86 research outputs found
Bacteria homologus to Aeromonas capable of microcystin degradation
Water blooms dominated by cyanobacteria
are capable of producing hepatotoxins known as
microcystins. These toxins are dangerous to people and
to the environment. Therefore, for a better understanding
of the biological termination of this increasingly
common phenomenon, bacteria with the potential to
degrade cyanobacteria-derived hepatotoxins and the
degradative activity of culturable bacteria were studied.
Based on the presence of the mlrA gene, bacteria with a
homology to the Sphingopyxis and Stenotrophomonas
genera were identified as those presenting potential for
microcystins degradation directly in the water samples
from the Sulejów Reservoir (SU, Central Poland). However,
this biodegrading potential has not been confirmed in in
vitro experiments. The degrading activity of the culturable
isolates from the water studied was determined in more
than 30 bacterial mixes. An analysis of the biodegradation
of the microcystin-LR (MC-LR) together with an analysis of
the phylogenetic affiliation of bacteria demonstrated for
the first time that bacteria homologous to the Aeromonas
genus were able to degrade the mentioned hepatotoxin,
although the mlrA gene was not amplified. The maximal
removal efficiency of MC-LR was 48%. This study
demonstrates a new aspect of interactions between the
microcystin-containing cyanobacteria and bacteria from
the Aeromonas genus.The authors would like to
acknowledge the European Cooperation in Science
and Technology, COST Action ES 1105 “CYANOCOST -
Cyanobacterial blooms and toxins in water resources:
Occurrence, impacts and management” for adding value
to this study through networking and knowledge sharing
with European experts and researchers in the field. The
Sulejów Reservoir is a part of the Polish National Long-
Term Ecosystem Research Network and the European
LTER site
Brane Bulk Couplings and Condensation from REA Fusion
The physical meaning of the Reflection Equation Algebras of hep-th/0107265
and hep-th/0203110 is elucidated in the context of Wess--Zumino--Witten D-brane
geometry, as determined by couplings of closed-string modes to the D-brane.
Particular emphasis is laid on the role of algebraic fusion of the matrix
generators of the Reflection Equation Algebras. The fusion is shown to induce
transitions among D-brane configurations admitting an interpretation in terms
of RG-driven condensation phenomena.Comment: 13 pages; an essentially re-structured version of the paper to appear
in JHE
Magnetic coupling in CuCr2X4 (X = S, Se) spinel compounds obtained via substitution of the chromium ions by nonmagnetic Sb or Al ions
Taking into account both the dc magnetic susceptibility and the magnetization measurements as well as the
high-temperature expansion of the magnetic susceptibility procedure the hopping integrals and superexchange
integrals for the first and second coordination sphere were evaluated. The two hopping integrals are positive
and many times greater than the superexchange ones. The obtained results testify to that in the stoichiometric
compounds under study the double-exchange magnetic interaction is the main mechanism responsible for very
strong, ferromagnetic coupling. Using the total hopping integral B the bandwidth of mixed valence band of
chromium ions was determined
Mid- to Late Holocene elemental record and isotopic composition of lead in a peat core from Wolbrom (S Poland)
Peat Core W3 was taken from the fen in Wolbrom (Silesian-Cracovian Upland, Southern Poland) in September 2015. Previous analyses of Core W3 showed a significant increase in lead concentration during the time of the Roman Empire as well as some changes in peat accumulation conditions. The work reported here investigates its geochemical composition in terms of major and trace elements (Pb, Zn, Na, K, Ca, Fe, Mg, Mn, Cu, Ni, Cr by AAS) as well as Pb isotopic composition, to identify the sources of metal pollution in the Wolbrom peat deposit. The geochemical record spans the period from 4900 BC to modern times, with a likely hiatus corresponding to the period from the Middle Ages to the beginning of the contemporary metallurgical industry. The Pb isotopic composition combined with a cluster analysis allows identification of the primary sources of Pb. In addition, Principal Component Analysis (PCA) helps to decipher the most important factors that affected the chemical composition of sediments at Wolbrom. These factors were linked to chemical denudation and human activity
Influence of substitution of the chromium ions by the nonmagnetic Sb and Al ions on the magnetization processes in CuCr2X4 (X = S, Se) spinels
Both the dc and ac magnetic susceptibilities as well as magnetization measurements were used to study
the influence of the dilution of the magnetic chromium subarray by nonmagnetic antimony and aluminium
