox in special relativity rests on the asymmetry of acceleration. Yet most students are not exposed to a satisfactory analysis of what exactly happens during the acceleration phase that results in the nonaccelerated observer's more rapid aging. The simple treatment presented here offers both graphical and quantitative solutions to the problem, leading to the correct result that the acceleration-induced age gap is 2Lβ years when the one-way distance L is expressed in light-years and velocity β ≡v/c .

  17. Holographic twin Higgs model.

    Science.gov (United States)

    Geller, Michael; Telem, Ofri

    2015-05-15

    We present the first realization of a "twin Higgs" model as a holographic composite Higgs model. Uniquely among composite Higgs models, the Higgs potential is protected by a new standard model (SM) singlet elementary "mirror" sector at the sigma model scale f and not by the composite states at m_{KK}, naturally allowing for m_{KK} beyond the LHC reach. As a result, naturalness in our model cannot be constrained by the LHC, but may be probed by precision Higgs measurements at future lepton colliders, and by direct searches for Kaluza-Klein excitations at a 100 TeV collider.

  18. Education in time: cohort differences in educational attainment in African-American twins.

    Directory of Open Access Journals (Sweden)

    Sarah L Szanton

    Full Text Available OBJECTIVES: Educational opportunities for African-Americans expanded throughout the 20(th century. Twin pairs are an informative population in which to examine changes in educational attainment because each twin has the same parents and childhood socioeconomic status. We hypothesized that correlation in educational attainment of older twin pairs would be higher compared to younger twin pairs reflecting changes in educational access over time and potentially reflecting a "ceiling effect" associated with Jim Crow laws and discrimination. METHODOLOGY AND PRINCIPAL FINDINGS: We used data from 211 same-sex twin pairs (98 identical, 113 fraternal in the Carolina African-American Twin Study of Aging who were identified through birth records. Participants completed an in-person interview. The twins were predominantly female (61%, with a mean age of 50 years (SD = 0.5. We found that older age groups had a stronger intra-twin correlation of attained educational level. Further analysis across strata revealed a trend across zygosity, with identical twins demonstrating more similar educational attainment levels than did their fraternal twin counterparts, suggesting a genetic influence. DISCUSSION: These findings suggest that as educational opportunities broadened in the 20th century, African-Americans gained access to educational opportunities that better matched their individual abilities.

  19. Transformation: From Twin to Individual

    Science.gov (United States)

    Magagna, Jeanne

    2007-01-01

    This article explores some of the complexities of psychotherapy with an identical twin. The difficulty of developing in psychotherapy while so much of what is oneself is located in the other twin will also be explored. The use of the countertransference as a therapeutic method will be considered as the young person develops her unique, separate…

  20. Hypertensive disorders in twin pregnancy

    NARCIS (Netherlands)

    J.G. Santema (Job); E. Koppelaar (Elin); H.C.S. Wallenburg (Henk)

    1995-01-01

    textabstractObjective: To compare the incidence and severity of pregnancy-induced hypertensive disorders in twin pregnancy and in singleton gestation. Study design: Case-control study in the setting of a University Hospital. Each pregnancy of a consecutive series of 187 twin pregnancies attending th

  1. Twin Studies of Atopic Dermatitis

    DEFF Research Database (Denmark)

    Elmose, Camilla; Thomsen, Simon Francis

    2015-01-01

    Aim. The aim of this study was to conduct a systematic review of population-based twin studies of (a) the concordance and heritability of AD and (b) the relationship between AD and asthma and, furthermore, to reinterpret findings from previous twin studies in the light of the emerging knowledge a...

  2. Twin Higgs WIMP Dark Matter

    CERN Document Server

    García, Isabel García; March-Russell, John

    2015-01-01

    Dark matter (DM) without a matter asymmetry is studied in the context of Twin Higgs (TH) theories in which the LHC naturalness problem is addressed. These possess a twin sector related to the Standard Model (SM) by a (broken) $\\mathbb{Z}_2$ symmetry, and interacting with the SM via a specific Higgs portal. We focus on the minimal realisation of the TH mechanism, the Fraternal Twin Higgs, with only a single generation of twin quarks and leptons, and $SU(3)'\\times SU(2)'$ gauge group. We show that a variety of natural twin-WIMP DM candidates are present (directly linked to the weak scale by naturalness), the simplest and most attractive being the $\\tau^\\prime$ lepton with a mass $m_{\\tau^\\prime} > m_{\\rm Higgs}/2$, although spin-1 $W^{\\prime\\pm}$ DM and multicomponent DM are also possible (twin baryons are strongly disfavoured by tuning). We consider in detail the dynamics of the possibly (meta)stable glueballs in the twin sector, the nature of the twin QCD phase transition, and possible new contributions to th...

  3. Nustar and Chandra Insight into the Nature of the 3-40 Kev Nuclear Emission in Ngc 253

    Science.gov (United States)

    Lehmer, Bret D.; Wik, Daniel R.; Hornschemeier, Ann E.; Ptak, Andrew; Antoniu, V.; Argo, M.K.; Bechtol, K.; Boggs, S.; Christensen, F.E.; Craig, W.W.; Hailey, C.J.; Harrison, F.A.; Krivonos, R.; Leyder, Jean-Christophe Xavier Georges; Maccarone, T.J.; Stern, D.; Venters, T.; Zezas, A.; Zhang, W.W.

    2013-01-01

    We present results from three nearly simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR) and Chandra monitoring observations between 2012 September 2 and 2012 November 16 of the local star-forming galaxy NGC 253. The 3-40 kiloelectron volt intensity of the inner approximately 20 arcsec (approximately 400 parsec) nuclear region, as measured by NuSTAR, varied by a factor of approximately 2 across the three monitoring observations. The Chandra data reveal that the nuclear region contains three bright X-ray sources, including a luminous (L (sub 2-10 kiloelectron volt) approximately few × 10 (exp 39) erg per s) point source located approximately 1 arcsec from the dynamical center of the galaxy (within the sigma 3 positional uncertainty of the dynamical center); this source drives the overall variability of the nuclear region at energies greater than or approximately equal to 3 kiloelectron volts. We make use of the variability to measure the spectra of this single hard X-ray source when it was in bright states. The spectra are well described by an absorbed (power-law model spectral fit value, N(sub H), approximately equal to 1.6 x 10 (exp 23) per square centimeter) broken power-law model with spectral slopes and break energies that are typical of ultraluminous X-ray sources (ULXs), but not active galactic nuclei (AGNs). A previous Chandra observation in 2003 showed a hard X-ray point source of similar luminosity to the 2012 source that was also near the dynamical center (Phi is approximately equal to 0.4 arcsec); however, this source was offset from the 2012 source position by approximately 1 arcsec. We show that the probability of the 2003 and 2012 hard X-ray sources being unrelated is much greater than 99.99% based on the Chandra spatial localizations. Interestingly, the Chandra spectrum of the 2003 source (3-8 kiloelectron volts) is shallower in slope than that of the 2012 hard X-ray source. Its proximity to the dynamical center and harder Chandra spectrum

  4. A Computational Discriminability Analysis on Twin Fingerprints

    Science.gov (United States)

    Liu, Yu; Srihari, Sargur N.

    Sharing similar genetic traits makes the investigation of twins an important study in forensics and biometrics. Fingerprints are one of the most commonly found types of forensic evidence. The similarity between twins’ prints is critical establish to the reliability of fingerprint identification. We present a quantitative analysis of the discriminability of twin fingerprints on a new data set (227 pairs of identical twins and fraternal twins) recently collected from a twin population using both level 1 and level 2 features. Although the patterns of minutiae among twins are more similar than in the general population, the similarity of fingerprints of twins is significantly different from that between genuine prints of the same finger. Twins fingerprints are discriminable with a 1.5%~1.7% higher EER than non-twins. And identical twins can be distinguished by examine fingerprint with a slightly higher error rate than fraternal twins.

  5. Sidewall morphology-dependent formation of multiple twins in Si nanowires.

    Science.gov (United States)

    Shin, Naechul; Chi, Miaofang; Filler, Michael A

    2013-09-24

    Precise placement of twin boundaries and stacking faults promises new opportunities to fundamentally manipulate the optical, electrical, and thermal properties of semiconductor nanowires. Here we report on the appearance of consecutive twin boundaries in Si nanowires and show that sidewall morphology governs their spacing. Detailed electron microscopy analysis reveals that thin {111} sidewall facets, which elongate following the first twin boundary (TB1), are responsible for deforming the triple-phase line and favoring the formation of the second twin boundary (TB2). While multiple, geometrically correlated defect planes are known in group III-V nanowires, our findings show that this behavior is also possible in group IV materials.

  6. Blocking effect of twin boundaries on partial dislocation emission from void surfaces.

    Science.gov (United States)

    Zhang, Lifeng; Zhou, Haofei; Qu, Shaoxing

    2012-03-02

    Recent discovery that nanoscale twin boundaries can be introduced in ultrafine-grained metals to improve strength and ductility has renewed interest in the mechanical behavior and deformation mechanisms of these nanostructured materials. By controlling twin boundary spacing, the effect of twin boundaries on void growth is investigated by using atomistic simulation method. The strength is significantly enhanced due to the discontinuous slip system associated with these coherent interfaces. Atomic-scale mechanisms underlying void growth, as well as the interaction between twin boundaries and the void, are revealed in details.

  7. Twin methodology in epigenetic studies

    DEFF Research Database (Denmark)

    Tan, Qihua; Christiansen, Lene; von Bornemann Hjelmborg, Jacob

    2015-01-01

    of diseases to molecular phenotypes in functional genomics especially in epigenetics, a thriving field of research that concerns the environmental regulation of gene expression through DNA methylation, histone modification, microRNA and long non-coding RNA expression, etc. The application of the twin method...... to molecular phenotypes offers new opportunities to study the genetic (nature) and environmental (nurture) contributions to epigenetic regulation of gene activity during developmental, ageing and disease processes. Besides the classical twin model, the case co-twin design using identical twins discordant...... for a trait or disease is becoming a popular and powerful design for epigenome-wide association study in linking environmental exposure to differential epigenetic regulation and to disease status while controlling for individual genetic make-up. It can be expected that novel uses of twin methods in epigenetic...

  8. Dramatically different dizygotic twins: will we include them in Research? Twin research reviews: congenital anomalies, mirror-image effects in conjoined twins, older mothers of twins; Twin statistics: 'Massachusetts, land of twins'; Tribute: Dr Victor A. McKusick.

    Science.gov (United States)

    Segal, Nancy L

    2008-10-01

    The increased frequency of interracial marriage is a likely source of unusual-looking dizygotic (DZ) twins. Some members of DZ twin pairs born to mixed-race couples inherit very different physical features from their parents. This raises several questions, such as: Will researchers wish to include such twins in their ongoing studies? Next, new twin research concerned with congenital anomalies, mirror-image effects in conjoined twins and older mothers of twins will be reviewed. New statistics on twinning rates in Massachusetts will also be summarized, followed by a tribute to the late medical geneticist Dr. Victor A. McKusick.

  9. Toward understanding twin–twin interactions in hcp metals: Utilizing multiscale techniques to characterize deformation mechanisms in magnesium

    Energy Technology Data Exchange (ETDEWEB)

    Morrow, B.M., E-mail: morrow@lanl.gov; Cerreta, E.K.; McCabe, R.J.; Tomé, C.N.

    2014-09-08

    The mechanical properties of hexagonal close-packed (hcp) metals depend heavily on both slip and twinning, and interactions between twins have important implications on hardening behavior. Electron backscatter diffraction (EBSD), as well as conventional, in situ straining, and high resolution (HR) transmission electron microscopy (TEM) are used to study these interactions. HRTEM is used to observe the twin boundary structure. Twin boundaries that deviate from the characteristic {101"¯2} twin planes at the macroscale are revealed to be a combination of perfect {101"¯2} boundaries and characteristic facets at the nanoscale. Faceting for tensile {101"¯2} twins adopts basal-prismatic (B-P) character, where basal planes in the matrix very nearly align with prism planes in the twin, or similarly, prism planes in the matrix align with basal planes in the twin. Such features play a significant role in twin boundaries, where faceting accommodates the large changes to boundary shape observed. in situ straining is used to study twin–twin interactions as they occur, and also detwinning behavior upon load reversal. During the initial interaction, considerable changes to the shape of the twin boundaries are observed, consistent with post-mortem analyses. On load reversal, detwinning is observed, and the interacting twins disengage from one another, however a change in boundary structure due to the interaction is retained.

  10. Mechanical twinning as stress indicator in fault rocks

    Science.gov (United States)

    Wenk, H.

    2011-12-01

    At low stresses and elevated temperatures rocks deform by dislocation movements and diffusion. At very high stresses they undergo brittle failure. For many minerals there is an intermediate regime where mechanical twinning occurs. This has been studied extensively in calcite (Turner, Griggs and Heard, GSA Mem. 1954) and also documented for quartz (Tullis, Science, 1972). In this study we use twinning microstructures to characterize rocks that were subjected to seismic stresses, specifically pseudotachylites and samples from the San Andreas Fault Observatory at Depth. For calcite in SAFOD samples, dislocation densities derived from TEM images as well as twin densities measured by optical microscopy, indicate stresses between 50 and 200 MPa. Similar residual stress magnitudes were obtained from preserved lattice distortion determined by synchrotron X-ray microdiffraction. Also quartz shows characteristic twin microstructures. Orientation maps with SEM-EBSD reveal that quartz associated with pseudotachylite veins is profusely twinned, similar to structures observed in quartz subjected to meteorite impacts. It suggests that local dynamic seismic stresses during earthquakes are responsible for Dauphiné twinning. Thus microstructures in minerals add information to constrain macroscopic conditions during faulting.

  11. ON THE OBSERVATION AND SIMULATION OF SOLAR CORONAL TWIN JETS

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jiajia; Wang, Yuming; Zhang, Quanhao [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, NO. 96, Jinzhai Road, Hefei, Anhui 230026 (China); Fang, Fang [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, 1234 Innovation Drive, Boulder, CO 80303 (United States); McIntosh, Scott W.; Fan, Yuhong [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

    2016-02-01

    We present the first observation, analysis, and modeling of solar coronal twin jets, which occurred after a preceding jet. Detailed analysis on the kinetics of the preceding jet reveals its blowout-jet nature, which resembles the one studied in Liu et al. However, the erupting process and kinetics of the twin jets appear to be different from the preceding one. Lacking detailed information on the magnetic fields in the twin jet region, we instead use a numerical simulation using a three-dimensional (3D) MHD model as described in Fang et al., and find that in the simulation a pair of twin jets form due to reconnection between the ambient open fields and a highly twisted sigmoidal magnetic flux, which is the outcome of the further evolution of the magnetic fields following the preceding blowout jet. Based on the similarity between the synthesized and observed emission, we propose this mechanism as a possible explanation for the observed twin jets. Combining our observation and simulation, we suggest that with continuous energy transport from the subsurface convection zone into the corona, solar coronal twin jets could be generated in the same fashion addressed above.

  12. Transformation twinning of Ni-Mn-Ga characterized with temperature-controlled atomic force microscopy.

    Science.gov (United States)

    Reinhold, Matthew; Watson, Chad; Knowlton, William B; Müllner, Peter

    2010-06-01

    The magnetomechanical properties of ferromagnetic shape memory alloy Ni-Mn-Ga single crystals depend strongly on the twin microstructure, which can be modified through thermomagnetomechanical training. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) were used to characterize the evolution of twin microstructures during thermomechanical training of a Ni-Mn-Ga single crystal. Experiments were performed in the martensite phase at 25 degrees C and in the austenite phase at 55 degrees C. Two distinct twinning surface reliefs were observed at room temperature. At elevated temperature (55 degrees C), the surface relief of one twinning mode disappeared while the other relief remained unchanged. When cooled back to 25 degrees C, the twin surface relief recovered. The relief persisting at elevated temperature specifies the positions of twin boundaries that were present when the sample was polished prior to surface characterization. AFM and MFM following thermomechanical treatment provide a nondestructive method to identify the crystallographic orientation of each twin and of each twin boundary plane. Temperature dependent AFM and MFM experiments reveal the twinning history thereby establishing the technique as a unique predictive tool for revealing the path of the martensitic and reverse transformations of magnetic shape memory alloys.

  13. 75 FR 7471 - Chandra Coffee and Rabun Boatworks, Complainants v. Georgia Power Company, Respondent; Notice of...

    Science.gov (United States)

    2010-02-19

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Chandra Coffee and Rabun Boatworks, Complainants v. Georgia Power Company... January 8, 2010, Chandra Coffee and Rabun Boatworks (Complainants) filed with the Federal...

  14. Chandra Finds Oxygen and Neon Ring in Ashes of Exploded Star

    Science.gov (United States)

    2000-01-01

    NASA's Chandra X-ray Observatory has revealed an expanding ring-like structure of oxygen and neon that was hurled into space by the explosion of a massive star. The image of E0102-72 provides unprecedented details about the creation and dispersal of heavy elements necessary to form planets like Earth. The results were reported by Professor Claude Canizares of the Massachusetts Institute of Technology (MIT), Cambridge, at the 195th national meeting of the American Astronomical Society in Atlanta, Ga. Drs. Kathryn Flanagan, David Davis, and John Houck of MIT collaborated with Canizares in this investigation. E0102-72 is the remnant of a supernova explosion located in our neighbor galaxy, the Small Magellanic Cloud, nearly 200,000 light years away. It was created by the explosion of a star that was more than ten times as massive as our Sun. We are seeing the aftermath of the explosion a thousand or more years after the outburst. Shock waves are heating gas to temperatures of nearly 10 million degrees, so it glows with X-rays that are detected by Chandra's instruments. By using the High Energy Transmission Grating Spectrometer (HETG), astronomers were able to pinpoint the distribution of each chemical element individually and measure the velocities of different parts of the expanding ring. They also show the shock wave in a kind of "freeze-frame," revealing the progressive heating of the stellar matter as it plows into the surrounding gas. This is the first time such detailed X-ray information has ever been obtained for a supernova remnant, and should provide critical clues to the nature of supernovas. The grating spectrometer, which was built by an MIT team led by Canizares, spreads the X-rays according to their wavelength, giving distinct images of the object at specific wavelengths characteristic of each chemical element. Small wavelength shifts caused by the Doppler effect are used to measure the expansion velocities of each element independently. "We've been

  15. Chandra Observations of Eight Sources Discovered by INTEGRAL

    Science.gov (United States)

    Tomsick, John A.; Krivonos, Roman; Wang, Qinan; Bodaghee, Arash; Chaty, Sylvain; Rahoui, Farid; Rodriguez, Jerome; Fornasini, Francesca M.

    2016-01-01

    We report on 0.3-10 keV observations with the Chandra X-ray Observatory of eight hard X-ray sources discovered within 8° of the Galactic plane by the International Gamma-ray Astrophysics Laboratory satellite. The short (˜5 ks) Chandra observations of the IGR source fields have yielded very likely identifications of X-ray counterparts for three of the IGR sources: IGR J14091-6108, IGR J18088-2741, and IGR J18381-0924. The first two have very hard spectra in the Chandra band that can be described by a power law with photon indices of Γ = 0.6 ± 0.4 and -{0.7}-0.3+0.4, respectively (90% confidence errors are given), and both have a unique near-IR counterpart consistent with the Chandra position. IGR J14091-6108 also displays a strong iron line and a relatively low X-ray luminosity, and we argue that the most likely source type is a cataclysmic variable (CV), although we do not completely rule out the possibility of a high mass X-ray binary. IGR J18088-2741 has an optical counterpart with a previously measured 6.84 hr periodicity, which may be the binary orbital period. We also detect five cycles of a possible 800-950 s period in the Chandra light curve, which may be the compact object spin period. We suggest that IGR J18088-2741 is also most likely a CV. For IGR J18381-0924, the spectrum is intrinsically softer with {{Γ }}={1.5}-0.4+0.5, and it is moderately absorbed, NH = (4 ± 1) × 1022 cm-2. There are two near-IR sources consistent with the Chandra position, and they are both classified as galaxies, making it likely that IGR J18381-0924 is an active galactic nucleus. For the other five IGR sources, we provide lists of nearby Chandra sources, which may be used along with further observations to identify the correct counterparts, and we discuss the implications of the low inferred Chandra count rates for these five sources.

  16. Chandra x-ray results on v426 ophiuchi

    Directory of Open Access Journals (Sweden)

    Lee Homer

    2004-01-01

    Full Text Available De las observaciones de 45 ks de Chandra de V426 Oph hemos obtenido espectros de rayos X de alta resoluci on con relaci on se~nal-a-ruido moderada, y una curva de luz no interrumpida de buena calidad. Los espectros se adaptan razonablemente a un modelo de ujo de enfriamiento, similar a EX Hya y U Gem. Nuestro an alisis de las curvas de luz de Chandra y las adicionales de rayos X/ optico revela una modulaci on persistente a 4.2 hr desde 1988 hasta 2003, probablemente el per odo de giro de la enana blanca, indicando una naturaleza polar intermedia para V426 Oph.

  17. Twins and Kindergarten Separation: Divergent Beliefs of Principals, Teachers, Parents, and Twins

    Science.gov (United States)

    Gordon, Lynn Melby

    2015-01-01

    Should principals enforce mandatory separation of twins in kindergarten? Do school separation beliefs of principals differ from those of teachers, parents of twins, and twins themselves? This survey questioned 131 elementary principals, 54 kindergarten teachers, 201 parents of twins, and 112 twins. A majority of principals (71%) believed that…

  18. First Results from the 7 Ms Chandra Deep Field-South Survey: A Good Hard Look at Growing Supermassive Black Holes in the Distant Universe

    Science.gov (United States)

    Brandt, William; Chandra Deep Fields Team

    2017-01-01

    Sensitive cosmic X-ray surveys with the Chandra, XMM-Newton, and now NuSTAR observatories have revolutionized our ability to find and study distant active galactic nuclei (AGNs), the main sites of supermassive black hole growth in the Universe. I will describe some recent discoveries about the demographics, physics, and ecology of distant AGNs coming from the deepest Chandra survey to date, the 7 Ms Chandra Deep Field-South. Some specific topics covered will include (1) robust X-ray spectral and variability characterization of the AGNs producing most of cosmic accretion power; (2) the demographics of AGNs in the first galaxies as revealed by direct detection and stacking; and (3) AGN/galaxy interactions as investigated via the host properties of X-ray AGNs. I will also briefly describe other remarkable discoveries coming from this survey; e.g., measurements of the evolving X-ray binary populations of normal and starburst galaxies.

  19. Best Practices for Twin Placement in School

    Science.gov (United States)

    Lacina, Jan

    2012-01-01

    The children's book "Two Is for Twins" celebrates twins and illustrates the many "twos" in a child's world. The uniqueness of twos does not have to mean separate classrooms for twins in child development programs, preschool, or elementary school settings. With recent dramatic increases in the US twin population, how should educators address the…

  20. Paternal age and telomere length in twins

    DEFF Research Database (Denmark)

    Hjelmborg, Jacob B; Dalgård, Christine; Mangino, Massimo

    2015-01-01

    . Based on two independent (discovery and replication) twin studies, comprising 889 twin pairs, we show an increase in the resemblance of leukocyte telomere length between dizygotic twins of older fathers, which is not seen in monozygotic twins. This phenomenon might result from a paternal age...

  1. Twin Higgs Asymmetric Dark Matter.

    Science.gov (United States)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  2. Twin methodology in epigenetic studies.

    Science.gov (United States)

    Tan, Qihua; Christiansen, Lene; von Bornemann Hjelmborg, Jacob; Christensen, Kaare

    2015-01-01

    Since the final decades of the last century, twin studies have made a remarkable contribution to the genetics of human complex traits and diseases. With the recent rapid development in modern biotechnology of high-throughput genetic and genomic analyses, twin modelling is expanding from analysis of diseases to molecular phenotypes in functional genomics especially in epigenetics, a thriving field of research that concerns the environmental regulation of gene expression through DNA methylation, histone modification, microRNA and long non-coding RNA expression, etc. The application of the twin method to molecular phenotypes offers new opportunities to study the genetic (nature) and environmental (nurture) contributions to epigenetic regulation of gene activity during developmental, ageing and disease processes. Besides the classical twin model, the case co-twin design using identical twins discordant for a trait or disease is becoming a popular and powerful design for epigenome-wide association study in linking environmental exposure to differential epigenetic regulation and to disease status while controlling for individual genetic make-up. It can be expected that novel uses of twin methods in epigenetic studies are going to help with efficiently unravelling the genetic and environmental basis of epigenomics in human complex diseases.

  3. Five Years of Stereo Magnetospheric Imaging by TWINS

    Science.gov (United States)

    Goldstein, J.; McComas, D. J.

    2013-12-01

    Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) is the first stereoscopic magnetospheric imager. TWINS is a NASA Explorer Mission of Opportunity performing simultaneous energetic neutral atom (ENA) imaging from two widely-separated Molniya orbits on two different spacecraft, and providing nearly continuous coverage of magnetospheric ENA emissions. The ENA imagers observe energetic neutrals produced from global ion populations, over a broad energy range (1-100 keV/u) with high angular (4∘×4∘) and time (about 1-minute) resolution. TWINS distinguishes hydrogen ENAs from oxygen ENAs. Each TWINS spacecraft also carries a Lyman- α geocoronal imager to monitor the cold exospheric hydrogen atoms that produce ENAs from ions via charge exchange. Complementing the imagers are detectors that measure the local charged particle environment around the spacecraft. During its first five years of science operations, TWINS has discovered new global properties of geospace plasmas and neutrals, fostered understanding of causal relationships, confirmed theories and predictions based on in situ data, and yielded key insights needed to improve geospace models. Analysis and modeling of TWINS data have: (1) obtained continuous (main phase through recovery) global ion spectra, (2) revealed a previously unknown local-time dependence of global pitch angle, (3) developed quantitative determination of ion fluxes from low altitude ENAs (4) determined dynamic connections between local pitch angle and global ion precipitation, (5) confirmed local-time dependence of precipitating ion temperature, (6) imaged global dynamic heating of the magnetosphere, (7) explained why the oxygen ring current survives longer into recovery than hydrogen, and (8) revealed new global exospheric density features and their influence upon ring current decay rates. Over the next several years of the solar cycle, TWINS observations of three-dimensional (3D) global ion dynamics, composition, origins and

  4. The vector-like twin Higgs

    Science.gov (United States)

    Craig, Nathaniel; Knapen, Simon; Longhi, Pietro; Strassler, Matthew

    2016-07-01

    We present a version of the twin Higgs mechanism with vector-like top partners. In this setup all gauge anomalies automatically cancel, even without twin leptons. The matter content of the most minimal twin sector is therefore just two twin tops and one twin bottom. The LHC phenomenology, illustrated with two example models, is dominated by twin glueball decays, possibly in association with Higgs bosons. We further construct an explicit four-dimensional UV completion and discuss a variety of UV completions relevant for both vector-like and fraternal twin Higgs models.

  5. The Vector-like Twin Higgs

    CERN Document Server

    Craig, Nathaniel; Longhi, Pietro; Strassler, Matthew

    2016-01-01

    We present a version of the twin Higgs mechanism with vector-like top partners. In this setup all gauge anomalies automatically cancel, even without twin leptons. The matter content of the most minimal twin sector is therefore just two twin tops and one twin bottom. The LHC phenomenology, illustrated with two example models, is dominated by twin glueball decays, possibly in association with Higgs bosons. We further construct an explicit four-dimensional UV completion and discuss a variety of UV completions relevant for both vector-like and fraternal twin Higgs models.

  6. Failure of vincristine induce twinning

    Science.gov (United States)

    Binder, M.

    1984-01-01

    Mammalian ova do not contain axes of symmetry from which are derived embryonic axes of symmetry. Mammalian axis determination is an early embryologic event occurring at about the time that monozygous twinning in mice. (Kaufma MH & O'Shea KS, 1978, Nature 276:707) and an attempt was made to reproduce their work in several strains of mice. Over 3200 embryos were examined without any twins being found. To rule out the possibility that vincristine caused twinning plus some lethal malformation (with subsequent resorption of the embryo) the embryos were examined 36-60 hours after vincristine treatment.

  7. Chandra Observations of MRK 273 Unveiling the Central AGN and the Extended Hot Gas Halo

    CERN Document Server

    Xia, X Y; Mao, S; Boller, T; Deng, Z G; Wu, H; Boller, Th.

    2001-01-01

    We report X-ray observations of the field containing the ultraluminous IRAS galaxy Mrk~273 Using the ACIS-S3 instrument on board Chandra. The high resolution X-ray image, for the first time, reveals a compact hard X-ray nucleus in Mrk~273. Its X-ray energy distribution is well described by a heavily obscured power-law spectrum plus a narrow $\\Feka$ emission line at 6.4 keV. The neutral hydrogen column density is about $4\\times10^{23}\\cm^{-2}$, implying an absorption -corrected X-ray luminosity (0.1--10 keV) for the nucleus of $\\Lx\\approx 6.5\\times 10^{43} \\ergs$. There are also bright soft X-ray clumps and diffuse soft X-ray emissions surrounding the central hard X-ray nucleus within the $10\\arcsec$ of the nuclear region. Its spectrum can be fitted by a MEKAL thermal model with temperature of about 0.8 keV and high metallicity ($Z\\sim 1.5Z_\\odot$) plus emission lines from $\\alpha$ elements and ions. Further outside the central region, the Chandra observations reveal a very extended hot gas halo with a project...

  8. Chandra view of the dynamically young cluster of galaxies A1367 II. point sources

    CERN Document Server

    Sun, M

    2002-01-01

    A 40 ks \\emph{Chandra} ACIS-S observation of the dynamically young cluster A1367 yields new insights on X-ray emission from cluster member galaxies. We detect 59 point-like sources in the ACIS field, of which 8 are identified with known cluster member galaxies. Thus in total 10 member galaxies are detected in X-rays when three galaxies discussed in paper I (Sun & Murray 2002; NGC 3860 is discussed in both papers) are included. The superior spatial resolution and good spectroscopy capability of \\chandra allow us to constrain the emission nature of these galaxies. Central nuclei, thermal halos and stellar components are revealed in their spectra. Four new low luminosity nuclei (LLAGN) are found, including an absorbed one (NGC 3861). This discovery makes the LLAGN/AGN content in this part of A1367 very high ($\\sim$ 20%). Thermal halos with temperatures around 0.5 - 0.8 keV are revealed in the spectra of two elliptical galaxies NGC 3842 and NGC 3837, which suggests that galactic coronae can survive in cluster...

  9. Chandra observations of the hyper-luminous infrared galaxy IRAS F15307+3252

    CERN Document Server

    Hlavacek-Larrondo, J; Hogan, M T; Gendron-Marsolais, M -L; Edge, A C; Fabian, A C; Russell, H R; Iwasawa, K; Mezcua, M

    2016-01-01

    Hyper-luminous infrared galaxies (HyLIRGs) lie at the extreme luminosity end of the IR galaxy population with L_IR>10^13L_sun. They are thought to be closer counterparts of the more distant sub-mm galaxies, and should therefore be optimal targets to study the most massive systems in formation. We present deep Chandra observations of IRAS F15307+3252 (100 ks), a classical HyLIRG located at z=0.93, hosting a radio-loud AGN (L_1.4GHz=3.5*10^25 W/Hz). The Chandra X-ray images reveal extended, asymmetric X-ray emission in the soft 0.3-2.0 keV band, extending to 160 kpc in the southern direction. VLA observations at 1.4 GHz and 8.4 GHz reveal no radio counterpart to this extended X-ray emission. The emission is therefore most likely of thermal origin originating from a hot intragroup or intracluster medium virializing in the potential. The temperature (2 keV) and bolometric X-ray luminosity (3*10^43 erg/s) of the gas follow the expected L_X-ray-T correlation for groups and clusters of galaxies. We also find that th...

  10. Applications for edge detection techniques using Chandra and XMM-Newton data: galaxy clusters and beyond

    Science.gov (United States)

    Walker, S. A.; Sanders, J. S.; Fabian, A. C.

    2016-09-01

    The unrivalled spatial resolution of the Chandra X-ray observatory has allowed many breakthroughs to be made in high-energy astrophysics. Here we explore applications of Gaussian gradient magnitude (GGM) filtering to X-ray data, which dramatically improves the clarity of surface brightness edges in X-ray observations, and maps gradients in X-ray surface brightness over a range of spatial scales. In galaxy clusters, we find that this method is able to reveal remarkable substructure behind the cold fronts in Abell 2142 and Abell 496, possibly the result of Kelvin-Helmholtz instabilities. In Abell 2319 and Abell 3667, we demonstrate that the GGM filter can provide a straightforward way of mapping variations in the widths and jump ratios along the lengths of cold fronts. We present results from our ongoing programme of analysing the Chandra and XMM-Newton archives with the GGM filter. In the Perseus cluster, we identify a previously unseen edge around 850 kpc from the core to the east, lying outside a known large-scale cold front, which is possibly a bow shock. In MKW 3s we find an unusual `V' shape surface brightness enhancement starting at the cluster core, which may be linked to the AGN jet. In the Crab nebula a new, moving feature in the outer part of the torus is identified which moves across the plane of the sky at a speed of ˜0.1c, and lies much further from the central pulsar than the previous motions seen by Chandra.

  11. A CHANDRA OBSERVATION OF THE ECLIPSING WOLF-RAYET BINARY CQ Cep

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Stephen L. [CASA, Univ. of Colorado, Boulder, CO 80309-0389 (United States); Zhekov, Svetozar A. [Space Research and Technology Institute, Akad. G. Bonchev Str., Sofia, 1113 (Bulgaria); Güdel, Manuel [Dept. of Astrophysics, Univ. of Vienna, Türkenschanzstr. 17, A-1180 Vienna (Austria); Schmutz, Werner, E-mail: stephen.skinner@colorado.edu, E-mail: szhekov@space.bas.bg, E-mail: manuel.guedel@univie.ac.at, E-mail: werner.schmutz@pmodwrc.ch [Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center (PMOD/WRC), Dorfstrasse 33, CH-7260 Davos Dorf (Switzerland)

    2015-02-01

    The short-period (1.64 d) near-contact eclipsing WN6+O9 binary system CQ Cep provides an ideal laboratory for testing the predictions of X-ray colliding wind shock theory at close separation where the winds may not have reached terminal speeds before colliding. We present results of a Chandra X-ray observation of CQ Cep spanning ∼1 day during which a simultaneous Chandra optical light curve was acquired. Our primary objective was to compare the observed X-ray properties with colliding wind shock theory, which predicts that the hottest shock plasma (T ≳ 20 MK) will form on or near the line-of-centers between the stars. The X-ray spectrum is strikingly similar to apparently single WN6 stars such as WR 134 and spectral lines reveal plasma over a broad range of temperatures T ∼ 4-40 MK. A deep optical eclipse was seen as the O star passed in front of the Wolf-Rayet star and we determine an orbital period P {sub orb} = 1.6412400 d. Somewhat surprisingly, no significant X-ray variability was detected. This implies that the hottest X-ray plasma is not confined to the region between the stars, at odds with the colliding wind picture and suggesting that other X-ray production mechanisms may be at work. Hydrodynamic simulations that account for such effects as radiative cooling and orbital motion will be needed to determine if the new Chandra results can be reconciled with the colliding wind picture.

  12. Twin-to-twin transfusion syndrome : from placental anastomoses to long-term outcome

    NARCIS (Netherlands)

    Lopriore, Enrico

    2006-01-01

    Twin-to-twin transfusion syndrome (TTTS) is a severe complication of monochorionic twin pregnancies associated with high perinatal mortality and morbidity rates. Placental vascular anastomoses, almost invariably present in monochorionic placentas, are the essential anatomical substrate for the devel

  13. The 3 Ms Chandra Campaign on Sgr A*: A Census of X-ray Flaring Activity from the Galactic Center

    CERN Document Server

    Neilsen, J; Gammie, C; Dexter, J; Markoff, S; Haggard, D; Nayakshin, S; Wang, Q D; Grosso, N; Porquet, D; Tomsick, J A; Degenaar, N; Fragile, P C; Houck, J C; Wijnands, R; Miller, J M; Baganoff, F K

    2013-01-01

    Over the last decade, X-ray observations of Sgr A* have revealed a black hole in a deep sleep, punctuated roughly once per day by brief flares. The extreme X-ray faintness of this supermassive black hole has been a long-standing puzzle in black hole accretion. To study the accretion processes in the Galactic Center, Chandra (in concert with numerous ground- and space-based observatories) undertook a 3 Ms campaign on Sgr A* in 2012. With its excellent observing cadence, sensitivity, and spectral resolution, this Chandra X-ray Visionary Project (XVP) provides an unprecedented opportunity to study the behavior of the closest supermassive black hole. We present a progress report from our ongoing study of X-ray flares, including the brightest flare ever seen from Sgr A*. Focusing on the statistics of the flares and the quiescent emission, we discuss the physical implications of X-ray variability in the Galactic Center.

  14. Cosmological constraints from Chandra observations of galaxy clusters.

    Science.gov (United States)

    Allen, Steven W

    2002-09-15

    Chandra observations of rich, relaxed galaxy clusters allow the properties of the X-ray gas and the total gravitating mass to be determined precisely. Here, we present results for a sample of the most X-ray luminous, dynamically relaxed clusters known. We show that the Chandra data and independent gravitational lensing studies provide consistent answers on the mass distributions in the clusters. The mass profiles exhibit a form in good agreement with the predictions from numerical simulations. Combining Chandra results on the X-ray gas mass fractions in the clusters with independent measurements of the Hubble constant and the mean baryonic matter density in the Universe, we obtain a tight constraint on the mean total matter density of the Universe, Omega(m), and an interesting constraint on the cosmological constant, Omega(Lambda). We also describe the 'virial relations' linking the masses, X-ray temperatures and luminosities of galaxy clusters. These relations provide a key step in linking the observed number density and spatial distribution of clusters to the predictions from cosmological models. The Chandra data confirm the presence of a systematic offset of ca. 40% between the normalization of the observed mass-temperature relation and the predictions from standard simulations. This finding leads to a significant revision of the best-fit value of sigma(8) inferred from the observed temperature and luminosity functions of clusters.

  15. Chandra: Ten Years of Amazing Science with a Great Observatory

    Science.gov (United States)

    Weisskopf, Martin C.

    2009-01-01

    We review briefly review the history of the development of the Chandra X-Ray Observatory, highlighting certain details that many attendees of this Conference might not be aware of. We then present a selection of scientific highlights of the first 10 years of this remarkable and unique mission.

  16. The Chandra X-Ray Observatory Radiation Environmental Model Update

    Science.gov (United States)

    Blackwell, William C.; Minow, Joseph I.; ODell, Stephen L.; Cameron, Robert A.; Virani, Shanil N.

    2003-01-01

    CRMFLX (Chandra Radiation Model of ion FLUX) is a radiation environment risk mitigation tool for use as a decision aid in planning the operation times for Chandra's Advanced CCD Imaging Spectrometer (ACIS) detector. The accurate prediction of the proton flux environment with energies of 100 - 200 keV is needed in order to protect the ACIS detector against proton degradation. Unfortunately, protons of this energy are abundant in the region of space where Chandra must operate. In addition, on-board particle detectors do not measure proton flux levels of the required energy range. CRMFLX is an engineering environment model developed to predict the proton flux in the solar wind, magnetosheath, and magnetosphere phenomenological regions of geospace. This paper describes the upgrades to the ion flux databases for the magnetosphere, magnetosheath, and solar wind regions. These data files were created by using Geotail and Polar spacecraft flux measurements only when the Advanced Composition Explorer (ACE) spacecraft's 0.14 MeV particle flux was below a threshold value. This new database allows for CRMFLX output to be correlated with both the geomagnetic activity level, as represented by the Kp index, as well as with solar proton events. Also, reported in this paper are results of analysis leading to a change in Chandra operations that successfully mitigates the false trigger rate for autonomous radiation events caused by relativistic electron flux contamination of proton channels.

  17. Romanticism or Reality? An Exploration of Frances Mary Hendry's "Chandra."

    Science.gov (United States)

    Johnson, Jilaine

    This paper singles out a novel written for children about India, "Chandra" (1995) by Frances Mary Hendry, as a powerful and useful novel to present to today's 11 to 14 year old students. The paper contends that the novel allows students to explore and consider different value systems, challenges them to become aware of prejudice and the…

  18. An Introduction to the Chandra Carina Complex Project

    CERN Document Server

    Townsley, Leisa K; Corcoran, Michael F; Feigelson, Eric D; Gagné, Marc; Montmerle, Thierry; Oey, M S; Smith, Nathan; Garmire, Gordon P; Getman, Konstantin V; Povich, Matthew S; Evans, Nancy Remage; Nazé, Yaël; Parkin, E R; Preibisch, Thomas; Wang, Junfeng; Wolk, Scott J; Chu, You-Hua; Cohen, David H; Gruendl, Robert A; Hamaguchi, Kenji; King, Robert R; Mac Low, Mordecai-Mark; McCaughrean, Mark J; Moffat, Anthony F J; Oskinova, L M; Pittard, Julian M; Stassun, Keivan G; ud-Doula, Asif; Walborn, Nolan R; Waldron, Wayne L; Churchwell, Ed; Nichols, J S; Owocki, Stanley P; Schulz, N S

    2011-01-01

    The Great Nebula in Carina provides an exceptional view into the violent massive star formation and feedback that typifies giant HII regions and starburst galaxies. We have mapped the Carina star-forming complex in X-rays, using archival Chandra data and a mosaic of 20 new 60ks pointings using the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer, as a testbed for understanding recent and ongoing star formation and to probe Carina's regions of bright diffuse X-ray emission. This study has yielded a catalog of properties of >14,000 X-ray point sources; >9800 of them have multiwavelength counterparts. Using Chandra's unsurpassed X-ray spatial resolution, we have separated these point sources from the extensive, spatially-complex diffuse emission that pervades the region; X-ray properties of this diffuse emission suggest that it traces feedback from Carina's massive stars. In this introductory paper, we motivate the survey design, describe the Chandra observations, and present some simple results, pr...

