2,992 research outputs found
(±)-Ethyl 6-(6-methoxy-2-naphthyl)-4-(4-methylphenyl)-2-oxocyclohex-3-ene-1-carboxylate
In the title compound, C27H26O4, the dihedral angle between the naphthalene ring system and the benzene ring is 73.10 (5)°. In the crystal, a weak C—H⋯O interaction occurs. Two C—H groups of the cyclohexene ring are disordered over two sets of sites in a 0.796 (5):0.204 (5) ratio, which corresponds to partial overlap of the two enantiomeric molecules
THE MEMS FLUX CONCENTRATOR: POTENTIAL LOW-COST, HIGHSENSITIVITY MAGNETOMETER
Progress on the development of a device, the MEMS flux concentrator, for mitigating the problem of 1/f noise in magnetic sensors will be presented. The MEMS flux concentrator essentially eliminates the effect of 1/f noise by increasing the operating frequency of the sensor to a frequency region where 1/f noise is small. This is accomplished by putting flux concentrators on MEMS structures whose motion modulates the magnetic field at the position of the magnetic sensor. Depending on the sensor, mitigating the effect of 1/f noise will increase the sensitivity of magnetic sensors by one to three orders of magnitude. Combining the MEMS flux concentrator with magnetic tunnel junctions with MgO barriers should lead to low cost magnetic sensors that are able to detect 1 pT signals at 1 Hz
The hidden burden of influenza: A review of the extra-pulmonary complications of influenza infection
Severe influenza infection represents a leading cause of global morbidity and mortality. Although influenza is primarily considered a viral infection that results in pathology limited to the respiratory system, clinical reports suggest that influenza infection is frequently associated with a number of clinical syndromes that involve organ systems outside the respiratory tract. A comprehensive MEDLINE literature review of articles pertaining to extra-pulmonary complications of influenza infection, using organ-specific search terms, yielded 218 articles including case reports, epidemiologic investigations, and autopsy studies that were reviewed to determine the clinical involvement of other organs. The most frequently described clinical entities were viral myocarditis and viral encephalitis. Recognition of these extra-pulmonary complications is critical to determining the true burden of influenza infection and initiating organ-specific supportive care
Characterizing the Youngest Herschel-detected Protostars I. Envelope Structure Revealed by CARMA Dust Continuum Observations
We present CARMA 2.9 mm dust continuum emission observations of a sample of
14 Herschel-detected Class 0 protostars in the Orion A and B molecular clouds,
drawn from the PACS Bright Red Sources (PBRS) sample (Stutz et al.). These
objects are characterized by very red 24 \micron\ to 70 \micron\ colors and
prominent submillimeter emission, suggesting that they are very young Class 0
protostars embedded in dense envelopes. We detect all of the PBRS in 2.9 mm
continuum emission and emission from 4 protostars and 1 starless core in the
fields toward the PBRS; we also report 1 new PBRS source. The ratio of 2.9 mm
luminosity to bolometric luminosity is higher by a factor of 5 on
average, compared to other well-studied protostars in the Perseus and Ophiuchus
clouds. The 2.9 mm visibility amplitudes for 6 of the 14 PBRS are very flat as
a function of uv-distance, with more than 50\% of the source emission arising
from radii 1500 AU. These flat visibility amplitudes are most consistent
with spherically symmetric envelope density profiles with
~~R. Alternatively, there could be a massive unresolved
structure like a disk or a high-density inner envelope departing from a smooth
power-law. The large amount of mass on scales 1500 AU (implying high
average central densities) leads us to suggest that that the PBRS with flat
visibility amplitude profiles are the youngest PBRS and may be undergoing a
brief phase of high mass infall/accretion and are possibly among the youngest
Class 0 protostars. The PBRS with more rapidly declining visibility amplitudes
still have large envelope masses, but could be slightly more evolved.Comment: Accepted to ApJ, 40 pages, 9 Figures, 4 Table
He I 10830 as a Probe of Winds in Accreting Young Stars
He I 10830 profiles acquired with Keck's NIRSPEC for 6 young low mass stars
with high disk accretion rates (AS 353A, DG Tau, DL Tau, DR Tau, HL Tau and SVS
13) provide new insight into accretion-driven winds. In 4 stars the profiles
have the signature of resonance scattering, and possess a deep and broad
blueshifted absorption that penetrates more than 50% into the 1 micron
continuum over a continuous range of velocities from near the stellar rest
velocity to the terminal velocity of the wind, unlike inner wind signatures
seen in other spectral features. This deep and broad absorption provides the
first observational tracer of the acceleration region of the inner wind and
suggests that this acceleration region is situated such that it occults a
significant portion of the stellar disk. The remaining 2 stars also have blue
absorption extending below the continuum although here the profiles are
dominated by emission, requiring an additional source of helium excitation
beyond resonant scattering. This is likely the same process that produces the
emission profiles seen at He I 5876
Evolution of Mass Outflow in Protostars
We have surveyed 84 Class 0, Class I, and flat-spectrum protostars in
mid-infrared [Si II], [Fe II] and [S I] line emission, and 11 of these in
far-infrared [O I] emission. We use the results to derive their mass outflow
rates. Thereby we observe a strong correlation of mass outflow rates with
bolometric luminosity, and with the inferred mass accretion rates of the
central objects, which continues through the Class 0 range the trend observed
in Class II young stellar objects. Along this trend from large to small
mass-flow rates, the different classes of young stellar objects lie in the
sequence Class 0 -- Class I/flat-spectrum -- Class II, indicating that the
trend is an evolutionary sequence in which mass outflow and accretion rates
decrease together with increasing age, while maintaining rough proportionality.
The survey results include two which are key tests of magnetocentrifugal
outflow-acceleration mechanisms: the distribution of the outflow/accretion
branching ratio b, and limits on the distribution of outflow speeds. Neither
rule out any of the three leading outflow-acceleration,
angular-momentum-ejection mechanisms, but they provide some evidence that disk
winds and accretion-powered stellar winds (APSWs) operate in many protostars.
An upper edge observed in the branching-ratio distribution is consistent with
the upper bound of b = 0.6 found in models of APSWs, and a large fraction
(0.31) of the sample have branching ratio sufficiently small that only disk
winds, launched on scales as large as several AU, have been demonstrated to
account for them.Comment: Version submitted to ApJ: 36 pages, 3 tables, 8 figure
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