1,135 research outputs found
On the stability of spacelike hypersurfaces
In this paper we study the strong stability of spacelike hypersurfaces with
constant -th mean curvature in Generalized Robertson-Walker spacetimes of
constant sectional curvature. In particular, we treat the case in which the
ambient spacetime is the de Sitter space
Laccase gene silencing negatively effects growth and development in Pleurotus ostreatus
42-51In this study we describe the effects of Pleurotus ostreatus transformants that have been silenced for laccase genes. Using the RNAi strategy, transformants with different levels of phenotypic alteration were obtained with respect to their oxidation capacity of 2,6-dimethoxyphenol (DMP). The analysis of laccase activity on DMP allowed us to select transformants with severe, medium and light phenotypic alteration in comparison to the PoB strain. The measurements of the average growth rate of the transformants with severe phenotypic alteration suggested that laccase expression could play a role in the vegetative growth of P. ostreatus. It was observed that both in solid and liquid cultures, PoB and the transformants express mRNA for lacc10, although the transformants with medium and severe phenotypic alteration present a decrease in intensity, especially in solid culture. This suggests that the product of this gene is responsible for the development of the mycelium and probably participates in the production of biomass in solid culture and also could be related to the decrease in the intensity of the constant isoenzyme observed in both culture systems
On the behavior of site effects in central Mexico (the Mexican volcanic belt – MVB), based on records of shallow earthquakes that occurred in the zone between 1998 and 2011
The Mexican volcanic belt (MVB) is a seismogenic zone that transects the
central part of Mexico with an eastâwest orientation. The seismic risk and
hazard of this seismogenic zone has not been studied in detail due to the
scarcity of instrumental data as well as because seismicity in the
continental regime of central Mexico is not too frequent. However, it is
known that there are precedents of large earthquakes (<i>M</i><sub>w</sub> > 6.0)
that have taken place in this zone. The valley of Mexico City (VM) is the
sole zone, within the MVB, that has been studied in detail. Studies have
mainly focused on the ground amplification during large events such as the
1985 subduction earthquake that occurred off coast of MichoacĂĄn. The
purpose of this article is to analyze the behavior of site effects in the MVB
zone based on records of shallow earthquakes (data not reported before) that
occurred in the zone between 1998 and 2011. We present a general overview of
site effects in the MVB, a classification of the stations in order to reduce
the uncertainty in the data when obtaining attenuation parameters in future
works, as well as some comparisons between the information presented here and
that presented in previous studies.
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A regional evaluation of site effects and Fourier acceleration spectrum
(FAS) shape was estimated based on 80 records of 22 shallow earthquakes
within the MVB zone. Data of 25 stations were analyzed. Site effects were
estimated by using the horizontal-to-vertical spectral ratio (HVSR)
methodology. The results show that seismic waves are less amplified in the
northeast sites of the MVB with respect to the rest of the zone and that it
is possible to classify two groups of stations: (1) stations with negligible
site amplification (NSA) and (2) stations with significant site amplification
(SSA). Most of the sites in the first group showed small (<3)
amplifications while the second group showed amplifications ranging from 4
to 6.5 at frequencies of about 0.35, 0.75, 15 and 23 Hz. With these groups
of stations, average levels of amplification were contrasted for the first
time with those caused by the subduction zone earthquakes. With respect to
the FAS shapes, most of them showed similarities at similar epicentral
distances. Finally, some variations of site effects were found when compared
to those obtained in previous studies on different seismicity regions. These
variations were attributed to the location of the source.
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These aspects help to advance the understanding about the amplification
behavior and of the expected seismic risk on central Mexico due to large
earthquakes within the MVB seismogenic zone
Non-standard grain properties, dark gas reservoir, and extended submillimeter excess, probed by Herschel in the Large Magellanic Cloud
Context. Herschel provides crucial constraints on the IR SEDs of galaxies, allowing unprecedented accuracy on the dust mass estimates. However, these estimates rely on non-linear models and poorly-known optical properties.
Aims. In this paper, we perform detailed modelling of the Spitzer and Herschel observations of the LMC, in order to: (i) systematically study the uncertainties and biases affecting dust mass estimates; and to (ii) explore the peculiar ISM properties of the LMC.
Methods. To achieve these goals, we have modelled the spatially resolved SEDs with two alternate grain compositions, to study the impact of different submillimetre opacities on the dust mass. We have rigorously propagated the observational errors (noise and calibration) through the entire fitting process, in order to derive consistent parameter uncertainties.
