Coronal mass ejections and high-speed solar wind streams effect on HF ionospheric communication channel

This article analyzes the degree of solar coronal mass ejections and high-speed solar wind streams influence on the ionospheric communication channel in the short-wavelength range. Regularities in the coronal mass ejections influence on the parameters of the ionosphere are revealed. It is shown that there is a decrease in the values of the used differential parameter of critical frequency of the ionosphere F2 layer after the onset of coronal mass ejections of the loop type, while no significant changes are observed from other types of coronal mass ejections. The contribution of the high-speed solar wind flux to the features of the behavior of ionospheric parameters is demonstrated. Deviations of critical frequency and maximum observed frequency of the ionosphere F2 layer indicate a change in conditions in the ionosphere, leading to disruption of radio communication in the short-wavelength range. The results of ground-based measurements of the ionospheric plasma parameters were obtained by the methods of oblique and vertical sounding of the ionosphere. The use of the method of oblique sounding made it possible to obtain data on the state of the ionosphere where there are no vertical sounding stations.

Curcumin-mediated photodynamic antimicrobial chemotherapy (PACT): a systematic review / Quimioterapia fotodinâmica antimicrobiana (PACT) mediada por curcumina: uma revisão sistemática

Light energy is known to be used to combat microbial growth. Photodynamic antimicrobial chemotherapy (PACT) has the potential to use different naturally-occurring compounds, such as photosensitizers. Curcumin is an example of a molecule of interest in different areas under different optics. This systematic review surveys the aims and scope of research on curcumin-mediated PACT published between January 2011 and December 2020. The search was carried out in MEDLINE, PubMed, EMBASE and Periódicos CAPES databases employing the keywords “Photodynamic antimicrobial chemotherapy”, “photosensitizer”, “curcumin” and the descriptor “Light-Emitting Diode”. It was observed that in the last decade little material meeting these criteria was published. Brazilian institutions concentrated most of their studies on cytotoxic activity. The most recent work, however, focused on antibiofilm activity. Gram-positive bacteria are more sensitive to curcumin-mediated PACT over a short wavelength range. Different concentrations and exposure time of the photosensitizer were evaluated, but the amount of information is still insufficient to establish the best treatment condition as the number of tested pathogens is still poor.

Complex Attosecond Waveform Synthesis at FEL FERMI

Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present the generation of attosecond pulse trains (APTs) at the seeded FEL FERMI using the beating of multiple phase-locked harmonics. We demonstrate the complex attosecond waveform shaping of the generated APTs, exploiting the ability to manipulate independently the amplitudes and the phases of the harmonics. The described generalized attosecond waveform synthesis technique with an arbitrary number of phase-locked harmonics will allow the generation of sub-100 as pulses with programmable electric fields.

Cd-Free Zn(O,S) as Alternative Buffer Layer for Chalcogenide and Kesterite Based Thin Films Solar Cells: A Review

Cd is categorized as a toxic material with restricted use in electronics as there are inherent problems of treating waste and convincing consumers that it is properly sealed inside without any threat of precarious leaks. Apart from toxicity, band-gap of CdS is about 2.40–2.50 eV, which results significant photon loss in short-wavelength range which restricts the overall performance of solar cells. Thin film of Zn(O,S) is a favorable contender to substitute CdS thin film as buffer layer for CuInGaSe2 (CIGS), CuInGa(S,Se)2 (CIGSSe), Cu2ZnSn(S,Se)4 (CZTSSe) Cu2ZnSnSe4 (CZTSe), Cu2ZnSnS4 (CZTS) thin film absorber material based photovoltaic due to it made from earth abundant, low cost, non-toxic materials and its ability to improve the efficiency of chalcogenide and kesterite based photovoltaic due to wider band-gap which results in reduction of absorption loss compared to CdS. In this review, apart from mentioning various deposition technique for Zn(O,S) thin films, changes in various properties i.e., optical, morphological, and opto-electrical properties of Zn(O,S) thin film deposited using various methods utilized for fabricating solar cell based on CIGS, CIGSSe, CZTS, CZTSe and CZTSSe thin films, the material has been evaluated for all the properties of buffer layer (high transparency for incident light, good conduction band lineup with absorber material, low interface recombination, high resistivity and good device stability).

