1,373 research outputs found
Brain connectivity analysis: a short survey
This short survey the reviews recent literature on brain connectivity studies. It encompasses all forms of static and dynamic
connectivity whether anatomical, functional, or effective. The last decade has seen an ever increasing number of studies devoted
to deduce functional or effective connectivity, mostly from functional neuroimaging experiments. Resting state conditions have
become a dominant experimental paradigm, and a number of resting state networks, among them the prominent default mode
network, have been identified. Graphical models represent a convenient vehicle to formalize experimental findings and to closely
and quantitatively characterize the various networks identified. Underlying these abstract concepts are anatomical networks, the
so-called connectome, which can be investigated by functional imaging techniques as well. Future studies have to bridge the gap between anatomical neuronal connections and related functional or effective connectivities
On contractions of classical basic superalgebras
We define a class of orthosymplectic and unitary
superalgebras which may be obtained from and
by contractions and analytic continuations in a similar way as the
special linear, orthogonal and the symplectic Cayley-Klein algebras are
obtained from the corresponding classical ones. Casimir operators of
Cayley-Klein superalgebras are obtained from the corresponding operators of the
basic superalgebras. Contractions of and are regarded as
an examples.Comment: 15 pages, Late
On two-dimensional Bessel functions
The general properties of two-dimensional generalized Bessel functions are
discussed. Various asymptotic approximations are derived and applied to analyze
the basic structure of the two-dimensional Bessel functions as well as their
nodal lines.Comment: 25 pages, 17 figure
Projective Hilbert space structures at exceptional points
A non-Hermitian complex symmetric 2x2 matrix toy model is used to study
projective Hilbert space structures in the vicinity of exceptional points
(EPs). The bi-orthogonal eigenvectors of a diagonalizable matrix are
Puiseux-expanded in terms of the root vectors at the EP. It is shown that the
apparent contradiction between the two incompatible normalization conditions
with finite and singular behavior in the EP-limit can be resolved by
projectively extending the original Hilbert space. The complementary
normalization conditions correspond then to two different affine charts of this
enlarged projective Hilbert space. Geometric phase and phase jump behavior are
analyzed and the usefulness of the phase rigidity as measure for the distance
to EP configurations is demonstrated. Finally, EP-related aspects of
PT-symmetrically extended Quantum Mechanics are discussed and a conjecture
concerning the quantum brachistochrone problem is formulated.Comment: 20 pages; discussion extended, refs added; bug correcte
Regulating Clothing Outwork: A Sceptic's View
By applying the strategies of international anti-sweatshop campaigns to the Australian context, recent regulations governing home-based clothing production hold retailers
responsible for policing the wages and employment conditions of clothing outworkers who manufacture clothing on their behalf. This paper argues that the new approach
oversimplifies the regulatory challenge by assuming (1) that Australian clothing production is organised in a hierarchical ‘buyer-led’ linear structure in which core
retail firms have the capacity to control their suppliers’ behaviour; (2) that firms act as unitary moral agents; and (3) that interventions imported from other times and places
are applicable to the contemporary Australian context. After considering some alternative regulatory approaches, the paper concludes that the new regulatory strategy effectively privatises responsibility for labour market conditions – a development that cries out for further debate
Complex magnetic monopoles, geometric phases and quantum evolution in vicinity of diabolic and exceptional points
We consider the geometric phase and quantum tunneling in vicinity of diabolic
and exceptional points. We show that the geometric phase associated with the
degeneracy points is defined by the flux of complex magnetic monopole. In
weak-coupling limit the leading contribution to the real part of geometric
phase is given by the flux of the Dirac monopole plus quadrupole term, and the
expansion for its imaginary part starts with the dipolelike field. For a
two-level system governed by the generic non-Hermitian Hamiltonian, we derive a
formula to compute the non-adiabatic complex geometric phase by integral over
the complex Bloch sphere. We apply our results to to study a two-level
dissipative system driven by periodic electromagnetic field and show that in
the vicinity of the exceptional point the complex geometric phase behaves as
