542 research outputs found
Anharmonic mixing in a magnetic trap
We have experimentally observed re-equilibration of a magnetically trapped
cloud of metastable neon atoms after it was put in a non-equilibrium state.
Using numerical simulations we show that anharmonic mixing, equilibration due
to the collisionless dynamics of atoms in a magnetic trap, is the dominant
process in this equilibration. We determine the dependence of its time on trap
parameters and atom temperature. Furthermore we observe in the simulations a
resonant energy exchange between the radial and axial trap dimensions at a
ratio of trap frequencies \omega_r / \omega_z = 3/2. This resonance is
explained by a simple oscillator model.Comment: 9 pages, 6 figure
Gram-negative antibiotic resistance: there is a price to pay
Resistance rates are increasing among several problematic Gram-negative pathogens that are often responsible for serious nosocomial infections, including Acinetobacter spp., Pseudomonas aeruginosa, and (because of their production of extended-spectrum β-lactamase) Enterobacteriaceae. The presence of multiresistant strains of these organisms has been associated with prolonged hospital stays, higher health care costs, and increased mortality, particularly when initial antibiotic therapy does not provide coverage of the causative pathogen. Conversely, with high rates of appropriate initial antibiotic therapy, infections caused by multiresistant Gram-negative pathogens do not negatively influence patient outcomes or costs. Taken together, these observations underscore the importance of a 'hit hard and hit fast' approach to treating serious nosocomial infections, particularly when it is suspected that multiresistant pathogens are responsible. They also point to the need for a multidisciplinary effort to combat resistance, which should include improved antimicrobial stewardship, increased resources for infection control, and development of new antimicrobial agents with activity against multiresistant Gram-negative pathogens
Історія України в джерелознавчих дослідженнях З. Анусіка
Рецензія на монографію: Zbigniew Anusik, Studia i szkice staropolskie, Łódź 2011, Wydawnictwo Uniwersytetu Łódzkiego, s. 853 (Збігнев Анусік. Старопольські дослідження і нариси (Лодзь, 2011)
Enhanced Pauli blocking of light scattering in a trapped Fermi gas
Pauli blocking of spontaneous emission by a single excited-state atom has
been predicted to be dramatic at low temperature when the Fermi energy
exceeds the recoil energy . The photon scattering
rate of a ground-state Fermi gas can also be suppressed by occupation of the
final states accessible to a recoiling atom, however suppression is diminished
by scattering events near the Fermi edge. We analyze two new approaches to
improve the visibility of Pauli blocking in a trapped Fermi gas. Focusing the
incident light to excite preferentially the high-density region of the cloud
can increase the blocking signature by 14%, and is most effective at
intermediate temperature. Spontaneous Raman scattering between imbalanced
internal states can be strongly suppressed at low temperature, and is
completely blocked for a final-state in the
high imbalance limit.Comment: 12 pages, 8 figures. v4: to appear in Journal of Physics B: Atomic,
Molecular, and Optical Physic
Speckle Imaging of Spin Fluctuations in a Strongly Interacting Fermi Gas
Spin fluctuations and density fluctuations are studied for a two-component
gas of strongly interacting fermions along the BEC-BCS crossover. This is done
by in-situ imaging of dispersive speckle patterns. Compressibility and magnetic
susceptibility are determined from the measured fluctuations. This new
sensitive method easily resolves a tenfold suppression of spin fluctuations
below shot noise due to pairing, and can be applied to novel magnetic phases in
optical lattices
Nuclear and Mitochondrial DNA Polymorphisms in three parthenogenetic meloidogyne SPP
In order to expand our understanding of the genetics of root-knot nematodes, thevariation in nuclear DNA and mitochondrial DNA in Meloidogyne incognita, M.arenaria and M. javanica was investigated. Despite the obligate mitoticparthenogenetic mode of reproduction, a large number of AFLP polymorphismswere observed among all 16 populations studied. Both UPGMA and principlecoordinate analyses revealed three distinct groups that corresponded with therespective species identities of the 16 populations. M. incognita was geneticallymost distinct. Amplification of 63 bp tandem repeats (TR) in mtDNA from singleindividuals enabled the calculation of diversity measures at three hierarchicallevels: within individuals, among individuals of a single population and amongpopulations. For all three species, the highest diversity was observed withinindividuals explaining 43 to 65% of the total diversity. Many individualscontained more than one mtDNA size variant. M. incognita harboured the mostheteroplasmic individuals and was the most homogenous at the population level.Only 13% of the total diversity was observed among populations, while thisfigure was 35% for M. arenaria. Both TR and AFLP data showed that M.arenaria is the most heterogeneous species. The comparison of the geneticdistances based on AFLPs and mtDNA size variants revealed a significantcorrelation for the six M. arenaria populations, whereas no consistent correlationwas observed for the populations of the other two species
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