Showing papers on "Light intensity published in 2001"

A closer look at United States and global surface temperature change

Abstract: We compare the United States and global surface air temperature changes of the past century using the current Goddard Institute for Space Studies (GISS) analysis and the U.S. Historical Climatology Network (USHCN) record [Karl et al., 1990]. Changes in the GISS analysis subsequent to the documentation by Hansen et al. [1999] are as follows: (1) incorporation of corrections for time-of-observation bias and station history adjustments in the United States based on Easterling et al. [1996a], (2) reclassification of rural, small-town, and urban stations in the United States, southern Canada, and northern Mexico based on satellite measurements of night light intensity [Imhoff et al., 1997], and (3) a more flexible urban adjustment than that employed by Hansen et al. [1999], including reliance on only unlit stations in the United States and rural stations in the rest of the world for determining long-term trends. We find evidence of local human effects (“urban warming”) even in suburban and small-town surface air temperature records, but the effect is modest in magnitude and conceivably could be an artifact of inhomogeneities in the station records. We suggest further studies, including more complete satellite night light analyses, which may clarify the potential urban effect. There are inherent uncertainties in the long-term temperature change at least of the order of 0.1°C for both the U.S. mean and the global mean. Nevertheless, it is clear that the post-1930s cooling was much larger in the United States than in the global mean. The U.S. mean temperature has now reached a level comparable to that of the 1930s, while the global temperature is now far above the levels earlier in the century. The successive periods of global warming (1900–1940), cooling (1940–1965), and warming (1965–2000) in the 20th century show distinctive patterns of temperature change suggestive of roles for both climate forcings and dynamical variability. The U.S. was warm in 2000 but cooler than the warmest years in the 1930s and 1990s. Global temperature was moderately high in 2000 despite a lingering La Nina in the Pacific Ocean.

Photooxidative N-demethylation of methylene blue in aqueous TiO2 dispersions under UV irradiation

Abstract: Methylene blue (MB) is a representative of a class of dyestuffs resistant to biodegradation Its decomposition was examined in aqueous TiO2 dispersions under UV illumination to assess the influence of temperature, pH, concentration of dissolved oxygen (DOC), initial concentration of MB, and light intensity on the kinetics of decomposition Hypsochromic effects (ie blue shifts of spectral bands) resulting from N-demethylation of the dimethylamino group in MB occurs concomitantly with oxidative degradation The maximum quantity of MB adsorbed on TiO2, and the kinetics of degradation of MB and of total organic carbon (TOC) removal were also measured at constant pH 4 Photobleaching of MB solutions takes place at low DOCs and is caused by a reversible reductive process involving photogenerated electrons on TiO2 The rate of degradation of MB remains fairly constant regardless of whether the dispersion was purged with oxygen prior to irradiation or with air during the light irradiation period The photocatalytic process depends on light intensity, but not on the total light energy absorbed The photoreaction followed pseudo-first-order kinetics even at high MB concentrations (03 mM) The temperature dependence of the photodegradation kinetics was assessed (E a =89 kJ/mol ) , as well as the relative photonic efficiency, ξr, relative to phenol (048)

Revisiting the method of cumulants for the analysis of dynamic light-scattering data

Abstract: The method of cumulants is a standard technique used to analyze dynamic light-scattering data measured for polydisperse samples. These data, from an intensity–intensity autocorrelation function of the scattered light, can be described in terms of a distribution of decay rates. The method of cumulants provides information about the cumulants and the moments of this distribution. However, the method does not permit independent determination of the long-time baseline of the intensity correlation function and can lead to inconsistent results when different numbers of data points are included in the fit. The method is reformulated in terms of the moments about the mean to permit more robust and satisfactory fits. The different versions of the method are compared by analysis of the data for polydisperse-vesicle samples.

DNA Microarray Analysis of Cyanobacterial Gene Expression during Acclimation to High Light

Abstract: DNA microarrays bearing nearly all of the genes of the unicellular cyanobacterium Synechocystis sp PCC 6803 were used to examine the temporal program of gene expression during acclimation from low to high light intensity. A complete pattern is provided of gene expression during acclimation of a photosynthetic organism to changing light intensity. More than 160 responsive genes were identified and classified into distinct sets. Genes involved in light absorption and photochemical reactions were downregulated within 15 min of exposure to high light intensity, whereas those associated with CO2 fixation and protection from photoinhibition were upregulated. Changes in the expression of genes involved in replication, transcription, and translation, which were induced to support cellular proliferation, occurred later. Several unidentified open reading frames were induced or repressed. The possible involvement of these genes in the acclimation to high light conditions is discussed.

