Short-wavelength Radiation Research Articles

相干衍射成像研究进展: 叠层扫描相干衍射成像和相干调制成像

Coherent diffraction imaging(CDI) is a lensless computational imaging technique, which reconstructs the amplitude and phase of an object directly from diffraction intensity measurement by solving the phase problem using iterative algorithms. CDI can provide images at the diffraction limit resolution that is only determined by the wavelength of radiation source and the effective numerical aperture of the recorded data. Since CDI has no need for high quality imaging optics, it is suitable for short wavelength radiations such as deep ultraviolet, X-rays, and electron beam, for which imaging optics of high performance are difficult to make. Meanwhile, the past 20 years have seen rapid progress of new type of light sources (cold emission electron guns, 3rd and 4th generation synchrotron X-rays sources, and free-electron lasers), array detectors with single particle sensitivity and broad dynamic range. All those progresses greatly promote the development of CDI. At present, CDI has shown some unique advantages over traditional methods in some study of materials science and biology, and gradually becomes a mainstream technology for certain applications. This paper briefly summarized the history of CDI with a focus on ptychography and coherent modulation imaging.

Soft X-ray Absorption Spectroscopy of Aqueous Solutions Using a Table-Top Femtosecond Soft X-ray Source.

We demonstrate the feasibility of soft X-ray absorption spectroscopy in the water window using a table-top laser-based approach with organic molecules and inorganic salts in aqueous solution. A high-order harmonic source delivers femtosecond pulses of short wavelength radiation in the photon energy range from 220 to 450 eV. We report static soft X-ray absorption measurements in transmission on the solvated compounds O=C(NH2)2, CaCl2, and NaNO3 using flatjet technology. We monitor the absorption of the molecular samples between the carbon (∼280 eV) and nitrogen (∼400 eV) K-edges and compare our results with previous measurements performed at the BESSYII facility. We discuss the roles of pulse stability and photon flux in the outcome of our experiments. Our work paves the way toward table-top femtosecond, solution-phase soft X-ray absorption spectroscopy in the water window.

Determination of the Ion Composition of the Outer Ionosphere from the Characteristics of ELF–VLF Waves Detected during the Operation of the Sura Facility

The propagation characteristics and physical nature of low-frequency waves observed in the ionosphere during heating of the near-Earth plasma by a powerful short-wavelength radiation are investigated using the singular value decomposition method. The experimental results obtained with the Sura midlatitude heating facility and detected by the onboard equipment of the DEMETER satellite were used. The ion composition of the near-Earth plasma is estimated from the spectral characteristics of the observed radio waves. The method is verified using results of full-scale measurements performed at altitudes corresponding to the Earth’s outer ionosphere.

High efficiency four-wave mixing in double asymmetry quantum dots

A theory analysis of the four-wave mixing (FWM) scheme in a double asymmetry quantum dots (QDs) system is performed. The efficiency of the generated field decreases in an oscillating mode for the penetration depth and is significantly enhanced because of three-wave mixing (TWM). The dependence of the conversion efficiency on the three coupling laser fields and decay rate is also discussed. High conversion efficiency up to 0.8 is demonstrated with small propagation length at low temperature. Such a solid-state system may be more practical due to the flexibility of QDs to generate coherent short-wavelength radiation.

Plasma polarization grating for circularly polarized high-order harmonic generation

Polarization grating (PG) is a kind of optical element based on the Pancharatnam-Berry phase, providing a unique capability of manipulating the polarization properties of output beams [Bomzon et al., Opt. Lett. 27, 1141–1143 (2002) and Oh and Escuti, Opt. Lett. 33, 2287–2289 (2008)]. Here, we extend this concept into the nonlinear domain of high-order harmonic generation from the laser-solid interaction. Through theoretical analysis and numerical simulations, we proposed a scheme of two non-collinear relativistic lasers of opposite handedness interacting with a solid target to generate angularly isolated, circularly polarized harmonics of both left and right handedness simultaneously. The physical mechanism was described as the confluence of PG and relativistically oscillating mirror, which can be defined as a new mechanism: “relativistically oscillating polarization grating mechanism.” This work provides a useful method for developing bright, near-monochromatic, short-wavelength radiation sources with desirable polarization for a broad range of applications.

