Surface solar ultraviolet radiation for paleoatmospheric levels of oxygen and ozone

Many investigators have concluded that the level of solar ultraviolet radiation (200–300 nm) reaching the surface was a key parameter in the origin and evolution of life on Earth. The level of solar ultraviolet radiation between 200 and 300 nm is controlled primarily by molecular absorption by ozone, whose presence is trongly coupled to the level of molecular oxygen. In this paper, we present a series of calculations of the solar ultraviolet radiation reaching the surface for oxygen levels ranging from 10^–4 present atmospheric level to the present level. The solar spectrum between 200 and 300 mn has been divided into 34 spectral intervals. For each spectral interval, we have calculated the solar ultraviolet radiation reaching the Earth's surface by considering the attenuation of the incoming beam due to ozone and oxygen absorption. A one-dimensional photochemical model of the atmosphere was used for these calculations.     

Daylight spectra (400–740 nm) beneath sunny,blue skies in Tasmania,and the effect of a forest canopy

Abstract The photosynthetically active radiation (PAR) incident on a horizontal surface at an open mountain site is positively correlated with solar altitude for sunny, blue sky conditions. The proportion of red light in PAR decreases with increasing solar altitude, while that of blue increases. These results are consistent with the wavelength dependency of Rayleigh and Mie scattering. The ratio of near infrared radiation to PAR decreases with increasing solar altitude towards solar noon and with decreasing solar altitude towards sunset. Thus surface reflection seems to be an important part of the light climate. The relative transmission of daylight through a forest canopy to a horizontal surface is not correlated with solar altitude for sunny, blue sky conditions at a mountain site. The amount of diffuse daylight is negatively correlated with per cent canopy interception, and the amount of direct sunlight is negatively correlated with per cent solar track interception. Daylength is negatively correlated with both canopy and solar track interceptions. The proportion of red light in PAR increases with increasing solar altitude, while that of blue decreases. These results are opposite those for the open site and are due to the spatial patterns of canopy obstruction of the sky vault, and of the spectral quality of daylight across the sky. The ratio of near infrared radiation to PAR in shadelight increases with increasing canopy interception due to the selective scattering properties of the canopy. The ratio for shadelight is positively correlated with the ratio for sunflecks.     

Conformational differences in protein disulfide linkages between normal hair and hair from subjects with trichothiodystrophy: a quantitative analysis by Raman microspectroscopy

Raman spectra of normal hair shafts and hair shafts from patients exhibiting trichothiodystrophy (TTD) were obtained using line focus laser illumination. Because hair from TTD patients has a significant decrease in the content of the sulfur-containing amino acids in comparison to normal hair, the 550-500 cm(-1) disulfide stretching mode region of the Raman spectrum was examined in detail. A quantitative spectral analysis demonstrates significant increases in the two energetically less favored gauche-gauche-trans (g-g-t) and trans-gauche-trans (t-g-t) forms. These observations suggest that the increased amounts of these less stable disulfide conformers are contributing factors to or associated with the hair brittleness observed for this congenital disorder. Structure-spectra correlations for the three dominant disulfide conformers are confirmed by quantum chemical calculations using modern density functional theory (DFT).     

Stardust component in tree rings

Tree-ring series collected from different parts of Arctic (Fennoscandia, Kola Peninsula and Northern Siberia) are investigated by means of the multi-taped method (MTM) of spectral analysis. Results of spectral analysis allow us to select the main periods of solar variability (22-, 30–33- and 80–90-year solar cycles) in Kola and Fennoscandia tree-ring chronologies. Besides it was found that only periodicities of around 20 years are present in Siberian and Stockholm series, respectively. With respect to 11-year periodicity, which is the most prominent one in sunspot number spectrum (Schwabe cycle) it may be said that it hardly appeared in Arctic tree-ring series. Although the 22-year cycles in climatic records are perceivable (it is also evident from our and other results), any physical mechanisms by which a reversal in the solar magnetic field could influence climate are still missing. To our mind, a potential cause of this phenomenon seems to be a variation of stardust flux inside the solar system. The most recent observations in frame of the DUST experiment on board the Ulysses spacecraft have shown that stardust level inside of the solar system was trebled during the recent solar maximum (Landgraf et al., 2003. Penetration of the heliosphere by the interstellar dust stream during solar maximum. Journal Geophysical Research 108, 8030). It is possible that the periodic increase of stardust in the solar system will influence the amount of extraterrestrial material that rains down to the Earth and consequently down to the Earth's atmosphere and may affect climate through alteration of atmospheric transparency and albedo.     

