944 research outputs found
Pt/Ti/SiO2/Si substrates
Pt/Ti/SiO2/Si structures have been studied to investigate the structural, chemical, and microstructural changes that occur during annealing. Grain growth of the as-deposited Pt columns was observed after annealing at 650 °C, and extensive changes in the Pt microstructure were apparent following a 750 °C anneal for 20 min. In addition, two types of defects were identified on the surfaces of annealed substrates. Defect formation was retarded when the surface was covered with a ferroelectric film. Concurrent with the annealing-induced Pt microstructure changes, Ti from the adhesion layer between the Pt and the SiO2 migrated into the Pt layer and oxidized. It was shown with spectroscopic ellipsometry and Auger electron spectroscopy that for long annealing times, the titanium oxide layer can reach the Pt surface. Consequently, at the processing temperatures utilized in preparing many ferroelectric thin films, the substrate is not completely inert or immobile. The changes associated with Ti migration could be especially problematic in techniques that require the substrate to be heated prior to film depositio
Embedding the Pentagon
The Pentagon Model is an explicit supersymmetric extension of the Standard
Model, which involves a new strongly-interacting SU(5) gauge theory at
TeV-scale energies. We show that the Pentagon can be embedded into an SU(5) x
SU(5) x SU(5) gauge group at the GUT scale. The doublet-triplet splitting
problem, and proton decay compatible with experimental bounds, can be
successfully addressed in this context. The simplest approach fails to provide
masses for the lighter two generations of quarks and leptons; however, this
problem can be solved by the addition of a pair of antisymmetric tensor fields
and an axion.Comment: 39 page
Naturalness and Higgs Decays in the MSSM with a Singlet
The simplest extension of the supersymmetric standard model - the addition of
one singlet superfield - can have a profound impact on the Higgs and its
decays. We perform a general operator analysis of this scenario, focusing on
the phenomenologically distinct scenarios that can arise, and not restricting
the scope to the narrow framework of the NMSSM. We reexamine decays to four b
quarks and four tau's, finding that they are still generally viable, but at the
edge of LEP limits. We find a broad set of Higgs decay modes, some new,
including those with four gluon final states, as well as more general six and
eight parton final states. We find the phenomenology of these scenarios is
dramatically impacted by operators typically ignored, specifically those
arising from D-terms in the hidden sector, and those arising from weak-scale
colored fields. In addition to sensitivity of m_Z, there are potential tunings
of other aspects of the spectrum. In spite of this, these models can be very
natural, with light stops and a Higgs as light as 82 GeV. These scenarios
motivate further analyses of LEP data as well as studies of the detection
capabilities of future colliders to the new decay channels presented.Comment: 3 figures, 1 appendix; version to appear in JHEP; typos fixed and
additional references and acknowledgements adde
QCD Corrections to K-Kbar Mixing in R-symmetric Supersymmetric Models
The leading-log QCD corrections to K-Kbar mixing in R-symmetric
supersymmetric models are computed using effective field theory techniques. The
spectrum topology where the gluino is significantly heavier than the squarks is
motivated and focused on. It is found that, like in the MSSM, QCD corrections
can tighten the kaon mass difference bound by roughly a factor of three. CP
violation is also briefly considered, where QCD corrections can constrain
phases to be as much as a factor of ten smaller than the uncorrected value.Comment: 11 pages, 11 pdf-figures; updated acknowledgments and references,
clarified relationship to Ref[17], clarified CP-violation sectio
Single stranded fully Modified-Phosphorothioate oligonucleotides can induce structured nuclear inclusions, alter nuclear protein localization and disturb the transcriptome In Vitro
Oligonucleotides and nucleic acid analogues that alter gene expression are now showing therapeutic promise in human disease. Whilst the modification of synthetic nucleic acids to protect against nuclease degradation and to influence drug function is common practice, such modifications may also confer unexpected physicochemical and biological properties. Gapmer mixed-modified and DNA oligonucleotides on a phosphorothioate backbone can bind non-specifically to intracellular proteins to form a variety of toxic inclusions, driven by the phosphorothioate linkages, but also influenced by the oligonucleotide sequence. Recently, the non-antisense or other off-target effects of 2′ O- fully modified phosphorothioate linkage oligonucleotides are becoming better understood. Here, we report chemistry-specific effects of oligonucleotides composed of modified or unmodified bases, with phosphorothioate linkages, on subnuclear organelles and show altered distribution of nuclear proteins, the appearance of highly stable and strikingly structured nuclear inclusions, and disturbed RNA processing in primary human fibroblasts and other cultured cells. Phosphodiester, phosphorodiamidate morpholino oligomers, and annealed complimentary phosphorothioate oligomer duplexes elicited no such consequences. Disruption of subnuclear structures and proteins elicit severe phenotypic disturbances, revealed by transcriptomic analysis of transfected fibroblasts exhibiting such disruption. Our data add to the growing body of evidence of off-target effects of some phosphorothioate nucleic acid drugs in primary cells and suggest alternative approaches to mitigate these effects