  19. Highlights and Discoveries from the Chandra X-ray Observatory

    CERN Document Server

    Tananbaum, H; Tucker, W; Wilkes, B; Edmonds, P

    2014-01-01

    Within 40 years of the detection of the first extrasolar X-ray source in 1962,NASA's Chandra X-ray Observatory has achieved an increase in sensitivity of 10 orders of magnitude, comparable to the gain in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. Chandra is unique in its capabilities for producing sub-arcsecond X-ray images with 100-200 eV energy resolution for energies in the range 0.08Chandra mission provides a long observing baseline with stable and well-calibrated instruments, enabling temporal studies over time-scales from milliseconds to years. In this report we present a selection of highlights that illustrate how observations using Chandra, sometimes alone, but often in conjunction with other telescopes, have deepened, and in some instances revolutionized, our understanding ...

  20. Highlights and discoveries from the Chandra X-ray Observatory

    Science.gov (United States)

    Tananbaum, H.; Weisskopf, M. C.; Tucker, W.; Wilkes, B.; Edmonds, P.

    2014-06-01

    Within 40 years of the detection of the first extra-solar x-ray source in 1962, NASA's Chandra X-ray Observatory has achieved an increase in sensitivity of 10 orders of magnitude, comparable to the gain in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. Chandra is unique in its capabilities for producing sub-arcsecond x-ray images with 100-200 eV energy resolution for energies in the range 0.08 cosmic phenomena. The extended Chandra mission provides a long observing baseline with stable and well-calibrated instruments, enabling temporal studies over timescales from milliseconds to years. In this report we present a selection of highlights that illustrate how observations using Chandra, sometimes alone, but often in conjunction with other telescopes, have deepened, and in some instances revolutionized, our understanding of topics as diverse as protoplanetary nebulae; massive stars; supernova explosions; pulsar wind nebulae; the superfluid interior of neutron stars; accretion flows around black holes; the growth of supermassive black holes and their role in the regulation of star formation and growth of galaxies; impacts of collisions, mergers, and feedback on growth and evolution of groups and clusters of galaxies; and properties of dark matter and dark energy.

  1. Discordant Epilepsy in Monozygous Twins

    OpenAIRE

    2001-01-01

    Twelve monozygotic twins, discordant for epilepsy, were analysed for nonhereditary etiological factors by clinical history, MRI, and quantitative brain volume studies at the Brain Research Institute, University of Melbourne, Victoria, Australia.

  2. Simultaneous Intussusception in Monozygotic Twins

    Directory of Open Access Journals (Sweden)

    Mete Kaya

    2014-12-01

    Full Text Available In this case report, it was aimed to present the simultaneously occurring intussusception in the monozygotic twins. In addition to genetic predisposition, environmental factors has been hypothesized to be responsible for the development of the disease.

  3. Chandra Observes Cosmic Traffic Pile-Up In Energetic Quasar Jet

    Science.gov (United States)

    2000-11-01

    Using the unrivaled high resolution of NASA's Chandra X-ray Observatory, astronomers have seen important new details in the powerful jet shooting from the quasar 3C273. This research, coupled with optical and radio data, may reveal how these very high velocity jets are driven from the supermassive black holes that scientists believe lurk in the center of quasars. "For the first time, Chandra has given us an X-ray view into the area between 3C273's core and the beginning of the jet," says MIT's Herman Marshall, lead author on the paper submitted to Astrophysical Journal Letters. "Instead of being void of X-ray emission, Chandra has enabled us to detect a faint, but definite, stream of energy." The high-powered jets driven from quasars, often at velocities very close to the speed of light, have long been perplexing for scientists. Instead of seeing a smooth stream of material driven from the core of the quasar, most optical, radio, and earlier X-ray observations have revealed inconsistent, "lumpy" clouds of gas. This newly discovered continuous X-ray flow in 3C273 from the core to the jet may reveal insight on the physical processes that power these jets. Scientists would like to learn why matter is violently ejected from the quasar's core, then appears to suddenly slow down. "If there is a slower car in front on a highway, a faster one from behind will eventually catch up and maybe cause a wreck," says Marshall. "If the jet flow velocity changes, then gas shocks may result, which are akin to car collisions. These gigantic clouds of high-energy electrons, now seen in X rays with Chandra, may indeed be the result of some sort of cosmic traffic pile-up." The X-ray power produced in one of these pile-ups is tremendous. For example, the X-ray output of the first knot in the jet is greater than that of most Seyfert galaxies, which are thought to be powered by supermassive black holes. The abundance of X-ray emission suggests that large amounts of energy may also be

  4. Hypertensive disorders in twin pregnancy

    OpenAIRE

    Santema, Job; Koppelaar, Elin; Wallenburg, Henk

    1995-01-01

    textabstractObjective: To compare the incidence and severity of pregnancy-induced hypertensive disorders in twin pregnancy and in singleton gestation. Study design: Case-control study in the setting of a University Hospital. Each pregnancy of a consecutive series of 187 twin pregnancies attending the antenatal clinic and booked before a gestational age of 24 weeks was matched for maternal age, parity, and gestational age at delivery with a singleton pregnancy delivered in the same year. Prima...

  5. The Danish political twin study

    DEFF Research Database (Denmark)

    Klemmensen, Robert; Hobolt, Sara B; Dinesen, Peter Thisted

    2012-01-01

    We compare a recent Danish twin survey on political attitudes and behaviors to a nationally representative survey covering similar topics. We find very similar means and variances for most of our constructed scales of political attitudes and behaviors in the two surveys, although even small...... differences tend to be statistically significant due to sample size. This suggests that the twin study can be used to make inferences on the heritability of several political traits in the Danish population....

  6. Looking at Dauphiné twins in vein quartz as a potential paleostress indicator

    Science.gov (United States)

    Sintubin, Manuel; Wenk, Hans-Rudolf

    2013-04-01

    Paleostress studies commonly call upon (1) a fault slip data inversion technique, (2) a calcite twin stress inversion technique, (3) recrystallized grain size piezometry for quartz, or (4) direct measurements of residual lattice strain. Recent advances in orientation imaging microscopy (OIM) using electron backscatter diffraction (EBSD) on a scanning electron microscope (SEM) have revealed that Dauphiné twinning is very common in quartz in naturally deformed quartz-bearing rocks in a wide range of tectonometamorphic conditions. It has long been known that mechanical Dauphiné twinning in quartz can be stress-induced. Based on the results of an extensive EBSD-OIM analysis on vein quartz, taken from well-studied early to late-orogenic veins in the High-Ardenne slate belt (Germany, Belgium), we explore the potential use of mechanical Dauphiné twins as a paleostress indicator, possibly completing our toolbox for reconstructing paleostresses in the Earth's crust. The vein quartz studied precipitated in low-grade tectonometamorphic conditions (~200-400°C), typical for the brittle-plastic transition zone at the base of the seismogenic crust (~7-15km). Quartz has only been weakly affected by low to moderate temperature (200 to 400°C) crystal-plastic deformation. The samples show grains with a high concentration of Dauphiné twin boundaries and others free of twin boundaries, thus being untwinned or completely twinned. This pattern depends on the crystallographic orientation. Twin boundaries are arrested by grain or subgrain boundaries, suggesting that Dauphiné twinning occurred on a pre-existing fabric that resulted from crystal-plastic deformation. An analysis of the orientation distribution of the rhombs in the twinned variant domains of individual quartz (sub-)grains reveals a particular preferred orientation of the poles to rhombs. We will discuss the possible significance of these observations with respect to paleostresses that may have caused the mechanical

  7. The Qingdao Twin Registry: a status update.

    Science.gov (United States)

    Duan, Haiping; Ning, Feng; Zhang, Dongfeng; Wang, Shaojie; Zhang, Dong; Tan, Qihua; Tian, Xiaocao; Pang, Zengchang

    2013-02-01

    In 1998, the Qingdao Twin Registry was initiated as the main part of the Chinese National Twin Registry. By 2005, a total of 10,655 twin pairs had been recruited. Since then new twin cohorts have been sampled, with one longitudinal cohort of adolescent twins selected to explore determinants of metabolic disorders and health behaviors during puberty and young adulthood. Adult twins have been sampled for studying heritability of multiple phenotypes associated with metabolic disorders. In addition, an elderly twin cohort has been recruited with a focus on genetic studies of aging-related phenotypes using twin modeling and genome-wide association analysis. Cross-cultural collaborative studies have been carried out between China, Denmark, Finland, and US cohorts. Ongoing data collection and analysis for the Qingdao Twin Registry will be discussed in this article.

  8. Congenital infantile myofibroma causing intrauterine death in a twin.

    Science.gov (United States)

    Aye, Christina Yi Ling; Gould, Steve; Akinsola, S Adeyemi

    2011-12-01

    While infantile myofibromatosis is the most common mesenchymal tumour of infancy, only around 300 cases have been reported. The authors report a 33-year-old para 1 with an uncomplicated, dichorionic diamniotic twin pregnancy who was diagnosed with an intrauterine death of one twin at 36+5 weeks gestation. At caesarean section, a macerated male stillborn weighing 2.72 kg was delivered. Postmortem examination revealed a pedunculated lesion attached to the left shoulder and underlying muscle consistent with a congenital myofibroma. The cause of death was postulated to be haemorrhage from the tumour surface causing fetal anaemia.

  9. Applications for edge detection techniques using Chandra and XMM-Newton data: galaxy clusters and beyond

    CERN Document Server

    Walker, S A; Fabian, A C

    2016-01-01

    The unrivalled spatial resolution of the Chandra X-ray observatory has allowed many breakthroughs to be made in high energy astrophysics. Here we explore applications of Gaussian Gradient Magnitude (GGM) filtering to X-ray data, which dramatically improves the clarity of surface brightness edges in X-ray observations, and maps gradients in X-ray surface brightness over a range of spatial scales. In galaxy clusters, we find that this method is able to reveal remarkable substructure behind the cold fronts in Abell 2142 and Abell 496, possibly the result of Kelvin Helmholtz instabilities. In Abell 2319 and Abell 3667, we demonstrate that the GGM filter can provide a straightforward way of mapping variations in the widths and jump ratios along the lengths of cold fronts. We present results from our ongoing programme of analysing the Chandra and XMM-Newton archives with the GGM filter. In the Perseus cluster we identify a previously unseen edge around 850 kpc from the core to the east, lying outside a known large ...

  10. The Northern Rims of SNR RCW 86 - Chandra's Recent Observations and their Implications for Particle Acceleration

    Science.gov (United States)

    Castro, D.

    2016-06-01

    The Chandra observations towards the northwest (NW) and northeast (NE) rims of supernova remnant (SNR) RCW 86 reveal great detail about the characteristics of the shocks, particle acceleration and the local environments in these 2 distinct regions. Both the NW and NE of RCW 86 show clear evidence of non-thermal X-ray emission, identified as synchrotron radiation from shock-accelerated electrons with TeV energies, interacting with the compressed, and probably amplified, local magnetic field. Magnetic field amplification (MFA) is broadly believed to result from, and contribute to, cosmic ray acceleration at the shocks of SNRs. However, we still lack a detailed understanding of the particle acceleration mechanism, and with this study we address the connection between the shock properties and ambient medium with MFA. The Chandra observations of RCW 86 allowed us to constrain the magnitude of the post-shock magnetic field in the NE and NW rims by deriving synchrotron filament widths, and also the densities in these regions, using thermal emission co-located with the non-thermal rims. I will discuss our analysis in detail and comment on how MFA appears to be related to certain characteristics of the SNR shock.

  11. Chandra observations of the pulsar PSR B1929+10 and its environment

    CERN Document Server

    Misanovic, Zdenka; Garmire, Gordon

    2007-01-01

    We report on two Chandra observations of the 3-Myr pulsar B1929+10, which reveal a faint compact (~9"x4") nebula elongated in the direction perpendicular to the pulsar's proper motion, two patchy wings, and a possible short (~3") jet emerging from the pulsar. In addition, we detect a tail extending up to at least 4' in the direction opposite to the pulsar's proper motion, aligned with the 15'-long tail detected in ROSAT and XMM-Newton observations. The overall morphology of the nebula suggests that the shocked pulsar wind is confined by the ram pressure due to the pulsar's supersonic speed. The shape of the compact nebula in the immediate vicinity of the pulsar seems to be consistent with the current MHD models. However, since these models do not account yet for the change of the flow velocity at larger distances from the pulsar, they are not able to constrain the extent of the long pulsar tail. The luminosity of the whole nebula as seen by Chandra is ~10^30 ergs/s in the 0.3-8 keV band, for the distance of 3...

  12. A Chandra/ACIS Study of 30 Doradus I. Superbubbles and Supernova Remnants

    CERN Document Server

    Townsley, L K; Broos, P S; Chu, Y H; Feigelson, E D; Garmire, G P; Pavlov, G G

    2006-01-01

    We present an X-ray tour of diffuse emission in the 30 Doradus star-forming complex in the Large Magellanic Cloud using high-spatial-resolution X-ray images and spatially-resolved spectra obtained with the Advanced CCD Imaging Spectrometer aboard the Chandra X-ray Observatory. The dominant X-ray feature of the 30 Doradus nebula is the intricate network of diffuse emission generated by interacting stellar winds and supernovae working together to create vast superbubbles filled with hot plasma. We construct maps of the region showing variations in plasma temperature (T = 3--9 million degrees), absorption (N_H = 1--6 x 10^{21} cm^{-2}), and absorption-corrected X-ray surface brightness (S_X = 3--126 x 10^{31} ergs s^{-1} pc^{-2}). Enhanced images reveal the pulsar wind nebula in the composite supernova remnant N157B and the Chandra data show spectral evolution from non-thermal synchrotron emission in the N157B core to a thermal plasma in its outer regions. In a companion paper we show that R136, the central mass...

  13. On the Observation and Simulation of Solar Coronal Twin Jets

    CERN Document Server

    Liu, Jiajia; Wang, Yuming; McIntosh, Scott W; Fan, Yuhong; Zhang, Quanhao

    2016-01-01

    We present the first observation, analysis and modeling of solar coronal twin jets, which occurred after a preceding jet. Detailed analysis on the kinetics of the preceding jet reveals its blowout-jet nature, which resembles the one studied in Liu et al. 2014. However the erupting process and kinetics of the twin jets appear to be different from the preceding one. In lack of the detailed information on the magnetic fields in the twin jet region, we instead use a numerical simulation using a three-dimensional (3D) MHD model as described in Fang et al. 2014, and find that in the simulation a pair of twin jets form due to reconnection between the ambient open fields and a highly twisted sigmoidal magnetic flux which is the outcome of the further evolution of the magnetic fields following the preceding blowout jet. Based on the similarity between the synthesized and observed emission we propose this mechanism as a possible explanation for the observed twin jets. Combining our observation and simulation, we sugges...

  14. A climb on the cosmic ladder with stellar twins

    CERN Document Server

    Jofre, P; Gilmore, G; Casey, A; Soubiran, C; Worley, C

    2015-01-01

    Distances to stars are key to revealing a three-dimensional view of the Milky Way, yet their determination is a major challenge in astronomy. Whilst the brightest nearby stars benefit from direct parallax measurements, fainter stars are subject of indirect determinations with uncertainties exceeding 30%. We present an alternative approach to measuring distances using spectroscopically-identified twin stars. Given a star with known parallax, the distance to its twin is assumed to be directly related to the difference in their apparent magnitudes. We found 175 twin pairs from the ESO public HARPS archives and report excellent agreement with Hipparcos parallaxes within 7.5%. Most importantly, the accuracy of our results does not degrade with increasing stellar distance. With the ongoing collection of high-resolution stellar spectra, our method is well-suited to complement Gaia.

  15. Epigenetic signature of birth weight discordance in adult twins

    DEFF Research Database (Denmark)

    Tan, Qihua; Nielsen, Morten Frost Munk; Heijmans, Bastiaan T

    2014-01-01

    Background: A low birth weight has been extensively related to poor adult health outcomes. Birth weight can be seen as a proxy for environmental conditions during prenatal development. Identical twin pairs discordant for birth weight provide an extraordinary model for investigating the association...... between birth weight and adult life health while controlling for not only genetics but also postnatal rearing environment. We performed an epigenome-wide profiling on blood samples from 150 pairs of adult monozygotic twins discordant for birth weight to look for molecular evidence of epigenetic signatures...... in association with birth weight discordance. Results: Our association analysis revealed no CpG site with genome-wide statistical significance (FDR twin...

  16. Estimating twin concordance for bivariate competing risks twin data.

    Science.gov (United States)

    Scheike, Thomas H; Holst, Klaus K; Hjelmborg, Jacob B

    2014-03-30

    For twin time-to-event data, we consider different concordance probabilities, such as the casewise concordance that are routinely computed as a measure of the lifetime dependence/correlation for specific diseases. The concordance probability here is the probability that both twins have experienced the event of interest. Under the assumption that both twins are censored at the same time, we show how to estimate this probability in the presence of right censoring, and as a consequence, we can then estimate the casewise twin concordance. In addition, we can model the magnitude of within pair dependence over time, and covariates may be further influential on the marginal risk and dependence structure. We establish the estimators large sample properties and suggest various tests, for example, for inferring familial influence. The method is demonstrated and motivated by specific twin data on cancer events with the competing risk death. We thus aim to quantify the degree of dependence through the casewise concordance function and show a significant genetic component.

  17. Chandra Opens New Line of Investigation on Dark Energy

    Science.gov (United States)

    2004-05-01

    Astronomers have detected and probed dark energy by applying a powerful, new method that uses images of galaxy clusters made by NASA's Chandra X-ray Observatory. The results trace the transition of the expansion of the Universe from a decelerating to an accelerating phase several billion years ago, and give intriguing clues about the nature of dark energy and the fate of the Universe. "Dark energy is perhaps the biggest mystery in physics," said Steve Allen of the Institute of Astronomy (IoA) at the University of Cambridge in England, and leader of the study. "As such, it is extremely important to make an independent test of its existence and properties." Abell 2029 Chandra X-ray Image of Abell 2029 Allen and his colleagues used Chandra to study 26 clusters of galaxies at distances corresponding to light travel times of between one and eight billion years. These data span the time when the Universe slowed from its original expansion, before speeding up again because of the repulsive effect of dark energy. "We're directly seeing that the expansion of the Universe is accelerating by measuring the distances to these galaxy clusters," said Andy Fabian also of the IoA, a co-author on the study. The new Chandra results suggest that the dark energy density does not change quickly with time and may even be constant, consistent with the "cosmological constant" concept first introduced by Albert Einstein. If so, the Universe is expected to continue expanding forever, so that in many billions of years only a tiny fraction of the known galaxies will be observable. More Animations Animation of the "Big Rip" If the dark energy density is constant, more dramatic fates for the Universe would be avoided. These include the "Big Rip," where dark energy increases until galaxies, stars, planets and eventually atoms are eventually torn apart. The "Big Crunch," where the Universe eventually collapses on itself, would also be ruled out. Chandra's probe of dark energy relies on the unique

  18. [Twin dystocia: about one case of compaction].

    Science.gov (United States)

    Desseauve, D; Voluménie, J-L

    2008-09-01

    We report a case of twin dystocia during the evacuation of full-term fetus both in cephalic presentation. A low-outlet forceps for second-phase arrest was performed for the first twin but the head remained stuck to maternal perineum, mimicking a shoulder dystocia. Digital examination found a twin compaction, that is the presence of the second twin's fetal head at the level of the first twin's chest. The discrepancy between fetal weights and the use of forceps could favor this rare complication. Various maneuvers were described previously attempted to solve the problem. Forcing back the second head may help to achieve delivery of the first twin.

  19. TWIN GESTATION : A CHALLENGING TASK

    Directory of Open Access Journals (Sweden)

    Vrunda V.

    2015-03-01

    Full Text Available INTRODUCTION In the era of modern obstetrics when multiple pregnancies are on increase it is very important to know the incidence and obstetric outcomes of twin deliveries. Twin pregnancy is still associated with increased maternal and perinatal morbidity and mortality as well as healthcare costs . ( 1 , 2 , 3 MATERIALS AND METHODS : This is a r etrospective study of twin deliveries done in the rural medical college teaching hospital over a period of 3 years. RESULTS : During the study period , incidence of twin delivery was 19.37 per 1000 deliveries. Majority cases of twins were young primies in ag e group (20 - 30 years . Preterm delivery occurred in 68% cases and was therefore , the most common morbidity followed by anaemia (38% and PIH (28%. Most common presentation was vertex (66% and malpresentation were present in 44% of cases. 54% were deliver ed by caesarean section. In 88% second baby delivered within 15 minutes. Uterine inertia , PROM , fetal distress , PPH , cord prolapse and abruption were complications during labour. There was no maternal mortality in present study. Average weight of first baby was 1679.63 gms and 2 nd baby was 1586.94 gms. Perinatal mortality of 1 st baby was 27.55 for 1 st baby and 37.25% for 2 nd baby . Average gestational age for patients in whom cervical encirclage was done was 34 weeks. CONCLUSION: P reterm delivery and low birth weight babies are main challenges to the obstetrician. Incidence of LSCS is quite high with malpresentation of leading (twin A baby is a major indication for LSCS . The use of antenatal care services and good intrapartum mana gement will help improve outcome in twin pregnancies.

  20. Simultaneous NuSTAR/Chandra observations of the Bursting Pulsar GRO J1744-28 during its third reactivation

    CERN Document Server

    Younes, G; Grefenstette, B W; Tomsick, J A; Tennant, A; Finger, M H; Furst, F; Pottschmidt, K; Bhalerao, V; Boggs, S E; Boirin, L; Chakrabarty, D; Christensen, F E; Craig, W W; Degenaar, N; Fabian, A C; Gandhi, P; Gogus, E; Hailey, C J; Harrison, F A; Kennea, J A; Miller, J M; Stern, D; Zhang, W W

    2015-01-01

    We report on a 10 ks simultaneous Chandra/HETG-NuSTAR observation of the Bursting Pulsar, GRO J1744-28, during its third detected outburst since discovery and after nearly 18 years of quiescence. The source is detected up to 60 keV with an Eddington persistent flux level. Seven bursts, followed by dips, are seen with Chandra, three of which are also detected with NuSTAR. Timing analysis reveals a slight increase in the persistent emission pulsed fraction with energy (from 10% to 15%) up to 10 keV, above which it remains constant. The 0.5-70 keV spectra of the persistent and dip emission are the same within errors, and well described by a blackbody (BB), a power-law with an exponential rolloff, a 10 keV feature, and a 6.7 keV emission feature, all modified by neutral absorption. Assuming that the BB emission originates in an accretion disc, we estimate its inner (magnetospheric) radius to be about 4x10^7 cm, which translates to a surface dipole field B~9x10^10 G. The Chandra/HETG spectrum resolves the 6.7 keV ...

  1. Twin-twin transfusion syndrome: neurodevelopmental screening test

    Directory of Open Access Journals (Sweden)

    Amabile Vessoni Arias

    2015-03-01

    Full Text Available Objective To assess the neurodevelopmental functions (cognition, language and motor function of survivors of twin-twin transfusion syndrome (TTTS. Method Observational cross-sectional study of a total of 67 monochorionic diamniotic twins who underwent fetoscopic laser coagulation (FLC for treatment of TTTS. The study was conducted at the Center for Investigation in Pediatrics (CIPED, Universidade Estadual de Campinas. Ages ranged from one month and four days to two years four months. Bayley Scales of Infant and Toddler Development Screening Test-III, were used for evaluation. Results Most children reached the competent category and were classified as having appropriate performance. The preterm children scored worse than term infants for gross motor subtest (p = 0.036. Conclusion The majority of children reached the expected development according to their age. Despite the good neurodevelopment, children classified at risk should be monitored for development throughout childhood.

  2. Alternating brittle and ductile response of coherent twin boundaries in nanotwinned metals

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Tanushree; Kulkarni, Yashashree, E-mail: ykulkarni@uh.edu [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204 (United States)

    2014-11-14

    Nanotwinned metals have opened exciting avenues for the design of high strength and high ductility materials. In this work, we investigate crack propagation along coherent twin boundaries in nanotwinned metals using molecular dynamics. Our simulations reveal that alternating twin boundaries exhibit intrinsic brittleness and ductility owing to the opposite crystallographic orientations of the adjoining twins. This is a startling consequence of the directional anisotropy of an atomically sharp crack along a twin boundary that favors cleavage in one direction and dislocation emission from the crack tip in the opposite direction. We further find that a blunt crack exhibits ductility in all cases albeit with very distinct deformation mechanisms and yield strength associated with intrinsically brittle and ductile coherent twin boundaries.

  3. Grain neighbour effects on twin transmission in hexagonal close-packed materials

    Science.gov (United States)

    Arul Kumar, M.; Beyerlein, I. J.; McCabe, R. J.; Tomé, C. N.

    2016-12-01

    Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.

  4. TwinMux Testing System

    CERN Document Server

    Wong, Wei Wen; CERN. Geneva. PH Department

    2015-01-01

    During the CERN summer school program, I joined the CMS Muon Drift Tube (DT) group, and mainly worked on two projects, which, both of them, are related to the electronics of a new data concentrator called the “TwinMux”. My first task within the TwinMux project was to build an integrated software test station in order to run several tests on the functionality of the TwinMux hardware. Essentially, I had to integrate existing testing scripts, adding several new ones, into a single user-friendly testing platform which can perform quick, convenient and automated hardware testing. Later, I was also involved in the design of the local technical triggering of the DT. Such system relies on some firmware functionality built in the TwinMux and controlled by software. I had attempted two different approaches to design the communication topology of all the 12 TwinMux cards in order to send a user-defined logical operation to the read-out electronics. The final goal of this system is to drive local trigger signal for...

  5. TWIN PREGNANCY WITH ACARDIUS ANCEPS

    Directory of Open Access Journals (Sweden)

    Padma

    2014-02-01

    Full Text Available Acardiac twin is an anomaly unique to monochorionic multiple pregnancies, characterized by formation of malformed fetus with an absent or rudimentary (nonfunctional heart. Acardiac twinning, often results from abnormal placental vascular anastomoses. A 20 year old primigravida admitted to the department of Obstetrics and Gynecology S .S. Medical College, Rewa, on 26th July 2012 at the gestation of 34 week with spontaneous monochorionic monoamniotic twin pregnancy and fetal acardius with oligohydramnios. Patient was taking her treatment from private Hospital; acardius was diagnosed at 27 week due to late booking. In view of oligohydramnios and hypoxic changes in color Doppler, elective LSCS was done on 28/7/13 at 34 week 2 day, after betnesol coverage. She delivered a live, healthy, female child with good APGAR score having apparently no congenital anomaly, with a birth weight of 2.3 kg .The other twin was fetus acardius, of about900 gm. with head and face partially developed . Upper limb was rudimentary and lower limb was partially developed and malformed. External genitalia were developed as female. Placenta was monochorionic and monoamniotic, weighing500 gm. The umbilical cord of the normal twin was20 cm with central attachment, while the other umbilical cord was10 cm long with peripheral attachment

  6. Complications arising in twin pregnancy: findings of prenatal ultrasonography

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Ah; Cho, Jeong Yeon; Lee, Young Ho; Song, Mi Jin; Min, Jee Yeon; Lee, Hak Jong; Han, Byoung Hee; Lee, Kyung Sang; Cho, Byung Jae; Chun, Yi Kyeong [Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2003-03-01

    Multifetal gestations are high-risk pregnancies involving higher perinatal morbidity and mortality, and are subject to unique complications including twin oligohydramnios- polyhydramnios sequence, twin-to-twin transfusion syndrome, acardiac twins, conjoined twins, co-twin demise, and heterotopic pregnancies. The purpose of this study is to describe the prenatal ultrasonographic and pathologic findings of these complications.

  7. Adapative software solutions: lessons learned from Chandra flight operations

    Science.gov (United States)

    Shropshire, Daniel P.; Bucher, Sabina; Rose, Joseph

    2006-06-01

    After over 6 highly successful years on orbit, the Chandra X-ray Observatory continues to deliver world class science to members of the X-ray community. Much of this success can be attributed to an excellent space vehicle, however; the creation of several unique software tools has allowed for extremely efficient and smooth running operations. The Chandra Flight Operations Team, staffed by members of Northrop Grumman Space Technology, has created a suite of software tools designed to help optimize on-console operations, mission planning and scheduling, and spacecraft engineering and trending. Many of these tools leverage COTS products and Web based technologies. We describe the original mission concepts, need for supplemental software tools, development and implementation, use of these tools in the current operations scenario, and efficiency improvements due to their use.

  8. Dark Matter Reality Check: Chandra Casts Cloud On Alternative Theory

    Science.gov (United States)

    2002-10-01

    New evidence from NASA's Chandra X-ray Observatory challenges an alternative theory of gravity that eliminates the need for dark matter. The observation also narrows the field for competing forms of dark matter, the elusive material thought to be the dominant form of matter in the universe. An observation of the galaxy NGC 720 shows it is enveloped in a slightly flattened, or ellipsoidal cloud of hot gas that has an orientation different from that of the optical image of the galaxy. The flattening is too large to be explained by theories in which stars and gas are assumed to contain most of the mass in the galaxy. "The shape and orientation of the hot gas cloud require it to be confined by an egg-shaped dark matter halo," said David Buote of the University of California, Irvine, and lead author of a report on this research in the 2002 September 20 issue of The Astrophysical Journal. "This means that dark matter is not just an illusion due to a shortcoming of the standard theory of gravity - it is real." According to the generally accepted standard theory of gravity, the hot X-ray cloud would need an additional source of gravity - a halo of dark matter - to keep the hot gas from expanding away. The mass of dark matter required would be about five to ten times the mass of the stars in the galaxy. If the dark matter tracked the optical light from the stars in the galaxy, the hot X-ray cloud would be more round than it is. The flattened shape of the hot gas cloud requires a flattened dark matter halo. An alternative theory of gravity called MOND, for Modified Newtonian Dynamics, was proposed in 1983 by Mordecai Milgrom of the Weizmann Institute in Israel, and has remained viable over the years. MOND does away with the need for dark matter by modifying the theory where the acceleration produced by gravity is very small, such as the outskirts of galaxies. However, MOND cannot explain the Chandra observation of NGC 720. This is apparently the first dynamical evidence that

  9. Variability of Optical Counterparts in the Chandra Galactic Bulge Survey

    CERN Document Server

    Britt, Christopher T; Johnson, C B; Baldwin, A; Jonker, P G; Nelemans, G; Torres, M A P; Maccarone, T; Steeghs, D; Greiss, S; Heinke, C; Bassa, C G; Collazzi, A; Villar, A; Gabb, M; Gossen, L

    2014-01-01

    We present optical lightcurves of variable stars consistent with the positions of X-ray sources identified with the Chandra X-ray Observatory for the Chandra Galactic Bulge Survey. Using data from the Mosaic-II instrument on the Blanco 4m Telescope at CTIO, we gathered time-resolved photometric data on timescales from $\\sim2$ hr to 8 days over the $\\frac{3}{4}$ of the X-ray survey containing sources from the initial GBS catalog. Among the lightcurve morphologies we identify are flickering in interacting binaries, eclipsing sources, dwarf nova outbursts, ellipsoidal variations, long period variables, spotted stars, and flare stars. $87\\%$ of X-ray sources have at least one potential optical counterpart. $24\\%$ of these candidate counterparts are detectably variable; a much greater fraction than expected for randomly selected field stars, which suggests that most of these variables are real counterparts. We discuss individual sources of interest, provide variability information on candidate counterparts, and di...

  10. Highlights and discoveries from the Chandra X-ray Observatory.

    Science.gov (United States)

    Tananbaum, H; Weisskopf, M C; Tucker, W; Wilkes, B; Edmonds, P

    2014-06-01

    Within 40 years of the detection of the first extra-solar x-ray source in 1962, NASA's Chandra X-ray Observatory has achieved an increase in sensitivity of 10 orders of magnitude, comparable to the gain in going from naked-eye observations to the most powerful optical telescopes over the past 400 years. Chandra is unique in its capabilities for producing sub-arcsecond x-ray images with 100-200 eV energy resolution for energies in the range 0.08 black holes; the growth of supermassive black holes and their role in the regulation of star formation and growth of galaxies; impacts of collisions, mergers, and feedback on growth and evolution of groups and clusters of galaxies; and properties of dark matter and dark energy.

  11. Nike Twins Seven Seven: Nigerian Batik Artist.

    Science.gov (United States)

    LaDuke, Betty

    1987-01-01

    Chronicles the personal and professional life of Nike Twins Seven Seven (born 1951), a Nigerian batik artist, and her husband, Twins Seven Seven, a musician-artist, both of whom have received international acclaim. (BJV)

  12. Preterm twin gestation and cystic periventricular leucomalacia

    NARCIS (Netherlands)

    Resch, B; Jammernegg, A; Vollaard, E; Maurer, U; Mueller, WD; Pertl, B

    2004-01-01

    Objective: To identify risk factors for the development of cystic periventricular leucomalacia (PVL) in twin gestation. Design: Retrospective case-control study. Setting: Tertiary care university hospital, Department of Paediatrics, Division of Neonatology, Graz, Austria. Patients: Preterm twin gest

  13. Breast-Feeding Twins: Making Feedings Manageable

    Science.gov (United States)

    ... more than one baby? Here's help breast-feeding twins or other multiples, from getting positioned and ensuring ... babies who are born prematurely, as are many twins and higher order multiples. Breast milk is easier ...

  14. Risk of Oral Clefts in Twins

    DEFF Research Database (Denmark)

    Grosen, Dorthe; Bille, Camilla; Petersen, Inge

    2011-01-01

    BACKGROUND:: Small studies have indicated that twinning increases the risk of oral cleft. METHODS:: We used data from a Danish national population-based cohort study to investigate whether twinning was associated with isolated oral cleft, and to estimate the twin probandwise concordance rate...... and heritability. Twins (207 affected/130,710) and singletons (7766 affected/4,798,526) born from 1936 through 2004 in Denmark were ascertained by linkage among the Danish Facial Cleft Database, the Danish Twin Registry, and the Civil Registration System. We computed oral cleft prevalence and prevalence proportion...... ratio for twins versus singletons, stratified for 3 subphenotypes. Probandwise concordance rates and heritability for twins were estimated for 2 phenotypes-cleft lip with or without cleft palate (CL/P) and cleft palate (CP). RESULTS:: The prevalence of oral cleft was 15.8 per 10,000 twins and 16.6 per...

  15. Having Twins? How to Stay Healthy

    Science.gov (United States)

    ... Listen Español Text Size Email Print Share Having Twins? How to Stay Healthy Page Content Article Body ... the eyes of obstetricians. Many would call a twin pregnancy a high-risk pregnancy , but don’t ...

  16. Total and regional fat distribution is strongly influenced by genetic factors in young and elderly twins

    DEFF Research Database (Denmark)

    Malis, Charlotte; Rasmussen, Eva L; Poulsen, Pernille

    2005-01-01

    OBJECTIVE: Indirect estimates of obesity such as BMI seem to be strongly influenced by genetic factors in twins. Precise measurements of total and regional fat as determined by direct techniques such as DXA scan have only been applied in a few twin studies. The aim of the present study was to est......OBJECTIVE: Indirect estimates of obesity such as BMI seem to be strongly influenced by genetic factors in twins. Precise measurements of total and regional fat as determined by direct techniques such as DXA scan have only been applied in a few twin studies. The aim of the present study...... was to estimate the heritability (h(2)) of total and regional fat distribution in young and elderly Danish twins. RESEARCH METHODS AND PROCEDURES: Monozygotic (108) and dizygotic (88) twins in two age groups (25 to 32 and 58 to 66 years) underwent anthropometric measurements and DXA scans. Intraclass correlations...... and etiologic components of variance were estimated for total and regional fat percentages using biometric modeling. RESULTS: The intraclass correlations demonstrated higher correlations for all fat percentages among monozygotic twins as compared with dizygotic twins. The biometric modeling revealed a major...

  17. Growing old but not growing apart: twin similarity in the latter half of the lifespan.

    Science.gov (United States)

    McGue, Matt; Christensen, Kaare

    2013-01-01

    While a substantial amount of behavioral genetic research has helped to characterize developmental trends in twin similarity in early life, relatively little is known about changes in twin similarity with age in adulthood. We investigated age moderation of twin similarity for a composite measure of cognitive ability, depression symptomatology and hand grip strength in a cross-sectional sample of 2,332 like-sex pairs of Danish twins age 46-96 years. All three outcomes were strongly correlated with age, indicating that the three phenotypes analyzed are not developmentally static. Nonetheless, in moderated regression analysis we found no evidence of declining twin similarity for any of the three outcomes in either zygosity group. Moreover, biometric analysis of the twin data revealed minimal differences in heritability estimates across the age range sampled. While small sample size limits our ability to draw firm conclusions at very advanced ages, these findings call into question the hypothesis that the cumulative impact of life experiences diminishes twin similarity at least through age 80. We hypothesize that twins are able to maintain similarity over extended periods of time because in part they are able to construct similar environments that reinforce that similarity.

  18. The role of deformation twinning in the fracture behavior and mechanism of basal textured magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ando, D., E-mail: dando@material.tohoku.ac.jp; Koike, J.; Sutou, Y.

    2014-04-01

    AZ31 magnesium alloys were deformed to 10% and to failure strain by tensile loading at room temperature. Scribed grids were drawn by a focused ion beam system (FIB) to visualize the local deformation in each grain. This showed that the magnitude of the strain was distributed non-uniformly in each grain. It was found that the low-strain grains accompanied {10–12} twins, while the severely strained grains accompanied {10–11}–{10–12} double twins. Cracks nucleated at the double twins and tended to propagate along {10–12} twin interfaces as well as within grains. Furthermore, fractography revealed three types of microstructural features: dimples, elliptic facets and sheared dimples. Most abundant were the dimples formed by ductile failure. The elliptic facets appeared to be due to crack propagation along the {10–12} twin interfaces. The sheared dimples were frequently observed in connection with localized shear deformation within the double twins. These results led us to conclude that premature and catastrophic failure of Mg alloys is mainly associated with double twins. Prevention of double twinning is essential to improve the ductility of Mg alloys.

  19. The fracture behavior of twinned Cu nanowires: A molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jiapeng, E-mail: sun.jiap@gmail.com [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Fang, Liang [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, Shaanxi Province (China); Ma, Aibin, E-mail: aibin-ma@hhu.edu.cn [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Jiang, Jinghua [College of Mechanics and Materials, Hohai University, Nanjing 210098 (China); Han, Ying [Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun 130012, Jilin Province (China); Chen, Huawei [Department of Applied Physics, School of Science, Xi’an Jiaotong University, Xi’an 710049, Shaanxi Province (China); Han, Jing [School of Mechanical and Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, Jiangsu Province (China)

    2015-05-14

    The molecular dynamics simulations are performed to explore the fracture behavior and the ductility of the twinned Cu nanowires containing orthogonally oriented growth CTBs due to the uniaxial tensile deformation. The results reveal that, the fracture behavior and the ductility of the twinned nanowires are not related to the length of the nanowires but also intensively related to the twin boundary spacing. When the twin boundary space is changed, the twinned nanowires undergo three distinct failure modes which include ductile fracture, brittle fracture and ductile-to-brittle transition depending on the length of the nanowires. We also find a reduction in the ductility of the twinned nanowires, which is ascribed to the deformation localization induced by the Lomer dislocation and the rapid necking resulted from the twinning partial slipping. Finally, the atomic-level process that occurs during deformation until final fracture are examined in detail, and a new formation mechanism of the Lomer dislocation is observed when a 90° partial dislocation transmits across a coherent twin boundary.

  20. Twin TQFTs and Frobenius Algebras

    Directory of Open Access Journals (Sweden)

    Carmen Caprau

    2013-01-01

    Full Text Available We introduce the category of singular 2-dimensional cobordisms and show that it admits a completely algebraic description as the free symmetric monoidal category on a twin Frobenius algebra, by providing a description of this category in terms of generators and relations. A twin Frobenius algebra (C,W,z,z∗ consists of a commutative Frobenius algebra C, a symmetric Frobenius algebra W, and an algebra homomorphism z:C→W with dual z∗:W→C, satisfying some extra conditions. We also introduce a generalized 2-dimensional Topological Quantum Field Theory defined on singular 2-dimensional cobordisms and show that it is equivalent to a twin Frobenius algebra in a symmetric monoidal category.

