1,726 research outputs found
Universal Decoherence in Solids
Symmetry implications for the decoherence of quantum oscillations of a
two-state system in a solid are studied. When the oscillation frequency is
small compared to the Debye frequency, the universal lower bound on the
decoherence due to the atomic environment is derived in terms of the
macroscopic parameters of the solid, with no unknown interaction constants.Comment: 4 pages, no figure
NMR linewidth and Skyrmion localization in quantum Hall ferromagnets
The non-monotonic behavior of the NMR signal linewidth in the 2D quantum Hall
system is explained in terms of the interplay between skyrmions localization,
due to the influence of disorder, and the non-trivial temperature dependent
skyrmion dynamics.Comment: 5 pages, 2 figure
Microanalysis Characterization of Bioactive Protein-Bound Polysaccharides Produced by Amanita Ponderosa Cultures
Different compounds of edible mushrooms are responsible for their bioactivity. The ability to
synthesize polysaccharides, namely protein–polysaccharide (PPS) complexes, is related to the antioxidant
capacity of these compounds and present great interest in preventing a number of diseases, including cancer,
cardiovascular and auto-immune diseases, and accelerated aging. Amanita ponderosa are wild edible mushrooms
that grow in Mediterranean “montado” areas [Portuguese name given to cork oak (Quercus suber) and holm oak
(Quercus ilex) forests]. The aim of this study was to evaluate the production of PPS complexes obtained from
A. ponderosa cultures using a new microanalytical approach to quickly and easily monitor the production process.
Microanalysis using Fourier-transform infrared using attenuated total reflection and Raman spectroscopy of PPS
samples showed spectra compatible with identification of this type of compound in culture extracts. PPS separated
by size-exclusion chromatography showed seven main complexes. Molecular weights of the main PPS complexes
isolated from cultures ranged between 1.5 and 20 kDa and did not present toxicity against Artemia salina,
demonstrating the potential of A. ponderosa as a source of biologically active compounds with nutraceutical value.
Application of this microanalytical approach to monitoring the production of PPS compounds can be successfully
applied in biotechnological processes
Exact C=1 Boundary Conformal Field Theories
We present a solution of the problem of a free massless scalar field on the
half line interacting through a periodic potential on the boundary. For a
critical value of the period, this system is a conformal field theory with a
non-trivial and explicitly calculable S-matrix for scattering from the
boundary. Unlike all other exactly solvable conformal field theories, it is
non-rational ({\it i.e.} has infinitely many primary fields). It describes the
critical behavior of a number of condensed matter systems, including
dissipative quantum mechanics and of barriers in ``quantum wires''.Comment: harvmac, 10 pages, PUPT-1432/IASSNS-HEP-93/7
Detection and Quantification of Grass and Olea Airborne Pollen Allergens in Outdoor Air Samples and its Correlation with Pollen Counts
Detection and Quantification of Grass and Olea Airborne Pollen Allergens in Outdoor Air Samples and its Correlation with Pollen Counts
R Ferro1*, R Ribeiro1*, MR Martins1,2, AT Caldeira1,3, E Caeiro6, CM Antunes1,5
& R BrandĂŁo2,4 and the HIALINE working group7
1Dep. of Chemistry, University of Evora, Portugal;
2Mediterranean Inst. Crop and Environment Sciences, Univ.Evora, Portugal;
3Centro QuĂmica, University of Évora, Portugal;
4Dep. Biology, University of Evora;
5Center for NeuroSciences and Cell Biology-University of Coimbra, Portugal;
6Soc.Portuguesa Alergol.Imunologia ClĂnica , Portugal
7 M. Thibaudon, France, M. Smith, United Kingdom, C. Galan, Spain R. Albertini, Italy, L. Grewling, Poland, G. Reese, Germany, A. Rantio-Lehtimäki, Finland, S. Jäger and U. Berger, Austria, M. Sofiev, Finland, I. Sauliene, Lithuania, L. Cecchi, Italy
Presenting author: [email protected] tel: +351 266760889
Introduction: Allergic respiratory diseases broken out after an exposure to airborne pollen, as asthma and allergic rhinitis, are deeply increasing and they represent one of the major public health problems nowadays, affecting about 40% of European population. In Portugal, grass and Olea europaea pollen are certainly one of the main sources of athmospheric aeroallergens and as such, one of the main causes of respiratory allergy.
For these reasons, it is useful the development of new strategies for prevention and treatment of these pathologies. The execution of aerobiological analysis including pollen calendars and/or immunoassays for the detection and quantification of allergens which could forecast the allergenic potential of the athmosphere are quite relevant since they would contribute to develop prevention measures of allergic respiratory diseases. The aim of this study was to evaluate the putative correlation between the concentration of some of the major allergens of and with their pollen counts.
