2,142 research outputs found
Health and Health-related Problems in a Cohort of Apprentices in Switzerland
Out of a cohort of 1200 apprentices in Switzerland, 781 boys and 417 girls completed a questionnaire on their perceived health and health problems in their selected apprenticeship. Each participant was interviewed afterwards by the school nurses in three state-owned professional schools where the apprentices attended their classes. Ninety-five per cent of the respondents enjoyed excellent health, 28 cases had nervous system or psychological problems, 17 cases had problems of a locomotor nature, 12 subjects had gastrointestinal or endocrinological symptoms, and there was one with a past history of a malignant disease. Twelve cases also had respiratory symptoms or diagnoses. One hundred and nineteen apprentices reported that they had been troubled by the workplace. Exposure to solvents, chemicals in general, dust, smoke and noise were often mentioned as causes. Thirty-eight of them had contacted their family physician in connection with these problems. The cohort had experienced, mostly during their first year, 191 cases of accident necessitating medical care. Cuts, shocks and falls were the most common occurrences. Meat cutters and butchers had the highest frequency of accidents. Near-accidents had been experienced so far by 46 per cent of the respondents. At the interviews, school nurses provided counsel and intervened in flagrant cases of occupational risks, It seems that an ordinary medical certificate does not predict accident-proneness or possible medical problems, while in-school health programmes could provide rapid intervention and suppor
Viscosity of andesite melts and its implication for magma mixing prior to Unzen 1991-1995 eruption
The viscosity of an iron-bearing melt with composition similar to Unzen andesite was
determined experimentally in the high (109-1010.5 Pa·s) and low (5-1000 Pa·s) viscosity range
using a parallel plate viscometer and the falling sphere method, respectively. Falling sphere
experiments were carried out in an internally heated argon pressure vessel and in a piston
cylinder apparatus at 1323 to 1573 K and 200 to 2000 MPa. Creep experiments were
performed in the temperature range of 747 - 845 K at 300 MPa. The water content of the melt
varies from nominally dry to 6.2 wt% H2O. The Fe2+/Fetot ratio was determined for each
sample in the quenched glass using a colorimetric method. Pressure has minor influence on
the viscosity compared with the effect of temperature, water content (main compositional
parameter controlling the viscosity) or with the Fe2+/Fetot ratio (especially important at low
water content of the melt). Based on our new viscosity data and literature data with measured
Fe2+/Fetot ratio we propose a new empirical equation to estimate the viscosity η (in Pa·s) of
andesitic melts as a function of temperature T (in K), water content w (in wt%) and Fe2+/Fetot
ratio. The derived relationship reproduces the experimental data (87 in total) in the viscosity
range from 100.5 to 1013 Pa·s with a 1σ standard deviation of 0.17 log units. However,
application of this calculation model is limited to Fe2+/Fetot>0.3 and to temperatures above Tg.
Moreover, in the high viscosity range the variation of viscosity with water content is
constrained only by few experimental data and needs verification by additional
measurements.
The viscosity data are used to interpret mixing processes in the Unzen magma chamber prior
to 1991-1995 eruption. We demonstrate that the viscosities of the rhyolite and andesite melts
from the two end-member magmas are nearly identical prior and during mixing, enabling
efficient magma mixing
Global Existence and Regularity for the 3D Stochastic Primitive Equations of the Ocean and Atmosphere with Multiplicative White Noise
The Primitive Equations are a basic model in the study of large scale Oceanic
and Atmospheric dynamics. These systems form the analytical core of the most
advanced General Circulation Models. For this reason and due to their
challenging nonlinear and anisotropic structure the Primitive Equations have
recently received considerable attention from the mathematical community.
In view of the complex multi-scale nature of the earth's climate system, many
uncertainties appear that should be accounted for in the basic dynamical models
of atmospheric and oceanic processes. In the climate community stochastic
methods have come into extensive use in this connection. For this reason there
has appeared a need to further develop the foundations of nonlinear stochastic
partial differential equations in connection with the Primitive Equations and
more generally.
In this work we study a stochastic version of the Primitive Equations. We
establish the global existence of strong, pathwise solutions for these
equations in dimension 3 for the case of a nonlinear multiplicative noise. The
proof makes use of anisotropic estimates, estimates on the
pressure and stopping time arguments.Comment: To appear in Nonlinearit
How the U.S. Air Force Space Command Optimizes Long-Term Investment in Space Systems
Interfaces, 33, p.p. 1-14.United States Air Force Space Command spends billions of dollars each year acquiring and
developing launch vehicles and space systems. The space systems in orbit must continually meet defensive and offensive requirements and remain interoperable over time. Space command can launch additional space systems only if it has a launch vehicle of sufficient capacity. Space planners using space and missile optimization analysis (SAMOA) consider a 24-year time horizon when determining which space assets and launch vehicles to fund and procure. A key tool which in SAMOA is an integer linear program called the space command optimizer of utility toolkit (SCOUT) that Space Command uses for long-range planning. SCOUT gives planner insight into the annual funding profiles needed to meet Space Command's acquisition goals. The 1999 portfolio of 74 systems will cost about #310 billion and includes systems that can lift satellites into orbit; yield information on space, surface, and subsurface events, activities, and threats; and destroy terrestrial, airborne, and space targets
Strong field limit analysis of gravitational retro-lensing
We present a complete treatment in the strong field limit of gravitational
retro-lensing by a static spherically symmetric compact object having a photon
sphere. The results are compared with those corresponding to ordinary lensing
in similar strong field situations. As examples of application of the
formalism, a supermassive black hole at the galactic center and a stellar mass
black hole in the galactic halo are studied as retro-lenses, in both cases
using the Schwarzschild and Reissner-Nordstrom geometries.Comment: 11 pages, 1 figure; v2: minor changes. Accepted for publication in
Physical Review
The viscosity of shoshonitic melts (Vulcanello Peninsula, Aeolian Islands, Italy): insight on the magma ascent in dikes
The viscosity of shoshonitic melts from Vulcanello Peninsula (Vulcano Island, Italy) is
experimentally determined at temperatures between 733 K and 1673 K. The water content of the
melts varies from 0.03 to 4.75 wt% H2O. The micropenetration technique is employed at ambient
pressure in the high viscosity range (109-1012 Pa·s). Falling sphere(s) experiments are performed
at 500 and 2000 MPa in the low viscosity range (100.5-103 Pa·s). Results show a decrease of about
2 orders of magnitude in viscosity if ~ 3 wt% of water is added to the dry melt at 1300 K. At high
temperature the viscosity of Vulcanello melts is intermediate between that of andesitic and
basaltic melts. In contrast, at low temperatures (≤1050 K), the shoshonitic melt is characterized
by a lower viscosity with respect to the two previous melts. Based on our new data set, a
calculation model is proposed to predict the viscosity of the shoshonitic melts as a function of
temperature and water content. The viscosity data are used to constrain the ascent velocity of
shoshonitic magmas from Vulcanello within dikes. Using petrological data (temperature and
crystal content of the magma) and volcanological information (geometrical parameters of the
eruptive fissure and depth of magma storage), we estimate the time scale for the ascent of magma
from the main reservoir to the surface. Results show time scales in the order of hours to few days.
We conclude that the rapid ascent of poorly evolved melts from Moho depths should be taken
into account for the hazard assessment of Vulcano Island
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