602 research outputs found

    U Geminorum: a test case for orbital parameters determination

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    High-resolution spectroscopy of U Gem was obtained during quiescence. We did not find a hot spot or gas stream around the outer boundaries of the accretion disk. Instead, we detected a strong narrow emission near the location of the secondary star. We measured the radial velocity curve from the wings of the double-peaked Hα\alpha emission line, and obtained a semi-amplitude value that is in excellent agreement with the obtained from observations in the ultraviolet spectral region by Sion et al. (1998). We present also a new method to obtain K_2, which enhances the detection of absorption or emission features arising in the late-type companion. Our results are compared with published values derived from the near-infrared NaI line doublet. From a comparison of the TiO band with those of late type M stars, we find that a best fit is obtained for a M6V star, contributing 5 percent of the total light at that spectral region. Assuming that the radial velocity semi-amplitudes reflect accurately the motion of the binary components, then from our results: K_em = 107+/-2 km/s; K_abs = 310+/-5 km/s, and using the inclination angle given by Zhang & Robinson(1987); i = 69.7+/-0.7, the system parameters become: M_WD = 1.20+/-0.05 M_sun,; M_RD = 0.42+/-0.04 M_sun; and a = 1.55+/- 0.02 R_sun. Based on the separation of the double emission peaks, we calculate an outer disk radius of R_out/a ~0.61, close to the distance of the inner Lagrangian point L_1/a~0.63. Therefore we suggest that, at the time of observations, the accretion disk was filling the Roche-Lobe of the primary, and that the matter leaving the L_1 point was colliding with the disc directly, producing the hot spot at this location.Comment: 36 pages, 14 figures, ccepted for publication in A

    Impact of exciton delocalization on exciton-vibration interactions in organic semiconductors

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    Organic semiconductors exhibit properties of individual molecules and extended crystals simultaneously. The strongly bound excitons they host are typically described in the molecular limit, but excitons can delocalize over many molecules, raising the question of how important the extended crystalline nature is. Using accurate Green's function based methods for the electronic structure and non-perturbative finite difference methods for exciton-vibration coupling, we describe exciton interactions with molecular and crystal degrees of freedom concurrently. We find that the degree of exciton delocalization controls these interactions, with thermally activated crystal phonons predominantly coupling to delocalized states, and molecular quantum fluctuations predominantly coupling to localized states. Based on this picture, we quantitatively predict and interpret the temperature and pressure dependence of excitonic peaks in the acene series of organic semiconductors, which we confirm experimentally, and we develop a simple experimental protocol for probing exciton delocalization. Overall, we provide a unified picture of exciton delocalization and vibrational effects in organic semiconductors, reconciling the complementary views of finite molecular clusters and periodic molecular solids

    The masses of the cataclysmic variables AC Cancri and V363 Aurigae

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    We present time-resolved spectroscopy and photometry of the double-lined eclipsing cataclysmic variables AC Cnc and V363 Aur (= Lanning 10). There is evidence of irradiation on the inner hemisphere of the secondary star in both systems, which we correct for using a model that reproduces the observations remarkably well. We find the radial velocity of the secondary star in AC Cnc to be KR= 176 ± 3 km s−1 and its rotational velocity to be v sin i= 135 ± 3 km s−1. From these parameters we obtain masses of M1= 0.76 ± 0.03 M⊙ for the white-dwarf primary and M2= 0.77 ± 0.05 M⊙ for the K2 ± 1V secondary star, giving a mass ratio of q= 1.02 ± 0.04. We measure the radial and rotational velocities of the G7 ± 2V secondary star in V363 Aur to be KR= 168 ± 5 km s−1 and v sin i= 143 ± 5 km s−1, respectively. The component masses of V363 Aur are M1= 0.90 ± 0.06 M⊙ and M2= 1.06 ± 0.11 M⊙, giving a mass ratio of q= 1.17 ± 0.07. The mass ratios for AC Cnc and V363 Aur fall within the theoretical limits for dynamically and thermally stable mass transfer. Both systems are similar to the SW Sex stars, exhibiting single-peaked emission lines with transient absorption features, high-velocity S-wave components and phase-offsets in their radial-velocity curves. The Balmer lines in V363 Aur show a rapid increase in flux around phase 0 followed by a rapid decrease, which we attribute to the eclipse of an optically thick region at the centre of the disc. This model could also account for the behaviour of other SW Sex stars where the Balmer lines show only a shallow eclipse compared to the continuum

    Neonates presenting with severe complications of frenotomy: a case series

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    <p>Abstract</p> <p>Introduction</p> <p>Tongue-tie or ankyloglossia is an anatomic variation in which the lingual frenulum is thick, short or tight. It may be asymptomatic, or present with complications like breast feeding difficulties or speech, dental and cosmetic problems. The treatment of this condition, where indicated, is frenotomy. This procedure usually has few or no complications. However, when it is done by untrained personnel, it may lead to life-threatening complications. This paper highlights complications that could arise from improper treatment of ankyloglossia.</p> <p>Case presentation</p> <p>Case 1 was a one-day-old male neonate, a Nigerian of Igbo ethnicity, who was admitted with bleeding from the mouth and passage of dark stools after clipping of the frenulum by a traditional birth attendant. He was severely pale and in hypovolemic shock, with a severed frenulum which was bleeding actively. His packed cell volume was 15%. He was resuscitated with intravenous fluids and a blood transfusion. The bleeding was controlled using an adrenaline pack. He also received antibiotics. He was discharged five days later.</p> <p>Case 2 was a three-day-old male neonate, a Nigerian of Ikwerre ethnicity, who was admitted with profuse bleeding from a soft tissue injury under the tongue, after clipping of the frenulum by a community health worker. He was severely pale and lethargic. He was resuscitated with intravenous fluids and a blood transfusion. The bleeding vessel was ligated with repair of the soft tissue. He also received antibiotics and was discharged home one week later.</p> <p>Conclusion</p> <p>Treatment of tongue-tie, a benign condition, when done by untrained personnel may result in life-threatening complications. Clinicians should pay more attention to parents' worries about this condition and give adequate counseling or refer them to trained personnel for surgical intervention where clinically indicated.</p

