4,587 research outputs found
Neural ODEs as a discovery tool to characterize the structure of the hot galactic wind of M82
Dynamic astrophysical phenomena are predominantly described by differential
equations, yet our understanding of these systems is constrained by our
incomplete grasp of non-linear physics and scarcity of comprehensive datasets.
As such, advancing techniques in solving non-linear inverse problems becomes
pivotal to addressing numerous outstanding questions in the field. In
particular, modeling hot galactic winds is difficult because of unknown
structure for various physical terms, and the lack of \textit{any} kinematic
observational data. Additionally, the flow equations contain singularities that
lead to numerical instability, making parameter sweeps non-trivial. We leverage
differentiable programming, which enables neural networks to be embedded as
individual terms within the governing coupled ordinary differential equations
(ODEs), and show that this method can adeptly learn hidden physics. We robustly
discern the structure of a mass-loading function which captures the physical
effects of cloud destruction and entrainment into the hot superwind. Within a
supervised learning framework, we formulate our loss function anchored on the
astrophysical entropy (). Our results demonstrate the
efficacy of this approach, even in the absence of kinematic data . We then
apply these models to real Chandra X-Ray observations of starburst galaxy M82,
providing the first systematic description of mass-loading within the
superwind. This work further highlights neural ODEs as a useful discovery tool
with mechanistic interpretability in non-linear inverse problems. We make our
code public at this GitHub repository
(https://github.com/dustindnguyen/2023_NeurIPS_NeuralODEs_M82).Comment: 9 Pages, 2 Figures, Accepted at the NeurIPS 2023 workshop on Machine
Learning and the Physical Science
Streptomycin-induced inflammation enhances Escherichia coli gut colonization through nitrate respiration.
UnlabelledTreatment with streptomycin enhances the growth of human commensal Escherichia coli isolates in the mouse intestine, suggesting that the resident microbial community (microbiota) can inhibit the growth of invading microbes, a phenomenon known as "colonization resistance." However, the precise mechanisms by which streptomycin treatment lowers colonization resistance remain obscure. Here we show that streptomycin treatment rendered mice more susceptible to the development of chemically induced colitis, raising the possibility that the antibiotic might lower colonization resistance by changing mucosal immune responses rather than by preventing microbe-microbe interactions. Investigation of the underlying mechanism revealed a mild inflammatory infiltrate in the cecal mucosa of streptomycin-treated mice, which was accompanied by elevated expression of Nos2, the gene that encodes inducible nitric oxide synthase. In turn, this inflammatory response enhanced the luminal growth of E. coli by nitrate respiration in a Nos2-dependent fashion. These data identify low-level intestinal inflammation as one of the factors responsible for the loss of resistance to E. coli colonization after streptomycin treatment.ImportanceOur intestine is host to a complex microbial community that confers benefits by educating the immune system and providing niche protection. Perturbation of intestinal communities by streptomycin treatment lowers "colonization resistance" through unknown mechanisms. Here we show that streptomycin increases the inflammatory tone of the intestinal mucosa, thereby making the bowel more susceptible to dextran sulfate sodium treatment and boosting the Nos2-dependent growth of commensal Escherichia coli by nitrate respiration. These data point to the generation of alternative electron acceptors as a by-product of the inflammatory host response as an important factor responsible for lowering resistance to colonization by facultative anaerobic bacteria such as E. coli
X-ray Properties of NGC 253's Starburst-Driven Outflow
We analyze image and spectral data from 365~ks of observations from
the {\it Chandra} X-ray Observatory of the nearby, edge-on starburst galaxy
NGC~253 to constrain properties of the hot phase of the outflow. We focus our
analysis on the 1.1 to 0.63 kpc region of the outflow and define several
regions for spectral extraction where we determine best-fit temperatures and
metal abundances. We find that the temperatures and electron densities peak in
the central 250 pc region of the outflow and decrease with distance.
