132 research outputs found
Graph Theory and Molecular Orbitals. XX. Local and Long Range Contributions to Bond Order
Local and longe range contributions to bond order are calculated
for several benzenoid and non-benzenoid alternant molecules.
The local effects are found to be linearly correlated with the bond
orders of benzenoid, but not of nonbenzenoid systems. On the basis
of these investigations a measure of the aromatic character of a
bond is introduced
Resolution of the Klein Paradox
We present a resolution of the Klein paradox within the framework of
one-particle relativistic quantum mechanics. Not only reflection becomes total
but the vacuum remains neutral as well. This is accomplished by replacing the
pair production process with virtual negative energy "incidence" within the
barrier in a similar manner to what is done with image charges in electrostatic
and virtual sources in optics.Comment: 9 pages, 8 figure
Building New University Hospital – What Citizens Know and Policy Makers Should be Aware of
Survey of citizens’ attitudes in the process of strategic decision making is one of the
most important methods for determining health care priorities. We describe the results
of a survey carried out in December 2001, with an aim to collect and analyze the attitudes
of the citizens and health care professionals toward the possibilities and strategies
of construction of the University Hospital in Blato, Zagreb. The first referendum on the
construction of the new hospital was conducted among Zagreb citizens in 1982, when
they agreed that the new University Hospital was much needed. Zagreb citizens confirmed
once again their attitudes toward and opinions on the need to continue the construction
of new hospital in the city outskirts. By 1992, when the construction of the hospital
was halted due to insufficient financial means, Zagreb citizens had already
invested over 150 million in the project. It is interesting that today, 89.4% of the citizens
and 74.5% of physicians agree that the new hospital building should be completed.
Also, 66.7% of the citizens and 88% of physicians think that this hospital should be a
University hospital that could offer the most complex treatments and medical education.
To finish the construction of the new hospital further 200 million needs to be invested.
Survey showed that 71% of citizens and 82.2% of physicians think that funds
should be raised from some form of credit or budget rather than by special local tax, additional
tax or voluntary tax. This project will significantly determine the future of hospital
and health care system in Croatia due to its capacities in terms of space, technology,
and staff. Before the decision to continue with the new hospital construction be
made, the expected future needs, demands, and supply of the health care services in hospital
sector in Zagreb and Croatia should be provided using SWOT analysis for each of
existing the facilities
Effective Hamiltonian and unitarity of the S matrix
The properties of open quantum systems are described well by an effective
Hamiltonian that consists of two parts: the Hamiltonian of the
closed system with discrete eigenstates and the coupling matrix between
discrete states and continuum. The eigenvalues of determine the
poles of the matrix. The coupling matrix elements
between the eigenstates of and the continuum may be very
different from the coupling matrix elements between the eigenstates
of and the continuum. Due to the unitarity of the matrix, the
\TW_k^{cc'} depend on energy in a non-trivial manner, that conflicts with the
assumptions of some approaches to reactions in the overlapping regime. Explicit
expressions for the wave functions of the resonance states and for their phases
in the neighbourhood of, respectively, avoided level crossings in the complex
plane and double poles of the matrix are given.Comment: 17 pages, 7 figure
Relativistic precession and spin dynamics of an elliptic Rydberg wave packet
Time evolution of wave packets built from the eigenstates of the Dirac
equation for a hydrogenic system is considered. We investigate the space and
spin motion of wave packets which, in the non-relativistic limit, are
stationary states with a probability density distributed uniformly along the
classical, elliptical orbit (elliptic WP). We show that the precession of such
a WP, due to relativistic corrections to the energy eigenvalues, is strongly
correlated with the spin motion. We show also that the motion is universal for
all hydrogenic systems with an arbitrary value of the atomic number Z.Comment: Latex2e, uses IOP style files (included), 10 pages, 5 jpg figures, 1
postscript figure. Relation between precession time and radiative liftime
added (eq.(12)). Accepted for publication in J. Phys.
Nuclear target search at the single molecule level: protein interactions define the exploration landscape
Gene regulation relies on highly mobile transcription factors (TFs) exploring the nucleoplasm in search of their targets. Our view of the nucleus has evolved from that of an isotropic and homogenous reactor to that of a highly organized yet very dynamic organelle. However important questions remain on how these regulatory factors explore the nuclear environment in search of their DNA or protein targets, and how their exploration strategy affects the kinetics of transcriptional regulation.
We implemented a single-molecule tracking assay to determine the TFs dynamics using photoactivatable tags in human cells. We investigated the mobility of several nuclear proteins, including the transcription factor c-Myc and the elongation factor P-TEFb. We found that, while their diffusion speed was comparable, these proteins largely differed in terms of their exploration geometry. We discovered that c-Myc is a global explorer diffusing in the nucleus without spatial constraints. In contrast, the positive transcription elongation factor P-TEFb is a local explorer that oversamples its environment, constrained by a fractal nuclear architecture. Consequently, each c-Myc molecule is equally available for all nuclear sites while P-TEFb reaches its targets in a position-dependent manner. We also measured the mobility of a P-TEFb mutant in which the interaction with the CTD of the RNA Pol II was truncated. In this case, the single-molecule experiments suggested a global exploration of the P-TEFb mutant, consistent with free diffusion.
Our observations are in line with a model in which the exploration geometry of TFs is constrained by their interactions and not by exclusion properties. Our findings have strong implications on how proteins react in the nucleus and how their function can be regulated in space and time
Prospective, randomized, double‐blind assessment of topical bakuchiol and retinol for facial photoageing
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147746/1/bjd16918_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147746/2/bjd16918.pd
Single-molecule tracking in live cells reveals distinct target-search strategies of transcription factors in the nucleus
Gene regulation relies on transcription factors (TFs) exploring the nucleus searching their targets. So far, most studies have focused on how fast TFs diffuse, underestimating the role of nuclear architecture. We implemented a single-molecule tracking assay to determine TFs dynamics. We found that c-Myc is a global explorer of the nucleus. In contrast, the positive transcription elongation factor P-TEFb is a local explorer that oversamples its environment. Consequently, each c-Myc molecule is equally available for all nuclear sites while P-TEFb reaches its targets in a position-dependent manner. Our observations are consistent with a model in which the exploration geometry of TFs is restrained by their interactions with nuclear structures and not by exclusion. The geometry-controlled kinetics of TFs target-search illustrates the influence of nuclear architecture on gene regulation, and has strong implications on how proteins react in the nucleus and how their function can be regulated in space and time
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