Increase In Radiation Intensity Research Articles

Density and age of invasive Robinia pseudoacacia modulate its impact on floodplain forests

The invasion of black locust (Robinia pseudoacacia L.) into nutrient-poor and dry habitats strongly alters resident species composition, species diversity and nutrient availability. However, less is known if its occurrence in more nutrient-rich habitats and dense forests causes similar effects, and if so, how the gradient of stand density and tree age affect soil properties and vegetation composition.We chose riparian forests of the Donau-Auen National Park in Eastern Austria and selected 28 plots which differed in R. pseudoacacia stand density and tree age. Vegetation composition, physical and chemical soil parameters were analyzed. Data analysis was performed using descriptive and bivariate statistics.We found that the content of soil nitrogen, NO3 and carbon increased with black locust density and stand age, respectively, while total C/N ratio appeared to be less affected. While plant diversity (Simpson index) did not show a significant variation neither among Robinia age classes nor along density gradients, some nitrophilous species gained abundance with increased density and some other species with increased age of R. pseudoacacia stands. Only one species (Anemone ranunculoides) became less abundant with Robinia stem density. We argue that these changes in species abundance are primarily due to altered mineral nitrogen availability, but increased radiation intensity under the open canopy of R. pseudoacacia and allelopathic qualities of the tree might also play a role. However, we found evidence that these effects imply certain thresholds and are not linearly scaled.

Effects of system parameters and inorganic salts on the photodecolourisation of textile dye Reactive Blue 19 by UV/H<sub>2</sub>O<sub>2</sub> process

The photodecolourisation of textile dye Reactive Blue 19 (RB 19), an anionic anthraquinone dye of the reactive class, was investigated using UV radiation in the presence of H2O2 in a batch photo-reactor with low-pressure mercury lamps. The effects of the system parameters: initial pH, initial dye concentration, concentration of peroxide and radiation intensity, as well as the presence of salts, (NaCl, Na2SO4, NaNO3, NaH2PO4) on dye decolourisation was examined. Increasing the initial pH resulted in an increase in decolourisation efficiency. Results showed that with an increase of dye concentration from 10 to 100 mg·l–1, the efficiency of the process decreases. The highest decolourisation rates were noted at H2O2 concentrations of approximately 30 mmol·l–1. The increase of radiation intensity from 730 to 1 950 µW·cm-2, linearly increases decolourisation efficiency. The inorganic ions investigated have inhibiting effects on RB 19 decolourisation by the UV/H2O2 process with inhibition intensities in the following order: H2PO4– > NO3- > SO42– > Cl-. This study has shown that the UV/H2O2 process is a promising technology for degradation of RB 19 in water and wastewater.Keywords: UV/H2O2 process, Reactive Blue 19, decolourisation, inorganic salts

Nonlinear photoresponse of field effect transistors terahertz detectors at high irradiation intensities

Terahertz power dependence of the photoresponse of field effect transistors, operating at frequencies from 0.1 to 3 THz for incident radiation power density up to 100 kW/cm2 was studied for Si metal–oxide–semiconductor field-effect transistors and InGaAs high electron mobility transistors. The photoresponse increased linearly with increasing radiation intensity up to the kW/cm2 range. Nonlinearity followed by saturation of the photoresponse was observed for all investigated field effect transistors for intensities above several kW/cm2. The observed photoresponse nonlinearity is explained by nonlinearity and saturation of the transistor channel current. A theoretical model of terahertz field effect transistor photoresponse at high intensity was developed. The model explains quantitative experimental data both in linear and nonlinear regions. Our results show that dynamic range of field effect transistors is very high and can extend over more than six orders of magnitudes of power densities (from ∼0.5 mW/cm2 to ∼5 kW/cm2).

Experimental Study of the Heat Flux Effect on Combustion Characteristics of Commonly Exterior Thermal Insulation Materials

For the sake of examining the heat flux effect on combustion characteristics of commonly exterior thermal insulation materials, the six kinds of exterior thermal insulation materials were tested by the cone calorimeter in this paper included rock wool, adhesive polystyrene granule, phenolic resin, EPS, XPS and RPU. The experimental results showed that the fire risk of different thermoplastic insulation materials arrange in descending order was XPS>RPU>EPS> adhesive polystyrene granule> phenolic resin> rock wool; with the increase of radiation intensity, the heat release peak rate of PS increased and the ignition time and the peak time reduced, the heat release peak rate and the peak time points showed inverse proportion; the peak HRR value of B2 RPU is 2 times of B1 RPU and the efficiency of fire retardant of B1 RPU increases by 37.53% compared to B2 RPU.