step-like function. Studying tunneling process near and at exceptional point,
we find two different regimes: coherent and incoherent. The coherent regime is
characterized by the Rabi oscillations and one-sheeted hyperbolic monopole
emerges in this region of the parameters. In turn with the incoherent regime
the two-sheeted hyperbolic monopole is associated. The exceptional point is the
critical point of the system where the topological transition occurs and both
of the regimes yield the quadratic dependence on time. We show that the
dissipation brings into existence of pulses in the complex geometric phase and
the pulses are disappeared when dissipation dies out. Such a strong coupling
effect of the environment is beyond of the conventional adiabatic treatment of
the Berry phase.Comment: 29 pages, 21 figure
BICEP2 / Keck Array V: Measurements of B-mode Polarization at Degree Angular Scales and 150 GHz by the Keck Array
The Keck Array is a system of cosmic microwave background (CMB) polarimeters,
each similar to the BICEP2 experiment. In this paper we report results from the
2012 and 2013 observing seasons, during which the Keck Array consisted of five
receivers all operating in the same (150 GHz) frequency band and observing
field as BICEP2. We again find an excess of B-mode power over the
lensed-CDM expectation of in the range
and confirm that this is not due to systematics using jackknife tests and
simulations based on detailed calibration measurements. In map difference and
spectral difference tests these new data are shown to be consistent with
BICEP2. Finally, we combine the maps from the two experiments to produce final
Q and U maps which have a depth of 57 nK deg (3.4 K arcmin) over an
effective area of 400 deg for an equivalent survey weight of 250,000
K. The final BB band powers have noise uncertainty a factor of 2.3
times better than the previous results, and a significance of detection of
excess power of .Comment: 13 pages, 9 figure
Regulatory mechanisms controlling biogenesis of ubiquitin and the proteasome
Analysis of several Saccharomyces cerevisiae ump mutants with defects in ubiquitin (Ub)-mediated proteolysis yielded insights into the regulation of the polyubiquitin gene UB14 and of proteasome genes. High-molecular weight Ub-protein conjugates accumulated in ump mutants with impaired proteasome function with a concomitant decrease in the amount of free Ub. In these mutants, transcriptional induction of UB14 was depending in part on the transcription factor Rpn4. Deletion of UB14 partially suppressed the growth defects of ump1 mutants, indicating that accumulation of polyubiquitylated proteins is deleterious to cell growth. Transcription of proteasome subunit genes was induced in ump mutants affecting the proteasome, as well as under conditions that mediate DNA damage or the formation of abnormal proteins. This induction required the transcriptional activator Rpn4. Elevated Rpn4 levels in proteasome-deficient mutants or as a response to abnormal proteins were due to increased metabolic stability. Up-regulation of proteasome genes in response to DNA damage, in contrast, is shown to operate via induction of RPN4 transcription. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.info:eu-repo/semantics/publishedVersio
BICEP2 / Keck Array VIII: Measurement of gravitational lensing from large-scale B-mode polarization
We present measurements of polarization lensing using the 150 GHz maps which
include all data taken by the BICEP2 & Keck Array CMB polarization experiments
up to and including the 2014 observing season (BK14). Despite their modest
angular resolution (), the excellent sensitivity (K-arcmin) of these maps makes it possible to directly reconstruct the
lensing potential using only information at larger angular scales (). From the auto-spectrum of the reconstructed potential we measure an
amplitude of the spectrum to be (Planck
CDM prediction corresponds to ), and reject
the no-lensing hypothesis at 5.8, which is the highest significance
achieved to date using an EB lensing estimator. Taking the cross-spectrum of
the reconstructed potential with the Planck 2015 lensing map yields
. These direct measurements of
are consistent with the CDM cosmology, and with
that derived from the previously reported BK14 B-mode auto-spectrum (). We perform a series of null tests and consistency
checks to show that these results are robust against systematics and are
insensitive to analysis choices. These results unambiguously demonstrate that
the B-modes previously reported by BICEP / Keck at intermediate angular scales
() are dominated by gravitational lensing. The
good agreement between the lensing amplitudes obtained from the lensing
reconstruction and B-mode spectrum starts to place constraints on any
alternative cosmological sources of B-modes at these angular scales.Comment: 12 pages, 8 figure
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