Hydrogen lines in the infrared region and spectral background for the thomson scattering diagnostics of the iter divertor plasma

Calculations are made of the plasma spectral background, which is important for the Thomson scattering diagnostics in the ITER divertor. Theoretical grounds have been elaborated for computing the hydrogen spectral line shapes in the infrared spectral region for a divertor plasma in ITER. The shape of the P-7 Paschen line (transition n = 7 → n = 3) located near the laser scattering signal has been calculated for various lines of sight in the ITER divertor. Contributions from different mechanisms of broadening the P-7 line have been examined. The spectral intensities of bremsstrahlung and photorecombination continuum have been calculated. All calculations use data on the spatial distribution of temperatures and densities of all species of plasma particles computed with the SOLPS4.3 code for basic operation regimes of the ITER divertor.     

The Detection of Peaks in Luteinizing Hormone Secretion

Fluctations in luteinizing hormone are believed to consist of irregularly spaced sharp increases separated by periods of exponential decay. A simple method is presented for analysing such fluctuations when the data consist of uniformly sampled observations of hormone. Specific allowance for the exponential decay in the absence of pulses is made via a time series model before assessing the number and extent of pulses. All calculations are done using MINITAB regression programs. The results have been compared with those obtained by three established models and are in general agreement.     

The Detection of Peaks in Luteinizing Hormone Secretion

Fluctations in luteinizing hormone are believed to consist of irregularly spaced sharp increases separated by periods of exponential decay. A simple method is presented for analysing such fluctuations when the data consist of uniformly sampled observations of hormone. Specific allowance for the exponential decay in the absence of pulses is made via a time series model before assessing the number and extent of pulses. All calculations are done using MINITAB regression programs. The results have been compared with those obtained by three established models and are in general agreement.     

Development of a Model to Compute the Extension of Life Supporting Zones for Earth-Like Exoplanets

A radiative convective model to calculate the width and the location of the life supporting zone (LSZ) for different, alternative solvents (i.e. other than water) is presented. This model can be applied to the atmospheres of the terrestrial planets in the solar system as well as (hypothetical, Earth-like) terrestrial exoplanets. Cloud droplet formation and growth are investigated using a cloud parcel model. Clouds can be incorporated into the radiative transfer calculations. Test runs for Earth, Mars and Titan show a good agreement of model results with observations.     

CD and MCD studies of the effects of component B variant binding on the biferrous active site of methane monooxygenase

The multicomponent soluble form of methane monooxygenase (sMMO) catalyzes the oxidation of methane through the activation of O 2 at a nonheme biferrous center in the hydroxylase component, MMOH. Reactivity is limited without binding of the sMMO effector protein, MMOB. Past studies show that mutations of specific MMOB surface residues cause large changes in the rates of individual steps in the MMOH reaction cycle. To define the structural and mechanistic bases for these observations, CD, MCD, and VTVH MCD spectroscopies coupled with ligand-field (LF) calculations are used to elucidate changes occurring near and at the MMOH biferrous cluster upon binding of MMOB and the MMOB variants. Perturbations to both the CD and MCD are observed upon binding wild-type MMOB and the MMOB variant that similarly increases O 2 reactivity. MMOB variants that do not greatly increase O 2 reactivity fail to cause one or both of these changes. LF calculations indicate that reorientation of the terminal glutamate on Fe2 reproduces the spectral perturbations in MCD. Although this structural change allows O 2 to bridge the diiron site and shifts the redox active orbitals for good overlap, it is not sufficient for enhanced O 2 reactivity of the enzyme. Binding of the T111Y-MMOB variant to MMOH induces the MCD, but not CD changes, and causes only a small increase in reactivity. Thus, both the geometric rearrangement at Fe2 (observed in MCD) coupled with a more global conformational change that may control O 2 access (probed by CD), induced by MMOB binding, are critical factors in the reactivity of sMMO.     

