765 research outputs found
Dehydroleucodin: a guaiane-type sesquiterpene lactone
Dehydroleucodin [systematic name: (1S,6S,2R)-9,13-dimethyl-5-methylene-3-oxatricyclo[8.3.0.02,6]trideca-9,12-diene-4,11-dione], C15H16O3, is a guanolide isolated from Artemisia douglasiana. The fused-ring system contains a seven-membered ring that adopts a chair conformation, a fused planar cyclopentenone ring and a five-membered lactone ring fused in envelope conformation. The absolute structure determined by X-ray analysis agrees with that previously assigned to this compound by NMR studies [Bohlmann & Zdero (1972 ▶). Tetrahedron Lett.
13, 621–624] and also with that of leucodine, a closely related guaianolide [Martinez et al. (1988 ▶). J. Nat. Prod.
51, 221–228]
Probing Minimal Supergravity at the CERN LHC for Large
For large values of the minimal supergravity model parameter , the
tau lepton and the bottom quark Yukawa couplings become large, leading to
reduced masses of -sleptons and -squarks relative to their first and
second generation counterparts, and to enhanced decays of charginos and
neutralinos to -leptons and -quarks. We evaluate the reach of the CERN
LHC collider for supersymmetry in the mSUGRA model parameter space. We
find that values of GeV can be probed with just 10
fb of integrated luminosity for values as high as 45, so
that mSUGRA cannot escape the scrutiny of LHC experiments by virtue of having a
large value of . We also perform a case study of an mSUGRA model at
where \tz_2\to \tau\ttau_1 and \tw_1\to \ttau_1\nu_\tau
with branching fraction. In this case, at least within our
simplistic study, we show that a di-tau mass edge, which determines the value
of m_{\tz_2}-m_{\tz_1}, can still be reconstructed. This information can be
used as a starting point for reconstructing SUSY cascade decays on an
event-by-event basis, and can provide a strong constraint in determining the
underlying model parameters. Finally, we show that for large there
can be an observable excess of leptons, and argue that signals
might serve to provide new information about the underlying model framework.Comment: 22 page REVTEX file including 8 figure
can a rapid local cooling intervention help young soccer players?
The effects of a cooling strategy following repeated high-intensity running (RHIR) on soccer kicking performance in a hot environment (>30ºC) were investigated in youth soccer players. Fifteen academy under-17 players participated. In Experiment 1, players completed an all-out RHIR protocol (10×30 m, with 30s intervals). In Experiment 2 (cross-over design), participants performed this running protocol under two conditions: (1) following RHIR 5 minutes of cooling where ice packs were applied to the quadriceps/hamstrings, (2) a control condition involving passive resting. Perceptual measures [ratings of
perceived exertion (RPE), pain and recovery], thigh temperature and kick-derived video three-dimensional kinematics (lower limb) and performance (ball speed and two-dimensional placement indices) were collected at baseline, post-exercise and intervention. In Experiment 1, RHIR led to small- to-large impairments (p < 0.03;d = −0.42–-1.83) across perceptual, kinematic and performance measures. In experiment 2, RPE (p < 0.01; Kendall’s W = 0.30) and mean radial error (p = 0.057; η2 = 0.234) increased only post-control. Significant small declines in ball speed were also observed post-control (p < 0.05; d = 0.35). Post-intervention foot centre-of-mass velocity was moderately faster in the cooling compared to control condition (p = 0.04; d = 0.60). In youth soccer players, a short cooling period was beneficial in counteracting declines in kicking performance, in particular ball placement, following intense running activity in the heat.9E1A-F9DD-3EB8 | Filipe Manuel ClementeN/
Supersymmetry Reach of Tevatron Upgrades: The Large Case
The Yukawa couplings of the tau lepton and the bottom quark become comparable
to, or even exceed, electroweak gauge couplings for large values of the SUSY
parameter . As a result, the lightest tau slepton \ttau_1 and
bottom squark \tb_1 can be significantly lighter than corresponding sleptons
and squarks of the first two generations. Gluino, chargino and neutralino
decays to third generation particles are significantly enhanced when
is large. This affects projections for collider experiment reach
for supersymmetric particles. In this paper, we evaluate the reach of the
Fermilab Tevatron collider for supersymmetric signals in the
framework of the mSUGRA model. We find that the reach via signatures with
multiple isolated leptons ( and ) is considerably reduced. For very
large , the greatest reach is attained in the multi-jet+\eslt
signature. Some significant extra regions may be probed by requiring the