Investigation of cryoemission characteristics during ethanol condensation

Physics of cryocondensates growth and properties is one of the research areas in which scientists deal with real and often non-equilibrium states, which represent a purely scientific and practical interest. In this case, there is a very limited list of factors that determine the growth process and morphology (structure) of received and test substances.This primarily refers to the thermodynamic parameters of cryocondensation – gas phase pressure and substrate temperature. The substrate material and its morphology can play a part at the initial stage of phase formation in the study of epitaxial layers in real cryocrystals properties formation, which is caused by an interaction between the gas particles and the substrate material, i.e. the adsorption nature of the earliest layers of condensate. Experiments series of detailed study of the cryoemission phenomenon, which was detected during the condensation of nitrous oxide and ethanol onto a cold substrate was carried out.The uniqueness of this phenomenon implies the fact that at the current time there is no theoretical determination of this radiation origin. The study of this phenomenon has revealed a number of characteristics that are related to both the thermodynamic parameters of the condensation and the actual radiation. Ethanol accompanied by radiation, when the substrate temperature is T = 16 – 60 K. On the other hand, when the condensing pressure is above 10-3Torr, radiation intensity increases. Furthermore, an optimal value of the gas phase pressure, in which the radiation intensity is maximum, exists for each of the condensation temperature in the range of 16-130 K. The main objectives of these studies are checking of a wider range of substances for their ability to cryocondensation radiation; study of the nature of radiation and its relaxation characteristics; study of thermally stimulated processes in condensed samples.

Physiological and morphological responses induced by α-particle radiation on Arabidopsis thaliana embryos

Alpha (α)-particle radiation has been thoroughly studied in the occupational and residential environments, but biological mechanisms induced by α-particle radiation on plants are not clearly understood. In this study, radiation effects were examined using different total doses (1, 10, 100 Gy, respectively) of 241Am, α-particle on Arabidopsis embryos. No significant difference in the germination percentage was observed between the 3 levels of doses and the control. Germination speed and root length were increased by treatment with the 1-Gy dose of a-particles, and decreased by treatment with 10- and 100-Gy doses. Moreover, the bending degree of roots increased with radiation dose, and the roots showed an "S" shape when treated with the 100-Gy dose. Root bending under the 100-Gy dose was inhibited by scavengers of reactive oxygen species (ROS). Root gravitropism and root length may respond to the consistency of ROS induced by irradiation. Further analysis of the physiological effects revealed that an increase in a-particle radiation intensity enhanced the activity of catalase and the content of malondialdehyde, but superoxide dismutase activity was reduced by treatment with 100-Gy radiation of a-particles, suggesting that the high linear energy transfer of a-particles may cause a relatively high level of membrane lipid preoxidation and high accumulation of ROS. ROS showed both physiological and morphological responses following exposure to α-particle radiation in Arabidopsis embryos.

Polarization response of an atomic system in a strong mid-IR field

The polarization response of a quantum system modeling a silver atom in a strong laser field in the mid-IR frequency band has been investigated by direct numerical integration of the Schrödinger equation. It is shown that free electrons in the continuum appearing from multiphoton or tunnel ionization change the sign of the dielectric susceptibility at the fundamental frequency with an increase of radiation intensity even at a low level of ionization. The features of the high-order susceptibility of a model silver atom are studied in the nonperturbative regime.

Effect of radiation intensity on the outcome of postharvest UV-C treatments

Studies on the use of UV-C radiation of fresh produce have focused on the selection of appropriate doses (energy per unit area) for different commodities, but little attention has been placed on the effect of radiation intensity (dose per unit time). In this study, tomatoes (Solanum lycopersicum cv. Elpida) and strawberries (Fragaria×ananassa cv. Camarosa), were harvested (breaker and 100% of surface red color respectively) and treated with 4kJm−2 of UV-C, at low (3Wm−2) or high (33Wm−2) radiation intensities. Untreated fruits were used as controls. After the treatments and at different storage times the incidence of postharvest rots and the changes in fruit physical and chemical properties were determined. UV-C treatments reduced decay, with the effects being were more marked in fruit exposed to high intensities. Mold counts were unaffected by the treatments, suggesting that improved disease control did not result from greater germicide effect. In both fruit species exposure to UV-C radiation delayed ripening, evidenced as lower color development, pigment accumulation and softening. UV-C-treated fruit maintained better quality than the control. In strawberry, high intensity treatments were more effective to prevent deterioration than in tomato where the differences between UV-C treatments were subtler. Soluble solids, titratable acidity and ethanol soluble antioxidants were not affected regardless of the UV-C intensity. Consumer tests showed higher preference of fruit treated at high UV-C intensity. Results show that in addition to the applied dose, radiation intensity is a main factor determining the effectiveness of UV-C treatments and should not be over-sighted. For a given dose, increasing radiation intensity may in some cases maximize the benefits of UV-C on fruit quality, while significantly reducing the treatments time.