Importance of the green color,absorption gradient,and spectral absorption of chloroplasts for the radiative energy balance of leaves

Terrestrial green plants absorb photosynthetically active radiation (PAR; 400–700 nm) but do not absorb photons evenly across the PAR waveband. The spectral absorbance of photosystems and chloroplasts is lowest for green light, which occurs within the highest irradiance waveband of direct solar radiation. We demonstrate a close relationship between this phenomenon and the safe and efficient utilization of direct solar radiation in simple biophysiological models. The effects of spectral absorptance on the photon and irradiance absorption processes are evaluated using the spectra of direct and diffuse solar radiation. The radiation absorption of a leaf arises as a consequence of the absorption of chloroplasts. The photon absorption of chloroplasts is strongly dependent on the distribution of pigment concentrations and their absorbance spectra. While chloroplast movements in response to light are important mechanisms controlling PAR absorption, they are not effective for green light because chloroplasts have the lowest spectral absorptance in the waveband. With the development of palisade tissue, the incident photons per total palisade cell surface area and the absorbed photons per chloroplast decrease. The spectral absorbance of carotenoids is effective in eliminating shortwave PAR (<520 nm), which contains much of the surplus energy that is not used for photosynthesis and is dissipated as heat. The PAR absorptance of a whole leaf shows no substantial difference based on the spectra of direct or diffuse solar radiation. However, most of the near infrared radiation is unabsorbed and heat stress is greatly reduced. The incident solar radiation is too strong to be utilized for photosynthesis under the current CO₂ concentration in the terrestrial environment. Therefore, the photon absorption of a whole leaf is efficiently regulated by photosynthetic pigments with low spectral absorptance in the highest irradiance waveband and through a combination of pigment density distribution and leaf anatomical structures.     

The penetration of ultraviolet radiation to the ground

The evolution of analytic formulas for characterizing the ultraviolet spectral ir-radiance penetrating to the ground is briefly described. Analytic spectral functions for the extraterrestrial solar spectral irradiance, the ozone absorption coefficient, Rayleigh scattering coefficients and aerosol scattering and absorption coefficients, which are used as basic inputs, are given. With Beer's law, these give immediately the direct solar spectral irradiance. A ratio technique described in quantitative detail gives a procedure for calculating the skylight component of the UV radiation reaching the ground. The influence of ground reflectivity, clouds and a possible connection between photobiology and radiological physics are discussed. Finally the advantages of multiwavelength monitoring are described, using monochromators similar to those used in satellite ozone sounding to serve the needs of the photobiology and the atmospheric science communities.     

Ultraviolet Radiation-Absorbing “Humic Pigments” of Cyanobacteria in Microbial Mats: Their Presumptive Photoprotective Function and Relevance to Early Precambrian Microbial Ecology and Evolution

Cyanobacteria that form the primary components of microbial mats in freshwater bogs and intertidal marine environments in the Bahamas produce water-soluble brown pigments whose spectral properties imply that they are a type of humic acid. These “humic pigments” are produced by vital processes of living cyanobacteria, not by decomposition of dead ones, as shown by decreases in the concentrations of humic pigments, ultraviolet (UV) radiation-absorbing photoprotective mycosporine-like amino acids (MAAs), and chlorophyll from upper to lower layers of the mats, and by the occurrence of humic pigments in cyanobacterial cultures. Unlike MAAs, which absorb UV radiation only within limited ranges of wavelengths, humic pigments absorb radiation spanning the entire UV spectrum, and absorbance increases with decreasing wavelength. These observations suggest that the biosynthesis of humic pigments originated as a photoprotective adaptation in the early Precambrian, enabling cyanobacteria to colonize shallow-water and terrestrial environments even though the atmosphere was virtually devoid of O₂ and O₃ and therefore transparent to all solar radiation in the UV region of the spectrum. Moreover, the evolution of this photoprotective mechanism may have been linked to the evolution of photosynthesis.     

