Metal halide perovskites are currently emerging as highly promising optoelectronic materials. It has been recently demonstrated that fully inorganic solution processed CsPbBr3 perovskite thin films ...show good electroluminescence properties combined with high thermal stability. In this work, we investigate in details the amplified spontaneous emission (ASE) properties of CsPbBr3 perovskite thin films, as a function of the temperature and the trap density, modified by changing the CsBr–PbBr2 precursor concentration. ASE is observed in samples from both CsBr-rich solution (low trap density) and equimolar solution (higher trap density), up to about 150 K, with a minimum threshold of 26 and 29 μJ cm–2 at 10 K, respectively. However, the different distribution of defect states, mainly above the first exciton level in the former and below it in the latter, strongly improved optical gain at 10 K and changed the ASE temperature dependence of CsBr-rich films.
Topological physics relies on the structure of the eigenstates of the Hamiltonians. The geometry of the eigenstates is encoded in the quantum geometric tensor
-comprising the Berry curvature
(crucial ...for topological matter)
and the quantum metric
, which defines the distance between the eigenstates. Knowledge of the quantum metric is essential for understanding many phenomena, such as superfluidity in flat bands
, orbital magnetic susceptibility
, the exciton Lamb shift
and the non-adiabatic anomalous Hall effect
. However, the quantum geometry of energy bands has not been measured. Here we report the direct measurement of both the Berry curvature and the quantum metric in a two-dimensional continuous medium-a high-finesse planar microcavity
-together with the related anomalous Hall drift. The microcavity hosts strongly coupled exciton-photon modes (exciton polaritons) that are subject to photonic spin-orbit coupling
from which Dirac cones emerge
, and to exciton Zeeman splitting, breaking time-reversal symmetry. The monopolar and half-skyrmion pseudospin textures are measured using polarization-resolved photoluminescence. The associated quantum geometry of the bands is extracted, enabling prediction of the anomalous Hall drift, which we measure independently using high-resolution spatially resolved epifluorescence. Our results unveil the intrinsic chirality of photonic modes, the cornerstone of topological photonics
. These results also experimentally validate the semiclassical description of wavepacket motion in geometrically non-trivial bands
. The use of exciton polaritons (interacting photons) opens up possibilities for future studies of quantum fluid physics in topological systems.
Bound states in the continuum (BICs)
are peculiar topological states that, when realized in a planar photonic crystal lattice, are symmetry-protected from radiating in the far field despite lying ...within the light cone
. These BICs possess an invariant topological charge given by the winding number of the polarization vectors
, similar to vortices in quantum fluids such as superfluid helium and atomic Bose-Einstein condensates. In spite of several reports of optical BICs in patterned dielectric slabs with evidence of lasing, their potential as topologically protected states with theoretically infinite lifetime has not yet been fully exploited. Here we show non-equilibrium Bose-Einstein condensation of polaritons-hybrid light-matter excitations-occurring in a BIC thanks to its peculiar non-radiative nature, which favours polariton accumulation. The combination of the ultralong BIC lifetime and the tight confinement of the waveguide geometry enables the achievement of an extremely low threshold density for condensation, which is reached not in the dispersion minimum but at a saddle point in reciprocal space. By bridging bosonic condensation and symmetry-protected radiation eigenmodes, we reveal ways of imparting topological properties onto macroscopic quantum states with unexplored dispersion features. Such an observation may open a route towards energy-efficient polariton condensation in cost-effective integrated devices, ultimately suited for the development of hybrid light-matter optical circuits.
Histone deacetylases (HDACs) are evolutionary conserved enzymes which operate by removing acetyl groups from histones and other protein regulatory factors, with functional consequences on chromatin ...remodeling and gene expression profiles. We provide here a review on the recent knowledge accrued on the zinc-dependent HDAC protein family across different species, tissues, and human pathologies, specifically focusing on the role of HDAC inhibitors as anti-cancer agents. We will investigate the chemical specificity of different HDACs and discuss their role in the human interactome as members of chromatin-binding and regulatory complexes.
