Context.
The Galactic plane has been observed extensively by a large number of Galactic plane surveys from infrared to radio wavelengths at an angular resolution below 40′′. However, a 21 cm line and ...continuum survey with comparable spatial resolution is lacking.
Aims.
The first half of THOR data (
l
= 14.0°−37.9°, and
l
= 47.1°−51.2°, |
b
|≤ 1.25°) has been published in our data release 1 paper. With this data release 2 paper, we publish all the remaining spectral line data and Stokes I continuum data with high angular resolution (10′′–40′′), including a new H
I
dataset for the whole THOR survey region (
l
= 14.0−67.4° and |
b
|≤ 1.25°). As we published the results of OH lines and continuum emission elsewhere, we concentrate on the H
I
analysis in this paper.
Methods.
With the
Karl G. Jansky
Very Large Array (VLA) in C-configuration, we observed a large portion of the first Galactic quadrant, achieving an angular resolution of ≤40′′. At
L
Band, the WIDAR correlator at the VLA was set to cover the 21 cm H
I
line, four OH transitions, a series of H
nα
radio recombination lines (RRLs;
n
= 151 to 186), and eight 128 MHz-wide continuum spectral windows, simultaneously.
Results.
We publish all OH and RRL data from the C-configuration observations, and a new H
I
dataset combining VLA C+D+GBT (VLA D-configuration and GBT data are from the VLA Galactic Plane Survey) for the whole survey. The H
I
emission shows clear filamentary substructures at negative velocities with low velocity crowding. The emission at positive velocities is more smeared-out, likely due to higher spatial and velocity crowding of structures at the positive velocities. Compared to the spiral arm model of the Milky Way, the atomic gas follows the Sagittarius and Perseus Arm well, but with significant material in the inter-arm regions. With the C-configuration-only H
I
+continuum data, we produce an H
I
optical depth map of the THOR areal coverage from 228 absorption spectra with the nearest-neighbor method. With this
τ
map, we corrected the H
I
emission for optical depth, and the derived column density is 38% higher than the column density with optically thin assumption. The total H
I
mass with optical depth correction in the survey region is 4.7 × 10
8
M
⊙
, 31% more than the mass derived assuming the emission is optically thin. If we applied this 31% correction to the whole Milky Way, the total atomic gas mass would be 9.4–10.5 × 10
9
M
⊙
. Comparing the H
I
with existing CO data, we find a significant increase in the atomic-to-molecular gas ratio from the spiral arms to the inter-arm regions.
Conclusions.
The high-sensitivity and resolution THOR H
I
dataset provides an important new window on the physical and kinematic properties of gas in the inner Galaxy. Although the optical depth we derive is a lower limit, our study shows that the optical depth correction issignificant for H
I
column density and mass estimation. Together with the OH, RRL and continuum emission from the THOR survey, these new H
I
data provide the basis for high-angular-resolution studies of the interstellar medium in different phases.
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Molecular clouds form from the atomic phase of the interstellar medium. However, characterizing the transition between the atomic and the molecular interstellar medium (ISM) is a complex ...observational task. Here we address cloud formation processes by combining H
I
self absorption (HISA) with molecular line data. Column density probability density functions (N-PDFs) are a common tool for examining molecular clouds. One scenario proposed by numerical simulations is that the N-PDF evolves from a log-normal shape at early times to a power-law-like shape at later times. To date, investigations of N-PDFs have been mostly limited to the molecular component of the cloud. In this paper, we study the cold atomic component of the giant molecular filament GMF38.1-32.4a (GMF38a, distance = 3.4 kpc, length ~ 230 pc), calculate its N-PDFs, and study its kinematics. We identify an extended HISA feature, which is partly correlated with the
13
CO emission. The peak velocities of the HISA and
13
CO observations agree well on the eastern side of the filament, whereas a velocity offset of approximately 4 km s
−1
is found on the western side. The sonic Mach number we derive from the linewidth measurements shows that a large fraction of the HISA, which is ascribed to the cold neutral medium (CNM), is at subsonic and transonic velocities. The column density of the CNM part is on the order of 10
20
to 10
21
cm
−2
. The column density of molecular hydrogen, traced by
13
CO, is an order of magnitude higher. The N-PDFs from HISA (CNM), H
I
emission (the warm and cold neutral medium), and
13
CO (molecular component) are well described by log-normal functions, which is in agreement with turbulent motions being the main driver of cloud dynamics. The N-PDF of the molecular component also shows a power law in the high column-density region, indicating self-gravity. We suggest that we are witnessing two different evolutionary stages within the filament. The eastern subregion seems to be forming a molecular cloud out of the atomic gas, whereas the western subregion already shows high column density peaks, active star formation, and evidence of related feedback processes.