ions on the magnetization processes for four spinel families under investigation. Substitution of the chromium
ions by the nonmagnetic Sb and Al ions in the compounds under study leads to the very hard magnetization
in the case of the compounds with Sb and very easy magnetization in the compounds with Al. This
effect is connected with the electronic configurations of the Sb and Al ions as well as with ionic radii of these cations
A Note on Anomalies in the AdS/CFT Correspondence
We test the AdS/CFT correspondence in the case of a d=4 N=2 SCFT by comparing
chiral anomalies which are of order N in the 't Hooft large N limit. These
include corrections of order 1/N to the conformal anomaly, thus testing the
correspondence beyond the extreme large N limit. The field theory anomalies are
reproduced by terms in the 7-brane effective action in the bulk.Comment: 13 pages, harvma
Multi-Instanton Corrections to Superpotentials in Type II Compactifications
We consider two simple examples of multi-instanton configurations in type II
4d N=1 superstring compactifications. The first one involves O(1) and U(1)
D2-instantons embedded in T^6/(Z_2 x Z_2') geometry with SU(4) gauge symmetry
coming from D6-branes and the second is related to quiver gauge theory of
orientifolded orbifold of conifold containing fractional D(-1)-instantons and
D3-branes. The additional zero modes of instantons which appear at the
intersection points are lifted through interactions stemming from dimensionally
reduced F- and D-terms. It is shown that multi-instanton configurations
effectively generate corrections to the usual non-perturbative superpotential
for chiral matter.Comment: LaTeX, 17 pages, 3 Postscript figure
Factors affecting medical students in formulating their specialty preferences in Jordan
<p>Abstract</p> <p>Background</p> <p>In recent years there has been a growing appreciation of the issues of career preference in medicine as it may affect student learning and academic performance. However, no such studies have been undertaken in medical schools in Jordan. Therefore, we carried out this study to investigate the career preferences of medical students at Jordan University of Science and Technology and determine factors that might influence their career decisions.</p> <p>Methods</p> <p>A cross-sectional questionnaire-based survey was carried out among second, fourth and sixth year medical students at the Jordan University of Science and Technology, Irbid, Jordan during the academic year 2006/2007. A total of 440 students answered the questionnaire which covered demographic characteristics, specialty preferences, and the factors that influenced these career preferences. Possible influences were selected on the basis of a literature review and discussions with groups of medical students and physicians. Students were asked to consider 14 specialty options and select the most preferred career preference.</p> <p>Results</p> <p>The most preferred specialty expressed by male students was surgery, followed by internal medicine and orthopaedics, while the specialty most preferred by female students was obstetrics and gynaecology, followed by pediatrics and surgery. Students showed little interest in orthopedics, ophthalmology, and dermatology. While 3.1% of females expressed interest in anesthesiology, no male students did. Other specialties were less attractive to most students.</p> <p>Intellectual content of the specialty and the individual's competencies were the most influential on their preference of specialty. Other influential factors were the "reputation of the specialty", "anticipated income", and "focus on urgent care".</p> <p>Conclusion</p> <p>Surgery, internal medicine, pediatrics, and obstetrics and gynaecology were the most preferred specialty preferences of medical students at Jordan University of Science and Technology.</p
Kondo flow invariants, twisted K-theory and Ramond-Ramond charges
We take a worldsheet point of view on the relation between Ramond-Ramond
charges, invariants of boundary renormalization group flows and K-theory. In
compact super Wess-Zumino-Witten models, we show how to associate invariants of
the generalized Kondo renormalization group flows to a given supersymmetric
boundary state. The procedure involved is reminiscent of the way one can probe
the Ramond-Ramond charge carried by a D-brane in conformal field theory, and
the set of these invariants is isomorphic to the twisted K-theory of the Lie
group. We construct various supersymmetric boundary states, and we compute the
charges of the corresponding D-branes, disproving two conjectures on this
subject. We find a complete agreement between our algebraic charges and the
geometry of the D-branes.Comment: 58 pages. V4 : Problem with the bibliography correcte
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