These temperature and density profiles are in disagreement with an adiabatic
spherically expanding starburst wind model and suggest the presence of
additional physics such as mass loading and non-spherical outflow geometry. Our
derived temperatures and densities yield few-Myr cooling times in the nuclear
region, which may imply that the hot gas can undergo bulk radiative cooling as
it escapes along the minor axis. Our metal abundances of O, Ne, Mg, Si, S, and
Fe all peak in the central region and decrease with distance along the outflow,
with the exception of Ne which maintains a flat distribution. The metal
abundances indicate significant dilution outside of the starburst region. We
also find estimates on the mass outflow rates which are
in the northern outflow and
in the southern outflow. Additionally, we detect emission from charge exchange
and find it has a significant contribution (\%) to the total broad-band
(~keV) X-ray emission in the central and southern regions of the
outflow.Comment: 15 pages, 9 figure
Sustainable livestock systems for high-producing animals
National audienc
Avifauna en un area perturbada del bosque andino en el parque nacional natural Farallones de Cali, corregimiento de Pance, Valle del Cauca (Colombia)
El presente conjunto de datos en el formato de archivo Darwin Core incluye información del monitoreo de la avifauna en un área perturbada del Parque Nacional Natural Farallones de Cali. Con el objetivo de caracterizar y determinar la composición y estructura de la avifauna, se llevaron a cabo censos visuales desde agosto 2008 hasta julio 2009 en las localidades de El Topacio y El Pato en recorridos de 2 km de longitud, a elevaciones entre 1550 y 1800 m s.n.m. En total se hicieron 2363 registros de 157 especies de aves, pertenecientes a 41 familias y
19 órdenes. Se observaron 12 especies nuevas para el área, 10 de las cuales son aves propias de áreas abiertas. Nueve especies que habían sido registradas en El Topacio en 1978, no lo fueron en el presente estudio y en consecuencia se consideran extintas y vulnerables localmente, lo cual ilustra y ratifica cómo el reemplazo de los hábitats naturales por potreros, la fragmentación y el efecto de borde afectan negativamente las comunidades de aves en áreas protegidas.This dataset in Darwin Core Archive format includes monitoring information about bird life in a disturbed area of the Farallones de Cali National Natural Park. Aiming to characterize and determine the composition and structure of bird life, visual censuses were carried out from August 2008 to July 2009 at both the El Pato and the El Topacio localities along line census of 2 km and from elevations between1550 to 1800 m a.s.l. A total of 2363 records were obtained of 157 species of 41 families and 19 orders. Twelve were new records for the area, 10 of which are common in open areas. Nine species previously recorded in 1978 at El Topacio were absent and considered locally extinct and vulnerable. This illustrates how the replacement of natural habitats with pasturelands, as well as fragmentation and border effect affect negatively bird communities in protected areas.Fil: Bermudez Vera, Julio Cesar . Universidad del Valle. Departamento de Biología; ColombiaFil: Duque Lopez, Juan Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagónicas; ArgentinaFil: Sanchez Martinez, Manuel A. . Universidad del Valle. Departamento de Biología; ColombiaFil: Tenorio, Elkin . Calima - Fundación para la Investigación de la Biodiversidad y Conservación en el Trópico; Colombi
Influence of Chemical Enhancers and Iontophoresis on the In Vitro Transdermal Permeation of Propranolol: Evaluation by Dermatopharmacokinetics
[EN] The aims of this study were to assess, in vitro, the possibility of administering propranolol transdermally and to evaluate the usefulness of the dermatopharmacokinetic (DPK) method in assessing the transport of drugs through stratum corneum, using propranolol as a model compound. Four chemical enhancers (decenoic and oleic acid, laurocapram, and R-(+)-limonene) and iontophoresis at two current densities, 0.25 and 0.5 mA/cm(2) were tested. R-(+)-limonene, and iontophoresis at 0.5 mA/cm(2) were proven to be the most efficient in increasing propranolol transdermal flux, both doubled the original propranolol transdermal flux. Iontophoresis was demonstrated to be superior than the chemical enhancer because it allowed faster delivery of the drug. The DPK method was sufficiently sensitive to detect subtle vehicle-induced effects on the skin permeation of propranolol. The shorter duration of these experiments and their ability to provide mechanistic information about partition between vehicle and skin and diffusivity through skin place them as practical and potentially insightful approach to quantify and, ultimately, optimize topical bioavailability.This research was funded by Ministerio de Ciencia e Innovación (AP2007-03456) and the Universidad CEU Cardenal Herrera.Calatayud-Pascual, M.; Sebastian-Morelló, M.; Balaguer-Fernandez, C.; Delgado-Charro, M.; Lopez-Castellano, A.; Merino Sanjuán, V. (2018). Influence of Chemical Enhancers and Iontophoresis on the In Vitro Transdermal Permeation of Propranolol: Evaluation by Dermatopharmacokinetics. Pharmaceutics. 10(4):1-15. https://doi.org/10.3390/pharmaceutics10040265S11510