  1. Twins or two single children

    Directory of Open Access Journals (Sweden)

    2002-08-01

    Full Text Available Based on Swedish register data, we compared the influence of a twin birth on the divorce risk with the influence of the sequential birth of two single children. The divorce risk for a woman with a very young child was lower than the risk for women without children or women with children older than 3.5 years. This behaviour was essentially independent of the number of children and whether or not the woman gave birth to twins. The effect of parity was much smaller than the effect of child age. The influence of twins on the divorce risk appeared to fall between that of a first and a second singleton.

  2. Twin Diamond Crystals Grown at High Temperature and High Pressure from the Fe-Ni-C System

    Institute of Scientific and Technical Information of China (English)

    尹龙卫; 袁泉; 李木森; 刘玉先; 许斌; 郝兆印

    2002-01-01

    Twin diamond crystals grown at high temperature and high pressure (HPHT) in the presence of FeNi catalyst have been examined by transmission electron microscopy (TEM). Direct observation by TEM shows that there are a large amount of twins which lie on the {111} planes in the HPHT-grown diamonds. The twins in the diamond may be formed and may extend into the inner crystal from the twin nucleus formed in the nucleation process.The twins can be formed due to the carbon atoms falling mistakenly into positions where a twin crystal can form during diamond growth, or condensation of supersaturated vacancies on the {111} plane. Some hexagonal dislocation loops related to supersaturated vacancies are found on the twins. The Moiré fringe image reveals that stacking faults terminate on the intersecting twin boundary. This suggests that, at the temperature that the HPHT diamond is grown, the bordering partial has propagated by gliding up to the twin interface, which can be described by the reaction of a Shockley partial dislocation with a twin on the {111} plane.

  3. Do Twin Boundaries Always Strengthen Metal Nanowires?

    OpenAIRE

    Zhang Yongfeng; Huang Hanchen

    2008-01-01

    Abstract It has been widely reported that twin boundaries strengthen nanowires regardless of their morphology—that is, the strength of nanowires goes up as twin spacing goes down. This article shows that twin boundaries do not always strengthen nanowires. Using classical molecular dynamics simulations, the authors show that whether twin boundaries strengthen nanowires depends on the necessary stress for dislocation nucleation, which in turn depends on surface morphologies. When nanowire...

  4. Studying the Evolving Universe with XMM-Newton and Chandra

    CERN Document Server

    Hasinger, G

    2003-01-01

    First indications of the warm/hot intergalactic medium, tracing out the large scale structure of the universe, have been obtained in sensitive Chandra and XMM-Newton high resolution absorption line spectroscopy of bright blazars. High resolution X-ray spectroscopy and imaging also provides important new constraints on the physical condition of the cooling matter in the centers of clusters, requiring major modifications to the standard cooling flow models. XMM-Newton and Chandra low resolution spectroscopy detected significant Fe K_alpha absorption features in the spectrum of the ultraluminous, high redshift lensed broad absorption line QSO APM 08279+5255, yielding new insights in the outflow geometry indicating a supersolar Fe/O ratio. Chandra high resolution imaging spectroscopy of the nearby ULIRG/obscured QSO NGC 6240 for the first time gave evidence of two active supermassive black holes in the same galaxy, likely bound to coalesce in the course of the ongoing major merger in this galaxy. Deep X-ray surve...

  5. Unveiling obscured accretion in the Chandra Deep Field South

    CERN Document Server

    Fiore, F; Santini, P; Puccetti, S; Brusa, M; Feruglio, C; Fontana, A; Giallongo, E; Comastri, A; Gruppioni, C; Pozzi, F; Zamorani, G; Vignali, C

    2007-01-01

    A large population of heavily obscured, Compton Thick AGNs is predicted by models of galaxy formation, models of Cosmic X-ray Background and by the ``relic'' super-massive black-hole mass function measured from local bulges. However, so far only a handful of Compton thick AGNs have been possibly detected using even the deepest Chandra and XMM surveys. Compton-thick AGNs can be recovered thanks to the reprocessing of the AGN UV emission in the infrared by selecting sources with AGN luminosity's in the mid-infrared and faint near-infrared and optical emission. To this purpose, we make use of deep HST, VLT, Spitzer and Chandra data on the Chandra Deep Field South to constrain the number of Compton thick AGN in this field. We show that sources with high 24micron to optical flux ratios and red colors form a distinct source population, and that their infrared luminosity is dominated by AGN emission. Analysis of the X-ray properties of these extreme sources shows that most of them are indeed likely to be highly obsc...

  6. Cross-matching within the Chandra Source Catalog

    Science.gov (United States)

    Rots, Arnold H.; Burke, Douglas J.; Civano, Francesca; Hain, Roger; Nguyen, Dan

    2017-01-01

    Cross-matching among overlapping source detections in the development of the Chandra Source Catalog (CSC) presents considerable challenges, since the Point Spread Function (PSF) of the Chandra X-ray Observatory varies significantly over the field of view. For the production of the second release of the CSC we have developed a cross-match tool that is based on the Bayesian algorithms by Budavari, Heinis, and Szalay (ApJ 679, 301 and 705, 739), making use of the error ellipses for the derived positions of the detections.However, calculating match probabilities only on the basis of error ellipses breaks down when the PSFs are significantly different. This is an issue that is not commonly addressed in cross-match tools. We have applied a satisfactory modification to the algorithm that, although not perfect, ameliorates the issue for the vast majority of such cases.A separate issue is that as the number of overlapping detections increases, the number of matches to be considered increases at an alarming rate, requiring procedural adjustments to ensure that the cross-matching finishes within a Hubble time.We intend to make the tool available as a general purpose cross-match engine for calculating match probabilities between sources in multiple catalogs simultaneously.This work has been supported by NASA under contract NAS 8-03060 to the Smithsonian Astrophysical Observatory for operation of the Chandra X-ray Center.

  7. Twins reunited: scientific and personal perspectives/twin research studies: multiple birth effects on IQ and body size; life style, muscles, and metabolism; monochorionic dizygotic twin with blood chimerism; amniocentesis for twins/twins in the media: identical doctors; freedom fighter for twins; twin scholarships; Auguste and Jean-Felix Piccard; twins born apart.

    Science.gov (United States)

    Segal, Nancy L; Mulligan, Christy A

    2014-04-01

    A reunion of 38-year-old female monozygotic twins took place in Daegu, South Korea, on January 14, 2014. Scientific and personal perspectives on this extraordinary event are provided. A review of timely twin research follows, covering the effects of multiple births on IQ and body size, lifestyle and physical fitness associations, a rare case of a dizygotic twin with blood chimerism and definitional issues surrounding amniocentesis-related loss in multiple birth pregnancies. Interesting and informative mention of twins in the media includes twin doctors, a twin freedom fighter, the availability of college scholarships for twins, a new book about the Piccard family (two of whose members were twins), and co-twins born before and after the new year. A follow-up to a previous mention of identical twin biatheletes is also provided.

  8. Twin and genetic effects on life events

    NARCIS (Netherlands)

    Middeldorp, C.M.; Cath, D.C.; Vink, J.M.; Boomsma, D.I.

    2005-01-01

    Twin studies that examine the effect of specific environmental risk factors on psychiatric disorders assume that there are no differences in prevalences of these risk factors between twins and singletons. Violation of this assumption signifies that the results from twin studies might not generalize

  9. [The diagnostic algorithm in twin pregnancy].

    Science.gov (United States)

    Ropacka-Lesiak, Mariola; Szaflik, Krzysztof; Breborowicz, Grzegorz H

    2015-03-01

    This paper presents the diagnostic algorithm in twin pregnancy. The most important sonographic parameters in the assessment of twins have been discussed. Moreover, the most significant complications of twin pregnancy as well as diagnostic possibilities and management, have been also presented and defined.

  10. Natal Influences and Twin Differences: Draft.

    Science.gov (United States)

    Van den Daele, Leland D.

    1972-01-01

    A classification of natal influences is proposed with a model of their operation. Natal influences affect maternal capacity, maternal load, and maternal efficiency. Since maternal load is increased in twin pregnancy, results of twin studies must be generalized with caution. The method of co-twin control is exemplified by examination of a small…

  11. A RARE CASE OF ACARDIAC TWIN

    OpenAIRE

    Padmaja; Nirmala,

    2015-01-01

    Fetus Acardiacus is a very rare manifestation of twin gestation . This happens due to TRAP sequence . That is Twin reversed arterial perfusion . In this case an amorphous mass was seen on a routine antenatal scan and followed as there was a live twin also . The case report highlights the importance of careful scanning and ...

  12. MIR phasing using merohedrally twinned crystals

    NARCIS (Netherlands)

    Terwisscha van Scheltinga, Anke C.; Valegård, Karin; Hajdu, Janos; Andersson, Inger

    2003-01-01

    Merohedral twinning is a crystal-growth disorder that seriously hinders the determination of macromolecular crystal structures by isomorphous replacement. The strategies used in the structures solved so far are discussed. Several methods can be used to determine the extent of twinning, the twin frac

  13. A Twin Study of Perthes Disease

    DEFF Research Database (Denmark)

    Metcalfe, David; Van Dijck, Stephanie; Parsons, Nicolas;

    2016-01-01

    and genetic associations with LCPD. METHODS: We extracted all twin pairs from the Danish Twin Registry (DTR) in which at least 1 individual had LCPD. The DTR captures every twin pair born alive in Denmark, and those with LCPD were identified by using health record linkage. Probanwise concordance...

  14. Multiple rectal carcinoid tumors in monozygotic twins.

    Science.gov (United States)

    Doi, Momoko; Ikawa, Osamu; Taniguchi, Hiroki; Kawamura, Takuji; Katsura, Kanade

    2016-08-01

    We report multiple rectal carcinoid tumors in monozygotic twins who, respectively, had 42 and 36 carcinoid tumors in the lower rectum. This is the first report about carcinoid tumors in monozygotic twins. Both twins developed a similar number of rectal carcinoids with a similar distribution. Investigation of their genetic background may provide information about the origin of these tumors.

  15. Concordance for multiple sclerosis in Danish twins

    DEFF Research Database (Denmark)

    Hansen, T; Skytthe, Axel; Stenager, Egon

    2005-01-01

    The occurrence of multiple sclerosis (MS) in twins has not previously been studied in complete nationwide data sets. The existence of almost complete MS and twin registries in Denmark ensures that essentially unbiased samples of MS cases among twins can be obtained. In this population-based study...

  16. The Charles Perkins Centre's Twins Research Node.

    Science.gov (United States)

    Ferreira, Lucas C; Craig, Jeffrey M; Hopper, John L; Carrick, Susan E

    2016-08-01

    Twins can help researchers disentangle the roles of genes from those of the environment on human traits, health, and diseases. To realize this potential, the Australian Twin Registry (ATR), University of Melbourne, and the Charles Perkins Centre (CPC), University of Sydney, established a collaboration to form the Twins Research Node, a highly interconnected research facility dedicated specifically to research involving twins. This collaboration aims to foster the adoption of twin designs as important tools for research in a range of health-related domains. The CPC hosted their Twins Research Node's launch seminar entitled 'Double the power of your research with twin studies', in which experienced twin researchers described how twin studies are supporting scientific discoveries and careers. The launch also featured twin pairs who have actively participated in research through the ATR. Researchers at the CPC were surveyed before the event to gauge their level of understanding and interest in utilizing twin research. This article describes the new Twins Research Node, discusses the survey's main results and reports on the launch seminar.

  17. Glide twinning and pseudotwinning in peristerite: twin morphology and propagation

    Science.gov (United States)

    Brown, William L.

    1989-07-01

    Optically visible Albite glide “twins” in a peristerite (˜An9Or1.6), identified from their tapering shape and relationship to grain boundaries, were studied by transmission electron microscopy. Near the tips in sections ⊥ a, the microstructure consists of small (˜400 nm long) lensshaped Albite twins centred exclusively on the oligoclase lamellae. The lenses extend partly outwards into the two adjacent low albite lamellae and induce strong inhomogeneous strain. Where the lenses are closer together, they form, depending on the sense of shear, nearly linear left or right-stepping en échelon arrays, with overlap of the strain fields. Slightly farther in from the tip, the twin domains coalesce to form continuous pinch-and-swell lamellae, being always thicker in the oligoclase. Because of Si,Al order, only elastic glide pseudotwins are possible in low albite. In oligoclase glide pseudotwins may be mechanically stable (metastable relative to Si,Al order) and may deviate only slightly from true twins. Pseudotwins develop first in the oligoclase, propagate dynamically by jumping across the intervening albite lamellae, extend lengthways and thicken sideways and finally coalesce. They are stabilized by diffusion-controlled inversion of Si,Al order giving rise to true twins described in a companion paper.

  18. NOTE: Increasing cardiac output and decreasing oxygenation sequence in pump twins of acardiac twin pregnancies

    Science.gov (United States)

    van Gemert, Martin J. C.; Umur, Asli; van den Wijngaard, Jeroen P. H. M.; Van Bavel, Ed; Vandenbussche, Frank P. H. A.; Nikkels, Peter G. J.

    2005-02-01

    An acardiac twin pregnancy is a rare but serious complication of monochorionic twinning and consists of an acardiac twin and a pump twin. The acardiac twin is a severely malformed fetus that lacks most organs, particularly a heart, but grows during pregnancy because it is perfused by the developmentally normal pump twin via a set of arterioarterial and venovenous placental anastomoses. Pump twins die intrauterine or neonatally in about 50% of the cases. Because the effects of an acardiac mass on the pump twin's development are incompletely known, methods for outcome prognosis are currently not available. We sought to derive simple relations for the pump twin's excess cardiac output and decreased oxygenation and to use available clinical cases for a preliminary test of the model. As a method, we used a theoretical flow model to represent the fetoplacental circulation of an acardiac twin pregnancy and estimated blood deoxygenation and reoxygenation following perfusion of the two bodies and placentas, respectively. The results show the pump twin's excess cardiac output and decrease of venous oxygen saturation to depend on the ratio of pump twin to acardiac twin umbilical blood flow, whose ratio can be measured by ultrasonography. The clinical cases show a decreasing umbilical flow ratio with gestation. In conclusion, prospective serial study is necessary to test whether measurement of umbilical flow ratios allows monitoring the pump twin's pathophysiologic development, possibly resulting in a guideline for prognosis of pump twin survival.

  19. Increasing cardiac output and decreasing oxygenation sequence in pump twins of acardiac twin pregnancies

    Energy Technology Data Exchange (ETDEWEB)

    Gemert, Martin J C van [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam (Netherlands); Umur, Asli [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam (Netherlands); Wijngaard, Jeroen P H M van den [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam (Netherlands); VanBavel, Ed [Department of Medical Physics, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Vandenbussche, Frank P H A [Department of Obstetrics, Leiden University Medical Center, Leiden (Netherlands); Nikkels, Peter G J [Department of Pathology, University Medical Center, Utrecht (Netherlands)

    2005-02-07

    An acardiac twin pregnancy is a rare but serious complication of monochorionic twinning and consists of an acardiac twin and a pump twin. The acardiac twin is a severely malformed fetus that lacks most organs, particularly a heart, but grows during pregnancy because it is perfused by the developmentally normal pump twin via a set of arterioarterial and venovenous placental anastomoses. Pump twins die intrauterine or neonatally in about 50% of the cases. Because the effects of an acardiac mass on the pump twin's development are incompletely known, methods for outcome prognosis are currently not available. We sought to derive simple relations for the pump twin's excess cardiac output and decreased oxygenation and to use available clinical cases for a preliminary test of the model. As a method, we used a theoretical flow model to represent the fetoplacental circulation of an acardiac twin pregnancy and estimated blood deoxygenation and reoxygenation following perfusion of the two bodies and placentas, respectively. The results show the pump twin's excess cardiac output and decrease of venous oxygen saturation to depend on the ratio of pump twin to acardiac twin umbilical blood flow, whose ratio can be measured by ultrasonography. The clinical cases show a decreasing umbilical flow ratio with gestation. In conclusion, prospective serial study is necessary to test whether measurement of umbilical flow ratios allows monitoring the pump twin's pathophysiologic development, possibly resulting in a guideline for prognosis of pump twin survival. (note)

  20. Peters Anomaly in Twins: A Case Report of a Rare Incident with Novel Comorbidities

    Directory of Open Access Journals (Sweden)

    Hashem S. Almarzouki

    2016-10-01

    Full Text Available Introduction: Peters anomaly is a rare developmental malformation involving the anterior segment of the eye, which culminates in amblyopia or congenital blindness. Multiple ocular and/or systemic malformations have been observed with this anomaly, and novel comorbidities continue to be reported. Case Presentation: The probands were monozygotic twin boys (twin I and twin II born to consanguineous parents at 36 weeks of gestation. Coarse facial features and deep-seated eyes were noted at birth. At 6 months, ophthalmic examination revealed that both twins were unable to blink in response to light, or to fixate and follow a moving object. Both twins had prominent horizontal nystagmus. Slit-lamp examination demonstrated varying degrees of central leukoma (corneal opacity associated with iridocorneal adhesion, which is characteristic of type I Peters anomaly. No cataractous changes were observed. Normal intraocular pressure and disorganized retina were observed. Pupillary abnormalities included bilaterally underdeveloped pupils and bilateral absence of pupils was noted. Ocular MRI showed bilateral microphthalmia and optic nerve hypoplasia, with a small optic chiasm in both twins. At this age, the diagnosis of Peters anomaly was made. At 16 months of age, both twins developed deep venous thrombosis and purpuric skin lesions. Investigations revealed a hereditary thrombophilia secondary to a homozygous mutation causing protein C deficiency, which is a rare thrombotic condition. Ocular ultrasonography revealed bilateral vitreous hemorrhaging linked to altered coagulation. One twin developed bilateral inguinal hernia and cryptorchidism. Conclusion: The novel concordance of Peters anomaly in these monozygotic twins sharing a mutation in PROC gene provides further evidence that this anomaly has a genetic basis. Hypoplasia of the optic nerves and optic chiasm, along with severe protein C deficiency and bilateral absence of the pupils, are associated

  1. Chandra Reviews Black Hole Musical: Epic But Off-Key

    Science.gov (United States)

    2006-10-01

    A gigantic sonic boom generated by a supermassive black hole has been found with NASA's Chandra X-ray Observatory, along with evidence for a cacophony of deep sound. This discovery was made by using data from the longest X-ray observation ever of M87, a nearby giant elliptical galaxy. M87 is centrally located in the Virgo cluster of galaxies and is known to harbor one of the Universe's most massive black holes. Scientists detected loops and rings in the hot, X-ray emitting gas that permeates the cluster and surrounds the galaxy. These loops provide evidence for periodic eruptions that occurred near the supermassive black hole, and that generate changes in pressure, or pressure waves, in the cluster gas that manifested themselves as sound. Chandra Low Energy X-ray Images of M87 Chandra Low Energy X-ray Images of M87 "We can tell that many deep and different sounds have been rumbling through this cluster for most of the lifetime of the Universe," said William Forman of the Harvard-Smithsonian Center for Astrophysics (CfA). The outbursts in M87, which happen every few million years, prevent the huge reservoir of gas in the cluster from cooling and forming many new stars. Without these outbursts and resultant heating, M87 would not be the elliptical galaxy it is today. "If this black hole wasn't making all of this noise, M87 could have been a completely different type of galaxy," said team member Paul Nulsen, also of the CfA, "possibly a huge spiral galaxy about 30 times brighter than the Milky Way." Chandra High Energy X-ray Image of M87 Chandra High Energy X-ray Image of M87 The outbursts result when material falls toward the black hole. While most of the matter is swallowed, some of it was violently ejected in jets. These jets are launched from regions close to the black hole (neither light nor sound can escape from the black hole itself) and push into the cluster's gas, generating cavities and sound which then propagate outwards. Chandra's M87 observations also

  2. Deep Chandra Observations of the Cool Core Clusters A2052 and A262

    Science.gov (United States)

    Blanton, Elizabeth L.; Randall, S. W.; Douglass, E. M.; Clarke, T. E.; Anderson, L. A.; Sarazin, C. L.; McNamara, B. R.

    2008-03-01

    We present deep Chandra observations of the cool core clusters Abell 2052 and Abell 262. New features, including ghost bubbles, ripples, edges, and a tunnel are revealed. Correlations of features seen in the X-ray and radio give evidence for multiple outbursts of the AGN. Comparison of the radio source energy input rates with the ICM cooling rates shows that the radio source can easily offset the cooling in A2052 and is much closer to offsetting the cooling in A262 than was estimated previously. Maps of pressure and temperature will be presented, as well as correlations between surface brightness features and optical-line emission. We constrain the temperature of diffuse, hot gas that may be filling the bubbles and providing pressure support to uphold the cool, dense shells surrounding the bubbles.

  3. PROBING WOLF–RAYET WINDS: CHANDRA/HETG X-RAY SPECTRA OF WR 6

    Energy Technology Data Exchange (ETDEWEB)

    Huenemoerder, David P.; Schulz, N. S. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 70 Vassar St., Cambridge, MA 02139 (United States); Gayley, K. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Hamann, W.-R.; Oskinova, L.; Shenar, T. [Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam (Germany); Ignace, R. [Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614 (United States); Nichols, J. S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS 34, Cambridge, MA 02138 (United States); Pollock, A. M. T., E-mail: dph@space.mit.edu, E-mail: ken.gayley@gmail.com, E-mail: wrh@astro.physik.uni-potsdam.de, E-mail: lida@astro.physik.uni-potsdam.de, E-mail: shtomer@astro.physik.uni-potsdam.de, E-mail: ignace@mail.etsu.edu, E-mail: jnichols@cfa.harvard.edu [European Space Agency, ESAC, Apartado 78, E-28691 Villanueva de la Cañada (Spain)

    2015-12-10

    With a deep Chandra/HETGS exposure of WR 6, we have resolved emission lines whose profiles show that the X-rays originate from a uniformly expanding spherical wind of high X-ray-continuum optical depth. The presence of strong helium-like forbidden lines places the source of X-ray emission at tens to hundreds of stellar radii from the photosphere. Variability was present in X-rays and simultaneous optical photometry, but neither were correlated with the known period of the system or with each other. An enhanced abundance of sodium revealed nuclear-processed material, a quantity related to the evolutionary state of the star. The characterization of the extent and nature of the hot plasma in WR 6 will help to pave the way to a more fundamental theoretical understanding of the winds and evolution of massive stars.

  4. A Very Deep Chandra Observation of Abell 2052: Bubbles, Shocks, and Sloshing

    CERN Document Server

    Blanton, E L; Clarke, T E; Sarazin, C L; McNamara, B R; Douglass, E M; McDonald, M

    2011-01-01

    We present first results from a very deep (~650 ksec) Chandra X-ray observation of Abell 2052, as well as archival VLA radio observations. The data reveal detailed structure in the inner parts of the cluster, including bubbles evacuated by the AGN's radio lobes, compressed bubble rims, filaments, and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one. On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiral has cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likely the result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidence for previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented.

  5. The Chandra X-ray Observatory is prepped for solar panel deployment

    Science.gov (United States)

    1999-01-01

    In the Vertical Processing Facility, a TRW technician checks the attachment of the solar panel array (out of sight to the right) to the Chandra X-ray Observatory, at left. Formerly called the Advanced X-ray Astrophysics Facility, Chandra comprises three major elements: the spacecraft, the science instrument module (SIM), and the world's most powerful X-ray telescope. Chandra will allow scientists from around the world to see previously invisible black holes and high-temperature gas clouds, giving the observatory the potential to rewrite the books on the structure and evolution of our universe. Chandra is scheduled for launch July 9 aboard Space Shuttle Columbia, on mission STS-93.

  6. Epigenetic Epidemiology of Complex Diseases Using Twins

    DEFF Research Database (Denmark)

    Tan, Qihua

    2013-01-01

    In the past decades, studies on twins have had a great impact on dissecting the genetic and environmental contributions to human diseases and complex traits. In the era of functional genomics, the valuable samples of twins help to bridge the gap between gene activity and environmental conditions...... through multiple epigenetic mechanisms. This paper reviews the new developments in using twins to study disease-related epigenetic alterations, links them to lifetime environmental exposure with a focus on the discordant twin design and proposes novel data-analytical approaches with the aim of promoting...... a more efficient use of twins in epigenetic studies of complex human diseases....

  7. Chandra Spectroscopy of a Remarkable Neutron Star

    Science.gov (United States)

    Miller, Jon

    2013-09-01

    IGR J17062-6143 is one of only 5 sources that have displayed a super-expansion burst. This requires a special mode of continuous low-level accretion that allows material to accumulate on the stellar surface, without triggering smaller bursts. Swift spectroscopy of a super-expansion burst in IGR J17062-6143 revealed the only strong detections of atomic emission and absorption lines in a burst observed at CCD or gratings resolution. Whereas atomic features from the stellar surface have not been detected in other neutron stars, the accretion mode in IGR J17062-6143 may provide the right conditions. To search for lines from the surface, and to better understand the nature of low-level accretion, we request a 100 ksec HETGS observation of IGR J17062-6143.

  8. Twin-Arginine Protein Translocation

    NARCIS (Netherlands)

    Goosens, Vivianne J; van Dijl, Jan Maarten

    2016-01-01

    Twin-arginine protein translocation systems (Tat) translocate fully folded and co-factor-containing proteins across biological membranes. In this review, we focus on the Tat pathway of Gram-positive bacteria. The minimal Tat pathway is composed of two components, namely a TatA and TatC pair, which a

  9. Discordance for Cri du Chat Syndrome in a dichorionic–diamniotic twin pregnancy

    Directory of Open Access Journals (Sweden)

    Mireia González-Comadran

    2015-07-01

    Full Text Available We report on the prenatal diagnosis through array CGH of a dichorionic–diamniotic (DC/DA twins discordant for Cri du Chat Syndrome. Structural anomalies on one of the twins lead to amniotic fluid sampling, which revealed a partial deletion on the short arm of the chromosome 5. Selective feticide of the affected twin was performed at 34 + 1 weeks' and elective Cesarean section at 37 + 2 weeks. Postnatal cytogenetic analysis confirmed pre-natal genetic findings.

  10. Search for Genomic Alterations in Monozygotic Twins Discordant for Cleft Lip and/or Palate

    DEFF Research Database (Denmark)

    Kimani, Jane W; Yoshiura, Koh-Ichiro; Shi, Min

    2009-01-01

    consisting of 1,536 SNPs, to scan for genomic alterations in a sample of monozygotic twin pairs with discordant cleft lip and/or palate phenotypes. Paired analysis for deletions, amplifications and loss of heterozygosity, along with sequence verification of SNPs with discordant genotype calls did not reveal...... any genomic discordance between twin pairs in lymphocyte DNA samples. Our results demonstrate that postzygotic genomic alterations are not a common cause of monozygotic twin discordance for isolated cleft lip and/or palate. However, rare or balanced genomic alterations, tissue-specific events...

  11. Fetal growth disorders in twin gestations.

    LENUS (Irish Health Repository)

    Breathnach, Fionnuala M

    2012-06-01

    Twin growth is frequently mismatched. This review serves to explore the pathophysiologic mechanisms that underlie growth aberrations in twin gestations, the prenatal recognition of abnormal twin growth, and the critical importance of stratifying management of abnormal twin growth by chorionicity. Although poor in utero growth of both twins may reflect maternal factors resulting in global uteroplacental dysfunction, discordant twin growth may be attributed to differences in genetic potential between co-twins, placental dysfunction confined to one placenta only, or one placental territory within a shared placenta. In addition, twin-twin transfusion syndrome represents a distinct entity of which discordant growth is a common feature. Discordant growth is recognized as an independent risk factor for adverse perinatal outcome. Intertwin birth weight disparity of 18% or more should be considered to represent a discordance threshold, which serves as an independent risk factor for adverse perinatal outcome. At this cutoff, perinatal morbidity is found to increase both for the larger and the smaller twin within a discordant pair. There remains uncertainty surrounding the sonographic parameters that are most predictive of discordance. Although heightening of fetal surveillance in the face of discordant twin growth follows the principles applied to singleton gestations complicated by fetal growth restriction, the timing of intervention is largely influenced by chorionicity.

  12. Twin vaginal delivery: innovate or abdicate.

    Science.gov (United States)

    Easter, Sarah Rae; Taouk, Laura; Schulkin, Jay; Robinson, Julian N

    2017-02-07

    Neonatal safety data along with national guidelines have prompted renewed interest in vaginal delivery of twins, particularly in the case of the noncephalic second twin. Yet, the rising rate of twin cesarean deliveries, coupled with the national decline in operative obstetrics, raises concerns about the availability of providers who are skilled in twin vaginal birth. Providers are key stakeholders for increasing rates of twin vaginal delivery. We surveyed a group of practicing obstetricians to explore potential barriers to the vaginal birth of twins with a focus on delivery of the noncephalic second twin. Among 107 responding providers, only 57% would deliver a noncephalic second twin by breech extraction. Providers who preferred breech extraction had a higher rate of maternal-fetal medicine subspecialty training (26.2% vs 4.3%; P30 sets of twins annually (57.4% vs 34.8%; P=.02). Most providers (54.2%) were familiar with the findings from the recent randomized trial that demonstrated the safety of twin vaginal birth. However, knowledge of the trial was not associated statistically with a preference for breech extraction (62.3% vs 43.5%; P=.05). Providers who preferred breech extraction were more likely to agree with recent society guidelines that encourage the vaginal birth of twins (86.9% vs 63.0%; Pinnovation. Without novel provider-focused strategies, we may relinquish passively the requisite skills for not only our patients but also for future generations of obstetricians.

  13. Do Twin Boundaries Always Strengthen Metal Nanowires?

    Science.gov (United States)

    Zhang, Yongfeng; Huang, Hanchen

    2009-01-01

    It has been widely reported that twin boundaries strengthen nanowires regardless of their morphology-that is, the strength of nanowires goes up as twin spacing goes down. This article shows that twin boundaries do not always strengthen nanowires. Using classical molecular dynamics simulations, the authors show that whether twin boundaries strengthen nanowires depends on the necessary stress for dislocation nucleation, which in turn depends on surface morphologies. When nanowires are circular cylindrical, the necessary stress of dislocation nucleation is high and the presence of twin boundaries lowers this stress; twin boundaries soften nanowires. In contrast, when nanowires are square cylindrical, the necessary stress of dislocation nucleation is low, and a higher stress is required for dislocations to penetrate twin boundaries; they strengthen nanowires.

  14. Do Twin Boundaries Always Strengthen Metal Nanowires?

    Directory of Open Access Journals (Sweden)

    Zhang Yongfeng

    2008-01-01

    Full Text Available Abstract It has been widely reported that twin boundaries strengthen nanowires regardless of their morphology—that is, the strength of nanowires goes up as twin spacing goes down. This article shows that twin boundaries do not always strengthen nanowires. Using classical molecular dynamics simulations, the authors show that whether twin boundaries strengthen nanowires depends on the necessary stress for dislocation nucleation, which in turn depends on surface morphologies. When nanowires are circular cylindrical, the necessary stress of dislocation nucleation is high and the presence of twin boundaries lowers this stress; twin boundaries soften nanowires. In contrast, when nanowires are square cylindrical, the necessary stress of dislocation nucleation is low, and a higher stress is required for dislocations to penetrate twin boundaries; they strengthen nanowires.

  15. TRAP Sequence - An Interesting Entity in Twins

    Directory of Open Access Journals (Sweden)

    R H Srinivas Prasad

    2012-01-01

    Full Text Available Twin reversed arterial perfusion (TRAP sequence, is a rare malformation occurring in monozygotic multiple gestations. One well-developed normal (pump twin and the other twin with absent cardiac structure (acardiac, who is hemodynamically dependent on the normal (pump twin are characteristic of this syndrome. The acardiac twin develops multiple anomalies that make survival difficult. The prognosis of the pump twin is variable with mortality rate ranging from 50% to 70%. Complications that affect the prognosis of the pump twin include complications of congestive cardiac failure due to increased cardiac demand, prematurity secondary to preterm delivery, and polyhydramnios. Because of these complications prompt detection, follow-up, and treatment of this condition is very important. We report two cases of TRAP sequence that emphasizes the importance of gray-scale and color Doppler imaging in diagnosis, detection of poor prognostic features, follow-up, and management of TRAP sequence.

  16. Finding the needle in the haystack: differentiating "identical" twins in paternity testing and forensics by ultra-deep next generation sequencing.

    Science.gov (United States)

    Weber-Lehmann, Jacqueline; Schilling, Elmar; Gradl, Georg; Richter, Daniel C; Wiehler, Jens; Rolf, Burkhard

    2014-03-01

    Monozygotic (MZ) twins are considered being genetically identical, therefore they cannot be differentiated using standard forensic DNA testing. Here we describe how identification of extremely rare mutations by ultra-deep next generation sequencing can solve such cases. We sequenced DNA from sperm samples of two twins and from a blood sample of the child of one twin. Bioinformatics analysis revealed five single nucleotide polymorphisms (SNPs) present in the twin father and the child, but not in the twin uncle. The SNPs were confirmed by classical Sanger sequencing. Our results give experimental evidence for the hypothesis that rare mutations will occur early after the human blastocyst has split into two, the origin of twins, and that such mutations will be carried on into somatic tissue and the germline. The method provides a solution to solve paternity and forensic cases involving monozygotic twins as alleged fathers or originators of DNA traces.

  17. Discordant sex in monozygotic XXY/XX twins: a case report.

    Science.gov (United States)

    Tachon, G; Lefort, G; Puechberty, J; Schneider, A; Jeandel, C; Boulot, P; Prodhomme, O; Meyer, P; Taviaux, S; Touitou, I; Pellestor, F; Geneviève, D; Gatinois, V

    2014-12-01

    We report a case of discordant phenotypic sex in monozygotic twins mosaic 47,XXY/46,XX: monozygotic heterokaryotypic twins. The twins presented with cognitive and comprehension delay, behavioural and language disorders, all symptoms frequently reported in Klinefelter syndrome. Molecular zygosity analysis with several markers confirmed that the twins are in effect monozygotic (MZ). Array comparative genomic hybridization found no evidence for the implication of copy number variation in the phenotypes. Ultrasound scans of the reproductive organs revealed no abnormalities. Endocrine tests showed a low testosterone level in Twin 1 (male phenotype) and a low gonadotrophin level in Twin 2 (female phenotype) which, combined with the results from ultrasound examination, provided useful information for potentially predicting the future fertility potential of the twins. Blood karyotypes revealed the presence of a normal 46,XX cell line and an aneuploïd 47,XXY cell line in both patients. Examination of the chromosome constitutions of various tissues such as blood, buccal smear and urinary sediment not surprisingly showed different proportions for the 46,XX and 47,XXY cell lines, which most likely explains the discordant phenotypic sex and mild Klinefelter features. The most plausible underlying biological mechanism is a post-zygotic loss of the Y chromosome in an initially 47,XXY zygote. This would result in an embryo with both 46,XX and 47,XXY cells lines which could subsequently divide into two monozygotic embryos through a twinning process. The two cell lines would then be distributed differently between tissues which could result in phenotypic discordances in the twins. These observations emphasize the importance of regular paediatric evaluations to determine the optimal timing for fertility preservation measures and to detect new Klinefelter features which could appear throughout childhood in the two subjects.

  18. Monochorionic twins with the same blood karyotype of 46,XY/47,XYY but different phenotypes.

    Science.gov (United States)

    Wuttikonsammakit, Piyawadee; Tanawattanacharoen, Somchai; Uerpairojkit, Boonchai

    2010-02-01

    We report the case of a 13-year-old woman who was pregnant with phenotypically discordant monochorionic twins: one with cystic hygroma and hydrops, the other one normal. Fetal blood sampling was performed by intrahepatic blood collection for karyotyping of both fetuses, revealing the same genotype of 46,XY/47,XYY in 2:1 proportion. Phenotypic discordance in monozygotic twins can have various causes, such as placental vascular anatomy, differences in allocation of the number of blastomeres or genetic postzygotic events.

  19. Electronic Origins of Anomalous Twin Boundary Energies in Hexagonal Close Packed Transition Metals

    OpenAIRE

    de Jong, M.; Kacher, J.; Sluiter, M.H.F.; L. Qi; Olmsted, D. L.; van de Walle, A.; Morris, J. W., Jr.; Minor, A. M.; Asta, M.

    2015-01-01

    Density-functional-theory calculations of twin-boundary energies in hexagonal close packed metals reveal anomalously low values for elemental Tc and Re, which can be lowered further by alloying with solutes that reduce the electron per atom ratio. The anomalous behavior is linked to atomic geometries in the interface similar to those observed in bulk tetrahedrally close packed phases. The results establish a link between twin-boundary energetics and the theory of bulk structural stability in ...

  20. VLBA AND CHANDRA OBSERVATIONS OF JETS IN FRI RADIO GALAXIES: CONSTRAINTS ON JET EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Kharb, P.; O' Dea, C. P. [Department of Physics, Rochester Institute of Technology (RIT), 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Tilak, A. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Baum, S. A. [Center for Imaging Science, Rochester Institute of Technology (RIT), 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Haynes, E.; Noel-Storr, J.; Fallon, C.; Christiansen, K. [Radcliffe Institute for Advanced Study, 10 Garden Street, Cambridge, MA 02138 (United States)

    2012-07-20

    We present here the results from new Very Long Baseline Array (VLBA) observations at 1.6 and 5 GHz of 19 galaxies of a complete sample of 21 Uppasala General Catalog (UGC) Fanaroff-Riley type I (FRI) radio galaxies. New Chandra data of two sources, viz., UGC 00408 and UGC 08433, are combined with the Chandra archival data of 13 sources. The 5 GHz observations of 10 'core-jet' sources are polarization-sensitive, while the 1.6 GHz observations constitute second-epoch total intensity observations of nine 'core-only' sources. Polarized emission is detected in the jets of seven sources at 5 GHz, but the cores are essentially unpolarized, except in M87. Polarization is detected at the jet edges in several sources, and the inferred magnetic field is primarily aligned with the jet direction. This could be indicative of magnetic field 'shearing' due to jet-medium interaction, or the presence of helical magnetic fields. The jet peak intensity I{sub {nu}} falls with distance d from the core, following the relation, I{sub {nu}}{proportional_to}d{sup a} , where a is typically {approx} - 1.5. Assuming that adiabatic expansion losses are primarily responsible for the jet intensity 'dimming,' two limiting cases are considered: (1) the jet has a constant speed on parsec scales and is expanding gradually such that the jet radius r{proportional_to}d 0{sup .4}; this expansion is, however, unobservable in the laterally unresolved jets at 5 GHz, and (2) the jet is cylindrical and is accelerating on parsec scales. Accelerating parsec-scale jets are consistent with the phenomenon of 'magnetic driving' in Poynting-flux-dominated jets. While slow jet expansion as predicted by case (1) is indeed observed in a few sources from the literature that are resolved laterally, on scales of tens or hundreds of parsecs, case (2) cannot be ruled out in the present data, provided the jets become conical on scales larger than those probed by VLBA. Chandra

  1. Yes, High School Students Can Analyze Chandra Data

    Science.gov (United States)

    Keohane, J. W.; Clearfield, C. R.; Olbert, C. M.

    2002-12-01

    For the past two years, high school students at the North Carolina School of Science and Math (NCSSM) have worked with new and archival Chandra data, and have produced interesting scientific results. These results have included one refereed paper in the Ap.J., and about a dozen presentations at scientific meetings (including three at this meeting). The students were selected, based on interest, from the junior class at NCSSM, to stay on campus and work intensively for 2 to 4 weeks over the summer. Each team of students selected an object with public Chandra ACIS data, and were taught how to produce data products such as images and spectra, as well as conduct a literature search. In most cases, a paper had already been published using those data, and the students were usually able to reproduce the results. As the students waded through the literature, they would search for a theory to test or an interesting new phenomenon. Often the students would request an image in another wavelength to compare in detail to the Chandra data. After the summer, many students continued to work throughout the following fall semester, producing a paper for submission to the Siemens Westinghouse Science and Technology Competition by the beginning of October. In the process of conducting research, the students learn to apply many physics concepts, and learn valuable scientific research and writing skills. Those students that choose to continue with astrophysics can often dive directly into a high-level research project immediately when they arrive at college. These programs have been funded by NASA, through E/PO grants attached to parent research grants.

  2. Lessons Learned Designing and Building the Chandra Telescope

    Science.gov (United States)

    Arenberg, Jonathan

    2016-04-01

    This poster offers some of the major lessons learned by key members of the Chandra Telescope team. These lessons are gleaned from our experiences developing, designing, building and testing the telescope and its subsystems, with 15 years of hindsight. Among the topics to be discussed are the early developmental tests, known as VETA-I and VETA-II, requirements derivation, the impact of late requirements and reflection on the conservatism in the design process. This poster offers some opinions on how these lessons can affect future missions.

  3. Chandra Cluster Cosmology Project III: Cosmological Parameter Constraints

    DEFF Research Database (Denmark)

    Vikhlinin, A.; Kravtsov, A. V.; Burenin, R. A.;

    2009-01-01

    function evolution to be used as a useful growth of a structure-based dark energy probe. In this paper, we present cosmological parameter constraints obtained from Chandra observations of 37 clusters with langzrang = 0.55 derived from 400 deg2 ROSAT serendipitous survey and 49 brightest z ≈ 0.05 clusters...... detected in the All-Sky Survey. Evolution of the mass function between these redshifts requires ΩΛ > 0 with a ~5σ significance, and constrains the dark energy equation-of-state parameter to w 0 = –1.14 ± 0.21, assuming a constant w and a flat universe. Cluster information also significantly improves...