Inactivation of Paecilomyces fumosoroseus conidia by diffuse and total solar radiation

Abstract: The detrimental photic effects of natural solar radiation on the conidial persistence of the entomopathogenic hyphomycete Paecilomyces fumosoroseus were investigated by exposing quiescent conidia either to total solar radiation or to its diffuse component. A given amount of UVB diffuse radiation was found to be as detrimental, and sometimes twice as detrimental, as the same amount of total solar radiation. The variability in quantity and spectral distribution of the diffuse component of UVB solar radiation reaching the earth's surface, observed through spectral measurements, may be responsible for the difference in biological effects.     

Calculation of the relative chemical stabilities of proteins as a function of temperature and redox chemistry in a hot spring

Uncovering the chemical and physical links between natural environments and microbial communities is becoming increasingly amenable owing to geochemical observations and metagenomic sequencing. At the hot spring known as Bison Pool in Yellowstone National Park, the cooling of the water in the outflow channel is associated with an increase in oxidation potential estimated from multiple field-based measurements. Representative groups of proteins whose sequences were derived from metagenomic data also exhibit an increase in average oxidation state of carbon in the protein molecules with distance from the hot-spring source. The energetic requirements of reactions to form selected proteins used in the model were computed using amino-acid group additivity for the standard molal thermodynamic properties of the proteins, and the relative chemical stabilities of the proteins were investigated by varying temperature, pH and oxidation state, expressed as activity of dissolved hydrogen. The relative stabilities of the proteins were found to track the locations of the sampling sites when the calculations included a function for hydrogen activity that increases with temperature and is higher, or more reducing, than values consistent with measurements of dissolved oxygen, sulfide and oxidation-reduction potential in the field. These findings imply that spatial patterns in the amino acid compositions of proteins can be linked, through energetics of overall chemical reactions representing the formation of the proteins, to the environmental conditions at this hot spring, even if microbial cells maintain considerably different internal conditions. Further applications of the thermodynamic calculations are possible for other natural microbial ecosystems.     

利用多光谱扫描仪测定空心莲子草冠层光谱的影响因素

【背景】太阳光的入射辐射是影响多光谱扫描仪测定植物冠层光谱反射率的主要因素。本研究旨在探讨不同测定条件对空心莲子草冠层光谱特征值的影响,确定应用多光谱扫描仪测定空心莲子草冠层光谱特征的适宜环境条件。【方法】采用多光谱扫描仪,在不同天气条件、仪器探头高度、太阳高度角、叶片湿度等外界因素条件下,测定空心莲子草冠层光谱反射率的变化。【结果】天气条件、仪器探头高度、太阳高度角、叶片湿度4个因素对空心莲子草冠层在绿光区560nm、黄光区660nm和近红外光区810nm3个特征波段处的光谱反射率均有显著影响。【结论与意义】利用多光谱扫描仪测定空心莲子草冠层光谱数据,应选择晴朗无云的天气,仪器探头距离冠层1.3m,适宜的数据采集时间为10：00～14：00,以保障适度的太阳高度角和干燥的叶面,从而保持稳定的光谱测量结果。本研究可为完善多光谱扫描评价技术提供理论依据。     

Tuning Plasmon Resonances for Light Coupling into Silicon: a “Rule of Thumb” for Experimental Design

For Si thin-film solar cells to become efficient, schemes to increase the optical absorption in the films are necessary. Scattering of light using plasmonic resonances in metal nanoparticles has been suggested as a feasible route. When placed on a dielectric layer on the front of a solar cell, such metal nanoparticles can scatter a large fraction of the incident light into the solar cell at the resonance wavelength, and hence increase the light collection. However, many related effects may lead to a reduction in photocurrent. Thus, nanoparticle plasmon resonances must be optimized in order to improve the overall light collection. From an experimentalist’s point of view, simple and fast experimental design tools should be explored. In this work, we investigate the plasmon-related photocurrent enhancements for Si test-solar cells with a number of different metal nanoparticle shapes and materials placed on top of a dielectric layer. The spectral position of the photocurrent-enhancement onset is compared to plasmon resonance calculations based on a fairly simple model. Despite the fact that the optical interactions in nanoparticle solar cell configurations can be quite complex, the photocurrent enhancement in the investigated test-solar cells can be predicted qualitatively well for particles with a plasmon resonance in the visible spectrum. This simple and fast model can be used as a rule of thumb in designing nanoparticle arrays for a specific photocurrent enhancement profile.     

