2,208 research outputs found
Imaging spontaneous imbibition in full Darcyâscale samples at poreâscale resolution by fast Xâray tomography
Spontaneous imbibition is a process occurring in a porous medium which describes wetting phase replacing nonwetting phase spontaneously due to capillary forces. This process is conventionally investigated by standardized, well-established spontaneous imbibition tests. In these tests, for instance, a rock sample is surrounded by wetting fluid. The following cumulative production of nonwetting phase versus time is used as a qualitative measure for wettability. However, these test results are difficult to interpret, because many rocks do not show a homogeneous but a mixed wettability in which the wetting preference of a rock varies from location to location. Moreover, during the test the flow regime typically changes from countercurrent to cocurrent flow and no phase pressure or pressure drop can be recorded. To help interpretation, we complement Darcy-scale production curves with X-ray imaging to describe the differences in imbibition processes between water-wet and mixed-wet systems. We found that the formation of a spontaneous imbibition front occurs only for water-wet systems; mixed-wet systems show localized imbibition events only. The asymmetry of the front depends on the occurrence of preferred production sites, which influences interpretation. Fluid layers on the outside of mixed-wet samples increase connectivity of the drained phase and the effect of buoyancy on spontaneous imbibition. The wider implication of our study is the demonstration of the capability of benchtop laboratory equipment to image a full Darcy-scale experiment while at the same time obtaining pore-scale information, resolving the natural length and time scale of the underlying processes
Syndrome de Miller Fisher avec anticorps anti GQ1b nĂ©gatif au cours dâune pneumonie Ă Mycoplasma pneumoniae
Le Syndrome de Miller Fisher est caractĂ©risĂ© par l'association d'une ophtalmoplĂ©gie, d'une ataxie et d'une arĂ©flexie ostĂ©o-tendineuse. Une infection virale est le plus souvent retrouvĂ©e dans les jours ou semaines qui prĂ©cĂšdent la symptomatologie. Nous rapportons un cas de syndrome de Miller Fisher survenu chez une femme de 75 ans, et ce au dĂ©cours d'une infection pulmonaire Ă Mycoplasma pneumoniae. Les sĂ©rologies virales habituelles Ă©taient nĂ©gatives. Les anticorps anti GQ1b Ă©taient absents. Il n'y avait pas de lĂ©sion du tronc cĂ©rĂ©bral Ă l'imagerie par rĂ©sonnance magnĂ©tique. L'Ă©volution clinique Ă©tait favorable aprĂšs perfusion d'immunoglobulines humaines polyvalentes et des macrolides en comprimĂ©s. La sĂ©rologie Mycoplasma pneumoniae doit ĂȘtre systĂ©matiquement recherchĂ©e dans le bilan du syndrome de Miller Fisher.Key words: Syndrome de Miller Fisher, Mycoplasma pneumoniae, ganglioside GQ1
ALMA reveals the feeding of the Seyfert 1 nucleus in NGC 1566
We report ALMA observations of CO(3-2) emission in the Seyfert 1 galaxy NGC
1566, at a spatial resolution of 25 pc. Our aim is to investigate the
morphology and dynamics of the gas inside the central kpc, and to probe nuclear
fueling and feedback phenomena. NGC 1566 has a nuclear bar of 1.7 kpc radius
and a conspicuous grand design spiral starting from this radius. The ALMA field
of view, of diameter 0.9 kpc, lies well inside the nuclear bar and reveals a
molecular trailing spiral structure from 50 to 300~pc in size, which is
contributing to fuel the nucleus, according to its negative gravity torques.
The spiral starts with a large pitch angle from the center and then winds up
in a pseudo-ring at the inner Lindblad resonance (ILR) of the nuclear bar.
This is the first time that a trailing spiral structure is clearly seen
driving the gas inwards inside the ILR ring of the nuclear bar. This phenomenon
shows that the massive central black hole has a significant dynamical influence
on the gas, triggering its fueling.
The gaseous spiral is well correlated with the dusty spiral seen through
extinction in HST images, and also with a spiral feature emitting 0.87mm
continuum. This continuum emission must come essentially from cold dust heated
by the interstellar radiation field. The HCN(4-3) and HCO+(4-3) lines were
simultaneously mapped and detected in the nuclear spiral. The HCO+(4-3) line is
3 times stronger than the HCN(4-3), as expected when star formation excitation
dominates over active galactic nucleus (AGN) heating. The CO(3-2)/HCO+(4-3)
integrated intensity ratio is \sim 100.
