559 research outputs found
Reversible inhibition of mammalian tubulin assembly in vitro and effects in Saccharomyces cerevisiae D61.M by mitomycin C
Gaulden reported a novel and unexpected mitomycin C (MMC) effect, namely a pronounced retardation of very late prophase and loss of chromosome orientation in neuroblasts of the grasshopper Chortophaga viridifasciate. Because this effect may be due to interactions of MMC with non-DNA targets, MMC was tested for its interaction with porcine brain tubulin assembly in vitro and for the induction of chromosomal malsegregation in the diploid yeast Saccharomyces cerevisiae strain D61.M. A reversible dose-dependent inhibition of tubulin assembly was observed. Since no biological activation system was present in the incubation mixture this inhibition seems to result from an interaction of unactivated MMC with the assembly process. The possible chemical activation of MMC by reduction with 1, 4-dithioerythritol (DTE) was investigated by omission of this compound during isolation and polymerization of tubulin. The absence of DTE resulted in a strong reduction of the net tubulin assembly. Also under these conditions MMC led to a dose-dependent inhibition of the assembly, indicating that the effect of MMC on tubulin assembly is independent of a reductive chemical modification. In S.cerevisiae D61.M, MMC did not induce chromosome loss, but induced other genetic events (possibly mutations, deletions or mitotic recombination) as was detected by an increase of the total number and of the frequency of cycloheximide-resistant colonies. This effect could be observed with and without the addition of rat liver S9 as an exogenous activation syste
On the construction of pseudo-hermitian quantum system with a pre-determined metric in the Hilbert space
A class of pseudo-hermitian quantum system with an explicit form of the
positive-definite metric in the Hilbert space is presented. The general method
involves a realization of the basic canonical commutation relations defining
the quantum system in terms of operators those are hermitian with respect to a
pre-determined positive definite metric in the Hilbert space. Appropriate
combinations of these operators result in a large number of pseudo-hermitian
quantum systems admitting entirely real spectra and unitary time evolution. The
examples considered include simple harmonic oscillators with complex angular
frequencies, Stark(Zeeman) effect with complex electric(magnetic) field,
non-hermitian general quadratic form of N boson(fermion) operators, symmetric
and asymmetric XXZ spin-chain in complex magnetic field, non-hermitian
Haldane-Shastry spin-chain and Lipkin-Meshkov-Glick model.Comment: 29 pages, revtex, minor changes, version to appear in Journal of
Physics A(v3
The Significance of the -Numerical Range and the Local -Numerical Range in Quantum Control and Quantum Information
This paper shows how C-numerical-range related new strucures may arise from
practical problems in quantum control--and vice versa, how an understanding of
these structures helps to tackle hot topics in quantum information.
We start out with an overview on the role of C-numerical ranges in current
research problems in quantum theory: the quantum mechanical task of maximising
the projection of a point on the unitary orbit of an initial state onto a
target state C relates to the C-numerical radius of A via maximising the trace
function |\tr \{C^\dagger UAU^\dagger\}|. In quantum control of n qubits one
may be interested (i) in having U\in SU(2^n) for the entire dynamics, or (ii)
in restricting the dynamics to {\em local} operations on each qubit, i.e. to
the n-fold tensor product SU(2)\otimes SU(2)\otimes >...\otimes SU(2).
Interestingly, the latter then leads to a novel entity, the {\em local}
C-numerical range W_{\rm loc}(C,A), whose intricate geometry is neither
star-shaped nor simply connected in contrast to the conventional C-numerical
range. This is shown in the accompanying paper (math-ph/0702005).
