6,429 research outputs found
Induced conjugacy classes, prehomogeneous varieties, and canonical parabolic subgroups
We extend the notion of induced conjugacy classes in reductive groups,
introduced by Lusztig and Spaltenstein for unipotent classes, to arbitrary
classes. We study properties of equivariant fibrations of prehomogeneous affine
spaces, especially the existence of relative invariants. We also detect
prehomogeneous affine spaces as subquotients of canonical parabolic subgroups
attached to elements of reductive groups in the sense of Jacobson-Morozov.
These results are prerequisites for making the geometric expansion of the
Arthur-Selberg trace formula more explicit.Comment: New proofs given for the results on induction of conjugacy classes in
section
How CEO Values and TMT Diversity Jointly Influence the Corporate Strategy Making Process
Understanding managerial behavior and its underlying motivations is
of key interest in times where the role of business in society is generally viewed
critically. While CEO influence on strategy making processes is almost undisputed,
little attention has explicitly been paid to how CEO values and the characteristics
of the top management team (TMT) interact in shaping corporate strategy making.
This is surprising if one follows the assumption that top managers who work closely
together will by necessity influence each other's actions. Hence, we would expect the
CEO-TMT interface to be vital in understanding how leadership influences strategy
making. To address this, we propose a model in which the personal values of the CEO
have a direct effect on the characteristics of corporate strategy making processes yet
where this association is moderated by TMT diversity. We test the model with
data from Austria and Germany obtained through a large-scale survey conducted in
spring 2015 and a follow-up survey conducted in fall 2015 and find general support
for our model. CEO values geared towards self-transcendence (as opposed to selfinterest)
seem to be associated with more formal strategy making processes, while
values geared towards openness to change (as opposed to conservation) are found
to be associated with more flexible and less externally open ones. TMT diversity
moderates all of these relationships. Our results add to upper echelon theory as well
as to strategy process research and highlight promising avenues for future research
Large nuclear spin polarization in gate-defined quantum dots using a single-domain nanomagnet
The electron-nuclei (hyperfine) interaction is central to spin qubits in
solid state systems. It can be a severe decoherence source but also allows
dynamic access to the nuclear spin states. We study a double quantum dot
exposed to an on-chip single-domain nanomagnet and show that its inhomogeneous
magnetic field crucially modifies the complex nuclear spin dynamics such that
the Overhauser field tends to compensate external magnetic fields. This turns
out to be beneficial for polarizing the nuclear spin ensemble. We reach a
nuclear spin polarization of ~50%, unrivaled in lateral dots, and explain our
manipulation technique using a comprehensive rate equation model
AdS Box Graphs, Unitarity and Operator Product Expansions
We develop a method of singularity analysis for conformal graphs which, in particular, is applicable to the holographic image of AdS supergravity theory. It can be used to determine the critical exponents for any such graph in a given channel. These exponents determine the towers of conformal blocks that are exchanged in this channel. We analyze the scalar AdS box graph and show that it has the same critical exponents as the corresponding CFT box graph. Thus pairs of external fields couple to the same exchanged conformal blocks in both theories. This is looked upon as a general structural argument supporting the Maldacena hypothesis
Towards Quantitative ICG Angiography: Fluorescence Monte Carlo Multi Cylinder
Intraoperative blood flow measurement is an effective way to assess the quality of bypass surgery. Flow quantification from indocyanine green (ICG) angiography promises to be an easy, contact-free method. It shows deviations compared to areference. These are given as factor , which dependson the vesseldiameter . The radiation transport within the vessel while recording the ICG passage might cause this. It is analyzed in silicoto disclose its impact on (). A Fluorescence Monte Carlo Multi Cylinder (FMCMC) model was developed as a static model, assuming homogeneous concentration of ICG. In contrast to published approaches utilizing a Monte Carlo MultiLayer (MCML) model assuming the deepest penetration location within a photon packetâs path to be the fluorescence location, the events aremodeled. Fluorescenceevent modeling, Multi Cylinder geometry and a homogeneous illumination as well as combinations of these were implemented in separate aspect models. Resulting ()were compared to ()from MCML. Deviations in ()derived from FMCMC and MCML in each aspect model were present. The Root Mean Square Error ranges from 6,8% to 36 %, ()also varied comparing the aspect models to each other. The model geometry, the modeled fluorescence location and illumination mode show a clear impact on simulated (). Therefore, our study shows that simplifications of previous studies are invalid.The developed FMCMC model considers the named aspects, allowing the analysis of radiation transport in ICG angiography. The FMCMC model assumes a homogeneous concentration of ICG which is not true in clinical cases. Obtaining the heterogeneous distributionof ICG is possible via fluid flow models. Coupling the fluid flow model and the developed radiation transport model as well as including a detailed camera optic is the task for future wor
Rapid enzymatic test for phenotypic HIV protease drug resistance
A phenotypic resistance test based on recombinant expression of the active HIV protease in E. coli from patient blood samples was developed. The protease is purified in a rapid onestep procedure as active enzyme and tested for inhibition by five selected synthetic inhibitors (amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir) used presently for chemotherapy of HIVinfected patients. The HPLC system used in a previous approach was replaced by a continuous fluorogenic assay suitable for highthroughput screening on microtiter plates. This reduces significantly the total assay time and allows the determination of inhibition constants (K-i). The Michaelis constant (K-m) and the inhibition constant (K-i) of recombinant wildtype protease agree well with published data for cloned HIV protease. The enzymatic test was evaluated with recombinant HIV protease derived from eight HIVpositive patients scored from sensitive to highly resistant according to mutations detected by genotypic analysis. The measured K-i values correlate well with the genotypic resistance scores, but allow a higher degree of differentiation. The noninfectious assay enables a more rapid yet sensitive detection of HIV protease resistance than other phenotypic assays
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