82 research outputs found
Molecular Hydrogen Kinematics in Cepheus A
We present the radial velocity structure of the molecular hydrogen outflows
associated to the star forming region Cepheus A. This structure is derived from
doppler shift of the H_2 v=1-0 S(1) emission line obtained by Fabry-Perot
spectroscopy. The East and West regions of emission, called Cep A(E) and Cep
A(W), show radial velocities in the range -20 to 0 km/s with respect to the
molecular cloud. Cep A(W) shows an increasing velocity with position offset
from the core indicating the existence of a possible accelarating machanism.
Cep A(E) has an almost constant mean radial velocity of -18 km/s along the
region although with a large dispersion in velocity, indicating the possibility
of a turbulent outflow. A detailed analysis of the Cep A(E) region shows
evidence for the presence of a Mach disk on that outflow. Also, we argue that
the presence of a velocity gradient in Cep A(W) is indicative of a C-shock in
this region. Following Riera et al. (2003), we analyzed the data using wavelet
analysis to study the line width and the central radial velocity distributions.
We found that both outflows have complex spatial and velocity structures
characteristic of a turbulent flow.Comment: 24 pages, 15 figure
Dynamic proteomic profiling of a unicellular cyanobacterium Cyanothece ATCC51142 across light-dark diurnal cycles
<p>Abstract</p> <p>Background</p> <p>Unicellular cyanobacteria of the genus <it>Cyanothece </it>are recognized for their ability to execute nitrogen (N<sub>2</sub>)-fixation in the dark and photosynthesis in the light. An understanding of these mechanistic processes in an integrated systems context should provide insights into how <it>Cyanothece </it>might be optimized for specialized environments and/or industrial purposes. Systems-wide dynamic proteomic profiling with mass spectrometry (MS) analysis should reveal fundamental insights into the control and regulation of these functions.</p> <p>Results</p> <p>To expand upon the current knowledge of protein expression patterns in <it>Cyanothece </it>ATCC51142, we performed quantitative proteomic analysis using partial ("unsaturated") metabolic labeling and high mass accuracy LC-MS analysis. This dynamic proteomic profiling identified 721 actively synthesized proteins with significant temporal changes in expression throughout the light-dark cycles, of which 425 proteins matched with previously characterized cycling transcripts. The remaining 296 proteins contained a cluster of proteins uniquely involved in DNA replication and repair, protein degradation, tRNA synthesis and modification, transport and binding, and regulatory functions. Functional classification of labeled proteins suggested that proteins involved in respiration and glycogen metabolism showed increased expression in the dark cycle together with nitrogenase, suggesting that N<sub>2</sub>-fixation is mediated by higher respiration and glycogen metabolism. Results indicated that <it>Cyanothece </it>ATCC51142 might utilize alternative pathways for carbon (C) and nitrogen (N) acquisition, particularly, aspartic acid and glutamate as substrates of C and N, respectively. Utilization of phosphoketolase (PHK) pathway for the conversion of xylulose-5P to pyruvate and acetyl-P likely constitutes an alternative strategy to compensate higher ATP and NADPH demand.</p> <p>Conclusion</p> <p>This study provides a deeper systems level insight into how <it>Cyanothece </it>ATCC51142 modulates cellular functions to accommodate photosynthesis and N<sub>2</sub>-fixation within the single cell.</p
The Physical Conditions for Massive Star Formation: Dust Continuum Maps and Modeling
Fifty-one dense cores associated with water masers were mapped at 350 micron.
These cores are very luminous, 10^3 < Lbol/Lsun < 10^6, indicative of the
formation of massive stars. Dust continuum contour maps and photometry are
presented for these sources. The spectral energy distributions and normalized
radial profiles of dust continuum emission were modeled for 31 sources using a
one-dimensional dust radiative transfer code, assuming a power law density
distribution in the envelope, n = n_f (r/r_f)^{-p}. The best fit density power
law exponent, p, ranged from 0.75 to 2.5 with = 1.8 +/- 0.4. The mean value
of p is comparable to that found in regions forming only low mass stars. The
mean p is incompatible with a logatropic sphere (p = 1), but other star
formation models cannot be ruled out. Different mass estimates are compared and
mean masses of gas and dust are reported within a half-power radius determined
from the dust emission and within a radius where the total density exceeds 10^4
cm^3. Evolutionary indicators commonly used for low mass star formation may
have some utility for regions forming massive stars. For comparison with
extragalactic star formation studies, the luminosity to dust mass ratio is
calculated for these sources with a method most parallel to that used in
studies of distant galaxies and is found to be similar to that seen in high
redshift starburst galaxies.Comment: 45 pages, 20 figures, accepted to ApJ Supplemen
Biological Interactions and Dynamics Science Theme Advisory Panel (BID-STAP)
This report contains the charge to the panel, the panel's discussions and panel recommendations
Mortality and causes of death among asylum seekers in the Netherlands, 2002-2005
Background The world's growing population of asylum seekers faces different health risks from the populations of their host countries because of risk factors before and after migration. There is a current lack of insight into their health status. Methods A unique notification system was designed to monitor mortality in Dutch asylum seeker centres (2002-2005). Results Standardised for age and sex, overall mortality among asylum seekers shows no difference from the Dutch population. However, it differs between subpopulations by sex, age and region of origin and by cause of death. Mortality among asylum seekers is higher than among the Dutch reference population at younger ages and lower at ages above 40. The most common causes of death among asylum seekers are cancer, cardiovascular diseases and external causes. Increased mortality was found from infectious diseases (males, standardised mortality ratio (SMR)=5.44 (95% CI 3.22 to 8.59); females, SMR=7.53 (95% CI 4.22 to 12.43)), external causes (males, SMR=1.95 (95% CI 0.52 to 2.46); females SMR=1.60 (95% CI 0.87 to 2.68)) and congenital anomalies in females (SMR 2.42; 95% CI 1.16 to 4.45). Considerable differences were found between regions of origin. Maternal mortality was increased (rate ratio 10.08; 95% CI 8.02 to 12.83) as a result of deaths among African women. Conclusion Certain subgroups of asylum seekers (classified by age, sex and region of origin) are at increased risk of certain causes of death compared with the host population. Policies and services for asylum seekers should address both causes for which asylum seekers are at increased risk and causes with large absolute mortality, taking into account differences between subgroup
- …