Exciton-phonon scattering and photo-excitation dynamics in J-aggregate microcavities

We have developed a model accounting for the photo-excitation dynamics and the photoluminescence of strongly coupled J-aggregate microcavities. Our model is based on a description of the J-aggregate film as a disordered Frenkel exciton system in which relaxation occurs due to the presence of a thermal bath of molecular vibrations. In a strongly coupled microcavity exciton-polaritons are formed, mixing superradiant excitons and cavity photons. The calculation of the microcavity steady-state photoluminescence, following a CW non resonant pumping, is carried out. The experimental photoluminescence intensity ratio between upper and lower polariton branches is accurately reproduced. In particular both thermal activation of the photoluminescence intensity ratio and its Rabi splitting dependence are a consequence of the bottleneck in the relaxation, occurring at the bottom of the excitonic reservoir. The effects due to radiative channels of decay of excitons and to the presence of a paritticular set of discrete optical molecular vibrations active in relaxation processes are investigared.Comment: 8 pages, 6 figure

Saproxylic beetles of the Po plain woodlands, Italy

Forest ecosystems play an important role for the conservation of biodiversity, and for the protection of ecological processes. The Po plain woodlands which once covered the whole Plain, today are reduced in isolated highly threatened remnants by modern intensive agriculture. These close to natural floodplain forests are one of the most scarce and endangered ecosystems in Europe. Saproxylic species represent a major part of biodiversity of woodlands. The saproxylic insects are considered one of the most reliable bio-indicators of high-quality mature woodlands and have a very important role in regard to the protection and monitoring of forest biodiversity due to their highly specific living environments. As a result of the dramatic reduction of mature forests and the decreased availability of deadwood most of the saproxylic communities are greatly diminishing. The study was conducted in the Ticino Valley Regional Park and the aim is to contribute to the expansion of knowledge on the saproxylic beetles of Lombardy. We investigated 6 sampling sites belonging to alluvial and riparian mixed forests. For each forest we selected 12 trees. For beetles’ collection we used two different traps: Eclector Traps and Trunk Window Traps (total of 72 traps and 864 samples collected). We determined 4.387 beetles from 87 saproxylic species belonging to 21 families. Of these species 51 were not included in the previous checklist of the Park. By comparing the two different techniques used for catching saproxylic beetles, we found a significantly high difference in species richness between Window Traps (WT) and Eclector Traps (ET) with a higher number of species captured in the Window Traps. However, the combined use of two different types of traps significantly expanded the spectrum of insects captured Among the species reported as Least Concern in the IUCN Red List, we found interesting species such as the Elateridae Calambus bipustulats, the Eucnemidae Melasis buprestoides and the following species never previously found in the Park: Cerambycidae Xylotrechus rusticus, the Cetoniidae Valgus hemipterus, the Elateridae Lacon punctatus, the Mycetophagidae Mycetophagus piceus, Litargus connexus. Although we didn’t find species listed in the Annexes of the EU Habitat Directive, some of the species found are locally threatened because of their rarity, local distribution, and strong linkage to old forests. Among these species there are the Bothrideridae Bothrideres bipunctatus, the Cerambycidae Prionus coriarius and Xylotrechus rusticus, the Dryophthoridae Dryophthorus corticalis, the Eucnemidae Nematodes filum (with only 1 individual captured in Alnus unmanged forest), the Histeridae Aeletes atomarius and Paromalus flavicornis, the Laemophloeidae Cryptolestes duplicatus, the Latridiidae Enicmus rugosus and Latridius hirtus, the Mycetophagidae Mycetophagus piceus, and the Zopheridae Colydium elongatum and Pycnomerus terebrans

Organic-inorganic heterostructures for nonlinear optics

We consider a hybrid heterostructure made of an inorganic quantum well in close proximity with an organic material overlayer, whereby the latter is used to funnel excitation energy to the former in order to exploit the optical nonlinearities of the two-dimensional Wannier excitons. The resonant optical pumping of the Frenkel excitons and their diffusion to the organic-inorganic interface can lead to an efficient indirect pumping of the inorganic quantum well turning on the corresponding nonlinearities. As organic material we consider a layer of anthracene or of tetracene. In the latter case, the singlet exciton has an energy which is close to twice the one of a triplet exciton and singlet exciton fission into two triplets can be efficient. In tetracene based hybrid heterostructures, the temperature dependence of fission opens the possibility to turn on and off the indirect pumping due to energy transfer from the organic into the inorganic subsystem. Finally, we show how a generic mechanism of dipole-dipole hybridization may lead to the formation of virtual heterodimers of organic molecules with an enhanced nonlinear optical response. Elsevier B.V. All rights reserved