  4. A Million-Second Chandra View of Cassiopeia A

    CERN Document Server

    Hwang, U; Badenes, C; Berends, F A; Blondin, J M; Cioffi, D; Delaney, T A; Dewey, D; Fesen, R A; Flanagan, K A; Fryer, C L; Ghavamian, P; Hughes, J P; Morse, J A; Plucinsky, P P; Petre, R; Pohl, M; Rudnick, L; Sankrit, R; Slane, P O; Smith, R K; Vink, J; Warren, J S; Hwang, Una; Badenes, Carles; Berendse, Fred; Blondin, John; Cioffi, Denis; Laney, Tracey De; Dewey, Daniel; Fesen, Robert; Flanagan, Kathryn A.; Fryer, Christopher L.; Ghavamian, Parviz; Hughes, John P.; Morse, Jon A.; Plucinsky, Paul P.; Petre, Robert; Pohl, Martin; Rudnick, Lawrence; Sankrit, Ravi; Slane, Patrick O.; Smith, Randall K.; Vink, Jacco; Warren, Jessica S.

    2004-01-01

    We introduce a million-second observation of the supernova remnant Cassiopeia A with the Chandra X-ray Observatory. The bipolar structure of the Si-rich ejecta (NE jet and SW counterpart) is clearly evident in the new images, and their chemical similarity is confirmed by their spectra. These are most likely due to jets of ejecta as opposed to cavities in the circumstellar medium, since we can reject simple models for the latter. The properties of these jets and the Fe-rich ejecta will provide clues to the explosion of Cas A.

  5. Chandra ACIS Observations of the Nearby Spiral Galaxy NGC 300

    Science.gov (United States)

    Bobar, Dale; Turner, Kevin; Schlegel, Eric M.

    2017-01-01

    The ACIS detector (Advanced CCD Imaging Spectrometer) onboard the Chandra X-ray Observatory has imaged the nearby spiral NGC 300 over three epochs for a total exposure of 1.885x102 ksec. We describe each observation as well as the merged data set. Each exposure contains 132 individual sources. We focus on the time variability and luminosity distributions of the sources. Initial results show no diffuse emissions in the galaxy. Finally, we compare the merged data set and the detected sources with other wavebands.

  6. Chandra Discovers the X-ray Signature of a Powerful Wind from a Galactic Microquasar

    Science.gov (United States)

    2000-11-01

    NASA's Chandra X-ray Observatory has detected, for the first time in X rays, a stellar fingerprint known as a P Cygni profile--the distinctive spectral signature of a powerful wind produced by an object in space. The discovery reveals a 4.5-million-mile-per-hour wind coming from a highly compact pair of stars in our galaxy, report researchers from Penn State and the Massachusetts Institute of Technology in a paper they will present on 8 November 2000 during a meeting of the High-Energy Astrophysics Division of the American Astronomical Society in Honolulu, Hawaii. The paper also has been accepted for publication in The Astrophysical Journal Letters. "To our knowledge, these are the first P Cygni profiles reported in X rays," say researchers Niel Brandt, assistant professor of astronomy and astrophysics at Penn State, and Norbert S. Schulz, research scientist at the Massachusetts Institute of Technology. The team made the discovery during their first observation of a binary-star system with the Chandra X-ray Observatory, which was launched into space in July 1999. The system, known as Circinus X-1, is located about 20,000 light years from Earth in the constellation Circinus near the Southern Cross. It contains a super-dense neutron star in orbit around a normal fusion-burning star like our Sun. Although Circinus X-1 was discovered in 1971, many properties of this system remain mysterious because Circinus X-1 lies in the galactic plane where obscuring dust and gas have blocked its effective study in many wavelengths. The P Cygni spectral profile, previously detected primarily at ultraviolet and optical wavelengths but never before in X rays, is the textbook tool astronomers rely on for probing stellar winds. The profile looks like the outline of a roller coaster, with one really big hill and valley in the middle, on a data plot with velocity on one axis and the flow rate of photons per second on the other. It is named after the famous star P Cygni, in which such

  7. Ecosensitivity and genetic polymorphism of somatic traits in the perinatal development of twins.

    Science.gov (United States)

    Waszak, Małgorzata; Cieślik, Krystyna; Skrzypczak-Zielińska, Marzena; Szalata, Marlena; Wielgus, Karolina; Kempiak, Joanna; Bręborowicz, Grzegorz; Słomski, Ryszard

    2016-04-01

    In view of criticism regarding the usefulness of heritability coefficients, the aim of this study was to analyze separately the information on genetic and environmental variability. Such an approach, based on the normalization of trait's variability for its value, is determined by the coefficients of genetic polymorphism (Pg) and ecosensitivity (De). The studied material included 1263 twin pairs of both sexes (among them 424 pairs of monozygotic twins and 839 pairs of dizygotic twins) born between the 22nd and 41st week of gestation. Variability of six somatic traits was analyzed. The zygosity of same-sex twins was determined based on the polymorphism of DNA from lymphocytes of the umbilical cord blood, obtained at birth. The coefficients of genetic polymorphism and ecosensitivity for analyzed traits of male and female twins born at various months of gestation were calculated. Our study revealed that a contribution of the genetic component predominated over that of the environmental component in determining the phenotypic variability of somatic traits of newborns from twin pregnancies. The genetically determined phenotypic variability in male twins was greater than in the females. The genetic polymorphism and ecosensitivity of somatic traits were relatively stable during the period of fetal ontogeny analyzed in this study. Only in the case of body weight, a slight increase in the genetic contribution of polygenes to the phenotypic variance could be observed with gestational age, along with a slight decrease in the influence of environmental factors.

  8. Role of five-fold twin boundary on the enhanced mechanical properties of fcc Fe nanowires.

    Science.gov (United States)

    Wu, J Y; Nagao, S; He, J Y; Zhang, Z L

    2011-12-14

    The role of 5-fold twin boundary on the structural and mechanical properties of fcc Fe nanowire under tension is explored by classical molecular dynamics. Twin-stabilized fcc nanowire with various diameters (6-24 nm) are examined by tension tests at several temperatures ranging from 0.01 to 1100 K. Significant increase in the Young's modulus of the smaller nanowires is revealed to originate from the central area of quinquefoliolate-like stress-distribution over the 5-fold twin, rather than from the surface tension that is often considered as the main source of such size-effects found in nanostructures. Because of the excess compressive stress caused by crossing twin-boundaries, the atoms in the center behave stiffer than those in bulk and even expand laterally under axial tension, providing locally negative Poisson's ratio. The yield strength of nanowire is also enhanced by the twin boundary that suppresses dislocation nucleation within a fcc twin-domain; therefore, the plasticity of nanowire is initiated by strain-induced fcc→bcc phase transformation that destroys the twin structure. After the yield, the nucleated bcc phase immediately spreads to the entire area, and forms a multigrain structure to realize ductile deformation followed by necking. As temperature elevated close to the critical temperature between bcc and fcc phases, the increased stability of fcc phase competes with the phase transformation under tension, and hence dislocation nucleations in fcc phase are observed exclusively at the highest temperature in our study.

  9. Fingerprint recognition with identical twin fingerprints.

    Directory of Open Access Journals (Sweden)

    Xunqiang Tao

    Full Text Available Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6 images. Compared to the previous work, our contributions are summarized as follows: (1 Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2 Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3 A larger sample (83 pairs was collected. (4 A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5 A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d For each of four fingers of identical twins, the probability of having same fingerprint type is similar.

  10. Long-term follow-up and analysis of monozygotic twins concordant for 45,X/46,XY peripheral blood karyotype but discordant for phenotypic sex.

    Science.gov (United States)

    Tho, Sandra P; Jackson, Robert; Kulharya, Anita S; Reindollar, Richard H; Layman, Lawrence C; McDonough, Paul G

    2007-11-01

    We report on the follow-up of a set of monozygotic (MZ) twins who were concordant for peripheral blood karyotype 45,X/46,XY but discordant for phenotypic sex. One twin is a phenotypically normal male and the other twin has asymetrical gonadal dysgenesis. The female twin has the mos45,X/46,XY karyotype in all four tissues: left testis, right streak, vas deferens, and clitoral skin. The normal male twin has the normal 46,XY karyotype in all three tissues tested: foreskin, scrotal skin, and testis. Follow-up of the twins at age 21, revealed persistence of mos45,X/46,XY karyotype in peripheral blood into adult life. However, the male grew up with normal male stature, reaching an adult height of 182 cm. The female twin received low dose estrogen replacement with complete breast development at age 14 years. She reached an adult height of 156 cm. At 21 years of age the male twin had normal testicular endocrine function, but severe oligospermia. The long-term follow-up of this set of MZ twins indicate that the male twin has the mosaicism confined to peripheral blood and has the normal 46,XY male constitution. This was further confirmed by his normal male stature and normal testicular endocrine function. The 45X cell line is likely due to his receiving these cells passively from his twin sister via placental anastomoses in utero. The exposure to these 45,X cells during development may have had an impact on his spermatogenesis.

  11. The relationship between twin language, twins' close ties, and social competence.

    Science.gov (United States)

    Hayashi, Chisato; Mikami, Hiroshi; Nishihara, Reiko; Maeda, Chiho; Hayakawa, Kazuo

    2014-02-01

    This study investigated the relationship between twin language, twins' close ties, and social competence in a prospective longitudinal study. We hypothesized that twins whose tie is close would be more likely to develop a twin language, and these twins would be less likely to develop social competence. In addition, we hypothesize that some environmental factors, such as having an older sibling, preschool attendance, zygosity, and sex are also related to twin language, twins' close ties, and social competence. At baseline in 1999 a mailed questionnaire survey was conducted, and a follow-up questionnaire was distributed in 2004 among 958 mothers. As a result, 516 respondents returned the questionnaire (53.9%). In this study, we used 261 twin pairs aged from 6 to 12 years (school-age children) for analysis, excluding those with missing values. In the present study, we found that zygosity and sex were associated with twins' close ties. Having an older sibling and preschool attendance did not affect the twins' close tie, twin language, or social competence. One of the most important findings was that social competence was not affected directly by twins' close tie, but was affected when a twin language was found.

  12. Chandra observations of the peculiar X-ray transient IGR J16358-4726

    Energy Technology Data Exchange (ETDEWEB)

    Patel, S.K.; Kouveliotou, C.; Tennant, A.; Woods, P.M.; Finger, M.; King, A.; Ubertini, P.; Winkler, C.; Courvoisier, T.J.-L.; Klis, M. van der; Wachter, S

    2004-06-01

    The new transient IGR J16358-4726 was discovered on 2003 March 19 with INTEGRAL. We detected the source serendipitously during our 2003 March 24 observation of SGR 1627 - 41 with the CHANDRA X-ray Observatory at the 1.7 x 10{sup -10} ergs s{sup -1} cm{sup -2} flux level (2-10 keV) with a very high absorption column (N{sub H}=3.3x10{sup 23} cm{sup -2}) and a hard power law spectrum of photon index 0.5(1). We discovered a very strong flux modulation with a period of 5880(50) s and peak-to-peak pulse fraction of 70(6) % (2-10 keV), clearly visible in the x-ray data. The nature, however, of IGR 16357-4726 remains unresolved. Most likely, we are looking at a galactic binary neutron star system as evidenced by the detection of rest frame fluorescence line emission from neutral Fe K (6.4 keV) in the Chandra spectrum. If the detected modulation is a spin period, this transient is a new kind of object, belonging to a class of very hard transients recently revealed with the unique INTEGRAL capabilities. The only neutron star systems known with similar spin periods are low luminosity persistent wind-fed pulsars, which exhibit very soft X-ray spectra. If this is an orbital period, then the system could be a compact Low Mass X-ray Binary.

  13. Chandra and XMM–Newton Observations of H2O Maser Galaxy Mrk 348

    Indian Academy of Sciences (India)

    J. Wang; J. S. Zhang; Q. Guo

    2014-09-01

    For H2O megamaser galaxy Mrk 348, Chandra and XMM–Newton data are analysed. The nuclear fitting results of XMM–Newton data suggest the possible existence of a heavily obscured AGN. But the nuclear spectrum extracted from Chandra cannot be well-fitted by the best fitting model for XMM–Newton. Further optimal fitting and discussions are needed.

  14. Historical Remembrances of the Chandra X-ray Observatory: How Partnerships Created Success

    Science.gov (United States)

    Burke, Robert

    2009-09-01

    As the astronomy community plans for new ventures in space, we're forced to find creative solutions to operate within the ever increasing fiscal constraints of the current economic environment. The Chandra X-ray Observatory program offers an example of how missions can be successfully developed within manageable budget constraints. The ten year anniversary offers us the chance to look back at the Chandra team's special partnership between scientists, managers, and industry that led to our success.Chandra experienced many of the challenges common to major observatories: state-of-the-art technical requirements, budget-induced slips, and restructurings. Yet the Chandra team achieved excellent performance for dramatically lower cost. In fact, Chandra completed its prime mission for billions of dollars less than originally planned. In 1992, NASA MSFC and Northrop Grumman (then TRW) together led a major restructure that saved approximately 3.4B in program cost, while we improved the imaging capability and observing efficiency of Chandra. This was accomplished by a combination of team-work, systems engineering, advanced technology insertion, and effective approaches for program implementation, combined with a high performance culture that aligned goals and focused on mission success. Northrop Grumman is proud of our role in supporting the NASA Marshall Space Flight Center and our academic partners in advancing the frontiers of x-ray astronomy and scientific discovery with Chandra. As Chandra continues its extended mission, the observatory continues to provide superb scientific performance.

  15. The Spread of Substance Use and Delinquency between Adolescent Twins

    Science.gov (United States)

    Laursen, Brett; Hartl, Amy C.; Vitaro, Frank; Brendgen, Mara; Dionne, Ginette; Boivin, Michel

    2017-01-01

    This investigation examines the spread of problem behaviors (substance use and delinquency) between twin siblings. A sample of 628 twins (151 male twin pairs and 163 female twin pairs) drawn from the Quebec Newborn Twin Study completed inventories describing delinquency and substance use at ages 13, 14, and 15. A 3-wave longitudinal actor-partner…

  16. Einstein's Clocks and Langevin's Twins

    CERN Document Server

    Weinstein, Galina

    2012-01-01

    In 1905 Einstein presented the Clock Paradox and in 1911 Paul Langevin expanded Einstein's result to human observers, the "Twin Paradox." I will explain the crucial difference between Einstein and Langevin. Einstein did not present the so-called "Twin Paradox." Later Einstein continued to speak about the clock paradox. Einstein might not have been interested in the question: what happens to the observers themselves. The reason for this could be the following; Einstein dealt with measurement procedures, clocks and measuring rods. Einstein's observers were measuring time with these clocks and measuring rods. Einstein might not have been interested in so-called biology of the observers, whether these observers were getting older, younger, or whether they have gone any other changes; these changes appeared to be out of the scope of his "Principle of relativity" or kinematics. The processes and changes occurring within observers seemed to be good for philosophical discussions. Later writers criticized Einstein's c...

  17. Identical twins in forensic genetics

    DEFF Research Database (Denmark)

    Tvedebrink, Torben; Morling, Niels

    2015-01-01

    The increase in the number of forensic genetic loci used for identification purposes results in infinitesimal random match probabilities. These probabilities are computed under assumptions made for rather simple population genetic models. Often, the forensic expert reports likelihood ratios, where...... published results accounting for close familial relationships. However, we revisit the discussion to increase the awareness among forensic genetic practitioners and include new information on medical and societal factors to assess the risk of not considering a monozygotic twin as the true perpetrator...

  18. Geographic Tongue in Monozygotic Twins

    OpenAIRE

    Shekhar M, Guna

    2014-01-01

    This article discusses a case of 5-year-old girl monozygotic twins who were suffering from geographic tongue (GT), a benign inflammatory disorder of the tongue which is characterized by circinate, irregular erythematous lesions on the dorsum and lateral borders of the tongue caused by loss of filiform papillae of the tongue epithelium. Whilst geographic tongue is a common entity, reports on this condition are uncommon in the literature. To best of our knowledge, this is the first report which...

  19. The jet and counterjet of 3C 270 (NGC 4261) viewed in the X-ray with Chandra

    CERN Document Server

    Worrall, D M; O'Sullivan, E; Zezas, A; Wolter, A; Trinchieri, G; Fabbiano, G

    2010-01-01

    The radio source 3C 270, hosted by NGC 4261, is the brightest known example of counterjet X-ray emission from a low-power radio galaxy. We report on the X-ray emission of the jet and counterjet from 130 ks of Chandra data. We argue that the X-ray emission is synchrotron radiation and that the internal properties of the jet and counterjet are remarkably similar. We find a smooth connection in X-ray hardness and X-ray to radio ratio between the jet and one of the X-ray components within the core spectrum. We observe wedge-like depressions in diffuse X-ray surface brightness surrounding the jets, and interpret them as regions where an aged population of electrons provides pressure to balance the interstellar medium of NGC 4261. About 20% of the mass of the interstellar medium has been displaced by the radio source. Treating 3C 270 as a twin-jet system, we find an interesting agreement between the ratio of jet-to-counterjet length in X-rays and that expected if X-rays are observed over the distance that an outflo...

  20. Thrombosis of anastomoses may affect the staging sequence of twin-twin transfusion syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Wijngaard, Jeroen P H M van den; Gemert, Martin J C van [Laser Center, Academic Medical Center-University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam (Netherlands); Ross, Michael G [Department of Obstetrics and Gynecology, Harbor-UCLA School of Medicine, Torrance, CA 90502 (United States)], E-mail: j.p.vandenwijngaard@amc.uva.nl

    2008-03-07

    Twin-twin transfusion syndrome (TTTS) is a severe complication of monozygotic (identical) twins, which share one single monochorionic placenta. It is caused by placental anastomoses which link the two fetoplacental circulations of the twins and allow a chronic net inter-twin transfusion to develop between the fetuses. Clinical presentation of TTTS manifestations has been classified into five different stages. In this paper, we used our computational model of TTTS and examined the possible differences between chronic and rapidly increasing inter-twin transfusion in the simulated TTTS staging sequence. Our results suggest that rapid alterations in the net inter-twin transfusion, e.g. due to thrombosis of placental anastomoses, may produce a different staging sequence than in TTTS caused by chronic inter-twin transfusion. These results may aid an improved knowledge of TTTS pathophysiology under conditions of a rapidly changing cardiovascular function, and contribute to the planning of optimal intervention under such circumstances. (note)

  1. Twins eye study in Tasmania (TEST): rationale and methodology to recruit and examine twins.

    Science.gov (United States)

    Mackey, David A; Mackinnon, Jane R; Brown, Shayne A; Kearns, Lisa S; Ruddle, Jonathan B; Sanfilippo, Paul G; Sun, Cong; Hammond, Christopher J; Young, Terri L; Martin, Nicholas G; Hewitt, Alex W

    2009-10-01

    Visual impairment is a leading cause of morbidity and poor quality of life in our community. Unravelling the mechanisms underpinning important blinding diseases could allow preventative or curative steps to be implemented. Twin siblings provide a unique opportunity in biology to discover genes associated with numerous eye diseases and ocular biometry. Twins are particularly useful for quantitative trait analysis through genome-wide association and linkage studies. Although many studies involving twins rely on twin registries, we present our approach to the Twins Eye Study in Tasmania to provide insight into possible recruitment strategies, expected participation rates and potential examination strategies that can be considered by other researchers for similar studies. Five separate avenues for cohort recruitment were adopted: (1) piggy-backing existing studies where twins had been recruited, (2) utilizing the national twin registry, (3) word-of-mouth and local media publicity, (4) directly approaching schools, and finally (5) collaborating with other research groups studying twins.

  2. The TWINS Science Data System after the launch of TWINS 1

    Science.gov (United States)

    Goldstein, J.; Valek, P.; Skoug, R.; Delapp, D.; Redfern, J.; Carruth, B.; McComas, D.

    2007-05-01

    The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) 1 satellite is in orbit and science data are expected to commence in the near future. TWINS-1 comprises half of the TWINS stereoscopic neutral atom imaging system that will advance our knowledge of the Earth's ring current. To support the expected data return, we have developed a Science Data System (SDS) for the TWINS mission. The TWINS SDS is an IDL- and Java- driven data interface that operates primarily via a web browser, and has as its spine an SQL-queryable database. Through this interface, TWINS science data will be provided to the TWINS team, the space science community, and the public. In this paper we present the current and future capabilities of the TWINS SDS, as well as how the SDS fits into virtual observatory infrastructure.

  3. Register-based research on twins

    DEFF Research Database (Denmark)

    Christensen, Kaare; Ohm Kyvik, Kirsten; Holm, Niels V

    2011-01-01

    Introduction: The Danish Twin Registry (DTR) has for more than 50 years been based on surveys and clinical investigations and over the two last decades also on register linkage. Currently these two approaches are merged within Statistics Denmark. Research topics: Here we report on three major...... groups of register-based research in the DTR that used the uniqueness of twinning. First, we focus on the ''long-term prognosis'' of being a twin compared with being a singleton and show that Danish twins have health trajectories in adulthood similar to singletons, which is a result of interest for twins...... and their families as well as a test of the fetal origins hypothesis that states that fetal growth restriction has long-term health consequences. Secondly, we summarise some of the most important register-based ''classical twin studies'', e.g. heritability studies on lifespan and exceptional longevity. Finally, we...

  4. Twin delivery: method, timing and conduct.

    Science.gov (United States)

    Barrett, Jon F R

    2014-02-01

    The incidence of twin pregnancy has increased worldwide over the past 10 years, largely as a consequence of the assisted reproductive technologies. Issues such as intrapartum monitoring and operative interventions, especially relating to the second twin, provide a unique challenge in labour and delivery. Epidemiological and cohort data suggest that twins have a three-fold higher mortality rate than singletons, and that the second twin might have a better outcome if delivered by lower segment caesarean section. The recently completed Twin Birth Study has found that planned vaginal lower segment caesarean section is not advantageous to the fetus. In the light of this large randomised-controlled trial, vaginal delivery if twin A presents by the vertex is recommended as long as guidelines for the conduct of such delivery are followed.

  5. (120) and (122-bar) monazite deformation twins

    Energy Technology Data Exchange (ETDEWEB)

    Hay, R.S

    2003-10-20

    Unusual features of (120) and (122-bar) deformation twins in monazite (monoclinic LaPO{sub 4}) are described and analyzed. These features are kinks and other irregularities in (120) twins, and V-shaped indentations on (120) and (122-bar) twin planes. Twinning shear analysis suggests that the kinks are a type II deformation twin mode with shear direction ({eta}{sub 1}) of [21-bar0]. This complements previous analysis based on atom shuffling considerations. Shear strain compatibility requires extensive plastic deformation in the kink. The V-shaped indentations may be analogous to similar structures in b.c.c metal deformation twins. Deformation mechanisms that may be associated with these structures are discussed.

  6. Fullerton Virtual Twin Study: an update.

    Science.gov (United States)

    Segal, Nancy L; McGuire, Shirley A; Graham, Jamie L; Stohs, Joanne Hoven

    2013-02-01

    Virtual twins (VTs) are same-age unrelated siblings reared together from early infancy. These unique sibling sets replicate twinship, but without the genetic link. The first VT pair was identified and studied at the University of Minnesota in 1990, launching the development of the Fullerton Virtual Twin Study at California State University, Fullerton (CSUF) in 1991. The registry currently includes 151 pairs, mostly children, with new pairs identified on a continuous basis. Research with VTs includes studies of general intelligence, body size, interpersonal trust, social coordination, social networks, and parenting. In some cases, VTs have been studied in conjunction with pairs of monozygotic twins, dizygotic twins, full siblings, and friends as part of TAPS (Twins, Adoptees, Peers and Siblings), a collaborative project conducted between CSUF and the University of San Francisco, 2002-2006. VTs will also serve as a comparison group for epigenetic analyses of young Chinese twins reared apart and together.

  7. Twinning of Polymer Crystals Suppressed by Entropy

    Directory of Open Access Journals (Sweden)

    Nikos Ch. Karayiannis

    2014-09-01

    Full Text Available We propose an entropic argument as partial explanation of the observed scarcity of twinned structures in crystalline samples of synthetic organic polymeric materials. Polymeric molecules possess a much larger number of conformational degrees of freedom than low molecular weight substances. The preferred conformations of polymer chains in the bulk of a single crystal are often incompatible with the conformations imposed by the symmetry of a growth twin, both at the composition surfaces and in the twin axis. We calculate the differences in conformational entropy between chains in single crystals and chains in twinned crystals, and find that the reduction in chain conformational entropy in the twin is sufficient to make the single crystal the stable thermodynamic phase. The formation of cyclic twins in molecular dynamics simulations of chains of hard spheres must thus be attributed to kinetic factors. In more realistic polymers this entropic contribution to the free energy can be canceled or dominated by nonbonded and torsional energetics.

  8. A Chandra Study of the Galactic Globular Cluster Omega Centauri

    CERN Document Server

    Haggard, Daryl; Davies, Melvyn B

    2009-01-01

    We analyze a ~70 ksec Chandra ACIS-I exposure of the globular cluster Omega Centauri (NGC 5139). The ~17 amin x 17 amin field of view fully encompasses three core radii and almost twice the half-mass radius. We detect 180 sources to a limiting flux of ~4.3x10^-16 erg/cm^2/s (Lx = 1.2x10^30 erg/s at 4.9 kpc). After accounting for the number of active galactic nuclei and possible foreground stars, we estimate that 45-70 of the sources are cluster members. Four of the X-ray sources have previously been identified as compact accreting binaries in the cluster--three cataclysmic variables (CVs) and one quiescent neutron star. Correlating the Chandra positions with known variable stars yields eight matches, of which five are probable cluster members that are likely to be binary stars with active coronae. Extrapolating these optical identifications to the remaining unidentified X-ray source population, we estimate that 20-35 of the sources are CVs and a similar number are active binaries. This likely represents most ...

  9. The Chandra COSMOS Legacy survey: optical/IR identifications

    CERN Document Server

    Marchesi, S; Elvis, M; Salvato, M; Brusa, M; Comastri, A; Gilli, R; Hasinger, G; Lanzuisi, G; Miyaji, T; Treister, E; Urry, C M; Vignali, C; Zamorani, G; Allevato, V; Cappelluti, N; Cardamone, C; Finoguenov, A; Griffiths, R E; Karim, A; Laigle, C; LaMassa, S M; Jahnke, K; Ranalli, P; Schawinski, K; Schinnerer, E; Silverman, J D; Smolcic, V; Suh, H; Trakhtenbrot, B

    2015-01-01

    We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6 Ms Chandra program on the 2.2 square degrees of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 micron identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6 micron information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while 54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is availa...

  10. Chandra Multiwavelength Project X-ray Point Source Catalog

    CERN Document Server

    Kim, M; Wilkes, B J; Green, P J; Kim, E; Anderson, C S; Barkhouse, W A; Evans, N R; Ivezic, Z; Karovska, M; Kashyap, V L; Lee, M G; Maksym, P; Mossman, A E; Silverman, J D; Tananbaum, H D; Kim, Minsun; Kim, Dong-Woo; Wilkes, Belinda J.; Green, Paul J.; Kim, Eunhyeuk; Anderson, Craig S.; Barkhouse, Wayne A.; Evans, Nancy R.; Ivezic, Zeljko; Karovska, Margarita; Kashyap, Vinay L.; Lee, Myung Gyoon; Maksym, Peter; Mossman, Amy E.; Silverman, John D.; Tananbaum, Harvey D.

    2006-01-01

    We present the Chandra Multiwavelength Project (ChaMP) X-ray point source catalog with ~6,800 X-ray sources detected in 149 Chandra observations covering \\~10 deg^2. The full ChaMP catalog sample is seven times larger than the initial published ChaMP catalog. The exposure time of the fields in our sample ranges from 0.9 to 124 ksec, corresponding to a deepest X-ray flux limit of f_{0.5-8.0} = 9 x 10^{-16} erg/cm2/sec. The ChaMP X-ray data have been uniformly reduced and analyzed with ChaMP-specific pipelines, and then carefully validated by visual inspection. The ChaMP catalog includes X-ray photometric data in 8 different energy bands as well as X-ray spectral hardness ratios and colors. To best utilize the ChaMP catalog, we also present the source reliability, detection probability and positional uncertainty. To quantitatively assess those parameters, we performed extensive simulations. In particular, we present a set of empirical equations: the flux limit as a function of effective exposure time, and the p...

  11. The BMW-Chandra survey. Serendipitous Source Catalogue

    CERN Document Server

    Romano, P; Campana, S; Moretti, A; Panzera, M R; Tagliaferri, G; Mottini, M

    2009-01-01

    We present the BMW-Chandra source catalogue derived from Chandra ACIS-I observations (exposure time >10ks) public as of March 2003 by using a wavelet detection algorithm (Lazzati et al. 1999; Campana et al. 1999). The catalogue contains a total of 21325 sources, 16758 of which are serendipitous. Our sky coverage in the soft band (0.5-2 keV, S/N =3) is ~8 deg^2 for F_X > 10^-13 erg cm^-2 s-1, and ~2 deg^2 for F_X >10^-15 erg cm^-2 s^-1. The catalogue contains information on positions, count rates (and errors) in three energy bands. (total, 0.5-7 keV; soft, 0.5-2 keV; and hard, 2-7keV), and in four additional energy bands, SB1 (0.5-1keV), SB2 (1-2 keV), HB1 (2-4 keV), and HB2 (4-7keV), as well as information on the source extension, and cross-matches with the FIRST, IRAS, 2MASS, and GSC-2 catalogues.

  12. The BMW-Chandra survey. Serendipitous Source Catalogue

    Science.gov (United States)

    Romano, P.; Mignani, R. P.; Campana, S.; Moretti, A.; Panzera, M. R.; Tagliaferri, G.; Mottini, M.

    2009-07-01

    We present the BMW-Chandra source catalogue derived from Chandra ACIS-I observations (exposure time > 10ks) public as of March 2003 by using a wavelet detection algorithm (Lazzati et al. 1999; Campana et al. 1999). The catalogue contains a total of 21325 sources, 16758 of which are serendipitous. Our sky coverage in the soft band (0.5-2keV, S/N=3) is ~ 8 deg2 for FX ≥ 10-13 erg cm-2 s-1, and ~ 2 deg2 for FX ≥ 10-15 erg cm-2 s-1. The catalogue contains information on positions, count rates (and errors) in three energy bands (total, 0.5-7keV; soft, 0.5-2keV; and hard, 2-7keV), and in four additional energy bands, SB1 (0.5-1keV), SB2 (1-2keV), HB1 (2-4keV), and HB2 (4-7keV), as well as information on the source extension, and cross-matches with the FIRST, IRAS, 2MASS, and GSC-2 catalogues.

  13. A Deep Chandra ACIS Survey of M51

    Science.gov (United States)

    Kuntz, K. D.; Long, Knox S.; Kilgard, Roy E.

    2016-08-01

    We have obtained a deep X-ray image of the nearby galaxy M51 using Chandra. Here we present the catalog of X-ray sources detected in these observations and provide an overview of the properties of the point-source population. We find 298 sources within the D 25 radii of NGC 5194/5, of which 20% are variable, a dozen are classical transients, and another half dozen are transient-like sources. The typical number of active ultraluminous X-ray sources in any given observation is ˜5, and only two of those sources persist in an ultraluminous state over the 12 yr of observations. Given reasonable assumptions about the supernova remnant population, the luminosity function is well described by a power law with an index between 1.55 and 1.7, only slightly shallower than that found for populations dominated by high-mass X-ray binaries (HMXBs), which suggests that the binary population in NGC 5194 is also dominated by HMXBs. The luminosity function of NGC 5195 is more consistent with a low-mass X-ray binary dominated population. Based on observations made with NASA's Chandra X-ray Observatory, which is operated by the Smithsonian Astrophysical Observatory under contract #NAS83060, and the data were obtained through program GO1-12115.

  14. Chandra Observation of the Starburst Galaxy NGC 2146

    CERN Document Server

    Inui, T; Tsuru, T G; Koyama, K; Matsushita, S; Peck, A B; Tarchi, A; Inui, Tatsuya; Matsumoto, Hironori; Tsuru, Takeshi Go; Koyama, Katsuji; Matsushita, Satoki; Peck, Alison B.; Tarchi, Andrea

    2004-01-01

    We present six monitoring observations of the starburst galaxy NGC 2146 using the Chandra X-ray Observatory. We have detected 67 point sources in the 8'.7 x 8'.7 field of view of the ACIS-S detector. Six of these sources were Ultra-Luminous X-ray Sources, the brightest of which has a luminosity of 5 x 10^{39} ergs s^{-1}. One of the source, with a luminosity of ~1 x 10^{39} ergs s^{-1}, is coincident with the dynamical center location, as derived from the ^{12}CO rotation curve. We suggest that this source may be a low-luminosity active galactic nucleus. We have produced a table where the positions and main characteristics of the Chandra-detected sources are reported. The comparison between the positions of the X-ray sources and those of compact sources detected in NIR or radio does not indicate any definite counterpart. Taking profit of the relatively large number of sources detected, we have derived a logN-logS relation and a luminosity function. The former shows a break at \\~10^{-15} ergs cm^{-2} s^{-1}, t...

  15. Chandra Observes the End of an Era SN 1987A

    CERN Document Server

    Frank, Kari A; Park, Sangwook; McCray, Richard; Dwek, Eli; Burrows, David N

    2016-01-01

    Updated imaging and photometric results from Chandra observations of SN 1987A, covering the last 16 years, are presented. We find that the 0.5-2 keV light curve has remained constant at ~8x10^-12 erg s^-1 cm^-2 since 9500 days, with the 3-8 keV light curve continuing to increase until at least 10000 days. The expansion rate of the ring is found to be energy dependent, such that after day 6000 the ring expands faster in the 2-10 keV band than it does at energies <2 keV. Images show a reversal of the east-west asymmetry between 7000 and 8000 days after the explosion. The latest images suggest the southeastern side of the equatorial ring is beginning to fade. Consistent with the latest optical and infrared results, our Chandra analysis indicates the blast wave is now leaving the dense equatorial ring, which marks the beginning of a major change in the evolutionary phase of the supernova remnant 1987A.

  16. VARIABILITY OF OPTICAL COUNTERPARTS IN THE CHANDRA GALACTIC BULGE SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Britt, C. T.; Hynes, R. I.; Johnson, C. B.; Baldwin, A.; Collazzi, A.; Gossen, L. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States); Jonker, P. G.; Torres, M. A. P. [SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Nelemans, G. [Department of Astrophysics, IMAPP, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands); Maccarone, T. [Department of Physics, Texas Tech University, Box 41051, Science Building, Lubbock, TX 79409-1051 (United States); Steeghs, D.; Greiss, S. [Astronomy and Astrophysics, Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Heinke, C. [Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB T6G 2E1 (Canada); Bassa, C. G. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Villar, A. [Department of Physics, Massachussettes Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307 (United States); Gabb, M. [Department of Physics, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431-0991 (United States)

    2014-09-01

    We present optical light curves of variable stars consistent with the positions of X-ray sources identified with the Chandra X-ray Observatory for the Chandra Galactic Bulge Survey (GBS). Using data from the Mosaic-II instrument on the Blanco 4 m Telescope at CTIO, we gathered time-resolved photometric data on timescales from ∼2 hr to 8 days over the 3/4 of the X-ray survey containing sources from the initial GBS catalog. Among the light curve morphologies we identify are flickering in interacting binaries, eclipsing sources, dwarf nova outbursts, ellipsoidal variations, long period variables, spotted stars, and flare stars. Eighty-seven percent of X-ray sources have at least one potential optical counterpart. Twenty-seven percent of these candidate counterparts are detectably variable; a much greater fraction than expected for randomly selected field stars, which suggests that most of these variables are real counterparts. We discuss individual sources of interest, provide variability information on candidate counterparts, and discuss the characteristics of the variable population.

  17. Prevention of preterm delivery in twin pregnancy

    DEFF Research Database (Denmark)

    Rode, Line; Tabor, Ann

    2014-01-01

    The incidence of twin gestation has increased markedly over the past decades, mostly because of increased use of assisted reproductive technologies. Twin pregnancies are at increased risk of preterm delivery (i.e. birth before 37 weeks of gestation). Multiple gestations therefore account for 2......, it is mandatory to evaluate the proposed treatments in randomised trials of multiple gestations. In this chapter, we describe the results of trials to prevent preterm delivery in twin pregnancies....

  18. Idiopathic intracranial hypertension in female homozygous twins.

    OpenAIRE

    Fujiwara, S; Sawamura, Y; Kato, T.; Abe, H.; Katusima, H

    1997-01-01

    The authors report on female homozygous twins with idiopathic intracranial hypertension. At the age of 12 years, both twins simultaneously developed visual disturbances with photophobia. At the age of 19 years, an ophthalmological examination disclosed papilloedema in both their eyes. At the age of 22 years, a lumbar puncture showed raised CSF pressure over (200 mm H2O) in both twins. Their neurological and radiological examinations were extremely similar; both of them had severely impaired v...

  19. Anaesthesia for the separation of conjoined twins

    Directory of Open Access Journals (Sweden)

    Jaya Lalwani

    2011-01-01

    Full Text Available Thoraco-omphalopagus is one of the most common type of conjoint twins accounting for 74% cases of conjoint twins. We report the anaesthetic management for successful separation of thoraco-omphalopagus conjoint twins, both of them surviving till date. We highlight the responsibility of anaesthesia team in anaesthetising the two individual patients simultaneously, need of careful monitoring and anticipation of complications like massive blood loss, hypotension, hypokalemia, hypoxia and hypercabia. Detailed description of successful management is reported.

  20. Culture systems: embryo culture and monozygotic twinning.

    Science.gov (United States)

    Sparks, Amy E

    2012-01-01

    The incidence of monozygotic twinning in pregnancies achieved with assisted reproductive technologies (ART) is significantly higher than spontaneously conceived pregnancies. The factors associated with ART that predispose the embryos to splitting are not well-characterized. Assisted hatching and extended embryo culture are two ART laboratory methods that have been risk factors for monozygotic twinning. The methods and strategies that may be employed to avoid monozygotic twinning are discussed in this chapter.

  1. The Solar Twin Planet Search II. A Jupiter twin around a solar twin

    CERN Document Server

    Bedell, M; Bean, J L; Ramirez, I; Asplund, M; Alves-Brito, A; Casagrande, L; Dreizler, S; Monroe, T; Spina, L; Maia, M Tucci

    2015-01-01

    Through our HARPS radial velocity survey for planets around solar twin stars, we have identified a promising Jupiter twin candidate around the star HIP11915. We characterize this Keplerian signal and investigate its potential origins in stellar activity. Our analysis indicates that HIP11915 hosts a Jupiter-mass planet with a 3600-day orbital period and low eccentricity. Although we cannot definitively rule out an activity cycle interpretation, we find that a planet interpretation is more likely based on a joint analysis of RV and activity index data. The challenges of long-period radial velocity signals addressed in this paper are critical for the ongoing discovery of Jupiter-like exoplanets. If planetary in nature, the signal investigated here represents a very close analog to the solar system in terms of both Sun-like host star and Jupiter-like planet.

  2. College-age twins: university admission policies / twin research: birth weight and neuromotor performance; transfusion syndrome markers; vanishing twins and fetal sex determination; mz twin discordance for wilson's disease / media: big at birth; planned separation of conjoined twins; x factor twins; Cinema: the identical.

    Science.gov (United States)

    Segal, Nancy L

    2014-12-01

    There is a lack of research findings addressing the unique college admissions issues faced by twins and other multiples. The advantages and disadvantage twins face, as reported by college administrators, twins and families are reviewed. Next, recent research addressing twins' birth weight and neuromotor performance, transfusion syndrome markers, the vanishing twin syndrome and monozygotic (MZ) twin discordance for Wilson's disease is described. News items concerning the birth of unusually large twins, the planned separation of conjoined twins, twin participants in the X Factor games and a film, The Identical, are also summarized.

  3. Discordance of oral-facial-digital syndrome type 1 in monozygotic twin girls.

    Science.gov (United States)

    Shotelersuk, V; Tifft, C J; Vacha, S; Peters, K F; Biesecker, L G

    1999-09-17

    The oral-facial-digital syndrome type 1 (OFD1) includes limb, facial, intraoral malformations and the gene for the disorder was recently mapped to Xp22.3-p22.2. We report on monozygotic twin girls discordant for OFD1. Monozygosity is supported by placental pathology (monochorionic diamniotic) and molecular studies with probability of dizygosity twin has oral cavity abnormalities including median cleft lip, cleft palate, lobulated hamartomatous tongue, aberrant hyperplastic oral frenula, alveolar notches, and absent lateral incisors. Facial manifestations include telecanthus, hypoplastic alae nasi, and transient neonatal facial milia. The patient also has short and deviated fingers with partial cutaneous syndactyly. At 10 years, she has not had central nervous system or kidney problems. X-inactivation study revealed similar X-inactivation patterns in the lymphoblasts of both twins. We conclude that skewed X-inactivation is an unlikely cause for the discordance, which is more likely due to a postzygotic mutation in the affected twin.

