139 research outputs found
Felling by a Five-Legged Walking Machine
A 1/11 scale model of a walking machine with five legs was constructed, and its operation as a feller-buncher investigated. As slopes steepen, the machine when positioned straight up the slope becomes more efficient than when positioned parallel to the contour lines, because the downward operational range of the machine decreases with increased slopes. In the experiments, the ground pressure of the legs on the end opposite the boom was nearly zero when the boom holding felled trees was positioned at the side of the body and extended farthest from the body. However, further investigations (including such factors as ground disturbance, the operation of the machine, the degrees and the length of slope, and the fuel consumption) of felling operations are needed. Feller-bunching tends to be less efficient as tree density increases assuming that felling time per tree remains constant as tree diameter changes. To obtain greater productivity with the machine as a feller-buncher, it is essential to achieve faster walking-time and shorter felling-time per tree
Ribosome Rescue and Translation Termination at Non-Standard Stop Codons by ICT1 in Mammalian Mitochondria
Release factors (RFs) govern the termination phase of protein synthesis. Human
mitochondria harbor four different members of the class 1 RF family:
RF1Lmt/mtRF1a, RF1mt, C12orf65 and ICT1. The homolog of the essential ICT1
factor is widely distributed in bacteria and organelles and has the peculiar
feature in human mitochondria to be part of the ribosome as a ribosomal
protein of the large subunit. The factor has been suggested to rescue stalled
ribosomes in a codon-independent manner. The mechanism of action of this
factor was obscure and is addressed here. Using a homologous mitochondria
system of purified components, we demonstrate that the integrated ICT1 has no
rescue activity. Rather, purified ICT1 binds stoichiometrically to
mitochondrial ribosomes in addition to the integrated copy and functions as a
general rescue factor, i.e. it releases the polypeptide from the peptidyl tRNA
from ribosomes stalled at the end or in the middle of an mRNA or even from
non-programmed ribosomes. The data suggest that the unusual termination at a
sense codon (AGA/G) of the oxidative-phosphorylation enzymes CO1 and ND6 is
also performed by ICT1 challenging a previous model, according to which
RF1Lmt/mtRF1a is responsible for the translation termination at non-standard
stop codons. We also demonstrate by mutational analyses that the unique
insertion sequence present in the N-terminal domain of ICT1 is essential for
peptide release rather than for ribosome binding. The function of RF1mt,
another member of the class1 RFs in mammalian mitochondria, was also examined
and is discussed
The effect of administration order of BU and CY on toxicity in hematopoietic SCT in humans
Universidade Federal de São Paulo, Div Bone Marrow Transplantat, São Paulo, BrazilUniversidade Federal de São Paulo, Div Bone Marrow Transplantat, São Paulo, BrazilWeb of Scienc
A Comparative Astrochemical Study Of The High-Mass Protostellar Objects NGC 7538 IRS 9 and IRS 1
We report the results of a spectroscopic study of the high-mass protostellar
object NGC 7538 IRS 9 and compare our observations to published data on the
nearby object NGC 7538 IRS 1. Both objects originated in the same molecular
cloud and appear to be at different points in their evolutionary histo- ries,
offering an unusual opportunity to study the temporal evolution of envelope
chemistry in objects sharing a presumably identical starting composition.
Observations were made with the Texas Echelon Cross Echelle Spectrograph
(TEXES), a sensitive, high spectral resolution (R = {\lambda}/{\Delta}{\lambda}
\simeq 100,000) mid-infrared grating spectrometer. Forty-six individual lines
in vibrational modes of the molecules C2H2, CH4, HCN, NH3 and CO were detected,
including two isotopologues (13CO, 12C18O) and one combination mode ({\nu}4 +
{\nu}5 C2H2). Fitting synthetic spectra to the data yielded the Doppler shift,
excitation temperature, Doppler b parameter, column density and covering factor
for each molecule observed; we also computed column density upper limits for
lines and species not detected, such as HNCO and OCS. We find differences among
spectra of the two objects likely attributable to their differing radiation and
thermal environments. Temperatures and column densities for the two objects are
generally consistent, while the larger line widths toward IRS 9 result in less
saturated lines than those toward IRS 1. Finally, we compute an upper limit on
the size of the continuum-emitting region (\sim2000 AU) and use this constraint
and our spectroscopy results to construct a schematic model of IRS 9.Comment: 23 pages, 15 figures, 6 tables; accepted for publication in Ap
The Formaldehyde Masers in NGC 7538 and G29.96-0.02: VLBA, MERLIN, and VLA Observations
The 6 cm formaldehyde (H2CO) maser sources in the compact HII regions NGC
7538-IRS1 and G29.96-0.02 have been imaged at high resolution (beams < 50 mas).