Sensitive disk resonator photonic biosensor

Abstract: We describe a photonic device based on a high-finesse, whispering-gallery-mode disk resonator that can be used for the detection of biological pathogens. This device operates by means of monitoring the change in transfer characteristics of the disk resonator when biological materials fall onto its active area. High sensitivity is achieved because the light wave interacts many times with each pathogen as a consequence of the resonant recirculation of light within the disk structure. Specificity of the detected substance can be achieved when a layer of antibodies or other binding material is deposited onto the active area of the resonator. Formulas are presented that allow the sensitivity of the device to be quantified and that show that, under optimum conditions, as few as 100 molecules can be detected.

Trap-limited recombination in dye-sensitized nanocrystalline metal oxide electrodes

Abstract: We use transient and steady-state optical spectroscopies to study the recombination reaction between electrons and dye cations in a dye-sensitized nanocrystalline ${\mathrm{TiO}}_{2}$ electrode in several different chemical environments. Kinetic decay curves are approximately stretched exponential, and the cation half-life, ${t}_{50%}$ varies with electron density n as ${t}_{50%}\ensuremath{\propto}{n}^{\ensuremath{-}1/\ensuremath{\alpha}},$ where \ensuremath{\alpha} is a constant in the range 0.2--0.5. We have developed a model of electron transport in the presence of an energetic distribution of trap states and consider two regimes. In the first, the continuous-time random-walk (CTRW) electrons are free to diffuse through the lattice, by means of multiple trapping events mediated by the conduction band. In the second, the hopping regime, trapped electrons are allowed to tunnel to other, vacant trap sites, or to the dye cation, according to a Miller-Abrahams model for the transition rate. We carry out Monte Carlo simulations of the recombination kinetics as a function of electron density, trap state distributions and other parameters. The CTRW reproduces both the dependence of ${t}_{50%}$ on n and the shape of the kinetic curves with only one free fitting parameter, for the case of an exponential density of trap states. The hopping model is ruled out by subnanosecond measurements. We conclude that multiple trapping with a broad energetic distribution of electron traps is responsible for the slow recombination kinetics. When applied to recombination in a nanocrystalline photovoltaic junction at open circuit, the model predicts a sublinear power-law variation of electron density with light intensity G, $n\ensuremath{\propto}{G}^{\ensuremath{\alpha}},$ compatible with the observed behavior.

The protective functions of carotenoid and flavonoid pigments against excess visible radiation at chilling temperature investigated in Arabidopsis npq and tt mutants.

Abstract: The npq1 mutant of Arabidopsis thaliana (L.) Heynh. has no xanthophyll cycle due to a lack of functional violaxanthin de-epoxidase. Short-term exposure (<2 days) of detached leaves or whole plants to the combination of high photon flux density (1,000 µmol m–2 s–1) and low temperature (10 °C) resulted in PSII photoinhibition which was more acute in npq1 than in the wild type. This increased photosensitivity of npq1 at chilling temperature was attributable to the inhibition of nonphotochemical energy quenching (NPQ) and not to the absence of zeaxanthin itself. In contrast to PSII, PSI was found to be phototolerant to chilling stress in the light in both genotypes. In the long term (10–12 days), PSII activity recovered in both npq1 and wild type, indicating that A. thaliana is able to acclimate to chilling stress in the light independently of the xanthophyll cycle. In npq1, photoacclimation involved a substantial reduction of the light-harvesting pigment antenna of PSII and an improvement of photosynthetic electron transport. Chilling stress also induced synthesis of early light-induced proteins (ELIPs) which, in the long term, disappeared in npq1 and remained stable in the wild type. In both genotypes, photoacclimation at low temperature induced the accumulation of various antioxidants including carotenoids (except β-carotene), vitamin E (α- and γ-tocopherol) and non-photosynthetic pigments (anthocyanins and other flavonoids). Analysis of flavonoid-deficient tt mutants revealed that UV/blue-light-absorbing flavonols have a strong protective function against excess visible radiations. In contrast to the defect in npq1, the absence of flavonoids could not be overcome in the long term by compensatory mechanisms, leading to extensive photooxidative and photoinhibitory damage to the chloroplasts. Depth profiling of the leaf pigments by phase-resolved photoacoustic spectroscopy showed that the flavonoid-related photoprotection was due to light trapping, which decreased chlorophyll excitation by blue light. In contrast to flavonoids, the xanthophyll cycle and the associated NPQ seem to be mainly relevant to the protection of photosynthesis against sudden increases in light intensity.

