2,186,275 research outputs found
Impact of CP phases on stop and sbottom searches
We study the decays of top squarks (stop_{1,2}) and bottom squarks
(sbottom_{1,2}) in the Minimal Supersymmetric Standard Model (MSSM) with
complex parameters A_t, A_b, mu and M_1. We show that including the
corresponding phases substantially affects the branching ratios of stop_{1,2}
and sbottom_{1,2} decays in a large domain of the MSSM parameter space. We find
that the branching ratios can easily change by a factor of 2 and more when
varying the phases. This could have an important impact on the search for
stop_{1,2} and sbottom_{1,2} and the determination of the MSSM parameters at
future colliders.Comment: 17 pages, 5 figures, LaTeX2
Impact of CP phases on SUSY particle production and decays
We report on the results of a phenomenological study of top squarks
(stop_{1,2}) and bottom squarks (sbottom_{1,2}) in the Minimal Supersymmetric
Standard Model (MSSM) with complex parameters A_t, A_b, mu and M_1. In
particular we focus on the CP phase dependence of the branching ratios of
stop_{1,2} and sbottom_{1,2} decays. We find that the effect of the phases on
the stop_{1,2} and sbottom_{1,2} decays can be quite significant in a large
region of the MSSM parameter space. We also study a CP asymmetry in sfermion
decays.Comment: 10 pages, 8 eps figures, LaTeX, uses JHEP3.cls; talk given at the
International Workshop on Astroparticle and High Energy Physics (AHEP),
Valencia, Spain, 14-18 Oct. 200
Could action research provide the key to true workplace collaboration?
Management practices that serve principles of "efficiency" and "effectiveness" in the capitalist understanding of such notions have generated work practices that purport to empower employees under the guise of employee participation programs. In the fieldwork reported here, action research was used as a vehicle to initiate collaborative workplace engagements for the benefit of an organization and its employees. Our results have implications for action researchers and for social construction theory. We found that collaborative behaviors, modeled through action research to all organization levels, have the potential to initiate change toward respectful pluralist engagements. Authentic participation requires a supportive environment in order for organizations and their employees to truly flourish. It became apparent that New Zealand employment law provided a framework within which to work collaboratively, but the will to do so was not fully evident. However, through action research, the participants began to construct their "common sense" (Berger & Luckmann, 1966: 37) of their shared workplace reality and goals
Why 1,2‑quinone derivatives are more stable than their 2,3‑analogues?
In this work, we have studied the relative stability
of 1,2- and 2,3-quinones. While 1,2-quinones have
a closed-shell singlet ground state, the ground state for
the studied 2,3-isomers is open-shell singlet, except for
2,3-naphthaquinone that has a closed-shell singlet ground
state. In all cases, 1,2-quinones are more stable than their
2,3-counterparts. We analyzed the reasons for the higher
stability of the 1,2-isomers through energy decomposition
analysis in the framework of Kohn–Sham molecular orbital
theory. The results showed that we have to trace the origin
of 1,2-quinones’ enhanced stability to the more efficient
bonding in the π-electron system due to more favorable
overlap between the SOMOπ of the ·C4n−2H2n–CH·· and
··CH–CO–CO· fragments in the 1,2-arrangement. Furthermore,
whereas 1,2-quinones present a constant trend with their elongation for all analyzed properties (geometric,
energetic, and electronic), 2,3-quinone derivatives present a
substantial breaking in monotonicity.European
Union in the framework of European Social Fund through the Warsaw
University of Technology Development Programme. O.A. S., H.
S. and T.M. K
Conjugacy in Baumslag's group, generic case complexity, and division in power circuits
The conjugacy problem belongs to algorithmic group theory. It is the
following question: given two words x, y over generators of a fixed group G,
decide whether x and y are conjugated, i.e., whether there exists some z such
that zxz^{-1} = y in G. The conjugacy problem is more difficult than the word
problem, in general. We investigate the complexity of the conjugacy problem for
two prominent groups: the Baumslag-Solitar group BS(1,2) and the
Baumslag(-Gersten) group G(1,2). The conjugacy problem in BS(1,2) is
TC^0-complete. To the best of our knowledge BS(1,2) is the first natural
infinite non-commutative group where such a precise and low complexity is
shown. The Baumslag group G(1,2) is an HNN-extension of BS(1,2). We show that
the conjugacy problem is decidable (which has been known before); but our
results go far beyond decidability. In particular, we are able to show that
conjugacy in G(1,2) can be solved in polynomial time in a strongly generic
setting. This means that essentially for all inputs conjugacy in G(1,2) can be
decided efficiently. In contrast, we show that under a plausible assumption the
average case complexity of the same problem is non-elementary. Moreover, we
provide a lower bound for the conjugacy problem in G(1,2) by reducing the
division problem in power circuits to the conjugacy problem in G(1,2). The
complexity of the division problem in power circuits is an open and interesting
problem in integer arithmetic.Comment: Section 5 added: We show that an HNN extension G = < H, b | bab^-1 =
{\phi}(a), a \in A > has a non-amenable Schreier graph with respect to the
base group H if and only if A \neq H \neq
Influence of mutations of Val226 on the catalytic rate of haloalkane dehalogenase
Haloalkane dehalogenase converts haloalkanes to their corresponding alcohols. The 3D structure, reaction mechanism and kinetic mechanism have been studied. The steady state kcat with 1,2-dichloroethane and 1,2-dibromoethane is limited mainly by the rate of release of the halide ion from the buried active-site cavity. During catalysis, the halogen that is cleaved off (Clα) from 1,2-dichloroethane interacts with Trp125 and the Clβ interacts with Phe172. Both these residues have van der Waals contacts with Val226. To establish the effect of these interactions on catalysis, and in an attempt to change enzyme activity without directly mutating residues involved in catalysis, we mutated Val226 to Gly, Ala and Leu. The Val226Ala and Val226Leu mutants had a 2.5-fold higher catalytic rate for 1,2-dibromoethane than the wild-type enzyme. A pre-steady state kinetic analysis of the Val226Ala mutant enzyme showed that the increase in kcat could be attributed to an increase in the rate of a conformational change that precedes halide release, causing a faster overall rate of halide dissociation. The kcat for 1,2-dichloroethane conversion was not elevated, although the rate of chloride release was also faster than in the wild-type enzyme. This was caused by a 3-fold decrease in the rate of formation of the alkyl-enzyme intermediate for 1,2-dichloroethane. Val226 seems to contribute to leaving group (Clα or Brα) stabilization via Trp125, and can influence halide release and substrate binding via an interaction with Phe172. These studies indicate that wild-type haloalkane dehalogenase is optimized for 1,2-dichloroethane, although 1,2-dibromoethane is a better substrate.
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