744 research outputs found
Tyrosinase and phenolic pressor amines
Basic to the consideration of the action of tyrosinase on the oxidation of phenolic pressor amines are the observations of Keilin and Mann (16) and of Nelson and his coworkers (17-19) that show that different preparations may vary considerably in their relative actions on monophenols and o-diphenols. Both of these types of activity appear to belong to the same enzyme complex, as they bear a proportionality to the same copper content. However, since the activities vary with the purity and method of purification, each enzyme preparation must be defined in terms of both monophenolase and o-diphenolase activities. This was done in the present studies, and modifications of previously described preparative methods were required to retain a reasonable proportioning of such activities in purified preparations
Pyramiding of Meloidogyne hapla resistance genes in potato does not result in an increase of resistance
High levels of resistance against Meloidogyne hapla have been identified in wild species of tuber-bearing potatoes, but only QTL with partial effects have been identified so far in back crosses with cultivated potato. This study was designed to test if pyramiding of two previously identified resistance genes, R Mh-tar and R Mh-chc A, will result in improved or even an absolute level of resistance. R Mh-tar and R Mh-chc A introgressed from the wild tuber-bearing potato species Solanum tarijense and Solanum chacoense were combined in a segregating diploid Solanum tuberosum population. With the aid of AFLP markers, descendants from this segregating population were classified into four groups, carrying no R gene, with only R Mh-tar , with only R Mh-chc A and a group with the pyramided R Mh-tar and R Mh-chc A. Upon inoculation with M. hapla isolate Bovensmilde, the group containing only R Mh-chc A showed a decline of 88% in average number of developed egg masses compared to the group without R Mh-chc A and R Mh-tar . The group of genotypes containing only R Mh-tar , but not R Mh-chc A, showed a decline of 55% in the number of developed egg masses compared to the group without R Mh-chc A and R Mh-tar . Unfortunately, the latter effect of R Mh-tar was not significant. The effect of both loci, R Mh-tar and R Mh-chc A combined, did not further reduce the number of egg masses compared to the level of R Mh-chc A alon
Topological Density and Instantons on a Lattice
We present an update on the study of topological structure of QCD. Issues
addressed include a comparison between the plaquette and the geometric methods
of calculating the topological density. We show that the improved gauge action
based on sqrt(3) blocking transformation suppresses the formation of
topologically charged dislocations with low action. Using a cooling method we
identify the instantons' location, estimate their size and density, and
calculate the renormalization constant Z_Q for the plaquette method.Comment: 3 Pages, submitted to Proceedings of XII International Symposium on
Lattice Field Theory (Lattice 94, Bielefeld). uuencoded tar file includes
figures as TeXDraw (.tex) file
Spin susceptibility of the superfluid He-B in aerogel
The temperature dependence of paramagnetic susceptibility of the superfluid
^{3}He-B in aerogel is found. Calculations have been performed for an arbitrary
phase shift of s-wave scattering in the framework of BCS weak coupling theory
and the simplest model of aerogel as an aggregate of homogeneously distributed
ordinary impurities. Both limiting cases of the Born and unitary scattering can
be easily obtained from the general result. The existence of gapless
superfluidity starting at the critical impurity concentration depending on the
value of the scattering phase has been demonstrated. While larger than in the
bulk liquid the calculated susceptibility of the B-phase in aerogel proves to
be conspicuously smaller than that determined experimentally in the high
pressure region.Comment: 10 pages, 4 figures, REVTe
Preliminary Results from NEOWISE: An Enhancement to the Wide-field Infrared Survey Explorer for Solar System Science
The Wide-field Infrared Survey Explorer (WISE) has surveyed the entire sky at four infrared wavelengths with greatly improved sensitivity and spatial resolution compared to its predecessors, the Infrared Astronomical Satellite and the Cosmic Background Explorer. NASA's Planetary Science Division has funded an enhancement to the WISE data processing system called "NEOWISE" that allows detection and archiving of moving objects found in the WISE data. NEOWISE has mined the WISE images for a wide array of small bodies in our solar system, including near-Earth objects (NEOs), Main Belt asteroids, comets, Trojans, and Centaurs. By the end of survey operations in 2011 February, NEOWISE identified over 157,000 asteroids, including more than 500 NEOs and ~120 comets. The NEOWISE data set will enable a panoply of new scientific investigations
Real-time and Freehand Multimodal Imaging: Combining White Light Endoscopy with All-Optical Ultrasound
Minimally invasive surgery offers significant benefits
over open surgery in terms of patient recovery, complication
rates, and cost. Accurate visualisation is key for successful interventions; however, no single imaging modality offers sufficient
resolution, penetration, and soft-tissue contrast to adequately
monitor interventional treatment. Consequently, multimodal interventional imaging is intensively investigated. All-optical ultrasound (AOUS) imaging is an emerging modality where light is
used to both generate and detect ultrasound. Using fibre-optics,
highly miniaturised imaging probes can be fabricated that yield
high-quality pulse-echo images and are readily integrated into
minimally invasive interventional instruments. In this work, we
present the integration of a miniature (diameter: 800 µm), highly
directional AOUS imaging probe into a commercially available
white light urethroscope, and demonstrate the first real-time, 3D
multimodal imaging combining AOUS and white light endoscopy.
Through the addition of an electromagnetic tracker, the position
and pose of the instrument could be continuously recorded.
This facilitated accurate real-time registration of the imaging
modalities, as well as freehand operation of the instrument. In addition, the freehand imaging paradigm allowed for “piece-wise”
scanning where the instrument was retracted and repositioned
without recalibration. The presented imaging probe and system
could significantly improve the quality of image guidance during
interventional surgery
Pseudoscalar Meson Nonet at Zero and Finite Temperature
Theoretical understanding of experimental results from relativistic heavy-ion
collisions requires a microscopic approach to the behavior of QCD n-point
functions at finite temperatures, as given by the hierarchy of Dyson-Schwinger
equations, properly generalized within the Matsubara formalism. The convergence
of sums over Matsubara modes is studied. The technical complexity of
finite-temperature calculations mandates modeling. We present a model where the
QCD interaction in the infrared, nonperturbative domain, is modeled by a
separable form. Results for the mass spectrum of light quark flavors (u, d, s)
and for the pseudoscalar bound-state amplitudes at finite temperature are
presented.Comment: 14 pages, 11 figures, accepted for publication in Physics of
Particles and Nuclei Letters, based on invited lectures at "Dense Matter In
Heavy Ion Collisions and Astrophysics", 21.08-01.09 2006, Dubna, Russi
Speeding up finite step-size updating of full QCD on the lattice
We propose various improvements of finite step-size updating for full QCD on
the lattice that might turn finite step-size updating into a viable alternative
to the hybrid Monte Carlo algorithm. These improvements are noise reduction of
the noisy estimator of the fermion determinant, unbiased inclusion of the
hopping parameter expansion and a multi-level Metropolis scheme. First
numerical tests are performed for the 2 dimensional Schwinger model with two
flavours of Wilson fermions and for QCD two flavours of Wilson fermions and
Schr"odinger functional boundary conditions.Comment: 22 pages, 1 figur
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