745 research outputs found
Evidence for an FU Orionis-like Outburst from a Classical T Tauri Star
We present pre- and post-outburst observations of the new FU Orionis-like
young stellar object PTF 10qpf (also known as LkHa 188-G4 and HBC 722). Prior
to this outburst, LkHa 188-G4 was classified as a classical T Tauri star on the
basis of its optical emission-line spectrum superposed on a K8-type
photosphere, and its photometric variability. The mid-infrared spectral index
of LkHa 188-G4 indicates a Class II-type object. LkHa 188-G4 exhibited a steady
rise by ~1 mag over ~11 months starting in Aug. 2009, before a subsequent more
abrupt rise of > 3 mag on a time scale of ~2 months. Observations taken during
the eruption exhibit the defining characteristics of FU Orionis variables: (i)
an increase in brightness by > 4 mag, (ii) a bright optical/near-infrared
reflection nebula appeared, (iii) optical spectra are consistent with a G
supergiant and dominated by absorption lines, the only exception being Halpha
which is characterized by a P Cygni profile, (iv) near-infrared spectra
resemble those of late K--M giants/supergiants with enhanced absorption seen in
the molecular bands of CO and H_2O, and (v) outflow signatures in H and He are
seen in the form of blueshifted absorption profiles. LkHa 188-G4 is the first
member of the FU Orionis-like class with a well-sampled optical to mid-infrared
spectral energy distribution in the pre-outburst phase. The association of the
PTF 10qpf outburst with the previously identified classical T Tauri star LkHa
188-G4 (HBC 722) provides strong evidence that FU Orionis-like eruptions
represent periods of enhanced disk accretion and outflow, likely triggered by
instabilities in the disk. The early identification of PTF 10qpf as an FU
Orionis-like variable will enable detailed photometric and spectroscopic
observations during its post-outburst evolution for comparison with other known
outbursting objects.Comment: 14 pages, 11 figures, ApJ accepte
PTF10fqs: A Luminous Red Nova in the Spiral Galaxy Messier 99
The Palomar Transient Factory (PTF) is systematically charting the optical
transient and variable sky. A primary science driver of PTF is building a
complete inventory of transients in the local Universe (distance less than 200
Mpc). Here, we report the discovery of PTF10fqs, a transient in the luminosity
"gap" between novae and supernovae. Located on a spiral arm of Messier 99, PTF
10fqs has a peak luminosity of Mr = -12.3, red color (g-r = 1.0) and is slowly
evolving (decayed by 1 mag in 68 days). It has a spectrum dominated by
intermediate-width H (930 km/s) and narrow calcium emission lines. The
explosion signature (the light curve and spectra) is overall similar to thatof
M85OT2006-1, SN2008S, and NGC300OT. The origin of these events is shrouded in
mystery and controversy (and in some cases, in dust). PTF10fqs shows some
evidence of a broad feature (around 8600A) that may suggest very large
velocities (10,000 km/s) in this explosion. Ongoing surveys can be expected to
find a few such events per year. Sensitive spectroscopy, infrared monitoring
and statistics (e.g. disk versus bulge) will eventually make it possible for
astronomers to unravel the nature of these mysterious explosions.Comment: 12 pages, 12 figures, Replaced with published versio
Recapitulation of Human Retinal Development from Human Pluripotent Stem Cells Generates Transplantable Populations of Cone Photoreceptors
Transplantation of rod photoreceptors, derived either from neonatal retinae or pluripotent stem cells (PSCs), can restore rod-mediated visual function in murine models of inherited blindness. However, humans depend more upon cone photoreceptors that are required for daylight, color, and high-acuity vision. Indeed, macular retinopathies involving loss of cones are leading causes of blindness. An essential step for developing stem cell-based therapies for maculopathies is the ability to generate transplantable human cones from renewable sources. Here, we report a modified 2D/3D protocol for generating hPSC-derived neural retinal vesicles with well-formed ONL-like structures containing cones and rods bearing inner segments and connecting cilia, nascent outer segments, and presynaptic structures. This differentiation system recapitulates human photoreceptor development, allowing the isolation and transplantation of a pure population of stage-matched cones. Purified human long/medium cones survive and become incorporated within the adult mouse retina, supporting the potential of photoreceptor transplantation for treating retinal degeneration
