351 research outputs found
Spitzer IRAC Detection and Analysis of Shocked Molecular Hydrogen Emission
We use statistical equilibrium equations to investigate the IRAC color space
of shocked molecular hydrogen. The location of shocked H_2 in [3.6]-[4.5] vs
[4.5]-[5.8] color is determined by the gas temperature and density of neutral
atomic hydrogen. We find that high excitation H_2 emission falls in a unique
location in the color-color diagram and can unambiguously be distinguished from
stellar sources. In addition to searching for outflows, we show that the IRAC
data can be used to map the thermal structure of the shocked gas. We analyze
archival Spitzer data of Herbig-Haro object HH 54 and create a temperature map,
which is consistent with spectroscopically determined temperatures.Comment: 4 page, 3 figures, accepted for publication in ApJ Letter
The Engagement Model of Person-Environment Interaction
This article focuses on growth-promoting aspects in the environment, and the authors propose a strength-based, dynamic model of person-environment interaction. The authors begin by briefly discussing the typical recognition of contextual variables in models that rely on the concept of person-environment fit. This is followed by a review of recent approaches to incorporating positive environmental factors in conceptualizations of human functioning. These approaches lead to an alternative model of person-environment interaction in which the engagement construct (i.e., the quality of a person-environment relationship determined by the extent to which negotiation, participation, and evaluation processes occur during the interaction) replaces the static notion of fit. Finally, the authors outline recommendations for overcoming environmental neglect in research, practice, and training
The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
Gas in galactic disks is collected by gravitational instabilities into giant
atomic-molecular complexes, but only the inner, molecular parts of these
structures are able to collapse to form stars. Determining what controls the
ratio of atomic to molecular hydrogen in complexes is therefore a significant
problem in star formation and galactic evolution. In this paper we use the
model of H_2 formation, dissociation, and shielding developed in the previous
paper in this series to make theoretical predictions for atomic to molecular
ratios as a function of galactic properties. We find that the molecular
fraction in a galaxy is determined primarily by its column density and
secondarily by its metallicity, and is to good approximation independent of the
strength of the interstellar radiation field. We show that the column of atomic
hydrogen required to shield a molecular region against dissociation is ~10 Msun
pc^-2 at solar metallicity. We compare our model to data from recent surveys of
the Milky Way and of nearby galaxies, and show that the both the primary
dependence of molecular fraction on column density and the secondary dependence
on metallicity that we predict are in good agreement with observed galaxy
properties.Comment: Accepted to ApJ. 22 pages, 13 figures, emulateapj format. This
version corrects a minor error in the binning procedure in section 4.1.2. The
remainder of the paper is unchange
Submillimetre line spectrum of the Seyfert galaxy NGC1068 from the Herschel-SPIRE Fourier Transform Spectrometer
The first complete submillimetre spectrum (190-670um) of the Seyfert 2 galaxy
NGC1068 has been observed with the SPIRE Fourier Transform Spectrometer onboard
the {\it Herschel} Space Observatory. The sequence of CO lines (Jup=4-13),
lines from water, the fundamental rotational transition of HF, two o-H_2O+
lines and one line each from CH+ and OH+ have been detected, together with the
two [CI] lines and the [NII]205um line. The observations in both single
pointing mode with sparse image sampling and in mapping mode with full image
sampling allow us to disentangle two molecular emission components, one due to
the compact circum-nuclear disk (CND) and one from the extended region
encompassing the star forming ring (SF-ring). Radiative transfer models show
that the two CO components are characterized by density of n(H_2)=10^4.5 and
10^2.9 cm^-3 and temperature of T=100K and 127K, respectively. The comparison
of the CO line intensities with photodissociation region (PDR) and X-ray
dominated region (XDR) models, together with other observational constraints,
such as the observed CO surface brightness and the radiation field, indicate
that the best explanation for the CO excitation of the CND is an XDR with
density of n(H_2) 10^4 cm^-3 and X-ray flux of 9 erg s^-1 cm^-2, consistent
with illumination by the active galactic nucleus, while the CO lines in the
SF-ring are better modeled by a PDR. The detected water transitions, together
with those observed with the \her \sim PACS Spectrometer, can be modeled by an
LVG model with low temperature (T_kin \sim 40K) and high density (n(H_2) in the
range 10^6.7-10^7.9 cm^-3).Comment: Accepted for publication on the Astrophysical Journal, 30 August 201
Science Impacts of the SPHEREx All-Sky Optical to Near-Infrared Spectral Survey: Report of a Community Workshop Examining Extragalactic, Galactic, Stellar and Planetary Science
SPHEREx is a proposed SMEX mission selected for Phase A. SPHEREx will carry
out the first all-sky spectral survey and provide for every 6.2" pixel a
spectra between 0.75 and 4.18 m [with R41.4] and 4.18 and 5.00
m [with R135]. The SPHEREx team has proposed three specific science
investigations to be carried out with this unique data set: cosmic inflation,
interstellar and circumstellar ices, and the extra-galactic background light.
