1,276 research outputs found
Effects of flow volume and grain size on mobility of dry granular flows of angular rock fragments: A functional relationship of scaling parameters
Flows of angular rock fragments are released down a concave upward chute in the laboratory
to study their mobility. This mobility is measured as the reciprocal of the apparent coefficient of
friction that is equal to the vertical drop of the centre of mass of the granular material divided by its
horizontal distance of travel. Our experiments show that the finer the grain size (all the other
features the same), the larger is the mobility of the centre of mass. We believe this to be due to the
fact that in finer grain size flows there are less agitated particles per unit of flow mass so that these
flows dissipate less energy per unit of travel distance. Our experiments show also that the larger the
volume (all the other features the same), the larger is the apparent coefficient of friction. We believe
this to be so because the frontal portion of a flow reaches the less steep part of a curved slope and
stops before the rear portion preventing the rear portion and the centre of mass from travelling
further downhill. This phenomenon (which is more prominent in larger volume flows whose rear
and frontal ends are more distant) counteracts the decrease of energy dissipation per unit of flow
mass, due to the decrease of particle agitation per unit of flow mass, that is expected when the
volume of a flow increases (all the other features the same). Our analysis generates a functional
relationship between the dimensionless apparent coefficient of friction and a scaling parameter
whose numerator is equal to the mean grain size multiplied by the cube root of the deposit volume
and whose denominator is the square of the channel width
AntimicrobialâResistant Enterococcus spp. in Wild Avifauna from Central Italy
Bacteria of the genus Enterococcus are opportunistic pathogens, part of the normal intestinal microflora of animals, able to acquire and transfer antimicrobial resistance genes. The aim of this study was to evaluate the possible role of wild avifauna as a source of antimicrobialâresistant enterococci. To assess this purpose, 103 Enterococcus spp. strains were isolated from the feces of wild birds of different species; they were tested for antimicrobial resistance against 21 molecules, vancomycin resistance, and highâlevel aminoglycosides resistance (HLAR). Furthermore, genes responsible for vancomycin, tetracycline, and HLAR were searched. E. faecium was the most frequently detected species (60.20% of isolates), followed by E. faecalis (34.95% of isolates). Overall, 99.02% of the isolated enterococci were classified as multidrugâresistant, with 19.41% extensively drugâresistant, and 2.91% possible pan drug-resistant strains. Most of the isolates were susceptible to amoxicillin/clavulanic acid (77.67%) and ampicillin (75.73%), with only 5.83% of isolates showing an ampicillin MIC â„ 64 mg/L. HLAR was detected in 35.92% of isolates, mainly associated with the genes ant(6)âIa and aac(6âČ)âIeâaph(2âČâ)âIa. Few strains (4.85%) were resistant to vancomycin, and the genes vanA and vanB were not detected. A percentage of 54.37% of isolates showed resistance to tetracycline; tet(M) was the most frequently detected gene in these strains. Wild birds may contribute to the spreading of antimicrobialâresistant enterococci, which can affect other animals and humans. Constant monitoring is essential to face up to the evolving antimicrobial resistance issue, and monitoring programs should include wild avifauna, to
Environmental Assessment of Renewable Fuel Energy Systems with Cross-Media Effects Approachâ
Abstract In the last years, the number of installed biofuels power plants is increased in northern Italy, due to favorable legislation on renewable energy sources, posing the issue to assess the resulting environmental effects. The European legislation on emissions for renewable fuels power plants provides guidelines to be integrated in the local regulations; moreover, local authorities have to identify the critical power plants in terms of pollution and the key parameters to grant licenses for the future plants. The aim of this paper is to describe a methodology and the calculation routine developed to assess the environmental effects of biomass plants in terms of simple indexes. The used approach is based on the Cross-Media Effects described by a European Commission Reference Document. In particular, several indexes are introduced to cover the most relevant environmental effects, as: air toxicity, global warming, acidification, eutrophication and photochemical ozone creation. For every considered pollutant (such as NOx, CO, etc.) directly emitted by the power plant, specific factors have been identified, in order to calculate the contribution to the different environmental indexes. Finally, a numerical evaluation of different biomass power plants, installed in Emilia Romagna region, is provided, in order to assess their environmental cross-media potential and to compare such kind of power plants with large scale, fossil-fuelled power plants
2D photonic-crystal optomechanical nanoresonator
We present the optical optimization of an optomechanical device based on a
suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based
on a 2D photonic-crystal geometry. We first identify by numerical simulation a
set of geometrical parameters providing a reflectivity higher than 99.8 % over
a 50-nm span. We then study the limitations induced by the finite value of the
optical waist and lateral size of the NWG pattern using different numerical
approaches. The NWG grating, pierced in a suspended InP 265 nm-thick membrane,
is used to form a compact microcavity involving the suspended nano-membrane as
end mirror. The resulting cavity has a waist size smaller than 10 m and a
finesse in the 200 range. It is used to probe the Brownian motion of the
mechanical modes of the nanomembrane
Thermoelastic dissipation in inhomogeneous media: loss measurements and displacement noise in coated test masses for interferometric gravitational wave detectors
The displacement noise in the test mass mirrors of interferometric
gravitational wave detectors is proportional to their elastic dissipation at
