510 research outputs found
Surface nano-patterning for the bottom-up growth of iii-v semiconductor nanowire ordered arrays
No full textOrdered arrays of vertically aligned semiconductor nanowires are regarded as promising candidates for the realization of all-dielectric metamaterials and artificial electromagnetic materials, whose properties can be engineered to enable new functions and enhanced device performances with respect to naturally existing materials. In this review we account for the recent progresses in substrate nanopatterning methods, strategies and approaches that overall constitute the preliminary step towards the bottom-up growth of arrays of vertically aligned semiconductor nanowires with a controlled location, size and morphology of each nanowire. While we focus specifically on III-V semiconductor nanowires, several concepts, mechanisms and conclusions reported in the manuscript can be invoked and are valid also for different nanowire materials
Micro-WNOp: A Gold Standard for the evaluation of automatically compiled lexical resources for Opinion Mining
No full textBisphenol a and bisphenol S oxidative effects in sheep red blood cells: An in vitro study
No full textBisphenols (BPs) are plastic components widely used worldwide and occurring in the environment. Exposure to these compounds is known to be harmful for animals and humans at different levels. The aim of this study was to evaluate and compare the oxidative effects of bisphenol A (BPA) and bisphenol S (BPS) in sheep. Reactive oxygen species (ROS) production and correlated structural alterations in sheep erythrocytes were investigated in vitro. Blood samples from four ewes were collected at fasting from the jugular vein using vacuum collection tubes containing EDTA. For ROS assay in erythrocytes, blood was properly diluted and BPA or BPS was added to obtain final bisphenol concentrations in the range between 1 and 300 μM. 2′,7′-Dichlorodihydrofluorescein diacetate (H2DCF-DA) 3 μM was added to the samples, and fluorescence was read in four replicates using a microplate reader. To evaluate erythrocyte shape, blood smears of blood treated with the different concentrations of BPS and BPA were prepared. A significant increase in ROS production was observed when concentrations of BPS and BPA increased from 1 to 100 μM (p < 0:05). At the higher concentrations of the two studied BPs (300 μM of BPS and 200-300 μM of BPA), a ROS decrease was observed when compared to the control group (p < 0:01). Erythrocytes' shape alterations were observed in cells treated with BPS and BPA 200-300 μM 4 hours after the beginning of the treatment. This study confirms that BPA and BPS exhibit oxidative effects on sheep erythrocytes. At higher concentrations, BPA was able to modify erythrocytes' shape, while BPS altered their membrane as a sign of a protein clustering that could lead to eryptosis. These BPs' effects are consequent to intracellular ROS increase
Semiconductor nanowire arrays for optical sensing: a numerical insight on the impact of array periodicity and density
No full textRecent advances in the nanofabrication and modelling of metasurfaces have shown the potential of these systems in providing unprecedented control over light-matter interactions at the nanoscale, enabling immediate and tangible improvement of features and specifications of photonic devices that are becoming always more crucial in enhancing everyday life quality. In this work, we theoretically demonstrate that metasurfaces made of periodic and non-periodic deterministic assemblies of vertically aligned semiconductor nanowires can be engineered to display a tailored effective optical response and provide a suitable route to realize advanced systems with controlled photonic properties particularly interesting for sensing applications. The metasurfaces investigated in this paper correspond to nanowire arrays that can be experimentally realized exploiting nanolithography and bottom-up nanowire growth methods: the combination of these techniques allow to finely control the position and the physical properties of each individual nanowire in complex arrays. By resorting to numerical simulations, we address the near- and far-field behavior of a nanowire ensemble and we show that the controlled design and arrangement of the nanowires on the substrate may introduce unprecedented oscillations of light reflectance, yielding a metasurface which displays an electromagnetic behavior with great potential for sensing. Finite-difference time-domain numerical simulations are carried out to tailor the nanostructure parameters and systematically engineer the optical response in the VIS-NIR spectral range. By exploiting our computational-methods we set-up a complete procedure to design and test metasurfaces able to behave as functional sensors. These results are especially encouraging in the perspective of developing arrays of epitaxially grown semiconductor nanowires, where the suggested design can be easily implemented during the nanostructure growth, opening the way to fully engineered nanowire-based optical metamaterials
Evaluation of curcuma and ginger mixture ability to prevent ROS production induced by bisphenol S: an in vitro study
No full textThe use of bisphenol S (BPS) as a substitute of Bisphenol A is increasing in several products and it can be found in different environmental and biological matrices. Its toxicity has been studied at different levels and one of BPS toxic mechanisms at high concentrations seems to be the induction of oxidative stress through the generation of reactive oxygen species (ROS). This study evaluates the ability of a curcuma and ginger (CG) mixture to exert an antioxidant effect on rat hepatocytes treated with BPS. The effects of the mixture were compared to those of a well-known antioxidant (Trolox). Three different BPS concentrations were used in order to verify ROS production. 70 μg/mL and 150 μg/mL of BPS generated a significant ROS increase (p < 0.01) as compared to control, while CG mixture was able to decrease this ROS production in hepatic cells, as compared to cells treated with 70 μg/ml of BPS (p < 0.01) restoring control levels. BPS 70 μg/mL was tested for total antioxidant capacity (TEAC), superoxide dismutase (SOD) and total thiols. TEAC and SOD significant decreased (p < 0.05 and p < 0.01, respectively) as compared to controls and CG mixture was able to restore control values. Given the widespread BPS use, results obtained in this study can be of high impact for the community, demonstrating the ability of a mixture of natural products to prevent BPS-induced oxidative stress
V. HURTADO, Llibre de deutes, trameses i rebudes de Jaume de Mitjavila i Companyia, 1345- 1370. Edició, estudi comptable i econòmic, CSIC, Instituciò Milà i Fontanals, Departament d’Estudis medievals, Barcelona, 2005, 652 pp.