The molecular gas is in remarkably regular rotation, with only slight
non-circular motions at the periphery of the nuclear spiral arms. These
perturbations are quite small, and no outflow nor AGN feedback is detected.Comment: 11 pages, 16 figures, accepted in Astronomy and Astrophysic
ALMA observations of feeding and feedback in nearby Seyfert galaxies: an AGN-driven outflow in NGC 1433
We report ALMA observations of CO(3-2) emission in the Seyfert 2
double-barred galaxy NGC1433, at the unprecedented spatial resolution of
0.5"=24 pc. Our aim is to probe AGN feeding and feedback phenomena through the
morphology and dynamics of the gas inside the central kpc. The CO map, which
covers the whole nuclear region (nuclear bar and ring), reveals a nuclear
gaseous spiral structure, inside the nuclear ring encircling the nuclear
stellar bar.
This gaseous spiral is well correlated with the dusty spiral seen in Hubble
Space Telescope images. The nuclear spiral winds up in a pseudo-ring at 200 pc
radius, which might correspond to the inner ILR. Continuum emission is detected
at 0.87 mm only at the very centre, and its origin is more likely thermal dust
emission than non-thermal emission from the AGN. It might correspond to the
molecular torus expected to exist in this Seyfert 2 galaxy. The HCN(4-3) and
HCO+(4-3) lines were observed simultaneously, but only upper limits are
derived, with a ratio to the CO(3-2) line lower than 1/60 at 3sigma, indicating
a relatively low abundance of very dense gas. The kinematics of the gas over
the nuclear disk reveal rather regular rotation only slightly perturbed by
streaming motions due to the spiral; the primary and secondary bars are too
closely aligned with the galaxy major or minor axis to leave a signature in the
projected velocities. Near the nucleus, there is an intense high-velocity CO
emission feature redshifted to 200 km/s (if located in the plane), with a
blue-shifted counterpart, at 2" (100 pc) from the centre. While the CO spectra
are quite narrow in the centre, this wide component is interpreted as an
outflow involving a molecular mass of 3.6 10^6 Mo and a flow rate 7 Mo/yr. The
flow could be in part driven by the central star formation, but is mainly
boosted by the AGN through its wind or radio jets.Comment: 11 pages, 9 figures, Accepted in Astronomy and Astrophysic
Derivation of tropospheric methane from TCCON CHâ and HF total column observations
The Total Carbon Column Observing Network (TCCON) is a global ground-based network of Fourier transform spectrometers that produce precise measurements of column-averaged dry-air mole fractions of atmospheric methane (CHâ). Temporal variability in the total column of CHâ due to stratospheric dynamics obscures fluctuations and trends driven by tropospheric transport and local surface fluxes that are critical for understanding CHâ sources and sinks. We reduce the contribution of stratospheric variability from the total column average by subtracting an estimate of the stratospheric CHâ derived from simultaneous measurements of hydrogen fluoride (HF). HF provides a proxy for stratospheric CHâ because it is strongly correlated to CHâ in the stratosphere, has an accurately known tropospheric abundance (of zero), and is measured at most TCCON stations. The stratospheric partial column of CHâ is calculated as a function of the zonal and annual trends in the relationship between CHâ and HF in the stratosphere, which we determine from ACE-FTS satellite data. We also explicitly take into account the CHâ column averaging kernel to estimate the contribution of stratospheric CHâ to the total column. The resulting tropospheric CHâ columns are consistent with in situ aircraft measurements and augment existing observations in the troposphere
Biomass and nutrient dynamics associated with slash fires in neotropical dry forests
Unprecedented rates of deforestation and biomass burning in tropical dry forests are dramatically influencing biogeochemical cycles, resulting in resource depletion, declines in biodiversity, and atmospheric pollution. We quantified the effects of defores- tation and varying levels of slash-fire severity on nutrient losses and redistribution in a second-growth tropical dry forest ("Caatinga") near Serra Talhada, Pernambuco, Brazil. Total aboveground biomass prior to burning was 74 Mg/ha. Nitrogen and phosphorus concentrations were highest in litter, leaves attached to slash, and fine wood debris (<0.64 cm diameter). While these components comprised only 30% of the prefire aboveground