Methane emissions from wetlands and their relationship with vascular plants: an Arctic example

Abstract: This paper investigates the relationship between vascular plant production and CH4 emissions from an arctic wet tundra ecosystem in north-east Greenland. Light intensity was manipulated by shading during three consecutive growing seasons (1998–2000). The shading treatment resulted in lower carbon cycling in the ecosystem as mean seasonal net ecosystem exchange (NEE) decreased from −336 to −196 mg CO2 m−2 h−1 and from −476 to −212 mg CO2 m−2 h−1 in 1999 and 2000, respectively, and total ecosystem respiration decreased from 125 to 94 mg CO2 m−2 h−1 in 1999 and from 409 to 306 mg CO2 m−2 h−1 in 2000. Seasonal mean CH4 emissions in controls and shaded plots were, respectively, 6.5 and 4.5 mg CH4 m−2 h−1 in 1999 and 8.3 and 6.2 mg CH4 m−2 h−1 in 2000. We found that CH4 emission was sensitive to NEE and carbon turnover, and it is reasonable to assume that the correlation was due to a combined effect of vegetative CH4 transport and substrate quality coupled to vascular plant production. Total above-ground biomass was correlated to mean seasonal CH4 emission, but separation into species showed that plant-mediated CH4 transport was highly species dependent. Potential CH4 production peaked at the same depth as maximum root density (5–15 cm) and treatment differences further suggest that substrate quality was negatively affected by decreased NEE in the shaded plots. The concentration of dissolved CH4 decreased in the control plots as the growing season progressed while it was relatively stable in the shaded plots. This suggests that a progressively better developed root system in the controls increased the capacity to transport CH4 from the soil to the atmosphere. In conclusion, vascular plant photosynthetic rate and subsequent allocation of recently fixed carbon to below-ground structures seemed to influence both vegetative CH4 transport and substrate quality.

Temporal Contrast Adaptation in the Input and Output Signals of Salamander Retinal Ganglion Cells

Abstract: We investigated how the light-evoked input and output signals of salamander retinal ganglion cells adapt to changes in temporal contrast, i.e., changes in the depth of the temporal fluctuations in the light intensity about the mean. Increasing the temporal contrast sped the kinetics and reduced the sensitivity of both the light-evoked input currents measured at the ganglion cell soma and the output spike trains of the cell. The decline in sensitivity of the input currents after an increase in contrast had two distinct kinetic components with fast (,2 sec) and slow (.10 sec) time constants. The recovery of sensitivity after a decrease in contrast was dominated by a single component with an intermediate (4‐18 sec) time constant. Contrast adaptation differed for ON and OFF cells, with both the kinetics and amplitude of the light-evoked currents of OFF cells adapting more strongly than those of ON cells. Contrast adaptation in the input currents of a ganglion cell, however, was unable to account for the extent of adaptation in the output spike trains of the cell, indicating that mechanisms intrinsic to the ganglion cell contributed. Indeed, when fluctuating currents were injected into a ganglion cell, the sensitivity of spike generation decreased with increased current variance. Pharmacological experiments indicated that adaptation of spike generation to the current variance was attributable to properties of tetrodotoxinsensitive Na 1 channels.

Killing of cutaneous microbial species by photodynamic therapy.

Abstract: Background Photodynamic therapy (PDT) utilizes photosensitizers and light. Whereas PDT use in cancer treatment has been widely accepted, antimicrobial PDT (APDT) is still in its early stages of development. Objectives To study microbial killing in vitro using APDT. Methods We used a combination of methylene blue and visible light, and a range of microbial species representative of those encountered on the skin in health and disease. Using standard light intensity conditions (slide projector, 25 cm distance from target, 42 mW cm(-2)) and methylene blue dye at 100 microg mL(-1), kill rates and subsequent D-values were determined against Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes, Corynebacterium minutissimum, Propionibacterium acnes and Candida albicans. Results D-values for these species were 72, 66, 48, 120, 30 and 660 s, respectively. The effects of light intensity on the killing of S. epidermidis showed the kill rate to be proportional to the light intensity. A high rate of cell kill was also obtained using natural sunlight. Conclusions Overall, these results indicate that APDT of the skin may represent a useful alternative to conventional antimicrobial treatment.