Determination of erythema-effective solar radiation in Japan and Germany with a spore monolayer film optimized for the detection of UVB and UVA – results of a field campaign

The available physical and biological broadband radiometers designed to determine erythema-effective radiation do not show any response or over/underestimate the biologically effective radiation to a high extent in the ultraviolet (UV)A spectral region. The data presented in this paper demonstrate that the biological system used in this study is the first one to make possible measurements of erythema-effective radiation in the sun in the UVA and UVB spectral region. These measurements were performed with a spore-film filter system as well as with spectroradiometers. It was demonstrated that this biotechnological method could be used to determine exact values expressed as minimal erythemal dose (MED). The spore-film system was tested in various field campaigns performed in Germany and in Japan. The seasonal daily variation of UV radiation in Germany determined in the period November 1995 to December 1996 using the spore-film filter system in sunny conditions tallied well with model calculations. The daily dose in Germany measured with the spore-film system close to the summer solstice, in sunny conditions (20.45 MED), was approximately 20 times higher than the lowest value measured close to the winter solstice (0.82 MED), a result which was in accordance with model calculations. The data determined with the spore-film filter system in Sapporo and Naha, Japan, fitted to the erythema-weighted data calculated from spectroradiometric measurements (Brewer), even at low solar radiation angles in a solar spectrum with less UVB but significant UVA. The spore-film dosimeter values were about 103 ± 8% of the integrated dose of the Brewer instrument. The standard deviation of the spore-film measurements obtained in Japan was 12.8%. The responsivity of the spore-film system towards longer wavelengths within the UVA spectrum was tested with the Okasaki Large Spectrograph with monochromatic radiation. At a wavelength of 365 nm – in a spectral region which is dominant in many tanning lamps and with minor importance for solar radiation in summer conditions – the tested spore-film system gave results that were close (112% compared to the calibration dose) to the calibration dose which was used for irradiation. Received: 27 January 1998 / Received last revision: 21 July 1998 / Accepted: 29 July 1998     

Clonal Age and the Proportion of Defective Progeny after Autogamy in PARAMECIUM AURELIA

The relation of mortality and the proportion of progeny with reduced fission after autogamy to the clonal age in Paramecium aurelia was investigated. This relation is not linear but the proportion of defective progeny increases stepwise. The observations are in agreement with those expected from the calculations of the number of deleterious mutations in the micronucleus.     

Efficacy of different indices derived from spectral reflectance of wheat for nitrogen stress detection

Abstract

The productivity of cereal crops is mainly related to their nitrogen status. It is hypothesized that the spectral reflectance data could be used to predict wheat nitrogen status with spectral indices and that their performance depends on the nature of the interaction of the solar radiation with the crop canopy. A wheat crop was raised with 12 levels of nitrogen treatments: 0, 15, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 kg ha^?1, with uniform phosphorous and potassium nutrition and uniform water and management practice. The spectral reflectance measurements of the crop canopy were taken at 5 nm intervals, throughout the crop growth period. Different spectral indices, both broadband (ratio as well as orthogonal) and hyperspectral indices were computed throughout the growing season. Canopy Colour Difference (ΔE), an index developed from the entire visible region and hence broader than the spectral indices developed hitherto, was also estimated from the reflectance data. Simple linear relationships developed between spectral indices versus applied nitrogen levels as well as the plant nitrogen content revealed that the hyperspectral indices are less sensitive in comparison to broadband indices. The result was reinforced by a higher correlation between the colour difference, NDVI and Greenness Index with plant nitrogen level/content, as opposed to hyperspectral indices.     

Necessary and sufficient conditions for Von Kries chromatic adaptation to give color constancy

Necessary and sufficient spectral conditions are presented for Von Kries chromatic adaptation to give color constancy. Von-Kries-invariant reflectance spectra are computed for illuminant spectral power distributions that are arbitrary linear combinations of the first three daylight phases. Experiments are suggested to test models of color constancy using computed spectra (either exact or approximate) within the illuminant-invariant framework.