presence of an identified -jet in jets+\eslt events, or by requiring one
of the identified leptons in clean trilepton events to actually be a hadronic 1
or 3 charged prong tau. In an appendix, we present formulae for chargino,
neutralino and gluino three body decays which are valid at large .Comment: 31 page Revtex file including 10 PS figure
A Supersymmetric Explanation of the Excess of Higgs-Like Events at LEP
Searches for the Standard Model Higgs boson by the four LEP experiments found
excess events in two mass ranges: a 2.3 sigma excess around 98 GeV, and an 1.7
sigma excess around 115 GeV. The latter has been discussed widely in the
literature, but the former has attracted little attention so far. In this paper
I explore the possibility of explaining the excess near 98 GeV through
production of the lighter CP--even Higgs boson in the Minimal Supersymmetric
Standard Model (MSSM). It is shown that this allows to simultaneously explain
the excess near 115 GeV through the production of the heavier CP--even MSSM
Higgs boson. The resulting light Higgs sector offers opportunities for charged
Higgs boson searches at the Tevatron and LHC. Neutral Higgs boson searches at
the LHC in the di--muon channel are also promising. However, conclusive tests
of this scenario may have to wait for the construction of a linear e+ e-
collider.Comment: LaTeX, 14 pages, 7 .eps-files (included). Added references and a
couple of footnotes; results unchanged. Version to appear in PR
Determining mehlich‐3 and DTPA extractable soil zinc optimum economic threshold for maize
Maize (Zea mays L.) is one of the most susceptible crops to zinc (Zn) deficiency. However, in much of the world, soil Zn tests are poorly calibrated, and thus determining a critical soil test, level for Zn is challenging. The objectives of this study were to: (i) produce a field calibration of the Zn Mehlich-3 (M3-Zn) method for predicting maize grain yield response to Zn fertilizer application, (ii) compare the capacity of DTPA extractable Zn (DTPA-Zn) with M3-Zn for predicting the response of maize yield to Zn fertilizer, (iii) determine whether inclusion of soil pH, organic matter (SOM) and extractable phosphorus in a M3-Zn model improves its predictive capacity and (iv) evaluate an economic approach for determining soil Zn thresholds. We conducted 55 field experiments covering a wide range of edaphic and climatic conditions. Maize responded to Zn fertilizer in 29% of the trials. The capacity of M3-Zn and DTPA-Zn to predict relative yield of maize was similar. Inclusion of other soil variables (pH, extractable phosphorus and SOM) did not or only slightly improve the prediction of M3-Zn. Based on the relationship between M3-Zn and DTPA-Zn (R2 = 0.89), one test can be predicted from the other without affecting the calibration. The M3-Zn 'economic threshold' ranged from 0.98 to 2.79 mg kg−1, while for DTPA-Zn it varied from 0.41 to 1.61 mg kg−1. The broad range of economic thresholds shows that differences in maize productivity and grain price between regions and seasons make establishing a single Zn threshold for all economic-productive situations inappropriate.Fil: Martínez Cuesta, Nicolás. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Wyngaard, Nicolás. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Innovación Para la Producción Agropecuaria y El Desarrollo Sostenible. - Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Buenos Aires Sur. Estacion Experimental Agropecuaria Balcarce. Instituto de Innovación Para la Producción Agropecuaria y El Desarrollo Sostenible.; ArgentinaFil: Sainz Rozas, Hernan Rene. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Reussi Calvo, Nahuel Ignacio. Laboratorio de Analisis de Suelos Fertilab; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carciochi, Walter Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Eyherabide, Mercedes. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Innovación Para la Producción Agropecuaria y El Desarrollo Sostenible. - Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Buenos Aires Sur. Estacion Experimental Agropecuaria Balcarce. Instituto de Innovación Para la Producción Agropecuaria y El Desarrollo Sostenible.; ArgentinaFil: Colazo, Juan Cruz. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Barraco, Mariano Manuel. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Guertal, Elizabeth A.. Auburn University.; Estados UnidosFil: Barbieri, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Innovación Para la Producción Agropecuaria y El Desarrollo Sostenible. - Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Buenos Aires Sur. Estacion Experimental Agropecuaria Balcarce. Instituto de Innovación Para la Producción Agropecuaria y El Desarrollo Sostenible.; Argentin
Particle Dark Matter Physics: An Update