Using the VLBA and MERLIN, we find the angular sizes of the NGC 7538 masers to
be ~10 mas (30 AU) corresponding to brightness temperatures ~10^8 K. The
angular sizes of the G29.96-0.02 masers are ~20 mas (130 AU) corresponding to
brightness temperatures ~10^7 K. Using the VLA, we detect 2 cm formaldehyde
absorption from the maser regions. We detect no emission in the 2 cm line,
indicating the lack of a 2 cm maser and placing limits on the 6 cm excitation
process. We find that both NGC 7538 maser components show an increase in
intensity on 5-10 year timescales while the G29.96-0.02 masers show no
variability over 2 years. A search for polarization provides 3-sigma upper
limits of 1% circularly polarized and 10% linearly polarized emission in NGC
7538 and of 15% circularly polarized emission in G29.96-0.02. A pronounced
velocity gradient of 28 km/s/arcsecond (1900 km/s/pc) is detected in the NGC
7538 maser gas.Comment: accepted to ApJ, 15 figures, 11 table
Outflows from the high-mass protostars NGC 7538 IRS1/2 observed with bispectrum speckle interferometry -- Signatures of flow precession
NGC 7538 IRS1 is a high-mass (approx. 30 M_sun) protostar with a CO outflow,
an associated UCHII region, and a linear methanol maser structure, which might
trace a Keplerian-rotating circumstellar disk. The directions of the various
associated axes are misaligned with each other. We investigate the
near-infrared morphology of the source to clarify the relations among the
various axes. K'-band bispectrum speckle interferometry was performed at two
6-meter-class telescopes -- the BTA 6m telescope and the 6.5m MMT.
Complementary IRAC images from the Spitzer Space Telescope Archive were used to
relate the structures detected with the outflow at larger scales. High-dynamic
range images show fan-shaped outflow structure in which we detect 18 stars and
several blobs of diffuse emission. We interpret the misalignment of various
outflow axes in the context of a disk precession model, including numerical
hydrodynamic simulations of the molecular emission. The precession period is
approx. 280 years and its half-opening angle is 40 degrees. A possible
triggering mechanism is non-coplanar tidal interaction of an (undiscovered)
close companion with the circumbinary protostellar disk. Our observations
resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with
separation of 195 mas. We find indications for shock interaction between the
outflow activities in IRS1 and IRS2. Indications of outflow precession have
been discovered to date in a number of massive protostars, all with large
precession angles 20--45 degrees. This might explain the difference between the
outflow widths in low- and high-mass stars and add support to a common
collimation mechanism.Comment: 20 pages; 8 figures; Accepted by A&A on April 10, 2006; Image quality
reduced due to astro-ph file size limitations; Please download a version with
high-quality images from
http://www.mpifr-bonn.mpg.de/staff/tpreibis/ngc7538.pd
Low Velocity Ionized Winds from Regions Around Young O Stars
We have observed seven ultracompact HII regions in hydrogen recombination
lines in the millimeter band. Toward four of these regions, there is a high
velocity (full width to half maximum 60-80 km/s) component in the line
profiles. The high velocity gas accounts for 35-70% of the emission measure
within the beam. We compare these objects to an additional seven similar
sources we have found in the literature. The broad recombination line objects
(BRLOs) make up about 30% of all sources in complexes containing ultracompact
HII regions. Comparison of spectral line and continuum data implies that the
BRLOs coincide with sources with rising spectral indices, >=0.4 up to 100 GHz.
