59,005 research outputs found
Distribution of heavy metals in sediments of Igbede, Ojo and Ojora rivers of Lagos, Nigeria
The distribution of some heavy metals,
namely Cd, Pb, Zn, Fe, Cu, Cr and Mn in epipellic
sediments of Igbede, Ojo and Ojora rivers of Lagos
was studied weekly in the early summer (November)
of 2003. The levels of selected trace metals were determined
using Atomic Absorption Spectrophotometer
(UNICAM 969 AAS SOLAR). Trends in heavy metal
burdens in the sediments revealed weekly variations in
all the rivers assessed. Statistical analyses also showed
different mean levels of trace metals in the aquatic environments,
the distribution of which followed the sequence
Fe > Zn > Mn > Pb > Cu > Cr > Cd, Fe
> Zn > Cu > Mn > Pb > Cr > Cd and Fe > Zn >
Mn > Cu > Cr > Pb > Cd in Igbede, Ojo and Ojora
rivers respectively. Fe recorded the highest concentration
levels (1,582.95 ± 96.57 μg/g–1,910.34 ± 723.19
ÎĽg/g) in all the sediments investigated while the Cd
levels (0.06 ± 0.10 μg/g–0.47 ± 0.36 μg/g) were the
lowest. Expectedly, trace metal concentrations in fine
grain muddy sediments of the Igbede and Ojo coastline
were much higher than those of Ojora which consist
of coarse and sandy deposits covering the near shore
area. Generally, the results obtained fell within toler-able limits stipulated by World Health Organization
(WHO)
Interaction Data Sets In The UK: An Audit
Interaction or flow data involves counts of flows between origin and destination areas and can be extracted from a range of sources. The Centre for Interaction Data Estimation and Research (CIDER) maintains a web-based system (WICID) that allows academic researchers to access and extract migration and commuting flow data (the so-called Origin-Destination Statistics) from the last three censuses. However, there are many other sources of interaction data other than the decadal census, including national administrative or registration procedures and large scale social surveys. This paper contains an audit of interaction data sets in the UK, providing detailed description and exemplification in each case and outlining the advantages and shortcomings of the different types of data where appropriate. The Census Origin-Destination Statistics have been described elsewhere in detail and only a short synopsis is provided here together with review of the interaction data that can be derived from other census products.
The primary aims of the audit are to identify those interaction data sets that exist that might complement the census origin-destination statistics currently contained in WICID and to assess their suitability and availability as potential data sets to be held in an expanded version of WICID. Tables or flow data sets are included for exemplification. The paper concludes with a series of recommendations as to which of these data sets should be incorporated into a new information system for interaction flows that complement the census data and also provide opportunities for new research projects
Lattice quark propagator with staggered quarks in Landau and Laplacian gauges
We report on the lattice quark propagator using standard and improved
Staggered quark actions, with the standard, Wilson gauge action. The standard
Kogut-Susskind action has errors of \oa{2} while the ``Asqtad'' action has
\oa{4}, \oag{2}{2} errors. The quark propagator is interesting for studying the
phenomenon of dynamical chiral symmetry breaking and as a test-bed for
improvement. Gauge dependent quantities from lattice simulations may be
affected by Gribov copies. We explore this by studying the quark propagator in
both Landau and Laplacian gauges. Landau and Laplacian gauges are found to
produce very similar results for the quark propagator.Comment: 11 pages, 15 figure
Highly-improved lattice field-strength tensor
We derive an O(a^4)-improved lattice version of the continuum field-strength
tensor. Discretization errors are reduced via the combination of several clover
terms of various sizes, complemented by tadpole improvement. The resulting
improved field-strength tensor is used to construct O(a^4)-improved topological
charge and action operators. We compare the values attained by these operators
as we cool several configurations to self-duality with a previously defined
highly-improved action and assess the relative scale of the remaining
discretization errors.Comment: 22 pages, 7 postscript figure
Modelling the quark propagator
The quark propagator is at the core of lattice hadron spectrum calculations
as well as studies in other nonperturbative schemes. We investigate the quark
propagator with an improved staggered action (Asqtad) and an improved gluon
action, which provides good quality data down to small quark masses. This is
used to construct ans\"{a}tze suitable for model hadron calculations as well as
adding to our intuitive understanding of QCD.Comment: Lattice2002(spectrum
Drug Repurposing for Targeting Acute Leukemia With KMT2A (MLL)-Gene Rearrangements
The treatment failure rates of acute leukemia with rearrangements of the Mixed Lineage Leukemia (MLL) gene highlight the need for novel therapeutic approaches. Taking into consideration the limitations of the current therapies and the advantages of novel strategies for drug discovery, drug repurposing offers valuable opportunities to identify treatments and develop therapeutic approaches quickly and effectively for acute leukemia with MLL-rearrangements. These approaches are complimentary to de novo drug discovery and have taken advantage of increased knowledge of the mechanistic basis of MLL-fusion protein complex function as well as refined drug repurposing screens. Despite the vast number of different leukemia associated MLL-rearrangements, the existence of common core oncogenic pathways holds the promise that many such therapies will be broadly applicable to MLL-rearranged leukemia as a whole
Role of center vortices in chiral symmetry breaking in SU(3) gauge theory
We study the behavior of the AsqTad quark propagator in Landau gauge on SU(3)
Yang-Mills gauge configurations under the removal of center vortices. In SU(2)
gauge theory, center vortices have been observed to generate chiral symmetry
breaking and dominate the infrared behavior of the quark propagator. In
contrast, we report a weak dependence on the vortex content of the gauge
configurations, including the survival of dynamical mass generation on
configurations with vanishing string tension.Comment: 8 pages, 9 figure
Gravitational Acceleration of Spinning Bodies From Lunar Laser Ranging Measurements
The Sun's relativistic gravitational gradient accelerations of Earth and
Moon, dependent on the motions of the latter bodies, act upon the system's
internal angular momentum. This spin-orbit force (which plays a part in
determining the gravity wave signal templates for astrophysical sources)
slightly accelerates the Earth-Moon system as a whole, but it more robustly
perturbs that system's internal dynamics with a 5 cm, synodically oscillating
range contribution which is presently measured to 4 mm precision by more than
three decades of lunar laser ranging.Comment: 10 pages, PCTex32.v3.
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