A modeling study of seasonal variations of sea ice and plankton in the Bering and Chukchi Seas during 2007–2008

A nutrient (N), phytoplankton (P), zooplankton (Z), and detritus (D) ecosystem model coupled to an ice‐ocean model was applied to the Bering and Chukchi Seas for 2007–2008. The model reasonably reproduces the seasonal cycles of sea ice, phytoplankton, and zooplankton in the Bering–Chukchi Seas. The spatial variation of the phytoplankton bloom was predominantly controlled by the retreat of sea ice and the increased gradient of the water temperature from the south to the north. The model captures the basic structure of the measured nutrients and chl‐a along the Bering shelf during 4–23 July 2008, and along the Chukchi shelf during 5–12 August 2007. In summer 2008, the Green Belt bloom was not observed by either the satellite measurements or the model. The model‐data comparison and analysis reveal the complexity of the lower trophic dynamics in the Bering and Chukchi Seas. The complexity is due to the nature that the physical and biological components interact at different manners in time and space, even in response to a same climate forcing, over the physically distinct geographic settings such as in the Bering and North Aleutian Slopes, deep Bering basins, Bering shelf, and Chukchi Sea. Sensitivity studies were conducted to reveal the underlying mechanisms (i.e., the bottom‐up effects) of the Bering–Chukchi ecosystem in response to changes in light intensity, nutrient input from open boundaries, and air temperature. It was found that (1) a 10% increase in solar radiation or light intensity for the entire year has a small impact on the intensity and timing of the bloom in the physical–biological system since the light is not a limiting factor in the study region; (2) a 20% increase in nutrients from all the open boundaries results in an overall 7% increase in phytoplankton, with the Slope region being the largest, and the Bering shelf and Chukchi being the smallest; and (3) an increase in air temperature by 2°C over the entire calculation period can result in an overall increase in phytoplankton by 11%.

Excitation mode characteristics in Bi2212 rectangular mesa structures

The rectangular mesa structure of single crystalline Bi2Sr2CaCu2O8+δ with the dimensions of 64 × 135 × 1.35 μm3 was fabricated by using Ar-ion milling with a metallic mask and focused ion beam. From this mesa, the radiation frequencies of 24.226 cm−1 and 17.296 cm−1 were observed at the different temperatures of 25 K and 40 K, respectively. The change of the radiation frequencies is also obviously reflected in the radiation pattern measurement. The radiation pattern observed at lower temperature seems to have an asymmetric shape and its intensity as a whole is slightly weak. In the higher temperature, however, the radiation intensity increases and the radiation pattern becomes almost symmetric shape. The radiation characteristics observed at higher temperature is well explained by the fundamental cavity resonance mode expected from the width of the mesa. This result may give us not only the suggestion of the existence of the adequate matching condition between the geometrical cavity and the ac Josephson current in the mesa but also the guide for the designing of the high efficiency of the radiation.

Power narrowing in coherent atomic excitation by smoothly shaped pulsed fields

When atoms are excited by laser radiation the conventional wisdom dictates that the spectral excitation profile – the excited-state population vs the detuning – broadens as the radiation intensity increases. This common expectation has been shown to be incorrect in the fluorescence signal following two-photon excitation of xenon atoms by a Gaussian laser pulse, which showed almost no power broadening [T. Halfmann, T. Rickes, N.V. Vitanov, K. Bergmann, Optics Communications, 220 (2003) 353] Here we go a step further and show that for a class of pulse shapes, the falling edges of which vanish as inverse powers of time, ∝t−n (with n>1), the spectral excitation profile must exhibit power narrowing, i.e. the spectral linewidth scales as Ω0−1/(n−1), where Ω0 is the Rabi frequency of the transition. We provide a simple physical explanation based upon the notions of adiabatic evolution and coherent population return and discuss important experimental applications.

Polarisation response of a gas medium in the field of a high-intensity ultrashort laser pulse: high order Kerr nonlinearities or plasma electron component?

