2,990 research outputs found
CP violation in the lepton sector with Majorana neutrinos
We study CP violation in the lepton sector in extended models with
right-handed neutrinos, without and with left-right symmetry, and with
arbitrary mass terms. We find the conditions which must be satisfied by the
neutrino and charged lepton mass matrices for CP conservation. These
constraints, which are independent of the choice of weak basis, are proven to
be also sufficient in simple cases. This invariant formulation makes apparent
the necessary requirements for CP violation, as well as the size of CP
violating effects. As an example, we show that CP violation can be much larger
in left-right symmetric models than in models with only additional right-handed
neutrinos, {\it i.e.}, without right-handed currents.Comment: 19 page
Seeing Star Formation Regions with Gravitational Microlensing
We qualitatively study the effects of gravitational microlensing on our view
of unresolved extragalactic star formation regions. Using a general
gravitational microlensing configuration, we perform a number of simulations
that reveal that specific imprints of the star forming region are imprinted,
both photometrically and spectroscopically, upon observations. Such
observations have the potential to reveal the nature and size of these star
forming regions, through the degree of variability observed in a monitoring
campaign, and hence resolve the star formation regions in distant galaxies
which are too small to be probed via more standard techniques.Comment: 7 pages, 8 figures, ApJ accepte
Sch 29482, laboratory evaluation of a new penem antibiotic
The antibacterial activity of a new penem antibiotic, Sch 29482 (SCH), was examined in comparison with appropriate cephalosporins and penicillins. The drug inhibited penicillinase-positive and negative staphylococci equally well, being 2-5 times more active than cephalothin or cefamandole and 10-20 times more active than methicillin. Staphylococci resistant to methicillin were susceptible to SCH in agar dilution tests. Staphylococci tolerant to methicillin were also tolerant to SCH. Streptococci and pneumococci were highly susceptible to the drug. The agent was of only moderate activity against enterococci, especially Streptococcus faecium strains. MICs of ampicillin and penicillin G against enterococci were 4-8 times lower than those of SCH. SCH was bactericidal. Neither the choice of the method used for susceptibility testing, nor the size of the inoculum nor various test media influenced the in-vitro activity of this drug against a representative collection of Gram-negative and Gram-positive bacteri
Quasar Microlensing: when compact masses mimic smooth matter
The magnification induced by gravitational microlensing is sensitive to the
size of a source relative to the Einstein radius, the natural microlensing
scale length. This paper investigates the effect of source size in the case
where the microlensing masses are distributed with a bimodal mass function,
with solar mass stars representing the normal stellar masses, and smaller
masses (down to M) representing a dark matter
component. It is found that there exists a critical regime where the dark
matter is initially seen as individual compact masses, but with an increasing
source size the compact dark matter acts as a smooth mass component. This study
reveals that interpretation of microlensing light curves, especially claims of
small mass dark matter lenses embedded in an overall stellar population, must
consider the important influence of the size of the source.Comment: 6 pages, to appear in ApJ. As ever, quality of figures reduce
Interactive and automated application of virtual microscopy
Virtual microscopy can be applied in an interactive and an automated manner. Interactive application is performed in close association to conventional microscopy. It includes image standardization suitable to the performance of an individual pathologist such as image colorization, white color balance, or individual adjusted brightness. The steering commands have to include selection of wanted magnification, easy navigation, notification, and simple measurements (distances, areas). The display of the histological image should be adjusted to the physical limits of the human eye, which are determined by a view angle of approximately 35 seconds. A more sophisticated performance should include acoustic commands that replace the corresponding visual commands. Automated virtual microscopy includes so-called microscopy assistants which can be defined similar to the developed assistants in computer based editing systems (Microsoft Word, etc.). These include an automated image standardization and correction algorithms that excludes images of poor quality (for example uni-colored or out-of-focus images), an automated selection of the most appropriate field of view, an automated selection of the best magnification, and finally proposals of the most probable diagnosis. A quality control of the final diagnosis, and feedback to the laboratory determine the proposed system. The already developed tools of such a system are described in detail, as well as the results of first trials. In order to enhance the speed of such a system, and to allow further user-independent development a distributed implementation probably based upon Grid technology seems to be appropriate. The advantages of such a system as well as the present pathology environment and its expectations will be discussed in detail
Corrections for gravitational lensing of supernovae: better than average?
