The inner 100 AU of HD 100546 is studied via far-ultraviolet long-slit spectroscopy with the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS). The star is surrounded by reflection ...nebulosity, which can be traced 100 AU in the continuum, and by emission from H I Lya, N I, Si II, and fluorescent H sub(2) transitions. The Lya emission can be traced up to 200 AU along the system semimajor axis and 300 AU along the semiminor axis. The radial surface brightness profile and the presence of both reflection nebulosity and molecular gas suggest that we have detected the flared surface of the disk predicted from analysis of the IR spectral energy distribution. When corrected for the r super(-2) falloff in illumination from the Herbig Be star, the reflection nebulosity, neutral atomic gas, and H sub(2) emission all reveal the presence of a central cavity extending 0".13 c 0".025 (13 AU) from the star, more than 20 times larger in radius than would be expected from dust sublimation alone. The reflection nebulosity within the cavity is centered on a location 0".05 (5 AU) to the southeast of the star along the system semimajor axis. The pericenter asymmetry in the cavity is inconsistent with cavity formation by the combined effects of ice sublimation, radiation pressure blowout on small grains, or other disk chemistry that should produce azimuthally symmetric features. The STIS data are also consistent with a current accretion rate onto the Herbig Be star no higher than a few times 10 super(-9) M sub( )yr super(-1), an order of magnitude lower than seen in 5-8 Myr old Herbig Ae stars. The low accretion rate, large cavity, pericenter asymmetry, and deficit of warm dust grain emission observed over 2-8 km are all consistent with dynamical sculpting of the disk by one or more bodies within the disk. An upper limit to the flux from any chromospherically active, low-mass companion is a factor of 5-10 fainter than AU Mic (M1 Ve; t = 12 Myr) at the distance of HD 100546. This upper limit firmly excludes a low-mass stellar companion within the cavity but does not exclude a less active and/or luminous brown dwarf. The absence of similar central clearing in younger Herbig Ae stars suggests that any companion must become externally detectable late in the evolution of the disk, favoring a giant planet as the source of the structure in the HD 100546 disk.
ABSTRACT Using Chandra, we have obtained imaging X-ray spectroscopy of the 10-16 Myr old F-star binary HD 113766. We individually resolve the 1 4 separation binary components for the first time in ...the X-ray and find a total 0.3-2.0 keV luminosity of 2.2 × 1029 erg s−1, consistent with previous RASS estimates. We find emission from the easternmost, infrared-bright, dusty member HD 113766A to be only ∼10% that of the western, infrared-faint member HD 113766B. There is no evidence for a 3rd late-type stellar or substellar member of HD 113766 with Lx > 6 × 1025 erg s−1 within 2′ of the binary pair. The ratio of the two stars' X-ray luminosity is consistent with their assignments as F2V and F6V by Pecaut et al. The emission is soft for both stars, kTApec = 0.30-0.50 keV, suggesting X-rays produced by stellar rotation and/or convection in young dynamos, but not accretion or outflow shocks, which we rule out. A possible 2.8 0.15 (2 ) hr modulation in the HD 113766B X-ray emission is seen, but at very low confidence and of unknown provenance. Stellar wind drag models corresponding to Lx ∼ 2 × 1029 erg s−1 argue for a 1 mm dust particle lifetime around HD 113766B of only ∼90,0000 years, suggesting that dust around HD 113766B is quickly removed, whereas 1 mm sized dust around HD 113766A can survive for >1.5 × 106 years. At 1028-1029 erg s−1 X-ray luminosity, astrobiologically important effects, like dust warming and X-ray photolytic organic synthesis, are likely for any circumstellar material in the HD 113766 systems.
Surveys of genetic variation within cosmopolitan marine species often uncover deep divergences, indicating historical separation and potentially cryptic speciation. Based on broad geographic (coastal ...eastern North America, Gulf of Mexico, western Africa, Australia, and Hawaii) and temporal sampling (1991-2003), mitochondrial (control region CR and cytochrome oxidase I COI) and nuclear gene (lactate dehydrogenase A intron 6 LDHA6) variation among 76 individuals was used to test for cryptic speciation in the scalloped hammerhead, Sphyrna lewini (Griffith and Smith). CR and COI gene trees confirmed previous evidence of divergence between Atlantic and Indo-Pacific scalloped hammerhead populations; populations were reciprocally monophyletic. However, the between-basin divergence recorded in the mtDNA genome was not reflected in nuclear gene phylogenies; alleles for LDHA6 were shared between ocean basins, and Atlantic and Indo-Pacific populations were not reciprocally monophyletic. Unexpectedly, CR, COI, and LDHA6 gene trees recovered a deep phylogenetic partition within the Atlantic samples. For mtDNA haplotypes, which segregated by basin, average genetic distances were higher among Atlantic haplotypes (CR: D sub(HKY)=0.036, COI: D sub(GTR)=0.016) than among Indo-Pacific haplotypes (CR: D sub(HKY)=0.010, COI: D sub(GTR)=0.006) and approximated divergences between basins for CR (D sub(HKY)=0.036 within Atlantic; D sub(HKY)=0.042 between basins). Vertebral counts for eight specimens representing divergent lineages from the western north Atlantic were consistent with the genetic data. Coexistence of discrete lineages in the Atlantic, complete disequilibrium between nuclear and mitochondrial alleles within lineages and concordant partitions in genetic and morphological characters indicates reproductive isolation and thus the occurrence of a cryptic species of scalloped hammerhead in the western north Atlantic. Effective management of large coastal shark species should incorporate this important discovery and the inference from sampling that the cryptic scalloped hammerhead is less abundant than S. lewini, making it potentially more susceptible to fishery pressure.