Porous Si-SiO2 UV Microcavities to Modulate the Responsivity of a Broadband Photodetector

Porous Si-SiO2 UV microcavities are used to modulate a broad responsivity photodetector (GVGR-T10GD) with a detection range from 300 to 510 nm. The UV microcavity filters modified the responsivity at short wavelengths, while in the visible range the filters only attenuated the responsivity. All microcavities had a localized mode close to 360 nm in the UV-A range, and this meant that porous Si-SiO2 filters cut off the photodetection range of the photodetector from 300 to 350 nm, where microcavities showed low transmission. In the short-wavelength range, the photons were absorbed and did not contribute to the photocurrent. Therefore, the density of recombination centers was very high, and the photodetector sensitivity with a filter was lower than the photodetector without a filter. The maximum transmission measured at the localized mode (between 356 and 364 nm) was dominant in the UV-A range and enabled the flow of high energy photons. Moreover, the filters favored light transmission with a wavelength from 390 nm to 510 nm, where photons contributed to the photocurrent. Our filters made the photodetector more selective inside the specific UV range of wavelengths. This was a novel result to the best of our knowledge.

Development and Experimental Study of APAA HF-Band with Controlled Radiation Pattern

There is a promising direction in the antenna field design of a stationary transmitting radio center short-wavelength range is the use of active phased array antennas with spatial power addition and a controlled directional pattern. The article considers the algorithm for calculating the V shaped antenna as a basic element of antenna array, apart from that it considers calculation of the four-element antenna array based on the V shaped antenna. This paper presents the track tests results to estimate the power increment depending on the operating elements in the antenna array, as well as horizontal controllability results.

Flexible High-Color-Purity Structural Color Filters Based on a Higher-Order Optical Resonance Suppression

We present flexible transmissive structural color filters with high-color-purity based on a higher-order resonance suppression by inserting an ultrathin absorbing layer in the middle of a cavity. A 3rd order Fabry–Pérot (F-P) resonance, which exhibits a narrower bandwidth than a fundamental F-P resonance, is used to produce transmissive colors with an improved color purity. The thin absorbing layer is properly placed at a center of the cavity to highly suppress only a 5th order F-P resonance appearing at a short wavelength range while not affecting the 3rd order F-P resonance for color generation, thus being able to attain the high-color-purity transmissive colors without reducing a transmission efficiency. In addition, angle-insensitive properties are achieved by compensating a net phase shift with a dielectric overlay and using a material with a high refractive index for the cavity medium. Moreover, the transmissive colors on a flexible substrate are demonstrated, presenting that changes in both the resonance wavelength and the transmission efficiency are nearly negligible when the color filters are bent with a bending radius of 5 mm and over 3000 times bending tests. The described approach could pave the way for various applications, such as colored displays, decorative solar panels, and image sensors.

On the Long-Wavelength Validation of the SWOT KaRIn Measurement

The Surface Water and Ocean Topography (SWOT) mission will measure the sea surface height (SSH) using a Ka-band radar interferometer (KaRIn) over a swath off the nadir of the satellite tracks. The mission requires calibration and validation (CalVal) of the SSH wavenumber spectrum at wavelengths between 15 and 1000 km. The CalVal in the short-wavelength range (15–150 km) requires in situ observations. In the long-wavelength range (150–1000 km), the CalVal will use the onboard Jason-class nadir altimeter. Using a high-resolution global ocean simulation, this study identifies the spatial scales beyond which the nadir and off-nadir observations can be considered comparable. Our results suggest that the ocean signals at nadir can represent off-nadir ocean signals at wavelengths longer than 120 and 70 km along the midswath and the inner edge of the KaRIn grid, respectively, indicating that the nadir altimeter is able to fulfill its goal to validate the long-wavelength KaRIn measurement. The wavelength along the inner edge is limited around 70 km because the onboard nadir altimeter cannot resolve spatial scales longer than ~70 km. These wavelengths provide a reference point for the required spatial coverage of the SWOT SSH in situ CalVal.