6,213 research outputs found
Mercury in the environs of the north slope of Alaska
The analysis of Greenland ice suggests that the flux of mercury from the continents
to the atmosphere has increased in recent times, perhaps partly as a result of the many of
man’s activities that effect an alteration of terrestrial surfaces. Upon the exposure of fresh
crustal matter, the natural outgassing of mercury vapor from the earth’s surface could be
enhanced.
Accordingly, mercury was measured in a variety of environmental materials gathered
from the North Slope of Alaska to provide background data prior to the anticipated increase
of activity in this environment. The materials were collected during the U. S. Coast Guard
WEBSEC 72-73 cruises as well as through the facilities provided by Naval Arctic Research
Laboratory in the spring of 1973.
The method of measurement depended upon radioactivation of mercury with neutrons
and the subsequent quantification of characteristic gamma radiations after radiochemical
purification.
Mercury concentrations in seawater at several locations in the vicinity of 151°W,
71°N averaged 20 parts per trillion. The waters from all stations east of this location showed
a significantly smaller concentration. This difference may relate to penetration o f Bering-
Chukchi Sea water into the southern Beaufort Sea to 151°W. Marine sediments on the shelf
and slope between 143°W and 153°W contained about 100 parts per billion mercury, except
for those on the continental shelf between Barter Island and the Canning River, where the
concentration was less than half this value. These results are consistent with sediment input
from the respective rivers when their mercury content and mineralogy are considered. The
mercury content of river waters was 18 ppt and in reasonable agreement with the average of
snow samples (13 ppt). The burden of mercury in plankton was 37 ppb.This work was supported by the office of Naval Research under grant N R 083-290
Impact of edge-removal on the centrality betweenness of the best spreaders
The control of epidemic spreading is essential to avoid potential fatal
consequences and also, to lessen unforeseen socio-economic impact. The need for
effective control is exemplified during the severe acute respiratory syndrome
(SARS) in 2003, which has inflicted near to a thousand deaths as well as
bankruptcies of airlines and related businesses. In this article, we examine
the efficacy of control strategies on the propagation of infectious diseases
based on removing connections within real world airline network with the
associated economic and social costs taken into account through defining
appropriate quantitative measures. We uncover the surprising results that
removing less busy connections can be far more effective in hindering the
spread of the disease than removing the more popular connections. Since
disconnecting the less popular routes tend to incur less socio-economic cost,
our finding suggests the possibility of trading minimal reduction in
connectivity of an important hub with efficiencies in epidemic control. In
particular, we demonstrate the performance of various local epidemic control
strategies, and show how our approach can predict their cost effectiveness
through the spreading control characteristics.Comment: 11 pages, 4 figure
Phase-locking at low-level of quanta
We discuss phase-locking phenomena at low-level of quanta for parametrically
driven nonlinear Kerr resonator (PDNR) in strong quantum regime. Oscillatory
mode of PDNR is created in the process of a degenerate down-conversion of
photons under interaction with a train of external Gaussian pulses. We
calculate the Wigner functions of cavity mode showing two-fold symmetry in
phase space and analyse formation of phase-locked states in the regular as well
as the quantum chaotic regime.Comment: 6 pages, 4 figure
Making sense of project value from a value-co-creation perspective: an exploratory conceptual framework
This paper proposes a conceptual framework to make sense of how project value is created in projects. We study the extant project management value creation literature using a value co-creation lens based on service-dominant (S-D) logic. We explore how project value is proposed, exchanged and then realized following a project life-cycle. This leads to the identification of an exploratory “value co-creation life-cycle” framework. This framework shows value as a whole transcends the limitation of measurable products value normally used to define the project value. In particular, it shows how operant resources (or actors) - typically referred to as stakeholders - within the project management system exchange services and integrate resources in order to co-create value. The exploratory framework, in turn, would enable future investigation of real projects with the view to unpacking the complex dynamic behavior of project value creation
Isotropic-medium three-dimensional cloaks for acoustic and electromagnetic waves
We propose a generalization of the two-dimensional eikonal-limit cloak
derived from a conformal transformation to three dimensions. The proposed cloak
is a spherical shell composed of only isotropic media; it operates in the
transmission mode and requires no mirror or ground plane. Unlike the well-known
omnidirectional spherical cloaks, it may reduce visibility of an arbitrary
object only for a very limited range of observation angles. In the
short-wavelength limit, this cloaking structure restores not only the
trajectories of incident rays, but also their phase, which is a necessary
ingredient to complete invisibility. Both scalar-wave (acoustic) and transverse
vector-wave (electromagnetic) versions are presented.Comment: 17 pages, 12 figure
Status Epilepticus and Delirium Associated with Ertapenem in a Very Elderly Patient with Chronic Kidney Disease and Silent Ischaemic Cerebrovascular Disease
Publisher PDFPeer reviewe
A Strict Test of Stellar Evolution Models: The Absolute Dimensions of Massive Benchmark Eclipsing Binary V578 Mon
We determine the absolute dimensions of the eclipsing binary V578 Mon, a
detached system of two early B-type stars (B0V + B1V, P2.40848 d) in the
star-forming region NGC 2244 of the Rosette Nebula. From the light curve
analysis of 40 yr of photometry and the analysis of HERMES spectra, we find
radii of Rsun and Rsun, and temperatures of ~K and K respectively. We find that our
disentangled component spectra for V578 Mon agree well previous spectral
disentangling from the literature. We also reconfirm the previous spectroscopic
orbit of V578 Mon finding that masses of Msun and Msun are fully compatible with the new analysis. We compare the absolute
dimensions to the rotating models of the Geneva and Utrecht groups and the
models of Granada group. We find all three sets of models marginally reproduce
the absolute dimensions of both stars with a common age within uncertainty for
gravity-effective temperature isochrones. However - there are some apparent age
discrepancies for the corresponding mass-radius isochrones. Models with larger
convective overshoot worked best. Combined with our previously
determined apsidal motion of deg cycle,
we compute the internal structure constants (tidal Love number) for the
newtonian and general relativistic contribution to the apsidal motion,
and respectively. We find
the relativistic contribution to the apsidal motion of be small . We find
that the prediction of of the Granada
models fully agrees with our observed .Comment: accepted for publication in AJ 05/02/201
- …