897 research outputs found
Implications of the Partial Width Z->bb for Supersymmetry Searches and Model-Building
Assuming that the actual values of the top quark mass at FNAL and of the
ratio of partial widths Z->bb/Z->hadrons at LEP are within their current
one-sigma reported ranges, we present a No-Lose Theorem for superpartner
searches at LEP II and an upgraded Tevatron. We impose only two theoretical
assumptions: the Lagrangian is that of the Minimal Supersymmetric Standard
Model with arbitrary soft-breaking terms, and all couplings remain perturbative
up to scales of order 10^16 GeV; there are no assumptions about the soft SUSY
breaking parameters, proton decay, cosmology, etc. In particular, if the LEP
and FNAL values hold up and supersymmetry is responsible for the discrepancy
with the SM prediction of the partial width of Z->bb, then we must have
charginos and/or top squarks observable at the upgraded machines. Furthermore,
little deviation from the SM is predicted within "super-unified" SUSY. Finally,
it appears to be extremely difficult to find any unified MSSM model, regardless
of the form of soft SUSY breaking, that can explain the partial width for large
tan(beta); in particular, no model with top-bottom-tau Yukawa coupling
unification appears to be consistent with the experiments.Comment: 15 pages, University of Michigan preprint UM-TH-94-23. LaTeX file
with 4 uuencoded figures sent separately. Compressed PS file (114Kb)
available by anonymous FTP from 141.211.96.66 in
/pub/preprints/UM-TH-94-23.ps.
Recommended from our members
Characteristic magnetic field and speed properties of interplanetary coronal mass ejections and their sheath regions
Prediction of the solar wind conditions in near-Earth space, arising from both quasi-steady and transient structures, is essential for space weather forecasting. To achieve forecast lead times of a day or more, such predictions must be made on the basis of remote solar observations. A number of empirical prediction schemes have been proposed to forecast the transit time and speed of coronal mass ejections (CMEs) at 1 AU. However, the current lack of magnetic field measurements in the corona severely limits our ability to forecast the 1 AU magnetic field strengths resulting from interplanetary CMEs (ICMEs). In this study we investigate the relation between the characteristic magnetic field strengths and speeds of both magnetic cloud and noncloud ICMEs at 1 AU. Correlation between field and speed is found to be significant only in the sheath region ahead of magnetic clouds, not within the clouds themselves. The lack of such a relation in the sheaths ahead of noncloud ICMEs is consistent with such ICMEs being skimming encounters of magnetic clouds, though other explanations are also put forward. Linear fits to the radial speed profiles of ejecta reveal that faster-traveling ICMEs are also expanding more at 1 AU. We combine these empirical relations to form a prediction scheme for the magnetic field strength in the sheaths ahead of magnetic clouds and also suggest a method for predicting the radial speed profile through an ICME on the basis of upstream measurements
Effects of feeding low levels of crude glycerin with or without other by-products on performance and carcass characteristics of feedlot heifers
Expansion of the renewable fuels industries has increased availability of by-products that are well suited for use as cattle feed. Glycerin is among the principal by-products of biodiesel production, comprising approximately 10% (by weight) of the soybean oil that is used to manufacture soy-based diesel fuel. Our previous research evaluated effects of including between 0% and 16% glycerin in flaked-corn finishing diets and revealed that optimal growth performance was achieved with 2% glycerin addition. Our laboratory experiments have suggested that even lower levels of glycerin may be effective at stimulating digestion. Therefore, the objective of this study was to evaluate effects of low levels of glycerin in the diet on performance and carcass characteristics of finishing cattle. Furthermore, because distillers grains and other by-products are increasingly common in feedlot rations, we opted to evaluate glycerin in corn-based finishing diets as well as in diets that consisted of a combination of corn grain, distillers grains, and soybean hulls
Post-Concussion Cognitive Declines and Symptomatology Are Not Related to Concussion Biomechanics in High School Football Players