No full textThe role of oxide interlayers in back reflector configurations for amorphous silicon solar cells
No full textThin oxide interlayers are commonly added to the back reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different back reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxide (SiOx:H) interlayers with different metals (silver, aluminium, and chromium) in standard p-i-n a-Si:H solar cells. We use a unique inverse modeling approach to show that in most back reflectors the internal metal reflectance is lower than expected theoretically. However, the metal reflectance is increased by the addition of an oxide interlayer. Our experiments demonstrate that SiOx:H forms an interesting alternative interlayer because unlike the more commonly used ZnO:Al it can be deposited by plasma-enhanced chemical vapour deposition and it does not reduce the fill factor. The largest efficiency enhancement is obtained with a double interlayer of SiOx:H and ZnO:Al.Electrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc
Surface Nano-Patterning for the Bottom-Up Growth of III-V Semiconductor Nanowire Ordered Arrays
No full textOrdered arrays of vertically aligned semiconductor nanowires are regarded as promising candidates for the realization of all-dielectric metamaterials, artificial electromagnetic materials, whose properties can be engineered to enable new functions and enhanced device performances with respect to naturally existing materials. In this review we account for the recent progresses in substrate nanopatterning methods, strategies and approaches that overall constitute the preliminary step towards the bottom-up growth of arrays of vertically aligned semiconductor nanowires with a controlled location, size and morphology of each nanowire. While we focus specifically on III-V semiconductor nanowires, several concepts, mechanisms and conclusions reported in the manuscript can be invoked and are valid also for different nanowire materials
Calibration‐Free and High‐Sensitivity Microwave Detectors Based on InAs/InP Nanowire Double Quantum Dots
No full textAt the cutting-edge of microwave detection technology, novel approaches which exploit the interaction between microwaves and quantum devices are rising. In this study, microwaves are efficiently detected exploiting the unique transport features of InAs/InP nanowire double quantum dot-based devices, suitably configured to allow the precise and calibration-free measurement of the local field. Prototypical nanoscale detectors are operated both at zero and finite source-drain bias, addressing and rationalizing the microwave impact on the charge stability diagram. The detector performance is addressed by measuring its responsivity, quantum efficiency and noise equivalent power that, upon impedance matching optimization, are estimated to reach values up to approximate to 2000 A W-1, 0.04 and root HZ, respectively. The interaction mechanism between the microwave field and the quantum confined energy levels of the double quantum dots is unveiled and it is shown that these semiconductor nanostructures allow the direct assessment of the local intensity of the microwave field without the need for any calibration tool. Thus, the reported nanoscale devices based on III-V nanowire heterostructures represent a novel class of calibration-free and highly sensitive probes of microwave radiation, with nanometer-scale spatial resolution, that may foster the development of novel high-performance microwave circuitries
Characterization of dynamic crossovers in bulk liquid water by molecular dynamics simulations
No full textDynamic cross-overs in bulk water are important for the study of glass-forming liquids and implicated in many phenomena of biological interest. Here we use classical molecular dynamics (MD) simulations to characterize the interplay between dynamic crossovers and microscopic behaviour of bulk liquid water in the temperature range 180 – 350 K.
In particular, we focused to the dynamic crossover, which is involved in favouring the unfolding of proteins, found experimentally at T* ~ 315 ± 5 K [1,2]. Computationally, a cross-over from Vogel-Fulcher-Tamman to linear trend for increasing temperature was detected from the Arrhenius plots of dynamic quantities, namely of the inverse diffusion coefficient and of the rotational constant and from the onset of a further heterogeneity in the rotational relaxation [4], but we propose some other possible statistical tools. We also verified that for the coefficient of thermal expansion AlphaP(T,P) the isobaric AlphaP (T) curves cross at about the same T* as in the experiment.
We used two different potential models for water: TIP4P-Ew and a recently proposed model (OPC) [3]. OPC was developed by Onufriev et al. through the optimization of the distribution of point charges to best describe the “electrostatics” of the water molecule, which reproduces a comprehensive set of bulk properties significantly more accurately than commonly used rigid models.
Simulations predict T* ~ 285 ± 5 K for the TIP4P-Ew models, but T* ~ 309 ± 5 K for the OPC model. The lifetimes of water hydrogen bonds and of the nearest neighbours were evaluated and were found to cross near T*, where the lifetimes are about 1 ps. For T T* water behaves more like a simple liquid. The fact that T* falls within the biologically relevant temperature range is a strong motivation for further analysis of the phenomenon and its possible consequences for biomolecular systems.
[1] F. Mallamace, C. Corsaro, H. E. Stanley. Sci. Rep. 2, 993 (2012).
[2] F. Mallamace, C. Corsaro, D. Mallamace, S. Vasi, C. Vasi, H. E. Stanley, J. Chem. Phys. 141, 18C504 (2014)
[3] S. Izadi, R. Anandakrishnan, A. V. Onufriev, J Chem, Phys. Lett. 5, 3863 (2014).
[4] P. Demontis, J. Gulín-González, M. Masia, M. Sant, G. B. Suffritti, J. Chem. Phys. 142, 244507 (2015
- …