Both the number of BRLOs and their frequency of occurrence within HII region
complexes, when coupled with their small size and large internal motions, mean
that the apparent contradiction between the dynamical and population lifetimes
for BRLOs is even more severe than for ultracompact HII regions. We evaluate a
number of models for the origin of the broad recombination line emission. The
lifetime, morphology, and rising spectral index of the sources argue for photo-
evaporated disks as the cause for BRLOs. Existing models for such regions,
however, do not account for the large amounts of gas observed at supersonic
velocities.Comment: 36 pages, 8 figure
A near-infrared study of the NGC 7538 star forming region
We present sub-arcsecond (FWHM ~ 0".7), NIR JHKs-band images and a high
sensitivity radio continuum image at 1280 MHz, using SIRIUS on UH 88-inch
telescope and GMRT. The NIR survey covers an area of ~ 24 arcmin^2 with
10-sigma limiting mags of ~ 19.5, 18.4, and 17.3 in J, H, and Ks-band,
respectively. Our NIR images are deeper than any JHK surveys to date for the
larger area of NGC 7538 star forming region. We construct JHK CC and J-H/J and
H-K/K CM diagrams to identify YSOs and to estimate their masses. Based on these
CC and CM diagrams, we identified a rich population of YSOs (Class I and Class
II), associated with the NGC 7538 region. A large number of red sources (H-K >
2) have also been detected around NGC 7538. We argue that these red stars are
most probably PMS stars with intrinsic color excesses. Most of YSOs in NGC 7538
are arranged from the N-W toward S-E regions, forming a sequence in age: the
diffuse H II region (N-W, oldest: where most of the Class II and Class I
sources are detected); the compact IR core (center); and the regions with the
extensive IR reflection nebula and a cluster of red young stars (S-E and S). We
find that the slope of the KLF of NGC 7538 is lower than the typical values
reported for the young embedded clusters, although equally low values have also
been reported in the W3 Main star forming region. From the slope of the KLF and
the analysis by Megeath et al. (1996), we infer that the embedded stellar
population is comprised of YSOs with an age of ~ 1 Myr. Based on the comparison
between models of PMS stars with the observed CM diagram we find that the
stellar population in NGC 7538 is primarily composed of low mass PMS stars
similar to those observed in the W3 Main star forming region.Comment: 36 pages, 13 figures in JPEG format. Accepted for the publication in
ApJ. Report is also available at : http://www.tifr.res.in/~ojha/NGC7538.htm
Intersubject and intrasubject variability of potential plasma and urine metabolite and protein biomarkers in healthy human volunteers
A limited understanding of intersubject and intrasubject variability hampers effective biomarker translation from in vitro/in vivo studies to clinical trials and clinical decision support. Specifically, variability of biomolecule concentration can play an important role in interpretation, power analysis, and sampling time designation. In the present study, a wide range of 749 plasma metabolites, 62 urine biogenic amines, and 1,263 plasma proteins were analyzed in 10 healthy male volunteers measured repeatedly during 12 hours under tightly controlled conditions. Three variability components in relative concentration data are determined using linear mixed models: between (intersubject), time (intrasubject), and noise (intrasubject). Biomolecules such as 3-carboxy-4-methyl-5-propyl-2-furanpropanoate, platelet-derived growth factor C, and cathepsin D with low noise potentially detect changing conditions within a person. If also the between component is low, biomolecules can easier differentiate conditions between persons, for example cathepsin D, CD27 antigen, and prolylglycine. Variability over time does not necessarily inhibit translatability, but requires choosing sampling times carefully.Analytical BioScience
The free energy of NOAA active region AR 11029
The NOAA active region AR 11029 was a small but highly active sunspot region
which produced 73 GOES soft X-ray flares. The flares appear to show a departure
from the well known power-law frequency-size distribution. Specifically, too
few GOES C-class and no M-class flares were observed by comparison with a
power-law distribution (Wheatland in Astrophys. J. 710, 1324, 2010). This was
conjectured to be due to the region having insufficient magnetic energy to
power large events. We construct nonlinear force-free extrapolations of the
coronal magnetic field of active region AR 11029 using data taken on 24 October
by the SOLIS Vector-SpectroMagnetograph (SOLIS/VSM), and data taken on 27
October by the Hinode Solar Optical Telescope SpectroPolarimeter (Hinode/SP).
Force-free modeling with photospheric magnetogram data encounters problems
because the magnetogram data are inconsistent with a force-free model, and we
employ a recently developed `self-consistency' procedure which addresses this
and accommodates uncertainties in the boundary data (Wheatland and Regnier in
Astrophys. J. 700, L88, 2009). We calculate the total energy and free energy of
the self-consistent solution and find that the free energy was 4x10^29 erg on
24 October, and 7x10^31 erg on 27 October. An order of magnitude scaling
between RHESSI non-thermal energy and GOES peak X-ray flux is established from
a sample of flares from the literature and is used to estimate flare energies
from observed GOES peak X-ray flux. Based on the scaling, we conclude that the
estimated free energy of AR 11029 on 27 October when the flaring rate peaked is
sufficient to power M-class or X-class flares, and hence the modeling does not
appear to support the hypothesis that the absence of large flares is due to the
region having limited energy.Comment: Accepted for publication in Solar Physic
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