Concussion is a major public health concern with nearly 4 million injuries occurring each year in the United States. In the acute post-injury stage, concussed individuals demonstrate cognitive function and motor control declines as well as reporting increased symptoms. Researchers have hypothesized that the severity of these impairments is related to impact magnitude. Using the Head Impact Telemetry System (HITS) to record head impact biomechanics, we sought to correlate pre- and post-concussive impact characteristics with declines in cognitive performance and increases in concussion-related symptoms. Over four seasons, 19 high school football athletes wearing instrumented helmets sustained 20 diagnosed concussions. Each athlete completed a baseline computer-based symptom and cognitive assessment during the pre-season and a post-injury assessment within 24-h of injury. Correlational analyses identified no significant relationships between symptoms and cognitive performance change scores and impact biomechanics (i.e., time from session start until injury, time from the previous impact, peak linear acceleration, peak rotational acceleration, and HIT severity profile [HITsp]). Nor were there any significant relationships between change scores and the number of impacts, cumulative linear acceleration, cumulative rotational acceleration, or cumulative HITsp values associated with all impacts prior to or following the injury. This investigation is the first to examine the relationship between concussion impact characteristics, including cumulative impact profiles, and post-morbid outcomes in high school athletes. There appears to be no association between head impact biomechanics and post-concussive outcomes. As such, the use of biomechanical variables to predict injury severity does not appear feasible at this time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90455/1/neu-2E2011-2E1905.pd
The diving behaviour of mammal-eating killer whales (Orcinus orca): variations with ecological not physiological factors
Mammal-eating killer whales (Orcinus orca (L., 1758)) are a rare example of social predators that hunt together in groups of sexually dimorphic adults and juveniles with diverse physiological diving capacities. Day–night ecological differences should also affect diving as their prey show diel variation in activity and mammal-eating killer whales do not rely on echolocation for prey detection. Our objective was to explore the extent to which physiological aerobic capacities versus ecological factors shape the diving behaviour of this breath-hold diver. We used suction-cup-attached depth recorders (Dtags) to record 7608 dives of 11 animals in southeast Alaska. Analysis of dive sequences revealed a strong bout structure in both dive depth and duration. Day–night comparisons revealed reduced rates of deep dives, longer shallow dives, and shallower long-duration dives at night. In contrast, dive variables did not differ by age–sex class. Estimates of the aerobic dive limit (cADL) suggest that juveniles exceeded their cADL during as much as 15% of long dives, whereas adult males and females never exceeded their cADL. Mammal-eating killer whales in this area appear to employ a strategy of physiological compromise, with smaller group members diving nearer their physiological limits and large-bodied males scaling down their physiological performance
The unspoken voice: applying John Shotter’s dialogic lens to qualitative data from people who have communication difficulties
As speech and language therapists, we explored theories of communication and voice that are familiar to our profession and found them an inadequate basis on which to generate deep and rich analysis of the qualitative data from people who have communication difficulties and who use augmentative and alternative communication. Expanding our conceptual toolkit to include the work of John Shotter allowed us to reconceptualise voice and where it is emergent in dialogue. Reimaging voice will inform clinical and research praxis with people who have communication difficulties as it allows practitioners to attend more closely to the complexity and nuance inherent in interactions with this population. Our proposition is exemplified with excerpts from a single participant who has communication difficulties to illustrate the value of dialogic theory in praxis. This article presents a provocation for the wider academy of qualitative health research; do we have the concepts and tools to develop meaning with people whose lived experiences may also be hard to voice in monologues
Early stage morphology of quench condensed Ag, Pb and Pb/Ag hybrid films
Scanning Tunneling Microscopy (STM) has been used to study the morphology of
Ag, Pb and Pb/Ag bilayer films fabricated by quench condensation of the
elements onto cold (T=77K), inert and atomically flat Highly Oriented Pyrolytic
Graphite (HOPG) substrates. All films are thinner than 10 nm and show a
granular structure that is consistent with earlier studies of QC films. The
average lateral diameter, , of the Ag grains, however, depends on
whether the Ag is deposited directly on HOPG ( = 13 nm) or on a Pb
film consisting of a single layer of Pb grains ( = 26.8 nm). In
addition, the critical thickness for electrical conduction () of Pb/Ag
films on inert glass substrates is substantially larger than for pure Ag films.
