795 research outputs found
Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy
Copolymer networks with methacrylate main chain and caprolactone and ethylene glycol side groups were obtained by free radical copolymerisation of caprolactone methacrylate (CLMA) and poly(ethylene glycol) methacrylate (PEGMA). Dielectric relaxation spectroscopy was used to analyse molecular mobility of the different groups in the system. Only one main dielectric relaxation process was found in CLMA/PEGMA copolymer networks, located between those of the corresponding homonetworks, indicating that the system does not present phase separation. The copolymers show a secondary relaxation process at temperatures below −50 °C, which can be assigned to the overlapping of the corresponding secondary processes for the homopolymer networks; one of them was related to the local mobility of caprolactone units in CLMA and the second one was assigned to the twisting motions within ethylene glycol moiety in PEGMA. Besides the relaxation processes, the mobility of space charges has been analysed by means of conductivity and electric modulus formalisms.The support from the Spanish Ministry of Economy and Competitiveness (MINECO) and FEDER funds under the project MAT2012-38359-C03-01 is gratefully acknowledged.Sabater I Serra, R.; Escobar Ivirico, JL.; Romero Colomer, FJ.; Andrio Balado, A.; Gómez Ribelles, JL. (2014). Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy. Journal of Non-Crystalline Solids. 404:109-115. https://doi.org/10.1016/j.jnoncrysol.2014.08.013S10911540
Linear Collider Capabilities for Supersymmetry in Dark Matter Allowed Regions of the mSUGRA Model
Recent comparisons of minimal supergravity (mSUGRA) model predictions with
WMAP measurements of the neutralino relic density point to preferred regions of
model parameter space. We investigate the reach of linear colliders (LC) with
and 1 TeV for SUSY in the framework of the mSUGRA model. We find
that LCs can cover the entire stau co-annihilation region provided \tan\beta
\alt 30. In the hyperbolic branch/focus point (HB/FP) region of parameter
space, specialized cuts are suggested to increase the reach in this important
``dark matter allowed'' area. In the case of the HB/FP region, the reach of a
LC extends well past the reach of the CERN LHC. We examine a case study in the
HB/FP region, and show that the MSSM parameters and can be
sufficiently well-measured to demonstrate that one would indeed be in the HB/FP
region, where the lightest chargino and neutralino have a substantial higgsino
component.Comment: 29 pages, 15 EPS figures; updated version slightly modified to
conform with published versio
RS1, Custodial Isospin and Precision Tests
We study precision electroweak constraints within a RS1 model with gauge
fields and fermions in the bulk. The electroweak gauge symmetry is enhanced to
SU(2)_L \times SU(2)_R \times U(1)_{B-L}, thereby providing a custodial isospin
symmetry sufficient to suppress excessive contributions to the T parameter. We
then construct complete models, complying with all electroweak constraints, for
solving the hierarchy problem, without supersymmetry or large hierarchies in
the fundamental couplings. Using the AdS/CFT correspondence our models can be
interpreted as dual to a strongly coupled conformal Higgs sector with global
custodial symmetry, gauge and fermionic matter being fundamental fields
external to the CFT. This scenario has interesting collider signals, distinct
from other RS models in the literature.Comment: 32 pages, 6 figures, latex2e, minor changes, references adde
Can forest management based on natural disturbances maintain ecological resilience?
Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance
Second Generation Leptoquark Search in p\bar{p} Collisions at = 1.8 TeV
We report on a search for second generation leptoquarks with the D\O\
detector at the Fermilab Tevatron collider at = 1.8 TeV.
This search is based on 12.7 pb of data. Second generation leptoquarks
are assumed to be produced in pairs and to decay into a muon and quark with
branching ratio or to neutrino and quark with branching ratio
. We obtain cross section times branching ratio limits as a function
of leptoquark mass and set a lower limit on the leptoquark mass of 111
GeV/c for and 89 GeV/c for at the 95%\
confidence level.Comment: 18 pages, FERMILAB-PUB-95/185-
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
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