We trace the disk of HD 169142 (A8 Ve) from 0.57" to 1.4" ( approximately 80-200 AU projected distance) in 1.1 mu m scattered light with HST NICMOS coronagraphy. The azimuthally symmetric disk has a ...peak azimuthally medianed surface brightness (SB) of approximately 5 mJy arcsec super(-2) at 0.57" from the star, and drops unk. This radial SB profile is consistent with the presence of spatially resolved PAH emission and a Meeus group I IR SED only if the inner disk is either substantially flatter than the outer disk or partially devoid of material. Analysis of new HST ACS FUV imagery in tandem with archival IUE data indicates unk less than or equal to 10 super(-9) M unk yr-1. We estimate the age of HD 169142 to be unk Myr by identifying 2MASS 18242929-2946559, located 9.3" to the southwest, as a 130 mas separation weak-line T Tauri binary that is comoving with HD 169142 at the 4 sigma confidence level. We find no evidence for any additional stellar companion in either the ACS or Chandra ACIS-S data at r less than or equal to 1". HD 169142 has previously been Interpreted as a slowly rotating, chemically peculiar star. However, by combining the disk inclination and unk from the literature, we find that the star has unk approximately 240 km s-1, making it a rapid rotator, similar to Altair or Vega. The UV data for HD 169142 are consistent with gravity darkening, while the X-ray luminosity and spectrum resembles early F stars at the age of the beta Pictoris moving group, rather than mid-A stars. In this context, spectral features previously interpreted as evidence for chemical peculiarity are more likely to reflect the presence of a strong photospheric latitudinal temperature gradient. With such a gradient, HD 169142 should closely resemble Vega at the epoch of central disk clearing.
ABSTRACT We have imaged GM Aurigae with the Hubble Space Telescope, detected its disk in scattered light at 1400 and 1650 Å, and compared these with observations at 3300 Å, 5550 Å, 1.1 m, and 1.6 m. ...The scattered light increases at shorter wavelengths. The radial surface brightness profile at 3300 Å shows no evidence of the 24 au radius cavity that has been previously observed in submillimeter observations. Comparison with dust grain opacity models indicates that the surface of the entire disk is populated with submicron grains. We have compiled a spectral energy distribution from 0.1 m to 1 mm and used it to constrain a model of the star + disk system that includes the submillimeter cavity using the Monte Carlo radiative transfer code by Barbara Whitney. The best-fit model image indicates that the cavity should be detectable in the F330W bandpass if the cavity has been cleared of both large and small dust grains, but we do not detect it. The lack of an observed cavity can be explained by the presence of submicron grains interior to the submillimeter cavity wall. We suggest one explanation for this that could be due to a planet of mass <9 MJ interior to 24 au. A unique cylindrical structure is detected in the far-UV data from the Advanced Camera for Surveys/Solar Blind Channel. It is aligned along the system semiminor axis, but does not resemble an accretion-driven jet. The structure is limb brightened and extends 190 35 au above the disk midplane. The inner radius of the limb brightening is 40 10 au, just beyond the submillimeter cavity wall.
ABSTRACT We present a new Subaru/HiCIAO high-contrast H-band polarized intensity (PI) image of a nearby transitional disk associated with TW Hydrae. The scattered light from the disk was detected ...from 0 2 to 1 5 (11-81 AU) and the PI image shows a clear axisymmetric depression in PI at ∼0 4 (∼20 AU) from the central star, similar to the ∼80 AU gap previously reported from Hubble Space Telescope images. The azimuthal PI profile also shows that the disk beyond 0 2 is almost axisymmetric. We discuss two possible scenarios explaining the origin of the PI depression: (1) a gap structure may exist at ∼20 AU from the central star because of a shallow slope seen in the PI profile, and (2) grain growth may be occurring in the inner region of the disk. Multi-band observations at near-infrared and millimeter/submillimeter wavelengths play a complementary role in investigating dust opacity and may help reveal the origin of the gap more precisely.
Tandem mass spectrometry (MS/MS) is rapidly being adopted by newborn screening programs to screen dried blood spots for >20 markers of disease in a single assay. Limited information is available for ...setting the marker cutoffs and for the resulting positive predictive values.