The polarisation response of quantum systems modelling silver and xenon atoms in the field of a high-intensity femtosecond Ti : sapphire laser (photon energy ħω ≈ 1.5 eV), has been investigated by direct numerical integration of the Schrödinger equation. The applicability ranges of the perturbation theory and polarisation expansion in powers of field are determined. The contributions of excited atoms and electrons in the continuous-spectrum states to the polarisation response at the fundamental frequency, which arise as a result of excitation and photoionisation, are analysed. It is shown that specifically ionisation changes the sign of dielectric susceptibility with an increase in radiation intensity for the systems under consideration.

Fluorescence imaging of light acclimation of brazilian atlantic forest tree species

In the pursuit of knowledge on the biological behavior of Brazilian Atlantic Forest tree species, this study evaluated the susceptibility of the light-demanding species, Schinus terebinthifolia Raddi., Pseudobombax grandiflorum (Cav.) A. Robyns and Joannesia princeps Vell., and of the shade-tolerant species, Hymenaea courbaril L. var. stilbocarpa and Lecythis pisonis Camb, to photoinhibition and acclimation capacity. These species were first cultivated under two irradiance conditions, I20 (20% direct sunlight radiation) and I100 (all-sky or direct sunlight) and then transferred from I20 to I100. The effects of the sudden increase in light radiation intensity on photosynthetic activity were then evaluated through chlorophyll (Chl) fluorescence imaging, HPLC xanthophylls analysis, and cell membrane lipid peroxidation measurements. Light-demanding species were found to present a higher photochemical efficiency and higher acclimation capacity under high light irradiance than shade-tolerant species. The higher photoinhibition tolerance observed in light-demanding species was associated to their higher capacity for photochemical dissipation and dissipation of excess excitation energy via the xanthophyll cycle, leading to a lower ROS generation. The obtained results suggested that a knowledge of acclimation capacity, by means of Chl fluorescence imaging yields, is a useful indicator of species successional grouping.

Microwave radiation in the upper atmosphere of the earth during strong geomagnetic disturbances

The influence of N2 and O2 molecules on spontaneous microwave radiation spectrum was studied over the decimeter range. This radiation appears in the D and E upper earth atmosphere layers during strong magnetic storms. It was shown to be caused by radiation transitions between medium-perturbed orbitally degenerate Rydberg atom and molecule states A** that occur without changes in the principal quantum number, δn = 0. The available experimental data were used to calculate the dependences of orbitally degenerate state populations on the density of medium and electron flux and temperature. Effective radiation bands were constructed for transitions between highly excited quasi-molecule levels A**N2 and A**O2. The emission spectrum was shown to be inhomogeneous and contain three frequency regions in which a noticeable decrease in the intensity of radiation occurred. The physical reason for the formation of these regions was a shift of the emission spectra of quasi-molecules containing unexcited N2 and O2 molecules. The frequency profiles of radiation intensity within these frequency regions were calculated as depending on the storm level. Radiation profiles were shown to noticeably change as the storm level increased, they strongly increased close to the right region edge corresponding to high transition frequencies. Nonmonotonic behavior of this profile in the middle of the lower region was observed; this was related to emission spectrum inhomogeneity. A sharp increase in radiation intensity as the magnetic storm level increased occurred in the region of frequencies situated close to the right edge of the upper region (50–100 GHz), which was most interesting for biophysical studies of the action of microwave radiation on living organisms during strong geomagnetic disturbances.

Numerical simulation of concentrating solar collector P2CC with a small concentrating ratio

Solar energy may be practically utilized directly through transformation into heat, electrical or chemical energy. A physical and mathematical model is presented, as well as a numerical procedure for predicting thermal performances of the P2CC solar concentrator. The demonstrated prototype has the reception angle of 110? at concentration ratio CR = 1.38, with the significant reception of diffuse radiation. The solar collector P2CC is designed for the area of middle temperature conversion of solar radiation into heat. The working fluid is water with laminar flow through a copper pipe surrounded by an evacuated glass layer. Based on the physical model, a mathematical model is introduced, which consists of energy balance equations for four collector components. In this paper, water temperatures in flow directions are numerically predicted, as well as temperatures of relevant P2CC collector components for various values of input temperatures and mass flow rates of the working fluid, and also for various values of direct sunlight radiation and for different collector lengths. The device which is used to transform solar energy to heat is referred to as solar collector. This paper gives numerical estimated changes of temperature in the direction of fluid flow for different flow rates, different solar radiation intensity and different inlet fluid temperatures. The increase in fluid flow reduces output temperature, while the increase in solar radiation intensity and inlet water temperature increases output temperature of water. Furthermore, the dependence on fluid output temperature is determined, along with the current efficiency by the number of nodes in the numerical calculation.