    Routes for breaching and protecting genetic privacy

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    We are entering the era of ubiquitous genetic information for research, clinical care, and personal curiosity. Sharing these datasets is vital for rapid progress in understanding the genetic basis of human diseases. However, one growing concern is the ability to protect the genetic privacy of the data originators. Here, we technically map threats to genetic privacy and discuss potential mitigation strategies for privacy-preserving dissemination of genetic data.Comment: Draft for comment

    Las interprofesionales: una oportunidad para la organización del sistema agroalimentario

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    122 p. Series Agroalimentarias. Cuadernos de Organización (IICA) no. 2000-01.En este documento se destacan las características esenciales de un tipo de organizaciones de carácter vertical que ha tenido un importante papel en la vertebración del sistema agroalimentario de algunos países europeos en pasadas décadas. En la actualidad, este tipo de organización se perfila como el más adecuado para facilitar la adaptación de la pequeña y mediana empresa con una visión integral de la cadena producción-transformación, a las nuevas exigencias del mercado y el consumidor. (MV

    Antibiotics Threaten Wildlife: Circulating Quinolone Residues and Disease in Avian Scavengers

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    Antibiotic residues that may be present in carcasses of medicated livestock could pass to and greatly reduce scavenger wildlife populations. We surveyed residues of the quinolones enrofloxacin and its metabolite ciprofloxacin and other antibiotics (amoxicillin and oxytetracycline) in nestling griffon Gyps fulvus, cinereous Aegypius monachus and Egyptian Neophron percnopterus vultures in central Spain. We found high concentrations of antibiotics in the plasma of many nestling cinereous (57%) and Egyptian (40%) vultures. Enrofloxacin and ciprofloxacin were also found in liver samples of all dead cinereous vultures. This is the first report of antibiotic residues in wildlife. We also provide evidence of a direct association between antibiotic residues, primarily quinolones, and severe disease due to bacterial and fungal pathogens. Our results indicate that, by damaging the liver and kidney and through the acquisition and proliferation of pathogens associated with the depletion of lymphoid organs, continuous exposure to antibiotics could increase mortality rates, at least in cinereous vultures. If antibiotics ingested with livestock carrion are clearly implicated in the decline of the vultures in central Spain then it should be considered a primary concern for conservation of their populations

    The Dwarf Novae During Quiescence

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    We present a synthetic spectral analysis of nearly the entire FUV IUE archive of spectra of DNe in or near quiescence. We have examined all of the systems for which S/N permitted an analysis. The study includes 53 systems of all DN subtypes both above and below the period gap. The spectra were uniformly analyzed using synthetic spectral codes for optically thick accretion disks and stellar photospheres along with the best-available distance measurements or estimates. We present newly determined approximate WD temperatures or upper limits and estimated accretion rates. The average temperature of WDs in DNe below the period gap is ~18,000K. For WDs in DNe above the period gap, the average WD temperature is ~26,000K. There is a flux component, in addition to a WD photosphere, which contributes >60% of the flux in the FUV in 53% of the quiescent DNe in this study. We find that for 41% of the DNe in our sample, a WD photosphere provides >60% of the FUV flux. Accretion rates estimated from the FUV alone for the sample of DNe during quiescence ranged from 10^-12 Msun/yr to 10^-10 Msun/yr.The additional flux component is almost certainly not an optically thick accretion disk since, according to the disk instability model, the disk should be optically thin and too cool during DN quiescence to be a significant FUV continuum emitter. Among the candidates for the second component of FUV light are the quiescent inner disk, a hot equatorial accretion belt, and a hot rotating ring. The implications of our study for disk accretion physics and CV evolution are discussed.Comment: 36 pages, 3 tables, 8 figures, final accepted version of manuscrip

    Highly-Efficient Perovskite Nanocrystal Light-Emitting Diodes Enabled by a Universal Cross-linking Method

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    This work was supported by the EPSRC [Grant numbers EP/M005143/1, EP/J017361/1 and EP/G037221/1]. G.L. thanks Gates Cambridge Trust for funding. F.W.R.R. is grateful for financial support from CNPq [Grant number 246050/2012-8]. N.J.L.K.D. thanks the Cambridge Commonwealth European and International Trust, Cambridge Australian Scholarships and Mr Charles K. Allen for financial support. F.W.R.R., F.D.P. and C.D. acknowledge funding from the ERC under grant number 259619 PHOTO-EM. C.D. acknowledges financial support from the EU under grant number 312483 ESTEEM2. F.G. acknowledges financial support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University.This is the final version of the article. It first appeared from Wiley via https://doi.org10.1002/adma.20160006
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