Effect of exposure duration and light spectra on nighttime melatonin suppression in adolescents and adults.

This study investigated how light exposure duration affects melatonin suppression, a well-established marker of circadian phase, and whether adolescents (13-18 years) are more sensitive to short-wavelength (blue) light than adults (32-51 years). Twenty-four participants (12 adolescents, 12 adults) were exposed to three lighting conditions during successive 4-h study nights that were separated by at least one week. In addition to a dim light (<5 lux) control, participants were exposed to two light spectra (warm (2700 K) and cool (5600 K)) delivering a circadian stimulus of 0.25 at eye level. Repeated measures analysis of variance revealed a significant main effect of exposure duration, indicating that a longer duration exposure suppressed melatonin to a greater degree. The analysis further revealed a significant main effect of spectrum and a significant interaction between spectrum and participant age. For the adolescents, but not the adults, melatonin suppression was significantly greater after exposure to the 5600 K intervention (43%) compared to the 2700 K intervention (29%), suggesting an increased sensitivity to short-wavelength radiation. These results will be used to extend the model of human circadian phototransduction to incorporate factors such as exposure duration and participant age to better predict effective circadian stimulus.

Tunneling-induced highly efficient four-wave mixing in asymmetric double quantum wells

The time-dependent analysis of four-wave mixing based on resonant tunneling is investigated in an asymmetric semiconductor double quantum well structure. We analytically demonstrate that a highly efficient mixing wave is found to be induced by resonant tunneling in such a quantum well scheme with low-light pump wave intensities. Especially for small propagation distances, a significant enhancement of four-wave mixing conversion efficiency can be achieved. Such an interesting scheme could be used to generate coherent short-wavelength radiation in solid-state materials.

Synthesis and characterization of Mn:ZnS quantum dots for photovoltaic applications

The field of photovoltaics has evolved over the past few decades and introduction of quantum dots (QDs) have further improved their ability to absorb shorter wavelength radiations, which further attracted investigation on quantum dots. Among the QDs, zinc sulfide has shown remarkable results as a semiconductor. It is a low cost and a non-toxic material. Mn:ZnS is synthesized by a hydrothermal process and is characterized by UV–Visible spectroscopy to calculate the optical band gap (3.86 eV) and by X-ray diffractometer (XRD), particle size was calculated (±40 nm) which was confirmed by scanning electron microscopy (SEM). Elemental analysis was carried out by energy dispersion spectroscopy (EDS) and X-ray photoemission spectroscopy (XPS). Here manganese is used as dopant to increase the luminescence property by red shift (587 nm), and thus, making a better candidate for photovoltaic applications. The ability of this material for photovoltaic application is evaluated by constructing a hybrid solar cell with P3HT and calculating the efficiency.

Self-absorption of violet radiation in ZnO thin films produced on ZnSe crystal surfaces by isovalent substitution method

Photoluminescence (PL) spectra of ZnO thin films produced by isovalent substitution method by means of thermal treatment of zinc selenide single crystal substrates in air are studied in 350 – 750 nm range at room temperature. Irrespective of annealing temperature (500 – 870 °C) and annealing time (20 – 120 min), PL spectra consist of a short-wavelength violet radiation with maximum localized between 396 and 423 nm and a long-wavelength yellow-orange radiation with maximum localized between 575 and 600 nm. Both PL bands are attributed to donor-acceptor (DA) pairs. It is shown that the violet PL band intensity decreases and the yellow-orange PL band intensity increases with increasing ZnO film thickness that is caused by self-absorption of the short-wavelength radiation and energy transmission to DA-pair centres of the long-wavelength radiation.

