Terahertz microscope with oblique subwavelength illumination: design principle

It is shown that the image contrast in the air when using a microscope based on dielectric microparticles with a size of the order of wavelength can be significantly enhanced with the help microparticles that provide the formation of the radiation localisation region at an angle to the direction of radiation incidence (at an angle to the optical axis). For this purpose, a screen is placed in front of the particle, which blocks part of the incident beam, forming a photonic hook or a photonic jet (terajet) with oblique illumination in the near field.

Properties of Holographic Elements Based on Periodic Structures in a Wide Range of Angles of Incidence

An experimental study is carried out on the diffraction and angular selectivity properties of gratings for a wide range of angles of incidence in three-dimensional space. Results for three grating types are presented: nonslanted volume gratings, slanted volume gratings, and hybrid structures. The study encompasses a wide range of directions of radiation incidence on structures and reveals grating orientations that can provide maximal diffraction efficiency for angles of incidence of more than 70°. Obtained data are used to assess the efficiency of diffractive deflectors on the basis of the considered structures, taking into account the trajectory of the Sun as applied to solar-energy problems.

Method for fast determination of the angle of ionizing radiation incidence from data measured by a Timepix3 detector

This paper presents a method of how to determine spatial angles of ionizing radiation incidence quickly, using a Timepix3 detector. This work focuses on the dosimetric applications where detectors and measured quantities show significant angle dependencies. A determined angle of incidence can be used to correct for the angle dependence of a planar Timepix3 detector. Up until now, only passive dosemeters have been able to provide a correct dose and preserve the corresponding incidence angle of the radiation. Unfortunately, passive dosemeters cannot provide this information in “real” time. In our special setup we were able to retrieve the spatial angles with a runtime of less than 600 ms. Employing the new Timepix3 detector enables the use of effective data analysis where the direction of incident radiation is computed from a simple photon event map. In order to obtain this angle, we combine the information extracted from the map with known 3D geometry surrounding the detector. Moreover, we analyze the computation time behavior, conditions and optimizations of the developed spatial angle calculation algorithm.

Seasonal Variations of Polyphenols Content, Sun Protection Factor and Antioxidant Activity of Two Lamiaceae Species

Secondary metabolite production by plants is influenced by external environmental factors that can change depending on the seasons, which makes it important to know how the plant, through its metabolism, is able to adapt to these variations. Mentha x villosa and Plectranthus amboinicus present in their chemical composition polyphenols, and through previous studies, it has been seen that these two species present promising in vitro photoprotective activity. The aim of this study was to evaluate seasonal alterations in photoprotective and antioxidant activities and the influence of factors such as precipitation levels and sun radiation incidence. Thus, polyphenol quantification, cromatographics (HPLC-DAD) and multivariate (PCA) analyses of extracts of the two species through twelve months were done. It was observed that the best months for photoprotective and antioxidant activities were September for M. villosa and July for P. amboinicus (SPF = 14.79). It was possible to conclude that solar radiation more clearly influences the production of phenolics and the increase of SPF in M. villosa, in addition to favoring the antioxidant activity of the two species, while precipitation seems to have no influence.

Radiative behavior and canopy light extinction coefficient in a savanna urban area

The knowledge of the radiative characteristics of an area is essential to understanding the flows of matter and energy. The value of the Light Extinction Coefficient (K) is a parameter that describes the efficiency of the interception of light in a given canopy, being required, as input, for several SWAP (Soil-Water-Atmosphere-Plant) models, which allow the characterization of the interactive properties among soil, plant and atmosphere concerning these exchanges of matter and energy. This study aimed to obtain the light extinction coefficient (K) for a savanna fragment located in the urban area of Cuiabá. The used data correspond to one measurement each month, totaling twelve measurements in 30 points during the period from October 2014 to September 2015. The measured variables were the LAI (Leaf Area Index), the photosynthetically active incident radiation (PARinc) and the transmitted radiation (PARtrans), and the calculated ones were the zenith angle (Zh) and the extinction coefficient (K). Was observed an annual variability for the light extinction coefficient between 0.49 and 0.69. There are seasonal changes that interfere with the canopy geometry and the position of the study area in relation to the solar radiation incidence, concluding that the K variability is predominantly temporal.

Robots for Cleaning Photovoltaic Panels: State of the Art and Future Prospects

The growing interest in use of renewable energy sources, such as photovoltaic energy systems, occurs due to the high cost of conventional energy sources and the environmental awareness linked to renewable sources. For photovoltaic panels efficient operation, it is necessary the system presents appropriate cleaning conditions to the dirt do not obstruct the solar radiation incidence. In this context, periodic cleaning of photovoltaic panels is an obvious necessity. This work aims to present a market survey and patent analysis on the use of robots to perform cleaning tasks on photovoltaic panels. For that, the Brazilian and international literature were consulted. As a result, it was noted the existence of different solutions for cleaning photovoltaic panels, all with positive and negative aspects in practical terms. With this study it was also possible to map the technology of robotics for cleaning photovoltaic panels.

CONVERSION COEFFICIENTS FROM AIR KERMA TO DIRECTIONAL DOSE EQUIVALENT H′(0.07) FOR PHOTONS

New conversion coefficients from air kerma free-in-air, Ka, to directional dose equivalent at 0.07mm depth, H′(0.07), are provided for monoenergetic values and for the spectra of the radiation qualities defined in ISO 4037-1. The interpolation procedure of the monoenergetic conversion coefficients from ICRU Report 57 was improved compared to former publications. The values resulting from the new interpolation procedure describe the energy dependence of the conversion coefficients more accurately and differ by up to 5% between 50keV and 100keV from former values. Due to an additional change of the extrapolation to low energies, the values for angles of radiation incidence above 60° and energies below 40keV changed by up to 50%. The influence on the spectrum weighted conversion coefficients is similar to the changes of the monoenergetic values.

Stokes-polarimetry of ultrathin Au and Sn island films

The optical properties of ultrathin Au and Sn islet films, obtained by the methods of magnetron sputtering and thermal evaporation, respectively, are considered in this paper. By measuring the Stokes vector of the beam reflected from the samples, polarized and depolarized radiation components were separated. The conditions of the polarization degree dependence on the surface structure for a series of islet films with different morphologies are analyzed. To determine the morphological structure of the metal layer, methods of atomic force microscopy and resistivity measurement were also employed. The parameters of discontinuous film, obtained by optical and non-optical methods, are compared. It is established that with an increase in the angle of radiation incidence onto the samples, the polarization degree of the reflected beam decreases. Such behavior can be explained by the Mie theory of light scattering by particles. The magnitude of depolarizing action of the samples also depends on the morphology of their surface, correlating with the number of inequalities on it. The applied method of Stokes polarimetry, thus, allows one to obtain additional information on the structure of the surface, which is its advantage.