17,748 research outputs found
Perturbative Tamm-Dancoff Renormalization
A new two-step renormalization procedure is proposed. In the first step, the
effects of high-energy states are considered in the conventional (Feynman)
perturbation theory. In the second step, the coupling to many-body states is
eliminated by a similarity transformation. The resultant effective Hamiltonian
contains only interactions which do not change particle number. It is subject
to numerical diagonalization. We apply the general procedure to a simple
example for the purpose of illustration.Comment: 20 pages, RevTeX, 10 figure
Growth regulator trials. Part 1
This summary covers 1981 trials on chlormequat plant growth regulant (formulated as Cycocel 750A or Halloween), ECO organic seed dressing and a range of organic foliar sprays. Rates and times of application of chlormequat on wheat. 81A22, 81BA3, 81Cl8, 81E25, 81M22, 81MT2, 81N4, 81SG36, 81WH4. Effects of chlormequat on wheat varieties (S4 trials). 81A6, 81BA7, 81C6, 81E6, 81M9, 81M13, 81MT9, 81N10, 81SG26, 81WH19. Trials comparing organic seed treatments, organic foliar sprays and plant growth regulators. 81WH61, 81LG34, 81LG48, 81ME27a, 81ME276, 81TS39, 81ES51, 81ES52, 81ES53, 81ES54, 81NA57, 81N4A, 81MT2A, 81TS38A. H. McCashney, Cadoux Un-numbered, Newdegate Research Station
Climate-related hydrological regimes and their effects on abundance of juvenile blue crabs (Callinectes sapidus) in the northcentral Gulf of Mexico
The abundance of juvenile blue crabs (Callinectes sapidus) in the northcentral Gulf of Mexico was investigated in response to climate-related hydrological regimes. Two distinct periods of blue crab abundance (1, 1973â94 and 2, 1997â2005) were associated with two opposite climaterelated
hydrological regimes. Period 1 was characterized by high numbers of crabs, whereas period 2 was characterized
by low numbers of crabs. The cold phase of the Atlantic Multidecadal Oscillation (AMO) and high north-south wind momentum were associated with period 1. Hydrological
conditions associated with phases of the AMO and North Atlantic Oscillation (NAO) in conjunction with the
north-south wind momentum may favor blue crab productivity by influencing blue crab predation dynamics through the exclusion of predators. About 25% (22â28%) of the variability in blue crab abundance was explained by a northâsouth wind momentum in concert with either salinity, precipitation, or the Palmer drought severity index, or by a combination of the NAO and preci
Experimental summaries.
Wheat Yield Potential Trials, 81BA4, 81WH7, 81KAS.Wheat-Regenerating Sandplain Lupin Rotation Trials, 79GE38, 79GE42.Nitrogen x Cycocel x Foliar Nutrients x Fungicide-on Wheat,81KA6. Historical Wheat Trials, 81A3, 81C4, 81SG22, 81WH6. Time of Planting on Cereal Yields, 81NA8, 81KA55
Initial bound state studies in light-front QCD
We present the first numerical QCD bound state calculation based on a
renormalization group-improved light-front Hamiltonian formalism. The QCD
Hamiltonian is determined to second order in the coupling, and it includes
two-body confining interactions. We make a momentum expansion, obtaining an
equal-time-like Schrodinger equation. This is solved for quark-antiquark
constituent states, and we obtain a set of self-consistent parameters by
fitting B meson spectra.Comment: 38 pages, latex, 5 latex figures include
The relationship between adiposity, bone density and microarchitecture is maintained in young women irrespective of diabetes status
Background:
The relationship between bone health and adiposity and how it may be affected in people with chronic metabolic conditions is complex.
Methods:
17 women with Type 1 diabetes mellitus (T1DM) and 9 age-matched healthy women with a median age of 22.6 yrs (range, 17.4, 23.8) were studied by 3T-MRI and MR spectroscopy to assess abdominal adiposity, tibial bone microarchitecture and vertebral bone marrow adiposity. Additional measures included DXA-based assessments of total body (TB), femoral neck (FN) and lumbar spine (LS) bone mineral density (BMD) and fat mass (FM).
Results:
Although women with T1DM had similar BMI and bone marrow adiposity to the controls, they had higher visceral and subcutaneous adiposity on MRI (p<0.05) and total body FM by DXA (p=0.03). Overall, in the whole cohort, a clear inverse association was evident between bone marrow adiposity and BMD at all sites (p<0.05). These associations remained significant after adjusting for age, BMI, FM, and abdominal adiposity. In addition, visceral adiposity, but not subcutaneous adiposity, showed a positive association with bone marrow adiposity (r,0.4, p=0.03), and a negative association with total body BMD (r,0.5, p=0.02). Apparent trabecular separation as assessed by MRI showed an inverse association to total body BMD by DXA (r,â0.4, p=0.04).
Conclusion:
Irrespective of the presence of an underlying metabolic condition, young women display a negative relationship between MRI-measured bone marrow adiposity and DXA-based assessment of bone mineral density. Furthermore, an association between bone marrow adiposity and visceral adiposity supports the notion of a common origin of these two fat depots
Design and operation of a prototype interaction point beam collision feedback system for the International Linear Collider
A high-resolution, intratrain position feedback system has been developed to
achieve and maintain collisions at the proposed future electron-positron
International Linear Collider (ILC). A prototype has been commissioned and
tested with a beam in the extraction line of the Accelerator Test Facility at
the High Energy Accelerator Research Organization in Japan. It consists of a
stripline beam position monitor (BPM) with analogue signal-processing
electronics, a custom digital board to perform the feedback calculation, and a
stripline kicker driven by a high-current amplifier. The closed-loop feedback
latency is 148 ns. For a three-bunch train with 154 ns bunch spacing, the
feedback system has been used to stabilize the third bunch to 450 nm. The
kicker response is linear, and the feedback performance is maintained, over a
correction range of over 60 {\mu}m. The propagation of the correction has
been confirmed by using an independent stripline BPM located downstream of the
feedback system. The system has been demonstrated to meet the BPM resolution,
beam kick, and latency requirements for the ILC
Phenomenology for the decay of energy-containing eddies in homogeneous MHD turbulence
We evaluate a number of simple, oneâpoint phenomenological models for the decay of energyâcontaining eddies in magnetohydrodynamic(MHD) and hydrodynamicturbulence. The MHDmodels include effects of cross helicity and AlfvĂ©nic couplings associated with a constant mean magnetic field, based on physical effects wellâdescribed in the literature. The analytic structure of three separate MHDmodels is discussed. The single hydrodynamic model and several MHDmodels are compared against results from spectralâmethod simulations. The hydrodynamic model phenomenology has been previously verified against experiments in wind tunnels, and certain experimentally determined parameters in the model are satisfactorily reproduced by the present simulation. This agreement supports the suitability of our numerical calculations for examining MHDturbulence, where practical difficulties make it more difficult to study physical examples. When the tripleâdecorrelation time and effects of spectral anisotropy are properly taken into account, particular MHDmodels give decay rates that remain correct to within a factor of 2 for several energyâhalving times. A simple model of this type is likely to be useful in a number of applications in space physics, astrophysics, and laboratory plasma physics where the approximate effects of turbulence need to be included
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