We present novel applications of the C-numerical range in quantum control
assisted by gradient flows on the local unitary group: (1) they serve as
powerful tools for deciding whether a quantum interaction can be inverted in
time (in a sense generalising Hahn's famous spin echo); (2) they allow for
optimising witnesses of quantum entanglement. We conclude by relating the
relative C-numerical range to problems of constrained quantum optimisation, for
which we also give Lagrange-type gradient flow algorithms.Comment: update relating to math-ph/070200
Local scale invariance and strongly anisotropic equilibrium critical systems
A new set of infinitesimal transformations generalizing scale invariance for
strongly anisotropic critical systems is considered. It is shown that such a
generalization is possible if the anisotropy exponent \theta =2/N, with N=1,2,3
... Differential equations for the two-point function are derived and
explicitly solved for all values of N. Known special cases are conformal
invariance (N=2) and Schr\"odinger invariance (N=1). For N=4 and N=6, the
results contain as special cases the exactly known scaling forms obtained for
the spin-spin correlation function in the axial next nearest neighbor spherical
(ANNNS) model at its Lifshitz points of first and second order.Comment: 4 pages Revtex, no figures, with file multicol.sty, to appear in PR
Efficient quantum state transfer in spin chains via adiabatic passage
We propose a method for quantum state transfer in spin chains using an
adiabatic passage technique. Modifying even and odd nearest-neighbour couplings
in time allows to achieve transfer fidelities arbitrarily close to one, without
the need for a precise control of coupling strengths and timing. We study in
detail transfer by adiabatic passage in a spin-1 chain governed by a
generalized Heisenberg Hamiltonian. We consider optimization of the transfer
process applying optimal control techniques. We discuss a realistic
experimental implementation using cold atomic gases confined in deep optical
lattices.Comment: 14 pages, 6 figures, to be published in New J. Phy
THE HIALINE PROJECT: ALLERGEN RELEASE FROM POLLEN ACROSS 10 EUROPEAN COUNTRIES
Exposure to allergens is one of severa1 factors determining sensitization and allergic symptoms in individuals. Exposure to aeroallergens from pollen is assessed by counting allergenic pollen in ambient air. However, proof is lacking that pollen count is representative for allergen exposure.
We therefore monitored simultaneously birch, grass and olive pollen counts and their corresponding major pollen allergens Bet v 1, Phl p 5 and Ole e 1 across Europe.
Already at one location in Europe in Munich, Germany, it has been found that the same amount of pollen from different years, different trees and even different days released up to lO-fold different amounts of
Bet v 1. Thus exposure to allergen is poorly monitored by only monitoring pollen countl-2. Monitoring the allergen itself in ambient air might be an improvement in allergen exposure assessment.
The objective of the HIALINE-project is to evaluate if these effects found in Munich, Germany are also measurable over a bigger geographic area like Europe, and at the same time implement an outdoor allergen early warning network, in addition to the pollen forecasts. Climatic factors that influence allergen exposure will be extracted and will be used to calculate the effect of climate change on local airborne allergen exposure.
The major allergens from the top 3 airborne allergens in Europe (grasses, birch and olive) are sampled with a cascade impactor, extracted and analyzed by allergen specific ELISA 's. Pollen counts are measured by standard pollen traps and correlated with the weather data. Allergen forecast will be calculated by incorporating the SILAM chemical transport model and compared with the observations of HIALINE aiming at a comprehensive parameterization of the allergen release and transport.
Expected outcomes are the implementation of a network of European outdoor allergen measurements to better predict allergic symptoms. Also the climatic factors that govern allergen exposure in outdoor air will
be established. These can be used to calculate the effect of climate change on the health effects of airborne allergens The research leading to these results has received funding from the Executive Agency for Health and Consumers under grant agreement No 2008 11 07
The European project HIALINE (Health Impacts of Airborne Allergen Information Network): results of pollen and allergen of Betula monitoring in Parma (2009)
Introduction. Exposure to allergens is pivotal in determining sensitization and allergic symptoms in individuals. Pollen grain counts in ambient air
have traditionally been assessed to estimate airborne allergen exposure. However, the exact allergen content in ambient air is unknown. HIALINE
therefore monitored atmospheric concentrations of Betula, Poaceae and Olea pollen grains and matched their major allergens Bet v1, Phl p5 and
Ole e1 across Europe. Monitoring the allergens themselves together with pollen in ambient air might be an improvement in allergen exposure
assessment. New knowledge through the use of new experimental approaches in the field of aerobiological monitoring will enable better in the
prevention and clinical management of pollinosis. In order to disseminate the knowledge of the project we present the results of first year of birch
pollen grains and the matched major pollen allergen Bet v1 monitored in Parma (UNIPR), Italy with a short reference to the results obtained by
the other participants and about developing models of dissemination and forecasts of pollen and allergens.
Materials and methods. The pollen was sampled by a Hirst pollen trap. Allergens was collected with a CHEMVOL® high-volume cascade
impactor, extracted from pollen and quantified by ELISA. Antibodies for analysis of Bet v1 are delivered by the industrial partner in this project.