Skin Temperature and Body Surface Section in Non-Uniform and Asymmetric Outdoor Thermal Environment

In indoor environments and shady outdoor environments, there is little influence of short-wavelength solar radiation, so a strikingly non-uniform and asymmetric environment is not formed. In outdoor sunny environment, however, shaded areas occur even for the same site of the body, and a remarkable difference in skin temperature is considered to occur under the influence of the short-wavelength solar radiation. The purpose of this study is to clarify the influence of the non-uniform and asymmetric thermal radiation of short-wavelength solar radiation in outdoor environment on the division of the body surface section and the calculation of the mean skin temperature. The skin temperature of the front of the coronal surface, which was facing the sun and where the body received direct short-wavelength solar radiation, and the skin temperature of the rear of the coronal surface, which was in the shadow and did not receive direct short-wavelength solar radiation were respectively measured. The feet, upper arm, forearm, hand and lower leg, which are susceptible to short-wavelength solar radiation in a standing posture, had a noticeable difference in skin temperature between sites in the sun and in shade. The mean skin temperature of sites facing the sun was significantly higher than the mean skin temperature of those in the shade.

The Influence of the Solar Radiation Absorptivity up on the Outdoor Thermal Environment Evaluation Index and the Thermal Sensory Perceptions

When the thermal environment is under heated conditions, short-wavelength solar radiation shows a strong influence on the human body and the heat is accumulated in the human body. In order to demonstrate the effect of the short-wavelength solar radiation absorptivity of clothing on physiological temperature in an outdoor space, the relationship between the thermal environment evaluation index, ETFe, and the thermal sensory perceptions of the human body was investigated. A significant temperature difference of 2.7°C was shown for an ETFe that was thermally neutral (neither hot nor cold). The effect of short-wavelength solar radiation absorptivity was strongly apparent in ETFe when direct solar radiation was strong and in warmer outdoor spaces. In an outdoor space where the effect of the sky factor and albedo was strong, the setting of the short-wavelength solar radiation absorptivity was demonstrated to greatly impact the estimation of perceived and physiological temperature. When interviewing subjects on clothing in an outdoor space, it is essential to obtain the hue of clothing.

Generation of high-power broadband terahertz radiation during stimulated backscattering of the pump wave by an intense relativistic electron beam

The possibility of generation of high-power (multi-megawatt) broadband terahertz radiation during stimulated backscattering of an intense millimeter-wavelength pump wave by a high-current relativistic electron beam (REB) is shown. With allowance for a significant parameter spread that is typical for intense REBs, the kinetic interaction regime is expedient. This regime leads to the broadening of the scattered-radiation spectrum, but simultaneously increases the efficiency of the beam energy conversion into short-wavelength radiation.

Can narrow-bandwidth light from UV-A to green alter secondary plant metabolism and increase Brassica plant defenses against aphids?

Light of different wavelengths is essential for plant growth and development. Short-wavelength radiation such as UV can shift the composition of flavonoids, glucosinolates, and other plant metabolites responsible for enhanced defense against certain herbivorous insects. The intensity of light-induced, metabolite-based resistance is plant- and insect species-specific and depends on herbivore feeding guild and specialization. The increasing use of light-emitting diodes (LEDs) in horticultural plant production systems in protected environments enables the creation of tailor-made light scenarios for improved plant cultivation and induced defense against herbivorous insects. In this study, broccoli (Brassica oleracea var. italica) plants were grown in a climate chamber under broad spectra photosynthetic active radiation (PAR) and were additionally treated with the following narrow-bandwidth light generated with LEDs: UV-A (365 nm), violet (420 nm), blue (470 nm), or green (515 nm). We determined the influence of narrow-bandwidth light on broccoli plant growth, secondary plant metabolism (flavonol glycosides and glucosinolates), and plant-mediated light effects on the performance and behavior of the specialized cabbage aphid Brevicoryne brassicae. Green light increased plant height more than UV-A, violet, or blue LED treatments. Among flavonol glycosides, specific quercetin and kaempferol glycosides were increased under violet light. The concentration of 3-indolylmethyl glucosinolate in plants was increased by UV-A treatment. B. brassicae performance was not influenced by the different light qualities, but in host-choice tests, B. brassicae preferred previously blue-illuminated plants (but not UV-A-, violet-, or green-illuminated plants) over control plants.

A physiological perspective on the origin and evolution of photosynthesis.