  4. Strain Hardening and Size Effect in Five-fold Twinned Ag Nanowires.

    Science.gov (United States)

    Narayanan, Sankar; Cheng, Guangming; Zeng, Zhi; Zhu, Yong; Zhu, Ting

    2015-06-10

    Metallic nanowires usually exhibit ultrahigh strength but low tensile ductility owing to their limited strain hardening capability. Here we study the unique strain hardening behavior of the five-fold twinned Ag nanowires by nanomechanical testing and atomistic modeling. In situ tensile tests within a scanning electron microscope revealed strong strain hardening behavior of the five-fold twinned Ag nanowires. Molecular dynamics simulations showed that such strain hardening was critically controlled by twin boundaries and pre-existing defects. Strain hardening was size dependent; thinner nanowires achieved more hardening and higher ductility. The size-dependent strain hardening was found to be caused by the obstruction of surface-nucleated dislocations by twin boundaries. Our work provides mechanistic insights into enhancing the tensile ductility of metallic nanostructures by engineering the internal interfaces and defects.

  5. Rapid onset of severe twin-twin transfusion syndrome caused by placental venous thrombosis

    NARCIS (Netherlands)

    Nikkels, PGJ; van Gemert, MJC; Sollie-Szarynska, KM; Molendijk, H; Timmer, B; Machin, GA

    2002-01-01

    We report a case of rapid onset of severe twin-twin transfusion syndrome (TTTS) at 25 weeks gestation in a monochorionic twin pregnancy that was uneventful before that time. Thrombosis of a main venous branch draining several arteriovenous (AV) anastomoses to the donor changed the previous hemodynam

  6. Atomistic deformation mechanisms in twinned copper nanospheres.

    Science.gov (United States)

    Bian, Jianjun; Niu, Xinrui; Zhang, Hao; Wang, Gangfeng

    2014-01-01

    In the present study, we perform molecular dynamic simulations to investigate the compression response and atomistic deformation mechanisms of twinned nanospheres. The relationship between load and compression depth is calculated for various twin spacing and loading directions. Then, the overall elastic properties and the underlying plastic deformation mechanisms are illuminated. Twin boundaries (TBs) act as obstacles to dislocation motion and lead to strengthening. As the loading direction varies, the plastic deformation transfers from dislocations intersecting with TBs, slipping parallel to TBs, and then to being restrained by TBs. The strengthening of TBs depends strongly on the twin spacing.

  7. Invasive treatment in complicated monochorionic twin pregnancies

    DEFF Research Database (Denmark)

    Sundberg, Karin; Søgaard, Kirsten; Jensen, Lisa Neerup;

    2012-01-01

    Objective. Monochorionic twin pregnancies are associated with increased risk of severe complications. Umbilical cord occlusion (UCO) and fetoscopic selective laser coagulation (FSLC) are used as invasive treatment. The study aim was to document treatment indications and pregnancy outcome where UCO...... and FSLC were used for treating fetal discrepancies and twin-to-twin transfusion syndrome (TTTS). Design. Cohort study of all consecutively treated monochorionic twin pregnancies 2004-2010. Setting. Tertiary care center. Population. One hundred and twenty pregnancies treated by FSLC (55) or UCO (65...

  8. Vascular distribution patterns in monochorionic twin placentas.

    Science.gov (United States)

    De Paepe, M E; DeKoninck, P; Friedman, R M

    2005-07-01

    Several recent publications have focused on the association between the occurrence of twin-to-twin transfusion syndrome (TTTS) in diamniotic-monochorionic twins and the presence of a number of selected anatomic placental characteristics (distribution of vascular territory, cord insertion, type and number of inter-twin anastomoses). In contrast, the potential importance of the vascular distribution patterns of the individual twins remains to be elucidated. Based on its gross architectural distribution pattern, chorionic vasculature is traditionally described as disperse, magistral or mixed. The aim of this study was (1) to determine the relative prevalence of these vascular distribution patterns in monochorionic twin placentas, and (2) to correlate these patterns with the presence of TTTS and known anatomic placental features linked to TTTS. The placentas of 89 consecutive diamniotic-monochorionic twins (15 with TTTS, 74 without TTTS), examined at Women and Infants Hospital, were studied. Disperse vascular patterns were seen in 53% of twins, and magistral or mixed patterns in 47%. The prevalence of magistral/mixed vascular patterns was significantly higher in TTTS gestations than in non-TTTS gestations (60% versus 44%, Ppatterns and marginal/velamentous cord insertion, low number of inter-twin anastomoses, and uneven distribution of the vascular territories. These findings suggest that the magistral/mixed vascular distribution pattern may represent an important placental architectural feature contributing to the complex pathophysiology of TTTS.

  9. Suzaku and Chandra Observations of CIZA J1700.8$-$3144, a Cluster of Galaxies in the Zone of Avoidance

    CERN Document Server

    Mori, Hideyuki; Ueda, Yoshihiro; Nakazawa, Kazuhiro; Tawara, Yuzuru

    2016-01-01

    We present the Chandra and Suzaku observations of 1RXS J170047.8$-$314442, located towards the Galactic bulge, to reveal a wide-band ($0.3$-$10$ keV) X-ray morphology and spectrum of this source. With the Chandra observation, no point source was found at the position of 1RXS J170047.8$-$314442. Alternatively, we revealed the presence of diffuse X-ray emission by the wide-band X-ray image obtained from the Suzaku XIS. Although the X-ray emission had a nearly circular shape with a spatial extent of $\\sim 3.5'$, the surface brightness profile was not axisymmetric; a bright spot-like emission was found at $\\sim 1'$ away in the north-western direction from the center. The radial profile of the surface brightness, except for this spot-like emission, was reproduced with a single $\\beta$-model; $\\beta$ and the core radius were found to be $1.02$ and $1.51'$, respectively. The X-ray spectrum of the diffuse emission showed an emission line at $\\sim 6$ keV, indicating an origin of a thermal plasma. The spectrum was well...

  10. Problem in twin pregnancy: Findings of prenatal sonography and autopsy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Ah; Cho, Jeong Yeon; Song, Mi Jin; Min, Jee Yeon; Lee, Young Ho; Lee, Hak Jong; Chun, Yi Kyeong; Kim, Yee Jeong; Hong, Sung Ran [Samsung Cheil Hospital, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2001-12-15

    Multifetal gestations are high risk pregnancies with higher perinatal morbidity and mortality. Multifetal gestations are subject to unique complications including conjoined twins, twin-to-twin transfusion syndrome (TTTS), acardiac twins, twin embization of co-twin demise and heterotopic pregnancies. Prenatal sonographic diagnosis of types and complications of multifetal gestations is important for antenatal care and prediction of fetal outcome. This study was performed to present the prenatal ultrasonographic findings and pathologic findings of the unique complications of twin pregnancy. Acardia is a lethal anomaly occurring in 1% of monozygotic twin. The acardiac twin has a parasitic existence and depends on the donor (pump) twin for its blood supply via placental anastomoses and retrograde perfusion of umbilical cord. This twin reversed arterial perfusion (TRAP) sequence is a most extreme manifestation on the TTTS. Doppler verification reversed flow in umbilical cord of the acardiac twin confirms the diagnosis.

  11. Being Pregnant with Twins, Triplets and Other Multiples

    Science.gov (United States)

    ... twins, triplets and other multiples Being pregnant with twins, triplets and other multiples E-mail to a ... embryos that grow into two or more babies. Twins are called identical when one fertilized egg splits ...

  12. Simultaneous NuSTAR/Chandra Observations of the Bursting Pulsar GRO J1744-28 during Its Third Reactivation

    Science.gov (United States)

    Younes, G.; Kouveliotou, C.; Grefenstette, B. W.; Tomsick, J. A.; Tennant, A.; Finger, M. H.; Fürst, F.; Pottschmidt, K.; Bhalerao, V.; Boggs, S. E.; Boirin, L.; Chakrabarty, D.; Christensen, F. E.; Craig, W. W.; Degenaar, N.; Fabian, A. C.; Gandhi, P.; Göğüş, E.; Hailey, C. J.; Harrison, F. A.; Kennea, J. A.; Miller, J. M.; Stern, D.; Zhang, W. W.

    2015-05-01

    We report on a 10 ks simultaneous Chandra/High Energy Transmission Grating (HETG)-Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the Bursting Pulsar, GRO J1744-28, during its third detected outburst since discovery and after nearly 18 yr of quiescence. The source is detected up to 60 keV with an Eddington persistent flux level. Seven bursts, followed by dips, are seen with Chandra, three of which are also detected with NuSTAR. Timing analysis reveals a slight increase in the persistent emission pulsed fraction with energy (from 10% to 15%) up to 10 keV, above which it remains constant. The 0.5-70 keV spectra of the persistent and dip emission are the same within errors and well described by a blackbody (BB), a power-law (PL) with an exponential rolloff, a 10 keV feature, and a 6.7 keV emission feature, all modified by neutral absorption. Assuming that the BB emission originates in an accretion disk, we estimate its inner (magnetospheric) radius to be about 4 × 107 cm, which translates to a surface dipole field B ≈ 9 × 1010 G. The Chandra/HETG spectrum resolves the 6.7 keV feature into (quasi-)neutral and highly ionized Fe xxv and Fe xxvi emission lines. XSTAR modeling shows these lines to also emanate from a truncated accretion disk. The burst spectra, with a peak flux more than an order of magnitude higher than Eddington, are well fit with a PL with an exponential rolloff and a 10 keV feature, with similar fit values compared to the persistent and dip spectra. The burst spectra lack a thermal component and any Fe features. Anisotropic (beamed) burst emission would explain both the lack of the BB and any Fe components.

  13. SIMULTANEOUS NuSTAR/CHANDRA OBSERVATIONS OF THE BURSTING PULSAR GRO J1744-28 DURING ITS THIRD REACTIVATION

    Energy Technology Data Exchange (ETDEWEB)

    Younes, G.; Finger, M. H. [Universities Space Research Association, 6767 Old Madison Pike, Suite 450, Huntsville, AL 35806 (United States); Kouveliotou, C.; Tennant, A. [Astrophysics Office, ZP 12, NASA-Marshall Space Flight Center, Huntsville, AL 35812 (United States); Grefenstette, B. W.; Fürst, F. [Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Tomsick, J. A.; Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Pottschmidt, K. [Center for Space Science and Technology, University of Maryland Baltimore County, Baltimore, MD 21250 (United States); Bhalerao, V. [Inter-University Center for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007 (India); Boirin, L. [Observatoire Astronomique de Strasbourg, 11 Rue de l' Université, F-67000 Strasbourg (France); Chakrabarty, D. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Christensen, F. E. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Degenaar, N. [Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109 (United States); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Gandhi, P. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Göğüş, E. [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); and others

    2015-05-01

    We report on a 10 ks simultaneous Chandra/High Energy Transmission Grating (HETG)–Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the Bursting Pulsar, GRO J1744-28, during its third detected outburst since discovery and after nearly 18 yr of quiescence. The source is detected up to 60 keV with an Eddington persistent flux level. Seven bursts, followed by dips, are seen with Chandra, three of which are also detected with NuSTAR. Timing analysis reveals a slight increase in the persistent emission pulsed fraction with energy (from 10% to 15%) up to 10 keV, above which it remains constant. The 0.5–70 keV spectra of the persistent and dip emission are the same within errors and well described by a blackbody (BB), a power-law (PL) with an exponential rolloff, a 10 keV feature, and a 6.7 keV emission feature, all modified by neutral absorption. Assuming that the BB emission originates in an accretion disk, we estimate its inner (magnetospheric) radius to be about 4 × 10{sup 7} cm, which translates to a surface dipole field B ≈ 9 × 10{sup 10} G. The Chandra/HETG spectrum resolves the 6.7 keV feature into (quasi-)neutral and highly ionized Fe xxv and Fe xxvi emission lines. XSTAR modeling shows these lines to also emanate from a truncated accretion disk. The burst spectra, with a peak flux more than an order of magnitude higher than Eddington, are well fit with a PL with an exponential rolloff and a 10 keV feature, with similar fit values compared to the persistent and dip spectra. The burst spectra lack a thermal component and any Fe features. Anisotropic (beamed) burst emission would explain both the lack of the BB and any Fe components.

  14. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    Science.gov (United States)

    2002-09-01

    Scientists at the Carnegie Observatories in Pasadena, California, have uncovered six times the expected number of active, supermassive black holes in a single viewing of a cluster of galaxies, a finding that has profound implications for theories as to how old galaxies fuel the growth of their central black holes. The finding suggests that voracious, central black holes might be as common in old, red galaxies as they are in younger, blue galaxies, a surprise to many astronomers. The team made this discovery with NASA'S Chandra X-ray Observatory. They also used Carnegie's 6.5-meter Walter Baade Telescope at the Las Campanas Observatory in Chile for follow-up optical observations. "This changes our view of galaxy clusters as the retirement homes for old and quiet black holes," said Dr. Paul Martini, lead author on a paper describing the results that appears in the September 10 issue of The Astrophysical Journal Letters. "The question now is, how do these black holes produce bright X-ray sources, similar to what we see from much younger galaxies?" Typical of the black hole phenomenon, the cores of these active galaxies are luminous in X-ray radiation. Yet, they are obscured, and thus essentially undetectable in the radio, infrared and optical wavebands. "X rays can penetrate obscuring gas and dust as easily as they penetrate the soft tissue of the human body to look for broken bones," said co-author Dr. Dan Kelson. "So, with Chandra, we can peer through the dust and we have found that even ancient galaxies with 10-billion-year-old stars can have central black holes still actively pulling in copious amounts of interstellar gas. This activity has simply been hidden from us all this time. This means these galaxies aren't over the hill after all and our theories need to be revised." Scientists say that supermassive black holes -- having the mass of millions to billions of suns squeezed into a region about the size of our Solar System -- are the engines in the cores of

  15. Chandra Looks Over a Cosmic Four-Leaf Clover

    Science.gov (United States)

    2004-07-01

    A careful analysis of observations by NASA's Chandra X-ray Observatory of a rare quadruple quasar has uncovered evidence that possibly a single star in a foreground galaxy magnified X-rays coming from the quasar. This discovery gives astronomers a new and extremely precise probe of the gas flow around the supermassive black hole that powers the quasar. "If our interpretation is correct, then we are seeing details around this black hole that are 50,000 times smaller than either the Hubble Space Telescope or Chandra could see under ordinary circumstances," said George Chartas of Penn State University in University Park, and lead author of a recent article on the Cloverleaf quasar in The Astrophysical Journal. The Cloverleaf quasar is a single object about 11 billion light years from Earth that appears as four images produced by a process known as gravitational lensing. If one or more galaxies lie along the line of sight to a more distant quasar, the gravitational field of the intervening galaxies can bend and magnify the light from the quasar and produce multiple images of it. The four images of the Cloverleaf quasar have been produced by one or more intervening galaxies. Cloverleaf Quasar Chandra X-ray Image of the Cloverleaf quasar One of the images (A), in the Cloverleaf is brighter than the others in both optical and X-ray light. Chartas and his colleagues found the relative brightness of this image was greater in X-ray than in optical light. The X-rays from iron atoms were also enhanced relative to X-rays at lower energies. Since the amount of brightening due to gravitational lensing does not vary with the wavelength, this means that an additional object has magnified the X-rays. The increased magnification of the X-ray light can be explained by gravitational microlensing, an effect which has been used to search for compact stars and planets in our galaxy. Microlensing occurs when a star or a multiple star system passes in front of light from a background object

  16. Chandra's Find of Lonely Halo Raises Questions About Dark Matter

    Science.gov (United States)

    2004-10-01

    Dark matter continues to confound astronomers, as NASA's Chandra X-ray Observatory demonstrated with the detection of an extensive envelope of dark matter around an isolated elliptical galaxy. This discovery conflicts with optical data that suggest a dearth of dark matter around similar galaxies, and raises questions about how galaxies acquire and keep such dark matter halos. The observed galaxy, known as NGC 4555, is unusual in that it is a fairly large, elliptical galaxy that is not part of a group or cluster of galaxies. In a paper to be published in the November 1, 2004 issue of the Monthly Notices of the Royal Astronomical Society, Ewan O'Sullivan of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA and Trevor Ponman of the University of Birmingham, United Kingdom, use the Chandra data to show that the galaxy is embedded in a cloud of 10-million-degree-Celsius gas. X-ray/Optical Composite of NGC 4555 X-ray/Optical Composite of NGC 4555 This hot gas cloud has a diameter of about 400,000 light years, about twice that of the visible galaxy. An enormous envelope, or halo, of dark matter is needed to confine the hot cloud to the galaxy. The total mass of the dark matter halo is about ten times the combined mass of the stars in the galaxy, and 300 times the mass of the hot gas cloud. A growing body of evidence indicates that dark matter - which interacts with itself and "normal" matter only through gravity - is the dominant form of matter in the universe. According to the popular "cold dark matter" theory, dark matter consists of mysterious particles left over from the dense early universe that were moving slowly when galaxies and galaxy clusters began to form. "The observed properties of NGC 4555 confirm that elliptical galaxies can posses dark matter halos of their own, regardless of their environment," said O'Sullivan. "This raises an important question: what determines whether elliptical galaxies have dark matter halos?" DSS Optical Image of NGC

  17. Phase Field Modeling of Twinning in Indentation of Transparent Crystals

    Science.gov (United States)

    2011-09-01

    twin boundaries . Equilibrium configurations of deformed and twinned crystals are attained via direct energy minimization. The theory is framed in the...phases: (i) the original crystal (the parent) and (ii) the twin. Interfaces between phases are twin boundaries . Order parameter η generally exhibits the...following values: η(X, •) = 0∀X ∈ parent, = 1∀X ∈ twin, ∈ (0, 1)∀X ∈ twin boundaries . (1) In linear elasticity, kinematic field variables are

  18. Weak phonon scattering effect of twin boundaries on thermal transmission.

    Science.gov (United States)

    Dong, Huicong; Xiao, Jianwei; Melnik, Roderick; Wen, Bin

    2016-01-29

    To study the effect of twin boundaries on thermal transmission, thermal conductivities of twinned diamond with different twin thicknesses have been studied by NEMD simulation. Results indicate that twin boundaries show a weak phonon scattering effect on thermal transmission, which is only caused by the additional twin boundaries' thermal resistance. Moreover, according to phonon kinetic theory, this weak phonon scattering effect of twin boundaries is mainly caused by a slightly reduced average group velocity.

  19. Weak phonon scattering effect of twin boundaries on thermal transmission

    OpenAIRE

    Huicong Dong; Jianwei Xiao; Roderick Melnik; Bin Wen

    2016-01-01

    To study the effect of twin boundaries on thermal transmission, thermal conductivities of twinned diamond with different twin thicknesses have been studied by NEMD simulation. Results indicate that twin boundaries show a weak phonon scattering effect on thermal transmission, which is only caused by the additional twin boundaries’ thermal resistance. Moreover, according to phonon kinetic theory, this weak phonon scattering effect of twin boundaries is mainly caused by a slightly reduced averag...

  20. [Social development of twins: the need for intervention to avoid adverse effects of twin language].

    Science.gov (United States)

    Hayashi, Chisato; Hayakawa, Kazuo; Maeda, Chiho; Nishihara, Reiko; Onoi, Miyuki

    2008-10-01

    Social competence is one of the most important accomplishments of human development, and this skill in human relationships is learned through communication. Therefore, it is considered that delays in language development could be a barrier to building human relationships and social competence. Although it is well known that there are delays in language development in twins compared with that of singletons, little is known about how these linguistic delays affect the development of social competence. Because twin language is a language that is unique to each pair of twins and cannot be understood by either their mother or others, it may be assumed that the social competence of twins who have a twin language is less than that of twins who don't have a twin language. Therefore, in this prospective longitudinal study we also investigated the relationship between twin language and social competence. A mailed questionnaire survey was conducted in 958 mothers as a follow-up of a study conducted in 2004. As a result, 522 respondents returned the questionnaire (53.9%). In this study, we used only 256 twins aged 6- 12-years-old (school-age children) for analysis, excluding those with missing values. Multiple logistic regression analysis was employed. In the second child of twins, a low birth weight, the appearance of twin language and gestosis of the mother were positively related with social unbalance (OR = 1.846, 2.022 and 1.903). On the other hand, with the first child, however, there was no such link. The present results indicate that twin language might influence social competence in school-age children. It has been believed that linguistic intervention is unnecessary, because most twin language disappears spontaneously. However, early intervention, for example linguistic assistance by public health nurses or psychologists and early enrollment in a preschool may be necessary for twins with a twin language, to avoid adverse consequences in social competence at school-age.

  1. Inversion of calcite twin data for stress (2) : EBSD as a tool for data measurements

    Science.gov (United States)

    Parlangeau, Camille; Lacombe, Olivier; Brisset, Francois; Kohler, Eric; Daniel, Jean-Marc; Schueller, Sylvie

    2015-04-01

    Inversion of calcite twin data are known to be a powerful tool to reconstruct the past state(s) of stress in carbonate rocks of the crust, especially in fold-and-thrust belts and sedimentary basins. Twin data measurements have been for long carried out optically using a Universal-Stage. This data collection is time-consuming and suffers from limitations and bias related to measurements of twin planes oblique at low angle or parallel to the thin section, or the unambiguous evaluation of the twinned/untwinned character of collected twin data. EBSD (electron backscatter diffraction) is a well-known technique applied to characterize textures and microstructures of metals or deformed fine-grained rocks. The challenge is to define a strategy for measuring calcite-twin orientations that should be fast, without any loss of information, and which must reconcile (1) the need for a large amount of calcite twin data (3 mutually perpendicular thin sections and at least 30 crystals per thin section), (2) the spacing between EBSD spots, that should take into account (3) the small width of twin lamellae within grains deformed at low pressure and temperature and (4) the large size (usually several hundreds of microns) of twinned calcite grains used for stress analysis. To date, these multiple requirements preclude any (classical) automatic twin data acquisition but instead imply a preliminary definition of the areas of the thin section to be scanned by the EBSD spots, including grain boundaries, because the stress inversion technique requires to know for each grain the orientations of the C axis and of the 3 potential e twin planes. In order to reconcile a perfectly polished surface as required by EBSD and the recognition of grain boundaries, we adopted the double etching technique (Herwegh, 2000) to first reveal grain and twin boundaries. Then, with a SEM and a very fine coating sample, the section is scanned using secondary electrons bin; each spot of interest is visually defined

  2. HA/UHMWPE Nanocomposite Produced by Twin-screw Extrusion

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin- screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0.23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.

  3. Haemodynamic resistance model of monochorionic twin pregnancies complicated by acardiac twinning

    Energy Technology Data Exchange (ETDEWEB)

    Umur, Asli [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam(Netherlands); Gemert, Martin J C van [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Wijngaard, Jeroen P H M van den [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Ross, Michael G [Department of Obstetrics and Gynecology, Harbor University of California-Los Angeles Medical Center, Torrence, CA 9050 (United States); Nikkels, Peter G J [Department of Pathology, University Medical Center, Utrecht (Netherlands)

    2004-07-21

    An acardiac twin is a severely malformed monochorionic twin fetus that lacks most organs, particularly a heart. It grows during pregnancy, because it is perfused by its developmentally normal co-twin (called the pump twin) via a set of placental arterioarterial and venovenous anastomoses. The pump twin dies intrauterine or neonatally in about 50% of the cases due to congestive heart failure, polyhydramnios and prematurity. Because the pathophysiology of this pregnancy is currently incompletely understood, we modified our previous haemodynamic model of monochorionic twins connected by placental vascular anastomoses to include the analysis of acardiac twin pregnancies. We incorporated the fetoplacental circulation as a resistance circuit and used the fetal umbilical flow that perfuses the body to define fetal growth, rather than the placental flow as done previously. Using this modified model, we predicted that the pump twin has excess blood volume and increased mean arterial blood pressure compared to those in the acardiac twin. Placental perfusion of the acardiac twin is significantly reduced compared to normal, as a consequence of an increased venous pressure, possibly implying reduced acardiac placental growth. In conclusion, the haemodynamic analysis may contribute to an increased knowledge of the pathophysiologic consequences of an acardiac body mass for the pump twin. (note)

  4. Vascular programming in twins: the effects of chorionicity and fetal therapy for twin-to-twin transfusion syndrome.

    Science.gov (United States)

    Gardiner, H M; Barlas, A; Matsui, H; Diemert, A; Taylor, M J O; Preece, J; Gordon, F; Greenwald, S E; Hecher, K

    2012-06-01

    We assessed vascular programming in genetically identical monochorionic twin pairs with twin-to-twin transfusion syndrome (TTTS) treated differently in utero by serial amnioreduction or fetal laser arterial photocoagulation. This case-control study re-assessed four twin groups at median 11 years comprising 20 pairs of monochorionic diamniotic twins: nine treated by amnioreduction (TTTS-amnio) and eleven by laser (TTTS-laser) with seven monochorionic and six dichorionic control pairs. Outcome measures were current blood pressure (BP), brachio-radial arterial stiffness derived from pulse wave velocity (PWV), resting microcirculation (Flux) and response to heating and post-occlusive reactive hyperaemia measured using laser Doppler. Potential confounders [PWV and BP at first study, current height, weight, heart rate and twin type (ex-recipient, ex-donor or heavier/lighter of pair)] were accounted for by Mixed Linear Models statistical methodology. PWV dichorionic > monochorionic (P = 0.024); systolic and diastolic BP dichorionic > TTTS-amnio and TTTS-laser (P = 0.004, P = 0.02 and P = 0.005, P = 0.02, respectively). Within-twin pair pattern of PWV discordance was similar in laser treated and dichorionic controls (heavier-born > lighter), opposite to TTTS-amnio and monochorionic controls. Flux monochorionic > dichorionic (P = 0.044) and heavier > lighter-born (P = 0.024). TTTS-laser and dichorionic diamniotic showed greatest hyperaemic responses (dichorionic > TTTS-amnio or monochorionic controls (P = 0.007, P = 0.025). Hyperaemic responses were slower in heavier-born twins (P = 0.005). In summary, monochorionic twins had lower BP, arterial stiffness and increased resting vasodilatation than dichorionic twins implying shared fetal circulation affects vascular development. Vascular responses in laser-TTTS were similar to dichorionic and opposite to TTTS-amnio suggesting a lasting effect of fetal therapy on vascular health.

  5. Twin-Foucault imaging method

    Science.gov (United States)

    Harada, Ken

    2012-02-01

    A method of Lorentz electron microscopy, which enables observation two Foucault images simultaneously by using an electron biprism instead of an objective aperture, was developed. The electron biprism is installed between two electron beams deflected by 180° magnetic domains. Potential applied to the biprism deflects the two electron beams further, and two Foucault images with reversed contrast are then obtained in one visual field. The twin Foucault images are able to extract the magnetic domain structures and to reconstruct an ordinary electron micrograph. The developed Foucault method was demonstrated with a 180° domain structure of manganite La0.825Sr0.175MnO3.

  6. A discrete twin-boundary approach for simulating the magneto-mechanical response of Ni-Mn-Ga

    Science.gov (United States)

    Faran, Eilon; Shilo, Doron

    2016-09-01

    The design and optimization of ferromagnetic shape memory alloys (FSMA)-based devices require quantitative understanding of the dynamics of twin boundaries within these materials. Here, we present a discrete twin boundary modeling approach for simulating the behavior of an FSMA Ni-Mn-Ga crystal under combined magneto-mechanical loading conditions. The model is based on experimentally measured kinetic relations that describe the motion of individual twin boundaries over a wide range of velocities. The resulting calculations capture the dynamic response of Ni-Mn-Ga and reveal the relations between fundamental material parameters and actuation performance at different frequencies of the magnetic field. In particular, we show that at high field rates, the magnitude of the lattice barrier that resists twin boundary motion is the important property that determines the level of actuation strain, while the contribution of twinning stress property is minor. Consequently, type II twin boundaries, whose lattice barrier is smaller compared to type I, are expected to show better actuation performance at high rates, irrespective of the differences in the twinning stress property between the two boundary types. In addition, the simulation enables optimization of the actuation strain of a Ni-Mn-Ga crystal by adjusting the magnitude of the bias mechanical stress, thus providing direct guidelines for the design of actuating devices. Finally, we show that the use of a linear kinetic law for simulating the twinning-based response is inadequate and results in incorrect predictions.

  7. Chandra Observations of Shock Kinematics in Supernova Remnant 1987A

    CERN Document Server

    Zhekov, S A; Borkowski, K J; Burrows, D N; Park, S

    2005-01-01

    We report the first results from deep X-ray observations of the SNR 1987A with the Chandra LETG. Temperatures inferred from line ratios range from 0.1 - 2 keV and increase with ionization potential. Expansion velocities inferred from X-ray line profiles range from 300 - 1700 km/s, much less than the velocities inferred from the radial expansion of the radio and X-ray images. We can account for these observations with a scenario in which the X-rays are emitted by shocks produced where the supernova blast wave strikes dense protrusions of the inner circumstellar ring, which are also responsible for the optical hot spots.

  8. Chandra LETG Observations of Supernova Remnant 1987A

    CERN Document Server

    Zhekov, S A; Burrows, D N; McCray, R; Park, S; Borkowski, Kazimierz J.; Burrows, David N.; Cray, Richard Mc; Park, Sangwook; Zhekov, Svetozar A.

    2006-01-01

    We discuss the results from deep Chandra LETG observations of the supernova remnant 1987A (SNR 1987A). We find that a distribution of shocks, spanning the same range of velocities (from 300 to 1700 km/s) as deduced in the first part of our analysis (Zhekov et al. 2005, ApJL, 628, L127), can account for the entire X-ray spectrum of this object. The post-shock temperature distribution is bimodal, peaking at kT 0.5 and 3 keV. Abundances inferred from the X-ray spectrum have values similar to those for the inner circumstellar ring, except that the abundances of nitrogen and oxygen are approximately a factor of two lower than those inferred from the optical/UV spectrum. The velocity of the X-ray emitting plasma has decreased since 1999, apparently because the blast wave has entered the main body of the inner circumstellar ring.

  9. Chandra LETGS and XMM-Newton observations of NGC 4593

    CERN Document Server

    Steenbrugge, K C; Blustin, A J; Branduardi-Raymont, G; Sako, M; Behar, E; Kahn, S M; Paerels, F B S; Walter, R

    2003-01-01

    In this paper, we analyze spectra of the Seyfert 1 galaxy NGC 4593 obtained with the Chandra Low Energy Transmission Grating Spectrometer (LETGS), the Reflection Grating Spectrometer (RGS) and the European Photon Imaging Camera's (EPIC) onboard of XMM-Newton. The two observations were separated by ~7 months. In the LETGS spectrum we detect a highly ionized warm absorber corresponding to an ionization state of 400x10^{-9} W m, visible as a depression at 10-18 AA. This depression is formed by multiple weak Fe and Ne lines. A much smaller column density was found for the lowly ionized warm absorber, corresponding to xi = 3x10^{-9} W m. However, an intermediate ionization warm absorber is not detected. For the RGS data the ionization state is hard to constrain. The EPIC results show a narrow Fe Kalpha line.

  10. Twin-Screw Extruders in Ceramic Extrusion

    Science.gov (United States)

    Wiedmann, Werner; Hölzel, Maria

    The machines mainly used for compounding plastics, chemicals and food are co-rotating, closely intermeshing twin-screw extruders. Some 30 000 such extruders are in use worldwide, about 1/3 are ZSKs from Coperion Werner & Pfleiderer, Stuttgart. In the chemical industry more and more batch mixers are being replaced by continuous twin-screw kneaders.

  11. Cord entanglement in monoamniotic twin pregnancies

    DEFF Research Database (Denmark)

    Lyndrup, J; Schouenborg, Lars Øland

    1987-01-01

    Monoamniotic twin pregnancy involves a heavy risk of fatal umbilical cord entanglement. Two cases are reported. In the first case, both twins were found dead in the 36th week, and the monoamnionicity was recognized at birth. In the second case, the monoamnionicity was discovered during...

  12. Optimal nutrition for improved twin pregnancy outcome.

    Science.gov (United States)

    Goodnight, William; Newman, Roger

    2009-11-01

    Twin pregnancies contribute a disproportionate degree to perinatal morbidity, partly because of increased risks of low birth weight and prematurity. Although the cause of the morbidity is multifactorial, attention to twin-specific maternal nutrition may be beneficial in achieving optimal fetal growth and birth weight. Achievement of body mass index (BMI)-specific weight gain goals, micronutrient and macronutrient supplementation specific to the physiology of twin gestations, and carbohydrate-controlled diets are recommended for optimal twin growth and pregnancy outcomes. The daily recommended caloric intake for normal-BMI women with twins is 40-45 kcal/kg each day, and iron, folate, calcium, magnesium, and zinc supplementation is recommended beyond a usual prenatal vitamin. Daily supplementation of docosahexaenoic acid and vitamin D should also be considered. Multiple gestation-specific prenatal care settings with a focus on nutritional interventions improve birth weight and length of gestation and should be considered for the care of women carrying multiples. Antepartum lactation consultation can also improve the rate of postpartum breastfeeding in twin pregnancies. Twin gestation-specific nutritional interventions seem effective in improving the outcome of these pregnancies and should be emphasized in the antepartum care of multiple gestations. This review examines the available evidence and offers recommendations for twin pregnancy-specific nutritional interventions.

  13. Fetal behavior in normal dichorionic twin pregnancy

    NARCIS (Netherlands)

    Mulder, E. J. H.; Derks, J. B.; de Laat, M. W. M.; Visser, G. H. A.

    2012-01-01

    Objectives: A prospective study was performed to compare fetal behavioral development in healthy dichorionic twins and singletons, and identify twin intra-pair associations (synchrony) of fetal movements and rest-activity cycles using different criteria to define synchrony. Subjects and methods: Twe

  14. Fatique life and twinning in alphazirconium

    DEFF Research Database (Denmark)

    Warren, M.R.; Beevers, C.J.

    1970-01-01

    stress for {11−21} twinning of ~0.5 kg mm−2 in zirconium containing 0.003 wt pct O. During observations confined to internal grains it was found that increasing grain size and decreasing oxygen content favored the formation of fatigue damage in association with these {11−21} twins. In external grains...

  15. A Danish Twin Study of Schizophrenia Liability

    DEFF Research Database (Denmark)

    Kläning, Ulla; Trumbetta, Susan L; Gottesman, Irving I

    2016-01-01

    We studied schizophrenia liability in a Danish population-based sample of 44 twin pairs (13 MZ, 31 DZ, SS plus OS) in order to replicate previous twin study findings using contemporary diagnostic criteria, to examine genetic liability shared between schizophrenia and other disorders, and to explo...

  16. THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Marchesi, S.; Civano, F.; Urry, C. M. [Yale Center for Astronomy and Astrophysics, 260 Whitney Avenue, New Haven, CT 06520 (United States); Elvis, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Salvato, M. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei München (Germany); Brusa, M.; Lanzuisi, G.; Vignali, C. [Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Comastri, A.; Gilli, R.; Zamorani, G.; Cappelluti, N. [INAF—Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Hasinger, G. [Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii, Honolulu, HI 96822 (United States); Miyaji, T. [Instituto de Astronomía sede Ensenada, Universidad Nacional Autónoma de México, Km. 103, Carret. Tijunana-Ensenada, Ensenada, BC (Mexico); Treister, E. [Universidad de Concepción, Departamento de Astronomía, Casilla 160-C, Concepción (Chile); Allevato, V.; Finoguenov, A. [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, FI-00014 Helsinki (Finland); Cardamone, C. [Department of Science, Wheelock College, Boston, MA 02215 (United States); Griffiths, R. E. [Physics and Astronomy Dept., Natural Sciences Division, University of Hawaii at Hilo, 200 W. Kawili Street, Hilo, HI 96720 (United States); Karim, A. [Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany); and others

    2016-01-20

    We present the catalog of optical and infrared counterparts of the Chandra  COSMOS-Legacy  Survey, a 4.6 Ms Chandra  program on the 2.2 deg{sup 2} of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 μm identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6 μm information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ≃54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2–10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.

  17. Automated classification of Chandra X-ray sources

    Science.gov (United States)

    Brehm, Derek; Kargaltsev, O.; Rangelov, B.; Volkov, I.; Pavlov, G. G.

    2014-01-01

    With the advent of the latest generation X-ray telescopes there has been a major influx of data associated with the detection of hundreds of thousands X-ray sources. As one can rarely tell a source type from its X-ray properties alone, the full potential of the X-ray catalogs can only be unlocked by correlating multiwavelength (MW) properties via cross-identification with other surveys. However, one would spend an enormous amount of time classifying these objects by their physical nature if the classification was to be done on a source-by-source basis by humans. Therefore, we are using a supervised learning algorithm to classify sources detected by the Chandra X-ray Observatory. The classifications are based on a training dataset which currently includes about 7,000 X-ray sources of known nature (main sequence stars, Wolf-Rayet stars, young stars, active galactic nuclei, low mass X-ray binaries, high mass x-ray binaries, and neutron stars). For each source, the training dataset includes up to 24 multiwavelength properties. The efficiency and accuracy of the classification is verified by dividing the training dataset in two and performing cross-validation. The results are also inspected by plotting source properties in 2D slices of the parameter space. As an application of our automated procedure we classified unidentified sources in the supernova remnant (SNR) G352.7-0.1, in the field of HESS J1809-193, and in part of the Chandra Source Catalog 1.0. We present the results of the verification tests and the classification results. This research was partially supported by NASA/SAO grant AR3-14017X.

  18. An investigation into a half page from Newton's Principia in the wake of Chandra

    CERN Document Server

    Snow, W M

    2002-01-01

    There is a section in Chandrashekar's ''Newton's Principia for the Common Reader '', (Clarendon Press, Oxford, 1995) in which he claims to find a small error in the Principia. . However we believe that there is a mistake of interpretation underlying Chandra's claim and that the Principia is correct as it stands. This short paper describes Chandra's misinterpretation of a geometric construction of Newton and gives an outline of Newton's demonstration by following the standard English version of the Principia line by line and converting it into modern mathematical notation in the spirit of Chandra's book.

  19. Searching for bulk motions in the ICM of massive, merging clusters with Chandra CCD data

    CERN Document Server

    Liu, Ang; Tozzi, Paolo; Zhu, Zong-Hong

    2016-01-01

    We search for bulk motions in the Intra Cluster Medium (ICM) of massive clusters showing evidence of an ongoing or a recent major merger, with spatially resolved spectroscopy in {\\sl Chandra} CCD data. We identify a sample of 6 merging clusters with >150 ks {\\sl Chandra} exposure in the redshift range 0.1 1000$ km/s in the ICM of massive merging clusters at 0.1 < z < 0.3. Despite the CCD spectral resolution is not sufficient for a detailed analysis of the ICM dynamics, {\\sl Chandra} CCD data constitute a key diagnostic tool complementary to X-ray bolometers onboard future X-ray missions.

  20. Utilizing twins as controls for non-twin case-materials in genome wide association studies.

    Directory of Open Access Journals (Sweden)

    Andrea Ganna

    Full Text Available Twin registries around the globe have collected DNA samples from large numbers of monozygotic and dizygotic twins. The twin sample collections are frequently used as controls in disease-specific studies together with non-twins. This approach is unbiased under the hypothesis that twins and singletons are comparable in terms of allele frequencies; i.e. there are no genetic variants associated with being a twin per se. To test this hypothesis we performed a genome-wide association study comparing the allele frequency of 572,352 single nucleotide polymorphisms (SNPs in 1,413 monozygotic (MZ and 5,451 dizygotic (DZ twins with 3,720 healthy singletons. Twins and singletons have been genotyped using the same platform. SNPs showing association with being a twin at P-value < 1 × 10(-5 were selected for replication analysis in 1,492 twins (463 MZ and 1,029 DZ and 1,880 singletons from Finland. No SNPs reached genome-wide significance (P-value < 5 × 10(-8 in the main analysis combining MZ and DZ twins. In a secondary analysis including only DZ twins two SNPs (rs2033541 close to ADAMTSL1 and rs4149283 close to ABCA1 were genome-wide significant after meta-analysis with the Finnish population. The estimated proportion of variance on the liability scale explained by all SNPs was 0.08 (P-value=0.003 when MZ and DZ were considered together and smaller for MZ (0.06, P-value=0.10 compared to DZ (0.09, P-value=0.003 when analyzed separately. In conclusion, twins and singletons can be used in genetic studies together with general population samples without introducing large bias. Further research is needed to explore genetic variances associated with DZ twinning.

  1. Contemporaneous Chandra HETG and Suzaku X-ray Observations of NGC 4051

    CERN Document Server

    Lobban, A P; Miller, L; Turner, T J; Braito, V; Kraemer, S B; Crenshaw, D M

    2011-01-01

    We present the results of a deep 300 ks Chandra HETG observation of the highly variable narrow-line Seyfert Type 1 galaxy NGC 4051. The HETG spectrum reveals 28 significant soft X-ray ionised lines in either emission or absorption; primarily originating from H-like and He-like K-shell transitions of O, Ne, Mg and Si (including higher order lines and strong forbidden emission lines from O VII and Ne IX) plus high ionisation L-shell transitions from Fe XVII to Fe XXII and lower ionisation inner-shell lines (e.g. O VI). Modelling the data with XSTAR requires four distinct ionisation zones for the gas, all outflowing with velocities < 1000 km/s. A selection of the strongest emission/absorption lines appear to be resolved with FWHM of ~600 km/s. We also present the results from a quasi-simultaneous 350 ks Suzaku observation of NGC 4051 where the XIS spectrum reveals strong evidence for blueshifted absorption lines at ~6.8 and ~7.1 keV, consistent with previous findings. Modelling with XSTAR suggests that this i...