R-symmetric gauge mediation
We present a version of Gauge Mediated Supersymmetry Breaking which preserves
an R-symmetry - the gauginos are Dirac particles, the A-terms are zero, and
there are four Higgs doublets. This offers an alternative way for gauginos to
acquire mass in the supersymmetry-breaking models of Intriligator, Seiberg, and
Shih. We investigate the possibility of using R-symmetric gauge mediation to
realize the spectrum and large sfermion mixing of the model of Kribs, Poppitz,
and Weiner.Comment: 26+ pages, 3 figures, BIBTEX; v2 published version: references added,
paragraph on spectrum running removed, section added on adjoint scalar
masses, clarification of the meaning of Table 3 adde
Solution and bulk properties of branched polyvinyl acetates IV--Melt viscosity
The melt viscosities of some randomly branched and some comb shaped branched polyvinyl acetate fractions were compared to the viscosities of linear polymer over a range of molecular weights. The melt viscosity of the branched polymer was usually higher than that of linear polymer of the same weight average molecular weight. The extent of this increase was related to the molecular weight of the branches but no correlation could be found which included the number of branches per molecule. This unusual behaviour is believed to be due to the fact that the length of the branches in the polymers of this study was above the critical chain length for polyvinyl acetate which made it possible for the branches to be engaged in intermolecular chain entanglements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32168/1/0000223.pd
Supersymmetry with a Chargino NLSP and Gravitino LSP
We demonstrate that the lightest chargino can be lighter than the lightest
neutralino in supersymmetric models with Dirac gaugino masses as well as within
a curious parameter region of the MSSM. Given also a light gravitino, such as
from low scale supersymmetry breaking, this mass hierarchy leads to an unusual
signal where every superpartner cascades down to a chargino that decays into an
on-shell W and a gravitino, possibly with a macroscopic chargino track. We
clearly identify the region of parameters where this signal can occur. We find
it is generic in the context of the R-symmetric supersymmetric standard model,
whereas it essentially only occurs in the MSSM when sign(M1) is not equal to
sign(M2) = sign(\mu) and tan(beta) is small. We briefly comment on the search
strategies for this signal at the LHC.Comment: 27 pages and 16 figure
Existence theorems in the geometrically non-linear 6-parametric theory of elastic plates
In this paper we show the existence of global minimizers for the
geometrically exact, non-linear equations of elastic plates, in the framework
of the general 6-parametric shell theory. A characteristic feature of this
model for shells is the appearance of two independent kinematic fields: the
translation vector field and the rotation tensor field (representing in total 6
independent scalar kinematic variables). For isotropic plates, we prove the
existence theorem by applying the direct methods of the calculus of variations.
Then, we generalize our existence result to the case of anisotropic plates. We
also present a detailed comparison with a previously established Cosserat plate
model.Comment: 19 pages, 1 figur
Exploring nu signals in dark matter detectors
We investigate standard and non-standard solar neutrino signals in direct
dark matter detection experiments. It is well known that even without new
physics, scattering of solar neutrinos on nuclei or electrons is an irreducible
background for direct dark matter searches, once these experiments each the ton
scale. Here, we entertain the possibility that neutrino interactions are
enhanced by new physics, such as new light force carriers (for instance a "dark
photon") or neutrino magnetic moments. We consider models with only the three
standard neutrino flavors, as well as scenarios with extra sterile neutrinos.
We find that low-energy neutrino--electron and neutrino--nucleus scattering
rates can be enhanced by several orders of magnitude, potentially enough to
explain the event excesses observed in CoGeNT and CRESST. We also investigate
temporal modulation in these neutrino signals, which can arise from geometric
effects, oscillation physics, non-standard neutrino energy loss, and
direction-dependent detection efficiencies. We emphasize that, in addition to
providing potential explanations for existing signals, models featuring new
physics in the neutrino sector can also be very relevant to future dark matter
searches, where, on the one hand, they can be probed and constrained, but on
the other hand, their signatures could also be confused with dark matter
signals.Comment: 38 pages, 8 figures, 1 table; v3: eq 3 and nuclear recoil plots
corrected, footnote added, conclusions unchange
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