► The study underlines the real performances of a PV system in South-eastern Italy. ► Power generated, final yield, PV efficiency are linked to climatic characteristics. ► The study shows the ...dependency of the efficiency from module temperature. ► AC power increases almost linearly with the solar irradiance. ► Comparisons with other PV systems located in different sites have been done.
The study is focused on the monitoring of the performances of a photovoltaic system, influenced of climatic characteristics of a particular geographical area, in which the PV system is installed.
This paper presents the results obtained by monitoring, from March to October 2012, a 960kWp photovoltaic system installed on the parking lots in the campus of the University of Salento, Italy and divided in two subfields with different tilt angle (3–15°) and different nominal powers (353.3kWp and 606.6kWp). The values of energy and power generated, final yield, reference yield, photovoltaic system efficiency, performance ratio and cell temperature losses are analyzed and linked to the climatic characteristics of the site, such as insolation (for the two distinct subfield), ambient temperature and wind speed. This study is part of the European Project “Buildings Energy Advanced Management System, BEAMS”, and its aim is to develop an advanced, integrated management system for buildings and special infrastructures of public use. This work offers a tool to estimate the performances of plants to be installed in sites with climatic characteristics similar to South-eastern Italy, and it is also useful as comparison to investigate the productivity of plants placed in different areas.
A dense glycocalix covers the surface of Trypanosoma cruzi, the agent of Chagas disease. Sialic acid in the surface of the parasite plays an important role in the infectious process, however, T. ...cruzi is unable to synthesize sialic acid or the usual donor CMP-sialic acid. Instead, T. cruzi expresses a unique enzyme, the trans-sialidase (TcTS) involved in the transfer of sialic acid from host glycoconjugates to mucins of the parasite. The mucins are the major glycoproteins in the insect stage epimastigotes and in the infective trypomastigotes. Both, the mucins and the TcTS are anchored to the plasma membrane by a glycosylphosphatidylinositol anchor. Thus, TcTS may be shed into the bloodstream of the mammal host by the action of a parasite phosphatidylinositol-phospholipase C, affecting the immune system. The composition and structure of the sugars in the parasite mucins is characteristic of each differentiation stage, also, interstrain variations were described for epimastigote mucins. This review focus on the characteristics of the interplay between the trans-sialidase and the mucins of T. cruzi and summarizes the known carbohydrate structures of the mucins.
All-optical polariton transistor Ballarini, D; De Giorgi, M; Cancellieri, E ...
Nature communications,
2013, Letnik:
4, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Although optical technology provides the best solution for the transmission of information, all-optical devices must satisfy several qualitative criteria to be used as logic elements. In particular, ...cascadability is difficult to obtain in optical systems, and it is assured only if the output of one stage is in the correct form to drive the input of the next stage. Exciton-polaritons, which are composite particles resulting from the strong coupling between excitons and photons, have recently demonstrated huge non-linearities and unique propagation properties. Here we show that polariton fluids moving in the plane of the microcavity can operate as input and output of an all-optical transistor, obtaining up to 19 times amplification and demonstrating the cascadability of the system. Moreover, the operation as an AND/OR gate is shown, validating the connectivity of multiple transistors in the microcavity plane and opening the way to the implementation of polariton integrated circuits.