This write--up gives a rather elementary introduction into particle physics
aspects of the cosmological Dark Matter puzzle. A fairly comprehensive list of
possible candidates is given; in each case the production mechanism and
possible ways to detect them (if any) are described. I then describe detection
of the in my view most promising candidates, weakly interacting massive
particles or WIMPs, in slightly more detail. The main emphasis will be on
recent developments.Comment: Invited talk at the 5th Workshop on Particle Physics Phenomenology,
Pune, India, January 1998; 21 pages, LaTeX with equation.st
Direct Detection of Neutralino Dark Matter and the Anomalous Dipole Moment of the Muon
We compare predictions for the spin-independent contribution to the
neutralino-proton scattering cross section \sig and for the anomalous
magnetic dipole moment of the muon, , in models with
gravity-mediated supersymmetry breaking. We nearly always find a positive
correlation between these two measurables, i.e. scenarios with larger
also tend to have larger \sig, but the detailed prediction differs greatly
between models. In particular, we find that for the popular mSUGRA scenario
with universal soft breaking masses at the scale of Grand Unification,
measurements of currently seem more promising. On the other hand, if
scalar soft breaking masses at the GUT scale receive sizable contributions from
SO(10) D-terms, one often finds scenarios with large \sig but below
the currently foreseen sensitivity. A string-inspired model with non-universal
scalar spectrum at the GUT scale falls between these two cases.Comment: Some references added and manuscript slightly modifie
The Neutralino Relic Density in Minimal N=1 Supergravity
We compute the cosmic relic (dark matter) density of the lightest
supersymmetric particle (LSP) in the framework of minimal Supergravity
models with radiative breaking of the electroweak gauge symmetry. To this end,
we re--calculate the cross sections for all possible annihilation processes for
a general, mixed neutralino state with arbitrary mass. Our analysis includes
effects of all Yukawa couplings of third generation fermions, and allows for a
fairly general set of soft SUSY breaking parameters at the Planck scale. We
find that a cosmologically interesting relic density emerges naturally over
wide regions of parameter space. However, the requirement that relic
neutralinos do not overclose the universe does not lead to upper bounds on SUSY
breaking parameters that are strictly valid for all combinations of parameters
and of interest for existing or planned collider experiments; in particular,
gluino and squark masses in excess of 5 TeV cannot strictly be excluded. On the
other hand, in the ``generic'' case of a gaugino--like neutralino whose
annihilation cross sections are not ``accidentally'' enhanced by a nearby Higgs
or pole, all sparticles should lie within the reach of the proposed
and supercolliders. We also find that requiring the LSP to provide all
dark matter predicted by inflationary models imposes a strict lower bound of 40
GeV on the common scalar mass at the Planck scale, while the lightest
sleptons would have to be heavierComment: 53 pages(8figs are not included), Latex file; DESY 92-101,
SLAC-PUB-586
Production and Decay of Scalar Stoponium Bound States
In this paper we discuss possible signatures for the production of scalar
\stst\ (stoponium) bound states \sigst\ at hadron colliders, where \st\ is the
lighter scalar top eigenstate. We first study the decay of \sigst; explicit
expressions are given for all potentially important decay modes. If \st\ has
unsuppressed two--body decays, they will always overwhelm the annihilation
decays of \sigst. Among the latter, we find that usually either the or
final state dominates, depending on the size of the off--diagonal entry of
the stop mass matrix; is the lighter neutral scalar Higgs boson of the
minimal supersymmetric model. If \msig\ happens to be close to the mass of one
of the neutral scalar Higgs bosons, final states dominate ( or
). \ww\ and final states are subdominant. We argue that \sigst
\rightarrow \gamgam decays offer the best signal for stoponium production at
hadron colliders. The tevatron should be able to close the light stop window
left open by LEP searches, but its mass reach is limited to \msig \leq 90
GeV. In contrast, at the LHC one should ultimately be able to probe the region
\msig \leq 700 GeV, if the partial width is not too large. We also
comment on the feasibility of searching for \sigst\ production at hadron
colliders in the and \fourtau\ final states, and briefly
mention \sigst\ production at \gamgam\ colliders.Comment: 31 pages plus 10 figures (available from DREES@WISCPHEN); LaTeX with
equation.sty; MAD/PH/808, KEK-TH-37
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