Effects of the Conditions on the Temperature Changes inside the Wood during Microwave Heating

In this study, the effects of microwave radiation intensity, initial moisture content and thickness on the properties of temperature development in Siberian Elm wood samples during the microwave drying have been investigated using a tailor made microwave drying equipment. The results show that with the increase of microwave radiation intensity and a decrease in initial moisture content and thickness, both the temperature and its rate of increase in wood rise rapidly. In the microwave drying, the temperature development curve presented three stages of variation: a sharp increase in temperature − a constant temperature − a slow warm-up.

Characterization of a nanoparticle-filled resin for application in scan-LED-technology

Scan-LED-technology is a new rapid prototyping technique with increasing applications in the production of custom-made medical products. The present work is dealing with the examination of a silica/urethandimethacrylate (UDMA) nanocomposite for application in scan-LED-technology. The use of specific LED in a photo-DSC unit enables the simulation of crucial parameters of nanoparticle-filled resins for their application in scan-LED-technology. The conversion of double bonds during the curing reaction and the rate of conversion were studied as a function of radiation intensity, silica nanoparticle content, and silanization of the nanoparticles with 3-methacryloyloxypropyl-trimethoxysilane (MPTMS). The conversion of double bonds is increasing with increasing radiation intensity. The increasing conversion of the nanoparticle-filled resins is discussed as a combined effect of increasing nanoparticle content, alternated initiator/double bond ratio and increasing radiation intensity. A significant dependence of the reaction rate on nanoparticle content could not be found. Only for the unfilled resin, the rate was increasing at higher radiation intensities. The influence of residual solvent on conversion and rate of reaction was also analyzed. TGA measurements combined with FTIR were used to study the silanization of the nanoparticles. The silane layer thickness on the surface of the silica nanoparticles was determined.

Kinetics of photorefractive light scattering in crystals of stoichiometric lithium niobate

The article discusses the investigations into photorefractive light scattering (PRLS) in nominally pure single crystals of stoichiometric composition (Li/Nb = 1) grown from a melt with 58.6 mol % Li2O. It is demonstrated that the asymmetric pattern of the scattering indicatrix depends on radiation intensity up to 160 mW. When the radiation intensity increases, the crystal is heated, resulting in a decrease in the scattering indicatrix.

Effects of Gamma Irradiation on the Structure and Mechanical Properties of Wild Silkworms and Bombyx Mori Silk Fibroin Films

The structure and mechanical properties of A. yamamai, A. perny and B. mori silk fibroin films irradiated by gamma ray with various doses of 0, 25, 50, 100 and 200 kGy, respectively were determined by XRD, FT-IR, DSC and Instron 3365 equipment. Results showed that the aggregation structure and molecular conformation of A. yamamai, A. perny and B. mori silk fibroin films irradiated by gamma ray with those doses mentioned above were not significantly changed. However, with the increase of radiation intensity, the thermal stability of silk fibroin films declined slightly, and the breaking strength and extensibility reduced significantly, due to the breakdown of parts of secondary bonds and covalent bonds. These results suggested that, when these silk fibroin materials were sterilized by gamma irradiation, smaller radiation doses should be used, otherwise irreversible damages on these materials would be caused.

Structure and Mechanical Property of Silk Fiber under Gamma Radiation

An attempt to change the structure of silk fibers and their properties for the biological application was studied by utilizing gamma radiation in various Co60 intensities (0 kGy, 30 kGy, 50 kGy, 100 kGy, 200 kGy, 500 kGy, 1000 kGy, 2000 kGy, 3000 kGy). With the increase of the gamma radiation intensity, SEM result shows that cracks and fragments were formed between microfibrils of the irradiated fiber significantly. Simultaneously SDS-PAGE results give the evidence that the molecular weight of the fibroin diminished. Furthermore, the breaking strength and elongation of irradiated fibers decreased gradually with the increasing Co60 intensity. Although no significant changes of the molecular conformations were found by FTIR and X-ray diffraction, the effects on molecular interactions of the silk fibroin, such as peptide bonding, hydrogen bond and intermolecular bonding force, were obviously observed and enhanced gradually with the increase of gamma radiation intensity.