92,547 research outputs found
Fitting Precision Electroweak Data with Exotic Heavy Quarks
The 1999 precision electroweak data from LEP and SLC persist in showing some
slight discrepancies from the assumed standard model, mostly regarding and
quarks. We show how their mixing with exotic heavy quarks could result in a
more consistent fit of all the data, including two unconventional
interpretations of the top quark.Comment: 7 pages, no figure, 2 typos corrected, 1 reference update
A Study of the LEP and SLD Measurements of
A systematic study is made of the data dependence of the parameter
, that, since 1995, has shown a deviation from the Standard Model
prediction of between 2.4 and 3.1 standard deviations. Issues addressed
include: the effect of particular measurements, values found by individual
experiments, LEP/SLD comparison, and the treatment of systematic errors. The
effect, currently at the 2.4 level, is found to vary in the range from
1.7 to 2.9 by excluding marginal or particularly sensitive
data. Since essentially the full LEP and SLD Z decay data sets are now analysed
the meaning of the deviation, (new physics, or marginal statistical
fluctuation) is unlikely to be given by the present generation of colliders.Comment: 15 pages 7 figures 7 table
Implementation on a nonlinear concrete cracking algorithm in NASTRAN
A computer code for the analysis of reinforced concrete structures was developed using NASTRAN as a basis. Nonlinear iteration procedures were developed for obtaining solutions with a wide variety of loading sequences. A direct access file system was used to save results at each load step to restart within the solution module for further analysis. A multi-nested looping capability was implemented to control the iterations and change the loads. The basis for the analysis is a set of mutli-layer plate elements which allow local definition of materials and cracking properties
Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes
Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. The areas covered were: (1) development of a theoretical expression for the rotating ring disk electrode technique; (2) determination of the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; (3) determination of oxygen reduction mechanism in trifluoreomethanesulfonic acid (TFMSA) which was considered as an alternate electrolyte for the acid fuel cells; and (4) the measurement of transport properties of the phosphoric acid electrolyte at high concentrations and temperatures
Origin of spin reorientation transitions in antiferromagnetic MnPt-based alloys
Antiferromagnetic MnPt exhibits a spin reorientation transition (SRT) as a
function of temperature, and off-stoichiometric Mn-Pt alloys also display SRTs
as a function of concentration. The magnetocrystalline anisotropy in these
alloys is studied using first-principles calculations based on the coherent
potential approximation and the disordered local moment method. The anisotropy
is fairly small and sensitive to the variations in composition and temperature
due to the cancellation of large contributions from different parts of the
Brillouin zone. Concentration and temperature-driven SRTs are found in
reasonable agreement with experimental data. Contributions from specific
band-structure features are identified and used to explain the origin of the
SRTs.Comment: 6 pages, 8 figure
Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes
Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. A theoretical expression for the rotating ring-disk electrode technique; the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; oxygen reduction mechanism in trifluoromethanesulfonic acid (TFMSA), considered as an alternate electrolyte for the acid fuel cells; and transport properties of the phosphoric acid electrolyte at high concentrations and temperatures are covered
Moral hazard under commercial and universal banking
Many claims have been made about the potential benefits, and the potential costs, of adopting a system of universal banking in the United States. We evaluate these claims using a model where there is a moral hazard problem between banks and “borrowers,” a moral hazard problem between banks and a deposit insurer, and a costly state verification problem. Under conditions we describe, allowing banks to take equity positions in firms strengthens their ability to extract surplus, and exacerbates problems of moral hazard. The incentives of universal banks to take equity positions will often be strongest when these problems are most severe.Universal banks
- …