It is readily apparent, however, that many other questions in astrophysics and
planetary sciences could be addressed with the SPHEREx data. The SPHEREx team
convened a community workshop in February 2016, with the intent of enlisting
the aid of a larger group of scientists in defining these questions. This paper
summarizes the rich and varied menu of investigations that was laid out. It
includes studies of the composition of main belt and Trojan/Greek asteroids;
mapping the zodiacal light with unprecedented spatial and spectral resolution;
identifying and studying very low-metallicity stars; improving stellar
parameters in order to better characterize transiting exoplanets; studying
aliphatic and aromatic carbon-bearing molecules in the interstellar medium;
mapping star formation rates in nearby galaxies; determining the redshift of
clusters of galaxies; identifying high redshift quasars over the full sky; and
providing a NIR spectrum for most eROSITA X-ray sources. All of these
investigations, and others not listed here, can be carried out with the nominal
all-sky spectra to be produced by SPHEREx. In addition, the workshop defined
enhanced data products and user tools which would facilitate some of these
scientific studies. Finally, the workshop noted the high degrees of synergy
between SPHEREx and a number of other current or forthcoming programs,
including JWST, WFIRST, Euclid, GAIA, K2/Kepler, TESS, eROSITA and LSST.Comment: Report of the First SPHEREx Community Workshop,
http://spherex.caltech.edu/Workshop.html , 84 pages, 28 figure
Quantification of clinically applicable stimulation parameters for precision near-organ neuromodulation of human splenic nerves
Abstract: Neuromodulation is a new therapeutic pathway to treat inflammatory conditions by modulating the electrical signalling pattern of the autonomic connections to the spleen. However, targeting this sub-division of the nervous system presents specific challenges in translating nerve stimulation parameters. Firstly, autonomic nerves are typically embedded non-uniformly among visceral and connective tissues with complex interfacing requirements. Secondly, these nerves contain axons with populations of varying phenotypes leading to complexities for axon engagement and activation. Thirdly, clinical translational of methodologies attained using preclinical animal models are limited due to heterogeneity of the intra- and inter-species comparative anatomy and physiology. Here we demonstrate how this can be accomplished by the use of in silico modelling of target anatomy, and validation of these estimations through ex vivo human tissue electrophysiology studies. Neuroelectrical models are developed to address the challenges in translation of parameters, which provides strong input criteria for device design and dose selection prior to a first-in-human trial
Deltaproteobacteria (Pelobacter) and Methanococcoides are responsible for choline-dependent methanogenesis in a coastal saltmarsh sediment
Coastal saltmarsh sediments represent an important source of natural methane emissions, much of which originates from quaternary and methylated amines, such as choline and trimethylamine. In this study, we combine DNA stable isotope probing with high throughput sequencing of 16S rRNA genes and 13C2-choline enriched metagenomes, followed by metagenome data assembly, to identify the key microbes responsible for methanogenesis from choline. Microcosm incubation with 13C2-choline leads to the formation of trimethylamine and subsequent methane production, suggesting that choline-dependent methanogenesis is a two-step process involving trimethylamine as the key intermediate. Amplicon sequencing analysis identifies Deltaproteobacteria of the genera Pelobacter as the major choline utilizers. Methanogenic Archaea of the genera Methanococcoides become enriched in choline-amended microcosms, indicating their role in methane formation from trimethylamine. The binning of metagenomic DNA results in the identification of bins classified as Pelobacter and Methanococcoides. Analyses of these bins reveal that Pelobacter have the genetic potential to degrade choline to trimethylamine using the choline-trimethylamine lyase pathway, whereas Methanococcoides are capable of methanogenesis using the pyrrolysine-containing trimethylamine methyltransferase pathway. Together, our data provide a new insight on the diversity of choline utilizing organisms in coastal sediments and support a syntrophic relationship between Bacteria and Archaea as the dominant route for methanogenesis from choline in this environment
Recombinant human complement component C2 produced in a human cell line restores the classical complement pathway activity in-vitro: an alternative treatment for C2 deficiency diseases
Background: Complement C2 deficiency is the most common genetically determined complete complement deficiency and is associated with a number of diseases. Most prominent are the associations with recurrent serious infections in young children and the development of systemic lupus erythematosus (SLE) in adults. The links with these diseases reflect the important role complement C2 plays in both innate immunity and immune tolerance. Infusions with normal fresh frozen plasma for the treatment of associated disease have demonstrated therapeutic effects but so far protein replacement therapy has not been evaluated. Results: Human complement C2 was cloned and expressed in a mammalian cell line. The purity of recombinant human C2 (rhC2) was greater than 95% and it was characterized for stability and activity. It was sensitive to C1s cleavage and restored classical complement pathway activity in C2-deficient serum both in a complement activation ELISA and a hemolytic assay. Furthermore, rhC2 could increase C3 fragment deposition on the human pathogen Streptococcus pneumoniae in C2-deficient serum to levels equal to those with normal serum. Conclusions: Taken together these data suggest that recombinant human C2 can restore classical complement pathway activity and may serve as a potential therapeutic for recurring bacterial infections or SLE in C2-deficient patients
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