These results are evidence that the structure of the underlying substrate
exerts an influence on the size of the grains in QC films. We propose a
qualitative explanation for this previously unencountered phenomenon.Comment: 11 pages, 3 figures and one tabl
Evaluation of Ralgro® on pasture and subsequent feedlot performance and carcass merit of mexican crossbred steers
A pasture/feedlot field study was conducted
to evaluate the effects of a single
Ralgro® implant during the stocker phase on
steer grazing performance and subsequent
feedlot performance and carcass merit. A
total of 2,764 steers of Mexican origin averaging
449 lb were assembled in Texas and
shipped to Kansas, where they grazed on
three intensively-early-stocked Flint Hills
pastures. At initial processing, the steers
were individually weighed and randomly
assigned to either a non-implanted control
group or a Ralgro implant group. Ralgro
steers gained more (23 lb; P<0.01) than
controls during the 82- to 93-day grazing
phase. Following the grazing phase, all steers
were shipped to a commercial feedlot in
southwestern Kansas where steers from each
pasture were individually weighed and given
a single Component E-S® implant. Immediately
after processing, steers from each
pasture were sorted into either a light- or
heavy-weight pen, regardless of pasture
implant treatment, resulting in six feedlot
pens. Days on feed ranged from 127 to 197.
Control steers gained faster (P<0.01) during
the feedlot phase; however, Ralgro steers had
higher cumulative weight gains across the
combined pasture and feedlot phases
(P<0.01) and averaged three fewer days on
feed (P<0.05). There were no significant
differences for marbling, fat thickness, ribeye
area, KPH fat, or yield grade. Ralgro
steers had lower (P<0.05) quality grades
because of a higher incidence (P<0.001) of
steers with B and C carcass maturities
Classical Logical versus Quantum Conceptual Thought: Examples in Economics, Decision theory and Concept Theory
Inspired by a quantum mechanical formalism to model concepts and their
disjunctions and conjunctions, we put forward in this paper a specific
hypothesis. Namely that within human thought two superposed layers can be
distinguished: (i) a layer given form by an underlying classical deterministic
process, incorporating essentially logical thought and its indeterministic
version modeled by classical probability theory; (ii) a layer given form under
influence of the totality of the surrounding conceptual landscape, where the
different concepts figure as individual entities rather than (logical)
combinations of others, with measurable quantities such as 'typicality',
'membership', 'representativeness', 'similarity', 'applicability', 'preference'
or 'utility' carrying the influences. We call the process in this second layer
'quantum conceptual thought', which is indeterministic in essence, and contains
holistic aspects, but is equally well, although very differently, organized
than logical thought. A substantial part of the 'quantum conceptual thought
process' can be modeled by quantum mechanical probabilistic and mathematical
structures. We consider examples of three specific domains of research where
the effects of the presence of quantum conceptual thought and its deviations
from classical logical thought have been noticed and studied, i.e. economics,
decision theory, and concept theories and which provide experimental evidence
for our hypothesis.Comment: 14 page
Higgs boson mass limits in perturbative unification theories
Motivated in part by recent demonstrations that electroweak unification into
a simple group may occur at a low scale, we detail the requirements on the
Higgs mass if the unification is to be perturbative. We do this for the
Standard Model effective theory, minimal supersymmetry, and next-to-minimal
supersymmetry with an additional singlet field. Within the Standard Model
framework, we find that perturbative unification with sin2(thetaW)=1/4 occurs
at Lambda=3.8 TeV and requires mh<460 GeV, whereas perturbative unification
with sin2(thetaW)=3/8 requires mh<200 GeV. In supersymmetry, the presentation
of the Higgs mass predictions can be significantly simplified, yet remain
meaningful, by using a single supersymmetry breaking parameter Delta_S. We
present Higgs mass limits in terms of Delta_S for the minimal supersymmetric
model and the next-to-minimal supersymmetric model. We show that in
next-to-minimal supersymmetry, the Higgs mass upper limit can be as large as
500 GeV even for moderate supersymmetry masses if the perturbative unification
scale is low (e.g., Lambda=10 TeV).Comment: 20 pages, latex, 6 figures, references adde
- …