the observation frequencies. In this paper, we analyze one fundamental source
of dissipation in thin coatings, thermoelastic damping associated with the
dissimilar thermal and elastic properties of the film and the substrate. We
obtain expressions for the thermoelastic dissipation factor necessary to
interpret resonant loss measurements, and for the spectral density of
displacement noise imposed on a Gaussian beam reflected from the face of a
coated mass. The predicted size of these effects is large enough to affect the
interpretation of loss measurements, and to influence design choices in
advanced gravitational wave detectors.Comment: 42 pages, 7 figures, uses REVTeX
Retrospective Molecular Survey on Bacterial and Protozoan Abortive Agents in Roe Deer (Capreolus capreolus) from Central Italy
Bacterial and protozoan agents can determine abortion and other reproductive disorders in domestic ruminants, but data regarding their occurrence in wild ruminants are scanty worldwide, including in Italy. The aim of this retrospective study was to verify the occurrence of the main bacterial and protozoan abortive agents in 72 spleen samples previously collected from roe deer (Capreolus capreolus) living in mountain areas of Central Italy. All samples were collected and submitted to DNA extraction for other investigations. Molecular analyses were carried out on the DNA samples to detect Brucella spp., Chlamydia abortus, Coxiella burnetii, Salmonella enterica, Listeria monocytogenes, Neospora caninum, and Toxoplasma gondii. Three (4.16%) roe deer resulted PCR positive for C. burnetii and one (1.38%) for T. gondii. These findings suggest that roe deer living in the investigated areas do not act as important reservoirs of the searched agents. However, the tested animals lived in a closed area without contact with domestic animals that are usually involved in the epidemiology of the investigated pathogens. Monitoring of wild ruminants is pivotal to verify changes in the epidemiological scenario from a One Health perspective, too
Measurement of the mechanical loss of a cooled reflective coating for gravitational wave detection
We have measured the mechanical loss of a dielectric multilayer reflective
coating (ion-beam sputtered SiO and TaO) in cooled mirrors. The
loss was nearly independent of the temperature (4 K 300 K), frequency,
optical loss, and stress caused by the coating, and the details of the
manufacturing processes. The loss angle was . The
temperature independence of this loss implies that the amplitude of the coating
thermal noise, which is a severe limit in any precise measurement, is
proportional to the square root of the temperature. Sapphire mirrors at 20 K
satisfy the requirement concerning the thermal noise of even future
interferometric gravitational wave detector projects on the ground, for
example, LCGT.Comment: 8 pages, 6 figures, 3 tables : accepted version (by Physical Review
D
Treatment of lupus nephritis with abatacept: the Abatacept and Cyclophosphamide Combination Efficacy and Safety Study
OBJECTIVE: To assess the efficacy and safety of a 24-week course of abatacept in the treatment of active lupus nephritis and to assess the potential of abatacept to induce clinical tolerance, defined as sustained clinical quiescence of lupus nephritis after discontinuation of immunosuppressive therapy. METHODS: Patients with active lupus nephritis (n = 134) were enrolled in a randomized, double-blind phase II add-on trial in which they received either abatacept or placebo in conjunction with the Euro-Lupus Nephritis Trial regimen of low-dose cyclophosphamide (CYC) followed by azathioprine (AZA). The primary efficacy outcome was the frequency of complete response at week 24. Thereafter, patients who met either complete or partial response criteria continued blinded treatment through week 52. During this phase of the study, subjects in the abatacept treatment group in whom a complete response was achieved at week 24 discontinued immunosuppressive therapy other than prednisone (10 mg/day). RESULTS: There were no statistically significant differences between groups with respect to the primary outcome or any of the secondary outcomes, including measures of safety. A complete response was achieved in 33% of the subjects in the treatment group and in 31% of the subjects in the control group at week 24. Fifty percent of the subjects in the treatment group who met complete response criteria and therefore discontinued immunosuppressive therapy at week 24 maintained their complete response status through week 52. CONCLUSION: The addition of abatacept to a regimen of CYC followed by AZA did not improve the outcome of lupus nephritis at either 24 or 52 weeks. No worrisome safety signals were encountered
Thermal noise in interferometric gravitational wave detectors due to dielectric optical coatings
We report on thermal noise from the internal friction of dielectric coatings
made from alternating layers of Ta2O5 and SiO2 deposited on fused silica
substrates. We present calculations of the thermal noise in gravitational wave
interferometers due to optical coatings, when the material properties of the
coating are different from those of the substrate and the mechanical loss angle
in the coating is anisotropic. The loss angle in the coatings for strains
parallel to the substrate surface was determined from ringdown experiments. We
measured the mechanical quality factor of three fused silica samples with
coatings deposited on them. The loss angle of the coating material for strains
parallel to the coated surface was found to be (4.2 +- 0.3)*10^(-4) for
coatings deposited on commercially polished slides and (1.0 +- 0.3)*10^{-4} for
a coating deposited on a superpolished disk. Using these numbers, we estimate
the effect of coatings on thermal noise in the initial LIGO and advanced LIGO
interferometers. We also find that the corresponding prediction for thermal
noise in the 40 m LIGO prototype at Caltech is consistent with the noise data.
These results are complemented by results for a different type of coating,
presented in a companion paper.Comment: Submitted to LSC (internal) review Sept. 20, 2001. To be submitted to
Phys. Lett.
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