Quality control has been carried out for the monitoring pollen activities and allergen concentrations.
Results. The project has highlighted that it is possible also to measure pollen allergen in ambient air in different European areas. The results
obtained from the center of Parma and other European partners have highlighted the different allergenic powers of pollen of Betula, in different
geographical areas. Moreover, daily in each area the allergenic power of pollen grains was very variable.
Discussion. HIALINE has been a very important project to understand the mechanisms of sensitization, clinical management of pollinosis and
to improve immunotherapy towards a tailored immunotherapy. The results of the project will help medical doctors, authorities and patients, to
better manage the different aspects related to pollinosis
Multi-particle structure in the Z_n-chiral Potts models
We calculate the lowest translationally invariant levels of the Z_3- and
Z_4-symmetrical chiral Potts quantum chains, using numerical diagonalization of
the hamiltonian for N <= 12 and N <= 10 sites, respectively, and extrapolating
N to infinity. In the high-temperature massive phase we find that the pattern
of the low-lying zero momentum levels can be explained assuming the existence
of n-1 particles carrying Z_n-charges Q = 1, ... , n-1 (mass m_Q), and their
scattering states. In the superintegrable case the masses of the n-1 particles
become proportional to their respective charges: m_Q = Q m_1. Exponential
convergence in N is observed for the single particle gaps, while power
convergence is seen for the scattering levels. We also verify that
qualitatively the same pattern appears for the self-dual and integrable cases.
For general Z_n we show that the energy-momentum relations of the particles
show a parity non-conservation asymmetry which for very high temperatures is
exclusive due to the presence of a macroscopic momentum P_m=(1-2Q/n)/\phi,
where \phi is the chiral angle and Q is the Z_n-charge of the respective
particle.Comment: 22 pages (LaTeX) plus 5 figures (included as PostScript),
BONN-HE-92-3
The asymmetric simple exclusion process: an integrable model for non-equilibrium statistical mechanics
The asymmetric simple exclusion process (ASEP) plays the role of a paradigm
in non-equilibrium statistical mechanics. We review exact results for the ASEP
obtained by Bethe ansatz and put emphasis on the algebraic properties of this
model. The Bethe equations for the eigenvalues of the Markov matrix of the ASEP
are derived from the algebraic Bethe ansatz. Using these equations we explain
how to calculate the spectral gap of the model and how global spectral
properties such as the existence of multiplets can be predicted. An extension
of the Bethe ansatz leads to an analytic expression for the large deviation
function of the current in the ASEP that satisfies the Gallavotti-Cohen
relation. Finally, we describe some variants of the ASEP that are also solvable
by Bethe ansatz.
Keywords: ASEP, integrable models, Bethe ansatz, large deviations.Comment: 24 pages, 5 figures, published in the "special issue on recent
advances in low-dimensional quantum field theories", P. Dorey, G. Dunne and
J. Feinberg editor
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Integrating research evidence in humanitarian health responses: analysing power and knowledge negotiation using the adapted Extended Normalization Process Theory
Background: People living in settings affected by conflicts face insecurity and live in fragmented social systems. Conducting research in these settings is essential, however integrating results into practices is complex. Implementation science tools are not used often in such environments. In this paper we explore how a convenience sample of interviewees experienced implementation in these settings, through the lens of the adapted Extended Normalization Process Theory (a-ENPT).
Methods: We conducted in-depth interviews with 26 participants (donors, academics, and humanitarian actors). We assessed what key issues interviewees met and how they negotiated them. We combined an inductive thematic analysis to identify implementation issues, and we applied the a-ENPT deductively to question power imbalances, engaging a group of humanitarian actors as co-authors along the way.
Results: The main challenges met by interviewees related to a) engaging frontline actors to produce knowledge; b) discussing the results critically; c) integrating research results in constrained learning spaces; and d) managing contextual instabilities in settings affected by conflicts. Interviewees negotiated these constraints through an early involvement of frontline actors, an institutional support, a meaningful engagement of communities, and balanced partnerships. Based on these findings we propose a tool to anticipate the power imbalances embedded in the implementation of research results in settings affected by conflicts, rooted in the a-ENPT constructs.
Conclusion: We identified mechanisms that allowed for the negotiation of important challenges and power imbalances, through an implementation science tool. Further research should focus on the perspectives of communities affected themselves
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