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This report summarizes the laboratory studies undertaken to identify the etiologic agent of the worldwide outbreak of the severe acute respiratory syndrome (SARS). In specimens from patients from ...seven countries, a coronavirus was identified by electron microscopy. The virus is only distantly related to previously sequenced coronaviruses. From serologic studies it appears that this virus has not previously circulated in humans.
One report summarizes laboratory studies on specimens from patients from six countries. Another report shows high concentrations of viral RNA in sputum. The full text of these articles is available free.
In late 2002, cases of life-threatening respiratory disease with no identifiable cause were reported from Guangdong Province, China; they were followed by reports from Vietnam, Canada, and Hong Kong of severe febrile respiratory illness that spread to household members and health care workers. The syndrome was designated “severe acute respiratory syndrome” (SARS) in March 2003,
1
–
5
and global efforts to understand the cause of this illness and prevent its spread were instituted in March 2003. Many cases can be linked through chains of transmission to a health care worker from Guangdong Province, China, who visited Hong Kong, where he was . . .
Ticks, including many that bite humans, are hosts to several obligate intracellular bacteria in the spotted fever group (SFG) of the genus Rickettsia. Only Rickettsia rickettsii, the agent of Rocky ...Mountain spotted fever, has been definitively associated with disease in humans in the United States. Herein we describe disease in a human caused by Rickettsia parkeri, an SFG rickettsia first identified >60 years ago in Gulf Coast ticks (Amblyomma maculatum) collected from the southern United States. Confirmation of the infection was accomplished using serological testing, immunohistochemical staining, cell culture isolation, and molecular methods. Application of specific laboratory assays to clinical specimens obtained from patients with febrile, eschar-associated illnesses following a tick bite may identify additional cases of R. parkeri rickettsiosis and possibly other novel SFG rickettsioses in the United States.
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We introduce the histogram of oriented gradients (HOG), a tool developed for machine vision that we propose as a new metric for the systematic characterization of spectral line observations of atomic ...and molecular gas and the study of molecular cloud formation models. In essence, the HOG technique takes as input extended spectral-line observations from two tracers and provides an estimate of their spatial correlation across velocity channels. We characterized HOG using synthetic observations of HI and 13CO (J = 1 → 0) emission from numerical simulations of magnetohydrodynamic (MHD) turbulence leading to the formation of molecular gas after the collision of two atomic clouds. We found a significant spatial correlation between the two tracers in velocity channels where vHI ≈ v13CO, almost independent of the orientation of the collision with respect to the line of sight. Subsequently, we used HOG to investigate the spatial correlation of the HI, from The HI/OH/recombination line survey of the inner Milky Way (THOR), and the 13CO (J = 1 → 0) emission from the Galactic Ring Survey (GRS), toward the portion of the Galactic plane 33°.75 ≤l ≤ 35°.25 and |b| ≤ 1°.25. We found a significant spatial correlation between the two tracers in extended portions of the studied region. Although some of the regions with high spatial correlation are associated with HI self-absorption (HISA) features, suggesting that it is produced by the cold atomic gas, the correlation is not exclusive to this kind of region. The HOG results derived for the observational data indicate significant differences between individual regions: some show spatial correlation in channels around vHI ≈ v13CO while others present spatial correlations in velocity channels separated by a few kilometers per second. We associate these velocity offsets to the effect of feedback and to the presence of physical conditions that are not included in the atomic-cloud-collision simulations, such as more general magnetic field configurations, shear, and global gas infall.
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We present first results for Faraday rotation of compact polarized sources (1-2 GHz continuum) in The H i/OH/Recombination line (THOR) survey of the inner Galaxy. In the Galactic longitude range 39° ...< < 52°, we find rotation measures (RMs) in the range −310 rad m−2 ≤ RM ≤ +4219 rad m−2, with the highest values concentrated within a degree of = 48° at the Sagittarius arm tangent. Most of the high RMs arise in diffuse plasma, along lines of sight that do not intersect H ii regions. For > 49°, RM drops off rapidly, while at < 47°, the mean RM is higher with a larger standard deviation than at > 49°. We attribute the RM structure to the compressed diffuse warm ionized medium in the spiral arm, upstream of the major star formation regions. The Sagittarius arm acts as a significant Faraday screen inside the Galaxy. This has implications for models of the Galactic magnetic field and the expected amount of Faraday rotation of fast radio bursts from their host galaxies. We emphasize the importance of sensitivity to high Faraday depth in future polarization surveys.