The origin and early evolution of photosynthesis are reviewed from an ecophysiological perspective. Earth's first ecosystems were chemotrophic, fueled by geological H2 at hydrothermal vents and, required flavin-based electron bifurcation to reduce ferredoxin for CO2 fixation. Chlorophyll-based phototrophy (chlorophototrophy) allowed autotrophs to generate reduced ferredoxin without electron bifurcation, providing them access to reductants other than H2. Because high-intensity, short-wavelength electromagnetic radiation at Earth's surface would have been damaging for the first chlorophyll (Chl)-containing cells, photosynthesis probably arose at hydrothermal vents under low-intensity, long-wavelength geothermal light. The first photochemically active pigments were possibly Zn-tetrapyrroles. We suggest that (i) after the evolution of red-absorbing Chl-like pigments, the first light-driven electron transport chains reduced ferredoxin via a type-1 reaction center (RC) progenitor with electrons from H2S; (ii) photothioautotrophy, first with one RC and then with two, was the bridge between H2-dependent chemolithoautotrophy and water-splitting photosynthesis; (iii) photothiotrophy sustained primary production in the photic zone of Archean oceans; (iv) photosynthesis arose in an anoxygenic cyanobacterial progenitor; (v) Chl a is the ancestral Chl; and (vi), anoxygenic chlorophototrophic lineages characterized so far acquired, by horizontal gene transfer, RCs and Chl biosynthesis with or without autotrophy, from the architects of chlorophototrophy—the cyanobacterial lineage.

The maximum theoretical performance of unconcentrated solar photovoltaic and thermoelectric generator systems

The maximum efficiency for photovoltaic (PV) and thermoelectric generator (TEG) systems without concentration is investigated. Both a combined system where the TEG is mounted directly on the back of the PV and a tandem system where the incoming sunlight is split, and the short wavelength radiation is sent to the PV and the long wavelength to the TEG, are considered. An analytical model based on the Shockley-Queisser efficiency limit for PVs and the TEG figure of merit parameter zT is presented. It is shown that for non-concentrated sunlight, even if the TEG operates at the Carnot efficiency and the PV performance is assumed independent of temperature, the maximum increase in efficiency is 4.5 percentage points (pp.) for the combined case and 1.8 pp. for the tandem case compared to a stand alone PV. For a more realistic case with a temperature dependent PV and a realistic TEG, the gain in performance is much lower. For the combined PV and TEG system it is shown that a minimum zT value is needed in order for the system to be more efficient than a stand alone PV system.

Controlling the macro- and micro-processes influenсing harmonic generation in laser-produced plasmas

We review the studies of the spatial conditions for the quasi-phase-matching in the multi-jet laserproduced silver plasma. These studies of the off-axis and on-axis spatial components of harmonics allowed the demonstration of significant enhancement of a group of harmonics in the latter case. We analyze the role of plasma emission, together with phase-mismatch, that deteriorate the conditions of high-order harmonic generation due to significant phase distortion between the interacting waves. We also discuss the resonanceinduced enhancement of single harmonic and the quasi-phase-matching-induced enhancement of the group of harmonics during propagation of the tunable mid-infrared femtosecond pulses through the perforated laser-produced indium plasma. Those studies have shown that the enhancement of harmonics using the macro-process of quasi-phase-matching is comparable with the one using micro-process of resonantly enhanced harmonic. We conclude that joint implementation of the two methods of the increase of harmonic yield could be a useful tool for generation of strong short-wavelength radiation in different spectral regions.