We screened >160 000 newborns by MS/MS. The markers were extracted from blood spots into a methanol solution with deuterium-labeled internal standards and then were derivatized before analysis by MS/MS. Multiple reaction monitoring of each sample for the markers of interest was accomplished in approximately 1.9 min. Cutoffs for each marker were set at 6-13 SD above the population mean.
We identified 22 babies with amino acid disorders (7 phenylketonuria, 11 hyperphenylalaninemia, 1 maple syrup urine disease, 1 hypermethioninemia, 1 arginosuccinate lyase deficiency, and 1 argininemia) and 20 infants with fatty and organic acid disorders (10 medium-chain acyl-CoA dehydrogenase deficiencies, 5 presumptive short-chain acyl-CoA dehydrogenase deficiencies, 2 propionic acidemias, 1 carnitine palmitoyltransferase II deficiency, 1 methylcrotonyl-CoA carboxylase deficiency, and 1 presumptive very-long chain acyl-CoA dehydrogenase deficiency). Approximately 0.3% of all newborns screened were flagged for either amino acid or acylcarnitine markers; approximately one-half of all the flagged infants were from the 5% of newborns who required neonatal intensive care or had birth weights <1500 g.
In screening for 23 metabolic disorders by MS/MS, an mean positive predictive value of 8% can be achieved when using cutoffs for individual markers determined empirically on newborns.
Despite its importance in the thermal balance of the gas and in the determination of primeval planetary atmospheres, the chemistry in protoplanetary discs remains poorly constrained with only a ...handful of detected species. We observed the emission from the disc around the Herbig Be star HD 100546 with the PACS instrument in the spectroscopic mode on board the Herschel Space Telescope as part of the GAS in Protoplanetary Systems (GASPS) programme and used archival data from the DIGIT programme to search for the rotational emission of CH+. We detected in both datasets an emission line centred at 72.16 μm that most likely corresponds to the J = 5−4 rotational emission of CH+. The J = 3−2 and 6−5 transitions are also detected albeit with lower confidence. Other CH+ rotational lines in the PACS observations are blended with water lines. A rotational diagram analysis shows that the CH+ gas is warm at 323\hbox{$^{+2320}_{-151}$}+2320-151 K with a mass of ~3 × 10-14−5 × 10-12 M⊙. We modelled the CH+ chemistry with the chemo-physical code ProDiMo using a disc density structure and grain parameters that match continuum observations and near- and mid-infrared interferometric data. The model suggests that CH+ is most abundant at the location of the disc rim at 10−13 AU from the star where the gas is warm, which is consistent with previous observations of hot CO gas emission.
Determining the optimal timing for extubation can be challenging in the intensive care. In this study, we aim to identify predictors for extubation failure in critically ill patients with COVID-19.
...We used highly granular data from 3464 adult critically ill COVID patients in the multicenter Dutch Data Warehouse, including demographics, clinical observations, medications, fluid balance, laboratory values, vital signs, and data from life support devices. All intubated patients with at least one extubation attempt were eligible for analysis. Transferred patients, patients admitted for less than 24 h, and patients still admitted at the time of data extraction were excluded. Potential predictors were selected by a team of intensive care physicians. The primary and secondary outcomes were extubation without reintubation or death within the next 7 days and within 48 h, respectively. We trained and validated multiple machine learning algorithms using fivefold nested cross-validation. Predictor importance was estimated using Shapley additive explanations, while cutoff values for the relative probability of failed extubation were estimated through partial dependence plots.
A total of 883 patients were included in the model derivation. The reintubation rate was 13.4% within 48 h and 18.9% at day 7, with a mortality rate of 0.6% and 1.0% respectively. The grandient-boost model performed best (area under the curve of 0.70) and was used to calculate predictor importance. Ventilatory characteristics and settings were the most important predictors. More specifically, a controlled mode duration longer than 4 days, a last fraction of inspired oxygen higher than 35%, a mean tidal volume per kg ideal body weight above 8 ml/kg in the day before extubation, and a shorter duration in assisted mode (< 2 days) compared to their median values. Additionally, a higher C-reactive protein and leukocyte count, a lower thrombocyte count, a lower Glasgow coma scale and a lower body mass index compared to their medians were associated with extubation failure.
The most important predictors for extubation failure in critically ill COVID-19 patients include ventilatory settings, inflammatory parameters, neurological status, and body mass index. These predictors should therefore be routinely captured in electronic health records.
While existing techniques are capable of automatically identifying and classifying various types of distribution-level power quality disturbances, they do not provide any information about the ...locations of the disturbance sources. This paper shows that it is possible to use sampled voltage and current waveforms to determine on which side of a recording device a disturbance originates. This is accomplished by examining the energy flow and peak instantaneous power for both capacitor energizing and voltage sag disturbances. The authors demonstrate the technique by testing it on both ATP-generated waveforms and actual field disturbance data. In both cases, they are able to accurately determine on which side of a recording device the disturbance originates. If enough recording devices are available in a network, the individual readings can be collectively used to pinpoint the locations of disturbance sources.
PDF