Supply assembly for a led lighting module

Abstract: A supply assembly for an LED lighting module includes a control switch for supplying a constant current to the LED lighting module. A dual switching signal composed of low frequency bursts of high frequency pulses is applied to the control switch. By varying the low frequency component of the dual switching signal, the average current through the LED lighting module may be varied in order to vary the light intensity outputted by the LED lighting module.

Aerial image measurement method and unit, optical properties measurement method and unit, adjustment method of projection optical system, exposure method and apparatus, making method of exposure apparatus, and device manufacturing method

Abstract: The exposure apparatus comprises a mark plate on which a plurality of types of measurement marks each used for self-measurement are formed, a reticle stage on which the mark plate is mounted, and an aerial image measurement unit. On a slit plate of the aerial image measurement unit, a slit is formed extending in the non-scanning direction which width in the measurement direction is equal to and under (wavelength λ/numerical aperture N.A of the projection optical system). Therefore, in a state where a predetermined pattern is illuminated with the illumination light to form an aerial image of the pattern via the projection optical system, and when the slit plate is scanned in the measurement direction with respect to the aerial image, the light having passed through the slit during the scanning is photo-electrically converted with the photoelectric conversion element. And, based on the photoelectric conversion signal, the control unit measures the light intensity corresponding to the aerial image with a sufficiently high accuracy in practical usage. In addition, various self-measurements become possible, by moving the reticle stage so as to position the plurality of types of measurement marks respectively in the vicinity of a focal position on the object side of the projection optical system.

Size-dependent control of the binding of biotinylated proteins to streptavidin using a polymer shield

Abstract: Many medical and biotechnological processes rely on controlling and manipulating the molecular-recognition capabilities of proteins1,2,3,4. This can be achieved using small molecules capable of competing for protein binding or by changing environmental parameters that affect protein structure and hence binding. An alternative is provided by stimuli-responsive polymers that change reversibly from a water-soluble expanded coil to a water-insoluble collapsed globule upon small changes in temperature, pH or light intensity: when attached to proteins in the vicinity of their binding sites, they reversibly block and release small ligands1,5,6,7. Here we show how this approach can be extended to achieve size-selective binding of large, macromolecular ligands. We use the thermally responsive polymer poly(N,N-diethylacrylamide) (PDEAAm), and attach it to the protein streptavidin approximately 20 A from the binding site for biotinylated proteins. Below the lower critical solution temperature of PDEAAm, the polymer is in its extended state and acts as a ‘shield’ to block the binding of large biotinylated proteins; above this temperature, it collapses and exposes the binding site, thereby allowing binding. We find that the degree of shielding depends on both the size of the biotinylated protein and the size of PDEAAm, suggesting that ‘smart’ polymer shields could be tailored to achieve a wide range of size-dependent ligand discrimination for use in affinity separations, biosensors and diagnostics technologies.

Photoelectrochemical Anticorrosion and Self-Cleaning Effects of a TiO2 Coating for Type 304 Stainless Steel

Abstract: We investigated the photoelectrochemical behavior of type 304 stainless steel (SUS 304) with TiO 2 thin film coatings, applied by a spray pyrolysis technique, for the purpose of cathodic photoprotection of the steel from corrosion. The photopotential of TiO 2 -coated SUS 304 was -350 mV vs. Ag/AgCl in an aerated aqueous solution containing 3 wt NaCl (pH 7) under illumination with 10 mW cm -2 ultraviolet (UV) light, which was more negative than the corrosion potential of the bare steel (-100 mV). The photopotential did not change in aqueous solutions containing from 0.01 to 5 wt % NaCl. No corrosion of TiO 2 -coated steel was observed at pH values greater than 3 in 3 wt % NaCl aqueous solution under UV illumination. TiO 2 films with coverages greater than 30% achieved photoprotection ability at pH 6. When the UV light intensity was 3 mW cm -2 , that is, comparable with a typical daylight UV intensity in Tokyo the photopotential of TiO 2 -coated SUS 304 was -220 mV in an aerated 3 wt % NaCl aqueous solution. In addition, the bleaching of methylene blue dye was confirmed on TiO 2 -coated SUS 304 under 1 mW cm -2 UV illumination. We conclude that TiO 2 thin film-coated SUS 304 exhibits both a cathodic photoprotection effect against corrosion and the previously reported photocatalytic self-cleaning effect.