  2. [Mono- and dizygotic twins in forensic paternity testing in practice at the Department of Forensic Medicine (Silesian Academy of Medicine, Katowice) in the years 1996-2003].

    Science.gov (United States)

    Raczek, Ewa

    2004-01-01

    Giving an opinion on disputable paternity, concerning monozygotic twins in practice at the Department of Forensic Medicine (Silesian Academy of Medicine, Katowice) demonstrated their ideal agreement according to examined genetic markers possible. Even the mutation, which was revealed using the RFLP-VNTR method was the same for both twin sisters. In the case of dizygotic twins a firm differentiation of paternity index and probability of paternity was proved. This was the consequence of independent features segregation in first, reductive meiotic division. While the rare, out-ladder allele 16 at the CSF1PO locus was transmitted to both twins: a daughter and a son by the putative father.

  3. Twins in Ancient Greece: a synopsis.

    Science.gov (United States)

    Malamitsi-Puchner, Ariadne

    2016-01-01

    This brief outline associates twins with several aspects of life in Ancient Greece. In Greek mythology twins caused ambivalent reactions and were believed to have ambivalent feelings for each other. Very often, they were viewed as the representatives of the dualistic nature of the universe. Heteropaternal superfecundation, which dominates in ancient myths, explains on one hand, the god-like qualities and, on the other hand, the mortal nature of many twins. An assumption is presented that legends referring to twins might reflect the territorial expansions of Ancient Greeks in Northern Mediterranean, around the Black Sea, in Asia Minor, as well as North East Africa. In conclusion, in Greek antiquity, twins have been used as transitional figures between myth and reality.

  4. Cosmological Signals of a Mirror Twin Higgs

    CERN Document Server

    Craig, Nathaniel; Trott, Timothy

    2016-01-01

    We investigate the cosmology of the minimal model of neutral naturalness, the mirror Twin Higgs. The softly-broken mirror symmetry relating the Standard Model to its twin counterpart leads to significant dark radiation in tension with BBN and CMB observations. We quantify this tension and illustrate how it can be mitigated in several simple scenarios that alter the relative energy densities of the two sectors while respecting the softly-broken mirror symmetry. In particular, we consider both the out-of-equilibrium decay of a new scalar as well as reheating in a toy model of twinned inflation, Twinflation. In both cases the dilution of energy density in the twin sector does not merely reconcile the existence of a mirror Twin Higgs with cosmological constraints, but predicts contributions to cosmological observables that may be probed in current and future CMB experiments. This raises the prospect of discovering evidence of neutral naturalness through cosmology rather than colliders.

  5. 'Biracial'-Looking Twins: A New Twin Type?/Twin Research: Twins with Cystic Teratomas; Sleep Quality and Body Mass Index; Previable Membrane Rupture/Print and Online Reports: Twins Born to a Sister Surrogate; NASA Twin Study; African-Cosmopolitan Twin Fashion Inspirations; Triplet Hockey Stars.

    Science.gov (United States)

    Segal, Nancy L

    2017-03-28

    Dizygotic (DZ) co-twins born to mothers and fathers from different racial or ethnic backgrounds often resemble one parent much more than the other. As such, these pairs comprise a unique subset of twins for investigating how others' responses to their different looks may affect their personalities and self-esteem. This article describes some of these twin pairs and some challenges of raising them, and suggests ways they may be used in research. Next, recent twin research on cystic teratomas, relations between sleep quality and body mass index, and previable membrane rupture is described. The final section concerns twins, twin studies, and related events in the media, namely: twins born to a sister surrogate, the NASA twin investigation, inspiring African-Cosmopolitan twins in fashion, and triplet Hockey Stars.

  6. Highlights from the 15th International Congress of Twin Studies/Twin Research: Differentiating MZ Co-twins Via SNPs; Mistaken Infant Twin-Singleton Hospital Registration; Narcolepsy With Cataplexy; Hearing Loss and Language Learning/Media Mentions: Broadway Musical Recalls Conjoined Hilton Twins; High Fashion Pair; Twins Turn 102; Insights From a Conjoined Twin Survivor.

    Science.gov (United States)

    Segal, Nancy L

    2015-02-01

    Highlights from the 15th International Congress of Twin Studies are presented. The congress was held November 16-19, 2014 in Budapest, Hungary. This report is followed by summaries of research addressing the differentiation of MZ co-twins by single nucleotide polymorphisms (SNPs), an unusual error in infant twin-singleton hospital registration, twins with childhood-onset narcolepsy with cataplexy, and the parenting effects of hearing loss in one co-twin. Media interest in twins covers a new Broadway musical based on the conjoined twins Violet and Daisy Hilton, male twins becoming famous in fashion, twins who turned 102 and unique insights from a conjoined twin survivor. This article is dedicated to the memory of Elizabeth (Liz) Hamel, DZA twin who met her co-twin for the first time at age seventy-eight years. Liz and her co-twin, Ann Hunt, are listed in the 2015 Guinness Book of Records as the longest separated twins in the world.

  7. Simulation of deformation twins and deformation texture in an AZ31 Mg alloy under uniaxial compression

    Energy Technology Data Exchange (ETDEWEB)

    Choi, S.-H. [Department of Materials Science and Metallurgical Engineering, Sunchon National University, Sunchon 540-742 (Korea, Republic of)]. E-mail: shihoon@sunchon.ac.kr; Shin, E.J. [Korea Atomic Energy Research Institute, Neutron Physics Department, Daejeon 305-600 (Korea, Republic of); Seong, B.S. [Korea Atomic Energy Research Institute, Neutron Physics Department, Daejeon 305-600 (Korea, Republic of)

    2007-07-15

    To investigate deformation twins and the evolution of deformation texture during plastic deformation, uniaxial compression tests on a hot-rolled AZ31 Mg alloy were carried out at 200 deg. C. Cylindrical specimens were then compressed in both the rolling and the normal directions. The findings revealed that texture evolution, work hardening and macroscopic anisotropy are strongly dependent on the loading direction. Electron backscattered diffraction analysis was used to examine the orientation of parent grains and twin bands in the AZ31 Mg alloy under uniaxial compression. A viscoplastic self-consistent model (VPSC) was theoretically employed to calculate the relative activities of slip and twin systems in polycrystalline hexagonal aggregates under uniaxial compression. Each deformed grain exhibited an independent number and type of twin variants under uniaxial compression. Neutron diffraction was used to measure the macroscopic texture of the AZ31 Mg alloy. The VPSC model was used to simulate texture evolution, work hardening and macroscopic anisotropy during the uniaxial compression. A modified predominant twin reorientation (PTR) scheme was suggested to explain the gradual increase in twin volume in deformed grains.

  8. Growth of "waist" ZnO twin rods through hydrothermal synthesis.

    Science.gov (United States)

    Tan, Lixia; Yu, Xianjin; Zhang, Lipeng; Yang, Ping

    2014-04-01

    The factors that govern the deposition and structure of "waist" ZnO twin rods from aqueous solution through hydrothermal synthesis were discussed in details. Pencil-like ZnO hexagonal twin rods were obtained in Zn(2+) + HMTA system on ITO glass substrates with ZnO buffer layer deposited in advance. As a contrast, a series of experiments were preceded with TBAB or on bare Cu sheet, Zn sheet, and Al sheet to research lattice-match influences on ZnO nucleation. A series of "waist" ZnO hexagonal twin rods were synthesized and the morphology of each "waist" was shown. The forming of different waists results from the different lattice-match effects between substrates and ZnO crystal. We demonstrated ZnO hexagonal twin rods synthesis on Cu, Al, Zn sheet by normal hydrothermal synthesis and revealed different forming schemes of these varying "waists" of the twin structures. On the basis of our research, not only some new ways of synthesizing ZnO twin rods were proposed but a new idea of applying metal to nano-devices used in piezoelectric area.

  9. Deep Chandra Observations of the Compact Starburst Galaxy Henize 2-10: X-rays from the Massive Black Hole

    CERN Document Server

    Reines, Amy; Miller, Jon; Sivakoff, Gregory; Greene, Jenny; Hickox, Ryan; Johnson, Kelsey

    2016-01-01

    We present follow-up X-ray observations of the candidate massive black hole (BH) in the nucleus of the low-mass, compact starburst galaxy Henize 2-10. Using new high-resolution observations from the Chandra X-ray Observatory totaling 200 ks in duration, as well as archival Chandra observations from 2001, we demonstrate the presence of a previously unidentified X-ray point source that is spatially coincident with the known nuclear radio source in Henize 2-10 (i.e., the massive BH). We show that the hard X-ray emission previously identified in the 2001 observation is dominated by a source that is distinct from the nucleus, with the properties expected for a high-mass X-ray binary. The X-ray luminosity of the nuclear source suggests the massive BH is radiating significantly below its Eddington limit (~10^-6 L_Edd), and the soft spectrum resembles other weakly accreting massive BHs including Sagittarius A*. Analysis of the X-ray light curve of the nucleus reveals the tentative detection of a ~9-hour periodicity, ...

  10. Chandra measurements of non-thermal X-ray emission from massive, merging, radio-halo clusters

    CERN Document Server

    Million, E T

    2008-01-01

    We report the discovery of spatially-extended, non-thermal or hot, quasi-thermal emission components in Chandra X-ray spectra for five of a sample of seven massive, merging galaxy clusters with powerful radio halos: Abell 665, 2163, 2255, 2319, and 1E0657-56. The emission components can be fitted by power-law models with mean photon indices in the range 1.4 20 keV. A control sample of regular, dynamically relaxed clusters without radio halos but with comparable thermal temperatures and luminosities shows no evidence for similar components in their Chandra spectra. Detailed X-ray spectral mapping reveals the complex thermodynamic states of the radio halo clusters. We report the discovery of a clear, large-scale shock front in Abell 2219. Our deepest observations, of the Bullet Cluster 1E0657-56, demonstrate a spatial correlation between the strongest power law X-ray emission, highest thermal pressure, and brightest 1.34GHz radio halo emission in this cluster. The integrated flux and mean spectral index of the...

  11. Markov Chain Monte Carlo Joint Analysis of Chandra X-Ray Imaging Spectroscopy and Sunyaev-Zel'dovich Effect Data

    Science.gov (United States)

    Bonamente, Massimillano; Joy, Marshall K.; Carlstrom, John E.; Reese, Erik D.; LaRoque, Samuel J.

    2004-01-01

    X-ray and Sunyaev-Zel'dovich effect data can be combined to determine the distance to galaxy clusters. High-resolution X-ray data are now available from Chandra, which provides both spatial and spectral information, and Sunyaev-Zel'dovich effect data were obtained from the BIMA and Owens Valley Radio Observatory (OVRO) arrays. We introduce a Markov Chain Monte Carlo procedure for the joint analysis of X-ray and Sunyaev- Zel'dovich effect data. The advantages of this method are the high computational efficiency and the ability to measure simultaneously the probability distribution of all parameters of interest, such as the spatial and spectral properties of the cluster gas and also for derivative quantities such as the distance to the cluster. We demonstrate this technique by applying it to the Chandra X-ray data and the OVRO radio data for the galaxy cluster A611. Comparisons with traditional likelihood ratio methods reveal the robustness of the method. This method will be used in follow-up paper to determine the distances to a large sample of galaxy cluster.

  12. A Very Deep Chandra Observation of the Galaxy Group NGC 5813: AGN Shocks, Feedback, and Outburst History

    CERN Document Server

    Randall, S W; Jones, C; Forman, W R; Bulbul, E; Clarke, T E; Kraft, R; Blanton, E L; David, L; Werner, N; Sun, M; Donahue, M; Giacintucci, S; Simionescu, A

    2015-01-01

    We present results from a very deep (650 ks) Chandra X-ray observation of the galaxy group NGC~5813, the deepest Chandra observation of a galaxy group to date. Earlier observations showed two pairs of cavities distributed roughly collinearly, with each pair associated with an elliptical shock front. The new observations confirm a third pair of outer cavities, collinear with the other pairs, and reveal an associated outer outburst shock at ~30 kpc. This system is therefore unique in exhibiting three cavity pairs, each associated with an unambiguous AGN outburst shock front. The implied mean kinetic power is roughly the same for each outburst, demonstrating that the average AGN kinetic luminosity can remain stable over long timescales (~50 Myr). The two older outbursts have larger, roughly equal total energies as compared with the youngest outburst, implying that the youngest outburst is ongoing. We find that the radiative cooling rate and the mean shock heating rate of the gas are well balanced at each shock f...

  13. A Twin Study of ADHD Symptoms in Early Adolescence: Hyperactivity-Impulsivity and Inattentiveness Show Substantial Genetic Overlap but Also Genetic Specificity

    Science.gov (United States)

    Greven, Corina U.; Rijsdijk, Fruhling V.; Plomin, Robert

    2011-01-01

    A previous paper in this journal revealed substantial genetic overlap between the ADHD dimensions of hyperactivity-impulsivity and inattentiveness in a sample of 8-year old twins drawn from a UK-representative population sample. Four years later, when the twins were 12 years old, more than 5,500 pairs drawn from the same sample were rated again on…

  14. Modelling the influence of amnionicity on the severity of twin-twin transfusion syndrome in monochorionic twin pregnancies

    Energy Technology Data Exchange (ETDEWEB)

    Wijngaard, Jeroen P H M van den [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Umur, Asli [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Ross, Michael G [Department of Obstetrics and Gynecology, Harbor University of California-Los Angeles Medical Center, Torrance, CA 90502 (United States); Gemert, Martin J C van [Laser Center and Department of Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands)

    2004-03-21

    Clinical treatment for diamniotic-monochorionic twin-twin transfusion syndrome (TTTS) may include conversion of diamniotic pregnancies to a monoamniotic-monochorionic state by disrupting the amnion septum. We sought to test the underlying hypothesis, i.e. that a monoamniotic state reduces the severity of TTTS. With use of our previously developed mathematical model of two equal fetoplacental circulatory units connected by various sizes and types of placental anastomoses, we compared the haemodynamic and amniotic fluid dynamics of monoamniotic and diamniotic twins that develop TTTS. We used three anastomotic patterns that produce severe, moderate or mild forms of TTTS, respectively, in our diamniotic-monochorionic twin model. Monoamnionicity was modelled by adding the two amniotic fluid volumes and using the volume-averaged amniotic fluid osmolality. The results were as follows: for severe TTTS, small differences develop between diamniotic and monoamniotic donor twins in fetal urine production, swallowed volume, blood volume, blood pressures, net fetofetal transfusion, and blood and amniotic fluid osmolality. However, the circulatory imbalance between the monoamniotic twins deteriorates similar to that of diamniotic twins. The pathophysiological differences tend to disappear for milder TTTS. In conclusion, our model suggests that the uncommon finding of TTTS in monoamniotic twins is not due to the presence of a single amniotic sac. Rather, clinically significant differences in anastomotic patterns and the delayed or lack of identification of manifestations in monoamniotic twins account for the reduced rate of TTTS diagnosis. Based on these results we expect the clinical disruption of the amnion septum in diamniotic-monochorionic TTTS pregnancies to have only minimal benefits. (note)

  15. NOTE: Thrombosis of anastomoses may affect the staging sequence of twin twin transfusion syndrome

    Science.gov (United States)

    van den Wijngaard, Jeroen P. H. M.; Ross, Michael G.; van Gemert, Martin J. C.

    2008-03-01

    Twin-twin transfusion syndrome (TTTS) is a severe complication of monozygotic (identical) twins, which share one single monochorionic placenta. It is caused by placental anastomoses which link the two fetoplacental circulations of the twins and allow a chronic net inter-twin transfusion to develop between the fetuses. Clinical presentation of TTTS manifestations has been classified into five different stages. In this paper, we used our computational model of TTTS and examined the possible differences between chronic and rapidly increasing inter-twin transfusion in the simulated TTTS staging sequence. Our results suggest that rapid alterations in the net inter-twin transfusion, e.g. due to thrombosis of placental anastomoses, may produce a different staging sequence than in TTTS caused by chronic inter-twin transfusion. These results may aid an improved knowledge of TTTS pathophysiology under conditions of a rapidly changing cardiovascular function, and contribute to the planning of optimal intervention under such circumstances. Supported in part by the European Community Euro-twin-2-twin project (JPHMvdW) and by the National Institutes of Health, grant HL40899 (MGR).

  16. Neonatal morbidity in growth-discordant monochorionic twins: comparison between the larger and the smaller twin.

    Science.gov (United States)

    Lopriore, Enrico; Sluimers, Carolien; Pasman, Suzanne A; Middeldorp, Johanna M; Oepkes, Dick; Walther, Frans J

    2012-08-01

    Fetal growth restriction in singletons has been shown to enhance fetal lung maturation and reduce the risk of respiratory distress syndrome due to increased endogenous steroid production. However, data on lung maturation in growth-discordant monochorionic (thus, identical) twins are lacking. Our objective was to compare the risk of severe neonatal morbidity between the larger and the smaller twin in monochorionic twins with birth weight discordance (BWD). We included in the study all consecutive monochorionic diamniotic pregnancies with severe BWD (≥25%) and two live-born twins delivered at our center (n=47 twin pairs). We compared the incidence of neonatal morbidity, particularly respiratory distress syndrome (RDS), and cerebral lesions between the larger and the smaller co-twin. The incidence of severe neonatal morbidity in the larger and smaller twin was 38% (18/47) and 19% (9/47), respectively (odds ratio (OR) 2.66, 95% confidence interval (CI) 0.94-7.44) and was due primarily to the higher incidence of RDS, 32% (15/47) and 6% (3/47), respectively (OR 6.88, 95% CI 1.66-32.83). In conclusion, this study shows that the larger twin in monochorionic twin pairs with BWD is at increased risk of severe neonatal morbidity, particularly RDS, compared to the smaller twin.

  17. Electron Heating and Cosmic Rays at a Supernova Shock from Chandra X-ray Observations of E0102.2-7219

    CERN Document Server

    Hughes, J P; Decourchelle, A; Hughes, John P.; Rakowski, Cara E.; Decourchelle, Anne

    2000-01-01

    In this Letter we use the unprecedented spatial resolution of the Chandra X-ray Observatory to carry out, for the first time, a measurement of the post-shock electron temperature and proper motion of a young SNR, specifically to address questions about the post-shock partition of energy among electrons, ions, and cosmic rays. The expansion rate, 0.100 +/- 0.025 percent per yr, and inferred age, ~1000 yr, of E0102.2-7219, from a comparison of X-ray observations spanning 20 years, are fully consistent with previous estimates based on studies of high velocity oxygen-rich optical filaments in the remnant. With a radius of 6.4 pc for the blast wave estimated from the Chandra image, our expansion rate implies a blast wave velocity of ~6000 km/s and a range of electron temperatures 2.5 - 45 keV, dependent on the degree of collisionless electron heating. Analysis of the Chandra ACIS spectrum of the immediate post-shock region reveals a thermal plasma with abundances and column density typical of the Small Magellanic ...

  18. The Making of the Chandra X-ray Observatory: the Project Scientist's Perspective

    CERN Document Server

    Weisskopf, Martin C

    2010-01-01

    We review the history of the development of the Chandra X-ray Observatory from our personal perspective. This review is necessarily biased and limited by space since it attempts to cover a time span approaching 5 decades.

  19. Pentalogy of Cantrell in twins: A case report

    Directory of Open Access Journals (Sweden)

    Ilić-Sabo Jelena R.

    2015-01-01

    Full Text Available Introduction. Pentalogy of Cantrell is a very rare congenital multiple malformation with the poor outcome. Syndrome included the following pentad: abdominal wall defect, a defect of the lower sternum, anterior diaphragm defect, ectopia cordis, as well as a variety of intracardiac anomalies. Case Report. In the fifteenth week of the twin pregnancy, ultrasound examination showed multiple anomalies in one, as well as the absence of the nose apex in the other twin. The autopsy of the fetuses was performed after the abortion had been approved by the Ethics Committee. The external examination of the fetus number one showed ectopic heart and omphalocele. The internal examination revealed the existence of sternum cleft, ectopic heart and part of the left lung outside the thoracic cavity, the presence of diaphragmatic hernia with protrusion of abdominal organs, heart with only one large vessel and the horseshoe kidney. The full expression of the Pentalogy of Cantrell was confirmed. The external and internal examination of the other twin showed just agenesis of the nose apex. Conclusion. Recognition and diagnosis of the syndrome is of the exceptional importance. Proper and timely diagnosis should contribute to good outcome of the pregnancy and delivery.

  20. Internal Dynamics of a Twin-layer Solar Prominence

    Science.gov (United States)

    Xia, C.; Keppens, R.

    2016-07-01

    Modern observations revealed rich dynamics within solar prominences. The globally stable quiescent prominences, characterized by the presence of thin vertical threads and falling knobs, are frequently invaded by small rising dark plumes. These dynamic phenomena are related to magnetic Rayleigh-Taylor instability, since prominence matter, 100 times denser than surrounding coronal plasma, is lifted against gravity by weak magnetic field. To get a deeper understanding of the physics behind these phenomena, we use three-dimensional magnetohydrodynamic simulations to investigate the nonlinear magnetoconvective motions in a twin-layer prominence in a macroscopic model from chromospheric layers up to 30 Mm height. The properties of simulated falling “fingers” and uprising bubbles are consistent with those in observed vertical threads and rising plumes in quiescent prominences. Both sheets of the twin-layer prominence show a strongly coherent evolution due to their magnetic connectivity, and demonstrate collective kink deformation. Our model suggests that the vertical threads of the prominence as seen in an edge-on view, and the apparent horizontal threads of the filament when seen top-down are different appearances of the same structures. Synthetic images of the modeled twin-layer prominence reflect the strong degree of mixing established over the entire prominence structure, in agreement with the observations.

  1. Microbiota conservation and BMI signatures in adult monozygotic twins.

    Science.gov (United States)

    Tims, Sebastian; Derom, Catherine; Jonkers, Daisy M; Vlietinck, Robert; Saris, Wim H; Kleerebezem, Michiel; de Vos, Willem M; Zoetendal, Erwin G

    2013-04-01

    The human gastrointestinal (GI) tract microbiota acts like a virtual organ and is suggested to be of great importance in human energy balance and weight control. This study included 40 monozygotic (MZ) twin pairs to investigate the influence of the human genotype on GI microbiota structure as well as microbial signatures for differences in body mass index (BMI). Phylogenetic microarraying based on 16S rRNA genes demonstrated that MZ twins have more similar microbiotas compared with unrelated subjects (Ptwins. Half of the twin pairs were selected on discordance in terms of BMI, which revealed an inverse correlation between Clostridium cluster IV diversity and BMI. Furthermore, relatives of Eubacterium ventriosum and Roseburia intestinalis were positively correlated to BMI differences, and relatives of Oscillospira guillermondii were negatively correlated to BMI differences. Lower BMI was associated with a more abundant network of primary fiber degraders, while a network of butyrate producers was more prominent in subjects with higher BMI. Combined with higher butyrate and valerate contents in the fecal matter of higher BMI subjects, the difference in microbial networks suggests a shift in fermentation patterns at the end of the colon, which could affect human energy homeostasis.

  2. The effect of chorionicity and twin-to-twin delivery time interval on short-term outcome of the second twin

    DEFF Research Database (Denmark)

    Hjortø, Sofie; Nickelsen, Carsten; Petersen, Janne;

    2013-01-01

    Abstract Objectives: To investigate the effect of chorionicity and twin-to-twin delivery time interval on short-term outcome in the second twin. Additionally, to investigate predictors of adverse outcome in both twins. Methods: Data included vaginally delivered twins (≥ 36 weeks) from Copenhagen...... University Hospitals (2001-09). The association between delivery interval and adverse outcome parameters were compared for monochorionic (MC) and dichorionic (DC) twins by multiple linear regression. Predictors were studied by logistic regression. Results: There were 554 twin pairs: 57 MC and 485 DC. We...... found no difference in the decrease of pH (p = 0.912) and Apgar (p = 0.609) in relation to increasing time interval. Neonatal unit (NICU) admissions did not differ (p = 0.167). Apgar ≤ 7 (p twin, whereas first (p = 0.001) or second (p twin Apgar...

  3. METHOD FOR CALCULATION OF STRESS-STRAIN STATE DUE TO SINGLE TWIN IN GRAIN OF VARIOUS FORMS

    Directory of Open Access Journals (Sweden)

    T. V. Drabysheuskaya

    2016-01-01

    Full Text Available The paper investigates a stress-strain state in a polycrystalline grain due to presence in its body of a single micro- twin in case of various grain boundary forms. A methodology for calculation of displacement and stress fields for the specified stress-strain state of a polygon-shaped grain has been developed in the paper. Nodal points in a polycrystalline grain that have a maximum stresses contributing to initiation of destruction have been revealed in the paper. The aim of this work has been to study the stress-strain state due to a single micro-twin in the polycrystalline grain and form of grain boundaries. The paper describes polycrystalline grains having a regular polygon shape and containing a single wedge twin in their body. Polycrystalline grain boundaries are presented as walls with complete dislocation. The investigated grains are located far from the surface of twinning material. The developed methodology for calculation of displacement and stresses created by wedge twin is based on the principle of superposition. Calculations on stress tensor components have been carried out for iron (Fe. The presented results of calculations for stress fields have indicated to validity of the used dislocation model. Twin and grain boundaries being stress concentrators are clearly visible on the obtained distributions of stress fields. Maximum normal stresses are observed on the twin boundaries; σxy maximum shear stresses are located at nodal points of the twin; σzy and σxz shear stresses are maximum on the grain boundaries. The conducted investigations have resulted in study of the stress-strain state due to a single wedge-shaped micro-twin in the polycrystalline grain and form of the grain boundaries. Zones of stress concentration in the polycrystalline grain have been identified in the presence of residual mechanical wedge twin. A method for evaluation of the given state has been developed in the paper.

  4. Intrapair Comparison of Life-Course Appetite and Physical Activity in Elderly Danish Twins: Reliability and Association With Subsequent Survival

    Science.gov (United States)

    Løkkegaard, Laura E.; Larsen, Lisbeth A.; Christensen, Kaare

    2016-01-01

    Avoiding overeating and being physically active is associated with healthy aging, but methodological issues challenge the quantification of the association. Intrapair comparison of twins is a study design that attempts to minimize social norm-driven biased self-reporting of lifestyle factors. We aimed to investigate the association between self-reported lifestyle factors and subsequent survival in 347 Danish twin pairs aged 70 years and older and, additionally, to investigate the reliability of these self-reports. The twins were interviewed in 2003 and followed for mortality until 2015. They were asked to compare their appetite and physical activity to that of their co-twins in different stages of life. On an individual level, we found a positive association between current self-reported physical activity and late-life survival for elderly twins. This was supported by the intrapair analyses, which revealed a positive association between midlife and current physical activity and late-life survival. A positive association between lower appetite and late-life survival was found generally over the life course in the individual level analyses but not in the intrapair analyses. Kappa values for the inter-twin agreement on who ate the most were 0.16 to 0.34 in different life stages, and for physical activity 0.19 to 0.26, corresponding to a slight-to-fair agreement. Approximately, 50% of the twin pairs were not in agreement regarding physical activity, and of these twins 75% (95% CI: 67–82%) considered themselves the most active twin. These findings indicate a still-existing tendency of answering according to social norms, even in a twin study designed to minimize this. PMID:27485765

  5. Dislocation Mechanism of Twinning in Ni-Mn-Ga

    Science.gov (United States)

    Zárubová, N.; Ge, Y.; Gemperlová, J.; Gemperle, A.; Hannula, S.-P.

    2012-03-01

    Tensile tests were performed in situ in a transmission electron microscope to investigate the twinning mechanism in non-modulated Ni-Mn-Ga martensite. The reorientation of the twin variants occurs via twinning dislocations. Their generation and movement were followed; the glide plane and Burgers vector were verified. Individual twinning dislocations were visualized.

  6. Chandra position of IGR J17454-2919 and discovery of a possible NIR counterpart

    DEFF Research Database (Denmark)

    Paizis, A.; Nowak, M.; Chati, S.;

    2015-01-01

    On 2014 November 3, we observed the recently discovered INTEGRAL source IGR J17454-2919 (ATels #6530, #6574 and #6602) with Chandra HETGS for 20ks. The J2000.0 Chandra position we obtain is RA: 17 45 27.689 DEC: -29 19 53.83 (90% uncertainty of 0.6") This position (2.4" away from the Swift positi...

  7. On the twinning in ZnPd.

    Science.gov (United States)

    Ivarsson, Dennis C A; Burkhardt, Ulrich; Heggen, Marc; Ormeci, Alim; Armbrüster, Marc

    2017-02-22

    The intermetallic compound ZnPd has demonstrated excellent catalytic properties in methanol steam reforming. While it is known that defects and microstructures influence the catalytic properties, little is known about the defects occurring in ZnPd. Due to recent advances in synthetic methods, coarse-grained ZnPd samples are accessible. This enables the detection and investigation of twinning in ZnPd by studying the twinned regions from the macroscopic scale by polarised light and electron backscattering diffraction (EBSD) down to the atomic scale by high-resolution transmission electron microscopy (HR-TEM). Twinning occurs in {101} and is coupled with a change in the c/a ratio in the vicinity of the twin boundary. Quantum chemical calculations result in only very small energy differences between the ideal and the twinned structure, explaining the experimentally observed thermal stability of the latter. The chemical bonding was investigated by the electron localizability indicator (ELI) and compared to the one in the ideal structure. The results confirm twinning along the {101} plane and demonstrate the high stability of the twin boundaries after formation.

  8. Twin and Triplet Drugs in Opioid Research

    Science.gov (United States)

    Fujii, Hideaki

    Twin and triplet drugs are defined as compounds that contain respectively two and three pharmacophore components exerting pharmacological effects in a molecule. The twin drug bearing the same pharmacophores is a "symmetrical twin drug", whereas that possessing different pharmacophores is a "nonsymmetrical twin drug." In general, the symmetrical twin drug is expected to produce more potent and/or selective pharmacological effects, whereas the nonsymmetrical twin drug is anticipated to show both pharmacological activities stemming from the individual pharmacophores (dual action). On the other hand, nonsymmetrical triplet drugs, which have two of the same pharmacophores and one different moiety, are expected to elicit both increased pharmacological action and dual action. The two identical portions could bind the same receptor sites simultaneously while the third portion could bind a different receptor site or enzyme. This review will mainly focus on the twin and triplet drugs with an evaluation of their in vivo pharmacological effects, and will also include a description of their pharmacology and synthesis.

  9. Mechanical twinning in small quartz crystals

    Science.gov (United States)

    Laughner, J. W.; Newnham, R. E.; Cross, L. E.

    1982-02-01

    Quartz is known to be ferrobielastic; that is, quartz crystals have domain states (Dauphiné twins) which differ in their elastic compliance values and which can be switched by an appropriately oriented stress. Polycrystalline quartz has also been reported (Tullis 1970) to show preferential orientation of these domains following application of large uniaxial stresses. These experiments were designed to study twinning of synthetic quartz “grains” (minimum size 0.07×0.07×0.02 cm) in specially-constructed composites and of grains in three natural quartz aggregates — a quartzite, a novaculite, and a jasper. Backreflection X-ray techniques were used to verify twinning in the composite grains, while special electroding and electrical detection allowed the twinning processes to be examined in “real time.” Small synthetic quartz crystals were found to behave identically to the massive samples previously studied. Electrical pulses due to the reversal of piezoelectric coefficient d 11 in twinned quartz were detected from quartzite and from the man-made composites. Novaculite also gave electrical pulses which were probably from twinning (evidenced by the correlation of expected and observed pulse sizes and shapes), while no pulses from the jaspers indicative of twinning were detected. Grain size distribution differences are considered the main structural reason for the different behaviors.

  10. Teaching about twins: college courses and public lectures.

    Science.gov (United States)

    Segal, Nancy L

    2013-12-01

    The present article describes teaching experiences and observations in college courses and public lectures on twins. It is concluded that much more information about twins, at both research and practical levels, requires general dissemination. This discussion is followed by reviews of recent twin research on the topics of obesity control, post-zygotic mutation, in vitro fertilization, and schisis-associated defects. Media reports of twins accused of rape, infant Chinese twins sold separately for profit, a twin CEO, and twins pursuing the same career are presented.

  11. Acardiac Parabiotic Fetus: A Rare Complication of Twin Pregnancy

    Directory of Open Access Journals (Sweden)

    Sood S

    2015-10-01

    Full Text Available Acardiac parabiotic fetus is sequelae of complication of monochorionic monoamniotic twin pregnancy also known as Twin Reversed Arterial Perfusion Sequence (TRAP. It is rare affecting 1 in 35,000 births and 1 % of monozygotic twins. Acardiac parabiotic twin commonly known as parasite occurs rarely and may lead to high output cardiac failure, hydrops or premature delivery in the pump fetus. In this report, we present a 23 years old primigravida with twin pregnancy, with twin reversed arterial perfusion sequence with one of the twins being acardiac anceps and the other normal pump fetus. This association is relatively uncommon and therefore rarely documented.

  12. Resolving galaxy cluster gas properties at z~1 with XMM-Newton and Chandra

    CERN Document Server

    Bartalucci, I; Pratt, G W; Démoclès, J; van der Burg, R F J; Mazzotta, P

    2016-01-01

    We present a pilot X-ray study of the five most massive ($M_{500}>5 \\times 10^{14} M_{\\odot}$), distant (z~1), galaxy clusters detected via the Sunyaev-Zeldovich effect. We optimally combine XMM-Newton and Chandra X-ray observations by leveraging the throughput of XMM to obtain spatially-resolved spectroscopy, and the spatial resolution of Chandra to probe the bright inner parts and to detect embedded point sources. Capitalising on the excellent agreement in flux-related measurements, we present a new method to derive the density profiles, constrained in the centre by Chandra and in the outskirts by XMM. We show that the Chandra-XMM combination is fundamental for morphological analysis at these redshifts, the Chandra resolution being required to remove point source contamination, and the XMM sensitivity allowing higher significance detection of faint substructures. The sample is dominated by dynamically disturbed objects. We use the combined Chandra-XMM density profiles and spatially-resolved temperature prof...

  13. Familial aggregation of atrial fibrillation: a study in Danish twins

    DEFF Research Database (Denmark)

    Christophersen, Ingrid Elisabeth; Ravn, Lasse Steen; Budtz-Joergensen, Esben

    2009-01-01

    BACKGROUND: Heritability may play a role in nonfamilial atrial fibrillation (AF). We hypothesized that a monozygotic (MZ) twin whose co-twin was diagnosed with AF would have an increased risk of the disease compared with a dizygotic (DZ) twin in the same situation. METHODS AND RESULTS: A sample...... of 1137 same-sex twin pairs (356 MZ and 781 DZ pairs) in which one or both members were diagnosed with AF were identified in The Danish Twin Registry. Concordance rates were twice as high for MZ pairs than for DZ pairs regardless of sex (22.0% versus 11.6%, P...-free survival times, we compared the time span between occurrences of disease in MZ and DZ twins. The unaffected twin was included when his or her twin-sibling (the index twin) was diagnosed with AF. After adjustment for age at entry, MZ twins had a significantly shorter event-free survival time (hazard ratio...

  14. Unequal but monozygous: a history of twin-twin transfusion syndrome.

    Science.gov (United States)

    Obladen, Michael

    2010-03-01

    Twin-twin transfusion is the major cause of mortality and morbidity in monochorionic twins. Its pathogenesis has been gradually elucidated over the last three centuries. Among obstetricians, there was a long-lasting controversy on the existence of placental anastomoses and whether or not to tie the placental end of the firstborn infant's cord. However, a twin pregnancy practically never could be excluded. Stalpart van der Wiel described a twin-twin vessel connection in 1687. Studies on interfetal anastomoses using injection of placental vessels were published by Smellie in 1752, Osiander in 1781, and Brachet in 1821. Different types of anastomoses, and their associated fetal disorders were classified by Schatz in a series of papers at the end of the 19(th) century. With the advent of ultrasound and laser techniques, prenatal diagnosis and treatment became available in the last decade of the 20(th) century.

  15. Intravenous nutrition during a twin pregnancy.

    Science.gov (United States)

    Karamatsu, J T; Boyd, A T; Cooke, J; Vinall, P S; McMahon, M J

    1987-01-01

    A case is reported of a woman in the third trimester of a twin pregnancy who required intravenous nutrition because of inadequate absorption of nutrients due to a jejunoileal bypass. Weight gain was poor, and there was evidence of intrauterine growth retardation before commencement of intravenous feeding. She received overnight intravenous nutrition for 6 weeks and gained weight with ultrasound evidence of fetal growth. During the 33rd week of gestation, she was delivered of healthy twin males who were at appropriate birth weights and development for their age of gestation. The considerations in intravenous nutrition for a twin pregnancy after jejunoileal bypass are discussed.

  16. New growth mode through decorated twin boundaries.

    Science.gov (United States)

    Bleikamp, Sebastian; Thoma, Arne; Polop, Celia; Pirug, Gerhard; Linke, Udo; Michely, Thomas

    2006-03-24

    Scanning tunneling microscopy and low energy electron diffraction were used to investigate the growth of partly twinned Ir thin films on Ir(111). A transition from the expected layer-by-layer to a defect dominated growth mode with a fixed lateral length scale and increasing roughness is observed. During growth, the majority of the film is stably transformed to twinned stacking. This transition is initiated by the energetic avoidance of the formation of intrinsic stacking faults compared to two independent twin faults. The atomistic details of the defect kinetics are outlined.

  17. Undiagnosed xiphopagus twins: a perinatal malady

    Directory of Open Access Journals (Sweden)

    Gowri Dorairajan

    2012-02-01

    Full Text Available Conjoined twins are a very rare entity. It is associated with poor survival rate in the presence of vital organ sharing. The entity can be diagnosed as early as the first trimester. A conjoined twin diagnosed late in labor is a malady with high perinatal mortality and maternal morbidity. We present one such case of xiphopagus twins. The management of a case diagnosed late in labor can be very challenging. Such obstetric challenges can be avoided by a meticulous early scan with a high index of suspicion, especially in the absence of separating membrane while scanning multiple pregnancies.

  18. Nanoscale growth twins in sputtered metal films

    Energy Technology Data Exchange (ETDEWEB)

    Misra, Amit [Los Alamos National Laboratory; Anderoglu, Osman [Los Alamos National Laboratory; Hoagland, Richard G [Los Alamos National Laboratory; Zhang, X [TEXAS A& M

    2008-01-01

    We review recent studies on the mechanical properties of sputtered Cu and 330 stainless steel films with {l_brace}1 1 1{r_brace} nanoscale growth twins preferentially oriented perpendicular to growth direction. The mechanisms of formation of growth twins during sputtering and the deformation mechanisms that enable usually high strengths in nanotwinned structures are highlighted. Growth twins in sputtered films possess good thermal stability at elevated temperature, providing an approach to extend the application of high strength nanostructured metals to higher temperatures.

  19. Spatial Correlation Function of the Chandra Selected Active Galactic Nuclei

    Science.gov (United States)

    Yang, Y.; Mushotzky, R. F.; Barger, A. J.; Cowie, L. L.

    2006-01-01

    We present the spatial correlation function analysis of non-stellar X-ray point sources in the Chandra Large Area Synoptic X-ray Survey of Lockman Hole Northwest (CLASXS). Our 9 ACIS-I fields cover a contiguous solid angle of 0.4 deg(exp 2) and reach a depth of 3 x 10(exp -15) erg/square cm/s in the 2-8 keV band. We supplement our analysis with data from the Chandra Deep Field North (CDFN). The addition of this field allows better probe of the correlation function at small scales. A total of 233 and 252 sources with spectroscopic information are used in the study of the CLASXS and CDFN fields respectively. We calculate both redshift-space and projected correlation functions in co-moving coordinates, averaged over the redshift range of 0.1 tau(sub 0 = 8.1(sup +1.2 sub -2.2) Mpc, and gamma = 2.1 +/- 0.5 for the CLASXS field, and tau(sub 0) = 5.8(sup +.1.0 sub -1.5) Mpc, gamma = 1.38(sup +0.12 sub -0.14 for the CDFN field. By comparing the real- and redshift-space correlation functions in the combined CLASXS and CDFN samples, we are able to estimate the redshift distortion parameter Beta = 0.4 +/- 0.2 at an effective redshift z = 0.94. We compare the correlation functions for hard and soft spectra sources in the CLASXS field and find no significant difference between the two groups. We have also found that the correlation between X-ray luminosity and clustering amplitude is weak, which, however, is fully consistent with the expectation using the simplest relations between X-ray luminosity, black hole mass, and dark halo mass. We study the evolution of the AGN clustering by dividing the samples into 4 redshift bins over 0.1 Mpcestimate the evolution of the bias, and find that the bias increases rapidly with redshift (b(z = 0.45) = 0.95 +/- 0.15 and b(z = 2.07) = 3.03 +/- 0.83): The typical mass of the dark matter halo derived from the bias estimates show little change with redshift. The average halo mass is found to be log (M(sub halo)/M(sun))approximates 12.1. Subject

  20. Cohort Profile : The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry)

    NARCIS (Netherlands)

    Gatz, Margaret; Harris, Jennifer R.; Kaprio, Jaakko; McGue, Matt; Smith, Nicholas L.; Snieder, Harold; Spiro, Avron; Butler, David A.