The HLA class II allele DRB1*1501 is over-represented in patients with idiopathic pulmonary fibrosis
Background: Idiopathic pulmonary fibrosis (IPF) is a progressive and medically refractory lung disease with a grim prognosis. Although the etiology of IPF remains perplexing, abnormal adaptive immune responses are evident in many afflicted patients. We hypothesized that perturbations of human leukocyte antigen (HLA) allele frequencies, which are often seen among patients with immunologic diseases, may also be present in IPF patients. Methods/Principal Findings: HLA alleles were determined in subpopulations of IPF and normal subjects using molecular typing methods. HLA-DRB1*15 was over-represented in a discovery cohort of 79 Caucasian IPF subjects who had lung transplantations at the University of Pittsburgh (36.7%) compared to normal reference populations. These findings were prospectively replicated in a validation cohort of 196 additional IPF subjects from four other U.S. medical centers that included both ambulatory patients and lung transplantation recipients. High-resolution typing was used to further define specific HLA-DRB1*15 alleles. DRB1*1501 prevalence in IPF subjects was similar among the 143 ambulatory patients and 132 transplant recipients (31.5% and 34.8%, respectively, p = 0.55). The aggregate prevalence of DRB1*1501 in IPF patients was significantly greater than among 285 healthy controls (33.1% vs. 20.0%, respectively, OR 2.0; 95%CI 1.3-2.9, p = 0.0004). IPF patients with DRB1*1501 (n = 91) tended to have decreased diffusing capacities for carbon monoxide (DLCO) compared to the 184 disease subjects who lacked this allele (37.8±1.7% vs. 42.8±1.4%, p = 0.036). Conclusions/Significance: DRB1*1501 is more prevalent among IPF patients than normal subjects, and may be associated with greater impairment of gas exchange. These data are novel evidence that immunogenetic processes can play a role in the susceptibility to and/or manifestations of IPF. Findings here of a disease association at the HLA-DR locus have broad pathogenic implications, illustrate a specific chromosomal area for incremental, targeted genomic study, and may identify a distinct clinical phenotype among patients with this enigmatic, morbid lung disease
A new biphasic osteoinductive calcium composite material with a negative Zeta potential for bone augmentation
The aim of the present study was to analyze the osteogenic potential of a biphasic calcium composite material (BCC) with a negative surface charge for maxillary sinus floor augmentation. In a 61 year old patient, the BCC material was used in a bilateral sinus floor augmentation procedure. Six months postoperative, a bone sample was taken from the augmented regions before two titanium implants were inserted at each side. We analyzed bone neoformation by histology, bone density by computed tomography, and measured the activity of voltage-activated calcium currents of osteoblasts and surface charge effects. Control orthopantomograms were carried out five months after implant insertion. The BCC was biocompatible and replaced by new mineralized bone after being resorbed completely. The material demonstrated a negative surface charge (negative Zeta potential) which was found to be favorable for bone regeneration and osseointegration of dental implants
Osteogenesis evaluation of duck’s feet derived collagen/hydroxyapatite sponges immersed in dexamethasone
Background: The aim of this study was to investigate the osteogenesis effects of DC and DC/HAp sponge immersed in without and with dexamethasone.
Methods: The experimental groups in this study were DC and DC/HAp sponge immersed in without dexamethasone (Dex(â )DC and Dex(â )-DC/HAp group) and with dexamethasone (Dex(+)-DC and Dex(+)-DC/HAp group). We characterized DC and DC/HAp sponge using compressive strength, scanning electron microscopy (SEM). Also, osteogenic differentiation of BMSCs on sponge (Dex(â )DC, Dex(â )-DC/HAp, Dex(+)-DC and Dex(+)-DC/HAp group) was assessed by SEM, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide (MTT) assay, alkaline phosphatase (ALP) activity assay and reverse transcription-PCR (RT-PCR).
Results: In this study, we assessed osteogenic differentiation of BMSCs on Duckâ s feet-derived collagen (DC)/ HAp sponge immersed with dexamethasone Dex(+)-DC/HAp. These results showed that Dex(+)-DC/HAp group increased cell proliferation and osteogenic differentiation of BMSCs during 28 days.