Illumination device for simulation of neon lighting

Abstract: An illumination device (10) for simulating neon lighting comprising a plurality of space point light sources (24) positioned adjacent a lateral light receiving surface (15) of a substantially rod-like waveguide (12) made of a material that preferentially scatters light entering the light receiving surface such that the light intensity pattern exiting a lateral light emitting surface (13) of the waveguide (12) has a substantially uniform light intensity pattern.

Electro-optic transceivers for terahertz-wave applications

Abstract: Because of the reciprocal behavior of the optical rectification and the electro-optic effect in a nonlinear optical crystal, an electro-optic transceiver can alternately transmit pulsed electromagnetic radiation (optical rectification) and detect the return signal (electro-optic effect) in the same crystal. However, the optimal condition of the electro-optic transceiver may be very different from that of the spatially separated emitter and receiver. We present a detailed description of the crystal-orientation dependence of the electro-optic terahertz devices (transmitter, receiver, and transceiver). It is found that for a (110) zinc-blende electro-optical crystal, the efficiency of the electro-optic transceiver will be optimized when the angle between the polarization of the optical pump beam and the crystallographic z axis [0, 0, 1] is 26°. Meanwhile, for a (111) crystal, the angle between the optical beam and the crystallographic direction [-1, -1, 2] should be 23°. The experimental results from a (110) ZnTe transceiver verify theoretical calculations and demonstrate a direct way to optimize the working efficiency of an electro-optic terahertz transceiver.

Role of light intensification by cracks in optical breakdown on surfaces.

Abstract: The intensity distribution of an initially plane light wave incident on planar and conical surface cracks is calculated numerically by using a wave propagation computer code. The results show that light intensity enhancements caused by interference of internal reflections at the crack and the surface are very sensitive to the light polarization, the beam angle of incidence, and the crack geometry (e.g., crack width and orientation with the surface). The light intensity enhancement factor (LIEF) can locally reach 2 orders of magnitude for conical cracks of ideal shape. The electric field direction relative to the crack surfaces determines the light intensity profile around the crack. For normal-incidence illumination on the output surface, total internal reflection at the crack and the surface can occur and leads to higher LIEFs. For identical geometry and illumination conditions, a crack located on the entrance surface of an optic generates electric field enhancements that are weaker than those on the exit surface. As cracks on polished surfaces are randomly oriented, the probability for large intensity enhancements to occur is high. The model is able to predict quantitatively the magnitude of surface laser-induced damage threshold drop and damage propagation enhancement in dielectric materials that are due to cracks.

Population divergence in the plasticity of the response of Quercus coccifera to the light environment

Abstract: Summary 1. Quercus coccifera , a slow-growing, evergreen oak, grows in contrasting environments in the Mediterranean Basin. Habitat-based selection may have promoted divergence between populations with respect to phenotypic plasticity and genetic variability. 2. We tested the hypothesis that populations of the Q. coccifera originating from a rock outcrop, a continental garrigue formation and an oceanic forest would differ in their plastic response to light intensity. Plants from these populations were grown from acorns in a common garden at 100% and 20% full sunlight. Light response analysis was based on photochemical efficiency, xanthophyll pool, nutrient allocation, growth, crown architecture and light absorption. 3. Light-responsive characters ranged from the subcellular to the whole-plant level. The greatest divergences between sun and shade phenotypes were observed in leaf size, leaf angle and leaf area ratio. However, plasticity in these traits depended on plant provenance. 4. Regardless of the level of organization, populations were invariably ranked in the same order of plasticity when averaged over light-responsive features, with plants ori ginating from the rock outcrop showing the least plasticity and those from the forest the largest. The forest population also had the greatest genetic variability with respect to the isoperoxidase polymorphism. 5. Among populations, plants originating from the phosphorus-deficient rock outcrop contained 30% more P per unit dry weight. Plants from the forest population had 5% more photoprotective xanthophylls, 30% larger total leaf area, with less lobed and larger leaves and a differential plasticity in leaf azimuth. 6. Differences among populations suggested ecotypic differentiation towards less phenotypic plasticity in the most homogeneous light environments. The ecological breadth of the species seemed to be derived not only from its tolerance of Mediterranean conditions but also from the specialization of its populations in contrasting habitats.