    2015-01-01

    The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry) is a comprehensive registry of White male twin pairs born in the USA between 1917 and 1927, both of the twins having served in the military. The purpose was medical research and ultimately improved clini

  1. Chandra X-ray observations of the hyper-luminous infrared galaxy IRAS F15307+3252

    Science.gov (United States)

    Hlavacek-Larrondo, J.; Gandhi, P.; Hogan, M. T.; Gendron-Marsolais, M.-L.; Edge, A. C.; Fabian, A. C.; Russell, H. R.; Iwasawa, K.; Mezcua, M.

    2017-01-01

    Hyper-luminous infrared galaxies (HyLIRGs) lie at the extreme luminosity end of the IR galaxy population with LIR > 1013 L⊙. They are thought to be closer counterparts of the more distant sub-millimeter galaxies, and should therefore be optimal targets to study the most massive systems in formation. We present deep Chandra observations of IRAS F15307+3252 (100 ks), a classical HyLIRG located at z = 0.93 and hosting a radio-loud AGN (L1.4 GHz ˜ 3.5 × 1025 W Hz-1). The Chandra images reveal the presence of extended (r = 160 kpc), asymmetric X-ray emission in the soft 0.3-2.0 keV band that has no radio counterpart. We therefore argue that the emission is of thermal origin originating from a hot intragroup or intracluster medium virializing in the potential. We find that the temperature (˜2 keV) and bolometric X-ray luminosity (˜3 × 1043 erg s-1) of the gas follow the expected LX-ray-T correlation for groups and clusters, and that the gas has a remarkably short cooling time of 1.2 Gyr. In addition, VLA radio observations reveal that the galaxy hosts an unresolved compact steep-spectrum (CSS) source, most likely indicating the presence of a young radio source similar to 3C186. We also confirm that the nucleus is dominated by a redshifted 6.4 keV Fe Kα line, strongly suggesting that the AGN is Compton-thick. Finally, Hubble images reveal an overdensity of galaxies and sub-structure in the galaxy that correlates with soft X-ray emission. This could be a snapshot view of on-going groupings expected in a growing cluster environment. IRAS F15307+3252 might therefore be a rare example of a group in the process of transforming into a cluster.

  2. Acute parvovirus B19 infection in identical twins unmasking previously unidentified hereditary spherocytosis.

    Science.gov (United States)

    Forde, Donall G; Cope, Alison; Stone, Ben

    2014-07-29

    Identical Caucasian male twins, previously fit, presented 1 week apart with short histories of fever and lethargy. The twins were febrile at presentation with profound pancytopaenia and evidence of haemolysis. There was no rash or arthralgia. Both required multiple red cell transfusions. The twins had positive IgM serology for Epstein-Barr virus (EBV), cytomegalovirus (CMV) and parvovirus B19. EBV viral capsid antigen and Epstein-Barr nuclear antigen IgGs were also positive however, suggesting past EBV exposure. Parvovirus B19 DNA was detected from peripheral blood PCR; CMV and EBV DNA PCRs were negative. Convalescent serology demonstrated no evolution of the CMV serological response, that is no IgG to CMV developed which implies an initial non-specific polyclonal IgM response. The twins recovered fully over 7 days, the first with a course of prednisolone and the second spontaneously. They were diagnosed with hereditary spherocytosis on convalescent blood films. On further questioning, a family history of hereditary spherocytosis was eventually revealed. The twins' maternal grandmother was known to have the condition asymptomatically. Their mother had prior to this never been tested, but later bloods would reveal a compatible biochemical picture.

  3. Chandra Observation of Abell 1142: A Cool-Core Cluster Lacking a Central Brightest Cluster Galaxy?

    CERN Document Server

    Su, Yuanyuan; Gastaldello, Fabio; van Weeren, Reinout

    2016-01-01

    Abell~1142 is a low-mass galaxy cluster at low redshift containing two comparable Brightest Cluster Galaxies (BCG) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters with each containing one BCG. The BCGs are merging at a relative velocity of ~1200 km/s. This ongoing merger may have shock-heated the ICM from ~ 2 keV to above 3 keV, which would explain the anomalous L_X--T_X scaling relation for this system. This merger may have displaced the metal-enriched "cool core" of eith...

  4. Spatial distribution of metal emissions in supernova remnant 3C 397 viewed with Chandra and XMM

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We present X-ray equivalent width imaging of 3C 397 for Mg Heα,Si Heα,S Heα,and Fe Kα complex lines with Chandra and XMM-Newton observations.The images revealed that the heavier the element is,the smaller the extent of the element distribution is.The Mg emission is evidently enhanced in the southeastern blow-out region,well along the radio boundary there,and appears to partially envelope the eastern Fe knot.Two bilateral hat-like Si line-emitting structures are along the northern and southern borders,roughly symmetric with respect to the south-east-northwest elongation axis.An S line-emitting shell is located just inside the northern radio and IR shell,indicating a layer of reversely shocked sulphur in the ejecta.A few enhanced Fe features are basically aligned along the diagonal of the rectangular shape of the SNR,which implicates an early asymmetric SN explosion.

  5. X-Ray Spectroscopy of diffuse Galactic Interstellar Matter with Chandra

    Science.gov (United States)

    Schulz, Norbert S.; Paerels, Frits

    One of the expectations with the advent of the High Energy Transmission Grating (HETG) spectrometer onboard the Chandra X-ray Observatory was to measure precise photoelectric edges of major cosmic elements such as O, Ne, Mg, Si, S, Ar, Ca, and Fe. Early studies revealed complex absorption structures around the O K, Fe L, and Ne K edges which were identified with absorption from the various phases of the interstellar medium and which could place limits on ionization fractions in these phases. The dust content in interstellar matter as well as, for example, the fraction of how much oxygen is locked into dust are issues of importance and here resolved X-ray edges can determine significant limits. I will review predictions made by cross-sections and depletion factors and compare with current observations specifically with respect to silicon absorption in the interstellar medium. Dust grain models and in conjunction with laboratory measurements are now used to improve current interstellar X-ray absorption models.

  6. A very deep Chandra view of metals, sloshing and feedback in the Centaurus cluster of galaxies

    CERN Document Server

    Sanders, J S; Taylor, G B; Russell, H R; Blundell, K M; Canning, R E A; Hlavacek-Larrondo, J; Walker, S A; Grimes, C K

    2016-01-01

    We examine deep Chandra X-ray observations of the Centaurus cluster of galaxies, Abell 3526. Applying a gradient magnitude filter reveals a wealth of structure, from filamentary soft emission on 100pc (0.5 arcsec) scales close to the nucleus to features 10s of kpc in size at larger radii. The cluster contains multiple high-metallicity regions with sharp edges. Relative to an azimuthal average, the deviations of metallicity and surface brightness are correlated, and the temperature is inversely correlated, as expected if the larger scale asymmetries in the cluster are dominated by sloshing motions. Around the western cold front are a series of ~7 kpc 'notches', suggestive of Kelvin-Helmholtz instabilities. The cold front width varies from 4 kpc down to close to the electron mean free path. Inside the front are multiple metallicity blobs on scales of 5-10 kpc, which could have been uplifted by AGN activity, also explaining the central metallicity drop and flat inner metallicity profile. Close to the nucleus are...

  7. Frontier Fields Clusters: Deep Chandra Observations of the Complex Merger MACS J1149.6+2223

    CERN Document Server

    Ogrean, G A; Jones, C; Forman, W; Dawson, W A; Golovich, N; Andrade-Santos, F; Murray, S S; Nulsen, P; Roediger, E; Zitrin, A; Bulbul, E; Kraft, R; Goulding, A; Umetsu, K; Mroczkowski, T; Bonafede, A; Randall, S; Sayers, J; Churazov, E; David, L; Merten, J; Donahue, M; Mason, B; Rosati, P; Vikhlinin, A; Ebeling, H

    2016-01-01

    The HST Frontier Fields cluster MACS J1149.6+2223 is one of the most complex merging clusters, believed to consist of four dark matter halos. We present results from deep (365 ks) Chandra observations of the cluster, which reveal the most distant cold front (z=0.544) discovered to date. In the cluster outskirts, we also detect hints of a surface brightness edge that could be the bow shock preceding the cold front. The substructure analysis of the cluster identified several components with large relative radial velocities, thus indicating that at least some collisions occur almost along the line of sight. The inclination of the mergers with respect to the plane of the sky poses significant observational challenges at X-ray wavelengths. MACS J1149.6+2223 possibly hosts a steep-spectrum radio halo. If the steepness of the radio halo is confirmed, then the radio spectrum, combined with the relatively regular ICM morphology, could indicate that MACS J1149.6+2223 is an old merging cluster.

  8. CHANDRA OBSERVATION OF ABELL 1142: A COOL-CORE CLUSTER LACKING A CENTRAL BRIGHTEST CLUSTER GALAXY?

    Energy Technology Data Exchange (ETDEWEB)

    Su, Yuanyuan; Weeren, Reinout van [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Buote, David A. [Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Gastaldello, Fabio, E-mail: yuanyuan.su@cfa.harvard.edu [INAF-IASF-Milano, Via E. Bassini 15, I-20133 Milano (Italy)

    2016-04-10

    Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s{sup −1}. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous L{sub X}–T{sub X} scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.

  9. Selected First Results from the 7 Ms Chandra Deep Field-South Survey

    Science.gov (United States)

    Brandt, W. Niel; Chandra Deep Field-South Team

    2017-01-01

    The exposure on the Chandra Deep Field-South (CDF-S) has recently been increased to 7 Ms, making it the most sensitive extragalactic X-ray survey by a wide margin. About 1050 X-ray sources have been detected, primarily distant active galactic nuclei (AGNs) and starburst/normal galaxies. The unmatched deep multiwavelength coverage for these sources allows superb follow-up investigations; e.g., 98.4% of the X-ray sources have multiwavelength counterparts, and 97.8% have spectroscopic/photometric redshifts. I will briefly describe the source catalog for the 7 Ms CDF-S and some exciting first science results. The latter will likely include (1) constraints on SMBH growth in the first galaxies as revealed by direct detection and stacking; (2) long-term variability studies of the AGNs producing most of cosmic accretion power; (3) AGN/galaxy interactions as investigated via the host properties of X-ray AGNs; and (4) measurements of the evolving X-ray binary populations of normal and starburst galaxies.

  10. Deep Chandra study of the truncated cool core of the Ophiuchus cluster

    CERN Document Server

    Werner, N; Canning, R E A; Allen, S W; King, A L; Sanders, J S; Simionescu, A; Taylor, G B; Morris, R G; Fabian, A C

    2016-01-01

    We present the results of a deep (280 ks) Chandra observation of the Ophiuchus cluster, the second-brightest galaxy cluster in the X-ray sky. The cluster hosts a truncated cool core, with a temperature increasing from kT~1 keV in the core to kT~9 keV at r~30 kpc. Beyond r~30 kpc the intra-cluster medium (ICM) appears remarkably isothermal. The core is dynamically disturbed with multiple sloshing induced cold fronts, with indications for both Rayleigh-Taylor and Kelvin-Helmholtz instabilities. The sloshing is the result of the strongly perturbed gravitational potential in the cluster core, with the central brightest cluster galaxy (BCG) being displaced southward from the global center of mass. The residual image reveals a likely subcluster south of the core at the projected distance of r~280 kpc. The cluster also harbors a likely radio phoenix, a source revived by adiabatic compression by gas motions in the ICM. Even though the Ophiuchus cluster is strongly dynamically active, the amplitude of density fluctuat...

  11. Chandra observation of two shock fronts in the merging galaxy cluster Abell 2146

    CERN Document Server

    Russell, H R; Fabian, A C; Baum, S A; Donahue, M; Edge, A C; McNamara, B R; O'Dea, C P

    2010-01-01

    We present a new Chandra observation of the galaxy cluster Abell 2146 which has revealed a complex merging system with a gas structure that is remarkably similar to the Bullet cluster (eg. Markevitch et al. 2002). The X-ray image and temperature map show a cool 2-3 keV subcluster with a ram pressure stripped tail of gas just exiting the disrupted 6-7 keV primary cluster. From the sharp jump in the temperature and density of the gas, we determine that the subcluster is preceded by a bow shock with a Mach number M=2.2+/-0.8, corresponding to a velocity v=2200^{+1000}_{-900} km/s relative to the main cluster. We estimate that the subcluster passed through the primary core only 0.1-0.3 Gyr ago. In addition, we observe a slower upstream shock propagating through the outer region of the primary cluster and calculate a Mach number M=1.7+/-0.3. Based on the measured shock Mach numbers M~2 and the strength of the upstream shock, we argue that the mass ratio between the two merging clusters is between 3 and 4 to one. B...

  12. In situ study of defect migration kinetics and self-healing of twin boundaries in heavy ion irradiated nanotwinned metals.

    Science.gov (United States)

    Li, J; Yu, K Y; Chen, Y; Song, M; Wang, H; Kirk, M A; Li, M; Zhang, X

    2015-05-13

    High energy particles introduce severe radiation damage in metallic materials, such as Ag. Here we report on the study on twin boundary (TB) affected zone in irradiated nanotwinned Ag wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. In situ studies also reveal surprising resilience and self-healing of TBs in response to radiation. This study provides further support for the design of radiation-tolerant nanotwinned metallic materials.

  13. Twin boundary energy and characterization of charge redistribution near the twin boundaries of cupperate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadi, Mahnaz [Faculty of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Khoshnevisan, Bahram, E-mail: m.mohammadi_2@grad.kashanu.ac.ir [Faculty of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Javad Hashemifar, S. [Department of Physics, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

    2014-12-15

    Highlights: • Ab initio simulation for twin boundary energy in YBCO system for the 1st time. • Study of the twin boundary energy variation versus the inserted strain. • Proportionality of twin lamella width by the inserted strain. • Local charge transfer and charge redistribution on the twin planes. • Total DOSs for the twined system at Fermi level is higher than the untwined one. • This explain the effect of twin boundaries in agreement with experimental data. - Abstract: Ab-initio calculations under general gradient approximation have been employed for the first time to find out twin boundary energy, γ, in twined YBCO systems. Despite a vast discrepancy in reported experimental values, our results show that the γ value falls in the range of 40–85 mJ/m{sup 2}. On the other hand, functional form of γ versus inserted strains shows that the mean value for the twin width lamella would tend to approach zero as the strain goes to zero. We have also investigated the local charge transfer and the modification of the electronic states of the basal and twin planes in YBCO, because the charge redistribution at interfaces can modify transport across the grains considerably and determine the applicability of high-T{sub c} superconductors in the electronic applications. The total density of electronic states at the Fermi level for the twined system is enhanced in comparison with the untwined one. Our results explain the influence of twin boundaries in superconductive properties of YBCO, in experimental situations.

  14. Removing the twin image in digital holography by segmented filtering of in-focus twin image

    OpenAIRE

    2008-01-01

    We propose and investigate a new digital method for the reduction of twin-image noise from digital Fresnel holograms. For the case of in-line Fresnel holography the unwanted twin is present as a highly corruptive noise when the object image is numerically reconstructed. We propose to firstly reconstruct the unwanted twin-image when it is in-focus and in this plane we calculate a segmentation mask that borders this in focus image. The twin-image is then segmented and removed by sim...

  15. Comparison of Naturally Conceived and IVF-DZ Twins in the Netherlands Twin Registry: A Developmental Study

    Directory of Open Access Journals (Sweden)

    Catharina E. M. van Beijsterveldt

    2011-01-01

    Full Text Available In a large set of twin pairs, we compared twins born after IVF to naturally conceived twins with respect to birth characteristics, growth, attainment of motor milestones, and emotional and behavioral problems. Twin families were registered with the Netherlands Twin Register. We included 1534 dizygotic (DZ twins born after IVF, 5315 naturally conceived (NC DZ twins, and 1504 control NC DZ twins who were matched to the IVF twins based on maternal age, maternal educational level, smoking during pregnancy, gestational age, and offspring sex. Data were obtained by longitudinal surveys sent to fathers, mothers, and teachers at ages 1, 2, 3, 7, 10, and 12 years. Results showed no differences in growth, in attainment of motor milestones, and in behavioral development between IVF and matched NC twins. It can be concluded that for nearly all aspects, development in IVF and NC children is similar.

  16. Sizing Up Red-Giant Twins

    Science.gov (United States)

    Kohler, Susanna

    2016-02-01

    -resolution ground-based spectroscopy at the Fred Lawrence Whipple Observatory and Apache Point Observatory, Rawls and collaborators established that the two stars have masses of 2.17 and 2.15 solar masses, and radii of 8.4 and 8.3 solar radii.Not Quite Twins?Intriguingly, when the authors measured the stellar oscillations from the binary, they were only able to pick out one signal. Using the scaling relations, their measurements reveal that the star producing the oscillations has a mass of 2.17 solar masses and radius of 8.3 radii consistent with both red giants in the system, within error bars. This provides excellent confirmation of the scaling relations for obtaining mass and radius, but it also raises a new question: why is only one star of this twin system producing oscillations?Rawls and collaborators have an idea: one star might be more magnetically active than the other, causing the suppression of oscillations in the more active star. The authors observations and detailed modeling support this idea, but similar analyses of the rest of the red-giant eclipsing binaries identified in the Kepler field will help to determine if KIC 9246715 is unusual, or if this behavior is common among such systems.CitationMeredith L. Rawls et al 2016 ApJ 818 108. doi:10.3847/0004-637X/818/2/108

  17. LOFAR, VLA, and Chandra observations of the Toothbrush galaxy cluster

    CERN Document Server

    van Weeren, R J; Brüggen, M; Andrade-Santos, F; Ogrean, G A; Williams, W L; Röttgering, H J A; Dawson, W A; Forman, W R; de Gasperin, F; Hardcastle, M J; Jones, C; Miley, G K; Rafferty, D A; Rudnick, L; Sabater, J; Sarazin, C L; Shimwell, T W; Bonafede, A; Best, P N; Bîrzan, L; Cassano, R; Chyży, K T; Croston, J H; Dijkema, T J; Ensslin, T; Ferrari, C; Heald, G; Hoeft, M; Horellou, C; Jarvis, M J; Kraft, R P; Mevius, M; Intema, H T; Murray, S S; Orrú, E; Pizzo, R; Sridhar, S S; Simionescu, A; Stroe, A; van der Tol, S; White, G J

    2016-01-01

    We present deep LOFAR observations between 120-181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of $\\alpha = -0.8 \\pm 0.1$ at the northern edge of the main radio relic, steepening towards the south to $\\alpha \\approx - 2$. The spectral index of the radio halo is remarkably uniform ($\\alpha = -1.16$, with an intrinsic scatter of $\\leq 0.04$). The observed radio relic spectral index gives a Mach number of $\\mathcal{M} = 2.8^{+0.5}_{-0.3}$, assuming diffusive shock acceleration (DSA). However, the gas density jump at the northern edge of the large radio r...

  18. AEGIS: Chandra Observation of DEEP2 Galaxy Groups and Clusters

    CERN Document Server

    Fang, T; Davis, D; Newman, J; Davis, M; Nandra, K; Laird, E; Koo, D; Coil, A; Cooper, M; Croton, D; Yan, R

    2006-01-01

    We present a 200 ksec Chandra observation of seven spectroscopically selected, high redshift (0.75 < z < 1.03) galaxy groups and clusters discovered by the DEEP2 Galaxy Redshift Survey in the Extended Groth Strip (EGS). X-ray emission at the locations of these systems is consistent with background. The 3-sigma upper limits on the bolometric X-ray luminosities (L_X) of these systems put a strong constraint on the relation between L_X and the velocity dispersion of member galaxies sigma_gal at z~1; the DEEP2 systems have lower luminosity than would be predicted by the local relation. Our result is consistent with recent findings that at high redshift, optically selected clusters tend to be X-ray underluminous. A comparison with mock catalogs indicates that it is unlikely that this effect is entirely caused by a measurement bias between sigma_gal and the dark matter velocity dispersion. Physically, the DEEP2 systems may still be in the process of forming and hence not fully virialized, or they may be defic...

  19. Chandra Phase-Resolved Spectroscopy of the Crab Pulsar

    CERN Document Server

    Weisskopf, M C; Paerels, F; Becker, W; Tennant, A F; Swartz, D A; Weisskopf, Martin C.; Dell, Stephen L. O'; Paerels, Frits; Becker, Werner; Tennant, Allyn F.; Swartz, Douglas A.

    2004-01-01

    We present the first phase-resolved study of the X-ray spectral properties of the Crab Pulsar that covers all pulse phases. The superb angular resolution of the Chandra X-ray Observatory enables distinguishing the pulsar from the surrounding nebulosity, even at pulse minimum. Analysis of the pulse-averaged spectrum measures interstellar X-ray extinction due primarily to photoelectric absorption and secondarily to scattering by dust grains in the direction of the Crab Nebula. We confirm previous findings that the line-of-sight to the Crab is underabundant in oxygen, although more-so than recently measured. Using the abundances and cross sections from Wilms, Allen & McCray (2000) we find [O/H] = (3.33 +/-0.25) x 10**-4. Analysis of the spectrum as a function of pulse phase measures the low-energy X-ray spectral index even at pulse minimum -- albeit with large statistical uncertainty -- and we find marginal evidence for variations of the spectral index. The data are also used to set a new (3-sigma) upper lim...

  20. Chandra Multiwavelength Project: Normal Galaxies at Intermediate Redshift

    CERN Document Server

    Kim, D W; Colmenero, E R; Green, P J; Kim, M; Mossman, A; Schlegel, E M; Silverman, J D; Aldcroft, T; Ivezic, Z; Anderson, C; Kashyap, V; Tananbaum, H; Wilkes, B J

    2005-01-01

    (abridged) We have investigated 136 Chandra extragalactic sources without broad optical emission lines, including 93 galaxies with narrow emission lines (NELG) and 43 with only absorption lines (ALG). Based on fx/fo, Lx, X-ray spectral hardness and optical emission line diagnostics, we have conservatively classified 36 normal galaxies (20 spirals and 16 ellipticals) and 71 AGNs. We found no statistically significant evolution in Lx/LB, within the limited z range. We have built log(N)-log(S), after correcting for completeness based on a series of simulations. The best-fit slope is -1.5 for both S and B energy bands, which is considerably steeper than that of the AGN-dominated cosmic background sources, but slightly flatter than the previous estimate, indicating normal galaxies will not exceed the AGN population until fx ~ 2 x 10-18 erg s-1 cm-2 (a factor of ~5 lower than the previous estimate). A group of NELGs appear to be heavily obscured in X-rays, i.e., a typical type 2 AGN. After correcting for intrinsic ...

  1. Coronal physics and the chandra emission line project

    Directory of Open Access Journals (Sweden)

    N. S. Brickhouse

    2000-01-01

    Full Text Available Con el lanzamiento del observatorio de rayos-X Chandra se ha iniciado la espectroscop a de alta resoluci on en rayos-X de las fuentes c osmicas. Observa- ciones profundas de tres fuentes estelares con emisi on coronal|Capela, Proci on y HR 1099|est an dando no s olo datos de calibraci on invaluables sino tambi en medios de comparaci on para los modelos de emisi on de plasmas. Estos modelos, que han sido cuestionados por los problemas para entender los datos de baja y moderada re- soluci on de ASCA y del EUVE, son necesarios para interpretar los datos de coronas estelares, galaxias y c umulos de galaxias, remanentes de supernova y otras fuentes. El Proyecto de L neas de Emisi on es una colaboraci on para mejorar los modelos y su primera fase es la comparaci on de los modelos con los espectros observados de Capela, Proci on y HR 1099. Las metas de la comparaci on son (1 determinar y veri car la precisi on y fortaleza de los diagn osticos y (2 identi car y priorizar los elementos de la espectroscop a que requieran m as trabajo tanto te orico como de laboratorio. Uno de los puntos cr ticos de esta labor es entender hasta que punto se pueden aplicar las hip otesis simpli cadoras comunmente usadas (equilibrio coro- nal, baja opacidad. Discutimos, en este contexto, los avances m as recientes en el entendimiento de las coronas estelares.

  2. Chandra Confirmation of a Pulsar Wind Nebula in DA 495

    CERN Document Server

    Arzoumanian, Z; Landecker, T L; Kothes, R; Camilo, F

    2008-01-01

    As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nonthermal nebula 40'' in diameter exhibiting a power-law spectrum with photon index Gamma = 1.6+/-0.3, typical of a pulsar wind nebula. The implied spin-down luminosity of the neutron star, assuming a conversion efficiency to nebular flux appropriate to Vela-like pulsars, is ~10^{35} ergs/s, again typical of objects a few tens of kyr old. Morphologically, the nebular flux is slightly enhanced along a direction, in projection on the sky, independently demonstrated to be of significance in radio polarization observations; we argue that this represents the orientation o...

  3. Chandra counterparts of CANDELS GOODS-S sources

    CERN Document Server

    Cappelluti, N; Fontana, A; Zamorani, G; Amorin, R; Castellano, M; Merlin, E; Santini, P; Elbaz, D; Schreiber, C; Shu, X; Wang, T; Dunlop, J S; Bourne, N; Bruce, V A; Buitrago, F; Michałowski, Michał J; Derriere, S; Ferguson, H C; Faber, S M; Vito, F

    2015-01-01

    Improving the capabilities of detecting faint X-ray sources is fundamental to increase the statistics on faint high-z AGN and star-forming galaxies.We performed a simultaneous Maximum Likelihood PSF fit in the [0.5-2] keV and [2-7] keV energy bands of the 4 Ms {\\em Chandra} Deep Field South (CDFS) data at the position of the 34930 CANDELS H-band selected galaxies. For each detected source we provide X-ray photometry and optical counterpart validation. We validated this technique by means of a raytracing simulation. We detected a total of 698 X-ray point-sources with a likelihood $\\mathcal{L}$$>$4.98 (i.e. $>$2.7$\\sigma$). We show that the prior knowledge of a deep sample of Optical-NIR galaxies leads to a significant increase of the detection of faint (i.e. $\\sim$10$^{-17}$ cgs in the [0.5-2] keV band) sources with respect to "blind" X-ray detections. By including previous catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the large...

  4. Chandra observation of the supernova remnant N11L

    Science.gov (United States)

    Sun, Wei; Chen, Yang; Chu, You-Hua; Williams, Rosa M.

    2016-06-01

    We performed a Chandra X-ray study of the supernova remnant (SNR) N11L in the Large Magellanic Cloud (LMC). The X-ray emission is predominantly distributed within the main shell and the northern loop-like filaments traced by the optical narrow band images, with an indistinct extension along the north area. The brightest emission comes from a northeast-southwest ridge, and peaks at two patches at center and southwest. Spectral analysis indicates that the blast wave is propagating in a inhomogenous environment, and the X-ray emission overall is dominated by thermal gas whose composition is consistent with the LMC average abundance. The ionization time of the hot plasma implied by the X-ray spectral analysis is consistent with the Sedov age of the SNR derived from the best-fit parameters and the apparent radius of the SNR based on the optical images, however, the consequent explosion energy is no only at least one order of magnitude less than the canonical value of 10^{51} ergs, but also takes a small portion of the thermal energy of the hot gas. That discrepancy supports the blown-out scenario.

  5. Investigating the cores of fossil systems with Chandra

    CERN Document Server

    Bharadwaj, V; Sanders, J S; Schellenberger, G

    2016-01-01

    We investigate the cores of fossil galaxy groups and clusters (`fossil systems') using archival Chandra data for a sample of 17 fossil systems. We determined the cool-core fraction for fossils via three observable diagnostics, the central cooling time, cuspiness, and concentration parameter. We quantified the dynamical state of the fossils by the X-ray peak/brightest cluster galaxy (BCG), and the X-ray peak/emission weighted centre separations. We studied the X-ray emission coincident with the BCG to detect the presence of potential thermal coronae. A deprojection analysis was performed for z < 0.05 fossils to obtain cooling time and entropy profiles, and to resolve subtle temperature structures. We investigated the Lx-T relation for fossils from the 400d catalogue to see if the scaling relation deviates from that of other groups. Most fossils are identified as cool-core objects via at least two cool-core diagnostics. All fossils have their dominant elliptical galaxy within 50 kpc of the X-ray peak, and mo...

  6. Stellar X-ray sources in the Chandra COSMOS survey

    CERN Document Server

    Wright, Nicholas J; Civano, Francesca

    2010-01-01

    We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160ks) and wide (0.9 deg2) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distances ranging from 30pc to ~12kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. This stellar sample extends the known coverage of the L_X-distance plane to greater distances and higher luminosities, but we do not detect as many intrinsically faint X-ray sources compared to previous surveys. Overall the sample is typically more...

  7. Invisible Giant: Chandra's Limits on X-rays from Betelgeuse

    CERN Document Server

    Posson-Brown, J; Pease, D O; Drake, J J; Posson-Brown, Jennifer; Kashyap, Vinay L.; Pease, Deron O.; Drake, Jeremy J.

    2006-01-01

    We have analyzed Chandra calibration observations of Betelgeuse ($\\alpha$ Ori, M2 Iab, $m_{V} = 0.58$, 131 pc) obtained at the aimpoint locations of the HRC-I (8 ks), HRC-S (8 ks), and ACIS-I (5 ks). Betelgeuse is undetected in all the individual observations as well as cumulatively. We derive $3\\sigma$ upper limits to its X-ray count rates and compute the corresponding X-ray flux upper limits for isothermal coronal plasma over a range of temperatures, $T=0.3-10$~MK. We place a flux limit at the telescope of $\\fx\\approx4\\times10^{-15}$~ergs~s$^{-1}$ cm$^{-2}$ at T=1~MK. The upper limit is lowered by a factor of $\\approx3$ at higher temperatures, roughly an order of magnitude lower than that obtained previously. Assuming that the entire stellar surface is active, these fluxes correspond to a surface flux limit that ranges from 30-7000~ergs~s$^{-1}$ cm$^{-2}$ at T=1~MK, to $\\approx 1$~ergs~s$^{-1}$ cm$^{-2}$ at higher temperatures, five orders of magnitude lower than the quiet Sun X-ray surface flux. We discuss...

  8. The Chandra COSMOS Legacy survey: overview and point source catalog

    CERN Document Server

    Civano, F; Comastri, A; Urry, M C; Elvis, M; Cappelluti, N; Puccetti, S; Brusa, M; Zamorani, G; Hasinger, G; Aldcroft, T; Alexander, D M; Allevato, V; Brunner, H; Capak, P; Finoguenov, A; Fiore, F; Fruscione, A; Gilli, R; Glotfelty, K; Griffiths, R E; Hao, H; Harrison, F A; Jahnke, K; Kartaltepe, J; Karim, A; LaMassa, S M; Lanzuisi, G; Miyaji, T; Ranalli, P; Salvato, M; Sargent, M; Scoville, N J; Schawinski, K; Schinnerer, E; Silverman, J; Smolcic, V; Stern, D; Toft, S; Trakhenbrot, B; Treister, E; Vignali, C

    2016-01-01

    The COSMOS-Legacy survey is a 4.6 Ms Chandra program that has imaged 2.2 deg$^2$ of the COSMOS field with an effective exposure of $\\simeq$160 ks over the central 1.5 deg$^2$ and of $\\simeq$80 ks in the remaining area. The survey is the combination of 56 new observations, obtained as an X-ray Visionary Project, with the previous C-COSMOS survey. We describe the reduction and analysis of the new observations and the properties of 2273 point sources detected above a spurious probability of 2$\\times 10^{-5}$. We also present the updated properties of the C-COSMOS sources detected in the new data. The whole survey includes 4016 point sources (3814, 2920 and 2440 in the full, soft and hard band). The limiting depths are 2.2 $\\times$ 10$^{-16}$, 1.5 $\\times$ 10$^{-15}$ and 8.9$\\times$ 10$^{-16}$ ${\\rm erg~cm}^{-2}~{\\rm s}^{-1}$ in the 0.5-2, 2-10 and 0.5-10 keV bands, respectively. The observed fraction of obscured AGN with column density $> 10^{22}$ cm$^{-2}$ from the hardness ratio (HR) is $\\sim$50$^{+17}_{-16}$%...

  9. Chandra's Darkest Bright Star: not so Dark after All?

    Science.gov (United States)

    Ayres, Thomas R.

    2008-11-01

    The Chandra High Resolution camera (HRC) has obtained numerous short exposures of the ultraviolet (UV)-bright star Vega (α Lyrae; HD 172167: A0 V), to calibrate the response of the detector to out-of-band (non-X-ray) radiation. A new analysis uncovered a stronger "blue leak" in the imaging section (HRC-I) than reported in an earlier study of Vega based on a subset of the pointings. The higher count rate—a factor of nearly 2 above prelaunch estimates—raised the possibility that genuine coronal X-rays might lurk among the out-of-band events. Exploiting the broader point-spread function of the UV leak compared with soft X-rays identified an excess of counts centered on the target, technically at 3σ significance. A number of uncertainties, however, prevent a clear declaration of a Vegan corona. A more secure result would be within reach of a deep uninterrupted HRC-I pointing.

  10. Imaging the Circumnuclear Region of NGC 1365 with Chandra

    CERN Document Server

    Wang, Junfeng; Elvis, M; Risaliti, G; Mazzarella, J M; Howell, J H; Lord, S

    2009-01-01

    We present the first Chandra/ACIS imaging study of the circumnuclear region of the nearby Seyfert galaxy NGC 1365. The X-ray emission is resolved into point-like sources and complex, extended emission. The X-ray morphology of the extended emission shows a biconical soft X-ray emission region extending ~5 kpc in projection from the nucleus, coincident with the high excitation outflow cones seen in optical emission lines particularly to the northwest. Harder X-ray emission is detected from a kpc-diameter circumnuclear ring, coincident with the star-forming ring prominent in the Spitzer mid-infrared images; this X-ray emission is partially obscured by the central dust lane of NGC 1365. Spectral fitting of spatially separated components indicates a thermal plasma origin for the soft extended X-ray emission (kT=0.57 keV). Only a small amount of this emission can be due to photoionization by the nuclear source. Detailed comparison with [OIII]5007 observations shows the hot interstellar medium (ISM) is spatially ant...

  11. Chandra Confirmation of a Pulsar Wind Nebula in DA 495

    Science.gov (United States)

    Arzoumanian, Z.; Safi-Harb, S.; Landecker, T.L.; Kothes, R.; Camilo, F.

    2008-01-01

    As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nontherma1 nebula 40" in diameter exhibiting a power-law spectrum with photon index Gamma = 1.63, typical of a pulsar wind nebula. Morphologically, the nebula appears to be slightly extended along a direction, in projection on the sky, previously demonstrated to be of significance in radio and ASCA observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5" from the point source, but energetic arguments suggest that it is not the resolved termination shock of the pulsar wind against the ambient medium. Finally, we argue based on synchrotron lifetimes in the nebular magnetic field that DA 495 represents the first example of a pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind.

  12. Temporal ghost imaging with twin photons

    Science.gov (United States)

    Denis, Séverine; Moreau, Paul-Antoine; Devaux, Fabrice; Lantz, Eric

    2017-03-01

    We use twin photons generated by spontaneous parametric down conversion to perform temporal ghost imaging of a single time signal. The retrieval of a binary signal containing eight bits is performed with an error rate below 1%.

  13. Prevention of preterm delivery in twin pregnancy.

    Science.gov (United States)

    Rode, Line; Tabor, Ann

    2014-02-01

    The incidence of twin gestation has increased markedly over the past decades, mostly because of increased use of assisted reproductive technologies. Twin pregnancies are at increased risk of preterm delivery (i.e. birth before 37 weeks of gestation). Multiple gestations therefore account for 2-3% of all pregnancies but constitute at least 10% of cases of preterm delivery. Complications from preterm birth are not limited to the neonatal period, such as in retinopathy of prematurity, intraventricular haemorrhage, necrotising enterocolitis, respiratory disorder and sepsis; they can also constitute sequelae such as abnormal neurophysiological development in early childhood and underachievement in school. Several treatment modalities have been proposed in singleton high-risk pregnancies. The mechanism of initiating labour may, however, be different in singleton and twin gestations. Therefore, it is mandatory to evaluate the proposed treatments in randomised trials of multiple gestations. In this chapter, we describe the results of trials to prevent preterm delivery in twin pregnancies.

  14. Twin Cities Metro Hybrid Landcover 2000 (Raster)

    Data.gov (United States)

    Minnesota Department of Natural Resources — The Hybrid Landcover is an attempt to clean up the University of Minnesota Remote Sensing Lab's 2000 LandSat Land Cover for the Twin Cities 7-county metropolitan...

  15. Spectroscopic study of solar twins and analogues

    CERN Document Server

    Datson, Juliet; Portinari, Laura

    2014-01-01

    Context. Many large stellar surveys have been and are still being carried out, providing huge amounts of data, for which stellar physical parameters will be derived. Solar twins and analogues provide a means to test the calibration of these stellar catalogues because the Sun is the best-studied star and provides precise fundamental parameters. Solar twins should be centred on the solar values. Aims. This spectroscopic study of solar analogues selected from the Geneva-Copenhagen Survey (GCS) at a resolution of 48,000 provides effective temperatures and metallicities for these stars. We test whether our spectroscopic parameters, as well as the previous photometric calibrations, are properly centred on the Sun. In addition, we search for more solar twins in our sample. Methods. The methods used in this work are based on literature methods for solar twin searches and on methods we developed in previous work to distinguish the metallicity-temperature degeneracies in the differential comparison of spectra of solar ...

  16. The Radiative Z2 Breaking Twin Higgs

    CERN Document Server

    Yu, Jiang-Hao

    2016-01-01

    In twin Higgs model, the Higgs boson mass is protected by a $Z_2$ symmetry. The $Z_2$ symmetry needs to be broken either explicitly or spontaneously to obtain misalignment between electroweak and new physics vacua. We propose a novel $Z_2$ breaking mechanism, in which the $Z_2$ is spontaneously broken by radiative corrections to the Higgs potential. Two twin Higgses with different vacua are needed, and vacuum misalignment is realized by opposite but comparable contributions from gauge and Yukawa interactions to the potential. Due to fully radiative symmetry breaking, the Higgs sector is completely determined by twin Higgs vacuum, Yukawa and gauge couplings. There are eight pseudo-Goldstone bosons: the Higgs boson, inert doublet Higgs, and three twin scalars. We show the 125 GeV Higgs mass and constraints from Higgs coupling measurements could be satisfied.

  17. Say No to Fake Twin Brothers

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    China vows to fight fake products that exploit a home appliance stimulus project in rural areas Haier Co. Ltd., China’s top home appliance manufacturer, is well known for its logo depicting a pair of twin

  18. Twin Screw Mixer/Fine Grind Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The 40-mm Twin-Screw Mixer/Extruder (TSE) pilot plant is a continuous, remotely operated, flexible facility that can significantly enhance safety and environmental...

  19. Infantile Perineal Protrusion in Two Monochorionic Twins

    Directory of Open Access Journals (Sweden)

    Paola Cavicchioli

    2014-11-01

    Full Text Available Case Report - Two female monochorionic-monoamniotic twins showed the same kind of infantile perineal protrusion (IPP at birth. Lesions in both twins progressively healed until resolution in 6 weeks' time; none of the twins have manifested, till date, alvus disturbances. Discussion and Literature Review - A literature review numbers approximately 100 reports of IPP. This condition has been classically classified into three categories: congenital/familiar (i.e., female sex, positive parental history of IPP, acquired (mainly due to constipation, and associated with lichen sclerosus et atrophicus. Conclusions and Final Remarks - This case report describes, for the first time, the presence of IPP in monochorionic-monoamniotic twins, supporting the existence of hereditary/genetic factors in the developing of this condition.

  20. Cooperative Research Twin Trawl Sweep Comparison Study

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The "Twin-Trawl Sweep Efficiency Study" was intended to compare the sweep efficiency and selectivity of the NEFSC standardized bottom trawl to that of a standardized...

  1. Twin screw subsurface and surface multiphase pumps

    Energy Technology Data Exchange (ETDEWEB)

    Dass, P. [CAN-K GROUP OF COMPANIES, Edmonton, Alberta (Canada)

    2011-07-01

    A new subsurface twin screw multiphase pump has been developed to replace ESP and other artificial lift technologies. This technology has been under development for a few years, has been field tested and is now going for commercial applications. The subsurface twin screw technology consists of a pair of screws that do not touch and can be run with a top drive or submersible motor; and it carries a lot of benefits. This technology is easy to install and its low slippage makes it highly efficient with heavy oil. In addition twin screw multiphase pumps are capable of handling high viscosity fluids and thus their utilization can save water when used in thermal applications. It also induces savings of chemicals because asphaltenes do not break down easily as well as a reduction in SOR. The subsurface twin screw multiphase pump presented herein is an advanced technology which could be used in thermal applications.