RadioLab is an Italian project, addressed to school-age people, and designed for the dissemination of scientific culture on the theme of environmental radioactivity, with particular regards to the ...importance of knowledge of radon gas exposure. The project is a nationwide initiative promoted by the National Institute of Nuclear Physics- INFN. First tool used by the project, and of immediate impact to assess the public awareness on radon, is the administration of the survey "do you know the radon gas?". In the survey, together with the knowledge of radon and of its sources, information on personal, cultural and territorial details regarding the interviewees are also taken. Reasonably, the survey invests not only young people, but also their relatives, school workers and, gradually, the public. The survey is administrated during exhibitions or outreach events devoted to schools, but also open to the public. The survey is in dual form: printed and online. The online mode clearly leads RadioLab project even outside the school environment. Based on the results of the survey, several statistical analyses have been performed and many conclusions are drawn about the knowledge of the population on the radon risk. The RadioLab benefit and the requirement to carry on the project goals, spreading awareness of environmental radioactivity from radon, emerge. The dataset involves all twenty Italian regions and consists of 28,612 entries covering the 5-year period 2018-2022.
► Temperature influences the cavitation number at two-phase flow regime transitions. ► FFT of the pressure are in accordance with the ones of the visual observations. ► Thermal effects are relevant ...at water temperature higher than 333K. ► The dominant frequencies depend on cavitation number and fluid temperature.
Experiments on a water cavitating orifice were conducted to investigate the influence of pressure and temperature on flow regime transition due to cavitation. The thermal effects could be important in cases with cryogenic cavitation or hot fluid injection. The investigations were based on CCD observations and a pressure fluctuations frequency analysis.
The high-speed photographic recordings were used to analyze the cavitation evolution and individuate the frequency content of the two-phase flow by processing the pixel-intensity time-series data.
The cavitating structures showed different behaviors and characteristics with variations in operating conditions, as the pressure inside the orifice and the flow temperature .
The flow regime map for the cavitating flow was obtained using experimental observations to analyze the occurrence of the different two-phase flow regime transitions at various operating conditions.
As the pressure at the orifice inlet increased, at the same downstream pressure, cavitation inception occurred. The decrease of the cavitation number brought a significant increase in cavitation zone extension. As the pressure drop inside the orifice increased, the cavitation was characterized by an evident increase in cavitation zone length to the outlet of the orifice. With a further cavitation number decrease, the transition to jet cavitation was evident.
The temperature influenced both the cavitation intensity and the cavitation number at which different two-phase flow regime transitions occurred, which tended to increase with temperature.
The vapor fraction was estimated using an image processing algorithm.
The frequency content given by the pressure fluctuations was analyzed and compared with the frequency spectra obtained from the visual observations. The behavior of the different cavitating flows could be correlated to the frequency spectrum of the pressure fluctuations measured upstream and downstream of the orifice. The cavitation number reduction and consequent increase in cavitating area width were related to a corresponding significant increase in the amplitude of typical frequency components. The transition to jet cavitation was characterized by a significant increase in the first peak in the frequency spectrum; weaker spectral peaks were also present at high cavitation numbers.
The forecasting techniques are affected by the renewable sources randomness. Improvements of the prediction models with more accurate results and lower error are necessary for future development of ...the microgrids projects and of the economic dispatch sector. The LS-SVM (Least Square Support Vector Machine), a relatively unexplored neural network known as GMDH (Group Method of Data Handling) and a novel hybrid algorithm GLSSVM (Group Least Square Support Vector Machine), based on the combination of the first two models, were implemented to forecast the PV (Photovoltaic) output power at several time horizons up to 24 h. In order to improve the forecasting accuracy, each model was combined with three strategies for multi-step ahead forecast (Direct, Recursive and DirRec). A detail analysis of the normalized mean error is carried out to compare the different forecasting methods, using the historical PV output power data of a 960 kWP grid connected PV system in the south of Italy. The outcomes demonstrate the GLSSVM method with the DirRec strategy can give a normalized error of 2.92% under different weather conditions with evident improvements respect to the traditional ANN (Artificial Neural Network).
•Photovoltaic forecast is performed by the historical PV power data.•LS-SVM and the GMDH models are applied to predict the PV output power at 24 h.•Multi-step ahead forecasting strategies (Direct, Recursive and DirRec) were implemented.•A comparative analysis based on the mean error is performed to evaluate the accuracy.•A hybrid method GLSSVM has been investigated.
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