Conclusion: From these results, Dex(+)-DC/HAp can be envisioned as a potential biomaterial for bone regeneration applications.This work was supported by Technology Commercialization Support Program [grant number 814005-03-3-HD020], Ministry for Food, Agriculture, Forestry and Fisheries (MIFAFF).info:eu-repo/semantics/publishedVersio
External validation of risk prediction models for incident colorectal cancer using UK Biobank.
BACKGROUND: This study aimed to compare and externally validate risk scores developed to predict incident colorectal cancer (CRC) that include variables routinely available or easily obtainable via self-completed questionnaire. METHODS: External validation of fourteen risk models from a previous systematic review in 373 112 men and women within the UK Biobank cohort with 5-year follow-up, no prior history of CRC and data for incidence of CRC through linkage to national cancer registries. RESULTS: There were 1719 (0.46%) cases of incident CRC. The performance of the risk models varied substantially. In men, the QCancer10 model and models by Tao, Driver and Ma all had an area under the receiver operating characteristic curve (AUC) between 0.67 and 0.70. Discrimination was lower in women: the QCancer10, Wells, Tao, Guesmi and Ma models were the best performing with AUCs between 0.63 and 0.66. Assessment of calibration was possible for six models in men and women. All would require country-specific recalibration if estimates of absolute risks were to be given to individuals. CONCLUSIONS: Several risk models based on easily obtainable data have relatively good discrimination in a UK population. Modelling studies are now required to estimate the potential health benefits and cost-effectiveness of implementing stratified risk-based CRC screening
Keldysh technique and non-linear sigma-model: basic principles and applications
The purpose of this review is to provide a comprehensive pedagogical
introduction into Keldysh technique for interacting out-of-equilibrium
fermionic and bosonic systems. The emphasis is placed on a functional integral
representation of underlying microscopic models. A large part of the review is
devoted to derivation and applications of the non-linear sigma-model for
disordered metals and superconductors. We discuss such topics as transport
properties, mesoscopic effects, counting statistics, interaction corrections,
kinetic equation, etc. The sections devoted to disordered superconductors
include Usadel equation, fluctuation corrections, time-dependent
Ginzburg-Landau theory, proximity and Josephson effects, etc. (This review is a
substantial extension of arXiv:cond-mat/0412296.)Comment: Review: 103 pages, 19 figure
The dependence of dijet production on photon virtuality in ep collisions at HERA
The dependence of dijet production on the virtuality of the exchanged photon,
Q^2, has been studied by measuring dijet cross sections in the range 0 < Q^2 <
2000 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of
38.6 pb^-1.
Dijet cross sections were measured for jets with transverse energy E_T^jet >
7.5 and 6.5 GeV and pseudorapidities in the photon-proton centre-of-mass frame
in the range -3 < eta^jet <0. The variable xg^obs, a measure of the photon
momentum entering the hard process, was used to enhance the sensitivity of the
measurement to the photon structure. The Q^2 dependence of the ratio of low- to
high-xg^obs events was measured.
Next-to-leading-order QCD predictions were found to generally underestimate
the low-xg^obs contribution relative to that at high xg^obs. Monte Carlo models
based on leading-logarithmic parton-showers, using a partonic structure for the
photon which falls smoothly with increasing Q^2, provide a qualitative
description of the data.Comment: 35 pages, 6 eps figures, submitted to Eur.Phys.J.
Beauty photoproduction measured using decays into muons in dijet events in ep collisions at =318 GeV
The photoproduction of beauty quarks in events with two jets and a muon has
been measured with the ZEUS detector at HERA using an integrated luminosity of
110 pb. The fraction of jets containing b quarks was extracted from the
transverse momentum distribution of the muon relative to the closest jet.
Differential cross sections for beauty production as a function of the
transverse momentum and pseudorapidity of the muon, of the associated jet and
of , the fraction of the photon's momentum participating in
the hard process, are compared with MC models and QCD predictions made at
next-to-leading order. The latter give a good description of the data.Comment: 32 pages, 6 tables, 7 figures Table 6 and Figure 7 revised September
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