Results. First, we show that using the integrated SED leads to underestimating the dust mass by â50% compared to the value obtained with sufficient spatial resolution, for the region we studied. This might be the case, in general, for unresolved galaxies. Second, we show that Milky Way type grains produce higher gas-to-dust mass ratios than what seems possible according to the element abundances in the LMC. A spatial analysis shows that this dilemma is the result of an exceptional property: the grains of the LMC have on average a larger intrinsic submm opacity (emissivity index ÎČ â 1.7 and opacity Îș_(abs)(160 ÎŒm) = 1.6 m^2 â kg^(-1)) than those of the Galaxy. By studying the spatial distribution of the gas-to-dust mass ratio, we are able to constrain the fraction of unseen gas mass between â10, and â100% and show that it is not sufficient to explain the gas-to-dust mass ratio obtained with Milky Way type grains. Finally, we confirm the detection of a 500 ÎŒm extended emission excess with an average relative amplitude of â15%, varying up to 40%. This excess anticorrelates well with the dust mass surface density. Although we do not know the origin of this excess, we show that it is unlikely the result of very cold dust, or CMB fluctuations
Totally Laparoscopic Roux-en-Y Duct-to-Mucosa Pancreaticojejunostomy After Middle Pancreatectomy A Consecutive Nine-case Series at a Single Institution
To present the results of a series of laparoscopic middle
pancreatectomies with roux-en-Y duct-to-mucosa pancreaticojejunostomy. SUMMARY OF
BACKGROUND DATA: Middle pancreatectomy makes it possible to preserve pancreatic
parenchyma in the resection of lesions that traditionally have been treated by
distal splenopancreatectomy or cephalic duodenopancreatectomy. The laparoscopic
approach could minimize the invasiveness of the procedure and enhance the
benefits of middle pancreatectomy. METHODS: From March 2005 to October 2007, 9
consecutive patients with benign or low malignant potential lesions in the
pancreatic neck or body underwent surgery. Laparoscopic middle pancreatectomy
with a roux-en-Y duct-to-mucosa pancreaticojejunostomy was planned on all of
them. In the first 2 patients, the pancreas was transected by endostapler; in the
last 7, the staple line was reinforced with absorbable polymer membrane. RESULTS:
The intervention was concluded laparoscopically in every case except 1
(laparoscopic-assisted) in which pancreaticojejunostomy was performed by means of
minilaparotomy. Mortality was 0% and perioperative morbidity was 33%, (fistula of
the cephalic stump in the first 2 patients (22%)). The pancreaticojejunostomy
fistula rate was 0%. The median postoperative hospital stay was 5 days (range,
3-41). In the last 7 patients, in which pancreas was transected with staple line
reinforcement material there were no stump fistulas; morbidity decreased to 14%
and the median hospital stay was 4 days (range, 3-30). CONCLUSIONS: Laparoscopic
middle pancreatectomy is feasible and safe. Duct-to-mucosa pancreaticojejunostomy
can be performed safely using this approach. The method of pancreatic transection
seems to be decisive in the incidence of cephalic stump fistulas
A Detailed Study of the Radio--FIR Correlation in NGC6946 with Herschel-PACS/SPIRE from KINGFISH
We derive the distribution of the synchrotron spectral index across NGC6946
and investigate the correlation between the radio continuum (synchrotron) and
far-infrared (FIR) emission using the KINGFISH Herschel PACS and SPIRE data.
The radio--FIR correlation is studied as a function of star formation rate,
magnetic field strength, radiation field strength, and the total gas surface
brightness. The synchrotron emission follows both star-forming regions and the
so-called magnetic arms present in the inter-arm regions. The synchrotron
spectral index is steepest along the magnetic arms (), while
it is flat in places of giant H{\sc ii} regions and in the center of the galaxy
(). The map of provides an observational
evidence for aging and energy loss of cosmic ray electrons propagating in the
disk of the galaxy. Variations in the synchrotron--FIR correlation across the
galaxy are shown to be a function of both star formation and magnetic fields.
We find that the synchrotron emission correlates better with cold rather than
with warm dust emission, when the interstellar radiation field is the main
heating source of dust. The synchrotron--FIR correlation suggests a coupling
between the magnetic field and the gas density. NGC6946 shows a power-law
behavior between the total (turbulent) magnetic field strength B and the star
formation rate surface density with an index of
0.14\,(0.16)0.01. This indicates an efficient production of the turbulent
magnetic field with the increasing gas turbulence expected in actively star
forming regions. The scale-by-scale analysis of the synchrotron--FIR
correlation indicates that the ISM affects the propagation of old/diffused
cosmic ray electrons, resulting in a diffusion coefficient of \,cm\,s for 2.2\,GeV CREs.Comment: 23 pages, 13 figures, accepted for publication in Astronomy &
Astrophysics Journa
Remote Working and Home Learning: How the Italian Academic Population Dealt with Changes Due to the COVID-19 Pandemic Lockdown
The COVID-19 pandemic introduced changes in people's lives that affected their mental health. Our study aimed to explore the level of psychological distress in the academic population during the lockdown period and investigate its association with the new working or studying conditions. The study sample included 9364 students and 2159 employees from five Italian universities from the study IO CONTO 2020. We applied linear regression models to investigate the association between home learning or remote working conditions and psychological distress, separately for students and employees. Psychological distress was assessed using the Hospital Anxiety and Depression Scale (HADS). In both students and employees, higher levels of distress were significantly associated with study/work-family conflicts, concerns about their future careers, and inadequacy of equipment; in employees, higher levels of distress were significantly associated with a lack of clarity on work objectives. Our results are in line with previous research on the impact of spaces and equipment in remote working/studying from home. Moreover, the study contributes to deepening the association between well-being and telework-family conflict, which in the literature is still equivocal. Practical implications require academic governance to promote sustainable environments both in remote and hybrid work conditions, by referring to a specific management by objectives approach
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