  2. Stolen twin: fascination and curiosity/twin research reports: evolution of sleep length; dental treatment of craniopagus twins; cryopreserved double embryo transfer; gender options in multiple pregnancy/current events: appendectomy in one twin; autistic twin marathon runners; 3D facial recognition; twin biathletes.

    Science.gov (United States)

    Segal, Nancy L

    2014-02-01

    The story of her allegedly stolen twin brother in Armenia is recounted by a 'singleton twin' living in the United States. The behavioral consequences and societal implications of this loss are considered. This case is followed by twin research reports on the evolution of sleep length, dental treatment of craniopagus conjoined twins, cryopreserved double embryo transfer (DET), and gender options in multiple pregnancy. Current events include the diagnosis of appendectomy in one identical twin, the accomplishments of autistic twin marathon runners, the power of three-dimensional (3D) facial recognition, and the goals of twin biathletes heading to the 2014 Sochi Olympics in Russia.

  3. Strong crystal size effect on deformation twinning

    DEFF Research Database (Denmark)

    Yu, Qian; Shan, Zhi-Wei; Li, Ju

    2010-01-01

    find that the stress required for deformation twinning increases drastically with decreasing sample size of a titanium alloy single crystal7, 8, until the sample size is reduced to one micrometre, below which the deformation twinning is entirely replaced by less correlated, ordinary dislocation....... The sample size in transition is relatively large and easily accessible in experiments, making our understanding of size dependence11, 12, 13, 14, 15, 16, 17 relevant for applications....

  4. Deformation Twinning During Nanoindentation of Nanocrystalline Ta

    OpenAIRE

    Wang, Y. M.; Hodge, A. M.; Biener, J.; Hamza, A.V.; Barnes, D E; Liu, Kai; Nieh, T. G.

    2005-01-01

    The deformation mechanism of body-centered cubic (bcc) nanocrystalline tantalum with grain sizes of 10–30 nm is investigated by nanoindentation, scanning electron microscopy and high-resolution transmission electron microscopy. In a deviation from molecular dynamics simulations and existing experimental observations on other bcc nanocrystalline metals, the plastic deformation of nanocrystalline Ta during nanoindentation is controlled by deformation twinning. The observation of multiple twin i...

  5. The morphology of the sella turcica in monozygotic twins.

    Science.gov (United States)

    Brock-Jacobsen, Mette T; Pallisgaard, Carsten; Kjaer, Inger

    2009-12-01

    The purpose was to compare the sella turcica morphology of individuals within pairs of monozygotic twins with normal karyotype and to analyze the similarity between the observed morphology and the morphology of non-twins at the same age with normal karyotype. Profile radiographs from 84 individuals of 42 twin pairs (18 male and 24 female pairs, aged 18-23 years) comprised the material. Sella turcica measurements from non-twins aged 6-21 years were used as normal reference. Length, depth and diameter of the sella turcica were measured and controlled by re-measurements. Pearson's correlation coefficient was used for comparison of individuals within twin pairs. For comparison of twins and non-twins, normal standard values for length, depth and diameter were subtracted from the twin values. For the mean values of these differences, confidence limits p values and t values were calculated. The study showed that the size of the sella turcica may be partly similar and partly dissimilar within the pair of monozygotic twins. Statistical evaluation of the data showed correlations between length, depth and diameter of the sella turcica between the two twin individuals in the same twin pair. Differences in sizes are observed between individuals in the twin material and individuals in the non-twin material. As a conclusion, the twin males were more similar within the twin pair, but deviated more from the non-twin material than the females. Female twins had more discrepancy within the twin pair, but deviated less from the non-twin material than the males.

  6. Twin pregnancy in the congenital malformed uterus.

    Science.gov (United States)

    Heinonen, Pentti K

    2016-07-01

    The frequency and outcome of twin pregnancies in women with uterine malformation were studied. The cohort comprised 13 (4.9%) women with twin pregnancy found among 263 women. They had 483 deliveries, 13 of them twins (2.7%; 95% CI 1.6-4.6%). Among 38 patients with unicornuate uterus 5 (6.8%) out of 74 deliveries were twins, 39 women with didelphic uterus 2 (3.2%) out of 62 deliveries and 147 women with septate or subseptate uterus 6 (2.3%) out of 264 deliveries were twins. The mean duration of gestation was 249 days (range 190-268 days), 5 (38%) out of 13 deliveries were premature, 25 out of 26 newborns were alive. Mean durations of gestation and mean weights of newborns did not differ when 7 cases with unicornuate or didelphic uterus were compared to 6 cases with complete or partial uterine septum. A congenital malformed uterus can bear twin pregnancy without severe complications apart from prematurity.

  7. Exotic Quarks in Twin Higgs Models

    CERN Document Server

    Cheng, Hsin-Chia; Salvioni, Ennio; Tsai, Yuhsin

    2015-01-01

    The Twin Higgs model provides a natural theory for the electroweak symmetry breaking without the need of new particles carrying the standard model gauge charges below a few TeV. In the low energy theory, the only probe comes from the mixing of the Higgs fields in the standard model and twin sectors. However, an ultraviolet completion is required below ~ 10 TeV to remove residual logarithmic divergences. In non-supersymmetric completions, new exotic fermions charged under both the standard model and twin gauge symmetries have to be present to accompany the top quark, thus providing a high energy probe of the model. Some of them carry standard model color, and may therefore be copiously produced at current or future hadron colliders. Once produced, these exotic quarks can decay into a top together with twin sector particles. If the twin sector particles escape the detection, we have the irreducible stop-like signals. On the other hand, some twin sector particles may decay back into the standard model particles ...

  8. The Finnish Twin Cohort Study: an update.

    Science.gov (United States)

    Kaprio, Jaakko

    2013-02-01

    In 2002 and 2006, review papers have described the Finnish Twin Cohort and studies conducted on these population-based, longitudinal data sets with extensive follow-up data. Three cohorts have been established: the older twin cohort in the 1970s, and the Finntwin12 and Finntwin16 studies initiated in the 1990s. The present review provides on update on the latest data collections conducted since the previous review. These cover the fourth waves of data collection in the older cohort (twins born before 1958) and Finntwin12 (twins born 1983-1987). The fifth wave of data collection in Finntwin16 (twins born 1975-1979) also included assessments of their spouses/partners. An analysis of mortality in the older cohort from 1975 to 2009 indicates that the mortality of adult twins (as individuals) does not differ from the population at large. Based on the cohorts, many sub-studies with more detailed phenotyping and collection of omics data have been conducted or are in progress. We also contribute to numerous national and international collaborations.

  9. Urticaria in monozygotic and dizygotic twins

    DEFF Research Database (Denmark)

    Thomsen, Simon Francis; van der Sluis, Sophie; Kyvik, Kirsten Ohm

    2012-01-01

    Aim. To identify risk factors for urticaria, to determine the relative proportion of the susceptibility to urticaria that is due to genetic factors in an adult clinical twin sample, and to further determine whether the genetic susceptibility to urticaria overlaps with the genetic susceptibility...... to atopic diseases. Methods. A total of 256 complete twin pairs and 63 single twins, who were selected from sibships with self-reported asthma via a questionnaire survey of 21,162 adult twins from the Danish Twin Registry, were clinically interviewed about a history of urticaria and examined for atopic.......36-2.72), P = 0.000; and atopic dermatitis, HR = 1.44 (1.02-2.06), P = 0.041 were significant risk factors for urticaria. After adjustment for sex and age at onset of urticaria in the index twin, the risk of urticaria was increased in MZ cotwins relative to DZ cotwins, HR = 1.42 (0.63-3.18), P = 0...

  10. Laying the ghost of twin paradox

    Directory of Open Access Journals (Sweden)

    Popović Marko

    2009-01-01

    Full Text Available Someone's true age is not written in his ID, but in his biomarkers. Aging process is not caused by time passing, but by thermodynamically laws. Entropy, extent of metabolic reaction, and temperature are Lorentz invariant, so these facts make twin paradox impossible because there is no way for one twin to age slower than the other even if the time in his frame is dilated. Entropy is the function of state, not time. So as much as standard thermodynamics concerns, the path between two points in space is equivalent to the path between two states. Whether the point B is reached by moving faster using the longer way (with time dilatation, or slower by using shortcut (without time dilatation, the state of the system after completing the road should be the same. This is supported by the fact that when two twins reach the same space-time point (point B in which the state parameters are the same. If we use entropy as an age parameter, then both twins have the same entropy value and are exactly the same biological age. Therefore, the twin paradox is a logical mistake based on wrong first premise. Bergson symmetry is not necessary any more to explain the impossibility of twin paradox.

  11. The Chandra X-ray Observatory is prepped for solar panel deployment copy form; photos beginning with

    Science.gov (United States)

    1999-01-01

    TRW workers in the Vertical Processing Facility check equipment after deployment of the solar panel array above them, attached to the Chandra X-ray Observatory. Formerly called the Advanced X-ray Astrophysics Facility, Chandra comprises three major elements: the spacecraft, the science instrument module (SIM), and the world's most powerful X-ray telescope. Chandra will allow scientists from around the world to see previously invisible black holes and high-temperature gas clouds, giving the observatory the potential to rewrite the books on the structure and evolution of our universe. Chandra is scheduled for launch July 9 aboard Space Shuttle Columbia, on mission STS-93.

  12. Shelter from the Storm: Protecting the Chandra X-ray Observatory from Radiation

    Science.gov (United States)

    Cameron, Robert A.; Morris, David C.; Virani, Shanil N.; Wolk, Scott J.; Blackwell, William C.; Minow, Joseph I.; O'dell, Stephen L.

    NASA's Chandra X-ray Observatory was launched in July 1999, and the first images were recorded by the ACIS x-ray detector in August 1999. Shortly after first light, degradation of the energy resolution and charge transfer efficiency in the ACIS CCD detectors was observed, and this was quickly attributed to cumulative particle radiation damage in the CCD's, in particular from 100 keV to 200 keV protons. Since the onset of this radiation damage to ACIS, several improvements have been made to autonomous Chandra operation and ground-based operations and mission planning, to limit the effects of radiation while preserving optimum observing efficiency for the Observatory. These changes include implementing an automatic science instrument radiation protection system on Chandra, implementing a real-time radiation monitoring and alert system by the Science Operations Team, and improving the radiation prediction models used in mission planning for the Observatory. These satellite- and ground-based systems provide protection for Chandra from passages through the Earth's trapped radiation belts and outer magnetosphere and from flares and coronal mass ejections from the Sun. We describe the design and performance of the automatic on-board radiation protection system on Chandra, and the ground-based software systems and data products for real-time radiation monitoring. We also describe the development and characterize the performance of the Chandra Radiation Model (CRM), which provides predictions of the solar wind and magnetospheric proton fluxes along Chandra's orbit, indexed by the geomagnetic activity index, Kp. We compare the observed and predicted damage rates to ACIS based on net mission proton fluence, and outline planned enhancements to the CRM.

  13. Strain gradients and melt pathways, Twin Sisters complex, Washington State

    Science.gov (United States)

    Kruckenberg, S. C.; Newman, J.; Tikoff, B.; Toy, V. G.

    2009-12-01

    The Twin Sisters complex in the North Cascades of Washington state is a large (~6 by 16 km), virtually unaltered ultramafic body that provides information about the relationships between the formation of compositional layering, structural fabrics and the formation of inferred melt pathways in naturally deforming peridotites. Compositional layering is largely defined by alternating layers of orthopyroxene-absent dunite (>95% olivine) and orthopyroxene-present (~15% orthopyroxene; ~85% olivine) harzburgite aligned parallel to a roughly N-S striking and steeply dipping foliation. Orthopyroxene- and clinopyroxene-bearing dikes occur throughout the Twin Sisters and crosscut the host dunite and harzburgite layering. Orthopyroxene dikes range in thickness from 1 cm to >1 m and are variably oriented and may be folded. Clinopyroxene-bearing dikes are thinner, more consistently oriented (~N-S), and generally more tabular than the orthopyroxene dikes. In the Twin Sisters, cm- to m-scale zones of porphyroclastic dunite cross-cut the main dunite-harzburgite compositional layering and display a variety of relationships with pyroxene dikes in the region. These porphyroclastic dunite bands locally contain single olivine grains >10 cm and likely represent former pathways of melt migration. Transect mapping along an E-W traverse across the Twin Sisters massif reveals that these inferred melt channels form at various angles relative to the main dunite-harzburgite layering. In the west, porphyroclastic olivine layers form at low angle to the main foliation and compositional layering. These zone form at systematically higher angles across the structural section of the Twin Sisters massif to the east and commonly form conjugate cross-cutting sets at high-angle to the main N-S dunite-harzburgite layering. This change in band angle correlates broadly with changes in the intensity of folding of orthopyroxene-bearing dikes, with more intensely deformed dikes in the west to more planar dikes

  14. Losing one twin in the NICU - A case study of parental experience

    DEFF Research Database (Denmark)

    Aagaard, Hanne; Storm, Ida; Klitgaard, Jeannett

    2016-01-01

    and revealed tree overall themes. These themes indicate that besides struggling with grief related to the loss of one infant, the parents were challenged by the medical discourse, the lack of staff continuity and space to develop parenthood. This case study emphasizes how the loss of a premature twin...

  15. Electronic Origins of Anomalous Twin Boundary Energies in Hexagonal Close Packed Transition Metals

    NARCIS (Netherlands)

    De Jong, M.; Kacher, J.; Sluiter, M.H.F.; Qi, L.; Olmsted, D.L.; Van de Walle, A.; Morris, J.W.; Minor, A.M.; Asta, M.

    2015-01-01

    Density-functional-theory calculations of twin-boundary energies in hexagonal close packed metals reveal anomalously low values for elemental Tc and Re, which can be lowered further by alloying with solutes that reduce the electron per atom ratio. The anomalous behavior is linked to atomic geometrie

  16. A critical assessment of the equal environment assumption of the twin method for schizophrenia

    Directory of Open Access Journals (Sweden)

    Roar eFosse

    2015-04-01

    Full Text Available The classical twin method (CTM is central to the view that schizophrenia is ~80% heritable. The CTM rests on the equal environments assumption (EEA that identical and fraternal twin pairs experience equivalent trait relevant environmental exposures. The EEA has not been directly tested for schizophrenia with measures of child social adversity, which is particularly etiologically relevant to the disorder. However, if child social adversity is more similar in identical than fraternal pairs in the general twin population, the EEA is unlikely to be valid for schizophrenia, a question which we tested in this study. Using results from prior twin studies, we tested if intraclass correlations for the following five categories of child social adversity are larger in identical than fraternal twins: bullying, sexual abuse, physical maltreatment, emotional neglect and abuse, and general trauma. Eleven relevant studies that encompassed 9119 twin pairs provided 24 comparisons of intraclass correlations, which we grouped into the five social exposure categories. Fisher’s z-test revealed significantly higher correlations in identical than fraternal pairs for each exposure category (z ≥ 3.53, p <.001. The difference remained consistent across gender, study site (country, sample size, whether psychometric instruments were used, whether interviewing was proximate or distant to the exposures, and whether informants were twins or third persons. Combined with other evidence that the differential intraclass correlation for child social adversity cannot be explained by evocative gene-environment covariation, our results indicate that the CTM does not provide any valid indication of genomic effects in schizophrenia.

  17. Suzaku and Chandra observations of CIZA J1700.8-3144, a cluster of galaxies in the Zone of Avoidance

    Science.gov (United States)

    Mori, Hideyuki; Maeda, Yoshitomo; Ueda, Yoshihiro; Nakazawa, Kazuhiro; Tawara, Yuzuru

    2017-02-01

    We present the Chandra and Suzaku observations of 1RXS J170047.8-314442, located towards the Galactic bulge, to reveal a wide-band (0.3-10 keV) X-ray morphology and spectrum of this source. With the Chandra observation, no point source was found at the position of 1RXS J170047.8-314442. Instead, we revealed the presence of diffuse X-ray emission, via the wide-band X-ray image obtained from the Suzaku XIS. Although the X-ray emission had a nearly circular shape with a spatial extent of ˜3{^'.}5, the surface brightness profile was not axisymmetric; a bright spot-like emission was found at ˜ 1' away in the northwestern direction from the center. The radial profile of the surface brightness, except for this spot-like emission, was reproduced with a single β-model; β and the core radius were found to be 1.02 and 1{^'.}51, respectively. The X-ray spectrum of the diffuse emission showed an emission line at ˜6 keV, indicating an origin of a thermal plasma. The spectrum was well explained with an absorbed, optically-thin thermal plasma model with a temperature of 6.2 keV and a redshift parameter of z = 0.14 ± 0.01. Hence, the X-ray emission was considered to arise from the hot gas associated with a cluster of galaxies. Our spectroscopic result confirmed the optical identification of 1RXS J170047.8-314442 by Kocevski et al. (2007, ApJ, 662, 224): CIZA J1700.8-3144, a member of the cluster catalogue in the Zone of Avoidance. The estimated bolometric X-ray luminosity of 5.9 × 1044 erg s-1 was among the lowest with this temperature, suggesting that this cluster is far from relaxed.

  18. Salivary cortisol in unaffected twins discordant for affective disorder

    DEFF Research Database (Denmark)

    Vinberg, Maj; Bennike, Bente; Kyvik, Kirsten Ohm

    2008-01-01

    -sectional high-risk study. Healthy monozygotic (MZ) and dizygotic (DZ) twins with (High-Risk twins) and without (Low-Risk twins) a co-twin history of affective disorder were identified through nationwide registers. Awakening and evening salivary cortisol levels were compared between the 190 High- and Low......-Risk twins. The 109 High-Risk twins had significantly higher evening cortisol levels than the 81 Low-Risk MZ twins, also after adjustment for age, sex, and the level of subclinical depressive symptoms. No significant difference was found in awakening cortisol levels between High-Risk and Low-Risk twins....... In conclusion, a high genetic liability to affective disorder was associated with a higher evening cortisol level, but not with awakening cortisol level. Future prospective family, high-risk and twin studies are needed to decide whether abnormalities in the HPA axis can be identified as an endophenotype...

  19. The End of Days -- Chandra Catches X-ray Glow From Supernova

    Science.gov (United States)

    1999-12-01

    Through a combination of serendipity and skill, scientists have used NASA's Chandra X-ray Observatory to capture a rare glimpse of X-radiation from the early phases of a supernova, one of the most violent events in nature. Although more than a thousand supernovas have been observed by optical astronomers, the early X-ray glow from the explosions has been detected in less than a dozen cases. The Chandra observations were made under the direction of a team of scientists from the Massachusetts Institute of Technology (MIT) in Cambridge, led by Walter Lewin and his graduate student, Derek Fox. When combined with simultaneous observations by radio and optical telescopes, the X-ray observations tell about the thickness of the shell that was blown off, its density, its speed, and how much material was shed by the star before it exploded. Chandra observed an X-ray glow from SN1999em with the total power of 50,000 suns. Ten days later it observed the supernova for another nine hours, and found that the X rays had faded to half their previous intensity. The optical luminosity, which had the brightness of 200 million suns, had faded somewhat less. No radio emission was detected at any time. With this information, the MIT group and their colleagues are already piecing together a picture of the catastrophic explosion. Observations by optical astronomers showed that SN1999em was a Type II supernova produced by the collapse of the core of a star ten or more times as massive as the Sun. The intense heat generated in the collapse produces a cataclysmic rebound that sends high speed debris flying outward at speeds in excess of 20 million miles per hour. The debris crashes into matter shed by the former star before the explosion. This awesome collision generates shock waves that heat expanding debris to three million degrees. The X-ray glow from this hot gas was detected by Chandra and gives astrophysicists a better understanding of the dynamics of the explosion, as well as the

  20. Dystocia due to schistosomus reflexus (cojoined twins in a Yankassa ewe

    Directory of Open Access Journals (Sweden)

    Ambali Hauwa Motunrayo

    2015-04-01

    Full Text Available A two years' old, white and brown Yankassa ewe, weighing 20 kg was presented with dystocia of about 48 h duration at Mabs Veterinary Centre Ltd, Lagos. On thorough physical and vaginal examination, there were evidences of feotal parts and foul smelling discharges per vagina. A systematic and calculated traction and retropulsion revealed schistosomus reflexus cojoined twins. There was a complete recovery of the ewe 3 days post operative management. Finally, this case reported a true schistosomus reflexus cojoined twins in Yankassa ewe which was successfully relieved through traction and retropulsion despite the supposedly small birth canal which precluded the procedure in ewes except for caesarian section or fetotomy

  1. Epigenome-wide association study on identical twins discordant for birth weight

    DEFF Research Database (Denmark)

    Tan, Qihua; Nielsen, Morten Frost Munk; Christiansen, Lene

    induces persistent epigenetic modification detectable at adult ages, we performed a genome-wide DNA methylation profiling in peripheral blood of 150 pairs of identical Danish twins discordant for birth weight using the Illumina Infinium HumanMethylation450 BeadChip featuring 485,000 CpG sites across...... the genome. After quality control and data preprocessing using free R package minfi, data were analysed by a mixed effects model including fixed effect variables such as birth weight difference, age and sex of twin pairs; random effect variables such as batch, well, and sample position on the array, etc....... Statistical analysis revealed 12 probes with p valuetwins is not associated...

  2. Genetic and Environmental Regulation on Longitudinal Change of Metabolic Phenotypes in Danish and Chinese Adult Twins

    DEFF Research Database (Denmark)

    Li, Shuxia; Kyvik, Kirsten Ohm; Pang, Zengchang

    2016-01-01

    OBJECTIVE: The rate of change in metabolic phenotypes can be highly indicative of metabolic disorders and disorder-related modifications. We analyzed data from longitudinal twin studies on multiple metabolic phenotypes in Danish and Chinese twins representing two populations of distinct ethnic...... environmental contribution to blood pressure but no genetic contribution to longitudinal change in body mass traits. CONCLUSION: Our results emphasize the major contribution of unique environment to the observed intra-individual variation in all metabolic phenotypes in both samples, and meanwhile reveal...... differential patterns of genetic and common environmental regulation on changes over time in metabolic phenotypes across the two samples....

  3. An all-fiber source of pulsed twin beams at telecom band for quantum communication

    CERN Document Server

    Guo, Xueshi; Liu, Nannan; Yang, Lei; Ou, Z Y

    2012-01-01

    Motivated by the pursuit of a simple system to produce non-classical light sources for long- distance quantum communication, we generate for the first time an all-fiber source of pulsed twin beams in 1550 nm band by using a high gain fiber optical parametric amplifier. The noise of intensity difference of the twin beams is below the shot noise limit by 3.1 dB (10.4 dB after correction for losses). A detailed study reveals a number of limiting factors for higher noise reduction. Therefore, further noise reduction will be feasible once care is taken for these limiting factors.

  4. Electronic Origins of Anomalous Twin Boundary Energies in Hexagonal Close Packed Transition Metals.

    Science.gov (United States)

    de Jong, Maarten; Kacher, J; Sluiter, M H F; Qi, L; Olmsted, D L; van de Walle, A; Morris, J W; Minor, A M; Asta, M

    2015-08-07

    Density-functional-theory calculations of twin-boundary energies in hexagonal close packed metals reveal anomalously low values for elemental Tc and Re, which can be lowered further by alloying with solutes that reduce the electron per atom ratio. The anomalous behavior is linked to atomic geometries in the interface similar to those observed in bulk tetrahedrally close packed phases. The results establish a link between twin-boundary energetics and the theory of bulk structural stability in transition metals that may prove useful in controlling mechanical behavior in alloy design.

  5. Dependence of Deformation Twinning on Grain Orientation and Texture Evolution of High Manganese TWIP Steels at Different Deformation Temperatures%Dependence of Deformation Twinning on Grain Orientation and Texture Evolution of High Manganese TWIP Steels at Different Deformation Temperatures

    Institute of Scientific and Technical Information of China (English)

    FANG Xiu-hui; YANG Ping; LU Fa-yun; MENG Li

    2011-01-01

    Mechanical properties, microstructure and texture evolution were studied in two tensile-deformed high manganese TWIP steels at different temperatures. Special attention was paid to the effects of deformation tempera- ture and grain orientation on twinning behavior. The results showed that, at --70 ℃ and at room temperature, both twins and hexagonal martensite were found in a lower manganese steel of 26Mn. With deformation temperature ris- ing, twins became less and they disappeared at 500 ℃. Strong 〈111〉 texture appeared at 300 ℃, while it weakened at 500 ℃ due to the low strain rate and higher stacking fault energy. EBSD measurement revealed the dependence of deformation twinning on grain orientation at all test temperatures.

  6. Severe preeclampsia cured by heparin in a patient with twin-twin transfusion syndrome

    Institute of Scientific and Technical Information of China (English)

    CHU Hong-nü; ZHOU Cai-yun

    2007-01-01

    @@ Heparin therapy for preeclampsia has been reported frequently.1-3 Most of the authors used heparin to prevent thrombosis and achieved good results. But its mechanism is not clear.4 Here we describe a case of severe early-onset preeclampsia complicated with hypercoagulable state, fetal growth restriction, and twin-twin transfusion syndrome, that responded well to heparin.

  7. Art for twins: Yorùbá artists and their statues/twin research studies: twins' education and conceptions; diurnal preference; inherited eye diseases; ultrasound counseling when twins are conjoined/popular twin reports: twin sisters (the film); rare pregnancy; diet test; French twins reared apart and reunited.

    Science.gov (United States)

    Segal, Nancy L

    2014-06-01

    The Yorùbá of Nigeria are well known for their high twinning rate and the statues they create to commemorate deceased twins. An impressive collection of this artwork was displayed at the University of California's Fowler Museum in Los Angeles between October 13, 2013 and March 2, 2014. An overview of this exhibit is provided. Next, twin research on maternal education and conception, diurnal preference, inherited eye diseases, and ultrasound counseling for couples with conjoined twins are briefly summarized. This article concludes with a discussion of media-based items related to twins. The topics include an award-winning twin film, a rare pregnancy, a diet test, and the separation and chance reunion of monozygotic female twins.

  8. Spondyloepiphyseal Dysplasia Tarda in Twins

    Directory of Open Access Journals (Sweden)

    Ferhat Çekmez

    2011-08-01

    Full Text Available Introduction: Spondyloepiphyseal dysplasia (SED is a genetically heterogeneous disorder often associated with the early onset of osteoarthrosis. The X-linked recessive form (SEDL affects boys and is characterized by reduced height, arm span exceeding total height, and barrel chest deformity. The radiographic phenotype comprises a hump-shaped deformity of vertebral bodies and mild epiphyseal dysplasia of the femoral head associated with early signs of hip arthrosis.The disorder is caused by mutations in the SEDL (or sedlin gene on Xp22.12-p22.31. SED should be kept in mind as a differential diagnosis in men with early “primary” bilateral osteoarthrosis.Case Report: Here, 11 years old twins diagnosed as SED due to walking disability, limitation of joint motion, pain at the hips and disability in standing for a long time were presented. Discussion: This rare skelatal dysplasia must be kept in mind in patients with painful spine and hip joints, and walking disability. (Jo­ur­nal of Cur­rent Pe­di­at­rics 2011; 9: 97-9

  9. Niobium and tantalum: indispensable twins

    Science.gov (United States)

    Schulz, Klaus; Papp, John

    2014-01-01

    Niobium and tantalum are transition metals almost always paired together in nature. These “twins” are difficult to separate because of their shared physical and chemical properties. In 1801, English chemist Charles Hatchett uncovered an unknown element in a mineral sample of columbite; John Winthrop found the sample in a Massachusetts mine and sent it to the British Museum in London in 1734. The name columbium, which Hatchet named the new element, came from the poetic name for North America—Columbia—and was used interchangeably for niobium until 1949, when the name niobium became official. Swedish scientist Anders Ekberg discovered tantalum in 1802, but it was confused with niobium, because of their twinned properties, until 1864, when it was recognized as a separate element. Niobium is a lustrous, gray, ductile metal with a high melting point, relatively low density, and superconductor properties. Tantalum is a dark blue-gray, dense, ductile, very hard, and easily fabricated metal. It is highly conductive to heat and electricity and renowned for its resistance to acidic corrosion. These special properties determine their primary uses and make niobium and tantalum indispensable.

  10. First Images From Chandra X-Ray Observatory to be Released

    Science.gov (United States)

    1999-08-01

    The first images from the world's most powerful X-ray telescope, NASA's Chandra X-ray Observatory, will be unveiled at a media briefing at 1 p.m. EDT, Thursday, Aug. 26. The briefing will be held in the James E. Webb Auditorium at NASA Headquarters, 300 E St. SW, Washington, DC. The images include the spectacular remnants of a supernova and other astronomical objects. Panelists will be: - Dr. Edward Weiler, Associate Administrator for Space Science, NASA Headquarters, Washington, DC; - Dr. Harvey Tananbaum, Director of the Smithsonian Astrophysical Observatory's Chandra X-ray Center, Cambridge, MA; - Dr. Martin Weisskopf, NASA's Chandra Project Scientist, NASA's Marshall Space Flight Center, Huntsville, AL; and - Dr. Robert Kirshner, astrophysicist, Harvard University, Cambridge, MA. The event will be carried live on NASA Television with question-and-answer capability for reporters covering the briefing from participating NASA centers and from the Chandra Operations Control Center in Cambridge. NASA Television is available on transponder 9C, satellite GE-2 at 85 degrees West longitude, vertical polarization, frequency 3880 MHz, audio of 6.8 MHz. Chandra has been undergoing activation and checkout since it was placed into orbit during Space Shuttle mission STS-93 in July. Chandra will examine exploding stars, black holes, colliding galaxies and other high-energy cosmic phenomena to help scientists gain a better understanding of the structure and evolution of the universe. Chandra images and additional information will be available following the briefing on the Internet at: http://chandra.nasa.gov and http://chandra.harvard.edu NASA press releases and other information are available automatically by sending an Internet electronic mail message to domo@hq.nasa.gov. In the body of the message (not the subject line) users should type the words "subscribe press-release" (no quotes). The system will reply with a confirmation via E-mail of each subscription. A second

  11. Development of pulsating twin jets mechanism for mixing flow heat transfer analysis.

    Science.gov (United States)

    Gitan, Ali Ahmed; Zulkifli, Rozli; Abdullah, Shahrir; Sopian, Kamaruzzaman

    2014-01-01

    Pulsating twin jets mechanism (PTJM) was developed in the present work to study the effect of pulsating twin jets mixing region on the enhancement of heat transfer. Controllable characteristics twin pulsed jets were the main objective of our design. The variable nozzle-nozzle distance was considered to study the effect of two jets interaction at the mixing region. Also, the phase change between the frequencies of twin jets was taken into account to develop PTJM. All of these factors in addition to the ability of producing high velocity pulsed jet led to more appropriate design for a comprehensive study of multijet impingement heat transfer problems. The performance of PTJM was verified by measuring the pulse profile at frequency of 20 Hz, where equal velocity peak of around 64 m/s for both jets was obtained. Moreover, the jet velocity profile at different pulsation frequencies was tested to verify system performance, so the results revealed reasonable velocity profile configuration. Furthermore, the effect of pulsation frequency on surface temperature of flat hot plate in the midpoint between twin jets was studied experimentally. Noticeable enhancement in heat transfer was obtained with the increasing of pulsation frequency.

  12. A unique case of craniopagus twins: considerations and challenges for dental rehabilitation.

    Science.gov (United States)

    Campbell, Karen M

    2013-01-01

    The purpose of this case report was to describe oral findings and outline challenges and considerations for general anesthetic (GA) and dental management of 4-year-old female craniopagus (cranially conjoined) twins, at high risk for medical comorbidity, who presented for treatment of severe early childhood caries. This hospital-based procedure required good interdisciplinary communication, cooperation, and presurgical planning to address unique challenges and ensure positive postoperative outcomes. Two separate anesthesia teams delivered GA simultaneously to each twin. To minimize anesthetic exposure, two pediatric dental teams completed dental care concurrently. Extensive plaque accumulation and unusual "mirror-image" caries distribution were attributed to frequency and postural pooling during feeding. The rehabilitation objective was to provide definitive dental management, minimizing future need for dental retreatment under GA. Two-month follow-up revealed intact dental restorations, good oral hygiene, and weight gain. For these unique twins however, the challenge of long-term oral health maintenance remains.

  13. Order twins in (111)-evaporated thin films of CuAu I. [Cu-Au

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, R.; Broitman, E. (Dept. de Fisica, Univ. de Buenos Aires (Argentina)); Harriague, S.; Terlisky, S. (Comision Nacional de Energia Atomica, Buenos Aires (Argentina))

    1990-10-15

    The structure of evaporated CuAu I films in (111) orientation was studied by electron transmission and diffraction microscopy. The single-crystal films of Cu-Au alloy were prepared by vacuum evaporation and CuAu I ordered alloy was obtained by heating the disordered f.c.c. alloy to a temperature of 350deg C for 1 h. The electron micrograph revealed the presence of an intricate pattern of antiphase domain boundaries and the presence of twin lamellae. No microtwinning was observed. The CuAu I films exhibit a complex diffraction pattern. The geometry of the expected (111) reciprocal lattice plane has been calculated and described in detail. Extra reflections were identified as {l brace}101{r brace} twin spots and double-diffraction spots which originated from the twins. (orig.).

  14. Application of Anand's constitutive model on twin roll casting process of AZ31 magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    HU Xiao-dong; JU Dong-ying

    2006-01-01

    Twin-roll thin strip casting process combines casting and hot rolling into a single process,in which thermal stress and thermal mechanical stress were involved. Considering the high temperature gradient,the existing of liquid and solid regions and rolling deformation,suitable constitutive model is the key to describe the process. Anand's model is a temperature-dependent,rate-dependent and unified of creep and plasticity model and the Jaumann derivative was employed in Anand's model which makes the constitutive model frame-indifferent or objective,therefore the highly nonlinearities behavior in the twin-roll casting process can be simulated. The parameters of the Anand's model were regressed based on the compression tests of AZ31 magnesium alloy. The simulation results reveal that the Anand's model can well describe the deformation characteristics of twin-roll casting process. Based on the simulation results,the form of evolution equations in Anand's model was discussed.

  15. Removal of stacking-fault tetrahedra by twin boundaries in nanotwinned metals.

    Science.gov (United States)

    Yu, K Y; Bufford, D; Sun, C; Liu, Y; Wang, H; Kirk, M A; Li, M; Zhang, X

    2013-01-01

    Stacking-fault tetrahedra are detrimental defects in neutron- or proton-irradiated structural metals with face-centered cubic structures. Their removal is very challenging and typically requires annealing at very high temperatures, incorporation of interstitials or interaction with mobile dislocations. Here we present an alternative solution to remove stacking-fault tetrahedra discovered during room temperature, in situ Kr ion irradiation of epitaxial nanotwinned Ag with an average twin spacing of ~8 nm. A large number of stacking-fault tetrahedra were removed during their interactions with abundant coherent twin boundaries. Consequently the density of stacking-fault tetrahedra in irradiated nanotwinned Ag was much lower than that in its bulk counterpart. Two fundamental interaction mechanisms were identified, and compared with predictions by molecular dynamics simulations. In situ studies also revealed a new phenomenon: radiation-induced frequent migration of coherent and incoherent twin boundaries. Potential migration mechanisms are discussed.

  16. Losing one twin in the NICU - A case study of parental experience

    DEFF Research Database (Denmark)

    Aagaard, Hanne; Storm, Ida; Klitgaard, Jeannett

    2016-01-01

    and revealed tree overall themes. These themes indicate that besides struggling with grief related to the loss of one infant, the parents were challenged by the medical discourse, the lack of staff continuity and space to develop parenthood. This case study emphasizes how the loss of a premature twin......The aim of this case study was to generate a deeper understanding of parents’ experiences of losing one twin in the NICU. In an in-depth interview the parents told their story of giving birth to twins born extremely preterm and shortly after losing one of them. A thematic analysis was conducted...... reinforced the parents’ need of an understandable dialogue with a team of nurses. Furthermore the nurses have to offer a close partnership and create the necessary space for parents to develop parenthood while simultaneously dealing with the unexpected and traumatising circumstances related to the loss...

  17. Intrapair Comparison of Life-Course Appetite and Physical Activity in Elderly Danish Twins

    DEFF Research Database (Denmark)

    Løkkegaard, Laura E; Larsen, Lisbeth A; Christensen, Kaare

    2016-01-01

    . They were asked to compare their appetite and physical activity to that of their co-twins in different stages of life. On an individual level, we found a positive association between current self-reported physical activity and late-life survival for elderly twins. This was supported by the intrapair......Avoiding overeating and being physically active is associated with healthy aging, but methodological issues challenge the quantification of the association. Intrapair comparison of twins is a study design that attempts to minimize social norm-driven biased self-reporting of lifestyle factors. We...... analyses, which revealed a positive association between midlife and current physical activity and late-life survival. A positive association between lower appetite and late-life survival was found generally over the life course in the individual level analyses but not in the intrapair analyses. Kappa...

  18. LOFAR, VLA, and Chandra Observations of the Toothbrush Galaxy Cluster

    Science.gov (United States)

    van Weeren, R. J.; Brunetti, G.; Brüggen, M.; Andrade-Santos, F.; Ogrean, G. A.; Williams, W. L.; Röttgering, H. J. A.; Dawson, W. A.; Forman, W. R.; de Gasperin, F.; Hardcastle, M. J.; Jones, C.; Miley, G. K.; Rafferty, D. A.; Rudnick, L.; Sabater, J.; Sarazin, C. L.; Shimwell, T. W.; Bonafede, A.; Best, P. N.; Bîrzan, L.; Cassano, R.; Chyży, K. T.; Croston, J. H.; Dijkema, T. J.; Enßlin, T.; Ferrari, C.; Heald, G.; Hoeft, M.; Horellou, C.; Jarvis, M. J.; Kraft, R. P.; Mevius, M.; Intema, H. T.; Murray, S. S.; Orrú, E.; Pizzo, R.; Sridhar, S. S.; Simionescu, A.; Stroe, A.; van der Tol, S.; White, G. J.

    2016-02-01

    We present deep LOFAR observations between 120 and 181 MHz of the “Toothbrush” (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of α =-0.8+/- 0.1 at the northern edge of the main radio relic, steepening toward the south to α ≈ -2. The spectral index of the radio halo is remarkably uniform (α =-1.16, with an intrinsic scatter of ≤slant 0.04). The observed radio relic spectral index gives a Mach number of { M }={2.8}-0.3+0.5, assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock ({ M }≈ 1.2, with an upper limit of { M }≈ 1.5). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks.

  19. Chandra Counterparts of CANDELS GOODS-S Sources

    Science.gov (United States)

    Cappelluti, N.; Comastri, A.; Fontana, A.; Zamorani, G.; Amorin, R.; Castellano, M.; Merlin, E.; Santini, P.; Elbaz, D.; Schreiber, C.; Shu, X.; Wang, T.; Dunlop, J. S.; Bourne, N.; Bruce, V. A.; Buitrago, F.; Michałowski, Michał J.; Derriere, S.; Ferguson, H. C.; Faber, S. M.; Vito, F.

    2016-06-01

    Improving the capabilities of detecting faint X-ray sources is fundamental for increasing the statistics on faint high-z active galactic nuclei (AGNs) and star-forming galaxies (SFGs). We performed a simultaneous maximum likelihood point-spread function fit in the [0.5-2] keV and [2-7] keV energy bands of the 4 Ms Chandra Deep Field South (CDFS) data at the position of the 34,930 CANDELS H-band selected galaxies. For each detected source we provide X-ray photometry and optical counterpart validation. We validated this technique by means of a ray-tracing simulation. We detected a total of 698 X-ray point sources with a likelihood { L }\\gt 4.98 (i.e., >2.7σ). We show that prior knowledge of a deep sample of optical-NIR galaxies leads to a significant increase in the detection of faint (i.e., ˜10-17 cgs in the [0.5-2] keV band) sources with respect to “blind” X-ray detections. By including previous X-ray catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. Our results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the new detected sources are likely SFGs or faint, absorbed AGNs. We identified a few sources with putative photometric redshift z > 4. Despite the low number statistics and the uncertainties on the photo z, this sample significantly increases the number of X-ray-selected candidate high-z AGNs.

  20. Treatment of twin-twin transfusion syndrome by fetoscopic laser photocoagulation

    Institute of Scientific and Technical Information of China (English)

    劉子建; 梁德楊; 馮德源; 梁子昂

    2004-01-01

    @@ Twin-twin transfusion syndrome (TTTS) is a serious obstetric complication, occurring in about 15% of monochorionic (MC) twin pregnancies. If untreated, the prognosis is poor, with an overall perinatal mortality of 80%.1 It is now clear that TTTS is the result of an unbalanced unidirectional blood flow through placental arteriovenous anastomoses (also termed deep anastomoses) between the two fetal circulations.2 The donor twin progressively becomes anemic, and develops growth restriction, oliguria, and oligohydramnios/anhydramnios; whereas the recipient becomes plethoric and polyuric, and develops congestive heart failure, cardiomegaly, polyhydramnios and fetal hydrops. Preterm labor is common because of gross polyhydramnios, and further deteriorations will lead to intrauterine death of both twins.