We investigate the possibility of correcting for the magnification due to
gravitational lensing of standard candle sources, such as Type Ia supernovae.
Our method uses the observed properties of the foreground galaxies along the
lines-of-sight to each source and the accuracy of the lensing correction
depends on the quality and depth of these observations as well as the
uncertainties in translating the observed luminosities to the matter
distribution in the lensing galaxies. The current work is limited to cases
where the matter density is dominated by the individual galaxy halos. However,
it is straightforward to generalize the method to include also gravitational
lensing from cluster scale halos. We show that the dispersion due to lensing
for a standard candle source at z=1.5 can be reduced from about 7% to ~< 3%,
i.e. the magnification correction is useful in reducing the scatter in the Type
Ia Hubble diagram, especially at high redshifts where the required long
exposure times makes it hard to reach large statistics and the dispersion due
to lensing becomes comparable to the intrinsic Type Ia scatter.Comment: Matches accepted version, includes clarifications and additional
issues. 28 pages, 7 figures, accepted for publication in Ap
Bounds on gamma from CP violation measurements in B -> pi+ pi- and B -> psi K_S
We study the determination of gamma from CP-violating observables in B -> pi+
pi- and B -> psi K_S. This determination requires theoretical input to one
combination of hadronic parameters. We show that a mild assumption about this
quantity may allow bounds to be placed on gamma, but we stress the pernicious
effects that an eightfold discrete ambiguity has on such an analysis. The
bounds are discussed as a function of the direct (C) and interference (S)
CP-violating observables obtained from time-dependent B -> pi+ pi- decays, and
their behavior in the presence of new physics effects in B-Bbar mixing is
studied. (V2: Misprints corrected. Slightly improved discussion.)Comment: 11 pages, RevTex 4, 5 eps figures include
Comparative activity of the penem antibiotic Sch 34343 against Gram-negative and Gram-positive bacteria with special reference to multiresistant strains
A new penem antibiotic, Sch 34343, was shown to be active against a large number of Gram-positive bacteria. The drug inhibited penicillinase-positive and -negative staphylococci equally well, being five times more active than cefamandole and ten times more active than methiallin. Most methicillin-rcsistant staphylococci were inhibited by concentrations between 0.25 and 4 mg/1, but a small group of highly resistant strains were observed. Sch 34343 was eight times less active than ampicillin and penicillin G, but as active as piperacilhn against enterococci. The drug showed excellent activity against various streptococci. Sch 34343 was as bactericidal as flucloxacillin, ampicillin and penicillin G against staphylococci, enterococci and streptococci, respectively, in killing kinetic tests Enterobacteriaceae susceptible to third-generation cephalosporins were approximately five times less susceptible to Sch 34343, but MICs were far below the susceptibility breakpoint Sch 34343 was equally active against Citrobacter and Enterobacter strains that were highly resistant to third-generation cephalosporins and to aztreonam. Together with thienamycin, this drug seems to be a good alternative for the treatment of infections caused by bacteria resistant to third-generation cephalosporins and to aztreona
A unique aminoglycoside-O-phosphorylating activity mediating resistance to aminoglycosides in Escherichia coli
Gravitational lensing as folds in the sky
We revisit the gravitational lensing phenomenon using a new visualization
technique. It consists in projecting the observers sky into the source plane,
what gives rise to a folded and stretched surface. This provides a clear
graphical tool to visualize some interesting well-known effects, such as the
development of multiple images of a source, the structure of the caustic
curves, the parity of the images and their magnification as a function of the
source position.Comment: 11 pages, 8 figure
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