Interaction of a quercetin derivative - lensoside Aβ with liposomal membranes

Lensoside Aβ, representing the flavonol glycosides, is a compound isolated from the aerial parts of edible lentil (Lens culinaris) cultivar Tina. This substance arouses interest because so far there is very little data about secondary metabolites isolated from the leaves and stems of this plant. Additionally, bioactive potential of flavonoids is directly coupled with the membranes as a primary target of their physiological and pharmacological activity. The aim of this study was to investigate the effect of lensoside Aβ on lipid membranes. Interaction of examined compound with liposomes formed with dipalmitoylphosphatidylcholine (DPPC) was investigated with application of FTIR spectroscopy and 1H NMR technique. Molecular localization and orientation of lensoside Aβ in a single lipid bilayer system represented by giant unilamellar vesicles, was also investigated with application of confocal fluorescence lifetime imaging microscopy (FLIM).FTIR analysis revealed that the tested compound incorporates into DPPC membranes via hydrogen bonding to lipid polar head groups in the PO2 group region and the COPOC segment. Furthermore 1H NMR analysis showed ordering effect in both the hydrophobic alkyl chains region and the polar heads of phospholipids. FLIM investigation has revealed roughly parallel orientation of its molecules in the membranes. This suggests that one of the possible physiological functions of this flavonol could be screening a cell against short-wavelength radiation.

Protective Role of a methanolic Extract of Spinach (Spinacia oleracea L.) Against Adverse Effects of UV-C Irradiation on Fenugreek (Trigonella foenum-graecum L.) Seedlings

Photosynthesis is an important process for plants in which plants utilize the energy from sunlight to manufacture and produce all their own food. Although UV-C damage is not physiologically relevant for plants growing in the sun, short-wavelength (UV-C) radiation from germicidal lamps has been used to study cell damage in animals as well as in plants. This study provides a review of the effects of a methanolic extract of spinach (SE) as a natural powerful antioxidants used at two concentrations (25 and 50 ppm) on fenugreek seedlings grown under UV-C stress conditions. The results revealed that exposure of fenugreek seedlings to low UV-C period (30 min) increased growth criteria of the produced seedlings. In addition, the contents of chlorophyll, total pigments, total protein, free amino acids, non-enzymatic (carotenoids, total phenol, flavonoids, α‑tocopherol & ascorbic acid contents) and enzymatic antioxidants were increased at this period. By increasing exposure periods of UV-C radiation, the growth criteria and chemical constitutes of the seedlings were decreased. Application of lower concentration of SE (25 ppm) improve the growth of the seedlings at 30-min UV-C and was able to protect seedlings from high periods of UV-C irradiation by increasing all measured parameters except CAT. These increases might be an adaptive mechanism to minimize the adverse effects of longer exposure of UV-C radiation. Moreover, treating the irradiated seedlings with spinach extract led to an obvious alteration in gene expression including synthesis of some proteins bands and disappearance of other protein sets of the protein profile.

Technology Options for the Built Environment in Kenya: Dye-Sensitized and Amorphous Silicon Photovoltaics for Application in NZE Buildings

Background: The performance of a Dye-Sensitized Solar Module (DSSM) has been investigated under different outdoor air mass (AM), irradiance intensity and temperature conditions in Wajir, Kitui, Vihiga and Kajiado Counties in Kenya. Methods: The performance was thereafter compared with that of Amorphous Silicon (a-Si) devices undertaken under similar weather conditions in Nigeria. The DSSM's good response to short wavelength radiation made it perform better at increased AM values than what has been reported of a- Si PV modules. Results: Studies on a-Si showed that their performance favors low AM conditions. The DSSM generally performed better than what is reported of a-Si, based on irradiance and temperature dependence. Nonetheless, a-Si devices performed better at higher irradiance intensities. These results show that Dye-Sensitized and a-Si technologies complement each others’ performance when subjected to the outdoor field AM, irradiance and temperature conditions. Conclusion: These findings can be applied in PV sizing, especially for application in Building Integrated Photovoltaics (BIPV) in the tropics. Keywords: Amorphous silicon, building integrated photovoltaics, complimentarily, dye-sensitized, geo-thermal, solar PV.

Raman scattering and photoluminescence in sodium uranyl acetate polycrystals

A technique of probe photoluminescence and Raman spectroscopy has been developed. This technique makes it possible to detect small (10−6 to 10−8 g) amounts of uranyl compounds at short exposure times (1−10 s). The photoluminescence spectra of Na[UO2CH3(COO)3] polycrystals recorded upon excitation by short-wavelength radiation of LEDs and lasers are found to contain equidistant bands with a shift of 854 cm−1, which corresponds to the frequency of totally symmetric uranyl vibration also manifesting itself in Raman spectra.