Temporal contrast adaptation in salamander bipolar cells.

Abstract: This work investigates how the light responses of salamander bipolar cells adapt to changes in temporal contrast: changes in the depth of the temporal fluctuations in light intensity about the mean. Contrast affected the sensitivity of bipolar cells but not of photoreceptors or horizontal cells, suggesting that adaptation occurred in signal transfer from photoreceptors to bipolars. This suggestion was confirmed by recording from photoreceptor-bipolar pairs and observing a direct dependence of the gain of signal transfer on the contrast of the light input. After an increase in contrast, the onset of adaptation in the bipolar cell had a time constant of 1-2 sec, similar to a fast component of contrast adaptation in the light responses of retinal ganglion cells (Kim and Rieke, 2001). Contrast adaptation was mediated by processes in the dendrites of both on and off bipolars. The functional properties of adaptation differed for the two bipolar types, however, with contrast having a much more pronounced effect on the kinetics of the responses of off cells than on cells.

Effects of nutrients and shade on tree-grass interactions in an East African savanna

Abstract: Savanna trees have a multitude of positive and negative effects on understorey grass production. but little is known about how these effects interact. We report on a fertilization and shading experiment carried out in a Tanzanian tropical city savanna around Acacia tortilis trees. In two years of study there was no difference in grass production under tree canopies or in open grassland, Fertilization, however, indicate that trees do affect the nutrient limitation of the grass layer with an N-limited system in open grassland to a P-limited system under the trees. The NT ratios of grass gave a reliable indication of the nature of nutrient limitation, but only when assessed at the end of the wet season, Mid-wet season nutrient concentrations of grasses were higher under than outside the tree canopy, suggesting that factors other than nutrients limit grass production. A shading experiment indicated that light may be such a limiting factor during the wet season when water and nutrients are sufficiently available. However, in the dry season when water is scarce, the effect of shade on plant production became positive. We conclude that whether trees increase or decrease production of the herbaceous layer depends on how positive effects (increased soil fertility) and negative effects (shade and soil water availability) interact and that these interactions may significantly change between wet and dry seasons.

Cytological basis of photoresponsive behavior in a sponge larva

Abstract: Ontogenetic changes in the photoresponse of larvae from the demosponge Reneira sp. were studied by analyzing the swimming paths of individual larvae exposed to diffuse white light. Larvae swam upward upon release from the adult, but were negatively phototactic until at least 12 hours after release. The larval photoreceptors are pre- sumed to be a posterior ring of columnar monociliated epithelial cells that possess 120-m-long cilia and pigment- filled protrusions. A sudden increase in light intensity caused these cilia to become rigidly straight. If the light intensity remained high, the cilia gradually bent over the pigmented vesicles in the adjacent cytoplasm, and thus covered one entire pole of the larva. The response was reversed upon a sudden decrease in light intensity. The ciliated cells were sensitive to changes in light intensity in larvae of all ages. This response is similar to the shadow response in tunicate larvae or the shading of the photore- ceptor in Euglena and is postulated to allow the larvae to steer away from brighter light to darker areas, such as under coral rubble—the preferred site of the adult sponge on the reef flat. In the absence of a coordinating system in cellular sponges, the spatial organization and autonomous behavior of the pigmented posterior cells control the rapid responses to light shown by these larvae.