Methodology: On a meteorological platform at the town center of Evora (south Portugal), ambient air was sampled at 800L/min with a Chemvol high-volume cascade impactor equipped with stages PM>10µm, 10 µm>PM>2.5µm. The polyurethane impacting substrate was extracted with 0.1M NH4HCO3, pH8.1, supplemented with 0.1% BSA. The major pollen allergens from grass Phleum p 5 and olive Ole e 1 were determined with allergen specific ELISA´s. Airborne pollen of and Olea europaea simultaneously monitored with a Burkard Seven Day Recording Volumetric Spore Trap* , between the 30th of April and the 8th of July of 2009. Both samplers were placed side-by-side with air input at the same level.
Results: During the pollen season of 2009, high values of grass pollen were recorded between May 2th and June 1 th. It was also observed that the air content of Phl p5 or Ole e1 aeroallergens were directly correlated with airborne pollen counts of Poaceae and Oleaceae, respectively.
Conclusions: These results suggest that the directly quantification of aeroallergens may contribute, together with pollen counts of air samples, to define the allergic risk with higher precision.
Acknowledgments: This study is integrated in the european project HIALINE (Executive Agency for Health and Consumers under grant agreement No 2008 11 07
Berry's Phase in the Presence of a Stochastically Evolving Environment: A Geometric Mechanism for Energy-Level Broadening
The generic Berry phase scenario in which a two-level system is coupled to a
second system whose dynamical coordinate is slowly-varying is generalized to
allow for stochastic evolution of the slow system. The stochastic behavior is
produced by coupling the slow system to a heat resevoir which is modeled by a
bath of harmonic oscillators initially in equilibrium at temperature T, and
whose spectral density has a bandwidth which is small compared to the
energy-level spacing of the fast system. The well-known energy-level shifts
produced by Berry's phase in the fast system, in conjunction with the
stochastic motion of the slow system, leads to a broadening of the fast system
energy-levels. In the limit of strong damping and sufficiently low temperature,
we determine the degree of level-broadening analytically, and show that the
slow system dynamics satisfies a Langevin equation in which Lorentz-like and
electric-like forces appear as a consequence of geometrical effects. We also
determine the average energy-level shift produced in the fast system by this
mechanism.Comment: 29 pages, RevTex, submitted to Phys. Rev.
An alternative approach for the dynamics of polarons in one dimension
We developed a new method based on functional integration to treat the
dynamics of polarons in one-dimensional systems. We treat the acoustical and
the optical case in an unified manner, showing their differences and
similarities. The mobility and diffusion coefficients are calculated in the
Markovian approximation in the strong coupling limit.Comment: 57 page
Non-Markoffian effects of a simple nonlinear bath
We analyze a model of a nonlinear bath consisting of a single two-level
system coupled to a linear bath (a classical noise force in the limit
considered here). This allows us to study the effects of a nonlinear,
non-Markoffian bath in a particularly simple situation. We analyze the effects
of this bath onto the dynamics of a spin by calculating the decay of the
equilibrium correlator of the spin's z-component. The exact results are
compared with those obtained using three commonly used approximations: a
Markoffian master equation for the spin dynamics, a weak-coupling
approximation, and the substitution of a linear bath for the original nonlinear
bath.Comment: 7 pages, 6 figure
Current fluctuations in a single tunnel junction
We study noise spectra of currents through a tunnel junction in weak
tunneling limit. We introduce effective capacitance to take into account the
interaction effect and explicitly incorporate the electromagnetic environment
of the junction into the formulation. We study the effect of charging energy
and macroscopic environment on noise spectra. We calculate current fluctuations
at tunneling barrier and fluctuations measured at leads. It is shown that two
fluctuations have different noise spectra and the relation between them is
nontrivial. We provide an explanation for the origin of the difference.
Experimental implications are discussed.Comment: 25 pages, Revtex 3.
Localization on short-range potentials in dissipative quantum mechanics
In this Letter the problem of the existence of a state localized on a weak
short-range attractive potential in the presence of dissipation is considered.
It is shown that, contrary to the pure quantum case, a localized state is
produced in any number of dimensions, while in low dimensions dissipation leads
to much stronger localization. The results have physical implications for the
dissipative dynamics of objects such as heavy particles in Fermi liquids and
for superconductivity in high- materials.Comment: RevTeX, 4 pages, 1 figure. Published versio
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