We present deep CCS and HC7N observations of the L1495-B218 filaments in the Taurus molecular cloud obtained using the K-band focal plane array on the 100 m Green Bank Telescope. We observed the ...L1495-B218 filaments in CCS JN = 21-10 and HC7N J = 21−20 with a spectral resolution of 0.038 km s−1 and an angular resolution of 31″. We observed strong CCS emission in both evolved and young regions and weak emission in two evolved regions. HC7N emission is observed only in L1495A-N and L1521D. We find that CCS and HC7N intensity peaks do not coincide with NH3 or dust continuum intensity peaks. We also find that the fractional abundance of CCS does not show a clear correlation with the dynamical evolutionary stage of dense cores. Our findings and chemical modeling indicate that the fractional abundances of CCS and HC7N are sensitive to the initial gas-phase C/O ratio, and they are good tracers of young condensed gas only when the initial C/O is close to solar value. Kinematic analysis using multiple lines, including NH3, HC7N, CCS, CO, HCN, and HCO+, suggests that there may be three different star formation modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has formed a stellar cluster with large-scale inward flows (fast mode), whereas L1521D, a core embedded in a filament, is slowly contracting because of its self-gravity (slow mode). There is also one isolated core that appears to be marginally stable and may undergo quasi-static evolution (isolated mode).
A paramyxovirus virus termed Nipah virus has been identified as the etiologic agent of an outbreak of severe encephalitis in people with close contact exposure to pigs in Malaysia and Singapore. The ...outbreak was first noted in late September 1998 and by mid-June 1999, more than 265 encephalitis cases, including 105 deaths, had been reported in Malaysia, and 11 cases of encephalitis or respiratory illness with one death had been reported in Singapore. Electron microscopic, serologic, and genetic studies indicate that this virus belongs to the family Paramyxoviridae and is most closely related to the recently discovered Hendra virus. We suggest that these two viruses are representative of a new genus within the family Paramyxoviridae. Like Hendra virus, Nipah virus is unusual among the paramyxoviruses in its ability to infect and cause potentially fatal disease in a number of host species, including humans.
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Incidental findings are discovered in neuroimaging research, ranging from trivial to life-threatening. We describe the prevalence and characteristics of incidental findings from 16,400 research brain ...MRIs, comparing spontaneous detection by nonradiology scanning staff versus formal neuroradiologist interpretation.
We prospectively collected 16,400 brain MRIs (7782 males, 8618 females; younger than 1 to 94 years of age; median age, 38 years) under an institutional review board directive intended to identify clinically relevant incidental findings. The study population included 13,150 presumed healthy volunteers and 3250 individuals with known neurologic diagnoses. Scanning staff were asked to flag concerning imaging findings seen during the scan session, and neuroradiologists produced structured reports after reviewing every scan.
Neuroradiologists reported 13,593/16,400 (83%) scans as having normal findings, 2193/16,400 (13.3%) with abnormal findings without follow-up recommended, and 614/16,400 (3.7%) with "abnormal findings with follow-up recommended." The most common abnormalities prompting follow-up were vascular (263/614, 43%), neoplastic (130/614, 21%), and congenital (92/614, 15%). Volunteers older than 65 years of age were significantly more likely to have scans with abnormal findings (
< .001); however, among all volunteers with incidental findings, those younger than 65 years of age were more likely to be recommended for follow-up. Nonradiologists flagged <1% of MRIs containing at least 1 abnormality reported by the neuroradiologists to be concerning enough to warrant further evaluation.
Four percent of individuals who undergo research brain MRIs have an incidental, potentially clinically significant finding. Routine neuroradiologist review of all scans yields a much higher rate of significant lesion detection than selective referral from nonradiologists who perform the examinations. Workflow and scan review processes need to be carefully considered when designing research protocols.
Heat-resistant superalloys (HRSAs) exhibit excellent mechanical strength and structural stability at elevated temperatures. Hence, aerospace and power industries have consistently chosen nickel-based ...superalloys over the years for manufacturing hot-section components. However, poor machinability of these alloys has always been a challenge. This paper investigates the cutting performance of new-generation SiAlON ceramics under extreme conditions of dry high-speed face milling of hardened Inconel 718. Comprehensive characterization of the ceramic tool and its milling performance were conducted using instrumented micro/nano-mechanical indentations, tool life studies, optical 3D imaging, and SEM/EDS investigation of wear patterns. Also, experimental results were linked to the finite element analysis (FEA) of temperature and stress profiles. It is demonstrated that a few major factors govern the ceramic tool life under the outlined cutting conditions: (1) High temperature at the cutting edge exceeding 1250 °C. This temperature is close to the melting point of Inconel 718, and moreover, it is highly localized around the cutting edge-chip interface. (2) High resultant mechanical stress on the tool of around 5.8 GPa. (3) Thermal and mechanical fatigue loading due to the discontinuity of the milling process, combined with (4) intensive built-up edge formation caused by severe weldability of the softened workpiece to the tool. Combination of these phenomena results in a significant change in the machinability of the workpiece material after surpassing a certain limit of cutting speed. The cutting forces, tool wear, and chipping show a significant decline with increasing the speed high enough, which is attributed to the change in the material properties of the workpiece and dissolution of the hard particles within the Inconel microstructure.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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