High-Precision Measurements of Delta alpha/alpha from QSO Absorption Spectra
Precise radial velocity measurements (delta v/c ~ 10^{-7}) of FeII lines in
damped Ly-alpha systems from very high quality VLT/UVES spectra of quasars
HE0515-4414 and Q1101-264 are used to probe cosmological time dependence of the
fine structure constant, alpha. It is found that between two redshifts z1 =
1.15 and z2 = 1.84 the value of Delta alpha/alpha changes at the level of a few
ppm: (alpha_z2 - alpha_z1)/alpha_0 = 5.43 +/- 2.52 ppm. Variations of alpha can
be considered as one of the most reliable method to constrain the dark energy
equation of state and improvements on the accuracy of the wavelength
calibration of QSO spectra are of great importance.Comment: 4 pages, 2 figures, Invited contribution to the proceedings of
"Precision Spectroscopy in Astrophysics", Aveiro, Portugal, 11-15 Sep. 2006,
eds. L. Pasquini, M. Romaniello and N. C. Santos (Springer-Verlag series "ESO
Astrophysics Symposia"
Subcellular spatial resolution achieved for deep-brain imaging in vivo using a minimally invasive multimode fiber
Achieving intravital optical imaging with diffraction-limited spatial resolution of deep-brain structures represents an important step toward the goal of understanding the mammalian central nervous system1,2,3,4. Advances in wavefront-shaping methods and computational power have recently allowed for a novel approach to high-resolution imaging, utilizing deterministic light propagation through optically complex media and, of particular importance for this work, multimode optical fibers (MMFs)5,6,7. We report a compact and highly optimized approach for minimally invasive in vivo brain imaging applications. The volume of tissue lesion was reduced by more than 100-fold, while preserving diffraction-limited imaging performance utilizing wavefront control of light propagation through a single 50-μm-core MMF. Here, we demonstrated high-resolution fluorescence imaging of subcellular neuronal structures, dendrites and synaptic specializations, in deep-brain regions of living mice, as well as monitored stimulus-driven functional Ca2+ responses. These results represent a major breakthrough in the compromise between high-resolution imaging and tissue damage, heralding new possibilities for deep-brain imaging in vivo
On the difference of torus geometry between hidden and non-hidden broad line active galactic nuclei
We present results from the fitting of infrared (IR) spectral energy
distributions of 21 active galactic nuclei (AGN) with clumpy torus models. We
compiled high spatial resolution (-- arcsec) mid-IR -band
spectroscopy, -band imaging and nuclear near- and mid-IR photometry from the
literature. Combining these nuclear near- and mid-IR observations, far-IR
photometry and clumpy torus models, enables us to put constraints on the torus
properties and geometry. We divide the sample into three types according to the
broad line region (BLR) properties; type-1s, type-2s with scattered or hidden
broad line region (HBLR) previously observed, and type-2s without any published
HBLR signature (NHBLR). Comparing the torus model parameters gives us the first
quantitative torus geometrical view for each subgroup. We find that NHBLR AGN
have smaller torus opening angles and larger covering factors than those of
HBLR AGN. This suggests that the chance to observe scattered (polarized) flux
from the BLR in NHBLR could be reduced by the dual effects of (a) less
scattering medium due to the reduced scattering volume given the small torus
opening angle and (b) the increased torus obscuration between the observer and
the scattering region. These effects give a reasonable explanation for the lack
of observed HBLR in some type-2 AGN.Comment: 13 pages, 5 figures, accepted for publication in Ap
A nearly symmetric double-image gravitational lens
We report the discovery of a new double-image gravitational lens resulting
from our search for lenses in the southern sky. Radio source PMN J2004-1349 is
composed of two compact components separated by 1.13 arcseconds in VLA, MERLIN
and VLBA images. The components have a flux ratio of 1:1 at radio frequencies
ranging from 5 GHz to 22 GHz. The I-band optical counterpart is also an equal
double, with roughly the same separation and position angle as the radio
double. Upon subtraction of the components from the I-band image, we identify a
dim pattern of residuals as the lens galaxy. While the present observations are
sufficient to establish that J2004-1349 is a gravitational lens, additional
information will be necessary (such as the redshifts of the galaxy and quasar,
and precise astrometry and photometry of the lens galaxy) before constructing
detailed mass models.Comment: 17 pp., 5 bitmapped figs. (contact [email protected] for nicer figs), in
press, A.J. (substantially revised
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