Phosphorus (P) efficiencies and mycorrhizal responsiveness of old and modern wheat cultivars

Abstract: A pot experiment was carried out in a growth chamber to investigate P efficiencies and mycorrhizal responsiveness of modern (Krichauff and Excalibur) and old (Khapstein, Bobin, Comeback and Purple Straw) wheat cultivars (Triticum aestivum). The arbuscular mycorrhizal fungus (AMF) used in this study was Glomus intraradices. The growth medium was a soil/sand mixture with NaHCO3-extractable P of 9.4 mg P kg−1 and no extra P was added. Plant P efficiencies (uptake, utilisation and agronomic) were found to differ significantly between cultivars, but no general trends of changes with the year of release of the cultivar were found. AMF colonisation was found to decrease plant growth under our experimental conditions with low light intensity. Mycorrhizal responsiveness (MR) was measured in terms of the improvement in plant P nutrition (shoot P concentrations). MR was found to be generally lower in modern cultivars than in old cultivars, indicating that modern breeding programs may have reduced the responsiveness of modern wheat cultivars to arbuscular mycorrhizal fungi. MR was also found to decrease in general with increased plant P utilisation efficiency.

Light- emitting diode (led) package and packaging method for shaping the external light intensity distribution.

Abstract: An LED package ( 10 ) includes LED die ( 12 ) mounted onto lead frame ( 14 ) and electrically connected thereto whereby LED die ( 12 ) is electrically energized through leads ( 16, 18 ). An encapsulant ( 20 ), preferably an epoxy resin, encapsulates and preferably hermetically seals LED die ( 12 ). Encapsulant ( 20 ) includes depression ( 24 ) defined by preselected curved surfaces ( 28 ), at least a portion of which are coated by reflective coating ( 26 ). Encapsulant ( 20 ) preferably also includes sides ( 22 ) with preselected curvature. In operation, LED die ( 12 ) emits light ( 32 ) directed approximately along LED die surface normal ( 36 ). Light rays ( 32 ) reflect from reflective surface ( 26 ) and reflected rays ( 38 ) are subsequently refracted by refracting surface ( 22 ) so that refracted rays ( 40 ) exit the capsule. The reflecting surface ( 26 ) and refracting surface ( 22 ) cooperate to convert LED die light distribution ( 32 ) into light distribution ( 40 ) which appears to emanate from an approximate point source ( 42 ).

Environmental blue light prevents stress in the fish Nile tilapia

Abstract: The present study aimed to test the effects of blue, green or white light on the stress response of the Nile tilapia, Oreochromis niloticus (L.). Each color was tested on two groups of isolated adult Nile tilapia (8 replicates each): one being subjected to confinement stress, and the other not (control). A different environmental color was imposed on each compartment by covering the light source with cellophane of the respective color (green or blue; no cellophane was used for white light). The intensity of green, white and blue lights was 250, 590 and 250 lux, respectively. Basal plasma cortisol levels were determined for each fish prior to the experimental procedures. The fish were confined by being displaced toward one side of the aquarium using an opaque partition for 1 h both in the morning and the afternoon of the two consecutive days of the test. At the end of this 48-h period, plasma cortisol levels were measured again. Basal cortisol levels (ng/ml) were similar for each group (ANOVA, F(2;42) = 0.77, P = 0.47). Thus, plasma cortisol levels were analyzed in terms of variation from their respective basal level. After confinement, plasma cortisol levels were not increased in fish submitted to a blue light environment. Thus, blue light prevents the confinement-induced cortisol response, an effect not necessarily related to light intensity.

Modeling the population of China using DMSP operational linescan system nighttime data

Abstract: Radiance-calibrated DMSP-OLS nighttime lights data of China acquired between March 1996 and January-February 1997 were evaluated for their potential as a source of population data at the provincial, county, and city levels The light clusters were classified into six categories of light intensity, and their areal extents were extracted from the image Mean pixel values of light clusters corresponding to the settlements were also extracted A light volume measure was developed to gauge the three-dimensional capacity of a settlement A density of light cluster measure known as percent light area was also calculated for each spatial unit Allometric growth models and linear regression models were developed to estimate the Chinese population and population densities at the three spatial levels using light area, light volume, pixel mean, and percent light area as independent variables It was found that the DMSP-OLS nighttime data produced reasonably accurate estimates of non-agricultural (urban) population at both the county and city levels using the allometric growth model and the light area or light volume as input Non-agricultural population density was best estimated using percent light area in a linear regression model at the county level The total sums of the estimates for non-agricultural population and even population overall closely approximated the true values given by the Chinese statistics at all three spatial levels It is concluded that the 1-km resolution radiance-calibrated DMSP-OLS nighttime lights image has the potential to provide population estimates of a country and shed light on its urban population from space