biomass, they accounted for -60% of the aboveground pools of N and P. Three experi- mental fires were conducted during the 1989 burning season. In these treatments con- sumption was 78, 88, and 95% of the total aboveground biomass. As much as 96% of the prefire aboveground N and C pools and 56% of the prefire aboveground P pool was lost during combustion processes. Nitrogen losses exceeded 500 kg/ha and P losses exceeded 20 kg/ha in the fires of the greatest severity. With increasing fire severity, the concentrations of N and P in ash decreased while the concentration of Ca increased. This indicates greater amounts of these nutrients were volatilized (i.e., greater ecosystem losses occurred) with increasing fire severity. Following fire, up to 47% of the residual aboveground N and 84% of the residual aboveground P were in the form of ash, which was quickly lost from the site via wind erosion. Fires appeared to have a minor immediate effect on total N, C, or P in the soils. However, soils in forests with no history of cultivation had significantly higher concentrations of C and P than second-growth forests. Based upon the measured losses of nutrients from these single slash-burning events, it would likely require a century
or more of fallow for reaccumulation to occur. However, current fallow periods in this region are 15 yr or less
Seroprevalence of Yersinia, Hepatitis E and Trichinella among migrant and nonmigrant populations in Berlin and Brandenburg (Germany)
Pork is a potential source of infection for Yersinia, Hepatitis E virus and Trichinella. In 2014, 2484 cases of yersiniosis, 671 hepatitis E cases and 1 trichinellosis case were reported in Germany. Although migrants represent 27% of Berlin inhabitants, data is lacking on subpopulation-specific exposure risks to zoonotic diseases. We aimed to estimate the seroprevalence and to identify potential risk factors for Yersinia, Hepatitis E and Trichinella in migrants and non-migrants in Berlin/Brandenburg
High-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1) and (3-2) lines
We present a detailed analysis of high resolution observations of the three
lowest CO transitions in two nearby active galaxies, NGC4569 and NGC4826. The
CO(1-0) and (2-1) lines were observed with the Plateau de Bure Interferometer
and the CO(3-2) line with the Submillimeter Array. Combining these data allows
us to compare the emission in the three lines and to map the line ratios,
R21=I_{CO(2-1)}/I_{CO(1-0)} and R32=I_{CO(3-2)}/I_{CO(1-0)} at a resolution of
~2", i.e., a linear resolution of 160 pc for NGC4569 and 40 pc for NGC4826. In
both galaxies the emission in the three lines is similarly distributed
spatially and in velocity, and CO is less excited (R32<0.6) than in the
Galactic Center or the centers of other active galaxies studied so far.
According to a pseudo-LTE model the molecular gas in NGC4569 is cold and mainly
optically thick in the CO(1-0) and (2-1) lines; less than 50% of the gas is
optically thin in the CO(3-2) line. LVG modeling suggests the presence of an
elongated ring of cold and dense gas coinciding with the ILR of the stellar
bar. More excited gas is resolved in the circumnuclear disk of NGC4826.
According to our pseudo-LTE model this corresponds to warmer gas with a ~50% of
the CO(3-2) emission being optically thin. LVG modeling indicates the presence
of a semicircular arc of dense and cold gas centered on the dynamical center
and ~70 pc in radius. The gas temperature increases and its density decreases
toward the center. A near side/far side asymmetry noticeable in the CO, R32 and
Pa-alpha maps suggests that opacity effects play a role. Examining published CO
maps of nearby active galaxies we find similar asymmetries suggesting that this
could be a common phenomenon in active galaxies. These mainly qualitative
results open new perspectives for the study of active galaxies with the future
Atacama Large Millimeter/submillimeter Array.Comment: accepted for publication in A&
Searching for New Physics Through AMO Precision Measurements
We briefly review recent experiments in atomic, molecular, and optical
physics using precision measurements to search for physics beyond the Standard
Model. We consider three main categories of experiments: searches for changes
in fundamental constants, measurements of the anomalous magnetic moment of the
electron, and searches for an electric dipole moment of the electron.Comment: Prepared for Comments on AMO Physics at Physica Script
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