On-site Experimental Study of HCFC-22 Substitution with HFCs Refrigerants

Abstract The European Regulation no 2037/2000 has banned manufacturing HCFC refrigerants from January 1st 2010, although its use is allowed up to 2015 if the fluids come from a recycling process. This situation creates the need for developing new working fluids to replace the HCFC in the refrigeration plants now in operation. Among all the HCFCs the R22 is the most widely used in a wide range of applications, especially in air conditioning. This paper presents the results of an experimental analysis comparing the performance of a vapour compression refrigerating unit operating with R22, and its performance in comparison to some HFCs fluids, substituting the former. In particular, the plant working efficiency was first tested with R22 and then with three HFC fluids: R417A, R407C and R404A. The investigation verified that the performance with HFCs refrigerants did not result as efficient as when using R2

Thermal Care of Functional Dyspepsia Based on Bicarbonate-Sulphate-Calcium Water: A Sequential Clinical Trial

Drug treatment of functional dyspepsia is often unsatisfactory. We assessed the efficacy of a bicarbonate-sulphate-calcium thermal water cycle of 12 days, in patients with functional dyspepsia. Patients with functional dyspepsia were sent by their general practitioners to 12 days of treatment with thermal water, 200–400 ml in the morning, at temperature of 33°C (91.4 F) and were evaluated on a strict intention to treat basis. Four efficacy endpoints were analyzed as follows: (i) reduction of the global symptoms score, (ii) reduction of intensity to a level not interfering with everyday activities, (iii) specific efficacy on ulcer-like or dysmotility-like dyspepsia and (iv) esophageal or abdominal-associated symptoms. Statistical significance was reached for all three primary outcomes after the first 29 consecutive patients. Thermal water reduced the global symptom score, reduced intensity of symptoms to a level not interfering with everyday activity, but was unable to completely suppress all symptoms. A parallel effect emerged for ulcer-like and dyspepsia-like subgroups. The effect on heartburn and abdominal symptoms was not significant, suggesting a specific effect of the water on the gastric and duodenal wall. The Roma II criteria identify a natural kind of dyspepsia that improves with thermal water. Ulcer-like and dysmotility-like are not therapeutically distinguishable subgroups. Patients with dominant esophageal or abdominal symptoms should receive a different therapy. Sequential methods are very effective for the evaluation of traditional care practices and should be considered preliminary and integrative to randomized controlled trials in this context

Quality of life of relatives of patients with Obsessive-Compulsive Disorder: relation to family accommodation and other socio-demographic and clinical characteristics

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Neuromodulation of Vegetative State through Spinal Cord Stimulation: Where Are We Now and Where Are We Going?

Background: Vegetative state (VS) is a complex condition that represents a challenging frontier for medicine and neuroscience research. Nowadays there is no scientifically validated treatment for VS patients, and their chronic long-term assistance is very demanding for healthcare systems worldwide. Objectives: The present paper is a systematic review of the role of spinal cord stimulation (SCS) as a treatment of patients with VS. Methods: Published literature on this topic was analyzed systematically. Clinical and epidemiological characteristics of VS, present therapeutic options and social costs of VS were also evaluated. Results: Only 10 papers have been published since 1988, and overall 308 VS patients have been treated with SCS worldwide; 51.6% displayed a clinical improvement and an amelioration of the environmental interaction. These effects are probably mediated by the stimulation of the reticular formation-thalamus-cortex pathway and by cerebral blood flow augmentation induced by SCS. Conclusions: The experience on this topic is still very limited, and on this basis it is still hard to make any rigorous assessment. However, the most recent experiments represent significant progress in the research on this topic and display SCS as a possible therapeutic tool in the treatment of VS

Parity-time-antisymmetric atomic lattices without gain

Lossy atomic photonic crystals can be suitably tailored so that the real and imaginary parts of the susceptibility are, respectively, an odd and an even function of position. Such a parity-time (PT) space antisymmetry in the susceptibility requires neither optical gain nor negative refraction, but is rather attained by a combined control of the spatial modulation of both the atomic density and their dynamic level shift. These passive photonic crystals made of dressed atoms are characterized by a tunable unidirectional reflectionlessness accompanied by an appreciable degree of transmission. Interestingly, such peculiar properties are associated with non-Hermitian degeneracies of the crystal scattering matrix, which can then be directly observed through reflectivity measurements via a straightforward phase modulation of the atomic dynamic level shift and even off resonance

Spin-dependent resonant tunneling in semiconductor nanostructures

The spin-dependent quantum transport of electrons in non magnetic III-V semiconductor nanos-tructures is studied theoretically within the envelope function approximation and the Kane model for the bulk. It is shown that an unpolarized beam of conducting electrons can be strongly polarized in zero magnetic field by resonant tunneling across asymmetric double-barrier structures, as an effect of the spin-orbit interaction. The electron transmission probability is calculated as a function of energy and angle of incidence. Specific results for tunneling across lattice matched politype Ga0.47In0.53As / InP/Ga0.47In0.53As / GaAs0.5Sb0.5 / Ga0.47In0.53 As double barrier heterostructures show sharp spin split resonances, corresponding to resonant tunneling through spin-orbit split quasi-bound electron states. The polarization of the transmitted beam is also calculated and is shown to be over 50%